Antral hyperplastic polyp causing intermittent gastric outlet obstruction: Case report

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Kurtkaya-Yapicier Ozlem

2003-06-01

Full Text Available Abstract Background Hyperplastic polyps are the most common polypoid lesions of the stomach. Rarely, they cause gastric outlet obstruction by prolapsing through the pyloric channel, when they arise in the prepyloric antrum. Case presentation A 62-year-old woman presented with intermittent nausea and vomiting of 4 months duration. Upper gastrointestinal endoscopy revealed a 30 mm prepyloric sessile polyp causing intermittent gastric outlet obstruction. Following submucosal injection of diluted adrenaline solution, the polyp was removed with a snare. Multiple biopsies were taken from the greater curvature of the antrum and the corpus. Rapid urease test for Helicobacter pylori yielded a negative result. Histopathologic examination showed a hyperplastic polyp without any evidence of malignancy. Biopsies of the antrum and the corpus revealed gastritis with neither atrophic changes nor Helicobacter pylori infection. Follow-up endoscopy after a 12-week course of proton pomp inhibitor therapy showed a complete healing without any remnant tissue at the polypectomy site. The patient has been symptom-free during 8 months of follow-up. Conclusions Symptomatic gastric polyps should be removed preferentially when they are detected at the initial diagnostic endoscopy. Polypectomy not only provides tissue to determine the exact histopathologic type of the polyp, but also achieves radical treatment.

Infective endocarditis causing mitral valve stenosis - a rare but deadly complication: a case report.

Science.gov (United States)

Hart, Michael A; Shroff, Gautam R

2017-02-17

Infective endocarditis rarely causes mitral valve stenosis. When present, it has the potential to cause severe hemodynamic decompensation and death. There are only 15 reported cases in the literature of mitral prosthetic valve bacterial endocarditis causing stenosis by obstruction. This case is even more unusual due to the mechanism by which functional mitral stenosis occurred. We report a case of a 23-year-old white woman with a history of intravenous drug abuse who presented with acute heart failure. Transthoracic echocardiography failed to show valvular vegetation, but high clinical suspicion led to transesophageal imaging that demonstrated infiltrative prosthetic valve endocarditis causing severe mitral stenosis. Despite extensive efforts from a multidisciplinary team, she died as a result of her critical illness. The discussion of this case highlights endocarditis physiology, the notable absence of stenosis in modified Duke criteria, and the utility of transesophageal echocardiography in clinching a diagnosis. It advances our knowledge of how endocarditis manifests, and serves as a valuable lesson for clinicians treating similar patients who present with stenosis but no regurgitation on transthoracic imaging, as a decision to forego a transesophageal echocardiography could cause this serious complication of endocarditis to be missed.

Causes of death from the randomized CoreValve US Pivotal High-Risk Trial.

Science.gov (United States)

Gaudiani, Vincent; Deeb, G Michael; Popma, Jeffrey J; Adams, David H; Gleason, Thomas G; Conte, John V; Zorn, George L; Hermiller, James B; Chetcuti, Stan; Mumtaz, Mubashir; Yakubov, Steven J; Kleiman, Neal S; Huang, Jian; Reardon, Michael J

2017-06-01

Explore causes and timing of death from the CoreValve US Pivotal High-Risk Trial. An independent clinical events committee adjudicated causes of death, followed by post hoc hierarchical classification. Baseline characteristics, early outcomes, and causes of death were evaluated for 3 time periods (selected based on threshold of surgical 30-day mortality and on the differences in the continuous hazard between the 2 groups): early (0-30 days), recovery (31-120 days), and late (121-365 days). Differences in the rate of death were evident only during the recovery period (31-120 days), whereas 15 patients undergoing transcatheter aortic valve replacement (TAVR) (4.0%) and 27 surgical aortic valve replacement (SAVR) patients (7.9%) died (P = .025). This mortality difference was largely driven by higher rates of technical failure, surgical complications, and lack of recovery following surgery. From 0 to 30 days, the causes of death were more technical failures in the TAVR group and lack of recovery in the SAVR group. Mortality in the late period (121-365 days) in both arms was most commonly ascribed to other circumstances, comprising death from medical complications from comorbid disease. Mortality at 1 year in the CoreValve US Pivotal High-Risk Trial favored TAVR over SAVR. The major contributor was that more SAVR patients died during the recovery period (31-121 days), likely affected by the overall influence of physical stress associated with surgery. Similar rates of technical failure and complications were observed between the 2 groups. This suggests that early TAVR results can improve with technical refinements and that high-risk surgical patients will benefit from reducing complications. Copyright © 2017 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Reoperation for non-structural valvular dysfunction caused by pannus ingrowth in aortic valve prosthesis.

Science.gov (United States)

Oh, Se Jin; Park, Samina; Kim, Jun Sung; Kim, Kyung-Hwan; Kim, Ki Bong; Ahn, Hyuk

2013-07-01

The authors' clinical experience is presented of non-structural valvular dysfunction of the prosthetic aortic valve caused by pannus ingrowth during the late postoperative period after previous heart valve surgery. Between January 1999 and April 2012, at the authors' institution, a total of 33 patients underwent reoperation for increased mean pressure gradient of the prosthetic aortic valve. All patients were shown to have pannus ingrowth. The mean interval from the previous operation was 16.7 +/- 4.3 years, and the most common etiology for the previous aortic valve replacement (AVR) was rheumatic valve disease. The mean effective orifice area index (EOAI) of the previous prosthetic valve was 0.97 +/- 0.11 cm2/m2, and the mean pressure gradient on the aortic prosthesis before reoperation was 39.1 +/- 10.7 mmHg. Two patients (6.1%) died in-hospital, and late death occurred in six patients (18.2%). At the first operation, 30 patients underwent mitral or tricuspid valve surgery as a concomitant procedure. Among these operations, mitral valve replacement (MVR) was combined in 24 of all 26 patients with rheumatic valve disease. Four patients underwent pannus removal only while the prosthetic aortic valve was left in place. The mean EOAI after reoperation was significantly increased to 1.16 +/- 0.16 cm2/m2 (p pannus ingrowth was shown in patients with a small EOAI of the prosthetic aortic valve and combined MVR for rheumatic disease. As reoperation for pannus overgrowth showed good clinical outcomes, an aggressive resection of pannus and repeated AVR should be considered in symptomatic patients to avoid the complications of other cardiac diseases.

Mitral valve stenosis caused by abnormal pannus extension over the prosthetic ring and leaflets after Duran ring mitral annuloplasty.

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Yunoki, Junji; Minato, Naoki; Katayama, Yuji; Sato, Hisashi

2009-01-01

We treated a 61-year-old woman with mitral stenosis caused by pannus formation after Duran ring annuloplasty. Pannus overgrowth on the ring with extension onto both leaflets narrowed the mitral orifice and severely restricted the mobility of the valve leaflets. Mitral valve replacement with a St. Jude Medical mechanical heart valve prosthesis was successfully performed, and the postoperative course was uneventful. Patients undergoing Duran ring annuloplasty should be followed up with the consideration of possible mitral stenosis caused by pannus extension, as the cause for pannus formation remains unclear.

ICDE project report: collection and analysis of common-cause failure of check valves

International Nuclear Information System (INIS)

Theiss, Klaus; Hessel, Philippe; Werner, Wolfgang

2003-05-01

This report documents a study performed on the set of Common Cause Failure (CCF) events of Check Valves (CVs). The events studied here were derived from the International CCF Data Exchange (ICDE) database. Organizations from Canada, Finland, France, Germany, Netherlands, Sweden, Switzerland and the United States contributed with data to this data exchange. This study examines 94 CCF events of CVs reported in the ICDE database by tabulating the data and observing trends. The database contains general information about event attributes like root cause, coupling factor, detection method and corrective action taken. As part of this study, most of these events were reviewed in more detail and characterized by failure cause and failure symptom categories. The study itself begins with an overview of the entire data set in chapter 5. Charts are provided for each of the above-mentioned event attributes. This chapter forms the baseline for chapter 6. The intention of chapter 6 is to give the reader a deeper qualitative insight in the database content beyond that obtained from using the event coding only. Chapter 7 contains the summary of the study results and the conclusions derived from. Approximately 8% of all ICDE events of CVs were complete CCFs (all redundant components had failed). The number of partial CCF events (at least two of the redundant components failed) accounted for 24%. In the remaining 68% of the ICDE events, less than two components had failed completely, and the other components of the observed group only suffered from small defects, incipient degradation or were not affected at all. However, it was found that for more than 75% of the ICDE events the causal factors had a high probability to be shared by all the redundant components. 88 of the 94 reported ICDE events were reviewed in some more detail in Section 6 of this report with respect to failure causes, failure symptoms and failure mechanism. All events classified with a low 'shared cause factor

Floating tumor debris. A cause of intermittent biliary obstruction.

Science.gov (United States)

Roslyn, J J; Kuchenbecker, S; Longmire, W P; Tompkins, R K

1984-11-01

Tumor debris, free-floating in the major biliary ductal system, is a cause of intermittent biliary obstruction that has previously not been recognized. Six patients had hepatic neoplasms with episodic jaundice and/or cholangitis due to floating tumor debris. Diagnosis included metastatic adenocarcinoma of the colon (n = 3), cholangiocarcinoma (n = 1), hepatocellular carcinoma (n = 1), and cavernous hemangioma (n = 1). All patients underwent biliary exploration, with hepatic resection and transhepatic intubation in two and T-tube placement in four. One patient died in the early postoperative period, and the major complication rate in the five survivors was 0%. Four of the five survivors had no further episodes suggestive of major bile duct obstruction. Our experience emphasizes the importance of distinguishing extrahepatic obstruction secondary to tumor debris from the more common causes of jaundice in patients with tumors and suggests that safe and effective palliation can be achieved in these patients.

Evaluation Of Factors Influencing On Causes Of Prosthetic Valve Re-operation And Early Postoperative Survival Tehran Emam hospital (1991-2001

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Rahmani Reaza

2003-06-01

Full Text Available Prosthetic valve re-operation has greater mortality and morbidity than primary valve replacement. By recognition of factors influencing on causes of redo operation and preoperative survival, one can select appropriate prosthesis at primary valve replacement and when operation performed at appropriate time, surgical risk can be reduced."nMethods and Materials: Two hundred patients that underwent prosthetic valve re-operation from October 1991 through November 2001 were included in this study. There were 68 men and 132 women with the mean age of 42:tl 1.8 years. Structural failure was the commonest cause of bio-prosthesis replacement (93%. Valve thrombosis was the common cause of mechanical valve replacement (32%. Age younger Than 50 (P= 0.01 and interval after the first implantation more than 10 years (P= 0.01 affected bio-prosthesis degeneration."nResults: Atrial fibrillation (P<0.01, Older age especially more than 40 (P<0.05 and mitral position (P<0.01 affected mechanical valve thrombosis. Cross clamp time (P= 0.005, Tricuspid insufficiency (P = 0.001, NYHA IV (P = 0.005 and emergent operation (P= 0.001 were independent determinants of hospital mortality."nConclusion: In conclusion, in patients with more than 10-years life expectancy and age younger than 50, mechanical valve can be selected for primary valve replacement. If operation performed before patients reach deteriorated condition, preoperative survival would be excellent.

Intermittent Hypoxia Causes Inflammation and Injury to Human Adult Cardiac Myocytes.

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Wu, Jing; Stefaniak, Joanna; Hafner, Christina; Schramel, Johannes Peter; Kaun, Christoph; Wojta, Johann; Ullrich, Roman; Tretter, Verena Eva; Markstaller, Klaus; Klein, Klaus Ulrich

2016-02-01

Intermittent hypoxia may occur in a number of clinical scenarios, including interruption of myocardial blood flow or breathing disorders such as obstructive sleep apnea. Although intermittent hypoxia has been linked to cardiovascular and cerebrovascular disease, the effect of intermittent hypoxia on the human heart is not fully understood. Therefore, in the present study, we compared the cellular responses of cultured human adult cardiac myocytes (HACMs) exposed to intermittent hypoxia and different conditions of continuous hypoxia and normoxia. HACMs were exposed to intermittent hypoxia (0%-21% O2), constant mild hypoxia (10% O2), constant severe hypoxia (0% O2), or constant normoxia (21% O2), using a novel cell culture bioreactor with gas-permeable membranes. Cell proliferation, lactate dehydrogenase release, vascular endothelial growth factor release, and cytokine (interleukin [IL] and macrophage migration inhibitory factor) release were assessed at baseline and after 8, 24, and 72 hours of exposure. A signal transduction pathway finder array was performed to determine the changes in gene expression. In comparison with constant normoxia and constant mild hypoxia, intermittent hypoxia induced earlier and greater inflammatory response and extent of cell injury as evidenced by lower cell numbers and higher lactate dehydrogenase, vascular endothelial growth factor, and proinflammatory cytokine (IL-1β, IL-6, IL-8, and macrophage migration inhibitory factor) release. Constant severe hypoxia showed more detrimental effects on HACMs at later time points. Pathway analysis demonstrated that intermittent hypoxia primarily altered gene expression in oxidative stress, Wnt, Notch, and hypoxia pathways. Intermittent and constant severe hypoxia, but not constant mild hypoxia or normoxia, induced inflammation and cell injury in HACMs. Cell injury occurred earliest and was greatest after intermittent hypoxia exposure. Our in vitro findings suggest that intermittent hypoxia

Uncoupling of Vascular Nitric Oxide Synthase Caused by Intermittent Hypoxia

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Mohammad Badran

2016-01-01

Full Text Available Objective. Obstructive sleep apnea (OSA, characterized by chronic intermittent hypoxia (CIH, is often present in diabetic (DB patients. Both conditions are associated with endothelial dysfunction and cardiovascular disease. We hypothesized that diabetic endothelial dysfunction is further compromised by CIH. Methods. Adult male diabetic (BKS.Cg-Dock7m +/+ Leprdb/J (db/db mice (10 weeks old and their heterozygote littermates were subjected to CIH or intermittent air (IA for 8 weeks. Mice were separated into 4 groups: IA (intermittent air nondiabetic, IH (intermittent hypoxia nondiabetic, IADB (intermittent air diabetic, and IHDB (intermittent hypoxia diabetic groups. Endothelium-dependent and endothelium-independent relaxation and modulation by basal nitric oxide (NO were analyzed using wire myograph. Plasma 8-isoprostane, interleukin-6 (IL-6, and asymmetric dimethylarginine (ADMA were measured using ELISA. Uncoupling of eNOS was measured using dihydroethidium (DHE staining. Results. Endothelium-dependent vasodilation and basal NO production were significantly impaired in the IH and IADB group compared to IA group but was more pronounced in IHDB group. Levels of 8-isoprostane, IL-6, ADMA, and eNOS uncoupling were ≈2-fold higher in IH and IADB groups and were further increased in the IHDB group. Conclusion. Endothelial dysfunction is more pronounced in diabetic mice subjected to CIH compared to diabetic or CIH mice alone. Oxidative stress, ADMA, and eNOS uncoupling were exacerbated by CIH in diabetic mice.

A case of native valve endocarditis caused by Burkholderia cepacia without predisposing factors

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Han Seong

2011-05-01

Full Text Available Abstract Background Infective endocarditis is rarely caused by Burkholderia cepacia. This infection is known to occur particularly in immunocompromised hosts, intravenous heroin users, and in patients with prosthetic valve replacement. Most patients with Burkholderia cepacia endocarditis usually need surgical treatment in addition to antimicrobial treatment. Case Presentation Here, we report the case of a patient who developed Burkholderia cepacia-induced native valve endocarditis with consequent cerebral involvement without any predisposing factors; she was successfully treated by antimicrobial agents only. Conclusion In this report, we also present literature review of relevant cases.

Anatomic, histopathologic, and echocardiographic features in a dog with an atypical pulmonary valve stenosis with a fibrous band of tissue and a patent ductus arteriosus.

Science.gov (United States)

Yoon, Hakyoung; Kim, Jaehwan; Nahm, Sang-Soep; Eom, Kidong

2017-07-11

Congenital pulmonary valve stenosis and patent ductus arteriosus are common congenital heart defects in dogs. However, concurrence of atypical pulmonary valve stenosis and patent ductus arteriosus is uncommon. This report describes the anatomic, histopathologic, and echocardiographic features in a dog with concomitant pulmonary valve stenosis and patent ductus arteriosus with atypical pulmonary valve dysplasia that included a fibrous band of tissue. A 1.5-year-old intact female Chihuahua dog weighing 3.3 kg presented with a continuous grade VI cardiac murmur, poor exercise tolerance, and an intermittent cough. Echocardiography indicated pulmonary valve stenosis, a thickened dysplastic valve without annular hypoplasia, and a type IIA patent ductus arteriosus. The pulmonary valve was thick line-shaped in systole and dome-shaped towards the right ventricular outflow tract in diastole. The dog suffered a fatal cardiac arrest during an attempted balloon pulmonary valvuloplasty. Necropsy revealed pulmonary valve dysplasia, commissural fusion, and incomplete opening and closing of the pulmonary valve because of a fibrous band of tissue causing adhesion between the right ventricular outflow tract and the dysplastic intermediate cusp of the valve. A fibrous band of tissue between the right ventricular outflow track and the pulmonary valve should be considered as a cause of pulmonary valve stenosis. Pulmonary valve stenosis and patent ductus arteriosus can have conflicting effects on diastolic and systolic dysfunction, respectively. Therefore, beta-blockers should always be used carefully, particularly in patients with a heart defect where there is concern about left ventricular systolic function.

Root cause analysis of pump valve failures of three membrane pump systems

NARCIS (Netherlands)

Buijs, L.J.; Eijk, A.; Hooft, L. van

2014-01-01

This paper will present the root cause analysis and the solution of fatigue failures of the pump valves of three membrane pump systems installed on a chemical plant of Momentive in Pernis, the Netherlands. The membrane pumps were installed approximately 30 years ago. Each system has encountered

Mitral Valve Stenosis

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... the left ventricle from flowing backward. A defective heart valve fails to either open or close fully. Risk factors Mitral valve stenosis is less common today than it once was because the most common cause, ... other heart valve problems, mitral valve stenosis can strain your ...

Aortic valve replacement and the stentless Freedom SOLO valve

NARCIS (Netherlands)

Wollersheim, L.W.L.M.

2016-01-01

Aortic valve stenosis has become the most prevalent valvular heart disease in Europe and North America, and is generally caused by age-related calcification of the aortic valve. For most patients, severe symptomatic aortic stenosis needs effective mechanical relief in the form of valve replacement

Native valve endocarditis due to Corynebacterium group JK.

Science.gov (United States)

Moffie, B G; Veenendaal, R A; Thompson, J

1990-12-01

We report a case of a 32-yr-old woman on chronic intermittent haemodialysis, who developed endocarditis due to a Corynebacterium group JK, involving both the native aortic and mitral valves. Despite a four-week treatment with vancomycin, an aortic root abscess developed. The diagnosis was confirmed on autopsy.

Design and performance characteristic analysis of servo valve-type water hydraulic poppet valve

International Nuclear Information System (INIS)

Park, Sung Hwan

2009-01-01

For water hydraulic system control, the flow or pressure control using high-speed solenoid valve controlled by PWM control method could be a good solution for prevention of internal leakage. However, since the PWM control of on-off valves cause extensive flow and pressure fluctuation, it is difficult to control the water hydraulic actuators precisely. In this study, the servo valve-type water hydraulic valve using proportional poppet as the main valve is designed and the performance characteristics of the servo valve-type water hydraulic valve are analyzed. Furthermore, it is demonstrated through experiments that a decline in control chamber pressure that follows the change of pilot flow is caused by the occurrence of cavitation around the proportional poppet, and that fundamental characteristics of the developed valve remain unaffected by the occurrence of cavitation

An audit of pressure sores caused by intermittent compression devices used to prevent venous thromboembolism.

Science.gov (United States)

Skillman, Joanna; Thomas, Sunil

2011-12-01

When intermittent compression devices (ICDs) are used to prevent venous thromboembolism (VTE) they can cause pressure sores in a selected group of women, undergoing long operations. A prospective audit pre and post intervention showed a reduced risk with an alternative device, without increasing the risk of VTE.

Recurrent infective endocarditis causing heart valve failure: A case report

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Victoria McIntyre, BASc Chemical Engineering (2018 candidate

2017-11-01

Full Text Available Infective endocarditis (IE is an infection that does not usually respond rapidly to treatment, often because its early symptoms are non-specific. The diseased valves (native or bioprosthetic may be calcified and the thrombotic vegetations on them typically friable and embolize easily. Left untreated IE leads to damage to the infected valve and to congestive heart failure (CHF. Its treatment usually requires heart valve replacement. Our 69-year-old patient had IE, and underwent aortic valve replacement (AVR with a bioprosthesis. This case stresses the complications of IE and its tendency to recur in patients with bioprosthetic heart valves (BHV who previously had IE.

Mitral Valve Prolapse

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Mitral valve prolapse (MVP) occurs when one of your heart's valves doesn't work properly. The flaps of the valve are "floppy" and ... to run in families. Most of the time, MVP doesn't cause any problems. Rarely, blood can ...

A case of infective endocarditis along with a ruptured valve caused by Streptococcus agalactiae in an immunocompetent man.

Science.gov (United States)

Suzuki, Kiyozumi; Hirai, Yuji; Morita, Fujiko; Uehara, Yuki; Oshima, Hiroko; Mitsuhashi, Kazunori; Amano, Atsushi; Naito, Toshio

2016-01-01

Streptococcus agalactiae ( S. agalactiae ) is a major cause of invasive disease in neonates and pregnant women, but has also recently been observed among non-pregnant adults, especially elderly persons or persons with underlying chronic disease. S. agalactiae is also a rare cause of infective endocarditis, and most cases require early surgery. We report the case of a 43-year-old previously healthy man who experienced rapid progressive culture-negative infective endocarditis with aortic valve vegetation and severe aortic regurgitation, which was complicated by lumbar spondylodiscitis. Emergency aortic valve replacement was performed on the day of his admission, which revealed a congenital bicuspid aortic valve was ruptured by the vegetation. The resected aortic valve specimen was submitted for 16S ribosomal RNA gene sequencing, which revealed that the pathogen was S. agalactiae . Therefore, S. agalactiae should be considered a potentially causative pathogen in cases of rapid progressive infective endocarditis, even if it occurs in a non-pregnant immunocompetent adult.

Prosthetic valve endocarditis caused by Staphylococcus capitis: report of 4 cases

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Wada Yuko

2011-10-01

Full Text Available Abstract Although Staphylococcus capitis is considered to be a rare causative organism for prosthetic valve endocarditis, we report 4 such cases that were encountered at our hospital over the past 2 years. Case 1 was a 79-year-old woman who underwent aortic valve replacement with a bioprosthetic valve and presented with fever 24 days later. Transesophageal echocardiography revealed an annular abscess in the aorto-mitral continuity and mild perivalvular regurgitation. We performed emergency surgery 5 days after the diagnosis of prosthetic valve endocarditis was made. Case 2 was a 79-year-old woman presenting with fever 40 days after aortic valve replacement with a bioprosthesis. Transesophageal echocardiography showed vegetation on the valve, and she underwent urgent surgery 2 days after prosthetic valve endocarditis was diagnosed. In case 3, a 76-year-old man presented with fever 53 days after aortic valve replacement with a bioprosthesis. Vegetation on the prosthetic leaflet could be seen by transesophageal echocardiography. He underwent emergency surgery 2 days after the diagnosis of prosthetic valve endocarditis was made. Case 4 was a 68-year-old woman who collapsed at her home 106 days after aortic and mitral valve replacement with bioprosthetic valves. Percutaneous cardiopulmonary support was started immediately after massive mitral regurgitation due to prosthetic valve detachment was revealed by transesophageal echocardiography. She was transferred to our hospital by helicopter and received surgery immediately on arrival. In all cases, we re-implanted another bioprosthesis after removal of the infected valve and annular debridement. All patients recovered without severe complications after 2 months of antibiotic treatment, and none experienced re-infection during 163 to 630 days of observation. Since the time interval between diagnosis of prosthetic valve endocarditis and valve re-replacement ranged from 0 to 5 days, early surgical removal

Coronary Emboli in a Young Patient with Mechanical Aortic Valve: A Rare Cause of Acute Myocardial Infarction

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Arash Gholoobi

2016-03-01

Full Text Available Coronary artery embolism is an uncommon cause of Acute Myocardial Infarction (AMI. Herein, we reported a 24-year-old male who was admitted with acute infero-posterior myocardial infarction and cerebral Transient Ischemic Attack (TIA. He had undergone mechanical Aortic Valve Replacement (AVR surgery 6 years ago. Surprisingly, the patient had decided to stop taking his medication (warfarin 20 days earlier without any medical advice. Coronary angiography revealed a thrombus located at the distal part of the left circumflex artery. Discontinuation of anticoagulant therapy in the presence of mechanical valve prosthesis, clinical evidence of coincidental TIA, and lack of atherosclerotic risk factors were highly suggestive of coronary thromboembolism as the cause of AMI. Overall, this case report emphasized the necessity of continuous education in patients with mechanical heart valves to prevent such undesired events.

Heart Valve Diseases

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Your heart has four valves. Normally, these valves open to let blood flow through or out of your heart, and then shut to keep it from flowing ... close tightly. It's one of the most common heart valve conditions. Sometimes it causes regurgitation. Stenosis - when ...

Check valve

Science.gov (United States)

Upton, H.A.; Garcia, P.

1999-08-24

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs.

Check valve

International Nuclear Information System (INIS)

Upton, H.A.; Garcia, P.

1999-01-01

A check valve for use in a GDCS of a nuclear reactor and having a motor driven disk including a rotatable armature for rotating the check valve disk over its entire range of motion is described. In one embodiment, the check valve includes a valve body having a coolant flow channel extending therethrough. The coolant flow channel includes an inlet end and an outlet end. A valve body seat is located on an inner surface of the valve body. The check valve further includes a disk assembly, sometimes referred to as the motor driven disc, having a counterweight and a disk shaped valve. The disk valve includes a disk base having a seat for seating with the valve body seat. The disk assembly further includes a first hinge pin member which extends at least partially through the disk assembly and is engaged to the disk. The disk valve is rotatable relative to the first hinge pin member. The check valve also includes a motor having a stator frame with a stator bore therein. An armature is rotatably positioned within the stator bore and the armature is coupled to the disk valve to cause the disk valve to rotate about its full range of motion. 5 figs

Face-Sealing Butterfly Valve

Science.gov (United States)

Tervo, John N.

1992-01-01

Valve plate made to translate as well as rotate. Valve opened and closed by turning shaft and lever. Interactions among lever, spring, valve plate, and face seal cause plate to undergo combination of translation and rotation so valve plate clears seal during parts of opening and closing motions.

Intermittent hypoxia simulating obstructive sleep apnea causes pulmonary inflammation and activates the Nrf2/HO-1 pathway.

Science.gov (United States)

Wang, Yeying; Chai, Yanling; He, Xiaojie; Ai, Li; Sun, Xia; Huang, Yiling; Li, Yongxia

2017-10-01

Obstructive sleep apnea (OSA) is a disorder with high morbidity in adults. OSA damages multiple organs and tissues, including the cardiovascular and cerebrovascular systems, the metabolism system, the lungs, liver and heart. OSA-induced damage is earliest and greatest to the pulmonary tissue. The present study established a rat OSA model of differing severity by inducing intermittent hypoxia with different concentrations of O 2 and it was determined that OSA caused a severe oxidative stress response and pulmonary inflammation in a dose-dependent manner. OSA increased serum levels of C-reactive protein and 8-isoprostane and elevated the expression of malondialdehyde, tumor necrosis factor α, interleukin (IL)-1β and IL-6 in the pulmonary tissue. Furthermore, the expression of two important antioxidants, superoxide dismutase and glutathione, was downregulated following intermittent hypoxia. By contrast, levels of cylooxygenase 2 and inducible nitric oxide synthase, which are crucial in the antioxidative response, increased. In addition, OSA activates the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase (OH)-1 antioxidative signaling pathway. Finally, all increases and decreases in levels of inflammatory and antioxidative substances were dependent on oxygen concentrations. Therefore, the present study demonstrated that OSA, simulated by intermittent hypoxia, caused an oxidative stress response and pulmonary inflammation, and activated the canonical antioxidative Nrf2/HO-1 signaling pathway in a dose-dependent manner. These results may facilitate the development of clinical therapies to treat pulmonary diseases caused by OSA.

Anterior urethral valves without diverticulum, a rare cause of infravesical obstruction and vesicoureteral reflux in children: Report of two cases and literature review

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Jyoti Bothra

2017-09-01

Full Text Available Congenital anterior urethral valve is a rare condition causing significant obstructive uropathy in pediatric age group. It is much rarer than posterior urethral valve. However, the clinical course is similar. We present two cases of anterior urethral valves in children

Diverticulum of the mitral valve, a rare cause of mitral regurgitation.

LENUS (Irish Health Repository)

Soo, Alan

2010-12-01

Non-infective mitral valve diverticulum is extremely rare. We present a case of intraoperatively diagnosed mitral valve diverticulum of a 69-year-old man presenting with mitral regurgitation who was successfully treated with mitral valve replacement.

Cryogenic Cam Butterfly Valve

Science.gov (United States)

McCormack, Kenneth J. (Inventor)

2016-01-01

A cryogenic cam butterfly valve has a body that includes an axially extending fluid conduit formed there through. A disc lug is connected to a back side of a valve disc and has a circular bore that receives and is larger than a cam of a cam shaft. The valve disc is rotatable for a quarter turn within the body about a lug axis that is offset from the shaft axis. Actuating the cam shaft in the closing rotational direction first causes the camming side of the cam of the cam shaft to rotate the disc lug and the valve disc a quarter turn from the open position to the closed position. Further actuating causes the camming side of the cam shaft to translate the valve disc into sealed contact with the valve seat. Opening rotational direction of the cam shaft reverses these motions.

Prolapsing Gastric Polyp Causing Intermittent Gastric Outlet Obstruction.

Science.gov (United States)

Kosai, Nik Ritza; Gendeh, Hardip Singh; Norfaezan, Abdul Rashid; Razman, Jamin; Sutton, Paul Anthony; Das, Srijit

2015-06-01

Gastric polyps are often an incidental finding on upper gastrointestinal endoscopy, with an incidence up to 5%. The majority of gastric polyps are asymptomatic, occurring secondary to inflammation. Prior reviews discussed Helicobacter pylori (H pylori)-associated singular gastric polyposis; however, we present a rare and unusual case of recurrent multiple benign gastric polyposis post H pylori eradication resulting in intermittent gastric outlet obstruction. A 70-year-old independent male, Chinese in ethnicity, with a background of diabetes mellitus, hypertension, and a simple renal cyst presented with a combination of melena, anemia, and intermittent vomiting of partially digested food after meals. Initial gastroscopy was positive for H pylori; thus he was treated with H pylori eradication and proton pump inhibitors. Serial gastroscopy demonstrated multiple sessile gastric antral polyps, the largest measuring 4 cm. Histopathologic examination confirmed a benign hyperplastic lesion. Computed tomography identified a pyloric mass with absent surrounding infiltration or metastasis. A distal gastrectomy was performed, whereby multiple small pyloric polyps were found, the largest prolapsing into the pyloric opening, thus explaining the intermittent nature of gastric outlet obstruction. Such polyps often develop from gastric ulcers and, if left untreated, may undergo neoplasia to form malignant cells. A distal gastrectomy was an effective choice of treatment, taking into account the polyp size, quantity, and potential for malignancy as opposed to an endoscopic approach, which may not guarantee a complete removal of safer margins and depth. Therefore, surgical excision is favorable for multiple large gastric polyps with risk of malignancy.

Basaloid Squamous Cell Carcinoma: An Unusual Ball-Valve Laryngeal Obstruction

Directory of Open Access Journals (Sweden)

Sien Hui Tan

2015-05-01

Full Text Available Introduction: A rare case of basaloid squamous cell carcinoma (BSCC of the larynx, which has not been previously reported, is described. Case Report: A 60-year-old man was presented to the Otolaryngology Department with progressive dyspnoea and dysphagia to solids for over a period of 1 week. Direct laryngoscopy revealed a tumour at the laryngeal aspect of the epiglottis, which prolapsed into the laryngeal inlet each time the patient inspired. This resulted in an inspiratory stridor despite adequate glottic opening and normal mobility of the vocal cords.   Conclusion:  Therefore, in cases where a ball-valve lesion causes intermittent life-threatening airway obstruction, BSCC of the larynx, though rare, must be considered as a differential diagnosis.

Aortic valve replacement for aortic stenosis caused by alkaptonuria.

Science.gov (United States)

Hiroyoshi, Junko; Saito, Aya; Panthee, Nirmal; Imai, Yasushi; Kawashima, Dai; Motomura, Noboru; Ono, Minoru

2013-03-01

We report a case of aortic stenosis associated with ochronosis in a 70-year-old man who underwent biologic aortic valve replacement. Intraoperative findings included ochronosis of a severely calcified pigmented aortic valve along with pigmentation of the intima of the aorta. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Causes of Death Following Transcatheter Aortic Valve Replacement: A Systematic Review and Meta-Analysis.

Science.gov (United States)

Xiong, Tian-Yuan; Liao, Yan-Biao; Zhao, Zhen-Gang; Xu, Yuan-Ning; Wei, Xin; Zuo, Zhi-Liang; Li, Yi-Jian; Cao, Jia-Yu; Tang, Hong; Jilaihawi, Hasan; Feng, Yuan; Chen, Mao

2015-09-21

Transcatheter aortic valve replacement (TAVR) is an effective alternative to surgical aortic valve replacement in patients at high surgical risk. However, there is little published literature on the exact causes of death. The PubMed database was systematically searched for studies reporting causes of death within and after 30 days following TAVR. Twenty-eight studies out of 3934 results retrieved were identified. In the overall analysis, 46.4% and 51.6% of deaths were related to noncardiovascular causes within and after the first 30 days, respectively. Within 30 days of TAVR, infection/sepsis (18.5%), heart failure (14.7%), and multiorgan failure (13.2%) were the top 3 causes of death. Beyond 30 days, infection/sepsis (14.3%), heart failure (14.1%), and sudden death (10.8%) were the most common causes. All possible subgroup analyses were made. No significant differences were seen for proportions of cardiovascular deaths except the comparison between moderate (mean STS score 4 to 8) and high (mean STS score >8) -risk patients after 30 days post-TAVR (56.0% versus 33.5%, P=0.005). Cardiovascular and noncardiovascular causes of death are evenly balanced both in the perioperative period and at long-term follow-up after TAVR. Infection/sepsis and heart failure were the most frequent noncardiovascular and cardiovascular causes of death. This study highlights important areas of clinical focus that could further improve outcomes after TAVR. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

The effect of varying degrees of stenosis on the characteristics of turbulent pulsatile flow through heart valves.

Science.gov (United States)

Bluestein, D; Einav, S

1995-08-01

Many problems and complications associated with heart valves are related to the dynamic behavior of the valve and the resultant unsteady flow patterns. An accurate depiction of the spatial and temporal velocity and rms distributions imparts better understanding of flow related valve complications, and may be used as a guideline in valve design. While the generalized correlation between increased turbulence level and the severity of the stenosis is well established, few studies addressed the issue of the intermittent nature of turbulence and its timing in the cardiac cycle, and almost none assessed the effect of a progressive stenosis on the flow characteristics through heart valves. In this experimental work we simulated the type of flow which is present in normal and stenosed valves and conducted a comprehensive investigation of valve hemodynamics, valvular turbulence and morphology under varying degrees of stenosis. The characteristics of valves and stenoses were simulated closely, to achieve the flow conditions that initiate turbulent flow conditions. Laser Doppler anemometry (LDA) measurements were carried out in a pulse duplicator system distal to trileaflet polyurethane prosthetic heart valves, installed at mitral and aortic positions. The effect of the degree of the stenosis was comparatively studied through the structure of the turbulent jets emerging from normal and stenotic heart valves. Maximum turbulence level was achieved during the decelerating phase and correlated to the severity of the stenosis, followed by relaminarization of the flow during the acceleration phase. The intermittent nature of the turbulence emphasized the importance of realizing the timing of the turbulence production and its spatial location for optimizing current valve designs. The plug flow through the normal aortic valve prosthesis was replaced by jet like behavior for a 65% stenosis, with the jet becoming narrower and stronger for a 90% stenosis. The morphology of the velocity

Identifying the cause of intermittent problems in diagnostic X-ray machines

International Nuclear Information System (INIS)

Addison, S.J.; O'Brien, M.J.; Robb, D.B.

1987-01-01

Quality assurance testing and performance evaluation of radiologic x-ray equipment is an important part of producing acceptable diagnostic quality images with minimum patient exposure. Regulatory and advisory agencies provide guidance for performing these tests, but it is often only obvious problems which are detected without extensive investigation. It is desirable for the Health Physicist to be able to determine the cause of an intermittent ''bad film'' with a minimum of test equipment. This paper relates some significant performance anomalies which have been identified in diagnostic x-ray equipment from installations in the Seattle area. Many of these problems eluded manufacturer's service personnel. Also included is a description of simple steps which can be included in test procedures to detect these equipment irregularities

Alternative causes of bioreaction to prosthetic heart valves: three cases with pannus formation.

Science.gov (United States)

Karakoyun, Süleyman; Gürsoy, Ozan Mustafa; Kalçık, Macit; Coban Kökten, Sermin; Ozkan, Mehmet

2014-01-01

Pannus formation is an infrequent but serious complication of prosthetic heart valve surgery. The cause of pannus is recognized as a bioreaction to the prostheses; histological investigations have shown that pannus comprises collagen and elastic tissues containing endothelial cells, chronic inflammatory cells, and myofibroblasts. However, the detailed mechanism of its formation has not been fully demonstrated. We aimed to evaluate the potential role of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-2 (MMP-2) in the pathogenesis of pannus formation in three patients with mechanical prosthetic heart valves. Pannus specimens removed from the prostheses were fixed in 10% neutral-buffered formalin for 24 hours after surgical removal and paraffin-embedded using standard procedures. Serial sections were cut at 4 µm for immunohistochemistry analysis. Hematoxylin and eosin (HE) was used in the histological analysis. VEGF and MMP-2 were studied in the immunohistochemistry analysis. Three patients with mechanical prosthetic obstruction due to pannus overgrowth underwent redo valve surgery. In the first and second patients, the mitral prosthesis was explanted along with the pannus overgrowth. The third patient had both aortic and mitral prostheses; the aortic prosthesis was explanted with obstructive pannus formation, whereas the mitral valve was spared with excision of the nonobstructive pannus. The immunohistochemical study demonstrated the expressions of MMP-2 and VEGF in all of the pannus specimens acquired from these cases. VEGF and MMP-2 may play a role in the mechanism of pannus formation as the elements of the chronic active inflammatory process.

Intermittent hypobaric hypoxia exposure does not cause sustained alterations in autonomic control of blood pressure in young athletes.

NARCIS (Netherlands)

Fu, Q.; Townsend, N.E.; Shiller, S.M.; Martini, E.R.; Okazaki, K.; Shibata, S.; Truijens, M.J.; Rodriquez, F.A.; Gore, C.J.; Stray-Gundersen, J.; Levine, B.D.

2007-01-01

Intermittent hypoxia (IH), which refers to the discontinuous use of hypoxia to reproduce some key features of altitude acclimatization, is commonly used in athletes to improve their performance. However, variations of IH are also used as a model for sleep apnea, causing sustained sympathoexcitation

Experience with control valve cavitation problems and their solutions

International Nuclear Information System (INIS)

Ozol, J.

1988-01-01

Pressure reduction in control valves can induce cavitation, which has three effects on the control valve. Firstly, it modifies or changes the hydraulic performance of the control valve. Since control valves are designed for noncavitating conditions, the result is usually reduced stability of the control valve or, in extreme cavitating conditions known as supercavitation, the valve may limit the flow rate and thus be undersized. Secondly, cavitation can cause material damage to valve parts, trim, or valve body, or erodes downstream piping; consequently, the valve or piping leaks. Thirdly, cavitation causes noise and vibration, which may cause major damage or destruction to equipment such as valve positioners, actuators, pipe supports and sometimes to other downstream valves. The purpose of this paper is twofold: (1) It describes the I.S.A. valve sizing equations and how they relate to cavitation. (2) It describes experiences with these three problems, and discusses corrective actions and practical approaches to their solution. This paper discusses thirteen cavitation experiences

Flow oscillations on the steam control valve in the middle opening condition. Clarification of the effects of valve body and valve seat by steam experiments

International Nuclear Information System (INIS)

Morita, Ryo; Inada, Fumio

2007-01-01

A steam control valve might cause vibrations of piping when the valve opening is in a middle condition. For rationalization of maintenance and management of the plant, the valve should be improved, but it is difficult to understand flow characteristics in detail by experiment because flow around the valve is complex 3D structure and becomes supersonic (M>1). Therefore, it is necessary to clarify the cause of the vibrations and to develop the countermeasures by CFD (Computational Fluid Dynamics) technology. In previous researches, we clarified a mechanism of the pressure fluctuations in the middle opening condition and suggested the new valve shape (named 'Extended Valve') that can suppress the pressure fluctuations by air experiments and CFD calculations. Then, we also conducted steam experiments and CFD calculations to understand the differences between air and the steam, and found that the pressure fluctuations in the middle opening condition also occurred in the steam tests and the differences between the air and steam were not remarkable. In this report, to clarify the effects of valve and valve seat shape in steam flow condition, we conduct the steam experiments with various valve and seat shape. As a result, we find the change of the valve seat can decrease the amplitude of pressure fluctuations, but can not quite suppress the pressure fluctuations in the middle opening condition. Then, we apply the 'Extended Valve' to clarify the valve shape effect, and find that the extended valve suppresses the pressure fluctuations in the middle opening condition completely and decreases the pressure amplitude drastically. (author)

Multifunctional four-port directional control valve constructed from logic valves

International Nuclear Information System (INIS)

Lisowski, E.; Czyżycki, W.; Rajda, J.

2014-01-01

Highlights: • Directional valve with standard ISO 440-08 has been constructed from logic valves. • Only one innovative valve may replace whole family of the standard valves. • CFD analysis and bench tests of the innovative valve has been carried. • Parameters of the innovative valve are equaling or surpassing the standard ones. • The innovative valve has additional possibilities of pressure and flow control. - Abstract: The paper refers to four-port solenoid pilot operated valves, which are subplate mounted in a hydraulic system in accordance with the ISO 4401 standard. Their widespread use in many machines and devices causes a continuing interest in the development of their design by both the scientific centers and the industry. This paper presents an innovative directional control valve based on the use of logic valves and a methodology followed for the design of it by using Solid Edge CAD and ANSYS/Fluent CFD software. The valve design methodology takes into account the need to seek solutions that minimize flow resistance through the valve. For this purpose, the flow paths are prepared by means of CAD software and pressure-flow curves are determined as a result of CFD analysis. The obtained curves are compared with the curves available in the catalogs of spool type directional control valves. The new solution allows to replace the whole family of spool type four-port directional control valves by one valve built of logic valves. In addition, the innovative directional control valve provides leak-proof shutting the flow paths off and also it can control flow rate and even pressure of working liquid. A prototype of the valve designed by the presented method has been made and tested on the test bench. The results quoted in the paper confirm that the developed logic type directional control valve is able to meet all designed connection configurations, and the obtained pressure-flow curves show very good conformity with the results of CFD analysis

An evaluation of the effects of long term cryopreservation, cause of death, and time between death and donation on heart valve leaflet viability

International Nuclear Information System (INIS)

Strachan, K.

1999-01-01

The protocol for cryopreservation of allograft heart valves at the Donor Tissue Bank of Victoria was based on validation studies on the viability of the heart valve leaflets at the time of processing. The heart block is removed within 24 hours of death and the aor-tic and pulmonary valves trimmed immediately following retrieval. Following this processing, the valves are incubated in antibiotics at 30 degree C for 6 to 8 hours before being frozen in 10% DMSO at a controlled rate. A sample of tricuspid valve leaflet is placed in Krebs solution at the time of trimfning and is used for viability studies. Leaflet viability studies have been perfon-ned on all heart valves retrieved from 1993 to the present day at the Donor Tissue Bank of Victoria. Viability involves a qualitative assessment of the cellular outgrowth by leaflet fibroblasts, this assessment ranging from '-' for no outgrowth to '++++' for maximum outgrowth. Surgeons do not request valves with any particular viability and will use them whether they are viable or not. This evaluation was to determine the effects of long-term cryopreservation, cause of death, and also time lapse of heart removal following death on the viability of the retrieved leaflets. The aim of investigating the effects of long-term cryopreservation was to determine whether there was any correlation between initial viability and viability following storage for several months to several years. It was also decided to investigate whether there was any correlation between time length between death and heart retrieval and the viability. It was also thought that the cause of death may have had an effect on the viability, for example, did death by carbon monoxide poisoning have an effect on the viability of heart valve cells. Heart valves, which had been cryopreserved but could not be transplanted for various reasons were used to study the effects of cryopreservation in this study. These were thawed according to protocol and a sample of the valve

Cavitation guide for control valves

Energy Technology Data Exchange (ETDEWEB)

Tullis, J.P. [Tullis Engineering Consultants, Logan, UT (United States)

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.

Cavitation guide for control valves

International Nuclear Information System (INIS)

Tullis, J.P.

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation

Technical evaluation: 300 Area steam line valve accident

International Nuclear Information System (INIS)

1993-08-01

On June 7, 1993, a journeyman power operator (JPO) was severely burned and later died as a result of the failure of a 6-in. valve that occurred when he attempted to open main steam supply (MSS) valve MSS-25 in the U-3 valve pit. The pit is located northwest of Building 331 in the 300 Area of the Hanford Site. Figure 1-1 shows a layout of the 300 Area steam piping system including the U-3 steam valve pit. Figure 1-2 shows a cutaway view of the approximately 10- by 13- by 16-ft-high valve pit with its various steam valves and connecting piping. Valve MSS-25, an 8-in. valve, is located at the bottom of the pit. The failed 6-in. valve was located at the top of the pit where it branched from the upper portion of the 8-in. line at the 8- by 8- by 6-in. tee and was then ''blanked off'' with a blind flange. The purpose of this technical evaluation was to determine the cause of the accident that led to the failure of the 6-in. valve. The probable cause for the 6-in. valve failure was determined by visual, nondestructive, and destructive examination of the failed valve and by metallurgical analysis of the fractured region of the valve. The cause of the accident was ultimately identified by correlating the observed failure mode to the most probable physical phenomenon. Thermal-hydraulic analyses, component stress analyses, and tests were performed to verify that the probable physical phenomenon could be reasonably expected to produce the failure in the valve that was observed

Oil pipeline valve automation for spill reduction

Energy Technology Data Exchange (ETDEWEB)

Mohitpour, Mo; Trefanenko, Bill [Enbridge Technology Inc, Calgary (Canada); Tolmasquim, Sueli Tiomno; Kossatz, Helmut [TRANSPETRO - PETROBRAS Transporte S.A., Rio de Janeiro, RJ (Brazil)

2003-07-01

Liquid pipeline codes generally stipulate placement of block valves along liquid transmission pipelines such as on each side of major river crossings where environmental hazards could cause or are foreseen to potentially cause serious consequences. Codes, however, do not stipulate any requirement for block valve spacing for low vapour pressure petroleum transportation, nor for remote pipeline valve operations to reduce spills. A review of pipeline codes for valve requirement and spill limitation in high consequence areas is thus presented along with a criteria for an acceptable spill volume that could be caused by pipeline leak/full rupture. A technique for deciding economically and technically effective pipeline block valve automation for remote operation to reduce oil spilled and control of hazards is also provided. In this review, industry practice is highlighted and application of the criteria for maximum permissible oil spill and the technique for deciding valve automation thus developed, as applied to ORSUB pipeline is presented. ORSUB is one of the three initially selected pipelines that have been studied. These pipelines represent about 14% of the total length of petroleum transmission lines operated by PETROBRAS Transporte S.A. (TRANSPETRO) in Brazil. Based on the implementation of valve motorization on these three pipeline, motorization of block valves for remote operation on the remaining pipelines is intended, depending on the success of these implementations, on historical records of failure and appropriate ranking. (author)

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis

Directory of Open Access Journals (Sweden)

Rajesh Janardhanan

2016-05-01

Full Text Available In intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Learning objectives: • Early recognition of a mitral valve aneurysm (MVA is important because it may rupture and produce catastrophic mitral regurgitation (MR in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR. • Real-time 3D-transesophageal echocardiography (RT-3DTEE is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA.

Anterior mitral valve aneurysm: a rare sequelae of aortic valve endocarditis.

Science.gov (United States)

Janardhanan, Rajesh; Kamal, Muhammad Umar; Riaz, Irbaz Bin; Smith, M Cristy

2016-03-01

SummaryIn intravenous drug abusers, infective endocarditis usually involves right-sided valves, with Staphylococcus aureus being the most common etiologic agent. We present a patient who is an intravenous drug abuser with left-sided (aortic valve) endocarditis caused by Enterococcus faecalis who subsequently developed an anterior mitral valve aneurysm, which is an exceedingly rare complication. A systematic literature search was conducted which identified only five reported cases in the literature of mitral valve aneurysmal rupture in the setting of E. faecalis endocarditis. Real-time 3D-transesophageal echocardiography was critical in making an accurate diagnosis leading to timely intervention. Early recognition of a mitral valve aneurysm (MVA) is important because it may rupture and produce catastrophic mitral regurgitation (MR) in an already seriously ill patient requiring emergency surgery, or it may be overlooked at the time of aortic valve replacement (AVR).Real-time 3D-transesophageal echocardiography (RT-3DTEE) is much more advanced and accurate than transthoracic echocardiography for the diagnosis and management of MVA. © 2016 The authors.

Heart Valve Surgery Recovery and Follow Up

Science.gov (United States)

... Guide: Understanding Your Heart Valve Problem | Spanish Symptom Tracker | Spanish Pre-surgery Checklist | Spanish What Is Heart ... Heart Valves • Heart Valve Problems and Causes • Risks, Signs and Symptoms • Accurate Diagnosis • Treatment Options • Recovery and ...

Intermittent straining accelerates the development of tissue properties in engineered heart valve tissue

NARCIS (Netherlands)

Rubbens, M.P.; Mol, A.; Boerboom, R.A.; Bank, R.A.; Baaijens, F.P.T.; Bouten, C.V.C.

2009-01-01

Tissue-engineered heart valves lack sufficient amounts of functionally organized structures and consequently do not meet in vivo mechanical demands. To optimize tissue architecture and hence improve mechanical properties, various in vitro mechanical conditioning protocols have been proposed, of

Guidelines for valves in tritium service

International Nuclear Information System (INIS)

Weaver, W.W.

1994-01-01

Some undesirable practices and misapplications that caused valve-related failures are examined, and future courses of action are recommended to avoid repetition of these events. Desirable valve characteristics and practices that should be considered when selecting valves for use in tritium service are also discussed. Supporting logic for the desirability of these features is presented by discussing the mechanisms of valve degradation followed by examples of related events. Desirable valve and system features and operational actions are grouped into two categories: strongly recommended and recommended. 13 refs., 1 fig

Bioprosthetic Valve Fracture to Facilitate Transcatheter Valve-in-Valve Implantation.

