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

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 98·4 % of LNS-C, 90·4 % of MNP-C and 75·5 % of MNP-W participants reported that they liked the product (P<0·05). Other measures of acceptability did not differ. Median consumption of sachets was highest in the LNS-C group (P<0·001). 'Good' adherence to the daily regimen (consumption of 75-125 % of recommended dose) was 89·1 % in the LNS-C, compared with 57·0 % in the MNP-C and 65·8 % in the MNP-W groups (P<0·001). 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 $0^+$ spurious states in the quasiparticle time blocking approximation

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 $0^+$ 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 $0^+$ spurious
states in the QTBA with the help of the projection technique. The method is
illustrated by calculations of $0^+$ excitations in $^{120}$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

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

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 $r_0$=1.138 fm and binding energy per nucleon $a_v$ = -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 $K_{\infty}$ 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

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

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

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

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

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

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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