Vivosorb (R), Bio-Gide (R), and Gore-Tex (R) as barrier membranes in rat mandibular defects : an evaluation by microradiography and micro-CT

NARCIS (Netherlands)

Gielkens, Pepijn F. M.; Schortinghuis, Jurjen; de Jong, Johan R.; Raghoebar, Gerry M.; Stegenga, Boudewijn; Bos, Ruud R. M.

Objectives: The objectives of this study were to determine whether a new degradable synthetic barrier membrane (Vivosorb (R)) composed of poly(DL-lactide-epsilon-caprolactone) (PDLLCL) can be useful in implant dentistry and to compare it with collagen and expanded polytetrafluoroethylene (ePTFE)

Induction of surface modification of polytetrafluoroethylene with proton ion beams

Energy Technology Data Exchange (ETDEWEB)

Noh, I S; Kim, H R; Choi, Y J; Park, H S [Seoul National Univ. of Technology, Seoul (Korea, Republic of)

2007-04-15

Cardiovascular disease is one of the leading causes of the death in the USA and developed countries. More than 570,000 artery bypass graft surgeries per USA are performed each year, though percutaneous devices have abounded in extreme cases. Based on the surgery follow-ups, large diameter expanded polytetrafluoroethylene (ePTFE) (>5 mm) are clinically employed with good results but its clinical applications in smaller vessels is still problematic due to thrombosis and neointima formation. Achievement of high patency grafts has been to some extent achieved by numerous methods of surface modification techniques, but its results are less than its initial hopes. As examples, endothelial cells coated on the luminal surface of ePTFE has demonstrated limited success after recirculation. Surface modifications of PTFE film with either argon ion beam or UV light from Xe-excimer lamp were reported to increase its interaction with vascular endothelial cell. Surface modification of poly(lactide-co-glycolide)[PLGA] is also very important in tissue engineering, in where induction of its initial high cellular adhesion and spreading is a critical step for development of tissue engineering medical products. We previously reported tissue engineering of the hybrid ePTFE scaffold by seeding smooth muscle cells and subsequently evaluation of its tissue regeneration behaviors and stabilities with circulation of pulsatile flow. To improve its tissue engineering more quickly, we here performed surface modification of ePTFE and porous PLGA scaffold and evaluated its subsequent chemical and biological properties after treating its surface with low energy ion beams. The porous ePTFE was prepared in a round shape (diameter = 1 cm) and dried after organic solvent extraction for ion beam treatment. Another porous PLGA layers (d = 1 cm, t = 1 cm with approximately 92% porosity) were fabricated and treated its surface by irradiating low energy either nitrogen or argon ion beams (1 keV, 1x1015 ions

Induction of surface modification of polytetrafluoroethylene with proton ion beams

International Nuclear Information System (INIS)

Noh, I. S.; Kim, H. R.; Choi, Y. J.; Park, H. S.

2007-04-01

Cardiovascular disease is one of the leading causes of the death in the USA and developed countries. More than 570,000 artery bypass graft surgeries per USA are performed each year, though percutaneous devices have abounded in extreme cases. Based on the surgery follow-ups, large diameter expanded polytetrafluoroethylene (ePTFE) (>5 mm) are clinically employed with good results but its clinical applications in smaller vessels is still problematic due to thrombosis and neointima formation. Achievement of high patency grafts has been to some extent achieved by numerous methods of surface modification techniques, but its results are less than its initial hopes. As examples, endothelial cells coated on the luminal surface of ePTFE has demonstrated limited success after recirculation. Surface modifications of PTFE film with either argon ion beam or UV light from Xe-excimer lamp were reported to increase its interaction with vascular endothelial cell. Surface modification of poly(lactide-co-glycolide)[PLGA] is also very important in tissue engineering, in where induction of its initial high cellular adhesion and spreading is a critical step for development of tissue engineering medical products. We previously reported tissue engineering of the hybrid ePTFE scaffold by seeding smooth muscle cells and subsequently evaluation of its tissue regeneration behaviors and stabilities with circulation of pulsatile flow. To improve its tissue engineering more quickly, we here performed surface modification of ePTFE and porous PLGA scaffold and evaluated its subsequent chemical and biological properties after treating its surface with low energy ion beams. The porous ePTFE was prepared in a round shape (diameter = 1 cm) and dried after organic solvent extraction for ion beam treatment. Another porous PLGA layers (d = 1 cm, t = 1 cm with approximately 92% porosity) were fabricated and treated its surface by irradiating low energy either nitrogen or argon ion beams (1 keV, 1x1015 ions

Pregnancy Outcomes After Myomectomy With Polytetrafluoroethylene Placement

OpenAIRE

Eaton, Jennifer L.; Milad, Magdy P.

2014-01-01

Background and Objectives: The aim of this study was to report preliminary data on pregnancy outcomes after myomectomy with placement of an expanded polytetrafluoroethylene adhesion barrier membrane. Methods: In this retrospective case series, 68 women who underwent myomectomy with expanded polytetrafluoroethylene membrane placement between January 1, 2003, and December 31, 2009, were identified. Of these women, 15 subsequently had documented pregnancies and were included in the final dataset...

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...

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.

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.

Cellular reactions of osteoblast-like cells to a novel nanocomposite membrane for guided bone regeneration

Energy Technology Data Exchange (ETDEWEB)

Meng Yao [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Department of Orthodontics, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Liu Man [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Stomatology Health Care Center, Shenzhen Maternity and Child Healthcare Hospital, Shenzhen 518048 (China); Wang Shaoan [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Mo Anchun [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China)], E-mail: moanchun@163.com; Huang, Cui [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Zuo Yi; Li Jidong [Research Center for Nano-biomaterials, Sichuan University, Chengdu 610041 (China)

2008-11-15

This study investigated the bioactivity and biocompatibility of hydroxyapatite nanoparticles (n-HA)/Polyamide-66 (PA66) nanocomposite membrane and expanded-polytetrafluoroethylene (e-PTFE) membrane (as control) to MG63 osteoblast-like cells. The attachment and proliferation of the cells on the porous surface of nHA/PA66 membrane and the surface of e-PTFE membrane were evaluated by scanning electron microscope (SEM) observation and the MTT assay. The bioactivity of the cells on the surface of the two membranes was evaluated by testing cell viability and alkaline phosphatase (ALP) activities. The results suggested that the bioresponse of MG63 osteoblast-like cells on the porous surface of nHA/PA66 membrane was better than the bioresponse on the opposite surface of e-PTFE membrane. Because of a better cell attachment manner, there is a potential utilization of the guided bone regeneration (GBR) membrane to substitute nHA/PA66 membrane for e-PTFE membra0008.

Cellular reactions of osteoblast-like cells to a novel nanocomposite membrane for guided bone regeneration

International Nuclear Information System (INIS)

Meng Yao; Liu Man; Wang Shaoan; Mo Anchun; Huang, Cui; Zuo Yi; Li Jidong

2008-01-01

This study investigated the bioactivity and biocompatibility of hydroxyapatite nanoparticles (n-HA)/Polyamide-66 (PA66) nanocomposite membrane and expanded-polytetrafluoroethylene (e-PTFE) membrane (as control) to MG63 osteoblast-like cells. The attachment and proliferation of the cells on the porous surface of nHA/PA66 membrane and the surface of e-PTFE membrane were evaluated by scanning electron microscope (SEM) observation and the MTT assay. The bioactivity of the cells on the surface of the two membranes was evaluated by testing cell viability and alkaline phosphatase (ALP) activities. The results suggested that the bioresponse of MG63 osteoblast-like cells on the porous surface of nHA/PA66 membrane was better than the bioresponse on the opposite surface of e-PTFE membrane. Because of a better cell attachment manner, there is a potential utilization of the guided bone regeneration (GBR) membrane to substitute nHA/PA66 membrane for e-PTFE membrane

Anti-inflammatory and Antibacterial Effects of Covalently Attached Biomembrane-Mimic Polymer Grafts on Gore-Tex Implants.

Science.gov (United States)

Jin, Young Ju; Kang, Sunah; Park, Pona; Choi, Dongkil; Kim, Dae Woo; Jung, Dongwook; Koh, Jaemoon; Jeon, Joohee; Lee, Myoungjin; Ham, Jiyeon; Seo, Ji-Hun; Jin, Hong-Ryul; Lee, Yan

2017-06-07

Expanded polytetrafluoroethylene (ePTFE), also known as Gore-Tex, is widely used as an implantable biomaterial in biomedical applications because of its favorable mechanical properties and biochemical inertness. However, infection and inflammation are two major complications with ePTFE implantations, because pathogenic bacteria can inhabit the microsized pores, without clearance by host immune cells, and the limited biocompatibility can induce foreign body reactions. To minimize these complications, we covalently grafted a biomembrane-mimic polymer, poly(2-methacryloyloxylethyl phosphorylcholine) (PMPC), by partial defluorination followed by UV-induced polymerization with cross-linkers on the ePTFE surface. PMPC grafting greatly reduced serum protein adsorption as well as fibroblast adhesion on the ePTFE surface. Moreover, the PMPC-grafted ePTFE surface exhibited a dramatic inhibition of the adhesion and growth of Staphylococcus aureus, a typical pathogenic bacterium in ePTFE implants, in the porous network. On the basis of an analysis of immune cells and inflammation-related factors, i.e., transforming growth factor-β (TGF-β) and myeloperoxidase (MPO), we confirmed that inflammation was efficiently alleviated in tissues around PMPC-grafted ePTFE plates implanted in the backs of rats. Covalent PMPC may be an effective strategy for promoting anti-inflammatory and antibacterial functions in ePTFE implants and to reduce side effects in biomedical applications of ePTFE.

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

Long-term survival of two dogs after mitral valve plasty

Directory of Open Access Journals (Sweden)

Isamu Kanemoto

2017-04-01

Full Text Available Two small 9-year-old dogs received mitral valve plasty (MVP for severe mitral regurgitation that could not be controlled via drug administration. MVP consisted of chordal reconstruction using expanded polytetrafluoroethylene (ePTFE sutures and semicircular suture annuloplasty using polypropylene sutures. In both cases, the clinical signs dramatically improved after MVP, although postoperative echocardiography revealed slight residual mitral regurgitant flow. Both dogs survived for several years after MVP without any signs of cardiac distress; one dog survived for 9 years and 1 month, and the other dog survived for 7 years and 10 months. These findings highlight the durability of ePTFE sutures as artificial chordae and the excellence of semicircular suture annuloplasty in small dogs.

Experimental study of physical properties of artificial materials for the development of the tissue-engineered valvular heart apparatus in comparison with biological analogs

Science.gov (United States)

Chiryatyeva, Aleksandra; Trebushat, Dmitry; Prokhorokhin, Aleksei; Khakhalkin, Vladimir; Andreev, Mark; Novokhreschenov, Aleksei; Kretov, Evgeny

2017-12-01

Cardiovascular diseases are the leading cause of death worldwide. Valvular heart disease often requires valve repair or replacement. Today, surgery uses xenograft—porcine or bovine pericardium. However, bioprosthetic valves do not ensure sufficient durability. We investigated 0.6% glutaraldehyde-treated porcine pericardium to define its properties. Using a tensile test stand, we studied characteristics of the polymeric material—expanded polytetrafluoroethylene (ePTFE)—and compared it to xenopericardium. The artificial material provides a better durability; it has higher elastic modulus and ultimate tensile strength. However, ePTFE samples demonstrated direction anisotropy due to extrusion features. It requires the enhancement of quality of the ePTFE sheet or investigation of other polymeric materials to find the adequate replacement for bioprosthetic heart valves.

Dilatation of aortic grafts over time: what to expect and when to be concerned

DEFF Research Database (Denmark)

Schroeder, Torben V; Eldrup, Nikolaj; Just, Sven

2009-01-01

Dilatation of aortic prosthetic grafts is commonly reported, but most reports are anecdotal, with little objective data in the literature. We performed a prospective trial of 303 patients who underwent prosthetic graft repair for aortic aneurysm or occlusive disease, randomizing patients between...... insertion of a woven polyester or expanded polytetrafluoroethylene (ePTFE) graft. Patients were followed with computed tomography and ultrasonography for up to 5 years in order to assess the frequency and magnitude of postoperative dilatation. Graft dilatation was documented in patients with polyester...... grafts at 12 months. Thereafter and up to 60 months, polyester grafts did not dilate further. After 5 years, polyester prostheses had dilated by 25% and ePTFE by 12.5%, as determined by computed tomography imaging. These observations suggest that dilatation of prosthetic grafts is more frequent...

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)

Endovascular Treatment of Occlusive Lesions in the Aortic Bifurcation with Kissing Polytetrafluoroethylene-Covered Stents

NARCIS (Netherlands)

Grimme, F.A.B.; Spithoven, J.H.; Zeebregts, C.J.A.; Scharn, D.M.; Reijnen, M.M.

2015-01-01

PURPOSE: To determine the clinical outcomes of polytetrafluoroethylene covered balloon expandable stents (CBESs) in occlusive lesions of the aortic bifurcation in a kissing stent configuration. MATERIALS AND METHODS: The study included 69 consecutive patients (29 men, 40 women) who underwent kissing

Endovascular Treatment of Occlusive Lesions in the Aortic Bifurcation with Kissing Polytetrafluoroethylene-Covered Stents

NARCIS (Netherlands)

Grimme, Frederike A. B.; Spithoven, J. Hans; Zeebregts, Clark J.; Scharn, Dirk M.; Reijnen, Michel M. P. J.

Purpose: To determine the clinical outcomes of polytetrafluoroethylene covered balloon expandable stents (CBESs) in occlusive lesions of the aortic bifurcation in a kissing stent configuration. Materials and Methods: The study included 69 consecutive patients (29 men, 40 women) who underwent kissing

Optimization of RNA preservation in granulation tissue in the expanded polytetrafluoroethylene (ePTFE) tube model

DEFF Research Database (Denmark)

Danielsen, Patricia L; Koudahl, V; Christensen, B

2009-01-01

, removed after ten days and randomized to four RNA preservation groups. Storage in RNAlater at 4 degrees C and snap freezing in methanol/acetone yielded significantly better RNA quality than snap freezing with liquid nitrogen and storage in RNAlater at -80 degrees C. Snap freezing in liquid nitrogen failed...

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.

A Modified Rabbit Ulna Defect Model for Evaluating Periosteal Substitutes in Bone Engineering: A Pilot Study

Energy Technology Data Exchange (ETDEWEB)

El Backly, Rania M. [DIMES, University of Genova, Genova (Italy); IRCCS AOU San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genova (Italy); Faculty of Dentistry, Alexandria University, Alexandria (Egypt); Chiapale, Danilo [IRCCS AOU San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genova (Italy); Muraglia, Anita [Biorigen S.R.L., Genova (Italy); Tromba, Giuliana [Sincrotrone Trieste S.C.P.A., Trieste (Italy); Ottonello, Chiara [Biorigen S.R.L., Genova (Italy); Santolini, Federico [IRCCS AOU San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genova (Italy); Cancedda, Ranieri; Mastrogiacomo, Maddalena, E-mail: maddalena.mastrogiacomo@unige.it [DIMES, University of Genova, Genova (Italy); IRCCS AOU San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genova (Italy)

2015-01-06

The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX{sup ®}) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12–16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX{sup ®}) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute.

A Modified Rabbit Ulna Defect Model for Evaluating Periosteal Substitutes in Bone Engineering: A Pilot Study

International Nuclear Information System (INIS)

El Backly, Rania M.; Chiapale, Danilo; Muraglia, Anita; Tromba, Giuliana; Ottonello, Chiara; Santolini, Federico; Cancedda, Ranieri; Mastrogiacomo, Maddalena

2015-01-01

The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX ® ) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12–16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX ® ) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute.

Functional cine MRI of the abdomen for the assessment of implanted synthetic mesh in patients after incisional hernia repair: initial results

Energy Technology Data Exchange (ETDEWEB)

Fischer, Tanja [Ludwig-Maximilians-University Munich, Department of Clinical Radiology, Munich (Germany); Ludwig-Maximilians-University Munich, Department of Clinical Radiology, Klinikum Innenstadt, Munich (Germany); Ladurner, Roland; Mussack, Thomas [Ludwig-Maximilians-University Munich, Department of Surgery and Traumatology, Klinikum Innenstadt, Munich (Germany); Gangkofer, Alexander; Reiser, Maximilian; Lienemann, Andreas [Ludwig-Maximilians-University Munich, Department of Clinical Radiology, Munich (Germany)

2007-12-15

The aim of our study was to develop a method that allows the vizualiation and evaluation of implanted mesh in patients after incisional hernia repair with MRI. Furthermore, we assessed problems typically related with mesh implantation like adhesions and muscular atrophy. We enrolled 28 patients after incisional hernia repair. In 10 patients mesh implantation was done by laparoscopy (expanded polytetrafluoroethylene=ePTFE mesh) and in 18 by laparotomy (polypropylene mesh). Functional MRI was performed on a 1.5-T system in supine position. Sagittal and axial TrueFISP images of the entire abdomen were acquired with the patient repeatedly straining. Evaluation included: correct position and intact fixation of the mesh, furthermore visceral adhesions, recurrent hernia and atrophy of the rectus muscle. The ePTFE mesh was visible in all cases; the polypropylene mesh was not detectable. In seven of the ten ePTFE meshes the fixation was not intact; two recurrent hernias were detected. Twenty of 28 patients had intraabdominal adhesions. In 5 cases mobility of the abdominal wall was reduced, and 16 patients showed an atropy of the rectus muscle. Functional cine MRI is a suitable method for follow-up studies in patients after hernia repair. ePTFE meshes can be visualized directly, and typical complications like intestinal adhesions and abdominal wall dysmotility can be assessed reliably. (orig.)

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.)

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.)

Porcine carotid artery replacement with biodegradable electrospun poly-e-caprolactone vascular prosthesis.

Science.gov (United States)

Mrówczyński, Wojciech; Mugnai, Damiano; de Valence, Sarra; Tille, Jean-Christophe; Khabiri, Ebrahim; Cikirikcioglu, Mustafa; Möller, Michael; Walpoth, Beat H

2014-01-01

There is a continuous search for shelf-ready small-caliber vascular prostheses with satisfactory early and late results. Biodegradable scaffolds, repopulated by recipient's cells regenerating a neovessel, can be a suitable option for adult and pediatric, urgent and elective cardiovascular procedures. This was a short-term experimental assessment of a new biodegradable vascular prosthesis for arterial replacement in the pig. Eleven pigs underwent bilateral carotid artery replacement with biodegradable electrospun poly-ε-caprolactone (PCL) nanofiber prostheses (internal diameter, 4 mm; length, 5 cm); or expanded polytetrafluoroethylene (ePTFE) prostheses as control. Perioperative anticoagulation was achieved with intravenous heparin (double baseline activated clotting time). Postoperatively, until conclusion of the study at 1 month, animals received aspirin and clopidogrel daily. Transit time flow was measured intraoperatively and at sacrifice. Doppler ultrasound (1 and 4 weeks) and a selective carotid angiography (4 weeks) were performed to assess patency. All explanted grafts were analyzed by histology, morphometry, and scanning electron microscopy in order to study graft-host interaction. Surgical handling and hemostasis of the new prostheses were excellent. Patency rate was 78% (7/9) for PCL grafts, compared with 67% (4/6) for ePTFE grafts. Transit time flow and Doppler ultrasound showed no significant changes in flow and velocity or diameter over time in both groups. Both prostheses showed no detectable in vivo compliance as compared with native carotid artery. Percent neoendothelialization was 86% for PCL and 58% for ePTFE grafts (P = .008). Neointima formation was equal in both grafts. More adventitial infiltration of macrophages, myofibroblasts, and capillaries was seen in PCL grafts with a milder foreign-body reaction when compared with ePTFE implants. Both grafts showed similar endoluminal thrombus formation. Biodegradable, electrospun PCL grafts showed

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.

76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan

Science.gov (United States)

2011-02-15

... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-386 (Third Review)] Granular Polytetrafluoroethylene Resin From Japan AGENCY: United States International Trade Commission. ACTION: Termination of five... revocation of the antidumping duty order on granular polytetrafluoroethylene resin from Japan would be likely...

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

75 FR 67105 - Granular Polytetrafluoroethylene Resin From Italy and Japan

Science.gov (United States)

2010-11-01

... Polytetrafluoroethylene Resin From Italy and Japan AGENCY: United States International Trade Commission. ACTION... resin from Italy and Japan. SUMMARY: The Commission hereby gives notice that it has instituted reviews... revocation of the antidumping duty orders on granular polytetrafluoroethylene resin from Italy and Japan...

The protective effect of vein cuffed anastomoses is not mechanical in origin.

Science.gov (United States)

Norberto, J J; Sidawy, A N; Trad, K S; Jones, B A; Neville, R F; Najjar, S F; Sidawy, M K; DePalma, R G

1995-04-01

Intimal hyperplasia (IH) is a proliferative process of vascular smooth muscle cells that occurs after an arterial injury, particularly at outflow anastomoses of prosthetic bypass grafts. IH causes stenosis that leads ultimately to graft flow reduction and thrombosis. We have demonstrated previously that vein cuff interposition between an expanded polytetrafluoroethylene (e-PTFE) graft and artery at distal anastomoses diminished IH formation in the arterial outflow as compared with noncuffed anastomoses. Improved long-term patency rates associated with the placement of an interposition vein cuff at the distal anastomosis of e-PTFE grafts to infrageniculate arteries have also been demonstrated clinically. This study examined the mechanical factors that may contribute to the protective effect of cuffed anastomoses. These factors include the expansibility of the vein cuff as compared with e-PTFE, as well as the angle of the cuffed anastomosis. Compatible animals were selected by use of platelet aggregation studies. Nine dogs, group A, received a 4 mm e-PTFE graft plus a 1 cm long interposition vein cuff at the distal anastomosis in the left carotid artery. The same procedure was done on the right side, and in addition the vein cuff was encircled by an e-PTFE jacket incorporated into the anastomosis to prevent the expansion of the vein cuff with arterial pulsation. To study the effect of distal anastomotic angle and geometry on the formation of IH, five dogs, group B, received a 4 mm e-PTFE graft in both sides. On the left, the distal anastomosis was performed between the graft and the artery at an acute angle as it is commonly done when a bypass graft is placed. On the right side a 1 cm long, 6 mm diameter e-PTFE segment was interposed between the artery and the graft at a perpendicular angle. This geometry mimicked the right angle of a vein cuff-to-artery anastomosis. After 10 weeks the grafts were harvested, and the thickness of IH was measured with an ocular

Recovery of ammonia from poultry litter using flat gas permeable membranes.

Science.gov (United States)

Rothrock, M J; Szögi, A A; Vanotti, M B

2013-06-01

The use of flat gas-permeable membranes was investigated as components of a new process to capture and recover ammonia (NH3) in poultry houses. This process includes the passage of gaseous NH3 through a microporous hydrophobic membrane, capture with a circulating dilute acid on the other side of the membrane, and production of a concentrated ammonium (NH4) salt. Bench- and pilot-scale prototype systems using flat expanded polytetrafluoroethylene (ePTFE) membranes and a sulfuric acid solution consistently reduced headspace NH3 concentrations from 70% to 97% and recovered 88% to 100% of the NH3 volatilized from poultry litter. The potential benefits of this technology include cleaner air inside poultry houses, reduced ventilation costs, and a concentrated liquid ammonium salt that can be used as a plant nutrient solution. Published by Elsevier Ltd.

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

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.

Science.gov (United States)

2010-04-01

... composite implant material. 878.3500 Section 878.3500 Food and Drugs FOOD AND DRUG ADMINISTRATION... Prosthetic Devices § 878.3500 Polytetrafluoroethylene with carbon fibers composite implant material. (a) Identification. A polytetrafluoroethylene with carbon fibers composite implant material is a porous device...

Wound Healing and ndash; A Proteomic Analysis of the Effect of Erythropoietin on Granulation Tissue Isolated from ePTFE Implants

Directory of Open Access Journals (Sweden)

Bekka Christensen

2014-02-01

Conclusion: Daily injection of recombinant human erythropoietin of 1000 IU/kg alters the protein expression of GAPDH, ENOA and TPIS in granulation tissue from wounds on postoperative day 9. The successful combination of proteomic analysis of wound tissue and the ePTFE wound model could advance our knowledge of the complex healing process. [Arch Clin Exp Surg 2014; 3(1.000: 26-33

Structure and properties of polymer-silicate nanocomposites based on polytetrafluoroethylene

Energy Technology Data Exchange (ETDEWEB)

Sleptsova, Sardana A.; Okhlopkova, Aitalina A. [North-Eastern Federal University, Yakutsk (Russian Federation)

2011-07-01

The results of physicomechanical, tribological , and structural investigation of polytetrafluoroethylene based polymers and natural layered silicates are reported. It is shown that the tribological behaviour of the composites can be significantly improved by introducing a small amount of activated silicates. The results of structural examination of the composite friction surfaces by scanning-probe microscopy and IR spectroscopy are discussed. Key words: polytetrafluoroethylene, layered silicates, wear resistance, friction coefficient, structure, IR-spectrum.

Radiation effect on polytetrafluoroethylene

International Nuclear Information System (INIS)

Deng Pengyang; Zhong Xiaoguang; Sun Jiazhen

1999-01-01

Polytetrafluoroethylene (PTFE) has always been regarded as a typical kind of radiation degradation polymer. But, in fact, PTFE can be induced crosslinking by γ-ray or electron beam at some special conditions (free oxygen and a narrow temperature region at 335 +- 5 degree C). Compared with radiation degradiation PTFE, cosslinking PTFE owns a lot of new properties. Some articles concerning with these have been published, which will be systematically reviewed in this

Performance of a 1 kW Class Nafion-PTFE Composite Membrane Fuel Cell Stack

Directory of Open Access Journals (Sweden)

Pattabiraman Krishnamurthy

2012-01-01

Full Text Available Composite membranes have been prepared by impregnation of Nafion into the expanded polytetrafluoroethylene (EPTFE matrix. Nafion loading in the composite membranes was kept constant at 2 mg/cm2. The lower amount of electrolyte per unit area in the composite membranes offers cost advantages compared to conventional membrane of 50 μm thickness with an electrolyte loading of ~9 mg/cm2. Composite membranes (30 μm thickness were found to have higher thermal stability and mechanical strength compared to the conventional membranes (50 μm thickness. The performance of the membrane electrode assembly made with these composite membranes was comparable to that of the conventional membranes. Single cells fabricated from these MEAs were tested for their performance and durability before scaling them up for large area. The performance of a 20-cell stack of active area 330 cm2 fabricated using these membranes is reported.

Differences in collagen distribution of healthy and regenerated periodontium. Histomorphometric study in dogs.

Science.gov (United States)

Souza, Sérgio L S; Macedo, Guilherme O; Silveira E Souza, Adriana M M; Taba, Mário; Novaes, Arthur B; Oliver, Constance; Jamur, Maria C; Correa, Vani M A

2013-10-01

Previous studies have shown that there is a relationship between periodontal disease and the distribution of collagen fibers. This study evaluated the distribution of collagen types I and III in regenerated bone and periodontal ligament, comparing them to the tissues near the regenerated area and to the healthy periodontium. In the third (P3) and fourth (P4) mandibular premolars of 5 healthy mongrel dogs, bilaterally, buccal class 2 furcation lesions were surgically created and chronified for 3 weeks. After that, full flaps were elevated and expanded polytetrafluoroethylene (e-PTFE) membranes were adapted, sutured and recovered by the flaps. Two weeks after surgery, two membranes on the same side were removed and the other membranes were removed four weeks after surgery. The dogs were euthanized at 12 weeks following placement of the e-PTFE membranes. P3 and P4 teeth as well as the second premolars (healthy control teeth) and their periodontal tissues were removed and histologically processed for Collagen Quantification (COLQ). The amount of type III collagen was higher in native bone compared to the regenerated area. For periodontal ligament, COLQ for type I collagen showed statistically significant differences (Tukeys's Multiple Comparison, p⟨0.05) between the regenerated groups and the control group. These differences were not found for type III COLQ. There are significant differences in collagen distribution among the regenerated, native and control tissues. Membrane removal 2 or 4 weeks postoperatively did not influence the collagen composition.

Radiolysis of polytetrafluoroethylene

International Nuclear Information System (INIS)

Ferreira, Max Passos; Ferreira, Roberta Viana; Verly, Rodrigo Moreira

2007-01-01

Polytetrafluoroethylene is a linear polymer with structure: -[-CF 2 -CF 2 -] n -. Due to its singular properties, it is ideal for use at high temperatures and in chemically aggressive environments. It is extremely sensitive to ionizing radiation and is quickly degraded. PTFE radiolysis has been extensively studied. However, despite the many published papers, its degradation mechanism remains much uncertain. The degradation of polytetrafluoroethylene by γ irradiation yields perfluorinated carboxylic acids, olefin mixtures, and paraffins with different molecular weights. This process is a new alternative for the synthesis of aliphatic perfluorinated compounds used as intermediates for obtaining special products such as fluoro surfactants, electrical materials, special products for the textile industry, etc. PTFE scraps were irradiated with a uniform source of 60 Co gamma rays in oxygen atmosphere with a dose of 3 MGy. The radiolysis of PTFE yielded a water soluble material (probably fluorinated hydrocarbons with low molecular weight and main chains with 10-20 carbon atoms) and a water insoluble brittle polymeric material. Spectroscopy analysis in the infrared region of irradiated and non-irradiated PTFE were carried out. X-ray diffractometry pointed to changes in the crystalline structure of PTFE; scanning electron microscopy indicated alterations in samples irradiated under different conditions. Mass spectrometry was also used to identify the compounds formed after sample irradiation. Comparison of irradiated and non-irradiated FTIR spectra showed the formation of bands at 3450 cm -1 , associated with the O-H stretching, and at 1631 cm -1 , associated with the C=O stretching. The bands are characteristic of carboxylic acid, which indicates its formation in irradiated PTFE. (author)

Radiation induced crosslinking of polytetrafluoroethylene

International Nuclear Information System (INIS)

Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Otsuhata, Kazushige; Kudoh, Hisaaki; Seguchi, Tadao.

1995-01-01

The Irradiation temperature effect on polytetrafluoroethylene (PTFE) from room temperature to 380degC was investigated by tensile test and thermal analysis. The behavior of tensile properties and changes of crystallinity on irradiation indicated the formation of a network structure in PTFE by radiation induced crosslinking in inert gas in the molten state just above the melting temperature of PTFE (327degC). The crosslinked PTFE showed a much improved radiation resistance in an atmospheric radiation field. (author)

Polytetrafluoroethylene-jacketed stirrer modified with graphene oxide and polydopamine for the efficient extraction of polycyclic aromatic hydrocarbons.

Science.gov (United States)

Zhang, Zinxin; Mwadini, Mwadini Ahmada; Chen, Zilin

2016-10-01

Steel stirrers jacketed with polytetrafluoroethylene can be regarded as an ideal substrate for stirrer bar sorptive extraction. However, it is still a great challenge to immobilize graphene onto a polytetrafluoroethylene stirrer due to the high chemical resistance of the surface of a polytetrafluoroethylene stirrer. We describe here a method to modify the surface of polytetrafluoroethylene stirrers with graphene. In this work, graphene was used as the sorbent due to its excellent adsorption capability for aromatic compounds, such as polycyclic aromatic compounds. Graphene was successfully immobilized onto polytetrafluoroethylene-stirrer by a bio-inspired polydopamine functionalization method. The graphene-modified polytetrafluoroethylene-stirrer shows good stability and tolerance to stirring, ultrasonication, strong acidic and basic solutions, and to organic solvents. The multilayer coating was characterized by scanning electronic microscopy and Fourier transform infrared spectroscopy. After the optimization of some experimental conditions, the graphene-modified polytetrafluoroethylene stirrer was used for the stirrer bar sorptive extraction of polycyclic aromatic hydrocarbons, in which the binding between the polycyclic aromatic hydrocarbons and the graphene layer was mainly based on π-π stacking and hydrophobic interactions. The graphene-modified polytetrafluoroethylene-stirrer-based stirrer bar sorptive extraction and high-performance liquid chromatography method was developed for the determination of polycyclic aromatic hydrocarbons with great extraction efficiency, with enrichment factors from 18 to 62. The method has low limits of detection of 1-5 pg/mL, wide linear range (5-100 and 10-200 pg/mL), good linearity (R ≥ 0.9957) and good reproducibility (RSD ≤ 6.45%). The proposed method has been applied to determine polycyclic aromatic hydrocarbons in real dust samples. Good recoveries were obtained, ranging from 88.53 to 109.43%. © 2016 WILEY-VCH Verlag

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

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

Cell microarrays on photochemically modified polytetrafluoroethylene

Czech Academy of Sciences Publication Activity Database

Mikulíková, R.; Moritz, S.; Gumpenberger, T.; Olbrich, M.; Romanin, C.; Bačáková, Lucie; Švorčík, V.; Heitz, J.

2005-01-01

Roč. 26, č. 27 (2005), s. 5572-5580 ISSN 0142-9612 R&D Projects: GA AV ČR(CZ) IAA5011301 Grant - others:CZ-AT(CZ) Scientific-Technical Cooperation 2004-9; Jubiläumsfonds der Österreichischen Nationalbank(AT) 10549 Institutional research plan: CEZ:AV0Z50110509 Keywords : polytetrafluoroethylene * surface modification * endothelial cells Subject RIV: EI - Biotechnology ; Bionics Impact factor: 4.698, year: 2005

Lipoplex gene transfer of inducible nitric oxide synthase inhibits the reactive intimal hyperplasia after expanded polytetrafluoroethylene bypass grafting.

Science.gov (United States)

Pfeiffer, Tomas; Wallich, Martina; Sandmann, Wilhelm; Schrader, Jürgen; Gödecke, Axel

2006-05-01

Intimal hyperplasia (IH) is most commonly the cause of graft occlusion in infrainguinal bypass grafting for arterial occlusive disease. We investigated the influence of nitric oxide on the IH of the arterial vessel wall at the region of prosthetic bypass anastomoses. Experiments were performed in 10 Foxhound dogs. We used a technique of inducible nitric oxide synthase (iNOS) overexpression by a non-virus-mediated, liposome-based iNOS gene transfer. The plasmid pSCMV-iNOS, which drives the expression of iNOS under control of the cytomegalovirus promoter, was complexed with cationic liposomes (lipoplexes). Segments of both carotid arteries were pretreated by intramural injection of a lipoplex solution by using an infiltrator balloon catheter (Infiltrator Drug Delivery Balloon System). In each dog, iNOS was administered at one side, and a control vector (pSCMV2) was administered at the contralateral side. Carotid arteries were ligated, and bypass grafts (expanded polytetrafluoroethylene, 6-mm, ring enforced) were implanted on both sides. The proximal and distal anastomoses (end-to-side fashion; running nonabsorbable sutures) were placed in the pretreated regions. After 6 months, the prostheses were excised, and the intimal thicknesses of 50 cross sections (orcein staining) of each anastomosis were measured planimetrically. The average reduction of the neointima thickness of the iNOS side in proximal anastomoses at the prosthetic wall, suture region, and arterial wall was 43%, 52%, and 81%, respectively. In distal anastomoses, the average reduction was 40%, 47%, and 52%, respectively. All differences of neointima thickness between the iNOS and control sides were statistically significant (Wilcoxon test; P < or = .05). Inducible NOS expression is an efficient approach for inhibition of IH. In contrast to earlier studies, which investigated the efficacy of gene therapeutic NOS expression at 3 to 4 weeks after intervention, the novelty of our findings is that a single

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.)

Surface Modification of Poly(tetrafluoroethylene) by Magnesium Amalgam

Czech Academy of Sciences Publication Activity Database

Kavan, Ladislav; Janda, Pavel; Weber, Jan

2001-01-01

Roč. 36, - (2001), s. 879-885 ISSN 0022-2461 R&D Projects: GA ČR GA203/98/1168; GA ČR GA203/98/1181 Institutional research plan: CEZ:AV0Z4040901 Keywords : poly(tetrafluoroethylene) * surface modification * ESCA Subject RIV: CG - Electrochemistry Impact factor: 0.728, year: 2001

Mechanisms of Contact Electrification at Aluminum-Polytetrafluoroethylene and Polypropylene-Water

KAUST Repository

Nauruzbayeva, Jamilya

2017-01-01

of electrons, but a comprehensive understanding of contact electrification at interfaces of electrical insulators, such as air, water, polytetrafluoroethylene (PTFE), polypropylene remains incomplete. In fact, a variety of mechanisms responsible for transfer

Improvement of Polytetrafluoroethylene Surface Energy by Repetitive Pulse Non-Thermal Plasma Treatment in Atmospheric Air

International Nuclear Information System (INIS)

Yang Guoqing; Zhang Guanjun; Zhang Wenyuan

2011-01-01

Improvement of polytetrafluoroethylene surface energy by non-thermal plasma treatment is presented, using a nanosecond-positive-edge repetitive pulsed dielectric barrier discharge generator in atmospheric air. The electrical parameters including discharging power, peak and density of micro-discharge current were calculated, and the electron energy was estimated. Surface treatment experiments of polytetrafluoroethylene films were conducted for both different applied voltages and different treating durations. Results show that the surface energy of polytetrafluoroethylene film could be improved to 40 mJ/m 2 or more by plasma treatment. Surface roughness measurement and surface X-ray photoelectron spectroscopy analysis indicate that there are chemical etching and implantation of polar oxygen groups in the sample surface treating process, resulting in the improvement of the sample surface energy. Compared with an AC source of 50 Hz, the dielectric barrier discharges generated by a repetitive pulsed source could provide higher peak power, lower mean power, larger micro-discharge current density and higher electron energy. Therefore, with the same applied peak voltage and treating duration, the improvement of polytetrafluoroethylene surface energy using repetitive pulsed plasma is more effective, and the plasma treatment process based on repetitive pulsed dielectric barrier discharges in air is thus feasible and applicable.

Structural changes in polytetrafluoroethylene molecular chains upon sliding against steel

NARCIS (Netherlands)

Shen, J.T.; Pei, Y.T.; Hosson, J.Th.M. De

In this work, the influence of dry sliding between a steel counterpart ball and polytetrafluoroethylene (PTFE) plate sample on the transformation of PTFE molecular structure is investigated. With X-ray diffraction, differential scanning calorimetry, Fourier transform infrared (FT-IR) spectroscopy

Influence of gamma-radiation on tensile strength properties of polytetrafluoroethylene (PTFE)

CERN Document Server

Gafurov, U G; Nemkova, N

2002-01-01

The tensile strength properties of polytetrafluoroethylene are studied at modification doses of gamma-irradiation. The main molecular process of polymer destruction is found to be the thermostimulated slippage of molecular chains. (author)

An in vivo comparative study of the e-polytetrafluoroethylene vascular prostheses: Vitaflon and Gore-Tex.

Science.gov (United States)

Dobrova, N B; Gorodkov, A J; Sidorenko, E S; Schekhter, A B; Baquey, C

1999-12-01

A comparative study was performed in order to validate new Russian e-PTFE vascular prostheses Vitaflon (St. Petersburg, Russia). The Gore-Tex prostheses were chosen as a referential model. The prostheses were implanted in the venous and arterial positions in 13 dog experiments. After the implantation time was over a comprehensive histological and histochemical examination of excized specimens was performed. It was demonstrated that there is no difference in healing and functional properties between the two studied prostheses. Copyright 1999 Kluwer Academic Publishers

Transcatheter pulmonary valve replacement by hybrid approach using a novel polymeric prosthetic heart valve: proof of concept in sheep.

Directory of Open Access Journals (Sweden)

Ben Zhang

Full Text Available Since 2000, transcatheter pulmonary valve replacement has steadily advanced. However, the available prosthetic valves are restricted to bioprosthesis which have defects like poor durability. Polymeric heart valve is thought as a promising alternative to bioprosthesis. In this study, we introduced a novel polymeric transcatheter pulmonary valve and evaluated its feasibility and safety in sheep by a hybrid approach.We designed a novel polymeric trileaflet transcatheter pulmonary valve with a balloon-expandable stent, and the valve leaflets were made of 0.1-mm expanded polytetrafluoroethylene (ePTFE coated with phosphorylcholine. We chose glutaraldehyde-treated bovine pericardium valves as control. Pulmonary valve stents were implanted in situ by a hybrid transapical approach in 10 healthy sheep (8 for polymeric valve and 2 for bovine pericardium valve, weighing an average of 22.5±2.0 kg. Angiography and cardiac catheter examination were performed after implantation to assess immediate valvular functionality. After 4-week follow-up, angiography, echocardiography, computed tomography, and cardiac catheter examination were used to assess early valvular function. One randomly selected sheep with polymeric valve was euthanized and the explanted valved stent was analyzed macroscopically and microscopically.Implantation was successful in 9 sheep. Angiography at implantation showed all 9 prosthetic valves demonstrated orthotopic position and normal functionality. All 9 sheep survived at 4-week follow-up. Four-week follow-up revealed no evidence of valve stent dislocation or deformation and normal valvular and cardiac functionality. The cardiac catheter examination showed the peak-peak transvalvular pressure gradient of the polymeric valves was 11.9±5.0 mmHg, while that of two bovine pericardium valves were 11 and 17 mmHg. Gross morphology demonstrated good opening and closure characteristics. No thrombus or calcification was seen macroscopically

The noncovalent bonding of antibiotics to a polytetrafluoroethylene-benzalkonium graft

International Nuclear Information System (INIS)

Harvey, R.A.; Greco, R.S.

1981-01-01

This study evaluates the noncovalent bonding of anionic antibiotics to polytetrafluoroethylene grafts using benzalkonium chloride as a cationic anchor. The binding of radiolabeled surfactants and antibiotics was evaluated by liquid scintillation and in an in vitro microbiologic assay against Staphylococcus aureus. Significant quantities of antibiotic were bound when the grafts were pretreated with benzalkonium in ethanol or aqueous solution at elevated temperature. Bound antibiotic is stable in aqueous salt solutions, but slowly dissociates in the presence of blood or serum. The ionic nature of the bonding process is clarified by the use of a variety of antibiotics and surfactants with complementary charges. The ability of the benzalkonium treated grafts to adsorb antibiotic from blood is, likewise, demonstrated and the possibility of concomitantly binding heparin and antibiotic simultaneously is evaluated. These studies support the ability to noncovalently bond antibiotics to polytetrafluoroethylene surfaces and form the basis of eventually utilizing these surfaces in the prevention of vascular prosthetic infections

Long-Term Outcomes of Double-Layered Polytetrafluoroethylene Membrane-Covered Self-Expandable Segmental Metallic Stents (Uventa) in Patients with Chronic Ureteral Obstructions: Is It Really Safe?

Science.gov (United States)

Kim, Myong; Hong, Bumsik; Park, Hyung Keun

2016-12-01

To evaluate the long-term clinical efficacy and safety of double-layered polytetrafluoroethylene membrane-covered self-expandable segmental metallic stents (Uventa) in patients with chronic ureteral obstruction. In a retrospective study, a total of 50 ureter units (44 patients) with chronic obstructions were included from July 2010 to May 2015. Indications for Uventa placement were primary stenting for malignant ureteral obstruction, failed conventional polymeric Double-J stent (PS), or percutaneous nephrostomy (PCN) technique, with comorbidities or fears limiting PS/PCN changes, or with irritation or pain due to PS/PCN. Patients underwent Uventa stent placement using the antegrade or retrograde approach. There were no immediate procedure-related complications, and all stents were placed in the proper sites. During the median follow-up of 30.9 (interquartile range [IQR], 8.1-49.0) months, the primary (no obstruction and no additional intervention) and overall success (no obstruction and no additional intervention except supplementary Uventa) was 30.0% and 34.0%, respectively. Moreover, 14 of 50 ureter units (28.0%) experienced major complications (≥Clavien-Dindo class IIIb), such as ureteroarterial fistula (three cases, 6.0%), ureteroenteric fistula (three, 6.0%), ureterovaginal fistula (one, 2.0%), ureter perforation (one, 2.0%), uncontrollable bleeding (one, 2.0%), and complete obstruction (five, 10.0%). On univariate analysis, major complications were associated with female (odds ratio [OR] = 6.000), cervical cancer (OR = 4.667), ureteral stricture length (≥6.0 cm, OR = 4.583), and placement duration (≥24.0 months, OR = 20.429; all p stent demonstrated poor treatment outcomes with frequent major complications in patients with chronic ureteral obstructions.

Treatment of intrabony defects with resorbable materials, non-resorbable materials and flap debridement.

Science.gov (United States)

Zybutz, M D; Laurell, L; Rapoport, D A; Persson, G R

2000-03-01

Different types of barriers are used in guided tissue regenerative procedures. This prospective study compared resorbable citric acid ester softened polylactic acid membranes (RM) and non-resorbable expanded polytetrafluoroethylene (ePTFE) barriers (NRM) in GTR treatment of intrabony defects. 29 subjects were randomly assigned to the RM group or NRM group. Each patient received one GTR procedure. An open flap debridement (FD) was performed at another site 2 weeks later to evaluate healing potential. Clinical treatment outcomes were finally evaluated 12 months after surgery for changes of pocket depth PD, probing attachment level PAL, and probing bone level PBL, and radiographically for bone change using standardised radiographs. No differences in healing patters after surgery were found between patients in the 2 study groups as evaluated from the FD surgical procedures. NRM treated sites showed less signs of post-surgical inflammation during the 1st 4 weeks of healing than did RM treated sites (p<0.05). GTR-treated defects in the RM group, initially 7.0+/-2.2 mm deep, showed PD reduction of 3.3+/-2.2 mm, PAL gain of 2.4+/-1.8 mm, PBL gain of 2.4+/-3.7 mm (28%) and a radiographic bone fill of 2.3+/-2.4 mm. Defects treated with the NRM exhibited PD reduction of 3.1+/-2.1 mm, PAL gain of 2.4+/-0.8 mm, PBL gain of 2.2+/-1.7 mm (25%) and a radiographic bone fill of 3.3+/-2.2 mm. All improvements were statistically significant (p<0.01) but there was no difference between RM and NRM treatments for any of the efficacy variables. The results of this study indicated that there was no clinically significant difference in treatment outcomes following GTR treatment of intrabony defects with citric acid ester softened polylactic acid membranes as compared to ePTFE barriers. The overall mean inter-proximal vertical bone defect fill at 12 months as assessed from intra-oral radiographs was 44% of the original mean defect depth. Thus, no clinically significant difference in

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.

Cell proliferation on UV-excimer lamp modified and grafted polytetrafluoroethylene

Czech Academy of Sciences Publication Activity Database

Švorčík, V.; Ročková, K.; Ratajová, E.; Heitz, J.; Huber, N.; Bäuerle, D.; Bačáková, Lucie; Dvořánková, B.; Hnatowicz, Vladimír

2004-01-01

Roč. 217, č. 2 (2004), s. 307-313 ISSN 0168-583X R&D Projects: GA AV ČR IAA5011301; GA ČR GA106/03/0514 Grant - others:CZ-AT(CZ) Aktion 2002-7 Institutional research plan: CEZ:AV0Z5011922 Keywords : polytetrafluoroethylene * UV-beam modification * grafting Subject RIV: EI - Biotechnology ; Bionics Impact factor: 0.997, year: 2004

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.

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

Growth of muscle cells on plasma-treated and gold nanoparticles-grafted polytetrafluoroethylene

Czech Academy of Sciences Publication Activity Database

Řezníčková, A.; Makajová, Z.; Kasálková-Slepičková, N.; Kolská, Z.; Bačáková, Lucie; Švorčík, V.

2014-01-01

Roč. 23, č. 3 (2014), s. 227-236 ISSN 1026-1265 R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:67985823 Keywords : polytetrafluoroethylene ( PTFE ) * nanoparticles * biocompatibility Subject RIV: EI - Biotechnology ; Bionics Impact factor: 1.806, year: 2014

Tribological behavior of polytetrafluoroethylene coating reinforced with black phosphorus nanoparticles

Science.gov (United States)

Peng, Shiguang; Guo, Yue; Xie, Guoxin; Luo, Jianbin

2018-05-01

This study compares the tribological performance of polytetrafluoroethylene (PTFE) thin film coating reinforced with black phosphorus (BP) or ball-milled graphite (BMG) nanoparticles, so as to elucidate their mechanism of action under reciprocating sliding test conditions. PTFE coatings with 0.5 wt.% BMG (BMG/PTFE) and 0.5 wt.% BP (BP/PTFE) were prepared on GCr15 bearing steel disk by using a spin coater. The friction and wear tests were carried out by using the ball-on-disk tribometer under a normal load of 1 N (contact pressure: 780 MPa), a frequency of 2 Hz, and 4.2 mm sliding displacement amplitude. The surface roughness, wear volume and surface morphology of the coatings were characterized by the three-dimensional white light, and Energy Dispersive X-ray Detector (EDX) analysis coupled with environmental scanning electron microscope (ESEM). It is found that BP/PTFE coating has better anti-wear and anti-friction performances than those of pure PTFE or BMG/PTFE coating. The coating with BP nanoparticles shows excellent tribological properties with the wear volume decreased from 3.52 × 106 μm3 to 1.64 × 106 μm3 and the coefficient of friction (COF) decreased from 0.117 to 0.046. More importantly, the BP layer probably expands and absorbs much energy due to its negative Poisson's ratio phenomenon under reciprocating sliding, and effectively reducing furrow and adhesive wear.

Radiation processing for carbon fiber-reinforced polytetrafluoroethylene composite materials

International Nuclear Information System (INIS)

Oshima, Akihiro; Udagawa, Akira; Morita, Yousuke

2001-01-01

The present work is an attempt to evaluate the performance of the fiber composites with crosslinked polytetrafluoroethylene (PTFE) as a polymer matrix by radiation. The uni-directional carbon fiber-reinforced composites were fabricated with PTFE fine powder impregnation method and then crosslinked by electron beams irradiation under selective conditions. The carbon fiber-reinforced crosslinked PTFE composites show good mechanical properties compared with crosslinked PTFE. The radiation resistance of crosslinked PTFE composites is improved more than that of crosslinked resin without fiber. (author)

Characterization of a tubular flow chamber for studying platelet interaction with biologic and prosthetic materials: deposition of indium 111-labeled platelets on collagen, subendothelium, and expanded polytetrafluoroethylene

International Nuclear Information System (INIS)

Badimon, L.; Turitto, V.; Rosemark, J.A.; Badimon, J.J.; Fuster, V.

1987-01-01

A plastic (Plexiglas) chamber for evaluating platelet deposition under controlled hemodynamic conditions has been developed. The perfusion chamber has been designed to retain the cylindrical shape typical of the vasculature, to be flexible enough to accept a variety of biologic and prosthetic materials, and to simulate a broad range of physiologic flow conditions in either an ex vivo or in vitro perfusion system. Three type of surfaces were exposed to blood flowing directly from the carotid artery of a heparinized pig through the perfusion chamber: de-endothelialized pig aorta, collagen strips from rabbit Achilles tendon, and an expanded polytetrafluoroethylene material (Gore-Tex). Platelets, previously radiolabeled with indium 111 and injected into the animal, were quantified on the material surface, and the total number of deposited platelets determined for a range of blood flow rates (5 to 40 ml/min) and exposure times (0.5 to 20 minutes). The deposition rates were correlated with theory for describing the mass transport of platelets to the test surface. At the wall shear rates investigated (105 to 850 sec-1), the deposition of platelets on subendothelium was strongly dependent on the local flow conditions. Values of deposition on Gore-Tex obtained at similar flow conditions (105 to 425 sec-1) were reduced compared with that observed on subendothelium and showed a markedly weaker dependence on the shear rate. In contrast, deposition of platelets on collagen was more than an order of magnitude greater than on subendothelium and showed a dependence on flow only at the lowest flow rate studied (10 ml/min). The results indicate that collagen is much more reactive than subendothelium and Gore-Tex with respect to the growth and stability of platelet aggregates and moreover suggest that flow mechanisms for depositing platelets on various surface may be substantially different

Characterization of a tubular flow chamber for studying platelet interaction with biologic and prosthetic materials: deposition of indium 111-labeled platelets on collagen, subendothelium, and expanded polytetrafluoroethylene

Energy Technology Data Exchange (ETDEWEB)

Badimon, L.; Turitto, V.; Rosemark, J.A.; Badimon, J.J.; Fuster, V.