Science.gov (United States)

Allen, Keith B; Chhatriwalla, Adnan K; Cohen, David J; Saxon, John T; Aggarwal, Sanjeev; Hart, Anthony; Baron, Suzanne; Davis, J Russell; Pak, Alex F; Dvir, Danny; Borkon, A Michael

2017-11-01

Valve-in-valve transcatheter aortic valve replacement is less effective in small surgical bioprostheses. We evaluated the feasibility of bioprosthetic valve fracture with a high-pressure balloon to facilitate valve-in-valve transcatheter aortic valve replacement. In vitro bench testing on aortic tissue valves was performed on 19-mm and 21-mm Mitroflow (Sorin, Milan, Italy), Magna and Magna Ease (Edwards Lifesciences, Irvine, CA), Trifecta and Biocor Epic (St. Jude Medical, Minneapolis, MN), and Hancock II and Mosaic (Medtronic, Minneapolis, MN). High-pressure balloons Tru Dilation, Atlas Gold, and Dorado (C.R. Bard, Murray Hill, NJ) were used to determine which valves could be fractured and at what pressure fracture occurred. Mitroflow, Magna, Magna Ease, Mosaic, and Biocor Epic surgical valves were successfully fractured using high-pressures balloon 1 mm larger than the labeled valve size whereas Trifecta and Hancock II surgical valves could not be fractured. Only the internal valve frame was fractured, and the sewing cuff was never disrupted. Manufacturer's rated burst pressures for balloons were exceeded, with fracture pressures ranging from 8 to 24 atmospheres depending on the surgical valve. Testing further demonstrated that fracture facilitated the expansion of previously constrained, underexpanded transcatheter valves (both balloon and self-expanding) to the manufacturer's recommended size. Bench testing demonstrates that the frame of most, but not all, bioprosthetic surgical aortic valves can be fractured using high-pressure balloons. The safety of bioprosthetic valve fracture to optimize valve-in-valve transcatheter aortic valve replacement in small surgical valves requires further clinical investigation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Idiopathic mitral valve prolapse with tricuspid, aortic and pulmonary valve involvement: An autopsy case report

Directory of Open Access Journals (Sweden)

Heena M Desai

2015-01-01

Full Text Available Mitral valve prolapse (MVP is usually asymptomatic, but can be associated with complications such as infective endocarditis, mitral regurgitation, thromboembolism and sudden cardiac death. It has been very rarely reported to occur in association with other valvular involvement. A 55-year-old male patient was brought dead and at autopsy the mitral valve orifice was stenotic and the leaflets were enlarged, myxoid and bulging suggestive of MVP and chordae tendinae were thickened, stretched and elongated. Similar changes were seen in the tricuspid valve. The pulmonary and aortic valves also showed myxomatous degeneration of their cusps. Myxomatous degeneration is the most common cause of MVP and it can be associated with involvement of the other valves. Concomitant involvement of the aortic valve has been reported, however it is very rare and simultaneous involvement of the pulmonary valve has not been reported in the literature so far. We report a case of MVP associated with myxomatous degeneration of the tricuspid, pulmonary and aortic valves.

A nuclear radiation actuated valve for a nuclear reactor

International Nuclear Information System (INIS)

Christiansen, D.W.; Schively, D.P.

1983-01-01

The valve has a first part (such as a valve rod with piston) and a second part (such as a valve tube surrounding the valve rod, with the valve tube having side slots surrounding the piston). Both valve parts have known nuclear radiation swelling characteristics which are different. The valve parts are positioned so that the valve's first and second parts create a valve orifice which changes in size due to the different nuclear radiation caused swelling of the valve's first part compared to the valve's second part. The valve may be used in a nuclear reactor's core coolant system. (author)

Changes in bone geometry and microarchitecture caused by intermittent administration of PTH. Comparison with those by exercise load

International Nuclear Information System (INIS)

Mori, Keiya

2010-01-01

There have been several studies showing that periodical intermittent medication with parathyroid hormone (PTH) causes increases in cancellous bone mass. However, there have been almost no reports comparing the effects of periodical intermittent PTH medication on bone microarchitecture with changes caused by physiological stimulation such as exercise load. In this study, we compared the effects of these two interventions on the microarchitecturural deterioration of femoral cancellous bone associated with unloading, using micro-computed tomography (micro-CT), and the effects of PTH administration and motion loading on improvement of the deteriorated structure. In the study, 32 eight-week-old male Wistar rats were divided into four groups: a control group without tail suspension (CON), a control recovery group after suspension (S+C), a suspension/PTH group (S+P), and a suspension/jumping exercise group (S+J). Periodical intermittent human PTH (1-34) was given periodically to the S+P group rats at a dose of 75 μg/kg/day five times a week for five weeks, after two weeks of exercise with suspension of the tail. The rats in the S+J group performed 40 cm-high jumping 10 times/day five times a week for five weeks. After this conditioning, upon examination, bilateral femurs were removed and the right distal metaphysis was scanned using micro-CT to obtain images of the cancellous bone region of the femur. Based on the tomographic data, indices of cancellous bone microarchitecture was the index of trabecular bone structure were determined by using three-dimensional image analysis system. In addition, to examine the geometric properties of the diaphysis, mid-portion images of the bone shaft of the left femur were obtained by micro-CT, and then the mechanical bone strength of the left femur was determined by performing a three-point bending test. Compared to the S+C group, the S+P and S+J groups showed significantly higher bone volume, bone surface mass values, superficial bone

Promising results after percutaneous mitral valve repair

DEFF Research Database (Denmark)

Ihlemann, Nikolaj; Franzen, Olaf; Jørgensen, Erik

2011-01-01

Mitral valve regurgitation (MR) is the secondmost frequent valve disease in Europe. Untreated MR causes considerable morbidity and mortality. In the elderly, as many as half of these patients are denied surgery because of an estimated high surgical risk. Percutaneous mitral valve repair with the ...... with the MitraClip system resembles the Alfieristitch where a clip is used to connect the tip of the mitral valve leaflets....

Intermittent pacemaker dysfunction caused by digital mobile telephones.

Science.gov (United States)

Naegeli, B; Osswald, S; Deola, M; Burkart, F

1996-05-01

This study was designed to evaluate possible interactions between digital mobile telephones and implanted pacemakers. Electromagnetic fields may interfere with normal pacemaker function. Development of bipolar sensing leads and modern noise filtering techniques have lessened this problem. However, it remains unclear whether these features also protect from high frequency noise arising from digital cellular phones. In 39 patients with an implanted pacemaker (14 dual-chamber [DDD], 8 atrial-synchronized ventricular-inhibited [VDD(R)] and 17 ventricular-inhibited [VVI(R)] pacemakers), four mobile phones with different levels of power output (2 and 8 W) were tested in the standby, dialing and operating mode. During continuous electrocardiographic monitoring, 672 tests were performed in each mode with the phones positioned over the pulse generator, the atrial and the ventricular electrode tip. The tests were carried out at different sensitivity settings and, where possible, in the unipolar and bipolar pacing modes as well. In 7 (18%) of 39 patients, a reproducible interference was induced during 26 (3.9%) of 672 tests with the operating phones in close proximity (phone and at maximal sensitivity of the pacemakers (maximal vs. nominal sensitivity, 6% vs. 1.8% positive test results, p = 0.009). When the bipolar and unipolar pacing modes were compared in the same patients, ventricular inhibition was induced only in the unipolar mode (12.5% positive test results, p = 0.0003). Digital mobile phones in close proximity to implanted pacemakers may cause intermittent pacemaker dysfunction with inappropriate ventricular tracking and potentially dangerous pacemaker inhibition.

Valve system incorporating single failure protection logic

Science.gov (United States)

Ryan, Rodger; Timmerman, Walter J. H.

1980-01-01

A valve system incorporating single failure protective logic. The system consists of a valve combination or composite valve which allows actuation or de-actuation of a device such as a hydraulic cylinder or other mechanism, integral with or separate from the valve assembly, by means of three independent input signals combined in a function commonly known as two-out-of-three logic. Using the input signals as independent and redundant actuation/de-actuation signals, a single signal failure, or failure of the corresponding valve or valve set, will neither prevent the desired action, nor cause the undesired action of the mechanism.

New-Onset Atrial Fibrillation After Surgical Aortic Valve Replacement and Transcatheter Aortic Valve Implantation

DEFF Research Database (Denmark)

Jørgensen, Troels Højsgaard; Thygesen, Julie Bjerre; Thyregod, Hans Gustav

2015-01-01

Surgical aortic valve replacement (SAVR) and, more recently, transcatheter aortic valve implantation (TAVI) have been shown to be the only treatments that can improve the natural cause of severe aortic valve stenosis. However, after SAVR and TAVI, the incidence of new-onset atrial fibrillation...... (NOAF) is 31%-64% and 4%-32%, respectively. NOAF is independently associated with adverse events such as stroke, death, and increased length of hospital stay. Increasing the knowledge of predisposing factors, optimal postprocedural monitoring, and prophylactic antiarrhythmic and antithrombotic therapy...

New-onset atrial fibrillation after surgical aortic valve replacement and transcatheter aortic valve implantation

DEFF Research Database (Denmark)

Jørgensen, Troels Højsgaard; Thygesen, Julie Bjerre; Thyregod, Hans Gustav

2015-01-01

Surgical aortic valve replacement (SAVR) and, more recently, transcatheter aortic valve implantation (TAVI) have been shown to be the only treatments that can improve the natural cause of severe aortic valve stenosis. However, after SAVR and TAVI, the incidence of new-onset atrial fibrillation...... (NOAF) is 31%-64% and 4%-32%, respectively. NOAF is independently associated with adverse events such as stroke, death, and increased length of hospital stay. Increasing the knowledge of predisposing factors, optimal postprocedural monitoring, and prophylactic antiarrhythmic and antithrombotic therapy...

Intermittent pressure decreases human keratinocyte proliferation in vitro.

Science.gov (United States)

Nasca, Maria R; Shih, Alan T; West, Dennis P; Martinez, Wanda M; Micali, Giuseppe; Landsman, Adam S

2007-01-01

The aim of this study was to investigate the correlation between pressure changes and keratinocyte proliferation by determining whether keratinocytes exposed to altered mechanical pressures would proliferate at different rates compared to control cells not subjected to pressure changes. Tissue culture flasks of human keratinocytes plated at an approximate density of 15,000 cells/cm(2) undergoing an intermittent cyclic pressure of 362 mm Hg at a frequency of 2.28 or 5.16 cycles/min (0.038 or 0.086 Hz) for 8 h were compared to control flasks grown at ambient room pressure. An in-line pressure transducer was used to monitor and adjust pressure within the cell chambers, using a solenoid valve. A thymidine incorporation assay assessed the amount of cell proliferation in each set of experiments. Differences in proliferation between keratinocytes subjected to cyclic pressure changes and control cells were found to be statistically significant (p < 0.05) in 4 out of 5 proliferation assays. Also, a higher frequency of pressure changes consistently generated a reduced proliferation rate compared to that seen in cells exposed to a lower frequency of pressure changes. These data indicate that keratinocytes undergoing intermittent pressure changes exhibit decreased proliferation rates compared to controls. Furthermore, an increased frequency rate seems to have a greater effect on proliferation than low-frequency rate pressure changes, suggesting that the stress caused by frequently changed pressure may play a greater role in reducing keratinocyte proliferation than the actual magnitude of load applied to the cells. Our results support the current treatment protocol of reducing speed and duration of walking on the site of the wound to promote healing of foot ulcers. (c) 2007 S. Karger AG, Basel.

Bioprosthetic Valve Fracture Improves the Hemodynamic Results of Valve-in-Valve Transcatheter Aortic Valve Replacement.

Science.gov (United States)

Chhatriwalla, Adnan K; Allen, Keith B; Saxon, John T; Cohen, David J; Aggarwal, Sanjeev; Hart, Anthony J; Baron, Suzanne J; Dvir, Danny; Borkon, A Michael

2017-07-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) may be less effective in small surgical valves because of patient/prosthesis mismatch. Bioprosthetic valve fracture (BVF) using a high-pressure balloon can be performed to facilitate VIV TAVR. We report data from 20 consecutive clinical cases in which BVF was successfully performed before or after VIV TAVR by inflation of a high-pressure balloon positioned across the valve ring during rapid ventricular pacing. Hemodynamic measurements and calculation of the valve effective orifice area were performed at baseline, immediately after VIV TAVR, and after BVF. BVF was successfully performed in 20 patients undergoing VIV TAVR with balloon-expandable (n=8) or self-expanding (n=12) transcatheter valves in Mitroflow, Carpentier-Edwards Perimount, Magna and Magna Ease, Biocor Epic and Biocor Epic Supra, and Mosaic surgical valves. Successful fracture was noted fluoroscopically when the waist of the balloon released and by a sudden drop in inflation pressure, often accompanied by an audible snap. BVF resulted in a reduction in the mean transvalvular gradient (from 20.5±7.4 to 6.7±3.7 mm Hg, P valve effective orifice area (from 1.0±0.4 to 1.8±0.6 cm 2 , P valves to facilitate VIV TAVR with either balloon-expandable or self-expanding transcatheter valves and results in reduced residual transvalvular gradients and increased valve effective orifice area. © 2017 American Heart Association, Inc.

Minimally invasive aortic valve replacement

DEFF Research Database (Denmark)

Foghsgaard, Signe; Schmidt, Thomas Andersen; Kjaergard, Henrik K

2009-01-01

In this descriptive prospective study, we evaluate the outcomes of surgery in 98 patients who were scheduled to undergo minimally invasive aortic valve replacement. These patients were compared with a group of 50 patients who underwent scheduled aortic valve replacement through a full sternotomy...... operations were completed as mini-sternotomies, 4 died later of noncardiac causes. The aortic cross-clamp and perfusion times were significantly different across all groups (P replacement...... is an excellent operation in selected patients, but its true advantages over conventional aortic valve replacement (other than a smaller scar) await evaluation by means of randomized clinical trial. The "extended mini-aortic valve replacement" operation, on the other hand, is a risky procedure that should...

Mechanisms of mechanical heart valve cavitation: investigation using a tilting disk valve model.

Science.gov (United States)

He, Z; Xi, B; Zhu, K; Hwang, N H

2001-09-01

The induction of mechanical heart valve (MHV) cavitation was investigated using a 27 mm Medtronic Hall (MH27) tilting disk valve. The MH27 valve was mounted in the mitral position of a simulating pulse flow system, and stroboscopic lighting used to visualize cavitation bubbles on the occluder inflow surface at the instant of valve closure. MHV cavitation was monitored using a digital camera with 0.04 mm/pixel resolution sufficient to render the tiny bubbles clearly visible on the computer monitor screen. Cavitation on MH27 valve was classified as five types according to the time, site and shape of the cavitation bubbles. Valve cavitation occurred at the instant of occluder impact with the valve seat at closing. The impact motion was subdivided into three temporal phases: (i) squeezing flow; (ii) elastic collision; and (iii) leaflet rebound. MHV cavitation caused by vortices was found to be initiated by the squeezing jet and/or by the transvalvular leakage jets. By using a tension wave which swept across the occluder surface immediately upon elastic impact, nuclei in the vortex core were expanded to form cavitation bubbles. Analysis of the shape and location of the cavitation bubbles permitted a better understanding of MHV cavitation mechanisms, based on the fluid dynamics of jet vortex and tension wave propagations.

Beneficial effects of intermittent suction and pressure treatment in intermittent claudication

DEFF Research Database (Denmark)

Mehlsen, J; Himmelstrup, H; Himmelstrup, Bodil

1993-01-01

administration. The treatment caused significant increments in the ADP thresholds for platelet aggregation, while the effects on fibrinolysis were uncertain. It is concluded that intermittent suction and pressure treatment offers a new approach for conservative treatment of intermittent claudication....... participated in an open trial investigating the possible effects of the treatment on platelet aggregation and fibrinolysis. Pain-free and maximal walking distances were measured on a treadmill, and systolic blood pressure was measured on the upper limb, the ankle, and the first toe bilaterally. The threshold...... for adenosine diphosphate (ADP)-induced platelet aggregation was tested, and the fibrinolytic activity was estimated from the euglobulin clot lysis time. Active treatment resulted in significant improvements in pain-free and maximal walking distances, whereas no changes could be found during placebo...

Pannus-Related Mechanical Valve Dysfunction Leading to Hemodynamic Shock

Directory of Open Access Journals (Sweden)

Manabu Shiraishi

2012-02-01

Full Text Available Mechanical prosthetic valve dysfunction caused by pannus formation is rare. Pannus restricts movement of prosthetic valve leaflets, resulting in severe aortic regurgitation. We describe the case of a 77-year-old woman who presented to the emergency room with increasing dyspnea, ischemia, and shock secondary to mechanical aortic valve dysfunction. Transesophageal echocardiography showed a blockade of the leaflets of the mechanical aortic valve, with severe aortic regurgitation. She underwent emergent cardiac surgery for aortic valve replacement. Pannus formation should be considered as a potential cause of acute severe aortic regurgitation in a patient with a small-sized mechanical aortic prosthesis in the supra-annular position. On a pathological exam, extensive pannus was found on the ventricular side of the prosthetic valve, extending from the ring into the central orifice. [Arch Clin Exp Surg 2012; 1(1.000: 50-53

Determinants and outcomes of acute transcatheter valve-in-valve therapy or embolization: a study of multiple valve implants in the U.S. PARTNER trial (Placement of AoRTic TraNscathetER Valve Trial Edwards SAPIEN Transcatheter Heart Valve).

Science.gov (United States)

Makkar, Raj R; Jilaihawi, Hasan; Chakravarty, Tarun; Fontana, Gregory P; Kapadia, Samir; Babaliaros, Vasilis; Cheng, Wen; Thourani, Vinod H; Bavaria, Joseph; Svensson, Lars; Kodali, Susheel; Shiota, Takahiro; Siegel, Robert; Tuzcu, E Murat; Xu, Ke; Hahn, Rebecca T; Herrmann, Howard C; Reisman, Mark; Whisenant, Brian; Lim, Scott; Beohar, Nirat; Mack, Michael; Teirstein, Paul; Rihal, Charanjit; Douglas, Pamela S; Blackstone, Eugene; Pichard, Augusto; Webb, John G; Leon, Martin B

2013-07-30

This study investigated the determinants and outcomes of acute insertion of a second transcatheter prosthetic valve (TV) within the first (TV-in-TV) or transcatheter valve embolization (TVE) after transcatheter aortic valve replacement (TAVR). TAVR failure can occur with both TV-in-TV and TVE as a consequence of TAVR malpositioning. Only case reports and limited series pertaining to these complications have been reported to date. Patients undergoing TAVR in the PARTNER (Placement of AoRTic TraNscathetER Valve Trial Edwards SAPIEN Transcatheter Heart Valve) randomized trial (cohorts A and B) and accompanying registries were studied. Data were dichotomized for those with and without TV-in-TV or TVE, respectively. From a total of 2,554 consecutive patients, 63 (2.47%) underwent TV-in-TV and 26 (1.01%) TVE. The indication for TV-in-TV was significant aortic regurgitation in most patients, often due not only to malpositioning but also to leaflet dysfunction. Despite similar aortic valve function on follow-up echoes, TV-in-TV was an independent predictor of 1-year cardiovascular mortality (hazard ratio [HR]: 1.86, 95% confidence interval [CI]: 1.03 to 3.38, p = 0.041), with a nonsignificant trend toward greater all-cause mortality (HR: 1.43, 95% CI: 0.88 to 2.33, p = 0.15). Technical and anatomical reasons accounted for most cases of TVE. A multivariable analysis found TVE to be an independent predictor of 1-year mortality (HR: 2.68, 95% CI: 1.34 to 5.36, p = 0.0055) but not cardiovascular mortality (HR: 1.30, 95% CI: 0.48 to 3.52, p = 0.60). Acute TV-in-TV and TVE are serious sequelae of TAVR, often resulting in multiple valve implants. They carry an excess of mortality and are caused by anatomic and technical factors, which may be avoidable with judicious procedural planning. Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Impact of valve failures on the safety and reliability of light water nuclear power plants

International Nuclear Information System (INIS)

Riddington, J.W.; Reyer, R.J.

1980-01-01

A study of the causes of, and solutions for, recurrent valve failures has been performed. The frequency and root causes of valve problems were identified from licensee event reports and meetings with utility, NSSS, and valve manufacturer personnel. Three generic problems (stem leakage, seat leakage, and inadequate specification) and four valve specific problems were identified. The four valve specific problems and their principal causes are: (1) BWR pilot operated safety relief valves (pilot valve leakage); (2) spring loaded safety relief valves (water solid and two-phase flow behavior); (3) PWR feedwater regulating valves (trim degradation and packing failures); and (4) air operated solenoid valves (jamming due to foreign matter in service air). The first two valve specific problems are the subject of current industry programs. Programs intended to address stem leakage, seat leakage, timely exchange of valve failure information, testing of valves, and adequate specification, selection, and maintenance of valves will be outlined

[Pannus Formation Six-years after Aortic and Mitral Valve Replacement with Tissue Valves;Report of a Case].

Science.gov (United States)

Nakamura, Makoto; Muraoka, Arata; Aizawa, Kei; Akutsu, Hirohiko; Kurumisawa, Soki; Misawa, Yoshio

2015-07-01

A 77-year-old man presented with exertional dyspnea. He had undergone aortic and mitral valve replacement with tissue valves 6-years earlier. The patient's hemoglobin level was 9.8 g/dl and serum aspartate aminotransferase (70 mU/ml) and lactate dehydrogenase (1,112 mU/ml) were elevated. Echocardiography revealed stenosis of the prosthetic valve in the aortic position with peak flow velocity of 3.8 m/second and massive mitral regurgitation. The patient underwent repeat valve replacement. Pannus formation around both implanted valves was observed. The aortic valve orifice was narrowed by the pannus, and one cusp of the prosthesis in the mitral position was fixed and caused the regurgitation, but they were free from cusp laceration or calcification. The patient's postoperative course was uneventful, and he continues to do well 14 months after surgery.

Energy intermittency

CERN Document Server

Sorensen, Bent

2014-01-01

The first book to consider intermittency as a key point of an energy system, Energy Intermittency describes different levels of variability for traditional and renewable energy sources, presenting detailed solutions for handling energy intermittency through trade, collaboration, demand management, and active energy storage. Addressing energy supply intermittency systematically, this practical text:Analyzes typical time-distributions and intervals between episodes of demand-supply mismatch and explores their dependence on system layouts and energy source characteristicsSimulates scenarios regar

Posterior Urethral Valves

Directory of Open Access Journals (Sweden)

Steve J. Hodges

2009-01-01

Full Text Available The most common cause of lower urinary tract obstruction in male infants is posterior urethral valves. Although the incidence has remained stable, the neonatal mortality for this disorder has improved due to early diagnosis and intensive neonatal care, thanks in part to the widespread use of prenatal ultrasound evaluations. In fact, the most common reason for the diagnosis of posterior urethral valves presently is the evaluation of infants for prenatal hydronephrosis. Since these children are often diagnosed early, the urethral obstruction can be alleviated rapidly through catheter insertion and eventual surgery, and their metabolic derangements can be normalized without delay, avoiding preventable infant mortality. Of the children that survive, however, early diagnosis has not had much effect on their long-term prognosis, as 30% still develop renal insufficiency before adolescence. A better understanding of the exact cause of the congenital obstruction of the male posterior urethra, prevention of postnatal bladder and renal injury, and the development of safe methods to treat urethral obstruction prenatally (and thereby avoiding the bladder and renal damage due to obstructive uropathy are the goals for the care of children with posterior urethral valves[1].

Check valve slam caused by air intrusion in emergency cooling water system

International Nuclear Information System (INIS)

Martin, C.S.

2011-01-01

Waterhammer pressures were experienced during periodic starting of Residual Heat Removal (RHR) pumps at a nuclear plant. Prior to an analytical investigation careful analysis performed by plant engineers indicated that the spring effect of entrapped air in a heat exchanger resulted in water hammer due to check valve slam following flow reversal. In order to determine in more detail the values of pertinent parameters controlling this water hammer a hydraulic transient analysis was performed of the RHR piping system, including essential elements such as the pump, check valve, and heat exchanger. Using characteristic torque and pressure loss curves the motion of the check valve was determined. By comparing output of the water hammer analysis with site recordings of pump discharge pressure the computer model was calibrated, allowing for a realistic estimate of the quantity of entrapped air in the heat exchanger. (author)

Echocardiographic evaluation of heart valve prosthetic dysfunction

Directory of Open Access Journals (Sweden)

Yuriy Ivaniv

2018-02-01

Full Text Available Patients with replaced heart valve submitted to echocardiographic examination may have symptoms related either to valvular malfunction or ventricular dysfunction from different causes. Clinical examination is not reliable in a prosthetic valve evaluation and the main information regarding its function could be obtained using different cardiac ultrasound modalities. This review provides a description of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. For the interpretation of echocardiography there is a need in special knowledge of prosthesis types and possible reasons of prosthetic function deterioration. Echocardiography allows to reveal valve thrombosis, pannus formation, vegetation and such complications of infective endocarditis as valve ring abscess or dehiscence. Transthoracic echocardiography requires different section plane angles and unconventional views. Transesophageal echocardiography is more often used than in native valve examination due to better visualization of prosthetic valve structure and function. Three-dimensional echocardiography could provide more detailed visual information especially in the assessment of paravalvular regurgitation or valve obstruction.

Echocardiographic Assessment of Heart Valve Prostheses

Science.gov (United States)

Sordelli, Chiara; Severino, Sergio; Ascione, Luigi; Coppolino, Pasquale; Caso, Pio

2014-01-01

Patients submitted to valve replacement with mechanical or biological prosthesis, may present symptoms related either to valvular malfunction or ventricular dysfunction from other causes. Because a clinical examination is not sufficient to evaluate a prosthetic valve, several diagnostic methods have been proposed to assess the functional status of a prosthetic valve. This review provides an overview of echocardiographic and Doppler techniques useful in evaluation of prosthetic heart valves. Compared to native valves, echocardiographic evaluation of prosthetic valves is certainly more complex, both for the examination and the interpretation. Echocardiography also allows discriminating between intra- and/or peri-prosthetic regurgitation, present in the majority of mechanical valves. Transthoracic echocardiography (TTE) requires different angles of the probe with unconventional views. Transesophageal echocardiography (TEE) is the method of choice in presence of technical difficulties. Three-dimensional (3D)-TEE seems to be superior to 2D-TEE, especially in the assessment of paravalvular leak regurgitation (PVL) that it provides improved localization and analysis of the PVL size and shape. PMID:28465917

Acoustic valve leak detection in nuclear plants

International Nuclear Information System (INIS)

Dimmick, J.G.; Dickey, J.W.

1983-01-01

Internal valve leakage is a hidden energy loss and can cause or prolong a forced outage. Recent advances in acoustic detection of internal valve leakage have reduced piping system maintenance costs, unnecessary downtime, and energy waste. Extremely short payback periods have been reported by plants applying this technology to preventive maintenance, troubleshooting, energy conservation and outage planning. Sensors temporarily attached to the outside of valves and connected to the instruments detect ultrasonic acoustic emissions which are characteristic of internal valve leakage. Since the sensors are attached to the outside of the valves, the time and expense of dismantling the valves or removing them from the systems are eliminated. This paper describes the instrumentation and specific applications to nuclear plant valves, including independent verification of initial findings. Guidelines for potential users, including instrumentation selection, training requirements, application planning, and the choice of in-house versus contract services are discussed

Diffuse Alveolar Hemorrhage due to Acute Mitral Valve Regurgitation

Directory of Open Access Journals (Sweden)

Creticus P. Marak

2013-01-01

Full Text Available Diffuse alveolar hemorrhage (DAH can be caused by several etiologies including vasculitis, drug exposure, anticoagulants, infections, mitral valve stenosis, and regurgitation. Chronic mitral valve regurgitation (MR has been well documented as an etiological factor for DAH, but there have been only a few cases which have reported acute mitral valve regurgitation as an etiology of DAH. Acute mitral valve regurgitation can be a life-threatening condition and often requires urgent intervention. In rare cases, acute mitral regurgitation may result in a regurgitant jet which is directed towards the right upper pulmonary vein and may specifically cause right-sided pulmonary edema and right-sided DAH. Surgical repair of the mitral valve results in rapid resolution of DAH. Acute MR should be considered as a possible etiology in patients presenting with unilateral pulmonary edema, hemoptysis, and DAH.

Intermittent Fasting Modulation of the Diabetic Syndrome in Streptozotocin-Injected Rats

OpenAIRE

Louiza Belkacemi; Ghalem Selselet-Attou; Emeline Hupkens; Evrard Nguidjoe; Karim Louchami; Abdullah Sener; Willy J. Malaisse

2012-01-01

This study investigates the effects of intermittent overnight fasting in streptozotocin-induced diabetic rats (STZ rats). Over 30 days, groups of 5-6 control or STZ rats were allowed free food access, starved overnight, or exposed to a restricted food supply comparable to that ingested by the intermittently fasting animals. Intermittent fasting improved glucose tolerance, increased plasma insulin, and lowered Homeostatis Model Assessment index. Caloric restriction failed to cause such benefic...

Radiological findings of congenital urethral valves

International Nuclear Information System (INIS)

Yeon, Kyung Mo; Kook, Shin Ho

1990-01-01

Congenital urethral valve is the common cause of hydronephrosis in newborn infants and the most common cause of bladder outlet obstruction in male children. We reviewed and analysed radiological findings and associated anomalies of 16 cases of congenital urethral valve which were examined during the period from January 1985 to December 1989. The most frequent age was under one year old (56%). The main symptoms were urinary dribbing (37.5%), weak stream (25%) and urinary frequency and incontinence (25%). Anterior urethral valve (AUV) was 5 cases (31%) and posterior urethral valve (PUV) was 11 cases(69%), in which 10 cases were Type I and one case was Type III. Bladder wall thickening was seen in all cases and its severity was partly correlated with the degree of vesicoureteral reflux (VUR). VUR was observed in 12 cases (75%), and relatively severe in older age group. The degree of VUR was milder in AUV than PUV. Hydronephrosis was more severe in PUV than in anterior one, and its degree was correlated with the severity of VUR. Associated anomalies were ectopic urethral opening (2 cases), PDA (1 case), congenital megacolon (1 case) and patent urachus (1 case) in PUV. So early diagnosis and treatment of congenital urethral valve is essential to the prevention of renal damage

Krox20 defines a subpopulation of cardiac neural crest cells contributing to arterial valves and bicuspid aortic valve.

Science.gov (United States)

Odelin, Gaëlle; Faure, Emilie; Coulpier, Fanny; Di Bonito, Maria; Bajolle, Fanny; Studer, Michèle; Avierinos, Jean-François; Charnay, Patrick; Topilko, Piotr; Zaffran, Stéphane

2018-01-03

Although cardiac neural crest cells are required at early stages of arterial valve development, their contribution during valvular leaflet maturation remains poorly understood. Here, we show in mouse that neural crest cells from pre-otic and post-otic regions make distinct contributions to the arterial valve leaflets. Genetic fate-mapping analysis of Krox20-expressing neural crest cells shows a large contribution to the borders and the interleaflet triangles of the arterial valves. Loss of Krox20 function results in hyperplastic aortic valve and partially penetrant bicuspid aortic valve formation. Similar defects are observed in neural crest Krox20 -deficient embryos. Genetic lineage tracing in Krox20 -/- mutant mice shows that endothelial-derived cells are normal, whereas neural crest-derived cells are abnormally increased in number and misplaced in the valve leaflets. In contrast, genetic ablation of Krox20 -expressing cells is not sufficient to cause an aortic valve defect, suggesting that adjacent cells can compensate this depletion. Our findings demonstrate a crucial role for Krox20 in arterial valve development and reveal that an excess of neural crest cells may be associated with bicuspid aortic valve. © 2018. Published by The Company of Biologists Ltd.

Intermittent Domestic Water Supply: A Critical Review and Analysis of Causal-Consequential Pathways

Directory of Open Access Journals (Sweden)

S. E. Galaitsi

2016-06-01

Full Text Available Communities in many parts of the world, especially in developing countries, face obstacles in supplying continuous water to household consumers. Authorities often cite water scarcity as the cause, but we demonstrate that environmental constraints constitute only one aspect of a multi-dimensional problem. By asking what causes intermittent domestic water supply, this literature review (129 articles identifies 47 conditions of intermittent systems and the causal-consequential pathways between them that can reinforce intermittency. These pathways span several disciplines including engineering, government administration and anthropology, and when viewed together they (1 emphasize the human drivers of intermittency; (2 suggest generalized interventions; and (3 reveal a gap in the literature in terms of meaningful categorizations of the reliability of intermittent supplies. Based on the reliability of consumers’ water access, we propose three categories of intermittency—predictable, irregular, and unreliable—to facilitate comparisons between case studies and transfers of solutions.

Survey of valve operator-related events occurring during 1978, 1979 and 1980

International Nuclear Information System (INIS)

Brown, E.J.; Ashe, F.S.

1983-01-01

The survey approach was to analyze several events and identify trends or patterns. The primary data source was licensee event reports (LERs) and consisted of 444 total valve operator events with 193 motor operator events which served as the basis for this study. The investigation revealed that motor-operated events could be grouped in three major categories which are torque switches, limit switches, and motors. The major findings are: (1) Torque switches do not appear to be a dominant cause of valve assembly inoperability. The reported information suggests torque switch events are an indication of symptomatic change with time in valve operability characteristics rather than a root cause of valve inoperability. (2) Repetitive problems are occurring with valve operators. It may occur on the same valve, a valve in similar service in a similar system, or a valve in similar service in a redundant train of the same system. (3) The plant operating staff objective appears to be a mode of finding measures to return inoperable equipment to operational status rather than to determine root causes of inoperability. (4) Motor burnout of valve motor operators has occurred quite frequently in High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) systems of BWR units. (orig./GL)

Intermittent, noncyclic dysfunction of a mechanical aortic prosthesis by pannus formation.

Science.gov (United States)

Giroux, Sylvie K; Labinaz, Marino X; Grisoli, Dominique; Klug, Andrew P; Veinot, John P; Burwash, Ian G

2010-01-01

Mechanical aortic prosthesis dysfunction can result from thrombosis or pannus formation. Pannus formation usually restricts systolic excursion of the occluding disk, resulting in progressive stenosis of the aortic prosthesis. Intermittent dysfunction of a mechanical aortic prosthesis is usually ascribed to thrombus formation. We describe an unusual case of intermittent, noncyclic dysfunction of a mechanical aortic prosthesis due to pannus formation in the absence of systolic restriction of disk excursion that presented with intermittent massive aortic regurgitation, severe ischemia, and shock. Pannus formation should be considered as a potential cause of acute intermittent severe aortic regurgitation in a patient with a mechanical aortic prosthesis.

Treatment of severe mitral regurgitation caused by lesions in both leaflets using multiple mitral valve plasty techniques in a small dog

Directory of Open Access Journals (Sweden)

Satoko Yokoyama

2017-11-01

Full Text Available Mitral valve plasty (MVP is preferred over mitral valve replacement (MVR for mitral regurgitation in humans because of its favorable effect on quality of life. In small dogs, it is difficult to repair multiple lesions in both leaflets using MVP. Herein, we report a case of severe mitral regurgitation caused by multiple severe lesions in the posterior leaflet (PL in a mixed Chihuahua. Initially, we had planned MVR with an artificial valve. However, MVP combined with artificial chordal reconstruction of both leaflets, semicircular suture annuloplasty, and valvuloplasty using a newly devised direct scallop suture for the PL was attempted in this dog. The dog recovered well and showed no adverse cardiac signs, surviving two major operations. The dog died 4 years and 10 months after the MVP due to non-cardiovascular disease. Our additional technique of using a direct scallop suture seemed useful for PL repair involving multiple scallops in a small dog.

The prognosis of infective endocarditis treated with biological valves versus mechanical valves: A meta-analysis.

Science.gov (United States)

Tao, Ende; Wan, Li; Wang, WenJun; Luo, YunLong; Zeng, JinFu; Wu, Xia

2017-01-01

Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves. Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis. A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520). The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients

Resurgery for recurrent heart valve diseases

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Chong-lei REN

2017-02-01

Full Text Available Objective　To summarize the experience with resurgery for recurrent valvular heart diseases. Methods　From June 2004 to June 2015, 28 patients (15 males and 13 females with ages ranging from 44 to 67 years (55.6±6.5 years with recurrent heart valve disease underwent resurgery. The reasons for resurgery included perivalvular leakage (7 cases, bioprosthetic valve decline (6 cases in mitral valve and 3 in tricuspid valve, mechanical prostheses dysfunction (2cases, infective endocarditis after valve replacement (2 cases, restenosis of repaired native valve (1 case, and severe tricuspid insufficiency after left-side valve surgery (7 cases. Resurgery included mitral valve replacement in 18 patients and tricuspid valve replacement in 10. All the patients underwent third or fourth or even fifth cardiac surgery for valve replacement. Results　There were 2 hospital deaths with a mortality of 7.1% (2/28. The main causes of early-stage deaths were low cardiac output syndrome. The main postoperative complications were respiratory failure in 3, low cardiac output syndrome in 2, reexploration for bleeding in 2 and serious infectious shock in 1. All the patients were found with the great improvement in heart function and the re-implanted prostheses worked well during follow-up. Conclusions　Although resurgery for recurrent heart valve disease poses a continuing challenge to cardiac surgeon, it could be performed with the satisfactory results. The keys to a successful cardiac resurgery include appropriate operational timing, refined surgical technique and reasonable perioperative managements. DOI: 10.11855/j.issn.0577-7402.2017.01.11

A chronic hemodialysis patient with isolated pulmonary valve infective endocarditis caused by non-albicans Candida: a rare case and literature review.

Science.gov (United States)

Chang, Chih-Hao; Huang, Myo-Ming; Yeih, Dong-Feng; Lu, Kuo-Cheng; Hou, Yi-Chou

2017-09-06

Isolated pulmonary valve infective endocarditis caused by Candida is rare in chronic hemodialysis patients. The 2009 Infectious Diseases Society of America guidelines suggest the combined use of surgery and antibiotics to treat candidiasis; however, successful nonsurgical treatment of Candida endocarditis has been reported. A 63-year-old woman with end-stage kidney disease was admitted to our hospital after experiencing disorientation for 5 days. The patient was permanently bedridden because of depression, and denied active intravenous drug use. She received maintenance hemodialysis through a tunneled-cuffed catheter. An initial blood culture grew Candida guilliermondii without other bacteria. Subsequent blood cultures and tip culture of tunneled-cuffed catheter also grew C. guilliermondii, even after caspofungin replaced fluconazole. A 1.2-cm mobile mass was observed on the pulmonary valve. Surgical intervention was suggested, but the family of the patient declined because of her multiple comorbidities. The patient was discharged with a prescription of fluconazole, but she died soon after. Our patient is the first case with isolated pulmonary valve endocarditis caused by C. guilliermondii in patients with uremia. Hematologic disorders, in addition to long-term central venous catheter use, prolonged antibiotic intravenous injection, and congenital cardiac anomaly, predispose to the condition. The diagnosis "isolated" pulmonary IE is difficult, and combing surgery with antifungal antibiotics is the appropriate therapeutic management for Candida related pulmonary IE.

Classification of heart valve condition using acoustic measurements

Energy Technology Data Exchange (ETDEWEB)

Clark, G. [Lawrence Livermore National Lab., CA (United States)

1994-11-15

Prosthetic heart valves and the many great strides in valve design have been responsible for extending the life spans of many people with serious heart conditions. Even though the prosthetic valves are extremely reliable, they are eventually susceptible to long-term fatigue and structural failure effects expected from mechanical devices operating over long periods of time. The purpose of our work is to classify the condition of in vivo Bjork-Shiley Convexo-Concave (BSCC) heart valves by processing acoustic measurements of heart valve sounds. The structural failures of interest for Bscc valves is called single leg separation (SLS). SLS can occur if the outlet strut cracks and separates from the main structure of the valve. We measure acoustic opening and closing sounds (waveforms) using high sensitivity contact microphones on the patient`s thorax. For our analysis, we focus our processing and classification efforts on the opening sounds because they yield direct information about outlet strut condition with minimal distortion caused by energy radiated from the valve disc.

Preliminary assessment of valve IST effectiveness

International Nuclear Information System (INIS)

Grove, E.; DiBiasio, A.; Carbonaro, J.

1994-01-01

A preliminary review of inservice testing effectiveness for Code Class 1,2, and 3 valves at nuclear power plants was performed. These requirements are specified by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI, and the Operations and Maintenance Standard. The Institute of Nuclear Power Operations Nuclear Plant Reliability Data System (NPRDS) database was used to provide failure reports for these components for 1988 to 1992. This time period coincides with the issuance of Generic Letter 89-04, which resulted in a more consistent application of the requirements by the licensees. For this time period, 8,593 valve failures were identified. From the review of the NPRDS database, the primary failure causes and failure modes for motor-operated valves (MOV), air-operated valves (AOV), and check valves (CV) were identified. Solenoid-operated valves were not reviewed in this study. Plant testing programs were effective in identifying approximately 60% of the CV failures, 46% of the AOV failures, and 44% of the MOV failures

Malfunction of a Heimlich flutter valve causing tension pneumothorax: case report of a rare complication

Directory of Open Access Journals (Sweden)

Braunstein Volker A

2010-06-01

Full Text Available Abstract Background Thoracic injuries play an important role in major trauma patients due to their high incidence and critical relevance. A serious consequence of thoracic trauma is pneumothorax, a condition that quickly can become life-threatening and requires immediate treatment. Decompression is the state of the art for treating tension pneumothorax. There are many different methods of decompression using different techniques, devices, valves and drainage systems. Referring to our case report we would like to discuss the utilization of these devices. Case presentation We report of a patient suffering from tension pneumothorax despite insertion of a chest drain at the accident scene. The decompression was by tube thoracostomy which was connected to a Heimlich flutter valve. During air transportation the patient suffered from cardiorespiratory arrest with asystole and was admitted to the trauma room undergoing manual chest compressions. The initial chest film showed a persisting tension pneumothorax, despite the chest tube that had been correctly placed and connected properly to the Heimlich valve. We assume that the Heimlich valve leaves did not open up and thus tension pneumothorax was not released. Conclusion We would like to raise awareness to the fact that if a Heimlich flutter valve is applied in the pre-hospital setting it should be used with caution. Failure in this type of valve may lead to recurrent tension pneumothorax.

Fracturing mechanics before valve-in-valve therapy of small aortic bioprosthetic heart valves.

Science.gov (United States)

Johansen, Peter; Engholt, Henrik; Tang, Mariann; Nybo, Rasmus F; Rasmussen, Per D; Nielsen-Kudsk, Jens Erik

2017-10-13

Patients with degraded bioprosthetic heart valves (BHV) who are not candidates for valve replacement may benefit from transcatheter valve-in-valve (VIV) therapy. However, in smaller-sized surgical BHV the resultant orifice may become too narrow. To overcome this, the valve frame can be fractured by a high-pressure balloon prior to VIV. However, knowledge on fracture pressures and mechanics are prerequisites. The aim of this study was to identify the fracture pressures needed in BHV, and to describe the fracture mechanics. Commonly used BHV of small sizes were mounted on a high-pressure balloon situated in a biplane fluoroscopic system with a high-speed camera. The instant of fracture was captured along with the balloon pressure. The valves were inspected for material protrusion and later dissected for fracture zone investigation and description. The valves with a polymer frame fractured at a lower pressure (8-10 atm) than those with a metal stent (19-26 atm). None of the fractured valves had elements protruding. VIV procedures in small-sized BHV may be performed after prior fracture of the valve frame by high-pressure balloon dilatation. This study provides tentative guidelines for expected balloon sizes and pressures for valve fracturing.

Apparent culture-negative prosthetic valve endocarditis caused by Peptostreptococcus magnus

NARCIS (Netherlands)

van der Vorm, E. R.; Dondorp, A. M.; van Ketel, R. J.; Dankert, J.

2000-01-01

In two patients with prosthetic valve endocarditis due to Peptostreptococcus magnus, blood cultures in the BacT/Alert and BACTEC 9240 systems were signal negative. The capability of the BacT/Alert system to detect various Peptostreptococcus species was assessed. P. magnus and P. anaerobius could not

Surgery for rheumatic mitral valve disease in sub-saharan African countries: why valve repair is still the best surgical option.

Science.gov (United States)

Mvondo, Charles Mve; Pugliese, Marta; Giamberti, Alessandro; Chelo, David; Kuate, Liliane Mfeukeu; Boombhi, Jerome; Dailor, Ellen Marie

2016-01-01

Rheumatic valve disease, a consequence of acute rheumatic fever, remains endemic in developing countries in the sub-Saharan region where it is the leading cause of heart failure and cardiovascular death, involving predominantly a young population. The involvement of the mitral valve is pathognomonic and mitral surgery has become the lone therapeutic option for the majority of these patients. However, controversies exist on the choice between valve repair or prosthetic valve replacement. Although the advantages of mitral valve repair over prosthetic valve replacement in degenerative mitral disease are well established, this has not been the case for rheumatic lesions, where the use of prosthetic valves, specifically mechanical devices, even in poorly compliant populations remains very common. These patients deserve more accurate evaluation in the choice of the surgical strategy which strongly impacts the post-operative outcomes. This report discusses the factors supporting mitral repair surgery in rheumatic disease, according to the patients' characteristics and the effectiveness of the current repair techniques compared to prosthetic valve replacement in developing countries.

Intermittent search strategies

Science.gov (United States)

Bénichou, O.; Loverdo, C.; Moreau, M.; Voituriez, R.

2011-01-01

This review examines intermittent target search strategies, which combine phases of slow motion, allowing the searcher to detect the target, and phases of fast motion during which targets cannot be detected. It is first shown that intermittent search strategies are actually widely observed at various scales. At the macroscopic scale, this is, for example, the case of animals looking for food; at the microscopic scale, intermittent transport patterns are involved in a reaction pathway of DNA-binding proteins as well as in intracellular transport. Second, generic stochastic models are introduced, which show that intermittent strategies are efficient strategies that enable the minimization of search time. This suggests that the intrinsic efficiency of intermittent search strategies could justify their frequent observation in nature. Last, beyond these modeling aspects, it is proposed that intermittent strategies could also be used in a broader context to design and accelerate search processes.

Management of patients with intermittent claudication

NARCIS (Netherlands)

S. Spronk (Sandra)

2008-01-01

textabstractIntermittent claudication is the first and mildest manifestation of peripheral arterial disease, caused by the atherosclerotic process of progressive narrowing of one or more of the arteries of the peripheral circulation.1 If the arterial system fails, it results in a progressive oxygen

Statins for aortic valve stenosis

Directory of Open Access Journals (Sweden)

Luciana Thiago

Full Text Available ABSTRACT BACKGROUND: Aortic valve stenosis is the most common type of valvular heart disease in the USA and Europe. Aortic valve stenosis is considered similar to atherosclerotic disease. Some studies have evaluated statins for aortic valve stenosis. OBJECTIVES: To evaluate the effectiveness and safety of statins in aortic valve stenosis. METHODS: Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, MEDLINE, Embase, LILACS - IBECS, Web of Science and CINAHL Plus. These databases were searched from their inception to 24 November 2015. We also searched trials in registers for ongoing trials. We used no language restrictions. Selection criteria: Randomized controlled clinical trials (RCTs comparing statins alone or in association with other systemic drugs to reduce cholesterol levels versus placebo or usual care. Data collection and analysis: Primary outcomes were severity of aortic valve stenosis (evaluated by echocardiographic criteria: mean pressure gradient, valve area and aortic jet velocity, freedom from valve replacement and death from cardiovascular cause. Secondary outcomes were hospitalization for any reason, overall mortality, adverse events and patient quality of life. Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias. The GRADE methodology was employed to assess the quality of result findings and the GRADE profiler (GRADEPRO was used to import data from Review Manager 5.3 to create a 'Summary of findings' table. MAIN RESULTS: We included four RCTs with 2360 participants comparing statins (1185 participants with placebo (1175 participants. We found low-quality evidence for our primary outcome of severity of aortic valve stenosis, evaluated by mean pressure gradient (mean difference (MD -0.54, 95% confidence interval (CI -1.88 to 0.80; participants = 1935; studies = 2, valve area (MD -0.07, 95% CI -0.28 to 0.14; participants = 127; studies = 2

Statins for aortic valve stenosis.

Science.gov (United States)

Thiago, Luciana; Tsuji, Selma Rumiko; Nyong, Jonathan; Puga, Maria Eduarda Dos Santos; Góis, Aécio Flávio Teixeira de; Macedo, Cristiane Rufino; Valente, Orsine; Atallah, Álvaro Nagib

2016-01-01

Aortic valve stenosis is the most common type of valvular heart disease in the USA and Europe. Aortic valve stenosis is considered similar to atherosclerotic disease. Some studies have evaluated statins for aortic valve stenosis. To evaluate the effectiveness and safety of statins in aortic valve stenosis. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS - IBECS, Web of Science and CINAHL Plus. These databases were searched from their inception to 24 November 2015. We also searched trials in registers for ongoing trials. We used no language restrictions.Selection criteria: Randomized controlled clinical trials (RCTs) comparing statins alone or in association with other systemic drugs to reduce cholesterol levels versus placebo or usual care. Data collection and analysis: Primary outcomes were severity of aortic valve stenosis (evaluated by echocardiographic criteria: mean pressure gradient, valve area and aortic jet velocity), freedom from valve replacement and death from cardiovascular cause. Secondary outcomes were hospitalization for any reason, overall mortality, adverse events and patient quality of life.Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias. The GRADE methodology was employed to assess the quality of result findings and the GRADE profiler (GRADEPRO) was used to import data from Review Manager 5.3 to create a 'Summary of findings' table. We included four RCTs with 2360 participants comparing statins (1185 participants) with placebo (1175 participants). We found low-quality evidence for our primary outcome of severity of aortic valve stenosis, evaluated by mean pressure gradient (mean difference (MD) -0.54, 95% confidence interval (CI) -1.88 to 0.80; participants = 1935; studies = 2), valve area (MD -0.07, 95% CI -0.28 to 0.14; participants = 127; studies = 2), and aortic jet velocity (MD -0.06, 95% CI -0.26 to 0

Gas-mixing system for drift chambers using solenoid valves

International Nuclear Information System (INIS)

Cooper, W.E.; Sugano, K.; Trentlage, D.B.

