2,742 research outputs found

    Proceedings of a Workshop on Antarctic Meteorite Stranding Surfaces

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    The discovery of large numbers of meteorites on the Antarctic Ice Sheet is one of the most exciting developments in polar science in recent years. The meteorites are found on areas of ice called stranding surfaces. Because of the sudden availability of hundreds, and then thousands, of new meteorite specimens at these sites, the significance of the discovery of meteorite stranding surfaces in Antarctica had an immediate and profound impact on planetary science, but there is also in this discovery an enormous, largely unrealized potential to glaciology for records of climatic and ice sheet changes. The glaciological interest derives from the antiquity of the ice in meteorite stranding surfaces. This exposed ice covers a range of ages, probably between zero and more than 500,000 years. The Workshop on Antarctic Meteorite Stranding Surfaces was convened to explore this potential and to devise a course of action that could be recommended to granting agencies. The workshop recognized three prime functions of meteorite stranding surfaces. They provide: (1) A proxy record of climatic change (i.e., a long record of climatic change is probably preserved in the exposed ice stratigraphy); (2) A proxy record of ice volume change; and (3) A source of unique nonterrestrial material

    A unified approach to computer analysis and modeling of spacecraft environmental interactions

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    A new, coordinated, unified approach to the development of spacecraft plasma interaction models is proposed. The objective is to eliminate the unnecessary duplicative work in order to allow researchers to concentrate on the scientific aspects. By streamlining the developmental process, the interchange between theories and experimentalists is enhanced, and the transfer of technology to the spacecraft engineering community is faster. This approach is called the UNIfied Spacecraft Interaction Model (UNISIM). UNISIM is a coordinated system of software, hardware, and specifications. It is a tool for modeling and analyzing spacecraft interactions. It will be used to design experiments, to interpret results of experiments, and to aid in future spacecraft design. It breaks a Spacecraft Ineraction analysis into several modules. Each module will perform an analysis for some physical process, using phenomenology and algorithms which are well documented and have been subject to review. This system and its characteristics are discussed

    Female reproductive strategy predicts preferences for sexual dimorphism in male faces

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    The aim of the current studies was to test an assumption that variation in female preferences for sexually dimorphic male facial characteristics reflects strategic optimisation of investment in offspring. A negative relationship was predicted between ideal number of children and preferences for masculine male face shapes, as the benefits of securing paternal investment should outweigh the benefits of securing good genes as the costs of raising offspring increase. In Study 1 desired number of children and preferences for masculine face shapes were compared in a sample of female students. In study 2, the prediction was tested in a sample with a wider age profile while controlling for relationship status. Preferences for explicit partner characteristics were also assessed. The prediction was supported: women who desired a higher number of children preferred more feminine male face shapes and ranked cues to investment of parental care over cues to immunocompetence in a partner more highly than those who desired fewer children. Results indicate that female mate preferences vary with reproductive strategy and support assumptions that preferences for feminine male faces reflect preferences for “good dads”

    The Mercury-Redstone project

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    Mercury-Redstone project development history, and contributions to future manned spacecraft design and operatio

    An Evaluation of Radar Metaphors for Providing Directional Stimuli Using Non-Verbal Sound

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    We compared four audio-based radar metaphors for providing directional stimuli to users of AR headsets. The metaphors are clock face, compass, white noise, and scale. Each metaphor, or method, signals the movement of a virtual arm in a radar sweep. In a user study, statistically significant differences were observed for accuracy and response time. Beat-based methods (clock face, compass) elicited responses biased to the left of the stimulus location, and non-beat-based methods (white noise, scale) produced responses biased to the right of the stimulus location. The beat methods were more accurate than the non-beat methods. However, the non-beat methods elicited quicker responses. We also discuss how response accuracy varies along the radar sweep between methods. These observations contribute design insights for non-verbal, nonvisual directional prompting

    Intercalation effect on hyperfine parameters of Fe in FeSe superconductor with Tc = 42 K

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    57Fe-Mossbauer spectra of superconducting beta-FeSe, the Li/NH3 intercalate product and a subsequent sample of this intercalate treated with moist He gas have been measured in temperature range 4.7 - 290 K. A correlation is established between hyperfine parameters and critical temperature Tc in these phases. A strong increase of isomer shift upon intercalation is explained by a charge transfer from the Li/NH3 intercalate to the FeSe layers resulting in an increase of Tc up to 42 K. A significant decrease of the quadrupole splitting above 240 K has been attributed to diffusive motion of Li+ ions within the interlamellar space.Comment: 6 pages, 5 figures, 1 tabl

    A Structure for Quasars

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    This paper proposes a simple, empirically derived, unifying structure for the inner regions of quasars. This structure is constructed to explain the broad absorption line (BAL) regions, the narrow `associated' ultraviolet and X-ray warm absorbers (NALs); and is also found to explain the broad emission line regions (BELR), and several scattering features, including a substantial fraction of the broad X-ray Iron-K emission line, and the bi-conical extended narrow emission line region (ENLR) structures seen on large kiloparsec scales in Seyfert images. Small extensions of the model to allow luminosity dependent changes in the structure may explain the UV and X-ray Baldwin effects and the greater prevalence of obscuration in low luminosity AGN.Comment: 35 pages, including 8 color figures (figures 4abc are big). Astrophysical Journal, in press. Expanded version of conference paper astro-ph/000516

    Additional application of the NASCAP code. Volume 1: NASCAP extension

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    The NASCAP computer program comprehensively analyzes problems of spacecraft charging. Using a fully three dimensional approach, it can accurately predict spacecraft potentials under a variety of conditions. Several changes were made to NASCAP, and a new code, NASCAP/LEO, was developed. In addition, detailed studies of several spacecraft-environmental interactions and of the SCATHA spacecraft were performed. The NASCAP/LEO program handles situations of relatively short Debye length encountered by large space structures or by any satellite in low earth orbit (LEO)
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