45,601 research outputs found

    Experimental determination of cosmic ray charged particle intensity profiles in the atmosphere

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    Absolute cosmic-ray free air ionization and charged particle fluxes and dose rates throughout the atmosphere were measured on a series of balloon flights that commenced in 1968. Argon-filled ionization chambers equipped with solid-state electrometers, with different gas pressures and steel wall thicknesses, and a pair of aluminum-wall Gm counters have provided the basic data. These data are supplemented by measurements with air-filled and tissue equivalent ionization chambers and a scintillation spectrometer. Laboratory experiments together with analyses of the theoretical aspects of the detector responses to cosmic radiation indicate that these profiles can be determined to an overall accuracy of + or - 5 percent

    Dense Molecular Filaments Feeding a Starburst: ALMA Maps of CO(3-2) in Henize 2-10

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    We present ALMA CO(3-2) observations at 0.3 arcsec resolution of He2-10, a starburst dwarf galaxy and possible high-z galaxy analogue. The warm dense gas traced by CO(3--2) is found in clumpy filaments that are kinematically and spatially distinct. The filaments have no preferred orientation or direction; this may indicate that the galaxy is not evolving into a disk galaxy. Filaments appear to be feeding the active starburst; the velocity field in one filament suggests acceleration onto an embedded star cluster. The relative strengths of CO(3-2) and radio continuum vary strongly on decaparsec scales in the starburst. There is no CO(3--2) clump coincident with the non-thermal radio source that has been suggested to be an AGN, nor unusual kinematics. The kinematics of the molecular gas show significant activity apparently unrelated to the current starburst. The longest filament, east of the starburst, has a pronounced shear of FWHM ∼40\sim40~\kms\ across its ∼\sim50~pc width over its entire ≈0.5\approx 0.5 kpc length. The cause of the shear is not clear. This filament is close in projection to a `dynamically distinct' CO feature previously seen in CO(1--0). The most complex region and the most highly disturbed gas velocities are in a region 200~pc south of the starburst. The CO(3--2) emission there reveals a molecular outflow, of linewidth FWZI ∼\sim 120-140 \kms, requiring an energy ≳1053 erg/s\gtrsim 10^{53} \rm~ erg/s. There is at present {\it no} candidate for the driving source of this outflow.Comment: This was revised 31 October to correct some typos and to replace Figure

    Quasi-Chemical and Structural Analysis of Polarizable Anion Hydration

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    Quasi-chemical theory is utilized to analyze the roles of solute polarization and size in determining the structure and thermodynamics of bulk anion hydration for the Hofmeister series Cl−^-, Br−^-, and I−^-. Excellent agreement with experiment is obtained for whole salt hydration free energies using the polarizable AMOEBA force field. The quasi-chemical approach exactly partitions the solvation free energy into inner-shell, outer-shell packing, and outer-shell long-ranged contributions by means of a hard-sphere condition. Small conditioning radii, even well inside the first maximum of the ion-water(oxygen) radial distribution function, result in Gaussian behavior for the long-ranged contribution that dominates the ion hydration free energy. The spatial partitioning allows for a mean-field treatment of the long-ranged contribution, leading to a natural division into first-order electrostatic, induction, and van der Waals terms. The induction piece exhibits the strongest ion polarizability dependence, while the larger-magnitude first-order electrostatic piece yields an opposing but weaker polarizability dependence. In addition, a structural analysis is performed to examine the solvation anisotropy around the anions. As opposed to the hydration free energies, the solvation anisotropy depends more on ion polarizability than on ion size: increased polarizability leads to increased anisotropy. The water dipole moments near the ion are similar in magnitude to bulk water, while the ion dipole moments are found to be significantly larger than those observed in quantum mechanical studies. Possible impacts of the observed over-polarization of the ions on simulated anion surface segregation are discussed.Comment: slight revision, in press at J. Chem. Phy

    Frozen Pre-Embryo Practice in Missouri

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    McQueen v. Gadberry was an Eastern District dissolution dispute over frozen pre-implantation embryos formed from McQueen’s eggs and Gadberry’s sperm. The St. Louis County trial court found the pre-embryos to be marital property of a special character and awarded them jointly to each of the former spouses. The appellate court affirmed. McQueen is an important decision because the finding that embryos are marital property was an issue of first impression that affects many Missouri families. Infertility is a common problem, couples frequently utilize assisted reproductive technologies (ART) to form families, and the extra frozen pre-implantation embryos (hereinafter pre-embryos) have fueled increasing legal disputes. Family law, health law, and estate planning attorneys should factor pre-embryo disposition into their repertoires

    Status of Nucleon Resonances with Masses M<MN+MÏ€M<M_N+M_{\pi}

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    We discuss different interpretations of peaks observed a few years ago by Tatischeff et al. in missing mass spectra of the reaction pp−>pi+pXpp->pi^+pX, which were declared as new exited nucleon states with small masses. A study of the possible production of such states in the process γp−>pi+N∗−>pi++γγn\gamma p->pi^+N^*->pi^+ +\gamma\gamma n by analyzing the invariant mass spectrum of γγn\gamma\gamma n is proposed. It is shown that the data, obtained recently at MAMI-B, can allow to analyze this process and to get information about an existence of exited nucleon states with small masses.Comment: 4 pages, 2 figures, LaTeX with ws-p8-50x6-00.cls. Talk presented at the NSTAR2001 Workshop, Mainz, Germany, March 7-10, 200
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