297 research outputs found

    Rapid acceptability and adherence testing of a lipid-based nutrient supplement and a micronutrient powder among refugee children and pregnant and lactating women in Algeria

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    OBJECTIVE: To assess the acceptability and adherence to daily doses of lipid-based nutrient supplement (LNS) among children and micronutrient powder (MNP) among children and pregnant and lactating women. DESIGN: Household interviews and sachet counting were conducted to measure acceptability and adherence, 15 and 30 d after product distribution. Qualitative information on product acceptability was collected using focus group discussions. SETTING: Saharawi refugee camps, Algeria, August-October 2009. SUBJECTS: LNS was distributed to 123 children aged 6-35 months (LNS-C), and MNP to 112 children aged 36-59 months (MNP-C) and 119 pregnant or lactating women (MNP-W). RESULTS: At the end of the test 98路4 % of LNS-C, 90路4 % of MNP-C and 75路5 % of MNP-W participants reported that they liked the product (P<0路05). Other measures of acceptability did not differ. Median consumption of sachets was highest in the LNS-C group (P<0路001). 'Good' adherence to the daily regimen (consumption of 75-125 % of recommended dose) was 89路1 % in the LNS-C, compared with 57路0 % in the MNP-C and 65路8 % in the MNP-W groups (P<0路001). Qualitative findings supported the quantitative measures and guided selection of local product names, packaging designs, distribution mechanisms, and the design of the information campaign in the subsequent programme scale-up. CONCLUSIONS: Acceptability, consumption and adherence were higher in participants receiving LNS compared with MNP. However, both products were found to be suitable when compared with predefined acceptability criteria. Acceptability studies are feasible and important in emergency nutrition programmes when the use of novel special nutritional products is considered

    Elimination of 0+0^+ spurious states in the quasiparticle time blocking approximation

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    The quasiparticle time blocking approximation (QTBA) is considered as a model for the description of excitations in open-shell nuclei. The QTBA is an extension of the quasiparticle random phase approximation that includes quasiparticle-phonon coupling. In the present version of the QTBA, the pairing correlations are included within the framework of the BCS approximation. Thus, in this model, the 0+0^+ spurious states appear, which are caused by the breaking of the symmetry related to the particle-number conservation. In this work, the method is described which solves the problem of the 0+0^+ spurious states in the QTBA with the help of the projection technique. The method is illustrated by calculations of 0+0^+ excitations in 120^{120}Sn nucleus.Comment: 12 pages, 3 figures - To appear in the proceedings of the 59-th International Meeting on Nuclear Spectroscopy and Nuclear Structure, June 15-19, 2009, Cheboksary, Russi

    On invariants of almost symplectic connections

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    We study the irreducible decomposition under Sp(2n, R) of the space of torsion tensors of almost symplectic connections. Then a description of all symplectic quadratic invariants of torsion-like tensors is given. When applied to a manifold M with an almost symplectic structure, these instruments give preliminary insight for finding a preferred linear almost symplectic connection on M . We rediscover Ph. Tondeur's Theorem on almost symplectic connections. Properties of torsion of the vectorial kind are deduced

    Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses

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    Starting with a two-body effective nucleon-nucleon interaction, it is shown that the infinite nuclear matter model of atomic nuclei is more appropriate than the conventional Bethe-Weizsacker like mass formulae to extract saturation properties of nuclear matter from nuclear masses. In particular, the saturation density thus obtained agrees with that of electron scattering data and the Hartree-Fock calculations. For the first time using nuclear mass formula, the radius constant r0r_0=1.138 fm and binding energy per nucleon ava_v = -16.11 MeV, corresponding to the infinite nuclear matter, are consistently obtained from the same source. An important offshoot of this study is the determination of nuclear matter incompressibility KK_{\infty} to be 288\pm 28 MeV using the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy. Rev. C

