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Sample records for expanded ptfe-covered nitinol

  1. Self-expandable polytetrafluoroethylene (PTFE)-covered nitinol stent for the palliative treatment of malignant biliary obstruction

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Oong; Jung, Gyoo Sik; Han, Byung Hoon; Shin, Dong Hoon [Gospel Hospital, College of Medicine, Kosin University, Busan (Korea, Republic of); Ko, Ji Ho [Masan Samsung Medical Center, Sungkyunkwan University School of Medicine, Masan (Korea, Republic of)

    2008-06-15

    We wanted to determine the technical and clinical efficacy of placing a self-expandable PTFE-covered nitinol stent for the management of inoperable malignant biliary obstruction. Thirty six patients with inoperable malignant biliary obstructions were treated by placement of self-expandable PTFE-covered nitinol stents (S and G Biotech Corporation, Seongnam, Korea). Clinical evaluation was done with assessment of the serum bilirubin and alkaline phosphatase levels, which were measured before and after stent placement within 1 week, at 1 month and at 3 months. The patient survival rate and stent patency rate were calculated with performing Kaplan-Meier survival analysis. Successful stent placement was achieved in all the patients without procedure-related complication. Pancreatitis as an early complication occurred in two cases. The serum bilirubin and alkaline phosphatase levels were significantly decreased after the procedure. During the follow-up, recurrent obstructive jaundice occurred in six cases; stent migration occurred in four cases and tumor overgrowth occurred in two cases. The survival rates were 97%, 80%, 67% and 59% at 1, 3, 6 and 9 months, respectively. The stent patency rates were 96%, 92%, 86% and 86% at 1, 3, 6 and 9 months, respectively. Self-expandable PTFE-covered nitinol stent placement seems to be technically feasible and effective for the palliative treatment of malignant biliary obstruction.

  2. Self-expandable polytetrafluoroethylene (PTFE)-covered nitinol stent for the palliative treatment of malignant biliary obstruction

    International Nuclear Information System (INIS)

    Yoo, Oong; Jung, Gyoo Sik; Han, Byung Hoon; Shin, Dong Hoon; Ko, Ji Ho

    2008-01-01

    We wanted to determine the technical and clinical efficacy of placing a self-expandable PTFE-covered nitinol stent for the management of inoperable malignant biliary obstruction. Thirty six patients with inoperable malignant biliary obstructions were treated by placement of self-expandable PTFE-covered nitinol stents (S and G Biotech Corporation, Seongnam, Korea). Clinical evaluation was done with assessment of the serum bilirubin and alkaline phosphatase levels, which were measured before and after stent placement within 1 week, at 1 month and at 3 months. The patient survival rate and stent patency rate were calculated with performing Kaplan-Meier survival analysis. Successful stent placement was achieved in all the patients without procedure-related complication. Pancreatitis as an early complication occurred in two cases. The serum bilirubin and alkaline phosphatase levels were significantly decreased after the procedure. During the follow-up, recurrent obstructive jaundice occurred in six cases; stent migration occurred in four cases and tumor overgrowth occurred in two cases. The survival rates were 97%, 80%, 67% and 59% at 1, 3, 6 and 9 months, respectively. The stent patency rates were 96%, 92%, 86% and 86% at 1, 3, 6 and 9 months, respectively. Self-expandable PTFE-covered nitinol stent placement seems to be technically feasible and effective for the palliative treatment of malignant biliary obstruction

  3. Treatment of Malignant Biliary Obstruction with a PTFE-Covered Self-Expandable Nitinol Stent

    International Nuclear Information System (INIS)

    Han, Young-Min; Kwak, Hyo-Sung; Jin, Gong-Yong; Lee, Seung-Ok; Chung, Gyung-Ho

    2007-01-01

    We wanted to determine the technical and clinical efficacy of using a PTFE-covered self-expandable nitinol stent for the palliative treatment of malignant biliary obstruction. Thirty-seven patients with common bile duct strictures caused by malignant disease were treated by placing a total of 37 nitinol PTFE stents. These stents were covered with PTFE with the exception of the last 5 mm at each end; the stent had an unconstrained diameter of 10 mm and a total length of 50 80 mm. The patient survival rate and stent patency rate were calculated by performing Kaplan-Meier survival analysis. The bilirubin, serum amylase and lipase levels before and after stent placement were measured and then compared using a Wilcoxon signed-rank test. The average follow-up duration was 27.9 weeks (range: 2 81 weeks). Placement was successful in all cases. Seventy-six percent of the patients (28/37) experienced adequate palliative drainage for the remainder of their lives. There were no immediate complications. Three patients demonstrated stent sludge occlusion that required PTBD (percutaneous transhepatic biliary drainage) irrigation. Two patients experienced delayed stent migration with stone formation at 7 and 27 weeks of follow-up, respectively. Stent insertion resulted in acute elevations of the amylase and lipase levels one day after stent insertion in 11 patients in spite of performing endoscopic sphincterotomy (4/6). The bilirubin levels were significantly reduced one week after stent insertion (p < 0.01). The 30-day mortality rate was 8% (3/37), and the survival rates were 49% and 27% at 20 and 50 weeks, respectively. The primary stent patency rates were 85%, and 78% at 20 and 50 weeks, respectively. The PTFE-covered self-expandable nitinol stent is safe to use with acceptable complication rates. This study is similar to the previous studies with regard to comparing the patency rates and survival rates

  4. Treatment of Malignant Biliary Obstruction with a PTFE-Covered Self-Expandable Nitinol Stent

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    Han, Young-Min; Kwak, Hyo-Sung; Jin, Gong-Yong; Lee, Seung-Ok; Chung, Gyung-Ho [Chonbuk National University Medical School and Hospital, Chonju (Korea, Republic of)

    2007-10-15

    We wanted to determine the technical and clinical efficacy of using a PTFE-covered self-expandable nitinol stent for the palliative treatment of malignant biliary obstruction. Thirty-seven patients with common bile duct strictures caused by malignant disease were treated by placing a total of 37 nitinol PTFE stents. These stents were covered with PTFE with the exception of the last 5 mm at each end; the stent had an unconstrained diameter of 10 mm and a total length of 50 80 mm. The patient survival rate and stent patency rate were calculated by performing Kaplan-Meier survival analysis. The bilirubin, serum amylase and lipase levels before and after stent placement were measured and then compared using a Wilcoxon signed-rank test. The average follow-up duration was 27.9 weeks (range: 2 81 weeks). Placement was successful in all cases. Seventy-six percent of the patients (28/37) experienced adequate palliative drainage for the remainder of their lives. There were no immediate complications. Three patients demonstrated stent sludge occlusion that required PTBD (percutaneous transhepatic biliary drainage) irrigation. Two patients experienced delayed stent migration with stone formation at 7 and 27 weeks of follow-up, respectively. Stent insertion resulted in acute elevations of the amylase and lipase levels one day after stent insertion in 11 patients in spite of performing endoscopic sphincterotomy (4/6). The bilirubin levels were significantly reduced one week after stent insertion (p < 0.01). The 30-day mortality rate was 8% (3/37), and the survival rates were 49% and 27% at 20 and 50 weeks, respectively. The primary stent patency rates were 85%, and 78% at 20 and 50 weeks, respectively. The PTFE-covered self-expandable nitinol stent is safe to use with acceptable complication rates. This study is similar to the previous studies with regard to comparing the patency rates and survival rates.

  5. Bronchobiliary Fistula Treated by Self-expanding ePTFE-Covered Nitinol Stent-Graft

    International Nuclear Information System (INIS)

    Gandini, Roberto; Konda, Daniel; Tisone, Giuseppe; Pipitone, Vincenzo; Anselmo, Alessandro; Simonetti, Giovanni

    2005-01-01

    A 71-year-old man, who had undergone right hepatectomy extended to the caudate lobe with terminolateral Roux-en-Y left hepatojejunostomy for a Klatskin tumor, developed bilioptysis 3 weeks postoperatively due to bronchobiliary fistula. Percutaneous transhepatic cholangiography revealed a non-dilated biliary system with contrast medium extravasation to the right subphrenic space through a resected anomalous right posterior segmental duct. After initial unsuccessful internal-external biliary drainage, the fistula was sealed with a VIATORR covered self-expanding nitinol stent-graft placed with its distal uncovered region in the hepatojejunal anastomosis and the proximal ePTFE-lined region in the left hepatic duct. A 10-month follow-up revealed no recurrence of bilioptysis and confirmed the complete exclusion of the bronchobiliary fistula

  6. Percutaneous Palliation of Pancreatic Head Cancer: Randomized Comparison of ePTFE/FEP–Covered Versus Uncovered Nitinol Biliary Stents

    International Nuclear Information System (INIS)

    Krokidis, Miltiadis; Fanelli, Fabrizio; Orgera, Gianluigi; Tsetis, Dimitrios; Mouzas, Ioannis; Bezzi, Mario; Kouroumalis, Elias; Pasariello, Roberto; Hatzidakis, Adam

    2011-01-01

    The purpose of this study was to compare the clinical effectiveness of expanded polytetrafluoroethylene/fluorinated-ethylene-propylene (ePTFE/FEP)–covered stents with that of uncovered nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer. Eighty patients were enrolled in a prospective randomized study. Bare nitinol stents were used in half of the patients, and ePTFE/FEP–covered stents were used in the remaining patients. Patency, survival, complications, and mean cost were calculated in both groups. Mean patency was 166.0 ± 13.11 days for the bare-stent group and 234.0 ± 20.87 days for the covered-stent group (p = 0.007). Primary patency rates at 3, 6, and 12 months were 77.5, 69.8, and 69.8% for the bare-stent group and 97.5, 92.2, and 87.6% for the covered-stent group, respectively. Mean secondary patency was 123.7 ± 22.5 days for the bare-stent group and 130.3 ± 21.4 days for the covered-stent group. Tumour ingrowth occurred exclusively in the bare-stent group in 27.5% of cases (p = 0.002). Median survival was 203.2 ± 11.8 days for the bare-stent group and 247.0 ± 20 days for the covered-stent group (p = 0.06). Complications and mean cost were similar in both groups. Regarding primary patency and ingrowth rate, ePTFE/FEP–covered stents have shown to be significantly superior to bare nitinol stents for the palliation of malignant jaundice caused by inoperable pancreatic head cancer and pose comparable cost and complications. Use of a covered stent does not significantly influence overall survival rate; nevertheless, the covered endoprosthesis seems to offer result in fewer reinterventions and better quality of patient life.

  7. Malignant duodenal obstructions: palliative treatment with covered expandable nitinol stent

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun Chul; Jung, Gyoo Sik; Lee, Sang Hee; Kim, Sung Min; Oh, Kyung Seung; Huh, Jin Do; Cho, Young Duk [College of Medicine, Kosin Univ, Pusan (Korea, Republic of); Song, Ho Young [College of Medicine, Ulsan Univ., Seoul (Korea, Republic of)

    2002-04-01

    To evaluate the feasibility and clinical effectiveness of using a polyurethane-covered expandable nitinol stent in the palliative treatment of malignant duodenal obstruction. Under fluoroscopic guidance, a polyurethane-covered expandable nitinol stent was placed in 12 consecutive patients with malignant duodenal obstructions. All presented with severe nausea and recurrent vomiting. The underlying causes of obstruction were duodenal carcinoma (n=4), pancreatic carcinoma (n=4), gall bladder carcinoma (n=2), distal CBD carcinoma (n=1), and uterine cervical carcinoma (n=1). The sites of obstruction were part I (n=1), part II (n=8), and III (n=3). Due to pre-existing jaundice, eight patients with part II obstructions underwent biliary decompression prior to stent placement. An introducer sheath with a 6-mm outer diameter and stents 16 mm in diameter were employed, and to place the stent, and after-loading technique was used. Stent placement was technically successful in ten patients, and no procedural complications occuured. In one of two patients in whom there was technical failure, and in whom the obstructions were located in part III, the stent was placed transgastrically. Stent migration occurred in one patient four days after the procedure, and treatment involved the palcement of a second, uncovered, nitinol stent. After stent placement, symptoms improved in all patients. During follow-up, obstructive symptoms due to stent stenosis (n=1), colonic obstruction (n=1), and multiple small bowel obstruction (n=1) recurred in three patients. Two of these were treated by placing additional stents in the duodenum and colon, respectively. One of the eight patients in whom a stent was placed in the second portion of the duodenum developed jaundice. The patients died a mean 14 (median, 9) weeks after stent placement. The placement of a polyurethane-covered expandable nitinol stent seems to be technically feasible, safe and effective for the palliative treatment of malignant

  8. Polyurethane-Covered Self-expandable Nitinol Stent for Malignant Biliary Obstruction: Preliminary Results

    International Nuclear Information System (INIS)

    Han, Young-Min; Hwang, Seung-Bae; Lee, Soo-Teik; Lee, Jeong-Min; Chung, Gyung-Ho

    2002-01-01

    Purpose: To evaluate the immediate and long-term results in ten patients with malignant biliary obstruction using a polyurethane-covered, self-expandable nitinol stent.Methods: A nitinol stent, fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of 60-80 mm, was placed transhepatically under fluoroscopic guidance in ten patients. The length of the biliary obstruction varied between 30-50 mm. The follow-up examination included a clinical assessment, serum bilirubin measurement, and ultrasound examinations at one-month intervals in all patients. Results: Initial stent deployment was successful in eight patients. Two patients experienced proximal migration,which was solved by insertion of two, uncovered Wallstents. One patient had the stent removed after two weeks because of severe nausea and vomiting. One patient had delayed migration of the covered stent after 40 weeks. The follow-up duration was 3-40 weeks (Mean: 16.9 weeks). Seven patients died(3-26 weeks) and three patients survived (24-40 weeks). The bilirubin measurements in all patients had significantly decreased one week after stent insertion. The levels of amylase and lipase had did not increase after stent insertion. Conclusions: Apolyurethane-covered, self-expandable nitinol stent can be used effectively and safely in the treatment of malignant biliary obstruction. The preliminary results are favorable, but there is a need for further large studies to determine both long-term survival and patency

  9. Management of malignant biliary obstruction: Technical and clinical results using an expanded polytetrafluoroethylene fluorinated ethylene propylene (ePTFE/FEP)-covered metallic stent after 6-year experience

    Energy Technology Data Exchange (ETDEWEB)

    Fanelli, Fabrizio; Orgera, Gianluigi; Bezzi, Mario; Rossi, Plinio; Allegritti, Massimiliano; Passariello, Roberto [University of Rome, Department of Radiological Sciences, Rome (Italy)

    2008-05-15

    To evaluate the efficacy and safety of an expanded polytetrafluoroethylene-fluorinated ethylene-propylene (ePTFE/FEP)-covered metallic stent in the management of malignant biliary obstruction. Eighty consecutive patients with malignant common bile duct strictures were treated by placement of 83 covered metallic stents. The stent-graft consists of an inner ePTFE/FEP lining and an outer supporting structure of nitinol wire. Clinical evaluation, assessment of serum bilirubin and liver enzyme levels were analyzed before biliary drainage, before stent-graft placement and during the follow-up period at 1, 3, 6, 9 and 12 months. Technical success was obtained in all cases. After a mean follow-up of 6.9{+-}4.63 months, the 30-day mortality rate was 14.2%. Survival rates were 40% and 20.2% at 6 and 12 months, respectively. Stent-graft patency rates were 95.5%, 92.6% and 85.7% at 3, 6 and 12 months, respectively. Complications occurred in five patients (6.4%); among these, acute cholecystitis was observed in three patients (3.8%). A stent-graft occlusion rate of 9% was observed. The percentage of patients undergoing lifetime palliation (91%) and the midterm patency rate suggest that placement of this ePTFE/FEP-covered stent-graft is safe and highly effective in achieving biliary drainage in patients with malignant strictures of the common bile duct. (orig.)

  10. Usefulness of a balloon-expandable, covered stent for the transjugular intrahepatic portosystemic shunt

    Directory of Open Access Journals (Sweden)

    Rössle M

    2018-01-01

    Full Text Available The availability of polytetrafluoroethylene (PTFE covered, self-expandable nitinol stents in 2001 considerably improved the patency, response rates and survival of the transjugular intrahepatic portosystemic shunt (TIPS. Side effects of portosystemic shunting such as hepatic encephalopathy (HE and worsening of hepatic function, however, remained a problem. To reduce HE, underdilatation of nitinol stents has been practiced for many years. However, as shown recently, underdilatation was a flop since, due to their intrinsic memory, nitinol stents always expanded to reach their nominal diameter of 8 or 10 mm. To overcome this problem and to be able to perform permanent shunts with a smaller diameter of < 8 mm, we studied the usefulness of a balloon-expandable, covered, metallic stent which allowed adjustment to any diameter between 5 and 12 mm. Methods: 30 patients with cirrhosis and symptomatic portal hypertension were included. The mean Child-Pugh score was 8 ± 2.17 patients had refractory ascites, 9 patients variceal bleeding and four patients other indications for the TIPS. Results: The TIPS was successfully implanted in all patients within 69.6 ± 21.8 min. The shunt reduced the portosystemic pressure gradient by 57.5 ± 14.2% with a mean stent diameter of 7.4 ± 1.0 mm (5 -10.3 mm. During a mean follow-up of 330 ± 249 days, shunt revision was necessary in 5 patients (17%, four of them had insufficient response and received stent dilatation and one patient had stent misplacement requiring a parallel shunt. Three patients (10% developed HE. Conclusions: The covered, balloon-expandable stent could be placed accurately and allowed creation of adapted shunts with smaller diameters as usual. This resulted in a comparatively low rate of HE.

  11. Nitinol Esophageal Stents: New Designs and Clinical Indications

    International Nuclear Information System (INIS)

    Strecker, Ernst-Peter; Boos, Irene; Vetter, Sylvia; Strohm, Michael; Domschke, Sigurd

    1996-01-01

    Purpose: To evaluate the clinical use of covered and noncovered, knitted nitinol stents in patients presenting new stent indications. Methods: Self-expandable, knitted nitinol stents were implanted in four patients for treatment of dysphagia. In two patients who had malignant strictures and had esophago-respiratory fistulae and in one patient with an esophagocutaneous fistula, polytetrafluoroethylene (PTFE)-covered stents were implanted. One patient received a noncovered stent, but a retrograde approach through a percutaneous endoscopic gastrostomy (PEG) fistula had to be chosen for recanalization of an esophageal occlusion. Two patients received stents for treatment of benign strictures. Results: Recanalization of the stricture and stent implantation were performed under fluoroscopic control without any procedure-related morbidity or mortality. Dysphagia improved in all patients and the esophageal fistulae could be sealed off by covered stents. During a maximum follow-up of 18 months, there was no stent migration or esophageal perforation. Complications observed were stent stenosis due to food impaction (1/4) and benign stent stenosis (2/2). Most complications could be treated by the interventional radiologist. Conclusion: Self-expandable, covered Nitinol stents provide an option for the treatment of dysphagia combined with esophageal fistulae. In combination with interventional radiology techniques, even complex strictures are accessible. For benign strictures, the value of stent treatment has not yet been proven

  12. Temporary placement of covered retrievable expandable nitinol stents with barbs in high-risk surgical patients with benign prostatic hyperplasia: work in progress.

    Science.gov (United States)

    Kim, Choung-Soo; Song, Ho-Young; Jeong, In Gab; Yeo, Hyun Jin; Kim, Eun-Young; Park, Jung-Hoon; Yoon, Chang Jin; Paick, Sung Hyun; Park, Sang Woo; Bae, Jae-Ik; Won, Je Hwan

    2011-10-01

    To report the use of a newly constructed, covered, retrievable, expandable nitinol stent with barbs to overcome the problem of stent migration associated with conventional covered prostatic expandable stents and to evaluate prospectively the technical feasibility and clinical effectiveness of the stents in patients with benign prostatic hyperplasia (BPH). A covered retrievable expandable nitinol stent with four barbs was placed with use of an 18-F stent delivery system in seven consecutive patients with symptomatic BPH who had high operative risks. Age range of patients was 62-83 years (mean 74 years). In cases in which the stent migrated, it was replaced with a stent with eight barbs. The stents were routinely removed 4 months after placement using a 21-F stent removal set. Stent placement was technically successful and well tolerated in six of the seven patients. The remaining patient needed a second stent placement after removal of the first stent. The stent with four barbs migrated into the urinary bladder in four patients (57%); three of these patients received a second stent with eight barbs with good results, and the fourth patient did not need further treatment because his symptoms improved. Routine removal of the stent 4 months after placement was performed in three of the seven patients with good results. Retrievable stents with eight barbs seem to overcome the problem of stent migration associated with conventional prostatic expandable stents. Preliminary results suggest that stents with barbs are both feasible and effective in patients with BPH. Copyright © 2011 SIR. Published by Elsevier Inc. All rights reserved.

  13. Endovascular Treatment of a Giant Superior Mesenteric Artery Pseudoaneurysm Using a Nitinol Stent-Graft

    International Nuclear Information System (INIS)

    Gandini, Roberto; Pipitone, Vincenzo; Konda, Daniel; Pendenza, Gianluca; Spinelli, Alessio; Stefanini, Matteo; Simonetti, Giovanni

    2005-01-01

    A 68-year-old woman presenting with gastrointestinal bleeding (hematocrit 19.3%) and in a critical clinical condition (American Society of Anesthesiologists grade 4) from a giant superior mesenteric artery pseudoaneurysm (196.0 x 131.4 mm) underwent emergency endovascular treatment. The arterial tear supplying the pseudoaneurysm was excluded using a 5.0 mm diameter and 31 mm long monorail expanded polytetrafluoroethylene (ePTFE)-covered self-expanding nitinol stent. Within 6 days of the procedure, a gradual increase in hemoglobin levels and a prompt improvement in the clinical condition were observed. Multislice CT angiograms performed immediately, 5 days, 30 days and 3 months after the procedure confirmed the complete exclusion of the pseudoaneurysm

  14. Treatment of malignant gastroduodenal obstruction with using a newly designed complex expandable nitinol stent: initial experiences

    International Nuclear Information System (INIS)

    Jung, Mi Hee; Ko, Ji Ho; Lee, Eun Jung; Oh, Kyeng Seung; Huh, Jin Do; Cho, Young Duk; Park, Seun Ja; Jung, Gyoo Sik

    2005-01-01

    We wanted to evaluate the usefulness of a new type of a complex expandable nitinol stent that was designed to reduce the stent's propensity to migration during the treatment of malignant gastroduodenal obstructions. Two types of expandable nitinol stent were constructed by weaving a single thread of 0.2mm nitinol wire in a tubular configuration: an uncovered stent 18mm in diameter and a covered stent 16mm in diameter. Both ends of the covered stent were fabricated by coaxially inserting the covered stent into the tubular uncovered stent and then attaching the two stents together with using nylon monofilament. Under fluoroscopic guidance, the stent was placed in 29 consecutive patients (20 men and 9 women, mean age: 65 years) who were suffering with malignant gastric outlet obstruction (n=20), duodenal obstruction (n=6) or combined obstruction (n=3). Clinical improvement was assessed by comparing the food intake capacity before and after the procedure. The complications were investigated during the follow up period. Stent placement was successful in all the patients. After stent placement, the symptoms improved in all but one patient. During the follow up, stent migration occurred in one patient (3%) at 34 days after the procedure. Despite the stent migration, the patient was able to resume a soft diet. Six patients developed recurrent symptoms of obstruction with tumor overgrowth at a mean of 145 days after the procedure; all the patients underwent coaxial placement of an additional stent with good results. One patient showed recurrence of obstruction due to tumor in-growth, and this was treated by placement of a second stent. Two patients with stent placement in the duodenum suffered from jaundice 26 days and 65 days, respectively, after their procedures. Placement of the newly designed complex expandable nitinol stent seems to be effective for the palliative treatment of malignant gastroduodenal obstructions. The new stent also seems to help overcome the

  15. Treatment of malignant gastroduodenal obstruction with using a newly designed complex expandable nitinol stent: initial experiences

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Mi Hee; Ko, Ji Ho; Lee, Eun Jung; Oh, Kyeng Seung; Huh, Jin Do; Cho, Young Duk; Park, Seun Ja [College of Medicine, Kosin University, Busan (Korea, Republic of); Jung, Gyoo Sik [Ulsan Hospital, Ulsan (Korea, Republic of)

    2005-12-15

    We wanted to evaluate the usefulness of a new type of a complex expandable nitinol stent that was designed to reduce the stent's propensity to migration during the treatment of malignant gastroduodenal obstructions. Two types of expandable nitinol stent were constructed by weaving a single thread of 0.2mm nitinol wire in a tubular configuration: an uncovered stent 18mm in diameter and a covered stent 16mm in diameter. Both ends of the covered stent were fabricated by coaxially inserting the covered stent into the tubular uncovered stent and then attaching the two stents together with using nylon monofilament. Under fluoroscopic guidance, the stent was placed in 29 consecutive patients (20 men and 9 women, mean age: 65 years) who were suffering with malignant gastric outlet obstruction (n=20), duodenal obstruction (n=6) or combined obstruction (n=3). Clinical improvement was assessed by comparing the food intake capacity before and after the procedure. The complications were investigated during the follow up period. Stent placement was successful in all the patients. After stent placement, the symptoms improved in all but one patient. During the follow up, stent migration occurred in one patient (3%) at 34 days after the procedure. Despite the stent migration, the patient was able to resume a soft diet. Six patients developed recurrent symptoms of obstruction with tumor overgrowth at a mean of 145 days after the procedure; all the patients underwent coaxial placement of an additional stent with good results. One patient showed recurrence of obstruction due to tumor in-growth, and this was treated by placement of a second stent. Two patients with stent placement in the duodenum suffered from jaundice 26 days and 65 days, respectively, after their procedures. Placement of the newly designed complex expandable nitinol stent seems to be effective for the palliative treatment of malignant gastroduodenal obstructions. The new stent also seems to help overcome the

  16. Placement of a covered self-expandable nitinol stent for bile duct stricture that caused by ischemic injury after transcatheter arterial chemoembolization in a patient with hepatocellular carcinoma: a case report

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Kweon; Seo, Tae Seok; Cha, In Ho; Huh, Sik; Byun, Kwan Soo [Guro Hospital, Korea University College of Medicine, Seoul (Korea, Republic of)

    2008-10-15

    The authors report here on a case of focal stricture in the common hepatic duct that was caused by ischemic bile duct injury after repeat TACE procedures for hepatocellular carcinoma, and the patient was successfully treated with a covered self-expandable nitinol stent.

  17. Sealed source and device design safety testing: Technical report on the findings of task 4 -- Investigation of failed Nitinol brachytherapy wire. Volume 2

    International Nuclear Information System (INIS)

    Benac, D.J.; Burghard, H.C.

    1996-03-01

    This report covers an investigation of the nature and cause of failure in Nitinol brachytherapy sourcewires. The investigation was initiated after two clinical incidents in which sourcewires failed during or immediately after a treatment. The investigation determined that the two clinical Nitinol sourcewires failed in a brittle manner, which is atypical for Nitinol. There were no material anomalies or subcritical flaws to explain the brittle failures. The bend tests also demonstrated that neither moist environment, radiation, nor low-temperature structural transformation was a likely root cause of the failures. However, degradation of the PTFE was consistently evident, and those sourcewires shipped or stored with PTFE sleeves consistently failed in laboratory bend tests. On the basis of the results of this study, it was concluded that the root cause of the in-service failures of the sourcewires was environmentally induced embrittlement due to the breakdown of the PTFE protective sleeves in the presence of the high-radiation field and subsequent reaction or interaction of the breakdown products with the Nitinol alloy

  18. Results of the new nitinol self-expandable stents for distal biliary structures

    NARCIS (Netherlands)

    Smits, M.; Huibregtse, K.; Tytgat, G.

    1995-01-01

    The nitinol stent is a self-expandable spiral stent made of nickel-titanium alloy. We performed a pilot study to evaluate the method of stent insertion and stent efficacy. Twenty-eight patients with irresectable malignancy had nitinol stents inserted for obstructive jaundice due to distal biliary

  19. Use of nitinol self-expandable stents in 26 dogs with tracheal collapse.

    Science.gov (United States)

    Beranek, J; Jaresova, H; Rytz, U

    2014-02-01

    A study was designed to describe a novel approach to the treatment of tracheal collapse (TC) in dogs using self-expandable nitinol stents. Medical records were reviewed retrospectively for 26 client owned dogs in which nitinol stents were deployed. The entire length of trachea was supported independently of the extent of TC. Two overlapping stents were used instead of one in cases where one stent was not spanning the entire trachea adequately. The diameter of the cranial radiolucent portion of trachea, just behind the cricoid cartilage, was measured as a specific landmark to select the appropriate size of the stent. Two self-expandable nitinol stents were inserted in 9 of 26 dogs; the trachea in the rest of the cases was supported with only one stent. A follow up tracheoscopy was performed in 10 of 26 cases with recurrent clinical signs. Secondary tracheal stenosis in these cases was caused by stent fracture, granuloma or excessive stent shortening. Additional stents were placed successfully to expand the stenotic lumen. A support of the entire trachea may decrease risk of nitinol fracture at the end of the implant. Long term clinical improvement (25 of 26 dogs, 96 %) is comparable with the results of other studies.

  20. Primary Self-Expandable Nitinol Stent Placement in Focal Lesions of Infrarenal Abdominal Aorta: Long Term Results

    International Nuclear Information System (INIS)

    Lastovickova, Jarmila; Peregrin, Jan H.

    2008-01-01

    Purpose. To evaluate the technical and clinical success, safety and long term results of percutaneous transluminal angioplasty/self-expandable nitinol stent placement of infrarenal abdominal aorta focal lesions. Materials and Methods. Eighteen patients underwent PTA of focal atherosclerotic occlusive disease of distal abdominal aorta. Two symptomatic occlusions and 16 stenoses in 10 male and 8 female patients (mean age 68.2 years) were treated with primary self-expandable nitinol stent placement. Results. Primary self-expandable nitinol stent placement was technically successful in all 18 procedures; clinical success was achieved in 100% of patients. No complications associated with the procedure occurred. During the 49.4 months of mean follow up (range 3-96, 4 months) all treated aortic segments remained patent. Conclusions. Endovascular treatment (primary self-expandable nitinol stent placement) of focal atherosclerotic lesions of distal abdominal aorta is a safe method with excellent primary technical and clinical success rates and favourable Long term results

  1. Self-expanding nanoplatinum-coated nitinol devices for atrial septal defect and patent ductus arteriosus closure: a swine model.

    Science.gov (United States)

    Lertsapcharoen, Pornthep; Khongphatthanayothin, Apichai; La-orkhun, Vidhavas; Supachokchaiwattana, Pentip; Charoonrut, Phingphol

    2006-01-01

    Our purpose was to evaluate self-expanding nanoplatinum-coated nitinol devices for transcatheter closure of atrial septal defects and patent ductus arteriosus in a swine model. The devices were braided from platinum-activated nitinol wires and filled with polyester to enhance thrombogenicity. The platinum activation of the nitinol wires was carried out with the help of Nanofusion technology. The coating of platinum covers the exposed surface of the nitinol wires and prevents the release of nickel into the blood stream after the implantation of the device but does not affect its shape memory, which makes the device self-expanding after it is loaded from the catheter. Atrial septal defects were created in 12 piglets by balloon dilation of the patent foramen ovale. The size of the device was selected on the basis of the diameter of the balloon and the size of the defect, measured by transthoracic echocardiography. The devices were successfully deployed in all 12 piglets under fluoroscopic study. Transthoracic color Doppler echocardiograms showed complete closure of the atrial septal defect within 15 minutes of device implantation. Twelve patent ductus arteriosus closure devices were deployed in the right or left subclavian arteries in 10 piglets. Angiograms showed complete occlusion of the subclavian arteries within a few minutes of device deployment. In the atrial septal defect cases, the autopsy findings showed complete organizing fibrin thrombus formation and complete neo-endothelialization on the outer surface of the devices within one week and six weeks of implantation, respectively. The use of self-expanding nanoplatinum-coated nitinol devices for the transcatheter closure of atrial septal defects and patent ductus arteriosus is feasible. The excellent occlusion result and complete neo-endothelialization of the devices in the swine model is an indication of the potential of these devices in human application.

  2. Self-expandable nitinol stent placement in homocysteinemic porcine aorta

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    Luís Henrique Gil França

    2008-01-01

    Full Text Available PURPOSE: To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs (induced with a methionine-rich diet following placement of a self-expanding nitinol stent. METHODS: Eighteen Macau pigs were used. They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C (control, was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis. RESULTS: Under microscopic evaluation, the intima was significantly thicker in Group C than in Group M. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. In group C the levels of plasma homocysteine ranged from 14,40 to 16,73µmol/l; in Group M, plasma homocysteine levels ranged from 17.47 to 59.80 µmol/l after 30 days of a methionine-rich diet. CONCLUSION: Compared to normal pigs, less intimal hyperplasia was observed in the abdominal aortas of hyperhomocysteinemic pigs thirty days after the insertion of a self-expandable nitinol stent.

  3. Feasibility study for the investigation of Nitinol self-expanding stents by neutron techniques

    International Nuclear Information System (INIS)

    Rogante, M.; Pasquini, U.; Rosta, L.; Lebedev, V.

    2011-01-01

    In this paper, neutron techniques - in particular, small angle neutron scattering (SANS) and neutron diffraction (ND) - are considered for the non-destructive characterization of Nitinol artery stents. This roughly equiatomic (50Ni-50Ti at%) shape memory alloy (SMA) exhibits significant properties of superelasticity and biocompatibility that make it suitable to be typically used as smart material for medical implants and devices. Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment. These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses. Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses. The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features. -- Research Highlights: → Neutron techniques can contribute to develop Nitinol self-expanding artery stents. → Neutrons investigations can help avoiding wear and fracture events in Nitinol stents. → Neutron techniques can yield trends adoptable in monitoring of Nitinol stent features. → SANS is able to perform a micro- and nano-scale characterization of Nitinol stents. → Neutron Diffraction helps assessing stresses due to the exercise in Nitinol stents.

  4. Treatment of Benign Tracheal Stenosis Utilizing Self-Expanding Nitinol Stents

    International Nuclear Information System (INIS)

    Sesterhenn, Andreas M.; Wagner, Hans-Joachim; Alfke, Heiko; Werner, Jochen A.; Lippert, Burkard M.

    2004-01-01

    We assessed the results of self-expanding metallic stent insertion into benign proximal tracheal stenosis in patients not appropriate or unfit for surgical repair. Proximal benign tracheal stenoses had occurred in 11 patients (7 men, 4 women, mean age 68.8 years) after long-time intubation (n = 6), tracheostomy (n = 4), or chondropathia (n = 1). Fourteen self-expanding nitinol stents were placed in the patients under general anesthesia with endoscopical and fluoroscopical guidance. Stent insertion was successful in all cases and led to immediate relief of the morphological and functional airway obstruction. No immediate complications were noted. During the mean follow-up period of 67.5 weeks we observed one recurrent dyspnea 3 months after implantation and granuloma formation at the stent insertion site in another patient. Both complications were successfully treated with additional stent insertion in one case and laser resection of granulomas in the other. Self-expanding nitinol stents should be considered for the treatment of benign proximal tracheal obstruction in selected patients for whom surgical repair is contraindicated

  5. USE OF COVERED SELF-EXPANDABLE NITINOL STENT FOR ANASTOMOTIC BILIARY STRUCTURE MANAGEMENT AFTER LIVER TRANSPLANTATION: THE FIRST EXPERIENCE

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    M. N. Kornilov

    2013-01-01

    Full Text Available Aim. The aim of this study focuses on the first experience with self-expandable stents, analysis of its efficacy and safety in the treatment of anastomotic strictures after liver transplantation. Materials and methods. There’re 136 liver transplantations performed from 2004 till 2012. To correct anastomotic strictures we’ve used only the self-expandable coated nitinol stent. We performed stenting in 7 recipient. Result. In 131 liver transplant recipients incidence of biliary strictures has been 5.3%. All of 5 patients have been managed by retrograde or antegrade way. Conclusion. Our first experience demonstrate efficacy and safety of the used tecniques up to 24 months. The analysis of more long-term results is required. 

  6. Transcatheter aortic value implantation with self-expandable nitinol valved stent: an experimental study in sheep

    International Nuclear Information System (INIS)

    Jiang Haibin; Huang Xinmiao; Bai Yuan

    2011-01-01

    Objective: to determine the feasibility and safety of transcatheter aortic valve implantation with domestic self-expandable nitinol valved stent in experimental sheep. Methods: A fresh pig pericardium was cross-linked with a 0.6% glutaraldehyde solution for 36 hours and then sutured on a nitinol self-expandable stent. Ten healthy sheep of (46.00±2.60) kg body weight were chosen for the study. Under general anesthesia, the device was delivered through catheter into the native aortic valve of the sheep via the femoral artery or abdominal aorta. The animals were followed up for three months. Results: Six devices were successfully delivered at the desired position in six sheep with no occurrence of complications. Angiographic and hemodynamic studies confirmed that the stents were fixed at correct position with competent valve function immediately and 90 days after the procedure. Technical failure or fatal complications occurred in the remaining four sheep. Conclusion: Implantation of a domestic nitinol self-expandable stent at the aortic valve position through a transcatheter approach is feasible in experimental sheep. (authors)

  7. Treatment of a Ruptured Anastomotic Esophageal Stricture Following Bougienage with a Dacron-Covered Nitinol Stent

    International Nuclear Information System (INIS)

    Heindel, Walter; Gossmann, Axel; Fischbach, Roman; Michel, Olaf; Lackner, Klaus

    1996-01-01

    A patient suffering from esophagorespiratory fistula after bougienage of a benign stricture at the site of the anastomosis between a jejunal interposition and the esophagus was referred for interventional treatment. A prototype nitinol stent centrally covered with Dacron was implanted under regional anesthesia and fluoroscopic guidance. The self-expanding prosthesis dilated the stenosis completely and closed the fistula, with consequent improvement in respiratory and nutritional status and thus the general quality of life. The patient was able to eat and drink normally until death 3 months later due to progression of his underlying malignant disease

  8. Self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty

    International Nuclear Information System (INIS)

    Tepe, Gunnar; Heller, Stephan; Wiskirchen, Jakub; Fischmann, Arne; Claussen, Claus D.; Zeller, Thomas; Coerper, Stephan; Beckert, Stefan; Balletshofer, Bernd

    2007-01-01

    The feasibility of self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty was assessed. Options for lower limb percutaneous revascularization are limited, especially for complex vessel obstruction. Depending on the lesion and the experience of the interventionalist, the failure rate of balloon angioplasty (PTA) ranges between 10 and 40%. Until recently, no self-expanding stent for the use in the infragenicular arteries was available. This is the first report of the results for 18 consecutive patients who received 4F sheath compatible self-expanding nitinol stents following unsuccessful PTA or early restenosis. Twenty-four stents were implanted in 21 lesions for various indications residual stenosis >50% due to heavy calcification, flow-limiting dissection, occluding thrombus resistant to thrombolyis, thrombaspiration, and PTA, and early restenosis after previous PTA. Stent implantation was feasible in all cases. No complications occurred. After the stent implantation, all primarily unsuccessful interventions could be transformed into successful procedures with no residual stenosis >30% in any case. After 6 ± 2 months, two of the 18 patients died, and 14 of the 16 remaining patients improved clinically. At follow-up, the patency could be assessed in 14 stented arteries. Three stents were occluded, one stent showed some neointimal hyperplasia (50-70% restenosis), the remaining ten stents showed no restenosis (0-30%). The use of self-expanding nitinol stents in tibioperoneal and popliteal arteries is a safe and feasible option for the treatment of unsuccessful PTA. The 6-months patency is high. (orig.)

  9. Comparison of visibility for four self-expanding nitinol bare stents in vitro

    International Nuclear Information System (INIS)

    Wiesinger, Benjamin; Stutz, Alexander; Schmehl, Joerg; Groezinger, Gerd; Claussen, Claus Detlef; Wiskirchen, Jakub

    2012-01-01

    Background Sufficient radiopacity of stents is a prerequisite for safe interventions and minimization of the radiation dose for the patient and the interventionist. Modern nitinol stents are considered less radiopaque compared to formerly used stents. Purpose To evaluate the objective detection rate (ODR) and the subjective radiopacity score (SRS) of four self-expanding nitinol stents with their markers on a phantom human pelvis. Material and Methods We evaluated the ODR (as a percentage of correctly identified stents) and the SRS (on a scale from 0 = not visible to 4 = excellent visibility) for four self-expanding nitinol stents (SinusSuperflex, SMART, Luminexx, Zilver) with 8 mm diameter and 40 mm length. Stents were placed on a phantom human pelvis and images of the stents were taken in four different positions (right and left lumbosacral joint and near the right and left limbus acetabuli) using the following modes: spotfilm, pulsed fluoroscopy (4, 7.5, 15, and 30 pulses/min) and at three different digital magnification modes. Dose area products (DAPs) were assessed. Results ODR and SRS, respectively, were significantly increased for the SMART stent compared to all other tested stents (P < 0.05): SMART 93.53% and 2.43, SinusSuperflex 90.81% and 2.21, Luminexx 90.39% and 2.20, and Zilver 89.28% and 2.21. ODR was significantly reduced in position 3 where the bone overlap was more pronounced for all stents (detection rates 77.14-79.56%). An increase in magnification significantly improved the ODR and SRS for all stents (70.33-99.25% and 1.07-3.28, respectively, P < 0.05). Increased pulsing frequency did not improve the ODR of the various stents but did increase the DAP. Conclusion The SMART stent had the best overall performance. In the presence of bone overlap, all self-expanding nitinol stents had poor results. Increased pulsing frequency did not improve ODR or SRS but did increase the DAP. Use of digital magnification modes had no effect on DAP increasing ODR

  10. Dysphagia with malignant stricture of esophagogastric junction: treatment with self-expandable nitinol stent

    International Nuclear Information System (INIS)

    Lee, Choon Hyeong; Oh, Joo Hyeong; Yoon, Yup

    1995-01-01

    To evaluate the effectiveness, patency and safety of a self-expandable nitinol stent for palliative treatment of malignant stricture of gastroesophageal junction. An esophageal stent was inserted in five consecutive patients with malignant stricture of esophagogastric junction. Histologically, four cases were adenocarcinoma, and one was squamous cell carcinoma. The location and severity of stricture were evaluated with gastrografin just before stent insertion. In one patient with past subtotal gastrectomy, esophagography revealed fistulous fract at stricture site. No technical failure or procedural complications occurred, and improvement of dysphagia was noted in all patients soon after stent insertion. On follow up esophagograms performed 3 to 7 days after stent insertion, all stents were completely expanded and unchanged in positions. In one patient with fistulous connection at stricture site, esophagogram immediately after the procedure revealed complete occlusion of the fistula. Three patients died within 4, 7 and 8 consecutive months after stent insertion. Two patients are alive maintaining adequate body weight and passing most diet. Seft-expandable nitinol stent with it's good longitudinal flexibility and efficient radial force was effective in the palliative treatment of dysphagia in patient with malignant stricture at esophagogastric junction

  11. Dysphagia with malignant stricture of esophagogastric junction: treatment with self-expandable nitinol stent

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Choon Hyeong; Oh, Joo Hyeong; Yoon, Yup [Kyung Hee University Hospital, Seoul (Korea, Republic of)

    1995-02-15

    To evaluate the effectiveness, patency and safety of a self-expandable nitinol stent for palliative treatment of malignant stricture of gastroesophageal junction. An esophageal stent was inserted in five consecutive patients with malignant stricture of esophagogastric junction. Histologically, four cases were adenocarcinoma, and one was squamous cell carcinoma. The location and severity of stricture were evaluated with gastrografin just before stent insertion. In one patient with past subtotal gastrectomy, esophagography revealed fistulous fract at stricture site. No technical failure or procedural complications occurred, and improvement of dysphagia was noted in all patients soon after stent insertion. On follow up esophagograms performed 3 to 7 days after stent insertion, all stents were completely expanded and unchanged in positions. In one patient with fistulous connection at stricture site, esophagogram immediately after the procedure revealed complete occlusion of the fistula. Three patients died within 4, 7 and 8 consecutive months after stent insertion. Two patients are alive maintaining adequate body weight and passing most diet. Seft-expandable nitinol stent with it's good longitudinal flexibility and efficient radial force was effective in the palliative treatment of dysphagia in patient with malignant stricture at esophagogastric junction.

  12. Polyorethaoe-covered nitinol strecker stents as primary palliative treatment of malignant biliary obstruction

    International Nuclear Information System (INIS)

    Kanasaki, Shuzo; Furukawa, Akira; Kane, Teruyuki; Murata, Kiyoshi

    2000-01-01

    Purpose: To evaluate the clinical efficacy of the polyure-thane-covered Nitinol Strecker stent in the treatment of patients with malignant biliary obstruction.Methods: Twenty-three covered stents produced by us were placed in 18 patients with malignant biliary obstruction. Jaundice was caused by cholangiocarcinoma (n=5), pancreatic Cancer (n=6), gallbladder Cancer (n=4), metastatic lymph nodes (n=2), and tumor of the papilla (n=1).Resulrs: The mean patency period of the Stents was 37.5 weeks (5-106 weeks). Recurrent obstructive jaundice occurred in two patients (11%). Adequate biliary drainage over 50 weeks or until death was achieved in 17 of 18 patients (94.4%). Late cholangitis was observed in two patients whose stents bridged the ampulla of Vater. Other late severe complications were not encountered.Conclusion: Although more study is necessary, our results suggest the clinical efficacy of our covered Nitinol Strecker stent in the management of obstructive jaundice caused by malignant diseases.

  13. Evaluation of the 4-French Pulsar-18 Self-expanding Nitinol Stent in Long Femoropopliteal Lesions.

    Science.gov (United States)

    Lichtenberg, Michael; Hailer, Birgit; Kaeunicke, Matthias; Stahlhoff, Wilhelm-Friedrich; Boese, Dirk; Breuckmann, Frank

    2014-01-01

    To evaluate the patency and the freedom of target lesion revascularization of the 4-French Pulsar-18 self-expandable (SE) nitinol stent for the treatment of long femoropopliteal occlusive disease in a two-center, prospective, all-comers registry with a follow-up period of 12 months. This registry enrolled 36 patients with symptomatic femoropopliteal long lesions for recanalization and implantation of the 4-French Pulsar-18 SE nitinol stent. Routine follow-up examination including duplex ultrasound was performed after 6 and 12 months. Primary patency was defined as no binary restenosis on duplex ultrasound (Peak systolic velocitiy ration (PSVR) Pulsar-18 SE nitinol stent for endovascular intervention of femoropopliteal disease with a mean lesion length of 182.3 ± 51.8 mm showed promising primary patency and fTLR rates after 6 and 12 months. Diabetes and renal insufficiency had no negative impact on the patency rate.

  14. Endovascular repair of arterial iliac vessel wall lesions with a self-expandable nitinol stent graft system.

    Directory of Open Access Journals (Sweden)

    Birger Mensel

    Full Text Available To assess the therapeutic outcome after endovascular repair of iliac arterial lesions (IALs using a self-expandable Nitinol stent graft system.Between July 2006 and March 2013, 16 patients (13 males, mean age: 68 years with a self-expandable Nitinol stent graft. A total of 19 lesions were treated: nine true aneurysms, two anastomotic aneurysms, two dissections, one arteriovenous fistula, two type 1B endoleaks after endovascular aneurysm repair, one pseudoaneurysm, and two perforations after angioplasty. Pre-, intra-, and postinterventional imaging studies and the medical records were analyzed for technical and clinical success and postinterventional complications.The primary technical and clinical success rate was 81.3% (13/16 patients and 75.0% (12/16, respectively. Two patients had technical failure due to persistent type 1A endoleak and another patient due to acute stent graft thrombosis. One patient showed severe stent graft kinking on the first postinterventional day. In two patients, a second intervention was performed. The secondary technical and clinical success rate was 87.5% (14/16 and 93.8% (15/16. The minor complication rate was 6.3% (patient with painful hematoma at the access site. The major complication rate was 6.3% (patient with ipsilateral deep vein thrombosis. During median follow-up of 22.4 months, an infection of the aneurysm sac in one patient and a stent graft thrombosis in another patient were observed.Endovascular repair of various IALs with a self-expandable Nitinol stent graft is safe and effective.

  15. Management of stent dislodgment in coarctoplasty of aorta with three overlapping self-expandable nitinol stents.

    Science.gov (United States)

    Ghazi, Payam; Haji-Zeinali, Ali-Mohammad

    2010-01-01

    We describe a case of native coarctation of aorta managed with three self-expandable nitinol stents. After balloon pre-dilation, the first and second stents were dislodged. The coarcted area was successfully treated with the third stent overlapped with the previous stents. During follow up (30 months), the patient was free of complications. It seems that implantation of multiple overlapping self-expandable stents in aortic coarctation patients, if needed, is safe and possible.

  16. How to design the optimal self-expandable oesophageal metallic stents: 22 years of experience in 645 patients with malignant strictures.

    Science.gov (United States)

    Na, Han Kyu; Song, Ho-Young; Kim, Jin Hyoung; Park, Jung-Hoon; Kang, Min Kyoung; Lee, Jongjin; Oh, Se Jin

    2013-03-01

    To evaluate the clinical efficacy and safety of self-expandable metallic stent (SEMS) placement for malignant oesophageal strictures and their relationship with stent designs. Seven generations of SEMS were used to treat 645 consecutive patients with oesophageal strictures. Logistic regression models were constructed to identify predictive factors associated with complications. Stent placement was technically successful in 641 of 645 patients (99.4%). The clinical success rate was 95.5%. There were 260 (40.3%) complications after stent placement. Due to complications, 68 stents were removed; 66 of 68 stents (97.1%) were removed successfully. Stainless steel (SS) stents (odds ratio [OR] 4.18; 95% confidence interval [CI] 2.10, 8.32) and radiation therapy (RT) before stent placement (OR 4.23; CI 2.02, 8.83) were significantly associated with severe pain. Flared ends (OR 9.63; CI 3.38, 27.43), stricture length stent diameter stent migration. Polyurethane membranes were associated with more frequent tumour ingrowth than polytetrafluoroethylene (PTFE) membranes (P = 0.002). Despite the relatively high complication rate, retrievable self-expandable PTFE-covered nitinol stents equipped with a head and a tail appeared to be an effective treatment for malignant oesophageal strictures.

  17. Biomechanical comparison of expanded polytetrafluoroethylene (ePTFE) and PTFE interpositional patches and direct tendon-to-bone repair for massive rotator cuff tears in an ovine model.

    Science.gov (United States)

    McKeown, Andrew Dj; Beattie, Rebekah F; Murrell, George Ac; Lam, Patrick H

    2016-01-01

    Massive irreparable rotator cuff tears are a difficult problem. Modalities such as irrigation and debridement, partial repair, tendon transfer and grafts have been utilized with high failure rates and mixed results. Synthetic interpositional patch repairs are a novel and increasingly used approach. The present study aimed to examine the biomechanical properties of common synthetic materials for interpositional repairs in contrast to native tendon. Six ovine tendons, six polytetrafluoroethylene (PTFE) felt sections and six expanded PTFE (ePTFE) patch sections were pulled-to-failure to analyze their biomechanical and material properties. Six direct tendon-to-bone surgical method repairs, six interpositional PTFE felt patch repairs and six interpositional ePTFE patch repairs were also constructed in ovine shoulders and pulled-to-failure to examine the biomechanical properties of each repair construct. Ovine tendon had higher load-to-failure (591 N) and had greater stiffness (108 N/mm) than either PTFE felt (296 N, 28 N/mm) or ePTFE patch sections (323 N, 34 N/mm). Both PTFE felt and ePTFE repair techniques required greater load-to-failure (225 N and 177 N, respectively) than direct tendon-to-bone surgical repairs (147 N) in ovine models. Synthetic materials lacked several biomechanical properties, including strength and stiffness, compared to ovine tendon. Interpositional surgical repair models with these materials were significantly stronger than direct tendon-to-bone model repairs.

  18. [Self-expanding nitinol stents in proximal tracheal stenosis].

    Science.gov (United States)

    Hafner, B; Mann, W; Heussel, C P; Scherhag, A; Schlegel, J; Kauczor, H U

    2000-03-01

    The use of silicone- or metal stents in stenosis of the distal trachea and the bronchial system is a customary procedure [1-4], for example after tumor invasion or cicatricial stenosis after transplantation. In the proximal part of the trachea, on smaller, short and soft strictures we try to stabilise the trachea by the implantation of rings. Other methods are tracheal plasty or transverse tracheal resectomy [5-7]. In the case of longer or nearer subglottal stenoses the positioning of self-expanding nitinol stents has proven a simple, gentle and well-tolerated alternative procedure even in very serious disorders [1, 8, 9]. These stents can be placed in short narcosis under endoscopic control without great strain on the patient. We placed nitinol-stents in the proximal part of the trachea in eleven cases. In five cases dyspnoea caused by a tracheal collapse improved. In two further cases a tracheal stenosis with massive granulation tissue and cicatricial pull under an inlaid tracheal cannula was removed and the tracheostoma was closed. In four cases a solid, scarred and cartilaginous stenosis in the area of the cricoid and the upper tracheal rings was widened with laser and later on stented. Over an observation time of two years no complications showed safe one case in which a directly postoperative dislocation was repositioned quickly. The patients live without restrictions through the tracheal stenosis or a tracheostoma. In the best possible case epithelialization over the metal meshes develops so that a nearly normal mucus transportation is possible [1, 10-12].

  19. Bleeding after expandable nitinol stent placement in patients with esophageal and upper gastrointestinal obstruction: incidence, management, and predictors.

    Science.gov (United States)

    Oh, Se Jin; Song, Ho-Young; Nam, Deok Ho; Ko, Heung Kyu; Park, Jung-Hoon; Na, Han Kyu; Lee, Jong Jin; Kang, Min Kyoung

    2014-11-01

    Placement of self-expandable nitinol stents is useful for the treatment of esophageal and upper gastrointestinal (GI) obstruction. However, complications such as stent migration, tumor overgrowth, and bleeding occur. Although stent migration and tumor overgrowth are well documented in previous studies, the occurrence of bleeding has not been fully evaluated. To evaluate the incidence, management strategies, and predictors of bleeding after placement of self-expandable nitinol stents in patients with esophageal and upper GI obstruction. We retrospectively reviewed the medical records and results of computed tomography and endoscopy of 1485 consecutive patients with esophageal and upper GI obstructions who underwent fluoroscopically guided stent placement. Bleeding occurred in 25 of 1485 (1.7%) patients 0 to 348 days after stent placement. Early stent-related bleeding occurred in 10 patients (40%) and angiographic embolization was used for 5/10. Late bleeding occurred in 15 patients (60%) and endoscopic hemostasis was used for 7/15. Twenty-two of 25 (88%) patients with bleeding had received prior radiotherapy and/or chemotherapy. Bleeding is a rare complication after placement of expandable nitinol stents in patients with esophageal and upper GI obstruction, but patients with early bleeding may require embolization for control. Care must be exercised on placing stents in patients who have received prior radiotherapy or chemotherapy. © The Foundation Acta Radiologica 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  20. Successful Exclusion of a Large Femoropopliteal Aneurysm with a Covered Nitinol Stent

    International Nuclear Information System (INIS)

    Dorffner, Roland; Winkelbauer, Friedrich; Kettenbach, Joachim; Staudacher, Michael; Lammer, Johannes

    1996-01-01

    A 70-year-old woman presented with a large femoropopliteal aneurysm. A covered nitinol stent was implanted successfully and complete exclusion of the aneurysm was achieved. At follow-up 5 months later the stent was still patent and the patient was free of symptoms. However, moderate stenosis was seen at the proximal end of the stent

  1. Extensive caustic esophageal stricture in children can be treated by serial dilatations interspersed with silicone-covered nitinol stenting

    Directory of Open Access Journals (Sweden)

    Veronica Alonso

    2016-01-01

    Full Text Available Recurrent esophageal stenosis secondary to caustic ingestion may be challenging to treat. Self-expandable esophageal stents may be an alternative to repetitive endoscopic esophageal dilatation. We report a case of a 2-year-old male child with an extensive esophageal caustic stricture successfully treated using a combination of endoscopic dilatation and stenting. After 5 months of serial balloon dilatations, three nitinol internal silicone covered self-expandable stents were placed through the patient′s gastrostomy spanning the entire esophagus. The stents were positioned using a combination of both endoscopic and fluoroscopic guidance. The procedure was repeated with only one stent 3 months later. A new stricture in the proximal esophagus needed surgical resection and anastomosis, followed by two pneumatic dilatations with progressively longer asymptomatic intervals. The results are promising with the patient able to use his own esophagus; however, this is a single case and optimal stent standing time is still to be determined.

  2. Repair of large abdominal wall defects with expanded polytetrafluoroethylene (PTFE).

    Science.gov (United States)

    Bauer, J J; Salky, B A; Gelernt, I M; Kreel, I

    1987-01-01

    Most abdominal wall incisional hernias can be repaired by primary closure. However, where the defect is large or there is tension on the closure, the use of a prosthetic material is indicated. Expanded polytetrafluoroethylene (PTFE) patches were used to repair incisional hernias in 28 patients between November 1983 and December 1986. Twelve of these patients (43%) had a prior failure of a primary repair. Reherniation occurred in three patients (10.7%). Wound infections developed in two patients (7.1%), both of whom had existing intestinal stomas, one with an intercurrent pelvic abscess. The prosthetic patch was removed in the patient with the abscess, but the infection was resolved in the other without sequelae. Septic complications did not occur after any operations performed in uncontaminated fields. None of the patients exhibited any undue discomfort, wound pain, erythema, or induration. Complications related to adhesions, erosion of the patch material into the viscera, bowel obstruction, or fistula formation did not occur. Based on this clinical experience, the authors believe that the PTFE patch appears to represent an advance in synthetic abdominal wall substitutes. Images Fig. 1. Fig. 2(left)., Fig. 3(right). PMID:3689012

  3. Physical properties of a new type of self-expandable nitinol stent

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Soo [Seoul Health College, Seoul (Korea, Republic of); Kim, Tae Hyung; Song, Sang Woo; Kang, Seong Gwon; Huh, Soo Jin; Song, Ho Young [Ulsan Univ. College of Medicine, Seoul (Korea, Republic of); Kim, Eun Sang [Stentech, Inc., Seoul (Korea, Republic of); Kim, Cheol Saeng [Solco Surgical Instruments Co., Ltd, Seoul (Korea, Republic of)

    1999-08-01

    To study the new physical properties including hoop strength and flexibility of a newly developed nitinol stent. The new stent was made of a single nitinol wire 0.15 - 0.25 mm in diameter. This was wound around a cylindrical metallic jig with a constant angle to the longitudinal direction, and stents which winding were constructed. Hoop strength of the stents was measured with a spring gauge and compared with that of Wallstent and Hanaro stents. The flexibility of the new stent was evaluated on the basis of changes in stent diameter when bent in the direction of 180 deg Hoop strength of the new nitinol stent was proportional to 3.8 ({+-}0.3)-th power of the wire thickness. A greater number of wires on a lateral cut surface or a greater number of longitudinal windings also resulted in increased strength. However, the former caused an increase in total wire area and the latter resulted increased stent length when compressed. Hoop strength of the new nitinol stent was superior to that of Wallstent and Hanaro stents, and stent diameter did not decrease when the stent was bent in the direction of 180 degrees. Hoop strength of the new nitinol stent was most significantly affected by wire thickness. The stent was very flexible and thus seemed suitable for an angled lumen.

  4. Midterm to long-term safety and efficacy of self-expandable nitinol stent implantation for coarctation of aorta in adults.

    Science.gov (United States)

    Haji Zeinali, Ali Mohammad; Sadeghian, Mohammad; Qureshi, Shakeel A; Ghazi, Payam

    2017-09-01

    Endovascular treatment of coarctation of aorta (CoA) by self-expandable Nitinol stents is one of the recognized treatment methods and may be an alternative to surgery or balloon-expandable stent implantation for CoA but there is little information about midterm to long term results of self-expandable stents. Sixty-two patients with CoA (40 men), with a mean age of 30.7 ± 11 years, (range 17-63 years) underwent stent implantation with Optimed self-expandable Nitinol stents between 2005 and 2014. Successful outcome was defined as peak systolic pressure gradient ≤20 mmHg after stent implantation. The patients were followed-up clinically and by echocardiography and in patients, in whom there was suspicion of recoarctation, CT angiography or recatheterization was performed. 65 stents were successfully implanted in all 62 patients. Peak systolic pressure gradient decreased from mean 62.4 ± 18 mmHg (range 35-100 mmHg) to mean 2.8 ± 5 mmHg (range 0-15 mmHg; P Stent displacement occurred in 3 patients during the procedure. These were managed successfully by an overlapping second stent. None of the patients had major complications such as aortic dissection, rupture, or vascular access problems. In follow up, only three patients had recoarctation, and two of these were managed successfully by balloon redilation or further stenting 16 and 18 months after the first procedure and one patient refused reintervention. There were two deaths, unrelated to the procedure, 12 and 78 months after the initial intervention. Follow-up of a mean of 45.5 ± 17 months (range 12-105 months) demonstrated no evidence of aneurysm formation or stent fracture. Self-expandable nitinol stents for the treatment of native and recurrent CoA is safe and has good efficacy with acceptable midterm to long-term outcome. © 2017 Wiley Periodicals, Inc.

  5. Esophageal leiomyoma in a dog causing esophageal distension and treated by transcardial placement of a self-expanding, covered, nitinol esophageal stent.

    Science.gov (United States)

    Robin, Elisabeth M; Pey, Pascaline B; de Fornel-Thibaud, Pauline; Moissonnier, Pierre H M; Freiche, Valérie

    2018-02-01

    CASE DESCRIPTION A 10-year-old spayed female Rottweiler was referred for evaluation because of a 2-month history of regurgitation and weight loss, despite no apparent change in appetite. The dog had received antiemetic and antacid treatment, without improvement. CLINICAL FINDINGS Physical examination revealed a low body condition score (2/5), but other findings were unremarkable. Diffuse, global esophageal dilatation was noted on plain thoracic radiographs, and normal motility was confirmed through videofluoroscopic evaluation of swallowing. Transhepatic ultrasonographic and CT examination revealed a circumferential, intraparietal lesion in the distal portion of the esophagus causing distal esophageal or cardial subobstruction and no metastases. Incisional biopsy of the lesion was performed, and findings of histologic examination supported a diagnosis of esophageal leiomyoma. TREATMENT AND OUTCOME In view of numerous possible complications associated with esophageal surgery, the decision was made to palliatively treat the dog by transcardial placement of a self-expanding, covered, nitinol esophageal stent under endoscopic guidance. Two weeks after stent placement, radiography revealed complete migration of the stent into the gastric lumen. Gastrotomy was performed, and the stent was replaced and fixed in place. Twenty-four months after initial stent placement, the dog had a healthy body condition and remained free of previous clinical signs. CLINICAL RELEVANCE Diffuse benign muscular neoplasia should be considered as a differential diagnosis for acquired esophageal dilatation in adult and elderly dogs. In the dog of this report, transcardial stent placement resulted in resolution of the clinical signs, with no apparent adverse effect on digestive function. The described procedure could be beneficial for nonsurgical treatment of benign esophageal tumors in dogs.

  6. A comparison of woven versus nonwoven polypropylene (PP) and expanded versus condensed polytetrafluoroethylene (PTFE) on their intraperitoneal incorporation and adhesion formation.

    Science.gov (United States)

    Raptis, Dimitri Aristotle; Vichova, Barbora; Breza, Jan; Skipworth, James; Barker, Stephen

    2011-07-01

    To compare known and novel synthetic materials useful for incisional hernia repair and to test independently, whether they justify common perceptions related to their use. Four types of synthetic materials were implanted in to 12 pigs to compare incorporation histology and adhesion formation 90 d after placement. Woven polypropylene (WPP), nonwoven polypropylene (NWPP), expanded polytetrafluoroethylene (ePTFE). and condensed polytetrafluoroethylene (cPTFE) were placed intraperitoneally (IP). Intraperitoneally, WPP became fully peritonealized, but generated thick and plentiful adhesions. NWPP became fully peritonealized and generated filmy and far less numerous adhesions. ePTFE formed some filmy adhesions and did not peritonealize. cPTFE and WPP became fully peritonealized. However, bowel became adherent on raised edges of cPTFE and WPP. We conclude that NWPP incorporates extremely well intraperitoneally, promotes few adhesions, and its use is likely to be suitable for hernia repair. cPTFE performs well and promotes few adhesions, but to minimize potentially serious complications, its edges must be secured around its entire circumference. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. The New Nitinol Conformable Self-Expandable Metal Stents for Malignant Colonic Obstruction: A Pilot Experience as Bridge to Surgery Treatment

    Directory of Open Access Journals (Sweden)

    Roberto Di Mitri

    2014-01-01

    Full Text Available Introduction. Self-expandable metal stents (SEMS are a nonsurgical option for treatment of malignant colorectal obstruction also as a bridge to surgery approach. The new nitinol conformable stent has improved clinical outcomes in these kinds of patients. We report a pilot experience with nitinol conformable SEMS placement as bridge to surgery treatment in patients with colorectal obstruction. Materials and Methods. Between April and August 2012, we collected data on colonic nitinol conformable SEMS placement in a cohort of consecutive symptomatic patients, with malignant colorectal obstruction, who were treated as a bridge to surgery. Technical success, clinical success, and adverse events were recorded. Results. Ten patients (7 male (70%, with a mean age of 69.2 ± 10.1, were evaluated. The mean length of the stenosis was 3.6 ± 0.6 cm. Five patients (50% were treated on an emergency basis. The median time from stent placement to surgery was 16 days (interquartile range 7–21. Technical and clinical success was achieved in all patients with a significant early improvement of symptoms. No adverse events due to the SEMS placement were observed. Conclusion. This pilot study confirmed the important role of nitinol conformable SEMS as a bridge to surgery option in the treatment of symptomatic malignant colorectal obstruction.

  8. Laparoscopic diaphragmatic hernia repair using expanded polytetrafluoroethylene (ePTFE) for delayed traumatic diaphragmatic hernia.

    Science.gov (United States)

    Jee, Yeseob

    2017-06-01

    Traumatic diaphragmatic hernia (TDH) is an uncommon surgical problem, and diagnosis is often delayed. However, the mortality from bowel necrosis can reach 80%. Therefore, suspicion is needed and surgery is required to prevent complications. A 50-year-old man was transferred due to abdominal pain and vomiting. Chest X-ray and computed tomography (CT) scan showed herniation of the stomach through the left diaphragm. The patient had fallen down 15 months ago and CT scan at that time revealed a small defect of the diaphragm without herniation. We diagnosed delayed herniation of TDH and the patient underwent laparoscopic repair using an expanded polytetrafluoroethylene (ePTFE) mesh. Recovery was uneventful and the CT scan at 3 months after the operation showed no recurrence. We reported a delayed presenting TDH and considered a laparoscopic approach to be safe and feasible during elective surgery. Moreover, use of an ePTFE mesh for repair of large diaphragmatic hernia was also feasible.

  9. Effect of antithrombotic agents on the patency of PTFE-Covered stents in the inferior vena cava: An experimental study

    International Nuclear Information System (INIS)

    Makutani, Shiro; Kichikawa, Kimihiko; Uchida, Hideo; Maeda, Munehiro; Konishi, Noboru; Hiasa, Yoshio; Yoshikawa, Tomohiro; Kimura, Yukio

    1999-01-01

    Purpose: To evaluate the efficacy of antithrombotic agents in the prevention of stenosis of polytetrafluororethylene (PTFE)-covered stents in the venous system.Methods: Spiral Z stents covered with PTFE (PTFE-covered stents) were placed in the inferior vena cava (IVC) of 34 dogs. Nineteen dogs, used as a control group, were sacrificed at 2, 4, and 12 weeks. Fifteen dogs, previously given antithrombotic agents [cilostazol (n=5), warfarin potassium (n=5), cilostazol plus warfarin potassium (n=5)] were sacrificed at 4 weeks, and then examined angiographically and histopathologically. The effect of the antithrombotic agents was compared between groups.Results: The patency rate of the antithrombotic agent group was 93% (14/15), which was higher than the control group rate of 63% (12/19). The mean stenosis rate of the patent stent at both ends and at the midportion was lower at 4 weeks in the antithrombotic agent group than in the control group. In particular, the mean stenosis rate in the cilostazol plus warfarin potassium group was significantly lower than the control group (Tukey's test, p < 0.05). The mean neointimal thickness of the patent stent at both ends and at the midportion was thinner at 4 weeks in the antithrombotic agent group than in the control group. In particular, the thickness of the neointima in the cilostazol plus warfarin potassium group was significantly decreased when compared with the control group (Tukey's test p < 0.05). At 4 weeks, endothelialization in the antithrombotic agent group tended to be almost identical to that in the control group.Conclusion: The present study suggests that administration of an antithrombotic agent is an effective way of preventing the stenosis induced by a neointimal thickening of PTFE-covered stents in the venous system.

  10. Evaluation of the Effects of Temporary Covered Nitinol Stent Placement in the Prostatic Urethra: Short-Term Study in the Canine Model

    International Nuclear Information System (INIS)

    Crisostomo, Veronica; Song, Ho Young; Maynar, Manuel; Sun, Fei; Soria, Federico; Lima, Juan Rafael; Yoon, Chang Jin; Uson-Gargallo, Jesus

    2007-01-01

    Purpose. To evaluate the effect of temporary stent placement on the canine prostatic urethra. Methods. Retrievable PTFE-covered nitinol stents were placed in the prostatic urethras of 8 beagle dogs under fluoroscopic guidance. Retrograde urethrography was obtained before and after stenting. Retrograde urethrography and endoscopy were performed 1 and 2 months after deployment. The endoscopic degree of hyperplasia was rated on a scale of 0 to 4 (0 absence, 4 = occlusion). On day 60, stents were removed and urethrography was performed immediately before euthanasia. Pathologic analysis was performed to determine the degree of glandular atrophy, periurethral fibrosis, and urethral dilation. Results. Stent deployment was technically successful in 7 animals, and failed in 1 dog due to a narrow urethral lumen. Complete migration was seen in 2 animals at 1 month, and an additional stent was deployed. On day 30, endoscopy showed slight hyperplasia (grade 1) in 3 animals. On day 60, moderate hyperplasia (grade 2) was evidenced in 4 cases. No impairment of urinary flow was seen during follow-up. Retrieval was technically easy to perform, and was successful in all dogs. The major histologic findings were chronic inflammatory cell infiltrates; prostate glandular atrophy, with a mean value of 1.86 (SD 0.90); periurethral fibrosis, with a mean ratio of 29.37 (SD 10.41); and dilatation of the prostatic urethra, with a mean ratio of 6.75 (SD 3.22). Conclusion. Temporary prostatic stent placement in dogs is safe and feasible, causing marked enlargement of the prostatic urethral lumen. Retrievable covered stents may therefore be an option for bladder outlet obstruction management in men

  11. Insertion of Self-Expandable Nitinol Stents Without Previous Balloon Angioplasty Reduces Restenosis Compared with PTA Prior to Stenting

    International Nuclear Information System (INIS)

    Harnek, Jan; Zoucas, Evita; Stenram, Unne; Cwikiel, Wojciech

    2002-01-01

    Purpose: To compare the development of intimal hyperplasia after deployment of a self-expanding nitinol stent with and without previous percutaneous transluminal balloon angioplasty (PTA), with the results after PTA alone. Methods: In nine healthy pigs, the iliac arteries were divided into three groups: group 1 (n = 6 arteries) was treated with PTA; group 2 n 6)with insertion of self-expanding stents after PTA; and group 3 (n = 6) with stent insertion without previous PTA. After 8 weeks the vessels were examined with intravascular ultrasonography,histologic examination and morphometric analysis. Results: Although the injury index in group 1 (0.17± 0.57) was lower (p <0.05) than in group 2 (0.26 ± 0.06) and group 3 (0.26 ± 0.08), PTA-treated arteries showed significantly (p <0.05) reduced mean luminal gain (0.53 ± 2.84) compared with arteries treated with PTA prior to stenting (2.58 ± 1.38) and compared with stenting alone (4.65 ±5.34). Stenting after PTA resulted in a higher (p<0.05) restenosis index (2.63 ± 1.06) compared with stenting without PTA (1.35 ± 0.59). Group 2 also had a significantly thicker intimap <0.05) and 83% and 74% higher intima/mediaratio (p <0.05) compared with groups 1 and 3, respectively. Conclusion: Insertion of a self-expandable nitinol stent without previous PTA results in less intimalhyperplasia than if PTA is performed prior to stenting, suggesting that direct stenting can be used in angioplasty sessions with a favorable outcome

  12. Catalytic activity of hydrophobic Pt/C/PTFE catalysts of different PTFE content for hydrogen-water liquid exchange reaction

    International Nuclear Information System (INIS)

    Hu Sheng; Xiao Chengjian; Zhu Zuliang; Luo Shunzhong; Wang Heyi; Luo Yangming; Wang Changbin

    2007-01-01

    10%Pt/C catalysts were prepared by liquid reduction method. PTFE and Pt/ C catalysts were adhered to porous metal and hydrophobic Pt/C/PTFE catalysts were prepared. The structure and size of Pt crystal particles of Pt/C catalysts were analyzed by XRD, and their mean size was 3.1 nm. The dispersion state of Pt/C and PTFE was analyzed by SEM, and they had good dispersion mostly, but PTFE membrane could be observed on local parts of Pt/C/PTFE surface. Because of low hydrophobicity, Pt/C/ PTFE catalysts have low activity when the mass ratio of PTFE and Pt/C is 0.5: 1, and their catalytic activity increases markedly when the ratio is 1:1. When the ratio increases again, more Pt active sites would be covered by PTFE and interior diffusion effect would increase, which result in the decrease of catalytic activity of Pt/C/PTFE. By PTFE pretreatment of porous metal carrier, the activity of Pt/C/PTFE catalysts decreases when the mass ratio of PTFE and Pt/C is 0.5:1, and their activity decreases when the mass ratio is 1:1. (authors)

  13. The influence of stent design on neointimal hyperplasia of an aortic stent covering the visceral arterial ostia: an experimental study in dogs using a self-expandable nitinol stent

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Yong Hu; Chung, Jin Wook; Choi, Seung Hong; Kim, Kwang Gi; Kim, Hyo Cheol; So, Young Ho; Jae, Hwan Jun; Lee, Whal; Park, Jae Hyung [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2008-05-15

    To assess the influence of stent design [interlacing (type A) vs. crossing method (type B)] on neointimal hyperplasia using a self-expandable nitinol stent, which crosses the side branches of the abdominal aorta. In seven mongrel dogs, nitinol stents with type A and B intersections were placed in the abdominal aorta across the main branches: 4 Niti-Ms and 3 Niti-Ds. Two months after the stent placement, a DSA was performed for a stent patency evaluation, followed by the extraction of the aortas. The degree of neointimal formation along the wire was evaluated by calculating the area ratio of intimal hyperplasia (type A vs. B). A Student's t-test was employed to investigate the differences in the neointimal hyperplasia between blood types A and B. The total number of wire intersections overlain at the ostia branch ostia was 23 for type A and 36 for type B. The area ratio of the neointimal hyperplasia, for a given area, was 29.09 {+-} 10.82% (type A) and 13.80 {+-} 6.94% (type B) ({rho} < 0.0001)]. Furthermore, the area ratios of the neointimal hyperplasia per area of stent-wire in the given area were 138.38 {+-} 10.84% (type A). 87.58 {+-} 7.36% (type B) ({rho} = 0.0002). In conclusion the interlacing pattern vs. the crossing pattern showed a higher level of neointimal formation than the crossing pattern.

  14. Investigation Of Interaction Between Nitinol Stent And A Vascular Plaque Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Recep Güneş

    2012-06-01

    Full Text Available In this study, the interaction between the Nitinol stent and the artery with plaque was investigated using finite element method. The occurring pressure values during the cardiac contraction (systolic and loosening (diastolic were applied as loading to the modeled system with Nitinol stent. In the light of the stress values, the suitability of the Nitinol stent in an artery with plaque was investigated. In the analysis, Nitinol stent was assumed to be shape memory alloy, and artery and plaque were assumed to behave linearly elastic. As a result, the stress and deformations in the plaque and artery due to the interference of Nitinol stent were discussed and concluded that the structure of artery with plaque can be expanded in accordance with Nitinol stent.

  15. Alternativa técnica no tratamento endovascular dos aneurismas da artéria poplítea A technical alternative for the endovascular treatment of popliteal artery aneurysms

    Directory of Open Access Journals (Sweden)

    Marcelo Ferreira

    2008-03-01

    Full Text Available O aneurisma de artéria poplítea é relativamente raro, porém representa cerca de 85% de todos os aneurismas arteriais periféricos. Apresenta-se geralmente com um quadro de complicação isquêmica e elevado risco de perda do membro acometido. Em função disso, preconiza-se seu tratamento eletivo, atualmente realizado com resultados satisfatórios pela técnica endovascular. Relatamos nossa experiência com a utilização do stent de nitinol auto-expansível revestido com PTFEe - Fluency (Bard, Alemanha, reforçado internamente com o stent de nitinol auto-expansível Zilver (Cook, EUA no tratamento de um aneurisma de artéria poplítea.Popliteal artery aneurysm is relatively rare, but represents around 85% of all peripheral arterial aneurysms. It is usually presented with ischemic complication and high risk of limb loss. For that reason, its elective treatment is indicated and currently carried through with satisfactory results using endovascular techniques. We describe our experience with the use of an ePTFE-covered nitinol self-expandable stent graft - Fluency (Bard, Germany, reinforced internally with the nitinol self-expandable Zilver stent (Cook, USA for the treatment of a popliteal artery aneurism.

  16. The influence of stent design on neointimal hyperplasia of an aortic stent covering the visceral arterial ostia: an experimental study in dogs using a self-expandable nitinol stent

    International Nuclear Information System (INIS)

    Yin, Yong Hu; Chung, Jin Wook; Choi, Seung Hong; Kim, Kwang Gi; Kim, Hyo Cheol; So, Young Ho; Jae, Hwan Jun; Lee, Whal; Park, Jae Hyung

    2008-01-01

    To assess the influence of stent design [interlacing (type A) vs. crossing method (type B)] on neointimal hyperplasia using a self-expandable nitinol stent, which crosses the side branches of the abdominal aorta. In seven mongrel dogs, nitinol stents with type A and B intersections were placed in the abdominal aorta across the main branches: 4 Niti-Ms and 3 Niti-Ds. Two months after the stent placement, a DSA was performed for a stent patency evaluation, followed by the extraction of the aortas. The degree of neointimal formation along the wire was evaluated by calculating the area ratio of intimal hyperplasia (type A vs. B). A Student's t-test was employed to investigate the differences in the neointimal hyperplasia between blood types A and B. The total number of wire intersections overlain at the ostia branch ostia was 23 for type A and 36 for type B. The area ratio of the neointimal hyperplasia, for a given area, was 29.09 ± 10.82% (type A) and 13.80 ± 6.94% (type B) (ρ < 0.0001)]. Furthermore, the area ratios of the neointimal hyperplasia per area of stent-wire in the given area were 138.38 ± 10.84% (type A). 87.58 ± 7.36% (type B) (ρ = 0.0002). In conclusion the interlacing pattern vs. the crossing pattern showed a higher level of neointimal formation than the crossing pattern

  17. PEACE I all-comers registry: patency evaluation after implantation of the 4-French Pulsar-18 self-expanding nitinol stent in femoropopliteal lesions.

