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Sample records for expanded polytetrafluoroethylene femoral-popliteal

  1. Expanded polytetrafluoroethylene augmentation of the lower face.

    PubMed

    Sherris, D A; Larrabee, W F

    1996-05-01

    Most options for rejuvenation of the lower face use soft-tissue fillers that augment the appropriate sites. Each of these options has associated risks and benefits. The U.S. Food and Drug Administration recently approved the use of expanded polytetrafluoroethylene (E-PTFE) as a soft-tissue filler in the face. From January 1991 through December 1993, the authors used E-PTFE soft-tissue patches for lower facial augmentation in 41 patients at 115 implant sites. Postsurgical follow-up has ranged from 2.5 to 4.5 years; during this time, complications have occurred in 4 patients. One implant had to be removed because of a seroma (1 patient), 4 implants required further secondary augmentation (2 patients), and 1 implant required revision because of malposition (1 patient). There have been no cases of implant infection, extrusion, long-term inflammation, or capsule formation. In this article, the authors review the technical aspects of E-PTFE use and discuss issues relating to the long-term efficacy of this new option for soft-tissue augmentation. The technique is also compared with other options for rejuvenation of the lower face.

  2. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Nonabsorbable expanded polytetrafluoroethylene surgical suture. 878.5035 Section 878.5035 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  3. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nonabsorbable expanded polytetrafluoroethylene surgical suture. 878.5035 Section 878.5035 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  4. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Nonabsorbable expanded polytetrafluoroethylene surgical suture. 878.5035 Section 878.5035 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  5. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Nonabsorbable expanded polytetrafluoroethylene surgical suture. 878.5035 Section 878.5035 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  6. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Nonabsorbable expanded polytetrafluoroethylene surgical suture. 878.5035 Section 878.5035 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  7. Mediastinal Abscess Caused by an Expanded Polytetrafluoroethylene Membrane.

    PubMed

    Matsuzaki, Kanji; Tsukada, Toru; Sato, Masataka; Watanabe, Yasunori; Ikeda, Akihiko; Konishi, Taisuke; Jikuya, Tomoaki

    2017-07-01

    A 76-year-old man who had undergone tricuspid annuloplasty 13 years earlier was admitted to our hospital because of a high fever. Although he was treated with antibiotics for pneumonia, a mild fever persisted. Computed tomography and gallium scintigraphy revealed a mediastinal abscess with an expanded polytetrafluoroethylene (ePTFE) membrane. There were no positive cultures or sternal changes indicating poststernotomy mediastinitis. The membrane was removed by a left parasternal approach without resternotomy, and its total removal was essential for the patient's recovery. This is the first reported case of sterile mediastinal abscess caused by an ePTFE membrane after a cardiac operation. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  8. Expanded Polytetrafluoroethylene for Chordal Replacement: Preventing Knot Failure.

    PubMed

    Miller, Jacob R; Deeken, Corey R; Ray, Shuddhadeb; Henn, Matthew C; Lancaster, Timothy S; Schuessler, Richard B; Damiano, Ralph J; Melby, Spencer J

    2015-12-01

    Expanded polytetrafluoroethylene suture is commonly used for chordal replacement in mitral valve repair, but due to material characteristics, knots can unravel. Our aim was to determine the knot security, including how many throws are necessary to prevent knot failure, with Gore-Tex (W.L. Gore and Associates, Elkton, MD) and the newly available Chord-X (On-X Life Technologies Inc, Austin, TX). Knots were evaluated for maximal load based on: number of throws (6, 8, 10, and 12), tension to secure each throw (10%, 50%, and 85%) and suture type (Gore-Tex CV-5 and Chord-X 3-0). A physiologic force of 2 N was used for comparison. We evaluated 240 knots. For all knots, the mean load to failure was 11.1 ± 5.8 N. Failure occurred due to unraveling in 141 knots (59%) at 7.1 ± 4.1 N and to breaking in 99 (41%) at 16.7 ± 2.0 N (p < 0.01). Gore-Tex failed at higher loads (12.6 ± 6.0 N vs 9.5 ± 5.2 N, p < 0.01); however, an equivalent number, 6 Gore-Tex and 6 Chord-X, unraveled at 2 N, all with fewer than 10 throws. Expanded polytetrafluoroethylene has adequate strength to prevent breakage; however, a risk of knot unraveling at physiologic conditions exists when fewer than 10 throws are performed. Copyright © 2015 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  9. A small arterial substitute: expanded microporous polytetrafluoroethylene: patency versus porosity.

    PubMed Central

    Campbell, C D; Goldfarb, D; Roe, R

    1975-01-01

    Eighty-nine grafts of expanded microporous polytetrafluoroethylene (PTFE) with a diameter of 4 mm, were placed in the carotid and femoral arteries of dogs. The animals were sacrificed at varying intervals beginning three days after operation. Four animals remain alive with patent grafts 10 months post-operatively. Twenty-four of 89 grafts were occluded, an overall patency of 73%. Fibril length (pore size) of the graft material was varied from 4 to 110 microns. Average pore size ranged from 9 to 65 microns. Wall thickness varied from 0.3 to 0.75 mm. Density ranged from 0.24 to 0.35 g/ml. Tissue ingrowth, neointimization and patency rate as compared to pore size, wall-thickness and density of expanded PTFE were observed. Pore size is the primary determinant of tissue ingrowth, neointimization and patency. Of 51 grafts with an average pore size of 22 microns or less, there were 6 occlusions, an 88% patency rate. There were 38 grafts with an average pore size of 34 microns or greater. In these 38 grafts, 18 occlusions were observed, a 53% patency rate. Patent grafts demonstrated tissue ingrowth, capillary formation an a thin neointima. Using small pore grafts, patency rates of 90% can be anticipated in the dog. Expanded microporous PTFE with its ease of handling, strength and pliability may be the vascular prosthesis of choice in man. Images Fig. 1. Fig. 3. Fig. 4. Fig. 5. PMID:1211990

  10. Expanded polytetrafluoroethylene (Gore-Tex) augmentation of deep nasolabial creases.

    PubMed

    Robertson, K M; Dyer, W K

    1999-04-01

    To evaluate the safety and efficacy of expanded polytetrafluoroethylene (PTFE) (Gore-Tex; W. L. Gore & Associates, Flagstaff, Ariz) for augmentation of deep nasolabial creases. Retrospective chart review with a minimum of 12 months of follow-up. Private practice ambulatory surgery center. One hundred consecutive patients (average age, 49 years) undergoing expanded PTFE augmentation of the nasolabial crease. A standardized, reproducible rating scale assessed preoperative crease severity. Clinical effectiveness was determined by the numerical degree of improvement in crease severity rating after surgery, and by the number of procedures required to achieve the desired aesthetic results. Patients initially had grade 1 (14.5%), grade 2 (54.0%), grade 3 (20.0%), or grade 4 (11.5%) crease severity ratings. On average, patients with grade 1 creases required 1.17 total augmentation procedures, those with grade 2 required 1.60, those with grade 3 required 1.93, and those with grade 4 required 1.86. On average, with each augmentation, patients with grade 1 improved 0.61 relative severity points; those with grade 2, 0.85; those with grade 3, 1.29; and those with grade 4, 1.28. Nine patients developed late postoperative sequelae. Four creases (2.0%) displayed an unnatural mounded appearance because of superficial expanded PTFE placement. All 4 creases underwent elective removal of a single superficial PTFE strip, with resultant return of aesthetically correct crease augmentation. Five creases (2.5%) developed implant site infections; in all 5 cases, the involved strips were removed and the infection was resolved with a 10-day course of oral antibiotics. Expanded PTFE augmentation presents a safe, effective method for softening deep nasolabial creases. Patients with more severe creases are likely to show more improvement with each augmentation, but are also more likely to require multiple procedures to achieve the desired aesthetic result.

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

    PubMed Central

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

    1987-01-01

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

  12. Management of complicated multirecurrent pterygia using multimicroporous expanded polytetrafluoroethylene

    PubMed Central

    Kim, Kyoung Woo; Kim, Jae Chan; Moon, Jun Hyung; Koo, Hyun; Kim, Tae Hyung; Moon, Nam Ju

    2013-01-01

    Aims To evaluate the efficiency of multimicroporous expanded polytetrafluoroethylene (e-PTFE) insertion in complicated multirecurrent pterygia. Methods A total of 62 eyes from 62 patients with a multirecurrent pterygium associated with symblepharon or motility restriction-related binocular diplopia were recruited. All eyes underwent pterygia excision followed by application of 0.033% mitomycin C, amniotic membrane transplantation and conjunctival limbal autograft. Multimicroporous e-PTFE was then inserted intraoperatively in 30 eyes between the transplanted amniotic membrane and the conjunctiva (group A), but not inserted in the other 32 eyes (group B). The main outcome measures were symblepharon formation, motility restriction, binocular diplopia, subjective score of conjunctival hyperaemia and postoperative pterygium recurrence. Results In the mean follow-up period of 17.2±2.3 months, symblepharon formation, motility restriction, diplopia and conjunctival hyperaemia were significantly improved after surgery in group A patients (p=0.000, 0.000, 0.008 and 0.000, respectively). Postoperative symblepharon formation, motility restriction and conjunctival hyperaemia were significantly less in group A compared to group B (p=0.024, 0.027 and 0.000, respectively). After surgery, corneal recurrence developed in one eye (3.3%) from group A, which was significantly lower than the eight eyes (25%) from group B (p=0.027). Conclusions Multimicroporous e-PTFE insertion may provide a novel approach for treating intractable complicated multirecurrent pterygia. PMID:23505304

  13. Histologic changes in transplanted expanded polytetrafluoroethylene in an animal model.

    PubMed

    Kim, Ji Heui; Park, Chan Hum; Lee, Ok Joo; Lee, Jun Ho; Hong, Seok Min

    2012-01-01

    Several materials have been used for nasal augmentation surgery. Expanded polytetrafluoroethylene (e-PTFE) (Gore-Tex; W. L. Gore & Associates, Flagstaff, AZ) has proven to be an ideal synthetic material for nasal augmentation. Gore-Tex contains numerous pores that stabilize an implant, but this advantage has been tempered by unpredictable outcomes. The purpose of this study was to evaluate morphologic and histologic changes in nonreinforced Gore-Tex in a rabbit model. In vivo study using a rabbit model. To analyze histologic changes, we used 20 New Zealand white rabbits. Gore-Tex was implanted into the nasal dorsum of the rabbits. Then, en bloc specimens containing the implant and surrounding soft tissues were sampled 1, 3, 6, and 12 months after implantation. We evaluated the three-dimensional size of the implants over time using light and electron microscopy to investigate histologic and morphologic changes. Following gross analysis, none of the implants were lost or extruded, and there was no evidence of wound infection. Diminution rates of thickness, width, and height in the implants were 22%, 2%, and 5%, respectively. Histologically, connective tissue growth was observed in all specimens, and the internodal space decreased owing to connective tissue ingrowth over time. Neovascularization was observed 3 months after implantation, and degenerative changes were also observed after 6 months. Gore-Tex should be carefully trimmed for use in augmentation because of its potential to decrease in size over time. Additional studies are necessary before these results can be applied in clinical practice. Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.

  14. Heparin-bonded expanded polytetrafluoroethylene femoropopliteal bypass grafts outperform expanded polytetrafluoroethylene grafts without heparin in a long-term comparison.

    PubMed

    Samson, Russell H; Morales, Ricardo; Showalter, David P; Lepore, Michael R; Nair, Deepak G

    2016-09-01

    Expanded polytetrafluoroethylene (ePTFE) grafts have become an acceptable prosthetic alternative to autologous vein for infrainguinal arterial reconstructions. Recently, heparin bonding to the graft's luminal surface has been used as an adjunctive method of improving graft patency. We retrospectively evaluated a prospective experience with heparin-bonded ePTFE (HePTFE) vs the results of a prior experience with standard ePTFE (SePTFE) to compare patency rates in above-knee (AK) and below-knee (BK) femoropopliteal bypass through the 5-year follow-up. Prosthetic femoropopliteal bypasses performed by our four-surgeon group were constructed using 6-mm SePTFE grafts before August 2007. Subsequently, all such bypasses were constructed using 6-mm HePTFE (Propaten graft; W. L. Gore & Associates, Flagstaff, Ariz). The surgical technique used in all cases throughout the study was similar irrespective of surgeon or graft material. Loss of primary patency was defined by graft thrombosis; duplex scan confirmed graft failure. Descriptive estimation of patency rates was carried out using standard Kaplan-Meier methods. Cox proportional hazards regression was used to analyze relationships between predictors and time to loss of patency. There were 192 AK (87 Propaten, 105 SePTFE) and 60 BK (42 Propaten, 18 SePTFE) grafts. Overall primary patency for Propaten was statistically better than SePTFE at years 1 (93.6% vs 84.2%), 2 (79.7% vs 73.8%), 3 (79.7% vs 69.5%), 4 (74.5% vs 59.9%) and 5 (74.5% vs 56.2%; log-rank test, P = .036). Five-year primary patency was superior for Propaten AK grafts (85.2% vs 59.3%; log-rank test, P = .028) and for Propaten BK grafts (59.6% vs 0.0/undeterminable; log-rank test, P = .016). Variables significantly associated with loss of patency for Propaten and SePTFE were claudication (hazard ratio [HR], 0.41), age (HR, 0.95), isolated popliteal artery (HR, 3.1-4.4), and ankle-brachial index after the procedure (HR, 0.10). Controlling for conduit effect

  15. [The treatment of upper eyelid sulcus using the expanded polytetrafluoroethylene implanted in orbit].

    PubMed

    Xu, Zhou; Min, Wei; Zheyuan, Yu; Jieneng, Wu

    2015-07-01

    To explore the feasibility of the treatment of upper eyelid sulcus using the expanded polytetrafluoroethylene implanted in orbit. From July 2009 to April 2011, a total of 16 patients with upper eyelid sulcus were treated for recreating youthful periorbital appearance. To correct this kind of clinical characteristic, expanded polytetrafluoroethylene with different size were used as the orbital implant to restore the orbital contents and reinforce the bony support. upper eyelid sulcus was reversed effectively. With average 2.5 year follow up, upper eyelid sulcus of 16 cases was reversed effectively. No postoperative complication related to globe or affected normal physical function was found. The technique of orbital implantation with Expanded Polytetrafluoroethylene is beneficial for the treatment of the upper eyelid sulcus.

  16. Occurrence of occlusive intimal changes in an expanded polytetrafluoroethylene graft.

    PubMed

    Carson, S N; Hunter, G; French, S; Lord, P; Wong, H N

    1980-01-01

    A case report is presented demonstrating pathologic changes in the neointima that formed when a polytetrafluoroethylene (PTFE) graft was placed in a 35 year old white male with severe arteriosclerosis. Representative sections of the patient's artery and graft were taken which demonstrated considerable smooth muscle proliferation in both along with full wall healing in the latter. Partial oclusion of the total length of the PTFE graft by a process similar to that occurring in the patient's own arteriosclerotic arteries was found. The consistency and extent of the involvement (> 10 cm in length) would appear to preclude entities such as neointimal fibrous hyperplasia and may point to another consequence of intimal injury and full wall graft healing which may be an undesirable effect of arteriosclerotic metabolism in the human. It is conceivable that full wall graft healing in an arteriosclerotic individual may have untoward events that need to be further investigated as new graft materials are developed.

  17. Histological study of expanded polytetrafluoroethylene (Gore-Tex) implanted in the human nose.

    PubMed

    Park, Chan Hum

    2008-12-01

    In rhinoplasty, various materials are used for nasal augmentation. Among these, expanded polytetrafluoroethylene (Gore-Tex) is commonly used because of its supposed high biocompatibility. However, most studies regarding histological changes associated with its implantation have been carried out in animal models, and very few data are available from long-term human studies. We used light and electron microscopy to investigate the histological changes associated with expanded polytetrafluoroethylene in nasal augmentation in 30 patients. Histologically, connective tissue ingrowth was observed in all specimens. However, the degree of foreign body reaction and collagen deposition varied from specimen to specimen and had no apparent relationship with duration. Neovascularization was observed in specimens with durations longer than 12 months, and degenerative calcification was observed in a 36-month-duration specimen. Unlike the findings in previous reports, differences among individual responses, degenerative changes, and partially calcified lesions were observed in the expanded polytetrafluoroethylene. Based on this study, expanded polytetrafluoroethylene is a biocompatible material, but further long-term studies are necessary to address histological changes associated with the implantation of the material in the human nose.

  18. Frontalis suspension with an expanded polytetrafluoroethylene sheet for congenital ptosis repair.

    PubMed

    Kokubo, Kenichi; Katori, Nobutada; Hayashi, Kengo; Kasai, Kenichiro; Kamisasanuki, Taro; Sueoka, Kentaro; Maegawa, Jiro

    2016-05-01

    Congenital ptosis with poor levator function is most often repaired with a frontalis suspension procedure. Autogenous fascia lata grafting is generally effective, with low rates of infection and granuloma formation. However, contraction of the grafted fascia lata may cause eyelash inversion, tarsal deformity, and/or lagophthalmos. Conversely, several synthetic suspensory materials have been used for frontalis suspension, among which polytetrafluoroethylene has been reported to be comparable to the fascia lata. However, in some studies using polytetrafluoroethylene strips or sutures, complications such as infection and granuloma formation were a significant problem. This study evaluated the outcomes of frontalis suspension with an expanded polytetrafluoroethylene sheet for congenital ptosis repair in 97 patients (130 eyelids). No ptosis recurrence was reported in an average follow-up of 31.6 months (range: 6-102 months). Six of the 130 eyelids (4.6%) had complications. Based on these results, frontalis suspension with an expanded polytetrafluoroethylene sheet for congenital ptosis repair can be considered safe and effective and be recommended for clinical use.

  19. A 25-year study of chordal replacement with expanded polytetrafluoroethylene in mitral valve repair†.

    PubMed

    Hata, Hiroki; Fujita, Tomoyuki; Shimahara, Yusuke; Sato, Shunsuke; Ishibashi-Ueda, Hatsue; Kobayashi, Junjiro

    2015-04-01

    This study examines the outcome of mitral valve repair with chordal replacement using expanded polytetrafluoroethylene over the past 25 years. From July 1988 to February 2013, 224 consecutive patients (mean age 57 years, 34% women) underwent mitral valve repair with chordal replacement using expanded polytetrafluoroethylene sutures at our institution. Isolated anterior leaflet prolapse was observed in 134 patients (60%), isolated posterior leaflet prolapse was observed in 13 patients (6%) and bileaflet prolapse was observed in 77 patients (34%). The number of replaced artificial chordae ranged from 2 to 12 (mean 3.7) per patient. Transthoracic echocardiography was performed pre- and postoperatively and in the follow-up period. The follow-up period ranged from 0.3 to 25.3 years (mean 7.4, median 6.2). There was 1 early death and 15 late deaths, of which 7 were cardiac related. The actuarial survival rates at 10 and 20 years were 92 and 81%, respectively. Thirty-three patients (15%) developed recurrent moderate or severe mitral regurgitation during the follow-up period and 30 patients (13%) required reoperation on the mitral valve. Rates of freedom from reoperation and freedom from recurrent moderate or severe mitral regurgitation were 84 and 82% at 10 years, and 74 and 59% at 20 years, respectively. Multivariate analysis revealed that the independent predictors of recurrent mitral regurgitation were mitral valve repair without annuloplasty ring and greater than mild postoperative mitral regurgitation; and the independent predictors of mitral reoperation were previous cardiac surgery and greater than mild postoperative mitral regurgitation. Histopathological analysis of the expanded polytetrafluoroethylene sutures removed during reoperation revealed complete endothelialization without calcification or microthrombi. Our 25-year follow-up demonstrated reliable long-term outcomes of chordal replacement with expanded polytetrafluoroethylene sutures. © The Author 2014

  20. An impedance matching of femoral-popliteal arterial grafts: a theoretical study.

    PubMed

    Hirayama, H; Nishimura, T; Fukuyama, Y

    1997-05-01

    We have proposed a mathematical method to investigate the matching conditions for an arterial graft in the femoral-popliteal region from a mechanical stand-point. Pulsatory blood flow, arterial wall motions, and conservation law are expressed by linear dynamical equations based on strict mechanical and constitutional considerations. To express the physiological blood flow in an actual arterial system, the tethering effects from the surrounding tissue and wall tensions were incorporated. The physiological parameters of arterial wall and tethering were utilized from reported experimental data. By complex analysis, mathematical expressions for the local impedance and reflection coefficient were obtained. They include not only blood properties such as viscosity and density, but also arterial properties including elastic modulus, radius, Poisson ratio, wall thickness, wall tension, frequency, and tethering effects from surrounding tissue. A matching condition was defined for minimizing the local impedance and reflection coefficient. The biophysical background was to reduce any mechanical mismatches, thus minimizing the disturbance of the flow velocity profile and shear stress distribution within the artery. Impedance matching in turn diminishes the negative factors for graft substitution represented by intimal hyperplasia and thrombosis. The calculated impedance and reflection coefficient inversed parabolically to functions of the resistance of the host artery, and there was one host arterial resistance that minimized the impedance and reflection coefficient. The present analysis revealed that for matching host artery with an elevated resistance, the dynamic elastic modulus of the wall of the graft that minimizes the impedance and reflection coefficient was increased. This indicates that for a host artery with a high resistance, an impedance matched stiff wall graft is preferable. For a large radius and a compliant host artery on the other hand, a large compliant graft

  1. Shorter duration of femoral-popliteal bypass is associated with decreased surgical site infection and shorter hospital length of stay.

    PubMed

    Tan, Tze-Woei; Kalish, Jeffrey A; Hamburg, Naomi M; Rybin, Denis; Doros, Gheorghe; Eberhardt, Robert T; Farber, Alik

    2012-10-01

    Duration of femoral-popliteal bypass is based on multiple patient-specific, system-specific, and surgeon-specific factors, and is subject to considerable variability. We hypothesized that shorter operative duration is associated with improved outcomes and might represent a potential quality-improvement measure. Patients who underwent primary femoral-popliteal bypass with autogenous vein between 2005 and 2009 were identified from the American College of Surgeons NSQIP dataset using ICD-9 codes. Operative duration quartiles (Q) were determined (Q1: ≤149 minutes, Q2: 150 to 192 minutes, Q3: 193 to 248 minutes; and Q4: ≥249 minutes). Perioperative outcomes included mortality, surgical site infection, cardiopulmonary complications, and length of hospital stay. Relevant patient-specific and system-specific confounders, including age, body mass index, smoking, diabetes, end-stage renal disease, indication, American Society of Anesthesiologists' class, type of anesthesia, intraoperative transfusion, nonoperative time in the operating room, and participation of a trainee during the procedure, were adjusted for using multivariable regression. There were 2,644 femoral-popliteal bypass procedures in our study. Mean age was 65.9 years and 62% of patients were male. Longer duration of surgery was associated with increased perioperative surgical site infection (Q1: 6.3%; Q2: 9.0%; Q3: 10.1%; and Q4: 13.9%; p < 0.001) and longer length of stay (5.4 ± 6.8 days; 6.1 ± 6.7 days; 7.0 ± 11.3 days; 8.1 ± 8.0 days, respectively; p < 0.001). In multivariable analysis, longer operative duration was independently associated with higher surgical site infection and longer hospital length of stay. Operative duration of ≥260 minutes increased the risk of surgical site infection by 50% compared with operative time of 150 minutes. Longer duration of femoral-popliteal bypass with autogenous vein was associated with a significantly higher risk of perioperative surgical site infection and

  2. Non-thermal ablation of expanded polytetrafluoroethylene with an intense femtosecond-pulse laser.

    PubMed

    Hashida, M; Mishima, H; Tokita, S; Sakabe, S

    2009-07-20

    Ablation of expanded polytetrafluoroethylene without disruption of the fine porous structure is demonstrated using an intense femtosecond-pulse laser. As a result of laser-matter interactions near ablation threshold fluence, high-energy ions are emitted, which cannot be produced by thermal dissociation of the molecules. The ion energy is produced by Coulomb explosion of the elements of (-CF(2)-CF(2)-)(n) and the energy spectra of the ions show contributions from the Coulomb explosions of the ions rather than those of thermal expansion to generate high-energy ions. The dependence of ion energy on the laser fluence of a 180-fs pulse, compared with that of a 400-ps pulse, also suggests that the high-energy ions are accelerated by Coulomb explosion.

  3. Simple Transposition Technique for Microvascular Decompression Using an Expanded Polytetrafluoroethylene “Belt”: Technical Note

    PubMed Central

    TANAKA, Yuichiro; UCHIDA, Masashi; ONODERA, Hidetaka; HIRAMOTO, Jun; YOSHIDA, Yasuyuki

    2014-01-01

    Microvascular decompression (MVD) is a standard surgical procedure for treating vascular compression syndromes. There are two basic ways to perform MVD: interposition using a prosthesis and transposition. With the transposition technique, adhesions and granuloma around the decompression site are avoided, but the required operation is more complex than that for the interposition method. We describe a simple, quick MVD transposition procedure that uses a small “belt” cut from a sheet of 0.3-mm-thick expanded polytetrafluoroethylene membrane. The belt has a hole at the wide end and the other end tapered to a point. The belt is encircled around offending vessels by inserting the pointed end into the hole. The pointed end is then passed through a dural tunnel over the posterior wall of the petrous bone and is tied two or three times. This method avoids the risks involved in handling a surgical needle close to the cranial nerves and vessels. PMID:24097088

  4. Simple transposition technique for microvascular decompression using an expanded polytetrafluoroethylene "belt": technical note.

    PubMed

    Tanaka, Yuichiro; Uchida, Masashi; Onodera, Hidetaka; Hiramoto, Jun; Yoshida, Yasuyuki

    2014-06-17

    Microvascular decompression (MVD) is a standard surgical procedure for treating vascular compression syndromes. There are two basic ways to perform MVD: interposition using a prosthesis and transposition. With the transposition technique, adhesions and granuloma around the decompression site are avoided, but the required operation is more complex than that for the interposition method. We describe a simple, quick MVD transposition procedure that uses a small "belt" cut from a sheet of 0.3-mm-thick expanded polytetrafluoroethylene membrane. The belt has a hole at the wide end and the other end tapered to a point. The belt is encircled around offending vessels by inserting the pointed end into the hole. The pointed end is then passed through a dural tunnel over the posterior wall of the petrous bone and is tied two or three times. This method avoids the risks involved in handling a surgical needle close to the cranial nerves and vessels.

  5. Stretch expanded polytetrafluoroethylene graft with intrawall radial support system: an advance in vascular access graft design.

    PubMed

    Davidson, I J A; Bartsch, C Cava; Bravo, K; Gable, D; Munschauer, C

    2004-01-01

    Vascular access expanded polytetrafluoroethylene (ePTFE) grafts with external support systems consisting of parallel rings or in a spiral configuration are designed to resist kinking and compression at the apex of loop grafts or when crossing a joint. However, during the implantation procedure, the rings or spiral must be removed from the portion of the graft that is cut to allow the graft to be divided at the desired angle and suture the anastomosis. A new ePTFE graft (Intering) with an intrawall radial support system and a smooth lumen permits easy division of the support segments at the chosen angle. Moreover, minimal resistance is encountered during suturing of the graft. The results of early experience with Intering grafts crossing the elbow joint, in short-segment revisions, and in primary forearm loop configurations are encouraging.

  6. Histological examination of expanded polytetrafluoroethylene artificial dura mater at 14 years after craniotomy: case report.

    PubMed

    Matsumoto, Yoshihisa; Aikawa, Hiroshi; Tsutsumi, Masanori; Narita, Sumito; Yoshida, Hidenori; Etou, Housei; Sakamoto, Kimiya; Kazekawa, Kiyoshi

    2013-01-01

    Expanded polytetrafluoroethylene (ePTFE) porous material (GORE(®) PRECLUDE(®) Dura Substitute) does not degenerate or deteriorate in vivo, and is currently used as artificial dura mater. This material does not adhere well to the surrounding tissues, but cerebrospinal fluid leakage along the suture line has been observed in several cases. We describe a case of craniotomy for tumor resection performed 14 years after dural repair with ePTFE sheet. Histological examination of the ePTFE sheet revealed that the sheet was structurally intact, with no evidence of tissue adhesion or cellular infiltration. However, collagen deposition was observed around the suture thread. When the suture thread was removed the collagen was also removed, and the original needle hole appeared again. No significant changes were observed in the features of the ePTFE sheet even 14 years postoperatively. The formation of fibrous tissue around the needle hole was important in preventing cerebrospinal fluid leakage.

  7. Stimulated endothelial cell adhesion and angiogenesis with laminin-5 modification of expanded polytetrafluoroethylene.

    PubMed

    Kidd, Kameha R; Dal Ponte, Donny; Stone, Alice L; Hoying, James B; Nagle, Raymond B; Williams, Stuart K

    2005-01-01

    Biomedical implants often exhibit poor clinical performance due to the formation of a periimplant avascular fibrous capsule. Surface modification of synthetic materials has been evaluated to accelerate the formation of functional microcirculation in association with implants. The current study used a flow-mediated protein deposition system to modify expanded polytetrafluoroethylene (ePTFE) with a laminin-5-rich conditioned growth medium and with medium from which laminin-5 had been selectively removed. An in vitro model of endothelial cell adherence determined that laminin-5 modification resulted in significantly increased adhesion of human microvessel endothelial cells to ePTFE. In vivo studies evaluating the periimplant vascular response to laminin-5-treated samples indicated that absorption of laminin-5-rich conditioned medium supported accelerated neovascularization of ePTFE implants. A flow system designed to treat porous implant materials facilitates laminin-5 modification of commercially available ePTFE, resulting in increased endothelial cell adhesion in vitro and increased vascularization in vivo.

  8. Morphology and albumin secretion of adult rat hepatocytes cultured on a hydrophobic porous expanded polytetrafluoroethylene membrane.

    PubMed

    Kurosawa, Hiroshi; Yuminamochi, Eri; Yasuda, Ruri; Amano, Yoshifumi

    2003-01-01

    Primary culture of rat hepatocytes was performed on a hydrophobic porous expanded polytetrafluoroethylene (ePTFE) membrane incorporated into the base of a culture dish. Two types of ePTFE membranes, a uniaxially expanded type (ePTFE-1) and a biaxially expanded type (ePTFE-2), could be used as the culture surfaces for hepatocytes. The formation of multicellular aggregates was observed in the culture dish when each membrane type was used. A pore size of 1 mum or higher was adequate for cell adhesion and albumin secretion for both membrane types. The activity of albumin secretion in the dish with the ePTFE membrane was markedly higher than that in the polystyrene dish. Spheroidal multicellular aggregates (spheroids) were observed when hepatocytes were cultured on the ePTFE-1 membrane. The ePTFE-1 membrane maintained the albumin secretion activity for a longer period than the non-expanded PTFE film. It was assumed that the cooperative action of membrane structure and oxygen permeability promoted the formation of cell aggregates and increased the albumin secretion activity.

  9. Venous outflow reconstruction using an expanded polytetrafluoroethylene vascular graft in living-donor liver transplant: a single-center experience.

    PubMed

    Lai, Chia-Yu; Han, Shao-Min; Chen, Yi-Ju; Huang, Shou-Sen; Wu, Cheng-Chung; Cheng, Shao-Bin

    2014-06-01

    Limited studies have focused on the feasibility and technical requirements of using expanded polytetrafluoroethylene vessel grafts for venous outflow reconstruction in a living-donor liver transplant using right liver grafts without the middle hepatic vein. Between August 2007 and December 2012, thirty-two patients who had received an expanded polytetrafluoroethylene vascular graft for outflow reconstruction during a living-donor liver transplant using a right liver graft without the middle hepatic vein were retrospectively reviewed. Preoperative and operative data, complications, and mortality were compared among patients who received the expanded polytetrafluoroethylene grafts with individual anastomoses (n = 18) or confluent anastomoses (n =14). For patients who had received an individual and a confluent anastomosis, graft reconstruction time was 25.8 and 14.9 minutes (P = .000). No cases of graft occlusion occurred during first 72 hours after surgery. Although 5 patients (15.6%) died within 90 days, none of the deaths were associated with the vascular grafts. Operative mortality was not statistically different between patients who had received an individual anastomosis (3/18, 16.7%) and those who had received a confluent anastomosis (2/14, 14.3%) (P = 1.000). Individual and confluent anastomoses using an expanded polytetrafluoroethylene vascular graft is a feasible approach to venous outflow reconstruction in a living-donor liver transplant using right liver grafts without the middle hepatic vein.

  10. Seven-year follow-up of expanded polytetrafluoroethylene (PTFE) femoropopliteal bypass grafts.

    PubMed Central

    McAuley, C E; Steed, D L; Webster, M W

    1984-01-01

    Expanded polytetrafluoroethylene (PTFE) grafts have proven to be an acceptable short-term alternative for femoropopliteal reconstruction in those patients without suitable autologous saphenous vein. One hundred and twenty-seven femoropopliteal arterial bypass operations utilizing PTFE grafts were performed in 105 patients. Seven-year follow-up is now available for 20 grafts, 6-year follow-up for 47 grafts, and 5-year follow-up for 62 grafts. Graft occlusion was determined by angiography, Doppler assessment, loss of previously palpable pulses, or return of symptoms. Thirty nonocclusive graft losses were due to death, infection, aneurysm, amputation, or proximal occlusive disease. Overall cumulative patency rate, according to occlusive criteria alone and calculated by the life-table method, was 74% at 6 months, 63% at 1 year, 48% at 3 years, 40% at 5 years, and 35% at 7 years. Excluding early bypass failures (less than 1 year patency), 75% of grafts were patent at 3 years, 63% at 5 years, and 55% patent 7 years following operation. Diabetes mellitus was associated with a significantly lower patency rate. Patency rates were not adversely affected by graft diameter, distal popliteal anastomotic site, number of patent runoff vessels, preoperative symptoms, or prior arterial reconstruction. In patients without suitable autologous saphenous vein, the PTFE graft has proven to be a durable and dependable long-term alternative for femoropopliteal reconstruction. PMID:6691731

  11. Ultrasonographic monitoring of implant thickness after augmentation rhinoplasty with expanded polytetrafluoroethylene.

    PubMed

    Jung, Yong Gi; Kim, Hyo Yeol; Dhong, Hun-Jong; Park, Ki Nam; Lee, Hyun Jong; Lim, Yoo Jung; Min, Jin-Young

    2009-01-01

    Expanded polytetrafluoroethylene (ePTFE), or Gore-Tex (W.L. Gore & Associates, Flagstaff, AZ), is widely used in augmentation rhinoplasty, and the histological changes that it undergoes in the human body have been studied for decades. However, changes in the thickness of ePTFE after its use in augmentation rhinoplasty with a noninvasive object method are not well understood. We report the results of 19 patients (10 male and 9 female patients) who had undergone an uncomplicated augmentation rhinoplasty with Gore-Tex. Ultrasonography was used to evaluate changes in the thickness of Gore-Tex implants and to detect inflammatory reactions around the implants 9-67 months after surgery. Gore-Tex implants were clearly distinguishable from the surrounding tissue with ultrasonography. The postoperative thickness of the implant was decreased by 29%. There was no significant correlation between the degree of change in implant thickness and the length of time after surgery. However, the amount of thickness reduction was associated with the implant's initial thickness at the time of the surgery (R = 0.448; p = 0.001). In addition, four patients (21%) showed fibrosis or granuloma formation around the implant that was detectable via ultrasonography. Gore-Tex implants lost thickness after nasal dorsal augmentation in proportion to their initial thickness, and ultrasonography was useful for evaluating changes in Gore-Tex thickness.

  12. Expanded polytetrafluoroethylene (Gore-Tex soft-tissue patch) in facial augmentation.

    PubMed

    Maas, C S; Gnepp, D R; Bumpous, J

    1993-09-01

    Expanded polytetrafluoroethylene (EPTFE) (Gore-Tex soft-tissue patch) has received favorable clinical reports for use in facial augmentation procedures. We evaluated the EPTFE soft-tissue patch in short-term (3-week), intermediate-term (6-month), and long-term (12-month) animal models. Nine pathogen-free male and female New Zealand white rabbits weighing 2 to 4 kg were used. After implantation of the EPTFE soft-tissue patch, the animals were carefully observed on a daily basis for signs of wound infection, seroma, or hematoma formation. The stability of the implant was evaluated and graded after the animals were killed. Tissue specimens, including skin, implant, and underlying bone, were removed en bloc. These blocks were sectioned and stained for histologic evaluation. A portion of these blocks were used for scanning electron microscopy. The material increased in stability over time and showed minimal inflammatory cell response and only a delicate fibrous capsule, even in long-term implants. Ultrastructural analysis demonstrated close apposition of the material to tissue, suggesting good interface bioactivity. The EPTFE soft-tissue patch appears to be safe and reliable material for augmentation, demonstrating high biocompatibility, low tissue reactivity, and increasing stability over time.

  13. The use of expanded polytetrafluoroethylene (Gore-Tex) in rhinoplasty. A 6-year experience.

    PubMed

    Godin, M S; Waldman, S R; Johnson, C M

    1995-10-01

    To determine the safety and efficacy of expanded polytetrafluoroethylene (Gore-Tex soft-tissue patch, W. L. Gore & Assoc Inc, Flagstaff, Ariz) as an implant in rhinoplasty. A retrospective study of 137 patients who underwent rhinoplasty including augmentation with Gore-Tex over a 6-year period. A review of the medical literature concerning the use of Gore-Tex as an implant in the head and neck was also conducted. Two major academic medical centers and two private office surgical centers. One hundred thirty-seven consecutive patients who received Gore-Tex implants in the course of rhinoplasty. Sixty-nine patients presented for primary rhinoplasty; the remaining 68 presented for revision surgery. All received Gore-Tex nasal implants to augment the nasal dorsum and/or base. The grafts ranged from 1 to 6 mm in thickness. Follow-up ranged from 6 to 80 months, with an average of 25 months. Clinically noted complications and patient satisfaction. Three (2.2%) of 137 grafts became infected and were removed. One graft was removed 5 months post-operatively because of excessive augmentation. None of the patients who underwent implant removal required subsequent augmentation. All 137 patients are pleased with their results. Gore-Tex is a safe and effective implant material to use in primary and revision rhinoplasty when augmentation is needed and autogenous material is not available or desirable.

  14. In vivo performance of dual ligand augmented endothelialized expanded polytetrafluoroethylene vascular grafts.

    PubMed

    Chan, Bernard P; Liu, Wenge; Klitzman, Bruce; Reichert, William M; Truskey, George A

    2005-01-15

    In this study, we examined combinations of three approaches to improve the adhesion of endothelial cells (EC) onto expanded polytetrafluoroethylene (ePTFE) vascular grafts placed at the femoral artery of rats: (1) high-affinity receptor-ligand binding of RGD-streptavidin (SA) and biotin to supplement integrin-mediated EC adhesion; (2) cell sodding to pressurize the seeded EC into the interstices of the ePTFE grafts; and (3) longer postseeding attachment time from 1 to 24 h prior to implantation. An in vitro system, which accounts for cell loss due to both graft handling and shear stress, was designed to optimize conditions for in vivo experiments. Results suggest that longer in vitro attachment time enabled the adherent EC to endure mechanical stresses by forming strong adhesions to the underlying extracellular matrix substrates; cell sodding helped to retain the adherent EC by physically docking the cells against the graft interstices; and the SA-biotin interaction enhanced the early attachment of EC but did not lead to better cell retention or reduced surface coverage of blood clot in the current study. Mechanical manipulation of cells during implantation is a limiting factor in maintaining a confluent EC layer on synthetic vascular grafts.

  15. Evaluation of tissue response to Gore-Tex (expanded polytetrafluoroethylene) implantation.

    PubMed

    Serin, Gediz; Baylancicek, Serdar; Aksoy, Elif; Polat, Senol; Sağlican, Yeşim; Inanli, Selcuk

    2013-07-01

    The aim of this study was to assess the tissue response to Gore-Tex (expanded polytetrafluoroethylene) in rats and compare the results of surgical placement modalities. Prospective animal study. Experiments were performed in 18 young Sprague-Dawley rats that were divided into 3 groups. Gore-Tex patches were implanted subcutaneously over the periosteum in the first group and under the periosteum in the other groups. Gore-Tex was immersed in an antibiotic-containing solution in the third group. All animals were killed 4 weeks after the procedure. The tissue samples were stained with hematoxylin and eosin stain and evaluated using a light microscope. The Gore-Tex patches were displaced and not observed at the originally implanted sites in the first group. The Gore-Tex patches were observed at the originally implanted sites in the other groups. In group 1, edema and inflammation were prominent. In the second group, ossification was detected in 5 rats and foreign-body reaction and edema were identified in 1 rat. In the third group, all of the rats were found to have developed ossification, but no inflammatory reactions were observed. The results suggest that implanting synthetic graft materials immersed in an antibiotic solution at the subperiosteal plane provides better stabilization and low complication rates.

  16. Correction of Midface Depression Using an Inverted m-shaped Expanded Polytetrafluoroethylene Implant Improves Gingival Exposure.

    PubMed

    Wei, Jiao; Herrler, Tanja; Xu, Hua; Deng, Ning; Li, Shiyu; Li, Qingfeng; Dai, Chuanchang

    2016-12-01

    Current approaches for the treatment of gingival exposure are often time- and cost-consuming and/or rather invasive. We previously observed a strong correlation between the presence of gingival excess and midfacial depression and here propose an easy 1-step correction technique as a new strategy to improve gingival exposure. From February 2004 to December 2012, 42 patients with gingival exposure associated with different degrees of midfacial depression, defined by Frankfort horizontal plane-labrale superius-subspinale angle and sella-nasion-A point angle, were treated by implantation of an inverted m-shaped expanded polytetrafluoroethylene at the base of the piriform aperture in a subperiosteal location. Patient pictures were taken preoperatively and postoperatively to assess gingival exposure at rest and fullest smile, as well as measurements of upper lip length, nasolabial angle, and facial convexity angle. A postoperative patient satisfaction survey was performed. The average maximum gingival exposure was 5.52 ± 1.64 mm preoperatively and significantly decreased to 1.79 ± 0.67 mm at 6 months after surgery (P < 0.05) along with a significantly improved nasolabial angle from initially 85.3° ± 6.21° to 95.2° ± 7.1° (P < 0.05). The majority of patients (90.5%) rated their postoperative outcome as highly improved and improved. Temporary discomfort involving upper lip numbness, foreign body sensation, and stiff smiling expression was complained at 1 month postoperatively and gradually returned to normal after 3 months. No late recurrence or other complications were seen in any of the patients. For cases involving midface depression, the present technique provides an effective and permanent treatment strategy to improve excessive gingival exposure. This single-step approach is a safe and technically easy therapeutic option which is associated with high patient acceptance.

  17. Hyaluronic acid enhancement of expanded polytetrafluoroethylene for small diameter vascular grafts

    NASA Astrophysics Data System (ADS)

    Lewis, Nicole R.

    Cardiovascular disease is the leading cause of mortality and morbidity in the United States and other developed countries. In the United States alone, 8 million people are diagnosed with peripheral arterial disease per year and over 250,000 patients have coronary bypass surgery each year. Autologous blood vessels are the standard graft used in small diameter (<6mm) arterial bypass procedures. Synthetic small diameter grafts have had limited success. While polyethylene (Dacron) and expanded polytetrafluoroethylene (ePTFE) are the most commonly used small diameter synthetic vascular graft materials, there are significant limitations that make these materials unfavorable for use in the low blood flow conditions of the small diameter arteries. Specifically, Dacron and ePTFE grafts display failure due to early thrombosis or late intimal hyperplasia. With the shortage of tissue donors and the limited supply of autologous blood vessels available, there is a need for a small diameter synthetic vascular graft alternative. The aim of this research is to create and characterize ePTFE grafts prepared with hyaluronic acid (HA), evaluate thrombogenic potential of ePTFE-HA grafts, and evaluate graft mechanical properties and coating durability. The results in this work indicate the successful production of ePTFE-HA materials using a solvent infiltration technique. Surface interactions with blood show increased platelet adhesion on HA-modified surfaces, though evidence may suggest less platelet activation and erythrocyte lysis. Significant changes in mechanical properties of HA-modified ePTFE materials were observed. Further investigation into solvent selection, uniformity of HA, endothelialization, and dynamic flow testing would be beneficial in the evaluation of these materials for use in small diameter vascular graft bypass procedures.

  18. Safety and Efficacy of Expanded Polytetrafluoroethylene Implants in the Surgical Management of Traumatic Nasal Deformity.

    PubMed

    Shadfar, Scott; Farag, Alexandar; Jarchow, Andrea M; Shockley, William W

    2015-08-01

    The ideal alloplastic implant for correction of traumatic nasal deformity has not been adequately examined. To evaluate the safety profile and postoperative results of expanded polytetrafluoroethylene (ePTFE) implants used in functional nasal surgery (FNS) in the setting of traumatic nasal deformity. We conducted a 13-year retrospective medical chart review for patients treated at a tertiary academic facial plastic and reconstructive surgery practice between July 1999 and July 2012. A total of 404 FNS procedures were performed by a single surgeon during this period, 255 to repair traumatic deformities, 35 of these involving ePTFE implants. Patient demographics, medical comorbidities, operative and technical considerations, functional and aesthetic results, complications, and postoperative course findings were collected from patient records. In addition, preoperative and postoperative photographic documents were examined. Functional nasal surgery. Postoperative complications or presentations necessitating revision. A total of 404 patients (197 male, 207 female) underwent FNS. Of those, 255 procedures were to treat traumatic deformities. Forty patients altogether required the use of an ePTFE implant, 35 of those 40 deformities being associated with a traumatic injury. One of the 35 patients in the ePTFE-repaired traumatic deformities group experienced postoperative infection. This patient ultimately developed exposure after the infection failed to resolve with oral antibiotics, and the implant was removed. An additional patient in the ePTFE group required revision of the implant owing to contour irregularity and aesthetic concerns. No infections or other complications occurred among the 220 patients with traumatic deformity treated with autologous grafts. Analysis of other variables including sex, tobacco use, diabetes, immunosuppression, implant thickness, suture material, and prior septorhinoplasty were not associated with increased rate of infection (P > .05

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

    PubMed Central

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

    2016-01-01

    Expanded polytetrafluoroethylene (ePTFE) has been extensively used for facial soft tissue augmentation procedures, and is regarded as safe and reliable and suitable as a permanent implant. This implant is generally used in the lower third of the face for lips filling, nasal augmentation, nasolabial folds and chin augmentation, and rarely for congenital or acquired depressed deformities of the face. The aim of the present study was to assess the effects of ePTFE in congenital or acquired depressed deformities of the face. From September, 2008 to January, 2014, 26 patients were implanted with the material ePTFE to correct depressed deformities of the face. The average age at operation was 23.2 years, with a range of 17–45 years. The depressed deformities were lateralized. The follow-up period was 6–18 months (average 9 months). The etiologies of the depressed deformities included stable hemifacial atrophy (3 cases), craniofacial microsomia (13 cases), bony depression after trauma (8 cases), and other unclear reasons (2 cases). The operations were performed under local anesthesia. ePTFE was inserted in different tissue planes that varied among the different subanatomical areas in the face: beneath the superficial temporal fascia in the temporal area, and on the surface of the superficial musculoaponeurotic system in the zygomatic area, cheek and mandibular area. All of the patients were followed up. Most of the patients [25 of 26 patients (96.2%)] were satisfied with the results, while 1 patient (3.8%) was not satisfied for incomplete correction of the depressed deformity. In conclusion, aside from lipofilling and a free flap transfer, the results showed that ePTFE was an alternative treatment for facial depressed deformity. PMID:27882130

  20. Materials characterization of explanted polypropylene, polyethylene terephthalate, and expanded polytetrafluoroethylene composites: spectral and thermal analysis.

    PubMed

    Cozad, Matthew J; Grant, David A; Bachman, Sharon L; Grant, Daniel N; Ramshaw, Bruce J; Grant, Sheila A

    2010-08-01

    This study utilized spectral and thermal analysis of explanted hernia mesh materials to determine material inertness and elucidate reasons for hernia mesh explantation. Composite mesh materials, comprised of polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE) mesh surrounded by a polyethylene terephthalate (PET) ring, were explanted from humans. Scanning electron microscopy (SEM) was conducted to visually observe material defects while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to find chemical signs of surface degradation. Modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA) gave thermal stability profiles that showed changes in heat of fusion and rate of percent weight loss, respectively. ATR-FTIR scans showed higher carbonyl peak areas as compared to pristine for 91% and 55% of ePTFE and PP explants, respectively. Ninety-one percent of ePTFE explants also exhibited higher C--H stretch peak areas. Seventy-three percent of ePTFE explants had higher heats of fusion while 64% of PP explants had lower heats of fusion with respect to their corresponding pristines. Only 9% of PET explants exhibited a lower heat of fusion than pristine. Seventy-three percent of ePTFE explants, 73% of PP explants, and only 18% of PET explants showed a decreased rate of percent weight loss as compared to pristine. The majority of the PP and ePTFE mesh explants demonstrated oxidation and crosslinking, respectively, while the PET ring exhibited breakdown at the sites of high stress. The results showed that all three materials exhibited varied degrees of chemical degradation suggesting that a lack of inertness in vivo contributes to hernia mesh failure.

  1. Ultrasound-induced thermal therapy of hyperplasia in ringed expanded polytetrafluoroethylene (eptfe) access grafts

    NASA Astrophysics Data System (ADS)

    Query, Michael Earl

    Hemodialysis vascular access, the interface between a dialysis patient and a dialysis machine, is quite literally the lifeblood of a patient's health. Vascular access dysfunction is the leading cause of hospitalization in hemodialysis patients. The occlusive growth of neointimal hyperplasia (NH) in expanded polytetrafluoroethylene (ePTFE) ringed grafts is the primary cause of failure. To further develop a proposed thermal ultrasound treatment to reduce or prevent NH in arteriovenous vascular grafts, the acoustic properties of ePTFE were studied in water and alcohol solutions. Previous reports of ePTFE acoustic properties are critiqued. It was found that the acoustic transmission and attenuation through ePTFE, and therefore the potential for an ultrasound-based therapy for NH, are heavily dependent on the medium in which the graft is immersed, suggesting that the acoustic properties of implanted grafts will change as grafts mature in vivo. The acoustic impedance and attenuation of water-soaked ePTFE were 0.478 +/- 1.43 x 10-2 MRayl and 1.78 +/- 0.111 Np/cm*MHz, respectively, while the acoustic impedance and attenuation of ePTFE in alcohol were 1.49 +/- 0.149 MRayl and 0.77 +/- 1.1 x 10-2 Np/cm*MHz, respectively. The use of focused ultrasound to heat implanted ringed ePTFE grafts was numerically modeled from 1.35- and 1.443-MHz transducers for in vitro geometries. Power deposition and heating, in turn, differed by an order of magnitude between various graft acoustic properties. Graft rings were predicted to be substantial absorbing and scattering features. In vitro phantom models were constructed: one with and one without thermocouples. At 1 W of acoustic power, the maximum temperature rise was 8˚ C. The thermocouple model containing a water-soaked graft did not experience heating in the far graft wall. The MRTI model confirmed that the graft rings are an absorbing/scattering feature. Heating was not prevented in the presence of water flow through the graft. Water

  2. Improved biomechanical resistance using an expanded polytetrafluoroethylene composite-structure prosthesis.

    PubMed

    Bellón, Juan M; Rodríguez, Marta; Serrano, Natalia; San-Martín, Antonio Carrera; Buján, Julia

    2004-05-01

    We designed a composite-structure (laminar-reticular) prosthesis using expanded polytetrafluoroethylene (ePTFE) as the biomaterial in an attempt to improve the biomechanical resistance of the same biomaterial in the form of a single lamina. Defects (7 x 5 cm) were created in the abdominal wall of male white New Zealand rabbits (n = 24). The defects, which comprised all the wall layers except the skin, were then repaired with one of two types of ePTFE prosthesis. One was a latest generation laminar prosthesis (DualMesh, or Gore-Tex) and the other was a composite of in-house design (CV-4 mesh composite) made by suturing a mesh woven out of ePTFE thread to an ePTFE lamina. After sacrificing the animals at 14 or 90 days after surgery, implant specimens were subjected to morphologic analysis (light microscopy and scanning electron microscopy); and adhesion formation, neoperitoneal thickness, and biomechanical strength were evaluated. No significant differences were recorded between the two prosthesis regarding the consistency of adhesions or the area occupied by adhesions (DM 0.17 +/- 0.06; CV-4 mesh composite 0.18 +/- 0.08 cm2) (p > 0.05). Notably, improved tissue integration was achieved using the composite prosthesis; its reticular side became infiltrated by dense connective tissue that enveloped the mesh filaments. In contrast, the DM prosthesis became encapsulated by host tissue. The neoperitoneum induced by both prostheses was homogeneous and orderly, with a layer of typical mesothelial cells lining its inner surface. The thickness of the neoperitoneum was similar (p > 0.05) for the two implants (385.0 +/- 3.4 vs. 390 +/- 3.1 microm), although significantly higher (p < 0.05) mechanical resistance values were recorded for the composite prosthesis (26.75 +/- 3.71 vs. 14.11 +/- 3.71 N). Our findings suggest that the use of a reticular and a laminar ePTFE layer in the same prosthesis leads to better repair and biomechanical behavior compared to the use of a single

  3. Comparison of the Surgical Outcomes of Dorsal Augmentation Using Expanded Polytetrafluoroethylene or Autologous Costal Cartilage.

    PubMed

    Joo, Yeon Hee; Jang, Yong Ju

    2016-09-01

    Dorsal augmentation material includes alloplastic implants and autologous tissues. However, there has been no comparison to date of dorsal augmentation using different materials performed by the same surgeon. To compare the aesthetic outcomes and complications of dorsal augmentation using expanded polytetrafluoroethylene (ePTFE) and autologous costal cartilage (ACC) in rhinoplasty. A retrospective review of the medical records of 244 patients who underwent dorsal augmentation performed by the same surgeon at the Asan Medical Center using ePTFE or ACC from March 1, 2003, through September 31, 2015. Patient demographics and surgical procedures were analyzed. The aesthetic outcomes were scored from 1 (worst) to 4 (best) by 3 otolaryngologists. Changes in dorsal height and radix height were measured by comparing preoperative and postoperative profile views. Postoperative complications were also evaluated. A total of 244 patients who underwent augmentation rhinoplasty were reviewed in this study, including 141 men (57.8%) and 103 women (42.2%). The ePTFE group included 176 patients, and the ACC group comprised 68 patients. In the ePTFE and ACC groups, 96 patients (54.5%) and 45 patients (66.2%) were male, respectively. The patient ages ranged from 11 to 69 years, with a mean (SD) age of 30.3 (11.49) years in the ePTFE group and 36.04 (12.65) years in the ACC group. The mean (SD) aesthetic outcome scores were comparable between the 2 groups: 2.99 (0.05) in the ePTFE group and 2.99 (0.06) in the ACC group (P = .93). The change of dorsal (2.64% in ePTFE group and 5.82% in ACC group) and radix (3.62% in ePTFE group and 3.77% in ACC group) heights were significantly increased after augmentation in both groups (P < .001) even though the dorsal height of the ACC group after augmentation showed a significantly greater increase compared to the ePTFE group (P < .001). However, the complication rate was significantly higher in the ACC group: 4.0% in ePTFE group and

  4. Transapical Beating-Heart Mitral Valve Repair With an Expanded Polytetrafluoroethylene Cordal Implantation Device: Initial Clinical Experience.

    PubMed

    Gammie, James S; Wilson, Peter; Bartus, Krzysztof; Gackowski, Andrzej; Hung, Judy; D'Ambra, Michael N; Kolsut, Piotr; Bittle, Gregory J; Szymanski, Piotr; Sadowski, Jerzy; Kapelak, Boguslaw; Bilewska, Agata; Kusmierczyk, Mariusz; Ghoreishi, Mehrdad

    2016-07-19

    Degenerative mitral valve (MV) disease is a common cause of severe mitral regurgitation (MR) and accounts for the majority of MV operations. Conventional MV surgery requires cardiopulmonary bypass, aortic cross-clamping, cardioplegia, and a thoracotomy or sternotomy and, therefore, is associated with significant disability, risks, and unpredictable rates of MV repair. Transesophageal echocardiography-guided beating-heart MV repair with expanded polytetrafluoroethylene cordal insertion has the potential to significantly reduce surgical morbidity. We report the first-in-human clinical experience with a novel preformed expanded polytetrafluoroethylene knot implantation device (Harpoon TSD-5) designed to treat degenerative MR. Through a small left thoracotomy, the device was inserted into the heart and guided by transesophageal echocardiography to the ventricular surface of the prolapsed leaflet. Multiple expanded polytetrafluoroethylene cords were anchored in the leaflet and then adjusted to the correct length to restore MV leaflet coaptation and secured at the epicardium. Eleven patients with posterior leaflet prolapse and severe MR, with mean±SD age of 65±13 years and mean ejection fraction of 69±7%, were treated with 100% procedural success. Immediate postprocedural mean MR grade was trace. At 1 month, the mean MR grade was mild with significant decreases in end-diastolic volume (139 to 107 mL; P=0.03) and left atrial volume (118 to 85 mL; P=0.04). A novel device used for beating-heart image-guided MV repair demonstrates a significant reduction in MR with favorable left ventricular and left atrial reverse remodeling. This approach has the potential to decrease invasiveness and surgical morbidity. Further follow-up is necessary to assess long-term efficacy. URL: https://clinicaltrials.gov. Unique identifier: NCT02432196. © 2016 American Heart Association, Inc.

  5. Polytetrafluoroethylene expanded prosthesis as replacement of the inferior vena cava in renal cell carcinoma with caval thrombus.

    PubMed

    Benkirane, Ahmed; Khodari, Muhieddine; Yakoubi, Rachid; Lambert, Marc; Koussa, Mohamad; Ghoneim, Tarek; Haulon, Stephan; Villers, Arnauld; Lemaitre, Laurent; Zini, Laurent

    2014-05-01

    To assess the outcomes of inferior vena cava replacement with polytetrafluoroethylene expanded prosthesis in patients with renal cell carcinoma and caval thrombosis. All patients who underwent radical nephrectomy with inferior vena cava replacement by polytetrafluoroethylene expanded prosthesis for renal cancer associated with inferior vena cava thrombosis and a suspicion of inferior vena cava wall invasion from January 2000 to June 2011 were considered for this study. Demographic data, postoperative course, graft patency and survival data were evaluated. A total of 26 patients (median age 59.5 years, range 19.9-85.6 years) were included in the analysis. The median tumor diameter was 10 cm (range 5-14 cm). Histological invasion of the wall of the inferior vena cava was found in 16 (61.5%) cases. The median follow up was 28 months (range 1-136). A graft thrombosis occurred in five (19.2%) patients within the first year. Four of these patients died before the end of the second year. Patency of the inferior vena cava graft at 6 and 12 months was 88% and 79%, respectively. Overall survival probability at 3 years was 64%. Prosthetic replacement of the inferior vena cava can be carried out when invasion of the wall of the inferior vena cava is suspected. The postoperative complication rate in this subset of high-risk patients undergoing radical nephrectomy seems acceptable, and the patency of the prostheses is good in most of the cases. © 2014 The Japanese Urological Association.

  6. [Effects of microporous polysaccharide on foreign body reaction induced by subcutaneously imbedding expanded polytetrafluoroethylene in mice].

    PubMed

    Liu, Y H; Chen, L; Wu, Y P; Cao, W

    2016-10-20

    Objective: To observe the effects of early applying of microporous polysaccharide on foreign body reaction induced by subcutaneously imbedding expanded polytetrafluoroethylene (e-PTFE) in mice. Methods: Ten wide type adult C57BL/6J mice were collected and made a full-thickness skin incision on both sides of their back. The two incisions on the back of each mouse were divided into two groups according the random number table, with 10 incisions in each group. A tube-shaped e-PTFE was imbedded into each incision in microporous polysaccharide group, and then 0.03 g microporous polysaccharide was evenly sprayed in the cavity. Whereas, a tube-shaped e-PTFE was imbedded into each incision in control group without other treatment. The incisions in two groups were performed with conventional full-thickness suture. On post operation day (POD) 14, the e-PTFE surrounded with fibrous capsule in each incision of two groups was taken out, and then fibrous capsule tissue was harvested. The thickness of fibrous capsule was observed and measured with HE staining. Collagen fiber distribution in fibrous capsule tissue was observed with Masson staining to calculate the collagen fiber index. Neovascularization and macrophage infiltration in fibrous capsule tissue were observed respectively with immunohistochemical staining, and the numbers of new vessels and macrophages were counted. Data were processed with t test. Results: On POD 14, the thickness of fibrous capsule surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was (127±19) μm, which was significantly thinner than that of control group [(250±35) μm, t=4.13, P<0.05]. On POD 14, the collagen fiber index of fibrous capsule tissue surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was 0.500±0.003, which was significantly higher than that of control group (0.488±0.004, t=5.00, P<0.05). On POD 14, the number of new vessels in fibrous capsule tissue surrounding e

  7. Bovine carotid artery biologic graft outperforms expanded polytetrafluoroethylene for hemodialysis access.

    PubMed

    Arhuidese, Isibor; Reifsnyder, Thomas; Islam, Tasnim; Karim, Omar; Nejim, Besma; Obeid, Tammam; Qazi, Umair; Malas, Mahmoud

    2017-03-01

    Arteriovenous grafts remain reliable substitutes for permanent hemodialysis access in patients without a suitable autogenous conduit. Advances in conduit design and endovascular management of access-related complications question the preference for synthetic conduits over biologic grafts in contemporary practice. In this study, we compared outcomes between a bovine carotid artery (BCA) biologic graft and expanded polytetrafluoroethylene (ePTFE) grafts for hemodialysis access in a recent cohort of patients. This was a single-institution retrospective review of 120 consecutive grafts placed in 98 patients between January 1, 2011, and June 30, 2014. Univariate methods (χ(2), analysis of variance, t-test) were used to compare demographic and medical characteristics of patients who received each graft type. Kaplan-Meier, log-rank tests, univariate and multivariate logistic analyses, and Cox regression analyses were used to evaluate patency and graft complications. Outcomes were defined and analyzed according to reporting guidelines published by the Society for Vascular Surgery. Of the 120 grafts studied, 52 (43%) were BCA and 68 (57%) were ePTFE. Successful graft use for dialysis was 96% (95% confidence interval [CI], 90%-100%) for BCA and 84% (95% CI, 74%-93%) for ePTFE (P = .055). Comparing BCA vs ePTFE, estimates for primary patency were 30% vs 43% at 1 year and 16% vs 29% at 2 years (P = .27). Primary assisted patency was 36% vs 45% at 1 year and 24% vs 35% at 2 years (P = .57). Secondary patency was 67% vs 48% at 1 year and 67% vs 38% at 2 years (P = .05). There were no differences in primary (hazard ratio [HR], 0.70; 95% CI, 0.40-1.28; P = .25) and primary assisted (HR, 0.87; 95% CI, 0.46-1.65; P = .67) patency for BCA compared with ePTFE. However, secondary patency was higher for BCA compared with ePTFE (HR, 2.92; 95% CI, 1.29-6.61; P = .01). Graft infection rates during the study period were 15.4% for BCA and 20.6% for ePTFE (P = .47). The

  8. Use of expanded polytetrafluoroethylen (ePTFE) stent graft in autogenic AV fistula with false aneurysm in lower extremity.

