263 research outputs found

    Neutrons from 9Be/alpha,n/ reaction for E alpha between 6 and 10 MeV

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    Neutron energy spectra measured as function of neutron emission angle and ion bombardment energ

    Calculations of three-body observables in ^8B breakup

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    We discuss calculations of three-body observables for the breakup of ^8B on a ^{58}Ni target at low energy using the coupled discretised continuum channels approach. Calculations of both the angular distribution of the ^7Be fragments and their energy distributions are compared with those measured at several laboratory angles. In these observables there is interference between the breakup amplitudes from different spin-parity excitations of the projectile. The resulting angle and the energy distributions reveal the importance of the higher-order continuum state couplings for an understanding of the measurements.Comment: 22 pages (postscript), accepted in Phys. Rev.

    A Microscopic T-Violating Optical Potential: Implications for Neutron-Transmission Experiments

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    We derive a T-violating P-conserving optical potential for neutron-nucleus scattering, starting from a uniquely determined two-body ρ\rho-exchange interaction with the same symmetry. We then obtain limits on the T-violating ρ\rho-nucleon coupling gρ\overline{g}_{\rho} from neutron-transmission experiments in 165^{165}Ho. The limits may soon compete with those from measurements of atomic electric-dipole moments.Comment: 8 pages, 2 uuencoded figures in separate files (replaces version sent earlier in the day with figures attached), in RevTeX 3, submitted to PR

    Many-body effects in 16O(e,e'p)

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    Effects of nucleon-nucleon correlations on exclusive (e,ep)(e,e'p) reactions on closed-shell nuclei leading to single-hole states are studied using 16O(e,ep)15N^{16}O(e,e'p)^{15}N (6.326.32 MeV, 3/23/2^-) as an example. The quasi-hole wave function, calculated from the overlap of translationally invariant many-body variational wave functions containing realistic spatial, spin and isospin correlations, seems to describe the initial state of the struck proton accurately inside the nucleus, however it is too large at the surface. The effect of short-range correlations on the final state is found to be largely cancelled by the increase in the transparency for the struck proton. It is estimated that the values of the spectroscopic factors obtained with the DWIA may increase by a few percent due to correlation effects in the final state.Comment: 21 Pages, PHY-7849-TH-9

    Sequential administration of temozolomide and fotemustine: Depletion of O6-alkyl guanine-DNA transferase in blood lymphocytes and in tumours

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    Background: The DNA repair protein O6-alkylguanine-DNA alkyl transferase (AT) mediates resistance to chloroethylnitro-soureas. Agents depleting AT such as DTIC and its new analogue temozolomide (TMZ) can reverse resistance to chloro-ethylnitrosoureas. We report the results of a dose finding study of TMZ in association with fotemustine. Patients and methods: Twenty-four patients with metastatic melanoma or recurrent glioma were treated with escalating dose of oral or intravenous TMZ ranging from 300 to 700 mg/m2, divided over two days. Fotemustine 100 mg/m2 was given intravenously on day 2, 4 hours after TMZ. AT depletion was measured in peripheral blood mononuclear cells (PBMCs) and in selected cases in melanoma metastases and was compared to TMZ pharmacokinetics. Results: The maximum tolerated dose (MTD) of TMZ was 400 mg/m2 (200 mg/m2/d) when associated with fotemustine the 2nd day with myelosuppression as dose limiting toxicity. The decrease of AT level in PBMCs was progressive and reached 34% of pretreatment values on day 2. There was however wide interindividual variability. AT reduction was neither dose nor route dependent and did not appear to be related to TMZ systemic exposure (AUC). In the same patients, AT depletion in tumour did not correlate with the decrease of AT observed in PBMCs. Conclusions: PBMCs may not be used as a surrogate of tumour for AT depletion. Further study should concentrate on the pharmacokinetic pharmacodynamic relationship in tumour to provide the basis for individually tailored therap

    Nuclear Transparency to Intermediate-Energy Protons

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    Nuclear transparency in the (e,e'p) reaction for 135 < Tp < 800 MeV is investigated using the distorted wave approximation. Calculations using density-dependent effective interactions are compared with phenomenological optical potentials. Nuclear transparency is well correlated with proton absorption and neutron total cross sections. For Tp < 300 MeV there is considerable sensitivity to the choice of optical model, with the empirical effective interaction providing the best agreement with transparency data. For Tp > 300 MeV there is much less difference between optical models, but the calculations substantially underpredict transparency data and the discrepancy increases with A. The differences between Glauber and optical model calculations are related to their respective definitions of the semi-inclusive cross section. By using a more inclusive summation over final states the Glauber model emphasizes nucleon-nucleon inelasticity, whereas with a more restrictive summation the optical model emphasizes nucleon-nucleus inelasticity; experimental definitions of the semi-inclusive cross section lie between these extremes.Comment: uuencoded gz-compressed tar file containing revtex and bbl files and 5 postscript figures, totalling 31 pages. Uses psfi
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