1,092 research outputs found

    UMIS & urban habilitation in Venezuela

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    The paper describes the Urban Management Information System (UMIS) designed to monitor and evaluated the execution of the Actions and Investments Program (AIP) elaborate with the actors implied in the urban HABILITATION of neighbourhoods, policy implemented by the National Housing Counsel (CONAVI) in Venezuela. This Geographical Information and Territorial Management System, permits the visualization and recognition of the plan’s advance through the execution of the AIP and makes possible the application of corrective actions to achieve a sustainable habitat, all of which impacts positively the quality of life in poor neighbourhoods, the urban agents legitimacy and the local gobernability.Peer Reviewe

    Relativistic analysis of the 208Pb(e,e'p)207Tl reaction at high momentum

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    The recent 208Pb(e,e'p)207Tl data from NIKHEF-K at high missing momentum (p_m>300 MeV/c) are compared to theoretical results obtained with a fully relativistic formalism previously applied to analyze data on the low missing momentum (p_m < 300 MeV/c) region. The same relativistic optical potential and mean field wave functions are used in the two p_m-regions. The spectroscopic factors of the various shells are extracted from the analysis of the low-p_m data and then used in the high-p_m region. In contrast to previous analyses using a nonrelativistic mean field formalism, we do not find a substantial deviation from the mean field predictions other than that of the spectroscopic factors, which appear to be consistent with both low- and high-p_m data. We find that the difference between results of relativistic and nonrelativistic formalisms is enhanced in the p_m<0 region that will be interesting to explore experimentally.Comment: 12 pages, LaTeX+Revtex, included 3 postscript figures. To appear in the Physical Review C (Rapid Communications

    Saturation properties of nuclear matter in a relativistic mean field model constrained by the quark dynamics

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    We have built an effective Walecka-type hadronic Lagrangian in which the hadron masses and the density dependence of the coupling constants are deduced from the quark dynamics using a Nambu-Jona-Lasinio model. In order to stabilize nuclear matter an eight-quark term has been included. The parameters of this Nambu-Jona-Lasinio model have been determined using the meson properties in the vacuum but also in the medium through the omega meson mass in nuclei measured by the TAPS collaboration. Realistic properties of nuclear matter have been obtained.Comment: 14 pages, 2 figures, submitted to Nuclear Physics

    Relativistic versus Nonrelativistic Optical Potentials in A(e,e'p)B Reactions

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    We investigate the role of relativistic and nonrelativistic optical potentials used in the analysis of (e,epe,e'p) data. We find that the relativistic calculations produce smaller (e,epe,e'p) cross sections even in the case in which both relativistic and nonrelativistic optical potentials fit equally well the elastic proton--nucleus scattering data. Compared to the nonrelativistic impulse approximation, this effect is due to a depletion in the nuclear interior of the relativistic nucleon current, which should be taken into account in the nonrelativistic treatment by a proper redefinition of the effective current operator.Comment: Added one new figure, the formalism section has been enlarged and the list of references updated. Added one appendix. This version will appear in Phys. Rev. C. Revtex 3.0, 6 figures (not included). Full postscript version of the file and figures available at http://www.nikhefk.nikhef.nl/projects/Theory/preprints

    Spectroscopic Factors in 40^{40}Ca and 208^{208}Pb from (e,ep)(e,e'p): Fully Relativistic Analysis

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    We present results for spectroscopic factors of the outermost shells in 40^{40}Ca and 208^{208}Pb, which have been derived from the comparison between the available quasielastic (e,epe,e'p) data from NIKHEF-K and the corresponding calculated cross-sections obtained within a fully relativistic formalism. We include exactly the effect of Coulomb distortion on the electron wave functions and discuss its role in the extraction of the spectroscopic factors from experiment. Without any adjustable parameter, we find spectroscopic factors of about 70\%, consistent with theoretical predictions. We compare our results with previous relativistic and nonrelativistic analyses of (e,epe,e'p) data. In addition to Coulomb distortion effects we discuss different choices of the nucleon current operator and also analyze the effects due to the relativistic treatment of the outgoing-distorted and bound nucleon wave functions.Comment: 9 pages RevTeX, 5 figures can be obtained from the author

    UMIS & urban habilitation in Venezuela

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    The paper describes the Urban Management Information System (UMIS) designed to monitor and evaluated the execution of the Actions and Investments Program (AIP) elaborate with the actors implied in the urban HABILITATION of neighbourhoods, policy implemented by the National Housing Counsel (CONAVI) in Venezuela. This Geographical Information and Territorial Management System, permits the visualization and recognition of the plan’s advance through the execution of the AIP and makes possible the application of corrective actions to achieve a sustainable habitat, all of which impacts positively the quality of life in poor neighbourhoods, the urban agents legitimacy and the local gobernability.Peer Reviewe

