71 research outputs found

    Is the LMA solar-neutrino solution ruled out by SN1987A data?

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    The development of new supernova neutrino detectors relies on the expected hard energy spectrum of the nu_mu and nu_tau emitted in the supernova. We show that SN1987A was sensitive to the large mixing angle (LMA) and "just so" solution to the solar neutrino problem. We review the previous analysis of the SN1987A data and propose a new analysis. The results of this analysis strongly disfavor the LMA solution, provided the nu_mu and nu_tau are hard as predictedComment: 4 pages; 6 figures. Presented at the Europhysics Neutrino Oscillation Workshop, NOW 2000 (EPS, Lecce, Italy, Sept. 9-16, 2000) and to be published in Nucl. Phys. B (PS) (North Holland, Amsterdam, 2001

    Aerodynamic Tests of the Space Launch System for Database Development

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    The Aerosciences Branch (EV33) at the George C. Marshall Space Flight Center (MSFC) has been responsible for a series of wind tunnel tests on the National Aeronautics and Space Administration's (NASA) Space Launch System (SLS) vehicles. The primary purpose of these tests was to obtain aerodynamic data during the ascent phase and establish databases that can be used by the Guidance, Navigation, and Mission Analysis Branch (EV42) for trajectory simulations. The paper describes the test particulars regarding models and measurements and the facilities used, as well as database preparations

    A Fresh Look at Axions and SN 1987A

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    We re-examine the very stringent limits on the axion mass based on the strength and duration of the neutrino signal from SN 1987A, in the light of new measurements of the axial-vector coupling strength of nucleons, possible suppression of axion emission due to many-body effects, and additional emission processes involving pions. The suppression of axion emission due to nucleon spin fluctuations induced by many-body effects degrades previous limits by a factor of about 2. Emission processes involving thermal pions can strengthen the limits by a factor of 3-4 within a perturbative treatment that neglects saturation of nucleon spin fluctuations. Inclusion of saturation effects, however, tends to make the limits less dependent on pion abundances. The resulting axion mass limit also depends on the precise couplings of the axion and ranges from 0.5x10**(-3) eV to 6x10**(-3) eV.Comment: 32 latex pages, 13 postscript figures included, uses revtex.sty, submitted to Physical Review

    Nucleon Spin Fluctuations and the Supernova Emission of Neutrinos and Axions

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    In the hot and dense medium of a supernova (SN) core, the nucleon spins fluctuate so fast that the axial-vector neutrino opacity and the axion emissivity are expected to be significantly modified. Axions with m_a\alt10^{-2}\,{\rm eV} are not excluded by SN~1987A. A substantial transfer of energy in neutrino-nucleon (νN\nu N) collisions is enabled which may alter the spectra of SN neutrinos relative to calculations where energy-conserving νN\nu N collisions had been assumed near the neutrinosphere.Comment: 8 pages. REVTeX. 2 postscript figures, can be included with epsf. Small modifications of the text, a new "Note Added", and three new references. To be published in Phys. Rev. Let

    A Self-Consistent Approach to Neutral-Current Processes in Supernova Cores

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    The problem of neutral-current processes (neutrino scattering, pair emission, pair absorption, axion emission, \etc) in a nuclear medium can be separated into an expression representing the phase space of the weakly interacting probe, and a set of dynamic structure functions of the medium. For a non-relativistic medium we reduce the description to two structure functions S_A(\o) and S_V(\o) of the energy transfer, representing the axial-vector and vector interactions. SVS_V is well determined by the single-nucleon approximation while SAS_A may be dominated by multiply interacting nucleons. Unless the shape of S_A(\o) changes dramatically at high densities, scattering processes always dominate over pair processes for neutrino transport or the emission of right-handed states. Because the emission of right-handed neutrinos and axions is controlled by the same medium response functions, a consistent constraint on their properties from consideration of supernova cooling should use the same structure functions for both neutrino transport and exotic cooling mechanisms.Comment: 33 pages, Te

    Is Large Lepton Mixing Excluded?

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    The original \bnum -(or νˉτ\bar{\nu}_{\tau}-) energy spectrum from the gravitational collapse of a star has a larger average energy than the spectrum for \bnue since the opacity of \bnue exeeds that of \bnum (or ντ\nu_{\tau}). Flavor neutrino conversion, \bnue \leftrightarrow \bnum, induced by lepton mixing results in partial permutation of the original \bnue and \bnum spectra. An upper bound on the permutation factor, p0.35p \leq 0.35 (99%\% CL) is derived using the data from SN1987A and the different models of the neutrino burst. The relation between the permutation factor and the vacuum mixing angle is established, which leads to the upper bound on this angle. The excluded region, sin22θ>0.70.9\sin^2 2\theta > 0.7 - 0.9, covers the regions of large mixing angle solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well as part of region of νeνμ\nu_{e} - \nu_{\mu} oscillation space which could be responsible for the atmospheric muon neutrino deficit. These limits are sensitive to the predicted neutrino spectrum and can be strengthened as supernova models improve.Comment: 20 pages, TeX file. For hardcopy with figures contact [email protected]. Institute for Advanced Study number AST 93/1

    Radiocarbon ages of pre-bomb clams and the hard-water effect in Lakes Michigan and Huron

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    Five radiocarbon ages, all determined by accelerator mass spectrometry, have been obtained for two pre-bomb bivalves from Lake Michigan and one from Lake Huron. After correcting those ages for the fractionation of 14 C in calcite and for the radioactively inert CO 2 in the atmosphere, we find residual ages, caused by the hard water effect, of about 250 years for Lake Michigan and 440 years for Lake Huron.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43072/1/10933_2004_Article_BF00682596.pd

    DNMT3A Loss Drives Enhancer Hypomethylation in FLT3-ITD-Associated Leukemias.

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    DNMT3A, the gene encoding the de novo DNA methyltransferase 3A, is among the most frequently mutated genes in hematologic malignancies. However, the mechanisms through which DNMT3A normally suppresses malignancy development are unknown. Here, we show that DNMT3A loss synergizes with the FLT3 internal tandem duplication in a dose-influenced fashion to generate rapid lethal lymphoid or myeloid leukemias similar to their human counterparts. Loss of DNMT3A leads to reduced DNA methylation, predominantly at hematopoietic enhancer regions in both mouse and human samples. Myeloid and lymphoid diseases arise from transformed murine hematopoietic stem cells. Broadly, our findings support a role for DNMT3A as a guardian of the epigenetic state at enhancer regions, critical for inhibition of leukemic transformation.L.Y. is funded by the Robert and Janice McNair Foundation as an MD/PhD McNair Scholar. This project was funded by CPRIT (RP110028, RP110471 and RP150292 ), the NIH (DK092883 and HG007538), and the Samuel Waxman Cancer Research Foundation. We also thank the Cytometry and Cell Sorting and Genomic and RNA Profiling Cores (NCI P30CA125123, P30 AI036211, P30 CA125123, and S10 RR024574 ) at Baylor College of Medicine. Authors declare no conflicts of interest.This is the author accepted manuscript. The final version is available from Cell Press via http://dx.doi.org/10.1016/j.ccell.2016.05.00
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