1983-04-01

We describe an inexpensive system for mixing argon and ethane drift chamber gas which is used for the E-605 experiment at Fermilab. This system is based on the idea of intermittent mixing of gases with fixed mixing flow rates. A dual-action pressure switch senses the pressure in a mixed gas reservoir tank and operates solenoid valves to control mixing action and regulate reservoir pressure. This system has the advantages that simple controls accurately regulate the mixing ratio and that the mixing ratio is nearly flow rate independent. We also report the results of the gas analysis of various samplings, and the reliability of the system in long-term running

Antithrombotic Therapy in Patients with Prosthetic Heart Valves

Directory of Open Access Journals (Sweden)

Mohamed HA

2009-01-01

Full Text Available Patients with mechanical valve prostheses require a lifelong anticoagulant treatment. The combined use of Warfarin and low-dose aspirin appears to reduce the risk of valve thrombosis and systemic embolism at a low risk of bleeding. The management of women with prosthetic heart valves during pregnancy poses a particular challenge, as there are no available controlled clinical trials to provide guidelines for effective antithrombotic therapy. Oral anticoagulants, such as Warfarin, cause foetal embryopathy; unfractionated heparin and low-molecular-weight heparin have been reported to be ineffective in preventing thromboembolic complications.This article discusses the available data and the most recent guidelines in the antithrombotic management of patients with prosthetic valves, and antithrombotic therapy in various clinical situations such as pregnant women with prosthetic heart valves, and patients with prosthetic heart valves undergoing noncardiac surgery.

NRC valve performance test program - check valve testing

International Nuclear Information System (INIS)

Jeanmougin, N.M.

1987-01-01

The Valve Performance Test Program addresses the current requirements for testing of pressure isolation valves (PIVs) in light water reactors. Leak rate monitoring is the current method used by operating commercial power plants to survey the condition of their PIVs. ETEC testing of three check valves (4-inch, 6-inch, and 12-inch nominal diameters) indicates that leak rate testing is not a reliable method for detecting impending valve failure. Acoustic emission monitoring of check valves shows promise as a method of detecting loosened internals damage. Future efforts will focus on evaluation of acoustic emission monitoring as a technique for determining check valve condition. Three gate valves also will be tested to evaluate whether the check valve results are applicable to gate type PIVs

Transcatheter, valve-in-valve transapical aortic and mitral valve implantation, in a high risk patient with aortic and mitral prosthetic valve stenoses

Directory of Open Access Journals (Sweden)

Harish Ramakrishna

2015-01-01

Full Text Available Transcatheter valve implantation continues to grow worldwide and has been used principally for the nonsurgical management of native aortic valvular disease-as a potentially less invasive method of valve replacement in high-risk and inoperable patients with severe aortic valve stenosis. Given the burden of valvular heart disease in the general population and the increasing numbers of patients who have had previous valve operations, we are now seeing a growing number of high-risk patients presenting with prosthetic valve stenosis, who are not potential surgical candidates. For this high-risk subset transcatheter valve delivery may be the only option. Here, we present an inoperable patient with severe, prosthetic valve aortic and mitral stenosis who was successfully treated with a trans catheter based approach, with a valve-in-valve implantation procedure of both aortic and mitral valves.

Infective endocarditis following transcatheter aortic valve replacement-

DEFF Research Database (Denmark)

Loh, Poay Huan; Bundgaard, Henning; S�ndergaard, Lars

2013-01-01

Transcatheter aortic valve replacement (TAVR) can improve the symptoms and prognosis of patients with severe aortic stenosis who, due to a high expected operative risk, would not have otherwise been treated surgically. If these patients develop prosthetic valve endocarditis, their presentations may...... be atypical causing a delay in the diagnosis and treatment. The management is also complicated by their comorbidities, and surgical treatment may not be feasible leading to a significant morbidity and mortality. We describe a case of an 85-year-old man with TAVI prosthetic valve endocarditis successfully...

Computed Flow Through An Artificial Heart Valve

Science.gov (United States)

Rogers, Stewart E.; Kwak, Dochan; Kiris, Cetin; Chang, I-Dee

1994-01-01

Report discusses computations of blood flow through prosthetic tilting disk valve. Computational procedure developed in simulation used to design better artificial hearts and valves by reducing or eliminating following adverse flow characteristics: large pressure losses, which prevent hearts from working efficiently; separated and secondary flows, which causes clotting; and high turbulent shear stresses, which damages red blood cells. Report reiterates and expands upon part of NASA technical memorandum "Computed Flow Through an Artificial Heart and Valve" (ARC-12983). Also based partly on research described in "Numerical Simulation of Flow Through an Artificial Heart" (ARC-12478).

[Mitral valve endocarditis after Turkish "Festival of Sacrifice"].

Science.gov (United States)

Blaich, A; Fasel, D; Kaech, C; Frei, R

2011-09-01

Erysipelothrix rhusiopathiae is the causative agent of swine erysipelas. Systemic infections caused by E. rhusiopathiae are rare, but often (90%) associated with endocarditis. In about 60% of cases endocarditis develops on normal heart valves, and despite appropriate antibiotic therapy about one-third of the patients requires valve replacement. We report the case of a housewife, who developed a mitral valve endocarditis due to E. rhusiopathiae after preparing meat for the Turkish "Festival of Sacrifice".

Butterfly valve torque prediction methodology

International Nuclear Information System (INIS)

Eldiwany, B.H.; Sharma, V.; Kalsi, M.S.; Wolfe, K.

1994-01-01

As part of the Motor-Operated Valve (MOV) Performance Prediction Program, the Electric Power Research Institute has sponsored the development of methodologies for predicting thrust and torque requirements of gate, globe, and butterfly MOVs. This paper presents the methodology that will be used by utilities to calculate the dynamic torque requirements for butterfly valves. The total dynamic torque at any disc position is the sum of the hydrodynamic torque, bearing torque (which is induced by the hydrodynamic force), as well as other small torque components (such as packing torque). The hydrodynamic torque on the valve disc, caused by the fluid flow through the valve, depends on the disc angle, flow velocity, upstream flow disturbances, disc shape, and the disc aspect ratio. The butterfly valve model provides sets of nondimensional flow and torque coefficients that can be used to predict flow rate and hydrodynamic torque throughout the disc stroke and to calculate the required actuation torque and the maximum transmitted torque throughout the opening and closing stroke. The scope of the model includes symmetric and nonsymmetric discs of different shapes and aspects ratios in compressible and incompressible fluid applications under both choked and nonchoked flow conditions. The model features were validated against test data from a comprehensive flowloop and in situ test program. These tests were designed to systematically address the effect of the following parameters on the required torque: valve size, disc shapes and disc aspect ratios, upstream elbow orientation and its proximity, and flow conditions. The applicability of the nondimensional coefficients to valves of different sizes was validated by performing tests on 42-in. valve and a precisely scaled 6-in. model. The butterfly valve model torque predictions were found to bound test data from the flow-loop and in situ testing, as shown in the examples provided in this paper

NRC Information No. 88-72: Inadequacies in the design of dc motor-operated valves

International Nuclear Information System (INIS)

Rossi, C.E.

1992-01-01

On July 1, 1988, a high pressure coolant injection (HPCI) steam admission valve failed to open during a post-maintenance test at the Brunswick nuclear power plant, Unit 1. The same valve had failed in December 1987 and on May 28, 1988. The licensee, Carolina Power and Light Company, established a team to investigate the cause of failure, and the team identified the most probable cause as a dc motor failure due to a shunt-winding to series-winding short circuit. The team believed that this condition was precipitated by thermal binding of the valve internals. The previous failure in May was also diagnosed as having been caused by thermal binding. As a result of these failures, the licensee reviewed the design of the dc motor-operated valves for both the HPCI and the reactor core isolation cooling (RCIC) systems. This review identified a number of significant design deficiencies going well beyond the problems with thermal binding. The deficiencies constitute a potential common cause failure mechanism for safety system valves. Unit 1 was shut down on July 14, 1988 to replace the failed HPCI valve motor and to implement design modifications to other motor-operated valves

Are anticoagulant independent mechanical valves within reach-fast prototype fabrication and in vitro testing of innovative bi-leaflet valve models.

Science.gov (United States)

Scotten, Lawrence N; Siegel, Rolland

2015-08-01

Exploration for causes of prosthetic valve thrombogenicity has frequently focused on forward or post-closure flow detail. In prior laboratory studies, we uncovered high amplitude flow velocities of short duration close to valve closure implying potential for substantial shear stress with subsequent initiation of blood coagulation pathways. This may be relevant to widely accepted clinical disparity between mechanical and tissue valves vis-à-vis thrombogenicity. With a series of prototype bi-leaflet mechanical valves, we attempt reduction of closure related velocities with the objective of identifying a prototype valve with thrombogenic potential similar to our tissue valve control. This iterative design approach may find application in preclinical assessment of valves for anticoagulation independence. Tested valves included: prototype mechanical bi-leaflet BVs (n=56), controls (n=2) and patented early prototype mechanicals (n=2) from other investigators. Pulsatile and quasi-steady flow systems were used for testing. Projected dynamic valve area (PDVA) was measured using previously described novel technology. Flow velocity over the open and closing periods was determined by volumetric flow rate/PDVA. For the closed valve interval, use was made of data obtained from quasi-steady back pressure/flow tests. Performance was ranked by a proposed thrombogenicity potential index (TPI) relative to tissue and mechanical control valves. Optimization of the prototype valve designs lead to a 3-D printed model (BV3D). For the mitral/aortic site, BV3D has lower TPI (1.10/1.47) relative to the control mechanical valve (3.44/3.93) and similar to the control tissue valve (ideal TPI ≤1.0). Using unique technology, rapid prototyping and thrombogenicity ranking, optimization of experimental valves for reduced thrombogenic potential was expedited and simplified. Innovative mechanical valve configurations were identified that merit consideration for further development which may bring

Intermittent subglottic secretion drainage may cause tracheal damage in patients with few oropharyngeal secretions.

Science.gov (United States)

Suys, E; Nieboer, K; Stiers, W; De Regt, J; Huyghens, L; Spapen, H

2013-12-01

Injurious prolapse of tracheal mucosa into the suction port has been reported in up to 50% of intubated patients receiving continuous aspiration of subglottic secretions. We investigated whether similar injury could be inflicted by automated intermittent aspiration. Six consecutive patients, intubated with the Mallinckrodt TaperGuard Evac™ endotracheal tube, were studied. A flow sensor was placed between the vacuum regulating system and the mucus collector. Intermittent suctioning was performed at a pressure of -125 mmHg with a 25s interval and duration of 15s. After 24h, a CT scan of the tracheal region was performed. Excessive negative suction pressure, a fast drop in aspiration flow to zero, and important "swinging" movements of secretions in the evacuation line were observed in all patients. Oral instillation of antiseptic mouthwash restored normal aspiration flow and secretion mobility. CT imaging showed marked entrapment of tracheal mucosa into the suction port in all patients. In patients with few oropharyngeal secretions, automated intermittent subglottic aspiration may result in significant and potential harmful invagination of tracheal mucosa into the suction lumen. A critical amount of fluid must be present in the oropharynx to assure adequate and safe aspiration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Transfemoral Aortic Valve Implantation with the New Edwards Sapien 3 Valve for Treatment of Severe Aortic Stenosis-Impact of Valve Size in a Single Center Experience.

Directory of Open Access Journals (Sweden)

Jochen Wöhrle

Full Text Available The third generation Edwards Sapien 3 (Edwards Lifesciences Inc., Irvine, California system was optimized to reduce residual aortic regurgitation and vascular complications.235 patients with severe symptomatic aortic stenosis were prospectively enrolled. Transcatheter aortic valve implantations (TAVI were performed without general anesthesia by transfemoral approach. Patients were followed for 30 days. Patients received 23mm (N = 77, 26mm (N = 91 or 29mm (N = 67 valve based on pre-procedural 256 multislice computer tomography. Mean oversizing did not differ between the 3 valves. There was no residual moderate or severe aortic regurgitation. Rate of mild aortic regurgitation and regurgitation index did not differ between groups. There was no switch to general anesthesia or conversion to surgery. Rate of major vascular complication was 3.0% with no difference between valve and delivery sheath sizes. Within 30 days rates of all cause mortality (2.6% and stroke (2.1% were low.In patients with severe aortic stenosis transfemoral TAVI with the Edwards Sapien 3 valve without general anesthesia was associated with a high rate of device success, no moderate or severe residual aortic regurgitation, low rates of major vascular complication, mortality and stroke within 30 days with no difference between the 3 valve sizes.ClinicalTrials.gov NCT02162069.

Control Valve Stiction Identification, Modelling, Quantification and Control - A Review

Directory of Open Access Journals (Sweden)

Srinivasan Arumugam

2011-09-01

Full Text Available Most of the processes found in process industries exhibit undesirable nonlinearity due to backlash, saturation, hysteresis, stiction (friction, dead-zone and stuck-fault existing in control valves. The control valve is the actuator for most process control loops and, as the only moving part in the loop, its function is to implement the control action. If the control valve malfunctions, the performance of the control loop is likely to deteriorate, no matter how good the controller is. Commonly encountered control valve problems include nonlinear responses to the demand signal caused by effects such as stiction, dead-band or saturation. Because of these problems, the control loop may be oscillatory, which in turn may cause oscillations in many process variables causing a range of operational problems including increased valve wear. Understanding nonlinear behaviour of control valves in order to maintain the quality of the end products in the industry, this review article surveys the identification, modelling, estimation and design of dynamic models of stiction nonlinearity and providing appropriate controller to obtain optimum responses of the process. The primary objective of this work is to present state-of-art-review of common nonlinear problems associated with mechanical and chemical processes for encouraging researchers, practicing engineers working in this field, so that readers can invent their goals for future research work on nonlinear systems identification and control.

Motor operated valves problems tests and simulations

Energy Technology Data Exchange (ETDEWEB)

Pinier, D.; Haas, J.L.

1996-12-01

An analysis of the two refusals of operation of the EAS recirculation shutoff valves enabled two distinct problems to be identified on the motorized valves: the calculation methods for the operating torques of valves in use in the power plants are not conservative enough, which results in the misadjustement of the torque limiters installed on their motorizations, the second problem concerns the pressure locking phenomenon: a number of valves may entrap a pressure exceeding the in-line pressure between the disks, which may cause a jamming of the valve. EDF has made the following approach to settle the first problem: determination of the friction coefficients and the efficiency of the valve and its actuator through general and specific tests and models, definition of a new calculation method. In order to solve the second problem, EDF has made the following operations: identification of the valves whose technology enables the pressure to be entrapped: the tests and numerical simulations carried out in the Research and Development Division confirm the possibility of a {open_quotes}boiler{close_quotes} effect: determination of the necessary modifications: development and testing of anti-boiler effect systems.

Motor operated valves problems tests and simulations

International Nuclear Information System (INIS)

Pinier, D.; Haas, J.L.

1996-01-01

An analysis of the two refusals of operation of the EAS recirculation shutoff valves enabled two distinct problems to be identified on the motorized valves: the calculation methods for the operating torques of valves in use in the power plants are not conservative enough, which results in the misadjustement of the torque limiters installed on their motorizations, the second problem concerns the pressure locking phenomenon: a number of valves may entrap a pressure exceeding the in-line pressure between the disks, which may cause a jamming of the valve. EDF has made the following approach to settle the first problem: determination of the friction coefficients and the efficiency of the valve and its actuator through general and specific tests and models, definition of a new calculation method. In order to solve the second problem, EDF has made the following operations: identification of the valves whose technology enables the pressure to be entrapped: the tests and numerical simulations carried out in the Research and Development Division confirm the possibility of a open-quotes boilerclose quotes effect: determination of the necessary modifications: development and testing of anti-boiler effect systems

Altitude valve for railway suspension control system

Science.gov (United States)

Zhang, Xuan; Zhang, Lihao; Li, Qingxuan; Chen, WanSong

2017-09-01

With the variation of people and material during vehicle service, the gravity of vehicle could be unbalanced. As a result it might cause accident. In order to solve this problem, altitude valve is assembled on board. It can adjust the gravity of vehicle by the intake and outlet progress of the spring in the altitude valve to prevent the tilt of vehicles.

Gamma Ray Sterilization of Starr-Edwards Heart Valve Prostheses

Energy Technology Data Exchange (ETDEWEB)

Gibbons, J. R. P.; Alladine, M. F. [London Chest Hospital, London (United Kingdom)

1967-09-15

Starr-Edwards valves have normally been sterilized by exposure to ethylene oxide or by autoclaving. Patients having a prosthetic valve replacement are known to have a higher incidence of endocarditis in comparison with patients in which no prosthesis has been used. Ethylene oxide will only sterilize the surface of the valve and autoclaving has caused distortion of the polytetrafluorethylene ring. Work has been done on the effect of gamma radiation on the components of these valve prostheses and is given in detail. The bacteriological efficiency, at a total absorbed dose of 2. 5 Mrad, has been established. Thirty valves treated by this method have now been inserted and twelve patients have been examined post-operatively for a period of one to two years. All valves are working normally and there has been no evidence of blood-borne infection or malfunction of the valve. (author)

Coronary artery assessment by multidetector computed tomography in patients with prosthetic heart valves

International Nuclear Information System (INIS)

Habets, Jesse; Mali, Willem P.T.M.; Budde, Ricardo P.J.; Brink, Renee B.A. van den; Uijlings, Ruben; Spijkerboer, Anje M.; Chamuleau, Steven A.J.

2012-01-01

Patients with prosthetic heart valves may require assessment for coronary artery disease. We assessed whether valve artefacts hamper coronary artery assessment by multidetector CT. ECG-gated or -triggered CT angiograms were selected from our PACS archive based on the presence of prosthetic heart valves. The best systolic and diastolic axial reconstructions were selected for coronary assessment. Each present coronary segment was scored for the presence of valve-related artefacts prohibiting coronary artery assessment. Scoring was performed in consensus by two observers. Eighty-two CT angiograms were performed on a 64-slice (n = 27) or 256-slice (n = 55) multidetector CT. Eighty-nine valves and five annuloplasty rings were present. Forty-three out of 1160 (3.7%) present coronary artery segments were non-diagnostic due to valve artefacts (14/82 patients). Valve artefacts were located in right coronary artery (15/43; 35%), left anterior descending artery (2/43; 5%), circumflex artery (14/43; 32%) and marginal obtuse (12/43; 28%) segments. All cobalt-chrome containing valves caused artefacts prohibiting coronary assessment. Biological and titanium-containing valves did not cause artefacts except for three specific valve types. Most commonly implanted prosthetic heart valves do not hamper coronary assessment on multidetector CT. Cobalt-chrome containing prosthetic heart valves preclude complete coronary artery assessment because of severe valve artefacts. circle Most commonly implanted prosthetic heart valves do not hamper coronary artery assessment circle Prosthetic heart valve composition determines the occurrence of prosthetic heart valve-related artefacts circle Bjoerk-Shiley and Sorin tilting disc valves preclude diagnostic coronary artery segment assessment. (orig.)

Adult ileocolic intussusception secondary to ileocaecal valve polyp.

LENUS (Irish Health Repository)

Chugthai, Saqib Zeeshan

2012-01-31

Intussusception is relatively common in children, but it is a rare cause of abdominal pain and intestinal obstruction in adults. The aetiology, clinical presentation and management of this condition differs in adults and children. Preoperative clinical diagnosis is usually difficult due to the non-specific and intermittent nature of the symptoms. Ultrasound and computed tomography can be helpful in establishing the diagnosis. We present a case of adult ileocolic intussusception with classical radiological signs and operative findings. In adults the diagnosis of intussusception should be considered in a case of intermittent abdominal pain, especially with clinical signs of intermittent bowel obstruction.

Heart valve surgery

Science.gov (United States)

... replacement; Valve repair; Heart valve prosthesis; Mechanical valves; Prosthetic valves ... surgery. Your heart valve has been damaged by infection ( endocarditis ). You have received a new heart valve ...

Radiological symptoms of the disfunction of artificial heart valves

Energy Technology Data Exchange (ETDEWEB)

Erdelyi, M Jr [Orszagos Roentgen es Sugarfizikai Intezet, Budapest (Hungary)

1981-01-31

The possible causes of the disfunction of artificial valves are detailed. Routine X-ray examinations of the chest only rarely reveal direct signs of disfunction, but the haemodynamic alterations (dilated heart chambers, or veins) must be considered as important indirect signs. The characteristics and possibly the cause of the valve insufficience can be analyzed on the basis of kino- and spot radiograms. The symptoms observed by these methods are reported in detail.

The influence of continuous and intermittent traffic noise on sleep

Science.gov (United States)

Eberhardt, J. L.; Stråle, L.-O.; Berlin, M. H.

1987-08-01

The effects of road traffic noise on sleep were studied in the laboratory using nine young male adults (aged 20-26). The subjects were exposed to noise with different temporal characteristics: (i) continuous traffic noise of 36 dB(A) or 45 dB(A), (ii) intermittent noise of 50 truck passages with L pmax = 45 dB(A) ( L eq = 29 dB(A)) or L pmax = 55 dB(A) ( L eq = 36 dB(A)), and (iii) a combination of continuous (45 dB(A)) and intermittent ( L pmax = 55 dB(A)) traffic noise. For one noise condition (intermittent 55 dB(A)) the effect of the use of ear plugs was also studied. The intermittent noise of L pmax = 45 dB(A) caused transitions towards lighter sleep, whereas 55 dB(A) was needed to induce awakening effects. It could be shown that the probability for arousal reactions depends on the emergence of the noise peaks from the background, rather than the absolute noise peak level. Continuous traffic noise of 45 dB(A) caused REM sleep deficits, while intermittent traffic noise of L pmax = 45 dB(A) caused stage III+IV deficits. The night with ear plugs was virtually undisturbed. After nights with REM sleep deficits the subjective sleep quality was rated lower and mood was influenced adversely. For the types of exposure used in the present investigation L eq alone is not an adequate descriptor of the noise dose, relating to the sleep disturbances observed. From the present experiment, together with other existing data, it might be concluded that the WHO recommendation of L eq = 35 dB(A) is adequate, but should be supplemented with a maximum noise level, as expressed for example in L pmax or LI, that should not be exceeded.

Isolated intermittent vertigo: A presenting feature of persistent trigeminal artery

Directory of Open Access Journals (Sweden)

Rajsrinivas Parthasarathy

2016-01-01

Full Text Available Embryonic carotid – basilar anastomosis when persistent in adult life can present with a variety of neurological symptoms. We present a patient with isolated intermittent vertigo attributable to the embryonic anastomosis and describe the different types of persistent trigeminal artery. A 76-year-old Caucasian man presented with isolated intermittent vertigo and symptoms suggestive of anterior and posterior circulation strokes. Impaired vasomotor reactivity was demonstrated on insonation of the anterior and posterior cerebral arteries in this patient with a persistent left trigeminal artery and 75% stenosis of the left internal carotid artery (ICA. The symptom of intermittent vertigo resolved with carotid endarterectomy. Decreased flow across the stenotic segment of the ICA which subserved the posterior circulation resulted in basilar insufficiency. Hypoperfusion to the flocculonodular lobe supplied by the anterior inferior cerebellar artery is a likely cause for the intermittent vertigo.

Review and analysis of check valve failure data

International Nuclear Information System (INIS)

Todd, M.D.; Casada, D.A.

1992-01-01

Check valve operating problems in recent years have resulted in significant operating transients, increased cost and decreased system availability. There has been, in response, additional attention given to check valves by utilities, as well as the US Nuclear Regulatory Commission and the American Society of Mechanical Engineers Operation and Maintenance Committee. All these organizations have the fundamental goal of ensuring reliable operation of check valves. A key ingredient to an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. Oak Ridge National Laboratory is currently conducting a detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System. The focus of the review is on check valve failures that have involved significant degradation of the valve internal parts. A variety of parameters are being considered during the review, including size, age, system of service, method of failure discovery, the affected valve parts, attributed causes, and corrective actions

Methodology for Check Valve Selection to Maintain the Integrity of Pipeline against the Check Valve Slam for the KIJANG Research Reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, Dayong; Yoon, Hyungi; Seo, Kyoungwoo; Kim, Seonhoon [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The check valve slam results in a water hammer and unexpected system pressure rise in the pipeline. Sometimes, the pressure rise by check valve slam in the pipeline exceeds the design pressure and then it causes the rupture of pipeline. Therefore, check valve slam significantly influences on the integrity of pipe. Especially, this it is most likely to occur by check valve installed in the discharge of pump when one pump trips among the two or more running in parallel pump system. This study focuses on the check valve selection to maintain the integrity of PCS pipeline against the check valve slam. If design head for KJRR PCS pipeline is higher than the sum of static head and 11 m, any type check valves can be installed at the discharge of pump. However, if design head for KJRR PCS pipeline is lower than the sum of static head and 11 m, installation of swing and ball check on the discharge of pump must be avoid to prevent the rupture of PCS pipeline.

Methodology for Check Valve Selection to Maintain the Integrity of Pipeline against the Check Valve Slam for the KIJANG Research Reactor

International Nuclear Information System (INIS)

Kim, Dayong; Yoon, Hyungi; Seo, Kyoungwoo; Kim, Seonhoon

2016-01-01

The check valve slam results in a water hammer and unexpected system pressure rise in the pipeline. Sometimes, the pressure rise by check valve slam in the pipeline exceeds the design pressure and then it causes the rupture of pipeline. Therefore, check valve slam significantly influences on the integrity of pipe. Especially, this it is most likely to occur by check valve installed in the discharge of pump when one pump trips among the two or more running in parallel pump system. This study focuses on the check valve selection to maintain the integrity of PCS pipeline against the check valve slam. If design head for KJRR PCS pipeline is higher than the sum of static head and 11 m, any type check valves can be installed at the discharge of pump. However, if design head for KJRR PCS pipeline is lower than the sum of static head and 11 m, installation of swing and ball check on the discharge of pump must be avoid to prevent the rupture of PCS pipeline

Anesthetic management for combined mitral valve replacement and aortic valve repair in a patient with osteogenesis imperfecta

Directory of Open Access Journals (Sweden)

Huang Jiapeng

2011-01-01

Full Text Available Osteogenesis imperfecta is a rare disorder of connective tissues and presents multiple challenges, including difficult airway, hyperthermia, coagulopathy and respiratory dysfunction, for anesthesiologists, especially during cardiac surgery. We present anesthetic management of a patient with osteogenesis impertecta during double valve surgery. Dexmedetomidine infusion minimized the risks of malignant hyperthermia. Glidescope and in-line stabilization facilitated endotracheal intubation and protected his oral structures and cervical spine. Transesophageal echocardiography (TEE diagnosed a flail A3 segment and redundant left coronary cusp causing mitral and aortic regurgitation. The mitral valve was replaced and the aortic valve repaired. Coagulopathy was corrected according to comprehensive coagulation analysis. Glidescope, dexmedetomidine, coagulation analysis and TEE could facilitate anesthetic management in these patients.

A global perspective on mechanical prosthetic heart valve thrombosis: Diagnostic and therapeutic challenges

Science.gov (United States)

Gürsoy, Mustafa Ozan; Kalçık, Macit; Yesin, Mahmut; Karakoyun, Süleyman; Bayam, Emrah; Gündüz, Sabahattin; Özkan, Mehmet

2016-01-01

Prosthetic valve thrombosis is one of the major causes of primary valve failure, which can be life-threatening. Multimodality imaging is necessary for determination of leaflet immobilization, cause of underlying pathology (thrombus versus pannus or both), and whether thrombolytic therapy attempt in the patient would be successful or surgery is needed. Current guidelines for the management of prosthetic valve thrombosis lack definitive class I recommendations due to lack of randomized controlled trials, and usually leave the choice of treatment to the clinician’s experience. In this review, we aimed to summarize the pathogenesis, diagnosis, and management of mechanical prosthetic valve thrombosis. PMID:28005024

Bioprosthetic Valve Fracture During Valve-in-valve TAVR: Bench to Bedside.

Science.gov (United States)

Saxon, John T; Allen, Keith B; Cohen, David J; Chhatriwalla, Adnan K

2018-01-01

Valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) has been established as a safe and effective means of treating failed surgical bioprosthetic valves (BPVs) in patients at high risk for complications related to reoperation. Patients who undergo VIV TAVR are at risk of patient-prosthesis mismatch, as the transcatheter heart valve (THV) is implanted within the ring of the existing BPV, limiting full expansion and reducing the maximum achievable effective orifice area of the THV. Importantly, patient-prosthesis mismatch and high residual transvalvular gradients are associated with reduced survival following VIV TAVR. Bioprosthetic valve fracture (BVF) is as a novel technique to address this problem. During BPV, a non-compliant valvuloplasty balloon is positioned within the BPV frame, and a highpressure balloon inflation is performed to fracture the surgical sewing ring of the BPV. This allows for further expansion of the BPV as well as the implanted THV, thus increasing the maximum effective orifice area that can be achieved after VIV TAVR. This review focuses on the current evidence base for BVF to facilitate VIV TAVR, including initial bench testing, procedural technique, clinical experience and future directions.

Mitral Valve Replacement with a Pulmonary Autograft in an Infant

Directory of Open Access Journals (Sweden)

Yong Ho Jeong

2018-04-01

Full Text Available A 76-day-old infant weighing 3.4 kg was referred for surgical intervention for severe mitral valve stenoinsufficiency caused by leaflet fibrosis and calcification. He had experienced a cerebral infarction in the left middle cerebral artery territory, which was deemed attributable to an embolism of a calcified particle from the dysmorphic mitral valve. Because mitral valve replacement using a prosthetic valve was not feasible in this small baby, mitral valve replacement with a pulmonary autograft was performed. After a brief period of extracorporeal membrane oxygenation (ECMO support, he was weaned from ECMO and was discharged home without further cardiovascular complications.

The Actuator Fault Diagnosis Based on the Valve Friction

Directory of Open Access Journals (Sweden)

Jiajiang Li

2014-08-01

Full Text Available Control valve (actuator is the frequently moving terminal Instrument of the control system. To avoid the leaking of the actuator, there is packing at the moving parts. However, the friction caused by the packing can do harm to the control of the system. The washing effect of the media, high temperature, high pressure, frequent movement and other effects can result in the leaking of the packing and the deformation of the valve stem, which causes the change of the friction. The study of the control of the friction has always been an interesting topic in the industry. In this paper, we theoretically analyze the relationship of the friction of the packing and the static performance of the control valve, and offer a method to check the quality of the moving parts by attaching a strain gage (strain rosette to the empty part of the valve stem. This method has been demonstrated via experiment and a method to do error detection is provided at last.

Studies of valve lifter for automotive heavy duty diesel engine by ceramic materials. II. Development of SiC valve lifter by injection molding method

Energy Technology Data Exchange (ETDEWEB)

Yun, H W [Technical Centre of KIA-ASIA MOTORS (Korea, Republic of); Han, I S [Korea Institute of Energy Research, Tajeon (Korea, Republic of); Lim, Y S; Chung, Y J [Myong Ji University (Korea, Republic of)

1998-02-01

Valve lifter, namely tappet, is supported by lifter hole which is located upper side of camshaft in cylinder block, transforms rotatic movement of camshaft into linear movement and helps to open and shut the engine valve as an engine parts. The face of valve lifter, which is continuously contacting with camshaft, brings about abnormal wears, such as unfair wear and early wear, because it is severely loaded in the valve train system. These wears act as a defect like over-clearance and cause imperfect combustion of fuel during the valve lifting in the combustion chamber. Consequently, this imperfect combustion makes the engine out-put decrease and has cause on air pollution. To prevent these wears, therefore, the valve lifter cast in metal developed into SiC ceramics valve lifter which has an excellence in wear and impact resistance. As a result, the optimum process conditions like injection condition, mixture ratio and debonding process could be established. After sintering, fine-sinered dual microstructure in which prior {alpha}-SiC, carbon and silicon was obtained. Based on the new SiC({beta}-SiC) produced by reaction among the {alpha}-SiC, carbon and silicon was obtained. Based on the study, it is verified that mechanical properties of SiC valve lifter are excellent in Vickers hardness 1100{approx}1200 bending strength (300{approx}350 Pa), fracture toughness (1.5{approx}1.7 MPacentre dotm{sup 1/2}). Through engine dynamo testing, SiC valve lifter and metal valve lifter are examined and compared into abnormal phenomena such early fracture, unfair and early wear. It is hoped that this research will serve as an important springboard for the future study of heavy duty diesel engine parts developed by ceramics which has a good wear resistance, reliability, and lightability.

NRC Information No. 90-21: Potential failure of motor-operated butterfly valves to operate because valve seat friction was underestimated

International Nuclear Information System (INIS)

Rossi, C.E.

1992-01-01

In October 1988, at Catawba Nuclear Station Unit 1, a motor-operated butterfly valve in the service water system failed to open under high differential pressure conditions. The licensee concluded that the valve manufacturer, BIF/General Signal Corporation, had underestimated the degree to which the material used in the valve seat would harden with age (the responsibility for these valves has been transferred to Paul-Munroe Enertech). This underestimation of the age hardening had led the manufacturer to assume valve seat friction forces that were less than the actual friction forces in the installed valve. To overcome the larger-than-anticipated friction forces, the licensee's engineering staff recommended the open torque switch for 56 butterfly valves be reset to the maximum allowable value. The systems in which these valves are located include the component cooling water system, service water system, and various ventilation systems. By July 26, 1989, the torque switch adjustments were completed at Catawba Units 1 and 2. After reviewing the final settings, the licensee's engineering staff determined that the actuators for three butterfly valves in the component cooling water system might not be able to overcome the friction forces resulting from maximum seat hardening. On December 13, 1989, the licensee determined that the failure of these BIF/General Signal motor-operated valves (MOVs) could cause a loss of cooling water to residual heat removal system heat exchangers. To resolve the concern regarding the operability of these BIF/General Signal valves, a torque switch bypass was installed on two of the actuators to allow full motor capability during opening

Prognostic Implications of Raphe in Bicuspid Aortic Valve Anatomy.

Science.gov (United States)

Kong, William K F; Delgado, Victoria; Poh, Kian Keong; Regeer, Madelien V; Ng, Arnold C T; McCormack, Louise; Yeo, Tiong Cheng; Shanks, Miriam; Parent, Sarah; Enache, Roxana; Popescu, Bogdan A; Liang, Michael; Yip, James W; Ma, Lawrence C W; Kamperidis, Vasileios; van Rosendael, Philippe J; van der Velde, Enno T; Ajmone Marsan, Nina; Bax, Jeroen J

2017-03-01

Little is known about the association between bicuspid aortic valve (BAV) morphologic findings and the degree of valvular dysfunction, presence of aortopathy, and complications, including aortic valve surgery, aortic dissection, and all-cause mortality. To investigate the association between BAV morphologic findings (raphe vs nonraphe) and the degree of valve dysfunction, presence of aortopathy, and prognosis (including need for aortic valve surgery, aortic dissection, and all-cause mortality). In this large international multicenter registry of patients with BAV treated at tertiary referral centers, 2118 patients with BAV were evaluated. Patients referred for echocardiography from June 1, 1991, through November 31, 2015, were included in the study. Clinical and echocardiographic data were analyzed retrospectively. The morphologic BAV findings were categorized according to the Sievers and Schmidtke classification. Aortic valve function was divided into normal, regurgitation, or stenosis. Patterns of BAV aortopathy included the following: type 1, dilation of the ascending aorta and aortic root; type 2, isolated dilation of the ascending aorta; and type 3, isolated dilation of the sinus of Valsalva and/or sinotubular junction. Association between the presence and location of raphe and the risk of significant (moderate and severe) aortic valve dysfunction and aortic dilation and/or dissection. Of the 2118 patients (mean [SD] age, 47 [18] years; 1525 [72.0%] male), 1881 (88.8%) had BAV with fusion raphe, whereas 237 (11.2%) had BAV without raphe. Bicuspid aortic valves with raphe had a significantly higher prevalence of valve dysfunction, with a significantly higher frequency of aortic regurgitation (622 [33.1%] vs 57 [24.1%], P < .001) and aortic stenosis (728 [38.7%] vs 51 [21.5%], P < .001). Furthermore, aortic valve replacement event rates were significantly higher among patients with BAV with raphe (364 [19.9%] at 1 year, 393 [21.4%] at 2 years, and 447

A new approach to heart valve tissue engineering

DEFF Research Database (Denmark)

Kaasi, Andreas; Cestari, Idágene A.; Stolf, Noedir A G.

2011-01-01

The 'biomimetic' approach to tissue engineering usually involves the use of a bioreactor mimicking physiological parameters whilst supplying nutrients to the developing tissue. Here we present a new heart valve bioreactor, having as its centrepiece a ventricular assist device (VAD), which exposes...... chamber. Subsequently, applied vacuum to the pneumatic chamber causes the blood chamber to fill. A mechanical heart valve was placed in the VAD's inflow position. The tissue engineered (TE) valve was placed in the outflow position. The VAD was coupled in series with a Windkessel compliance chamber...

Control Valve

Energy Technology Data Exchange (ETDEWEB)

Moore, Wayne R.

2018-03-20

A control valve includes a first conduit having a first inlet and a first outlet and defining a first passage; a second conduit having a second inlet and a second outlet and defining a second passage, the second conduit extending into the first passage such that the second inlet is located within the first passage; and a valve plate disposed pivotably within the first passage, the valve plate defining a valve plate surface. Pivoting of the valve plate within the first passage varies flow from the first inlet to the first outlet and the valve plate is pivotal between a first position and a second position such that in the first position the valve plate substantially prevents fluid communication between the first passage and the second passage and such that in the second position the valve plate permits fluid communication between the first passage and the second passage.

Intermittent Fasting Modulation of the Diabetic Syndrome in Streptozotocin-Injected Rats

Directory of Open Access Journals (Sweden)

Louiza Belkacemi

2012-01-01

Full Text Available This study investigates the effects of intermittent overnight fasting in streptozotocin-induced diabetic rats (STZ rats. Over 30 days, groups of 5-6 control or STZ rats were allowed free food access, starved overnight, or exposed to a restricted food supply comparable to that ingested by the intermittently fasting animals. Intermittent fasting improved glucose tolerance, increased plasma insulin, and lowered Homeostatis Model Assessment index. Caloric restriction failed to cause such beneficial effects. The β-cell mass, as well as individual β-cell and islet area, was higher in intermittently fasting than in nonfasting STZ rats, whilst the percentage of apoptotic β-cells appeared lower in the former than latter STZ rats. In the calorie-restricted STZ rats, comparable findings were restricted to individual islet area and percentage of apoptotic cells. Hence, it is proposed that intermittent fasting could represent a possible approach to prevent or minimize disturbances of glucose homeostasis in human subjects.

Check valve diagnostics utilizing acoustic and magnetic technologies

International Nuclear Information System (INIS)

Agostinelli, A.

1991-01-01

The potential hazards associated with check valve failures make it necessary to detect check valve problems before they cause significant damage. In the nuclear industry, check valve failures are known to have resulted in damaging water hammer conditions, overpressurization of low pressure systems, steam binding of auxiliary feedwater pumps, and other serious component damage in power plant environments. Similar problems exist in fossil power and various process industries, but the resources dedicated to valve maintenance issues are greatly reduced. However, the trend toward plant life extension, predictive maintenance, and maximum operating efficiency will raise the general awareness of check valve maintenance in commercial (non-nuclear) applications. Although this paper includes specific references to the nuclear industry, the check valve problem conditions and diagnostic techniques apply across all power and process plant environments. The ability to accurately diagnose check valve conditions using non-intrusive, predictive maintenance testing methods allows for a more cost-efficient, productive maintenance program. One particular diagnostic system, called Quickcheck trademark, assists utilities in addressing these concerns. This article presents actual field test data and analysis that demonstrate the power of check valve diagnostics. Prior to presenting the field data, a brief overview of the system is overviewed

Aortic regurgitation after valve-sparing aortic root replacement: modes of failure.

Science.gov (United States)

Oka, Takanori; Okita, Yutaka; Matsumori, Masamichi; Okada, Kenji; Minami, Hitoshi; Munakata, Hiroshi; Inoue, Takeshi; Tanaka, Akiko; Sakamoto, Toshihito; Omura, Atsushi; Nomura, Takuo

2011-11-01

Despite the positive clinical results of valve-sparing aortic root replacement, little is known about the causes of reoperations and the modes of failure. From October 1999 to June 2010, 101 patients underwent valve-sparing aortic root replacement using the David reimplantation technique. The definition of aortic root repair failure included the following: (1) intraoperative conversion to the Bentall procedure; (2) reoperation performed because of aortic regurgitation; and (3) aortic regurgitation equal to or greater than a moderate degree at the follow-up. Sixteen patients were considered to have repair failure. Three patients required intraoperative conversion to valve replacement, 3 required reoperation within 3 months, and another 8 required reoperation during postoperative follow-up. At initial surgery 5 patients had moderate to severe aortic regurgitation, 6 patients had acute aortic dissections, 3 had Marfan syndrome, 2 had status post Ross operations, 3 had bicuspid aortic valves, and 1 had aortitis. Five patients had undergone cusp repair, including Arantius plication in 3 and plication at the commissure in 2. The causes of early failure in 6 patients included cusp perforation (3), cusp prolapse (3), and severe hemolysis (1). The causes of late failure in 10 patients included cusp prolapse (4), commissure dehiscence (3), torn cusp (2), and cusp retraction (1). Patients had valve replacements at a mean of 23 ± 20.9 months after reimplantation and survived. Causes of early failure after valve-sparing root replacement included technical failure, cusp lesions, and steep learning curve. Late failure was caused by aortic root wall degeneration due to gelatin-resorcin-formalin glue, cusp degeneration, or progression of cusp prolapse. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Intermittent degradation and schizotypy

Directory of Open Access Journals (Sweden)

Matthew W. Roché

2015-06-01

Full Text Available Intermittent degradation refers to transient detrimental disruptions in task performance. This phenomenon has been repeatedly observed in the performance data of patients with schizophrenia. Whether intermittent degradation is a feature of the liability for schizophrenia (i.e., schizotypy is an open question. Further, the specificity of intermittent degradation to schizotypy has yet to be investigated. To address these questions, 92 undergraduate participants completed a battery of self-report questionnaires assessing schizotypy and psychological state variables (e.g., anxiety, depression, and their reaction times were recorded as they did so. Intermittent degradation was defined as the number of times a subject’s reaction time for questionnaire items met or exceeded three standard deviations from his or her mean reaction time after controlling for each item’s information processing load. Intermittent degradation scores were correlated with questionnaire scores. Our results indicate that intermittent degradation is associated with total scores on measures of positive and disorganized schizotypy, but unrelated to total scores on measures of negative schizotypy and psychological state variables. Intermittent degradation is interpreted as potentially derivative of schizotypy and a candidate endophenotypic marker worthy of continued research.

Mitral Valve Disease

Science.gov (United States)

... for mitral valve replacement—mechanical valves (metal) or biological valves (tissue). The principal advantage of mechanical valves ... small risk of stroke due to blood clotting. Biological valves usually are made from animal tissue. Biological ...

Delayed-onset streptococcus pyogenes endophthalmitis following Ahmed glaucoma valve implantation.

Science.gov (United States)

Bayraktar, Zerrin; Kapran, Ziya; Bayraktar, Sükrü; Acar, Nur; Unver, Yaprak Banu; Gök, Kemran

2005-01-01

To report a case of delayed-onset Streptococcus pyogenes endophthalmitis following implantation of an Ahmed glaucoma valve. A 10-year-old patient presented with acute endophthalmitis 1 year after Ahmed glaucoma valve implantation. The conjunctiva and Tenon's capsule over the valve plate had been penetrated by one of the polypropylene fixation sutures. The valve was removed, and pars plana vitrectomy was performed. Vitreous specimens and removal of the discharge over the plate revealed Streptococcus pyogenes. This is the first documented case of Streptococcus pyogenes endophthalmitis following Ahmed glaucoma valve implantation. We think the conjunctival buttonhole caused by the polypropylene suture provided an entry site for the infection. (c) Japanese Ophthalmological Society 2005.

Valve thrombosis following transcatheter aortic valve implantation: a systematic review.

Science.gov (United States)

Córdoba-Soriano, Juan G; Puri, Rishi; Amat-Santos, Ignacio; Ribeiro, Henrique B; Abdul-Jawad Altisent, Omar; del Trigo, María; Paradis, Jean-Michel; Dumont, Eric; Urena, Marina; Rodés-Cabau, Josep

2015-03-01

Despite the rapid global uptake of transcatheter aortic valve implantation, valve trombosis has yet to be systematically evaluated in this field. The aim of this study was to determine the clinical characteristics, diagnostic criteria, and treatment outcomes of patients diagnosed with valve thrombosis following transcatheter aortic valve implantation through a systematic review of published data. Literature published between 2002 and 2012 on valve thrombosis as a complication of transcatheter aortic valve implantation was identified through a systematic electronic search. A total of 11 publications were identified, describing 16 patients (mean age, 80 [5] years, 65% men). All but 1 patient (94%) received a balloon-expandable valve. All patients received dual antiplatelet therapy immediately following the procedure and continued to take either mono- or dual antiplatelet therapy at the time of valve thrombosis diagnosis. Valve thrombosis was diagnosed at a median of 6 months post-procedure, with progressive dyspnea being the most common symptom. A significant increase in transvalvular gradient (from 10 [4] to 40 [12] mmHg) was the most common echocardiographic feature, in addition to leaflet thickening. Thrombus was not directly visualized with echocardiography. Three patients underwent valve explantation, and the remaining received warfarin, which effectively restored the mean transvalvular gradient to baseline within 2 months. Systemic embolism was not a feature of valve thrombosis post-transcatheter aortic valve implantation. Although a rare, yet likely under-reported complication of post-transcatheter aortic valve implantation, progressive dyspnea coupled with an increasing transvalvular gradient on echocardiography within the months following the intervention likely signifies valve thrombosis. While direct thrombus visualization appears difficult, prompt initiation of oral anticoagulation therapy effectively restores baseline valve function. Copyright © 2014

[Reoperative valve replacement in patients undergoing cardiac reoperation: a report of 104 cases].

Science.gov (United States)

Zou, Liang-jian; Xu, Zhi-yun; Wang, Zhi-nong; Lang, Xi-long; Han, Lin; Lu, Fang-lin; Xu, Ji-bin; Tang, Hao; Ji, Guang-yu; Wang, Er-song; Wang, Jun; Qu, Yi

2010-08-15

To review the experience of reoperative valve replacement for 104 patients. From January 2002 to December 2009, 104 patients underwent heart valve replacement in reoperations, accounting for 2.92% of the total patient population (3557 cases) who had valve replacement during this period. In this group, 53 male and 51 female patients were included with a median age of 46 years (ranged from 13 to 72 years). The reasons of reoperation included 28 cases suffered from another valve lesion after valve replacement, 10 cases suffered from valve lesion after mitral valvuloplasty, 19 cases suffered from perivalvular leakage after valve replacement, 18 cases suffered from valve lesion after previous correction of congenital heart defect, 7 cases suffered from bioprosthetic valve decline, 10 cases suffered from prosthetic valve endocarditis, 9 cases suffered from dysfunction of machine valve, and 3 cases suffered from other causes. The re-operations were mitral and aortic valve replacement in 2 cases, mitral valve replacement in 59 cases, aortic valve replacement in 24 cases, tricuspid valve replacement in 16 cases, and Bentall's operation in 3 cases. The interval from first operation to next operation was 1 month-19 years. There were 8 early deaths from heart failure, renal failure and multiple organ failure (early mortality 7.69%). Major complications were intraoperative hemorrhage in 2 cases, re-exploration for mediastinal bleeding in 2 cases and sternotomy surgical site infection in 1 case. Complete follow-up (3 months-7 years and 2 months) was available for all patients. Two patients died, one patient died of intracranial hemorrhage, and another cause was unknown. Satisfactory short-term and long-term results can be obtained in reoperative valve replacement with appropriate timing of operation control, satisfactory myocardial protection, accurate surgical procedure and suitable perioperative treatment.

Overview of Prevention for Water Hammer by Check Valve Action in Nuclear Reactor

International Nuclear Information System (INIS)

Kim, Dayong; Yoon, Hyungi; Seo, Kyoungwoo; Kim, Seonhoon

2016-01-01

Water hammer can cause serious damage to pumping system and unexpected system pressure rise in the pipeline. In nuclear reactor, water hammer can influence on the integrity of safety related system. Water hammer in nuclear reactor have been caused by voiding in normally water-filled lines, steam condensation line containing both steam and water, as well as by rapid check valve action. Therefore, this study focuses on the water hammer by check valve among the sources of water hammer occurrence and suggests proper methodology for check valve type selection against water hammer. This study focuses on the water hammer by check valve action among the sources of water hammer occurrence and suggests proper methodology for check valve type selection against water hammer. If the inadvertent pump trip or pipe rupture in high velocity and pressure pipe is predicted, the fast response check valve such as tiled disc, dual disc and nozzle check valve should be installed in the system. If the inadvertent pump trip or pipe rupture in very high velocity and pressure pipe and excessively large revered flow velocity are predicted, the very slowly closing check valve such as controlled closure check valve should be installed in the system

Overview of Prevention for Water Hammer by Check Valve Action in Nuclear Reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, Dayong; Yoon, Hyungi; Seo, Kyoungwoo; Kim, Seonhoon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Water hammer can cause serious damage to pumping system and unexpected system pressure rise in the pipeline. In nuclear reactor, water hammer can influence on the integrity of safety related system. Water hammer in nuclear reactor have been caused by voiding in normally water-filled lines, steam condensation line containing both steam and water, as well as by rapid check valve action. Therefore, this study focuses on the water hammer by check valve among the sources of water hammer occurrence and suggests proper methodology for check valve type selection against water hammer. This study focuses on the water hammer by check valve action among the sources of water hammer occurrence and suggests proper methodology for check valve type selection against water hammer. If the inadvertent pump trip or pipe rupture in high velocity and pressure pipe is predicted, the fast response check valve such as tiled disc, dual disc and nozzle check valve should be installed in the system. If the inadvertent pump trip or pipe rupture in very high velocity and pressure pipe and excessively large revered flow velocity are predicted, the very slowly closing check valve such as controlled closure check valve should be installed in the system.

Swirling flow in bileaflet mechanical heart valve

Science.gov (United States)

Gataulin, Yakov A.; Khorobrov, Svyatoslav V.; Yukhnev, Andrey D.

2018-05-01

Bileaflet mechanical valves are most commonly used for heart valve replacement. Nowadays swirling blood flow is registered in different parts of the cardiovascular system: left ventricle, aorta, arteries and veins. In present contribution for the first time the physiological swirling flow inlet conditions are used for numerical simulation of aortic bileaflet mechanical heart valve hemodynamics. Steady 3-dimensional continuity and RANS equations are employed to describe blood motion. The Menter SST model is used to simulate turbulence effects. Boundary conditions are corresponded to systolic peak flow. The domain was discretized into hybrid tetrahedral and hexahedral mesh with an emphasis on wall boundary layer. A system of equations was solved in Ansys Fluent finite-volume package. Noticeable changes in the flow structure caused by inlet swirl are shown. The swirling flow interaction with the valve leaflets is analyzed. A central orifice jet changes its cross-section shape, which leads to redistribution of wall shear stress on the leaflets. Transvalvular pressure gradient and area-averaged leaflet wall shear stress increase. Physiological swirl intensity noticeably reduces downstream of the valve.

Turbulence downstream of subcoronary stentless and stented aortic valves.

