Characterization of polybenzimidazole (PBI) film at high temperatures

Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kilo-Hz. These properties, which include the dielectric constant and dielectric loss, were also obtained in a temperature range from 20 C to 300 C with an electrical stress of 60 Hz, 50 V/mil present. The alternating and direct current breakdown voltages of silicone oil impregnated films as a function of temperature were also determined. The results obtained indicate that while the film remained relatively stable up to 200 C, it exhibited an increase in its dielectric properties as the temperature was raised to 300 C. It was also found that conditioning of the film by heat treatment at 60 C for six hours tended to improve its dielectric and breakdown properties. The results are discussed and conclusions made concerning the suitability of the film as a high temperature capacitor dielectric

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments

Nanotechnology, a Revolutionary Technique in the Food Industry: Systematic Review

Nanotechnology has a great role in food industry in terms of processing, packaging, preservation and storage. Nanotechnology provides a wide variety of possibilities in food industry applications. Nanotechnology is now leading in the main field of food industry with the development of other technologies. Usage of nanoencapsulation technique to use the bioactive compound for successful delivery. In addition, nanoencapsulation enables the control of flavour release during processing and storage at the desired time and the prevention of flavour degradation. The use of nano biosensors in packaging technique that definitely detects harmful components in food, pathogen identification, changes in food characteristics and food quality. Nonetheless, there is no question that nanotechnology is making a significant contribution to the newly developed advanced technique but safety is also a major concern, when it comes to the use of this technique in food industry, growth and protection should be pushed in parallel to the overall progress of the food industry and consumers

Cosmogenic effects in Mbale chondrite

This article does not have an abstract

Measurement of fecal glucocorticoid metabolites and evaluation of udder characteristics to estimate stress after sudden dry-off in dairy cows with different milk yields

Sudden dry-off is an established management practice in the dairy industry. But milk yield has been increasing continuously during the last decades. There is no information whether the dry-off procedure, which often results in swollen and firm udders, causes stress, particularly in high-producing dairy cows. Therefore, we evaluated the effect of a sudden dry-off on extramammary udder pressure and the concentration of fecal glucocorticoid metabolites (i.e., 11,17-dioxoandrostane, 11,17-DOA) as an indirect stress parameter. Measurements were carried out within the last week before dry-off and until 9d after dry-off considering 3 groups of milk yield (i.e., low: <15 kg/d, medium: 15-20 kg/d, and high: >20 kg/d). Udder pressure increased in all yield groups after dry-off, peaked at d 2 after dry-off and decreased afterwards. Pressures were highest in high-yielding cows and lowest in low-yielding cows. But only in high-yielding cows was udder pressure after dry-off higher than before dry- off. Baseline 11,17-DOA concentrations depended on milk yield. They were highest in low-yielding (121.7 ± 33.3 ng/g) and lowest in high-yielding cows (71.1 ± 30.0 ng/g). After dry-off, 11,17-DOA increased in all yield groups and peaked at d 3. Whereas in medium- and high-yielding cows 11,17-DOA levels differed significantly from their respective baseline during the whole 9-d measuring period, low-yielding cows showed elevated 11,17-DOA levels only on d 3 after dry-off. However, especially the increase in 11,17-DOA after dry-off between the 3 yield groups was considerably different. Mean 11,17-DOA increase from baseline to d 3 was highest in high-yielding cows (129.1%) and considerably lower in low-yielding cows (40.1%). The highest fecal 11,17-DOA concentrations were measured on d 3 after dry-off, indicating that the stress was most intense on d 2, which is due to an 18-h time lag; at about the same time, udder pressure peaked. Our results showed a negligible effect of a sudden dry-off on low-yielding cows. High-yielding cows, however, faced high extramammary pressures and increased glucocorticoid production. Considering animal welfare aspects, a review of the current dry-off strategies might be warranted

Cosmogenic records in the recently fallen Devgaon (H4) chondrite

A stony meteorite fell in the village Devgaon, Bastar district, Chattisgarh, Central India on 2001 February 12. The meteorite was fully covered with fusion crust and weighed about 12 kg. Chemical composition, cosmogenic nuclear tracks, radionuclides and noble gases have been studied to determine its classification, the preatmospheric size and the irradiation history

Sunstein, Statutes, and the Common Law – Reconciling Markets, the Communal Impulse, and the Mammoth State

