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

Comparison of Arc Tracking Tests in Various Aerospace Environments

Momentary short-circuit arcs between a polyimide insulated wire with defective insulation and another conductor may cause pyrolization of the insulation resulting in a conductive path capable of sustaining the arc. These sustained arcs may propagate along the wires or to neighboring wires leading to complete failure of the wire bundle. Wire insulation susceptibility to arc tracking may be dependent on its environment. Because all wire insulation types tested to date arc track, a test procedure has been developed to compare different insulation types with respect to their arc tracking susceptibility. This test procedure is presented along with a comparison of arc tracking in the following three environments: (1) Air at atmospheric pressure and 1 gravitational(g) force; (2) Vacuum (2.67 x 10(exp -3) Pa) and 1g, and (3) Air at atmospheric pressure and microgravity (less than 0.04g)

Individual level peer interventions for gay and bisexual men who have sex with men between 2000 and 2020: A scoping review

Background Peer-led interventions are central to the global HIV response for gay and bisexual men who have sex with men [GBMSM]. Since the year 2000, technological advancements in HIV and an increased response to the health disparities faced by GBMSM outside of HIV, have contributed to the expanding scope of their content and delivery. This review sets out to characterise the evidence base for individual level peer interventions for GBMSM, overview approaches to implementing and evaluating them and identify future priorities for their delivery and evaluation. Methods A scoping review methodology was applied and evaluations of peer programs for GBMSM published in peer reviewed journals were identified via subject heading and keyword searches across five electronic databases. Titles and abstracts were reviewed, and full texts were assessed against eligibility criteria. A coding framework was used to extract data from included studies against intervention implementation and evaluation components. Results A total of 38 studies evaluating peer led interventions against effectiveness outcomes were deemed eligible for inclusion and coded into four intervention modalities; peer counselling [n = 6], groupwork programs [n = 15], peer navigation [n = 7] and peer education [n = 10]. Most addressed HIV [n = 32] and across intervention modalities, evaluations demonstrated compelling evidence of significant effect. Intervention effects on broader indicators of psychosocial wellbeing were not extensively evaluated. Expertise regarding the implementation and evaluation of peer interventions addressing HIV among GBMSM ought to be leveraged to expand the scope of peer intervention to meet the diverse health and wellbeing needs of GBMSM

Studying the production mechanisms of light meson resonances in two-pion photoproduction: a Regge approach

A calculation of the angular moments of two-pion photoproduction is presented. The underlying theoretical model encodes the prominent $\rho(770)$ resonance and the expected leading background contribution coming from the Deck mechanism. The model contains a number of free parameters which are fit to experimental data. A good description of the angular moments is obtained.Comment: 5 pages, 3 figures. Prepared as proceedings contribution for the 20th International Conference on Hadron Spectroscopy and Structure (HADRON 2023), Genova, Italy, 5-9/6/202

Trust, Familiarity, Optimism, and Pleasure: Australian Gay Men Accounting for Inconsistent HIV Prevention Practices in the PrEP Era

Despite an increase in the range of effective HIV risk reduction strategies that are available, some gay and bisexual men (GBM) do not use any of them consistently. Understanding why GBM do not always use a protective strategy may help develop more effective responses. Semi-structured interviews with 24 sexually active GBM in Sydney, Australia were conducted and analyzed using thematic analysis. The main characteristics of encounters featuring little or no use of HIV risk reduction strategies were familiarity and trust with partners, pleasure and intoxication, expectations that partners were using HIV pre-exposure prophylaxis or treatment as prevention, and in some cases feelings of inevitability about acquiring HIV. An increase in pleasure and a reduction in anxiety about sex were noted by some GBM who had commenced PrEP. Encouraging GBM to adopt a strategy such as PrEP and to use it consistently may be easier by emphasizing benefits to mental health and the quality of sex and intimacy it can offer. However, even with the increased availability of effective biomedical HIV risk reduction strategies, not all GBM are able to consistently manage HIV risk and some continue to hold optimistic and potentially inaccurate beliefs about sexual partners that may increase HIV risk

Impact of Total Ionizing Dose Radiation Testing and Long-Term Thermal Cycling on the Operation of CMF20120D Silicon Carbide Power MOSFET

Power systems designed for use in NASA space missions are required to work reliably under harsh conditions including radiation, thermal cycling, and extreme temperature exposures. Silicon carbide devices show great promise for use in future power electronics systems, but information pertaining to performance of the devices in the space environment is very scarce. A silicon carbide N-channel enhancement-mode power MOSFET called the CMF20120 is of interest for use in space environments. Samples of the device were exposed to radiation followed by long-term thermal cycling to address their reliability for use in space applications. The results of the experimental work are presentd and discussed

Attitudes and perceived social norms towards drug use among gay and bisexual men in Australia

Background: Gay and bisexual men (GBM) report distinctive patterns and contexts of drug use, yet little has been published about their attitudes towards drug use. Objectives: We developed measures of attitudes and perceived social norms towards drug use, and examined covariates of more accepting attitudes and norms among GBM in Australia. Methods: We analysed baseline data from the [removed for blinded review] study. This is an online prospective observational study of drug use among Australian GBM. We used principal components factor analysis to generate two attitudinal scales assessing “drug use for social and sexual enhancement” and “perceptions of drug risk”. A third perceived social norms scale examined “acceptability of drug use among gay friends”. Results: Among 2,112 participants, 61% reported illicit drug use in the preceding 6 months. Stronger endorsement of drug use for social and sexual engagement and lower perceptions of drug risk were found among men who were more socially engaged with other gay men and reported regular drug use and drug use for sex. In multivariate analyses, all three scales were associated with recent drug use (any use in the previous six months), but only the drug use for social and sexual enhancement scale was associated with regular (at least monthly) use. Conclusions: Drug use and sex are difficult to disentangle for some GBM, and health services and policies could benefit from a better understanding of attitudinal and normative factors associated with drug use in gay social networks, while recognising the role of pleasure in substance use

Quantitative Serum Glycomics of Esophageal Adenocarcinoma, and Other Esophageal Disease Onsets

Aberrant glycosylation has been implicated in various types of cancers and changes in glycosylation may be associated with signaling pathways during malignant transformation. Glycomic profiling of blood serum, in which cancer cell proteins or their fragments with altered glycosylation patterns are shed, could reveal the altered glycosylation. We performed glycomic profiling of serum from patients with no known disease (N=18), patients with high grade dysplasia (HGD, N=11) and Barrett’s (N=5), and patients with esophageal adenocarcinoma (EAC, N=50) in an attempt to delineate distinct differences in glycosylation between these groups. The relative intensities of 98 features were significantly different among the disease onsets; 26 of these correspond to known glycan structures. The changes in the relative intensities of three of the known glycan structures predicted esophageal adenocarcinoma with 94% sensitivity and better than 60% specificity as determined by receiver operating characteristic (ROC) analysis. We have demonstrated that comparative glycomic profiling of EAC reveals a subset of glycans that can be selected as candidate biomarkers. These markers can differentiate disease-free from HGD, disease-free from EAC, and HGD from EAC. The clinical utility of these glycan biomarkers requires further validation