    PubMed

    Sieroń, Dominik; Wiggermann, Philipp; Knap, Daniel; Wawrzynek, Wojciech; Stroszczynski, Christian

    2012-04-01

    A 28-year-old German-Caucasian man arrived with deep vein thrombosis DVT, pain, oedema and rubor of right lower limb and drug abuse. The US Doppler imaging showed an autogenic AV fistula and false aneurysm of the right superficial femoral artery and femoral vein. The CT imaging showed additional closing of the left external iliac artery and common femoral artery, and of the distal and middle parts of the superficial femoral artery. The patient was treated within the angiography suite using a 8/25 mm (8 mm diameter/25 mm length) peripheral graft with expanded polytetrafluoroethylen ePTFE stent. After stent deployment, the dilatation was performed using 8/20 mm (8 mm diameter/20 mm length) balloons. After intervention, the digital subtraction angiography showed a good stent position with complete exclusion of false aneurysm and AV fistula. The outcome of US Doppler imaging also confirmed successful intervention.

  9. A prospective randomized study of three expanded polytetrafluoroethylene (PTFE) grafts as small arterial substitutes.

    PubMed Central

    Hastings, O M; Jain, K M; Hobson, R W; Swan, K G

    1978-01-01

    A prospective, double-blind, randomized study was performed to determine the relative patency rate of polytetrafluoroethylene (PTFE) grafts, Gore-Tex, Impra, and a Surgikos prototype PTFE graft. The 48 grafts (40 x 4 mm) replaced excised segments of femoral arteries in adult mongrel dogs, whose mean weight was 20.6 +/- 0.9 kg; the grafts were removed after 12 weeks. Sterile technique and antibiotic therapy were included in the study. Anticoagulation was not employed. Anastomoses were performed with 6 = 0 polypropylene. Angiographic assessment of each anastomosis was made at surgery and prior to sacrifice. Patency was assessed daily by palpation and Doppler flow signals, as well as angiographically, prior to sacrifice. The overall patency rate was 62.5%. There were no statistically significant differences in patency rates among the three groups (Gore-Tex, 56%; Impra, 75%, Surgikos, 56%). Histologic evaluation revealed incomplete neointima formation and significant pannus formation in all three types of grafts without any significant discernible difference among them. The results suggest that further experimental evaluation of PTFE, as a small vessel substitute, is indicated prior to its use clinically in preference to autogenous vein. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:367297

  10. Development of a synthetic replacement for flexor tendon pulleys using expanded polytetrafluoroethylene membrane.

    PubMed

    Bartle, B K; Telepun, G M; Goldberg, N H

    1992-03-01

    Reconstruction or replacement of the damaged pulley is a difficult surgical problem because of the need to find suitable biological material, the bulkiness of the repair, and adhesion formation between the pulley and flexor tendons. Therefore, a method was developed to reconstruct the fibro-osseous pulleys with polytetrafluoroethylene (PTFE) membrane. Twenty White Leghorn chickens had the A3 pulley of the long digit excised; this was followed by a standard injury to the flexor profundus tendon. The A3 pulley was then reconstructed with PTFE membrane. In the opposite foot, the A3 pulley was transected laterally, the tendon injured in the same manner, and the native pulley sutured. Seven control chickens had a PTFE pulley reconstruction without tendon injury in one foot and the opposite foot did not undergo surgery. At postoperative days 0, 21, and 35, the animals were killed to evaluate the effectiveness of the PTFE pulleys. Flexor tendon function was assessed by determining the active range of motion of the digit. There was no significant difference between the PTFE pulleys and suture repair of the native pulleys at postoperative days 21 and 35. This indicates that the PTFE pulleys were capable of preventing tendon bow-stringing and did not significantly impair tendon gliding. The breaking strength of the PTFE pulley was less than that of the normal A3 pulleys, but it was sufficient to allow immediate mobilization of the digits postoperatively without fear of pulley rupture. The synthetic PTFE pulley appears to have the potential to function as an effective immediate replacement for the fibro-osseous pulleys.

  11. Poly(styrenesulfonate)/poly(allylamine) multilayers: a route to favor endothelial cell growth on expanded poly(tetrafluoroethylene) vascular grafts.

    PubMed

    Moby, Vanessa; Boura, Cédric; Kerdjoudj, Halima; Voegel, Jean-Claude; Marchal, Luc; Dumas, Dominique; Schaaf, Pierre; Stoltz, Jean-François; Menu, Patrick

    2007-07-01

    Small-diameter synthetic vascular grafts of expanded poly(tetrafluoroethylene) (ePTFE) polymer concern one of the most common alternatives for the replacement of diseased vessels. However, high failure rates arise especially due to the lack of endothelial cells (ECs). EC seeding was developed to build a monolayer on the luminal surface. Because ECs show little or no adhesion on synthetic prostheses, it is necessary to promote their retention. On ePTFE surfaces we successfully deposited polyelectrolyte multilayer films (PMFs) consisting of poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) to obtain PEI-(PSS-PAH)3 films. EC adhesion and spreading on modified ePTFE were assessed by scanning electron and confocal microscopies. Cell viability was evaluated by Alamar Blue assay. After 7 days of culture, the ePTFE modified with PMF exhibited improvements of EC viability as compared to that of the controls (nonmodified ePTFE) or even ePTFE coated by a PAH monolayer (p < 0.05). Moreover, the spreading of ECs was largely enhanced compared to that of the same controls, resulting in a healthy confluent cell monolayer formation. Positive staining for the von Willebrand factor confirmed the EC phenotype. Promoting EC attachment and function on ePTFE modified with PMFs could become in the future a promising treatment for synthetic small-diameter vascular grafts.

  12. Effect of shear stress on platelet adhesion to expanded polytetrafluoroethylene, a silicone sheet, and an endothelial cell monolayer.

    PubMed

    Furukawa, K S; Ushida, T; Sugano, H; Tamaki, T; Ohshima, N; Tateishi, T

    2000-01-01

    We visualized in real-time platelets adhering to the surface of three representative biomaterials, by using an apparatus consisting of a modified cone and plate rheometer combined with an upright epifluorescence microscope under two shear flows (0.1 and 5.0 dyne/cm2). The materials were expanded polytetrafluoroethylene (ePTFE), silicone sheet, and a monolayer of bovine endothelial cells (ECs) formed on glass, all of which are opaque materials used for artificial blood vessels and medical devices. According to quantitative analysis, the monolayer of ECs formed on glass had better blood compatibility than did either the ePTFE or the silicone sheet under shear flow conditions. Under a shear flow condition of 0.1 dyne/cm2, platelet adhesion was silicone sheet > ePTFE. In contrast, under a shear flow condition of 5.0 dyne/cm2, ePTFE > silicone sheet. These results indicate that the intensity of shear stress could modify the order of hemocompatibility of the materials. Therefore, direct observation of platelet adhesion under shear flow conditions is indispensable for testing and screening biomaterials and for providing a precise quantitative evaluation of platelet adhesion.

  13. Heparin-bonded expanded polytetrafluoroethylene grafts for infragenicular bypass in patients with critical limb ischemia: 2-year results.

    PubMed

    Dorrucci, V; Griselli, F; Petralia, G; Spinamano, L; Adornetto, R

    2008-04-01

    The use of prosthetic grafts in below-knee (BK) bypasses may be necessary in patients with no available autologous vein and critical limb ischemia not amenable to angioplasty. Such conduits, however, have generally yielded disappointing results. A new heparin-bonded expanded polytetrafluoroethylene graft (Gore-Tex Propaten Vascular Graft) designed to provide resistance to thrombosis may be associated with decreased early graft failure and increased patency. This graft was implanted in 27 limbs (26 patients; 18 men; mean age 71 years; Rutherford class 4 to 6 disease) in a BK femoropopliteal and femorodistal location, without perioperative complications and with immediate graft patency. During a mean follow-up time of 24 months, 4 cases of thrombosis occurred, all at least 6 months postoperatively: 2 cases resolved after fibrinolytic treatment, 1 required surgical revision and in 1 case, amputation was required because of a delay in seeking treatment for thrombosis. Two patients died of cardiac disease during follow-up. The 2-year primary and secondary patency rates for the BK bypasses were 85% and 93%, respectively; the limb-salvage rate was 96%. These results are encouraging for a prosthetic graft, especially in the light of the severity of the vascular disease in the limbs treated.

  14. Surface zwitterionization of expanded poly(tetrafluoroethylene) membranes via atmospheric plasma-induced polymerization for enhanced skin wound healing.

    PubMed

    Jhong, Jheng-Fong; Venault, Antoine; Hou, Chun-Chung; Chen, Sheng-Han; Wei, Ta-Chin; Zheng, Jie; Huang, James; Chang, Yung

    2013-07-24

    Development of bioinert membranes to prevent blood clotting, tissue adhesion, and bacterial attachment is important for the wound healing process. In this work, two wound-contacting membranes of expanded poly(tetrafluoroethylene) (ePTFE) grafted with zwitterionic poly(sulfobetaine methacrylate) (PSBMA) and hydrophilic poly(ethylene glycol) methacrylate (PEGMA) via atmospheric plasma-induced surface copolymerization were studied. The surface grafting chemical structure, hydrophilicity, and hydration capability of the membranes were determined to illustrate the correlations between bioadhesive properties and wound recovery of PEGylated and zwitterionic ePTFE membranes. Bioadhesive properties of the membranes were evaluated by the plasma protein adsorption, platelet activation, blood cell hemolysis, tissue cell adhesion, and bacterial attachment. It was found that the zwitterionic PSBMA-grafted ePTFE membrane presented high hydration capability and exhibited the best nonbioadhesive character in contact with protein solution, human blood, tissue cells, and bacterial medium. This work shows that zwitterionic membrane dressing provides a moist environment, essential for "deep" skin wound healing observed from the animal rat model in vivo and permits a complete recovery after 14 days, with histology of repaired skin similar to that of normal skin tissue. This work suggests that the bioinert nature of grafted PSBMA polymers obtained by controlling grafting structures gives them great potential in the molecular design of antibioadhesive membranes for use in skin tissue regeneration.

  15. Surface chemistry of grafted expanded poly(tetrafluoroethylene) membranes modifies the in vitro proinflammatory response in macrophages.

    PubMed

    Chandler-Temple, Adrienne; Kingshott, Peter; Wentrup-Byrne, Edeline; Cassady, A Ian; Grøndahl, Lisbeth

    2013-04-01

    A series of surface-modified expanded poly(tetrafluoroethylene) membranes showed varied levels of in vitro macrophage proinflammatory response. Membranes containing a mixture of phosphate and hydroxyl groups (as determined by X-ray photoelectron spectroscopy analysis) stimulate greater macrophage activation than samples containing a mixture of phosphate and carboxylic acid segments. The types of proteins that adsorbed irreversibly from serum onto the two samples with the highest and lowest cellular response were investigated using surface-matrix-assisted laser desorption ionisation time-of-flight mass spectrometry. Distinct differences in the number and type of proteins that adsorbed were observed between these samples. A correlation was found between the main protein components adsorbed onto the surfaces and the resulting in vitro proinflammatory response. This study strongly supports the hypothesis that the cellular response is not controlled directly by surface properties but is mediated by specific protein adsorption events. This in turn highlights the importance of better understanding and controlling the properties of intelligent surface-modified biomaterials.

  16. Reduced platelet deposition on seeded versus unseeded segments of expanded polytetrafluoroethylene grafts: Clinical observations after a 6-month follow-up

    SciTech Connect

    Ortenwall, P.; Wadenvik, H.; Risberg, B. )

    1989-10-01

    The concept of autologous endothelial cell seeding has proved successful in animal models with respect to decrease of graft thrombogenicity and increase in patency. In the present study, application of this method in humans was explored. In 23 patients, random halves of expanded polytetrafluoroethylene grafts, used for lower limb arterial reconstructions, were seeded with endothelial cells at a seeding density of 3500 cells/cm{sup 2}. These cells were derived from the saphenous vein by enzymatic harvesting. The other half was sham seeded with culture medium. Graft thrombogenicity was estimated by measuring platelet deposition on graft surface 1 and 6 months after surgery, with indium 111-labeled platelets and external gamma-camera imaging. Seeded graft segments accumulated significantly (p less than 0.03) fewer platelets at all imaging times. It is concluded that seeding of expanded polytetrafluoroethylene vascular grafts in humans reduces graft surface thrombogenicity. The clinical implications of this remain to be demonstrated.

  17. Comparative study of morphological and histological changes between differently structured expanded polytetrafluoroethylene implants in an animal model.

    PubMed

    Kim, Ji Heui; Lee, Jung Min; Ju, Hyung Woo; Lee, Jun Ho; Jun, Ah Young; Park, Chan Hum

    2013-01-01

    Expanded polytetrafluoroethylene (e-PTFE) is a popular graft material used in augmentation rhinoplasty. New e-PTFE has thicker fibrils and is more compact than first developed e-PTFE. This study aimed to compare morphological and histological changes between differently structured e-PTFE implants in a rat model. Two types of e-PTFE were implanted in the cranial region of 30 adult male rats. En bloc specimens containing the implants and surrounding soft tissues were sampled 1, 3, and 6 months after implantation. We measured the three-dimensional size of the implants over time and evaluated histological changes using light and electron microscopy. Grossly, no implants were extruded, and there was no evidence of wound infection. All first developed e-PTFE samples were fixed to surrounding tissues after 1 month, whereas new e-PTFE samples tended to migrate and were easily separated from surrounding tissues until 3 months after implantation. The first developed e-PTFE height diminution rate was 14.7% of the initial value after 6 months; however, new e-PTFE size was not changed. Diameter and height diminution rates for first developed e-PTFE were significantly greater than those for new e-PTFE after 6 months. Histologically, connective tissue in growth was observed in first developed e-PTFE after 1 month, and the internodal space decreased over time; however, connective tissue did not infiltrate into new e-PTFE until 6 months and the internodal space was not significantly changed. First developed e-PTFE should be carefully trimmed in augmentation because of its potential to decrease in size over time, whereas new e-PTFE is more likely to show migration and instability.

  18. A simple technique for the correction of maxillonasal dysplasia using customized expanded polytetrafluoroethylene (ePTFE) implants.

    PubMed

    Wei, Jiao; Luo, Jiawen; Herrler, Tanja; Xu, Hua; Deng, Ning; Li, Qingfeng; Dai, Chuanchang

    2017-09-01

    The treatment of maxillonasal dysplasia in Binder's syndrome using autologous costal bone and cartilage is well established, but postoperative results may be compromised by scarring, unpredictable absorption of transferred autologous tissue, and donor site morbidity. Here, we propose a simple surgical technique to improve maxillonasal dysplasia using an expanded polytetrafluoroethylene (ePTFE) implant. From February 1999 to May 2014, fifty-eight patients affected by maxillonasal dysplasia with different degrees of flattened nose and midfacial depression underwent surgical correction by augmentation of the nasal dorsum using an "L"-shaped ePTFE and subperiosteal implantation of an inverted "m"-shaped ePTFE at the base of the piriform aperture. The outcome was evaluated based on preoperative and postoperative patient pictures, 3D imaging technology for the assessment of nasolabial angle and facial convexity angle, and a postoperative patient satisfaction survey. Postoperative results showed improved facial aesthetics with a significantly increased nasolabial angle from initially 74.1° ± 8.9° to 93.7° ± 6.1° at 6 months postoperatively (p < 0.05). Temporary discomfort involving upper lip numbness, foreign body sensation, and stiff smiling expression were complained during the first 3 months postoperatively, but spontaneously resolved within 6 months. Complications included infection (2 cases), implant migration (2 cases), and implant exposure (1 case). The vast majority of patients (95.7%) rated their postoperative outcome as highly improved and improved. The present therapeutic strategy provides a simple and effective treatment for the correction of maxillonasal dysplasia with high patient acceptance in a single step approach. Further research is required to determine long-term outcomes. Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  19. Designing a three-dimensional expanded polytetrafluoroethylene-poly(lactic-co-glycolic acid) scaffold for tissue engineering.

    PubMed

    Shao, Hung-Jen; Chen, Chiang Sang; Lee, I-Chi; Wang, Jyh-Horng; Young, Tai-Horng

    2009-04-01

    The purpose of this study was to design a three-dimensional expanded polytetrafluoroethylene (ePTFE)-poly(lactic-co-glycolic acid) (PLGA) scaffold for tissue engineering. To test the feasibility of this composite scaffold, a series of two-dimensional culture experiments were performed to investigate the behavior of anterior cruciate ligament (ACL) cells on the ePTFE and PLGA membranes. It was found PLGA provided a cell-favorable substrate for cell adhesion, migration, and growth, indicating PLGA is an ACL cell-conductive material. Conversely, poor adhesion and proliferation of ACL cells were observed on the ePTFE, even on the collagen-coated ePTFE. Therefore, the scaffold was not fabricated by coating PLGA on the ePTFE surface because it is difficult to coat anything on the extremely hydrophobic ePTFE surface. Instead, the ePTFE embedded in the PLGA matrix was prepared by immersing ePTFE scrim yarns into the PLGA solution, and then precipitating PLGA to form a three-dimensional construction with porous morphology. The role of ePTFE is regarded as a reinforcing constituent to improve the mechanical strength of porous PLGA matrix to provide early repair strength for tissue healing. However, porous PLGA matrix acts as a supportive environment for allowing cell adhesion, migration, and growth to guide the repair and regeneration of ligament tissue. To test this assumption, a preliminary animal experiment of rabbit ACL wound healing with this three-dimensional ePTFE-PLGA scaffold was performed. These results are very encouraging because such a new scaffold made of ePTFE scrim yarns embedded in PLGA may serve as ACL prostheses in the ligament tissue engineering.

  20. Guided bone regeneration utilizing expanded polytetrafluoroethylene membranes in combination with submerged and nonsubmerged dental implants in beagle dogs.

    PubMed

    Fiorellini, J P; Engebretson, S P; Donath, K; Weber, H P

    1998-05-01

    Treatment of partial and total edentulism with submerged and nonsubmerged dental implants which follows the concept of osseointegration has become an accepted treatment modality. With compromised implant sites, practitioners have begun to combine one-stage implants with established techniques including guided bone regeneration. However, the clinical evaluation of this technique is limited. Therefore, the purpose of this study was to evaluate osseointegration and bone regeneration around nonsubmerged or submerged implants placed directly into surgically created osseous defects with or without expanded polytetrafluoroethylene (ePTFE) membranes. A total of 24 implants were placed in the mandibles of 4 beagle dogs and randomly assigned to 1 of 3 treatment groups. In group A, nonsubmerged implants were placed into osseous defects and treated with a poncho style ePTFE membrane. These membranes had a hole punched into the center and were slipped over the nonsubmerged implants. In group B, nonsubmerged implants were placed into osseous defects without an ePTFE membrane. In group C, submerged implants were placed into osseous defects and covered with an ePTFE membrane. Histometric measurements of each treatment group were made to determine percent bone gain or loss along the implant surface. Although a number of membrane removals occurred during the healing period, histological analysis indicated osseous ingrowth and osseointegration around nonsubmerged and submerged implants. An overall comparison of the treatment groups with ANOVA revealed that there were no significant differences between treatment groups, P > or = 0.05. However, when the data were stratified into sites which retained or lost the ePTFE membrane, the percent of bone regeneration was reduced in group A. Therefore, it may be recommended that nonsubmerged implants be placed with a submerged or "semi-submerged" protocol when utilized in conjunction with ePTFE membranes.

  1. Equivalent outcomes with standard and heparin-bonded expanded polytetrafluoroethylene grafts used as conduits for hemodialysis access.

    PubMed

    Davies, Mark G; Anaya-Ayala, Javier E; El-Sayed, Hosam F

    2016-09-01

    Obtaining and maintaining dialysis access after failure of autologous access sites remains a significant concern for patients on hemodialysis. Polytetrafluoroethylene (PTFE) is the most common conduit used. Heparin-bonded expanded PTFE (HB-PTFE) grafts have recently been introduced as an improved conduit, with suggestions that HB offers benefits because of its resistance to thrombosis. In this retrospective study, the outcomes of HB-PTFE were compared with standard wall PTFE (S-PTFE) arteriovenous grafts (AVGs). From January 2004 to December 2014, 483 adults (46% male; mean age, 60 years; range, 25-87 years) with end-stage renal disease underwent placement of AVGs (234 HB-PTFE and 248 S-PTFE). The two groups did not differ significantly in demographics or access history. Patency, reintervention, infection, and functional dialysis rates were examined. Technical success was 99% in HB-PTFE and 98% in S-PTFE. The 30-day major adverse cardiovascular events were 2% in HB-PTFE and 3% in S-PTFE. Mean time to access was 5.1 ± 1.8 weeks for HB-PTFE and 6.9 ± 1.9 weeks for S-PTFE (P = .0001). Median follow-up was 23 months. The 2-year primary, assisted primary, and secondary patency rates were 20% ± 7% vs 18% ± 8% (P = .85), 35% ± 8% vs 28% ± 7% (P = .51), and 38% ± 6% vs 36% ± 7% (P = .83) for HB-PTFE vs S-PTFE, respectively. Both groups underwent a similar number of secondary interventions (2.1 and 1.9 interventions per person-year of follow-up for HB-PTFE vs S-PTFE respectively; P = .87). There were no significant differences in infection (11% vs 12%) or pseudoaneurysm formation (5% vs 6%) between HB-PTFE and S-PTFE groups. Functional dialysis durations were equivalent between HB-PTFE and S-PTFE groups. HB-PTFE grafts offer no distinct advantage over S-PTFE grafts for hemodialysis and should not be considered a preferential conduit for AVG. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

  2. Long-term dilatation of polyester and expanded polytetrafluoroethylene tube grafts after open repair of infrarenal abdominal aortic aneurysms.

    PubMed

    Stollwerck, Peter L; Kozlowski, Bartosz; Sandmann, Wilhelm; Grabitz, Klaus; Pfeiffer, Tomas

    2011-06-01

    Since 1995, expanded polytetrafluoroethylene (ePTFE) grafts have been implemented in open surgical repair (OSR) of abdominal aortic aneurysms (AAA) and are supposed to show less dilatation than polyester grafts. This study examined differences in graft dilatation and clinical outcome. This single-center long-term, prospective randomized study monitored 99 consecutive patients after OSR of AAA. Implanted were 90 tube ePTFE Gore-Tex Stretch grafts, 56 tube Dacron grafts (Uni-Graft KDV, polyester, B. Braun, knitted), and 51 tube Dacron grafts (Gelseal Plus, polyester, Vascutek, triaxial knitted). Follow-up with ultrasound examination was performed at discharge, at 12 months, and at 6 years. Patients were a mean age of 67 years. Thirty-day mortality was 2.5% (n = 5 of 199), without significant differences among the groups. The Kaplan-Meier analysis showed 5-year survivals of 0.82 (ePTFE/Gore), 0.81 (polyester/Braun), and 0.83 (polyester/Vascutek). Mean ± standard deviation dilatation of the midgraft segment was 1% ± 5% (ePTFE/Gore), 10% ± 9% (polyester/Braun), and 7% ± 8% (polyester/Vascutek) (P ≤ .001) at discharge; 8% ± 11% (ePTFE/Gore), 24% ± 7% (polyester/Braun), and 20% ± 13% (polyester/Vascutek; P ≤ .001) after 12 months; and 19% ± 21% (ePTFE/Gore), 33% ± 22% (polyester/Braun), and 23% ± 19% (polyester/Vascutek; (P ≤ .001) after 6 years. No graft failure or rupture occurred. Graft patency was 100%. After a mean implantation of 6 years, the ePTFE/Gore, polyester/Braun, and polyester/Vascutek tube grafts presented with significant differences. The ePTFE grafts showed a stronger resistance against dilatation than the two types of polyester grafts. Owing to similar perioperative and postoperative courses, no advantage could be identified in any group concerning the overall outcome. Vascular implants for OSR of AAA made of ePTFE and polyester are safe, even after a long implantation time. Therefore, the choice of the suitable graft does not depend on

  3. The effect of locally administered anti-growth factor antibodies on neointimal hyperplasia formation in expanded polytetrafluoroethylene grafts.

    PubMed

    Sapienza, Paolo; di Marzo, Luca; Cucina, Alessandra; Borrelli, Valeria; Mosiello, Giovanni; Basile, Ursula; Iacovitti, Simonetta; Cavallaro, Antonino

    2009-01-01

    The selective blockage of platelet-derived growth factor BB (PDGF-BB), basic fibroblast growth factor (bFGF), and transforming growth factor beta1 (TGF-beta1) by specific antibodies coated into expanded polytetrafluoroethylene (ePTFE) grafts may diminish neointimal hyperplasia. Sixty pigs were divided into two groups (n = 30 each) and then further divided into five subgroups. Group 1 had a bilateral iliac artery ePTFE interposition graft precoated with Matrigel. Three subgroups (A, B, and C) received a specific monoclonal antibody against PDGF-BB, bFGF, or TGF-beta1. One (D) received all antibodies, and one served as control (nonimmune immunoglobulin G [IgG] isotypes) (E). Group 2 had a bilateral iliac artery endothelial cell (EC)-seeded ePTFE interposition graft precoated with Matrigel. Three subgroups (A, B, and C) received a specific antibody against PDGF-BB, bFGF, or TGF-beta1. One (D) received all antibodies, and one served as control (nonimmune IgG isotypes) (E). Light microscopy and immunohistochemical stain showed that neointimal hyperplasia formation was significantly reduced in subgroups D compared to the others (p < 0.05). In subgroups D, the different precoating influenced neointimal hyperplasia formation. It was more pronounced in the prosthesis precoated with EC and Matrigel (p < 0.05). In organ culture, the amount of PDGF-BB, bFGF, and TGF-beta1 release was reduced in subgroup D animals compared to the others (p < 0.05). In subgroups D, the release of PDGF-BB, bFGF, and TGF-beta1 depended on ePTFE seeding. A higher amount of these growth factors was released in the prostheses precoated with EC and Matrigel (p < 0.05), and the bromodeoxyuridine labeling index confirmed higher incorporation in this subgroup (p < 0.001). The combined use of locally administered anti-PDGF-BB, bFGF, and TGF-beta1 monoclonal antibodies reduces neointimal hyperplasia formation.

  4. Long-term outcome of femoral above-knee popliteal artery bypass using autologous saphenous vein versus expanded polytetrafluoroethylene grafts.

    PubMed

    Sala, Florent; Hassen-Khodja, Reda; Lecis, Alexandre; Bouillanne, Pierre-Jean; Declemy, Serge; Batt, Michel

    2003-07-01

    Despite a recent flurry of publications on preferred techniques for femoral above-knee popliteal artery bypass, controversy persists over the use of autologous saphenous vein and expanded polytetrafluoroethylene (ePTFE) grafts. The purpose of this study was to compare our long-term results using these two bypass materials. In a series of 474 infrainguinal bypasses performed between January 1993 and December 1998, we performed a total of 75 femoral above-knee popliteal artery bypass using an autologous saphenous vein graft in 48 cases (64%) and an ePTFE graft in 27 cases (36%). Prosthetic grafts were used by choice in 17 cases and by necessity due to the absence of useable vein in 10 cases. There were 55 men and 18 women with a mean age of 70 years. The indication for bypass was lower extremity arterial occlusive disease at stage II in 17 cases (22.7%), stage III in 9 cases (12%), and stage IV in 36 cases (48%); subacute ischemia in 8 cases (10.7%); and femoropopliteal aneurysm in 5 cases (6.7%). Preoperative arteriography demonstrated three patent leg arteries in 15.5% of cases, two patent leg arteries in 43.5%, and one patent leg artery in 41%. There was no significance difference between the vein graft and ePTFE graft groups with regard to indications and arteriographic findings. No patient died during the immediate postoperative period. The mean duration of follow-up was 25.5 months (range, 3 to 108 months). The primary patency rate at 4 years was 82.2 +/- 8% for venous bypass vs. 80.6 +/- 11.8% for ePTFE bypass (p = 0.42). The secondary patency rate at 4 years was 84.7 +/- 7.4% for vein bypasses and 79.5 +/- 12% for ePTFE bypasses (p = 0.26). In our experience, there was no statistically significant difference in long-term outcome of femoral above-knee popliteal artery bypass using autologous vein grafts or prosthetic ePTFE grafts.

  5. TIPS for refractory ascites: a 6-year single-center experience with expanded polytetrafluoroethylene-covered stent-grafts.

    PubMed

    Bercu, Zachary L; Fischman, Aaron M; Kim, Edward; Nowakowski, F Scott; Patel, Rahul S; Schiano, Thomas D; Chang, Charissa Y; Lookstein, Robert A

    2015-03-01

    OBJECTIVE. This single-center study evaluated the use of expanded polytetrafluoroethylene (ePTFE)-covered stent-grafts for transjugular intrahepatic portosystemic shunt (TIPS) placement to manage portal hypertension-related refractory ascites. MATERIALS AND METHODS. One hundred patients at a single tertiary care center in a major metropolitan hospital underwent TIPS placement with an ePTFE-covered stent-graft (Viatorr TIPS Endoprosthesis). Patients with portal hypertension-related ascites and preexisting hepatocellular carcinoma or liver transplant were excluded from the analysis. Records were reviewed for demographic characteristics, technical success of the TIPS procedures, and stent follow-up findings. Clinical results were assessed at 90- and 180-day intervals. RESULTS. Immediate technical success of the TIPS procedure was 100%. Of the 61 patients with documented follow-up, 55 (90.2%) had a partial or complete ascites response to TIPS creation. Of these 55 patients, nine experienced severe encephalopathy. Six of 61 patients (9.8%) did not experience a significant ascites response. Overall survival was 78.7% at 365-day follow-up. The 365-day survival was 84.2% for patients with a model for end-stage liver disease (MELD) score of less than 15, 67.0% for those with a score of 15-18, and 53.8% for those with a score of greater than 18 (p = 0.01). For patients with a MELD score of less than 18, the 365-day survival was 88.0% for those with an albumin value of 3 mg/dL or greater and 72.8% for those with an albumin value of less than 3 mg/dL (p = 0.04). CONCLUSION. TIPS placement using an ePTFE-covered stent-graft is an efficacious therapy for refractory ascites. Patients with preserved liver function-characterized by a MELD score of less than 15 or a MELD score of less than 18 and an albumin value of 3 mg/dL or greater-experience the greatest survival benefit.

  6. Expanded polytetrafluoroethylene and dental rubber dam barrier membranes in the treatment of periodontal intrabony defects. A comparative clinical trial.

    PubMed

    Paolantonio, M; D'Archivio, D; Di Placido, G; Tumini, V; Di Peppe, G; Del Giglio Matarazzo, A; De Luca, M

    1998-11-01

    As observed in previous case reports, dental rubber dam (DRD) can be utilized as a barrier membrane in the guided tissue regeneration (GTR) technique for the treatment of periodontal intrabony defects. The purpose of the present study was (1) to confirm the validity of DRD as a suitable material in regenerative procedures and (2) to compare, in a split-mouth clinical trial, the effectiveness of DRD-made membranes in the treatment of periodontal intrabony defects versus that of expanded polytetrafluoroethylene (e-PTFE) barriers. 22 systemically healthy non-smoker adult periodontitis patients (7 male, 15 female) aged between 35 to 58 years were selected for the study. In each patient, a couple of 2-3 wall intrabony defects, located in different quadrants, were treated by a GTR technique using DRD (test sites) and e-PTFE (control sites), respectively. Performing a strict control of the oral hygiene level and of the marginal gingival health during the whole period of study, clinical (pocket probing depth, PPD; probing attachment level, PAL; gingival recession, GR) and intrasurgical (depth of the defect's intraosseous component, IOC; level of the alveolar crest, ACL) parameters were recorded at baseline and at the 1-year re-entry procedure in each experimental site. Furthermore, the coronal level of the newly formed tissue from the base of the defect (NFTL) and the vertical bone gain (VBG) were calculated at the time of membrane removal and after the re-entry procedure respectively. Membranes were removed from both test and control sites after 5 weeks; however, exposure of the membrane always occurred in test sites whereas it was observed in only 6 out of 22 control sites, this fact leading to an incomplete coverage of the regenerated tissue by the gingival flap in 18 out of 22 test sites. In both test and control sites, a statistically significant improvement of clinical and intrasurgical parameters occurred at the end of the study period; however, a significantly

  7. Comparison of direct site endovascular repair utilizing expandable polytetrafluoroethylene stent grafts versus standard vascular shunts in a porcine (Sus scrofa) model.

    PubMed

    Davidson, Anders J; Neff, Lucas P; Grayson, J Kevin; Clement, Nathan F; DeSoucy, Erik S; Simon Logan, Meryl A; Abbot, Christopher M; Sampson, James B; Williams, Timothy K

    2017-09-01

    The small diameter of temporary vascular shunts for vascular trauma management may restrict flow and result in ischemia or early thrombosis. We have previously reported a clinical experience with direct, open surgical reconstruction using expandable polytetrafluoroethylene stent grafts to create a "sutureless" anastomosis as an alternative to standard temporary vascular shunts. We sought to characterize patency and flow characteristics of these grafts compared with standard shunts in a survival model of porcine vascular injury. Twelve Yorkshire-cross swine received a 2-cm-long near-circumferential defect in the bilateral iliac arteries. A 14 Fr Argyle shunt was inserted into one randomly assigned artery, with a self-expanding expandable polytetrafluoroethylene stent deployed in the other. At 72 hours, conduit patency was evaluated by angiography. Arterial flow measurements were obtained at baseline, immediately after intervention, and after 72 hours via direct measurement with perivascular flow meters. Blood pressure proximal and distal to the conduits and arterial samples for histopathology were obtained during the terminal procedure. Angiography revealed no difference in patency at 72 hours (p = 1.0). While there was no difference in baseline arterial flow between arteries (p = 0.63), the stent grafts demonstrated significantly improved blood flow compared with shunts both immediately after intervention (390 ± 36 mL/min vs. 265 ± 25 mL/min, p = 0.002) and at 72 hours (261 ± 29 mL/min vs. 170 ± 36 mL/min, p = 0.005). The pressure gradient across the shunts was greater than that of the stent grafts (11.5 mm Hg [interquartile range, 3-19 mm Hg] vs. 3 mm Hg [interquartile range, 3-5 mm Hg], p = 0.013). The speed of deployment was similar between the two devices. Open "sutureless" direct site repair using commercially available stent grafts to treat vascular injury is a technically feasible strategy for damage control management of peripheral vascular injury and

  8. Use of the Viatorr Expanded Polytetrafluoroethylene-Covered Stent-Graft for Transjugular Intrahepatic Portosystemic Shunt Creation in Children: Initial Clinical Experience

    SciTech Connect

    Mermuys, Koen; Maleux, Geert Heye, Sam; Lombaerts, Rita; Nevens, Frederik

    2008-07-15

    Four children, three boys and one girl, with a median age of 9 years 8 months, underwent transjugular intrahepatic portosystemic shunt creation with an expanded polytetrafluoroethylene (e-PTFE)-covered nitinol stent. The stent-graft was successfully placed in all four patients without any complication. Clinical and biochemical improvement was noted in all four patients during follow-up. Radiological follow-up with use of duplex ultrasound showed a recurrent stenosis of the shunt 180 days after stent-graft implantation in one patient. This was treated with placement of an additional stent-graft, re-expanding completely the recurrent stenosis. In the other three patients, the stent-graft remained fully patent until the end of the study or until orthotopic liver transplantation. These preliminary results suggest that use of the Viatorr ePTFE-covered stent-graft in children is safe and feasible, with potentially the same high patency rate and improved clinical outcome as reported in adult patients.

  9. Intravascular US-guided direct intrahepatic portocaval shunt with an expanded polytetrafluoroethylene-covered stent-graft.

    PubMed

    Hoppe, Hanno; Wang, Stephen L; Petersen, Bryan D

    2008-01-01

    To retrospectively evaluate the midterm patency rate of the nitinol (Viatorr, W.L. Gore and Associates, Flagstaff, Ariz) stent-graft for direct intrahepatic portacaval shunt (DIPS) creation. Institutional Review Board approval for this retrospective HIPAA-compliant study was obtained with waiver of informed consent. DIPS was created in 18 men and one woman (median age, 54 years; range, 45-65 years) by using nitinol polytetrafluoroethylene (PTFE)-covered stent-grafts. The primary indications were intractable ascites (n = 14), acute variceal bleeding (n = 3), and hydrothorax (n = 2). Follow-up included Doppler ultrasonography at 1, 6, and 12 months and venography with manometry at 6-month intervals after the procedure. Shunt patency and cumulative survival were evaluated by using the Kaplan-Meier method and survival curves were plotted. Differences in mean portosystemic gradients (PSGs) were evaluated by using the Student t test. Multiple regression analysis for survival and DIPS patency were performed for the following parameters: Child-Pugh class, model of end-stage liver disease score, pre- and post-DIPS PSGs, pre-DIPS liver function tests, and pre-DIPS creatinine levels. DIPS creation was successful in all patients. Effective portal decompression and free antegrade shunt flow was achieved in all patients. Intraperitoneal bleeding occurred in one patient during the procedure and was controlled during the same procedure by placing a second nitinol stent-graft. The primary patency rate was 100% at all times during the follow-up period (range, 2 days to 30 months; mean, 256 days; median, 160 days). Flow restrictors were deployed in two (11%) of 19 patients. The 1-year mortality rate was 37% (seven of 19). Patency after DIPS creation with the nitinol PTFE-covered stent-graft was superior to that after TIPS with the nitinol stent-graft. RSNA, 2008

  10. Development of expanded polytetrafluoroethylene cardiovascular graft platform based on immobilization of poly lactic-co-glycolic acid nanoparticles using a wet chemical modification technique.

    PubMed

    Al Meslmani, Bassam M; Mahmoud, Gihan F; Bakowsky, Udo

    2017-08-30

    Expanded polytetrafluoroethylene ePTFE grafts are mostly employed to replace damaged blood vessels and to restore normal blood flow. However, the dilemma of early thrombosis, inflammation, and development of biofilms after implantation limit ePTFE long-term patency and restrict the patient's life quality. In this study, poly lactic-co-glycolic acid (PLGA) nanoparticles were covalently immobilized on ePTFE surface for local therapeutic purposes. First, the ePTFE surface was primarily oxidized by H2O2/H2SO4 solution to create hydroxyl groups. Consequently, free amino groups were introduced onto ePTFE surface by an aminolyzation reaction of the activated hydroxyl groups using 3-aminopropyl triethoxysilane. The produced amino groups were further used as anchor sites for covalent immobilization of previously prepared PLGA nanoparticles. The functional groups originated on ePTFE surface were confirmed by FTIR analysis. Furthermore, the scanning electron microscopy visualization evidenced a homogeneous distribution pattern of the immobilized PLGA nanoparticles on the surface. The immobilized PLGA nanoparticles showed stability on ePTFE surface under blood flow mimetic conditions. Additionally, light microscopy observation confirmed the biocompatibility of mouse L929 fibroblasts on the nano-coated ePTFE graft. The cellular adhesion and growth did not reveal remarkable cytotoxicity in the tested modified ePTFE grafts. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Comparative analysis of adherence, viability, proliferation and morphology of umbilical cord tissue-derived mesenchymal stem cells seeded on different titanium-coated expanded polytetrafluoroethylene scaffolds.

    PubMed

    Hollweck, Trixi; Marschmann, Michaela; Hartmann, Isabel; Akra, Bassil; Meiser, Bruno; Reichart, Bruno; Eblenkamp, Markus; Wintermantel, Erich; Eissner, Günther

    2010-12-01

    Umbilical cord tissue comprises an attractive new source for mesenchymal stem cells. Umbilical cord tissue-derived mesenchymal stem cells (UCMSC) exhibit self-renewal, multipotency and immunological naivity, and they can be obtained without medical intervention. The transfer of UCMSC to the ischemic region of the heart may have a favorable impact on tissue regeneration. Benefit from typical cell delivery by injection to the infarcted area is often limited due to poor cell retention and survival. Another route of administration is to use populated scaffolds implanted into the infarcted zone. In this paper, the seeding efficiency of UCMSC on uncoated and titanium-coated expanded polytetrafluoroethylene (ePTFE) scaffolds with different surface structures was determined. Dualmesh (DM) offers a corduroy-like surface in contrast to the comparatively planar surface of cardiovascular patch (CVP). The investigation of adherence, viability and proliferation of UCMSC demonstrates that titanium-coated scaffolds are superior to uncoated scaffolds, independent of the surface structure. Microscopic images reveal spherical UCMSC seeded on uncoated scaffolds. In contrast, UCMSC on titanium-coated scaffolds display their characteristic spindle-shaped morphology and a homogeneous coverage of CVP. In summary, titanium coating of clinically approved CVP enhances the retention of UCMSC and thus offers a potential cell delivery system for the repair of the damaged myocardium.

  12. Evaluations of blood compatibility via protein adsorption treatment of the vascular scaffold surfaces fabricated with polylactide and surface-modified expanded polytetrafluoroethylene for tissue engineering applications.

    PubMed

    Choi, Yoon Jeong; Choung, Sung Kwang; Hong, Choong Man; Shin, In Soo; Park, Sue Nie; Hong, Seung Hwa; Park, Han Ki; Park, Young Hwan; Son, Youngsook; Noh, Insup

    2005-12-15

    Blood compatibility was evaluated by short-term in vitro blood perfusion on candidate vascular scaffold surfaces of a biodegradable, porous polylactide scaffold and a chemically surface-modified expanded polytetrafluoroethylene (ePTFE) over a clinical ePTFE, by measuring blood cell adhesion either directly or after adsorption treatment with albumin and fibrinogen. The results indicated that the extent of blood cell adhesion was affected by scaffold surface properties and pre-adsorption of proteins such as fibrinogen and albumin. Surface morphologies and porosity of the scaffolds were characterized by scanning electron microscopy and porosimetry, and the amount of fibrinogen and albumin adsorbed on the scaffolds was measured and verified by employing radiolabeled C(14) albumin and I(125) fibrinogen by a scintillation counter and a gamma counter, respectively. Even though treatment of fibrinogen adsorption on the samples in advance led to higher induction of blood cell adhesion than those with no fibrinogen adsorption, the polylactide scaffold surface itself induced highest amount of the adhered blood cells in this study judged by analyses of their surface area. These results would be employed as guidance in determining a choice of the implant methods, in vitro versus in vivo tissue engineering, of the novel chemically modified ePTFE and the biodegradable polylactide scaffolds.

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

    SciTech Connect

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

    2011-02-15

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

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

    SciTech Connect

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

    1987-12-01

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

  15. Smaller-Sized Expanded Polytetrafluoroethylene Conduits With a Fan-Shaped Valve and Bulging Sinuses for Right Ventricular Outflow Tract Reconstruction.

    PubMed

    Yamashita, Eijiro; Yamagishi, Masaaki; Miyazaki, Takako; Maeda, Yoshinobu; Yamamoto, Yusuke; Kato, Nobuyasu; Asada, Satoshi; Hongu, Hisayuki; Yaku, Hitoshi

    2016-10-01

    One of the critical factors limiting conduit longevity in right ventricular outflow tract (RVOT) reconstruction with homografts and xenografts is the small size of the conduit. The aim of our study was to assess the outcome of using smaller-sized expanded polytetrafluoroethylene (ePTFE) conduits with a fan-shaped valve and bulging sinuses for RVOT reconstruction. This retrospective review examined 303 patients who underwent RVOT reconstruction with ePTFE conduits at 63 Japanese hospitals between 2003 and 2014. Inclusion criteria were a conduit size less than or equal to 16 mm and the use of operative treatment as the primary correction for underlying heart disease. Patients undergoing palliative procedures were excluded. Median follow-up was 1.7 years. Freedom from conduit replacement and freedom from conduit reintervention were 90.1% ± 4.8% and 77.2% ± 5.6%, respectively. The most common indication for conduit reintervention was pulmonary artery (PA) bifurcation stenosis (82%). Modeling z-scores as a dichotomous variable revealed that freedom from conduit reintervention for PA bifurcation stenosis was significantly decreased for conduits with a z-score greater than or equal to 1.4 compared with z-scores less than 1.4 (p = 0.036). There were 30 patients (9.9%) who experienced at least moderate conduit stenosis and 21 patients (6.9%) with at least moderate conduit insufficiency. Univariate Cox regression analysis showed that conduit size was a significant factor for conduit stenosis (p = 0.006). Excellent midterm outcomes were achieved with ePTFE valved conduits, even when using smaller sizes. Conduit z-scores around 1.4 were optimal for RVOT reconstruction in younger patients. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  16. Assessing the Safety of Expanded Polytetrafluoroethylene Synthetic Grafts in Living Donor Liver Transplantation: Graft Migration Into Hollow Viscous Organs - Diagnosis and Treatment Options.

    PubMed

    Hsu, Shih-Chao; Thorat, Ashok; Yang, Horng-Ren; Poon, Kin-Shing; Li, Ping-Chun; Yeh, Chun-Chieh; Chen, Te-Hung; Jeng, Long-Bin

    2017-07-06

    BACKGROUND Our recent studies have highlighted the importance and safety of backtable venoplasty for middle hepatic vein (MHV) and inferior right hepatic veins (IRHV) reconstruction using expanded polytetrafluoroethylene (ePTFE) vascular grafts. In this study, we aim to analyze the complications associated with ePTFE graft use and discuss the management of the rare, but, potentially life threatening complications directly related to ePTFE conduits. MATERIAL AND METHODS From January 2012 to October 2015 a total of 397 patients underwent living donor liver transplantation (LDLT). The ePTFE vascular grafts were used during the backtable venoplasty for outflow reconstruction in 262 of the liver allografts. Recipients who developed ePTFE-related complications were analyzed. RESULTS ePTFE-related complications developed in 1.52% (4/262) of the patients. One patient (0.38%) developed complete thrombosis with sepsis at 24 months post-transplantation and died due to multiorgan failure. Three patients (1.1%) developed graft migration into the second portion of the duodenum, without overt peritonitis. Surgical exploration and ePTFE graft removal was done in all the patients. One patient died due to overwhelming sepsis. CONCLUSIONS ePTFE graft migration into the duodenum causing perforation is a new set of complications that has been recently described in LDLT and can be treated effectively by surgical removal of the infected vascular graft and duodenal perforation closure. Despite of such complications, in our experience, ePTFE use in LDLT continues to have wide safety margin, with a complication rate of only 1.52%.

  17. Clinical and histologic response of subcutaneous expanded polytetrafluoroethylene (Gore-Tex) and porous high-density polyethylene (Medpor) implants to acute and early infection.

    PubMed

    Sclafani, A P; Thomas, J R; Cox, A J; Cooper, M H

    1997-03-01

    To examine the responses of subcutaneously implanted expanded polytetrafluoroethylene (e-PTFE, Gore-Tex) and porous high-density polyethylene (PHDPE, Medpor) to experimentally induced infection. Sprague-Dawley rats were implanted subcutaneously with either e-PTFE or PHDPE implants. Inocula of Staphylococcus aureus were injected directly over the implants and the wounds were observed for clinical signs of infection. After the animals were killed, the implants were harvested and underwent Histologic examination. Twenty-eight adult male Sprague-Dawley rats weighing 200 to 250 g. A 8-mm diameter, 1-mm-thick implant of either e-PTFE or PHDPE was placed in a subcutaneous pocket over each animal's dorsum. Either at the time of implantation or 14 days afterward, an inoculum of 10(9) colony-forming units of S aureus was injected transcutaneously directly over each implant. The animals were observed for 7 days before being killed. The implants were harvested and examined by both conventional light and scanning electron microscopy, and the degree of capsule reaction, infection, inflammation, and implant degradation was evaluated. Implants inoculated at the time of implantation were more likely to become clinically infected. Results for e-PTFE and PHDPE implants were similar in this group (5 of 5 e-PTFE and 5 of 5 PHDPE implants infected). The PHDPE implants inoculated 14 days after implantation were less likely to become infected (1 of 4 infected) than e-PTFE implants (3 of 4 infected), and were statistically less likely to become infected than PHDPE implants inoculated immediately after implantation (25% vs 100%; P < .02). Histologically, this resistance to infection correlated with increasing fibrovascular ingrowth into the PHDPE implants. The infected PHDPE implant had little to no ingrowth compared with PHDPE control implants. The uninfected e-PTFE implant had evidence of early fibrovascular ingrowth into the peripheral pores of the implant. Because of differences in pore

  18. A comparison of tibial artery bypass performed with heparin-bonded expanded polytetrafluoroethylene and great saphenous vein to treat critical limb ischemia.

    PubMed

    Neville, Richard F; Capone, Avery; Amdur, Richard; Lidsky, Michael; Babrowicz, Joseph; Sidawy, Anton N

    2012-10-01

    Expanded polytetrafluoroethylene (ePTFE) bonded with heparin (HePTFE) has been reported to perform equivalent to saphenous vein graft (SVG) for below-knee bypass. This series examines outcomes for tibial artery bypass using HePTFE and SVG over a contemporaneous time period. A retrospective analysis of prospectively collected data was conducted for 112 tibial bypasses (62 HePTFE, 50 SVG) performed from November 2006 to January 2009. Demographics for age, sex, race, diabetes mellitus, and end-stage renal disease were similar. Indications for revascularization were also similar: disabling claudication, 9%; rest pain, 25%; and tissue loss, 66%. The HePTFE group included more reoperative procedures (45% vs 26%). All HePTFE bypasses were performed using an autologous vein patch at the distal anastomosis. Postoperative graft surveillance by pulse examination, ankle-brachial index, and duplex ultrasound imaging occurred at 1, 3, 6, and 12 months. Follow-up ranged from 1 to 12 months. Kaplan-Meier and Cox regression analysis evaluated results in patients with no missing variables. HePTFE and SVG bypasses demonstrated no significant differences in target tibial artery distribution: anterior tibial (15 vs 17), dorsalis pedis (4 vs 5), posterior tibial (22 vs 16), and peroneal (21 vs 12). Graft occlusion occurred in 19 patients (16.9%) during follow-up. Primary patency at 1 year was 75.4% for HePTFE and 86.0% for SVG. There was no significant difference in primary patency due to sex (male, 78%; female, 84%), race (white, 82%; African American, 77%), or diabetes mellitus (no diabetes mellitus, 84%; diabetes mellitus, 76%). End-stage renal disease resulted in decreased patency (57%), with an eightfold reduction (95% confidence interval, 1.8%-39.8%; P = .006). SVG patients had a lower risk of occlusion/death (95% confidence interval, 14.2%-94.5%; P > .05). Sixteen amputations were performed, with no significant difference based on conduit. This experience indicates a trend for

  19. A multicenter comparison between autologous saphenous vein and heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft in the treatment of critical limb ischemia in diabetics.

    PubMed

    Dorigo, Walter; Pulli, Raffaele; Castelli, Patrizio; Dorrucci, Vittorio; Ferilli, Fiore; De Blasis, Giovanni; Monaca, Vincenzo; Vecchiati, Enrico; Pratesi, Carlo

    2011-11-01

    The aim of this study was to evaluate early and follow-up results of below-knee bypasses performed using a bioactive heparin-treated expanded polytetrafluoroethylene (ePTFE) graft in diabetic patients with critical limb ischemia (CLI) in a multicenter retrospective registry involving seven Italian vascular centers and to compare them with those obtained in patients operated on with autologous saphenous vein (ASV) in the same centers in the same period of time. Over an 8-year period, ending in 2009, a heparin-bonded prosthetic graft (Propaten Gore-Tex; W. L. Gore & Associates Inc, Flagstaff, Ariz) was implanted in 180 diabetic patients undergoing below-knee revascularization for CLI in seven Italian hospitals (group 1). In the same period in these seven centers, 133 below-knee bypasses with ipsilateral ASV in diabetics with CLI were performed (group 2). Data concerning these interventions were retrospectively collected in a multicenter registry with a dedicated database. Early (<30 days) results were analyzed in terms of graft patency, major amputation rates, and mortality. Follow-up results were analyzed in terms of primary and secondary graft patency, limb salvage, and survival. The interventions consisted of below-knee bypasses in 132 cases in group 1 (73%) and in 45 cases in group 2 (33%; P < .001); 48 patients in group 1 (27%) and 88 patients in group 2 (67%; P < .001) had distal tibial anastomosis. Patients in group 1 had more frequently adjunctive procedures performed at distal anastomotic sites to improve run-off status. Postoperative and long-term medical treatment consisted of single antiplatelet therapy in 93 cases (52%) in group 1 and in 64 cases (48%, P = ns) in group 2, of double antiplatelet therapy in 18 cases (10%) in group 1 and in four cases (3%; P = .05) in group 2 and of oral anticoagulants in 69 patients in group 1 (38%) and in 65 (49%; P = .02) in group 2. Mean duration of follow-up was 28.3 ± 21.4 months; 308 patients (98%) had at least one

  20. Pregnancy outcomes after myomectomy with polytetrafluoroethylene placement.

    PubMed

    Eaton, Jennifer L; Milad, Magdy P

    2014-01-01

    The aim of this study was to report preliminary data on pregnancy outcomes after myomectomy with placement of an expanded polytetrafluoroethylene adhesion barrier membrane. In this retrospective case series, 68 women who underwent myomectomy with expanded polytetrafluoroethylene membrane placement between January 1, 2003, and December 31, 2009, were identified. Of these women, 15 subsequently had documented pregnancies and were included in the final dataset. Eighteen pregnancies were documented among 15 women. There were no reported cases of preterm labor, preterm premature rupture of membranes, or uterine rupture. In this case series, there were no documented cases of preterm labor, preterm premature rupture of membranes, or uterine rupture after myomectomy with expanded polytetrafluoroethylene membrane placement.

  1. Pregnancy Outcomes After Myomectomy With Polytetrafluoroethylene Placement

    PubMed Central

    Milad, Magdy P.

    2014-01-01

    Background and Objectives: The aim of this study was to report preliminary data on pregnancy outcomes after myomectomy with placement of an expanded polytetrafluoroethylene adhesion barrier membrane. Methods: In this retrospective case series, 68 women who underwent myomectomy with expanded polytetrafluoroethylene membrane placement between January 1, 2003, and December 31, 2009, were identified. Of these women, 15 subsequently had documented pregnancies and were included in the final dataset. Results: Eighteen pregnancies were documented among 15 women. There were no reported cases of preterm labor, preterm premature rupture of membranes, or uterine rupture. Conclusion: In this case series, there were no documented cases of preterm labor, preterm premature rupture of membranes, or uterine rupture after myomectomy with expanded polytetrafluoroethylene membrane placement. PMID:25392651

  2. Biomechanical evaluation of microbial cellulose (Zoogloea sp.) and expanded polytetrafluoroethylene membranes as implants in repair of produced abdominal wall defects in rats.

    PubMed

    Falcão, Suyiene Cordeiro; Coelho, Antônio Roberto de Barros; Evêncio Neto, Joaquim

    2008-01-01

    To evaluate the Load of Rupture of implants of membranes of microbial cellulose (Zoogloea sp.) and extended polytetrafuoroethylene in sharp defects of abdominal wall of rats. Sixty Wistar male rats, with a mean weight of 437,7 g +/- 40,9, anesthetized by a mixture of ketamine (5mg/100g) and xylazine (2mg/100g), were submitted to a rectangular (2 x 3 cm) excision of the abdominal wall, including fascia, muscle and peritoneum, and treated with membranes of microbial cellulose (MC) (MC Group- 30 animals) or extended polytetrafluoroethylene (ePTFE) (ePTFE Group- 30 animals). Each group was subdivided in 14th POD, 28th POD and 60th POD Subgroups. Under anesthesia, animals were submitted to euthanasia at 14th POD, 28th POD and 60th POD for evaluation of Load of Rupture. Load of Rupture levels were significantly elevated (p<0, 05) among 14th, 28th and 60th postoperative days from each Group. When compared between groups, values of Load of Rupture were significantly larger (p<0, 05) in ePTFE Group than in MC Group. Resistance to strength at implant/host interface was more pronounced in PTFEe Group than in MC Group.

  3. PEPE II--a multicenter study with an end-point heparin-bonded expanded polytetrafluoroethylene vascular graft for above and below knee bypass surgery: determinants of patency.

    PubMed

    Hugl, B; Nevelsteen, A; Daenens, K; Perez, M Alonso; Heider, P; Railo, M; Schelzig, H; Gluecklich, B; Balzer, K; Vermassen, F; De Smit, P; Fraedrich, G

    2009-04-01

    The Propaten European Product Evaluation (PEPE II) study was a product evaluation intended to characterize the performance of the GORE PROPATEN vascular graft in above-knee (AK) and below-knee bypass (BK) surgery. This prospective multicenter trial enrolled 142 patients with peripheral arterial disease. In 87 patients AK and in 52 patients BK bypasses (including 15 femorocrural) were implanted (67.6% males, 32.4% females). The one-year overall primary and secondary patency rates were 80% and 84.7%, respectively. Overall limb salvage rate at 12-months was 96.2%. The primary patency rate for AK bypasses was 82.7%, for BK femoro-popliteal bypasses 74.2% and for BK tibial-peroneal bypasses 79.4%. Secondary patency rates were 87.3%, 78.8% and 85.1%, respectively. Primary patency rates decreased depending on the number of patent run-off vessels (three 84.3%, two 80.8%, one 73.3%). Subgroup analysis showed that female patients had a significantly higher primary patency rate for BK bypasses (95.5% vs. 67.8%, P=0.037 ) compared to male patients. Subgroup analysis comparing patients younger and older than 70 years did not show a statistically significant difference in patency rates. Twenty-one patients underwent 42 reinterventions after bypass surgery. Present data show that the end-point heparin-bonded polytetrafluoroethylene graft yields patency rates comparable to those obtained with other graft material in above-knee locations. The encouraging results for BK bypasses suggests that this graft is an excellent option for small diameter vascular reconstructions when autologous vein is unavailable.

  4. Experimental study of materials for patch graft on right ventricular outflow tract under extracorporeal circulation in dogs--comparison between Denacol EX-313-treated bovine jugular vein graft and expanded polytetrafluoroethylene (EPTFE) graft.

    PubMed

    Matsumoto, H; Sugiyama, S; Shibazaki, A; Tanaka, R; Takashima, K; Noishiki, Y; Yamane, Y

    2001-09-01

    A comparison between a bovine jugular vein treated with a hydrophilic polyepoxy compound cross-linker (Denacol), and expanded polytetrafluoroethylene (EPTFE), an artificial material, as a patch graft for the reconstruction of the right ventricular outflow tract under extracorporeal circulation in dogs, as if they had pulmonic stenosis, was made. Hemodynamic and histological examinations were conducted two weeks after the transplantation. Hemodynamic problems were not observed in either the Denacol or EPTFE groups. Macroscopically, organization of new tissue on the graft surface was more marked in the EPTFE group than in the Denacol group, and newly-formed tissue was seen surrounding the border of the graft and burying it in the EPTFE group. In the Denacol group, microscopic findings revealed the presence of inflammatory cells and fibroblasts, and an invasion of the graft by collagen fibers and elastic fibers. In the EPTFE group, there was minimal cellular infiltration of the graft and a thick layer consisting of collagen fibers and fibroblasts was observed around the graft. These results indicated that two weeks after transplantation the graft was better assimilated and organized with blood vasculature in the patch graft in the Denacol group than in the EPTFE group.

