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Sample records for expanded polytetrafluoroethylene femoral-popliteal

  1. In Vivo Quantification of Femoral-Popliteal Compression during Isometric Thigh Contraction: Assessment using MR Angiography

    PubMed Central

    Brown, Ryan; Nguyen, Thanh D.; Spincemaille, Pascal; Prince, Martin R.; Wang, Yi

    2009-01-01

    Purpose To quantify femoral-popliteal vessel deformation during thigh contraction. Materials and Methods Eleven subjects underwent an MR examination of the femoral-popliteal vasculature on a 1.5 T system. A custom 3D balanced steady state free precession (SSFP) sequence was implemented to image a 15–20 cm segment of the vasculature during relaxation and voluntary isometric thigh contraction. The arterial and venous lumina were outlined using a semi-automated method. For the artery, this outline was fit to an ellipse whose aspect ratio was used to describe arterial deformation, while venous deformation was characterized by its cross-sectional area. Results Focal compression of the femoral-popliteal artery during contraction was observed 94 to 143 mm superior to the condyle that corresponds to the distal adductor canal (AC) immediately superior to the adductor hiatus. This was illustrated by a significant reduction (p ≤ 0.05) in aspect ratio from 0.88 ± 0.06 during relaxation to 0.77 ± 0.09 during contraction. A negligible change in arterial aspect ratio was observed inferior to the AC and in the proximal AC. Similarly, venous area was dramatically reduced in the distal AC region during contraction. Conclusion Rapid 3D SSFP MR angiography of the femoral-popliteal vasculature during thigh contraction demonstrated focal compression of the artery in the distal AC region. This may help explain the high stent failure rate and the high likelihood of atherosclerotic disease in the AC. PMID:19388112

  2. 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...; Guidance for Industry and FDA.” See § 878.1(e) for the availability of this guidance document....

  3. 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

  4. 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. PMID:26887686

  5. Salvage repair of anastomotic dehiscence following colon surgery using an expanded polytetrafluoroethylene graft.

    PubMed

    Uzun, M A; Koksal, N; Ozkan, O F; Kayahan, M; Gumrukcu, G

    2012-04-01

    Anastomotic dehiscence is a serious complication of colorectal surgery that causes death in up to 40% of cases in which it occurs. Edema and inflammation due to abdominal sepsis can prevent the use of standard management (i.e., colostomy, ileostomy or Hartmann's procedure), in which case alternative salvage repair methods are required. The present report describes the treatment of a 73-year-old female patient at high risk of mortality because of intraabdominal sepsis due to suture dehiscence following a right hemicolectomy and ileo-transversostomy. Several surgical repair procedures were tried, but all failed. We then used an expanded polytetrafluoroethylene (ePTFE) graft in salvage repair, and this approach proved successful. This is the first report to describe clinical, macroscopic and histopathological findings, following use of an ePTFE graft in colorectal repair in humans. PMID:20694495

  6. Antibacterial effects of the povidone-iodine vacuum impregnation technique in expanded polytetrafluoroethylene augmentation rhinoplasty.

    PubMed

    Lee, Jung Min; Lee, Joong Seob; Kim, Dong-Kyu; Lee, Jun Ho; Park, Hae Sang; Lee, Ho Jun; Bae, Sung Hee; Jang, Ji Su; Lee, Jae Jun; Park, Chan Hum

    2016-06-01

    Expanded polytetrafluoroethylene (e-PTFE) is a popular graft material for augmentation rhinoplasty. Gore-Tex and Surgiform are two types of e-PTFE; Surgiform has thicker fibrils and is more compact than Gore-Tex. We conducted an ex vivo study to evaluate the ability of povidone-iodine (PVP-I) vacuum pretreatment to prevent infection with these two types of e-PTFE. Gore-Tex and Surgiform specimens were cut into 2-mm(3) pieces, which were separated into two groups. One group for each e-PTFE was disinfected with vacuum PVP-I impregnation and the other group was not disinfected. Using the pieces of implant material, swabs were obtained from the nasal cavities of 20 healthy adults, and the specimens were incubated on agar plates and viewed by scanning electron microscopy (SEM). We found that PVP-I treatment significantly reduced the bacterial colony counts in both the Gore-Tex and Surgiform groups. In the SEM images, bacterial colonies were observed both inside and outside the untreated Gore-Tex; on the untreated Surgiform, they were found primarily on the surface. Few bacteria were detected in the PVP-I-treated Gore-Tex and Surgiform groups. Our findings suggest that PVP-I pretreatment can reduce the risk of infection associated with e-PTFE. PMID:27304448

  7. 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.

  8. Repair of Full-Thickness Defects in Alimentary Tract Wall With Patches of Expanded Polytetrafluoroethylene

    PubMed Central

    Oh, Daniel S.; Manning, Melanie M.; Emmanuel, Janson; Broyles, Stuart E.; Stone, H. Harlan

    2002-01-01

    Objectives To test the efficacy of patches of expanded polytetrafluoroethylene (ePTFE) for the repair of full-thickness defects in alimentary tract wall. Summary Background Data A recent report of successful replacement of duodenal wall with patches of ePTFE was met with skepticism and clearly warranted confirmation as well as evaluation in repair of other segments of the abdominal intestinal tract. Methods Defects of 4 cm2 were created in various segments of canine abdominal alimentary tract (stomach, duodenum, small bowel, and colon) as well as in bladder dome. For the duodenum in 13 dogs, three different ePTFE fabrications were used: CVX (cardiovascular), PDX (preclude dura membrane), and DLM (dual mesh plus). In repair of the other areas in six dogs, the PDX patch was used. When the animals were killed, both gross inspection of the parietes and tissue for histologic study became the basis for evaluation. Peritoneal and intraluminal cultures of the specific study viscera were also taken. Results There were no patch failures. Only six significant adhesions were noted in 3 of the 19 dogs. Serosal surface healing was complete without exception by 1 week in all animals. Patches of CVX and PDX had heaping mucosa at the margin of well-sealed patch edges in the study involving duodenum. However, the DLM patch had an undergrowth of mucosa with partial patch separation by 1 week, beginning patch extrusion into gut lumen at 3 weeks, and total separation of patch with complete mucosal repair at 6 weeks. The fate of the PDX patches at 6 weeks in stomach, small bowel, colon, and bladder was identical to what had been observed for the PDX patch in the duodenum. All peritoneal and bladder cultures had no growth, whereas the contents of the alimentary tract grew expected flora. Conclusions These observations suggest that ePTFE may well be an acceptable membrane for at least temporary replacement of full-thickness hollow viscus defects, even in the face of heavy bacterial

  9. 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

  10. Transjugular intrahepatic portosystemic shunt using the FLUENCY expanded polytetrafluoroethylene-covered stent.

    PubMed

    Wu, Qinghua; Jiang, Jianwei; He, Yujie; Jiang, Tianpeng; Zhou, Shi

    2013-01-01

    The aim of this study was to evaluate the feasibility of transjugular intrahepatic portosystemic shunts using FLUENCY expanded polytetraf luoroethylene (PTFE)-covered stents and the effect on the patency rate. A total of 114 cirrhotic patients who were treated by transjugular intrahepatic portosystemic stent shunt (TIPS) placement using a FLUENCY expanded, PTFE-covered stent were enrolled in the present study. Of the patients, 15 underwent an additional bare metal stent implantation on the portal side of the covered stent, simultaneously. Patients underwent Doppler sonography during the follow-up. Mean portal venous pressure dropped from 2.499±0.588 cmHg to 1.764±0.294 cmHg. The cumulative patency rates for one and two years were 86.7% and 75.2%, respectively. The results demonstrate the feasibility of TIPS placement with the FLUENCY expanded PTFE-covered stent. TIPS placement with the FLUENCY expanded PTFE-covered stent was able to improve patency when compared with the use of conventional bare-metal stents. PMID:23251280

  11. Thermal treatment of expanded polytetraflu-oroethylene (ePTFE) membranes for reconstruction of a valved conduit.

    PubMed

    Zhu, Guangyu; Yuan, Qi; Hock Yeo, Joon; Nakao, Masakazu

    2015-01-01

    The unique micro porous structure of expanded polytetrafluoroethylene (ePTFE) that allows bio-integration for fixation, as well as overall mechanical integrity make it used successfully in a number of biomedical and clinical applications, which include the reconstruction of the pulmonary valve in in right ventricular outflow tract reconstruction (RVOT) operations. The objective of this study was to determine the effects of the thermal treatment on physical and mechanical properties of ePTFE membranes. ePTFE sheets were cut into 16 rectangle strips (10 mm by 60 mm) and evenly separated into 4 groups. One group was the blank control (group A), while the rest of the three groups (group B to D) were heated to 350°C and cooled to 24°C at different cooling rates (10°C/min, 20°C/min and rapid ambient air cooling) in a temperature controlled atmosphere. The mechanical and morphological characteristics of all the samples were tested using a tensile test machine and a scanning electron microscopy (SEM). The results show that the elastic modulus of group B to D was 24.95%, 33.45% and 72.76% higher than group A. The percentage elongation of groups B to D was found to be between 2.3% and 40.45% lower than group A. The proportion of pores in the ePTFE membrane was reduced following the thermal treatment. There were no morphology differences observed between groups B to D. In summary, the selection of cooling rate was important for preserving the mechanical properties of ePTFE membranes under thermal treatment. These findings may provide useful information for the preparation of molded ePTFE valve in RVOT operations. PMID:26406048

  12. 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. PMID:25714299

  13. 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.

  14. 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.

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

    PubMed Central

    McKeown, Andrew DJ; Beattie, Rebekah F; Murrell, George AC

    2015-01-01

    Background Massive irreparable rotator cuff tears are a difficult problem. Modalities such as irrigation and debridement, partial repair, tendon transfer and grafts have been utilized with high failure rates and mixed results. Synthetic interpositional patch repairs are a novel and increasingly used approach. The present study aimed to examine the biomechanical properties of common synthetic materials for interpositional repairs in contrast to native tendon. Methods Six ovine tendons, six polytetrafluoroethylene (PTFE) felt sections and six expanded PTFE (ePTFE) patch sections were pulled-to-failure to analyze their biomechanical and material properties. Six direct tendon-to-bone surgical method repairs, six interpositional PTFE felt patch repairs and six interpositional ePTFE patch repairs were also constructed in ovine shoulders and pulled-to-failure to examine the biomechanical properties of each repair construct. Results Ovine tendon had higher load-to-failure (591 N) and had greater stiffness (108 N/mm) than either PTFE felt (296 N, 28 N/mm) or ePTFE patch sections (323 N, 34 N/mm). Both PTFE felt and ePTFE repair techniques required greater load-to-failure (225 N and 177 N, respectively) than direct tendon-to-bone surgical repairs (147 N) in ovine models. Conclusions Synthetic materials lacked several biomechanical properties, including strength and stiffness, compared to ovine tendon. Interpositional surgical repair models with these materials were significantly stronger than direct tendon-to-bone model repairs. PMID:27582997

  16. Comparison of Small-Intestinal Submucosa and Expanded Polytetrafluoroethylene as a Vascular Conduit in the Presence of Gram-Positive Contamination

    PubMed Central

    Shell, Daniel H.; Croce, Martin A.; Cagiannos, Catherine; Jernigan, T Wright; Edwards, Norma; Fabian, Timothy C.

    2005-01-01

    Objective: As a vascular conduit, expanded polytetrafluoroethylene (ePTFE) is susceptible to graft infection with Gram-positive organisms. Biomaterials, such as porcine small-intestinal submucosa (SIS), have been successfully used clinically as tissue substitutes outside the vascular arena. Summary Background Data: In the present study, we compared a small-diameter conduit of SIS to ePTFE in the presence of Gram-positive contamination to evaluate infection resistance, incorporation and remodeling, morphometry, graft patency, and neointimal hyperplasia (NH) development. Methods: Adult male mongrel pigs were randomized to receive either SIS or ePTFE (3-cm length, 6-mm diameter) and further randomized to 1 of 3 groups: Control (no graft inoculation), Staphylococcus aureus, or mucin-producing S epidermidis (each graft inoculation with 108 colonies/mL). Pressure measurements were obtained proximal and distal to the graft to create the iliac/aorta pressure ratio. Morphometric analysis of the neointima and histopathologic examinations was performed. Other outcomes included weekly WBC counts, graft incorporation, and quantitative culture of explanted grafts. Results: Eighteen animals were randomized. All grafts were patent throughout the 6-week study period. Infected SIS grafts had less NH and little change in their iliac/aorta indices compared with infected ePTFE grafts. Quantitative cultures at euthanasia demonstrated no growth in either SIS group compared with 1.7 × 104 colonies for ePTFE S aureus and 6 × 102 for ePTFE S epi (each P < 0.001). All SIS grafts were incorporated. Histology demonstrated remodeling into host artery with smooth muscle and capillary ingrowth in all SIS groups. Scanning electron micrography illustrated smooth and complete endothelialization of all SIS grafts. Conclusions: Compared with ePTFE, SIS induces host tissue remodeling, exhibits a decreased neointimal response to infection, and is resistant to bacterial colonization. SIS may provide a

  17. 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

  18. 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.

  19. Reflectance of polytetrafluoroethylene for xenon scintillation light

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    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 (λ ≃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.

  20. 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...

  1. 21 CFR 872.3680 - Polytetrafluoroethylene (PTFE) vitreous carbon materials.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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.

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

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  7. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  8. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  9. 21 CFR 878.5035 - Nonabsorbable expanded polytetrafluoroethylene surgical suture.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical..., including cardiovascular surgery. It may be undyed or dyed with an approved color additive and may...

  10. 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 §...

  11. 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 §...

  12. 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 §...

  13. 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 §...

  14. 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 §...

  15. 76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-15

    ... December 22, 2010, because ``the domestic parties did not participate in this review.'' (76 FR 3614... 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....

  16. 75 FR 67105 - Granular Polytetrafluoroethylene Resin From Italy and Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-01

    ... granular polytetrafluoroethylene resin from Japan (53 FR 32267). On August 30, 1988, Commerce issued an... from Italy and Japan (65 FR 6147, February 8, 2000). Following second five-year reviews by Commerce and... orders on imports of granular polytetrafluoroethylene resin from Italy and Japan (70 FR 76026)....

  17. 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. PMID:27621646

  18. [Ways to improve patency of the femoral-popliteal-crural bypass grafts].

    PubMed

    Sazhinov, A P; Lukinskiĭ, A V; Chupin, A V

    2014-01-01

    Chronic obliterating diseases of lower-limb arteries account for more than 20% of all manifestations of cardiovascular pathology. A surgical method of treatment for this pathology remains most effective. The types of operations below the inguinal fold currently used are as follows: bypass grafting, endarterectomy, and angioplasty. The vein is the material of choice and if it is not easily available allografts may be used. Differing elastic properties of the artery and prosthesis lead to progression of the neointima thus negatively affecting patency of bypass grafts. This article describes venous bypass grafts, their efficacy, methods of improving patency of allografts, as well as variants of combined operations. PMID:24722032

  19. 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

  20. 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.

  1. Thermal degradation of polytetrafluoroethylene in tube reactors

    NASA Technical Reports Server (NTRS)

    Mckinnon, J. Thomas; Duan, H. M.

    1995-01-01

    We have studied the thermal degradation of polytetrafluoroethylene (PTFE) in wet air, dry air and nitrogen gas at temperatures ranging from 310 to 520 C. The principal gas product was tetrafluoroethylene (TFE). The nitrogen experiments yielded only TFE, but experiments in dry and wet air also produced several other minor gas products. The dry air experiments produced the most smoke and the least gas products, with the nitrogen experiments giving no smoke and the highest amounts of gas products. Wet air experiments gave intermediate results for smoke and gas formation. The rate of degradation in wet air showed an apparent activation energy of 103 kca/mol. We also performed FTIR analyses of the smoke particulate, determining that the particulate formed in dry air is different than that formed in wet air.

  2. 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.

  3. Annealing of gold nanostructures sputtered on polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Siegel, Jakub; Krajcar, Robert; Kolská, Zdeňka; Hnatowicz, Vladimír; Švorčík, Václav

    2011-11-01

    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.

  4. 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

  5. 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.

  6. Light scattering of semitransparent sintered polytetrafluoroethylene films.

    PubMed

    Li, Qinghe; Lee, Bong Jae; Zhang, Zhuomin M; Allen, David W

    2008-01-01

    Polytetrafluoroethylene (PTFE) is a strongly scattering material and has been regarded to have optical properties similar to biological tissues. In the present study, the bidirectional reflectance distribution function (BRDF) and the bidirectional transmittance distribution function (BTDF) of several PTFE films, with thicknesses from 0.11 to 10 mm, are measured using a laser scatterometer at the wavelength of 635 nm. The directional-hemispherical reflectance (R) and transmittance (T) were obtained by integrating BRDF and BTDF for normal incidence. Comparison of the ratio of the measured R and T with that calculated from the adding-doubling method allows the determination of the reduced scattering coefficient. Furthermore, the effect of surface scattering is investigated by measuring the polarization-dependent BRDF and BTDF at oblique incidence. By analyzing the measurement uncertainty of BTDF in the near-normal observation angles at normal incidence, the present authors found that the scattering coefficient of PTFE should exceed 1200 cm(-1), which is much greater than that of biological tissues. On the other hand, the absorption coefficient of PTFE must be less than 0.01 cm(-1), much smaller than that of biological tissues, a necessary condition to achieve R > or =0.98 with a 10-mm-thick slab. PMID:19021442

  7. Constitutive modeling of shock response of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Resnyansky, A. D.; Bourne, N. K.; Millett, J. C. F.; Brown, E. N.

    2011-08-01

    Polytetrafluoroethylene (PTFE) is a polymer with a simple atomic structure that shows complex behavior under pressure and demonstrates a highly variable metastable phase structure in shock waves with amorphous and crystalline components. In turn, the crystalline component has four known phases with the high-pressure transition of the crystalline domain from crystalline phase IV at ambient through phase II to III. At the same time, as has been recently studied using spectrometry, the crystalline region nucleates from the amorphous one with load. Stress and velocity shock-wave profiles acquired recently with embedded gauges demonstrate features that may be related to the impedance mismatch between the phase domains subjected to such transitions resulting in variations of mechanical and thermophysical characteristics. We consider the inter-phase non-equilibrium and the amorphous-to-crystalline and inter-crystalline transitions that are associated with the high pressure and temperature transformations under shock wave loading as possible candidates for the analysis. The present work utilizes a multi-phase constitutive model that considers strength effects to describe the observed response under shock loading of the PTFE material. Experimental plate impact shock-wave histories are compared with calculated profiles using kinetics describing the transitions. The study demonstrates that the inter-phase pressure non-equilibrium of the state parameters plays the key role in the delay of the shock wave attenuation. At the same time, the forward transition associated with the crystallization might be responsible for the velocity spike in the experimental velocity profiles at high impact velocity and the modulus variation at low impact velocity. On the other hand, an accelerated attenuation of the velocity in the rarefaction wave is associated with another transition resulting in the residual crystallinity change during unloading.

  8. 21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Polytetrafluoroethylene with carbon fibers... Prosthetic Devices § 878.3500 Polytetrafluoroethylene with carbon fibers composite implant material. (a) Identification. A polytetrafluoroethylene with carbon fibers composite implant material is a porous...

  9. 21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Polytetrafluoroethylene with carbon fibers... Prosthetic Devices § 878.3500 Polytetrafluoroethylene with carbon fibers composite implant material. (a) Identification. A polytetrafluoroethylene with carbon fibers composite implant material is a porous...

  10. 21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polytetrafluoroethylene with carbon fibers... Prosthetic Devices § 878.3500 Polytetrafluoroethylene with carbon fibers composite implant material. (a) Identification. A polytetrafluoroethylene with carbon fibers composite implant material is a porous...

  11. 21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Polytetrafluoroethylene with carbon fibers... Prosthetic Devices § 878.3500 Polytetrafluoroethylene with carbon fibers composite implant material. (a) Identification. A polytetrafluoroethylene with carbon fibers composite implant material is a porous...

  12. Phase dependent fracture and damage evolution of polytetrafluoroethylene (PTFE)

    SciTech Connect

    Brown, E. N.; Rae, P.; Orler, E. B.; Thissell, W. R.; Dattelbaum, D. M.

    2004-01-01

    Compared with other polymers, polytetrafluoroethylene (PTFE) presents several advantages for load-bearing structural components including higher strength at elevated temperatures and higher toughness at lowered temperatures. Failure sensitive applications of PTFE include surgical implants, aerospace components, and chemical barriers. Polytetrafluoroethylene is semicrystalline in nature with their linear chains forming complicated phases near room temperature and ambient pressure. The presence of three unique phases near room temperature implies that failure during standard operating conditions may be strongly dependent on the phase. This paper presents a comprehensive and systematic study of fracture and damage evolution in PTFE to elicit the effects of temperature-induced phase on fracture mechanisms. The fracture behavior of PTFE is observed to undergo transitions from brittle-fracture below 19 C to ductile-fracture with crazing and some stable crack growth to plastic flow aver 30 C. The bulk failure properties are correlated to failure mechanisms through fractography and analysis of the crystalline structure.

  13. Viscoelastic Characterization of Polytetrafluoroethylene (PTFE) Polymer by Sharp Indentation

    NASA Astrophysics Data System (ADS)

    Stan, Felicia; Munteanu, Ana V.; Fetecau, Catalin

    2011-01-01

    In this paper, indentation of polytetrafluoroethylene (PTFE) polymer with a sharp indenter is investigated in order to identify the material parameters. The indentation creep, i.e., the relative change of the indentation depth under constant load, is investigated based on a hereditary integral and on a rheological model which describes a viscoelastic plastic response. Experimental data were fitted to the model in order to identify the model parameters.

  14. 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.

  15. 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. PMID:27119260

  16. 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.

  17. Lip rejuvenation using chemical abrasion and padding with expanded polytetrafluoroethylene implants.

    PubMed

    Mole, B

    1996-01-01

    Aesthetic improvement of the lips is a problem that must be treated in a totally independent way from the rest of the face because degeneration of the lips is tied to genetic or acquired factors for which no long-term procedure is effective. The effectiveness of resurfacing of large and small wrinkles using chemical abrasion has long been recognized. Labial padding, using supple Gore-Tex(R) implants that are cut to size and placed where necessary provides the desired result while preserving the function of the lip. Usually requested by the younger patient, it can be used in combination with chemical abrasion in the more mature patient. This technique is not only quick, tested, very effective, and definitive, but totally reversible if needed, which allows us to widen the indications with great safety. PMID:8670390

  18. EPA FABRIC FILTRATION STUDIES: 3. PERFORMANCE OF FILTER BAGS MADE FROM EXPANDED PTFE LAMINATE

    EPA Science Inventory

    The report, third in an EPA Fabric Filtration series, gives results of an evaluation of fabric filters made of an expanded polytetrafluoroethylene (PTFE) film supported on a woven Nomex scrim--the Gore Tex/Nomex fabric. Filtration efficiency was very high and other performance pa...

  19. 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.

  20. 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.

  1. 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

    ... resin (``PTFE resin'') from Japan. See Initiation of Five-Year (``Sunset'') Review, 75 FR 67082... Antidumping Duty Order; Granular Polytetrafluoroethylene Resin From Japan, 53 FR 32267 (August 24, 1988). On... of Antidumping Duty Orders on Granular Polytetrafluoroethylene Resin from Italy and Japan, 70...

  2. Sliding orientation effects on the tribological properties of polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Jang, Inkook; Burris, David L.; Dickrell, Pamela L.; Barry, Peter R.; Santos, Catherine; Perry, Scott S.; Phillpot, Simon R.; Sinnott, Susan B.; Sawyer, W. Gregory

    2007-12-01

    The chemical inertness, high melting point, and intrinsic lubricity of polytetrafluoroethylene (PTFE) have been used to develop solid lubricating parts for operation in extreme environments, from frying pans to satellites. The atomic-level mechanisms associated with friction and wear at PTFE surfaces are elucidated here by systematic investigations of the frictional anisotropy measured with respect to chain orientation. In particular, a combination of atomic-scale simulations, nanometer-scale atomic force microscopy experiments, micrometer-scale microtribometers experiments, and macroscale pin-on-disk experiments are used. Data across these length scales, from both the computational and experimental approaches, provide a consistent view of the mechanisms by which the structural orientation of PTFE contributes to its unique tribological properties.

  3. Selective deposition of copper on poly(tetrafluoroethylene)

    SciTech Connect

    Rye, R.R.; Chi, K.M.; Hampden-Smith, M.; Kodas, T.T.

    1991-12-31

    An additive three step process has been developed for patterned deposition of Cu onto poly(tetrafluoroethylene) (PTFE). The first step involves patterned irradiation with X-rays or electrons which is thought to cross link the PTFE surface; step two involves chemical etching with the result that only the non-irradiated areas are etched; and step three involves selective chemical vapor deposition (CVD) of Cu onto the etched surface at 200 C using (hexafluoroacetylacetonato)Cu(I) trimethylphosphine ((hfac)Cu(PMe{sub 3})). The non-irradiated areas of the surface are covered by a continuous, dense Cu film with X-ray photoelectron spectra show to contain only surface impurities that are easily removed by a short Ar ion sputter. The irradiated areas show the presence of only C and F, characteristic of PTFE.

  4. 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.

  5. 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

  6. Change in surface morphology of polytetrafluoroethylene by reactive ion etching

    NASA Astrophysics Data System (ADS)

    Takahashi, Tomohiro; Hirano, Yuki; Takasawa, Yuya; Gowa, Tomoko; Fukutake, Naoyuki; Oshima, Akihiro; Tagawa, Seiichi; Washio, Masakazu

    2011-02-01

    Polytetrafluoroethylene (PTFE) was exposed to Ar, CF 4, N 2 and O 2 plasmas using a reactive ion etching facility. After the exposure, the change in the surface morphology of PTFE was examined and characterization studies were performed for the etching rate, surface roughness, radical yields, chemical structures, water repellency and so on. The etching rates of Ar, CF 4, N 2 and O 2 plasmas were 0.58, 7.2, 4.4 and 17 μm/h, respectively. It was observed that needle-like nano-fiber structures on the surface were irregularly fabricated by the CF 4 plasma. In addition, when the water repellency of exposed samples was evaluated by contact angle, they showed super-hydrophobic properties: contact angle over 150°.

  7. Modification of polytetrafluoroethylene surfaces using H2S plasma treatment

    NASA Astrophysics Data System (ADS)

    Vesel, Alenka; Kovac, Janez; Zaplotnik, Rok; Modic, Martina; Mozetic, Miran

    2015-12-01

    A process for modifying the surface properties of polytetrafluoroethylene (PTFE) polymer using sulfur-containing gaseous plasma is presented in this paper. Samples of PTFE foils were treated in pure H2S gaseous plasma sustained by an electrode-less radio-frequency discharge in the E-mode. The samples were kept at a floating potential. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities and morphology. An extremely thin film of chemically bonded sulfur was formed on the surface after a few seconds of plasma treatment, whereas a treatment duration of more than a minute resulted in the deposition of pure sulfur. The deposited film remained as thin as a few nanometers, even after half an hour of treatment.

  8. Expanding Universe

    NASA Astrophysics Data System (ADS)

    Schrödinger, E.

    2011-02-01

    Preface; Part I. The de Sitter Universe: 1. Synthetic construction; 2. The reduced model: geodesics; 3. The elliptic interpretation; 4. The static frame; 5. The determination of parallaxes; 6. The Lemaître-Robertson frame; Part II. The Theory of Geodesics: 7. On null geodesics; i. Determination of the parameter for null lines in special cases; ii. Frequency shift; 8. Free particles and light rays in general expanding spaces, flat or hyperspherical; i. Flat spaces; ii. Spherical spaces; iii. The red shift for spherical spaces; Part III. Waves in General Riemannian Space-Time: 9. The nature of our approximation; 10. The Hamilton-Jacobi theory in a gravitational field; 11. Procuring approximate solutions of the Hamilton-Jacobi equation from wave theory; Part IV. Waves in an Expanding Universe: 12. General considerations; 13. Proper vibrations and wave parcels; Bibliography.

  9. Expanding Gravity

    NASA Astrophysics Data System (ADS)

    Aisenberg, Sol

    2005-04-01

    Newton's gravitational constant Gn and Laws of Gravity are based upon observations in our solar system. Mysteries appear when they are used far outside our solar system Apparently, Newton's gravitational constant can not be applied at large distances. Dark matter was needed to explain the observed flat rotational velocity curves of spiral galaxies (Rubin), and of groups of remote galaxies (Zwicky). Our expansion of Newton's gravitational constant Gn as a power series in distance r, is sufficient to explain these observations without using dark matter. This is different from the MOND theory of Milgrom involving acceleration. Also, our Expanded Gravitational Constant (EGC) can show the correct use of the red shift. In addition to the Doppler contribution, there are three other contributions and these depend only upon gravity. Thus, velocity observations only based on the red shift can not be used to support the concept of the expanding universe, the accelerating expansion, or dark energy. Our expanded gravity constant can predict and explain Olbers' paradox (dark sky), and the temperature of the CMB (cosmic microwave background). Thus, CMB may not support the big bang and inflation.

  10. Percutaneous bail-out treatment of vein graft rupture with a polytetrafluoroethylene-covered stent.

    PubMed

    Pavlidis, Antonios N; Karamasis, Grigorios V; Clapp, Brian R

    2013-12-01

    Vessel perforation is an undesirable and life-threatening complication during vein graft angioplasty. We report on a case of vein graft rupture during angioplasty, which was successfully managed with deployment of a polytetrafluoroethylene-covered stent. PMID:24160712

  11. ADSORPTION OF ORGANIC COMPOUNDS FROM WATER WITH POROUS POLY(TETRAFLUOROETHYLENE)

    EPA Science Inventory

    The use of Chromosorb T, an aggregate of poly(tetrafluoroethylene) (PTFE, Teflon), to concentrate trace organic substances from aqueous solution by column chromatography is investigated. Differences in capacity between two different PTFE aggregates are linked to differences in su...

  12. 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.

  13. New methods for circuit fabrication 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. )

    1994-12-01

    By combining conventional integrated-circuit processing techniques with chemical etching for strong Cu film adhesion, three processes for the fabrication of the fine (< 20 [mu]m, a factor of five smaller than existing technology), adherent conducting feature on poly(tetrafluoroethylene) (PTFE) substrates have been developed. Metal features are defined using a lift-off technology, electroless plating, or a combination of electroless and electroplating. The third process requires additional processing steps but is also the most versatile technique enabling 4 [mu]m thick metal features with high lateral resolution. These three processes results in a less expensive process for patterning metal features on an etched PFTE substrate with resolution of at least a factor of five better than existing processes. Adhesion of the metal features depends upon successful substrate preparation by etching the PTFE in a sodium naphalenide solution. Using the three processes discussed above, coupled-line quadrature (Lange) couplers that demonstrate equal power splitting between 5 and 14 GHz have been fabricated on a PTFE substrate. Lange couplers have extensive applications as passive hybrid device components in microwave and radio-frequency (RF) systems.

  14. Characterization of a nanometer-thick sputtered polytetrafluoroethylene film

    NASA Astrophysics Data System (ADS)

    Li, Lei; Jones, Paul M.; Hsia, Yiao-Tee

    2011-02-01

    Fast growth of nanotechnology, e.g. hard disk drive (HDD) and microelectromechanical system/nanoelectromechanical system (MEMS/NEMS), requires nanometer-thick protection films with high thermal stability and low surface energy. In this paper, we report the characterization results of a nanometer-thick sputtered polytetrafluoroethylene (PTFE) film prepared by radio frequency (RF) sputtering. Atomic force microscopy (AFM) and X-ray reflectivity (XRR) results show that the nanometer-thick sputtered PTFE film has good uniformity. Thermally programmed desorption (TPD) results show that the film is thermally stable up to 430 °C. Surface energy measurement via contact angle method shows that the film has low surface energy with the thickness as low as 1.5 nm. X-ray photoelectron spectroscopy (XPS) data suggests that the film has crosslinked molecular structure, which results in amorphous morphology as shown by X-ray diffraction (XRD) data. Nano-indentation testing shows that the sputtered film has higher hardness and modulus than bulk PTFE. The structure-property relationship has been discussed.

  15. 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.

