46,899 research outputs found

    Pharmacologic counter measures minimizing post-space flight orthostatic intolerance

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    The effect of bed rest on drug disposition and physiological function was investigated as part of a project to determine the cardiovascular effects of space flight. One group of subjects was given doses of lidocane, penicillin-G, and ICG during a control period and following seven days of bed rest. Cardiac function was evaluated by echo-cardiography. Renal function was evaluated in a second group before and after several days of bed rest. Inulin, para-aminohippurate, and dextran clearances were studied. In the first group, the post-bed rest parameters were not statistically different from the pre-bed rest valves. In the second study, renal function did not change significantly after seven days of bed rest. Plans for future research are reviewed

    Polymeric foams from cross-linkable poly-N-ary lenebenzimidazoles

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    Foamed cross-linked poly-N-arylenebinzimidazoles are prepared by mixing an organic tetraamine and an ortho substituted aromatic dicarboxylic acid anhydride in the presence of a blowing agent, and then heating the prepolymer to a temperature sufficient to complete polymerization and foaming of the reactants. In another embodiment of the process, the reactants are heated to form a prepolymer. The prepolymer is then cured at higher temperatures to complete foaming and polymerization

    Heisenberg exchange in magnetic monoxides

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    The superexchange intertacion in transition-metal oxides, proposed initially by Anderson in 1950, is treated using contemporary tight-binding theory and existing parameters. We find also a direct exchange for nearest-neighbor metal ions, larger by a factor of order five than the superexchange. This direct exchange arises from Vddm coupling, rather than overlap of atomic charge densities, a small overlap exchange contribution which we also estimate. For FeO and CoO there is also an important negative contribution, related to Stoner ferromagnetism, from the partially filled minority-spin band which broadens when ionic spins are aligned. The corresponding J1 and J2 parameters are calculated for MnO, FeO, CoO, and NiO. They give good accounts of the Neel and the Curie-Weiss temperatures, show appropriate trends, and give a reasonable account of their volume dependences. For MnO the predicted value for the magnetic susceptibility at the Neel temperature and the crystal distortion arising from the antiferromagnetic transition were reasonably well given. Application to CuO2 planes in the cuprates gives J=1220oK, compared to an experimental 1500oK, and for LiCrO2 gives J1=4 50oK compared to an experimental 230oK.Comment: 21 pages, 1 figure, submitted to Phys. Rev. B 1/19/07. Realized J=4V^2/U applies generally, as opposed to J=2V^2/U from one-electron theory (1/28 revision

    Gamma-Ray Burst Spectral Features: Interpretation as X-ray Emission From A Photoionized Plasma

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    Numerous reports have been made of features, either in emission or absorption, in the 10 - 1000 keV spectra of some gamma-ray bursts. Originally interpreted in the context of Galactic neutron star models as cyclotron line emission and e+ee^+ - e^- annihilation features, the recent demonstration that the majority of GRBs lie at cosmological distances make these explanations unlikely. In this letter, we adopt a relativistic fireball model for cosmological GRBs in which dense, metal rich blobs or filaments of plasma are entrained in the relativistic outflow. In the context of this model, we investigate the conditions under which broadband features, similar to those detected, can be observed. We find a limited region of parameter space capable of reproducing the observed GRB spectra. Finally, we discuss possible constraints further high-energy spectral observations could place on fireball model parameters.Comment: Accepted for publication in Astrophysical Journal Letters Four pages, 2 figure

    Evaluation of the cardiovascular system during various circulatory stresses Progress report, 1 Sep. 1968 - 1 May 1969

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    Cardiac response to chemotherapy after myocardial infraction and diagnostic methods of heart disease in man and animal

    An Operational evaluation of head up displays for civil transport operations. NASA/FAA phase 3 report

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    The advantages and disadvantages of head-up displays (HUDs) in commercial jet transport approach and landing operations was evaluated. Ten airline captains currently qualified in the B-727 aircraft flew a series of instrument landing system (ILS) and nonprecision approaches in a motion base simulator using both a flight director HUD concept and a flightpath HUD concept as well as conventional head-down instruments under a variety of environmental and operational conditions to assess: (1) the potential benefits of these HUDs in airline operations; (2) problems which might be associated with their use; and (3) flight crew training requirements and flight crew operating procedures suitable for use with the HUDs. Results are presented in terms of objective simulator based performance measures, subject pilot opinion and rating data, and observer data

    Energy dependence on fractional charge for strongly interacting subsystems

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    The energies of a pair of strongly-interacting subsystems with arbitrary noninteger charges are examined from closed and open system perspectives. An ensemble representation of the charge dependence is derived, valid at all interaction strengths. Transforming from resonance-state ionicity to ensemble charge dependence imposes physical constraints on the occupation numbers in the strong-interaction limit. For open systems, the chemical potential is evaluated using microscopic and thermodynamic models, leading to a novel correlation between ground-state charge and an electronic temperature.Comment: 4 pages, 3 figs.; as accepted (Phys. Rev. Lett.

    Museums Otherwise: A Compendium of Possible Futures

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    This book is not a typical academic edited volume. Nor does it subscribe to the usual dictates of an exhibition catalogue. It does not seek to provide a comprehensive overview of work on climate change and museums or claim to have discovered One Quick Trick to Solve the Climate Emergency. Instead, the book reflects the main characteristics of the Reimagining Museums for Climate Action project: it is collaborative, distributed, conversational, subversive, nomadic and, at times, playful. The arguments it puts forward emerge through dialogue and speculation just as much as they respond to and build on empirical research. In this sense, the book is perhaps best seen as a partial and in many ways still evolving artefact of the Reimagining Museums project. It can be read from cover-to-cover, or its varied contents can be traversed in a less rigid fashion. It is one “output” among many, and its main aim is to prompt further transdisciplinary alliances, rather than set out a particular position or manifesto. To this end, the book invites peripatetic readings and strange deviations. It is anchored by eight concepts that reflect the diversity and creativity of museums, but it is also motivated by a desire to (re)situate this field within a broader set of debates on the roots of social and environmental injustice, and the role of museums in these histories
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