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

    PubMed

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

    2016-12-01

    To evaluate the long-term clinical efficacy and safety of double-layered polytetrafluoroethylene membrane-covered self-expandable segmental metallic stents (Uventa) in patients with chronic ureteral obstruction. In a retrospective study, a total of 50 ureter units (44 patients) with chronic obstructions were included from July 2010 to May 2015. Indications for Uventa placement were primary stenting for malignant ureteral obstruction, failed conventional polymeric Double-J stent (PS), or percutaneous nephrostomy (PCN) technique, with comorbidities or fears limiting PS/PCN changes, or with irritation or pain due to PS/PCN. Patients underwent Uventa stent placement using the antegrade or retrograde approach. There were no immediate procedure-related complications, and all stents were placed in the proper sites. During the median follow-up of 30.9 (interquartile range [IQR], 8.1-49.0) months, the primary (no obstruction and no additional intervention) and overall success (no obstruction and no additional intervention except supplementary Uventa) was 30.0% and 34.0%, respectively. Moreover, 14 of 50 ureter units (28.0%) experienced major complications (≥Clavien-Dindo class IIIb), such as ureteroarterial fistula (three cases, 6.0%), ureteroenteric fistula (three, 6.0%), ureterovaginal fistula (one, 2.0%), ureter perforation (one, 2.0%), uncontrollable bleeding (one, 2.0%), and complete obstruction (five, 10.0%). On univariate analysis, major complications were associated with female (odds ratio [OR] = 6.000), cervical cancer (OR = 4.667), ureteral stricture length (≥6.0 cm, OR = 4.583), and placement duration (≥24.0 months, OR = 20.429; all p < 0.05). In long-term follow-up, the Uventa stent demonstrated poor treatment outcomes with frequent major complications in patients with chronic ureteral obstructions.

  6. A Prospective, Randomized Study of an Expanded Polytetrafluoroethylene Stent Graft versus Balloon Angioplasty for In-Stent Restenosis in Arteriovenous Grafts and Fistulae: Two-Year Results of the RESCUE Study.

    PubMed

    Falk, Abigail; Maya, Ivan D; Yevzlin, Alexander S

    2016-10-01

    To assess the safety and efficacy of an expanded polytetrafluoroethylene stent graft versus balloon angioplasty for the treatment of in-stent restenosis in the venous outflow of hemodialysis access grafts and fistulae. Two hundred seventy-five patients were randomized at 23 US sites to stent-graft placement or percutaneous transluminal angioplasty (PTA). Primary study endpoints were access circuit primary patency (ACPP) at 6 months and safety through 30 days; secondary endpoints were evaluated through 24 months. ACPP at 6 months was significantly higher in the stent-graft group (18.6%) versus the PTA group (4.5%; P < .001), and freedom from safety events (30 days) was comparable (stent graft, 96.9%; PTA, 96.4%; P = .003 for noninferiority). The separation in ACPP survival curves remained through 12 months (stent graft, 6.2%; PTA, 1.5%). Treatment area primary patency (TAPP) was superior for the stent-graft group (66.4%) versus the PTA group (12.3%) at 6 months (P < .001), with a survivorship difference in favor of stent-graft placement maintained through 24 months (stent graft, 15.6%; PTA, 2.2%). ACPP and TAPP for the stent-graft group were better than those for the PTA group when compared within central and peripheral vein subgroups (P < .001). In central veins, TAPP was 13.6% in the stent-graft group versus 4.3% in the PTA group at 24 months (P < .001). Stent-graft use provided better ACPP and TAPP than PTA when treating in-stent restenosis in patients receiving dialysis with arteriovenous grafts and fistulae. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

  7. Reflectance of polytetrafluoroethylene for xenon scintillation light

    SciTech Connect

    Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F.

    2010-03-15

    Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region ({lambda}{approx_equal}175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

  8. 21 CFR 872.3680 - Polytetrafluoroethylene (PTFE) vitreous carbon materials.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Polytetrafluoroethylene (PTFE) vitreous carbon... Polytetrafluoroethylene (PTFE) vitreous carbon materials. (a) Identification. Polytetrafluoroethylene (PTFE) vitreous carbon material is a device composed of polytetrafluoroethylene (PTFE) vitreous carbon intended for...

  9. 21 CFR 872.3680 - Polytetrafluoroethylene (PTFE) vitreous carbon materials.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Polytetrafluoroethylene (PTFE) vitreous carbon... Polytetrafluoroethylene (PTFE) vitreous carbon materials. (a) Identification. Polytetrafluoroethylene (PTFE) vitreous carbon material is a device composed of polytetrafluoroethylene (PTFE) vitreous carbon intended for...

  10. 21 CFR 872.3680 - Polytetrafluoroethylene (PTFE) vitreous carbon materials.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Polytetrafluoroethylene (PTFE) vitreous carbon... Polytetrafluoroethylene (PTFE) vitreous carbon materials. (a) Identification. Polytetrafluoroethylene (PTFE) vitreous carbon material is a device composed of polytetrafluoroethylene (PTFE) vitreous carbon intended for...

  11. 21 CFR 872.3680 - Polytetrafluoroethylene (PTFE) vitreous carbon materials.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Polytetrafluoroethylene (PTFE) vitreous carbon... Polytetrafluoroethylene (PTFE) vitreous carbon materials. (a) Identification. Polytetrafluoroethylene (PTFE) vitreous carbon material is a device composed of polytetrafluoroethylene (PTFE) vitreous carbon intended for...

  12. Pathology of explanted polytetrafluoroethylene vascular grafts.

    PubMed

    Mehta, Rupal I; Mukherjee, Arnob K; Patterson, Tyler D; Fishbein, Michael C

    2011-01-01

    Graft occlusion is a well-documented etiology for arteriovenous fistulae failure. However, there is little morphologic information elucidating why synthetic vascular grafts fail. The purpose of this study was to examine the tissue responses occurring within and adjacent to explanted polytetrafluoroethylene grafts that were utilized during cardiovascular procedures and subsequently removed. Forty explanted polytetrafluoroethylene grafts (including 32 failed vascular grafts) originating from 18 females and 22 males who ranged in age from 6 to 82 years (mean age, 36 years) were evaluated. Duration of engraftment varied from 1 to 255 months (mean engraftment period, 64 months). In addition to neointimal hyperplasia, foreign body reaction, and thrombosis, an unexpected finding was calcification involving the graft material, as well as luminal thrombus and adjacent soft tissues. Twenty-seven of forty cases (68%) showed evidence of calcification, either within or adjacent to polytetrafluoroethylene grafts. Histologic examination revealed variable degrees and patterns of calcification within and adjacent to explanted polytetrafluoroethylene membranes and conduits (arterial, arteriovenous, or cardiac grafts). A significantly longer duration of engraftment (P=.015) was identified in calcified versus noncalcified polytetrafluoroethylene materials. Patient age, serum calcium, creatinine level, and blood urea nitrogen level showed no statistically significant differences between patients with calcified grafts and patients without calcified grafts. Interstitial calcification is frequently found within explanted polytetrafluoroethylene grafts and is associated with graft disruption. These findings suggest that calcification of polytetrafluoroethylene biomaterials may play a role in eventual graft failure. A better understanding of the process of polytetrafluoroethylene graft calcification may lead to novel therapies that aid in the prevention of polytetrafluoroethylene vascular

  13. Polytetrafluoroethylene-Impregnated Anodization For Aluminum

    NASA Technical Reports Server (NTRS)

    Danford, Merlin D.

    1990-01-01

    Technical memorandum describes experiments on ability of two commercial coatings and of standard hard anodization to protect aluminum against corrosion. Both commercial coatings, Polylube and Tufram, polytetrafluoroethylene-impregnated anodizations. Standard hard-anodized coating found to provide greatest protection.

  14. Refractory-metal compound impregnation of polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Leibecki, H. F.

    1969-01-01

    Process impregnates polytetrafluoroethylene /PTFE/ with rhenium or molybdenum compounds. The refractory metals impregnated PTFE combines chemical inertness with electrical conductivity. They are useful for electro-chemical cells, chemical processing equipment, catalysts, electrostatic charge removal, RF gasketing, and cable shielding.

  15. Equation of state of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Bourne, N. K.; Gray, G. T.

    2003-06-01

    The present drive to make munitions as safe as is feasible and to develop predictive models describing their constitutive response, has led to the development and production of plastic bonded explosives and propellants. There is a range of elastomers used as binder materials with the energetic components. One of these is known as Kel-F-800™ (poly-chloro-trifluroethylene) whose structure is in some ways analogous to that of poly-tetrafluoroethylene (PTFE or Teflon). Thus, it is of interest to assess the mechanical behavior of Teflon and to compare the response of five different production Teflon materials, two of which were produced in pedigree form, one as-received product, and two from previous in-depth literature studies. The equations of state of these variants were quantified by conducting a series of shock impact experiments in which both pressure-particle velocity and shock velocity-particle velocity dependencies were measured. The compressive behavior of Teflon, based upon the results of this study, appears to be independent of the production route and additives introduced.

  16. 76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-15

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Granular Polytetrafluoroethylene Resin From Japan AGENCY: United States International Trade... polytetrafluoroethylene resin from Japan would be likely to lead to continuation or recurrence of material injury. On...

  17. Coronary artery bypass grafting with an expanded polytetrafluoroethylene graft.

    PubMed

    Weyand, M; Kerber, S; Schmid, C; Rolf, N; Scheld, H H

    1999-05-01

    We report our experience with the Perma-Flow aortocoronary-right heart graft in 15 patients in whom autologous conduits were not available. Fifteen patients received 39 coronary anastomoses--10 to left anterior descending coronary artery branches, 15 to circumflex coronary artery branches, and 14 to branches of the right coronary artery. Early angiography was done in 11 patients. One patient died on postoperative day 17 of multiorgan failure. The graft was patent at postmortem examination. Of 30 coronary anastomoses at risk, 24 were patent. Three connections to the left anterior descending system were occluded in patients with an additional internal mammary artery graft to the same coronary system, and three connections to the circumflex system were occluded in patients with a history of major posterior infarction. Three of five distal anastomoses to the right atrial appendage were occluded, whereas all six connections to the superior vena cava were patent. None of the patients had shown recurrent angina at a mean follow-up of 10.9 months (range, 2-39 months). The synthetic Perma-Flow coronary graft appears to be a safe alternative in patients in whom arterial or venous conduits are not available. Competitive flow may lead to anastomotic occlusions. The appropriate site for the distal arteriovenous fistula seems to be the superior vena cava.

  18. 75 FR 67105 - Granular Polytetrafluoroethylene Resin From Italy and Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-01

    ... COMMISSION Granular Polytetrafluoroethylene Resin From Italy and Japan AGENCY: United States International... granular polytetrafluoroethylene resin from Italy and Japan. SUMMARY: The Commission hereby gives notice... polytetrafluoroethylene resin from Italy and Japan would be likely to lead to continuation or recurrence of material...

  19. 21 CFR 878.4520 - Polytetrafluoroethylene injectable.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Polytetrafluoroethylene injectable. 878.4520 Section 878.4520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  20. 21 CFR 878.4520 - Polytetrafluoroethylene injectable.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Polytetrafluoroethylene injectable. 878.4520 Section 878.4520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  1. 21 CFR 878.4520 - Polytetrafluoroethylene injectable.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Polytetrafluoroethylene injectable. 878.4520 Section 878.4520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  2. 21 CFR 878.4520 - Polytetrafluoroethylene injectable.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polytetrafluoroethylene injectable. 878.4520 Section 878.4520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  3. 21 CFR 878.4520 - Polytetrafluoroethylene injectable.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Polytetrafluoroethylene injectable. 878.4520 Section 878.4520 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices §...

  4. Revascularization of popliteal and below-knee arteries with polytetrafluoroethylene.

    PubMed

    Christenson, J T; Broomé, A; Norgren, L; Eklöf, B

    1985-02-01

    The expanded polytetrafluoroethylene (PTFE) graft (Gore-tex) is the most frequently used synthetic graft when an alternative to autologous saphenous vein is required. Early results have been encouraging. In the present paper we report on 6 years of results from 153 above-knee (AK) femoropopliteal bypass grafts, 74 below-knee (BK) femoropopliteal bypass grafts, and 54 femorotibial/peroneal bypass grafts. The main indication for the vascular reconstruction was severe ischemia. Preventive antibiotics were given to 95% of the patients. Minimum observation time was 1 year after implantation. There was no operative death. Graft infection was seen in less than 5% of patients. The 6-year cumulative limb salvage rate was 87% for patients with severe ischemia in the AK femoropopliteal bypass group, 59% for those in the BK femoropopliteal bypass group, and 57% for those in the femorotibial/peroneal bypass group. The graft patency rate was 88% at 2 years and 78% at 6 years for the AK femoropopliteal bypass group, for whom the operative indication was disabling claudication, and 81% and 68%, respectively, when the indication for the vascular procedure was severe ischemia. The cumulative graft patency rate was 53% and 43% at 2 and 6 years, respectively, after implantation of BK femoropopliteal bypass grafts and 43% and 39% for femorotibial/peroneal bypass procedures. The expanded PTFE (Gore-tex) graft seems therefore to be a good alternative when an autologous vein is not available, even for reconstructions well below the knee joint.

  5. A Novel Method for the Treatment of Bilateral Hypogastric Aneurysms Using Hybrid Polytetrafluoroethylene Graft.

    PubMed

    Tyagi, Sam; Pineda, D; Zheng, H; Dougherty, M; Calligaro, K; Troutman, D

    2017-05-01

    Open aortic aneurysm repair in the setting of bilateral hypogastric aneurysms is technically challenging. We present a novel technique for open surgical repair for bilateral hypogastric aneurysms using the Gore hybrid vascular graft (GVHG; W. L. Gore and Associates Inc, Flagstaff, Arizona). The GVHG is an expanded polytetrafluoroethylene graft with a nitinol stent at 1 end designed for hemodialysis access. The GVHG has been also been used for aortic debranching and treatment of occlusive disease. We describe the first report using GVHG to repair hypogastric aneurysms.

  6. Treatment of a Left Internal Mammary Artery to Pulmonary Artery Fistula with Polytetrafluoroethylene Covered Stents: A Case Report and Review of the Literature

    SciTech Connect

    Abbott, J. Dawn; Brennan, Joseph J.; Remetz, Michael S.

    2004-01-15

    Internal mammary artery (IMA) to pulmonary artery (PA) fistula is a rare complication of coronary artery bypass grafting (CABG) that may present as myocardial ischemia. We describe a case of left IMA-to-PA fistula treated with balloon expandable coronary polytetrafluoroethylene (PTFE) graft stents and review previously reported cases of this entity.

  7. Radiation Degradation of Polytetrafluoroethylene-Lead Composites

    NASA Astrophysics Data System (ADS)

    Karmakar, Sanat; Lawrence, Falix; Mallika, C.; Mudali, U. Kamachi

    2015-11-01

    Composites of polytetrafluoroethylene (PTFE) with Pb (0-15 wt.%) were fabricated and irradiated up to 50 kGy in a 60Co-gamma chamber to evaluate the effect of Pb in improving the radiation tolerance of PTFE. Thermal and mechanical properties were measured for the irradiated and un-irradiated PTFE samples and its composites. The number average molecular weight of PTFE was estimated at different doses from the enthalpy of crystallization values obtained by Differential Scanning Calorimetry. Reduction in the percentage increase in the enthalpy of crystallization and melting of PTFE-15% Pb composite, during irradiation indicated the stabilizing effect of lead on PTFE. Surface morphology of PTFE and its composites revealed that the formation of micro-cracks and blisters in PTFE, owing to radiation damage was controlled by lead. Elongation at break values and SEM images of the irradiated composites indicated that 15% Pb offered better stability to PTFE than 10% Pb.

  8. Polytetrafluoroethylene or Acellular Dermal Matrix for Diaphragmatic Reconstruction?

    PubMed

    Bassuner, Juri K; Rice, David C; Antonoff, Mara B; Correa, Arlene M; Walsh, Garrett L; Vaporciyan, Ara A; Garg, Naveen; Sepesi, Boris; Swisher, Stephen G; Hofstetter, Wayne L; Roth, Jack A; Mehran, Reza J

    2017-06-01

    We aimed to evaluate the impact of collagen matrix in the reconstruction of the diaphragm. We queried the electronic medical record for patients who had resection of the diaphragm and simultaneous pulmonary resection between 1999 and 2016. All reconstructions were performed with either polytetrafluoroethylene or acellular dermal matrix. We evaluated the rate of empyema and herniation in each group. A total of 208 patients met inclusion criteria. Polytetrafluoroethylene was used in 168 cases (80.8%) and dermal matrix in 40 cases (19.2%). Dermal matrix was used in 8 extrapleural pneumonectomies (5.4%), in 26 pleurectomy decortications (55.3%), and in 6 other types of resections (40%). Follow-ups were for a median of 15.0 months in the polytetrafluoroethylene group and 11.6 months in the dermal matrix group. Patients in the dermal matrix group had a chest tube for a median of 2.5 days longer than patients with polytetrafluoroethylene (p = 0.006). Empyema occurred in 11 polytetrafluoroethylene reconstructions (6.5%) and 3 dermal matrix reconstructions (7.5%) (p = 0.735). Seven patients (63.6%) with polytetrafluoroethylene infection required removal of the graft, whereas none in the dermal matrix group needed removal (p = 0.351). There were nine herniations in the polytetrafluoroethylene group and four in the dermal matrix group (p = 0.281), all were acute and due to anchorage failure. Although infection rates were similar between polytetrafluoroethylene and acellular dermal matrix, re-operation for removal was not necessary in the latter. The use of a thick acellular dermal matrix may be a reasonable option when diaphragmatic reconstruction is potentially associated with a higher risk of infection. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  9. High-density polytetrafluoroethylene membranes in guided bone and tissue regeneration procedures: a literature review.

    PubMed

    Carbonell, J M; Martín, I Sanz; Santos, A; Pujol, A; Sanz-Moliner, J D; Nart, J

    2014-01-01

    Expanded polytetrafluoroethylene (e-PTFE) has been used successfully as a membrane barrier for regeneration procedures. However, when exposed to the oral cavity, its high porosity increases the risk of early infection, which can affect surgical outcomes. An alternative to e-PTFE is non-expanded and dense polytetrafluoroethylene (n-PFTE), which results in lower levels of early infection following surgical procedures. The aim of this literature review was to analyze and describe the available literature on n-PFTE, report the indications for use, advantages, disadvantages, surgical protocols, and complications. The medical databases Medline-PubMed and Cochrane Library were searched and supplemented with a hand search for reports published between 1980 and May 2012 on n-PTFE membranes. The search strategy was limited to animal, human, and in vitro studies in dental journals published in English. Twenty-four articles that analyzed the use of n-PTFE as a barrier membrane for guided tissue regeneration and guided bone regeneration around teeth and implants were identified: two in vitro studies, seven experimental studies, and 15 clinical studies. There is limited clinical and histological evidence for the use of n-PTFE membranes at present, with some indications in guided tissue regeneration and guided bone regeneration in immediate implants and fresh extraction sockets.

  10. Annealing of gold nanostructures sputtered on polytetrafluoroethylene

    PubMed Central

    2011-01-01

    Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness. PMID:22078024

  11. Antibiotic bonding to polytetrafluoroethylene with tridodecylmethylammonium chloride

    SciTech Connect

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

    1982-09-01

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

  12. Cell microarrays on photochemically modified polytetrafluoroethylene.

    PubMed

    Mikulikova, Regina; Moritz, Sieglinde; Gumpenberger, Thomas; Olbrich, Michael; Romanin, Christoph; Bacakova, Lucie; Svorcik, Vaclav; Heitz, Johannes

    2005-09-01

    We studied the adhesion, proliferation, and viability of human umbilical vein endothelial cells (HUVEC) and human embryonic kidney cells (HEK) on modified spots at polytetrafluoroethylene (PTFE) surfaces. The viability of the cells was assessed using an aqueous non-radioactive cell proliferation assay. Round spots with a diameter of 100 microm were modified by exposure to the ultraviolet (UV) light of a Xe(2)(*)-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere employing a contact mask. The spots were arranged in a quadratic pattern with 300 microm center-to-center spot distances. With optimized degree of modification, the cells adhered to the modified spots with a high degree of selectivity (70-90%). The adhered cells on the spots proliferated. This resulted in a significant increase in the number of adhering HUVECS or HEK cells after seeding and in the formation of confluent cell clusters after 3-4 days. With higher start seeding density, these clusters were not only confined to the modified spots but extended several micrometer to the neighborhood. The high potential of the cell microarrays for gene analysis in living cells was demonstrated with HEK cells transfected by yellow fluorescent protein (YFP).

  13. Results with heparin bonded polytetrafluoroethylene grafts for femorodistal bypasses.

    PubMed

    Peeters, P; Verbist, J; Deloose, K; Bosiers, M

    2006-08-01

    Expanded polytetrafluoroethylene (ePTFE) grafts are commonly used for femoropopliteal (FP) and femorocrural (FC) bypass grafting. Especially in below-knee (BK) reconstructions, patency is often inferior to the outcome in patients eligible for venous bypass grafting. This study assesses whether the Carmeda BioActive Surface (CBAS), which employs covalent end-point linkage to retain heparin on the device surface, as it is used on the Propaten vascular graft successfully, can prolong patency. From June 2002 to December 2005, 138 patients (97 men and 41 women; mean age: 73 years) received the CBAS-ePTFE graft for 153 infrainguinal bypass procedures. Seventy-five above-knee (AK) and 78 BK (including 37 FC) procedures were performed. Follow-up evaluations consisted of clinical examinations, ultrasonographic studies, and distal pulse assessments. Patency and limb salvage rates were assessed by using life-table analyses. The overall primary and secondary 2-year patency rates were 73.6% and 86%, respectively. Two-year primary patency rates according to bypass type were 76.2%, 72.6%, and 68.9% for AK FP, BK FP, and FC bypasses, respectively; the corresponding secondary patency rates were 87.5%, 87.8%, and 79.4%. The 2-year limb salvage rate in patients with critical limb ischemia (n=68) was 89.9%. Our findings show that CBAS-ePTFE bypass grafts appear to give prolonged patency rates and indicate that the use of this graft may represent a viable alternative for BK bypasses, which have traditionally yielded less than desirable outcomes. A prospective randomized trial is required to provide more definitive information about the graft's patency and limb salvage performance.

  14. Valved Polytetrafluoroethylene Conduits for Right Ventricular Outflow Tract Reconstruction.

    PubMed

    Shinkawa, Takeshi; Tang, Xinyu; Gossett, Jeffrey M; Mustafa, Thikra; Hategekimana, Festus; Watanabe, Fumiya; Miyazaki, Takako; Yamagishi, Masaaki; Imamura, Michiaki

    2015-07-01

    The purposes of this study were to review our early outcomes using valved expanded polytetrafluoroethylene (ePTFE) conduits, with or without bulging sinus structure, for right ventricular outflow tract reconstruction and to examine the mechanical properties of the ePTFE material after bulging sinuses were created. A retrospective review was performed of all patients who received the valved ePTFE conduit between 2008 and 2014 at a single institution. The surface morphologies and the mechanical strengths of the ePTFE conduit with bulging sinuses examined by scanning electron microscopy and unidirectional pull test were compared with those of the original ePTFE material. There were 120 operations with the valved ePTFE conduit (60 with bulging sinuses). The patients median age and weight were 6.9 years and 23.7 kg. The conduits were a median size of 22 mm. At 5 years, freedom from conduit reoperation was 92.7% (95% confidence interval, 82.7% to 97.0%), and freedom from severe conduit insufficiency or more than a 50 mm Hg gradient was 74.8% (95% confidence interval, 60.8% to 84.4%). No significant differences in the surface morphologies were observed by the scanning electron microscopy or in the maximum tolerated loads obtained by the pull test between the original ePTFE material and the ePTFE with bulging sinuses (121 and 122 N in longitudinal direction and 115 and 121 N in circumferential direction; p = 0.88 and p = 0.68). The valved ePTFE conduits demonstrated excellent early clinical outcomes. The mechanical property examinations showed no obvious difference after bulging sinuses were created on the ePTFE material. Copyright © 2015 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

  15. Critical appraisal of paclitaxel balloon angioplasty for femoral-popliteal arterial disease.

    PubMed

    Herten, Monika; Torsello, Giovanni B; Schönefeld, Eva; Stahlhoff, Stefan

    2016-01-01

    Peripheral arterial disease, particularly critical limb ischemia, is an area with urgent need for optimized therapies because, to date, vascular interventions often have limited life spans. In spite of initial encouraging technical success after femoropopliteal percutaneous transluminal angioplasty or stenting, postprocedural restenosis remains the major problem. The challenging idea behind the drug-coated balloon (DCB) concept is the biological modification of the injury response after balloon dilatation. Antiproliferative drugs administered via DCBs or drug-eluting stents are able to suppress neointimal hyperplasia, the main cause of restenosis. This article reviews the results of DCB treatments of femoropopliteal and infrapopliteal lesions in comparison to standard angioplasty with uncoated balloons. A systematic literature search was performed in 1) medical journals (ie, MEDLINE), 2) international registers for clinical studies (ie, www.clinicaltrials.gov), and 3) abstracts of scientific sessions. Several controlled randomized trials with follow-up periods of up to 5 years demonstrated the efficacy of paclitaxel -DCB technology. However, calcified lesions seem to affect the efficacy of DCB. Combinations of preconditioning methods with DCBs showed promising results. Although the mechanical abrasion of calcium via atherectomy or laser ablation showed favorable periprocedural results, the long-term impact on restenosis and clinical outcome has to be demonstrated. Major advantages of the DCBs are the rapid delivery of drug at uniform concentrations with a single dose, their efficacy in areas wherein stents have been contraindicated until now (ie, bifurcation, ostial lesions), and in leaving no stent scaffold behind. Reinterventions are easier to perform because DCBs leave no metal behind. Various combinations of DCBs with other treatment modalities may prove to be viable options in future. The follow-up results of clinical studies will evaluate the long-term impact of DCBs.

  16. Current Approach to the Diagnosis and Treatment of Femoral-Popliteal Arterial Disease. A Systematic Review

    PubMed Central

    Kasapis, Christos; Gurm, Hitinder S

    2009-01-01

    Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis affecting 5 million adults in the United States, with an age-adjusted prevalence of 4% to 15% and increasing up to 30% with age and the presence of cardiovascular risk factors. In this article we focus on lower extremity PAD and specifically on the superficial femoral and proximal popliteal artery (SFPA), which are the most common anatomic locations of lower extremity atherosclerosis. We summarize current evidence and perform a systematic review on the diagnostic evaluation as well as the medical, endovascular and surgical management of SFPA disease. PMID:21037847

  17. Polytetrafluoroethylene gas intoxication in broiler chickens.

    PubMed

    Boucher, M; Ehmler, T J; Bermudez, A J

    2000-01-01

    A poultry research facility that housed 2400 Peterson x Hubbard cross broilers (48 pens of 50 chicks each) experienced 4% mortality within 24 hr of chick placement. Mortality started within 4 hr of placement, and within 72 hr, cumulative mortality had reached 52%. Mild dyspnea was the only clinical sign noted in some chicks prior to death. The primary gross lesion noted in the chicks submitted was moderate to severe pulmonary congestion. The lungs of four of these chicks sank in formalin, and blood-tinged fluid was noted in the mouth and nares of two chicks. The microscopic lesions noted in the affected chicks were moderate to severe pulmonary edema and congestion. The diagnosis indicated to the submitter was that pulmonary edema caused by exposure to an unidentified noxious gas caused the death of the chicks. The poultry house environment was tested for sulfur dioxide, oxides of nitrogen, carbon monoxide, carbon dioxide, and volatile organic compounds (as produced by combustion engines); all tests were negative for significant levels of these compounds. A second broiler flock was placed in the same facility and the mortality at 6 wk was 11%, which was greater than the 2.5%-4.7% mortality seen in the previous four flocks on the farm. Further investigation revealed that the only change in management practice in this facility prior to the onset of the severe mortality problem was the replacement of 48 heat lamp bulbs (one for each pen). The new heat lamp bulbs were polytetrafluoroethylene (PTFE) coated. PTFE gas intoxication has been reported in several exotic avian species, but this intoxication has not been previously reported in a poultry flock.

  18. 78 FR 11627 - Certain Granular Polytetrafluoroethylene Resin From Italy: Rescission of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-19

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE International Trade Administration Certain Granular Polytetrafluoroethylene Resin From Italy: Rescission of... on certain granular polytetrafluoroethylene (``PTFE'') resin from Italy. The period of review...

  19. 76 FR 29008 - Granular Polytetrafluoroethylene Resin From Italy; Correction of Notice of Scheduling

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-19

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Granular Polytetrafluoroethylene Resin From Italy; Correction of Notice of Scheduling AGENCY... expedited five-year review on an antidumping duty order on granular polytetrafluoroethylene resin from...

  20. 76 FR 39896 - Granular Polytetrafluoroethylene Resin From Italy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-07

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Granular Polytetrafluoroethylene Resin From Italy Determination On the basis of the record \\1\\ developed in the subject five-year review, the United States International Trade Commission (Commission) determines, pursuant to section 751(c) of...

  1. Excimer laser induced surface chemical modification of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Révész, K.; Hopp, B.; Bor, Z.

    1997-02-01

    Polytetrafluoroethylene has a notoriously non adhesive and non reactive character. Its successful surface photochemical modification was performed by irradiating the polytetrafluoroethylene/liquid triethylamine interface with an ArF excimer laser (λ=193 nm). Due to the photochemical treatment the polytetrafluoroethylene surface became more hydrophilic. The water receding contact angle decreased from 94° to 43°. The reaction cross section was determined from the decrease of the contact angles. It was found to be as high as 6.4×10-18 cm2. XPS measurements evidenced the removal of fluorine from the polytetrafluoroethylene, incorporation of alkyl carbon and nitrogen. Photochemical dissociation path of the triethylamine makes probable that it bonded to the fluoropolymer backbone via the α-carbon atom of an ethyl group. A radical, or a photoinduced electron transfer mechanism was suggested to describe this reaction. A selective area electroless plating of silver was performed after pretreating the sample with patterned photomodification. The increased adhesion of the sample was proved by gluing with epoxy resin. As a result of the surface modification the tensile strength of gluing increased by 210× and reached 24% of the value characteristic for the bulk material.

  2. One hundred percent patency of one-millimeter polytetrafluoroethylene (Gore-tex) grafts in the carotid arteries of rats.

    PubMed

    Cuadros, C L

    1984-01-01

    Expanded polytetrafluoroethylene arterial interposition grafts with an internal diameter of 1.0 mm were placed in the carotid arteries of rats. At 2 weeks, 100% patency rate was achieved by the use of strict sterile technique in 23 rats. In contrast, only 1 out of 21 grafts remained open in rats operated using standard clean but nonsterile technique, 5% patency. All thrombosed grafts showed evidence of infection. Orally administered aspirin at therapeutic doses prolonged bleeding times in the rats but did not affect patency results in either group.

  3. Polytetrafluoroethylene pulmonary valve conduit implantation for chronic pulmonary insufficiency.

    PubMed

    Quintessenza, James A

    2014-12-01

    Pulmonary valve replacement in patients with congenital cardiac disease is now being performed with more liberal indications in light of the data that chronic pulmonary insufficiency is not a benign lesion. The beneficial effects of valve replacement with low operative mortality and morbidity support this approach. Many options exist for a pulmonary valve prosthesis, which underscores the fact that there is no ideal valve available. Our efforts are focussed around a synthetic valve that avoids the bio-degeneration of a bio-prosthesis and avoids the need for life-long coumadin. We developed a bicuspid (bileaflet) polytetrafluoroethylene valve design, which has now gone through three major revisions in >200 patients over 14 years. We began the experience utilising a polytetrafluoroethylene hand-sewn bicuspid valve in the right ventricular outflow tract, initially using 0.6 mm and more recently 0.1 mm polytetrafluoroethylene. The 0.1 mm thickness material functions well as a leaflet, maintaining a relatively thin and flexible nature. It does not calcify or initiate thromboses at least for the first several years. We identified issues with dehiscence of the leaflet from the right ventricular outflow tract muscle, especially in the larger, potentially expansive right ventricular outflow tracts, and this prompted our latest design change to place the valve within a polytetrafluoroethylene tube. This current version of the polytetrafluoroethylene valve conduit has excellent short-to-intermediate-term function. Further follow-up is necessary to determine late durability and life-long valve-related procedural risk for our patients.

  4. Low-Thermal-Expansion Filled Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Shapiro, Sanford S.

    1989-01-01

    PTFE made thermally compatible with aluminum without changing dielectric constant. Manufactured with fillers and pores to reduce coefficient of thermal expansion by factor of 6 to match aluminum. Material retains 2.1 dielectric constant of pure PTFE. Combines filler and micropore concepts. Particles and voids embedded in PTFE matrix function cooperatively. Particles take up compressive stress imposed by contracting PTFE, and voids take up expanding material. Increases dielectric constant, while voids reduce it.

  5. Low-Thermal-Expansion Filled Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Shapiro, Sanford S.

    1989-01-01

    PTFE made thermally compatible with aluminum without changing dielectric constant. Manufactured with fillers and pores to reduce coefficient of thermal expansion by factor of 6 to match aluminum. Material retains 2.1 dielectric constant of pure PTFE. Combines filler and micropore concepts. Particles and voids embedded in PTFE matrix function cooperatively. Particles take up compressive stress imposed by contracting PTFE, and voids take up expanding material. Increases dielectric constant, while voids reduce it.

  6. Diffusely reflecting paints including polytetrafluoroethylene and method of manufacture

    NASA Technical Reports Server (NTRS)

    Schutt, J. B.; Shai, M. C. (Inventor)

    1985-01-01

    The invention pertains to a high diffuse, reflective paint comprising an alcohol soluble binder, polytetrafluoroethylene (TFE) and an alcohol for coating a substrate and forming an optical reference with a superior Lambertian characteristic. A method for making the paint by first mixing the biner and alcohol, and thereafter by mixing in outgassed TFE is described. A wetting agent may be employed to aid the mixing process.

  7. Responses of endothelial cells, smooth muscle cells, and platelets dependent on the surface topography of polytetrafluoroethylene.

    PubMed

    Lamichhane, Sujan; Anderson, Jordan A; Remund, Tyler; Sun, Hongli; Larson, Mark K; Kelly, Patrick; Mani, Gopinath

    2016-09-01

    In this study, the effect of different structures (flat, expanded, and electrospun) of polytetrafluoroethylene (PTFE) on the interactions of endothelial cells (ECs), smooth muscle cells (SMCs), and platelets was investigated. In addition, the mechanisms that govern the interactions between ECs, SMCs, and platelets with different structures of PTFE were discussed. The surface characterizations showed that the different structures of PTFE have the same surface chemistry, similar surface wettability and zeta potential, but uniquely different surface topography. The viability, proliferation, morphology, and phenotype of ECs and SMCs interacted with different structures of PTFE were investigated. Expanded PTFE (ePTFE) provided a relatively better surface for the growth of ECs. In case of SMC interactions, although all the different structures of PTFE inhibited SMC growth, a maximum inhibitory effect was observed for ePTFE. In case of platelet interactions, the electrospun PTFE provided a better surface for preventing the adhesion and activation of platelets. Thus, this study demonstrated that the responses of ECs, SMCs, and platelets strongly dependent on the surface topography of the PTFE. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2291-2304, 2016.

  8. Thermal expander

    NASA Astrophysics Data System (ADS)

    Huang, Junying; Shen, Xiangying; Jiang, Chaoran; Wu, Zuhui; Huang, Jiping

    2017-08-01

    One type of thermal device, named as thermal expander, is proposed and verified through both simulation and experiment. The thermal expander performs an efficient way to expand a heat flow of line-shape front. Moreover, the thermal expander shows an advantage in rectifying a heat flow from crooked front to line-shape front, which indicates that the thermal expander could act as an efficient point-to-line heat source convertor. We suggest that the thermal expander would be of help to energy saving and emission reduction, especially in thermal circuits and thermal management.

  9. Using electrochemistry in device processing on poly(tetrafluoroethylene) substrates

    SciTech Connect

    Howard, A.J.; Rye, R.R.; Ricco, A.J.; Rieger, D.J.; Lovejoy, M.L.; Sloan, L.R.; Mitchell, M.A.

    1994-10-01

    By combining electrochemical and electroless metal deposition processes with standard optical lithography and wet chemical etching, the authors have developed techniques for the fabrication of fine (<20 {mu}m), adherent, conducting features on poly(tetrafluoroethylene) (PTFE) substrates. These techniques are less expensive and have demonstrated resolution of at least a factor of five better than existing printed wiring board-based processes. Using these PTFE-based processes, the authors have fabricated {approximately} 10 GHz coupled-line quadrature (Lange) couplers, for which test results will be presented.

  10. Surface modification of polytetrafluoroethylene by excimer-laser radiation

    SciTech Connect

    Nishii, M.; Sugimoto, S.; Shimizu, Y.; Suzuki, N.; Kewanishi, S.; Nagese, T.; Endo, M.; Eguchi, Y.

    1993-12-31

    The adhesive strength of polytetrafluoroethylene (PTFE) films was enhanced remarkably by KrF-laser irradiation in air when a small amount of aromatic polymers such as aromatic polyester, polyetheretherketone and polyimide were blended with PTFE. From the surface analysis of the laser-irradiated PTFE by an X-ray photoelectron spectroscopy and a scanning electron microscopy, it was found that the enhancement in the adhesive properties was attributable to both the chemical effect owing to the formation of the polar groups such as carbonyl group and ethylene linkage and the physical one owing to the formation of the uneveness by the KrF-laser irradiation.

  11. Synthesis of silicon carbide nanocrystals from waste polytetrafluoroethylene.

    PubMed

    Wang, Liangbiao; Cheng, Qinglin; Qin, Hengfei; Li, Zhongchun; Lou, Zhengsong; Lu, Juanjuan; Zhang, Junhao; Zhou, Quanfa

    2017-02-28

    Resource utilization of waste plastic could solve the problem of environmental pollution and simultaneously relieve energy shortages, achieving sustainable development. In this study, the conversion of waste polytetrafluoroethylene (PTFE) to cubic silicon carbide (SiC) nanoparticles has been described. The structures and morphologies of the obtained SiC were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, the FTIR spectrum of the obtained SiC sample suggests that the waste PTFE was completely converted into SiC in our approach.

  12. Expanded polytetrafluoroethylene reinforced polyvinylidenefluoride-hexafluoropropylene separator with high thermal stability for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Xiong, Ming; Tang, Haolin; Wang, Yadong; Lin, Yu; Sun, Meiling; Yin, Zhuangfei; Pan, Mu

    2013-11-01

    PVDF-HFP/ePTFE composite separator with high thermal stability and low thermal shrinkage characteristic has been developed. The PVDF-HFP acts to absorb the electrolyte and shutdown at elevated temperature. The thermally stable ePTFE matrix is adopted to improve the mechanical strength and sustain the insulation after the shutdown. This novel separator presents good ion conductivity (up to 1.29 mS cm-1) and has a low thermal shrinkage of 8.8% at 162 °C. The composite separator shutdown at 162 °C and keep its integrity before 329 °C. Cells based on the composite separator show excellent capacities at high rate discharge and stable cycling performance.

  13. Distal polytetrafluoroethylene bypasses in patients older than 75 years.

    PubMed

    Illuminati, G; Bertagni, A; Caliò, F G; Papaspyropoulos, V

    2000-07-01

    Polytetrafluoroethylene (PTFE) alone is justified for infrapopliteal arterial grafting in elderly patients with critical ischemia of the lower limbs who lack a suitable, autogenous saphenous vein. A consecutive sample clinical study with a mean follow-up of 16 months. The surgical department of an academic tertiary care center and an affiliated secondary care center. Thirty-one patients older than 75 years with critical ischemia of the lower limbs received 34 PTFE bypass grafts to the infrapopliteal arteries: 12 patients to the anterior tibial, 8 to the peroneal, 8 to the posterior tibial, and 2 to the dorsalis pedis artery. Cumulative survival, primary graft patency, and limb salvage rates expressed by standard life-table analysis. Operative mortality rate was 3%. Cumulative survival rate was 80% at 2 years (SE, 9.2%) and 43% at 3 years (SE, 11.4%). Cumulative primary patency rate was 67% at 2 years (SE 9.1%), and 61% at 3 years (SE, 12.7%). Cumulative limb salvage rate was 77% at 2 years (SE, 8.7%) and 70% at 3 years (SE, 12.8%). Polytetrafluoroethylene alone is justified as graft material for infrapopliteal bypass grafts in elderly patients with critical ischemia of the lower limbs and without a suitable autogenous saphenous vein.

  14. Human saphenous vein endothelial cell adhesion and expansion on micropatterned polytetrafluoroethylene.

    PubMed

    Boivin, Marie-Claude; Chevallier, Pascale; Hoesli, Corinne A; Lagueux, Jean; Bareille, Reine; Rémy, Murielle; Bordenave, Laurence; Durrieu, Marie-Christine; Laroche, Gaétan

    2013-03-01

    Intimal hyperplasia and thrombosis are responsible for the poor patency rates of small-diameter vascular grafts. These complications could be avoided by a rapid and strong adhesion of endothelial cells to the prosthetic surfaces, which typically consist of expanded polytetrafluoroethylene (PTFE) for small-diameter vessels. We have previously described two peptide micropatterning strategies that increase the endothelialization rates of PTFE. The micropatterns were generated either by inkjet printing 300 μm squares or by spraying 10.1 ± 0.1 μm diameter droplets of the CGRGDS cell adhesion peptide, while the remaining surface was functionalized using the CWQPPRARI cell migration peptide. We now directly compare these two micropatterning strategies and examine the effect of hydrodynamic stress on human saphenous vein endothelial cells grown on the patterned surfaces. No significant differences in cell adhesion were observed between the two micropatterning methods. When compared to unpatterned surfaces treated with a uniform mixture of the two peptides, the cell expansion was significantly higher on sprayed or printed surfaces after 9 days of static cell culture. In addition, after 6 h of exposure to hydrodynamic stress, the cell retention and cell cytoskeleton reorganization on the patterned surfaces was improved when compared to untreated or random treated surfaces. These results indicate that micropatterned surfaces lead to improved rates of PTFE endothelialization with higher resistance to hydrodynamic stress.

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

    PubMed

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

    2015-09-01

    To determine the clinical outcomes of polytetrafluoroethylene covered balloon expandable stents (CBESs) in occlusive lesions of the aortic bifurcation in a kissing stent configuration. The study included 69 consecutive patients (29 men, 40 women) who underwent kissing stent procedures with CBESs between January 2003 and April 2009 in a single center. Patients who were previously treated with a CBES were excluded. Follow-up consisted of clinical investigation and duplex ultrasound examination. The primary patency was 88.1% at 1 year and 71.5% at 4 years, with secondary patency rates of 88.1% and 75.3%, respectively. For patients receiving a stent for the first time, primary patency was 91.3% at 1 year and 77.1% at 4 years. For patients who had received previous stents, patency was 83.6% at 1 year and 65.2% at 4 years (P = .83). There were no differences in secondary patency and freedom from target lesion reintervention (TLR). Loss of primary patency was mainly caused by stent occlusions (14 cases [78%]). The freedom from TLR at 4 years was 76.8%. Patency rates and freedom from TLR of CBESs in the kissing stent configuration with up to 4 years of follow-up were satisfying and mainly affected by stent occlusions. Studies focusing on optimizing stent configuration and medical care to reduce the incidence of thrombosis are indicated to improve results further. Copyright © 2015 SIR. Published by Elsevier Inc. All rights reserved.

  16. Reflectance dependence of polytetrafluoroethylene on thickness for xenon scintillation light

    NASA Astrophysics Data System (ADS)

    Haefner, J.; Neff, A.; Arthurs, M.; Batista, E.; Morton, D.; Okunawo, M.; Pushkin, K.; Sander, A.; Stephenson, S.; Wang, Y.; Lorenzon, W.

    2017-06-01

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

  17. Bypass Surgery in Limb Salvage: Polytetrafluoroethylene Prosthetic Bypass

    PubMed Central

    Naoum, Joseph J.; Arbid, Elias J.

    2012-01-01

    Polytetrafluoroethylene (PTFE) grafts have proven to be an adequate alternative conduit for peripheral bypass operations. Whether or not one uses PTFE depends on several factors: surgeon preference, individual patient circumstances, or when autologous greater saphenous vein is not available or adequate. These conventional grafts have evolved and undergone modification. The intraluminal surface has been coated with carbon or bonded with heparin. The structure of grafts has been modified with the creation of a hood or cuff, with the incorporation of a stent-graft segment for a sutureless anastomosis, or the fusion of PTFE with an outer polyester layer to minimize suture hole bleeding. This evolution intends to limit graft thrombogenicity, ameliorate the formation of intimal hyperplasia, decrease complications, and improve overall graft patency. PMID:23342188

  18. Reconstruction of recurrent diaphragmatic eventration with an elongated polytetrafluoroethylene sheet

    PubMed Central

    Ikeda, Masaki; Sonobe, Makoto; Bando, Toru; Date, Hiroshi

    2013-01-01

    We report the case of a 31-year old woman with recurrence of left diaphragmatic eventration 3 years after a previous surgery for this condition. At the initial occurrence, she had experienced dyspnoea on exercise and subsequently underwent laparoscopic plication of the diaphragm with an endo-stapler at a local hospital. Immediately after the operation, the diaphragm was torn and the intestine entered the thorax. Therefore, plication involving sewing was performed. Then, 3 years later, the patient again experienced dyspnoea and was diagnosed as having recurrence of left diaphragmatic eventration. Observation under thoracoscopy revealed that the centre of the left diaphragm was thin but not torn. We reconstructed the left diaphragm with an elongated polytetrafluoroethylene sheet on the naïve diaphragm. The patient was discharged from our hospital 5 days after surgery. Her respiratory function improved and she has not experienced recurrence. PMID:23644727

  19. Fabrication of polytetrafluoroethylene/carbon fiber composites using radiation crosslinking

    NASA Astrophysics Data System (ADS)

    Oshima, Akihiro; Udagawa, Akira; Tanaka, Shigeru

    2001-07-01

    A fabrication method for fiber-reinforced plastic (FRP) composites based on carbon fibers and polytetrafluoroethylene (PTFE) which was crosslinked by electron beam (EB) irradiation under specific conditions was studied. Though the fabricated composite showed high mechanical properties compared with a ready-made PTFE composite (non-crosslinked PTFE with 5˜20 wt% filler), mechanical properties of laminated panels were a bit poor compared with those of usual FRP. It was found that the toughness of the PTFE matrix is poor in the composite. On the other hand, the one-ply sheet of carbon fibers and crosslinked PTFE composite showed good mechanical properties for sheet-shape materials. The wettability of the obtained crosslinked PTFE composite is hardly changed by crosslinking and reinforcement.

  20. Nerve Cell Patterning Using Polytetrafluoroethylene and Poly-D-Lysine

    NASA Astrophysics Data System (ADS)

    Kusunoki, Masanobu; Togo, Yoshitaka; Wada, Takuto; Hashimoto, Yoshiya; Nishikawa, Hiroaki; Hontsu, Shigeki

    We developed a patterning technique for nerve cells that uses polytetrafluoroethylene (PTFE) and poly-D-lysine (PDL). The PDL layer on the PTFE substrate acted as a buffer for nerve cell adhesion, while Ar ion-irradiated areas on PTFE were used for separation of nerve cells. This structure was then used as a scaffold. A matrix circuit of nerve cells with dendrites or axons was subsequently observed on the scaffold after a week of cell culture. The Ar ion-irradiated area exhibited graphite or amorphous carbon, and PDL was detached from carbon grains by mechanical stress during cell culture. A possible explanation for the adhesion between PDL and PTFE is the van der Waals force. The stress between PDL/PTFE was reduced by the flexibility of PDL gel, which prevented separation of PDL from PTFE.

  1. Polytetrafluoroethylene transfer film studied with X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1980-01-01

    Polytetrafluoroethylene (PTFE) was rubbed against nickel in ultrahigh vacuum at loads up to 3.9 N and speeds up to 94 mm/sec. The transfer film formed on the nickel was analyzed using X-ray phototectron spectroscopy. The film was indistinguishable from bulk PTFE except for the possible presence of a small amount of NiF2. The transfer film was found to be about 1 molecule (0.5 nm) thick under all conditions; but at speeds above 10 mm/sec, there was evidence of bulk transfer in the form of fragments as well. The thickness measurements required a choice among conflicting published values of the inelastic mean free path for electrons in polymers. The values chosen gave internally consistent results.

  2. The effect of normal load on polytetrafluoroethylene tribology.

    PubMed

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

    2009-04-08

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

  3. Charge dynamic characteristics in corona-charged polytetrafluoroethylene film electrets.

    PubMed

    Chen, Gang-Jin; Xiao, Hui-Ming; Zhu, Chun-Feng

    2004-08-01

    In this work, the charge dynamics characteristics of injection, transport and decay in porous and non-porous polytetrafluoroethylene (PTFE) film electrets were investigated by means of corona charging, isothermal and thermal stimulating surface-potential decay measurements. The results showed that the initial surface potential, whether positively or negatively charging, is much higher in non-porous PTFE than in porous PTFE. For porous film the value of initial surface potentials increases with increase of film thickness. Higher charging temperature can remarkably improve charge stability. The charge dynamics are correlated to materials microstructure according to their scanning electron micrographs. For non-porous PTFE films, polarizability change of C-F bonds is the main origin of electret charges; but for porous PTFE film a large number of bulk and interface type traps are expected because of the greater area of interface and higher crystallinity.

  4. Preparing polymer brushes on polytetrafluoroethylene films by free radical polymerization

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

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

  5. Reconstruction of recurrent diaphragmatic eventration with an elongated polytetrafluoroethylene sheet.

    PubMed

    Ikeda, Masaki; Sonobe, Makoto; Bando, Toru; Date, Hiroshi

    2013-08-01

    We report the case of a 31-year old woman with recurrence of left diaphragmatic eventration 3 years after a previous surgery for this condition. At the initial occurrence, she had experienced dyspnoea on exercise and subsequently underwent laparoscopic plication of the diaphragm with an endo-stapler at a local hospital. Immediately after the operation, the diaphragm was torn and the intestine entered the thorax. Therefore, plication involving sewing was performed. Then, 3 years later, the patient again experienced dyspnoea and was diagnosed as having recurrence of left diaphragmatic eventration. Observation under thoracoscopy revealed that the centre of the left diaphragm was thin but not torn. We reconstructed the left diaphragm with an elongated polytetrafluoroethylene sheet on the naïve diaphragm. The patient was discharged from our hospital 5 days after surgery. Her respiratory function improved and she has not experienced recurrence.

  6. Comparison of hexagonal crystal structures between fluorapatite and polytetrafluoroethylene.

    PubMed

    Okazaki, Masayuki

    2017-01-01

    The crystallographic properties of fluorapatite (FAp) and polytetrafluoroethylene (PTFE) as biomedical materials were compared. Both materials contain fluorine and casually belong to the hexagonal crystal system. It is interesting that FAp is an inorganic ionic crystal, while PTFE is an organic covalent-bond crystal. Generally, fluorine contributes to the physicochemical stability and in some cases to the biocompatibility. The crystal structure of FAp was initially analyzed in 1930 by Náray-Szabó, although the analysis of hydroxyapatite (HAp) was markedly delayed until 1964. The computer graphics display demonstrated that fluoride ions serve to stabilize the hydroxyapatite crystals and prevent dental caries. On the other hand, PTFE crystal analysis was reported in 1954 by Bunn and Howells. The PTFE temperature-pressure phase diagram accepted for over 60 years is very complicated and insufficient. PTFE delicately changes its phase near room temperature, although at a glance it appears to have a simple form compared with DNA.

  7. Analysis of Decompressive Craniectomies with Subsequent Cranioplasties in the Presence of Collagen Matrix Dural Substitute and Polytetrafluoroethylene as an Adhesion Preventative Material.

    PubMed

    Pierson, Matt; Birinyi, Paul V; Bhimireddy, Sujit; Coppens, Jeroen R

    2016-02-01

    Decompressive craniectomy is an established treatment for malignant intracranial hypertension. Cranioplasty is performed once cerebral swelling has resolved. Complications include infection, postoperative fluid collections, hematoma, reoperation, and seizures. Our experience using a double layer technique during craniectomy with a collagen matrix onlay dural substitute and expanded polytetrafluoroethylene for antiadhesive properties during cranioplasty was reviewed. This is a retrospective chart review of 39 consecutive patients who underwent craniectomy with placement of collagen matrix dural onlay and expanded polytetrafluoroethylene and subsequent cranioplasty. Demographic data, size of craniectomy defect, estimated blood loss, operative time, time between operations, presence of dural tackups, and postoperative complications were analyzed. Mean operative time was 132 minutes and estimated blood loss was 112 mL. Overall complication rate was 25.6% and no mortality was encountered. Nine patients had postoperative fluid collections measuring ≥ 10 mm in thickness and/or 5 mm of midline shift. Two patients required reoperation for these collections. Two patients developed infections requiring bone flap removal. Three patients developed seizures after cranioplasty. Five patients required shunt placement for hydrocephalus. Our dual layer closure technique at time of decompressive craniectomy carries a similar reduction in operative time and estimated blood loss when compared with cranioplasty series with other antiadhesives present. The technique described enables easy dissection of the musculocutaneous flap from the dural plane during cranioplasty and increases the safety of the operation. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Cross-linking of polytetrafluoroethylene during room-temperature irradiation

    SciTech Connect

    Pugmire, David L; Wetteland, Chris J; Duncan, Wanda S; Lakis, Rollin E; Schwartz, Daniel S

    2008-01-01

    Exposure of polytetrafluoroethylene (PTFE) to {alpha}-radiation was investigated to detennine the physical and chemical effects, as well as to compare and contrast the damage mechanisms with other radiation types ({beta}, {gamma}, or thermal neutron). A number of techniques were used to investigate the chemical and physical changes in PTFE after exposure to {alpha}-radiation. These techniques include: Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and fluorescence spectroscopy. Similar to other radiation types at low doses, the primary damage mechanism for the exposure of PTFE to {alpha}-radiation appears to be chain scission. Increased doses result in a change-over of the damage mechanism to cross-linking. This result is not observed for any radiation type other than {alpha} when irradiation is performed at room temperature. Finally, at high doses, PTFE undergoes mass-loss (via smallfluorocarbon species evolution) and defluorination. The amount and type of damage versus sample depth was also investigated. Other types of radiation yield damage at depths on the order of mm to cm into PTFE due to low linear energy transfer (LET) and the correspondingly large penetration depths. By contrast, the {alpha}-radiation employed in this study was shown to only induce damage to a depth of approximately 26 {mu}m, except at very high doses.

  9. Air-breakdown charging mechanism of fibrous polytetrafluoroethylene films

    NASA Astrophysics Data System (ADS)

    Hu, Z.; von Seggern, H.

    2005-07-01

    Recently air-breakdown phenomena have gained increasing interest with respect to porous electrets for use as piezoelectric polymers. A strong discrepancy between porous (closed-porous) polypropylene and fibrous (open-porous) polytetrafluoroethylene (PTFE) has been recognized concerning the obtainable polarization and the related piezoelectric d33 coefficients. The present study aims to clarify the reasons for a poor charge separation ability of fibrous materials when exposed to electrical breakdown in its air voids. Therefore air-breakdown phenomenon of 91% fibrous PTFE films has been studied in detail, utilizing a corona triode for voltage application. At sufficient surface potential air breakdown sets in at an average field strength of 11.7MV/m, which corresponds to the value expected by Paschen breakdown in air. For higher applied voltages and therewith higher electric-field strengths in the film, the current generated by such electrical breakdown limits the maximum obtainable surface potential. It will be shown that this limitation is caused by a "breakdown-induced conductivity," which increases with increasing grid voltage. Such breakdown-induced conductivity hinders the formation of a large internal polarization by mutual charge compensation and therewith accounts for the obtainable low piezoelectric d33 coefficients in fibrous materials.

  10. XPS Study of Plasma- and Argon Ion-Sputtered Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Kliss, Mark (Technical Monitor)

    1997-01-01

    The similarity of plasma-polymerized tetrafluoroethylene (PPTFE) and the fluoropolymer film deposited by rf (radio frequency) plasma sputtering (SPTFE) of polytetrafluoroethylene (PTFE), noted earlier in the literature, has been reconfirmed. FT-IR (Fourier Transform Infrared), XPS (X ray Photoelectron Spectroscopy) and UV (ultraviolet) spectroscopy has been employed in apparently the first study to involve preparation of PPTFE and SPTFE in the same reactor and under comparable low-power plasma conditions. Most of the work concerned the use of He or Ar as sputtering gas, but some runs were also carried out with the other rare gases Ne, Kr and Xe. The C1s XPS spectra of SPTFE films displayed a relatively higher content of CF2 groups, and yielded higher F/C (fluorine / carbon) ratios, than PPTFE films, while the SPTFE films were somewhat more transparent in the UV than PPTFE. The F/C ratios for SPTFE were essentially independent of the rare gas used for sputtering. Increasing rf power from 10 to 50 W for Xe plasma-sputtering of PTFE resulted in successively lower F/C ratios (1.55 to 1.21), accompanied by sputtering of the glass reactor occurring at 40 W and above. Some limited XPS, FT-IR and UV data are presented on Ar ion-sputtered PTFE.

  11. Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal.

    PubMed

    Feng, Shasha; Zhong, Zhaoxiang; Zhang, Feng; Wang, Yong; Xing, Weihong

    2016-04-06

    Polytetrafluoroethylene (PTFE) membrane is an extensively used air filter, but its oleophilicity leads to severe fouling of the membrane surface due to organic aerosol deposition. Herein, we report the fabrication of a new amphiphobic 1H,1H,2H,2H-perfluorodecyl acrylate (PFDAE)-grafted ZnO@PTFE membrane with enhanced antifouling functionality and high removal efficiency. We use atomic-layer deposition (ALD) to uniformly coat a layer of nanosized ZnO particles onto porous PTFE matrix to increase surface area and then subsequently graft PFDAE with plasma. Consequently, the membrane surface showed both superhydrophobicity and oleophobicity with a water contact angle (WCA) and an oil contact angle (OCA) of 150° and 125°, respectively. The membrane air permeation rate of 513 (m(3) m(-2) h(-1) kPa(-1)) was lower than the pristine membrane rate of 550 (m(3) m(-2) h(-1) kPa(-1)), which indicates the surface modification slightly decreased the membrane air permeation. Significantly, the filtration resistance of this amphiphobic membrane to the oil aerosol system was much lower than the initial one. Moreover, the filter exhibited exceptional organic aerosol removal efficiencies that were greater than 99.5%. These results make the amphiphobic PTFE membranes very promising for organic aerosol-laden air-filtration applications.

  12. Synthesis of polytetrafluoroethylene based olefinic copolymer by gamma radiation grafting

    NASA Astrophysics Data System (ADS)

    Ferreto, H. F. R.; Lima, L. F. C. P.; Parra, D. F.; Zaia, V.; Lugão, A. B.

    2007-12-01

    High speed extrusion of linear low density polyethylene (LLDPE) is limited by processes shortcoming known as 'melt fracture' and 'sharkskin', which are surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and with poor surface properties. The fluoropolymer processing additives are used to eliminate the surface defect by coating the die wall and inducing slip at the coated fluoropolymer surface/LLDPE interface. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer grafted with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by grafting an olefinic monomer the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to allow recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. The olefinic monomer used was 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). The obtained copolymer (0.2-2.0 wt%) was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the developed process rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect 'melt fracture'.

  13. Computer Simulations of Polytetrafluoroethylene in the Solid State

    NASA Astrophysics Data System (ADS)

    Holt, D. B.; Farmer, B. L.; Eby, R. K.; Macturk, K. S.

    1996-03-01

    Force field parameters (Set I) for fluoropolymers were previously derived from MOPAC AM1 semiempirical data on model molecules. A second set (Set II) was derived from the AM1 results augmented by ab initio calculations. Both sets yield reasonable helical and phase II packing structures for polytetrafluoroethylene (PTFE) chains. However, Set I and Set II differ in the strength of van der Waals interactions, with Set II having deeper potential wells (order of magnitude). To differentiate which parameter set provides a better description of PTFE behavior, molecular dynamics simulations have been performed with Biosym Discover on clusters of PTFE chains which begin in a phase II packing environment. Added to the model are artificial constraints which allow the simulation of thermal expansion without having to define periodic boundary conditions for each specific temperature of interest. The preliminary dynamics simulations indicate that the intra- and intermolecular interactions provided by Set I are too weak. The degree of helical disorder and chain motion are high even at temperatures well below the phase II-phase IV transition temperature (19 C). Set II appears to yield a better description of PTFE in the solid state.

  14. Pulsed laser deposition of compact high adhesion polytetrafluoroethylene thin films

    NASA Astrophysics Data System (ADS)

    Smausz, Tomi; Hopp, Béla; Kresz, Norbert

    2002-08-01

    Polytetrafluoroethylene (PTFE) thin films were prepared from pressed powder pellets via pulsed laser deposition by using ArF (193 nm) excimer laser. The applied laser fluences were in the 1.6-10 J cm-2 range, the substrate temperature was varied between 27°C and 250°C and post-annealing of the films was carried out in air at temperatures between 320°C and 500°C. Films deposited at 250°C substrate temperature were found to be stoichiometric while those prepared at lower temperatures were fluorine deficient. Morphological analyses proved that the film thickness did not significantly depend on the substrate temperature and the post annealing at 500°C resulted in a thickness reduction of approximately 50%. It was demonstrated that the films prepared at 8.2 J cm-2 fluence and annealed at 500°C followed by cooling at 1°C min-1 rate were compact, pinhole-free layers. The adherence of films to the substrates was determined by tensile strength measurements. Tensile strength values up to 2.4 MPa were obtained. These properties are of great significance when PTFE films are fabricated for the purpose of protecting coatings.

  15. Shock, release and Taylor impact of the semicrystalline thermoplastic polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Bourne, N. K.; Brown, E. N.; Millett, J. C. F.; Gray, G. T.

