264 research outputs found

    The origin of aubrites: Evidence from lithophile trace element abundances and oxygen isotope compositions

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    We report the abundances of a selected set of “lithophile” trace elements (including lanthanides, actinides and high field strength elements) and high-precision oxygen isotope analyses of a comprehensive suite of aubrites. Two distinct groups of aubrites can be distinguished: (a) the main-group aubrites display flat or light-REE depleted REE patterns with variable Eu and Y anomalies; their pyroxenes are light-REE depleted and show marked negative Eu anomalies; (b) the Mount Egerton enstatites and the silicate fraction from Larned display distinctive light-REE enrichments, and high Th/Sm ratios; Mount Egerton pyroxenes have much less pronounced negative Eu anomalies than pyroxenes from the main-group aubrites. Leaching experiments were undertaken to investigate the contribution of sulfides to the whole rock budget of the main-group aubrites. Sulfides contain in most cases at least 50% of the REEs and of the actinides. Among the elements we have analyzed, those displaying the strongest lithophile behaviors are Rb, Ba, Sr and Sc. The homogeneity of the Δ17O values obtained for main-group aubrite falls [Δ17O = +0.009 ± 0.010‰ (2σ)] suggests that they originated from a single parent body whose differentiation involved an early phase of large-scale melting that may have led to the development of a magma ocean. This interpretation is at first glance in agreement with the limited variability of the shapes of the REE patterns of these aubrites. However, the trace element concentrations of their phases cannot be used to discuss this hypothesis, because their igneous trace-element signatures have been modified by subsolidus exchange. Finally, despite similar O isotopic compositions, the marked light-REE enrichments displayed by Mount Egerton and Larned suggest that they are unrelated to the main-group aubrites and probably originated from a distinct parent body

    An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

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    For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types

    Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

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    Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

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    We present the first measurement of directed flow (v1v_1) at RHIC. v1v_1 is found to be consistent with zero at pseudorapidities η\eta from -1.2 to 1.2, then rises to the level of a couple of percent over the range 2.4<η<42.4 < |\eta| < 4. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

    Azimuthal anisotropy: the higher harmonics

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    We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding

    All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

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    We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio

    Strange Resonance Production in p+p and Au+Au Collisions at RHIC Energies

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    Resonance yields and spectra from elementary p+p and Au+Au collisions at sNN=\sqrt{s_{\rm NN}} = 200 GeV from the STAR experiment at RHIC are presented and discussed in terms of chemical and thermal freeze-out conditions. Thermal models do not adequately describe the yields of the resonance production in central Au+Au collisions. The approach to include elastic hadronic interactions between chemical freeze-out and thermal freeze-out suggests a time of Δτ>\Delta \tau>5 fm/c.Comment: 4 pages, 7 figures, proceedings of the Quark Matter 2004, in Oakland, California, to be published in Journal of Physics G: Nuclear and Particle Physic

    Identified particles at large transverse momenta in STAR in Au+Au collisions @ sqrt(s_NN) = 200 GeV

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    We report measurements of the ratios of identified hadrons (pi,K,p,Lambda) in Au+Au collisions at sqrt(s_NN) = 200 GeV as a function of both collision centrality and transverse momentum (p_T). Ratios of anti-baryon to baryon yields are independent of p_T within 2<p_T <6 GeV/c indicating that, for such a range, our measurements are inconsistent with theoretical pQCD calculations predicting a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, a strong baryon enhancement relative to meson yields is observed as a function of collision centrality in this intermediate p_T region, leading to p/pi and Lambda/K ratios greater than unity. The nuclear modification factor, R_cp (central relative to peripheral collisions), is used to illustrate the interplay between jet quenching and hadron production. The physics implications of these measurements are discussed with reference to different theoretical models.Comment: 5 pages, 4 figures. Proceedings of Quark Matter 2004 Conference, Jan 2004, Oakland, USA. Submitted to Journal of Physics

    High-pTp_{T} electron distributions in d+Au and p+p collisions at RHIC

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    We present preliminary measurements of electron and positron spectra in d+Au and p+p collisions at sNN=200\sqrt{s_{NN}}=200 GeV for 1.5<pT<7.01.5 < p_{T} < 7.0 GeV/c. These measurements were carried out using the STAR Time Projection Chamber (TPC) and the Barrel Electromagnetic calorimeter (EMC). Overall hadron rejection factors in the range of 10510^{5} have been achieved. In this work we describe the measurement technique used to discriminate electrons from hadrons and compare the results for single electron spectra with Pythia based pQCD calculations for electrons from heavy-quark semi-leptonic decays.Comment: Quark Matter 2004 conference proceeding

    Correlations and Fluctuations in STAR

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    We report measurements for the balance function, transverse momentum fluctuations, and net charge fluctuations from Au+Au collisions at 20, 130, and 200 GeV as well as p+p and d+Au collisions at 200 GeV using STAR at RHIC. For Au+Au collisions at 200 GeV, we observe a narrowing of the balance function in central collisions. We observe dynamic transverse momentum fluctuations at all incident energies. Observables related to transverse momentum fluctuations and net charge fluctuations are similar for peripheral Au+Au collisions and inclusive p+p collisions while central Au+Au collisions deviate significantly from HIJING predictions.Comment: 4 pages, 3 figures, Contribution to Quark Matter 2004 Proceeding
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