  16. Mechanical characterization of sub-micron polytetrafluoroethylene (PTFE) thin films

    SciTech Connect

    Lucas, B.N.; Oliver, W.C.; Rosenmayer, C.T.

    1998-12-31

    This study reports the results of an investigation of the mechanical properties of polytetrafluoroethylene (PTFE) thin films on silicon substrates in the 0.5 to 15 {micro}m thickness regime using frequency specific depth-sensing indentation. All measurements were conducted at an excitation frequency of 45 Hz using a constant (1/P dP/dt) load ramp of 0.1 s{sup {minus}1}. The modulus of the PTFE at a depth of 5% of the film thickness was measured to be approximately 1 GPa ({nu} = 0.46) independent of film thickness. These values are somewhat higher than the values obtained from free-standing 15 {micro}m film measurements of 0.4 GPa for the tensile modulus and 0.49 GPa for the storage modulus {at} 1.1 Hz. The film hardness at these depths was observed to range between 30 and 55 MPa with no correlation observed between the hardness and respective film thickness. While reliability modeling for interconnects currently uses interlayer dielectric mechanical properties data determined from free-standing films with thicknesses of several microns, these in-situ results should more closely mimic the constrained deformation that occurs during service and perhaps lead to a better understanding of the electromigration resistance of PTFE.

  17. Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal.

    PubMed

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

    2016-04-01

    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. PMID:27002786

  18. Expanded Yegua

    SciTech Connect

    Hart, R.E.; Grayson, S.; Benes, J.

    1988-01-01

    The upper Eocene Yegua Formation expands dramatically across a regional flexure generally 12-15 km wide. During each of several postulated Yegua sea level drops, this flexure became a focal point for deltaic deposition of good to excellent reservoir-quality sands. From the western edge of the Houston salt dome basin to the San Marcos arch, this trend has yielded, since 1982, at least seven noteworthy discoveries: Toro Grande and Lost Bridge fields in Jackson County, and Black Owl, Shanghai, Shanghai East, El Campo, and Phase Four fields in Wharton County, Texas. El Campo field in Wharton County, Texas, was discovered in December 1985 by Ladd Petroleum Corporation with the drilling of the Ladd Petroleum 1 Popp well. Mud logs acquired while drilling indicated that a very sandy reservoir, with encouraging quantities of natural gas and condensate had been encountered. Subsequent open-hold logging generated more questions than answers about the prospective sand section. Additional open hole logs (EPT/ML,SHDT) were run to identify what turned out to be an extremely laminated sand-shale sequence over 400 ft thick. Subsequent development drilling and the acquisition of a 120 ft whole core provided valuable data in analyzing this prolific, geopressured natural gas and condensate Yegua reservoir. Whole-core data, open-hole logs, and computer logs were integrated to develop petro-physical evaluation procedures and to determine the environment of deposition. El Campo field is believed to represent an extremely thick, delta front slope to distal delta front facies.

  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. 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. PMID:27150739

  2. 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. PMID:21347955

  3. 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

  4. ENVIRONMENTALLY-BENIGN POLYTETRAFLUOROETHYLENE (PTFE) COATINGS FOR MOLD RELEASE - PHASE II

    EPA Science Inventory

    GVD proposes to develop high performance, volatile organic compound (VOC)-free and perfluorooctanoic acid (PFOA)-free, non-stick mold release coatings based on its novel polytetrafluoroethylene (PTFE) fluoropolymer technology. Most commercial mold release agents make use of...

  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. 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. PMID:27133329

  7. 76 FR 29008 - Granular Polytetrafluoroethylene Resin From Italy; Correction of Notice of Scheduling

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-19

    ... Federal Register May 12, 2011 (76 FR 27663), the Commission published a notice of scheduling of an expedited five-year review on an antidumping duty order on granular polytetrafluoroethylene resin from Italy..., 2011. FOR FURTHER INFORMATION CONTACT: Stefania Pozzi Porter (202-205-3177;...

  8. 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. PMID:25631168

  9. 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

  10. The effects of low earth orbit atomic oxygen on the properties of Polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Hooshangi, Zhila; Hossein Feghhi, Seyed Amir; Saeedzadeh, Rezgar

    2016-02-01

    Polymers are widely used in space systems as the structural materials. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen. Exposure of polymeric materials to atomic oxygen results in destructive effects on the chemical, electrical, thermal, optical and mechanical properties as well as surface degradation. In the present work, the effects of atomic oxygen on the mechanical, thermal, and optical properties of Polytetrafluoroethylene film have been investigated. The atomic oxygen density was calculated by SPENVIS tool. After the atomic oxygen exposure by using radio-frequency (RF) plasma source, the appearance of the samples changed, and the mass of the samples reduced because of outgassing. The results of thermal analysis showed that atomic oxygen flux does not affect thermal degradation of samples regarding TGA diagrams. By increasing the atomic oxygen flux, the amount of absorbance increased showing that atomic oxygen had damaged the surface of Polytetrafluoroethylene, and it had oxidized the surface of the polymer.

  11. 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.

  12. Near Infrared 45°/0° Reflectance Factor of Pressed Polytetrafluoroethylene (PTFE) Powder

    PubMed Central

    Nadal, Maria E.; Barnes, P. Yvonne

    1999-01-01

    Pressed polytetrafluoroethylene (PTFE) powder is commonly used as a reflectance standard for bidirectional and hemispherical geometries. The wavelength dependence of the reflectance factor of PTFE is presented for the near-infrared spectral region (800 nm to 1600 nm) for the 45°/0° geometry, as well as in the visible spectral region (380 nm to 800 nm) for comparison with previously published results.

  13. Immobilization of fluorous oligosaccharide recognized by influenza virus on polytetrafluoroethylene filter.

    PubMed

    Tojino, Mami; Mori, Masako; Kasuya, Maria Carmelita Z; Hatanaka, Kenichi; Kawaguchi, Atsushi; Nagata, Kyosuke; Shirai, Takashi; Mizuno, Mamoru

    2012-01-15

    The lactoside with PEG-fluorous tag was introduced to BHK-21(C-13) cells to generate a GM3-type oligosaccharide (Siaα2-3Galβ1-4Glc). The GM3-type oligosaccharide obtained was easily immobilized by spotting onto commercially available polytetrafluoroethylene (PTFE) filter through non-covalent fluorous affinity and simply assessed by dot blot method using the interaction of carbohydrate- with proteins which recognize sialic acid such as virus membrane proteins. PMID:22177082

  14. 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.

  15. Life-threatening common carotid artery blowout: rescue treatment with a newly designed self-expanding covered nitinol stent.

    PubMed

    Kim, H S; Lee, D H; Kim, H J; Kim, S J; Kim, W; Kim, S Y; Suh, D C

    2006-03-01

    Carotid blowout is a devastating complication in patients with head and neck malignancy. A covered stent offers an alternative to treatment of a carotid blowout patient thought to be at high risk for surgery or carotid occlusion. Stent placement in the common carotid artery or carotid bulb is a technical challenge because of large luminal diameter and luminal calibre discrepancy between internal carotid artery and common carotid artery. We present four patients with common carotid rupture and massive bleeding who were treated with self-expanding covered stents, among them, two cases were treated with newly designed self-expanding polytetrafluoroethylene (PTFE)-covered nitinol stents. PMID:16498035

  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. PMID:26628035

  17. UPS study of VUV-photodegradation of polytetrafluoroethylene (PTFE) ultrathin film by using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Ono, Masaki; Yamane, Hiroyuki; Fukagawa, Hirohiko; Kera, Satoshi; Yoshimura, Daisuke; Okudaira, Koji K.; Morikawa, Eizi; Seki, Kazuhiko; Ueno, Nobuo

    2005-07-01

    The VUV-photodegradation of polytetrafluoroethylene (PTFE) ultra-thin film was studied by ultraviolet photoelectron spectroscopy and quadrupole mass spectrometry. These results were compared with the previous photodegradation studies of the polyvinylidenefluoride (PVDF) and polyethylene (PE). Generation of new peak, π-band originated from the Cdbnd C bond, was observed in the low binding energy region of the UPS spectra in both PVDF and PE during the photodegradation. In contrast, no new peak generation was observed in the UPS of the photodegraded PTFE. Mass spectrometry analysis also suggested that the Cdbnd C bond generation is not a major mechanism in the VUV photodegradation of PTFE.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  19. 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.

  20. Combustion synthesis of silicon carbide assisted by a magnesium plus polytetrafluoroethylene mixture

    SciTech Connect

    Ayral, R.M.; Rouessac, F.; Massoni, N.

    2009-11-15

    In this study, the use of SiC combustion synthesis for immobilization of {sup 14}C was considered. Due to the low exothermicity of the reaction between silicon and graphite, a highly exothermic mixture (magnesium and polytetrafluoroethylene) was used both as a chemical oven and activate additive in the mixture. With this configuration the reaction between graphite and silicon was initiated and propagated on the whole sample. The self-propagating high temperature synthesis samples were characterized by using scanning electron microscopy and X-ray diffraction.

  1. Temperature dependence of catalytic cyclohexane partial oxidation in a polytetrafluoroethylene reactor

    NASA Astrophysics Data System (ADS)

    Lončarević, D.; Krstić, J.; Banković, P.; Anić, S.; Čupić, Ž.

    2007-09-01

    Polymer-supported Co(II) catalyst was prepared and its activity and selectivity in the partial oxidation of cyclohexane was determined at several temperatures in a polytetrafluoroethylene reactor (PTFE). The catalyst was characterized by means of SEM-EDX, FTIR, diffuse reflectance UV-Vis, N2 sorption, and mecury porosimetry. Activation energies were determined under steady state conditions for the net production of cyclohexanone and cyclohexanol and for cyclohexane and oxygen net consumption. Some activation energies were lower than the ones reported for the uncatalyzed process, indicating that the catalyst played an important role in the initiation of the free-radical reaction.

  2. 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.

  3. 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.

  4. A facile method to fabricate superamphiphobic polytetrafluoroethylene surface by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fan, Wenzhong; Qian, Jing; Bai, Feng; Li, Yangbo; Wang, Chengwei; Zhao, Quan-Zhong

    2016-01-01

    We report a simple method to fabricate superamphiphobic polytetrafluoroethylene (PTFE) surfaces by femtosecond laser direct irradiation. After femtosecond laser direct writing, a dual-scale composite structure combined a groove-like microstructure with a lamellar submicron structure forms on the PTFE surface, enhancing its hydrophobic properties with a contact angle increasing from 109° to 156.88°, as well as exhibiting transition from intrinsic oleophilicity to superoleophobicity. Meanwhile, the wettability of the surface can be tuned by changing the roughness and the interval between two adjacent micro-grooves. Furthermore, we also explain the relationship between the interval width and the contact angle using the Cassie-Baxter model.

  5. Shock and Recovery of Polytetrafluoroethylene Above and Below the Phase II to Phase III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Rae, Philip J.; Trujillo, Carl P.; Dattelbaum, Dana M.; Gray, George T.; Bourne, Neil K.

    2006-07-01

    Polytetrafluoroethylene (PTFE) is a semi-crystalline polymer exhibiting complicated pressure and temperature dependent phases. High strain rate applications in aerospace, defense, and automotive industries have lead to interest in the shock response of PTFE and resulting changes in the polymer structure. Experimental studies on pressure-induced phase transitions using shock-loading techniques and the resulting changes in crystalline structure are presented. Gas launcher experiments were performed on pedigreed PTFE 7C momentum trapped assemblies with impact pressures from 0.4 to 0.85 GPa to investigate the material response above and below the phase II to phase III crystalline transition. [LAUR-05-5945

  6. Interaction of proton microbeam with the inner surface of a polytetrafluoroethylene macrocapillary

    NASA Astrophysics Data System (ADS)

    Rajta, I.; Nagy, G. U. L.; Bereczky, R. J.; Tőkési, K.

    2015-07-01

    The transmission of 1 MeV proton microbeam through a single, cylindrically shaped, micrometre-sized polytetrafluoroethylene capillary was studied. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and the small beam divergence disabled the geometrical transmission of the beam through the target. The time dependence of the intensity, the charge-state and the deflection of the transmitted beam were investigated. We found that pure guided transmission of a MeV/amu energy ion beam is possible through an insulator capillary.

  7. Polarized XANES studies on the mechanical rubbing effect of poly(tetrafluoroethylene) and its model compound

    NASA Astrophysics Data System (ADS)

    Nagayama, K.; Mitsumoto, R.; Araki, T.; Ouchi, Y.; Seki, K.

    1995-02-01

    The structural change of the evaporated perfluorotetracosane (PFT) n-CF 3 (CF 2) 22CF 3 and poly(tetrafluoroethylene) (PTFE) (CF 2) n films by the mechanical rubbing process was examined with use of XANES spectroscopy. In the PTFE film the chains were almost parallel to the surface and were uniaxially realigned along the rubbing direction, while in the PFT film the chains after evaporation were oriented normal to the surface, and this orientation was hardly affected by the rubbing process. The chains of the PFT evaporated on the rubbed PTFE film aligned along the rubbing direction.

  8. 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.

  9. 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.

  10. 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. PMID:25325550

  11. Effect of Pulse Duration on Polytetrafluoroethylene Shocked above the Crystalline Phase II-Iii Transition

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. 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% and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  12. [gamma]-Irradiation-induced grafting of poly(styrenesulfonate) to poly(tetrafluoroethylene) shielded microelectrodes

    SciTech Connect

    Ramos, B.L.; Blubaugh, E.A.; Ridgway, T.H.; Heineman, W.R. )

    1994-06-01

    A new method for the fabrication and polymer modification of microelectrodes is described. These electrodes are constructed by heat sealing the electroactive material in dual shrink/melt poly(tetrafluoroethylene) (PTFE) under vacuum. The PTFE shield may be activated to provide a support upon which polymers of interest may be grafted. [gamma]-Irradiation was used to graft polymerize styrene to the surface. The poly-(styrene) was subsequently sulfonated with chlorosulfonic acid to form poly(styrenesulfonate). Scanning electron microscopy and Raman microspectroscopy provide evidence that the poly-(styrenesulfonate) film has been formed and extends over the electrode material. Voltammetry indicates that hexaammine-ruthenium(III) cation is preconcentrated and stabilized via an association with the polymer film. 24 refs., 8 figs., 2 tabs.

  13. A comparative study of the structure and cytotoxicity of polytetrafluoroethylene after ion etching and ion implantation

    NASA Astrophysics Data System (ADS)

    Shtansky, D. V.; Glushankova, N. A.; Kiryukhantsev-Korneev, F. V.; Sheveiko, A. N.; Sigarev, A. A.

    2011-03-01

    The ion-plasma treatment has been widely used for modifying the surface structure of polymers in order to improve their properties, but it can lead to destruction of the surface and, as a consequence, to an increase in their toxicity. A comparative study of the structure and cytotoxicity of polytetrafluoroethylene (PTFE) after the ion etching (IE) and ion implantation (II) for 10 min with energy densities of 363 and 226 J/cm2, respectively, has been performed. It has been shown that, unlike the ion implantation, the ion etching results in the destruction of the polymer and in the appearance of the cytotoxicity. The factors responsible for this effect, which are associated with the bulk and surface treatment, as well as with the influence of the temperature, have been discussed.

  14. Surface modification of porous poly(tetrafluoroethylene) film via cold plasma treatment

    NASA Astrophysics Data System (ADS)

    Shi, Tongna; Shao, Meiling; Zhang, Hongrui; Yang, Qing; Shen, Xinyuan

    2011-12-01

    In this study, cold plasma technology was applied for the surface modification of porous polytetrafluoroethylene (PTFE) film to improve the hydrophilicity. The surface properties of PTFE, modified by air, helium (He) or acrylic acid (AAc), were investigated with scanning electron microscopy (SEM), scanning probe microscope (SPM), in situ X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The changes of the surface property before and after plasma treatment were discussed. According to SEM and SPM measurements, the surface roughness increased at different levels after plasma treatment. Compared to air and AAc plasma treatment, the He plasma treatment introduced large amounts of oxygen into the surface, as known from XPS results. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly improved due to the surface roughness and changes of chemical elements on the PTFE surface.

  15. Mechanical characterization of polytetrafluoroethylene polymer using full-field displacement method

    NASA Astrophysics Data System (ADS)

    Nunes, L. C. S.

    2011-05-01

    The aim of this work is to estimate two important material properties of the polytetrafluoroethylene (PTFE) polymer by means of a single experimental test. The displacement fields around a crack tip are used for estimating the modulus of elasticity (or, Young's modulus) and Poisson's ratio. These parameters are evaluated by fitting linear fracture mechanic expression of displacement fields in the vicinity of the crack, for mode I, to the experimental data. Measurements of these displacements are carried out using digital image correlation (DIC) method. In this way, the experimental procedure is conducted by loading a double-edge-cracked plate specimen. In order to validate the results, two available experimental tests have been performed. The modulus of elasticity is determined by means of the tensile test, using a standard test machine. Moreover, the Poisson's ratio is obtained by measuring lateral compressive and longitudinal extensional strain using DIC method.

  16. Radiation resistance evaluation of cross-linked polytetrafluoroethylene by the investigation of friction and wear behavior

    NASA Astrophysics Data System (ADS)

    Tang, Zhongfeng; Wang, Mouhua; Zhao, Yanning; Wu, Guozhong

    2011-03-01

    Radiation resistance of cross-linked polytetrafluoroethylene (XPTFE) sheets was evaluated by measuring the friction and wear properties as well as observing the morphology after γ-irradiation in air at room temperature. The wear resistance of XPTFE was confirmed to be much higher than that of virgin PTFE. The friction coefficient of XPTFE decreased with increasing dose, whereas the wear resistance remained stable until a critical dose was reached and then decreased sharply with dose. The critical dose of wear resistance was dependent on the crosslinking density or crosslinking dose of XPTFE. The radiation resistance of XPTFE improved significantly due to the formation of three-dimensional crosslinking networks by irradiation in the molten state. In addition, morphologies of the abraded debris of virgin PTFE and XPTFE were also compared and a clear difference was observed.

  17. Plasma-induced Styrene Grafting onto the Surface of Polytetrafluoroethylene Powder for Proton Exchange Membrane Application

    NASA Astrophysics Data System (ADS)

    Lan, Yan; Cheng, Cheng; Zhang, Suzhen; Ni, Guohua; Chen, Longwei; Yang, Guangjie; Nagatsu, M.; Meng, Yuedong

    2011-10-01

    Low-temperature plasma treatment was adopted to graft styrene onto polytetrafluoroethylene (PTFE) powder, which is widely used in the fabrication of proton exchange membrane (PEM). The grafted PTFE powder was sulfonated in chlorosulfonic acid and fabricated into a membrane, which was used as inexpensive PEM material for a proton exchange membrane fuel cell (PEMFC). Fourier transform infrared spectroscopy attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analysis were used to characterize the structure of the sulfonated PTFE powder. The results showed that all the PTFE powders were successfully grafted by nitrogen plasma and then sulfonated under such experimental conditions. A scanning electron microscopy (SEM) image indicated that the fabricated membrane exhibits flat morphology and homogenous structure. The ion exchange capacity (IEC) of this kind of PEM was also investigated.

  18. Facile fabrication of superhydrophobic polytetrafluoroethylene surface by cold pressing and sintering

    NASA Astrophysics Data System (ADS)

    Jiang, Cheng; Hou, Weixin; Wang, Qihua; Wang, Tingmei

    2011-03-01

    A series of superhydrophobic polytetrafluoroethylene (PTFE) surfaces were prepared by a facile cold pressing and sintering method, and their microstructures and wetting behaviors could be artificially tailored by altering sintering temperature and using different masks. Specifically, the microstructures mainly depended on the sintering temperature, whereas the wetting behaviors, water contact angle (WCA) and sliding angle (SA), greatly hinged on both the sintering temperature and mask. Then a preferable superhydrophobic surface with WCA of 162 ± 2° and SA of 7° could be obtained when the sintering temperature was 360 °C and the 1000 grit abrasive paper was used as a mask. In addition, it was worth noting that the as-prepared surfaces exhibited excellent stability under UV illumination, which was the most key factor for them toward practical applications.

  19. Fluorescent analysis of polytetrafluoroethylene treated by γ-irradiation near the melting point

    NASA Astrophysics Data System (ADS)

    Khatipov, Sergei; Nurmukhametov, Ravil; Sakhno, Yuriy; Klimenko, Vasiliy; Seliverstov, Denis; Sakhno, Tamara

    2011-03-01

    Radiation-modified polytetrafluoroethylene (PTFE), which exhibits intense fluorescence in the visible spectral region, was prepared. Radiation modification was performed with 60Co rays at 330 °C, at a dose of 0.2 MGy and an atmospheric air pressure ranging from 10 -3 to 100 mbar. The fluorescence and electronic absorption spectra of film and block PTFE specimens irradiated under the given conditions were studied. It was concluded that polyene systems of π-bonds -CF 2-(CF=CF) n-CF 2- ( n=4-7) in the product are responsible for fluorescence. A scheme for the radiation-chemical transformation resulting in π-conjugated structures was proposed. The important role of molecular oxygen in radiation-chemical processes responsible for the generation and build-up of fluorescing entities was revealed.

  20. Super hydrophobic surface of polytetrafluoroethylene fabricated by picosecond laser and phenomenon of total internal reflection underwater

    NASA Astrophysics Data System (ADS)

    Jiang, Yijian; Cao, Wenshen; Zhao, Yan; Wu, Yan; Ji, Lingfei

    2015-03-01

    A groove-shaped array with average 25 μm interval, 25 μm wall thickness, 75 μm depth and a columnar array with average 30 μm side length, 25 μm interval, 43 μm depth are processed by 1064 nm picosecond laser on polytetrafluoroethylene (PTFE) surface at room temperature. The water contact angle of modified PTFE surface can reach 167°, which show super hydrophobic surface of PTFE is prepared. It is observed super hydrophobic surface reflects metal luster underwater through the glassware when super hydrophobic PTFE entirely immerses in pure water. The experiment conducts super hydrophobic surface will enhance intensity of reflection of visible light underwater, which is due to total internal reflection of super hydrophobic surface und erwater.

  1. Water dispersible polytetrafluoroethylene microparticles prepared by grafting of poly(acrylic acid)

    NASA Astrophysics Data System (ADS)

    Yang, Changqiao; Xu, Lu; Zeng, Hongyan; Tang, Zhongfeng; Zhong, Lei; Wu, Guozhong

    2014-10-01

    Due to the hydrophobic nature and high gravimetric density, it is very difficult to obtain water dispersible polytetrafluoroethylene (PTFE) powder. In this work, hydrophilic PTFE microparticles were successfully prepared by grafting of poly(acrylic acid) onto PTFE micropowder via a pre-irradiation method. The as-obtained hydrophilic PTFE microparticles were analyzed by FT-IR, 1H NMR, CA, SEM and TGA. After neutralization by sodium hydroxide, the water contact angle decreased from 145.69° for pristine PTFE to 63.38° for PTFE-g-NaAA. The obtained micropowder can be easily dispersed in water to form a dispersion with very high stability. Furthermore, the presence of grafted PAA shows no obvious influence on degradation temperature of PTFE backbones.

  2. 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.

  3. 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.

  4. 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.

  5. Percutaneous pulmonary vein stenosis angioplasty complicated by rupture: successful stenting with a polytetrafluoroethylene-covered stent.

    PubMed

    Matsumoto, Takashi; Zahn, Evan M; Kar, Saibal

    2014-06-01

    A 47-year-old-man with prior pulmonary vein (PV) isolation for atrial fibrillation developed progressive shortness of breath and was found to have total occlusion of the left lower and significant stenosis in left upper PV. A ventilation/perfusion scan showed decreased left lung perfusion. Percutaneous PV stenosis angioplasty was complicated by the rupture of left lower PV with pericardial tamponade; successful stenting with a polytetrafluoroethylene-covered stent was performed. Follow-up studies at nine months showed patency of both veins with a normal ventilation perfusion scan. In this article, we will discuss acquired PV stenosis following PV isolation, percutaneous PV intervention, and the literature supporting the procedure. PMID:24590687

  6. Stabilization of positive charge on polytetrafluoroethylene electret films treated with titanium-tetrachloride vapor

    SciTech Connect

    Rychkov, Dmitry; Gerhard, Reimund

    2011-03-21

    The surface of polytetrafluoroethylene films was treated with titanium-tetrachloride vapor. The treatment was carried out in a flow reactor by means of molecular-layer deposition, a method from the arsenal of chemical nanotechnology. X-ray photoelectron spectroscopy reveals that such a treatment results in considerable changes in the chemical composition at and near the surface of the fluoropolymer film. Both, defluorination and oxidation of the surface were observed. At the same time, samples treated with titanium tetrachloride show a significant enhancement in the thermal stability of the positive homocharge. The thermally stimulated surface-potential-decay curves were observed to shift to higher temperatures by more than 100 deg. C

  7. Fibroporous polytetrafluoroethylene modified with iron nanoparticles: Structure and electronic and magnetic properties

    NASA Astrophysics Data System (ADS)

    Vasil'kov, A. Yu.; Suzdalev, I. P.; Maksimov, Yu. V.; Nikitin, L. N.; Naumkin, A. V.; Abramchuk, S. S.; Tolstopyatov, E. M.; Grakovich, P. N.

    2013-06-01

    A method for synthesizing iron-containing nanocomposite based on fibroporous polytetrafluoroethylene (PTFE) is described. Fibroporous PTFE obtained under the radiation of a CO2 laser on block PTFE is modified in supercritical carbon dioxide (sc CO2) to form micro- and nanoporous structures. Porous fluoropolymer is treated with a solution of bis(toluene)iron(0) obtained by metal-vapor synthesis (MVS). The composition and structure of iron-containing fluoropolymer is studied by transmission electron microscopy and X-ray photoelectron and Mössbauer spectroscopy. Fe nanoparticles with an average size of 9 nm, consisting of ˜30% FeO and ˜70% Fe3+, are registered in the sample. Fe0 nanoparticles are stabilized in fluoropolymer pores and are coated with nanoparticles of nonstoichiometric iron oxides that have superparamagnetic properties.

  8. 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.

  9. 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.

  10. 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.

  11. Single-crystalline polytetrafluoroethylene-like nanotubes prepared from atmospheric plasma discharge

    SciTech Connect

    Zhang, J.; Guo, Y.; Xu, J.Z.; Fang, X.S.; Xie, H.K.; Shi, D.L.; He, P.; Ooij, W.J. van

    2005-03-28

    Atmospheric plasma polymerization of perfluorohexane was investigated in this letter. A large quantity of single-crystalline polytetrafluoroethylene (PTFE)-like nanotubes were formed on a simultaneously deposited film at room temperature without any catalysts or templates. The outer diameter of the nanotubes varied from 60 to 1200 nm with a maximum aspect ratio up to 100:1. Transmission electron microscopy and x-ray diffraction results indicated a single crystal close-packed hexagonal (cph) structure in the nanotubes. Polarization optical micrographs of the nanotubes showed their thermal stability comparable to PTFE. It is suggested that the plasma filament played a key role in the rapid formation of the nanotubes. This atmospheric plasma discharge synthesis can serve as a common method for nanofabrication of many other single-crystalline polymer systems.

  12. 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

    2016-05-01

    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.

  13. 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.

  14. Improved adhesion of Ni films on X-ray damaged polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    The considered investigation shows that the adhesion of evaporated Ni on polytetrafluoroethylene (PTFE) is enhanced by irradiating the PTFE surface prior to evaporation. Evidence obtained with the aid of X-ray photoelectron spectroscopy is presented concerning the association of the enhanced adhesion with an interfacial chemical reaction. Evaporated Ni clearly adheres better to the X-ray damaged PTFE surface than to the undamaged surface. There is evidence that the improved adhesion is not related to the Ni-C bond, but rather to the NiF2. A possible mechanism which may be consistent with the data is the formation of a F-Ni-C complex, where C is a member of the polymer chain.

  15. Effect of Pulse Duration on Polytetrafluoroethylene Shocked Above the Crystalline Phase II--III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Gray, George T., III; Rae, Philip J.; Trujillo, Carl P.; Bourne, Neil K.

    2007-06-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. 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, DSC) and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  16. Shock and Recovery of Polytetrafluoroethylene Above and Below the Phase II To Phase III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Bourne, Neil K.

    2005-07-01

    Polytetrafluoroethylene (PTFE) is semi-crystalline in nature with its linear chains forming complicated temperature and pressure dependent phases. Due to its desirable mechanical properties applications of PTFE include structures designed for dynamic largescale plasticity excursions. Experimental studies on pressure-induced phase transitions using shock-loading techniques and the resulting changes in crystalline structure are presented. Disks of pedigreed PTFE 7C have been shock loaded in momentum trapped assemblies using a 80 mm gas launcher. Challenges in momentum trapping and soft recovery arising from the low yield stress of PTFE (9 MPa at room temperature) are discussed. Experiments were performed with impact pressures from 0.4 to 0.85 GPa to investigate the material response above and below the phase II to phase III crystalline transition. Changes in crystalline structure of the recovered materials were quantified using dynamic scanning calorimetry (DSC) and density.

  17. 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.

  18. 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.

  19. Stabilization of positive charge on polytetrafluoroethylene electret films treated with titanium-tetrachloride vapor

    NASA Astrophysics Data System (ADS)

    Rychkov, Dmitry; Gerhard, Reimund

    2011-03-01

    The surface of polytetrafluoroethylene films was treated with titanium-tetrachloride vapor. The treatment was carried out in a flow reactor by means of molecular-layer deposition, a method from the arsenal of chemical nanotechnology. X-ray photoelectron spectroscopy reveals that such a treatment results in considerable changes in the chemical composition at and near the surface of the fluoropolymer film. Both, defluorination and oxidation of the surface were observed. At the same time, samples treated with titanium tetrachloride show a significant enhancement in the thermal stability of the positive homocharge. The thermally stimulated surface-potential-decay curves were observed to shift to higher temperatures by more than 100 °C

  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. Silicon microfabricated beam expander

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  2. 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.

  3. 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…

  4. EXPANDED BED BIOLOGICAL TREATMENT

    EPA Science Inventory

    A three-year pilot-scale research investigation at the EPA Lebanon Pilot Plant was conducted to evaluate the feasibility of a unique biological secondary treatment process, designated the Expanded Bed Biological Treatment Process (EBBT). The EBBT process is a three-phase (oxygen/...

  5. 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…

  6. Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities

    NASA Astrophysics Data System (ADS)

    Künstler, W.; Xia, Z.; Weinhold, T.; Pucher, A.; Gerhard-Multhaupt, R.

    Single-film bipolar electrets of porous polytetrafluoroethylene are generated by means of a two-step corona-charging process at elevated temperatures. Quasi-static direct piezoelectric coefficients of up to 0.15 nC/N have been observed on these films. In addition, multiple-layer stacks of porous and non-porous polytetrafluoroethylene films with monopolar charge were also investigated. While the piezoelectric responses of the stacks were not as high as those of the single films, the multiple-film arrangements may have other advantages such as better electrical shielding or tunable mechanical properties and adjustable acoustical impedance. Our new results are discussed in the context of the emerging field of porous polymer electrets with many potential device applications.

  7. External iliac artery polytetrafluoroethylene graft interposition: An effective rescuer for kidney transplant in progressive intimal dissection of external iliac artery

    PubMed Central

    Dar, Tanveer Iqbal; Tyagi, Vipin; Khawaja, Abdul Rouf; Chadha, Sudhir; Jauhari, Harsha

    2016-01-01

    Aims and Objective: The aim of this study is to highlight the use of polytetrafluoroethylene (PTFE) interposition graft as an important salvage procedure in case of irreparable intimal injury of external iliac artery during renal transplant recipient surgery. Materials and Methods: Since 1987, we encountered irreparable intimal dissection of external iliac artery in five cases just after opening the clamp. It was successfully managed by PTFE interposition graft with subsequent end to side anastomosis of donor renal artery to the vascular graft. Results: No patient had bleeding or infective complications related to the graft and three patients had immediate diuresis. Normal immediate graft function was present in three patients while the other two had delayed graft function. Conclusion: Polytetrafluoroethylene interposition graft is a successful procedure to salvage the kidney and lower limb in case of progressive intimal dissection of external iliac artery during renal transplant surgery. PMID:27141197

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Graft Polymerization of Acrylic Acid on a Polytetrafluoroethylene Panel by an Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Lan, Yan; You, Qingliang; Cheng, Cheng; Zhang, Suzhen; Ni, Guohua; Nagatsu, M.; Meng, Yuedong

    2011-02-01

    Surface modification on a polytetrafluoroethylene (PTFE) panel was performed with sequential nitrogen plasma treatments and surface-initiated polymerization. By introducing COO- groups to the surface of the PTFE panel through grafting polymerization of acrylic acid (AA), a transparent poly (acrylic acid) (PAA) membrane was achieved from acrylic acid solution. Grafting polymerization initiating from the active groups was achieved on the PTFE panel surface after the nitrogen plasma treatment. Utilizing the acrylic acid as monomers, with COO- groups as cross link sites to form reticulation structure, a transparent poly (acrylic acid) membrane with arborescent macromolecular structure was formed on the PTFE panel surface. Analysis methods, such as fourier transform infrared spectroscopy (FTIR), microscopy and X-ray photoelectron spectroscopy (XPS), were utilized to characterize the structures of the macromolecule membrane on the PTFE panel surface. A contact angle measurement was performed to characterize the modified PTFE panels. The surface hydrophilicities of modified PTFE panels were significantly enhanced after the plasma treatment. It was shown that the grafting rate is related to the treating time and the power of plasma.