    2008-04-01

    The high strain-rate response of polymers is a subject that has gathered interest over recent years due to their increasing engineering importance, particularly in load bearing applications subject to extremes of pressure and strain rate. The current work presents two specific sets of experiments interrogating the effect of dynamic, high-pressure loading in the regime of the phase II to phase III pressure-induced crystalline phase transition in polytetrafluoroethylene (PTFE). These are gas-gun driven plate- and Taylor impact. Together these experiments highlight several effects associated with the dynamic, pressure-induced phase transitions in PTFE. An elevated release wave speed shows evidence of a pressure-induced phase change at a stress commensurate with that observed statically. It is shown that convergence between analytic derivations of release wave speed and the data requires the phase II to III transition to occur. Taylor impact is an integrated test that highlights continuum behavior that has origin in mesoscale response. There is a rapid transition from ductile to brittle behavior observed that occurs at a pressure consistent with this phase transition.

  16. Adhesive and morphological characteristics of surface chemically modified polytetrafluoroethylene films

    NASA Astrophysics Data System (ADS)

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

    2004-01-01

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

  17. Inertial cavitation initiated by polytetrafluoroethylene nanoparticles under pulsed ultrasound stimulation.

    PubMed

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

    2016-09-01

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

  18. Airborne nanoparticle concentrations in the manufacturing of polytetrafluoroethylene (PTFE) apparel.

    PubMed

    Vosburgh, Donna J H; Boysen, Dane A; Oleson, Jacob J; Peters, Thomas M

    2011-03-01

    One form of waterproof, breathable apparel is manufactured from polytetrafluoroethylene (PTFE) membrane laminated fabric using a specific process to seal seams that have been sewn with traditional techniques. The sealing process involves applying waterproof tape to the seam by feeding the seam through two rollers while applying hot air (600 °C). This study addressed the potential for exposure to particulate matter from this sealing process by characterizing airborne particles in a facility that produces more than 1000 lightweight PTFE rain jackets per day. Aerosol concentrations throughout the facility were mapped, breathing zone concentrations were measured, and hoods used to ventilate the seam sealing operation were evaluated. The geometric mean (GM) particle number concentrations were substantially greater in the sewing and sealing areas (67,000 and 188,000 particles cm⁻³)) compared with that measured in the office area (12,100 particles cm⁻³). Respirable mass concentrations were negligible throughout the facility (GM = 0.002 mg m⁻³) in the sewing and sealing areas). The particles exiting the final discharge of the facility's ventilation system were dominated by nanoparticles (number median diameter = 25 nm; geometric standard deviation of 1.39). The breathing zone particle number concentrations of the workers who sealed the sewn seams were highly variable and significantly greater when sealing seams than when conducting other tasks (p < 0.0001). The sealing workers' breathing zone concentrations ranged from 147,000 particles cm⁻³ to 798,000 particles cm⁻³, and their seam responsibility significantly influenced their breathing zone concentrations (p = 0.03). The finding that particle number concentrations were approximately equal outside the hood and inside the local exhaust duct indicated poor effectiveness of the canopy hoods used to ventilate sealing operations.

  19. Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

    SciTech Connect

    Uçar, A.; Çopuroğlu, M.; Suzer, S.; Baykara, M. Z.; Arıkan, O.

    2014-10-28

    We investigated the tribological interaction between polytetrafluoroethylene (PTFE) and silicon oxide surfaces. A simple rig was designed to bring about a friction between the surfaces via sliding a piece of PTFE on a thermally oxidized silicon wafer specimen. A very mild inclination (∼0.5°) along the sliding motion was also employed in order to monitor the tribological interaction in a gradual manner as a function of increasing contact force. Additionally, some patterns were sketched on the silicon oxide surface using the PTFE tip to investigate changes produced in the hydrophobicity of the surface, where the approximate water contact angle was 45° before the transfer. The nature of the transferred materials was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS results revealed that PTFE was faithfully transferred onto the silicon oxide surface upon even at the slightest contact and SEM images demonstrated that stable morphological changes could be imparted onto the surface. The minimum apparent contact pressure to realize the PTFE transfer is estimated as 5 kPa, much lower than reported previously. Stability of the patterns imparted towards many chemical washing processes lead us to postulate that the interaction is most likely to be chemical. Contact angle measurements, which were carried out to characterize and monitor the hydrophobicity of the silicon oxide surface, showed that upon PTFE transfer the hydrophobicity of the SiO{sub 2} surface could be significantly enhanced, which might also depend upon the pattern sketched onto the surface. Contact angle values above 100° were obtained.

  20. Polytetrafluoroethylene Toxicosis in Recently Hatched Chickens (Gallus domesticus)

    PubMed Central

    Shuster, Katherine A; Brock, Kristie L; Dysko, Robert C; DiRita, Victor J; Bergin, Ingrid L

    2012-01-01

    Two groups of chickens (Gallus domesticus; White Leghorn; age, 4 d and 2 wk) housed in a university research vivarium were found dead or moribund without prior signs of illness. The overall mortality rates were 92.3% (60 of 65 birds) for the 4-d-old birds and 80% (8 of 10) for the 2-wk-old birds. All chicks were housed in brooders with heat lamps in a temperature- and humidity-controlled room. Primary gross findings were mild to moderate dehydration and hepatic lipidosis. The most consistent histologic findings were pulmonary hemorrhage and edema in all 7 of the 4-d-old birds evaluated and in all 4 of the 2-wk-old birds assessed. In addition, 1 of the 4-d-old birds had multifocal centrilobular hepatic necrosis. These findings suggested an inhaled toxicant and hypoxia, respectively. Inspection of the animal room revealed that approximately 50% of the heat lamp bulbs in the brooder cage were coated with polytetrafluoroethylene (PTFE). Two published case reports detail similar experiences in birds exposed to PTFE-coated heat-lamp bulbs. Birds are highly sensitive to inhaled toxicants owing to the high efficiency of their respiratory systems, and PTFE toxicosis is known to cause pulmonary edema and hemorrhage in pet birds after exposure to overheated nonstick cookware. In the present case, the bulbs were replaced, and no similar problems subsequently have been noted. This case illustrates the sensitivity of avian species to respiratory toxicants and serves as a reminder that toxicosis can be encountered even in the controlled environment of a laboratory vivarium. PMID:22330651

  1. Airborne Nanoparticle Concentrations in the Manufacturing of Polytetrafluoroethylene (PTFE) Apparel

    PubMed Central

    Vosburgh, Donna J.H.; Boysen, Dane A.; Oleson, Jacob J.; Peters, Thomas M.

    2016-01-01

    One form of waterproof, breathable apparel is manufactured from polytetrafluoroethylene (PTFE) membrane laminated fabric, using a specific process to seal seams that have been sewn with traditional techniques. The sealing process involves applying waterproof tape to the seam by feeding the seam through two rollers while applying hot air (600°C). This study addressed the potential for exposure to particulate matter from this sealing process, by characterizing airborne particles in a facility that produces over 1,000 lightweight PTFE rain jackets per day. Aerosol concentrations throughout the facility were mapped, breathing zone concentrations were measured, and hoods used to ventilate the seam sealing operation were evaluated. The geometric mean (GM) particle number concentrations were substantially greater in the sewing and sealing areas (67,000 and 188,000 particles cm−3) compared to that measured in the office area (12,100 particles cm−3). Respirable mass concentrations were negligible throughout the facility (GM=0.002 mg m−3 in the sewing and sealing areas). The particles exiting the final discharge of the facility's ventilation system were dominated by nanoparticles (number median diameter = 25 nm; geometric standard deviation of 1.39). The breathing zone particle number concentrations of the workers who sealed the sewn seams were highly variable and significantly greater when sealing seams than when conducting other tasks (p<0.0001). The sealing workers’ breathing zone concentrations ranged from 147,000 particles cm−3 to 798,000 particles cm−3, and their seam responsibility significantly influenced their breathing zone concentrations (p=0.03). The finding that particle number concentrations were approximately equal outside the hood and inside the local exhaust duct indicated poor effectiveness of the canopy hoods used to ventilate sealing operations. PMID:21347955

  2. Expanded Dengue.

    PubMed

    Kadam, D B; Salvi, Sonali; Chandanwale, Ajay

    2016-07-01

    The World Health Organization (WHO) has coined the term expanded dengue to describe cases which do not fall into either dengue shock syndrome or dengue hemorrhagic fever. This has incorporated several atypical findings of dengue. Dengue virus has not been enlisted as a common etiological agent in several conditions like encephalitis, Guillain Barre syndrome. Moreover it is a great mimic of co-existing epidemics like Malaria, Chikungunya and Zika virus disease, which are also mosquito-borne diseases. The atypical manifestations noted in dengue can be mutisystemic and multifacetal. In clinical practice, the occurrence of atypical presentation should prompt us to investigate for dengue. Knowledge of expanded dengue helps to clinch the diagnosis of dengue early, especially during ongoing epidemics, avoiding further battery of investigations. Dengue has proved to be the epidemic with the ability to recur and has a diverse array of presentation as seen in large series from India, Srilanka, Indonesia and Taiwan. WHO has given the case definition of dengue fever in their comprehensive guidelines. Accordingly, a probable case is defined as acute febrile illness with two or more of any findings viz. headache, retro-orbital pain, myalgia, arthralgia, rash, hemorrhagic manifestations, leucopenia and supportive serology. There have been cases of patients admitted with fever, altered mentation with or without neck stiffness and pyramidal tract signs. Some had seizures or status epilepticus as presentation. When they were tested for serology, dengue was positive. After ruling out other causes, dengue remained the only culprit. We have come across varied presentations of dengue fever in clinical practice and the present article throws light on atypical manifestations of dengue. © Journal of the Association of Physicians of India 2011.

  3. 76 FR 3614 - Granular Polytetrafluoroethylene Resin From Japan: Final Results of Sunset Review and Revocation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-20

    ... International Trade Administration Granular Polytetrafluoroethylene Resin From Japan: Final Results of Sunset... resin (``PTFE resin'') from Japan. See Initiation of Five-Year (``Sunset'') Review, 75 FR 67082..., the Department published an antidumping duty order on imports of PTFE resin from Japan. See...

  4. In vivo delamination of coronary guidewire polytetrafluoroethylene layer - A dreaded complication.

    PubMed

    Gupta, Anshul Kumar; Basappa, Harsha; Sadananda, K S; Manjunath, C N

    2016-01-01

    Coronary guidewires are coated with polytetrafluoroethylene (PTFE) layer to decrease resistance and enhance trackability. Delamination and embolization of PTFE material can be detrimental during percutaneous coronary interventions. We report an occurrence of such delamination and discuss the implications and possible mechanism of this dreaded complication. Copyright © 2015 Cardiological Society of India. Published by Elsevier B.V. All rights reserved.

  5. 76 FR 42114 - Granular Polytetrafluoroethylene Resin From Italy: Continuation of Antidumping Duty Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-18

    ... FR 67082 (November 1, 2010). As a result of its review, the ] Department determined that revocation... Expedited Sunset Review of the Antidumping Duty Order, 76 FR 12939 (March 9, 2011). On July 7, 2011, the ITC... Granular Polytetrafluoroethylene Resin From Italy, 76 FR 39896 (July 7, 2011), and USITC Publication...

  6. Plasma-enhanced atomic layer deposition: a gas-phase route to hydrophilic, glueable polytetrafluoroethylene.

    PubMed

    Roy, Amit K; Dendooven, Jolien; Deduytsche, Davy; Devloo-Casier, Kilian; Ragaert, Kim; Cardon, Ludwig; Detavernier, Christophe

    2015-02-28

    This communication reports an approach based on plasma-enhanced atomic layer deposition of aluminium oxide for the functionalization of polytetrafluoroethylene (PTFE or "Teflon") surfaces. Alternating exposure of PTFE to oxygen plasma and trimethylaluminium causes a permanent hydrophilic effect, and a more than 10-fold improvement of the "glueability" of PTFE to aluminium.

  7. Application of radiation-crosslinked polytetrafluoroethylene to fiber-reinforced composite materials

    NASA Astrophysics Data System (ADS)

    Oshima, Akihiro; Udagawa, Akira; Morita, Yousuke

    2001-01-01

    Plain-woven carbon fiber-filled polytetrafluoroethylene (PTFE) composites were fabricated by radiation-crosslinking under selective conditions. High mechanical and frictional properties are found in the composite materials compared with crosslinked PTFE without fiber. The composite materials with optional shapes, which are laminated after electron beam (EB) crosslinking treatment of each mono-layer could also be fabricated.

  8. A technique to eliminate subgingival cement adhesion to implant abutments by using polytetrafluoroethylene tape.

    PubMed

    Hess, Timothy A

    2014-08-01

    Residual excess cement adhered subgingivally to an implant abutment has the potential to cause periimplant mucositis or periimplant disease. This article describes a procedure in which polytetrafluoroethylene (PTFE) tape is used to protect dental cements from adhering to the implant abutment. This technique ensures complete removal of cement from the implant abutment after seating of the crown.

  9. Polytetrafluoroethylene fume-induced pulmonary edema: a case report and review of the literature.

    PubMed

    Hamaya, Rikuta; Ono, Yuko; Chida, Yasuyuki; Inokuchi, Ryota; Kikuchi, Ken; Tameda, Tadanobu; Tase, Choichiro; Shinohara, Kazuaki

    2015-05-14

    Polytetrafluoroethylene is ubiquitous in materials commonly used in cooking and industrial applications. Overheated polytetrafluoroethylene can generate toxic fumes, inducing acute pulmonary edema in some cases. However, neither the etiology nor the radiological features of this condition have been determined. For clarification, we report an illustrative case, together with the first comprehensive literature review. A previously healthy 35-year-old Japanese man who developed severe dyspnea presented to our hospital. He had left a polytetrafluoroethylene-coated pan on a gas-burning stove for 10 hours while unconscious. Upon admission, he was in severe respiratory distress. A chest computed tomographic scan showed massive bilateral patchy consolidations with ground-glass opacities and peripheral area sparing. A diagnosis of polytetrafluoroethylene fume-induced pulmonary edema was made. He was treated with non-invasive positive pressure ventilation and a neutrophil elastase inhibitor, which dramatically alleviated his symptoms and improved his oxygenation. He was discharged without sequelae on hospital day 11. A literature review was performed to survey all reported cases of polytetrafluoroethylene fume-induced pulmonary edema. We searched the PubMed, Embase, Web of Science and OvidSP databases for reports posted between the inception of the databases and 30 September 2014, as well as several Japanese databases (Ichushi Web, J-STAGE, Medical Online, and CiNii). Two radiologists independently interpreted all chest computed tomographic images. Eighteen relevant cases (including the presently reported case) were found. Our search revealed that (1) systemic inflammatory response syndrome was frequently accompanied by pulmonary edema, and (2) common computed tomography findings were bilateral ground-glass opacities, patchy consolidation and peripheral area sparing. Pathophysiological and radiological features were consistent with the exudative phase of acute respiratory

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

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

    PubMed

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

    2016-10-01

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

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

    PubMed Central

    Nakauchi, Kazuaki; Mito, Hidenori; Mimura, Osamu

    2013-01-01

    Background The frontalis suspension technique is the surgical method of choice in patients with ptosis and a levator function of 4 mm or less. Several types of materials have been used, including Gore-Tex®, which has been used successfully as a frontalis sling material since 1986. Recently, a Gore-Tex sheet (wider than a sling or strip) suspension was reported. This paper reports the results of 27 eyes from 20 patients with congenital ptosis treated using the frontalis suspension technique with the newly developed Gore-Tex Most Versatile Patch (MVP) sheet. Methods All patients underwent surgery between April 2007 and September 2011 and were followed up for at least one year. The average follow-up duration was 18 months, with a range of 12–36 months. The average patient age was 45 (5–85) years, and the group included 11 males and nine females. Thirteen cases demonstrated ptosis in one eye, and seven cases involved both eyes. The patients were divided by age into a younger group and an older group. All ptosis procedures were performed using the Gore-Tex MVP sheet. The implant was normally 7 mm wide for adults and 5 mm wide for children. The implantation method was the same as that used for the sheet shape fascia. Results In all patients, satisfactory functional results were observed at the 6-month follow-up examination. Eyelid opening heights were also obtained. The average marginal reflex distance (MRD) was −0.5 mm preoperatively, which improved to +1.9 mm after surgery. After one year, average MRD was +1.6 mm. MRD attenuation was more frequent in the younger group. There were no cases requiring redo surgery and only one case of exposure. PMID:23345967

  13. Digital pulley reconstruction with expanded polytetrafluoroethylene (PTFE) membrane at the time of tenorrhaphy in an experimental animal model.

    PubMed

    Semer, N B; Bartle, B K; Telepun, G M; Goldberg, N H

    1992-05-01

    Digital pulley reconstruction with a synthetic material, PTFE membrane, was compared with suture repair of the native A3 pulley at the time of tenorrhaphy in the chicken model. The surgically treated foot was immobilized in flexion for either 28 or 35 days and then allowed full ambulation for periods of up to 42 days postoperatively. At sacrifice digits underwent range-of-motion testing, and the pulley and tenorrhaphy sites were explored. No disruptions were noted in the reconstructed PTFE pulleys. The number of tenorrhaphy disruptions was similar between the PTFE pulley group (11%) and the suture repair of the native pulley group (14%). No decrease in range of motion was demonstrated in the PTFE pulley digits, and no deleterious effect of increasing immobilization time (35 days versus 28 days) was noted. The results indicate that this synthetic pulley did not interfere with normal tendon healing processes. PTFE membrane may prove to be a promising reconstructive alternative when the native pulley is irreparably damaged.

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

    PubMed

    Nakauchi, Kazuaki; Mito, Hidenori; Mimura, Osamu

    2013-01-01

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

  15. The noncovalent bonding of antibiotics to a polytetrafluoroethylene-benzalkonium graft

    SciTech Connect

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

    1981-01-01

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

  16. The noncovalent bonding of antibiotics to a polytetrafluoroethylene-benzalkonium graft.

    PubMed Central

    Harvey, R A; Greco, R S

    1981-01-01

    This study evaluates the noncovalent bonding of anionic antibiotics to polytetrafluoroethylene grafts using benzalkonium chloride as a cationic anchor. The binding of radiolabeled surfactants and antibiotics was evaluated by liquid scintillation and in an in vitro microbiologic assay against Staphylococcus aureus. Significant quantities of antibiotic were bound when the grafts were pretreated with benzalkonium in ethanol or aqueous solution at elevated temperature. Bound antibiotic is stable in aqueous salt solutions, but slowly dissociates in the presence of blood or serum. The ionic nature of the bonding process is clarified by the use of a variety of antibiotics and surfactants with complementary charges. The ability of the benzalkonium treated grafts to adsorb antibiotic from blood is, likewise, demonstrated and the possibility of concomitantly binding heparin and antibiotic simultaneously is evaluated. These studies support the ability to noncovalently bond antibiotics to polytetrafluoroethylene surfaces and form the basis of eventually utilizing these surfaces in the prevention of vascular prosthetic infections. PMID:7294935

  17. Self-assembly of polytetrafluoroethylene nanoparticle films using repulsive electrostatic interactions.

    PubMed

    Du, Chuan; Wang, Jiadao; Chen, Darong

    2014-02-04

    An approach for manufacturing polytetrafluoroethylene nanoparticle films using repulsive electrostatic interactions was developed. This approach used the strong repulsive force between colloidal nanoparticles and a substrate surface to cause the colloidal nanoparticles to suspend and self-assemble at a near-wall equilibrium position. A suspended monolayer was formed and was subsequently deposited on the substrate surface. A relatively large-area (3 × 3 cm(2)), close-packed unordered monolayer of polytetrafluoroethylene nanoparticles was observed. Multilayer nanoparticle films were also generated by increasing the particle concentration and deposition time. This work confirms the feasibility of nanoparticle self-assembly under repulsive electrostatic interactions and provides new routes for the large-area fabrication of monolayer and multilayer close-packed nanoparticle films.

  18. Successful delivery of polytetrafluoroethylene-covered stent using rapid exchange guide extension catheter.

    PubMed

    Fujimoto, Yoshihide; Tonoike, Norimasa; Kobayashi, Yoshio

    2017-04-01

    Deployment of polytetrafluoroethylene (PTFE)-covered stent is a useful technique to seal coronary perforation. However, the high profile and low flexibility compromise its deliverability. To facilitate stent delivery, a guide extension catheter (GuideLiner™ catheter) through a 6 Fr guiding catheter has been used. This case report describes a successful deployment of a PTFE-covered stent using a 6 Fr GuideLiner catheter to seal coronary perforation.

  19. Three-dimensional analysis of initial biofilm formation on polytetrafluoroethylene in the oral cavity.

    PubMed

    Fuchslocher Hellemann, C; Grade, S; Heuer, W; Dittmer, M P; Stiesch, M; Schwestka-Polly, R; Demling, A P

    2013-11-01

    There is published evidence that polytetrafluoroethylene (PTFE) exhibits beneficial surface characteristics by means of long-term biofilm accumulation. The purpose of this study was to investigate and compare early biofilm formation on polytetrafluoroethylene, ceramic-reinforced polytetrafluoroethylene and as the control group, stainless steel. This study comprised 10 healthy volunteers (5 females and 5 males) with a mean age of 27.3 ± 3.7 years. Three different slabs (two PTFE coatings: one pure and one ceramic-reinforced polytetrafluoroethylene, and stainless steel) were placed in random order on a splint in the mandibular molar region. Intraoral splints were inserted for 48 h. After 48 h, we removed the slabs from the splints and stained the biofilm with a two-color fluorescence assay for bacterial viability (LIVE/DEAD BacLight-Bacterial Viability Kit 7012, Invitrogen, Mount Waverley, Australia). The amount of biofilm accumulation was assessed using confocal laser scanning microscopy (CLSM). The biofilm surface coverage was 55.8 ± 39.8% on pure PTFE-coated probes, 55.9 ± 35.0% on ceramic-reinforced PTFE-coated probes, and 33.3 ± 37.8% on stainless steel. The differences among the three groups were not significant (p = 0.301). Biofilm depth was 5.6 ± 5.4 μm on pure PTFE-coated probes, 5.2 ± 3.8 μm on ceramic-reinforced PTFE-coated probes, and 2.4 ± 2.9 μm on stainless steel. The Friedman test revealed a significant difference in biofilm depth (p = 0.002). Pairwise comparison of biofilm accumulation yielded a significant difference between pure PTFE and ceramic-reinforced PTFE compared to stainless steel (p = 0.017; p = 0.005). Our results indicate that the beneficial surface characteristics of PTFE coatings by reducing long-term biofilm are not a result of inhibiting initial bacterial adhesion.

  20. AB186. Laparoscopic nephropexy using a self-designed polytetrafluoroethylene “basket”

    PubMed Central

    Li, Gang; Quan, Changyi; Niu, Yuanjie

    2016-01-01

    Objectives Laparoscopic nephropexy has been reported as a minimally invasive approach for symptomatic nephroptosis. We performed five cases of laparoscopic nephropexy using a self-made polytetrafluoroethylene “basket” to fix the inferior parts of kidneys to 12th rib. Methods All patients (four women and one man) had symptomatic nephroptosis presenting with flank pain, repeat hemoturine or hydronephrosis. Preoperative ultrasonography, intravenous urography and renal CT scan in supine and upright positions were done for nephroptosis diagnosis. Transperitoneal laparoscopic nephropexy were carried out using self-prepared “basket” made of stripes cutting from polytetrafluoroethylene herniorrhaphy mesh. After the kidney was completely dissected from surrounding perirenal fat, it was put into the non-absorbable polytetrafluoroethylene “basket” through multiple suturing and fixation to renal capsule. Then suspended the kidney by fixation the lower pole of kidney to the twelfth rib, and reinforced by suturing the posterior surface of the kidney to the quadratus lumborum muscle. Results The operation was successfully completed laparoscopically in all cases without major perioperative complications. The average operative time was 95 minutes, and the mean estimated blood loss was less than 60 mL. Hospital stay was 4.5 days (range, 3–6 days). Postoperative urography or ultrasound revealed complete resolution of loin pain and nephroptosis with a median follow-up of 8 months (range, 2–15 months). Conclusions Laparoscopic nephropexy using self-made polytetrafluoroethylene “basket” with a modified three-point fixation technique is an effective minimally invasive procedure for treating symptomatic nephroptosis with excellent short-term results.

  1. Management of radial artery perforation during transradial catheterization using a polytetrafluoroethylene-covered coronary stent.

    PubMed

    Chatterjee, Arka; White, Jeremy S; Leesar, Massoud A

    2017-03-01

    An 88-year-old woman underwent attempted percutaneous coronary intervention (PCI) through a right radial approach. Catheterization was complicated by radial artery perforation. Conservative therapeutic options including external compression, advancement of a diagnostic catheter distal to the perforation, and balloon tamponade failed to control the bleeding requiring deployment of a Polytetrafluoroethylene (PTFE)-covered stent to seal the perforation. We describe the stepwise approach advocated for managing a radial perforation and summarize relevant literature available for the same.

  2. Which prosthesis is more resistant to vascular graft infection: polytetrafluoroethylene or Omniflow II biosynthetic grafts?

    PubMed

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

    2016-03-01

    The aim of this study was to determine whether polytetrafluoroethylene grafts or Omniflow II biosynthetic grafts are more resistant to infection caused by Staphylococcus aureus. Sixty rats were divided into six groups. In Groups 1A, 1B and 1C, a polytetrafluoroethylene graft was implanted in each rat, and, in Groups 2A, 2B and 2C, a biosynthetic graft was implanted in each rat. Staphylococcus aureus was inoculated into Groups 1B, 1C, 2B and 2C, and the rats in Groups 1C and 2C were treated with teicoplanin. One week later, the rats were euthanized, the grafts were removed and a microbiological count was performed. A histopathological examination was subsequently carried out, and the C-reactive protein, prealbumin and leukocyte levels were investigated. There were no significant differences in the C-reactive protein, prealbumin and leukocyte levels. The differences in the results of the microbiological evaluations between the groups were significant. The quantitative culture results showed no bacterial growth in Groups 1A, 1C and 2A. The number of bacteria in Group 1B was statistically lower than that in Group 2B. When the groups receiving treatment were compared, Group 2C had bacterial growth, whereas Group 1C did not. The histopathological examinations showed similar results. Omniflow II grafts are more susceptible to infection than polytetrafluoroethylene grafts.

  3. Comparison of nylon monofilament suture and polytetrafluoroethylene sheet for frontalis suspension surgery in eyes with congenital ptosis.

    PubMed

    Hayashi, Kengo; Katori, Nobutada; Kasai, Kenichiro; Kamisasanuki, Taro; Kokubo, Kenichi; Ohno-Matsui, Kyoko

    2013-04-01

    To compare nylon monofilament suture with polytetrafluoroethylene sheet for frontalis suspension surgery to treat eyes with congenital ptosis. Retrospective, nonrandomized, comparative, interventional case series. We reviewed the medical records of 49 patients who had undergone 79 eyelid frontalis suspension surgeries to treat congenital ptosis. All of the patients were younger than 16 years and had congenital ptosis with poor levator muscle function. They were treated with frontalis suspension surgery with either a nylon suture or a polytetrafluoroethylene sheet and were followed up for at least 1 year. A single rhomboid loop sling was used for the nylon suture surgery. For the polytetrafluoroethylene sheet, an incision was made in the eyelid crease, and one end of the sheet was fixed to the tarsus and the other was fixed to the frontalis muscle. The main outcome measures were postoperative recurrences and complications. We evaluated 37 eyelids of 25 patients after nylon suture surgery and 42 eyelids of 31 patients after polytetrafluoroethylene sheet surgery. Among these, 9 eyelids of 7 patients were included in both groups. The median postoperative follow-up period was 32 months in both groups. The recurrence rates were 62.2% for the nylon suture group and 0% for the polytetrafluoroethylene sheet group (P < .001). The postoperative complication rates were 0% for the nylon suture group and 7.1% for the polytetrafluoroethylene sheet group (P > .05). Frontalis suspension using a polytetrafluoroethylene sheet with direct tarsus and frontalis muscle fixation is a reasonable technique with low rates of recurrences and complications. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Scanning electron microscope study of polytetrafluoroethylene sliding on aluminum single crystals

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1973-01-01

    Friction experiments were conducted in air with polytetrafluoroethylene (PTFE) sliding on aluminum single crystals. Mechanical scoring of the crystals with (110) and (100) orientations was observed with a single pass of the PTFE slider. No scoring was observed on the (111). The degree of scoring of the crystals is related to the hardness, with the hardest surface (111) showing no damage and the softest surface (110) showing the most severe scoring. Scoring is caused by work-hardened pieces of aluminum which, as a consequence of the adhesion between PTFE and aluminum, were pulled out of the bulk and became embedded in the PTFE polymer.

  5. Surface Vibrational Spectroscopy on Shear-Aligned Poly(tetrafluoroethylene) Films

    NASA Astrophysics Data System (ADS)

    Ji, Na; Ostroverkhov, Victor; Lagugné-Labarthet, Francois; Shen, Y. R.

    2004-03-01

    Sum-frequency vibrational spectroscopy was used to obtain the first surface vibrational spectra of shear-deposited highly-oriented poly(tetrafluoroethylene) (PTFE) thin films. The analysis of spectra taken with different polarization combinations of the input and output beams allowed us to assess orientation of the polymer chains on the film surface. The surface PTFE chains appeared to lie along the shearing direction. Vibrational modes observed at 1142 and 1204 cm-1 were found to have the E1 symmetry, in support of some earlier analysis in the long-lasting controversy over the assignment of these modes.

  6. Fabrication of super-hydrophobic surfaces on aluminum alloy substrates by RF-sputtered polytetrafluoroethylene coatings

    SciTech Connect

    Wang, Yang; Liu, Xiao Wei; Zhang, Hai Feng Zhou, Zhi Ping

    2014-03-15

    In this work, we present a method of fabricating super-hydrophobic surface on aluminum alloy substrate. The etching of aluminum surfaces has been performed using Beck's dislocation etchant for different time to create micrometer-sized irregular steps. An optimised etching time of 50 s is found to be essential before polytetrafluoroethylene (PTFE) coating, to obtain a highest water contact angle of 165±2° with a lowest contact angle hysteresis as low as 5±2°. The presence of patterned microstructure as revealed by scanning electron microscopy (SEM) together with the low surface energy ultrathin RF-sputtered PTFE films renders the aluminum alloy surfaces highly super-hydrophobic.

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

    NASA Astrophysics Data System (ADS)

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

    2001-07-01

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

  8. Correlation between Adhesion Strength of Plasma-Polymerized Hexamethyldisiloxane Films to Polytetrafluoroethylene and Partial Discharge Resistance

    NASA Astrophysics Data System (ADS)

    Kusabiraki, Minoru; Aozasa, Masao

    1995-09-01

    Polytetrafluoroethylene (PTFE) films were coated with plasma-polymerized hexamethyldisiloxane (PPHMDS) films in a dc glow discharge system. The correlation between the adhesion of the PPHMDS films to the PTFE films and the partial discharge resistance of the composite films was investigated. The voltage endurance of the composite films in the presence of partial discharges increased with the adhesion of the PPHMDS films. From an observation of the deteriorated surface scars, it was shown that the deterioration is affected by the formation of cracks in the PPHMDS film.

  9. Pervaporation of model acetone-butanol-ethanol fermentation product solutions using polytetrafluoroethylene membranes

    SciTech Connect

    Vrana, D.L.; Meagher, M.M.; Hutkins, R.W.; Duffield, B. )

    1993-10-01

    A pervaporation apparatus was designed and tested in an effort to develop an integrated fermentation and product recovery process for acetone-butanol-ethanol(ABE) fermentation. A crossflow membrane module able to accommodate flat sheet hydrophobic membranes was used for the experiments. Permeate vapors were collected under vacuum and condensed in a dry ice/ethanol cold trap. The apparatus containing polytetrafluoroethylene membranes was tested using butanol-water and model solutions of ABE products. Parameters such as product concentration, component effect, temperature, and permeate side pressure were examined. 25 refs., 3 figs., 5 tabs.

  10. The influence of ultrasonic exposure on polytetrafluoroethylene structure modified with boron nitride

    NASA Astrophysics Data System (ADS)

    Negrov, D. A.; Eremin, E. N.

    2017-06-01

    The purpose of study is to state influence patterns of ultrasonic exposure on the density and porosity change of the synthesized polymer composite material based on polytetrafluoroethylene, modified with boron nitride. The density of 5 % boron nitride samples manufactured by ultrasonic pressing is 9% higher than the similar samples manufactured by cold pressing have and this confirms the structure defectiveness results received by electron microscopy. As the result of carried studies it was stated that polymer composite material pressing with ultrasonic vibration is an active technology increasing efficiency of matrix structure modification and affecting significantly the structure formation processes in it.

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

    PubMed

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

    2011-06-01

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

  12. Irradiation performance of polytetrafluoroethylene (Teflon ®) in a mixed fast neutron and gamma radiation field

    NASA Astrophysics Data System (ADS)

    Harling, Otto K.; Kohse, Gordon E.; Riley, Kent J.

    2002-07-01

    Samples of polytetrafluoroethylene have been irradiated with a mixed field of fast neutrons and gamma rays using the MIT Research Reactor. Dose levels from ˜0.3 to ˜50×10 6 Gy for gamma and from ˜0.13 to 80×10 4 Gy for fast neutrons were used. Weight loss, fluorine loss, and swelling were measured quantitatively. Subjective mechanical property tests were also performed to assess embrittlement. Aside from high levels of embrittlement, no large changes, ≳1.5%, were observed in the properties which were assayed even at the highest doses.

  13. Packing of poly(tetrafluoroethylene) in the liquid state: Molecular dynamics simulation and theory

    NASA Astrophysics Data System (ADS)

    Tsige, Mesfin; Curro, John G.; Grest, Gary S.

    2008-12-01

    Molecular dynamics simulations and polymer reference interaction site model theory calculations were carried out on the C48F98 oligomer of poly(tetrafluoroethylene) (PTFE) at 500 and 600 K. The exp-6 force field of Borodin, Smith, and Bedrov, was used in both the simulation and theory. The agreement between theory and simulation was equivalent to earlier studies on polyolefin melts. The intermolecular pair correlation functions of PTFE were shifted to larger distances relative to polyethylene (PE) due to the difference in the van der Waals radii of F and H atoms. A similar shift to lower wave vectors was found in the structure factor of PTFE relative to PE.

  14. Fluorocarbon Thin Films Fabricated using Carbon Nanotube/Polytetrafluoroethylene Composite Polymer Targets via Mid-Frequency Sputtering.

    PubMed

    Kim, Sung Hyun; Kim, Cheol Hwan; Choi, Woo Jin; Lee, Tae Gon; Cho, Seong Keun; Yang, Yong Suk; Lee, Jae Heung; Lee, Sang-Jin

    2017-05-03

    Carbon nanotube/polytetrafluoroethylene composite polymer targets are proposed for use in the fabrication of fluorocarbon thin films using the mid-frequency sputtering process. Fluorocarbon thin films deposited using carbon nanotube/polytetrafluoroethylene composite targets exhibit an amorphous phase with a smooth surface and show a high water contact angle, optical transmittance, and surface hardness. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies reveal that as the carbon nanotube concentration increased in the composite target, a carbon cross-linked structure was formed, which enhanced the film hardness and the modulus of the fluorocarbon thin film. Large-area fluorocarbon thin films with a substrate width of 700 mm were successfully fabricated by a pilot-scale roll-to-roll sputtering system using a carbon nanotube/polytetrafluoroethylene composite target.

  15. The behavior of different types of polytetrafluoroethylene (PTFE) prostheses in the reparative scarring process of abdominal wall defects.

    PubMed

    Buján, J; Contreras, L A; Carrera-San Martín, A; Bellón, J M

    1997-07-01

    Currently one of the most widely used prosthetic materials in the repair of abdominal wall defects, is expanded polytetrafluoroethylene (ePTFE). It has been suggested that its behavior with respect to the reparative process may depend on its structure. The aim of the present study was to evaluate the effect of the structure of 3 ePTFE prostheses on the scarring process in an abdominal-wall-defect experimental model. The prostheses employed were the Soft Tissue Patch (STP) which is laminar in structure, Mycro Mesh (MM) which is multilaminar with perforations, and the Dual Mesh (DM) prosthesis which has one non-porous surface. Abdominal wall defects (7 x 5 cm) were created in 36 New Zealand rabbits and repaired using fragments of STP, MM and DM. Follow-up periods were 14, 30, 60 and 90 days post-implant. At these times prostheses were macroscopically examined for the presence of infection and/or rejection and the formation of adhesions to abdominal viscera. Specimens were also taken for microscopic analysis (optical and scanning electron) and for immunohistochemical analysis using the rabbit macrophage-specific monoclonal antibody RAM-11. Labelled macrophage counts were performed at each follow-up session. No cases of infection or rejection were found. Loose adhesions between prosthesis and underlying viscera were observed in 2 of the STP, 4 of the MM and 2 of the DM implants. STP and DM implants were progressively encapsulated by organized connective tissue on both peritoneal and subcutaneous surfaces. Cellular colonization was observed on both STP surfaces and on the porous surface of the DM although no more than a third of the biomaterial was penetrated by cells in either case. Colonization was very slight at prosthesis anchorage points. MM implants differed only in the formation of connective tissue bridges in perforated areas, and cellular infiltration in interlaminar spaces. Macrophage response was similar in the 3 prostheses with a reduction in RAM-11 labelled

  16. What Expands in an Expanding Universe?

    PubMed

    Pacheco, José A De Freitas

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    In the previous articles concerning the treatment of poly(tetrafluoroethylene) (PTFE) with potassium permanganate/nitric acid mixture, the conversion of a hydrophobic to a hydrophilic surface was partially assigned to the defluorination of PTFE and then the introduction of carbonyl and hydroxyl groups into the defluorinated sites. In the present work, PTFE sheets were treated with potassium permanganate/nitric acid, and the surfaces before and after treatment were comparatively characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface sediments of the treated PTFE were also determined by atomic absorption spectroscopy (AAS). The results indicate that the conversion of the hydrophobicity to the hydrophilicity on the modified PTFE surface is mainly due to the deposition of hydrophilic manganese oxides which covered the fluorocarbon surface, and no detectable chemical reactions of PTFE occur in the treating process.

  18. Surface energy changes produced by ultraviolet-ozone irradiation of poly(methylmethacrylate), polycarbone and polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Ponter, A. B.; Jones, W. R., Jr.; Jansen, R. H.

    1994-01-01

    Contact angles of water and methylene iodide were measured as a function of UV/O3 treatment time for three polymers: poly(methylmethacrylate) (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE). Surface roughnesses were also measured. Surface free energies were then calculated using relationships developed by Kaelble and Neumann. The surface energy of polycarbonate was found to increase (60 percent) during UV/O3 treatment. However, calculations on PMMA were hampered by the formation of a water soluble surface product. On PTFE surfaces, the UV/O3 treatment etched the surface causing large increases in surface roughness, rendering contact angle measurements impossible. It is concluded that care must be taken in interpreting contact angle measurements and surface energy calculations on UV/O3 treated polymer surfaces.

  19. Preparation of microstructure-controllable superhydrophobic polytetrafluoroethylene porous thin film by vacuum thermal-evaporation

    NASA Astrophysics Data System (ADS)

    Yi, Na; Bao, Shanhu; Zhou, Huaijuan; Xin, Yunchuan; Huang, Aibin; Ma, Yining; Li, Rong; Jin, Ping

    2016-09-01

    The three-dimensional porous network polytetrafluoroethylene (PTFE) thin films were achieved by a vacuum technique through evaporating the pure PTFE powders. The surfaces of PTFE thin films showed various morphologies by adjusting the evaporation temperature and the corresponding contact angle ranging from 133° to 155°. Further analyses of surface chemical composition and morphology by FTIR and FE-SEM revealed that the origin of hydrophobicity for the PTFE thin films could be ascribed to the fluorine-containing groups and the surface morphologies, indicating that abundant -CF2 groups and network structures with appropriate pore sizes played a vital role in superhydrophobicity. By characterization of UV-Vis, the films also showed high transmittance and antireflection effect. The films prepared by this simple method have potential applications such as waterproof membrane and self-cleaning coating.

  20. Bio-inspired superhydrophobic polyphenylene sulfide/polytetrafluoroethylene coatings with high performance.

    PubMed

    Sun, Na; Qin, Shan; Wu, Juntao; Cong, Chuanbo; Qiao, Yucong; Zhou, Qiong

    2012-09-01

    Bio-inspired superhydrophobic Polyphenylene sulfide/Polytetrafluoroethylene (PPS/PTFE) coatings were prepared by a simple curing process. The surface morphology characterization by SEM shows that these superhydrophobic coatings have the similar macro-nano-structures to that of lotus leaf. Effect of the content of PTFE as well as the curing condition on the water contact angle of the superhydrophobic coating surface was then systematically studied. A series of tests show that the superhydrophobic coatings exhibit high cohesional strength, excellent impact resistance and high thermal stability. Moreover, we studied the stability of chemical resistance of the as-prepared superhydrophobic PPS/PTFE coatings, and the electrochemical impedance values kept on a high level even after 8 days. The superhydrophobic PPS/PTFE coatings with high performance have potential applications in some specific fields.

  1. X-ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Wheeler, Donald R.; Pepper, Stephen V.

    1990-01-01

    Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The apparent annealing of the radiation damage was found to be due to the covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

  2. Observation of Individual Fluorine Atoms from Highly Oriented Poly(Tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, J. A.

    2000-01-01

    Direct observation of the film thickness, molecular structure, and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction-transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.7 and 0.54 A respectively.

  3. Measurement of the absolute reflectance of polytetrafluoroethylene (PTFE) immersed in liquid xenon

    NASA Astrophysics Data System (ADS)

    Neves, F.; Lindote, A.; Morozov, A.; Solovov, V.; Silva, C.; Bras, P.; Rodrigues, J. P.; Lopes, M. I.

    2017-01-01

    The performance of a detector using liquid xenon (LXe) as a scintillator is strongly dependent on the collection efficiency for xenon scintillation light, which in turn is critically dependent on the reflectance of the surfaces that surround the active volume. To improve the light collection in such detectors the active volume is usually surrounded by polytetrafluoroethylene (PTFE) reflector panels, used due to its very high reflectance—even at the short wavelength of scintillation light of LXe (peaked at 178 nm). In this work, which contributed to the overall R&D effort towards the LUX-ZEPLIN (LZ) experiment, we present experimental results for the absolute reflectance measurements of three different PTFE samples (including the material used in the LUX detector) immersed in LXe for its scintillation light. The obtained results show that very high bi-hemispherical reflectance values (>= 97%) can be achieved, enabling very low energy thresholds in liquid xenon scintillator-based detectors.

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

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

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

  5. Effect of X-ray flux on polytetrafluoroethylene in X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The effect of the X-ray flux in X-ray photoelectron spectroscopy (STAT) on the constitution of the polytetrafluoroethylene (PTFE) surface has been examined. The radiation dose rate for our specimen was about 10 to the 7th rad/s. The structure, magnitude and binding energy of the C(1s) and F(1s) features of the XPS spectrum and the mass spectrum of gaseous species evolved during irradiation are observed. The strong time dependence of these signals over a period of several hours indicated that the surface constitution of PTFE is greatly affected by this level of radiation dose. The results are consistent with the development of a heavily cross-linked or branched structure in the PTFE surface region and the evolution of short chain fragments into the gas phase.

  6. Adhesion and transfer of polytetrafluoroethylene to tungsten studied by field ion microscopy

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1972-01-01

    Mechanical contacts between polytetrafluoroethylene (PTFE) and tungsten field ion tips were made in situ in the field ion microscope. Both load and force of adhesion were measured for varying contact times and for clean and contaminated tungsten tips. Strong adhesion between the PTFE and clean tungsten was observed at contact times greater than 2.5 min (forces of adhesion were greater than three times the load). For times less than 2.5 min, the force of adhesion was immeasurably small. The increase in adhesion with contact time after 2.5 min can be attributed to the increase in true contact area by creep of PTFE. No adhesion was measurable at long contact times with contaminated tungsten tips. Neon field ion micrographs taken after the contacts show many linear and branched arrays which appear to represent PTFE that remains adhered to the surface even at the high electric fields required for imaging.

  7. Scleral fixation of a foldable intraocular lens with polytetrafluoroethylene sutures through a Hoffman pocket.

    PubMed

    Das, Sudeep; Nicholson, Maneck; Deshpande, Kalyani; Kummelil, Mathew Kurian; Nagappa, Somshekar; Shetty, Bhujang K

    2016-07-01

    Scleral fixation of intraocular lenses (IOLs) is traditionally performed after conjunctival dissection and preparation of scleral flaps. The Hoffman pocket technique creates scleral pockets without conjunctival dissection. We describe a technique that uses a Hoffman pocket and 7-0 polytetrafluoroethylene (Gore-Tex) sutures for scleral fixation of a foldable posterior chamber IOL in patients with insufficient capsule support. The technique eliminates the need for conjunctival dissection, scleral cauterization, knot rotation, and sutured wound closure. The favorable properties of the suture material and the use of a small incision to insert a foldable IOL are additional advantages. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  8. Air-to-surface missile wound of the thorax reconstructed with a polytetrafluoroethylene patch: case report.

    PubMed

    Flis, V; Antonic, J; Crnjac, A; Zorko, A

    1993-11-01

    A method of reconstructing a chest wall defect following non-guided air-to-surface missile injury is described. The wall defect was simply closed with a polytetrafluoroethylene patch. The high risk of infection following use of the described method is well recognized. No infection occurred in this case. It could be stated that under the exigencies of the moment the use of prosthetic material to reconstruct the chest is not invariably followed by infection. However, when the patient is stable this latter problem can then be addressed by a variety of standard methods. It is concluded that the described method is particularly suitable in war circumstances, when it is usually necessary to attend to a large number of patients in a short period of time.

  9. Experience with the modified Blalock-Taussig operation using polytetrafluoroethylene (Impra) grafts.

    PubMed Central

    Kay, P H; Capuani, A; Franks, R; Lincoln, C

    1983-01-01

    Between June 1978 and January 1982, 115 patients underwent 122 subclavian artery-pulmonary artery shunts using polytetrafluoroethylene (PTFE Impra) grafts. Forty-six of the patients had a ductus dependent pulmonary circulation, the patency of which was maintained by an infusion of prostaglandin E2 in 29 cases. There were nine hospital deaths, four of which were related to shunt failure. Five patients underwent a second shunt procedure within one week of the first. There were two cases of late graft occlusion. Twelve shunts were considered to have failed. The actuarial estimate of shunt patency was 90% (+/- 3%) at two years for all patients and 74% (+/- 10%) for neonates. There was no statistically significant difference in two year shunt patency between 4 mm grafts (88 +/- 5%) and 6 mm grafts (96 +/- 3%). The modified Blalock shunt using a PTFE graft is an effective pulmonary-systemic shunt with a good short term patency. Images PMID:6830670

  10. Cell proliferation on UV-excimer lamp modified and grafted polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

    Polytetrafluoroethylene (PTFE) was modified by irradiation with 172 nm light from an UV-excimer lamp in reactive ammonia atmosphere. Then, the samples were exposed to aqueous solutions of amino acids (glycine, alanine and leucine). The samples were characterized by water contact angle measurement, UV-VIS spectroscopy and laser-induced fluorescence (LIF). The results indicate, that the amino acids are bound onto the polymer chain. The amount of incorporated amino acid is a decreasing function of its molecular size. By in vitro experiments it was shown that the incorporated amino acids support adhesion and proliferation of rat aortic smooth muscle cells and mouse embryonic 3T3 fibroblasts on the polymer surface. The maximum effect was observed for smallest molecule of glycine.

  11. Extreme ultraviolet (EUV) surface modification of polytetrafluoroethylene (PTFE) for control of biocompatibility

    NASA Astrophysics Data System (ADS)

    Ahad, Inam Ul; Butruk, Beata; Ayele, Mesfin; Budner, Bogusław; Bartnik, Andrzej; Fiedorowicz, Henryk; Ciach, Tomasz; Brabazon, Dermot

    2015-12-01

    Extreme ultraviolet (EUV) surface modification of polytetrafluoroethylene (PTFE) was performed in order to enhance the degree of biocompatibility. Polymer samples were irradiated by different number of EUV shots using a laser-plasma based EUV source in the presence of nitrogen gas. The physical and chemical properties of EUV modified PTFE samples were studied using Atomic Force Microscopy, X-ray photoelectron spectroscopy and water contact angle (WCA) methods. Pronounced wall type micro and nano-structures appeared on the EUV treated polymer surfaces resulting in increased surface roughness and hydrophobicity. Stronger cell adhesion and good cell morphology were observed on EUV modified surfaces by in-vitro cell culture studies performed using L929 fibroblasts.

  12. Potential space debris shield structure using impact-initiated energetic materials composed of polytetrafluoroethylene and aluminum

    NASA Astrophysics Data System (ADS)

    Wu, Qiang; Zhang, Qingming; Long, Renrong; Zhang, Kai; Guo, Jun

    2016-03-01

    A whipple shield using Al/PTFE (polytetrafluoroethylene) energetic material to protect against space debris is presented. The hypervelocity impact characteristics were investigated experimentally using a two-stage light gas gun at velocities between 3 and 6 km/s. A good protection of the shield was obtained through comparative experiments which used the same bumper areal density. The results showed that the critical projectile diameter can be improved by 28% by contrast with the Christiansen ballistic limit equations. The Al/PTFE energetic material bumper can break up the projectile into smaller, less massive, and slower projectiles due to the combined effect of impact and explosion, thereby producing a sharp rise in the spacecraft protection ability.

  13. Adhesion and proliferation of human endothelial cells on photochemically modified polytetrafluoroethylene.

    PubMed

    Gumpenberger, T; Heitz, J; Bäuerle, D; Kahr, H; Graz, I; Romanin, C; Svorcik, V; Leisch, F

    2003-12-01

    We studied the adhesion and proliferation of human endothelial cells on photochemically modified polytetrafluoroethylene samples. The polymer surfaces were modified by exposure to the ultraviolet light of a Xe(2)(*)-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. Treatment times were between 10 and 20 min. The endothelial cell density was determined 1, 3 and 8 days after seeding by image analysis. Surface modification of the samples resulted in a significant increase in the number of adhering cells and in the formation of a confluent cell layer after 3-8 days. The results were comparable than those obtained on polystyrene Petri dishes, which are used as standard substrates in cell cultivation. Thus modified PTFE appears to be a promising material for the fabrication of artificial vascular prostheses coated with endothelial cells.

  14. Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  15. Removing hepatitis C virus from polytetrafluoroethylene-coated orthodontic archwires and other dental instruments.

    PubMed

    Ramadan, A A

    2003-05-01

    The efficacy of removing, rather than destroying, hepatitis C virus (HCV) from polytetrafluoroethylene (PTFE)-coated orthodontic archwirs was tested. PTFE-coated archwires, pieces of PTFE and endodontic files (20 each) were immersed in HCV-infected blood for 24 hours. Half were washed under running water for 10 seconds while the remainder were thoroughly scrubbed with a toothbrush under running water for 10 seconds. Items were kept in separate dishes of distilled water for 24 hours. Reverse transcription polymerase chain reaction was used for viral replication. Viruses were detected by the gel method using a transilluminator. Only scrubbed PTFE pieces and coated archwires were negative for HCV. This suggests that PTFE coating of dental instruments inhibited HCV adhesion when thoroughly scrubbed.

  16. Preparation and characterization of porous composite filter medium by polytetrafluoroethylene foam coating.

    PubMed

    Park, Byung Hyun; Lee, Myong-Hwa; Kim, Sang Bum; Kim, Gyung Soo; Jo, Young Min

    2010-02-01

    The high costs of ceramic and Teflon filter media for hot gas cleaning has limited their industrial applications. This paper presents a foam coating technology that can be used to produce an inexpensive and highly efficient filter for industrial applications. A new apparatus was designed and built that coats porous glass mats with liquid-phase polytetrafluoroethylene (PTFE). The machine generates bubbles, enables the formation of uniform micropores less than 45 microm in diameter, and produces a product with air permeability greater than 5.5 cm3/cm2/sec. The resulting filter was found to be thermally stable up to 270 degrees C without any visible distortion and was comparable in dust collection efficiency to other commercial filter media. In addition, its de-dusting efficiency was greater than 85%, which is similar to that of other test filter media.

  17. Effect of X-ray flux on polytetrafluoroethylene in X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The effect of the X-ray flux in X-ray photoelectron spectroscopy (STAT) on the constitution of the polytetrafluoroethylene (PTFE) surface has been examined. The radiation dose rate for our specimen was about 10 to the 7th rad/s. The structure, magnitude and binding energy of the C(1s) and F(1s) features of the XPS spectrum and the mass spectrum of gaseous species evolved during irradiation are observed. The strong time dependence of these signals over a period of several hours indicated that the surface constitution of PTFE is greatly affected by this level of radiation dose. The results are consistent with the development of a heavily cross-linked or branched structure in the PTFE surface region and the evolution of short chain fragments into the gas phase.

  18. Tensile deformation of polytetrafluoroethylene hollow fiber membranes used for water purification.

    PubMed

    Yonezu, Akio; Iio, Shouichi; Itonaga, Takehiro; Yamamura, Hiroshi; Chen, Xi

    2014-01-01

    The tensile deformation behavior of polytetrafluoroethylene (PTFE) hollow fiber membranes is studied. PTFE membranes at present have sub-micron pores with an open cell structure, which plays a critical role in water purification. One of the main challenges in water purification is that the pore structure becomes covered with biofouling, leading to blocked pores. To maintain the capacity for water purification, physical cleaning along with mechanical deformation is usually conducted. Thus, it is crucial to understand the mechanical properties, in particular the deformation behavior, of the membrane fibers. Using uniaxial tension experiments, we established a fundamental discrete model to describe the deformation behavior of a porous structure using a finite element method. The present model enables the prediction of the macroscopic deformation behavior of the membrane, by taking into account the changes of pore structure. The insight may be useful for porous membrane fabrication and provide insights for the reliable operation of water purification.

  19. The use of polytetrafluoroethylene (Gore-Tex) grafts in reconstruction of the urinary bladder.

    PubMed

    Senel, F M; Akman, R Y; Arikan, A Y; Gürdal, M; Can, C

    1999-01-01

    The safety and histopathologic effects of polytetrafluoroethylene (Gore-Tex) grafts in reconstruction of the urinary bladder were examined. Following partial excision of the bladder Gore-Tex was placed, and the rats were sacrificed at days 7, 14 and 30. Gore-Tex did not cause urine infection, and there was no peritonitis or sepsis in any of the rats. Inflammation around the Gore-Tex diminished after four weeks. Some mononuclear cells and exudate were observed on the inner surface of the Gore-Tex. There was no inflammation or fibrosis in the mucosa and muscular layers of the remaining bladder. In this study the Gore-Tex graft was found to be an infection resistant, urine impermeable material, with no adverse effects on the urinary bladder. Gore-Tex is suggested as a safe material for the reconstruction of the urinary bladder.

  20. Characterization of plastic deformation and chemical reaction in titanium-polytetrafluoroethylene mixture

    NASA Astrophysics Data System (ADS)

    Davis, Jeffery Jon

    1998-09-01

    The subject of this dissertation is the deformation process of a single metal - polymer system (titanium - polytetrafluoroethylene) and how this process leads to initiation of chemical reaction. Several different kinds of experiments were performed to characterize the behavior of this material to shock and impact. These mechanical conditions induce a rapid plastic deformation of the sample. All of the samples tested had an initial porosity which increased the plastic flow condition. It is currently believed that during the deformation process two important conditions occur: removal of the oxide layer from the metal and decomposition of the polymer. These conditions allow for rapid chemical reaction. The research from this dissertation has provided insight into the complex behavior of plastic deformation and chemical reactions in titanium - polytetrafluoroethylene (PTFE, Teflon). A hydrodynamic computational code was used to model the plastic flow for correlation with the results from the experiments. The results from this work are being used to develop an ignition and growth model for metal/polymer systems. Three sets of experiments were used to examine deformation of the 80% Ti and 20% Teflon materials: drop- weight, gas gun, and split-Hopkinson pressure bar. Recovery studies included post shot analysis of the samples using x-ray diffraction. Lagrangian hydrocode DYNA2D modeling of the drop-weight tests was performed for comparison with experiments. One of the reactions know to occur is Ti + C → TiC (s) which results in an exothermic release. However, the believed initial reactions occur between Ti and fluorine which produces TixFy gases. The thermochemical code CHEETAH was used to investigate the detonation products and concentrations possible during Ti - Teflon reaction. CHEETAH shows that the Ti - fluorine reactions are thermodynamically favorable. This research represents the most comprehensive to date study of deformation induced chemical reaction in metal/polymers.

  1. Temperature measurements for shocked polymethylmethacrylate, epoxy resin, and polytetrafluoroethylene and their equations of state

    NASA Astrophysics Data System (ADS)

    Bordzilovskii, S. A.; Karakhanov, S. M.; Merzhievskii, L. A.; Voronin, M. S.

    2016-10-01

    This paper presents the results of computational and experimental studies of the temperature along the shock adiabat for three polymers. Measurements of the brightness temperatures of shock-compressed epoxy resin and polymethylmethacrylate and the brightness and color temperatures of shock-compressed polytetrafluoroethylene were carried out. The temperatures of the shock-compressed polymethylmethacrylate were determined in the range 1390-1900 K for shock pressures of 22-39 GPa. Similar measurements performed for epoxy resin in the pressure range of 18-40 GPa showed values of 940-1900 K, and the temperatures of polytetrafluoroethylene in the pressure range of 30-50 GPa were equal to 2000-3200 K. The equation of state for the three polymers with a nonspherical strain tensor was constructed to describe shock-wave and high-temperature processes in a wide range of thermodynamic parameters. In the proposed model, two Grüneisen parameters were used: the thermodynamic parameter corresponding to intrachain vibrations and the lattice parameter representing the contribution of interchain vibrations. The brightness temperatures of shocked-compressed polymethylmethacrylate and epoxy resin showed a good agreement with calculations using the proposed model and with the results of earlier calculation methods. Time dependences of the observed intensity of light were used to determine the absorption coefficients of the shocked polymers and estimate the effective thickness of the radiating layer. A typical feature of all the polymers is the width of the radiating layer of 0.8 to 2.5 mm, depending on the material and shock pressure.

  2. Secondary vascular procedures with polytetrafluoroethylene grafts for lower extremity ischemia in a male veteran population.

    PubMed

    Dennis, J W; Littooy, F N; Greisler, H P; Baker, W H

    1988-08-01

    Secondary vascular procedures to below-knee vessels for lower extremity ischemia present a challenge to the vascular surgeon. Autogenous vein is often unavailable and failure of the previous bypass often limits the choice of distal vessels suitable for revascularization. This dilemma raises the question of amputation vs secondary vascular surgery. To address this question we reviewed the results of our previous aggressive approach to revascularization in a select group of 25 patients (26 limbs) who had secondary procedures with polytetrafluoroethylene grafts to tibial vessels or the infragenicular popliteal artery with single-vessel runoff. Nine of these 26 bypasses (35%) have remained patent for a mean of 17.2 months and no amputations have been done in this group. The other 17 bypasses (65%) have occluded from 1 day to 36 months postoperatively (mean 4.3 months); 15 of these limbs have required major amputation (58%). Ten were performed within the first 3 months postoperatively. Thirteen of the 25 patients died in the follow-up period (mean 27.5 months); five of these patients had viable limbs. Of 12 surviving patients (mean follow-up 19.9 months), six had viable limbs and six have required amputation. These results indicate that patients having secondary vascular surgical procedures with polytetrafluoroethylene grafts to tibial vessels have a high amputation rate and poor overall survival. Within this select group of patients, those who could walk with the aid of a prosthesis should be considered as candidates for primary amputation. This would facilitate rehabilitation and avoid the anguish of recurrent graft failure and multiple procedures.

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

    PubMed

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

    2014-01-01

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

  4. Functionalized expanded porphyrins

    DOEpatents

    Sessler, Jonathan L; Pantos, Patricia J

    2013-11-12

    Disclosed are functionalized expanded porphyrins that can be used as spectrometric sensors for high-valent actinide cations. The disclosed functionalized expanded porphyrins have the advantage over unfunctionalized systems in that they can be immobilized via covalent attachment to a solid support comprising an inorganic or organic polymer or other common substrates. Substrates comprising the disclosed functionalized expanded porphyrins are also disclosed. Further, disclosed are methods of making the disclosed compounds (immobilized and free), methods of using them as sensors to detect high valent actinides, devices that comprise the disclosed compounds, and kits.

  5. Wall Shear Stress Measurement Using Phase Contrast Magnetic Resonance Imaging With Phase Contrast Magnetic Resonance Angiography in Arteriovenous Polytetrafluoroethylene Grafts

    PubMed Central

    Misra, Sanjay; Fu, Alex A.; Misra, Khamal D.; Glockner, James F.; Mukhopadhyay, Debabrata

    2016-01-01

    Purpose The purpose of the present article was to determine the changes in luminal vessel area, blood flow, and wall shear stress in both the inflow artery and the venous stenosis of arteriovenous polytetrafluoroethylene (PTFE) grafts. Methods and materials Polytetrafluoroethylene grafts were placed from the carotid artery to the ipsilateral jugular vein in 8 castrated juvenile male pigs. Contrast-enhanced magnetic resonance angiography (MRA) with cine phase-contrast magnetic resonance imaging (MRI) was performed 2 weeks after graft placement. Results The mean wall shear stress at the venous stenosis was 4 times higher than the control vein, while the inflow artery was only 2-fold higher. By day 14, venous stenosis had formed, which was characterized by narrowed area and elevated blood flow. Conclusion By day 14, there is venous stenosis formation in porcine arteriovenous PTFE grafts with increased shear stress with decreased area when compared to control vein. PMID:19625275

  6. Wall shear stress measurement using phase contrast magnetic resonance imaging with phase contrast magnetic resonance angiography in arteriovenous polytetrafluoroethylene grafts.

