443 research outputs found

    A surface-fitting program for areally- distributed data from the earth sciences and remote sensing

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    Fortran II program for analysis of data from earth sciences and remote sensin

    Validation of techniques to mitigate copper surface contamination in CUORE

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    In this article we describe the background challenges for the CUORE experiment posed by surface contamination of inert detector materials such as copper, and present three techniques explored to mitigate these backgrounds. Using data from a dedicated test apparatus constructed to validate and compare these techniques we demonstrate that copper surface contamination levels better than 10E-07 - 10E-08 Bq/cm2 are achieved for 238U and 232Th. If these levels are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit on the number of background counts in the region of interest is 0.02-0.03 counts/keV/kg/y depending on the adopted mitigation technique.Comment: 10 pages, 6 figures, 6 table

    Low pH immobilizes and kills human leukocytes and prevents transmission of cell-associated HIV in a mouse model

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    BACKGROUND: Both cell-associated and cell-free HIV virions are present in semen and cervical secretions of HIV-infected individuals. Thus, topical microbicides may need to inactivate both cell-associated and cell-free HIV to prevent sexual transmission of HIV/AIDS. To determine if the mild acidity of the healthy vagina and acid buffering microbicides would prevent transmission by HIV-infected leukocytes, we measured the effect of pH on leukocyte motility, viability and intracellular pH and tested the ability of an acidic buffering microbicide (BufferGel(®)) to prevent the transmission of cell-associated HIV in a HuPBL-SCID mouse model. METHODS: Human lymphocyte, monocyte, and macrophage motilities were measured as a function of time and pH using various acidifying agents. Lymphocyte and macrophage motilities were measured using video microscopy. Monocyte motility was measured using video microscopy and chemotactic chambers. Peripheral blood mononuclear cell (PBMC) viability and intracellular pH were determined as a function of time and pH using fluorescent dyes. HuPBL-SCID mice were pretreated with BufferGel, saline, or a control gel and challenged with HIV-1-infected human PBMCs. RESULTS: Progressive motility was completely abolished in all cell types between pH 5.5 and 6.0. Concomitantly, at and below pH 5.5, the intracellular pH of PBMCs dropped precipitously to match the extracellular medium and did not recover. After acidification with hydrochloric acid to pH 4.5 for 60 min, although completely immotile, 58% of PBMCs excluded ethidium homodimer-1 (dead-cell dye). In contrast, when acidified to this pH with BufferGel, a microbicide designed to maintain vaginal acidity in the presence of semen, only 4% excluded dye at 10 min and none excluded dye after 30 min. BufferGel significantly reduced transmission of HIV-1 in HuPBL-SCID mice (1 of 12 infected) compared to saline (12 of 12 infected) and a control gel (5 of 7 infected). CONCLUSION: These results suggest that physiologic or microbicide-induced acid immobilization and killing of infected white blood cells may be effective in preventing sexual transmission of cell-associated HIV

    Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au+Au Collisions at sNN\sqrt{s_{NN}} = 200 GeV

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    Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au+Au and p+p\textit{p+p} collisions at sNN\sqrt{s_{NN}} = 200 GeV. Strong short and long range correlations (LRC) are seen in central Au+Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short range correlations are observed in peripheral Au+Au collisions. Both the Dual Parton Model (DPM) and the Color Glass Condensate (CGC) predict the existence of the long range correlations. In the DPM the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC longitudinal color flux tubes generate the LRC. The data is in qualitative agreement with the predictions from the DPM and indicates the presence of multiple parton interactions.Comment: 6 pages, 3 figures The abstract has been slightly modifie

    Measurements of D0D^{0} and DD^{*} Production in pp + pp Collisions at s\sqrt{s} = 200 GeV

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    We report measurements of charmed-hadron (D0D^{0}, DD^{*}) production cross sections at mid-rapidity in pp + pp collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays D0Kπ+D^{0}\rightarrow K^{-}\pi^{+}, D+D0π+Kπ+π+D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+} and their charge conjugates, covering the pTp_T range of 0.6-2.0 GeV/cc and 2.0-6.0 GeV/cc for D0D^{0} and D+D^{*+}, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is dσ/dyy=0ccˉd\sigma/dy|_{y=0}^{c\bar{c}} = 170 ±\pm 45 (stat.) 59+38^{+38}_{-59} (sys.) μ\mub. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.

    Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at sNN=200\sqrt{s_{NN}}=200 GeV

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    Dihadron azimuthal correlations containing a high transverse momentum (\pt) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to \pp\ and \dAu\ collisions. The modification increases with the collision centrality, suggesting a path-length dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20-60\%) Au+Au collisions at \snn=200~GeV as a function of the trigger particle's azimuthal angle relative to the event plane, \phis=|\phit-\psiEP|. The azimuthal correlation is studied as a function of both the trigger and associated particle \pt. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (\zyam), are described. The away-side correlation is strongly modified, and the modification varies with \phis, which is expected to be related to the path-length that the away-side parton traverses. The pseudo-rapidity (\deta) dependence of the near-side correlation, sensitive to long range \deta correlations (the ridge), is also investigated. The ridge and jet-like components of the near-side correlation are studied as a function of \phis. The ridge appears to drop with increasing \phis while the jet-like component remains approximately constant. ...Comment: 50 pages, 39 figures, 6 table

    Longitudinal Spin Transfer to Λ\Lambda and Λˉ\bar{\Lambda} Hyperons in Polarized Proton-Proton Collisions at s\sqrt{s} = 200 GeV

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    The longitudinal spin transfer, DLLD_{LL}, from high energy polarized protons to Λ\Lambda and Λˉ\bar{\Lambda} hyperons has been measured for the first time in proton-proton collisions at s=200GeV\sqrt{s} = 200 \mathrm{GeV} with the STAR detector at RHIC. The measurements cover pseudorapidity, η\eta, in the range η<1.2|\eta| < 1.2 and transverse momenta, pTp_\mathrm{T}, up to 4GeV/c4 \mathrm{GeV}/c. The longitudinal spin transfer is found to be DLL=0.03±0.13(stat)±0.04(syst)D_{LL}= -0.03\pm 0.13(\mathrm{stat}) \pm 0.04(\mathrm{syst}) for inclusive Λ\Lambda and DLL=0.12±0.08(stat)±0.03(syst)D_{LL} = -0.12 \pm 0.08(\mathrm{stat}) \pm 0.03(\mathrm{syst}) for inclusive Λˉ\bar{\Lambda} hyperons with =0.5 = 0.5 and =3.7GeV/c = 3.7 \mathrm{GeV}/c. The dependence on η\eta and pTp_\mathrm{T} is presented.Comment: 5 pages, 4 figure

    Studying Parton Energy Loss in Heavy-Ion Collisions via Direct-Photon and Charged-Particle Azimuthal Correlations

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    Charged-particle spectra associated with direct photon (γdir\gamma_{dir} ) and π0\pi^0 are measured in pp+pp and Au+Au collisions at center-of-mass energy sNN=200\sqrt{s_{_{NN}}}=200 GeV with the STAR detector at RHIC. A hower-shape analysis is used to partially discriminate between γdir\gamma_{dir} and π0\pi^0. Assuming no associated charged particles in the γdir\gamma_{dir} direction (near side) and small contribution from fragmentation photons (γfrag\gamma_{frag}), the associated charged-particle yields opposite to γdir\gamma_{dir} (away side) are extracted. At mid-rapidity (η<0.9|\eta|<0.9) in central Au+Au collisions, charged-particle yields associated with γdir\gamma_{dir} and π0\pi^0 at high transverse momentum (8<pTtrig<168< p_{T}^{trig}<16 GeV/cc) are suppressed by a factor of 3-5 compared with pp + pp collisions. The observed suppression of the associated charged particles, in the kinematic range η<1|\eta|<1 and 3<pTassoc<163< p_{T}^{assoc} < 16 GeV/cc, is similar for γdir\gamma_{dir} and π0\pi^0, and independent of the γdir\gamma_{dir} energy within uncertainties. These measurements indicate that the parton energy loss, in the covered kinematic range, is insensitive to the parton path length.Comment: submitted to Phys. Rev. Lett, 6 pages, 4 figure

    K/pi Fluctuations at Relativistic Energies

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    We report results for K/πK/\pi fluctuations from Au+Au collisions at sNN\sqrt{s_{NN}} = 19.6, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. Our results for K/πK/\pi fluctuations in central collisions show little dependence on the incident energies studied and are on the same order as results observed by NA49 at the Super Proton Synchrotron in central Pb+Pb collisions at sNN\sqrt{s_{NN}} = 12.3 and 17.3 GeV. We also report results for the collision centrality dependence of K/πK/\pi fluctuations as well as results for K+/π+K^{+}/\pi^{+}, K/πK^{-}/\pi^{-}, K+/πK^{+}/\pi^{-}, and K/π+K^{-}/\pi^{+} fluctuations. We observe that the K/πK/\pi fluctuations scale with the multiplicity density, dN/dηdN/d\eta, rather than the number of participating nucleons.Comment: 6 pages, 4 figure
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