  13. 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.

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

    PubMed

    Gabriel, Matthias; Niederer, Kerstin; Frey, Holger

    2016-01-01

    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. PMID:27584937

  15. 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.

  16. 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.

  17. 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.

  18. Triboelectrification-Induced Large Electric Power Generation from a Single Moving Droplet on Graphene/Polytetrafluoroethylene.

    PubMed

    Kwak, Sung Soo; Lin, Shisheng; Lee, Jeong Hwan; Ryu, Hanjun; Kim, Tae Yun; Zhong, Huikai; Chen, Hongsheng; Kim, Sang-Woo

    2016-08-23

    Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 μW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. PMID:27415838

  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. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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. PMID:26799324

  5. Dielectric Properties of Layered ZnTa2O6/Poly(tetrafluoroethylene) Composites

    NASA Astrophysics Data System (ADS)

    Jeon, Chang Jun; Kim, Eung Soo

    2012-11-01

    The effects of ZnTa2O6 content and layered structure on the dielectric properties of ZnTa2O6/poly(tetrafluoroethylene) (PTFE) composites were investigated at microwave frequency. With increasing ZnTa2O6 content, the dielectric constant (K) and dielectric loss (tan δ) of the composites increased due to the K values of the individual components and the microstructure. For the composites with layered structures, tan δ was dependent on the internal strain of the composites. Several types of theoretical models were employed to predict the effective K of the composites and the predicted values were compared with experimental data. The temperature coefficient of resonant frequency (TCF) was also discussed as it characterises the thermal stability of the composites. Typically, K of 4.24, tan δ of 1.36 ×10-3 and, TCF of 4.75 ppm/°C were obtained for the single layered PTFE composites with 0.2 volume fraction (Vf) of ZnTa2O6.

  6. 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.

  7. Optical coherence tomographic observations of polytetrafluoroethylene-covered sirolimus-eluting coronary arterial stent.

    PubMed

    Hou, Jingbo; Jia, Haibo; Huang, Xingtao; Yu, Huai; Ren, Xuefeng; Fang, Yan; Han, Zhigang; Yang, Shuang; Meng, Lingbo; Zhang, Shaosong; Yu, Bo; Jang, Ik-Kyung

    2013-04-15

    The aim of this study was to evaluate neointimal coverage obtained using a new method of polytetrafluoroethylene-covered stent (PCS) implantation combined with underlying longer sirolimus-eluting stent (SES) implantation using optical coherence tomography. Nine patients were enrolled in this study, including patients with coronary artery perforations, original coronary aneurysms, and acquired coronary aneurysms after drug-eluting stent implantation. All patients were first treated with long SES implantation and then with focal PCS implantation. Postprocedural and follow-up angiographic and optical coherence tomographic examinations were performed in all patients, and intravascular ultrasound was performed in 5 patients. All patients were asymptomatic during follow-up, without recurrent angina. There was no stent-edge or stent-segment binary restenosis. Values of late loss for proximal SES segments, PCS segments, and distal SES segments were similar (0.09, 0.07, and 0.04 mm, respectively, p = 0.8113). The mean neointimal thickness of PCS was less than that of proximal and distal SES. However, no malapposed cross sections or uncovered cross sections were found in PCS segments compared with SES segments (p = 0.0011). In conclusion, the combination of PCS and underlying longer SES implantation can offer better angiographic follow-up results. High-resolution optical coherence tomography provided convincing proof of full neointimal coverage of PCS. This new method of combined PCS and SES implantation may be a better choice compared with direct PCS implantation in certain clinical settings. PMID:23351458

  8. 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. PMID:27552028

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

    SciTech Connect

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

    2003-06-15

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

  10. Optical characteristics of poly(tetrafluoroethylene) thin film prepared by a vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Ohnishi, Yasutaka; Kita, Rio; Tsuchiya, Kazuyoshi; Iwamori, Satoru

    2016-02-01

    Poly(tetrafluoroethylene) (PTFE) thin films were deposited onto a glass slide substrate by a heat-resistance type vacuum evaporation apparatus due to changing the evaporation conditions. Transparency of the PTFE thin films prepared by the vacuum evaporation depended on the deposition conditions, i.e., temperatures of the basket, and distance between the evaporation source and substrate. To elucidate relationship between the molecular structure and transparency of the PTFE thin film prepared by the vacuum evaporation, chemical structures, crystallinity and thermophysical property were investigated. The chemical bonding state of the PTFE thin film prepared by the vacuum evaporation was almost the same as that of the pristine PTFE, however, the crystalinity was different. Although the pristine PTFE was crystal structure, the transparent evaporated thin film was estimated to be microcrystal structure. In addition, endothermic peaks in a differential scanning calorimeter (DSC) spectrum of the PTFE thin film were different from that of the pristine PTFE. These endothermic peaks of the PTFE thin film prepared by the vacuum evaporation shifted lower temperature compared to the pristine PTFE, which suggests that molecular weight of the PTFE thin film prepared by the vacuum evaporation decreased compared with that of the pristine PTFE.

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

    PubMed

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

    2016-07-01

    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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  14. 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. PMID:26142857

  15. 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.

  16. High incidence of perigraft seroma formation with gelatin-coated polytetrafluoroethylene grafts.

    PubMed

    Ladenheim, Eric D; Lum, Craig; Chadwick, Nathan; Agrawal, Siddartha

    2012-01-01

    We reviewed the effectiveness of a gelatin-coated polytetrafluoroethylene (PTFE) graft designed to reduce suture line bleeding and graft weeping. Twenty-nine adults with end-stage renal disease underwent implantation the graft (n = 30) in the arm. All had preoperative ultrasound vascular mapping to assess their options for an autogenous arteriovenous fistula and patients with a history of prior central venous devices or sternotomy underwent contrast venography. A 4- to 7-mm tapered graft (n = 10) was used if the inflow artery was <4.0 mm in diameter, and a 6-mm straight graft (n = 20) was used if the artery was ≥4.0 mm. Intraoperative volume flows were measured by duplex methodology. Precautions to prevent ultrafiltration and seroma development were taken. Eleven clinically significant seromas were detected in 30 sealed PTFE grafts (36.7%), 10 in the 6-mm grafts (50%), and 1 in a 4- to 7-mm graft (10%), a significant difference between graft types. There were no significant differences in flow between the graft types and between grafts with seromas versus no seromas. Five grafts were explanted and one was ligated, resulting in cannulation delays from 2 to 4 months. We conclude that the gelatin-sealed PTFE vascular graft is not the ideal prosthesis for hemodialysis access. PMID:22686492

  17. 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.

  18. 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.

  19. Expanding hollow metal rings

    DOEpatents

    Peacock, Harold B.; Imrich, Kenneth J.

    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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Theoretical study of the surface properties of poly(dimethylsiloxane) and poly(tetrafluoroethylene).

    PubMed

    Michalkova, Andrea; Tulyani, Sonia; Beals, James; Leszczynski, Jerzy

    2012-01-01

    Molecular dynamics (MD) simulations of poly(dimethylsiloxane) (PDMS) and poly(tetrafluoroethylene) (PTFE) were carried out to determine their surface properties and energies. This study helps to gain better insight into the molecular modeling of PDMS and PTFE, in particular how different approaches affect calculations of surface energy. Current experimental and theoretical data were used to further understand the surface properties of PDMS and PTFE as well as to validate and verify results obtained from the combination of density functional theory (DFT) calculations (including periodic boundary conditions) and MD simulations. Detailed analysis of the structure and electronic properties (by calculation of the projected density of states) of the bulk and surface models of PDMS and PTFE was performed. The sensitivity of the surface energy calculation of these two polymers to the chemistry and model preparation was indicated. The balance between the molecular density, weight (which also reflects bond orientation in the surface region), bond flexibility, and intramolecular interactions including bond stretching was revealed to govern the results obtained. In modeling, the structural organization of polymer near a given surface (types and number of end groups and broken bonds due to application of different cut offs of the periodic structure) also significantly affects the final results. Besides the structural differences, certain simulation parameters, such the DFT functionals and simulation boxes utilized, play an important role in determining surface energy. The models used here were shown to be sufficient due to their good agreement with experimental and other theoretical data related to surface properties and surface energies. PMID:21523541

  5. 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.

  6. Inexpensive Method for Growing Unidirectional Oriented Materials Using Friction-Transferred Poly(tetrafluoroethylene) Substrates

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    In recent years, there has been an increasing interest in properties of unidirectional materials grown on highly oriented polymer surfaces such as the poly(tetrafluoroethylene) (PTFE) films coated onto smooth glass surfaces. In this technique, a thin PTFE film is deposited by sliding or rubbing a Teflon bar over a heated glass surface at a specific temperature. Depending on the pressure, temperature and sliding rate the thickness of deposited layers can be varied from 30 A to 150 A. The PTFE-coated substrate is simple yet surprising versatile for oriented growth of many organic, inorganic and polymer. The significant aspect of PTFE films is their unusual ability to molecularly align a wide variety of materials grown onto them from solution, melt or vapor phase deposition, at temperature below the melting point of PTFE (approx. 340 C). The PTFE structure may be derived, in part, from the multitude of ridges forming in the film and these ridges can presumably provide effective nucleation sites to induce the unidirectional growth of variety of materials. Electron diffraction studies of these films revealed that the PTFE macromolecules are oriented parallel to each other along the sliding direction. Direct observation of the film thickness, molecular structure and individual fluorine atoms from these highly oriented films were achieved using atomic force microscopy (AFM). In this paper, we also report the first direct observation of individual fluorine atoms, and the measurement of the fluorine-helix and carbon-helix radii to be 1.70 A and 0.54 A, respectively.

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

    SciTech Connect

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

    1988-07-01

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

  8. 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.

  9. Long-term patency (9 1/2 years) and atherosclerosis of a polytetrafluoroethylene (Gortex) coronary artery bypass graft.

    PubMed

    Vlay, S C; Malik, A Z

    1998-01-01

    The patency of a polytetrafluoroethylene (Gortex) graft 9 1/2 years after coronary artery bypass graft surgery (CABG) is demonstrated. While this material is not commonly used as a conduit because of limited success in the past, this case demonstrates that, given the right circumstances, long-term patency is possible. Since available conduits for CABG are quite often limited, viable alternatives may be lifesaving and require further evaluation. In addition to mechanical considerations such as size, length, and material, anticoagulation and strict management of hyperlipidemia may be critical. PMID:9474468

  10. Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film

    SciTech Connect

    Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N.

    2007-02-02

    The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films.

  11. Expander chunked codes

    NASA Astrophysics Data System (ADS)

    Tang, Bin; Yang, Shenghao; Ye, Baoliu; Yin, Yitong; Lu, Sanglu

    2015-12-01

    Chunked codes are efficient random linear network coding (RLNC) schemes with low computational cost, where the input packets are encoded into small chunks (i.e., subsets of the coded packets). During the network transmission, RLNC is performed within each chunk. In this paper, we first introduce a simple transfer matrix model to characterize the transmission of chunks and derive some basic properties of the model to facilitate the performance analysis. We then focus on the design of overlapped chunked codes, a class of chunked codes whose chunks are non-disjoint subsets of input packets, which are of special interest since they can be encoded with negligible computational cost and in a causal fashion. We propose expander chunked (EC) codes, the first class of overlapped chunked codes that have an analyzable performance, where the construction of the chunks makes use of regular graphs. Numerical and simulation results show that in some practical settings, EC codes can achieve rates within 91 to 97 % of the optimum and outperform the state-of-the-art overlapped chunked codes significantly.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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. PMID:26608781

  20. 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. PMID:24987742

  1. 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.

  2. 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.

  3. Effect of through-plane polytetrafluoroethylene distribution in gas diffusion layers on performance of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Iwamura, Takuya; Someya, Satoshi; Munakata, Tetsuo; Nakano, Akihiro; Heo, Yun; Ishida, Masayoshi; Nakajima, Hironori; Kitahara, Tatsumi

    2016-02-01

    This experimental study identifies the effect of through-plane polytetrafluoroethylene (PTFE) distribution in gas diffusion backing (GDB) on the performance of proton exchange membrane fuel cells (PEMFC). PTFE-drying under vacuum pressure created a relatively uniform PTFE distribution in GDB compared to drying under atmospheric pressure. Carbon paper samples with different PTFE distributions due to the difference in drying conditions were prepared and used for the cathode gas diffusion layer (GDL) of PEMFCs. Also investigated is the effect of MPL application on the performance for those samples. The current density (i) - voltage (V) characteristics of these PEMFCs measured under high relative humidity conditions clearly showed that, with or without MPL, the cell using the GDL with PTFE dried under vacuum condition showed better performance than that dried under atmospheric condition. It is suggested that this improved performance is caused by the efficient transport of liquid water through the GDB due to the uniform distribution of PTFE.

  4. Radiation-induced graft polymermization of acrylamide onto poly(tetrafluoroethylene/ Hexaflouropropylene/vinylidene fluoride) (TFB) films

    NASA Astrophysics Data System (ADS)

    Dessouki, A. M.; Taher, N. H.; El-Boohy, H. A.

    Radiation-induced graft polymerization of acrylamide (AAm) onto poly(tetrafluoroethylene/ hexafluoropropylene/vinylidene fluoride) (TFB) films has been investigated. The appropriate reaction conditions at which the graft polymerization was carried out successfully were selected. It was observed that the grafting process was enhanced remarkably by using distilled water as diluent. In this grafting system ammonium ferrous sulphate (Mohr's salt) was used as inhibitor to minimize the homopolymerization of AAm and the suitable concentration of such inhibitor was found to be 3.5wt%. The dependence of the grafting rate on the monomer concentration was calculated to be 2.8 order. Some properties of the grafted films such as water uptake, electrical conductivity, mechanical properties and chemical and thermal stability were investigated. An improvement in these properties was observed which makes possible the use of these membranes in some practical applications.

  5. Detection and measurement of a cellular immune-reactivity towards polyester and polytetrafluoroethylene grafts. Leukocyte adherence inhibition test.

    PubMed

    Cavallini, G; Lanfredi, M; Lodi, M; Govoni, M; Pampolini, M

    1987-03-01

    Several studies were performed on polyester (Dacron) and polytetrafluoroethylene (PTFE) vascular substitute thrombogenicity. However, to date, the host-graft interactions have yet to be studied from an immunological point of view. For this reason, 4 classes of 10 patients each (Class 1: Dacron-+PTFE-grafted patients, Class 2: Dacron-, Class 3: PTFE-, and Class 4: controls) were submitted to a cellular immune-reactivity test: leukocyte adherence inhibition (LAI), in which leukocytes fail to adhere to glass on contact with a sensitizing antigen. The following blood cell populations were used: total leukocytes (PBL), mononuclear cells (MNC), T and B lymphocytes. This research demonstrated that a T cellular immune-reactivity towards Dacron and PTFE respectively occurs in Dacron- and PTFE-grafted patients, and that this reactivity is greater in the case of Dacron. More studies are required to determine the immuno-competent system role in fabric prosthesis patency. PMID:2955626

  6. Separation and characterization of poly(tetrafluoroethylene) latex particles by asymmetric flow field flow fractionation with light-scattering detection.

    PubMed

    Collins, Melissa E; Soto-Cantu, Erick; Cueto, Rafael; Russo, Paul S

    2014-04-01

    Poly(tetrafluoroethylene) (PTFE) latex particles have been analyzed and sorted according to size using asymmetric flow field flow fractionation (AF4) coupled with multiple-angle light scattering (MALS). Characterization of fractions by regular and depolarized dynamic light scattering confirmed that smaller particles elute prior to larger ones, as expected for field flow fractionation. The measured radii of the optically and geometrically anisotropic particles are consistent with those determined from transmission electron microscopy (TEM). A certain amount of heterogeneity remains in the fractions, but their uniformity for use as diffusion probes is improved. Full characterization of PTFE colloids will require a difficult assessment of the distribution, even within fractions, of the optical anisotropy. A general method to obtain number versus size distributions is presented. This approach is valid even when an online concentration detector is not available or ineffective. The procedure is adaptable to particles of almost any regular shape. PMID:24635125

  7. 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.

  8. Characterization of Adsorbed Molecular Water on the Surface of a Stretched Polytetrafluoroethylene Tape Analyzed by (1)H NMR.

    PubMed

    Wakai, Chihiro; Shimoaka, Takafumi; Hasegawa, Takeshi

    2016-03-10

    A single molecule often exhibits a largely different material character from a bulk matter. Although a perfluoroalkyl (Rf) compound is a representative one, many interests have mostly been devoted to the bulk character only thus far, leaving the single molecular character unclear. Recently, a new theoretical framework, stratified dipole-arrays (SDA) theory, has appeared for comprehensive understanding of Rf compounds in terms of both single and bulk systems. On this theory, a mechanically stretched polytetrafluoroethylene (PTFE) is expected to exhibit a single-molecular character having dipole-driven properties, which should attract molecular water. In the present study, a stretched PTFE tape is revealed to attract molecular water (not water droplet) in fact, and the adsorbed water molecules are highly restricted in motion by the dipole-dipole interaction studied by using (1)H NMR, which agrees with the prediction by the SDA theory. PMID:26848611

  9. Dynamics of changes in the colored form of spiroantrooxazine incorporated into polytetrafluoroethylene F-42 in a supercritical carbon dioxide medium

    NASA Astrophysics Data System (ADS)

    Kopylov, A. S.; Glagolev, N. N.; Timashev, P. S.; Cherkasova, A. V.; Timashev, S. F.; Solov'eva, A. B.

    2015-09-01

    It is shown that the incorporation of spiroantrooxazine (SAO), which has pronounced photochromic properties, into polytetrafluoroethylene F-42 in supercritical carbon dioxide medium leads to the formation of metastable colored photochromic states of different structure. In the subsequent relaxation of the polymer-SAO system, these states give rise to the most thermodynamically stable isomeric form of SAO for the given system. The kinetics of these reactions is analyzed in supercritical CO2 medium and after placing the test sample in air upon the formation of the unstable colored form of the photochromic molecule in the polymeric matrix. It is noted that in these cases, comparison of the rate constants of relaxation transitions allows us to numerically assess how the matrix plasticization by carbon dioxide affects the formation of photochromic colored states and the relaxation reorganization of the photochromic metastable forms.

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

    NASA Astrophysics Data System (ADS)

    Xi, Zhen-Yu; Xu, You-Yi; Zhu, Li-Ping; Liu, Fu; Zhu, Bao-Ku

    2008-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Akinobu; Kido, Hideki; Ukita, Yoshiaki; Kishihara, Mitsuyoshi; Utsumi, Yuichi

    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.

  12. 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.

  13. 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.

  14. 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.

  15. 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. PMID:19875014

  16. 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 for educating…

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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…

  2. 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 horizons of…

  3. Expanding the eukaryotic genetic code

    DOEpatents

    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.

  4. Paul Hanna and "Expanding Communities"

    ERIC Educational Resources Information Center

    Stallones, Jared R.

    2004-01-01

    The development and promotion of the "expanding communities" curriculum design model for teaching elementary school social studies was a crucial episode in the history of social studies. This article profiles how the model developed in the mind of its most effective promoter, Paul Robert Hanna. Paul Hanna understood early in his career the…

  5. Expanding the eukaryotic genetic code

    DOEpatents

    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.

  6. Expanding the eukaryotic genetic code

    DOEpatents

    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.

  7. Expanding the eukaryotic genetic code

    DOEpatents

    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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. A polytetrafluoroethylene porous membrane and dimethylhexadecylamine quaternized poly (vinyl benzyl chloride) composite membrane for intermediate temperature fuel cells

    NASA Astrophysics Data System (ADS)

    Cao, Yuan-Cheng; Xu, Chenxi; Zou, Linling; Scott, Keith; Liu, Jiyan

    2015-10-01

    A composite material for phosphoric acid (PA) loaded membrane was prepared using a porous polytetrafluoroethylene (PTFE) thin film. N, N-Dimethylhexadecylamine partially quaternized poly (vinyl benzyl chloride) (qPVBzCl-) was synthesized as the substrate for the phosphoric acid loaded polymer membrane. SEM observation indicated that the pores were filled with the qPVBzCl-. The maximum PA loading level was calculated to be 4.67-5.12 per repeat unit on average. TGA results showed that resultant composite membrane was stable in the intermediate temperature from 100 °C to 200 °C. The composite membrane tensile stress was 56.23 MPa, and the Young's Modulus was 0.25 GPa, and the fractured elongation was 23%. The conductivity of the composite membrane after the PA addition (H3PO4@PTFE/qPVBzCl-) increased from 0.085 S cm-1 to 0.11 S cm-1 from 105 °C to 180 °C. The peak power density of the H2/O2 at 175 °C under low humidity condition (<1%) for H3PO4@PTFE/qPVBzCl- membranes was 360 mW cm-2.

  13. Hydrophobic properties of polytetrafluoroethylene thin films fabricated at various catalyzer temperatures through catalytic chemical vapor deposition using a tungsten catalyzer.

    PubMed

    Cha, Jeong Ok; Yeo, Seung Jun; Pode, Ramchandra; Ahn, Jeung Sun

    2011-07-01

    Using the catalytic chemical vapor deposition (Cat-CVD) method, polytetrafluoroethylene (PTFE) thin films were fabricated on Si(100) substrates at various catalyzer temperatures, using a tungsten catalyzer, and Fourier transform infrared (FTIR) spectroscopy and X-ray photoemission spectroscopy (XPS) were used to confirm the fabrication of the films. An atomic-force microscope (AFM) and a scanning electron microscope (SEM) were employed to study the correlation between the wettability and surface morphology of the samples. It was found that the wettability of the PTFE thin films fabricated via Cat-CVD is strongly correlated with the sizes of the film surfaces' nanoprotrusions, and that superhydrophobic PTFE thin-film surfaces can be easily achieved by controlling the sizes of the nanoprotrusions through the catalyzer temperature. The comparison of the wettability values and surface morphologies of the films confirmed that nanoscale surface roughness enhances the hydrophobic properties of PTFE thin films. Further, the detailed analysis of the films' surface morphologies from their AFM images with the use of the Wenzel and Cassie models confirmed that the nanoscale surface roughness enhanced the hydrophobic property of the PTFE films. Further, the variations of the wettability of the PTFE thin films prepared via Cat-CVD are well explained by the Cassie model. It seems that the increase in the trapping air and the reduction of the liquid-solid contact area are responsible for the superhydrophobicity of the PTFE thin films prepared via Cat-CVD. PMID:22121615

  14. Enhanced performance of gas diffusion electrode for electrochemical reduction of carbon dioxide to formate by adding polytetrafluoroethylene into catalyst layer

    NASA Astrophysics Data System (ADS)

    Wang, Qinian; Dong, Heng; Yu, Han; Yu, Hongbing

    2015-04-01

    Gas diffusion electrode (GDE) with Nafion bonded catalyst layer (CL) for electrochemical reduction of CO2 to formate (ERCF) suffers from CO2 mass transfer limitation. In this work, polytetrafluoroethylene (PTFE) with contents of 5.9 wt%, 7.7 wt%, 11.1 wt% and 20 wt% are added into the CL of the GDE with Sn catalyst (P-SGDE) for ERCF. The morphologies and porous structures of the P-SGDEs are examined by scanning electron microscope and mercury intrusion measurement, respectively. The electrochemical performances of the P-SGDEs are investigated by linear sweep voltammetry, electrochemical impedance spectroscopy and constant potential electrolysis. The results show that the Faraday efficiency (86.75 ± 2.89%) and current density (21.67 ± 1.29 mA cm-2) for ERCF were improved by 25.4% and 25.8% respectively when the content of PTFE is 11.1 wt%, probably owing to the enhancement in the catalyst active surface area and CO2 diffusion. This Faraday efficiency is the highest one found for ERCF with Sn GDE under similar conductions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  16. Microwave Band-Pass Filter with Aerosol-Deposited Al2O3-Polytetrafluoroethylene Composite Thick Films.

    PubMed

    Lee, Ji-Won; Koh, Jung-Hyuk

    2015-03-01

    Fabrication of microwave band-pass filter with coplanar waveguide with ground structure was realized by employing Al2O3-polytetrafluoroethylene (Al2O3-PTFE) composite thick films for integrated substrates produced by aerosol deposition (AD). In order to predict the performance of the band-pass filter, 3-D electromagnetic simulations were performed by high-frequency structure analysis. The thick Al2O3-PTFE composite films prepared by the AD process had submicron-sized Al2O3 crystallites due to the shock-absorbing effect of PTFE during the film growth. The thick films were characterized by X-ray diffraction and scanning electron microscopy. The Cu transmission lines with the thickness of 300 nm were deposited by electron-beam evaporation to form the band-pass filter. The fabricated band-pass filter showed similar characteristics to the simulation results. The insertion loss and resonance frequency were 9.5 dB and 2.3 GHz, respectively. PMID:26413656

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

    PubMed

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

    2016-01-01

    The energy performance of solid energetic materials (Al, Mg, etc.) is typically restricted by a natural passivation layer and the diffusion-limited kinetics between the oxidizer and the metal. In this work, we use polytetrafluoroethylene (PTFE) as the fluorine carrier and the shielding layer to construct a new type of nano-Al based fuels. The PTFE shell not only prevents nano-Al layers from oxidation, but also assists in enhancing the reaction kinetics, greatly improving the stability and reactivity of fuels. An in situ chemical vapor deposition combined with the electrical explosion of wires (EEW) method is used to fabricate core-shell nanostructures. Studies show that by controlling the stoichiometric ratio of the precursors, the morphology of the PTFE shell and the energy performance can be easily tuned. The resultant composites exhibit superior energy output characters than that of their physically mixed Al/PTFE counterparts. This synthetic strategy might provide a general approach to prepare other high-energy fuels (Mg, Si). PMID:26612396

  18. 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.

  19. 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.

  20. Perioperative rupture of the LIMA graft leading to cardiogenic shock, emergency angiography, and stenting with a polytetrafluoroethylene-covered stent.

    PubMed

    Yeow, Wen-Loong; Edwards, Mark; Yong, Gerald

    2012-03-01

    A 58-year-old man underwent an elective coronary bypass graft for severe four-vessel stenosis. Cardiogenic shock developed just after coronary bypass grafting with a left internal mammary artery (LIMA) to left anterior descending (LAD) artery and superficial venous graft to 1st and 2nd obtuse marginal (OM1/OM2) arteries the posterior descending artery (PDA) was too small to graft. Despite significant inotropes and an intra-aortic balloon pump, the patient deteriorated in intensive care unit with cardiogenic shock and ventricular arrhythmia. Urgent coronary angiography revealed a rupture or torn LIMA graft with extravasation of contrast into the left pleural cavity. There was no distal LIMA to LAD flow probably due to graft thrombosis. Revascularisation was performed on the severe ostial native LAD stenosis with a drug eluting stent. The rupture graft was then stented with a polytetrafluoroethylene-covered stent, which stopped the bleeding, and latter, led to total graft thrombosis. The patient improved significantly and supportive inotropes could be weaned down. At 11 month follow-up, the patient had mild left ventricular dysfunction, widely patent ostial LAD stent and thrombosed LIMA graft. PMID:21542101

  1. 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.

  2. 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.

  3. 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. PMID:26602072

  4. Selective insulation with poly(tetrafluoroethylene) of substrate electrodes for electrochemical background reduction in scanning electrochemical microscopy.

    PubMed

    Rodriguez-Lopez, Joaquin; Alpuche-Aviles, Mario A; Bard, Allen J

    2008-03-01

    We describe a wet process for the fabrication of poly(tetrafluoroethylene) (PTFE)-covered electrodes in which arrays of holes ( approximately 200 microm) are formed. The PTFE coating provides electrical insulation of most of the electrode surface with selected regions exposed for electrochemical experiments. The arrays of microholes can be controllably patterned and filled with precursor solutions using a piezoelectric dispenser. A micrometer spot of electrocatalyst is produced after reduction of the precursor. The application is tested for scanning electrochemical microscopy (SECM) in the tip generation-substrate collection (TG-SC) studies of electrocatalysts. The method is shown to reduce the substrate background currents that are included in the electrochemical signal read from the local perturbation induced with the SECM tip to the substrate in the TG-SC mode of SECM. This background current reduction is consistent with the decrease in the exposed area of the electrode. The general methodology for the fabrication of the substrate electrodes and two proof-of-concept applications in the TG-SC SECM modality are described. PMID:18251520

  5. 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.

  6. 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.

  7. Assessment of Wall Shear Stress Changes in Arteries and Veins of Arteriovenous Polytetrafluoroethylene Grafts Using Magnetic Resonance Imaging

    SciTech Connect

    Misra, Sanjay Woodrum, David A.; Homburger, Jay; Elkouri, Stephane; Mandrekar, Jayawant N.; Barocas, Victor; Glockner, James F.; Rajan, Dheeraj K.; Mukhopadhyay, Debabrata

    2006-08-15

    The purpose of the study was to determine simultaneously the temporal changes in luminal vessel area, blood flow, and wall shear stress (WSS) in both the anastomosed artery (AA) and vein (AV) of arteriovenous polytetrafluoroethylene (PTFE) grafts. PTFE grafts were placed from the iliac artery to the ipsilateral iliac vein in 12 castrated juvenile male pigs. Contrast-enhanced magnetic resonance angiograpgy with cine phase-contrast magnetic resonance imaging was performed. Luminal vessel area, blood flow, and WSS in the aorta, AA, AV, and inferior vena cava were determined at 3 days (D3), 7 days (D7), and 14 days (D14) after graft placement. Elastin von Gieson staining of the AV was performed. The average WSS of the AA was highest at D3 and then decreased by D7 and D14. In contrast, the average WSS and intima-to-media ratio of the AV increased from D3 to D7 and peaked by D14. Similarly, the average area of the AA was highest by D7 and began to approximate the control artery by D14. The average area of the AV had decreased to its lowest by D7. High blood flows through the AA causes a decrease in average WSS and increase in the average luminal vessel area, whereas at the AV, the average WSS and intima-to-media ratio both increase while the average luminal vessel area decreases.

  8. Elevated cholinesterase activity and increased urinary excretion of inorganic fluorides in the workers producing fluorine-containing plastic (polytetrafluoroethylene)

    SciTech Connect

    Baohui Xu |; Jiusun Zhang; Guaogeng Mao; Guifen Yang; Aini Chen; Aoyama, Kohji; Matsushita, Toshio; Ueda, Atsushi

    1992-07-01

    Fluoropolymers are widely used in thermal and electrical industries. Polytetrafluoroethylene (PTFE) plastic is a typical one. During its production, workers are occupationally exposed to many organic fluorides, especially tetrafluoroethylene, chlorodifluoromethane, PTFE and its thermal decomposition products. Of these compounds, it has been documented that following inhalation of combustion products of PTFE the focal hemorrhages, edema, fibrin deposition in lungs and renal infarcts were observed in rats. Odum and Green have demonstrated a marked damage to proximal tubule of kidney with no effects on the liver in rats exposed to 6000 ppm tetrafluoroethylene for 6 hr. The investigations of the hazards of these compounds to workers have been mainly focused on acute toxicity. There have been some reports that polymers and its pyrolysis caused polymer fume fever and pulmonary edema. In practice, workers engaged in PTFE manufacture are chronically exposed to the above-mentioned chemicals, but little was known about the hazards ascribed to these chemicals. To clarify the influences of the exposed chemicals on health in PTFE production we conducted a mass survey investigation in a PTFE production factory. As a result, in addition to the nephrotoxicity characterized by elevated ALP and NAG activities in urine, more interestingly, we have also found a reversible increase in cholinesterase (ChE) activity and enhanced urinary excretion of inorganic fluorides in workers engaged in PTFE production. We report here these findings and discuss their physiological significance. 18 refs., 4 tabs.