    Science.gov (United States)

    Lichtenberg, Michael; Kolks, Oliver; Hailer, Birgit; Stahlhoff, Wilhelm-Friedrich; Tiefenbacher, Christiane; Nolte-Ernsting, Claus; Arjumand, Jawed; Wittenberg, Guenther

    2014-06-01

    To evaluate the 1-year patency of the 4-F Pulsar-18 self-expanding nitinol stent for treatment of femoropopliteal occlusive disease in a national, prospective, multicenter, all-comers registry. Between January and June 2012, the German PEACE I all-comers prospective registry enrolled 148 patients with symptomatic femoropopliteal lesions (Rutherford category 2-5) undergoing recanalization and implantation of the Pulsar-18 SE nitinol stent at 6 clinical centers. Thirty patients did not have the 12-month follow-up visit (18 declined reevaluation, 5 withdrew consent, and 7 died), leaving 118 patients (64 men; mean 71.9±9.6 age years) for the 1-year evaluation. The average lesion length was 111.5±71.4 mm, and 38 of the 118 lesions were classified as TASC II D. More than half the lesions (67, 56.7%) were chronic total occlusions (CTO). The popliteal segment was involved in 22 (18.7%) lesions. The mean stented length was 122.7±64.5 mm. Routine follow-up included duplex ultrasound at 6 and 12 months. Outcome measures were primary patency and no clinically driven target lesion revascularization (TLR) within 12 months. The overall primary patency rates after 6 and 12 months were 87.4% and 79.5%, respectively; in the popliteal segments, the rate was 71.4% after 12 months. The overall freedom from TLR was 93.2% after 6 months and 81% after 12 months. Ankle-brachial index, pain-free walking distance, and Rutherford category all improved significantly (pPulsar-18 self-expanding nitinol stent in femoropopliteal lesions averaging 111.5 mm long showed promising primary patency and freedom from TLR after 6 and 12 months. Diabetes had no negative impact on patency. Primary patency in the popliteal segments was acceptable at 12 months.

  18. Initial and mid-term results of a 4F compatible self-expanding low strut profile nitinol stent in the superficial femoral artery

    International Nuclear Information System (INIS)

    Muehlenbruch, G.; Brock, H.; Das, M.; Hohl, C.; Mahnken, A.H.; Wildberger, J.; Guenther, R.W.; Haage, P.

    2007-01-01

    Purpose: To evaluate the initial and mid-term results of a new self-expanding low strut profile nitinol stent for treatment of atherosclerotic lesions stenoses and occlusions in the superficial femoral artery (SFA). Materials and Methods: In 8 patients (4 male, 4 female, mean age 74.8 ± 8.8 years) with SFA lesions and non-satisfying results after PTA treatment alone, 10 self-expanding nitinol Xpert stents were deployed via a 4 F sheath. Stent characteristics and handling were graded by the interventionalist. Fontaine classification, duplex flow measurements and ankle brachial index (ABI) at rest and stress were taken prior and one day after stent placement. Patients were followed 3, 6 and 12 months after the procedure obtaining the same parameters at each appointment. Results: Initial stent treatment was successful in all patients. Stent handling and positioning were rated very good and safe. All patients improved clinically by at least one Fontaine stage (range before treatment: stage IIb to IV). The mean ABI at rest (stress) improved initially from 0.68 (0.70) to 1.07 (0.99). During a mean follow-up period of 8.3 months no case of clinically relevant in-stent stenosis was observed with stable values of ABI at rest and stress. (orig.)

  19. Transjugular Intrahepatic Portosystemic Shunt Flow Reduction with Adjustable Polytetrafluoroethylene-Covered Balloon-Expandable Stents Using the “Sheath Control” Technique

    Energy Technology Data Exchange (ETDEWEB)

    Blue, Robert C., E-mail: Robert.c.blue@gmail.com; Lo, Grace C.; Kim, Edward; Patel, Rahul S.; Scott Nowakowski, F.; Lookstein, Robert A.; Fischman, Aaron M. [Icahn School of Medicine at Mount Sinai, Interventional Radiology Section, Department of Radiology (United States)

    2016-06-15

    PurposeA complication of transjugular intrahepatic portosystemic shunts (TIPS) placement is refractory portosystemic encephalopathy (PSE) often requiring TIPS reduction. We report the results of a “sheath control technique” utilizing constraining sheaths during deployment of polytetrafluoroethylene (PTFE)-covered balloon-expandable stents, minimizing stent migration, and providing additional procedural control.MethodsTIPS reduction was performed in 10 consecutive patients for PSE using Atrium iCast covered stents (Atrium Maquet Getinge Group, Germany). Within the indwelling TIPS stent, a 9 mm × 59 mm iCast stent was deployed with 2 cm exposed from the sheath’s distal end and the majority of the stent within the sheath to create the distal hourglass shape. During balloon retraction, the stent was buttressed by the sheath. The proximal portion of the stent was angioplastied to complete the hourglass configuration, and the central portion of the stent was dilated to 5 mm. Demographics, pre- and post-procedure laboratory values, and outcomes were recorded.ResultsTen patients underwent TIPS reduction with 100 % technical success. There was no stent migration during stent deployment. All patients experienced initial improvement of encephalopathy. One patient ultimately required complete TIPS occlusion for refractory PSE, and another developed TIPS occlusion 36 days post-procedure. There was no significant trend toward change in patients’ MELD scores immediately post-procedure or at 30 days (p = 0.46, p = 0.47, respectively).ConclusionTIPS reduction using Atrium iCast PTFE balloon-expandable stents using the “sheath control technique” is safe and effective, and minimizes the risk of stent migration.

  20. Sutures for inguinal herniorrhaphy--a comparison of monofilaments with PTFE.

    Science.gov (United States)

    Cahill, J.; Northeast, A. D.; Jarret, P. E.; Leach, R. D.

    1989-01-01

    Polybutester (Novafil, Davis & Geck) and expanded polytetrafluoroethylene PTFE (Gore-tex, W L Gore) were compared with nylon (Ethilon, Ethicon UK) for elective inguinal herniorrhaphy. PTFE had the best handling characteristics, but is expensive, and increased wound sepsis attended its use. Polybutester had significantly better handling characteristics, and is an attractive alternative to nylon for hernia repair. PMID:2705719

  1. Long-Term Primary Patency Rate After Nitinol Self-Expandable Stents Implantation in Long, Totally Occluded Femoropopliteal (TASC II C & D) Lesions.

    Science.gov (United States)

    Elmahdy, Mahmoud Farouk; Buonamici, Piergiovanni; Trapani, Maurizio; Valenti, Renato; Migliorini, Angela; Parodi, Guido; Antoniucci, David

    2017-06-01

    Endovascular therapy for long femoropopliteal lesions using percutaneous transluminal balloon angioplasty or first-generation of peripheral stents has been associated with unacceptable one-year restenosis rates. However, with recent advances in equipment and techniques, a better primary patency rate is expected. This study was conducted to detect the long-term primary patency rate of nitinol self-expandable stents implanted in long, totally occluded femoropopliteal lesions TransAtlantic Inter-Society Census (TASC II type C & D), and determine the predictors of reocclusion or restenosis in the stented segments. The demographics, clinical, anatomical, and procedural data of 213 patients with 240 de novo totally occluded femoropopliteal (TASC II type C & D) lesions treated with nitinol self-expandable stents were retrospectively analysed. Of these limbs, 159 (66.2%) presented with intermittent claudication, while 81 (33.8%) presented with critical limb ischaemia. The mean-time of follow-up was 36±22.6 months, (range: 6.3-106.2 months). Outcomes evaluated were, primary patency rate and predictors of reocclusion or restenosis in the stented segments. The mean age of the patients was 70.9±9.3 years, with male gender 66.2%. Mean pre-procedural ABI was 0.45±0.53. One-hundred-and-seventy-five (73%) lesions were TASC II type C, while 65 (27%) were type D lesions. The mean length of the lesions was 17.9±11.3mm. Procedure related complications occurred in 10 (4.1%) limbs. There was no periprocedural mortality. Reocclusion and restenosis were detected during follow-up in 45 and 30 limbs respectively, and all were re-treated by endovascular approach. None of the patients required major amputation. Primary patency rates were 81.4±1.1%, 77.7±1.9% and 74.4±2.8% at 12, 24, and 36 months respectively. Male gender, severe calcification, and TASC II D lesion were independent predictors for reocclusion, while predictors of restenosis were DM, smoking and TASC II D lesions

  2. [E-PTFE Membrane for the Management of Perforated Corneal Ulcer].

    Science.gov (United States)

    Pahor, D; Pahor, A

    2016-10-01

    Purpose: To present the surgical management of perforated corneal ulcer using PRECLUDE® Pericardial Membrane, composed of expanded polytetrafluoroethylene (e-PTFE; GORE-TEX®), as an alternative surgical procedure in patients at high risk of graft rejections and to evaluate side effects for a prolonged period. Patients and Methods: The study included all patients who were admitted to our department and underwent surgical repair of perforated corneal ulcer with the e-PTFE membrane between 2010 and 2015. In total, 8 patients (8 eyes) were enrolled. Medical records of all patients were retrospectively reviewed. The operation was performed under peribulbar anaesthesia. Non-absorbable, microporous, watertight 0.1 mm thick e-PTFE membrane was used to close the corneal ulcer. The membrane was cut to overlap the defect adequately and to achieve the desired tissue attachment without preparing the conjunctiva or superficial trephination of the cornea. The membrane was fixed to the healthy cornea with several non-absorbable sutures (Prolene® 10.0), in order to achieve the proper stress without wrinkling. Results: Five of 8 patients were treated for systemic immunological diseases. Sjögren's syndrome was diagnosed in 2 patients, granulomatosis with polyangiitis in one, vasculitis with a history of previous sclerokeratitis in one and systemic lupus erythematosus in one. In 2 patients, corneal perforation was observed as a complication of corneal infection and in one patient as a late complication of a severe chemical burn. Corneal perforations were successfully covered with e-PTFE membrane in all patients. E-PTFE membrane was well tolerated in all patients and the eye was always preserved. After 3 to 4 months, the membrane was removed in 7 patients. The underlying cornea was thin, firm, stable and vascularised. In one patient with Sjögren's syndrome, the e-PTFE membrane is still in place. Conclusion: Surgical management of perforated corneal ulcer using E-PTFE membrane

  3. Long-term results of PTFE grafts.

    Science.gov (United States)

    Hedin, Ulf

    2015-01-01

    Vascular surgeons are essential in "lifeline" creation for hemodialysis patients and should be the central player in any multidisciplinary access service together with nephrologists, dialysis staff and interventional radiology. In this position, access surgeons are involved in complicated clinical decision making regarding primary and secondary access selection, which throughout the last decade has been largely aided, and influenced, by national and international guidelines as well as other initiatives. These recommendations, unanimously and appropriately, advocate the placement of native fistulas over synthetic grafts (the majority grafts from expanded polytetrafluoroethylene, ePTFE, herein referred to as PTFE) based on the superiority of fistulas with respect to complications such as infections and thrombosis. Nevertheless, the use of PTFE grafts for hemodialysis access is an accepted and firmly established alternative to native fistulas where data today reveal unwanted consequences to overinterpretation of established guidelines such as increased catheter use. This information highlights a need for an adjustment of access selection strategies based on patient-centered algorithms. Here, available results on PTFE graft performance in hemodialysis access is recapitulated, with respect to both conventional grafts and technical modifications, and conclude with a modified approach to primary access selection.

  4. Enterocutaneous fistula associated with ePTFE mesh: case report and review of the literature.

    Science.gov (United States)

    Foda, M; Carlson, M A

    2009-06-01

    A case of enterocutaneous fistula secondary to the erosion of an expanded polytetrafluoroethylene (ePTFE) prosthesis into the jejunum is described. This case is unusual secondary to the long experience with ePTFE and the lack of published cases similar to this one. The technical details of this case reveal extenuating circumstances associated with the fistula formation, and it is concluded that this particular case does not provide sufficient evidence to implicate ePTFE, by itself, as an etiologic agent for gastrointestinal fistulization. In addition, the published safety record of ePTFE in abdominal wall surgery is reviewed.

  5. Use of retrievable self-expanding stent in treating childhood benign oesophageal stricture

    International Nuclear Information System (INIS)

    Yu Juming; Fan Guoping; Zhong Weixing; Zhu Ming

    2007-01-01

    Objective: To evaluate the methods and effect of retrievable self-expanding esophageal stent in treating benign esophageal stenosis of children. Methods: The covered retrievable expandable nitinol stents were placed in 10 children with corrosive esophageal stenosis and post-anastomotic stenosis, age ranged from 2 to 12 years, the dysphagia scores were 3, Barium esophagography was taken before the use of retrievable stent. Results: The stents were placed safely in all patients without complications and were successfully removed after all. After the stent placement, all patients could take solid food without dysphagia. During 6 to 12 months follow-up after the stent removal, all children could eat satisfactorily with the dysphagia score as 0. Conclusion: The use of covered retrievable expandable stent is effective and safe in treating childhood benign esophageal stenosis. (authors)

  6. Are TIPS Stent-Grafts a Contraindication for Future Liver Transplantation?

    International Nuclear Information System (INIS)

    Maleux, Geert; Pirenne, Jacques; Vaninbroukx, Johan; Aerts, Raymond; Nevens, Frederik

    2004-01-01

    Our purpose was to assess the feasibility of orthotopic liver transplantation (OLT) in patients priorly having undergone transjugular intrahepatic portosystemic shunt (TIPS) with an expanded tetrafluoroethylene (e-PTFE)-covered endoprosthesis. In 48 patients an e- PTFE-covered endoprosthesis was inserted to treat severe complications of portal hypertension. In 36 patients the endoprosthesis was inserted during TIPS creation (de novo TIPS); in the other 12 patients the endoprosthesis was placed to repermeabilize the previously created, but occluded bare stent (revision TIPS). Eight of them (5 de novo and 3 revision cases) later underwent an OLT. The hospital records of these patients were reviewed from initial admission, through TIPS, the pre-OLT period, and OLT to current postoperative status. Five de novo and 3 revision cases underwent OLT 4-279 days (mean delay: 80.8 days) after TIPS procedure. All OLT's were performed under veno-venous bypass surgery. De visu surgical inspection confirmed correct positioning of the fully patent stent graft, starting in the portal vein and ending at the junction of the hepatic vein to the inferior caval vein. No surgical difficulty was observed during proximal or distal clamping or during resection of the diseased liver. Correctly positioned e-PTFE-covered nitinol endoprostheses do not interfere with a later OLT and may not be considered as a contraindication in patients who need a TIPS as a bridge to OLT

  7. Control of cell behavior on PTFE surface using ion beam irradiation

    International Nuclear Information System (INIS)

    Kitamura, Akane; Kobayashi, Tomohiro; Meguro, Takashi; Suzuki, Akihiro; Terai, Takayuki

    2009-01-01

    A polytetrafluoroethylene (PTFE) surface is smooth and biologically inert, so that cells cannot attach to it. Ion beam irradiation of the PTFE surface forms micropores and a melted layer, and the surface is finally covered with a large number of small protrusions. Recently, we found that cells could adhere to this irradiated PTFE surface and spread over the surface. Because of their peculiar attachment behavior, these surfaces can be used as biological tools. However, the factors regulating cell adhesion are still unclear, although some new functional groups formed by irradiation seem to contribute to this adhesion. To control cell behavior on PTFE surfaces, we must determine the effects of the outermost irradiated surface on cell adhesion. In this study, we removed the thin melted surface layer by postirradiation annealing and investigated cell behavior on the surface. On the surface irradiated with 3 x 10 16 ions/cm 2 , cells spread only on the remaining parts of the melted layer. From these results, it is clear that the melted layer had a capacity for cell attachment. When the surface covered with protrusions was irradiated with a fluence of 1 x 10 17 ions/cm 2 , the distribution of cells changed after the annealing process from 'sheet shaped' into multicellular aggregates with diameters of around 50 μm. These results indicate that we can control cell behavior on PTFE surfaces covered with protrusions using irradiation and subsequent annealing. Multicellular spheroids can be fabricated for tissue engineering using this surface.

  8. On the Mechanical Properties and Microstructure of Nitinol forBiomedical Stent Applications

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Scott W. [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic material constants associated with specific devices. Instead, the research utilizes a hybrid of standard test techniques (fracture mechanics and x-ray micro-diffraction) and custom-designed testing apparatus for the determination of the fracture properties of specimens that are suitable representations of self-expanding Nitinol stents. Specifically, the role of texture (crystallographic alignment of atoms) and the austenite-to-martensite phase transformation on the propagation of cracks in Nitinol was evaluated under simulated body conditions and over a multitude of stresses and strains. The results determined through this research were then used to create conservative safe operating and inspection criteria to be used by the biomedical community for the determination of specific device vulnerability to failure by fracture and/or fatigue.

  9. Heparin-bonded, expanded polytetrafluoroethylene-lined stent graft in the treatment of femoropopliteal artery disease: 1-year results of the VIPER (Viabahn Endoprosthesis with Heparin Bioactive Surface in the Treatment of Superficial Femoral Artery Obstructive Disease) trial.

    Science.gov (United States)

    Saxon, Richard R; Chervu, Arun; Jones, Paul A; Bajwa, Tanvir K; Gable, Dennis R; Soukas, Peter A; Begg, Richard J; Adams, John G; Ansel, Gary M; Schneider, Darren B; Eichler, Charles M; Rush, Michael J

    2013-02-01

    To evaluate the performance of a heparin-bonded, expanded polytetrafluoroethylene (ePTFE)-lined nitinol endoprosthesis in the treatment of long-segment occlusive disease of the femoropopliteal artery (FPA) and to identify factors associated with loss of patency. In a single-arm, prospective, 11-center study (VIPER [Gore Viabahn Endoprosthesis with Heparin Bioactive Surface in the Treatment of Superficial Femoral Artery Obstructive Disease] trial), 119 limbs (113 patients; 69 men; mean age, 67 y), including 88 with Rutherford category 3-5 disease and 72 with Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II) C or D lesions of the FPA, underwent stent graft implantation. The mean lesion length was 19 cm; 56% of lesions were occlusions. Follow-up evaluations included color duplex ultrasonography in all patients, with patency defined as a peak systolic velocity ratio20% was 70% (P = .047). Primary patency was not significantly affected by device diameter (5 vs 6 vs 7 mm) or lesion length (≤20 cm vs>20 cm). The 30-day major adverse event rate was 0.8%. The heparin-bonded, ePTFE/nitinol stent graft provided clinical improvement and a primary patency rate of 73% at 1 year in the treatment of long-segment FPA disease. Careful sizing of the device relative to vessel landing zones is essential for achieving optimal outcomes. Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.

  10. Self-Expanding Nitinol Renal Artery Stents: Comparison of Safety and Efficacy of Bare Versus Polyzene-F Nanocoated Stents in a Porcine Model

    International Nuclear Information System (INIS)

    Kurz, P.; Stampfl, U.; Christoph, P.; Henn, C.; Satzl, S.; Radeleff, B.; Berger, I.; Richter, G. M.

    2011-01-01

    Objective: To investigate the safety and efficacy of a Polyzene-F nanocoat on new low-profile self-expandable nitinol stents in minipig renal arteries. Materials and Methods: Ten bare nitinol stents (BNS) and 10 stents coated with a 50 nm-thin Polyzene-F coating were randomly implanted into renal arteries of 10 minipigs (4- and 12-week follow-up, 5 animals/group). Thrombogenicity, on-stent surface endothelialization, vessel wall injury, late in-stent stenosis, and peristrut vessel wall inflammation were determined by quantitative angiography and postmortem histomorphometry. Results: In 6 of 10 BNS, >50% stenosis was found, but no stenosis was found in stents with a nanothin Polyzene-F coating. Histomorphometry showed a statistically significant (p < 0.05) different average maximum luminal loss of 55.16% ± 8.43% at 12 weeks in BNS versus 39.77% ± 7.41% in stents with a nanothin Polyzene-F coating. Stents with a nanothin Polyzene-F coating had a significantly (p < 0.05) lower inflammation score after 12 weeks, 1.31 ± 1.17 versus 2.17 ± 0.85 in BNS. The results for vessel wall injury (0.6 ± 0.58 for Polyzene-F-coated stents; 0.72 ± 0.98 for BNS) and re-endothelialization, (1.16 ± 0.43 and 1.23 ± 0.54, respectively) were not statistically significant at 12-week follow-up. No thrombus deposition was observed on the stents at either follow-up time point. Conclusion: Nitinol stents with a nanothin Polyzene-F coating successfully decreased in-stent stenosis and vessel wall inflammation compared with BNS. Endothelialization and vessel wall injury were found to be equal. These studies warrant long-term pig studies (≥120 days) because 12 weeks may not be sufficient time for complete healing; thereafter, human studies may be warranted.

  11. Esophagorespiratory fistula: treatment with self-expanding covered stent

    International Nuclear Information System (INIS)

    Zang Jian; Dou Yongchong; Wang Zheng; Kong Jian

    2002-01-01

    Objective: To evaluate self-expanding covered stent in the management of esophagorespiratory fistula. Methods: A self-expanding esophageal covered stent was implanted under fluoroscopic guidance in 13 patients with esophagorespiratory fistula. In this series patients aged 31-73 years (60.2 years in average). All patients had a pre-procedure fast of 6-41 days (17.3 days in average), in which 12 patients had pulmonary infection. Results: All fistulas were excluded and swallowing function was restored. No stend-related complication was observed. Pulmonary infection was managed in 10 patients out of 13. The mean survived time was 33.3 wks (1-178 wks) in follow-up. Conclusion: Covered self-expanding stent implantation is a safe and effective treatment of ERF

  12. Multidetector-Row Computed Tomography in the Evaluation of Transjugular Intrahepatic Portosystemic Shunt Performed with Expanded-Polytetrafluoroethylene-Covered Stent-Graft

    International Nuclear Information System (INIS)

    Fanelli, Fabrizio; Bezzi, Mario; Bruni, Antonio; Corona, Mario; Boatta, Emanuele; Lucatelli, Pierleone; Passariello, Roberto

    2011-01-01

    We assessed, in a prospective study, the efficacy of multidetector spiral computed tomography (MDCT) in the evaluation of transjugular intrahepatic portosystemic shunt (TIPS) patency in patients treated with the Viatorr (Gore, Flagstaff, AZ) expanded-polytetrafluoroethylene (e-PTFE)-covered stent-graft. Eighty patients who underwent TIPS procedure using the Viatorr self-expanding e-PTFE stent-graft were evaluated at follow-up of 1, 3, 6, and 12 months with clinical and laboratory tests as well as ultrasound–color Doppler (USCD) imaging. In case of varices, upper gastrointestinal endoscopy was also performed. In addition, the shunt was evaluated using MDCT at 6 and 12 months. In all cases of abnormal findings and discrepancy between MDCT and USCD, invasive control venography was performed. MDCT images were acquired before and after injection of intravenous contrast media on the axial plane and after three-dimensional reconstruction using different algorithms. MDCT was successfully performed in all patients. No artefacts correlated to the Viatorr stent-graft were observed. A missing correlation between UCSD and MDCT was noticed in 20 of 80 (25%) patients. Invasive control venography confirmed shunt patency in 16 (80%) cases and shunt malfunction in 4 (20%) cases. According to these data, MDCT sensitivity was 95.2%; specificity was 96.6%; and positive (PPV) and negative predictive values (NPV) were 90.9 and 98.2%, respectively. USCD sensitivity was 90%; specificity was 75%; and PPV and NPV were 54.5 and 95.7%, respectively. A high correlation (K value = 0.85) between MDCT and invasive control venography was observed. On the basis of these results, MDCT shows superior sensitivity and specificity compared with USCD in those patients in whom TIPS was performed with the Viatorr stent-graft. MDCT can be considered a valid tool in the follow-up of these patients.

  13. Medical uses of nitinol

    Energy Technology Data Exchange (ETDEWEB)

    Pelton, A.R.; Stoeckel, D.; Duering, T.W. [Nitinol Devices and Components - Cordis Corp., Fremont, CA (United States)

    2000-07-01

    The growth of nitinol in the medical industries has exploded in the past ten years. Patients and care providers have encouraged the transition from traditional open-surgical procedures, which require long hospital stays, to less-invasive techniques, which are often performed in out-patient clinics. This demand for minimally invasive procedures has allowed novel instrumentation and implants to be designed. An increasing number of these devices use nitinol as the critical component. Examples of medical applications range from orthodontic archwires and endoscopic instruments to endovascular stents. This paper will focus on key performance attributes of nitinol that make it an ideal material for medical applications. Specific applications will be introduced through their use of the enabling features. (orig.)

  14. Carbon protrusions on PTFE surface prepared by ion irradiation and chemical defluorination

    Science.gov (United States)

    Kobayashi, T.; Iwaki, M.

    2006-01-01

    A surface of PTFE was covered with small protrusions by ion-beam irradiation. In this study, we converted PTFE protrusions into carbon protrusions by a defluorination (carbonization) process using sodium vapor. The morphology, composition and structure were analyzed by SEM-EDX, Raman spectroscopy and TEM. The irradiated PTFE sheets were packed in evacuated glass tubes with a sodium block and kept at 473 K for 2-48 h. The samples were then rinsed in HCl and distilled water to remove NaF precipitates. The EDX measurement showed that the NaF precipitates were completely removed by washing, and the percentage of carbon atoms was controlled from 60% to 99% by the treatment. Raman spectra showed that graphite structures grow during the defluorination process. TEM micrographs showed that the protrusions have a bubble structure and are covered with a thin wall. The carbonized protrusions were conductive and grew perpendicular to the substrate.

  15. Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices

    Science.gov (United States)

    Weaver, J. D.; Gutierrez, E. J.; Nagaraja, S.; Stafford, P. R.; Sivan, S.; Di Prima, M.

    2017-09-01

    Processing of nitinol medical devices has evolved over the years as manufacturers have identified methods of reducing surface defects such as inclusions. One recent method proposes to soak nitinol medical devices in a 6% sodium hypochlorite (NaClO) solution as a means of identifying surface inclusions. Devices with surface inclusions could in theory then be removed from production because inclusions would interact with NaClO to form a visible black material on the nitinol surface. To understand the effects of an NaClO soak on performance, we compared as-received and NaClO-soaked nitinol wires with two different surface finishes (black oxide and electropolished). Pitting corrosion susceptibility was equivalent between the as-received and NaClO-soaked groups for both surface finishes. Nickel ion release increased in the NaClO-soaked group for black oxide nitinol, but was equivalent for electropolished nitinol. Fatigue testing revealed a lower fatigue life for NaClO-soaked black oxide nitinol at all alternating strains. With the exception of 0.83% alternating strain, NaClO-soaked and as-received electropolished nitinol had similar average fatigue life, but the NaClO-soaked group showed higher variability. NaClO-soaked electropolished nitinol had specimens with the lowest number of cycles to fracture for all alternating strains tested with the exception of the highest alternating strain 1.2%. The NaClO treatment identified only one specimen with surface inclusions and caused readily identifiable surface damage to the black oxide nitinol. Damage from the NaClO soak to electropolished nitinol surface also appears to have occurred and is likely the cause of the increased variability of the fatigue results. Overall, the NaClO soak appears to not lead to an improvement in nitinol performance and seems to be damaging to the nitinol surface in ways that may not be detectable with a simple visual inspection for black material on the nitinol surface.

  16. Comparison of diamond-like carbon-coated nitinol stents with or without polyethylene glycol grafting and uncoated nitinol stents in a canine iliac artery model

    Science.gov (United States)

    Kim, J H; Shin, J H; Shin, D H; Moon, M-W; Park, K; Kim, T-H; Shin, K M; Won, Y H; Han, D K; Lee, K-R

    2011-01-01

    Objective Neointimal hyperplasia is a major complication of endovascular stent placement with consequent in-stent restenosis or occlusion. Improvements in the biocompatibility of stent designs could reduce stent-associated thrombosis and in-stent restenosis. We hypothesised that the use of a diamond-like carbon (DLC)-coated nitinol stent or a polyethylene glycol (PEG)-DLC-coated nitinol stent could reduce the formation of neointimal hyperplasia, thereby improving stent patency with improved biocompatibility. Methods A total of 24 stents were implanted, under general anaesthesia, into the iliac arteries of six dogs (four stents in each dog) using the carotid artery approach. The experimental study dogs were divided into three groups: the uncoated nitinol stent group (n = 8), the DLC-nitinol stent group (n = 8) and the PEG-DLC-nitinol stent group (n = 8). Results The mean percentage of neointimal hyperplasia was significantly less in the DLC-nitinol stent group (26.7±7.6%) than in the nitinol stent group (40.0±20.3%) (p = 0.021). However, the mean percentage of neointimal hyperplasia was significantly greater in the PEG-DLC-nitinol stent group (58.7±24.7%) than in the nitinol stent group (40.0±20.3%) (p = 0.01). Conclusion Our findings indicate that DLC-coated nitinol stents might induce less neointimal hyperplasia than conventional nitinol stents following implantation in a canine iliac artery model; however, the DLC-coated nitinol stent surface when reformed with PEG induces more neointimal hyperplasia than either a conventional or DLC-coated nitinol stent. PMID:21325363

  17. Biomimetic Fluorocarbon Surfactant Polymers Reduce Platelet Adhesion on PTFE/ePTFE Surfaces

    Science.gov (United States)

    Wang, Shuwu; Gupta, Anirban Sen; Sagnella, Sharon; Barendt, Pamela M.; Kottke-Marchant, Kandice; Marchant, Roger E.

    2010-01-01

    We describe a series of fluorocarbon surfactant polymers designed as surface-modifying agents for improving the thrombogenicity of ePTFE vascular graft materials by the reduction of platelet adhesion. The surfactant polymers consist of a poly(vinyl amine) backbone with pendent dextran and perfluoroundecanoyl branches. Surface modification is accomplished by a simple dip-coating process in which surfactant polymers undergo spontaneous surface-induced adsorption and assembly on PTFE/ePTFE surface. The adhesion stability of the surfactant polymer on PTFE was examined under dynamic shear conditions in PBS and human whole blood with a rotating disk system. Fluorocarbon surfactant polymer coatings with three different dextran to perfluorocarbon ratios (1:0.5, 1:1 and 1:2) were compared in the context of platelet adhesion on PTFE/ePTFE surface under dynamic flow conditions. Suppression of platelet adhesion was achieved for all three coated surfaces over the shear-stress range of 0–75 dyn/cm2 in platelet-rich plasma (PRP) or human whole blood. The effectiveness depended on the surfactant polymer composition such that platelet adhesion on coated surfaces decreased significantly with increasing fluorocarbon branch density at 0 dyn/cm2. Our results suggest that fluorocarbon surfactant polymers can effectively suppress platelet adhesion and demonstrate the potential application of the fluorocarbon surfactant polymers as non-thrombogenic coatings for ePTFE vascular grafts. PMID:19323880

  18. Culture of Iris Pigment Epithelial Cells on Expanded-Polytetrafluroethylene (ePTFE Substrates for the Treatment of Age-Related Macular Degeneration

    Directory of Open Access Journals (Sweden)

    S Nian

    2011-05-01

    Full Text Available Introduction: Transplantation of an intact differentiated retinal pigment epithelial (RPE cell layer may provide a means to treat Age-Related Macular Degeneration (AMD. However, harvesting RPE cells can be a technically complicated procedure. Our current work aimed to prepare intact differentiated iris pigment epithelial (IPE cell layers, which are easy to obtain and have the same embryonic origin and similar properties as RPE cells, on ePTFE substrates for transplantation purposes to rescue deteriorated photoreceptors in AMD. Methods: IPE cells isolated from rat eyes were seeded on different substrates, including fibronectin n-heptylamine (HA ePTFE substrates, HA ePTFE substrates, ePTFE substrates and fibronectin tissue culture polystyrene (TCPS as control. Cell number and morphology were assessed at each time interval. The formation of tight junction was examined by immunostaining of junction proteins. Results: An obvious increasing trend of cell number was observed in IPE cells on fibronectin n-heptylamine (HA ePTFE substrate, exhibiting heavy pigmentation and epithelial morphology. At Day 28, tight junction formation was indicated by cell-cell junctional proteins along cell borders. Conclusion: Harvested IPE cells cultured on fibronectin HA-ePTFE substrates can differentiate and form a cell monolayer that may be suitable for transplantation.

  19. Endovascular treatment of intrahepatic inferior vena cava obstruction from malignant hepatocellular tumor thrombus utilizing Luminexx self-expanding nitinol stents

    International Nuclear Information System (INIS)

    Stambo, Glenn W.; Leto, John; George, Christopher; Van Epps, Kelly; Woeste, Troy; Berlet, Mathew

    2008-01-01

    Inferior vena cava (IVC) obstruction is a well-described clinical entity. Most IVC obstructions from malignant neoplasms are a direct result of tumor compression [Oviedo J, Cerda S. Vascular invasion by hepatocellular carcinoma. Arch Pathol Lab Med 2001;125: 454-5; Furui S, Sawada S, et al. Gianturco stent placement in malignant caval obstruction: analysis of factors for predicting the outcome. Radiology 1995;195:147-52; Fletcher WS, Lakin PC, et al. Results of treatment of inferior vena cava syndrome with expandable metallic stents. Arch Surg 1998;133:935-8]. The symptoms of IVC obstruction include progressive ascites, scrotal edema and lower body edema. These constellations of symptoms are described as IVC syndrome and are devastating to a patient with end-stage cancer. We describe a palliative therapy utilizing Luminexx nitinol self-expanding stents to treat intracaval hepatoma thrombus obstructing the IVC. The procedure is rapidly performed, technically reliable, and has essentially no morbidity or mortality. This procedure can be performed in the interventional radiology suite with excellent results resolving the IVC syndrome soon after placement of the stents. We believe endovascular stenting as an excellent palliative therapy for patients with IVC syndrome and should be the treatment of choice for caval obstructions due to intraluminal tumor thrombus

  20. Endovascular treatment of intrahepatic inferior vena cava obstruction from malignant hepatocellular tumor thrombus utilizing Luminexx self-expanding nitinol stents

    Energy Technology Data Exchange (ETDEWEB)

    Stambo, Glenn W. [Division of Vascular and Interventional Radiology, Department of Radiology, St. Joseph' s Hospital and Medical Center, 4516 North Armenia Avenue, Tampa, FL 33603 (United States)], E-mail: xraydoc2@yahoo.com; Leto, John [Division of Vascular and Interventional Radiology, Department of Radiology, St. Joseph' s Hospital and Medical Center, 3001 W. Dr. Martin Luther King Jr. Blvd., Tampa, FL 33607 (United States); George, Christopher [Department of Hematology and Oncology, St. Joseph' s Hospital and Medical Center, 4301 W. Habana Avenue, Suite 1, Tampa, FL 33607 (United States); Van Epps, Kelly; Woeste, Troy; Berlet, Mathew [Division of Vascular and Interventional Radiology, Department of Radiology, St. Joseph' s Hospital and Medical Center, 4516 North Armenia Avenue, Tampa, FL 33603 (United States)

    2008-05-15

    Inferior vena cava (IVC) obstruction is a well-described clinical entity. Most IVC obstructions from malignant neoplasms are a direct result of tumor compression [Oviedo J, Cerda S. Vascular invasion by hepatocellular carcinoma. Arch Pathol Lab Med 2001;125: 454-5; Furui S, Sawada S, et al. Gianturco stent placement in malignant caval obstruction: analysis of factors for predicting the outcome. Radiology 1995;195:147-52; Fletcher WS, Lakin PC, et al. Results of treatment of inferior vena cava syndrome with expandable metallic stents. Arch Surg 1998;133:935-8]. The symptoms of IVC obstruction include progressive ascites, scrotal edema and lower body edema. These constellations of symptoms are described as IVC syndrome and are devastating to a patient with end-stage cancer. We describe a palliative therapy utilizing Luminexx nitinol self-expanding stents to treat intracaval hepatoma thrombus obstructing the IVC. The procedure is rapidly performed, technically reliable, and has essentially no morbidity or mortality. This procedure can be performed in the interventional radiology suite with excellent results resolving the IVC syndrome soon after placement of the stents. We believe endovascular stenting as an excellent palliative therapy for patients with IVC syndrome and should be the treatment of choice for caval obstructions due to intraluminal tumor thrombus.

  1. Utilization of d-PTFE Barriers for Post-Extraction Bone Regeneration in Preparation for Dental Implants.

    Science.gov (United States)

    Greenstein, Gary; Carpentieri, Joseph R

    2015-01-01

    Guided bone regeneration (GBR) can be used to restore a defective alveolar ridge after extractions before or in combination with implant placement. It may also be employed after extractions to reduce crestal bone resorption and maximize bone fill of sockets. Resorbable or nonresorbable barriers (eg, expanded polytetrafluoroethylene [e-PTFE]) can be used when performing GBR procedures, but they need to be completely submerged to attain optimal results. Dense polytetrafluoroethylene (d-PTFE) is a type of nonresorbable barrier that circumvents the necessity to attain primary closure after placement of bone grafts, thereby reducing patient morbidity. This article addresses topics pertaining to d-PTFE utilization, including characteristics and advantages of d-PTFE barriers, time needed for osteoid tissue to become impervious to penetration by flap connective tissue, relevant clinical studies, and limitations of available data. Clinical photographs and radiographs of successfully treated cases are presented to illustrate the efficacy of d-PTFE barriers in regenerating defective bony plates after extractions.

  2. Microfabrication of crosslinked PTFE by synchrotron radiation

    International Nuclear Information System (INIS)

    Sato, Yasunori; Yamaguchi, Daichi; Oshima, Akihiro; Washio, Masakazu; Katoh, Takanori; Aoki, Yasushi; Ikeda, Shigetoshi; Tanaka, Shigeru

    2003-01-01

    Microfabrication of crosslinked polytetrafluoroethylene (PTFE) using synchrotron radiation (SR) has been demonstrated for production of micro-components applicable to radiation fields. The method of microfabrication was readily capable of obtaining a microstructure with aspect-ratio of 25 made of crosslinked PTFE. The etching rate of crosslinked PTFE was higher than that of non-crosslinked PTFE. The results show that the etching rate of crosslinked PTFE depends only on the degree of crosslinking. The effect of molecular motion on etching process was discussed from temperature dependence on etching rate. Moreover, in order to examine whether any change of chemical structures and crystallinity would be induced by SR-irradiation on PTFE, SR-irradiated PTFE was measured by NMR spectroscopy and DSC analysis. The results showed that the crosslinking reaction of PTFE would be induced by SR-irradiation in the solid state. (author)

  3. Esophageal carcinoma treatment with self-expanding covered stent implanted in esophagus

    International Nuclear Information System (INIS)

    Liu Mingguo; Ji Yan; He Nengwei

    2006-01-01

    Objective: To investigate the clinical significance of the treatment to esophageal cancer by self- expanding covered stent implanted into esophagus. Methods: Under fluoroscopic guidance and with guidance wire , 20 self-expanding covered stents were implanted into stenotic part of esophagus to recanalize the esophagus, then follow up to observe the clinical symptom improved. Results: Technical success was obtained 20 cases without any complication. Clinical symptom were improved in shot time. Conclusions: self-expanding covered stent is implanted in stenotic part of esophageal carcinoma to treat esophageal stenosis and enable to improved clinical symptom in shot time, if combined with transcatheter arterial infusion and embolization, Radiotherapy, Chinese medical treatment, it enable to lengthen life time remarkably. (authors)

  4. Partially covered versus uncovered self-expandable nitinol stents with anti-migration properties for the palliation of malignant distal biliary obstruction: A randomized controlled trial.

    Science.gov (United States)

    Yang, Min Jae; Kim, Jin Hong; Yoo, Byung Moo; Hwang, Jae Chul; Yoo, Jun Hwan; Lee, Ki Seong; Kang, Joon Koo; Kim, Soon Sun; Lim, Sun Gyo; Shin, Sung Jae; Cheong, Jae Youn; Lee, Kee Myung; Lee, Kwang Jae; Cho, Sung Won

    2015-01-01

    Covered self-expandable metal stents (SEMSs) are increasingly used as alternatives to uncovered SEMSs for the palliation of inoperable malignant distal biliary obstruction to counteract tumor ingrowth. We aimed to compare the outcomes of partially covered and uncovered SEMSs with identical mesh structures and anti-migration properties, such as low axial force and flared ends. One hundred and three patients who were diagnosed with inoperable malignant distal biliary obstruction between January 2006 and August 2013 were randomly assigned to either the partially covered (n = 51) or uncovered (n = 52) SEMS group. There were no significant differences in the cumulative stent patency, overall patient survival, stent dysfunction-free survival and overall adverse events, including pancreatitis and cholecystitis, between the two groups. Compared to the uncovered group, stent migration (5.9% vs. 0%, p = 0.118) and tumor overgrowth (7.8% vs. 1.9%, p = 0.205) were non-significantly more frequent in the partially covered group, whereas tumor ingrowth showed a significantly higher incidence in the uncovered group (5.9% vs. 19.2%, p = 0.041). Stent migration in the partially covered group occurred only in patients with short stenosis of the utmost distal bile duct (two in ampullary cancer, one in bile duct cancer), and did not occur in any patients with pancreatic cancer. For the palliation of malignant distal biliary obstruction, endoscopic placement of partially covered SEMSs with anti-migration designs and identical mesh structures to uncovered SEMSs failed to prolong cumulative stent patency or reduce stent migration.

  5. Molecular level analyses of mechanical properties of PTFE sterilized by Co-60 γ-ray irradiation for clinical use

    Science.gov (United States)

    Furuta, Masakazu; Matsugaki, Aira; Nakano, Takayoshi; Hirata, Isao; Kato, Koichi; Oda, Takashi; Sato, Mamoru; Okazaki, Masayuki

    2017-10-01

    Recently, Co-60 gamma-ray irradiation has become markedly popular for the sterilization of biomedical materials, including expanded PTFE. However, its effect on the properties of PTFE has not been thoroughly examined. In this study, changes in the properties of PTFE before and after irradiation were analyzed physicochemically and discussed crystallographically. The tensile breaking strengths of PTFE decreased markedly on irradiation at 1 kGy, and were maintained at almost one fourth of the original value (44.3±2.5 N/mm2) ranging from 5 to 100 kGy. XPS analysis indicated that the atomic concentrations of carbon (C) and fluorine (F) of PTFE were not different among samples irradiated at various dosages. Raman spectra of PTFE showed a slight increase of the absorption peak intensity at 735 cm-1 in an irradiation dosage-dependent manner. X-ray diffraction showed that the crystal size of PTFE (56.7±1.0 nm) became smaller after radiation at 100 kGy (48.5±0.6 nm). These results are consistent with the above results of Raman analysis. It is suggested that the observed changes in the mechanical properties of PTFE may be due to nano-scale C-C bond scission by gamma ray irradiation, and not due to the formation of micro-scale cracks.

  6. Recycling of PTFE by means of ionizing rays

    International Nuclear Information System (INIS)

    Lee, D.W.

    1994-01-01

    By treatment with beta or gamma rays, PTFE waste is converted to high-grade PTFE fine powder. High-molecular weight PTFE is degraded to low-molecular weight PTFE. Due to this the density, the degree of crystallinity, and the melt flow index are increased, which enhances the brittleness of the material. Irradiation of PTFE thus facilitates milling and makes the material pourable and free-flowing. Milled PTFE fine powder, lie PTFE plastic, combines temperature resistance, weather fastness, and chemical stability with good slip behaviour and antiadhesive properties. Areas of application for fine powder include additives for plastics, printing inks, nonstick coatings, and antifriction lacquers. (orig.) [de

  7. A fine surface roughness electroless Ni–P–PTFE composite modified stamper for light guide plate application

    International Nuclear Information System (INIS)

    Pan, K; Fu, C

    2010-01-01

    Electroless Ni–P–PTFE composite coating technology takes advantage of the beneficial properties from both Ni–P alloy and PTFE, such as good wear resistance, good anti-adhesion, dry lubrication, low coefficient of friction and good corrosion resistance. It has been applied in many mold industries. However, the Ni–P–PTFE composite coating suffers from bad surface roughness, when the PTFE particles incorporate into a Ni–P matrix. This severely hampers the technology to be applied to optical grade applications. In this paper, we propose a trick to generate a fine surface roughness (FSR) electroless Ni–P–PTFE composite to modify a nickel stamper. Using this new method, the nickel stamper can be covered by a Ni–P–PTFE functional layer and can keep the original surface property at the same time, namely the optical properties. We have chosen 4.5 inch (97 mm × 59 mm × 0.6 mm) light guide plates (LGPs) to demonstrate the effectiveness of the procedure. For the sake of comparison, the LGPs were produced by injection molding with three kinds of stampers including an original SUS430 master, an electroless Ni–P–PTFE composite coated nickel stamper and an FSR electroless Ni–P–PTFE composite modified stamper. We measured and discussed the optical performances at both the element level and system level, namely complete back light units.

  8. Chemiluminescence emission from irradiated polytetrafluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Zhong Xiaoguang; Sun Jiazhen; Yoshii, Fumio; Sasaki, Takashi; Makuuchi, Keizo

    2000-01-01

    PTFE is well known for its chemical and high temperature resistance and also for its high-energy radiation sensitivity. The present work deals with the radiation-induced emission of chemiluminescence from PTFE film, which is generally thought as a measure of radiation induced oxidation reaction in irradiated polymer. The observation that the much stronger chemiluminescence emission from PTFE than that from other polymeric system indicate the unusual high degree of radiation induced oxidation in PTFE. On the other hand the temperature and atmosphere effect during radiation on emission of chemiluminescence were also reported. (author)

  9. Simon-nitinol filter

    International Nuclear Information System (INIS)

    Simon, M.; Kim, D.; Porter, D.H.; Kleshinski, S.

    1989-01-01

    This paper discusses a filter that exploits the thermal shape-memory properties of the nitinol alloy to achieve an optimized filter shape and a fine-bore introducer. Experimental methods and materials are given and results are analyzed

  10. Modification of PTFE nanopowder by controlled electron beam irradiation: A useful approach for the development of PTFE coupled EPDM compounds

    Directory of Open Access Journals (Sweden)

    2008-04-01

    Full Text Available Low-temperature reactive mixing of controlled electron beam modified Polytetrafluoroethylene (PTFE nanopowder with Ethylene-Propylene-Diene-Monomer (EPDM rubber produced PTFE coupled EPDM rubber compounds with desired physical properties. The radiation-induced chemical alterations in PTFE nanopowder, determined by electron spin resonance (ESR and Fourier transform infrared (FTIR spectroscopy, showed increasing concentration of radicals and carboxylic groups (–COOH with increasing irradiation dose. The morphological variations of the PTFE nanopowder including its decreasing mean agglomerate size with the absorbed dose was investigated by particle size and scanning electron microscopy (SEM analysis. With increasing absorbed dose the wettability of the modified PTFE nanopowder determined by contact angle method increased in accordance with the (–COOH concentration. Transmission electron microscopy (TEM showed that modified PTFE nanopowder is obviously enwrapped by EPDM. This leads to a characteristic compatible interphase around the modified PTFE. Crystallization studies by differential scanning calorimetry (DSC also revealed the existence of a compatible interphase in the modified PTFE coupled EPDM.

  11. Study design and rationale of the 'Balloon-Expandable Cobalt Chromium SCUBA Stent versus Self-Expandable COMPLETE-SE Nitinol Stent for the Atherosclerotic ILIAC Arterial Disease (SENS-ILIAC Trial) Trial': study protocol for a randomized controlled trial.

    Science.gov (United States)

    Choi, Woong Gil; Rha, Seung Woon; Choi, Cheol Ung; Kim, Eung Ju; Oh, Dong Joo; Cho, Yoon Hyung; Park, Sang Ho; Lee, Seung Jin; Hur, Ae Yong; Ko, Young Guk; Park, Sang Min; Kim, Ki Chang; Kim, Joo Han; Kim, Min Woong; Kim, Sang Min; Bae, Jang Ho; Bong, Jung Min; Kang, Won Yu; Seo, Jae Bin; Jung, Woo Yong; Cho, Jang Hyun; Kim, Do Hoi; Ahn, Ji Hoon; Kim, Soo Hyun; Jang, Ji Yong

    2016-06-25

    The self-expandable COMPLETE™ stent (Medtronic) has greater elasticity, allowing it to regain its shape after the compression force reduces, and has higher trackability, thus is easier to maneuver through tortuous vessels, whereas the balloon-expandable SCUBA™ stent (Medtronic) has higher radial stiffness and can afford more accurate placement without geographic miss, which is important in aortoiliac bifurcation lesions. To date, there have been no randomized control trials comparing efficacy and safety between the self-expanding stent and balloon-expandable stent in advanced atherosclerotic iliac artery disease. The purpose of our study is to examine primary patency (efficacy) and incidence of stent fracture and geographic miss (safety) between two different major representative stents, the self-expanding nitinol stent (COMPLETE-SE™) and the balloon-expanding cobalt-chromium stent (SCUBA™), in stenotic or occlusive iliac arterial lesions. This trial is designed as a prospective, randomized, multicenter trial to demonstrate a noninferiority of SCUBA™ stent to COMPLETE-SE™ stent following balloon angioplasty in iliac arterial lesions, and a total of 280 patients will be enrolled. The primary end point of this study is the rate of primary patency in the treated segment at 12 months after intervention as determined by catheter angiography, computed tomography angiography, or duplex ultrasound. The SENS-ILIAC trial will give powerful insight into whether the stent choice according to deployment mechanics would impact stent patency, geographic miss, or stent fracture in patients undergoing stent implantation in iliac artery lesions. National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov identifier: NCT01834495 ), registration date: May 8, 2012.

  12. Studying the Effect of the Concentration of PTFE Nanoparticles on the Tribological Behavior of Ni-P-PTFE Composite Coatings

    Directory of Open Access Journals (Sweden)

    Hamid Rahmati

    2015-10-01

    Full Text Available In the past 30 years, electroless nickel (EN plating has grown to such proportions that these coatings and their applications are now found underground, in outer space, and in a myriad of areas in between. Moreover, in order to further improve the mechanical and tribological properties of the nickel-phosphorous (Ni-P coatings, Ni-P/PTFE composite coatings can be obtained, which provides even greater friction behavior and lubricity than the one naturally occurring in the nickel-phosphorous alloy deposit. In this paper, The Ni-P-PTFE coating was deposited on mild carbon steel surface via electroless deposition process. The friction behavior and wear mechanisms of Ni-P-PTFE nanocomposite coating were studied at different concentrations of PTFE. Frictional behavior was examined using a pin on disk wear test method. Surface morphology and worn surface was evaluated using field emission scanning electron microscopy (FESEM and energy dispersive spectroscopy (EDS analysis. The results showed that the incorporation of PTFE nanoparticles can reduce the wear rate of Ni-P coating from 33.07×10-6 mm3/Nm to 12.46×10-6 mm3/Nm for the Ni-P PTFE containing 10 g/l PTFE and decrease the friction coefficient from 0.64 to 0.2. Thus the tribological behavior of Ni-P coating is much improved in the presence of PTFE nanoparticles and 10 g/l is the optimized concentration of PTFE in the electroless bath.

  13. Development of a Diehard GEM using PTFE insulator substrate

    International Nuclear Information System (INIS)

    Wakabayashi, M; Tamagawa, T; Takeuchi, Y; Aoki, K; Taketani, A; Komiya, K; Hamagaki, H

    2014-01-01

    We have developed the gas electron multiplier (GEM) using polytetrafluoroethylene (PTFE) insulator substrate (PTFE-GEM). Carbonization on insulator layer by discharges shorts the GEM electrodes, causing permanent breakdown. Since PTFE is hard to be carbonized against arc discharges, PTFE-GEM is expected to be robust against breakdown. Gains as high as 2.6 × 10 4 were achieved with PTFE-GEM (50 μm thick) in Ar/CO 2 = 70%/30% gas mixture at V GEM = 730 V. PTFE-GEM never showed a permanent breakdown even after suffering more than 40000 times discharges during the experiment. The result demonstrates that PTFE-GEM is really robust against discharges. We conclude that PTFE is an excellent insulator material for the GEM productions

  14. Radiation processing for PTFE composite reinforced with carbon fiber

    International Nuclear Information System (INIS)

    Akihiro Oshima; Akira Udagawa; Yousuke Morita

    1999-01-01

    The present work is an attempt to evaluate the performance of crosslinked PTFE as a polymer matrix for carbon fiber-reinforced composite materials. The carbon fiber-reinforced PTFE pre-composite, which is laminated with PTFE fine powder, is crosslinked by electron beam irradiation. Mechanical and frictional properties of the crosslinked PTFE composite obtained are higher than those of PTFE resin. The crosslinked PTFE composite with high mechanical and radiation resistant performance is obtained by radiation crosslinking process

  15. Peroxi-coagulation degradation of C.I. Basic Yellow 2 based on carbon-PTFE and carbon nanotube-PTFE electrodes as cathode

    International Nuclear Information System (INIS)

    Zarei, Mahmoud; Salari, Darioush; Niaei, Aligoli; Khataee, Alireza

    2009-01-01

    The electrochemical treatment of solutions containing C.I. Basic Yellow 2 (BY2) in aqueous solutions with carbon-PTFE (polytetrafluoroethylene) and carbon nanotube (CNT)-PTFE electrodes as cathode has been studied. The fabricated electrodes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The amount of electrogenerated H 2 O 2 on the surface of these electrodes was investigated, too. The results showed that the amount of H 2 O 2 obtained with the CNT-PTFE electrode was nearly three times higher than that of carbon-PTFE electrode. The decolorization efficiency of BY2 in peroxi-coagulation process reached 62% and 96% in the first 10 min by carbon-PTFE and CNT-PTFE electrodes at 100 mA, respectively. The effect of operational parameters such as applied current, initial pH and initial dye concentration was studied in an attempt to reach higher decolorization efficiency. The degradation and mineralization of BY2 using CNT-PTFE electrode were followed by total organic carbon (TOC) and GC-MS analysis. The results of TOC measurements indicated that peroxi-coagulation with carbon-PTFE allowed 81% mineralization after 6 h of electrolysis; whereas peroxi-coagulation with CNT-PTFE yields 92% mineralization under the same conditions. GC-MS analysis verified the identity of intermediates and a reaction pathway based on them was proposed.

  16. Engineering based assessment for a shape design of a pediatric ePTFE pulmonary conduit valve.

    Science.gov (United States)

    Tsuboko, Yusuke; Shiraishi, Yasuyuki; Yamada, Akihiro; Yambe, Tomoyuki; Miura, Hidekazu; Mura, Seitaro; Yamagishi, Masaaki

    2016-08-01

    The authors examined the hemodynamic characteristics of expanded polytetrafluoroethylene (ePTFE) pulmonary valved conduits quantitatively by our originally developed pediatric pulmonary mechanical circulatory system, in order to suggest the optimal shape design. The system consisted of pneumatically driven right atrium and ventricle model, a pulmonary valve chamber, and elastic pulmonary compliance model with peripheral vascular resistance units, a venous reservoir. We employed two different types of ePTFE valve and evaluated the relationship between the leaflets motion and hemodynamic characteristics by using a high-speed video camera. As a result, we successfully reproduced hemodynamic simulations in our pediatric pulmonary mock system. We confirmed that the presence of bulging sinuses in the pulmonary valved conduit reduced the transvalvular energy loss and increased the valve opening area during systolic period. Our engineering-based in vitro analysis could be useful for proposing a shape design optimization of sophisticated pediatric ePTFE pulmonary valve.

  17. Development of a Diehard GEM using PTFE insulator substrate

    OpenAIRE

    Wakabayashi, M.; Komiya, K.; Tamagawa, T.; Takeuchi, Y.; Aoki, K.; Taketani, A.; Hamagaki, H.

    2014-01-01

    We have developed the gas electron multiplier (GEM) using polytetrafluoroethylene (PTFE) insulator substrate (PTFE-GEM). Carbonization on insulator layer by discharges shorts the GEM electrodes, causing permanent breakdown. Since PTFE is hard to be carbonized against arc discharges, PTFE-GEM is expected to be robust against breakdown. Gains as high as 2.6x10^4 were achieved with PTFE-GEM (50 um thick) in Ar/CO2 = 70%/30% gas mixture at V_GEM = 730V. PTFE-GEM never showed a permanent breakdown...

  18. Improved patency and reduced intimal hyperplasia in PTFE grafts with luminal immobilized heparin compared with standard PTFE grafts at six months in a sheep model.

    Science.gov (United States)

    Pedersen, G; Laxdal, E; Ellensen, V; Jonung, T; Mattsson, E

    2010-06-01

    The aim of this study was to compare the performance of polytetrafluoroethylene (PTFE) grafts with luminal coating of immobilized heparin to that of standard PTFE grafts at six months. Twenty-eight common carotid arteries in fourteen sheep were bypassed with heparin-coated PTFE grafts (6 mm diameter, 6 cm length) on one side and standard PTFE grafts on the other. The grafts were explanted after six months. The thickness of intimal hyperplasia (IH) in open grafts was measured with histomorphometrical methods. Two of 14 heparinized PTFE grafts and nine of 14 grafts in the control PTFE-group were occluded at explantation (P=0.006). Six-month patency rates for heparinized PTFE grafts and for standard PTFE grafts were 86% and 36%, respectively. Mean graft anastomotic IH thickness in open grafts were 0.074 mm for heparinized PTFE grafts and 0.259 mm for PTFE-grafts (P=0.006). PTFE grafts with luminal coating containing immobilized heparin had significantly better patency and recruited less intimal hyperplasia than standard PTFE grafts at six months.

  19. Scalable bonding of nanofibrous polytetrafluoroethylene (PTFE) membranes on microstructures

    Science.gov (United States)

    Mortazavi, Mehdi; Fazeli, Abdolreza; Moghaddam, Saeed

    2018-01-01

    Expanded polytetrafluoroethylene (ePTFE) nanofibrous membranes exhibit high porosity (80%-90%), high gas permeability, chemical inertness, and superhydrophobicity, which makes them a suitable choice in many demanding fields including industrial filtration, medical implants, bio-/nano- sensors/actuators and microanalysis (i.e. lab-on-a-chip). However, one of the major challenges that inhibit implementation of such membranes is their inability to bond to other materials due to their intrinsic low surface energy and chemical inertness. Prior attempts to improve adhesion of ePTFE membranes to other surfaces involved surface chemical treatments which have not been successful due to degradation of the mechanical integrity and the breakthrough pressure of the membrane. Here, we report a simple and scalable method of bonding ePTFE membranes to different surfaces via the introduction of an intermediate adhesive layer. While a variety of adhesives can be used with this technique, the highest bonding performance is obtained for adhesives that have moderate contact angles with the substrate and low contact angles with the membrane. A thin layer of an adhesive can be uniformly applied onto micro-patterned substrates with feature sizes down to 5 µm using a roll-coating process. Membrane-based microchannel and micropillar devices with burst pressures of up to 200 kPa have been successfully fabricated and tested. A thin layer of the membrane remains attached to the substrate after debonding, suggesting that mechanical interlocking through nanofiber engagement is the main mechanism of adhesion.

  20. Properties of PTFE tape as a semipermeable membrane in fluorous reactions

    Directory of Open Access Journals (Sweden)

    Brendon A. Parsons

    2015-06-01

    Full Text Available In a PTFE tape phase-vanishing reaction (PV-PTFE, a delivery tube sealed with PTFE tape is inserted into a vessel which contains the substrate. The reagent diffuses across the PTFE tape barrier into the reaction vessel. PTFE co-polymer films have been found to exhibit selective permeability towards organic compounds, which was affected by the presence of solvents. In this study, we attempted to establish general trends of permeability of PTFE tape to different compounds and to better describe the process of solvent transport in PV-PTFE bromination reactions. Though PTFE tape has been reported as impermeable to some compounds, such as dimethyl phthalate, solvent adsorption to the tape altered its permeability and allowed diffusion through channels of solvent within the PTFE tape. In this case, the solvent-filled pores of the PTFE tape are chemically more akin to the adsorbed solvent rather than to the PTFE fluorous structure. The solvent uptake effect, which was frequently observed in the course of PV-PTFE reactions, can be related to the surface tension of the solvent and the polarity of the solvent relative to the reagent. The lack of pores in bulk PTFE prevents solvents from altering its permeability and, therefore, bulk PTFE is impermeable to most solvents and reagents. However, bromine, which is soluble in liquid fluorous media, diffused through the bulk PTFE. A better understanding of the PTFE phase barrier will make it possible to further optimize the PV-PTFE reaction design.

  1. Comparison of TEVAR resin beads, PAN fibers, and ePTFE membranes as a solid support for Aliquat-336 in immobilized liquid extraction chromatography for separation of actinides

    International Nuclear Information System (INIS)

    Joe Dauner; Steve Workman

    2012-01-01

    The following paper covers a comparison of two new systems to traditional TEVA R resin systems for the analytical separation of actinides by immobilized liquid-liquid extraction using Aliquat-336. The new systems are using expanded polytetrafluroethane (ePTFE) membrane or polyacrylonitrile (PAN) fibers as the solid support. The systems are compared in two ways. First in how much Aliquat-336 they contain with the Vs, ratio of volume of Aliquat-336 to volume of polymeric support, being 0.158, 0.483, and 0.590 for the TEVA R resin, PAN fibers, and the ePTFE systems, respectively. The second comparison is in their performance capacity of extraction of uranyl chloride anion complex. The fiber and resins systems show similar capacities, and the membrane system being an order of magnitude less than the other systems. A cost comparison demonstrates the savings advantages of using a fiber based support compared with resin and membrane support systems. (author)

  2. Design, Manufacturing, and In Vitro Testing of a Patient-Specific Shape-Memory Expander for Nose Reconstruction With Forehead Flap Technique.

    Science.gov (United States)

    Borghi, Alessandro; Rodgers, Will; Schievano, Silvia; Ponniah, Allan; O'Hara, Justine; Jeelani, Owase; Dunaway, David

    2016-01-01

    Forehead skin is widely acknowledged as a good donor site for total nasal reconstruction, thanks to its matching color, texture, and abundant vascularity. The forehead flap technique uses an axial pattern flap forehead skin to replace missing nasal tissue. To increase the amount of available tissue and reduce the size of the tissue defect after flap mobilization, tissue expanders may be used. Although this is a relatively established technique, limitations include reduced moldability of the forehead skin (which is thicker than the nasal skin), and the need for multiple sessions of expansion to achieve a sufficient yield to close the forehead.Shape-memory metals, such as nitinol, can be programmed to "remember" complex shapes. In this work, the methodology for producing a prototype of nitinol tissue expander able to mold the skin in a predetermined patient-specific skin shape is described. A realistic nose mold was manufactured using metal rapid prototyping; nitinol sheet and mesh were molded into nose-shape constructs, having hyperelastic as well as shape-memory capability. Computed tomography scanning was performed to assess the ability of the structure to regain its shape after phase transformation upon cooling within 2% of initial dimensions. The prototypes were implanted in a pig forehead to test its ability to impose a nose shape to the forehead skin.The shape-memory properties of nitinol offer the possibility of producing bespoke tissue expanders able to deliver complex, precisely designed skin envelopes. The hyperelastic properties of nitinol allow constant preprogrammed expansion forces to be generated throughout the expansion process.

  3. Assessment of a Polyester-Covered Nitinol Stent in the Canine Aorta and Iliac Arteries

    International Nuclear Information System (INIS)

    Castaneda, Flavio; Ball-Kell, Susan M.; Young, Kate; Li Ruizong

    2000-01-01

    Purpose: To evaluate the patency and healing characteristics of a woven polyester fabric-covered stent in the canine model.Methods: Twenty-four self-expanding covered stents were placed in the infrarenal aorta and bilateral common iliac arteries of eight dogs and evaluated at 1 (n = 2), 3 (n = 2), and 6 (n = 4) months. Stent assessment was done using angiography prior to euthanasia, and light and scanning electron microscopy.Results: Angiographically, just prior to euthanasia, 8 of 8 aortic and 14 of 16 iliac endovascular covered stents were patent. Histologically, the stented regions showed complete endothelialization 6 months after graft implantation. A neointima had formed inside the stented vessel regions resulting in complete encasement of the fabric-covered stent by 3 months after graft implantation. Medial compression with smooth muscle cell atrophy was present in all stented regions. Explanted stent wires, examined by scanning electron microscopy, showed pitting but no cracks or breakage.Conclusion: The covered stent demonstrated predictable healing and is effective in preventing stenosis in vessels 10.0 mm or greater in diameter but does not completely preclude stenosis in vessels 6.0 mm or less in diameter

  4. Nitinol: Tubing versus sputtered film - microcleanliness and corrosion behavior.

    Science.gov (United States)

    Wohlschlögel, Markus; Lima de Miranda, Rodrigo; Schüßler, Andreas; Quandt, Eckhard

    2016-08-01

    Corrosion behavior and microcleanliness of medical-device grade Nitinol tubing (Nix Ti1- x , x = 0.51; outer diameter 7 mm, wall thickness 0.5 mm), drawn from various ingot qualities, are compared to the characteristics of sputtered Nitinol film material (Nix Ti1- x , x = 0.51; thickness 50 µm). Electropolished tubing half-shell samples are tested versus as-received sputtered film samples. Inclusion size distributions are assessed using quantitative metallography and corrosion behavior is investigated by potentiodynamic polarization testing in phosphate-buffered saline at body temperature. For the sputtered film samples, the surface chemistry is additionally analyzed employing Auger Electron Spectroscopy (AES) composition-depth profiling. Results show that the fraction of breakdowns in the potentiodynamic polarization test correlates with number and size of the inclusions in the material. For the sputtered Nitinol film material no inclusions were detectable by light microscopy on the one hand and no breakdowns were found in the potentiodynamic polarization test on the other hand. As for electropolished Nitinol, the sputtered Nitinol film material reveals Nickel depletion and an Oxygen-to-Titanium intensity ratio of ∼2:1 in the surface oxide layer, as measured by AES. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1176-1181, 2016. © 2015 Wiley Periodicals, Inc.

  5. Percutaneous treatment of adult isthmic aortic coarctation: acute and long-term clinical and imaging outcome with a self-expandable uncovered nitinol stent.

    Science.gov (United States)

    Kische, Stephan; D'Ancona, Giuseppe; Stoeckicht, Yannik; Ortak, Jasmin; Elsässer, Albrecht; Ince, Hüseyin

    2015-01-01

    To present perioperative and long-term results of percutaneous treatment of adult isthmic coarctation of the aorta by means of a self-expandable closed-web uncovered nitinol stent (Sinus-XL, Optimed, Esslingen, Germany). Preoperative, perioperative, and long-term clinical and computed tomographic angiography data were collected and analyzed prospectively. A total of 52 consecutive patients were treated with the Sinus-XL stent. Mean age was 36.6 (21-67) years, peak invasive trans-coarctation of the aorta gradient was 54.7 ± 9.9 mm Hg, and upper body hypertension unresponsive to medical treatment was present in all patients. Mean stent diameter and length were 24.2 mm (22-28 mm) and 70.4 mm (40-80 mm), respectively. Eight patients (15.4%) required coarctation of the aorta predilatation. All patients underwent poststent dilatation with a noncompliant balloon. Postoperative peak gradient (3.3 ± 2.5 mm Hg) was reduced significantly (P stent collapse and secondary migration and documented stability in aortic diameter (18.3 ± 2.7 mm). Thirty patients (57.7%) were completely weaned-off antihypertensive medications and their use dropped from 2.6 to 0.9 drugs/patient (P self-expandable uncovered stent is safe and durable. The peculiar stent design maintains adequate localized radial strength over time with minimal trauma on the adjacent aortic wall and negligible device-related complications. Blood pressure control optimization is immediate and persistent even at long-term follow-up. © 2015 American Heart Association, Inc.

  6. Comparison of covered and uncovered self-expandable stents in the treatment of malignant biliary obstruction.

    Science.gov (United States)

    Flores Carmona, Diana Yamel; Alonso Lárraga, Juan Octavio; Hernández Guerrero, Angélica; Ramírez Solís, Mauro Eduardo

    2016-05-01

    Drainage with metallic stents is the treatment of choice in malignant obstructive jaundice. Technical and clinical success with metallic stents is obtained in over 90% and 80% of cases, respectively. There are self-expandable metallic stents designed to increase permeability. The aim of this study was to describe the results obtained with totally covered self-expandable and uncovered self-expandable metallic stents in the palliative treatment of malignant biliary obstruction. Sixty eight patients with malignant obstructive jaundice secondary to pancreatobiliary or metastatic disease not amenable to surgery were retrospectively included. Two groups were created: group A (covered self-expandable metallic stents) (n = 22) and group B (uncovered self-expandable metallic stents) (n = 46). Serum total bilirubin, direct bilirubin, alkaline phosphatase and gamma glutamyl transferase levels decreased in both groups and no statistically significant difference was detected (p = 0.800, p = 0.190, p = 0.743, p = 0.521). Migration was greater with covered stents but it was not statistically significant either (p = 0.101). Obstruction was greater in the group with uncovered stents but it was not statistically significant either (p = 0.476). There are no differences when using covered self-expandable stents or uncovered self-expandable stents in terms of technical and clinical success or complications in the palliative treatment of malignant obstructive jaundice.

  7. ESR study on free radicals trapped in crosslinked polytetrafluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Seguchi, Tadao

    1997-01-01

    Free radicals in crosslinked PTFE which formed by 60 Co γ-rays irradiation at 77 K and at room temperature were studied by electron spin resonance (ESR) spectroscopy. The crosslinked PTFE specimens with different crosslinking density were prepared by electron beam irradiation in the molten state. The ESR spectra observed in the irradiated crosslinked PTFE are much different from those in non-crosslinked PTFE (virgin); a broad singlet component increases with increasing the crosslinking density, G-value of radicals is much higher in crosslinked PTFE than in non-crosslinked one. Free radicals related to the broad component are trapped in the non-crystalline region of crosslinked PTFE and rather stable at room temperature, whereas radicals trapped in amorphous non-crosslinked PTFE are unstable at room temperature. It is thought that most of free radicals trapped in the crosslinked PTFE are formed in the crosslinked amorphous region. The trapped radicals decays around 383 K (110 o C) due to the molecular motion of α-relaxation. (Author)

  8. Properties of PTFE tape as a semipermeable membrane in fluorous reactions

    OpenAIRE

    Brendon A. Parsons; Olivia Lin Smith; Myeong Chae; Veljko Dragojlovic

    2015-01-01

    Summary In a PTFE tape phase-vanishing reaction (PV-PTFE), a delivery tube sealed with PTFE tape is inserted into a vessel which contains the substrate. The reagent diffuses across the PTFE tape barrier into the reaction vessel. PTFE co-polymer films have been found to exhibit selective permeability towards organic compounds, which was affected by the presence of solvents. In this study, we attempted to establish general trends of permeability of PTFE tape to different compounds and to better...

  9. Radiation-induced branching and crosslinking of poly(tetrafluoroethylene) (PTFE)

    International Nuclear Information System (INIS)

    Lappan, U.; Geissler, U.; Haeussler, L.; Jehnichen, D.; Pompe, G.; Lunkwitz, K.

    2001-01-01

    The effect of electron beams on poly(tetrafluoroethylene) (PTFE) at elevated temperatures above the melting point on oxygen-free conditions has been studied using differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), Fourier-transform infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and tensile test. The investigations have shown that the chemical structure and several properties of PTFE are greatly altered by the irradiation. DSC and WAXS indicate that the crystallinity of the PTFE irradiated with high doses is reduced. CF 3 side groups and branched structures are assumed to hinder the crystallization. TGA has shown that the thermal stability of the radiation-modified PTFE is considerably lower than that of unirradiated PTFE

  10. Endoscopically placed nitinol stents for pediatric tracheal obstruction.

    Science.gov (United States)

    Prasad, Mukesh; Bent, John P; Ward, Robert F; April, Max M

    2002-11-11

    To provide preliminary clinical data regarding endoscopically placed nitinol stents for children with tracheal obstruction as a temporizing measure to allow for trach tube decannulation while awaiting growth to allow for tracheal resection. This case series describes the experiences of two children (ages 5 and 15) who were dependent upon tracheotomy because of acquired tracheal obstruction. Both patients had combined tracheomalacia and tracheal stenosis. After failing tracheoplasty with rib graft augmentation both patients suffered from extensive tracheal disease, which was too long to allow for immediate tracheal resection. Endoscopic placement of nitinol stents in the obstructed tracheal segment using fluoroscopic guidance. All tracheotomy tubes were removed immediately after successful stent deployment with the patient still under general anesthesia. Four stents were placed in total. The first patient's initial stent was too narrow and was, therefore, removed and replaced at a later date with a larger diameter stent. The second patient experienced distal migration of his initial stent requiring stent removal and replacement at a later date. Both patients remain successfully decannulated (follow-up, 25 and 26 months) and are currently living more normal lives as they grow and await tracheal resection. Preliminary use of nitinol stents for pediatric tracheal obstruction has enabled successful decannulation in two children with complicated airways. Our results with this series of patients suggest that nitinol stents can be safely used in children as a temporizing measure until tracheal resection can be safely performed. With this approach children can live free from the hassles of trach care, social isolation and peer ridicule. Limited pediatric experience exists in the literature about nitinol stents. Thus, our experience with stent selection and placement will help others avoid problems encountered in this initial series. Copyright 2002 Elsevier Science Ireland

  11. Distribution of nickel after modified nitinol stent implantation in animals

    Science.gov (United States)

    Chepeleva, E.; Sergeevichev, D.; Lotkov, A.; Kashin, O.; Korobeynikov, A.; Kozyr, K.; Baystrukov, V.; Zubarev, D.; Kretov, E.; Pokushalov, E.

    2017-09-01

    Intravascular stenting of arteries in atherosclerotic lesions is one of the most frequently performed procedures in cardiovascular surgery today. Most stents are made of various stainless-steel alloys and other metals (such as nitinol). Nitinol is a biocompatible, superplastic and corrosion resistant material with an important feature of shape memory. However, the composition of this alloy includes nickel, which shows toxicity to the kidneys, liver, lungs, heart and other organs when it accumulates in the organism. In this research we investigated the nickel content in serum, urine and hair of the laboratory animals after implantation of nitinol stents treated with plasma ionic surface modification by silicon.

  12. Recent observations of particulates in Nitinol

    International Nuclear Information System (INIS)

    Shabalovskaya, S.; Anderegg, J.; Humbeeck, J. van

    2008-01-01

    In spite of 40 years of history of Nitinol, the issues regarding its inclusions have been poorly explored. In our brief studies, conducted within the projects on surface design using Auger, energy-dispersive X-ray spectroscopy and scanning electrons microscopy, we discovered that particulates in NiTi medical alloys were always based on Ti: either ∼Ti 2 NiO oxide, titanium dioxide, titanium carbide or oxidized titanium carbide. Nonmetallic particles were rather brittle, had various shapes and sizes, and revealed different solubility in chemical solutions. The matrix material surrounding inclusions showed a tendency to localized corrosion. It was hypothesized that release of inclusion debris in the human body due to corrosion might compromise biocompatibility of Nitinol

  13. [NITINOL shape memory staple for osteosynthesis of the scaphoid].

    Science.gov (United States)

    Winkel, Reiner; Schlageter, Michael

    2009-11-01

    Reconstruction of the scaphoid with use of NITINOL shape "memory" staples. Unstable fractures and nonunion of the middle third of the scaphoid, which need open reduction and internal fixation from palmar. The staples can only be used, if the arms of the staples can be inserted parallel to and at a distance of 3 mm to the fracture line. Allergy to nickel. Cases in which the arms of the staple cannot be inserted parallel to and at best 3 mm apart from the fracture line. In fractures, open reduction of the scaphoid through a palmar approach. If necessary, interposition of a bone graft and Kirschner wire transfixation. Drilling of the drill holes parallel and at a distance of 3 mm to the fracture line. Insertion of the NITINOL staple. In nonunion, excision of the fibrous nonunion, refreshening of the fracture surfaces, interposition of a bone graft and, if needed, fixation with a Kirschner wire. Drilling of the drill holes for the NITINOL staple and insertion of the staple. Within a few minutes the warming-up staple contracts and thereby compresses the scaphoid. Immobilization in a short cast with thumb support for 6 weeks. Control for bone healing by radiographs or computed tomography. Staples, which do not cause hardware problems, are not removed. Kirschner wires are removed after bone healing. From October 1995 to December 2006, the authors used NITINOL staples for 65 osteosyntheses of the scaphoid. Indications were 15 unstable fractures, 47 nonunions, and three partial necroses. 61 out of 65 scaphoids healed without further surgery, three of the 61 patients showed a delayed healing. Two of the four nonunions were related to the use of the NITINOL staples. Seven staples were removed, one for loosening. NITINOL shape memory staples have proven to be very helpful for osteosynthesis in fractures and nonunion of the scaphoid, if the prerequisites are given for their use.

  14. Study of PTFE wick structure applied to loop heat pipe

    International Nuclear Information System (INIS)

    Wu, Shen-Chun; Gu, Tzu-Wei; Wang, Dawn; Chen, Yau-Ming

    2015-01-01

    This study investigated the use of sintered PTFE (polytetrafluoroethylene) particles as the wick material of loop heat pipe (LHP), taking advantage of PTFE's low thermal conductivity to reduce the heat leakage problem during LHP's operation. Different PTFE particle sizes were tried to find the one that resulted in the best wick; LHP performance tests were then conducted, and PTFE's potential for application to LHP was examined. Using PTFE particles ranging from 300–500 μm in size, the best wick properties were effective pore radius of 1.7 μm, porosity of 50%, and permeability of 6.2 × 10 −12  m 2 . LHP performance tests showed that, under typical electronic devices' operating temperature of 85 °C, the heat load reached 450 W, the thermal resistance was 0.145 °C/W, and the critical heat load (dryout heat load) reached 600 W. Compared to LHP with a nickel wick, LHP with a PTFE wick had a significantly lower operating temperature, indicating reduced heat leakage during operation, while having comparable performance; also, during the manufacturing process, a PTFE wick required lower sintering temperature, needed shorter sintering time, and had no need for hydrogen gas during sintering. The results of this study showed that, for high heat transfer capacity cooling devices, PTFE wicks possess great potential for applications to LHPs. - Highlights: • The performances of PTFE and nickel wicks in LHP are comparable for the first time. • PTFE wick allows for lower operating temperature and thus pressure in LHP system. • A wick requiring lower temperature and manufacturing cost and less time was made. • PTFE wick has potential to replace metal wick and enhance performance of LHP

  15. Fatigue of Nitinol: The state-of-the-art and ongoing challenges.

    Science.gov (United States)

    Mahtabi, M J; Shamsaei, Nima; Mitchell, M R

    2015-10-01

    Nitinol, a nearly equiatomic alloy of nickel and titanium, has been considered for a wide range of applications including medical and dental devices and implants as well as aerospace and automotive components and structures. The realistic loading condition in many of these applications is cyclic; therefore, fatigue is often the main failure mode for such components and structures. The fatigue behavior of Nitinol involves many more complexities compared with traditional metal alloys arising from its uniqueness in material properties such as superelasticity and shape memory effects. In this paper, a review of the present state-of-the-art on the fatigue behavior of superelastic Nitinol is presented. Various aspects of fatigue of Nitinol are discussed and microstructural effects are explained. Effects of material preparation and testing conditions are also reviewed. Finally, several conclusions are made and recommendations for future works are offered. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Treatment of esophagopleural fistulas using covered retrievable expandable metallic stents.