1987-12-01

A plastic (Plexiglas) chamber for evaluating platelet deposition under controlled hemodynamic conditions has been developed. The perfusion chamber has been designed to retain the cylindrical shape typical of the vasculature, to be flexible enough to accept a variety of biologic and prosthetic materials, and to simulate a broad range of physiologic flow conditions in either an ex vivo or in vitro perfusion system. Three type of surfaces were exposed to blood flowing directly from the carotid artery of a heparinized pig through the perfusion chamber: de-endothelialized pig aorta, collagen strips from rabbit Achilles tendon, and an expanded polytetrafluoroethylene material (Gore-Tex). Platelets, previously radiolabeled with indium 111 and injected into the animal, were quantified on the material surface, and the total number of deposited platelets determined for a range of blood flow rates (5 to 40 ml/min) and exposure times (0.5 to 20 minutes). The deposition rates were correlated with theory for describing the mass transport of platelets to the test surface. At the wall shear rates investigated (105 to 850 sec-1), the deposition of platelets on subendothelium was strongly dependent on the local flow conditions. Values of deposition on Gore-Tex obtained at similar flow conditions (105 to 425 sec-1) were reduced compared with that observed on subendothelium and showed a markedly weaker dependence on the shear rate. In contrast, deposition of platelets on collagen was more than an order of magnitude greater than on subendothelium and showed a dependence on flow only at the lowest flow rate studied (10 ml/min). The results indicate that collagen is much more reactive than subendothelium and Gore-Tex with respect to the growth and stability of platelet aggregates and moreover suggest that flow mechanisms for depositing platelets on various surface may be substantially different.

Endovascular Placement of an Extraluminal Femoropopliteal Bypass Graft in Human Cadavers

International Nuclear Information System (INIS)

Maynar, Manuel; Llorens, Rafael; Lopez-Sanchez, Carmen; Garcia-Martinez, Virginio; Qian Zhong; Lopera, Jorge; Castaneda, Wilfrido R.

2005-01-01

Purpose. A method to create an extraluminal femoropopliteal bypass graft using endovascular techniques was evaluated in situ on cadaver extremities in an attempt to develop a minimally invasive alternative technique for the management of infrainguinal occlusive arterial disease. Methods. The endovascular placement of an extraluminal femoropopliteal bypass graft was undertaken in 5 cadaver legs. Following percutaneous access to the popliteal artery (PA) or common femoral artery (CFA), a Rosch-Uchida needle was used to perforate the vascular wall, followed by the creation of an extraluminal tract using a looped wire and catheter. Once the desired level was reached the needle was again used to perforate the vascular wall of the proximal superficial femoral artery (SFA) or PA depending on the access used. Self-expanding expanded polytetrafluoroethylene (ePTFE) stent-grafts were then deployed to establish the extraluminal femoropopliteal bypass connecting the two arterial puncture sites. Following dilatation of the stent-graft, angiography was performed to assess the endoprostheses and to look for contrast leaks. Results. Technical success was achieved in all 5 legs. Procedure time varied from 15 to 30 min. The angiographic studies performed immediately after completion of the bypass procedure showed patency of the grafts with no evidence of kinking or leakage in any of the cases. Conclusion. This study has proved that the endovascular placement of an extraluminal femoropopliteal bypass graft in human cadaver legs using endovascular techniques under fluoroscopic control is technically feasible

Characterizing the Performance of Gas-Permeable Membranes as an Ammonia Recovery Strategy from Anaerobically Digested Dairy Manure.

Science.gov (United States)

Fillingham, Melanie; VanderZaag, Andrew; Singh, Jessica; Burtt, Stephen; Crolla, Anna; Kinsley, Chris; MacDonald, J Douglas

2017-10-07

Capturing ammonia from anaerobically digested manure could simultaneously decrease the adverse effects of ammonia inhibition on biogas production, reduce reactive nitrogen (N) loss to the environment, and produce mineral N fertilizer as a by-product. In this study, gas permeable membranes (GPM) were used to capture ammonia from dairy manure and digestate by the diffusion of gaseous ammonia across the membrane where ammonia is captured by diluted acid, forming an aqueous ammonium salt. A lab-scale prototype using tubular expanded polytetrafluoroethylene (ePTFE) GPM was used to (1) characterize the effect of total ammonium nitrogen (TAN) concentration, temperature, and pH on the ammonia capture rate using GPM, and (2) to evaluate the performance of a GPM system in conditions similar to a mesophilic anaerobic digester. The GPM captured ammonia at a rate between 2.2 to 6.3% of gaseous ammonia in the donor solution per day. Capture rate was faster in anaerobic digestate than raw manure. The ammonia capture rate could be predicted using non-linear regression based on the factors of total ammonium nitrogen concentration, temperature, and pH. This use of membranes shows promise in reducing the deleterious impacts of ammonia on both the efficiency of biogas production and the release of reactive N to the environment.

Microfabrication of high quality polytetrafluoroethylene films by synchrotron radiation

International Nuclear Information System (INIS)

Yoshida, A.; Matsumoto, E.; Yamada, H.; Okada, H.; Wakahara, A.

2003-01-01

We deposited polytetrafluoroethylene (PTFE) thin films both from the PTFE target by using synchrotron radiation (SR) beam and from PTFE emulsion by spin-coat process. The X-ray diffraction analyses showed a sharp peak due to (1 0 0) PTFE crystalline part, and only C-F 2 bonding was found in Fourier transform infrared spectrophotometer spectra. From electron spectroscopy for chemical analysis measurements, no impurities were found. The fabricated PTFE films were easily etched by SR beam on the limited area of the surface on a microscale through a suitably patterned mask

Physicomechanical evaluation of polypropylene, polyester, and polytetrafluoroethylene meshes for inguinal hernia repair.

Science.gov (United States)

Deeken, Corey R; Abdo, Michael S; Frisella, Margaret M; Matthews, Brent D

2011-01-01

For meshes to be used effectively for hernia repair, it is imperative that engineers and surgeons standardize the terminology and techniques related to physicomechanical evaluation of these materials. The objectives of this study were to propose standard techniques, perform physicomechanical testing, and classify materials commonly used for inguinal hernia repair. Nine meshes were evaluated: 4 polypropylene, 1 polyester, 1 polytetrafluoroethylene, and 3 partially absorbable. Physical properties were determined through image analysis, laser micrometry, and density measurements. Biomechanical properties were determined through suture retention, tear resistance, uniaxial, and ball burst testing with specimens tested in 2 different orientations. A 1-way ANOVA with Tukey's post-test or a t-test were performed, with p INFINIT (WL Gore & Associates) did not resist tearing as effectively as the others. All meshes exhibited supraphysiologic burst strengths except INFINIT and ULTRAPRO. Significant differences exist between the physicomechanical properties of polypropylene, polyester, polytetrafluoroethylene, and partially absorbable mesh prostheses commonly used for inguinal hernia repair. Orientation of the mesh was also shown to be critical for the success of meshes, particularly those demonstrating anisotropy. Copyright © 2011 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

Radiation degradation and crosslinking of polytetrafluoroethylene and its application

International Nuclear Information System (INIS)

Wu Guozhong; Wang Mouhua; Tang Zhongfeng

2009-01-01

Polytetrafluoroethylene (PTFE) is a high-performance engineering plastic and known as a typical material of radiation degradation. PTFE can be degraded by radiation under various conditions and PTFE micro-powder is usually fabricated by a combination of radiation and milling. PTFE can also be crosslinked by irradiation in the melt state (330∼340 degree C). The materials can be applied as a special additive due to its excellent wear resistance. Crosslinked PTFE may also be applied in lithography and fuel cell membrane in the future. In this paper, history and application of PTFE degradation and crosslinking products are reviewed. (authors)

Deposition of nanostructured fluorocarbon plasma polymer films by RF magnetron sputtering of polytetrafluoroethylene

Energy Technology Data Exchange (ETDEWEB)

Kylian, Ondrej, E-mail: ondrej.kylian@gmail.com; Drabik, Martin; Polonskyi, Oleksandr; Cechvala, Juraj; Artemenko, Anna; Gordeev, Ivan; Choukourov, Andrei; Matolinova, Iva; Slavinska, Danka; Biederman, Hynek, E-mail: bieder@kmf.troja.mff.cuni.cz

2011-07-29

The RF magnetron sputtering of polytetrafluoroethylene target is studied with the aim to find out conditions leading to the deposition of super-hydrophobic thin films. It is shown that such coatings can be prepared at elevated pressures and a longer distance between the sputtered target and the substrate. This is explained by an increase in the density of longer C{sub x}F{sub y} molecules that reach the substrate and a lower flux of ions and CF{sub 2} radicals on the surface of growing film under such deposition conditions, as observed by optical emission spectroscopy and mass spectrometry. Such changes in plasma composition result in a deposition of rough films having F/C ratio close to 2 as observed by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. These findings clearly distinguish our results from the previous investigations of polytetrafluoroethylene sputtering performed at shorter distances from the target, where either low F/C ratio or low roughness of the deposited films did not allow reaching super-hydrophobic character of the coatings.

Frontal suspension for congenital ptosis using an expanded polytetrafluoroethylene (Gore-Tex® sheet: one-year follow-up

Directory of Open Access Journals (Sweden)

Nakauchi K

2013-01-01

Full Text Available Kazuaki Nakauchi,1 Hidenori Mito,2 Osamu Mimura11Hospital of Hyogo College of Medicine, Hyogo, 2Ide Eye Hospital, Yamagata, JapanBackground: The frontalis suspension technique is the surgical method of choice in patients with ptosis and a levator function of 4 mm or less. Several types of materials have been used, including Gore-Tex®, which has been used successfully as a frontalis sling material since 1986. Recently, a Gore-Tex sheet (wider than a sling or strip suspension was reported. This paper reports the results of 27 eyes from 20 patients with congenital ptosis treated using the frontalis suspension technique with the newly developed Gore-Tex Most Versatile Patch (MVP sheet.Methods: All patients underwent surgery between April 2007 and September 2011 and were followed up for at least one year. The average follow-up duration was 18 months, with a range of 12–36 months. The average patient age was 45 (5–85 years, and the group included 11 males and nine females. Thirteen cases demonstrated ptosis in one eye, and seven cases involved both eyes. The patients were divided by age into a younger group and an older group. All ptosis procedures were performed using the Gore-Tex MVP sheet. The implant was normally 7 mm wide for adults and 5 mm wide for children. The implantation method was the same as that used for the sheet shape fascia.Results: In all patients, satisfactory functional results were observed at the 6-month follow-up examination. Eyelid opening heights were also obtained. The average marginal reflex distance (MRD was -0.5 mm preoperatively, which improved to +1.9 mm after surgery. After one year, average MRD was +1.6 mm. MRD attenuation was more frequent in the younger group. There were no cases requiring redo surgery and only one case of exposure.Keywords: polytetrafluoroethylene, Gore-Tex®, frontalis suspension, congenital ptosis, recurrence

Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)

Science.gov (United States)

Zhang, Yu; Zhang, Daixian; Wu, Jianjun; Li, Jian; He, Zhaofu

2017-11-01

The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.

Wet-chemical approach for the cell-adhesive modification of polytetrafluoroethylene

International Nuclear Information System (INIS)

Gabriel, Matthias; Dahm, Manfred; Vahl, Christian-F

2011-01-01

Polytetrafluoroethylene (PTFE), a frequently utilized polymer for the fabrication of synthetic vascular grafts, was surface-modified by means of a wet-chemical process. The inherently non-cell-adhesive polymer does not support cellular attachment, a prerequisite for the endothelialization of luminal surface grafts in small diameter applications. To impart the material with cell-adhesive properties a treatment with sodium-naphthalene provided a basis for the subsequent immobilization of the adhesion promoting RGD-peptide using a hydroxy- and amine-reactive crosslinker. Successful conjugation was shown with cell culture experiments which demonstrated excellent endothelial cell growth on the modified surfaces.

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

Poly-electrolyte fuel cell membrane based on crosslinked polytetrafluoroethylene by radiation-grafting

International Nuclear Information System (INIS)

Ichizuri, Shogo; Asano, Saneto; Li, Jingye

2004-01-01

Poly-electrolyte fuel cell (PEFC) membranes based on crosslinked Polytetrafluoroethylene (RX-PTFE) have been fabricated by radiation-grafting with reactive styrene monomers using γ-ray irradiation in air at room temperature / electron beam irradiation under N 2 gas atmosphere at room temperature. The characteristic properties of obtained materials have been measured by DSC, TGA and FT-IR spectroscopy, and so on. Ion exchange capacity of sulfonated crosslinked PTFE has been achieved 2.8meq/g. (author)

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.

Cold crystallization of polytetrafluoroethylene by γ irradiation

International Nuclear Information System (INIS)

Takenaga, M.; Yamagata, K.

1980-01-01

Changes in density and in the corresponding degree of crystallinity with radiation dose are studied experimentally for γ-irradiated polytetrafluoroethylene (PTFE) in the dose range from 1 x 10 3 to 1 x 10 9 R. The relation between the amorphous fraction and the radiation dose is derived from a quantitative analysis of cold crystallization by scission of polymer backbone chains. The characteristic radiation dose, at which one break occurs on the average per initial molecule, is estimated as about 3 x 10 4 R on the basis of a derived kinetic equation. The theoretical relation is modified by considering microvoids produced in the irradiated samples. The radii of microvoids in the form of spheres are evaluated as about 0.2 nm, and are also related to cage spheres relevant to the chain scission process. Good agreement between the modified theoretical relation and experimental data is attained over the entire range of radiation dose. 4 figures, 1 table

Growth properties of poly(tetrafluoroethylene) films by synchrotron radiation ablation

International Nuclear Information System (INIS)

Guo, Qixin; Kugino, Takashi; Kume, Yusuke; Mitsuishi, Yoshiaki; Tanaka, Tooru; Nishi, Mitsuhiro; Ogawa, Hiroshi

2007-01-01

High-quality poly(tetrafluoroethylene) (PTFE) films have been grown on Si substrates by synchrotron radiation ablation of a PTFE target. Only doublet absorption structures assigned to C-F asymmetric and symmetric stretching vibrations in CF 2 groups are observed, suggesting that the CF 2 groups in the grown PTFE film are organized in an ordered manner through linear attachment. The growth rate of the PTFE films increases with increasing target temperature, while it decreases with increasing substrate temperature. It has been shown that the thickness of the PTFE film with a high-spatial-resolution structure can be easily controlled at nanometer order by changing the synchrotron radiation irradiation dose. (author)

The effect of normal load on polytetrafluoroethylene tribology.

Science.gov (United States)

Barry, Peter R; Chiu, Patrick Y; Perry, Scott S; Sawyer, W Gregory; Phillpot, Simon R; Sinnott, Susan B

2009-04-08

The tribological behavior of oriented poly(tetrafluoroethylene) (PTFE) sliding surfaces is examined as a function of sliding direction and applied normal load in classical molecular dynamics (MD) simulations. The forces are calculated with the second-generation reactive empirical bond-order potential for short-range interactions, and with a Lennard-Jones potential for long-range interactions. The range of applied normal loads considered is 5-30 nN. The displacement of interfacial atoms from their initial positions during sliding is found to vary by a factor of seven, depending on the relative orientation of the sliding chains. However, within each sliding configuration the magnitude of the interfacial atomic displacements exhibits little dependence on load over the range considered. The predicted friction coefficients are also found to vary with chain orientation and are in excellent quantitative agreement with experimental measurements.

Comparative study of the monomer grafting: ethylene, acetylene, 1,3-butadiene and estyrene in the matrix of recycled polytetrafluoroethylene (PTFE)

International Nuclear Information System (INIS)

Ikari, Carolina T.; Rosner, Gerhardyne O.; Oliveira, Ana C.F.; Ferreto, Helio F.R.; Lima, Luiz F.C.P.; Lugao, Ademar B.; Moreira, Otavio M.

2009-01-01

In this study it is used the recycled polytetrafluoroethylene (PTFE), that with the gamma radiation under inert atmosphere or in presence of air, it is obtained free radicals and a posterior the monomer grafting (ethylene, acetylene, styrene or 1.3 butadiene), obtaining the copolymer polytetrafluoroethylene-g-monomer. It is studied the obtention of the polymer by two methods: by direct way, via grafting, where the polymer is irradiated in presence of monomer, and via grafting when the polymer is irradiated in absence of monomer and under inert or air. The characterization of the copolymer was performed by the techniques of infrared region absorption spectroscopy with Fourier transformation (FTIR), thermogravimetric (TGA) and derivative thermogravimetry (DTG), and percentage of mass grafting (DOG)

Recycling of Polytetrafluoroethylene Scarp for Useful Practical Applications

International Nuclear Information System (INIS)

El-Nemr, K.F.; Youssef, H.A.; Abd-El Aziz, M.M.; El-Miligy, A.A.

1999-01-01

Radiation vulcanization of NBR based composites were prepared whereby polytetrafluoroethylene, PTFE scrap was utilized as additive. The thermal property of composites, using TGA technique was investigated as a function of irradiation dose as well as the degree of loading with Teflon scarp. Moreover, the effect of gasoline solvent of varying content of toluene on the swelling characteristics of prepared composites has been followed up at 100 degree whereby, the irradiation dose was kept at 100 kGy. It was found that due to incorporation of PTFE powder , the solid composites obtained possess good thermal stability as well as swelling resistance. The best swelling resistance was obtained for the gasoline which does not contains toluene. The prepared rubber composites would be recommended for manufacturing rubber articles characterized by having self-lubricating property used as rubber seals under static condition, that may be at temperatures as high as 100 degree

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.

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)

Chemical structure and physical properties of radiation-induced crosslinking of polytetrafluoroethylene

International Nuclear Information System (INIS)

Oshima, Akihiro; Ikeda, Shigetoshi; Katoh, Etsuko; Tabata, Yoneho

2001-01-01

The chemical structure and physical properties of polytetrafluoroethylene (PTFE) that has been crosslinked by radiation have been studied by various methods. It has been found that a Y-type crosslinking structure and a Y-type structure incorporating a double bond (modified Y-type) is formed in PTFE by radiation-crosslinking in the molten state. In addition, various types of double bond structures, excluding the crosslinking site, have been identified. The crosslinked PTFE has a good light transparency due to the loss of crystallites, whilst it retains the excellent properties of electrical insulation and heat resistance. The coefficient of abrasion and the permanent creep are also greatly improved by crosslinking

The friction and wear of γ-irradiated polytetrafluoroethylene

International Nuclear Information System (INIS)

Briscoe, B.J.; Ni, Z.

1984-01-01

The exposure of polytetrafluoroethylene (PTFE) to γ radiation significantly reduces the molecular weight but below the gross softening temperature suppresses the overall molecular domain mobility. The shear modulus and creep resistance increase but the toughness is reduced. Data are presented to substantiate these trends and to interpret their influence on the friction and wear of γ-damaged PTFE. The sliding friction on smooth rigid counterfaces increases but the wear in this configuration is decreased. The rate of abrasion on rough rigid counterfaces is increased. There is also an improvement in the ultimate load-bearing capacity. All the changes produced are a function of the exposure but most of the effects are fully manifested by 20 Mrad. The general conclusion is that the extent of the molecular mobility or migration induced by mechanical stresses, imposed in both the interface and the bulk of the polymer, has a critical effect on the friction and wear processes. (Auth.)

Fabrication of polymer-alloy based on polytetrafluoroethylene by radiation-crosslinking

International Nuclear Information System (INIS)

Oshima, A.; Asano, S.; Hyunga, T.; Ichizuri, S.; Washio, M.

2003-01-01

Perfluoropolymer such as polytetrafluoroethylene (PTFE), tetrafluoroethylene co-perfluoroalkylvinylether (PFA) and tetrafluoroethylene-co-hexafluoropropylene (FFP) have been classified to be a typical polymer of radiation-induced degradation. However, we confirmed that the crosslinking of PTFE, PFA and FEP proceed by irradiation under selective condition where oxygen-free and high temperature above the melting temperature of them. In this study, fabrication of polymer-alloy based on PTFE has been demonstrated by radiation-crosslinking techniques. The polymer alloy, which was PTFE fine powder contained with other polymeric materials, was obtained by electron beams irradiation under oxygen-free atmosphere. Characterization of polymer-alloy based on PTFE has been studied by various measurements such as solid state 19F- and 13C-NMR spectroscopy, thermal analysis (DSC, TGA)

High-rate anisotropic ablation and deposition of polytetrafluoroethylene using synchrotron radiation process

International Nuclear Information System (INIS)

Inayoshi, Muneto; Ikeda, Masanobu; Hori, Masaru; Goto, Toshio; Hiramatsu, Mineo; Hiraya, Atsunari.

1995-01-01

Both anisotropic ablation and thin film formation of polytetrafluoroethylene (PTFE) were successfully demonstrated using synchrotron radiation (SR) irradiation of PTFE, that is, the SR ablation process. Anisotropic ablation by the SR irradiation was performed at an extremely high rate of 3500 μm/min at a PTFE target temperature of 200degC. Moreover, a PTFE thin film was formed at a high rate of 2.6 μm/min using SR ablation of PTFE. The chemical structure of the deposited film was similar to that of the PTFE target as determined from Fourier transform infrared absorption spectroscopy (FT-IR) analysis. (author)

EFEITOS DA TELA DE POLITETRAFLUOROETILENO EXPANDIDO COLOCADA NO ESPAÇO PRÉ-PERITONEAL POR VIDEOLAPAROSCOPIA EM SUÍNOS

Directory of Open Access Journals (Sweden)

Sandra Crippa Brandão

1998-07-01

Full Text Available Com o objetivo de observar os efeitos produzidos pela tela de politetrafluoroetileno expandido (PTFE-e, no espaço pré-peritoneal, foram utilizados 20 suínos (n=20 da raça Large White, todos machos, distribuídos em dois grupos de dez animais. A técnica operatória utilizada foi a videolaparoscopia transabdominal. De um lado, na região inguinal, o espaço pré-peritoneal foi dissecado e a tela fixada; na região contralateral, o procedimento foi o mesmo, sem a colocação da tela, servindo como controle. O peritônio parietal local foi aproximado com uma sutura contínua de poliglactina 910. A eutanásia foi realizada aos sete e vinte um dias de pós-operatório. No primeiro grupo, um animal apresentou aderência no local de implantação da tela e, no segundo grupo, um animal também apresentou aderência, mas no lado controle. Concluiu-se, baseado na presente pesquisa, que a tela de PTFE-e não provocou a formação de aderências, quando colocada no espaço pré-peritoneal em suínos.Twenty (20 Large White male pigs (n=20 divided in groups of ten were used to observe the effects produced by the use of expanded polytetrafluoroethylene (e-PTFE mesh, in the preperitoneal space. The operative approach was the laparoscopic transabdominal technique. On one side, in the inguinal region, the preperitoneal space was dissected and the mesh was fixed. On the other side, as a control, the same procedure has been done without the utilization of mesh. The local parietal peritoneum was approximated with a polyglactin 910 continuous suture. The animals were submitted to euthanasia at the 7th and the 21th days of postoperative evolution. In the first group, one animal presented adhesion formation where the mesh was placed and, in the second group, there was also one animal with adhesion formation but in the control side. It was concluded that e-PTFE mesh did not incited significant adhesion formation when placed in the preperitoneal space in a swine

X-ray photoelectron spectroscopy study of synchrotron radiation irradiation of a polytetrafluoroethylene surface

CERN Document Server

Haruyama, Y; Matsui, S; Ideta, T; Ishigaki, H

2003-01-01

The effect of synchrotron radiation (SR) irradiation of a polytetrafluoroethylene (PTFE) surface was investigated using X-ray photoelectron spectroscopy (XPS). After the SR irradiation, the relative intensity of the F ls peak to the C ls peak decreased markedly. The chemical composition ratio to the F atoms to C atoms was estimated to be 0.29. From the curve fitting analysis of C ls and F ls XPS spectra, the chemical components and their intensity ratio were determined. The reason for the chemical composition change by the SR irradiation was discussed. (author)

Manufacture of small calibre quadruple lamina vascular bypass grafts using a novel automated extrusion-phase-inversion method and nanocomposite polymer.

Science.gov (United States)

Sarkar, Sandip; Burriesci, Gaetano; Wojcik, Adam; Aresti, Nicholas; Hamilton, George; Seifalian, Alexander M

2009-04-16

Long-term patency of expanded polytetrafluoroethylene (ePTFE) small calibre cardiovascular bypass prostheses (hyperplasia due to low compliance, stimulating the search for elastic alternatives. Wall porosity allows effective post-implantation graft healing, encouraging endothelialisation and a measured fibrovascular response. We have developed a novel poly (carbonate) urethane-based nanocomposite polymer incorporating polyhedral oligomeric silsesquioxane (POSS) nanocages (UCL-NANO) which shows anti-thrombogenicity and biostability. We report an extrusion-phase-inversion technique for manufacturing uniform-walled porous conduits using UCL-NANO. Image analysis-aided wall measurement showed that two uniform wall-thicknesses could be specified. Different coagulant conditions revealed the importance of low-temperature phase-inversion for graft integrity. Although minor reduction of pore-size variation resulted from the addition of ethanol or N,N-dimethylacetamide, high concentrations of ethanol as coagulant did not provide uniform porosity throughout the wall. Tensile testing showed the grafts to be elastic with strength being directly proportional to weight. The ultimate strengths achieved were above those expected from haemodynamic conditions, with anisotropy due to the manufacturing process. Elemental analysis by energy-dispersive X-ray analysis did not show a regional variation of POSS on the lumen or outer surface. In conclusion, the automated vertical extrusion-phase-inversion device can reproducibly fabricate uniform-walled small calibre conduits from UCL-NANO. These elastic microporous grafts demonstrate favourable mechanical integrity for haemodynamic exposure and are currently undergoing in-vivo evaluation of durability and healing properties.

Antibiotic bonding to polytetrafluoroethylene with tridodecylmethylammonium chloride

International Nuclear Information System (INIS)

Harvey, R.A.; Alcid, D.V.; Greco, R.S.

1982-01-01

Polytetrafluoroethylene (PTFE) treated with the cationic surfactant, triodecylmethylammonium chloride (TDMAC), binds 14 C-penicillin (1.5 to 2 mg antibiotic/cm graft), whereas untreated PTFE or PTFE treated with anionic detergents shows little binding of antibiotic. TDMAC-treated PTFE concomitantly binds penicillin and heparin, generating a surface that potentially can resist both infection and thrombosis. The retention of these biologically active molecules is not due to passive entrapment in the PTFE but reflects an ionic interaction between the anionic ligands and surface-bound TDMAC. Penicillin bound to PTFE is not removed by exhaustive washing in aqueous buffers but is slowly released in the presence of plasma or when the PTFE is placed in a muscle pouch in the rat. Muscle tissue adjacent to the treated PTFE shows elevated levels of antibiotic following implantation. PTFE treated with TDMAC and placed in a muscle pouch binds 14 C-penicillin when it is locally irrigated with antibiotic or when penicillin is administered intravenously. Thus, the TDMAC surface treated either in vitro or in vivo with penicillin provides an effective in situ source for the timed release of antibiotic

Structural surprises in friction-deposited films of poly(tetrafluoroethylene)

DEFF Research Database (Denmark)

Breiby, Dag Werner; Sølling, Theis Ivan; Bunk, Oliver

2005-01-01

Thin films of poly(tetrafluoroethylene) (PTFE) produced by friction deposition were studied using grazing incidence X-ray diffraction as the principal tool. The structure of the deposited thin films was compared with that of the surface of the PTFE bar used for depositing the films. Both exhibited...... the 15/7 helix conformation characteristic of crystal PTFE phase IV. A high degree of biaxial orientation was found for the highly crystalline thin films. Whereas the unit cell of the bar surface material appeared to be single-stem hexagonal, the film displayed diffraction characteristics consistent...... the possibility of a continuous transition between the low-order single-stem hexagonal and the multistem high-order unit cell. The degree of chain orientation was much lower at the surface of the bar than in the thin film. A modification of the commonly accepted mechanism for the transfer of material from the bar...

Reflectance dependence of polytetrafluoroethylene on thickness for xenon scintillation light

Energy Technology Data Exchange (ETDEWEB)

Haefner, J.; Neff, A.; Arthurs, M.; Batista, E.; Morton, D.; Okunawo, M.; Pushkin, K.; Sander, A. [Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Stephenson, S. [Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); University of California Davis, Department of Physics, One Shields Ave., Davis, CA 95616 (United States); Wang, Y. [Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Lorenzon, W., E-mail: lorenzon@umich.edu [Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

2017-06-01

Many rare event searches including dark matter direct detection and neutrinoless double beta decay experiments take advantage of the high VUV reflective surfaces made from polytetrafluoroethylene (PTFE) reflector materials to achieve high light collection efficiency in their detectors. As the detectors have grown in size over the past decade, there has also been an increased need for ever thinner detector walls without significant loss in reflectance to reduce dead volumes around active noble liquids, outgassing, and potential backgrounds. We report on the experimental results to measure the dependence of the reflectance on thickness of two PTFE samples at wavelengths near 178 nm. No change in reflectance was observed as the wall thickness of a cylindrically shaped PTFE vessel immersed in liquid xenon was varied between 1 mm to 9.5 mm.

Preparing polymer brushes on polytetrafluoroethylene films by free radical polymerization

International Nuclear Information System (INIS)

Sun Wei; Chen Yiwang; Deng Qilan; Chen Lie; Zhou Lang

2006-01-01

Films of polytetrafluoroethylene (PTFE) were exposed to sodium naphthalenide (Na/naphtha) etchant so as to defluorinate the surface for obtaining hydroxyl functionality. Surface-initiators were immobilized on the PTFE films by esterification of 4,4'-azobis(4-cyanopentanoic acid) (ACP) and the hydroxyl groups covalently linked to the surface. Grafting of polymer brushes on the PTFE films was carried out by the surface-initiated free radical polymerization. Homopolymers brushes of methyl methacrylate (MMA) were prepared by free radical polymerization from the azo-functionalized PTFE surface. The chemical composition and topography of the graft-functionalized PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) FT-IR spectroscopy and atomic force microscopy (AFM). Water contact angles on PTFE films were reduced by surface grafting of MMA

Photolithography of polytetrafluoroethylene for tailored adhesion

International Nuclear Information System (INIS)

Rye, R.R.; Martinez, R.J.

1988-01-01

Irradiation of polytetrafluoroethylene (PTFE) with Mg (Kα) x-rays is shown to protect the surface against the chemical etching steps used to prepare PTFE for adhesion. Pre-irradiated etched samples of PTFE have adhesions strengths of less than 3% of that for non-irradiated etched samples. The major portion of this decrease in adhesion strength occurs for x-ray exposures of less than 10 min ∼4.8 x10 3 mrads) and failure in every case occurs in PTFE and not in the bonded transition region. XPS measurements (20 angstrom sampling depth) show little difference in F content between irradiated and non-irradiated samples, but thermal desorption shows increasing fluorocarbon desorption with irradiation time. These results are consistent with the known radiation chemistry of PTFE. Irradiation produced free radicals lead to branching and/ or cross-linking, and a surface rich in low molecular weight fluorocarbons. The more rigid cross-linked surface is resistant to deep (10,000 angstrom chemical attack and the bond formed is with a surface rich in short chain flurocarbons. Both a thin boundary region and bonding to short chain species is expected to lead to weak adhesive bonding. Electron irradiation is shown to lead to protection against chemical etching comparable to that obtained with X-rays. With electrons one has the patterns with resolution limited by the beam diameter

A bioactive metallurgical grade porous silicon-polytetrafluoroethylene sheet for guided bone regeneration applications.

Science.gov (United States)

Chadwick, E G; Clarkin, O M; Raghavendra, R; Tanner, D A

2014-01-01

The properties of porous silicon make it a promising material for a host of applications including drug delivery, molecular and cell-based biosensing, and tissue engineering. Porous silicon has previously shown its potential for the controlled release of pharmacological agents and in assisting bone healing. Hydroxyapatite, the principle constituent of bone, allows osteointegration in vivo, due to its chemical and physical similarities to bone. Synthetic hydroxyapatite is currently applied as a surface coating to medical devices and prosthetics, encouraging bone in-growth at their surface and improving osseointegration. This paper examines the potential for the use of an economically produced porous silicon particulate-polytetrafluoroethylene sheet for use as a guided bone regeneration device in periodontal and orthopaedic applications. The particulate sheet is comprised of a series of microparticles in a polytetrafluoroethylene matrix and is shown to produce a stable hydroxyapatite on its surface under simulated physiological conditions. The microstructure of the material is examined both before and after simulated body fluid experiments for a period of 1, 7, 14 and 30 days using Scanning Electron Microscopy. The composition is examined using a combination of Energy Dispersive X-ray Spectroscopy, Thin film X-ray diffraction, Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy and the uptake/release of constituents at the fluid-solid interface is explored using Inductively Coupled Plasma-Optical Emission Spectroscopy. Microstructural and compositional analysis reveals progressive growth of crystalline, 'bone-like' apatite on the surface of the material, indicating the likelihood of close bony apposition in vivo.

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

International Nuclear Information System (INIS)

Jafari, R.; Menini, R.; Farzaneh, M.

2010-01-01

A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon). Scanning electron microscopy images showed a 'bird's nest'-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ∼165 deg. with a very low contact angle hysteresis of ∼3 deg. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF 3 and CF 2 groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate.

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

Science.gov (United States)

Jafari, R.; Menini, R.; Farzaneh, M.

2010-12-01

A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon ®). Scanning electron microscopy images showed a " bird's nest"-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ˜165° with a very low contact angle hysteresis of ˜3°. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF 3 and CF 2 groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate.

IMPROVED HEALING OF SMALL-CALIBER POLYTETRAFLUOROETHYLENE PROSTHESES BY INDUCTION OF A CLOT LAYER - A REVIEW OF EXPERIMENTAL STUDIES IN RATS

NARCIS (Netherlands)

VANDERLEI, B; STRONCK, JW; WILDEVUUR, CRH

1991-01-01

This report reviews our experiments that have been undertaken to test the hypothesis whether the induction of a clot layer on the graft surface of small-caliber polytetrafluoroethylene ( PTFE) prostheses might improve their healing. 1 2 PTFE prostheses with a fibril length of 30-mu-m, PTFE

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.

Solution casting Nafion/polytetrafluoroethylene membrane for vanadium redox flow battery application

International Nuclear Information System (INIS)

Teng, Xiangguo; Sun, Cui; Dai, Jicui; Liu, Haiping; Su, Jing; Li, Faqiang

2013-01-01

Highlights: ► Nafion/polytetrafluoroethylene (PTFE) blend membranes were prepared by solution casting method. ► The blend membranes were tested for vanadium redox flow battery (VRB) application. ► The blend membranes show lower vanadium ion permeability than that of recast Nafion membrane. ► In VRB single cell test, the blend membrane shows superior performances than that of pure recast Nafion. -- Abstract: Solution casting method was adopted using Nafion and polytetrafluoroethylene (PTFE) solution to prepare Nafion/PTFE blend membranes for vanadium redox flow battery application. The physicochemical properties of the membranes were characterized by using water uptake, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis (TA). The electrochemical properties of the membranes were examined by using electrochemical impedance spectroscopy (EIS) and single cell test. Despite the high miscibility of PTFE with Nafion, the addition of hydrophobic PTFE reduces the water uptake, ion exchange capacity (IEC) and conductivity of blend membranes. But PTFE can increase the crystallinity, thermal stability of Nafion/PTFE membranes and reduce the vanadium permeability. The blend membrane with PTFE (30 wt%, N 0.7 P 0.3 ) was chosen and investigated for VRB single cell test. The energy efficiency of this VRB with N 0.7 P 0.3 membrane was 85.1% at current density of 50 mA cm −2 , which was superior to that of recast Nafion (r-Nafion) membrane (80.5%). Self-discharge test shows that the decay of open circuit potential of N 0.7 P 0.3 membrane is much lower than that of r-Nafion membrane. More than 50 cycles charge–discharge test proved that the N 0.7 P 0.3 membrane possesses high stability in long time running. Chemical stabilities of the chosen N 0.7 P 0.3 membrane are further proved by soaking the membrane for 3 weeks in highly oxidative V(V) solution. All results suggest that the addition of PTFE is a simple and effective way to

Thermodynamic properties and transport coefficients of a two-temperature polytetrafluoroethylene vapor plasma for ablation-controlled discharge applications

International Nuclear Information System (INIS)

Wang, Haiyan; Qi, Haiyang; Wang, Weizong; Yan, Joseph D; Geng, Jinyue; Wu, Yaowu

2017-01-01

Ablation-controlled plasmas have been used in a range of technical applications where local thermodynamic equilibrium (LTE) is often violated near the wall due to the strong cooling effect caused by the ablation of wall materials. The thermodynamic and transport properties of ablated polytetrafluoroethylene (PTFE) vapor, which determine the flowing plasma behavior in such applications, are calculated based on a two-temperature model at atmospheric pressure. To our knowledge, no data for PTFE have been reported in the literature. The species composition and thermodynamic properties are numerically determined using the two-temperature Saha equation and the Guldberg–Waage equation according to van de Sanden et al ’s derivation. The transport coefficients, including viscosity, thermal conductivity and electrical conductivity, are calculated with the most recent collision interaction potentials using Devoto’s electron and heavy-particle decoupling approach but expanded to the third-order approximation (second-order for viscosity) in the frame of the Chapman–Enskog method. Results are computed for different degrees of thermal non-equilibrium, i.e. the ratio of electron to heavy-particle temperatures, from 1 to 10, with electron temperature ranging from 300 to 40 000 K. Plasma transport properties in the LTE state obtained from the present work are compared with existing published results and the causes for the discrepancy analyzed. The two-temperature plasma properties calculated in the present work enable the modeling of wall ablation-controlled plasma processes. (paper)

Thermodynamic properties and transport coefficients of a two-temperature polytetrafluoroethylene vapor plasma for ablation-controlled discharge applications

Science.gov (United States)

Wang, Haiyan; Wang, Weizong; Yan, Joseph D.; Qi, Haiyang; Geng, Jinyue; Wu, Yaowu

2017-10-01

Ablation-controlled plasmas have been used in a range of technical applications where local thermodynamic equilibrium (LTE) is often violated near the wall due to the strong cooling effect caused by the ablation of wall materials. The thermodynamic and transport properties of ablated polytetrafluoroethylene (PTFE) vapor, which determine the flowing plasma behavior in such applications, are calculated based on a two-temperature model at atmospheric pressure. To our knowledge, no data for PTFE have been reported in the literature. The species composition and thermodynamic properties are numerically determined using the two-temperature Saha equation and the Guldberg-Waage equation according to van de Sanden et al’s derivation. The transport coefficients, including viscosity, thermal conductivity and electrical conductivity, are calculated with the most recent collision interaction potentials using Devoto’s electron and heavy-particle decoupling approach but expanded to the third-order approximation (second-order for viscosity) in the frame of the Chapman-Enskog method. Results are computed for different degrees of thermal non-equilibrium, i.e. the ratio of electron to heavy-particle temperatures, from 1 to 10, with electron temperature ranging from 300 to 40 000 K. Plasma transport properties in the LTE state obtained from the present work are compared with existing published results and the causes for the discrepancy analyzed. The two-temperature plasma properties calculated in the present work enable the modeling of wall ablation-controlled plasma processes.

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.

Production of polytetrafluoroethylene by means of polymerization induced by gamma radiation

International Nuclear Information System (INIS)

Sugao, A.B.

1986-01-01

The process of polytetrafluoroethylene (PTFE) production, is studied. The TFE monomer was prepared by pyrolisis of clorodifluoromethane (R-22) and purified by low temperature fractional distillation. The bulk polymerization of tetrafluoroethylene (TFE) induced by gamma rays from a 185 TBq (5000 Ci) Co-60 source was studied at several temperatures (0 0 C, -23 0 C e -78 0 C). The purified monomer was introduced into stainless steel cylindres of 15 and 60 ml under vacuum. Glass cylindres of 10,50 and 700 ml were also used for irradiation at -78 0 C. The polymer was obtained as white agglomerated particles. The I.R. spectra of polymer samples were consistent with those of commercial PTFE. The melting points of samples were between 327 and 331 0 C. (Author) [pt

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

Energy Technology Data Exchange (ETDEWEB)

Jafari, R., E-mail: rjafari@uqac.ca [NSERC / Hydro-Quebec / UQAC Industrial Chair on Atmospheric Icing of Power Network Equipment (CIGELE) and Canada Research Chair on Engineering of Power Network Atmospheric Icing (INGIVRE), Universite du Quebec a Chicoutimi, Chicoutimi, QC (Canada); Menini, R.; Farzaneh, M. [NSERC / Hydro-Quebec / UQAC Industrial Chair on Atmospheric Icing of Power Network Equipment (CIGELE) and Canada Research Chair on Engineering of Power Network Atmospheric Icing (INGIVRE), Universite du Quebec a Chicoutimi, Chicoutimi, QC (Canada)

2010-12-15

A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon). Scanning electron microscopy images showed a 'bird's nest'-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of {approx}165 deg. with a very low contact angle hysteresis of {approx}3 deg. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF{sub 3} and CF{sub 2} groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate.

Management of carotid Dacron patch infection: a case report using median sternotomy for proximal common carotid artery control and in situ polytetrafluoroethylene grafting.

Science.gov (United States)

Illuminati, Giulio; Calio', Francesco G; D'Urso, Antonio; Ceccanei, Gianluca; Pacilè, Maria Antonietta

2009-01-01

We report on a 58-year-old male who presented with an enlarging cervical hematoma 3 months following carotid endarterectomy with Dacron patch repair, due to septic disruption of the Dacron patch secondary to presumed infection. The essential features of this case are the control of the proximal common carotid artery gained through a median sternotomy, because the patient was markedly obese with minimal thyromental distance, and the treatment consisting of in situ polytetrafluoroethylene bypass grafting, due to the absence of a suitable autogenous saphenous vein. Median sternotomy is rarely required in case of reintervention for septic false aneurysms and hematomas following carotid endarterectomy but should be considered whenever difficult control of the common carotid artery, when entering the previous cervicotomy, is anticipated. In situ polytetrafluoroethylene grafting can be considered if autogenous vein material is lacking.

Formation of SiO2/polytetrafluoroethylene hybrid superhydrophobic coating

International Nuclear Information System (INIS)

Zheng Yansheng; He Yi; Qing Yongquan; Zhuo Zhihao; Mo Qian

2012-01-01

Highlights: ► The coating showed the water contact angle of 165° and the water sliding angle of 6°. ► The hierarchical structure with the low surface energy leads to surface superhydrophobicity. ► We demonstrated a simple yet efficient approach to preparing superhydrophobic surface. - Abstract: Superhydrophobic coating has been fabricated on the glass substrates with modified SiO 2 sol and polytetrafluoroethylene emulsion through a sol–gel process. SiO 2 sol was modified with γ-glycidoxypropyl trimethoxysilane. The coatings were characterized by water contact angle measurement, Scanning electron microscope, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and thermal synthetic analysis. The experimental results show that coatings exhibited superhydrophobic and heat-resistant property with a water average contact angle of 156° and sliding angle of 6°, coating has a rough surface with both micro- and nanoscale structures, γ-glycidoxypropyl trimethoxysilane enhanced the hydrophobicity of the coatings. Low surface energy of polymer and special structure of the coatings were responsible for the hydrophobic of the surfaces.

Ablation of polytetrafluoroethylene using a continuous CO2 laser beam

International Nuclear Information System (INIS)

Tolstopyatov, E M

2005-01-01

The ablation of polytetrafluoroethylene (PTFE) is studied using a continuous CO 2 laser beam of 30-50 W at a mean intensity of 0.05-50 MW m -2 . The ablation products and changes in the target layer are examined using infrared spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction and electron microscopy. The main experiments were conducted with an unfocused beam of intensity 0.9-1.2 MW m -2 . The radiation-polymer interaction characteristics were found to change appreciably as the ablation conditions are approached. Within the polymer layer, light scattering diminishes and true resonant light absorption increases. Two distinct polymer components, which differ primarily in their resistance to CO 2 laser radiation, were found to exist under ablation conditions. The less stable component depolymerizes intensively, while the more resistant component is blown up into fibres by intense gas flow. The reasons behind this behaviour are discussed. Preliminary gamma irradiation of PTFE is found to have a significant influence on the laser ablation process

 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.

Superhydrophobic polytetrafluoroethylene thin films with hierarchical roughness deposited using a single step vapor phase technique

International Nuclear Information System (INIS)

Gupta, Sushant; Arjunan, Arul Chakkaravarthi; Deshpande, Sameer; Seal, Sudipta; Singh, Deepika; Singh, Rajiv K.

2009-01-01

Superhydrophobic polytetrafluoroethylene films with hierarchical surface roughness were deposited using pulse electron deposition technique. We were able to modulate roughness of the deposited films by controlling the beam energy and hence the electron penetration depth. The films deposited at higher beam energy showed contact angle as high as 166 o . The scanning electron and atomic force microscope studies revealed clustered growth and two level sub-micron asperities on films deposited at higher energies. Such dual-scale hierarchical roughness and heterogeneities at the water-surface interface was attributed to the observed contact angle and thus its superhydrophobic nature.

Superhydrophobic polytetrafluoroethylene thin films with hierarchical roughness deposited using a single step vapor phase technique

Energy Technology Data Exchange (ETDEWEB)

Gupta, Sushant, E-mail: sushant3@ufl.ed [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Arjunan, Arul Chakkaravarthi [Sinmat Incorporated, 2153 SE Hawthorne Road, 129, Gainesville, Florida 32641 (United States); Deshpande, Sameer; Seal, Sudipta [Advanced Material Processing and Analysis Center, University of Central Florida, Orlando, Florida 32816 (United States); Singh, Deepika [Sinmat Incorporated, 2153 SE Hawthorne Road, 129, Gainesville, Florida 32641 (United States); Singh, Rajiv K. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)

2009-06-30

Superhydrophobic polytetrafluoroethylene films with hierarchical surface roughness were deposited using pulse electron deposition technique. We were able to modulate roughness of the deposited films by controlling the beam energy and hence the electron penetration depth. The films deposited at higher beam energy showed contact angle as high as 166{sup o}. The scanning electron and atomic force microscope studies revealed clustered growth and two level sub-micron asperities on films deposited at higher energies. Such dual-scale hierarchical roughness and heterogeneities at the water-surface interface was attributed to the observed contact angle and thus its superhydrophobic nature.

Mechanistic insights into the room temperature transitions of polytetrafluoroethylene during electron-beam irradiation

Science.gov (United States)

Fu, Congli; Yu, Xianwei; Zhao, Xiaofeng; Wang, Xiuli; Gu, Aiqun; Xie, Meiju; Chen, Chen; Yu, Zili

2017-11-01

In order to recognize the characteristic thermal transitions of polytetrafluoroethylene (PTFE) occurring at 19 °C and 30 °C, PTFE is irradiated on electron beam accelerator at room temperature and analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results suggest that the two transition temperatures decrease considerably with increasing irradiation doses. Based on the results of structural analysis, the decrease of the two transition temperatures is supposed to be highly relevant to the structural changes. In particular, the content and structure of the side groups generated in PTFE are responsible for the variations of the two thermal transitions after irradiation, offering fundamental insights into the reaction mechanisms of PTFE during irradiation.

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.

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.

Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

Science.gov (United States)

Xia, Wei; Chen, Qiusong; Zhang, Jian; Wang, Hui; Cheng, Qian; Jiang, Yulong; Zhu, Guodong

2018-04-01

In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

Decomposition pathways of polytetrafluoroethylene by co-grinding with strontium/calcium oxides.

Science.gov (United States)

Qu, Jun; He, Xiaoman; Zhang, Qiwu; Liu, Xinzhong; Saito, Fumio

2017-06-01

Waste polytetrafluoroethylene (PTFE) could be easily decomposed by co-grinding with inorganic additive such as strontium oxide (SrO), strontium peroxide (SrO 2 ) and calcium oxide (CaO) by using a planetary ball mill, in which the fluorine was transformed into nontoxic inorganic fluoride salts such as strontium fluoride (SrF 2 ) or calcium fluoride (CaF 2 ). Depending on the kind of additive as well as the added molar ratio, however, the reaction mechanism of the decomposition was found to change, with different compositions of carbon compounds formed. CO gas, the mixture of strontium carbonate (SrCO 3 ) and carbon, only SrCO 3 were obtained as reaction products respectively with equimolar SrO, excess SrO and excess SrO 2 to the monomer unit CF 2 of PTFE were used. Excess amount of CaO was needed to effectively decompose PTFE because of its lower reactivity compared with strontium oxide, but it promised practical applications due to its low cost.

Novel Ultrafine Fibrous Poly(tetrafluoroethylene Hollow Fiber Membrane Fabricated by Electrospinning

Directory of Open Access Journals (Sweden)

Qinglin Huang

2018-04-01

Full Text Available Novel poly(tetrafluoroethylene (PTFE hollow fiber membranes were successfully fabricated by electrospinning, with ultrafine fibrous PTFE membranes as separation layers, while a porous glassfiber braided tube served as the supporting matrix. During this process, PTFE/poly(vinylalcohol (PVA ultrafine fibrous membranes were electrospun while covering the porous glassfiber braided tube; then, the nascent PTFE/PVA hollow fiber membrane was obtained. In the following sintering process, the spinning carrier PVA decomposed; meanwhile, the ultrafine fibrous PTFE membrane shrank inward so as to further integrate with the supporting matrix. Therefore, the ultrafine fibrous PTFE membranes had excellent interface bonding strength with the supporting matrix. Moreover, the obtained ultrafine fibrous PTFE hollow fiber membrane exhibited superior performances in terms of strong hydrophobicity (CA > 140°, high porosity (>70%, and sharp pore size distribution. The comprehensive properties indicated that the ultrafine fibrous PTFE hollow fiber membranes could have potentially useful applications in membrane contactors (MC, especially membrane distillation (MD in harsh water environments.

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.

High-performance membrane-electrode assembly with an optimal polytetrafluoroethylene content for high-temperature polymer electrolyte membrane fuel cells

DEFF Research Database (Denmark)

Jeong, Gisu; Kim, MinJoong; Han, Junyoung

2016-01-01

Although high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) have a high carbon monoxide tolerance and allow for efficient water management, their practical applications are limited due to their lower performance than conventional low-temperature PEMFCs. Herein, we present a high......-performance membrane-electrode assembly (MEA) with an optimal polytetrafluoroethylene (PTFE) content for HT-PEMFCs. Low or excess PTFE content in the electrode leads to an inefficient electrolyte distribution or severe catalyst agglomeration, respectively, which hinder the formation of triple phase boundaries...

Characteristics improvement of hydrophobic polytetrafluoroethylene-platinum catalysts for tritium separation

International Nuclear Information System (INIS)

Popescu, I.; Ionita, Gh.; Dobrinescu, D.; Varlam, C.; Stefanescu, I.

2006-01-01

Full text: Based on the long experience of the authors in the preparation, testing and evaluation of the performances of hydrophobic catalysts and based on the reviewed references, this paper presents up-to-date R and D activities on the preparation methods and applications of the hydrophobic catalysts in tritium separation. The objectives of the paper are: how to improve the characteristics and performance of platinum hydrophobic catalysts; to assess and find a new procedure for the preparation of a new improved hydrophobic catalyst. From reviewed references one can conclude that platinum is the most active and efficient catalytic metal while the polytetrafluoroethylene is the best wet-proofing agent. A new improved hydrophobic Pt-catalyst has been proposed and its testing is now underway. The main steps and experimental conditions of preparation are thoroughly discussed. A new wet-proofing agent and new binders (titanium dioxide, cerium dioxide, zirconium dioxide) with a catalytic role are proposed and tested. The physico-structural parameters of the improved catalyst have been determined and are discussed in detail. The new proposal is a promising idea to improve the performance of conventional hydrophobic Pt-catalysts. (authors)

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.

Use of X-ray photoelectron spectroscopy to study radiation and thermal effects in polytetrafluoroethylene

International Nuclear Information System (INIS)

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

1990-01-01

X-ray photoelectron spectroscopy of the surface and mass spectroscopy of the gas evolved during irradiation and subsequent heating of irradiated polytetrafluoroethylene (PTFE) indicated that the effect of electron irradiation was the same as that of x-irradiation. Saturated fluorocarbon gas was evolved during irradiation and a cross-linked or branched network formed in the surface region. Heating irradiated PTFE to temperatures below 200C resulted in the evolution of additional saturated fluorocarbon gas but no change in the surface. From 200C to 300C, lightly damaged PTFE did not change further, but severely damaged PTFE emitted unsaturated fluorocarbons while the surface underwent apparent partial recovery. These observations demonstrate the thermal instability of the irradiated PTFE surface and allow elaboration of the existing model of radiation damage in PTFE

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

Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

Energy Technology Data Exchange (ETDEWEB)

Cho, Yong Ki [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Park, Daewon; Kim, Hoonbae [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Lee, Hyerim; Park, Heonyong [Department of Molecular Biology, Dankook University, Yongin 448-701 (Korea, Republic of); Kim, Hong Ja [Department of Internal Medicine, Dankook University, Cheonan 330-714 (Korea, Republic of); Jung, Donggeun, E-mail: djung@skku.ac.kr [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2014-03-01

Graphical abstract: - Highlights: • The surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts. • Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment using micro plasma discharge. - Abstract: Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature

Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

International Nuclear Information System (INIS)

Cho, Yong Ki; Park, Daewon; Kim, Hoonbae; Lee, Hyerim; Park, Heonyong; Kim, Hong Ja; Jung, Donggeun

2014-01-01

Graphical abstract: - Highlights: • The surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts. • Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment using micro plasma discharge. - Abstract: Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature

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.