  9. Dilatation of Stent-Grafts by Luminal Pressures: Experimental Evaluation of Polytetrafluoroethylene (PTFE) and Woven Polyester Grafts

    SciTech Connect

    Suzuki, Kojiro; Ishiguchi, Tsuneo; Kawatsu, Shoji; Iwai, Hiroyoshi; Maruyama, Kunihiro; Ishigaki, Takeo

    2001-03-15

    Purpose: To evaluate the effect on dilatation of three types of covering materials used for endovascular stent-grafts.Methods: Stent-grafts with three types of covering material [0.1-mm polytetrafluoroethylene (PTFE), 0.2-mm PTFE, and 0.15-mm woven polyester] were placed in a fluid circuit. For the pulsatile pressure test, the luminal pressure of 190/130 mmHg was loaded up to 300,000 pulses. For the static pressure test, the luminal pressure was increased from 50 to 300 mmHg at 50-mmHg increments. The percent of dilatation of each stent-graft was compared.Results: The 0.1-mm PTFE stent-graft was significantly more dilated than the 0.2-mm PTFE and the 0.15-mm woven polyester stent-graft (p < 0.005) in both examinations. There was no significant difference between the 0.2-mm PTFE and the 0.15-mm woven polyester stent-grafts. The dilatation of the 0.1-mm PTFE stent-graft was irreversible.Conclusion: The 0.15-mm woven polyester and the 0.2-mm PTFE stent-grafts may be preferable to the 0.1-mm PTFE stent-graft with regard to dilatation and deformity.

  10. 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.

  11. Transparent Thin Films Deposited onto Polyester Film Substrate by Radio Frequency Sputtering with a Poly(tetrafluoroethylene) Target

    NASA Astrophysics Data System (ADS)

    Seino, Shou; Nagai, Yuki; Kobayashi, Masashi; Iwamori, Satoru; Noda, Kazuhiro

    2013-05-01

    Improvement technologies for antireflection property of transparent plastic substrates are required in computer displays. Inorganic coatings have been used to reduce the surface reflection. We have already reported that fluorocarbon thin films sputtered with a poly(tetrafluoroethylene) (PTFE) target are transparent and can be used for an antireflection film, although the pristine PTFE plate used for the sputtering target is white. The fluorocarbon thin films were deposited onto a polyester (PET) film substrate by an rf sputtering, and characterized their optical properties. Elemental ratio, fluorine for carbon, of the thin films increased and degree of cross-linking of the thin films decreased with an increase of the rf power. Arithmetical surface roughness of the fluorocarbon thin films slightly increased with an increase of the rf power. Surface roughness of the fluorocarbon thin film affects the transmittance as well as the chemical structure of the thin film. To enhance the transparency, the diffuse transmittance should be suppressed, and flat surface thin films should be prepared by the sputtering at lower rf power and pressure.

  12. Evaluating the effect of polytetrafluoroethylene and extractum cepae-heparin-allantoin gel in peripheral nerve injuries in a rat model

    PubMed Central

    Kahraman, Ahmet; Kahveci, Ramazan

    2015-01-01

    BACKGROUND: Peripheral nerves can be injured by congenital, mechanical, thermal or chemical causes. Peripheral nerve injuries are increasing in frequency, particularly in countries that are becoming more industrialized. Nerve and extremity injuries result in work loss and high treatment costs, and can lead to separation of patients from their social environment. Failure of nerve repair causes muscle functional losses, sensory losses and painful neuropathies. OBJECTIVES: To compare the effects of condensed polytetrafluoroethylene (cPTFE) and cPTFE-extractum cepae-heparin-allantoin (cPTFE-EHA) gel compound on nerve and functional recovery, and the prevention of adhesion and scar tissue formation after total peripheral nerve injury repaired by primary suture in a rat model. RESULTS: cPTFE alone and cPTFE-EHA gel was found to provide better functional recovery and nerve regeneration compared with primary repair only. In the macroscopic evaluation, the cPTFE-EHA gel was found to have no negative effect on wound healing and, despite increasing extra-neural scar tissue and adhesions, it had no negative effect on nerve function; in addition, it facilitated functional recovery. CONCLUSIONS: Compared with the cPTFE application alone, the application of perineural cPTFE-EHA gel during peripheral nerve surgery appeared to provide better functional recovery without causing any significant changes in epineural and extraneural scar tissue formation. PMID:25821766

  13. 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.

  14. The Advanced Expander Test Bed

    NASA Technical Reports Server (NTRS)

    Masters, Arthur I.; Tabata, William K.

    1990-01-01

    The principal goals and design concepts of the Advanced Expander Test Bed (AETB) program are briefly reviewed. The AETB is planned as the focal point for the development and demonstration of high-performance oxygen/hydrogen engine technology and advanced component technology for the next space engine. The engine will operate at pressures up to 1200 psia over a wide range of conditions, easily accommodating mission-focused components. The discussion covers design requirements, design approach, conceptual design, the AETB cycle, and the AETB control system.

  15. 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

  16. 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. PMID:23478651

  17. 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.

  18. Environmentally benign etching process of amorphous silicon and tungsten using species evaporated from polytetrafluoroethylene and fluorinated ethylene propylene

    NASA Astrophysics Data System (ADS)

    Fujita, Kazushi; Hori, Masaru; Goto, Toshio; Ito, Masafumi

    2003-01-01

    Environmentally benign etching process of amorphous silicon (a-Si) and tungsten (W) by using a plasma process with an evaporation of solid materials system has been developed for replacing a conventional plasma process using green house gases, such as SF6 gas and perfluorocompound gases causing global warming. The evaporation system was designed to generate fluorocarbon species from solid materials by a CO2 laser irradiation. An electron cyclotron resonance (ECR) plasma using O2 accompanied with injection of species evaporated from solid materials has been applied to a-Si and W etching for cleaning process in chemical vapor deposition chamber. Fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are selected as the solid material and the etching characteristics between FEP and PTFE have been compared. Furthermore, the etching of a-Si and W films has been performed in the divergent magnetic field ECR downstream plasma [electron density (ne); ~1010 cm-3, electron temperature (Te); 1.5-2.8 eV] and a planar ECR plasma [ne ~1010 cm-3, Te 3.4-4.4 eV] using O2 gas with FEP evaporation. As a result, high etching rates of a-Si and W films of above 100 nm/min were successfully obtained at a substrate temperature of 400 °C in the planar ECR plasma of higher electron temperature. CFx (x=1-3) radical densities and F atom density in plasmas were measured by an infrared diode laser absorption spectroscopy and an actinometric optical emission spectroscopy, respectively. On the basis of these measurements of species, the etching mechanisms of a-Si and W films are discussed.

  19. 32 CFR 147.21 - Expanding investigations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Standards § 147.21 Expanding investigations. Investigations and reinvestigations may be expanded under the provisions of Executive Order 12968 (60 FR 40245, 3 CFR 1995 Comp., p. 391) and other applicable statutes...

  20. 32 CFR 147.21 - Expanding investigations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Standards § 147.21 Expanding investigations. Investigations and reinvestigations may be expanded under the provisions of Executive Order 12968 (60 FR 40245, 3 CFR 1995 Comp., p. 391) and other applicable statutes...

  1. Heat expanded starch-based compositions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 their open-cell structure precluded them from expanding further when heated. Non-porous beads, p...

  2. Expander for Thin-Wall Tubing

    NASA Technical Reports Server (NTRS)

    Pessin, R.

    1983-01-01

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

  3. Engelhard expands oxidation catalysts portfolio

    SciTech Connect

    Rotman, D.

    1997-02-26

    Engelhard says its agreement earlier this month to market Amoco Chemical`s proprietary maleic anhydride catalyst reflects an effort to expand its speciality catalysts business (CW, Feb. 19, p.5). In particular, the company says it is looking for additional alliances to bolster its oxidation catalysts portfolio. {open_quotes}There are some areas of oxidation catalysis that are reasonably attractive,{close_quotes} says Paul Lamb, marketing director/chemical catalysts. He says that while Engelhard is not interested in commodity oxidation catalysts, such as those used to make sulfuric acid, it does want to boost offerings for higher-value oxidation catalysts. Engelhard is collaborating with Geon to offer oxychlorination catalysts for making ethylene dichloride. It also markets oxidation catalysts for vinyl acetate production.

  4. 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

  5. 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.

  6. 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.

  7. 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. PMID:26444726

  8. Generation of over 5 MeV carbon ions from a fibrous polytetrafluoroethylene film irradiated with a 2.4 TW, 50 fs tabletop laser

    SciTech Connect

    Okihara, Shin-Ichiro; Fujimoto, Masatoshi; Takahashi, Hironori; Matsukado, Koji; Ohsuka, Shinji; Aoshima, Shin-Ichiro; Okazaki, Shigetoshi; Ito, Toshiaki; Tsuchiya, Yutaka

    2006-09-18

    The authors generated energetic carbon ions C{sup 4+} above 5 MeV by focusing 2.4 TW, 50 fs, 10 Hz laser pulses onto a fibrous polytetrafluoroethylene (PTFE) film. The PTFE film is composed only of carbon and fluorine and has microporous structure. A laser target made of this film is useful in generating carbon ions. A polyethyleneterephthalate film was also used as an alternative target for comparison. The results show that the number of carbon ions emitted from the PTFE target was approximately two orders of magnitude greater than that from a polyethyleneterephthalate target.

  9. Effects of long pulse width and high pulsing frequency on surface superhydrophobicity of polytetrafluoroethylene in quasi-direct-current plasma immersion ion implantation

    SciTech Connect

    Kwok, Dixon T. K.; Wang Huaiyu; Yeung, Kelvin W. K.; Chu, Paul K.; Zhang Yumei

    2009-03-01

    Long pulse, high frequency quasi-direct-current (dc) oxygen plasma immersion ion implantation (PIII) is utilized to create a superhydrophobic polytetrafluoroethylene (PTFE) surface with a water contact angle of over 150 deg. This technique allows the use of a high duty cycle without deleterious effects such as extensive sample heating encountered in conventional PIII. Scanning electron microscopy images review submicrometer-nanometer structures on the PTFE surface after long pulse, high frequency PIII indicative of ion implantation. On the other hand, plasma modification is the dominant effect in short pulse, low frequency PIII. Quasi-dc PIII is demonstrated to offer adjustable synergistic plasma and ion beam effects.

  10. 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.

  11. 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.

  12. 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.

  13. Transitions in expanding cosmological spacetimes

    NASA Astrophysics Data System (ADS)

    Berger, Beverly K.

    2015-04-01

    One may easily construct a sequence of vacuum spacetimes by starting with the spatially homogeneous, anisotropic, vacuum Kasner solution and adding one direction of spatial dependence (polarized Gowdy), rotations in the spatial symmetry plane (generic Gowdy), and the remaining allowed spatial rotations (Gowdy plus twists). In the time-direction of expanding spatial volume, the spatially dependent cases may be analyzed as averaged background spacetimes containing gravitational waves. The nature of the averaged background spacetime is known to change abruptly in moving from Kasner to Gowdy to Gowdy with twists. In addition, as pointed out by Ringstrom, generic Gowdy models exhibit two distinct behaviors for the averaged wave amplitude. The focus is on transitions involving the introduction of twists where the phenomenology is not well understood. Numerical simulations are used to study the details of the behavior in the transition from one case to another especially to investigate possible scaling relationships. A final topic will be the effect of the addition of matter and/or a cosmological constant to these models.

  14. 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.

  15. Improving and expanding NGO programmes.

    PubMed

    Mukhopadhyay, A

    1993-06-01

    India has massive problems and is in need of improving and expanding non governmental organization (NGO) programs by broadening the scope of NGO activities, identifying successful NGO activities, and by moving closer to the community to participate in their activities. The problems and experience in the last few decades indicate that with expansion bureaucratization takes place. The institution begins to depend on donors and follows donor-driven agendas. As more money is given by the government, many more so called GONGO or Government-NGO projects materialize. Another problem is that the government almost always approaches the NGOs for the implementation of a project, and there is complete lack of cooperation at the planning stage. The government is considering a loan from the World Bank and UNICEF to launch a mother and child health program, but there has not been any discussion with the dozens of people who have worked on issues concerning mother and child health issues for many years. There is a need to be more demanding of the government about the various programs that are implemented for the government. Very few NGO health and family welfare projects are run by ordinary nurses or ordinary Ayurvedic doctors under ordinary conditions. Since successful NGO work has to be extended to other parts of the country, they will have to be run by ordinary people with very ordinary resources. Over the years, the NGO community has become preoccupied with its own agenda. Today, despite very sophisticated equipment and infrastructure, they are not able to reach the 60,000-70,000 workers and employees. Some of the ideas with respect to the strengthens and weaknesses of community participation have to be shared. NGOs should include all the existing non governmental organizations throughout the country, and have a dialogue with other nongovernmental bodies such as trade unions. The challenge is to adjust the current agenda, prevailing style, and present way of operating and move

  16. 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.

  17. Separation of craniopagus twins utilizing tissue expanders.

    PubMed

    Shively, R E; Bermant, M A; Bucholz, R D

    1985-11-01

    An example of craniopagus Siamese twins is presented. The methods used in their separation using skin expanders and scalp flaps to achieve primary closure of the wounds with hair-bearing scalp are outlined. A detailed discussion of the planning and the mathematical considerations of these skin expanders and scalp flaps is included. PMID:4059416

  18. 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.

  19. 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.…

  20. Study on the anti-wear performance of Ni-base composite coating sucker joint that contains nano-diamond and nano-polytetrafluoroethylene.

    PubMed

    Wang, Wei-Zhang; Yan, Xiang-Zhen; Wang, Hai-Wen; Wang, Ming-Bo

    2009-02-01

    With the development of oilfields, the problem of eccentric wear between casing and sucker rod in rod-pumped wells operation is more and more severe. Investigations on the eccentric wear show that the abrasion of sucker rod joint is more serious than the sucker rod itself. A new method of producing the Ni-base composite coating that contains nano-diamond and nano-polytetrafluoroethylene (PTFE) on sucker joint obtained by electrodeposition is presented in this paper. The test results show that the anti-wear performance and hardness of the sucker rod improve significantly with the increase of nano-diamond. The addition of nano-PTFE particle is useful in reducing the friction factor. Field tests demonstrate that the life of the sucker rod joint is increased and the maintenance cycle of the rod-pumped well is prolonged. PMID:19441509

  1. 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.

  2. Long-term outcome of transcatheter polytetrafluoroethylene-covered stent implantation in a giant coronary aneurysm of a child with Kawasaki disease.

    PubMed

    Waki, Kenji; Arakaki, Yoshio; Mitsudo, Kazuaki

    2013-03-01

    We report the long-term outcome of a child with Kawasaki disease (KD), who had a giant aneurysm with stenotic lesions in the right coronary artery, resulting in the transcatheter implantation of a polytetrafluoroethylene (PTFE)-covered stent at the age of 8. Quantitative coronary angiography analysis later showed the increase of the diameter stenosis at both stent edges for the first 10 months after implantation; however, the stenosis did not develop thereafter. Coronary perfusion was still well maintained at follow-up coronary angiography 5.5 years after implantation (diameter stenosis was 36.5% at proximal and 37.4% at distal edge, respectively). Although further follow-up is necessary, the long-term outcome of a PTFE-covered stent implantation for a KD patient is satisfactory in this instance. Implantation of a covered stent in a giant aneurysm is considered a promising treatment option. PMID:22605684

  3. 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. PMID:24557981

  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. PMID:18382562

  5. Expanding Space: the Root of all Evil?

    NASA Astrophysics Data System (ADS)

    Francis, Matthew J.; Barnes, Luke A.; James, J. Berian; Lewis, Geraint F.

    2007-07-01

    While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity.

  6. 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.

  7. Expandable insert serves as screw anchor

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Expandable self-locking adapter secures components to panels having one accessible side. Mounting holes in the panels may not be threaded to accommodate screws, therefore, the adapter contains a female thread that will mate a mounting screw.

  8. Expanding Patient Options: Minilaparotomy for Hysterectomy

    MedlinePlus Videos and Cool Tools

    Expanding Patient Options: Minilaparotomy for Hysterectomy Covidien Energy Based Devices Concord, California May 26, 2010 Welcome to this OR Live program presented by Covidien energy-based devices. Good evening, and thank ...

  9. 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)

  10. Injuries Soar as Trampoline Parks Expand

    MedlinePlus

    ... news/fullstory_160184.html Injuries Soar as Trampoline Parks Expand Broken bones, fractures the most common complaints ... MONDAY, Aug. 1, 2016 (HealthDay News) -- As trampoline parks spring up across the United States, injuries to ...

  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. Expanding Literacy and Integrating Curricula through Dance.

    ERIC Educational Resources Information Center

    Birch, James R.

    2000-01-01

    Dance embodies all of the multiple intelligences and uses Sternberg's intellectual components (memory, analysis, creativity, practicality). Integrated into the curriculum, dance can expand literacy and make learning more interactive. (SK)

  13. 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.

  14. 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.

  15. 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.

  16. Preparation and microwave characterization of BaNd{sub 2-x}Sm{sub x}Ti{sub 4}O{sub 12} (0 {<=} x {<=} 2) ceramics and their effect on the temperature coefficient of dielectric constant in polytetrafluoroethylene composites

    SciTech Connect

    Stanly Jacob, K.; Satheesh, R.; Ratheesh, R.

    2009-10-15

    High dielectric and temperature-stable ceramic compositions have been prepared through solid-state ceramic route. The structure and microstructure of the ceramics have been studied using powder X-ray diffraction and scanning electron microscopic techniques. The dielectric properties of well-sintered ceramics are studied in the microwave frequency region using Hakki and Coleman post-resonator technique. The samples exhibited high dielectric constant (>77), relatively high quality factor (>1500) and near zero temperature coefficient of resonant frequency. Phase pure calcined ceramic materials are incorporated in the polytetrafluoroethylene matrix through a proprietary process comprising of sigma mixing, extrusion, calendering followed by hot pressing for the fabrication of planar circuit laminates. The effect of temperature coefficient of dielectric constant of the resultant polytetrafluoroethylene/ceramic composite materials is studied with respect to compositional variation of the filler materials.

  17. Design of an Advanced Expander Test Bed

    NASA Technical Reports Server (NTRS)

    Mitchell, John C.; Tabata, William K.

    1993-01-01

    The final design of the Advanced Expander Test Bed (AETB) is discussed. The AETB is a cryogenic rocket ground test unit being designed and built for NASA to enable validation of mission-focused technologies for advanced space engines. Based on the split expander cycle, it will operate at a nominal thrust of 20,000 lbf, a chamber pressure of 1200 psia, and may be operated off-design over a wide range of throttling conditions and mixture ratios. The design approach and configuration of the major components are described.

  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. 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.

  20. Properties of extruded expandable breadfruit products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  1. 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…

  2. 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. PMID:26980105

  3. 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…

  4. Expanding Assessment Methods and Moments in History

    ERIC Educational Resources Information Center

    Frost, Jennifer; de Pont, Genevieve; Brailsford, Ian

    2012-01-01

    History courses at The University of Auckland are typically assessed at two or three moments during a semester. The methods used normally employ two essays and a written examination answering questions set by the lecturer. This study describes an assessment innovation in 2008 that expanded both the frequency and variety of activities completed by…

  5. 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,…

  6. 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…

  7. 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 approaches to…

  8. 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)

  9. Descending entropy in expanding the universe

    NASA Astrophysics Data System (ADS)

    Portnov, Yuriy A.

    2015-11-01

    Inter-relation between 1-form of nonmetricity and change of entropy in the course of time is considered in the study. It is shown that change of entropy in expanding universe will be always negative. The obtained result contravenes the second law of thermodynamics, however it explains available ordered macrostructures in the universe.

  10. 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

  11. 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…

  12. Utah's Cane Creek horizontal play expanding

    SciTech Connect

    Price, R.B.

    1991-08-12

    This paper reports on one of the U.S. horizontal plays that continues to gather steam in southern Utah. And because it is expanding in an environmentally sensitive area, development is being watched closely by the Bureau of Land Management and environmental groups. One operator planning a wildcat in the vicinity has been forced to postpone drilling for environmental reasons.

  13. 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…

  14. 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,…

  15. 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. PMID:17432870

  16. 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.

  17. 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

  18. Radiolytic preparation of poly(styrene sulfonic acid) - grafted poly(tetrafluoroethylene- co-perfluorovinyl vinyl ether) membranes with highly cross-linked networks

    NASA Astrophysics Data System (ADS)

    Kang, Sung-A.; Shin, Junhwa; Fei, Geng; Ko, Beom-Seok; Kim, Chong-Yeal; Nho, Young-Chang

    2010-11-01

    In this study, various amounts of a divinylbenzene (DVB) cross-linking agent (5˜30%) were introduced during a simultaneous irradiation grafting of styrene onto a PFA film of a 25 μm thickness in order to prepare a series of poly(styrene sulfonic acid)-grafted poly(tetrafluoroethylene- co-perfluorovinyl vinyl ether) (PFA) membranes with various degrees of cross-linking and grafting (29˜74%). The effects of the DVB cross-linking agent on the properties of the prepared membranes, such as water uptake, proton conductivity, methanol permeability, and chemical stability, were also investigated in this study. The results indicated that the ion exchange capacity (IEC) slightly decreased with increasing DVB content, whereas the water uptake, proton conductivity, and methanol permeability of the membrane greatly decreased. The chemical stability of the prepared membranes was found to be significantly improved with increasing DVB content. The results indicated that the cross-linked network membranes are promising for application in a direct methanol fuel cell.

  19. 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. PMID:23852192

  20. Polymer dynamics near the surface and in the bulk of poly(tetrafluoroethylene) probed by zero-field muon-spin-relaxation spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  1. 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.

  2. Papillaes-enhanced hydrophobicity of large-sized polytetrafluoroethylene-polyphenylene sulfite soft film prepared by layer-by-layer construction

    NASA Astrophysics Data System (ADS)

    Hou, Cheng Cheng; Wang, Wen Jun; Zhang, Yu; Guan, Zi Sheng

    2012-07-01

    Large-sized superhydrophobic soft film with hierarchical structures were prepared by combining papillaes on the polytetrafluoroethylene-polyphenylene sulfite (PTFE-PPS) surface via layer-by-layer construction on the glass substrate and heat treatment processes, therein, the papillaes were formed by 0.1 μm PTFE coated on the pollen grains. The water contact angles (CAs) and sliding angles (SAs) of the films are strongly dependent on the number density of the papillaes on the PTFE-PPS surface. A superhydrophobic surface with a water CA = 151.5° and SA = 4° was obtained when the number density was about 649 mm-2. The papillaes with micro/submicroscale structures play an important role in the formation of the superhydrophobic surface and can change Wenzel-type surface into Cassie-Baxter-type surface. The condensation of water vapor on the Cassie-Baxter-type PTFE-PPS film is much more difficult than that of on the Wenzel-type film. Our method may develop into a facile method to prepare large-sized soft film with low cost, which limited only by the size of the loading substrates.

  3. 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. PMID:25353500

  4. 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. PMID:25491987

  5. 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.

  6. 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

  7. Expanding Advanced Civilizations in the Universe

    NASA Astrophysics Data System (ADS)

    Gros, C.

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

  8. Demands of Expanding Populations and Development Planning

    NASA Astrophysics Data System (ADS)

    Lim, Bo

    2010-04-01

    This book is a practical resource for development planners, demographers, and organizations involved with development projects related to improving the well-being and welfare of expanding human populations. Demands of Expanding Populations and Development Planning essentially is a treatment on sustainability and includes a heavy emphasis on major issues of environmental pollution over the last 3 decades. The book's coverage of ecosystems, atmospheric chemistry, water availability and quality, and soils is comprehensive. The author's extensive teaching experience makes this somewhat of an authoritative book on air quality and emissions from natural and anthropogenic sources, volatile heavy metals, carbon monoxide, radon, and nuclear waste. Most of the book focuses on the atmospheric chemistry of air pollution, whether the pollution source is from energy, industrial production, and manufacturing processes or from the treatment of waste products from such processes.

  9. Texaphyrins: Tumor Localizing Redox Active Expanded Porphyrins

    PubMed Central

    Arambula, Jonathan F.; Preihs, Christian; Borthwick, Derric; Magda, Darren; Sessler, Jonathan L.

    2011-01-01

    Texaphyrins, a class of tumor selective expanded porphyrins capable of coordinating large metals, have been found to act as redox mediators within biological systems. This review summarizes studies involving their experimentaluse in cancer chemotherapy. Mechanistic insights involving their presumed mode of action are also described, as well as certain structure activity relationships. Finally, newer texaphyrin-based applications associated with targeted drug delivery are presented. PMID:21355841

  10. Joule-Thomson expander and heat exchanger

    NASA Technical Reports Server (NTRS)

    Norman, R. H.

    1976-01-01

    The Joule-Thomson Expander and Heat Exchanger Program was initiated to develop an assembly (JTX) which consists of an inlet filter, counterflow heat exchanger, Joule-Thomson expansion device, and a low pressure jacket. The program objective was to develop a JTX which, when coupled to an open cycle supercritical helium refrigerating system (storage vessel), would supply superfluid helium (He II) at 2 K or less for cooling infrared detectors.

  11. Anaerobic expanded bed treatment of whey

    SciTech Connect

    Switzenbaum, M.S.; Danskin, S.C.

    1982-01-01

    The use of anaerobic attached film expanded bed (AAFEB) for whey treatment is described and the potential for implementation of substitute natural gas from whey is discussed. A significant portion (less than or equal to 46%) of the energy needs at cheese-production plants could be recovered by CH/sub 4/ manufactured from whey. Efficient treatment of whey is possible by AAFEB at low retention times and at high organic loading rates.

  12. Femoral midshaft fractures: expandable versus locked nailing.

    PubMed

    Zhou, Zhen-Tao; Song, Yu-Chen; Zhou, Xiao-Zhong; Zhou, Hai-Bin; Luo, Zong-Ping; Dong, Qi-Rong

    2015-04-01

    Femoral midshaft fracture is one of the most common clinical injuries and is often caused by high-energy traffic accidents. Intramedullary nailings, plates, and external fixators are all used as treatment alternatives for a variety of patients depending on fracture location, displacement, comminution, soft tissue condition, and local tradition. Locked intramedullary nailing is currently the preferred treatment method for most diaphyseal fractures and has good clinical results. The goal of this study was to compare expandable and locked intramedullary nailing for the treatment of AO type 32A and 32B1 femoral midshaft fractures. The authors performed a retrospective analysis of 46 patients (33 men and 13 women; mean age, 32.3 years; range, 22-52 years) with femoral midshaft fractures who were divided into 2 groups-one treated with an expandable intramedullary nailing method and the other with a conventional locked intramedullary nailing. The 2 groups were compared with respect to operation time, fluoroscopic time, amount of estimated blood loss, hospitalization time, healing time, and complications. Patients were followed for at least 1 year. The results of this study showed that all of the patients achieved bone union within 12 to 24 months. Expandable nailing performed better than locked nailing in operation time, fluoroscopic time, amount of estimated blood loss, and healing time (P<.001). There was no difference in hospitalization time and no visible shortening or severe complications were observed in either group. Based on the results of this study, the expandable intramedullary nailing is an easy and effective treatment for AO type 32A and 32B1 diaphyseal femoral fractures. PMID:25901625

  13. Short wavelength striations on expanding plasma clouds

    SciTech Connect

    Winske, D.; Gary, S.P.

    1989-01-01

    The growth and evolution of short wavelength (expanding across an ambient magnetic field have been actively studied in recent years, both by means of experiments in the laboratory as well as in space and through numerical simulations. We review the relevant observations and simulations results, discuss the instability mechanism and related linear theory, and describe recent work to bring experiments and theory into better agreement. 30 refs., 6 figs.

  14. Measurements of an expanding surface flashover plasma

    SciTech Connect

    Harris, J. R.

    2014-05-21

    A better understanding of vacuum surface flashover and the plasma produced by it is of importance for electron and ion sources, as well as advanced accelerators and other vacuum electronic devices. This article describes time-of-flight and biased-probe measurements made on the expanding plasma generated from a vacuum surface flashover discharge. The plasma expanded at velocities of 1.2–6.5 cm/μs, and had typical densities of 10{sup 10}–10{sup 12} cm{sup −3}. The expansion velocity of the plasma leading edge often exhibited a sharp increase at distances of about 50 mm from the discharge site. Comparison with biased-probe data suggests that, under most conditions, the plasma leading edge was dominated by negative ions, with the apparent increase in velocity being due to fast H{sup −} overtaking slower, heavier ions. In some cases, biased-probe data also showed abrupt discontinuities in the plasma energy distribution co-located with large changes in the intercepted plasma current, suggesting the presence of a shock in the leading edge of the expanding plasma.

  15. Atom counting in expanding ultracold clouds

    SciTech Connect

    Braungardt, Sibylle; Rodriguez, Mirta; Sen, Aditi; Sen, Ujjwal; Lewenstein, Maciej

    2011-10-15

    We study the counting statistics of ultracold bosonic atoms that are released from an optical lattice. We show that the counting probability distribution of the atoms collected at a detector located far away from the optical lattice can be used to characterize the initially trapped states. We consider trapped superfluid and insulating states with different occupation patterns. We analyze how the correlations between the modes that develop during the expansion in the gravitational field appear in the counting distribution and find that the ratio of the detector size with respect to the expanded wave function determines whether short-range or long-range correlations of the initial state are reflected in the counting statistics. We find that detectors which are large compared to the size of the expanded wave function distinguish insulating and superfluid phases irrespective of the occupation pattern. We show that using detectors that are small compared to the size of the expanded wave function, occupation patterns in insulating and supersolid states can be distinguished. Finally, we show how the magnetic phase patterns are dramatically reflected in the number distribution.

  16. Expandable Metal Liner For Downhole Components

    DOEpatents

    Hall, David R.; Fox, Joe R.

    2004-10-05

    A liner for an annular downhole component is comprised of an expandable metal tube having indentations along its surface. The indentations are formed in the wall of the tube either by drawing the tube through a die, by hydroforming, by stamping, or roll forming and may extend axially, radially, or spirally along its wall. The indentations accommodate radial and axial expansion of the tube within the downhole component. The tube is inserted into the annular component and deformed to match an inside surface of the component. The tube may be expanded using a hydroforming process or by drawing a mandrel through the tube. The tube may be expanded in such a manner so as to place it in compression against the inside wall of the component. The tube is useful for improving component hydraulics, shielding components from contamination, inhibiting corrosion, and preventing wear to the downhole component during use. It may also be useful for positioning conduit and insulated conductors within the component. An insulating material may be disposed between the tube and the component in order to prevent galvanic corrosion of the downhole component.

  17. 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. PMID:25496745

  18. Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models

    SciTech Connect

    Selvakumar, N.; Barshilia, Harish C.; Rajam, K. S.

    2010-07-15

    We have studied the effect of substrate roughness on the wettability and the apparent surface free energy (SFE) of sputter deposited polytetrafluoroethylene (PTFE) coatings deposited on untreated glass (average roughness, R{sub a}=2.0 nm), plasma etched glass (R{sub a}=7.4 nm), and sandblasted glass (R{sub a}=4500 nm) substrates. The wettability of the PTFE coatings deposited on substrates with varying roughnesses was evaluated by measuring the apparent contact angle (CA) using a series of probe liquids from nonpolar aprotic to polar protic. The wettability measurements indicate that an apparent water CA of 152 deg. with a sliding angle of 8 deg. was achieved for PTFE coatings deposited on a substrate with R{sub a}=4500 nm. The superhydrophobicity observed in these coatings is attributed to the presence of dual scale roughness, densely packed microstructure and the presence of CF{sub 3} groups. Unlike the bulk PTFE which is mainly dispersive, the sputter deposited PTFE coatings are expected to have some degree of polar component due to the plasma treatment. In order to calculate the dispersive SFE of PTFE coatings, we have used the Girifalco-Good-Fowkes (GGF) method and validated it with the Zisman model. Furthermore, the Owens-Wendt model has been used to calculate the dispersive and the polar components of the apparent SFE of the PTFE coatings. These results are further corroborated using the Fowkes method. Finally, an ''equation of state'' theory proposed by Neumann has been used to calculate the apparent SFE values of the PTFE coatings. The results indicate that the apparent SFE values of the PTFE coatings obtained from the Owens-Wendt and the Fowkes methods are comparable to those obtained from the Neumann's method. The analyses further demonstrate that the GGF and the Zisman methods underestimate the apparent SFE values of the sputter deposited PTFE coatings.