    Science.gov (United States)

    Kim, Tae-Hyung; Shin, Ji Hoon; Kim, Kyung Rae; Park, Jung-Hoon; Kim, Jin Hyoung; Song, Ho-Young

    2014-04-01

    To evaluate the clinical efficacy of placement of covered retrievable expandable metallic stents for esophagopleural fistulas (EPFs). During the period 1997-2013, nine patients with EPF were treated using covered retrievable expandable metallic stents. The underlying causes of EPF were esophageal carcinoma (n = 6), lung cancer (n = 2), and postoperative empyema for Boerhaave syndrome (n = 1). Technical success was achieved in eight patients (88.9%). In one patient, incomplete EPF closure was due to incomplete stent expansion. Clinical success, defined as complete EPF closure within 7 days, was achieved in five patients (55.6%). Overall fistula persistence (n = 1) or reopening (n = 4) occurred in five patients (55.6%) 0-15 days after stent placement. The causes of reopening were due to the gap between the stent and the esophagus (n = 3) or stent migration (n = 1). For fistula persistence or reopening, additional interventional management, such as gastrostomy, stent removal, or stent reinsertion, was performed. Stent migration occurred as a complication in one patient with EPF from a benign cause secondary to postoperative empyema. In the eight patients who died during the follow-up period, the mean and median survival times were 78.8 days and 46 days, respectively. Placement of a covered expandable metallic esophageal stent for the palliative treatment of EPF is technically feasible, although the rate of clinical success was poor secondary to fistula persistence or reopening. Fistula reopening was caused by the gap between the stent and the esophagus or by stent migration, and additional interventional treatment was useful to ensure enteral nutritional support. Copyright © 2014 SIR. Published by Elsevier Inc. All rights reserved.

  17. The use of expanded microporous polytetrafluoroethylene for limb salvage: a preliminary report.

    Science.gov (United States)

    Campbell, C D; Brooks, D H; Webster, M W; Bahnson, H T

    1976-05-01

    Initial laboratory and clinical evaluations of a new prosthetic material, expanded microporous polytetrafluoroethylene (PTFE), for small vessel replacement is promising and encourages further clinical trial. Frequently the autogenous saphenous vein is not available for bypass procedures, and alternative arterial substitutes have not proved reliable for replacement of small vessels. In this study, 15 patients with impending loss of limb and no available saphenous vein underwent revascularization of the lower extremity with expanded microporous PTFE grafts. Thirteen of 15 patients now demonstrate viable extremities with a resulting over-all early patency and limb salvage rate of 87 percent for this series. Follow-up ranges from one to 8 months. Seven patients had diabetes mellitus and eight had atherosclerotic heart disease. Nine grafts crossed the knee joint. In all patients arterial runoff was poor. Six patients had previous femoropopliteal bypasses, five with autogenous veins and one with Dacron velour. Two patients had multiple previous operations that failed, first with autogenous vein and later with fabric grafts. The current limb salvage and patency rate of 87 percent in high-risk patients suggests that expanded PTFE may be the prosthesis of choice when an autogenous vein is not available and possibly an equally good substitute when the venous autograft is available.

  18. Thermal radiation properties of PTFE plasma

    Science.gov (United States)

    Liu, Xiangyang; Wang, Siyu; Zhou, Yang; Wu, Zhiwen; Xie, Kan; Wang, Ningfei

    2017-06-01

    To illuminate the thermal transfer mechanism of devices adopting polytetrafluoroethylene (PTFE) as ablation materials, the thermal radiation properties of PTFE plasma are calculated and discussed based on local thermodynamic equilibrium (LTE) and optical thin assumptions. It is clarified that line radiation is the dominant mechanism of PTFE plasma. The emission coefficient shows an opposite trend for both wavelength regions divided by 550 nm at a temperature above 15 000 K. The emission coefficient increases with increasing temperature and pressure. Furthermore, it has a good log linear relation with pressure. Equivalent emissivity varies complexly with temperature, and has a critical point between 20 000 K to 25 000 K. The equivalent cross points of the average ionic valence and radiation property are about 10 000 K and 15 000 K for fully single ionization.

  19. The Scandinavian Propaten(®) trial - 1-year patency of PTFE vascular prostheses with heparin-bonded luminal surfaces compared to ordinary pure PTFE vascular prostheses - a randomised clinical controlled multi-centre trial

    DEFF Research Database (Denmark)

    Lindholt, J S; Gottschalksen, B; Johannesen, N

    2011-01-01

    To compare 1-year potencies' of heparin-bonded PTFE [(Hb-PTFE) (Propaten(®))] grafts with those of ordinary polytetraflouroethylene (PTFE) grafts in a blinded, randomised, clinically controlled, multi-centre study.......To compare 1-year potencies' of heparin-bonded PTFE [(Hb-PTFE) (Propaten(®))] grafts with those of ordinary polytetraflouroethylene (PTFE) grafts in a blinded, randomised, clinically controlled, multi-centre study....

  20. Preparation and Properties of PTFE-PMMA Core-Shell Nanoparticles and Nanocomposites

    Directory of Open Access Journals (Sweden)

    Diego Antonioli

    2012-01-01

    Full Text Available The preparation of polytetrafluoroethylene-poly(methyl methacrylate (PTFE-PMMA core-shell particles was described, featuring controlled size and narrow size distribution over a wide compositional range, through a seeded emulsion polymerization starting from a PTFE seed of 26 nanometers. Over the entire MMA/PTFE range, the particle size increases as the MMA/PTFE ratio increases. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomer and the PTFE seed. Particles in the 80–240 nm range can be prepared with uniformity indexes suited to build 2D and 3D colloidal crystals. These core-shell particles were employed to prepare nanocomposites with different compositions, through an annealing procedure at a temperature higher than the glass transition temperature of the shell forming polymer. A perfect dispersion of the PTFE particles within the PMMA matrix was obtained and optically transparent nanocomposites were prepared containing a very high PTFE amount.

  1. Transjugular Intrahepatic Portosystemic Shunts in Patients with Cirrhosis with Refractory Ascites: Comparison of Clinical Outcomes by Using 8- and 10-mm PTFE-covered Stents.

    Science.gov (United States)

    Miraglia, Roberto; Maruzzelli, Luigi; Tuzzolino, Fabio; Petridis, Ioannis; D'Amico, Mario; Luca, Angelo

    2017-07-01

    Purpose To compare the efficacy and complications of transjugular intrahepatic portosystemic shunt (TIPS) creation performed by using a 10-mm or an 8-mm-diameter polytetrafluoroethylene (PTFE)-covered stent in a consecutive series of patients with cirrhosis with refractory ascites (RA). Materials and Methods The institutional review board approved this retrospective study and informed consent was waived. One hundred seventy-one patients with RA (mean age, 58.7 years ± 10.3; 95% confidence interval [CI]: 57.2 years, 60.3 years) had undergone TIPS placement by using 10-mm (60 patients) or 8-mm (111 patients) covered stent between January 2004 and December 2012. Median follow-up time was 16.8 months (range, 3.4-84.8 months). Hemodynamic changes, incidence of hepatic encephalopathy, and long-term (>3 months) need for paracentesis after TIPS placement were evaluated and calculated by using the Kaplan-Meier method and were compared by using the log-rank test. Results Pre-TIPS demographics and clinical characteristics of the two groups were comparable. The portosystemic gradient before TIPS was 17.0 mm Hg ± 4.2 (95% CI: 15.9 mm Hg, 18.1 mm Hg) in the 10-mm group versus 16.1 mm Hg ± 3.7 (95% CI: 15.4 mm Hg, 16.8 mm Hg) in the 8-mm group (P = .164). After TIPS, the portosystemic gradient was 6.5 mm Hg ± 3.4 (95% CI: 5.7 mm Hg, 7.4 mm Hg) in the 10-mm group versus 7.5 mm Hg ± 2.6 (95% CI: 6.9 mm Hg, 7.9 mm Hg) in the 8-mm group (P = .039). The long-term need for paracentesis was greater in the 8-mm group (64 of 111 patients [58%] vs 18 of 60 patients [31%], P = .003). Overall, hepatic encephalopathy was similar in both groups (45 of 111 patients [41%] vs 26 of 60 patients [44%], P = .728). Conclusion A10-mm PTFE-covered stent leads to better control of RA secondary to portal hypertension in patients with cirrhosis, compared with an 8-mm stent, without increasing the incidence of hepatic encephalopathy. © RSNA, 2017.

  2. The corrosion resistance of Nitinol alloy in simulated physiological solutions

    International Nuclear Information System (INIS)

    Milošev, Ingrid; Kapun, Barbara

    2012-01-01

    The corrosion behaviour of Nitinol alloy containing nearly equi-atomic composition of nickel and titanium and its constituent metals (nickel and titanium) was investigated in simulated Hanks physiological solution (pH value 7.5) and pH modified simulated Hanks physiological solution (pH values 4.5 and 6.5) and by electrochemical method of anodic potentiodynamic polarization at 37 °C. In this chloride-rich medium the corrosion stability of Nitinol is limited by the susceptibility to localized corrosion and is in that sense more similar to nickel than to titanium. The corrosion stability of Nitinol is strongly dependent on the surface preparation—grinding, polishing or chemical etching. Whereas a ground surface is not resistant to localized corrosion, polished and chemically etched surfaces are resistant to this type of corrosion attack. The reasons for this behaviour were investigated through metallurgical, topographical and chemical properties of the surface as a function of surface preparation. For that purpose, scanning electron microscopy combined with chemical analysis, confocal microscopy and X-ray photoelectron spectroscopy were used. The surface roughness decreased in the following order: chemically etched > ground > polished surface. Besides differences in topography, distinct differences in the chemical composition of the outermost surface are observed. Ground, rough surfaces comprised mainly titanium oxides and small amounts of nickel metal. Chemically etched and, especially, polished surfaces are composed of a mixture of titanium, nickel and titanium oxides, as studied by angle resolved X-ray photoelectron spectroscopy. These results emphasize the importance of detailed investigation of the metal surface since small differences in surface preparation may induce large differences in corrosion stability of material when exposed to corrosive environments. - Highlights: ► The corrosion resistance of Nitinol is dependent on the surface preparation.

  3. Magnetorheological fluid based on thixotropic PTFE-oil organogel

    Science.gov (United States)

    Zhang, Hansong; Yan, Hua; Hu, Zhide; Yang, Jianjian; Niu, Fanghao

    2018-04-01

    Polytetrafluoroethylene (PTFE) micropowders were employed in this work to fabricate PTFE-oil organogel, then carbonyl iron particles were dispersed in this thixotropic organogel to prepare magnetorheological fluids without any other additives. By performing a comparative investigation of MRFs' performances, enhanced magnetorheological response, suspension stability and tribological performance were obtained contrast to pure silicon oil based MRFs. The experimental results revealed a changeable viscosity of organogel, considerable increases in thixotropy also can be observed with the increase of PTFE content. Sedimentation tests demonstrated a much better suspension stability of MRFs based on organogel, suggesting that the internal network microstructures formed by hydrogen bonds between PTFE microparticles and oil molecular chains are likely to impose the gaps among magnetic particles thus hinder the particle aggregation and sedimentation. Moreover, a critical PTFE volume fraction about 4.7 vol% was recognized in this study, lower content organogels tended to display enhanced yield stresses contrast to pure silicon oil based MRFs while high content organogels showed slightly lower ones. It may suggest a compromise between nonmagnetic particle adsorption and the reinforcement effect of network microstructures. The adsorption is likely to decrease the saturation magnetization of carbonyl iron particles and to hinder the formation of field-induced chains, however, the reinforcement effect tends to strengthen these magnetic chains. Besides, the tribological tests confirmed the lubricant effects of PTFE-oil organogel by acquiring rather sharp decreases in friction coefficients of organogel based MRFs especially in the presence of magnetic field.

  4. Wear resistant PTFE thin film enabled by a polydopamine adhesive layer

    International Nuclear Information System (INIS)

    Beckford, Samuel; Zou, Min

    2014-01-01

    The influence of a polydopamine (PDA) adhesive layer on the friction and wear resistance of polytetrafluoroethylene (PTFE) thin films coated on stainless steel was investigated. The friction and wear tests were carried out using a ball on flat configuration under a normal load of 50 g, sliding speed of 2.5 mm/s, and stroke length of 15 mm. It is found that the PDA/PTFE film is able to withstand approximately 500 times more rubbing cycles than the PTFE film alone. X-ray photoelectron spectroscopy (XPS) results show that a tenacious layer of PTFE remains adhered to the PDA layer, which enables the durability of the PDA/PTFE film. Because of the relatively low thickness of the film, PDA/PTFE shows great potential for use in applications where durable, thin films are desirable

  5. Early and long-term clinical and radiological follow-up results of expanded-polytetrafluoroethylene-covered stent-grafts for transjugular intrahepatic portosystemic shunt procedures

    International Nuclear Information System (INIS)

    Maleux, Geert; Heye, Sam; Thijs, Maria; Wilms, Guy; Nevens, Frederik; Verslype, Chris; Wilmer, Alexander

    2004-01-01

    The purpose of this study was to assess the therapeutic efficacy and immediate and long-term safety of expanded-tetrafluoroethylene covered stent-grafts for transjugular intrahepatic portosystemic shunts in patients with portal hypertension-related complications. A cohort of 56 patients suffering from severe portal hypertension-related complications underwent implantation of an expanded-polytetrafluoroethylene-covered stent-graft. All patients suffered from severe liver cirrhosis graded Child-Pugh A (n=8; 16%), B (n=13; 21%) or C (n=35; 63%). In 44 patients, the stent-graft was placed during the initial TIPS procedure (de novo TIPS); in the other 12 patients, the stent-graft was placed to repermeabilize the previously placed bare stent (TIPS revision). Follow-up was performed with clinical assessment, duplex ultrasound and, if abnormal or inconclusive, with invasive venography and pressure measurements. Per- en immediate post-procedural complications occurred in four patients (4/56, 7%). None of them was lethal. During follow-up, stent occlusion appeared in one patient and stenosis in two; no recurrence of bleeding was noted in all patients treated for variceal bleeding (n=28), and 24 of the 28 patients (86%) suffering from refractory ascites and/or hepatic hydrothorax were free of regular paracenteses and/or drainage of pleural effusion after shunt creation. The 30-day and global mortality for the total study population (n=56) was, respectively, 7% (n=4) and 28.5% (n=16). In the patient subgroup with variceal bleeding (n=28), 30-day mortality was 3.5% (n=1) and global mortality 14.2% (n=4). In the ascites and/or hydrothorax subgroup (n=28), 8.1% (n=3) mortality at 30 days was found and global mortality was 32.4% (n=12). In 10 patients of the 56 studied patients (18%), isolated hepatic encephalopathy occurred, which was lethal in 4 (Child C) patients (7%). Three of these four patients died within the 1st month after TIPS placement. A very high primary patency rate

  6. Early and long-term clinical and radiological follow-up results of expanded-polytetrafluoroethylene-covered stent-grafts for transjugular intrahepatic portosystemic shunt procedures

    Energy Technology Data Exchange (ETDEWEB)

    Maleux, Geert; Heye, Sam; Thijs, Maria; Wilms, Guy [University Hospitals Gasthuisberg, Department of Radiology, Leuven (Belgium); Nevens, Frederik; Verslype, Chris [University Hospitals Gasthuisberg, Department of Hepatology, Leuven (Belgium); Wilmer, Alexander [University Hospitals Gasthuisberg, Department of Medical Intensive Care Unit, Leuven (Belgium)

    2004-10-01

    The purpose of this study was to assess the therapeutic efficacy and immediate and long-term safety of expanded-tetrafluoroethylene covered stent-grafts for transjugular intrahepatic portosystemic shunts in patients with portal hypertension-related complications. A cohort of 56 patients suffering from severe portal hypertension-related complications underwent implantation of an expanded-polytetrafluoroethylene-covered stent-graft. All patients suffered from severe liver cirrhosis graded Child-Pugh A (n=8; 16%), B (n=13; 21%) or C (n=35; 63%). In 44 patients, the stent-graft was placed during the initial TIPS procedure (de novo TIPS); in the other 12 patients, the stent-graft was placed to repermeabilize the previously placed bare stent (TIPS revision). Follow-up was performed with clinical assessment, duplex ultrasound and, if abnormal or inconclusive, with invasive venography and pressure measurements. Per- en immediate post-procedural complications occurred in four patients (4/56, 7%). None of them was lethal. During follow-up, stent occlusion appeared in one patient and stenosis in two; no recurrence of bleeding was noted in all patients treated for variceal bleeding (n=28), and 24 of the 28 patients (86%) suffering from refractory ascites and/or hepatic hydrothorax were free of regular paracenteses and/or drainage of pleural effusion after shunt creation. The 30-day and global mortality for the total study population (n=56) was, respectively, 7% (n=4) and 28.5% (n=16). In the patient subgroup with variceal bleeding (n=28), 30-day mortality was 3.5% (n=1) and global mortality 14.2% (n=4). In the ascites and/or hydrothorax subgroup (n=28), 8.1% (n=3) mortality at 30 days was found and global mortality was 32.4% (n=12). In 10 patients of the 56 studied patients (18%), isolated hepatic encephalopathy occurred, which was lethal in 4 (Child C) patients (7%). Three of these four patients died within the 1st month after TIPS placement. A very high primary patency rate

  7. Improvement of radiation resistance for polytetrafluoroethylene(PTFE) by radiation cross-linking

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Seguchi, Tadao.

    1996-01-01

    The crosslinked polytetrafluoroethylene(PTFE) was prepared by electron beams irradiation technique in the molten state at 340degC ± 3degC in inert gas atmosphere. The crosslinking density was changed by the irradiation dose. The radiation resistance of crosslinked PTFE was investigated on the mechanical properties after irradiation by γ-rays at room temperature under vacuum and in air. The dose at half value of elongation at break was about 1MGy for 500kGy-crosslinked PTFE, while the dose for non-crosslinked PTFE was only 3.5kGy. It was found that the radiation resistance of PTFE was extremely improved by crosslinking. (author)

  8. Degradation and crosslinking of PTFE due to irradiation

    International Nuclear Information System (INIS)

    Tutiya, Mituaki

    1995-01-01

    In this report, we summarized all our experimental results concerning about the effects of Co-60 γ rays irradiation on polytetrafluoroethylene (PTFE). The NMR spectra, the mechanical properties and others of PTFE were measured. The increase in the degree of crystallinity, the lowering of the 19degC transition temperature and that of the melting temperature due to irradiation were observed. The effect of post-irradiation heat treatment were also observed. In each case, the main causes of these effects were attributed to the radiation-induced main chain scission. In the case of PTFE irradiated at 320-360degC in vacuum, we found that the effect of radiation-induced crosslinking were observed. By using our new theories, these experimental results which were measured in the crystalline and the amorphous regions of the irradiated PTFE were discussed, and a satisfactory agreement between the theories and the experiments was obtained. (author)

  9. Superficial femoral artery TASC D Registry: twelve-month effectiveness analysis of the Pulsar-18 SE nitinol stent in patients with critical limb ischemia.

    Science.gov (United States)

    Lichtenberg, M; Stahlhoff, W; Boese, D

    2013-08-01

    Single center observational study analyzing the primary patency rate and freedom from target lesions revascularization rate of the Pulsar-18 nitinol stent after recanalization of long superficial femoral artery (SFA) occlusions (TASC D) in 22 patients with critical limb ischemia (CLI). Between 1/2011 and 7/2011, 22 consecutive patients (9 male, 13 female) with chronic total occlusions (CTO) of the femoro-popliteal arteries presenting with CLI (17 patients with Rutherford 4 score, and 5 patients with Rutherford 5 score) were enrolled and successfully recanalized using the Pulsar-18 self-expanding (SE) nitinol stent (BIOTRONIK AG, Buelach, Switzerland). Primary patency at 12 months was defined as no binary restenosis (>50%) on Duplex ultrasound (PSVRPulsar-18 SE nitinol stent was 77% with a per protocol restenosis in 5 of 22 patients. Seventeen patients showed a walking capacity on treadmill test >300 meters (Rutherford II). Two patients with a documented restenosis were Rutherford, these patients were treated conservatively. Three patients with restenosis and a Rutherford III score were scheduled for an endovascular target lesion revascularization leading to a freedom from target lesion revascularization rate of 86%. Endovascular intervention of long SFA occlusions using subintimal or intraluminal recanalization technique with implantation of the Pulsar-18 SE nitinol stent in CLI patients is safe and clinically effective with a primary patency rate after 12 months of 77% and a freedom from target lesion revascularization rate of 86%.

  10. The effects of Nitinol phases on corrosion and fatigue behavior

    Science.gov (United States)

    Denton, Melissa

    The purpose of these studies was to provide a detailed understanding of Nitinol phases and their effects on corrosion and fatigue life. The two primary phases, austenite and martensite, were carefully evaluated with respect to material geometry, corrosion behavior, wear, and fatigue life. Material characterization was performed using several techniques that include metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray photoelectron spectrum (XPS), and Auger electron spectroscopy (AES). Uniaxial tensile tests were conducted to determine the mechanical properties such as elongation, ultimate tensile strength, modulus, transformation strain, and plateau stress. In addition, accelerated wear testing and four point bend fatigue testing were completed to study the fatigue life and durability of the material. The corrosion of Nitinol was found to be dependent on various surface conditions. Electrochemical corrosion behavior of each phase was investigated using cyclic potentiodyamic polarization testing. The corrosion response of electropolished Nitinol was found to be acceptable, even after durability testing. Stress-induced martensite had a lower breakdown potential due to a rougher surface morphology, while thermally induced martensite and austenite performed similarly well. The surface conditioning also had a significant effect on Nitinol mechanical properties. Electropolishing provided a smooth mirror finish that reduced localized texture and enhanced the ductility of the material. Quasi-static mechanical properties can be good indicators of fatigue life, but further fatigue testing revealed that phase transformations had an important role as well. The governing mechanisms for the fatigue life of Nitinol were determined to be both martesitic phase transformations and surface defects. A new ultimate dislocation strain model was proposed based on specific accelerated step-strain testing.

  11. Effect of gamma radiation on graphite - PTFE dry lubrication system

    Science.gov (United States)

    Singh, Sachin; Tyagi, Mukti; Seshadri, Geetha; Tyagi, Ajay Kumar; Varshney, Lalit

    2017-12-01

    An effect of gamma radiation on lubrication behavior of graphite -PTFE dry lubrication system has been studied using (TR-TW-30L) tribometer with thrust washer attachment in plane contact. Different compositions of graphite and PTFE were prepared and irradiated by gamma rays. Gamma radiation exposure significantly improves the tribological properties indicated by decrease in coefficient of friction and wear properties of graphite -PTFE dry lubrication system. SEM and XRD analysis confirm the physico-chemical modification of graphite-PTFE on gamma radiation exposure leading to a novel dry lubrication system with good slip and anti friction properties.

  12. Study on poly-electrolyte membrane of crosslinked PTFE by radiation-grafting

    International Nuclear Information System (INIS)

    Sato, Kohei; Ikeda, Shigetoshi; Iida, Minoru; Oshima, Akihiro; Tabata, Yoneho; Washio, Masakazu

    2003-01-01

    Polymer electrolyte fuel cell membrane based on crosslinked polytetrafluoroethylene (PTFE) [RX-PTFE] has been processed by radiation-grafting with reactive styrene monomers by γ-rays under atmospheric circumstances, and the characteristic properties of the obtained membranes have been studied. The grafting yields of styrene monomer onto RX-PTFE, which have various crosslinking densities, were in the range of 5-100%. At the reaction period of 24 h, the grafting yields for RX-PTFE with low crosslinking density, which was reacted at 60 deg. C, achieved 94%. As a tendency, the lower grafting temperature gives higher grafting ratio of styrene onto RX-PTFE. Moreover, the yields of subsequent sulfonation for all samples were close to 100%. Mechanical properties were decreased with increasing grafting yields; especially the membrane with higher grafting yields was brittle. Ion exchange capacity of sulfonated RX-PTFE reached 1.1 meq/g while maintaining the mechanical properties

  13. Immobilisation of a fibrillin-1 fragment enhances the biocompatibility of PTFE.

    Science.gov (United States)

    Hajian, Hamid; Wise, Steven G; Bax, Daniel V; Kondyurin, Alexey; Waterhouse, Anna; Dunn, Louise L; Kielty, Cay M; Yu, Young; Weiss, Anthony S; Bilek, Marcela M M; Bannon, Paul G; Ng, Martin K C

    2014-04-01

    Current vascular biomaterials exhibit poor biocompatibility characterised by failure to promote endothelialisation, predisposition to neoinitmal hyperplasia and excessive thrombogenicity. Fibrillin-1, a major constituent of microfibrils is associated with elastic fibres in the arterial wall. Fibrillin-1 binds to endothelial cells through an RGD cell adhesion motif in the fourth TB module. The RGD motif is present in PF8, a recombinant fibrillin-1 fragment. We investigated the potential of PF8 to improve the biocompatibility of PTFE. PF8 enhanced endothelial cell attachment and cell proliferation to a greater extent than fibronectin (pPTFE using plasma immersion ion implantation (PIII), retained these favourable cell interactive properties, again promoting endothelial cell attachment and proliferation. The thrombogenicity of covalently bound PF8 on PTFE was assessed in both static and dynamic conditions. In static conditions, uncoated PIII treated PTFE was more thrombogenic than untreated PTFE, while PF8 coating reduced thrombogenicity. Under flow, there was no difference in the thrombogenicity of PF8 coated PTFE and untreated PTFE. Immobilised PF8 shows a striking ability to promote attachment and growth of endothelial cells on PTFE, while providing a non-thrombogenic surface. These features make PF8 a promising candidate to improve the biocompatibility of current synthetic vascular grafts. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  14. Fully covered self-expandable metal stents (SEMS), partially covered SEMS and self-expandable plastic stents for the treatment of benign esophageal ruptures and anastomotic leaks.

    Science.gov (United States)

    van Boeckel, Petra G A; Dua, Kulwinder S; Weusten, Bas L A M; Schmits, Ruben J H; Surapaneni, Naveen; Timmer, Robin; Vleggaar, Frank P; Siersema, Peter D

    2012-02-29

    Benign esophageal ruptures and anastomotic leaks are life-threatening conditions that are often treated surgically. Recently, placement of partially and fully covered metal or plastic stents has emerged as a minimally invasive treatment option. We aimed to determine the clinical effectiveness of covered stent placement for the treatment of esophageal ruptures and anastomotic leaks with special emphasis on different stent designs. Consecutive patients who underwent placement of a fully covered self-expandable metal stent (FSEMS), a partially covered SEMS (PSEMS) or a self-expanding plastic stent (SEPS) for a benign esophageal rupture or anastomotic leak after upper gastrointestinal surgery in the period 2007-2010 were included. Data on patient demographics, type of lesion, stent placement and removal, clinical success and complications were collected A total of 52 patients received 83 esophageal stents (61 PSEMS, 15 FSEMS, 7 SEPS) for an anastomotic leak (n=32), iatrogenic rupture (n=13), Boerhaave's syndrome (n=4) or other cause (n=3). Endoscopic stent removal was successful in all but eight patients treated with a PSEMS due to tissue ingrowth. Clinical success was achieved in 34 (76%, intention-to-treat: 65%) patients (PSEMS: 73%, FSEMS: 83%, SEPS: 83%) after a median of 1 (range 1-5) stent and a median stenting time of 39 (range 7-120) days. In total, 33 complications in 24 (46%) patients occurred (tissue in- or overgrowth (n=8), stent migration (n=10), ruptured stent cover (all Ultraflex; n=6), food obstruction (n=3), severe pain (n=2), esophageal rupture (n=2), hemorrhage (n=2)). One (2%) patient died of a stent-related cause. Covered stents placed for a period of 5-6 weeks may well be an alternative to surgery for treating benign esophageal ruptures or anastomotic leaks. As efficacy between PSEMS, FSEMS and SEPS is not different, stent choice should depend on expected risks of stent migration (SEPS and FSEMS) and tissue in- or overgrowth (PSEMS).

  15. Proton exchange membranes prepared by grafting of styrene/divinylbenzene into crosslinked PTFE membranes

    International Nuclear Information System (INIS)

    Li Jingye; Ichizuri, Shogo; Asano, Saneto; Mutou, Fumihiro; Ikeda, Shigetoshi; Iida, Minoru; Miura, Takaharu; Oshima, Akihiro; Tabata, Yoneho; Washio, Masakazu

    2005-01-01

    Thin PTFE membranes were prepared by coating the PTFE dispersion onto the aluminum films. Thus the thin crosslinked PTFE (RX-PTFE) membranes were obtained by means of electron beam irradiation above the melting temperature of PTFE under oxygen-free atmosphere. The RX-PTFE membranes were pre-irradiated and grafted by styrene with or without divinylbenzene (DVB) in liquid phase. The existence of DVB accelerated the initial grafting rate. The styrene grafted RX-PTFE membranes are white colored, on the other hand, the styrene/DVB grafted RX-PTFE membranes are colorless. The proton exchange membranes (PEMs) were obtained by sulfonating the grafted membranes using chlorosulfonic acid. The ion exchange capacity (IEC) values of the PEMs ranging from 1.5 to 2.8 meq/g were obtained. The PEMs made from the styrene/DVB grafted membranes showed higher chemical stability than those of the styrene grafted membranes under oxidative circumstance

  16. Method of radiation degradation of PTFE under vacuum conditions

    Energy Technology Data Exchange (ETDEWEB)

    Korenev, Sergey E-mail: sergey_korenev@steris.com

    2004-10-01

    A new method of radiation degradation of Polytetrafluoroethylene (PTFE) under vacuum conditions is considered in this report. The combination of glow gas discharge and electrical surface discharge (on surface and inside PTFE) increases the efficiency of thermal-radiation degradation. The main mechanism of this degradation method consists of the breaking of C-C and C-F bonds. The vacuum conditions allow decreasing of the concentration of toxic compounds, such as a HF. Experimental results for degradation of PTFE are presented.

  17. Method of radiation degradation of PTFE under vacuum conditions

    Science.gov (United States)

    Korenev, Sergey

    2004-09-01

    A new method of radiation degradation of Polytetrafluoroethylene (PTFE) under vacuum conditions is considered in this report. The combination of glow gas discharge and electrical surface discharge (on surface and inside PTFE) increases the efficiency of thermal-radiation degradation. The main mechanism of this degradation method consists of the breaking of C-C and C-F bonds. The vacuum conditions allow decreasing of the concentration of toxic compounds, such as a HF. Experimental results for degradation of PTFE are presented.

  18. Improved conductivity of carbon-nano-fiber (CNF)/polytetrafluoroethylene (PTFE) composite

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sarita; Kalra, G. S.; Pushkar, Vinay K.; Gill, Fateh Singh, E-mail: drfatehs@gmail.com [Graphic Era University, Bell Road, Clement Town, Dehradun (India); Panwar, Variz [School of Materials Science and Engineering, Gwangju Institute of Science Technology (GIST), Gwangju 500-712 (Korea, Republic of); Gupta, Himanshu; Pal, Pankaj K.; Pathak, Trilok K.; Purohit, L. P. [Gurukul Kangri University, Haridwar-249404 (India)

    2016-05-23

    A series of CNF/PTFE composite loaded with different weight % of CNFs as 0.01, 0.02, 0.03, 0.05, 1, 2, 3, 4, 5 into PTFE is fabricated. In this work, the 5wt% heat-treated CNFs were used as filler in PTFE. Current-voltage (I-V) study of the samples confirmed the samples as conducting composite. In scanning electron microscope (SEM) study, the conducting CNFs channels were observed from upper surface to inside throughout the polymer matrix. A sintered composite of 5 wt% loading of CNFs showed an improved conductivity and SEM image exhibited a good binding of CNFs into PTFE.

  19. Improved conductivity of carbon-nano-fiber (CNF)/polytetrafluoroethylene (PTFE) composite

    International Nuclear Information System (INIS)

    Chandra, Sarita; Kalra, G. S.; Pushkar, Vinay K.; Gill, Fateh Singh; Panwar, Variz; Gupta, Himanshu; Pal, Pankaj K.; Pathak, Trilok K.; Purohit, L. P.

    2016-01-01

    A series of CNF/PTFE composite loaded with different weight % of CNFs as 0.01, 0.02, 0.03, 0.05, 1, 2, 3, 4, 5 into PTFE is fabricated. In this work, the 5wt% heat-treated CNFs were used as filler in PTFE. Current-voltage (I-V) study of the samples confirmed the samples as conducting composite. In scanning electron microscope (SEM) study, the conducting CNFs channels were observed from upper surface to inside throughout the polymer matrix. A sintered composite of 5 wt% loading of CNFs showed an improved conductivity and SEM image exhibited a good binding of CNFs into PTFE.

  20. Ionizing radiation effects on ISS ePTFE jacketed cable assembly

    Science.gov (United States)

    Koontz, S. L.; Golden, J. L.; Lorenz, M. J.; Pedley, M. D.

    2003-09-01

    Polytetrafluoroethylene (PTFE), which is susceptible to embrittlement by ionizing radiation, is used as a primary material in the Mobile Transporter's (MT) Trailing Umbilical System (TUS) cable on the International Space Station (ISS). The TUS cable provides power and data service between the ISS truss and the MT. The TUS cable is normally stowed in an uptake reel and is fed out to follow the MT as it moves along rails on the ISS truss structure. For reliable electrical and mechanical performance, TUS cable polymeric materials must be capable of >3.5% elongation without cracking or breaking. The MT TUS cable operating temperature on ISS is expected to range between -100°C and +130°C. The on-orbit functional life requirement for the MT TUS cable is 10 years. Analysis and testing were performed to verify that the MT TUS cable would be able to meet full-life mechanical and electrical performance requirements, despite progressive embrittlement by the natural ionizing radiation environment. Energetic radiation belt electrons (trapped electrons) are the principal contributor to TUS cable radiation dose. TUS cable specimens were irradiated, in vacuum, with both energetic electrons and gamma rays. Electron beam energy was chosen to minimize charging effects on the non-conductive ePTFE (expanded PTFE) targets. Tensile testing was then performed, over the expected range of operating temperatures, as a function of radiation dose. When compared to the expected in-flight radiation dose/depth profile, atomic oxygen (AO) erosion of the radiation damaged TUS cable jacket surfaces is more rapid than the development of radiation induced embrittlement of the same surfaces. Additionally, the layered construction of the jacket prevents crack growth propagation, leaving the inner layer material compliant with the design elongation requirements. As a result, the TUS cable insulation design was verified to meet performance life requirements.

  1. The Scandinavian Propaten(®) trial - 1-year patency of PTFE vascular prostheses with heparin-bonded luminal surfaces compared to ordinary pure PTFE vascular prostheses - a randomised clinical controlled multi-centre trial.

    Science.gov (United States)

    Lindholt, J S; Gottschalksen, B; Johannesen, N; Dueholm, D; Ravn, H; Christensen, E D; Viddal, B; Flørenes, T; Pedersen, G; Rasmussen, M; Carstensen, M; Grøndal, N; Fasting, H

    2011-05-01

    To compare 1-year potencies' of heparin-bonded PTFE [(Hb-PTFE) (Propaten(®))] grafts with those of ordinary polytetraflouroethylene (PTFE) grafts in a blinded, randomised, clinically controlled, multi-centre study. Eleven Scandinavian centres enrolled 569 patients with chronic functional or critical lower limb ischaemia who were scheduled to undergo femoro-femoral bypass or femoro-poplitaeal bypass. The patients were randomised 1:1 stratified by centre. Patency was assessed by duplex ultrasound scanning. A total of 546 patients (96%) completed the study with adequate follow-up. Perioperative bleeding was, on average, 370 ml with PTFE grafts and 399 ml with Heparin-bonded PTFE grafts (p = 0.32). Overall, primary patency after 1 year was 86.4% for Hb-PTFE grafts and 79.9% for PTFE grafts (OR = 0.627, 95% CI: 0.398; 0.989, p = 0.043). Secondary patency was 88% in Hb-PTFE grafts and 81% in PTFE grafts (OR = 0.569 (0.353; 0.917, p = 0.020)). Subgroup analyses revealed that significant reduction in risk (50%) was observed when Hb-PTFE was used for femoro-poplitaeal bypass (OR = 0.515 (0.281; 0.944, p = 0.030)), and a significant reduction in risk (50%) was observed with Hb-PTFE in cases with critical ischaemia (OR = 0.490 (0.249; 0.962, p = 0.036)). The Hb-PTFE graft significantly reduced the overall risk of primary graft failure by 37%. Risk reduction was 50% in femoro-poplitaeal bypass cases and in cases with critical ischaemia. Copyright © 2011. Published by Elsevier Ltd.

  2. Socket Preservation with d-PTFE Membrane: Histologic Analysis of the Newly Formed Matrix at Membrane Removal.

    Science.gov (United States)

    Laurito, Domenico; Cugnetto, Riccardo; Lollobrigida, Marco; Guerra, Fabrizio; Vestri, Annarita; Gianno, Francesca; Bosco, Sandro; Lamazza, Luca; De Biase, Alberto

    This study aimed to evaluate the efficacy of an exposed high-density polytetrafluoroethylene (d-PTFE) membrane in preventing epithelial migration in postextraction sockets. For this purpose, a histologic description of the newly formed soft tissue underlying the membrane is presented. The periodontal status of the adjacent teeth was also evaluated to assess the gingival response. Ten premolar extraction sockets were treated. After tooth extraction, the sockets were filled with nanocrystalline hydroxyapatite and covered with d-PTFE membranes. Subperiosteal pockets were created to ensure the stability of the membranes. Membranes were left intentionally exposed and were atraumatically removed after 28 days. At that time, a bioptic specimen of the newly formed soft tissue under the membranes was taken. All the histologic samples showed a dense connective tissue without epithelial cells and no signs of foreign body reaction. No significant variation of the periodontal indices was observed on the teeth adjacent to the extraction sites. The study results indicate that exposed d-PTFE membranes can prevent epithelial migration in healing sockets without consequences on the periodontal health.

  3. Use of covered self-expandable stents for benign colorectal disorders in children.

    Science.gov (United States)

    Lange, Bettina; Sold, Moritz; Kähler, Georg; Wessel, Lucas M; Kubiak, Rainer

    2017-01-01

    There is a lack of experience with covered self-expandable stents for benign colorectal disorders in children. Five children (4M, 1F) with a median age of 5years (range, 6months-9years) who underwent treatment with covered self-expandable plastic (SEPSs) or self-expandable metal stents (SEMSs) for a benign colorectal condition between April 2005 and November 2013 were recruited to this retrospective study. Etiologies included: anastomotic stricture with (n=1) or without (n=3) simultaneous enterocutaneous fistula, as well as an anastomotic leak associated with enterocutaneous fistula (n=1). All children suffered from either Hirschsprung's disease (n=3) or total colonic aganglionosis (Zuelzer-Wilson syndrome) (n=2). Median duration of individual stent placement was 23days (range, 1-87days). In all cases up to five different stents were placed over time. At follow-up two patients were successfully treated without further intervention. In another patient the anastomotic stricture resolved fully, but a coexisting enterocutaneous fistula persisted. Overall, three patients did not improve completely following stenting and required definite surgery. Stent-related problems were noted in all cases. There was one perforation of the colon at stent insertion. Further complications consisted of stent dislocation (n=4), obstruction (n=1), formation of granulation tissue (n=1), ulceration (n=1) and discomfort (n=3). Covered self-expandable stents enrich the armamentarium of interventions for benign colorectal disorders in children including anastomotic strictures and intestinal leaks. A stent can be applied either as an emergency procedure (bridge to surgery) or as an adjuvant treatment further to endoscopy and dilatation. Postinterventional problems are frequent but there is a potential for temporary or definite improvement following stent insertion. Copyright © 2017. Published by Elsevier Inc.

  4. Polyester composite versus PTFE in laparoscopic ventral hernia repair.

    Science.gov (United States)

    Colon, Modesto J; Telem, Dana A; Chin, Edward; Weber, Kaare; Divino, Celia M; Nguyen, Scott Q

    2011-01-01

    Both polyester composite (POC) and polytetrafluoroethylene (PTFE) mesh are commonly used for laparoscopic ventral hernia repair. However, sparse information exists comparing perioperative and long-term outcome by mesh repair. A prospective database was utilized to identify 116 consecutive patients who underwent laparoscopic ventral hernia repair at The Mount Sinai Hospital from 2004-2009. Patients were grouped by type of mesh used, PTFE versus POC, and retrospectively compared. Follow-up at a mean of 12 months was achieved by telephone interview and office visit. Of the 116 patients, 66 underwent ventral hernia repair with PTFE and 50 with POC mesh. Patients were well matched by patient demographics. No difference in mean body mass index (BMI) was demonstrated between the PTFE and POC group (31.8 vs. 32.5, respectively; P=NS). Operative time was significantly longer in the PTFE group (136 vs.106 minutes, PPTFE group and none in the POC group (P NS). No other major complications occurred in the immediate postoperative period (30 days). At a mean follow-up of 12 months, no significant difference was demonstrated between the PTFE and POC groups in hernia recurrence (3% vs. 2%), wound complications (1% vs. 0%), mesh infection, requiring removal (3% vs. 0%), bowel obstruction (3% vs. 2%), or persistent pain or discomfort (28% vs. 32%), respectively (P=NS). Our study demonstrated no significant association between types of mesh used and postoperative complications. In the 12-month follow-up, no differences were noted in hernia recurrence.

  5. MgTiO3 filled PTFE composites for microwave substrate applications

    International Nuclear Information System (INIS)

    Yuan, Y.; Zhang, S.R.; Zhou, X.H.; Li, E.Z.

    2013-01-01

    MgTiO 3 filled PTFE composite substrates were fabricated for microwave circuit applications. The filler content in the PTFE matrix was varied from 30 to 70 wt%. Low loss MgTiO 3 ceramic powder was prepared by the solid state ceramic route. The phase formation of MgTiO 3 was studied by powder X-ray diffraction analysis. Morphology of the composites and dispersion of filler in the PTFE matrix was studied using scanning electron microscopy. Microwave dielectric properties of the composites with respect to filler loading were measured by stripline resonator method using Vector Network Analyzer. Different theoretical modeling approaches were used to predict the dielectric constant of PTFE ceramic composites with respect to filler loading. The linear coefficient of thermal expansion of the composites was investigated. Moisture absorption of the composites was found out conforming to IPC-TM-650 2.6.2. - Highlights: • We prepare MT/PTFE composite by cold pressing and hot treating. • Increasing MT will increase ε r , tan δ and moisture absorption. • Increasing MT will decrease thermal expansion coefficient. • MT/PTFE composite has an ε r of 4.3 and a tan δ of 0.00097 at 50 wt% filler loading. • MT/PTFE composite are promising candidates for microwave circuit applications

  6. Optimal Covering Material for Stent-Grafts Placed in the Portal Vein in a Canine Model

    International Nuclear Information System (INIS)

    Ishii, Seigo; Sato, Morio; Sonomura, Tetsuo; Yamada, Katsuyuki; Tanihata, Hirohiko; Ishikawa, Hime; Terada, Masaki; Sahara, Shinya; Kawai, Nobuyuki; Kimura, Masashi; Mori, Ichiro

    2005-01-01

    Purpose. We evaluated the suitability of Dacron, polytetrafluoroethylene (PTFE), and small intestinal submucosa (SIS) as a covering material for stent-grafts placed in the portal vein as compared with a bare stent. Methods. Using 24 beagle dogs, either bare stents or stent-grafts covered with Dacron, PTFE, or SIS were placed in the main trunk of the portal vein in 6 animals each. Portography was performed immediately after stent placement, and at 2, 4, and 12 weeks thereafter. Next, the extracted stents or stent-grafts were examined histopathologically. Neointimal thickness adjacent to the stent wire and at the midportion between the stent wires was compared among the groups. Then, the neointimal thickness at the sub- and supragraft sites was compared between each stent-graft group. Serial changes in the histologic features of the thickened neointima were also investigated. Results. No significant difference was noted in the mean stenotic ratio of the portal vein diameter between the bare stent and PTFE groups, whereas it was significantly higher in the Dacron and SIS groups compared with the bare stent group. In neither of the studies on neointimal thickness adjacent to the stent wire and at the midportion between the stent wires were any significant differences noted between the neointimal thickness of the bare stent group and the sum of the neointimal thickness of the PTFE group, whereas the sum of the neointimal thickness of the Dacron and SIS groups was significantly greater than that of the bare stent group at both sites. In the comparison of the supragraft neointimal thickness, the SIS group showed significantly greater thickness than the PTFE group, while the difference between the Dacron and PTFE groups was not significant. In the comparison of the subgraft neointimal thickness, the Dacron and SIS groups showed significantly greater thickness than the PTFE group. Conclusion. The present results indicate that of the three covering materials examined here

  7. Radiation-induced crosslinking of short Fiber-filled polytetrafluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Udagawa, Akira; Morita, Yousuke

    1999-02-01

    The radiation-induced crosslinking of PTFE mixed with short fibers as glass or carbon fibers was studied for processing the composite materials. The crosslinking behaviors did not change by mixing of the fiber under the irradiation condition in oxygen-free atmosphere at temperature at temperature of 330degC - 350degC. The effect of reinforcement by the fibers in the fabricated composite materials was supposed to be a morphological change of PTFE because and adhesion between PTFE and the fibers was hardly observed in the composite materials. (author)

  8. Effect of gamma radiation on graphite – PTFE dry lubrication system

    International Nuclear Information System (INIS)

    Singh, Sachin; Tyagi, Mukti; Seshadri, Geetha; Tyagi, Ajay Kumar; Varshney, Lalit

    2017-01-01

    An effect of gamma radiation on lubrication behavior of graphite -PTFE dry lubrication system has been studied using (TR-TW-30L) tribometer with thrust washer attachment in plane contact. Different compositions of graphite and PTFE were prepared and irradiated by gamma rays. Gamma radiation exposure significantly improves the tribological properties indicated by decrease in coefficient of friction and wear properties of graphite -PTFE dry lubrication system. SEM and XRD analysis confirm the physico-chemical modification of graphite-PTFE on gamma radiation exposure leading to a novel dry lubrication system with good slip and anti friction properties. - Highlights: • Novel dry lubrication system of graphite -PTFE using gamma radiation. • Gamma radiation processing. • Reduction in coefficient of friction, frictional torque and wear loss of developed dry lubrication system.

  9. Intrasellar Iatrogenic Carotid Pseudoaneurysm: Endovascular Treatment with a Polytetrafluoroethylene-Covered S tent

    International Nuclear Information System (INIS)

    Vanninen, R. L.; Manninen, H. I.; Rinne, J.

    2003-01-01

    This case illustrates successful treatment of a large postoperative intrasellar pseudoaneurysm with a polytetrafluoroethylene (PTFE)-covered stent. The advantages and potential disadvantages of this novel method of treatment are discussed. A previously healthy 59-year-old man underwent transsphenoidal operative treatment for hypophyseal macroadenoma,complicated by bleeding. On the 17 th postoperative day the patient had profuse arterial bleeding from his nose requiring posterior tamponade. Subsequent angiography of the left internal carotid artery(ICA) revealed a large pseudoaneurysm located intrasellarly, with the orifice in the anteromedial wall in the ophthalmic segment of the ICA.Surgical treatment of the pseudoaneurysm was considered very risky. A12-mm PTFE-covered stent (JoMed, Ulestraten, Netherlands), manually compressed on a PTCA-balloon (Maxxum 4.5/13 mm, Boston Scientific,Ireland) was endovascularly delivered covering the orifice of the pseudoaneurysm. Control angiography immediately after the intervention and one year later revealed no flow into the pseudoaneurysm and the ICA was fully patent. In conclusion, deployment of a PTFE-covered stent proved to be feasible and successful in the treatment of an intrasellariatrogenic ICA pseudoaneurysm. Adequate anticoagulative treatment after the procedure is essential to prevent thrombotic complications

  10. Synchrotron radiation induced direct photo-etching and surface modification of PTFE

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Washio, Masakazu

    2003-01-01

    In the first part of this article, we have described and discussed the measurement results of etching rates by direct photo-etching using Synchrotron Radiation (SR) for various kind of crosslinked PTFEs, which were prepared by different crosslinking doses, comparing with the non-crosslinked PTFE. It has been found that the etching rates obtained for crosslinked PTFE were much larger than that of non-crosslinked one. These results are not described by simple consideration such as the G values of main chain scission. We propose that the etching rates should be discussed by the complex mechanism through at least two different steps such as polymer decomposition and fragment desorption. In the second part of the article, we have described and discussed the abnormal reaction induced at the surface region after the SR etching for non-crosslinked PTFE. Through the measurements using DSC and solid state 19 F-NMR, we have confirmed the crosslinking reaction of PTFE even in solid state PTFE. This should be induced by the very high density radical formation in very thin area of PTFE films by SR radiation. (author)

  11. Rapid, Reliable Shape Setting of Superelastic Nitinol for Prototyping Robots.

    Science.gov (United States)

    Gilbert, Hunter B; Webster, Robert J

    Shape setting Nitinol tubes and wires in a typical laboratory setting for use in superelastic robots is challenging. Obtaining samples that remain superelastic and exhibit desired precurvatures currently requires many iterations, which is time consuming and consumes a substantial amount of Nitinol. To provide a more accurate and reliable method of shape setting, in this paper we propose an electrical technique that uses Joule heating to attain the necessary shape setting temperatures. The resulting high power heating prevents unintended aging of the material and yields consistent and accurate results for the rapid creation of prototypes. We present a complete algorithm and system together with an experimental analysis of temperature regulation. We experimentally validate the approach on Nitinol tubes that are shape set into planar curves. We also demonstrate the feasibility of creating general space curves by shape setting a helical tube. The system demonstrates a mean absolute temperature error of 10°C.

  12. Treatment of carotid artery aneurysms with covered stents; Aneurysmabehandlung der Arteria carotis interna mit gecoverten Stents

    Energy Technology Data Exchange (ETDEWEB)

    Rohr, A.; Alfke, K.; Doerner, L.; Jansen, O. [UKSH Kiel (Germany). Neurochirurgie Neuroradiologie; Bartsch, T.; Stingele, R. [UKSH Kiel (Germany). Neurologie

    2007-10-15

    Purpose: Evaluation of the use of covered stents in treating pseudoaneurysms of the cervical and intracranial/extradural carotid artery and determination of the periprocedural and short- to mid-term complication rate. Materials and Methods: 8 patients with 9 spontaneous dissecting aneurysms of the cervical carotid artery - 5 of which were symptomatic - plus one patient with ofthalmoplegia due to an aneurysm of the cavernous carotid artery were studied. While the latter was treated with a PTFE-covered balloon-mounted stainless steel stent (Jostent/Graftmaster), a self-expanding PTFE-covered Nitonol Stent (Symbiot) was used in all other cases. Intervention was performed with local anesthesia. Aspirin and Clopidogrel were both used as antiplatelet drugs. Clinical signs and symptoms and vascular imaging with DS, MR, CT angiography and ultrasound were recorded during patient follow-up, with a mean follow-up period of 14.6 months (4 - 30). Results: We were able to treat 8 out of 10 aneurysms (80 %) using covered stents. The aneurysms were immediately occluded and the associated stenoses of the parent vessel were eliminated. No clinically relevant complications occurred during the procedure or in the follow-up interval. In two cases, elongation of the carotid artery prevented the stent from being positioned over the aneurysm neck. These cases were shown to be stable with the use of antiplatelet drugs. Conclusion: Covered stents can be used in the treatment of pseudoaneurysms of the carotid artery as an alternative to long-term antithrombotic medication or surgery. In our study treatment was effective (80 %) and free of complications in the short- and mid-term follow-up. Possible indications, technique and the use of imaging modalities for patient follow-up are discussed. (orig.)

  13. Fabrication and Characteristics of Al/PTFE Multilayers and Application in Micro-initiator

    Science.gov (United States)

    Zhang, Yuxin; Jiang, Hongchuan; Zhao, Xiaohui; Zhang, Wanli; Li, Yanrong

    2017-12-01

    In this paper, a micro-initiator was designed and fabricated by integrating Al/PTFE multilayers with a Cu film bridge. The regularity layer structure and interface composition of Al/PTFE multilayers was analysed by transmission electron microscope and X-ray photoelectron spectroscopy, respectively. The heat release reaction in Al/PTFE multilayers can be triggered with reaction temperature of 430 °C, and the overall heat of reaction is 3192 J/g. Al/PTFE multilayers with bilayer thickness of 200 nm was alternately deposited on a Cu film bridge to improve the electric explosion performances. Compared to Cu film bridge, the Al/PTFE/Cu integrated film bridge exhibits improved performances with longer explosion duration time, more violent explosion phenomenon and larger quantities of ejected product particles.

  14. Laser shape setting of superelastic nitinol wires: Functional properties and microstructure

    Science.gov (United States)

    Tuissi, Ausonio; Coduri, Mauro; Biffi, Carlo Alberto

    Shape setting is one of the most important steps in the production route of Nitinol Shape Memory Alloys (SMAs), as it can fix the functional properties, such as the shape memory effect and the superelasticity (SE). The conventional method for making the shape setting is performed at 400-500∘C in furnaces. In this work, a laser beam was adopted for performing straight shape setting on commercially available austenitic Nitinol thin wires. The laser beam, at different power levels, was moved along the wire length for inducing the functional performances. Calorimetric, pseudo-elastic and microstructural features of the laser annealed wires were studied through differential scanning calorimetry, tensile testing and high energy X-ray diffraction, respectively. It can be stated that the laser technology can induce SE in thin Nitinol wires: the wire performances can be modulated in function of the laser power and improved functional properties can be obtained.

  15. Thermal and radiation process for nano-/micro-fabrication of crosslinked PTFE

    International Nuclear Information System (INIS)

    Kobayashi, Akinobu; Oshima, Akihiro; Okubo, Satoshi; Tsubokura, Hidehiro; Takahashi, Tomohiro; Oyama, Tomoko Gowa; Tagawa, Seiichi; Washio, Masakazu

    2013-01-01

    Nano-/micro-fabrication process of crosslinked poly(tetrafluoroethylene) (RX-PTFE) is proposed as a novel method using combined process which is thermal and radiation process for fabrication of RX-PTFE (TRaf process). Nano- and micro-scale patterns of silicon wafers fabricated by EB lithography were used as the molds for TRaf process. Poly(tetrafluoroethylene) (PTFE) dispersion was dropped on the fabricated molds, and then PTFE was crosslinked with doses from 105 kGy to 1500 kGy in its molten state at 340 °C in nitrogen atmosphere. The obtained nano- and micro-structures by TRaf process were compared with those by the conventional thermal fabrication process. Average surface roughness (R a ) of obtained structures was evaluated with atomic force microscope (AFM) and scanning electron microscope (SEM). R a of obtained structures with the crosslinking dose of 600 kGy showed less than 1.2 nm. The fine nano-/micro-structures of crosslinked PTFE were successfully obtained by TRaf process

  16. Thermally stimulated current in PTFE and its application in radiation dosimetry

    International Nuclear Information System (INIS)

    Ozdemir, S.

    1985-01-01

    Thermally Stimulated Current (TSC) measurement was made on PTFE (Polytetrafluoro ethylene) in an attempt to develop an integrating radiation dosimeter material and the system. TSC spectra, dose response, energy response, fading and background charge stability characteristics were used as a measure of suitability of various untreated and heat treated PTFE samples for dosimetry applications. For practical TSC dosimetry system, it was discovered that the PTFE samples should be subjected to a specific heat treatment in order to produce samples with better dosimeter characteristics. A treatment at a temperature of 240 C produces a high dose response and low fading characteristics. It was found that the spurious charges due to storage and low sensitivity to irradiation caused the limitation in the measurement of low doses with PTFE samples for personnel protection. However, a TSC Dosimetry system using PTFE is proposed which is suitable for radiation doses in the radiotherapy range from *approx* 50 to *approx* 800 mGy. (author)

  17. Improved extraction of ePTFE and medical adhesive modified defibrillation leads from the coronary sinus and great cardiac vein.

    Science.gov (United States)

    Wilkoff, Bruce L; Belott, Peter H; Love, Charles J; Scheiner, Avram; Westlund, Randy; Rippy, Marian; Krishnan, Mohan; Norlander, Barry E; Steinhaus, Bruce; Emmanuel, Janson; Zeller, Peter J

    2005-03-01

    Permanent leads with shocking coils for defibrillation therapy are sometimes implanted in the coronary sinus (CS) and great cardiac vein (GCV). These shocking coils, as documented by pathologic examination of animal investigations, often become tightly encapsulated by fibrosis and can be very difficult to remove. One of three configurations of the Guidant model 7109 Perimeter coronary sinus shocking lead was implanted into the distal portion of the GCV of 24 sheep for up to 14 months. Group 1 had unmodified coils (control), group 2 had coils backfilled with medical adhesive (MA), and Group 3 had coils coated with expanded polytetrafluoroethylene (ePTFE). Eighteen leads, three from each group at 6 and 14 months were transvenously extracted from the left jugular vein. The remaining six animals were not subject to extraction. All animals were euthanized for pathological and microscopic examination. All six of the control, three of the MA, and one of the ePTFE leads required the use of an electrosurgical dissection sheath (EDS) for extraction. Five control, two MA, and none of the ePTFE leads had significant fibrotic attachments to the shocking coils. Significant trauma was observed at necropsy for those leads requiring the use of the EDS for extraction. Tissue ingrowth is a major impediment to the removal of defibrillation leads implanted in the CS and GCV of sheep. Reduction of tissue ingrowth by coating the shocking coils with ePTFE or by backfilling with MA facilitates transvenous lead removal with reduced tissue trauma.

  18. Preparation of Pt-PTFE hydrophobic catalyst for hydrogen-water isotope exchange

    International Nuclear Information System (INIS)

    Li Junhua; Kang Yi; Han Yande; Ruan Hao; Dou Qincheng; Hu Shilin

    2001-01-01

    The hydrophobic catalyst used in the hydrogen-water isotope exchange is prepared with Pt as the active metal, PTFE as the hydrophobic material, active carbon or silicon dioxide as the support. The isotope catalytic exchange reaction between hydrogen and water is carried out in the trickle bed and the effects of different carriers, mass fraction of Pt and PTFE on the catalytic activity are discussed. The experimental results show that the activity of Pt-C-PTFE hydrophobic catalyst with the ratio between PTFE and Pt-C from 1 to 2 is higher than other kinds of catalysts and the overall volume transfer coefficient is increased with the increasing of the hydrogen flow rate and reaction temperature

  19. Preparation, Properties, and Self-Assembly Behavior of PTFE-Based Core-Shell Nanospheres

    Directory of Open Access Journals (Sweden)

    Katia Sparnacci

    2012-01-01

    Full Text Available Nanosized PTFE-based core-shell particles can be prepared by emulsifier-free seed emulsion polymerization technique starting from spherical or rod-like PTFE seeds of different size. The shell can be constituted by the relatively high Tg polystyrene and polymethylmethacrylate as well as by low Tg polyacrylic copolymers. Peculiar thermal behavior of the PTFE component is observed due to the high degree of PTFE compartmentalization. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomers and the PTFE seed. In addition, the particle size distribution self-sharpens as the ratio monomer/PTFE increases. Samples with uniformity ratios suited to build 2D and 3D colloidal crystals are easily prepared. In particular, 2D colloidal crystal of spheres leads to very small 2D nanostructuration, useful for the preparation of masks with a combination of nanosphere lithography and reactive ion etching. 3D colloidal crystals were also obtained featuring excellent opal quality, which is a direct consequence of the monodispersity of colloids used for their growth.

  20. Preparation, Properties, and Self-Assembly Behavior of PTFE-Based Core-Shell Nanospheres

    International Nuclear Information System (INIS)

    Sparnacci, K.; Antonioli, D.; Deregibus, S.; Laus, M.; Zuccheri, G.; Boarino, L.; De Leo, N.; Comoretto, D.

    2012-01-01

    Nano sized PTFE-based core-shell particles can be prepared by emulsifier-free seed emulsion polymerization technique starting from spherical or rod-like PTFE seeds of different size. The shell can be constituted by the relatively high Tg polystyrene and polymethylmethacrylate as well as by low Tg polyacrylic copolymers. Peculiar thermal behavior of the PTFE component is observed due to the high degree of PTFE compartmentalization. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomers and the PTFE seed. In addition, the particle size distribution self-sharpens as the ratio monomer/PTFE increases. Samples with uniformity ratios suited to build 2D and 3D colloidal crystals are easily prepared. In particular, 2D colloidal crystal of spheres leads to very small 2D nanostructuration, useful for the preparation of masks with a combination of nanosphere lithography and reactive ion etching. 3D colloidal crystals were also obtained featuring excellent opal quality, which is a direct consequence of the monodispersity of colloids used for their growth.

  1. Adhesion, vitality and osteogenic differentiation capacity of adipose derived stem cells seeded on nitinol nanoparticle coatings.

    Directory of Open Access Journals (Sweden)

    Sarah Strauss

    Full Text Available Autologous cells can be used for a bioactivation of osteoimplants to enhance osseointegration. In this regard, adipose derived stem cells (ASCs offer interesting perspectives in implantology because they are fast and easy to isolate. However, not all materials licensed for bone implants are equally suited for cell adhesion. Surface modifications are under investigation to promote cytocompatibility and cell growth. The presented study focused on influences of a Nitinol-nanoparticle coating on ASCs. Possible toxic effects as well as influences on the osteogenic differentiation potential of ASCs were evaluated by viability assays, scanning electron microscopy, immunofluorescence and alizarin red staining. It was previously shown that Nitinol-nanoparticles exert no cell toxic effects to ASCs either in soluble form or as surface coating. Here we could demonstrate that a Nitinol-nanoparticle surface coating enhances cell adherence and growth on Nitinol-surfaces. No negative influence on the osteogenic differentiation was observed. Nitinol-nanoparticle coatings offer new possibilities in implantology research regarding bioactivation by autologous ASCs, respectively enhancement of surface attraction to cells.

  2. Nano-Impact (Fatigue Characterization of As-Deposited Amorphous Nitinol Thin Film

    Directory of Open Access Journals (Sweden)

    Rehan Ahmed

    2012-08-01

    Full Text Available This paper presents nano-impact (low cycle fatigue behavior of as-deposited amorphous nitinol (TiNi thin film deposited on Si wafer. The nitinol film was 3.5 µm thick and was deposited by the sputtering process. Nano-impact tests were conducted to comprehend the localized fatigue performance and failure modes of thin film using a calibrated nano-indenter NanoTest™, equipped with standard diamond Berkovich and conical indenter in the load range of 0.5 mN to 100 mN. Each nano-impact test was conducted for a total of 1000 fatigue cycles. Depth sensing approach was adapted to understand the mechanisms of film failure. Based on the depth-time data and surface observations of films using atomic force microscope, it is concluded that the shape of the indenter test probe is critical in inducing the localized indentation stress and film failure. The measurement technique proposed in this paper can be used to optimize the design of nitinol thin films.

  3. Nano-structuring of PTFE surface by plasma treatment, etching, and sputtering with gold

    International Nuclear Information System (INIS)

    Reznickova, Alena; Kolska, Zdenka; Hnatowicz, Vladimir; Svorcik, Vaclav

    2011-01-01

    Properties of pristine, plasma modified, and etched (by water and methanol) polytetrafluoroethylene (PTFE) were studied. Gold nanolayers sputtered on this modified PTFE have been also investigated. Contact angle, measured by goniometry, was studied as a function of plasma exposure and post-exposure aging times. Degradation of polymer chains was examined by etching of plasma modified PTFE in water or methanol. The amount of ablated and etched layer was measured by gravimetry. In the next step the pristine, plasma modified, and etched PTFE was sputtered with gold. Changes in surface morphology were observed using atomic force microscopy. Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS). Surface chemistry of the samples was investigated by electrokinetic analysis. Sheet resistance of the gold layers was measured by two-point technique. The contact angle of the plasma modified PTFE decreases with increasing exposure time. The PTFE amount, ablated by the plasma treatment, increases with the plasma exposure time. XPS measurements proved that during the plasma treatment the PTFE macromolecular chains are degraded and oxidized and new –C–O–C–, –C=O, and –O–C=O groups are created in modified surface layer. Surface of the plasma modified PTFE is weakly soluble in methanol and intensively soluble in water. Zeta potential and XPS shown dramatic changes in PTFE surface chemistry after the plasma exposure, water etching, and gold deposition. When continuous gold layer is formed a rapid decrease of the sheet resistance of the gold layer is observed.

  4. Addressing Machining Issues for the Intermetallic Compound 60-NITINOL

    Science.gov (United States)

    Stanford, Malcolm K.; Wozniak, Walter A.; McCue, Terry R.

    2012-01-01

    60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

  5. Creation and Validation of Sintered PTFE BRDF Targets & Standards.

    Science.gov (United States)

    Durell, Christopher; Scharpf, Dan; McKee, Greg; L'Heureux, Michelle; Georgiev, Georgi; Obein, Gael; Cooksey, Catherine

    2015-09-21

    Sintered polytetrafluoroethylene (PTFE) is an extremely stable, near-perfect Lambertian reflecting diffuser and calibration standard material that has been used by national labs, space, aerospace and commercial sectors for over two decades. New uncertainty targets of 2 % on-orbit absolute validation in the Earth Observing Systems community have challenged the industry to improve is characterization and knowledge of almost every aspect of radiometric performance (space and ground). Assuming "near perfect" reflectance for angular dependent measurements is no longer going to suffice for many program needs. The total hemispherical spectral reflectance provides a good mark of general performance; but, without the angular characterization of bidirectional reflectance distribution function (BRDF) measurements, critical data is missing from many applications and uncertainty budgets. Therefore, traceable BRDF measurement capability is needed to characterize sintered PTFE's angular response and provide a full uncertainty profile to users. This paper presents preliminary comparison measurements of the BRDF of sintered PTFE from several laboratories to better quantify the BRDF of sintered PTFE, assess the BRDF measurement comparability between laboratories, and improve estimates of measurement uncertainties under laboratory conditions.

  6. On the Electrodeposition of Ca-P Coatings on Nitinol Alloy: A Comparison Between Different Surface Modification Methods

    Science.gov (United States)

    Etminanfar, M. R.; Khalil-Allafi, J.

    2016-02-01

    In this study, a combination of surface modification process and the electrochemical deposition of Ca-P coatings was used for the modification of the Nitinol shape memory alloy. DSC, SEM, GIB-XRD, FT-Raman, XPS, and FTIR measurements were performed for the characterization of the samples. Results indicated that chemical etching and boiling of the samples in distilled water formed TiO film on the surface. After the chemical modification, subsequent aging of the sample, at 470 °C for 30 min, converted the oxide film to a stable structure of titanium dioxide. In that case, the treated substrate indicated a superelastic behavior. At the same electrochemical condition, the treated substrate revealed more stable and uniform Ca-P coatings in comparison with the abraded Nitinol substrate. This difference was attributed to the presence of hydroxyl groups on the titanium dioxide surface. Also, after soaking the sample in SBF, the needle-like coating on the treated substrate was completely covered with the hydroxyapatite phase which shows a good bioactivity of the coating.

  7. Preparation of PVDF and PTFE membranes for fuel cell use; Preparacao de membranas de PVDF e PTFE enxertadas e sulfonadas para uso em celula a combustivel

    Energy Technology Data Exchange (ETDEWEB)

    Geraldes, Adriana N.; Zen, Heloisa A.; Ferreira, Henrique P.; Parra, Duclerc F.; Lugao, Ademar B.; Linardi, Marcelo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)], e-mail: angeral@ipen.br

    2007-07-01

    Grafting of styrene onto polyvinylidenefluoride (PVDF), polytetrafluoroethylene (PTFE) was studied using styrene/toluene solutions. First, PTFE and PVDF films were prepared and the process was conducted by radiation induced graft polymerization of styrene, by a Co{sup 60} source. Films of PTFE and PVDF were immersed in styrene/toluene at 1:1 (v/v) concentration and then submitted to gamma radiation at 20 kGy doses. After irradiation, the samples were evaluated at the period of 21 days at room temperature in order to observe the grafting degree. Chemical changes in the PVDF and PTFE films after styrene grafting were monitored and the results were evaluated by FTIR, DSC, TGA and degree of grafting (DOG). The ion exchange capacity (IEC) after sulfonation of 1, 2 and 24 hours were also determined. (author)

  8. Fully Covered Self-Expandable Metal Stents for Treatment of Both Benign and Malignant Biliary Disorders

    Directory of Open Access Journals (Sweden)

    Ahmed Abdel Samie

    2012-01-01

    Full Text Available Transpapillary stents are increasingly being used for biliary strictures, whether benign or malignant. However, there are different stent types and available data is controversial. Recently, completely covered self-expandable metal stents (CSEMSs have been proposed as an alternative therapeutic option in different biliary indications, including strictures of the distal bile duct, anastomotic stenosis after orthotopic liver transplantation, bile duct leaks, periampullary perforation following endoscopic sphincterotomy (ES, and postsphincterotomy bleeding. Despite the higher costs of these devices, fully covered self-expanding metal stents seem to be a suitable therapeutic option to relief biliary obstruction due to bile duct stenosis, regardless of the underlying cause.

  9. Fully Covered Self-Expandable Metal Stents for Treatment of Both Benign and Malignant Biliary Disorders

    Science.gov (United States)

    Abdel Samie, Ahmed; Theilmann, Lorenz

    2012-01-01

    Transpapillary stents are increasingly being used for biliary strictures, whether benign or malignant. However, there are different stent types and available data is controversial. Recently, completely covered self-expandable metal stents (CSEMSs) have been proposed as an alternative therapeutic option in different biliary indications, including strictures of the distal bile duct, anastomotic stenosis after orthotopic liver transplantation, bile duct leaks, periampullary perforation following endoscopic sphincterotomy (ES), and postsphincterotomy bleeding. Despite the higher costs of these devices, fully covered self-expanding metal stents seem to be a suitable therapeutic option to relief biliary obstruction due to bile duct stenosis, regardless of the underlying cause. PMID:22761543

  10. Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents

    International Nuclear Information System (INIS)

    Fu, C.H.; Liu, J.F.; Guo, Andrew

    2015-01-01

    Graphical abstract: - Highlights: • Precision kerf with tight tolerance of Nitinol stents can be cut by fiber laser. • No HAZ in the subsurface was detected due to large grain size. • Recast layer has lower hardness than the bulk. • Laser cutting speed has a higher influence on surface integrity than laser power. - Abstract: Nitinol alloys have been widely used in manufacturing of vascular stents due to the outstanding properties such as superelasticity, shape memory, and superior biocompatibility. Laser cutting is the dominant process for manufacturing Nitinol stents. Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone (HAZ), and recast layer. To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed. The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters.

  11. Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents

    Energy Technology Data Exchange (ETDEWEB)

    Fu, C.H., E-mail: cfu5@crimson.ua.edu [Dept of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Liu, J.F. [Dept of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Guo, Andrew [Dept of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); College of Arts and Science, Vanderbilt University, Nashville, TN 37235 (United States)

    2015-10-30

    Graphical abstract: - Highlights: • Precision kerf with tight tolerance of Nitinol stents can be cut by fiber laser. • No HAZ in the subsurface was detected due to large grain size. • Recast layer has lower hardness than the bulk. • Laser cutting speed has a higher influence on surface integrity than laser power. - Abstract: Nitinol alloys have been widely used in manufacturing of vascular stents due to the outstanding properties such as superelasticity, shape memory, and superior biocompatibility. Laser cutting is the dominant process for manufacturing Nitinol stents. Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone (HAZ), and recast layer. To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed. The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters.

  12. Multiscale electrochemical analysis of the corrosion of titanium and nitinol for implant applications

    International Nuclear Information System (INIS)

    Izquierdo, J.; González-Marrero, M.B.; Bozorg, M.; Fernández-Pérez, B.M.; Vasconcelos, H.C.; Santana, J.J.; Souto, R.M.

    2016-01-01

    Highlights: • Direct screening of differences in the surface reactivity of the passive layers formed on pure titanium and nitinol. • Distinct effect of polarization on the passive layers. • Detection of nickel soluble species released from corrosion pits. - Abstract: Surface electrochemical activity of titanium and nitinol biomaterials in naturally aerated Ringer’s physiological solution was investigated using potentiodynamic polarization and scanning electrochemical microscopy (SECM) techniques. SECM was operated in feedback and redox competition modes as a function of potential applied to the substrate. The kinetics of the electron transfer rate on both materials was characterized by mathematical modelling of the Z-approach curves monitored under feedback conditions. The rate constant values greatly depended on the characteristics of the passive layers formed over the metals under potentiostatic control. A more insulating film was found on nitinol when biased at low polarizations, resulting in smaller tip current increments during tip approach to the investigated surface under positive feedback and competition operation modes. However, at higher anodic polarizations, nitinol passive layers experience breakdown, and therefore tip current values reflect the release of metal cations from the biomaterial surface.

  13. Surface modification of PTFE sheet by synchrotron radiation in the soft X-ray region

    International Nuclear Information System (INIS)

    Kato, Y.; Kanda, K.; Haruyama, Y.; Matsui, S.

    2004-01-01

    Full text: The surface properties of poly (tetrafluoroethylene) (PTFE) are changed by the exposure to synchrotron radiation (SR). We succeeded in controlling the wettability of the PTFE surface from hydrophobic to hydrophilic by varying the substrate temperature during the SR irradiation and found that the wettability was ascribable to microstructure and chemical composition of surface.In these previous works, oxygen atoms were found to inhabit on the hydrophobic surface of PTFE. In this study, we investigated the surface modification of PTFE from the SR exposure experiment under the O 2 gas atmosphere. The SR exposure to the PTFE sheet was carried out at beamline 6 (BL6) of the New- SUBARU. The PTFE sheet was irradiated to the white beam, ranging 50-1000 eV at BL6 at room temperature. The gas cell was mounted at the irradiation chamber. The O 2 gas pressure in the gas cell can be maintained at about 0.20 Pa during the SR exposure using 5mm φ hole window. The wettability of PTFE surface was evaluated by the contact angle of a small water drop. Contact angle was measured with the water drop of 1 μl using the contact angle meter. Fig.1 shows the SR dose dependence of contact angle of PTFE surface under the O 2 gas atmosphere and under the vacuum. Contact angle decreased monotonically with SR dose. The decrease rate of contact angle of the PTFE surface irradiated under the O 2 gas atmosphere was larger than that of the PTFE surface irradiated without O 2 gas. Therefore, the combination of O atom to the PTFE surface was enhanced by the O 2 gas in the reaction region. These results suggested that the bonding of O atom on the hydrophobic PTFE surface is dominantly produced in the sample chamber during SR irradiation, but not in the air atmosphere after the SR irradiation

  14. Influence of covered stent versus bare stent on long-term efficacy of transjugular intrahepatic portosystemic shunt: a meta-analysis

    Directory of Open Access Journals (Sweden)

    XU Lu

    2016-10-01

    Full Text Available Objective To investigate the long-term postoperative efficacy of transjugular intrahepatic portosystemic shunt (TIPS using polytetrafluoroethylene (PTFE-covered stent or bare stent, and to provide a basis of evidence-based medicine for the selection of stent in TIPS. Methods CBM, Wanfang Data, CNKI, VIP, MEDLINE, and PubMed were searched for controlled trials on TIPS in the treatment of cirrhotic portal hypertension published form 1989 to 2015; the studies which met the inclusion criteria were selected, and quality assessment was performed for these articles. RevMan 5.3 software was used to analyze the incidence rates of stent dysfunction and hepatic encephalopathy and 1-year survival rate after TIPS, and funnel plots were used to analyze publication bias. Results A total of 11 studies were included, consisting of 698 patients in PTFE-covered stent group and 1283 patients in bare stent group. The results of the meta-analysis showed that the PTFE-covered stent group showed a significantly lower incidence rate of stent dysfunction than the bare stent group (14.8% vs 47.0%, OR=0.18, 95% CI: 0.13-0.24, P<0.001. There was no significant difference in the incidence rate of hepatic encephalopathy between the two groups (23.5% vs 25.7%, OR=0.88, 95% CI: 0.66-1.17, P=0.37. The PTFE-covered stent group had a significantly higher 1-year survival rate than the bare stent group (76.9% vs 62.7%, OR=2.10, 95% CI: 1.54-2.85, P<0.001. The funnel plots which were plotted based on the incidence rates of stent dysfunction and hepatic encephalopathy and 1-year survival rate lacked symmetry, which suggested that a certain degree of publication bias might exist. Conclusion Compared with the bare stent, the PTFE-covered stent can improve stent dysfunction and 1-year survival rate after TIPS, while there is no significant change in the incidence rate of hepatic encephalopathy. Therefore, the PTFE-covered stent has certain advantages over the bare stent in TIPS. In

  15. Synthesis and Characterization of Nano-Hydroxyapatite/mPEG-b-PCL Composite Coating on Nitinol Alloy

    Directory of Open Access Journals (Sweden)

    Mohamadreza Etminanfar

    2017-12-01

    Full Text Available In this study the bioactivity of hydroxyapatite/poly(ε-caprolactone–poly(ethylene glycol bilayer coatings on Nitinol superelastic alloy was investigated. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating. The surface morphology of coatings was studied using FE-SEM and SEM. The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized flakes and the polymer coating is uniformly covered the sublayer. Also, High resolution TEM studies on the hydroxyapatite samples revealed that each flake contains nano-crystalline grains with a diameter of about 15 nm. The hydroxyapatite monolayer coating was rapidly covered by calcium phosphate crystals (Ca/P=1.7 after immersion in simulated body fluid confirming the bioactivity of the nanostructured flakes. However, the flakes were weak against applied external forces because of their ultra-fine thickness. Scratch test was applied on hydroxyapatite/polymer coating to evaluate delamination of the coating from substrate. It was shown that, the polymer coating has a great influence on toughening the hydroxyapatite coating. To assess the degradation effect of the polymer layer on hydroxyapatite coating, samples were immersed in phosphate-buffered saline at 37 ᵒC. SEM studies on the samples revealed that the beneath layer of hydroxyapatite appears after 72 h without any visible change in morphology. It seems that, application of a biodegradable polymer film on the nanostructured hydroxyapatite coating is a good way to support the coating during implantation processes

  16. Constitutive modeling of shock response of PTFE

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Eric N [Los Alamos National Laboratory; Reanyansky, Anatoly D [DSTO, AUSTRALIA; Bourne, Neil K [AWE, UK; Millett, Jeremy C F [AWE, UK

    2009-01-01

    The PTFE (polytetrafluoroethylene) material is complex and attracts attention of the shock physics researchers because it has amorphous and crystalline components. In turn, the crystalline component has four known phases with the high pressure transition to phase III. At the same time, as has been recently studied using spectrometry, the crystalline region is growing with load. Stress and velocity shock-wave profiles acquired recently with embedded gauges demonstrate feature that may be related to impedance mismatches between the regions subjected to some transitions resulting in density and modulus variations. We consider the above mentioned amorphous-to-crystalline transition and the high pressure Phase II-to-III transitions as possible candidates for the analysis. The present work utilizes a multi-phase rate sensitive model to describe shock response of the PTFE material. One-dimensional experimental shock wave profiles are compared with calculated profiles with the kinetics describing the transitions. The objective of this study is to understand the role of the various transitions in the shock response of PTFE.