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.

Self-Expandable Metal Stents and Trans-stent Light Delivery: Are Metal Stents and Photodynamic Therapy Compatible?

Science.gov (United States)

Wang, Luo-Wei; Li, Li-Bo; Li, Zhao-Shen; Chen, Yang K; Hetzel, Fred W.; Huang, Zheng

2008-01-01

Background and Objectives: Obstructive non-small cell lung cancer and obstructive esophageal cancer are US FDA approved indications of photodynamic therapy (PDT). The usefulness of PDT for the treatment of cholangiocarcinoma is currently under clinical investigation. Endoscopic stenting for lumen restoration is a common palliative intervention for those indications. It is important to assess whether self-expandable metal stents are compatible with trans-stent PDT light delivery. Study Design/Materials and Methods: Direct effects of various components of metal biliary (n = 2), esophageal (n = 2), and bronchial (n = 1) stents on PDT light transmittance and distribution were examined using a point or linear light source (630 or 652 nm diode laser). Resected pig biliary duct and esophageal wall tissues were used to examine the feasibility of PDT light delivery through the fully expanded metal stents. Results: While using a point light source, the metal components (thread and joint) of the stent could cause a significant shadow effect. The liner material (polytetrafluoroethylene or polyurethane) could cause various degrees of light absorption. When the stent was covered with a thin layer of biliary duct and esophageal tissues containing all wall layers, the shadow effect could be mitigated due to tissue scattering. Conclusions: This study clearly demonstrates that it is feasible to combine stenting and PDT for the treatment of luminal lesions. PDT light dose should be adjusted to counteract the reduction of light transmittance caused by the metal and liner materials of stent. PMID:18951422

Changes in the chemical structure of polytetrafluoroethylene induced by electron beam irradiation in the molten state

CERN Document Server

Lappan, U; Lunkwitz, K

2000-01-01

Polytetrafluoroethylene (PTFE) was exposed to electron beam radiation at elevated temperature above the melting point under nitrogen atmosphere and in vacuum for comparison. Fourier-transform infrared (FTIR) spectroscopy was used to study the changes in the chemical structure. The irradiation under nitrogen atmosphere leads to the same structures as described recently for PTFE irradiated in vacuum. Trifluoromethyl branches and double bond structures were detected. The concentrations of terminal and internal double bonds are higher after irradiation under nitrogen than in vacuum. Annealing experiments have shown that the thermal oxidative stability of the radiation-modified PTFE is reduced compared to unirradiated PTFE. The reason are the formation of unstable structures such as double bonds.

Adhesion, friction and wear between polytetrafluoroethylene and nitrogen-implanted stainless steel

International Nuclear Information System (INIS)

Yang, E.; Hirvonen, J.P.; Raesaenen, M.; Toivanen, R.O.

1992-01-01

Adhesion, friction and wear of polytetrafluoroethylene (PTFE), carbon-reinforced PTFE, and glass-reinforced PTFE in sliding contact with nitrogen-implanted and unimplanted AISI 316 stainless steel were determined. The transfer of PTFE within the first 10 unidirectional traverses was investigated using the 19 F(p,αγ) 16 O nuclear reaction. External proton beam induced X-ray emission (PIXE) was used to determine the metal transfer from AISI 316 to pin heads. Nitrogen implantation considerably reduced the transfer of PTFE to the steel surface, and the transfer of the metallic elements from stainless steel to the PTFE-based composites. Furthermore, a lower friction coefficient was observed for nitrogen-implanted samples within the first 400 revolutions. The wear of PTFE, glass-reinforced and carbon-reinforced PTFE pins was only slightly reduced on the nitrogen-implanted surface, although a significant improvement in the wear of the steel was observed. Transmission electron microscopy (TEM) examination of wear debris revealed that PTFE was amorphized during the transfer process. However, no change in the structure of the pin head prior to the transfer was detected with an IR spectrophotometer. (orig.)

Study on surface adhesion of Plasma modified Polytetrafluoroethylene hollow fiber membrane

Science.gov (United States)

Chen, Jiangrong; Zhang, Huifeng; Liu, Guochang; Guo, Chungang; Lv, Jinglie; Zhangb, Yushan

2018-01-01

Polytetrafluoroethylene (PTFE) is popular membrane material because of its excellent thermal stability, chemical stability and mechanical stability. However, the low surface energy and non-sticky property of PTFE present challenges for modification. In the present study, plasma treatment was performed to improve the surface adhesion of PTFE hollow fiber membrane. The effect of discharge voltage, treatment time on the adhesion of PTFE hollow fiber membrane was symmetrically evaluated. Results showed that the plasma treatment method contributed to improve the surface activity and roughness of PTFE hollow fiber membrane, and the adhesion strength depend significantly on discharge voltage, which was beneficial to seepage pressure of PTFE hollow fiber membrane module. The adhesion strength of PTFE membrane by plasma treated at 220V for 3min reached as high as 86.2 N, far surpassing the adhesion strength 12.7 N of pristine membrane. Furthermore, improvement of content of free radical and composition analysis changes of the plasma modified PTFE membrane were investigated. The seepage pressure of PTFE membrane by plasma treated at 220V for 3min was 0.375 MPa, which means that the plasma treatment is an effective technique to improve the adhesion strength of membrane.

Polytetrafluoroethylene surface modification by filamentary and homogeneous dielectric barrier discharges in air

International Nuclear Information System (INIS)

Fang Zhi; Hao Lili; Yang Hao; Xie Xiangqian; Qiu Yuchang; Edmund, Kuffel

2009-01-01

In this paper, polytetrafluoroethylene (PTFE) films are modified using non-equilibrium plasma generated by homogeneous DBD in air at medium pressure, and the results are compared to those treated by using filamentary DBD in air at atmospheric pressure. The surface properties of PTFE films before and after the treatments are studied using contact angle and surface energy measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the plasma treatments modify the PTFE surface in both morphology and composition. The PTFE films modified in both treatments show a remarkable decrease in water contact and a remarkable increase in surface energy. XPS analysis reveals that oxygen-containing polar groups are introduced onto the PTFE surface, and SEM analysis shows that the surfaces of the films are etched after both the treatments. It is found that homogeneous DBD is more effective in PTFE surface modification than filamentary DBD as it can make the contact angle decline to a lower level by introducing more oxygen-containing groups, and the possible reason for this effect is discussed.

Adhesive and morphological characteristics of surface chemically modified polytetrafluoroethylene films

International Nuclear Information System (INIS)

Hopp, B.; Kresz, N.; Kokavecz, J.; Smausz, T.; Schieferdecker, H.; Doering, A.; Marti, O.; Bor, Z.

2004-01-01

In the present paper, we report an experimental determination of adhesive and topographic characteristics of chemically modified surface of polytetrafluoroethylene (PTFE) films. The surface chemistry was modified by ArF excimer laser irradiation in presence of triethylene-tetramine photoreagent. The applied laser fluence was varied in the range of 0.4-9 mJ/cm 2 , and the number of laser pulses incident on the same area was 1500. To detect the changes in the adhesive features of the treated Teflon samples, we measured receding contact angle for distilled water and adhesion strength, respectively. It was found that the receding contact angle decreased from 96 deg. to 30-37 deg. and the adhesion strength of two-component epoxy glue to the treated sample surface increased from 0.03 to 9 MPa in the applied laser fluence range. Additionally, it was demonstrated that the adhesion of human cells to the modified Teflon samples is far better than to the untreated ones. The contact mode and pulsed force mode atomic force microscopic investigations of the treated samples demonstrated that the measured effective contact area of the irradiated films does not differ significantly from that of the original films, but the derived adhesion force is stronger on the modified samples than on the untreated ones. Hence, the increased adhesion of the treated Teflon films is caused by the higher surface energy

An evaluation of the effectiveness of different techniques for intraoperative infiltration of antibiotics into alloplastic implants for use in facial reconstruction.

Science.gov (United States)

Keefe, Morgan S; Keefe, Michael A

2009-01-01

Reconstruction in the head and neck can be difficult owing to the size of the defect or characteristics of the tissue that needs to be replaced. Facial wounds or reconstruction sites can be subject to contamination, thereby risking infection of any implanted material even under ideal circumstances. Particular areas of concern are sites where minimizing the bacterial contamination prior to placing an implant is difficult (eg, the oral cavity and internal nose). Reconstruction involves the facial subcutaneous soft tissue and/or bone, and the ideal implant provides support and natural feel, as well as a low risk of infection. The biocompatibility of alloplastic implants depends on the tissue inertness of the implant and the porosity, allowing connective tissue ingrowth, which in turn decreases the susceptibility to infection. Scalafani et al demonstrated that alloplastic implants contaminated prior to fibrovascular ingrowth had a much higher incidence of infection and rejection. To examine the effectiveness of several techniques for infiltrating antibiotics into alloplastic implants of different porosity using 2 commonly used alloplastic implants, expanded polytetrafluoroethylene (e-PTFE, or GORE-TEX) and porous high-density polyethylene (Medpor). Using an in vitro bacterial growth inhibition model, we found that suction infiltration of the implant with antibiotics was the most effective technique, with a statistically significant advantage over other techniques used. The advantages of the suction impregnation were seen to be most effective using alloplasts with a smaller pore size (20-30 microm) (P < .001), but there was a statistically significant difference even with implants with a larger pore size (150-200 microm) (P < .001). Suction infiltration of antibiotics into porous implants seems to be the most effective method identified using an in vitro testing protocol. Further experiments will be needed to confirm the effectiveness in reducing the perioperative risk

Comparative analysis of histopathologic effects of synthetic meshes based on material, weight, and pore size in mice.

Science.gov (United States)

Orenstein, Sean B; Saberski, Ean R; Kreutzer, Donald L; Novitsky, Yuri W

2012-08-01

While synthetic prosthetics have essentially become mandatory for hernia repair, mesh-induced chronic inflammation and scarring can lead to chronic pain and limited mobility. Mesh propensity to induce such adverse effects is likely related to the prosthetic's material, weight, and/or pore size. We aimed to compare histopathologic responses to various synthetic meshes after short- and long-term implantations in mice. Samples of macroporous polyester (Parietex [PX]), heavyweight microporous polypropylene (Trelex[TX]), midweight microporous polypropylene (ProLite[PL]), lightweight macroporous polypropylene (Ultrapro[UP]), and expanded polytetrafluoroethylene (DualMesh[DM]) were implanted subcutaneously in mice. Four and 12 wk post-implantation, meshes were assessed for inflammation, foreign body reaction (FBR), and fibrosis. All meshes induced varying levels of inflammatory responses. PX induced the greatest inflammatory response and marked FBR. DM induced moderate FBR and a strong fibrotic response with mesh encapsulation at 12 wk. UP and PL had the lowest FBR, however, UP induced a significant chronic inflammatory response. Although inflammation decreased slightly for TX, marked FBR was present throughout the study. Of the three polypropylene meshes, fibrosis was greatest for TX and slightly reduced for PL and UP. For UP and PL, there was limited fibrosis within each mesh pore. Polyester mesh induced the greatest FBR and lasting chronic inflammatory response. Likewise, marked fibrosis and encapsulation was seen surrounding ePTFE. Heavier polypropylene meshes displayed greater early and persistent fibrosis; the reduced-weight polypropylene meshes were associated with the least amount of fibrosis. Mesh pore size was inversely proportional to bridging fibrosis. Moreover, reduced-weight polypropylene meshes demonstrated the smallest FBR throughout the study. Overall, we demonstrated that macroporous, reduced-weight polypropylene mesh exhibited the highest degree of

An implantable centrifugal blood pump with a recirculating purge system (Cool-Seal system).

Science.gov (United States)

Yamazaki, K; Litwak, P; Tagusari, O; Mori, T; Kono, K; Kameneva, M; Watach, M; Gordon, L; Miyagishima, M; Tomioka, J; Umezu, M; Outa, E; Antaki, J F; Kormos, R L; Koyanagi, H; Griffith, B P

1998-06-01

A compact centrifugal blood pump has been developed as an implantable left ventricular assist system. The impeller diameter is 40 mm, and pump dimensions are 55 x 64 mm. This first prototype, fabricated from titanium alloy, resulted in a pump weight of 400 g including a brushless DC motor. The weight of a second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon (DLC) to improve blood compatibility. Flow rates of over 7 L/min against 100 mm Hg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system (Cool-Seal) is used for the shaft seal. In this seal system, the seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. Purge fluid is continuously purified and sterilized by an ultrafiltration unit which is incorporated in the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular (LV) apex descending aorta bypass was performed utilizing an expanded polytetrafluoroethylene (ePTFE) vascular graft with the pump placed in the left thoracic cavity. In 2 in vivo experiments, the pump flow rate was maintained at 5-9 L/min, and pump power consumption remained stable at 9-10 W. All plasma free Hb levels were measured at less than 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (<0.5 ml/day). In both calves, the pumps demonstrated trouble free continuous function over 6 month (200 days and 222 days).

Manufacturing Technology of Composite Materials-Principles of Modification of Polymer Composite Materials Technology Based on Polytetrafluoroethylene.

Science.gov (United States)

Panda, Anton; Dyadyura, Kostiantyn; Valíček, Jan; Harničárová, Marta; Zajac, Jozef; Modrák, Vladimír; Pandová, Iveta; Vrábel, Peter; Nováková-Marcinčínová, Ema; Pavelek, Zdeněk

2017-03-31

The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer-solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment.

Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma

International Nuclear Information System (INIS)

Wang Chen; Chen Jierong; Li Ru

2008-01-01

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108-58 o and 65.2 o , respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction

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

Long term results of polytetrafluoroethylene in above knee femoropopliteal bypass for critical ischaemia.

LENUS (Irish Health Repository)

Kavanagh, E G

2012-02-03

Ninety-six consecutive above-knee femoropopliteal bypasses, using polytetrafluoroethylene (PTFE) preferentially, were performed for limb-threatening ischaemia. Cumulative primary graft patency was 68 per cent, 49 per cent and 36 per cent and limb salvage 93 per cent, 85 per cent and 75 per cent at 1, 3 and 5 yr respectively. As a result of poor long term survival (51 per cent at 5 yr), and the healing of remedial lesions before graft occlusion, 68 patients (72 per cent) required no further intervention. Eighteen secondary bypasses were undertaken, 12 using ipsilateral saphenous vein. In this group of elderly patients with poor life expectancy, where a limited operation is desirable, the use of PTFE provided excellent limb salvage with low morbidity. Although we can no longer justify our continued use of PTFE in every case of critical ischaemia because of its inferior patency to autogenous vein, we continue to use it preferentially in patients whose lifespan is likely to be short and in cases where a remedial lesion is present.

ExpandED Options: Learning beyond High School Walls

Science.gov (United States)

ExpandED Schools, 2014

2014-01-01

Through ExpandED Options by TASC, New York City high school students get academic credit for learning career-related skills that lead to paid summer jobs. Too many high school students--including those most likely to drop out--are bored or see classroom learning as irrelevant. ExpandED Options students live the connection between mastering new…

Cell adhesion and proliferation on poly(tetrafluoroethylene) with plasma-metal and plasma-metal-carbon interfaces

Science.gov (United States)

Reznickova, Alena; Kvitek, Ondrej; Kolarova, Katerina; Smejkalova, Zuzana; Svorcik, Vaclav

2017-06-01

The aim of this article is to investigate the effect of the interface between plasma activated, gold and carbon coated poly(tetrafluoroethylene) (PTFE) on in vitro adhesion and spreading of mouse fibroblasts (L929). Surface properties of pristine and modified PTFE were studied by several experimental techniques. The thickness of a deposited gold film is an increasing function of the sputtering time, conversely thickness of carbon layer decreases with increasing distance between carbon source and the substrate. Because all the used surface modification techniques take place in inert Ar plasma, oxidized degradation products are formed on the PTFE surface, which affects wettability of the polymer surface. Cytocompatibility tests indicate that on samples with Au/C interface, the cells accumulate on the part of sample with evaporated carbon. Number of L929 cells proliferated on the studied samples is comparable to tissue culture polystyrene standard.

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.)

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.)

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.

A proton-exchange membrane prepared by the radiation grafting of styrene and silica into polytetrafluoroethylene films

Science.gov (United States)

Yu, Hongyan; Shi, Jianheng; Zeng, Xinmiao; Bao, Mao; Zhao, Xinqing

2009-07-01

A polytetrafluoroethylene (PTFE) based organic-inorganic hybrid proton-exchange membrane was prepared from simultaneous radiation grafting of styrene (St) into porous PTFE membrane with the in situ sol-gel reaction of tetraethoxysilane (TEOS) followed by sulfonation in fuming sulfonic acid. The effect of radiation on the sol-gel reaction was studied. The results show that radiation promotes the sol-gel reaction with the help of St at room temperature. Incorporated silica gel helps to produce higher degree of grafting (DOG). SEM analysis was conducted to confirm that the inorganic silicon oxide was introduced to produce hybrid membrane in this work. The proton conductivity of membrane evaluated using electrochemical impedance spectroscopy is much higher (14.3×10 -2 S cm -1) than that of Nafion ® 117 at temperature of 80 °C with acceptable water uptake 51 wt%.

Manufacturing Technology of Composite Materials—Principles of Modification of Polymer Composite Materials Technology Based on Polytetrafluoroethylene

Directory of Open Access Journals (Sweden)

Anton Panda

2017-03-01

Full Text Available The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer–solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment.

Surgical treatment of pulmonic stenosis in dogs under cardiopulmonary bypass: outcome in nine dogs.

Science.gov (United States)

Bristow, P; Sargent, J; Luis Fuentes, V; Brockman, D

2018-01-01

To describe the outcome for nine dogs with pulmonic stenosis treated by open patch grafting using expanded polytetrafluoroethylene under cardiopulmonary bypass. Data were collected from the hospital records of all dogs that had undergone right ventricular outflow tract grafting with an expanded polytetrafluoroethylene patch under cardiopulmonary bypass between 2006 and 2012 for the treatment of pulmonic stenosis. Echocardiographic images were reviewed and the pressure gradient across the right ventricular outflow tract re-measured. Owners of dogs still alive at the time of writing were invited to return to the hospital for reassessment. Nine dogs met the inclusion criteria. Median pressure gradient preoperatively was 118 mmHg, (range 102 to 259 mmHg) reducing to a median of 20 mmHg (range 7 to 53 mmHg) at 48 hours postoperatively and 14 mmHg (range 10 to 70 mmHg), with a median percentage reduction of 89% (range 41 to 94%) at long-term follow-up. Eight of nine dogs survived surgery, with six of nine surviving to hospital discharge. Two dogs were still alive over 6 and 8 years postoperatively. No long-term deaths were believed to be attributable to pulmonic stenosis. Expanded polytetrafluoroethylene patch grafting of the right ventricular outflow tract for treatment of severe pulmonic stenosis in dogs is feasible and can be an effective method to reduce the severity of right ventricular outflow tract obstruction. © 2017 British Small Animal Veterinary Association.

Insensitive high-energy energetic structural material of tungsten-polytetrafluoroethylene-aluminum composites

Directory of Open Access Journals (Sweden)

Liu Wang

2015-11-01

Full Text Available Energetic structural material is a kind of materials that are inert under normal conditions but could produce exothermic chemical reaction when subjected to impact. This report shows a kind of energetic structural material of tungsten (W-polytetrafluoroethylene (PTFE-aluminum (Al with density of 4.12 g/cm3, excellent ductility and dynamic compressive strength of 96 MPa. Moreover, 50W-35PTFE-15Al (wt% can exhibit a high reaction energy value of more than 2 times of TNT per unit mass and 5 times of TNT per unit volume, respectively, but with excellent insensitivity compared with traditional explosives. Under thermal conditions, the W-PTFE-Al composite can keep stable at 773 K. Under impact loading, when the strain rate up to ∼4820 s−1 coupled with the absorbed energy per unit volume of 120 J/cm3, deflagration occurs and combustion lasts for 500 μs. During impact compressive deformation, the PTFE matrix is elongated into nano-fibers, thus significantly increases the reaction activity of W-PTFE-Al composites. The nano-fiber structure is necessary for the reaction of W-PTFE-Al composites. The formation of PTFE nano-fibers must undergo severe plastic deformation, and therefore the W-PTFE-Al composites exhibit excellent insensitivity and safety. Furthermore, the reaction mechanisms of W-PTFE-Al composites in argon and in air are revealed.

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)

Fabrication of TiO2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

Science.gov (United States)

Qian, Yingjia; Chi, Lina; Zhou, Weili; Yu, Zhenjiang; Zhang, Zhongzhi; Zhang, Zhenjia; Jiang, Zheng

2016-01-01

Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO2, we successfully fixed TiO2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti4+. The TiO2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel

Science.gov (United States)

Wang, Shibo; Niu, Chengchao

2016-01-01

In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324

Full four-dimensional and reciprocal Mueller matrix bidirectional reflectance distribution function of sintered polytetrafluoroethylene.

Science.gov (United States)

Germer, Thomas A

2017-11-20

We measured the Mueller matrix bidirectional reflectance distribution function (BRDF) of a sintered polytetrafluoroethylene (PTFE) sample over the scattering hemisphere for six incident angles (0°-75° in 15° steps) and for four wavelengths (351 nm, 532 nm, 633 nm, and 1064 nm). The data for each wavelength were fit to a phenomenological description for the Mueller matrix BRDF, which is an extension of the bidirectional surface scattering modes developed by Koenderink and van Doorn [J. Opt. Soc. Am. A.15, 2903 (1998)JOAOD60740-323210.1364/JOSAA.15.002903] for unpolarized BRDF. This description is designed to be complete, to obey the appropriate reciprocity conditions, and to provide a full description of the Mueller matrix BRDF as a function of incident and scattering directions for each wavelength. The description was further extended by linearizing the surface scattering mode coefficients with wavelength. This data set and its parameterization provides a comprehensive on-demand description of the reflectance properties for this commonly used diffuse reflectance reference material over a wide range of wavelengths.

Comparative study of the monomer grafting: ethylene, acetylene, 1,3-butadiene and estyrene in the matrix of recycled polytetrafluoroethylene (PTFE); Estudo comparativo da enxertia dos monomeros: etileno, acetileno, 1,3-butadieno e estireno na matriz de politetrafluoroetileno (PTFE) reciclado

Energy Technology Data Exchange (ETDEWEB)

Ikari, Carolina T.; Rosner, Gerhardyne O.; Oliveira, Ana C.F. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente (CQMA); Faculdades Oswaldo Cruz, Sao Paulo, SP (Brazil); Ferreto, Helio F.R.; Lima, Luiz F.C.P.; Lugao, Ademar B., E-mail: hferreto@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente (CQMA); Moreira, Otavio M. [Faculdades Oswaldo Cruz, Sao Paulo, SP (Brazil)

2009-07-01

In this study it is used the recycled polytetrafluoroethylene (PTFE), that with the gamma radiation under inert atmosphere or in presence of air, it is obtained free radicals and a posterior the monomer grafting (ethylene, acetylene, styrene or 1.3 butadiene), obtaining the copolymer polytetrafluoroethylene-g-monomer. It is studied the obtention of the polymer by two methods: by direct way, via grafting, where the polymer is irradiated in presence of monomer, and via grafting when the polymer is irradiated in absence of monomer and under inert or air. The characterization of the copolymer was performed by the techniques of infrared region absorption spectroscopy with Fourier transformation (FTIR), thermogravimetric (TGA) and derivative thermogravimetry (DTG), and percentage of mass grafting (DOG)

Expanded polytetrafluoroethylene membrane alters tissue response to implanted Ahmed glaucoma valve.

Science.gov (United States)

DeCroos, Francis Char; Ahmad, Sameer; Kondo, Yuji; Chow, Jessica; Mordes, Daniel; Lee, Maria Regina; Asrani, Sanjay; Allingham, R Rand; Olbrich, Kevin C; Klitzman, Bruce

2009-07-01

Long-term intraocular pressure control by glaucoma drainage implants is compromised by the formation of an avascular fibrous capsule that surrounds the glaucoma implant and increases aqueous outflow resistance. It is possible to alter this fibrotic tissue reaction and produce a more vascularized and potentially more permeable capsule around implanted devices by enclosing them in a porous membrane. Ahmed glaucoma implants modified with an outer 5-microm pore size membrane (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) and unmodified glaucoma implants were implanted into paired rabbit eyes. After 6 weeks, the devices were explanted and subject to histological analysis. A tissue response containing minimal vascularization, negligible immune response, and a thick fibrous capsule surrounded the unmodified Ahmed glaucoma implant. In comparison, the tissue response around the PRIME-Ahmed demonstrated a thinner fibrous capsule (46.4 +/- 10.8 microm for PRIME-Ahmed versus 94.9 +/- 21.2 microm for control, p vascularized near the tissue-material interface. A prominent chronic inflammatory response was noted as well. Encapsulating the aqueous outflow pathway with a porous membrane produces a more vascular tissue response and thinner fibrous capsule compared with a standard glaucoma implant plate. Enhanced vascularity and a thinner fibrous capsule may reduce aqueous outflow resistance and improve long-term glaucoma implant performance.

Studies on surface grafting of AAc/SSS binary monomers onto polytetrafluoroethylene by dielectric barrier discharge initiation

International Nuclear Information System (INIS)

Xi Zhenyu; Xu Youyi; Zhu Liping; Liu Fu; Zhu Baoku

2008-01-01

Polytetrafluoroethylene (PTFE) films were pre-treated by dielectric barrier discharge in atmospheric pressure with air as carrier gas. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effects of binary monomer ratio, reaction solution concentration and polymerization time on the degree of grafting were investigated. The surface chemical change was determined by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological changes on the film surface were described using field emitting scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. It was found that the water contact angle of the film surface reduced significantly when compared with the original one, indicating the introduction of hydrophilic groups and improvement of the surface hydrophilicity

Tissue expander infections in children: look beyond the expander pocket.

Science.gov (United States)

Mason, A C; Davison, S P; Manders, E K

1999-11-01

Infection of the expander pocket is the most common complication encountered with soft-tissue expansion. It is usually due to direct inoculation with skin flora either at the time of expander insertion or from extrusion of the device. The authors report two cases of infection of tissue expanders in which the children had concomitant infected sites distant from the prosthesis. Etiological bacteria of common pediatric infections like otitis media and pharyngitis were cultured from the infected expander pocket, raising suspicion that translocation of the organism to the expander had occurred. Aggressive antibiotic treatment, removal of the prosthesis, and flap advancement is advocated.

Plasma-Functionalized Polytetrafluoroethylene Nanoparticles for Improved Wear in Lubricated Contact

Energy Technology Data Exchange (ETDEWEB)

Sharma, Vinay [Materials Science; Timmons, Richard [Chemistry and Biochemistry, University of Texas at Arlington, P.O. Box 19065, Arlington, Texas 76019, United States; Erdemir, Ali [Argonne National Lab, Argonne, Illinois 60439, United States; Aswath, Pranesh B. [Materials Science

2017-07-20

Plasma-functionalized polytetrafluoroethylene (PTFE) nanoparticles were employed to evaluate their utility in improving the lubrication property of a group III mineral oil with a significantly low amount of zinc dialkyl dithiophosphate (ZDDP). The particles were coated with two consecutive films; the initial coating contained silica to enhance amorphous glassy tribofilm formation, followed by a methacrylate film to protect the silica coating and enhance dispersibility in the oil. The functionalized nanoparticles were evaluated for their tribological performance using a high-frequency reciprocating rig, in a cylinder-on-flat configuration. The oil formulations containing ZDDP (350 ppm phosphorus level) and the functionalized nanoparticles resulted in dramatic reductions in the friction coefficient and overall wear compared to the samples containing nonfunctionalized PTFE nanoparticles, ZDDP (350 ppm P), and samples devoid of nanoparticles but containing ZDDP with a 700 ppm P treat rate. XPS and XANES spectroscopy were employed to characterize the tribological films formed on the test samples. The samples with functionalized particles and ZDDP clearly exhibited tribofilms with Si- and F-doped polyphosphates of Zn coupled with the presence of ZnS at the metal-tribofilm interface. On the other hand, oils without the functionalized nanoparticles have oxides of Fe and to a lesser extent short-chain phosphates of Zn. The overall results suggest that the synergism between plasma-coated PTFE nanoparticles and ZDDP contributed to the development of protective tribofilms even at reduced amount of phosphorus in the oil. This new method of employing nanoparticles to deliver novel antifriction and antiwear chemistries at the tribological interfaces stands out as a promising approach to further reduce P levels in oils without compromising friction and wear performance.

Intraarterial 9-beta-methyl carbacyclin improves canine polytetrafluoroethylene graft patency

International Nuclear Information System (INIS)

Dacey, L.J.; Hees, P.S.; Cronenwett, J.L.

1988-01-01

This study examined the effect of 9-beta-methyl carbacyclin, a synthetic, stable prostacyclin analog, on canine polytetrafluoroethylene (PTFE) graft patency. Twenty-five dogs had 4 mm x 7 cm PTFE grafts implanted bilaterally into the femoral arteries. A subcutaneous infusion pump was used to deliver either saline solution (control) or 9-beta-methyl carbacyclin (Ciprostine) at 100 (CARB-100) or 200 ng/kg/min (CARB-200) through a femoral artery branch just proximal to one of the femoral grafts, with the contralateral graft serving as a noninfused control. Graft-platelet deposition (with 111 In-labeled platelets) was measured between the fifth and seventh days, with patency determined on the seventh day. Dogs were classified as aggregators (AGG [+]) if the preoperative epinephrine-enhanced sodium arachidonate platelet aggregation was greater than 20%. CARB-200 infusion significantly improved ipsilateral graft patency (80%) compared with noninfused grafts (50%, p less than 0.05), or grafts in control and CARB-100 dogs (43%, p less than 0.05). Anastomotic platelet deposition was decreased bilaterally in CARB-200 dogs by 45% to 59% compared with CARB-100 and control dogs (p less than 0.05). With the exception of grafts infused with CARB-200, AGG (+) dogs had significantly lower graft patency (26%) than nonaggregator AGG (-) dogs (71%, p less than 0.01). CARB-200 infusion significantly improved graft patency in AGG (+) dogs (71%), compared with control and CARB-100-infused grafts (19%, p less than 0.025). Intra-arterial 9-beta-methyl carbacyclin improved early PTFE graft patency and inhibited platelet deposition in a severe canine model, independent of baseline platelet aggregation status, which also had an important effect on graft patency

Effect of gamma irradiation on the structural, mechanical and optical properties of polytetrafluoroethylene sheet

Science.gov (United States)

Mohammadian-Kohol, M.; Asgari, M.; Shakur, H. R.

2018-04-01

In this study, the effects of gamma radiation on the chemical structure, mechanical and optical properties of polytetrafluoroethylene (PTFE) sheet were investigated with various doses up to 12 kGy. The chemical changes in the structure were studied by FTIR spectroscopy. Also, effects of radiation on the different mechanical parameters such as Young's modulus, toughness, strain, and stress were studied at the maximum tolerable force and the fracture points. Furthermore, changing the various optical parameters such as absorption coefficient, Urbach energy, optical band gaps, refractive index, optical dispersion parameters and plasma resonance frequency were studied by UV-visible spectroscopy. Formation of a band at 1594 cm-1, which was belonged to double carbon bonds, indicated that chain-scission was occurred at 12 kGy gamma irradiation dose. As well, the mechanical results showed an increase in the elastic behavior of PTFE sheets and a decrease in the plastic behavior of it with absorbed dose increasing. Moreover, the results showed that gamma irradiation can effectively change the various optical properties of PTFE sheets due to different phenomena such as degradation of the main chains, occurring chain-scission, formation of free radicals and cross-linking in the polymer structure.

The significant adhesion enhancement of Ag–polytetrafluoroethylene antibacterial coatings by using of molecular bridge

Energy Technology Data Exchange (ETDEWEB)

Guo, Ruijie, E-mail: guoruijie@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan, 030024 (China); Yin, Guangda; Sha, Xiaojuan [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan, 030024 (China); Zhao, Qi [Division of Mechanical Engineering and Mechatronics, University of Dundee, Dundee, DD1 4HN (United Kingdom); Wei, Liqiao; Wang, Huifang [Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan, 030024 (China)

2015-06-30

Highlights: • The more effective coupling agent is employed to modify surface. • S–Ag displays more intensive bond strength than that of N–Ag. • The coatings possess the highest level of adhesion. - Abstract: Weak adhesion between the metal-based antibacterial coatings and polymer substrates limits their clinical applications; surface modification is an effective way to solve this intrinsic problem. In this study, UV irradiation was employed to activate the inert silicon rubber substrates, and the grafting of coupling agent (3-mercaptopropyl) trimethoxy silane into the UV-irradiated substrates generated reactive surface containing −SH groups. During electroless plating S which has lone pair electrons anchored Ag{sup +} and produced antibacterial coatings with improved adhesion. The grafting of (3-mercaptopropyl) trimethoxy silane into silicon rubber was verified by X-ray photoelectron spectroscopy (XPS). The adhesion was tested by American Society of Testing Materials (ASTM D 3359-02). Surface elements content and distribution were observed and analyzed by X-ray energy disperse spectroscopy (EDS). The antibacterial performance was characterized by inhibition halo test and shake flash method. The results showed that the as-prepared composite Ag–polytetrafluoroethylene coatings possessed remarkably enhanced adhesion and superior antibacterial activity.

Grafted functional groups on expanded tetrafluoroethylene (ePTFE) support for fuel cell and water transport membranes

Science.gov (United States)

Fuller, Timothy J.; Jiang, Ruichun

2017-01-24

A method for forming a modified solid polymer includes a step of contacting a solid fluorinated polymer with a sodium sodium-naphthalenide solution to form a treated fluorinated solid polymer. The treated fluorinated solid polymer is contacted with carbon dioxide, sulfur dioxide, or sulfur trioxide to form a solid grafted fluorinated polymer. Characteristically, the grafted fluorinated polymer includes appended CO.sub.2H or SO.sub.2H or SO.sub.3H groups. The solid grafted fluorinated polymer is advantageously incorporated into a fuel cell as part of the ion-conducting membrane or a water transport membrane in a humidifier.

Analysis of explanted ePTFE cardiovascular grafts (modified BT shunt)

Energy Technology Data Exchange (ETDEWEB)

Doble, Mukesh [Department of Biotechnology, Indian Institute of Technology, Chennai 600 036 (India); Makadia, Nilesh; Pavithran, Sreeja; Kumar, R Suresh [Department of Pediatric Cardiology, Institute of Cardio-Vascular Diseases, Madras Medical Mission, Chennai, 600 037 (India)], E-mail: mukeshd@iitm.ac.in

2008-09-01

Structural, chemical, mechanical and surface changes were studied in expanded polytetrafluroethylene vascular grafts explanted from children undergoing planned surgical management of congenital heart disease. These grafts were implanted when recipients were aged 7 days to 8 years (median-48 weeks) and they had been in circulation for a period of 10-52 months (median-74 weeks). While no chemical changes were observed in the shunt, on average the tensile strength had decreased by 50%, total elongation by 61% and crystallinity by 3%. No salt deposits were observed on the surface of the graft. Soluble and insoluble proteins were bound to the polymer surface, which had made the surface hydrophilic. The external surface roughness had increased by 254.5 and the internal surface roughness by 2.6 times the initial value. The fine polymer structure had become fused and clumped. The fusing of strands on the polymer surface became more pronounced with longer duration of implantation. In one instance of previously documented graft stenosis, the heat capacity was found to be more than that of the unimplanted sample, indicating an increase in crystallinity. A longer period of study with a larger sample size would likely shed more light on the relation between physico-chemical changes and graft stenosis.

Analysis of explanted ePTFE cardiovascular grafts (modified BT shunt)

International Nuclear Information System (INIS)

Doble, Mukesh; Makadia, Nilesh; Pavithran, Sreeja; Kumar, R Suresh

2008-01-01

Structural, chemical, mechanical and surface changes were studied in expanded polytetrafluroethylene vascular grafts explanted from children undergoing planned surgical management of congenital heart disease. These grafts were implanted when recipients were aged 7 days to 8 years (median-48 weeks) and they had been in circulation for a period of 10-52 months (median-74 weeks). While no chemical changes were observed in the shunt, on average the tensile strength had decreased by 50%, total elongation by 61% and crystallinity by 3%. No salt deposits were observed on the surface of the graft. Soluble and insoluble proteins were bound to the polymer surface, which had made the surface hydrophilic. The external surface roughness had increased by 254.5 and the internal surface roughness by 2.6 times the initial value. The fine polymer structure had become fused and clumped. The fusing of strands on the polymer surface became more pronounced with longer duration of implantation. In one instance of previously documented graft stenosis, the heat capacity was found to be more than that of the unimplanted sample, indicating an increase in crystallinity. A longer period of study with a larger sample size would likely shed more light on the relation between physico-chemical changes and graft stenosis

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

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.

Inertial cavitation initiated by polytetrafluoroethylene nanoparticles under pulsed ultrasound stimulation.

Science.gov (United States)

Jin, Qiaofeng; Kang, Shih-Tsung; Chang, Yuan-Chih; Zheng, Hairong; Yeh, Chih-Kuang

2016-09-01

Nanoscale gas bubbles residing on a macroscale hydrophobic surface have a surprising long lifetime (on the order of days) and can serve as cavitation nuclei for initiating inertial cavitation (IC). Whether interfacial nanobubbles (NBs) reside on the infinite surface of a hydrophobic nanoparticle (NP) and could serve as cavitation nuclei is unknown, but this would be very meaningful for the development of sonosensitive NPs. To address this problem, we investigated the IC activity of polytetrafluoroethylene (PTFE) NPs, which are regarded as benchmark superhydrophobic NPs due to their low surface energy caused by the presence of fluorocarbon. Both a passive cavitation detection system and terephthalic dosimetry was applied to quantify the intensity of IC. The IC intensities of the suspension with PTFE NPs were 10.30 and 48.41 times stronger than those of deionized water for peak negative pressures of 2 and 5MPa, respectively. However, the IC activities were nearly completely inhibited when the suspension was degassed or ethanol was used to suspend PTFE NPs, and they were recovered when suspended in saturated water, which may indicates the presence of interfacial NBs on PTFE NPs surfaces. Importantly, these PTFE NPs could sustainably initiate IC for excitation by a sequence of at least 6000 pulses, whereas lipid microbubbles were completely depleted after the application of no more than 50 pulses under the same conditions. The terephthalic dosimetry has shown that much higher hydroxyl yields were achieved when PTFE NPs were present as cavitation nuclei when using ultrasound parameters that otherwise did not produce significant amounts of free radicals. These results show that superhydrophobic NPs may be an outstanding candidate for use in IC-related applications. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Sequential diffusion of ammonium and nitrate from soil extracts to a polytetrafluoroethylene trap for ¹⁵N determination

DEFF Research Database (Denmark)

Sørensen, P.; Jensen, E.S.

1991-01-01

A novel diffusion method was used for preparation of NH4+- and NO3--N samples from soil extracts for N-15 determination. Ammonium, and nitrate following reduction to ammonia, are allowed to diffuse to an acid-wetted glass filter enclosed in polytetrafluoroethylene tape. The method was evaluated...... with simulated soil extracts obtained using 50 ml of 2 M potassium chloride solution containing 130-mu-g of NH4+-N (2.3 atom% N-15) and 120-mu-g of NO3--N (natural N-15 abundance). No cross-over in the N-15 abundances of NH4+-N and NO3--N was observed, indicating a quantitative diffusion process (72 h, 25...

Anticorrosion Coating of Carbon Nanotube/Polytetrafluoroethylene Composite Film on the Stainless Steel Bipolar Plate for Proton Exchange Membrane Fuel Cells

Directory of Open Access Journals (Sweden)

Yoshiyuki Show

2013-01-01

Full Text Available Composite film of carbon nanotube (CNT and polytetrafluoroethylene (PTFE was formed from dispersion fluids of CNT and PTFE. The composite film showed high electrical conductivity in the range of 0.1–13 S/cm and hydrophobic nature. This composite film was applied to stainless steel (SS bipolar plates of the proton exchange membrane fuel cell (PEMFC as anticorrosion film. This coating decreased the contact resistance between the surface of the bipolar plate and the membrane electrode assembly (MEA of the PEMFC. The output power of the fuel cell is increased by 1.6 times because the decrease in the contact resistance decreases the series resistance of the PEMFC. Moreover, the coating of this composite film protects the bipolar plate from the surface corrosion.

Properties of carbon composite paper derived from coconut coir as a function of polytetrafluoroethylene content

Science.gov (United States)

Destyorini, Fredina; Indriyati; Indayaningsih, Nanik; Prihandoko, Bambang; Zulfia Syahrial, Anne

2018-03-01

The carbon composite papers were produced by utilizing carbon materials from coconut coir. In the present work, carbon composite papers (CCP) were prepared by mixing carbon materials in the form of powder and fibre with polymer (ethylene vinyl acetate and polyethylene glycol) in xylene at 100°C. Then, polytetrafluoroethylene (PTFE) with different content was used to treat the surface of CCP. The properties of PTFE-coated CCP were analysed by means of contact angle measurement, tensile testing, porosity, density, and electrical conductivity measurements. As expected, all CCP’s surfaces treated with PTFE were found to be hydrophobic with contact angle >120° and relatively constant during 60 minutes measurement. Furthermore, water contact angle, density, and mechanical properties of CCP generally increase with increasing PTFE content. However, the porosity and electrical conductivity of CCP decrease slightly as the PTFE content increased from 0 wt% to 30 wt%. Based on the observation and analysis, the optimum PTFE content on CCP was 20 %, in which the mechanical properties and hydrophobicity behaviour were improved significantly, but it was only caused a very small drop in porosity and electrical conductivity

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

In vitro evaluation of electrospun chitosan mats crosslinked with genipin as guided tissue regeneration barrier membranes

Science.gov (United States)

Norowski, Peter Andrew, Jr.

Guided tissue regeneration (GTR) is a surgical technique commonly used to exclude bacteria and soft tissues from bone graft sites in oral/maxillofacial bone graft sites by using a barrier membrane to maintain the graft contour and space. Current clinical barrier membrane materials based on expanded polytetrafluoroethylene (ePTFE) and bovine type 1 collagen are non-ideal and experience a number of disadvantages including membrane exposure, bacterial colonization/biofilm formation and premature degradation, all of which result in increased surgical intervention and poor bone regeneration. These materials do not actively participate in tissue regeneration, however bioactive materials, such as chitosan, may provide advantages such as the ability to stimulate wound healing and de novo bone formation. Our hypothesis is that electrospun chitosan GTR membranes will support cell attachment and growth but prevent cell infiltration/penetration of membrane, demonstrate in vitro degradation predictive of 4--6 month in vivo functionality, and will deliver antibiotics locally to prevent/inhibit periopathogenic complications. To test this hypothesis a series of chitosan membranes were electrospun, in the presence or absence of genipin, a natural crosslinking agent, at concentrations of 5 and 10 mM. These membranes were characterized by scanning electron microscopy, tensile testing, suture pullout testing, Fourier transform infrared spectroscopy, X-ray diffraction, and gel permeation chromatography, and in vitro biodegradation for diameter/morphology of fibers, membrane strengths, degree of crosslinking, crystallinity, molecular weight, and degradation kinetics, respectively. Cytocompability of membranes was evaluated in osteoblastic, fibroblastic and monocyte cultures. The activity of minocycline loaded and released from the membranes was determined in zone of inhibition tests using P. gingivalis microbe. The results demonstrated that genipin crosslinking extended the in vitro

What Expands in an Expanding Universe?

Science.gov (United States)

Pacheco, José A De Freitas

2015-01-01

In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

What Expands in an Expanding Universe?

Directory of Open Access Journals (Sweden)

JOSÉ A. DE FREITAS PACHECO

2015-12-01

Full Text Available ABSTRACT In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

Budget impact analysis of heparin-bonded polytetrafluoroethylene grafts (Propaten) against standard polytetrafluoroethylene grafts for below-the-knee bypass in patients with critical limb ischaemia in France

Science.gov (United States)

Vergnaud, Simon; Riche, Valéry-Pierre; Tessier, Philippe; Mauduit, Nicolas; Kaladji, Adrien; Gouëffic, Yann

2018-01-01

Objectives To evaluate the budget impact of progressive replacement of standard polytetrafluoroethylene (PTFE) grafts by heparin-bound PTFE (Propaten) for below-the-knee (BTK) bypass in patients with critical limb ischaemia (CLI). Design From a review of the scientific literature, we calculated a theoretical BTK primary patency for Propaten grafts. Using the French hospital expenditure database (PMSI), we retrospectively estimated a rehospitalisation rate for standard PTFE grafts. From these data, a model was created to assess the budget impact of a progressive replacement from standard PTFE grafts to Propaten grafts over a 5-year horizon. We performed an univariate sensitivity analysis to assess the robustness of our results. Setting French National Health Insurance (FNHI) perspective. Participant Patients with CLI. Main outcome measures Budget impact analysis. Results Data extraction from the PMSI revealed that 656 patients were treated with PTFE grafts in 2011 in French public hospitals for a BTK bypass. Assuming a 2-year survival rate of 76.8%, observed reinterventions rate for standard PTFE grafts at 24 months from the PMSI was 35.1%. The mean rehospitalisation cost was €10 689. The budget impact analysis based on these data found a net cumulative 5-year payer budget reduction of €112 420 in favour of Propaten, under the assumption of a 75.6% primary patency for Propaten grafts for a projected population of 3215 patients of which 801 received a Propaten graft. Conclusions Our budget impact analysis showed a positive impact on the national health insurance budget of the replacement of standard PTFE grafts by Propaten grafts for BTK bypass in patients with CLI in France. This supports the enactment of a reimbursement policy by the FNHI. PMID:29490953

Self-lubricating layer consist of polytetrafluoroethylene micropowders and fluorocarbon acrylate resin formation on surface of geotextile

Science.gov (United States)

Long, Xiaoyun; He, Lifen; Zhang, Yan; Ge, Mingqiao

2018-04-01

In this study, the self-lubricating layer consist of polytetrafluoroethylene (PTFE) micropowders and two types fluorocarbon acrylate resin were formed on the surface of geotextile, to improves the evenness and decreases the frictional angle value of geotextile surface. The surface and cross section morphology of geotextile were examined by scanning electron microscopy (SEM). It was determined that composite resin emulsion was evenly coated on the surface of geotextile, to form a even and complete self-lubricating layer, and it was strongly combined with the geotextile due to formation of the transition layer. The tensile fracture stress and strain values of samples were evaluated by mechanical properties measurement, the tensile fracture stress of the untreated and treated sample was approximately 5329 kN/m and 5452 kN/m while the elongation at the yield of them was approximately 85% to 83.9%, respectively. In addition, the frictional angle values of municipal solid waste (MSW)/geotextile interface was measured by the tilt table test, the values of untreated sample was 28.1° and 24.2° under the dry and moist condition, the values of treated sample was 16.2° and 9.8°, respectively.

Effect of flow on vascular endothelial cells grown in tissue culture on polytetrafluoroethylene grafts

International Nuclear Information System (INIS)

Sentissi, J.M.; Ramberg, K.; O'Donnell, T.F. Jr.; Connolly, R.J.; Callow, A.D.

1986-01-01

Vascular grafts lined with endothelial cells (EC) grown to confluence in culture before implantation may provide a thromboresistant flow surface. Growth of EC on and their adherence to currently available prosthetic materials under conditions of flow are two impediments remaining in the development of such a graft. To address these problems, 22 polytetrafluoroethylene grafts (PTFE) (5 cm by 4 mm inside diameter) were pretreated with collagen and fibronectin, seeded with 2 to 3 X 10(6) bovine aortic EC per graft, and placed in tissue culture (seeded grafts). Twenty-two grafts pretreated with collagen and fibronectin alone served as controls. After 2 weeks morphologic studies revealed that 20/22 seeded grafts were lined with a confluent endothelial layer. Indium 111-oxine was then used to label the EC-seeded grafts. After exposure to either low (25 ml/min) or high (200 ml/min) flow rates for 60 minutes in an in vitro circuit, examination of the luminal surface of the graft by light microscopy and scanning electron microscopy revealed minimal loss of EC. These findings were corroborated by radionuclide scans that showed an insignificant loss of the EC-associated indium label during exposure to flow (7% low flow, 11% high flow). Pretreatment of PTFE grafts with collagen and fibronectin thus promotes both attachment and adherence of EC even under flow conditions

Wear Process Analysis of the Polytetrafluoroethylene/Kevlar Twill Fabric Based on the Components’ Distribution Characteristics

Directory of Open Access Journals (Sweden)

Gu Dapeng

2017-12-01

Full Text Available Polytetrafluoroethylene (PTFE/Kevlar fabric or fabric composites with excellent tribological properties have been considered as important materials used in bearings and bushing, for years. The components’ (PTFE, Kevlar, and the gap between PTFE and Kevlar distribution of the PTFE/Kevlar fabric is uneven due to the textile structure controlling the wear process and behavior. The components’ area ratio on the worn surface varying with the wear depth was analyzed not only by the wear experiment, but also by the theoretical calculations with our previous wear geometry model. The wear process and behavior of the PTFE/Kevlar twill fabric were investigated under dry sliding conditions against AISI 1045 steel by using a ring-on-plate tribometer. The morphologies of the worn surface were observed by the confocal laser scanning microscopy (CLSM. The wear process of the PTFE/Kevlar twill fabric was divided into five layers according to the distribution characteristics of Kevlar. It showed that the friction coefficients and wear rates changed with the wear depth, the order of the antiwear performance of the previous three layers was Layer III>Layer II>Layer I due to the area ratio variation of PTFE and Kevlar with the wear depth.

Expanding subjectivities

DEFF Research Database (Denmark)

Lundgaard Andersen, Linda; Soldz, Stephen

2012-01-01

A major theme in recent psychoanalytic thinking concerns the use of therapist subjectivity, especially “countertransference,” in understanding patients. This thinking converges with and expands developments in qualitative research regarding the use of researcher subjectivity as a tool......-Saxon and continental traditions, this special issue provides examples of the use of researcher subjectivity, informed by psychoanalytic thinking, in expanding research understanding....

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

Investigation on surface structure of potassium permanganate/nitric acid treated poly(tetrafluoroethylene)

International Nuclear Information System (INIS)

Fu, Congli; Liu, Shuling; Gong, Tianlong; Gu, Aiqun; Yu, Zili

2014-01-01

Highlights: • A new transformation (conversion) mechanism of PTFE surface from a hydrophobicity to a hydrophilicity was proposed through the treatment of KMnO 4 /HNO 3 . • Chemical reactions or defluorination of PTFE described in the reported paper was testified to be a misconceived conclusion by the combination of several testing measurements (IR, XPS, XRD and so on) in our present work. • Deposition of manganese oxide and/or manganese hydroxide on PTFE surface contributed to the hydrophilic property of the modified PTFE with KMnO 4 /HNO 3 treated. • The deposition thickness on the modified PTFE surface was about 5 μm, which was significantly helpful in enhancing the adhesive strength of PTFE with other materials. - Abstract: In the previous articles concerning the treatment of poly(tetrafluoroethylene) (PTFE) with potassium permanganate/nitric acid mixture, the conversion of a hydrophobic to a hydrophilic surface was partially assigned to the defluorination of PTFE and then the introduction of carbonyl and hydroxyl groups into the defluorinated sites. In the present work, PTFE sheets were treated with potassium permanganate/nitric acid, and the surfaces before and after treatment were comparatively characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface sediments of the treated PTFE were also determined by atomic absorption spectroscopy (AAS). The results indicate that the conversion of the hydrophobicity to the hydrophilicity on the modified PTFE surface is mainly due to the deposition of hydrophilic manganese oxides which covered the fluorocarbon surface, and no detectable chemical reactions of PTFE occur in the treating process

Investigation on surface structure of potassium permanganate/nitric acid treated poly(tetrafluoroethylene)

Energy Technology Data Exchange (ETDEWEB)

Fu, Congli; Liu, Shuling; Gong, Tianlong; Gu, Aiqun; Yu, Zili, E-mail: ziliyu@scu.edu.cn

2014-10-30

Highlights: • A new transformation (conversion) mechanism of PTFE surface from a hydrophobicity to a hydrophilicity was proposed through the treatment of KMnO{sub 4}/HNO{sub 3}. • Chemical reactions or defluorination of PTFE described in the reported paper was testified to be a misconceived conclusion by the combination of several testing measurements (IR, XPS, XRD and so on) in our present work. • Deposition of manganese oxide and/or manganese hydroxide on PTFE surface contributed to the hydrophilic property of the modified PTFE with KMnO{sub 4}/HNO{sub 3} treated. • The deposition thickness on the modified PTFE surface was about 5 μm, which was significantly helpful in enhancing the adhesive strength of PTFE with other materials. - Abstract: In the previous articles concerning the treatment of poly(tetrafluoroethylene) (PTFE) with potassium permanganate/nitric acid mixture, the conversion of a hydrophobic to a hydrophilic surface was partially assigned to the defluorination of PTFE and then the introduction of carbonyl and hydroxyl groups into the defluorinated sites. In the present work, PTFE sheets were treated with potassium permanganate/nitric acid, and the surfaces before and after treatment were comparatively characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface sediments of the treated PTFE were also determined by atomic absorption spectroscopy (AAS). The results indicate that the conversion of the hydrophobicity to the hydrophilicity on the modified PTFE surface is mainly due to the deposition of hydrophilic manganese oxides which covered the fluorocarbon surface, and no detectable chemical reactions of PTFE occur in the treating process.