  19. Expanded mode lasers for telecommunications applications

    NASA Astrophysics Data System (ADS)

    Lealman, Ian F.

    This thesis describes the development of a long wavelength (1.55 μm) expanded mode semiconductor laser. The increased spot size of the laser improves both the coupling efficiency to cleaved fibre and fibre alignment tolerances and reduces packaging cost. In this type of device the strength of the waveguide is gradually reduced towards the front facet allowing the mode to adiabatically expand so that the laser mode is better matched in size to that of a cleaved fibre. This can be achieved by either reducing the refractive index of the guide or reducing the amount of material in the core. The structure chosen was a buried heterostructure laser that utilised a twin guide consisting of an upper higher refractive index guide (the active region of the laser) above a weak passive guide. The width of the active region was reduced along part of the device allowing the mode to expand into the weak underlying guide. The guide structure was optimised using a variable grid finite difference mode solver, and the taper length calculated by an approximation to Love's method. Detailed results are presented for the measured light-current characteristic, farfield and coupling loss to cleaved fibre. These coupling losses were compared to the calculated data thus allowing the waveguide design to be optimised. Several iterations in the design of the device were undertaken, with the aim of reducing the coupling loss to cleaved single mode fibre without significantly compromising the laser performance. The final device design had extremely low coupling losses as low as 1.2 dB to cleaved fibre. Finally, the positive impact this device had on passive alignment using a silicon motherboard is examined, and the application this technology to a range of other optoelectronic components is discussed.

  20. Short wavelength striations on expanding plasma clouds

    NASA Technical Reports Server (NTRS)

    Winske, D.; Gary, S. P.

    1990-01-01

    The present evaluation of current understanding of the growth and evolution of less-than-1 ion gyroradius 'flute modes' on a plasma as it expands across and ambient magnetic field notes that the mechanism by which the instability is generated, and its approximate linear theory (encompassing nonlocal, finite-beta, and collisional effects), have reached a satisfactory degree of development. AMPTE Ba releases have been the bases of most of the observational studies. Substantial progress is also noted in the development of a nonlinear mode-coupling theory which can resolve remaining differences between theory and observation.

  1. Expandable tubulars for use in geologic structures

    DOEpatents

    Spray, Jeffery A.; Svedeman, Steven; Walter, David; Mckeighan, Peter; Siebanaler, Shane; Dewhurst, Peter; Hobson, Steven; Foss, Doug; Wirz, Holger; Sharpe, Aaron; Apostal, Michael

    2014-08-12

    An expandable tubular includes a plurality of leaves formed from sheet material that have curved surfaces. The leaves extend around a portion or fully around the diameter of the tubular structure. Some of the adjacent leaves of the tubular are coupled together. The tubular is compressed to a smaller diameter so that it can be inserted through previously deployed tubular assemblies. Once the tubular is properly positioned, it is deployed and coupled or not coupled to a previously deployed tubular assembly. The tubular is useful for all types of wells and boreholes.

  2. Ion acceleration in expanding ionospheric plasmas

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Schunk, R. W.

    1986-01-01

    Plasma expansion along the ambient magnetic field in regions of density gradients provides a mechanism for accelerating ions. A brief review of the basic phenomenon of plasma expansion is given. Estimates of the energies of the accelerated ions in an expanding ionospheric plasma along geomagnetic flux tubes are obtained by solving the time-dependent hydrodynamic equations. It is found that, over certain altitude ranges, each ion species can be the most energetic; the maximum energies of the different ions are found to be limited to less than about 10 eV for H(+), 5 eV for He(+), and less than about 1.5 eV for O(+).

  3. SnapShot: Expanding the Ubiquitin Code.

    PubMed

    Rajalingam, Krishnaraj; Dikic, Ivan

    2016-02-25

    The Ubiquitin (Ub) system coordinates vital cellular processes by controlling lifetime, signaling, and binding properties of proteins. Ub serves as a multivalent protein tag that is further diversified by post-translational modifications. Specialized Ub receptors then convert the encoded signals into cellular responses. This SnapShot highlights the importance of the rapidly expanding Ub code in biology as well as novel pharmacological approaches to target the Ub system in multiple diseases. To view this SnapShot, open or download the PDF. PMID:26919436

  4. Mining Energy in an Expanding Universe

    NASA Astrophysics Data System (ADS)

    Harrison, Edward R.

    1995-06-01

    In principle, the expansion of the universe can be harnessed to provide energy. In a gedankenexperiment, energy is gained by connecting together widely separated bodies with strings. The tension and the energy generated are calculated for single strings. Mining energy in an expanding universe in this way raises unresolved issues concerning the conservation of energy. Apparently, the tethered-body experiment delivers "nascent" energy that previously did not exist in any identifiable and quantifiable form. It is argued that energy in a homogeneous and unbounded universe, in general, is not conserved on the cosmic scale.

  5. FOAM: Expanding the horizons of climate modeling

    SciTech Connect

    Tobis, M.; Foster, I.T.; Schafer, C.M.

    1997-10-01

    We report here on a project that expands the applicability of dynamic climate modeling to very long time scales. The Fast Ocean Atmosphere Model (FOAM) is a coupled ocean atmosphere model that incorporates physics of interest in understanding decade to century time scale variability. It addresses the high computational cost of this endeavor with a combination of improved ocean model formulation, low atmosphere resolution, and efficient coupling. It also uses message passing parallel processing techniques, allowing for the use of cost effective distributed memory platforms. The resulting model runs over 6000 times faster than real time with good fidelity, and has yielded significant results.

  6. Expanding Slayer Statutes to Elder Abuse.

    PubMed

    Piel, Jennifer

    2015-09-01

    Common law has a dictum that people must not benefit from their crimes. In years past, states have enacted slayer rules to prevent killers from inheriting from their victims. The specific criteria and applicability of slayer rules vary by jurisdiction. Recently, several states, including Washington, have expanded their slayer rules to disqualify persons from inheriting if they have been involved in abuse or financial exploitation of the deceased. Reviewed herein are the abuse disinheritance laws, the relationship of the laws to concepts of testamentary capacity and undue influence, and the relevance to forensic psychiatric evaluations. PMID:26438815

  7. Expanding NASA Science Cooperation with New Partners

    NASA Astrophysics Data System (ADS)

    Allen, Marc; Bress, Kent

    Expanding NASA Science Cooperation with New Partners When NASA was created in 1958, it was given a goal of "cooperation by the United States with other nations and groups of nations in work done pursuant to this Act and in the peaceful application of the results." As science has become increasingly globalized during the past 50 years, NASA and its many partners in space and Earth science research have benefited enormously from pooling ideas, skills, and resources for joint undertakings. The discoveries made have powerfully advanced public awareness of science and its importance all over the world. Today, the U.S. Administra-tion is encouraging NASA to expand its cooperation with new and emerging partners. NASA space and Earth science cooperation is founded on scientist-to-scientist research collaboration. Space missions are very costly and technically challenging, but there are many other important areas for international cooperation. Areas ripe for expansion with new partners include space data sharing, scientist-to-scientist collaborative research, international research program plan-ning and coordination, Earth applications for societal benefit, ground-based measurements for Earth system science, and education and public outreach. This presentation lays out NASA's general principles for international science cooperation, briefly describes each of these opportu-nity areas, and suggests avenues for initiating new cooperative relationships.

  8. Historical Notes on the Expanding Universe

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  9. String and Cluster Formation in Expanded Sodium

    NASA Astrophysics Data System (ADS)

    Pfaffenzeller, O.; Hohl, D.; Kwon, I.; Kress, J.; Collins, L.

    1996-03-01

    At multimegabar pressures and elevated temperatures short-lived strings of atoms form in dense H in regimes where metallization of H and dissociation of H2 occur (D.Hohl et. al.), Phys. Rev. Lett. 71, 541 (1993); I.Kwon et. al., Phys. Rev. E 49, R4771 (1994).. We have investigated similar behavior in another group IA element, Na, by searching for string-like entities in the regime of the insulator-metal transition. Whereas H had to be strongly compressed, Na under normal conditions is an atomic metal and must be expanded. We performed simulations for densities of 1.28, 0.74, 0.47, 0.31 and 0.16 g/cm^3. These densities represent a system expanded up to eight times its normal solid volume. Across the liquid-vapor boundary, we have observed the formation of strings and clusters of atoms. We report the properties of these structural entities as a function of density and temperature. The simulations were performed within the Car-Parrinello approach, using a local pseudopotential. As a test, we obtained very good agreement with experimental results for the pair-correlation functions and self-diffusion coefficients in the temperature regime between melting and boiling at normal solid density.

  10. The Expanding Marketplace for Applied Geophysics

    NASA Astrophysics Data System (ADS)

    Carlson, N.; Sirles, P.

    2012-12-01

    While the image of geophysics for the proverbial "layman" often seems limited to volcanoes and earthquakes, and to the geoscientist this image enlarges to include oil or minerals exploration and whole earth studies, there has been a steady increase in the application of geophysics into the realm of "daily life", such as real estate deals, highway infrastructure, and flood protection. This expansion of applications can be attributed to the improved economics from advances in equipment and interpretation. Traditional geophysical methods that at one time often only fit within the budgets of oil, gas, and minerals exploration programs can now be economically applied to much smaller scale needs like contaminant mapping, landfill delineation, and levee investigations. A real-world, economic example of this expanding marketplace is our company, which began very small and was aimed almost exclusively at the minerals exploration market. Most of our growth has been in the last 10 years, when we have expanded to five offices and a staff with almost 40 geoscientist degrees (21 in geophysics); much of this growth has been in the non-oil, non-minerals arenas. While much of our work still includes minerals exploration, other projects this year include wind-farm foundation studies, cavity detection above underground nuclear tests, landfill studies, acid mine drainage problems, and leaks in evaporation ponds. A methodology example of this expanding market is the induced polarization (IP) survey, once primarily used for minerals exploration, particularly large porphyry copper deposits, but now efficient enough to also use in environmental studies. The IP method has been particularly useful in delineating and characterizing old, poorly documented landfills, and recent research suggests it may also be useful in monitoring the accelerated biodegradation processes used in some cases to rehabilitate the sites. Compared to temperature monitoring systems, IP may be more useful in providing

  11. Optical cavity resonator in an expanding universe

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei M.

    2015-02-01

    We study the cosmological evolution of frequency of a standing electromagnetic wave in a resonant optical cavity placed to the expanding manifold described by the Robertson-Walker metric. Because of the Einstein principle of equivalence (EEP), one can find a local coordinate system (a local freely falling frame), in which spacetime is locally Minkowskian. However, due to the conformal nature of the Robertson-Walker metric the conventional transformation to the local inertial coordinates introduces ambiguity in the physical interpretation of the local time coordinate, . Therefore, contrary to a common-sense expectation, a straightforward implementation of EEP alone does not allow us to unambiguously decide whether atomic clocks based on quantum transitions of atoms, ticks at the same rate as the clocks based on electromagnetic modes of a cavity. To resolve this ambiguity we have to analyse the cavity rigidity and the oscillation of its electromagnetic modes in an expanding universe by employing the full machinery of the Maxwell equations irrespectively of the underlying theory of gravity. We proceed in this way and found out that the size of the cavity and the electromagnetic frequency experience an adiabatic drift in conformal (unphysical) coordinates as the universe expands in accordance with the Hubble law. We set up the oscillation equation for the resonant electromagnetic modes, solve it by the WKB approximation, and reduce the coordinate-dependent quantities to their counterparts measured by a local observer who counts time with atomic clock. The solution shows that there is a perfect mutual cancellation of the adiabatic drift of cavity's frequency by space transformation to local coordinates and the time counted by the clocks based on electromagnetic modes of cavity has the same rate as that of atomic clocks. We conclude that if general relativity is correct and the local expansion of space is isotropic there should be no cosmological drift of frequency of a

  12. 46 CFR 56.30-15 - Expanded or rolled joints.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Expanded or rolled joints. 56.30-15 Section 56.30-15... APPURTENANCES Selection and Limitations of Piping Joints § 56.30-15 Expanded or rolled joints. (a) Expanded or rolled joints may be used where experience or test has demonstrated that the joint is suitable for...

  13. 46 CFR 56.30-15 - Expanded or rolled joints.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Expanded or rolled joints. 56.30-15 Section 56.30-15... APPURTENANCES Selection and Limitations of Piping Joints § 56.30-15 Expanded or rolled joints. (a) Expanded or rolled joints may be used where experience or test has demonstrated that the joint is suitable for...

  14. 46 CFR 56.30-15 - Expanded or rolled joints.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Expanded or rolled joints. 56.30-15 Section 56.30-15... APPURTENANCES Selection and Limitations of Piping Joints § 56.30-15 Expanded or rolled joints. (a) Expanded or rolled joints may be used where experience or test has demonstrated that the joint is suitable for...

  15. 46 CFR 56.30-15 - Expanded or rolled joints.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Expanded or rolled joints. 56.30-15 Section 56.30-15... APPURTENANCES Selection and Limitations of Piping Joints § 56.30-15 Expanded or rolled joints. (a) Expanded or rolled joints may be used where experience or test has demonstrated that the joint is suitable for...

  16. 46 CFR 56.30-15 - Expanded or rolled joints.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Expanded or rolled joints. 56.30-15 Section 56.30-15... APPURTENANCES Selection and Limitations of Piping Joints § 56.30-15 Expanded or rolled joints. (a) Expanded or rolled joints may be used where experience or test has demonstrated that the joint is suitable for...

  17. Expanding the phenotype of GMPPB mutations.

    PubMed

    Cabrera-Serrano, Macarena; Ghaoui, Roula; Ravenscroft, Gianina; Johnsen, Russell D; Davis, Mark R; Corbett, Alastair; Reddel, Stephen; Sue, Carolyn M; Liang, Christina; Waddell, Leigh B; Kaur, Simranpreet; Lek, Monkol; North, Kathryn N; MacArthur, Daniel G; Lamont, Phillipa J; Clarke, Nigel F; Laing, Nigel G

    2015-04-01

    Dystroglycanopathies are a heterogeneous group of diseases with a broad phenotypic spectrum ranging from severe disorders with congenital muscle weakness, eye and brain structural abnormalities and intellectual delay to adult-onset limb-girdle muscular dystrophies without mental retardation. Most frequently the disease onset is congenital or during childhood. The exception is FKRP mutations, in which adult onset is a common presentation. Here we report eight patients from five non-consanguineous families where next generation sequencing identified mutations in the GMPPB gene. Six patients presented as an adult or adolescent-onset limb-girdle muscular dystrophy, one presented with isolated episodes of rhabdomyolysis, and one as a congenital muscular dystrophy. This report expands the phenotypic spectrum of GMPPB mutations to include limb-girdle muscular dystrophies with adult onset with or without intellectual disability, or isolated rhabdomyolysis. PMID:25681410

  18. Gravitational wave memory in an expanding universe

    NASA Astrophysics Data System (ADS)

    Tolish, Alexander; Wald, Robert

    2016-03-01

    We investigate the gravitational wave memory effect in an expanding FLRW spacetime. We find that if the gravitational field is decomposed into gauge-invariant scalar, vector, and tensor modes after the fashion of Bardeen, only the tensor mode gives rise to memory, and this memory can be calculated using the retarded Green's function associated with the tensor wave equation. If locally similar radiation source events occur on flat and FLRW backgrounds, we find that the resulting memories will differ only by a redshift factor, and we explore whether or not this factor depends on the expansion history of the FLRW universe. We compare our results to related work by Bieri, Garfinkle, and Yau.

  19. Web Content Analysis: Expanding the Paradigm

    NASA Astrophysics Data System (ADS)

    Herring, Susan C.

    Are established methods of content analysis (CA) adequate to analyze web content, or should new methods be devised to address new technological developments? This article addresses this question by contrasting narrow and broad interpretations of the concept of web content analysis. The utility of a broad interpretation that subsumes the narrow one is then illustrated with reference to research on weblogs (blogs), a popular web format in which features of HTML documents and interactive computer-mediated communication converge. The article concludes by proposing an expanded Web Content Analysis (WebCA) paradigm in which insights from paradigms such as discourse analysis and social network analysis are operationalized and implemented within a general content analytic framework.

  20. NOVAE EJECTA AS DISCRETE ADIABATICALLY EXPANDING GLOBULES

    SciTech Connect

    Williams, Robert

    2013-09-15

    Available data for novae show that the X-ray and visible spectral regions correlate with each other as they evolve. Large differences in ionization exist simultaneously in the two wavelength regimes, and a straightforward model is proposed that explains the characteristics observed in both spectral regimes. Its key features are (1) ejected blobs of very high density gas from the white dwarf (WD) that expand to create within each clump a wide range of emitting density, ionization, and velocity, and (2) a more homogeneous circumbinary envelope of gas that is produced by secondary star mass loss. The relative mass loss rates from the two stars determine whether the He/N or the Fe II visible spectrum predominates during decline, when hard X-rays are detected, and when the WD can be detected as a super soft X-ray source.

  1. Expanding the Genetic Code for Biological Studies

    PubMed Central

    Wang, Qian; Parrish, Angela R.; Wang, Lei

    2009-01-01

    Summary Using an orthogonal tRNA-synthetase pair, unnatural amino acids can be genetically encoded with high efficiency and fidelity; and over forty unnatural amino acids have been site-specifically incorporated into proteins in E. coli, yeast, or mammalian cells. Novel chemical or physical properties embodied in these amino acids enable new means for tailored manipulation of proteins. This review summarizes the methodology and recent progress in expanding this technology to eukaryotic cells. Applications of genetically encoded unnatural amino acids are highlighted with reports on labeling and modifying proteins, probing protein structure and function, identifying and regulating protein activity, and generating proteins with new properties. Genetic incorporation of unnatural amino acids provides a powerful method for investigating a wide variety of biological processes both in vitro and in vivo. PMID:19318213

  2. Expanding roles for GILT in immunity

    PubMed Central

    West, Laura Ciaccia

    2015-01-01

    Gamma-interferon-inducible lysosomal thiol reductase (GILT), a thioredoxin-related oxidoreductase, functions in MHC class II-restricted antigen processing and MHC class I-restricted cross-presentation by reducing disulfide bonds of endocytosed proteins and facilitating their unfolding and optimal degradation. However, recent reports have greatly expanded our understanding of GILT’s function. Several studies of GILT and antigen processing have shown that the influence of GILT on the peptide repertoire can alter the character of the immune response and affect central tolerance. Furthermore, a few unexpected roles for GILT have been uncovered: as a host factor for Listeria monocytogenes infection, in the maintenance of cellular glutathione levels (GSH), and possibly outside the cell, as enzymatically active GILT is secreted by activated macrophages. PMID:23246037

  3. Study of an expanding magnetic cloud

    NASA Astrophysics Data System (ADS)

    Nakwacki, M. S.; Dasso, S.; Mandrini, C. H.; Démoulin, P.

    Magnetic Clouds (MCs) transport into the interplanetary medium the magnetic flux and helicity released in coronal mass ejections by the Sun. At 1 AU from the Sun, MCs are generally modelled as static flux ropes. However, the velocity profile of some MCs presents signatures of expansion. We analise here the magnetic structure of an expanding magnetic cloud observed by Wind spacecraft. We consider a dynamical model, based on a self-similar behaviour for the cloud radial velocity. We assume a free expansion for the cloud, and a cylindrical linear force free field (i.e., the Lundquist's field) as the initial condition for its magnetic configuration. We derive theoretical expressions for the magnetic flux across a surface perpendicular to the cloud axis, for the magnetic helicity and magnetic energy per unit length along the tube using the self-similar model. Finally, we compute these magntitudes with the fitted parameters. FULL TEXT IN SPANISH

  4. Alice and Bob in an expanding spacetime

    NASA Astrophysics Data System (ADS)

    Alexander, Helder; de Souza, Gustavo; Mansfield, Paul; Sampaio, Marcos

    2015-09-01

    We investigate the teleportation of a qubit between two observers Alice and Bob in an asymptotically flat Robertson-Walker expanding spacetime. We use scalar or fermionic field modes inside Alice's and Bob's ideal cavities and show the degradation of the teleportation quality, as measured by the fidelity, through a mechanism governed by spacetime expansion. This reduction is demonstrated to increase with the rapidity of the expansion and to be highly sensitive to the coupling of the field to spacetime curvature, becoming considerably stronger as it reduces from conformal to minimal. We explore a perturbative approach in the cosmological parameters to compute the Bogoliubov coefficients in order to evaluate and compare the fidelity degradation of fermionic and scalar fields.

  5. Expanding a Comprehensive Lung Cancer Screening Program.

    PubMed

    Jansak, Buffy

    2015-01-01

    The OhioHealth Lung Cancer Screening Program is a high quality multi-disciplinary program that was launched in July 2013 at OhioHealth Riverside Methodist Hospital, OhioHealth Doctors Hospital, and OhioHealth Grant Medical Center in Columbus, Ohio. With the assistance of the AHRA & Toshiba Putting Patients First grant, we were able to expand community access for people at high risk of developing lung cancer by opening several more programs at OhioHealth Marion General and OhioHealth Grady Memorial Hospitals. A subsequent patient educational video was developed to highlight the comprehensive program, nurse navigational involvement, potential risks, benefits, and tobacco cessation. The tobacco cessation educational skills of the OhioHealth Lung Nurse Navigators were enhanced with the completion of the Tobacco Treatment Specialist certification. PMID:26710574

  6. Expanding the role of the oncology nurse

    PubMed Central

    Quinn, A

    2008-01-01

    Oncology nursing continues to evolve in response to advances in cancer treatment, information and biotechnology. As new scientific and technological discoveries are integrated into cancer care, oncology nurses need to play a key role in the management of this patient population. The role of the oncology nurse has expanded significantly and can differ greatly across cultures. Sophisticated treatments and the growth of targeted therapies will create the challenge of ensuring that all nurses working in this arena are well-educated, independent thinkers. Thus the future success of oncology nurses will focus on enhancement of nursing practice through advanced education. The increased globalisation of healthcare offers exciting opportunities to accomplish this goal by allowing for collaborative relationships among oncology nurses across the globe. PMID:21611002

  7. Expandable and reconfigurable instrument node arrays

    NASA Technical Reports Server (NTRS)

    Hilliard, Lawrence M. (Inventor); Deshpande, Manohar (Inventor)

    2012-01-01

    An expandable and reconfigurable instrument node includes a feature detection means and a data processing portion in communication with the feature detection means, the data processing portion configured and disposed to process feature information. The instrument node further includes a phase locked loop (PLL) oscillator in communication with the data processing portion, the PLL oscillator configured and disposed to provide PLL information to the processing portion. The instrument node further includes a single tone transceiver and a pulse transceiver in communication with the PLL oscillator, the single tone transceiver configured and disposed to transmit or receive a single tone for phase correction of the PLL oscillator and the pulse transceiver configured and disposed to transmit and receive signals for phase correction of the PLL oscillator. The instrument node further includes a global positioning (GPA) receiver in communication with the processing portion, the GPS receiver configured and disposed to establish a global position of the instrument node.

  8. An Expanded View of Progressive Cardiorenal Disorders.

    PubMed

    Re, Richard N

    2016-06-01

    Chronic renal diseases and congestive heart failure are progressive disorders, which cannot be completely controlled by established therapies. It has been argued that intracrine biology involving the formation of self-sustaining intracrine regulatory loops accounts for the progression of these disorders and for the inability of standard therapies to stop disease spread. The renin-angiotensin system is a prime candidate to be involved in any such process, and an amplifying role for mineralocorticoid activation is also consistent with this view. Here, the notion of intracrine participation in congestive heart failure and chronic renal disease is expanded to include consideration of the participation of other intracrines including transforming growth factor beta 1, parathyroid hormone-related protein and vascular endothelial growth factor among others. The possibility that intracrine expression patterns account for disease phenotypes is explored. The therapeutic implications of this view are discussed. PMID:27238929

  9. Expandable metal stents in chronic pancreatitis

    PubMed Central

    Charnley, RM

    2003-01-01

    Background Biliary obstruction in chronic pancreatitis may be relieved by the insertion of a biliary endoprosthesis. Stenting is usually achieved with a plastic device, but self-expandable metal stents may also be used. Case outlines Two patients are described with severe chronic pancreatitis complicated by biliary obstruction and portal vein thrombosis, who underwent insertion of metallic biliary endoprostheses. In both patients the endoprostheses became occluded, at 12 and 7 months respectively, which necessitated open operation. Both patients experienced surgical complications and one patient died postoperatively. Discussion The use of metal endoprostheses in chronic pancreatitis may result in occlusion, necessitating open operation. Such stents should be used with caution in these patients, who are likely to be high-risk surgical candidates. PMID:18332959

  10. The law's interface with expanding technology

    NASA Technical Reports Server (NTRS)

    Green, H. P.

    1972-01-01

    The role of the law in technology assessment is described in generalized terms of a legal system as it confronts expanding technology. The functions of a technology assessment are considered to be twofold; provide for legislative action designed to channel technological advance along lines which are regarded as optimal from the standpoint of society's interests; and encourage and promote legislative action which will deal decisively with the potential disruptions and injuries caused by technology at a much earlier stage of the growth of the technology than is feasible under the present legal system. It is concluded that since new law always has a disruptive effect on expectations and commitments arrived at under old law, it is generally desirable that new legislation should make the least possible change in the law consistant with accomplishing the desired objective.

  11. The expanding spectrum of cutaneous borreliosis.

    PubMed

    Eisendle, K; Zelger, B

    2009-04-01

    The known spectrum of skin manifestations in cutaneous Lyme disease is continuously expanding and can not be regarded as completed. Besides the classical manifestations of cutaneous borreliosis like erythema (chronicum) migrans, borrelial lymphocytoma and acrodermatitis chronica atrophicans evidence is growing that at least in part also other skin manifestations, especially morphea, lichen sclerosus and cases of cutaneous B-cell lymphoma are causally related to infections with Borrelia. Also granuloma annulare and interstitial granulomatous dermatitis might be partly caused by Borrelia burgdorferi or similar strains. There are also single reports of other skin manifestations to be associated with borrelial infections like cutaneous sarcoidosis, necrobiosis lipoidica and necrobiotic xanthogranuloma. In addition, as the modern chameleon of dermatology, cutaneous borreliosis, especially borrelial lymphocytoma, mimics other skin conditions, as has been shown for erythema annulare centrifugum or lymphocytic infiltration (Jessner Kanof) of the skin. PMID:19357623

  12. Cosmic strings in an expanding spacetime

    SciTech Connect

    Stein-Schabes, J.A.; Burd, A.B.

    1987-04-01

    We investigate the stability of a static, infinitely long and straight vacuum string solution under inhomogeneous axisymmetric time-dependent perturbations. We find it to be perturbatively stable. We further extend our work by finding a string solutions in an expanding Universe. The back reaction of the string on the gravitational field has been ignored. The background is assumed to be a Friedman-Robertson-Walker (FRW) cosmology. By numerically integrating the field equations in a radiation and matter dominated models, we discover oscillatory solutions. The possible damping of these oscillations is discussed. For late times the solution becomes identical to the static one studied in the first part of the paper. 19 refs., 8 figs.

  13. High temperature expanding cement composition and use

    DOEpatents

    Nelson, Erik B.; Eilers, Louis H.

    1982-01-01

    A hydratable cement composition useful for preparing a pectolite-containing expanding cement at temperatures above about 150.degree. C. comprising a water soluble sodium salt of a weak acid, a 0.1 molar aqueous solution of which salt has a pH of between about 7.5 and about 11.5, a calcium source, and a silicon source, where the atomic ratio of sodium to calcium to silicon ranges from about 0.3:0.6:1 to about 0.03:1:1; aqueous slurries prepared therefrom and the use of such slurries for plugging subterranean cavities at a temperature of at least about 150.degree. C. The invention composition is useful for preparing a pectolite-containing expansive cement having about 0.2 to about 2 percent expansion, by volume, when cured at at least 150.degree. C.

  14. Towards an expanded definition of value.

    PubMed

    Smith, Matthew J; Standaert, Christopher J

    2013-11-01

    Much of the change being sought in the United State's health-care system is predicated on improving value. Value is most simply defined as quality divided by cost, and physicians increasingly rely on the quality-adjusted life year as the numerical measure to justify their services. However, there are many other definitions of value being advocated by various stakeholders in the health-care reform effort. Incentive programs and pilot studies implemented by private and public payers are steering much of the current change. Expanding our understanding of how value is defined by health-care economists and policy makers can help spine providers navigate the evolving health-care landscape. PMID:23582428

  15. Expandable pallet for space station interface attachments

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J. (Inventor)

    1988-01-01

    Described is a foldable expandable pallet for Space Station interface attachments with a basic square configuration. Each pallet consists of a series of struts joined together by node point fittings to make a rigid structure. The struts have hinge fittings which are spring loaded to permit collapse of the module for stowage transport to a Space Station in the payload bay of the Space Shuttle, and development on orbit. Dimensions of the pallet are selected to provide convenient, closely spaced attachment points between the node points of the relatively widely spaced trusses of a Space Station platform. A pallet is attached to a strut at four points: one close fitting hole, two oversize holes, and a slot to allow for thermal expansion/contraction and for manufacturing tolerances. Applications of the pallet include its use in rotary or angular joints; servicing of splints; with gridded plates; as instrument mounting bases; and as a roadbed for a Mobile Service Center (MSC).

  16. Expandable pallet for space station interface attachments

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J. (Inventor)

    1989-01-01

    A foldable expandable pallet having a basic square configuration is disclosed. Each pallet is comprised of a plurality of struts, joined together by node point fittings to make a rigid structure. Some of the struts have hinge fittings and are spring loaded to permit collapse of the module for stowage and transport to a space station. Dimensions of the pallet are selected to provide convenient, closely spaced attachment points between the relatively widely spaced trusses of a space station platform. A pallet is attached to a truss at four points; one close fitting hole; two oversize holes; and a slot; to allow for thermal expansion/contraction and for manufacturing tolerances. Applications of the pallet include its use in rotary or angular joints; servicing of splints; with gridded plates; as an instrument mounting bases; and as a roadbed for a Mobile Service Center (MSC).

  17. Henry Norris Russell and the Expanding Universe

    NASA Astrophysics Data System (ADS)

    DeVorkin, D.

    2013-04-01

    Henry Norris Russell, one of the most influential American astronomers of the first half of the 20th Century, had a special place in his heart for the Lowell Observatory. Although privately critical of the founder for his pronouncements about life on Mars and the superiority of the Mars Hill observing site, he always supported the Observatory in public and professional circles. He staunchly supported Tombaugh's detection of a planet as leading from Lowell's prediction, and always promoted V. M. Slipher's spectroscopic investigations of planetary and stellar phenomena. But how did he react to Slipher's puzzling detection of the extreme radial velocities of spiral nebulae starting in 1912, and how did he regard the extension and interpretation of those observations by Hubble and others in following decades? Here we describe the arc of Russell's reactions, dating from Slipher's first detection, as an indicator of how mainstream stellar astronomers reacted to the concept of an expanding universe.