    PubMed

    Misra, Sanjay; Fu, Alex A; Misra, Khamal D; Glockner, James F; Mukhopadhyay, Debabrata

    2009-01-01

    The purpose of the present article was to determine the changes in luminal vessel area, blood flow, and wall shear stress in both the inflow artery and the venous stenosis of arteriovenous polytetrafluoroethylene (PTFE) grafts. Polytetrafluoroethylene grafts were placed from the carotid artery to the ipsilateral jugular vein in 8 castrated juvenile male pigs. Contrast-enhanced magnetic resonance angiography (MRA) with cine phase-contrast magnetic resonance imaging (MRI) was performed 2 weeks after graft placement. The mean wall shear stress at the venous stenosis was 4 times higher than the control vein, while the inflow artery was only 2-fold higher. By day 14, venous stenosis had formed, which was characterized by narrowed area and elevated blood flow. By day 14, there is venous stenosis formation in porcine arteriovenous PTFE grafts with increased shear stress with decreased area when compared to control vein.

  7. Expanding the Universe

    NASA Astrophysics Data System (ADS)

    Sterken, Christiaan; Leedjärv, Laurits; Tempel, Elmo

    2011-12-01

    Proceedings of the International Conference EXPANDING THE UNIVERSE, On the occasion of the 200th anniversary of the Tartu Observatory, Tartu, Estonia 2011 April 27-29. C. Sterken, L. Leedjarv, E. Tempel (Eds.)

  8. The adsorption of cetyltrimethylammonium bromide and propanol mixtures with regard to wettability of polytetrafluoroethylene II. Adsorption at polytetrafluoroethylene-aqueous solution interface and wettability.

    PubMed

    Zdziennicka, Anna; Jańczuk, Bronisław

    2008-02-01

    Measurements of contact angles (theta) of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and propanol mixtures at constant CTAB concentration equal to 1x10(-5), 1x10(-4), 6x10(-4) and 1x10(-3) M on polytetrafluoroethylene (PTFE) were carried out. The obtained results indicate that the wettability of PTFE by aqueous solutions of these mixtures depends on their composition and concentration. They also indicate that, contrary to Zisman, there is no linear relationship between cos theta and the surface tension (gamma(LV)), but a linear relationship exists between the adhesional (gamma(LV)cos theta) and surface tension of aqueous solutions of CTAB and propanol mixtures. Curve gamma(LV)cos theta vs gamma(LV) has a slope equal -1 suggesting that adsorption of CTAB and propanol mixtures and the orientation of their molecules at aqueous solution-air and PTFE-aqueous solution interfaces is the same. Extrapolating this curve to the value of gamma(LV)cos theta corresponding to theta=0, the value of the critical tension of PTFE wetting equal 23.4 mN/m was determined. This value was higher than that obtained from contact angles of n-alkanes on PTFE surface (20.24 mN/m). The difference between the critical surface tension values of wetting probably resulted from the fact that at cos theta=1 the PTFE-aqueous solution of CTAB and propanol mixture interface tension was not equal to zero. This tension was determined on the basis of the measured contact angles and Young equation. It appeared that the values of PTFE-aqueous solution of the CTAB and propanol mixtures interface tension can be satisfactorily determined by modified Szyszkowski equation only for solutions in which probably CTAB and propanol molecules are present in monomeric form. However, it appeared that using the equation of Miller et al., in which the possibility of aggregation of propanol molecules in the interface layer is taken into account, it is possible to describe the PTFE-solution interfacial tension

  9. Dynamic-tensile-extrusion response of polytetrafluoroethylene (EPFE) and polychlorotrifluoroethylene (PCTFE)

    SciTech Connect

    Trujillo, Carl P; Brown, Eric N; Gray, George T

    2010-01-01

    Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) experiments have been utilized to probe the dynamic tensile responses of polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE). These fluoropolymers exhibit more irregular deformation and stochastic-based damage and failure mechanisms than the stable plastic elongation and shear instabilities observed in metals. The technique elucidates a number of tensile mechanisms that are consistent with quasi-static, SHPB, and Taylor Impact results. Similar to the observed ductile-to-brittle transition for Taylor Impact loading, PCTFE failure occurs at a peak velocity greater than for PTFE. However, for the Dyn-Ten-Ext PCTFE exhibits even greater resistance to failure due to the tensile stress-state. While PTFE generates a large number of small fragments when extruded through the die, PCTFE draws out a smaller number of larger particles that dynam ically evolve during the extrusion process through a com bination of local necking mechanisms and bulk relaxation. Under Dyn-Ten-Ext loading, the propensity of PTFE to fail along normal planes is observed without indication of any localization, while the PCTFE clearly forms necks during the initial extrusion process that continue to evolve.

  10. Ar plasma treated polytetrafluoroethylene films for a highly efficient triboelectric generator

    NASA Astrophysics Data System (ADS)

    Kim, Dong Yeong; Kim, Hyun Soo; Jung, Jong Hoon

    2016-12-01

    We report an Ar plasma treated polytetrafluoroethylene (PTFE) film based triboelectric device for a highly enhanced electric power generation. The plasma treatment of the PTFE in flowing Ar gas results in a sharp increase in surface roughness ( 46 nm), as compared with the as-received film ( 25 nm). In addition, the F ion content decreases whereas the O ion increases with increasing plasma reaction time. Because of the increased number of polar O ions, the surface becomes hydrophilic, as confirmed by water contact angle measurements. After the Ar plasma treatment, the PTFE based triboelectric device, which is periodically contacted with and separated from the ITO electrode, generates a 715 V open-circuit voltage and a 16 μA closed-circuit current, which are almost 79 and 32 times larger than those for as-received PTFE based device. Using the Ar plasma treated PTFE based triboelectric generator, we can turn on the 120 light emitting diodes (LEDs) without any batteries.

  11. Polytetrafluoroethylene Ingestion as a Way to Increase Food Volume and Hence Satiety Without Increasing Calorie Content

    PubMed Central

    Naftalovich, Rotem; Naftalovich, Daniel; Greenway, Frank L.

    2016-01-01

    Since satiety is largely due to stretch of the stomach and people tend to eat a consistent weight of food, increasing food volume and mass increases satiety. This can be achieved without increasing the calories of food by mixing food with a material that cannot be metabolized. Such a material should be inert, safe, resistant to stomach acid, lack taste, available in powder form, smooth, resistant to heat, and cost effective. Polytetrafluoroethylene (PTFE) is an ideal substance for this purpose. It is a soft plastic that is widely considered to be the most inert material known and is extremely stable. Animal feeding trials showed that rats fed a diet of 25% PTFE for 90 days had no signs of toxicity and that the rats lost weight. This article publishes the data from these subchronic animal feeding trials, reviews the relevant available literature, and hypothesizes that increasing the volume of food by mixing the food with PTFE powder at a ratio of 3 parts food to 1 part PTFE by volume will substantially improve satiety and reduce caloric consumption in people. PMID:26810925

  12. Vacuum isostatic micro molding of reflective micro-optical structures into polytetrafluoroethylene materials

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.; Ohar, Orest

    2008-04-01

    Polytetrafluoroethylene (PTFE) is an ideal material for use in industrial, automotive and consumer electronics. Specifically, PTFE has outstanding physical properties; such as chemical inertness and resistance to chemical corrosion, even when exposed to a strong acid, alkali and oxidants. Its properties provide for superior electrical insulation and thermal stability, which is not affected by wide ranges in temperature and frequency. Its non-absorption of moisture makes it a perfect material for consideration in micro optical, retro-reflector or diffuser type devices used in optical sensor applications in harsh environments as well as in automotive, aerospace, industrial and home lighting. This paper presents an overview of a unique fabrication method that incorporates a variety of technologies to establish a processing technique that can form micro scale diffractive and retro-reflective structures into fused and semi-fused PTFE materials. Example structures and a single design will that was function tested will be presented with comparison metrology of the micro-structure geometry formed on the sample as compared to the original design mandrel geometry.

  13. Piezoelectrets from laminated sandwiches of porous polytetrafluoroethylene films and nonporous fluoroethylenepropylene films

    NASA Astrophysics Data System (ADS)

    Huang, Jinfeng; Zhang, Xiaoqing; Xia, Zhongfu; Wang, Xuewen

    2008-04-01

    In this paper, the piezoelectric properties of laminated films made of polytetrafluoroethylene (PTFE) and tetrafluoroethylene-hexafluoropropylene (FEP) copolymer by an improved process and charged by a corona method are investigated by measurements of the pressure dependence of the piezoelectric d33 coefficents, the isothermal decay of d33 at various temperatures, and thermally stimulated discharge current spectra. The results show that the structure of the laminated films is mechanically stable. The quasistatic piezoelectric d33 coefficents can reach 400pC/N and they are relatively independent of the static pressure in the range up to 16kPa. The decay of the d33 coefficients is primarily due to charge detrapping. Compared to polypropylene ferroelectrets, the thermal stability of the piezoelectric activity in such laminated films at 90°C is improved by a factor of 2 with respect to the percentage of the d33 values remaining. The dominant drift path of the detrapped charges at temperatures of about 130°C is most likely along the surface of the PTFE fibers, while charge drift through the solid layer of FEP is possibly prevailing at temperatures of around 210°C.

  14. Audio and ultrasonic responses of laminated fluoroethylenepropylene and porous polytetrafluoroethylene films with different charge distributions

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoqing; Sessler, Gerhard M.; Xue, Yuan; Ma, Xingchen

    2016-05-01

    Laminated fluoropolymer films with a regular microstructure were made from compact fluoroethylenepropylene (FEP) and porous polytetrafluoroethylene (PTFE) using a process consisting of patterning and fusion bonding steps. The fabricated films were rendered piezoelectric via the contact charging or corona charging methods. The piezoelectric responses of such piezoelectret films were measured in the frequency range 100 Hz-100 kHz. The results show that the acoustic impedance of the FEP/PTFE films is around 0.014-0.030 MRayl. Dynamic piezoelectric d 33 coefficients of up to 500 pC N-1 were achieved at 100 Hz for these films. Microphones built with such films exhibit flat response curves in a broad frequency range if the diffraction effects are eliminated. Bonded films with all positive charges deposited in the porous PTFE layers show the best thermal stability: after annealing for 1100 min at 125 °C, the remaining d 33 at 1020 Hz is about 30% of the initial value, corresponding to 105 pC N-1, and it remains relatively stable at this temperature. This remarkable thermal stability has to be attributed to the fact that positive charges are more permanent in porous PTFE than in FEP. The entire charge distribution exhibits much better thermal stability than is achievable for customary polypropylene piezoelectrets.

  15. Patency rate and complications of polytetrafluoroethylene grafts compared with polyurethane grafts for hemodialysis access

    PubMed Central

    2010-01-01

    Background The survival of hemodialysis patients requiring dialysis depends on the long-term functioning and patency of the vascular access. Prosthetic vascular grafts are inevitably used for patients whose vessels are unsuitable for an autogenous arteriovenous (AV) fistula. The purpose of this study was to compare the patency rate and associated complications using different types of grafts. Methods This prospective study was conducted on patients who did not have an appropriate vein for arteriovenous fistula from January 2004 through July 2006. They were divided into two groups, sex, age, and basic data matched. Polytetrafluoroethylene (PTFE) and polyurethane (PVAG) were the two types of grafts used in this study. The functionality of the graft was assessed immediately 1 day and 2 weeks after operation. The clinical follow-up was performed each 3 months until 24 months. Results One-year patency rate was reported to be 64% and 52% in the PTFE and PVAG groups, respectively. There was no significant difference in 1-year (64% versus 52%) and 2-year (49% versus 41%) patency rate of the PTFE and PVAG grafts used as vascular access. There was also no difference between the numbers of complications reported in the two groups. Conclusion It could be concluded that either PTFE or PVAG grafts can be used with the same expected outcomes. PMID:20218943

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

    SciTech Connect

    Wang, Liu; Liu, Jinxu Zhang, Xinbo; Li, Shukui

    2015-11-15

    Energetic structural material is a kind of materials that are inert under normal conditions but could produce exothermic chemical reaction when subjected to impact. This report shows a kind of energetic structural material of tungsten (W)-polytetrafluoroethylene (PTFE)-aluminum (Al) with density of 4.12 g/cm{sup 3}, excellent ductility and dynamic compressive strength of 96 MPa. Moreover, 50W-35PTFE-15Al (wt%) can exhibit a high reaction energy value of more than 2 times of TNT per unit mass and 5 times of TNT per unit volume, respectively, but with excellent insensitivity compared with traditional explosives. Under thermal conditions, the W-PTFE-Al composite can keep stable at 773 K. Under impact loading, when the strain rate up to ∼4820 s{sup −1} coupled with the absorbed energy per unit volume of 120 J/cm{sup 3}, deflagration occurs and combustion lasts for 500 μs. During impact compressive deformation, the PTFE matrix is elongated into nano-fibers, thus significantly increases the reaction activity of W-PTFE-Al composites. The nano-fiber structure is necessary for the reaction of W-PTFE-Al composites. The formation of PTFE nano-fibers must undergo severe plastic deformation, and therefore the W-PTFE-Al composites exhibit excellent insensitivity and safety. Furthermore, the reaction mechanisms of W-PTFE-Al composites in argon and in air are revealed.

  17. Formation of optical color and fluorescence centers in polytetrafluoroethylene under γ-irradiation

    NASA Astrophysics Data System (ADS)

    Seliverstov, D. I.; Nurmukhametov, R. N.; Sergeev, A. M.; Klimenko, V. G.; Khatipov, S. A.

    2011-09-01

    Fluorescent properties and colors of polytetrafluoroethylene (PTFE) samples were studied as functions of absorbed dose of γ-radiation at a temperature above the melting temperature of the crystallites (327°C) in the dose range 0.2-0.8 MGy. The samples were irradiated at low pressure (10-6 Torr) in glass ampuls and at atmospheric pressure in a chamber purged with argon. Samples in ampuls acquired an off-white tint and fluoresced weakly. The fluorescence intensity increased slowly as the radiation dose increased from 0.2 to 0.6 MGy and decreased at 0.8 MGy. Samples irradiated in the chamber fluoresced more strongly and acquired colors that changed from gray (0.2 MGy) to dark-brown (0.8 MGy). Color centers were formed only in the sample surface layer. Their appearance was associated with the adsorption of particles of an unknown nature from the environment. The argon-purged samples turned white upon removing their surface layer (50 μm). The intensity and shape of fluorescence bands emitted by these samples remained essentially unaltered, i.e., depended weakly on the absorbed dose in the range 0.2-0.8 MGy.

  18. Fluoropolymer Films Deposited by RF Plasma Sputtering of Polytetrafluoroethylene Using Inert Gases

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Kliss, Mark (Technical Monitor)

    1998-01-01

    The FT-IR (Fourier Transform Infrared), UV (Ultraviolet) and XPS (X Ray Photoelectron Spectroscopy) spectra of fluoropolymer films (SPTFE) deposited by rf (radio frequency) plasma sputtering of polytetrafluoroethylene (PTFE), using Ne, Kr and Xe as sputtering gases, were obtained and compared with prior spectra for SPTFE formed using He and Ar. The F/C (fluorine / carbon) ratios for SPTFE films (1.44-1.55), obtained at a rf power of 10 W, were essentially the same for all five rare gases, there being no trend of decreasing fluorine content in the SPTFE product with increasing atomic weight of the sputtering gas - contrary to the momentum transfer notion advanced by M. E. Ryan, et al. Increasing rf power from 10 to 50 W resulted in successively lower F/C ratios for SPTFE (e.g., from 1.55 to 1.21 in the case of Xe plasma-sputtered PTFE), accompanied by sputtering of the glass reactor and deposition of fragments of sodium aluminum silicate occurring at 40 W and above. In order to achieve a "Teflon-like" SPTFE structure (i.e., products with as high a F/C ratio as possible) in a given plasma reactor, an optimum rf power must be found, which in the present case was approximately 10 W.

  19. Enhanced cathode performance of nano-sized lithium iron phosphate composite using polytetrafluoroethylene as carbon precursor

    NASA Astrophysics Data System (ADS)

    Avci, Ercan

    2014-12-01

    Herein we report a facile and efficient solid state synthesis of carbon coated lithium iron phosphate (LiFePO4/C) cathode material achieved through the pyrolysis of polytetrafluoroethylene (PTFE). The current investigation is comparatively analyzed with the results of the composites of LiFePO4/C (LFP/C) synthesized using polystyrene-block-polybutadiene (PS-b-PBD), polyethyhylene (PE) and sucrose as carbon precursors. The optimized LFP/CPTFE composite is synthesized at 700 °C using 10 wt.% PTFE. The composite exhibits remarkable improvement in capacity, cyclability and rate capability compared to those of LFP/C synthesized using (PS-b-PBD), PE and sucrose. The specific discharge capacities as high as 166 mA h g-1 (theoretical capacity: 170 mA h g-1) at 0.2 C and 114 mA h g-1 at 10 C rates were achieved with LFP/CPTFE. In addition, the composite exhibits a long-term cycling stability with the capacity loss of only 11.4% after 1000 cycles. PTFE shifts the size distribution of the composite to nanometer scale (approximately 120 nm), however the addition of sucrose and other polymers do not have such an effect. According to TEM and XPS analysis, LFP/CPTFE particles are mostly coated with a few nanometers thick carbon layer forming a core-shell structure. Residual carbon does not contain fluorine.

  20. The significant adhesion enhancement of Ag-polytetrafluoroethylene antibacterial coatings by using of molecular bridge

    NASA Astrophysics Data System (ADS)

    Guo, Ruijie; Yin, Guangda; Sha, Xiaojuan; Zhao, Qi; Wei, Liqiao; Wang, Huifang

    2015-06-01

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

  1. Soft recovery of polytetrafluoroethylene shocked through the crystalline phase II-III transition

    NASA Astrophysics Data System (ADS)

    Brown, E. N.; Trujillo, C. P.; Gray, G. T.; Rae, P. J.; Bourne, N. K.

    2007-01-01

    Polymers are increasingly being utilized as monolithic materials and composite matrices for structural applications historically reserved for metals. High strain-rate applications in aerospace, defense, and the automotive industries have lead to interest in the shock response of polytetrafluoroethylene (PTFE) and the ensuing changes in polymer structure due to shock prestraining. We present an experimental study of crystalline structure evolution due to pressure-induced phase transitions in a semicrystalline polymer using soft-recovery, shock loading techniques coupled with mechanical and chemical postshock analyses. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II-III transition was seen to cause both an increase in crystallinity from 38% to ˜53% (by differential scanning calorimetry) and a finer crystalline microstructure, and changed the yield and flow stress behavior.

  2. Cultivation of endothelial progenitor cells on fibrin matrix and layering on dacron/polytetrafluoroethylene vascular grafts.

    PubMed

    Sreerekha, Perumcherry Raman; Krishnan, Lissy K

    2006-04-01

    Completely biological tissue-engineered vascular graft is an upcoming substitute for damaged blood vessel, but its clinical use is currently limited due to poor mechanical strength. Therefore, at present, polymeric small-diameter vascular grafts lined with endothelial cells (ECs) to reduce graft thrombosis may be a more viable option. Successful construction of EC-seeded artificial grafts faces some challenges such as (i) retention of endothelial lining; and (ii) availability of differentiated autologous cells. Biomaterial surfaces that are modified by depositing extracellular matrix (ECM) components may stabilize cells in the lumen against forces of blood flow. Adult stem cells such as endothelial progenitor cells (EPCs) circulate in the blood and they usually attach to the exposed matrix at the injured blood vessel site. Depending on the signaling capabilities of ECM, cells may differentiate into ECs,, and if a similar composition of the matrix is provided in vitro, EPCs isolated from blood might get differentiated and thus autologous cells for tissue engineering may be obtained. In this in vitro study, ECM scaffold consisting of biomolecules such as fibrin, fibronectin, and gelatin along with growth factors is found to have supported differentiation of EPC into EC. Further, the ECM precoated on Dacron and polytetrafluoroethylene is found to have supported the formation of EC monolayer that synthesized nitric oxide, and resisted shear stress. Thus, biomimetic fibrin composite is found to be suitable not only to seed cells on currently available artificial grafts but also to obtain differentiated EC from EPC.

  3. Initial deposition of calcium phosphate ceramic on polystyrene and polytetrafluoroethylene by rf magnetron sputtering deposition

    NASA Astrophysics Data System (ADS)

    Feddes, B.; Wolke, J. G. C.; Jansen, J. A.; Vredenberg, A. M.

    2003-03-01

    Calcium phosphate (CaP) coatings can be applied to improve the biological performance of polymeric medical implants. A strong interfacial bond between ceramic and polymer is required for clinical applications. Because the chemical structure of an interface plays an important role in the adhesion of a coating, we studied the formation of the interface between CaP and polystyrene (PS) and polytetrafluoroethylene (PTFE). The coating was deposited in a radio frequency (rf) magnetron sputtering deposition system. Prior to the deposition, some samples received an oxygen plasma pretreatment. We found that the two substrates show a strongly different reactivity towards CaP. On PS a phosphorus and oxygen enrichment is present at the interface. This is understood from POx complexes that are able to bind to the PS. The effects of the plasma pretreatment are overruled by the deposition process itself. On PTFE, a calcium enrichment and an absence of phosphorus is found at the interface. The former is the result of CaF2-like material being formed at the interface. The latter may be the result of phosphorus reacting with escaping fluorine to a PF3 molecule, which than escapes from the material as a gas molecule. We found that the final structure of the interface is mostly controlled by the bombardment of energetic particles escaping either from the plasma or from the sputtering target. The work described here can be used to understand and improve the adhesion of CaP coatings deposited on medical substrates.

  4. Surface characterization of binary grafting of AAc/NIPAAm onto poly(tetrafluoroethylene) (PTFE)

    NASA Astrophysics Data System (ADS)

    Adem, E.; Avalos-Borja, M.; Bucio, E.; Burillo, G.; Castillon, F. F.; Cota, L.

    2005-07-01

    The present study shows results on radiation grafting of acrylic acid (AAc) and N-isopropylacrylamide (NIPAAm) mixtures onto polytetrafluoroethylene (PTFE) films. The main objective is to use the modified polymer for immobilization of the avidin-streptavidin systems or other bio-compounds. Grafting onto PTFE was carried out by the pre-irradiation oxidative method in air at different dose rates and irradiation doses. The irradiation was produced with the electron beam of a 2 MV van de Graaff accelerator, and gamma-rays, from a Gamma Beam 651 PT. The samples were placed in glass ampoules with the AAc and NIPAAm mixtures, in an aqueous solution. Graft polymerization was performed by heating of the polymer-monomer composition in an argon atmosphere at temperature of 50 °C. Surface funcionalization was studied by X-ray photoelectron spectroscopy (XPS); morphology of the surface was studied by scanning electron microscopy (SEM) and hydrophylization of the surface, by contact angle measurements (static method).

  5. Electret Polyvinylidene Fluoride Nanofibers Hybridized by Polytetrafluoroethylene Nanoparticles for High-Efficiency Air Filtration.

    PubMed

    Wang, Shan; Zhao, Xinglei; Yin, Xia; Yu, Jianyong; Ding, Bin

    2016-09-14

    Airborne particulate matter (PM) pollution has become a severe environmental concern calling for electret fibrous materials with high filtration efficiency and low pressure drop. However, restraining the dissipation of the electric charges in service to ensure the stabilized electrostatic force of the fibers for effectively adsorbing particles is extremely important and also challenging. Herein, we report novel electret nanofibrous membranes with numerous charges and desirable charge stability using polyvinylidene fluoride (PVDF) as the matrix polymer and polytetrafluoroethylene nanoparticles (PTFE NPs) as an inspiring charge enhancer through the in situ charging technology of electrospinning. Benefiting from the employment of PTFE NPs and optimized injection energy, the fibrous membranes are endowed with elevated surface potentials from 0.42 to 3.63 kV and reduced decrement of charges from 75.4 to 17.5%, which contribute to the ameliorative stability of filtration efficiency. Significantly, an electret mechanism is proposed, while deepened depth of the energy level and incremental polarized dipole charges with increasing PTFE NP concentrations and injection energy have been confirmed through the measurement of open-circuit thermally stimulated discharge and surface potential decay. Ultimately, the resultant fibrous membrane exhibited a high filtration efficiency of 99.972%, a low pressure drop of 57 Pa, a satisfactory quality factor of 0.14 Pa(-1), and superior long-term service performance. The successful fabrication of such an intriguing material may provide a new approach for the design and development of electret materials for PM2.5 governance.

  6. XPS study of the effect of hydrocarbon contamination on polytetrafluoroethylene (teflon) exposed to atomic oxygen

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Cormia, Robert D.

    1991-01-01

    The presence of hydrocarbon contamination on the surface of polytetrafluoroethylene (PTFE) markedly affects the oxygen uptake, and hence the wettability, of this polymer when exposed to an oxygen plasma. As revealed by X-ray photoelectron spectroscopy (XPS) analysis, the oxygen-to-carbon ratio (O/C) for such a polymer can increase sharply, and correspondingly the fluorine-to-carbon ratio (F/C) can decrease sharply, at very short exposure times; at longer times, however, such changes in the O/C and F/C ratios reverse direction, and these ratios then assume values similar to those of the unexposed PTFE. The greater the extent of hydrocarbon contamination in the PTFE, the larger are the amplitudes of the 'spikes' in the O/C- and F/C-exposure time plots. In contrast, a pristine PTFE experiences a very small, monotonic increase of surface oxidation or O/C ratio with time of exposure to oxygen atoms, while the F/C ratio is virtually unchanged from that of the unexposed polymer (2.0). Unless the presence of adventitious hydrocarbon is taken into account, anomalous surface properties relating to polymer adhesion may be improperly ascribed to PTFE exposed to an oxygen plasma.

  7. Wet Chemistry and Peptide Immobilization on Polytetrafluoroethylene for Improved Cell-adhesion.

    PubMed

    Gabriel, Matthias; Niederer, Kerstin; Frey, Holger

    2016-08-15

    Endowing materials surface with cell-adhesive properties is a common strategy in biomaterial research and tissue engineering. This is particularly interesting for already approved polymers that have a long standing use in medicine because these materials are well characterized and legal issues associated with the introduction of newly synthesized polymers may be avoided. Polytetrafluoroethylene (PTFE) is one of the most frequently employed materials for the manufacturing of vascular grafts but the polymer lacks cell adhesion promoting features. Endothelialization, i.e., complete coverage of the grafts inner surface with a confluent layer of endothelial cells is regarded key to optimal performance, mainly by reducing thrombogenicity of the artificial interface. This study investigates the growth of endothelial cells on peptide-modified PTFE and compares these results to those obtained on unmodified substrate. Coupling with the endothelial cell adhesive peptide Arg-Glu-Asp-Val (REDV) is performed via activation of the fluorin-containing polymer using the reagent sodium naphthalenide, followed by subsequent conjugation steps. Cell culture is accomplished using Human Umbilical Vein Endothelial Cells (HUVECs) and excellent cellular growth on peptide-immobilized material is demonstrated over a two-week period.

  8. Cell adhesion on polytetrafluoroethylene modified by UV-irradiation in an ammonia atmosphere.

    PubMed

    Heitz, J; Svorcík, V; Bacáková, L; Rocková, K; Ratajová, E; Gumpenberger, T; Bäuerle, D; Dvoránková, B; Kahr, H; Graz, I; Romanin, C

    2003-10-01

    We report on the modification of polytetrafluoroethylene (PTFE) by exposure to the ultraviolet (UV) light of a Xe(2)*-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. Typical treatment times were up to 30 min. Subsequently, the samples were grafted with the amino acid alanine from an aqueous solution. The samples were characterized by means of optical transmission spectroscopy, laser-induced fluorescence and contact-angle measurements. We studied the adhesion of rat aortic smooth muscle cells (SMC) and mouse fibroblasts (3T3 cells) to the modified polymer samples using an in vitro technique, where the population density and spread of adhering cells is determined 24 h after seeding by image analysis. For both cell types the exposure of PTFE to UV-light in an ammonia atmosphere resulted in a significant increase in the number of adhering cells and in the size of their spreading area. The grafting with alanine enhanced this effect. Additional experiments with human endothelial cells (HEC) also demonstrated improved adhesion to modified PTFE. Thus, PTFE modified by our method appears to be a promising material for fabrication of artificial vascular prostheses and implants or for cultivation of skin substitutes.

  9. Polytetrafluoroethylene/TiO2 Composite Pellets as Sulfur Adsorbents for Pressure Oxidation Leaching of Chalcopyrite

    NASA Astrophysics Data System (ADS)

    Govindaiah, Patakamuri; Grundy, Mark; Guerra, Eduard; Choi, Yeonuk; Ye, Zhibin

    2015-04-01

    In this study, we report the use of polytetrafluoroethylene/titanium dioxide (PTFE/TiO2) composite pellets as sulfur adsorbents in the extraction of copper from chalcopyrite by pressure oxidation leaching. PTFE/TiO2 composites of various compositions were prepared by compression molding followed by pelletization. The mass percentage of TiO2 filler in the PTFE matrix was varied from 0 to 35 wt pct. With the use of the composite pellets, significant enhancements in copper leaching were observed, indicating their role as adsorbents for the adsorption of molten elemental sulfur. In particular, the enhancement in copper extraction was increasingly pronounced (from 75 to 89 pct) with the increase of the mass percentage of TiO2 in the composite pellets from 0 to 35 wt pct. This is reasoned to result from the loss of TiO2 domains from the pellet surface, which creates additional rough hydrophobic surface to better capture elemental sulfur. The composite pellet adsorbents show excellent reusability, with the performance well maintained for 10 leaching cycles. In addition, the effectiveness of composite adsorbents at different chalcopyrite pulp densities was also investigated.

  10. Novel bipolar forceps with protein repellence using gold-polytetrafluoroethylene composite film.

    PubMed

    Mikami, Takeshi; Minamida, Yoshihiro; Koyanagi, Izumi; Houkin, Kiyohiro

    2007-02-01

    Advancement in new technology has been necessary for the development of surgical hemostasis. The purpose of this study was to assess novel bipolar forceps plated with gold-polytetrafluoroethylene (PTFE) composite film. Novel bipolar forceps with gold-PTFE composite film were invented and compared with commercially available forceps with 50-mum gold-plated tips in terms of their physical properties and coagulation performance. The contact angle was measured to determine the degree of wetting tension. Then the surface roughness, electric resistance, and changes in local temperature on the surface of the tip were recorded. Coagulation performance of the two sets of bipolar forceps was determined comparing the amount of protein in the adhered coagulum on the tips and comparing the ease with which the coagulum could be removed. This gold-PTFE composite film-plated metal has a significantly higher contact angle than conventional gold-plated metal, and the plating maintains the matrix metal property. The amount of coagulum sticking was smaller than with the ordinary gold-plated forceps. The ease of removal was also superior with the gold-PTFE composite film-plated forceps. The concept of promotion of protein repellence is important for achieving reduced adherence of protein to neurosurgical instruments. This protein repellent plating is indispensable to achieve safer and more accurate microneurosurgery.

  11. Ion-implanted polytetrafluoroethylene enhances Saccharomyces cerevisiae biofilm formation for improved immobilization

    PubMed Central

    Tran, Clara T. H.; Kondyurin, Alexey; Hirsh, Stacey L.; McKenzie, David R.; Bilek, Marcela M. M.

    2012-01-01

    The surface of polytetrafluoroethylene (PTFE) was modified using plasma immersion ion implantation (PIII) with the aim of improving its ability to immobilize yeast. The density of immobilized cells on PIII-treated and -untreated PTFE was compared as a function of incubation time over 24 h. Rehydrated yeast cells attached to the PIII-treated PTFE surface more rapidly, with higher density, and greater attachment strength than on the untreated surface. The immobilized yeast cells were removed mechanically or chemically with sodium hydroxide and the residues left on the surfaces were analysed with Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). The results revealed that the mechanism of cell attachment on both surfaces differs and a model is presented for each. Rapid attachment on the PIII-treated surface occurs through covalent bonds of cell wall proteins and the radicals on the treated surface. In contrast, on the untreated surface, only physisorbed molecules were found in the residue and lipids were more highly concentrated than proteins. The presence of lipids in the residue was found to be a consequence of damage to the plasma membrane during the rehydration process and the increased cell stress was also apparent by the amount of Hsp12 in the protein residue. The immobilized yeast cells on PIII-treated PTFE were found to be as active as yeast cells in suspension. PMID:22696486

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

    PubMed Central

    Wang, Shibo; Niu, Chengchao

    2016-01-01

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

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

    PubMed

    Huang, Kang; Goddard, Julie M

    2015-09-01

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

  14. Inflammatory responses of primary human dendritic cells towards polydimethylsiloxane and polytetrafluoroethylene.

    PubMed

    Roch, Toralf; Kratz, Karl; Ma, Nan; Lendlein, Andreas

    2016-01-01

    Although frequently used as implants materials, both polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE) are often associated with adverse effects including foreign body responses. Dendritic cells (DC) are crucial for the initiation of immune reactions and could also play a role in foreign body associated inflammations. Therefore, the interaction of DC with PDMS and PTFE was investigated regarding their capacity to induce undesired cell activation. Medical grade PDMS and PTFE films were embedded into polystyrene PS inserts via injection molding to prevent the DC from migrating below the substrate and thereby, interacting not only with the test sample but also with the culture vessel material. The viability, the expression of co-stimulatory molecules, and the cytokine/chemokine profiles were determined after 24 hours incubation of the DC with PDMS or PTFE. Blank PS inserts and tissue culture polystyrene (TCP) served as reference materials. The viability of DC was not substantially influenced after incubation with PDMS and PTFE. However, both polymers induced DC activation indicated by the upregulation of co-stimulatory molecules. The release profiles of 14 soluble inflammatory mediators showed substantial differences between PDMS, PTFE, PS, and TCP. This study showed the potential of PTFE and PDMS to activate primary human dendritic cells, which could be an explanation for the often observed inflammatory events associated with the implantation of these polymers.

  15. Small airway-centered granulomatosis caused by long-term exposure to polytetrafluoroethylene.

    PubMed

    Choi, Won-Il; Jung, Hye Ra; Shehu, Esmeralda; Rho, Byung Hak; Lee, Mi-Young; Kwon, Kun Young

    2014-06-01

    To date, there have been no reports of chronic pulmonary granulomatosis associated with exposure to polytetrafluoroethylene (PTFE). Here, we report three cases of small airway-centered granulomatous lesions in workers employed at facilities that apply coatings to pans and other utensils. The workers were repeatedly exposed to PTFE particles that were probably generated by the drying process when PTFE coatings are dried in a convection oven at high temperatures (380-420 °C). The duration of inhalational PTFE exposure was between 7 and 20 years. We found granulomatous lung lesions around the small airways in lung biopsy specimens obtained from the workers. Scanning electron microscopy/energy-dispersive x-ray spectroscopy analysis was performed focusing on areas where the PTFE particles were suspected to be located in macrophages. The scanning electron microscopy/energy-dispersive x-ray spectroscopy analyses revealed fluorine in the particles. Lung tissue samples from all cases were analyzed using a fully automated Fourier transform infrared spectrometer. Analysis of the spectrum extracted from the position of the foreign particles enabled precise identification of the foreign bodies as PTFE. Fourier transform infrared revealed that all of the lung tissue samples had bands at 1,202 to 1,148 cm(-1) and 1,202 to 1,146 cm(-1), which are characteristic of the asymmetric and symmetric stretching vibrations of the C-F bonds of PTFE. These cases suggest that recurrent inhalational exposure to PTFE particles causes chronic pulmonary granulomatosis.

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

    PubMed

    Wang, Shibo; Niu, Chengchao

    2016-01-01

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

  17. Fluoropolymer Films Deposited by RF Plasma Sputtering of Polytetrafluoroethylene Using Inert Gases

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Kliss, Mark (Technical Monitor)

    1998-01-01

    The FT-IR (Fourier Transform Infrared), UV (Ultraviolet) and XPS (X Ray Photoelectron Spectroscopy) spectra of fluoropolymer films (SPTFE) deposited by rf (radio frequency) plasma sputtering of polytetrafluoroethylene (PTFE), using Ne, Kr and Xe as sputtering gases, were obtained and compared with prior spectra for SPTFE formed using He and Ar. The F/C (fluorine / carbon) ratios for SPTFE films (1.44-1.55), obtained at a rf power of 10 W, were essentially the same for all five rare gases, there being no trend of decreasing fluorine content in the SPTFE product with increasing atomic weight of the sputtering gas - contrary to the momentum transfer notion advanced by M. E. Ryan, et al. Increasing rf power from 10 to 50 W resulted in successively lower F/C ratios for SPTFE (e.g., from 1.55 to 1.21 in the case of Xe plasma-sputtered PTFE), accompanied by sputtering of the glass reactor and deposition of fragments of sodium aluminum silicate occurring at 40 W and above. In order to achieve a "Teflon-like" SPTFE structure (i.e., products with as high a F/C ratio as possible) in a given plasma reactor, an optimum rf power must be found, which in the present case was approximately 10 W.

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

    PubMed

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

    2016-09-23

    Waste polytetrafluoroethylene (PTFE) could be easily decomposed by co-grinding with inorganic additive such as strontium oxide (SrO), strontium peroxide (SrO2) and calcium oxide (CaO) by using a planetary ball mill, in which the fluorine was transformed into nontoxic inorganic fluoride salts such as strontium fluoride (SrF2) or calcium fluoride (CaF2). Depending on the kind of additive as well as the added molar ratio, however, the reaction mechanism of the decomposition was found to change, with different compositions of carbon compounds formed. CO gas, the mixture of strontium carbonate (SrCO3) and carbon, only SrCO3 were obtained as reaction products respectively with equimolar SrO, excess SrO and excess SrO2 to the monomer unit CF2 of PTFE were used. Excess amount of CaO was needed to effectively decompose PTFE because of its lower reactivity compared with strontium oxide, but it promised practical applications due to its low cost.

  19. Silicon microfabricated beam expander

    SciTech Connect

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

    2015-03-30

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

  20. Expanding Views on Transition.

    ERIC Educational Resources Information Center

    Repetto, Jeanne B.; Correa, Vivian I.

    1996-01-01

    This position paper proposes an expanded definition of transition, based on common components of early childhood and secondary perspectives. It advocates for a seamless model of transition service delivery for students with disabilities, including program planning, from birth through age 21. The model addresses curriculum, location of services,…

  1. Expanded Roles for HRD.

    ERIC Educational Resources Information Center

    1998

    This document contains three papers from a symposium on expanded roles for human resource development (HRD). "The Roles of Consultants in Gainsharing Firms: Empirical Results" (Eunsang Cho, Gary N. McLean) reports findings that consultants are moderately involved at the separation, preparation, evaluation, and design stages and have low…

  2. Expand Your Hiring Horizons.

    ERIC Educational Resources Information Center

    Leske, Lucy Apthorp; Archer-Martin, Nancy

    1999-01-01

    To succeed in recruiting development officers, colleges and universities must use more aggressive methods to reach alumni, people with ties to the campus, and local business people; expand their selection criteria, perhaps including candidates with little or no experience; streamline the hiring process; and train new professionals. (MSE)

  3. ExpandED Options: Learning beyond High School Walls

    ERIC Educational Resources Information Center

    ExpandED Schools, 2014

    2014-01-01

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

  4. Polytetrafluoroethylene physisorption-assisted emulsification microextraction as a cleanup and preconcentration step in the gas chromatography determination of aliphatic hydrocarbons in marine sediment samples.

    PubMed

    Molaei, Saeideh; Saleh, Abolfazl; Ghoulipour, Vanik; Seidi, Shahram

    2017-02-01

    For the first time, the application of polytetrafluoroethylene powder as an extractant phase collector or holder in liquid-phase microextraction has been developed. For this purpose, the analytical performances of two different ways of applying polytetrafluoroethylene powder in microextraction methods including polytetrafluoroethylene physisorption-assisted emulsification microextraction and dispersive liquid-phase microextraction via polytetrafluoroethylene extractant phase holders have been compared for analysis of aliphatic hydrocarbons in aqueous phases. Under the same conditions, the former showed better extraction efficiencies over the latter and as a result, it was applied as preconcentration and cleanup step in the analysis of aliphatic hydrocarbons in sediment samples followed by gas chromatography analysis. The linearity of the polytetrafluoroethylene physisorption-assisted emulsification microextraction method was obtained over a range of 3.7 and 2000 ng/g (R(2) > 0.993). The relative standard deviations were less than 6.5% (n = 3). The limits of detection and quantification obtained by this method were 1.1-9.0 and 3.7-30 ng/g, respectively, indicating that satisfactory results were achieved by the procedure.

  5. Comparison of a New Polytetrafluoroethylene-Covered Metallic Stent to a Noncovered Stent in Canine Ureters

    SciTech Connect

    Chung, Hwan-Hoon Lee, Seung Hwa; Cho, Sung Bum; Park, Hong Suk; Kim, Young Sik; Kang, Byung Chul; Frisoli, Joan K.; Razavi, Mahmood K.

    2008-05-15

    The aim of this study was to determine the feasibility of using a newly designed polytetrafluoroethylene (PTFE)-covered metallic stent in the ureter by comparing its effectiveness with that of the noncovered stent in a canine model. We placed 14 stents in the ureters of seven mongrel dogs that weighed 30-40 kg each. The covered and noncovered stents were deployed in the right and left ureters, respectively, of six dogs. In the seventh dog, a covered stent and a double-J catheter were inserted in the right ureter, and a covered stent only was inserted in the left ureter. The first six dogs were sacrificed at 5, 10, and 15 weeks after deployment of the stents (two for each follow-up period), and the seventh dog was sacrificed at 30 weeks. There was no migration or poor expansion of any of the stents observed on plain radiography. On intravenous pyelogram and retrograde pyelogram, all of the covered stents at each follow-up period had patent lumens at the stented segments without hydronephrosis, and the passage of contrast material through it was well preserved. The noncovered stents in the dogs sacrificed at 5 and 10 weeks and one of the two dogs sacrificed at 15 weeks showed near-complete occlusion of the stent lumen due to ingrowth of the soft tissue, and severe hydronephrosis was also noted. The noncovered stent in the other dog sacrificed at 15 weeks showed the passage of contrast material without hydronephrosis, but the lumen of the stent was still nearly occluded by the soft tissue. There was no evidence of hydronephrosis or passage disturbance of the contrast material in both ureters of the dog sacrificed at 30 weeks. We conclude that the newly designed PTFE-covered stent effectively prevented the luminal occlusion caused by urothelial hyperplasia compared to the near-total occlusion of the noncovered stents, and no migration of the covered stents was noted.

  6. Immobilization of laccase on polymer grafted polytetrafluoroethylene membranes for biosensor construction.

    PubMed

    Tastan, Evren; Onder, Sakip; Kok, Fatma Nese

    2011-04-15

    In this study, Trametes versicolor laccase was immobilized on polytetrafluoroethylene (PTFE) membranes using two different techniques, entrapment to gelatin and covalent immobilization to the surface. For surface immobilization, functional groups were formed on PTFE surface by radiofrequency (RF) plasma treatment followed by polymer grafting. Two different polymers, polyacrylamide (pAAm) and polyacrylic acid (pAAc) were tried. For polyacrylamide grafted PTFE, a two-step polymerization process was used. The membranes were first treated with hydrogen plasma and pAAm grafted PTFE (pAAm-g-PTFE) was then formed by argon plasma treatment. To produce pAAc grafted PTFE (pAAc-g-PTFE), the surface was first treated with argon plasma and AAc was then attached to the surface by heat treatment (70°C, 6h). For both cases, an optimized carbodiimide coupling reaction was used for laccase immobilization. Enzyme activity was measured by an oxygen electrode using guaiacol as substrate. All three biosensing membranes were characterized and compared in terms of optimum working conditions, storage stability and reusability. Our study concluded that although a higher activity was obtained by gelatin entrapped laccase, its mechanical instability and poor storage life makes the gelatin biosensor unattractive for multiple usages and for field measurements. pAAc-g-PTFE biosensor was found to be more stable and highly reusable (ca. 50 times) when compared with the other two biosensors. In addition, its sensitivity was suitable for field applications. Therefore, the pAAc-g-PTFE biosensor could be proposed as an alternative on-site detection tool for phenolic compound monitoring. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Plasma-Functionalized Polytetrafluoroethylene Nanoparticles for Improved Wear in Lubricated Contact.

    PubMed

    Sharma, Vinay; Timmons, Richard; Erdemir, Ali; Aswath, Pranesh B

    2017-08-02

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

  8. Vacuum isostatic micro molding of microfluidic structures into polytetrafluoroethylene (PTFE) materials

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd E.

    2008-04-01

    Polytetrafluoroethylene (PTFE) is an ideal material for use in microfluidic applications, such as industrial inkjet and biomedical analysis devices. PTFE has outstanding physical properties; such as chemical inertness and resistance to chemical corrosion, even when exposed to a strong acid, alkali and oxidants. Its properties provide for superior electrical insulation and thermal stability, which is not affected by wide ranges in temperature and frequency. Its non-absorption of moisture makes it a perfect material for consideration in micro-fluidic devices used in chemical analysis, fluidic photonic sensors and biomedical diagnostics. This paper presents an overview of a unique fabrication method that incorporates a variety of elements to establish a processing technique that can form micro channels, complex filter arrays and reflective micro mirror structures into PTFE materials for such applications. Using a modified isostatic compression molding process, this new technique incorporates the addition of a vacuum to assist in the reliable molding of micron structures and further densification of the fused or semi-fused PTFE. Various micro-structured electroformed and micro-machined shims are demonstrated to form small microstructures into the surface of the PTFE material. The combination of the vacuum and the electroformed shim within the molding process noticeably increases the precision, reproducibility and resolution of microstructures that can be realized. The paper will describe the molding hardware involved, process parameters and the resulting microfluidic channels and complex filter and capillary structures formed. Function testing and metrology of the micro-structure geometry formed on each sample will be compared to the original design mandrel geometry.

  9. Proliferation of endothelial cell on polytetrafluoroethylene vascular graft materials carried VEGF gene plasmid*

    PubMed Central

    Tao, Si-feng; Chen, Li; Zheng, Yi-xiong; Xu, Yuan; Chen, Jian; Yu, Hong

    2006-01-01

    Objective: To investigate whether vascular endothelial growth factor (VEGF) gene plasmid carried by polytetrafluoroethylene (PTFE) vascular graft materials could transfect endothelial cells (ECs) and promote their growth. Methods: PTFE vascular graft materials carried with pCDI-hVEGF121, pCDI or pEGFP were incubated in Tris-buffer solution and the values of optical density of 260 nm at different time were plotted, then the DNA controlled release curve was made. ECs derived from human umbilical vein were seeded on the pCDI-hVEGF121/pCDI/pEGFP-PTFE materials or tissue culture plates, ECs numbers were counted and VEGF protein concentrations at different time were measured by enzyme-linked immunoadsorbent assay method. Green fluorescent protein (GFP) expression in ECs on pEGFP-PTFE materials was examined with fluorescence microscopy. Results: The controlled release curve showed that the gene released from PTFE materials was rapid within 8 h, then slowed down and that the gene released continuously even after 72 h. At 24, 72 and 120 h, ECs number and proliferation rate of pCDI-hVEGF121-PTFE materials were higher than those of pCDI or pEGFP-PTFE materials (P<0.05). VEGF protein concentration of pCDI-hVEGF121-PTFE materials was higher than that of pCDI or pEGFP-PTFE materials at 6, 24, 72 and 120 h (P<0.01). GFP expression in ECs on the pEGFP-PTFE materials could be detected by fluorescence microscopy. Conclusion: PTFE graft can be used as a carrier of VEGF gene plasmid, VEGF gene carried by PTFE can transfect ECs and promote ECs growth. PMID:16691635

  10. Fluoropolymer Films Deposited by Argon Ion-Beam Sputtering of Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Banks, Bruce A.; Kliss, Mark (Technical Monitor)

    1998-01-01

    The FT-IR, XPS and UV spectra of fluoropolymer films (SPTFE-I) deposited by argon ion-beam sputtering of polytetrafluoroethylene (PTFE) were obtained and compared with prior corresponding spectra of fluoropolymer films (SPTFE-P) deposited by argon rf plasma sputtering of PTFE. Although the F/C ratios for SPTFE-I and -P (1.63 and 1.51) were similar, their structures were quite different in that there was a much higher concentration of CF2 groups in SPTFE-I than in SPTFE-P, ca. 61 and 33% of the total carbon contents, respectively. The FT-IR spectra reflect that difference, that for SPTFE-I showing a distinct doublet at 1210 and 1150 per centimeter while that for SPTFE-P presents a broad, featureless band at ca. 1250 per centimeter. The absorbance of the 1210-per centimeter band in SPTFE-I was proportional to the thickness of the film, in the range of 50-400 nanometers. The SPTFE-I was more transparent in the UV than SPTFE-P at comparable thickness. The mechanism for SPTFE-I formation likely involves "chopping off" of oligomeric segments of PTFE as an accompaniment to "plasma" polymerization of TFE monomer or other fluorocarbon fragments generated in situ from PTFE on impact with energetic Ar ions. Data are presented for SPTFE-I deposits and the associated Ar(+) bombarded PTFE targets where a fresh target was used for each run or a single target was used for a sequence of runs.

  11. Surface tension of polytetrafluoroethylene and its wetting by aqueous solution of some surfactants and their mixtures

    NASA Astrophysics Data System (ADS)

    Mańko, Diana; Zdziennicka, Anna; Jańczuk, Bronisław

    2017-01-01

    Measurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-D-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension (γSV) as well as the Lifshitz-van der Waals component of the water surface tension (γWLW). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γSV and γWLW . It occured that by using the values of γSV , γWLW and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.

  12. Mechanistical studies on the electron-induced degradation of polymers: polyethylene, polytetrafluoroethylene, and polystyrene.

    PubMed

    Ennis, Courtney P; Kaiser, Ralf I

    2010-12-07

    Mechanisms of the electron-induced degradation of three polymers utilized in aerospace applications (polyethylene (PE), polytetrafluoroethylene (PTFE), and polystyrene (PS)) were examined over a temperature range of 10 K to 300 K at ultra high vacuum conditions (∼10(-11) Torr). These processes simulate the interaction of secondary electrons generated in the track of galactic cosmic ray particles in the near-Earth space environment with polymer material. The chemical alterations at the macromolecular level were monitored on-line and in situ by Fourier-transform infrared spectroscopy and mass spectrometry. These data yielded important information on the temperature dependent kinetics on the formation of, for instance, trans-vinylene groups (-CH=CH-) in PE, benzene (C(6)H(6)) production in PS, fluorinated trans-vinylene (-CF=CF-) and terminal vinyl (-CF=CF(2)) groups in PTFE together with molecular hydrogen release in PE and PS. Additional data on the radiation-induced development of unsaturated, conjugated bonds were collected via UV-vis spectroscopy. Temperature dependent G-values for trans-vinylene formation (G(-CH=CH-) ≈ 25-2.5 × 10(-4) units (100 eV)(-1) from 10-300 K) and molecular hydrogen evolution (G(H(2)) ≈ 8-80 × 10(-5) molecules (100 eV)(-1) from 10-300 K) for irradiated PE were calculated to quantify the degree of polymer degradation following electron irradiation. These values are typically two to three orders of magnitude less than G-values previously published for the irradiation of polymers with energetic particles of higher mass.

  13. Cannula thrombophlebitis: a study in volunteers comparing polytetrafluoroethylene, polyurethane, and polyamide-ether-elastomer cannulae.

    PubMed

    Larsson, N; Stenberg, K; Linder, L E; Curelaru, I

    1989-04-01

    Cannulae made of polytetrafluoroethylene (PTFE: n = 11), thermoplastic polyether-urethane (TPEU: n = 11), and a new test material, polyamide-ether-elastomer (XLON: n = 10) were inserted into the veins of the dorsum of the hand in 32 healthy volunteers (10 women and 22 men), 21-50 years old. The cannulae were intended to be left in place for 5 days. No infusion was given and the dressings were not exchanged. The resulting thrombophlebitis, defined as two or more of the symptoms pain, redness, oedema and hardness, was estimated on a scale which took into account the incidence, location, intensity, and duration of the symptoms. Except for one volunteer in the XLON group, all the volunteers developed thrombophlebitis, generally observed on the third day of cannulation, and being more frequent and intense over the cannulae (P less than 0.001) and at the tip (P less than 0.01) than at the insertion sites. Pain and oedema were, on the whole, the most frequent and severe symptoms during the period of indwelling. After withdrawal, hardness was the most intense, and together with pain, the most long-lasting (up to 10 days) symptom. The differences between the materials in thrombophlebitis incidence and intensity were statistically significant only when each symptom was analysed separately. Thus, the PTFE cannulae caused more pain and hardness (probably because of greater platelet adhesion and a relatively greater stiffness), while the TPEU and XLON cannulae produced more periphlebitis (redness and oedema), probably because of potentially irritant and antigenic substances leaking from them (polyurethane oligomers and polyamide/polyethyleneglycol oligomers).

  14. Irradiation effect of carbon negative-ion implantation on polytetrafluoroethylene for controlling cell-adhesion property

    NASA Astrophysics Data System (ADS)

    Sommani, Piyanuch; Tsuji, Hiroshi; Kojima, Hiroyuki; Sato, Hiroko; Gotoh, Yasuhito; Ishikawa, Junzo; Takaoka, Gikan H.

    2010-10-01

    We have investigated the irradiation effect of negative-ion implantation on the changes of physical surface property of polytetrafluoroethylene (PTFE) for controlling the adhesion property of stem cells. Carbon negative ions were implanted into PTFE sheets at fluences of 1 × 10 14-1 × 10 16 ions/cm 2 and energies of 5-20 keV. Wettability and atomic bonding state including the ion-induced functional groups on the modified surfaces were investigated by water contact angle measurement and XPS analysis, respectively. An initial value of water contact angles on PTFE decreased from 104° to 88° with an increase in ion influence to 1 × 10 16 ions/cm 2, corresponding to the peak shifting of XPS C1s spectra from 292.5 eV to 285 eV with long tail on the left peak-side. The change of peak position was due to decrease of C-F 2 bonds and increase of C-C bonds with the formation of hydrophilic oxygen functional groups of OH and C dbnd O bonds after the ion implantation. After culturing rat mesenchymal stem cells (MSC) for 4 days, the cell-adhesion properties on the C --patterned PTFE were observed by fluorescent microscopy with staining the cell nuclei and their actin filament (F-actin). The clear adhesion patterning of MSCs on the PTFE was obtained at energies of 5-10 keV and a fluence of 1 × 10 15 ions/cm 2. While the sparse patterns and the uncontrollable patterns were found at a low fluence of 3 × 10 14 ions/cm 2 and a high fluence of 3 × 10 15 ions/cm 2, respectively. As a result, we could improve the surface wettability of PTFE to control the cell-adhesion property by carbon negative-ion implantation.

  15. Thermal desorption mass spectrometric and x-ray photoelectron studies of etched surfaces of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Rye, R. R.; Kelber, J. A.

    1987-12-01

    The etching of polytetrafluoroethylene (PTFE) with Na solutions is known to lead to a loss of F, a loss which is correlated with enhanced adhesion. Subsequent heating partially restores surface F with a concurrent loss of adhesion strength. We have combined X-ray photoelectron spectroscopy (XPS) and gas phase mass spectroscopy for in situ measurements of the processes that occur as the fluorocarbon is heated. An array of volatile products, which vary with the specific treatment, desorb from etched PTFE. Among these are: N 2 and low molecular weight fluorocarbons, the amounts of which monotonically decrease with increasing exposure to the etching solution (and probably result from the bulk); species such as CO and CO 2, which in part result from surface impurities; and water and acetone which result from the rinse steps following the etching process. XPS measurements show that etching produces a major loss of surface F and a gain of surface O. The latter probably results from the subsequent rinse steps. Heating produces a substantial recovery in surface F with only a small decrease in the surface O, and the gain in surface F is shown to occur at a higher temperature than the desorption of any species from the surface. Thus, desorption of products from the surface is decoupled, in terms of both the distribution of products and their relative temperatures, from the surface changes as monitored by XPS. This decoupling suggests that the increase in surface F results from diffusion of low molecular weight fluorocarbons from the bulk or a transition region, or from a rearrangement of the sponge-like surface region produced in the etching process.

  16. The wettability of polytetrafluoroethylene by aqueous solution of cetyltrimethylammonium bromide and Triton X-100 mixtures.

    PubMed

    Szymczyk, Katarzyna; Jańczuk, Bronisław

    2006-11-01

    Measurements of the advancing contact angle (theta) were carried out for aqueous solution of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycol), Triton X-100 (TX100) mixtures on polytetrafluoroethylene (PTFE). The obtained results indicate that the wettability of PTFE depends on the concentration and composition of the surfactants mixture. There is a minimum of the dependence between contact angle and composition of the mixtures for PTFE for each concentration at a monomer mole fraction of CTAB, alpha, equal 0.2, which points to the synergism in the wettability of PTFE. In contrast to Zisman, there is no linear dependence between costheta and the surface tension of aqueous solution of CTAB and TX100 mixtures for all studied systems, but a linear dependence exists between the adhesional tension and surface tension for PTFE in the whole concentration range, the slope of which is -1, that suggests that the surface excess of the surfactant concentration at the PTFE-solution interface is the same as that at the solution-air interface for a given bulk concentration. It was also found that the work of adhesion of aqueous solution of surfactants to PTFE surface did not depend on the type of surfactant and its concentration. It means that the interactions across PTFE-solution interface were constant for the systems studied, and they were largely Lifshitz-van de Waals type. On the basis of the surface tension of PTFE and the Young equation and thermodynamic analysis of the adhesion work of aqueous solution of surfactant to the polymer surface it was found that in the case of PTFE the changes of the contact angle as a function of the mixture of nonionic and cationic surfactants concentration resulted only from changes of the polar component of solution surface tension.

  17. [Effect of extracellular matrix components on adhesion of bone marrow multipotent mesenchymal stromal cells to polytetrafluoroethylene].

    PubMed

    Karpenko, A A; Rozanova, I A; Poveshchenko, O V; Lykov, A P; Bondarenko, N A; Kim, I I; Nikonorova, Iu V; Podkhvatilina, N A; Sergeevichev, D S; Popova, I V; Konenkov, V I

    2015-01-01

    Search for new bioengineering materials for creation of small-diameter vascular grafts is currently a priority task. One of the promising trends of creating tissue engineering constructions is coating the internal layer of implants made of polytetrafluoroethylene (PTFE) with autologous mesenchymal multipotent stromal cells. In the study we assessed the ability of separate components of the extracellular matrix such as fibronectin, type I collagen and type IV collagen to influence adhesion, proliferation and morphology of mesenchymal multipotent stromal cells being cultured on PTFE. Bone marrow multipotent stromal cells taken from second-passage Wistar rats in the amount of 106 per 1 cm2 were applied onto PTFE. We used the following variants of preliminary treatment of the material prior to seeding: fibronectin with type I collagen, fibronectin with type IV collagen, fibronectin with a mixture of type I and IV collagens, as well as a control group without coating. After six weeks of cell growth on PTFE patches the samples were subjected to fixation in 10% formalin followed by haematoxylin-eosin stain and morphometric assessment of adhered cells by calculation using the software AxioVision (Carl Zeiss), assessing the number of cells, area of the cellular monolayer, dimensions and ratios of the area of separate cells and the area of cellular nuclei. The maximal area of the monolayer from mesenchymal multipotent stromal cells on the PTFE surface was revealed while culturing with a mixture of fibronectin and type I and IV collagens. Cell colonization density while treatment of the synthetic material with mixtures of fibronectin with type I collagen, type IV collagen and type I and IV collagens demonstrated the results exceeding the parameters of the control specimen 5-, 2.5- and 7-fold, respectively. Hence, extracellular matrix components considerably increase enhance adhesion of cells to PTFE, as well as improve formation of a monolayer from mesenchymal multipotent

  18. Osteoblast behavior on polytetrafluoroethylene modified by long pulse, high frequency oxygen plasma immersion ion implantation.