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.

Stability of nonfouling electroless nickel-polytetrafluoroethylene coatings after exposure to commercial dairy equipment sanitizers.

Science.gov (United States)

Huang, Kang; Goddard, Julie M

2015-09-01

Application of nonfouling coatings on thermal processing equipment can improve operational efficiency. However, to enable effective commercial translation, a need exists for more comprehensive studies on the stability of nonfouling coatings after exposure to different sanitizers. In the current study, the influence of different commercial dairy equipment sanitizers on the nonfouling properties of stainless steel modified with electroless Ni-polytetrafluoroethylene (PTFE) coatings was determined. Surface properties, such as dynamic contact angle, surface energy, surface morphology, and elemental composition, were measured before and after the coupons were exposed to the sanitizers for 168 cleaning cycles. The fouling behavior of Ni-PTFE-modified stainless steel coupons after exposure was also evaluated by processing raw milk on a self-fabricated benchtop-scale plate heat exchanger. The results indicated that peroxide sanitizer had only minor effect on the Ni-PTFE-modified stainless steel surface, whereas chlorine- and iodine-based sanitizers influenced the surface properties drastically. The coupons after 168 cycles of exposure to peroxide sanitizer accumulated the least amount of fouling material (4.44±0.24mg/cm(2)) compared with the coupons exposed to the other 3 sanitizers. These observations indicated that the Ni-PTFE nonfouling coating retained antifouling properties after 168 cycles of exposure to peroxide-based sanitizer, supporting their potential application as nonfouling coatings for stainless steel dairy processing equipment. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Development of high performance lubricant through the compatibilization of polyalphaolefin, polyurea and irradiated polytetrafluoroethylene

International Nuclear Information System (INIS)

Ratao, Natalia T.; Zen, Heloisa A.; Lugao, Ademar B.

2013-01-01

High performance lubricants are essential for shipping and oil exploration industries for working under severe conditions of temperature, pressure and contamination. Polytetrafluoroethylene (PTFE) is widely used as a lubricating additive in greases for presenting the lowest known coefficient of friction, is commercially found irradiated in air, by this way can be grinded and oxygenated terminal groups can be formed. PTFE processed by ionizing radiation with 4μ average particle size was supplied by Uniflon and compared with the ultraviolet-irradiated PTFE with the same average particle size, from Dupont. The characterization of functional proprieties by drop point, oil separation and four ball test was conducted with a polyurea base grease additive with both types of PTFE. The chemical characterization was done with Differential Scanning Calorimetry (DSC). The drop point and oil separation tests showed that the Uniflon irradiated PTFE improved the thermal resistance and stability of polyurea grease due to the greater presence of the end groups increase the compatibility of the additive with the fluid. Four ball tests showed that the grease with Uniflon irradiated PTFE also has a better antiwear and extreme pressure performance because of the greater polarity of the molecules improving the dispersion and anchoring of the PTFE in metal surface voids, reducing wear. The PTFE processed by ionizing radiation showed greater compatibility with polyurea grease and polyalphaolefin fluid and the grease functional characteristics met the requirements for a high performance lubricant. (author)

Five-year outcomes following a randomized trial of femorofemoral and femoropopliteal bypass grafting with heparin-bonded or standard polytetrafluoroethylene grafts

DEFF Research Database (Denmark)

Lindholt, Jes S.; Houlind, K.; Gottschalksen, B

2016-01-01

BACKGROUND: Cohort studies suggest superior long-term patency of luminal heparin-bonded polytetrafluoroethylene (Hb-PTFE) bypass grafts compared with standard PTFE grafts. The aim of this study was to compare the outcomes of Hb-PTFE grafts with those of standard PTFE grafts 5 years after...... a randomized trial. METHODS: Patients with intermittent claudication or critical limb ischaemia requiring femorofemoral or femoropopliteal bypass grafting were randomized in a clinical trial of Hb-PTFE versus standard PTFE in 11 Scandinavian centres between 2005 and 2009. Patients were followed up for 5 years...... of the primary outcome. Use of Hb-PTFE significantly improved patency by 37 per cent at 2 years, but 5 years after randomization there was no difference in primary patency (adjusted hazard ratio (HR) 0·95, 95 per cent c.i. 0·71 to 1·28; P = 0·748). In patients with critical limb ischaemia the use of Hb-PTFE...

Ag-polytetrafluoroethylene composite coating on stainless steel as bipolar plate of proton exchange membrane fuel cell

Energy Technology Data Exchange (ETDEWEB)

Fu, Yu. [Laboratory of Fuel Cells, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road, Dalian 116023 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Hou, Ming; Shao, Zhigang; Yi, Baolian [Laboratory of Fuel Cells, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road, Dalian 116023 (China); Xu, Hongfeng; Hou, Zhongjun; Ming, Pingwen [Sunrise Power Co., Ltd., Dalian 116025 (China)

2008-08-01

Forming a coating on metals by surface treatment is a good way to get high performance bipolar plate of proton exchange membrane fuel cell (PEMFC). In our research, Ag-polytetrafluoroethylene (PTFE) composite film was electrodeposited with silver-gilt solution of nicotinic acid by a bi-pulse electroplating power supply on 316 L stainless steel bipolar plate of PEMFC. Surface topography, contact angle, interfacial conductivity and corrosion resistance of the bipolar plate samples were investigated. Results showed that the defects on the Ag-PTFE composite coating are greatly reduced compared with those on the pure Ag coating fabricated under the same condition; and the contact angle of the Ag-PTFE composite coating with water is 114 , which is much bigger than that of the pure Ag coating (73 ). In addition, the interfacial contact resistance of the composite coating stays as low as the pure Ag coating; and the bipolar plate sample with composite coating shows a close corrosion resistance to the pure Ag coating sample in potentiodynamic and potentiostatic tests. Coated 316 L stainless steel plate with Ag-PTFE composite coating exhibits well hydrophobic characteristic, less defects, high interfacial conductivity and good corrosion resistance, which shows a great potential of the application in PEMFC. (author)

Fabrication of TiO_2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

International Nuclear Information System (INIS)

Qian, Yingjia; Chi, Lina; Zhou, Weili; Yu, Zhenjiang; Zhang, Zhongzhi; Zhang, Zhenjia; Jiang, Zheng

2016-01-01

Graphical abstract: - Highlights: • Multifunctional TiO_2/PAA/PTFE ultrafiltration membrane was fabricated via tight coating of TiO_2 functional layer onto the plasma-assisted graft of PAA on PTFE. • The high water flux rate, remarkable enhanced ultrafiltration performance and excellent self-cleaning ability were demonstrated. • The formation of COO−Ti bidentate coordination between TiO_2 and PAA was responsible for the successful coating. - Abstract: Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO_2, we successfully fixed TiO_2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO_2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti"4"+. The TiO_2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO_2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO_2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

The Effect of Temperature on the Free Volume in Polytetrafluoroethylene Studied by Positron Annihilation Spectroscopy

International Nuclear Information System (INIS)

Abdel-Latif, R.M.; Mohamed, H.F.M.; Abdel-Hady, E.E.; Mohamed, S.S.

2005-01-01

The positron annihilation techniques have been applied to investigate the free volume holes in pure and doped polytetrafluoroethylene (PTFE) with glass as a function of temperature. The measurements were performed from room temperature up to 250 degree C. The lifetime spectra were analyzed using two methods; 1) Finite-term analysis to determine the average values of the orthopositronium (o-Ps) lifetime and its intensity using PATFIT program, 2) Continuous lifetime analysis to obtain the o-Ps lifetime and o-Ps hole volume distributions using MELT program. The ortho-positronium (o-Ps) lifetimes, (T3 and T4) are found to be vary depending upon the phase of the polymer. Within the temperature range two transitions can be observed. The first one is related to the glass transition temperature, T g (at 130 degree C for pure PTFE and at 110 degree C for doped PTFE with glass). The second one is the crystalline temperature at 210 degree C for the two samples. It was found that, T g is shifted toward the lower values (110 degree C) for doped PTFE with glass, which could be attributed to the increase in the degree of crystallinity. This is in consistent with the wide-angle x-ray scattering data. A correlation between the positron annihilation parameters and the electrical conductivity was achieved

Comparison of self-expandable and balloon-expanding stents for hybrid ductal stenting in hypoplastic left heart complex.

Science.gov (United States)

Goreczny, Sebastian; Qureshi, Shakeel A; Rosenthal, Eric; Krasemann, Thomas; Nassar, Mohamed S; Anderson, David R; Morgan, Gareth J

2017-07-01

We aimed to compare the procedural and mid-term performance of a specifically designed self-expanding stent with balloon-expandable stents in patients undergoing hybrid palliation for hypoplastic left heart syndrome and its variants. The lack of specifically designed stents has led to off-label use of coronary, biliary, or peripheral stents in the neonatal ductus arteriosus. Recently, a self-expanding stent, specifically designed for use in hypoplastic left heart syndrome, has become available. We carried out a retrospective cohort comparison of 69 neonates who underwent hybrid ductal stenting with balloon-expandable and self-expanding stents from December, 2005 to July, 2014. In total, 43 balloon-expandable stents were implanted in 41 neonates and more recently 47 self-expanding stents in 28 neonates. In the balloon-expandable stents group, stent-related complications occurred in nine patients (22%), compared with one patient in the self-expanding stent group (4%). During follow-up, percutaneous re-intervention related to the ductal stent was performed in five patients (17%) in the balloon-expandable stent group and seven patients (28%) in self-expanding stents group. Hybrid ductal stenting with self-expanding stents produced favourable results when compared with the results obtained with balloon-expandable stents. Immediate additional interventions and follow-up re-interventions were similar in both groups with complications more common in those with balloon-expandable stents.

Mechanisms of Contact Electrification at Aluminum-Polytetrafluoroethylene and Polypropylene-Water

KAUST Repository

Nauruzbayeva, Jamilya

2017-04-01

Contact electrification refers to the transfer of electrical charges between two surfaces, similar and dissimilar, as they are brought into contact and separated; this phenomenon is also known as static electrification or triboelectrification. For example, everyone has experienced weak electrical shocks from metal doorknobs, wool and synthetic clothing on dry days. While contact electrification might appear insignificant, it plays a key role in numerous natural and industrial processes, including atmospheric lightning, accumulation of dust on solar panels, charging of liquids during pipetting and flow in the tubes, and fire hazards in granular media. Contact electrification at metal-metal interfaces is well understood in terms of transfer of electrons, but a comprehensive understanding of contact electrification at interfaces of electrical insulators, such as air, water, polytetrafluoroethylene (PTFE), polypropylene remains incomplete. In fact, a variety of mechanisms responsible for transfer of electrical charges during mechanical rubbing, slipping, sliding, or flow at interfaces have been proposed via: electrons, ions, protons, hydroxide ions from water, specific orientation of dipoles, mechanoradicals, cryptoelectrons, and transfer of material. We have noticed that the extent of contact electrification of solids in water is influenced by surface free energies, mobile ions, surface roughness, duration of contact, sliding speeds, and relative humidity. Herein, we present results of our experimental investigation of contact electrification at the following interfaces: (i) PTFE-aluminum in air and (ii) polypropylene-water interfaces. To identify the underlying mechanism, we started with various hypotheses and exploited a variety of experimental techniques to falsify most of them until we got an answer; our techniques included high-voltage power supply (0-10,000 V), Faraday cages, Kelvin probe force microscopy, electrodeposition, X-ray photoelectron spectroscopy

Two Types of Expanding Lie Algebra and New Expanding Integrable Systems

International Nuclear Information System (INIS)

Dong Huanhe; Yang Jiming; Wang Hui

2010-01-01

From a new Lie algebra proposed by Zhang, two expanding Lie algebras and its corresponding loop algebras are obtained. Two expanding integrable systems are produced with the help of the generalized zero curvature equation. One of them has complex Hamiltion structure with the help of generalized Tu formula (GTM). (general)

Influence of epoxy, polytetrafluoroethylene (PTFE) and rhodium surface coatings on surface roughness, nano-mechanical properties and biofilm adhesion of nickel titanium (Ni-Ti) archwires

Science.gov (United States)

Asiry, Moshabab A.; AlShahrani, Ibrahim; Almoammar, Salem; Durgesh, Bangalore H.; Kheraif, Abdulaziz A. Al; Hashem, Mohamed I.

2018-02-01

Aim. To investigate the effect of epoxy, polytetrafluoroethylene (PTFE) and rhodium surface coatings on surface roughness, nano-mechanical properties and biofilm adhesion of nickel titanium (Ni-Ti) archwires Methods. Three different coated (Epoxy, polytetrafluoroethylene (PTFE) and rhodium) and one uncoated Ni-Ti archwires were evaluated in the present study. Surface roughness (Ra) was assessed using a non-contact surface profilometer. The mechanical properties (nano-hardness and elastic modulus) were measured using a nanoindenter. Bacterial adhesion assays were performed using Streptococcus mutans (MS) and streptococcus sobrinus (SS) in an in-vitro set up. The data obtained were analyzed using analyses of variance, Tukey’s post hoc test and Pearson’s correlation coefficient test. Result. The highest Ra values (1.29 ± 0.49) were obtained for epoxy coated wires and lowest Ra values (0.29 ± 0.16) were obtained for the uncoated wires. No significant differences in the Ra values were observed between the rhodium coated and uncoated archwires (P > 0.05). The highest nano-hardness (3.72 ± 0.24) and elastic modulus values (61.15 ± 2.59) were obtained for uncoated archwires and the lowest nano-hardness (0.18 ± 0.10) and elastic modulus values (4.84 ± 0.65) were observed for epoxy coated archwires. No significant differences in nano-hardness and elastic modulus values were observed between the coated archwires (P > 0.05). The adhesion of Streptococcus mutans (MS) to the wires was significantly greater than that of streptococcus sobrinus (SS). The epoxy coated wires demonstrated an increased adhesion of MS and SS and the uncoated wires demonstrated decreased biofilm adhesion. The Spearman correlation test showed that MS and SS adhesion was positively correlated with the surface roughness of the wires. Conclusion. The different surface coatings significantly influence the roughness, nano-mechanical properties and biofilm adhesion parameters of the archwires. The

Expander for Thin-Wall Tubing

Science.gov (United States)

Pessin, R.

1983-01-01

Tool locally expands small-diameter tubes. Tube expander locally expands and deforms tube: Compressive lateral stress induced in elastomeric sleeve by squeezing axially between two metal tool parts. Adaptable to situations in which tube must have small bulge for mechanical support or flow control.

In Vitro Comparison of Self-Expanding Versus Balloon-Expandable Stents in a Human Ex Vivo Model

International Nuclear Information System (INIS)

Grenacher, Lars; Rohde, Stefan; Gaenger, Ellen; Deutsch, Jochen; Kauffmann, Guenter W.; Richter, Goetz M.

2006-01-01

The objective was to compare the radial strength and expansile precision of self-expanding stents and balloon-expandable stents in a human cadaver bifurcation model. Seven different self-expanding (LUMINEXX, JOSTENT SelfX, JOSTENT SelfX hrf, Sinus-Repo, Sinus SuperFlex, Easy Wallstent, SMART) and four different balloon-expandable stent models (Palmaz, Sinus Stent, SAXX Medium, JOSTENT peripheral), each type 10 stents (total n = 110 stents) were implanted into the common iliac arteries of human cadaver corpses. The maximum stent diameter was 10 mm for all models. After stent implantation, the specimens were filled with silicone caoutchouc. After 24 h, the vascular walls including the stents were removed from the hardened casts. Diameters were taken and the weight of the cast cylinders was measured in air and in purified water to calculate the volume of the bodies (according to Archimedes Law) as a relative but precise degree for the radial strength of the implanted stents. The cylindrical casts of the self-expanding stents showed lower mean diameters (8.2 ± 1.0 mm) and mean volumes (0.60 ± 0.14 ml/cm) than in the balloon-expandable stent group (10.1 ± 0.3 mm and 0.71 ± 0.04 ml/cm, respectively; p < 0.01). The nominal maximum diameter of 10 mm was not achieved in any of the self-expanding stents, but this was achieved in more than 70% (29/40) of the balloon-expandable stent specimens (p < 0.05). The variation between achieved volumes was significantly larger in self-expanding (range: 0.23-0.78 ml/cm) than in balloon-expandable stents (range: 0.66-0.81 ml/cm; p < 0.05). Self-expanding stents presented considerably lower radial expansion force and lower degree of precision than balloon-expandable stents

Effects of polytetrafluoroethylene treatment and compression on gas diffusion layer microstructure using high-resolution X-ray computed tomography

Science.gov (United States)

Khajeh-Hosseini-Dalasm, Navvab; Sasabe, Takashi; Tokumasu, Takashi; Pasaogullari, Ugur

2014-11-01

The microstructure of a TGP-H-120 Toray paper gas diffusion layer (GDL) was investigated using high resolution X-ray computed tomography (CT) technique, with a resolution of 1.8 μm and a field of view (FOV) of ∼1.8 × 1.8 mm. The images obtained from the tomography scans were further post processed, and image thresholding and binarization methodologies are presented. The validity of Otsu's thresholding method was examined. Detailed information on bulk porosity and porosity distribution of the GDL at various Polytetrafluoroethylene (PTFE) treatments and uniform/non-uniform compression pressures was provided. A sample holder was designed to investigate the effects of non-uniform compression pressure, which enabled regulating compression pressure between 0, and 3 MPa at a gas channel/current collector rib configuration. The results show the heterogeneous and anisotropic microstructure of the GDL, non-uniform distribution of PTFE, and significant microstructural change under uniform/non-uniform compression. These findings provide useful inputs for numerical models to include the effects of microstructural changes in the study of transport phenomena within the GDL and to increase the accuracy and predictability of cell performance.

Development of high performance lubricant through the compatibility of polyalphaolefin, polyurea and irradiated polytetrafluoroethylene

International Nuclear Information System (INIS)

Ratao, Natalia Torres

2013-01-01

Lubricants are gaseous, liquid, semi solid or solid (powder) materials those form a film between two parties preventing friction. High performance lubricants are designed to work under severe conditions of temperature, pressure, and contamination. The most used are liquids (oils) and semi solids (greases). Greases are applied where oils can drain or in inaccessible places and are divided generally into two classes, soap and no soap. The most used non soap grease is polyurea, obtained by the reaction between amine and isocyanate, has highly thixotropic, high dielectric strength and excellent anticorrosive property, so it is widely used for lubrication of electric motors and shipbuilding machinery. For a grease with high performance, in this study was used a synthetic lubricant fluid, polyalphaolefin, and was also employed solid lubricant additive polytetrafluoroethylene (PTFE) due its lowest coefficient of friction, is found commercially irradiated in air to obtain smaller particles and to produce oxygenated terminal groups those are more compatible with the metal surface. The tests conducted were comparatively between pure polyurea grease and with PTFE additive. The characterizations were made by infrared spectroscopy and elemental analysis of C, N and H and Free NCO index, proving the formation of four carbons polyurea (tetraurea). The functional analysis of drop point and oil separation showed high stability and compatibility between the polymers increased when PTFE was added. The excellent resistance of pure tetraurea grease to wear and extreme pressure were demonstrated by four-ball and practical bearings tests, characterizing this grease as a high performance lubricant, when compared to most used greases in the market. (author)

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.

Comparison of Polytetrafluoroethylene Flat-Sheet Membranes with Different Pore Sizes in Application to Submerged Membrane Bioreactor

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Manabu Motoori

2012-06-01

Full Text Available This study focused on phase separation of activated sludge mixed liquor by flat-sheet membranes of polytetrafluoroethylene (PTFE. A 20 liter working volume lab-scale MBR incorporating immersed PTFE flat-sheet membrane modules with different pore sizes (0.3, 0.5 and 1.0 μm was operated for 19 days treating a synthetic wastewater. The experiment was interrupted twice at days 5 and 13 when the modules were removed and cleaned physically and chemically in sequence. The pure water permeate flux of each membrane module was measured before and after each cleaning step to calculate membrane resistances. Results showed that fouling of membrane modules with 0.3 μm pore size was more rapid than other membrane modules with different pore sizes (0.5 and 1.0 μm. On the other hand, it was not clear whether fouling of the 0.5 μm membrane module was more severe than that of the 1.0 μm membrane module. This was partly because of the membrane condition after chemical cleaning, which seemed to determine the fouling of those modules over the next period. When irreversible resistance (R_i i.e., differences in membrane resistance before use and after chemical cleaning was high, the transmembrane pressure increased quickly during the next period irrespective of membrane pore size.

Facile fabrication and characterization of poly(tetrafluoroethylene)@polypyrrole/nano-silver composite membranes with conducting and antibacterial property

Science.gov (United States)

Shi, Zhiquan; Zhou, Hui; Qing, Xutang; Dai, Tingyang; Lu, Yun

2012-06-01

Porous poly(tetrafluoroethylene) (PTFE) membranes play an important role in air purification and separation engineering. To achieve the bi-functionality of conducting and antibacterial property, two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes have been prepared. One involves hydrophobic polypyrrole/nano-silver composite with hollow capsule nanostructures immobilized on the surface of the PTFE membranes. The other is a type of composite membranes with polypyrrole/nano-silver composite wholly packed on the fibrils of the expand PTFE membrane to form core/shell coaxial cable structures. The structure and morphology of the two kinds of composite membranes have been characterized by FTIR, UV-vis, XRD, TGA and SEM measurements. Possible formation mechanisms of the hollow capsules and the core/shell nanocable structures have been discussed in detail. The antibacterial effects of composite membranes are also briefly investigated.

Histomorphometric Analysis of Periodontal Tissue Regeneration by the Use of High Density Polytetrafluoroethylen Membrane in Grade II Furcation Defects of Dogs

Directory of Open Access Journals (Sweden)

Raoofi S

2015-09-01

Full Text Available Statement of Problem: There are limited histomorphometric studies on biologic efficacy of high density tetrafluoroethylen (d-PTFE membrane. Objectives: To investigate the healing of surgically induced grade II furcation defects in dogs following the use of dense polytetrafluoroethylene as the barrier membrane and to compare the results with the contra lateral control teeth without the application of any membrane. Materials andMethods: Mandibular and maxillary 3rd premolar teeth of 18 young adult male mongrel dogs were used for the experiment. The furcation defects were created during the surgery. 5 weeks later, regenerative surgery was performed. The third premolar teeth were assigned randomly to control and test groups. In the test group, after a full thickness flap reflection, the d-PTFE membrane was placed over furcation defects. In the control group, no membrane was placed over the defect. 37 tissue blocks containing the teeth and surrounding hard and soft tissues were obtained three months post-regenerative surgery. The specimens were demineralized, serially sectioned, mounted and stained with Hematoxylin and Eosin staining technique. From each tissue block, 35-45 sections of 10 μm thickness within 60μm interval captured the entire surgically created defect. The histological images were transferred to computer and then the linear measurement ranges of the defects area, interadicular alveolar bone, epithelial attachment and coronal extension of the new cementum were done. Then, the volume and area of aforementioned parameters were calculated considering the thickness and interval of the sections. To compare the parameters between the control and test teeth, we calculated the amount of each one proportionally to the original amount of defects. Results: The mean interradicular root surface areas of original defects covered with new cementum was 74.46% and 29.59% for the membrane and control defects, respectively (p < 0.0001. Corresponding

Microbial Biofilms and Breast Tissue Expanders

Directory of Open Access Journals (Sweden)

Melissa J. Karau

2013-01-01

Full Text Available We previously developed and validated a vortexing-sonication technique for detection of biofilm bacteria on the surface of explanted prosthetic joints. Herein, we evaluated this technique for diagnosis of infected breast tissue expanders and used it to assess colonization of breast tissue expanders. From April 2008 to December 2011, we studied 328 breast tissue expanders at Mayo Clinic, Rochester, MN, USA. Of seven clinically infected breast tissue expanders, six (85.7% had positive cultures, one of which grew Propionibacterium species. Fifty-two of 321 breast tissue expanders (16.2%, 95% CI, 12.3–20.7% without clinical evidence of infection also had positive cultures, 45 growing Propionibacterium species and ten coagulase-negative staphylococci. While vortexing-sonication can detect clinically infected breast tissue expanders, 16 percent of breast tissue expanders appear to be asymptomatically colonized with normal skin flora, most commonly, Propionibacterium species.

Preparation of organic monolithic columns in polytetrafluoroethylene tubes for reversed-phase liquid chromatography

International Nuclear Information System (INIS)

Catalá-Icardo, M.; Torres-Cartas, S.; Meseguer-Lloret, S.; Gómez-Benito, C.; Carrasco-Correa, E.; Simó-Alfonso, E.F.; Ramis-Ramos, G.; Herrero-Martínez, J.M.

2017-01-01

In this work, a method for the preparation and anchoring of polymeric monoliths in a polytetrafluoroethylene (PTFE) tubing as a column housing for microbore HPLC is described. In order to assure a covalent attachment of the monolith to the inner wall of the PTFE tube, a two-step procedure was developed. Two surface etching reagents, a commercial sodium naphthalene solution (Fluoroetch"®), or mixtures of H_2O_2 and H_2SO_4, were tried and compared. Then, the obtained hydroxyl groups on the PTFE surface were modified by methacryloylation. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the successful modification of the tubing wall and the stable anchorage of monolith to the wall, respectively. Special emphasis was also put on the reduction of the unwanted effects of shrinking of monolith during polymerization, by using an external proper mold and by selecting the adequate monomers in order to increase the flexibility of the polymer. Poly(glycidyl methacrylate-co-divinylbenzene) monoliths were in situ synthesized by thermal polymerization within the confines of surface-vinylized PTFE tubes. The modified PTFE tubing tightly held the monolith, and the monolithic column exhibited good pressure resistance up to 20 MPa. The column performance was also evaluated via the isocratic separation of a series of alkylbenzenes in the reversed-phase mode. The optimized monolithic columns gave plate heights ranged between 70 and 80 μm. The resulting monoliths were also satisfactorily applied to the separation of proteins. - Highlights: • Successful surface etching of PTFE inner wall tubing was done. • The modified PTFE support was next methacryloylated with GMA. • Organic polymeric monolith was in situ prepared in the functionalized PTFE tube. • The monolithic columns gave suitable pressure resistance and separation of proteins.

Preparation of organic monolithic columns in polytetrafluoroethylene tubes for reversed-phase liquid chromatography

Energy Technology Data Exchange (ETDEWEB)

Catalá-Icardo, M., E-mail: mocaic@qim.upv.es [Research Institute for Integrated Management of Coastal Areas, Universitat Politècnica de València, Paranimf 1, 46730, Grao de Gandía, Valencia (Spain); Torres-Cartas, S.; Meseguer-Lloret, S.; Gómez-Benito, C. [Research Institute for Integrated Management of Coastal Areas, Universitat Politècnica de València, Paranimf 1, 46730, Grao de Gandía, Valencia (Spain); Carrasco-Correa, E.; Simó-Alfonso, E.F.; Ramis-Ramos, G. [Department of Analytical Chemistry, Universitat de València, Dr. Moliner 50, 46100, Burjassot, Valencia (Spain); Herrero-Martínez, J.M., E-mail: jmherrer@uv.es [Department of Analytical Chemistry, Universitat de València, Dr. Moliner 50, 46100, Burjassot, Valencia (Spain)

2017-04-01

In this work, a method for the preparation and anchoring of polymeric monoliths in a polytetrafluoroethylene (PTFE) tubing as a column housing for microbore HPLC is described. In order to assure a covalent attachment of the monolith to the inner wall of the PTFE tube, a two-step procedure was developed. Two surface etching reagents, a commercial sodium naphthalene solution (Fluoroetch{sup ®}), or mixtures of H{sub 2}O{sub 2} and H{sub 2}SO{sub 4}, were tried and compared. Then, the obtained hydroxyl groups on the PTFE surface were modified by methacryloylation. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the successful modification of the tubing wall and the stable anchorage of monolith to the wall, respectively. Special emphasis was also put on the reduction of the unwanted effects of shrinking of monolith during polymerization, by using an external proper mold and by selecting the adequate monomers in order to increase the flexibility of the polymer. Poly(glycidyl methacrylate-co-divinylbenzene) monoliths were in situ synthesized by thermal polymerization within the confines of surface-vinylized PTFE tubes. The modified PTFE tubing tightly held the monolith, and the monolithic column exhibited good pressure resistance up to 20 MPa. The column performance was also evaluated via the isocratic separation of a series of alkylbenzenes in the reversed-phase mode. The optimized monolithic columns gave plate heights ranged between 70 and 80 μm. The resulting monoliths were also satisfactorily applied to the separation of proteins. - Highlights: • Successful surface etching of PTFE inner wall tubing was done. • The modified PTFE support was next methacryloylated with GMA. • Organic polymeric monolith was in situ prepared in the functionalized PTFE tube. • The monolithic columns gave suitable pressure resistance and separation of proteins.

Optimum concentration gradient of the electrocatalyst, Nafion® and poly(tetrafluoroethylene) in a membrane-electrode-assembly for enhanced performance of direct methanol fuel cells.

Science.gov (United States)

Liu, Jing Hua; Jeon, Min Ku; Lee, Ki Rak; Woo, Seong Ihl

2010-12-14

A combinatorial library of membrane-electrode-assemblies (MEAs) which consisted of 27 different compositions was fabricated to optimize the multilayer structure of direct methanol fuel cells. Each spot consisted of three layers of ink and a gradient was generated by employing different concentrations of the three components (Pt catalyst, Nafion® and polytetrafluoroethylene (PTFE)) of each layer. For quick evaluation of the library, a high-throughput optical screening technique was employed for methanol electro-oxidation reaction (MOR) activity. The screening results revealed that gradient layers could lead to higher MOR activity than uniform layers. It was found that the MOR activity was higher when the concentrations of Pt catalyst and Nafion ionomer decreased downward from the top layer to the bottom layer. On the other hand, higher MOR activity was observed when PTFE concentration increased downward from the top to the bottom layer.

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

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.

The effect of irradiation atmosphere on NMR absorption of 60Co γ-rays irradiated polytetrafluoroethylene

International Nuclear Information System (INIS)

Tutiya, Mituaki

1975-01-01

The radiation stability of polytetrafluoroethylene (PTFE) is sensitive to the presence of oxygen during irradiation. In semicrystalline polymers such as PTFE, it is expected that the influence of irradiation differs in crystalline and amorphous regions, therefore the magnitude of irradiation effect in amorphous region was compared with that in crystalline region of PTFE. In the NMR measurement by the author, the main difference between the PTFE samples annealed after irradiation in air and in vacuum was that the increase in crystallinity and the lowering of crystalline transition temperature Tsub(t) were accelerated in the former case. The scission probability of C-C bonds r can be estimated from the radiation-induced increase in crystallinity in the amorphous region of PTFE, and the value of r in the crystalline region can also be calculated. According to previous papers, the ratio of the scission probability in air to that in vacuum was estimated to be about 7 in the amorphous region and 1.8 in the crystalline region of PTFE. From this fact, the following conclusions were drawn. Main chain scission was accelerated when PTFE was irradiated in air. In PTFE, the amorphous region was affected more by irradiation atmosphere than the crystalline region. In both air and vacuum irradiation, the scission probability in the amorphous region was larger than that in the crystalline region. The effect of irradiation on PTFE was affected by oxygen diffusion, the life time of free radicals, and the degree of packing of molecular chains. (Kako, I.)

Suspended polytetrafluoroethylene nanostructure electret film in dual variable cavities for self-powered micro-shock sensing

Science.gov (United States)

Zhu, Jianxiong; Chen, Cong; Guo, Xiaoyu

2018-04-01

We report a suspended polytetrafluoroethylene (PTFE) nanostructure electret film in dual variable cavities for a self-powered micro-shock sensing application. The prototype contained series variable air cavities, a suspended nanostructure PTFE electret film and independent electrode films. The charges on the suspended nanostructure PTFE electret film provided the electrostatic field around the electret film in the series variable air cavities. When the reported device was driven by a micro-shock pressure, the inducted electrostatic charges on both the top and bottom electrodes would vary as the micro-shock pressing or releasing. Experimental results showed that the maximum of a short-circuit current density (J sc ) and an open-circuit voltage (V oc ) reached 3 ± 0.1 nA cm‑2 and 3.6 ± 0.1 V, respectively. It was found that the parameter J sc was more advantageous in identifying stronger shocks (parameter acceleration a bigger than 0.1 m s‑2), whereas the parameter V oc was more sensitive for weaker shocks, such as acceleration a smaller than 0.1 m s‑2. Moreover, finger continuous micro-shock pressure taps application was used to demonstrate the mechanical energy conversion performance with 4.5 ± 0.2 V open-circuit voltages. The research on the nanostructure electret PTFE film in series dual variable air cavities not only gave us a fresh idea about the principle and design of the shocking sensor, but also provided an easy fabrication and a low cost shocking sensor for the Internet of Things (IoT) systems.

Silicon microfabricated beam expander

Science.gov (United States)

Othman, A.; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A.; Ain, M. F.

2015-03-01

The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

Bigelow Expandable Activity Module Project

Data.gov (United States)

National Aeronautics and Space Administration — The Bigelow Expandable Activity Module (BEAM) project is a NASA-industry partnership with Bigelow Aerospace (BA) that has developing the first human-rated expandable...

Fabrication of TiO{sub 2}-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

Energy Technology Data Exchange (ETDEWEB)

Qian, Yingjia [School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China); Chi, Lina, E-mail: lnchi@sjtu.edu.cn [School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China); Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Zhou, Weili; Yu, Zhenjiang [School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China); Zhang, Zhongzhi [College of Chemical Engineering, China University of Petroleum, Beijing 102249 (China); Zhang, Zhenjia [School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240 (China); Jiang, Zheng, E-mail: z.jiang@soton.ac.uk [Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2016-01-01

Graphical abstract: - Highlights: • Multifunctional TiO{sub 2}/PAA/PTFE ultrafiltration membrane was fabricated via tight coating of TiO{sub 2} functional layer onto the plasma-assisted graft of PAA on PTFE. • The high water flux rate, remarkable enhanced ultrafiltration performance and excellent self-cleaning ability were demonstrated. • The formation of COO−Ti bidentate coordination between TiO{sub 2} and PAA was responsible for the successful coating. - Abstract: Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO{sub 2}, we successfully fixed TiO{sub 2} functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO{sub 2} attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti{sup 4+}. The TiO{sub 2} surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO{sub 2}/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO{sub 2}, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

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.

Efficacy of linezolid, teicoplanin, and vancomycin in prevention of an experimental polytetrafluoroethylene graft infection model caused by methicillin-resistant Staphylococcus aureus.

Science.gov (United States)

Mese, Bulent; Bozoglan, Orhan; Elveren, Serdal; Eroglu, Erdinc; Gul, Mustafa; Celik, Ahmet; Ciralik, Harun; Yildirimdemir, Halil Ibrahim; Yasim, Alptekin

2015-03-27

The aim of this study was to evaluate the effectiveness of linezolid, teicoplanin, and vancomycin in prevention of prosthetic vascular graft infections in a vascular graft infection model. Fifty rats were divided into 5 groups. A polytetrafluoroethylene graft was implanted on the back of each rat. Methicillin-resistant Staphylococcus aureus (MRSA) strain was inoculated into all rats except Group 1. Group 2 was not given any treatment, Group 3 received linezolid, Group 4 received vancomycin, and Group 5 received teicoplanin. The grafts were removed for microbiological and histological examinations on the 7th day. In addition, C-reactive protein and prealbumin levels and leukocyte counts in obtained blood specimens were determined. Group 1 did not have infection. Group 2 had bacteria 5.7 × 10(4) CFU/cm(2). Group 3 and Group 4 had less bacterial growth. Group 5 had no bacterial growth. The number of bacteria was significantly higher in Group 2 than in the other experimental groups and the control group (pprevention of prosthetic vascular graft infections.

Helium turbo-expander with an alternator

International Nuclear Information System (INIS)

Akiyama, Yoshitane

1980-01-01

Study was made on a helium turbo-expander, the heart of helium refrigerator systems, in order to develop a system which satisfies the required conditions. A helium turbo-expander with externally pressurized helium gas bearings at the temperature of liquid nitrogen and an alternator as a brake have been employed. The essential difference between a helium turbo-expander and a nitrogen turbo-expander was clarified. The gas bearing lubricated with nitrogen at room temperature and the gas bearing lubricated with helium at low temperature were tested. The flow rate of helium in a helium refrigerator for a large superconducting magnet is comparatively small, therefore a helium turbine must be small, but the standard for large turbine design can be applied to such small turbine. Using the alternator as a brake, the turbo-expander was easily controllable electrically. The prototype turbo-expander was made, and the liquefaction test with it and MHD power generation test were carried out. (Kako, I.)

Silicon microfabricated beam expander

International Nuclear Information System (INIS)

Othman, A.; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A.; Ain, M. F.

2015-01-01

The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed

Silicon microfabricated beam expander

Energy Technology Data Exchange (ETDEWEB)

Othman, A., E-mail: aliman@ppinang.uitm.edu.my; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A. [Faculty of Electrical Engineering, Universiti Teknologi MARA Malaysia, 40450, Shah Alam, Selangor (Malaysia); Ain, M. F. [School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300,Nibong Tebal, Pulau Pinang (Malaysia)

2015-03-30

The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

Surgical treatment of tetralogy of Fallot with absent pulmonary valve syndrome.

Science.gov (United States)

Tanaka, Yuki; Miyamoto, Takashi; Naito, Yuji; Yoshitake, Shuichi

2016-06-01

The patient was a 3-month-old girl weighting 3.6 kg, diagnosed with tetralogy of Fallot and absent pulmonary valve syndrome. We surgically repaired the tetralogy of Fallot by patch closure of the ventricular septal defect, right ventricular outflow tract reconstruction using an expanded polytetrafluoroethylene monocusp patch with a bulging sinus, and removal of the bronchial obstruction by anterior translocation of the pulmonary artery using the Lecompte maneuver. © The Author(s) 2015.

Influences of irradiation on the anastomotic sites of artificial graft

International Nuclear Information System (INIS)

Ogawa, Junichi; Inoue, Hiroshi; Koide, Shirosaku; Kawada, Shimei; Shotsu, Akira

1989-01-01

To examine the acute influences of irradiation on the anastomotic sites of EPTFE vascular grafts, experimental study was performed using canine dogs. After replacement of superior vena cava and bilateral femoral arteries with EPTFE grafts, a total of 20 to 100 Gy doses were given at the anastomotic sites of superior vena cava and right femoral artery. There were no degradation of grafts themselves or rupture in the anastomoses at cumulative anastomotic sites of superior vena cava, stenoses and/or overgrowth of granulation tissues were observed, although at those of right femoral artery, no remarkable differences were observed between dogs which received irradiation and those which did not receive. (author)

Simultaneous and long-lasting hydrophilization of inner and outer wall surfaces of polytetrafluoroethylene tubes by transferring atmospheric pressure plasmas

International Nuclear Information System (INIS)

Chen, Faze; Song, Jinlong; Huang, Shuai; Xu, Wenji; Sun, Jing; Liu, Xin; Xu, Sihao; Xia, Guangqing; Yang, Dezheng

2016-01-01

Plasma hydrophilization is a general method to increase the surface free energy of materials. However, only a few works about plasma modification focus on the hydrophilization of tube inner and outer walls. In this paper, we realize simultaneous and long-lasting plasma hydrophilization on the inner and outer walls of polytetrafluoroethylene (PTFE) tubes by atmospheric pressure plasmas (APPs). Specifically, an Ar atmospheric pressure plasma jet (APPJ) is used to modify the PTFE tube’s outer wall and meanwhile to induce transferred He APP inside the PTFE tube to modify its inner wall surface. The optical emission spectrum (OES) shows that the plasmas contain many chemically active species, which are known as enablers for various applications. Water contact angle (WCA) measurements, x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) are used to characterize the plasma hydrophilization. Results demonstrate that the wettability of the tube walls are well improved due to the replacement of the surface fluorine by oxygen and the change of surface roughness. The obtained hydrophilicity decreases slowly during more than 180 d aging, indicating a long-lasting hydrophilization. The results presented here clearly demonstrate the great potential of transferring APPs for surface modification of the tube’s inner and outer walls simultaneously. (paper)

Expander Codes

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 1. Expander Codes - The Sipser–Spielman Construction. Priti Shankar. General Article Volume 10 ... Author Affiliations. Priti Shankar1. Department of Computer Science and Automation, Indian Institute of Science Bangalore 560 012, India.

Surface modification of poly(tetrafluoroethylene) films by low energy Ar+ ion-beam activation and UV-induced graft copolymerization

International Nuclear Information System (INIS)

Zhang Yan; Huan, A.C.H.; Tan, K.L.; Kang, E.T.

2000-01-01

Surface modification of poly(tetrafluoroethylene) (PTFE) films by Ar + ion-beam irradiation with varying ion energy and ion dose was carried out. The changes in surface composition of the irradiated PTFE films were characterized, both in situ and after exposure to air, by X-ray photoelectron spectroscopy (XPS). The possible mechanisms of chemical reaction induced by the incident ion beam on the surface of PTFE film included defluorination, chain scission and cross-linking, as indicated by the presence of the characteristic peak components associated with the - - -CF 3 , - - -CF, and C(CF 2 ) 4 species in the C 1s core-level spectra, the decrease in surface [F]/[C] ratio, and the increase in surface micro-hardness of the Ar + ion-beam-treated PTFE films. Furthermore, the free radicals generated by the ion-beam could react with oxygen in the air to give rise to oxidized carbon species, such as the peroxides, on the PTFE surface. Thus, after exposure to air, the Ar + ion-beam-pretreated PTFE films were susceptible to further surface modification by UV-induced graft copolymerization with a vinyl monomer, such as acrylamide (AAm). The graft concentrations were deduced from the XPS-derived surface stoichiometries. The Ar + ion energy and the ion dose affected not only the surface composition of the treated films but also the graft copolymerization efficiency of the corresponding pretreated films

Bioactive surface modifications on inner walls of poly-tetra-fluoro-ethylene tubes using dielectric barrier discharge

Science.gov (United States)

Cho, Yong Ki; Park, Daewon; Kim, Hoonbae; Lee, Hyerim; Park, Heonyong; Kim, Hong Ja; Jung, Donggeun

2014-03-01

Bioactive surface modification can be used in a variety of medical polymeric materials in the fields of biochips and biosensors, artificial membranes, and vascular grafts. In this study, the surface modification of the inner walls of poly-tetra-fluoro-ethylene (PTFE) tubing was carried out to improve vascular grafts, which are made of biocompatible material for the human body in the medical field. Focus was centered on the cell attachment of the inner wall of the PTFE by sequential processes of hydrogen plasma treatment, hydrocarbon deposition, and reactive plasma treatment on the PFTE surface using micro plasma discharge. Micro plasma was generated by a medium-frequency alternating current high-voltage generator. The preliminary modification of PTFE was conducted by a plasma of hydrogen and argon gases. The hydrocarbon thin film was deposited on modified PTFE with a mixture of acetylene and argon gases. The reactive plasma treatment using oxygen plasma was done to give biocompatible functionality to the inner wall surface. The hydrophobic surface of bare PTFE is made hydrophilic by the reactive plasma treatment due to the formation of carbonyl groups on the surface. The reactive treatment could lead to improved attachment of smooth muscle cells (SMCs) on the modified PTFE tubing. Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and water contact angle measurement were used for the analysis of the surface modification. The SMC-attached PTFE tube developed will be applicable to in vitro human vasculature-mimetic model systems, and to medical vascular grafts.

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.

A Rapidly Expanding Bose-Einstein Condensate: An Expanding Universe in the Lab

Science.gov (United States)

Eckel, S.; Kumar, A.; Jacobson, T.; Spielman, I. B.; Campbell, G. K.

2018-04-01

We study the dynamics of a supersonically expanding, ring-shaped Bose-Einstein condensate both experimentally and theoretically. The expansion redshifts long-wavelength excitations, as in an expanding universe. After expansion, energy in the radial mode leads to the production of bulk topological excitations—solitons and vortices—driving the production of a large number of azimuthal phonons and, at late times, causing stochastic persistent currents. These complex nonlinear dynamics, fueled by the energy stored coherently in one mode, are reminiscent of a type of "preheating" that may have taken place at the end of inflation.

In vitro analysis of biopolymer coating with glycidoxypropyltrimethoxysilane on hernia meshes.

Science.gov (United States)

Metzler, Steffen; Zankovych, Sergiy; Rauchfuß, Falk; Dittmar, Yves; Jandt, Karin; Jandt, Klaus D; Settmacher, Utz; Scheuerlein, Hubert

2017-07-01

Certain coatings may improve the biocompatibility of hernia meshes. The coating with self-assembled monolayers, such as glycidoxypropyltrimethoxysilane (GOPS) can also improve the materials characteristics of implants. This approach was not yet explored in hernia meshes. It was the aim of this work to clarify if and how hernia meshes with their three-dimensional structure can be coated with GOPS and with which technique this coating can be best characterized. Commercially available meshes made from polypropylene (PP), polyester (PE), and expanded polytetrafluorethylene (ePTFE) have been coated with GOPS. The coatings were analyzed via X-ray photoelectron spectroscopy (XPS), confocal laser scanning microscopy (CLSM), and cell proliferation test (mouse fibroblasts). Cell viability and cytotoxicity were tested by MTT test. With the GOPS surface modification, the adherence of mouse fibroblasts on polyester meshes and the proliferation on ePTFE meshes were increased compared to noncoated meshes. Both XPS and CLSM are limited in their applicability and validity due to the three-dimensional mesh structure while CLSM was overall more suitable. In the MTT test, no negative effects of the GOPS coating on the cells were detected after 24 h. The present results show that GOPS coating of hernia meshes is feasible and effective. GOPS coating can be achieved in a fast and cost-efficient way. Further investigations are necessary with respect to coating quality and adverse effects before such a coating may be used in the clinical routine. In conclusion, GOPS is a promising material that warrants further research as coating of medical implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1083-1090, 2017. © 2016 Wiley Periodicals, Inc.

A Rapidly Expanding Bose-Einstein Condensate: An Expanding Universe in the Lab

Directory of Open Access Journals (Sweden)

S. Eckel

2018-04-01

Full Text Available We study the dynamics of a supersonically expanding, ring-shaped Bose-Einstein condensate both experimentally and theoretically. The expansion redshifts long-wavelength excitations, as in an expanding universe. After expansion, energy in the radial mode leads to the production of bulk topological excitations—solitons and vortices—driving the production of a large number of azimuthal phonons and, at late times, causing stochastic persistent currents. These complex nonlinear dynamics, fueled by the energy stored coherently in one mode, are reminiscent of a type of “preheating” that may have taken place at the end of inflation.

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

The Expanding Universe: Dark Energy

Energy Technology Data Exchange (ETDEWEB)

Lincoln, Don [Fermilab; Nord, Brian [Fermilab

2014-09-01

In 1998, observations of distant supernovae led physicists that not only was the universe expanding, but the expansion was speeding up. In this article, we describe the evidence for an expanding universe and describe what physicists and cosmologists have learned in the intervening years. The target audience for this article is high school physics teachers and college physics professors at teaching institutions.

Screw expander for light duty diesel engines

Science.gov (United States)

1983-01-01

Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

Reactivity of Cu with poly(tetrafluoroethylene) and poly(vinyl chloride): Effect of pre- and post-metallization modification on the metal/polymer interface

International Nuclear Information System (INIS)

Perry, C.C.; Torres, J.; Carlo, S.R.; Fairbrother, D. Howard

2002-01-01

The reactivity of Cu with poly(tetrafluoroethylene) (PTFE) and poly(vinylchloride) (PVC) during thermal evaporation, as well as the effect of pre- and post-metallization Ar + ion and x-ray mediated surface modification treatments on the metal/polymer interface, have been studied using in situ x-ray photoelectron spectroscopy (XPS) and ex situ atomic force microscopy (AFM). During thermal evaporation, copper was unreactive on PTFE but reacted with PVC to form CuCl. Pretreatment of PTFE or PVC surfaces by Ar + ion or x-ray irradiation did not modify the chemical reactivity of the polymer surface during subsequent Cu deposition, although significant morphological changes were observed on PTFE by AFM. In contrast, post-metallization modification of the Cu/PTFE interface by Ar + ion or x-ray irradiation lead to the production of CuF 2 , and increased the yield of CuCl in the Cu/PVC system. In either the Cu/PTFE or Cu/PVC systems, the maximum concentration of copper halide formed and dependence upon treatment time was found to be similar for either Ar + ion or x-ray irradiation post-metallization treatment strategies, suggesting a common reaction mechanism

Study on radiation grafting of acrylic acid onto fluorine-containing polymers. II. Properties of membrane obtained by preirradiation grafting onto poly(tetrafluoroethylene)

International Nuclear Information System (INIS)

Hegazy, E.S.A.; Ishigaki, I.; Rabie, A.; Dessouki, A.M.; Okamoto, J.

1981-01-01

Some properties of the membranes obtained by the preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene) (PTFE) film have been studied. The dimensional change by grafting and swelling, water uptake, electric conductivity, and mechanical properties of the grafted PTFE films were measured and were found to increase as the grafting proceeds. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions except higher monomer concentration (80 wt %). The electric conductivity and mechanical properties of the membranes at 80 wt % monomer concentration is lower than those at a lower monomer concentration. The results suggest that the membranes obtained at 80-wt % acrylic acid solution have a somewhat heterogeneous distribution of electrolyte groups as compared with those prepared at a monomer concentration less than 60 wt %. X-ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the center with progressive diffusion of monomer to give finally the homogeneous distribution of electrolyte groups. The membranes show good electrochemical and mechanical properties which make them acceptable for the practical uses as cation exchange membrane

A-coupled-expanding and distributional chaos

International Nuclear Information System (INIS)

Kim, Cholsan; Ju, Hyonhui; Chen, Minghao; Raith, Peter

2015-01-01

The concept of A-coupled-expanding maps is one of the more natural and useful ideas generalized from the horseshoe map which is commonly known as a criterion of chaos. It is well known that distributional chaos is one of the concepts which reflect strong chaotic behavior. In this paper, we focus on the relationship between A-coupled-expanding and distributional chaos. We prove two theorems which give sufficient conditions for a strictly A-coupled-expanding map to be distributionally chaotic in the senses of two kinds, where A is an m × m irreducible transition matrix

Stability of expanded plasma focus

International Nuclear Information System (INIS)

Soliman, H.M.

1994-01-01

In this study, the stabilization of the expanded plasma focus formed by 4.5 kJ plasma focus device of Mather type by magnetic field is presented. The experimental results of the induced axial magnetic field and electric probe measurements of the expanded plasma focus show that, the plasma consists of three plasmoids, electron temperature measurements off the plasmoids at a point close to the muzzle are 26 eV, 30 eV and 27 eV respectively and the electron densities are 6.6 x 10 14 , 6.1 x 10 14 / cm 3 respectively. The presence of external axial magnetic field (B 2 = 1.6 kg) at the mid distance between the breech and the muzzle has a less effect on the stability of expanded focus and it causes a restriction for the plasma motion. the electron temperature of the three plasmoids are found to increase in that case by 23%, 18.5% respectively. When this axial magnetic field is applied at the muzzle end, it leads to a more stable expanded plasma focus which consists mainly of one plasmoid with electron temperature of 39 eV and density of 3.4 x 10 14 / cm 3 . 5 figs

Expanding/Extending English: Interdisciplinarity and Internationalism.

Science.gov (United States)

Fleishman, Avrom

1994-01-01

Discusses the recent efforts to expand literary studies into numerous allied fields and the possible effects that such attempts toward interdisciplinarity and internationalism might have. Warns against possible negative consequences of interdisciplinary approaches. Calls for an expanded view of English as a field of study. (HB)

Geothermal ORC Systems Using Large Screw Expanders

OpenAIRE

Biederman, Tim R.; Brasz, Joost J.