  18. Withdrawal: Expanding a Key Addiction Construct.

    PubMed

    Piper, Megan E

    2015-12-01

    Withdrawal is an essential component of classical addiction theory; it is a vital manifestation of dependence and motivates relapse. However, the traditional conceptualization of withdrawal as a cohesive collection of symptoms that emerge during drug deprivation and decline with either the passage of time or reinstatement of drug use, may be inadequate to explain scientific findings or fit with modern theories of addiction. This article expands the current understanding of tobacco withdrawal by examining: (1) withdrawal variability; (2) underlying causes of withdrawal variability, including biological and person factors, environmental influences, and the influence of highly routinized behavioral patterns; (3) new withdrawal symptoms that allow for enhanced characterization of the withdrawal experience; and (4) withdrawal-related cognitive processes. These topics provide guidance regarding the optimal assessment of withdrawal and illustrate the potential impact modern withdrawal conceptualization and assessment could have on identifying treatment targets. PMID:25744958

  19. Wave Propagation in Expanding Cell Layers

    NASA Astrophysics Data System (ADS)

    Utuje, Kazage J. Christophe; Banerjee, Shiladitya; Marchetti, M. Cristina

    2014-03-01

    The coordinated migration of groups of cells drives important biological processes, such as wound healing and morphogenesis. In this talk we present a minimal continuum model of an expanding cell monolayer coupling elastic deformations to myosin-based activity in the cells. The myosin-driven contractile activity is quantified by the chemical potential difference for the process of ATP hydrolysis by myosin motors. A new ingredient of the model is a feedback of the local strain rate of the monolayer on contractility that naturally yields a mechanism for viscoelasticity of the cellular medium. By combining analytics and numerics we show that this simple model reproduces qualitatively many experimental findings, including the build-up of contractile stresses at the center of the cell monolayer, and the existence of traveling mechanical waves that control spreading dynamics and stress propagation in the cell monolayer. KJCU and MCM were supported by the NSF through grants DMR-1004789 and DGE-1068780.

  20. Microfluidics Expanding the Frontiers of Microbial Ecology

    PubMed Central

    Rusconi, Roberto; Garren, Melissa; Stocker, Roman

    2014-01-01

    The ability afforded by microfluidics to observe the behaviors of microbes in highly controlled and confined microenvironments, across scales from a single cell to mixed communities, has significantly contributed to expand the frontiers of microbial ecology over the last decade. Spatially and temporally varying distributions of organisms and chemical cues that mimic natural microbial habitats can now be established by exploiting physics at the micrometer scale and by incorporating structures with specific geometries and materials. Here we review applications of microfluidics that have resulted in highly insightful discoveries on fundamental aspects of microbial life, ranging from growth and sensing to cell-cell interactions and population dynamics. We anticipate that this flexible, multidisciplinary technology will continue to facilitate discoveries regarding the ecology of microorganisms and help uncover strategies to control phenomena such as biofilm formation and antibiotic resistance. PMID:24773019

  1. Financing Expanded Learning Time in Schools: A Look at Five District-Expanded Time Schools

    ERIC Educational Resources Information Center

    Kaplan, Claire; Farbman, David A.; Deich, Sharon; Padgette, Heather Clapp

    2014-01-01

    Over the last several years, public education in the U.S. has experienced a remarkable growth in the number of schools that have expanded their schedules beyond the conventional calendar of 180 6.5-hour days. Spurred by significant policy activity at the federal, state, and local levels, more and more educators have capitalized on opportunities to…

  2. BOOK REVIEW: The Artful Universe Expanded

    NASA Astrophysics Data System (ADS)

    Bassett, B. A.

    2005-07-01

    The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music—a new type of `cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson,\\endcolumn hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature’s code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one’s mind a vision that unifies science, art and culture and glimpse a universal tapestry of great

  3. Expanded Small-Scale Shock Reactivity Test

    NASA Astrophysics Data System (ADS)

    Granholm, Richard

    2005-07-01

    Explosives react from a strong shock, even in quantities too small for detonation. The potential for a new material to be an explosive can be evaluated from this shock reactivity. The recently developed small-scale shock reactivity test (SSRT)ootnotetextH. W. Sandusky, R. H. Granholm, D. G. Bohl, ``Small-Scale Shock Reactivity Test,'' NSWC Technical Report (in publication), Naval Surface Warfare Center, Indian Head, MD 20640 uses very high confinement to allow prompt reactions to occur in less than half-gram samples well below critical diameter, with the reactions quantified by a dent in a soft aluminum witness block. This test has been expanded to simultaneously measure both early and late-time reactions from a single sample subjected to the output from an RP-80 detonator. The sample apparatus is further confined within a small chamber instrumented with a pressure gage for internal air blast. This provides a measure of late-time reactions, such as from fuel/air combustion. Results are shown from several simultaneous early- and late-reaction measurements.

  4. Is Space Really Expanding? A Counterexample

    NASA Astrophysics Data System (ADS)

    Chodorowski, Michał J.

    2007-03-01

    In all Friedman models, the cosmological redshift is widely interpreted as a consequence of the general-relativistic phenomenon of expansion of space. Other commonly believed consequences of this phenomenon are superluminal recession velocities of distant galaxies, and the distance to the particle horizon greater than ct (where t is the age of the Universe), in apparent conflict with special relativity. Here, we study a particular Friedman model: empty universe. This model exhibits both cosmological redshift, superluminal velocities and infinite distance to the horizon. However, we show that the cosmological redshift is there simply a relativistic Doppler shift. Moreover, apparently superluminal velocities and ‘acausal’ distance to the horizon are in fact a direct consequence of special-relativistic phenomenon of time dilation, as well as of the adopted definition of distance in cosmology. There is no conflict with special relativity, whatsoever. In particular, inertial recession velocities are subluminal. Since in the real Universe, sufficiently distant galaxies recede with relativistic velocities, these special-relativistic effects must be at least partly responsible for the cosmological redshift and the aforementioned ‘superluminalities’, commonly attributed to the expansion of space. Let us finish with a question resembling a Buddhism-Zen ‘koan’: in an empty universe, what is expanding?

  5. Erotized transference reconsidered: expanding the countertransference dimension.

    PubMed

    Eber, M

    1990-01-01

    A reconsideration of the erotized transference from a contemporary perspective has been presented utilizing detailed case material provided by Stoller. The main thesis is that this type of transference, traditionally conceived as a product of a particular kind of patient often felt to be borderline, is better understood as arising in a specific intersubjective context involving both participants in the psychoanalytic situation. The focus is on the intricate interaction of analyst and patient, recognizing that either may serve as a selfobject for the other. This view assumes a more expanded countertransference role than recognized in the earlier literature. The psychoanalytic situation can be erotized by either or both participants. A corollary thesis is that the details of a patient's fantasy should also be viewed as codetermined and that imbedded within it might be the patient's subjective experience of the psychoanalytic interaction. Alluded to peripherally is that the erotized transference in the interaction between male analyst and female patient is, in part, a manifestation of traditional roles assumed in situations involving a male authority figure in close engagement with a female who perceives herself as relatively powerless. This issue has recently received considerable attention from writers who have addressed themselves to the important gender issues in psychoanalysis. PMID:2111560

  6. The expanding universe of prion diseases.

    PubMed

    Watts, Joel C; Balachandran, Aru; Westaway, David

    2006-03-01

    Prions cause fatal and transmissible neurodegenerative disease. These etiological infectious agents are formed in greater part from a misfolded cell-surface protein called PrP(C). Several mammalian species are affected by the diseases, and in the case of "mad cow disease" (BSE) the agent has a tropism for humans, with negative consequences for agribusiness and public health. Unfortunately, the known universe of prion diseases is expanding. At least four novel prion diseases--including human diseases variant Creutzfeldt-Jakob disease (vCJD) and sporadic fatal insomnia (sFI), bovine amyloidotic spongiform encephalopathy (BASE), and Nor98 of sheep--have been identified in the last ten years, and chronic wasting disease (CWD) of North American deer (Odocoileus Specis) and Rocky Mountain elk (Cervus elaphus nelsoni) is undergoing a dramatic spread across North America. While amplification (BSE) and dissemination (CWD, commercial sourcing of cervids from the wild and movement of farmed elk) can be attributed to human activity, the origins of emergent prion diseases cannot always be laid at the door of humankind. Instead, the continued appearance of new outbreaks in the form of "sporadic" disease may be an inevitable outcome in a situation where the replicating pathogen is host-encoded. PMID:16609731

  7. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 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. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. 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.

  8. Shock Initiation of Thermally Expanded TATB

    NASA Astrophysics Data System (ADS)

    Mulford, Roberta; Swift, Damian

    2011-06-01

    The plastic-bonded explosive PBX-9502 undergoes unusual hysteretic thermal expansion, or ``ratchet growth'' as a consequence of the uniaxial thermal expansion of the graphitic structure of the major component, TATB explosive. Upon thermal cycling, the density of the material can be reduced by as much as 9%, resulting in a distinct increase in the shock sensitivity of the solid. Run distances to detonation have been measured in thermally expanded samples of PBX-9502, using embedded particle velocity gauges and shock tracker gauges. Uniaxial shocks were generated using a light gas gun, to provide a repeatable stimulus for initiation of detonation. We have applied a porosity model to adjust standard Pop plot data to the reduced density of our samples, to investigate whether the sensitivity of the PBX 9502 increases ideally with the decreasing density, or whether the microscopically non-uniform expansion that occurs during ``ratchet growth'' leads to abnormal sensitivity, possibly as a result of cracking or debonding from the binder, as observed in micrographs of the sample.

  9. Expandable Purge Chambers Would Protect Cryogenic Fittings

    NASA Technical Reports Server (NTRS)

    Townsend, Ivan I., III

    2004-01-01

    Expandable ice-prevention and cleanliness-preservation (EIP-CP) chambers have been proposed to prevent the accumulation of ice or airborne particles on quick-disconnect (QD) fittings, or on ducts or tubes that contain cryogenic fluids. In the original application for which the EIP-CP chambers were conceived, there is a requirement to be able to disconnect and reconnect the QD fittings in rapid succession. If ice were to form on the fittings by condensation and freezing of airborne water vapor on the cold fitting surfaces, the ice could interfere with proper mating of the fittings, making it necessary to wait an unacceptably long time for the ice to thaw before attempting reconnection. By keeping water vapor away from the cold fitting surfaces, the EIP-CP chambers would prevent accumulation of ice, preserving the ability to reconnect as soon as required. Basically, the role of an EIP-CP chamber would be to serve as an enclosure for a flow of dry nitrogen gas that would keep ambient air away from QD cryogenic fittings. An EIP-CP chamber would be an inflatable device made of a fabriclike material. The chamber would be attached to an umbilical plate holding a cryogenic QD fitting.

  10. The Expanding Universe of Prion Diseases

    PubMed Central

    Watts, Joel C; Balachandran, Aru; Westaway, David

    2006-01-01

    Prions cause fatal and transmissible neurodegenerative disease. These etiological infectious agents are formed in greater part from a misfolded cell-surface protein called PrPC. Several mammalian species are affected by the diseases, and in the case of “mad cow disease” (BSE) the agent has a tropism for humans, with negative consequences for agribusiness and public health. Unfortunately, the known universe of prion diseases is expanding. At least four novel prion diseases—including human diseases variant Creutzfeldt-Jakob disease (vCJD) and sporadic fatal insomnia (sFI), bovine amyloidotic spongiform encephalopathy (BASE), and Nor98 of sheep—have been identified in the last ten years, and chronic wasting disease (CWD) of North American deer (Odocoileus Specis) and Rocky Mountain elk (Cervus elaphus nelsoni) is undergoing a dramatic spread across North America. While amplification (BSE) and dissemination (CWD, commercial sourcing of cervids from the wild and movement of farmed elk) can be attributed to human activity, the origins of emergent prion diseases cannot always be laid at the door of humankind. Instead, the continued appearance of new outbreaks in the form of “sporadic” disease may be an inevitable outcome in a situation where the replicating pathogen is host-encoded. PMID:16609731

  11. Gravitomagnetic Instabilities in Anisotropically Expanding Fluids

    NASA Astrophysics Data System (ADS)

    Kleidis, Kostas; Kuiroukidis, Apostolos; Papadopoulos, Demetrios B.; Vlahos, Loukas

    Gravitational instabilities in a magnetized Friedman-Robertson-Walker (FRW) universe, in which the magnetic field was assumed to be too weak to destroy the isotropy of the model, are known and have been studied in the past. Accordingly, it became evident that the external magnetic field disfavors the perturbations' growth, suppressing the corresponding rate by an amount proportional to its strength. However, the spatial isotropy of the FRW universe is not compatible with the presence of large-scale magnetic fields. Therefore, in this paper we use the general-relativistic version of the (linearized) perturbed magnetohydrodynamic equations with and without resistivity, to discuss a generalized Jeans criterion and the potential formation of density condensations within a class of homogeneous and anisotropically expanding, self-gravitating, magnetized fluids in curved space-time. We find that, for a wide variety of anisotropic cosmological models, gravitomagnetic instabilities can lead to subhorizontal, magnetized condensations. In the nonresistive case, the power spectrum of the unstable cosmological perturbations suggests that most of the power is concentrated on large scales (small k), very close to the horizon. On the other hand, in a resistive medium, the critical wave-numbers so obtained, exhibit a delicate dependence on resistivity, resulting in the reduction of the corresponding Jeans lengths to smaller scales (well bellow the horizon) than the nonresistive ones, while increasing the range of cosmological models which admit such an instability.

  12. Microstructural analysis of Iberian expanded clay aggregates.

    PubMed

    Bogas, J Alexandre; Mauricio, António; Pereira, M F C

    2012-10-01

    This article presents a detailed study of the microstructure of Iberian expanded clay lightweight aggregates (LWA). Other than more commonly used mercury porosimetry (MP) and water absorption methods, the experimental study involves optical microscopy, scanning electron microscopy (SEM), and microtomography (μ-CT). Pore connectivity and how it is deployed are shown to some degree, and the pore size spectrum is estimated. LWA are in general characterized by a dense outer shell up to 200 μm thick, encasing an inner cellular structure of 10-100 times bigger pore size. Aggregate pore sizes may span from some hundreds of nanometers up to over 1 mm, though the range of 1-25 μm is more typical. A noteworthy fraction of these pores is closed, and they are mainly up to 1 μm. It is also shown that macropore spatial arrangement is affected by the manufacturing process. A step forward is given to understanding how the outer shell and the inner pore network influence the mechanical and physical LWA properties, particularly the density and water absorption. The joint consideration of μ-CT and SEM seems to be the most appropriate methodology to study LWA microstructure. MP analysis is likely to distort LWA pore spectrum assessment. PMID:23031601

  13. Tachyonic resonance preheating in an expanding universe

    NASA Astrophysics Data System (ADS)

    Abolhasani, Ali Akbar; Firouzjahi, Hassan; Sheikh-Jabbari, M. M.

    2010-02-01

    In this paper the tachyonic resonance preheating generated from the bosonic trilinear ϕχ2 interactions in an expanding universe is studied. In λϕ4/4 inflationary model the trilinear interaction, in contrast to the four-legs ϕ2χ2, breaks the conformal symmetry explicitly and the resonant source term becomes nonperiodic, making the Floquet theorem inapplicable. We find that the occupation number of the produced χ particles has a nonlinear exponential growth with exponent ˜x3/2, where x is the conformal time. This should be contrasted with preheating from a periodic resonant source arising, for example, from the four-legs ϕ2χ2 interaction, where the occupation number has a linear exponential growth. We present an analytic method to compute the interference term coming from phases accumulated in nontachyonic scattering regions and show that the effects of the interference term cause ripples on x3/2 curve, a result which is confirmed by numerical analysis. Studying the effects of backreaction of the χ particles, we show that tachyonic resonance preheating in our model can last long enough to transfer most of the energy from the background inflation field ϕ, providing an efficient model for preheating in the chaotic inflation models.

  14. The expanding fireball of Nova Delphini 2013.

    PubMed

    Schaefer, G H; ten Brummelaar, T; Gies, D R; Farrington, C D; Kloppenborg, B; Chesneau, O; Monnier, J D; Ridgway, S T; Scott, N; Tallon-Bosc, I; McAlister, H A; Boyajian, T; Maestro, V; Mourard, D; Meilland, A; Nardetto, N; Stee, P; Sturmann, J; Vargas, N; Baron, F; Ireland, M; Baines, E K; Che, X; Jones, J; Richardson, N D; Roettenbacher, R M; Sturmann, L; Turner, N H; Tuthill, P; van Belle, G; von Braun, K; Zavala, R T; Banerjee, D P K; Ashok, N M; Joshi, V; Becker, J; Muirhead, P S

    2014-11-13

    A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common-envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 ± 0.59 kiloparsecs from the Sun. PMID:25363778

  15. Homogeneous cosmology with aggressively expanding civilizations

    NASA Astrophysics Data System (ADS)

    Olson, S. Jay

    2015-11-01

    In the context of a homogeneous Universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the Universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions spanning several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the Universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available pressureless matter into radiation. We conclude that the existence of life, if certain advanced technologies are practical, could have a significant influence on the future large-scale evolution of the Universe.

  16. Branching instability in expanding bacterial colonies

    PubMed Central

    Giverso, Chiara; Verani, Marco; Ciarletta, Pasquale

    2015-01-01

    Self-organization in developing living organisms relies on the capability of cells to duplicate and perform a collective motion inside the surrounding environment. Chemical and mechanical interactions coordinate such a cooperative behaviour, driving the dynamical evolution of the macroscopic system. In this work, we perform an analytical and computational analysis to study pattern formation during the spreading of an initially circular bacterial colony on a Petri dish. The continuous mathematical model addresses the growth and the chemotactic migration of the living monolayer, together with the diffusion and consumption of nutrients in the agar. The governing equations contain four dimensionless parameters, accounting for the interplay among the chemotactic response, the bacteria–substrate interaction and the experimental geometry. The spreading colony is found to be always linearly unstable to perturbations of the interface, whereas branching instability arises in finite-element numerical simulations. The typical length scales of such fingers, which align in the radial direction and later undergo further branching, are controlled by the size parameters of the problem, whereas the emergence of branching is favoured if the diffusion is dominant on the chemotaxis. The model is able to predict the experimental morphologies, confirming that compact (resp. branched) patterns arise for fast (resp. slow) expanding colonies. Such results, while providing new insights into pattern selection in bacterial colonies, may finally have important applications for designing controlled patterns. PMID:25652464

  17. Gene family matters: expanding the HGNC resource

    PubMed Central

    2012-01-01

    The HUGO Gene Nomenclature Committee (HGNC) assigns approved gene symbols to human loci. There are currently over 33,000 approved gene symbols, the majority of which represent protein-coding genes, but we also name other locus types such as non-coding RNAs, pseudogenes and phenotypic loci. Where relevant, the HGNC organise these genes into gene families and groups. The HGNC website http://www.genenames.org/ is an online repository of HGNC-approved gene nomenclature and associated resources for human genes, and includes links to genomic, proteomic and phenotypic information. In addition to this, we also have dedicated gene family web pages and are currently expanding and generating more of these pages using data curated by the HGNC and from information derived from external resources that focus on particular gene families. Here, we review our current online resources with a particular focus on our gene family data, using it to highlight our new Gene Symbol Report and gene family data downloads. PMID:23245209

  18. Transparency parameters from relativistically expanding outflows

    SciTech Connect

    Bégué, D.; Iyyani, S.

    2014-09-01

    In many gamma-ray bursts a distinct blackbody spectral component is present, which is attributed to the emission from the photosphere of a relativistically expanding plasma. The properties of this component (temperature and flux) can be linked to the properties of the outflow and have been presented in the case where there is no sub-photospheric dissipation and the photosphere is in coasting phase. First, we present the derivation of the properties of the outflow for finite winds, including when the photosphere is in the accelerating phase. Second, we study the effect of localized sub-photospheric dissipation on the estimation of the parameters. Finally, we apply our results to GRB 090902B. We find that during the first epoch of this burst the photosphere is most likely to be in the accelerating phase, leading to smaller values of the Lorentz factor than the ones previously estimated. For the second epoch, we find that the photosphere is likely to be in the coasting phase.

  19. Expanding the conceptual toolkit of organ gifting.

    PubMed

    M Shaw, Rhonda

    2015-07-01

    In jurisdictions where the sale of body tissue and organs is illegal, organ transplantation is often spoken of as a gift of life. In the social sciences and bioethics this concept has been subject to critique over the course of the last two decades for failing to reflect the complexities of organ and tissue exchange. I suggest that a new ethical model of organ donation and transplantation is needed to capture the range of experiences in this domain. The proposed model is both analytical and empirically oriented, and draws on research findings linking a series of qualitative sociological studies undertaken in New Zealand between 2007 and 2013. The studies were based on document analysis, field notes and 127 semi-structured in-depth interviews with people from different cultural and constituent groups directly involved in organ transfer processes. The aim of the article is to contribute to sociological knowledge about organ exchange and to expand the conceptual toolkit of organ donation to include the unconditional gift, the gift relation, gift exchange, body project, and body work. The rationale for the proposed model is to provide an explanatory framework for organ donors and transplant recipients and to assist the development of ethical guidelines and health policy discourse. PMID:25728628

  20. Gene family matters: expanding the HGNC resource.

    PubMed

    Daugherty, Louise C; Seal, Ruth L; Wright, Mathew W; Bruford, Elspeth A

    2012-01-01

    The HUGO Gene Nomenclature Committee (HGNC) assigns approved gene symbols to human loci. There are currently over 33,000 approved gene symbols, the majority of which represent protein-coding genes, but we also name other locus types such as non-coding RNAs, pseudogenes and phenotypic loci. Where relevant, the HGNC organise these genes into gene families and groups. The HGNC website http://www.genenames.org/ is an online repository of HGNC-approved gene nomenclature and associated resources for human genes, and includes links to genomic, proteomic and phenotypic information. In addition to this, we also have dedicated gene family web pages and are currently expanding and generating more of these pages using data curated by the HGNC and from information derived from external resources that focus on particular gene families. Here, we review our current online resources with a particular focus on our gene family data, using it to highlight our new Gene Symbol Report and gene family data downloads. PMID:23245209

  1. Expanding the role of internal facility assessments

    SciTech Connect

    Kolpa, R.L.; Levenson, J.B.; Weaver, M.A.

    1996-05-01

    The US Air Force (USAF) Environmental Compliance Assessment and Management Program (ECAMP) is an effective and comprehensive system to evaluate environmental compliance at individual USAF installations. The ECAMP assessment is typically performed by a team of experts from the installation`s Major Command (MAJCOM) Headquarters, and is often augmented with technical contractor support. As directed by Air Force policy, an external ECAMP assessment is required at a minimum of every three years for each installation. In the intervening years, each installation is required to perform an internal ECAMP assessment, with its own personnel and resources. Even though team composition differs, the internal and external ECAMP assessments are likely to be very similar in scope, objectives, and deliverables. For over nine years, Argonne National Laboratory (ANL) has supported several Air Force MAJCOMs in performing their external ECAMP assessments. More recently, ANL has also had the opportunity to provide technical support and training at individual installations during their preparation and conduct of internal ECAMP assessments. From that experience, the authors have learned that the quality and value of the internal assessment is enhanced by making it a vehicle for training, planning, and interaction among organizations. Various strategies and techniques have been successfully employed to derive maximum benefit and insight from the internal assessment process. Experiences that involve expanding the scope and objectives of internal assessments to meet specific goals are presented. The expansion of scope and objectives include preassessment training, planning, and evaluator interactions as part of the overall internal assessment process.

  2. Amorphous microcellular polytetrafluoroethylene foam film

    NASA Astrophysics Data System (ADS)

    Tang, Chongzheng

    1991-11-01

    We report herein the preparation of novel low-density ultramicrocellular fluorocarbon foams and their application. These fluorocarbon foams are of interest for the biochemistry arena in numerous applications including foodstuff, pharmacy, wine making, beer brewery, fermentation medical laboratory, and other processing factories. All of those require good quality processing programs in which, after eliminating bacterium and virus, compressed air is needed. Ordinarily, compressed air contains bacterium and virus, its size is 0.01 - 2 micrometers fluorocarbon foam films. Having average porous diameter 0.04 - 0.1 micrometers , these are stable to high temperature (280 degree(s)C) and chemical environments, and generally have good engineering and mechanical properties (e.g., low coefficient of thermal expansion, high modulus, and good dimensional stability). Our new process for preparing low density fluorocarbon foams provides materials with unique properties. As such, they offer the possibility for being superior to earlier materials for a number of the filter applications mentioned.

  3. Spherical Accretion in a Uniformly Expanding Universe

    NASA Astrophysics Data System (ADS)

    Colpi, Monica; Shapiro, Stuart L.; Wasserman, Ira

    1996-10-01

    We consider spherically symmetric accretion of material from an initially homogeneous, uniformly expanding medium onto a Newtonian point mass M. The gas is assumed to evolve adiabatically with a constant adiabatic index F, which we vary over the range Γ ɛ [1, 5/3]. We use a one-dimensional Lagrangian code to follow the spherical infall of material as a function of time. Outflowing shells gravitationally bound to the point mass fall back, giving rise to a inflow rate that, after a rapid rise, declines as a power law in time. If there were no outflow initially, Bondi accretion would result, with a characteristic accretion time-scale ta,0. For gas initially expanding at a uniform rate, with a radial velocity U = R/t0 at radius R, the behavior of the flow at all subsequent times is determined by ta,0/t0. If ta,0/t0 ≫ 1, the gas has no time to respond to pressure forces, so the fluid motion is nearly collisionless. In this case, only loosely bound shells are influenced by pressure gradients and are pushed outward. The late-time evolution of the mass accretion rate Mdot is close to the result for pure dust, and we develop a semianalytic model that accurately accounts for the small effect of pressure gradients in this limit. In the opposite regime, ta,0/t0 ≪ 1, pressure forces significantly affect the motion of the gas. At sufficiently early times, t ≤ ttr, the flow evolved along a sequence of quasi-stationary, Bondi-like states, with a time-dependent Mdot determined by the slowly varying gas density at large distances. However, at later times, t ≥ ttr, the fluid flow enters a dustllke regime; ttr is the time when the instantaneous Bondi accretion radius reaches the marginally bound radius. The transition time ttr depends sensitively on ta,0/t0 for a given Γ and can greatly exceed t0. We show that there exists a critical value Γ = 11/9, below which the transition from fluid to ballistic motion disappears. As one application of our calculations, we consider the

  4. Equations of motion in an Expanding Universe

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei M.; Petrov, Alexander N.

    2015-06-01

    We make use of an effective field-theoretical approach to derive post-Newtonian equations of motion of hydrodynamical inhomogeneities in cosmology. The matter Lagrangian for the perturbed cosmological model includes dark matter, dark energy, and ordinary baryonic matter. The Lagrangian is expanded in an asymptotic Taylor series around a Friedmann-Lemaître-Robertson-Walker background. The small parameter of the decomposition is the magnitude of the metric tensor perturbation. Each term of the expansion series is gauge-invariant and all of them together form a basis for the successive post-Newtonian approximations around the background metric. The approximation scheme is covariant and the asymptotic nature of the Lagrangian decomposition does not require the post-Newtonian perturbations to be small though computationally it works the most effectively when the perturbed metric is close enough to the background metric. Temporal evolution of the background metric is governed by dark matter and dark energy and we associate the large-scale inhomogeneities of matter as those generated by the primordial cosmological perturbations in these two components with δρ/ρ ≤ 1. The small scale inhomogeneities are generated by the baryonic matter which is considered as a bare perturbation of the background gravitational field, dark matter and energy. Mathematically, the large scale structure inhomogeneities are given by the homogeneous solution of the post-Newtonian equations while the small scale inhomogeneities are described by a particular solution of these equations with the stress-energy tensor of the baryonic matter that admits δρ/ρ ≫ 1. We explicitly work out the field equations of the first post-Newtonian approximation in cosmology and derive the post-Newtonian equations of motion of the large and small scale inhomogeneities which generalize the covariant law of conservation of stress-energy-momentum tensor of matter in asymptotically-flat spacetime.

  5. PROFAM expands Mexican family planning clinics.

    PubMed

    1983-01-01

    Mexico's private, nonprofit social marketing company, known as PROFAM, intends to expand its family planning clinics to marginal urban areas. The clinics are part of PROFAM's push to diversify social marketing outlets for contraceptive products and other birth control methods. PROFAM expects to establish 3 new clinics, possibly including a pregnancy test laboratory, a small 1-doctor clinic, and a large clinic housing an operating room. 1 clinic will be located outside the Mexico City area, the program's traditional boundaries. The company currently runs 2 small clinics and a pregnancy testing laboratory in Ciudad Netzahualcoyti, a community of 3.5 million on Mexico City's outskirts. PROFAM recently obtaine d government approval to sell condoms in food stores, which should increase distribtuion and sales. Currently, the company sells over 1 million high quality, lubricated condoms each month, accounting for over half of the Mexican market. Distribution covers 85% of the country's drugstore. Program setbacks occurred in 1981, when the Mexican government cancelled PROFAM's sales permits for all contraceptive products except condoms. Cancelled products included an oral contraceptive and 3 vaginal spermicides. These 4 products had provided nearly 100,000 couple years of protection in 1979 and an estimated 120,000 CYP 1980. During 1979 and 1980, condoms provided about 27,000 and 60,000 CYP, respectively. PROFAM had relied heavily on the pill and spermicides because its early studies showed condoms had a negative image in Mexico, due largely to the product's association with extramarital affairs. To counter this, PROFAM launched a widespread, free product sampling program in 1979, along with a continuing educational and advertising drive. Subsequent consumer surveys revealed a marked increase in product acceptance, with PROFAM's condom becoming the most widely known brand available in Mexico. PMID:12267250

  6. Celestial dynamics and astrometry in expanding universe

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei

    2012-08-01

    Post - Newtonian theory of motion of celestial bodies and propagation of light was instrumental in conducting the critical experimental tests of general relativity and in building the astronomical ephemerides of celestial bodies in the solar system with an unparalleled precision. The cornerstone of the theory is the postulate that the solar system is gravitationally isolated from the rest of the universe and the background spacetime is asymptotically flat. The present talk abolishes this postulate and lays down the principles of celestial dynamics of particles and light moving in gravitational field of a localized astronomical system embedded to the expanding universe. We formulate the precise mathematical concept of the Newtonian limit of Einstein ’s field equations in the conformally - flat spacetime and analyse the geodesic equations of motion o f particles and light in this limit. We demonstrate that the equations of motion of particles and light can be reduced to their Newtonian counterparts by doing conformal transformations of time and space coordinates. However, the Newtonian equations for particles and light differ by terms of the first order in the Hubble constant. This leads to the important conclusion that the equations of motion used currently by Space Navigation Centres and Astronomical Observatories for calculating orbits of celestial bodies, are incomplete and missing some terms of cosmological origin. We explicitly identify the missing terms and demonstrate that they bring about a noticeable discrepancy between the observed and calculated astronomical ephemerides. We argue that a number of observed celestial anomalies in the solar system can be explained as caused by the Hubble expansion of the universe.

  7. Celestial ephemerides in an expanding universe

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei M.

    2012-09-01

    The post-Newtonian theory of motion of celestial bodies and propagation of light was instrumental in conducting the critical experimental tests of general relativity and in building the astronomical ephemerides of celestial bodies in the Solar System with unparalleled precision. The cornerstone of the theory is the postulate that the Solar System is gravitationally isolated from the rest of the Universe and the background spacetime is asymptotically flat. The present article extends this theoretical concept and formulates the principles of celestial dynamics of particles and light moving in the gravitational field of a localized astronomical system embedded to the expanding Friedmann-Lemaître-Robertson-Walker universe. We formulate the precise mathematical concept of the Newtonian limit of Einstein’s field equations in the conformally flat Friedmann-Lemaître-Robertson-Walker spacetime and analyze the geodesic motion of massive particles and light in this limit. We prove that by doing conformal spacetime transformations, one can reduce the equations of motion of particles and light to the classical form of the Newtonian theory. However, the time arguments in the equations of motion of particles and light differ from each other in terms being proportional to the Hubble constant H. This leads to the important conclusion that the equations of light propagation used currently by space navigation centers for fitting range and Doppler-tracking observations of celestial bodies are missing some terms of the cosmological origin that are proportional to the Hubble constant H. We also analyze the effect of the cosmological expansion on motion of electrons in atoms. We prove that the Hubble expansion does not affect the atomic frequencies and hence does not affect the atomic time scale used in the creation of astronomical ephemerides. We derive the cosmological correction to the light travel time equation and argue that its measurement opens an exciting opportunity to

  8. Expanding Lookout Capabilities for Architectural Analysis

    NASA Astrophysics Data System (ADS)

    Shick, B.