    PubMed

    Wang, Huaiyu; Kwok, Dixon T K; Wang, Wei; Wu, Zhengwei; Tong, Liping; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Polytetrafluoroethylene (PTFE) is a commonly used medical polymer due to its biological stability and other attractive properties such as high hardness and wear resistance. However, the low surface energy and lack of functional groups to interact with the cellular environment have severely limited its applications in bone or cartilage replacements. Plasma immersion ion implantation (PIII) is a proven effective surface modification technique. However, when conducted on polymeric substrates, conventional PIII experiments typically employ a low pulsing frequency and short pulse duration in order to avoid sample overheating, charging, and plasma sheath extension. In this paper, a long pulse, high frequency O(2) PIII process is described to modify PTFE substrates by implementing a shielded grid in the PIII equipment without these aforementioned adverse effects. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements are carried out to reveal the surface effects of PTFE after long pulse, high frequency O(2) PIII and the results are compared to those obtained from conventional short pulse, low frequency O(2) PIII, O(2) plasma immersion, and the untreated control samples. Our results show that less oxygen-containing, rougher, and more hydrophobic surfaces are produced on PTFE after long pulse, high frequency O(2) PIII compared to the other 2 treatments. Cell viability assay, ALP activity test, and real-time PCR analysis are also performed to investigate the osteoblast behavior. It is clear that all 3 surface modification techniques promote osteoblast adhesion and proliferation on the PTFE substrates. Improvements on the ALP, OPN, and ON expression of the seeded osteoblasts are also obvious. However, among these treatments, only long pulse, high frequency O(2) PIII can promote the OCN expression of osteoblasts when the incubation time is 12 days. Our data unequivocally disclose that the long pulse, high frequency O(2) PIII

  19. A High-Temperature, Thermal Non-equilibirum Thermochemical Model for Polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Sonoda, Shiho; Henrikson, Erik; Mikellides, Pavlos

    2011-09-01

    A comprehensive thermochemical model for polytetrafluoroethylene (PTFE), also known as Teflon®, is developed for use with computational fluid dynamic and magnetohydrodynamic computer codes. The model computes the thermodynamic properties of PTFE for a temperature range of 500 K to 580 230 K (50 eV) and extends to density values as low as 10-8 kg · m-3. The 23 equation nonlinear system produced under the assumptions of ideal gas and two-temperature local thermodynamic equilibrium (LTE) was solved numerically using the Newton-Raphson method. The extended thermochemical model is verified for both the composition and thermodynamic properties by comparisons to existing thermochemical models in the literature. These comparisons verify the model for the available, yet limited, temperature and density ranges. The properties display expected trends such as an increase in the degree of ionization with decreasing density, while almost independent of the electron to heavy-particle temperature ratio ( θ e/h = T e/ T h). The specific internal energy adheres to a fairly predictable curve, i.e., the specific internal energy is linear as the mixture stays at a fairly constant composition over some T e range. However, over the T e range where reactions occur, it was observed that such variation shows a steeper positive slope that represents energy deposition to the internal modes of the gas as opposed to heating. That is, the density is the main factor in deviations from one curve to the next while θ had a slight effect. Likewise, for the specific internal energy, the density had the greatest impact.

  20. Use of an intraperitoneal ventricular assist device with a polytetrafluoroethylene barrier decreases infections.

    PubMed

    Holman, William L; Pamboukian, Salpy V; Bellot, S Chris; Blood, Peggy S; Tallaj, Jose A; Sharpton, Jessica L; Kirklin, James K

    2008-03-01

    Infection rates for ventricular assist devices (VADs) are improving but the presence of infections remains problematic. Intraperitoneal pump placement may decrease the rate of infection. This study is a single-institution, retrospective comparison of infections for an extraperitoneal vs an intraperitoneal position with a polytetrafluoroethylene (PTFE) sheet separating the VAD from visceral organs. Implants were performed by a single surgical team from January 1, 2002 to May 31, 2006 (n = 65) for bridge-to-transplant or destination therapy. Patients with paracorporeal pumps (17 patients) or implant times of <30 days (n = 7; 4 died, 3 ongoing, 0 with pocket infections) were excluded. Thirty-five pulsatile left VADs were analyzed, whereas 6 rotary VADs were excluded from analysis. Twenty-three pulsatile VADs were placed in an extraperitoneal pocket (pocket patients) in 18 patients (5 patients had more than one left VAD implant), whereas 12 patients had intraperitoneal (IP patients) VAD placement. Infection with the implanted VAD occurred in 8 of 23 pocket implants (mean support 310 +/- 249 days) and 0 of 12 IP implants (mean support 220 +/- 131 days; pocket vs IP infections: p = 0.003). Staphylococcus and Enterococcus accounted for most of the infections. Four infections in the pocket group recurred during VAD support. Two infected pocket patients had dehiscence of the mid-line wound. Infections of implanted VADs are associated with serious morbidity (e.g., prolonged antibiotic therapy, recurrent device infections and wound dehiscence). Placing VADs in an intraperitoneal position with a PTFE barrier to protect the viscera may reduce the prevalence of these infections.

  1. Grazing incidence beam expander

    SciTech Connect

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

    1985-01-01

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

  2. Grazing incidence beam expander

    NASA Astrophysics Data System (ADS)

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

    1985-01-01

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

  3. Expandable LED array interconnect

    DOEpatents

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  4. Discovering the Expanding Universe

    NASA Astrophysics Data System (ADS)

    Nussbaumer, Harry; Bieri, Lydia; Sandage, Foreword by Allan

    2009-03-01

    Acknowledgments; Foreword; 1. Introduction; 2. Cosmological concepts at the end of the Middle Ages; 3. Nebulae as a new astronomical phenomenon; 4. On the construction of the Heavens; 5. Island universes turn into astronomical facts: a universe of galaxies; 6. The early cosmology of Einstein and de Sitter; 7. The dynamical universe of Friedmann; 8. Redshifts: how to reconcile Slipher and de Sitter?; 9. Lemaître discovers the expanding universe; 10. Hubble's contribution of 1929; 11. The breakthrough for the expanding universe; 12. Hubble's anger about de Sitter; 13. Robertson and Tolman join the game; 14. The Einstein-de Sitter universe; 15. Are Sun and Earth older than the universe?; 16. In search of alternative tracks; 17. The seed for the Big Bang; 18. Summary and Postscript; Appendix; References; Index.

  5. Expanding the HAWC Observatory

    SciTech Connect

    Mori, Johanna

    2016-08-17

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

  6. Prevention of pacemaker-associated contact dermatitis by polytetrafluoroethylene sheet and conduit coating of the pacemaker system.

    PubMed

    Taguchi, Takahiro; Maeba, Satoru; Sueda, Taijiro

    2014-09-01

    A 73-year-old female with sick sinus syndrome and atrial fibrillation was implanted with a ventricular demand inhibit pacemaker. She subsequently developed multiple episodes of skin irritation and necrosis. Skin patch testing revealed sensitivity to almost every component of the pacemaker system. The pacemaker was removed and replaced with a new pacemaker in which the generator was covered with a polytetrafluoroethylene (PTFE) sheet and the lead was covered with PTFE conduit. The patient suffered no further episodes of pacemaker-associated contact dermatitis.

  7. Cavo-atrial bypass with a polytetrafluoroethylene graft for the treatment of a complete, traumatic transection of the suprahepatic inferior vena cava.

    PubMed

    Prevot, Flavien; Berna, Pascal; Badoux, Louise; Regimbeau, Jean-Marc

    2017-02-01

    In the event of injury to the vena cava, the surgeon's goal is to control the bleeding and then repair the vascular damage. Given the wide range of lesions observed, the repair step has not been standardized. There are a few case reports of simple venoplasty or cavocaval bypass with a polytetrafluoroethylene graft. The present report introduces another treatment option for total avulsion of the suprahepatic inferior vena cava when a lack of remnant venous tissue below the heart prevents direct repair: cavo-atrial bypass with a polytetrafluoroethylene graft. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

  8. Erosion of small intestine with necrotising fasciitis of over lying abdominal wall after expanded poly-tetrafluoroethylene mesh implantation: A rare complication after laparoscopic incisional hernia repair

    PubMed Central

    Shrivastava, Ashish; Gupta, Akshara; Gupta, Achal; Shrivastava, Jyoti

    2013-01-01

    Complications such as bowel erosions, enterocutaneous fistulae are rare with the use of expandedpoly-tetrafluoroethylene (ePTFE) mesh in laparoscopic incisional hernia repair (LIHR). This unusual case patient presented to us with necrotising fasciitis of overlying anterior abdominal wall with peritonitis withsepticaemia and underwent aLIHR6 weeks before, which has not been reported till yet. We report a case of LIHR, presented to us with necrotising fasciitis of overlying anterior abdominal wall, peritonitis and septicaemia which was managed by small bowel segmental resection and exteriorisation of the ends, debridement of overlying anterior abdominal wall and maximum resection of implanted mesh. This case is unusual secondary to long experience with ePTFE mesh and the lack of published cases similar to this one. A brief review of relevant literature has been included in the article. We recommend pre-peritoneal placement of dual mesh fixed preferably by trans-abdominal polypropylene suture in LIHR. PMID:24019695

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  10. Elucidation of atomic scale mechanisms for polytetrafluoroethylene tribology using molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Barry, Peter R.

    Polytetrafluoroethylene (PTFE) is a polymer that has been widely exploited commercially as a result of its low friction, 'non-stick' properties. The polymer has found usage as 'non-stick,' chemically resistant coatings for bearings, valves, rollers and pipe linings with applications in industries ranging from food and chemical processing to construction, automotive and aerospace. The major drawback of PTFE in low friction applications involves its excessive wear rate. For decades, scientists and engineers have sought to improve the polymer's wear resistance while maintaining its low sliding friction by reinforcing the polymer matrix with a host of filler materials ranging from fibril to particulate. In this study, a different approach is taken in which the atomic scale phenomena between two crystalline PTFE surfaces in sliding contact are examined. The goal is to obtain atomic-level insights into PTFE's low friction and high wear rate to aid in the designing of effective polymer based tribological composites for extreme condition applications. To accomplish this, several tribological conditions were varied. These included sliding direction of the two polymer surfaces with respect to their chain alignment, sliding velocity, degree of crystalline phase rigidity, interfacial contact pressure, sample temperature and the presence of fluorocarbon fluids between the two crystalline PTFE surfaces. From these studies, it was found that crystalline PTFE-PTFE sliding demonstrates friction anisotropy. Low friction and molecular wear was observed when sliding in the direction of the chain alignment with high friction and wear behavior dominating when sliding in a direction perpendicular to the chain alignment. For the range of cross-link density (average linear density of 6.2 to 11.1 A) and sliding rate (5 m/s to 20 m/s) explored, a significant change in friction behavior or wear mechanisms was not observed. Under conditions of increased normal load or low temperature however

  11. The wettability of polytetrafluoroethylene and polymethyl methacrylate by aqueous solution of two cationic surfactants mixture.

    PubMed

    Szymczyk, Katarzyna; Zdziennicka, Anna; Jańczuk, Bronisław; Wójcik, Wiesław

    2006-01-01

    Advancing contact angle (theta) measurements were carried out for aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) mixtures on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA). The obtained results indicate that the wettability of PTFE and PMMA by aqueous solutions of CTAB and CPyB mixtures depends on the composition and concentration of the mixture; however, synergism in the wettability does not exist. In the range of low concentrations of aqueous solution mixtures there is a linear dependence between the contact angle and composition of the mixtures, but at a concentration close to CMC a deviation from linear dependence is observed. In contrast to Zisman, there is no linear dependence between costheta and the surface tension of aqueous solution of CTAB and CPyB mixtures, but a linear dependence exists between the adhesional and surface tension, and these lines have a slope -1 and -0.34 for PTFE and PMMA, respectively, which suggests that adsorption of CTAB and CPyB mixtures at water-air and PTFE-water is the same, and the orientation of the CTAB and CPyB molecules at both interfaces in the saturated monolayer should also be the same. Adsorption of these mixtures at water-air interface is considerably higher than at PMMA-water interface, and CTAB and CPyB molecules should be parallelly oriented to PMMA surface in the saturated monolayer. Extrapolation of the straight lines to the points corresponding to the surface tension of aqueous solution, which completely spreads over the PTFE and PMMA surface, gives a critical surface tension of wetting equal to 23.44 and 33.13 mN/m, respectively. The value of 23.44 mN/m is higher than that of the surface tension of PTFE, but the value of 33.13 is lower than that of Lifshitz-van der Waals components of PMMA surface tension. On the basis of the critical surface tension, the surface tension of PTFE and PMMA, the Young equation, and thermodynamic analysis of the

  12. Integration of polytetrafluoroethylene low-k dielectric material in a chemical vapor deposited aluminum metallization scheme

    NASA Astrophysics Data System (ADS)

    Wickland, Heidi Lee

    In order to increase speed and functionality, computer chip technology continues its evolution towards higher device density and reduced feature size. As interconnect signal delay has become prohibitively high for traditional Al/SiO2 architectures, there is a pressing need to pursue integration of low-k materials into back-end-of-the-line interconnect architectures. To this end, polytetrafluoroethylene (PTFE) was integrated with aluminum, implementing titanium nitride as a barrier layer. SPEEDFILM, a version of PTFE, has a low dielectric constant of 1.9--2.0. With the use of an adhesion promoter, SPEEDFILM can be easily spun-cast onto patterned aluminum substrates, allowing for implementation into existing interconnect process flows. CVD aluminum/PVD TiN binary stacks have been successfully grown on spin-cast films of PTFE. Elemental analysis revealed compositionally pure aluminum, showing virtually no fluorine contamination in as-deposited and annealed binary stacks, and resistivity as low as 3.2 muO-cm have been obtained. Thermal annealing studies indicate titanium nitride is an effective barrier against thermally-driven fluorine diffusion from PTFE. A fabrication flow for a two-level Al/PTFE test structure was identified in order to examine key integration issues and produce an electrically testable demonstration vehicle. Many integration milestones have been met. In particular, XPS studies of plasma-treated PTFE surfaces demonstrated that an NH3 plasma can defluorinate the PTFE surface, allowing sufficient adhesion of a subsequently-deposited SiO2 cap to survive chemical-mechanical polishing. First pass work also indicated promising etching and photoresist stripping results of SiO2/PTFE stacks, which are designed for use at the via level of this two-level structure. This is a particularly useful result since low-k dielectrics are often difficult to pattern due to their degradation upon exposure to traditional photoresist stripping chemistries. Finally, in

  13. Adsorption of sodium bis(2-ethylhexyl) sulfosuccinate and wettability in polytetrafluoroethylene solution air system

    NASA Astrophysics Data System (ADS)

    Harkot, Joanna; Jańczuk, Bronisław

    2007-06-01

    The role of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) adsorption at water-air and polytetrafluoroethylene-water (PTFE) interfaces in wetting of low energy PTFE was established from measurements of the contact angle of aqueous AOT solutions in PTFE-solution drop-air systems and the aqueous AOT solution surface tension measurements. For calculations of the adsorption at these interfaces the relationship between adhesion tension ( γLV cos θ) and surface tension ( γLV), and the Gibbs and Young equations were taken into account. On the basis of the measurements and calculations the slope of the γLV cos θ- γLV curve was found to be constant and equal -1 over the whole range of surfactant concentration in solution. It means that the amount of surfactant adsorbed at the PTFE-water interface, ΓSL, is essentially equal to its amount adsorbed at water-air interface, ΓLV. By extrapolating the linear dependence between γLV cos θ and γLV to cos θ = 1 the determined value of critical surface tension of PTFE surface wetting, γC, was obtained (23.6 mN/m), and it was higher than the surface tension of PTFE (20.24 mN/m). Using the value of PTFE surface tension and the measured surface tension of aqueous AOT solution in Young equation, the PTFE-solution interface tension, γSL, was also determined. The shape of the γSL-log C curve occurred to be similar to the isotherm of AOT adsorption at water-air interface, and a linear dependence existed between the PTFE-solution interfacial tension and polar component of aqueous AOT solution. The dependence was found to be established by the fact that the work of adhesion of AOT solution to the PTFE surface was practically constant amounting 46.31 mJ/m 2 which was close to the work of water adhesion to PTFE surface.

  14. The wettability of polytetrafluoroethylene and polymethylmethacrylate by aqueous solutions of Triton X-100 and propanol mixtures

    NASA Astrophysics Data System (ADS)

    Zdziennicka, Anna

    2009-01-01

    Measurements of advancing contact angles ( θ) were carried out for aqueous solutions of Triton X-100 (TX-100) and propanol mixtures at constant TX-100 concentration equal to 1 × 10 -7, 1 × 10 -6, 1 × 10 -5, 1 × 10 -4, 6 × 10 -4 and 1 × 10 -3 M, respectively, on polytetrafluoroethylene (PTFE) and polymethyhmethacrylate (PMMA). Using obtained results the changes of cos θ and adhesional tension against surface tension of all series of aqueous solutions of TX-100 and propanol mixtures ( γLV) for PTFE and PMMA surfaces were shown. On the basis of these changes it was deduced that adsorption of TX-100 and propanol mixtures at PTFE-solution and solution-air interfaces is the same but the adsorption of TX-100 and propanol mixtures at solution-air interface is considerably higher than at PMMA-solution one. In the case of PTFE this conclusion was confirmed by relationship between cos θ and the reciprocal of the surface tension of solution. Extrapolation of the relationships between cos θ and/or adhesional tension and the surface tension of solutions to the points corresponding to the cos θ = 1 and adhsional tension equal to the surface tension of solution, the critical surface tension of PTFE and PMMA wetting was determined. The average values of critical surface tension of wetting determined from these relationships for PTFE are lying in the range of its surface tension values determined from contact angles of different kinds of liquids, which can be find in the literature, but for PMMA are considerably lower than the surface tension. The double value of the critical surface tension of PTFE wetting is equal to adhesion work of the solution to its surface and for PMMA there is not any correlation between these magnitudes. Using the measured values of the contact angles and Young equation the PTFE(PMMA)-aqueous solution interfacial tension was determined. The interfacial tension values of PTFE-aqueous solution were also calculated from the Fainerman and Miller

  15. Wettability of a polytetrafluoroethylene surface by an aqueous solution of two nonionic surfactant mixtures.

    PubMed

    Szymczyk, Katarzyna; Jańczuk, Bronisław

    2007-08-14

    Measurements of the advancing contact angle (theta) were carried out for an aqueous solution of p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol)s (Triton X-100 (TX100) and Triton X-165 (TX165) mixtures) on polytetrafluoroethylene (PTFE). The obtained results indicate that the wettability of PTFE depends on the concentration and composition of the surfactant mixture. The minimum of the dependence between the contact angle and composition of the mixtures for PTFE for each concentration at a monomer mole fraction of TX100, alpha = 0.8, points to synergism in the wettability of PTFE. This effect was confirmed by the negative values of interaction parameters calculated on the basis of the contact angle and by the Rosen approach. In contrast to Zisman, there was no linear dependence between cos theta and the surface tension of an aqueous solution of TX100 and TX165 mixtures for all studied systems, but a linear dependence existed between the adhesional tension and surface tension for PTFE over the whole concentration range, the slope of which was -1, indicating that the surface excess of the surfactant concentration at the PTFE-solution interface was the same as that at the solution-air interface for a given bulk concentration. Similar values of monomer mole fractions of the surfactants at water-air and PTFE-water interfaces calculated on the basis of the surface tension and contact angles showed that adsorption at these two interfaces was the same. It was also found that the work of adhesion of an aqueous solution of surfactants to the PTFE surface did not depend on the type of surfactant and its concentration. This means that for the studied systems the interaction across the PTFE-solution interface was constant and was largely of Lifshitz-van der Waals type. On the basis of the surface tension of PTFE, the Young equation, and the thermodynamic analysis of the adhesion work of an aqueous solution of surfactant to the polymer surface, it was found that in the

  16. Superhydrophobic and oleophilic open-cell foams from fibrillar blends of polypropylene and polytetrafluoroethylene.

    PubMed

    Rizvi, Ali; Chu, Raymond K M; Lee, Jung H; Park, Chul B

    2014-12-10

    Effective removal of oils from water is of global significance for environmental protection. In this study, we investigate the hydrophobicity and oleophilicity of open-cell polymer foams prepared in a continuous and scalable extrusion process. The material used to prepare the open-cell foams is a fibrillar blend of polypropylene (PP) and polytetrafluoroethylene (PTFE). Scanning electron microscopy (SEM) images of the morphology of the PP/PTFE fibrillar blend reveal that the PTFE has a fibrillar morphology in the PP matrix. SEM micrograph of the extruded foam shows the formation of an interconnected open-cell structure. Using nitrogen pycnometry, the open-cell content is estimated to be 97.7%. A typical bulk density of the open-cell foam is measured to be about 0.07 g cm(-3) corresponding to a void fraction of 92%. Thus, a large three-dimensional space is made available for oil storage. A drop of water on the cross-section of the extruded open-cell foam forms a contact angle of 160° suggesting that the open-cell foam exhibits superhydrophobicity. The open-cell foam can selectively absorb various petroleum products, such as octane, gasoline, diesel, kerosene, light crude oil, and heavy crude oil from water and the uptake capacities range from about 5 to 24 g g(-1). The uptake kinetics can be enhanced by exposing the open-cell foam to high intensity ultrasound which increases the surface porosity of the thin, impervious, foam "skin" layer. The reusability of the foam can be improved by using a matrix polymer which demonstrates superior elastic properties and prevents the foams from undergoing a large permanent deformation upon compression to "squeeze out" the oil. For example, when the PP homopolymer matrix is replaced with a PP random copolymer, the permanent deformation for 10 compressive cycles is reduced from about 30% to 10%. To the best of our knowledge, these PP-based open-cell foams outperform PP-based absorbents conventionally used for oil-spill cleanup

  17. Wettability of polytetrafluoroethylene by aqueous solutions of two anionic surfactant mixtures.

    PubMed

    Zdziennicka, Anna; Jańczuk, Bronisław; Wójcik, Wiesław

    2003-12-01

    Advancing contact angle (theta) measurements were carried out on mixtures of aqueous solutions of sodium dodecyl sulfate (SDDS) and sodium hexadecyl sulfonate (SHDSs) on polytetrafluoroethylene (PTFE). The obtained results indicate that there were only small contact angle changes over the range of surfactant concentrations in the solution, corresponding to the unsaturated surfactant layer at the aqueous solution-air interface. However, when saturation of the surfactant layer was achieved a considerable decrease in the contact angle (increase in costheta) as a function of concentration was observed. The dependence of costheta on the monomer mole fraction of SHDSs in the mixture of the surfactants (alpha) for aqueous solutions of mixtures at concentrations corresponding to the critical micelle concentration (CMC) had a maximum at alpha=0.2. From the results of these measurements and application of the Gibbs and Young equations the ratio of the excess concentration of surfactants at the solid-aqueous solution interface to the excess of their concentration at the aqueous solution-air interface was calculated. On the basis of the measurements and calculations it was found that there was a straight linear relationship between the adhesion tension and surface tension of aqueous solutions of surfactant mixtures at a given alpha, and that the slope of the obtained straight lines was equal to -1, which suggests that the surface excess of the surfactant concentrations at the PTFE-solution interface is the same as that at the solution-air interface for a given bulk concentration of the surfactant mixtures. The dependence of the surface concentration excess at the PTFE-solution interface on the monomer mole fraction of SHDSs in the mixture of the surfactants for the concentration region of the mixture of aqueous solutions, corresponding to a saturated monolayer, had a maximum at alpha=0.4, probably resulting from increased degree of binding between adsorbed surface-active ions

  18. Are polytetrafluoroethylene (Gore-Tex) implants an alternative material for nasal dorsal augmentation in Asians?

    PubMed

    Hong, Joon Pio; Yoon, Ji Young; Choi, Jong Woo

    2010-11-01

    Augmentation rhinoplasty is a relatively common procedure in Korea. Alloplastic materials such as silicone, supramid mesh, Proplast, Mersiline, Medpor, and hydroxyapatite are frequently used for dorsal augmentation. Alloplastic implants have advantages, such as ready availability and no donor-site morbidity, but are associated with higher infection and extrusion rates than are autogenous materials. Although polytetrafluoroethylene (Gore-Tex) implants have recently been introduced, such implants are yet to be established as an alternative for nasal augmentation because of a lack of relevant reports. From March 1998 to March 2007, we operated on 873 nasal dorsum augmentation patients using hard-type Gore-Tex implants. The patients were all of Korean ethnicity. There were 826 female and 47 male patients and aged ranging from 18 to 57 years (mean, 24 y). The Gore-Tex implant thicknesses were 3.1 to 4.9 mm (used in 59% of cases), 2 to 3 mm (8%), or 5 to 6 mm (33%). The Gore-Tex implants were used only for dorsal augmentation, whereas conchal or septal cartilage was used for nasal tip plasty. Of the total of 873 patients, 257 received long-term follow-up (mean follow-up, 34 mo). Apart from 34 patients with revision, no patient reported dissatisfaction, and there were no reports of problems with nasal contour, implant migration, or resorption of the implant material. The overall complication rate was 3.8%. Of the 257 long-term follow-up patients, 34 (13.5%) required revision. Four of these patients involved minor complications that were managed conservatively, whereas 30 patients required implant removal and revision procedures. These 30 cases included irregularity, infection, deviation, unfavorable dorsum height, and apparent implant silhouette, in addition to obvious supratip deformity. A review of the literature revealed that Gore-Tex implants seemed to have a lower implant removal rate than silicone implants. However, the overall complication rates seemed to be

  19. Miniaturized Dual Band Multislotted Patch Antenna on Polytetrafluoroethylene Glass Microfiber Reinforced for C/X Band Applications

    PubMed Central

    Islam, M. T.; Samsuzzaman, M.

    2014-01-01

    This paper introduces a new configuration of compact, triangular- and diamond-slotted, microstrip-fed, low-profile antenna for C/X band applications on polytetrafluoroethylene glass microfiber reinforced material substrate. The antenna is composed of a rectangular-shaped patch containing eight triangles and two diamond-shaped slots and an elliptical-slotted ground plane. The rectangular-shaped patch is obtained by cutting two diamond slots in the middle of the rectangular patch, six triangular slots on the left and right side of the patch, and two triangular slots on the up and down side of the patch. The slotted radiating patch, the elliptical-slotted ground plane, and the microstrip feed enable the matching bandwidth to be widened. A prototype of the optimized antenna was fabricated on polytetrafluoroethylene glass microfiber reinforced material substrate using LPKF prototyping machine and investigated to validate the proposed design. The simulated results are compared with the measured data, and good agreement is achieved. The proposed antenna offers fractional bandwidths of 13.69% (7.78–8.91 GHz) and 10.35% (9.16–10.19 GHz) where S11 < −10 dB at center frequencies of 8.25 GHz and 9.95 GHz, respectively, and relatively stable gain, good radiation efficiency, and omnidirectional radiation patterns in the matching band. PMID:24987742

  20. Tricuspid Anterior Leaflet Replacement with Autologous Pericardium and Polytetrafluoroethylene Chordae, Followed by Edge-to-Edge Repair

    PubMed Central

    García-Rinaldi, Raúl

    2007-01-01

    Treatment of endocarditis of the tricuspid valve is very complex. Valvectomy without replacement can result in significant postoperative morbidity, and replacement is hazardous due to the possibility of prosthetic infection. Repair of the tricuspid valve is the best alternative. Many ingenious methods have been devised to repair the tricuspid valve in patients with infective endocarditis. However, repair of the endocarditic anterior leaflet presents a difficult surgical problem. We have developed a technique to replace the central portion of the anterior leaflet, in which most of the leaflet is excised and replaced with autologous pericardium. By preserving a small rim of the leaflet, we preserve the lateral and medial chordal attachments. Supplemental neochordae are created with polytetrafluoroethylene sutures. An edge-to-edge repair is used to correct residual insufficiency of the valve. We have used this technique in 4 patients. One patient died 1 month after surgery, but with a competent tricuspid valve. Three patients are now alive, 48, 34, and 1.5 months after surgery. Their tricuspid valves are functional, moving well, and competent. We conclude that the centrally infected anterior leaflet of the tricuspid valve can be replaced with autologous pericardium. The implantation of polytetrafluoroethylene neochordae and edge-to-edge repair can be used to achieve valve competence. Short- and medium-term follow-up in patients who have been treated with these techniques demonstrates that the valve remains fully mobile and competent. PMID:17948081

  1. Miniaturized dual band multislotted patch antenna on polytetrafluoroethylene glass microfiber reinforced for C/X band applications.

    PubMed

    Islam, M T; Samsuzzaman, M

    2014-01-01

    This paper introduces a new configuration of compact, triangular- and diamond-slotted, microstrip-fed, low-profile antenna for C/X band applications on polytetrafluoroethylene glass microfiber reinforced material substrate. The antenna is composed of a rectangular-shaped patch containing eight triangles and two diamond-shaped slots and an elliptical-slotted ground plane. The rectangular-shaped patch is obtained by cutting two diamond slots in the middle of the rectangular patch, six triangular slots on the left and right side of the patch, and two triangular slots on the up and down side of the patch. The slotted radiating patch, the elliptical-slotted ground plane, and the microstrip feed enable the matching bandwidth to be widened. A prototype of the optimized antenna was fabricated on polytetrafluoroethylene glass microfiber reinforced material substrate using LPKF prototyping machine and investigated to validate the proposed design. The simulated results are compared with the measured data, and good agreement is achieved. The proposed antenna offers fractional bandwidths of 13.69% (7.78-8.91 GHz) and 10.35% (9.16-10.19 GHz) where S11 < -10 dB at center frequencies of 8.25 GHz and 9.95 GHz, respectively, and relatively stable gain, good radiation efficiency, and omnidirectional radiation patterns in the matching band.

  2. Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High-Performance All-Vanadium Redox Flow Battery Membrane

    SciTech Connect

    Wei, Xiaoliang; Nie, Zimin; Luo, Qingtao; Li, Bin; Chen, Baowei; Simmons, Kevin L.; Sprenkle, Vincent L.; Wang, Wei

    2013-09-02

    Driven by the motivation of searching for low-cost membrane alternatives, a novel nanoporous polytetrafluoroethylene/silica composite separator has been prepared and evaluated for its use in all-vanadium mixed-acid redox flow battery. This separator consisting of silica particles enmeshed in a polytetrafluoroethylene fibril matrix has no ion exchange capacity and is featured with unique nanoporous structures, which function as the ion transport channels in redox flow battery operation, with an average pore size of 38nm and a porosity of 48%. This separator has produced excellent electrochemical performance in the all-vanadium mixed-acid system with energy efficiency delivery comparable to Nafion membrane and superior rate capability and temperature tolerance. The separator also demonstrates an exceptional capacity retention capability over extended cycling, offering additional operational latitude towards conveniently mitigating the capacity decay that is inevitable for Nafion. Because of the inexpensive raw materials and simple preparation protocol, the separator is particularly low-cost, estimated to be at least an order of magnitude more inexpensive than Nafion. Plus the proven chemical stability due to the same backbone material as Nafion, this separator possesses a good combination of critical membrane requirements and shows great potential to promote market penetration of the all-vanadium redox flow battery by enabling significant reduction of capital and cycle costs.

  3. Selective isolation of hydrophobin SC3 by solid-phase extraction with polytetrafluoroethylene microparticles and subsequent mass spectrometric analysis.

    PubMed

    Kupčík, Rudolf; Zelená, Miroslava; Řehulka, Pavel; Bílková, Zuzana; Česlová, Lenka

    2016-02-01

    Hydrophobins are small proteins that play a role in a number of processes during the filamentous fungi growth and development. These proteins are characterized by the self-assembly of their molecules into an amphipathic membrane at hydrophilic-hydrophobic interfaces. Isolation and purification of hydrophobins generally present a challenge in their analysis. Hydrophobin SC3 from Schizophyllum commune was selected as a representative of class I hydrophobins in this work. A novel procedure for selective and effective isolation of hydrophobin SC3 based on solid-phase extraction with polytetrafluoroethylene microparticles loaded in a small self-made microcolumn is reported. The tailored binding of hydrophobins to polytetrafluoroethylene followed by harsh elution conditions resulted in a highly specific isolation of hydrophobin SC3 from the model mixture of ten proteins. The presented isolation protocol can have a positive impact on the analysis and utilization of these proteins including all class I hydrophobins. Hydrophobin SC3 was further subjected to reduction of its highly stable disulfide bonds and to chymotryptic digestion followed by mass spectrometric analysis. The isolation and digestion protocols presented in this work make the analysis of these highly hydrophobic and compact proteins possible.

  4. Expanding hollow metal rings

    DOEpatents

    Peacock, Harold B [Evans, GA; Imrich, Kenneth J [Grovetown, GA

    2009-03-17

    A sealing device that may expand more planar dimensions due to internal thermal expansion of a filler material. The sealing material is of a composition such that when desired environment temperatures and internal actuating pressures are reached, the sealing materials undergoes a permanent deformation. For metallic compounds, this permanent deformation occurs when the material enters the plastic deformation phase. Polymers, and other materials, may be using a sealing mechanism depending on the temperatures and corrosivity of the use. Internal pressures are generated by either rapid thermal expansion or material phase change and may include either liquid or solid to gas phase change, or in the gaseous state with significant pressure generation in accordance with the gas laws. Sealing material thickness and material composition may be used to selectively control geometric expansion of the seal such that expansion is limited to a specific facing and or geometric plane.

  5. Mechanically expandable annular seal

    DOEpatents

    Gilmore, R.F.

    1983-07-19

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces is described. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluid tight barrier. A counter rotation removes the barrier. 6 figs.

  6. Mechanically expandable annular seal

    DOEpatents

    Gilmore, Richard F.

    1983-01-01

    A mechanically expandable annular reusable seal assembly to form an annular hermetic barrier between two stationary, parallel, and planar containment surfaces. A rotatable ring, attached to the first surface, has ring wedges resembling the saw-tooth array of a hole saw. Matching seal wedges are slidably attached to the ring wedges and have their motion restricted to be perpendicular to the second surface. Each seal wedge has a face parallel to the second surface. An annular elastomer seal has a central annular region attached to the seal wedges' parallel faces and has its inner and outer circumferences attached to the first surface. A rotation of the ring extends the elastomer seal's central region perpendicularly towards the second surface to create the fluidtight barrier. A counterrotation removes the barrier.

  7. X-Ray Photoelectron Spectroscopy Study of the Effect of Hydrocarbon Contamination on Poly(Tetrafluoroethylene) Exposed to a Nitrogen Plasma

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Lopata, Eugene S.; Finney, Lorie S.

    1993-01-01

    In this note, we show that X-ray photoelectron Spectroscopy (XPS) data and the changes in surface properties attending exposure of poly(tetrafluoroethylene) (PTFE) films to a nitrogen plasma can likewise be misinterpreted when the interfering role of minor surface hydrocarbon contamination is not taken into account.

  8. Initial clinical experience with a polytetrafluoroethylene vascular dialysis graft reinforced with nitinol at the venous end.

    PubMed

    Benedetto, Filippo; Spinelli, Domenico; Pipitò, Narayana; Gagliardo, Giambattista; Noto, Alberto; Villari, Simona; David, Antonio; Spinelli, Francesco

    2017-01-01

    The purpose of this study was to examine the outcomes of a vascular hybrid polytetrafluoroethylene (PTFE) graft, provided with a nitinol-reinforced section (NRS) on one end, in hemodialysis vascular access placement. A retrospective study was conducted including all the consecutive patients who underwent Gore Hybrid Vascular Graft (GHVG; W. L. Gore & Associates, Flagstaff, Ariz) implantation for hemodialysis access placement between October 2013 and November 2015. A propensity-matched control group was obtained from consecutive patients who underwent standard PTFE arteriovenous graft implantation between January 2010 and July 2013. The selection criteria were inadequate venous material for autogenous arteriovenous fistula placement, patent deep venous circulation, and vein diameter of 4 to 8.5 mm. The implantation technique involves the insertion of the NRS some centimeters into the target vein. Fluoroscopic guidance helps deploy the device in the desired landing zone (ie, position of the proximal end of the NRS), based on anatomic landmarks. Survival, functional patency rates, and complications were compared with a propensity-matched historical control group. Vein diameter, previous vascular access placement, and diabetes were tested as predictors of reintervention with a logistic regression analysis. There were 32 patients (14 men; mean age, 69 ± 14 years) who received the GHVG graft. The historical control group included 43 patients. Technical success was 100%. The graft configuration was brachial-axillary (n = 22 [69%]), brachial-basilic loop (n = 5 [16%]), brachial-antecubital loop (n = 3 [9%]), axilloaxillary loop (n = 1 [3%]), and femoral-femoral loop (n = 1 [3%]). Mean NRS oversize was 20% ± 7% (range, 3%-34%; median, 19%). Perioperative complications requiring revision included acute limb ischemia treated with thrombectomy (n = 1 [3%]) and graft infection requiring explantation (n = 2 [6%]). Two patients (6%) died in the hospital of unrelated

  9. Soviet gas processing expands

    SciTech Connect

    Sagers, M.J.

    1987-09-01

    The Soviet gas processing industry expanded with the recent completion of two new gas processing plants, the Krasnoleninskiy and Noyabr'sk plants, both located in West Siberia. Both process associated gas from nearby oil fields to remove valuable liquid hydrocarbons before putting the dry gas into pipelines; previously the gas was flared or vented. These plants represent part of a major program, ongoing since the 1970s, to increase the level of utilization of the tremendous amount of valuable associated gas now being produced in West Siberia. Another major effort to develop gas processing is under way in western Kazakhstan at the Tengiz and Zhanazhol' fields. At Zhanazhol', a small gas recovery plant went into operation in late 1984 in conjunction with a separation plant with a processing capacity of 1 million tons of oil per year. A much larger enterprise to refine oil and process associated gas is under construction at the Tengiz field. This enterprise is different from the major petrochemical operation planned to use feedstocks from Tengiz; the petrochemical operation will be constructed at Kulsary, 120 kilometers from Tengiz, and produce polyethylene, polypropylene, and other plastics.

  10. Transient bond scission of polytetrafluoroethylene under laser-induced shock compression studied by nanosecond time-resolved Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazutaka; Wakabayashi, Kunihiko; Konodo, Ken-Ichi

    2001-06-01

    Nanosecond time-resolved Raman spectroscopy has been performed to study polymer films, polytetrafluoroethylene (PTFE), under laser driven shock compression at laser power density of 4.0 GW/cm^2. The overtone-mode line of PTFE showed red shift (18 cm-1) at delay time of 9.3 ns due to the shock compression and corresponding pressure was estimated to be approximately 2.7 GPa by analyzing static and shock compression data. The estimated pressure was in good agreement with that estimated by ablation pressure in glass-confined geometry. A new vibrational line at 1900 cm-1 appeared only under shock compression and was assigned to the C=C streching in transient species such as a monomer (C_2F_4) produced by the shock-induced bond scission. Intensity of the new line increased with increasing delay time along propagation of the shock compression with a shock velocity of 2.5 km/s.

  11. Permanent hydrophilization of outer and inner surfaces of polytetrafluoroethylene tubes using ambient air plasma generated by surface dielectric barrier discharges

    SciTech Connect

    Pavliňák, D.; Galmiz, O.; Zemánek, M.; Brablec, A.; Čech, J.; Černák, M.

    2014-10-13

    We present an atmospheric pressure ambient air plasma technique developed for technically simple treatment of inner and/or outer surfaces of plastic tubes and other hollow dielectric bodies. It is based on surface dielectric barrier discharge generating visually diffuse plasma layers along the treated dielectric surfaces using water-solution electrodes. The observed visual uniformity and measured plasma rotational and vibrational temperatures of 333 K and 2350 K indicate that the discharge can be readily applied to material surface treatment without significant thermal effect. This is exemplified by the obtained permanent surface hydrophilization of polytetrafluoroethylene tubes related to the replacement of a high fraction (more than 80%) of the surface fluorine determined by X-ray photoelectron spectroscopy. A tentative explanation of the discharge mechanism based on high-speed camera observations and the discharge current and voltage of measurements is outlined.

  12. Evaluation of the Mechanism of the Gold Cluster Growth during Heating of the Composite Gold-Polytetrafluoroethylene Thin Film

    PubMed Central

    Grytsenko, Konstantin; Lozovski, Valeri; Strilchuk, Galyna; Schrader, Sigurd

    2012-01-01

    Nanocomposite films consisting of gold inclusions in the polytetrafluoroethylene (PTFE) matrix were obtained by thermal vacuum deposition. Annealing of the obtained films with different temperatures was used to measure varying of film morphologies. The dependence of optical properties of the films on their morphology was studied. It was established that absorption and profile of the nanocomposite film obtained by thermal vacuum deposition can be changed with annealing owing to the fact that different annealing temperatures lead to different average particle sizes. A method to calculate the optical properties of nanocomposite thin films with inclusions of different sizes was proposed. Thus, comparison of experimental optical spectra with the spectra obtained during the simulation enables estimating average sizes of inclusions. The calculations give the possibility of understanding morphological changes in the structures.

  13. Thermal stability of electron-irradiated poly(tetrafluoroethylene) - X-ray photoelectron and mass spectroscopic study

    NASA Technical Reports Server (NTRS)

    Wheeler, Donald R.; Pepper, Stephen V.

    1990-01-01

    Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species were evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS spectrum that were associated with damage diminished, giving the appearance that the radiation damage had annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

  14. Anisotropic pyrochemical microetching of poly(tetrafluoroethylene) initiated by synchrotron radiation-induced scission of molecule bonds

    SciTech Connect

    Yamaguchi, Akinobu E-mail: utsumi@lasti.u-hyogo.ac.jp; Kido, Hideki; Utsumi, Yuichi E-mail: utsumi@lasti.u-hyogo.ac.jp; Ukita, Yoshiaki; Kishihara, Mitsuyoshi

    2016-02-01

    We developed a process for micromachining polytetrafluoroethylene (PTFE): anisotropic pyrochemical microetching induced by synchrotron X-ray irradiation. X-ray irradiation was performed at room temperature. Upon heating, the irradiated PTFE substrates exhibited high-precision features. Both the X-ray diffraction peak and Raman signal from the irradiated areas of the substrate decreased with increasing irradiation dose. The etching mechanism is speculated as follows: X-ray irradiation caused chain scission, which decreased the number-average degree of polymerization. The melting temperature of irradiated PTFE decreased as the polymer chain length decreased, enabling the treated regions to melt at a lower temperature. The anisotropic pyrochemical etching process enabled the fabrication of PTFE microstructures with higher precision than simultaneously heating and irradiating the sample.

  15. ESCA study of the effect of hydrocarbon contamination on poly(tetrafluoroethylene) exposed to atomic oxygen plasma

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Wydeven, Theodore; Cormia, Robert D.

    1991-01-01

    The ESCA spectra and data obtained by Morra et al. (1989) on poly(tetrafluoroethylene) (PTFE) exposed to atomic oxygen plasma are closely reexamined. It is shown that the spikes observed in Morra et al. plots of O/C or F/C versus time of the exposure of PTFE to atomic oxygen plasma were not characteristic of PTFE per se but were instead a result of a contamination by hydrocarbon present in their PTFE samples. This was demonstrated experimentally by comparing data derived for a very clean PTFE sample exposed for 10, 20, and 30 min to oxygen plasma with data obtained on PTFE samples with very small amounts of hydrocarbon contamination.

  16. Thermal stability of electron-irradiated poly(tetrafluoroethylene) - X-ray photoelectron and mass spectroscopic study

    NASA Technical Reports Server (NTRS)

    Wheeler, Donald R.; Pepper, Stephen V.

    1990-01-01

    Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 C. The behavior of the material as a function of radiation dose and temperature was studied by X-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. Lightly damaged material heated to 300 C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species were evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS spectrum that were associated with damage diminished, giving the appearance that the radiation damage had annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

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

    PubMed Central

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

    2017-01-01

    The results of the investigations into the technological formation of new wear-resistant polymer composites based on polytetrafluoroethylene (PTFE) filled with disperse synthetic and natural compounds are presented. The efficiency of using PTFE composites reinforced with carbon fibers depends on many factors, which influence the significant improvement of physicomechanical characteristics. The results of this research allow stating that interfacial and surface phenomena of the polymer–solid interface and composition play a decisive role in PTFE composites properties. Fillers hinder the relative movement of the PTFE molecules past one another and, in this way, reduce creep or deformation of the parts, reducing the wear rate of parts used in dynamic applications as well as the coefficient of thermal expansion. The necessary structural parameters of such polymer composites are provided by regimes of process equipment. PMID:28772733

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

  19. Permanent implantation of a reinforced polytetrafluoroethylene vascular graft for treatment of artificial defects of the teat cistern mucosa in cows.

    PubMed

    Metzger, L; Hirsbrunner, G; Waldvogel, A; Eicher, R; Schällibaum, M; Steiner, A

    1999-01-01

    To evaluate use of a reinforced polytetrafluoroethylene vascular graft for treatment of an artificial defect of mucosa of the teat cistern in lactating cows. Prospective study. 9 clinically normal lactating dairy cows. A 20-mm wide circumferential area of mucosa was sharply excised from the cistern of 1 teat on each cow 10 days after spontaneous calving, and the lesion was covered by a graft. After 14 days of passive milk drainage, routine milking was resumed. Follow-up examinations were performed during the next 2 lactation periods and included evaluation of wound healing, location and sonographic appearance of the implant, milk flow and yield, and somatic cell counts. Cows were slaughtered, and teats and mammary glands were examined microscopically. Implants had partially to totally collapsed within 30 to 90 days. Milk flow was significantly increased by day 15 of the first lactation, but decreased significantly by day 300 of lactation 1. At the end of lactation 1, milk flow had ceased in 3 out of 7 quarters. Only 3 of 9 quarters drained through grafted teats were milkable at the end of the study. Somatic cell counts of these quarters were significantly increased in the first lactation period. At necropsy, 2 grafts were in the teat cistern, but only 1 was incorporated into the mucosa by connective tissue. The mucosa was thickened in all teats with grafts, and there was epithelial metaplasia and granulation tissue proliferation. Use of a polytetrafluoroethylene graft can preserve patency in the first lactation period. However, the graft may not be sufficiently incorporated into the mucosa if routine machine milking is resumed 2 weeks after implantation. )

  20. Expanding contraceptive options.

    PubMed

    1989-01-01

    The goals of Family Health International (FHI) have been to introduce a variety of birth control options to people in developing countries, and to provide information to the user on the advantages and disadvantages of each method. FHI has worked with many developing countries in clinical trials of established as well as new contraceptive methods. These trials played an important part in making 2 sterilization procedures, laparoscopy and minilaparotomy popular for women. Further research improved the methods and have made them the most popular in the world, chosen by 130 million users. FHI is doing clinical trials on a new IUD, that is a copper bearing T-shaped device called the TCu380A. they have collected data on over 10,000 women using IUD's and early analysis indicates TCu380A is more effective than others. FHI is also evaluating devices such as Norplant that will prevent pregnancy up to 5 years by implanting the capsules in the arm. More than 8,000 women are being tested to determine the acceptability of implants in different geographical locations. Other research groups are doing work in 10 additional countries: Bangladesh will expand its program to 24,000 women and Nepal to 8,000 women. Trials are also being conducted on progestogen pills, since they do not lesson the volume of milk in breast feeding. FHI has also worked to introduce creative community-based distribution channels. In one case, specially trained health workers delivered contraceptives door-to-door in over 150,000 households. They found that 2 of 3 women accepted the pills and in a follow up survey 90% were still using them. FHI is now focusing on ways to improve moving new contraceptives from clinical testing on everyday use. They will coordinate training programs, educational material, media campaigns, and efforts with other international organizations, government agencies, and family planning groups.

  1. The Artful Universe Expanded

    NASA Astrophysics Data System (ADS)

    Barrow, John D.

    2005-07-01

    Our love of art, writes John Barrow, is the end product of millions of years of evolution. How we react to a beautiful painting or symphony draws upon instincts laid down long before humans existed. Now, in this enhanced edition of the highly popular The Artful Universe , Barrow further explores the close ties between our aesthetic appreciation and the basic nature of the Universe. Barrow argues that the laws of the Universe have imprinted themselves upon our thoughts and actions in subtle and unexpected ways. Why do we like certain types of art or music? What games and puzzles do we find challenging? Why do so many myths and legends have common elements? In this eclectic and entertaining survey, Barrow answers these questions and more as he explains how the landscape of the Universe has influenced the development of philosophy and mythology, and how millions of years of evolutionary history have fashioned our attraction to certain patterns of sound and color. Barrow casts the story of human creativity and thought in a fascinating light, considering such diverse topics as our instinct for language, the origins and uses of color in nature, why we divide time into intervals as we do, the sources of our appreciation of landscape painting, and whether computer-generated fractal art is really art. Drawing on a wide variety of examples, from the theological questions raised by St. Augustine and C.S. Lewis to the relationship between the pure math of Pythagoras and the music of the Beatles, The Artful Universe Expanded covers new ground and enters a wide-ranging debate about the meaning and significance of the links between art and science.

  2. Advanced expander test bed program

    NASA Technical Reports Server (NTRS)

    Masters, A. I.; Mitchell, J. C.

    1991-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Chemical Transfer Propulsion Program for development and demonstration of expander cycle oxygen/hydrogen engine technology component technology for the next space engine. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced missions focused components and new health monitoring techniques. The split-expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust.

  3. Advanced expander test bed engine

    NASA Technical Reports Server (NTRS)

    Mitchell, J. P.

    1992-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Space Chemical Engine Technology Program for development and demonstration of expander cycle oxygen/hydrogen engine and advanced component technologies applicable to space engines as well as launch vehicle upper stage engines. The AETB will be used to validate the high pressure expander cycle concept, study system interactions, and conduct studies of advanced mission focused components and new health monitoring techniques in an engine system environment. The split expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust.

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

    PubMed

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

    2009-01-01

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

  5. Monolithical aspherical beam expanding systems

    NASA Astrophysics Data System (ADS)

    Fuchs, U.; Matthias, Sabrina

    2014-10-01

    Beam expanding is a common task, where Galileo telescopes are preferred. However researches and customers have found limitations when using these systems. A new monolithical solution which is based on the usage of only one aspherical component will be presented. It will be shown how to combine up to five monolithical beam expanding systems and to keep the beam quality at diffraction limitation. Insights will be given how aspherical beam expanding systems will help using larger incoming beams and reducing the overall length of such a system. Additionally an add-on element for divergence and wavelength adaption will be presented.

  6. Advanced expander test bed program

    NASA Technical Reports Server (NTRS)

    Riccardi, D. P.; Mitchell, J. C.

    1993-01-01

    The Advanced Expander Test Bed (AETB) is a key element in NASA's Space Chemical Engine Technology Program for development and demonstration of expander cycle oxygen/hydrogen engine and advanced component technologies applicable to space engines as well as launch vehicle upper stage engines. The AETB will be used to validate the high-pressure expander cycle concept, investigate system interactions, and conduct investigations of advanced mission focused components and new health monitoring techniques in an engine system environment. The split expander cycle AETB will operate at combustion chamber pressures up to 1200 psia with propellant flow rates equivalent to 20,000 lbf vacuum thrust. Contract work began 27 Apr. 1990. During 1992, a major milestone was achieved with the review of the final design of the oxidizer turbopump in Sep. 1992.

  7. High-performance LiFePO4/C electrode with polytetrafluoroethylene as an aqueous-based binder

    NASA Astrophysics Data System (ADS)

    Gao, Shiyan; Su, Yuefeng; Bao, Liying; Li, Ning; Chen, Lai; Zheng, Yu; Tian, Jun; Li, Jian; Chen, Shi; Wu, Feng

    2015-12-01

    An environmental-friendly and low-cost polymer, polytetrafluoroethylene (PTFE) has been applied as an aqueous-based binder for the fabrication of LiFePO4/C electrode. The electrode with PTFE has been compared to the electrode with the conventional binder, polyvinylidene fluoride (PVDF) via Rheology test, X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and electrochemical tests. The Rheology test indicates that the viscosity of the slurry prepared with PTFE as a binder is better than that prepared with PVDF. The electrochemical measurements demonstrate that the electrode with PTFE binder displays a higher discharge capacity of 161.1 mAh g-1 compared to the electrode with PVDF binder, which shows a discharge capacity of 150.7 mAh g-1. The EIS analysis indicates the LiFePO4/C electrode with PTFE binder shows a higher ionic conductivity and a smaller increasing in charge transfer rate compared to the LiFePO4/C electrode with PVDF binder. In addition, the electrodes applying the aqueous-based binder have been optimized by controlling the moisture content in the electrodes. The electrochemical enhancement of these electrodes can be achieved by controlling the vacuum drying temperature and time during the preparation of the electrodes.

  8. Particle size effect on strength, failure, and shock behavior in polytetrafluoroethylene-Al-W granular composite materials

    NASA Astrophysics Data System (ADS)

    Herbold, E. B.; Nesterenko, V. F.; Benson, D. J.; Cai, J.; Vecchio, K. S.; Jiang, F.; Addiss, J. W.; Walley, S. M.; Proud, W. G.

    2008-11-01

    The variation of metallic particle size and sample porosity significantly alters the dynamic mechanical properties of high density granular composite materials processed using a cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders. Quasistatic and dynamic experiments are performed with identical constituent mass fractions with variations in the size of the W particles and pressing conditions. The relatively weak polymer matrix allows the strength and fracture modes of this material to be governed by the granular type behavior of agglomerated metal particles. A higher ultimate compressive strength was observed in relatively high porosity samples with small W particles compared to those with coarse W particles in all experiments. Mesoscale granular force chains of the metallic particles explain this unusual phenomenon as observed in hydrocode simulations of a drop-weight test. Macrocracks forming below the critical failure strain for the matrix and unusual behavior due to a competition between densification and fracture in dynamic tests of porous samples were also observed. Numerical modeling of shock loading of this granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix can be tailored by the W particle size distribution.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  11. Comparison of polytetrafluoroethylene flat-sheet membranes with different pore sizes in application to submerged membrane bioreactor.

    PubMed

    Nittami, Tadashi; Hitomi, Tetsuo; Matsumoto, Kanji; Nakamura, Kazuho; Ikeda, Takaharu; Setoguchi, Yoshihiro; Motoori, Manabu

    2012-06-01

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

  12. POLYTETRAFLUOROETHYLENE-RICH POLYPHENLENESULFIDE BLEND TOP COATINGS FOR MITIGATING CORROSION OF CARBON STEEL IN 300 DEGREE CELCIUS BRINE.

    SciTech Connect

    SUGAMA, T.; JUNG, D.

    2006-06-01

    We evaluated usefulness of a coating system consisting of an underlying polyphenylenesulfide (PPS) layer and top polytetrafluoroethylene (PTFE)-blended PPS layer as low friction, water repellent, anti-corrosion barrier film for carbon steel steam separators in geothermal power plants. The experiments were designed to obtain information on kinetic coefficient of friction, surface free energy, hydrothermal oxidation, alteration of molecular structure, thermal stability, and corrosion protection of the coating after immersing the coated carbon steel coupons for up to 35 days in CO{sub 2}-laden brine at 300 C. The superficial layer of the assembled coating was occupied by PTFE self-segregated from PPS during the melt-flowing process of this blend polymer; it conferred an outstanding slipperiness and water repellent properties because of its low friction and surface free energy. However, PTFE underwent hydrothermal oxidation in hot brine, transforming its molecular structure into an alkylated polyfluorocarboxylate salt complex linked to Na. Although such molecular transformation increased the friction and surface free energy, and also impaired the thermal stability of PTFE, the top PTFE-rich PPS layer significantly contributed to preventing the permeation of moisture and corrosive electrolytes through the coating film, so mitigating the corrosion of carbon steel.

  13. Radiolytic preparation and characterization of hydrophilic poly(acrylonitrile-co-vinylsulfonate)-grafted porous poly(tetrafluoroethylene) substrates

    NASA Astrophysics Data System (ADS)

    Park, Byeong-Hee; Sohn, Joon-Yong; Shin, Junhwa

    2016-01-01

    In this study, a hydrophilic copolymer of acrylonitrile (AN) and sodium vinylsulfonate (SVS) was grafted into a highly hydrophobic porous poly(tetrafluoroethylene) (PTFE) substrate using a gamma-ray irradiation method and the grafted substrate was used as a substrate for impregnating a hydrophilic ionomer, Nafion. The results of FT-IR and TGA analysis of the prepared substrate showed that the SVS/AN monomers were successfully grafted into the porous PTFE film. The results of degree of grafting, elemental analyzer, and contact angle analysis showed that the hydrophilicity of the prepared PTFE-g-P(AN-co-VS) substrate was increased with an increase in the amount of SVS/AN graft copolymers. Also, the results of FE-SEM and Gurley number measurement showed that the pores in the substrate were reduced as the amount of SVS/AN copolymers grafted into the substrate increased. The prepared porous PTFE-g-P(AN-co-VS) substrate at an irradiation dose of 70 kGy was found to impregnate Nafion ionomer effectively compared to the original porous PTFE substrate. These results suggest that the prepared PTFE-g-P(AN-co-VS) substrate can be effectively used for the impregnation of polymer electrolyte (Nafion) to prepare a reinforced composite membrane.

  14. Thermodynamic properties and transport coefficients of air thermal plasmas mixed with ablated vapors of Cu and polytetrafluoroethylene

    SciTech Connect

    Zhang, JunMin E-mail: guanyg@tsinghua.edu.cn; Lu, ChunRong; Guan, YongGang E-mail: guanyg@tsinghua.edu.cn; Liu, WeiDong

    2015-10-15

    Because the fault arc in aircraft electrical system often causes a fire, it is particularly important to analyze its energy and transfer for aircraft safety. The calculation of arc energy requires the basic parameters of the arc. This paper is mainly devoted to the calculations of equilibrium composition, thermodynamic properties (density, molar weight, enthalpy, and specific heat at constant pressure) and transport coefficients (thermal conductivity, electrical conductivity, and viscosity) of plasmas produced by a mixture of air, Cu, and polytetrafluoroethylene under the condition of local thermodynamic equilibrium. The equilibrium composition is determined by solving a system of equations around the number densities of each species. The thermodynamic properties are obtained according to the standard thermodynamic relationships. The transport coefficients are calculated using the Chapman-Enskog approximations. Results are presented in the temperature range from 3000 to 30 000 K for pressures of 0.08 and 0.1 MPa, respectively. The results are more accurate and are reliable reference data for theoretical analysis and computational simulation of the behavior of fault arc.

  15. Thermodynamic properties and transport coefficients of air thermal plasmas mixed with ablated vapors of Cu and polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Zhang, JunMin; Lu, ChunRong; Guan, YongGang; Liu, WeiDong

    2015-10-01

    Because the fault arc in aircraft electrical system often causes a fire, it is particularly important to analyze its energy and transfer for aircraft safety. The calculation of arc energy requires the basic parameters of the arc. This paper is mainly devoted to the calculations of equilibrium composition, thermodynamic properties (density, molar weight, enthalpy, and specific heat at constant pressure) and transport coefficients (thermal conductivity, electrical conductivity, and viscosity) of plasmas produced by a mixture of air, Cu, and polytetrafluoroethylene under the condition of local thermodynamic equilibrium. The equilibrium composition is determined by solving a system of equations around the number densities of each species. The thermodynamic properties are obtained according to the standard thermodynamic relationships. The transport coefficients are calculated using the Chapman-Enskog approximations. Results are presented in the temperature range from 3000 to 30 000 K for pressures of 0.08 and 0.1 MPa, respectively. The results are more accurate and are reliable reference data for theoretical analysis and computational simulation of the behavior of fault arc.

  16. Laparoscopic intraperitoneal polytetrafluoroethylene (PTFE) prosthetic patch repair of ventral hernia. Prospective comparison to open prefascial polypropylene mesh repair.

    PubMed

    DeMaria, E J; Moss, J M; Sugerman, H J

    2000-04-01

    The purpose of this study was to determine whether laparoscopic intraperitoneal polytetrafluoroethylene (PTFE) prosthetic patch (LIPP) repair of a ventral hernia is superior to open prefascial polypropylene mesh (OPPM) repair in a tertiary care university hospital in an urban environment. Data on 39 consecutive patients undergoing either LIPP repair (n = 21) or OPPM repair (n = 18) were compared. Findings showed that LIPP repair is characterized by less painful recovery and shorter hospital stay, with 90% of patients treated successfully as outpatients as compared with 7% in the OPPM group. The total facility costs for the LIPP repair ($8,273+/-$2,950) was significantly lower than for the OPPM repair ($12,461+/-$5,987) (p<0.05). Two serious delayed complications in the LIPP group were treated by reoperation (colocutaneous fistula, mesh infection), but the higher readmission costs in this group did not negate the overall cost advantage for LIPP repair. In the follow-up evaluation, 1 hernia recurrence was found in the LIPP repair group, and none in the OPPM group. Initial experience suggests that LIPP repair has advantages over OPPM repair in terms of decreased hospitalization, postoperative pain, and disability. Refinements in the technique to reduce complications may make LIPP repair the procedure of choice for repair of ventral hernias.

  17. Effect of through-plane distribution of polytetrafluoroethylene in carbon paper on in-plane gas permeability

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Abe, Katsuya; Ishida, Masayoshi; Nakano, Akihiro; Maeda, Tetsuhiko; Munakata, Tetsuo; Nakajima, Hironori; Kitahara, Tatsumi

    2014-02-01

    In-plane permeability of gas diffusion backing (GDB) of proton exchange membrane fuel cells (PEMFCs) was investigated experimentally. Toray-paper and SGL-paper were selected as GDB test samples. Several Toray-papers were treated in-house with polytetrafluoroethylene (PTFE) using the immersion technique, dried either under atmospheric or vacuum pressure, and then sintered. The dependence of PTFE distribution in the through-plane direction on the PTFE drying conditions was examined using scanning electron microscopy (SEM)-based energy dispersive X-ray spectroscopy (EDS) imaging. The EDS image maps revealed that the PTFE distribution strongly depended on the drying condition, and PTFE drying under vacuum pressure yielded a relatively uniform PTFE distribution. The measured in-plane permeability suggests that the homogeneous distribution of PTFE achieved by the vacuum drying produces a porosity-leveling effect. In addition, the relationship between the in-plane permeability and porosity of the Toray-paper samples followed the Kozeny-Carman relation, whereas due to non-fibrous solids such as binder, that of the SGL-paper samples did not.

  18. The management of massive ultrafiltration distending the aneurysm sac after abdominal aortic aneurysm repair with a polytetrafluoroethylene aortobiiliac graft.

