34,254 research outputs found

    Modification to the Automatic Ionization Chamber

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    The automatic ionization chamber has been described previously [1,2]. It has proven quite reliable in service and has many desirable features, especially for balloon-borne equipment. A disadvantage has been that the time of discharge was dependent upon the potential applied to the quartz fiber. Thus, during the comparison of the instrument to be used with the standards, careful measurement of the potential used on the standards was required. Furthermore, care was required to make sure that the battery used during the flight remained constant in potential. It has now been found that the time between rechargings can be made nearly independent of the potential of the fiber by inserting a metal conductor inside and insulating it from the outer conductor surrounding the quartz fiber, and making the potential of this inner conductor the same as that of the fiber

    A tough high performance composite matrix

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    This invention is a semi-interpenetrating polymer network which includes a high performance thermosetting polyimide having a nadic end group acting as a crosslinking site and a high performance linear thermoplastic polyimide. An improved high temperature matrix resin is provided which is capable of performing in the 200 to 300 C range. This resin has significantly improved toughness and microcracking resistance, excellent processability, mechanical performance and moisture and solvent resistances

    Pneumatic inflatable end effector

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    The invention relates to an end effector device for robot or teleoperated type space vehicle which includes an inflatable balloon member carried on the end of tubular member which has a hollow center or conduit through which a suitable pressurized fluid is supplied. The device may be inserted into a variety of shaped openings or truss-type structures for handling in space

    Laser net - A concept for monitoring wingtip vortices on runways

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    Network of laser beams passes over runway to photodetectors on opposite side, magnitude of beam deflection indicates magnitude of density gradient encountered. Visual display of beam deflections affects go, no-go decision for takeoff and landing

    Techniques Useful in Evacuating and Pressurizing Metal Chambers

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    The aforementioned problems arose in connection with the automatic ionization chamber described previously (1). It was fund that the functioning of these instruments was more consistent if the ion chamber was baked at 350°C for several hours and then filled with pure argon. This procedure resulted in the elimination of organic impurities from the inner surfaces. The impurities, settling on the gold-coated quartz fiber and the collector, apparently altered the contact, resulting in some uncertainty in the recharging. The baking procedure has completely curved this difficulty

    Impaired Dendritic Expression and Plasticity Of H-Channels in the fmr1(-/Y) Mouse Model of Fragile X Syndrome

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    Despite extensive research into both synaptic and morphological changes, surprisingly little is known about dendritic function in fragile X syndrome (FXS). We found that the dendritic input resistance of CA1 neurons was significantly lower in fmr1(-/y) versus wild-type mice. Consistent with elevated dendritic I-h, voltage sag, rebound, and resonance frequency were significantly higher and temporal summation was lower in the dendrites of fmr1(-/y) mice. Dendritic expression of the h-channel subunit HCN1, but not HCN2, was higher in the CA1 region of fmr1(-/y) mice. Interestingly, whereas mGluR-mediated persistent decreases in Ih occurred in both wildtype and fmr1(-/y) mice, persistent increases in Ih that occurred after LTP induction in wild-type mice were absent in fmr1(-/y) mice. Thus, chronic upregulation of dendritic Ih in conjunction with impairment of homeostatic h-channel plasticity represents a dendritic channelopathy in this model of mental retardation and may provide a mechanism for the cognitive impairment associated with FXS.FRAXAUniversity of Texas Austin Undergraduate Research FellowshipNational Institutes of Health Grant MH048432Center for Learning and Memor

    Analysis of Gray Fox (Urocyon cinereoargenteus) Fur Harvests in Arkansas

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    An investigation was conducted on gray fox (Urocyon cinereoargenteus) fur harvest in Arkansas. Data were gathered from a mail survey of Arkansas trappers and from Arkansas Game and Fish Commission fur harvest records from 1939 to 1983. Analyses of these data demonstrated: 1) gray fox were abundant statewide with lower levels in the Delta region; 2) there was a need for fox trappers to keep better records on their trapping efforts, success and composition of catch, including sex and age data; 3) market price: harvest correlation was high (r = 0.956, p \u3c .001); 4) over the past 10 years, the Ozark Mountain region provided the greatest contribution to annual fox harvests, the Ouachita Mountain and Gulf Coastal Plain regions were similar to each other, but lower than the Ozarks, and the Delta region contributed the least, but with a generally stable harvest

    Distribution automation applications of fiber optics

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    Motivations for interest and research in distribution automation are discussed. The communication requirements of distribution automation are examined and shown to exceed the capabilities of power line carrier, radio, and telephone systems. A fiber optic based communication system is described that is co-located with the distribution system and that could satisfy the data rate and reliability requirements. A cost comparison shows that it could be constructed at a cost that is similar to that of a power line carrier system. The requirements for fiber optic sensors for distribution automation are discussed. The design of a data link suitable for optically-powered electronic sensing is presented. Empirical results are given. A modeling technique that was used to understand the reflections of guided light from a variety of surfaces is described. An optical position-indicator design is discussed. Systems aspects of distribution automation are discussed, in particular, the lack of interface, communications, and data standards. The economics of distribution automation are examined

    Effect of exposure cycle on hot salt stress corrosion of a titanium alloy

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    The influence of exposure cycle on the hot-salt stress-corrosion cracking resistance of the Ti-8Al-1Mo-1V alloy was determined. Both temperature and stress were cycled simultaneously to simulate turbine-powered aircraft service cycles. Temperature and stress were also cycled independently to determine their individual effects. Substantial increases in crack threshold stresses were observed for cycles in which both temperature and stress or temperature alone were applied for 1 hour and removed for 3 hours. The crack threshold stresses for these cyclic exposures were twice those determined for continuous exposure for the same total time of 96 hours

    The evolution of the moon and the terrestrial planets

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    The thermal evolutions of the Moon, Mars, Venus and Mercury are calculated theoretically starting from cosmochemical condensation models. An assortment of geological, geochemical and geophysical data are used to constrain both the present day temperatures and the thermal histories of the planets' interiors. Such data imply that the planets were heated during or shortly after formation and that all the terrestrial planets started their differentiations early in their history. The moon, smallest in size, is characterized as a differentiated body with a crust, a thick solid mantle and an interior region which may be partially molten. Mars, intermediate in size, is assumed to have differentiated an Fe-FeS core. Venus is characterized as a planet not unlike the earth in many respects. Core formation has occurred probably during the first billion years after the formation. Mercury, which probably has a large core, may have a 500 km thick solid lithosphere and a partially molten core if it is assumed that some heat sources exist in the core
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