    Optimization of Phenolic Antioxidant Extraction from Wuweizi (Schisandra chinensis) Pulp Using Random-Centroid Optimazation Methodology

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    The extraction optimization and composition analysis of polyphenols in the fresh pulp of Wuweizi (Schisandra chinensis) have been investigated in this study. The extraction process of polyphenols from Wuweizi pulp was optimized using Random-Centroid Optimization (RCO) methodology. Six factors including liquid and solid ratio, ethanol concentration, pH, temperature, heating time and extraction times, and three extraction targets of polyphenol content, antioxidant activity and extract yield were considered in the RCO program. Three sets of optimum proposed factor values were obtained corresponding to three extraction targets respectively. The set of optimum proposed factor values for polyphenol extraction given was chosen in further experiments as following: liquid and solid ratio (v/w) 8, ethanol 67.3% (v/v), initial pH 1.75, temperature 55 °C for 4 h and extraction repeated for 4 times. The Wuweizi polyphenol extract (WPE) was obtained with a yield of 16.37 mg/g and composition of polyphenols 1.847 mg/g, anthocyanins 0.179 mg/g, sugar 9.573 mg/g and protein 0.327 mg/g. The WPE demonstrated high scavenging activities against DPPH radicals

    Self-consistent Green's function method for nuclei and nuclear matter

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    Recent results obtained by applying the method of self-consistent Green's functions to nuclei and nuclear matter are reviewed. Particular attention is given to the description of experimental data obtained from the (e,e'p) and (e,e'2N) reactions that determine one and two-nucleon removal probabilities in nuclei since the corresponding amplitudes are directly related to the imaginary parts of the single-particle and two-particle propagators. For this reason and the fact that these amplitudes can now be calculated with the inclusion of all the relevant physical processes, it is useful to explore the efficacy of the method of self-consistent Green's functions in describing these experimental data. Results for both finite nuclei and nuclear matter are discussed with particular emphasis on clarifying the role of short-range correlations in determining various experimental quantities. The important role of long-range correlations in determining the structure of low-energy correlations is also documented. For a complete understanding of nuclear phenomena it is therefore essential to include both types of physical correlations. We demonstrate that recent experimental results for these reactions combined with the reported theoretical calculations yield a very clear understanding of the properties of {\em all} protons in the nucleus. We propose that this knowledge of the properties of constituent fermions in a correlated many-body system is a unique feature of nuclear physics.Comment: 110 pages, accepted for publication on Prog. Part. Nucl. Phy

    Quaiselastic scattering from relativistic bound nucleons: Transverse-Longitudinal response

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    Predictions for electron induced proton knockout from the p1/2p_{1/2} and p3/2p_{3/2} shells in 16^{16}O are presented using various approximations for the relativistic nucleonic current. Results for the differential cross section, transverse-longitudinal response (RTLR_{TL}) and left-right asymmetry ATLA_{TL} are compared at Q2=0.8|Q^2|=0.8 (GeV/c)2^2 corresponding to TJNAF experiment 89-003. We show that there are important dynamical and kinematical relativistic effects which can be tested by experiment.Comment: 10 pages, including 2 figures. Removed preliminary experimental data from the figure

    Axion monodromy in a model of holographic gluodynamics

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    The low energy field theory for N type IIA D4-branes at strong 't Hooft coupling, wrapped on a circle with antiperiodic boundary conditions for fermions, is known to have a vacuum energy which depends on the θ\theta angle for the gauge fields, and which is a multivalued function of this angle. This gives a field-theoretic realization of "axion monodromy" for a nondynamical axion. We construct the supergravity solution dual to the field theory in the metastable state which is the adiabatic continuation of the vacuum to large values of θ\theta. We compute the energy of this state and show that it initially rises quadratically and then flattens out. We show that the glueball mass decreases with θ\theta, becoming much lower than the 5d KK scale governing the UV completion of this model. We construct two different classes of domain walls interpolating between adjacent vacua. We identify a number of instability modes -- nucleation of domain walls, bulk Casimir forces, and condensation of tachyonic winding modes in the bulk -- which indicate that the metastable branch eventually becomes unstable. Finally, we discuss two phenomena which can arise when the axion is dynamical; axion-driven inflation, and axion strings.Comment: 43 pages, 10 figures. v2: references update
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