    PubMed

    Williams, G M

    1998-09-01

    Collections of serous fluid surrounding prosthetic grafts can be caused by infection or transudation of serum, and making the distinction is often troublesome. Bergamini and his colleagues developed a dog model of low-grade prosthetic graft contamination with Staphylococcus epidermatis. All animals developed evidence of graft infection, and 13 of 18 dogs developed a fluid-filled perigraft cyst. Signs of systemic infection, however, were present in only 1 animal, and the Staphylococcus epidermatis study strain was isolated from the tissue surrounding the graft in only 1 dog. The authors had to disrupt the biofilm to achieve positive cultures in 14 of 18 animals. This animal model seemed to conform to clinical experience and placed great emphasis on the role of indolent infections in the pathogenesis of perigraft fluid collection. It is equally clear that perigraft fluid collections may result from transudation of fluid through the prosthetic surfaces, which act similar to a dialysis membrane under certain circumstances. Noninfectious seromas are characterized generally by the accumulation of clear serous fluid with a protein and glucose content of serum and the lack of acute inflammatory cells when the sediment is examined. The need to distinguish between these 2 forms of fluid accumulation became important in the treatment of a 62-year-old man who was seen 2 1/2 years after the repair of an abdominal aortic aneurysm with an aortobiiliac stretch polytetrafluoroethylene (PTFE) prosthesis. There was no evidence of infection, and there was a 12 cm cystic mass surrounding a patent PTFE prosthesis.

  19. Cell attachment and biocompatibility of polytetrafluoroethylene (PTFE) treated with glow-discharge plasma of mixed ammonia and oxygen.

    PubMed

    Chen, Meng; Zamora, Paul O; Som, Prantika; Peña, Louis A; Osaki, Shigemasa

    2003-01-01

    The plasma generated from a gas mixture of NH3 plus O2 (NH3 + O2) has been used to impart unique chemical and biological characteristics to polytetrafluoroethylene (PTFE). PTFE treated with NH3 + O2 plasma was physiochemically distinct from surfaces treated with plasma of either NH3 or O2 alone, as determined by electron spectroscopy for chemical analysis (ESCA). The contact angle analysis revealed that the PTFE surfaces became less hydrophobic after plasma treatments. ESCA results indicate the presence of oxygen-containing groups and nitrogen-containing groups at the plasma-treated surfaces. PTFE treated with NH3 + O2 plasma resisted the attachment of platelets and leukocytes in a manner similar to untreated PTFE; however, the attachment of bovine aorta endothelial cells was substantially increased. Once attached, these cells grew to confluency. The increased endothelial cell attachment was higher than that observed following plasma treatment with each gas used separately, which could be attributed to the considerable amount of CF(OR)2-CF2 formed on the NH3 + O2 plasma-treated PTFE surface. At 14 days after subcutaneous implantation in rats, the PTFE wafers treated with NH3 + O2 plasma demonstrated less encapsulation and lower levels of inflammatory cells compared to controls. Collectively, the results suggest that NH3 + O2 plasma treatment imparts a unique character to PTFE and could be useful in certain in vivo applications.

  20. Electrically driven biofouling release of a poly(tetrafluoroethylene) membrane modified with an electrically induced reversibly cross-linked polymer.

    PubMed

    Chuo, Tsai-Wei; Wei, Ta-Chin; Chang, Yung; Liu, Ying-Ling

    2013-10-23

    Electrically induced reversible reactions between ferrocene (Fc) and β-cyclodextrin (β-CD) groups have been utilized for preparation of poly(tetrafluoroethylene) (PTFE) membranes exhibiting electrically driven biofouling release properties. PTFE membrane is surface-modified with polymer chains possessing Fc pendant groups. The surface layer is then cross-linked with a difunctional β-CD compound by means of the Fc/β-CD complexation reaction. The electrically induced reversibly cross-linking and de-cross-linking behaviors of the surface layer of the modified PTFE membrane have been characterized with Fourier transform Infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy. The surface-modified PTFE membrane has been fouled with protein absorption. Electrical treatment of the fouled membrane results in a protein detachment from the membrane surface driven by the surface structure change accompanied with the electrically induced de-cross-linking reaction of the Fc/β-CD linkages. A smart membrane exhibiting a novel cleaning technology for membrane fouling has been developed.

  1. Worsening of preoperative foot ischemia after occlusion of polytetrafluoroethylene femorotibial grafts: a comparison with saphenous vein grafts.

    PubMed

    Cavallaro, Antonino; Sterpetti, Antonio V; DiMarzo, Luca; Sapienza, Paolo

    2013-07-01

    The aim of this study was to determine the hemodynamic and clinical changes after occlusion of polytetrafluoroethylene (PTFE) femorotibial grafts. Twenty-seven patients were randomly selected from all patients who underwent femorotibial bypass grafting in our department. In 10 patients, the reversed autologous saphenous vein was used as graft, and in 17 patients a PTFE prosthesis was used. Out of the latter 17 patients, 10 began long-term aspirin therapy and 7 began oral anticoagulation with warfarin. Nine out of the 10 patients with occluded PTFE grafts and who received only aspirin therapy had a critical ischemia after occlusion of the graft, and 4 underwent major amputation. Among the 10 patients with occluded autologous vein bypass, critical ischemia was present in only 4 patients, and only 2 required some form of surgical therapy with no case of major amputation. After occlusion of a PTFE femorotibial graft, there is a condition of critical ischemia that is less common after occlusion of a vein graft. Oral anticoagulation seems to prevent these negative changes. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Short-Term and Long-Term Outcomes After Polytetrafluoroethylene-Covered Stent Implantation for the Treatment of Coronary Perforation.

    PubMed

    Kawamoto, Hiroyoshi; Tanaka, Kentaro; Ruparelia, Neil; Takagi, Kensuke; Yabushita, Hiroto; Watanabe, Yusuke; Mitomo, Satoru; Matsumoto, Takahiro; Naganuma, Toru; Fujino, Yusuke; Ishiguro, Hisaaki; Tahara, Satoko; Kurita, Naoyuki; Nakamura, Shotaro; Hozawa, Koji; Nakamura, Sunao

    2015-12-15

    This study sought to evaluate the short-term and 3-year outcomes of polytetrafluoroethylene-covered stent (PCS) for patients with coronary perforation. Implantation of a PCS has improved the immediate clinical outcomes of patients with coronary perforation. However, there are few reports regarding long-term outcomes. We evaluated a total of 57 patients who were treated with PCS for coronary perforation from April 2004 to March 2015 at a single high-volume center in Japan. Landmark analysis was performed at 30 days to determine short-term and long-term outcomes. Major adverse cardiac events (MACE) were defined as death, myocardial infarction, target vessel revascularization, and requirement for surgical repair. Of 285 patients who experienced coronary perforation, 57 patients (20%) were treated with PCS. The MACE rates were 28% at 30 days, 22% at 1 year, and 38% at 3 years. 30-day MACE was mainly driven by high rates of myocardial infarction (18%) and surgical repair (16%). The rates of target lesion revascularization were 8% and 12% at 1 and 3 years, respectively. Definite stent thrombosis was reported in 2 patients during the follow-up period. In conclusion, despite the relatively high incidence of MACE during early stage of follow-up, implantation of a PCS provides acceptable late clinical outcomes.

  3. Teleteach Expanded Delivery System: Evaluation.

    ERIC Educational Resources Information Center

    Christopher, G. Ronald; Milam, Alvin L.

    In order to meet the demand for Air Force Institute of Technology (AFIT) professional continuing education (PCE) courses within the School of Systems and Logistics and the School of Engineering, the Teleteach Expanded Delivery System (TEDS) for instruction of Air Force personnel at remote locations was developed and evaluated. TEDS uses a device…

  4. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G

    2015-02-03

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  5. Expanding the eukaryotic genetic code

    DOEpatents

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2017-02-28

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  6. Expanding Frontiers of Humanoid Robotics

    DTIC Science & Technology

    2000-08-01

    From the IEEE Intelligent Systems Special Issue on Humanoid Robotics , July/August 2000 GUEST EDITORS’ Expanding Frontiers of Humanoid Robotics ...Mark L. Swinson, DARPA David J. Bruemmer, Strategic Analysis Mobile robots pose a unique set of challenges to artificial intelligence researchers...the constraints of logical correctness but also some assortment of crosscutting, physical constraints. Particularly interesting among these robots

  7. Common Ground: Expanding Our Horizons.

    ERIC Educational Resources Information Center

    McDevitt, Michele J.

    In "Common Ground: Dialogue, Understanding, and the Teaching of Composition," Kurt Spellmeyer seeks to familiarize students and teachers with the linguistic and cultural no-man's-land separating them. Reinstating the value of two writing conventions often used by traditional students--expressive and commonplaces--can help expand on the…

  8. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2012-05-08

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  9. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2013-01-22

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  10. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2012-02-14

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  11. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2010-09-14

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  12. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2009-12-01

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  13. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W; Cropp, T Ashton; Anderson, J Christopher; Schultz, Peter G

    2009-10-27

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  14. Expanding the eukaryotic genetic code

    SciTech Connect

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2009-11-17

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  15. Expanding the Universe of Education.

    ERIC Educational Resources Information Center

    Parsons, Elizabeth

    1996-01-01

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

  16. Emotional Giftedness: An Expanded View.

    ERIC Educational Resources Information Center

    Piechowski, Michael M.

    This paper discusses an expanded definition of the concept of emotional giftedness in children as defined by Annemarie Roeper. In contrast to examples of academic and artistic prodigies, cases are reviewed that illustrate less tangibly measured examples of children's giftedness, such as expressions of compassion, moral sensitivity, positive…

  17. Tree Decay - An Expanded Concept

    Treesearch

    Alex L. Shigo

    1979-01-01

    The purpose of this publication is to clarify further the tree decay concept that expands the classical concept to include the orderly response of the tree to wounding and infection-compartmentalization-and the orderly infection of wounds by many microorganisms-successions. The heartrot concept must be abandoned because it deals only with decay-causing fungi and it...

  18. Tree decay an expanded concept

    Treesearch

    Alex L. Shigo

    1979-01-01

    This publication is the final one in a series on tree decay developed in cooperation with Harold G. Marx, Research Application Staff Assistant, U.S. Department of Agriculture, Forest Service, Washington, D.C. The purpose of this publication is to clarify further the tree decay concept that expands the classical concept to include the orderly response of the tree to...

  19. The Expanding Frontier of Pluralism.

    ERIC Educational Resources Information Center

    King, Edmund

    1983-01-01

    Looks at the expanding frontier of pluralism in terms of reappraising the relationship of formal education to the advent of the constant change (occupational and social) accelerated by the microprocessor revolution and readjusting provisions in educational systems to meet the different needs of different populations. (AH)

  20. Expandable Shelter/Container Report.

    DTIC Science & Technology

    1973-06-01

    without removing whatever payload might be in the contai ner. Equ i pment located in the expanded porti on of the ES/C durin g norma l operat i ons is...and Supply BattalIon , Div isi on Support Coianand. In addition , divisional avIation battalions have an A Irc raft Maintenance Company. The TOE

  1. Expanded civil judicial referral procedures

    SciTech Connect

    Not Available

    1986-08-28

    The directive provides guidance on procedures for civil judicial referrals to the Department of Justice. The memorandum expands the current direct referral program, indicates that Headquarters should not establish mandatory requirements for pre-referral negotiations, mandates use of hold action cases only for strategic or tactical reasons and offers guidance on the preparation of bankruptcy cases.

  2. Finite simple groups as expanders

    PubMed Central

    Kassabov, Martin; Lubotzky, Alexander; Nikolov, Nikolay

    2006-01-01

    We prove that there exist k ∈ ℕ and 0 < ε ∈ ℝ such that every non-abelian finite simple group G, which is not a Suzuki group, has a set of k generators for which the Cayley graph Cay(G; S) is an ε-expander. PMID:16601101

  3. Monolithical aspherical beam expanding systems

    NASA Astrophysics Data System (ADS)

    Fuchs, U.

    2014-02-01

    In complex laser systems, such as those for material processing, and in basically all laboratory applications passive optical components are indispensable. Matching beam diameters is a common task, where Galileo type telescopes are preferred for beam expansion. Nevertheless researches and customers have found various limitations when using these systems. Some of them are the complicated adjustment, very small diameter for the incoming beam (1/e2), fixed and non-modifiable magnifications. Above that, diffraction-limitation is only assured within the optical design and not for the real world setup of the beam expanding system. Therefore, we will discuss limitations of currently used beam expanding systems to some extent. We will then present a new monolithical solution, which is based on the usage of only one aspherical component. It will be shown theoretically how the beam quality can be significantly improved by using aspherical lenses. As it is in the nature of things aspheres are working diffraction limited in the design, it will be shown how to combine up to five monolithical beam expanding systems and to keep the beam quality at diffraction limitation. Data of the culminated wavefront error will be presented. Last but not least insights will be given how beam expanding systems based on aspheres will help to use larger incoming beams and to reduce the overall length of such a system.

  4. Adhesion of leucocytes onto polytetrafluoroethylene (PTFE) vascular grafts and the effect of low molecular weight dextran (LMWD).

    PubMed

    al-Huneidi, W; Owunwanne, A; Christenson, J T

    1990-01-01

    Platelets are known to interact with the surface of synthetic grafts. In the present study we have investigated another blood constituent, the white blood cell, to evaluate the contribution of leucocyte adhesion onto synthetic vascular graft surfaces. Furthermore the effect of low molecular weight dextran (LMWD) was evaluated in vivo. Polytetrafluoroethylene (PTFE) grafts were interpositioned in the femoral circulation in 12 healthy adult sheep. Autologous leucocytes were labelled with Indium-111-oxine and re-injected i.v. after purity and functional evaluation. Graft uptake of 111In-labelled leucocytes were studied continuously for 2.5 hours and two consecutive days using a gamma camera. Six animals received LMWD, 15 ml/h, i.v. infusion during the first day while the other six animals were infused with normal saline in the same amount and rate (controls). The labelled leucocytes showed normal phagocytosis of bacterias and the leucocyte purity was 74 +/- 6%. There was a rapid increase in graft activity initially. In control animals a continuous increase of graft activity was observed throughout the experiment. In the LMWD-treated animals graft activity remained on a steady level after the initial built up of activity and after 2.5 hours there was a highly significant difference between the groups, p less than 0.001. These differences were confirmed by in vitro activity measurement, autoradiography and histological examination of the grafts at the end of the experiment. It was concluded that leucocyte adhesion onto the surface of PTFE grafts occur during the early period after implantation and could therefore be a contributing factor in the thrombogenesis. Administration of LMWD seems to have a beneficial effect since less leucocyte adhesion occurred in those animals treated with LMWD.

  5. In vivo biocompatibility and hemocompatibility of a polytetrafluoroethylene small diameter vascular graft modified with sulfonated silk fibroin.

    PubMed

    Zhang, Jiaqing; Huang, Hexi; Ju, Ruihong; Chen, Kuntang; Li, Shaobin; Wang, Wujun; Yan, Yusheng

    2017-01-01

    To evaluate the biocompatibility and hemocompatibility of an enhanced polytetrafluoroethylene (ePTFE) graft modified with sulfonated silk fibroin (SF) and to compare the patency rate of the modified graft to that of the commercially available unmodified ePTFE graft in a rabbit model. Twelve SF-modified grafts were used to replace a section of the lower abdominal aortic artery in rabbits, and 10 unmodified ePTFE grafts were used as controls. The patency rates of these grafts were examined according to physical findings, ultrasonic examination, and scanning electron microscopy (SEM). The patency rates of SF-modified ePTFE grafts on day 3, from day 4 to 3 months, and at 3 months were 100%, 91.7%, and 91.7%, respectively, and these values were higher than those for the unmodified grafts (60.0%, 33.3%, and 20.0%, respectively, with P = 0.029, 0.022, and 0.002, respectively). SEM images of grafts harvested 3 months postoperatively showed that approximately 84% of the inner surface of the SF-modified grafts was covered with endothelial cells growing longitudinally with extensive cell-cell connections. In comparison, endothelial cells covered only approximately 11% of the inner lumen of the unmodified grafts, and the inner surface of these grafts was covered with activated platelets, erythrocytes, and newly formed extracellular matrix. We also have developed a rabbit model to evaluate the patency rate of small diameter vessel graft by replacing the lower abdominal aortic artery with graft. The SF-modified ePTFE graft had a higher patency rate than the unmodified PTFE graft in vivo. In addition, replacement of the rabbit abdominal aortic artery represents a feasible and convenient model for evaluating the patency of small diameter vascular grafts. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Chemical alteration of poly(tetrafluoroethylene) TFE teflon induced by exposure to electrons and inert-gas ions.

    PubMed

    Everett, Michael L; Hoflund, Gar B

    2005-09-08

    In this study the chemical alterations of poly(tetrafluoroethylene) (TFE Teflon) by approximately 1.0-keV electrons and 1.0-keV He and Ar ions have been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.99 decreases to a steady-state value of 1.48 after 48 h of electron exposure. Exposure to either He+ or Ar+ decreases the initial F/C atom ratio from approximately 2 to a steady-state value of 1.12. The high-resolution XPS C 1s data indicate that new chemical states of carbon form as the F is removed and that the relative amounts of these states depend on the F content of the near-surface region. These states are most likely due to C bonded only to one F atom, C bonded only to other C atoms and C that have lost a pair of electrons through emission of F-. Exposures of the electron-damaged and He+- or Ar+-damaged surfaces to research-grade O2 result in chemisorption of very small amounts of O indicating that large quantities of reactive sites are not formed during the chemical erosion. Further exposure to the electron or ion fluxes quickly removes this chemisorbed oxygen. Exposure of the He+-damaged surface to air at room temperature results in the chemisorption of a larger amount of O than the O2 exposure but no N is adsorbed. The chemical alterations due to electrons and ions are compared with those caused by hyperthermal (approximately 5 eV) atomic oxygen (AO) and vacuum ultraviolet (VUV) radiation. The largest amount of damage is caused by AO followed by VUV, inert-gas ions, and then electrons.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  8. Implantation of a reinforced polytetrafluoroethylene vascular graft for treatment of obstructions of the teat and mammary gland cisternae in cattle.

    PubMed

    Hirsbrunner, G; Metzger, L; Steiner, A

    1998-05-01

    To evaluate use of an artificial vascular graft as treatment for obstructions of the teat and mammary gland cisternae in lactating cattle. Prospective clinical study. 14 lactating dairy cows. After physical examination that included palpation, ultrasonography, evaluation of milk flow, and California mastitis test, each cow underwent surgical excision of obstructive tissue and implantation of a reinforced polytetrafluoroethylene vascular graft. Milk drained passively for 10 to 14 days after surgery. Follow-up evaluation was performed by telephone questionnaire of owners 1, 6, and 12 months after surgery regarding somatic cell count, time needed to milk affected quarter, compared with that of the contralateral quarter, and frequency of mastitis. After the subsequent nonlactation period and calving, milk flow was tested, using a quarter milking machine, and ultrasonographic examination of the affected teat was performed. Milk could be obtained from affected quarters from all cows 14 days after surgery, from 13 (93%) cows 1 month after surgery, from 10 (71%) cows 6 months after surgery, and from 3 (21%) cows 12 months after surgery, but milk flow in these 3 cows was considerably reduced. This technique failed because of collapse of the implant (4 cows), chronic mastitis (1), migration of the implant (4), and ingrowth of obstructive tissue between the distal aspect of the implant and the ridges of mucous membrane that radiate from the internal orifice of the streak canal (4), or a combination of these. Implantation of this vascular graft is a useful technique to restore teat patency for 6 months. A longer period of passive drainage of milk appears necessary for sufficient ingrowth of the graft. Lesions that extend to the distal most aspect of the teat cistern have a poor prognosis, because this area cannot be sufficiently overlapped by the graft.

  9. Bicuspid pulmonary valve implantation using polytetrafluoroethylene membrane: early results and assessment of the valve function by magnetic resonance imaging.

    PubMed

    Lee, Cheul; Lee, Chang-Ha; Kwak, Jae Gun; Song, Jin Young; Shim, Woo-Sup; Choi, Eun Young; Lee, Sang Yun; Kim, Yang Min

    2013-03-01

    The durability of bioprosthetic valves in the pulmonary position is suboptimal. The objectives of this study were to evaluate the early results of polytetrafluoroethylene (PTFE) bicuspid pulmonary valve (PV) implantation and to better define the function of this valve by magnetic resonance imaging (MRI). Fifty-six patients who underwent PTFE bicuspid PV implantation between June 2009 and August 2011 were retrospectively analysed. The median age was 17.5 years and median valve size was 26 mm. Fundamental diagnoses were tetralogy of Fallot (n = 38), pulmonary atresia with ventricular septal defect (n = 8), double outlet right ventricle (n = 7) and absent PV syndrome (n = 3). Thirty-two patients with pulmonary regurgitation (PR) underwent MRI preoperatively and 22 of them underwent follow-up MRI at a median of 6.7 months postoperatively. There was one early death. Postoperative echocardiography (n = 53) showed no or trivial PR in 49 patients and mild PR in 4. Median follow-up duration was 15.2 months. There was no late death or reoperation. Follow-up echocardiography (n = 41) performed at a median of 7.5 months postoperatively showed no or trivial PR in 33 patients and mild PR in 8 patients. Follow-up MRI showed a significant reduction in right ventricular volumes and improvement in biventricular function. The median PR fraction of this valve was 10%. Early results of bicuspid PV implantation using PTFE membrane were satisfactory. PTFE bicuspid PV demonstrated excellent performance for the short term as evidenced by echocardiography and MRI. Long-term follow-up is mandatory to determine the durability of this valve.

  10. Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.; Dufrane, K. F.; Zugaro, F. F.

    1981-01-01

    Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.

  11. PolyDOPA Mussel-Inspired Coating as a Means for Hydroxyapatite Entrapment on Polytetrafluoroethylene Surface for Application in Periodontal Diseases.

    PubMed

    Nardo, Tiziana; Chiono, Valeria; Ciardelli, Gianluca; Tabrizian, Maryam

    2016-02-01

    Inert polytetrafluoroethylene (PTFE) membranes for periodontal regeneration suffer from weak osteoconductive properties. In this work, a strategy for hydroxyapatite (HAp) coating on PTFE films through an adhesive layer of self-polymerized 3,4-dihydroxy-DL-phenylalanine (polyDOPA) was developed to improve surface properties. Physico-chemical and morphological analysis demonstrated the deposition of polyDOPA and HAp, with an increase in surface roughness and wettability. A discontinuous coating was present after 14 days in PBS and MC3T3-E1 cells proliferation and adhesion were improved. Results confirmed the potential application of polyDOPA/HAp-coated films for periodontal disease treatments.

  12. Seal-less cryogenic expander

    SciTech Connect

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

    1987-12-08

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

  13. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  14. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  15. Echinocandins: The Expanding Antifungal Armamentarium.

    PubMed

    Aguilar-Zapata, Daniel; Petraitiene, Ruta; Petraitis, Vidmantas

    2015-12-01

    The echinocandins are large lipopeptide molecules that, since their discovery approximately 41 years ago, have emerged as important additions to the expanding armamentarium against invasive fungal diseases. Echinocandins exert in vitro and in vivo fungicidal action against most Candida species and fungistatic action against Aspergillus species. However, the population of patients at risk for developing invasive fungal infections continues to increase. New therapeutic strategies using echinocandins are needed to improve clinical outcomes in patients with invasive fungal disease.

  16. Entropy in an expanding universe.

    PubMed

    Frautschi, S

    1982-08-13

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

  17. Entropy in an expanding universe

    NASA Astrophysics Data System (ADS)

    Frautschi, S.

    1982-08-01

    The evolution of organized structures from initial chaos in the expanding universe is demonstrated to be reconcilable with the second law of thermodynamics, and the effects of expansion and gravity on this problem are emphasized. Numerical estimates of the major sources of entropy increase are calculated, including the entropy increase in stars, the earth, black hole formation and decay, quantum tunneling of matter into black holes, positronium formation and decay, etc. An expanding 'causal' region is defined in which the entropy, though increasing, tends to fall further and further behind its maximum possible value, thus allowing for the development of order. That is, the classical heat death argument does not hold, because an expanding universe never achieves equilibrium and never reaches a constant temperature. Also considered are questions of whether entropy will continue increasing without limit in the future, and whether such increase in the form of Hawking radiation or radiation from positronium might enable life to maintain itself permanently. Attempts to find a scheme for preserving life based on solid structures fail because events such as quantum tunneling recurrently disorganize matter on a very long but fixed time scale.

  18. Plasma treatment of expanded PTFE offers a way to a biofunctionalization of its surface

    NASA Astrophysics Data System (ADS)

    Baquey, Ch.; Palumbo, F.; Porte-Durrieu, M. C.; Legeay, G.; Tressaud, A.; d'Agostino, R.

    1999-05-01

    Biointegration is the ideal outcome which is expected for an artificial implant. That means that the phenomena which seats at the interface between the implant and the host tissues does not induce neither any deleterious effect, such as chronic inflammatory response, nor the formation of unusual tissues. Thus it is of paramount importance to design biomaterials, used for the fabrication of implants, with the best appropriate surface properties. At the same time these biomaterials must feature bulk properties which meet other requirements, especially mechanical properties, deriving from the intended function of the implant in which they are involved. As it is quite impossible to design biomaterials which fulfil at the same time both types of requirements, it is commonly agreed that the solution to this issue goes through the selection or the design of biomaterials with adequate bulk properties, and a further treatment of the surface which would improve the properties of the latter. In this respect ionizing radiations and plasma based treatments, offer a wide panel of possibilities; as an example we describe here how the surface of expanded poly(tetrafluoroethylene) samples can be activated using cold plasma, in order to open a way to chemical modifications of such a surface. Subsequently, Radio Frequency Glow Discharge (RFGD) containing oligopeptides, known for their role in mediating the adhesion of cells to the extracellular matrix, were bound to the modified surface, and the affinity of endothelial cells for the latter was investigated.

  19. Endovascular Treatment for Infra-inguinal Autologous Saphenous Vein Graft Occlusion Using Self Expanding Nitinol Stents.

    PubMed

    Yanagiuchi, T; Kimura, M; Shiraishi, J; Sawada, T

    2016-01-01

    For patients with infra-inguinal autologous vein bypass graft occlusion, conventional open surgical repair or endovascular treatment (EVT) for native vessel occlusion have generally been performed. A 73 year old female with non-healing ulcer and gangrene of the left lower leg was diagnosed as having infra-inguinal autologous saphenous vein graft occlusion. In this case, surgical repair such as patch angioplasty, interposition graft, or replacement graft did not seem promising because of repeated previous infection in the polytetrafluoroethylene (PTFE) vascular prosthesis and absence of available autologous vein due to past surgery. Moreover, there was no chance of crossing the native vessel, since the proximal superficial femoral artery (SFA) had already been resected. Thus, EVT was performed for the occluded autologous vein graft, implanting multiple self expanding bare nitinol stents throughout the vein graft achieving complete revascularization, good medium term patency, and dramatically improved wound healing. Endovascular recanalization using multiple bare stents could be an alternative treatment for infra-inguinal autologous vein graft occlusion.

  20. Prospective repair of Ventral Hernia Working Group type 3 and 4 abdominal wall defects with condensed polytetrafluoroethylene (MotifMESH) mesh.

    PubMed

    Cheesborough, Jennifer E; Liu, Jing; Hsu, Derek; Dumanian, Gregory A

    2016-01-01

    Treatment of clean-contaminated and contaminated ventral hernia defects remains controversial. Newer prosthetic materials may play an important role in these patients. Ten patients with Ventral Hernia Working Group types 3 and 4 were prospectively enrolled and subsequently treated with direct supported repairs with condensed fenestrated polytetrafluoroethylene mesh. The primary outcome was hernia occurrence at 1 year after surgery. Secondary outcomes included surgical site infection, surgical site occurrence, medical complications, pain, and other patient-reported outcomes. There were no immediate postoperative infections and one minor postoperative hematoma treated in the office. One patient required delayed mesh removal 9 months after placement. Importantly, the mesh removal procedure was straightforward because of the material properties of the mesh. Of the 9 patients still with mesh, there were no hernia recurrences at the repair site with one full year of follow-up. Contaminated and clean-contaminated abdominal wall defects can be effectively and durably treated with condensed polytetrafluoroethylene mesh. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  1. Subtask 1.15-Passive Diffusion Sample Bags Made from Expanded Polytetrafluorethylene (ePTFE) to Measure VOC Concentrations in Groundwater

    SciTech Connect

    Barry W. Botnen

    2006-08-01

    With laboratory testing of expanded polytetrafluoroethylene (ePTFE) membranes complete, collected data support that volatile organic compound (VOC) molecules will readily diffuse across ePTFE membranes. Membrane samples, supplied by BHA Technologies (GE Osmonics), were tested to determine diffusion rates for VOCs in groundwater. Tests were conducted using membranes with two different pore sizes, with and without thermally laminated spun bond backing, and multiple concentrations of contaminated groundwater. Results suggest that typical residence times associated with traditional samplers constructed of polyethylene (2 weeks) can be reduced by 1 week using ePTFE membranes (reducing project costs) and that VOCs will diffuse more readily at lower temperatures (2.2-3.3 C) across ePTFE materials.

  2. Shell may expand detergent alcohols

    SciTech Connect

    1996-10-23

    Shell Chemical is studying plans to expand detergent alcohols capacity in the US, CW has learned. The company is considering adding capacity for about 80 million lbs/year. If the project is approved, it would be implemented at the company`s Geismar, LA site. Shell will make a final decision on whether to proceed with the project within six months. It has been rumored to be considering a capacity addition as a result of tightening supply of natural and synthetic detergent alcohols.

  3. Advanced Expander Test Bed Engine

    DTIC Science & Technology

    1992-03-01

    performance data will be provided to NASA -LeRC for verifying the ROCETS computer model and evaluating various RLI0 modifications. 22 SECTION IV CURRENT...RL10 modeling data for the ROCETS computer program. 23 NASA Report Documentation Page Nafi~aj AfWflWuIC Wd Sow@ Ad-lvhlsto, 1 eport No. 2. Government... NASA have identified the need for a new Space Transfer Vehicle (STV) Propulsion System. The new system will be an oxygen/hydrogen expander cycle engine

  4. Unconventional microfluidics: expanding the discipline.

    PubMed

    Nawaz, Ahmad Ahsan; Mao, Xiaole; Stratton, Zackary S; Huang, Tony Jun

    2013-04-21

    Since its inception, the discipline of microfluidics has been harnessed for innovations in the biomedicine/chemistry fields-and to great effect. This success has had the natural side-effect of stereotyping microfluidics as a platform for medical diagnostics and miniaturized lab processes. But microfluidics has more to offer. And very recently, some researchers have successfully applied microfluidics to fields outside its traditional domains. In this Focus article, we highlight notable examples of such "unconventional" microfluidics applications (e.g., robotics, electronics). It is our hope that these early successes in unconventional microfluidics prompt further creativity, and inspire readers to expand the microfluidics discipline.

  5. Semigroup Actions of Expanding Maps

    NASA Astrophysics Data System (ADS)

    Carvalho, Maria; Rodrigues, Fagner B.; Varandas, Paulo

    2017-01-01

    We consider semigroups of Ruelle-expanding maps, parameterized by random walks on the free semigroup, with the aim of examining their complexity and exploring the relation between intrinsic properties of the semigroup action and the thermodynamic formalism of the associated skew-product. In particular, we clarify the connection between the topological entropy of the semigroup action and the growth rate of the periodic points, establish the main properties of the dynamical zeta function of the semigroup action and relate these notions to recent research on annealed and quenched thermodynamic formalism. Meanwhile, we examine how the choice of the random walk in the semigroup unsettles the ergodic properties of the action.

  6. Unconventional microfluidics: expanding the discipline

    PubMed Central

    Nawaz, Ahmad Ahsan; Mao, Xiaole; Stratton, Zackary S.; Huang, Tony Jun

    2014-01-01

    Since its inception, the discipline of microfluidics has been harnessed for innovations in the biomedicine/chemistry fields—and to great effect. This success has had the natural side-effect of stereotyping microfluidics as a platform for medical diagnostics and miniaturized lab processes. But microfluidics has more to offer. And very recently, some researchers have successfully applied microfluidics to fields outside its traditional domains. In this Focus article, we highlight notable examples of such “unconventional” microfluidics applications (e.g., robotics, electronics). It is our hope that these early successes in unconventional microfluidics prompt further creativity, and inspire readers to expand the microfluidics discipline. PMID:23478651

  7. Expanding the repertoire of deadenylases.

    PubMed

    Skeparnias, Ilias; Αnastasakis, Dimitrios; Shaukat, Athanasios-Nasir; Grafanaki, Katerina; Stathopoulos, Constantinos

    2017-03-07

    Deadenylases belong to an expanding family of exoribonucleases involved mainly in mRNA stability and turnover, with the exception of PARN which has additional roles in the biogenesis of several important non-coding RNAs, including miRNAs and piRNAs. Recently, PARN in C. elegans and its homolog PNLDC1 in B. mori were reported as the elusive trimmers mediating piRNA biogenesis. In addition, characterization of mammalian PNLDC1 in comparison to PARN, showed that is specifically expressed in embryonic stem and germ cells, as well as during early embryo development. Moreover, its expression is correlated with epigenetic events mediated by the de novo DNMT3b methyltransferase and knockdown in stem cells upregulates important genes that regulate multipotency. The recent data suggest that at least some new deadenylases may have expanded roles in cell metabolism as regulators of gene expression, through mRNA deadenylation, ncRNAs biogenesis and ncRNA-mediated mRNA targeting, linking essential mechanisms that regulate epigenetic control and transition events during differentiation. The possible roles of mammalian PNLDC1 along those dynamic networks are discussed in the light of new extremely important findings.

  8. Expanding Your School. Is It Worth It?

    ERIC Educational Resources Information Center

    Friedberg, Richard; And Others

    1986-01-01

    Identifies concerns and potential problems that will surface while trying to expand a school. The decision to expand and the criterion to be considered in reaching that critical judgment is comprehensively discussed. (CT)

  9. Expanding Your School. Is It Worth It?

    ERIC Educational Resources Information Center

    Friedberg, Richard; And Others

    1986-01-01

    Identifies concerns and potential problems that will surface while trying to expand a school. The decision to expand and the criterion to be considered in reaching that critical judgment is comprehensively discussed. (CT)

  10. Bigelow Expandable Activity Module (BEAM) Monitoring System

    NASA Technical Reports Server (NTRS)

    Wells, Nathan

    2017-01-01

    What is Bigelow Expandable Activity Module (BEAM)? The Bigelow Expandable Activity Module (BEAM) is an expandable habitat technology demonstration on ISS; increase human-rated inflatable structure Technology Readiness Level (TRL) to level 9. NASA managed ISS payload project in partnership with Bigelow Aerospace. Launched to ISS on Space X 8 (April 8th, 2016). Fully expanded on May 28th, 2016. Jeff Williams/Exp. 48 Commander first entered BEAM on June 5th, 2016.

  11. Expandable Lunar Habitat (X-Hab)

    NASA Image and Video Library

    2010-09-23

    Expandable Lunar Habitat (X-Hab).ILC Dover, under contract by NASA Langley Research Center, and in cooperation with NASA Johnson Space Center has designed and manufactured an expandable lunar habitat. This cylindrical habitat, or Expandable Lunar Habitat (X-Hab) is a hybrid system with two hard end caps and a deployable softgoods section in the center.

  12. Balloon-expandable covered stent therapy of complex endovascular pathology.

    PubMed

    Giles, Heath; Lesar, Christopher; Erdoes, Luke; Sprouse, Richard; Myers, Stuart

    2008-11-01

    The current study was designed to investigate our hypotheses that balloon-expandable covered stents display acceptable function over longitudinal follow-up in patients with complex vascular pathology and provide a suitable alternative for the treatment of recurrent in-stent restenosis. All stents were Atrium iCast, which is a balloon-mounted, polytetrafluoroethylene-covered stent with a 6F/7F delivery system. A retrospective review was performed of 49 patients with 66 stented lesions. Data were analyzed with life tables and t-tests. The most commonly treated vessels were the iliac (61%) and renal (24%) arteries. Indications for covered stent placement were unstable atheromatous lesions (50%), recurrent in-stent restenosis (24%), aneurysm (8%), aortic bifurcation reconstruction (7.5%), dissection (4.5%), endovascular aneurysm repair-related (4.5%), and stent fracture (1.5%). Patency was assessed by angiogram or duplex ultrasonography. The primary end point was patency and secondary end points were technical success and access-site complications. Mean follow-up was 13 months (range 1.5-25). The technical success rate was 97%. Unsuccessful outcomes were due to deployment error (n=1) and stent malpositioning (n=1). The cohort (n=64) 6- and 12-month primary patency rates were 96% and 84%, respectively. Twelve-month assisted primary patency was 98%. Iliac artery stents (n=38) had a primary patency of 97% at 6 months and 84% at 12 months with an assisted primary patency of 100% at 12 months. Renal artery stents (n=16) had a primary patency of 92% at 6 months and 72% at 12 months with an assisted primary patency of 92% at 6 and 12 months. Stents placed for recurrent in-stent restenosis (n=16) had a primary patency of 85%, assisted primary patency of 93%, and a 15% restenosis rate at 12 months. Specifically, stents placed for renal artery recurrent in-stent restenosis (n=10) had a primary patency of 73%, assisted primary patency of 82%, and a restenosis rate of 27%. The

  13. Leak detection with expandable coatings

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Developed and evaluated is a system for leak detection that can be easily applied over separable connectors and that expands into a bubble or balloon if a leak is present. This objective is accomplished by using thin films of Parafilm tape wrapped over connectors, which are then overcoated with a special formulation. The low yield strength and the high elongation of the envelope permit bubble formation if leakage occurs. This system is appropriate for welds and other hardware besides separable connectors. The practical limit of this system appears to be for leaks exceeding 0.000001 cc/sec. If this envelope is used to trap gases for mass spectrometer inspection, leaks in the range of ten to the minus 8th power cc/sec. may be detectable.

  14. OCT Expanded Clinical Data Analysis

    NASA Technical Reports Server (NTRS)

    Van Baalen, Mary; Tafreshi, Ali; Patel, Nimesh; Young, Millennia; Mason, Sara; Otto, Christian; Samuels, Brian; Koslovsky, Matthew; Schaefer, Caroline; Taiym, Wafa; hide

    2017-01-01

    Vision changes identified in long duration space fliers has led to a more comprehensive clinical monitoring protocol. Optical Coherence Tomography (OCT) was recently implemented on board the International Space Station in 2013. NASA is collaborating with Heidelberg Engineering to expand our current OCT data analysis capability by implementing a volumetric approach. Volumetric maps will be created by combining the circle scan, the disc block scan, and the radial scan. This assessment may provide additional information about the optic nerve and further characterize changes related microgravity exposure. We will discuss challenges with collection and analysis of OCT data, present the results of this reanalysis and outline the potential benefits and limitations of the additional data.

  15. Expanding Human Cognition and Communication

    SciTech Connect

    Spohrer, Jim; Pierce, Brian M.; Murray, Cherry A.; Golledge, Reginald G.; Horn, Robert E.; Turkle, Sherry; Yonas, Gerold; Glicken Turnley, Jessica; Pollack, Jordan; Burger, Rudy; Robinett, Warren; Wilson, Larry Todd; Bainbridge, W. S.; Canton, J.; Kuekes, P.; Loomis, J.; Penz, P.

    2013-01-01

    To be able to chart the most profitable future directions for societal transformation and corresponding scientific research, five multidisciplinary themes focused on major goals have been identified to fulfill the overall motivating vision of convergence described in the previous pages. The first, “Expanding Human Cognition and Communication,” is devoted to technological breakthroughs that have the potential to enhance individuals’ mental and interaction abilities. Throughout the twentieth century, a number of purely psychological techniques were offered for strengthening human character and personality, but evaluation research has generally failed to confirm the alleged benefits of these methods (Druckman and Bjork 1992; 1994). Today, there is good reason to believe that a combination of methods, drawing upon varied branches of converging science and technology, would be more effective than attempts that rely upon mental training alone.

  16. Shear Acceleration in Expanding Flows

    NASA Astrophysics Data System (ADS)

    Rieger, F. M.; Duffy, P.

    2016-12-01

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi-Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).

  17. Deep Brain Stimulation: Expanding Applications

    PubMed Central

    TEKRIWAL, Anand; BALTUCH, Gordon

    2015-01-01

    For over two decades, deep brain stimulation (DBS) has shown significant efficacy in treatment for refractory cases of dyskinesia, specifically in cases of Parkinson's disease and dystonia. DBS offers potential alleviation from symptoms through a well-tolerated procedure that allows personalized modulation of targeted neuroanatomical regions and related circuitries. For clinicians contending with how to provide patients with meaningful alleviation from often debilitating intractable disorders, DBSs titratability and reversibility make it an attractive treatment option for indications ranging from traumatic brain injury to progressive epileptic supra-synchrony. The expansion of our collective knowledge of pathologic brain circuitries, as well as advances in imaging capabilities, electrophysiology techniques, and material sciences have contributed to the expanding application of DBS. This review will examine the potential efficacy of DBS for neurologic and psychiatric disorders currently under clinical investigation and will summarize findings from recent animal models. PMID:26466888

  18. Preventive Ethics Through Expanding Education.

    PubMed

    Ho, Anita; MacDonald, Lisa Mei-Hwa; Unger, David

    2016-03-01

    Healthcare institutions have been making increasing efforts to standardize consultation methodology and to accredit both bioethics training programs and the consultants accordingly. The focus has traditionally been on the ethics consultation as the relevant unit of ethics intervention. Outcome measures are studied in relation to consultations, and the hidden assumption is that consultations are the preferred or best way to address day-to-day ethical dilemmas. Reflecting on the data from an internal quality improvement survey and the literature, we argue that having general ethics education as a key function of ethics services may be more important in meeting the contemporaneous needs of acute care settings. An expanded and varied ethics education, with attention to the time constraints of healthcare workers' schedules, was a key recommendation brought forward by survey respondents. Promoting ethical reflection and creating a culture of ethics may serve to prevent ethical dilemmas or mitigate their effects.

  19. Expanding the Trilinos developer community.

    SciTech Connect

    Heroux, Michael Allen

    2010-10-01

    The Trilinos Project started approximately nine years ago as a small effort to enable research, development and ongoing support of small, related solver software efforts. The 'Tri' in Trilinos was intended to indicate the eventual three packages we planned to develop. In 2007 the project expanded its scope to include any package that was an enabling technology for technical computing. Presently the Trilinos repository contains over 55 packages covering a broad spectrum of reusable tools for constructing full-featured scalable scientific and engineering applications. Trilinos usage is now worldwide, and many applications have an explicit dependence on Trilinos for essential capabilities. Users come from other US laboratories, universities, industry and international research groups. Awareness and use of Trilinos is growing rapidly outside of Sandia. Members of the external research community are becoming more familiar with Trilinos, its design and collaborative nature. As a result, the Trilinos project is receiving an increasing number of requests from external community members who want to contribute to Trilinos as developers. To-date we have worked with external developers in an ad hoc fashion. Going forward, we want to develop a set of policies, procedures, tools and infrastructure to simplify interactions with external developers. As we go forward with multi-laboratory efforts such as CASL and X-Stack, and international projects such as IESP, we will need a more streamlined and explicit process for making external developers 'first-class citizens' in the Trilinos development community. This document is intended to frame the discussion for expanding the Trilinos community to all strategically important external members, while at the same time preserving Sandia's primary leadership role in the project.

  20. An experimental reciprocating expander for cryocooler application

    NASA Technical Reports Server (NTRS)

    Minta, M.; Smith, J. L., Jr.

    1985-01-01

    An experimental reciprocating expander was designed with features appropriate for cryocooler cycles. The expander has a displacer piston, simple valves, and a hydraulic/pneumatic stroking mechanism. The expander has a valve in head configuration with the valves extending out the bottom of the vacuum enclosure while the piston extends out the top. The expander was tested using a CTI 1400 liquefier to supply 13 atm in the temperature range 4.2 to 12 K. Expander efficiency was measured in the range 84 to 93% while operating the apparatus as a supercritical wet expander and in the range 91 to 93% aa a single phase expander. The apparatus can also be modified to operate as a compressor for saturated helium vapor.

  1. Production of biodiesel using expanded gas solvents

    SciTech Connect

    Ginosar, Daniel M; Fox, Robert V; Petkovic, Lucia M

    2009-04-07

    A method of producing an alkyl ester. The method comprises providing an alcohol and a triglyceride or fatty acid. An expanding gas is dissolved into the alcohol to form a gas expanded solvent. The alcohol is reacted with the triglyceride or fatty acid in a single phase to produce the alkyl ester. The expanding gas may be a nonpolar expanding gas, such as carbon dioxide, methane, ethane, propane, butane, pentane, ethylene, propylene, butylene, pentene, isomers thereof, and mixtures thereof, which is dissolved into the alcohol. The gas expanded solvent may be maintained at a temperature below, at, or above a critical temperature of the expanding gas and at a pressure below, at, or above a critical pressure of the expanding gas.

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

    NASA Astrophysics Data System (ADS)

    Jeong, Gisu; Kim, MinJoong; Han, Junyoung; Kim, Hyoung-Juhn; Shul, Yong-Gun; Cho, EunAe

    2016-08-01

    Although high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) have a high carbon monoxide tolerance and allow for efficient water management, their practical applications are limited due to their lower performance than conventional low-temperature PEMFCs. Herein, we present a high-performance membrane-electrode assembly (MEA) with an optimal polytetrafluoroethylene (PTFE) content for HT-PEMFCs. Low or excess PTFE content in the electrode leads to an inefficient electrolyte distribution or severe catalyst agglomeration, respectively, which hinder the formation of triple phase boundaries in the electrodes and result in low performance. MEAs with PTFE content of 20 wt% have an optimal pore structure for the efficient formation of electrolyte/catalyst interfaces and gas channels, which leads to high cell performance of approximately 0.5 A cm-2 at 0.6 V.

  3. Effect of polytetrafluoroethylene-treatment and microporous layer-coating on the in-plane permeability of gas diffusion layers used in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ismail, M. S.; Damjanovic, T.; Ingham, D. B.; Ma, L.; Pourkashanian, M.

    The in-plane permeability has been experimentally estimated for a number of carbon substrates and microporous layer (MPL)-coated gas diffusion layers (GDLs) as used in proton exchange membrane (PEM) fuel cells. The results show that the in-plane permeability of the tested carbon substrates decreases with increasing polytetrafluoroethylene (PTFE) loading and, in contrast, the greater is the PTFE loading in the MPL, the greater is the permeability. It has been shown that the in-plane permeability of the carbon substrates is reduced by an order of magnitude if they are coated with MPLs. Further, the permeability is different from one in-plane principal direction to another by a factor of about two. Finally, ignoring the inertial terms (for the reported flow rates) and the compressibility of the flowing air results in significant errors in the obtained values of the permeability.

  4. Infrared, spectral, directional-hemispherical reflectance of fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating.

    PubMed

    Persky, Merle J; Szczesniak, Martin

    2008-04-01

    Infrared, spectral, directional-hemispherical reflectivity measurements of polished fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating are provided. The reflectance was measured with an estimated accuracy of 0.01 to 0.02 units and a precision of 0.005 units. All the surfaces were measured at ambient temperatures. Additionally, the chrome oxide ceramic particle surface was measured at 486 K and the Pyromark 2500 at four temperatures to 877 K. Polarization measurements are also provided for fused silica, Duraflect, chrome oxide ceramic particle surface, and Pyromark 2500 paint. Separate diffuse and specular reflectance components for the Duraflect and chrome oxide ceramic surfaces are included. Fresnel-based predictions for fused silica parallel and perpendicular polarized reflections are compared to measurements. It is notable that the Pyromark 2500 and chrome oxide ceramic particle surfaces exhibit a significant lack of manufacturing repeatability.

  5. Infrared, spectral, directional-hemispherical reflectance of fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating

    NASA Astrophysics Data System (ADS)

    Persky, Merle J.; Szczesniak, Martin

    2008-04-01

    Infrared, spectral, directional-hemispherical reflectivity measurements of polished fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating are provided. The reflectance was measured with an estimated accuracy of 0.01 to 0.02 units and a precision of 0.005 units. All the surfaces were measured at ambient temperatures. Additionally, the chrome oxide ceramic particle surface was measured at 486 K and the Pyromark 2500 at four temperatures to 877 K. Polarization measurements are also provided for fused silica, Duraflect, chrome oxide ceramic particle surface, and Pyromark 2500 paint. Separate diffuse and specular reflectance components for the Duraflect and chrome oxide ceramic surfaces are included. Fresnel-based predictions for fused silica parallel and perpendicular polarized reflections are compared to measurements. It is notable that the Pyromark 2500 and chrome oxide ceramic particle surfaces exhibit a significant lack of manufacturing repeatability.

  6. Successful recanalization of a left circumflex artery jailed with a polytetrafluoroethylene-covered stent after coronary perforation during stent implantation in the left main bifurcation.

    PubMed

    Taniguchi, Norimasa; Takahashi, Akihiko; Mizuguchi, Yukio; Yamada, Takeshi; Hata, Tetsuya; Nakajima, Shunsuke

    2015-01-01

    An 88-year-old woman underwent emergency percutaneous coronary intervention (PCI) to treat circulatory collapse with severe stenosis in the distal left main coronary artery (LMCA). After 3.5/18-mm stent deployment from the LMCA to the left anterior descending artery (LAD), coronary perforation occurred in the LAD ostium. Therefore, we implanted a polytetrafluoroethylene (PTFE)-covered stent crossing over the left circumflex artery (LCX), and achieved successful hemostasis. Additional PCI was undertaken to recanalize the LCX. A Confienza 8-20 guidewire was able to penetrate the wall of the PTFE-covered stent, and coronary flow was successfully recovered after deployment of a 2.5/8-mm stent in the proximal LCX.

  7. Model of An Expanding Heliosphere

    NASA Astrophysics Data System (ADS)

    Song, P.; Vasyliunas, V. M.

    2015-12-01

    Conventional models of the heliosphere assume that the heliopause is formed, similarly to the magnetopause of a planet, at the location where the total pressure of the exterior (interstellar) medium is balanced by the total pressure of the interior (heliospheric) medium. The heliosphere, however, differs greatly from a planetary magnetosphere in being dominated by a continuous interior source of mass (present in some planetary magnetospheres, notably Jupiter and Saturn, but not to anything like the same extent), and it differs as well from systems with large interior mass sources such as comets (to which it has also been compared) in being threaded by magnetic flux from its central object (the Sun). The heliosphere must thus expand continually as more and more mass is put into it by the solar wind, with the heliopause marching into the interstellar medium at some non-zero speed while maintaining the plasma total (thermal plus magnetic) pressure equal to that of the interstellar medium. A steady state heliosphere is, strictly speaking, impossible unless and until the distinction between the heliospheric and the interstellar medium has disappeared. The geometry of the expansion can be visualized in different ways. Conventionally it is taken for granted that the expansion is deflected by interstellar flow sideways and channeled into an extended wake/tail region, the rest of the heliosphere being in apparently steady state. Even if this may occur, it would be at a distance much larger than commonly assumed. We explore the alternative possibility of a heliosphere expanding predominantly in the radial direction and describe some of its properties. The input from solar wind and interplanetary magnetic field during each solar cycle forms a shell, with subsequent cycles adding shells of alternating magnetic polarities. The ultimate extent of the heliosphere (in all directions) and the number of shells can be limited by the time until either the solar output or the

  8. Cat Scratch Disease: Expanded Spectrum

    PubMed Central

    Aziz, Hassan A.; Plesec, Thomas P.; Sabella, Camille; Udayasankar, Unni K.; Singh, Arun D.

    2016-01-01

    Background To expand the spectrum of ophthalmic manifestations in cat scratch disease. Methods Case report. Results A 7-year-old male was referred for evaluation of his left optic disc after failing vision screening test at school. His visual acuity was 20/20 OD and light perception OS. Fundus examination showed a left optic disc lesion associated with an exudative retinal detachment and vitreous seeding. Ultrasonography revealed a 7 × 7.5 × 3.8 mm lesion with a possible 6.3 mm of retrolaminar extension into the substance of the optic nerve. Brain MRI did not show evidence of optic nerve involvement but revealed a 6-mm nodule of the pineal gland suggestive of a pineoblastoma. Enucleation was performed and histopathology revealed a suppurative granulomatous inflammation suggestive of Bartonella infection. Upon further questioning, the patient had recent exposure to kittens with areas of cat scratches along both of his arms. He was subsequently referred to and treated with a 2-week course of trimethoprim-sulfamethoxazole and rifampin by the pediatric infectious disease specialist. Repeat brain MRI showed interval total resolution of enlarged pineal gland. Conclusion: Optic nerve granulomas are a rare presentation of cat scratch disease and could potentially masquerade as retinoblastoma. PMID:27843905

  9. Male contraception: expanding reproductive choice.

    PubMed

    Rajalakshmi, M

    2005-11-01

    The development of steroid-based oral contraceptives had revolutionized the availability of contraceptive choice for women. In order to expand the contraceptive options for couples by developing an acceptable, safe and effective male contraceptive, scientists have been experimenting with various steroidal/non-steroidal regimens to suppress testicular sperm production. The non-availability of a long-acting androgen was a limiting factor in the development of a male contraceptive regimen since all currently tested anti-spermatogenic agents also concurrently decrease circulating testosterone levels. A combination regimen of long-acting progestogen and androgen would have advantage over an androgen-alone modality since the dose of androgen required would be much smaller in the combination regimen, thereby decreasing the adverse effects of high steroid load. The progestogen in the combination regimen would act as the primary anti-spermatogenic agent. Currently, a number of combination regimens using progestogen or GnRH analogues combined with androgen are undergoing trials. The side effects of long-term use of androgens and progestogens have also undergone evaluation in primate models and the results of these studies need to be kept in view, while considering steroidal regimens for contraceptive use in men. Efforts are also being made to popularize non-scalpel vasectomy and to develop condoms of greater acceptability. The development of contraceptive vaccines for men, using sperm surface epitopes not expressed in female reproductive tract as source, still requires considerable research efforts.

  10. Chronic Expanding Hematoma Following Abdominoplasty.

    PubMed

    Tatsuta, Sayo; Morioka, Daichi; Murakami, Naoki; Ohkubo, Fumio

    2017-02-01

    Chronic expanding hematoma (CEH) is a relatively rare complication of trauma or surgery. We report a patient with CEH as a late complication of abdominoplasty. A 58-year-old woman underwent conventional abdominoplasty and thereafter refused to use a compression binder, citing discomfort. One month postoperatively, she presented with a gradually enlarging, painful abdominal mass. The results of ultrasonography and computed tomography were highly suspicious for CEH. The lesion was completely removed, together with surrounding fibrous tissue. Histopathology revealed a chronic hemorrhage collection with a fibrous capsule, consistent with CEH. This condition as a late complication of abdominoplasty has not previously been reported in the literature. However, an online medical consultation site features several abdominoplasty patients asking about persistent hematomas that sound suspicious for CEH. CEH might be underdiagnosed by surgeons. Although a postoperative binder may increase the risk of skin necrosis and deep vein thrombosis, appropriate compression treatment is necessary to prevent hematoma formation. Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

  11. Cat Scratch Disease: Expanded Spectrum.

    PubMed

    Aziz, Hassan A; Plesec, Thomas P; Sabella, Camille; Udayasankar, Unni K; Singh, Arun D

    2016-10-01

    To expand the spectrum of ophthalmic manifestations in cat scratch disease. Case report. A 7-year-old male was referred for evaluation of his left optic disc after failing vision screening test at school. His visual acuity was 20/20 OD and light perception OS. Fundus examination showed a left optic disc lesion associated with an exudative retinal detachment and vitreous seeding. Ultrasonography revealed a 7 × 7.5 × 3.8 mm lesion with a possible 6.3 mm of retrolaminar extension into the substance of the optic nerve. Brain MRI did not show evidence of optic nerve involvement but revealed a 6-mm nodule of the pineal gland suggestive of a pineoblastoma. Enucleation was performed and histopathology revealed a suppurative granulomatous inflammation suggestive of Bartonella infection. Upon further questioning, the patient had recent exposure to kittens with areas of cat scratches along both of his arms. He was subsequently referred to and treated with a 2-week course of trimethoprim-sulfamethoxazole and rifampin by the pediatric infectious disease specialist. Repeat brain MRI showed interval total resolution of enlarged pineal gland. Conclusion: Optic nerve granulomas are a rare presentation of cat scratch disease and could potentially masquerade as retinoblastoma.

  12. FMC: Expanding its chemical universe

    SciTech Connect

    Wood, A.

    1992-12-23

    With a portfolio ranging from defense systems to gold to food machinery - the source of its name - FMC Corp. (Chicago) ranks as a diversified conglomerate. The company's industrial chemicals operation consists of alkali chemicals, chiefly soda ash and derivatives: peroxygen chemicals, made up of hydrogen peroxide and other peroxygens; and phosphorus chemicals. FMC has about a 30% market share in each of these three. It also includes the Foret (Barcelona) division, part of FMC Europe. Moving lithium into FMC's specialties group reflects the R D-intensive nature of many lithium compounds, explains F. Wyman Morgan, director/group technology for the chemical product and specialty chemicals groups. FMC is also involved in collaborative research programs to develop lithium-based batteries and fuel cells. We have a decentralized business-oriented R D focus, Morgan says. The main thrusts in lithium are in developing organolithiums for drug synthesis. FMC also has a major industrial lithium business; it recently added a new butyl lithium unit in Texas and is looking to expand production through the development of lithium deposits in Latin America. But lithium is growing fastest in the downstream areas, says W. Reginald Hall, v.p. and group manager/specialty chemicals group. It has an unbelievable range of uses, he says, including catalytic applications in the pharmaceuticals industry. We are working on lithium compounds that allow you to drop a functional organic group into a molecule in a reliable way.

  13. Towards expanding megasonic cleaning capability

    NASA Astrophysics Data System (ADS)

    Han, Zhenxing; Ferstl, Berthold; Oetter, Günter; Dietze, Uwe; Samayoa, Martin; Dattilo, Davide

    2016-10-01

    Megasonic cleaning remains the industry's workhorse technology for particle removal on advanced 193i and extreme ultraviolet (EUV) photomasks. Several megasonic cleaning technologies and chemistries have been proposed and implemented over the years in diverse production environments. The operational range of these process technologies, over a wide array of applications, is ultimately defined by measurable capability limits. As geometries continue to scale-down and new materials are introduced, existing cleaning technologies will naturally fade out of range and new capability is ultimately required. This paper presents a novel fundamental approach for expanding cleaning capability by use of high-frequency megasonics and tenside-based additives (BASF SELECTIPUR C-series). To this end, a sonoluminescence-based experimental test bench was configured to characterize and study the effects of various process parameters on cleaning performance, with a particular emphasis on cavitation-induced damage and enhancement of particle removal capabilities. The results from the fundamental studies provide a path forward towards delivering new cleaning capability by enabling high-frequency megasonic systems and tenside-based additives.

  14. The expanding role of immunotherapy.

    PubMed

    Martin-Liberal, Juan; Ochoa de Olza, María; Hierro, Cinta; Gros, Alena; Rodon, Jordi; Tabernero, Josep

    2017-02-11

    The use of agents able to modulate the immune system to induce or potentiate its anti-tumour activity is not a new strategy in oncology. However, the development of new agents such as immune checkpoint inhibitors has achieved unprecedented efficacy results in a wide variety of tumours, dramatically changing the landscape of cancer treatment in recent years. Ipilimumab, nivolumab, pembrolizumab or atezolizumab are now standard of care options in several malignancies and new indications are being approved on a regular basis in different tumours. Moreover, there are many other novel immunotherapy strategies that are currently being assessed in clinical trials. Agonists of co-stimulatory signals, adoptive cell therapies, vaccines, virotherapy and others have raised interest as therapeutic options against cancer. In addition, many of these novel approaches are being developed both in monotherapy and as part of combinatory regimes in order to synergize their activity. The results from those studies will help to define the expanding role of immunotherapy in cancer treatment in a forthcoming future.

  15. Expanding the yeast prion world

    PubMed Central

    Suzuki, Genjiro; Tanaka, Motomasa

    2013-01-01

    Mammalian and fungal prion proteins form self-perpetuating β-sheet-rich fibrillar aggregates called amyloid. Prion inheritance is based on propagation of the regularly oriented amyloid structures of the prion proteins. All yeast prion proteins identified thus far contain aggregation-prone glutamine/asparagine (Gln/Asn)-rich domains, although the mammalian prion protein and fungal prion protein HET-s do not contain such sequences. In order to fill this gap, we searched for novel yeast prion proteins lacking Gln/Asn-rich domains via a genome-wide screen based on cross-seeding between two heterologous proteins and identified Mod5, a yeast tRNA isopentenyltransferase, as a novel non-Gln/Asn-rich yeast prion protein. Mod5 formed self-propagating amyloid fibers in vitro and the introduction of Mod5 amyloids into non-prion yeast induced dominantly and cytoplasmically heritable prion state [MOD+], which harbors aggregates of endogenous Mod5. [MOD+] yeast showed an increased level of membrane lipid ergosterol and acquired resistance to antifungal agents. Importantly, enhanced de novo formation of [MOD+] was observed when non-prion yeast was grown under selective pressures from antifungal drugs. Our findings expand the family of yeast prions to non-Gln/Asn-rich proteins and reveal the acquisition of a fitness advantage for cell survival through active prion conversion. PMID:23117914

  16. Attitudes toward expanding nurses' authority.

    PubMed

    Kerzman, Hana; Van Dijk, Dina; Eizenberg, Limor; Khaikin, Rut; Phridman, Shoshi; Siman-Tov, Maya; Goldberg, Shoshi

    2015-01-01

    In recent years, an increasing number of care procedures previously under the physician's authority have been placed in the hands of registered nurses. The purpose of this study was to examine the attitudes of nurses towards expanding nurses' authority and the relationships between these attitudes and job satisfaction facets, professional characteristics, and demographics. A cross-sectional study was conducted between 2010 and 2011 in three major medical centers in Israel. Participants included 833 nurses working in 89 departments. Attitudes toward the expansion of nurses' authority were assessed by self-report questionnaire, as well as job satisfaction facets including perception of professional autonomy, nurse-physician working relations, workload and burnout, perceptions of quality of care, and nursing staff satisfaction at work. Nurses reported positive attitudes toward the expansion of nurses' authority and moderate attitudes for interpretation of diagnostic tests in selected situations. The results of multivariate regression analyses demonstrate that the nurses' satisfaction from professional autonomy and work relations were the most influential factors in explaining their attitudes toward the expansion of nurses' authority. In addition, professionally young nurses tend to be more positive regarding changes in nurses' authority. In the Israeli reality of a nurse's shortage, we are witnessing professional transitions toward expansion of the scope of nurses' accountability and decision-making authority. The current research contributes to our understanding of attitudes toward the expansion of nurses' authority among the nursing staffs. The findings indicate the necessity of redefining the scope of nursing practice within the current professional context.