Science.gov (United States)

Funder, Jonas Amstrup; Frost, Markus Winther; Wierup, Per; Klaaborg, Kaj-Erik; Hjortdal, Vibeke; Nygaard, Hans; Hasenkam, J Michael

2011-08-11

Regions of turbulence downstream of bioprosthetic heart valves may cause damage to blood components, vessel wall as well as to aortic valve leaflets. Stentless aortic heart valves are known to posses several hemodynamic benefits such as larger effective orifice areas, lower aortic transvalvular pressure difference and faster left ventricular mass regression compared with their stented counterpart. Whether this is reflected by diminished turbulence formation, remains to be shown. We implanted either stented pericardial valve prostheses (Mitroflow), stentless valve prostheses (Solo or Toronto SPV) in pigs or they preserved their native valves. Following surgery, blood velocity was measured in the cross sectional area downstream of the valves using 10MHz ultrasonic probes connected to a dedicated pulsed Doppler equipment. As a measure of turbulence, Reynolds normal stress (RNS) was calculated at two different blood pressures (baseline and 50% increase). We found no difference in maximum RNS measurements between any of the investigated valve groups. The native valve had significantly lower mean RNS values than the Mitroflow (p=0.004), Toronto SPV (p=0.008) and Solo valve (p=0.02). There were no statistically significant differences between the artificial valve groups (p=0.3). The mean RNS was significantly larger when increasing blood pressure (p=0.0006). We, thus, found no advantages for the stentless aortic valves compared with stented prosthesis in terms of lower maximum or mean RNS values. Native valves have a significantly lower mean RNS value than all investigated bioprostheses. Copyright © 2011 Elsevier Ltd. All rights reserved.

David valve-sparing aortic root replacement: equivalent mid-term outcome for different valve types with or without connective tissue disorder.

Science.gov (United States)

Kvitting, John-Peder Escobar; Kari, Fabian A; Fischbein, Michael P; Liang, David H; Beraud, Anne-Sophie; Stephens, Elizabeth H; Mitchell, R Scott; Miller, D Craig

2013-01-01

Although implicitly accepted by many that the durability of valve-sparing aortic root replacement in patients with bicuspid aortic valve disease and connective tissue disorders will be inferior, this hypothesis has not been rigorously investigated. From 1993 to 2009, 233 patients (27% bicuspid aortic valve, 40% Marfan syndrome) underwent Tirone David valve-sparing aortic root replacement. Follow-up averaged 4.7 ± 3.3 years (1102 patient-years). Freedom from adverse outcomes was determined using log-rank calculations. Survival at 5 and 10 years was 98.7% ± 0.7% and 93.5% ± 5.1%, respectively. Freedom from reoperation (all causes) on the aortic root was 92.2% ± 3.6% at 10 years; 3 reoperations were aortic valve replacement owing to structural valve deterioration. Freedom from structural valve deterioration at 10 years was 96.1% ± 2.1%. No significant differences were found in survival (P = .805, P = .793, respectively), reoperation (P = .179, P = .973, respectively), structural valve deterioration (P = .639, P = .982, respectively), or any other functional or clinical endpoints when patients were stratified by valve type (tricuspid aortic valve vs bicuspid aortic valve) or associated connective tissue disorder. At the latest echocardiographic follow-up (95% complete), 202 patients (94.8%) had none or trace aortic regurgitation, 10 (4.7%) mild, 0 had moderate to severe, and 1 (0.5%) had severe aortic regurgitation. Freedom from greater than 2+ aortic regurgitation at 10 years was 95.3% ± 2.5%. Six patients sustained acute type B aortic dissection (freedom at 10 years, 90.4% ± 5.0%). Tirone David reimplantation valve-sparing aortic root replacement in carefully selected young patients was associated with excellent clinical and echocardiographic outcome in patients with either a tricuspid aortic valve or bicuspid aortic valve. No demonstrable adverse influence was found for Marfan syndrome or connective tissue disorder on durability, clinical outcome

Tight valve

International Nuclear Information System (INIS)

Guedj, F.

1987-01-01

This sealed valve is made with a valve seat, an axial valve with a rod fixed to its upper end, a thick bell surrounding the rod and welded by a thin join on the valve casing, a threated ring screwed onto the upper end of the rod and a magnet or electromagnet rotating the ring outside the bell [fr

Pulmonary valve endocarditis associated to a septal interventricular defect and infundibular and pulmonary valve Stenosis

International Nuclear Information System (INIS)

Echeverri, Juan G; Diaz, Alejandro; Jaramillo, Nicolas; Gonzalez, Sergio

2004-01-01

Ventricular septal defects generate 10% of all adult congenital cardiopathies. 4% to 8% of patients to whom the defect has not been corrected are in risk of developing endocarditis. Pulmonary valve endocarditis is a rare event (1.5% to 2% of all endocarditis cases) and its mean etiology is intravenous drug abuse. The most frequently isolated microorganism in these cases is staphylococcus aurous. We report a case of pulmonary valve endocarditis associated with ventricular septal defect and valvular and infundibular pulmonary stenosis caused by streptococcus sp. in a patient without past medical history of drug abuse, alcoholism or previous invasive procedures

Diaphragms in air-operated valves

Energy Technology Data Exchange (ETDEWEB)

Groeger, J.E.

1996-12-01

The author will present current issues related to diaphgrams in air-operated valves. Altran Materials Engineering, Inc., often performs root-cause analyses for nuclear power plant owners. The author will discuss various analyses that have been performed or are currently underway.

Application of risk-based methods to inservice testing of check valves

Energy Technology Data Exchange (ETDEWEB)

Closky, N.B.; Balkey, K.R.; McAllister, W.J. [and others

1996-12-01

Research efforts have been underway in the American Society of Mechanical Engineers (ASME) and industry to define appropriate methods for the application of risk-based technology in the development of inservice testing (IST) programs for pumps and valves in nuclear steam supply systems. This paper discusses a pilot application of these methods to the inservice testing of check valves in the emergency core cooling system of Georgia Power`s Vogtle nuclear power station. The results of the probabilistic safety assessment (PSA) are used to divide the check valves into risk-significant and less-risk-significant groups. This information is reviewed by a plant expert panel along with the consideration of appropriate deterministic insights to finally categorize the check valves into more safety-significant and less safety-significant component groups. All of the more safety-significant check valves are further evaluated in detail using a failure modes and causes analysis (FMCA) to assist in defining effective IST strategies. A template has been designed to evaluate how effective current and emerging tests for check valves are in detecting failures or in finding significant conditions that are precursors to failure for the likely failure causes. This information is then used to design and evaluate appropriate IST strategies that consider both the test method and frequency. A few of the less safety-significant check valves are also evaluated using this process since differences exist in check valve design, function, and operating conditions. Appropriate test strategies are selected for each check valve that has been evaluated based on safety and cost considerations. Test strategies are inferred from this information for the other check valves based on similar check valve conditions. Sensitivity studies are performed using the PSA model to arrive at an overall IST program that maintains or enhances safety at the lowest achievable cost.

Experimental apparatus to test air trap valves

Science.gov (United States)

Lemos De Lucca, Y. de F.; de Aquino, G. A.; Filho, J. G. D.

2010-08-01

It is known that the presence of trapped air within water distribution pipes can lead to irregular operation or even damage to the distribution systems and their components. The presence of trapped air may occur while the pipes are being filled with water, or while the pumping systems are in operation. The formation of large air pockets can produce the water hammer phenomenon, the instability and the loss of pressure in the water distribution networks. As a result, it can overload the pumps, increase the consumption of electricity, and damage the pumping system. In order to avoid its formation, all of the trapped air should be removed through "air trap valves". In Brazil, manufacturers frequently have unreliable sizing charts, which cause malfunctioning of the "air trap valves". The result of these malfunctions causes accidents of substantial damage. The construction of a test facility will provide a foundation of technical information that will be used to help make decisions when designing a system of pipelines where "air trap valves" are used. To achieve this, all of the valve characteristics (geometric, mechanic, hydraulic and dynamic) should be determined. This paper aims to describe and analyze the experimental apparatus and test procedure to be used to test "air trap valves". The experimental apparatus and test facility will be located at the University of Campinas, Brazil at the College of Civil Engineering, Architecture, and Urbanism in the Hydraulics and Fluid Mechanics laboratory. The experimental apparatus will be comprised of various components (pumps, steel pipes, butterfly valves to control the discharge, flow meter and reservoirs) and instrumentation (pressure transducers, anemometer and proximity sensor). It should be emphasized that all theoretical and experimental procedures should be defined while taking into consideration flow parameters and fluid properties that influence the tests.

Experimental apparatus to test air trap valves

Energy Technology Data Exchange (ETDEWEB)

Lemos De Lucca, Y de F [CTH-DAEE-USP/FAAP/UNICAMP (Brazil); Aquino, G A de [SABESP/UNICAMP (Brazil); Filho, J G D, E-mail: yvone.lucca@gmail.co [Water Resources Department, University of Campinas-UNICAMP, Av. Albert Einstein, 951, Cidade Universitaria-Barao Geraldo-Campinas, S.P., 13083-852 (Brazil)

2010-08-15

It is known that the presence of trapped air within water distribution pipes can lead to irregular operation or even damage to the distribution systems and their components. The presence of trapped air may occur while the pipes are being filled with water, or while the pumping systems are in operation. The formation of large air pockets can produce the water hammer phenomenon, the instability and the loss of pressure in the water distribution networks. As a result, it can overload the pumps, increase the consumption of electricity, and damage the pumping system. In order to avoid its formation, all of the trapped air should be removed through 'air trap valves'. In Brazil, manufacturers frequently have unreliable sizing charts, which cause malfunctioning of the 'air trap valves'. The result of these malfunctions causes accidents of substantial damage. The construction of a test facility will provide a foundation of technical information that will be used to help make decisions when designing a system of pipelines where 'air trap valves' are used. To achieve this, all of the valve characteristics (geometric, mechanic, hydraulic and dynamic) should be determined. This paper aims to describe and analyze the experimental apparatus and test procedure to be used to test 'air trap valves'. The experimental apparatus and test facility will be located at the University of Campinas, Brazil at the College of Civil Engineering, Architecture, and Urbanism in the Hydraulics and Fluid Mechanics laboratory. The experimental apparatus will be comprised of various components (pumps, steel pipes, butterfly valves to control the discharge, flow meter and reservoirs) and instrumentation (pressure transducers, anemometer and proximity sensor). It should be emphasized that all theoretical and experimental procedures should be defined while taking into consideration flow parameters and fluid properties that influence the tests.

Aortic valve bypass

DEFF Research Database (Denmark)

Lund, Jens T; Jensen, Maiken Brit; Arendrup, Henrik

2013-01-01

In aortic valve bypass (AVB) a valve-containing conduit is connecting the apex of the left ventricle to the descending aorta. Candidates are patients with symptomatic aortic valve stenosis rejected for conventional aortic valve replacement (AVR) or transcatheter aortic valve implantation (TAVI). ...

The JUPITER registry: 1-year results of transapical aortic valve implantation using a second-generation transcatheter heart valve in patients with aortic stenosis.

Science.gov (United States)

Silaschi, Miriam; Treede, Hendrik; Rastan, Ardawan J; Baumbach, Hardy; Beyersdorf, Friedhelm; Kappert, Utz; Eichinger, Walter; Rüter, Florian; de Kroon, Thomas L; Lange, Rüdiger; Ensminger, Stephan; Wendler, Olaf

2016-11-01

Transcatheter aortic valve replacement (TAVR) is an established therapy for patients with aortic stenosis (AS) at high surgical risk. The JenaValve™ is a second-generation, self-expanding transcatheter heart valve (THV), implanted through transapical access (TA). During stent deployment, a specific 'clipping-mechanism' engages native aortic valve cusps for fixation. We present 1-year outcomes of the JUPITER registry, a post-market registry of the JenaValve for TA-TAVR. The JUPITER registry is a prospective, multicentre, uncontrolled and observational European study to evaluate the long-term safety and effectiveness of the Conformité Européenne-marked JenaValve THV. A total of 180 patients with AS were enrolled between 2012 and 2014. End-points were adjudicated in accordance with the valve academic research consortium document no. 1 definitions. The mean age was 80.4 ± 5.9 years and the mean logistic European system for cardiac operative risk evaluation I 21.2 ± 14.7%. The procedure was successful in 95.0% (171/180), implantation of a second THV (valve-in-valve) was performed in 2.2% (4/180) and conversion to surgical aortic valve replacement (SAVR) was necessary in 2.8% (5/180). No annular rupture or coronary ostia obstruction occurred. Two patients required SAVR after the day of index procedure (1.1%). All-cause mortality at 30 days was 11.1% (20/180), being cardiovascular in 7.2% (13/180). A major stroke occurred in 1.1% (2/180) at 30 days, no additional major strokes were observed during 1 year. All-cause mortality after 30 days was 13.1% (21/160) and combined efficacy at 1 year was 80.8% (122/151). At 1-year follow-up, no patient presented with more than moderate paravalvular leakage, while 2 patients (3.2%) showed moderate, 12 (19.0%) mild and 49 (82.4%) trace/none paravalvular regurgitation. In a high-risk cohort of patients undergoing TA-TAVR for AS, the use of the JenaValve THV is safe and effective. In patients at higher risk for coronary ostia

Intermittent Aeration Suppresses Nitrite-Oxidizing Bacteria in Membrane-Aerated Biofilms: A Model-Based Explanation

DEFF Research Database (Denmark)

Ma, Yunjie; Domingo Felez, Carlos; Plósz, Benedek G.

2017-01-01

. On the basis of dissolved oxygen (DO), ammonium, nitrite, and nitrate profiles within the biofilm and in the bulk, a 1-dimensional nitrifying biofilm model was developed and calibrated. The model was utilized to explore the potential mechanisms of NOB suppression associated with intermittent aeration...... nitritation, strategies to suppress nitrite-oxidizing bacteria (NOB) are needed, which are ideally grounded on an understanding of underlying mechanisms. In this study, a nitrifying MABR was operated under intermittent aeration. During eight months of operation, AOB dominated, while NOB were suppressed...... during intermittent aeration was mostly explained by periodic inhibition caused by free ammonia due to periodic transient pH upshifts. Dissolved oxygen limitation did not govern NOB suppression. Different intermittent aeration strategies were then evaluated for nitritation success in intermittently...

An intermittency route to global instability in low-density jets

Science.gov (United States)

Murugesan, Meenatchidevi; Zhu, Yuanhang; Li, Larry K. B.

2017-11-01

Above a critical Reynolds number (Re), a low-density jet can become globally unstable, transitioning from a steady state (i.e. a fixed point) to a self-excited oscillatory state (i.e. a limit cycle) via a Hopf bifurcation. In this experimental study, we show that this transition can sometimes involve intermittency. When Re is just slightly above the critical point, intermittent bursts of high-amplitude periodic oscillations emerge amidst a background of low-amplitude aperiodic fluctuations. As Re increases further, these intermittent bursts persist longer in time until they dominate the overall dynamics, causing the jet to transition fully to a periodic limit cycle. We identify this as Type-II Pomeau-Manneville intermittency by quantifying the statistical distribution of the duration of the aperiodic fluctuations at the onset of intermittency. This study shows that the transition to global instability in low-density jets is not always abrupt but can involve an intermediate state with characteristics of both the initial fixed point and the final limit cycle. This work was supported by the Research Grants Council of Hong Kong (Project No. 16235716 and 26202815).

Developing an optimal valve closing rule curve for real-time pressure control in pipes

Energy Technology Data Exchange (ETDEWEB)

Bazarganlari, Mohammad Reza; Afshar, Hossein [Islamic Azad University, Tehran (Iran, Islamic Republic of); Kerachian, Reza [University of Tehran, Tehran (Iran, Islamic Republic of); Bashiazghadi, Seyyed Nasser [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

2013-01-15

Sudden valve closure in pipeline systems can cause high pressures that may lead to serious damages. Using an optimal valve closing rule can play an important role in managing extreme pressures in sudden valve closure. In this paper, an optimal closing rule curve is developed using a multi-objective optimization model and Bayesian networks (BNs) for controlling water pressure in valve closure instead of traditional step functions or single linear functions. The method of characteristics is used to simulate transient flow caused by valve closure. Non-dominated sorting genetic algorithms-II is also used to develop a Pareto front among three objectives related to maximum and minimum water pressures, and the amount of water passes through the valve during the valve-closing process. Simulation and optimization processes are usually time-consuming, thus results of the optimization model are used for training the BN. The trained BN is capable of determining optimal real-time closing rules without running costly simulation and optimization models. To demonstrate its efficiency, the proposed methodology is applied to a reservoir-pipe-valve system and the optimal closing rule curve is calculated for the valve. The results of the linear and BN-based valve closure rules show that the latter can significantly reduce the range of variations in water hammer pressures.

Rapid repair advisor for motor-operated valves

International Nuclear Information System (INIS)

Somsel, J.K.

1991-01-01

This paper reports on the initial proposed application for the Rapid Repair Advisor project for motor-operated valves (MOVs). The expected benefits from an MOV testing expert system depend on the purpose of the testing. Straight acceptance testing (post-maintenance and surveillance) could benefit from field verification of test validity. Troubleshooting of failed operators is seldom difficult. Intermittent problems are difficult to resolve suggesting that trace recording capabilities are needed. Predictive diagnosis places the most demands on the interpretive skills of the engineer. However, the limit to predictive capabilities seems to lie in the design of the MOV and the measurable parameters. Utilities are expected to require a knowledgeable MOV maintenance engineer to make decisions on MOV maintenance and operability. The economics of developing an expert system are comparable to improved training for the end-users

Experimental investigation of the check valve behaviour when the flow is reversing

Directory of Open Access Journals (Sweden)

Himr D.

2017-01-01

Full Text Available Check valve in a pipeline is supposed to prevent the reverse flow and to allow the flow in the positive direction. The construction of check valves follows these requirements, but the check valve must not cause pressure pulsations in transients. It means when the fluid is accelerating or decelerating. The article describes an experimental investigation of a swing check valve when the flow is changing its direction. The check valve was placed in an experimental circuit, where the pressure on the upstream and downstream side of the valve was measured and the current value of flow rate was determined. The goal was to simulate conditions in the real system, where the check valve slam had been observed.

Transcatheter aortic valve implantation in failed bioprosthetic surgical valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John G; Bleiziffer, Sabine

2014-01-01

for patients with structural valve deterioration; however, a comprehensive evaluation of survival after the procedure has not yet been performed. OBJECTIVE: To determine the survival of patients after transcatheter valve-in-valve implantation inside failed surgical bioprosthetic valves. DESIGN, SETTING......, stroke, and New York Heart Association functional class. RESULTS: Modes of bioprosthesis failure were stenosis (n = 181 [39.4%]), regurgitation (n = 139 [30.3%]), and combined (n = 139 [30.3%]). The stenosis group had a higher percentage of small valves (37% vs 20.9% and 26.6% in the regurgitation...... and combined groups, respectively; P = .005). Within 1 month following valve-in-valve implantation, 35 (7.6%) patients died, 8 (1.7%) had major stroke, and 313 (92.6%) of surviving patients had good functional status (New York Heart Association class I/II). The overall 1-year Kaplan-Meier survival rate was 83...

[Pannus Formation Two Years after Bioprosthetic Aortic Valve Implantation;Report of a Case].

Science.gov (United States)

Ono, Kimiyo; Kuroda, Hiroaki

2015-08-01

We report a case of early deterioration of the bioprosthetic aortic valve 23 months postoperatively. A 77-year-old man who had undergone aortic valve replacement with a 23-mm Epic valve( St. Jude Medical [SJM])presented to us after a syncopal episode. Echocardiography revealed severe aortic stenosis, and redo aortic valve replacement with a 21-mm SJM mechanical valve was performed. All 3 cusps of the tissue valve were thickened by fibrous pannus overgrowth. Neither calcification nor invasion of inflammatory cells was observed. The cause of pannus formation at such an early stage after implantation remains unknown.

Effect of permanent pacemaker on mortality after transcatheter aortic valve replacement

DEFF Research Database (Denmark)

Engborg, Jonathan; Riechel-Sarup, Casper; Gerke, Oke

2017-01-01

OBJECTIVES: Transcatheter aortic valve implantation (TAVI) is an established treatment for high-grade aortic valve stenosis in patients found unfit for open heart surgery. The method may cause cardiac conduction disorders requiring permanent pacemaker (PPM) implantation, and the long-term effect...

Transcatheter aortic-valve replacement with a self-expanding prosthesis.

Science.gov (United States)

Adams, David H; Popma, Jeffrey J; Reardon, Michael J; Yakubov, Steven J; Coselli, Joseph S; Deeb, G Michael; Gleason, Thomas G; Buchbinder, Maurice; Hermiller, James; Kleiman, Neal S; Chetcuti, Stan; Heiser, John; Merhi, William; Zorn, George; Tadros, Peter; Robinson, Newell; Petrossian, George; Hughes, G Chad; Harrison, J Kevin; Conte, John; Maini, Brijeshwar; Mumtaz, Mubashir; Chenoweth, Sharla; Oh, Jae K

2014-05-08

We compared transcatheter aortic-valve replacement (TAVR), using a self-expanding transcatheter aortic-valve bioprosthesis, with surgical aortic-valve replacement in patients with severe aortic stenosis and an increased risk of death during surgery. We recruited patients with severe aortic stenosis who were at increased surgical risk as determined by the heart team at each study center. Risk assessment included the Society of Thoracic Surgeons Predictor Risk of Mortality estimate and consideration of other key risk factors. Eligible patients were randomly assigned in a 1:1 ratio to TAVR with the self-expanding transcatheter valve (TAVR group) or to surgical aortic-valve replacement (surgical group). The primary end point was the rate of death from any cause at 1 year, evaluated with the use of both noninferiority and superiority testing. A total of 795 patients underwent randomization at 45 centers in the United States. In the as-treated analysis, the rate of death from any cause at 1 year was significantly lower in the TAVR group than in the surgical group (14.2% vs. 19.1%), with an absolute reduction in risk of 4.9 percentage points (upper boundary of the 95% confidence interval, -0.4; P<0.001 for noninferiority; P = 0.04 for superiority). The results were similar in the intention-to-treat analysis. In a hierarchical testing procedure, TAVR was noninferior with respect to echocardiographic indexes of valve stenosis, functional status, and quality of life. Exploratory analyses suggested a reduction in the rate of major adverse cardiovascular and cerebrovascular events and no increase in the risk of stroke. In patients with severe aortic stenosis who are at increased surgical risk, TAVR with a self-expanding transcatheter aortic-valve bioprosthesis was associated with a significantly higher rate of survival at 1 year than surgical aortic-valve replacement. (Funded by Medtronic; U.S. CoreValve High Risk Study ClinicalTrials.gov number, NCT01240902.).

Multidetector computed tomography sizing of bioprosthetic valves: guidelines for measurement and implications for valve-in-valve therapies

International Nuclear Information System (INIS)

Rajani, R.; Attia, R.; Condemi, F.; Webb, J.; Woodburn, P.; Hodson, D.; Nair, A.; Preston, R.; Razavi, R.; Bapat, V.N.

2016-01-01

Aim: To describe a technique for bioprosthetic multidetector computed tomography (MDCT) sizing and to compare MDCT-derived values against manufacturer-provided sizing. Materials and methods: Fourteen bioprosthetic stented valves commonly used in the aortic valve position were evaluated using a Philips 256 MDCT system. All valves were scanned using a dedicated cardiac CT protocol with a four-channel electrocardiography (ECG) simulator. Measurements were made of major and minor axes and the area and perimeter of the internal stent using varying reconstruction kernels and window settings. Measurements derived from MDCT (MDCT ID) were compared against the stent internal diameter (Stent ID) as provided by the valve manufacturer and the True ID (Stent ID + insertion of leaflets). All data were collected and analysed using SPSS for Mac (version 21). Results: The mean difference between the MDCT ID and Stent ID was 0.6±1.9 mm (r=0.649, p=0.012) and between MDCT ID and True ID 2.1±2 mm (r=0.71, p=0.005). There was no difference in the major (p=0.90), minor (p=0.87), area (p=0.92), or perimeter (p=0.92) measurements when sharp, standard, and detailed stent kernels were used. Similarly, the measurements remained consistent across differing windowing levels. Conclusion: Bioprosthetic stented valves may be reliably sized using MDCT in patients requiring valve-in-valve (VIV) interventions where the valve type and size are unknown. In these cases, clinicians should be aware that MDCT has a tendency to overestimate the True ID size. - Highlights: • Cardiac CT is likely to be ideally suited for bioprosthetic aortic valve sizing for valve in valve procedures. • We compared MDCT sizing for 14 varying bioprosthetic aortic valves across varying window settings and reconstruction kernels. • We provide “normal” MDCT sizing for varying valves and show their relationship to surgical sizing. • Bioprosthetic valves may be reliably sized by MDCT but require adjustment owing to

Swing check valve

International Nuclear Information System (INIS)

Eminger, H.E.

1977-01-01

A swing check valve which includes a valve body having an inlet and outlet is described. A recess in the valve body designed to hold a seal ring and a check valve disc swingable between open and closed positions. The disc is supported by a high strength wire secured at one end in a support spacer pinned through bearing blocks fixed to the valve body and at its other end in a groove formed on the outer peripheral surface of the disc. The parts are designed and chosen such to provide a lightweight valve disc which is held open by minimum velocity of fluid flowing through the valve which thus reduces oscillations and accompanying wear of bearings supporting the valve operating parts. (Auth.)

FEATURES OF CONTROLLING ELECTROPNEUMATIC VALVES OF ACTUATOR TO CONTROL ITS CLUTCH WITH ACCELERATION VALVE

Directory of Open Access Journals (Sweden)

O. A. Yaryta

2018-01-01

Full Text Available The article deals with one of the ways to control an actuator of the automated clutch control system. The aim is to design control of the electropneumatic actuator, to control its coupling with the acceleration valve on the basis of experimental research as well as to provide rational parameters of the automated clutch control system for the robotic transmission. The feature of the system is an acceleration valve in the design of the electropneumatic actuator to control the clutch. New links demand to adjust the way to control the actuator. The connection of Pulse-Width Modulation (PWM with single power supply pulses to control electropneumatic valves is substantiated. The quantitative characteristics of single control pulses and PWM ones are determined. The error of operation accuracy for various ways of the control of the electropneumatic actuator to control the clutch of the robotic transmission is determined. Obtained separate PWM area is designed to suppress the initial hysteresis when the rod of the clutch actuator is moved. An algorithm for the operation of a clutch control system is proposed, taking into account the use of two modes of operation of solenoid valves. A graphical interpretation of the clutch control algorithm is presented, which gives an idea of the location of the constant signal feeding zones to the solenoid valve, as well as the operation areas of the solenoid valve in PWM mode. The control algorithm of the clutch booster provides a mode of guaranteed absence of excess pressure in the pneumatic cylinder after releasing the clutch pedal, provided that two normally closed solenoid valves are used. This configuration of the electro-pneumatic clutch control system allows the use of an emergency clutch release system in case of voltage absence. The reference algorithm for filtering the array of data coming from the feedback sensor, as well as the numerical values of the delay caused by the presence of a filter, are given.

Platypnea-Orthodeoxia Syndrome after Transcatheter Aortic Valve Implantation

Directory of Open Access Journals (Sweden)

Andrew K. Roy

2016-01-01

Full Text Available Progressive dyspnea and hypoxaemia in the subacute phase after transcatheter aortic valve implantation (TAVI are uncommon and warrant immediate assessment of valve and prosthesis leaflet function to exclude thrombosis, as well as investigation for other causes related to the procedure, such as left ventricular dysfunction, pulmonary embolism, and respiratory sepsis. In this case, we report the observation of a patient presenting two weeks after TAVI with arterial hypoxaemia in an upright position, relieved by lying flat, and coupled with an intracardiac shunt detected on echocardiography in the absence of pulmonary hypertension, raising the suspicion of Platypnea-Orthodeoxia Syndrome (POS. Invasive intracardiac haemodynamic assessment showed a significant right-to-left shunt (Qp/Qs = 0.74, which confirmed the diagnosis, with subsequent closure of the intracardiac defect resulting in immediate relief of symptoms and hypoxaemia. To our knowledge, this is the first reported case of an interatrial defect and shunt causing Platypnea-Orthodeoxia Syndrome after transcatheter aortic valve implantation, resolved by percutaneous device closure.

Light water reactor pressure isolation valve performance testing

International Nuclear Information System (INIS)

Neely, H.H.; Jeanmougin, N.M.; Corugedo, J.J.

1990-07-01

The Light Water Reactor Valve Performance Testing Program was initiated by the NRC to evaluate leakage as an indication of valve condition, provide input to Section XI of the ASME Code, evaluate emission monitoring for condition and degradation and in-service inspection techniques. Six typical check and gate valves were purchased for testing at typical plant conditions (550F at 2250 psig) for an assumed number of cycles for a 40-year plant lifetime. Tests revealed that there were variances between the test results and the present statement of the Code; however, the testing was not conclusive. The life cycle tests showed that high tech acoustic emission can be utilized to trend small leaks, that specific motor signature measurement on gate valves can trend and indicate potential failure, and that in-service inspection techniques for check valves was shown to be both feasible and an excellent preventive maintenance indicator. Life cycle testing performed here did not cause large valve leakage typical of some plant operation. Other testing is required to fully understand the implication of these results and the required program to fully implement them. (author)

Outlet strut fracture of Björk-Shiley convexo-concave valves: can valve-manufacturing characteristics explain the risk?

Science.gov (United States)

Omar, R Z; Morton, L S; Beirne, M; Blot, W J; Lawford, P V; Hose, R; Taylor, K M

2001-06-01

Björk-Shiley 60 degrees convexo-concave prosthetic heart valves (Shiley, Inc, Irvine, Calif, a subsidiary of Pfizer, Inc) continue to be a concern for approximately 35,000 nonexplanted patients worldwide, with approximately 600 events reported to the manufacturer to date. Fractures of the outlet struts of the valves began to appear in the early 1980s and have continued to the present, but their causes are only partially understood. A matched case-control study was conducted evaluating manufacturing records for 52 valves with outlet strut fractures and 248 control subjects matched for age at implantation, valve size, and valve position. In addition to the risk factors recognized as determinants of outlet strut fracture, the United Kingdom case-control study has observed 7- to 9-fold increased risk with performance of multiple hook deflection tests. This test was performed more than once, usually after rework on the valve. Six valves in this study underwent multiple hook deflection tests, of which 4 experienced an outlet strut fracture. Cracks and further rework were noted for these valves. Significant associations were also observed between outlet strut fracture and disc-to-strut gap measurements taken before the attachment of the sewing ring. It is our view that a combination of factors related to valve design, manufacturing process, and patient characteristics are responsible for outlet strut fractures of Björk-Shiley convexo-concave valves. Multiple hook deflection tests have emerged as a potential new risk factor for outlet strut fracture in both The Netherlands and the United Kingdom. This factor appears to be correlated with the presence of other abnormalities. A further study is needed to investigate the factors correlated with multiple hook deflection tests. On confirmation of risk, the presence of multiple hook deflection tests may be added to equations, quantifying the risk of outlet strut fracture for comparison against risk of mortality and serious

Aperture Valve for the Mars Organic Molecule Analyzer (MOMA)

Science.gov (United States)

Hakun, Claef F.; Engler, Charles D.; Barber, Willie E.; Canham, John S.

2014-01-01

NASA's participation in the multi-nation ExoMars 2018 Rover mission includes a critical astrobiology Mass Spectrometer Instrument on the Rover called the Mars Organic Molecule Analyzer (MOMA). The Aperture Valve is a critical electromechanical valve used by the Mass Spectrometer to facilitate the transfer of ions from Martian soil to the Mass Spectrometer for analysis. The MOMA Aperture Valve development program will be discussed in terms of the Initial valve design and subsequent improvements that resulted from prototype testing. The Initial Aperture Valve concept seemed promising, based on calculations and perceived merits. However, performance results of this design were disappointing, due to delamination of TiN and DLC coatings applied to the Titanium base metals, causing debris from the coatings to seize the valve. While peer reviews and design trade studies are important forums to vet a concept design, results from testing should not be underestimated.Despite the lack of development progress to meet requirements, valuable information from weakness discovered in the Initial Valve design was used to develop a second, more robust Aperture valve. Based on a check-ball design, the ETU flight valve design resulted in significantly less surface area to create the seal. Moreover, PVD coatings were eliminated in favor of hardened, nonmagnetic corrosion resistant alloys. Test results were impressive, with the valve achieving five orders of magnitude better sealing leak rate over end of life requirements. Cycle life was equally impressive, achieving 280,000 cycles without failure.

Valve Disease

Science.gov (United States)

... blood. There are 4 valves in the heart: tricuspid, pulmonary, mitral, and aortic. Two types of problems can disrupt blood flow through the valves: regurgitation or stenosis. Regurgitation is also called insufficiency or incompetence. Regurgitation happens when a valve doesn’ ...

Mitral Valve Surgery in Patients with Systemic Lupus Erythematosus

Science.gov (United States)

Hekmat, Manouchehr; Ghorbani, Mohsen; Ghaderi, Hamid; Majidi, Masoud; Beheshti, Mahmood

2014-01-01

Valvular heart disease is the common cardiac manifestation of systemic lupus erythematosus (SLE) with a tendency for mitral valve regurgitation. In this study we report a case of mitral valve replacement for mitral stenosis caused by Libman-Sacks endocarditis in the setting of SLE. In addition, we provide a systematic review of the literature on mitral valve surgery in the presence of Libman-Sacks endocarditis because its challenge on surgical options continues. Surgical decision depends on structural involvement of mitral valve and presence of active lupus nephritis and antiphospholipid antibody syndrome. Review of the literature has also shown that outcome is good in most SLE patients who have undergone valvular surgery, but association of antiphospholipid antibody syndrome with SLE has negative impact on the outcome. PMID:25401131

A Study of System Pressure Transients Generated by Isolation Valve Open/Closure in Orifice Manifold

Energy Technology Data Exchange (ETDEWEB)

Kim, M. [KEPCO, Daejeon (Korea, Republic of); Bae, S. W.; Kim, J. I.; Park, S. J. [KHNP, Abu Dhabi (United Arab Emirates)

2016-05-15

In this study, we explore the effects of pressure transients on peak and minimal pressures caused by the actuation of isolation valve and control valve reacting to the combined orifice operation of orifice manifold with motor-operated valve installed in the rear of the orifice. We then use the collected data to direct our effort towards cause analysis and propose improvements to efficiency and safety of operation. This formation is used to by domestic and foreign nuclear power plants as a mean to control flow rate, producing required flow rate jointly together by combination of the orifices. No significant impacts on the internals of manifold orifice due to peak pressure has been observed, although chance of cavitation at the outlet of control valve is significant. Considering the peak pressure, as well as minimum pressure occurs in low flow rate conditions, the pressure transient is more so affected by the characteristics (modified equal percentage) of control valve. Isolation valve of the orifice and control valve operate organically, therefore stroke time for valves need to be applied in order for both valves to cooperatively formulate an optimized operation.

Capnocytophaga canimorsus: a rare case of conservatively treated prosthetic valve endocarditis.

Science.gov (United States)

Jalava-Karvinen, Päivi; Grönroos, Juha O; Tuunanen, Helena; Kemppainen, Jukka; Oksi, Jarmo; Hohenthal, Ulla

2018-05-01

We describe a rare case of prosthetic valve endocarditis caused by the canine bacterium Capnocytophaga canimorsus in a male aged 73 years. The diagnosis of infective endocarditis was unequivocal, as it blood cultures were positive for C. canimorsus and vegetations were detected on transesophageal echocardiography; the modified Duke criteria were fulfilled. PET-CT showed intense 18 F-FDG uptake of the prosthetic valve area. The patient was treated with antibiotics alone (no surgery), and is now on life-long suppressive antibiotic therapy. To our knowledge, this is the third reported case of prosthetic valve endocarditis caused by C. canimorsus and the first one to have been treated conservatively. © 2018 APMIS. Published by John Wiley & Sons Ltd.

241-AN-A valve pit manifold valves and position indication acceptance test procedure

Energy Technology Data Exchange (ETDEWEB)

VANDYKE, D.W.

1999-08-25

This document describes the method used to test design criteria for gear actuated ball valves installed in 241-AN-A Valve Pit located at 200E Tank Farms. The purpose of this procedure is to demonstrate the following: Equipment is properly installed, labeled, and documented on As-Built drawings; New Manifold Valves in the 241-AN-A Valve Pit are fully operable using the handwheel of the valve operators; New valve position indicators on the valve operators will show correct valve positions; New valve position switches will function properly; and New valve locking devices function properly.

Subsurface Controls on Stream Intermittency in a Semi-Arid Landscape

Science.gov (United States)

Dohman, J.; Godsey, S.; Thackray, G. D.; Hale, R. L.; Wright, K.; Martinez, D.

2017-12-01

Intermittent streams currently constitute 30% to greater than 50% of the global river network. In addition, the number of intermittent streams is expected to increase due to changes in land use and climate. These streams provide important ecosystem services, such as water for irrigation, increased biodiversity, and high rates of nutrient cycling. Many hydrological studies have focused on mapping current intermittent flow regimes or evaluating long-term flow records, but very few have investigated the underlying causes of stream intermittency. The disconnection and reconnection of surface flow reflects the capacity of the subsurface to accommodate flow, so characterizing subsurface flow is key to understanding stream drying. We assess how subsurface flow paths control local surface flows during low-flow periods, including intermittency. Water table dynamics were monitored in an intermittent reach of Gibson Jack Creek in southeastern Idaho. Four transects were delineated with a groundwater well located in the hillslope, riparian zone, and in the stream, for a total of 12 groundwater wells. The presence or absence of surface flow was determined by frequent visual observations as well as in situ loggers every 30m along the 200m study reach. The rate of surface water drying was measured in conjunction with temperature, precipitation, subsurface hydraulic conductivity, hillslope-riparian-stream connectivity and subsurface travel time. Initial results during an unusually wet year suggest different responses in reaches that were previously observed to occasionally cease flowing. Flows in the intermittent reaches had less coherent and lower amplitude diel variations during base flow periods than reaches that had never been observed to dry out. Our findings will help contribute to our understanding of mechanisms driving expansion and contraction cycles in intermittent streams, increase our ability to predict how land use and climate change will affect flow regimes, and

Aortic Valve Stenosis

Science.gov (United States)

... most cases, doctors don't know why a heart valve fails to develop properly, so it isn't something you could have prevented. Calcium buildup on the valve. With age, heart valves may accumulate deposits of calcium (aortic valve ...

BWR control rod drive scram pilot valve monitoring system

International Nuclear Information System (INIS)

Soden, R.A.; Kelly, V.

1984-01-01

The control rod drive system in a Boiling Water Reactor is the most important safety system in the power plant. All components of the system can be verified except the solenoid operated, scram pilot valves without scramming a rod. The pilot valve mechancial works is the weak link to the control rod drive system. These pilot valves control the hydraulic system which applies pressure to the ''insert'' side of the control rod piston and vents the ''withdraw'' side of the piston causing the rods to insert during a scam. The only verification that the valve is operating properly is to scram the rod. The concern for this portion of the system is demonstrated by the high number of redundant components and complete periodic testing of the electrical circuits. The pilot valve can become hung-up through wear, fracture of internal components, mechanical binding, foreign material or chemicals left in the valve during maintenance, etc. If the valve becomes hung-up the electrical tests performed will not indicate this condition and scramming the rod is in jeopardy. Only an attempt to scram a rod will indicate the hung-up valve. While this condition exists the rod is considered inoperative. This paper describes a system developed at a nuclear power plant that monitors the pilot valves on the control rod drive system. This system utilizes pattern recognition to assure proper internal workings of the scram pilot valves to plant operators. The system is totally automatic such that each time the valve is operated on a ''half scram'', a printout is available to the operator along with light indication that each of the 370 valves (on one unit of a BWR) is operating properly. With this monitoring system installed, all components of the control rod drive system including the solenoid pilot valves can be verified as operational without scramming any rods

BWR control rod drive scram pilot valve monitoring program

International Nuclear Information System (INIS)

Soden, R.A.; Kelly, V.

1986-01-01

The control rod drive system in a Boiling Water Reactor is the most important safety system in the power plant. All components of the system can be verified except the solenoid operated, scram pilot valves without scramming a rod. The pilot valve mechanical works is the weak link to the control rod drive system. These pilot valves control the hydraulic system which applies pressure to the insert side of the control rod piston and vents the withdraw side of the piston causing the rods to insert during a scram. The only verification that the valve is operating properly is to scram the rod. The concern for this portion of the system is demonstrated by the high number of redundant components and complete periodic testing of the electrical circuits. The pilot valve can become hung-up through wear, fracture of internal components, mechanical binding, foreign material or chemicals left in the valve during maintenance, etc. If the valve becomes hung-up the electrical tests performed will not indicate this condition and scramming the rod is in jeopardy. Only an attempt to scram a rod will indicate the hung-up valve. While this condition exists the rod is considered inoperative. This paper describes a system developed at a nuclear power plant that monitors the pilot valves on the control rod drive system. This system utilizes pattern recognition to assure proper internal workings of the scram pilot valves to plant operators. The system is totally automatic such that each time the valve is operated on a half scram, a printout is available to the operator along with light indication that each of the 370 valves (on one unit of a BWR) is operating properly. With this monitoring system installed, all components of the control rod drive system including the solenoid pilot valves can be verified as operational without scramming any rods

Intermittent Explosive Disorder

Directory of Open Access Journals (Sweden)

Lut Tamam

2011-09-01

Full Text Available Intermittent explosive disorder is an impulse control disorder characterized by the occurrence of discrete episodes of failure to resist aggressive impulses that result in violent assault or destruction of property. Though the prevalence intermittent explosive disorder has been reported to be relatively rare in frontier studies on the field, it is now common opinion that intermittent explosive disorder is far more common than previously thought especially in clinical psychiatry settings. Etiological studies displayed the role of both psychosocial factors like childhood traumas and biological factors like dysfunctional neurotransmitter systems and genetics. In differential diagnosis of the disorder, disorders involving agression as a symptom such as alcohol and drug intoxication, antisocial and borderline personality disorders, personality changes due to general medical conditions and behavioral disorder should be considered. A combination of pharmacological and psychotherapeutic approaches are suggested in the treatment of the disorder. This article briefly reviews the historical background, diagnostic criteria, epidemiology, etiology and treatment of intermittent explosive disorder.

Enhancement of pressurizer safety valve operability by seating design improvement

International Nuclear Information System (INIS)

Moisidis, N.T.; Ratiu, M.D.

1994-01-01

Operating conditions specific to Pressurizer Safety Valves (PSVs) have led to numerous problems and have caused industry and NRC concerns regarding the adequacy of spring loaded self-actuated safety valves for Reactor Coolant System (RCS) overpressure protection. Specific concerns are: setpoint drift, spurious actuations and leakage. Based on testing and valve construction analysis of a Crosby model 6M6 PSV, it was established that the primary contributor to the valve problems is a susceptibility to weak seating. To eliminate spring instability, a new spring washer was designed, which guides the spring and precludes its rotation from the reference installed position. Results of tests performed on a prototype PSV equipped with the modified upper spring washer has shown significant improvements in valve operability and a consistent setpoint reproducibility to less than ±1% of the PSV setpoint (testing of baseline, unmodified valve, resulted in a setpoint drift of ±2%). Enhanced valve operability will result in a significant decrease in operating and maintenance costs associated with valve maintenance and testing. In addition, the enhanced setpoint reproducibility will allow the development of a nitrogen to steam correlation for future in-house PSV testing which will result in further reductions in costs associated with valve testing

Rare early prosthesis obstruction after mitral valve replacement: a case report and literature review

Directory of Open Access Journals (Sweden)

Shi Jun

2012-07-01

Full Text Available Abstract As a dreadful complication after the mechanical heart valve replacement, prosthetic valve obstruction caused by pannus formation occurs increasingly with time. The authors here present a case of 42-year-old woman who was urgently admitted to hospital with acute heart failure symptoms due to the mechanical mitral valve failure only 3 months after surgery. Transthoracic and transesophageal echocardiography demonstrated that the bileaflet of the mitral prosthesis were completely immobilized with only a small transvalvular jet remained. During the reoperation, the reason of the prosthetic valve obstruction was attributed to the noncircular pannus ingrowth extending from the atrioventricular side. For a better understanding of the prosthetic valve dysfunction caused by pannus formation, the authors then compile a literature review to briefly discuss the status quo of the clinical characteristics of this uncommon complication.

Valve assembly

International Nuclear Information System (INIS)

Sandling, M.

1981-01-01

An improved valve assembly, used for controlling the flow of radioactive slurry, is described. Radioactive contamination of the air during removal or replacement of the valve is prevented by sucking air from the atmosphere through a portion of the structure above the valve housing. (U.K.)

Structural valve deterioration in a starr-edwards mitral caged-disk valve prosthesis.

Science.gov (United States)

Aoyagi, Shigeaki; Tayama, Kei-Ichiro; Okazaki, Teiji; Shintani, Yusuke; Kono, Michitaka; Wada, Kumiko; Kosuga, Ken-Ichi; Mori, Ryusuke; Tanaka, Hiroyuki

2013-01-01

The durability of the Starr-Edwards (SE) mitral caged-disk valve, model 6520, is not clearly known, and structural valve deterioration in the SE disk valve is very rare. Replacement of the SE mitral disk valve was performed in 7 patients 23-40 years after implantation. Macroscopic examination of the removed disk valves showed no structural abnormalities in 3 patients, in whom the disk valves were removed at valves excised >36 years after implantation in 4 patients. Disk fracture, a longitudinal split in the disk along its circumference at the site of incorporation of the titanium ring, was detected in the valves removed 36 and 40 years after implantation, respectively, and many cracks were also observed on the outflow aspect of the disk removed 40 years after implantation. Disk fracture and localized disk wear were found in the SE mitral disk valves implanted >36 years previously. The present results suggest that SE mitral caged-disk valves implanted >20 years previously should be carefully followed up, and that those implanted >30 years previously should be electively replaced with modern prosthetic valves

Neurotrophin 3 upregulates proliferation and collagen production in human aortic valve interstitial cells: a potential role in aortic valve sclerosis.

Science.gov (United States)

Yao, Qingzhou; Song, Rui; Ao, Lihua; Cleveland, Joseph C; Fullerton, David A; Meng, Xianzhong

2017-06-01

Calcific aortic valve disease (CAVD) is a leading cardiovascular disorder in the elderly. Diseased aortic valves are characterized by sclerosis (fibrosis) and nodular calcification. Sclerosis, an early pathological change, is caused by aortic valve interstitial cell (AVIC) proliferation and overproduction of extracellular matrix (ECM) proteins. However, the mechanism of aortic valve sclerosis remains unclear. Recently, we observed that diseased human aortic valves overexpress growth factor neurotrophin 3 (NT3). In the present study, we tested the hypothesis that NT3 is a profibrogenic factor to human AVICs. AVICs isolated from normal human aortic valves were cultured in M199 growth medium and treated with recombinant human NT3 (0.10 µg/ml). An exposure to NT3 induced AVIC proliferation, upregulated the production of collagen and matrix metalloproteinase (MMP), and augmented collagen deposition. These changes were abolished by inhibition of the Trk receptors. NT3 induced Akt phosphorylation and increased cyclin D1 protein levels in a Trk receptor-dependent fashion. Inhibition of Akt abrogated the effect of NT3 on cyclin D1 production. Furthermore, inhibition of either Akt or cyclin D1 suppressed NT3-induced cellular proliferation and MMP-9 and collagen production, as well as collagen deposition. Thus, NT3 upregulates cellular proliferation, ECM protein production, and collagen deposition in human AVICs. It exerts these effects through the Trk-Akt-cyclin D1 cascade. NT3 is a profibrogenic mediator in human aortic valve, and overproduction of NT3 by aortic valve tissue may contribute to the mechanism of valvular sclerosis. Copyright © 2017 the American Physiological Society.

Chronic intermittent fasting improves cognitive functions and brain structures in mice.

Directory of Open Access Journals (Sweden)

Liaoliao Li

Full Text Available Obesity is a major health issue. Obesity started from teenagers has become a major health concern in recent years. Intermittent fasting increases the life span. However, it is not known whether obesity and intermittent fasting affect brain functions and structures before brain aging. Here, we subjected 7-week old CD-1 wild type male mice to intermittent (alternate-day fasting or high fat diet (45% caloric supplied by fat for 11 months. Mice on intermittent fasting had better learning and memory assessed by the Barnes maze and fear conditioning, thicker CA1 pyramidal cell layer, higher expression of drebrin, a dendritic protein, and lower oxidative stress than mice that had free access to regular diet (control mice. Mice fed with high fat diet was obese and with hyperlipidemia. They also had poorer exercise tolerance. However, these obese mice did not present significant learning and memory impairment or changes in brain structures or oxidative stress compared with control mice. These results suggest that intermittent fasting improves brain functions and structures and that high fat diet feeding started early in life does not cause significant changes in brain functions and structures in obese middle-aged animals.

Chronic intermittent fasting improves cognitive functions and brain structures in mice.

Science.gov (United States)

Li, Liaoliao; Wang, Zhi; Zuo, Zhiyi

2013-01-01

Obesity is a major health issue. Obesity started from teenagers has become a major health concern in recent years. Intermittent fasting increases the life span. However, it is not known whether obesity and intermittent fasting affect brain functions and structures before brain aging. Here, we subjected 7-week old CD-1 wild type male mice to intermittent (alternate-day) fasting or high fat diet (45% caloric supplied by fat) for 11 months. Mice on intermittent fasting had better learning and memory assessed by the Barnes maze and fear conditioning, thicker CA1 pyramidal cell layer, higher expression of drebrin, a dendritic protein, and lower oxidative stress than mice that had free access to regular diet (control mice). Mice fed with high fat diet was obese and with hyperlipidemia. They also had poorer exercise tolerance. However, these obese mice did not present significant learning and memory impairment or changes in brain structures or oxidative stress compared with control mice. These results suggest that intermittent fasting improves brain functions and structures and that high fat diet feeding started early in life does not cause significant changes in brain functions and structures in obese middle-aged animals.

Tomographic and echocardiographic diagnosis of mitral prosthetic valve thrombosis

International Nuclear Information System (INIS)

Sainz Gonzalez de la Penna, Benito; Ramos Gutierrez, Luis Benito; Gonzalez Artiles, Iovank

2010-01-01

Despite the progress achieved in the design of mechanical prosthetic valves, prosthetic valve thrombosis remains a frequent cause of morbidity, usually due to incorrect anticoagulation. A patient was presented with mitral prosthetic thrombosis one year after implantation, who had been diagnosed by transthoracic transesophageal echocardiography imaging and 64-slice computed tomography. Thrombolytic therapy was successful and led to the satisfactory evolution of the patient

Microfluidic sieve valves

Science.gov (United States)

Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

2015-01-13

Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle.