  17. The production and characterization of Ptfe bonded Nd-Fe-B magnets

    International Nuclear Information System (INIS)

    Mokal, B.; Williams, A.J.; Hay, J.N.; Harris, I.R.

    1996-01-01

    A study of the processing and characteristics of PTFE bonded Nd Fe B magnets has been carried out. PTFE was used because of its low coefficient of friction, thus enabling its flow between the particles of Nd Fe B powder. PTFE also increases the resistance to corrosion of the magnet. In these investigations, the production of bonded magnets by cold compaction and by hot processing (HP) of MQ powders using PTFE as the binder was investigated . Magnetic, microstructural, and mechanical properties were investigated and are presented together with a correlation with the different processing techniques used. The corrosion behaviour of the hot pressed magnets was also investigated. These studies could lead to the development of simpler and more effective processing routes for the production of bonded magnets. (author)

  18. Mechanical Stability of H3PO4-Doped PBI/Hydrophilic-Pretreated PTFE Membranes for High Temperature PEMFCs

    International Nuclear Information System (INIS)

    Park, Jaehyung; Wang, Liang; Advani, Suresh G.; Prasad, Ajay K.

    2014-01-01

    Graphical abstract: - Highlights: • PBI/PTFE membrane was prepared by porous PTFE with hydrophilic surface pretreatment. • The durability of the prepared PBI/PTFE membrane was compared with pure PBI, PBI with untreated PTFE, and PBI-Nafion with untreated PTFE membranes. • Accelerated durability tests and SEM showed improved durability based the PBI/PTFE membrane with pretreated PTFE. - Abstract: A novel polybenzimidazole (PBI)/poly(tetrafluoroethylene) (PTFE) composite membrane doped with phosphoric acid was fabricated for high temperature operation in a polymer electrolyte membrane (PEM) fuel cell. A hydrophilic surface pretreatment was applied to the porous PTFE matrix film to improve its interfacial adhesion to the PBI polymer, thereby avoiding the introduction of Nafion ionomer which is traditionally used as a coupling agent. The pretreated PTFE film was embedded within the composite membrane during solution-casting using 5wt% PBI/DMAc solution. The mechanical stability and durability of three types of MEAs assembled with PBI only, PBI with pretreated PTFE, and PBI-Nafion with untreated PTFE membranes were evaluated under an accelerated degradation testing protocol employing extreme temperature cycling. Degradation was characterized by recording polarization curves, hydrogen crossover, and proton resistance. Cross-sections of the membranes were examined before and after thermal cycling by scanning electron microscope. Energy-dispersive X-ray spectroscopy verified that the PBI is dispersed homogeneously in the porous PTFE matrix. Results show that the PBI composite membrane with pretreated PTFE has a lower degradation rate than the Nafion/PBI membrane with untreated PTFE. Thus, the hydrophilic pretreatment employed here greatly improved the mechanical stability of the composite membrane, which resulted in improved durability under an extreme thermal cycling regime

  19. Surface modification and adhesion improvement of PTFE film by ion beam irradiation

    International Nuclear Information System (INIS)

    Lee, S.W.; Hong, J.W.; Wye, M.Y.; Kim, J.H.; Kang, H.J.; Lee, Y.S.

    2004-01-01

    The polytetrafluoroethylene (PTFE) surfaces, modified by 1 kV Ar + or O 2 + ion beam irradiation, was investigated with in-situ X-ray photoelectron spectroscopy (XPS), scanning electron micrographs (SEM), atomic force microscopy (AFM) measurements. The surface of PTFE films modified by Ar + ion irradiation was carbonized and the surface roughness increased with increasing ion doses. The surface of PTFE films modified by both Ar + ion in O 2 atmosphere and O 2 + ion irradiation formed the oxygen function group on PTFE surface, and the surface roughness change was relatively small. The adhesion improvement in Ar + ion irradiated PTFE surface is attributed to mechanical interlocking due to the surface roughness and -CF-radical, but that in Ar + ion irradiation in an O 2 atmosphere was contributed by the C-O complex and -CF-radical with mechanical interlocking. The C-O complex and -CF-radical in O 2 + ion irradiated surface contributed to the adhesion

  20. Renal vessel reconstruction in kidney transplantation using a polytetrafluoroethylene (PTFE) vascular graft.

    Science.gov (United States)

    Kamel, Mohamed H; Thomas, Anil A; Mohan, Ponnusamy; Hickey, David P

    2007-04-01

    We report a rare experience in reconstructing short renal vessels in kidney transplantation using polytetrafluroethylene (PTFE) vascular grafts. The short renal vessels in three kidney grafts were managed by the interposition of PTFE vascular grafts. Two grafts were from deceased donors and the third was a renal auto-transplant graft. PTFE grafts were used to lengthen short renal veins in two kidney grafts and a short renal artery in one. The warm ischaemia time was under 1 h and all kidneys functioned well post-operatively. Excellent blood perfusion in the three renal grafts was present on postoperative MAG 3 renal scan. No intra-operative or post-operative complications were encountered. In the three described patients, the use of PTFE vascular graft presented no additional morbidity to the kidney transplant operation and no post-oerative complication was related to its use. However, more data are necessary to conclude that PTFE graft can be used safely in kidney transplantation.

  1. Acid Aging Effects on Surfaces of PTFE Gaskets Investigated by Thermal Analysis

    Directory of Open Access Journals (Sweden)

    C. Fragassa

    2016-12-01

    Full Text Available This paper investigates the effect of a prolonged acid attack on the surface of PTFE by Thermogravimetric Analysis (TGA and Differential Scanning Calorimetry (DSC. PTFE is very non-reactive, partly because of the strength of carbon–fluorine bonds and for its high crystallinity, and, as a consequence, it is often used in containers and pipework with reactive and corrosive chemicals. The PTFE under analysis is commercialized by two alternative producers in form of Teflon tapes. These tapes are adopted, as gaskets, in process plants where tires moulds are cleaned by acid solutions inside a multistage ultrasonic process. In this case, PTFE shows, in a relatively short operation time, inexplicably phenomena of surface degradation, which could be related, in general terms, to an acid attack. But, even considering the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the risk of the extreme erosion phenomena as observed. The present experimental research aim at investigating this contradiction. A possible explanation could be related to the presence in the cleaning solution of unexpected fluorides, able to produce fluorinating agents and, thus, degrade carbon-fluorine bonds. Considering more the 300 chemical elements a tire compound consists in, it is really complex to preserve the original chemical composition of the cleaning solution. In this research PTFE samples have been treated with different mixtures of acids with the aim at investigating the different aging effects. The thermal analysis has permitted the experimental characterization of PTFE surface properties after acid attack, providing evidence of the degradation phenomena. In particular, the different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers.

  2. Dacron or PTFE for above-knee femoropopliteal bypass. a multicenter randomised study

    DEFF Research Database (Denmark)

    Jensen, L P; Lepäntalo, M; Fossdal, J E

    2007-01-01

    To compare polytetrafluorethylene (PTFE) and polyester grafts (Dacron) for above knee femoropopliteal bypass.......To compare polytetrafluorethylene (PTFE) and polyester grafts (Dacron) for above knee femoropopliteal bypass....

  3. Nitinol for Prosthetic and Orthotic Applications

    Science.gov (United States)

    Henderson, Emma; Buis, Arjan

    2011-07-01

    As global populations age, conditions such as stroke and diabetes require individuals to use rehabilitation technology for many years to come due to chronic musculoskeletal, sensory, and other physical impairments. One in four males currently aged 45 will experience a stroke within 40 years and will often require access to prolonged rehabilitation. In addition, worldwide, one individual loses a limb every 30 s due to the complications of diabetes. As a result, innovative ideas are required to devise more effective prosthetic and orthotic devices to enhance quality of life. While Nitinol has already found much favor within the biomedical industry, one area, which has not yet exploited its unique properties, is in the field of physical rehabilitation, ranging from prosthetic and orthotic devices to assistive technology such as wheelchairs. Improved intervention capabilities based on materials such as Nitinol have the potential to vastly improve patients' quality of life and in the case of orthoses, may even reduce the severity of the condition over time. It is hoped that this study will spark discussion and interest for the materials community in a field which has yet to be fully exploited.

  4. Comparison of FLIXENE™ and standard PTFE arteriovenous graft for early haemodialysis.

    Science.gov (United States)

    Chiang, Nathaniel; Hulme, Katherine Ria; Haggart, Paul Charles; Vasudevan, Thodur

    2014-01-01

    The purpose is to compare the outcomes of FLIXENE™ arteriovenous graft (AVG) to standard polytetrafluoroethylene (PTFE) AVG for early haemodialysis. This is a prospective observational study of all AVGs placed over a 40-month period between 2008 and 2011 at our vascular unit. Primary outcome was to examine early cannulation rates for FLIXENE™. Secondary outcomes included patency rates, usability of grafts, complications in particular infections, interventions and death in comparison to standard PTFE grafts. Forty-five FLIXENE™ and 19 standard PTFE AVGs were placed in the study period; 89% of FLIXENE™ grafts were used for dialysis, with 78% cannulated within 3 days. At 18 months, primary patency (FLIXENE™ 34% vs standard PTFE 24%), primary assisted patency (35% vs 36%) and secondary patency rate (51% vs 48%) were not statistically different; 20.2% of FLIXENE™ grafts were infected at 18 months requiring explantation compared with 40.3% of standard PTFE grafts (p=0.14). FLIXENE™ can be cannulated for dialysis within 3 days. It has similar patency and complication rates as other prosthetic grafts in the market. In patients who have no access and require urgent dialysis, FLIXENE™ is a viable option.

  5. A new self-expanding nitinol stent (Enterprise) for the treatment of wide-necked intracranial aneurysms: initial clinical and angiographic results in 31 aneurysms

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Werner; Kuehne, Dietmar [Alfried Krupp Hospital, Department of Radiology and Neuroradiology, Essen (Germany); Bendszus, Martin; Solymosi, Laszlo [University of Wuerzburg, Department of Neuroradiology, Wuerzburg (Germany); Kis, Bernhard [University of Duisburg-Essen, Research Unit, Rheinische Kliniken Essen, Department of Psychiatry and Psychotherapy, Essen (Germany); Boulanger, Thierry [Centre Hospitalier of Luxembourg, Service of Neuroradiology, Luxembourg (Luxembourg)

    2007-07-15

    We report the results of a prospective clinical study using a new self-expanding nitinol stent (Enterprise) designed for the treatment of wide-necked intracranial aneurysms. We treated 31 saccular, wide-necked intracranial aneurysms in 30 patients. Ten aneurysms had recanalized after prior endovascular treatment without a stent, and 21 aneurysms had not been treated before. Stent deployment was successful in all procedures. Additional coil embolization was performed in all aneurysms. Initial complete angiographic occlusion was achieved in 6 aneurysms, a neck remnant was left in 18 aneurysms and there were 7 residual aneurysms. Angiographic follow-up examinations of 30 lesions after 6 months demonstrated 15 complete occlusions, 8 neck remnants and 7 residual aneurysms. One patient refused the 6-month angiographic follow-up. Spontaneous occlusion of the aneurysm had occurred in 14 patients, and 6 aneurysms showed recanalization. Four of these residual aneurysms were retreated. At the 6-month follow-up, 29 parent arteries were unaffected, whereas two parent vessels demonstrated minor asymptomatic narrowing at the stent site. Two patients experienced one or more possible or probable device-related serious adverse events during the 6-month follow-up period. There was no procedural morbidity or mortality at 6 months after the procedure. The reported results demonstrated the safety and feasibility of the Cordis Neurovascular Enterprise stent in the treatment of wide-necked intracranial aneurysms. Initial clinical and angiographic results are favorable. (orig.)

  6. Nitinol stents in the treatment of benign proximal tracheal stenosis or tracheomalacia.

    Science.gov (United States)

    Isa, A Y; Macandie, C; Irvine, B W

    2006-01-01

    Nitinol stents have been used in the treatment of benign tracheal stenosis. A retrospective review of five patients treated at Stobhill Hospital over the last six and a half years is presented. Age at presentation ranged from 17 to 76 years. The minimum follow-up period was 23 months and the maximum was 78 months. All our patients were successfully decannulated, with none requiring recannulation. Four patients developed granulation tissue related to the stent at intervals ranging from three weeks to 41 months post stenting. Topical mitomycin C application has been useful after resection of granulations using the carbon dioxide (CO2) laser. Stent migration occurred in one patient three weeks after insertion. Nitinol stents are easy to insert and effective in the treatment of tracheal stenosis, but can have associated morbidity. Their use should be considered carefully, as insertion should be regarded as permanent. Publications reporting experience and outcome with the use of Nitinol stents in the trachea are reviewed.

  7. Electrophoretic deposition of PTFE particles on porous anodic aluminum oxide film and its tribological properties

    International Nuclear Information System (INIS)

    Zhang, Dongya; Dong, Guangneng; Chen, Yinjuan; Zeng, Qunfeng

    2014-01-01

    Polytetrafluoroethylene (PTFE) composite film was successfully fabricated by depositing PTFE particles into porous anodic aluminum oxide film using electrophoretic deposition (EPD) process. Firstly, porous anodic aluminum oxide film was synthesized by anodic oxidation process in sulphuric acid electrolyte. Then, PTFE particles in suspension were directionally deposited into the porous substrate. Finally, a heat treatment at 300 °C for 1 h was utilized to enhance PTFE particles adhesion to the substrate. The influence of anodic oxidation parameters on the morphology and micro-hardness of the porous anodic aluminum oxide film was studied and the PTFE particles deposited into the pores were authenticated using energy-dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Tribological properties of the PTFE composite film were investigated under dry sliding. The experimental results showed that the composite film exhibit remarkable low friction. The composite film had friction coefficient of 0.20 which deposited in 15% PTFE emulsion at temperature of 15 °C and current density of 3 A/dm 2 for 35 min. In addition, a control specimen of porous anodic aluminum oxide film and the PTFE composite film were carried out under the same test condition, friction coefficient of the PTFE composite film was reduced by 60% comparing with the control specimen at 380 MPa and 100 mm/s. The lubricating mechanism was that PTFE particles embedded in porous anodic aluminum oxide film smeared a transfer film on the sliding path and the micro-pores could support the supplement of solid lubricant during the sliding, which prolonged the lubrication life of the aluminum alloys.

  8. Study of the formation process and the characteristics of tantalum layers electrodeposited on Nitinol plates in the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid

    International Nuclear Information System (INIS)

    Maho, A.; Delhalle, J.; Mekhalif, Z.

    2013-01-01

    Highlights: ► Tantalum electrodeposition on Nitinol plates in the [BMP]Tf 2 N ionic liquid at room temperature. ► Generation of intrinsically nanostructured porous tantalum layers in “soft” cathodic current conditions. ► Important impact of substrate nature, working solution composition and electrodeposition duration. ► Primary assessment of surface corrosion resistance and bioactivity. -- Abstract: Thanks to excellent mechanical and biochemical properties, the nickel–titanium shape memory alloy (Nitinol) constitutes an increasingly praised platform material in dental, cardiovascular and orthopedic biomedical devices. In order to strengthen their protective abilities toward corrosion, to reinforce their biocompatibility and to confer them specific osseointegrative capacities, Nitinol plates are covered with a thin tantalum layer by electrodeposition in the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid. XPS and SEM/EDX analyses highlight the chemical and morphological characteristics of the deposits: notably, these present an intrinsic dimpled nanometric structuration which is particularly remarkable considering the “soft” experimental conditions and very interesting for fundamental and applied bioactive perspectives. The present study investigates the specific and synergic effects of the Ni occurrence on the surface of the Nitinol substrates, the presence of fluorine species in the working bath, and the electrodeposition duration on the resulting formation process, morphology and chemical composition of the tantalum coating. Finally, samples are submitted to electrochemical characterizations and in vitro hydroxyapatite growth tests for a primary assessment of their corrosion resistance and osseoinductive features

  9. In vitro microbiologic evaluation of PTFE and cotton as spacer materials.

    Science.gov (United States)

    Paranjpe, Avina; Jain, Sumita; Alibhai, Karim J; Wadhwani, Chandur P; Darveau, Richard P; Johnson, James D

    2012-09-01

    To microbiologically evaluate the efficacy of cotton and polytetrafluoroethylene (PTFE) tape used as spacer materials. Twenty-six extracted human molars were restored using either cotton or PTFE tape as spacers under a standardized provisional restorative material (Cavit). The teeth were incubated for 7 days in a culture of Streptococcus gordonii or in liquid media alone. The spacers were removed and tested for bacterial contamination. The access cavities were also evaluated for bacterial contamination. Nine of 10 teeth with cotton spacers and one of 10 teeth with PTFE spacers were positive for S gordonii growth. The nine teeth in the cotton group also showed contamination of the access cavities. Even under optimal conditions, cotton spacers may cause leakage into the access cavities. Cotton fibers may serve as a route for bacterial contamination of the access cavities and root canal space. In contrast, PTFE tape did not provide an avenue for bacterial contamination.

  10. Biocompatibility assessment of porous chitosan-Nafion and chitosan-PTFE composites in vivo.

    Science.gov (United States)

    Liu, Bo-Ji; Ma, Li-Nan; Su, Juan; Jing, Wei-Wei; Wei, Min-Jie; Sha, Xian-Zheng

    2014-06-01

    Chitosan (CS) is widely used as a scaffold material in tissue engineering. The objective of this study was to test whether porous chitosan membrane (PCSM) coating for Nafion used in implantable sensor reduced fibrous capsule (FC) density and promoted superior vascularization compared with PCSM coating for polytetrafluoroethylene (PTFE). PCSM was fabricated with solvent casting/particulate leaching method using silica gel as porogen and characterized in vitro. Then, PCSM-Nafion and PCSM-PTFE composites were assembled with hydrated PCSM and implanted subcutaneously in rats. The histological analysis was performed in comparison with Nafion and PTFE. Implants were explanted 35, 65, and 100 days after the implantation. Histological assessments indicated that both composites achieved presumed effects of porous coatings on decreasing collagen deposition and promoting angiogenesis. PCSM-PTFE exerted higher collagen deposition by area ratio, both within and outside, compared with that of PCSM-Nafion. Angiogenesis within and outside the PCSM-Nafion both increased over time, but that of the PCSM-PTFE within decreased. Copyright © 2013 Wiley Periodicals, Inc.

  11. Pulse electrodeposition of self-lubricating Ni–W/PTFE nanocomposite coatings on mild steel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sangeetha, S. [Advanced Nanocomposite Coatings Laboratory, Department of Industrial Chemistry, Alagappa University, Karaikudi 630 003 (India); Kalaignan, G. Paruthimal, E-mail: pkalaignan@yahoo.com [Advanced Nanocomposite Coatings Laboratory, Department of Industrial Chemistry, Alagappa University, Karaikudi 630 003 (India); Anthuvan, J. Tennis [M. Kumarasamy College of Engineering, Karur, Tamil Nadu (India)

    2015-12-30

    Graphical abstract: - Highlights: • PTFE polymer inclusion on Ni–W alloy matrix was electrodeposited by pulse current method. • Tribological properties and electrochemical characterizations of the nanocomposite coatings were analyzed. • The hydrophobic behaviour of Ni–W/PTFE nanocomposite coating was measured. • Ni–W/PTFE nanocomposite coatings have showed superior tribological properties and corrosion resistance relative to that of the Ni–W alloy matrix. - Abstract: Ni–W/PTFE nanocomposite coatings with various contents of PTFE (polytetafluoroethylene) particles were prepared by pulse current (PC) electrodeposition from the Ni–W plating bath containing self lubricant PTFE particles to be co-deposited. Co-deposited PTFE particulates were uniformly distributed in the Ni–W alloy matrix. The coatings were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), X-ray Diffractometry (XRD) and Vicker's micro hardness tester. Tafel Polarization and electrochemical Impedance methods were used to evaluate the corrosion resistance behaviour of the nanocomposite coatings in 3.5% NaCl solution. It was found that, the Ni–W/PTFE nanocomposite coating has better corrosion resistance than the Ni–W alloy coating. Surface roughness and friction coefficient of the coated samples were assessed by Mitutoyo Surftest SJ-310 (ISO1997) and Scratch tester TR-101-M4 respectively. The contact angle (CA) of a water droplet on the surface of nanocomposite coating was measured by Optical Contact Goniometry (OCA 35). These results indicated that, the addition of PTFE in the Ni–W alloy matrix has resulted moderate microhardness, smooth surface, less friction coefficient, excellent water repellency and enhanced corrosion resistance of the nanocomposite coatings.

  12. Efeitos a curto prazo de "stents" não recobertos e recobertos com politetrafluoroetileno em aorta de suínos: um modelo experimental Short-term effects of polytetrafluoroethylene covered and uncovered metallic "stents" in pig aorta: an experimental model

    Directory of Open Access Journals (Sweden)

    Marco Aurélio Grüdtner

    2004-04-01

    Full Text Available OBJETIVO: Descrever um estudo experimental avaliando através da morfometria digital o espessamento intimal na parede arterial após o implante de "stents" metálicos auto-expansíveis recobertos ou não com politetrafluoroetileno (PTFE na aorta de suínos. MÉTODOS: Em três grupos de suínos jovens uma bainha introdutora de 12 F foi inserida na aorta abdominal distal. Os animais do grupo I (n=5 foram considerados controle. Os animais do grupo II (n=10 receberam o implante de um stent metálico auto-expansível não recoberto. No grupo III (n=10 um stent auto-expansível recoberto com PTFE foi inserido. Após quatro semanas os animais foram sacrificados e os espécimes arteriais foram retirados, sendo o espessamento intimal quantificado pela análise morfométrica. RESULTADOS: Na comparação entre os grupos I, II e III quanto às áreas da íntima, média e índice intimal, não foi observada variação estatisticamente significativa. Diferenças foram observadas entre os grupos em relação às áreas luminais proximais (p=0,0036 e distais (p=0,044. Através dos testes de comparação múltipla para Kruskal-Wallis foi identificada uma diferença entre os grupos I e II. Entretanto, quando essas variáveis foram controladas pelo fator peso (relação área luminal/peso, a diferença não foi mais observada. CONCLUSÕES: Nesse estudo a curto prazo, o revestimento de PTFE não esteve associado a adicional espessamento intimal além daquele promovido pelo dispositivo metálico em artérias de grande calibre e condições de alto fluxo.PURPOSE: To report an experimental study evaluating, through digital morphometry, the intimal thickening of the arterial wall after the implant of auto-expandable stainless steel stents covered or not with polytetrafluoroethylene (PTFE in the pig aorta. METHODS: In three groups of pigs a 12 F sheath was inserted in distal abdominal aorta. Group I animals (n=5 served as control. Group II animals (n=10 received an auto-expandable

  13. Experience of usage of forming rings and protective caps made of PTFE on the single-component implants

    Directory of Open Access Journals (Sweden)

    S. A. Chertov

    2014-04-01

    Full Text Available Relevance. The main reason that limits the usage of single-component implants, as compared with collapsible (two-component implants is the high risk of infectious and inflammatory complications in the postoperative period and problems in prosthetics in the esthetically important areas. Therefore, the usage of elements that contribute to healing of the mucous membrane in the early stages of implantation is particularly up-to-date. Work objective is to determine the clinical effectiveness of usage of forming rings and protective caps made of PTFE on the single-component implants in the prevention of peri-implant pathology on a one-step surgical implantation. Materials and methods of the investigation. For this work we used the treatment results of 24 patients with various dentition defects. According to the single-component implant procedure 52 single-component implants were mounted. The head of monolithic implants (38 p. were isolated by rings or caps made of PTFE. For comparison, 14 implants remained bare for 2-6 weeks before the temporary prosthesis. Postoperatively, subjective feelings were noted in patients, the presence or absence of pain complaints during the examination and palpation, the nature and extent of edema, the phenomena of inflammation around the implant neck were checked. At the stage of sutures removal the degree of soft plaque deposits on the healing elements and titanium implant heads was assessed. Results of the investigation and their discussion. No effects of mucosal hyperemia around the supporting elements made of PTFE were revealed, there was no soft and hard plaque on the rings and caps in most patients of the main group. In patients of the control group, on the contrary, the appearance of the biofilm that covered the head and the implant shoulder on all abutments, which were not protected by a ring or cap, was noted. The healing period of mucous membrane in patients of the control group was longer, the quality of

  14. Conformable covered versus uncovered self-expandable metallic stents for palliation of malignant gastroduodenal obstruction: a randomized prospective study.

    Science.gov (United States)

    Lim, Sun Gyo; Kim, Jin Hong; Lee, Kee Myung; Shin, Sung Jae; Kim, Chan Gyoo; Kim, Kyung Ho; Kim, Ho Gak; Yang, Chang Heon

    2014-07-01

    A conformable self-expandable metallic stent was developed to overcome the limitation of previous self-expandable metallic stents. The aim of this study was to evaluate outcomes after placement of conformable covered and uncovered self-expandable metallic stents for palliation of malignant gastroduodenal obstruction. A single-blind, randomized, parallel-group, prospective study were conducted in 4 medical centres between March 2009 and July 2012. 134 patients with unresectable malignant gastroduodenal obstruction were assigned to a covered double-layered (n=66) or uncovered unfixed-cell braided (n=68) stent placement group. Primary analysis was performed to compare re-intervention rates between two groups. 120 patients were analysed (59 in the covered group and 61 in the uncovered group). Overall rates of re-intervention were not significantly different between the two groups: 13/59 (22.0%) in the covered group vs. 13/61 (21.3%) in the uncovered group, p=0.999. Stent migration was more frequent in the covered group than in the uncovered group (p=0.003). The tumour ingrowth rate was higher in the uncovered group than in the covered group (p=0.016). The rates of re-intervention did not significantly differ between the two stents. Conformable covered double-layered and uncovered unfixed-cell braided stents were associated with different patterns of stent malfunction. Copyright © 2014 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

  15. Treatment of cuff-related tracheal stenosis with a fully covered retrievable expandable metallic stent

    International Nuclear Information System (INIS)

    Chen, G.; Wang, Z.; Liang, X.; Wang, Y.; Wang, Y.; Wang, Z.; Xian, J.

    2013-01-01

    Aim: To investigate the clinical effectiveness, complications, and optimal duration of use of covered retrievable expandable metallic stents in the management of cuff-related tracheal stenosis. Materials and methods: Twenty-one patients with cuff-related tracheal stenosis, Meyer–Cotton grade II (29%) and III (71%), who underwent fluoroscopically guided placement of covered retrievable expandable metallic stents were studied. Sixty-four-section computed tomography (CT) and bronchovideoscopy were performed prior to stent insertion, 1 month after stent insertion, in the case of stent-related complications, and after stent removal. Clinical manifestations, Hugh–Jones classification, and forced expiratory volume in 1 s (FEV1) were used to evaluate respiratory function before and after stent insertion and removal. The diameter of the stricture and FEV1 changes before insertion and after removal were analysed using the paired samples t-test. A p-value of ≤0.05 was considered statistically significant. Results: Twenty-one patients had 27 covered retrievable expandable metallic stents placed. Stents were electively removed from 20 patients. The median duration of stent placement was 5 months (range 4–12 months). One stent was not removed due to mucopolysaccharidosis type II (MPS II or Hunter syndrome) with tracheomalacia. After stent removal, airway dimensions increased and airway occlusion was symptomatically relieved in all patients. CT and bronchovideoscopy showed patent lumens with increased dimensions. Stent-related complications occurred in 19 (91%) patients, including granulation tissue formation (n = 18, 86%), stent migration and stent expectoration (n = 2, 10%), mucus plugging (n = 1, 5%), and halitosis (n = 6, 29%). Some patients experienced multiple complications, which were all managed effectively while the stent was still in place. There was a statistically significant difference in the diameter of the stricture and FEV1 between the time of stent

  16. Treatment of cuff-related tracheal stenosis with a fully covered retrievable expandable metallic stent.

    Science.gov (United States)

    Chen, G; Wang, Z; Liang, X; Wang, Y; Wang, Y; Wang, Z; Xian, J

    2013-04-01

    To investigate the clinical effectiveness, complications, and optimal duration of use of covered retrievable expandable metallic stents in the management of cuff-related tracheal stenosis. Twenty-one patients with cuff-related tracheal stenosis, Meyer-Cotton grade II (29%) and III (71%), who underwent fluoroscopically guided placement of covered retrievable expandable metallic stents were studied. Sixty-four-section computed tomography (CT) and bronchovideoscopy were performed prior to stent insertion, 1 month after stent insertion, in the case of stent-related complications, and after stent removal. Clinical manifestations, Hugh-Jones classification, and forced expiratory volume in 1 s (FEV1) were used to evaluate respiratory function before and after stent insertion and removal. The diameter of the stricture and FEV1 changes before insertion and after removal were analysed using the paired samples t-test. A p-value of ≤0.05 was considered statistically significant. Twenty-one patients had 27 covered retrievable expandable metallic stents placed. Stents were electively removed from 20 patients. The median duration of stent placement was 5 months (range 4-12 months). One stent was not removed due to mucopolysaccharidosis type II (MPS II or Hunter syndrome) with tracheomalacia. After stent removal, airway dimensions increased and airway occlusion was symptomatically relieved in all patients. CT and bronchovideoscopy showed patent lumens with increased dimensions. Stent-related complications occurred in 19 (91%) patients, including granulation tissue formation (n = 18, 86%), stent migration and stent expectoration (n = 2, 10%), mucus plugging (n = 1, 5%), and halitosis (n = 6, 29%). Some patients experienced multiple complications, which were all managed effectively while the stent was still in place. There was a statistically significant difference in the diameter of the stricture and FEV1 between the time of stent insertion and removal. An improvement in

  17. High-resolution 3D X-ray imaging of intracranial nitinol stents

    International Nuclear Information System (INIS)

    Snoeren, Rudolph M.; With, Peter H.N. de; Soederman, Michael; Kroon, Johannes N.; Roijers, Ruben B.; Babic, Drazenko

    2012-01-01

    To assess an optimized 3D imaging protocol for intracranial nitinol stents in 3D C-arm flat detector imaging. For this purpose, an image quality simulation and an in vitro study was carried out. Nitinol stents of various brands were placed inside an anthropomorphic head phantom, using iodine contrast. Experiments with objects were preceded by image quality and dose simulations. We varied X-ray imaging parameters in a commercially interventional X-ray system to set 3D image quality in the contrast-noise-sharpness space. Beam quality was varied to evaluate contrast of the stents while keeping absorbed dose below recommended values. Two detector formats were used, paired with an appropriate pixel size and X-ray focus size. Zoomed reconstructions were carried out and snapshot images acquired. High contrast spatial resolution was assessed with a CT phantom. We found an optimal protocol for imaging intracranial nitinol stents. Contrast resolution was optimized for nickel-titanium-containing stents. A high spatial resolution larger than 2.1 lp/mm allows struts to be visualized. We obtained images of stents of various brands and a representative set of images is shown. Independent of the make, struts can be imaged with virtually continuous strokes. Measured absorbed doses are shown to be lower than 50 mGy Computed Tomography Dose Index (CTDI). By balancing the modulation transfer of the imaging components and tuning the high-contrast imaging capabilities, we have shown that thin nitinol stent wires can be reconstructed with high contrast-to-noise ratio and good detail, while keeping radiation doses within recommended values. Experimental results compare well with imaging simulations. (orig.)

  18. Radiation syntheses and characteristics of PTFE-g-PSSA ion exchange membranes for applications in vanadium redox battery

    International Nuclear Information System (INIS)

    Peng Jinfen; Qiu Jinyi; Zhai Maolin; Xu Peng; Peng Jing; Li Jiuqiang; Wei Genshuan

    2006-01-01

    Radiation-induced grafting of styrene onto polyterafluorothylene (PTFE) films was studied by simultaneous irradiation technique. The grafting was induced by 60 Co γ-rays at room temperatures. Effects of the solvent, absorbed dose, dose rate, atmosphere and initial monomer concentration on the grafting yield were investigated and optimal grafting conditions were obtained. Subsequently, sulphonation of the grafted PTFE films (PTFE-g-PS) was investigated and a series of ion exchange membranes (PTFE-g-PSSA) was prepared. FTIR, TGA, XRD and SEM measurements showed that grafting and sulfonation of the PTFE films were successfully carried out; moreover, grafting of styrene mainly occurred in the pores of PTFE films and crystallization degree of the PTFE films decreased with increase grafting yield. Water uptake, ion exchange capacity (IEC) and conductivity of the PTFE-g-PSSA membrane increased with the grafting yield. The results indicated that by 20 kGy irradiation, ion exchange membrane which was suitable for vanadium redox battery can be prepared. (authors)

  19. Biocompatibility of a new device of self-expandable covered and non-covered tracheal stent: comparative study in rats

    Directory of Open Access Journals (Sweden)

    Olavo Ribeiro Rodrigues

    2013-01-01

    Full Text Available PURPOSE: To investigate the compatibility of a new model of self-expandable tracheal stent in rats. METHODS: A new device of polyurethane covered and non - covered stent was placed in the trachea of Wistar rats. Animals were distributed in two groups: the polyurethane covered and non-covered group. Macroscopic parameters included position within the tracheal lumen, adherence to the mucosa, degree of dilatation, permeability and internal diameter. Microscopic findings evaluated were: incorporation, inflammatory activity, granulation tissue and epithelial revetment injuries. The observation follow-up was six weeks. All parameters were quantified based on determined score values. Incorporation of the stents was evaluated based on the observation if the stent was fixed into the trachea or if it could be removed. Degree of dilatation was performed by external diameter measurements. Granulation tissue was evaluated by measurements of height of the tissue growing into the tracheal lumen. RESULTS: 100% of non-covered stents had total attachment to mucosa and 100% of polyurethane covered type had adherence only. Regarding dilatation, granulation tissue, inflammatory activity and internal diameter measurements, there were no significant differences between the groups. Pathological tracheal wall injuries were present in both groups. CONCLUSION: Both models of stent demonstrated biocompatibility with the trachea. Rats are suitable for an experimental model of tracheal stent study.

  20. Structure-property effects on mechanical, friction and wear properties of electron modified PTFE filled EPDM composite

    Directory of Open Access Journals (Sweden)

    2009-01-01

    Full Text Available Tribological properties of Ethylene-Propylene-Diene-rubber (EPDM containing electron modified Polytetrafluoroethylene (PTFE have been investiagted with the help of pin on disk tribometer without lubrication for a testing time of 2 hrs in atmospheric conditions at a sliding speed and applied normal load of 0.05 m•s–1 and FN = 1 N, respectively. Radiation-induced chemical changes in electron modified PTFE powders were analyzed using Electron Spin Resonance (ESR and Fourier Transform Infrared (FTIR specroscopy to characterize the effects of compatibility and chemical coupling of modified PTFE powders with EPDM on mechanical, friction and wear properties. The composites showed different friction and wear behaviour due to unique morphology, dispersion behaviour and radiation functionalization of PTFE powders. In general, EPDM reinforced with electron modified PTFE powder demonstrated improvement both in mechanical and tribological properties. However, the enhanced compatibility of PTFE powder resulting from the specific chemical coupling of PTFE powder with EPDM has been found crucial for mechanical, friction and wear properties.

  1. Novel self-expandable, stent-based transcatheter pulmonic valve: a preclinical animal study.

    Science.gov (United States)

    Kim, Gi Beom; Lim, Hong-Gook; Kim, Yong Jin; Choi, Eun Young; Kwon, Bo Sang; Jeong, Saeromi

    2014-04-15

    Because transcatheter implantation of pulmonary valve is indicated for limited-size dysfunctional right ventricular outflow tract only as a balloon-expandable stent, we investigated the feasibility of a large-diameter self-expandable valved stent and the durability of the valve after >6 months. We made a nitinol-wire-based, self-expandable valved stent with leaflets made from porcine pericardium. The porcine pericardium was treated with α-galactosidase, glutaraldehyde, and glycine after decellularization. After cutting the inguinal or cervical area, we implanted a valved stent in 12 sheep through the femoral or jugular vein by using an 18-Fr delivery catheter, controlling the catheter handles and hook block under fluoroscopic and echocardiographic guidance. The mean body weight of sheep was 43.9 kg. We successfully implanted valved stents (diameter: 24 mm in 7 sheep, 26 mm in 5 sheep) in good position in 8 sheep, in the main pulmonary artery (PA) in 2 sheep, and in the right ventricular outlet tract (RVOT) in 2 sheep. We sacrificed 8 sheep (6 sheep in good position, 1 sheep in the main PA, and 1 sheep in the RVOT) after >6 months. Five of the 6 sheep implanted in good position showed well-preserved valve morphology at the time of sacrifice. Histologic findings after routine sacrifice showed well-maintained collagen wave structure and no visible calcification in all explanted valve leaflets. Transcatheter implantation of a nitinol-wire-based, self-expandable valved stent in the pulmonic valve was feasible, and stents implanted in good position showed well-preserved valve leaflets with functional competence in the mid-term results. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  2. Hardness and Microstructure of Binary and Ternary Nitinol Compounds

    Science.gov (United States)

    Stanford, Malcolm K.

    2016-01-01

    The hardness and microstructure of twenty-six binary and ternary Nitinol (nickel titanium, nickel titanium hafnium, nickel titanium zirconium and nickel titanium tantalum) compounds were studied. A small (50g) ingot of each compound was produced by vacuum arc remelting. Each ingot was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the ingots were then heat treated at 800, 900, 1000 or 1100 degree C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline material (55-Nitinol, 55 at.% nickel - 45 at.% titanium, after heat treatment at 900 degC). The results show that eleven of the studied compounds had higher hardness values than the baseline material. Moreover, twelve of the studied compounds had measured hardness values greater 600HV at heat treatments from 800 to 900 degree C.

  3. The underdilation of nitinol stents at TIPS implantation: Solution or illusion?

    Energy Technology Data Exchange (ETDEWEB)

    Mollaiyan, Ashkan [University Hospital, Department of Radiology, Hugstetterstrasse 55, 79106 Freiburg (Germany); Bettinger, Dominik [University Hospital, Department of Gastroenterology, Hugstetterstrasse 55, 79106 Freiburg (Germany); Berta-Ottenstein-Programme, Faculty of Medicine, University of Freiburg (Germany); Rössle, Martin, E-mail: Martin-Roessle@t-online.de [University Hospital, Department of Gastroenterology, Hugstetterstrasse 55, 79106 Freiburg (Germany); Praxiszentrum für Gastroenterologie, Bertoldstrasse 48, 79098 Freiburg (Germany)

    2017-04-15

    Purpose: This study investigates the behaviour of self-expanding nitinol stents at the time of TIPS-implantation and thereafter. Methods: Hundred consecutive patients with cirrhosis receiving a TIPS revision were included. The smallest stent diameter was measured radiologically immediately after implantation and before shunt revision. Accuracy of the measurement was assessed by comparing the nominal stent diameter with the largest stent diameter measured at the time of revision. Results: Pearson correlation between largest measured and nominal diameters was excellent (r = 0.952, p < 0.001) showing that measurements are accurate. At TIPS implantation all stents were markedly underdilated reaching only 76–92% of their nominal diameter. Smallest measured diameters were similar (8 mm) irrespective of the nominal diameter (8, 9, 10 mm) of the stent. In addition, smallest diameters of 10 mm stents were similar irrespective whether 8, 9 or 10 mm balloons were used. During a mean follow-up of 12.7 ± 17.8 months (median 3 months, range 1–81) stents expanded by 0.5–1.6 mm dependent on the nominal stent size (8, 9, 10 mm) and the grade of primary underdilation. No significant difference was found between Viatorr and bare stents. Conclusions: At TIPS-implantation, the compliance of the surrounding tissue predominantly determines the stent diameter. The nominal size of the stent or the dilatation balloon has little influence. Accurate adjustment of a desired pressure gradient is, therefore, not possible. During follow-up, stents expand towards their nominal diameter questioning the usefulness of underdilation.

  4. The underdilation of nitinol stents at TIPS implantation: Solution or illusion?

    International Nuclear Information System (INIS)

    Mollaiyan, Ashkan; Bettinger, Dominik; Rössle, Martin

    2017-01-01

    Purpose: This study investigates the behaviour of self-expanding nitinol stents at the time of TIPS-implantation and thereafter. Methods: Hundred consecutive patients with cirrhosis receiving a TIPS revision were included. The smallest stent diameter was measured radiologically immediately after implantation and before shunt revision. Accuracy of the measurement was assessed by comparing the nominal stent diameter with the largest stent diameter measured at the time of revision. Results: Pearson correlation between largest measured and nominal diameters was excellent (r = 0.952, p < 0.001) showing that measurements are accurate. At TIPS implantation all stents were markedly underdilated reaching only 76–92% of their nominal diameter. Smallest measured diameters were similar (8 mm) irrespective of the nominal diameter (8, 9, 10 mm) of the stent. In addition, smallest diameters of 10 mm stents were similar irrespective whether 8, 9 or 10 mm balloons were used. During a mean follow-up of 12.7 ± 17.8 months (median 3 months, range 1–81) stents expanded by 0.5–1.6 mm dependent on the nominal stent size (8, 9, 10 mm) and the grade of primary underdilation. No significant difference was found between Viatorr and bare stents. Conclusions: At TIPS-implantation, the compliance of the surrounding tissue predominantly determines the stent diameter. The nominal size of the stent or the dilatation balloon has little influence. Accurate adjustment of a desired pressure gradient is, therefore, not possible. During follow-up, stents expand towards their nominal diameter questioning the usefulness of underdilation.

  5. Synthesis and characterization of c-PTFE-g-styrene copolymer by preirradiation method

    International Nuclear Information System (INIS)

    Oktaviani; Ambyah Suliwarno; Tita Puspitasari

    2011-01-01

    Crosslinked-poly(tetrafluoroethylene)-graf-styrene (c-PTFE-g-styrene) copolymer has been synthesized by copolymerization preirradiation method. Irradiation onto c-PTFE films was carried out by γ-ray with irradiation doses of 15, 30, and 45 kGy at room temperature. Styrene was grafted into irradiated c-PTFE films in the temperature range of between 600-90°C. Parameter observed in the grafting process was degree of grafting. The results showed that the degree of grafting increased with increasing of irradiation doses. The highest degree of grafting was 25,44 % obtained at temperature of 70°C and still increased up to 25,73% with increasing of the grafting time. The optimum grafting time was 2 hours. Chemical and physical properties of c-PTFE-g-styrene film were analyzed by IR spectrophotometer and Scanning Electron Microscopy (SEM). (author)

  6. Annealing dependent evolution of columnar nanostructures in RF magnetron sputtered PTFE films for hydrophobic applications

    Science.gov (United States)

    Tripathi, S.; De, Rajnarayan; Maidul Haque, S.; Divakar Rao, K.; Misal, J. S.; Prathap, C.; Das, S. C.; Patidar, Manju M.; Ganesan, V.; Sahoo, N. K.

    2018-01-01

    Present communication focuses on a relatively less explored direction of producing rough polytetrafluoroethylene (PTFE) surfaces for possible hydrophobic applications. The experiments were carried out to make rough PTFE films without losing much of the transmission, which is an important factor while designing futuristic solar cell protection covers. After annealing temperature optimization, as grown RF magnetron sputtered PTFE films (prepared at 160 W RF power) were subjected to vacuum annealing at 200 °C for different time durations ranging from 1 to 4 h. The films show morphological evolution exhibiting formation and growth of columnar nanostructures that are responsible for roughening of the films due to annealing induced molecular migration and rearrangement. In agreement with this, qualitative analysis of corresponding x-ray reflectivity data shows modification in film thickness, which may again be attributed to the growth of columns at the expense of the atoms of remaining film molecules. However, the observations reveal that the film annealed at 200 °C for 2 h gives a combination of patterned columnar structures and reasonable transmission of >85% (in 500-1000 nm wavelength range), both of which are deteriorated when the films are annealed either at high temperature beyond 200 °C or for long durations >3 h. In addition, attenuated total reflection-Fourier transform infrared spectroscopy results reveal that the molecular bonds remain intact upon annealing at any temperature within the studied range indicating the stable nature of the films.

  7. Radiation grafting of styrene and maleic anhydride onto PTFE membranes and sequent sulfonation for applications of vanadium redox battery

    International Nuclear Information System (INIS)

    Qiu Jingyi; Ni Jiangfeng; Zhai Maolin; Peng Jing; Zhou Henghui; Li Jiuqiang; Wei Genshuan

    2007-01-01

    Using γ-radiation technique, poly(tetrafluoroethylene) (PTFE) membrane was grafted with styrene (St) (PTFE-graft-PS) or binary monomers of St and maleic anhydride (MAn) (PTFE-graft-PS-co-PMAn), respectively. Then grafted membranes were further sulfonated with chlorosulfonic acid into ion-exchange membranes (denoted as PTFE-graft-PSSA and PTFE-graft-PSSA-co-PMAc, respectively) for application of vanadium redox battery (VRB). Micro-FTIR analysis indicated that PTFE was successfully grafted and sulfonated at the above two different conditions. However, a higher degree of grafting (DOG) was obtained in St/MAn binary system at the same dose due to a synergistic effect. Comparing with PTFE-graft-PSSA, PTFE-graft-PSSA-co-PMAc membrane showed higher water uptake and ion-exchange capacity (IEC) and lower area resistance (AR) at the same DOG. In addition, PTFE-graft-PSSA-co-PMAc with 6% DOG also showed a higher IEC and higher conductivity compared to Nafion membrane. Radiation grafting of PTFE in St/MAn binary system and sequent sulfonation is an appropriate method for preparing ion-exchange membrane of VRB

  8. The use of expanded polytetrafluoroethylene in depressed deformities of the face.

    Science.gov (United States)

    Liu, Xiaowei; Zhang, Yiming; Wang, Shaoliang; Lei, Zeyuan; Li, Xiang; Fan, Dongli

    2016-11-01

    Expanded polytetrafluoroethylene (ePTFE) has been extensively used for facial soft tissue augmentation procedures, and is regarded as safe and reliable and suitable as a permanent implant. This implant is generally used in the lower third of the face for lips filling, nasal augmentation, nasolabial folds and chin augmentation, and rarely for congenital or acquired depressed deformities of the face. The aim of the present study was to assess the effects of ePTFE in congenital or acquired depressed deformities of the face. From September, 2008 to January, 2014, 26 patients were implanted with the material ePTFE to correct depressed deformities of the face. The average age at operation was 23.2 years, with a range of 17-45 years. The depressed deformities were lateralized. The follow-up period was 6-18 months (average 9 months). The etiologies of the depressed deformities included stable hemifacial atrophy (3 cases), craniofacial microsomia (13 cases), bony depression after trauma (8 cases), and other unclear reasons (2 cases). The operations were performed under local anesthesia. ePTFE was inserted in different tissue planes that varied among the different subanatomical areas in the face: beneath the superficial temporal fascia in the temporal area, and on the surface of the superficial musculoaponeurotic system in the zygomatic area, cheek and mandibular area. All of the patients were followed up. Most of the patients [25 of 26 patients (96.2%)] were satisfied with the results, while 1 patient (3.8%) was not satisfied for incomplete correction of the depressed deformity. In conclusion, aside from lipofilling and a free flap transfer, the results showed that ePTFE was an alternative treatment for facial depressed deformity.

  9. Spray-coating process in preparing PTFE-PPS composite super-hydrophobic coating

    Directory of Open Access Journals (Sweden)

    Rui Weng

    2014-03-01

    Full Text Available In order to improve the performance of a liquid-floated rotor micro-gyroscope, the resistance of the moving interface between the rotor and the floating liquid must be reduced. Hydrophobic treatment can reduce the frictional resistance between such interfaces, therefore we proposed a method to prepare a poly-tetrafluoroethylene (PTFE-poly-phenylene sulphide (PPS composite super-hydrophobic coating, based on a spraying process. This method can quickly prepare a continuous, uniform PTFE-PPS composite super-hydrophobic surface on a 2J85 material. This method can be divided into three steps, namely: pre-treatment; chemical etching; and spraying. The total time for this is around three hours. When the PTFE concentration is 4%, the average contact angle of the hydrophobic coating surface is 158°. If silicon dioxide nanoparticles are added, this can further improve the adhesion and mechanical strength of the super-hydrophobic composite coating. The maximum average contact angle can reach as high as 164° when the mass fraction of PTFE, PPS and silicon dioxide is 1:1:1.

  10. Spray-coating process in preparing PTFE-PPS composite super-hydrophobic coating

    Science.gov (United States)

    Weng, Rui; Zhang, Haifeng; Liu, Xiaowei

    2014-03-01

    In order to improve the performance of a liquid-floated rotor micro-gyroscope, the resistance of the moving interface between the rotor and the floating liquid must be reduced. Hydrophobic treatment can reduce the frictional resistance between such interfaces, therefore we proposed a method to prepare a poly-tetrafluoroethylene (PTFE)-poly-phenylene sulphide (PPS) composite super-hydrophobic coating, based on a spraying process. This method can quickly prepare a continuous, uniform PTFE-PPS composite super-hydrophobic surface on a 2J85 material. This method can be divided into three steps, namely: pre-treatment; chemical etching; and spraying. The total time for this is around three hours. When the PTFE concentration is 4%, the average contact angle of the hydrophobic coating surface is 158°. If silicon dioxide nanoparticles are added, this can further improve the adhesion and mechanical strength of the super-hydrophobic composite coating. The maximum average contact angle can reach as high as 164° when the mass fraction of PTFE, PPS and silicon dioxide is 1:1:1.

  11. The Mechanical and Reaction Behavior of PTFE/Al/Fe2O3 under Impact and Quasi-Static Compression

    Directory of Open Access Journals (Sweden)

    Jun-yi Huang

    2017-01-01

    Full Text Available Quasi-static compression and drop-weight test were used to characterize the mechanical and reaction behavior of PTFE/Al/Fe2O3 composites. Two kinds of PTFE/Al/Fe2O3 composites were prepared with different mass of PTFE, and the reaction phenomenon and stress-strain curves were recorded; the residuals after reaction were analyzed by X-ray diffraction (XRD. The results showed that, under quasi-static compression condition, the strength of the materials is increased (from 37.1 Mpa to 77.2 Mpa with the increase of PTFE, and the reaction phenomenon occurred only in materials with high PTFE content. XRD analysis showed that the reaction between Al and Fe2O3 was not triggered with identical experimental conditions. In drop-weight tests, PTFE/Al/Fe2O3 specimens with low PTFE content were found to be more insensitive by high-speed photography, and a High Temperature Metal Slag Spray (HTMSS phenomenon was observed in both kinds of PTFE/Al/Fe2O3 composites, indicating the existence of thermite reaction, which was confirmed by XRD. In PTFE/Al/Fe2O3 system, the reaction between PTFE and Al precedes the reaction between Al and Fe2O3.

  12. Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity

    International Nuclear Information System (INIS)

    Bayat, A.; Ebrahimi, M.; Nourmohammadi, A.; Moshfegh, A.Z.

    2015-01-01

    Highlights: • Thin layer of Teflon was deposited on ZnO nanorods using RF sputtering technique. • Water contact angle was measured from 3° for ZnO to 160° for the PTFE/ZnO. • Very low contact angle hysteresis of ∼2° and sliding angle of ∼1° was measured. • Excellent stability under UV illumination was observed for the PTFE/ZnO sample. • We have proposed a model to describe wettability property supporting our data. - Abstract: In this research, initially anodization process was used to fabricate ZnO nanorods on Zn substrate and then RF sputtering technique was applied to grow a thin layer of polytetrafluoroethylene (PTFE, Teflon) on the coated ZnO nanorods for producing a superhydrophobic surface. According to scanning electron microscopy (SEM) observations, ZnO nanorods were formed with average diameter and length of about ∼180 nm and 14 μm, respectively. Superhydrophilic property of ZnO nanorods and superhydrophobic property of PTFE/ZnO nanorods was investigated by water contact angle (WCA) measurements. It was found that the contact angle varied with the PTFE deposition time. The highest contact angle measurement was obtained at 160° for the PTFE (60 min coating)/ZnO as optimum sample which indicates its superhydrophobic property. X-ray photoelectron spectroscopy (XPS) determined surface chemical composition and F/C ratio of about 1.27 for this sample. A change of water contact angle from 3° to 160° indicates transition from superhydrophilic to superhydrophobic state. Very low contact angle hysteresis (CAH) of ∼2° and sliding angle (SA) of ∼1° as well as unchanged contact angle under UV illumination was observed for the synthesized optimum PTFE/ZnO sample exhibits an excellent superhydrophobic property. Based on our data analysis, the ZnO nanorods and the PTFE/ZnO nanorods obey Wenzel and Cassie–Baxter model, respectively

  13. Production of porous PTFE-Ag composite thin films by pulsed laser deposition

    International Nuclear Information System (INIS)

    Kecskeméti, Gabriella; Hopp, Béla; Smausz, Tomi; Tóth, Zsolt; Szabó, Gábor

    2012-01-01

    The suitability of pulsed laser deposition technique for preparation of polytetrafluoroethylene (PTFE) and silver (Ag) composite thin films was demonstrated. Disk-shaped targets combined from silver and Teflon with various percentages were ablated with pulses of an ArF excimer laser. The chemical composition of the deposited layers was estimated based on deposition rates determined for the pure PTFE and Ag films. EDX and SEM analyses using secondary electron and backscattered electron images proved that the morphology of the layers is determined by the PTFE which is the main constituent and it is transferred mostly in form of grains and clusters forming a sponge-like structure with high specific surface. The Ag content is distributed over the surface of the PTFE structure. Contact angle measurements showed that with increasing the amount of Ag in the deposited layers the surface significantly enhanced the wetting properties. Conductivity experiments demonstrated that when the average silver content of the layers was increased from 0.16 to 3.28 wt% the resistance of our PTFE-Ag composite films decreased with about three orders of magnitudes (from ∼10 MΩ to ∼10 kΩ). The properties of these films suggest as being a good candidate for future electrochemical sensor applications.

  14. Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

    Science.gov (United States)

    Sivan, Shiril; Di Prima, Matthew; Weaver, Jason D.

    2017-09-01

    Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F2129 are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential. However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life. Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

  15. Thermal desorption study of physical forces at the PTFE surface

    Science.gov (United States)

    Wheeler, D. R.; Pepper, S. V.

    1987-01-01

    Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possible role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

  16. Monitorizing nitinol alloy surface reactions for biofouling studies

    International Nuclear Information System (INIS)

    Dinu, C.Z.; Dinca, V.C.; Soare, S.; Moldovan, A.; Smarandache, D.; Scarisoareanu, N.; Barbalat, A.; Birjega, R.; Dinescu, M.; DiStefano, V. Ferrari

    2007-01-01

    Growth and deposition of unwanted bacteria on implant metal alloys affect their use as biomedical samples. Monitoring any bacterial biofilm accumulation will provide early countermeasures. For a reliable antifouling strategy we prepared nitinol (NiTi) thin films on Ti-derived substrates by using a pulsed laser deposition (PLD) method. As the microstructure of Ti-alloy is dictated by the tensile strength, fatigue and the fracture toughness we tested the use of hydrogen as an alloying element. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) investigated the crystalline structure, chemical composition and respectively the surface morphology of the nitinol hydrogen and hydrogen-free samples. Moreover, the alloys were integrated and tested using a cellular metric and their responses were systematic evaluated and quantified. Our attractive approach is meant to select the suitable components for an effective and trustworthy anti-fouling strategy. A greater understanding of such processes should lead to novel and effective control methods that would improve in the future implant stability and capabilities

  17. Emulsion Electrospinning of Polytetrafluoroethylene (PTFE) Nanofibrous Membranes for High-Performance Triboelectric Nanogenerators.

    Science.gov (United States)

    Zhao, Pengfei; Soin, Navneet; Prashanthi, Kovur; Chen, Jinkai; Dong, Shurong; Zhou, Erping; Zhu, Zhigang; Narasimulu, Anand Arcot; Montemagno, Carlo D; Yu, Liyang; Luo, Jikui

    2018-02-14

    Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (V oc ) of up to ∼900 V, a short-circuit current density (J sc ) of ∼20 mA m -2 , and a corresponding charge density of ∼149 μC m -2 , which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m -2 with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the

  18. Temporary urethral covered stent - third year of experience

    International Nuclear Information System (INIS)

    Stojanovis, V.; Maksimovis, H.; Markovis, B.; Markovis, Z.

    2006-01-01

    Full text: In October 2003, a new generation of urethral stents ALLIUM, produced in Israel, were used at the Department of Interventional Radiology, CCS, in 18 patients with chronic stricture of bulbar urethra. The indications for insertion were determined according to well-known and recognized therapeutical protocols. The stent is made of nitinol wire with polyurethane cover. It is inserted under local anesthesia by a special self-expandable system that may be fixed or flexible. The stents we used were 3-6 cm long and 28 Fr wide. Radioscopic-assisted insertion was performed over formerly placed metal guide. Prior to insertion, balloon-catheter dilatation of stricture matching the stent width was carried out. Pre-insertion urethrotomy was performed in one case. The insertion technique is simple, presupposing the knowledge of older generations of techniques of urethral dilatation and insertion of self-expandable stents. The follow-up of results was done according to a priori established protocol including the following: UCG, uroflowmetry and interview with patients. Due to stent migration, the 'stent over stent' technique was applied in one case, while reposition by balloon-catheter outward traction was performed in two cases of caudal migration. No irritative discomforts were reported in the first 4 months after stent dwelling. Uroflowmetric controls verified at least four times better results than before the insertion. Given it is the question of covered stent, there is no possibility of proliferative secondary lumen obstruction. On account of soft structure and conic shape of posterior part of stent, no lesions of the external urethral sphincter were manifested. The stent is simply withdrawn after 6 months by outward traction using the forceps at the time when the stent construction turns into soft and straight wire. The first clinical experiences are very favorable and ALLIUM stent may be expected to be the stent of choice for chronic bulbar strictures

  19. Influence of porous PTFE/LDPE/PP composite electret in skin ultrastructure

    International Nuclear Information System (INIS)

    Jiang, J; Liang, Y Y; Tang, Y; Ye, X T; Yang, Y J; Song, M H; Cui, L L; Hou, X M

    2008-01-01

    Corona charging and heat melting method were used to prepare porous PTFE electret and porous PTFE/LDPE/PP composite electret, respectively. After 0.5, 1, 1.5, 3 and 4 hour's action of fluorescein sodium (FINa) and -300V porous PTFE/LDPE/PP composite electret on the excised abdominal skin of rat, the skin structure was studied by means of scanning electron microscopy, transmission electron microscopy and confocal laser scanning microscopy, respectively, to probe the mechanism of electret on transdermal drug delivery. The results indicated that negative electret could increase the transdermal delivery of FINa due to its effect on changing the organized structure of stratum corneum, enlarging the hair follicles, which may be the mechanism of electret in enhancing transdermal drug delivery.

  20. Ion beam deposition of DLC and nitrogen doped DLC thin films for enhanced haemocompatibility on PTFE

    International Nuclear Information System (INIS)

    Srinivasan, S.; Tang, Y.; Li, Y.S.; Yang, Q.; Hirose, A.

    2012-01-01

    Diamond-like carbon (DLC) and N-doped DLC (DLC:N) thin films have been synthesized on polytetrafluroethylene (PTFE) and silicon wafers using ion beam deposition. Raman spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and scanning electron microscopy were used to study the structural and morphological properties of the coated surface. The results show that the ion beam deposited DLC thin films exhibit high hardness and Young's modulus, low coefficient of friction and high adhesion to the substrate. Low concentration of nitrogen doping in DLC improves the mechanical properties and reduces the surface roughness. DLC coating decreases the surface energy and improves the wettability of PTFE. The platelet adhesion results show that the haemocompatibility of DLC coated PTFE, especially DLC:N coated PTFE, has been significantly enhanced as compared with uncoated PTFE. SEM observations show that the platelet reaction on the DLC and DLC:N coated PTFE was minimized as the platelets were much less aggregated and activated.

  1. XPS analysis of the effect of fillers on PTFE transfer film development in sliding contacts

    Science.gov (United States)

    Blanchet, T. A.; Kennedy, F. E.; Jayne, D. T.

    1993-01-01

    The development of transfer films atop steel counterfaces in contact with unfilled and bronze-filled PTFE has been studied using X-ray photoelectron spectroscopy. The sliding apparatus was contained within the vacuum of the analytical system, so the effects of the native oxide, hydrocarbon, and adsorbed gaseous surface layers of the steel upon the PTFE transfer behavior could be studied in situ. For both the filled and the unfilled PTFE, cleaner surfaces promoted greater amounts of transfer. Metal fluorides, which formed at the transfer film/counterface interface, were found solely in cases where the native oxide had been removed to expose the metallic surface prior to sliding. These fluorides also were found at clean metal/PTFE interfaces formed in the absence of frictional contact. A fraction of these fluorides resulted from irradiation damage inherent in XPS analysis. PTFE transfer films were found to build up with repeated sliding passes, by a process in which strands of transfer filled in the remaining counterface area. Under these reported test conditions, the transfer process is not expected to continue atop previously deposited transfer films. The bronze-filled composite generated greater amounts of transfer than the unfilled PTFE. The results are discussed relative to the observed increase in wear resistance imparted to PTFE by a broad range of inorganic fillers.

  2. Electrophoretic deposition (EPD) of hydrous ruthenium oxides with PTFE and their supercapacitor performances

    International Nuclear Information System (INIS)

    Jang, Jong H.; Machida, Kenji; Kim, Yuri; Naoi, Katsuhiko

    2006-01-01

    The effect of PTFE addition was investigated for the electrophoretic deposition (EPD) of hydrous ruthenium oxide electrodes. Mechanical stability of electrode layers, together with deposition yield, was enhanced by using hydrous ruthenium oxide/PTFE dispersions. High supercapacitor performance was obtained for the electrodes prepared with 2% PTFE and 10% water. When PTFE content was higher, the rate capability became poor with low electronic conductivity; higher water content than 10% resulted in non-uniform depositions with poor cycleability and power capability. When electrodes were heat treated at 200 deg. C for 10 h, the specific energy was as high as 17.6 Wh/kg based on single electrode (at 200 W/kg); while utilizable energy was lower with heat treatment time of 1 and 50 h, due to the high resistance and gradual crystallization, respectively. With PTFE addition and heat treatment at 200 deg. C for 10 h, the specific capacitance was increased by 31% (460 → 599 F/g at ca. 0.6 mg/cm 2 ) at 10 mV/s, and the deposition weight was increased up to 1.7 mg/cm 2 with initial capacitance of 350 F/g

  3. Comparison of the performance of natural latex membranes prepared with different procedures and PTFE membrane in guided bone regeneration (GBR) in rabbits.

    Science.gov (United States)

    Moura, Jonas M L; Ferreira, Juliana F; Marques, Leonardo; Holgado, Leandro; Graeff, Carlos F O; Kinoshita, Angela

    2014-09-01

    This work assessed the performance of membranes made of natural latex extracted from Hevea brasiliensis prepared with three different methods: polymerized immediately after collection without the use of ammonia (L1); polymerized after preservation in ammonia solution (L2); and polymerized after storage in ammonia, followed by Soxhlet technique for the extraction of substances (L3). Polytetrafluoroethylene (PTFE) membrane was used as control. Two 10-mm diameter bone defects were surgically made in the calvaria of thirty adult male New Zealand rabbits. Defects (total n = 60) were treated with guided bone regeneration (GBR) using L1, L2, L3 or PTFE membranes (n = 15 for each membrane). Ten animals were euthanized after 7, 20 and 60 days postoperatively so that five samples (n = 5) of each treatment were collected at each time, and bone regeneration was assessed microscopically. The microscopic analysis revealed defects filled with blood clot and new bone formation at the margins of the defect in all 7-day samples, while 20-day defects were mainly filled with fibrous connective tissue. After 60 days defects covered with L1 membranes showed a significantly larger bone formation area in comparison to the other groups (P PTFE membranes was also investigated in six additional rabbits. The animals were subjected to the same surgical procedure for the confection of one 10-mm diameter bone defect that was treated with L1 (n = 3) or PTFE (n = 3). Fifty-three days later, a second surgery was performed to make a second defect, which was treated with the same type of membrane used in the first surgery. Seven days later, the animals were euthanized and samples analyzed. No differences among L1 and PTFE samples collected from sensitized and non-sensitized animals were found (P > 0.05, Kruskal-Wallis). Therefore, the results demonstrated that latex membranes presented performance comparable to PTFE membranes, and that L1 membranes induced higher bone formation. L1 and

  4. Multi-layer composite structure covered polytetrafluoroethylene for visible-infrared-radar spectral Compatibility

    Science.gov (United States)

    Qi, Dong; Cheng, Yongzhi; Wang, Xian; Wang, Fang; Li, Bowen; Gong, Rongzhou

    2017-12-01

    In this paper, a polytetrafluoroethylene (PTFE) top-covered multi-layer composite structure PTFE/H s/(Ge/ZnS)3 (H s represents the surface layer ZnS with various thicknesses) for spectral compatibility is proposed and investigated theoretically and experimentally. A substantial decline of glossiness from over 200 Gs to 74.2 Gs could be realized, due to high roughness and interface reflection of the 800 nm PTFE protection layer. In addition, similar to the structure of H s/(Ge/ZnS)3, the designed structure with a certain color exhibits ultra-low emissivity of average 0.196 at 8-14 µm and highly transparent performance of 96.45% in the radar frequency range of 2-18 GHz. Our design will provide an important reference for the practical applications of the spectral compatible multilayer films.

  5. Synthesis and Characterization of Nano-Hydroxyapatite/mPEG-b-PCL Composite Coating on Nitinol Alloy

    OpenAIRE

    Mohamadreza Etminanfar; Jafar Khalil-Allafi; Kiyumars Jalili

    2017-01-01

    In this study the bioactivity of hydroxyapatite/poly(ε-caprolactone)–poly(ethylene glycol) bilayer coatings on Nitinol superelastic alloy was investigated. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating. The surface morphology of coatings was studied using FE-SEM and SEM. The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized fl...

  6. Dosimetric characterization of KMgF{sub 3}:Tb+PTFE; Caracterizacion dosimetrica de KMgF{sub 3}:Tb+PTFE

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez R, M. I.; Garcia S, L.; Villicana M, M.; Huirache A, R.; Apolinar C, J. [Universidad Michoacana de San Nicolas de Hidalgo, Facultad de Ingenieria Quimica, Francisco J. Mujica s/n, Ciudad Universitaria, Col. Felicitas del Rio, 58030 Morelia, Michoacan (Mexico); Gonzalez M, P. R., E-mail: itcraf_15@hotmail.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2017-10-15

    In this work the results obtained from the dosimetric characterization of the new radiation detectors of KMgF{sub 3}:Tb+PTFE are presented. The host salt was obtained by means of the microwave technique, with the polycrystalline powder obtained, dosimeters were made in tablet form, using as Ptfe binder. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy of {sup 60}Co gamma radiation, the reproducibility test in the measurements, during ten cycles of heat treatment, irradiation and reading presented ± 3.7% Ds, in the stability test of thermoluminescent signal, during two months showed that the fading is practically null. Due to the results obtained, this new detector could be very useful for the dosimetry of ionizing radiation in different clinical applications. (Author)

  7. Preparation and characterization of PTFE coating in new polymer quartz piezoelectric crystal sensor for testing liquor products

    International Nuclear Information System (INIS)

    Gu Yu; Li Qiang

    2015-01-01

    A new method was developed based on the electron beam vacuum dispersion (EBVD) technology to prepare the PTFE polymer coating of the new polymer quartz piezoelectric crystal sensor for testing liquor products. The new method was applied in the new EBVD equipment which we designed. A real-time system monitoring the polymer coating’s thickness was designed for the new EBVD equipment according to the quartz crystal microbalance (QCM) principle, playing an important role in preparing stable and uniform PTFE polymer coatings of the same thickness. 30 pieces of PTFE polymer coatings on the surface of the quartz crystal basis were prepared with the PTFE polymer ultrafine powder (purity ≥ 99.99%) as the starting material. We obtained 30 pieces of new PTFE polymer sensors. By using scanning electron microscopy (SEM), the structure of the PTFE polymer coating’s column clusters was studied. One sample from the 30 pieces of new PTFE polymer sensors was analysed by SEM in four scales, i.e., 400×, 1000×, 10000×, and 25000×. It was shown that under the condition of high bias voltage and low bias current, uniformly PTFE polymer coating could be achieved, which indicates that the new EBVD equipment is suitable for mass production of stable and uniform polymer coating. (paper)

  8. Adhesion and removal kinetics of Bacillus cereus biofilms on Ni-PTFE modified stainless steel.

    Science.gov (United States)

    Huang, Kang; McLandsborough, Lynne A; Goddard, Julie M

    2016-01-01

    Biofilm control remains a challenge to food safety. A well-studied non-fouling coating involves codeposition of polytetrafluoroethylene (PTFE) during electroless plating. This coating has been reported to reduce foulant build-up during pasteurization, but opportunities remain in demonstrating its efficacy in inhibiting biofilm formation. Herein, the initial adhesion, biofilm formation, and removal kinetics of Bacillus cereus on Ni-PTFE-modified stainless steel (SS) are characterized. Coatings lowered the surface energy of SS and reduced biofilm formation by > 2 log CFU cm(-2). Characterization of the kinetics of biofilm removal during cleaning demonstrated improved cleanability on the Ni-PTFE coated steel. There was no evidence of biofilm after cleaning by either solution on the Ni-PTFE coated steel, whereas more than 3 log and 1 log CFU cm(-2) of bacteria remained on the native steel after cleaning with water and an alkaline cleaner, respectively. This work demonstrates the potential application of Ni-PTFE non-fouling coatings on SS to improve food safety by reducing biofilm formation and improving the cleaning efficiency of food processing equipment.

  9. Non-Cyanide Electrodeposited Ag–PTFE Composite Coating Using Direct or Pulsed Current Deposition

    Directory of Open Access Journals (Sweden)

    Raymond Sieh

    2016-07-01

    Full Text Available The effects of FC-4 cationic surfactant on electrodeposited Ag–PTFE composite coating using direct or pulsed currents were studied using scanning electron microscope (SEM, energy dispersive X-ray (EDS, optical microscope, and a linear tribometer. FC-4:PTFE in various ratios were added to a non-cyanide succinimide silver complex bath. Direct or pulsed current method was used at a constant current density to enable comparison between both methods. A high incorporation rate of PTFE was successfully achieved, with pulsed current being highly useful in increasing the amount of PTFE in the composite coating. The study of coating wear under sliding showed that a large majority of the electrodeposited coatings still managed to adhere to the substrate, even after 10 wear cycles of sliding tests. Performance improvements were achieved on all the samples with a coefficient of friction (CoF between 0.06 and 0.12.

  10. Friction coefficients of PTFE bearing liner

    Science.gov (United States)

    Daniels, C. M.

    1979-01-01

    Data discusses frictional characteristics of PTFE (polytetrafluoroethylene) under temperature extremes and in vacuum environment. Tests were also run on reduced scale hardware to determine effects of vacuum. Data is used as reference by designers of aircraft-control system rod-end bearings and for bearings used in polar regions.

  11. Evaluation of anti-migration properties of biliary covered self-expandable metal stents.

    Science.gov (United States)

    Minaga, Kosuke; Kitano, Masayuki; Imai, Hajime; Harwani, Yogesh; Yamao, Kentaro; Kamata, Ken; Miyata, Takeshi; Omoto, Shunsuke; Kadosaka, Kumpei; Sakurai, Toshiharu; Nishida, Naoshi; Kudo, Masatoshi

    2016-08-14

    To assess anti-migration potential of six biliary covered self-expandable metal stents (C-SEMSs) by using a newly designed phantom model. In the phantom model, the stent was placed in differently sized holes in a silicone wall and retracted with a retraction robot. Resistance force to migration (RFM) was measured by a force gauge on the stent end. Radial force (RF) was measured with a RF measurement machine. Measured flare structure variables were the outer diameter, height, and taper angle of the flare (ODF, HF, and TAF, respectively). Correlations between RFM and RF or flare variables were analyzed using a linear correlated model. Out of the six stents, five stents were braided, the other was laser-cut. The RF and RFM of each stent were expressed as the average of five replicate measurements. For all six stents, RFM and RF decreased as the hole diameter increased. For all six stents, RFM and RF correlated strongly when the stent had not fully expanded. This correlation was not observed in the five braided stents excluding the laser cut stent. For all six stents, there was a strong correlation between RFM and TAF when the stent fully expanded. For the five braided stents, RFM after full stent expansion correlated strongly with all three stent flare structure variables (ODF, HF, and TAF). The laser-cut C-SEMS had higher RFMs than the braided C-SEMSs regardless of expansion state. RF was an important anti-migration property when the C-SEMS did not fully expand. Once fully expanded, stent flare structure variables plays an important role in anti-migration.

  12. Active screen cage pulsed dc discharge for implanting copper in polytetrafluoroethylene (PTFE)

    Science.gov (United States)

    Zaka-ul-Islam, Mujahid; Naeem, Muhammad; Shafiq, Muhammad; Sitara; Jabbar Al-Rajab, Abdul; Zakaullah, Muhammad

    2017-07-01

    Polymers such as polytetrafluoroethylene (PTFE) are widely used in artificial organs where long-term anti-bacterial properties are required to avoid bacterial proliferation. Copper or silver ion implantation on the polymer surface is known as a viable method to generate long-term anti-bacterial properties. Here, we have tested pulsed DC plasma with copper cathodic cage for the PTFE surface treatment. The surface analysis of the treated specimens suggests that the surface, structural properties, crystallinity and chemical structure of the PTFE have been changed, after the plasma treatment. The copper release tests show that copper ions are released from the polymer at a slow rate and quantity of the released copper increases with the plasma treatment time.

  13. Fluoropolymer-coated dacron versus PTFE grafts for femorofemoral crossover bypass: randomised trial

    DEFF Research Database (Denmark)

    Eiberg, JP; Røder, Ole Christian; Stahl-Madsen, M

    2006-01-01

    To investigate whether patency of a thin walled 8 mm fluoropassivated Dacron graft was similar to that of a standard 8mm PTFE graft for femorofemoral crossover bypass surgery.......To investigate whether patency of a thin walled 8 mm fluoropassivated Dacron graft was similar to that of a standard 8mm PTFE graft for femorofemoral crossover bypass surgery....

  14. Effect of gamma radiation on dielectric and mechanical properties of modified fluoroplastic PTFE

    Science.gov (United States)

    Romanov, Boris; Kostromin, Valeriy; Bedenko, Sergey; Knyshev, Vladimir; Mukhnurov, Ilya; Matias, Rodrigo Roman

    2018-03-01

    The influence of gamma radiation on dielectric and mechanical characteristics of modified fluoroplast PTFE-4 MBK is considered in this paper. The material was exposed to Gamma-ray source GU-200 (Joint-stock company «Research Institute of Instruments», Lytkarino, Russia). The results of the research have shown that the relative permittivity and the tangent of the dielectric loss angle of PTFE-4 MBK samples at doses 4.105-1.106 Gy monotonically increase by 2.9 and 9.4%, respectively, compared to un-exposed material. The research of the mechanical properties of PTFE-4 MBK showed a maximum stress of up to 13.8 MPa and a maximum strain of 252% at doses of 8.104 Gy. It has been demonstrated that modified PTFE-4 MBK has good dielectric characteristics and withstanding high mechanical stress. We propose to use the results of the research for choosing cables and wiring location used in nuclear and space industry.

  15. Surface modification of BMN particles with silane coupling agent for composites with PTFE

    Science.gov (United States)

    Qi, Yanyuan; Luo, Qing; Shen, Jie; Zheng, Liu; Zhou, Jing; Chen, Wen

    2017-08-01

    Polymer-ceramic dielectric composites, which possess better dielectric properties, flexibility, ease in processing and shaping since they combine the advantages of polymers and dielectric ceramics, are widely used in microwave substrate applications. In order to optimize the properties of the composites, it is necessary to enhance the compatibility between the polymer matrix and ceramic filler because of their tremendous difference. In this paper, the vinyltrimethoxysilane (VTMS) is used to modify the Ba(Mg1/3Nb2/3)O3 (BMN) ceramic particles which can improve the compatibility between BMN ceramics and PTFE and the distribution of BMN in polytetrafluoroethylene (PTFE). The modification of VTMS has no influence on the crystal structure of BMN ceramics and the compact VTMS modified BMN/PTFE composites with satisfactory uniformity and less cavities are obtained. The relative permittivity (εr) of VTMS modified BMN/PTFE composite substrate is 5.84 while the loss tangent reaches 1.5 × 10-3 at microwave frequencies (around 10 GHz).

  16. Drastic Improvement in Adhesion Property of Polytetrafluoroethylene (PTFE) via Heat-Assisted Plasma Treatment Using a Heater.

    Science.gov (United States)

    Ohkubo, Yuji; Ishihara, Kento; Shibahara, Masafumi; Nagatani, Asahiro; Honda, Koji; Endo, Katsuyoshi; Yamamura, Kazuya

    2017-08-25

    The heating effect on the adhesion property of plasma-treated polytetrafluoroethylene (PTFE) was examined. For this purpose, a PTFE sheet was plasma-treated at atmospheric pressure while heating using a halogen heater. When plasma-treated at 8.3 W/cm 2 without using the heater (Low-P), the surface temperature of Low-P was about 95 °C. In contrast, when plasma-treated at 8.3 W/cm 2 while using the heater (Low-P+Heater), the surface temperature of Low-P+Heater was controlled to about 260 °C. Thermal compression of the plasma-treated PTFE with or without heating and isobutylene-isoprene rubber (IIR) was performed, and the adhesion strength of the IIR/PTFE assembly was measured via the T-peel test. The adhesion strengths of Low-P and Low-P+Heater were 0.12 and 2.3 N/mm, respectively. Cohesion failure of IIR occurred during the T-peel test because of its extremely high adhesion property. The surfaces of the plasma-treated PTFE with or without heating were investigated by the measurements of electron spin resonance, X-ray photoelectron spectroscopy, nanoindentation, scanning electron microscopy, and scanning probe microscopy. These results indicated that heating during plasma treatment promotes the etching of the weak boundary layer (WBL) of PTFE, resulting in a sharp increase in the adhesion property of PTFE.

  17. Gas barrier properties of diamond-like carbon films coated on PTFE

    International Nuclear Information System (INIS)

    Ozeki, K.; Nagashima, I.; Ohgoe, Y.; Hirakuri, K.K.; Mukaibayashi, H.; Masuzawa, T.

    2009-01-01

    Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE substrate was modified with a N 2 plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N 2 plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N 2 plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N 2 plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2 μm. The DLC-coated PTFE with the N 2 plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.