    Recent breakthroughs in Skyrme-Hartree-Fock-Bogoliubov mass formulas

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    We review our recent achievements in the construction of microscopic mass tables based on the Hartree-Fock-Bogoliubov method with Skyrme effective interactions. In the latest of our series of HFB-mass models, we have obtained our best fit ever to essentially all the available mass data, by treating the pairing more realistically than in any of our earlier models. The rms deviation on the 2149 measured masses of nuclei with N and Z>8 has been reduced for the first time in a mean field approach to 0.581 MeV. With the additional constraint on the neutron-matter equation of state, this new force is thus very well-suited for the study of neutron-rich nuclei and for the description of astrophysical environments like supernova cores and neutron-star crusts.Comment: Proceedings of the Fifth International Conference on Exotic Nuclei and Atomic Masses, September 7-13 2008, Ryn (Poland). To appear in the European Physical Journal

    RPA vs. exact shell-model correlation energies

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    The random phase approximation (RPA) builds in correlations left out by mean-field theory. In full 0-hbar-omega shell-model spaces we calculate the Hartree-Fock + RPA binding energy, and compare it to exact diagonalization. We find that in general HF+RPA gives a very good approximation to the ``exact'' ground state energy. In those cases where RPA is less satisfactory, however, there is no obvious correlation with properties of the HF state, such as deformation or overlap with the exact ground state wavefunction.Comment: 6 pages, 7 figures, submitted to Phys Rev

    Combinatorial nuclear level density by a Monte Carlo method

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    We present a new combinatorial method for the calculation of the nuclear level density. It is based on a Monte Carlo technique, in order to avoid a direct counting procedure which is generally impracticable for high-A nuclei. The Monte Carlo simulation, making use of the Metropolis sampling scheme, allows a computationally fast estimate of the level density for many fermion systems in large shell model spaces. We emphasize the advantages of this Monte Carlo approach, particularly concerning the prediction of the spin and parity distributions of the excited states, and compare our results with those derived from a traditional combinatorial or a statistical method. Such a Monte Carlo technique seems very promising to determine accurate level densities in a large energy range for nuclear reaction calculations.Comment: 30 pages, LaTex, 7 figures (6 Postscript figures included). Fig. 6 upon request to the autho

    Axially symmetric Hartree-Fock-Bogoliubov Calculations for Nuclei Near the Drip-Lines

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    Nuclei far from stability are studied by solving the Hartree-Fock-Bogoliubov (HFB) equations, which describe the self-consistent mean field theory with pairing interaction. Calculations for even-even nuclei are carried out on two-dimensional axially symmetric lattice, in coordinate space. The quasiparticle continuum wavefunctions are considered for energies up to 60 MeV. Nuclei near the drip lines have a strong coupling between weakly bound states and the particle continuum. This method gives a proper description of the ground state properties of such nuclei. High accuracy is achieved by representing the operators and wavefunctions using the technique of basis-splines. The detailed representation of the HFB equations in cylindrical coordinates is discussed. Calculations of observables for nuclei near the neutron drip line are presented to demonstrate the reliability of the method.Comment: 13 pages, 4 figures. Submitted to Physical Review C on 05/08/02. Revised on Dec/0

    The two-proton shell gap in Sn isotopes

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    We present an analysis of two-proton shell gaps in Sn isotopes. As the theoretical tool we use self-consistent mean-field models, namely the relativistic mean-field model and the Skyrme-Hartree-Fock approach, both with two different pairing forces, a delta interaction (DI) model and a density-dependent delta interaction (DDDI). We investigate the influence of nuclear deformation as well as collective correlations and find that both effects contribute significantly. Moreover, we find a further significant dependence on the pairing force used. The inclusion of deformation plus correlation effects and the use of DDDI pairing provides agreement with the data.Comment: gzipped tar archiv containing LaTeX source, bibliography file (*.bbl), all figures as *.eps, and the style file

    Shell structure of superheavy nuclei in self-consistent mean-field models

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    We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models -- the Skyrme-Hartree-Fock approach and the relativistic mean-field model -- using a large number of parameterizations. Results obtained with the Folded-Yukawa potential are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. While all relativistic models give a reasonable description of spin-orbit splittings, all non-relativistic models show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%-80%. Spherical doubly-magic superheavy nuclei are found at (Z=114,N=184), (Z=120,N=172) or (Z=126,N=184) depending on the parameterization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in Pb208. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for (Z=120,N=172) to be the next spherical doubly-magic superheavy nucleus.Comment: 22 pages REVTeX, 16 eps figures, accepted for publication in Phys. Rev.
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