Science.gov (United States)

Liu, K; Chen, L E; Seaber, A V; Johnson, G W; Urbaniak, J R

1999-01-01

Intermittent pneumatic compression has been established as a method of clinically preventing deep vein thrombosis, but the mechanism has not been documented. This study observed the effects of intermittent pneumatic compression of legs on the microcirculation of distant skeletal muscle. The cremaster muscles of 80 male rats were exposed, a specially designed intermittent pneumatic-compression device was applied to both legs for 60 minutes, and the microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed significant vasodilation in arterial and venous vessels during the application of intermittent pneumatic compression, which disappeared after termination of the compression. The vasodilation reached a maximum 30 minutes after initiation of the compression and could be completely blocked by an inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine (10 micromol/min). A 120-minute infusion of NG-monomethyl-L-arginine, beginning coincident with 60 minutes of intermittent pneumatic compression, resulted in a significant decrease in arterial diameter that remained at almost the same level after termination of the compression. The magnitude of the decrease in diameter in the group treated with intermittent pneumatic compression and NG-monomethyl-L-arginine was comparable with that in the group treated with NG-monomethyl-L-arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermittent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilation.

Cobalt reduction of NSSS valve hardfacings for ALARA

Energy Technology Data Exchange (ETDEWEB)

Kim, Joo Hak; Lee, Sang Sub [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author).

Cobalt reduction of NSSS valve hardfacings for ALARA

International Nuclear Information System (INIS)

Kim, Joo Hak; Lee, Sang Sub

1994-07-01

This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author)

Main feedwater valve diagnostics at Waterford 3 nuclear generating station

International Nuclear Information System (INIS)

Fitzgerald, W.V.

1991-01-01

Pneumatically-operated control valves are coming under increasing scrutiny in nuclear power plants because of their relatively high incident rate. The theory behind a device that could make performance evaluation of these valves simpler and more effective was first described at the original EPRI Power Plant Valve Symposium. The development of this Diagnostic System was completed in 1989, and it was recently used to troubleshoot two main feedwater valves at Louisiana Power and Light's Waterford 3 Power Station. During a cold snap last December, these valves failed to respond to the input signal and, as a result, the plant came off line. An incident report had to be filed, and the plant chose to contact the original equipment manufacturer (OEM) for assistance. This paper describes the original incident involving these valves and then gives a brief description of the diagnostic system and how it works. The balance of the paper then reviews how the OEM and plant personnel utilized the system to evaluate each component of the control valve assembly (I/P transducer, positioner, volume boosters, actuator, and valve body assembly). By simply stroking the valve and monitoring pneumatic signals and valve position, the problem was traced to a malfunctioning positioner and a volume booster that was leaking. The problems were corrected and new performance signatures run for the valves using the system to document their improved operation. This case study demonstrates how new Diagnostic Technology along with OEM involvement can effectively address problems with pneumatically-operated control valves so that root-cause solutions can be implemented

Acute obstruction by Pannus in patients with aortic medtronic-hall valves: 30 years of experience.

Science.gov (United States)

Ellensen, Vegard Skalstad; Andersen, Knut Sverre; Vitale, Nicola; Davidsen, Einar Skulstad; Segadal, Leidulf; Haaverstad, Rune

2013-12-01

Acute dysfunction of mechanical aortic valve prostheses is a life-threatening adverse event. Pannus overgrowth, which is fibroelastic hyperplasia originating from the periannular area, is one cause of dysfunction. The aim of this study was to determine the annual incidence of readmittance resulting from acute obstruction caused by pannus during 30 years of observation in patients with Medtronic-Hall aortic valve prostheses and to analyze the risk factors associated with pannus development. From 1982 to 2004, 1,187 patients in our department underwent aortic valve replacement with Medtronic-Hall mechanical monoleaflet valve prostheses. As of December 31, 2012, 27 of these patients (2.3%) had presented with acute valve dysfunction caused by pannus obstruction. The annual incidence of pannus was 0.7 per 1,000. The median time from the primary operation to prosthetic dysfunction was 11.1 years (range, 1.2 to 26.8 years). Of the 20 patients who underwent reoperation, 2 died. Seven patients died before reoperation. Women had a higher risk for the development of obstructing pannus, and patients with pannus obstruction were younger. Valve size was not an independent risk factor. Women and younger patients are at higher risk for pannus development. When acute dysfunction by pannus is suspected in a mechanical aortic valve, an immediate echocardiogram and an emergency aortic valve replacement should be carried out because of the potential of a fatal outcome. Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Organic evaporator steam valve failure

International Nuclear Information System (INIS)

Jacobs, R.A.

1992-01-01

Defense Waste Processing Facility (DWPF) Technical has requested an analysis of the capacity of the Organic Evaporator (OE) condenser (OEC) be performed to determine its capability in the case where the OE steam flow control valve fails open. Calculations of the OE boilup and the OEC heat transfer coefficient indicate the OEC will have more than enough capacity to remove the heat at maximum OE boilup. In fact, the Salt Cell Vent Condenser (SCVC) should also have sufficient capacity to handle the maximum OE boilup. Therefore, it would require simultaneous loss of OEC and/or SCVC condensing capacity for the steam valve failure to cause high benzene in the Process Vessel Vent System (PVVS)

Midterm Results of Aortic Valve Replacement with Cryopreserved Homografts

Directory of Open Access Journals (Sweden)

Emre Özker

2012-06-01

Full Text Available Objective: The aim of this study was to analyze the midterm clinical results of aortic valve replacement with cryopreserved homografts.Materials and Methods: Aortic valve replacement was performed in 40 patients with cryopreserved homograft. The indications were aortic valve endocarditis in 20 patients (50%, truncus arteriosus in 6 patients (15%, and re-stenosis or regurtitation after aortic valve reconstruction in 14 (35% patients. The valve sizes ranged from 10 to 27mm. A full root replacement technique was used for homograft replacement in all patients.Results: The 30-day postoperative mortality rate was 12.5% (5 patients. There were four late deaths. Only one of them was related to cardiac events. Overall mortality was 22.5%. Thirty-three patients were followed up for 67±26 months. Two patients needed reoperation due to aortic aneurysm caused by endocarditis. The mean transvalvular gradient significantly decreased after valve replacement (p<0.003. The last follow up showed that the 27 (82% patients had a normal left ventricular function.Conclusion: Cryopreserved homografts are safe alternatives to mechanical valves that can be used when there are proper indications. Although it has a high perioperative mortality rate, cryopreserved homograft implantation is an alternative for valve replacement, particularly in younger patients and for complex surgical problems such as endocarditis that must be minimalized.

Quantitative assessment of an aortic and pulmonary valve function according to valve fenestration

International Nuclear Information System (INIS)

Mirkhani, S.H.; Golestani, M.G.; Hosini, M.; Kazemian, A.

1999-01-01

There are some reasons for malfunction of aortic and pulmonary valve like fibrosis, calcification, and atheroma. Although, in some papers fenestration were known as a pathologic sign, but it is not generally accepted, while this matter is important in choosing suitable Homograft Heart Valve. In this paper fenestrations and its size, numbers and situation effect was studied. We collected 98 hearts, the donors died because of accident, we excluded valves with atheroma, calcification, fibrosis and unequal cusps, 91 aortic and 93 pulmonary valves were given further consideration. We classified valves according to situation, number and size of fenestration. Each valve was tested with 104 cm of non-nal saline column pressure which is equal to 76 mm Hg. Valve efficacy was detected by fluid flow assay. With study of 184 valves, 95 had no fenestration, 64 had less than 2 fenestration and 25 had more than 2 fenestration. Valve efficacy in condition of less than 2 fenestration was more than others (p <0.01). Malfunction effects of fenestration increased in larger valve and it will be decreased if their situation would be marginal (free margin of cusp). In the comparison of aortic and pulmonary valve we saw that malfunction effect of fenestration in pulmonary valve was more than aortic valve. Our experience in Immam Khomeini Homograft Valve Bank has shown that a great deal of valves is fenestrated. It seems that fenestration must be considered as a quality criterion in homograft valve preparation, especially in pulmonary and large aortic valves; but complementary studies is necessary

Myxomatous mitral valve disease in dogs - an update and perspectives

Directory of Open Access Journals (Sweden)

Aleksandra Domanjko Petrič

2015-03-01

Full Text Available Myxomatous mitral valve disease is a common cause of congestive heart failure in geriatric dogs. Many studies have been done in terms of epidemiology, pathology, associated neurohormonal changes in the disease progression, prognostic factors, and survival and treatment modalities. The presented paper presents a review of some of the studies in the mitral valve disease story.

Sequential transcatheter aortic valve implantation due to valve dislodgement - a Portico valve implanted over a CoreValve bioprosthesis.

Science.gov (United States)

Campante Teles, Rui; Costa, Cátia; Almeida, Manuel; Brito, João; Sondergaard, Lars; Neves, José P; Abecasis, João; M Gabriel, Henrique

2017-03-01

Transcatheter aortic valve implantation (TAVI) has become an important treatment in high surgical risk patients with severe aortic stenosis (AS), whose complications need to be managed promptly. The authors report the case of an 86-year-old woman presenting with severe symptomatic AS, rejected for surgery due to advanced age and comorbidities. The patient underwent a first TAVI, with implantation of a Medtronic CoreValve ® , which became dislodged and migrated to the ascending aorta. Due to the previous balloon valvuloplasty, the patient's AS became moderate, and her symptoms improved. After several months, she required another intervention, performed with a St. Jude Portico ® repositionable self-expanding transcatheter aortic valve. There was a good clinical response that was maintained at one-year follow-up. The use of a self-expanding transcatheter bioprosthesis with repositioning features is a solution in cases of valve dislocation to avoid suboptimal positioning of a second implant, especially when the two valves have to be positioned overlapping or partially overlapping each other. Copyright © 2017 Sociedade Portuguesa de Cardiologia. Publicado por Elsevier España, S.L.U. All rights reserved.

Intermittent heating of buildings

Energy Technology Data Exchange (ETDEWEB)

Kohonen, K

1983-02-01

Conditions for intermittent heating of buildings are considered both theoretically and experimentally. Thermal behaviour of buildings adn rooms in intermittent heating is simulated by a program based on the convective heat balance equation and by simplified RC-models. The preheat times and the heating energy savings compared with continuous heating are presented for typical lightweight, mediumweight and heavyweight classroom and office modules. Formulaes for estimating the oversizing of the radiator network, the maximum heat output of heat exchangers in district heating and the efficiency of heating boilers in intermittent heating are presented. The preheat times and heating energy savings with different heating control systems are determined also experimentally in eight existing buildings. In addition some principles for the planning and application of intermittent heating systems are suggested.

Proving test on the reliability for nuclear valves

International Nuclear Information System (INIS)

Kajiyama, Yasuo; Tashiro, Hisao; Uga, Takeo; Maeda, Shunichi.

1986-01-01

Since valves are the most common components, they could be the most frequent causes of troubles in nuclear power plants. This proving test, therefore, has an important meaning to examine and verify the reliability of various valves under simulating conditions of abnormal and transient operations of the nuclear power plant. The test was performed mainly for the various types and pressure ratings of valves which were used in the primary and secondary systems in BWR and PWR nuclear power plants and which had major operating or safety related functions in those nuclear power plants. The results of the proving test, confirmed for more than four years, showed relatively favourable performance of the tested valves. It is concluded that performances of valves including operability, seat sealing and structural integrity were proved under the thermal cycling, vibration and pipe reaction load conditions. Operating functions during and after accident such as loss of coolant accident were satisfactory. From these results, it was considered that the purpose of this proving test was satisfactorily fulfilled. Several data accumulated by the test would be useful to get better reliability if it was evaluated with the actually experienced data of valves in the nuclear power plants. (Nogami, K.)

Perivalvular pannus and valve thrombosis: two concurrent mechanisms of mechanical valve prosthesis dysfunction.

Science.gov (United States)

Arnáiz-García, María Elena; González-Santos, Jose María; Bueno-Codoñer, María E; López-Rodríguez, Javier; Dalmau-Sorlí, María José; Arévalo-Abascal, Adolfo; Arribas-Jiménez, Antonio; Diego-Nieto, Alejandro; Rodríguez-Collado, Javier; Rodríguez-López, Jose María

2015-02-01

A 78-year-old woman was admitted to our institution with progressive dyspnea. She had previously been diagnosed with rheumatic heart disease and had undergone cardiac surgery for mechanical mitral valve replacement ten years previously. Transesophageal echocardiography revealed blockage of the mechanical prosthesis and the patient was scheduled for surgery, in which a thrombus was removed from the left atrial appendage. A partial thrombosis of the mechanical prosthesis and circumferential pannus overgrowth were concomitantly detected. Prosthetic heart valve blockage is a rare but life-threatening complication, the main causes of which are thrombosis and pannus formation. The two conditions are different but both are usually misdiagnosed. Two concurrent mechanisms of prosthesis blockage were found in this patient. Copyright © 2014 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

Tricuspid valve endocarditis with pulmonary infarction caused by central venous catheter

International Nuclear Information System (INIS)

Grabbe, E.; Guthoff, A.; Hamburg Univ.

1981-01-01

Knowledge of common complications of central venous catheters is completed by a case of bacterial tricuspid endocarditis with recurrent pulmonary infarction. This rare, life threatening complication should be considered in differential diagnosis, when in case of central venous catheter sepsis, changing pulmonary infiltrations with pleural effusion as well as different auscultatory findings above the tricuspid valve do occur. The diagnosis can be supported by echocardiographic demonstration of tricuspid vegetations. (orig.) [de

Tricuspid valve endocarditis with pulmonary infarction caused by central venous catheter

Energy Technology Data Exchange (ETDEWEB)

Grabbe, E; Guthoff, A

1981-02-01

Knowledge of common complications of central venous catheters is completed by a case of bacterial tricuspid endocarditis with recurrent pulmonary infarction. This rare, life threatening complication should be considered in differential diagnosis, when in case of central venous catheter sepsis, changing pulmonary infiltrations with pleural effusion as well as different auscultatory findings above the tricuspid valve do occur. The diagnosis can be supported by echocardiographic demonstration of tricuspid vegetations.

Bicuspid aortic valve demonstrated with multislice computed tomography - a case report

International Nuclear Information System (INIS)

Marzec, M.; Lasek, W.; Serafin, Z.; Laskowska, K.; Swiatkiewicz, I.; Kubica, J.

2004-01-01

Bicuspid aortic valve (BAV) is one of the most common congenital heart defects and often coexists with other congenital abnormalities of the heart and great vessels. A standard diagnostic technique for valve imaging is echocardiography. However, suboptimal images may cause a diagnostic problem, especially in obese patients, women and in case of significant valve calcifications. The paper reports a case of a 27-year-old male patient with recurrent chest pain, appearing regardless of exertion. Routine physical examination, laboratory tests and echocardiography were negative. Multislice computed tomography (MSCT) showed normal coronary arteries and bicuspid aortic valve. The diagnostics of bicuspid aortic valve and the diagnostic value of MSCT are discussed. MSCT seems to be an important point in cardiac diagnostic algorithms, being an alternative modality for MR in BAV imaging. The presented case emphasizes the potential of MSCT for the diagnostics of cardiac valve congenital diseases. (author)

IE Information Notice No. 85-17, Supplement 1: Possible sticking of ASCO solenoid valves

International Nuclear Information System (INIS)

Jordan, E.L.

1992-01-01

This notice is to inform recipients of the results of follow up investigations regarding the reasons for sticking of Automatic Switch Company (ASCO) solenoid valves used to shut main steam isolation valves (MSIVs) under accident conditions. GE has recommend that the licensee replace the potentially contaminated MSIV solenoid valves and institute a periodic examination and cleaning of the MSIV solenoid valves. Grand Gulf has replaced the eight MSIV HTX832320V dual solenoid valves with fully environmentally qualified ASCO Model NP 8323A20E dual solenoid valves. The environmentally qualified valve Model NP 8323A20E was included in a control sample placed in the test ovens with the solenoid valves that stuck at Grand Gulf. The environmentally qualified model did not stick under the test conditions that cause sticking in the other solenoid valves

Enhancing wastewater degradation and biogas production by intermittent operation of UASB reactors

International Nuclear Information System (INIS)

Nadais, Helena; Barbosa, Marta; Capela, Isabel; Arroja, Luis; Ramos, Christian G.; Grilo, Andre; Sousa, Silvia A.; Leitao, Jorge H.

2011-01-01

The present work establishes intermittent operation of UASB reactors as a novel form of enhancing the anaerobic degradation of complex wastewaters and its conversion to usable biogas. Results show that the average methane production rate is 25% higher with the intermittent operation than with the continuous mode, meaning that it could produce 25% more electricity or heat. The methanization efficiency obtained in intermittent UASB reactors is around 20% higher than in the continuous systems, confirming a higher biological degradation of the substrates. It has been suggested that intermittent operation causes a forced adaptation of the biomass towards the degradation of complex substrates and results from morphological analyses of the biomass developed in intermittent and continuous UASB reactors showed marked differences between them. In order to gain a deeper knowledge on how microbial populations are affected by these operational parameters, a strategy involving the amplification, cloning, and analysis of the nucleotide sequences of genes encoding the 16S ribosomal RNA was undertaken and is described in this work. This strategy allowed the identification of a total of 49 different sequences. Results from the molecular characterization of the microbial populations are consistent with the higher methanization efficiency of the intermittent mode of operation.

Rotary pneumatic valve

Science.gov (United States)

Hardee, Harry C.

1991-01-01

A rotary pneumatic valve which is thrust balanced and the pneumatic pressure developed produces only radial loads on the valve cylinder producing negligible resistance and thus minimal torque on the bearings of the valve. The valve is multiplexed such that at least two complete switching cycles occur for each revolution of the cylinder spindle.

Scissor thrust valve actuator

Science.gov (United States)

DeWall, Kevin G.; Watkins, John C; Nitzel, Michael E.

2006-08-29

Apparatus for actuating a valve includes a support frame and at least one valve driving linkage arm, one end of which is rotatably connected to a valve stem of the valve and the other end of which is rotatably connected to a screw block. A motor connected to the frame is operatively connected to a motor driven shaft which is in threaded screw driving relationship with the screw block. The motor rotates the motor driven shaft which drives translational movement of the screw block which drives rotatable movement of the valve driving linkage arm which drives translational movement of the valve stem. The valve actuator may further include a sensory control element disposed in operative relationship with the valve stem, the sensory control element being adapted to provide control over the position of the valve stem by at least sensing the travel and/or position of the valve stem.

Heavy gas valves

Energy Technology Data Exchange (ETDEWEB)

Steier, L [Vereinigte Armaturen Gesellschaft m.b.H., Mannheim (Germany, F.R.)

1979-01-01

Heavy gas valves must comply with special requirements. Apart from absolute safety in operation there are stringent requirements for material, sealing and ease of operation even in the most difficult conditions. Ball valves and single plate pipe gate valves lateral sealing rings have a dual, double sided sealing effect according to the GROVE sealing system. Single plate gate valves with lateral protective plates are suitable preferably for highly contaminated media. Soft sealing gate valves made of cast iron are used for low pressure applications.

Enhancement of pressurizer safety valve operability by seating design improvement

International Nuclear Information System (INIS)

Moisidis, N.T.; Ratiu, M.D.

1995-01-01

Operating conditions specific to pressurizer safety valves (PSVs) have led to numerous problems and have caused industry and NRC concerns regarding the adequacy of spring-loaded self-actuated safety valves for reactor coolant system (RCS) overpressure protection. Specific concerns are: setpoint drift, spurious actuations, and pressure protection. Specific concerns are: setpoint drift, spurious actuations, and leakage. Based on testing and valve construction analysis of a Crosby model 6M6 PSV (Moisidis and Ratiu, 1992), it was established that the primary contributor to the valve problems is a susceptibility to weak seating. To eliminate spring instability, a new spring washer was designed, which guides the spring and precludes its rotation from the reference installed position. Results of tests performed on a prototype PSV equipped with the modified upper spring washer has shown significant improvements in valve operability and a consistent setpoint reproducibility to less than ±1% of the PSV setpoint (testing of baseline, unmodified valve, resulted in a setpoint drift of ± 2%). Enhanced valve operability will result in a significant decrease in operating and maintenance costs associated with valve maintenance and testing. In addition, the enhanced setpoint reproducibility will allow the development of a nitrogen to steam correlation for future in-house PSV testing which will result in further reductions in costs associated with valve testing

Corrosion produced failures in valves made of micro-melted stainless steel. Valve disk

International Nuclear Information System (INIS)

Abuin, G.; Alanis, I.; Berardo, L.

1991-01-01

Cast stainless steels show different metallographic structure than equivalent laminated steels where the former presents good resistance in media containing chlorides. In the present work, an analysis is made of the causes for the fracture of an AISI 316 micro-melted stainless steel disk for a valve in a cleaning agents feeding circuit in a food processing plant. (Author) [es

Tricuspid valve repair for severe tricuspid regurgitation due to pacemaker leads.

Science.gov (United States)

Uehara, Kyokun; Minakata, Kenji; Watanabe, Kentaro; Sakaguchi, Hisashi; Yamazaki, Kazuhiro; Ikeda, Tadashi; Sakata, Ryuzo

2016-07-01

Tricuspid valve regurgitation due to pacemaker leads is a well-known complication. Although some reports have suggested that pacemaker leads should be surgically explanted, strongly adhered leads cannot always be removed. The aim of this study was to describe our tricuspid valve repair techniques with pacemaker leads left in situ. Our retrospective study investigated 6 consecutive patients who required tricuspid valve surgery for severe regurgitation induced by pacemaker leads. From the operative findings, we identified 3 patterns of tricuspid valve and pacemaker lead involvement. In 3 patients, the leads were caught in the chordae, in 2 patients, tricuspid regurgitation was caused by lead impingement on the septal leaflet, and in 3 patients, tricuspid valve leaflets had been perforated by the pacemaker leads. During surgery, all leads were left in situ after being separated from the leaflet or valvular apparatus. In addition, suture annuloplasty was performed for annular dilatation in all cases. In one patient, the lead was reaffixed to the annulus after the posterior leaflet was cut back towards the annulus, and the leaflet was then closed. There was one hospital death due to sepsis. The degree of tricuspid regurgitation was trivial in all surviving patients at discharge. During a mean follow-up of 21 months, one patient died from pneumonia 20 months after tricuspid valve repair. In patients undergoing tricuspid valve surgery due to severe tricuspid regurgitation caused by pacemaker leads, the leads can be left in situ after proper repair with annuloplasty. © The Author(s) 2016.

THE RESULTS OF SURGICAL TREATMENT OF TRICUSPID VALVE INFECTIVE ENDOCARDITIS USING VALVE REPAIR AND VALVE REPLACEMENT OPERATIONS

Directory of Open Access Journals (Sweden)

S. A. Kovalev

2015-01-01

Full Text Available Aim. To evaluate in-hospital and long-term results of surgical treatment of patients with infective endocarditis of the tricuspid valve, to compare the effectiveness of valve repair and valve replacement techniques, and to identify risk factors of mortality and reoperations. Materials and methods. 31 surgical patients with tricuspid valve infective endocarditis were evaluated. Patients were divided into 2 groups. In Group 1 (n = 14 repairs of the tricuspid valve were performed, in Group 2 (n = 17 patients had undergone tricuspid valve replacements. Epidemiological, clinical, microbiological and echocardiographic data were studied. Methods of comparative analysis, the Kaplan–Meier method, and Cox risk models were applied. Results. The most common complication of in-hospital stay was atrioventricular block (17.7% of cases in Group 2. In Group 1, this type of complication was not found. Hospital mortality was 7.14% in Group 1, and 0% in Group 2. Long-term results have shown the significant reduction of heart failure in general cohort and in both groups. In Group 1 the severity of heart failure in the long term was less than in Group 2. No significant differences in the severity of tricuspid regurgitation were found between the groups. In 7-year follow up no cases of death were registered in Group 1. Cumulative survival rate in Group 2 within 60 months was 67.3 ± 16.2%. No reoperations were performed in patients from Group 1. In Group 2, the freedom from reoperation within 60 months was 70.9 ± 15.3%. Combined intervention was found as predictor of postoperative mortality. Prosthetic valve endocarditis was identified as risk factor for reoperation. Conclusion. Valve repair and valve replacement techniques of surgical treatment of tricuspid valve endocarditis can provide satisfactory hospital and long-term results. Tricuspid valve repair techniques allowed reducing the incidence of postoperative atrioventricular block. In the long-term, patients

Multidimensional intermittency in hadronic collisions

International Nuclear Information System (INIS)

Pan, J.; Hwa, R.C.

1992-06-01

The study of intermittency in high-energy hadronic collisions by the Monte Carlo code ECCO is extended to 3-dimensional phase space. Strong intermittency is found in agreement with the data. Fluctuation in the impact parameter is responsible for the intermittency in lnp T , and the transverse-momentum conservation leads to negative intermittency slopes in the azimuthal angle φ. The Ochs-Wosiek plots are linear in all dimensions having universal slopes. An exponent ν = 1.448 emerges to characterize multiparticle production in pp collisions. The properties of G moments are also examined, and the fractal dimensions determined

Extrinsic mechanism obstructing the opening of a prosthetic mitral valve: an unusual case of suture entrapment.

Science.gov (United States)

Ozkan, Mehmet; Astarcioglu, Mehmet Ali; Karakoyun, Suleyman; Balkanay, Mehmet

2012-02-01

Obstruction to a prosthetic cardiac valve is a well-recognized complication of cardiac valve replacement. Malfunction of the mobile component of a prosthetic valve to open or close correctly may occur in consequence of intrinsic or extrinsic causes (thrombus, vegetation, entrapment of left ventricular myocardium, suture entanglement, and pannus formation) that may result prosthetic valve stenosis and/or insufficiency. In the case we report a 48-year-old female with valve dysfunction occurred early after surgery, as one valve leaflet was only able to partially open due to suture entrapment. © 2011, Wiley Periodicals, Inc.

Force measuring valve assemblies, systems including such valve assemblies and related methods

Science.gov (United States)

DeWall, Kevin George [Pocatello, ID; Garcia, Humberto Enrique [Idaho Falls, ID; McKellar, Michael George [Idaho Falls, ID

2012-04-17

Methods of evaluating a fluid condition may include stroking a valve member and measuring a force acting on the valve member during the stroke. Methods of evaluating a fluid condition may include measuring a force acting on a valve member in the presence of fluid flow over a period of time and evaluating at least one of the frequency of changes in the measured force over the period of time and the magnitude of the changes in the measured force over the period of time to identify the presence of an anomaly in a fluid flow and, optionally, its estimated location. Methods of evaluating a valve condition may include directing a fluid flow through a valve while stroking a valve member, measuring a force acting on the valve member during the stroke, and comparing the measured force to a reference force. Valve assemblies and related systems are also disclosed.

Three-dimentional simulation of flow-induced platelet activation in artificial heart valves

Science.gov (United States)

Hedayat, Mohammadali; Asgharzadeh, Hafez; Borazjani, Iman

2015-11-01

Since the advent of heart valve, several valve types such as mechanical and bio-prosthetic valves have been designed. Mechanical Heart Valves (MHV) are durable but suffer from thromboembolic complications that caused by shear-induced platelet activation near the valve region. Bio-prosthetic Heart Valves (BHV) are known for better hemodynamics. However, they usually have a short average life time. Realistic simulations of heart valves in combination with platelet activation models can lead to a better understanding of the potential risk of thrombus formation in such devices. In this study, an Eulerian approach is developed to calculate the platelet activation in three-dimensional simulations of flow through MHV and BHV using a parallel overset-curvilinear immersed boundary technique. A curvilinear body-fitted grid is used for the flow simulation through the anatomic aorta, while the sharp-interface immersed boundary method is used for simulation of the Left Ventricle (LV) with prescribed motion. In addition, dynamics of valves were calculated numerically using under-relaxed strong-coupling algorithm. Finally, the platelet activation results for BMV and MHV are compared with each other.

Magnetically operated check valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-06-01

A magnetically operated check valve is disclosed. The valve is comprised of a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

Analysis of vibration of exhaust valve pipeline in nuclear power plant

International Nuclear Information System (INIS)

Tan Ping

2005-01-01

Pipeline system for conveying pressurized steam often operates under time-varying conditions due to the valve operations. This may cause vibration problems as a result the pipeline system suffered vibration damage. In this paper, a finite element formulation for the exhaust dynamic equations that include the effect of all pipe supports, and hangers is introduced and applied to the dynamic analysis of the pipeline system used in a nuclear power plant. the vibration response of steam-conveying pipeline induced by valve exhaust has been studied. The model is validated with a fieldwork experimental pipeline system. the mechanical vibrations from steam exhaust valves can be eliminated by careful design of the valve plug and seat. (authors)

Effects of valve characteristics and pipe diameter on water hammer phenomena

International Nuclear Information System (INIS)

Hur, J.; Kim, T. H.; Mun, B. H.; Choi, H. Y.; Lee, K. W.; Noh, T. S.

2001-01-01

The water hammer phenomena mean that the dynamic loads are induced on the pipe, the pipe support and the equipments in the system due to the sudden change of the flow velocity inside the pipe. The sudden changes are mainly caused by the valve sudden on/off and pump sudden start/trip. To develop a selection criterion of the parts to be analyzed for the water hammer, the effects of the valve characteristics and pipe diameter on the water hammer are analyzed. The analyses using Method of Characteristics (MOC) show that the effects of the valve pressure difference and the valve opening time are very significant, but the effects of the pipe diameter are not dominant

Mitral valve prolapse: an underestimated cause of sudden cardiac death-a current review of the literature.

Science.gov (United States)

Spartalis, Michael; Tzatzaki, Eleni; Spartalis, Eleftherios; Athanasiou, Antonios; Moris, Demetrios; Damaskos, Christos; Garmpis, Nikolaos; Voudris, Vassilis

2017-12-01

Mitral valve prolapse (MVP) is a common valve abnormality in general population. Despite the general belief of a benign disorder, several articles since the 1980s report sudden cardiac death (SCD) in MVP patients, with a substantial percentage of asymptomatic young individuals. The problem is to detect those patients at increased risk and implement methods that are suitable to prevent cardiac arrest. This review investigates the correlation between MVP and SCD, the understanding of the pathophysiology, the strategies for detecting those at risk and treatment options. A complete literature survey was performed using PubMed database search to gather available information regarding MVP and SCD. A total of 33 studies met selection criteria for inclusion in the review. MVP is an underrated cause of arrhythmic SCD. The subset of patients with malignant MVP who may be at greater risk for SCD is characterized by young women with bileaflet MVP, biphasic or inverted T waves in the inferior leads, and frequent complex ventricular ectopic activity with documented ventricular bigeminy or ventricular tachycardia (VT) and premature ventricular contractions (PVCs) configurations of outflow tract alternating with fascicular origin or papillary muscle. MVP is a common condition in the general population and is often encountered in asymptomatic individuals. The existing literature continues to generate significant controversy regarding the association of MVP with ventricular arrhythmias and SCD. Early echocardiography and cardiac magnetic resonance (CMR) are essential, as is a greater understanding of the potential electrophysiological processes of primary arrhythmogenesis and the evaluation of the genetic substrate.

A remote control valve

International Nuclear Information System (INIS)

Cachard, Maurice de; Dumont, Maurice.

1976-01-01

This invention concerns a remote control valve for shutting off or distributing a fluid flowing at a high rate and low pressure. Among the different valves at present in use, electric valves are the most recommended for remote control but their reliability is uncertain and they soon become costly when large diameter valves are used. The valve described in this invention does away with this drawback owing to its simplicity and the small number of moving parts, this makes it particularly reliable. It mainly includes: a tubular body fitted with at least one side opening; at least one valve wedge for this opening, coaxial with the body, and mobile; a mobile piston integral with this wedge. Several valves to the specifications of this invention can be fitted in series (a shut-off valve can be used in conjunction with one or more distribution valves). The fitting and maintenance of the valve is very simple owing to its design. It can be fabricated in any material such as metals, alloys, plastics and concrete. The structure of the valve prevents the flowing fluid from coming into contact with the outside environment, thereby making it particularly suitable in the handling of dangerous or corrosive fluids. Finally, the opening and shutting of the valve occurs slowly, thereby doing away with the water hammer effect so frequent in large bore pipes [fr

Very long-term results (more than 20 years) of valve repair with carpentier's techniques in nonrheumatic mitral valve insufficiency.

Science.gov (United States)

Braunberger, E; Deloche, A; Berrebi, A; Abdallah, F; Celestin, J A; Meimoun, P; Chatellier, G; Chauvaud, S; Fabiani, J N; Carpentier, A

2001-09-18

Mitral valve repair is considered the gold standard in surgery of degenerative mitral valve insufficiency (MVI), but the long-term results (>20 years) are unknown. We reviewed the first 162 consecutive patients who underwent mitral valve repair between 1970 and 1984 for MVI due to nonrheumatic disease. The cause of MVI was degenerative in 146 patients (90%) and bacterial endocarditis in 16 patients (10%). MVI was isolated or, in 18 cases, associated with tricuspid insufficiency. The mean age of the 162 patients (104 men and 58 women) was 56+/-10 years (age range 22 to 77 years). New York Heart Association functional class was I, II, III, and IV in 2%, 39%, 52%, and 7% of patients, respectively. The mean cardiothoracic ratio was 0.58+/-0.07 (0.4 to 0.8), and 72 (45%) patients had atrial fibrillation. Valve analysis showed that the main mechanism of MVI was type II Carpentier's functional classification in 152 patients. The leaflet prolapse involved the posterior leaflet in 93 patients, the anterior leaflet in 28 patients, and both leaflets in 31 patients. Surgical technique included a Carpentier's ring annuloplasty in all cases, a valve resection in 126 patients, and shortening or transposition of chordae in 49 patients. During the first postoperative month, there were 3 deaths (1.9%) and 3 reoperations (2 valve replacements and 1 repeat repair [1.9%]). Six patients were lost to follow-up. The remaining 151 patients with mitral valve repair were followed during a median of 17 years (range 1 to 29 years; 2273 patient-years). The 20-year Kaplan-Meier survival rate was 48% (95% CI 40% to 57%), which is similar to the survival rate for a normal population with the same age structure. The 20-year rates were 19.3% (95% CI 11% to 27%) for cardiac death and 26% (95% CI 17% to 35%) for cardiac morbidity/mortality (including death from a cardiac cause, stroke, and reoperation). During the 20 years of follow-up, 7 patients were underwent surgery at 3, 7, 7, 8, 8, 10, or 12

Valve Corporation: Composing Internal Markets

OpenAIRE

Todd R. Zenger

2015-01-01

Discussions of the Valve Corporation are always enlightening. The skeptic wonders how much is rhetoric and recruiting ploy and how much is real. Is there clear evidence that this organizational design actually works – that it is efficient in this setting? While revenues per employee are quite remarkable, cause and effect are unclear. Is “boss-less-ness” the cause of high sales per employee or simply the result of high sales per employee, fueled from earlier success? The same question could be...

Quantifying spatial and temporal patterns of flow intermittency using spatially contiguous runoff data

Science.gov (United States)

Yu (于松延), Songyan; Bond, Nick R.; Bunn, Stuart E.; Xu, Zongxue; Kennard, Mark J.

2018-04-01

River channel drying caused by intermittent stream flow is a widely-recognized factor shaping stream ecosystems. There is a strong need to quantify the distribution of intermittent streams across catchments to inform management. However, observational gauge networks provide only point estimates of streamflow variation. Increasingly, this limitation is being overcome through the use of spatially contiguous estimates of the terrestrial water-balance, which can also assist in estimating runoff and streamflow at large-spatial scales. Here we proposed an approach to quantifying spatial and temporal variation in monthly flow intermittency throughout river networks in eastern Australia. We aggregated gridded (5 × 5 km) monthly water-balance data with a hierarchically nested catchment dataset to simulate catchment runoff accumulation throughout river networks from 1900 to 2016. We also predicted zero flow duration for the entire river network by developing a robust predictive model relating measured zero flow duration (% months) to environmental predictor variables (based on 43 stream gauges). We then combined these datasets by using the predicted zero flow duration from the regression model to determine appropriate 'zero' flow thresholds for the modelled discharge data, which varied spatially across the catchments examined. Finally, based on modelled discharge data and identified actual zero flow thresholds, we derived summary metrics describing flow intermittency across the catchment (mean flow duration and coefficient-of-variation in flow permanence from 1900 to 2016). We also classified the relative degree of flow intermittency annually to characterise temporal variation in flow intermittency. Results showed that the degree of flow intermittency varied substantially across streams in eastern Australia, ranging from perennial streams flowing permanently (11-12 months) to strongly intermittent streams flowing 4 months or less of year. Results also showed that the

Pressure locking and thermal binding of gate valves

Energy Technology Data Exchange (ETDEWEB)

Kelly, E.M.

1996-12-01

Pressure locking and thermal binding represent potential common mode failure mechanisms that can cause safety-related power-operated gate valves to fail in the closed position, thus rendering redundant safety-related systems incapable of performing their safety functions. Supplement 6 to Generic Letter 89-10, {open_quotes}Safety-Related Motor-Operated Gate Valve Testing and Surveillance,{close_quotes} provided an acceptable approach to addressing pressure locking and thermal binding of gate valves. More recently, the NRC has issued Generic Letter 95-07, {open_quotes}Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves,{close_quotes} to request that licensees take certain actions to ensure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of performing their safety functions within the current licensing bases. Over the past two years, several plants in Region I determined that valves in certain systems were potentially susceptible to pressure locking and thermal binding, and have taken various corrective actions. The NRC Region I Systems Engineering Branch has been actively involved in the inspection of licensee actions in response to the pressure locking and thermal binding issue. Region I continues to maintain an active involvement in this area, including participation with the Office of Nuclear Reactor Regulation in reviewing licensee responses to Generic Letter 95-07.

Isolation valve control device for nuclear power plant

International Nuclear Information System (INIS)

Yukinori, Shigeru.

1990-01-01

The present invention provides an isolation valve control device for detecting pipeline rupture accidents in a BWR type nuclear power plant at an early stage to close an isolation valve thereby reducing the amout of radioactivity released to the circumstance. That is, isolation valves are disposed in the pipeline for each of the systems in the nuclear power plant and flow ratemeters are disposed to at least two positions in each of the pipelines. If a meaningful difference is shown for the measured values by these flow ratemeters, the isolation valve is closed. In this way, if pipeline rupture such as leak before break (LBB) is caused to a portion of a system pipelines, the measured value from the flow ratemeters at the downstream of the pipeline is lowered. Accordingly, when a meaningful difference is formed between the value of the flow ratematers at the upstream and the downstream, occurrence of pipe rutpture between both of the flow ratemeters can be detected. As a result, the isolation valves of the system can be closed. According to the present invention, it is possible to detect the pipeline rupture at an early stage irrespective of the kind of the systems, diameter of the pipelines and the magnitude of the ruptured area, and the isolation valve can be closed. (I.S.)

Infective Endocarditis of the Aortic Valve with Anterior Mitral Valve Leaflet Aneurysm

NARCIS (Netherlands)

Tomsic, Anton; Li, Wilson W. L.; van Paridon, Marieke; Bindraban, Navin R.; de Mol, Bas A. J. M.

2016-01-01

Mitral valve leaflet aneurysm is a rare and potentially devastating complication of aortic valve endocarditis. We report the case of a 48-year-old man who had endocarditis of the native aortic valve and a concomitant aneurysm of the anterior mitral valve leaflet. Severe mitral regurgitation occurred

The effect of intermittent fasting on blood pressure variability in patients with newly diagnosed hypertension or prehypertension.

Science.gov (United States)

Erdem, Yunus; Özkan, Gülsüm; Ulusoy, Şükrü; Arıcı, Mustafa; Derici, Ülver; Şengül, Şule; Sindel, Şükrü; Ertürk, Şehsuvar

2018-01-01

Intermittent fasting is a phenomenon which can be observed in most humans. The effect of intermittent fasting on blood pressure variability (BPV) has not previously been investigated. The purpose of this study was to assess the effect of fasting on blood pressure (BP) (with office, home, central, and ambulatory blood pressure monitoring [ABPM]) and on BPV. Sixty individuals were included in the study. Office, home, ABPM, and central BP measurements were performed before and during intermittent fasting. Standard deviation and coefficient variation were used for office and home BPV measurement, while the smoothness index was used to calculate ABPM variability. Patients' BP and BPV values before and during intermittent fasting were then compared. Intermittent fasting resulted in a significant decrease in office BP values and ABPM measurements but caused no significant change in home and central BP measurements. Twenty-four hour urinary sodium excretion decreased. Smoothness values obtained from ABPM measurements were low; in other words, BPV was greater. BPV was higher in patients who woke up to eat before sunrise, but BPV was low in patients with high body mass index. Intermittent fasting produced a significant decrease in BP values in terms of office and ABPM measurements in this study but caused no significant change in central BP and home measurements. We also identified an increase in BPV during intermittent fasting, particularly in patients who rose before sunrise. Copyright © 2017 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

Outcomes of Aortic Valve-Sparing Operations in Marfan Syndrome.

Science.gov (United States)

David, Tirone E; David, Carolyn M; Manlhiot, Cedric; Colman, Jack; Crean, Andrew M; Bradley, Timothy

2015-09-29

In many cardiac units, aortic valve-sparing operations have become the preferred surgical procedure to treat aortic root aneurysm in patients with Marfan syndrome, based on relatively short-term outcomes. This study examined the long-term outcomes of aortic valve-sparing operations in patients with Marfan syndrome. All patients with Marfan syndrome operated on for aortic root aneurysm from 1988 through 2012 were followed prospectively for a median of 10 years. Follow-up was 100% complete. Time-to-event analyses were calculated using the Kaplan-Meier method with log-rank test for comparisons. A total of 146 patients with Marfan syndrome had aortic valve-sparing operations. Reimplantation of the aortic valve was performed in 121 and remodeling of the aortic root was performed in 25 patients. Mean age was 35.7 ± 11.4 years and two-thirds were men. Nine patients had acute, 2 had chronic type A, and 3 had chronic type B aortic dissections before surgery. There were 1 operative and 6 late deaths, 5 caused by complications of dissections. Mortality rate at 15 years was 6.8 ± 2.9%, higher than the general population matched for age and sex. Five patients required reoperation on the aortic valve: 2 for endocarditis and 3 for aortic insufficiency. Three patients developed severe, 4 moderate, and 3 mild-to-moderate aortic insufficiency. Rate of aortic insufficiency at 15 years was 7.9 ± 3.3%, lower after reimplantation than remodeling. Nine patients developed new distal aortic dissections during follow-up. Rate of dissection at 15 years was 16.5 ± 3.4%. Aortic valve-sparing operations in patients with Marfan syndrome were associated with low rates of valve-related complications in long-term follow-up. Residual and new aortic dissections were the leading cause of death. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Aortic valve insufficiency in the teenager and young adult: the role of prosthetic valve replacement.

Science.gov (United States)

Bradley, Scott M

2013-10-01

The contents of this article were presented in the session "Aortic insufficiency in the teenager" at the congenital parallel symposium of the 2013 Society of Thoracic Surgeons (STS) annual meeting. The accompanying articles detail the approaches of aortic valve repair and the Ross procedure.(1,2) The current article focuses on prosthetic valve replacement. For many young patients requiring aortic valve surgery, either aortic valve repair or a Ross procedure provides a good option. The advantages include avoidance of anticoagulation and potential for growth. In other patients, a prosthetic valve is an appropriate alternative. This article discusses the current state of knowledge regarding mechanical and bioprosthetic valve prostheses and their specific advantages relative to valve repair or a Ross procedure. In current practice, young patients requiring aortic valve surgery frequently undergo valve replacement with a prosthetic valve. In STS adult cardiac database, among patients ≤30 years of age undergoing aortic valve surgery, 34% had placement of a mechanical valve, 51% had placement of a bioprosthetic valve, 9% had aortic valve repair, and 2% had a Ross procedure. In the STS congenital database, among patients 12 to 30 years of age undergoing aortic valve surgery, 21% had placement of a mechanical valve, 18% had placement of a bioprosthetic valve, 30% had aortic valve repair, and 24% had a Ross procedure. In the future, the balance among these options may be altered by design improvements in prosthetic valves, alternatives to warfarin, the development of new patch materials for valve repair, and techniques to avoid Ross autograft failure.

Leaflet escape in a new bileaflet mechanical valve: TRI technologies.

Science.gov (United States)

Bottio, Tomaso; Casarotto, Dino; Thiene, Gaetano; Caprili, Luca; Angelini, Annalisa; Gerosa, Gino

2003-05-13

Leaflet escape is a mode of structural valve failure for mechanical prostheses. This complication previously has been reported for both monoleaflet and bileaflet valve models. We report 2 leaflet escape occurrences observed in 2 patients who underwent valve replacement with a TRI Technologies valve prosthesis. At the University of Padua, between November 2000 and February 2002, 36 TRI Technologies valve prostheses (26 aortic and 10 mitral) were implanted in 34 patients (12 women and 22 men) with a mean age of 59.9+/-10.3 years (range, 30 to 75 years). There were 5 deaths: 3 in hospital, 1 early after discharge, and 1 late. Two patients experienced a catastrophic prosthetic leaflet escape; the first patient was a 52-year-old man who died 10 days after aortic valve and ascending aorta replacement, and the second was a 58-year-old man who underwent a successful emergency reoperation 20 months after mitral valve replacement. Examination of the explanted prostheses showed in both cases a leaflet escape caused by a leaflet's pivoting system fracture. Prophylactic replacement was then successfully accomplished so far in 12 patients, without evidence of structural valve failure in any of them. Among other significant postoperative complications, we observed 3 major thromboembolisms, 1 hemorrhage, and 1 paravalvular leak. These catastrophes prompted us to interrupt the implantation program, and they cast a shadow on the durability of the TRI Technologies valve prosthesis because of its high risk of structural failure.

Transcatheter aortic valve-in-valve treatment of degenerative stentless supra-annular Freedom Solo valves: A single centre experience.

Science.gov (United States)

Cockburn, James; Dooley, Maureen; Parker, Jessica; Hill, Andrew; Hutchinson, Nevil; de Belder, Adam; Trivedi, Uday; Hildick-Smith, David

2017-02-15

Redo surgery for degenerative bioprosthetic aortic valves is associated with significant morbidity and mortality. Report results of valve-in-valve therapy (ViV-TAVI) in failed supra-annular stentless Freedom Solo (FS) bioprostheses, which are the highest risk for coronary occlusion. Six patients with FS valves (mean age 78.5 years, 50% males). Five had valvular restenosis (peak gradient 87.2 mm Hg, valve area 0.63 cm 2 ), one had severe regurgitation (AR). Median time to failure was 7 years. Patients were high risk (mean STS/Logistic EuroScore 10.6 15.8, respectively). FS valves ranged from 21 to 25 mm. Successful ViV-TAVI was achieved in 4/6 patients (67%). Of the unsuccessful cases, (patient 1 and 2 of series) patient 1 underwent BAV with simultaneous aortography which revealed left main stem occlusion. The procedure was stopped and the patient went forward for repeat surgery. Patient 2 underwent successful ViV-TAVI with a 26-mm CoreValve with a guide catheter in the left main, but on removal coronary obstruction occurred, necessitating valve snaring into the aorta. Among the successful cases, (patients 3, 4, 5, 6) the TAVIs used were CoreValve Evolut R 23 mm (n = 3), and Lotus 23 mm (n = 1). In the successful cases the peak gradient fell from 83.0 to 38.3 mm Hg. No patient was left with >1+ AR. One patient had a stroke on Day 2, with full neurological recovery. Two patients underwent semi-elective pacing for LBBB and PR >280 ms. ViV-TAVI in stentless Freedom Solo valves is high risk. The risk of coronary occlusion is high. The smallest possible prosthesis (1:1 sizing) should be used, and strategies to protect the coronary vessels must be considered. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Intermittency in branching models

International Nuclear Information System (INIS)

Chiu, C.B.; Texas Univ., Austin; Hwa, R.C.; Oregon Univ., Eugene

1990-01-01

The intermittency properties of three branching models have been investigated. The factorial moments show power-law behavior as function of small rapidity width. The slopes and energy dependences reveal different characteristics of the models. The gluon model has the weakest intermittency. (orig.)

Left-sided native valve Staphylococcus aureus endocarditis

NARCIS (Netherlands)

Slabbekoorn, M.; Horlings, H. M.; van der Meer, J. T. M.; Windhausen, A.; Van der Sloot, J. A. P.; Lagrand, W. K.

2010-01-01

Despite improved diagnostic tools and expanded treatment options, left-sided native valve endocarditis caused by Staphylococcus aureus infection remains a serious and destructive disease. The high morbidity and mortality, however, can be reduced by early recognition, correct diagnosis, and

Which valve is which?

Directory of Open Access Journals (Sweden)

Pravin Saxena

2015-01-01

Full Text Available A 25-year-old man presented with a history of breathlessness for the past 2 years. He had a history of operation for Tetralogy of Fallot at the age of 5 years and history suggestive of Rheumatic fever at the age of 7 years. On echocardiographic examination, all his heart valves were severely regurgitating. Morphologically, all the valves were irreparable. The ejection fraction was 35%. He underwent quadruple valve replacement. The aortic and mitral valves were replaced by metallic valve and the tricuspid and pulmonary by tissue valve.

Cor triatriatum dexter: A rare cause of cyanosis during neonatal period.

Science.gov (United States)

Alghamdi, Mohammed Hussien

2016-01-01

Cor-triatriatum dexter is an extremely rare congenital heart defect in which there is complete persistence of the right valve of embryonic sinus venosus that results in partitioning of the right atrium into a smooth and trabeculated portion. The smooth portion receives venous blood from inferior vena cava, superior vena cava, and coronary sinus while the trabeculated portion contains the right atrial appendage and the opening of tricuspid valve. We report a 1-week-old child who presented with intermittent episodes of central cyanosis. Echocardiography, established, and bubble contrast study confirmed the diagnosis of an isolated cor-triatriatum dexter. The baby initially underwent an intervention by cardiac catheterization, which was unsuccessful in disrupting the membrane and re-direct the systemic venous flow to the right heart chambers. She subsequently had the cor-triatriatum dexter membrane resected via an uncomplicated open-heart surgery.

Anterior Urethral Valves

Directory of Open Access Journals (Sweden)

Vidyadhar P. Mali

2006-07-01

Full Text Available We studied the clinical presentation and management of four patients with anterior urethral valves; a rare cause of urethral obstruction in male children. One patient presented antenatally with oligohydramnios, bilateral hydronephrosis and bladder thickening suggestive of an infravesical obstruction. Two other patients presented postnatally at 1 and 2 years of age, respectively, with poor stream of urine since birth. The fourth patient presented at 9 years with frequency and dysuria. Diagnosis was established on either micturating cystourethrogram (MCU (in 2 or on cystoscopy (in 2. All patients had cystoscopic ablation of the valves. One patient developed a postablation stricture that was resected with an end-to-end urethroplasty. He had an associated bilateral vesicoureteric junction (VUJ obstruction for which a bilateral ureteric reimplantation was done at the same time. On long-term follow-up, all patients demonstrated a good stream of urine. The renal function is normal. Patients are continent and free of urinary infections. Anterior urethral valves are rare obstructive lesions in male children. The degree of obstruction is variable, and so they may present with mild micturition difficulty or severe obstruction with hydroureteronephrosis and renal impairment. Hence, it is important to evaluate the anterior urethra in any male child with suspected infravesical obstruction. The diagnosis is established by MCU or cystoscopy and the treatment is always surgical, either a transurethral ablation or an open resection. The long-term prognosis is good.