  18. Annealing induced morphological modifications in PTFE films deposited by magnetron sputtering

    Science.gov (United States)

    Tripathi, S.; De, Rajnarayan; Rao, K. Divakar; Haque, S. Maidul; Misal, J. S.; Prathap, C.; Das, S. C.; Ganesan, V.; Sahoo, N. K.

    2017-05-01

    As grown RF magnetron sputtered polytetrafluoroethylene (PTFE) thin films were subjected to vacuum annealing at optimized elevated temperature of 200° C for varying time duration and corresponding surface morphological changes were recorded. The columnar structures appearing after an annealing duration of 2 hours are interesting for fabrication of rough PTFE surfaces towards possible applications in hydrophobicity along with high transmission. Supported by transmission data, the AFM images show a transformation of smooth PTFE surface with less than 2 nm rms roughness to a very rough surface. The results are interpreted in terms of thermal energy induced modifications only at the surface without any change in the original bonding structure on the surface and inside the sample. Preliminary studies indicate that the optimization of roughness and transmission together on such surfaces may lead to high water contact angles.

  19. Microwave plasma initiated graft copolymerization modification of monomers onto PTFE surface

    International Nuclear Information System (INIS)

    Guan Weishu; Wen Yunjian; Fang Yan; Yin Yongxiang

    1996-02-01

    A graft copolymerization modification technique of monomers onto polytetrafluoroethylene (PTFE) surface initiated by a 2.45 GHz non-equilibrium microwave plasma has been investigated. Standard X-Ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (sEM) and wetting techniques were used for examination and analysis of samples. Considerable changes in chemical structure, composition and in morphology of grafted surface of PTFE were found. Results showed the occurrence of noticeable defluorination and cross-linked structure on grafted surface, and indicated that different kinds and contents of oxygen-containing functional groups were introduced into the surface of PTFE. Wetting and adhesion experiment of the sample proved that significant improvements in hydrophilicity and adhesion of surface were exhibited. These results confirmed the success of grafting. (8 refs., 7 figs., 1 tab.)

  20. Comparison between uncovered and covered self-expandable metal stent placement in malignant duodenal obstruction.

    Science.gov (United States)

    Kim, Ji Won; Jeong, Ji Bong; Lee, Kook Lae; Kim, Byeong Gwan; Ahn, Dong Won; Lee, Jae Kyung; Kim, Su Hwan

    2015-02-07

    To compare the clinical outcomes of uncovered and covered self-expandable metal stent placements in patients with malignant duodenal obstruction. A total of 67 patients were retrospectively enrolled from January 2003 to June 2013. All patients had symptomatic obstruction characterized by nausea, vomiting, reduced oral intake, and weight loss. The exclusion criteria included asymptomatic duodenal obstruction, perforation or peritonitis, concomitant small bowel obstruction, or duodenal obstruction caused by benign strictures. The technical and clinical success rate, complication rate, and stent patency were compared according to the placement of uncovered (n = 38) or covered (n = 29) stents. The technical and clinical success rates did not differ between the uncovered and covered stent groups (100% vs 96.6% and 89.5% vs 82.8%). There were no differences in the overall complication rates between the uncovered and covered stent groups (31.6% vs 41.4%). However, stent migration occurred more frequently with covered than uncovered stents [20.7% (6/29) vs 0% (0/38), P stent patency was longer in uncovered than in covered stents [251 d (95%CI: 149.8 d-352.2 d) vs 139 d (95%CI: 45.5 d-232.5 d), P stent (70 d) and covered stent groups (60 d). Uncovered stents may be preferable in malignant duodenal obstruction because of their greater resistance to stent migration and longer stent patency than covered stents.

  1. PTFE-ALUMINUM films serve as neutral density filters

    Science.gov (United States)

    Burks, H. D.

    1966-01-01

    Polytetrafluoroethylene /PTFE/ films coated with aluminum films act as neutral density filters in the wavelength range 0.3 to 2.1 microns. These filters are effective in the calibration of photometric systems.

  2. Short- and long-term results of chordal reconstruction using artificial suture material (polytetrafluoroethylene and polypropylene in the dog

    Directory of Open Access Journals (Sweden)

    Isamu Kanemoto

    2017-04-01

    Full Text Available No previous reports have compared the suitability of expanded polytetrafluoroethylene (ePTFE and polypropylene as artificial suture materials for chordal reconstruction in mitral valve plasty (MVP in the dog. Twelve normal dogs were subjected to MVP using surfaceinduced deep hypothermia. In the short-term group (1.5-4 months after surgery, all ePTFE sutures were covered by a tissue sheath including the paired suture arms, which gave the appearance of native chordae from 2 months after surgery. In contrast, all polypropylene sutures were not covered by tissue, and appeared the same as the paired polypropylene suture arms at the operation. In the long-term group (12 months after surgery, all ePTFE sutures were covered by a tissue sheath, which appeared the same as that in the short-term group, and had flexibility without increased thickness with time. In contrast, although the polypropylene suture was covered completely by a tissue sheath in 1 dog, all the other polypropylene sutures were exposed except for both ends of the suture. ePTFE may be superior to polypropylene as an artificial suture material for chordal reconstruction in MVP.

  3. Fabrication of micro-prominences on PTFE surface using proton beam writing

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, Akane, E-mail: ogawa.akane@jaea.go.jp [Department of Advanced Radiation Technology, Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-Machi, Takasaki, Gunma 370-1292 (Japan); Satoh, Takahiro; Koka, Masashi [Department of Advanced Radiation Technology, Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-Machi, Takasaki, Gunma 370-1292 (Japan); Kobayashi, Tomohiro [Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 350-0198 (Japan); Kamiya, Tomihiro [Department of Advanced Radiation Technology, Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki-Machi, Takasaki, Gunma 370-1292 (Japan)

    2013-07-01

    Polytetrafluoroethylene (PTFE) is a typical fluoropolymer and it has several desirable technological properties such as electrical insulation, solid lubrication etc. However, the conventional microstructuring methods have not been well applied to PTFE due to its chemical inertness. Some effective micromachining using synchrotron radiation or ion beam irradiation has been reported. In this study, we create micro-prominences by raising the original surface using proton beam writing (PBW) without chemical etching. A conical prominence was formed by spiral drawing from the center with a 3 MeV proton beam. The body was porous, and the bulk PTFE below the prominence changed to fragmented structures. With decreasing writing speed, the prominence became taller but the height peaked. The prominence gradually reduced in size after the speed reached the optimum value. We expect that these porous projections with high aspect ratio will be versatile in medical fields and microelectromechanical systems (MEMS) technology.

  4. A Novel Non-Planar Transverse Stretching Process for Micro-Porous PTFE Membranes and Resulting Characteristics

    KAUST Repository

    Chang, Y.-H.; Chen, S.-C.; Wang, T.-J.; Guo, J.

    2018-01-01

    Polytetrafluoroethylene (PTFE) micro-porous membranes were prepared from PTFE fine powder through extruding, rolling, and uniaxial longitudinally stretching. In contrast to conventional planar transverse stretching, a novel 3D mold design of non

  5. Tribological behavior of Nano-Al2O3 and PEEK reinforced PTFE composites

    Science.gov (United States)

    Wang, Banghan; Lv, Qiujuan; Hou, Genliang

    2017-01-01

    The Nano-Al2O3 and PEEK particles synergetic filled PTFE composites were prepared by mechanical blending-molding-sintering method. The tribological behavior of composites with different volume fraction of fillers was tested on different test conditions by a MMW-1A block-on-ring friction and wear tester. The transfer film on counterpart 5A06 Aluminum alloy ring was inspected and anslyzed with scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The results demonstrated that the lowest friction coefficient was gained when the PTFE composite was filled with only 10% PEEK. The friction coefficient decreases gradually with the increasing content of PEEK. The special wear rate of 10% PEEK/PTFE were decreased clearly with filled different contents of nano-Al2O3 particles. The special wear rate of the sample with 5% nano-Al2O3 and 10% PEEK had the lowest volume wear rate. The sliding speed effect significantly on the tribological behavior of nano-Al2O3/PEEK/PTFE composites.

  6. Dosimetric characterization of KMgF3:Tb+PTFE

    International Nuclear Information System (INIS)

    Ramirez R, M. I.; Garcia S, L.; Villicana M, M.; Huirache A, R.; Apolinar C, J.; Gonzalez M, P. R.

    2017-10-01

    In this work the results obtained from the dosimetric characterization of the new radiation detectors of KMgF 3 :Tb+PTFE are presented. The host salt was obtained by means of the microwave technique, with the polycrystalline powder obtained, dosimeters were made in tablet form, using as Ptfe binder. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy of 60 Co gamma radiation, the reproducibility test in the measurements, during ten cycles of heat treatment, irradiation and reading presented ± 3.7% Ds, in the stability test of thermoluminescent signal, during two months showed that the fading is practically null. Due to the results obtained, this new detector could be very useful for the dosimetry of ionizing radiation in different clinical applications. (Author)

  7. Indirect induction of endothelial cell injury by PU- or PTFE-mediated activation of monocytes.

    Science.gov (United States)

    Liu, Xin; Xue, Yang; Sun, Jiao

    2010-01-01

    Polyurethanes (PUs) and polytetrafluoroethylene (PTFE) are widely used for making cardiovascular devices, but thrombus formation on the surfaces of these devices is inevitable. Since endothelial injury can lead to thrombosis, most of the studies on PUs or PTFE focused on their damage to endothelial cells. However, few studies have attempted to clarify whether the use of foreign objects as biomaterials can cause endothelial injury by activating the innate immune system. In this study, we aimed to investigate the roles of PU- or PTFE-stimulated immune cells in endothelial-cell injury. First, monocytes (THP-1 cells) were stimulated with PU or PTFE for 24 h and, subsequently, human umbilical vein endothelial cells (HUVECs) were treated with the supernatants of the stimulated cells for 24 h. We measured the generation of intracellular reactive oxygen species (ROS) from THP-1 cells treated with PU and PTFE for 24 h, meanwhile hydrogen dioxide (H(2)O(2)), tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the supernatants were also detected. Then, we assessed the apoptosis rate of the HUVECs and determined the expression of NO, inducible nitric oxide synthase (iNOS), and apoptosis-related proteins (p53, Bax, Bcl-2) in the HUVECs. The results showed that large amounts of ROS and low levels of pro-inflammatory cytokines (TNF-α and IL-1β) were produced by the stimulated THP-1 cells. After culturing with the supernatants of the PU- or PTFE-stimulated THP-1 cells, the apoptosis rate, NO production and expression of iNOS, p53 and Bax in the HUVECs were up-regulated, while Bcl-2 expression was down-regulated. In conclusion, the release of ROS by PU- or PTFE-treated THP-1 cells may induce iNOS expression and cause apoptosis in HUVECs via the p53, Bax and Bcl-2 proteins. These data provide the interesting finding that endothelial injury in the process of biomaterial-induced thrombosis can be initiated through the release of soluble mediators by monocytes.

  8. Robust non-wetting PTFE surfaces by femtosecond laser machining.

    Science.gov (United States)

    Liang, Fang; Lehr, Jorge; Danielczak, Lisa; Leask, Richard; Kietzig, Anne-Marie

    2014-08-08

    Nature shows many examples of surfaces with extraordinary wettability,which can often be associated with particular air-trapping surface patterns. Here,robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters,both of which make it a strong candidate for industrial applications.

  9. Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

    Directory of Open Access Journals (Sweden)

    Fang Liang

    2014-08-01

    Full Text Available Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE. The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications.

  10. Measurement of absorbed dose for high energy electron using CaSO4: Tm-PTFE TLD

    International Nuclear Information System (INIS)

    Park, Myeong Hwan; Kim, Do Sung

    2000-01-01

    In this study, the highly sensitive CaSO 4 : Tm-PTFE TLDs has been fabricated for the purpose of measurement of high energy electron. CaSO 4 : Tm phosphor powder was mixed with polytetrafluoroethylene(PTFE) powder and moulded in a disk type(diameter 8.5mm, thickness 90mg/cm 2 ) by cold pressing. The absorbed dose distribution and ranges for high energy electron were measured by using the CaSO 4 : Tm-PTFE TLDs. The ranges determined were R 100 =3D14.5mm, R 50 =3D24.1mm and R p =3D31.8mm, respectively and the beam flatness, the variation of relative dose in 80% of the field size, was 4.5%. The fabricated CaSO 4 : Tm-PTFE TLDs may be utilized in radiation dosimetry for personal, absorbed dose and environmental monitoring.=20

  11. [Evaluation of stents in treating childhood benign esophageal strictures].

    Science.gov (United States)

    Reinshagen, K; Kähler, G; Manegold, B C; Waag, K-L

    2009-01-01

    Esophageal stenting is a popular of treatment of esophageal strictures in adults. It has also been described for children with benign strictures who did not respond to standard dilatation therapy. The aim of the study was to evaluate weather esophageal stents could be used safely and effectively in the treatment of benign esophageal strictures in children. From 1993 to 2005 stenting therapy was performed in 12 children with complicated esophageal strictures. Etiologies of the strictures were caustic burns in 9 patients, postoperative strictures due to complicated esophageal atresia in 2 patients and iatrogenic esophageal injury in 1 patient. Esophageal silicon tubi, covered retrievable expandable nitinol and plastic stents were placed endoscopically. The clinical course and the long term follow up were evaluated retrospectively The stents and tubi were placed in all patients without complications and were later removed successfully. 6 patients were treated with a self expanding plastic stent. The plastic stents showed a distinct tendency to migrate but in 5/6 patients esophageal stricture was treated successfully. 3 patients were treated by a covered self expanding nitinol stent. No migration occurred. One patient was asymptomatic after therapy, one required further dilatation therapy and the third had esophageal resection. 3 patients were treated by esophageal tubi. 2 patients required surgery in the follow up, one patient is asymptomatic. The use of stenting devices in children to treat benign esophageal strictures is safe and efficient. The self expanding plastic stents had the best long term results but required high compliance of parents and children due to the tendency of stent migration. Self expanding nitinol stents are more traumatic at the extraction procedure and are useful in patients with low compliance. Recurrence of strictures occurred most often after esophageal tubi possibly due to the lack of radial expansion.

  12. Characterization of structural modifications induced by x radiation on poly-tetra-fluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Takata, Neide H.

    1995-01-01

    This work deal mainly with the effect induced by X-ray radiation in PTFE as sheet and powder, and the characterization of unirradiated and irradiated samples. Several techniques such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), Raman scattering, infrared photoacoustic spectroscopy (PAS) and electronic absorption spectroscopy were used to characterize the PTFE samples. The irradiation dose up to 640 kGy promoted a slight increase in the crystallinity degree of PTFE, which has been observed by X-ray diffraction, in DSC curves and in the PA spectra. For more than 640 kGy doses, the crystallinity degree remains constant. The increase in crystallinity can be attributed to the scissions of the chain in the amorphous region. (author). 87 refs., 18 figs., 3 tabs

  13. Self-Expanding Transcatheter Aortic Valve System for Symptomatic High-Risk Patients With Severe Aortic Stenosis

    DEFF Research Database (Denmark)

    Reichenspurner, Hermann; Schaefer, Andreas; Schäfer, Ulrich

    2017-01-01

    BACKGROUND: The CENTERA transcatheter heart valve (THV) is a low-profile, self-expanding nitinol valve made from bovine pericardial tissue that is 14-F compatible with a motorized delivery system allowing for repositionability. OBJECTIVES: The pivotal study evaluated safety and efficacy of this THV...... permanent pacemaker was implanted in 4.5% of patients receiving the THV (4.9% for patients at risk). CONCLUSIONS: The herein described THV is safe and effective at 30 days with low mortality, significant improvements in hemodynamic outcomes, and low incidence of adverse events. Of particular interest...... is the low incidence of permanent pacemaker implantations. (Safety and Performance Study of the Edwards CENTERA-EU Self-Expanding Transcatheter Heart Valve [CENTERA-2]; NCT02458560)....

  14. Tribological study of PTFE composites loaded with porcelain tile waste; Estudo tribologico de compositos de PTFE carregados com rejeito de porcelanato

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, P.M.; Araujo Neto, A.P.; Souza, J.R.; Medeiros, J.T.N., E-mail: plinio_rpg@hotmail.com [Universidade Federal do Rio Grande do Norte (GET/UFRN), Natal, RN (Brazil). Grupo de Estudos de Tribologia e Integridade Estrutural

    2016-07-01

    The Brazilian northeast is one of the largest producers of clays that burn in the white form and disposal of tailings from the process of polishing the ceramic pieces of porcelain stands out as a major source of environmental degradation. This problem can be reduced by adding such material as filler in composites, in order to improve the mechanical properties of the polymeric matrix. Polytetrafluoroethylene (PTFE) is characterized as a good solid lubricant, because it has excellent properties such as low coefficient of friction (0.01 < μ < 0.1), thermal stability at high temperatures and chemical resistance. However, the pure PTFE has high wear rates (greater than 10-13m2/N) leading to early failures of various components. To reuse the Tailings of Porcelain (TP), composites of PTFE + TP were developed in three different compositions (85:15, 75:25 and 65:35). For this investigation the particle size distribution and some chemical characteristics of the tailings by testing XRD, XRF, SEM and EDS were performed, registering a large amount of silica, aluminum and other metals. Roughness, wettability and sclerometry also were performed. It was noted that the values of arithmetic average roughness, Ra, is higher for composites with higher percentage of TP, in addition they have a lower contact angle and higher surface energy to distilled water, characterized as hydrophilic. The results of energy of deformation provided by the sclerometry test were non-linear. (author)

  15. Radiation grafting of pH and thermosensitive N-isopropylacrylamide and acrylic acid onto PTFE films by two-steps process

    International Nuclear Information System (INIS)

    Bucio, E.; Burillo, G.

    2007-01-01

    Polytetrafluoroethylene (PTFE) was grafted (g) with acrylic acid (AAc) by γ-ray pre-irradiation method to get PTFE-g-AAc films, then N-isopropylacrylamide (NIPAAm) was grafted onto PTFE-g-AAc films with γ-ray to get (PTFE-g-AAc)-g-NIPAAm. PTFE films were irradiated in air at a dose rate of 3.0 kGy h -1 and different radiation dose. The irradiated films were placed in glass ampoules, which contained aqueous solutions with different monomer concentration (AAc), and then they were heated at different temperatures and reaction time. NIPAAm onto PTFE-g-AAc was carried out with the same procedure with monomer concentration of 1 mol L -1 . The thermosensitivity of the samples was defined and calculated as the ratio of the grafted samples swelling at 28 and 35 o C, and pH sensitivity defined as the ratio of the grafted samples swelling at pH 2 and 8

  16. Expanded polytetrafluoroethylene graft fistula for chronic hemodialysis.

    Science.gov (United States)

    Tellis, V A; Kohlberg, W I; Bhat, D J; Driscoll, B; Veith, F J

    1979-01-01

    In a retrospective study of 66 PTFE arteriovenous fistulae and 71 BCH arteriovenous fistulae for dialysis access, PTFE had a higher patency rate than BCH at 12 months (62.4 versus 32.5%). PTFE was easier to work with and easier to handle in the face of infection. The lateral upper arm approach to placement of the PTFE graft is desirable in patients who have had multiple previous access procedures because this area is usually free from scarring, is distant from neurovascular structures, and provides a greater length of graft for needle punctures.

  17. Preparation and performance of Pt/PTFE/Foam SiC as a hydrophobic catalyst for LPCE

    International Nuclear Information System (INIS)

    He, Jianchao; Wang, Heyi; Xiao, Chengjian; Li, Jiamao; Chen, Ping; Hou, Jingwei

    2016-01-01

    Highlights: • A new type of foam material, Foam SiC with three-dimensional network structure, was chosen as the carrier of catalyst. • Foam SiC was hydrophobic treated by PTFE, and achieved a good hydrophobic property. • Pt/PTFE/Foam SiC was prepared by impregnation method with Pt-organic solution and gaseous phase reduction method. • The hydrophobic catalysts were packed with Dixon phosphor bronze gauze rings (about 3 mm × 3 mm) in LPCE system to test the catalytic performance. • The effect of different size of the catalyst on LPCE was been tested. - Abstract: Platinum catalysts supported on a composite of polytetrafluoroethylene (PTFE) and Foam SiC (Pt/PTFE/Foam SiC) have been proposed and prepared by an impregnation method. The as-prepared Pt/PTFE/Foam SiC was characterized by compression load testing, dynamic contact angle measurement, SEM, XRD, and TEM. The results show that the catalyst prepared by triple hydrophobic treatment had an initial contact angle of 134.2°, a good compression performance of 3.2 MPa, and platinum nanoparticles of 12.1 nm (average size). The catalytic activity of the catalyst was tested with different packing methods, reaction temperatures, and gas-liquid ratios. An excellent hydrogen isotope exchange performance was observed using a hydrophilic packing material-to-catalyst ratio of 25% and reaction temperature of 80 °C. Pt/PTFE/Foam SiC may be used as a hydrophobic catalyst for a water detritiation system (WDS) via a liquid-phase catalytic exchange process (LPCE).

  18. Preparation and performance of Pt/PTFE/Foam SiC as a hydrophobic catalyst for LPCE

    Energy Technology Data Exchange (ETDEWEB)

    He, Jianchao; Wang, Heyi, E-mail: hywang@caep.cn; Xiao, Chengjian; Li, Jiamao; Chen, Ping; Hou, Jingwei

    2016-12-15

    Highlights: • A new type of foam material, Foam SiC with three-dimensional network structure, was chosen as the carrier of catalyst. • Foam SiC was hydrophobic treated by PTFE, and achieved a good hydrophobic property. • Pt/PTFE/Foam SiC was prepared by impregnation method with Pt-organic solution and gaseous phase reduction method. • The hydrophobic catalysts were packed with Dixon phosphor bronze gauze rings (about 3 mm × 3 mm) in LPCE system to test the catalytic performance. • The effect of different size of the catalyst on LPCE was been tested. - Abstract: Platinum catalysts supported on a composite of polytetrafluoroethylene (PTFE) and Foam SiC (Pt/PTFE/Foam SiC) have been proposed and prepared by an impregnation method. The as-prepared Pt/PTFE/Foam SiC was characterized by compression load testing, dynamic contact angle measurement, SEM, XRD, and TEM. The results show that the catalyst prepared by triple hydrophobic treatment had an initial contact angle of 134.2°, a good compression performance of 3.2 MPa, and platinum nanoparticles of 12.1 nm (average size). The catalytic activity of the catalyst was tested with different packing methods, reaction temperatures, and gas-liquid ratios. An excellent hydrogen isotope exchange performance was observed using a hydrophilic packing material-to-catalyst ratio of 25% and reaction temperature of 80 °C. Pt/PTFE/Foam SiC may be used as a hydrophobic catalyst for a water detritiation system (WDS) via a liquid-phase catalytic exchange process (LPCE).

  19. Compressive Properties of PTFE/Al/Ni Composite Under Uniaxial Loading

    Science.gov (United States)

    Wang, Huai-xi; Li, Yu-chun; Feng, Bin; Huang, Jun-yi; Zhang, Sheng; Fang, Xiang

    2017-05-01

    To investigate the mechanical properties of pressed and sintered PTFE/Al/Ni (polytetrafluoroethylene/aluminum/nickel) composite, uniaxial quasi-static and dynamic compression experiments were conducted at strain rates from 10-2 to 3 × 103/s. The prepared samples were tested by an electrohydraulic press with 300 kN loading capacity and a split Hopkinson pressure bar (SHPB) device at room temperature. Experimental results show that PTFE/Al/Ni composite exhibits evident strain hardening and strain rate hardening. Additionally, a bilinear relationship between stress and {{log(}}\\dot{ɛ} ) is observed. The experimental data were fit to Johnson-Cook constitutive model, and the results are in well agreement with measured data.

  20. Designing and simulating a nitinol-based micro ejector

    Directory of Open Access Journals (Sweden)

    Yesid Mora Sierra

    2012-01-01

    Full Text Available This paper describes pico-droplet ejector design and simulation. The actuation system was based on two interconnected nitinol membranes’ shape memory effect. Ejected volume was 12pL and it operated at 30°C to 64°C. Ejecting excitation voltage was 12V and the ejecting energy required by actuator operation was 26µJ per drop. These pico-liter ejectors could have applications in making, lubricating and cooling integrated circuits.

  1. Optimization for Tribological Properties of Glass Fiber-Reinforced PTFE Composites with Grey Relational Analysis

    Directory of Open Access Journals (Sweden)

    Firojkhan Pathan

    2016-01-01

    Full Text Available Most recent history shows that polytetrafluoroethylene (PTFE is widely used as antifrictional materials in industry for wide speed range. A high antifriction property of PTFE makes it suitable for dry friction bearing. Main disadvantage of using PTFE is its high wear rate, so extensive research had been carried out to improve the wear resistance with addition of filler material. This study focuses on four input parameters load, sliding speed, sliding distance, and percentage of glass fiber as a filler material. Taguchi method was used for experimentation; each parameter is having 3 levels with L27 orthogonal array. Grey relational analysis is used to convert multiple response parameters, namely, wear and coefficient of friction, into single grey relation grade. The optimal input parameters were selected based on the S/N ratio. It was observed that load 3 kg, sliding speed 5.1836 m/s (900 rpm, sliding distance 2 km, and 15% of glass fiber are optimal input parameters for PTFE without significantly affecting the wear rate and coefficient of friction.

  2. Experimental Study on Reaction Characteristics of PTFE/Ti/W Energetic Materials under Explosive Loading

    Directory of Open Access Journals (Sweden)

    Yan Li

    2016-11-01

    Full Text Available Metal/fluoropolymer composites represent a new category of energetic structural materials that release energy through exothermic chemical reactions initiated under shock loading conditions. This paper describes an experiment designed to study the reaction characteristics of energetic materials with low porosity under explosive loading. Three PTFE (polytetrafluoroethylene/Ti/W mixtures with different W contents are processed through pressing and sintering. An inert PTFE/W mixture without reactive Ti particles is also prepared to serve as a reference. Shock-induced chemical reactions are recorded by high-speed video through a narrow observation window. Related shock parameters are calculated based on experimental data, and differences in energy release are discussed. The results show that the reaction propagation of PTFE/Ti/W energetic materials with low porosity under explosive loading is not self-sustained. As propagation distance increases, the energy release gradually decreases. In addition, reaction failure distance in PTFE/Ti/W composites is inversely proportional to the W content. Porosity increased the failure distance due to higher shock temperature.

  3. Evolution of patency rates of self-expandable bare metal stents for endovascular treatment of femoro-popliteal arterial occlusive disease: Does stent design matter?

    Science.gov (United States)

    Treitl, Karla Maria; Woerner, Benedikt; Schinner, Regina; Czihal, Michael; Notohamiprodjo, Susan; Hoffmann, Ulrich; Treitl, Marcus

    2017-09-01

    To analyse the patency rates of femoro-popliteal stenting with different self-expandable Nitinol stent-designs. Two hundred and twenty-two patients (142 (64%) male; age 72.4 ± 11.6 years) with symptomatic femoro-popliteal peripheral arterial occlusive disease (PAOD) underwent percutaneous transluminal angioplasty (PTA) and stenting with three different Nitinol stents (interwoven IW: n = 70; closed-cell CC: n = 85; open-cell OC: n = 67). One-year post-procedural target lesion revascularization (TLR_12M) rates were investigated with regard to co-morbidities: diabetes (DBM), hyperlipidaemia (HLP), hypertension (RR), coronary artery disease (CAD) and degree of calcification. Twelve-month follow-up data were available for 60, 69 and 50 patients in the IW, OC and CC groups (179 patients in total). The cumulative patency (IW: 52 (86.7%); OC: 50 (72.5%); CC: 23 (46.0%); P stent and the highest TLR_12M for the CC stent. The interwoven stent-design was superior to the standard open- and closed-cell stent-designs in endovascular treatment of femoro-popliteal PAOD in a follow-up period of 12 months. • Results of femoro-popliteal stenting are still unsatisfactory. • Comparative studies for currently available different Nitinol stent-designs are lacking. • This is a first comparative study on long-term patency of different Nitinol stent-designs. • Interwoven stent-design leads to improved long-term patency. • Interwoven stent-design leads to lower TLR than other stent-designs.

  4. Self expandable polytetrafluoroethylene stent for carotid blowout syndrome.

    Science.gov (United States)

    Tatar, E C; Yildirim, U M; Dündar, Y; Ozdek, A; Işik, E; Korkmaz, H

    2012-01-01

    Carotid blowout syndrome (CBS) is an emergency complication in patients undergoing treatment for head and neck cancers. The classical management of CBS is the ligation of the common carotid artery, because suturing is not be possible due to infection and necrosis of the field. In this case report, we present a patient with CBS, in whom we applied a self-expandable polytetrafluoroethylene (PTFE) stent and observed no morbidity. Endovascular stent is a life-saving technique with minimum morbidity that preserves blood flow to the brain. We believe that this method is preferable to ligation of the artery in CBS.

  5. Thermoluminescence sensitivity variations in LiF PTFE dosemeters incurred by improper handling procedures

    CERN Document Server

    Mason, E W; MacKinlay, Alistair F; Saunders, D

    1975-01-01

    A systematic study of some anomalous darkening effects and thermoluminescence sensitivity variations observed in LiF:PTFE thermoluminescent dosemeters is described. Various likely causes of such effects have been investigated. The manufacturer's recommended cleaning procedures have been found to be inadequate and, in some cases, have been found to actually promote discolouration of the dosemeters. Recommendations are given for the successful use of LiF:PTFE thermoluminescent dosemeters in personal dosimetry.

  6. Use of Nitinol Stents Following Recanalization of Central Venous Occlusions in Hemodialysis Patients

    International Nuclear Information System (INIS)

    Rajan, Dheeraj K.; Saluja, Jasdeep S.

    2007-01-01

    Purpose. To retrospectively review the patency of endovascular interventions with nitinol stent placement for symptomatic central venous occlusions in hemodialysis patients. Methods. A retrospective review of all patients who underwent endovascular interventions for dysfunctional hemodialysis grafts and fistulas was performed from April 2004 to August 2006. A total of 6 patients presented with arm and/or neck and facial swelling and left brachiocephalic vein occlusion. The study group consisted of 3 men and 3 women with a mean age of 79.5 years (SD 11.2 years). Of these 6 patients, 1 had a graft and 5 had fistulas in the left arm. The primary indication for nitinol stent placement was technical failure of angioplasty following successful traversal of occluded central venous segments. Patency was assessed from repeat fistulograms and central venograms performed when patients redeveloped symptoms or were referred for access dysfunction determined by the ultrasound dilution technique. No patients were lost to follow-up. Results. Nitinol stent placement to obtain technically successful recanalization of occluded venous segments was initially successful in 5 of 6 patients (83%). In 1 patient, incorrect stent positioning resulted in partial migration to the superior vena cava requiring restenting to prevent further migration. Clinical success was observed in all patients (100%). Over the follow-up period, 2 patients underwent repeat intervention with angioplasty alone. Primary patency was 83.3% (95% CI 0.5-1.2) at 3 months, and 66.7% at 6 and 12 months (0.2-1.1, 0.1-1.2). Secondary patency was 100% at 12 months with 3 patients censored over that time period. Mean primary patency was 10.4 months with a mean follow-up of 12.4 months. No complications related to recanalization of the occluded central venous segments were observed. Conclusion. Our initial experience has demonstrated that use of nitinol stents for central venous occlusion in hemodialysis patients is

  7. Ordered arrays of polymeric nanopores by using inverse nanostructured PTFE surfaces

    International Nuclear Information System (INIS)

    Martín, Jaime; Martín-González, Marisol; Del Campo, Adolfo; Reinosa, Julián J; Fernández, José Francisco

    2012-01-01

    We present a simple, efficient, and high-throughput methodology for the fabrication of ordered nanoporous polymeric surfaces with areas in the range of cm 2 . The procedure is based on a two-stage replication of a master nanostructured pattern. The process starts with the preparation of an ordered array of poly(tetrafluoroethylene) (PTFE) free-standing nanopillars by wetting self-ordered porous anodic aluminum oxide templates with molten PTFE. The nanopillars are 120 nm in diameter and approximately 350 nm long, while the array extends over cm 2 . The PTFE nanostructuring process induces surface hydrocarbonation of the nanopillars, as revealed by confocal Raman microscopy/spectroscopy, which enhances the wettability of the originally hydrophobic material and facilitates its subsequent use as an inverse pattern. Thus, the PTFE nanostructure is then used as a negative master for the fabrication of macroscopic hexagonal arrays of nanopores composed of biocompatible poly(vinylalcohol). In this particular case, the nanopores are 130–140 nm in diameter and the interpore distance is around 430 nm. Features of such characteristic dimensions are known to be easily recognized by living cells. Moreover, the inverse mold is not destroyed in the pore array demolding process and can be reused for further pore array fabrication. Therefore, the developed method allows the high-throughput production of cm 2 -scale biocompatible nanoporous surfaces that could be interesting as two-dimensional scaffolds for tissue repair or wound healing. Moreover, our approach can be extrapolated to the fabrication of almost any polymer and biopolymer ordered pore array. (paper)

  8. PTFE grafts versus tunneled cuffed catheters for hemodialysis: which is the second choice when arteriovenous fistula is not feasible?

    Science.gov (United States)

    Donati, Gabriele; Cianciolo, Giuseppe; Mauro, Raffaella; Rucci, Paola; Scrivo, Anna; Marchetti, Antonio; Giampalma, Emanuela; Golfieri, Rita; Panicali, Laura; Iorio, Mario; Stella, Andrea; La Manna, Gaetano; Stefoni, Sergio

    2015-02-01

    Vascular access-related complications are still one of the leading causes of morbidity in hemodialysis patients. The aim of this study was to compare polytetrafluoroethylene (PTFE) grafts versus tunneled cuffed permanent catheters (TCCs) in terms of vascular access and patients' survival. An observational study was carried out with a 2-year follow-up. Eighty-seven chronic hemodialysis patients were enrolled: 31 with a PTFE graft as vascular access for hemodialysis versus 56 with a TCC. Patients' mean age was 63.8 ± 14.6 (grafts) versus 73.5 ± 11.3 years (TCCs), P = 0.001. Significantly more patients with TCC had atrial fibrillation than patients with grafts (30.3% versus 6.5%, P = 0.01). In an unadjusted Kaplan-Meier analysis, median TCC survival at 24 months was 5.4 months longer than that of PTFE grafts but not significantly (log-rank test = 1.3, P = ns). In a Cox regression analysis adjusted for age, gender, number of previous vascular accesses, diabetes, atrial fibrillation, smoking, and any complication, this lack of significant difference in survival of the vascular access between TCC and PTFE groups was confirmed and diabetes proved to be an independent risk factor for the survival of both vascular accesses considered (P = 0.02). In an unadjusted Kaplan-Meier analysis, a higher mortality was found in the TCC group than in the PTFE group at 24 months (log-rank test = 10.07, P PTFE grafts. When an arteriovenous fistula (AVF) is not possible, PTFE grafts can be considered the vascular access of second choice, whereas TCCs can be used when an AVF or PTFE graft are not feasible or as a bridge to AVF or PTFE graft creation. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  9. Enhanced tribological behavior of anodic films containing SiC and PTFE nanoparticles on Ti6Al4V alloy

    International Nuclear Information System (INIS)

    Li, Songmei; Zhu, Mengqi; Liu, Jianhua; Yu, Mei; Wu, Liang; Zhang, Jindan; Liang, Hongxing

    2014-01-01

    Highlights: • An environmental friendly sodium tartrate (C 4 O 6 H 4 Na 2 ) electrolyte is used. • SiC and PTFE nanoparticles reduce friction coefficient of composite films. • SiC and PTFE nanoparticles demonstrate a favorable synergistic effect on improving tribological properties of composite films. • Lubricating mechanisms of SiC and PTFE nanoparticles are discussed. - Abstract: Anodic films containing SiC and polytetrafluoroethylene (PTFE) nanoparticles were successfully fabricated on Ti6Al4V alloy by using anodic oxidation method in an environmental friendly electrolyte. The morphology, structure and composition of the films were studied with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that the film contained a layered structure and have a surface full of petaloid bulges, which was totally different from the common anodic oxide film of the porous kind. The tribological properties of the films were investigated with dry friction tests in terms of the friction coefficient, wear rate and the morphology of worn surfaces. The results indicated that the SiC/PTFE composite film exhibited much better anti-wear and anti-friction performances than that of the SiC composite film, the PTFE composite film and the ordinary film without nanoparticles. The SiC/PTFE composite film has friction coefficient of 0.1 and wear rate of 20.133 mg/m, which was decreased respectively by 80% and 44.5% compared with that of the ordinary film. The lubricating mechanisms of the composite film containing SiC and PTFE nanoparticles were discussed. PTFE nanoparticles could lead to the formation of lubricating layer while SiC nanoparticles inside the lubricating layer turned sliding friction to rolling friction

  10. Thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE irradiated with high energy electron beams; Caracteristicas termoluminiscentes del CaSO{sub 4}:Dy+PTFE irradiado con haces de electrones de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, R.; Rivera, T.; Calderon, J. A.; Jimenez, Y. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Rodriguez, J. [Hospital General de Mexico, Dr. Balmis 148, Col. Doctores, 06726 Mexico D. F. (Mexico); Oviedo, O. [Centro Medico ABC, Sur 136 No. 116, Col. Las Americas, 01120 Mexico D. F. (Mexico); Azorin, J., E-mail: chagua@hotmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, 09340 Mexico D. F. (Mexico)

    2011-10-15

    In the present work thermoluminescent response of dysprosium doped calcium sulfate embedded in polytetrafluorethylene (CaSO{sub 4}:Dy+PTFE) under high electron beam irradiations from linear accelerator for clinical applications was investigated. The irradiations were carried out using high electron beams (6 to 18 MeV) from a linear accelerator Varian, C linac 2300C/D, for clinical practice purpose. The electron irradiations were obtained by using the water solid in order to guarantee electronic equilibrium conditions. Field shaping for electron beams was obtained with electron cones. Glow curve and other thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE were conducted under high electron beams irradiations. The thermoluminescent response of the pellets showed and intensity peak centered at around 235 C. Thermoluminescent response of CaSO{sub 4}:Dy+PTFE as a function of high electron absorbed dose showed a linearity in a wide range. To obtain reproducibility characteristic, a set of pellets were exposed repeatedly for the same electron absorbed dose. The results obtained in this study can suggest the applicability of CaSO{sub 4}:Dy+PTFE pellets for high electron beam dosimetry, provided fading is correctly accounted for. (Author)

  11. Thermophysical Properties of 60-NITINOL for Mechanical Component Applications

    Science.gov (United States)

    Stanford, Malcolm K.

    2012-01-01

    The linear thermal expansion coefficient, specific heat capacity, electrical resistivity and thermal conductivity of 60- NITINOL were studied over a range of temperatures representing the operating environment of an oil-lubricated bearing. The behavior of this material appears to follow wellestablished theories applicable to either metal alloys, in general, or to intermetallic compounds, more specifically and the measured data were found to be comparable to those for conventional bearing alloys.

  12. Impact of lubrication on the tribological behaviour of PTFE ...

    Indian Academy of Sciences (India)

    bronze and bronze + molybdenum disulfide (MoS2) were considered. These composites were ... the PTFE composites have significantly been reduced in the lubricated condition ... there are no strong bonds between the fillers and the matrix in.

  13. Tl response of KMgF{sub 3}: Lu + PTFE at ultraviolet radiation; Respuesta Tl de KMgF{sub 3}: Lu + PTFE a radiacion ultravioleta

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, P R [Instituto Nacional de Investigaciones Nucleares, A.P. 18 -1027, 11801 Mexico D.F. (Mexico); Alarcon, N G [Facultad de Quimica, Universidad Autonoma del Estado de Mexico. Paseo Tollocan, Esq. con Jesus Carranza, 50180 Toluca, Estado de Mexico (Mexico); Furetta, C; Azorin, J [Universidad Autonoma Metropolitana- Iztapalapa, San Rafael Atlixco 186, 09340 Mexico. D.F. (Mexico)

    2003-07-01

    Ionizing radiation has different types of interaction with a crystalline solid. However, only few effects are interesting to optimize some thermoluminescent (Tl) properties of certain Tl materials. This paper presents results obtained by irradiating KMgF{sub 3}: Lu + Ptfe Tl dosimeters with ultraviolet (UV) radiation previously exposed to gamma radiation. These results showed that those dosimeters not exposed previously to gamma radiation did not presented any Tl signal. Meanwhile, those previously submitted to gamma irradiation showed that their sensitivity was increased as the gamma dose increased. The glow curve of sensitized KMgF{sub 3}: Lu + Ptfe exposed to UV radiation, presented the dosimetric pea at 212 C. This makes this material to be promissory for measuring UV radiation. (Author)

  14. Thermoluminescent characteristics of CaSO4:Dy+PTFE irradiated with high energy electron beams

    International Nuclear Information System (INIS)

    Alvarez, R.; Rivera, T.; Calderon, J. A.; Jimenez, Y.; Rodriguez, J.; Oviedo, O.; Azorin, J.

    2011-10-01

    In the present work thermoluminescent response of dysprosium doped calcium sulfate embedded in polytetrafluorethylene (CaSO 4 :Dy+PTFE) under high electron beam irradiations from linear accelerator for clinical applications was investigated. The irradiations were carried out using high electron beams (6 to 18 MeV) from a linear accelerator Varian, C linac 2300C/D, for clinical practice purpose. The electron irradiations were obtained by using the water solid in order to guarantee electronic equilibrium conditions. Field shaping for electron beams was obtained with electron cones. Glow curve and other thermoluminescent characteristics of CaSO 4 :Dy+PTFE were conducted under high electron beams irradiations. The thermoluminescent response of the pellets showed and intensity peak centered at around 235 C. Thermoluminescent response of CaSO 4 :Dy+PTFE as a function of high electron absorbed dose showed a linearity in a wide range. To obtain reproducibility characteristic, a set of pellets were exposed repeatedly for the same electron absorbed dose. The results obtained in this study can suggest the applicability of CaSO 4 :Dy+PTFE pellets for high electron beam dosimetry, provided fading is correctly accounted for. (Author)

  15. The fabrication, nano/micro-structure, heat- and wear-resistance of the superhydrophobic PPS/PTFE composite coatings.

    Science.gov (United States)

    Wang, Huaiyuan; Zhao, Jingyan; Zhu, Youzhuang; Meng, Yang; Zhu, Yanji

    2013-07-15

    A simple engineering method was used to fabricate stability and wear-resistance of superhydrophobic PPS-based PPS/PTFE surfaces through nano/micro-structure design and modification of the lowest surface energy groups (-CF2-), which was inspired by the biomimic lotus leaves. The hydrophobic properties and wear-resistance of the coatings were measured by a contact angle meter and evaluated on a pin-on-disk friction and wear tester, respectively. Moreover, the surfaces of the PPS/PTFE composite coatings were investigated by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and thermogravimetry (TG) analysis. Results showed that the highest contact angle of the PPS/PTFE surface, with papillae-like randomly distributed double-scale structure, could reach up to 162°. When 1 wt.% PDMS was added, the highest contact angle could hold is 172°. The coatings also retained superhydrophobicity, even under high temperature environment. The investigation also indicated that the coatings were not only superhydrophobic but also oleophobic behavior at room temperature, such as the crude oil, glycerol, and oil-water mixture. The PPS/45%PTFE coatings had more stable friction coefficient and excellent wear-resistance (331,407 cycles) compared with those with less than 45% of PTFE. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. BRDF Calibration of Sintered PTFE in the SWIR

    Science.gov (United States)

    Georgiev, Georgi T.; Butler, James J.

    2009-01-01

    Satellite instruments operating in the reflective solar wavelength region often require accurate and precise determination of the Bidirectional Reflectance Distribution Function (BRDF) of laboratory-based diffusers used in their pre-flight calibrations and ground-based support of on-orbit remote sensing instruments. The Diffuser Calibration Facility at NASA's Goddard Space Flight Center is a secondary diffuser calibration standard after NEST for over two decades, providing numerous NASA projects with BRDF data in the UV, Visible and the NIR spectral regions. Currently the Diffuser Calibration Facility extended the covered spectral range from 900 nm up to 1.7 microns. The measurements were made using the existing scatterometer by replacing the Si photodiode based receiver with an InGaAs-based one. The BRDF data was recorded at normal incidence and scatter zenith angles from 10 to 60 deg. Tunable coherent light source was setup. Broadband light source application is under development. Gray-scale sintered PTFE samples were used at these first trials, illuminated with P and S polarized incident light. The results are discussed and compared to empirically generated BRDF data from simple model based on 8 deg directional/hemispherical measurements.

  17. Less Than Total Excision of Infected Prosthetic PTFE Graft Does Not Increase the Risk of Reinfection.

    Science.gov (United States)

    Sgroi, Michael D; Kirkpatrick, Vincent E; Resnick, Karen A; Williams, Russell A; Wilson, Samuel E; Gordon, Ian L

    2015-01-01

    Traditional treatment of infected polytetrafluoroethylene (PTFE) grafts consist of removal of the entire prosthesis. Closure of the native vessels may compromise vascular patency. We examined the outcomes for patients in whom a PTFE remnant of an infected graft was retained on the vessel. We reviewed the operating room log from 2000 to 2011 and identified all patients who had partial removal of an infected PTFE graft used for hemodialysis or peripheral bypass. These patients were examined for subsequent complications. Twenty-seven patients underwent 30 partial graft excisions with mean follow-up of 27 months. A total of 17% (5 of 30) of the partial graft resection procedures resulted in complications. Of 48 total remnants left behind at the arterial or venous anastomoses, reinfection occurred in 15%. Leaving a well-incorporated small 1-to 5-mm PTFE remnant at the arterial or venous anastomoses can be performed safely with a low risk of complications. © The Author(s) 2015.

  18. Tracheal Self-Expandable Metallic Stents: A Comparative Study of Three Different Stents in a Rabbit Model.

    Science.gov (United States)

    Serrano, Carolina; Lostalé, Fernando; Rodríguez-Panadero, Francisco; Blas, Ignacio de; Laborda, Alicia; de Gregorio, Miguel Angel

    2016-03-01

    The objective of this study was to assess tracheal reactivity after the deployment of different self-expandable metal stents (SEMS). Forty female New Zealand rabbits were divided into four groups. Three groups received three different SEMS: steel (ST), nitinol (NiTi), or nitinol drug-eluting stent (DES); the fourth group was the control group (no stent). Stents were deployed percutaneously under fluoroscopic guidance. Animals were assessed by multi-slice, computed tomography (CT) scans, and tracheas were collected for anatomical pathology (AP) study. Data from CT and AP were statistically analyzed and correlated. The DES group had the longest stenosis (20.51±14.08mm vs. 5.84±12.43 and 6.57±6.54mm in NiTi and ST, respectively, day 30; Pstent. CT was more effective in detecting wall thickening (positive correlation of 68.9%; Pstent, while DES caused significant lesions that may be related to drug dosage. This type of DES stent is therefore not recommended for the treatment of tracheobronchial stenosis. Copyright © 2015 SEPAR. Published by Elsevier Espana. All rights reserved.

  19. Hierarchical periodic micro/nano-structures on nitinol and their influence on oriented endothelialization and anti-thrombosis

    International Nuclear Information System (INIS)

    Nozaki, Kosuke; Shinonaga, Togo; Ebe, Noriko; Horiuchi, Naohiro; Nakamura, Miho; Tsutsumi, Yusuke; Hanawa, Takao; Tsukamoto, Masahiro; Yamashita, Kimihiro; Nagai, Akiko

    2015-01-01

    The applications of hierarchical micro/nano-structures, which possess properties of two-scale roughness, have been studied in various fields. In this study, hierarchical periodic micro/nano-structures were fabricated on nitinol, an equiatomic Ni–Ti alloy, using a femtosecond laser for the surface modification of intravascular stents. By controlling the laser fluence, two types of surfaces were developed: periodic nano- and micro/nano-structures. Evaluation of water contact angles indicated that the nano-surface was hydrophilic and the micro/nano-surface was hydrophobic. Endothelial cells aligned along the nano-structures on both surfaces, whereas platelets failed to adhere to the micro/nano-surface. Decorrelation between the responses of the two cell types and the results of water contact angle analysis were a result of the pinning effect. This is the first study to show the applicability of hierarchical periodic micro/nano-structures for surface modification of nitinol. - Highlights: • Hierarchical micro/nano-structures were created on nitinol using a femtosecond laser. • The nano-surface was hydrophilic and the micro/nano-surface was hydrophobic. • Endothelial cells aligned along the nano-structures • Platelets failed to adhere to the micro/nano-surface

  20. Hierarchical periodic micro/nano-structures on nitinol and their influence on oriented endothelialization and anti-thrombosis

    Energy Technology Data Exchange (ETDEWEB)

    Nozaki, Kosuke [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062 (Japan); Shinonaga, Togo [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Ebe, Noriko; Horiuchi, Naohiro; Nakamura, Miho; Tsutsumi, Yusuke; Hanawa, Takao [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062 (Japan); Tsukamoto, Masahiro [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Yamashita, Kimihiro [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062 (Japan); Nagai, Akiko, E-mail: nag-bcr@tmd.ac.jp [Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda, Tokyo 101-0062 (Japan)

    2015-12-01

    The applications of hierarchical micro/nano-structures, which possess properties of two-scale roughness, have been studied in various fields. In this study, hierarchical periodic micro/nano-structures were fabricated on nitinol, an equiatomic Ni–Ti alloy, using a femtosecond laser for the surface modification of intravascular stents. By controlling the laser fluence, two types of surfaces were developed: periodic nano- and micro/nano-structures. Evaluation of water contact angles indicated that the nano-surface was hydrophilic and the micro/nano-surface was hydrophobic. Endothelial cells aligned along the nano-structures on both surfaces, whereas platelets failed to adhere to the micro/nano-surface. Decorrelation between the responses of the two cell types and the results of water contact angle analysis were a result of the pinning effect. This is the first study to show the applicability of hierarchical periodic micro/nano-structures for surface modification of nitinol. - Highlights: • Hierarchical micro/nano-structures were created on nitinol using a femtosecond laser. • The nano-surface was hydrophilic and the micro/nano-surface was hydrophobic. • Endothelial cells aligned along the nano-structures • Platelets failed to adhere to the micro/nano-surface.

  1. Silicone covered vs. Non- covered endotracheal self expandable metallic stent: An experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Do, Young Soo; Lee, Byung Hee; Kim, Soo Ah; Kim, Kie Hwan; Chin, Soo Yil; Cho, Kyung Ja; Cho, Dae Soon [Korea Cancer Center Hospital, Seoul (Korea, Republic of)

    1994-10-15

    To evaluate pathologic changes of the trachea and the lung after insertion of silicone covered and non covered Gianturco stent in the trachea of dog. Silicone covered(covered) and non covered(bare) Gianturco stent, six in each, were inserted into the tracheal lumen of six consecutive dogs. After 1-10 weeks observation, the dogs were sacrificed and their tracheas and lungs were examined grossly and histopathologically. Serial chest radiographs were performed to evaluate pneumonia and stent migration every 3-5 days. Pneumonia was observed in one of bare stent group and five of covered stent group. Stent migration was noted in three of covered stent group. In bare stent group, the epithelium of the trachea was markedly thickened by hyperplasia and stent was covered by granulation tissue from 6 weeks after stent insertion. Inflammation was focal at contact site between the stent and the trachea. In covered stent group, the epithelium was denuded at multiple areas and there were multifocal squamous metaplasia of the mucosa. Inflammatory reaction of the trachea was diffuse. Inflammatory reaction was more severe and stent migration was more frequent in covered stent group. The use of covered stent in the trachea should be studied further.

  2. Clinical Application of Fully Covered Self-Expandable Metal Stents in the Treatment of Bronchial Fistula.

    Science.gov (United States)

    Cao, Ming; Zhu, Qiang; Wang, Wei; Zhang, Tian Xiao; Jiang, Min Zhong; Zang, Qi

    2016-09-01

    Background The study was designed to access the feasibility, safety, and efficacy of fully covered self-expandable metal stents in the treatment of bronchial fistula. Methods Clinical data of nine patients (seven males and two females) who were treated with placement of tracheobronchial or bronchial fully covered self-expandable metal stents from August 2005 to November 2011 were analyzed retrospectively. Among these patients, seven were diagnosed with bronchopleural fistula, one with tracheopleural fistula, and one with left main bronchoesophageal fistula. Eight had accompanying thoracic empyema. The fistula orifices ranged from 3.5 mm to 25 mm in diameter. All patients received topical anesthesia. L-shaped stents were placed in six patients and I-shaped stents in three under fluoroscopic guidance. After stent placement, patients with empyema were treated with pleural lavage. Results Stent placement in the tracheobronchial tree was successful in all patients, without procedure-related complications. The operating time was 5 to 16 minutes. A small amount of bubble overflowed from the intrathoracic drainage tube of only one patient. In the other patients, the bubble in the intrathoracic drainage tube disappeared immediately or angiography showed no overflow of contrast agent from the fistula orifice. The effective rate of fistula orifice closure after stent placement was 100%, with 88.9% rated as excellent. One patient coughed the stent out 5 days after placement and hence a new stent was placed. Among the patients with empyema, one died of septicemia arising from empyema on day 8 and another died of brain metastases of lung cancer 6 months after stent insertion with persistent empyema. In the other six patients, empyema resolved after 2 to 5 months (cure rate 75%). Seven patients were followed up for 3 to 36 months. During follow-up, one stent was removed 8 months after implantation due to difficult expectoration, without recurrent empyema. The remaining

  3. Introduction of oxygen vacancies and fluorine into TiO2 nanoparticles by co-milling with PTFE

    International Nuclear Information System (INIS)

    Senna, Mamoru; Šepelák, Vladimir; Shi, Jianmin; Bauer, Benjamin; Feldhoff, Armin; Laporte, Vincent; Becker, Klaus-Dieter

    2012-01-01

    Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO 2 nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm −1 (1140 nm) was attributed to the change in the electronic states, viz. electrons trapped at the oxygen vacancies (Vo) and d–d transitions of titanium ions. Incorporation of fluorine into n-TiO 2 was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO 2 was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO 2 lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO 6−n Vo n , located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO 2 particles, where local non-crystalline states predominate. - Graphical abstract: Scheme of the reaction processes: (a) pristine mixture, (b) oxygen abstraction from TiO 2 and (c) fluorine migration from PTFE to TiO 2 . Highlights: Transfer of fluorine from PTFE to n-TiO 2 in a dry solid state process was confirmed. ► 40% of F in PTFE was incorporated to the near surface region of n-TiO 2 nanoparticles. ► The transfer process is

  4. cancerous esophagotracheal fistula: treatment of placement with covered self-expanding metallic stent

    International Nuclear Information System (INIS)

    Han Xinwei; Li Tianxiao; Wang Ruilin; Fan Qingxia

    1997-01-01

    Purpose: To treat the esophagotracheal fistula that was the main cause of death in patients with esophageal carcinoma, the placement of the stent was studied. Materials and methods: Under the fluoroscopic guidance, 28 stents (5 stents made in USA and 23 in China) were successfully implanted in all the 28 patients with esophagotracheal fistula. Results: The aphagia of the patients was greatly improved and a normal diet could be swallowed at once after the placement of the stents. The 27 cases of inhalation pneumonia that caused by the fistula was recovered. Conclusion: The result indicated that the treatment with the placement of the covered self-expanding stent is simple, safe, and effective for most patients with aphagia and pneumonia due to esophagotracheal fistula

  5. SIMULATION OF POROSITY AND PTFE CONTENT IN GAS DIFFUSION LAYER ON PROTON EXCHANGE MEMBRANE FUEL CELL PERFORMANCE

    Directory of Open Access Journals (Sweden)

    NUR H. MASLAN

    2016-01-01

    Full Text Available Numerous research and development activities have been conducted to optimize the operating parameters of a proton exchange membrane fuel cell (PEMFC by experiments and simulations. This study explains the development of a 3D model by using ANSYS FLUENT 14.5 to determine the optimum PEMFC parameters, namely, porosity and polytetrafluoroethylene (PTFE content, in the gas diffusion layer (GDL. A 3D model was developed to analyze the properties and effects of GDL. Simulation results showed that the increase in GDL porosity significantly improved the performance of PEMFC in generating electrical power. However, the performance of PEMFC decreased with increasing PTFE content in GDL. Thus, the PTFE content in the GDL must be optimized and the optimum PTFE content should be 5 wt%. The model developed in this simulation showed good capability in simulating the PEMFC parameters to assist the development process of PEMFC design.

  6. Microbiologic Evaluation of Cotton and Polytetrafluoroethylene (PTFE) Tape as Endodontic Spacer Materials in Primary Molars An in Vivo Study.

    Science.gov (United States)

    Prabhakar, Attiguppe Ramasetty; Dixit, Kratika; Raju, O S

    PTFE tape, which is commonly used as plumber's tape is an inorganic, non-fibrous, ribbon like material. The aim of this study was to evaluate PTFE tape as endodontic spacer material and to compare it with commonly used spacer material that is cotton, in primary teeth. Seventeen children undergoing pulpectomy of lower second primary molar bilaterally were included in the study. Cotton and PTFE tape were placed as spacers on each side randomly. Samples were taken from the access cavity at baseline and after seven days to check for microbial leakage. Spacer materials were also checked for microbial contamination. The results revealed that there was a significant increase in the bacterial colony count after seven days in cotton group. The access cavities were also positive for microbial leakage in the cotton group where the spacers showed positive growth. In PTFE group only two samples showed microbial contamination of spacer and out of two only one sample showed contamination of access cavity along with spacer. Within the limitations of this study, it can be concluded that PTFE tape performed better than cotton as endodontic spacer material. Thus, PTFE tape can be recommended as an endodontic spacer material as an alternative to cotton in primary teeth.

  7. Surface modification and fatigue behavior of nitinol for load bearing implants

    Science.gov (United States)

    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  8. Linker-free covalent immobilization of heparin, SDF-1α, and CD47 on PTFE surface for antithrombogenicity, endothelialization and anti-inflammation.

    Science.gov (United States)

    Gao, Ang; Hang, Ruiqiang; Li, Wan; Zhang, Wei; Li, Penghui; Wang, Guomin; Bai, Long; Yu, Xue-Feng; Wang, Huaiyu; Tong, Liping; Chu, Paul K

    2017-09-01

    Small-diameter vascular grafts made of biomedical polytetrafluoroethylene (PTFE) suffer from the poor long-term patency rate originating from thrombosis and intimal hyperplasia, which can be ascribed to the insufficient endothelialization and chronic inflammation of the materials. Hence, bio-functionalization of PTFE grafts is highly desirable to circumvent these disadvantages. In this study, a versatile "implantation-incubation" approach in which the biomedical PTFE is initially modified by plasma immersion ion implantation (PIII) is described. After the N 2 PIII treatment, the surface of biomedical PTFE is roughened with nanostructures and more importantly, the abundant free radicals generated underneath the surface continuously migrate to the surface and react with environmental molecules. Taking advantage of this mechanism, various biomolecules with different functions can be steadily immobilized on the surface of PTFE by simple solution immersion. As examples, three typical biomolecules, heparin, SDF-1α, and CD47, are covalently grafted onto the PTFE. In addition to retaining the bioactivity, the surface-functionalized PTFE exhibits reduced thrombogenicity, facilitates the recruitment of endothelial progenitor cells, and even alleviates the inflammatory immune responses of monocytes-macrophages and is thus promising to the development of small-diameter prosthetic vascular grafts with good long-term patency. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. The EPIC nitinol stent system in the treatment of iliac artery lesions: one-year results from the ORION clinical trial.

    Science.gov (United States)

    Clair, Daniel G; Adams, Julie; Reen, Bernard; Feldman, Robert; Starr, Jean; Diaz-Cartelle, Juan; Dawkins, Keith D

    2014-04-01

    To report the 1-year results of a pivotal study for a new-generation nitinol stent for the treatment of iliac atherosclerotic lesions. The ORION trial (ClinicalTrials.gov identifier NCT00896337) was a single-arm, non-randomized, prospective, multicenter clinical trial that enrolled 125 patients (81 men; mean age 61.1±9.3 years) implanted with the EPIC self-expanding nitinol stent system in 166 de novo or restenotic iliac artery lesions ≤13 cm long. The primary endpoint was the 9-month major adverse event rate [i.e., device- or procedure-related death within 30 days, myocardial infarction during the index hospitalization, target vessel revascularization (TVR), or index limb amputation]. Follow-up occurred at hospital discharge and at 1, 9, and 12 months. An independent core laboratory evaluated ultrasound results at 1, 9, and 12 months. The primary endpoint met the prespecified performance goal, with only 3.4% (4/117) of patients experiencing a major adverse event by 9 months (p<0.0001). By 12 months, 6 (5.4%) of 111 patients had TVR; none had an index limb amputation. The ankle-brachial index, Walking Impairment Questionnaire, and Rutherford classifications all showed sustained improvements through 12 months. Primary patency was 94.4% with comparable results for lesions classified as complex (TASC II C/D 95.5%) or non-complex (TASC II A/B 95.0%). The EPIC stent system demonstrated safety and effectiveness through 12 months, including improvements for complex lesions. The EPIC stent is a viable alternative to surgery for patients with either complex or non-complex lesions.

  10. PTFE effect on the electrocatalysis of the oxygen reduction reaction in membraneless microbial fuel cells.

    Science.gov (United States)

    Guerrini, Edoardo; Grattieri, Matteo; Faggianelli, Alessio; Cristiani, Pierangela; Trasatti, Stefano

    2015-12-01

    Influence of PTFE in the external Gas Diffusion Layer (GDL) of open-air cathodes applied to membraneless microbial fuel cells (MFCs) is investigated in this work. Electrochemical measurements on cathodes with different PTFE contents (200%, 100%, 80% and 60%) were carried out to characterize cathodic oxygen reduction reaction, to study the reaction kinetics. It is demonstrated that ORR is not under diffusion-limiting conditions in the tested systems. Based on cyclic voltammetry, an increase of the cathodic electrochemical active area took place with the decrease of PTFE content. This was not directly related to MFC productivity, but to the cathode wettability and the biocathode development. Low electrodic interface resistances (from 1 to 1.5 Ω at the start, to near 0.1 Ω at day 61) indicated a negligible ohmic drop. A decrease of the Tafel slopes from 120 to 80 mV during productive periods of MFCs followed the biological activity in the whole MFC system. A high PTFE content in the cathode showed a detrimental effect on the MFC productivity, acting as an inhibitor of ORR electrocatalysis in the triple contact zone.

  11. Dosimetric properties of LIF:Mg,CuP+PTFE

    International Nuclear Information System (INIS)

    Gonzalez Martinez, P.R.; Azorin Nieto, J.; Ramirez Luna, A.

    1998-01-01

    The work presents the preparation method, as well as the characterization of the dosemeters of LiF;Mg,Cu+PTFE developed in the National Institute of Nuclear Investigations (ININ) Mexico, Among the carried out tests can mention, sensibility, detection threshold, equivalent of bottom, uniformity, reproducibility, dissipation, answer in function of the dose and kinetic parameters

  12. Tl response of KMgF3: Lu + PTFE at ultraviolet radiation

    International Nuclear Information System (INIS)

    Gonzalez, P.R.; Alarcon, N.G.; Furetta, C.; Azorin, J.

    2003-01-01

    Ionizing radiation has different types of interaction with a crystalline solid. However, only few effects are interesting to optimize some thermoluminescent (Tl) properties of certain Tl materials. This paper presents results obtained by irradiating KMgF 3 : Lu + Ptfe Tl dosimeters with ultraviolet (UV) radiation previously exposed to gamma radiation. These results showed that those dosimeters not exposed previously to gamma radiation did not presented any Tl signal. Meanwhile, those previously submitted to gamma irradiation showed that their sensitivity was increased as the gamma dose increased. The glow curve of sensitized KMgF 3 : Lu + Ptfe exposed to UV radiation, presented the dosimetric pea at 212 C. This makes this material to be promissory for measuring UV radiation. (Author)

  13. Core-Shell Al-Polytetrafluoroethylene (PTFE) Configurations to Enhance Reaction Kinetics and Energy Performance for Nanoenergetic Materials.

    Science.gov (United States)

    Wang, Jun; Qiao, Zhiqiang; Yang, Yuntao; Shen, Jinpeng; Long, Zhang; Li, Zhaoqian; Cui, Xudong; Yang, Guangcheng

    2016-01-04

    The energy performance of solid energetic materials (Al, Mg, etc.) is typically restricted by a natural passivation layer and the diffusion-limited kinetics between the oxidizer and the metal. In this work, we use polytetrafluoroethylene (PTFE) as the fluorine carrier and the shielding layer to construct a new type of nano-Al based fuels. The PTFE shell not only prevents nano-Al layers from oxidation, but also assists in enhancing the reaction kinetics, greatly improving the stability and reactivity of fuels. An in situ chemical vapor deposition combined with the electrical explosion of wires (EEW) method is used to fabricate core-shell nanostructures. Studies show that by controlling the stoichiometric ratio of the precursors, the morphology of the PTFE shell and the energy performance can be easily tuned. The resultant composites exhibit superior energy output characters than that of their physically mixed Al/PTFE counterparts. This synthetic strategy might provide a general approach to prepare other high-energy fuels (Mg, Si). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Carbon fibre and nitinol needles for MRI-guided interventions: First in vitro and in vivo application

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Christoph, E-mail: Christoph.thomas@med.uni-tuebingen.de [Department of Diagnostic and Interventional Radiology, University of Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen (Germany); Wojtczyk, Hanne [Section of Experimental Radiology, University of Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen (Germany); Rempp, Hansjoerg; Clasen, Stephan; Horger, Marius [Department of Diagnostic and Interventional Radiology, University of Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen (Germany); Lassberg, Christoph von [Department of Sports Medicine, University of Tuebingen, Silcherstrasse 5, 72076 Tuebingen (Germany); Fritz, Jan [Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, MD 21287 (United States); Claussen, Claus D. [Department of Diagnostic and Interventional Radiology, University of Tuebingen, Hoppe-Seyler-Strasse 3, 72076 Tuebingen (Germany); Pereira, Philippe L. [Department of Radiology, Minimally Invasive Therapies and Nuclearmedicine, SLK-Kliniken Heilbronn GmbH, Am Gesundbrunnen 20-26, 74078 Heilbronn (Germany)

    2011-09-15

    Objective: To assess the artefact properties of a MR-compatible carbon fibre needle with a nitinol mandrin in vitro and to report first clinical experiences. Materials and methods: In vitro, the carbon fibre/nitinol needle was imaged at different angles against the main magnetic field (1.5 T open bore magnet). A gradient echo MR fluoroscopy sequence (GRE: TR 9.3 ms, TE 3.12 ms, bandwidth 200 Hz/pixel, flip-angle 12{sup o}) and a fast turbo spin echo sequence (FSE: TR 412 ms, TE 9.7 ms, bandwidth 200 Hz/pixel, flip-angle 150{sup o}) were used. Artefact width, needle intensity contrast and needle tip location errors were assessed. In vivo, lumbar periradicular corticosteroid injections and one sclerotherapy were performed with carbon fibre needles (10 procedures) and with titanium alloy needles (2 procedures). The artefact sizes and contrasts were measured. Results: In vitro, artefact diameters of the carbon fibre needle ranged from 3.3 to 4.6 mm, contrasts from 0.11 to 0.52, with larger artefact contrasts and widths with the GRE sequence. Needle tip location errors of -2.1 to -2.8 mm were observed. Decreasing angles to the main field lead to smaller artefacts. In vivo, the carbon fibre/nitinol needle produced smaller artefacts (mean width FSE/GRE: 2.8 mm/4.6 mm) with lower contrast (0.30-0.42) than the titanium alloy needle (mean width FSE/GRE: 4.1 mm/7.5 mm, contrast 0.60-0.73). Conclusions: The carbon fibre/nitinol needle is useful for performing MR-guided interventions at 1.5 T, producing more subtle artefacts than a titanium alloy needle, but with an incomplete depiction and thus inaccurate localization of the needle tip.

  15. Reversal of Transjugular Intrahepatic Portosystemic Shunt (TIPS)-Induced Hepatic Encephalopathy Using a Strictured Self-Expanding Covered Stent

    International Nuclear Information System (INIS)

    Cox, Mitchell W.; Soltes, George D.; Lin, Peter H.; Bush, Ruth L.; Lumsden, Alan B.

    2003-01-01

    Hepatic encephalopathy is a known complication following percutaneous transjugular intrahepatic portosystemic shunt (TIPS) placement. We describe herein a simple and effective strategy of TIPS revision by creating an intraluminal stricture within a self-expanding covered stent, which is deployed in the portosystemic shunt to reduce the TIPS blood flow. This technique was successful in reversing a TIPS-induced hepatic encephalopathy in our patient

  16. Study on the performance of MoS2 modified PTFE composites by molding process

    Science.gov (United States)

    Ma, Weiqiang; Hou, Genliang; Bi, Song; Li, Ping; Li, Penghui

    2017-10-01

    MoS2 filled PTFE composites were prepared by cold pressing and sintering molding. The compressive and creep properties of composite materials were analyzed by controlling the size of molded composites during molding. The results show that the composites have the best compressive and creep resistance when the molding pressure is 55 MPa in the MoS2 composites with 15% mass fraction, which is a practical reference for the preparation of MoS2-modified PTFE composites.

  17. A Novel Non-Planar Transverse Stretching Process for Micro-Porous PTFE Membranes and Resulting Characteristics

    KAUST Repository

    Chang, Y.-H.

    2018-02-26

    Polytetrafluoroethylene (PTFE) micro-porous membranes were prepared from PTFE fine powder through extruding, rolling, and uniaxial longitudinally stretching. In contrast to conventional planar transverse stretching, a novel 3D mold design of non-planar transverse stretching process was employed in this study to produce micro-porous structure. The morphology, membrane thickness, mean pore size, and porosity of the PTFE membrane were investigated. The results show that the non-planar transverse stretched membranes exhibit more uniform average pore diameter with thinner membrane thickness. Morphological changes induced by planar and non-planar transverse stretching for pore characteristics were investigated. The stretching conditions, stretching temperature and rate, affect the stretched membrane. Increasing temperature facilitated the uniformity of pore size and uniformity of membrane thickness. Moreover, increase in stretching rate resulted in finer pore size and thinner membrane.

  18. Effect of gamma and neutron irradiation on the mechanical properties of Spectralon™ porous PTFE

    Energy Technology Data Exchange (ETDEWEB)

    Gourdin, William H., E-mail: gourdin1@llnl.gov [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA USA (United States); Datte, Philip; Jensen, Wayne; Khater, Hesham; Pearson, Mark [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA USA (United States); Girard, Sylvain [Laboratoire Hubert Curien − UMR CNRS 5516, 18 rue du Pr. Benoît Lauras, F-42000 Saint Etienne (France); Paillet, Philippe; Alozy, Eric [CEA, DAM, DIF, F-91297 Arpajon (France)

    2016-11-15

    Highlights: • The effects of neutrons and gammas on PTFE are equivalent for a given absorbed dose. • A neutron fluence of 10{sup 13} n/cm{sup 2} corresponds to a gamma dose of 200 Gy. • The dose-to-fluence conversion factor is approximately 5 × 10{sup 10} n/(cm{sup 2}-Gy). • Irradiation in a low-oxygen environment enhances loads and elongations. • Mechanical properties of PTFE will deteriorate at a neutron fluence of 10{sup 13} n/cm{sup 2}. - Abstract: We establish a correspondence between the mechanical properties (maximum load and failure elongation) of Spectralon™ porous PTFE irradiated with 14 MeV neutrons and 1.17 and 1.33 MeV gammas from a cobalt-60 source. From this correspondence we infer that the effects of neutrons and gammas on this material are approximately equivalent for a given absorbed dose.

  19. PTFE Additive and Re-annealing Effect on Thermoluminescence Response of CaSO4:Dy Derived from Co-precipitation Method

    Science.gov (United States)

    Nuraeni, Nunung; Dwi Septianto, Ricky; Iskandar, Ferry; Haryanto, Freddy; Waris, Abdul; Hiswara, Eri

    2017-07-01

    Effect of re-annealing treatment in thermoluminescence response of thermoluminescent dosimeter (TLD) CaSO4:Dy and CaSO4:Dy with PTFE (Polytetrafluoroethylene) addition was investigated. CaSO4:Dy was prepared by a co-precipitation method. The PTFE was added before re-annealing treatment which the mass ratio of CaSO4:Dy and PTFE was fixed to 2:3. The re-annealing treatments of the samples were done at temperature 700 °C for 1 hr. The obtained samples were characterized using a Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) to observe the molecule bonding in sample and crystal properties, respectively. From the experimental results, it was observed that the thermoluminescence intensity of CaSO4:Dy, CaSO4:Dy re-annealed at 700 °C, and CaSO4:Dy + PTFE re-annealed at 700 °C are 57.03, 75.15, and 1191.11 nC, respectively. The intensity of 700 °C-re-annealed CaSO4:Dy increased significantly after PTFE addition.

  20. Acid Aging Effects on Surfaces of PTFE Gaskets Investigated by Fourier Transform Infrared Spectroscopy

    Directory of Open Access Journals (Sweden)

    L. Giorgini

    2016-09-01

    Full Text Available This paper investigates the effect of a prolonged acid and thermal attack, on the surface of PTFE by Fourier Transform Infrared Micro-Spectroscopy (FT-IR. The materials are commercialized by two alternative producers in form of Teflon tapes. These tapes are installed in process plants where tires moulds are cleaned inside a multistage ultrasonic process. In these cases, Teflon tapes, having a role of gaskets, show inexplicably phenomena of degradation in relatively short operation periods. Even considering that these gaskets are exposed to the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of these severe erosion phenomena. An interesting explanation can be related to the potential presence in the cleaning solution, mainly based on sulfamic acid, of highly reactive chemical compounds, as chlorides and fluorides, originated by the disaggregation of elements from the tire composition and/or additives used as processing aids and/or by catalytic effect generated by fluorine produced by PTFE degradation. In general, up to 300 different chemical elements, both organic and inorganic, natural and synthetic, are merged in a tire. Since this composition is practically unknown, especially regarding additives and “unusual elements”, representing a secrecy of each tire manufactures, it is really complex to define the chemical composition of the cleaning solution with an appropriate precision. As a consequence, the gaskets have been treated with different mixtures of acids in the way to combine a larger range of possibilities. Thus, the FT-IR experimental characterization of PTFE surface properties followed an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use. The different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but

  1. Safety and efficacy of nano lamellar TiN coatings on nitinol atrial septal defect occluders in vivo

    International Nuclear Information System (INIS)

    Zhang, Zhi xiong; Fu, Bu fang; Zhang, De yuan; Zhang, Zhi wei; Cheng, Yan; Sheng, Li yuan; Lai, Chen; Xi, Ting fei

    2013-01-01

    Atrial septal defect (ASD) occlusion devices made of nickel–titanium (NiTi) have a major shortcoming in that they release nickel into the body. We modified NiTi occluders using Arc Ion Plating technology. Nano lamellar titanium–nitrogen (TiN) coatings were formed on the surfaces of the occluders. The safety and efficacy of the modified NiTi occluders were evaluated in animal model. The results showed that 38 out of 39 rams (97%) survived at the end of the experiment. Fibrous capsules formed on the surfaces of the devices. Gradual endothelialization took place through the attachment of endothelial progenitor cells from the blood and the migration of endothelial cells from adjacent endocardium. The neo-endocardium formed more quickly in the coated group than in the uncoated group, as indicated by the evaluation of the six month study group. After TiN coating, there was no significant difference in endothelial cell cycle. TiN coating significantly reduced the release of nickel in both in vivo and in vitro indicating an improved biocompatibility of the nitinol ASD occluders. Superior and modified ASD occluders may provide a good choice for people with nickel allergies after sFDA registration, which is expected in one to two years. - Highlights: ► The nano lamella TiN coating did not change the shape-memory behavior and flexibility of the nitinol occluder. ► Nano lamella TiN coating modifications significantly reduced nickel release from nitinol ASD occluder. ► The new ASD occluder was found to be superior to nitinol ASD occluder with respect to both safety and efficacy

  2. Safety and efficacy of nano lamellar TiN coatings on nitinol atrial septal defect occluders in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhi xiong, E-mail: Top5460@163.com [Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Fu, Bu fang, E-mail: fubnicpbp@163.com [National Institutes for Food and Drug Control, Beijing (China); Zhang, De yuan, E-mail: Deyuanzhangcn@yahoo.com.cn [Lifetech Scientific (Shenzhen) Co., Ltd., Shenzhen (China); Zhang, Zhi wei, E-mail: Zhzhx65@163.com [Guangdong Cardiovascular Institute, Guangzhou (China); Cheng, Yan, E-mail: chengyan@pku.edu.cn [Academy for Advanced Interdisciplinary Studies, Peking University, Beijing (China); Sheng, Li yuan, E-mail: lysheng@yeah.net [Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Lai, Chen, E-mail: laichen1110@163.com [Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Xi, Ting fei, E-mail: Xitingfie@pku.edu.cn [Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Academy for Advanced Interdisciplinary Studies, Peking University, Beijing (China)

    2013-04-01

    Atrial septal defect (ASD) occlusion devices made of nickel–titanium (NiTi) have a major shortcoming in that they release nickel into the body. We modified NiTi occluders using Arc Ion Plating technology. Nano lamellar titanium–nitrogen (TiN) coatings were formed on the surfaces of the occluders. The safety and efficacy of the modified NiTi occluders were evaluated in animal model. The results showed that 38 out of 39 rams (97%) survived at the end of the experiment. Fibrous capsules formed on the surfaces of the devices. Gradual endothelialization took place through the attachment of endothelial progenitor cells from the blood and the migration of endothelial cells from adjacent endocardium. The neo-endocardium formed more quickly in the coated group than in the uncoated group, as indicated by the evaluation of the six month study group. After TiN coating, there was no significant difference in endothelial cell cycle. TiN coating significantly reduced the release of nickel in both in vivo and in vitro indicating an improved biocompatibility of the nitinol ASD occluders. Superior and modified ASD occluders may provide a good choice for people with nickel allergies after sFDA registration, which is expected in one to two years. - Highlights: ► The nano lamella TiN coating did not change the shape-memory behavior and flexibility of the nitinol occluder. ► Nano lamella TiN coating modifications significantly reduced nickel release from nitinol ASD occluder. ► The new ASD occluder was found to be superior to nitinol ASD occluder with respect to both safety and efficacy.

  3. A fully covered self-expandable metal stent with antimigration features for benign biliary strictures : a prospective, multicenter cohort study

    NARCIS (Netherlands)

    Walter, Daisy; Laleman, Wim; Jansen, Jeroen M; van Milligen de Wit, A W M; Weusten, Bas L; van Boeckel, Petra G; Hirdes, Meike M; Vleggaar, FP; Siersema, Peter D

    2015-01-01

    BACKGROUND: Self-expandable metal stents (SEMSs) are increasingly used for the treatment of benign biliary strictures (BBSs). A new fully covered SEMS (FCSEMS) with flared ends and high conformability was designed to prevent migration of the stent. OBJECTIVE: To evaluate the efficacy of a novel

  4. A fully covered self-expandable metal stent with antimigration features for benign biliary strictures: a prospective, multicenter cohort study

    NARCIS (Netherlands)

    Walter, D.; Laleman, W.; Jansen, J.M.; Milligen de Wit, A.W. van; Weusten, B.L.; Boeckel, P.G. van; Hirdes, M.M.; Vleggaar, F.P.; Siersema, P.D.