  17. Expanding discourse repertoires with hybridity

    NASA Astrophysics Data System (ADS)

    Kelly, Gregory J.

    2012-09-01

    In "Hybrid discourse practice and science learning" Kamberelis and Wehunt present a theoretically rich argument about the potential of hybrid discourses for science learning. These discourses draw from different forms of "talk, social practice, and material practices" to create interactions that are "intertextually complex" and "interactionally dynamic." The hybrid discourse practices are described as involving the dynamic interplay of at least three key elements: "the lamination of multiple cultural frames, the shifting relations between people and their discourse, and the shifting power relations between and among people." Each of these elements requires a respective unit of analysis and are often mutually reinforcing. The authors present a theoretically cogent argument for the study of hybrid discourse practices and identify the potential such discourses may have for science education. This theoretical development leads to an analysis of spoken and written discourse around a set of educational events concerning the investigation of owl pellets by two fifth grade students, their classmates, and teacher. Two discourse segments are presented and analyzed by the authors in detail. The first is a discourse analysis of the dissection of the owl pellet by two students, Kyle and Max. The second analysis examines the science report of these same two students. In this article, I pose a number of questions about the study with the hope that by doing so I expand the conversation around the insightful analysis presented.

  18. Expanding the knowledge translation metaphor.

    PubMed

    Engebretsen, Eivind; Sandset, Tony Joakim; Ødemark, John

    2017-03-13

    Knowledge translation (KT) is a buzzword in modern medical science. However, there has been little theoretical reflection on translation as a process of meaning production in KT. In this paper, we argue that KT will benefit from the incorporation of a more theoretical notion of translation as an entangled material, textual and cultural process. We discuss and challenge fundamental assumptions in KT, drawing on theories of translation from the human sciences. We show that the current construal of KT as separate from and secondary to the original scientific message is close to the now deeply compromised literary view of translation as the simple act of copying the original. Inspired by recent theories of translation, we claim that KT can be more adequately understood in terms of a 'double supplement' - on the one hand, KT offers new approaches to the communication of scientific knowledge to different groups in the healthcare system with the aim of supplementing a lack of knowledge among clinicians (and patients). On the other, it demonstrates that a textual and cultural supplement, namely a concern with target audiences (clinicians and patients), is inevitable in the creation of an 'autonomous' science. Hence, the division between science and its translation is unproductive and impossible to maintain. We discuss some possible implications of our suggested shift in concept by drawing on pharmaceutical interventions for the prevention of HIV as a case. We argue that such interventions are based on a supplementary and paradoxical relation to the target audiences, both presupposing and denying their existence. More sophisticated theories of translation can lay the foundation for an expanded model of KT that incorporates a more adequate and reflective description of the interdependency of scientific, cultural, textual and material practices.

  19. 24 CFR 3285.502 - Expanding rooms.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Optional Features § 3285.502 Expanding rooms. The... the home manufacturer or prepared by a registered professional engineer or registered architect,...

  20. 24 CFR 3285.502 - Expanding rooms.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Optional Features § 3285.502 Expanding rooms. The... the home manufacturer or prepared by a registered professional engineer or registered architect,...

  1. 24 CFR 3285.502 - Expanding rooms.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Optional Features § 3285.502 Expanding rooms. The... the home manufacturer or prepared by a registered professional engineer or registered architect,...

  2. Expanding Enceladus' Impact Crater Database

    NASA Astrophysics Data System (ADS)

    Kirchoff, M. R.; Schenk, P.

    2016-12-01

    Enceladus is a mid-sized, icy satellite of Saturn with a diameter of 500 km. Most of its surface has been modified by the formation of tectonic grooves and ridges throughout Enceladus' history and only a relatively small area of ancient cratered terrain remains - mostly in the northern latitudes. Examining impact crater density variations is currently the only way to constrain how old the cratered terrains are and when tectonic activity occurred. Analyzing crater distributions also provides insight into other types of activity modifying craters, such as viscous relaxation due to increased heat flow and burial by plume material [e.g., 1,2]. Since the original release of our Enceladus crater database in [1], which only covered the trailing hemisphere, there have been several new images from the Cassini Imaging Science Subsystem cameras at pixel scales of 100 m/pixel or better, including complete coverage of the leading hemisphere. Therefore, we are recording the diameter and location of craters 1 km and larger in these new images to expand the areal coverage of the database. We are also aligning the original database to the new coordinate system [3], which has changed by a few degrees longitude and also has a minor latitude shift. Finally, we are adding the following information for all craters: crater morphology, crater degradation (or preservation) class, observer confidence that the feature is a crater, and if the crater is cut by tectonic features. This additional information will increase the scientific usefulness of the crater database. We report on progress and similarity/differences to crater distributions derived in previous work [1,4-6].References: [1] Kirchoff, M. R. & P. Schenk. Icarus 202 (2009): 656-68. [2] Bland, M. T., et al. GRL 39 (2012): L17204, doi:10.1029/2012GL052736. [3] Roatsch, Th., et al. PSS 77 (2013): 118-25. [4] Plescia, J. B. & J. M. Boyce. Nature 301 (1983): 666-70. [5] Pozio, S. & J. S. Kargel. LPSC XXI (1990): 975-76. [6] Kinczyk, M

  3. Expanding your horizons in science and mathematics

    NASA Technical Reports Server (NTRS)

    Palmer, Cynthia E. A.

    1995-01-01

    The purpose of the 'Expanding Your Horizons in Science and Mathematics' program is to interest young women in grades six through twelve in a variety of careers where mathematics and science are important. Progress in encouraging young women to take courses in mathematics, science, and technological subjects is discussed. Also included are adult, student, and organizational information packets used for 'Expanding Your Horizons' conferences.

  4. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

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

  5. Endovascular Treatment of Peripheral Artery Disease with Expanded PTFE-Covered Nitinol Stents: Interim Analysis from a Prospective Controlled Study

    SciTech Connect

    Duda, S.H.; Bosiers, M.; Pusich, B.; Huettl, K.; Oliva, V.; Mueller-Huelsbeck, S.; Bray, A.; Luz, O.; Remy, C.; Hak, J.B.; Beregi, J.-P.

    2002-10-15

    Purpose: Current covered peripheral stent designs have significant drawbacks in terms of stent delivery characteristics and flexibility. The aim of this study was to analyze the technical performance, safety and initial clinical efficacy of expanded polytetrafluoroethylene (PTFE)-covered nitinol stents for arteriosclerotic peripheral artery disease. Methods:Eighty-two patients underwent implantation of PTFE-covered nitinol stents for iliac and/or femoral obstructions. The study was conducted prospectively in seven European centers and one Canadian center. Patients were controlled clinically and by duplex ultrasound follow-up. Data up to discharge were collected in 79 patients. Seventy-four patients have thus far received 1 month follow-up and 32 patients, 6 month follow-up examinations. Results: The average lesion length measured 47 mm for the common and external iliac arteries and 50 mm for the femoral arteries. The mean severity of the stenoses was reduced from 94% to 4% in the iliac arteries and from 98% to 7% in the femoral arteries after stent placement and dilatation. One device deviation (inadvertent stent misplacement) and one puncture-related severe adverse event with formation of a pseudoaneurysm occurred. There were occlusions of the stent in five patients. No infections were noticed. Conclusion: The interim analysis of this trial using PTFE-covered nitinol stents indicates that a strategy using primary implantation of this stent type is technically feasible, has an acceptable safety profile and is effective from a short-term perspective.

  6. ExpandED Schools National Demonstration: Lessons for Scale and Sustainability

    ERIC Educational Resources Information Center

    Russell, Christina A.; Hildreth, Jeanine L.; Stevens, Pamela

    2016-01-01

    The ExpandED Schools model for expanded learning is designed to transform schools by changing the use of time, both as experienced by students in learning and by teachers in instruction. The model is grounded in the belief that strategically adding time to the school day can enhance skills and knowledge and broaden horizons by engaging students in…

  7. Time to Grow: Year Two Report on ExpandED Schools. A TASC Report

    ERIC Educational Resources Information Center

    Traill, Saskia; Brohawn, Katie

    2014-01-01

    An analysis of data from the second year of The After-School Corporation's (TASC's) national demonstration of an expanded school day for elementary and middle school students shows that ExpandED Schools improved school culture, decreased rates of students' chronic absenteeism and helped students develop positive learning habits and attitudes.…

  8. Time to Grow: Year Two Report on ExpandED Schools. A TASC Report

    ERIC Educational Resources Information Center

    Traill, Saskia; Brohawn, Katie

    2014-01-01

    An analysis of data from the second year of The After-School Corporation's (TASC's) national demonstration of an expanded school day for elementary and middle school students shows that ExpandED Schools improved school culture, decreased rates of students' chronic absenteeism and helped students develop positive learning habits and attitudes.…

  9. Optimization of the use of skin expanders.

    PubMed

    Pamplona, D C; Weber, H I; Leta, F R

    2014-11-01

    Skin expansion is a physiological process that is defined as the ability of the human skin to increase its superficial area in response to stress or to a given deformation. Skin expanders are silicon bags that are implanted underneath the skin. Because the skin presents creep or relaxation, the resulting stress decreases after a time due to the imposed deformation. Skin expansions are used to reconstruct burned areas and breasts after a mastectomy or to hide scars. The question that constantly arises during skin expansion is whether it creates a sufficient amount of skin or, in other words, whether the achieved expansion is sufficient to resurface the defect. These questions are answered with information about how much new tissue is required to achieve the reconstruction in a given context and calculating the required tissue (surface area) in relationship with the volume infiltrated. Surface formulas for round and rectangular, and finite elements method for crescent skin expanders are used to calculate the relation between infiltrated volume and surface area. Those results were corrected or validated by an experimental work using 3D scanners to calculate the relation between surface area and internal volumes for the three types of expanders in question. The research provides information to determine the type, number, and volume of skin expanders necessary to obtain an extra amount of skin to repair a specific medical condition and to determine the amount of skin obtained even in cases when the expansion does not come to term. fci, Correcting factor, which corrects the mathematical formulas using the experimental results, for i skin expander; i, geometry of the expander, round (c), rectangular (r), or crescent (cresc/cr); Sd , surface of the defect; Sds , surface area of the donor site; Sfi, surface area obtained using a mathematical calculation for the i skin expander; S¯fi, surface area obtained experimentally for the i skin expander; Sfi∗, corrected surface

  10. 24 CFR 3285.502 - Expanding rooms.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... support and anchoring systems for expanding rooms must be installed in accordance with designs provided by the home manufacturer or prepared by a registered professional engineer or registered architect,...

  11. Dual-action expanded-latch mechanism

    NASA Technical Reports Server (NTRS)

    Spencer, R. A.; Tewell, J. R.; Tobey, W. H.

    1978-01-01

    Single drive actuator operates novel mechanism that expands, attaches to object, and withdraws to latch object firmly to another part. Packaging is extremely simple and compact, and eliminates need for machined parts or close tolerances.

  12. PROLANG: an expandable software in protein chemistry.

    PubMed

    Petrilli, P; Caporale, C; Sepe, C

    1990-04-01

    PROLANG is an improved version of the PROSOFT program. Improvements to the old commands were made and new ones were added, PROLANG is an open software that users with BASIC programming experience can easily expand.

  13. An Expanded Classification of the Plant Kingdom.

    ERIC Educational Resources Information Center

    Rushton, B. S.

    1981-01-01

    Presents an expanded classification of the plant kingdom, emphasizing major evolutionary steps and differences in levels of complexity. Describes subdivisions and suggests that this classification, reflecting unity and diversity, may be logical, understandable, and useful to students. (JN)

  14. Properties of hot expanded liquid aluminum

    SciTech Connect

    Gathers, G.R.; Ross, M.

    1983-07-01

    Measurements of temperature, volume, enthalpy, and electrical resistivity have been made on aluminum expanded isobarically by 50% in volume to temperatures of about 4000/sup 0/K. These measurements are compared with the predictions of liquid-metal pseudopotential theory.

  15. Expanding European markets for immunotherapy drugs.

    PubMed

    1992-11-01

    Exploding markets for immunotherapeutics have hastened research and development of new drugs to treat patients in institutions and at home. Recent figures reveal just how quickly this market is expanding.

  16. Heroin Epidemic Expands Its Grip on America

    MedlinePlus

    ... gov/news/fullstory_164350.html Heroin Epidemic Expands Its Grip on America Use of the narcotic grew ... people transition from painkillers to heroin, Martins explained. It is also related to availability, lower cost and ...

  17. Helical rotary screw expander power system

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.; Sprankle, R. S.

    1974-01-01

    An energy converter for the development of wet steam geothermal fields is described. A project to evaluate and characterize a helical rotary screw expander for geothermal applications is discussed. The helical screw expander is a positive displacement machine which can accept untreated corrosive mineralized water of any quality from a geothermal well. The subjects of corrosion, mineral deposition, the expansion process, and experience with prototype devices are reported.

  18. Joule-Thomson Expander Without Check Valves

    NASA Technical Reports Server (NTRS)

    Chan, C. K.; Gatewood, J. R.

    1989-01-01

    Cooling effected by bidirectional, reciprocating flow of gas. Type of Joule-Thomson (J-T) expander for cryogenic cooling requires no check valves to prevent reverse flow of coolant. More reliable than conventional J-T expander, containing network of check valves, each potential source of failure. Gas flows alternately from left to right and right to left. Heat load cooled by evaporation of liquid from left or right compartment, whichever at lower pressure.

  19. Exceedingly expanded retroauricular flaps for microtia reconstruction.

    PubMed

    Chen, Zhenyu; Zhang, Weina; Huang, Jinjun; Ren, Jizhen; Zhu, Yuehua

    2011-11-01

    The authors propose here a new strategy to obtain exceedingly expanded retroauricular mastoid skin for sufficient coverage of the three-dimensional autogenous costal cartilage framework generally used in auricular reconstruction surgery. From February 2000 to September 2009, 42 microtia reconstructions were performed using this new strategy. Auricular reconstruction was performed in three surgical stages. In the first stage, a 50-ml kidney-shaped expander was inserted subcutaneously in the retroauricular mastoid region. From 5 to 8 ml saline was then injected into the expander every 4 days until the final volume of the expander reached 100-120 ml. In the second stage, we divided the expanded mastoid skin into a superior two-third region (flap A) and an inferior one-third region (flap B, rotation flap). Autogenous costal cartilage framework was then enveloped by these expanded flaps. Tragus construction and conchal excavation was performed in the third stage. All patients were followed up from 6 months to 4 years after reconstruction. A total of 36 cases reported to be satisfied with the appearance of good shape, accurate size, right orientation, and duplication of well-detailed structures. Further revision was requested by six of the total. Complications in this series includes one case of haematoma, two cases of partial evection of the expanded skin and two cases of partial skin necrosis of the helix. All the complications were treated appropriately. Exceeding expansion can provide sufficient retroauricular non-hair-bearing skin tissues for draping the auricular cartilage framework. Skin grafts and retroauricular fascial flap are not needed any more. Patients are usually satisfied with their reconstructive auricles as regards the size, location, projection, convolution, skin-colour matching, etc. Exceedingly expanded retroauricular flaps are the appropriate envelope for the auricular cartilage framework. Copyright © 2011 British Association of Plastic

  20. Hand-Operated Hydraulic Tube Expander

    NASA Technical Reports Server (NTRS)

    Hagan, David W.; Wolff, Edwin D.

    1995-01-01

    Hand-operated tool expands end portion of narrow metal or plastic tube to slightly larger diameter. Used on tubes with original inner diameters as small as 0.060 in. Includes replaceable tip comprising ferrule and tubular expansion sleeve sized for sliding fit into tube to be expanded. Expansion sleeve swells in response to internal hydraulic pressure generated by turning handle and thereby advancing piston.

  1. Kinetics of a methyl methacrylate polymerization initiated by the stable free radicals in irradiated polytetrafluoroethylene and properties of the resultant graft polymer

    SciTech Connect

    Donato, K.A.E.

    1987-01-01

    The kinetics of the polymerization of methyl methacrylate (MMA) initiated by the stable free radicals in commercially available irradiated polytetrafluoroethylene micropowder and the rheological, thermal, chemical, and mechanical properties of the resultant graft polymer are described. Test tube runs using different ratios of MMA to PTFE were made to determine the feasibility of the reaction and optimum reaction conditions. The amount of graft produced was equal to the weight gain of the solids after removal of the adventitious homopolymer by extraction in acetone. Test quantities of material were produced in a 500 milliliter agitated reactor. A higher ratio of PTFE to excess MMA and longer reaction times result in higher conversion in test tubes. A kinetic model was developed to relate the original concentration of PTFE free radical to the amount of MMA polymer. Graft polymer containing PTFE micropowder, PMMA graft, and PMMA homopolymer in a ratio of 18:5:1 was used for property characterization. The graft material extrudes well at 513K and has a viscosity comparable to that of PMMA homopolymer. The material is stable upon re-extrusion. DSC thermograms show that the heat of transition of the PTFE melting peak is proportional to the amount of PTFE in the sample. Good solvents for PMMA are detrimental to the structural integrity of the graft extrudate; heat treatment improves the chemical resistance. The PTFE block controls the mechanical properties of the graft.

  2. High-Pressure-High Temperature (HP-HT) Stability of Polytetrafluoroethylene: Raman Spectroscopic Study Up to 10 GPa and 600 ℃.

    PubMed

    Likhacheva, Anna Yu; Chanyshev, Artem D; Goryainov, Sergey V; Rashchenko, Sergey V; Litasov, Konstantin D

    2017-01-01

    The increasing demand for use of polymers at extreme conditions makes important the exploration of their behavior in a wide pressure and temperature range, which remains unknown for polytetrafluoroethylene (PTFE), one of the most common materials. An in situ Raman spectroscopic study of PTFE shows that it is stable within the range of 2-6 GPa at 500 ℃ and up to 12 GPa at 400 ℃. At T > 500 ℃ and P > 3.5 GPa, the graphitization of PTFE is observed, but judging from the preservation of liquid run products, PTFE can be used as a material for sample container up to 600 ℃ at this pressure. The obtained data allow the suggestion that the triple point between liquid, solid, and decomposed (carbonized) PTFE is located between 3 and 4 GPa at about 550 ℃, by analogy with the behavior of polycyclic aromatic hydrocarbons.

  3. Coupling sodium dodecyl sulfate-capillary polyacrylamide gel electrophoresis with matrix-assisted laser desorption ionization time-of-flight mass spectrometry via a poly(tetrafluoroethylene) membrane.

    PubMed

    Lu, Joann J; Zhu, Zaifang; Wang, Wei; Liu, Shaorong

    2011-03-01

    Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) is a fundamental analytical technique for proteomic research, and SDS-capillary gel electrophoresis (CGE) is its miniaturized version. Compared to conventional slab-gel electrophoresis, SDS-CGE has many advantages such as increased separation efficiency, reduced separation time, and automated operation. SDS-CGE is not widely accepted in proteomic research primarily due to the difficulties in identifying the well-resolved proteins. MALDI-TOF-MS is an outstanding platform for protein identifications. Coupling the two would solve the problem but is extremely challenging because the MS detector has no access to the SDS-CGE-resolved proteins and the SDS interferes with MS detection. In this work we introduce an approach to address these issues. We discover that poly(tetrafluoroethylene) (PTFE) membranes are excellent materials for collecting SDS-CGE-separated proteins. We demonstrate that we can wash off the SDS bound to the collected proteins and identify these proteins on-membrane with MALDI-TOF-MS. We also show that we can immunoblot and Coomassie-stain the proteins collected on these membranes.

  4. Reconstruction of a defect of the rotator cuff with polytetrafluoroethylene felt graft. Recovery of tensile strength and histocompatibility in an animal model.

    PubMed

    Kimura, A; Aoki, M; Fukushima, S; Ishii, S; Yamakoshi, K

    2003-03-01

    We reconstructed defects in the infraspinatus tendon u sing polytetrafluoroethylene (PTFE) felt grafts in 31 beagle dogs and examined the mechanical responses and histocompatibility. Except for one infected specimen, all the reconstructed infraspinatus tendons healed. We examined eight specimens each immediately after surgery and at six and 12 weeks. The ultimate tensile strength of the reconstructed tendons was 60.84 N, 172.88 N, and 306.51 N immediately after surgery and at six and 12 weeks, respectively. The stiffness of the specimens at the PTFE felt-bone interface was 9.61 kN/m, 64.67 kN/m, and 135.09 kN/m immediately after surgery and at six and 12 weeks, respectively. Six tendons were examined histologically at three, six, 12 and 24 weeks. Histological analysis showed that there was ingrowth of fibrous tissue between the PTFE fibres. Foreign-body reactionswere found at the margin of the PTFE-bone interface between 12 and 24 weeks. The mechanical recovery and tissue affinity of PTFE felt to bone and to tendon support its use for reconstruction of the rotator cuff. The possible development of a foreign-body reaction should be borne in mind.

  5. Irradiation of poly(tetrafluoroethylene) surfaces by CF4 plasma to achieve robust superhydrophobic and enhanced oleophilic properties for biological applications.

    PubMed

    Salapare, Hernando S; Suarez, Beverly Anne T; Cosiñero, Hannah Shamina O; Bacaoco, Miguel Y; Ramos, Henry J

    2015-01-01

    Poly(tetrafluoroethylene) (PTFE) was irradiated by CF4 plasma produced in the gas discharge ion source facility to produce stable and robust superhydrophobic surfaces and to enhance the materials' oleophilic property for biological applications. The characterizations employed on the samples are contact angle measurements, analysis of the surface morphology (scanning electron microscopy), surface roughness measurements (atomic force microscopy) and analysis of the surface chemistry (Fourier transform infrared spectroscopy). Superhydrophobic behavior with water contact angles as high as 156° was observed. The wettability of all the treated samples was found to be stable in time as evidenced by the statistically insignificant differences in the hysteresis contact angles. The level of enhanced hydrophobicity depended on the plasma energies (i.e. irradiation times, discharge current, and discharge voltage); higher plasma energies produced surfaces with high hydrophobicity. The plasma treatment also enhanced the oleophilic property of the materials' surface as evidenced by the decrease in the PDMS-oil contact angle from 33° to as low as 10°. The superhydrophobicity of the modified PTFE and the enhancement of its oleophilic property were due to (1) the changes in the roughness of the surface, (2) the formation of nanoparticles or nanostructures on the surface, and (3) the changes in the surface chemistry.

  6. Effect of polytetrafluoroethylene (PTFE) phase transition at 19°C on the use of Spectralon as a reference standard for reflectance.

    PubMed

    Ball, Christopher P; Levick, Andrew P; Woolliams, Emma R; Green, Paul D; Dury, Martin R; Winkler, Rainer; Deadman, Andrew J; Fox, Nigel P; King, Martin D

    2013-07-10

    Sintered polytetrafluoroethylene (PTFE) is highly reflective and is widely used as a reference standard in remote sensing, radiometry, and spectroscopy. The relative change in output flux from a PTFE integrating sphere over the room temperature phase transition at 19°C has been measured at a monochromatic wavelength of 633 nm as 1.82±0.21%. The change in output flux was attributed to a small change of 0.09±0.02% in the total hemispherical reflectance of PTFE, caused by a change in its material density as a result of the phase transition. For the majority of users, this small change measured in total hemispherical reflectance is unlikely to impact significantly the accuracy of PTFE flat panel reflectors used as reference standards. However, owing to the multiple reflections that occur inside an integrating sphere cavity, the effect is multiplied and remedial action should be applied, either via a mathematical correction or through temperature stabilization of the integrating sphere when high accuracy (<5%) measurements of flux, irradiance, or radiance are required from PTFE-based integrating spheres at temperatures close to the phase transition at 19°C.

  7. Effect of ionizing radiation on the chemical composition, crystalline content and structure, and flow properties of polytetrafluoroethylene. [0. 5 to 0. 8 MeV electron beams

    SciTech Connect

    Fisher, W.K.; Corelli, J.C.

    1981-10-01

    This article describes a study of ionizing radiation-induced changes in the chemical composition, crystalline content and structure, and flow properties in polytetrafluoroethylene (PTFE). Irradiations conducted in the presence of oxygen cause acid fluoride end groups to be formed, which on exposure to water vapor hydrolyze to form carboxylic acid end groups. Analyses by infrared (IR) spectroscopy indicate that when irradiated in a vacuum PTFE exhibits defect absorption bands which have been attributed to branch and crosslink formation. The crystalline content of PTFE which increases after exposure to radiation was monitored by IR spectroscopy, density, x-ray diffraction on unoriented samples, and differential scanning calorimetry (DSC) as the measurement probes. The melt viscosity of PTFE exposed to various radiation doses in air decreases dramatically after irradiation. Between 2.5 and 5 Mrd an increase in viscosity is attributed to the formation of branches and crosslinks. The effects of preirradiation crystallinity and postirradiation heat treatment were studied. A model is presented to explain the mechanism of the observed radiation effects.

  8. Effect of surface reactions on steel, Al2O3 and Si3N4 counterparts on their tribological performance with polytetrafluoroethylene filled composites

    NASA Astrophysics Data System (ADS)

    Shen, J. T.; Top, M.; Ivashenko, O.; Rudolf, P.; Pei, Y. T.; De Hosson, J. Th. M.

    2015-03-01

    The influence of surface reactions on the tribo-performance of steel, Al2O3 and Si3N4 balls sliding against polytetrafluoroethylene/SiO2/epoxy composites was investigated. Al2O3 ball were found to exhibit the best tribo-performance, namely a low coefficient of friction and the lowest wear rates of both the composites and the counterpart ball, when sliding against the PTFE filled composites. The difference in the tribo-performance of the Al2O3 ball and the Si3N4 ball can neither be attributed to the different morphology of the worn composite surfaces nor to the amount of PTFE transferred onto the wear surfaces. Instead we found that the friction is greatly reduced in the case of the Al2O3 ball because two fluoro-terminated surfaces are sliding over each other; in fact, the formation of Alsbnd F bonding was confirmed by X-ray photoelectron spectroscopy.

  9. Above-knee polytetrafluoroethylene femoropopliteal bypass graft: Is it a reasonable alternative to the below-knee reversed autogenous vein graft?

    PubMed

    O'Donnell, T F; Farber, S P; Richmand, D M; Deterling, R A; Callow, A D

    1983-07-01

    To determine whether an above-knee polytetrafluoroethylene (AK-PTFE) femoropopliteal bypass graft might be an acceptable alternative to a below-knee reversed autogenous saphenous vein (BK-ASV) bypass graft, we compared 51 AK-PTFE grafts to 39 concurrently performed BK-ASV grafts. All patients were staged by preoperative noninvasive vascular laboratory criteria into limiting claudication or limb salvage groups and by intraoperative arteriography according to degree of runoff. There was no significant difference in the primary graft patency at 36 months between the AK-PTFE group (63%) and the BK-ASV group (72%). Secondary graft patency among the AK-PTFE group was improved by minor distal graft revision to 88% at 36 months. The preoperative noninvasive hemodynamic evaluation status was an influential factor; the graft patency rate among the patients with limiting claudication was superior to that among the limb salvage group, but the degree of runoff as shown by intraoperative angiography did not appear to have an effect on cumulative patency. Resting Doppler ankle/brachial artery pressure ratios did not predict subsequent occlusion of AK-PTFE grafts. Atherosclerosis is a progressive and systemic disease that frequently involves both the coronary and tibial vessels. AK-PTFE spares autogenous saphenous vein so that it can be reserved for use in coronary artery bypass or in subsequent treatment of more distal tibial vessel disease.

  10. Seven-year experience with polytetrafluoroethylene as above-knee femoropopliteal bypass graft. Is is worthwhile to preserve the autologous saphenous vein?

    PubMed

    Sterpetti, A V; Schultz, R D; Feldhaus, R J; Peetz, D J

    1985-11-01

    A 7-year experience with 90 polytetrafluoroethylene (PTFE) femoropopliteal bypass grafts in the above-knee (AK) position is presented. The 5- and 7-year actuarial patency rate was 58.3%. No statistical difference was found between the patency rate of this series and that of a group of 17 AK and 77 below-knee (BK) femoropopliteal bypass grafts performed during the same period with the autologous saphenous vein (ASV). During the follow-up period (range 6 to 84 months, mean 42 months) a new bypass in a more distal location was required in 20 limbs. The ASV was available in seven of the eight PTFE graft failures and in only one of the 12 ASV failures. The 3-year patency rate of these new groups was 58.3% and 16.7%, respectively (p less than 0.02). Eighteen of the 48 deaths occurring during the follow-up period were related to atherosclerotic heart disease, whereas only one patient underwent coronary artery bypass grafting. Five hundred patients randomly selected from our series of myocardial revascularization procedures were reviewed. In five a femorodistal reconstruction was performed before coronary artery bypass, and in only two (0.4%), the ASV was not available. PTFE use in the AK position may be a reasonable alternative to the ASV to preserve it for additional treatment of more distal occlusive disease. There is no evidence that such a need exists for further treatment of coronary artery disease.

  11. Polymer dynamics near the surface and in the bulk of poly(tetrafluoroethylene) probed by zero-field muon-spin-relaxation spectroscopy.

    PubMed

    McKenzie, Iain; Salman, Zaher; Giblin, Sean R; Han, Yun Yu; Leach, Gary W; Morenzoni, Elvezio; Prokscha, Thomas; Suter, Andreas

    2014-02-01

    The results of many experiments on polymers such as polystyrene indicate that the polymer chains near a free surface exhibit enhanced dynamics when compared with the bulk. We have investigated whether this is the case for poly(tetrafluoroethylene) (PTFE) by using zero-field muon-spin-relaxation spectroscopy to characterize a local probe, the F-Mu(+)-F state, which forms when spin-polarized positive muons are implanted in PTFE. Low-energy muons (implantation energies from 2.0 to 23.0 keV) were used to study the F-Mu(+)-F state between ∼ 23 and 191 nm from the free surface of PTFE. Measurements were also made with surface muons (4.1 MeV) where the mean implantation depth is on the order of ∼ 0.6 mm. The relaxation rate of the F-Mu(+)-F state up to ∼ 150 K was found to be significantly higher for muons implanted at 2.0 keV than for higher implantation energies, which suggests that the polymer chains in a region on the order of a few tens of nanometers from the free surface are more mobile than those in the bulk.

  12. The linker-free covalent attachment of collagen to plasma immersion ion implantation treated polytetrafluoroethylene and subsequent cell-binding activity.

    PubMed

    Bax, Daniel V; McKenzie, David R; Weiss, Anthony S; Bilek, Marcela M M

    2010-03-01

    It is desirable that polymers used for the fabrication of prosthetic implants promote biological functions such as cellular adhesion, differentiation and viability. In this study, we have used plasma immersion ion implantation (PIII) to modify the surface of polytetrafluoroethylene (PTFE), thereby modulating the binding mechanism of collagen. The amount of collagen bound to the polymer surface following PIII-treatment was similar to that bound by non-covalent physisorption. In a manner consistent with previous enzyme and tropoelastin binding data, the collagen bound to the PIII-treated PTFE surface was resistant to sodium dodecyl sulfate (SDS) elution whilst collagen bound to the untreated surface was fully removed. This demonstrates the capability of PIII-treated surfaces to covalently attach collagen without employing chemical linking molecules. Only the collagen bound to the PIII-treated PTFE surface supported human dermal fibroblast attachment and spreading. This indicates that collagen on the PIII-treated surface possesses increased adhesive activity as compared to that on the untreated surface. Cell adhesion was inhibited by EDTA when the collagen was bound to PIII-treated PTFE, as expected for integrin involvement. Additionally this adhesion was sensitive to the conformation of the bound collagen. Increased actin cytoskeletal assembly was observed on cells spreading onto collagen-coated PIII-treated PTFE compared to the collagen-coated untreated PTFE. These data demonstrate the retention of collagen's biological properties following its attachment to PIII-treated PTFE, suggesting advantages for tissue engineering and prosthetic design.

  13. Ex-vivo release of Pipeline Embolization Device polytetrafluoroethylene (PTFE) sleeves for improved distal landing zone accuracy in-vivo: A technical note.

    PubMed

    Griessenauer, Christoph J; Gupta, Raghav; Moore, Justin; Thomas, Ajith J; Ogilvy, Christopher S

    2016-12-01

    Distal landing zone accuracy is critical in some intracranial aneurysms treated with the Pipeline Embolization Device (PED), and delayed opening of the distal end of the device can complicate the procedure. Here, we report a technical nuance that facilitates accurate placement of the distal end of the PED by ex-vivo, pre-implantation release of the PED Flex polytetrafluoroethylene (PTFE) sleeves. The PED Flex is partially pushed out of the introducer sheath ex-vivo, pre-implantation until the distal PED opens entirely and the PTFE sleeves are located distal to the device. Without inverting the PTFE sleeves, the PED is carefully pulled back into the introducer sheath placing the PTFE sleeves inside the device. The PED is loaded into the microcatheter and advanced toward the site of implantation. When the PED is initially deployed and pushed out of the microcatheter, it opens immediately and provides an anchor for the remainder of the deployment process. We present a video (supplementary material) that illustrates the technique along with an illustrative case. Ex-vivo, pre-implantation release of the PTFE sleeves is an option in aneurysm treatment where distal landing accuracy is critical. Even without the protection of the PTFE sleeves, our clinical observation shows that the PED can be advanced safely through the microcatheter in selected cases. © The Author(s) 2016.

  14. Successful deployment of polytetrafluoroethylene-covered stent to seal left internal mammary artery graft perforation due to guide catheter extension system.

    PubMed

    Ichimoto, Eiji; De Gregorio, Joseph

    2016-12-01

    Coronary artery bypass graft perforation during percutaneous coronary intervention is a rare complication. Perforation of a left internal mammary artery (LIMA) graft due to a guide catheter extension system has not been described. We report the successful deployment of a polytetrafluoroethylene (PTFE)-covered stent to seal the LIMA graft perforation due to the guide catheter extension system. Percutaneous coronary intervention was performed for a culprit lesion of the distal left circumflex via the LIMA graft. A balloon catheter failed to be delivered because the LIMA graft was very long and tortuous. The guide catheter extension system was introduced, and the balloon was delivered and inflated. However, the LIMA graft perforation with continuous extravasation was caused by the edge of deeper intubated guide extension catheter when a coronary stent was attempted to be delivered to the culprit lesion. A long balloon inflation was performed, but the perforation was not completely sealed. The PTFE-covered stent was successfully deployed and sealed the LIMA graft perforation. This case describes that the rapid deployment of PTFE-covered stent is effective to treat severe coronary artery bypass graft perforation due to the guide catheter extension system.

  15. Planning the milking center in expanding dairies.

    PubMed

    Smith, J F; Armstrong, D V; Gamroth, M J; Martin, J G

    1997-08-01

    This paper focuses on dairies that want to expand and milk more cows through an existing parlor or by building new parlor. The expansion process can be divided into the following three phases: 1) financial evaluation, 2) design, and 3) construction. A financial evaluation should be carried out first to determine the resources that are available for expanding the dairy operation. This phase is extremely important, considering that 68% of the dairies that expand have cash flow problems within the first 2 yr of operation. The next phase is to design the milking center, and options include expanding the present parlor or constructing a new parlor. The present parlor can be expanded by addition of stalls, but group size must also expand to maintain cow flow at the larger parlor size. Group size can often be increased by combining corrals or free-stall alleys. The third phase in the expansion is to determine the most efficient milking procedure during the construction or remodeling of the facilities.

  16. Expanded Schools: Developing Mindsets to Support Academic Success. Research Brief

    ERIC Educational Resources Information Center

    ExpandED Schools, 2014

    2014-01-01

    The national demonstration of ExpandED Schools, The After-School Corporation's (TASC) expanded learning model, was launched in 2011-12 in New York City, Baltimore, and New Orleans. The ExpandED Schools demonstration is being evaluated by Policy Studies Associates (PSA) and is rolling out at a time when there is heightened awareness among…

  17. Evaluation of injury to expanded and expanding leaves of peas exposed to sulfur dioxide and ozone

    SciTech Connect

    Olszyk, D.M.; Tibbitts, T.W.

    1982-03-01

    Necrosis, chlorophyll concentration, dry weight and surface area measurements were made to evaluate injury to leaves of Pisum sativum L. cv Alsweet grown under controlled environments and exposed to sulfur dioxide, ozone and combinations of sulfur dioxide plus ozone. Injury evaluations were made at low pollutant levels causing slight necrotic injury and high levels causing severe necrotic injury. At low levels, expanded leaves with a trace of necrotic injury had a 10% reduction in chlorophyll concentration but no reductions in dry weight or surface area, while expanding leaves, also with a trace of necrotic injury, had a reduction in chlorophyll concentration accompanied by reductions in dry weight and surface area. At high pollutant levels, expanded leaves with severe necrotic injury had a 70% reduction in chlorophyll concentration and significant reductions in dry weight and surface area, while expanding leaves had a smaller amount of necrotic injury and a smaller reduction in chlorophyll concentration, but reductions in dry weight and surface area similar to those in expanded leaves. Thus, the following measurements are proposed as reliable indicators of injury at pollutant concentrations just above the threshold for injury: chlorophyll concentration for expanded leaves and surface area for expanding leaves. Reliable indicators of injury at higher concentrations causing serious injury to leaves are: necrosis for expanded leaves and chlorophyll concentration, dry weight, and surface area for expanding leaves. 19 references, 4 figures, 3 tables.

  18. Expanding your horizons in science and mathematics

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Through the presentation of its Expanding Your Horizons in Science and Mathematics career education conferences for secondary school young women, the Math/Science Network continues its efforts to remove the educational, psychological, and cultural barriers which prevent women from entering math-and science-based careers. The Expanding Your Horizons conferences were presented on 77 college, university and high school campuses across the United States. This year, these unique one day conferences reached 15,500 students, 3,000 parents and educators, and involved 3,000 career women who volunteered their services as conference planners, workshop leaders, speakers, and role models.

  19. Negative energy particle as an expanding wormhole

    NASA Astrophysics Data System (ADS)

    Culetu, Hristu

    2015-04-01

    The properties of a dynamic wormhole are investigated. Using a particular equation of state for the fluid on the wormhole throat, we reached an equation of motion for the throat (a hyperbola) that leads to a negative surface energy density σ. The throat expands with the same acceleration 2π|σ| as the Ipser-Sikivie domain wall. We found the Lagrangian leading to the above equation of motion of the throat. The associated Hamiltonian corresponds to a relativistic free particle of a time-dependent negative energy -ℏc/R, where R is the throat radius, similar in form with the Casimir energy inside an expanding spherical box.

  20. DYNAMICAL MODEL OF AN EXPANDING SHELL

    SciTech Connect

    Pe'er, Asaf

    2012-06-10

    Expanding blast waves are ubiquitous in many astronomical sources, such as supernova remnants, X-ray emitting binaries, and gamma-ray bursts. I consider here the dynamics of such an expanding blast wave, both in the adiabatic and the radiative regimes. As the blast wave collects material from its surroundings, it decelerates. A full description of the temporal evolution of the blast wave requires consideration of both the energy density and the pressure of the shocked material. The obtained equation is different from earlier works in which only the energy was considered. The solution converges to the familiar results in both the ultrarelativistic and the sub-relativistic (Newtonian) regimes.

  1. Transition Metal Complexes of Expanded Porphyrins

    PubMed Central

    Sessler, Jonathan L.; Tomat, Elisa

    2008-01-01

    Over the last two decades, the rapid development of new synthetic routes for the preparation of expanded porphyrin macrocycles has allowed exploration of a new frontier consisting of “porphyrin-like” coordination chemistry. In this Account, we summarize our exploratory forays into the still relatively poorly explored area of oligopyrrolic macrocycle metalation chemistry. Specifically, we describe our successful formation of both mono- and binuclear complexes and in doing so highlight the diversity of coordination modes available to expanded porphyrin-type ligands. The nature of the inserted cation, the emerging role of tautomeric equilibria, and the importance of hydrogen-bonding interactions in regulating this chemistry are also discussed. PMID:17397134

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

    PubMed

    Lindholt, J S; Houlind, K; Gottschalksen, B; Pedersen, C N; Ravn, H; Viddal, B; Pedersen, G; Rasmussen, M; Wedel, C; Bramsen, M B

    2016-09-01

    Cohort studies suggest superior long-term patency of luminal heparin-bonded polytetrafluoroethylene (Hb-PTFE) bypass grafts compared with standard PTFE grafts. The aim of this study was to compare the outcomes of Hb-PTFE grafts with those of standard PTFE grafts 5 years after a randomized trial. Patients with intermittent claudication or critical limb ischaemia requiring femorofemoral or femoropopliteal bypass grafting were randomized in a clinical trial of Hb-PTFE versus standard PTFE in 11 Scandinavian centres between 2005 and 2009. Patients were followed up for 5 years with clinical assessment and surveillance Duplex ultrasound imaging. The primary endpoint of this study was primary patency. Secondary endpoints included major amputation and mortality. Overall, 569 patients were enrolled in the randomized trial. Some 552 had follow-up data available for analysis of the primary outcome. Use of Hb-PTFE significantly improved patency by 37 per cent at 2 years, but 5 years after randomization there was no difference in primary patency (adjusted hazard ratio (HR) 0·95, 95 per cent c.i. 0·71 to 1·28; P = 0·748). In patients with critical limb ischaemia the use of Hb-PTFE reduced the 5-year risk of loss of primary patency by 37 per cent (HR 0·63, 0·40 to 0·99; P = 0·049). In this study there was no difference in primary graft patency between Hb-PTFE and standard PTFE grafts. Patients receiving Hb-PTFE grafts for critical limb ischaemia were more likely to have a patent graft at 5 years than those with standard PTFE grafts. © 2016 BJS Society Ltd Published by John Wiley & Sons Ltd.

  3. Assessment of fibronectin conformation adsorbed to polytetrafluoroethylene surfaces from serum protein mixtures and correlation to support of cell attachment in culture.

    PubMed

    Grainger, David W; Pavon-Djavid, Graciella; Migonney, Veronique; Josefowicz, Marcel

    2003-01-01

    Surfaces of polytetrafluoroethylene (PTFE) were exposed to buffered aqueous solutions containing radio-labeled human fibronectin ([125I]Fn), Fn/bovine serum albumin (BSA) binary mixtures of various ratios or whole human plasma dilutions for 1 h. Total adsorbed Fn and albumin adsorption following rinsing was quantified on this surface. 125I-labeled monoclonal antibodies against either the tenth type-III Fn repeat unit (containing the cell-binding RGDS integrin recognition motif) or the Fn amino-terminal domain were used to probe the accessibility of each of these respective Fn regions post-adsorption. Human umbilical vein endothelial cells (HUVECs) were cultured on PTFE surfaces pre-exposed to each of these protein adsorption conditions and compared to identical conditions on tissue culture polystyrene (TCPS). Fn adsorption to PTFE is dependent upon the concentration of albumin co-adsorbing from solution: albumin out-competes Fn for PTFE surface sites even at non-physiological Fn/HSA ratios 10-100-fold biased in Fn. Antibodies against Fn do not readily recognize Fn adsorbed on PTFE as the HSA co-adsorption concentration in either binary mixtures or in plasma increases, indicating albumin masking of adsorbed Fn. At Fn/HSA ratios rich in Fn (1:1, 1:100), albumin co-adsorption actually improves anti-Fn antibody recognition of adsorbed Fn. HUVEC attachment efficiency to PTFE after protein adsorption correlates with amounts of Fn adsorbed and levels of anti-Fn antibody recognition of Fn on PTFE, linking cell attachment to integrin recognition of both adsorbed Fn density and Fn adsorbed conformation on PTFE surfaces.

  4. Emission of perfluoroalkyl carboxylic acids (PFCA) from heated surfaces made of polytetrafluoroethylene (PTFE) applied in food contact materials and consumer products.

    PubMed

    Schlummer, Martin; Sölch, Christina; Meisel, Theresa; Still, Mona; Gruber, Ludwig; Wolz, Gerd

    2015-06-01

    Polytetrafluoroethylene (PTFE) has been widely discussed as a source of perfluorooctanoic acid (PFOA), which has been used in the production of fluoropolymers. PTFE may also contain unintended perfluoroalkyl carboxylic acids (PFCAs) caused by thermolysis of PTFE, which has been observed at temperatures above 300°C. Common PTFE coated food contact materials and consumer goods are operated at temperatures above 200°C. However, knowledge on possible emissions of PFCAs is limited. Therefore, it was the aim of this study to investigate and evaluate the emission of PFCAs from PTFE coated products with both, normal use and overheating scenarios. Four pans, claimed to be PFOA free, and nine consumer products were investigated. At normal use conditions (<230°C), emissions from PTFE surfaces were trapped for 1h. Overheating scenarios (>260°C) recorded emissions during a 30min heating of empty pans on a stove. Emissions were analyzed by LC-ESI-MS. Results indicate the emission of PFCAs, whereas no perfluorinated sulfonic acids were traced. At normal use conditions total emissions of PFCAs accounted for 4.75ng per hour. Overheated pans, however, released far higher amounts with up to 12190ng PFCAs per hour at 370°C. Dominating contributors where PFBA and PFOA at normal use and PFBA and PFPeA during overheating. Temperature seems to be the main factor controlling the emission of PFCAs. A worst case estimation of human exposure revealed that emissions of PFCAs from heated PTFE surfaces would be far below the TDI of 1500ng PFOA per kg body weight.

  5. Expanding Arts Education in a Digital Age

    ERIC Educational Resources Information Center

    Choi, Haeryun; Piro, Joseph M.

    2009-01-01

    This article proposes a way to expand the study of arts education within new contexts of technology and globalization. Drawing upon theories that have informed arts and aesthetic education in the past, the authors suggest new applications for these ideas to ensure that arts education sustains its significance in twenty-first-century society. The…

  6. Expanding the Boundaries of Adult Religious Education

    ERIC Educational Resources Information Center

    Isaac, E. Paulette

    2012-01-01

    Religious institutions wear many hats. In addition to meeting spiritual needs, they also serve as educational, cultural, political, and social centers. Like the world in general, many of them have responded to societal changes. They have expanded their contextual, geographical, and physical boundaries. Also, as demonstrated throughout this…

  7. Responsible implementation of expanded carrier screening.

    PubMed

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-06-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines.

  8. Consonant confusions in amplitude-expanded speech.

    PubMed

    Freyman, R L; Nerbonne, G P

    1996-12-01

    The perceptual consequences of expanding the amplitude variations in speech were studied under conditions in which spectral information was obscured by signal correlated noise that had an envelope correlated with the speech envelope, but had a flat amplitude spectrum. The noise samples, created individually from 22 vowel-consonant-vowel nonsense words, were used as maskers of those words, with signal-to-noise ratios ranging from -15 to 0 dB. Amplitude expansion was by a factor of 3.0 in terms of decibels. In the first experiment, presentation level for speech peaks was 80 dB SPL. Consonant recognition performance for expanded speech by 50 listeners with normal hearing was as much as 30 percentage points poorer than for unexpanded speech and the types of errors were dramatically different, especially in the midrange of S-N ratios. In a second experiment presentation level was varied to determine whether reductions in consonant levels produced by expansion were responsible for the differences between conditions. Recognition performance for unexpanded speech at 40 dB SPL was nearly equivalent to that for expanded speech at 80 dB SPL. The error patterns obtained in these two conditions were different, suggesting that the differences between conditions in Experiment 1 were due largely to expanded amplitude envelopes rather than differences in audibility.

  9. Expanding the Reader Landscape of Histone Acylation.

    PubMed

    Khan, Abid; Bridgers, Joseph B; Strahl, Brian D

    2017-04-04

    In this issue of Structure,Klein et al. (2017) expand our understanding of what reader domains bind to by showing that MORF, a double PHD domain containing lysine acetyltransferase, is a preferential reader of histone lysine acylation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. An Expanding Universe in the Classroom.

    ERIC Educational Resources Information Center

    Chandler, David

    1991-01-01

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

  11. Improving Accountability through Expanded Measures of Performance

    ERIC Educational Resources Information Center

    Hamilton, Laura S.; Schwartz, Heather L.; Stecher, Brian M.; Steele, Jennifer L.

    2013-01-01

    Purpose: The purpose of this paper is to examine how test-based accountability has influenced school and district practices and explore how states and districts might consider creating expanded systems of measures to address the shortcomings of traditional accountability. It provides research-based guidance for entities that are developing or…

  12. Virginia expands HIV testing, licenses viatical firms.

    PubMed

    1997-05-02

    Virginia Governor George Allen signed H.B. 2174, H.B. 871, and S.B. 788 on March 25, 1997. The legislation expands HIV testing of criminal defendants, requires viatical settlement companies to obtain licenses, and imposes civil penalties for physician-assisted suicides.

  13. Virginia rejects assisted suicide, expands mandatory testing.

    PubMed

    1997-03-07

    Virginia legislators ended their 1997 session by adopting measures that impact AIDS patients, physicians, advocates, and their families. Gov. George Allen may sign into law bills imposing penalties for doctor-assisted suicide, requiring viatical settlement companies to obtain licenses, and expanding mandatory HIV testing of criminal defendants. Republican lawmakers are working to rescind Virginia's medical marijuana law.

  14. Heat expanded starch-based compositions.

    PubMed

    Glenn, Gregory M; Klamczynski, Artur K; Holtman, Kevin M; Shey, Justin; Chiou, Bor-Sen; Berrios, Jose; Wood, Delilah; Orts, William J; Imam, Syed H

    2007-05-16

    A heat expansion process similar to that used for expanded bead polystyrene was used to expand starch-based compositions. Foam beads made by solvent extraction had the appearance of polystyrene beads but did not expand when heated due to an open-cell structure. Nonporous beads, pellets, or particles were made by extrusion or by drying and milling cooked starch slurries. The samples expanded into a low-density foam by heating 190-210 degrees C for more than 20 s at ambient pressures. Formulations containing starch (50-85%), sorbitol (5-15%), glycerol (4-12%), ethylene vinyl alcohol (EVAL, 5-15%), and water (10-20%) were studied. The bulk density was negatively correlated to sorbitol, glycerol, and water content. Increasing the EVAL content increased the bulk density, especially at concentrations higher than 15%. Poly(vinyl alcohol) (PVAL) increased the bulk density more than EVAL. The bulk density was lowest in samples made of wheat and potato starch as compared to corn starch. The expansion temperature for the starch pellets decreased more than 20 degrees C as the moisture content was increased from 10 to 25%. The addition of EVAL in the formulations decreased the equilibrium moisture content of the foam and reduced the water absorption during a 1 h soaking period.

  15. Women Engineering Faculty: Expanding the Pipeline

    ERIC Educational Resources Information Center

    Greni, Nadene Deiterman

    2006-01-01

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

  16. Utilities expand baseload power plant plans

    SciTech Connect

    Smock, R.

    1993-04-01

    This article examines the plans being made by electric utilities to expand the number of baseload plants to accommodate increasing power demands. The results of a survey of utility's construction plans is presented. The topics include current construction, construction planning in the Southeast, current baseload technology, nuclear potential, and incorporation of environmental externalities impact in planning.

  17. Properties of extruded expandable breadfruit products

    USDA-ARS?s Scientific Manuscript database

    Dried breadfruit was extruded with a twin screw extruder to develop a value-added expanded fruit product. This research studied the effects of barrel temperature (120-160°C), moisture content (13-25%), feeding rate (13-25 kg/h) and screw speed (115-175rpm) on physicochemical properties (bulk densit...

  18. Responsible implementation of expanded carrier screening

    PubMed Central

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-01-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines. PMID:26980105

  19. A Curriculum Model for the Expanded Role

    ERIC Educational Resources Information Center

    Zornow, Ruth Ann

    1977-01-01

    If the expanded role is conceived in terms of five levels of functioning, organizing theoretical instruction and clinical preparation within a school's program is facilitated. The levels are: Basic nursing level, assessment level, screening level, management level, and diagnostic level. (Editor/TA)

  20. Expanding the Boundaries of Adult Religious Education

    ERIC Educational Resources Information Center

    Isaac, E. Paulette

    2012-01-01

    Religious institutions wear many hats. In addition to meeting spiritual needs, they also serve as educational, cultural, political, and social centers. Like the world in general, many of them have responded to societal changes. They have expanded their contextual, geographical, and physical boundaries. Also, as demonstrated throughout this…

  1. Digital Storytelling: Expanding Media Possibilities for Learning

    ERIC Educational Resources Information Center

    McLellan, Hilary, Ed.

    2008-01-01

    Stories offer a powerful framework for engagement, reflection, and other important skills that young people need to learn. As digital media have expanded, so have the possibilities for creating stories. Here, several examples of those new possibilities are examined, examples that highlight student-produced online broadcasting initiatives,…

  2. Expanding Perspectives on HRD Research. Symposium.

    ERIC Educational Resources Information Center

    2002

    This document contains three papers from a symposium on expanding perspectives in human resource development (HRD) research. "The Concept of Culture in International and Comparative HRD Research: Methodological Problems and Possible Solutions" (Alexander Ardichvili, K. Peter Kuchinke) discusses the following topics: (1) alternative…

  3. E-Books: Expanding the School Library

    ERIC Educational Resources Information Center

    Cavanaugh, Terence

    2005-01-01

    E-Books are books or other forms of text in digital form, an enhanced book without paper and at little or no cost, technologies that are already available at most schools can be used to expand the library media center's collection of books, at the same time making many books more accessible to students. Many tools are available for free to convert…

  4. Parachute Line Hook Includes Integral Loop Expander

    NASA Technical Reports Server (NTRS)

    Bayless, G. B.

    1983-01-01

    Parachute packing simplified with modified line hook. One person packs parachutes for test recovery vehicles faster than previously two-person team. New line hook includes expander that opens up two locking loops so parachute lines are pulled through them. Parachutes are packed at high pressure to be compressed into limited space available in test vehicles.

  5. Successful educational geophysics field program expands

    NASA Astrophysics Data System (ADS)

    The Summer of Applied Geophysical Experience (SAGE), a program that gives students an opportunity to apply a variety of modern geophysical methods in a challenging geologic environment, has expanded.A 2-year grant awarded in 1993 by the National Science Foundation's Research Experiences for Undergraduate's (REU) initiative allowed the program to include fourteen U.S. undergraduate students last summer.

  6. An Expanding Universe in the Classroom.

    ERIC Educational Resources Information Center

    Chandler, David

    1991-01-01

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

  7. Expanded Learning the LA's BEST Way

    ERIC Educational Resources Information Center

    Sanger, Carla; Heckman, Paul E.

    2011-01-01

    As federal and state policymakers and many education researchers and experts suggest, expanding the learning day for students makes sense. Given the demographic trends--women increasingly entering the workforce and low-income families working multiple jobs--children and youth need supervision and opportunities to learn in the hours between 3:00…

  8. Digital Storytelling: Expanding Media Possibilities for Learning

    ERIC Educational Resources Information Center

    McLellan, Hilary, Ed.

    2008-01-01

    Stories offer a powerful framework for engagement, reflection, and other important skills that young people need to learn. As digital media have expanded, so have the possibilities for creating stories. Here, several examples of those new possibilities are examined, examples that highlight student-produced online broadcasting initiatives,…

  9. Replicating an expanded genetic alphabet in cells.

    PubMed

    Chaput, John C

    2014-09-05

    Recent advances in synthetic biology have made it possible to replicate an unnatural base pair in living cells. This study highlights the technologies developed to create a semisynthetic organism with an expanded genetic alphabet and the potential challenges of moving forward. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Expanding the Focus of Career Assessment.

    ERIC Educational Resources Information Center

    Lock, Jared D.; Hogan, Robert

    2000-01-01

    Issues affecting career assessment include change in the focus and definition of career, emphasis on quality of work life, expansion of career paths, increased amount of career information available on the Internet, and questionable quality of online assessment. An expanded model of career assessment now includes technical fit, personal fit,…

  11. Expanding Analytic Possibilities of Rokeach Values Data.

    ERIC Educational Resources Information Center

    Chapman, David W.; And Others

    1983-01-01

    This study investigated the validity of Hayes's formula for converting rank-ordered Rokeach Values data to a normal distribution theoretically achieved through the use of rated data. Findings support the validity of Hayes's formula and expand the analytic possibilities of data collected on the Rokeach instrument. (Author/PN)

  12. E-Books: Expanding the School Library

    ERIC Educational Resources Information Center

    Cavanaugh, Terence

    2005-01-01

    E-Books are books or other forms of text in digital form, an enhanced book without paper and at little or no cost, technologies that are already available at most schools can be used to expand the library media center's collection of books, at the same time making many books more accessible to students. Many tools are available for free to convert…

  13. Expanding CTE Opportunities through Blended Learning

    ERIC Educational Resources Information Center

    McKinstry, Elizabeth

    2012-01-01

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

  14. Expanding the Audience for the Performing Arts.

    ERIC Educational Resources Information Center

    Andreasen, Alan R.

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

  15. Expanding Educational Excellence: The Power of Schools

    ERIC Educational Resources Information Center

    Coleman, Mary Ruth; Winn, Donna-Marie; Harradine, Christine

    2012-01-01

    In this paper, the authors explore four major barriers to academic success that must be addressed, briefly describe two projects that have worked to address these barriers, and make recommendations for moving forward as they work to expand educational excellence for all students. They provide examples of the myriad ways in which schools have the…

  16. Smaragdyrins: emeralds of expanded porphyrin family.

    PubMed

    Pareek, Yogita; Ravikanth, M; Chandrashekar, T K

    2012-10-16

    Porphyrins are tetrapyrrolic 18 π electron conjugated macrocycles with wide applications that range from materials to medicine. Expanded porphyrins, synthetic analogues of porphyrins that contain more than 18 π electrons in the conjugated pathway, have an increased number of pyrroles or other heterocyles or multiple meso-carbon bridges. The expanded porphyrins have attracted tremendous attention because of unique features such as anion binding or transport that are not present in porphyrins. Expanded porphyrins exhibit wide applications that include their use in the coordination of large metal ions, as contrasting agents in magnetic resonance imaging (MRI), as sensitizers for photodynamic therapy (PDT) and as materials for nonlinear optical (NLO) studies. Pentaphyrin 1, sapphyrin 2, and smaragdyrin 3 are expanded porphyrins that include five pyrroles or heterocyclic rings. They differ from each other in the number of bridging carbons and direct bonds that connect the five heterocyclic rings. Sapphyrins were the first stable expanded porphyrins reported in the literature and remain one of the most extensively studied macrocycles. The strategies used to synthesize sapphyrins are well established, and these macrocycles are versatile anion binding agents. They possess rich porphyrin-like coordination chemistry and have been used in diverse applications. This Account reviews developments in smaragdyrin chemistry. Although smaragdyrins were discovered at the same time as sapphyrins, the chemistry of smaragdyrins remained underdeveloped because of synthetic difficulties and their comparative instability. Earlier efforts resulted in the isolation of stable β-substituted smaragdyrins and meso-aryl isosmaragdyrins. Recently, researchers have synthesized stable meso-aryl smaragdyrins by [3 + 2] oxidative coupling reactions. These results have stimulated renewed research interest in the exploration of these compounds for anion and cation binding, energy transfer

  17. Refrigeration generation using expander-generator units

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  18. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective.

  19. The radiological findings in chronic expanding hematoma.

    PubMed

    Aoki, T; Nakata, H; Watanabe, H; Maeda, H; Toyonaga, T; Hashimoto, H; Nakamura, T

    1999-07-01

    To identify the characteristic MRI findings of chronic expanding hematoma correlated with the pathology. Three patients who had a chronic expanding hematoma involving the musculoskeletal system were reviewed retrospectively. Huge soft tissue masses suggestive of malignancy with destruction of the bony structure were revealed on radiography and computed tomography. MRI showed the masses to exhibit heterogeneous signal intensity on both T1 and T2-weighted images with a peripheral rim of low signal intensity, reflecting the central zones of fluid collection due to fresh and altered blood with a wall of collagenous fibrous tissue. These MRI findings were seen in all three patients and are considered to be characteristic; they assist in differentiation from neoplasm in consideration of the history of trauma or surgery.

  20. Controlling the statistical properties of expanding maps

    NASA Astrophysics Data System (ADS)

    Galatolo, Stefano; Pollicott, Mark

    2017-07-01

    How can one change a system, in order to change its statistical properties in a prescribed way? In this note we consider a control problem related to the theory of linear response. Given an expanding map of the unit circle with an associated invariant density, we can consider the inverse problem of finding which first order changes in the transformation can achieve a given first order perturbation in the density. We show the general mathematical structure of the problem, the existence of many solutions in the case of expanding maps of the circle and the existence of optimal ones. We investigate in depth the example of the doubling map, where we give a complete solution of the problem.