79 research outputs found

    On the Relativistic Description of the Nucleus

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    We discuss a relativistic theory of the atomic nuclei in the framework of the hamiltonian formalism and of the mesonic model of the nucleus. Attention is paid to the translational invariance of the theory. Our approach is centered on the concept of spectral amplitude, a function in the Dirac spinor space. We derive a Lorentz covariant equation for the latter, which requires as an input the baryon self-energy. For this we either postulate the most general Lorentz-Poincar\'e invariant expression or perform a calculation via a Bethe-Salpeter equation starting from a nucleon-nucleus interaction. We discuss the features of the nuclear spectrum obtained in the first instance. Finally the general constraints the self-energy should satisfy because of analyticity and Poincar\'e covariance are discussed

    Role of the Nuclear and Electromagnetic Interactions in the Coherent Dissociation of the Relativistic 7^7Li Nucleus into the 3^3H + 4^4He Channel

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    The differential cross section in the transverse momentum QQ and a total cross section of (31±4)(31\pm4) mb for the coherent dissociation of a 3-A-GeV/cc 7^7Li nucleus through the 3^3H+4+^4He channel have been measured on emulsion nuclei. The observed QQ dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction (Q400Q\le400 MeV/cc) and Coulomb (Q50(Q\le50 MeV/cc) dissociations are calculated to be 40.7 and 4 mb, respectively.Comment: ISSN 0021-3640, Pleiades Publishing, Ltd., 200

    Effects of Short Range Correlations on Ca Isotopes

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    The effect of Short Range Correlations (SRC) on Ca isotopes is studied using a simple phenomenological model. Theoretical expressions for the charge (proton) form factors, densities and moments of Ca nuclei are derived. The role of SRC in reproducing the empirical data for the charge density differences is examined. Their influence on the depletion of the nuclear Fermi surface is studied and the fractional occupation probabilities of the shell model orbits of Ca nuclei are calculated. The variation of SRC as function of the mass number is also discussed.Comment: 11 pages (RevTex), 6 Postscript figures available upon request at [email protected] Physical Review C in prin

    Microscopic theories of neutrino-^{12}C reactions

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    In view of the recent experiments on neutrino oscillations performed by the LSND and KARMEN collaborations as well as of future experiments, we present new theoretical results of the flux averaged 12C(νe,e)12N^{12}C(\nu_e,e^-)^{12}N and 12C(νμ,μ)12N^{12}C(\nu_{\mu},{\mu}^-)^{12}N cross sections. The approaches used are charge-exchange RPA, charge-exchange RPA among quasi-particles (QRPA) and the Shell Model. With a large-scale shell model calculation the exclusive cross sections are in nice agreement with the experimental values for both reactions. The inclusive cross section for νμ\nu_{\mu} coming from the decay-in-flight of π+\pi^+ is 15.2×1040cm215.2 \times 10^{-40} cm^2 to be compared to the experimental value of 12.4±0.3±1.8×1040cm212.4 \pm 0.3 \pm 1.8 \times 10^{-40} cm^2, while the one due to νe\nu_{e} coming from the decay-at-rest of μ+\mu^+ is 16.4×1042cm216.4 \times 10^{-42} cm^2 which agrees within experimental error bars with the measured values. The shell model prediction for the decay-in-flight neutrino cross section is reduced compared to the RPA one. This is mainly due to the different kind of correlations taken into account in the calculation of the spin modes and partially due to the shell-model configuration basis which is not large enough, as we show using arguments based on sum-rules.Comment: 17 pages, latex, 5 figure

    Estimating the Capacity for ART Provision in Tanzania with the Use of Data on Staff Productivity and Patient Losses

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    BACKGROUND: International targets for access to antiretroviral therapy (ART) have over-estimated the capacity of health systems in low-income countries in Sub-Saharan Africa. The WHO target for number on treatment by end 2005 for Tanzania was 10 times higher than actually achieved. The target of the national Care and Treatment Plan (CTP) was also not reached. We aimed at estimating the capacity for ART provision and created five scenarios for ART production given existing resource limitations. METHODS: A situation analysis including scrutiny of staff factors, such as available data on staff and patient factors including access to ART and patient losses, made us conclude that the lack of clinical staff is the main limiting factor for ART scale-up, assuming that sufficient drugs and supplies are provided by donors. We created a simple formula to estimate the number of patients on ART based on availability and productivity of clinical staff, time needed to initiate vs maintain a patient on ART and patient losses using five different scenarios with varying levels of these parameters. FINDINGS: Our scenario assuming medium productivity (40% higher than that observed in 2002) and medium loss of patients (20% in addition to 15% first-year mortality) coincides with the actual reported number of patients initiated on ART up to 2008, but is considerably below the national CTP target of 90% coverage for 2009, corresponding to 420,000 on ART and 710,000 life-years saved (LY's). Our analysis suggests that a coverage of 40% or 175,000 on treatment and 350,000 LY's saved is more achievable. CONCLUSION: A comparison of our scenario estimations and actual output 2006-2008 indicates that a simple user-friendly dynamic model can estimate the capacity for ART scale-up in resource-poor settings based on identification of a limiting staff factor and information on availability of this staff and patient losses. Thus, it is possible to set more achievable targets

    Economic Support to Patients in HIV and TB Grants in Rounds 7 and 10 from the Global Fund to Fight AIDS, Tuberculosis and Malaria.

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    People with TB and/or HIV frequently experience severe economic barriers to health care, including out-of-pocket expenses related to diagnosis and treatment, as well as indirect costs due to loss of income. These barriers can both aggravate economic hardship and prevent or delay diagnosis, treatment and successful outcome, leading to increased transmission, morbidity and mortality. WHO, UNAIDS and the ILO argue that economic support of various kinds is essential to enable vulnerable people to protect themselves from infection, avoid delayed diagnosis and treatment, overcome barriers to adherence, and avert destitution. This paper analyses successful country proposals to the Global Fund to Fight AIDS, Tuberculosis and Malaria that include economic support in Rounds 7 and 10; 36 and 20 HIV and TB grants in Round 7 and 32 and 26, respectively, in Round 10. Of these, up to 84 percent included direct or indirect economic support for beneficiaries, although the amount constituted a very small proportion of the total grant. In TB grants, the objectives of economic support were generally clearly stated, and focused on mechanisms to improve treatment uptake and adherence, and the case was most clearly made for MDR-TB patients. In HIV grants, the objectives were much broader in scope, including mitigation of adverse economic and social effects of HIV and its treatment on both patients and families. The analysis shows that economic support is on the radar for countries developing Global Fund proposals, and a wide range of economic support activities are in place. In order to move forward in this area, the wealth of country experience that exists needs to be collated, assessed and disseminated. In addition to trials, operational research and programme evaluations, more precise guidance to countries is needed to inform evidence-based decision about activities that are cost-effective, affordable and feasible
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