    2015-01-01

    BACKGROUND: Self-expandable metal stents (SEMSs) are increasingly used for the treatment of benign biliary strictures (BBSs). A new fully covered SEMS (FCSEMS) with flared ends and high conformability was designed to prevent migration of the stent. OBJECTIVE: To evaluate the efficacy of a novel

  5. Covered Balloon-Expanding Stents in Airway Stenosis.

    Science.gov (United States)

    Majid, Adnan; Kheir, Fayez; Chung, Jey; Alape, Daniel; Husta, Bryan; Oh, Scott; Folch, Erik

    2017-04-01

    The balloon-expanding stents are widely available but rarely described for use within the tracheobronchial tree. This report describes our experience with these stents in airway stenosis particularly as a lobar salvage therapy. This was a retrospective review of all records in which the balloon-expanding stents were used at a tertiary medical center. Ages, sex, location of stenosis, etiology of stenosis, stent size, duration of stent placement and associated interventions for airway stenosis were recorded. Patient's self-reported respiratory symptoms, dyspnea scale, and radiographic imaging at baseline and after stent placement were also reported. Twenty-one Atrium iCAST stents were inserted in 18 patients with malignant and benign airway disease. The median age was 69.5 years (interquartile range, 53.5 to 74). Most stents (n=20, 95%) were deployed in the lobar airways. There was a significant improvement in the modified Medical Research Council dyspnea scale from median of 3 to 2 (Pstent placement was achieved in 15 patients (83%). No deaths were related to airway stenting complications. Adverse events related to stents included migration (n=2, 9.5%), granulation tissue formation (n=2, 9.5%) and mucus plugging (n=1, 4.8%). Lobar stenting with balloon-expanding metallic stents appears feasible, safe and improves symptoms as well as radiographic atelectasis in patients with lobar airway stenosis in this small case series. Larger studies are needed to confirm this observation and to address long-term safety.

  6. Effect of Slip Time in Forming Neo-Esophageal Stenosis After Replacement of a Thoracic Esophagus With Nitinol Artificial Esophagus.

    Science.gov (United States)

    Liang, Xian-Liang; Liang, Jian-Hui

    2015-07-01

    Attempts have been made to investigate the effect of slip time of nitinol artificial esophagus for forming neo-esophageal stenosis after replacement of a thoracic esophagus with nitinol artificial esophagus in 20 experimental pigs. The pigs whose slip time was less than 90 days postoperatively had severe dysphagia (Bown's III) immediately after they were fed, and the dysphagia aggravated gradually later on (Bown's III-IV). The pigs whose slip time was more than 90 days postoperatively had mild/moderate dysphagia (Bown's I-II) immediately after they were fed, and the dysphagia relieved gradually later on (Bown's II-I-0). The ratios between the diameter of neo-esophagus in different slip time and normal esophagus were 25% (at 2 months postoperatively), 58% (at 4 months postoperatively), and 93% (at 6 months postoperatively), respectively. The relationship between nitinol artificial esophagus slip time and neo-esophageal stenosis showed a positive correlation. After replacement of a thoracic esophagus with nitinol artificial esophagus, the artificial esophageal slip time not only affected the original diameter of the neo-esophagus immediately, but also affected the neo-esophageal scar stricture forming process later on. The narrowing of neo-esophagus is caused by overgrowth of scar tissue. But there is the positive correlation between artificial esophagus slip time and neo-esophageal stenosis, so this can be a way of overcoming neo-esophageal stenosis by delaying slip time of artificial esophagus. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  7. Internal and External Flow over Laser-Textured Superhydrophobic Polytetrafluoroethylene (PTFE).

    Science.gov (United States)

    Ahmmed, K M Tanvir; Patience, Christian; Kietzig, Anne-Marie

    2016-10-12

    In this work, internal and external flows over superhydrophobic (SH) polytetrafluoroethylene (PTFE) were studied. The SH surface was fabricated by a one-step femtosecond laser micromachining process. The drag reduction ability of the textured surface was studied experimentally both in microscale and macroscale internal flows. The slip length, which indicates drag reduction in fluid flow, was determined in microscale fluid flow with a cone-and-plate rheometer, whereas a pressure channel setup was used for macroscale flow experiments. The textured PTFE surface reduced drag in both experiments yielding comparable slip lengths. Moreover, the experimentally obtained slip lengths correspond well to the result obtained applying a semianalytical model, which considers the solid fraction of the textured surface. In addition to the internal flow studies, we fabricated SH PTFE spheres to test their drag reduction abilities in an external flow experiment, where the terminal velocities of the falling spheres were measured. These experiments were conducted at three different Reynolds numbers in both viscous and inertial flow regimes with pure glycerol, a 30% glycerol solution, and water. Surprisingly, the drag on the SH spheres was higher than the measured drag on the non-SH spheres. We hypothesize that the increase in form drag outweighs the decrease in friction drag on the SH sphere. Thus, the overall drag increased. These experiments demonstrate that a superhydrophobic surface that reduces drag in internal flow might not reduce drag in external flow.

  8. Tribological study of PTFE composites loaded with porcelain tile waste

    International Nuclear Information System (INIS)

    Oliveira, P.M.; Araujo Neto, A.P.; Souza, J.R.; Medeiros, J.T.N.

    2016-01-01

    The Brazilian northeast is one of the largest producers of clays that burn in the white form and disposal of tailings from the process of polishing the ceramic pieces of porcelain stands out as a major source of environmental degradation. This problem can be reduced by adding such material as filler in composites, in order to improve the mechanical properties of the polymeric matrix. Polytetrafluoroethylene (PTFE) is characterized as a good solid lubricant, because it has excellent properties such as low coefficient of friction (0.01 < μ < 0.1), thermal stability at high temperatures and chemical resistance. However, the pure PTFE has high wear rates (greater than 10-13m2/N) leading to early failures of various components. To reuse the Tailings of Porcelain (TP), composites of PTFE + TP were developed in three different compositions (85:15, 75:25 and 65:35). For this investigation the particle size distribution and some chemical characteristics of the tailings by testing XRD, XRF, SEM and EDS were performed, registering a large amount of silica, aluminum and other metals. Roughness, wettability and sclerometry also were performed. It was noted that the values of arithmetic average roughness, Ra, is higher for composites with higher percentage of TP, in addition they have a lower contact angle and higher surface energy to distilled water, characterized as hydrophilic. The results of energy of deformation provided by the sclerometry test were non-linear. (author)

  9. Tl response of LiF:Mg, Cu, P + PTFE to Am-Be neutrons

    International Nuclear Information System (INIS)

    Gonzalez M, P.R.

    2000-01-01

    In different laboratories of the world it is followed the research about development of new Tl materials, whose main characteristics should be their equivalence with the tissue and their high sensibility to any type of radiation. The study consists in to measure the Tl peak intensity which TLD-100 presents at being irradiated with neutrons and that appears over 250 Centigrade, for compare it with the Tl intensity of the LiF: Mg, Cu, P + PTFE dosemeters. However, not all dosemeters of the same group show the interesting peak, by this only can be the total Tl intensity of dosemeters studied. In the ININ dosemeters development laboratory, we have developed a Tl material of lithium fluoride activated with magnesium, copper and phosphorus (LiF: Mg, Cu, P) that in polycrystalline powder form is almost 35 times more sensitive than the TLD-100 commercial dosemeter of Harshaw/Filtrol, USA. With the use of polytetrafluorethylene (PTFE) and with the above described Tl material, it has been possible to obtain dosemeters in pellet form of LiF: Mg, Cu, P + PTFE. (Author)

  10. Feasibility of using bulk metallic glass for self-expandable stent applications.

    Science.gov (United States)

    Praveen Kumar, Gideon; Jafary-Zadeh, Mehdi; Tavakoli, Rouhollah; Cui, Fangsen

    2017-10-01

    Self-expandable stents are widely used to restore blood flow in a diseased artery segment by keeping the artery open after angioplasty. Despite the prevalent use of conventional crystalline metallic alloys, for example, nitinol, to construct self-expandable stents, new biomaterials such as bulk metallic glasses (BMGs) are being actively pursued to improve stent performance. Here, we conducted a series of analyses including finite element analysis and molecular dynamics simulations to investigate the feasibility of using a prototypical Zr-based BMG for self-expandable stent applications. We model stent crimping of several designs for different percutaneous applications. Our results indicate that BMG-based stents with diamond-shaped crowns suffer from severe localization of plastic deformation and abrupt failure during crimping. As a possible solution, we further illustrate that such abrupt failure could be avoided in BMG-based stents without diamond shape crowns. This work would open a new horizon for a quest toward exploiting superior mechanical and functional properties of metallic glasses to design future stents. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1874-1882, 2017. © 2016 Wiley Periodicals, Inc.

  11. [Clinical application of a fully covered self-expandable metallic stent in treatment of airway fistula].

    Science.gov (United States)

    Zhu, Qiang; Zang, Qi; Jiang, Zhong-min; Wang, Wei; Cao, Ming

    2013-06-01

    To assess the feasibility, safety and efficacy of the use of a fully covered self-expandable stent for the treatment of airway fistula. From August 2005 to November 2011, 9 patients underwent treatment by the introduction of a tracheo-bronchial or bronchial fully covered self-expandable metallic stent. There were 7 males and 2 females, aged from 28-65 years with a mean of 46 years. In this group, 7 cases were diagnosed as bronchopleural fistula, 1 case as tracheopleural fistula, 1 case as broncho-esophageal fistula, 8 cases with thoracic empyema. The fistula orifices were from 3.5-25.0 mm in diameter with a mean 8.4 mm. All patients received topical anesthesia, and L-shaped stent was placed in 6 patients and I-shaped stent in 3 patients under fluoroscopic guidance. After the stent placement, the patients with empyema were treated with continual irrigation of the empyema cavity. Stent placement in the tracheo-bronchial tree was technically successful in all patients, without procedure-related complications. The operating time was from 5-16 minutes, mean time (10 ± 4) minutes. Except for 1 patient, immediate closure of the airway fistula was achieved in the other patients after the procedure, as shown by the immediate cessation of bubbling in the chest drain system or the contrast examination. In this study, 1 patient coughed the inserted stent out due to irritable cough on the 5th day and had to receive repositioning of a new stent. Among the patients who were with empyema, 1 patient died of septicemia on the 8th day and 1 patient died of brain metastases from lung cancer 6 months after the stent insertion with empyema not cured, the other 6 patients' empyema healed from 2-5 months, mean time 3.7 months. Seven patients were followed from 3 to 36 months with a median of 13.5 months. During follow-up, 1 stent was removed from a patient 8 months after the stent implantation without empyema recurred. The remaining patient presented good tolerability to the existence of

  12. Mechanisms of Loss of Agricultural Odorous Compounds in Sample Bags of Nalophan, Tedlar, and PTFE.

    Science.gov (United States)

    Kasper, Pernille Lund; Oxbøl, Arne; Hansen, Michael Jørgen; Feilberg, Anders

    2018-03-01

    Alteration of the chemical composition of odor samples during storage in polymer sample bags can significantly impair the accuracy of subsequent odor evaluations. To overcome or minimize this effect, the mechanisms determining compound loss must be more thoroughly understood. The present study examines the storage stability of a selection of key odorants from livestock production in polymer sample bags of Nalophan, Tedlar, and polytetrafluoroethylene (PTFE). The compounds included are acetic acid, butanoic acid, propanoic acid, 3-methylbutanoic acid, hydrogen sulfide, methanethiol, dimethyl sulfide, trimethylamine, and 4-methylphenol. The fate of the unrecovered compound fractions is clarified by means of thermal desorption and concentric double bags, allowing estimation of the magnitude of losses due to adsorption and diffusion, respectively. The degree of recovery was found to be PTFE > Tedlar > Nalophan, and smaller ratios of bag surface area to sample volume improved the recovery significantly. Furthermore, PTFE bags were found far superior for maintaining the original sample humidity and for storing 4-methylphenol. Analysis of sample humidity, partitioning coefficients, and thermal desorption suggested that the loss in PTFE bags was mainly controlled by adsorption, whereas for Nalophan and Tedlar, compound loss is a combined effect of adsorption and diffusion. It is suggested to heat the bags when evacuating the sample for analysis, as this was found to improve the recovery significantly. For a 5-L PTFE bag, all odorants could be found at concentration levels between 71.6 and 98.8% even after 48 h of storage when heated to 57°C prior to analysis. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  13. Expandable stents.

    Science.gov (United States)

    Nesbitt, J C; Carrasco, H

    1996-05-01

    Expandable metallic stents are effective in selected patients with malignant or benign airway stenoses. When used for malignant lesions, the primary purpose of the stent is to improve the quality of life; stents are usually chosen for palliation of symptoms in recognition of the low likelihood of success for other therapy. For patients with benign stenoses, the stents provide a permanent source of structural support to alleviate the narrowed segment. The advantages of the expandable metallic stents are as follows: (1) they can be inserted through an endotracheal tube or under local anesthesia with relative simplicity under fluoroscopic guidance; (2) they do not impair the drainage of sputum because ciliary movement is not interrupted; (3) over a period of a few weeks, the meshwork is gradually covered with mucosa as the stent becomes incorporated into the airway wall; (4) ventilation usually is not impaired if the metallic mesh stent covers another nonstenosed bronchus, because the interstices of the stent are nonobstructive; and (5) they are dynamic and continue to expand over time, particularly if concurrent treatment achieves an effect on the lesion that caused stenosis. Disadvantages of the expandable stent include (1) they often are only temporarily effective for tracheobronchial stenosis due to intraluminal tumor or granulation tissue, both of which can grow between the wires; (2) they are considered permanent stents because removal is difficult; and (3) they can be poorly positioned during placement or can become displaced by progressive migration after placement, and they cannot be repositioned. A relative contraindication to insertion is an inflammatory process or infection that can predispose to granulation formation, particularly at the points of maximal contact pressure of the stent to the airway mucosa. In the presence of inflammation, it may be better to use a silicone prosthesis until the inflammatory process subsides and fibrosis occurs. Granulation

  14. Role of Fully Covered Self-Expandable Metal Stent for Treatment of Benign Biliary Strictures and Bile Leaks

    Energy Technology Data Exchange (ETDEWEB)

    Pausawasadi, Nonthalee [Department of Medicine, Siriraj Hospital, Mahidol University, Bangkok (Thailand); Soontornmanokul, Tanassanee; Rerknimitr, Rungsun [Department of Medicine, Chulalongkorn University, Bangkok (Thailand)

    2012-02-15

    Endoscopic therapy by balloon dilation and placement of multiple large-bore plastic stents is the treatment of choice for benign biliary stricture. This approach is effective but it typically requires multiple endoscopic sessions given the short duration of stent patency. The endoscopic approach for treatment of bile leak involves the placement of a stent with or without biliary sphincterotomy. The self-expandable metal stent (SEMS) has traditionally been used for palliation of malignant biliary strictures given the long duration of stent patency owing to their larger stent diameter. Recently, SEMS has been used in a variety of benign biliary strictures and leaks, especially with the design of the covered self-expandable metal stent (CSEMS), which permits endoscopic-mediated stent removal. The use of CSEMS in benign biliary stricture could potentially result in a decrease in endoscopic sessions and it is technically easier when compared to placement of multiple plastic stents. However, complications such as cholecystitis due to blockage of cystic duct, stent migration, infection and pancreatitis have been reported. The potential subsegmental occlusion of contralateral intrahepatic ducts also limits the use of CSEMS in hilar stricture. Certain techniques and improvement of stent design may overcome these challenges in the future. Thus, CSEMS may be appropriate in only highly selected conditions, such as refractory benign biliary stricture, despite multiple plastic stent placement or difficult to treat bile duct stricture from chronic pancreatitis, and should not be used routinely. This review focuses on the use of fully covered self-expandable metal stent for benign biliary strictures and bile leaks.

  15. Role of Fully Covered Self-Expandable Metal Stent for Treatment of Benign Biliary Strictures and Bile Leaks

    International Nuclear Information System (INIS)

    Pausawasadi, Nonthalee; Soontornmanokul, Tanassanee; Rerknimitr, Rungsun

    2012-01-01

    Endoscopic therapy by balloon dilation and placement of multiple large-bore plastic stents is the treatment of choice for benign biliary stricture. This approach is effective but it typically requires multiple endoscopic sessions given the short duration of stent patency. The endoscopic approach for treatment of bile leak involves the placement of a stent with or without biliary sphincterotomy. The self-expandable metal stent (SEMS) has traditionally been used for palliation of malignant biliary strictures given the long duration of stent patency owing to their larger stent diameter. Recently, SEMS has been used in a variety of benign biliary strictures and leaks, especially with the design of the covered self-expandable metal stent (CSEMS), which permits endoscopic-mediated stent removal. The use of CSEMS in benign biliary stricture could potentially result in a decrease in endoscopic sessions and it is technically easier when compared to placement of multiple plastic stents. However, complications such as cholecystitis due to blockage of cystic duct, stent migration, infection and pancreatitis have been reported. The potential subsegmental occlusion of contralateral intrahepatic ducts also limits the use of CSEMS in hilar stricture. Certain techniques and improvement of stent design may overcome these challenges in the future. Thus, CSEMS may be appropriate in only highly selected conditions, such as refractory benign biliary stricture, despite multiple plastic stent placement or difficult to treat bile duct stricture from chronic pancreatitis, and should not be used routinely. This review focuses on the use of fully covered self-expandable metal stent for benign biliary strictures and bile leaks.

  16. Role of Fully Covered Self-Expandable Metal Stent for Treatment of Benign Biliary Strictures and Bile Leaks

    Science.gov (United States)

    Pausawasadi, Nonthalee; Soontornmanokul, Tanassanee

    2012-01-01

    Endoscopic therapy by balloon dilation and placement of multiple large-bore plastic stents is the treatment of choice for benign biliary stricture. This approach is effective but it typically requires multiple endoscopic sessions given the short duration of stent patency. The endoscopic approach for treatment of bile leak involves the placement of a stent with or without biliary sphincterotomy. The self-expandable metal stent (SEMS) has traditionally been used for palliation of malignant biliary strictures given the long duration of stent patency owing to their larger stent diameter. Recently, SEMS has been used in a variety of benign biliary strictures and leaks, especially with the design of the covered self-expandable metal stent (CSEMS), which permits endoscopic-mediated stent removal. The use of CSEMS in benign biliary stricture could potentially result in a decrease in endoscopic sessions and it is technically easier when compared to placement of multiple plastic stents. However, complications such as cholecystitis due to blockage of cystic duct, stent migration, infection and pancreatitis have been reported. The potential subsegmental occlusion of contralateral intrahepatic ducts also limits the use of CSEMS in hilar stricture. Certain techniques and improvement of stent design may overcome these challenges in the future. Thus, CSEMS may be appropriate in only highly selected conditions, such as refractory benign biliary stricture, despite multiple plastic stent placement or difficult to treat bile duct stricture from chronic pancreatitis, and should not be used routinely. This review focuses on the use of fully covered self-expandable metal stent for benign biliary strictures and bile leaks. PMID:22563290

  17. Covered versus uncovered self-expandable metal stents for malignant biliary strictures: A meta-analysis and systematic review.

    Science.gov (United States)

    Moole, Harsha; Bechtold, Matthew L; Cashman, Micheal; Volmar, Fritz H; Dhillon, Sonu; Forcione, David; Taneja, Deepak; Puli, Srinivas R

    2016-09-01

    Self-expandable metal stents (SEMS) are used for palliating inoperable malignant biliary strictures. It is unclear if covered metal stents are superior to uncovered metal stents in these patients. We compared clinical outcomes in patients with covered and uncovered stents. Studies using covered and uncovered metallic stents for palliation in patients with malignant biliary stricture were reviewed. Articles were searched in MEDLINE, PubMed, and Ovid journals. Fixed and random effects models were used to calculate the pooled proportions. Initial search identified 1436 reference articles, of which 132 were selected and reviewed. Thirteen studies (n = 2239) for covered and uncovered metallic stents which met the inclusion criteria were included in this analysis. Odds ratio for stent occlusion rates in covered vs. uncovered stents was 0.79 (95 % CI = 0.65 to 0.96). Survival benefit in patients with covered vs. uncovered stents showed the odds ratio to be 1.29 (95 % CI = 0.95 to 1.74). Pooled odds ratio for migration of covered vs. uncovered stents was 9.9 (95 % CI = 4.5 to 22.3). Covered stents seemed to have significantly lesser occlusion rates, increased odds of migration, and increased odds of pancreatitis compared to uncovered stents. There was no statistically significant difference in the survival benefit, overall adverse event rate, and patency period of covered vs. uncovered metal stents in patients with malignant biliary strictures.

  18. Stress Corrosion Evaluation of Nitinol 60 for the International Space Station Water Recycling System

    Science.gov (United States)

    Torres, P. D.

    2016-01-01

    A stress corrosion cracking (SCC) evaluation of Nitinol 60 was performed because this alloy is considered a candidate bearing material for the Environmental Control and Life Support System (ECLSS), specifically in the Urine Processing Assembly of the International Space Station. An SCC evaluation that preceded this one during the 2013-2014 timeframe included various alloys: Inconel 625, Hastelloy C-276, titanium (Ti) commercially pure (CP), Ti 6Al-4V, extra-low interstitial (ELI) Ti 6Al-4V, and Cronidur 30. In that evaluation, most specimens were exposed for a year. The results of that evaluation were published in NASA/TM-2015-218206, entitled "Stress Corrosion Evaluation of Various Metallic Materials for the International Space Station Water Recycling System,"1 available at the NASA Scientific and Technical Information program web page: http://www.sti.nasa.gov. Nitinol 60 was added to the test program in 2014.

  19. Repair of steam generator heating tubes by roll-expanded plugs: approach to cover multiple national regulations

    Energy Technology Data Exchange (ETDEWEB)

    Beck, J.; Ziegler, B.; Schoenheit, N. [AREVA NP Gmbh, Erlangen (Germany); Kostroun, F. [AREVA NP Canada Ltd., Pickering, ON (Canada)

    2012-07-01

    During operation, steam generators in nuclear power plants are subject to degradation mechanisms which have an impact on the component life-time. Most affected are the heating tubes which constitute the barrier of the contaminated primary cycle to the secondary side. Various corrosive attacks may cause wall thinning which requires tube repair. A common repair method is to plug the tubes by roll expanded plugs. This is a fast method, easily applicable and requires less equipment or personnel qualification as needed for weld plugs. After insertion, the plugs act as a pressure boundary from primary to secondary side. Although the function of the roll plug is simple, the different national regulations define the requirements which need to be fulfilled by a roll plug differently. In order to reduce the tooling as well as the plug types to a minimum, an approach according to one common design for different regulations and steam generator types is profitable. It was found, that the regulations according to the ASME Boiler and Pressure Vessel code in combination with the German Safety Standards of the German Nuclear Safety Standards Commission covers the regulations of the majority of utilities. To develop a roll plug which suits the different regulatory demands, efforts were made to consider all technical and regulatory boundary conditions implied on roll expanded plugs. This covering approach had an impact on the plug design, which was required to be Helium tight after installation and suitable for a 40 year component lifetime also in accident and emergency conditions. To prove the suitability of the plug design a comprehensive testing programme of the mechanical and chemical properties of the designed roll-expanded plug was launched. A summary of the plug design and testing as well as the main test results are described. (author)

  20. Repair of steam generator heating tubes by roll-expanded plugs: approach to cover multiple national regulations

    International Nuclear Information System (INIS)

    Beck, J.; Ziegler, B.; Schoenheit, N.; Kostroun, F.

    2012-01-01

    During operation, steam generators in nuclear power plants are subject to degradation mechanisms which have an impact on the component life-time. Most affected are the heating tubes which constitute the barrier of the contaminated primary cycle to the secondary side. Various corrosive attacks may cause wall thinning which requires tube repair. A common repair method is to plug the tubes by roll expanded plugs. This is a fast method, easily applicable and requires less equipment or personnel qualification as needed for weld plugs. After insertion, the plugs act as a pressure boundary from primary to secondary side. Although the function of the roll plug is simple, the different national regulations define the requirements which need to be fulfilled by a roll plug differently. In order to reduce the tooling as well as the plug types to a minimum, an approach according to one common design for different regulations and steam generator types is profitable. It was found, that the regulations according to the ASME Boiler and Pressure Vessel code in combination with the German Safety Standards of the German Nuclear Safety Standards Commission covers the regulations of the majority of utilities. To develop a roll plug which suits the different regulatory demands, efforts were made to consider all technical and regulatory boundary conditions implied on roll expanded plugs. This covering approach had an impact on the plug design, which was required to be Helium tight after installation and suitable for a 40 year component lifetime also in accident and emergency conditions. To prove the suitability of the plug design a comprehensive testing programme of the mechanical and chemical properties of the designed roll-expanded plug was launched. A summary of the plug design and testing as well as the main test results are described. (author)

  1. Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance

    Science.gov (United States)

    Maleckis, Kaspars; Anttila, Eric; Aylward, Paul; Poulson, William; Desyatova, Anastasia; MacTaggart, Jason; Kamenskiy, Alexey

    2018-01-01

    Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease (PAD) due to its minimally invasive nature and associated reductions in short-termmorbidity and mortality. The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement. Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery (FPA) is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion. It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent. In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol, specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD. PMID:29470746

  2. Nitinol Stents in the Femoropopliteal Artery: A Mechanical Perspective on Material, Design, and Performance.

    Science.gov (United States)

    Maleckis, Kaspars; Anttila, Eric; Aylward, Paul; Poulson, William; Desyatova, Anastasia; MacTaggart, Jason; Kamenskiy, Alexey

    2018-05-01

    Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease (PAD) due to its minimally invasive nature and associated reductions in short-term morbidity and mortality. The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement. Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery (FPA) is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion. It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent. In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol, specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD.

  3. Influence of Nitinol wire surface treatment on oxide thickness and composition and its subsequent effect on corrosion resistance and nickel ion release.

    Science.gov (United States)

    Clarke, B; Carroll, W; Rochev, Y; Hynes, M; Bradley, D; Plumley, D

    2006-10-01

    Medical implants and devices are now used successfully in surgical procedures on a daily basis. Alloys of nickel and titanium, and in particular Nitinol are of special interest in the medical device industry, because of their shape memory and superelastic properties. The corrosion behavior of nitinol in the body is also of critical importance because of the known toxicological effects of nickel. The stability of a NiTi alloy in the physiological environment is dependant primarily on the properties of the mostly TiO(2) oxide layer that is present on the surface. For the present study, a range of nitinol wires have been prepared using different drawing processes and a range of surface preparation procedures. It is clear from the results obtained that the wire samples with very thick oxides also contain a high nickel content in the oxide layer. The untreated samples with the thicker oxides show the lowest pitting potential values and greater nickel release in both long and short-term experiments. It was also found that after long-term immersion tests breakdown potentials increased for samples that exhibited lower values initially. From these results it would appear that surface treatment is essential for the optimum bioperformance of nitinol. (c) 2006 Wiley Periodicals, Inc

  4. Palliation of patients with esophagogastric neoplasms by insertion of a covered expandable modified Gianturco-Z endoprosthesis: experiences in 153 patients

    NARCIS (Netherlands)

    Bartelsman, J. F.; Bruno, M. J.; Jensema, A. J.; Haringsma, J.; Reeders, J. W.; Tytgat, G. N.

    2000-01-01

    We aimed to evaluate the short- and long-term outcomes of treatment by insertion of a covered expandable modified Gianturco-Z endoprosthesis (Song stent) in patients with esophagogastric malignancies. Consecutive patients with esophagogastric malignancies in whom a Song stent was inserted were

  5. Expanding Thurston maps

    CERN Document Server

    Bonk, Mario

    2017-01-01

    This monograph is devoted to the study of the dynamics of expanding Thurston maps under iteration. A Thurston map is a branched covering map on a two-dimensional topological sphere such that each critical point of the map has a finite orbit under iteration. It is called expanding if, roughly speaking, preimages of a fine open cover of the underlying sphere under iterates of the map become finer and finer as the order of the iterate increases. Every expanding Thurston map gives rise to a fractal space, called its visual sphere. Many dynamical properties of the map are encoded in the geometry of this visual sphere. For example, an expanding Thurston map is topologically conjugate to a rational map if and only if its visual sphere is quasisymmetrically equivalent to the Riemann sphere. This relation between dynamics and fractal geometry is the main focus for the investigations in this work.

  6. Emission of perfluoroalkyl carboxylic acids (PFCA) from heated surfaces made of polytetrafluoroethylene (PTFE) applied in food contact materials and consumer products.

    Science.gov (United States)

    Schlummer, Martin; Sölch, Christina; Meisel, Theresa; Still, Mona; Gruber, Ludwig; Wolz, Gerd

    2015-06-01

    Polytetrafluoroethylene (PTFE) has been widely discussed as a source of perfluorooctanoic acid (PFOA), which has been used in the production of fluoropolymers. PTFE may also contain unintended perfluoroalkyl carboxylic acids (PFCAs) caused by thermolysis of PTFE, which has been observed at temperatures above 300°C. Common PTFE coated food contact materials and consumer goods are operated at temperatures above 200°C. However, knowledge on possible emissions of PFCAs is limited. Therefore, it was the aim of this study to investigate and evaluate the emission of PFCAs from PTFE coated products with both, normal use and overheating scenarios. Four pans, claimed to be PFOA free, and nine consumer products were investigated. At normal use conditions (PTFE surfaces were trapped for 1h. Overheating scenarios (>260°C) recorded emissions during a 30min heating of empty pans on a stove. Emissions were analyzed by LC-ESI-MS. Results indicate the emission of PFCAs, whereas no perfluorinated sulfonic acids were traced. At normal use conditions total emissions of PFCAs accounted for 4.75ng per hour. Overheated pans, however, released far higher amounts with up to 12190ng PFCAs per hour at 370°C. Dominating contributors where PFBA and PFOA at normal use and PFBA and PFPeA during overheating. Temperature seems to be the main factor controlling the emission of PFCAs. A worst case estimation of human exposure revealed that emissions of PFCAs from heated PTFE surfaces would be far below the TDI of 1500ng PFOA per kg body weight. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Highly oriented poly(di-n-alkylsilylene) films on oriented PTFE substrates

    NARCIS (Netherlands)

    Frey, H.H.; Frey, Holger; Sheiko, Sergej; Sheiko, S.; Moller, M.; Möller, Martin; Wittmann, Jean-Claude; Lot, Bernard

    1993-01-01

    Highly oriented polysilylene layers have potential applications in electrophotography, nonlinear optics, display fabrication, and microlithography. The preparation of such layers by crystallization on a highly oriented PTFE substrate is reported, and their assessment by optical birefringence,

  8. Combustion of PTFE: The Effects of Gravity and Pigmentation on Ultrafine Particle Generation

    Science.gov (United States)

    McKinnon, J. Thomas; Srivastava, Rajiv; Todd, Paul

    1997-01-01

    Ultrafine particles generated during polymer thermodegradation are a major health hazard, owing to their unique pathway of processing in the lung. This hazard in manned spacecraft is poorly understood, because the particulate products of polymer thermodegradation are generated under low gravity conditions. Particulate generated from the degradation of PolyTetraFluoroEthylene (PTFE), insulation coating for 20 AWG copper wire (representative of spacecraft application) under intense ohmic heating were studied in terrestrial gravity and microgravity. Microgravity tests were done in a 1.2-second drop tower at the Colorado School of Mines (CSM). Thermophoretic sampling was used for particulate collection. Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) were used to examine the smoke particulates. Image software was used to calculate particle size distribution. In addition to gravity, the color of PTFE insulation has an overwhelming effect on size, shape and morphology of the particulate. Nanometer-sized primary particles were found in all cases, and aggregation and size distribution was dependent on both color and gravity; higher aggregation occurred in low gravity. Particulates from white, black, red and yellow colored PTFE insulations were studied. Elemental analysis of the particulates shows the presence of inorganic pigments.

  9. Wear and friction performance of PTFE filled epoxy composites with a high concentration of SiO2 particles

    NARCIS (Netherlands)

    Shen, J.T.; Top, M.; Pei, Y.T.; de Hosson, Jeff

    2015-01-01

    In this work, the tribological performance of PTFE filled SiO2 particles–epoxy composites is investigated. Under a load of 60 N (~140 MPa contact pressure), the optimum content of PTFE lies between 10 and 15 wt%, which yields an ultralow coefficient of friction (CoF) in conjunction with a low wear

  10. Change of wettability of PTFE surface by sputter etching and excimer laser. Sputter etching oyobi excimer laser ni yoru PTFE hyomen no shinsuika

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, S. (Nitto Denko Corp., Osaka (Japan)); Kubo, U. (Kinki University, Osaka (Japan))

    1994-06-20

    The wettability of PTFE (polytetrafluoroethylene) surfaces was improved by sputter etching and excimer laser irradiation. In sputter etching, the PTFE surface was treated by reactive sputter etching with H2O gas to give active groups on the surface. In laser irradiation, the surface was irradiated in pure water by high-energy KrF excimer laser. As the surface wettability was evaluated with a contact angle to water, the contact angle decreased remarkably in both treatments resulting in a good improvement effect. In sputter etching, various new chemical bonds such as F-C=O, F2C-FC-O, F2C-C-O and C-O were observed because of a decrease in F and incorporation of oxygen. Such chemical bonds could be eliminated by ultraviolet ray irradiation, and the treated surface condition approached the initial condition after irradiation of 200 hours. In laser irradiation, it was suggested that C-F bonds were broken, and OH groups were added to the surface by dissociation of H2O to H and OH. 7 refs., 8 figs., 1 tab.

  11. Studies on surface graft polymerization of acrylic acid onto PTFE film by remote argon plasma initiation

    International Nuclear Information System (INIS)

    Wang Chen; Chen Jierong

    2007-01-01

    The graft polymerization of acrylic acid (AAc) was carried out onto poly(tetrafluoroethylene) (PTFE) films that had been pretreated with remote argon plasma and subsequently exposed to oxygen to create peroxides. Peroxides are known to be the species responsible for initiating the graft polymerization when PTFE reacts with AAc. We chose different parameters of remote plasma treatment to get the optimum condition for introducing maximum peroxides (2.87 x 10 -11 mol/cm 2 ) on the surface. The influence of grafted reaction conditions on the grafting degree was investigated. The maximum grafting degree was 25.2 μg/cm 2 . The surface microstructures and compositions of the AAc grafted PTFE film were characterized with the water contact angle meter, Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle measurements revealed that the water contact angle decreased from 108 o to 41 o and the surface free energy increased from 22.1 x 10 -5 to 62.1 x 10 -5 N cm -1 by the grafting of the AAc chains. The hydrophilicity of the PTFE film surface was greatly enhanced. The time-dependent activity of the grafted surface was better than that of the plasma treated film

  12. Effect of polytetrafluoroethylene (PTFE) phase transition at 19°C on the use of Spectralon as a reference standard for reflectance.

    Science.gov (United States)

    Ball, Christopher P; Levick, Andrew P; Woolliams, Emma R; Green, Paul D; Dury, Martin R; Winkler, Rainer; Deadman, Andrew J; Fox, Nigel P; King, Martin D

    2013-07-10

    Sintered polytetrafluoroethylene (PTFE) is highly reflective and is widely used as a reference standard in remote sensing, radiometry, and spectroscopy. The relative change in output flux from a PTFE integrating sphere over the room temperature phase transition at 19°C has been measured at a monochromatic wavelength of 633 nm as 1.82±0.21%. The change in output flux was attributed to a small change of 0.09±0.02% in the total hemispherical reflectance of PTFE, caused by a change in its material density as a result of the phase transition. For the majority of users, this small change measured in total hemispherical reflectance is unlikely to impact significantly the accuracy of PTFE flat panel reflectors used as reference standards. However, owing to the multiple reflections that occur inside an integrating sphere cavity, the effect is multiplied and remedial action should be applied, either via a mathematical correction or through temperature stabilization of the integrating sphere when high accuracy (PTFE-based integrating spheres at temperatures close to the phase transition at 19°C.

  13. Treatment of a Left Internal Mammary Artery to Pulmonary Artery Fistula with Polytetrafluoroethylene Covered Stents: A Case Report and Review of the Literature

    International Nuclear Information System (INIS)

    Abbott, J. Dawn; Brennan, Joseph J.; Remetz, Michael S.

    2004-01-01

    Internal mammary artery (IMA) to pulmonary artery (PA) fistula is a rare complication of coronary artery bypass grafting (CABG) that may present as myocardial ischemia. We describe a case of left IMA-to-PA fistula treated with balloon expandable coronary polytetrafluoroethylene (PTFE) graft stents and review previously reported cases of this entity

  14. Design and fabrication of a PET/PTFE-based piezoelectric squeeze mode drop-on-demand inkjet printhead with interchangeable nozzle

    KAUST Repository

    Li, Erqiang

    2010-09-01

    A PET/PTFE-based piezoelectric squeeze mode drop-on-demand inkjet printhead with interchangeable nozzles is designed and fabricated. The printhead chamber is comprised of PET (polyethylene terephthalate) tubing or PTFE (polytetrafluoroethylene, or Teflon) tubing, which of a much softer material, than the conventionally used glass tubing. Applying the same electrical voltage, PET/PTFE-based printhead will generate a larger volume change in the material to be dispensed. The novel printhead fabricated herein has successfully dispensed liquids with viscosities up to 100 cps, as compared to 20 cps for the commercial printheads. Furthermore, PTFE-based printhead provides excellent anti-corrosive property when strongly corrosive inks are involved. The interchangeable nozzle design enables the same printhead to be fitted with nozzles of different orifice size, thus a clogged nozzle can be easily removed for cleaning or replacement. The characteristics of this novel printhead are also studied by dispensing glycerin-water solutions. © 2010 Elsevier B.V. All rights reserved.

  15. Ex-vivo release of Pipeline Embolization Device polytetrafluoroethylene (PTFE) sleeves for improved distal landing zone accuracy in-vivo: A technical note.

    Science.gov (United States)

    Griessenauer, Christoph J; Gupta, Raghav; Moore, Justin; Thomas, Ajith J; Ogilvy, Christopher S

    2016-12-01

    Distal landing zone accuracy is critical in some intracranial aneurysms treated with the Pipeline Embolization Device (PED), and delayed opening of the distal end of the device can complicate the procedure. Here, we report a technical nuance that facilitates accurate placement of the distal end of the PED by ex-vivo, pre-implantation release of the PED Flex polytetrafluoroethylene (PTFE) sleeves. The PED Flex is partially pushed out of the introducer sheath ex-vivo, pre-implantation until the distal PED opens entirely and the PTFE sleeves are located distal to the device. Without inverting the PTFE sleeves, the PED is carefully pulled back into the introducer sheath placing the PTFE sleeves inside the device. The PED is loaded into the microcatheter and advanced toward the site of implantation. When the PED is initially deployed and pushed out of the microcatheter, it opens immediately and provides an anchor for the remainder of the deployment process. We present a video (supplementary material) that illustrates the technique along with an illustrative case. Ex-vivo, pre-implantation release of the PTFE sleeves is an option in aneurysm treatment where distal landing accuracy is critical. Even without the protection of the PTFE sleeves, our clinical observation shows that the PED can be advanced safely through the microcatheter in selected cases. © The Author(s) 2016.

  16. Dacron® vs. PTFE as bypass materials in peripheral vascular surgery – systematic review and meta-analysis

    Science.gov (United States)

    Roll, Stephanie; Müller-Nordhorn, Jacqueline; Keil, Thomas; Scholz, Hans; Eidt, Daniela; Greiner, Wolfgang; Willich, Stefan N

    2008-01-01

    Background In peripheral vascular bypass surgery different synthetic materials are available for bypass grafting. It is unclear which of the two commonly used materials, polytetrafluoroethylene (PTFE) or polyester (Dacron®) grafts, is to be preferred. Thus, the aim of this meta-analysis and systematic review was to compare the effectiveness of these two prosthetic bypass materials (Dacron® and PTFE). Methods We performed a systematic literature search in MEDLINE, Cochrane-Library – CENTRAL, EMBASE and other databases for relevant publications in English and German published between 1999 and 2008. Only randomized controlled trials were considered for inclusion. We assessed the methodological quality by means of standardized checklists. Primary patency was used as the main endpoint. Random-effect meta-analysis as well as pooling data in life table format was performed to combine study results. Results Nine randomized controlled trials (RCT) were included. Two trials showed statistically significant differences in primary patency, one favouring Dacron® and one favouring PTFE grafts, while 7 trials did not show statistically significant differences between the two materials. Meta-analysis on the comparison of PTFE vs. Dacron® grafts yielded no differences with regard to primary patency rates (hazard ratio 1.04 (95% confidence interval [0.85;1.28]), no significant heterogeneity (p = 0.32, I2 = 14%)). Similarly, there were no significant differences with regard to secondary patency rates. Conclusion Systematic evaluation and meta-analysis of randomized controlled trials comparing Dacron® and PTFE as bypass materials for peripheral vascular surgery showed no evidence of an advantage of one synthetic material over the other. PMID:19099583

  17. A novel method of creation of a fenestration in nitinol occluder devices used in closure of hypertensive patent arterial ducts

    Directory of Open Access Journals (Sweden)

    Anil Kumar Singhi

    2016-01-01

    Full Text Available Test occlusion with a balloon is done to predict operability of large hypertensive patent ductus arteriosus (PDA. If the fall in the pulmonary artery pressures is inadequate, a complete closure is not desired. To create a predictable premeasured fenestration in a nitinol occluder device used for closing hypertensive PDA. A large nitinol occluder device was punctured with an 18G needle to advance a 0.035½ stiff guide wire through the occluder before loading it into the delivery system. The occluder with the guidewire was then deployed across the PDA. A coronary guide catheter was later threaded through the guidewire into the fabric of the device, which was still held by the delivery cable. A coronary stent was deployed across the fenestration in the occluder to keep it patent. An 8-year-old boy with Down syndrome and hypertensive PDA was hemodynamically assessed. Even though there was a fall in the pulmonary vascular resistance index and pressures on test occlusion, the pulmonary artery pressures were labile with fluctuations. A customized fenestration was made in a 16 mm muscular ventricular septal defect occluder (MVSO with a 4.5 mm bare-metal coronary stent. The pulmonary artery pressures remained at half of the aortic pressures after the procedure. This fenestration model precisely and predictably fenestrated a large occluder device used to close a hypertensive large PDA. Long-term patency of these fenestrations has to be assessed on the follow-up, and may be improved through larger fenestrations, systemic anticoagulation and use of covered stents.

  18. The Primary Patency and Fracture Rates of Self-Expandable Nitinol Stents Placed in the Popliteal Arteries, Especially in the P2 and P3 Segments, in Korean Patients

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Il Soo; Chee, Hyun Keun; Park, Sang Woo; Yun, Ik Jin; Hwang, Jae Joon; Lee, Song Am; Kim, Jun Seok; Chang, Seong Hwan; Jung, Hong Geun [Konkuk University Hospital, Seoul (Korea, Republic of)

    2011-04-15

    We wanted to evaluate the status of self-expandable nitinol stents implanted in the P2 and P3 segments of the popliteal artery in Korean patients. We retrospectively analyzed 189 consecutive patients who underwent endovascular treatment for steno occlusive lesions in the femoropopliteal artery from July 2003 to March 2009, and 18 patients who underwent stent placement in popliteal arterial P2 and P3 segments were finally enrolled. Lesion patency was evaluated by ultrasound or CT angiography, and stent fracture was assessed by plain X-rays at 1, 3, 6 and 12 months and annually thereafter. At the 1-month follow-up, stent fracture (Type 2) was seen in one limb (up to P3, 1 of 18, 6%) and it was identified in seven limbs at the 3-month follow-up (Type 2, Type 3, Type 4) (n = 1: up to P2: n = 6: P3). At the 6-month follow-up, one more fracture (Type 1) (up to P3) was noted. At the 1-year follow-up, there were no additional stent fractures. Just four limbs (up to P2) at the 2-year follow-up did not have stent fracture. The primary patency was 94%, 61% and 44% at 1, 3 and 6 months, respectively, and the group with stent implantation up to P3 had a higher fracture rate than that of the group that underwent stenting up to P2 (p < 0.05). We suggest that stent placement up to the popliteal arterial P3 segment and over P2 in an Asian population can worsen the stent patency owing to stent fracture. It may be necessary to develop a stent design and structure for the Asian population that can resist the bending force in the knee joint

  19. Self-expandable covered metallic esophageal stent impregnated with beta-emitting radionuclide: an experimental study in canine esophagus

    International Nuclear Information System (INIS)

    Won, Je Hwan; Lee, Jong Doo; Wang, Hee Jung; Kim, Gui-Eon; Kim, Bong Wan; Yim, Hyunee; Han, Sang Keon; Park, Chan H.; Joh, Chul Woo; Kim, Kyung-Hwa; Park, Kyung Bae; Shin, Kyong-Min

    2002-01-01

    Purpose: A specially designed self-expandable covered metallic stent impregnated with the β-emitting radioisotope 166 Ho ( 166 Ho, energy: 1.85 and 1.76 MeV, T((1)/(2)): 26.8 h) was developed at our institute for the purpose of intraluminal palliative brachytherapy, as well as for treating malignant esophageal stricture and swallowing difficulty. The aim of this study was to evaluate the tissue response to brachytherapy and the safety of the radioactive metallic stent with regard to the normal canine esophagus before clinical application. Methods and Materials: 166 Ho was impregnated into the polyurethane membrane (50 μ thickness) covering the outer surface of a self-expandable metallic stent (diameter, 18 mm; length, 40 mm). Stents with radioactivity 4.0-7.8 mCi (Group A, n=15), 1.0-1.8 mCi (Group B, n 5), and 0.5-0.7 mCi (Group C, n=5) were placed in the esophagi of 25 healthy beagle dogs, and the stents were tightly anchored surgically to prevent migration. The estimated radiation dose calculated by Monte Carlo simulation was 194-383 Gy in Group A, 48-90 Gy in Group B, and 23-32 Gy in Group C. The dogs were killed 8-12 weeks after insertion of the stents, and histologic examinations of the esophageal walls were performed. Results: In Group A, 3 of 15 dogs died of wound infection, so specimens were obtained from only 12 dogs; all 12 cases showed esophageal stricture with mucosal ulceration. Microscopically, severe fibrosis and degeneration of the muscular propria were found in 3 dogs, complete fibrosis of the entire esophageal wall was found in 7 dogs, and esophageal fibrosis with radiation damage within periesophageal soft tissue was found in 2 dogs. However, esophageal perforation did not develop, despite extremely high radiation doses. In Group B, glandular atrophy and submucosal fibrosis were found, but the muscular layer was intact. In Group C, no histologic change was found in 3 dogs, but submucosal inflammation and glandular atrophy with intact mucosa

  20. Low-Flammability PTFE for High-Oxygen Environments

    Science.gov (United States)

    Walle, E.; Fallon, B.; Sheppard, A.

    1986-01-01

    Modified forming process removes volatile combustible materials. Flammability of cable-wrapping tape reduced by altering tape-manufacturing process. In new manufacturing process, tape formed by proprietary process of screw extrusion, followed by washing in solvent and drying. Tape then wrapped as before. Spectrogram taken after extrusion, washing, and drying shows lower hydrocarbon content. PTFE formed by new process suited to oxygen-rich environments. Safe in liquid oxygen of Space Shuttle tank and in medical uses; thin-wall shrinkable tubing in hospital test equipment, surgical instruments, and implants.

  1. A Novel Partially Covered Self-Expandable Metallic Stent with Proximal Flare in Patients with Malignant Gastric Outlet Obstruction.

    Science.gov (United States)

    Takahara, Naminatsu; Isayama, Hiroyuki; Nakai, Yousuke; Yoshida, Shuntaro; Saito, Tomotaka; Mizuno, Suguru; Yagioka, Hiroshi; Kogure, Hirofumi; Togawa, Osamu; Matsubara, Saburo; Ito, Yukiko; Yamamoto, Natsuyo; Tada, Minoru; Koike, Kazuhiko

    2017-07-15

    Endoscopic placement of self-expandable metal stents (SEMSs) has emerged as a palliative treatment for malignant gastric outlet obstruction (GOO). Although covered SEMSs can prevent tumor ingrowth, frequent migration of covered SEMSs may offset their advantages in preventing tumor ingrowth. We conducted this multicenter, single-arm, retrospective study at six tertiary referral centers to evaluate the safety and efficacy of a partially covered SEMS with an uncovered large-bore flare at the proximal end as an antimigration system in 41 patients with symptomatic malignant GOO. The primary outcome was clinical success, and the secondary outcomes were technical success, stent dysfunction, adverse events, and survival after stent placement. The technical and clinical success rates were 100% and 95%, respectively. Stent dysfunctions occurred in 17 patients (41%), including stent migration in nine (23%), tumor ingrowth in one (2%), and tumor overgrowth in four (10%). Two patients (5%) developed adverse events: one pancreatitis and one perforation. No procedure-related death was observed. A novel partially covered SEMS with a large-bore flare proximal end was safe and effective for malignant GOO but failed to prevent stent migration. Further research is warranted to develop a covered SEMS with an optimal antimigration system.

  2. The effect of nitrogen and oxygen plasma on the wear properties and adhesion strength of the diamond-like carbon film coated on PTFE

    International Nuclear Information System (INIS)

    Ozeki, K.; Hirakuri, K.K.

    2008-01-01

    Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using a radiofrequency plasma chemical vapour deposition method. Prior to DLC coating, the PTFE substrates were modified with O 2 and N 2 plasma to enhance the adhesion strength of the DLC film to the substrate. The effect of the plasma pre-treatment on the chemical composition and the surface energy of the plasma pre-treated PTFE surface was investigated by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, respectively. A pull-out test and a ball-on-disc test were carried out to evaluate the adhesion strength and the wear properties of the DLC-coated PTFE. In the N 2 plasma pre-treatment, the XPS result indicated that defluorination and the nitrogen grafting occurred on the plasma pre-treated PTFE surface, and the water contact angle decreased with increasing the plasma pre-treatment time. In the O 2 plasma pre-treatment, no grafting of the oxygen occurred, and the water contact angle slightly increased with the treatment time. In the pull-out test, the adhesion strength of the DLC film to the PTFE substrate was improved with the plasma pre-treatment to the PTFE substrate, and N 2 plasma pre-treatment was more effective than the O 2 plasma pre-treatment. In the ball-on-disc test, the DLC film with the N 2 plasma pre-treatment showed good wear resistance, compared with that with O 2 plasma pre-treatment

  3. Dacron® vs. PTFE as bypass materials in peripheral vascular surgery – systematic review and meta-analysis

    Directory of Open Access Journals (Sweden)

    Eidt Daniela

    2008-12-01

    Full Text Available Abstract Background In peripheral vascular bypass surgery different synthetic materials are available for bypass grafting. It is unclear which of the two commonly used materials, polytetrafluoroethylene (PTFE or polyester (Dacron® grafts, is to be preferred. Thus, the aim of this meta-analysis and systematic review was to compare the effectiveness of these two prosthetic bypass materials (Dacron® and PTFE. Methods We performed a systematic literature search in MEDLINE, Cochrane-Library – CENTRAL, EMBASE and other databases for relevant publications in English and German published between 1999 and 2008. Only randomized controlled trials were considered for inclusion. We assessed the methodological quality by means of standardized checklists. Primary patency was used as the main endpoint. Random-effect meta-analysis as well as pooling data in life table format was performed to combine study results. Results Nine randomized controlled trials (RCT were included. Two trials showed statistically significant differences in primary patency, one favouring Dacron® and one favouring PTFE grafts, while 7 trials did not show statistically significant differences between the two materials. Meta-analysis on the comparison of PTFE vs. Dacron® grafts yielded no differences with regard to primary patency rates (hazard ratio 1.04 (95% confidence interval [0.85;1.28], no significant heterogeneity (p = 0.32, I2 = 14%. Similarly, there were no significant differences with regard to secondary patency rates. Conclusion Systematic evaluation and meta-analysis of randomized controlled trials comparing Dacron® and PTFE as bypass materials for peripheral vascular surgery showed no evidence of an advantage of one synthetic material over the other.

  4. [Research on ultrasonic permeability of low intensity pulsed ultrasound through PTFE membrane and Bio-Gide collagen membrane].

    Science.gov (United States)

    Chai, Zhaowu; Zhao, Chunliang; Song, Jinlin; Deng, Feng; Yang, Ji; Gao, Xiang; Liu, Minyi

    2013-12-01

    The aim of the present study was to detect the transmission rate of ultrasonic low intensity pulsed ultrasound (LIPUS) through polytetrafluoroethylene (PTFE) membrane (Thickness: 0.01 mm) and Bio-Gide collagen membrane, and to provide the basis for the barrier membrane selection on the study of LIPUS combined with guided tissue regeneration (GTR). The ultrasonic (LIPUS, frequency 1.5 MHz, pulse width 200 micros, repetition rate 1.0 kHz) transmission coefficient of the two kinds of barrier membrane were detected respectively through setting ten groups from 10 to 100mW/cm2 every other 10 mW/cm2. We found in the study that the ultrasonic transmission coefficient through 0.01 mm PTFE membrane was 78.1% to 92.%, and the ultrasonic transmission coefficient through Bio-Gide collagen membrane was 43.9% to 55.8%. The ultrasonic transmission coefficient through PTFE membrane was obviously higher than that through Bio-Gide collagen membrane. The transmission coefficient of the same barrier membrane of the ultrasonic ion was statistically different under different powers (P PTFE membrane and Bio-Gide collagen membrane were relatively high. We should select barrier membranes based on different experimental needs, and exercise ultrasonic transmission coefficient experiments to ensure effective power.

  5. Experimental Study on Impact-Induced Reaction Characteristics of PTFE/Ti Composites Enhanced by W Particles

    Directory of Open Access Journals (Sweden)

    Yan Li

    2017-02-01

    Full Text Available Metal/fluoropolymer composites are a category of energetic structural materials that release energy through exothermic chemical reactions initiated under highly dynamic loadings. In this paper, the chemical reaction mechanism of PTFE (polytetrafluoroethylene/Ti/W composites is investigated through thermal analysis and composition analysis. These composites undergo exothermic reactions at 510 °C to 600 °C, mainly producing TiFx. The tungsten significantly reduces the reaction heat due to its inertness. In addition, the dynamic compression properties and impact-induced reaction behaviors of PTFE/Ti/W composites with different W content prepared by pressing and sintering are studied using Split Hopkinson Pressure Bar and high speed photography. The results show that both the mechanical strength and the reaction degree are significantly improved with the increasing strain rate. Moreover, as W content increases, the mechanical strength is enhanced, but the elasticity/plasticity is decreased. The PTFE/Ti/W composites tend to become more inert with the increasing W content, which is reflected by the reduced reaction degree and the increased reaction threshold for the impact ignition.

  6. Endoscopic management of unresectable malignant gastroduodenal obstruction with a nitinol uncovered metal stent: A prospective Japanese multicenter study

    Science.gov (United States)

    Sasaki, Reina; Sakai, Yuji; Tsuyuguchi, Toshio; Nishikawa, Takao; Fujimoto, Tatsuya; Mikami, Shigeru; Sugiyama, Harutoshi; Yokosuka, Osamu

    2016-01-01

    AIM: To determine the safety and efficacy of endoscopic duodenal stent placement in patients with malignant gastric outlet obstruction. METHODS: This prospective, observational, multicenter study included 39 consecutive patients with malignant gastric outlet obstruction. All patients underwent endoscopic placement of a nitinol, uncovered, self-expandable metal stent. The primary outcome was clinical success at 2 wk after stent placement that was defined as improvement in the Gastric Outlet Obstruction Scoring System score relative to the baseline. RESULTS: Technical success was achieved in all duodenal stent procedures. Procedure-related complications occurred in 4 patients (10.3%) in the form of mild pneumonitis. No other morbidities or mortalities were observed. The clinical success rate was 92.3%. The mean survival period after stent placement was 103 d. The mean period of stent patency was 149 d and the patency remained acceptable for the survival period. Stent dysfunction occurred in 3 patients (7.7%) on account of tumor growth. CONCLUSION: Endoscopic management using duodenal stents for patients with incurable malignant gastric outlet obstruction is safe and improved patients’ quality of life. PMID:27076769

  7. Treatment of Complex Fistula-in-Ano With a Nitinol Proctology Clip

    DEFF Research Database (Denmark)

    Nordholm-Carstensen, Andreas; Krarup, Peter-Martin; Hagen, Kikke

    2017-01-01

    BACKGROUND: The treatment of complex anocutaneous fistulas remains a major therapeutic challenge balancing the risk of incontinence against the chance of permanent closure. OBJECTIVE: The purpose of this study was to investigate the efficacy of a nitinol proctology clip for closure of complex ano...... with those of other noninvasive, sphincter-sparing techniques for high-complex anocutaneous fistulas, with no risk of incontinence. Predictive parameters for fistula healing using this technique remain uncertain. See Video Abstract at http://links.lww.com/DCR/A347....

  8. Characterization of the melting process of PTFE using positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Honda, Y; Nishijima, S

    2015-01-01

    Poly(tetrafluoroethylene) (PTFE) is a semi-crystalline polymer and the lifetime of ortho-positronium(o-Ps) is known to be able to be separated into two components due to annihilation in the crystal region and in the amorphous region. The melting process of PTFE was investigated using positron annihilation spectroscopy and X-ray diffraction. The results indicated that volume expansion with an increase of temperature is dominantly due to the expansion of the amorphous region and a Ps bubble is formed at melting in both regions. The o-Ps relating to the crystal region definitely remains on the surface of crystal at the time of annihilation. The production of lower energy electrons at melting was deduced by the analysis of the Doppler broadened annihilation photopeak, and the increase in the number of such electrons was found to have great influence on the formation of the o-Ps and annihilation processes of positron and o-Ps. (paper)

  9. Investigation of graft copolymerization modification of PTFE surface using microwave plasma

    International Nuclear Information System (INIS)

    Wen Yunjian; Guan Weishu; Fang Yan; Ying Yongxiang

    1995-03-01

    Investigation of graft copolymerization modification of PTFE surface with kind of one or another reactive monomers was performed by using non-equilibrium microwave plasma at 2.45 GHz under various operating conditions. Untreated clean samples and grafted samples were examined and analyzed with different surface analytical techniques such as X-Ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Scanning Electron Microscopy (SEM). The results showed that the occurrence of noticeable de-fluorination and cross linking on grafted surface, and different polar groups and content of oxygen-containing were introduced into the grafted surface of PTFE. Fibriform hetero-structure layer was also formed. These results confirmed the success of graft and indicated that the hydrophilicity of the grafted surface is excellent and a significant improvement in adhesion characteristics has been achieved. The experiments revealed that the changes in surface properties are correlated closely to the changes in chemical structure, composition and morphology. (8 figs., 1 refs.)

  10. THE USE OF NITINOL RODS IN SURGICAL TREATMENT OF DEGENERATIVE SCOLIOSIS. 2.5-YEAR FOLLOW-UP

    Directory of Open Access Journals (Sweden)

    Natalia Sergeyevna Morozova

    2016-03-01

    Full Text Available ABSTRACT Objectives: To compare the outcomes of surgical treatment with lumbar fixation using nitinol rods without fusion and with standard lumbar fixation with titanium rods and interbody fusion. Methods: Treatment results of 70 patients with degenerative lumbar scoliosis aged 40 to 82 were analyzed. In all cases pedicle screws and nitinol rods with a diameter of 5.5 mm were used. Thirty patients underwent fixation at L1-S1 and 40 patients underwent fixation at L1-L5. Spinal fusion was not performed. All patients had radiography, CT and MRI performed. The results were assessed according to the Oswestry scale, SRS 22, SF 36 and VAS. The minimum follow-up period for all patients was 2.5 years. For the control group, consisting of 72 patients, pedicle fixation with titanium rods and interbody fusion in the lumbosacral region were performed. Results: The average level of deformity correction equaled 25° (10° - 38°. The analysis of X-ray and CT-scans revealed a single patient with implant instability, two patients with bone resorption around the screws and one patient with rod fractures. Functional radiography 2.5 years after surgery showed an average mobility of the lumbar spine of 21° (15° - 30°. There were no problems at the adjacent levels. Conclusions: The use of nitinol rods in spinal deformity surgery is promising. This technology is an alternative to rigid fixation. Continued gathering of clinical data and its further evaluation is necessary.

  11. A torsional artificial muscle from twisted nitinol microwire

    Science.gov (United States)

    Mirvakili, Seyed M.; Hunter, Ian W.

    2017-04-01

    Nitinol microwires of 25 μm in diameter can have tensile actuation of up to 4.5% in less than 100 ms. A work density of up to 480 MPa can be achieved from these microwires. In the present work, we are showing that by twisting the microwires in form of closed-loop two-ply yarn we can create a torsional actuator. We achieved a revisable torsional stroke of 46°/mm with peak rotational speed of up to 10,000 rpm. We measured a gravimetric torque of up to 28.5 N•m/kg which is higher than the 3 - 6 N•m/kg for direct-drive commercial electric motors. These remarkable performance results are comparable to those of guest-infiltrated carbon nanotube twisted yarns.

  12. A case of rectovagino-vesical fistula due to radiation therapy for uterine cancer treated with covered expandable metallic stent

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsukasa, Shunroh; Okabe, Satoshi; Tanami, Hideaki [Tokyo Medical and Dental Univ. (Japan). School of Medicine] (and others)

    2002-04-01

    A 65-year-old woman had received a panhysterectomy and radiation therapy for a uterine cancer in 1974 and underwent a drainage operation for a peritonitis due to rupture of the bladder associated with radiation cystitis in 1983. A rectovesical fistula was revealed and partial resection of the bladder and rectum was performed in 1996. In 1998, rectovesical fistula recurred and symptom of fecaluria and contact-type dermatitis at perineal region subsequently worsened. In February, 2000, colonoscopy and gastrograffin-enema revealed a giant recto-vagino-vesical fistula. Although we recommended ileostomy, the patient refused our offer. She gave informed consent to our proposal about the insertion of a covered expandable metallic stent (EMS) into the rectum to treat for fecaluria. After insertion of a covered EMS, fecaluria and contact-type dermatitis at perineal region subsequently improved. Three months later, fecaluria appeared again. Finally, seven months later, severe inflammation occurred at perineal and pubic region because of migration of the covered EMS into the bladder, then we removed the covered EMS and performed ileostomy. It is difficult to use the covered EMS treatment for benign rectovesical or rectovaginal fistula for a long term. (author)

  13. Diaphragms obtained by radiochemical grafting in PTFE

    International Nuclear Information System (INIS)

    Nenner, T.; Fahrasmane, A.

    1984-01-01

    Diaphragms for alkaline water electrolysis are prepared by radiochemical grafting of PTFE fabric with styrene, which is later on sulfonated, or with acrylic acid. The diaphragms obtained are mechanically resistant to potash at temperatures up to 200 0 C, but show some degrafting, which limits the lifetime. The sulfonated styrene group has been found to be more stable in electrolysis than the acrylic acid. In both cases, the incorporation of a cross-linking agent like divinyl benzene improves the lifetime of the diaphragms. Electrolysis during 500 hours at 120 0 C and 10 kAm 2 could be performed. (author)

  14. Investigation on Mechanical Properties and Reaction Characteristics of Al-PTFE Composites with Different Al Particle Size

    Directory of Open Access Journals (Sweden)

    Jia-xiang Wu

    2018-01-01

    Full Text Available Al-PTFE (aluminum-polytetrafluoroethylene serves as one among the most promising reactive materials (RMs. In this work, six types of Al-PTFE composites with different Al particle sizes (i.e., 50 nm, 1∼2 μm, 6∼7 μm, 12∼14 μm, 22∼24 μm, and 32∼34 μm were prepared, and quasistatic compression and drop weight tests were conducted to characterize the mechanical properties and reaction characteristics of Al-PTFE composites. The reaction phenomenon and stress-strain curves were recorded by a high-speed camera and universal testing machine. The microstructure of selected specimens was anatomized through adopting a scanning electron microscope (SEM to correlate the mesoscale structural characteristics to their macroproperties. As the results indicated, in the case of quasistatic compression, the strength of the composites was decreased (the yield strength falling from 22.7 MPa to 13.6 MPa and the hardening modulus declining from 33.3 MPa to 25 MPa with the increase of the Al particle size. The toughness rose firstly and subsequently decreased and peaked as 116.42 MJ/m3 at 6∼7 μm. The reaction phenomenon occurred only in composites with the Al particle size less than 10 μm. In drop weight tests, six types of specimens were overall reacted. As the Al particle size rose, the ignition energy of the composites enhanced and the composites turned out to be more insensitive to reaction. In a lower strain rate range (10−2·s−1∼102·s−1, Al-PTFE specimens take on different mechanical properties and reaction characteristics in the case of different strain rates. The formation of circumferential open cracks is deemed as a prerequisite for Al-PTFE specimens to go through a reaction.

  15. Low-Pressure H2, NH3 Microwave Plasma Treatment of Polytetrafluoroethylene (PTFE) Powders: Chemical, Thermal and Wettability Analysis

    Science.gov (United States)

    Hunke, Harald; Soin, Navneet; Shah, Tahir H.; Kramer, Erich; Pascual, Alfons; Karuna, Mallampalli Sri Lakshmi; Siores, Elias

    2015-01-01

    Functionalization of Polytetrafluoroethylene (PTFE) powders of ~6 μm particle size is carried out using low-pressure 2.45 GHz H2, NH3 microwave plasmas for various durations (2.5, 10 h) to chemically modify their surface and alter their surface energy. The X-ray Photoelectron Spectroscopy (XPS) analyses reveal that plasma treatment leads to significant defluorination (F/C atomic ratio of 1.13 and 1.30 for 10 h NH3 and H2 plasma treatments, respectively vs. 1.86 for pristine PTFE), along with the incorporation of functional polar moieties on the surface, resulting in enhanced wettability. Analysis of temperature dependent XPS revealed a loss of surface moieties above 200 °C, however, the functional groups are not completely removable even at higher temperatures (>300 °C), thus enabling the use of plasma treated PTFE powders as potential tribological fillers in high temperature engineering polymers. Ageing studies carried over a period of 12 months revealed that while the surface changes degenerate over time, again, they are not completely reversible. These functionalised PTFE powders can be further used for applications into smart, high performance materials such as tribological fillers for engineering polymers and bio-medical, bio-material applications.

  16. Oxygen Compatibility of Brass-Filled PTFE Compared to Commonly Used Fluorinated Polymers for Oxygen Systems

    Science.gov (United States)

    Herald, Stephen D.; Frisby, Paul M.; Davis, Samuel Eddie

    2009-01-01

    Safe and reliable seal materials for high-pressure oxygen systems sometimes appear to be extinct species when sought out by oxygen systems designers. Materials that seal well are easy to find, but these materials are typically incompatible with oxygen, especially in cryogenic liquid form. This incompatibility can result in seals that leak, or much worse, seals that easily ignite and burn during use. Materials that are compatible with oxygen are easy to find, such as the long list of compatible metals, but these metallic materials are limiting as seal materials. A material that seals well and is oxygen compatible has been the big game in the designer's safari. Scientists at the Materials Combustion Research Facility (MCRF), part of NASA/Marshall Space Flight Center (MSFC), are constantly searching for better materials and processes to improve the safety of oxygen systems. One focus of this effort is improving the characteristics of polymers used in the presence of an oxygen enriched environment. Very few systems can be built which contain no polymeric materials; therefore, materials which have good impact resistance, low heat of combustion, high auto-ignition temperature and that maintain good mechanical properties are essential. The scientists and engineers at the Materials Combustion Research Facility, in cooperation with seal suppliers, are currently testing a new formulation of polytetrafluoroethylene (PTFE) with Brass filler. This Brass-filled PTFE is showing great promise as a seal and seat material for high pressure oxygen systems. Early research has demonstrated very encouraging results, which could rank this material as one of the best fluorinated polymers ever tested. This paper will compare the data obtained for Brass-filled PTFE with other fluorinated polymers, such as TFE-Teflon (PTFE) , Kel-F 81, Viton A, Viton A-500, Fluorel , and Algoflon . A similar metal filled fluorinated polymer, Salox-M , was tested in comparison to Brass-filled PTFE to

  17. Tribological properties of polymers PI, PTFE and PEEK at cryogenic temperature in vacuum

    Science.gov (United States)

    Wang, Qihua; Zheng, Fei; Wang, Tingmei

    2016-04-01

    The effects of temperature, sliding speed and load on the tribological properties of polyimide (PI), polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) at cryogenic temperature in vacuum were investigated using a ball-on-disk tribometer. At cryogenic temperature, polymers show higher hardness which results in decreasing contact area between the friction pairs. Moreover, the real surface area in contact between steel ball and polymer disk determines the friction coefficient instead of the formation and adhesion of the transfer film. Thus, the friction coefficients at cryogenic temperatures are lower than at room temperature. On the other hand, wear rates of the three polymers decrease as temperature decreases since molecular mobility and migration are limited at cryogenic temperatures. For the visco-elasticity of PI, PTFE and PEEK, the friction coefficients fall as the load increases.

  18. Pilot study of a novel, large-bore, fully covered self-expandable metallic stent for unresectable distal biliary malignancies.

    Science.gov (United States)

    Mukai, Tsuyoshi; Yasuda, Ichiro; Isayama, Hiroyuki; Iwashita, Takuji; Itoi, Takao; Kawakami, Hiroshi; Kogure, Hirofumi; Nakai, Yousuke

    2016-09-01

    In patients with unresectable malignant distal biliary obstruction, covered self-expandable metallic stents (CSEMS) may remain patent longer than uncovered self-expandable metallic stents as a result of tumor ingrowth prevention. One main cause of recurrent biliary obstruction (RBO) in CSEMS is sludge formation, which can be prevented using a large-bore stent. Therefore, we developed a novel, 12-mm diameter fully covered SEMS (FCSEMS) and investigated its clinical safety, efficacy, and rate of adverse events. This prospective, multicenter pilot study, which ran between June 2011 and November 2012, included 38 consecutive patients with unresectable malignant distal biliary obstruction. All patients underwent endoscopic insertion of our novel stent. Primary endpoint was non-RBO rate 6 months after placement. Technical and functional success rates of the procedures were 100%. Six-month non-RBO rate was 50%, and median time to RBO was 184 days. Median survival time was 241 days. Twelve patients died within 6 months after stent placement without RBO. RBO was observed in 10 patients (26%), with seven experiencing stent occlusion and three experiencing stent migration. Adverse events other than RBO (at Stent removal for reintervention was successfully completed in eight patients. Our novel FCSEMS may be safe and effective for managing malignant distal obstruction with an acceptable incidence of adverse events. © 2016 Japan Gastroenterological Endoscopy Society.

  19. THE USE OF CHLOROSULFONIC ACID ON SULFONATION OF cPTFE FILM GRAFTED STYRENE FOR PROTON EXCHANGE MEMBRANE

    Directory of Open Access Journals (Sweden)

    Yohan Yohan

    2010-06-01

    Full Text Available Sulfonation of g-ray iradiated and styrene-grafted crosslinked polytetrafluoro ethylene film (cPTFE-g-S film have been done. The aim of the research was to make hydrophyl membrane as proton exchange membrane fuel cell. Sulfonation was prepared by using chlorosulfonic acid in chloroethane under various conditions. The impact of the percentage of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film were examined. The results show that sulfonation of surface-grafted films was incomplete at room temperature. Increasing concentration of chlorosulfonic acid and reaction temperature accelerate the reaction but they also favor side reactions. These lead to the decrease of the ion-exchange capacity, water uptake, and proton conductivity but the increase of the resistance to oxidation in a perhydrol solution. The resulted cPTFE-g-SS membraneis stabile in a H2O2 30% solution for 20 h.   Keywords: Chorosulfonic acid, sulfonation, PTFE film, proton excange membrane.

  20. Friction transfer of polytetrafluoroethylene (PTFE) to produce nanoscale features and influence cellular response in vitro.

    Science.gov (United States)

    Kearns, V R; Doherty, P J; Beamson, G; Martin, N; Williams, R L

    2010-07-01

    A large number of cell types are known to respond to chemical and topographical patterning of substrates. Friction transfer of polytetrafluoroethylene (PTFE) onto substrates has been shown to produce continuous, straight, parallel nanofibres. Ammonia plasma treatment can be used to defluorinate the PTFE, decreasing the dynamic contact angle. Fibroblast and epithelial cells were elongated and oriented with their long axis parallel to the fibres, both individually and in clusters. The fibres restricted cell migration. Cell alignment was slightly reduced on the plasma-treated fibres. These results indicated that although surface topography can affect cellular response, surface chemistry also mediates the extent of this response.

  1. HEALING OF MICROVENOUS PTFE PROSTHESES IMPLANTED INTO THE RAT FEMORAL VEIN

    NARCIS (Netherlands)

    VANDERLEI, B; DIJK, F; JONGEBLOED, WL; ROBINSON, PH; Bartels, H.

    44 PTFE prostheses (Gore-Tex(R); ID 1 mm) were implanted into rats' femoral veins by means of the sleeve anastomotic technique and were evaluated at regular intervals from 1 h up till 24 weeks after implantation by means of light and electron microscopy to study in detail their healing process. All

  2. The mechanism of PTFE and PE friction deposition: a combined scanning electron and scanning force microscopy study on highly oriented polymeric sliders

    NARCIS (Netherlands)

    Schönherr, Holger; Schaeben, H.; Vancso, Gyula J.

    1998-01-01

    The mechanism of friction deposition of polytetrafluoroethylene (PTFE) and polyethylene (PE) was studied by scanning electron (SEM) and scanning force microscopy (SFM) on the worn surfaces of PTFE and PE sliders that were used in friction deposition on glass substrates. These surfaces exhibited a

  3. On phase transformation models for thermo-mechanically coupled response of Nitinol

    KAUST Repository

    Sengupta, Arkaprabha

    2011-03-31

    Fully coupled thermomechanical models for Nitinol at the grain level are developed in this work to capture the inter-dependence between deformation and temperature under non-isothermal conditions. The martensite transformation equations are solved using a novel algorithm which imposes all relevant constraints on the volume fractions. The numerical implementation of the resulting models within the finite element method is effected by the monolithic solution of the momentum and energy equations. Validation of the models is achieved by means of thin-tube experiments at different strain rates. © 2011 Springer-Verlag.

  4. Covered duodenal self-expandable metal stents prolong biliary stent patency in double stenting: The largest series of bilioduodenal obstruction.

    Science.gov (United States)

    Hori, Yasuki; Naitoh, Itaru; Hayashi, Kazuki; Kondo, Hiromu; Yoshida, Michihiro; Shimizu, Shuya; Hirano, Atsuyuki; Okumura, Fumihiro; Ando, Tomoaki; Jinno, Naruomi; Takada, Hiroki; Togawa, Shozo; Joh, Takashi

    2018-03-01

    Endoscopic biliary and duodenal stenting (DS; double stenting) is widely accepted as a palliation therapy for malignant bilioduodenal obstruction. The aim of the current study was to investigate the patency and adverse events of duodenal and biliary stents in patients with DS. Patients who underwent DS from April 2004 to March 2017 were analyzed retrospectively with regard to clinical outcomes and predictive factors of recurrent biliary and duodenal obstruction (recurrent biliary obstruction [RBO] and recurrent duodenal obstruction [RDO]). A total of 109 consecutive patients was enrolled. Technical success of DS was achieved in 108 patients (99.1%). Symptoms due to biliary and duodenal obstruction were improved in 89 patients (81.7%). RBO occurred in 25 patients (22.9%) and RDO in 13 (11.9%). The median times to RBO and RDO from DS were 87 and 76 days, respectively. Placement of a duodenal uncovered self-expandable metal stent (U-SEMS) was significantly associated with RBO in the multivariable analysis (P = 0.007). Time to RBO was significantly longer in the duodenal covered self-expandable metal stent group than in the U-SEMS group (P = 0.003). No predictive factors of RDO were detected, and duodenal stent type was not associated with the time to RDO (P = 0.724). Double stenting was safe and effective for malignant bilioduodenal obstruction. Duodenal U-SEMS is a risk factor for RBO. The covered self-expandable metal stent is the preferred type of duodenal SEMS in patients with DS (Clinical trial registration number: UMIN000027606). © 2017 Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.

  5. Nitinol laser cutting: microstructure and functional properties of femtosecond and continuous wave laser processing

    Science.gov (United States)

    Biffi, C. A.; Tuissi, A.

    2017-03-01

    Thermal processing can affect the properties of smart materials, and the correct selection of the best manufacturing technology is fundamental for producing high tech smart devices, containing embedded functional properties. In this work cutting of thin superelastic Nitinol plates using a femtosecond (fs) and continuous wave (CW) laser was studied. Diamond shaped elements were cut to characterize the kerf qualitative features; microstructural analysis of the cross sections allowed identification of thermal damage characteristics introduced into the material during the laser processes. A thermally undamaged microstructure was observed for fs laser cutting, while CW was seen to be characterized by a large heat-affected zone. Functional properties were investigated by differential scanning calorimetry and tensile testing of laser cut microelements and of the reference material. It was seen that the martensitic transformation behavior of Nitinol is not affected by fs regime, while cw cutting provokes an effect equivalent to a high temperature thermal treatment in the material surrounding the cutting kerf, degradating the material properties. Finally, tensile testing indicated that superelastic performances were guaranteed by fs regime, while strong reduction of the recoverable strain was detected in the CW processed sample.

  6. High energy electron beams characterization using CaSO{sub 4}:Dy+PTFE Phosphors for clinical therapy applications

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, T., E-mail: trivera@ipn.mx [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, Col. Irrigacion. 11500 Mexico DF (Mexico); Espinoza, A.; Von, S.M. [Centro Estatal de Cancerologia de los Servicios de Salud de Nayarit, Enfermeria S/n, Fracc, Fray Junipero Serra, 63169 Tepic Nay (Mexico); Alvarez, R.; Jimenez, Y. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Legaria, IPN. Av. Legaria 694, Col. Irrigacion. 11500 Mexico DF (Mexico)

    2012-07-15

    In the present work high energy electron beam dosimetry from linear accelerator (LINACs) for clinical applications using dysprosium doped calcium sulfate embedded in polytetrafluorethylene (CaSO{sub 4}:Dy+PTFE) was studied. The irradiations were carried out using high electron beams (6 to 18 MeV) from a linear accelerator (LINAC) Varian, CLINAC 2300C/D, for clinical practice purpose. The electron irradiations were obtained using the water solid in order to guarantee electronic equilibrium conditions (EEC). Field shaping for electron beams was obtained with electron cones. Glow curve and other thermoluminescent characteristics of CaSO{sub 4}:Dy+PTFE were conducted under high electrons beams irradiations. The TL response of the pellets showed an intensity peak centered at around 215 Degree-Sign C. TL response of CaSO{sub 4}:Dy+PTFE as a function of high electron absorbed dose showed a linearity in a wide range. To obtain reproducibility characteristic, a set of pellets were exposed repeatedly for the same electron absorbed dose. The results obtained in this study can suggest the applicability of CaSO{sub 4}:Dy+PTFE pellets for high electron beam dosimetry, provided fading is correctly accounted for. - Highlights: Black-Right-Pointing-Pointer Developing of CaSO{sub 4}:Dy to electron beams dosimetry. Black-Right-Pointing-Pointer Characterization of caSO{sub 4}:Dy to radiation safety in LINACs. Black-Right-Pointing-Pointer TL characteristics of CaSO{sub 4}:Dy for electron beams quality control.

