223 research outputs found

    Cumulative structure function in terms of nucleonic wave function of the nucleus

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    The structure function of the nucleus in the cumulative region x>1x>1 is studied in terms of nucleon degrees of freedom. At high Q2Q^2 the resulting expressions are presented as a sum of contributions from few-nucleon correlations. Two-nucleon correlations are studied in some detail. Spin variables are averaged out. In the region 1<x<21<x<2 the structure functions are calculated for the relativistic interaction proposed by F.Gross {\it et al}. They are found to fall with xx faster than the exponential. For Carbon at x=1.05x=1.05, where the method is not rigorously applicable, they turn out to be rougly twice larger than the experimental data.Comment: text and 2 figures in LaTex, 7 figures in P

    Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

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    The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C) in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization (in horizontal direction). The formed films produce intensive photoluminescence (PL) with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO2 defected interface layers

    High temperature measurements and condensed matter analysis of the thermo-physical properties of ThO2

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    Values are presented for thermal conductivity, specific heat, spectral and total hemispherical emissivity of ThO2 (a potential nuclear fuel material) in a temperature range representative of a nuclear accident - 2000 K to 3050 K. For the first time direct measurements of thermal conductivity have been carried out on ThO2 at such high temperatures, clearly showing the property does not decrease above 2000 K. This could be understood in terms of an electronic contribution (arising from defect induced donor/acceptor states) compensating the degradation of lattice thermal conductivity. The increase in total hemispherical emissivity and visible/near-infrared spectral emissivity is consistent with the formation of donor/acceptor states in the band gap of ThO2. The electronic population of these defect states increases with temperature and hence more incoming photons (in the visible and near-infrared wavelength range) can be absorbed. A solid state physics model is used to interpret the experimental results. Specific heat and thermal expansion coefficient increase at high temperatures due to the formation of defects, in particular oxygen Frenkel pairs. Prior to melting a gradual increase to a maximum value is predicted in both properties. These maxima mark the onset of saturation of oxygen interstitial sites

    A Pair Polarimeter for Linearly Polarized High Energy Photons

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    A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first results of a polarimeter test on the laser back-scattering photon beam at SPring-8/LEPS are presented

    Phase Ib study of CP-868,596, a PDGFR inhibitor, combined with docetaxel with or without axitinib, a VEGFR inhibitor

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    BACKGROUND: Tumoural interstitial hypertension, possibly modulated by platelet-derived and vascular endothelial growth factor receptors (PDGFR and VEGFR), may mediate resistance to chemotherapy. METHODS: Forty-eight patients with advanced solid tumours received oral PDGFR inhibitor CP-868,596 (60-100 mg twice daily (BID)) and docetaxel (75-100 mg m⁻²), or CP-868,596 (60 mg BID), docetaxel (75 mg m⁻²), and VEGFR inhibitor axitinib (5 mg BID). RESULTS: The CP-868,596/docetaxel was escalated as above. The CP-868,596/docetaxel/axitinib was not dose escalated because of increased incidence of mucositis-like adverse events (AEs) with concurrent neutropenia relative to that expected for docetaxel. All tested regimens were tolerable, including 100 mg BID CP-868,596 (recommended phase II dose) plus 100 mg m⁻² docetaxel (maximum approved dose). Most treatment-emergent AEs were mild-moderate and reversible, commonly including nausea, diarrhoea, vomiting, constipation, fatigue, and anaemia (CP-868,596/docetaxel), and hypertension, lethargy, diarrhoea, and fatigue (CP-868,596/docetaxel/axitnib). Pharmacokinetics were unaffected by co-administration. Twenty-one patients achieved stable disease, including all seven evaluable on CP-868,596/docetaxel/axitinib. All nine CP-868,596/docetaxel/axitinib patients received therapy for a median of six (range, 3-16) cycles. CONCLUSIONS: The CP-868,596/docetaxel was well tolerated, but increased efficacy was not observed. Addition of axitinib delivered greater benefits than expected in the number of patients achieving prolonged stable disease with a moderate increase in AEs

    Compton Scattering Cross Section on the Proton at High Momentum Transfer

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    Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical accuracy of a few percent. The scaling power for the s-dependence of the cross section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.Comment: 5 pages, 5 figure

    Cross Section Measurement of Charged Pion Photoproduction from Hydrogen and Deuterium

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    We have measured the differential cross section for the gamma n --> pi- p and gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon energies greater than 3.3 GeV exhibit a global scaling behavior for both pi- and pi+ photoproduction, consistent with the constituent counting rule and the existing pi+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi- to pi+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams
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