Effects of high pressure nitrogen on the thermal stability of SiC fibers

Polymer-derived SiC fibers were exposed to nitrogen gas pressures of 7 and 50 atm at temperatures up to 1800 C. The fiber weight loss, chemical composition, and tensile strength were then measured at room temperature in order to understand the effects of nitrogen exposure on fiber stability. High pressure nitrogen treatments limited weight loss to 3 percent or less for temperatures up to 1800 C. The bulk Si-C-O chemical composition of the fiber remained relatively constant up to 1800 C with only a slight increase in nitrogen content after treatment at 50 atm; however, fiber strength retention was significantly improved. To further understand the effects of the nitrogen atmosphere on the fiber stability, the results of previous high pressure argon treatments were compared to those of the high pressure nitrogen treatments. High pressure inert gas can temporarily maintain fiber strength by physically inhibiting the evolution of gaseous species which result from internal reactions. In addition to this physical effect, it would appear that high pressure nitrogen further improved fiber temperature capability by chemically reacting with the fiber surface, thereby reducing the rate of gas evolution. Subsequent low pressure argon treatments following the initial nitrogen treatments resulted in stronger fibers than after argon treatment alone, further supporting the chemical reaction mechanism and its beneficial effects on fiber strength

Pressure effects on the thermal stability of SiC fibers

Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures

Rhythmic Leptin Is Required for Weight Gain from Circadian Desynchronized Feeding in the Mouse

The neuroendocrine and metabolic effects of leptin have been extensively researched since the discovery, and the later identification, of the leptin gene mutated within the ob/ob mouse. Leptin is required for optimal health in a number of physiological systems (e.g. fertility, bone density, body weight regulation). Despite the extensive leptin literature and many observations of leptin’s cyclical pattern over the 24-hour day, few studies have specifically examined how the circadian rhythm of leptin may be essential to leptin signaling and health. Here we present data indicating that a rhythmic leptin profile (e.g. 1 peak every 24 hours) leads to excessive weight gain during desynchronized feeding whereas non-rhythmic leptin provided in a continuous manner does not lead to excessive body weight gain under similar feeding conditions. This study suggests that feeding time can interact with leptin’s endogenous rhythm to influence metabolic signals, specifically leading to excessive body weight gains during ‘wrongly’ timed feeding

The knowledge, the will and the power : a plan of action to meet the HIV prevention needs of Africans living in England

The Knowledge, The Will and The Power is a statement of what we, the NAHIP Partners, plan to do to prevent HIV transmissions occurring during sexual activity among the diverse population of Africans living in England (Chapter 1). We describe the size and context of Africans living in England (Chapter 2), the size of the HIV epidemic and the number of new infections occurring (Chapter 3), as well as the behaviours and facilitators of new infections (Chapter 4). We then articulate how the NAHIP partners intend to influence future behaviours (Chapter 5). The final three chapters describe what is required in order to meet the HIV prevention needs of individual African people (Chapter 6), of NAHIP partner organisations (Chapter 7) and of those undertaking decisions related to policy, planning and research (Chapter 8)

Medication treatment perceptions, concerns and expectations among depressed individuals with Type I Bipolar Disorder

BACKGROUND: Subjective experience of illness affects outcomes among populations with bipolar disorder (BD). This cross-sectional study combined qualitative and quantitative approaches to evaluate perceived treatment effects, concerns and expectations among 90 individuals with BD. METHODS: Adults with type I BD, mean age 36.6 years, 51% women, completed a semi-structured interview that was audio taped, transcribed, coded and analyzed along emergent themes. Quantitative scales measured depressive symptoms (Hamilton Depression Scale/HAMD), psychopathology (Clinical Global Impression/CGI), and insight and treatment attitudes (Insight and Treatment Attitudes Questionnaire/ITAQ). RESULTS: Individuals had moderate depression and psychopathology with good insight into need for treatment. Drug treatment was perceived as beneficial, by “stabilizing” or “balancing” mood (42%, N=38), decreasing anxiety/depressive symptoms (19%, N=17) and improving sleep (10%, N=9). While 39%, (N=35) of individuals denied medication concerns, nearly 29%, (N=26) feared possible long-term effects, particularly diabetes or liver/kidney damage. Media stories and advertisements contributed to medication fears. Hopes and expectations for treatment ranged from those that were symptom or functional status-based, such as desiring mood stabilization and elimination of specific symptoms (23%, N=21), to more global hopes such as “being normal” (20%, N=18) or “cured” (18%, N=16). LIMITATIONS: Limitations include relatively small sample, lack of a comparator, inclusion of only depressed individuals and those willing to discuss their illness experience. CONCLUSIONS: While individuals with BD appreciate the effects of medications, concerns regarding adverse effects and discrepancy between actual and hoped-for outcomes can be substantial. Subjective experience with medications using qualitative and quantitative methods should be explored in order to optimize treatment collaboration and outcomes

Hospital Community Benefits After the ACA: Partnerships for Community Health Improvement

Examines states' and localities' efforts to promote community health and systemic change through collaborations focused on community health needs assessments, priority setting, strategic planning, and the implementation of health improvement initiatives

Advanced Ceramics for NASA's Current and Future Needs

Ceramic composites and monolithics are widely recognized by NASA as enabling materials for a variety of aerospace applications. Compared to traditional materials, ceramic materials offer higher specific strength which can enable lighter weight vehicle and engine concepts, increased payloads, and increased operational margins. Additionally, the higher temperature capabilities of these materials allows for increased operating temperatures within the engine and on the vehicle surfaces which can lead to improved engine efficiency and vehicle performance. To meet the requirements of the next generation of both rocket and air-breathing engines, NASA is actively pursuing the development and maturation of a variety of ceramic materials. Anticipated applications for carbide, nitride and oxide-based ceramics will be presented. The current status of these materials and needs for future goals will be outlined. NASA also understands the importance of teaming with other government agencies and industry to optimize these materials and advance them to the level of maturation needed for eventual vehicle and engine demonstrations. A number of successful partnering efforts with NASA and industry will be highlighted

We Will Eat Stones

article written in protest against the overthro

Acquisitions Unit Annual Report 1995-1996

Annual report of the Acquisitions Unit, University Library, University of Rhode Island for fiscal year 1995-1996. Covers staffing, technology, acquisitions of monographs and serials, binding and processing. For monographs, includes four years of monthly statistics (1992/93-1995/96) on requests searched, duplicates returned, titles ordered, titles claimed, volumes added by acquisition type, approvals returned, microforms added, media added, and invoices processed. For serials and processing, includes four years of monthly statistics (1992/93-1995/96) on volumes withdrawn, titles added, volumes added, volumes bound, volumes processed, volumes mended, and microforms added