  7. Relationship of Adhesive, Contact and Electret Properties of PTFE Modified by DC Discharge

    Science.gov (United States)

    Yablokov, M.; Piskarev, M.; Gilman, A.; Kechek'yan, A.; Kuznetsov, A.

    2018-02-01

    The relationship between the contact, adhesive and electret properties of PTFE films modified by direct current glow discharge has been studied. The film samples of 40 μm thickness were placed at the anode and cathode and treated in the air as a working gas. The contact properties of polymer surface were characterized by the values of deionized water contact angle. The peel strength was determined using T-peel test for the Scotch®810/PTFE film contact. The electret potential was measured by the compensation technique using dynamic capacitor, and from the measured potential value the effective surface charge density was calculated. It has been found that there is an undoubted correlation between the change in the value of water contact angle, the peel strength of the DC discharge-treated film, and the magnitude of the effective surface charge.

  8. Functional properties of poly(tetrafluoroethylene) (PTFE) gasket working in nuclear reactor conditions

    Science.gov (United States)

    Wyszkowska, Edyta; Leśniak, Magdalena; Kurpaska, Lukasz; Prokopowicz, Rafal; Jozwik, Iwona; Sitarz, Maciej; Jagielski, Jacek

    2018-04-01

    In this study structural and nanomechanical properties of polytetrafluoroethylene (PTFE) used as a gasket in the nuclear reactor have been deeply investigated. In order to reveal structural changes caused by long-term pressure, temperature and irradiation (possibly neutron and gamma), methods such as SEM, X-ray diffraction and Raman Spectroscopy have been used. Nanomechanical properties such as Young Modulus and hardness were investigated by means of the nanoindentation technique. Presented study confirmed the influence of working (radiative) environment on the functional properties of PTFE. The results of Raman spectroscopy and X-ray diffraction techniques revealed shift of the major band positions and band intensities increase. Moreover, changes of hardness and Young Modulus values of the irradiated material with respect to the virgin specimen have been recorded. This phenomenon can be attributed to the modifications in crystallinity of the material. Presented work suggest that morphology of the irradiated material altered from well-ordered parallel fibers to more dense and thicker ones.

  9. Removable fully covered self-expandable metal stents in the treatment of common bile duct strictures due to chronic pancreatitis: a case series

    NARCIS (Netherlands)

    Cahen, D. L.; Rauws, E. A.; Gouma, D. J.; Fockens, P.; Bruno, M. J.

    2008-01-01

    The aim of this study was to test the removability of fully covered self-expandable metal stents (FCSEMS) in patients with a benign common bile duct (CBD) stricture. A FCSEMS was inserted in six patients with a CBD stricture due to chronic pancreatitis who were considered to be unfit for surgery,

  10. Fully covered self-expanding metal stents are effective for benign esophagogastric disruptions and strictures.

    Science.gov (United States)

    Wilson, Jennifer L; Louie, Brian E; Farivar, Alexander S; Vallières, Eric; Aye, Ralph W

    2013-12-01

    Self-expanding fully covered metal stents (CSs) are ideal for use in benign esophagogastric disease. We reviewed our experience with CS to evaluate outcomes, to determine a role for CS in a standard treatment for benign esophageal conditions, and to compare our results with recently published studies. We performed a retrospective chart review from 2005 to 2012. A total of 57 CSs were placed in 44 patients. Indications were stricture (11 patients), anastomotic leak (20), perforation (7), and tracheoesophageal fistulae (6). For GI tract disruptions, open repair or diversion was avoided in 31/33 patients (93.9 %) but required an associated drainage procedure in 22/33 (67 %) patients. Resolution does not depend on achieving radiological control with 6/26 (23 %) having evidence of a persistent leak. Benign strictures were dilated at a mean of 3.7 times prior to stenting. Adjunctive intra-mucosal steroid injections were used in 8/11 patients. Stents were removed at a mean of 33 days. At a mean of 283 days of follow-up, 6/11 (54.5 %) had symptom resolution. The most common complication was stent migration occurring in 17.5 % of patients overall. Covered stents are an effective adjunct in the management of benign upper gastrointestinal tract fistulae, leaks, perforations and benign strictures.

  11. Layer-by-layer assembly of thin organic films on PTFE activated by cold atmospheric plasma

    Directory of Open Access Journals (Sweden)

    Tóth András

    2014-12-01

    Full Text Available An air diffuse coplanar surface barrier discharge is used to activate the surface of polytetrafluoroethylene (PTFE samples, which are subsequently coated with polyvinylpyrrolidone (PVP and tannic acid (TAN single, bi- and multilayers, respectively, using the dip-coating method. The surfaces are characterized by X-ray Photoelectron Spectroscopy (XPS, Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR and Atomic Force Microscopy (AFM. The XPS measurements show that with plasma treatment the F/C atomic ratio in the PTFE surface decreases, due to the diminution of the concentration of CF2 moieties, and also oxygen incorporation through formation of new C–O, C=O and O=C–O bonds can be observed. In the case of coated samples, the new bonds indicated by XPS show the bonding between the organic layer and the surface, and thus the stability of layers, while the gradual decrease of the concentration of F atoms with the number of deposited layers proves the creation of PVP/TAN bi- and multi-layers. According to the ATR-FTIR spectra, in the case of PVP/TAN multilayer hydrogen bonding develops between the PVP and TAN, which assures the stability of the multilayer. The AFM lateral friction measurements show that the macromolecular layers homogeneously coat the plasma treated PTFE surface.

  12. Preparation Nano-Structure Polytetrafluoroethylene (PTFE Functional Film on the Cellulose Insulation Polymer and Its Effect on the Breakdown Voltage and Hydrophobicity Properties

    Directory of Open Access Journals (Sweden)

    Jian Hao

    2018-05-01

    Full Text Available Cellulose insulation polymer is an important component of oil-paper insulation, which is widely used in power transformer. The weight of the cellulose insulation polymer materials is as high as tens of tons in the larger converter transformer. Excellent performance of oil-paper insulation is very important for ensuring the safe operation of larger converter transformer. An effective way to improve the insulation and the physicochemical property of the oil impregnated insulation pressboard/paper is currently a popular research topic. In this paper, the polytetrafluoroethylene (PTFE functional film was coated on the cellulose insulation pressboard by radio frequency (RF magnetron sputtering to improve its breakdown voltage and the hydrophobicity properties. X-ray photoelectron spectroscopy (XPS results show that the nano-structure PTFE functional film was successfully fabricated on the cellulose insulation pressboard surface. The scanning electron microscopy (SEM and X-ray diffraction (XRD present that the nanoscale size PTFE particles were attached to the pressboard surface and it exists in the amorphous form. Atomic force microscopy (AFM shows that the sputtered pressboard surface is still rough. The rough PTFE functional film and the reduction of the hydrophilic hydroxyl of the surface due to the shielding effect of PTFE improve the breakdown and the hydrophobicity properties of the cellulose insulation pressboard obviously. This paper provides an innovative way to improve the performance of the cellulose insulation polymer.

  13. Safety and efficacy of a fully covered large-diameter self-expanding metal stent for the treatment of upper gastrointestinal perforations, anastomotic leaks, and fistula

    NARCIS (Netherlands)

    van den Berg, M. W.; Kerbert, A. C.; van Soest, E. J.; Schwartz, M. P.; Bakker, C. M.; Gilissen, L. P. L.; van Hooft, J. E.

    2016-01-01

    Upper gastrointestinal perforations, fistula, and anastomotic leaks are severe conditions with high mortality. Temporary endoscopic placement of fully covered self-expanding metal stent (fSEMS) has emerged as treatment option. Stent migration is a major drawback of currently used stents. Migration

  14. Chemically robust carbon nanotube–PTFE superhydrophobic thin films with enhanced ability of wear resistance

    Institute of Scientific and Technical Information of China (English)

    Kewei Wang; Pan Xiong; Xiuping Xu; Kan Wang; YanLong Li; Yufeng Zheng

    2017-01-01

    A chemically robust superhydrophobic nanocomposite thin film with enhanced wear resistance is prepared from a composite comprising polytetrafluoroethylene (PTFE) and carbon nanotubes. The superhydrophobic thin films with hierarchical structure are fabricated by spraying an environmentally friendly aqueous dispersion containing carbon nanotubes and PTFE resin on silicon wafer. Thin films with a contact angle of 154.1° ± 2° and a sliding angle less than 2° remain superhydrophobic after abrading over 500 times under a pressure of 50 g/cm2. The thin film is also extremely stable even under much stress conditions. To further the understanding of the enhancement of wear resistance, we investigated the formation of microsized structure and their effects. The growth of microbumps is caused by attracting solution droplet to the hydrophilic islands on hydrophobic surface.

  15. Clinical feasibility of a new through-the-scope fully covered esophageal self-expandable metallic stent: an in vivo animal study.

    Science.gov (United States)

    Cheon, Young Koog; Lee, Tae Yoon; Sung, In Kyung; Shim, Chan Sup

    2014-01-01

    Most delivery devices used for esophageal stents for obstructing esophageal cancer have a diameter of 5-8 mm, a size that is too large to pass through the endoscopic working channel. The conventional esophageal stent requires multiple endoscopic procedures for implantation. The purpose of the present study was to evaluate the clinical feasibility of a newly developed fully covered, self-expanding, through-the-scope (TTS) esophageal stent in a porcine model. Eight mini pigs were used. Each animal underwent placement of a fully covered TTS stent (Hanarostent® Esophagus TTS) and the upper part of the stent was fixed by suturing with nylon. Fluoroscopy was carried out every week to assess migration of the stent. Follow-up endoscopy was done every month for 3 months to evaluate the status of the membrane, stent mesh, grade of tissue hyperplasia, and mucosal changes at both ends of the stent. All stents were successfully and easily deployed, and were placed without any distortion in the stent or without rupture of the membrane. In two cases, stent migration was observed after 8 weeks. No case of membrane disruption, stent mesh disruption or tissue hyperplasia at either end of the stent was found at the completion of the study. Our findings indicate that the new fully covered self-expanding TTS esophageal stent is easy and simple to implant, and no significant distortion of mesh or disruption of membrane was observed. © 2013 The Authors. Digestive Endoscopy © 2013 Japan Gastroenterological Endoscopy Society.

  16. Dacron or PTFE for Above-knee Femoropopliteal Bypass. A Multicenter Randomised Study

    DEFF Research Database (Denmark)

    Jensen, L. P.; Lepäntalo, M.; Fossdal, J. E.

    2007-01-01

    more often than patients operated on for intermittent claudication, 10 and 3 respectively (p=0.003), and had higher mortality rates, 20% and 8% respectively (p=0.001). CONCLUSION: This trial confirms that Dacron is at least as durable as PTFE for above-knee bypass procedures, and might even be superior....

  17. Whole shaft visibility and mechanical performance for active MR catheters using copper-nitinol braided polymer tubes

    Directory of Open Access Journals (Sweden)

    McVeigh Elliot R

    2009-08-01

    Full Text Available Abstract Background Catheter visualization and tracking remains a challenge in interventional MR. Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance. Results The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability and antenna (signal attenuation properties. With this configuration, the temperature increase remained less than 2°C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo. Conclusion We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.

  18. The expanding universe: an introduction

    OpenAIRE

    Pössel, Markus

    2017-01-01

    An introduction to the physics and mathematics of the expanding universe, using no more than high-school level / undergraduate mathematics. Covered are the basics of scale factor expansion, the dynamics of the expanding universe, various distance concepts and the generalized redshift-luminosity relation, among other topics.

  19. Comparison of a New Polytetrafluoroethylene-Covered Metallic Stent to a Noncovered Stent in Canine Ureters

    International Nuclear Information System (INIS)

    Chung, Hwan-Hoon; Lee, Seung Hwa; Cho, Sung Bum; Park, Hong Suk; Kim, Young Sik; Kang, Byung Chul; Frisoli, Joan K.; Razavi, Mahmood K.

    2008-01-01

    The aim of this study was to determine the feasibility of using a newly designed polytetrafluoroethylene (PTFE)-covered metallic stent in the ureter by comparing its effectiveness with that of the noncovered stent in a canine model. We placed 14 stents in the ureters of seven mongrel dogs that weighed 30-40 kg each. The covered and noncovered stents were deployed in the right and left ureters, respectively, of six dogs. In the seventh dog, a covered stent and a double-J catheter were inserted in the right ureter, and a covered stent only was inserted in the left ureter. The first six dogs were sacrificed at 5, 10, and 15 weeks after deployment of the stents (two for each follow-up period), and the seventh dog was sacrificed at 30 weeks. There was no migration or poor expansion of any of the stents observed on plain radiography. On intravenous pyelogram and retrograde pyelogram, all of the covered stents at each follow-up period had patent lumens at the stented segments without hydronephrosis, and the passage of contrast material through it was well preserved. The noncovered stents in the dogs sacrificed at 5 and 10 weeks and one of the two dogs sacrificed at 15 weeks showed near-complete occlusion of the stent lumen due to ingrowth of the soft tissue, and severe hydronephrosis was also noted. The noncovered stent in the other dog sacrificed at 15 weeks showed the passage of contrast material without hydronephrosis, but the lumen of the stent was still nearly occluded by the soft tissue. There was no evidence of hydronephrosis or passage disturbance of the contrast material in both ureters of the dog sacrificed at 30 weeks. We conclude that the newly designed PTFE-covered stent effectively prevented the luminal occlusion caused by urothelial hyperplasia compared to the near-total occlusion of the noncovered stents, and no migration of the covered stents was noted

  20. Use of DSC and DMA Techniques to Help Investigate a Material Anomaly for PTFE Used in Processing a Piston Cup for the Urine Processor Assembly (UPA) on International Space Station (ISS)

    Science.gov (United States)

    Wingard, Doug

    2010-01-01

    Human urine and flush water are eventually converted into drinking water with the Urine Processor Assembly (UPA) aboard the International Space Station (ISS). This conversion is made possible through the Distillation Assembly (DA) of the UPA. One component of the DA is a molded circular piston cup made of virgin polytetrafluoroethylene (PTFE). The piston cup is assembled to a titanium component using eight fasteners and washers. Molded PTFE produced for spare piston cups in the first quarter of 2010 was different in appearance and texture, and softer than material molded for previous cups. For the suspect newer PTFE material, cup fasteners were tightened to only one-half the required torque value, yet the washers embedded almost halfway into the material. The molded PTFE used in the DA piston cup should be Type II, based on AMS 3667D and ASTM D4894 specifications. The properties of molded PTFE are considerably different between Type I and II materials. Engineers working with the DA thought that if Type I PTFE was molded by mistake instead of Type II material, that could have resulted in the anomalous material properties. Typically, the vendor molds flat sheet PTFE from the same material lot used to mold the piston cups, and tensile testing as part of quality control should verify that the PTFE is Type II material. However, for this discrepant lot of material, such tensile data was not available. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were two of the testing techniques used at the NASA/Marshall Space Flight Center (MSFC) to investigate the anomaly for the PTFE material. Other techniques used on PTFE specimens were: Shore D hardness testing, tensile testing on dog bone specimens and a qualitative estimation of porosity by optical and scanning electron microscopy.

  1. Electrochemical, Polarization, and Crevice Corrosion Testing of Nitinol 60, A Supplement to the ECLSS Sustaining Materials Compatibility Study

    Science.gov (United States)

    Lee, R. E.

    2016-01-01

    In earlier trials, electrochemical test results were presented for six noble metals evaluated in test solutions representative of waste liquids processed in the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). Subsequently, a seventh metal, Nitinol 60, was added for evaluation and subjected to the same test routines, data analysis, and theoretical methodologies. The previous six test metals included three titanium grades, (commercially pure, 6Al-4V alloy and 6Al-4V low interstitial alloy), two nickel-chromium alloys (Inconel(RegisteredTrademark) 625 and Hastelloy(RegisteredTrademark) C276), and one high-tier stainless steel (Cronidur(RegisteredTrademark) 30). The three titanium alloys gave the best results of all the metals, indicating superior corrosive nobility and galvanic protection properties. For this current effort, the results have clearly shown that Nitinol 60 is almost as noble as titanium, being very corrosion-resistant and galvanically compatible with the other six metals electrochemically and during long-term exposure. is also quite noble as it is very corrosion resistant and galvanically compatible with the other six metals from both an electrochemical perspective and long-term crevice corrosion scenario. This was clearly demonstrated utilizing the same techniques for linear, Tafel and cyclic polarization, and galvanic coupling of the metal candidate as was done for the previous study. The high nobility and low corrosion susceptibility for Nitinol 60 appear to be intermediate to the nickel/chromium alloys and the titanium metals with indications that are more reflective of the titanium metals in terms of general corrosion and pitting behavior.

  2. Changes in the tribological behavior of an epoxy resin by incorporating CuO nanoparticles and PTFE microparticles

    DEFF Research Database (Denmark)

    Larsen, Thomas Ricco Ølholm; Andersen, Tom Løgstrup; Thorning, Bent

    2008-01-01

    by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which show a relatively good dispersion of both kinds of particles. Differential scanning calorimetry (DSC) and Vickers hardness measurements show no clear changes in glass transition temperature or hardness as a function...... of the composites using a smoother counterface. This gives rise to significantly less wear, which for composites without PTFE is attributed to formation of a protective transfer film. At a pv condition of 1.16 MPa, 1.0 m1s the following is found: composites without PTFE generally show an unsteady behavior with high...

  3. Clinical impact and risk stratification of balloon angioplasty for femoropopliteal disease in nitinol stenting era: Retrospective multicenter study using propensity score matching analysis

    Directory of Open Access Journals (Sweden)

    Taketsugu Tsuchiya

    2016-07-01

    Full Text Available Objective: Nitinol stenting could bring the better outcome in endovascular therapy for femoropopliteal disease. However, it might be expected that recent marked advances in both device technology and operator technique had led to improved efficacy of balloon angioplasty even in this segment. The aims of this study were to evaluate the clinical impact of balloon angioplasty for femoropopliteal disease and make risk stratification clear by propensity score matching analysis. Methods: Based on the multicenter retrospective data, 2758 patients (balloon angioplasty: 729 patients and nitinol stenting: 2029 patients, those who underwent endovascular therapy for femoropopliteal disease, were analyzed. Results: The propensity score matching procedure extracted a total of 572 cases per group, and the primary patency rate of balloon angioplasty and nitinol stenting groups after matching was significantly the same (77.2% vs 82.7% at 1 year; 62.2% vs 64.3% at 3 years; 47.8% vs 54.3% at 5 years. In multivariate Cox hazard regression analysis, significant predictors for primary patency were diabetes mellitus, regular dialysis, cilostazol use, chronic total occlusion, and intra-vascular ultra-sonography use. The strategy of balloon angioplasty was not evaluated as a significant predictor for the primary patency. After risk stratification using five items (diabetes mellitus, regular dialysis, no use of intra-vascular ultra-sonography, chronic total occlusion, and no use of cilostazol: the DDICC score, the estimated primary patency rates of each group (low, DDICC score 0–2; moderate, DDICC score 3; high risk, DDICC score 4–5 were 88.6%, 78.3%, and 63.5% at 1 year; 75.2%, 60.7%, and 39.8% at 3 years; and 66.0%, 47.1%, and 26.3% at 5 years (p < 0.0001. The primary patency rate of balloon angioplasty and nitinol stenting groups was significantly the same in each risk stratification. Conclusion: This study suggests that balloon angioplasty does

  4. Effect of biologically active coating on biocompatibility of Nitinol devices designed for the closure of intra-atrial communications

    NARCIS (Netherlands)

    Kong, XQ; Grabitz, RG; van Oeveren, W; Klee, D; van Kooten, TG; Freudenthal, F; Qing, M; von Bernuth, G; Seghaye, MC

    Anti-thrombogenicity and rapid endothelialisation are prerequisites for the use of closure devices of intra-atrial communications in order to reduce the risk of cerebral embolism. The purpose of this study was therefore to assess the effect of bioactive coatings on biocompatibility of Nitinol coils

  5. Modeling the constitutive and frictional behavior of PTFE flexible stamps for nanoimprint lithography

    DEFF Research Database (Denmark)

    Sonne, Mads Rostgaard; Hattel, Jesper Henri

    2013-01-01

    was verified through an experiment, where a PTFE sheet was deformed by a steel sphere mounted in a tensile test machine. Good agreement between simulations and experimental results is found, both regarding force–displacement and corresponding principal strain measurements. As expected, applying the correct...

  6. Biomedical engineering in design and application of nitinol stents with shape memory effect

    Science.gov (United States)

    Ryklina, E. P.; Khmelevskaya, I. Y.; Morozova, Tamara V.; Prokoshkin, S. D.

    1996-04-01

    Our studies in the field of endosurgery in collaboration with the physicians of the National Research Center of Surgery of the Academy of Medical Sciences are carried out beginning in 1983. These studies laid the foundation for the new direction of X-ray surgery--X-ray Nitinol stenting of vessels and tubular structures. X-ray nitinol stents are unique self-fixing shells based on the shape memory effect and superelasticity of nickel-titanium alloys self- reconstructed under human body temperature. Applied for stenting of arteries in cases of stenosis etc., bile ducts in cases of benign and malignant stenoses, digestive tract in cases of oesophageal cancer and cervical canal uterus in cases of postsurgical atresiss and strictures of uterine. The purpose of stenting is restoration of the shape of artery or tubular structure by a cylinder frame formation. The especially elaborated original method of stenting allows to avoid the traditional surgical operation, i.e. the stenting is performed without blood, narcosis and surgical knife. The stent to be implanted is transported into the affected zone through the puncture under the X-ray control. Clinical applications of X-ray endovascular stenting has been started in March 1984. During this period nearly 400 operations on stenting have been performed on femoral, iliac, brachio-cephalic, subclavian arteries, bile ducts, tracheas, digestive tract and cervical canal uterus.

  7. Nitinol Embolic Protection Filters: Design Investigation by Finite Element Analysis

    Science.gov (United States)

    Conti, Michele; de Beule, Matthieu; Mortier, Peter; van Loo, Denis; Verdonck, Pascal; Vermassen, Frank; Segers, Patrick; Auricchio, Ferdinando; Verhegghe, Benedict

    2009-08-01

    The widespread acceptance of carotid artery stenting (CAS) to treat carotid artery stenosis and its effectiveness compared with surgical counterpart, carotid endarterectomy (CEA), is still a matter of debate. Transient or permanent neurological deficits may develop in patients undergoing CAS due to distal embolization or hemodynamic changes. Design, development, and usage of embolic protection devices (EPDs), such as embolic protection filters, appear to have a significant impact on the success of CAS. Unfortunately, some drawbacks, such as filtering failure, inability to cross tortuous high-grade stenoses, malpositioning and vessel injury, still remain and require design improvement. Currently, many different designs of such devices are available on the rapidly growing dedicated market. In spite of such a growing commercial interest, there is a significant need for design tools as well as for careful engineering investigations and design analyses of such nitinol devices. The present study aims to investigate the embolic protection filter design by finite element analysis. We first developed a parametrical computer-aided design model of an embolic filter based on micro-CT scans of the Angioguard™ XP (Cordis Endovascular, FL) EPD by means of the open source pyFormex software. Subsequently, we used the finite element method to simulate the deployment of the nitinol filter as it exits the delivery sheath. Comparison of the simulations with micro-CT images of the real device exiting the catheter showed excellent correspondence with our simulations. Finally, we evaluated circumferential basket-vessel wall apposition of a 4 mm size filter in a straight vessel of different sizes and shape. We conclude that the proposed methodology offers a useful tool to evaluate and to compare current or new designs of EPDs. Further simulations will investigate vessel wall apposition in a realistic tortuous anatomy.

  8. Preliminary study of blood compatibility of PTFE copolymerized with DMAA through gamma rays compared to PET and aflon films

    International Nuclear Information System (INIS)

    Queiroz, A.A.A. de; Higa, O.Z.

    1990-01-01

    The new method developed by Imai and Nosa was used for the evaluation of blood compatibility of poly(tetrafluoroethylene) (PTFE) grafted films with N,N - dimethylacrylamide (DMAA). The amount of the formed thrombus was measured gravimetrically at an appropriate interval of time after calcium chloride being added to the ACD blood in contact to the tested material. It was concluded that the method of modifying the polymeric surface of PTFE by grafting the hydrophilic monomer DMAA improved its blood compatibility. (author)

  9. Removal of retrievable self-expandable urethral stents: experience in 58 stents

    International Nuclear Information System (INIS)

    Shin, Ji Hoon; Song, Ho-Young; Kim, Jin Hyoung; Ko, Heung-Kyu; Kim, Yong Jae; Woo, Chul-Woong; Kim, Tae-Hyung; Ko, Gi-Young; Yoon, Hyun-Ki; Sung, Kyu-Bo; Park, Hyungkeun

    2006-01-01

    The purpose of this study was to retrospectively evaluate the safety and efficacy of removing retrievable self-expandable urethral stents using a retrieval hook wire. Under fluoroscopic guidance, the removal of 58 polyurethane or PTFE (polytetrafluoroethylene)-covered stents was attempted in 33 patients using a retrieval hook wire. Indications for removal were elective removal (n=21), stent migration (n=19), formation of tissue hyperplasia around or inside of the stent (n=14), stent deformity (n=3), and severe pain (n=1). The mean time the stents remained in place was 64.8±42.9 days (range, 1-177 days). Fifty-six (97%) of the 58 stents were successfully removed using the retrieval hook wire despite the following difficulties; hook wire disconnection (n=2), untied drawstrings (n=3), and polyurethane membrane disruption/separation (n=4). The removal procedure using a retrieval hook wire failed in two stents (3%) which had migrated into the urinary bladder. One of the two stents with migration into the urinary bladder was removed using a snare through the cystostomy route. The overall complication rate was 14% (seven hematuria cases and one urethral tear case), and all were minor and spontaneously resolved without further treatment. In conclusion, removal of retrievable urethral stents using a retrieval hook wire was safe and effective despite some technical difficulties. It is a useful method for allowing temporary stent placement and solving various complications of stent use. (orig.)

  10. Removal of retrievable self-expandable urethral stents: experience in 58 stents

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Ji Hoon; Song, Ho-Young; Kim, Jin Hyoung; Ko, Heung-Kyu; Kim, Yong Jae; Woo, Chul-Woong; Kim, Tae-Hyung; Ko, Gi-Young; Yoon, Hyun-Ki; Sung, Kyu-Bo [Asan Medical Center, Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Seoul (Korea); Park, Hyungkeun [Asan Medical Center, Department of Urology, University of Ulsan College of Medicine, Seoul (Korea)

    2006-09-15

    The purpose of this study was to retrospectively evaluate the safety and efficacy of removing retrievable self-expandable urethral stents using a retrieval hook wire. Under fluoroscopic guidance, the removal of 58 polyurethane or PTFE (polytetrafluoroethylene)-covered stents was attempted in 33 patients using a retrieval hook wire. Indications for removal were elective removal (n=21), stent migration (n=19), formation of tissue hyperplasia around or inside of the stent (n=14), stent deformity (n=3), and severe pain (n=1). The mean time the stents remained in place was 64.8{+-}42.9 days (range, 1-177 days). Fifty-six (97%) of the 58 stents were successfully removed using the retrieval hook wire despite the following difficulties; hook wire disconnection (n=2), untied drawstrings (n=3), and polyurethane membrane disruption/separation (n=4). The removal procedure using a retrieval hook wire failed in two stents (3%) which had migrated into the urinary bladder. One of the two stents with migration into the urinary bladder was removed using a snare through the cystostomy route. The overall complication rate was 14% (seven hematuria cases and one urethral tear case), and all were minor and spontaneously resolved without further treatment. In conclusion, removal of retrievable urethral stents using a retrieval hook wire was safe and effective despite some technical difficulties. It is a useful method for allowing temporary stent placement and solving various complications of stent use. (orig.)

  11. The Effect of Various Quenchants on the Hardness and Microstructure of 60-NITINOL

    Science.gov (United States)

    Thomas, Fransua

    2015-01-01

    The effect of various quenching media on the hardness and microstructure of 60 NITINOL (60 NiTi) were evaluated. Specimens of 60 NiTi were heat treated in air at 1000 degC for 30 min or 2 hr, then quench cooled by one of seven different methods. The microstructure and hardness of this material was examined post heat treatment. The results indicated that the quench method had little effect on the resulting hardness and microstructure of 60 NiTi.

  12. Characterization of the early pulmonary inflammatory response associated with PTFE fume exposure

    Science.gov (United States)

    Johnston, C. J.; Finkelstein, J. N.; Gelein, R.; Baggs, R.; Oberdorster, G.; Clarkson, T. W. (Principal Investigator)

    1996-01-01

    Heating of polytetrafluoroethylene (PTFE) has been described to release fumes containing ultrafine particles (approximately 18 nm diam). These fumes can be highly toxic in the respiratory tract inducing extensive pulmonary edema with hemorrhagic inflammation. Fischer-344 rats were exposed to PTFE fumes generated by temperatures ranging from 450 to 460 degrees C for 15 min at an exposure concentration of 5 x 10(5) particles/cm3, equivalent to approximately 50 micrograms/m3. Responses were examined 4 hr post-treatment when these rats demonstrated 60-85% neutrophils (PMNs) in their lung lavage. Increases in abundance for messages encoding the antioxidants manganese superoxide dismutase and metallothionein (MT) increased 15- and 40-fold, respectively. For messages encoding the pro- and anti-inflammatory cytokines: inducible nitric oxide synthase, interleukin 1 alpha, 1 beta, and 6 (IL-1 alpha, IL-1 beta, and IL-6), macrophage inflammatory protein-2, and tumor necrosis factor-alpha (TNF alpha) increases of 5-, 5-, 10-, 40-, 40-, and 15-fold were present. Vascular endothelial growth factor, which may play a role in the integrity of the endothelial barrier, was decreased to 20% of controls. In situ sections were hybridized with 33P cRNA probes encoding IL-6, MT, surfactant protein C, and TNF alpha. Increased mRNA abundance for MT and IL-6 was expressed around all airways and interstitial regions with MT and IL-6 demonstrating similar spatial distribution. Large numbers of activated PMNs expressed IL-6, MT, and TNF alpha. Additionally, pulmonary macrophages and epithelial cells were actively involved. These observations support the notion that PTFE fumes containing ultrafine particles initiate a severe inflammatory response at low inhaled particle mass concentrations, which is suggestive of an oxidative injury. Furthermore, PMNs may actively regulate the inflammatory process through cytokine and antioxidant expression.

  13. Use of PTFE patch for pericardial closure after minimal invasive LVAD implantation.

    Science.gov (United States)

    Mohite, Prashant N; Sabashnikov, Anton; Popov, Aron F; Fatullayev, Javid; Simon, André R

    2016-07-01

    The left ventricular assist device (LVAD) is now a routine therapy for advanced heart failure. The thoracotomy approach for LVAD implantation, in which the left ventricle is approached through a pericardial rent, is becoming popular. We demonstrate closure of the pericardial rent with a polytetrafluoroethylene (PTFE) patch and its advantages. © The Author(s) 2015.

  14. Sulfonation of cPTFE Film grafted Styrene for Proton Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Yohan Yohan

    2010-10-01

    Full Text Available Sulfonation of γ-ray iradiated and styrene-grafted crosslinked polytetrafluoroethylene film (cPTFE-g-S film have been done. The aim of the research is to make hydropyl membrane as proton exchange membrane fuel cell. Sulfonation was prepared with chlorosulfonic acid in chloroethane under various conditions. The impact of the percent of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film is examinated. The results show that sulfonation of surface-grafted films is incomplete at room  temperature. The increasing of concentration of chlorosulfonic acid and reaction temperature accelerates the reaction but they also add favor side reactions. These will lead to decreasing of the ion-exchange capacity, water uptake, and proton conductivity but increasing the resistance to oxidation in a perhidrol solution. The cPTFE-g-SS membrane which is resulted has stability in a H2O2 30% solution for 20 hours.

  15. Pan-nitinol occluder and special delivery device for closure of patent ductus arteriosus: a canine-model feasibility study.

    Science.gov (United States)

    Jiang, Hai-bin; Bai, Yuan; Zong, Gang-jun; Han, Lin; Li, Wei-ping; Lu, Yang; Qin, Yong-wen; Zhao, Xian-xian

    2013-01-01

    The aim of this study was to evaluate a new type of occluder for patent ductus arteriosus. Patent ductus arteriosus was established in a canine model by anastomosing a length of autologous jugular vein to the descending aorta and the left pulmonary artery in an end-to-side fashion. Transcatheter closure of each patent ductus arteriosus was performed on 10 dogs, which were then monitored for as long as 6 months with aortography, echocardiography, and histologic evaluation. Transcatheter closure with use of the novel pan-nitinol device was successful in all canine models. Postoperative echocardiography showed that the location and shape of the occluders were normal, without any residual shunting. Further histologic evaluation confirmed that the occluder surface was completely endothelialized 3 months after implantation. Transcatheter patent ductus arteriosus closure with the pan-nitinol occluder can be performed safely and successfully in a canine model and shows good biological compatibility and low mortality rates.

  16. Novel phosphate-grafted ePTFE copolymers for optimum in vitro mineralization

    International Nuclear Information System (INIS)

    Wentrup-Byrne, Edeline; Suzuki, Shuko; Groendahl, Lisbeth; Suwanasilp, Juthakarn Jessica

    2010-01-01

    Surface modification via graft copolymerization is an attractive method for optimizing polymers used in biomedical applications. We developed a novel method using a mixed solvent system (either water and dichloromethane (DCM) or water, methanol and DCM) consisting of two solvent phases for grafting 2-(methacryloyloxy)ethyl phosphate onto expanded polytetrafluoroethylene (ePTFE). This new method resulted in the fabrication of grafted membranes with greater grafting extents (GEs) (as evaluated from x-ray photoelectron spectroscopy (XPS)) in the organic phase than those obtained when grafting was carried out in a single phase. It also made it possible to graft in the aqueous phase, a process that is otherwise inhibited by the concomitant formation of large amounts of highly crystalline homopolymer. Thorough characterization of the grafted membranes using gravimetric, XPS and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) not only permitted evaluation of the grafting outcomes but also made it possible to analyze their dependence on monomer concentration and solvent composition. A selection of membranes was tested for their in vitro mineralization capacity using simulated body fluid. It was found that an 'ideal' mineralization outcome, i.e. a uniform coating of carbonated hydroxyapatite (cHAP) formed on the sample grafted in the aqueous phase of the water/DCM two-phase solvent system. A detailed discussion bringing together these results, as well as results from a series of earlier studies, allows conclusions regarding polymer chemistry and the topology necessary for cHAP mineralization.

  17. Multi-institutional Evaluation of Upper Urinary Tract Biopsy Using Backloaded Cup Biopsy Forceps, a Nitinol Basket, and Standard Cup Biopsy Forceps.

    Science.gov (United States)

    Lama, Daniel J; Safiullah, Shoaib; Patel, Roshan M; Lee, Thomas K; Balani, Jyoti P; Zhang, Lishi; Okhunov, Zhamshid; Margulis, Vitaly; Savage, Stephen J; Uchio, Edward; Landman, Jaime

    2018-04-06

    To compare the performance of 3 contemporary ureteroscopic biopsy devices for the histopathologic diagnosis of upper tract urothelial carcinoma (UTUC). We retrospectively reviewed 145 patients who underwent 182 urothelial biopsies using 2.4F backloaded cup biopsy forceps, a nitinol basket, or 3F standard cup biopsy forceps at 3 tertiary academic centers between 2011 and 2016. Experienced genitourinary pathologists provided an assessment of each specimen without knowledge of the device used for biopsy. For patients who underwent nephroureterectomy without neoadjuvant chemotherapy within 3 months of biopsy-proven UTUC diagnosis, the biopsy grade was compared with both the grade and stage of the surgical specimen. Biopsy utilization varied among the 3 institutions (P cup forceps was rated similarly to the nitinol basket (P >.05) and was favored over standard cup forceps specimens. Grade concordance was not affected by specimen size (P >.05), morphology (P >.1), or location (P >.5). No difference existed among the devices in the rate of acquiring a grade concordant biopsy; however, the backloaded cup forceps provided concordant biopsies that could be distinguished as low- and high-grade (P = .02). The backloaded cup forceps and nitinol basket obtained a higher quality urothelial specimen compared with standard cup forceps. Ureteroscopic biopsy device selection did not significantly impact the accuracy of the histologic diagnosis of UTUC. Copyright © 2018 Elsevier Inc. All rights reserved.

  18. Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film

    International Nuclear Information System (INIS)

    Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N.

    2007-01-01

    The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films

  19. Characterization of the personal thermoluminescent dosemeter of LiF: Mg, Ti + Ptfe

    International Nuclear Information System (INIS)

    Azorin N, J.; Gutierrez C, A.; Gonzalez M, P.

    1991-01-01

    The objective of this work is to characterize the thermoluminescent dosemeters taken place in the laboratory in form of pellets of LiF: Mg, Ti + Ptfe like personal dosemeters, subjecting them to the operation tests proposed by the international standards and comparing them with the TLD-100, the Tl dosemeter more used at the moment for personal dosimetry

  20. Full covered self-expandable metal stents for the treatment of anastomotic leak using a silk thread.

    Science.gov (United States)

    Choi, Cheol Woong; Kang, Dae Hwan; Kim, Hyung Wook; Park, Su Bum; Kim, Su Jin; Hwang, Sun Hwi; Lee, Si Hak

    2017-07-01

    To evaluate the safety and effectiveness of fixation of the fully covered self-expandable metal stent (SEMS) placement using a silk thread for complete closure of an anastomotic leak. An anastomotic leak is a life-threatening complication after gastrectomy. Although the traditional treatment of choice was surgical re-intervention, an endoscopic SEMS can be used alternatively.During the study period, we retrospectively reviewed consecutive patients who received a modified covered SEMS capable of being fixed using a silk thread (Shim technique) due to an anastomotic leak after gastrectomy to prevent stent migration. Demographic data, stent placement and removal, clinical success, time to resolution, and complications were evaluated.A total of 7 patients underwent fully covered SEMS with a silk thread placement for an anastomotic leak after gastrectomy to treat gastric cancer. The patients' mean age was 71.3 ± 8.0 years. Man sex was predominant (85.7%). All patients' American Society of Anesthesiologists (ASA) scores were between I and III. Total gastrectomy was performed in 5 patients (71.4%) and proximal gastrectomy was performed in 2 patients (28.6%). The time between gastrectomy and stent insertion was 22.3 ± 11.1 days. The size of the leaks was 27.1 ± 11.1 mm. Technical success and complete leak closure were achieved in all patients. Stent migration was absent. All stents were removed between 4 and 6 weeks. Delayed esophageal stricture was found in 1 patient (14.2) and successfully resolved after endoscopic balloon dilation.For an anastomotic leak after gastrectomy, fully covered SEMS placement with a silk thread is an effective and safe treatment option without stent migration. The stent extraction time between 4 and 6 weeks was optimal without severe complications.

  1. Oversizing and Restenosis with Self-Expanding Stents in Iliofemoral Arteries

    International Nuclear Information System (INIS)

    Saguner, Ardan M.; Traupe, Tobias; Räber, Lorenz; Hess, Nina; Banz, Yara; Saguner, Arhan R.; Diehm, Nicolas; Hess, Otto M.

    2012-01-01

    Purpose: Uncoated self-expanding nitinol stents (NS) are commonly oversized in peripheral arteries. In current practice, 1-mm oversizing is recommended. Yet, oversizing of NS may be associated with increased restenosis. To provide further evidence, NS were implanted in porcine iliofemoral arteries with a stent-to-artery-ratio between 1.0 and 2.3. Besides conventional uncoated NS, a novel self-expanding NS with an antiproliferative titanium-nitride-oxide (TiNOX) coating was tested for safety and efficacy. Methods: Ten uncoated NS and six TiNOX-coated NS (5–6 mm) were implanted randomly in the iliofemoral artery of six mini-pigs. After implantation, quantitative angiography (QA) was performed for calculation of artery and minimal luminal diameter. Follow-up was performed by QA and histomorphometry after 5 months. Results: Stent migration, stent fracture, or thrombus formation were not observed. All stents were patent at follow-up. Based on the location of the stent (iliac/femoral) and the stent-to-artery-ratio, stent segments were divided into “normal-sized” (stent-to-artery-ratio < 1.4, n = 12) and “oversized” (stent-to-artery-ratio ≥ 1.4, n = 9). All stent segments expanded to their near nominal diameter during follow-up. Normal-sized stent segments increased their diameter by 6% and oversized segments by 29%. A significant correlation between oversizing and restenosis by both angiography and histomorphometry was observed. Restenosis rates were similar for uncoated NS and TiNOX-coated NS. Conclusions: TiNOX-coated NS are as safe and effective as uncoated NS in the porcine iliofemoral artery. All stents further expand to near their nominal diameter during follow-up. Oversizing is linearly and positively correlated with neointimal proliferation and restenosis, which may not be reduced by TiNOX-coating.

  2. Removal of I, Rn, Xe and Kr from off gas streams using PTFE membranes

    Science.gov (United States)

    Siemer, Darryl D.; Lewis, Leroy C.

    1990-01-01

    A process for removing I, R, Xe and Kr which involves the passage of the off gas stream through a tube-in-shell assembly, whereby the tubing is a PTFE membrane which permits the selective passages of the gases for removing and isolating the gases.

  3. Does patency after a vein collar and PTFE-bypass depend on sex and age?

    DEFF Research Database (Denmark)

    Lundgren, F; Schroeder, Torben Veith

    2012-01-01

    Randomized studies evaluating the effect of a vein collar at the distal anastomosis of PTFE-grafts show conflicting results. The study of the Joint Vascular Research Group (JVRG) of UK found improved primary patency while the Scandinavian Miller Collar Study (SCAMICOS) found neither any effect...

  4. Nitrogen and Fluorine co-doped carbon catalyst with high oxygen reduction performance, prepared by pyrolyzing a mixture of melamine and PTFE

    International Nuclear Information System (INIS)

    Peng, Hongliang; Liu, Fangfang; Qiao, Xiaochang; Xiong, Ziang; Li, Xiuhua; Shu, Ting; Liao, Shijun

    2015-01-01

    Graphical abstract: A novel N and F co-doped metal-free doped carbon catalyst with three dimensional vesicles structures and ultra thin walls are prepared by pyrolyzing the mixture of melamine and PTFE. The catalyst has high N and F contents (13 and 6 at.%), and exhibits high ORR activity, high stability, and high limitation current density in both alkaline and acid medium. - Highlights: • N and F co-doped carbon catalyst was derived from the mixture of PTFE and melamine. • The N and F contents of the catalyst are up to 13 and 6 at.%, respectively. • The catalyst has three dimensional vesicles structure with ultra thin walls. • ORR activity of the catalyst is superior to that of Pt/C catalyst in alkaline medium. - Abstract: A novel nitrogen and fluorine co-doped carbon catalyst (C-Mela-PTFE) is prepared by pyrolyzing a mixture of melamine and polytetrafluoroethylene (PTFE), the catalyst has a three-dimensional vesicular structure with ultrathin wall, and exhibits excellent ORR performance in both alkaline and acidic mediums. In an alkaline medium, the catalyst exhibits superior ORR activity to that of commercial Pt/C catalyst. Notably, the ORR activity of the catalyst is just slightly lower than that of Pt/C catalyst in acidic medium. It is interesting that the ORR limiting current density of our C-Mela-PTFE catalyst is much higher than that of Pt/C catalyst. The effects of the melamine/PTFE ratio and the pyrolysis temperature on the catalyst's ORR performance are investigated. The optimal melamine/PTFE ratio by weight is 1:1.5, and the optimal pyrolysis temperature is 950 °C. The catalyst samples are characterized by XRD, SEM/TEM, Raman analysis, and XPS, the results reveal the ultra-thin-walled vesicular structure, high surface area and porosity, and high doping amounts of N and F of the catalyst. For the optimal sample, the N and F contents are up to 13 and 6 at.%, respectively, the proportion of pyridinic N is up to 45 at.% according to the

  5. Wireless implantable chip with integrated nitinol-based pump for radio-controlled local drug delivery.

    Science.gov (United States)

    Fong, Jeffrey; Xiao, Zhiming; Takahata, Kenichi

    2015-02-21

    We demonstrate an active, implantable drug delivery device embedded with a microfluidic pump that is driven by a radio-controlled actuator for temporal drug delivery. The polyimide-packaged 10 × 10 × 2 mm(3) chip contains a micromachined pump chamber and check valves of Parylene C to force the release of the drug from a 76 μL reservoir by wirelessly activating the actuator using external radio-frequency (RF) electromagnetic fields. The rectangular-shaped spiral-coil actuator based on nitinol, a biocompatible shape-memory alloy, is developed to perform cantilever-like actuation for pumping operation. The nitinol-coil actuator itself forms a passive 185 MHz resonant circuit that serves as a self-heat source activated via RF power transfer to enable frequency-selective actuation and pumping. Experimental wireless operation of fabricated prototypes shows successful release of test agents from the devices placed in liquid and excited by radiating tuned RF fields with an output power of 1.1 W. These tests reveal a single release volume of 219 nL, suggesting a device's capacity of ~350 individual ejections of drug from its reservoir. The thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants.

  6. BRONZ KATKILI POLİ-TETRA-FLOR-ETİLEN (PTFE) KOMPOZİTLERİN PASLANMAZ ÇELİK MALZEMEYE KARŞI AŞINMA VE SÜRTÜNME DAVRANIŞLARI

    OpenAIRE

    Ünal, Hüseyin; Yetkin, Salih Hakan; Poyraz, Bayram

    2018-01-01

    Bu deneysel çalışmada, katkısızpoli-tetra-flor-etilen (PTFE) polimeri ile %25 bronz katkılı PTFE kompoziti ve%40 bronz katkılı PTFE kompozitlerin, kuru kayma şartları altında paslanmazçelik malzemeye karşı tribolojik performansları incelenmiştir. Tribolojiktestler, pim-disk aşınma cihazında ve oda sıcaklığında gerçekleştirilmiştir.Aşınma ve sürtünme testleri, 50N, 100N ve 150N yüklerde ve 1.0, 1.5 ve 2.0m/skayma hızlarında yapılmıştır. Aşınma test sonuçlarına göre, %40 bronz katkılıPTFE kompo...

  7. The Measurement and Interpretation of Transformation Temperatures in Nitinol

    Science.gov (United States)

    Duerig, T. W.; Pelton, A. R.; Bhattacharya, K.

    2017-12-01

    A previous paper (Duerig and Bhattacharya in Shap Mem Superelasticity 1:153-161, 2015) introduced several engineering considerations surrounding the R-phase in Nitinol and highlighted a common, if not pervasive, misconception regarding the use of the term Af by the medical device industry. This paper brings additional data to bear on the issue and proposes more accurate terminology. Moreover, a variety of tools are used to establish the forward and reverse stress-temperature phase diagrams for a superelastic wire typical of that used in medical devices. Once established, the two most common methods of measuring transformation temperatures, Differential Scanning Calorimetry and Bend Free Recovery, are tested against the observed behavior. Light is also shed upon the origin of the Clausius-Clapeyron ratio (d σ/d T), the triple point, and why such large variations are reported in superelastic alloys.

  8. Ridge Preservation Comparing a Nonresorbable PTFE Membrane to a Resorbable Collagen Membrane: A Clinical and Histologic Study in Humans.

    Science.gov (United States)

    Arbab, Hussain; Greenwell, Henry; Hill, Margaret; Morton, Dean; Vidal, Ricardo; Shumway, Brian; Allan, Nicholas D

    2016-02-01

    The primary aim of this randomized, controlled, blinded clinical trial was to compare the effect of a resorbable collagen membrane (CM group) versus a nonresorbable high-density polytetrafluoroethylene membrane (PTFE group) on the clinical and histologic outcomes of a ridge preservation procedure. All 24 sites received an intrasocket cancellous allograft and a buccal overlay bovine derived xenograft. The change in horizontal crestal ridge width was -1.4 ± 1.2 mm for the CM group, whereas the PTFE group lost -2.2 ± 1.5 mm, which was not statistically significant between groups (P > 0.05). Vertical ridge height change was -1.2 ± 1.5 for the CM group, whereas the PTFE group lost -0.5 ± 1.6, which was not significantly different between groups (P > 0.05). The percent vital bone was similar and not significantly different between groups. Primary closure was not obtained and the exposed membrane portion over the socket opening healed with keratinized tissue. The choice of a resorbable versus a nonresorbable barrier membrane did not affect the clinical or the histologic outcome of ridge preservation treatment.

  9. Proton/gamma relative thermoluminescence efficiencies of LiF:Mg,Cu,P+PTFE prepared at ININ and TLD-100H

    International Nuclear Information System (INIS)

    Avila, O.; Gonzalez, P.; Murillo, G.

    2009-10-01

    Properties of LiF:Mg,Cu,P+PTFE dosemeters developed at ININ have been investigated in order to evaluate their performance compared to those of equivalent commercial dosemeters. In this work both LiF:Mg,Cu,P+PTFE and TLD-100H pellets were exposed to low fluence 3 MeV protons and to low dose gamma radiation to evaluate experimental proton/gamma efficiencies. Gamma irradiation was performed using the Vic krad irradiator at ININ at varying doses between 25 and 500 mGy. For proton irradiation the Tandem Van de Graaff accelerator at ININ was used. Dosemeters were placed on a holder inside a scattering chamber where protons impinge on a gold target and scatter in all directions. The holder allows for several angular positions so that dosemeters receive proton fluence between 10 6 and 10 1 0 p/cm 2 . Experimental efficiency values found for LiF:Mg,Cu,P+PTFE and TLD-100H were 0.18 +- 03 and 0.23 +- 0.03, respectively. These results allow to confirm the reliability of the dosemeters developed at ININ. (Author)

  10. Filtration of Oil-furnace Carbon Black Dust Particles from the Tail Gases by Filter Bags With PTFE Membrane

    Directory of Open Access Journals (Sweden)

    Čuzela, D.

    2010-01-01

    Full Text Available During the industrial production of oil furnace carbon black, tail gases containing oil-furnace carbon black dust particles are emitted to the atmosphere. In the carbon black plant, Petrokemija d. d., there are six exhaust stacks for tail gases. Each of them has installed process equipment for cleaning tail gases. Efficiency of cleaning mainly depends on equipment construction and cleaning technology. The vicinity of the town, quality of the air in the region of Kutina, regarding floating particles PM10, and corporate responsibility for further enviromental improvement, imposes development of new methods that will decrease the emmision of oil-furnace carbon black dust particles in the air. Combining centrifugal percipitator and filter, special construction of cyclofilter for filtration of oil-furnace carbon black dust particles from tail gases by using PTFE (polytetrafluoroethylene membrane filter bags, was designed. Developed filtration technique provides η = 99.9 % efficiency of filtration. Construction part of the filter contains the newest generation of PTFE membrane filter bags with the ability of jet pulse cleaning. Using the PTFE membrane filter bags technology, filtration efficiency for oil-furnace carbon black dust particles in tail gases of maximum γ=5mgm-3can be achieved. The filtration efficiency was monitored continuously measuring the concentration of the oil-furnace carbon black dust particles in the tail gases with the help of in situ electronic probe. The accomplished filtration technology is the base for the installation of the PTFE membrane filter bags in the main operation filters which will provide better protection of the air in the town of Kutina against floating particles PM10.

  11. Plasma polymer films rf sputtered from PTFE under various argon pressures

    Czech Academy of Sciences Publication Activity Database

    Stelmashuk, Vitaliy; Biederman, H.; Slavinská, D.; Zemek, Josef; Trchová, Miroslava

    2005-01-01

    Roč. 77, č. 2 (2005), s. 131-137 ISSN 0042-207X R&D Projects: GA MŠk(CZ) OC 527.10; GA MŠk(CZ) OC 527.90 Grant - others:EUREKAΣ2080(XE) OE57 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z20430508 Keywords : RF sputtering * PTFE * fluorcarbon plasma polymers * thin film * teflon * deposition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.909, year: 2005

  12. Thermoluminescent response of CaSO{sub 4}: Dy + PTFE to beta particles; Respuesta termoluminiscente de CaSO{sub 4}: Dy + PTFE a particulas beta

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre C, A.; Azorin N, J. [Colegio de Bachilleres No. 13, Xochimilco-Tepepan, 16000 Mexico D.F. (Mexico)

    2000-07-01

    In this work the results of studying the thermoluminescent properties of CaSO{sub 4}: Dy + PTFE are presented when it is irradiated with beta particles. The conclusion was the obtention of the Tl response curve in function of dose is that to desexcite the dosemeters at temperature 300 C during 30 minutes and after that were irradiated at different times in groups and to do the reading of dosemeter, it can be observed that a greater irradiation time major is the Tl response and this depends of the material has been used. (Author)

  13. Investigation of PTFE transfer films by infrared emission spectroscopy and phase-locked ellipsometry

    Science.gov (United States)

    Lauer, James L.; Bunting, Bruce G.; Jones, William R., Jr.

    1988-01-01

    When a PTFE sheet was rubbed unidirectionally over a smooth surface of stainless steel an essentially monomolecular transfer film was formed. by ellipsometric and emission infrared spectroscopic techniques it was shown that the film was 10 to 15 A thick and birefringent. From the intensity differences of infrared bands obtained with a polarizer passing radiation polarized in mutually perpendicular planes, it was possible to deduce transfer film orientation with the direction of rubbing. After standing in air for several weeks the transfer films apparently increased in thickness by as much as threefold. At the same time both the index of refraction and the absorption index decreased. Examination of the surfaces by optical and electron microscopies showed that the films had become porous and flaky. These observations were consistent with previous tribological measurements. The coefficients of friction decreased with the formation of the transfer film but increased again as the film developed breaks. The applicability of the ellipsometric and polarized infrared emission techniques to the identification of monomolecular tribological transfer films of polymers such as PTFE has been demonstrated.

  14. ENHANCED HEALING OF 30-MU-M GORE-TEX PTFE MICROARTERIAL PROSTHESES BY ALCOHOL-PRETREATMENT

    NARCIS (Netherlands)

    VANDERLEI, B; STRONCK, JW; WILDEVUUR, CRH

    1991-01-01

    Polytetrafluoroethylene (PTFE) microvascular prostheses with a fibril length of 30-mu-m were pretreated with alcohol (n = 18), implanted into the abdominal aorta of rats and were evaluated at 1 day (n = 3), 1 week (n = 3), 3 weeks (n = 6) and 6 weeks (n = 6) to determine whether alcohol-pretreatment

  15. Thermal–Hydrodynamic Behaviour of Coated Pivoted Pad Thrust Bearings: Comparison between Babbitt, PTFE and DLC

    Directory of Open Access Journals (Sweden)

    Konstantinos Katsaros

    2018-05-01

    Full Text Available The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuity and Navier–Stokes equations, which are solved numerically with the Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC method. The analysis focuses on a single pivoted pad of the thrust bearing. The thermal properties of the coating material are taken into account and the resulting thermal and flow fields are solved. The basic hydrodynamic and tribological characteristics are calculated for an uncoated, a Babbitt coated, a PTFE coated and a diamond like carbon (DLC coated pivoted pad thrust bearing. The pressure and the film thickness distribution, as well as the load capacity and the frictional forces, are determined for several pad positions and velocities of the rotor. A mineral oil lubricant is used to estimate the shear thinning or thickening effects on the pad tribological performance. The results indicate that pads coated with PTFE and DLC show lower friction forces compared to the common steel and Babbitt applications. At the same time, the DLC coating seems to affect the bearing’s flow and thermal fields less than the PTFE, making it more suitable for thrust bearings applications.

  16. PTFE treatment by remote atmospheric Ar/O2 plasmas : a simple reaction scheme model proposal

    NARCIS (Netherlands)

    Carbone, E.A.D.; Verhoeven, M.W.G.M.; Keuning, W.; van der Mullen, J.J.A.M.

    2016-01-01

    Polytetrafluoroethylene (PTFE) samples were treated by a remote atmospheric pressure microwave plasma torch and analyzed by water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS). In the case of pure argon plasma a decrease of WCA is observed meanwhile an increase of hydrophobicity was

  17. Highly oriented thin films of a substituted oligo(para-phenylenevinylene) on friction-transferred PTFE substrates

    NARCIS (Netherlands)

    Gill, R.E; Hadziioannou, G; Lang, P.; Garnier, F.; Wittmann, J.C.

    Communication: Highly oriented thin films of oligo(p-phenylenevinylene)s, oligoPPVs, provide information about the structure of polyPPV and structure-property relationships. It is shown that deposition of a substituted oligoPPV onto highly preoriented PTFE substrates leads to highly oriented thin

  18. Pt-Fe catalyst nanoparticles supported on single-wall carbon nanotubes: Direct synthesis and electrochemical performance for methanol oxidation

    Science.gov (United States)

    Ma, Xiaohui; Luo, Liqiang; Zhu, Limei; Yu, Liming; Sheng, Leimei; An, Kang; Ando, Yoshinori; Zhao, Xinluo

    2013-11-01

    Single-wall carbon nanotubes (SWCNTs) supported Pt-Fe nanoparticles have been prepared by one-step hydrogen arc discharge evaporation of carbon electrode containing both Pt and Fe metal elements. The formation of SWCNTs and Pt-Fe nanoparticles occur simultaneously during the evaporation process. High-temperature hydrogen treatment and hydrochloric acid soaking have been carried out to purify and activate those materials in order to obtain a new type of Pt-Fe/SWCNTs catalyst for methanol oxidation. The Pt-Fe/SWCNTs catalyst performs much higher electrocatalytic activity for methanol oxidation, better stability and better durability than a commercial Pt/C catalyst according to the electrochemical measurements, indicating that it has a great potential for applications in direct methanol fuel cells.

  19. SPIE 9639-49 Creation and Validation of Sintered PTFE BRDF Targets & Standards

    OpenAIRE

    Durell, Christopher; Scharpf, Dan; McKee, Greg; L’Heureux, Michelle; Georgiev, Georgi; Obein, Gael; Cooksey, Catherine

    2015-01-01

    Sintered polytetrafluoroethylene (PTFE) is an extremely stable, near-perfect Lambertian reflecting diffuser and calibration standard material that has been used by national labs, space, aerospace and commercial sectors for over two decades. New uncertainty targets of 2 % on-orbit absolute validation in the Earth Observing Systems community have challenged the industry to improve is characterization and knowledge of almost every aspect of radiometric performance (space and ground). Assuming “n...

  20. Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

    Science.gov (United States)

    Duman, M. S.; Kaplan, E.; Cuvalcı, O.

    2018-01-01

    The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

  1. Synthesis of a gamma irradiation grafted polytetrafluoroethylene (PTFE) based olefinic copolymer

    International Nuclear Information System (INIS)

    Ferreto, Helio Fernando Rodrigues

    2006-01-01

    The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as 'melt fracture' or 'sharkskin', which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect 'melt fracture'. (author)

  2. Superhydrophobic photocatalytic PTFE – Titania coatings deposited by reactive pDC magnetron sputtering from a blended powder target

    Energy Technology Data Exchange (ETDEWEB)

    Ratova, Marina, E-mail: marina_ratova@hotmail.com; Kelly, Peter J.; West, Glen T.

    2017-04-01

    The production of photocatalytic coatings with superhydrophobic properties, as opposed to the conventional hydrophilic properties, is desirable for the prevention of adhesion of contaminants to photocatalytic surfaces with subsequent deterioration of photocatalytic properties. In this work polytetrafluoroethylene (PTFE) – TiO{sub 2} composite thin films were deposited using a novel method of reactive pulsed direct current (pDC) magnetron sputtering of a blended PTFE – titanium oxide powder target. The surface characteristics and photocatalytic properties of the deposited composite coatings were studied. The as-deposited coatings were annealed at 523 K in air and analysed with Raman spectroscopy, optical profilometry and scanning electron microscopy. Hydrophobicity was assessed though measurements of water contact angles, and photocatalytic properties were studied via methylene blue dye degradation under UV irradiation. It was found that variations of gas flow and, hence, process pressures allowed deposition of samples combining superhydrophobicity with stable photocatalytic efficiency under UV light irradiation. Reversible wettability behaviour was observed with the alternation of light-dark cycles. - Highlights: • PTFE-TiO{sub 2} coatings were deposited by pDC reactive magnetron sputtering. • Blended powder target was used for coatings deposition. • Deposited coatings combined superhydrophobic and photocatalytic properties. • Under UV irradiation coatings exhibited reversible wettability.

  3. Performances of an expanding insect under elevated CO{sub 2} and snow cover in the Alps

    Energy Technology Data Exchange (ETDEWEB)

    Battisti, B.; Petrucco-Toffolo, E. [University of Padova, Legnaro (Italy). Dept. of Environmental Agronomy

    2008-09-30

    Variations of phenology and distribution have been recently highlighted in numerous insect species and attributed to climate change, particularly the increase of temperature and atmospheric carbon dioxide (CO{sub 2}). Both have been shown to have direct and indirect effects on insect species of various ecosystems, though the responses are often species-specific. The pine processionary moth, Thaumetopoea pityocampa (Lepidoptera, Notodontidae) is an important pest of conifers in the Mediterranean region, and has been recently shown to expand its altitudinal range in the Alps, including the mountain pine Pinus mugo as a novel host. We had the opportunity to transplant colonies of the pine processionary moth to a high elevation site well outside of the current range of the insect (Stillberg, Davos, Switzerland, 2180 m), where trees of the mountain pine have been grown for five years under ambient and elevated CO{sub 2} concentrations (ca. 570 ppm). The aim of the study was to evaluate the response of first instar larvae to extreme conditions of temperature and to an altered performance induced by the change of host metabolism under elevated CO{sub 2}. Larval mortality and relative growth rate did not differ between host trees grown in ambient or elevated CO{sub 2}. As extended snow cover may be an important mortality factor of larval colonies on the dwarf trees of mountain pine, we tested the survival of colonies transplanted at two extreme sites of Eastern Alps. The snow cover extended over more than one month proved to be an important mortality factor of larval colonies on mountain pine. We concluded that the first instar larvae of the pine processionary moth are not concerned by unusually low temperature and CO{sub 2} increase whereas they can be later strongly affected by snow accumulation. The decrease of snow cover observed in the last decades, however, may reduce such a risk.

  4. Electrostatic Properties of PE and PTFE Subjected to Atmospheric Pressure Plasma Treatment; Correlation of Experimental Results with Atomistic Modeling

    Science.gov (United States)

    Trigwell, Steve; Boucher, Derrick; Calle, Carlos

    2006-01-01

    The use of an atmospheric pressure glow discharge (APGD) plasma was used at KSC to increase the hydrophilicity of spaceport materials to enhance their surface charge dissipation and prevent possible ESD in spaceport operations. Significant decreases in charge decay times were observed after tribocharging the materials using the standard KSC tribocharging test. The polarity and amount of charge transferred was dependent upon the effective work function differences between the respective materials. In this study, polyethylene (PE) and polytetrafluoroethylene (PTFE) were exposed to a He+O2 APGD. The pre and post treatment surface chemistry was analyzed by X-ray photoelectron spectroscopy and contact angle measurements. Semi-empirical and ab initio calculations were performed to correlate the experimental results with some plausible molecular and electronic structure features of the oxidation process. For the PE, significant surface oxidation was observed, as indicated by XPS showing C-O, C=O, and O-C=O bonding, and a decrease in the surface contact angle from 98.9 deg to 61.2 deg. For the PTFE, no C-O bonding appeared and the surface contact angle increased indicating the APGD only succeeded in cleaning the PTFE surface without affecting the surface structure. The calculations using the PM3 and DFT methods were performed on single and multiple oligomers to simulate a wide variety of oxidation scenarios. Calculated work function results suggest that regardless of oxidation mechanism, e.g. -OH, =0 or a combination thereof, the experimentally observed levels of surface oxidation are unlikely to lead to a significant change in the electronic structure of PE and that its increased hydrophilic properties are the primary reason for the observed changes in its electrostatic behavior. The calculations for PTFE argue strongly against significant oxidation of that material, as confirmed by the XPS results.

  5. Effectiveness and Safety of Endoscopic Treatment of Benign Biliary Strictures Using a New Fully Covered Self Expandable Metal Stent

    Directory of Open Access Journals (Sweden)

    Mihir S. Wagh

    2013-01-01

    Full Text Available Background. In patients with benign biliary strictures, the use of fully covered self-expandable metal stents (SEMS has been proposed as an alternative to plastic stenting, but high quality prospective data are sparse. This study was performed to evaluate the long-term effectiveness and safety of a new fully covered SEMS for benign biliary strictures. Methods. All consecutive patients with benign biliary strictures were treated with placement of a fully covered SEMS (WallFlex for 6 months. Short- and long-term stricture resolution, adverse events, and ease of stent removal were recorded. Results. 23 patients were enrolled. Stricture etiology was chronic pancreatitis (14, postorthotopic liver transplant (4, idiopathic (4, and biliary stones (1. All ERCPs were technically successful. All stents were successfully removed. Short-term stricture resolution was seen in 22/23 (96% patients. Long-term success was 15/18 (83.3%. All 3 failures were patients with biliary strictures in the setting of chronic calcific pancreatitis. Conclusions. The use of the new SEMS for the treatment of benign biliary strictures led to short-term stricture resolution in the vast majority of patients. Over a long-term followup the success rate appears favorable compared to historical results achieved with multiple plastic stenting, particularly in patients with chronic pancreatitis. The study was registered with ClinicalTrials.gov (NCT01238900.

  6. On the potential for fibronectin/phosphorylcholine coatings on PTFE substrates to jointly modulate endothelial cell adhesion and hemocompatibility properties.

    Science.gov (United States)

    Montaño-Machado, Vanessa; Chevallier, Pascale; Mantovani, Diego; Pauthe, Emmanuel

    2015-01-01

    The use of biomolecules as coatings on biomaterials is recognized to constitute a promising approach to modulate the biological response of the host. In this work, we propose a coating composed by 2 biomolecules susceptible to provide complementary properties for cardiovascular applications: fibronectin (FN) to enhance endothelialization, and phosphorylcholine (PRC) for its non thrombogenic properties. Polytetrafluoroethylene (PTFE) was selected as model substrate mainly because it is largely used in cardiovascular applications. Two approaches were investigated: 1) a sequential adsorption of the 2 biomolecules and 2) an adsorption of the protein followed by the grafting of phosphorylcholine via chemical activation. All coatings were characterized by immunofluorescence staining, X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy analyses. Assays with endothelial cells showed improvement on cell adhesion, spreading and metabolic activity on FN-PRC coatings compared with the uncoated PTFE. Platelets adhesion and activation were both reduced on the coated surfaces when compared with uncoated PTFE. Moreover, clotting time tests exhibited better hemocompatibility properties of the surfaces after a sequential adsorption of FN and PRC. In conclusion, FN-PRC coating improves cell adhesion and non-thrombogenic properties, thus revealing a certain potential for the development of this combined deposition strategy in cardiovascular applications.

  7. Improved results of the vacuum assisted closure and Nitinol clips sternal closure after postoperative deep sternal wound infection.

    Science.gov (United States)

    Tocco, Maria Pia; Costantino, Alberto; Ballardini, Milva; D'Andrea, Claudio; Masala, Marcello; Merico, Eusebio; Mosillo, Luigi; Sordini, Paolo

    2009-05-01

    Postoperative deep sternal wound infection is a severe complication of cardiac surgery, with a high mortality rate and a high morbidity rate. The objective of this prospective study is to report our experience with the vacuum assisted closure (VAC) system for the management of deep wound infection. We also devised an innovative closure technique post VAC therapy using thermo reactive clips. The advantage of this technique is that the posterior face of the sternum does not have to be separated from the mediastinal structures thus minimising the risk of damage. From October 2006 to October 2008, we prospectively evaluated 21 patients affected by mediastinitis after sternotomy. Nineteen patients had sternotomy for coronary artery bypass grafting (CABG), one patient for aortic valve replacement (AVR) and another one for ascending aortic replacement (AAR). All patients were treated with the VAC system at the time of infection diagnosis. When the wound tissue appeared viable and the microbiological cultures were negative, the chest was closed using the most suitable procedure for the patient in question; nine patients were closed using pectoralis flaps, nine patients using Nitinol clips, one patient with a combined technique (use of Nitinol clips and muscle flap), one patient with a direct wound closure and another patient, who needed AAR with a homograft performed in another institution, was closed using sternal wires. We had no mortality; wound healing was successfully achieved in all patients. In more than 50% of the patients, the VAC therapy allowed direct sternal resynthesis. The average duration of the vacuum therapy was 26 days (range 14-37 days). VAC is a safe and effective option in the treatment of post-sternotomy mediastinitis, with excellent survival and immediate improvement of local wound conditions; furthermore, the use of Nitinol clips after VAC therapy demonstrated to be a safe and non-invasive option for sternal resynthesis. After VAC therapy, a

  8. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Gotman, Irena, E-mail: gotman@technion.ac.il; Gutmanas, Elazar Y., E-mail: gutmanas@technion.ac.il [Department of Materials Science and Engineering, Techion-Israel Institute of Technology, Haifa, 32000 Israel (Israel); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Zaretzky, Asaph [The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096 Israel (Israel); Psakhie, Sergey G. [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength “trabecular Nitinol” scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1–1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  9. Thermoluminescent response of CaSO4: Dy + PTFE to beta particles

    International Nuclear Information System (INIS)

    Aguirre C, A.; Azorin N, J.

    2000-01-01

    In this work the results of studying the thermoluminescent properties of CaSO 4 : Dy + PTFE are presented when it is irradiated with beta particles. The conclusion was the obtention of the Tl response curve in function of dose is that to desexcite the dosemeters at temperature 300 C during 30 minutes and after that were irradiated at different times in groups and to do the reading of dosemeter, it can be observed that a greater irradiation time major is the Tl response and this depends of the material has been used. (Author)

  10. A new self-expandable aortic valved stent deployed above native leaflets for aortic insufficiency: an in vitro study.

    Science.gov (United States)

    Huang, H; Zhou, Y; Shao, J; Cai, J; Mei, Y; Wang, Y

    2012-12-01

    The aim of this paper was to develop a new self-expandable aortic valved stent following the shape of the sinus of Valsalva, which can be deployed above native leaflets for aortic regurgitation, and study it's effect on coronary artery flow when orthotopic implantation in and above native leaflets. New self-expandable aortic valved stent consist of nitinol stent and bovine pericardium, and was designed following the shape of the sinus of Valsalva, the bovine pericardium was tailed as native leaflet. Thirty-six swine hearts were divided into three equal groups of twelve. In Group A (N.=12), the new self-expandable aortic valved stents deployed in native leaflets. In Group B (N.=12), the new self-expandable aortic valved stents deployed above native leaflets. In Group C (N.=12), the cylinder-like valved stents deployed only in native leaflets. The measurements of each coronary flow rate and endoscopic inspections were repeated post-implantation. In Group A and C, valve implantation in native leaflets resulted in a significant decrease in both left and right coronary flows. In Group B, no significant change in either right or left coronary flow was found after new self-expandable aortic valved stent placement. Endoscopic inspections showed that in group A and C the native leaflets sandwiched between valved stent and aortic wall, whereas, in group B the native leaflets were under the artificial leaflets. Two kinds of stents deployed in native leaflets affect left and right coronary flows significantly. No significant effect was found when the new self-expandable aortic valved stent deployed above native leaflets. This new self-expandable aortic valved stent can be deployed above the native leaflets, which avoids the obstruction of native leaflets on coronary flow.

  11. Efficacy and safety of a new fully covered self-expandable non-foreshortening metal esophageal stent.

    Science.gov (United States)

    Dua, Kulwinder S; Latif, Sahibzada U; Yang, Juliana F; Fang, Tom C; Khan, Abdul; Oh, Young

    2014-10-01

    Fully covered esophageal self-expandable metal stents (SEMSs) are potentially removable but can be associated with high migration rates. For precise positioning, non-foreshortening SEMSs are preferred. Recently, a new fully covered non-foreshortening SEMS with anti-migration features was introduced. To evaluate the efficacy and safety of this new esophageal SEMS. Retrospective study. Single, tertiary-care center. Consecutive patients with malignant and benign strictures with dysphagia grade of ≥3 and patients with fistulas/leaks were studied. Stent placement and removal. Technical success in stent deployment/removal, efficacy in relieving dysphagia and sealing fistulas/leaks, and adverse events. Forty-three stents were placed in 35 patients (mean [± standard deviation] age 65 ± 11 years; 31 male), 24 for malignant and 11 for benign (5 strictures, 6 leaks) indications. Technical success in precise SEMS placement was 100%. The after-stent dysphagia grade improved significantly (at 1 week: 1.5 ± 0.7; at 4 weeks: 1.2 ± 0.4; baseline: 3.8 ± 0.4; P stents were removed for clinical indications, with technical success of 100%. All leaks sealed after SEMS placement and did not recur after stent removal. All benign strictures recurred after stent removal. Adverse events included migration (14%), chest pain (11%), and dysphagia from tissue hyperplasia (6%). There was no stent-related mortality. Nonrandomized, single-center study. The new esophageal SEMS was effective in relieving malignant dysphagia, allowed for precise placement, and was easily removable. It was effective in treating benign esophageal fistulas and leaks. Stent-related adverse events were acceptable. Copyright © 2014 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.

  12. How to increase the hydrophobicity of PTFE surfaces using an r.f. atmospheric-pressure plasma torch

    NARCIS (Netherlands)

    Carbone, E.A.D.; Boucher, N.; Sferrazza, M.; Reniers, F.

    2010-01-01

    An experimental investigation of the surface modification of polytetrafluoroethylene (PTFE) by an Ar and Ar/O2 plasma created with an atmospheric-pressure radio frequency (r.f.) torch is presented here. The surfaces were analyzed by atomic force microscopy (AFM), XPS and water contact angle (WCA) to

  13. Scenarios of land cover in China

    Science.gov (United States)

    Yue, Tian Xiang; Fan, Ze Meng; Liu, Ji Yuan

    2007-02-01

    A method for surface modeling of land cover change (SMLC) is developed on the basis of establishing transition probability matrixes between land cover types and HLZ types. SMLC is used to simulate land cover scenarios of China for the years 2039, 2069 and 2099, for which HLZ scenarios are first simulated in terms of HadCM3 climatic scenarios that are downscaled in zonal model of spatial climate change in China. This paper also analyzes spatial distribution of land cover types, area change and mean center shift of each land cover type, ecotope diversity, and patch connectivity under the land cover scenarios. The results show that cultivated land would decrease and woodland would expand greatly with climatic change, which coincides with consequences expected by implementation of Grain-for-Green policy. Nival area would shrink, and desertification area would expand at a comparatively slow rate in future 100 years. Climate change would generally cause less ecotope diversity and more patch connectivity. Ecosystems in China would have a pattern of beneficial cycle after efficient ecological conservation and restoration. However, if human activities would exceed regulation capacity of ecosystems themselves, the ecosystems in China might deteriorate more seriously.

  14. Immobilization of Ochrobactrum tritici As5 on PTFE thin films for arsenite biofiltration.

    Science.gov (United States)

    Branco, Rita; Sousa, Tânia; Piedade, Ana P; Morais, Paula V

    2016-03-01

    Ochrobactrum tritici SCII24T bacteria is an environmental strain with high capacity to resist to arsenic (As) toxicity, which makes it able to grow in the presence of As(III). The inactivation of the two functional arsenite efflux pumps, ArsB and ACR3_1, resulted in the mutant O. tritici As5 exhibiting a high accumulation of arsenite. This work describes a method for the immobilization of the mutant cells O. tritici As5, on a commercial polymeric net after sputtered modified by the deposition of poly(tetrafluoroethylene) (PTFE) thin films, and demonstrates the capacity of immobilized cells to accumulate arsenic from solutions. Six different set of deposition parameters for PTFE thin films were developed and tested in vitro regarding their ability to immobilize the bacterial cells. The surface that exhibited a mild zeta potential value, hydrophobic characteristics, the lowest surface free energy but with a high polar component and the appropriate ratio of chemical reactive groups allowed cells to proliferate and to grow as a biofilm. These immobilized cells maintained their ability to accumulate the surrounding arsenite, making it a great arsenic biofilter to be used in bioremediation processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Lamp system with conditioned water coolant and diffuse reflector of polytetrafluorethylene(PTFE)

    Science.gov (United States)

    Zapata, Luis E.; Hackel, Lloyd

    1999-01-01

    A lamp system with a very soft high-intensity output is provided over a large area by water cooling a long-arc lamp inside a diffuse reflector of polytetrafluorethylene (PTFE) and titanium dioxide (TiO.sub.2) white pigment. The water is kept clean and pure by a one micron particulate filter and an activated charcoal/ultraviolet irradiation system that circulates and de-ionizes and biologically sterilizes the coolant water at all times, even when the long-arc lamp is off.

