2,878 research outputs found

    LDEF Space Plasma-High Voltage Drainage Experiment post-flight results

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    The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) was comprised of two identical experimental trays. With one tray located on the leading (ram facing, B10) edge and the other located on the trailing (wake facing, D4) edge of the Long Duration Exposure Facility (LDEF), it was possible to directly compare the effects of ram and wake spacecraft environments on charged dielectric materials. Six arrays of Kapton dielectric samples of 2 mil, 3 mil, and 5 mil thicknesses maintained at +/- 300, +/- 500, and +/- 1000 voltage bias formed the experimental matrix of each tray. In addition, each tray carried two solar cell strings, one biased at +300 volts and the other at -300 volts, to study current leakage from High Voltage Solar Arrays (HVSA). The SP-HVDE provides the first direct, long-term, in-flight measurements of average leakage current through dielectric materials under electric stress. The experiment also yields information on the long term stability of the bulk dielectric properties of such materials. Data and findings of the SP-HVDE are an extension of those from shorter term flight experiments such as the PIX-1 (Plasma Interaction Experiment) and PIX-2 and are therefore valuable in the design and evaluation of long-lived space systems with high voltage systems exposed to the low earth orbital environment. A summary of the SP-HVDE post flight analysis final report delivered to the LDEF Project Office under contract to the National Aeronautics and Space Administration is presented

    Development of an animal-borne blood sample collection device and its deployment for the determination of cardiovascular and stress hormones in phocid seals

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    The research was supported by Bilateral Program between Japan and the United Kingdom and a Grant-in-Aid for Scientific Research (23247010) to Y. Takei and by Grant-in-Aid for challenging Exploratory Research (15K14567) to I. Suzuki from the Japan Society for the Promotion of Science. This work was also supported by funding from the U.K. Natural Environment Research Council (Grant SMRU1001).An animal-borne blood sampler with data-logging functions was developed for phocid seals, which collected two blood samples for the comparison of endocrino-logical/biochemical parameters under two different conditions. The sampler can be triggered by preset hydrostatic pressure, acceleration (descending or ascending), temperature, and time, and also man-ually by light. The sampling was reliable with 39/50 (78%) successful attempts to collect blood samples. Contamination of fluids in the tubing to the next blood sample was 1%, following the prior clearance of the tubing to a waste syringe. In captive harbor seals (Phoca vitulina), the automated blood-sampling method was less stressful than direct blood withdrawal, as evidenced by lower levels of stress hormones (P < 0.05 for ACTH and P = 0.078 for cortisol). HPLC analyses showed that both cortisol and cortisone were circu-lating in seal blood. Using the sampler, plasma levels of cardiovascular hormones, atrial natriuretic peptide (ANP), AVP, and ANG II were compared in grey seals (Halichoerus grypus), between samples collected when the animals were on land and in the water. HPLC analyses determined that [Met12] ANP (1-28) and various forms of angiotensins (ANG II, III, and IV) were circulating in seal blood. Although water immersion profoundly changes the plasma levels of cardiovascular hormones in terrestrial mammals, there were only tendencies toward an increase in ANP (P = 0.069) and a decrease in AVP (P = 0.074) in the seals. These results suggest that cardiovascular regulation in phocid seals may have undergone adaptation during evolution of the carnivore to a semiaquatic lifestyle.PostprintPeer reviewe
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