2014-01-01

Geothermal ORC Systems using Large Screw Expanders Tim Biederman Cyrq Energy Abstract This paper describes a low-temperature Organic Rankine Cycle Power Recovery system with a screw expander a derivative of developed of Kaishan's line of screw compressors, as its power unit. The screw expander design is a modified version of its existing refrigeration compressor used on water-cooled chillers. Starting the ORC development program with existing refrigeration screw compre...

Factors leading to tracheobronchial self-expandable metallic stent fracture.

Science.gov (United States)

Chung, Fu-Tsai; Lin, Shu-Min; Chen, Hao-Cheng; Chou, Chun-Liang; Yu, Chih-Teng; Liu, Chien-Ying; Wang, Chun-Hua; Lin, Horng-Chyuan; Huang, Chien-Da; Kuo, Han-Pin

2008-11-01

This retrospective study was to determine factors that contribute to self-expandable metallic stent fracture in patients with tracheobronchial disease. From 2001 to 2006, 139 patients (age, 62.1 +/- 15.4 years; range, 23-87 years) with benign (n = 62) and malignant (n = 77) tracheobronchial disease received 192 Ultraflex (Boston Scientific, Natick, Mass) self-expandable metallic stents (98 in patients with benign disease and 94 in patients with malignant disease). Seventeen fractured self-expandable metallic stents were found; the incidence was 12.2% (17/139 patients) among patients with tracheobronchial disease. Tortuous airway (odds ratio, 4.06; 95% confidence interval, 1.04-18.34; P = .04) independently predicted self-expandable metallic stent fracture. Most self-expandable metallic stent fractures (64.7%, 11/17) were detected 500 to 1000 days after self-expandable metallic stent implantation. Clinical presentations for patients with fractured self-expandable metallic stents included dyspnea exacerbation (70.6%, 12/17) and cough (23.5%, 4/17). Self-expandable metallic stent fracture is not uncommon in patients with tracheobronchial disease. Tortuous airway is an independent predictor for it. Although management of the fractured self-expandable metallic stent in our study was feasible and safe, self-expandable metallic stents should be restricted to a more select population.

Neutrinos in an expanding Universe

International Nuclear Information System (INIS)

Wigmans, Richard

2015-01-01

The Universe contains several billion neutrinos for each nucleon. In this paper, we follow the history of these relic neutrinos as the Universe expanded. At present, their typical velocity is a few hundred km/s and, therefore, their spectra are affected by gravitational forces. This may have led to a phenomenon that could explain two of todays great mysteries: The large-scale structure of the Universe and the increasing rate at which it expands. (paper)

Free-piston reciprocating cryogenic expander utilizing phase controller

Science.gov (United States)

Cha, Jeongmin; Park, Jiho; Kim, Kyungjoong; Jeong, Sangkwon

2017-02-01

In a free-piston expander which eliminates mechanical linkages, a prescribed behaviour of the free-piston movement is the key to an expander performance. In this paper, we have proposed an idea of reducing complexity of the free-piston expander. It is to replace both multiple solenoid valves and reservoirs that are indispensable in a previous machine with a combination of a single orifice-reservoir assembly. It functions as a phase controller like that of a pulse tube refrigerator so that it generates time-delay of pressure variation between the warm-end and the reservoir resulting in the intended expansion of the cold-end volume down to the pre-set reservoir pressure. The modeling of this unique free-piston reciprocating expander utilizing phase controller is developed to understand and predict the performance of the new-type expander. Additionally, the operating parameters are analysed at the specified conditions to enable one to develop a more efficient free-piston type cryogenic expander.

New generation expandable sand screens

OpenAIRE

Syltøy, Christer

2014-01-01

Master's thesis in Petroleum engineering This thesis aims to give a general insight into sand control and various sorts of sand control measures and applications of sand control tools. Special focus will be given to expandable sand screens – a technology which came about in the late 1990’s through the use of flexible, expandable tubulars as base pipe in sand screens. More specifically Darcy’s Hydraulic Endurance Screens, a compliant sand screen system using hydraulic activation, and the fu...

Synergism of carbon fiber and polyimide in polytetrafluoroethylene-based composites: Friction and wear behavior under sea water lubrication

International Nuclear Information System (INIS)

Chen, Beibei; Wang, Jianzhang; Yan, Fengyuan

2012-01-01

Highlights: ► The effect of PI and CF on the microstructure of PTFE was investigated. ► PI and CF had synergism on the improvement of tribological property of PTFE. ► PTFE-4 (with 5% PI and 15% CF) showed promising application in ocean environment. -- Abstract: Polytetrafluoroethylene-based (PTFE-based) composites reinforced simultaneously with carbon fiber (CF) and polyimide (PI) of different volume fractions were prepared. The microstructure and phase composition of as-prepared PTFE-based composites were analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, their friction and wear behavior under sea water lubrication was evaluated in relation to the synergistic effect between CF and PI using a ring-on-block test rig, and their worn surfaces were also analyzed using SEM. Results showed that the incorporation of PI induced loosening of the microstructure of PTFE but increased the wear resistance. Contrary to the above, the incorporation of CF led to increased compactness of PTFE, and the compactness as well as wear resistance of the PTFE-based composites increased with the increase of CF content. More importantly, the simultaneous incorporation of PI and CF at a proper volume fraction led to drastically reduced wear rate of PTFE under sea water lubrication. This implies that there exists synergistic friction-reducing and wear-resistant effect between PI and CF. As a result, the PTFE-based composite containing 5% PI (volume fraction) and 15% CF had the best wear resistance, showing promising application in ocean environment.

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

Partition expanders

Czech Academy of Sciences Publication Activity Database

Gavinsky, Dmitry; Pudlák, Pavel

2017-01-01

Roč. 60, č. 3 (2017), s. 378-395 ISSN 1432-4350 R&D Projects: GA ČR GBP202/12/G061 Institutional support: RVO:67985840 Keywords : expanders * pseudorandomness * communication complexity Subject RIV: BA - General Mathematics OBOR OECD: Computer sciences, information science, bioinformathics (hardware development to be 2.2, social aspect to be 5.8) Impact factor: 0.645, year: 2016 http://link.springer.com/article/10.1007%2Fs00224-016-9738-5

Flow boiling in expanding microchannels

CERN Document Server

Alam, Tamanna

2017-01-01

This Brief presents an up to date summary of details of the flow boiling heat transfer, pressure drop and instability characteristics; two phase flow patterns of expanding microchannels. Results obtained from the different expanding microscale geometries are presented for comparison and addition to that, comparison with literatures is also performed. Finally, parametric studies are performed and presented in the brief. The findings from this study could help in understanding the complex microscale flow boiling behavior and aid in the design and implementation of reliable compact heat sinks for practical applications.

Aortic annulus eccentricity before and after transcatheter aortic valve implantation: Comparison of balloon-expandable and self-expanding prostheses

International Nuclear Information System (INIS)

Schuhbaeck, Annika; Weingartner, Christina; Arnold, Martin; Schmid, Jasmin; Pflederer, Tobias; Marwan, Mohamed; Rixe, Johannes; Nef, Holger; Schneider, Christian; Lell, Michael; Uder, Michael; Ensminger, Stephan; Feyrer, Richard; Weyand, Michael; Achenbach, Stephan

2015-01-01

Highlights: • Post-implant geometry of catheter-based aortic valve prostheses is influenced by aortic valve calcification. • Balloon-expandable prostheses are more circular as compared to self-expanding prostheses. • The impact of post-implant geometry on valve function needs to be investigated. - Abstract: Introduction: The geometry of the aortic annulus and implanted transcatheter aortic valve prosthesis might influence valve function. We investigated the influence of valve type and aortic valve calcification on post-implant geometry of catheter-based aortic valve prostheses. Methods: Eighty consecutive patients with severe aortic valve stenosis (mean age 82 ± 6 years) underwent computed tomography before and after TAVI. Aortic annulus diameters were determined. Influence of prosthesis type and degree of aortic valve calcification on post-implant eccentricity were analysed. Results: Aortic annulus eccentricity was reduced in patients after TAVI (0.21 ± 0.06 vs. 0.08 ± 0.06, p < 0.0001). Post-TAVI eccentricity was significantly lower in 65 patients following implantation of a balloon-expandable prosthesis as compared to 15 patients who received a self-expanding prosthesis (0.06 ± 0.05 vs. 0.15 ± 0.07, p < 0.0001), even though the extent of aortic valve calcification was not different. After TAVI, patients with a higher calcium amount retained a significantly higher eccentricity compared to patients with lower amounts of calcium. Conclusions: Patients undergoing TAVI with a balloon-expandable prosthesis show a more circular shape of the implanted prosthesis as compared to patients with a self-expanding prosthesis. Eccentricity of the deployed prosthesis is affected by the extent of aortic valve calcification

Entropy in an expanding universe

International Nuclear Information System (INIS)

Frautschi, S.

1982-01-01

The question of how the observed evolution of organized structures from initial chaos in the expanding universe can be reconciled with the laws of statistical mechanics is studied, with emphasis on effects of the expansion and gravity. Some major sources of entropy increase are listed. An expanding causal region is defined in which the entropy, though increasing, tends to fall further and further behind its maximum possible value, thus allowing for the development of order. The related questions of whether entropy will continue increasing without limit in the future, and whether such increase in the form of Hawking radiation or radiation from positronium might enable life to maintain itself permanently, are considered. Attempts to find a scheme for preserving life based on solid structures fail because events such as quantum tunneling recurrently disorganize matter on a very long but fixed time scale, whereas all energy sources slow down progressively in an expanding universe. However, there remains hope that other modes of life capable of maintaining themselves permanently can be found

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.

Solid expandable systems put deepwater targets within reach

Energy Technology Data Exchange (ETDEWEB)

Perez-Roca, Eduardo [Enventure Global Technology L.L.C., Houston, TX (United States). Latin America; Fristch, Jerry [Enventure Global Technology L.L.C., Houston, TX (United States)

2008-07-01

Enabling technologies that take drilling operations to deeper objectives have made a significant impact on the practicality of many projects, especially deep water offshore targets. Increasing vertical depth and lateral reach requires adequate hole size to attain the desired objectives of the well bore. Solid expandable technology can maintain and retain hole size to address both the physical limitations and the economic feasibility of deep water operations. With each and every casing point, the potential for adequate hole size at total depth (TD) decreases. Solid expandable open hole liners and single-diameter systems reduce and eliminate, respectively, the well bore tapering that dictates hole size at TD and subsequent completion size. Successful mitigation of this tapering, whether through the entire well bore or through select zones, enables operators to gain access to previously unreachable reserves. Solid expandable systems have proven to be reliable and effective with over 1,000 installations in a myriad of conditions and environments worldwide. To date, over 115 of those applications have been in deep water environments. The current operating envelope for solid expandable systems include the deepest installation at {approx}28,750 ft (8,763 m) and the longest at 6,867 ft (2,083 m) in water depth over 3,150 ft (960 m). This record-length application consisted of an open hole liner installed and expanded in a single run. This paper will discuss the effectiveness of solid expandable systems in deep water operations and how the technology brings value to offshore projects especially when planned into the initial design. Case histories will be used to further illustrate the features, advantages, and benefits of expandable technology. In addition, this paper will examine the state of the solid expandable technology and its continuing evolution to provide even more drilling solutions. (author)

Superhydrophobic coatings fabricated with polytetrafluoroethylene and SiO2 nanoparticles by spraying process on carbon steel surfaces

International Nuclear Information System (INIS)

Wang, Haibin; Chen, Eryu; Jia, Xianbu; Liang, Lijun; Wang, Qi

2015-01-01

Graphical abstract: - Highlights: • The SiO 2 and PTFE NP-filled coatings exhibit excellent superhydrophobicity. • PTFE-filled coatings show denser structures and better liquid resistance than SiO 2 . • Air pocket of Wentzel model explains the difference in the superhydrophobicity. - Abstract: Superhydrophobicity is extensively investigated because of the numerous methods developed for water-repellant interface fabrication. Many suitable functional materials for the production of superhydrophobic surfaces on various substrates are still being explored. In this study, inorganic SiO 2 and organic polytetrafluoroethylene (PTFE) nanoparticles (NPs) are used for a comparative study on the performance of superhydrophobic coating on carbon steel surfaces. The NPs are added to PTFE coating emulsions by physical blending to form coating mixtures. Raw SiO 2 NPs are then hydrophobized using KH-570 and validated by Fourier transform-infrared spectroscopy (FT-IR) and Dynamic Laser Scattering (DLS) grain size analyses. The microstructures of the surfaces are characterized by contact angle (CA) measurements and field emission-scanning electron microscope (FE-SEM) images. The prepared surfaces are subjected to adhesion, hardness, water resistance, and acid/alkali erosion tests. Hydrophobized SiO 2 -filled coating surfaces are found to have better uniformity than raw SiO 2 regardless of their similar maximum static contact angles (SCAs) about 150°. A SCA of 163.1° is obtained on the PTFE NP-filled coating surfaces that have a considerably denser structure than SiO 2 . Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses reveal that all fabricated surfaces have good thermal stability and tolerate temperatures up to 550 °C. The PTFE NP-filled coating surfaces also exhibit excellent water and acid resistance. A possible mechanism concerning the amount of trapped air is proposed in relation to practical superhydrophobic surface fabrication

Novel power MOSFET-based expander for high frequency ultrasound systems.

Science.gov (United States)

Choi, Hojong; Shung, K Kirk

2014-01-01

The function of an expander is to obstruct the noise signal transmitted by the pulser so that it does not pass into the transducer or receive electronics, where it can produce undesirable ring-down in an ultrasound imaging application. The most common type is a diode-based expander, which is essentially a simple diode-pair, is widely used in pulse-echo measurements and imaging applications because of its simple architecture. However, diode-based expanders may degrade the performance of ultrasonic transducers and electronic components on the receiving and transmitting sides of the ultrasound systems, respectively. Since they are non-linear devices, they cause excessive signal attenuation and noise at higher frequencies and voltages. In this paper, a new type of expander that utilizes power MOSFET components, which we call a power MOSFET-based expander, is introduced and evaluated for use in high frequency ultrasound imaging systems. The performance of a power MOSFET-based expander was evaluated relative to a diode-based expander by comparing the noise figure (NF), insertion loss (IL), total harmonic distortion (THD), response time (RT), electrical impedance (EI) and dynamic power consumption (DPC). The results showed that the power MOSFET-based expander provided better NF (0.76 dB), IL (-0.3 dB) and THD (-62.9 dB), and faster RT (82 ns) than did the diode-based expander (NF (2.6 dB), IL (-1.4 dB), THD (-56.0 dB) and RT (119 ns)) at 70 MHz. The -6 dB bandwidth and the peak-to-peak voltage of the echo signal received by the transducer using the power MOSFET-based expander improved by 17.4% and 240% compared to the diode-based expander, respectively. The new power MOSFET-based expander was shown to yield lower NF, IL and THD, faster RT and lower ring down than the diode-based expander at the expense of higher dynamic power consumption. Copyright © 2013 Elsevier B.V. All rights reserved.

Device-modified trabeculectomy for glaucoma.

Science.gov (United States)

Wang, Xue; Khan, Rabeea; Coleman, Anne

2015-12-01

Glaucoma is an optic neuropathy that leads to vision loss and blindness. It is the second most common cause of irreversible blindness worldwide. The main treatment for glaucoma aims to reduce intraocular pressure (IOP) in order to slow or prevent further vision loss. IOP can be lowered with medications, and laser or incisional surgeries. Trabeculectomy is the most common incisional surgical procedure to treat glaucoma. Device-modified trabeculectomy is intended to improve drainage of the aqueous humor to lower IOP. Trabeculectomy-modifying devices include Ex-PRESS, Ologen, amniotic membrane, expanded polytetrafluoroethylene (E-PTFE) membrane, Gelfilm and others. However, the effectiveness and safety of these devices are uncertain. To assess the relative effectiveness, primarily with respect to IOP control and safety, of the use of different devices as adjuncts to trabeculectomy compared with standard trabeculectomy in eyes with glaucoma. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2014, Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2014), EMBASE (January 1980 to December 2014), PubMed (1948 to December 2014), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to December 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 22 December 2014. We included randomized controlled trials comparing devices used during trabeculectomy with trabeculectomy alone. We also included studies where antimetabolites were used in either or both treatment groups. We used standard procedures

Origin and dynamics of expanding neutral hydrogen supershells

International Nuclear Information System (INIS)

Kolesnik, I.G.; Silich, S.A.

1987-01-01

The evolutionary model of expanding supershells regulated by induced star formation is proposed. It is suggested that giant expanding shells are formed n superclouds at late evolutionary stage of star complexes. To understand the dynamics of the most huge supershells it is necessary to take into account that expanding shells can trigger star formation in cold dense pre-exosting cloudlets. Efficiency of induced star formation must be less than one percent to fit observational properties of supershells

Seal-less cryogenic expander

International Nuclear Information System (INIS)

Faria, L.E.; Christopher, E.H.

1987-01-01

In an expander for use in a split Stirling cycle refrigeration system of the type wherein a displacer moves with reciprocating motion inside an expander housing, and wherein a plunger force and a regenerator force are formed on the displacer, the plunger force cyclically varying and having a time of minimum and maximum plunger force amplitude, and the regenerator force cyclically varying and having a time of minimum and maximum regenerator force amplitude, the improvement is described comprising: (a) means for maintaining displacer forces, such that the maximum plunger force amplitude is substantially equal to the maximum regenerator force amplitude; and (b) means for adjusting a time difference, the time difference being the time between the time of maximum plunger force and the time of maximum regenerator force such that a measure of the cooling power of the refrigeration system is maximized

Semiclassical expanding discrete space-times

International Nuclear Information System (INIS)

Cobb, W.K.; Smalley, L.L.

1981-01-01

Given the close ties between general relativity and geometry one might reasonably expect that quantum effects associated with gravitation might also be tied to the geometry of space-time, namely, to some sort of discreteness in space-time itself. In particular it is supposed that space-time consists of a discrete lattice of points rather than the usual continuum. Since astronomical evidence seems to suggest that the universe is expanding, the lattice must also expand. Some of the implications of such a model are that the proton should presently be stable, and the universe should be closed although the mechanism for closure is quantum mechanical. (author)

Refrigeration generation using expander-generator units

Science.gov (United States)

Klimenko, A. V.; Agababov, V. S.; Koryagin, A. V.; Baidakova, Yu. O.

2016-05-01

The problems of using the expander-generator unit (EGU) to generate refrigeration, along with electricity were considered. It is shown that, on the level of the temperatures of refrigeration flows using the EGU, one can provide the refrigeration supply of the different consumers: ventilation and air conditioning plants and industrial refrigerators and freezers. The analysis of influence of process parameters on the cooling power of the EGU, which depends on the parameters of the gas expansion process in the expander and temperatures of cooled environment, was carried out. The schematic diagram of refrigeration generation plant based on EGU is presented. The features and advantages of EGU to generate refrigeration compared with thermotransformer of steam compressive and absorption types were shown, namely: there is no need to use the energy generated by burning fuel to operate the EGU; beneficial use of the heat delivered to gas from the flow being cooled in equipment operating on gas; energy production along with refrigeration generation, which makes it possible to create, using EGU, the trigeneration plants without using the energy power equipment. It is shown that the level of the temperatures of refrigeration flows, which can be obtained by using the EGU on existing technological decompression stations of the transported gas, allows providing the refrigeration supply of various consumers. The information that the refrigeration capacity of an expander-generator unit not only depends on the parameters of the process of expansion of gas flowing in the expander (flow rate, temperatures and pressures at the inlet and outlet) but it is also determined by the temperature needed for a consumer and the initial temperature of the flow of the refrigeration-carrier being cooled. The conclusion was made that the expander-generator units can be used to create trigeneration plants both at major power plants and at small energy.

EXPANDED POLYTETRAFLUOROETHYLENE PATCH VERSUS POLYPROPYLENE MESH FOR THE REPAIR OF CONTAMINATED DEFECTS OF THE ABDOMINAL-WALL

NARCIS (Netherlands)

BLEICHRODT, RP; SIMMERMACHER, RKJ; VANDERLEI, B; SCHAKENRAAD, JM

Contaminated defects of the abdominal wall continue to be a significant problem for patients and surgeons. The lack of sufficient tissue may require the insertion of a prosthetic material. Polypropylene (PP) mesh is still the most widely used material for this purpose, although the propensity to

Second Generation Self-Inflating Tissue Expanders: A Two-Year Experience

Directory of Open Access Journals (Sweden)

Jamal Omran Al Madani

2014-01-01

Full Text Available Background. Tissue expansion is a well-established surgical technique that produces an additional amount of normal skin to cover a defect. This technique is appealing because the skin quality and color are from the patient’s own. The widely used injectable expanders are of great reliability but carry the disadvantage of being painful during injection and most of the time require multiple clinic visits. So the idea of self-inflation became attractive and hydrogel expanders were developed and became widely known for being painless during clinic visit and decrease number of visits. The first generation expanders were modified by adding an enclosing plastic shell to decrease the unopposed expansion that occurred in the first generation expanders, which lead to pressure necrosis of the skin flaps. This made it an attractive option for tissue expansion in children and some adult patients. Patients, Materials, and Methods. Charts of 17 patients were retrospectively reviewed, all of them had second generation self-inflating expanders implanted over a 2-year period for one of two purposes, the treatment of giant nevi or burn scars. Results. Fifteen patients were females and 2 were males. The indication was large burn scar in 14 cases (14/17, in which 47/55 expanders were implanted, and giant nevus in 3/17 cases in which 8/55 expanders were implanted. Extrusion of the expander occurred in 8/55 expanders (14.5%, which occurred in 6/14 patients. The highest percentage of extrusion occurred in the neck in which two out of three expanders extruded; otherwise this complication does not seem to be related to the indication, gender, nor age of the patients. It seems to be that it is technical in nature. The patients did not have to get any injections to fill the tissue expanders, which made the expansion process less painful and more convenient. Conclusion. This seems to be currently the largest published review in which second generation expanders were used

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.

Strength analysis of expandable tubulars for well applications

Energy Technology Data Exchange (ETDEWEB)

Aguiar, A.C.C. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Fonseca, C.E. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Netto, T.A. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE)

2008-07-01

Solid expandable tube technology has many advantages when compared to conventional wells. The expansion of tubes in situ allows developing reserves in many of the challenging scenarios found in oil industry, as pre-salt layer, HPHT wells, deep reservoirs, or ultra-deep water. Besides, this procedure has good compatibility with directional and horizontal wells and facilitates side-tracks operations. Although the expansion of tubes is very attractive, a better understanding of its influence on the tube mechanical strength is necessary. In this work, experimental tests and numerical analyses were performed in order to determine the effect of parameters such as diameter-to-thickness ratio and expansion rate on the collapse resistance of expandable tubes. An experimental apparatus was designed and built to reproduce full-scale tube expansion. Three 2 meter long specimens were expanded 10% their original diameters and subjected to hydrostatic pressure inside a vessel until collapse. Three non-expanded tubes were also tested for comparison. At the same time, non-linear numerical models were developed using the finite element method. After calibration, they were used to further analyze the mechanical behavior of solid expandable tubes and the influence of expansion on its resistance against collapse. (author)

An Isothermal Steam Expander for an Industrial Steam Supplying System

Directory of Open Access Journals (Sweden)

Chen-Kuang Lin

2015-01-01

Full Text Available Steam is an essential medium used in the industrial process. To ensure steam quality, small and middle scale boilers are often adopted. However, because a higher steam pressure (compared to the necessary steam pressure is generated, the boiler’s steam pressure will be reduced via a pressure regulator before the steam is directed through the process. Unfortunately, pressure is somewhat wasted during the reducing process. Therefore, in order to promote energy efficiency, a pressure regulator is replaced by a steam expander. With this steam expander, the pressure will be transformed into mechanical energy and extracted during the expansion process. A new type of isothermal steam expander for an industrial steam supplying system will be presented in the paper. The isothermal steam expander will improve the energy efficiency of a traditional steam expander by replacing the isentropic process with an isothermal expansion process. With this, steam condensation will decrease, energy will increase, and steam quality will be improved. Moreover, the mathematical model of the isothermal steam expander will be established by using the Schmidt theory, the same principle used to analyze Stirling engines. Consequently, by verifying the correctness of the theoretical model for the isothermal steam expander using experimental data, a prototype of 100 c.c. isothermal steam expander is constructed.

Numerical modelling of multi-vane expander operating conditions in ORC system

Science.gov (United States)

Rak, Józef; Błasiak, Przemysław; Kolasiński, Piotr

2017-11-01

Multi-vane expanders are positive displacement volumetric machines which are nowadays considered for application in micro-power domestic ORC systems as promising alternative to micro turbines and other volumetric expanders. The multi-vane expander features very simple design, low gas flow capacity, low expansion ratios, an advantageous ratio of the power output to the external dimensions and are insensitive to the negative influence of the gas-liquid mixture expansion. Moreover, the multi-vane expander can be easily hermetically sealed, which is one of the key issues in the ORC system design. A literature review indicates that issues concerning the application of multi-vane expanders in such systems, especially related to operating of multi-vane expander with different low-boiling working fluids, are innovative, not fully scientifically described and have the potential for practical implementation. In this paper the results of numerical investigations on multi-vane expander operating conditions are presented. The analyses were performed on three-dimensional numerical model of the expander in ANSYS CFX software. The numerical model of the expander was validated using the data obtained from the experiment carried out on a lab test-stand. Then a series of computational analysis were performed using expanders' numerical model in order to determine its operating conditions under various flow conditions of different working fluids.

Expanded-bed chromatography in primary protein purification.

Science.gov (United States)

Anspach, F B; Curbelo, D; Hartmann, R; Garke, G; Deckwer, W D

1999-12-31

Chromatography in stable expanded beds enables proteins to be recovered directly from cultivations of microorganisms or cells and preparations of disrupted cells, without the need for prior removal of suspended solids. The general performance of an expanded bed is comparable to a packed bed owing to reduced mixing of the adsorbent particles in the column. However, optimal operating conditions are more restricted than in a packed bed due to the dependence of bed expansion on the size and density of the adsorbent particles as well as the viscosity and density of the feedstock. The feedstock composition may become the most limiting restriction owing to interactions of adsorbent particles with cell surfaces, DNA and other substances, leading to their aggregation and consequently to bed instabilities and channeling. Despite these difficulties, expanded-bed chromatography has found widespread applications in the large scale purification of proteins from mammalian cell and microbial feedstocks in industrial bioprocessing. The basics and implementation of expanded-bed chromatography, its advantages as well as problems encountered in the use of this technique for the direct extraction of proteins from unclarified feedstocks are addressed.

First order phase transition of expanding matter and its fragmentation

International Nuclear Information System (INIS)

Chikazumi, Shinpei; Iwamoto, Akira

2002-01-01

Using an expanding matter model with a Lennard-Jones potential, the instability of the expanding system is investigated. The pressure, the temperature, and the density fluctuations are calculated as functions of density during the time evolution of the expanding matter, which are compared to the coexistence curve calculated by the Gibbs ensemble. The expanding matter undergoes the first order phase transition in the limit of the quasistatic expansion. The resultant fragment mass distributions are also investigated. (author)

Grazing incidence beam expander

Energy Technology Data Exchange (ETDEWEB)

Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

1985-01-01

A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

The Expanded Large Scale Gap Test

Science.gov (United States)

1987-03-01

NSWC TR 86-32 DTIC THE EXPANDED LARGE SCALE GAP TEST BY T. P. LIDDIARD D. PRICE RESEARCH AND TECHNOLOGY DEPARTMENT ’ ~MARCH 1987 Ap~proved for public...arises, to reduce the spread in the LSGT 50% gap value.) The worst charges, such as those with the highest or lowest densities, the largest re-pressed...Arlington, VA 22217 PE 62314N INS3A 1 RJ14E31 7R4TBK 11 TITLE (Include Security CIlmsilficatiorn The Expanded Large Scale Gap Test . 12. PEIRSONAL AUTHOR() T

Laparoscopic creation of neovagina and neocervix, followed by their reconstruction with polytetrafluoroethylene graft/buccal mucosa and pudendal artery perforator flap

Directory of Open Access Journals (Sweden)

Yi-Chieh Li

2015-11-01

Full Text Available Congenital cervical agenesis of is a rare Müllerian anomaly that may be associated with partial or complete vaginal aplasia and renal anomalies. Symptoms such as amenorrhea and abdominal pain usually develop shortly after menarche, when the absence or obstruction of the cervical canal results in blood accumulation in the uterus and fallopian tubes, and finally in the peritoneal cavity. Physical examination sometimes reveals normally developed external sex organs. Delayed diagnosis and treatment may potentially result in extensive endometriosis, which may potentially cause severe adhesion and damage to reproductivity. Such consequences could complicate further the management of the disease. Traditionally, hysterectomy has been the treatment of choice in these cases because of the high failure rate of canalization procedures and risk of serious ascending infection. With advanced laparoscopic techniques, conservative management seems feasible and has been recommended. We herein present a patient with complete cervical and vaginal agenesis. Creation of a neovagina and uterovaginal anastomosis were performed first under the guidance of laparoscopy (Figure 1. A neocervix was composed of a polytetrafluoroethylene graft and a piece of oral mucosa retrieved from the buccal area. The neovagina was reconstructed with an external pudendal artery perforator flap. A cervical Fr 16 size Foley was left in place as a stent. The patient had uneventful postoperative recovery and fair wound healing at the outpatient follow-up. Congenital agenesis of the uterine cervix and vagina can be differentiated accurately and reconstructed laparoscopically. Using mesh-buccal mucosa composite and pudendal perforator flap is a practical way to reconstruct neocervix and neovagina after their creation.

Acquisition of reproducible transmission near-infrared (NIR) spectra of solid samples with inconsistent shapes by irradiation with isotropically diffused radiation using polytetrafluoroethylene (PTFE) beads.

Science.gov (United States)

Lee, Jinah; Duy, Pham Khac; Yoon, Jihye; Chung, Hoeil

2014-06-21

A bead-incorporated transmission scheme (BITS) has been demonstrated for collecting reproducible transmission near-infrared (NIR) spectra of samples with inconsistent shapes. Isotropically diffused NIR radiation was applied around a sample and the surrounding radiation was allowed to interact homogeneously with the sample for transmission measurement. Samples were packed in 1.40 mm polytetrafluoroethylene (PTFE) beads, ideal diffusers without NIR absorption, and then transmission spectra were collected by illuminating the sample-containing beads using NIR radiation. When collimated radiation was directly applied, a small portion of the non-fully diffused radiation (NFDR) propagated through the void space of the packing and eventually degraded the reproducibility. Pre-diffused radiation was introduced by placing an additional PTFE disk in front of the packing to diminish NFDR, which produced more reproducible spectral features. The proposed scheme was evaluated by analyzing two different solid samples: density determination for individual polyethylene (PE) pellets and identification of mining locality for tourmalines. Because spectral collection was reproducible, the use of the spectrum acquired from one PE pellet was sufficient to accurately determine the density of nine other pellets with different shapes. The differentiation of tourmalines, which are even more dissimilar in appearance, according to their mining locality was also feasible with the help of the scheme.

Numerical modelling of multi-vane expander operating conditions in ORC system

Directory of Open Access Journals (Sweden)

Rak Józef

2017-01-01

Full Text Available Multi-vane expanders are positive displacement volumetric machines which are nowadays considered for application in micro-power domestic ORC systems as promising alternative to micro turbines and other volumetric expanders. The multi-vane expander features very simple design, low gas flow capacity, low expansion ratios, an advantageous ratio of the power output to the external dimensions and are insensitive to the negative influence of the gas-liquid mixture expansion. Moreover, the multi-vane expander can be easily hermetically sealed, which is one of the key issues in the ORC system design. A literature review indicates that issues concerning the application of multi-vane expanders in such systems, especially related to operating of multi-vane expander with different low-boiling working fluids, are innovative, not fully scientifically described and have the potential for practical implementation. In this paper the results of numerical investigations on multi-vane expander operating conditions are presented. The analyses were performed on three-dimensional numerical model of the expander in ANSYS CFX software. The numerical model of the expander was validated using the data obtained from the experiment carried out on a lab test-stand. Then a series of computational analysis were performed using expanders' numerical model in order to determine its operating conditions under various flow conditions of different working fluids.

Conference Offers Girls Opportunity to Expand Career Horizons

Science.gov (United States)

Offers Girls Opportunity to Expand Career Horizons For more information contact: e:mail: Public Affairs Golden, Colo., Feb. 11, 1997 -- Expanding Your Horizons, a conference for girls grades 6 - 9 and Employed Women, Girls Incorporated of Metro Denver, King Soopers, McDonalds, the TCI Adult Program and the

Development of cryogenic free-piston reciprocating expander utilizing phase controller

Energy Technology Data Exchange (ETDEWEB)

Cha, Jeong Min; Park, Ji Ho; Kim, Kyung Joong; Jeong, Sang Kwon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2016-06-15

A free-piston reciprocating expander is a device which operates without any mechanical linkage to a stationary part. Since the motion of the floating piston is only controlled by the pressure difference at two ends of the piston, this kind of expander may indispensably require a sophisticated active control system equipped with multiple valves and reservoirs. In this paper, we have suggested a novel design that can further reduce complexity of the previously developed cryogenic free-piston expander configuration. It is a simple replacement of both multiple valves and reservoirs by a combination of an orifice valve and a reservoir. The functional characteristic of the integrated orifice-reservoir configuration is similar to that of a phase controller applied in a pulse tube refrigerator so that we designate the one as a phase controller. Depending on the orifice valve size in the phase controller, the different PV work which affects the expander performance is generated. The numerical model of this unique free-piston reciprocating expander utilizing a phase controller is established to understand and analyze quantitatively the performance variation of the expander under different valve timing and orifice valve size. The room temperature experiments are carried out to examine the performance of this newly developed cryogenic expander.

Development of cryogenic free-piston reciprocating expander utilizing phase controller

International Nuclear Information System (INIS)

Cha, Jeong Min; Park, Ji Ho; Kim, Kyung Joong; Jeong, Sang Kwon

2016-01-01

A free-piston reciprocating expander is a device which operates without any mechanical linkage to a stationary part. Since the motion of the floating piston is only controlled by the pressure difference at two ends of the piston, this kind of expander may indispensably require a sophisticated active control system equipped with multiple valves and reservoirs. In this paper, we have suggested a novel design that can further reduce complexity of the previously developed cryogenic free-piston expander configuration. It is a simple replacement of both multiple valves and reservoirs by a combination of an orifice valve and a reservoir. The functional characteristic of the integrated orifice-reservoir configuration is similar to that of a phase controller applied in a pulse tube refrigerator so that we designate the one as a phase controller. Depending on the orifice valve size in the phase controller, the different PV work which affects the expander performance is generated. The numerical model of this unique free-piston reciprocating expander utilizing a phase controller is established to understand and analyze quantitatively the performance variation of the expander under different valve timing and orifice valve size. The room temperature experiments are carried out to examine the performance of this newly developed cryogenic expander

Fabricating PFPE Membranes for Microfluidic Valves and Pumps

Science.gov (United States)

Greer, Frank; White, Victor E.; Lee, Michael C.; Willis, Peter A.; Grunthaner, Frank J.; Rolland, Jason; Rolland, Jason

2009-01-01

A process has been developed for fabricating membranes of a perfluoropolyether (PFPE) and integrating them into valves and pumps in laboratory-on-achip microfluidic devices. Membranes of poly(tetrafluoroethylene) [PTFE] and poly(dimethylsilane) [PDMS] have been considered for this purpose and found wanting. By making it possible to use PFPE instead of PTFE or PDMS, the present process expands the array of options for further development of microfluidic devices for diverse applications that could include detection of biochemicals of interest, detection of toxins and biowarfare agents, synthesis and analysis of proteins, medical diagnosis, and synthesis of fuels.

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

Crystallization degree change of expanded graphite by milling and annealing

International Nuclear Information System (INIS)

Tang Qunwei; Wu Jihuai; Sun Hui; Fang Shijun

2009-01-01

Expanded graphite was ball milled with a planetary mill in air atmosphere, and subsequently thermal annealed. The samples were characterized by using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). It was found that in the milling initial stage (less than 12 h), the crystallization degree of the expanded graphite declined gradually, but after milling more than 16 h, a recrystallization of the expanded graphite toke place, and ordered nanoscale expanded graphite was formed gradually. In the annealing initial stage, the non-crystallization of the graphite occurred, but, beyond an annealing time, recrystallizations of the graphite arise. Higher annealing temperature supported the recrystallization. The milled and annealed expanded graphite still preserved the crystalline structure as raw material and hold high thermal stability.

New York: Expanding Time, Increasing Opportunities for Achievement

Science.gov (United States)

Miller, Tiffany D.

2014-01-01

New York is poised to take an important step to improve student achievement by expanding learning time for students attending high-poverty, low-performing schools. Recent district- and state-level investments in expanded learning time--a promising strategy to close achievement and opportunity gaps--will give students more time to learn core…

Innovative isothermal oil-free co-rotating scroll compressor–expander for energy storage with first expander tests

International Nuclear Information System (INIS)

Iglesias, A.; Favrat, D.

2014-01-01

Highlights: • Doing a new concept of small scale compressed air energy storage. • Presenting a new working process of scroll machinery. • Updating a thermodynamic model of scroll compressor that take into account water injection. • Updating a mathematical model of volumetric loses that take into account sealing effect of liquid water. • Encouraging results to investigate more deeply this new concept. - Abstract: The development of an efficient isothermal turbine and compressor is essential for the realization of a small-scale compressed air energy storage (CAES). This article presents the theoretical development of an oil-free co-rotating scroll air compressor and turbine working with water injection to make the operations of expansion and compression as isothermal as possible. First experimental results in expander mode are shown. The theoretical performance is predicted with the help of a mathematical model using the equations of energy and mass conservation and the equation of state. This model takes into account the effects of water injection and volumetric losses. The experimental prototype is an oil-free scroll air compressor with the distinctive feature of having two mobile involutes working in synchronized co-rotation one relative to another. The prime-mover is an electric motor driving the two scrolls with two synchronizing belts. Water injection in the housing intends to provide a quasi-isothermal compression. The same device is used as an isothermal expander by supplying high-pressure air with water when it rotates backwards in expander mode, the electric motor acting then as a generator. Expected improvements to a standard scroll compressor and expander are a better volumetric efficiency and a greater power density due to a higher rotational speed of the scrolls, thanks to their symmetrical masses. The isothermal processes increase also the overall performance

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.

Is sonographic surveillance of polytetrafluoroethylene-covered transjugular intrahepatic portosystemic shunts (TIPS) necessary? A single centre experience comparing both types of stents

Energy Technology Data Exchange (ETDEWEB)

Pan, J.-J.; Chen, C. [Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, Section of Hepatobiliary Disease, University of Florida, Gainesville, FL (United States); Geller, B. [Department of Radiology, University of Florida, Gainesville, FL (United States); Firpi, R.; Machicao, V.I. [Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, Section of Hepatobiliary Disease, University of Florida, Gainesville, FL (United States); Caridi, J.G. [Department of Radiology, University of Florida, Gainesville, FL (United States); Nelson, D.R. [Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, Section of Hepatobiliary Disease, University of Florida, Gainesville, FL (United States); Morelli, G. [Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, Section of Hepatobiliary Disease, University of Florida, Gainesville, FL (United States)], E-mail: morelgj@medicine.ufl.edu

2008-10-15

Aim: To investigate whether sonographic (US) surveillance of polytetrafluoroethylene covered transjugular intrahepatic portosystemic shunts (TIPS) is necessary. Materials and methods: We identified 128 patients who underwent TIPS for complications of portal hypertension between January 2001 and December 2005 at a large tertiary centre. Procedural data were retrospectively analysed. US surveillance of the TIPS was performed at baseline with scheduled follow-up or whenever shunt dysfunction was suspected. Clinical and radiology reports were compared to assess US surveillance of the TIPS. Results: Four hundred and twenty-six US studies were performed, with a median of three per patient (range 1-5). The median follow-up period was 378 days (range 1-1749 days). Twenty-three patients (18%) had baseline US studies performed only whereas 105 (82%) also had follow-up studies. Forty-one (32%) of 128 patients [32 (78%) Wallstent, nine (22%) Viatorr] had Doppler ultrasound abnormalities noted. Venography was performed in all 41 patients. Abnormal venography and elevated hepatic venous pressure gradient (HVPG) was seen in 34 (82.9%) of the 41 patients [29 (85.3%) Wallstent, five (14.7%) Viatorr]. Among the 34 patients, 17 (50%) [13 (76.5%) Wallstent, four (23.5%) Viatorr] had venographic abnormalities noted at the hepatic venous end accompanied by increased HVPG. All four of the Viatorr patients had minor narrowing at the hepatic venous end and HVPG measurements that ranged 3-4 mm Hg above 12 mm Hg. Conclusion: Considering the improved patency of covered stents in TIPS, US surveillance may be superfluous after the baseline study.

Expanding the Game Design Space

DEFF Research Database (Denmark)

Larsen, Lasse Juel; Majgaard, Gunver

2016-01-01

This article considers game design research in educational settings. Its focus is on how undergraduate students – particularly engineering students – learn computer game design. From observations conducted during our game design courses we have developed a model of expanded game design space...... layer establishes correspondence between formal elements of computer games and the structure of problem-based creativity. It addresses how game design challenges should be formulated and how creative solutions can be measured. The fourth and final layer demonstrates how clear framing can act....... It encapsulates the entire development process from the first ideas to the final game with emphasis on game design thinking. Our model of expanded game design space consists of four separate – yet interconnected – layers in the process of game development. The first layer addresses the importance of framing...

Self-expanding/shrinking structures by 4D printing

Science.gov (United States)

Bodaghi, M.; Damanpack, A. R.; Liao, W. H.

2016-10-01

The aim of this paper is to create adaptive structures capable of self-expanding and self-shrinking by means of four-dimensional printing technology. An actuator unit is designed and fabricated directly by printing fibers of shape memory polymers (SMPs) in flexible beams with different arrangements. Experiments are conducted to determine thermo-mechanical material properties of the fabricated part revealing that the printing process introduced a strong anisotropy into the printed parts. The feasibility of the actuator unit with self-expanding and self-shrinking features is demonstrated experimentally. A phenomenological constitutive model together with analytical closed-form solutions are developed to replicate thermo-mechanical behaviors of SMPs. Governing equations of equilibrium are developed for printed structures based on the non-linear Green-Lagrange strain tensor and solved implementing a finite element method along with an iterative incremental Newton-Raphson scheme. The material-structural model is then applied to digitally design and print SMP adaptive lattices in planar and tubular shapes comprising a periodic arrangement of SMP actuator units that expand and then recover their original shape automatically. Numerical and experimental results reveal that the proposed planar lattice as meta-materials can be employed for plane actuators with self-expanding/shrinking features or as structural switches providing two different dynamic characteristics. It is also shown that the proposed tubular lattice with a self-expanding/shrinking mechanism can serve as tubular stents and grippers for bio-medical or piping applications.

Analysis of a rotating spool expander for Organic Rankine Cycle applications

Science.gov (United States)

Krishna, Abhinav

Increasing interest in recovering or utilizing low-grade heat for power generation has prompted a search for ways in which the power conversion process may be enhanced. Amongst the conversion systems, the Organic Rankine Cycle (ORC) has generated an enormous amount of interest amongst researchers and system designers. Nevertheless, component level technologies need to be developed and match the range of potential applications. In particular, technical challenges associated with scaling expansion machines (turbines) from utility scale to commercial scale have prevented widespread adoption of the technology. In this regard, this work focuses on a novel rotating spool expansion machine at the heart of an Organic Rankine Cycle. A comprehensive, deterministic simulation model of the rotating spool expander is developed. The comprehensive model includes a detailed geometry model of the spool expander and the suction valve mechanism. Sub-models for mass flow, leakage, heat transfer and friction within the expander are also developed. Apart from providing the ability to characterize the expander in a particular system, the model provides a valuable tool to study the impact of various design variables on the performance of the machine. The investigative approach also involved an experimental program to assess the performance of a working prototype. In general, the experimental data showed that the expander performance was sub-par, largely due to the mismatch of prevailing operating conditions and the expander design criteria. Operating challenges during the shakedown tests and subsequent sub-optimal design changes also detracted from performance. Nevertheless, the results of the experimental program were sufficient for a proof-of-concept assessment of the expander and for model validation over a wide range of operating conditions. The results of the validated model reveal several interesting details concerning the expander design and performance. For example, the match

Rupture of an expander prosthesis mimics axillary cancer recurrence.

LENUS (Irish Health Repository)

Ismael, T

2005-10-01

Regional silicone gel migration from a ruptured breast implant has been reported at different locations including the upper extremity, chest wall muscles, axilla and back. We report a patient who presented with an axillary mass that mimicked a regional recurrence 5 years after breast cancer reconstruction with a latissimus dorsi musculocutaneous flap and silicon gel expander-prosthesis. Surgical exploration revealed that the mass contained silicone gel around the port of the breast expander that had ruptured. The mass was confluent with an intracapsular silicone leak through a tract along the tube of the expander port.

Evidence for radiation induced crosslinking in polytetrafluoroethylene by means of high-resolution solid-state 19F high-speed MAS NMR

International Nuclear Information System (INIS)

Katoh, Etsuko; Sugisawa, Hisashi; Oshima, Akihiro; Tabata, Yoneho; Seguchi, Tadao; Yamazaki, Toshimasa

1999-01-01

Radiation effects on molecular structure of polytetrafluoroethylene (PTFE) were studied by high-resolution solid-state 19 F high speed magic angle spinning (HS MAS) NMR spectroscopy. Samples used for the NMR studies were prepared by electron beam irradiation of PTFE with a wide range of irradiation doses from 0.5-10 MGy in the molten state at 340 deg. C under oxygen-free atmosphere. While the non-irradiated PTFE displayed only an intense peak of the internal CF 2 , several new signals corresponding to CF 3 , CF 2 and CF groups were observed for the PTFE which was high temperature irradiated at 340 deg. C in oxygen-free atmosphere (hti-PTFE). Intensities of these new signals increased with an increase of irradiation dose. The present solid-state 19 F HS MAS NMR studies provide not only the first experimental evidence regarding the existence of crosslinking structure in hti-PTFE, directly detected as the CF signal, but also the crosslinking density which can be estimated from a proportion of the CF versus total fluorine signal intensities. The higher the irradiation dose, the higher the crosslinking density; hti-PTFE with 10 MGy contains one crosslinking site per approximately 24 CF 2 groups, while the hti-PTFE with 5 MGy contains one crosslinking site per approximately 36 CF 2 groups. Further, G value of crosslinking (G(x)) was estimated from the signal intensities of 19 F HS MAS NMR spectra. The highest G(x)-value, 1.85, was observed for the 2MGy hti-PTFE sample, suggesting that crosslinking of PTFE is formed most efficaciously with 2 MGy irradiation in the molten state at 340 deg. C under oxygen-free atmosphere

Hubble Diagram Test of Expanding and Static Cosmological Models: The Case for a Slowly Expanding Flat Universe

Directory of Open Access Journals (Sweden)

Laszlo A. Marosi

2013-01-01

Full Text Available We present a new redshift (RS versus photon travel time ( test including 171 supernovae RS data points. We extended the Hubble diagram to a range of z = 0,0141–8.1 in the hope that at high RSs, the fitting of the calculated RS/ diagrams to the observed RS data would, as predicted by different cosmological models, set constraints on alternative cosmological models. The Lambda cold dark matter (ΛCDM, the static universe model, and the case for a slowly expanding flat universe (SEU are considered. We show that on the basis of the Hubble diagram test, the static and the slowly expanding models are favored.

Intermittency Statistics in the Expanding Solar Wind

Science.gov (United States)

Cuesta, M. E.; Parashar, T. N.; Matthaeus, W. H.

2017-12-01

The solar wind is observed to be turbulent. One of the open questions in solar wind research is how the turbulence evolves as the solar wind expands to great distances. Some studies have focused on evolution of the outer scale but not much has been done to understand how intermittency evolves in the expanding wind beyond 1 AU (see [1,2]). We use magnetic field data from Voyager I spacecraft from 1 to 10AU to study the evolution of statistics of magnetic discontinuities. We perform various statistical tests on these discontinuities and make connections to the physical processes occurring in the expanding wind.[1] Tsurutani, Bruce T., and Edward J. Smith. "Interplanetary discontinuities: Temporal variations and the radial gradient from 1 to 8.5 AU." Journal of Geophysical Research: Space Physics 84.A6 (1979): 2773-2787.[2] Greco, A., et al. "Evidence for nonlinear development of magnetohydrodynamic scale intermittency in the inner heliosphere." The Astrophysical Journal 749.2 (2012): 105.

Evaluation of the stiffness characteristics of rapid palatal expander screws

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Luca Lombardo

2016-11-01

Full Text Available Abstract Background The aim of this study is to evaluate the mechanical properties of the screws used for rapid expansion of the upper jaw. Methods Ten types of expansion screw were assessed, seven with four arms: Lancer Philosophy 1, Dentaurum Hyrax Click Medium, Forestadent Anatomic Expander type “S”, Forestadent Anatomic Expander type “S” for narrow palates, Forestadent Memory, Leone A 2620-10 with telescopic guide, and Leone A 0630-10 with orthogonal arms; and three with two arms: Dentaurum Variety S.P., Target Baby REP Veltri, and Leone A 362113. A test expander with the mean dimensions taken from measurements on a sample of 100 expanders was constructed for each screw. The test expanders were connected to the supports of an Instron 4467 (Instron Corp., USA mechanical testing machine equipped with a 500 N load cell, and the compression force exerted after each activation was measured. The mean forces expressed by the two- and four-arm expanders were then compared. Results After five activations, the forces expressed by the two-arm devices were double than those expressed by the four-arm devices on average (224 ± 59.9 N vs. 103 ± 32.9 N, and such values remained high after subsequent activations. Conclusions The expanders tested demonstrated stiffness characteristics compatible with opening of the palatine sutures in pre-adolescent patients. The stiffness of such devices can be further increased during the construction phase.

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

Expanded tenses in the old English orosius a syntactic strengthening*

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Frančiška Trobevšek Drobnak

1990-12-01

Full Text Available The present chapter reports the investigation into certain aspects of the periphrastic construction to be +present participle (e.g. NE: "he is teaching"; OE. "he is laerende" viewed as an example of a syntactic strengthening. The construc­ tion is usually referred to as "continuous tenses/form" or "progressive tenses/form", whereas Nickel (1966 uses "expanded form". Coming closest to this latter term, the "expanded tenses" employed here seems a convenient label for two reasons: a  the use of expanded tenses is not restricted to the expression of verbal aspect (Aspekt or mode of verbal action (Aktionsart, which is implied by the use of either the term "continuous  tenses/form" or the term "progressive tenses/form"; b  the expanded tenses are integrated into the English tense system, in the sense that they can be substituted  with the respective non-expanded tenses without any change in the syntax of the clause, e.g.

Femoro-Supragenicular Popliteal Bypass with a Bridging Stent Graft in a Diffusely Diseased Distal Target Popliteal Artery: Alternative to Below-Knee Popliteal Polytetrafluoroethylene Bypass

Directory of Open Access Journals (Sweden)

Joung Hun Byun

2017-10-01

Full Text Available Background: Lesions in distal target arteries hinder surgical bypass procedures in patients with peripheral arterial occlusive disease. Methods: Between April 2012 and October 2015, 16 patients (18 limbs with lifestyle- limiting claudication (n=12 or chronic critical limb ischemia (n=6 underwent femoral–above-knee (AK polytetrafluoroethylene (PTFE bypass grafts with a bridging stent graft placement between the distal target popliteal artery and the PTFE graft. Ring-supported PTFE grafts were used in all patients with no available vein for graft material. Follow-up evaluations assessed clinical symptoms, the ankle-brachial index, ultrasonographic imaging and/or computed tomography angiography, the primary patency rate, and complications. Results: All procedures were successful. The mean follow-up was 12.6 months (range, 11 to 14 months, and there were no major complications. The median baseline ankle-brachial index of 0.4 (range, 0.2 to 0.55 significantly increased to 0.8 (range, 0.5 to 1.0 at 12 months (p＜0.01. The primary patency rate at 12 months was 83.3%. The presenting symptoms resolved within 2 weeks. Conclusion: In AK bypasses with a diffusely diseased distal target popliteal artery or when below-knee (BK bypass surgery is impossible, this procedure could be clinically effective and safe when used as an alternative to femoral-BK bypass surgery.