PARAMETER ESTIMATION OF VALVE STICTION USING ANT COLONY OPTIMIZATION

Directory of Open Access Journals (Sweden)

S. Kalaivani

2012-07-01

Full Text Available In this paper, a procedure for quantifying valve stiction in control loops based on ant colony optimization has been proposed. Pneumatic control valves are widely used in the process industry. The control valve contains non-linearities such as stiction, backlash, and deadband that in turn cause oscillations in the process output. Stiction is one of the long-standing problems and it is the most severe problem in the control valves. Thus the measurement data from an oscillating control loop can be used as a possible diagnostic signal to provide an estimate of the stiction magnitude. Quantification of control valve stiction is still a challenging issue. Prior to doing stiction detection and quantification, it is necessary to choose a suitable model structure to describe control-valve stiction. To understand the stiction phenomenon, the Stenman model is used. Ant Colony Optimization (ACO, an intelligent swarm algorithm, proves effective in various fields. The ACO algorithm is inspired from the natural trail following behaviour of ants. The parameters of the Stenman model are estimated using ant colony optimization, from the input-output data by minimizing the error between the actual stiction model output and the simulated stiction model output. Using ant colony optimization, Stenman model with known nonlinear structure and unknown parameters can be estimated.

Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve

DEFF Research Database (Denmark)

Aagaard, Jan; Geha, Alexander S.

2007-01-01

BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area....... This study evaluates the authors' clinical experience with Top Hat supra-annular aortic valve size selection, and the technical aspects of implantation. METHODS: Between January 1999 and October 2005, a total of 251 consecutive patients underwent 252 aortic valve replacements with Top Hat supra...... required unplanned coronary bypass, and 30-day mortality was 2.0% (5/251), indicating a good safety profile for the valves implanted in this series. CONCLUSION: The general distribution of implant sizes in the US indicates that cardiac surgeons may be under-sizing the Top Hat supra-annular aortic valve...

Autopsy after transcatheter aortic valve implantation

NARCIS (Netherlands)

van Kesteren, F.; Wiegerinck, E. M. A.; Rizzo, S.; Baan, J.; Planken, R. N.; von der Thüsen, J. H.; Niessen, H. W. M.; van Oosterhout, M. F. M.; Pucci, A.; Thiene, G.; Basso, C.; Sheppard, M. N.; Wassilew, K.; van der Wal, A. C.

2017-01-01

Autopsy after transcatheter aortic valve implantation (TAVI) is a new field of interest in cardiovascular pathology. To identify the cause of death, it is important to be familiar with specific findings related to the time interval between the procedure and death. We aimed to provide an overview of

Dynamics of the nozzle valve with regard to the properties of the piping system

Directory of Open Access Journals (Sweden)

Klas Roman

2018-01-01

Full Text Available It is obvious that the main function of the nozzle valve is to shut off the stream of fluid in the piping system. The response rate of the valve to the decreasing or reversing flow in the system will then depend on the valve properties and equally on the properties of the piping system. The interaction of these two elements is also important for the origin of pressure pulsations in the system. While the pressure pulsations were the cause for design of this particular valve it should be noted that the general design of the valve for any pipeline system is not possible. The valve cannot properly work under all circumstances and operating conditions. With respect to this, the dynamic properties of the valve will be assessed on the basis of the valve equation of motion and the pipeline model. An adequate response of the whole system can be obtained by combining both approaches. The valve equations of motion are also complemented by CFD simulations, which enable to capture the movement of the valve disc with respect to flow rate.

Metabolic Effects of Intermittent Fasting.

Science.gov (United States)

Patterson, Ruth E; Sears, Dorothy D

2017-08-21

The objective of this review is to provide an overview of intermittent fasting regimens, summarize the evidence on the health benefits of intermittent fasting, and discuss physiological mechanisms by which intermittent fasting might lead to improved health outcomes. A MEDLINE search was performed using PubMed and the terms "intermittent fasting," "fasting," "time-restricted feeding," and "food timing." Modified fasting regimens appear to promote weight loss and may improve metabolic health. Several lines of evidence also support the hypothesis that eating patterns that reduce or eliminate nighttime eating and prolong nightly fasting intervals may result in sustained improvements in human health. Intermittent fasting regimens are hypothesized to influence metabolic regulation via effects on (a) circadian biology, (b) the gut microbiome, and (c) modifiable lifestyle behaviors, such as sleep. If proven to be efficacious, these eating regimens offer promising nonpharmacological approaches to improving health at the population level, with multiple public health benefits.

Investigation of valve failure problems in LWR power plants

International Nuclear Information System (INIS)

1980-04-01

An analysis of component failures from information in the computerized Nuclear Safety Information Center (NSIC) data bank shows that for both PWR and BWR plants the component category most responsible for approximately 19.3% of light water reactor (LWR) power plant shutdowns. This investigation by Burns and Roe, Inc. shows that the greatest cause of shutdowns in LWRs due to valve failures is leakage from valve stem packing. Both BWR plants and PWR plants have stem leakage problems

AREVA's innovative solutions for valve diagnostics and in-situ valve repair

International Nuclear Information System (INIS)

Damies, H.; Breitenberger, U.; Munoz, L.; Kostroun, F.

2012-01-01

Optimized maintenance strategies are a key aspect for safe and undisturbed plant operation. Innovative valve service solutions can support that in an efficient way. The ADAM®/SIPLUG® valve monitoring system allows full online monitoring of valves and actuators with automatic evaluation and assessment. Especially for safety-related and operation-related valves this provides valuable information on components condition to ensure proper function and contribute to optimization of maintenance strategies as well as effective maintenance performance. More than 25 years of experience in various plants worldwide show that application of ADAM®/SIPLUG® valve diagnostics solution leads to increased plant safety and availability. With the innovative AVARIS technology an in-situ valve repair is possible. It has the unique ability to conduct several steps in-situ, to maintain the sealing seat of gate or check valves. By applying AVARIS, the valve is restored in its original state, the system remains unchanged. Thus, all original documents remain valid and applicable. In comparison to previous procedures like cutting valves out of the pipeline and repairing hard facings or damaged seal seats in a separate workshop or alternatively replacement by a new valve body the new AVARIS technology avoids costs, risk and effort. (author)

HDR-investigations of check valve closure and resultant water hammer effects

International Nuclear Information System (INIS)

Scholl, K.D.

1983-01-01

The presented investigations are based on the Loss of Coolant Accident (LOCA). They concentrate on the first blowdown phase after pipe break of a feedwater line. The effect of such a break is moderated by quick closing check valves, by which the loss of coolant water is reduced and optimal post accident conditions are obtained. Unfortunately the closure of the valve can cause high pressure peaks (water hammer effects) in the feedwater system which potentially could produce safety relevant secondary damage. The system loading by these effects has been analysed. The HDR-Investigation-results led to an improvement of the feedwater system safety by verifying damping measures of quick closing check valves. Pressure peaks obtained with undamped valves in the range of 300 bars, are reduced to zero or a few bars above the normal operation pressure in feedwater systems. For the analytical simulation of valve closure the following dominant acting forces are identified: the blowdown flow resistance of the valve cone and the damping pistong force. The analytical description and quantification of the forces depends on blowdown flow and valve friction parameters. These have been evaluated and are presented for practical use. (orig.)

Prosthetic valve endocarditis after transcatheter aortic valve implantation

DEFF Research Database (Denmark)

Olsen, Niels Thue; De Backer, Ole; Thyregod, Hans G H

2015-01-01

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is an advancing mode of treatment for inoperable or high-risk patients with aortic stenosis. Prosthetic valve endocarditis (PVE) after TAVI is a serious complication, but only limited data exist on its incidence, outcome, and procedural......%) were treated conservatively and 1 with surgery. Four patients (22%) died from endocarditis or complications to treatment, 2 of those (11%) during initial hospitalization for PVE. An increased risk of TAVI-PVE was seen in patients with low implanted valve position (hazard ratio, 2.8 [1.1-7.2]), moderate...

Valve monitoring ITI-MOVATS

International Nuclear Information System (INIS)

Moureau, S.

1993-01-01

ITI-MOVATS provides a wide range of test devices to monitor the performance of valves: motor operated gate or globe valve, butterfly valve, air operated valve, and check valve. The ITI-MOVATS testing equipment is used in the following three areas: actuator setup/baseline testing, periodic/post-maintenance testing, and differential pressure testing. The parameters typically measured with the MOVATS diagnostic system as well as the devices used to measure them are described. (Z.S.)

The nordic aortic valve intervention (NOTION) trial comparing transcatheter versus surgical valve implantation

DEFF Research Database (Denmark)

Thyregod, Hans Gustav; Søndergaard, Lars; Ihlemann, Nikolaj

2013-01-01

Degenerative aortic valve (AV) stenosis is the most prevalent heart valve disease in the western world. Surgical aortic valve replacement (SAVR) has until recently been the standard of treatment for patients with severe AV stenosis. Whether transcatheter aortic valve implantation (TAVI) can...

Gasoline New Timing and Flux Adjustable Rotary Valve Design (Hereinafter: Rotary Valve

Directory of Open Access Journals (Sweden)

Du huiqi

2016-01-01

Full Text Available Conventional gasoline engine with an umbrella valve control cylinder intake and exhaust, in order to achieve sealing effect, the valve is driven by the spring force; at the same time, when the cam opens the valve to overcome the spring force acting. Sealing the better, the more power consumed in the engine mechanical losses, the valve mechanism consumes about 30%, which is not a small loss! This article describes a new type of rotary valve is to significantly reduce mechanical losses, so as to achieve energy saving purposes.

Fluid control valves

International Nuclear Information System (INIS)

Rankin, J.

1980-01-01

A fluid control valve is described in which it is not necessary to insert a hand or a tool into the housing to remove the valve seat. Such a valve is particularly suitable for the control of radioactive fluids since maintenance by remote control is possible. (UK)

What Is Heart Valve Surgery?

Science.gov (United States)

... working correctly. Most valve replacements involve the aortic Tricuspid valve and mitral valves. The aortic valve separates ... where it shouldn’t. This is called incompetence, insufficiency or regurgitation. • Prolapse — mitral valve flaps don’t ...

What Is Heart Valve Disease?

Science.gov (United States)

... and replacing it with a man-made or biological valve. Biological valves are made from pig, cow, or human ... the valve. Man-made valves last longer than biological valves and usually don’t have to be ...

Relief valve testing study

International Nuclear Information System (INIS)

BROMM, R.D.

2001-01-01

Reclosing pressure-actuated valves, commonly called relief valves, are designed to relieve system pressure once it reaches the set point of the valve. They generally operate either proportional to the differential between their set pressure and the system pressure (gradual lift) or by rapidly opening fully when the set pressure is reached (pop action). A pop action valve allows the maximum fluid flow through the valve when the set pressure is reached. A gradual lift valve allows fluid flow in proportion to how much the system pressure has exceeded the set pressure of the valve (in the case of pressure relief) or has decreased below the set pressure (vacuum relief). These valves are used to protect systems from over and under pressurization. They are used on boilers, pressure vessels, piping systems and vacuum systems to prevent catastrophic failures of these systems, which can happen if they are under or over pressurized beyond the material tolerances. The construction of these valves ranges from extreme precision of less than a psi tolerance and a very short lifetime to extremely robust construction such as those used on historic railroad steam engines that are designed operate many times a day without changing their set pressure when the engines are operating. Relief valves can be designed to be immune to the effects of back pressure or to be vulnerable to it. Which type of valve to use depends upon the design requirements of the system

Isolated mitral valve prolapse: chordal architecture as an anatomic basis in older patients

NARCIS (Netherlands)

van der Bel-Kahn, J.; Duren, D. R.; Becker, A. E.

1985-01-01

Ten patients with an average age of 58 years underwent valve replacement because of isolated mitral valve prolapse with severe regurgitation. None had clinical evidence of Marfan's syndrome or another systemic disease that would indicate that a primary connective tissue disorder was the cause of the

3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV.

Science.gov (United States)

D'Avenio, Giuseppe; Grigioni, Mauro; Daniele, Carla; Morbiducci, Umberto; Hamilton, Kathrin

2015-01-01

Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs. The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis. A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry. The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

Application Of Light Valves For Continuous-Tone Printing

Science.gov (United States)

Vergona, Albert B.

1989-07-01

New opportunities are emerging in the graphic-arts pre-press market stimulated by the need for digitally created images. To meet this need, we have designed a cost-effective three-color digital printer using PLZT light valves. Transparent lead lanthanum zirconate titanate (PLZT) ceramic crystals when used as a linear modulator offer a number of significant benefits. The primary advantage is that the light valve is an efficient modulator of incoherent light providing a broad spectral output ranging from 400nm to well into the infrared region. In addition, light valves offer the advantages of being small, low cost, have a wide dynamic range (>1000 to 1), and can be used with simple optical designs. The characteristics of the PLZT material plays an important role in the performance of the light valve. A number of variables such as ceramic composition, electrode spacing, and ceramic thickness can be altered to affect its quadratic electrooptic behavior. Additionally, the modulator design requires a closed-loop servo to eliminate the errors caused by the device's remanent polarization and nonlinear behavior.

Prosthetic tricuspid valve dysfunction assessed by three-dimensional transthoracic and transesophageal echocardiography.

Science.gov (United States)

Yuasa, Toshinori; Takasaki, Kunitsugu; Mizukami, Naoko; Ueya, Nami; Kubota, Kayoko; Horizoe, Yoshihisa; Chaen, Hideto; Kuwahara, Eiji; Kisanuki, Akira; Hamasaki, Shuichi

2013-09-01

A 39-year-old male who had undergone tricuspid valve replacement for severe tricuspid regurgitation was admitted with palpitation and general edema. Two-dimensional (2D) echocardiography showed tricuspid prosthetic valve dysfunction. Additional three-dimensional (3D) transthoracic and transesophageal echocardiography (TEE) could clearly demonstrate the disabilities of the mechanical tricuspid valve. Particularly, 3D TEE demonstrated a mass located on the right ventricular side of the tricuspid prosthesis, which may have caused the stuck disk. This observation was confirmed by intra-operative findings.

[Aortic valve insufficiency due to rupture of the cusp in a patient with multiple trauma].

Science.gov (United States)

Vidmar, J; Brilej, D; Voga, G; Kovacic, N; Smrkolj, V

2003-06-01

Lesions of the heart valve caused by blunt chest trauma is rare, but when it does occur it can significantly injure the patient. On the basis of autopsy studies, research shows that heart valves are injured in less than 5% of patients who have died due to impact thoracic trauma. Among the heart valves, the aortic valve is the most often lacerated, which has been proved by relevant autopsy and clinical studies. Aortic valve lesions can be the only injury, but it is possible that additional heart or large vessel injuries are also present (myocardial contusion, rupture of the atrial septum, aortic rupture, rupture of the left common carotid artery). The force that causes such an injury is often great and often causes injuries to other organs and organ systems. In a multiple trauma patient, it is very important to specifically look for heart-related injuries because it is possible that they may be overlooked or missed by the surgeon, because of other obvious injuries. We describe the case of a 41-year-old man with multiple trauma who was diagnosed with aortic valve insufficiency due to rupture of the left coronary cusp 6 weeks after a road accident. Valvuloplasty was performed. Seven years later the patient is free of symptoms and is in good physical condition. Echocardiography showed normal dimensions of the heart chambers, a normal thickness of the heart walls, and normal systolic and diastolic function of the left ventricle. Heart valves are morphologically normal, and only an unimportant aortic insufficiency was noticed by echocardiography.

Comparative study between CardiaMed valves (freely floating valve leaflets versus St. Jude Medical (fixed valve leaflets in mitral valve replacement surgery

Directory of Open Access Journals (Sweden)

Mostafa Ahmed

2017-09-01

Conclusions: CardiaMed freely floating leaflet prostheses showed good hemodynamic characteristics. The prosthesis adequately corrects hemodynamics and is safe and no worse than the St. Jude Medical valve in the mitral valve position.

Acute intermittent porphyria: Diagnostic dilemma and treatment options

Directory of Open Access Journals (Sweden)

Mohan Deep Kaur

2015-01-01

Full Text Available Acute intermittent porphyria (AIP presents with diverse group of symptoms making its early diagnosis difficult. Delaying diagnosis and treatment of AIP can be fatal or can cause long term or permanent neurological damage. We present here a case report of AIP where the diagnosis was missed. The diversity of symptoms and details concerning the treatment options for AIP are discussed.

Acute intermittent porphyria: Diagnostic dilemma and treatment options

Science.gov (United States)

Kaur, Mohan Deep; Hazarika, Nita; Saraswat, Namita; Sood, Rajesh

2015-01-01

Acute intermittent porphyria (AIP) presents with diverse group of symptoms making its early diagnosis difficult. Delaying diagnosis and treatment of AIP can be fatal or can cause long term or permanent neurological damage. We present here a case report of AIP where the diagnosis was missed. The diversity of symptoms and details concerning the treatment options for AIP are discussed. PMID:26330726

Electromagnetically powered electrolytic pump and thermo-responsive valve for drug delivery

KAUST Repository

Yi, Ying; Zaher, Amir; Yassine, Omar; Buttner, Ulrich; Kosel, Jü rgen; Foulds, Ian G.

2015-01-01

A novel drug delivery device is presented, implementing an electrolytic pump and a thermo-responsive valve. The device is remotely operated by an AC electromagnetic field (40.5∼58.5 mT, 450 kHz) that provides the power for the pump and the valve. It is suitable for long-term therapy applications, which use a solid drug in reservoir (SDR) approach and avoids unwanted drug diffusion. When the electromagnetic field is on, the electrolytic pump drives the drug towards the valve. The valve is made of a magnetic composite consisting of a smart hydrogel: Poly (N-Isopropylacrylamide) (PNIPAm) and iron powder. The heat generated in the iron powder via magnetic losses causes the PNIPAm to shrink, allowing the drug to flow past it. When the electromagnetic field is off, the PNIPAm swells, sealing the outlet. In the meantime, the bubbles generated by electrolysis recombine into water, causing a pressure reduction in the pumping chamber. This draws fresh fluid from outside the pump into the drug reservoir before the valve is fully sealed. The recombination can be accelerated by a platinum (Pt) coated catalytic reformer, allowing more fluid to flow back to the drug reservoir and dissolve the drug. By repeatedly turning on and off the magnetic field, the drug solution can be delivered cyclically. © 2015 IEEE.

Electromagnetically powered electrolytic pump and thermo-responsive valve for drug delivery

KAUST Repository

Yi, Ying

2015-04-01

A novel drug delivery device is presented, implementing an electrolytic pump and a thermo-responsive valve. The device is remotely operated by an AC electromagnetic field (40.5∼58.5 mT, 450 kHz) that provides the power for the pump and the valve. It is suitable for long-term therapy applications, which use a solid drug in reservoir (SDR) approach and avoids unwanted drug diffusion. When the electromagnetic field is on, the electrolytic pump drives the drug towards the valve. The valve is made of a magnetic composite consisting of a smart hydrogel: Poly (N-Isopropylacrylamide) (PNIPAm) and iron powder. The heat generated in the iron powder via magnetic losses causes the PNIPAm to shrink, allowing the drug to flow past it. When the electromagnetic field is off, the PNIPAm swells, sealing the outlet. In the meantime, the bubbles generated by electrolysis recombine into water, causing a pressure reduction in the pumping chamber. This draws fresh fluid from outside the pump into the drug reservoir before the valve is fully sealed. The recombination can be accelerated by a platinum (Pt) coated catalytic reformer, allowing more fluid to flow back to the drug reservoir and dissolve the drug. By repeatedly turning on and off the magnetic field, the drug solution can be delivered cyclically. © 2015 IEEE.

Piezoelectric valve for massive gas injection in ASDEX upgrade

Energy Technology Data Exchange (ETDEWEB)

Dibon, Mathias; Neu, Rudolf [Max-Planck-Institute for Plasmaphysics, Boltzmannstr. 2, 85748 Garching (Germany); Technical University Munich, Boltzmannstr. 15, 85748 Garching (Germany); Herrmann, Albrecht; Mank, Klaus; Mertens, Vitus; Pautasso, Gabriella; Ploeckl, Bernhard [Max-Planck-Institute for Plasmaphysics, Boltzmannstr. 2, 85748 Garching (Germany)

2016-07-01

A sudden loss of plasma temperature can cause a disruption, which poses a significant problem for current Tokamaks and future fusion devices. Hence, mitigating forces and thermal loads during disruptions is important for the integrity of the vessel and first wall components. Therefore, high speed gas valves are used to deliver a pulse of noble gas onto the plasma, which irradiates the thermal energy quickly, avoiding localized heat loads and mechanical stress due to induced currents. A new design for such a valve is currently under development. The valve plate is driven by two piezoelectric stack actuators. The stroke of the actuators (0.07 mm) is amplified by a monolithic titanium frame and reaches 2 mm. The frame also serves as spring to pre-load the actuators. In the idle state, it also presses the conical valve plate into the seal, closing the gas chamber (42 cm{sup 3}). The actuators accelerate the stem and the valve plate until it is fully opened after 2 ms. The orifice of the valve has a diameter of 14 mm. This allows a peak mass flow rate of the gas up to 8 . 10{sup 4} (Pa.m)/(s) after 1.8 ms and an average mass flow rate of 2 . 10{sup 4} (Pa.m)/(s) over the evacuation time of 10 ms. Therefore, one valve would be sufficient to deliver the required amount of gas to mitigate disruptions at ASDEX Upgrade.

Transapical JenaValve in a patient with mechanical mitral valve prosthesis.

LENUS (Irish Health Repository)

O' Sullivan, Katie E

2014-01-29

We report the first case of transcatheter aortic valve replacement implantation using JenaValve™ in a patient with mechanical mitral valve prosthesis. We believe that the design features of this valve may be particularly suited for use in this setting. © 2014 Wiley Periodicals, Inc.

Workshop on gate valve pressure locking and thermal binding

International Nuclear Information System (INIS)

Brown, E.J.

1995-07-01

The purpose of the Workshop on Gate Valve Pressure Locking and Thermal Binding was to discuss pressure locking and thermal binding issues that could lead to inoperable gate valves in both boiling water and pressurized water reactors. The goal was to foster exchange of information to develop the technical bases to understand the phenomena, identify the components that are susceptible, discuss actual events, discuss the safety significance, and illustrate known corrective actions that can prevent or limit the occurrence of pressure locking or thermal binding. The presentations were structured to cover U.S. Nuclear Regulatory Commission staff evaluation of operating experience and planned regulatory activity; industry discussions of specific events, including foreign experience, and efforts to determine causes and alleviate the affects; and valve vendor experience and recommended corrective action. The discussions indicated that identifying valves susceptible to pressure locking and thermal binding was a complex process involving knowledge of components, systems, and plant operations. The corrective action options are varied and straightforward

A review of historical check valve failure data

International Nuclear Information System (INIS)

Casada, D.A.; Todd, M.D.

1992-01-01

Check valve operating problems in recent years have resulted in significant operating transients, increased cost, and decreased system availability. In response, additional attention has been given to check valves by utilities, as well as the US Nuclear Regulatory Commission (NRC) and the American Society of Mechanical Engineers Operation and Maintenance Committee. All these organizations have the fundamental goal of ensuring reliable operation of check valves. A key ingredient of an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. Oak Ridge National Laboratory is currently conducting a detailed review of historical failure data available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System. The focus of the review is on check valve failures that have involved significant degradation of the valve internal parts. A variety of parameters are being considered during the review, including size, age, system of service, method of failure discovery, the affected valve parts, attributed causes, and corrective actions. This work is being carried out under the auspices of the NRC's Nuclear Plant Aging Research program. At this time, the study is approximately 50% complete. All failure records have been reviewed and categorized, and preliminary tabulation and correlation of data is underway. The bulk of the tabulation and correlation portion of the work is expected to be completed by the end of June 1992. A report draft is expected in the fall of 1992

Butterfly valves for seawater

International Nuclear Information System (INIS)

Yamanaka, Katsuto

1991-01-01

Recently in thermal and nuclear power stations and chemical plants which have become large capacity, large quantity of cooling water is required, and mostly seawater is utilized. In these cooling water systems, considering thermal efficiency and economy, the pipings become complex, and various control functions are demanded. For the purpose, the installation of shut-off valves and control valves for pipings is necessary. The various types of valves have been employed, and in particular, butterfly valves have many merits in their function, size, structure, operation, maintenance, usable period, price and so on. The corrosion behavior of seawater is complicated due to the pollution of seawater, therefore, the environment of the valves used for seawater became severe. The structure and the features of the butterfly valves for seawater, the change of the structure of the butterfly valves for seawater and the checkup of the butterfly valves for seawater are reported. The corrosion of metallic materials is complicatedly different due to the locating condition of plants, the state of pipings and the condition of use. The corrosion countermeasures for butterfly valves must be examined from the synthetic viewpoints. (K.I.)

Cosmic Rays in Intermittent Magnetic Fields

International Nuclear Information System (INIS)

Shukurov, Anvar; Seta, Amit; Bushby, Paul J.; Wood, Toby S.; Snodin, Andrew P.

2017-01-01

The propagation of cosmic rays in turbulent magnetic fields is a diffusive process driven by the scattering of the charged particles by random magnetic fluctuations. Such fields are usually highly intermittent, consisting of intense magnetic filaments and ribbons surrounded by weaker, unstructured fluctuations. Studies of cosmic-ray propagation have largely overlooked intermittency, instead adopting Gaussian random magnetic fields. Using test particle simulations, we calculate cosmic-ray diffusivity in intermittent, dynamo-generated magnetic fields. The results are compared with those obtained from non-intermittent magnetic fields having identical power spectra. The presence of magnetic intermittency significantly enhances cosmic-ray diffusion over a wide range of particle energies. We demonstrate that the results can be interpreted in terms of a correlated random walk.

Cosmic Rays in Intermittent Magnetic Fields

Energy Technology Data Exchange (ETDEWEB)

Shukurov, Anvar; Seta, Amit; Bushby, Paul J.; Wood, Toby S. [School of Mathematics and Statistics, Newcastle University, Newcastle Upon Tyne NE1 7RU (United Kingdom); Snodin, Andrew P., E-mail: a.seta1@ncl.ac.uk, E-mail: amitseta90@gmail.com [Department of Mathematics, Faculty of Applied Science, King Mongkut’s University of Technology North Bangkok, Bangkok 10800 (Thailand)

2017-04-10

The propagation of cosmic rays in turbulent magnetic fields is a diffusive process driven by the scattering of the charged particles by random magnetic fluctuations. Such fields are usually highly intermittent, consisting of intense magnetic filaments and ribbons surrounded by weaker, unstructured fluctuations. Studies of cosmic-ray propagation have largely overlooked intermittency, instead adopting Gaussian random magnetic fields. Using test particle simulations, we calculate cosmic-ray diffusivity in intermittent, dynamo-generated magnetic fields. The results are compared with those obtained from non-intermittent magnetic fields having identical power spectra. The presence of magnetic intermittency significantly enhances cosmic-ray diffusion over a wide range of particle energies. We demonstrate that the results can be interpreted in terms of a correlated random walk.

Supra-annular valve strategy for an early degenerated transcatheter balloon-expandable heart valve.

Science.gov (United States)

Kamioka, Norihiko; Caughron, Hope; Corrigan, Frank; Block, Peter; Babaliaros, Vasilis

2018-01-23

Currently, there are no recommendations regarding the selection of valve type for a transcatheter heart valve (THV)-in-THV procedure. A supra-annular valve design may be superior in that it results in a larger effective orifice area and may have a lower chance of valve thrombosis after THV-in-THV. In this report, we describe the use of a supra-annular valve strategy for an early degenerated THV. © 2018 Wiley Periodicals, Inc.

Investigation of valve failure problems in LWR power plants

Energy Technology Data Exchange (ETDEWEB)

None

1980-04-01

An analysis of component failures from information in the computerized Nuclear Safety Information Center (NSIC) data bank shows that for both PWR and BWR plants the component category most responsible for approximately 19.3% of light water reactor (LWR) power plant shutdowns. This investigation by Burns and Roe, Inc. shows that the greatest cause of shutdowns in LWRs due to valve failures is leakage from valve stem packing. Both BWR plants and PWR plants have stem leakage problems (BWRs, 21% and PWRs, 34%).

Investigation of intermittency in simulated and experimental turbulence data by wavelet analysis

International Nuclear Information System (INIS)

Mahdizadeh, N.; Ramisch, M.; Stroth, U.; Lechte, C.; Scott, B.D.

2004-01-01

Turbulent transport in magnetized plasmas has an intermittent nature. Peaked probability density functions and a 1/frequency decay of the power spectra have been interpreted as signs of self-organized criticality generated, similar to a sand pile, by the critical gradients of ion- (ITG) or electron-temperature-gradient (ETG) driven instabilities. In order to investigate the degree of intermittency in toroidally confined plasmas in the absence of critical pressure or temperature gradients, data from the drift-Alfven-wave turbulence code DALF3 [B. Scott, Plasma Phys. Controlled Fusion 39, 1635 (1997)], running with a fixed background pressure gradient, and from a weakly driven low-temperature plasma are analyzed. The intermittency is studied on different temporal scales, which are separated by a wavelet transform. Simulated and experimental data reproduce the results on intermittent transport found in fusion plasmas. It can therefore be expected that in fusion plasmas, too, a substantial fraction of the bursty nature of turbulent transport is not related to avalanches caused by a critical gradient as generated by ITG or ETG turbulence

Outcomes in nonagenarians after heart valve replacement operation.

Science.gov (United States)

Edwards, Maria-Benedicta; Taylor, Kenneth M

2003-03-01

Changes in the age profile of the United Kingdom population and improvements in preoperative and postoperative care have resulted in increasing numbers of very elderly patients undergoing heart valve replacement (HVR) operations. Although HVR operations in nonagenarians are relatively uncommon, the demand for cardiac operations in this age group may increase over time. Outcomes after HVR operations in nonagenarians have not been well described yet. Therefore, the aim of this study was to determine outcomes in terms of early mortality and long-term survival in 35 nonagenarians after HVR operation. Data from the United Kingdom Heart Valve Registry were analyzed and nonagenarian patients were identified. Additional analyzed data include gender, valve position, valve type, valve size, operative priority, follow-up time, and date and cause of death. Kaplan-Meier actuarial curves were calculated to determine accurate 30-day mortality and long-term survival. On average five HVR operations are performed annually in the United Kingdom in nonagenarians with equal numbers of males and females. Aortic valve replacement with a bioprosthetic valve was the most common operation and 86% were elective admissions. Fourteen patients died within the review period; mean time to death was 402 days. Overall 30-day mortality was 17%, which was higher for males compared with females; females also displayed better long-term survival. HVR operations in nonagenarians carry a significantly higher risk of early mortality and reduced long-term survival. Despite increases in the age profile of the population, elective HVR operation with patients aged 90 years or older is likely to remain an infrequent surgical procedure reserved for very carefully selected patients.

Modeling valve leakage

International Nuclear Information System (INIS)

Bell, S.R.; Rohrscheib, R.

1994-01-01

The American Society of Mechanical Engineers (ASME) Code requires individual valve leakage testing for Category A valves. Although the U.S. Nuclear Regulatory Commission (USNRC) has recognized that it is more appropriate to test containment isolation valves in groups, as allowed by 10 CFR 50, Appendix J, a utility seeking relief from these Code requirements must provide technical justification for the relief and establish a conservative alternate acceptance criteria. In order to provide technical justification for group testing of containment isolation valves, Illinois Power developed a calculation (model) for determining the size of a leakage pathway in a valve disc or seat for a given leakage rate. The model was verified experimentally by machining leakage pathways of known size and then measuring the leakage and comparing this value to the calculated value. For the range of values typical of leakage rate testing, the correlation between the experimental values and calculated values was quote good. Based upon these results, Illinois Power established a conservative acceptance criteria for all valves in the inservice testing (IST) program and was granted relief by the USNRC from the individual leakage testing requirements of the ASME Code. This paper presents the results of Illinois Power's work in the area of valve leakage rate testing

The serpentine mitral valve and cerebral embolism

Directory of Open Access Journals (Sweden)

Ker James

2011-02-01

Full Text Available Abstract Valvular strands, well-delineated filiform masses, attached to cardiac valve edges are associated with cerebral embolism and stroke. Strokes, caused by emboli from valvular strands, tend to occur among younger persons. In this case report a valvular strand, giving a peculiar serpentine appearance to the mitral valve is described. This mitral valvular strand was the only explanation for an episode of cerebral embolism, presenting with a transient right sided hemiparesis. It is proposed that a randomized study involving combined treatment with aspirin and clopidogrel is warranted in young patients with valvular strands, presenting with a first episode of cerebral embolism.

Preventative valve-sparing aortic root replacement and pregnancy outcome in Marfan syndrome.

Science.gov (United States)

Sokol, Vesna; Zlopasa, Gordan; Herman, Mislav; Planinić, Pavao; Micevska, Ana

2012-06-01

In Marfan syndrome, with dilatation of the aortic root secondary to an underlying connective tissue defect, pregnancy can cause hemodynamic stress leading to the development of an aortic aneurysm and even a fatal aortic dissection. In the presence of existing aortic root enlargement and a family history of aortic dissection, preventative elective surgery is suggested. Aortic root replacement with or without a valve-sparing procedure is superior to total aortic root replacement with prosthetic valve/tube graft. It provides excellent survival with low rates of aortic - valve related complications.

Use of a valve operation test and evaluation system to enhance valve reliability

International Nuclear Information System (INIS)

Lowry, D.A.

1990-01-01

Power plant owners have emphasized the need for assuring safe, reliable operation of valves. While most valves must simply open or close, the mechanisms involved can be quite complex. Motor operated valves (MOVs) must be properly adjusted to assure operability. Individual operator components determine the performance of the entire MOV. Failure in MOVs could cripple or shut down a unit. Thus, a complete valve program consisting of design reviews, operational testing, and preventive and predictive maintenance activities will enhance an owner's confidence level that his valves win operate as expected. Liberty's Valve Operation Test and Evaluation System (VOTES) accurately measures stein thrust without intruding on valve operation. Since mounting a strain gage to a valve stem is a desirable but impractical way of obtaining precise stem thrust, Liberty developed a method to obtain identical data by placing a strain gage sensor on the valve yoke. VOTES provides information which effectively eliminates costly, unscheduled downtime. This paper presents the results of infield VOTES testing. The system's proven ability to identify and characterize actuator and valve performance is demonstrated. Specific topics of discussion include the ability of VOTES to ease a utility's IE Bulletin 8543 concerns and conclusively diagnose MOV components. Data from static and differential pressure testing are presented. Technical, operational, and financial advantages resulting from VOTES technology are explored in detail

Multiple-port valve

International Nuclear Information System (INIS)

Doody, T.J.

1978-01-01

A multiple-port valve assembly is designed to direct flow from a primary conduit into any one of a plurality of secondary conduits as well as to direct a reverse flow. The valve includes two mating hemispherical sockets that rotatably receive a spherical valve plug. The valve plug is attached to the primary conduit and includes diverging passageways from that conduit to a plurality of ports. Each of the ports is alignable with one or more of a plurality of secondary conduits fitting into one of the hemispherical sockets. The other hemispherical socket includes a slot for the primary conduit such that the conduit's motion along that slot with rotation of the spherical plug about various axes will position the valve-plug ports in respect to the secondary conduits

Intermittent Smoothing Approaches for Wind Power Output: A Review

Directory of Open Access Journals (Sweden)

Muhammad Jabir

2017-10-01

Full Text Available Wind energy is one of the most common types of renewable energy resource. Due to its sustainability and environmental benefits, it is an emerging source for electric power generation. Rapid and random changes of wind speed makes it an irregular and inconsistent power source when connected to the grid, causing different technical problems in protection, power quality and generation dispatch control. Due to these problems, effective intermittent smoothing approaches for wind power output are crucially needed to minimize such problems. This paper reviews various intermittent smoothing approaches used in smoothing the output power fluctuations caused by wind energy. Problems associated with the inclusion of wind energy resources to grid are also briefly reviewed. From this review, it has been found that battery energy storage system is the most suitable and effective smoothing approach, provided that an effective control strategy is available for optimal utilization of battery energy system. This paper further demonstrates different control strategies built for battery energy storage system to obtain the smooth output wind power.

Infective endocarditis caused by Neisseria elongata on a native tricuspid valve and confirmed by DNA sequencing.

Science.gov (United States)

Yoo, Yeon Pyo; Kang, Ki-Woon; Yoon, Hyeon Soo; Yoo, Seungmin; Lee, Myung-Shin

2014-04-01

Neisseria elongata, a common oral bacterium, has been recognized as a cause of infections such as infective endocarditis, septicemia, and osteomyelitis. Neisseria-induced infective endocarditis, although infrequently reported, typically arises after dental procedures. Without antibiotic therapy, its complications can be severe. We report the case of a 27-year-old man who presented with fever, severe dyspnea, and a leg abscess from cellulitis. An echocardiogram showed a vegetation-like echogenic structure on the septal leaflet of the patient's native tricuspid valve, and an insignificant Gerbode defect. Three blood cultures grew gram-negative, antibiotic-susceptible coccobacilli that were confirmed to be N. elongata. Subsequent DNA sequencing conclusively isolated N. elongata subsp nitroreducens as the organism responsible for the infective endocarditis. The patient recovered after 21 days of antibiotic therapy. In addition to the patient's unusual case, we discuss the nature and isolation of N. elongata and its subspecies.

Nuclear reactor steam depressurization valve

International Nuclear Information System (INIS)

Moore, G.L.

1991-01-01

This patent describes improvement in a nuclear reactor plant, an improved steam depressurization valve positioned intermediate along a steam discharge pipe for controlling the venting of steam pressure from the reactor through the pipe. The improvement comprises: a housing including a domed cover forming a chamber and having a partition plate dividing the chamber into a fluid pressure activation compartment and a steam flow control compartment, the valve housing being provided with an inlet connection and an outlet connection in the steam flow control compartment, and a fluid duct in communication with a source of fluid pressure for operating the valve; a valve set mounted within the fluid flow control compartment comprising a cylindrical section surrounding the inlet connection with one end adjoining the connection and having a radially projecting flange at the other end with a contoured extended valve sealing flange provided with an annular valve sealing member, and a valve cylinder traversing the partition plate and reciprocally movable within an opening in the partition plate with one terminal and extending into the fluid pressure activation compartment and the other terminal end extending into the steam flow control compartment coaxially aligned with the valve seat surrounding the inlet connection, the valve cylinder being surrounded by two bellow fluid seals and provided with guides to inhibit lateral movement, an end of the valve cylinder extending into the fluid flow control compartment having a radially projecting flange substantially conterminous with the valve seat flange and having a contoured surface facing and complimentary to the contoured valve seating surface whereby the two contoured valve surfaces can meet in matching relationship, thus providing a pressure actuated reciprocatable valve member for making closing contact with the valve seat and withdrawing therefrom for opening fluid flow through the valve

Redo mitral valve surgery

Directory of Open Access Journals (Sweden)

Redoy Ranjan

2018-03-01

Full Text Available This study is based on the findings of a single surgeon’s practice of mitral valve replacement of 167 patients from April 2005 to June 2017 who developed symptomatic mitral restenosis after closed or open mitral commisurotomy. Both clinical and color doppler echocardiographic data of peri-operative and six months follow-up period were evaluated and compared to assess the early outcome of the redo mitral valve surgery. With male-female ratio of 1: 2.2 and after a duration of 6 to 22 years symptom free interval between the redo procedures, the selected patients with mitral valve restenosis undergone valve replacement with either mechanical valve in 62% cases and also tissue valve in 38% cases. Particular emphasis was given to separate the adhered pericardium from the heart completely to ameliorate base to apex and global contraction of the heart. Besides favorable post-operative clinical outcome, the echocardiographic findings were also encouraging as there was statistically significant increase in the mitral valve area and ejection fraction with significant decrease in the left atrial diameter, pressure gradient across the mitral valve and pulmonary artery systolic pressure. Therefore, in case of inevitable mitral restenosis after closed or open commisurotomy, mitral valve replacement is a promising treatment modality.

Double-disc gate valve

International Nuclear Information System (INIS)

Wheatley, S.J.

1979-01-01

The invention relates to an improvement in a conventional double-disc gate valve having a vertically movable gate assembly including a wedge, spreaders slidably engaged therewith, a valve disc carried by the spreaders. When the gate assembly is lowered to a selected point in the valve casing, the valve discs are moved transversely outward to close inlet and outlet ports in the casing. The valve includes hold-down means for guiding the disc-and-spreader assemblies as they are moved transversely outward and inward. If such valves are operated at relatively high differential pressures, they sometimes jam during opening. Such jamming has been a problem for many years in gate valves used in gaseous diffusion plants for the separation of uranium isotopes. The invention is based on the finding that the above-mentioned jamming results when the outlet disc tilts about its horizontal axis in a certain way during opening of the valve. In accordance with the invention, tilting of the outlet disc is maintained at a tolerable value by providing the disc with a rigid downwardly extending member and by providing the casing with a stop for limiting inward arcuate movement of the member to a preselected value during opening of the valve

Intro to Valve Guide Reconditioning. Automotive Mechanics. Valves. Instructor's Guide [and] Student Guide.

Science.gov (United States)

Horner, W.

This instructional package, one in a series of individualized instructional units on tools and techniques for repairing worn valve guides in motor vehicles, provides practical experience for students in working on cylinder heads. Covered in the module are reaming valve guides that are oversized to match a new oversized valve, reaming valve guides…

Guide to prosthetic cardiac valves

International Nuclear Information System (INIS)

Morse, D.; Steiner, R.M.; Fernandez, J.

1985-01-01

This book contains 10 chapters. Some of the chapter titles are: The development of artificial heart valves: Introduction and historical perspective; The radiology of prosthetic heart valves; The evaluation of patients for prosthetic valve implantation; Pathology of cardiac valve replacement; and Bioengineering of mechanical and biological heart valve substitutes

Prolapsed bilateral ureteroceles leading to intermittent outflow obstruction.

LENUS (Irish Health Repository)

Stunell, H

2012-02-01

A ureterocele refers to a cystic dilatation of the distal ureter. It may be unilateral or bilateral and may be associated with a duplex system in some cases. We present an unusual case where a young patient was found to have large bilateral ureteroceles which prolapsed into the urethra, causing intermittent incontinence and obstruction. We discuss the case and review the literature concerning this rare anomaly.

Trans-apical aortic valve implantation in a patient with stentless valve degeneration.

Science.gov (United States)

Kapetanakis, Emmanouil I; MacCarthy, Philip; Monaghan, Mark; Wendler, Olaf

2011-06-01

Trans-apical valve-in-valve trans-catheter aortic valve implantation (TAVI) has successfully been performed in selected, high-risk patients, who suffered prosthetic degeneration after aortic valve replacement using stented xenografts. We report the case of a 79-year-old male patient who underwent one of the first successful TAVIs in a failing stentless bioprosthesis. Copyright © 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.

Early clinical outcome of aortic transcatheter valve-in-valve implantation in the Nordic countries

DEFF Research Database (Denmark)

Ihlberg, Leo; Nissen, Henrik Hoffmann; Nielsen, Niels Erik

2013-01-01

Transcatheter valve-in-valve implantation has emerged as an option, in addition to reoperative surgical aortic valve replacement, to treat failed biologic heart valve substitutes. However, the clinical experience with this approach is still limited. We report the comprehensive experience...

Nuclear valves latest development

International Nuclear Information System (INIS)

Isaac, F.; Monier, M.

1993-01-01

In the frame of Nuclear Power Plant upgrade (Emergency Power Supply and Emergency Core Cooling), Westinghouse had to face a new valve design philosophy specially for motor operated valves. The valves have to been designed to resist any operating conditions, postulated accident or loss of control. The requirements for motor operated valves are listed and the selected model and related upgrading explained. As part of plant upgrade and valves replacement, Westinghouse has sponsored alternative hardfacing research programme. Two types of materials have been investigated: nickel base alloys and iron base alloys. Programme requirements and test results are given. A new globe valve model (On-Off or regulating) is described developed by Alsthom Velan permitting the seat replacement in less than 10 min. (Z.S.) 2 figs

Magnetic Check Valve

Science.gov (United States)

Morris, Brian G.; Bozeman, Richard J., Jr.

1994-01-01

Poppet in proposed check valve restored to closed condition by magnetic attraction instead of spring force. Oscillations suppressed, with consequent reduction of wear. Stationary magnetic disk mounted just upstream of poppet, also containing magnet. Valve body nonmagnetic. Forward pressure or flow would push poppet away from stationary magnetic disk so fluid flows easily around poppet. Stop in valve body prevents poppet from being swept away. When flow stopped or started to reverse, magnetic attraction draws poppet back to disk. Poppet then engages floating O-ring, thereby closing valve and preventing reverse flow. Floating O-ring facilitates sealing at low loads.

Effects of valve timing, valve lift and exhaust backpressure on performance and gas exchanging of a two-stroke GDI engine with overhead valves

International Nuclear Information System (INIS)

Dalla Nora, Macklini; Lanzanova, Thompson Diórdinis Metzka; Zhao, Hua

2016-01-01

Highlights: • Two-stroke operation was achieved in a four-valve direct injection gasoline engine. • Shorter valve opening durations improved torque at lower engine speeds. • The longer the valve opening duration, the lower was the air trapping efficiency. • Higher exhaust backpressure and lower valve lift reduced the compressor work. - Abstract: The current demand for fuel efficient and lightweight powertrains, particularly for application in downsized and hybrid electric vehicles, has renewed the interest in two-stroke engines. In this framework, an overhead four-valve spark-ignition gasoline engine was modified to run in the two-stroke cycle. The scavenging process took place during a long valve overlap period around bottom dead centre at each crankshaft revolution. Boosted intake air was externally supplied at a constant pressure and gasoline was directly injected into the cylinder after valve closure. Intake and exhaust valve timings and lifts were independently varied through an electrohydraulic valve train, so their effects on engine performance and gas exchanging were investigated at 800 rpm and 2000 rpm. Different exhaust backpressures were also evaluated by means of exhaust throttling. Air trapping efficiency, charging efficiency and scavenge ratio were calculated based on air and fuel flow rates, and exhaust oxygen concentration at fuel rich conditions. The results indicated that longer intake and exhaust valve opening durations increased the charge purity and hence torque at higher engine speeds. At lower speeds, although, shorter valve opening durations increased air trapping efficiency and reduced the estimated supercharger power consumption due to lower air short-circuiting. A strong correlation was found between torque and charging efficiency, while air trapping efficiency was more associated to exhaust valve opening duration. The application of exhaust backpressure, as well as lower intake/exhaust valve lifts, made it possible to increase

Randomized, controlled trial comparing synchronized intermittent mandatory ventilation and synchronized intermittent mandatory ventilation plus pressure support in preterm infants.

Science.gov (United States)

Reyes, Zenaida C; Claure, Nelson; Tauscher, Markus K; D'Ugard, Carmen; Vanbuskirk, Silvia; Bancalari, Eduardo

2006-10-01

Prolonged mechanical ventilation is associated with lung injury in preterm infants. In these infants, weaning from synchronized intermittent mandatory ventilation may be delayed by their inability to cope with increased respiratory loads. The addition of pressure support to synchronized intermittent mandatory ventilation can offset these loads and may facilitate weaning. The purpose of this work was to compare synchronized intermittent mandatory ventilation and synchronized intermittent mandatory ventilation plus pressure support in weaning from mechanical ventilation and the duration of supplemental oxygen dependency in preterm infants with respiratory failure. Preterm infants weighing 500 to 1000 g at birth who required mechanical ventilation during the first postnatal week were randomly assigned to synchronized intermittent mandatory ventilation or synchronized intermittent mandatory ventilation plus pressure support. In both groups, weaning followed a set protocol during the first 28 days. Outcomes were assessed during the first 28 days and until discharge or death. There were 107 infants enrolled (53 synchronized intermittent mandatory ventilation plus pressure support and 54 synchronized intermittent mandatory ventilation). Demographic and perinatal data, mortality, and morbidity did not differ between groups. During the first 28 days, infants in the synchronized intermittent mandatory ventilation plus pressure support group reached minimal ventilator settings and were extubated earlier than infants in the synchronized intermittent mandatory ventilation group. Total duration of mechanical ventilation, duration of oxygen dependency, and oxygen need at 36 weeks' postmenstrual age alone or combined with death did not differ between groups. However, infants in synchronized intermittent mandatory ventilation plus pressure support within the 700- to 1000-g birth weight strata had a shorter oxygen dependency. The results of this study suggest that the addition of

Transcatheter Aortic Valve Replacement for Degenerative Bioprosthetic Surgical Valves

DEFF Research Database (Denmark)

Dvir, Danny; Webb, John; Brecker, Stephen

2012-01-01

Transcatheter aortic valve-in-valve implantation is an emerging therapeutic alternative for patients with a failed surgical bioprosthesis and may obviate the need for reoperation. We evaluated the clinical results of this technique using a large, worldwide registry....

Congenital absence of anterior papillary muscle of the tricuspid valve and surgical repair with artificial chordae.

Science.gov (United States)

Tian, Chuan; Pan, Shiwei

2017-02-01

We report the case of a 26-year old woman who underwent successful tricuspid valve repair for the absence of the anterior papillary of the tricuspid valve. Preoperative echocardiography revealed grade IV tricuspid valve regurgitation, caused by congenital absence of the anterior papillary muscle and prolapse of the anterior leaflet. Tricuspid valve repair was performed using artificial chords consisting of two polytetrafluoroethylene sutures and a concomitant ring annuloplasty. Postoperative echocardiography revealed mild tricuspid valve regurgitation. This approach represented a safe and effective technique for tricuspid valve repair in congenital absence of papillary muscle. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

A characterization of check valve degradation and failure experience in the nuclear power industry

International Nuclear Information System (INIS)

Casada, D.A.; Todd, M.D.

1993-09-01

Check valve operating problems in recent years have resulted in significant operating transients, increased cost and decreased system availability. As a result, additional attention has beau given to check valves by utilities (resulting in the formation of the Nuclear Industry Check Valve Group), as well as the US Nuclear Regulatory Commission and the American Society of Mechanical Engineers Operation and Maintenance Committee. All these organizations have the fundamental goal of ensuring reliable operation of check valves. A key ingredient to an engineering-oriented reliability improvement effort is a thorough understanding of relevant historical experience. A detailed review of historical failure data, available through the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System, has been conducted. The focus of the review is on check valve failures that have involved significant degradation of the valve internal parts. A variety of parameters are considered, including size, age, system of service, method of failure discovery, the affected valve parts, attributed causes, and corrective actions

Transcatheter aortic valve replacement

Science.gov (United States)

... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

Failure and life cycle evaluation of watering valves.

Science.gov (United States)

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-09-01

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves' internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a 'drying out' period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure.

Overflow control valve

International Nuclear Information System (INIS)

Kessinger, B.A.; Hundal, R.; Parlak, E.A.