    SMC/SYSW/ENY's Lookout tool provides a M&S capability for architectural analysis. It models the contributions of ground and space-based assets in several mission threads and scenarios to quantify overall Space Situational Awareness (SSA) capability. Plotting performance results versus costs enables decision makers to identify and evaluate Best Value families of systems and combinations of architectures. Currently, SMC intends to use Lookout to impact the Fiscal Year 2012 budget programming cycle, the National SSA Initial Capabilities Document (ICD) and Architecture definition effort, planning for programs of record, and AFSPC & SMC leadership. Ultimately, Lookout will enable additional space superiority analysis. Previous Lookout work focused on modeling the metric tracking capabilities of the Space Surveillance Network (detecting and tracking) and proposed concepts to close identified collection shortfalls. SMC/SYSW/ENY leveraged some of the lessons learned in developing and implementing the metric tracking models to expand Lookout to develop an initial characterization capability, including non-resolved space object identification (SOI), imaging, and Foreign Instrumentation and Signals (FIS) Intelligence. Characterization collection phenomenologies added in FY08 and FY09 include mechanical tracking and phased array radars, visible telescopes, and signals collection. Lookout enables evaluating the characterization collections for quantity, quality, and timeliness. Capturing the Tasking, Collection, Processing, Exploitation, and Dissemination processes represent one of the biggest challenges in including characterization capabilities in mission thread and scenario-based analysis. The SMC/SYSW/ENY team met with several representatives of the community and held community-wide Technical Interchange Meetings. Based on feedback from these meetings, SMC created an infrastructure for modeling the tasking processes and scales to relate collection quality to intelligence

  9. AstroCom NYC: Expanding the Partnership

    NASA Astrophysics Data System (ADS)

    Paglione, Timothy; Ford, Saavik; Agueros, Marcel A.; Mac Low, Mordecai-Mark; Robbins, Dennis

    2015-01-01

    AstroCom NYC is an undergraduate mentoring program designed to improve urban minority student access to opportunities in astrophysical research by greatly enhancing partnerships between research astronomers in New York City (City University of New York - an MSI, American Museum of Natural History, and Columbia). AstroCom NYC provides centralized, personalized mentoring as well as financial and academic support, to CUNY undergraduates throughout their studies, plus the resources and opportunities to further CUNY faculty research with students. The goal is that students' residency at AMNH helps them build a sense of belonging in the field, and readies and inspires them for graduate study. AstroCom NYC provides a rigorous Methods of Scientific Research course developed specifically to this purpose, a laptop, research and career mentors, outreach activities, scholarships and stipends, Metrocards, and regular assessment for maximum effectiveness. Stipends in part alleviate the burdens at home typical for CUNY students so they may concentrate on their academic success. AMNH serves as the central hub for our faculty and students, who are otherwise dispersed among all five boroughs of the City. For our second cohort, we dramatically improved the application and screening process, implemented a number of tools to evaluate their potential for grad school, and began growing a network of potential hosts for summer internships around NY State and the US. We review these implementations and outcomes, as well as plans for Year 3, when we expect many of our current students to compete for external summer REUs, and after greatly expanding the program reach through a NASA community college initiative.

  10. Infrastructure Requirements for an Expanded Fuel Ethanol Industry

    SciTech Connect

    Reynolds, Robert E.

    2002-01-15

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

  11. Expanding the scope of lamellar keratoplasty.

    PubMed Central

    Rich, L F

    1999-01-01

    PURPOSE: To investigate whether applications of current technology, such as cryolathe and excimer laser, might improve outcomes and increase use of lamellar keratoplasty. METHODS: Six studies were performed, beginning with animals and progressing to human subjects. The first study compared cryolathed with hand-dissected rabbit corneas to ascertain which created a smoother donor interface. The second animal pilot study was done to determine whether thickness of donor cornea resection could be accurately predicted with the cryolathe. A prospective animal trial was then undertaken to compare lamellar keratoplasty outcomes using cryolathed versus hand-dissected tissue. The fourth work extrapolated previous animal findings to lamellar keratoplasty in human disease. Finally, two ongoing studies are described. The first explores the possibility of sutureless lamellar keratoplasty. The second utilizes the excimer laser to dissect the recipient stromal bed. RESULTS: The initial animal pilot study demonstrated a clearer stromal surface in cryolathed versus hand-dissected corneal tissue. The second pilot showed that plano-powered donor tissue could be generated to predetermined thickness. The prospective animal trial revealed that clear grafts of intended thickness could be obtained with cryolathing. Human studies suggested that lamellar keratoplasty using cryolathe-prepared donor tissue may offer superior results to free-hand dissection. Finally, one ongoing study indicates that sutureless lamellar keratoplasty is untenable, and the other shows that clear grafts can be obtained by combining cryolathed donor tissue with recipient photoablation. CONCLUSION: This body of work demonstrates that use of new lamellar keratoplasty technology may offer expanded scope and better outcomes than traditional lamellar keratoplasty techniques. Images FIGURE 1 FIGURE 3 FIGURE 4A FIGURE 4B FIGURE 8A FIGURE 8B FIGURE 9 FIGURE 10 FIGURE 10B FIGURE 11A FIGURE 11B FIGURE 12A FIGURE 12B FIGURE 13

  12. Expanding policy options for educating teenagers.

    PubMed

    Stern, David

    2009-01-01

    David Stern argues that some basic features of the American high school must be modified if it is to serve all students successfully. He notes, for example, that only three-quarters of U.S. high school students graduate four years after beginning ninth grade and that the National Assessment of Educational Progress found no improvement in reading or mathematics for seventeen-year-olds between 1971 and 2004. The nation's system for educating teenagers, says Stern, seems to be stuck, despite the constant efforts of teachers and repeated waves of reform. Citing two widely accepted public purposes of educating teenagers-preparation for civic participation and for economic self-sufficiency-Stern proposes four new strategies to achieve those goals. He draws on empirical evidence suggesting that these are promising directions for research and policy, but acknowledges that existing studies provide only limited guidance. First, he says, schools should continue the current trend toward integrating educational options to provide young people with skills and experiences that pave the way to both college and careers. Second, states and districts should tie education funding not simply to the number of students attending school, but also to what young people learn, whether they graduate, and whether they find jobs or enroll in postsecondary education. Such a move, he argues, would encourage teaching and learning formats that use students' time more effectively. Third, more adults in addition to classroom teachers should be involved in educating teenagers. Other adults acting as academic advisers, learning coaches, student advocates, internship supervisors, mentors, and college counselors could help guide the education of teenagers inside and outside of school and provide some relief for the chronic shortage of teachers. Fourth, schools should expand the options for educating teenagers outside of geographically fixed schools. Combining improved Internet-based curriculum with

  13. [The Expanded Programme on Immunization in 1988].

    PubMed

    Levy-bruhl, D

    1989-12-01

    Only 40-50% of the world's children are correctly vaccinated, and each year about 3.5 million children die or become invalids following illnesses preventable by vaccination. It is hoped that new strategies and simplification of vaccination schedules will permit a rapid increase in vaccination coverage so that the UNICEF goal of vaccination of all the world's children by 1990 will be met. As of June 1987, it was estimated that 45% of children in developing countries excluding China had been vaccinated against tuberculosis, 21% against neonatal tetanus, 30% against measles, 45% against whooping cough, and 44% against polio. Most of the illnesses covered by the Expanded Program of Immunization (EPI) can occur very early in life in developing countries. The World Health Organization recommends that children under 1 year old be considered a target group for vaccination. BCG and an extra polio dose should be administered at birth. The DPT injections and oral polio doses should be administered at 6, 10, and 14 weeks. The measles and, where necessary, yellow fever vaccines should be administered at 9 months. The oral polio dose at birth does not always cause antibody synthesis and is intended to provide temporary protection only. The minimum interval between DPT and polio doses is 4 weeks. There is no maximum interval and no need to restart an interrupted series. Vaccination of mothers against tetanus protects the newborn against neonatal tetanus. Pregnant women should be vaccinated twice at intervals of at least 1 month and with the 2nd dose at least 30 days before delivery. The WHO recommends that the target group for tetanus vaccination be enlarged to include all fertile aged women. In the EPI, all vaccines may be administered simultaneously, with DPT, polio, and BCG before 9 months for children seen for the 1st time. Malnourished children should receive priority in vaccination. Premature infants should be given BCG and a preliminary dose of oral polio vaccine before

  14. In vitro comparison of self-expanding versus balloon-expandable stents in a human ex vivo model.

    PubMed

    Grenacher, Lars; Rohde, Stefan; Gänger, Ellen; Deutsch, Jochen; Kauffmann, Günter W; Richter, Götz M

    2006-01-01

    The objective was to compare the radial strength and expansile precision of self-expanding stents and balloon-expandable stents in a human cadaver bifurcation model. Seven different self-expanding (LUMINEXX, JOSTENT SelfX, JOSTENT SelfX hrf, Sinus-Repo, Sinus SuperFlex, Easy Wallstent, SMART) and four different balloon-expandable stent models (Palmaz, Sinus Stent, SAXX Medium, JOSTENT peripheral), each type 10 stents (total n = 110 stents) were implanted into the common iliac arteries of human cadaver corpses. The maximum stent diameter was 10 mm for all models. After stent implantation, the specimens were filled with silicone caoutchouc. After 24 h, the vascular walls including the stents were removed from the hardened casts. Diameters were taken and the weight of the cast cylinders was measured in air and in purified water to calculate the volume of the bodies (according to Archimedes Law) as a relative but precise degree for the radial strength of the implanted stents. The cylindrical casts of the self-expanding stents showed lower mean diameters (8.2 +/- 1.0 mm) and mean volumes (0.60 +/- 0.14 ml/cm) than in the balloon-expandable stent group (10.1 +/- 0.3 mm and 0.71 +/- 0.04 ml/cm, respectively; p < 0.01). The nominal maximum diameter of 10 mm was not achieved in any of the self-expanding stents, but this was achieved in more than 70% (29/40) of the balloon-expandable stent specimens (p < 0.05). The variation between achieved volumes was significantly larger in self-expanding (range: 0.23-0.78 ml/cm) than in balloon-expandable stents (range: 0.66-0.81 ml/cm; p < 0.05). Self-expanding stents presented considerably lower radial expansion force and lower degree of precision than balloon-expandable stents. PMID:16328696

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

    SciTech Connect

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

    2006-04-15

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

  16. Study and design of beam expander with wide aperture

    NASA Astrophysics Data System (ADS)

    Guo, Ming; Jin, Guangyong; Cai, Jixing; Zhang, Wei; Wei, Zhi

    2014-12-01

    In order to improve the capacity of beam collimation for laser beam expander, it is necessary to design a more reasonable and feasible structure of beam expander system. Laser beam expander is used to compress the laser divergence angle, in order to reduce the energy losing in long distance scanning acquisition system. This paper introduces the working principle and design idea of the laser beam expander, the collimating multiplying power focal length and the collimated magnification formula of expander main, secondary mirror. According to the third-order aberration theory, Considering the spherical aberration, sine difference and divergence angle, the reasonable analysis of optical path, ZEMAX optical design software was used to design large-diameter laser beam expander and analysis and optimize, And given the actual design data and results. Display the maximum optical path difference is +/-0.01λ of the main light ray and each light ray. To combination the rear- group objective lens of Galileo and Kepler beam expander, a large-diameter(1.475m) laser beam expander was designed with 0.2m in the diameter, 1/2m in the relative caliber. In the objective lens System, a high-order aspherical was used to the aberration of extra-axial point. we can see that the image quality is close to the diffraction limit from the curves of wavefront. In addition to improve image quality effectively, the system has the characteristics of simple structure, less costly and less design difficulty to compare with the other beam expanding system. And make the output beam's divergence angle smaller, energy density higher, and the beam quality has been greatly improved. The results show that the beam expander is fully meet the design requirements, the use effect is good. Design and research of laser beam expanding system not only improves the quality of the laser beam in the laser system, but also enlarge the application field of laser technology in photoelectric system.

  17. Challenging the Expanding Environment Model of Teaching Elementary Social Studies.

    ERIC Educational Resources Information Center

    Palmer, Jesse

    1989-01-01

    Looks at criticism of the Expanding Environments Model in the elementary school social studies curriculum. Cites recent reports that recommend a history-centered elementary curriculum. States that teaching methods may be the cause of historical, civic, and geographic illiteracy rather than the Expanding Environments Model. (LS)

  18. New York: Expanding Time, Increasing Opportunities for Achievement

    ERIC Educational Resources Information Center

    Miller, Tiffany D.

    2014-01-01

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

  19. Still Not Equal: Expanding Educational Opportunity in Society

    ERIC Educational Resources Information Center

    Brown, M. Christopher, II, Ed.

    2007-01-01

    "Still Not Equal: Expanding Educational Opportunity in Society" addresses the successes and failures of "Brown v. Board of Education" and the Civil Rights Act of 1964, as well as the continuing challenge of expanding educational opportunity in the United States and across the Black diaspora. The educational, political, and social influence…

  20. Hyperdispersion Grating Arrangements for Compact Pulse Compressors and Expanders

    SciTech Connect

    Fittinghoff, D N; Molander, W A; Barty, C J

    2004-04-20

    A novel, but general, arrangement of parallel sets of gratings is presented that can effectively increase the dispersion of pulse compressors and expanders by over an order of magnitude. These arrangements will dramatically reduce the footprint of the pulse compressors and expanders used in CPA.

  1. Supporting Student Success: The Promise of Expanded Learning Opportunities

    ERIC Educational Resources Information Center

    NGA Center for Best Practices, 2010

    2010-01-01

    Expanded learning opportunities (ELOs) support state education goals by providing safe, structured learning environments for students outside the regular school day. ELOs include after-school and summer learning programs, as well as before-school, evening, and weekend programs. Although research demonstrates that high-quality expanded learning…

  2. Expanding the Horizons of Quantitative Remote Sensing

    NASA Astrophysics Data System (ADS)

    Christensen, P. R.

    2011-12-01

    and deconvolved with a similarly degraded and reduced spectral library, whose endmember selection was informed by the hyperspectral results. Using these carefully chosen endmembers, the deconvolved spectra provide results that are similar to the hyperspectral analysis in many, but not all cases; future work is needed to understand exactly why and when. Analysis of high-spectral-resolution data reveals that the subtle spectral variations present in the multi-spectral data represent true variations in surface composition. Nine distinct compositional units can be identified, with subtle composition variations within these units that are confirmed by analysis of spectra of collected samples and field inspection. This compositional mapping is accurate enough to confidently map the details of the highly complex, structurally rotated and thrusted terrain of the Granite Wash Mtns, Arizona. This work illustrates that even a limited amount of high spectral and spatial resolution data provide extremely powerful tools to extend the analysis of the satellite multi-spectral data, significantly increasing the accuracy of, and confidence in, the use of these data for quantitative compositional mapping. Until hyperspectral remote sensing systems become available, these approaches provide a means to meaningfully expand the utility and use of existing multi-spectral data.

  3. The helical screw expander evaluation project. [for geothermal wells

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.

    1977-01-01

    A positive-displacement helical-screw expander of the Lysholm type has been adapted for geothermal service and successfully demonstrated in a 50 kW prototype power system. Evaluation of the expander by tests of a new model in a 1 MW power system under wellhead conditions in selected liquid-dominated geothermal fields is proposed. The objectives are to determine the performance characteristics of the expander and power system over a broad range of operating conditions and also to examine the concept of wellhead power plants. Throttling and fractionation of the fluids from the test wells is planned to simulate a wide range of wellhead pressures and steam fractions. Variation in the expander exhaust pressure is also planned. The investigation will include expander efficiency, corrosion, erosion, scale formation and control, and endurance testing. Interaction studies with the wells and an electric grid are also proposed.

  4. Characteristics and Young's Modulus of Collagen Fibrils from Expanded Skin Using Anisotropic Controlled Rate Self-Inflating Tissue Expander.

    PubMed

    Manssor, Nur Aini S; Radzi, Zamri; Yahya, Noor Azlin; Mohamad Yusof, Loqman; Hariri, Firdaus; Khairuddin, Nurul Hayah; Abu Kasim, Noor Hayaty; Czernuszka, Jan T

    2016-01-01

    Mechanical properties of expanded skin tissue are different from normal skin, which is dependent mainly on the structural and functional integrity of dermal collagen fibrils. In the present study, mechanical properties and surface topography of both expanded and nonexpanded skin collagen fibrils were evaluated. Anisotropic controlled rate self-inflating tissue expanders were placed beneath the skin of sheep's forelimbs. The tissue expanders gradually increased in height and reached equilibrium in 2 weeks. They were left in situ for another 2 weeks before explantation. Expanded and normal skin samples were surgically harvested from the sheep (n = 5). Young's modulus and surface topography of collagen fibrils were measured using an atomic force microscope. A surface topographic scan showed organized hierarchical structural levels: collagen molecules, fibrils and fibers. No significant difference was detected for the D-banding pattern: 63.5 ± 2.6 nm (normal skin) and 63.7 ± 2.7 nm (expanded skin). Fibrils from expanded tissues consisted of loosely packed collagen fibrils and the width of the fibrils was significantly narrower compared to those from normal skin: 153.9 ± 25.3 and 106.7 ± 28.5 nm, respectively. Young's modulus of the collagen fibrils in the expanded and normal skin was not statistically significant: 46.5 ± 19.4 and 35.2 ± 27.0 MPa, respectively. In conclusion, the anisotropic controlled rate self-inflating tissue expander produced a loosely packed collagen network and the fibrils exhibited similar D-banding characteristics as the control group in a sheep model. However, the fibrils from the expanded skin were significantly narrower. The stiffness of the fibrils from the expanded skin was higher but it was not statistically different. PMID:26836267

  5. Distant Supernovae Indicate Ever-Expanding Universe

    NASA Astrophysics Data System (ADS)

    1998-12-01

    ESO Astronomers Contribute towards Resolution of Cosmic Puzzle Since the discovery of the expansion of the Universe by American astronomer Edwin Hubble in the 1920's, by measurement of galaxy velocities, astronomers have tried to learn how this expansion changes with time. Until now, most scientists have been considering two possibilities: the expansion rate is slowing down and will ultimately either come to a halt - whereafter the Universe would start to contract, or it will continue to expand forever. However, new studies by two independent research teams, based on observations of exploding stars ( supernovae ) by ESO astronomers [1] with astronomical telescopes at the La Silla Observatory as well as those of their colleagues at other institutions, appear to show that the expansion of the Universe is accelerating . The results take the discovery of the cosmological expansion one step further and challenge recent models of the Universe. If the new measurements are indeed correct, they show that the elusive "cosmological constant" , as proposed by Albert Einstein , contributes significantly to the evolution of the Universe. The existence of a non-zero cosmological constant implies that a repulsive force, counter-acting gravity, currently dominates the universal expansion , and consequently leads to an ever-expanding Universe. This new research is being named as the "Breakthrough of the Year" by the renowned US science journal Science in the December 18, 1998, issue. A Press Release is published by the journal on this occasion. "Fundamental Parameters" of the Universe Three fundamental parameters govern all cosmological models based on the theory of General Relativity. They are 1. the current expansion rate as described by Hubble's constant , i.e. the proportionality factor between expansion velocity and distance 2. the average matter density in the Universe, and 3. the amount of "other energy" present in space. From the measured values of these fundamental

  6. Tissue regeneration during tissue expansion and choosing an expander

    PubMed Central

    Agrawal, K.; Agrawal, S.

    2012-01-01

    This paper reviews the various aspects of tissue regeneration during the process of tissue expansion. “Creep” and mechanical and biological “stretch” are responsible for expansion. During expansion, the epidermis thickens, the dermis thins out, vascularity improves, significant angiogenesis occurs, hair telogen phase becomes shorter and the peripheral nerves, vessels and muscle fibres lengthen. Expansion is associated with molecular changes in the tissue. Almost all these biological changes are reversible after the removal of the expander.This study is also aimed at reviewing the difficulty in deciding the volume and dimension of the expander for a defect. Basic mathematical formulae and the computer programmes for calculating the dimension of tissue expanders, although available in the literature, are not popular. A user-friendly computer programme based on the easily available Microsoft Excel spread sheet has been introduced. When we feed the area of defect and base dimension of the donor area or tissue expander, this programme calculates the volume and height of the expander. The shape of the expander is decided clinically based on the availability of the donor area and the designing of the future tissue movement. Today, tissue expansion is better understood biologically and mechanically. Clinical judgement remains indispensable in choosing the size and shape of the tissue expander. PMID:22754146

  7. Electromagnetic scattering by harmonically expanding surfaces and related complex resonances

    NASA Astrophysics Data System (ADS)

    Censor, D.

    1985-02-01

    A relativistically exact iterative method is developed for scattering of electromagnetic waves by expanding surfaces. In particular, the problems of the expanding cylinder and sphere are computed. It is shown that expanding scatterers respond to harmonic excitation by radiating nonharmonic waves. These waves involve complex frequencies, which are computed here. The method involves secular terms in t; therefore its validity for harmonic excitation is limited to early times. However, in the case of impulse excitation and transient scattering this problem is automatically resolved by the fact that the signal is exponentially decaying and the secular terms have no large-time effect.

  8. Cryogenic expander/recompressor control for maximizing liquids production

    SciTech Connect

    Batson, B.W.

    1999-07-01

    In this paper a new method is described to control cryogenic expander/recompressor units to improve natural gas liquid production. This method employs the antisurge valve associated with the recompressor to load the expander without increasing the flow through it. This method can be applied to continuous control or speed limiting control. A crucial aspect of this method of control is the interaction of the two control loops--expander inlet nozzle control and antisurge valve control. These loops are highly coupled, requiring loop decoupling to assure stable control.

  9. Complementary and Alternative Medicine (CAM): Expanding Horizons of Health Care

    MedlinePlus

    ... Past Issues Special Section CAM Expanding Horizons of Health Care Past Issues / Winter 2009 Table of Contents For ... and why it is important to tell your health care providers about your use of CAM. We hope ...

  10. 21 CFR 884.4250 - Expandable cervical dilator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Classification. Class III (premarket approval). (c) Date PMA or notice of completion of a PDP is required. A PMA... other expandable cervical dilator shall have an approved PMA or a declared completed PDP in...

  11. 21 CFR 884.4250 - Expandable cervical dilator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) Classification. Class III (premarket approval). (c) Date PMA or notice of completion of a PDP is required. A PMA... other expandable cervical dilator shall have an approved PMA or a declared completed PDP in...

  12. Nitrogen expander cycles for large capacity liquefaction of natural gas

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  13. Nitrogen expander cycles for large capacity liquefaction of natural gas

    SciTech Connect

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

    2014-01-29

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

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

    SciTech Connect

    1999-02-01

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

  15. The Rate of Expanded Inner Speech During Spontaneous Sentence Productions.

    PubMed

    Netsell, Ronald; Kleinsasser, Steven; Daniel, Todd

    2016-10-01

    The rate of expanded inner speech and speech aloud was compared in 20 typical adults (3 males, 17 females; M age = 24 years, SD = 4). Participants generated and timed spontaneous sentences with both expanded inner speech and speech aloud following the instruction to say "the first thing that comes to mind." The rate of expanded inner speech was slightly, but significantly, faster than the rate of speech aloud. The findings supported the hypothesis that expanded inner speech was faster than speech aloud because of the time required to move the articulators in the latter. Physical measures of speaking rate are needed to validate self-timed measures. Limitations of the study and directions for research are discussed. PMID:27562695

  16. Shifted genus expanded W ∞ algebra and shifted Hurwitz numbers

    NASA Astrophysics Data System (ADS)

    Zheng, Quan

    2016-05-01

    We construct the shifted genus expanded W ∞ algebra, which is isomorphic to the central subalgebra A ∞ of infinite symmetric group algebra and to the shifted Schur symmetrical function algebra Λ* defined by Okounkov and Olshanskii. As an application, we get some differential equations for the generating functions of the shifted Hurwitz numbers; thus, we can express the generating functions in terms of the shifted genus expanded cut-and-join operators.

  17. A Computational Study of Expanded Heterocyclic Nucleosides in DNA

    PubMed Central

    O'Daniel, Peter I.; Jefferson, Malcolm; Wiest, Olaf; Seley-Radtke, Katherine L.

    2008-01-01

    The first molecular dynamics study of a series of heterospacer-expanded tricyclic bases in DNA using modified force field parameters in AMBER is detailed. The expanded purine nucleoside monomers have been designed to probe the effects of a heteroaromatic spacer ring on the structure, function, and dynamics of the DNA helix. The heterobase scaffold has been expanded with a furan, pyrrole, or thiophene spacer ring. This structural modification increases the polarizability of the bases and provides an additional hydrogen bond donor with the amine hydrogen of the pyrrole ring or hydrogen bond acceptor with the furan or thiophene ring free electron pairs. The polarizability of the expanded bases were determined by AM1 calculations and the results of the MD simulations of 20-mers predict that the modified curvature of the expanded base leads to a much larger major groove, while the effect on the minor groove is negligible. Overall, the structure resembles A-DNA. MD simulations of 10-mers suggest that the balance between base pairing vs. base stacking and intercalation can be shifted towards the latter due to the increased surface area and polariz-ability of the expanded bases. PMID:18808194

  18. Role of self expandable stents in management of colorectal cancers

    PubMed Central

    Cetinkaya, Erdinc; Dogrul, Ahmet Bulent; Tirnaksiz, Mehmet Bulent

    2016-01-01

    Acute malignant colorectal obstruction is a complication of colorectal cancer that can occur in 7%-29% of patients. Self-expanding metallic stent placement for malignant colorectal obstruction has gained popularity as a safe and effective procedure for relieving obstruction. This technique can be used in the palliation of malignant colorectal obstruction, as a bridge to elective surgery for resectable colorectal cancers, palliation of extracolonic malignant obstruction, and for nonmalignant etiologies such as anastomotic strictures, Crohn’s disease, radiation therapy, and diverticular diseases. Self-expanding metallic stent has its own advantages and disadvantages over the surgery in these indications. During the insertion of the self-expanding metallic stent, and in the follow-up, short term and long term morbidities should be kept in mind. The most important complications of the stents are perforation, stent obstruction, stent migration, and bleeding. Additionally, given the high risk of perforation, if a patient is treated or being considered fortreatmentwith antiangiogenic agents such as bevacizumab, it is not recommended to use self-expanding metallic stent as a palliative treatment for obstruction. Therefore, there is a need for careful clinical evaluation for each patient who is a candidate for this procedure. The purpose of this review was to evaluate self-expanding metallic stent in the management of the obstruction of the colon due to the colorectal and extracolonic obstruction. PMID:26798442

  19. Testing the Expanding-Contracting Polar Cap Paradigm

    NASA Astrophysics Data System (ADS)

    Sotirelis, T.; Keller, M. R.; Smith, D.; Barnes, R. J.; Talaat, E. R.; Newell, P. T.; Baker, J. B.

    2013-12-01

    The expanding-contracting polar cap (ECPC) paradigm is tested. Under the ECPC paradigm ionospheric convection in the polar cap is driven by the combined effects of dayside merging and nightside reconnection, as opposed to being mapped down from higher altitudes. The ECPC paradigm is tested by separately examining convection when the polar cap is expanding versus contracting. The open magnetic flux is estimated from SuperDARN observations of the convection reversal boundary (CRB) made simultaneously at different local times. (Sotirelis et al. [2005] established the CRB as a proxy for the Open-Closed Boundary (OCB).) The correlation of the ionospheric convection potential with solar wind/IMF driving is indeed found to depend on whether the polar cap is expanding or contracting. Specifically, when the polar cap is expanding, ionospheric convection correlates best (0.86) with the most recent 10 minutes of solar wind/IMF driving (versus 0.57 for contracting). When contracting, convection correlates best (0.87) with 90-minute averages of solar wind/IMF driving (versus 0.51 for expanding). This is consistent with ECPC expectations.

  20. Numerical simulation of a twin screw expander for performance prediction

    NASA Astrophysics Data System (ADS)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

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

  1. The effect of code expanding optimizations on instruction cache design

    NASA Technical Reports Server (NTRS)

    Chen, William Y.; Chang, Pohua P.; Conte, Thomas M.; Hwu, Wen-Mei W.

    1991-01-01

    It is shown that code expanding optimizations have strong and non-intuitive implications on instruction cache design. Three types of code expanding optimizations are studied: instruction placement, function inline expansion, and superscalar optimizations. Overall, instruction placement reduces the miss ratio of small caches. Function inline expansion improves the performance for small cache sizes, but degrades the performance of medium caches. Superscalar optimizations increases the cache size required for a given miss ratio. On the other hand, they also increase the sequentiality of instruction access so that a simple load-forward scheme effectively cancels the negative effects. Overall, it is shown that with load forwarding, the three types of code expanding optimizations jointly improve the performance of small caches and have little effect on large caches.

  2. Repair of a postappendectomy massive ventral hernia using tissue expanders

    PubMed Central

    Celebi, Fatih; Erozgen, Fazilet; Ergun, Selma Sonmez; Akaydin, Murat; Kaplan, Rafet

    2013-01-01

    Reconstruction of large abdominal wall defects is a challenging problem. Various reconstructive techniques have been described in the surgical literature each with its advantages and disadvantages. In this report we describe our experience in treating a patient with large abdominal wall defect by staged abdominal wall reconstruction utilizing prosthetic mesh in conjunction with tissue expanders. A 41-year-old male presented with abdominal pain. Exploratory laparotomy showed perforated appendicitis with intraabdominal abscess of 1,500 mL. Postoperatively, he developed intraperitoneal sepsis. To prevent abdominal compartment syndrome, he was reoperated and left with "open abdomen". After several open abdomen lavages, his abdominal wall defect was allowed to granulate. After epithelization of the defect, the abdominal wall was reconstructed using prosthetic mesh and tissue expanders. The tissue expansion process was well tolerated. We suggest that the use of tissue expanders provides reliable and well-vascularized soft-tissue coverage in abdominal wall reconstruction. PMID:23323238

  3. Expanded bed adsorption of an alkaline lipase from Pseudomona cepacia.

    PubMed

    da Silva Padilha, Giovana; Curvelo-Santana, José Carlos; Alegre, Ranulfo Monte; Tambourgi, Elias Basile

    2009-02-15

    An extracellular lipase was isolated from Pseudomona cepacia by expanded bed adsorption on an Amberlite 410 ion-exchange resin. Enzyme characterization and hydrodynamic study of a chromatography column were done. Enzyme purification was done at three condition of expanded bed height (H): at one and half (6cm), at two (8cm) and at three (12cm) times the fixed bed height (H(0)=4cm). The results showed that the experimental data was fitted to the Richardson and Zaki equation, and the comparison between the experimental and calculated terminal velocities showed low relative error. In enzyme purification for better condition, a purification factor of about 80 times was found at 6cm of expanded bed height, or 1.5 times of expansion degree. Purified lipase had an optimal pH and a temperature of 8 and 37 degrees C, respectively. PMID:19162572

  4. Computation of surface tensions using expanded ensemble simulations.

    PubMed

    de Miguel, Enrique

    2008-04-17

    A method for the direct simulation of the surface tension is examined. The technique is based on the thermodynamic route to the interfacial tension and makes use of the expanded ensemble simulation method for the calculation of the free energy difference between two inhomogeneous systems with the same number of particles, temperature, and volume, but different interfacial area. The method is completely general and suitable for systems with either continuous or discontinuous interactions. The adequacy of the expanded ensemble method is assessed by computing the interfacial tension of the planar vapor-liquid interface of Lennard-Jones, Lennard-Jones dimers, Gay-Berne, and square-well model fluids; in the latter, the interactions are discontinuous and the present method does not exhibit the asymmetry of other related methods, such as the test area. The expanded ensemble simulation results are compared with simulation data obtained from other techniques (mechanical and test area) with overall good agreement. PMID:18358023

  5. [Esophageal Injury Treated with a Covered Expandable Metallic Stent].

    PubMed

    Kamimura, Go; Aoki, Masaya; Nakamura, Yoshihiro; Suenaga, Toyokuni; Sato, Masami

    2016-07-01

    We report a case of iatrogenic esophageal injury treated with a covered expandable metallic stent after thoracoscopic chest drainage. A 70-year-old man who had stricture of the esophagus after endoscopic submucosal dissection underwent balloon dilation. Chest computed tomography revealed esophageal rupture. Initially, continuous intra-esophageal drainage was carried out, however, due to the development of mediastinitis with enlarged abscess around the descending aorta and the left pneumothorax, thoracoscopic chest drainage was performed. Since direct closure was thought to be in appropriate, an intra-esophageal approach was chosen and a covered expandable metallic stent was mounted under fluorography on the next day. After the treatment, the patient was able to eat, and was able to discharge 42 days later. Intra-esophageal covered expandable metallic stent can be an alternative treatment for esophageal rupture. PMID:27365065

  6. An Expanded CAG Repeat in Huntingtin Causes +1 Frameshifting.

    PubMed

    Saffert, Paul; Adamla, Frauke; Schieweck, Rico; Atkins, John F; Ignatova, Zoya

    2016-08-26

    Maintenance of triplet decoding is crucial for the expression of functional protein because deviations either into the -1 or +1 reading frames are often non-functional. We report here that expression of huntingtin (Htt) exon 1 with expanded CAG repeats, implicated in Huntington pathology, undergoes a sporadic +1 frameshift to generate from the CAG repeat a trans-frame AGC repeat-encoded product. This +1 recoding is exclusively detected in pathological Htt variants, i.e. those with expanded repeats with more than 35 consecutive CAG codons. An atypical +1 shift site, UUC C at the 5' end of CAG repeats, which has some resemblance to the influenza A virus shift site, triggers the +1 frameshifting and is enhanced by the increased propensity of the expanded CAG repeats to form a stem-loop structure. The +1 trans-frame-encoded product can directly influence the aggregation of the parental Htt exon 1. PMID:27382061

  7. Corrosion behavior of the expandable tubular in formation water

    NASA Astrophysics Data System (ADS)

    Gao, Shu-jun; Dong, Chao-fang; Fu, An-qing; Xiao, Kui; Li, Xiao-gang

    2015-02-01

    The corrosion behavior of expandable tubular materials was investigated in simulated downhole formation water environments using a series of electrochemical techniques. The corrosion morphologies in the real downhole environment after three months of application were also observed by stereology microscopy and scanning electron microscopy (SEM). The results show that, compared with the unexpanded sample, the area of ferrite increases dramatically after a 7.09% expansion. The expanded material shows a higher corrosion current in the polarization curve and a lower corrosion resistance in the electrochemical impedance spectroscopy (EIS) plot at every studied temperature. The determined critical pitting temperatures (CPT) before and after expansion are 87.5°C and 79.2°C, respectively. SEM observations demonstrate stress corrosion cracks, and CO2 corrosion and H2S corrosion also occur in the downhole environment. Due to additional defects generated during the plastic deformation, the corrosion performance of the expanded tubing deteriorates.

  8. The osmotic tissue expander: a three-year clinical experience.

    PubMed

    Obdeijn, Miryam C; Nicolai, Jean-Philippe A; Werker, Paul M N

    2009-09-01

    Closure of defects after trauma or excision of neoplasms is a basic skill in plastic surgery. Local, regional and distant flaps lead to additional scars. Skin recruitment by serial excision or skin expansion is a less damaging option for defects that must be closed. Advantages of tissue expansion include good colour and texture match. Disadvantages are the need for a second operation, use of an implant with the attendant risk of infection, time needed for inflation of the device, repeat visits to the clinic, and punctures to inflate the expander. To overcome the last disadvantage, an osmotic expander was developed in Germany in 1999 by OSMED GmbH (Ilmenau). PMID:18755643

  9. Uniformly expanding vacuum: A possible interpretation of the dark energy

    NASA Astrophysics Data System (ADS)

    Huang, Peng; Yuan, Fang-Fang

    2016-06-01

    Following the spirit of the equivalence principle, we take a step further to recognize the free fall of the observer as a method to eliminate causes that would lead the perceived vacuum to change its original state. Thus, it is expected that the vacuum should be in a rigid Minkowski state or be uniformly expanding. By carefully investigating the impact on measurement caused by the expansion, we clarify the exact meaning of the uniformly expanding vacuum and find that this proposal may be able to explain the current observations of an accelerating universe.

  10. Preparation and characterization of low-temperature expandable graphite

    SciTech Connect

    Ying Zongrong Lin Xuemei; Qi Yu; Luo Jie

    2008-10-02

    The low-temperature expandable graphite was successfully prepared with perchloric acid, phosphoric acid and KMnO{sub 4} by chemical process. The optimum weight ratio of perchloric acid to phosphoric acid in mixed acid was 1:0.2, and the weight ratio of the mixed acid, KMnO{sub 4} and natural flake graphite was preferably 1.5:0.1:1. The expanded volume can reach 260 mL/g at a relatively low temperature of 300 deg. C. Meanwhile, the prepared samples were characterized by means of Fourier transform infrared, thermogravimetry-differential scanning calorimetry and X-ray diffraction.

  11. A new magnetic expanded graphite for removal of oil leakage.

    PubMed

    Ding, Xiaohui; Wang, Rong; Zhang, Xin; Zhang, Yanzong; Deng, Shihuai; Shen, Fei; Zhang, Xiaohong; Xiao, Hong; Wang, Lilin

    2014-04-15

    Magnetic expanded graphite (MEG) was prepared using the blended calcination method under a nitrogen atmosphere. MEG was characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and vibrating sample magnetization (VSM). Results show that the cobalt ferrite nanoparticles were uniformly and efficiently deposited on expanded graphite (EG). The saturation magnetization reached 55.05 emu g(-1), and the adsorption capacity of MEG under the optimal condition was 35.72 g g(-1) for crude oil. PMID:24559739

  12. Expanded Endoscopic Endonasal Approaches to Skull Base Meningiomas

    PubMed Central

    Prosser, J. Drew; Vender, John R.; Alleyne, Cargill H.; Solares, C. Arturo

    2012-01-01

    Anterior cranial base meningiomas have traditionally been addressed via frontal or frontolateral approaches. However, with the advances in endoscopic endonasal treatment of pituitary lesions, the transphenoidal approach is being expanded to address lesions of the petrous ridge, anterior clinoid, clivus, sella, parasellar region, tuberculum, planum, olfactory groove, and crista galli regions. The expanded endoscopic endonasal approach (EEEA) has the advantage of limiting brain retraction and resultant brain edema, as well as minimizing manipulation of neural structures. Herein, we describe the techniques of transclival, transphenoidal, transplanum, and transcribiform resections of anterior skull base meningiomas. Selected cases are presented. PMID:23730542

  13. The paradox of HIV/AIDS as expanding consciousness.

    PubMed

    Lamendola, F P; Newman, M A

    1994-03-01

    A heuristic approach employing Newman's method for pattern identification was used to examine the theory of health as expanding consciousness in persons with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). Themes derived from the interview of nine gay men portrayed a pattern of alienation during childhood, followed by a breaking away from family, and progressing to cycles of aloneness and searching. Recognition of HIV/AIDS in their lives brought them to a turning point of more meaningful connectedness. This pattern is viewed as expanding consciousness and possibly a phenomenon of cultural evolution. PMID:8203827

  14. Stability of the anisotropically inflating Bianchi type VI expanding solutions

    SciTech Connect

    Kao, W. F.; Lin, Ing-Chen

    2011-03-15

    A special class of the Bianchi type VI expanding solutions was speculated to break the cosmic no-hair theorem that will not approach the late-time de Sitter solution. We will show that an unstable mode always exists when the perturbation of the field equations is applied to the system. In addition to a model-independent perturbation formula, a simplification is also achieved by the introduction of a {delta}R=0 solution good for quadratic models in all Bianchi spaces. The result shows that this special class of anisotropically expanding solutions is unstable.

  15. Self-expandable CoreValve implantation without contrast media.

    PubMed

    Bruschi, Giuseppe; Colombo, Paola; De Marco, Federico; Barosi, Alberto; Mauri, Silvia; Klugmann, Silvio

    2016-09-01

    Transcatheter aortic valve implantation has been designed to treat high-risk surgical patients affected by severe aortic stenosis, many of whom are affected by chronic kidney disease. To perform transcatheter self-expandable valve implantation, multiple contrast injections are required to monitor the procedure, so these patients are at increased risk of acute kidney injury. We described self-expandable transcatheter aortic valve implantation without contrast media in an 80-year-old man affected by severe aortic stenosis and endstage chronic kidney disease. PMID:26068936

  16. Flow injection on-line solid phase extraction coupled with inductively coupled plasma mass spectrometry for determination of (ultra)trace rare earth elements in environmental materials using maleic acid grafted polytetrafluoroethylene fibers as sorbent.

    PubMed

    Wang, Zhao-Hui; Yan, Xiu-Ping; Wang, Zhi-Peng; Zhang, Zheng-Pu; Liu, Li-Wen

    2006-09-01

    A new sorbent, maleic acid grafted polytetrafluoroethylene fiber (MA-PTFE), was prepared and evaluated for on-line solid-phase extraction coupled with inductively coupled plasma mass spectrometry (ICP-MS) for fast, selective, and sensitive determination of (ultra)trace rare earth elements (REEs) in environmental samples. The REEs in aqueous samples at pH = 3.0 were selectively extracted onto a microcolumn packed with the MA-PTFE fiber, and the adsorbed REEs were subsequently eluted on-line with 0.9 mol l(-1) HNO3 for ICP-MS determination. The new sorbent extraction system allows effective preconcentration and separation of the REEs from the major matrix constituents of alkali and alkali earth elements, particularly their separation from barium that produces considerable isobaric interferences of 134Ba16O1H+, 135Ba16O+, 136Ba16O1H+, and 137Ba16O+ on 151Eu+ and 153Eu+. With the use of a sample loading flow rate of 7.4 ml min(-1) for 120 s preconcentration, enhancement factors of 69-97 and detection limits (3s) of 1-20 pg l(-1) were achieved at a sample throughput of 22 samples h(-1). The precision (RSD) for 16 replicate determinations of 50 ng l(-1) of REEs was 0.5-1.1%. The developed method was successfully applied to the determination of (ultra)trace REEs in sediment, soil, and seawater samples. PMID:16814561

  17. Role of low-level impurities and intercalated molecular gases in the {alpha} particle radiolysis of polytetrafluoroethylene examined by static time-of-flight secondary-ion-mass spectrometery

    SciTech Connect

    Fisher, Gregory L.; Szakal, Christopher; Wetteland, Christopher J.; Winograd, Nicholas

    2006-07-15

    The structural degradation of polytetrafluoroethylene (PTFE) upon irradiation with MeV alpha ({alpha}) particles is accompanied by the proliferation of hydrogenated and oxygen-functionalized fluorocarbon species. In this article, we explore the origin of monoxide- and dioxide-functionalized fluorocarbon species that emerge upon {alpha} particle irradiation of PTFE. Samples of neat PTFE were irradiated to {alpha} doses in the range of 10{sup 7}-5x10{sup 10} rad using 5.5 MeV {sup 4}He{sup 2+} ions produced in a tandem accelerator. Static time-of-flight secondary-ion-mass spectrometry (TOF-SIMS), using a 20 keV C{sub 60}{sup +} source, was employed to probe chemical changes as a function of {alpha} particle irradiation. Chemical images and high-resolution mass spectra were collected in both the positive and negative polarities. Residual gas analysis, utilized to monitor the liberation of molecular gases during {alpha} particle irradiation of the PTFE in vacuum, is discussed in relationship to the TOF-SIMS data.

  18. The application of sewage sludge as an expanding agent in the production of lightweight expanded clay aggregate mass.

    PubMed

    Latosińska, J; Zygadło, M

    2011-10-01

    Sewage sludge can be used as an expanding agent in the production of lightweight expanded clay aggregate (LECA) mass. The addition of sewage sludge increases the total porosity and decreases the bulk density of a sinter. The addition of sewage sludge to a raw material used in the production of LECA enabled a decrease in the burning temperature for the maintained operational parameters of a lightweight aggregate. The optimum content of sewage sludge added to a raw material used in LECA production was 5% to 15% of dry mass. The addition of sewage sludge in an amount of 5% and 10% caused an increase in closed porosity. PMID:22329137

  19. Contracting/expanding self-sealing cryogenic tube seals

    NASA Technical Reports Server (NTRS)

    Jia, Lin X. (Inventor)

    1997-01-01

    Contracting/expanding self-sealing cryogenic tube seals are disclosed which use the different properties of thermal contraction and expansion of selected dissimilar materials in accord with certain design criteria to yield self-tightening seals via sloped-surface sealing. The seals of the subject invention are reusable, simple to assemble, adaptable to a wide variety of cryogenic applications.

  20. Expanding Access to Adult Literacy with Online Distance Education.

    ERIC Educational Resources Information Center

    Askov, Eunice N.; Johnston, Jerome; Petty, Leslie I.; Young, Shannon J.

    This monograph examines benefits, challenges, and methods of expanding access to adult literacy with online distance education (ODE). The following are among the topics discussed: (1) reasons for considering ODE (new technologies and delivery systems in education; ODE in higher education, business training, and adult basic education; state-level…

  1. 2010 Impacts: The Expanded Food and Nutrition Education Program (EFNEP)

    ERIC Educational Resources Information Center

    National Institute of Food and Agriculture, 2011

    2011-01-01

    Since 1969, the Expanded Food and Nutrition Education Program (EFNEP) has improved the diets and food-related behaviors of program participants. Each year EFNEP enrolls more than half a million new program participants. In 2010, EFNEP reached 137,814 adults and 463,530 youth directly and nearly 400,000 family members indirectly. This paper…

  2. Study of torque matching of revolving vane compressor and expander

    NASA Astrophysics Data System (ADS)

    Subiantoro, A.; Ooi, K. T.

    2015-08-01

    An investigation was carried out to find the most optimum configuration, particularly the torque matching characteristics, of an integrated Revolving Vane compressor- expander. To carry out the study, a mathematical model of the integrated compressor-expander was developed. An open cycle air refrigeration system was adopted. The controlled parameter was the angle shift between the compressor and the expander. The observed parameters were the peak torque requirement and the bearing load. The results show that when properly matched, the peak torque can be reduced by more than 65% while the bearing loads can be reduced by up to 25%, depending on operating conditions. Unfortunately, the optimum angle shifts for peak torque do not always coincide with those for bearing load. When the pressure and inertial components of the torques are comparable or when the inertial component is dominant, the optimum angle shifts for peak torque and bearing load are around 180° and 330°, respectively. When the pressure component is dominant, the optimum angle shift for peak torque is equal to the angle difference between the pressure peak torques of the compressor and the expander while for bearing load is around 150°.

  3. DEMONSTRATION OF PACKAGING MATERIALS ALTERNATIVES TO EXPANDED POLYSTYRENE

    EPA Science Inventory

    This report represents the second demonstration of cleaner technologies to support the goals of the 33/50 Program under the EPA Cooperative Agreement No. CR-821848. The report presents assessment results of alternative packaging materials which could potentially replace expanded...

  4. Crowd Around: Expanding Your Donor Pool with Crowdfunding

    ERIC Educational Resources Information Center

    Jarrell, Andrea

    2013-01-01

    At most institutions, annual fund-giving is down. Crowdfunding sites allow people with a great idea or worthy cause to bypass traditional funding methods and take their case directly to web-savvy investors and donors. This article describes how higher education institutions are expanding their donor pool through such crowdfunding sites as USEED,…

  5. The Instructional Values of Humanistic Educators: An Expanded, Empirical Analysis.

    ERIC Educational Resources Information Center

    Shapiro, Stewart B.

    1987-01-01

    Expanded a previous factorial study of the writings of 40 humanistic educators by including 89 educators. Revealed two new factors--self-determined evaluation and a spiritual-transpersonal factor--as important principles of humanistic education. Confirmed the original factors, a general humanistic instructional paradigm, democratically induced…

  6. Expanding the Knowledge Base: A Rejoinder to Townsend (1998).

    ERIC Educational Resources Information Center

    Brent, Brian O.

    1998-01-01

    Provides a further examination of nonresidential expanded tax base (ETB) approaches to school finance. Disagrees with Townsend's optimism that more equitable distribution formulas can be found in existing state aid systems, and with Townsend's concern that the specification of distribution formulas will be subject to political manipulation.…

  7. Building an Expanded Learning Time and Opportunities School: Principals' Perspectives

    ERIC Educational Resources Information Center

    Malone, Helen Janc

    2011-01-01

    Expanded learning time and opportunities (ELTO) requires a committed school leader who is willing to partner with community-based organizations in order to provide strong academic and enrichment daily experiences for his or her students. This article examines four such leaders and the diverse approaches they took to implement ELTO in their…

  8. Shifting Expectations: Bringing STEM to Scale through Expanded Learning Systems

    ERIC Educational Resources Information Center

    Donner, Jessica; Wang, Yvonne

    2013-01-01

    Expanded learning opportunities, such as afterschool and summer programs, are particularly well positioned to help address science, technology, engineering, and mathematics (STEM) education crisis. A large percentage of youth participating in afterschool programs are members of groups traditionally underrepresented in STEM fields. Additionally,…

  9. Browsing Your Virtual Library: The Case of Expanding Universe.

    ERIC Educational Resources Information Center

    Daniels, Wayne; Enright, Jeanne; Mackenzie, Scott

    1997-01-01

    Describes "Expanding Universe: a classified search tool for amateur astronomy," a Web site maintained by the Metropolitan Toronto Reference Library which uses a modified form of the Dewey Decimal Classification to organize a large file of astronomy hotlinks. Highlights include structure, HTML coding, design requirements, and future possibilities.…

  10. The Expanded Food and Nutrition Education Program (EFNEP)

    ERIC Educational Resources Information Center

    National Institute of Food and Agriculture, 2010

    2010-01-01

    Obesity, poor health, and limited physical activity are major health concerns. The Expanded Food and Nutrition Education Program (EFNEP) improves the health and well-being of limited resource families and youth. Additionally, EFNEP leads to public savings. Research shows that better health is associated with reduced health care costs, less…

  11. Views of Nonprint Media: A Case for Expanded Literacy.

    ERIC Educational Resources Information Center

    Ruth, Deborah Dashow

    The process of becoming literate today means both visual and verbal literacy. There is no need, however, to choose between print and nonprint media as teaching tools. Today's "new media" serve to expand and accentuate the world of printed words and provide valuable means of learning in and of themselves. Visual literacy implies developing an…

  12. Reflections on Using Blogs to Expand In-Class Discussion

    ERIC Educational Resources Information Center

    Wang, Shiang-Kwei; Hsua, Hui-Yin

    2008-01-01

    Originally, blogs served as personal journaling tools. Recently, blogs have facilitated the formation of online communities and have thus expanded to more extensive uses in education. Little has been learned about using blogs as a collaboration tool in educational contexts. In this article, the authors share their experiences with using blogs to…

  13. 78 FR 37431 - Expanding America's Leadership in Wireless Innovation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-20

    .... (Presidential Sig.) THE WHITE HOUSE, Washington, June 14, 2013. [FR Doc. 2013-14971 Filed 6-19-13; 11:15 am... Documents#0;#0; ] Memorandum of June 14, 2013 Expanding America's Leadership in Wireless Innovation... innovation, private investment, and smart policy has positioned the United States as the global leader...

  14. Strengthening and Expanding Prekindergarten in the Children First Reorganization

    ERIC Educational Resources Information Center

    Boressoff, Todd

    2012-01-01

    This policy brief examines the infrastructure needed to support early education at the Department of Education in the coming years. The Department's newly announced reform agenda will reshape how prekindergarten is managed. It's goal is to help inform the decisions the City must make to integrate an expanding prekindergarten program into Children…

  15. Contracting/expanding self-sealing cryogenic tube seals

    NASA Technical Reports Server (NTRS)

    Jia, Lin X. (Inventor)

    1997-01-01

    Contracting/expanding self-sealing cryogenic tube seals are disclosed which use the different properties of thermal contraction and expansion of selected dissimilar materials in accord with certain design criteria to yield self-tightening seals via sloped-surface sealing. The seals of the subject invention are reusable, simple to assemble, and adaptable to a wide variety of cryogenic applications.

  16. Cantilever springs maintain tension in thermally expanded wires

    NASA Technical Reports Server (NTRS)

    Terselic, R. A.

    1965-01-01

    Two deflected cantilever springs strung with wire provide force displacement compensation to maintain tension in the wires as they undergo thermal expansion. This method of maintaining tension in thermally expanded wires is used in electric space heaters and residential heat exchangers.

  17. Expanding the Oral Hygiene Curriculum in a Nursing Program.

    ERIC Educational Resources Information Center

    Briggs, Susan; Griego, Elizabeth

    A program was implemented to expand the curriculum materials within the Licensed Practical Nursing (LPN) Program at Clark County Community College (CCCC) which relate to oral hygiene care for the hospital patient. The instructional materials included a video tape and a written instructional packet which were researched, prepared, and presented by…

  18. Expanding Distribution of Lethal Amphibian Fungus Batrachochytrium salamandrivorans in Europe.

    PubMed

    Spitzen-van der Sluijs, Annemarieke; Martel, An; Asselberghs, Johan; Bales, Emma K; Beukema, Wouter; Bletz, Molly C; Dalbeck, Lutz; Goverse, Edo; Kerres, Alexander; Kinet, Thierry; Kirst, Kai; Laudelout, Arnaud; Marin da Fonte, Luis F; Nöllert, Andreas; Ohlhoff, Dagmar; Sabino-Pinto, Joana; Schmidt, Benedikt R; Speybroeck, Jeroen; Spikmans, Frank; Steinfartz, Sebastian; Veith, Michael; Vences, Miguel; Wagner, Norman; Pasmans, Frank; Lötters, Stefan

    2016-07-01

    Emerging fungal diseases can drive amphibian species to local extinction. During 2010-2016, we examined 1,921 urodeles in 3 European countries. Presence of the chytrid fungus Batrachochytrium salamandrivorans at new locations and in urodeles of different species expands the known geographic and host range of the fungus and underpins its imminent threat to biodiversity. PMID:27070102

  19. Expanding Library Support of Faculty Research: Exploring Readiness

    ERIC Educational Resources Information Center

    Brown, Jeanne M.; Tucker, Cory

    2013-01-01

    The changing research and information environment requires a reexamination of library support for research. This study considers research-related attitudes and practices to identify elements indicating readiness or resistance to expanding the library's role in research support. A survey of faculty conducted at the University of Nevada Las…

  20. Spreading of ultrarelativistically expanding shell: An application to GRBs

    NASA Astrophysics Data System (ADS)

    Ruffini, R.; Siutsou, I. A.; Vereshchagin, G. V.

    2014-02-01

    Optically thick energy dominated plasma created in the source of Gamma-Ray Bursts (GRBs) expands radially with acceleration and forms a shell with constant width measured in the laboratory frame. When strong Lorentz factor gradients are present within the shell it is supposed to spread at sufficiently large radii. There are two possible mechanisms of spreading: hydrodynamical and thermal ones. We consider both mechanisms evaluating the amount of spreading that occurs during expansion up to the moment when the expanding shell becomes transparent for photons. We compute the hydrodynamical spreading of an ultrarelativistically expanding shell. In the case of thermal spreading we compute the velocity spread as a function of two parameters: comoving temperature and bulk Lorentz factor of relativistic Maxwellian distribution. Based on this result we determine the value of thermal spreading of relativistically expanding shell. We found that thermal spreading is negligible for typical GRB parameters. Instead hydrodynamical spreading appears to be significant, with the shell width reaching ˜1010 cm for total energy E=1054 erg and baryonic loading B=10-2. Within the fireshell model such spreading will result in the duration of Proper Gamma-Ray Bursts up to several seconds.

  1. Do Loans Really Expand Opportunities for Community College Students?

    ERIC Educational Resources Information Center

    England-Siegerdt, Christy

    2011-01-01

    In order to understand whether loans actually expand opportunities among community college students, it is important to understand who is borrowing and who is not. A binary logistic regression was used to determine which financially needy students are likely to borrow from federal loan programs. The current study found that the following types of…

  2. An Expanded Framework for Analyzing General Chemistry Exams

    ERIC Educational Resources Information Center

    Smith, K. Christopher; Nakhleh, Mary B.; Bretz, Stacey Lowery

    2010-01-01

    This paper describes an expanded framework to aid chemical educators in constructing exams for their courses. The framework has three primary levels: definition, algorithmic, and conceptual. These primary levels have often been used in chemical education research to analyze and describe exam questions, but in this study the definition,…

  3. Expanding the Role of Connectionism in SLA Theory

    ERIC Educational Resources Information Center

    Language Learning, 2013

    2013-01-01

    In this article, I explore how connectionism might expand its role in second language acquisition (SLA) theory by showing how some symbolic models of bilingual and second language lexical memory can be reduced to a biologically realistic (i.e., neurally plausible) connectionist model. This integration or hybridization of the two models follows the…

  4. Expanding Doctoral Education in South Africa: Pipeline or Pipedream?

    ERIC Educational Resources Information Center

    Herman, Chaya

    2011-01-01

    The purpose of this paper is to discuss both the status of the PhD in South Africa and the feasibility of the country's aspiration to increase by fivefold the production of PhDs by 2025. Based on the first empirical studies on doctoral education in South Africa, it argues that in order to move towards this target, an expanded and coordinated…

  5. Apprenticeship Programs Expand with Help of Community Colleges

    ERIC Educational Resources Information Center

    Gonzalez, Jennifer

    2011-01-01

    The apprenticeship system, long considered an educational relic by some educators and policy makers, is gaining new attention as a model for improving job skills and meeting national college-completion goals. A number of states and community and technical colleges are working to strengthen and expand apprenticeship opportunities. They offer…

  6. Expanding Perspectives for Comprehending Visual Images in Multimodal Texts

    ERIC Educational Resources Information Center

    Serafini, Frank

    2011-01-01

    The texts that adolescents encounter today are often multimodal, meaning they incorporate a variety of modes, including visual images, hypertext, and graphic design elements along with written text. Expanding the perspectives readers use to make sense of the multimodal texts is an important aspect of comprehension instruction. Moving beyond the…

  7. EVALUATION OF ANAEROBIC EXPANDED BED REACTOR FOR SEWAGE TREATMENT

    EPA Science Inventory

    Bench scale anaerobic expanded bed reactors were operated at the U.S. EPA Test and Evaluation Facility to determine the effect of relative concentrations between organics and sulfate on the organics removal. The bench scale results showed that less organics were removed as the su...

  8. Children's Books in Review: Expand Kids' Knowledge with Nonfiction Books.

    ERIC Educational Resources Information Center

    Winfield, Evelyn T.

    1991-01-01

    Examines several current nonfiction books that can expand a child's knowledge of a wide variety of subjects, noting that the breadth of a child's knowledge base affects his or her reading development. Subjects discussed include dinosaurs, animal preservation, insects, ecology, history, and drugs and alcohol. (SM)

  9. Expanding Schooling Opportunities for 4-Year-Olds

    ERIC Educational Resources Information Center

    Leuven, Edwin; Lindahl, Mikael; Oosterbeek, Hessel; Webbink, Dinand

    2010-01-01

    We use a novel quasi-experimental strategy to estimate the effect of expanding early schooling enrollment possibilities on early achievement. It exploits two features of the school system in The Netherlands. The first is rolling admissions; children are allowed to start school immediately after their 4th birthday instead of at the beginning of the…

  10. Expanding Dual Enrollment: Increasing Postsecondary Access for All?

    ERIC Educational Resources Information Center

    Pretlow, Josh; Wathington, Heather D.

    2014-01-01

    This study investigated the dual enrollment outcomes associated with a 2005 policy change intended to expand dual enrollment participation in Virginia. Results indicated that overall access to and participation in dual enrollment courses increased following the policy change. However, data showed this increase was not uniform, and minority groups…

  11. Expanding the Landscape of Social Justice: A Critical Ecological Analysis

    ERIC Educational Resources Information Center

    Furman, Gail C.; Gruenewald, David A.

    2004-01-01

    The social justice discourse in education has been critiqued by Bowers and others for its lack of attention to a broad range of related ecological issues. This article analyzes and critiques the current discourse of social justice in the field of educational leadership and offers an expanded concept of socioecological justice in schools. Arguing…

  12. Reducing Dropout Rates through Expanded Learning Opportunities. Issue Brief

    ERIC Educational Resources Information Center

    Harris, Laura; Princiotta, Daniel

    2009-01-01

    Expanded learning opportunities (ELOs), which include afterschool, summer learning, and extended day and extended year programs, can help states reduce dropout rates and increase graduation rates. Effective elementary, middle, and high school ELOs support academic rigor, boost student engagement, and provide students with supportive relationships.…

  13. Analysis of nitrogen condensation in an expanding nozzle flow

    NASA Technical Reports Server (NTRS)

    Wang, F. C.

    1976-01-01

    Condensation of nitrogen flow in an expanding nozzle flow is analyzed using one-dimensional gas dynamic equations and the equations for nucleation and droplet growth. Effects of variations in the Tolman constant and the mass accommodation factor are discussed as well as the effect of foreign nuclei. Comparisons are made with experimental data obtained from a small, contoured nozzle.

  14. Expanding the Vision of Self: Why the Arts Matter

    ERIC Educational Resources Information Center

    Nathan, Linda F.

    2013-01-01

    In this reflective essay, Linda F. Nathan, the founding headmaster of the Boston Arts Academy and currently the executive director of Center for Arts in Education at Boston Arts Academy, shares a story about how one student, Ronald, expands his vision of self through his engagement with the arts. In presenting this reflection on Ronald's…

  15. Diaspora, Migration, and Globalization: Expanding the Discourse of Adult Education

    ERIC Educational Resources Information Center

    Alfred, Mary V.

    2015-01-01

    This article explores how notions of diaspora, migration, and globalization intersect to inform identities and social realities of those who leave their homeland and resettle in other nations. It calls for expanding the discourse of adult education to incorporate critical studies of the diaspora to make visible the inequality and imbalance of…

  16. Expanding Distribution of Lethal Amphibian Fungus Batrachochytrium salamandrivorans in Europe

    PubMed Central

    Spitzen-van der Sluijs, Annemarieke; Martel, An; Asselberghs, Johan; Bales, Emma K.; Beukema, Wouter; Bletz, Molly C.; Dalbeck, Lutz; Goverse, Edo; Kerres, Alexander; Kinet, Thierry; Kirst, Kai; Laudelout, Arnaud; Marin da Fonte, Luis F.; Nöllert, Andreas; Ohlhoff, Dagmar; Sabino-Pinto, Joana; Schmidt, Benedikt R.; Speybroeck, Jeroen; Spikmans, Frank; Steinfartz, Sebastian; Veith, Michael; Vences, Miguel; Wagner, Norman; Pasmans, Frank

    2016-01-01

    Emerging fungal diseases can drive amphibian species to local extinction. During 2010–2016, we examined 1,921 urodeles in 3 European countries. Presence of the chytrid fungus Batrachochytrium salamandrivorans at new locations and in urodeles of different species expands the known geographic and host range of the fungus and underpins its imminent threat to biodiversity. PMID:27070102

  17. Validation of the Chinese Expanded Euthanasia Attitude Scale

    ERIC Educational Resources Information Center

    Chong, Alice Ming-Lin; Fok, Shiu-Yeu

    2013-01-01

    This article reports the validation of the Chinese version of an expanded 31-item Euthanasia Attitude Scale. A 4-stage validation process included a pilot survey of 119 college students and a randomized household survey with 618 adults in Hong Kong. Confirmatory factor analysis confirmed a 4-factor structure of the scale, which can therefore be…

  18. Collaborative Planning in Massachusetts Expanded Learning Time (ELT). Issue Brief

    ERIC Educational Resources Information Center

    Caven, Meghan; Checkoway, Amy; Gamse, Beth

    2012-01-01

    The Massachusetts Expanded Learning Time (ELT) initiative is designed to improve academic outcomes by increasing the amount of learning time for students. Schools are expected to provide opportunities to teachers for collaborative planning and professional development as well as add time to the school day or year for instructional and enrichment…

  19. Expanding Possibilities through Metaphor: Breaking Biases to Improve Crisis Management

    ERIC Educational Resources Information Center

    Cirka, Carol C.; Corrigall, Elizabeth A.

    2010-01-01

    In this article, we demonstrate that an exercise using metaphors to overcome cognitive biases helped students to proactively imagine and prepare for an expanded set of potential crises. The exercise complements traditional textbook approaches to crisis management and incorporates creativity skill building in a realistic context. Learning outcomes…

  20. Addressing School Readiness: Expanding School Psychology in Early Education

    ERIC Educational Resources Information Center

    Hojnoski, Robin L.; Missall, Kristen N.

    2006-01-01

    Historically, the school psychologist's work in early education has been restricted primarily to providing services to young children with special education needs. A more contemporary model calls for an expanded role with a focus on school readiness and the provision of services to all young children and their families in a prevention-oriented…