Some design features of CO2 swing piston expander

International Nuclear Information System (INIS)

Guan Haiqing; Ma Yitai; Li Minxia

2006-01-01

CO 2 is a potential substitute for synthesized refrigerants with favorable environmental properties. To improve the coefficient of performance (COP) of CO 2 heat pump systems, a swing piston expander prototype has been developed for replacing the throttling valve based on the thermodynamic analysis of the operating conditions of a CO 2 transcritical cycle. The measures on reducing the loss of friction and leakage are paramount important to improve the efficiency of the expander. The performance of the CO 2 swing expander prototype was actually tested in a CO 2 transcritical cycle water-to-water heat pump test rig, and the test results illustrate that the isentropic efficiency of the prototype can be more than 28% when running steadily and up to a maximum of about 44%. Some operating characteristics of the swing piston expander are presented according to the analysis of the test results

Endovascular therapy of carotid stenosis with self-expandable stent

International Nuclear Information System (INIS)

Liu Jianmin; Huang Qinghai; Hong Bo; Xu Yi; Zhao Wenyuan; Zhang Yongwei; Zhang Long; Zhou Xiaoping

2002-01-01

Objective: To summarize the experience of endovascular treatment of carotid stenosis with expandable stents. Methods: Fifty-two patients with carotid stenosis who experienced repeated transient ischemic attacks or cerebral infarction were admitted to our hospital. The stenosis was pre-expanded with undetachable balloon, and self-expandable stents were implanted across the stenosis. A balloon catheter was used to further expand stents in 29 patients. Results: The stent was accurately implanted, and total disappearance of stenosis was obtained in 34 patients, the degree of stenosis reduced more than 90% in 16 patients, and more than 70% in 2 patients. The patients recovered well and no complications related to the procedure occurred. None experienced TIA or infarction postoperatively in 52 cases and follow-up imaging in 19 patients (6 - 12 months) demonstrated no restenosis. Conclusion: Endovascular stenting may be a safe and valid choice for the treatment of extracranial carotid stenosis

49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

Science.gov (United States)

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Polymeric beads, expandable and Plastic molding... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non-bulk shipments of Polymeric beads (or granules), expandable, evolving flammable vapor and Plastic...

Operation of an organic Rankine cycle dependent on pumping flow rates and expander torques

International Nuclear Information System (INIS)

Yang, Xufei; Xu, Jinliang; Miao, Zheng; Zou, Jinghuang; Yu, Chao

2015-01-01

An ORC (organic Rankine cycle) was developed with R123 as the working fluid. The heat capacity is in ∼100 kW. The match between pump and expander is investigated. Lower pump frequencies (f 10 Hz) adapt low expander torques only, and cause unstable flow and pump cavitation for larger expander torques. Ultra-low expander torques generate sufficiently high vapor superheatings to decrease expander efficiencies. Ultra-high expander torques achieve saturation vapor at the expander inlet, causing liquid droplets induced shock wave to worsen expander performance. An optimal range of expander torques exists to have better expander performance. A liquid subcooling of 20 °C is necessary to avoid pump cavitation. Expander powers and efficiencies show parabola shapes versus expander torques, or vapor superheatings at the expander inlet. The optimal vapor superheating is 13 °C. The cavitation mechanisms and measures to avoid cavitation are analyzed. This paper notes the overestimation of ORC performance by equilibrium thermodynamic analysis. Assumptions should be dependent on experiments. Future studies are suggested on organic fluid flow, heat transfer and energy conversion in various components. - Highlights: • The match between pump and expander is investigated. • A liquid subcooling of 20 °C is needed at pump inlet. • A vapor superheating of 13 °C is necessary at expander inlet. • Cavitation in pumps and expanders are analyzed. • The equilibrium thermodynamics overestimate ORC performances.

Cryo-electron Microscopy Structures of Expanded Poliovirus with VHHs Sample the Conformational Repertoire of the Expanded State.

Science.gov (United States)

Strauss, Mike; Schotte, Lise; Karunatilaka, Krishanthi S; Filman, David J; Hogle, James M

2017-02-01

By using cryo-electron microscopy, expanded 80S-like poliovirus virions (poliovirions) were visualized in complexes with four 80S-specific camelid VHHs (Nanobodies). In all four complexes, the VHHs bind to a site on the top surface of the capsid protein VP3, which is hidden in the native virus. Interestingly, although the four VHHs bind to the same site, the structures of the expanded virus differ in detail in each complex, suggesting that each of the Nanobodies has sampled a range of low-energy structures available to the expanded virion. By stabilizing unique structures of expanded virions, VHH binding permitted a more detailed view of the virus structure than was previously possible, leading to a better understanding of the expansion process that is a critical step in infection. It is now clear which polypeptide chains become disordered and which become rearranged. The higher resolution of these structures also revealed well-ordered conformations for the EF loop of VP2, the GH loop of VP3, and the N-terminal extensions of VP1 and VP2, which, in retrospect, were present in lower-resolution structures but not recognized. These structural observations help to explain preexisting mutational data and provide insights into several other stages of the poliovirus life cycle, including the mechanism of receptor-triggered virus expansion. When poliovirus infects a cell, it undergoes a change in its structure in order to pass RNA through its protein coat, but this altered state is short-lived and thus poorly understood. The structures of poliovirus bound to single-domain antibodies presented here capture the altered virus in what appear to be intermediate states. A careful analysis of these structures lets us better understand the molecular mechanism of infection and how these changes in the virus lead to productive-infection events. Copyright © 2017 American Society for Microbiology.

Tissue Expander Overfilling: Achieving New Dimensions of Customization in Breast Reconstruction.

Science.gov (United States)

Treiser, Matthew D; Lahair, Tracy; Carty, Matthew J

2016-02-01

Overfill of tissue expanders is a commonly used modality to achieve customized dimensions in breast reconstruction. Little formal study of the dynamics of hyperexpansion of these devices has been performed to date, however. Overfill trials were performed using both Natrelle 133 MV and Mentor 8200 tissue expanders of indicated capacities ranging from 250 to 800 mL. Each expander was initially filled to its indicated capacity with normal water and then injected in regular increments to 400% overfill. Measurements of each expander's width, height, and projection were made at indicated capacity and with each successive incremental overfill injection, and these results were then recorded, collated, and analyzed. Over the first 50% overfill, all expanders demonstrated a logarithmic increase in projection (mean increase, 143 ± 9%) while maintaining essentially stable base dimensions. Overfill levels in excess of 50% were accompanied by linear increases in height, width, and projection, during which projection approached, but never equaled, base dimensions. Stress versus strain analyses demonstrated nonlinear biomechanical dynamics during the first 50% overfill, followed by standard elastic dynamics up to 400% overfill. At no point during the study, did expander tensions outstrip elastic properties, thereby explaining the lack of device rupture. Through overfilling, tunable geometries of tissue expanders can be accessed that may provide for increasing customization of reconstructions, particularly at overfill volumes up to 50% over indicated capacity. This study should serve to guide tissue expander selection and fill volumes that surgeons may implement in obtaining ideal reconstructed breast shapes.

Flexural Behaviour Of Reinforced Concrete Beams Containing Expanded Glass As Lightweight Aggregates

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Khatib Jamal

2015-12-01

Full Text Available The flexural properties of reinforced concrete beams containing expanded glass as a partial fine aggregate (sand replacement are investigated. Four concrete mixes were employed to conduct this study. The fine aggregate was replaced with 0%, 25%, 50% and 100% (by volume expanded glass. The results suggest that the incorporation of 50% expanded glass increased the workability of the concrete. The compressive strength was decreasing linearly with the increasing amount of expanded glass. The ductility of the concrete beam significantly improved with the incorporation of the expanded glass. However, the load-carrying capacity of the beam and load at which the first crack occurs was reduced. It was concluded that the inclusion of expanded glass in structural concrete applications is feasible.

Theoretical models for recombination in expanding gas

International Nuclear Information System (INIS)

Avron, Y.; Kahane, S.

1978-09-01

In laser isotope separation of atomic uranium, one is confronted with the theoretical problem of estimating the concentration of thermally ionized uranium atoms. To investigate this problem theoretical models for recombination in an expanding gas and in the absence of local thermal equilibrium have been constructed. The expansion of the gas is described by soluble models of the hydrodynamic equation, and the recombination by rate equations. General results for the freezing effect for the suitable ranges of the gas parameters are obtained. The impossibility of thermal equilibrium in expanding two-component systems is proven

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

Differences in Endothelial Injury After Balloon Angioplasty, Insertion of Balloon-Expanded Stents or Release of Self-Expanding Stents: An Electron Microscopic Experimental Study

International Nuclear Information System (INIS)

Harnek, Jan; Zoucas, Evita; Carlemalm, Erik; Cwikiel, Wojciech

1999-01-01

Purpose: To evaluate which of six different commonly available stents inserted into an artery without percutaneous transluminal angioplasty (PTA) causes the least endothelial damage. To compare the degree of endothelial injury after insertion of such a stent with injury caused by PTA. Methods: Twelve healthy pigs were used in the experiments. In the first part of the study six different types of stents were inserted into the common iliac arteries. In the second part of the study self-expanding stents with large spaces between the wires were used. PTA was performed in the contralateral iliac artery. The pigs were killed immediately after the procedure and resected specimens examined after fixation, using scanning electron microscopy. Results: All procedures but two were accomplished successfully. More endothelium was preserved after insertion of self-expanding stents with large spaces between the wires, compared with stents with small spaces and balloon-expanded stents. After insertion of self-expanding stents with large spaces, 50.1% ± 16.4% of the endothelium remained intact, compared with only 5.6% ± 7.7% after PTA. The difference was statistically significant (p < 0.001). Conclusion: Self-expanding stents with large spaces between the wires, inserted without PTA, cause less damage to the endothelium than other stents and significantly less damage than PTA

Study on paraffin/expanded graphite composite phase change thermal energy storage material

International Nuclear Information System (INIS)

Zhang Zhengguo; Fang Xiaoming

2006-01-01

A paraffin/expanded graphite composite phase change thermal energy storage material was prepared by absorbing the paraffin into an expanded graphite that has an excellent absorbability. In such a composite, the paraffin serves as a latent heat storage material and the expanded graphite acts as the supporting material, which prevents leakage of the melted paraffin from its porous structure due to the capillary and surface tension forces. The inherent structure of the expanded graphite did not change in the composite material. The solid-liquid phase change temperature of the composite PCM was the same as that of the paraffin, and the latent heat of the paraffin/expanded graphite composite material was equivalent to the calculated value based on the mass ratio of the paraffin in the composite. The heat transfer rate of the paraffin/expanded graphite composite was obviously higher than that of the paraffin due to the combination with the expanded graphite that had a high thermal conductivity. The prepared paraffin/expanded graphite composite phase change material had a large thermal storage capacity and improved thermal conductivity and did not experience liquid leakage during its solid-liquid phase change

Expanded function allied dental personnel and dental practice productivity and efficiency.

Science.gov (United States)

Beazoglou, Tryfon J; Chen, Lei; Lazar, Vickie F; Brown, L Jackson; Ray, Subhash C; Heffley, Dennis R; Berg, Rob; Bailit, Howard L

2012-08-01

This study examined the impact of expanded function allied dental personnel on the productivity and efficiency of general dental practices. Detailed practice financial and clinical data were obtained from a convenience sample of 154 general dental practices in Colorado. In this state, expanded function dental assistants can provide a wide range of reversible dental services/procedures, and dental hygienists can give local anesthesia. The survey identified practices that currently use expanded function allied dental personnel and the specific services/procedures delegated. Practice productivity was measured using patient visits, gross billings, and net income. Practice efficiency was assessed using a multivariate linear program, Data Envelopment Analysis. Sixty-four percent of the practices were found to use expanded function allied dental personnel, and on average they delegated 31.4 percent of delegatable services/procedures. Practices that used expanded function allied dental personnel treated more patients and had higher gross billings and net incomes than those practices that did not; the more services they delegated, the higher was the practice's productivity and efficiency. The effective use of expanded function allied dental personnel has the potential to substantially expand the capacity of general dental practices to treat more patients and to generate higher incomes for dental practices.

Correct integration of compressors and expanders in above ambient heat exchanger networks

International Nuclear Information System (INIS)

Fu, Chao; Gundersen, Truls

2016-01-01

The Appropriate Placement concept (also referred to as Correct Integration) is fundamental in Pinch Analysis. The placement of reactors, distillation columns, evaporators, heat pumps and heat engines in heat exchanger networks is well established. The placement of pressure changing equipment such as compressors and expanders is complex and less discussed in literature. A major difficulty is that both heat and work (not only heat) are involved. The integration of compressors and expanders separately into heat exchanger networks was recently investigated. A set of theorems were proposed for assisting the design. The problem is even more complex when both compressors and expanders are to be integrated. An important concern is about the sequence of integration with compressors and expanders, i.e. should compressors or expanders be implemented first. This problem is studied and a new theorem is formulated related to the Correct Integration of both compressors and expanders in above ambient heat exchanger networks. The objective is to minimize exergy consumption for the integrated processes. A graphical design methodology is developed for the integration of compressors and expanders into heat exchanger networks above ambient temperature. - Highlights: • The correct integration of compressors and expanders in heat exchanger networks is studied. • A theorem is proposed for heat integration between compressors and expanders. • The total exergy consumption is minimized.

Nitrogen expander cycles for large capacity liquefaction of natural gas

Energy Technology Data Exchange (ETDEWEB)

Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun [Hong Ik University, Department of Mechanical Engineering, Seoul, 121-791 (Korea, Republic of); Choe, Kun Hyung [Korea Gas Corporation, Incheon, 406-130 (Korea, Republic of)

2014-01-29

Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity.

Nitrogen expander cycles for large capacity liquefaction of natural gas

Science.gov (United States)

Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun; Choe, Kun Hyung

2014-01-01

Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity.

Nitrogen expander cycles for large capacity liquefaction of natural gas

International Nuclear Information System (INIS)

Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun; Choe, Kun Hyung

2014-01-01

Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity

Environmental assessment, expanded Ponnequin wind energy project, Weld County, Colorado

International Nuclear Information System (INIS)

1999-02-01

The US Department of Energy (DOE) has considered a proposal from the State of Colorado, Office of Energy Conservation (OEC), for funding construction of the Expanded Ponnequin Wind Project in Weld County, Colorado. OEC plans to enter into a contracting arrangement with Public Service Company of Colorado (PSCo) for the completion of these activities. PSCo, along with its subcontractors and business partners, are jointly developing the Expanded Ponnequin Wind Project. The purpose of this Final Environmental Assessment (EA) is to provide DOE and the public with information on potential environmental impacts associated with the Expanded Ponnequin Wind Energy Project. This EA, and public comments received on it, were used in DOE's deliberations on whether to release funding for the expanded project under the Commercialization Ventures Program

Environmental assessment, expanded Ponnequin wind energy project, Weld County, Colorado

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-02-01

The US Department of Energy (DOE) has considered a proposal from the State of Colorado, Office of Energy Conservation (OEC), for funding construction of the Expanded Ponnequin Wind Project in Weld County, Colorado. OEC plans to enter into a contracting arrangement with Public Service Company of Colorado (PSCo) for the completion of these activities. PSCo, along with its subcontractors and business partners, are jointly developing the Expanded Ponnequin Wind Project. The purpose of this Final Environmental Assessment (EA) is to provide DOE and the public with information on potential environmental impacts associated with the Expanded Ponnequin Wind Energy Project. This EA, and public comments received on it, were used in DOE`s deliberations on whether to release funding for the expanded project under the Commercialization Ventures Program.

Self-Expanding, Tough Biodegradable Elastomers for Wound Stasis

Science.gov (United States)

2015-08-06

the civilian setting, with no effective therapies available at point of injury. We previously reported that a self- expanding polyurethane foam...setting, with no effective therapies available at point of injury. We previously reported that a self-expanding polyurethane foam significantly...care in accor- dance with the Guide of the Care and Use of Laboratory Ani- mals (Health, 2011 #17). 2.2. Instrumentation and monitoring All swine (n

EFFECT OF INCORPORATING EXPANDED POLYSTYRENE ...

African Journals Online (AJOL)

2012-11-03

Nov 3, 2012 ... Incorporating expanded polystyrene granules in concrete matrix can produce lightweight polystyrene aggregate concrete of ... structure. [1] reported that the standard workability tests are not suitable for the polystyrene aggregate concrete since they are sensitive to the unit weight of concrete. [2] made ...

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...

Expandable Total Humeral Replacement in a Child with Osteosarcoma

Directory of Open Access Journals (Sweden)

Eric R. Henderson

2015-01-01

Full Text Available Case. A right-handed 8-year-old female patient presented with a conventional, high-grade osteosarcoma involving her right humerus; through-shoulder amputation was recommended. After consultation, total humerus resection with expandable, total humeral endoprosthesis reconstruction was performed with a sleeve to encourage soft-tissue ingrowth. At three-year follow-up she has received one lengthening procedure and her functional scores are excellent. Conclusion. Total humeral resection and replacement in the pediatric population are rare and although early reports of expandable total humeral endoprosthesis outcomes demonstrate high failure rates, this patient’s success indicates that expandable total humeral replacement is a viable option.

Principles of the fifth order tuning of beam expanders

International Nuclear Information System (INIS)

Meot, F.; Aniel, T.

1995-01-01

An analytical treatment of the third and fifth order optics of beam expanders is described, which allows precise tuning of the optical elements of the beam line, and efficient optimization of the beam uniformizing at the extended target. An application to a two-dimensional expander is given as an illustration. (authors)

Theoretical investigation of flash vaporisation in a screw expander

Science.gov (United States)

Vasuthevan, Hanushan; Brümmer, Andreas

2017-08-01

In the present study flash vaporisation of liquid injection in a twin screw expander for a Trilateral Flash Cycle (TFC) is examined theoretically. The TFC process comprises a pressure increase in the working fluid, followed by heating the liquid close to boiling point. The hot liquid is injected into the working chamber of a screw expander. During this process the pressure of the liquid drops below the saturation pressure, while the temperature of the liquid remains virtually constant. Hence the liquid is superheated and in a metastable state. The liquid jet seeks to achieve a stable state in thermodynamic equilibrium and is therefore partially vaporised. This effect is referred to as flash vaporisation. Accordingly, a two-phase mixture, consisting of vapour and liquid, exists in the working chamber. Thermodynamic simulations were carried out using water as the working fluid for representative screw expander geometry. The simulations presented are performed from two different aspects during the filling process of a screw expander. The first case is the vaporisation of the injected liquid in a state of thermodynamic equilibrium, whereby the two-phase mixture is treated entirely as a compressible and homogeneous gas. The second case considers flashing efficiency. It describes the quantity of flashed vapour and consists of a liquid and vapour domain. Both models are compared and analysed with respect to the operational behaviour of a screw expander.

Expanding the HAWC Observatory

Energy Technology Data Exchange (ETDEWEB)

Mori, Johanna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-08-17

The High Altitude Water Cherenkov Gamma-Ray Observatory is expanding its current array of 300 water tanks to include 350 outrigger tanks to increase sensitivity to gamma rays above 10 TeV. This involves creating and testing hardware with which to build the new tanks, including photomultiplier tubes, high voltage supply units, and flash analog to digital converters. My responsibilities this summer included preparing, testing and calibrating that equipment.

Expanding the Universe of Education.

Science.gov (United States)

Parsons, Elizabeth

1996-01-01

Definitions of "education" and "rural" are debunked and expanded. The three major tasks of rural education are educating people to understand their own needs, the unavoidable changes that will transform rural Australia within their lifetimes, and the range of technologies that can enhance their well-being. Presents a strategy…

Can microcarrier-expanded chondrocytes synthesize cartilaginous tissue in vitro?

Science.gov (United States)

Surrao, Denver C; Khan, Aasma A; McGregor, Aaron J; Amsden, Brian G; Waldman, Stephen D

2011-08-01

Tissue engineering is a promising approach for articular cartilage repair; however, it is challenging to produce adequate amounts of tissue in vitro from the limited number of cells that can be extracted from an individual. Relatively few cell expansion methods exist without the problems of de-differentiation and/or loss of potency. Recently, however, several studies have noted the benefits of three-dimensional (3D) over monolayer expansion, but the ability of 3D expanded chondrocytes to synthesize cartilaginous tissue constructs has not been demonstrated. Thus, the purpose of this study was to compare the properties of engineered cartilage constructs from expanded cells (monolayer and 3D microcarriers) to those developed from primary chondrocytes. Isolated bovine chondrocytes were grown for 3 weeks in either monolayer (T-Flasks) or 3D microcarrier (Cytodex 3) expansion culture. Expanded and isolated primary cells were then seeded in high density culture on Millicell™ filters for 4 weeks to evaluate the ability to synthesize cartilaginous tissue. While microcarrier expansion was twice as effective as monolayer expansion (microcarrier: 110-fold increase, monolayer: 52-fold increase), the expanded cells (monolayer and 3D microcarrier) were not effectively able to synthesize cartilaginous tissue in vitro. Tissues developed from primary cells were substantially thicker and accumulated significantly more extracellular matrix (proteoglycan content: 156%-292% increase; collagen content: 70%-191% increase). These results were attributed to phenotypic changes experienced during the expansion phase. Monolayer expanded chondrocytes lost their native morphology within 1 week, whereas microcarrier-expanded cells were spreading by 3 weeks of expansion. While the use of 3D microcarriers can lead to large cellular yields, preservation of chondrogenic phenotype during expansion is required in order to synthesize cartilaginous tissue.

The expanding universe

CERN Document Server

Lew, Kristi

2011-01-01

People have always been fascinated with the stars above and the universe that contains them. Over the years, astronomers have developed numerous theories to explain how the universe began, how it works, and what its ultimate fate will be. But all of the scientists' questions are far from answered. The Expanding Universe goes beyond the creation of the universe to explain how scientists think the universe works, grows, and changes, including what great thinkers Isaac Newton and Albert Einstein had to say about its fate. Readers will also learn about how researchers are slowly shedding light on

Osseointegration of subperiosteal implant via guided tissue regeneration. A pilot study

DEFF Research Database (Denmark)

Hjørting-Hansen, E; Helbo, M; Aaboe, M

1995-01-01

The principle of guided tissue regeneration was applied in an attempt to generate bone to cover a subperiosteal implant. Titanium frame works, casted on individual impressions of the anterior surface of the tibia of 4 Copenhagen White rabbits, were stabilized to the tibia by microscrews, and half...... of them were covered by an expanded polytetrafluoroethylene augmentation membrane. The observation period was 12 weeks. Guided bone regeneration partly covering the implants was seen at all experimental sides; on the control sides the implants were mainly embedded in fibrous tissue. Studies...... are in progress with the aim of reducing marked marrow space formation observed in all the regenerated areas....

Ecological and evolutionary processes at expanding range margins

OpenAIRE

Thomas, C.D.; Bodsworth, E.J.; Wilson, R.J.; Simmons, A.D.; Davies, Z.G.; Musche, M.; Conradt, L.

2001-01-01

Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded\\ud rapidly in association with recent climate warming3±10. We examined four insect species that have expanded their geographical\\ud ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety ...

Black holes in an expanding universe.

Science.gov (United States)

Gibbons, Gary W; Maeda, Kei-ichi

2010-04-02

An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state (P = w rho with -1 < or = for all w < or = 1). It is an exact solution of the Einstein-scalar-Maxwell system, in which we have two Maxwell-type U(1) fields coupled to the scalar field. The potential of the scalar field is an exponential. We find a regular horizon, which depends on one parameter [the ratio of the energy density of U(1) fields to that of the scalar field]. The horizon is static because of the balance on the horizon between gravitational attractive force and U(1) repulsive force acting on the scalar field. We also calculate the black hole temperature.

Parameter estimation for an expanding universe

Directory of Open Access Journals (Sweden)

Jieci Wang

2015-03-01

Full Text Available We study the parameter estimation for excitations of Dirac fields in the expanding Robertson–Walker universe. We employ quantum metrology techniques to demonstrate the possibility for high precision estimation for the volume rate of the expanding universe. We show that the optimal precision of the estimation depends sensitively on the dimensionless mass m˜ and dimensionless momentum k˜ of the Dirac particles. The optimal precision for the ratio estimation peaks at some finite dimensionless mass m˜ and momentum k˜. We find that the precision of the estimation can be improved by choosing the probe state as an eigenvector of the hamiltonian. This occurs because the largest quantum Fisher information is obtained by performing projective measurements implemented by the projectors onto the eigenvectors of specific probe states.

Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

International Nuclear Information System (INIS)

Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

2011-01-01

Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

Energy Technology Data Exchange (ETDEWEB)

Thomas, Rijo Jacob, E-mail: rijojthomas@gmail.com [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India); Ghosh, Parthasarathi; Chowdhury, Kanchan [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India)

2011-06-15

Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

Coupled-expanding maps and one-sided symbolic dynamical systems

International Nuclear Information System (INIS)

Shi Yuming; Ju, Hyonhui; Chen Guanrong

2009-01-01

This paper studies relationships between coupled-expanding maps and one-sided symbolic dynamical systems. The concept of coupled-expanding map is extended to a more general one: coupled-expansion for a transitive matrix. It is found that the subshift for a transitive matrix is strictly coupled-expanding for the matrix in certain disjoint compact subsets; the topological conjugacy of a continuous map in its compact invariant set of a metric space to a subshift for a transitive matrix has a close relationship with that the map is strictly coupled-expanding for the matrix in some disjoint compact subsets. A certain relationship between strictly coupled-expanding maps for a transitive matrix in disjoint bounded and closed subsets of a complete metric space and their topological conjugacy to the subshift for the matrix is also obtained. Dynamical behaviors of subshifts for irreducible matrices are then studied and several equivalent statements to chaos are obtained; especially, chaos in the sense of Li-Yorke is equivalent to chaos in the sense of Devaney for the subshift, and is also equivalent to that the domain of the subshift is infinite. Based on these results, several new criteria of chaos for maps are finally established via strict coupled-expansions for irreducible transitive matrices in compact subsets of metric spaces and in bounded and closed subsets of complete metric spaces, respectively, where their conditions are weaker than those existing in the literature.

Expanded-boundary approach to impurity control in tokamaks

International Nuclear Information System (INIS)

Ohyabu, N.

1981-01-01

It is proposed to expand the outermost flux surfaces in tokamaks to divert the heat flux emerging from the plasma core. The expanded flux surfaces provide a large volume for radiative cooling. The radiative power at the boundary is enhanced by the effects of plasma flow as well as by a volumetric factor, and the resultant edge cooling and reduced heat load on the limiter may significantly retard impurity generation. Furthermore, it seems to be compatible with reactor engineering requirements. (author)

Influence Of Collapsing Matter On The Enveloping Expanding Universe

OpenAIRE

Choudhury, A. Latif

2005-01-01

Using a collapsing matter model at the center of an expanding universe as described by Weinberg we assume a special type of generated pressure. This pressure transmits into the surrounding expanding universe. Under certain restriction the ensuing hubble parameter is positive. The deacceleration parameter fluctuates with time, indicating that the universe accelerates for certain time and decelerates for other time intervals.

Analogue cosmological particle creation: Quantum correlations in expanding Bose-Einstein condensates

International Nuclear Information System (INIS)

Prain, Angus; Liberati, Stefano; Fagnocchi, Serena

2010-01-01

We investigate the structure of quantum correlations in an expanding Bose-Einstein condensate (BEC) through the analogue gravity framework. We consider both a 3+1 isotropically expanding BEC as well as the experimentally relevant case of an elongated, effectively 1+1 dimensional, expanding condensate. In this case we include the effects of inhomogeneities in the condensate, a feature rarely included in the analogue gravity literature. In both cases we link the BEC expansion to a simple model for an expanding spacetime and then study the correlation structure numerically and analytically (in suitable approximations). We also discuss the expected strength of such correlation patterns and experimentally feasible BEC systems in which these effects might be detected in the near future.

Chronic expanding hematoma in the retroperitoneal space: a case report

Science.gov (United States)

2013-01-01

Background Chronic expanding hematoma is a rare condition that develops after surgery, trauma, or injury. It can also develop at any location in the body in the absence of trauma. Clinical findings and various diagnostic imaging modalities can aid in the differential diagnosis of this condition. In general, hematomas are naturally reabsorbed and rarely cause serious problems. However, hematomas that develop slowly without a history of trauma, surgery, or bleeding disorders could be difficult to differentiate from soft tissue neoplasms. In the present case, we describe a patient, without any history or physical evidence of trauma, who exhibited a large chronic expanding hematoma in the retroperitoneal space that resulted in hydronephrosis because of the pressure exerted on the left ureter. Case presentation A 69-year-old man presented to our hospital with a swollen lesion in the left flank. A mass, 19 cm in diameter, was detected in the retroperitoneal space by computed tomography. We suspected the presence of a chronic expanding hematoma, soft tissue tumor, or left renal artery aneurysm. Surgical treatment was performed. However, postoperative histopathological examination indicated that the mass was a nonmalignant chronic expanding hematoma. No recurrence was observed during a 2-year follow-up period. Conclusion In patients without a history of trauma who present slowly growing masses, the differential diagnosis should include chronic expanding hematoma in addition to cysts and soft tissue tumors. Moreover, the use of magnetic resonance imaging and computed tomography is essential to differentiate between chronic expanding hematoma and soft tissue tumors. PMID:24237992

Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

OpenAIRE

Weerasinghe, Rohitha; Hounsham, Sandra

2017-01-01

Heat recovery bottoming cycles for internal combustion engines have opened new avenues for research into small steam expanders [1]. Dependable data for small steam expanders will allow us to predict on their suitability as bottoming cycle engines and the fuel economy achieved by using them as bottoming cycles. Wankel Engines, with its lower resistance properties at small scale provide excellent contenders for bottoming cycle expanders. Present paper is based on results of experiments carried ...

Experimental Investigation of the Performance of a Hermetic Screw-Expander Organic Rankine Cycle

Directory of Open Access Journals (Sweden)

Sung-Wei Hsu

2014-09-01

Full Text Available In this study, the authors experimentally investigate the performance of the organic Rankine cycle (ORC and screw expander under the influence of supply pressure and pressure ratio over the expander. Three tests were performed with expander pressure ratios of 2.4–3.5, 3.0–4.6, and 3.3–6.1, which cover the over-expansion and under-expansion operating modes. The test results show a maximum expander isentropic efficiency of 72.4% and a relative cycle efficiency of 10.5% at an evaporation temperature of 101 °C and condensation temperature of 45 °C. At a given pressure ratio over the expander, a higher supply pressure to the expander causes a higher expander isentropic efficiency and higher cycle efficiency in the over-expansion mode. However, in the under-expansion mode, the higher supply pressure results in a lower expander isentropic efficiency and adversely affects the cycle efficiency. The results also show that under the condition of operation at a given pressure ratio, a higher supply pressure yields a larger power output owing to the increased mass flow rate at the higher supply pressure. The study results demonstrate that a screw-expander ORC can be operated with a wide range of heat sources and heat sinks with satisfactory cycle efficiency.

Generating higher-order Lie algebras by expanding Maurer-Cartan forms

International Nuclear Information System (INIS)

Caroca, R.; Merino, N.; Salgado, P.; Perez, A.

2009-01-01

By means of a generalization of the Maurer-Cartan expansion method, we construct a procedure to obtain expanded higher-order Lie algebras. The expanded higher-order Maurer-Cartan equations for the case G=V 0 +V 1 are found. A dual formulation for the S-expansion multialgebra procedure is also considered. The expanded higher-order Maurer-Cartan equations are recovered from S-expansion formalism by choosing a special semigroup. This dual method could be useful in finding a generalization to the case of a generalized free differential algebra, which may be relevant for physical applications in, e.g., higher-spin gauge theories.

Dynamical 3-Space: Black Holes in an Expanding Universe

Directory of Open Access Journals (Sweden)

Rothall D. P.

2013-10-01

Full Text Available Black holes are usually studied without including effects of the expanding universe. However in some recent studies black holes have been embedded in an expanding universe, in order to determine the interplay, if any, of these two dynamical processes. Dynamical 3-space theory contains time independent solutions for black holes, which are spatial in-flows, and separately the time dependent Hubble expansion. This theory has explained numerous puzzles in observational astrophysics and contains 3 constants; G, - which from experimental data turns out to be the fine structure constant, and - which is a small but nonzero distance, possibly a Planck-type length. The Hubble expansion in the dynamical 3-space theory cannot be “switched o”, forcing the study, first, of isolated black holes coexisting with the expanding universe. It is shown that a time dependent black hole and expanding universe solution exists. The nature and implications of these solutions are discussed as they evolve over time. A dynamical network of black holes and induced linking cosmic filaments forming bubble structures is discussed, as a consequence of dynamical 3-space undergoing a dynamical breakdown of homogeneity and isotropy, even in the absence of baryonic matter.

'In situ' expanded graphite extinguishant

International Nuclear Information System (INIS)

Cao Qixin; Shou Yuemei; He Bangrong

1987-01-01

This report is concerning the development of the extinguishant for sodium fire and the investigation of its extinguishing property. The experiment result shows that 'in situ' expanded graphite developed by the authors is a kind of extinguishant which extinguishes sodium fire quickly and effectively and has no environment pollution during use and the amount of usage is little

An Expanding Universe in the Classroom.

Science.gov (United States)

Chandler, David

1991-01-01

Two computer-generated star charts that can be used as overlay transparencies to show an expanding universe are presented. Directions on how to use the star charts to determine the Hubble constant and the age of the universe are provided. (KR)

Expanding Your Horizon 2015

CERN Multimedia

Kaltenhauser, Kristin

2015-01-01

Expanding your horizons is a bi-annual “Science Day” for girls aged 11 to 14, held at the University of Geneva on 14 November. The girls had the opportunity to take part in hands-on workshops held by local professional women in the field of science, mathematics, engineering and technology. For the fourth time, CERN was part of this event, offering three workshops as well as a booth at the Discovery Fair, including Higgnite, an interactive visualization of the Higgs Field.

Production of durable expanded perlite microspheres in a Vertical Electrical Furnace

Science.gov (United States)

Panagiotis, M.; Angelopoulos, P.; Taxiarchou, M.; Paspaliaris, I.

2016-04-01

Expanded perlite constitutes one of the most competitive insulating materials that is widely used in construction and manufacturing industry due to its unique properties combination; it is white, natural, lightweight, chemically inert, and exhibits superior insulating properties (thermal and acoustic) and fire resistance. Conventionally, perlite expansion is performed in vertical gas-fired furnaces; the conventional perlite expansion process has certain disadvantages which affect expanded products quality, thus limiting their performance and range of applications. In order to overcome the drawbacks of the conventional expansion technique, a new perlite expansion process has been designed based on a vertical electrical furnace (VEF). In the current study, fine perlite samples (-150 μm) from Milos Island, Greece, were expansed in the novel VEF and a conventional gas-fired furnace with the aim to evaluate and compare the main physical properties of the expanded products. The novel expanded perlite particles were characterised by superior properties, namely increased compression strength, competitive water and oil absorption capability, size homogeneity, spherical shape and decreased surface porosity in comparison to conventionally expanded samples.

Functional Self-Expandable Metal Stents in Biliary Obstruction

Science.gov (United States)

Kwon, Chang-Il; Ko, Kwang Hyun; Hahm, Ki Baik

2013-01-01

Biliary stents are widely used not only for palliative treatment of malignant biliary obstruction but also for benign biliary diseases. Each plastic stent or self-expandable metal stent (SEMS) has its own advantages, and a proper stent should be selected carefully for individual condition. To compensate and overcome several drawbacks of SEMS, functional self-expandable metal stent (FSEMS) has been developed with much progress so far. This article looks into the outcomes and defects of each stent type for benign biliary stricture and describes newly introduced FSEMSs according to their functional categories. PMID:24143314

Expanding Your Horizons Conference in Geneva

CERN Multimedia

Chromek-Burckhart, Doris

2011-01-01

CERN and its experiments participated in Expanding Your Horizons (EYH) in Science and Mathematics conference in Geneva on 12th November. EYH nurture girls' interest in science and math courses to encourage them to consider careers in science, technology, engineering, and math.

Expanding economic opportunities in protracted displacement

OpenAIRE

Miki Takahashi; Michael Moroz; Jonathan Peters; Jason Pronyk; Richard Barltrop

2018-01-01

Welcome progress has been made towards realising commitments made by international donors and host country governments to expand economic opportunities for Syrian refugees and host communities in neighbouring countries. However targets and commitments also bring new challenges, and evidence must underpin new policies.

Expanding Advanced Civilizations in the Universe

Science.gov (United States)

Gros, C.

The 1950 lunch-table remark by Enrico Fermi `Where is everybody' has started intensive scientific and philosophical discussions about what we call nowadays the `Fermi paradox': If there had been ever a single advanced civilization in the cosmological history of our galaxy, dedicated to expansion, it would have had plenty of time to colonize the entire galaxy via exponential growth. No evidence of present or past alien visits to earth are known to us, leading to the standard conclusion that no advanced expanding civilization has ever existed in the milky-way. This conclusion rest fundamentally on the ad-hoc assumption, that any alien civilizations dedicated to expansion at one time would remain dedicated to expansions forever. Considering our limited knowledge about alien civilizations we need however to relax this basic assumption. Here we show that a substantial and stable population of expanding advanced civilization might consequently exist in our galaxy.

Numerical simulation of a twin screw expander for performance prediction

Science.gov (United States)

Papes, Iva; Degroote, Joris; Vierendeels, Jan

2015-08-01

With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are considered as constant and they are derived from 3D Computational Fluid Dynamic calculations at given working conditions and applied to all other working conditions. The outcome of the mathematical model is the P-V indicator diagram which is compared to CFD results of the same twin screw expander. Since CFD calculations require significant computational time, developed mathematical model can be used for the faster performance prediction.

Expanded austenite, crystallography and residual stress

DEFF Research Database (Denmark)

Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

2010-01-01

The identity of expanded austenite as developing during low temperature nitriding and/or carburising of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article, recent results obtained with (a) homogeneous samples of various uniform ...

Expanded austenite; crystallography and residual stress

DEFF Research Database (Denmark)

Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

2009-01-01

The identity of expanded austenite as developing during low temperature nitriding and/or carburizing of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article recent results obtained with i) homogeneous samples of various uniform co...

Coping with expanding nursing practice, knowledge, and technology.

Science.gov (United States)

Gaudinski, M A

1979-10-01

Nurses utilize transcultural, transactional, systems, primary, and interdisciplinary approaches to physiological and psychosocial components of patient care. Expanded roles, as well as advances in knowledge and technology have prepared nurses for critical, specialized, primary, aerospace, and independent nursing practice. Exciting as they are, nursing's expanded roles and practices frequently contribute to the burnout and distress phenomena increasingly observed in practicing health care professionals. Causes and symptoms of the burnout distress phenomena are many and varied. Selye, Shubin, Maslach, and others adeptly identified and wrote on the phenomena as it specifically relates to nurses and the many facets of nursing practice. Rather than utilizing crisis intervention coping techniques, preventive strategies and adaptations are suggested. This paper reviews and discusses: 1. Factors associated with burnout-distress phenomena identified in professional literature; 2. Identification of factors associated with expanded roles and practice which contribute to burnout stress; 3. Identification of factors in military and civilian air ambulance and aeromedical evacuation systems which contribute to burnout stress; 4. Recommendations for strategies to prevent and cope with burnout distress factors.

Dynamics of a radially expanding liquid sheet: Experiments

Science.gov (United States)

Majumdar, Nayanika; Tirumkudulu, Mahesh

2017-11-01

A recent theory predicts that sinuous waves generated at the center of a radially expanding liquid sheet grow spatially even in absence of a surrounding gas phase. Unlike flat liquid sheets, the thickness of a radially expanding liquid sheet varies inversely with distance from the center of the sheet. To test the predictions of the theory, experiments were carried out on a horizontal, radially expanding liquid sheet formed by collision of a single jet on a solid impactor. The latter was placed on a speaker-vibrator with controlled amplitude and frequency. The growth of sinuous waves was determined by measuring the wave surface inclination angle using reflected laser light under both atmospheric and sub-atmospheric pressure conditions. It is shown that the measured growth rate matches with the predictions of the theory over a large range of Weber numbers for both pressure conditions suggesting that the thinning of the liquid sheet plays a dominant role in setting the growth rate of sinuous waves with minimal influence of the surrounding gas phase on its dynamics. IIT Bombay.

Why has medicine expanded? The role of consumers.

Science.gov (United States)

Zheng, Hui

2015-07-01

In the past 50years, the field of medicine has expanded dramatically in many Western societies. Despite substantial improvements in objective health measures, there has not been a commensurate increase in assessments of subjective health. We hypothesize that medical expansion may lower people's subjective health perceptions, leading to an increase in health care utilization, and, in turn, fueling further medical expansion. We use OECD (Organization for Economic Co-operation and Development) Health Data, World Development Indicators, the World Values Survey, and the European Values Study to fit a difference-in-differences model that removes unobserved cross-national heterogeneity and any period trend that is shared across nations. We find that three dimensions of medical expansion at the societal level (medical investment, medical professionalization/specialization, and an expanded pharmaceutical industry) negatively affect individual subjective health. These findings are robust to different model specifications. We conclude by discussing possible explanations for the adverse effect of medical expansion on subjective health, and how this effect may be related to other mechanisms through which medicine expands. Copyright © 2015 Elsevier Inc. All rights reserved.

ASPS clinical practice guideline summary on breast reconstruction with expanders and implants.

Science.gov (United States)

Alderman, Amy; Gutowski, Karol; Ahuja, Amy; Gray, Diedra

2014-10-01

After reading this article, participants should be able to: 1. Understand the evidence regarding the timing of expander/implant breast reconstruction in the setting of radiation therapy. 2. Discuss the implications of a patient's risk factors for possible outcomes and complications of expander/implant breast reconstruction. 3. Implement proper prophylactic antibiotic protocols. 4. Use the guidelines to improve their own clinical outcomes and reduce complications. In March of 2013, the Executive Committee of the American Society of Plastic Surgeons approved an evidence-based guideline on breast reconstruction with expanders and implants, as developed by a guideline-specific work group commissioned by the society's Health Policy Committee. The guideline addresses ten clinical questions: patient education, immediate versus delayed reconstruction, risk factors, radiation therapy, chemotherapy, hormonal therapy, antibiotic prophylaxis, acellular dermal matrix, monitoring for cancer recurrence, and oncologic outcomes associated with implant-based reconstruction. The evidence indicates that patients undergoing mastectomy should be offered a preoperative referral to a plastic surgeon. Evidence varies regarding the association between postoperative complications and timing of postmastectomy expander/implant breast reconstruction. Evidence is limited regarding the optimal timing of expand/implant reconstruction in the setting of radiation therapy but suggests that irradiation to the expander or implant is associated with an increased risk of postoperative complications. Evidence also varies regarding the association between acellular dermal matrix and surgical complications in the setting of postmastectomy expander/implant reconstruction. Data support the use of an appropriate preoperative antibiotic, but antibiotics should be discontinued within 24 hours of the procedure, unless a surgical drain is present. Furthermore, postmastectomy expander/implant breast reconstruction

Expanding economic opportunities in protracted displacement

Directory of Open Access Journals (Sweden)

Miki Takahashi

2018-02-01

Full Text Available Welcome progress has been made towards realising commitments made by international donors and host country governments to expand economic opportunities for Syrian refugees and host communities in neighbouring countries. However targets and commitments also bring new challenges, and evidence must underpin new policies.

Magnetic fields in an expanding universe

International Nuclear Information System (INIS)

Kastor, David; Traschen, Jennie

2014-01-01

We find a solution to 4D Einstein–Maxwell theory coupled to a massless dilaton field, for all values of the dilaton coupling, describing a Melvin magnetic field in an expanding universe with ‘stiff matter’ equation of state parameter w = +1. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling a<1/√3 and more dispersed for a>1/√3. An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For a = 0 the magnetic flux through a disc of fixed comoving radius is proportional to the proper area of the disc. This result disagrees with the usual expectation based on a test magnetic field that this flux should be constant, and we show why this difference arises. We also find a Melvin solution in an accelerating universe with w = −7/9 for a dilaton field with a certain exponential potential. (paper)

The Army’s Military Decision Making: Adequate or Update and Expand

Science.gov (United States)

2008-05-22

requires creative efforts by every Soldier and Marine.”63 Expanding the soldier base would allow for greater creativity in order to better deal with...military can overcome these deficiencies? I believe that to achieve the initial stage of success would be to create a segment of soldier telecommuters ...problems. By expanding the thinking base, the Army can expand the breadth and depth into areas currently unreachable. Telecommuting allows for several

Performance study of a twin-screw expander used in a geothermal organic Rankine cycle power generator

International Nuclear Information System (INIS)

Tang, Hao; Wu, Huagen; Wang, Xiaolin; Xing, Ziwen

2015-01-01

The ORC (organic Rankine cycle) system is an effective technology to generate electricity from low temperature heat sources. The twin-screw expander is a key component that is commonly used in the small-to-medium capacity ORC system to convert thermal energy into work. In this paper, the performance of a twin-screw expander is theoretically and experimentally studied. A mathematical model is developed and subsequently validated using experimental data. The effect of several important factors including expander speed, suction pressure and inlet superheat on the expander performance is investigated. Results indicate that the expander speed and suction pressure have large influences on the expander performance, while the inlet superheat has relatively small effect. The isentropic efficiency of the expander decreases from 0.88 to 0.6 and the expander volumetric efficiency decreases from 0.88 to 0.7 as the expander rotational speed increases from 1250 to 6000 rpm. The results further show that the expander volumetric efficiency decreases from 0.91 to 0.85 as the expander suction pressure increases from 0.33 to 0.47 MPa. Furthermore, the energy conversion efficiency of the studied ORC system using the twin-screw expander is as high as 7.5% under the site conditions. - Highlights: • Performance of a twin-screw expander used in an ORC (organic Rankine cycle) system was studied. • A thermodynamic model was developed for this purpose and experimentally validated. • Effect of several key factors on the expander performance was investigated. • Suction pressure has a large influence on the expander performance. • Twin-screw expanders can be operated with a wide range of heat source temperatures.

Custom Ontologies for Expanded Network Analysis

Science.gov (United States)

2006-12-01

for Expanded Network Analysis. In Visualising Network Information (pp. 6-1 – 6-10). Meeting Proceedings RTO-MP-IST-063, Paper 6. Neuilly-sur-Seine...Even to this day, current research groups are working to develop an approach that involves taking all available text, video, imagery and audio and

Effect of expansion temperature of expandable graphite on microstructure evolution of expanded graphite during high-energy ball-milling

International Nuclear Information System (INIS)

Yue Xueqing; Li Liang; Zhang Ruijun; Zhang Fucheng

2009-01-01

Two expanded graphites (EG), marked as EG-1 and EG-2, were prepared by rapid heating of expandable graphite to 600 and 1000 deg. C, respectively, and ball milled in a high-energy mill (planetary-type) under air atmosphere. The microstructure evolution of the ball-milled samples was characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD analysis shows that the evolution degree of the average crystallite thickness along the c-axis (L c ) of EG-2 is lower than that of EG-1 during the milling process. From the HRTEM images of the samples after 100 h ball-milling, slightly curved graphene planes can be frequently observed both in the two EGs, however, EG-1 and EG-2 exhibit sharply curved graphene planes and smoothly curved graphene planes with high bending angles, respectively.

Effects of silicone expanders and implants on echocardiographic image quality after breast reconstruction.

Science.gov (United States)

Pignatti, Marco; Mantovani, Francesca; Bertelli, Luca; Barbieri, Andrea; Pacchioni, Lucrezia; Loschi, Pietro; De Santis, Giorgio

2013-08-01

Use of silicone expanders and implants is the most common breast reconstruction technique after mastectomy. Postmastectomy patients often need echocardiographic monitoring of potential cardiotoxicity induced by cancer chemotherapy. The impairment of the echocardiographic acoustic window caused by silicone implants for breast augmentation has been reported. This study investigates whether the echocardiographic image quality was impaired in women reconstructed with silicone expanders and implants. The records of 44 consecutive women who underwent echocardiographic follow-up after breast reconstruction with expanders and implants at the authors' institution from January of 2000 to August of 2012 were reviewed. The population was divided into a study group (left or bilateral breast expanders/implants, n=30) and a control group (right breast expanders/implants, n=14). The impact of breast expanders/implants on echocardiographic image quality was tested (analysis of covariance model). Patients with a breast expander/implant (left or bilateral and right breast expanders/implants) were included. The mean volume of the breast devices was 353.2±125.5 cc. The quality of the echocardiographic images was good or sufficient in the control group; in the study group, it was judged as adequate in only 50 percent of cases (15 patients) and inadequate in the remaining 15 patients (pimplants in postmastectomy left breast reconstruction considerably reduce the image quality of echocardiography. This may have important clinical implications, given the need for periodic echocardiographic surveillance before and during chemotherapy. Therapeutic, III.

Interlayer expanded molybdenum disulfide nanosheets assembly for electrochemical supercapacitor with enhanced performance

International Nuclear Information System (INIS)

Xiao, Huaqing; Wang, Shutao; Zhang, Shuo; Wang, Yihe; Xu, Qingfei; Hu, Wenjie; Zhou, Yan; Wang, Zhaojie; An, Changhua; Zhang, Jun

2017-01-01

Rational structural design for electrode materials is essential for fabricating high performance supercapacitors. In this work, we demonstrated a novel way to prepare incompact MoS_2 nanosheets assembled nanorods with the interlayer of MoS_2 nanosheets expanded to 0.89 nm, namely layer expanded MoS_2 nanorods (LE-MoS_2 NRs). The material was characterized by XRD, XPS and electron microscopes. The XRD data and HRTEM images confirmed the existence of expanded interlayer of MoS_2 nanosheets. N_2 adsorption-desorption isotherms of LE-MoS_2 NRs indicated high specific area up to 37.0 m"2 g"−"1. It was found that the expanded interlayer spacing can benefit the ion transportation within the MoS_2 interlayers. The as-prepared electrode material showed capacitance up to 231 F g"−"1 at 1 A g"−"1 charge-discharge current and cycling stability test indicated high capacitance of 177 F g"−"1 was retained after 1000 cycles. - Highlights: • High performance electrochemical supercapacitor electrode material. • Interlayer expanded MoS_2 to achieve enhanced capacitance. • Facile hydrothermal synthesis of interlayer expanded MoS_2. • MoS_2 nanosheets assembled incompact nanorods.

Industrial implementation of plasma deposition using the expanding thermal plasma technique

NARCIS (Netherlands)

Sanden, van de M.C.M.; Oever, van den P.J.; Creatore, M.; Schaepkens, M.; Miebach, T.; Iacovangelo, C.D.; Bosch, R.C.M.; Bijker, M.D.; Evers, M.F.J.; Schram, D.C.; Kessels, W.M.M.

2004-01-01

Two successful industrial implementations of the expanding thermal plasma setup, a novel plasma source, obtaining high deposition rate are discussed. The Ar/O2/hexamethyldisiloxane and Ar/O2/octamethyl-cyclosiloxane-fed expanding thermal plasma setup is used to deposit scratch resistant silicone

DISRUPTIVE TECHNOLOGIES: AN EXPANDED VIEW

OpenAIRE

JAMES M. UTTERBACK; HAPPY J. ACEE

2005-01-01

The term "disruptive technology" as coined by Christensen (1997, The Innovator's Dilemma; How New Technologies Cause Great Firms to Fail. Harvard Business School Press) refers to a new technology having lower cost and performance measured by traditional criteria, but having higher ancillary performance. Christensen finds that disruptive technologies may enter and expand emerging market niches, improving with time and ultimately attacking established products in their traditional markets. This...

Women Engineering Faculty: Expanding the Pipeline

Science.gov (United States)

Greni, Nadene Deiterman

2006-01-01

The purpose for this case study was to explore the features of undergraduate engineering departmental and college support that influenced the persistence of women students. Women engineering faculty members were among the participants at three Land Grant universities in the Midwest. The data revealed the theme, Expanding the Pipeline, and…

Porous expandable device for attachment to bone tissue

Science.gov (United States)

Rybicki, Edmund F.; Wheeler, Kenneth Ray; Hulbert, Lewis E.; Karagianes, Manuel Tom; Hassler, Craig R.

1977-01-01

A device for attaching to substantially solid living bone tissue, comprising a body member having an outer surface shaped to fit approximately into an empty space in the tissue and having pores into which the tissue can grow to strengthen the bond between the device and the tissue, and adjustable means for expanding the body member against the tissue to an extent such as to provide a compressive stress capable of maintaining a snug and stable fit and of enhancing the growth of the tissue into the pores in the body member. The expanding means is adjustable to provide a stress between the tissue and the body member in the range of about 150 to 750 psi, typically 150 to 350 psi. Typically the body member comprises an expandable cylindrical portion having at least one radial slit extending longitudinally from a first end to the vicinity of the opposite (second) end thereof, at least one radial slit extending longitudinally from the second end to the vicinity of the first end thereof, and a tapered cylindrical hole extending coaxially from a wider circular opening in the first end to a narrower circular opening communicating with the second end.

