351 research outputs found
Relativistic Ring-Diagram Nuclear Matter Calculations
A relativistic extension of the particle-particle hole-hole ring-diagram
many-body formalism is developed by using the Dirac equation for
single-particle motion in the medium. Applying this new formalism, calculations
are performed for nuclear matter. The results show that the saturation density
is improved and the equation of state becomes softer as compared to
corresponding Dirac-Brueckner-Hartree-Fock calculations. Using the Bonn A
potential, nuclear matter is predicted to saturate at an energy per nucleon of
--15.30 MeV and a density equivalent to a Fermi momentum of 1.38 fm, in
excellent agreement with empirical information. The compression modulus is 152
MeV at the saturation point.Comment: 23 pages text (LaTex) and 2 figures (paper, will be faxed upon
request), UI-NTH-92-0
Common determinants of dental caries and obesity in children : a multi-ethnic nested birth cohort study in the United Kingdom
The article examines the common determinants of childhood dental caries and obesity. Longitudinal data from the Born in Bradford cohort study (BiB1000) (n = 1735) and dental data (dental general anaesthetics (GA) and oral health survey 2014/15) (n = 171) were used to test a framework on the social determinants of childhood dental caries (decayed, missing, filled teeth (dmft) index) and obesity (body mass index (BMI)). The BiB1000 data were collected at pregnancy week 26â28 and after birth at 6, 12, 18, 24 and 36 months. The determinants were demographics, wellbeing, socio-economic status (SES), dietary behaviours and physical activity behaviour of the children. Missing data were accounted for through multiple imputation (MI). The framework was tested through structural equation modelling. Overall, the model fit was adequate. No alcohol consumption of the mother after giving birth, higher frequency of child drinking sugar-sweetened beverages, emotional and behavioural difficulties of the child and being male were directly associated with both BMI and dental caries. Caregivers uninvolved or indulgent feeding style were associated with higher BMI and less dental caries. Social deprivation was associated with lower BMI and higher dmft. Five determinants were directly associated with BMI only. Fifteen indirect paths were significant for both child dental caries and BMI. The findings suggest common determinants for both childhood obesity and dental caries. Common risk factor approach seems appropriate for planning future health promotion programmes
Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces
We discuss two different approximation schemes for the self-consistent
solution of the {\it relativistic} Brueckner-Hartree-Fock equation for finite
nuclei. In the first scheme, the Dirac effects are deduced from corresponding
nuclear matter calculations, whereas in the second approach the local-density
approximation is used to account for the effects of correlations. The results
obtained by the two methods are very similar. Employing a realistic
one-boson-exchange potential (Bonn~A), the predictions for energies and radii
of O and Ca come out in substantially better agreement with
experiment as compared to non-relativistic approaches. As a by-product of our
study, it turns out that the Fock exchange-terms, ignored in a previous
investigation, are not negligible.Comment:
Predictions for the 4 GeV TJNAF inclusive electron scattering experiment and for FSI effects in EMC ratios
We express nuclear structure functions as generalized convolutions of
the structure function of a nucleon and of a nucleus, composed of
point-nucleons. In computations of the latter we include Final State
Interactions and results for are compared with a few directly measured
data on C and Fe. The above are primarily used for predictions of the
TJNAF 89-008 inclusive scattering experiment of 4 GeV electrons on various
targets. Those cover a broad angular, and correspondingly wide range,
where the nucleon-inelastic part dominates large sections of the covered
kinematics. The same model has been applied to the study of hitherto neglected
Final State Interaction effects in the nuclear component in EMC ratios in the
region .Comment: 12 page
Rigidity percolation in a field
Rigidity Percolation with g degrees of freedom per site is analyzed on
randomly diluted Erdos-Renyi graphs with average connectivity gamma, in the
presence of a field h. In the (gamma,h) plane, the rigid and flexible phases
are separated by a line of first-order transitions whose location is determined
exactly. This line ends at a critical point with classical critical exponents.
Analytic expressions are given for the densities n_f of uncanceled degrees of
freedom and gamma_r of redundant bonds. Upon crossing the coexistence line, n_f
and gamma_r are continuous, although their first derivatives are discontinuous.