1982-01-01

An overflow control valve for use in a liquid sodium coolant pump tank which can be remotely engaged with and disengaged from the pump tank wall to thereby permit valve removal. An actuating shaft for controlling the valve also has means for operating a sliding cylinder against a spring to retract the cylinder from sealing contact with the pump tank nozzle. (author)

Intermittency in 197Au fragmentation

International Nuclear Information System (INIS)

Dabrowska, A.; Holynski, R.; Olszewski, A.; Szarska, M.; Wilczynska, B.; Wolter, W.; Wosiek, B.; Cherry, M.L.; Deines-Jones, P.; Jones, W.V.; Sengupta, K.; Wefel, B.

1995-07-01

The concept of factorial moments was applied to an analysis of the dynamical fluctuations in the charge distributions of the fragments emitted from gold nuclei with energies 10.6 and < 1.0 GeV/n interacting with emulsion nuclei. Clear evidence for intermittent fluctuations has been found in an analysis using all the particles released from the gold projectile, with a stronger effect observed below 1 GeV/n than at 10.6 GeV/n. For the full data sets, however, the intermittency effect was found to be very sensitive to the singly charged particles, and neglecting these particles strongly reduces the intermittency signal. When the analysis is restricted to the multiply charged fragments, an intermittency effect is revealed only for multifragmentation events, although one that is enhanced as compared to the analysis of all, singly and multiply charged, particles. The properties of the anomalous fractal dimensions suggest a sequential decay mechanism, rather than the existence of possible critical behaviour in the process of nuclear fragmentation. The likely influence of the charge conservation effects and the finite size of decaying systems on the observed intermittency signals was pointed out. (author). 37 refs, 9 figs, 5 tabs

Steel castings of valves for nuclear power station

International Nuclear Information System (INIS)

Yamasaki, Yutaka

1975-01-01

The manufacturing of the steel castings of valves for nuclear power plants is reported. The report is divided in six parts. The first part describes the reliability of the steel castings of valves for nuclear power plants. Particular attention must be paid to larger diameter and lower pressure rating for the valves in nuclear power plants than those in thermal power plants. The second part describes the characteristics of steel casting quality, defects and their cause. The defects that may be produced in steel castings are as follows: (a) cavities caused by the insufficient supply of molten steel, (b) sand bites caused by the mold destruction due to thermal shock, and (c) pinholes caused by the gas absorption of molten steel. The third part describes the clarification of quality level and the measures quality project. Gaseous defects and the indications detected by magnetic powder test are attributed to electric furnace steel making. In particular, the method to minimize gas content is important. The fourth part describes the quality control of manufacturing processes. In practice, thirteen semi-automatic testers using gamma radiation are employed. A full automatic inspection plant having capacity of 20,000 radiographs per month is under design. The fifth part describes a quality warrant system. A check sheet system concerning quality and safety is employed in all work shops. The reliability of all testers and measuring instruments as well as the skill of workmen are examined periodically. The seventh part deals with future problems. The manufacturing plan must be controlled so that non-destructive inspection becomes the main means for quality control. (Iwakiri, K.)

Comparative study of Butterfly valves

International Nuclear Information System (INIS)

Galmes Belmonte, F.B.

1998-01-01

This work tries to justify the hydrodynamic butterfly valves performance, using the EPRI tests, results carried out in laboratory and in situ. This justification will be possible if: - The valves to study are similar - Their performance is calculated using EPRI's methodology Looking for this objective, the elements of the present work are: 1. Brief EPRI butterfly valve description it wild provide the factors which are necessary to define the butterfly valves similarity. 2. EPRI tests description and range of validation against test data definition. 3. Description of the spanish butterfly analyzed valves, and comparison with the EPRI performance results, to prove that this valves are similar to the EPRI test valves. In this way, it will not be necessary to carry out particular dynamic tests on the spanish valves to describe their hydrodynamic performance. (Author)

Fluid mechanics of heart valves.

Science.gov (United States)

Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S

2004-01-01

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Intelligent Flow Control Valve

Science.gov (United States)

Kelley, Anthony R (Inventor)

2015-01-01

The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.

The organ specificity in pathological damage of chronic intermittent hypoxia: an experimental study on rat with high-fat diet.

Science.gov (United States)

Wang, Hui; Tian, Jian-li; Feng, Shu-zhi; Sun, Ning; Chen, Bao-yuan; Zhang, Yun

2013-09-01

It is known today that sleep apnea hypopnea syndrome and its characteristic chronic intermittent hypoxia can cause damages to multiple organs, including the cardiovascular system, urinary system, and liver. It is still unclear, however, whether the damage caused by sleep apnea hypopnea syndrome and the severity of the damage are organ-specific. This research observed the pathological effects of chronic intermittent hypoxia on rat's thoracic aorta, myocardium, liver, and kidney, under the condition of lipid metabolism disturbance, through establishing the rat model of chronic intermittent hypoxia with high-fat diet by imitating the features of human sleep apnea hypopnea syndrome. In this model, 24 male Wistar rats were randomly divided into three groups: a control group fed by regular diet, a high-fat group fed by high-fat diet, and a high-fat plus intermittent hypoxia group fed by high-fat diet and treated with intermittent hypoxia 7 h a day. At the end of the ninth week, the pathological changes of rat's organs, including the thoracic aorta, myocardium, liver, and kidney are observed (under both optical microscopy and transmission electron microscopy). As the result of the experiment shows, while there was no abnormal effect observed on any organs of the control group, slight pathological changes were found in the organs of the high-fat group. For the high-fat plus intermittent hypoxia group, however, remarkably severer damages were found on all the organs. It also showed that the severity of the damage varies by organ in the high-fat plus intermittent hypoxia group, with the thoracic aorta being the worst, followed by the liver and myocardium, and the kidney being the slightest. Chronic intermittent hypoxia can lead to multiple-organ damage to rat with high-fat diet. Different organs appear to have different sensitivity to chronic intermittent hypoxia.

Causes and indications for reoperation in valve replacement and coronary artery bypass graft (CABG in 915 patients in cardiac surgery department in Imam Khomeini Hospital, 1374-77

Directory of Open Access Journals (Sweden)

Radmehr H

2001-08-01

Full Text Available Valvular and coronary artery disease are among the most important causes of disability and death in the world and Iran as well. Every year, half a million death because of these diseases is reported in United State. The incidence of degenerative and valvular diseases of heart is increasing. Considering the industrialization of our country, the incidence of these kind of problems are increasing as well. In this study, there is an attempt to recognize the causes of cardiac surgery. We conducted a retrospective study in 915 cardiac surgery patients (630 CABG and 285 valve replacement from 1374 to 1377. In CABG patients, there were 46 cases of reoperation (78.3 percent male 21.7 percent female. The most reoperations for bleeding was less than 24 hours in 90.3 percent. In valvular patients the causes of reoperation were: A Valvular complications (female/male=3/1, B Non valvular complications (female/male=1/3. The most common nonvalvular complication was bleeding (66.6 percent. The most common valvular complication was bioprosthetic valve degeneration. The meantime between two operation in valvular complications was 11.8 years. In all cases (915 the incidence of bleeding was 3.8 percent, mediastinitis 0.8 percent, cardiac tamponade 0.8 percent and GI bleeding 0.5 percent.

Experience with valves for PHWR reactors

International Nuclear Information System (INIS)

Narayan, K.; Mhetre, S.G.

1977-01-01

Material specifications and inspection and testing requirements of the valves meant for use in nuclear reactors are mentioned. In the heavy water systems (both primary and moderator) of a PHWR type reactor, the valves used are gate valves, globe valves, diaphragm valves, butterfly valves, check valves and relief valves. Their locations and functions they perform in the Rajasthan Atomic Power Station Unit-1 are described. Experience with them is given. The major problems encountered with them have been : (1) leakage from the stem seals and body bonnet joint, (2) leakage due to failure of diaphragm and/or washout of the packing and (3) malfunctioning. Measures taken to solve these are discussed. Finally a mention has been made of improved versions of valves, namely, metal diaphragm valve and inverted relief valve. (M.G.B.)

Leaving Moderate Tricuspid Valve Regurgitation Alone at the Time of Pulmonary Valve Replacement: A Worthwhile Approach.

Science.gov (United States)

Kogon, Brian; Mori, Makoto; Alsoufi, Bahaaldin; Kanter, Kirk; Oster, Matt

2015-06-01

Pulmonary valve disruption in patients with tetralogy of Fallot and congenital pulmonary stenosis often results in pulmonary insufficiency, right ventricular dilation, and tricuspid valve regurgitation. Management of functional tricuspid regurgitation at the time of subsequent pulmonary valve replacement remains controversial. Our aims were to (1) analyze tricuspid valve function after pulmonary valve replacement through midterm follow-up and (2) determine the benefits, if any, of concomitant tricuspid annuloplasty. Thirty-five patients with tetralogy of Fallot or congenital pulmonary stenosis were analyzed. All patients had been palliated in childhood by disrupting the pulmonary valve, and all patients had at least moderate tricuspid valve regurgitation at the time of subsequent pulmonary valve replacement. Preoperative and serial postoperative echocardiograms were analyzed. Pulmonary and tricuspid regurgitation, along with right ventricular dilation and dysfunction were scored as 0 (none), 1 (mild), 2 (moderate), and 3 (severe). Right ventricular volume and area were also calculated. Comparisons were made between patients who underwent pulmonary valve replacement alone and those who underwent concomitant tricuspid valve annuloplasty. At 1 month after pulmonary valve replacement, there were significant reductions in pulmonary valve regurgitation (mean 3 vs 0.39, p tricuspid valve regurgitation (mean 2.33 vs 1.3, p tricuspid regurgitation 1 month postoperatively between patients who underwent concomitant tricuspid annuloplasty and those who underwent pulmonary valve replacement alone (mean 1.31 vs 1.29, p = 0.81). However, at latest follow-up (mean 7.0 ± 2.8 years), the degree of tricuspid regurgitation was significantly higher in the concomitant annuloplasty group (mean 1.87 vs 1.12, p = 0.005). In patients with at least moderate tricuspid valve regurgitation, significant improvement in tricuspid valve function and right ventricular size occurs in the first

Retrieval of a leaflet escaped in a Tri-technologies bileaflet mechanical prosthetic valve.

Science.gov (United States)

Cianciulli, Tomás F; Lax, Jorge A; Saccheri, María C; Guidoin, Robert; Salvado, César M; Fernández, Adrián J; Prezioso, Horacio A

2008-01-01

The escape of the prosthetic heart valve disc is one of the causes of prosthetic dysfunction that requires emergency surgery. The removal of the embolized disc should be carried out because of the risk of a progressive extrusion on the aortic wall. Several imaging techniques can be used for the detection of the missing disc localization. In this report we describe a 32-year-old man who underwent mitral valve replacement with a Tri-technologies bileaflet valve three years ago, and was admitted in cardiogenic shock. Transesophageal echocardiography showed acute-onset massive mitral regurgitation. The patient underwent emergency replacement of the prosthetic valve. Only one of the two leaflets remained in the removed prosthetic valve. The missing leaflet could not be found within the cardiac cavity. The abdominal fluoroscopic study and plain radiography were unable to detect the escaped leaflet. The abdominal computed tomography scan and the ultrasound showed the escaped leaflet in the terminal portion of the aortic bifurcation. To retrieve the embolized disc laparotomy and aortotomy were performed three months later. The escaped leaflet shows a fracture of one of the pivot systems caused by structural failure. This kind of failure mode is usually the result of high stress concentration.

Intermittent control: a computational theory of human control.

Science.gov (United States)

Gawthrop, Peter; Loram, Ian; Lakie, Martin; Gollee, Henrik

2011-02-01

The paradigm of continuous control using internal models has advanced understanding of human motor control. However, this paradigm ignores some aspects of human control, including intermittent feedback, serial ballistic control, triggered responses and refractory periods. It is shown that event-driven intermittent control provides a framework to explain the behaviour of the human operator under a wider range of conditions than continuous control. Continuous control is included as a special case, but sampling, system matched hold, an intermittent predictor and an event trigger allow serial open-loop trajectories using intermittent feedback. The implementation here may be described as "continuous observation, intermittent action". Beyond explaining unimodal regulation distributions in common with continuous control, these features naturally explain refractoriness and bimodal stabilisation distributions observed in double stimulus tracking experiments and quiet standing, respectively. Moreover, given that human control systems contain significant time delays, a biological-cybernetic rationale favours intermittent over continuous control: intermittent predictive control is computationally less demanding than continuous predictive control. A standard continuous-time predictive control model of the human operator is used as the underlying design method for an event-driven intermittent controller. It is shown that when event thresholds are small and sampling is regular, the intermittent controller can masquerade as the underlying continuous-time controller and thus, under these conditions, the continuous-time and intermittent controller cannot be distinguished. This explains why the intermittent control hypothesis is consistent with the continuous control hypothesis for certain experimental conditions.

ICDE project report: collection and analysis of common-cause failures of motor operated valves

International Nuclear Information System (INIS)

2001-07-01

This report documents a study performed on the set of common cause failures (CCF) of motor operated valves (MOV). The data studied here were derived from the International CCF Data Exchange (ICDE) database, to which several countries have submitted CCF event data. The purpose of the ICDE is to allow multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses that include CCF modeling. Because CCF events are typically rare events, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, yields sufficient data for more rigorous analyses. This report is the result of an in-depth review of the MOV events and presents several insights about them. The objective of this document is to look beyond the CCF parameter estimates that can be obtained from the CCF data, to gain further understanding of why CCF events occur and what measures may be taken to prevent, or at least mitigate the effect of MOV CCF events. The report presents details of the ICDE project, a quantitative presentation of the MOV events, and a discussion of some engineering aspects of the events. (authors)

Spatio-temporal intermittency on the sandpile

International Nuclear Information System (INIS)

Erzan, A.; Sinha, S.

1990-08-01

The self-organized critical state exhibited by a sandpile model is shown to correspond to motion on an attractor characterized by an invariant distribution of the height variable. The largest Lyapunov exponent is equal to zero. The model nonetheless displays intermittent chaos, with a multifractal distribution of local expansion coefficients in history space. Laminar spatio-temporal regions are interrupted by chaotic bursts caused by avalanches. We introduce the concept of local histories in configuration space and show that their expansion parameters also exhibit a multifractal distribution in time and space. (author). 22 refs, 5 figs

Anesthetic Management and Complications of Percutaneous Aortic Valve Implantation

Directory of Open Access Journals (Sweden)

Tailur Alberto Grando

2013-05-01

Full Text Available Background and objective: Aortic stenosis is a highly prevalent and life-threatening disease. In elderly patients with comorbidities, percutaneous valve implantation is an option. The aim of the study was to describe the anesthetic management and complications of general anesthesia Method: Case series with 30-day and 24-month follow-ups after implantation of the CoreValve device performed at the Institute of Cardiology/University Foundation of Cardiology between December 2008 and January 2012. The patients underwent general anesthesia monitored with mean arterial pressure (PAM, electrocardiogram (ECG, pulse oximetry, capnography, transesophageal echocardiography, thermometry, and transvenous pacemaker. Results: Twenty-eight patients, mean age 82.46 years, 20.98% mean EuroSCORE, functional class III/IV, successfully underwent valve implantation. Nine patients required permanent pacemaker implantation. During follow-up, two patients died: one during surgery due to LV perforation and the other on the third day of unknown causes. At 24 months, one patient diagnosed with multiple myeloma died. This anesthetic technique proved to be safe. Conclusion: The initial experience with percutaneous aortic valve implantation under general anesthesia has proven to be safe and effective, with no significant anesthetic complications during this procedure. Keywords: Aesthesia, General, Cardiac Surgical Procedures, Aortic Valve Stenosis, Aged.

Intermittent magnetic reconnection in TS-3 merging experiment

International Nuclear Information System (INIS)

Ono, Y.; Hayashi, Y.; Ii, T.; Tanabe, H.; Ito, S.; Kuwahata, A.; Ito, T.; Kamino, Y.; Yamada, T.; Inomoto, M.

2011-01-01

Ejection of current sheet with plasma mass causes impulsive and intermittent magnetic reconnection in the TS-3 spherical tokamak (ST) merging experiment. Under high guide toroidal field, the sheet resistivity is almost classical due to the sheet thickness much longer than the ion gyroradius. Large inflow flux and low current-sheet resistivity result in flux and plasma pileup followed by rapid growth of the current sheet. When the pileup exceeds a critical limit, the sheet is ejected mechanically from the squeezed X-point area. The reconnection (outflow) speed is slow during the flux/plasma pileup and is fast during the ejection, suggesting that intermittent reconnection similar to the solar flare increases the averaged reconnection speed. These transient effects enable the merging tokamaks to have the fast reconnection as well as the high-power reconnection heating, even when their current-sheet resistivity is low under high guide field.

Hemolytic Anemia after Aortic Valve Replacement: a Case Report

Directory of Open Access Journals (Sweden)

Feridoun Sabzi

2015-10-01

Full Text Available Hemolytic anemia is exceedingly rare and an underestimated complication after aortic valve replacement (AVR.The mechanism responsible for hemolysis most commonly involves a regurgitated flow or jet that related to paravalvar leak or turbulence of subvalvar stenosis. It appears to be independent of its severity as assessed by echocardiography. We present a case of a 24-year-old man with a history of AVR in 10 year ago that developed severe hemolytic anemia due to a mild subvalvar stenosis caused by pannus formation and mild hypertrophic septum. After exclusion of other causes of hemolytic anemia and the lack of clinical and laboratory improvement, the patient underwent redo valve surgery with pannus and subvalvar hypertrophic septum resection. Anemia and heart failure symptoms gradually resolved after surgery

The Double-Orifice Valve Technique to Treat Tricuspid Valve Incompetence.

Science.gov (United States)

Hetzer, Roland; Javier, Mariano; Delmo Walter, Eva Maria

2016-01-01

A straightforward tricuspid valve (TV) repair technique was used to treat either moderate or severe functional (normal valve with dilated annulus) or for primary/organic (Ebstein's anomaly, leaflet retraction/tethering and chordal malposition/tethering, with annular dilatation) TV incompetence, and its long-term outcome assessed. A double-orifice valve technique was employed in 91 patients (mean age 52.6 ± 23.2 years; median age 56 years; range: 0.6-82 years) with severe tricuspid regurgitation. Among the patients, three had post-transplant iatrogenic chordal rupture, five had infective endocarditis, 11 had mitral valve insufficiency, 23 had Ebstein's anomaly, and 47 had isolated severe TV incompetence. The basic principle was to reduce the distance between the coapting leaflets, wherein the most mobile leaflet could coapt to the opposite leaflet, by creating two orifices, ensuring valve competence. The TV repair was performed through a median sternotomy or right anterior thoracotomy in the fifth intercostal space under cardiopulmonary bypass. The degree and extent of creating a double-valve orifice was determined by considering the minimal body surface area (BSA)-related acceptable TV diameter. Repair was accomplished by passing pledgeted mattress sutures from the middle of the true anterior annulus to a spot on the opposite septal annulus, located approximately two-thirds of the length of the septal annulus to avoid injury to the bundle of His. The annular apposition divides the TV into a larger anterior and a smaller posterior orifices, enabling valve closure, on both sides. In adults, the diameter of the anterior valve orifice should be 23-25 mm, and the posterior orifice 15-18 mm; thus, the total valve orifice area is 5-6 cm2. In children, the total valve orifice should be a standard deviation of 1.7 mm for a BSA of 1.0m2. During a mean follow up of 8.7 ± 1.34 years (median 10 years; range: 1.5-25.9 years) there have been no reoperations for TV insufficiency

Percutaneous aortic valve implantation of the Medtronic CoreValve self-expanding valve prosthesis via left subclavian artery access: the first case report in Greece.

Science.gov (United States)

Karavolias, George K; Georgiadou, Panagiota; Houri, Mazen; Sbarouni, Eftihia; Thomopoulou, Sofia; Tsiapras, Dimitrios; Smirli, Anna; Balanika, Marina; Voudris, Vassilis

2010-01-01

This case report describes a percutaneous aortic valve implantation with the Medtronic CoreValve selfexpanding valve prosthesis in a patient with severe aortic stenosis. The approach was made via the left subclavian artery because of the lack of femoral vessel access. The patient was a 78-year-old female with breathlessness on minimal effort, a recent hospitalisation due to pulmonary oedema, and frequent episodes of pre-syncope; surgical valve replacement had been ruled out. The prosthetic valve was successfully implanted with mild paravalvular aortic regurgitation. At 30 days, the patient's clinical condition had significantly improved, with excellent functioning of the aortic valve prosthesis.

Acute failure of a St. Jude's prosthetic aortic valve: large pannus formation masked by a small thrombus.

Science.gov (United States)

Hurwitz, Seth Eric; Waxman, Daniel; Hecht, Susan

2009-09-01

Pannus formation and valve thrombus can cause prosthetic valve failure. The authors report the case of a 50-year-old woman who presented to the emergency room with decompensated heart failure secondary to mechanical valve dysfunction. On two-dimensional and transesophageal echocardiography, the patient had severe aortic stenosis and regurgitation. A thrombus seen on the valve was felt to be the etiology of her prosthetic valve failure. She underwent emergent cardiac surgery for aortic valve replacement. Pathology revealed that although a small thrombus was present, extensive pannus was the underlying mechanism of valve dysfunction. Differentiation between pannus and thrombus may have important clinical implications, but this case illustrates that distinguishing between these entities by echocardiographic and clinical criteria may not be possible.

Mitral valve perforation appearing years after radiofrequency ablation

DEFF Research Database (Denmark)

Fisch-Thomsen, Marie; Jensen, Jesper K; Egeblad, Henrik

2011-01-01

The case is reported of a young adult with Wolff-Parkinson-White (WPW) syndrome who, three years after a complicated radiofrequency (RF) catheter ablation procedure, developed dyspnea on exertion. Echocardiography revealed severe mitral valve regurgitation caused by a perforation of the posterior...

CONDITIONED ANALYSIS OF HIGH-LATITUDE SOLAR WIND INTERMITTENCY

International Nuclear Information System (INIS)

D'Amicis, R.; Consolini, G.; Bavassano, B.; Bruno, R.

2012-01-01

The solar wind is a turbulent medium displaying intermittency. Its intermittent features have been widely documented and studied, showing how the intermittent character is different in fast and slow wind. In this paper, a statistical conditioned analysis of the solar wind intermittency for a period of high-latitude fast solar wind is presented. In particular, the intermittent features are investigated as a function of the Alfvénic degree of fluctuations at a given scale. The results show that the main contribution to solar wind intermittency is due to non-Alfvénic structures, while Alfvénic increments are found to be characterized by a smaller level of intermittency than the previous ones. Furthermore, the lifetime statistics of Alfvénic periods are discussed in terms of a multiscale texture of randomly oriented flux tubes.

Aortic valve replacement with the Biocor PSB stentless xenograft.

Science.gov (United States)

Bertolini, P; Luciani, G B; Vecchi, B; Pugliese, P; Mazzucco, A

1998-08-01

The midterm clinical results after aortic valve replacement with the Biocor PSB stentless xenograft on all patients operated between October 1992 and October 1996 were reviewed. One hundred six patients, aged 70+/-6 years, had aortic valve replacement for aortic stenosis (67%), regurgitation (11%), or both (22%). Associated procedures were done in 49 patients (46%), including coronary artery bypass in 30 patients, mitral valve repair/replacement in 16, and ascending aorta replacement in 5 patients. Aortic cross-clamp and cardiopulmonary bypass times were 96+/-24 and 129+/-31 minutes, respectively. There were 3 (3%) early deaths due to low output (2 patients) and cerebrovascular accident (1 patient). Follow-up of survivors ranged from 6 to 66 months (mean, 39+/-14 months). Survival was 94%+/-2% and 90%+/-3% at 1 and 5 years. There were 5 late deaths due to cardiac cause (2), cancer (2), and pulmonary embolism (1 patient). No patient had structural valve deterioration, whereas 100% and 95%+/-3% were free from valve-related events at 1 and 5 years. There were two reoperations due to narrowing of the left coronary ostium and endocarditis, with an actuarial freedom from reoperation of 99%+/-1% and 98+/-1% at 1 and 5 years, respectively. Functional results demonstrated a mean peak transprosthetic gradient of 16+/-12 mm Hg, with only 1 patient (1%) with a 55 mm Hg gradient. No cases of valve regurgitation greater than mild were recorded at follow-up. Assessment of New York Heart Association functional class demonstrated a significant improvement (2.9+/-0.6 versus 1.4+/-0.7; p=0.01). All patients were free from anticoagulation. Aortic valve replacement using the Biocor PSB stentless xenograft offers excellent midterm survival, negligible valve deterioration, and a very low rate of valve-related events, which are comparable to estimates reported with other models of stentless xenografts and currently available stented xenografts. Hemodynamic performance is favorable and

Recurrent acute pulmonary oedema after aortic and mitral valve surgery due to trachea malacia and obstructive sleep apnoea syndrome

NARCIS (Netherlands)

Sankatsing, S. U. C.; Hanselaar, W. E. J. J.; van Steenwijk, R. P.; Van der Sloot, J. A. P.; Broekhuis, E.; Kok, W. E. M.

2008-01-01

In this report we describe a patient with recurrent episodes of acute pulmonary oedema after aortic and mitral valve surgery. The first episode of pulmonary oedema was caused by mitral valve dysfunction. The second episode of pulmonary oedema was not clearly associated with a mitral valve problem,

Effects of the blockage ratio of a valve disk on loss coefficient in a butterfly valve

International Nuclear Information System (INIS)

Rho, Hyung Joon; Lee, Jee Keun; Choi, Hee Joo

2008-01-01

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk

Door valve for fuel handling path

International Nuclear Information System (INIS)

Makishima, Katsuhiko.

1969-01-01

A door valve is provided which seals cover gas from a liquid metal cooled reactor without leakage therefrom. A threaded shaft is screwed into a heavy box press which is packed with lead. The shaft is adapted to be rotated by an electric motor or a manually operated wheel which is disposed outside of the door valve. A valve plate is suspended from the box press by four guide wheels mounted thereon. The guide wheels are fitted into inclined guide grooves formed at the valve plate and into grooved formed in the inner wall of a valve casing. A locking ball is provided at each side of the valve plate. In operation the shaft rotates and travels to permit the box press and the valve plate to move into the door valve casing, thus releasing the locking balls. The valve plate does not contact the bottom of the casing. When the box press reaches the home position, the valve plate is carried on the valve opening, and the box press presses the valve plate to increase the tightness. The valve plate does not suffer wear as it does not slide over other parts. (Yamaguchi, T.)

Continuous use of intermittent bladder catheterization - can social support contribute?

Directory of Open Access Journals (Sweden)

Marjoyre Anne Lindozo Lopes

2014-06-01

Full Text Available OBJECTIVE: to investigate the factors affecting the adequate continuous use of intermittent catheterization and its relation with social support.METHOD: sectional, descriptive and correlational study involving 49 patients with neuropathic bladder caused by spinal cord injury.RESULTS: almost all (92% participants continued the intermittent catheterization, but 46.9% made some changes in the technique. The complications (28.6% of the sample were mainly infection and vesicolithiasis. There were high scores for social support in relation to people that were part of the patient's social support.CONCLUSION: All of them noticed great support from the family, but not from the society in general. The difficulties were related to the lack of equipment and inadequate infrastructure, leading to changes that increased urologic complications.

Characterization of a bioprosthetic bicuspid venous valve hemodynamics: implications for mechanism of valve dynamics.

Science.gov (United States)

Tien, W-H; Chen, H Y; Berwick, Z C; Krieger, J; Chambers, S; Dabiri, D; Kassab, G S

2014-10-01

Chronic venous insufficiency (CVI) of the lower extremities is a common clinical problem. Although bioprosthetic valves have been proposed to treat severe reflux, clinical success has been limited due to thrombosis and neointima overgrowth of the leaflets that is, in part, related to the hemodynamics of the valve. A bioprosthetic valve that mimics native valve hemodynamics is essential. A computational model of the prosthetic valve based on realistic geometry and mechanical properties was developed to simulate the interaction of valve structure (fluid-structure interaction, FSI) with the surrounding flow. The simulation results were validated by experiments of a bioprosthetic bicuspid venous valve using particle image velocimetry (PIV) with high spatial and temporal resolution in a pulse duplicator (PD). Flow velocity fields surrounding the valve leaflets were calculated from PIV measurements and comparisons to the FSI simulation results were made. Both the spatial and temporal results of the simulations and experiments were in agreement. The FSI prediction of the transition point from equilibrium phase to valve-closing phase had a 7% delay compared to the PD measurements, while the PIV measurements matched the PD exactly. FSI predictions of reversed flow were within 10% compared to PD measurements. Stagnation or stasis regions were observed in both simulations and experiments. The pressure differential across the valve and associated forces on the leaflets from simulations showed the valve mechanism to be pressure driven. The flow velocity simulations were highly consistent with the experimental results. The FSI simulation and force analysis showed that the valve closure mechanism is pressure driven under the test conditions. FSI simulation and PIV measurements demonstrated that the flow behind the leaflet was mostly stagnant and a potential source for thrombosis. The validated FSI simulations should enable future valve design optimizations that are needed for

Intermittency '93

International Nuclear Information System (INIS)

Bialas, A.

1993-01-01

The existing data definitely indicate the existence of intermittency, i.e. of self similar structures in the systems of particles created in high-energy collisions. The effect seems universal: it was found in most of the processes investigated and its measures parameters depend only weakly (if at all) on the process in question. Strong HBT effect was found, suggesting that intermittency is related to space-time structure of the pion source rather than to detailed momentum structure of the production amplitudes. There are indications that this space time structure may be fractal, but more data is needed to establish this. The theoretical explanation remains obscure: it seems that both parton cascade and hadronization play an important role. Their interrelation, however, remains a mystery. 5 figs., 19 refs

A method for evaluating pressure locking and thermal binding of gate valves

Energy Technology Data Exchange (ETDEWEB)

Dogan, T.

1996-12-01

A method is described to evaluate the susceptibility of gate valves to pressure locking and thermal binding. Binding of the valve disc in the closed position due to high pressure water trapped in the bonnet cavity (pressure locking) or differential thermal expansion of the disk in the seat (thermal binding) represents a potential mechanism that can prevent safety-related systems from functioning when called upon. The method described here provides a general equation that can be applied to a given gate valve design and set of operating conditions to determine the susceptibility of the valve to fail due to disc binding. The paper is organized into three parts. The first part discusses the physical mechanisms that cause disc binding. The second part describes the mathematical equations. The third part discusses the conclusions.

Small valve area index: its influence on early mortality after mitral valve replacement

NARCIS (Netherlands)

Yazdanbakhsh, A. P.; van den Brink, R. B.; Dekker, Egbert; de Mol, B. A.

2000-01-01

OBJECTIVE: To test the hypothesis that mitral valve prosthesis-patient mismatch increases postoperative mortality. METHODS AND RESULTS: The effect of mitral valve prosthesis-patient mismatch on survival in a cohort of consecutive patients after mitral valve replacement with a mechanical prosthesis

Björk-Shiley convexoconcave valves: susceptibility artifacts at brain MR imaging and mechanical valve fractures.

Science.gov (United States)

van Gorp, Maarten J; van der Graaf, Yolanda; de Mol, Bas A J M; Bakker, Chris J G; Witkamp, Theo D; Ramos, Lino M P; Mali, Willem P T M

2004-03-01

To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Björk-Shiley convexoconcave (BSCC) valves. MR images of the brain were obtained in 58 patients with prosthetic heart valves: 20 patients had BSCC valve replacements, and 38 had other types of heart valves. Two experienced neuroradiologists determined the presence or absence of susceptibility artifacts in a consensus reading. Artifacts were defined as characteristic black spots that were visible on T2*-weighted gradient-echo MR images. The statuses of the 20 explanted BSCC valves-specifically, whether they were intact or had an outlet strut fracture (OSF) or a single-leg fracture (SLF)-had been determined earlier. Number of artifacts seen at brain MR imaging was correlated with explanted valve status, and differences were analyzed with nonparametric statistical tests. Significantly more patients with BSCC valves (17 [85%] of 20 patients) than patients with other types of prosthetic valves (18 [47%] of 38 patients) had susceptibility artifacts at MR imaging (P =.005). BSCC valve OSFs were associated with a significantly higher number of artifacts than were intact BSCC valves (P =.01). No significant relationship between SLF and number of artifacts was observed. Susceptibility artifacts at brain MR imaging are not restricted to patients with BSCC valves. These artifacts can be seen on images obtained in patients with various other types of fractured and intact prosthetic heart valves. Copyright RSNA, 2004

Low noise control valve

International Nuclear Information System (INIS)

Christie, R.S.

1975-01-01

Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included

Autopsy after transcatheter aortic valve implantation

DEFF Research Database (Denmark)

van Kesteren, F; Wiegerinck, E M A; Rizzo, S

2017-01-01

Autopsy after transcatheter aortic valve implantation (TAVI) is a new field of interest in cardiovascular pathology. To identify the cause of death, it is important to be familiar with specific findings related to the time interval between the procedure and death. We aimed to provide an overview...... different cause of death as was clinically determined. Autopsy on patients who underwent TAVI reveals specific patterns of cardiovascular pathology that clearly relate to the time interval between TAVI and death and significantly adds to the clinical diagnosis. Our data support the role of autopsy including...

Role of recent research in improving check valve reliability at nuclear power plants

International Nuclear Information System (INIS)

Kalsi, M.S.; Horst, C.L.; Wang, J.K.; Sharma, V.

1990-01-01

Check valve failures at nuclear power plants in recent years have led to serious safety concerns, and caused extensive damage to other plant components which had a significant impact on plant availability. In order to understand the failure mechanism and improve the reliability of check valves, a systematic research effort was proposed by Kalsi Engineering, Inc. to U.S. Nuclear Regulatory Commission (NRC). The overall goal of the research was to develop models for predicting the performance and degradation of swing check valves in nuclear power plant systems so that appropriate preventive maintenance or design modifications can be performed to improve the reliability of check valves. Under Phase I of this research, a large matrix of tests was run with instrumented swing check valves to determine the stability of the disc under a variety of upstream flow disturbances, covering a wide range of disc stop positions and flow velocities in two different valve sizes. The goals of Phase II research were to develop predictive models which quantify the anticipated degradation of swing check valves that have flow disturbances closely upstream of the valve and are operating under flow velocities that do not result in full disc opening. This research allows the inspection/maintenance activities to be focussed on those check valves that are more likely to suffer premature degradation. The quantitative wear and fatigue prediction methodology can be used to develop a sound preventive maintenance program. The results of the research also show the improvements in check valve performance/reliability that can be achieved by certain modifications in the valve design

Impact of pannus formation on hemodynamic dysfunction of prosthetic aortic valve: pannus extent and its relationship to prosthetic valve motion and degree of stenosis.

Science.gov (United States)

Koo, Hyun Jung; Ha, Hojin; Kang, Joon-Won; Kim, Jeong A; Song, Jae-Kwan; Kim, Hwa Jung; Lim, Tae-Hwan; Yang, Dong Hyun

2018-02-19

Although pannus is an important cause of prosthetic valve dysfunction, the minimum pannus size that can induce hemodynamic dysfunction has not yet been determined. This study investigated the correlation between the limitation of motion (LOM) of the prosthetic valve and pannus extent and determined the pannus extent that could induce severe aortic stenosis. This study included 49 patients who underwent mechanical aortic valve replacement (AVR) and showed pannus on cardiac computed tomography (CT). Pannus width, ratio of pannus width to valve diameter, pannus area, effective orifice area, encroachment ratio by pannus, pannus involvement angle and percent LOM of mechanical valves were evaluated on CT. Transvalvular peak velocity (TPV) and transvalvular pressure gradient (TPG) were measured by transesophageal echocardiography to determine the degree of aortic stenosis. The relationship between percent LOM of the prosthetic valve and pannus extent and the cut-off of pannus extent required to induce severe aortic stenosis were evaluated. The mean interval between AVR and pannus formation was 11 years and was longer in patients with than without severe aortic stenosis (14.0 vs. 7.3 years). On CT, the percent LOM of the prosthetic valve was significantly associated with the extent of pannus only in patients with pannus involvement angle > 180° (r = 0.55-0.68, P Pannus width, effective orifice area, and encroachment ratio were significantly associated with increased TPV and TPG (r = 0.51-0.62, P Pannus width > 3.5 mm, pannus width/valve inner diameter > 0.15, and encroachment ratio > 0.14 were significantly associated with severe aortic stenosis (TPV > 4 m/s; mean TPG ≥ 35 mmHg), with c-indices of 0.74-079 (P pannus extent parameters are good indicators of significant hemodynamic changes with increased TPV and mean TPG.

Valve for closing a steam line

International Nuclear Information System (INIS)

Meyer, W.; Potrykus, G.

1976-01-01

Instead of several control elements, the quick-closing valve, especially in the main-steam line between steam generator and turbine of a power station has the valve cone itself as the only movable part, acting with its inner surface as a piston within a second cylinder space. The valve shaft is at the same time a piston rod with a stepped piston at the upper end. This piston is loaded in a cylinder at the upspace below the valve cover on one hand by a spring, on the other hand by its own medium. Two non-return valves, one of it in a bore of the valve cone, connect the first-mentioned cylinder space with the steam-loaded inlet resp. outlet side of the valve. For controlling the valve, a magnet valve is sufficient. By automatic control of the valve cone coupled with several pistons several control lines can be omitted. There are also no pressurized control lines outside the valve which could be damaged by exterior influences. (ERA) [de

Simulation of the behaviour of a servo actuated check valve upon rupture of the feedwater pipe

International Nuclear Information System (INIS)

Lucas, A.M. de; Perezagua, R.L.; Rosa, B. de la; Sanz, J.

1995-01-01

The steam generator replacement programme at Almaraz NPP, provides for the installation of a replacement damped non-return valve for the feedwater system. the function of this valve is to protect the steam generator in the event of a rupture in the feedwater pipe. Sudden closure of the check valve, against the flow and following rupture of the feedwater pipe, causes overpressure in the valve which is transmitted to the steam generator nozzle. It is therefore necessary to know this when designing the internal systems of the steam generator. Using the RELAP5/MODE3 code, it has been possible to simulate the dynamic behaviour of a check valve upon rupture of a feedwater pipe postulated outside the containment. The calculation model has been applied to different types of check valve. (Author)

Positive effects of intermittent fasting in ischemic stroke.

Science.gov (United States)

Fann, David Yang-Wei; Ng, Gavin Yong Quan; Poh, Luting; Arumugam, Thiruma V

2017-03-01

Intermittent fasting (IF) is a dietary protocol where energy restriction is induced by alternate periods of ad libitum feeding and fasting. Prophylactic intermittent fasting has been shown to extend lifespan and attenuate the progress and severity of age-related diseases such as cardiovascular (e.g. stroke and myocardial infarction), neurodegenerative (e.g. Alzheimer's disease and Parkinson's disease) and cancerous diseases in animal models. Stroke is the second leading cause of death, and lifestyle risk factors such as obesity and physical inactivity have been associated with elevated risks of stroke in humans. Recent studies have shown that prophylactic IF may mitigate tissue damage and neurological deficit following ischemic stroke by a mechanism(s) involving suppression of excitotoxicity, oxidative stress, inflammation and cell death pathways in animal stroke models. This review summarizes data supporting the potential hormesis mechanisms of prophylactic IF in animal models, and with a focus on findings from animal studies of prophylactic IF in stroke in our laboratory. Copyright © 2017 Elsevier Inc. All rights reserved.

Infusion of the solid coal using pressure independent valves to regulate flow

Energy Technology Data Exchange (ETDEWEB)

Goretz, H G; Betting, K

1979-01-01

In order to improve infusion into the solid coal, attempts were made to effect this through several holes using a single pump; however, the regulation of the quantity of water directed into each hole by a ball-valve tap connected to the injection pump was shown to lack precision - gives the causes of this defect. Satisfactory regulation was obtained by means of pressure- independent flow valves which operate on the principle of hydrodynamic pressure balance; describes method of operation. Underground tests proved satisfactory even with large pressure variations. The problem of dirt penetration during down times was eliminated by installing a check valve. The system proves economical to run.

Coherent and intermittent ensemble oscillations emerge from networks of irregular spiking neurons.

Science.gov (United States)

Hoseini, Mahmood S; Wessel, Ralf

2016-01-01

Local field potential (LFP) recordings from spatially distant cortical circuits reveal episodes of coherent gamma oscillations that are intermittent, and of variable peak frequency and duration. Concurrently, single neuron spiking remains largely irregular and of low rate. The underlying potential mechanisms of this emergent network activity have long been debated. Here we reproduce such intermittent ensemble oscillations in a model network, consisting of excitatory and inhibitory model neurons with the characteristics of regular-spiking (RS) pyramidal neurons, and fast-spiking (FS) and low-threshold spiking (LTS) interneurons. We find that fluctuations in the external inputs trigger reciprocally connected and irregularly spiking RS and FS neurons in episodes of ensemble oscillations, which are terminated by the recruitment of the LTS population with concurrent accumulation of inhibitory conductance in both RS and FS neurons. The model qualitatively reproduces experimentally observed phase drift, oscillation episode duration distributions, variation in the peak frequency, and the concurrent irregular single-neuron spiking at low rate. Furthermore, consistent with previous experimental studies using optogenetic manipulation, periodic activation of FS, but not RS, model neurons causes enhancement of gamma oscillations. In addition, increasing the coupling between two model networks from low to high reveals a transition from independent intermittent oscillations to coherent intermittent oscillations. In conclusion, the model network suggests biologically plausible mechanisms for the generation of episodes of coherent intermittent ensemble oscillations with irregular spiking neurons in cortical circuits. Copyright © 2016 the American Physiological Society.

Trend analysis of incidents involving setpoint drift in safety or safety/relief valves at U.S. LWRs

International Nuclear Information System (INIS)

Watanabe, Norio

2008-01-01

Since the beginning of the 1980's, in the United States, there have been many licensee event reports (LERs) involving setpoint drift in safety or safety/relief valves. The United States Nuclear Regulatory Commission (NRC) has issued a lot of generic communications on this issue and the industry has made efforts to resolve the issue. However, the NRC staff recently highlighted that over 70 LERs involved instances where safety or safety/relief valves failed to meet the allowed setpoint tolerance from 2001 through August 2006. In the present study, we analyzed the U.S. experience with setpoint drift in safety/relief valves (SRVs) at BWRs, pressurizer safety valves (PSVs), and main steam safety valves (MSSVs) at PWRs by reviewing approximately 90 LERs from 2000 to 2006 and examined the trend focusing on causes and setpoint deviation ranges. This study indicates that for SRVs and MSSVs, disc-seat bonding is a dominant cause of the setpoint drifting high and has a tendency to result in a relatively large deviation of the setpoint. This means that disc-seat bonding might be a safety concern from the view point of overpressure protection. For PSVs, the deviation of setpoints is generally small, although its causes are not specified in many instances. (author)

Door valve for fuel handling path

International Nuclear Information System (INIS)

Makishima, Katsuhiko.

1969-01-01

A door valve is provided which seals cover gas from a liquid metal cooled reactor without leakage therefrom. A threaded shaft is screwed into a heavy box press which is packed with lead. The shaft is adapted to be rotated by an electric motor or a manually operated wheel which is disposed outside of the door valve. From the box press a valve plate is suspended by four linkage bars, one for each corner. Each linkage bar is provided with two wheels which are respectively mounted at the connections with the box press and the valve plate. The wheels are carried on the horizontal grooves formed in a door valve casing. In operation the shaft rotates and travels to permit the box press and the valve plate to move into the door valve casing while the valve plate does not contact the casing. When the box press reaches the home position, the wheels drop into the recesses which are disposed at the ends of the grooves, the valve plate is carried on the valve opening, and the box press presses the valve plate to increase the tightness. The valve plate does not suffer wear as it does not over other parts. (Yamaguchi, T.)

The importance of preoperative magnetic resonance imaging in valve surgery for active infective endocarditis

International Nuclear Information System (INIS)

Takagi, Yasushi; Higuchi, Yoshiro; Kondo, Hiroshi; Akita, Kiyotoshi; Ishida, Michiko; Kaneko, Kan; Hoshino, Ryo; Sato, Masato; Ando, Motomi

2011-01-01

Valve surgery for active infective endocarditis (IE) can cause fatal brain hemorrhage. Our current study aimed to evaluate the incidence of septic cerebral lesions in active IE patients by performing preoperative magnetic resonance imaging (MRI) including T 2 *-weighted sequences and magnetic resonance angiography (MRA) before urgent valve surgery, and to investigate whether such preoperative evaluation affects postoperative outcomes. Eighteen patients were referred to our department for native valve IE during 2006-2010. Urgent surgery was indicated in cases of hemodynamic failure resulting from valve destruction, refractory sepsis, and mobile vegetations measuring >10 mm. For these patients, we performed preoperative MRI and MRA. Males comprised 67% of the subjects, with average age 53±15 years. No clinical evidence of acute stroke was noted. Of the 18 patients, urgent surgery was indicated in 15; of these, 10 (67%) showed a brain lesion related to IE: 6 patients had acute or subacute brain infarctions, 2 patients had brain infarction with brain abscess, and 2 patients had hemorrhagic brain infarction and so did not undergo urgent surgery. Thus, 13 patients underwent urgent valve surgery. Among the 5 patients who did not undergo urgent surgery, 4 patients later underwent valve surgery for healed IE. No hospital deaths or neurological complications occurred. MRI of patients with active IE revealed a high incidence of cerebral lesions caused by IE. The use of MRI to detect septic embolism and intracerebral hemorrhage may provide important information for better surgical outcomes. (author)

Intermittent hypoxia from obstructive sleep apnea may cause neuronal impairment and dysfunction in central nervous system: the potential roles played by microglia

Directory of Open Access Journals (Sweden)

Yang Q

2013-08-01

Full Text Available Qingchan Yang,1,* Yan Wang,2,* Jing Feng,2 Jie Cao,2 Baoyuan Chen2 1Graduate School of Tianjin Medical University, 2Respiratory Department, Tianjin Medical University General Hospital, Tianjin, People's Republic of China *These authors contributed equally to this work Abstract: Obstructive sleep apnea (OSA is a common condition characterized by repetitive episodes of complete (apnea or partial (hypopnea obstruction of the upper airway during sleep, resulting in oxygen desaturation and arousal from sleep. Intermittent hypoxia (IH resulting from OSA may cause structural neuron damage and dysfunction in the central nervous system (CNS. Clinically, it manifests as neurocognitive and behavioral deficits with oxidative stress and inflammatory impairment as its pathophysiological basis, which are mediated by microglia at the cellular level. Microglia are dominant proinflammatory cells in the CNS. They induce CNS oxidative stress and inflammation, mainly through mitochondria, reduced nicotinamide adenine dinucleotide phosphate oxidase, and the release of excitatory toxic neurotransmitters. The balance between neurotoxic versus protective and anti- versus proinflammatory microglial factors might determine the final roles of microglia after IH exposure from OSA. Microglia inflammatory impairments will continue and cascade persistently upon activation, ultimately resulting in clinically significant neuron damage and dysfunction in the CNS. In this review article, we summarize the mechanisms of structural neuron damage in the CNS and its concomitant dysfunction due to IH from OSA, and the potential roles played by microglia in this process. Keywords: intermittent hypoxia, obstructive sleep apnea, microglia, inflammation, apoptosis

Pressure Autoregulation Measurement Techniques in Adult Traumatic Brain Injury, Part I: A Scoping Review of Intermittent/Semi-Intermittent Methods.

Science.gov (United States)

Zeiler, Frederick A; Donnelly, Joseph; Calviello, Leanne; Menon, David K; Smielewski, Peter; Czosnyka, Marek

2017-12-01

The purpose of this study was to perform a systematic, scoping review of commonly described intermittent/semi-intermittent autoregulation measurement techniques in adult traumatic brain injury (TBI). Nine separate systematic reviews were conducted for each intermittent technique: computed tomographic perfusion (CTP)/Xenon-CT (Xe-CT), positron emission tomography (PET), magnetic resonance imaging (MRI), arteriovenous difference in oxygen (AVDO 2 ) technique, thigh cuff deflation technique (TCDT), transient hyperemic response test (THRT), orthostatic hypotension test (OHT), mean flow index (Mx), and transfer function autoregulation index (TF-ARI). MEDLINE ® , BIOSIS, EMBASE, Global Health, Scopus, Cochrane Library (inception to December 2016), and reference lists of relevant articles were searched. A two tier filter of references was conducted. The total number of articles utilizing each of the nine searched techniques for intermittent/semi-intermittent autoregulation techniques in adult TBI were: CTP/Xe-CT (10), PET (6), MRI (0), AVDO 2 (10), ARI-based TCDT (9), THRT (6), OHT (3), Mx (17), and TF-ARI (6). The premise behind all of the intermittent techniques is manipulation of systemic blood pressure/blood volume via either chemical (such as vasopressors) or mechanical (such as thigh cuffs or carotid compression) means. Exceptionally, Mx and TF-ARI are based on spontaneous fluctuations of cerebral perfusion pressure (CPP) or mean arterial pressure (MAP). The method for assessing the cerebral circulation during these manipulations varies, with both imaging-based techniques and TCD utilized. Despite the limited literature for intermittent/semi-intermittent techniques in adult TBI (minus Mx), it is important to acknowledge the availability of such tests. They have provided fundamental insight into human autoregulatory capacity, leading to the development of continuous and more commonly applied techniques in the intensive care unit (ICU). Numerous methods of

Effects of pressure and temperature on gate valve unwedging

Energy Technology Data Exchange (ETDEWEB)

Damerell, P.S.; Harrison, D.H.; Hayes, P.W.; Simons, J.W.; Walker, T.A.

1996-12-01

The stem thrust required to unwedge a gate valve is influenced by the pressure and temperature when the valve is closed and by the changes in these conditions between closure and opening. {open_quotes}Pressure locking{close_quotes} and {open_quotes}thermal binding{close_quotes} refer to situations where pressure and temperature effects cause the unwedging load to be much higher than normal. A model of these phenomena has been developed. Wedging (closure) is modeled as developing an {open_quotes}interference{close_quotes} between the disk and its seat rings in the valve. The effects of pressure and temperature are analyzed to determine the change in this disk-to-seat {open_quotes}interference{close_quotes}. Flexibilities, of the disk, body, stem and yoke strongly influence the unwedging thrust. Calculations and limited comparisons to data have been performed for a range of valve designs and scenarios. Pressure changes can increase the unwedging load when there is either a uniform pressure decrease, or a situation where the bonnet pressure exceeds the pressures in the adjacent piping. Temperature changes can increase the unwedging load when: (1) valve closure at elevated system temperature produces a delayed stem expansion, (2) a temperature increase after closure produces a bonnet pressure increase, or (3) a temperature change after closure produces an increase in the disk-to-seat {open_quotes}interference{close_quotes} or disk-to-seat friction.

Effects of pressure and temperature on gate valve unwedging

International Nuclear Information System (INIS)

Damerell, P.S.; Harrison, D.H.; Hayes, P.W.; Simons, J.W.; Walker, T.A.