  16. Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

    Science.gov (United States)

    Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

    2018-01-01

    Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 ( D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 ( D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 ( x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant ( ɛ r > 7.19) and extremely low moisture absorption (ceramic particles served as barriers and improved the thermal stability of the PTFE polymer, retarding its decomposition. The temperature coefficient of dielectric constant ( τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

  17. Mechanical properties and the evolution of matrix molecules in PTFE upon irradiation with MeV alpha particles

    International Nuclear Information System (INIS)

    Fisher, Gregory L.; Lakis, Rollin E.; Davis, Charles C.; Szakal, Christopher; Swadener, John G.; Wetteland, Christopher J.; Winograd, Nicholas

    2006-01-01

    The morphology, chemical composition, and mechanical properties in the surface region of α-irradiated polytetrafluoroethylene (PTFE) have been examined and compared to unirradiated specimens. Samples were irradiated with 5.5 MeV 4 He 2+ ions from a tandem accelerator to doses between 1 x 10 6 and 5 x 10 10 Rad. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), using a 20 keV C 60 + source, was employed to probe chemical changes as a function of α dose. Chemical images and high resolution spectra were collected and analyzed to reveal the effects of α particle radiation on the chemical structure. Residual gas analysis (RGA) was utilized to monitor the evolution of volatile species during vacuum irradiation of the samples. Scanning electron microscopy (SEM) was used to observe the morphological variation of samples with increasing α particle dose, and nanoindentation was engaged to determine the hardness and elastic modulus as a function of α dose. The data show that PTFE nominally retains its innate chemical structure and morphology at α doses 9 Rad. At α doses ≥10 9 Rad the polymer matrix experiences increased chemical degradation and morphological roughening which are accompanied by increased hardness and declining elasticity. At α doses >10 10 Rad the polymer matrix suffers severe chemical degradation and material loss. Chemical degradation is observed in ToF-SIMS by detection of ions that are indicative of fragmentation, unsaturation, and functionalization of molecules in the PTFE matrix. The mass spectra also expose the subtle trends of crosslinking within the α-irradiated polymer matrix. ToF-SIMS images support the assertion that chemical degradation is the result of α particle irradiation and show morphological roughening of the sample with increased α dose. High resolution SEM images more clearly illustrate the morphological roughening and the mass loss that accompanies high doses of α particles. RGA confirms the supposition that

  18. Covered self-expandable metallic stent placement for a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer

    International Nuclear Information System (INIS)

    Lee, Woon Ha; Jung, Gyoo Sik; Kim, Kyu Jong; Lee, Sang Ho; Ko, Ji Ho; Jeong, Kyung Soon

    2007-01-01

    To evaluate the technical feasibility and clinical effectiveness of stent placement for the treatment of a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer. Under fluoroscopic guidance, one or two covered stents were placed in 20 consecutive patients (age range, 44-75 years) with an anastomotic stricture due to a recurrent gastric malignancy. Before stent placement, all patients had severe nausea and recurrent vomiting after ingestion. Stent placement was technically successful for all patients, and no procedural complications occurred. After stent placement, 18 of 20 (90.0%) patients were able to ingest at least a liquid diet and had a markedly decreased incidence of vomiting. During the follow-up of 2-116 weeks (mean, 25.5 weeks), stent migration occurred in two patients (10.0%) on one day after the procedure. All patients with stent migration were treated successfully by means of placing a second stent. Three patients showed a recurrence of the stricture due to tumor overgrowth; two of the patients were treated with coaxial placement of a second stent. Another patient refused additional management. Covered self-expandable metallic stent placement seems to be technically feasible and effective for palliative treatment of a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer

  19. Covered self-expandable metallic stent placement for a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Woon Ha; Jung, Gyoo Sik; Kim, Kyu Jong; Lee, Sang Ho [Gospel Hospital, College of Medicine, Kosin University, Busan (Korea, Republic of); Ko, Ji Ho [Masan Samsung Medical Center, Sungkyunkwan University School of University, Masan (Korea, Republic of); Jeong, Kyung Soon [University of Ulsan Colleg of Medicine, Asan Medical Center, Seoul (Korea, Republic of)

    2007-09-15

    To evaluate the technical feasibility and clinical effectiveness of stent placement for the treatment of a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer. Under fluoroscopic guidance, one or two covered stents were placed in 20 consecutive patients (age range, 44-75 years) with an anastomotic stricture due to a recurrent gastric malignancy. Before stent placement, all patients had severe nausea and recurrent vomiting after ingestion. Stent placement was technically successful for all patients, and no procedural complications occurred. After stent placement, 18 of 20 (90.0%) patients were able to ingest at least a liquid diet and had a markedly decreased incidence of vomiting. During the follow-up of 2-116 weeks (mean, 25.5 weeks), stent migration occurred in two patients (10.0%) on one day after the procedure. All patients with stent migration were treated successfully by means of placing a second stent. Three patients showed a recurrence of the stricture due to tumor overgrowth; two of the patients were treated with coaxial placement of a second stent. Another patient refused additional management. Covered self-expandable metallic stent placement seems to be technically feasible and effective for palliative treatment of a post-operative malignant anastomotic stricture secondary to recurrent gastric cancer.

  20. Histopathological changes in the human larynx following expanded polytetrafluroethylene (Gore-Tex® implantation

    Directory of Open Access Journals (Sweden)

    Sheffield E

    2005-01-01

    Full Text Available Abstract Background Expanded polytetrafluroethelyne (e PTFE, Gore-Tex® has been advocated as an implant material for medialization of the vocal fold. Animal studies involving rabbits and a porcine model have demonstrated host tolerance of the implant. There have been no reports describing the histological changes in a human laryngectomy specimen with a Gore-Tex implant. Case presentation The histological findings in a laryngectomy specimen of a patient previously implanted with e PTFE for medialization of a paralyzed vocal fold following excision of a vagal neurofibroma were studied. Histopathology revealed a mild foreign-body giant cell granulomatous reaction with some associated fibrosis. The granulomatous response was limited to the periphery of the Gore-Tex and although it closely followed the profile of the material it did not encroach into or significantly break up the material. There was no significant neutrophilic or lymphocytic inflammation. Conclusions Our findings are consistent with the animal models confirming that Gore-Tex implantation does not result in a significant granulomatous reaction in the human larynx over a 13-month period. Moreover, there is no evidence of resorption or infection. Further, the lack of lymphocytes in association with the granulomas indicates that there is no significant immunological hypersensitivity. Histologically, the slight permeation by connective tissue is similar to that seen in Gore-Tex vascular and cardiac implants. The degree of the slight giant cell response appears to be dependent on the profile of the material; a sharp edge incited more of a response than a flat surface.

  1. Determination of the parameters of traps in thermoluminescent dosemeters of ZrO2: Eu + Ptfe

    International Nuclear Information System (INIS)

    Nieto H, B.; Azorin N, J.; Rivera M, T.

    2002-01-01

    In this work the manufacture of dosemeters in pellets form of ZrO 2 : Eu + Ptfe is described; which after were exposed to UV radiation (260 nm) were generated the corresponding thermoluminescent curves and in the basis to the properties of symmetry of the curves it was determined the kinetic order using the Chen and the Balarin criteria. (Author)

  2. Evaluation of the small intestinal submucosa covered stent in preventing restenosis after percutaneous transluminal angioplasty in the swine

    International Nuclear Information System (INIS)

    Wang Xiaobai; Li Jinglei; Zhang Hong; Zhang Yan

    2012-01-01

    Objective: To compare the performance of small intestinal submucosa (SIS)-covered endografts (SCEs) to bare nitinol stents (BSs) in injured swine iliac arteries. Materials and methods: Twenty-eight nitinol stents were used: 14 externally SCEs and 14 BSs. Devices were implanted in each side of balloon-injured external iliac arteries of 14 swine via carotid approach. Arteriograms were obtained before and after implantation and before animal sacrifice at 4, 8, and 12 weeks. Histopathological and electron microscopy studies of explanted specimens were performed. Results: Implantation of all SCEs and BSs was technically successful, but one SCE and one BS were obstructed at 8 weeks after implantation. At sacrifice, the other 26 stents were patent, with angiogram showing no significant different luminal narrowing between SCEs and BSs. Proliferating cell nuclear antigen (PCNA) immunohistochemistry examination revealed that the percentage of PCNA(+) cells were lower in SCEs (p < 0.05). Additionally, histomorphological analysis indicated that the neointima area and percentage of narrowing area were greater in SCEs, but there was no statistical significance. Greater endothelial cell count in SCEs than in BSs per visual field at 4000 times magnification by scanning electron microscope (p < 0.05). Conclusion: Compared to BSs, no definite decrease of neointima and restenosis was found in SCEs in the present study. However, it is effective in promoting endothelial regeneration and strengthening endothelial function.

  3. Fully covered stents versus partially covered stents for palliative treatment of esophageal cancer: Is there a difference?

    Science.gov (United States)

    Alonso Lárraga, J O; Flores Carmona, D Y; Hernández Guerrero, A; Ramírez Solís, M E; de la Mora Levy, J G; Sánchez Del Monte, J C

    2018-02-26

    Malignant dysphagia is difficulty swallowing resulting from esophageal obstruction due to cancer. The goal of palliative treatment is to reduce the dysphagia and improve oral dietary intake. Self-expandable metallic stents are the current treatment of choice, given that they enable the immediate restoration of oral intake. The aim of the present study was to describe the results of using totally covered and partially covered esophageal stents for palliating esophageal cancer. A retrospective study was conducted on patients with inoperable esophageal cancer treated with self-expandable metallic stents. The 2 groups formed were: group A, which consisted of patients with a fully covered self-expandable stent (SX-ELLA ® ), and group B, which was made up of patients with a partially covered self-expandable stent (Ultraflex ® ). Of the 69-patient total, 50 were included in the study. Group A had 19 men and 2 women and their mean age was 63.6 years (range 41-84). Technical success was achieved in 100% (n=21) of the cases and clinical success in 90.4% (n=19). Group B had 24 men and 5 women and their mean age was 67.5 years (range 43-92). Technical success was achieved in 100% (n=29) of the cases and clinical success in 89.6% (n=26). Complications were similar in both groups (33.3 vs. 51.7%). There was no difference between the 2 types of stent for the palliative treatment of esophageal cancer with respect to technical success, clinical success, or complications. Copyright © 2018 Asociación Mexicana de Gastroenterología. Publicado por Masson Doyma México S.A. All rights reserved.

  4. Tl response of LiF: Mg, Cu, P+Ptfe at X rays of 24, 42 and 100 KeV; Respuesta TL de LiF: Mg, Cu, P+Ptfe a rayos X de 24, 42 y 100 KeV

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez M, P.R.; Tovar M, V.M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Azorin N, J. [UAM-I, 09340 Mexico D.F. (Mexico); Furetta, C. [Universita degli Studi di Roma ' La Sapienza' , Piazzale Aldo Moro 2, 00185 Roma (Italy); Quiroz C, M.C. [Facultad de Medicina, UAEM, 50180 Toluca, Estado de Mexico (Mexico)

    2005-07-01

    In this work the obtained results of the irradiation of thermoluminescent dosemeters (Tl) of LiF: Mg,Cu,P + Ptfe with X rays for the effective radiation energy of 24, 42 and 100 keV, in an interval of Kerma in air in the sinus of the air between 0.05 and 1.0 Gy are presented. The rate of Kerma in air was determined with an ionization chamber PTW-1152, gauged by the Laboratoire Central des Industries Electriques (LCIE). As reference commercial TLD-100 dosemeters was used. The results showed that the studied Tl dosemeters presented a lineal response in the interval of mentioned Kerma. On the other hand the estimated Kerma with the Tl dosemeter in the calibration curves for X rays, were similar to the one measured with the previously gauged ionization chamber. The Tl of LiF: Mg, Cu, P + Ptfe, developed in the ININ, are highly reliable for X-ray dosimetry. (Author)

  5. The use of macro and micro proton beams to study the variation in PIXE yield from metal targets insulated with PTFE, glass and nylon

    International Nuclear Information System (INIS)

    Pillay, A.E.

    1999-01-01

    Proton beams of diameters of 3 mm and 3 μm, were used to observe the differences in PIXE yield from pure metal targets encapsulated with PTFE, glass (macor) and nylon. The beam energy was kept constant at 700 keV. Beam currents varied from about 200 pA with the microbeam and between 1-10 nA with the macrobeam. Considerable enhancement was observed mainly with the use of PTFE, up to about a factor of 18 with the macrobeam and 306 with the microbeam. (author)

  6. The Effect of Hydroxyapatite Coatings on the Passivation Behavior of Oxidized and Unoxidized Superelastic Nitinol Alloys

    Science.gov (United States)

    Etminanfar, M. R.; Khalil-Allafi, J.; Sheykholeslami, S. O. R.

    2018-02-01

    Nitinol alloys have been used in various biological applications due to their superior properties. In this study, a bipolar pulsed current electrodeposition technique was applied to produce a hydroxyapatite (HA) film on the Nitinol alloy. Also, the protection performance of the coating was evaluated on both abraded and thermochemically modified alloy. According to obtained data, reducing the electrocrystallization rate by the pulse deposition technique can promote HA formation on both abraded and modified substrates. Based on scanning electron microscopy and high-resolution transmission electron microscopy data, the HA coatings revealed a flake-like morphology and each flake was composed of nano-crystalline grains. Atomic force microscopy images revealed that flakes on the abraded substrate were smaller in size than that of the modified alloy. Comparing the corrosion resistance of the bare substrates revealed that the modified alloy has a higher corrosion resistance than the abraded alloy and the modified surface is well passivized during anodic polarization in Ringer's solution. However, this condition is reversed after the deposition of HA film. It seems that because of the lower crystallization sites on the abraded alloy, the produced HA film is denser and more protective against the corrosive mediums as compared to the coating on the modified alloy. Although the HA coating can improve the bioactivity of both substrates, the resulted film on the oxidized alloy is porous and deteriorates the implant permanence in the vicinity of body fluids.

  7. Endoscopic removal of laser-cut covered self-expandable metallic biliary stents: A report of six cases.

    Science.gov (United States)

    Tanisaka, Yuki; Ryozawa, Shomei; Kobayashi, Masanori; Harada, Maiko; Kobatake, Tsutomu; Omiya, Kumiko; Iwano, Hirotoshi; Arai, Shin; Nonaka, Kouichi; Mashimo, Yumi

    2018-02-01

    Covered self-expandable metallic stents (CSEMS) may provide palliative drainage for unresectable distal malignant biliary strictures. Laser-cut CSEMS allows easy positioning due to its characteristic of minimal stent shortening. Endoscopic stent removal is sometimes recommended for recurrent biliary obstruction (RBO). However, there are no previous reports of endoscopic removal of laser-cut CSEMS. The current study presents data from 6 patients who were placed a laser-cut CSEMS for unresectable distal malignant biliary strictures, and later endoscopic stent removal was attempted for RBO at the present institute. The duration of stent placement, the procedural success rate, the procedural duration, and accidental complications were evaluated. The mean duration of stent placement was 156±37.9 days (range, 117-205). The procedural success rate was 100%. The mean procedural duration was 11.8±7.5 min (range, 5-24). No complications were reported. Laser-cut CSEMS were safely removed from all patients. The present case report is the first to demonstrate that Endoscopic stent removal of laser-cut CSEMS was safely performed.

  8. Airborne nanoparticle concentrations in the manufacturing of polytetrafluoroethylene (PTFE) apparel.

    Science.gov (United States)

    Vosburgh, Donna J H; Boysen, Dane A; Oleson, Jacob J; Peters, Thomas M

    2011-03-01

    One form of waterproof, breathable apparel is manufactured from polytetrafluoroethylene (PTFE) membrane laminated fabric using a specific process to seal seams that have been sewn with traditional techniques. The sealing process involves applying waterproof tape to the seam by feeding the seam through two rollers while applying hot air (600 °C). This study addressed the potential for exposure to particulate matter from this sealing process by characterizing airborne particles in a facility that produces more than 1000 lightweight PTFE rain jackets per day. Aerosol concentrations throughout the facility were mapped, breathing zone concentrations were measured, and hoods used to ventilate the seam sealing operation were evaluated. The geometric mean (GM) particle number concentrations were substantially greater in the sewing and sealing areas (67,000 and 188,000 particles cm⁻³)) compared with that measured in the office area (12,100 particles cm⁻³). Respirable mass concentrations were negligible throughout the facility (GM = 0.002 mg m⁻³) in the sewing and sealing areas). The particles exiting the final discharge of the facility's ventilation system were dominated by nanoparticles (number median diameter = 25 nm; geometric standard deviation of 1.39). The breathing zone particle number concentrations of the workers who sealed the sewn seams were highly variable and significantly greater when sealing seams than when conducting other tasks (p < 0.0001). The sealing workers' breathing zone concentrations ranged from 147,000 particles cm⁻³ to 798,000 particles cm⁻³, and their seam responsibility significantly influenced their breathing zone concentrations (p = 0.03). The finding that particle number concentrations were approximately equal outside the hood and inside the local exhaust duct indicated poor effectiveness of the canopy hoods used to ventilate sealing operations.

  9. Custom-made covered transjugular intrahepatic portosystemic shunt (TIPS) in an infant with trisomy 22 and biliary atresia

    International Nuclear Information System (INIS)

    Chlapoutaki, Chrysanthi Emmanouil; Franchi-Abella, Stephanie; Pariente, Daniele; Habes, Dalila

    2009-01-01

    We report an 8-month-old girl with portal hypertension secondary to biliary atresia. The decision to treat with TIPS was made at the age of 8 months due to recurrent variceal bleeding. The procedure was carried out with a 6-mm bare stent due to her small size. Radiological follow-up with Doppler US showed gradual stenosis and finally occlusion of the stent 80 days after implantation. Revision was performed with placement of an additional 6-mm expanded polytetrafluoroethylene (e-PTFE) stent-graft that had remained patent for 9 months, proving that in small children with a portal vein diameter less than 8 mm, the combination of a bare stent and stent-graft can provide excellent results. (orig.)

  10. Custom-made covered transjugular intrahepatic portosystemic shunt (TIPS) in an infant with trisomy 22 and biliary atresia

    Energy Technology Data Exchange (ETDEWEB)

    Chlapoutaki, Chrysanthi Emmanouil; Franchi-Abella, Stephanie; Pariente, Daniele [Bicetre Hospital University Paris XI, Assistance Publique Hopitaux de Paris, Department of Paediatric Radiology, Paris (France); Habes, Dalila [Bicetre Hospital University Paris XI, Assistance Publique Hopitaux de Paris, Pediatric Hepatology and National Reference Center for Biliary Atresia, Paris (France)

    2009-07-15

    We report an 8-month-old girl with portal hypertension secondary to biliary atresia. The decision to treat with TIPS was made at the age of 8 months due to recurrent variceal bleeding. The procedure was carried out with a 6-mm bare stent due to her small size. Radiological follow-up with Doppler US showed gradual stenosis and finally occlusion of the stent 80 days after implantation. Revision was performed with placement of an additional 6-mm expanded polytetrafluoroethylene (e-PTFE) stent-graft that had remained patent for 9 months, proving that in small children with a portal vein diameter less than 8 mm, the combination of a bare stent and stent-graft can provide excellent results. (orig.)

  11. Dosimetry of beta particles using Li:Mg, Cu, P + Ptfe

    International Nuclear Information System (INIS)

    Olvera, L.; Azorin, J.; Rivera, T.

    2003-01-01

    This paper presents the experimental results of determining the thermoluminescence (Tl) response of LiF: Mg, Cu, P + Ptfe pellets excited with 90 Sr/ 90 Y beta radiation. The glow curve exhibited three peaks which appear at 121 C, 178 C and 217 C . Its relative sensitivity is 49 with respect to that of the TLD-100 dosemeter taken as a reference. The minimal dose that could be measured was 750 mGy. The Tl response as a function of dose was linear in the range of 0.7 mGy to 22.5 mGy. The study of the repeatability of the information contained in the pellets showed a standard deviation of 2 %. (Author)

  12. PTFE Graft as a "Bridge" to Communicating Veins Maturation in the Treatment of an Intrahepatic Cholangiocarcinoma Involving the 3 Hepatic Veins. The Minor-but-Complex Liver Resection.

    Science.gov (United States)

    Urbani, Lucio; Balestri, Riccardo; Sidoti, Francesco; Bernardini, Juri Riccardo; Arces, Francesco; Licitra, Gabriella; Leoni, Chiara; Forfori, Francesco; Colombatto, Piero; Boraschi, Piero; Castagna, Maura; Buccianti, Piero

    2016-12-01

    Parenchyma-sparing liver surgery allows resecting hepatic veins (HV) at the hepatocaval confluence with minor (PTFE graft can be used as a bridge to communicating-veins maturation to ensure the correct outflow of the spared liver. We present a video of an intrahepatic cholangiocarcinoma (IC) involving the three HV at the hepatocaval confluence treated with this approach. In a 50-year old obese (BMI 44.8) male a 6-cm IC involving the hepatocaval confluence was identified during the follow-up for a kidney malignancy. At the preoperative CT scan the left HV was not detectable, the middle HV was incorporated within the tumor, and right HV had a 3-cm contact with the tumor. No communicating veins were evident at preoperative imaging. After a J-shape thoracophrenolaparotomy, the resection of segments II-III-IVa was partially extended to segment VIII-VII and I. The right HV was detached from the tumor, and the middle HV was reconstructed with a 7-mm ringed-armed PTFE graft anastomosed to V8. Surgery lasted 20 h and 55 min with an estimated blood loss of 3500 ml, but the postoperative course was uneventful and the patient was discharged on the 14th postoperative day. One month later the CT scan showed a patent PTFE graft with the maturation of communicating-veins. One year later a complete thrombosis of the PTFE graft was observed with normal liver perfusion and function, and the patient was disease-free. PTFE-based parenchyma-sparing liver resection is a new tool to treat tumors located at the hepatocaval confluence exploiting the maturation of intrahepatic communicating-veins between main HV.

  13. Tailoring Novel PTFE Surface Properties: Promoting Cell Adhesion and Antifouling Properties via a Wet Chemical Approach.

    Science.gov (United States)

    Gabriel, Matthias; Niederer, Kerstin; Becker, Marc; Raynaud, Christophe Michel; Vahl, Christian-Friedrich; Frey, Holger

    2016-05-18

    Many biomaterials used for tissue engineering applications lack cell-adhesiveness and, in addition, are prone to nonspecific adsorption of proteins. This is especially important for blood-contacting devices such as vascular grafts and valves where appropriate surface properties should inhibit the initial attachment of platelets and promote endothelial cell colonization. As a consequence, the long-term outcome of the implants would be improved and the need for anticoagulation therapy could be reduced or even abolished. Polytetrafluoroethylene (PTFE), a frequently used polymer for various medical applications, was wet-chemically activated and subsequently modified by grafting the endothelial cell (EC) specific peptide arginine-glutamic acid-aspartic acid-valine (REDV) using a bifunctional polyethylene glycol (PEG)-spacer (known to reduce platelet and nonspecific protein adhesion). Modified and control surfaces were both evaluated in terms of EC adhesion, colonization, and the attachment of platelets. In addition, samples underwent bacterial challenges. The results strongly suggested that PEG-mediated peptide immobilization renders PTFE an excellent substrate for cellular growth while simultaneously endowing the material with antifouling properties.

  14. Expanding Greenland’s Glacial Record

    DEFF Research Database (Denmark)

    Bjørk, Anders Anker

    . On order to expand the glacial history of Greenland, this thesis explores physical and geological archives for evidence of the glaciers’ past response to climatic variations. Using aerial photographs, the dynamic history of the Greenland Ice Sheet is extended back to 1900 C.E. Glacier changes covering...

  15. Thermoluminescent signal fading of encapsulated lif: Mg,Ti detectors in PTFE-Teflon registered trademark

    International Nuclear Information System (INIS)

    Sasho Nikolovski, Sasho; Nikolovska, Lidija; Velevska, Marija; Velev, Velko

    2010-01-01

    Fading is a process when the latent information of a detector is unintentionally lost mainly due to the thermal influence. Thermoluminescent (TL) detectors have different sensitivities as far as the fading effect. Encapsulated TL detectors mounted within shielded filter holders are used during the personal monitoring of occupationally exposed persons in R. Macedonia. PTFE-Teflon registered trademark polymer is an example of encapsulation material that has a temperature resistance and it allows the luminescence signal to pass through. Since the encapsulated TL detectors cannot be submitted to annealing treatment in an oven, another fading reduction method is needed. The TL evaluation method suggested in this work is based on a specific glow-curve region. Irradiations were conducted using 90Sr/90Y source. Post-irradiation fade investigations were conducted for evaluation periods that varied up to 4 months. Two areas of the TL glow-curve were selected with the WimRems software. They correspond to the high and the low fading emission peaks (the lower temperature peaks display a greater degree of thermal fading than the higher temperature peaks). Post-irradiation fade is a contributing factor that affects the response of a thermoluminescent (TL) phosphor as a function of time. PTFE - Polytetrafluoroethylene most well known by the DuPont brand name Teflon registered trademark. (Author)

  16. Effects of 108 Days Tritium Exposure on UHMW-PE, PTFE, and Vespel(R)

    International Nuclear Information System (INIS)

    Clark, E.A.

    2003-01-01

    Samples of three polymers, Ultra-High Molecular Weight Polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE), also known as Teflon(R), and Vespel(R) polyimide were exposed to 1 atmosphere of tritium gas at ambient temperature for 108 days. Sample mass and size measurements to calculate density, spectra-colorimetry, dynamic mechanical analysis (DMA), and Fourier-transform infrared spectroscopy (FT-IR) were employed to characterize the effects of this exposure on these samples. This technical report is the first report from this research program

  17. SELECTIVE HYDROGENATION OF CINNAMALDEHYDE WITH Pt AND Pt-Fe CATALYSTS: EFFECTS OF THE SUPPORT

    Directory of Open Access Journals (Sweden)

    A.B. da Silva

    1998-06-01

    Full Text Available Low-temperature reduced TiO2-supported Pt and Pt-Fe catalysts are much more active and selective for the liquid–phase hydrogenation of cinnamaldehyde to unsaturated cinnamyl alcohol than the corresponding carbon-supported catalysts. High-temperature reduced catalysts, where the SMSI effect should be present, are almost inactive for this reaction. There is at present no definitive explanation for this effect but an electronic metal-support interaction is most probably involved.

  18. Assessment of safety and efficacy of an indigenous self-expandable fully covered esophageal metal stent for palliation of esophageal cancer.

    Science.gov (United States)

    Padhan, R K; Nongthombam, S K; Venuthurimilli, A; Dhingra, R; Sahni, P; Garg, P K

    2016-01-01

    Patients with unresectable esophageal cancer require palliation for dysphagia. Placement of a self-expandable metal stent (SEMS) is the procedure of choice for palliation of dysphagia. To evaluate the safety and efficacy of an indigenous fully-covered SEMS in patients with esophageal cancer. Eligible patients with unresectable esophageal cancer requiring palliation for dysphagia were included in the study. An indigenous fully covered SEMS of appropriate length was placed under endoscopic and fluoroscopic guidance. Outcome measures assessed were adverse events and improvement in dysphagia. Twenty one patients (mean age 57.71±13.14 years; 17 males) were included. After stenting, dysphagia score decreased from 3.2+0.4 to 0.35+0.74 at 4 weeks. Adverse events included retrosternal pain, respiratory distress and aspiration pneumonia in 12, 2 and 1 patients respectively. Five patients required repeat stenting due to stent migration in 4 (following radiotherapy in 3) and tumour ingrowth in 1. There was primary stent malfunction in one patient. The median survival of patients was 140 (76-199) days, which was higher in those who received radiotherapy. The stent was reasonably safe and effective to relieve dysphagia due to unresectable esophageal cancer.

  19. Study of the Behavior of a Bell-Shaped Colonic Self-Expandable NiTi Stent under Peristaltic Movements

    Directory of Open Access Journals (Sweden)

    Sergio Puértolas

    2013-01-01

    Full Text Available Managing bowel obstruction produced by colon cancer requires an emergency intervention to patients usually in poor conditions, and it requires creating an intestinal stoma in most cases. Regardless of that the tumor may be resectable, a two-stage surgery is mandatory. To avoid these disadvantages, endoscopic placement of self-expanding stents has been introduced more than 10 years ago, as an alternative to relieve colonic obstruction. It can be used as a bridge to elective single-stage surgery avoiding a stoma or as a definitive palliative solution in patients with irresectable tumor or poor estimated survival. Stents must be capable of exerting an adequate radial pressure on the stenosed wall, keeping in mind that stent must not move or be crushed, guaranteeing an adequate lumen when affected by peristaltic waves. A finite element simulation of bell-shaped nitinol stent functionality has been done. Catheter introduction, releasing at position, and the effect of peristaltic wave were simulated. To check the reliability of the simulation, a clinical experimentation with porcine specimens was carried out. The stent presented a good deployment and flexibility. Stent behavior was excellent, expanding from the very narrow lumen corresponding to the maximum peristaltic pressure to the complete recovery of operative lumen when the pressure disappears.

  20. Ignition of PTFE-lined flexible hoses by rapid pressurization with oxygen

    Science.gov (United States)

    Janoff, Dwight; Bamford, Larry J.; Newton, Barry E.; Bryan, Coleman J.

    1989-01-01

    A high-volume pneumatic-impact system has been used to test PTFE-lined stainless steel braided hoses, in order to characterize the roles played in the mechanism of oxygen-induced ignition by impact pressure, pressurization rate, and upstream and downstream volumes of the hose. Ignitions are noted to have occurred at impact pressures well below the working pressure of the hoses, as well as at pressurization rates easily obtainable through manual operation of valves. The use of stainless steel hardlines downstream of the hose prevented ignitions at all pressures and pressurization rates; internal observations have shown evidence of shock ionization in the oxygen prior to ignition.

  1. Synthesis of a gamma irradiation grafted polytetrafluoroethylene (PTFE) based olefinic copolymer; Estudo da sintese de copolimero olefinico a base de politetrafluoroetileno (PTFE) por meio da enxertia induzida por radiacao gama

    Energy Technology Data Exchange (ETDEWEB)

    Ferreto, Helio Fernando Rodrigues

    2006-07-01

    The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as 'melt fracture' or 'sharkskin', which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect 'melt fracture'. (author)

  2. Design and fabrication of a PET/PTFE-based piezoelectric squeeze mode drop-on-demand inkjet printhead with interchangeable nozzle

    KAUST Repository

    Li, Erqiang; Xu, Qian; Sun, Jie; Fuh, Jerry; Wong, Yokesan; Thoroddsen, Sigurdur T

    2010-01-01

    , or Teflon) tubing, which of a much softer material, than the conventionally used glass tubing. Applying the same electrical voltage, PET/PTFE-based printhead will generate a larger volume change in the material to be dispensed. The novel printhead fabricated

  3. Dextran grafting on PTFE surface for cardiovascular applications

    Science.gov (United States)

    Michel, Eléonore C; Montaño-Machado, Vanessa; Chevallier, Pascale; Labbé-Barrère, Amélie; Letourneur, Didier; Mantovani, Diego

    2014-01-01

    The modification of biomaterial surfaces with biomolecules influences the biological response. In this work, caboxymethyldextrans (CMD) with different degrees of substitution have been grafted to surfaces by introduction of amino moieties directly onto the substrate surface. Polytetrafluoroethylene was selected as a model substrate for biomaterial as it is already largely used for cardiovascular clinical applications. Firstly, CMD polymers were characterized by FTIR, 1H-NMR, and conductimetric titration. Then, the coatings have been analyzed by XPS to confirm the grafting and determine the composition. Once characterized, biological performances of CMD coatings were investigated. The hemocompatibility was ascertained using the free hemoglobin method. The effects on endothelial and smooth muscle cell adhesion were also studied. Results indicated that CMD at a 0.2 substitution degree, significantly influenced the biological property of PTFE by exhibiting non-thrombogenic properties as well as enhancing endothelial cell adhesion along with limiting smooth muscle cell adhesion. This work suggested the creation of versatile pro-active biomaterials suitable for different biomedical applications. PMID:25482414

  4. Investigation of counterface surface topography effects on the wear and transfer behaviour of a POM-20% PTFE composite

    NARCIS (Netherlands)

    Franklin, S.E.; de Kraker, A.

    2003-01-01

    In order to gain greater insight into the relation between the wear rate, counterface surface topography and the characteristics of the transfer layer formed, a series of wear experiments have been performed with a commercial POM-20% PTFE composite sliding against hardened tool steel counterfaces in

  5. KTP laser stapedotomy with a self-crimping, thermal shape memory Nitinol piston: follow-up study reporting intermediate-term hearing.

    Science.gov (United States)

    Gerlinger, Imre; Bakó, Péter; Piski, Zalán; Révész, Péter; Ráth, Gábor; Karosi, Tamás; Lujber, László

    2014-12-01

    The aim of this study was an evaluation of the mid-term hearing results after the implantation of a self-crimping heat memory Nitinol piston in stapes surgery. The 12-month postoperative results were compared with those at a minimum of 3 years (maximum 6.7, average 4.4 years). The medical records of all 44 patients who underwent surgery with a Nitinol piston for stapes fixation between November 2005 and January 2007 were evaluated retrospectively. The prostheses used in all cases measured either 4.5 or 4.75 × 0.6 mm. We hypothesized that the 12-month postoperative hearing results would be permanent after an average follow-up of 4.4 years. Thirty-two of the 44 consecutive patients were females and 12 were males. Their mean age was 40.4 years (range 27-69). All underwent a 12-month postoperative audiometric evaluation. 38 (30 females, 8 males, average age 45, range 28-77 years) of the 44 were available for mid-term 4.4-year (minimum 3 years, maximum 6.7 years) postoperative audiometric evaluation. The mean air-bone gap (ABG) for the frequencies 0.5, 1, 2 and 3 kHz at the 12-month postoperative follow-up was 11 dB (SD 4.1) and that after an average 4.4-year postoperative evaluation was 6.4 dB (SD 3.6). The mean decrease in ABG after 12 months was 19.5 dB, and that after the average 4.4 years was 21.3 dB. ABG closure within 10 dB was achieved in 77.2 % after 12 months and in 89.5 % after the average 4.4 years. No patient with an ABG > 20 dB was recorded after the average 4.4 years. The mean air conduction threshold at 4 kHz was examined pre and postoperatively so as to indicate any possible inner ear damage. At the 12-month follow-up, the difference between the pre and postoperative values was -2.5 dB, whereas after the average 4.4 years the difference was surprisingly +13 dB. The individual AC improvements were also demonstrated with the use of Amsterdam Hearing Evaluation Plots (AHEPs). The Nitinol prosthesis allowed excellent intraoperative handling and no

  6. A globally complete map of supraglacial debris cover and a new toolkit for debris cover research

    Science.gov (United States)

    Herreid, Sam; Pellicciotti, Francesca

    2017-04-01

    A growing canon of literature is focused on resolving the processes and implications of debris cover on glaciers. However, this work is often confined to a handful of glaciers that were likely selected based on criteria optimizing their suitability to test a specific hypothesis or logistical ease. The role of debris cover in a glacier system is likely to not go overlooked in forthcoming research, yet the magnitude of this role at a global scale has not yet been fully described. Here, we present a map of debris cover for all glacierized regions on Earth including the Greenland Ice Sheet using 30 m Landsat data. This dataset will begin to open a wider context to the high quality, localized findings from the debris-covered glacier research community and help inform large-scale modeling efforts. A global map of debris cover also facilitates analysis attempting to isolate first order geomorphological and climate controls of supraglacial debris production. Furthering the objective of expanding the inclusion of debris cover in forthcoming research, we also present an under development suite of open-source, Python based tools. Requiring minimal and often freely available input data, we have automated the mapping of: i) debris cover, ii) ice cliffs, iii) debris cover evolution over the Landsat era and iv) glacier flow instabilities from altered debris structures. At the present time, debris extent is the only globally complete quantity but with the expanding repository of high quality global datasets and further tool development minimizing manual tasks and computational cost, we foresee all of these tools being applied globally in the near future.

  7. Plasma treatment of expanded PTFE offers a way to a biofunctionalization of its surface

    International Nuclear Information System (INIS)

    Baquey, Ch.; Palumbo, F.; Porte-Durrieu, M.C.; Legeay, G.; Tressaud, A.; D'Agostino, R.

    1999-01-01

    Biointegration is the ideal outcome which is expected for an artificial implant. That means that the phenomena which seats at the interface between the implant and the host tissues does not induce neither any deleterious effect, such as chronic inflammatory response, nor the formation of unusual tissues. Thus it is of paramount importance to design biomaterials, used for the fabrication of implants, with the best appropriate surface properties. At the same time these biomaterials must feature bulk properties which meet other requirements, especially mechanical properties, deriving from the intended function of the implant in which they are involved. As it is quite impossible to design biomaterials which fulfil at the same time both types of requirements, it is commonly agreed that the solution to this issue goes through the selection or the design of biomaterials with adequate bulk properties, and a further treatment of the surface which would improve the properties of the latter. In this respect ionizing radiations and plasma based treatments, offer a wide panel of possibilities; as an example we describe here how the surface of expanded poly(tetrafluoroethylene) samples can be activated using cold plasma, in order to open a way to chemical modifications of such a surface. Subsequently, Radio Frequency Glow Discharge (RFGD) containing oligopeptides, known for their role in mediating the adhesion of cells to the extracellular matrix, were bound to the modified surface, and the affinity of endothelial cells for the latter was investigated

  8. Effect of sintering temperature on the morphology and mechanical properties of PTFE membranes as a base substrate for proton exchange membrane

    Directory of Open Access Journals (Sweden)

    Nor Aida Zubir

    2002-11-01

    Full Text Available This paper reports the development of PTFE membranes as the base substrates for producing proton exchange membrane by using radiation-grafting technique. An aqueous dispersion of PTFE, which includes sodium benzoate, is cast in order to form suitable membranes. The casting was done by usinga pneumatically controlled flat sheet membrane-casting machine. The membrane is then sintered to fuse the polymer particles and cooled. After cooling process, the salt crystals are leached from the membrane by dissolution in hot bath to leave a microporous structure, which is suitable for such uses as a filtration membrane or as a base substrate for radiation grafted membrane in PEMFC. The effects of sintering temperature on the membrane morphology and tensile strength were investigated at 350oC and 385oC by using scanning electron microscopy (SEM and EX 20, respectively. The pore size and total void space are significantly smaller at higher sintering temperature employed with an average pore diameter of 11.78 nm. The tensile strength and tensile strain of sintered PTFE membrane at 385oC are approximately 19.02 + 1.46 MPa and 351.04 + 23.13 %, respectively. These results were indicated at 385oC, which represents significant improvements in tensile strength and tensile strain, which are nearly twice those at 350oC.

  9. Partial ion yield and NEXAFS of 2-(perfluorooctyl)ethanethiol self-assembled monolayer: Comparison with PTFE results

    CERN Document Server

    Setoyama, H; Murase, T; Imamura, M; Mase, K; Okudaira, K K; Hara, M; Ueno, N

    2003-01-01

    Partial-ion-yield (PIY) spectra using ion time-of-flight (TOF) method and near-edge absorption fine structure (NEXAFS) spectra were measured for 2-(perfluorooctyl)ethanethiol [CF sub 3 (CF sub 2) sub 7 (CH sub 2) sub 2 SH] self-assembled monolayer (F8-SAM) on Au(1 1 1) near carbon K-edge. The PIY spectra of the F8-SAM at the magic angle, where -CF sub 3 groups exist at the surface were compared with those of the rubbed polytetrafluoroethylene (PTFE) thin film. The F sup + intensity from the F8-SAM at the photon energy of the sharp peak of the NEXAFS, which originates from the excitation of C1s electron to sigma sup * (C-F) states at -CF sub 2 - chain, was extremely smaller than that from the rubbed PTFE film. This result clearly indicates that the ions observed by PIY do not originate from the film inside but from the surface. This was confirmed by changes in ion-TOF mass spectra during soft X-ray induced etching of the F8-SAM. The NEXAFS peaks of the F8-SAM were also assigned by considering PIY results.

  10. Transcatheter closure of membranous ventricular septal defects with home-made nitinol occluder

    Energy Technology Data Exchange (ETDEWEB)

    Yongwen, Qin; Xianxian, Zhao; Xing, Zheng; Jijun, Ding; Jiang, Cao [Second Military Medical Univ., Shanghai (China). Changhai Hospital, Dept. of Cardiology

    2004-04-01

    Objective: To evaluate the feasibility and efficacy of transcatheter perimembranous ventricular septal defects (VSD) occlusion with home-made nitinol occluder. Methods: Transcatheter closure was attempted in 196 patients with perimembranous VSD. The diameter of VSD measured by echocardiography was 3 to 15 mm, mean (4.94 {+-} 2.23) mm. The angiographic diameter of the VSD was 3 to 6 mm, mean (3.92 {+-} 1.44) mm. A 7-10 F delivery sheath was advanced across the perimembranous VSD over a wire from femoral vein to deploy the occluder with the guidance of echocardiography and fluoroscopy. The device diameter selected was from 4 to 20 mm, mean (6.68 {+-} 2.76) mm. Left ventriculography and transthoracic echocardiography were repeated to assess the closure of the defects 15 min after the procedure. Continuous electrocardiogram monitoring lasted for 5 days. The echocardiography and electrocardiogram examination were scheduled for 1, 6 and 12 months of follow-up. Results: The occluders were successfully deployed in 191 patients. There were five procedural failures, two with device-related aortic insufficiency, and three of inability to pass through VSD. After deployment of the devices, there were no residual shunt in 180 of 191 patients, 11 patients with a trivial residual shunt that disappeared in 8 patients after one month of follow up. 3 patients developed mild tricuspid insufficiency. 12 developed transient complete right bundle branch block, and 5 transient complete left bundle branch block, and 2 transient complete atrioventricular block. There were repetitive nonparoxysmal ventricular tachycardia in 4 patients 1 week after the procedure. One patient had a detached device embolized into the left pulmonary artery but with a successful catheter retrieval by snare and transcatheter closure. The devices were similarly applied to patients with VSD associated with patent ductus arteriosus, and 4 patients with VSD complicated by atrial septal defects. The fluoroscopy time

  11. Estudo comparativo das reações teciduais ao implante de pericárdio bovino e a inclusão de politetrafluoroetileno expandido em ratos A comparison of tissue reactions to bovine pericardial implants and expanded polytetrafluoroethylene inclusions in a rat model

    Directory of Open Access Journals (Sweden)

    Douglas Haddad Filho

    2004-04-01

    Full Text Available OBJETIVO: Comparar a reação tecidual à inclusão de politetrafluoroetileno-expandido com a reação tecidual ao implante de pericárdio bovino. MÉTODOS: Vinte ratos foram divididos em dois grupos iguais: 7 e 30 dias. Um disco de cada material foi introduzido no dorso de cada animal. As peças e o tecido reacional foram retirados 7 e 30 dias após a introdução, para a realização do estudo morfométrico. Para análise estatística foram aplicados os testes de Mann-Whitney e Wilcoxon. RESULTADOS: No PTFE-E, no grupo 30 dias, houve um aumento significante no número de fibroblastos e uma diminuição significante no número de neutrófilos, linfócitos e apilares. Em relação ao pericárdio bovino, ocorreu uma diminuição significante no número de fibroblastos. Quando os mesmos períodos foram comparados, o número de fibroblastos foi significativamente maior no PTFE-E, aos 30 dias, assim como o número de plasmócitos e linfócitos no grupo 30 dias , no pericárdio bovino. CONCLUSÕES: A reposta inflamatória foi menor e menos durável no PTFE-E; a reparação foi menor no PTFE-E e não houve reação de corpo estranho para ambos os materiais.PURPOSE: It is to compare tissue reactions of the expanded polytetrafluoroethyele (E-PTFE implantation and the tissue reaction of the bovine pericardium implants. METHODS: Twenty male rats were divided into two equal groups: 7 and 30 days. A disc-shaped specimen of test material was introduced into each animal's paraspinal region. The material and the tissue were resected 7 and 30 days after the introduction, for morphometric analysis. The Mann-Whitney and Wilcoxon tests were applied for statistical analysis of the results. RESULTS: E-PTFE demonstrated a significant increase in the number of fibroblast at 30 days. A significant drop was noted in the number of neutrophils, lymphocytes and porcentage of capilaries within the time periods. Bovine pericadium displayed a strinking drop in the number of

  12. On compression and damage evolution in PTFE and PEEK

    Science.gov (United States)

    Rau, C.; Parry, S.; Garcea, S. C.; Bourne, N. K.; McDonald, S. A.; Eastwood, D. S.; Brown, E. N.; Withers, P. J.

    2017-01-01

    The well-known Taylor cylinder impact test, that follows the impact of a flat-ended cylindrical rod onto a rigid stationary anvil, is conducted over a range of impact speeds for two polymers, PTFE and PEEK. In previous work experiments and a model were developed to capture the deformation behaviour of the rod after impact. A distinctive feature of these works was that a region in which both spatial and temporal variation of both longitudinal and radial deformation showed evidence of changes in phase within the material. This region is X-ray imaged in a range of impacted targets at the I13 Imaging and Coherence beam line at the Diamond synchrotron. Further techniques were fielded to resolve compressed regions within the recovered polymer cylinders that showed a fracture zone in the impact region. This shows the transit of damage from ductile to brittle failure results from previously undetected internal failure.

  13. Tl response of LiF: Mg, Cu, P+Ptfe at X rays of 24, 42 and 100 KeV

    International Nuclear Information System (INIS)

    Gonzalez M, P.R.; Tovar M, V.M.; Azorin N, J.; Furetta, C.; Quiroz C, M.C.

    2005-01-01

    In this work the obtained results of the irradiation of thermoluminescent dosemeters (Tl) of LiF: Mg,Cu,P + Ptfe with X rays for the effective radiation energy of 24, 42 and 100 keV, in an interval of Kerma in air in the sinus of the air between 0.05 and 1.0 Gy are presented. The rate of Kerma in air was determined with an ionization chamber PTW-1152, gauged by the Laboratoire Central des Industries Electriques (LCIE). As reference commercial TLD-100 dosemeters was used. The results showed that the studied Tl dosemeters presented a lineal response in the interval of mentioned Kerma. On the other hand the estimated Kerma with the Tl dosemeter in the calibration curves for X rays, were similar to the one measured with the previously gauged ionization chamber. The Tl of LiF: Mg, Cu, P + Ptfe, developed in the ININ, are highly reliable for X-ray dosimetry. (Author)

  14. Covered self-expandable metal stents in pancreatic malignancy regardless of resectability: a new concept validated by a decision analysis.

    Science.gov (United States)

    Kahaleh, M; Brock, A; Conaway, M R; Shami, V M; Dumonceau, J M; Northup, P G; Tokar, J; Rich, T A; Adams, R B; Yeaton, P

    2007-04-01

    The current treatment model for the management of malignant biliary obstruction is to place a plastic stent for unstaged pancreatic cancer. In patients with unresectable disease but a life expectancy of more than 6 months, self-expandable metal stents (SEMS) are favored because of their more prolonged patency. We analyzed the efficacy and cost-effectiveness of covered SEMS (CSEMS) in patients with pancreatic cancer and distal biliary obstruction without regard to surgical resectability. Between March 2001 and March 2005, 101 consecutive patients with obstructive jaundice secondary to pancreatic cancer underwent placement of a CSEMS. Patients with resectable tumor were offered pancreaticoduodenectomy. A model was developed to compare the costs of CSEMS and polyethylene and DoubleLayer stents. A total of 21 patients underwent staging laparoscopy, of whom 16 had a resection (76%). The 85 patients who did not have a resection had a mean survival of 5.9 months (range 1-25 months) and a mean CSEMS patency duration of 5.5 months (range 1-16 months). Life-table analysis demonstrated CSEMS patency rates of 97% at 3 months, 85% at 6 months, and 68% at 12 months. In a cost model that accounted for polyethylene and DoubleLayer stent malfunction and surgical resections, initial CSEMS placement (3177 euros per patient) was a less costly intervention than either DoubleLayer stent placement (3224 euros per patient) or polyethylene stent placement with revision (3570 euros per patient). Covered SEMS are an effective treatment for distal biliary obstructions caused by pancreatic carcinoma. Their prolonged patency and removability makes them an attractive option for biliary decompression, regardless of resectability. The strategy of initial covered SEMS placement might be the most cost-effective strategy in these patients.

  15. Comparative Efficacy of Pulse-Spray Thrombolysis and Angioplasty Versus Surgical Salvage Procedures for Treatment of Recurrent Occlusion of PTFE Dialysis Access Grafts

    International Nuclear Information System (INIS)

    Polak, Joseph F.; Berger, Markus F.; Pagan-Marin, Heriberto; Aruny, John E.; Meyerovitz, Michael F.

    1998-01-01

    Purpose: To compare the efficacy of surgery versus pulse-spray thrombolysis and angioplasty in patients with recurrent thrombosis of polytetrafluoroethylene (PTFE) dialysis access grafts. Methods: We analyzed 96 consecutive interventions for thrombosed PTFE dialysis access grafts in 18 patients. Primary patency after thrombolysis and angioplasty (n= 25) was compared with primary patency following thrombectomy alone (n= 50) or thrombectomy followed by graft revision (n= 21) using life-table analysis. A Cox proportional hazards model that accounted for graft age and number of previous interventions was used to generate the relative risk for recurrent occlusion following therapy. Results: Life-table analysis showed that patency after thrombolysis and angioplasty was greater than that following thrombectomy alone (p= 0.02). After accounting for the age of the graft and the number of previous interventions (average six per patient), the relative risk for recurrent occlusion [3.0; 95% confidence intervals (CI): 1.5, 6.4] was greater for thrombectomy alone than for thrombolysis/angioplasty [0.6; CI = 0.3, 1.3]. The relative risks of repeat occlusion following thrombolysis/angioplasty [0.6; CI = 0.3, 1.3] and thrombectomy/surgical revision [1.0; CI = 0.5, 1.7] were similar. Conclusion: Outcome data from our retrospective study on recurrent thrombosis of PTFE dialysis access grafts suggest that thrombolysis/angioplasty is superior to thrombectomy alone, and equivalent to thrombectomy/surgical revision

  16. PTFE-based microreactor system for the continuous synthesis of full-visible-spectrum emitting cesium lead halide perovskite nanocrystals

    Directory of Open Access Journals (Sweden)

    Chengxi Zhang

    2017-11-01

    Full Text Available Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX3, X = Cl, Br, I or a mixture thereof have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene (PTFE capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19–35 nm, high fluorescence quantum yield of 47.8–90.55%, and photoluminescence emission in the range of 450–700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices.

  17. The effect of addition of PTFE or urea on luminescence response of copper-doped lithium tetraborate

    Science.gov (United States)

    Iskandar, Ferry; Fajri, Annisa; Nuraeni, Nunung; Stavila, Erythrina; Aimon, Akfiny H.; Nuryadin, Bebeh W.

    2018-04-01

    Lithium tetraborate (Li2B4O7) is a promising material for application in personal dosimetry due to its tissue equivalent properties. The addition of copper as a dopant in Li2B4O7 is known to increase the sensitivity for both photoluminescent (PL) and thermoluminescent (TL) emission. Therefore, in this paper, synthesis of Li2B4O7:Cu is reported. The optimum synthesis condition was achieved using the solution-assisted method, followed by calcination at 700 °C for 2 h. The addition of 0.1 wt% Cu resulted in the highest PL and TL emissions. Further investigation of the influence of polytetrafluoroethylene (PTFE) or urea addition on the luminescence response of Li2B4O7:Cu is described. All samples were characterized by x-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometry, photoluminescence spectrofluorophotometer, thermoluminescence reader, scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) spectroscopy. The addition of PTFE decreased the PL emission of the Li2B4O7:Cu but slightly increased its TL emission. Meanwhile, the addition of urea increased the luminescence emission for both PL and TL of the Li2B4O7:Cu.

  18. Tl response of LiF: Mg, Cu, P + PTFE (Mexico) and GR200A (China) dosemeters

    International Nuclear Information System (INIS)

    Gonzalez M, P.R.; Azorin N, J.; Furetta, C.

    2003-01-01

    TLD-100 was the commercial dosemeter more known since some decades ago. This dosemeter was considered for many research groups as the reference material for developing new Tl materials for ionizing radiation dosimetry. Actually it seems that TLD-100 is going to be replaced by the Chinese material GR200A, as reference material due that this material in addition to be considered as a tissue equivalent material, is 30 to 35 times more sensitive that TLD- 100. Results of the study of the Tl response of LiF: Mg, Cu, P + Ptfe developed at ININ-Mexico, comparing them with those of GR200A are presented. These results showed that the sensitivity (s = Tl intensity/weight x dose) to gamma radiation of the LiF: Mg, Cu, P + Ptfe dosimeters was 4.34 meanwhile that of the commercial dosemeter was 3.41. Detection threshold of the dosemeters studied was 2.22 and 0.52 μGy respectively Repeatability after 10 cycles Irradiation-reading-annealing was ±1.39% and ±1.86% respectively. Both types of dosemeters presented a linear response as a function of gamma radiation in the range from 0.02 mGy and 100 Gy. (Author)

  19. Development of tissue-engineered self-expandable aortic stent grafts (Bio stent grafts) using in-body tissue architecture technology in beagles.

    Science.gov (United States)

    Kawajiri, Hidetake; Mizuno, Takeshi; Moriwaki, Takeshi; Ishibashi-Ueda, Hatsue; Yamanami, Masashi; Kanda, Keiichi; Yaku, Hitoshi; Nakayama, Yasuhide

    2015-02-01

    In this study, we aimed to describe the development of tissue-engineered self-expandable aortic stent grafts (Bio stent graft) using in-body tissue architecture technology in beagles and to determine its mechanical and histological properties. The preparation mold was assembled by insertion of an acryl rod (outer diameter, 8.6 mm; length, 40 mm) into a self-expanding nitinol stent (internal diameter, 9.0 mm; length, 35 mm). The molds (n = 6) were embedded into the subcutaneous pouches of three beagles for 4 weeks. After harvesting and removing each rod, the excessive fragile tissue connected around the molds was trimmed, and thus tubular autologous connective tissues with the stent were obtained for use as Bio stent grafts (outer diameter, approximately 9.3 mm in all molds). The stent strut was completely surrounded by the dense collagenous membrane (thickness, ∼150 µm). The Bio stent graft luminal surface was extremely flat and smooth. The graft wall of the Bio stent graft possessed an elastic modulus that was almost two times higher than that of the native beagle abdominal aorta. This Bio stent graft is expected to exhibit excellent biocompatibility after being implanted in the aorta, which may reduce the risk of type 1 endoleaks or migration. © 2014 Wiley Periodicals, Inc.

  20. Optimization of the obtaining method of CaSO{sub 4}: Dy + Ptfe dosimeters; Optimizacion del metodo de obtencion de dosimetros de CaSO{sub 4}: Dy + PTFE

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, J.; Rioja Ch, J.; Torijano C, E.; Azorin N, J., E-mail: blink19871@hotmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico)

    2012-10-15

    This work contain the obtained results of studying the response when irradiating to different dose of X-rays, dosimeters of CaSO{sub 4}: Dy + Ptfe using different lapses of time in their preparation (a lot of selected dosimeters of an elaboration process of 3 days and another of an elaboration process of 2 hours). For the elaboration of the powdered material, the evaporation method was used; the irradiation were carried out in a lineal accelerator Elekta Synergy property of the National Medical Center, 20 de November. The similarities and differences are shown among the two dosimeters lots together with an analysis of the shine curves and of calibration selecting those that presented a better behaviour and a more rea liable response. (Author)

  1. [The application of Y-shaped self-expandable covered metal stents in the thoracostomach-airway fistula: a single center, 11 years experience].

    Science.gov (United States)

    Fang, Yi; Li, Tengfei; Han, Xinwei; Wu, Gang; Ren, Jianzhuang; Ren, Kewei; Lu, Huibin; Zhang, Quanhui; Li, Zongming

    2015-08-01

    To investigate the clinical feasibility and efficacy of Y-shaped self-expandable covered metal stents (Y-stents) in the management of thoracostomach-airway fistula. Retrospective analysis was performed for 108 patients treated for thoracostomach-airway fistula with Y-shaped self-expandable coated metal stents between April 2003 and October 2014. Y-stents were designed based on the dimensions of trachea and bronchus and sites of the fistula and then were inserted under DSA monitoring. There were 65 cases with single big Y-stent placement, 26 cases with single small Y-stent placement, 23 cases with double Y-stents placement, and 1 case with 3 Y-stents placement. Stent implantation was successfully accomplished with single manipulation in all patients. Complete occlusion of the fistula was obtained in 104 patients after the primary manipulation, and 4 patients required a secondary manipulation where a double Y-stents was inserted because of failure of primary manipulate. Ninety-two patients completed the follow-up , while 16 were lost. Fifty-nine patients died while 33 were alive with marked improvement in their quality of life. The placement of Y-stents can effectively occlude the thoracostomach-airway fistula in patients who had had the esophageal tumors resected. The technique is not only feasible but reliable to improve the quality of life of the patients.

  2. Mechanical stability of the diamond-like carbon film on nitinol vascular stents under cyclic loading

    International Nuclear Information System (INIS)

    Kim, Hyun-Jong; Moon, Myoung-Woon; Lee, Kwang-Ryeol; Seok, Hyun-Kwang; Han, Seung-Hee; Ryu, Jae-Woo; Shin, Kyong-Min; Oh, Kyu Hwan

    2008-01-01

    The mechanical stability of diamond-like carbon (DLC) films coated on nitinol vascular stents was investigated under cyclic loading condition by employing a stent crimping system. DLC films were coated on the vascular stent of a three dimensional structure by using a hybrid ion beam system with rotating jig. The cracking or delamination of the DLC coating occurred dominantly near the hinge connecting the V-shaped segments of the stent where the maximum strain was induced by a cyclic loading of contraction and extension. However the failures were significantly suppressed as the amorphous Si (a-Si) buffer layer thickness increased. Interfacial adhesion strength was estimated from the spalled crack size in the DLC coating for various values of the a-Si buffer layer thickness

  3. Non-proximate mass spectrometry using a heated 1-m long PTFE tube and an air-tight APCI ion source

    International Nuclear Information System (INIS)

    Usmanov, Dilshadbek T.; Hiraoka, Kenzo; Wada, Hiroshi; Matsumura, Masaya; Sanada-Morimura, Sachiyo; Nonami, Hiroshi; Yamabe, Shinichi

    2017-01-01

    Direct and rapid trace-level gas analysis is highly needed in various fields such as safety and security, quality control, food analysis, and forensic medicine. In many cases, the real samples are bulky and are not accessible to the space-limited ion source of the mass spectrometer. In order to circumvent this problem, we developed an airtight atmospheric-pressure chemical ionization (APCI) ion source equipped with a flexible 1-m-long, 2-mm-i.d. PTFE sniffing tube. The ambient air bearing sample gas was sucked into the heated PTFE tube (130 °C) and was transported to the air-tight ion source without using any extra pumping system or a Venturi device. Analytes were ionized by an ac corona discharge located at 1.5 mm from the inlet of the mass spectrometer. By using the airtight ion source, all the ionized gas in the ion source was introduced into the vacuum of the mass spectrometer via only the evacuation of the mass spectrometer (1.6 l min"−"1). Sub-pg limits of detection were obtained for carbaryl and trinitrotoluene. Owing to its flexibility and high sensitivity, the sniffing tube coupled with a mass spectrometer can be used as the stethoscope for the high-sensitive gas analysis. The experimental results obtained for drugs, hydrogen peroxide and small alkanes were discussed by DFT calculations. - Highlights: • Non-proximate mass spectrometry for the trace-level gas analysis was developed. • Using a 1-m long flexible PTFE tube, it can be applicable to complicated-shape real-world samples. • By atmospheric pressure chemical ionization in the airtight ion source, sub-pg limits of detection were attained. • Adsorption of less-volatility compounds was negligible with the tube temperature at 130° C. • Novel experimental results obtained were fully examined by density functional theory calculations.

  4. Non-proximate mass spectrometry using a heated 1-m long PTFE tube and an air-tight APCI ion source

    Energy Technology Data Exchange (ETDEWEB)

    Usmanov, Dilshadbek T. [Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, Yamanashi, 400-8511 (Japan); Institute of Ion-Plasma and Laser Technologies, Durmon Yoli Street 33, 100125, Tashkent (Uzbekistan); Hiraoka, Kenzo, E-mail: hiraoka@yamanashi.ac.jp [Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, Yamanashi, 400-8511 (Japan); Wada, Hiroshi [Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, 496 Izumi, Chikugo, Fukuoka 833-0041 (Japan); Matsumura, Masaya; Sanada-Morimura, Sachiyo [Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Suya 2421, shiKo, Kumamoto 861-1192 (Japan); Nonami, Hiroshi [Plant Biophysics/Biochemistry Research Laboratory, Faculty of Agriculture, Ehime University, 3-5-7 T Tarumi, 790-0905, Matsuyama (Japan); Yamabe, Shinichi, E-mail: yamabesh@gmail.com [Department of Material Science, Nara Institute of Science and Technology, Takayama-cho, 8916-5, Ikoma, Nara, 630−0101 (Japan)

    2017-06-22

    Direct and rapid trace-level gas analysis is highly needed in various fields such as safety and security, quality control, food analysis, and forensic medicine. In many cases, the real samples are bulky and are not accessible to the space-limited ion source of the mass spectrometer. In order to circumvent this problem, we developed an airtight atmospheric-pressure chemical ionization (APCI) ion source equipped with a flexible 1-m-long, 2-mm-i.d. PTFE sniffing tube. The ambient air bearing sample gas was sucked into the heated PTFE tube (130 °C) and was transported to the air-tight ion source without using any extra pumping system or a Venturi device. Analytes were ionized by an ac corona discharge located at 1.5 mm from the inlet of the mass spectrometer. By using the airtight ion source, all the ionized gas in the ion source was introduced into the vacuum of the mass spectrometer via only the evacuation of the mass spectrometer (1.6 l min{sup −1}). Sub-pg limits of detection were obtained for carbaryl and trinitrotoluene. Owing to its flexibility and high sensitivity, the sniffing tube coupled with a mass spectrometer can be used as the stethoscope for the high-sensitive gas analysis. The experimental results obtained for drugs, hydrogen peroxide and small alkanes were discussed by DFT calculations. - Highlights: • Non-proximate mass spectrometry for the trace-level gas analysis was developed. • Using a 1-m long flexible PTFE tube, it can be applicable to complicated-shape real-world samples. • By atmospheric pressure chemical ionization in the airtight ion source, sub-pg limits of detection were attained. • Adsorption of less-volatility compounds was negligible with the tube temperature at 130° C. • Novel experimental results obtained were fully examined by density functional theory calculations.

  5. Study of critical dependence of stable phases in Nitinol on heat treatment using electrical resistivity probe

    International Nuclear Information System (INIS)

    Uchil, J.; Mohanchandra, K.P.; Kumara, K.G.; Mahesh, K.K.

    1998-01-01

    Phase transformations in 40% cold-worked Nitinol as a function of heat treatment have been studied using electrical resistivity variation with temperature. The stabilisation of austenitic, rhombohedral and martensitic phases is shown to critically depend on the temperatures of heat treatment by the analysis of temperature dependence of electrical resistivity in heating and cooling parts of the cycle. Characteristic values of electrical resistivity of the stable phases are determined. The R-phase has been found to form continuously with increasing heat-treatment temperature starting from room temperature and to suddenly disappear beyond heat-treatment at 683 K. The observed presence or absence of R-phase is confirmed by heat capacity measurements as a function of temperature. (orig.)

  6.  Evaluation of the humoral and cellular immune responses after implantation of a PTFE vascular prosthesis.

    Science.gov (United States)

    Skóra, Jan; Pupka, Artur; Dorobisz, Andrzej; Barć, Piotr; Korta, Krzysztof; Dawiskiba, Tomasz

    2012-07-02

    The experiment was designed in order to determine the immunological processes that occur during the healing in synthetic vascular grafts, especially to establish the differences in the location of the complement system proteins between the proximal and distal anastomosis and the differences in the arrangement of inflammatory cells in those anastomoses. The understanding of those processes will provide a true basis for determining risk factors for complications after arterial repair procedures. The experiment was carried out on 16 dogs that underwent implantation of unilateral aorto-femoral bypass with expanded polytetrafluoroethylene (ePTFE). After 6 months all animals were euthanized to dissect the vascular grafts. Immunohistochemical assays and electron microscopic examinations were performed. Immunohistochemical findings in the structure of neointima between anastomoses of vascular prostheses demonstrated significant differences between humoral and cellular responses. The area of proximal anastomosis revealed the presence of fibroblasts, but no macrophages were detected. The histological structure of the proximal anastomosis indicates that inflammatory processes were ended during the prosthesis healing. The immunological response obtained in the distal anastomosis corresponded to the chronic inflammatory reaction with the presence of macrophages, myofibroblasts and deposits of complement C3. The identification of differences in the presence of macrophages and myofibroblasts and the presence of the C3 component between the anastomoses is the original achievement of the present study. In the available literature, no such significant differences have been shown so far in the humoral and cellular immune response caused by the presence of an artificial vessel in the arterial system.

  7. Transcatheter closure of membranous ventricular septal defects with home-made nitinol occluder

    International Nuclear Information System (INIS)

    Qin Yongwen; Zhao Xianxian; Zheng Xing; Ding Jijun; Cao Jiang

    2004-01-01

    Objective: To evaluate the feasibility and efficacy of transcatheter perimembranous ventricular septal defects (VSD) occlusion with home-made nitinol occluder. Methods: Transcatheter closure was attempted in 196 patients with perimembranous VSD. The diameter of VSD measured by echocardiography was 3 to 15 mm, mean (4.94 ± 2.23) mm. The angiographic diameter of the VSD was 3 to 6 mm, mean (3.92 ± 1.44) mm. A 7-10 F delivery sheath was advanced across the perimembranous VSD over a wire from femoral vein to deploy the occluder with the guidance of echocardiography and fluoroscopy. The device diameter selected was from 4 to 20 mm, mean (6.68 ± 2.76) mm. Left ventriculography and transthoracic echocardiography were repeated to assess the closure of the defects 15 min after the procedure. Continuous electrocardiogram monitoring lasted for 5 days. The echocardiography and electrocardiogram examination were scheduled for 1, 6 and 12 months of follow-up. Results: The occluders were successfully deployed in 191 patients. There were five procedural failures, two with device-related aortic insufficiency, and three of inability to pass through VSD. After deployment of the devices, there were no residual shunt in 180 of 191 patients, 11 patients with a trivial residual shunt that disappeared in 8 patients after one month of follow up. 3 patients developed mild tricuspid insufficiency. 12 developed transient complete right bundle branch block, and 5 transient complete left bundle branch block, and 2 transient complete atrioventricular block. There were repetitive nonparoxysmal ventricular tachycardia in 4 patients 1 week after the procedure. One patient had a detached device embolized into the left pulmonary artery but with a successful catheter retrieval by snare and transcatheter closure. The devices were similarly applied to patients with VSD associated with patent ductus arteriosus, and 4 patients with VSD complicated by atrial septal defects. The fluoroscopy time for the

  8. Retrievable Airway Stent Placement for Stoma Stricture after Anterior Mediastinal Tracheostomy: Case Report

    International Nuclear Information System (INIS)

    Hwang, Jae Yeon; Shin, Ji Hoon; Kim, Yong Hee; Song, Ho Young; Kim, Jin Hyoung; Lee, Yeoun Joo

    2013-01-01

    Anterior mediastinal tracheostomy (AMT) is performed to establish an airway after resection of advanced tumors in the cervicothoracic region. We report a case of successful placement of a covered retrievable self-expandable nitinol stent for a stoma stricture that developed after AMT in a patient with adenoid cystic carcinoma of the trachea. Two stent placements and removals, at two and three months after their initial placement, were performed due to loosening of the stents. Although we did not achieve long-term results as the patient died of massive hemorrhage, the stent placement was both feasible and safe, thus suggesting that temporary stent placement may be a valuable option for treating stoma stricture occurring after AMT.

  9. Retrievable Airway Stent Placement for Stoma Stricture after Anterior Mediastinal Tracheostomy: Case Report

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jae Yeon; Shin, Ji Hoon; Kim, Yong Hee; Song, Ho Young; Kim, Jin Hyoung [Dept. of University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Lee, Yeoun Joo [Dept. of Pediatrics, Pusan National University Children' s Hospital, Yangsan (Korea, Republic of)

    2013-06-15

    Anterior mediastinal tracheostomy (AMT) is performed to establish an airway after resection of advanced tumors in the cervicothoracic region. We report a case of successful placement of a covered retrievable self-expandable nitinol stent for a stoma stricture that developed after AMT in a patient with adenoid cystic carcinoma of the trachea. Two stent placements and removals, at two and three months after their initial placement, were performed due to loosening of the stents. Although we did not achieve long-term results as the patient died of massive hemorrhage, the stent placement was both feasible and safe, thus suggesting that temporary stent placement may be a valuable option for treating stoma stricture occurring after AMT.

  10. Vascular Biocompatibility of a Triple Layered Self Expanding Stent-Graft in a Dog Mode

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jae Ik; Won, Je Hwan; Jang, Eun Ho; Lee, Sung Yeong; Ko, Kwang Tae [Dept. of Radiology, Ajou University School of Medicine, Suwon (Korea, Republic of); Jin, Bo Hwan [Medical Science Research Center, Ajou University School of Medicine, Suwon (Korea, Republic of); Lee, June Woo [Dept. of Radiology, Busan National University College of Medicine, Busan (Korea, Republic of)

    2012-02-15

    To evaluate performance and biocompatibility of a newly designed self-expanding stent graft, which consisted of two nitinol stents and an intervening expanded polytetrafluoroethylene membrane in a dog artery model. Twelve stent grafts were placed in the aorta of 6 dogs (beagle, mean body weight 11 kg) for 4 weeks (n = 4) and 12 weeks (n = 8). Luminal diameters were measured for each segment (the proximal bare, the middle graft, the distal bare) by angiographies after implantation and follow up periods. Percent luminal stenosis based on angiographies, histomorphometric, histologic, and scanning electron microscopic analyses of each segments were performed. Blood flow through the stent grafts was good after implantation and during the follow up period, without thrombotic occlusion or stent graft migration. The mean percent luminal stenosis of the proximal bare, the middle grafted and the distal bare segments after 12 weeks were 13.5%, 3.9%, 9.6% retrospectively. The mean neointimal areas of the middle grafted segment were 4.39 mm{sup 2} (4 week) and 4.92 mm{sup 2} (12 week). Mature endothelialization was evident in over 70% of the area of the stented artery after 4 weeks and in over 90% after 12 weeks. The stent graft was well placed in the attempted area without migration. During the 12-week-follow up period, it showed a good patency without thrombotic occlusion or significant in-stent luminal stenosis. Endothelialization was rapid and nearly complete. Neointima was thin and smooth on the middle graft segment and thicker and irregular on the bare segments.

  11. Vascular Biocompatibility of a Triple Layered Self Expanding Stent-Graft in a Dog Mode

    International Nuclear Information System (INIS)

    Bae, Jae Ik; Won, Je Hwan; Jang, Eun Ho; Lee, Sung Yeong; Ko, Kwang Tae; Jin, Bo Hwan; Lee, June Woo

    2012-01-01

    To evaluate performance and biocompatibility of a newly designed self-expanding stent graft, which consisted of two nitinol stents and an intervening expanded polytetrafluoroethylene membrane in a dog artery model. Twelve stent grafts were placed in the aorta of 6 dogs (beagle, mean body weight 11 kg) for 4 weeks (n = 4) and 12 weeks (n = 8). Luminal diameters were measured for each segment (the proximal bare, the middle graft, the distal bare) by angiographies after implantation and follow up periods. Percent luminal stenosis based on angiographies, histomorphometric, histologic, and scanning electron microscopic analyses of each segments were performed. Blood flow through the stent grafts was good after implantation and during the follow up period, without thrombotic occlusion or stent graft migration. The mean percent luminal stenosis of the proximal bare, the middle grafted and the distal bare segments after 12 weeks were 13.5%, 3.9%, 9.6% retrospectively. The mean neointimal areas of the middle grafted segment were 4.39 mm 2 (4 week) and 4.92 mm 2 (12 week). Mature endothelialization was evident in over 70% of the area of the stented artery after 4 weeks and in over 90% after 12 weeks. The stent graft was well placed in the attempted area without migration. During the 12-week-follow up period, it showed a good patency without thrombotic occlusion or significant in-stent luminal stenosis. Endothelialization was rapid and nearly complete. Neointima was thin and smooth on the middle graft segment and thicker and irregular on the bare segments.

  12. Passive base isolation with superelastic nitinol SMA helical springs

    International Nuclear Information System (INIS)

    Huang, Bin; Zhang, Haiyang; Wang, Han; Song, Gangbing

    2014-01-01

    Seismic isolation of structures such as multi-story buildings, nuclear reactors, bridges, and liquid storage tanks should be designed to preserve structural integrity. By implementing seismic isolation technology, the deformation of superstructures can be dramatically reduced, consequently helping to protect their safety as well. In this paper, an innovative type of passive base isolation system, which is mainly composed of superelastic nitinol SMA helical springs, is developed. In order to verify the effectiveness of the proposed system, a two-story experimental steel frame model is constructed, and two superelastic SMA helical springs are thermo-mechanically built in the laboratory. To describe the nonlinear mechanical properties of the superelastic SMA helical springs under reciprocating load, a phenomenological model is presented in terms of a series of tensile tests. Afterwards, a numerical model of the two-story frame with the suggested isolation system is set up to simulate the response of the isolated frame subjected to an earthquake. Both the experimental and the numerical simulation results indicate that the proposed base isolation system can remarkably suppress structural vibrations and has improved isolation effects when compared with a steel spring isolation system. Due to the capabilities of energy dissipation as well as fully re-centering, it is very applicable to utilize the suggested isolation system in base isolated structures to resist earthquakes. (paper)

  13. Silver deposition on polypyrrole films electrosynthesised onto Nitinol alloy. Corrosion protection and antibacterial activity.

    Science.gov (United States)

    Saugo, M; Flamini, D O; Brugnoni, L I; Saidman, S B

    2015-11-01

    The electrosynthesis of polypyrrole films onto Nitinol from sodium salicylate solutions of different concentrations is reported. The morphology and corrosion protection properties of the resulting coatings were examined and they both depend on the sodium salicylate concentration. The immobilisation of silver species in PPy films constituted by hollow rectangular microtubes was studied as a function of the polymer oxidation degree. The highest amount of silver was deposited when the coated electrode was prepolarised at -1.00V (SCE) before silver deposition, suggesting an increase in the amount of non-oxidised segments in the polymer. Finally, the antibacterial activity of the coating against the Gram positive Staphylococcus aureus and Staphylococcus epidermidis bacteria was evaluated. Both strains resulted sensitive to the modified coatings, obtaining a slightly better result against S. aureus. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Coupling sequential injection on-line preconcentration using a PTFE beads packed column to direct injection nebulization inductively coupled plasma mass spectrometry

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2002-01-01

    An automated sequential injection on-line preconcentration procedure for trace metals by using a PTFE bead-packed microcolumn coupled to ICP-MS is described, and used for simultaneous analyses of cadmium and lead. In dilute nitric acid (0.5%, v/v), neutral complexes between the analytes...

  15. Percutaneous Endoluminal Stent-Graft Repair of an Old Traumatic Femoral Arteriovenous Fistula

    International Nuclear Information System (INIS)

    Uflacker, Renan; Elliott, Bruce M.

    1996-01-01

    A stent-graft was custom made to close a high-flow traumatic arteriovenous fistula of the left superficial femoral artery, present for 30 years, in a 60-year-old man with congestive heart failure and ischemic ulceration in the left foot. A balloon expandable Palmaz stent (P394; 2.5 mm x 3.9 cm) was covered with a polytetrafluoroethylene (PTFE) graft and was inserted percutaneously through an 11 Fr vascular sheath. Follow-up Doppler ultrasound at 6 months demonstrated occlusion of the arteriovenous fistula, patency of the artery, and luminal integrity of the artery and vein

  16. Histological evaluation of different biodegradable and non-biodegradable membranes implanted subcutaneously in rats

    DEFF Research Database (Denmark)

    Zhao, S; Pinholt, E M; Madsen, J E

    2000-01-01

    Different types of biodegradable membranes have become available for guided tissue regeneration. The purpose of this study was to evaluate histologically three different biodegradable membranes (Bio-Gide, Resolut and Vicryl) and one non-biodegradable membrane (expanded polytetrafluoroethylene/e-PTFE...... that e-PTFE was well tolerated and encapsulated by a fibrous connective tissue capsule. There was capsule formation around Resolut and Vicryl and around Bio-Gide in the early phase there was a wide inflammatory zone already. e-PTFE and Vicryl were stable materials while Resolut and Bio-Gide fragmented...

  17. Accelerated electron beams for production of heat shrinkable polymeric products and PTFE wastes recovery

    Energy Technology Data Exchange (ETDEWEB)

    Marin, Gh; Marcuta, M [SC ICPE Electrostatica SA, Bucharest (Romania); Jipa, S [' Valahia' University, Targoviste (Romania)

    2001-07-01

    Radiation curing, i.e. curing under the action of ionizing radiation (predominantly electron beams) is one of the most important areas of radiation processing. There are many practical applications of electron beam processing. Our research activity was focused on two of them: radiation cross-linking of polymeric materials; recovery of PTFE wastes. For this purpose we have used: an industrial electron accelerator ILU-6 with 2.5 MeV electron energy and 40kW beam power; equipment for the transport of materials under the electron beam; and a technologic line with typical equipment for the expansion process.

  18. Accelerated electron beams for production of heat shrinkable polymeric products and PTFE wastes recovery

    International Nuclear Information System (INIS)

    Marin, Gh.; Marcuta, M.; Jipa, S.

    2001-01-01

    Radiation curing, i.e. curing under the action of ionizing radiation (predominantly electron beams) is one of the most important areas of radiation processing. There are many practical applications of electron beam processing. Our research activity was focused on two of them: radiation cross-linking of polymeric materials; recovery of PTFE wastes. For this purpose we have used: an industrial electron accelerator ILU-6 with 2.5 MeV electron energy and 40kW beam power; equipment for the transport of materials under the electron beam; and a technologic line with typical equipment for the expansion process

  19. Safety and Efficacy of a Fully Covered Self-Expandable Metallic Stent in Benign Airway Stenosis.

    Science.gov (United States)

    Fortin, Marc; Lacasse, Yves; Elharrar, Xavier; Tazi-Mezalek, Rachid; Laroumagne, Sophie; Guinde, Julien; Astoul, Philippe; Dutau, Hervé

    2017-01-01

    The use of self-expandable metallic stents (SEMS) in benign airway disease was the object of a boxed warning from the United States Food and Drug Administration in 2005 due to the risk of stent-related complications and difficulties associated with their removal. Third-generation fully covered SEMS have been commercialized since this warning and theoretically should not present the same difficulties associated with removal as they cannot become embedded in the airway mucosa. We aimed to examine the safety and efficacy of a specific third-generation SEMS, the Silmet stent. We reviewed the records of all patients treated for benign airway stenosis with third-generation Silmet SEMS from January 2011 to December 2015 at the North Hospital of Marseilles, France. Forty SEMS were inserted in 30 patients over this period. Twenty (50.0%) stents were removed because of stent-related complications after a median of 77.0 ± 96.6 days (migration 32.5%, granulation tissue formation 7.5%, subjective intolerance 5.0%, mucus plugging 2.5%, laryngeal edema 2.5%). There were no cases of stent-related mortality. All complications were managed successfully endoscopically. Thirty-six stents (90.0%) were removed successfully after a median of 122.0 ± 113.2 days without any complications. The clinical success rate of stent treatment was 40.7%. Third-generation SEMS are a safe treatment option for complex benign airway stenosis, but complications requiring stent removal are frequent. Further studies are needed to compare the performance of third-generation SEMS and silicone stents in benign airway stenosis. © 2017 S. Karger AG, Basel.

  20. Optimization of the obtaining method of CaSO4: Dy + Ptfe dosimeters

    International Nuclear Information System (INIS)

    Galicia A, J.; Rioja Ch, J.; Torijano C, E.; Azorin N, J.

    2012-10-01

    This work contain the obtained results of studying the response when irradiating to different dose of X-rays, dosimeters of CaSO 4 : Dy + Ptfe using different lapses of time in their preparation (a lot of selected dosimeters of an elaboration process of 3 days and another of an elaboration process of 2 hours). For the elaboration of the powdered material, the evaporation method was used; the irradiation were carried out in a lineal accelerator Elekta Synergy property of the National Medical Center, 20 de November. The similarities and differences are shown among the two dosimeters lots together with an analysis of the shine curves and of calibration selecting those that presented a better behaviour and a more rea liable response. (Author)