Prospects for expanded utilization of biogas in Germany

International Nuclear Information System (INIS)

Poeschl, Martina; Ward, Shane; Owende, Philip

2010-01-01

The prospects for expanded utilization of biogas systems in German was analysed, by identifying the operational and policy factors affecting the complete chain of processes from implementation process for biogas plants, through to biogas production and utilization. It was found that the Renewable Energies Act (EEG) and energy tax reliefs provide bases for the support of expanded utilization. Upgrading of biogas to natural gas quality for utilization in the transportation sector was arguably the most promising technology that could support rapid utilization expansion. Sustainable deployment of biogas systems in light of the unstable feedstock prices and availability, and the need for subsidy-free operation in the long term requires; enhancement of feedstock flexibility and quality characteristics to maximise gas yield, and optimisation of the anaerobic digestion process management. Assessment of energy balance and potential environmental impacts of the integrated process chain provides a holistic assessment of sustainability. The results also support the development and foster of policies and framework for development of biogas as environmentally friendly energy resource, among a mix of renewable energy sources, hence, compete favourably with fossil fuels to enhance the prospects for expanded utilization. (author)

An automated baseline correction protocol for infrared spectra of atmospheric aerosols collected on polytetrafluoroethylene (Teflon) filters

Science.gov (United States)

Kuzmiakova, Adele; Dillner, Ann M.; Takahama, Satoshi

2016-06-01

A growing body of research on statistical applications for characterization of atmospheric aerosol Fourier transform infrared (FT-IR) samples collected on polytetrafluoroethylene (PTFE) filters (e.g., Russell et al., 2011; Ruthenburg et al., 2014) and a rising interest in analyzing FT-IR samples collected by air quality monitoring networks call for an automated PTFE baseline correction solution. The existing polynomial technique (Takahama et al., 2013) is not scalable to a project with a large number of aerosol samples because it contains many parameters and requires expert intervention. Therefore, the question of how to develop an automated method for baseline correcting hundreds to thousands of ambient aerosol spectra given the variability in both environmental mixture composition and PTFE baselines remains. This study approaches the question by detailing the statistical protocol, which allows for the precise definition of analyte and background subregions, applies nonparametric smoothing splines to reproduce sample-specific PTFE variations, and integrates performance metrics from atmospheric aerosol and blank samples alike in the smoothing parameter selection. Referencing 794 atmospheric aerosol samples from seven Interagency Monitoring of PROtected Visual Environment (IMPROVE) sites collected during 2011, we start by identifying key FT-IR signal characteristics, such as non-negative absorbance or analyte segment transformation, to capture sample-specific transitions between background and analyte. While referring to qualitative properties of PTFE background, the goal of smoothing splines interpolation is to learn the baseline structure in the background region to predict the baseline structure in the analyte region. We then validate the model by comparing smoothing splines baseline-corrected spectra with uncorrected and polynomial baseline (PB)-corrected equivalents via three statistical applications: (1) clustering analysis, (2) functional group quantification

Expanding CTE Opportunities through Blended Learning

Science.gov (United States)

McKinstry, Elizabeth

2012-01-01

The global economy, 21st century skills, knowledge society, college and career readiness, digital and project-based learning are all common terms to educators who are expanding their learning environments beyond the classroom to meet the needs of all students. It is common knowledge that the rapid technological advances of this century have…

Quark and gluon production from a boost-invariantly expanding color electric field

Science.gov (United States)

Taya, Hidetoshi

2017-07-01

Particle production from an expanding classical color electromagnetic field is extensively studied, motivated by the early stage dynamics of ultrarelativistic heavy ion collisions. We develop a formalism at one-loop order to compute the particle spectra by canonically quantizing quark, gluon, and ghost fluctuations under the presence of such an expanding classical color background field; the canonical quantization is done in the τ -η coordinates in order to take into account manifestly the expanding geometry. As a demonstration, we model the expanding classical color background field by a boost-invariantly expanding homogeneous color electric field with lifetime T , for which we obtain analytically the quark and gluon production spectra by solving the equations of motion of QCD nonperturbatively with respect to the color electric field. In this paper we study (i) the finite lifetime effect, which is found to modify significantly the particle spectra from those expected from the Schwinger formula; (ii) the difference between the quark and gluon production; and (iii) the quark mass dependence of the production spectra. Implications of these results to ultrarelativistic heavy ion collisions are also discussed.

On the Propagation of Light in an Expanding Universe

Directory of Open Access Journals (Sweden)

Yuri Heymann

2013-07-01

Full Text Available The equation of the propagation of light in an expanding Universe is derived based on the definition of comoving distances. A numerical method is proposed to solve this equation jointly with the Friedmann equation. As the equation of the propagation of light in an expanding Universe defines a horizon of the visible Universe, this puts a constraint on cosmological models in order to be consistent with an upper limit for redshifts observed from galaxies. This puzzle is challenging current expansionist cosmological models.

Interlayer expanded molybdenum disulfide nanosheets assembly for electrochemical supercapacitor with enhanced performance

Energy Technology Data Exchange (ETDEWEB)

Xiao, Huaqing; Wang, Shutao; Zhang, Shuo; Wang, Yihe; Xu, Qingfei; Hu, Wenjie [College of Science, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China); Zhou, Yan, E-mail: yanzhou@upc.edu.cn [College of Science, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China); State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China); Wang, Zhaojie [College of Science, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China); An, Changhua [College of Science, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China); College of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, 300384 (China); Zhang, Jun, E-mail: zhangj@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao Economic Development Zone, Qingdao, Shandong, 266580 (China)

2017-05-01

Rational structural design for electrode materials is essential for fabricating high performance supercapacitors. In this work, we demonstrated a novel way to prepare incompact MoS{sub 2} nanosheets assembled nanorods with the interlayer of MoS{sub 2} nanosheets expanded to 0.89 nm, namely layer expanded MoS{sub 2} nanorods (LE-MoS{sub 2} NRs). The material was characterized by XRD, XPS and electron microscopes. The XRD data and HRTEM images confirmed the existence of expanded interlayer of MoS{sub 2} nanosheets. N{sub 2} adsorption-desorption isotherms of LE-MoS{sub 2} NRs indicated high specific area up to 37.0 m{sup 2} g{sup −1}. It was found that the expanded interlayer spacing can benefit the ion transportation within the MoS{sub 2} interlayers. The as-prepared electrode material showed capacitance up to 231 F g{sup −1} at 1 A g{sup −1} charge-discharge current and cycling stability test indicated high capacitance of 177 F g{sup −1} was retained after 1000 cycles. - Highlights: • High performance electrochemical supercapacitor electrode material. • Interlayer expanded MoS{sub 2} to achieve enhanced capacitance. • Facile hydrothermal synthesis of interlayer expanded MoS{sub 2}. • MoS{sub 2} nanosheets assembled incompact nanorods.

13 CFR 120.835 - Application to expand an Area of Operations.

Science.gov (United States)

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Application to expand an Area of Operations. 120.835 Section 120.835 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION BUSINESS... program responsibilities in the proposed area. (b) Local Economic Area Expansion. A CDC seeking to expand...

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.

CFD simulations of compressed air two stage rotary Wankel expander – Parametric analysis

International Nuclear Information System (INIS)

Sadiq, Ghada A.; Tozer, Gavin; Al-Dadah, Raya; Mahmoud, Saad

2017-01-01

Highlights: • CFD ANSYS-Fluent 3D simulation of Wankel expander is developed. • Single and two-stage expander’s performance is compared. • Inlet and outlet ports shape and configurations are investigated. • Isentropic efficiency of two stage Wankel expander of 91% is achieved. - Abstract: A small scale volumetric Wankel expander is a powerful device for small-scale power generation in compressed air energy storage (CAES) systems and Organic Rankine cycles powered by different heat sources such as, biomass, low temperature geothermal, solar and waste heat leading to significant reduction in CO_2 emissions. Wankel expanders outperform other types of expander due to their ability to produce two power pulses per revolution per chamber additional to higher compactness, lower noise and vibration and lower cost. In this paper, a computational fluid dynamics (CFD) model was developed using ANSYS 16.2 to simulate the flow dynamics for a single and two stage Wankel expanders and to investigate the effect of port configurations, including size and spacing, on the expander’s power output and isentropic efficiency. Also, single-stage and two-stage expanders were analysed with different operating conditions. Single-stage 3D CFD results were compared to published work showing close agreement. The CFD modelling was used to investigate the performance of the rotary device using air as an ideal gas with various port diameters ranging from 15 mm to 50 mm; port spacing varying from 28 mm to 66 mm; different Wankel expander sizes (r = 48, e = 6.6, b = 32) mm and (r = 58, e = 8, b = 40) mm both as single-stage and as two-stage expanders with different configurations and various operating conditions. Results showed that the best Wankel expander design for a single-stage was (r = 48, e = 6.6, b = 32) mm, with the port diameters 20 mm and port spacing equal to 50 mm. Moreover, combining two Wankel expanders horizontally, with a larger one at front, produced 8.52 kW compared

Historical Notes on the Expanding Universe

Science.gov (United States)

Way, Michael J.; Belenkyi, Ari; Nussbaumer, Harry; Peacock, John

2014-01-01

The article Measuring the Hubble constant by Mario Livio and Adam Riess (Physics Today, October 2013, page 41) reviewed studies of the expanding universe from the 1920s to the present. Although the history of the subject underwent considerable compression to fit the length of a magazine article, we think it may leave a misleading impression of some of the key steps to our current understanding. We therefore offer the following clarifications. Most significantly, papers by Arthur Eddington and by Willem de Sitter in 1930, who successfully promoted Georges Lematres 1927 article for the Scientific Society of Brussels, effected a paradigm shift in interpretation of extragalactic redshifts in 1930. Before then, the astronomical community was generally unaware of the existence of nonstatic cosmological solutions and did not broadly appreciate that redshifts could be thought of locally as Doppler shifts in an expanding matter distribution. Certainly, in 1929 Edwin Hubble referred only to the de Sitter solution of 1917. At the time, the relation between distance and redshift predicted in that model was generally seen purely as a manifestation of static spacetime curvature.

Determination of the concentration dependent diffusion coefficient of nitrogen in expanded austenite

DEFF Research Database (Denmark)

Christiansen, Thomas; Somers, Marcel A. J.

2008-01-01

The concentration dependent diffusion coefficient of nitrogen in expanded austenite was determined from of the rate of retracting nitrogen from thin initially N-saturated coupons. Nitrogen saturated homogeneous foils of expanded austenite were obtained by nitriding AISI 304 and AISI 316 in pure...... in the composition range where nitrogen can be extracted by hydrogen gas at the diffusion temperature. Numerical simulation of the denitriding experiments shows that the thus determined concentration dependent diffusion coefficients are an accurate approximation of the actual diffusivity of nitrogen in expanded...... ammonia at 693 K and 718 K. Denitriding experiments were performed by equilibrating the foils with a successively lower nitrogen activity, as imposed by a gas mixture of ammonia and hydrogen. The concentration dependent diffusion coefficient of nitrogen in expanded austenite was approximated...

Expanding the Education Universe: A Fifty-State Strategy for Course Choice

Science.gov (United States)

Brickman, Michael

2014-01-01

After twenty years of expanding school-choice options, state leaders, educators, and families have a new tool: course choice, a strategy for students to learn from unconventional providers that might range from top-tier universities or innovative community colleges to local employers, labs, or hospitals. In "Expanding the Education Universe:…

Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application

Directory of Open Access Journals (Sweden)

Osoko Shonda

2012-06-01

Full Text Available Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in fuel consumption. One solution is to integrate a heat recovery system based on a steam Rankine cycle. The key component in such a system is the expander, which has a strong impact on the system’s performance. A survey of different expander technologies leads us to select the reciprocating expander as the most promising one for an automotive application. This paper therefore proposes a steady-state semi-empirical model of the expander device developed under the Engineering Equation Solver (EES environment. The ambient and mechanical losses as well as internal leakage were taken into account by the model. By exploiting the expander manufacturer’s data, all the parameters of the expander model were identified. The model computes the mass flow rate, the power output delivered and the exhaust enthalpy of the steam. The maximum deviation between predictions and measurement data is 4.7%. A performance study of the expander is carried out and shows that the isentropic efficiency is quite high and increases with the expander rotary speed. The mechanical efficiency depends on mechanical losses which are quite high, approximately 90%. The volumetric efficiency was also evaluated.

The motion of an isolated gas group in expanding universe

International Nuclear Information System (INIS)

Zhang Banggu

1993-01-01

The contraction of an isolated gas group in the expanding universe has been discussed. It is found that in addition to the contracted conditions of the static isolated gas group, the initial gas group is straticulate statistical uniform and the initial radius is larger than a critical value D γ -1 , the contracted conditions of expanding case also include that the Hubble constant H is smaller than a constant D t

Intelligent Flexible Materials for Space Structures: Expandable Habitat Engineering Development Unit

Science.gov (United States)

Hinkle, Jon; Sharpe, George; Lin, John; Wiley, Cliff; Timmers, Richard

2010-01-01

Expandable habitable elements are an enabling technology for human exploration in space and on planetary surfaces. Large geometries can be deployed from a small launch volume, allowing greater mission capability while reducing mass and improving robustness over traditional rigid shells. This report describes research performed by ILC Dover under the Intelligent Flexible Materials for Space Structures program on the design and manufacture of softgoods for LaRC's Expandable Habitat Engineering Development Unit (EDU). The EDU is a full-scale structural test article of an expandable hybrid habitat, integrating an expandable softgoods center section with two rigid end caps. The design of the bladder, restraint layer and a mock-up Thermal Micrometeoroid Cover is detailed together with the design of the interface hardware used to attach them to the end caps. The integration and design of two windows and a floor are also covered. Analysis was performed to study the effects of the open weave design, and to determine the correct webbing and fabric configuration. Stress analyses were also carried out on the interfaces between the softgoods and the end caps and windows. Testing experimentally determined the strength of the fabric and straps, and component testing was used to proof several critical parts of the design. This program established new manufacturing and design techniques that can be applied to future applications in expandable structures.

Measuring the Plasma Density of a Ferroelectric Plasma Source in an Expanding Plasma

International Nuclear Information System (INIS)

Dunaevsky, A.; Fisch, N.J.

2003-01-01

The initial density and electron temperature at the surface of a ferroelectric plasma source were deduced from floating probe measurements in an expanding plasma. The method exploits negative charging of the floating probe capacitance by fast flows before the expanding plasma reaches the probe. The temporal profiles of the plasma density can be obtained from the voltage traces of the discharge of the charged probe capacitance by the ion current from the expanding plasma. The temporal profiles of the plasma density, at two different distances from the surface of the ferroelectric plasma source, could be further fitted by using the density profiles for the expanding plasma. This gives the initial values of the plasma density and electron temperature at the surface. The method could be useful for any pulsed discharge, which is accompanied by considerable electromagnetic noise, if the initial plasma parameters might be deduced from measurements in expanding plasma

Preparation, quantitative surface analysis, intercalation characteristics and industrial implications of low temperature expandable graphite

Science.gov (United States)

Peng, Tiefeng; Liu, Bin; Gao, Xuechao; Luo, Liqun; Sun, Hongjuan

2018-06-01

Expandable graphite is widely used as a new functional carbon material, especially as fire-retardant; however, its practical application is limited due to the high expansion temperature. In this work, preparation process of low temperature and highly expandable graphite was studied, using natural flake graphite as raw material and KMnO4/HClO4/NH4NO3 as oxidative intercalations. The structure, morphology, functional groups and thermal properties were characterized during expanding process by Fourier transform infrared spectroscopy (FTIR), Raman spectra, thermo-gravimetry differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope (SEM). The analysis showed that by oxidation intercalation, some oxygen-containing groups were grafted on the edge and within the graphite layer. The intercalation reagent entered the graphite layer to increase the interlayer spacing. After expansion, the original flaky expandable graphite was completely transformed into worm-like expanded graphite. The order of graphite intercalation compounds (GICs) was proposed and determined to be 3 for the prepared expandable graphite, based on quantitative XRD peak analysis. Meanwhile, the detailed intercalation mechanisms were also proposed. The comprehensive investigation paved a benchmark for the industrial application of such sulfur-free expanded graphite.

Tunneling in expanding Universe: Euclidean and Hamiltonian approaches

International Nuclear Information System (INIS)

Goncharov, A.S.; Linde, A.D.

1986-01-01

The theory of the false vacuum decay in de Sitter space and in the inflationary Universe, and also the theory of the Universe creation ''from nothing'' are discussed. This explained why tunneling in the inflationary Universe differs from that in de Sitter space and cannot be exactly homogeneous. It is shown that in several important cases the Euclidean approach should be considerably modified or is absolutely inapplicable for the description of tunneling in the expanding Universe and of the process of the quantum creation of the Universe. The Hamiltonian approach to the theory of tunneling in expanding Universe is developed. The results obtained by this method are compared with the results obtained by the Euclidean approach

Infrastructure Requirements for an Expanded Fuel Ethanol Industry

Energy Technology Data Exchange (ETDEWEB)

Reynolds, Robert E. [Downstream Alternatives, Inc., South Bend, IN (United States)

2002-01-15

This report provides technical information specifically related to ethanol transportation, distribution, and marketing issues. This report required analysis of the infrastructure requirements for an expanded ethanol industry.

Waste Heat-to-Power Using Scroll Expander for Organic Rankine Bottoming Cycle

Energy Technology Data Exchange (ETDEWEB)

Dieckmann, John [TIAX LLC, Lexington, MA (United States); Smutzer, Chad [TIAX LLC, Lexington, MA (United States); Sinha, Jayanti [TIAX LLC, Lexington, MA (United States)

2017-05-30

The objective of this program was to develop a novel, scalable scroll expander for conversion of waste heat to power; this was accomplished and demonstrated in both a bench-scale system as well as a full-scale system. The expander is a key component in Organic Rankine Cycle (ORC) waste heat recovery systems which are used to convert medium-grade waste heat to electric power in a wide range of industries. These types of waste heat recovery systems allow for the capture of energy that would otherwise just be exhausted to the atmosphere. A scroll expander has the benefit over other technologies of having high efficiency over a broad range of operating conditions. The speed range of the TIAX expander (1,200 to 3,600 RPM) enables the shaft power output to directly drive an electric generator and produce 60 Hz electric power without incurring the equipment costs or losses of electronic power conversion. This greatly simplifies integration with the plant electric infrastructure. The TIAX scroll expander will reduce the size, cost, and complexity of a small-scale waste heat recovery system, while increasing the system efficiency compared to the prevailing ORC technologies at similar scale. During this project, TIAX demonstrated the scroll expander in a bench-scale test setup to have isentropic efficiency of 70-75% and operated it successfully for ~200 hours with minimal wear. This same expander was then installed in a complete ORC system driven by a medium grade waste heat source to generate 5-7 kW of electrical power. Due to funding constraints, TIAX was unable to complete this phase of testing, although the initial results were promising and demonstrated the potential of the technology.

The impact of [corrected] expanded nursing practice on professional identify in Denmark.

Science.gov (United States)

Piil, Karin; Kolbæk, Raymond; Ottmann, Goetz; Rasmussen, Bodil

2012-01-01

This article explores the concept of professional identity of Danish nurses working in an expanded practice. The case study explores the experiences of a small group of Danish nurses with a new professional category that reaches into a domain that customarily belonged to physicians. The aim of this case study was to explore the impact of "nurse consultations," representing an expanded nursing role, of 5 nurses focusing on their perception of autonomy, self-esteem, and confidence. The case study used semistructured interviews with 5 participants triangulated and validated with participant observations, a focus group interview, and theoretically derived insights. This study indicates that nurses working within a new expanded professional practice see themselves as still engaged in nursing and not as substitute physicians. The study also suggests that the involved nurses gained a higher sense of autonomy, self-esteem, and confidence in their practice. These elements have a positive impact on their professional identity. The research demonstrates that for the nurses involved in expanded professional practice, the boundaries of professional practice have shifted significantly. The research indicates that an expanded practice generates a new domain within the professional identity of nurses.

Alkali-silica reactivity of expanded glass granules in structure of lightweight concrete

International Nuclear Information System (INIS)

Bumanis, G; Bajare, D; Korjakins, A; Locs, J

2013-01-01

Main component in the lightweight concrete, which provides its properties, is aggregate. A lot of investigations on alkali silica reaction (ASR) between cement and lightweight aggregates have been done with their results published in the academic literature. Whereas expanded glass granules, which is relatively new product in the market of building materials, has not been a frequent research object. Therefore lightweight granules made from waste glass and eight types of cement with different chemical and mineralogical composition were examined in this research. Expanded glass granules used in this research is commercially available material produced by Penostek. Lightweight concrete mixtures were prepared by using commercial chemical additives to improve workability of concrete. The aim of the study is to identify effect of cement composition to the ASR reaction which occurs between expanded glass granules and binder. Expanded glass granules mechanical and physical properties were determined. In addition, properties of fresh and hardened concrete were determined. The ASR test was processed according to RILEM AAR-2 testing recommendation. Tests with scanning electron microscope and microstructural investigations were performed for expanded glass granules and hardened concrete specimens before and after exposing them in alkali solution

Influence of Surgical Staples on Radiofrequency Ablation Using Multitined Expandable Electrodes

International Nuclear Information System (INIS)

Sakuhara, Yusuke; Shimizu, Tadashi; Abo, Daisuke; Hasegawa, Yu; Kato, Fumi; Kodama, Yoshihisa; Shirato, Hiroki

2007-01-01

Purpose. During radiofrequency ablation (RFA), there is a risk that the multitined expandable electrode will come into contact with one of the surgical staples used to treat local recurrence after surgical operations. Our objective was to evaluate whether a surgical staple would influence the RFA of egg white using a multitined expandable electrode. Methods. Multitined expandable electrodes, LeVeen needles (expandable diameter 3.0 cm), were sunk into an egg white bath with (a) no surgical staple, (b) a surgical staple touching one of the tines, or (c) a surgical staple touching two of the tines simultaneously. By connecting the LeVeen needle and copper plate at the bottom of the bath, RFA was then performed on the egg whites as a substitute for human tissue. Ten egg white baths were ablated under each of conditions (a), (b), and (c), for a total of 30 sets of coagulated egg white. Results. There was no significant difference in the time from the power-on to the roll-off (i.e., the completion and shutting off of the electric circuit) or in the maximum diameter of the thermal lesion between conditions (a) and (b) or (a) and (c). However, the minimum diameter of the thermal lesion was significantly smaller in (c) compared with (a) (p < 0.01). Conclusions. Surgical staples have the capacity to interfere with the electromagnetic field and decrease the minimum diameter of the thermal lesion in the event that a staple touches two of the tines of a multitined expandable electrode during RFA. Although the difference might be small enough to be neglected under many clinical circumstances, we recommend that, if possible, the tines not be expanded near metallic material

Focusing of geodesic congruences in an accelerated expanding Universe

International Nuclear Information System (INIS)

Albareti, F.D.; Cembranos, J.A.R.; Cruz-Dombriz, A. de la

2012-01-01

We study the accelerated expansion of the Universe through its consequences on a congruence of geodesics. We make use of the Raychaudhuri equation which describes the evolution of the expansion rate for a congruence of timelike or null geodesics. In particular, we focus on the space-time geometry contribution to this equation. By straightforward calculation from the metric of a Robertson-Walker cosmological model, it follows that in an accelerated expanding Universe the space-time contribution to the Raychaudhuri equation is positive for the fundamental congruence, favoring a non-focusing of the congruence of geodesics. However, the accelerated expansion of the present Universe does not imply a tendency of the fundamental congruence to diverge. It is shown that this is in fact the case for certain congruences of timelike geodesics without vorticity. Therefore, the focusing of geodesics remains feasible in an accelerated expanding Universe. Furthermore, a negative contribution to the Raychaudhuri equation from space-time geometry which is usually interpreted as the manifestation of the attractive character of gravity is restored in an accelerated expanding Robertson-Walker space-time at high speeds

Focusing of geodesic congruences in an accelerated expanding Universe

Energy Technology Data Exchange (ETDEWEB)

Albareti, F.D.; Cembranos, J.A.R. [Departamento de Física Teórica I, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid (Spain); Cruz-Dombriz, A. de la, E-mail: fdalbareti@estumail.ucm.es, E-mail: cembra@fis.ucm.es, E-mail: alvaro.delacruz-dombriz@uct.ac.za [Astrophysics, Cosmology and Gravity Centre (ACGC), University of Cape Town, 7701 Rondebosch, Cape Town (South Africa)

2012-12-01

We study the accelerated expansion of the Universe through its consequences on a congruence of geodesics. We make use of the Raychaudhuri equation which describes the evolution of the expansion rate for a congruence of timelike or null geodesics. In particular, we focus on the space-time geometry contribution to this equation. By straightforward calculation from the metric of a Robertson-Walker cosmological model, it follows that in an accelerated expanding Universe the space-time contribution to the Raychaudhuri equation is positive for the fundamental congruence, favoring a non-focusing of the congruence of geodesics. However, the accelerated expansion of the present Universe does not imply a tendency of the fundamental congruence to diverge. It is shown that this is in fact the case for certain congruences of timelike geodesics without vorticity. Therefore, the focusing of geodesics remains feasible in an accelerated expanding Universe. Furthermore, a negative contribution to the Raychaudhuri equation from space-time geometry which is usually interpreted as the manifestation of the attractive character of gravity is restored in an accelerated expanding Robertson-Walker space-time at high speeds.

Expandable metallic stents for tracheobronchial stenoses in esophageal cancer.

Science.gov (United States)

Takamori, S; Fujita, H; Hayashi, A; Tayama, K; Mitsuoka, M; Ohtsuka, S; Shirouzu, K

1996-09-01

Tracheobronchial stenosis in patients with esophageal cancer can be life threatening. Few reports have discussed use of expandable metallic stents for central airway stenoses in patients with esophageal cancer. Twelve patients with esophageal cancer underwent placement of expandable metallic stents for respiratory distress caused by tracheobronchial stricture. Single or double metallic stents were placed in the stenotic airways under fluoroscopic guidance. Improvement in respiratory symptoms and clinical outcome were assessed. Most stenoses were located in the trachea or the left main bronchus. From one to four expandable metallic stents were placed in each stricture site, with immediate relief of respiratory symptoms in 8 patients. One patient with tracheomalacia in alive 3 years after stent placement and another is alive 6 months after stent insertion. The other 10 patients lived from 10 to 70 days (mean; survival, 35 days) after stent placement. Death was due to progression of disease. Although metallic stents are useful for relieving respiratory distress in patients with advanced esophageal cancer, additional therapies should be considered.

Photon beam dose distributions for patients with implanted temporary tissue expanders

Science.gov (United States)

Asena, A.; Kairn, T.; Crowe, S. B.; Trapp, J. V.

2015-01-01

This study examines the effects of temporary tissue expanders (TTEs) on the dose distributions of photon beams in breast cancer radiotherapy treatments. EBT2 radiochromic film and ion chamber measurements were taken to quantify the attenuation and backscatter effects of the inhomogeneity. Results illustrate that the internal magnetic port present in a tissue expander causes a dose reduction of approximately 25% in photon tangent fields immediately downstream of the implant. It was also shown that the silicone elastomer shell of the tissue expander reduced the dose to the target volume by as much as 8%. This work demonstrates the importance for an accurately modelled high-density implant in the treatment planning system for post-mastectomy breast cancer patients.

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)

Structural and magnetic properties of {open_quotes}expanded{close_quotes} Mn

Energy Technology Data Exchange (ETDEWEB)

Grigorov, I.L.; Walker, J.C. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland21218 (United States); Hawley, M.E.; Brown, G.W. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico87545 (United States); Luett, M.; Fitzsimmons, M.R. [Manuel Lujan Jr. Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico87545 (United States)

1998-06-01

Structural and magnetic properties of {open_quotes}expanded{close_quotes} Mn deposited on (111) oriented fcc noble metals were studied with single-crystal x-ray diffraction and exchange bias measurements. A single peak corresponding to this phase was found at momentum transfer q=2.86{Angstrom}{sup {minus}1} along six equivalent [11{bar 2}] directions of the noble metal substrate. Magnetic hysteresis of the field cooled Fe/Mn bilayers exhibited a characteristic shift along the field axis, indicating antiferromagnetic order in the expanded Mn with T{sub N}{ge}20K. The magnetic and structural data are consistent with understanding the expanded phase as trigonally distorted {alpha}-Mn. {copyright} {ital 1998 American Institute of Physics.}

Gravitational instability in a multicomponent expanding medium

International Nuclear Information System (INIS)

Solov'eva, L.V.; Nurgaliev, I.S.

1985-01-01

In the Newtonian approximation we consider the gravitational instability of a two- or N-component medium in an expanding universe. The system of density-perturbation equations is solved in the short- and long-wave limits. For small values of the wave vector k, a result obtained for the stationary case continues to hold true: at most there can exist only one unstable mode. If k is kept fixed, the introduction of a perturbation component delta/sub i/ will speed the growth of fluctuations delta/sub j/, provided the adiabatic indices γ/sub i/>γ/sub j/. In the large-k limit, ordinary acoustic waves result. Other components will begin to manifest themselves in the first-order terms when the oscillation amplitude is expanded in powers of k -1 : provided γ/sub j/>γ/sub i/> or =4/3, the ith-component amplitude will decay more slowly than otherwise

Long-term implications of observing an expanding cosmological civilization

Science.gov (United States)

Olson, S. Jay

2018-01-01

Suppose that advanced civilizations, separated by a cosmological distance and time, wish to maximize their access to cosmic resources by rapidly expanding into the universe. How does the presence of one limit the expansionistic ambitions of another, and what sort of boundary forms between their expanding domains? We describe a general scenario for any expansion speed, separation distance and time. We then specialize to a question of particular interest: What are the future prospects for a young and ambitious civilization if they can observe the presence of another at a cosmological distance? We treat cases involving the observation of one or two expanding domains. In the single-observation case, we find that almost any plausible detection will limit one's future cosmic expansion to some extent. Also, practical technological limits to expansion speed (well below the speed of light) play an interesting role. If a domain is visible at the time one embarks on cosmic expansion, higher practical limits to expansion speed are beneficial only up to a certain point. Beyond this point, a higher speed limit means that gains in the ability to expand are more than offset by the first-mover advantage of the observed domain. In the case of two visible domains, it is possible to be `trapped' by them if the practical speed limit is high enough and their angular separation in the sky is large enough, i.e. one's expansion in any direction will terminate at a boundary with the two visible civilizations. Detection at an extreme cosmological distance has surprisingly little mitigating effect on our conclusions.

Successful range-expanding plants experience less above-ground and below-ground enemy impact.

Science.gov (United States)

Engelkes, Tim; Morriën, Elly; Verhoeven, Koen J F; Bezemer, T Martijn; Biere, Arjen; Harvey, Jeffrey A; McIntyre, Lauren M; Tamis, Wil L M; van der Putten, Wim H

2008-12-18

Many species are currently moving to higher latitudes and altitudes. However, little is known about the factors that influence the future performance of range-expanding species in their new habitats. Here we show that range-expanding plant species from a riverine area were better defended against shoot and root enemies than were related native plant species growing in the same area. We grew fifteen plant species with and without non-coevolved polyphagous locusts and cosmopolitan, polyphagous aphids. Contrary to our expectations, the locusts performed more poorly on the range-expanding plant species than on the congeneric native plant species, whereas the aphids showed no difference. The shoot herbivores reduced the biomass of the native plants more than they did that of the congeneric range expanders. Also, the range-expanding plants developed fewer pathogenic effects in their root-zone soil than did the related native species. Current predictions forecast biodiversity loss due to limitations in the ability of species to adjust to climate warming conditions in their range. Our results strongly suggest that the plants that shift ranges towards higher latitudes and altitudes may include potential invaders, as the successful range expanders may experience less control by above-ground or below-ground enemies than the natives.

4. Cirugía reparadora mitral, resultados a 2 años utilizando neocuerdas de politetrafluoroetileno en 33 casos

Directory of Open Access Journals (Sweden)

O. Araji

2010-01-01

Conclusiones: Nuestra experiencia con neocuerdas de EPTFE confirma la experiencia de otras instituciones en cuanto a que es una técnica segura, eficaz, reproducible y duradera. Creemos que tenemos excelentes resultados a corto y medio plazo y que debe intentarse la reparación valvular mitral siempre que sea posible, sobre todo si es de etiología degenerativa.

Non-Immunogenic Structurally and Biologically Intact Tissue Matrix Grafts for the Immediate Repair of Ballistic-Induced Vascular and Nerve Tissue Injury in Combat

Science.gov (United States)

2004-12-01

the absence of dilatation, aneurysm formation or neointimal hyperplasia . The 2003 report described the failure to provide appropriate carotid grafts...growth of fibrovascular tissue, sometimes accompanied by inflammatory cells and pigment-laden macrophages. Fragmentation of the umbilical vein...were also present within the device interstices. A fibrovascular stroma (all animals, mild to marked) was also noted within the lumen of the ePTFE

Lattice expansion of carbon-stabilized expanded austenite

DEFF Research Database (Denmark)

Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

2010-01-01

The lattice parameter of expanded austenite was determined as a function of the content of interstitially dissolved carbon in homogeneous, carburized thin stainless steel foils. For the first time this expansion of the face-centered cubic lattice is determined on unstrained austenite. It is found...

Technical Note: Effect of Incorporating Expanded Polystyrene ...

African Journals Online (AJOL)

Incorporating expanded polystyrene granules in concrete matrix can produce lightweight polystyrene aggregate concrete of various densities. Workability which is an important property of concrete, aects the rate of placement and the degree of compaction of concrete. Inadequate compaction leads to reduction in both ...

Expanding Sex-Role Definitions by Self-Discovery.

Science.gov (United States)

Kahn, Sharon E.; Greenberg, Leslie S.

1980-01-01

Counselors who stimulate client self-discovery may help these clients experience undeveloped parts of themselves and expand their definitions of themselves and their sex-role possibilities. Stimulation methods actively involve clients in the exploration of sex-role concerns to change restrictive self-concepts. (Author)

Expanding CEP290 mutational spectrum in ciliopathies

NARCIS (Netherlands)

Travaglini, Lorena; Brancati, Francesco; Attie-Bitach, Tania; Audollent, Sophie; Bertini, Enrico; Kaplan, Josseline; Perrault, Isabelle; Iannicelli, Miriam; Mancuso, Brunella; Rigoli, Luciana; Rozet, Jean-Michel; Swistun, Dominika; Tolentino, Jerlyn; Dallapiccola, Bruno; Gleeson, Joseph G.; Valente, Enza Maria; Zankl, A.; Leventer, R.; Grattan-Smith, P.; Janecke, A.; D'Hooghe, M.; Sznajer, Y.; van Coster, R.; Demerleir, L.; Dias, K.; Moco, C.; Moreira, A.; Kim, C. Ae; Maegawa, G.; Petkovic, D.; Abdel-Salam, G. M. H.; Abdel-Aleem, A.; Zaki, M. S.; Marti, I.; Quijano-Roy, S.; Sigaudy, S.; de Lonlay, P.; Romano, S.; Touraine, R.; Koenig, M.; Lagier-Tourenne, C.; Messer, J.; Collignon, P.; Wolf, N.; Philippi, H.; Kitsiou Tzeli, S.; Halldorsson, S.; Johannsdottir, J.; Ludvigsson, P.; Phadke, S. R.; Udani, V.; Stuart, B.; Magee, A.; Lev, D.; Michelson, M.; Ben-Zeev, B.; Fischetto, R.; Benedicenti, F.; Stanzial, F.; Borgatti, R.; Accorsi, P.; Battaglia, S.; Fazzi, E.; Giordano, L.; Pinelli, L.; Boccone, L.; Bigoni, S.; Ferlini, A.; Donati, M. A.; Caridi, G.; Divizia, M. T.; Faravelli, F.; Ghiggeri, G.; Pessagno, A.; Briguglio, M.; Briuglia, S.; Salpietro, C. D.; Tortorella, G.; Adami, A.; Castorina, P.; Lalatta, F.; Marra, G.; Riva, D.; Scelsa, B.; Spaccini, L.; Uziel, G.; del Giudice, E.; Laverda, A. M.; Ludwig, K.; Permunian, A.; Suppiej, A.; Signorini, S.; Uggetti, C.; Battini, R.; Di Giacomo, M.; Cilio, M. R.; Di Sabato, M. L.; Leuzzi, V.; Parisi, P.; Pollazzon, M.; Silengo, M.; de Vescovi, R.; Greco, D.; Romano, C.; Cazzagon, M.; Simonati, A.; Al-Tawari, A. A.; Bastaki, L.; Mégarbané, A.; Sabolic Avramovska, V.; de Jong, M. M.; Stromme, P.; Koul, R.; Rajab, A.; Azam, M.; Barbot, C.; Martorell Sampol, L.; Rodriguez, B.; Pascual-Castroviejo, I.; Teber, S.; Anlar, B.; Comu, S.; Karaca, E.; Kayserili, H.; Yüksel, A.; Akcakus, M.; Al Gazali, L.; Sztriha, L.; Nicholl, D.; Woods, C. G.; Bennett, C.; Hurst, J.; Sheridan, E.; Barnicoat, A.; Hennekam, R.; Lees, M.; Blair, E.; Bernes, S.; Sanchez, H.; Clark, A. E.; DeMarco, E.; Donahue, C.; Sherr, E.; Hahn, J.; Sanger, T. D.; Gallager, T. E.; Dobyns, W. B.; Daugherty, C.; Krishnamoorthy, K. S.; Sarco, D.; Walsh, C. A.; McKanna, T.; Milisa, J.; Chung, W. K.; de Vivo, D. C.; Raynes, H.; Schubert, R.; Seward, A.; Brooks, D. G.; Goldstein, A.; Caldwell, J.; Finsecke, E.; Maria, B. L.; Holden, K.; Cruse, R. P.; Swoboda, K. J.; Viskochil, D.

2009-01-01

Ciliopathies are an expanding group of rare conditions characterized by multiorgan involvement, that are caused by mutations in genes encoding for proteins of the primary cilium or its apparatus. Among these genes, CEP290 bears an intriguing allelic spectrum, being commonly mutated in Joubert

Fiber-optic coupling based on nonimaging expanded-beam optics.

Science.gov (United States)

Moslehi, B; Ng, J; Kasimoff, I; Jannson, T

1989-12-01

We have fabricated and experimentally tested low-cost and mass-producible multimode fiber-optic couplers and connectors based on nonimaging beam-expanding optics and Liouville's theorem. Analysis indicates that a pair coupling loss of -0.25 dB can be achieved. Experimentally, we measured insertion losses as low as -0.38 dB. The beam expanders can be mass produced owing to the use of plastic injection-molding fabrication techniques and packaged in standard connector housings. This design is compatible with the fiber geometry and can yield highly stable coupling owing to its high tolerance for misalignments.

Scalar-Tensor Black Holes Embedded in an Expanding Universe

Science.gov (United States)

Tretyakova, Daria; Latosh, Boris

2018-02-01

In this review we focus our attention on scalar-tensor gravity models and their empirical verification in terms of black hole and wormhole physics. We focus on a black hole, embedded in an expanding universe, describing both cosmological and astrophysical scales. We show that in scalar-tensor gravity it is quite common that the local geometry is isolated from the cosmological expansion, so that it does not backreact on the black hole metric. We try to extract common features of scalar-tensor black holes in an expanding universe and point out the gaps that must be filled.

Scalar-Tensor Black Holes Embedded in an Expanding Universe

Directory of Open Access Journals (Sweden)

Daria Tretyakova

2018-02-01

Full Text Available In this review, we focus our attention on scalar-tensor gravity models and their empirical verification in terms of black hole and wormhole physics. We focus on black holes, embedded in an expanding universe, describing both cosmological and astrophysical scales. We show that in scalar-tensor gravity it is quite common that the local geometry is isolated from the cosmological expansion, so that it does not backreact on the black hole metric. We try to extract common features of scalar-tensor black holes in an expanding universe and point out the issues that are not fully investigated.

Expanding Agricultural and Rural Extension Roles for Sustainable ...

African Journals Online (AJOL)

Expanding Agricultural and Rural Extension Roles for Sustainable Extension ... privatization of the public sector of national economies of developing nations has ... include marketing extension, non-farm rural micro enterprise development, ...

Evaluation of external heat loss from a small-scale expander used in organic Rankine cycle

International Nuclear Information System (INIS)

Li Jing; Pei Gang; Li Yunzhu; Ji Jie

2011-01-01

With the scaling down of the Organic Rankine Cycle (ORC), the engine shaft power is not only determined by the enthalpy drop in the expansion process but also the external heat loss from the expander. Theoretical and experimental support in evaluating small-scale expander heat loss is rare. This paper presents a quantitative study on the convection, radiation, and conduction heat transfer from a kW-scale expander. A mathematical model is built and validated. The results show that the external radiative or convective heat loss coefficient was about 3.2 or 7.0 W/K.m 2 when the ORC operated around 100 o C. Radiative and convective heat loss coefficients increased as the expander operation temperature increased. Conductive heat loss due to the connection between the expander and the support accounted for a large proportion of the total heat loss. The fitting relationships between heat loss and mean temperature difference were established. It is suggested that low conductivity material be embodied in the support of expander. Mattress insulation for compact expander could be eliminated when the operation temperature is around 100 o C. - Highlights: → A close examination of external heat loss from a small expander is presented. → Theoretical analysis and experimental test were conducted. → The established formulas can be applied to other small ORC expanders. → The results are useful in further research of small-scale ORC.

Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breast reconstruction?

Science.gov (United States)

Celet Ozden, Burcu; Guven, Erdem; Aslay, Isik; Kemikler, Gonul; Olgac, Vakur; Soluk Tekkesin, Merva; Serarslan, Bengul; Tumerdem Ulug, Burcak; Bilgin Karabulut, Aylin; Arinci, Atilla; Emekli, Ufuk

2012-02-20

The optimum protocol for expander volume adjustment with respect to the timing and application of radiotherapy remains controversial. Eighteen New Zealand rabbits were divided into three groups. Metallic port integrated anatomic breast expanders of 250 cc were implanted on the back of each animal and controlled expansion was performed. Group I underwent radiotherapy with full expanders while in Group II, expanders were partially deflated immediately prior to radiotherapy. Control group did not receive radiotherapy.The changes in blood flow at different volume adjustments were investigated in Group II by laser Doppler flowmetry. Variations in the histopathologic properties of the irradiated tissues including the skin, capsule and the pocket floor, were compared in the biopsy specimens taken from different locations in each group. A significant increase in skin blood flow was detected in Group II with partial expander deflation. Overall, histopathologic exam revealed aggravated findings of chronic radiodermatitis (epidermal atrophy, dermal inflammation and fibrosis, neovascularisation and vascular changes as well as increased capsule thickness) especially around the lower expander pole, in Group II. Expander deflation immediately prior to radiotherapy, may augment the adverse effects, especially in the lower expander pole, possibly via enhanced radiosensitization due to a relative increase in the blood flow and tissue oxygenation.

Does partial expander deflation exacerbate the adverse effects of radiotherapy in two-stage breast reconstruction?

Directory of Open Access Journals (Sweden)

Celet Ozden Burcu

2012-02-01

Full Text Available Abstract Background The optimum protocol for expander volume adjustment with respect to the timing and application of radiotherapy remains controversial. Methods Eighteen New Zealand rabbits were divided into three groups. Metallic port integrated anatomic breast expanders of 250 cc were implanted on the back of each animal and controlled expansion was performed. Group I underwent radiotherapy with full expanders while in Group II, expanders were partially deflated immediately prior to radiotherapy. Control group did not receive radiotherapy. The changes in blood flow at different volume adjustments were investigated in Group II by laser Doppler flowmetry. Variations in the histopathologic properties of the irradiated tissues including the skin, capsule and the pocket floor, were compared in the biopsy specimens taken from different locations in each group. Results A significant increase in skin blood flow was detected in Group II with partial expander deflation. Overall, histopathologic exam revealed aggravated findings of chronic radiodermatitis (epidermal atrophy, dermal inflammation and fibrosis, neovascularisation and vascular changes as well as increased capsule thickness especially around the lower expander pole, in Group II. Conclusions Expander deflation immediately prior to radiotherapy, may augment the adverse effects, especially in the lower expander pole, possibly via enhanced radiosensitization due to a relative increase in the blood flow and tissue oxygenation.

Hybrid Scenarios, Transmedia Storytelling, Expanded Ethnography

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Daniel Domínguez Figaredo

2012-10-01

Full Text Available The transformation of social scenarios due to the impact of digital technologies, introduces new possibilities for ethnographic research. Once the initial approaches focused on the dichotomy of “physical-virtual spaces” have been overcame, it comes a stage of maturity that allows the ethnographers to open new avenues for conceptual and analytical methodology applied in techno-social scenarios. This article discusses the evolution of some key dimensions of ethnography according to the new social and epistemological framework. The discussion is based on the analysis of expanded practices that take place in the new techno-social spaces, defined as hybrid environments, where technologies are embedded in the physical life of the subjects. On the one hand, we consider the production of actions based on the assembly of ideas, meanings and objects through digital mediation devices. It is also analysed the transmedia component of the narratives that make sense to allow the experiments. Underlying the analysis, some elements are introduced for discussion on the scope of expanded ethnographic research, the influence of transmedia phenomenon in the notion of “field” and the methods for determining the significance through digital storytelling.

Bank Directors’ Perceptions of Expanded Auditor's Reports

DEFF Research Database (Denmark)

Boolaky, Pran Krishansing; Quick, Reiner

2016-01-01

Subsequent to the financial crisis, standard setters developed suggestions for enhancing the audit function, in order to increase financial stability. One related idea is to expand the audit report disclosed to the public, to ensure that it is fit for purpose. This study investigates the impact o...

Parameter Sensitivity Study for Typical Expander-Based Transcritical CO2 Refrigeration Cycles

Directory of Open Access Journals (Sweden)

Bo Zhang

2018-05-01

Full Text Available A sensitivity study was conducted for three typical expander-based transcritical CO2 cycles with the developed simulation model, and the sensitivities of the maximum coefficient of performance (COP to the key operating parameters, including the inlet pressure of gas cooler, the temperatures at evaporator inlet and gas cooler outlet, the inter-stage pressure and the isentropic efficiency of expander, were obtained. The results showed that the sensitivity to the gas cooler inlet pressure differs greatly before and after the optimal gas cooler inlet pressure. The sensitivity to the intercooler outlet temperature in the two-stage cycles increases sharply to near zero and then keeps almost constant at intercooler outlet temperature of higher than 45 °C. However, the sensitivity stabilizes near zero when the evaporator inlet temperature is very low of −26.1 °C. In two-stage compression with an intercooler and an expander assisting in driving the first-stage compressor (TEADFC cycle, an abrupt change in the sensitivity of maximum COP to the inter-stage pressure was observed, but disappeared after intercooler outlet temperature exceeds 50 °C. The sensitivity of maximum COP to the expander isentropic efficiency increases almost linearly with the expander isentropic efficiency.

GWDC Expands High-End Market Share

Institute of Scientific and Technical Information of China (English)

无

2008-01-01

@@ It is a decision of great significance for GWDC to expand high-end market share in order to realize its transformation of development strategy and improve its development quality. As an important step of GWDC to explore high-end market, Oman PDO Project marks the first time that the Chinese petroleum engineering service team cooperates with the transnational petroleum corporations ranking first three in the world.

Expanding the Visibility of Women's Work: Policy Implications.

Science.gov (United States)

Messias, DeAnne K. Hilfinger; Regev, Hanna; Im, Eun-Ok; Spiers, Judith A.; Van, Paulina; Meleis, Afaf Ibrahim

1997-01-01

Social conceptualization and media images of women's work affect health and social policy formation. Nurses can expand the visibility of women's work and promote gender-sensitive policies within and outside the profession. (SK)

The expanding plasma jet

International Nuclear Information System (INIS)

Sanden, M.C.M. van den.

1991-01-01

This thesis concerns the fundamental aspects of an argon plasma expanding from a cascaded arc. This type of plasma is not only used for fundamental research but also for technologically orientated research on plasma deposition and plasma sources. The important characteristics of the plasma are a strong supersonic expansion in which the neutral particle and ion densities decrease three orders of magnitude, followed by a stationary shock front. After the shock front the plasma expands further subsonically. A part of this thesis is devoted to the discussion of a newly constructed combined Thomson-Rayleigh scattering set up. With this set up the electron density, the electron temperature and the neutral particle density are measured locally in the plasma for different conditions. In the analysis of the measured spectra weak coherent effects and the measured apparatus profile are included. The inaccuracies are small, ranging from 1 to 4 percent for the electron density and 2 to 6 percent for the electron temperature, depending on the plasma conditions. The inaccuracy of the neutral particle density determination is larger and ranges from 10 to 50 percent. The detection limits for the electron and neutral particle density are 7.10 17 m -3 and 1.10 20 m -3 respectively. A side path in this thesis is the derivation of the Saha equation for a two-temperature plasma. The reason for this derivation was the dispute in the literature about the correct form of this equation. In this thesis it is shown, from the correct extension of the second law of thermodynamics and from the non-equilibrium formalism of Zubarev, That in the limit of m e /m h ->0 the generalized Saha equation depends on the electron temperature only. (author). 221 refs.; 54 figs.; 13 tabs

Circle diffeomorphisms forced by expanding circle maps

NARCIS (Netherlands)

Homburg, A.J.

2012-01-01

We discuss the dynamics of skew product maps defined by circle diffeomorphisms forced by expanding circle maps. We construct an open class of such systems that are robustly topologically mixing and for which almost all points in the same fiber converge under iteration. This property follows from the

Quantifying the impact of expanded age group campaigns for polio eradication.

Science.gov (United States)

Wagner, Bradley G; Behrend, Matthew R; Klein, Daniel J; Upfill-Brown, Alexander M; Eckhoff, Philip A; Hu, Hao

2014-01-01

A priority of the Global Polio Eradication Initiative (GPEI) 2013-2018 strategic plan is to evaluate the potential impact on polio eradication resulting from expanding one or more Supplementary Immunization Activities (SIAs) to children beyond age five-years in polio endemic countries. It has been hypothesized that such expanded age group (EAG) campaigns could accelerate polio eradication by eliminating immunity gaps in older children that may have resulted from past periods of low vaccination coverage. Using an individual-based mathematical model, we quantified the impact of EAG campaigns in terms of probability of elimination, reduction in polio transmission and age stratified immunity levels. The model was specifically calibrated to seroprevalence data from a polio-endemic region: Zaria, Nigeria. We compared the impact of EAG campaigns, which depend only on age, to more targeted interventions which focus on reaching missed populations. We found that EAG campaigns would not significantly improve prospects for polio eradication; the probability of elimination increased by 8% (from 24% at baseline to 32%) when expanding three annual SIAs to 5-14 year old children and by 18% when expanding all six annual SIAs. In contrast, expanding only two of the annual SIAs to target hard-to-reach populations at modest vaccination coverage-representing less than one tenth of additional vaccinations required for the six SIA EAG scenario-increased the probability of elimination by 55%. Implementation of EAG campaigns in polio endemic regions would not improve prospects for eradication. In endemic areas, vaccination campaigns which do not target missed populations will not benefit polio eradication efforts.

Subclinical leaflet thickening and stent frame geometry in self-expanding transcatheter heart valves

DEFF Research Database (Denmark)

Fuchs, Andreas; De Backer, Ole; Brooks, Matthew

2017-01-01

AIMS: This study aimed to assess the potential relationship between subclinical leaflet thickening and stent frame geometry in patients who underwent aortic valve replacement with a self-expanding transcatheter heart valve (THV). METHODS AND RESULTS: Seventy-five patients with a self-expanding THV....... CONCLUSIONS: Regional THV stent frame underexpansion is associated with an increased risk of leaflet thickening. Post-dilatation of self-expanding THV as well as a supra-annular valve position seem to reduce the occurrence of this phenomenon....

Esophagojejunal anastomotic leak managed with self expandable metallic stent

Directory of Open Access Journals (Sweden)

Arvind Madurandagam Annapillai

2013-01-01

Full Text Available Esophagealjejunal anastomotic leak after gastrectomy is a serious surgical emergency with high mortality. This report describes a 57-year-old male with esophagojejunal anastomotic leak following total gastrectomy for gastric cancer and was managed successfully with self-expandable metallic stent. To our knowledge this is the first such report from India. This case report highlights the need of interdisciplinary coordination in managing this difficult clinical situation. Endotherapy with self-expandable metallic stent (SEM provided twin benefits of improving respiratory embarrassment and the joy of eating. Therapy of such difficult cases must be individualized; however, and SEM stent usage is a viable option

Dissipation and fluctuation of quantum fields in expanding universes

International Nuclear Information System (INIS)

Morikawa, M.

