163 research outputs found

    Capabilities of GRO/OSSE for observing solar flares

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    The launch of the Gamma Ray Observatory (GRO) near solar maximum makes solar flare studies early in the mission particularly advantageous. The Oriented Scintillation Spectrometer Experiment (OSSE) on GRO, covering the energy range 0.05 to 150 MeV, has some significant advantages over the previous generation of satellite-borne gamma-ray detectors for solar observations. The OSSE detectors will have about 10 times the effective area of the Gamma-Ray Spectrometer (GRS) on Solar Maximum Mission (SMM) for both photons and high-energy neutrons. The OSSE also has the added capability of distinguishing between high-energy neutrons and photons directly. The OSSE spectral accumulation time (approx. 4s) is four times faster than that of the SMM/GRS; much better time resolution is available in selected energy ranges. These characteristics will allow the investigation of particle acceleration in flares based on the evolution of the continuum and nuclear line components of flare spectra, nuclear emission in small flares, the anisotropy of continuum emission in small flares, and the relative intensities of different nuclear lines. The OSSE observational program will be devoted primarily to non-solar sources. Therefore, solar observations require planning and special configurations. The instrumental and operational characteristics of OSSE are discussed in the context of undertaking solar observations. The opportunities for guest investigators to participate in solar flare studies with OSSE is also presented

    Comparative Pitching Biomechanics Among Adolescent Baseball Athletes: Are There Fundamental Differences Between Pitchers and Non-pitchers?

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    # Background Approximately 25% of youth baseball players pitch, with most young athletes predominately playing multiple positions. While some youth baseball players may primarily pitch, other players may only pitch on occasion, potentially creating a pitching skill level discrepancy. Understanding potential kinematic and kinetic differences between pitching and non-pitching baseball players can inform injury risk reduction strategies for amateur athletes. # Purpose/Hypothesis To analyze differences in pitching biomechanics for fastballs, breaking balls, and change-ups in adolescent youth baseball players that identify as pitchers and non-pitchers. # Study Design Retrospective cross-sectional study # Methods Baseball players were designated as pitchers or non-pitchers, who then threw fastballs (FB), breaking balls (BB), and change-ups (CH) during a biomechanical assessment. T-tests, Mann-Whitney U tests, and ANOVAs with Bonferroni correction, and effect sizes (ES) were performed. # Results Sixty baseball players (pitchers = 40; non-pitchers = 20; Age: 15.0 (1.1); Left-handed: 15%; Height 1.77 (0.09) m; Weight: 70.0 (12.5) kg) threw 495 pitches (FB: 177, BB: 155, CH: 163) for analysis. Pitchers threw 2 m/s faster and produced greater trunk rotation velocity (ES: 0.71 (95% CI: 0.39, 1.30, p\<0.0001) than non-pitchers. Furthermore, pitchers demonstrated greater ground reaction force for FB compared to CH (ES: 0.48 (95% CI: 0.01, 0.94), p\<0.0001). No other biomechanical differences were observed between pitchers and non-pitchers or between pitch types. # Conclusion Despite throwing at greater velocity for all pitch types, baseball players that identify primarily as pitchers had overall similar kinematics and kinetics in comparison to baseball players that primarily identify as non-pitchers. Self-identified pitching baseball athletes have improved force transfer strategies for ball propulsion, utilizing different force production and attenuation strategies across different pitch types when compared to non-pitchers. Coaches should consider that novice pitchers may potentially have dissimilar trunk and ground reaction strategies in comparison to primary pitchers when designing appropriate pitch loading and recovery strategies. # Level of Evidence

    Enhancing West Nile Virus Surveillance, United States

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    We provide a method for constructing a county-level West Nile virus risk map to serve as an early warning system for human cases. We also demonstrate that mosquito surveillance is a more accurate predictor of human risk than monitoring dead and infected wild birds

    Density-functional Study of Small Molecules within the Krieger-Li-Iafrate Approximation

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    We report density-functional studies of several small molecules (H2,N2,CO,H2OH_{2}, N_{2}, CO, H_{2}O, and CH4CH_{4}) within the Krieger-Li-Iafrate (KLI) approximation to the exact Kohn-Sham local exchange potential, using a three-dimensional real-space finite-difference pseudopotential method. It is found that exchange-only KLI leads to markedly improved eigenvalue spectra compared to those obtained within the standard local-density approximation (LDA), the generalized gradient approximation (GGA), and the Hartree-Fock (HF) method. For structural properties, exchange-only KLI results are close to the corresponding HF values. We find that the addition of LDA or GGA correlation energy functionals to the KLI exact exchange energy functional does not lead to systematic improvements.Comment: 16 pages including 1 fugure, to be published in Phys. Rev. A Nov. 1 '9

    Mesoscale physical–biological–biogeochemical linkages in the open ocean : an introduction to the results of the E-Flux and EDDIES programs

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    Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1133-1138, doi:10.1016/j.dsr2.2008.03.001.Mesoscale currents, fronts, and eddies are ubiquitous and energetic features of ocean circulation. These phenomena, sometimes referred to as the “internal weather of the sea,” accommodate a diverse set of physical, chemical, and biological interactions that influence marine biogeochemistry on a wide range of timescales. These biogeochemical processes include the “biological pump”, i.e. the transfer or flux of biologically produced organic matter and associated elements from the surface ocean to depth (Ducklow et al., 2001; Volk and Hoffert, 1985). Within ~ 80% of the world’s oceans, the productivity and species composition of the autotrophic organisms that contribute to the biological pump are typically limited by major nutrients (e.g. nitrogen, phosphorus, and silica), or trace metals (e.g. iron). Primary production in such oligotrophic regions therefore depends mostly on intense recycling of nutrients within the surface sunlit waters, with only a small fraction supported by that entering from the atmosphere, or from the physical transport of nutrients from nutrient-rich deep waters below. Evidence that mesoscale and submesoscale phenomena play a role in the latter process dates back more than two decades (Angel and Fasham, 1983; Franks et al., 1986; Ring Group, 1981; Tranter et al., 1980; Venrick, 1990; Woods, 1988).E-Flux and EDDIES were supported by the National Science Foundation Chemical, Biological, and Physical Oceanography Programs. Additional support for the EDDIES project was provided by NASA

    Neurology

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    Contains reports on six research projects.U. S. Public Health Service (B-3055-4, B-3090-4, MH-06175-02)U. S. Air Force (AF49(638)-1313)U.S. Navy. Office of Naval Research (Nonr-1841(70)

    Wei Hua's Four Parameter Potential Comments and Computation of Moleculer Constants \alpha_e and \omega_e x_e

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    The value of adjustable parameter CC and the four-parameter potential U(r)=De[1exp[b(rre)]1Cexp[b(rre)]]2U(r) = D_{e}\left [ \frac{1-{exp}[-b(r-r_{e})]}{1-C{exp} [-b(r-r_{e})]} \right ]^{2} has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed, with CC derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei Hua. Average mean deviation has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from Levine2, Varshni and Morse potentials, respectively. Also Dunham's method has been used to express rotation-vibration interaction constant (αe)(\alpha_{e}) and anharmonocity constant (ωexe)(\omega_{e}x_{e}) in terms of CC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states. For αe\alpha_{e}, the average mean deviation is 7.2% compared to 19.7% for Lippincott's potential which is known to be the best to predict the values. Average mean deviation for (ωexe)(\omega_{e}x_{e}) turns out to be 17.4% which is almost the same as found from Lippincott's potential function.Comment: 19 RevTex Pages, 1 Ps figure, submitted to J. Phys.

    Memory for Self-Performed Actions in Individuals with Asperger Syndrome

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    Memory for action is enhanced if individuals are allowed to perform the corresponding movements, compared to when they simply listen to them (enactment effect). Previous studies have shown that individuals with Autism Spectrum Disorders (ASD) have difficulties with processes involving the self, such as autobiographical memories and self performed actions. The present study aimed at assessing memory for action in Asperger Syndrome (AS). We investigated whether adults with AS would benefit from the enactment effect when recalling a list of previously performed items vs. items that were only visually and verbally experienced through three experimental tasks (Free Recall, Old/New Recognition and Source Memory). The results showed that while performance on Recognition and Source Memory tasks was preserved in individuals with AS, the enactment effect for self-performed actions was not consistently present, as revealed by the lower number of performed actions being recalled on the Free Recall test, as compared to adults with typical development. Subtle difficulties in encoding specific motor and proprioceptive signals during action execution in individuals with AS might affect retrieval of relevant personal episodic information. These disturbances might be associated to an impaired action monitoring system
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