We extend, for the case of nonzero field, a recently proposed hypothesis,
namely that the density of uncanceled degrees of freedom is a ``free energy''
for Rigidity Percolation. Analytic expressions are obtained for the energy,
entropy, and specific heat. Some analogies with a liquid-vapor transition are
discussed. Particularizing to zero field, we find that the existence of a
(g+1)-core is a necessary condition for rigidity percolation with g degrees of
freedom. At the transition point gamma_c, Maxwell counting of degrees of
freedom is exact on the rigid cluster and on the (g+1)-rigid-core, i.e. the
average coordination of these subgraphs is exactly 2g, although gamma_r, the
average coordination of the whole system, is smaller than 2g. gamma_c is found
to converge to 2g for large g, i.e. in this limit Maxwell counting is exact
globally as well. This paper is dedicated to Dietrich Stauffer, on the occasion
of his 60th birthday.Comment: RevTeX4, psfig, 16 pages. Equation numbering corrected. Minor typos
correcte
Muscular Torque Can Explain Biases in Haptic Length Perception: A Model Study on the Radial-Tangential Illusion
Special and inclusive education in the Republic of Ireland: reviewing the literature from 2000 to 2009
Provision for pupils with special educational needs in Ireland has undergone considerable change and review in the first decade of the twenty first century. In response to international demands for a more equitable education system which recognises diversity and considers how schools might address the needs of pupils who have been previously marginalised, Irish legislation has focused upon the development of inclusive schooling. Researchers during this period have endeavoured to understand how responses to the demand for greater inclusion have impacted upon the perceived need for change. This paper reviews the research literature for this period and identifies four key themes under which research has been conducted. The literature pertaining to these themes is explored and a possible agenda for future researchers identifie
Measurement of the Nucleon Structure Function F2 in the Nuclear Medium and Evaluation of its Moments
We report on the measurement of inclusive electron scattering off a carbon
target performed with CLAS at Jefferson Laboratory. A combination of three
different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an
invariant mass of the final-state hadronic system W~2.4 GeV with four-momentum
transfers Q2 ranging from 0.2 to 5 GeV2. These data, together with previous
measurements of the inclusive electron scattering off proton and deuteron,
which cover a similar continuous two-dimensional region of Q2 and Bjorken
variable x, permit the study of nuclear modifications of the nucleon structure.
By using these, as well as other world data, we evaluated the F2 structure
function and its moments. Using an OPE-based twist expansion, we studied the
Q2-evolution of the moments, obtaining a separation of the leading-twist and
the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist
contributions to the F2 moments exhibits the well known EMC effect, compatible
with that discovered previously in x-space. The total higher-twist term in the
carbon nucleus appears, although with large systematic uncertainites, to be
smaller with respect to the deuteron case for n<7, suggesting partial parton
deconfinement in nuclear matter. We speculate that the spatial extension of the
nucleon is changed when it is immersed in the nuclear medium.Comment: 37 pages, 15 figure
Inclusive scattering data on light nuclei as a precision tool for the extraction of G_M^n
We demonstrate that refinements in the analysis of inclusive scattering data
on light nuclei enable the extraction of, generally accurate, values of the
neutron magnetic form factor G_M^n(Q^2). In particular, a recent
parametrization of ep inclusive resonance excitation enables a reliable
calculation of the inelastic background, and as a consequence a separation of
quasi-elastic and inelastic contributions. A far larger number of data points
than previously considered is now available for analysis and enables a more
reliable extraction of G_M^n from cross section and R_T data on D and He. The
achieved accuracy appears mainly limited by the present uncertainties in the
knowledge of proton form factors and by the accuracy of the data.Comment: new version with minor changes in the text and figures, added
references and 5 figure
Quasielastic axial-vector mass from experiments on neutrino-nucleus scattering
We analyze available experimental data on the total and differential
charged-current cross sections for quasielastic neutrino and antineutrino
scattering off nucleons, measured with a variety of nuclear targets in the
accelerator experiments at ANL, BNL, FNAL, CERN, and IHEP, dating from the end
of sixties to the present day. The data are used to adjust the poorly known
value of the axial-vector mass of the nucleon.Comment: 27 pages, 19 figures. Typos corrected; tables, figures and references
added, discussion extended; matches published versio
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