1990-01-01

A stochastic dynamics of a long-wavelength part of a scalar field in an expanding universe is derived by using the influence functional method. Dissipation as well as fluctuation are derived for general parameters: a mass, a coupling to the scalar curvature, and a cutoff scale parameter. A dissipation-fluctuation relation is found with a temperature which is proportional to the Hawking temperature, but system dependent. The method is further applied to an expanding universe with a power law and yields the dispersion which agrees with that obtained by the regularization method. The back reaction to the background de Sitter space itself is also obtained

The mechanical properties of infrainguinal vascular bypass grafts: their role in influencing patency.

Science.gov (United States)

Sarkar, S; Salacinski, H J; Hamilton, G; Seifalian, A M

2006-06-01

When autologous vein is unavailable, prosthetic graft materials, particularly expanded polytetrafluoroethylene are used for peripheral arterial revascularisation. Poor long term patency of prosthetic materials is due to distal anastomotic intimal hyperplasia. Intimal hyperplasia is directly linked to shear stress abnormalities at the vessel wall. Compliance and calibre mismatch between native vessel and graft, as well as anastomotic line stress concentration contribute towards unnatural wall shear stress. High porosity reduces graft compliance by causing fibrovascular infiltration, whereas low porosity discourages the development of an endothelial lining and hence effective antithrombogenicity. Therefore, consideration of mechanical properties is necessary in graft development. Current research into synthetic vascular grafts concentrates on simulating the mechanical properties of native arteries and tissue engineering aims to construct a new biological arterial conduit.

Expanding Business Opportunities for African Youth in Agricultural ...

International Development Research Centre (IDRC) Digital Library (Canada)

Expanding Business Opportunities for African Youth in Agricultural Value ... sector actors who can help commercialize them and achieve large-scale impacts. ... CultiAF supports research to achieve long-term food security in Eastern and ...

Overview of the APT high-energy beam transport and beam expanders

International Nuclear Information System (INIS)

Shafer, R.E.; Blind, B.; Gray, E.R.

1997-01-01

The APT high energy beam transport (HEBT) and beam expanders convey the 1700-MeV, 100-mA cw proton beam from the linac to the tritium target/blanket assembly, or a tuning beam stop. The HEBT includes extensive beam diagnostics, collimators, and beam jitter correction, to monitor and control the 170-MW beam prior to expansion. A zero-degree beamline conveys the beam to the beam stop, and an achromatic bend conveys the beam to the tritium production target. Nonlinear beam expanders make use of higher-order multipole magnets and dithering dipoles to expand the beam to a uniform-density, 16-cm wide by 160-cm high rectangular profile on the tritium-production target. The overall optics design will be reviewed, and beam simulations will be presented

Impaired heat shock response in cells expressing full-length polyglutamine-expanded huntingtin.

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Sidhartha M Chafekar

Full Text Available The molecular mechanisms by which polyglutamine (polyQ-expanded huntingtin (Htt causes neurodegeneration in Huntington's disease (HD remain unclear. The malfunction of cellular proteostasis has been suggested as central in HD pathogenesis and also as a target of therapeutic interventions for the treatment of HD. We present results that offer a previously unexplored perspective regarding impaired proteostasis in HD. We find that, under non-stress conditions, the proteostatic capacity of cells expressing full length polyQ-expanded Htt is adequate. Yet, under stress conditions, the presence of polyQ-expanded Htt impairs the heat shock response, a key component of cellular proteostasis. This impaired heat shock response results in a reduced capacity to withstand the damage caused by cellular stress. We demonstrate that in cells expressing polyQ-expanded Htt the levels of heat shock transcription factor 1 (HSF1 are reduced, and, as a consequence, these cells have an impaired a heat shock response. Also, we found reduced HSF1 and HSP70 levels in the striata of HD knock-in mice when compared to wild-type mice. Our results suggests that full length, non-aggregated polyQ-expanded Htt blocks the effective induction of the heat shock response under stress conditions and may thus trigger the accumulation of cellular damage during the course of HD pathogenesis.

Non-activated high surface area expanded graphite oxide for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Vermisoglou, E.C.; Giannakopoulou, T.; Romanos, G.E.; Boukos, N.; Giannouri, M. [Institute of Nanoscience and Nanotechnology “Demokritos”, 153 43 Ag. Paraskevi, Attikis (Greece); Lei, C.; Lekakou, C. [Division of Mechanical, Medical, and Aerospace Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH (United Kingdom); Trapalis, C., E-mail: c.trapalis@inn.demokritos.gr [Institute of Nanoscience and Nanotechnology “Demokritos”, 153 43 Ag. Paraskevi, Attikis (Greece)

2015-12-15

Graphical abstract: - Highlights: • One-step exfoliation and reduction of graphite oxide via microwave irradiation. • Effect of pristine graphite (type, flake size) on the microwave expanded material. • Effect of pretreatment and oxidation cycles on the produced expanded material. • Expanded graphene materials with high BET surface areas (940 m{sup 2}/g–2490 m{sup 2}/g). • Non-activated graphene based materials suitable for supercapacitors. - Abstract: Microwave irradiation of graphite oxide constitutes a facile route toward production of reduced graphene oxide, since during this treatment both exfoliation and reduction of graphite oxide occurs. In this work, the effect of pristine graphite (type, size of flakes), pretreatment and oxidation cycles on the finally produced expanded material was examined. All the types of graphite that were tested afforded materials with high BET surface areas ranging from 940 m{sup 2}/g to 2490 m{sup 2}/g, without intervening an activation stage at elevated temperature. SEM and TEM images displayed exfoliated structures, where the flakes were significantly detached and curved. The quality of the reduced graphene oxide sheets was evidenced both by X-ray photoelectron spectroscopy and Raman spectroscopy. The electrode material capacitance was determined via electrochemical impedance spectroscopy and cyclic voltammetry. The materials with PEDOT binder had better performance (∼97 F/g) at low operation rates while those with PVDF binder performed better (∼20 F/g) at higher rates, opening up perspectives for their application in supercapacitors.

Response of Balloon-Expandable Endoprosthetic Metallic Stents Subjected to Over-Expansion In Vitro

International Nuclear Information System (INIS)

Montague, B. J.; Kakimoto, W. M.; Arepally, A.; Razavi, M.; Dake, M. D.; Hofmann, L. V.

2004-01-01

We attempted to evaluate the in vitro behavior and performance of balloon-expandable endoprosthetic metallic stents subjected to over-expansion (OE). Seventy-two balloon-expandable endoprosthetic stents, representing 22 models from six manufacturers, were over- expanded in vitro. Stents were initially expanded to their maximum manufacturer- recommended diameter and then over-expanded incrementally to their endpoints. Endpoints for OE were either stent disarticulation or an inability to undergo further expansion despite balloon insufflation to maximum burst pressure. Measurements of stent dimensions were recorded at each overexpanded diameter and comparisons were made to manufacturer's specifications. A total of 288 balloon-driven expansions were performed on 72 stents. Sixteen stents were expanded to large diameters (≥ 16 mm), 20 stents underwent OE of 50% or greater. One model tended to disarticulate after OE greater than 50%. There were five models that had a tendency to disarticulate after minimal OE. Five models were resistant to OE (25% or less OE) but did not disarticulate. Nearly all stents showed some degree of foreshortening with OE, while 36 stents underwent foreshortening of 30% or more. Models that are not recommended for OE include Intrastent, Intrastent DoubleStrut, NIR Royale and Omniflex. Good candidates for OE include Intrastent DoubleStrut LD, Palmaz large, Medtronic Extra Support Biliary Plus and Medtronic Flexible Biliary. Palmaz XL remains the only model available for expansion from 20 to 28 mm in diameter. For the remaining stents, OE is possible, however, caution should be used

Expanding the Audience for the Performing Arts.

Science.gov (United States)

Andreasen, Alan R.

Becoming involved in the arts is a process that involves movement through several stages, from disinterest to active attendance at and enthusiasm for performing arts events. Since target consumers at any time will differ in their placement on this continuum, marketing programs to expand arts audiences must first identify where each target segment…

Evaluation of a simple polytetrafluoroethylene (PTFE)-based membrane for blood-feeding of malaria and dengue fever vectors in the laboratory.

Science.gov (United States)

Siria, Doreen J; Batista, Elis P A; Opiyo, Mercy A; Melo, Elizangela F; Sumaye, Robert D; Ngowo, Halfan S; Eiras, Alvaro E; Okumu, Fredros O

2018-04-11

Controlled blood-feeding is essential for maintaining laboratory colonies of disease-transmitting mosquitoes and investigating pathogen transmission. We evaluated a low-cost artificial feeding (AF) method, as an alternative to direct human feeding (DHF), commonly used in mosquito laboratories. We applied thinly-stretched pieces of polytetrafluoroethylene (PTFE) membranes cut from locally available seal tape (i.e. plumbers tape, commonly used for sealing pipe threads in gasworks or waterworks). Approximately 4 ml of bovine blood was placed on the bottom surfaces of inverted Styrofoam cups and then the PTFE membranes were thinly stretched over the surfaces. The cups were filled with boiled water to keep the blood warm (~37 °C), and held over netting cages containing 3-4 day-old inseminated adults of female Aedes aegypti, Anopheles gambiae (s.s.) or Anopheles arabiensis. Blood-feeding success, fecundity and survival of mosquitoes maintained by this system were compared against DHF. Aedes aegypti achieved 100% feeding success on both AF and DHF, and also similar fecundity rates (13.1 ± 1.7 and 12.8 ± 1.0 eggs/mosquito respectively; P > 0.05). An. arabiensis had slightly lower feeding success on AF (85.83 ± 16.28%) than DHF (98.83 ± 2.29%) though these were not statistically different (P > 0.05), and also comparable fecundity between AF (8.82 ± 7.02) and DHF (8.02 ± 5.81). Similarly, for An. gambiae (s.s.), we observed a marginal difference in feeding success between AF (86.00 ± 10.86%) and DHF (98.92 ± 2.65%), but similar fecundity by either method. Compared to DHF, mosquitoes fed using AF survived a similar number of days [Hazard Ratios (HR) for Ae. aegypti = 0.99 (0.75-1.34), P > 0.05; An. arabiensis = 0.96 (0.75-1.22), P > 0.05; and An. gambiae (s.s.) = 1.03 (0.79-1.35), P > 0.05]. Mosquitoes fed via this simple AF method had similar feeding success, fecundity and longevity. The method could potentially be used for laboratory colonization of mosquitoes

Low-order models of a single-screw expander for organic Rankine cycle applications

Science.gov (United States)

Ziviani, D.; Desideri, A.; Lemort, V.; De Paepe, M.; van den Broek, M.

2015-08-01

Screw-type volumetric expanders have been demonstrated to be a suitable technology for organic Rankine cycle (ORC) systems because of higher overall effectiveness and good part-load behaviour over other positive displacement machines. An 11 kWe single-screw expander (SSE) adapted from an air compressor has been tested in an ORC test-rig operating with R245fa as working fluid. A total of 60 steady-steady points have been obtained at four different rotational speeds of the expander in the range between 2000 rpm and 3300 rpm. The maximum electrical power output and overall isentropic effectiveness measured were 7.3 kW and 51.9%, respectively. In this paper, a comparison between two low-order models is proposed in terms of accuracy of the predictions, the robustness of the model and the computational time. The first model is the Pacejka equation-based model and the second is a semi-empirical model derived from a well-known scroll expander model and modified to include the geometric aspects of a single screw expander. The models have been calibrated with the available steady-state measurement points by identifying the proper parameters.

The option to expand a project: its assessment with the binomial options pricing model

Directory of Open Access Journals (Sweden)

Salvador Cruz Rambaud

Full Text Available Traditional methods of investment appraisal, like the Net Present Value, are not able to include the value of the operational flexibility of the project. In this paper, real options, and more specifically the option to expand, are assumed to be included in the project information in addition to the expected cash flows. Thus, to calculate the total value of the project, we are going to apply the methodology of the Net Present Value to the different scenarios derived from the existence of the real option to expand. Taking into account the analogy between real and financial options, the value of including an option to expand is explored by using the binomial options pricing model. In this way, estimating the value of the option to expand is a tool which facilitates the control of the uncertainty element implicit in the project. Keywords: Real options, Option to expand, Binomial options pricing model, Investment project appraisal

Chinese IP expands with self-reliance.

Science.gov (United States)

1999-05-01

In 1999, program officers from JOICFP visited five of 10 projects where JOICFP has provided direct assistance during 1993-95 to enhance health education in China's integrated family planning, maternal-child health programs. The JOICFP team and three members of the Chinese National Steering Committee of the Integrated Projects visited project areas in remote and mountainous areas that are characterized by underdevelopment, low income rates, low rates of hospital deliveries, and high rates of parasitic infection. The monitoring team found that all project areas continued the projects after completion of the 3-year period and even expanded efforts to cover other areas. By 1998, more than a million people had been served, which is quadruple the initial target number. The team found that the program could benefit from additional assistance in training new staff to interact with the public and to use IEC (information, education, communication) materials appropriately. One project area, Shaowu City, opened a new Family Health Service Center in August 1998 with a grant from the Japanese Grant Assistance for Grassroots Projects and assistance from its provincial and local government. This Center serves women and children and adolescents on a fee-charged basis and hopes to expand its service area.

The expanding EU

DEFF Research Database (Denmark)

Zank, Wolfgang

In this paper I try to explore whether the EU can go on expanding and thereby become culturally ever more diversified, and at the same retain its stability. The answer is, in principle, affirmative. Europe has always been much diversified, and therefore it is not possible to define a European...... identity in terms of particular cultural traditions. However, in spite of their diversity, the EU-member countries are united by their adherence to the principles of democracy, rule by law and human rights. Countries which do not share this basic consensus would not be accepted as members, nor is it likely...... that they would apply for it. An essential part is the willingness of member states to accept a reduction of national sovereignty on some important policy fields. The EU project is basically about lifting the principles of democracy and rule by law on the international level, most and foremost among the member...

Visual Narratives and (AntiExpanded Cinema in Julião Sarmento

Directory of Open Access Journals (Sweden)

Miguel Mesquita Duarte

2015-02-01

Full Text Available Beyond the difficulties in circumscribing expanded cinema theoretical and epistemological field – due to the plurality and multiple developments that it comprises, - one of the most pressing aspects concerning expanded cinema refers its relation with problems of narrativity. Although less obvious, the mention to Julião Sarmento’s work in this field seems to us particularly useful; to begin with, for the way his work is animated by a counter-narrative compulsion which, building up in the interior of a specific dialectic between cinema and photography, efficiently undermines structural centeredness and the linearity of sequential images. Following a thread encompassing the experimental films from the mid-70s to the installations of 2000s, we seek to argue that the importance of structuralism, as well the genealogical approach to the history and memory of cinema, constitute, within Sarmento’s oeuvre, increasingly important aspects to assess the new forms of perceptive, cognitive and topological arrangements that go along the emergence of the so called expanded cinema. Ultimately, the originality and the critical stance maintained by the artist leads us towards the consideration of an anti-expanded-cinema: more than a thematic traced within the limits of technological development and multi-disciplinary spreading, in Sarmento’s case, the expansion of cinema concerns, mostly, the expansion of the criteria related with the circulation of thought and desire throughout a topology of infra-signification that emerges from the new possibilities of narration, of making and exhibiting cinema. Accordingly, what is at issue is an overall distinct possibility of identify, designate and problematize the category of expanded cinema, beyond its orthodox definition.

Small Engines as Bottoming Cycle Steam Expanders for Internal Combustion Engines

Directory of Open Access Journals (Sweden)

Rohitha Weerasinghe

2017-01-01

Full Text Available Heat recovery bottoming cycles for internal combustion engines have opened new avenues for research into small steam expanders (Stobart and Weerasinghe, 2006. Dependable data for small steam expanders will allow us to predict their suitability as bottoming cycle engines and the fuel economy achieved by using them as bottoming cycles. Present paper is based on results of experiments carried out on small scale Wankel and two-stroke reciprocating engines as air expanders and as steam expanders. A test facility developed at Sussex used for measurements is comprised of a torque, power and speed measurements, electronic actuation of valves, synchronized data acquisition of pressure, and temperatures of steam and inside of the engines for steam and internal combustion cycles. Results are presented for four engine modes, namely, reciprocating engine in uniflow steam expansion mode and air expansion mode and rotary Wankel engine in steam expansion mode and air expansion mode. The air tests will provide base data for friction and motoring effects whereas steam tests will tell how effective the engines will be in this mode. Results for power, torque, and p-V diagrams are compared to determine the change in performance from air expansion mode to steam expansion mode.

Exergy analysis of transcritical carbon dioxide refrigeration cycle with an expander

International Nuclear Information System (INIS)

Yang Junlan; Ma Yitai; Li Minxia; Guan Haiqing

2005-01-01

In this paper, a comparative study is performed for the transcritical carbon dioxide refrigeration cycles with a throttling valve and with an expander, based on the first and second laws of thermodynamics. The effects of evaporating temperature and outlet temperature of gas cooler on the optimal heat rejection pressure, the coefficients of performance (COP), the exergy losses, and the exergy efficiencies are investigated. In order to identify the amounts and locations of irreversibility within the two cycles, exergy analysis is employed to study the thermodynamics process in each component. It is found that in the throttling valve cycle, the largest exergy loss occurs in the throttling valve, about 38% of the total cycle irreversibility. In the expander cycle, the irreversibility mainly comes from the gas cooler and the compressor, approximately 38% and 35%, respectively. The COP and exergy efficiency of the expander cycle are on average 33% and 30% higher than those of the throttling valve cycle, respectively. It is also concluded that an optimal heat rejection pressure can be obtained for all the operating conditions to maximize the COP. The analysis results are of significance to provide theoretical basis for optimization design and operation control of the transcritical carbon dioxide cycle with an expander

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.

Gravitational instantons and separation of an expanding Universe

International Nuclear Information System (INIS)

Rubakov, V.A.; Tinyakov, P.G.

1988-01-01

Instanton, describing the separation of closed small-size classically inflating Universe from the plane Universe, was found in the model of gravitational field, interacting with matter fields. Existence of such instantons provides the possibility of expanding Universe self-birth

Expanded and combined uncertainty in measurements by GM counters

International Nuclear Information System (INIS)

Stankovic, K.; Arandjic, D.; Lazarevic, Dj.; Osmokrovic, P.

2007-01-01

This paper deals with possible ways of obtaining expanded and combined uncertainty in measurements for four types of GM counters with a same counter's tube, in cases when the contributors of these uncertainties are cosmic background radiation and induced overvoltage phenomena. Nowadays, as a consequence of electromagnetic radiation, the latter phenomenon is especially marked in urban environments. Based on experimental results obtained, it has been established that the uncertainties of an influenced random variable 'number of pulses from background radiation' and 'number of pulses induced by overvoltage' depend on the technological solution of the counter's reading system and contribute in different ways to the expanded and combined uncertainty in measurements of the applied types of GM counters. (author)

Adipose tissue expandability and the early origins of PCOS.

Science.gov (United States)

de Zegher, Francis; Lopez-Bermejo, Abel; Ibáñez, Lourdes

2009-11-01

The most prevalent phenotypes of polycystic ovary syndrome (PCOS) are characterized by insulin resistance and androgen excess. The adipose tissue (AT) expandability hypothesis explains the development of insulin resistance in obesity and in cases of AT deficit. In line with this hypothesis, we propose that hyperinsulinemic androgen excess in PCOS is often underpinned by exhaustion of the capacity to expand subcutaneous AT in a metabolically safe way. Such exhaustion might occur when a positive energy imbalance meets a normal fat-storage capacity and/or when a normal energy balance faces a low fat storage capacity. This concept thus explains how PCOS phenotypes might result from obesity, prenatal growth restraint or a genetic lipodystrophy, or, experimentally, from prenatal androgen excess.

The Dichotomous Cosmology with a Static Material World and Expanding Luminous World

Directory of Open Access Journals (Sweden)

Heymann Y.

2014-07-01

Full Text Available The dichotomous cosmology is an alternative to the expanding Universe theory, and consists of a static matter Universe, where cosmological redshifts are explained by a tired-light model with an expanding luminous world. In this model the Hubble constant is also the photon energy decay rate, and the luminous world i s expanding at a constant rate as in de Sitter cosmology for an empty Universe. The present model explains both the luminosity distance versus redshift relationship of supernovae Ia, and ageing of spectra observed with the stretching of supernovae light curves. Furthermore, it is consistent with a radiation energy density factor (1 + z 4 inferred from the Cosmic Microwave Background Radiation.

Self-Expanding Metal Stenting for Palliation of Patients with Malignant Colonic Obstruction

DEFF Research Database (Denmark)

Meisner, Søren; González-Huix, Ferran; Vandervoort, Jo G

2012-01-01

Background. Self-expanding metal stents can alleviate malignant colonic obstruction in incurable patients and avoid palliative stoma surgery. Objective. Evaluate stent effectiveness and safety on palliation of patients with malignant colorectal strictures. Design. Two prospective, one Spanish....... Interventions(s). Self-expanding metal stent placement. Main Outcome Measures. Procedural success, clinical success, and safety. Results. Procedural success was 98.4% (251). Clinical success rates were 87.8% at 30 days, 89.7% at 3 months, 92.8% at 6 months, and 96% at 12 months. Overall perforation rate was 5...... for patients with malignant colonic obstruction should be self-expanding metal stent placement due to high rates of technical success and efficacy in symptom palliation and few complications....

Pancreatitis-Associated Splenic Artery Pseudoaneurysm: Endovascular Treatment with Self-Expandable Stent-Grafts

International Nuclear Information System (INIS)

Brountzos, Elias N.; Vagenas, Kostantinos; Apostolopoulou, Sotiria C.; Panagiotou, Irene; Lymberopoulou, Dimitra; Kelekis, Dimitrios A.

2003-01-01

We present a patient with a splenic arterypseudoaneurysm (SAPA) treated with placement of self-expandable stent-grafts. The procedure was complicated by stent-graft migration,but successful management resulted in lasting exclusion of the SAPA,while the patency of the splenic artery was preserved. This is the first report of self-expandable stent-graft treatment of SAPA

On the elusive crystal structure of expanded austenite

DEFF Research Database (Denmark)

Brink, Bastian; Ståhl, Kenny; Christiansen, Thomas Lundin

2017-01-01

No consistent structural description exists for expanded austenite that accurately accounts for the hkl-dependent peak shifts and broadening observed in diffraction experiments. The best available description for homogeneous samples is a face-centered cubic lattice with stacking faults. Here Deby...

DEMONSTRATION OF PACKAGING MATERIALS ALTERNATIVES TO EXPANDED POLYSTYRENE

Science.gov (United States)

This report represents the second demonstration of cleaner technologies to support the goals of the 33/50 Program under the EPA Cooperative Agreement No. CR-821848. The report presents assessment results of alternative packaging materials which could potentially replace expanded...

Building the Case: Changing Consumer Perceptions of the Value of Expanded Community Pharmacist Services.

Science.gov (United States)

Steckowych, Kathryn; Smith, Marie; Spiggle, Susan; Stevens, Andrew; Li, Hao

2018-01-01

The role of the community pharmacist has traditionally been a medication dispenser; however, community pharmacists' responsibilities must expand to include more direct patient care services in order to transform primary care practice. Use case-based scenarios to (1) determine factors that contribute to positive and negative consumer perceptions of expanded community pharmacist patient care roles, (2) identify facilitators and barriers that contribute to consumer perceptions of the value of expanded community pharmacist patient care services, and (3) develop a successful approach and strategies for increasing consumer advocacy for the value of expanded community pharmacist patient care services. Two consumer focus groups used scenario-based guided discussions and Likert scale questionnaires to elicit consumer reactions, facilitators, and barriers to expanded community pharmacist services. Convenience, timeliness, and accessibility were common positive reactions across all 3 scenarios. Team approach to care and trust were viewed as major facilitators. Participant concerns included uncertainty about pharmacist training and qualifications, privacy, pharmacists' limited bandwidth to accept new tasks, and potential increased patient costs. Common barriers to service uptake included a lack of insurance payment and physician preference to provide the services. Consumer unfamiliarity with non-traditional community pharmacist services is likely an influencer of consumers' hesitancy to utilize such services; therefore, an opportunity exists to engage consumers and advocacy organizations in supporting expanded community pharmacist roles. This study can inform consumers, advocates, community pharmacists, primary care providers, and community-based organizations on methods to shape consumer perceptions on the value of community pharmacist expanded services.

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

Robust size illusion produced by expanding and contracting flow fields.

Science.gov (United States)

Dong, Xue; Bai, Jianying; Bao, Min

2017-04-01

A new illusion is described. Randomly positioned dots moved radially within an imaginary annular window. The dots' motion periodically changed the direction, leading to an alternating percept of expanding and contracting motion. Strikingly, the apparent size of the enclosed circular region shrank during the dots' expanding phases and dilated during the contracting phases. We quantitatively measured the illusion, and found that the presence of energy at the local kinetic edge could not account for the illusion. Besides, we reproduced the illusion on a natural scene background seen from a first-person point of view that moved forward and backward periodically. Blurring the boundaries of motion areas could not reverse the illusion in all subjects. Taken together, our observed illusion is likely induced by optic flow processing with some components of motion contrast. Expanding or contracting dots may induce the self-motion perception of either approaching or leaving way from the circle. These will make the circle appear smaller or larger since its retinal size remains constant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nano-Engineered Catalysts for Direct Methanol Fuel Cells

Science.gov (United States)

Myung, Nosang; Narayanan, Sekharipuram; Wiberg, Dean

2008-01-01

Nano-engineered catalysts, and a method of fabricating them, have been developed in a continuing effort to improve the performances of direct methanol fuel cells as candidate power sources to supplant primary and secondary batteries in a variety of portable electronic products. In order to realize the potential for high energy densities (as much as 1.5 W h/g) of direct methanol fuel cells, it will be necessary to optimize the chemical compositions and geometric configurations of catalyst layers and electrode structures. High performance can be achieved when catalyst particles and electrode structures have the necessary small feature sizes (typically of the order of nanometers), large surface areas, optimal metal compositions, high porosity, and hydrophobicity. The present method involves electrodeposition of one or more catalytic metal(s) or a catalytic-metal/polytetrafluoroethylene nanocomposite on an alumina nanotemplate. The alumina nanotemplate is then dissolved, leaving the desired metal or metal/polytetrafluoroethylene-composite catalyst layer. Unlike some prior methods of making fine metal catalysts, this method does not involve processing at elevated temperature; all processing can be done at room temperature. In addition, this method involves fewer steps and is more amenable to scaling up for mass production. Alumina nanotemplates are porous alumina membranes that have been fabricated, variously, by anodizing either pure aluminum or aluminum that has been deposited on silicon by electronbeam evaporation. The diameters of the pores (7 to 300 nm), areal densities of pores (as much as 7 x 10(exp 10)sq cm), and lengths of pores (up to about 100 nm) can be tailored by selection of fabrication conditions. In a given case, the catalytic metal, catalytic metal alloy, or catalytic metal/ polytetrafluoroethylene composite is electrodeposited in the pores of the alumina nanotemplate. The dimensions of the pores, together with the electrodeposition conditions

Expanding the Bethe/Gauge dictionary

Science.gov (United States)

Bullimore, Mathew; Kim, Hee-Cheol; Lukowski, Tomasz

2017-11-01

We expand the Bethe/Gauge dictionary between the XXX Heisenberg spin chain and 2d N = (2, 2) supersymmetric gauge theories to include aspects of the algebraic Bethe ansatz. We construct the wave functions of off-shell Bethe states as orbifold defects in the A-twisted supersymmetric gauge theory and study their correlation functions. We also present an alternative description of off-shell Bethe states as boundary conditions in an effective N = 4 supersymmetric quantum mechanics. Finally, we interpret spin chain R-matrices as correlation functions of Janus interfaces for mass parameters in the supersymmetric quantum mechanics.

Expanding the taxonomy of the diagnostic criteria for temporomandibular disorders.

Science.gov (United States)

Peck, C C; Goulet, J-P; Lobbezoo, F; Schiffman, E L; Alstergren, P; Anderson, G C; de Leeuw, R; Jensen, R; Michelotti, A; Ohrbach, R; Petersson, A; List, T

2014-01-01

There is a need to expand the current temporomandibular disorders' (TMDs) classification to include less common but clinically important disorders. The immediate aim was to develop a consensus-based classification system and associated diagnostic criteria that have clinical and research utility for less common TMDs. The long-term aim was to establish a foundation, vis-à-vis this classification system, that will stimulate data collection, validity testing and further criteria refinement. A working group [members of the International RDC/TMD Consortium Network of the International Association for Dental Research (IADR), members of the Orofacial Pain Special Interest Group (SIG) of the International Association for the Study of Pain (IASP), and members from other professional societies] reviewed disorders for inclusion based on clinical significance, the availability of plausible diagnostic criteria and the ability to operationalise and study the criteria. The disorders were derived from the literature when possible and based on expert opinion as necessary. The expanded TMDs taxonomy was presented for feedback at international meetings. Of 56 disorders considered, 37 were included in the expanded taxonomy and were placed into the following four categories: temporomandibular joint disorders, masticatory muscle disorders, headache disorders and disorders affecting associated structures. Those excluded were extremely uncommon, lacking operationalised diagnostic criteria, not clearly related to TMDs, or not sufficiently distinct from disorders already included within the taxonomy. The expanded TMDs taxonomy offers an integrated approach to clinical diagnosis and provides a framework for further research to operationalise and test the proposed taxonomy and diagnostic criteria. © 2014 John Wiley & Sons Ltd.

The Expanding Marketplace for Applied Geophysics

Science.gov (United States)

Carlson, N.; Sirles, P.

2012-12-01

While the image of geophysics for the proverbial "layman" often seems limited to volcanoes and earthquakes, and to the geoscientist this image enlarges to include oil or minerals exploration and whole earth studies, there has been a steady increase in the application of geophysics into the realm of "daily life", such as real estate deals, highway infrastructure, and flood protection. This expansion of applications can be attributed to the improved economics from advances in equipment and interpretation. Traditional geophysical methods that at one time often only fit within the budgets of oil, gas, and minerals exploration programs can now be economically applied to much smaller scale needs like contaminant mapping, landfill delineation, and levee investigations. A real-world, economic example of this expanding marketplace is our company, which began very small and was aimed almost exclusively at the minerals exploration market. Most of our growth has been in the last 10 years, when we have expanded to five offices and a staff with almost 40 geoscientist degrees (21 in geophysics); much of this growth has been in the non-oil, non-minerals arenas. While much of our work still includes minerals exploration, other projects this year include wind-farm foundation studies, cavity detection above underground nuclear tests, landfill studies, acid mine drainage problems, and leaks in evaporation ponds. A methodology example of this expanding market is the induced polarization (IP) survey, once primarily used for minerals exploration, particularly large porphyry copper deposits, but now efficient enough to also use in environmental studies. The IP method has been particularly useful in delineating and characterizing old, poorly documented landfills, and recent research suggests it may also be useful in monitoring the accelerated biodegradation processes used in some cases to rehabilitate the sites. Compared to temperature monitoring systems, IP may be more useful in providing

Uranium requirements for advanced fuel cycles in expanding nuclear power systems

International Nuclear Information System (INIS)

Banerjee, S.; Tamm, H.

1978-01-01

When considering advanced fuel cycle strategies in rapidly expanding nuclear power systems, equilibrium analyses do not apply. A computer simulation that accounts for system delay times and fissile inventories has been used to study the effects of different fuel cycles and different power growth rates on uranium consumption. The results show that for a given expansion rate of installed capacity, the main factors that affect resource requirements are the fissile inventory needed to introduce the advanced fuel cycle and the conversion (or breeding) ratio. In rapidly expanding systems, the effect of fissile inventory dominates, whereas in slowly expanding systems, conversion or breeding ratio dominates. Heavy-water-moderated and -cooled reactors, with their high conversion ratios, appear to be adaptable vehicles for accommodating fuel cycles covering a wide range of initial fissile inventories. They are therefore particularly suitable for conserving uranium over a wide range of nuclear power system expansion rates

Renal Transplant Ureteral Stenosis: Treatment by Self-Expanding Metallic Stent

International Nuclear Information System (INIS)

Cantasdemir, Murat; Kantarci, Fatih; Numan, Furuzan; Mihmanli, Ismail; Kalender, Betul

2003-01-01

We report the use of a metallic stent in a transplant ureteral stenosis. A 28-year-old man with chronic renal failure due to chronic pyelonephritis, who received a living-donor renal transplant, presented with transplant ureteral stenosis. The stenosis was unresponsive to balloon dilation and was treated by antegrade placement of a self-expanding Memotherm stent. The stentedureter stayed patent for 3 years. It may be reasonable to treat post-transplant ureteral stenosis resistant to balloon dilation with self-expanding metallic stents. However, long-term follow-up is required to evaluate the efficacy of this treatment

Expanded Mixed Multiscale Finite Element Methods and Their Applications for Flows in Porous Media

KAUST Repository

Jiang, L.

2012-01-01

We develop a family of expanded mixed multiscale finite element methods (MsFEMs) and their hybridizations for second-order elliptic equations. This formulation expands the standard mixed multiscale finite element formulation in the sense that four unknowns (hybrid formulation) are solved simultaneously: pressure, gradient of pressure, velocity, and Lagrange multipliers. We use multiscale basis functions for both the velocity and the gradient of pressure. In the expanded mixed MsFEM framework, we consider both separable and nonseparable spatial scales. Specifically, we analyze the methods in three categories: periodic separable scales, G-convergent separable scales, and a continuum of scales. When there is no scale separation, using some global information can significantly improve the accuracy of the expanded mixed MsFEMs. We present a rigorous convergence analysis of these methods that includes both conforming and nonconforming formulations. Numerical results are presented for various multiscale models of flow in porous media with shale barriers that illustrate the efficacy of the proposed family of expanded mixed MsFEMs. © 2012 Society for Industrial and Applied Mathematics.

The Artful Universe Expanded

International Nuclear Information System (INIS)

Bassett, B A

2005-01-01

The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music-a new type of 'cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson, hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature's code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one's mind a vision that unifies science, art and culture and glimpse a universal tapestry of great beauty. (book review)

The Artful Universe Expanded

Energy Technology Data Exchange (ETDEWEB)

Bassett, B A [Institute of Cosmology and Gravitation, University of Portsmouth (United Kingdom)

2005-07-29

The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music-a new type of 'cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson, hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature's code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one's mind a vision that unifies science, art and culture and glimpse a universal tapestry of great

Early recurrence of obstructive jaundice after placement of a self-expanding metal endoprosthesis

NARCIS (Netherlands)

Fockens, P.; Waxman, I.; Davids, P. H.; Huibregtse, K.; Tytgat, G. N.

1992-01-01

Self-expanding metal endoprostheses have ben used in the treatment of malignant obstructive jaundice for a few years. We report on a patient with obstructive jaundice due to a metastasis of a squamous cell lung cancer into the pancreatic head who received an expandable metal endoprosthesis and

Einstein's conversion from his static to an expanding universe

Science.gov (United States)

Nussbaumer, Harry

2014-02-01

In 1917 Einstein initiated modern cosmology by postulating, based on general relativity, a homogenous, static, spatially curved universe. To counteract gravitational contraction he introduced the cosmological constant. In 1922 Alexander Friedman showed that Albert Einstein's fundamental equations also allow dynamical worlds, and in 1927 Georges Lemaître, backed by observational evidence, concluded that our universe was expanding. Einstein impetuously rejected Friedman's as well as Lemaître's findings. However, in 1931 he retracted his former static model in favour of a dynamic solution. This investigation follows Einstein on his hesitating path from a static to the expanding universe. Contrary to an often advocated belief the primary motive for his switch was not observational evidence, but the realisation that his static model was unstable.

Agricultural residues and expanded clay in Oncidium baueri Lindl. orchid cultivation

Directory of Open Access Journals (Sweden)

Matheus Marchezi Mora

2015-02-01

Full Text Available For orchid cultivation in containers is essential to select the right substrate, since this will influence the quality of the final product, it serve as a support for the root system of the plants. This study aimed to evaluate different agricultural residues and expanded clay in Oncidium baueri Lindl. orchid cultivation. The plants were subjected to treatments: pinus husk + carbonized rice husk, pinus husk + coffee husk, pinus husk + fibered coconut, pecan nut husk, expanded clay, fibered coconut, coffee husk, carbonized rice husk, pinus husk. After eleven months of the experiment, the following variables were evaluated: plant height; largest pseudo-bulb diameter; number of buds; shoot fresh dry matter; the longest root length; number of roots; root fresh matter; root dry matter; and electric conductivity; pH and water retention capacity of the substrates. Except the expanded clay, the other substrates showed satisfactory results in one or more traits. Standing out among these substrates pinus husk + coffee husk and pine bark + fibered coconut, which favored the most vegetative and root characteristic of the orchid. The mixture of pinus husk + coffee husk and pinus husk + fibered coconut, provided the best results in vegetative and root growth of the orchid Oncidium baueri and the expanded clay did not show favorable results in the cultivation of this species.

Comparison of Expandable and Fixed Interbody Cages in a Human Cadaver Corpectomy Model: Fatigue Characteristics.

Science.gov (United States)

Pekmezci, Murat; Tang, Jessica A; Cheng, Liu; Modak, Ashin; McClellan, Robert T; Buckley, Jenni M; Ames, Christopher P

2016-11-01

In vitro cadaver biomechanics study. The goal of this study is to compare the in situ fatigue life of expandable versus fixed interbody cage designs. Expandable cages are becoming more popular, in large part, due to their versatility; however, subsidence and catastrophic failure remain a concern. This in vitro analysis investigates the fatigue life of expandable and fixed interbody cages in a single level human cadaver corpectomy model by evaluating modes of subsidence of expandable and fixed cages as well as change in stiffness of the constructs with cyclic loading. Nineteen specimens from 10 human thoracolumbar spines (T10-L2, L3-L5) were biomechanically evaluated after a single level corpectomy that was reconstructed with an expandable or fixed cage and anterior dual rod instrumentation. All specimens underwent 98 K cycles to simulate 3 months of postoperative weight bearing. In addition, a third group with hyperlordotic cages was used to simulate catastrophic failure that is observed in clinical practice. Three fixed and 2 expandable cages withstood the cyclic loading despite perfect sagittal and coronal plane fitting of the endcaps. The majority of the constructs settled in after initial subsidence. The catastrophic failures that were observed in clinical practice could not be reproduced with hyperlordotic cages. However, all cages in this group subsided, and 60% resulted in endplate fractures during deployment of the cage. Despite greater surface contact area, expandable cages have a trend for higher subsidence rates when compared with fixed cages. When there is edge loading as in the hyperlordotic cage scenario, there is a higher risk of subsidence and intraoperative fracture during deployment of expandable cages.

Electromagnetic fields in an expanding universe

International Nuclear Information System (INIS)

Hogan, P.A.; Ellis, G.F.R.

1989-01-01

The asymptotic form of the electromagnetic field due to a bounded distribution of charge current in an open, expanding Friedmann--Lemaitre--Robertson--Walker universe is studied. The technique used is to first describe a mechanism for passing from a solution of Maxwell's vacuum field equations on Minkowskian space-time to a solution of Maxwell's field equations in a region free of charge current on the cosmological background. This is tested on the field of an accelerating point charge and then applied to the rigorous treatment of the asymptotic electromagnetic field of a bounded charge-current distribution in Minkowskian space-time given by Goldberg and Kerr [J. Math. Phys. 5, 172 (1964)]. A ''peeling expansion'' of the electromagnetic field in the expanding universe is obtained in inverse powers of a parameter that is proportional to the area distance along the generators of future null cones with vertices on the world line of a fundamental observer. The algebraic character of the two leading coefficients in the expansion is the same as that of the two leading coefficients in the Goldberg--Kerr expansion in Minkowskian space-time. In addition, bounds can be calculated, at any instant in the history of a fundamental observer, on all the coefficients in the peeling expansion, as a consequence of the evaluation of such bounds by Goldberg and Kerr in the case treated by them

Hubble, Hubble's Law and the Expanding Universe

Indian Academy of Sciences (India)

Srimath

H ubble's nam e is associated closely w ith the idea of an expanding universe as he discovered the relation between the recession velocity and the distances of galaxies. H ubble also did a lot of pioneering w ork on the distribution of galaxies in the universe. In this article we take a look at H ubble's law and discuss how it ...

Remedial Action Plan for Expanded Bioventing System Facility 6454

National Research Council Canada - National Science Library

1996-01-01

This draft remedial action plan (RAP) presents the scope for an expanded bioventing system for in situ treatment of fuel-contaminated soils at Site 6454 at Vandenberg Air Force Base (AFB), California...

Expanded Mixed Multiscale Finite Element Methods and Their Applications for Flows in Porous Media

KAUST Repository

Jiang, L.; Copeland, D.; Moulton, J. D.

2012-01-01

We develop a family of expanded mixed multiscale finite element methods (MsFEMs) and their hybridizations for second-order elliptic equations. This formulation expands the standard mixed multiscale finite element formulation in the sense that four

On Dark Energy and Matter of the Expanding Universe

Directory of Open Access Journals (Sweden)

Lehnert B.

2009-04-01

Full Text Available At present the expanding universe is observed to be dominated by the not fully under- stood concepts of dark energy and matter, in a conceived almost flat Euclidian geometry. As one of the possible efforts to understand the global behaviour of the expanding uni- verse, the present paper attempts to explain these concepts in terms of the pressure force and gravity of a spherical photon gas cloud of zero point energy, in a flat geometry. A difficult point of the conventional theory concerns the frequency distribution of the zero point energy oscillations which leads to the unacceptable result of an infinite total en- ergy per unit volume. A modification of this distribution is therefore proposed which results in finite energy density. A corresponding equilibrium state is investigated, as well as small dynamic deviations from it, to form a basis for a model of the expanding universe. Provided that the crucial points of the present approach hold true, the model satisfies the requirements of cosmic linear dimensions, results in an estimated accelera- tion of the expansion being of the order of the observed one, presents a possible solution of the coincidence problem of dark energy and matter, and provides one of the possible explanations of the observed excess of high-energy electrons and positrons in recent balloon and satellite experiments.

Stability of stagnation via an expanding accretion shock wave

International Nuclear Information System (INIS)

Velikovich, A. L.; Giuliani, J. L.; Murakami, M.; Taylor, B. D.; Zalesak, S. T.; Iwamoto, Y.

2016-01-01

Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

Stability of stagnation via an expanding accretion shock wave

Energy Technology Data Exchange (ETDEWEB)

Velikovich, A. L.; Giuliani, J. L. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Murakami, M. [Institute of Laser Engineering, Osaka University, Osaka 565-0871 (Japan); Taylor, B. D. [Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington, DC 20375 (United States); Zalesak, S. T. [Berkeley Research Associates, Beltsville, Maryland 20705 (United States); Iwamoto, Y. [Ehime University, Matsuyama, Ehime Pref. 790-8577 (Japan)

2016-05-15

Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

Stability of stagnation via an expanding accretion shock wave

Science.gov (United States)

Velikovich, A. L.; Murakami, M.; Taylor, B. D.; Giuliani, J. L.; Zalesak, S. T.; Iwamoto, Y.

2016-05-01

Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

Experimental performance of a piston expander in a small- scale organic Rankine cycle

Science.gov (United States)

Oudkerk, J. F.; Dickes, R.; Dumont, O.; Lemort, V.

2015-08-01

Volumetric expanders are suitable for more and more applications in the field of micro- and small-scale power system as waster heat recovery or solar energy. This paper present an experimental study carried out on a swatch-plate piston expander. The expander was integrated into an ORC test-bench using R245fa. The performances are evaluated in term of isentropic efficiency and filling factor. The maximum efficiency and power reached are respectively 53% and 2 kW. Inside cylinder pressure measurements allow to compute mechanical efficiency and drown P-V diagram. A semi-empirical simulation model is then proposed, calibrated and used to analyse the different sources of losses.

Expanded clinical spectrum of enhanced S-cone syndrome

NARCIS (Netherlands)

Yzer, Suzanne; Barbazetto, Irene; Allikmets, Rando; van Schooneveld, Mary J.; Bergen, Arthur; Tsang, Stephen H.; Jacobson, Samuel G.; Yannuzzi, Lawrence A.

2013-01-01

New funduscopic findings in patients with enhanced S-cone syndrome (ESCS) may help clinicians in diagnosing this rare autosomal recessive retinal dystrophy. To expand the clinical spectrum of ESCS due to mutations in the NR2E3 gene. Retrospective, noncomparative case series of 31 patients examined

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)

Expanding beyond individualism: Engaging critical perspectives on occupation.

Science.gov (United States)

Gerlach, Alison J; Teachman, Gail; Laliberte-Rudman, Debbie; Aldrich, Rebecca M; Huot, Suzanne

2018-01-01

Perspectives that individualize occupation are poorly aligned with socially responsive and transformative occupation-focused research, education, and practice. Their predominant use in occupational therapy risks the perpetuation, rather than resolution, of occupational inequities. In this paper, we problematize taken-for-granted individualistic analyses of occupation and illustrate how critical theoretical perspectives can reveal the ways in which structural factors beyond an individual's immediate control and environment shape occupational possibilities and occupational engagement. Using a critically reflexive approach, we draw on three distinct qualitative research studies to examine the potential of critical theorizing for expanding beyond a reliance on individualistic analyses and practices. Our studies highlight the importance of addressing the socio-historical and political contexts of occupation and demonstrate the contribution of critical perspectives to socially responsive occupational therapy. In expanding beyond individualistic analyses of occupation, critical perspectives advance research and practices towards addressing socio-political mediators of occupational engagement and equity.

Wiggler magnetic field assisted third harmonic generation in expanding clusters

Science.gov (United States)

Vij, Shivani

2018-04-01

A simple theoretical model is constructed to study the wiggler magnetic field assisted third harmonic generation of intense short pulse laser in a cluster in its expanding phase. The ponderomotive force of laser causes density perturbations in cluster electron density which couples with wiggler magnetic field to produce a nonlinear current that generates transverse third harmonic. An intense short pulse laser propagating through a gas embedded with atomic clusters, converts it into hot plasma balls via tunnel ionization. Initially, the electron plasma frequency inside the clusters ω pe > \\sqrt{3}{ω }1 (with ω 1 being the frequency of the laser). As the cluster expands under Coulomb force and hydrodynamic pressure, ω pe decreases to \\sqrt{3}{ω }1. At this time, there is resonant enhancement in the efficiency of the third harmonic generation. The efficiency of third harmonic generation is enhanced due to cluster plasmon resonance and by phase matching due to wiggler magnetic field. The effect of cluster size on the expansion rate is studied to observe that the clusters of different radii would expand differently. The impact of laser intensity and wiggler magnetic field on the efficiency of third harmonic generation is also explored.

Basic Study on Engine with Scroll Compressor and Expander

Science.gov (United States)

Morishita, Etsuo; Kitora, Yoshihisa; Nishida, Mitsuhiro

Scroll compressors are becoming popular in air conditioning and refrigeration. This is primarily due to their higher efficiency and low noise/vibration characteristics. The scroll principle can be applied also to the steam expander and the Brayton cycle engine,as shown in the past literature. The Otto cycle spark-ignition engine with a scroll compressor and expander is studied in this report. The principle and basic structure of the scroll engine are explained,and the engine characteristic are calculated based on the idealized cycles and processes. A prototype model has been proposed and constructed. The rotary type engine has always had a problem with sealing. The scroll engine might overcome this shortcoming with its much lower rubbing speed compared to its previous counterparts,and is therefore worth investigating.

Tear Gas, Expanding Bullets and Plain-Clothed Personnel

DEFF Research Database (Denmark)

Wiesener, Cornelius Rust

2017-01-01

This article examines the interplay between human rights law and humanitarian law in relation to riot control agents (such as tear gas), expanding bullets and plain-clothed forces. While outlawed under humanitarian law, they are widely used by police in peace time and not subject to similar bans...

Expanding Library Support of Faculty Research: Exploring Readiness

Science.gov (United States)

Brown, Jeanne M.; Tucker, Cory

2013-01-01

The changing research and information environment requires a reexamination of library support for research. This study considers research-related attitudes and practices to identify elements indicating readiness or resistance to expanding the library's role in research support. A survey of faculty conducted at the University of Nevada Las Vegas…

Assessing Community Needs for Expanding Environmental Education Programming

Science.gov (United States)

Hintz, Carly J.; Lackey, Brenda K.

2017-01-01

Based on increased demand for educational programming, leadership at Schmeeckle Reserve, a campus natural area in Stevens Point, WI explored the needs for expanded environmental education efforts. In 2014, a three-phased needs assessment framework was employed to explore educational programming offered in the community. Results from interviews and…

Expander graphs in pure and applied mathematics

OpenAIRE

Lubotzky, Alexander

2012-01-01

Expander graphs are highly connected sparse finite graphs. They play an important role in computer science as basic building blocks for network constructions, error correcting codes, algorithms and more. In recent years they have started to play an increasing role also in pure mathematics: number theory, group theory, geometry and more. This expository article describes their constructions and various applications in pure and applied mathematics.

Safety of endoscopic removal of self-expandable stents after treatment of benign esophageal diseases

NARCIS (Netherlands)

van Halsema, Emo E.; Wong Kee Song, Louis M.; Baron, Todd H.; Siersema, Peter D.; Vleggaar, Frank P.; Ginsberg, Gregory G.; Shah, Pari M.; Fleischer, David E.; Ratuapli, Shiva K.; Fockens, Paul; Dijkgraaf, Marcel G. W.; Rando, Giacomo; Repici, Alessandro; van Hooft, Jeanin E.

2013-01-01

Temporary placement of self-expandable stents has been increasingly used for the management of benign esophageal diseases. To evaluate the safety of endoscopic removal of esophageal self-expandable stents placed for the treatment of benign esophageal diseases. Multicenter retrospective study. Six

Farmer's market, demonstration gardens, and research projects expand outreach of Extension Master Gardeners

Science.gov (United States)

Pamela J. Bennett; Ellen M. Bauske; Alison Stoven O' Connor; Jean Reeder; Carol Busch; Heidi A. Kratsch; Elizabeth Leger; Angela O' Callaghan; Peter J. Nitzche; Jim Downer

2013-01-01

Extension Master Gardener (EMG) volunteers are central to expanding the outreach and engagement of extension staff. A workshop format was used at the Annual Conference of the American Society for Horticultural Science on 31 July 2012 in Miami, FL to identify successful management techniques and projects that expand EMG volunteer outreach, leading to increased extension...

Gravitational mass in an expanding universe

International Nuclear Information System (INIS)

Sannan, S.

1986-01-01

A test for the Hawking definition of mass is given in a Tolman--Bondi model that asymptotically approaches the open Friedmann universe. An expanding universe filled with dustlike matter of zero pressure is considered. The matter distribution is spherically symmetric but nonhomogeneous. With appropriate boundary conditions, the calculation yields a finite and nonzero value for the Hawking mass, measured as a deviation from a ''renormalized'' zero mass in the unperturbed Friedmann model. These boundary conditions are more restrictive than those found for a model with gravitational radiation

Effect of surface reactions on steel, Al{sub 2}O{sub 3} and Si{sub 3}N{sub 4} counterparts on their tribological performance with polytetrafluoroethylene filled composites

Energy Technology Data Exchange (ETDEWEB)

Shen, J.T.; Top, M. [Materials Innovation Institute M2i, Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Ivashenko, O.; Rudolf, P. [Department of Surfaces and Thin Films, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Pei, Y.T., E-mail: y.pei@rug.nl [Materials Innovation Institute M2i, Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Department of Advanced Production Engineering, Engineering and Technology Institute Groningen, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); De Hosson, J.Th.M., E-mail: j.t.m.de.hosson@rug.nl [Materials Innovation Institute M2i, Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

2015-03-15

Highlights: • The influence of surface reactions with PTFE on the tribo-performance of different counterparts is revealed. • Experiments confirm that friction can be greatly reduced by two F-terminated surfaces sliding over each other. • Al−F and Fe−F chemical bonding form on the surface of alumina and steel counterpart balls during sliding against PTFE-containing composite. • No Si−F bonding formed on Si{sub 3}N{sub 4} ball under the same condition, leading to higher friction and wear. - Abstract: The influence of surface reactions on the tribo-performance of steel, Al{sub 2}O{sub 3} and Si{sub 3}N{sub 4} balls sliding against polytetrafluoroethylene/SiO{sub 2}/epoxy composites was investigated. Al{sub 2}O{sub 3} ball were found to exhibit the best tribo-performance, namely a low coefficient of friction and the lowest wear rates of both the composites and the counterpart ball, when sliding against the PTFE filled composites. The difference in the tribo-performance of the Al{sub 2}O{sub 3} ball and the Si{sub 3}N{sub 4} ball can neither be attributed to the different morphology of the worn composite surfaces nor to the amount of PTFE transferred onto the wear surfaces. Instead we found that the friction is greatly reduced in the case of the Al{sub 2}O{sub 3} ball because two fluoro-terminated surfaces are sliding over each other; in fact, the formation of Al−F bonding was confirmed by X-ray photoelectron spectroscopy.