Professor Cass Sunstein\u27s new book, After the Rights Revolution: Reconceiving the Regulatory State, builds upon, and in important ways seeks to integrate, much of Professor Sunstein\u27s work over the past several years. He has been one of our most prolific and influential writers on issues of governmental structure, approaching the subject both from more or less conventional administrative law perspectives and from the constitutional perspectives of separation of powers. His work has dealt with a tension often addressed in the literature, that between the eighteenth-century Madisonian constitutional engine of limited, internally checked government and the realities of our sprawling contemporary structures. A particular contribution of Sunstein\u27s has been to insist on bringing forward the Madisonian visions, on their accommodation, not their abandonment. This contribution entails rather vigorous disagreement with the economics-driven theorists of public choice, on the right, and those of deconstructionism, on the left. Sunstein wants to build a conceptual framework for contemporary government that embraces the Madisonian ideal of government structured to serve genuinely public ends in face of the risk of faction; that vision entails both reaching agreement on appropriate distinctions between public and private ends, and finding effective contemporary expression of such ideas as checks and balances

Electrical Transport properties of Ni-Cr binary alloys

Electrical transport properties viz. electrical resistivity and thermal conductivity of Ni-Cr binary alloys are determine by our recognized single parametric model potential in wide range of Cr concentration. In this work, screening functions (Ichimaru and Utsumi, Farid et al. and Sarkar et al.) are employed along with the Hartree and Taylor functions to study the relative influence of the exchange and correlation effect. Given liquid alloys are studied as a function of their composition at three different temperatures according to Faber-Ziman model. Computed values of electrical transport properties are in good agreement with the experimental data available in literature

Solar cosmic ray produced noble gases and tracks in lunar fines 10084 and 14163

This article does not have an abstract

Acquired HIV drug resistance among adults living with HIV receiving first-line antiretroviral therapy in Rwanda: a cross-sectional nationally representative survey

BACKGROUND: We assessed the prevalence of acquired HIV drug resistance (HIVDR) and associated factors among patients receiving first-line antiretroviral therapy (ART) in Rwanda. METHODS: This cross-sectional study included 702 patients receiving first-line ART for at least 6 months with last viral load (VL) results >/=1000 copies/mL. Blood plasma samples were subjected to VL testing; specimens with unsuppressed VL were genotyped to identify HIVDR-associated mutations. Data were analysed using STATA/SE. RESULTS: Median time on ART was 86.4 months (interquartile range [IQR], 44.8-130.2 months), and median CD4 count at ART initiation was 311 cells/mm(3) (IQR, 197-484 cells/mm(3)). Of 414 (68.2%) samples with unsuppressed VL, 378 (88.3%) were genotyped. HIVDR included 347 (90.4%) non-nucleoside reverse transcriptase inhibitor- (NNRTI), 291 (75.5%) nucleoside reverse transcriptase inhibitor- (NRTI) and 13 (3.5%) protease inhibitor (PI) resistance-associated mutations. The most common HIVDR mutations were K65R (22.7%), M184V (15.4%) and D67N (9.8%) for NRTIs and K103N (34.4%) and Y181C/I/V/YC (7%) for NNRTIs. Independent predictors of acquired HIVDR included current ART regimen of zidovudine + lamivudine + nevirapine (adjusted odds ratio [aOR], 3.333 [95% confidence interval (CI): 1.022-10.870]; p = 0.046) for NRTI resistance and current ART regimen of tenofovir + emtricitabine + nevirapine (aOR, 0.148 [95% CI: 0.028-0.779]; p = 0.025), zidovudine + lamivudine + efavirenz (aOR, 0.105 [95% CI: 0.016-0.693]; p = 0.020) and zidovudine + lamivudine + nevirapine (aOR, 0.259 [95% CI: 0.084-0.793]; p = 0.019) for NNRTI resistance. History of ever switching ART regimen was associated with NRTI resistance (aOR, 2.53 [95% CI: 1.198-5.356]; p = 0.016) and NNRTI resistance (aOR, 3.23 [95% CI: 1.435-7.278], p = 0.005). CONCLUSION: The prevalence of acquired HIV drug resistance (HIVDR) was high among patient failing to re-suppress VL and was associated with current ART regimen and ever switching ART regimen. The findings of this study support the current WHO guidelines recommending that patients on an NNRTI-based regimen should be switched based on a single viral load test and suggests that national HIV VL monitoring of patients receiving ART has prevented long-term treatment failure that would result in the accumulation of TAMs and potential loss of efficacy of all NRTI used in second-line ART as the backbone in combination with either dolutegravir or boosted PIs