8,485 research outputs found

    Manned Mars mission vehicle design requirements for aerocapture

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    Vehicle design requirements of a reusable system for manned Mars missions which employ aerocapturing techniques to obtain desired orbital velocities are defined. Requirements for vehicle L/D and ballistic coefficient are determined for expected aerocapture velocities. Conclusions are presented concerning g-loads environment and TPS requirements for a vehicle that aerocaptures at Mars and Earth. Although the goal of a reusable system (based on current state-of-art technologies) was not obtained, the viability of aerocapture at Mars and Earth was established

    Altruism and Voluntary Provision of Public Goods

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    We study how people's predisposition towards altruism, as measured by tools developed by psychologists, affects their behavior in a voluntary contributions public good experiment. Earlier experiments provide evidence against the strong free rider hypothesis; however, contributions to the public good decrease with repetition. We investigate whether a high level of contributions can be sustained in groups of subjects who have been pre-selected on the basis of their altruistic inclinations. In the first stage of the experiment, each subject responds to a psychology questionnaire that measures various dimensions of one's personality. The subjects are then matched in groups according to their altruism scores, and engage in a voluntary contribution game. We consider whether the levels and dynamics of group contributions differ significantly between the groups with altruists and non-altruists. We find that subjects' altruism has a weak but positive effect on group behavior in the public good game.

    A Tribute To Lewis F. Powell, Jr.

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    Altruism and voluntary provision of public goods

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    We study how people's predisposition towards altruism affects their behavior in a voluntary contributions public good experiment. We investigate whether a high level of contributions can be sustained in groups of subjects who have been pre-selected on the basis of their altruistic inclinations. In the first stage of the experiment, each subject responds to a psychology questionnaire that measures various dimensions of one''s personality. The subjects are then matched in groups according to their altruism scores, and engage in a voluntary contributions game. We consider whether the levels and dynamics of group contributions differ significantly between the groups with altruists and non-altruists. We find that subjects'' altruism has only a weak positive effect on group behavior in the public good game.Altruism

    Synthetic, structural and molecular modelling studies of organoiron complexes of catalytic importance

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    Includes bibliography.The synthesis and characterization of a series of new alkyl dicarbonyl pentaznethylcyclopentadienyl iron compounds, [(η⁵-C₅(CH₃)₅)Fe(CO)₂R], is the starting point for an investigation of these compounds and their relevance as models for catalytic reactions. The compounds have been synthesized by the reaction of Na[(η⁵-C₅(CH₃)₅)Fe(CO)₂] with the appropriate n-alkyl chloride or bromide (R=n-C₃H₇ to n-C₁₂H₂₅). The majority of the compounds are new and have been fully characterized by microanalysis, IR, ¹H, and ¹³C NMR and mass spectrometry. The data are discussed and some properties and reactions of the compounds are described

    Aero-Assisted Orbital Transfer Vehicle (AOTV)

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    The AOTV will make use of the atmosphere to provide braking on return from a planetary mission or geosynchronous orbit. The minimum altitude for aerobraking is typically 255,000 ft at the equator. Time of the braking maneuver is typically 480 sec from 400,000 ft to 255,000 ft and back out - about 8 min. The problem is to design a control system that will be able to handle density irregularities such as those that have shown up in shuttle data near 280,000 ft. To obtain data, one has to use model-produced statistics or information obtained during the atmospheric transit time. The Global Reference Atmosphere Model (GRAM) appears to bracket the shuttle data, but it is not clear that the statistics are correct. The model-data exhibits strong density shears over small step size that are probably an artifact

    Reflections on Brown and the Future

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    Glycaemic control in people with diabetes following acute myocardial infarction

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    Diabetes is a highly prevalent disease associated with considerable cardiovascular end organ damage and mortality. Despite significant changes to the management of acute myocardial infarction over the last two decades, people with diabetes remain at risk of complications and mortality following a myocardial infarct for a multitude of reasons, including increased coronary atherosclerosis, associated coronary microvascular dysfunction, and diabetic cardiomyopathy. Dysglycaemia causes significant endothelial dysfunction and upregulation of inflammation within the vasculature and epigenetic changes mean that these deleterious effects may persist despite subsequent efforts to tighten glycaemic control. Whilst clinical guidelines advocate for the avoidance of both hyper- and hypoglcyaemia in the peri-infarct period, the evidence base is lacking, and currently there is no consensus on the benefits of glycaemic control beyond this period. Glycaemic variability contributes to the glycaemic milieu and may have prognostic importance following myocardial infarct. The use of continuous glucose monitoring means that glucose trends and parameters can now be captured and interrogated, and its use, along with newer medicines, may provide novel opportunities for intervention after myocardial infarction in people with diabetes

    Automated three-component synthesis of a library of γ-lactams

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    A three-component method for the synthesis of γ-lactams from commercially available maleimides, aldehydes, and amines was adapted to parallel library synthesis. Improvements to the chemistry over previous efforts include the optimization of the method to a one-pot process, the management of by-products and excess reagents, the development of an automated parallel sequence, and the adaption of the method to permit the preparation of enantiomerically enriched products. These efforts culminated in the preparation of a library of 169 γ-lactams.The authors are grateful to Ben Neuenswander for carrying out the purification of the libraries and to the National Institutes of General Medical Sciences for financial support through the University of Kansas Chemical Methodologies and Library Development center (P50 GM69663)
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