1996-01-01

The stem thrust required to unwedge a gate valve is influenced by the pressure and temperature when the valve is closed and by the changes in these conditions between closure and opening. open-quotes Pressure lockingclose quotes and open-quotes thermal bindingclose quotes refer to situations where pressure and temperature effects cause the unwedging load to be much higher than normal. A model of these phenomena has been developed. Wedging (closure) is modeled as developing an open-quotes interferenceclose quotes between the disk and its seat rings in the valve. The effects of pressure and temperature are analyzed to determine the change in this disk-to-seat open-quotes interferenceclose quotes. Flexibilities, of the disk, body, stem and yoke strongly influence the unwedging thrust. Calculations and limited comparisons to data have been performed for a range of valve designs and scenarios. Pressure changes can increase the unwedging load when there is either a uniform pressure decrease, or a situation where the bonnet pressure exceeds the pressures in the adjacent piping. Temperature changes can increase the unwedging load when: (1) valve closure at elevated system temperature produces a delayed stem expansion, (2) a temperature increase after closure produces a bonnet pressure increase, or (3) a temperature change after closure produces an increase in the disk-to-seat open-quotes interferenceclose quotes or disk-to-seat friction

Impact of bicuspid aortic valve on complications and death in infective endocarditis of native aortic valves.

Science.gov (United States)

Kahveci, Gokhan; Bayrak, Fatih; Pala, Selcuk; Mutlu, Bulent

2009-01-01

We retrospectively investigated the impact of bicuspid aortic valve on the prognosis of patients who had definite infective endocarditis of the native aortic valve.Of 51 patients, a bicuspid aortic valve was present in 22 (43%); the other 29 had tricuspid aortic valves. On average, the patients who had bicuspid valves were younger than those who had tricuspid valves. Patients with a tricuspid valve had larger left atrial diameters and were more likely to have severe mitral regurgitation.Periannular complications, which we detected in 19 patients (37%), were much more common in the patients who had a bicuspid valve (64% vs 17%, P = 0.001). The presence of a bicuspid valve was the only significant independent predictor of periannular complications. The in-hospital mortality rate in the bicuspid group was lower than that in the tricuspid group; however, this figure did not reach statistical significance (9% vs 24%, P = 0.15). In multivariate analysis, left atrial diameter was the only independent predictor associated with an increased risk of death (hazard ratio, 2.19; 95% confidence interval, 1.1-4.5; P = 0.031).In our study, patients with infective endocarditis in a bicuspid aortic valve were younger and had a higher incidence of periannular complications. Although a worse prognosis has been reported previously, we found that infective endocarditis in a native bicuspid aortic valve is not likely to increase the risk of death in comparison with infective endocarditis in native tricuspid aortic valves.

Gate valve performance prediction

International Nuclear Information System (INIS)

Harrison, D.H.; Damerell, P.S.; Wang, J.K.; Kalsi, M.S.; Wolfe, K.J.

1994-01-01

The Electric Power Research Institute is carrying out a program to improve the performance prediction methods for motor-operated valves. As part of this program, an analytical method to predict the stem thrust required to stroke a gate valve has been developed and has been assessed against data from gate valve tests. The method accounts for the loads applied to the disc by fluid flow and for the detailed mechanical interaction of the stem, disc, guides, and seats. To support development of the method, two separate-effects test programs were carried out. One test program determined friction coefficients for contacts between gate valve parts by using material specimens in controlled environments. The other test program investigated the interaction of the stem, disc, guides, and seat using a special fixture with full-sized gate valve parts. The method has been assessed against flow-loop and in-plant test data. These tests include valve sizes from 3 to 18 in. and cover a considerable range of flow, temperature, and differential pressure. Stem thrust predictions for the method bound measured results. In some cases, the bounding predictions are substantially higher than the stem loads required for valve operation, as a result of the bounding nature of the friction coefficients in the method

Mitral Valve Prolapse

Science.gov (United States)

... valve syndrome . What happens during MVP? Watch an animation of mitral valve prolapse When the heart pumps ( ... our brochures Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Heart Attack Symptoms ...

Application of ceramics to the sliding seat of valve bridge; Valve bridge yodobu eno ceramics tekiyo

Energy Technology Data Exchange (ETDEWEB)

Matsui, T; Ono, T [Mitsubishi Motors Corp., Tokyo (Japan)

1997-10-01

For use in the valve train, using an OHV (over head valve) configuration. of a 4 valve diesel engine for trucks and buses; we developed a valve bridge, a component of a valve train, with a ceramic head that is made of silicon nitride(Si3N4) in contact with a rocker arm in order to reduce cost and improve wear resistance for further diesel engine emissions regulations. In order to evaluate the effect of this valve bridge, RIG tests and durability tests on actual engines were carried out. 7 figs., 2 tabs.

Transcatheter Mitral Valve-in-Ring Implantation

LENUS (Irish Health Repository)

Tanner, RE

2018-05-01

Failed surgical mitral valve repair using an annuloplasty ring has traditionally been treated with surgical valve replacement or repair1. For patients at high risk for repeat open heart surgery, placement of a trans-catheter aortic valve (i.e., TAVI valve) within the mitral ring (i.e., Mitral-Valve-in-Ring, MViR) has emerged as a novel alternative treatment strategy2-5 . We describe our experience of a failed mitral valve repair that was successfully treated with a TAVI valve delivered via the trans-septal approach, and summarise the data relating to this emerging treatment strategy.

A new one-step procedure for pulmonary valve implantation of the melody valve: Simultaneous prestenting and valve implantation.

Science.gov (United States)

Boudjemline, Younes

2018-01-01

To describe a new modification, the one-step procedure, that allows interventionists to pre-stent and implant a Melody valve simultaneously. Percutaneous pulmonary valve implantation (PPVI) is the standard of care for managing patients with dysfunctional right ventricular outflow tract, and the approach is standardized. Patients undergoing PPVI using the one-step procedure were identified in our database. Procedural data and radiation exposure were compared to those in a matched group of patients who underwent PPVI using the conventional two-step procedure. Between January 2016 and January 2017, PPVI was performed in 27 patients (median age/range, 19.1/10-55 years) using the one-step procedure involving manual crimping of one to three bare metal stents over the Melody valve. The stent and Melody valve were delivered successfully using the Ensemble delivery system. No complications occurred. All patients had excellent hemodynamic results (median/range post-PPVI right ventricular to pulmonary artery gradient, 9/0-20 mmHg). Valve function was excellent. Median procedural and fluoroscopic times were 56 and 10.2 min, respectively, which significantly differed from those of the two-step procedure group. Similarly, the dose area product (DAP), and radiation time were statistically lower in the one-step group than in the two-step group (P step procedure is a safe modification that allows interventionists to prestent and implants the Melody valve simultaneously. It significantly reduces procedural and fluoroscopic times, and radiation exposure. © 2017 Wiley Periodicals, Inc.

Space Vehicle Valve System

Science.gov (United States)

Kelley, Anthony R. (Inventor); Lindner, Jeffrey L. (Inventor)

2014-01-01

The present invention is a space vehicle valve system which controls the internal pressure of a space vehicle and the flow rate of purged gases at a given internal pressure and aperture site. A plurality of quasi-unique variable dimension peaked valve structures cover the purge apertures on a space vehicle. Interchangeable sheet guards configured to cover valve apertures on the peaked valve structure contain a pressure-activated surface on the inner surface. Sheet guards move outwardly from the peaked valve structure when in structural contact with a purge gas stream flowing through the apertures on the space vehicle. Changing the properties of the sheet guards changes the response of the sheet guards at a given internal pressure, providing control of the flow rate at a given aperture site.

Isolated Tricuspid Valve Libman-Sacks Endocarditis in Systemic Lupus Erythematosus with Secondary Antiphospholipid Syndrome.

Science.gov (United States)

Unic, Daniel; Planinc, Mislav; Baric, Davor; Rudez, Igor; Blazekovic, Robert; Senjug, Petar; Sutlic, Zeljko

2017-04-01

Libman-Sacks endocarditis, one of the most prevalent cardiac presentations of systemic lupus erythematosus, typically affects the aortic or mitral valve; tricuspid valve involvement is highly unusual. Secondary antiphospholipid syndrome increases the frequency and severity of cardiac valvular disease in systemic lupus erythematosus. We present the case of a 47-year-old woman with lupus and antiphospholipid syndrome whose massive tricuspid regurgitation was caused by Libman-Sacks endocarditis isolated to the tricuspid valve. In addition, we discuss this rare case in the context of the relevant medical literature.

Replica sizing strategy for aortic valve replacement improves haemodynamic outcome of the epic supra valve.

Science.gov (United States)

Gonzalez-Lopez, David; Faerber, Gloria; Diab, Mahmoud; Amorim, Paulo; Zeynalov, Natig; Doenst, Torsten

2017-10-01

Current sizing strategies suggest valve selection based on annulus diameter despite supra-annular placement of biological prostheses potentially allowing placement of a larger size. We assessed the frequency of selecting a larger prosthesis if prosthesis size was selected using a replica (upsizing) and evaluated its impact on haemodynamics. We analysed all discharge echocardiograms between June 2012 and June 2014, where a replica sizer was used for isolated aortic valve replacement (Epic Supra: 266 patients, Trifecta: 49 patients). Upsizing was possible in 71% of the Epic Supra valves (by 1 size: 168, by 2 sizes: 20) and in 59% of the Trifectas (by 1 size: 26, by 2 sizes: 3). Patients for whom upsizing was possible had the lowest pressure gradients within their annulus size groups. The difference was significant in annulus diameters of 21-22 or 25-26 mm (Epic Supra) and 23-24 mm (Trifecta). Trifecta gradients were the lowest. However, the ability to upsize the Epic Supra by 2 sizes eliminated the differences between Epic Supra and Trifecta. Upsizing did not cause intraoperative complications. Using replica sizers for aortic prosthesis size selection allows the implantation of bigger prostheses than recommended in most cases and reduces postoperative gradients, specifically for Epic Supra. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Emergency heart valve replacement: an analysis of 170 patients.

Science.gov (United States)

Louw, J W; Kinsley, R H; Dion, R A; Colsen, P R; Girdwood, R W

1980-05-01

The results of 170 emergency heart valve procedures performed during a 4 1/2-year period were analyzed. Five pathological groups of patients were recognized: those with infective endocarditis (Group 1, 28 patients); acute rheumatic carditis (Group 2, 43 patients); previous valve operation (Group 3, 29 patients); acute-on-chronic cardiac disease (Group 4, 67 patients); and miscellaneous conditions (Group 5, 3 patients). Mitral, aortic, and multiple valve procedures were performed on 58, 65, and 44 patients, respectively. The most common functional lesion was regurgitation. Hospital mortality was highest in Groups 3 (34%) and 4 (31%). By contrast, among the hospital survivors, the highest rate of attrition was in Group 2. Myocardial failure was the predominat cause of death. In view of the hopeless prognosis without operation, the 52% overall 3-year actuarial survival is a gratifying salvage. Unnecessary procrastination can only jeopardize the prospects for surgical cure.

Transcatheter valve-in-valve implantation due to severe aortic regurgitation in a degenerated aortic homograft

DEFF Research Database (Denmark)

Olsen, Lene Kjaer; Engstrøm, Thomas; Søndergaard, Lars

2009-01-01

Transcatheter aortic valve implantation (TAVI) in severe aortic stenosis has proven to be a feasible and effective treatment modality for inoperable patients. Until now, neither aortic regurgitation nor degenerated bioprostheses has been an indication for TAVI. However, this article reports...... a successful valve-in-valve implantation of a CoreValve aortic valve prosthesis through the right subclavian artery in a case of severe aortic regurgitation within a degenerated aortic homograft. The case exemplifies the possibilities of expanding the indications for TAVI, as well as other vascular access...

Thermally induced pressure locking of gate valves: A survey of valve bonnet pressurization rates

International Nuclear Information System (INIS)

Ezekoye, L.I.; Moore, W.E.

1996-01-01

Closed, water filled gate valves run the risk of becoming pressurized due to heat input from the environment or from adjacent connected piping. Thermal pressurization of gate valve bonnets may lead to the valves failing to open on demand and can even induce structural failure of valves. This paper presents an analytical prediction of the pressurization rate of a closed pressure vessel subject to uniform heating which may be considered as an upper bound to the pressurization rate that may occur in the field. Then actual valve experiences described in the literature are reviewed to determine the expected pressurization rate in existing hardware designs. A statistical approach is applied to reconcile the differing pressurization rates reported in the literature and determine a rate that can be applied in valve evaluations. The limitations of the reconciled rate are discussed

Colombian experience with transcatheter aortic valve implantation of medtronic CoreValve.

Science.gov (United States)

Dager, Antonio E; Nuis, Rutger-Jan; Caicedo, Bernardo; Fonseca, Jaime A; Arana, Camilo; Cruz, Lidsa; Benitez, Luis M; Nader, Carlos A; Duenas, Eduardo; de Marchena, Eduardo J; O'Neill, William W; de Jaegere, Peter P

2012-01-01

At our institutions, increasing numbers of aortic stenosis patients were not candidates for surgical aortic valve replacement. Accordingly, we initiated the Cali Colombian Transcatheter Aortic Valve Implantation (TAVI) program. From March 2008 through January 2011, 53 consecutive patients (mean age, 79 ± 6 yr; men, 58%) underwent TAVI with the Medtronic CoreValve System, and data were prospectively collected. Our study's endpoints conformed with Valve Academic Research Consortium recommendations. We report our clinical results.Predicted mortality rates were 25% (interquartile range, 17%-34%) according to logistic EuroSCORE and 6% (interquartile range, 3%-8%) according to the Society of Thoracic Surgeons score. The 30-day mortality rate was 9% (3 intraprocedural deaths, 5 total). The combined 30-day safety endpoint was 30% (major vascular sequelae, 23%; life-threatening bleeding, 12%; myocardial infarction, 4%; major stroke, 4%; and acute kidney injury [stage 3], 2%). Eight patients (15%) required post-implantation balloon dilation and 2 (4%) required valve-in-valve implantation, for a technical device success rate of 77%. Mean peak transvalvular gradient decreased from 74 ± 29 to 17 ± 8 mmHg and mean transvalvular gradient from 40 ± 17 to 8 ± 4 mmHg (both P=0.001). Moderate or severe aortic regurgitation decreased from 32% to 18% (P=0.12) and mitral regurgitation from 32% to 13% (P=0.002). The 1-year survival rate was 81%.We found that TAVI with the CoreValve prosthesis was safe and feasible, with sustained long-term results, for treating aortic stenosis in patients at excessive surgical risk; nonetheless, serious adverse events occurred in 30% of the patients.

Traumatic Mitral Valve and Pericardial Injury

Directory of Open Access Journals (Sweden)

Nissar Shaikh

2013-01-01

Full Text Available Cardiac injury after blunt trauma is common but underreported. Common cardiac trauma after the blunt chest injury (BCI is cardiac contusion; it is very rare to have cardiac valve injury. The mitral valve injury during chest trauma occurs when extreme pressure is applied at early systole during the isovolumic contraction between the closure of the mitral valve and the opening of the aortic valve. Traumatic mitral valve injury can involve valve leaflet, chordae tendineae, or papillary muscles. For the diagnosis of mitral valve injury, a high index of suspicion is required, as in polytrauma patients, other obvious severe injuries will divert the attention of the treating physician. Clinical picture of patients with mitral valve injury may vary from none to cardiogenic shock. The echocardiogram is the main diagnostic modality of mitral valve injuries. Patient’s clinical condition will dictate the timing and type of surgery or medical therapy. We report a case of mitral valve and pericardial injury in a polytrauma patient, successfully treated in our intensive care unit.

Optimal intermittent search strategies

International Nuclear Information System (INIS)

Rojo, F; Budde, C E; Wio, H S

2009-01-01

We study the search kinetics of a single fixed target by a set of searchers performing an intermittent random walk, jumping between different internal states. Exploiting concepts of multi-state and continuous-time random walks we have calculated the survival probability of a target up to time t, and have 'optimized' (minimized) it with regard to the transition probability among internal states. Our model shows that intermittent strategies always improve target detection, even for simple diffusion states of motion

Transapical aortic valve implantation without angiography: proof of concept.

Science.gov (United States)

Ferrari, Enrico; Sulzer, Christopher; Marcucci, Carlo; Rizzo, Elena; Tozzi, Piergiorgio; von Segesser, Ludwig K

2010-06-01

Cardiac computed tomographic scans, coronary angiograms, and aortographies are routinely performed in transcatheter heart valve therapies. Consequently, all patients are exposed to multiple contrast injections with a following risk of nephrotoxicity and postoperative renal failure. The transapical aortic valve implantation without angiography can prevent contrast-related complications. Between November 2008 and November 2009, 30 consecutive high-risk patients (16 female, 53.3%) underwent transapical aortic valve implantation without angiography. The landmarks identification, the stent-valve positioning, and the postoperative control were routinely performed under transesophageal echocardiogram and fluoroscopic visualization without contrast injections. Mean age was 80.1 +/- 8.7 years. Mean valve gradient, aortic orifice area, and ejection fraction were 60.3 +/- 20.9 mm Hg, 0.7 +/- 0.16 cm(2), and 0.526 +/- 0.128, respectively. Risk factors were pulmonary hypertension (60%), peripheral vascular disease (70%), chronic pulmonary disease (50%), previous cardiac surgery (13.3%), and chronic renal insufficiency (40%) (mean blood creatinine and urea levels: 96.8 +/- 54 microg/dL and 8.45 +/- 5.15 mmol/L). Average European System for Cardiac Operative Risk Evaluation was 32.2 +/- 13.3%. Valve deployment in the ideal landing zone was 96.7% successful and valve embolization occurred once. Thirty-day mortality was 10% (3 patients). Causes of death were the following: intraoperative ventricular rupture (conversion to sternotomy), right ventricular failure, and bilateral pneumonia. Stroke occurred in one patient at postoperative day 9. Renal failure (postoperative mean blood creatinine and urea levels: 91.1 +/- 66.8 microg/dL and 7.27 +/- 3.45 mmol/L), myocardial infarction, and atrioventricular block were not detected. Transapical aortic valve implantation without angiography requires a short learning curve and can be performed routinely by experienced teams. Our report

Anterior urethral valves: not such a benign condition…

Directory of Open Access Journals (Sweden)

Omar eCruz-Diaz

2013-11-01

Full Text Available Purpose: Anterior urethral valves (AUV is an unusual cause of congenital obstruction of the male urethra, being 15 to 30 times less common than posterior urethral valves (PUV. It has been suggested that patients with congenital anterior urethral obstruction have a better prognosis than those with PUV.The long term prognosis of anterior urethral valves is not clear in the literature. In this report we describe our experience and long-term follow up of patients with AUV.Materials and methods: We retrospectively identified 13 patients who presented with the diagnosis of AUV in our institutions between 1994 and 2012. From the 11 patients included, we evaluated the gestational age, ultrasound and voiding cystourethrogram findings, age upon valve ablation, micturition pattern, creatinine and clinical follow up.Results: Between 1994 and 2012 we evaluated 150 patients with the diagnosis of urethral valves, where 11 patients (7.3% had AUV and an adequate follow up. Mean follow up is 6.3 years. 5 patients (45.4% had pre-natal diagnosis of AUV. The most common prenatal ultrasonographic finding was bilateral hydronephrosis and distended bladder.The mean gestational age was 37.6 weeks. Postnatally, 90% had trabeculated bladder, 80% hydronephrosis and 40% renal dysplasia. The most common clinical presentation was urinary tract infection in 5 patients (45.4%.7 patients (63.6% had primary transurethral valve resection or laser ablation and 3 patients (27.2% had primary vesicostomies. One boy (9.1% had urethrostomy with urethral diverticulum excision. 2 patients (18.2% developed end-stage renal disease (ESRD.Conclusions: Early urinary tract obstruction resulted in ESRD in 18% of our patient population. In our series, the complication rate and the evolution to renal failure are high and similar to patients with PUV. In patients with AUV we recommend long-term follow up and close evaluation of patient’s bladder and renal function.

Fairchild Stratos Division's Type II prototype lockhopper valve: METC Prototype Test Valve No. F-1 prototype lockhopper valve-testing and development project. Static test report

Energy Technology Data Exchange (ETDEWEB)

Goff, D. R.; Cutright, R. L.; Griffith, R. A.; Loomis, R. B.; Maxfield, D. A.; Moritz, R. S.

1981-10-01

METC Prototype Test Valve No. F-1 is a hybrid design, based on a segmented ball termed a visor valve, developed and manufactured by Fairchild Stratos Division under contract to the Department of Energy. The valve uses a visor arm that rotates into position and then translates to seal. This valve conditionally completed static testing at METC with clean gas to pressures of 1600 psig and internal valve temperatures to 600/sup 0/F. External leakage was excessive due to leakage through the stuffing box, purge fittings, external bolts, and other assemblies. The stuffing box was repacked several times and redesigned midway through the testing, but external leakage was still excessive. Internal leakage through the seats, except for a few anomalies, was very low throughout the 2409 cycles of testing. As shown by the low internal leakage, the visor valve concept appears to have potential for lock-hopper valve applications. The problems that are present with METC Prototype Test Valve No. F-1 are in the seals, which are equivalent to the shaft and bonnet seals in standard valve designs. The operating conditions at these seals are well within the capabilities of available seal designs and materials. Further engineering and minor modifications should be able to resolve the problems identified during static testing.

Prevalence of pannus formation after aortic valve replacement: clinical aspects and surgical management.

Science.gov (United States)

Sakamoto, Yoshimasa; Hashimoto, Kazuhiro; Okuyama, Hiroshi; Ishii, Shinichi; Shingo, Taguchi; Kagawa, Hiroshi

2006-01-01

Pannus formation after aortic valve replacement is not common, but obstruction due to chronic pannus is one of the most serious complications of valve replacement. The causes of pannus formation are still unknown and effective preventive methods have not been fully elucidated. We reviewed our clinical experience of all patients who underwent reoperation for prosthetic aortic valve obstruction due to pannus formation between 1973 and 2004. We compared the initial 18-year period of surgery, when the Björk-Shiley tilting-disk valve was used, and the subsequent 13-year period of surgery, when the St. Jude Medical valve was used. Seven of a total of 390 patients (1.8%) required reoperation for prosthetic aortic valve obstruction due to pannus formation. All seven patients were women; four patients underwent resection of the pannus and three patients needed replacement of the valve. The frequency of pannus formation in the early group was 2.4% (6/253), whereas it was 0.73% (1/137) in the late group (P Pannus was localized at the minor orifice of the Björk-Shiley valve in the early group and turbulent transvalvular blood flow was considered to be one of the important factors triggering its growth. We also consider that small bileaflet valves have the possibility of promoting pannus formation and that the implantation of a larger prosthesis can contribute to reducing the occurrence of pannus.

Design And Analysis Of A Camless Valve Mechanism For I.C Engines Using Rotary Disc Valves

Directory of Open Access Journals (Sweden)

Vivek Jitendra Panchal

2017-09-01

Full Text Available It is the object of the presented paper to provide an electromechanical rotary valve actuating system for opening and closing valves of an internal combustion engine capable of separately controlling both the inlet and exhaust valve operations of each individual cylinder in a multi-cylinder engine. This indicates that only one valve will be required for each cylinder of the engine. Previously published versions of this concept require a separate valve for intake and exhaust in each cylinder. The system provides an alternative to the camshaft assembly in an attempt to overcome the limitations and inadequacies inevitably posed by a fully mechanical system. The prototype development is approached in a theoretical manner beginning with the conceptualization and design of a rotating disk with a notches and corresponding closure surfaces to open and close the flow path. The actuated disk and notch design is then refined and followed by the design of an inlet and exhaust manifold to correspond to the valve design and the theorizing and design of a sealing gasket. The rotating speed of the valve is determined by a general idling speed and can be varied to provide variable valve timing with the motor. The final assembly eliminates a majority of the moving parts currently used in camshaft systems like the cam camshaft rocker arm push rod and springs and results in a significantly lighter valve actuation system. By eliminating the translatory motion of valves the problem of valves slamming on the valve seats at high velocities is eliminated thus greatly reducing engine wear.

Double Valve Replacement (Mitral and Aortic for Rheumatic Heart Disease: A 20-year experience with 300 patients.

Directory of Open Access Journals (Sweden)

Prashant Mishra

2016-09-01

Full Text Available Introduction: Rheumatic heart disease still remains one of the leading causes of congestive heart failure and death owing to valvular pathologies, in developing countries. Valve replacement still remains the treatment of choice in such patients.The aim of this study wasto analyze the postoperative outcome of  double valve replacement (Mitral and Aortic in patients of rheumatic heart disease. Materials and Methods: Between 1988 and 2008, 300 patients of rheumatic heart disease underwent double (Mitral and Aortic valve replacement with Starr Edwards valve or St Jude mechanical valve prosthesis were implanted. These patients were studied retrospectively for preoperative data and postoperative outcome including causes of early and late deaths and the data was analyzed statistically. Results: The 30-day hospital death rate was 11.3% andlate death occurred in 11.6%. Anticoagulant regimen was followed to maintain the target pro-thrombin time at 1.5 times the control value. The actuarial survival (exclusive of hospital mortality was 92.4%, 84.6%, and 84.4%, per year at 5, 10, and 20 years, respectively Conclusions: In view of the acknowledged advantageof superior durability, increased thromboresistance in our patient population, and its cost effectiveness the Starr-Edwards ball valve or St. Jude valve is the mechanical prosthesis of choice for advanced combined valvular disease. The low-intensity anticoagulant regimen has offered suffcient protection against thromboembolism as well as hemorrhage.

Steam Turbine Control Valve Stiction Effect on Power System Stability

International Nuclear Information System (INIS)

Halimi, B.

2010-01-01

One of the most important problems in power system dynamic stability is low frequency oscillations. This kind of oscillation has significant effects on the stability and security of the power system. In some previous papers, a fact was introduced that a steam pressure continuous fluctuation in turbine steam inlet pipeline may lead to a kind of low frequency oscillation of power systems. Generally, in a power generation plant, steam turbine system composes of some main components, i.e. a boiler or steam generator, stop valves, control valves and turbines that are connected by piping. In the conventional system, the turbine system is composed with a lot of stop and control valves. The steam is provided by a boiler or steam generator. In an abnormal case, the stop valve shuts of the steal flow to the turbine. The steam flow to the turbine is regulated by controlling the control valves. The control valves are provided to regulate the flow of steam to the turbine for starting, increasing or decreasing the power, and also maintaining speed control with the turbine governor system. Unfortunately, the control valve has inherent static friction (stiction) nonlinearity characteristics. Industrial surveys indicated that about 20-30% of all control loops oscillate due to valve problem caused by this nonlinear characteristic. In this paper, steam turbine control valve stiction effect on power system oscillation is presented. To analyze the stiction characteristic effect, firstly a model of control valve and its stiction characteristic are derived by using Newton's laws. A complete tandem steam prime mover, including a speed governing system, a four-stage steam turbine, and a shaft with up to for masses is adopted to analyze the performance of the steam turbine. The governor system consists of some important parts, i.e. a proportional controller, speed relay, control valve with its stiction characteristic, and stem lift position of control valve controller. The steam turbine has

Simulant Development for Hanford Tank Farms Double Valve Isolation (DVI) Valves Testing

Energy Technology Data Exchange (ETDEWEB)

Wells, Beric E.

2012-12-21

Leakage testing of a representative sample of the safety-significant isolation valves for Double Valve Isolation (DVI) in an environment that simulates the abrasive characteristics of the Hanford Tank Farms Waste Transfer System during waste feed delivery to the Waste Treatment and Immobilization Plant (WTP) is to be conducted. The testing will consist of periodic leak performed on the DVI valves after prescribed numbers of valve cycles (open and close) in a simulated environment representative of the abrasive properties of the waste and the Waste Transfer System. The valve operations include exposure to cycling conditions that include gravity drain and flush operation following slurry transfer. The simulant test will establish the performance characteristics and verify compliance with the Documented Safety Analysis. Proper simulant development is essential to ensure that the critical process streams characteristics are represented, National Research Council report “Advice on the Department of Energy's Cleanup Technology Roadmap: Gaps and Bridges”

Stent valve implantation in conventional redo aortic valve surgery to prevent patient-prosthesis mismatch.

Science.gov (United States)

Ferrari, Enrico; Franciosi, Giorgio; Clivio, Sara; Faletra, Francesco; Moccetti, Marco; Moccetti, Tiziano; Pedrazzini, Giovanni; Demertzis, Stefanos

2017-03-01

The goal was to show the technical details, feasibility and clinical results of balloon-expandable stent valve implantation in the aortic position during conventional redo open-heart surgery in selected obese patients with a small aortic prosthesis and severe patient-prosthesis mismatch. Two symptomatic overweight patients (body mass index of 31 and 38), each with a small aortic prosthesis (a 4-year-old, 21-mm Hancock II biological valve and a 29-year-old, 23-mm Duromedic mechanical valve), increased transvalvular gradients (59/31 and 74/44 mmHg) and a reduced indexed effective orifice area (0.50 and 0.43 cm 2 /m 2 ) underwent implantation of two 26-mm balloon-expandable Sapien 3 valves during standard on-pump redo valve surgery. Using full re-sternotomy, cardiopulmonary bypass and cardioplegic arrest, the two balloon-expandable stent valves were implanted under direct view using a standard aortotomy, after prosthesis removal and without annulus enlargement. Aortic cross-clamp times were 162 and 126 min; cardiopulmonary bypass times were 178 and 180 min; total surgical times were 360 and 318 min. At discharge, echocardiograms showed transvalvular peak and mean gradients of 13/9 and 23/13 mmHg and indexed effective orifice areas of 0.64 and 1.08 cm 2 /m 2 . The 3-month echocardiographic follow-up showed transvalvular peak and mean gradients of 18/9 and 19/11 mmHg and indexed effective orifice areas of 0.78 cm 2 /m 2 and 0.84 cm 2 /m 2 , with improved symptoms (New York Heart Association class 1). Implantation of a balloon-expandable stent valve during redo aortic valve surgery is feasible in selected cases and prevents patient-prosthesis mismatch in obese patients without need for aortic annulus enlargement. Moreover, in the case of stent valve degeneration, this approach permits additional valve-in-valve procedures with large stent valves and prevents re-redo surgery. © The Author 2016. Published by Oxford University Press on behalf of the

Cyclonic valve test: preliminary results

Energy Technology Data Exchange (ETDEWEB)

Monteiro, Andre Sampaio; Moraes, Carlos Alberto C.; Marins, Luiz Philipe M.; Soares, Fabricio; Oliveira, Dennis; Lima, Fabio Soares de; Airao, Vinicius [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Ton, Tijmen [Twister BV, Rijswijk (Netherlands)

2012-07-01

For many years, the petroleum industry has been developing a valve that input less shear to the flow for a given required pressure drop and this can be done using the cyclonic concept. This paper presents a comparison between the performances of a cyclonic valve (low shear) and a conventional globe valve. The aim of this work is to show the advantages of using a cyclonic low shear valve instead of the commonly used in the primary separation process by PETROBRAS. Tests were performed at PETROBRAS Experimental Center (NUEX) in Aracaju/SE varying some parameters: water cut; pressure loss (from 4 kgf/cm2 to 10 kgf/cm2); flow rates (30 m3/h and 45 m3/h). Results indicates a better performance of the cyclonic valve, if compared with a conventional one, and also that the difference of the performance, is a function of several parameters (emulsion stability, water content free, and oil properties). The cyclonic valve tested can be applied as a choke valve, as a valve between separation stages (for pressure drop), or for controlling the level of vessels. We must emphasize the importance to avoid the high shear imposed by conventional valves, because once the emulsion is created, it becomes more difficult to break it. New tests are being planned to occur in 2012, but PETROBRAS is also analyzing real cases where the applications could increase the primary process efficiency. In the same way, the future installations are also being designed considering the cyclonic valve usage. (author)

Bioprinting a cardiac valve.

Science.gov (United States)

Jana, Soumen; Lerman, Amir

2015-12-01

Heart valve tissue engineering could be a possible solution for the limitations of mechanical and biological prostheses, which are commonly used for heart valve replacement. In tissue engineering, cells are seeded into a 3-dimensional platform, termed the scaffold, to make the engineered tissue construct. However, mimicking the mechanical and spatial heterogeneity of a heart valve structure in a fabricated scaffold with uniform cell distribution is daunting when approached conventionally. Bioprinting is an emerging technique that can produce biological products containing matrix and cells, together or separately with morphological, structural and mechanical diversity. This advance increases the possibility of fabricating the structure of a heart valve in vitro and using it as a functional tissue construct for implantation. This review describes the use of bioprinting technology in heart valve tissue engineering. Copyright © 2015 Elsevier Inc. All rights reserved.

Intermittency in {sup 197}Au fragmentation

Energy Technology Data Exchange (ETDEWEB)

Dabrowska, A; Holynski, R; Olszewski, A; Szarska, M; Wilczynska, B; Wolter, W; Wosiek, B [Institute of Nuclear Physics, Cracow (Poland); Cherry, M L; Deines-Jones, P; Jones, W V; Sengupta, K; Wefel, B [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Physics and Astronomy; Waddington, C J [Minnesota Univ., Minneapolis, MN (United States). School of Physics and Astronomy; Pozharova, E A; Skorodko, T Yu [Inst. of Theoretical and Experimental Physics, Moscow (Russian Federation); KLMM Collaboration

1995-07-01

The concept of factorial moments was applied to an analysis of the dynamical fluctuations in the charge distributions of the fragments emitted from gold nuclei with energies 10.6 and < 1.0 GeV/n interacting with emulsion nuclei. Clear evidence for intermittent fluctuations has been found in an analysis using all the particles released from the gold projectile, with a stronger effect observed below 1 GeV/n than at 10.6 GeV/n. For the full data sets, however, the intermittency effect was found to be very sensitive to the singly charged particles, and neglecting these particles strongly reduces the intermittency signal. When the analysis is restricted to the multiply charged fragments, an intermittency effect is revealed only for multifragmentation events, although one that is enhanced as compared to the analysis of all, singly and multiply charged, particles. The properties of the anomalous fractal dimensions suggest a sequential decay mechanism, rather than the existence of possible critical behaviour in the process of nuclear fragmentation. The likely influence of the charge conservation effects and the finite size of decaying systems on the observed intermittency signals was pointed out. (author). 37 refs, 9 figs, 5 tabs.

Diseases of the Tricuspid Valve

Science.gov (United States)

... stenosis. Tricuspid Regurgitation Tricuspid regurgitation is also called tricuspid insufficiency or tricuspid incompetence. It means there is a ... require valve surgery. Tags: heart valves , tricuspid incompetence , ... tricuspid regurgitation , tricuspid stenosis , valve disease Related Links ...

Aortic root surgery in Marfan syndrome: Comparison of aortic valve-sparing reimplantation versus composite grafting.

Science.gov (United States)

Karck, Matthias; Kallenbach, Klaus; Hagl, Christian; Rhein, Christine; Leyh, Rainer; Haverich, Axel

2004-02-01

The objective of this study was to compare the results of aortic valve-sparing reimplantation and aortic root replacement with mechanical valve conduits in patients with Marfan syndrome undergoing operation for aortic root aneurysms. Patients and methods Between March 1979 and April 2002, 119 patients with clinical evidence of Marfan syndrome underwent composite graft replacement with mechanical valve conduits (n = 74) or aortic valve-sparing reimplantation according to David (n = 45). The underlying causes were aortic dissection type A (43 patients) and aneurysms (76 patients). Patients undergoing aortic valve reimplantation were younger compared with patients undergoing composite grafting (28 vs 35 years, P =.002) and had longer intraoperative aortic crossclamp times (125 vs 78 minutes, P valve reimplantation (P =.15). Mean follow-up was 30 months for patients undergoing aortic valve reimplantation and 114 months for patients undergoing composite grafting. Freedom from reoperation and death after 5 years postoperatively was 92% and 89% in patients undergoing composite grafting and 84% and 96% in patients undergoing aortic valve reimplantation (P =.31; P =.54), respectively. Thromboembolic complications or late postoperative bleeding occurred in 17 patients undergoing composite grafting, and an early postoperative event occurred in 1 patient undergoing aortic valve reimplantation. The results of aortic valve reimplantation and composite grafting of the aortic valve and ascending aorta with mechanical valve conduits are similar with regard to early and mid-term postoperative mortality and to the incidence of late reoperations in patients with Marfan syndrome. The low risk of thromboembolic or bleeding complications favors aortic valve reimplantation in these patients.

THE EFFECT OF ADRENAL MEDULLECTOMY ON METABOLIC RESPONSES TO CHRONIC INTERMITTENT HYPOXIA

Science.gov (United States)

Shin, Mi-Kyung; Han, Woobum; Bevans-Fonti, Shannon; Jun, Jonathan C.; Punjabi, Naresh M.; Polotsky, Vsevolod Y.

2014-01-01

Obstructive sleep apnea causes intermittent hypoxia (IH) and is associated with insulin resistance and type 2 diabetes. IH increases plasma catecholamine levels, which may increase insulin resistance and suppress insulin secretion. The objective of this study was to determine if adrenal medullectomy (MED) prevents metabolic dysfunction in IH. MED or sham surgery was performed in 60 male C57BL/6J mice, which were then exposed to IH or control conditions (intermittent air) for 6 weeks. IH increased plasma epinephrine and norepinephrine levels, increased fasting blood glucose and lowered basal and glucose-stimulated insulin secretion. MED decreased baseline epinephrine and prevented the IH induced increase in epinephrine, whereas the norepinephrine response remained intact. MED improved glucose tolerance in mice exposed to IH, attenuated the impairment in basal and glucose-stimulated insulin secretion, but did not prevent IH-induced fasting hyperglycemia or insulin resistance. We conclude that the epinephrine release from the adrenal medulla during IH suppresses insulin secretion causing hyperglycemia. PMID:25179887

Water quality effects of intermittent water supply in Arraiján, Panama.

Science.gov (United States)

Erickson, John J; Smith, Charlotte D; Goodridge, Amador; Nelson, Kara L

2017-05-01

Intermittent drinking water supply is common in low- and middle-income countries throughout the world and can cause water quality to degrade in the distribution system. In this study, we characterized water quality in one study zone with continuous supply and three zones with intermittent supply in the drinking water distribution network in Arraiján, Panama. Low or zero pressures occurred in all zones, and negative pressures occurred in the continuous zone and two of the intermittent zones. Despite hydraulic conditions that created risks for backflow and contaminant intrusion, only four of 423 (0.9%) grab samples collected at random times were positive for total coliform bacteria and only one was positive for E. coli. Only nine of 496 (1.8%) samples had turbidity >1.0 NTU and all samples had ≥0.2 mg/L free chlorine residual. In contrast, water quality was often degraded during the first-flush period (when supply first returned after an outage). Still, routine and first-flush water quality under intermittent supply was much better in Arraiján than that reported in a previous study conducted in India. Better water quality in Arraiján could be due to better water quality leaving the treatment plant, shorter supply outages, higher supply pressures, a more consistent and higher chlorine residual, and fewer contaminant sources near pipes. The results illustrate that intermittent supply and its effects on water quality can vary greatly between and within distribution networks. The study also demonstrated that monitoring techniques designed specifically for intermittent supply, such as continuous pressure monitoring and sampling the first flush, can detect water quality threats and degradation that would not likely be detected with conventional monitoring. Copyright © 2017 Elsevier Ltd. All rights reserved.

Numerical study on cavitation inception in the rotary valve of the hydraulic power steering system

International Nuclear Information System (INIS)

Ryu, Gwang Nyeon; Cho, Myung Hwan; Yoo, Jung Yul; Park, Sun Hong

2009-01-01

The rotary valve directs the power steering oil to either side of a power piston and relieves the driver of the effort to turn the wheel, when a driver begins to operate the vehicle. It is well known that the hiss noise occurring at that moment is caused mainly by cavitation of the oil inside the rotary valve. In this paper, two types of rotary valve (round and straight type) have been analyzed numerically using three-dimensional cavitation model embedded in the commercial code, FLUENT v6.2 and the results have been compared with the measured hiss noise level in a semi-anechoic chamber. The volume of the oil vapor generated from cavitation was larger in Round type valve which has a convex shape of the sleeve grooves than in Straight type valve which has a rectangular shape of the sleeve grooves. The hiss noise level of Round type valve was higher than that of Straight type valve as well. These results mean that the hiss noise can be reduced by the change of the shape of the grooves.

A Rare Case of Intermittent Claudication Associated with Impaired Arterial Vasodilation

Directory of Open Access Journals (Sweden)

J. J. Posthuma

2017-01-01

Full Text Available Exercise-related intermittent claudication is marked by reduced blood flow to extremities caused by either stenosis or impaired vascular function. Although intermittent claudication is common in the elderly, it rarely occurs in the young and middle-aged individuals. Here, we report a case of exercise-related claudication in a 41-year-old woman, in the absence of overt vascular pathology. Using a series of imaging and functional tests, we established that her complaints were due to impaired arterial vasodilation, possibly due to a defect in nitrous oxide-mediated dilation. The symptoms were reversible upon administration of a calcium antagonist, showing reversibility of the vascular impairment. Identification of reversible vascular “stiffness” merits consideration in young and otherwise healthy subjects with claudication of unknown origin.

Optimal intermittent search strategies

Energy Technology Data Exchange (ETDEWEB)

Rojo, F; Budde, C E [FaMAF, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina); Wio, H S [Instituto de Fisica de Cantabria, Universidad de Cantabria and CSIC E-39005 Santander (Spain)

2009-03-27

We study the search kinetics of a single fixed target by a set of searchers performing an intermittent random walk, jumping between different internal states. Exploiting concepts of multi-state and continuous-time random walks we have calculated the survival probability of a target up to time t, and have 'optimized' (minimized) it with regard to the transition probability among internal states. Our model shows that intermittent strategies always improve target detection, even for simple diffusion states of motion.

Optimal results of aortic valve replacement with small mechanical valves (< 19 mm).

Science.gov (United States)

Kato, Yasuyuki; Hattori, Koji; Motoki, Manabu; Takahashi, Yosuke; Kotani, Shinsuke; Nishimura, Shinsuke; Shibata, Toshihiko

2013-07-01

Controversy exists regarding the optimal operative method or type of prosthesis for patients with a small aortic root. The aim of this retrospective study was to investigate the early and mid-term outcomes of standard aortic valve replacement (AVR) using 16 mm or 18 mm ATS Advanced Performance (AP) or 17 mm St. Jude Medical (SJM) Regent valves for a small aortic root. Between April 2003 and August 2009, 78 patients (age range: 50-86 years; 86% aged > or = 65 years) underwent AVR with 16 mm or 18 mm ATS AP valves (16AP group: n = 21, 18AP group: n = 32), or a 17 mm SJM Regent valve (17Regent group: n = 25). Fifty-six patients (72%) had a body surface area (BSA) of regression was similar among the groups (-30%, -25% and -28% in the 16AP, 17Regent and 18AP groups, respectively; p = 0.844). The early and mid-term results of AVR with 16 mm or 18 mm ATS AP valves, or with a 17 mm SJM Regent valve, were satisfactory. Therefore, standard AVR using these small mechanical prostheses, which avoids the need to enlarge the annulus or to conduct stentless bioprosthesis implantation, might represent an acceptable method, especially in elderly patients with a small aortic root.

Study on Friction and Wear Characteristics of Aluminum Alloy Hydraulic Valve Body and Its Antiwear Mechanism

Directory of Open Access Journals (Sweden)

Rong Li

2017-03-01

Full Text Available In order for the working status of the aluminum alloyed hydraulic valve body to be controlled in actual conditions, a new friction and wear design device was designed for the cast iron and aluminum alloyed valve bodies comparison under the same conditions. The results displayed that: (1 The oil leakage of the aluminum alloyed hydraulic valve body was higher than the corresponding oil leakage of the iron body during the initial running stage. Besides during a later running stage, the oil leakage of the aluminum alloyed body was lower than corresponding oil leakage of the iron body; (2 The actual oil leakage of different materials consisted of two parts: the foundation leakage that was the leakage of the valve without wear and wear leakage that was caused by the worn valve body; (3 The aluminum alloyed valve could rely on the dust filling furrow and melting mechanism that led the body surface to retain dynamic balance, resulting in the valve leakage preservation at a low level. The aluminum alloy modified valve body can meet the requirements of hydraulic leakage under pressure, possibly constituting this alloy suitable for hydraulic valve body manufacturing.

Transcatheter mitral valve repair in osteogenesis imperfecta associated mitral valve regurgitation.

Science.gov (United States)

van der Kley, Frank; Delgado, Victoria; Ajmone Marsan, Nina; Schalij, Martin J

2014-08-01

Osteogenesis imperfecta is associated with increased prevalence of significant mitral valve regurgitation. Surgical mitral valve repair and replacement are feasible but are associated with increased risk of bleeding and dehiscence of implanted valves may occur more frequently. The present case report describes the outcomes of transcatheter mitral valve repair in a patient with osteogenesis imperfecta. A 60 year-old patient with osteogenesis imperfecta and associated symptomatic moderate to severe mitral regurgitation underwent transthoracic echocardiography which showed a nondilated left ventricle with preserved systolic function and moderate to severe mitral regurgitation. On transoesophageal echocardiography the regurgitant jet originated between the anterolateral scallops of the anterior and posterior leaflets (A1-P1). Considering the comorbidities associated with osteogenesis imperfecta the patient was accepted for transcatheter mitral valve repair using the Mitraclip device (Abbott vascular, Menlo, CA). Under fluoroscopy and 3D transoesophageal echocardiography guidance, a Mitraclip device was implanted between the anterolateral and central scallops with significant reduction of mitral regurgitation. The postoperative evolution was uneventful. At one month follow-up, transthoracic echocardiography showed a stable position of the Mitraclip device with no mitral regurgitation. Transcatheter mitral valve repair is feasible and safe in patients with osteogenesis imperfecta and associated symptomatic significant mitral regurgitation. Copyright © 2014 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

49 CFR 393.49 - Control valves for brakes.

Science.gov (United States)

2010-10-01

... in paragraphs (b) and (c) of this section, every motor vehicle manufactured after June 30, 1953, which is equipped with power brakes, must have the braking system so arranged that one application valve must when activated cause all of the service brakes on the motor vehicle or combination motor vehicle...

Development of an effective valve packing program

Energy Technology Data Exchange (ETDEWEB)

Hart, K.A.

1996-12-01

Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV`s and AOV`s, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance.

Inverse spin-valve effect in nanoscale Si-based spin-valve devices

Science.gov (United States)

Hiep, Duong Dinh; Tanaka, Masaaki; Hai, Pham Nam

2017-12-01

We investigated the spin-valve effect in nano-scale silicon (Si)-based spin-valve devices using a Fe/MgO/Ge spin injector/detector deposited on Si by molecular beam epitaxy. For a device with a 20 nm Si channel, we observed clear magnetoresistance up to 3% at low temperature when a magnetic field was applied in the film plane along the Si channel transport direction. A large spin-dependent output voltage of 20 mV was observed at a bias voltage of 0.9 V at 15 K, which is among the highest values in lateral spin-valve devices reported so far. Furthermore, we observed that the sign of the spin-valve effect is reversed at low temperatures, suggesting the possibility of a spin-blockade effect of defect states in the MgO/Ge tunneling barrier.

Mechanical versus bioprosthetic aortic valve replacement.

Science.gov (United States)

Head, Stuart J; Çelik, Mevlüt; Kappetein, A Pieter

2017-07-21

Mechanical valves used for aortic valve replacement (AVR) continue to be associated with bleeding risks because of anticoagulation therapy, while bioprosthetic valves are at risk of structural valve deterioration requiring reoperation. This risk/benefit ratio of mechanical and bioprosthetic valves has led American and European guidelines on valvular heart disease to be consistent in recommending the use of mechanical prostheses in patients younger than 60 years of age. Despite these recommendations, the use of bioprosthetic valves has significantly increased over the last decades in all age groups. A systematic review of manuscripts applying propensity-matching or multivariable analysis to compare the usage of mechanical vs. bioprosthetic valves found either similar outcomes between the two types of valves or favourable outcomes with mechanical prostheses, particularly in younger patients. The risk/benefit ratio and choice of valves will be impacted by developments in valve designs, anticoagulation therapy, reducing the required international normalized ratio, and transcatheter and minimally invasive procedures. However, there is currently no evidence to support lowering the age threshold for implanting a bioprosthesis. Physicians in the Heart Team and patients should be cautious in pursuing more bioprosthetic valve use until its benefit is clearly proven in middle-aged patients. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Latest design of gate valves

Energy Technology Data Exchange (ETDEWEB)

Kurzhofer, U.; Stolte, J.; Weyand, M.

1996-12-01

Babcock Sempell, one of the most important valve manufacturers in Europe, has delivered valves for the nuclear power industry since the beginning of the peaceful application of nuclear power in the 1960s. The latest innovation by Babcock Sempell is a gate valve that meets all recent technical requirements of the nuclear power technology. At the moment in the United States, Germany, Sweden, and many other countries, motor-operated gate and globe valves are judged very critically. Besides the absolute control of the so-called {open_quotes}trip failure,{close_quotes} the integrity of all valve parts submitted to operational forces must be maintained. In case of failure of the limit and torque switches, all valve designs have been tested with respect to the quality of guidance of the gate. The guidances (i.e., guides) shall avoid a tilting of the gate during the closing procedure. The gate valve newly designed by Babcock Sempell fulfills all these characteristic criteria. In addition, the valve has cobalt-free seat hardfacing, the suitability of which has been proven by friction tests as well as full-scale blowdown tests at the GAP of Siemens in Karlstein, West Germany. Babcock Sempell was to deliver more than 30 gate valves of this type for 5 Swedish nuclear power stations by autumn 1995. In the presentation, the author will report on the testing performed, qualifications, and sizing criteria which led to the new technical design.

Thermal fatigue behavior of valves

International Nuclear Information System (INIS)

Moinereau, D.; Scliffet, L.; Capion, J.C.; Genette, P.

1991-01-01

This paper reports that valves of pressurized water reactors are exposed to thermal shocks during transient operations. The numerous thermal shock tests performed on valves on the EDF test facilities have shown the sensibility of fillets and geometrical discontinuities to thermal fatigue: cracks can appear in those areas and grow through the valve body. Valves systems designated as level 1 must be designed to withstand fatigue up to the second isolation valve: the relevant rule is specified in the paragraph B 3500 of the French RCCM code. It is a simplified method which doesn't require finite element calculations. Many valve systems have been designed according to this rule and have been operated without accident. However, in one case, important cracks were found in the fillet of a check-valve after numerous thermal shocks. Calculation of the valve's behavior according to the RCCM code to estimate the fatigue damage resulting from thermal shocks led to a low damage factor, which doesn't agree with the experimental results. This was confirmed by new testings and showed the inadequacy of B 3500 rule for thermal transients. On this base a new rule is proposed to estimate fatigue damage resulting from thermal shocks. An experimental program has been realized to validate this rule. Axisymetrical analytical mock-ups with different geometries and one check-valve in austenitic stainless steel 316 L have been submitted to hot thermal shocks of 210 degrees C magnitude

Surge-damping vacuum valve

International Nuclear Information System (INIS)

Bullock, J.C.; Kelley, B.E.

1977-01-01

A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve