Measurement of mechanical and thermophysical properties of dimensionally stable materials for space applications

Mechanical, thermal, and physical property test data was generated for as-fabricated advanced composite materials at room temperature (RT), -150 and 250 F. The results are documented of mechanical and thermophysical property tests of IM7/PEEK and discontinuous SiC/Al (particulate (p) and whisker (w) reinforced) composites which were tested at three different temperatures to determine the effect of temperature on material properties. The specific material systems tested were IM7/PEEK (0)8, (0, + or - 45, 90)s, (+ or - 30, 04)s, 25 vol. pct. (v/o) SiCp/Al, and 25 v/o SiCw/Al. RT material property results of IM7/PEEK were in good agreement with the predicted values, providing a measure of consolidation integrity attained during fabrication. Results of mechanical property tests indicated that modulus values at each test temperature were identical, whereas the strength (e.g., tensile, compressive, flexural, and shear) values were the same at -150 F, and RT, and gradually decreased as the test temperature was increased to 250 F. Similar trends in the strength values was also observed in discontinuous SiC/Al composites. These results indicate that the effect of temperature was more pronounced on the strength values than modulus values

Silicon-on-insulator photonic crystal miniature devices with slow light enhanced third-order nonlinearities

The effects of the slow-down factor on third-order nonlinear effects in silicon-on-insulator photonic crystal channel waveguides were investigated. In the slow light regime, with a group index equal to 99, these nonlinear effects are enhanced but the enhancement produced depends on the input peak power level. Simulations indicate the possibility of soliton-like propagation of 1 ps pulses at an input peak power level of 50 mW inside such a photonic crystal waveguide. The increase in the induced phase shift produced by lower group velocities can be used to decrease the size and power requirements needed to operate devices such as optical switches, logic gates, and wavelength translators

'The risks of playing it safe': a prospective longitudinal study of response to reward in the adolescent offspring of depressed parents

BACKGROUND Alterations in reward processing may represent an early vulnerability factor for the development of depressive disorder. Depression in adults is associated with reward hyposensitivity and diminished reward seeking may also be a feature of depression in children and adolescents. We examined the role of reward responding in predicting depressive symptoms, functional impairment and new-onset depressive disorder over time in the adolescent offspring of depressed parents. In addition, we examined group differences in reward responding between currently depressed adolescents, psychiatric and healthy controls, and also cross-sectional associations between reward responding and measures of positive social/environmental functioning. Method We conducted a 1-year longitudinal study of adolescents at familial risk for depression (n = 197; age range 10-18 years). Reward responding and self-reported social/environmental functioning were assessed at baseline. Clinical interviews determined diagnostic status at baseline and at follow-up. Reports of depressive symptoms and functional impairment were also obtained. RESULTS Low reward seeking predicted depressive symptoms and new-onset depressive disorder at the 1-year follow-up in individuals free from depressive disorder at baseline, independently of baseline depressive symptoms. Reduced reward seeking also predicted functional impairment. Adolescents with current depressive disorder were less reward seeking (i.e. bet less at favourable odds) than adolescents free from psychopathology and those with externalizing disorders. Reward seeking showed positive associations with social and environmental functioning (extra-curricular activities, humour, friendships) and was negatively associated with anhedonia. There were no group differences in impulsivity, decision making or psychomotor slowing. CONCLUSIONS Reward seeking predicts depression severity and onset in adolescents at elevated risk of depression. Adaptive reward responses may be amenable to change through modification of existing preventive psychological interventions

Composite materials for space applications

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values

Growth and Coagulation in a Herding Model

We discuss various existing models which mimic the herding effect in financial markets and introduce a new model of herding which incorporates both growth and coagulation. In this model, at each time step either (i) with probability p the system grows through the introduction of a new agent or (ii) with probability q=1-p two groups are selected at random and coagulate. We show that the size distribution of these groups has a power law tail with an exponential cut-off. A variant of our basic model is also discussed where rates are proportional to the size of a grou

EVALUATION OF HEPATOPROTECTIVE POTENTIALS OF METHANOL EXTRACT OF TEPHROSIA VILLOSA AGAINST THIOACETAMIDE INDUCED LIVER TOXICITY IN ALBINO RATS

Objective: The present study was conducted to determine the hepatoprotective potentials of methanol s extracts of Tephrosia villosa leaves against thioacetamide (TAA) induced liver damage in rats. Methodology: The acute oral toxicity study was conducted as per OECD guidelines, and the extract was proved to be safe up to the dose of 2000 mg/kg. The total duration of the study was 21 days, and animals were divided into six groups. Hepatotoxicity was induced in the animals of all groups except normal control by single dose administration of TAA (100 mg/kg) at 1st day of the study followed by animals were treated daily with standard drug silymarin and methanol extract of T. villosa (100 mg/kg, 200 mg/kg and 400 mg/kg) to respective groups for 21 days. Variations in biochemical parameters such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, direct bilirubin, albumin, total protein, ions and others parameters such as clotting time and weight of the liver were considered to determine beneficial effect of the extract. At the end of the study liver samples were collected and subjected to histopathological evaluation. Results: In control animals treated with TAA alone, there were variations in the above mentioned parameters. However in the animals treated with methanol extract and standard drug silymarin, all the parameters were normal possibly due to their beneficial property in protecting the liver against TAA induced hepatotoxicity. Conclusion: The results obtained in the above study suggesting that, the methanol extract of T. villosa possess significant hepatoprotective activity

Observational cross-sectional study to evaluate the effects of self-medication with topical agents used by patients for superficial fungal skin infection at tertiary care hospital in Mumbai

Background: Superficial fungal infections of the hair, skin, and nails are a major cause of morbidity in the world and their incidence continues to increase. While self-medication is also one of the major health concerns for health authorities worldwide. The aim of the study was to evaluate the effects of topical agents used by patients for self-medication, to enlisting the topical agents used by patients for self-medication, to ensure by whose suggestion’s patients engaged in self-medication.Methods: It was an observational cross-sectional study which was conducted at the outpatient department (OPD) of dermatology in tertiary care hospital. A detailed history of the participant was recorded regarding topical agents used for self-medication and their effects were documented in a predesigned case record form.Results: The population consisted of 128 males and 87 females. All these 215 participants had used 61 topical agents of different brand names and the majority of were irritant, corticosteroids and antifungal much high in use. Among 215 participants, 111 had temporary relief from the infection and reoccurred after stopping its use. 98 showed aggravation in their infection among which 90 showed effects like irritation, burning and itching at the application site, while 8 participants showed dryness or flaking of skin.Conclusions: Self-medication is widely practiced among patients with a superficial fungal skin infection in Mumbai. A pharmacist was the major source for obtaining these topical agents. We can conclude, there is a need to counsel and discourage patients from self-medication and regulations for dispensing the prescribed drugs should be made stringent

Evaluation of Representative Microbiological Sampling Sites of Goat and Sheep Dressed Carcasses

Statistical analysis of data of number of sampling points for microbial counts representing the entire goat/sheep carcass was carried out. Thirtytwo sampling points were evaluated out of which fourteen were found to represent the entire dressed carcass for assessing its hygienic efficacy