1,231 research outputs found
The Nutritional Status of Elites in India, Kenya, and Zambia: An appropriate guide for developing reference standards for undernutrition?
Assessments of undernutrition are typically based on comparisons between anthropometric indicators of children and a reference standard from the US. Due to a number of problems associated with this reference standard, WHO is currently engaged in generating a new international reference standard for child growth based on wellÂtoÂdo populations in a sample of poor and rich countries. The focus on socioeconomic elites is to ensure that the measured growth reflects their genetic potential (and not according their constrained environment). Based on an analysis of the Demographic and Health Surveys from Kenya, India, and Zambia, we identify a number of problems associated with using socioeconomic elites as representative of the genetic potential of a population. First, there are several, nonÂoverlapping ways to identify elites. Second, the anthropometric status of elites appears to depend to a considerable degree on the nutrition and health status of nonÂelites. Third, there is a danger that the elites are not a random sample of the growth potential of the population. And lastly, it appears that the nutritional status of elites differs substantially between the three countries so that it is unclear how one can combine them to generate one international reference standard
Analysis of the Determinants of Fertility Decline in the Czech Republic
In this paper we study the decline in total fertility rates in the Czech Republic during the transition process. To identify transition-specific features of this decline we use a multiperiod model of birth process and apply it to the family and fertility survey of 1998. In a standard duration analysis setting the model allows for time-dependence of information sets, on which the decision about the next birth is made. It also enables to estimate probabilities of early exit from childbearing. In this work we find that the negative effect of transition on TFR is mostly translated through a sharply increased negative influence of higher education on fertility, and through the apparent lack of adequate childcare facilities
Evidence for Factorization Breaking in Diffractive Low-Q^2 Dijet Production
We calculate diffractive dijet production in deep-inelastic scattering at
next-to-leading order of perturbative QCD, including contributions from direct
and resolved photons, and compare our predictions to preliminary data from the
H1 collaboration at HERA. In contrast to recent experimental claims, evidence
for factorization breaking is found only for resolved, and not direct, photon
contributions. No evidence is found for large normalization uncertainties in
diffractive parton densities. The results confirm theoretical expectations for
the (non-)cancellation of soft singularities in diffractive scattering as well
as previous results for (almost) real photoproduction.Comment: 4 pages, 3 figure
Suppression factors in diffractive photoproduction of dijets
After new publications of H1 data for the diffractive photoproduction of
dijets, which overlap with the earlier published H1 data and the recently
published data of the ZEUS collaboration, have appeared, we have recalculated
the cross sections for this process in next-to-leading order (NLO) of
perturbative QCD to see whether they can be interpreted consistently. The
results of these calculations are compared to the data of both collaborations.
We find that the NLO cross sections disagree with the data, showing that
factorization breaking occurs at that order. If direct and resolved
contributions are both suppressed by the same amount, the global suppression
factor depends on the transverse-energy cut. However, by suppressing only the
resolved contribution, also reasonably good agreement with all the data is
found with a suppression factor independent of the transverse-energy cut.Comment: 28 pages, 11 figures, 3 table
Factorization Breaking in Dijet Photoproduction with a Leading Neutron
The production of dijets with a leading neutron in ep-interactions at HERA is
calculated in leading order and next-to-leading order of perturbative QCD using
a pion-exchange model. Differential cross sections for deep-inelastic
scattering (DIS) and photoproduction are presented as a function of several
kinematic variables. By comparing the theoretical predictions for DIS dijets to
recent H1 data, the pion flux factor together with the parton distribution
functions of the pion is determined. The dijet cross sections in
photoproduction show factorization breaking if compared to the H1
photoproduction data. The suppression factor is S = 0.48 (0.64) for resolved
(global) suppression.Comment: 16 pages, 5 figure
Ghost contributions to charmonium production in polarized high-energy collisions
In a previous paper [Phys. Rev. D 68, 034017 (2003)], we investigated the
inclusive production of prompt J/psi mesons in polarized hadron-hadron,
photon-hadron, and photon-photon collisions in the factorization formalism of
nonrelativistic quantum chromodynamics providing compact analytic results for
the double longitudinal-spin asymmetry A_{LL}. For convenience, we adopted a
simplified expression for the tensor product of the gluon polarization
four-vector with its charge conjugate, at the expense of allowing for ghost and
anti-ghosts to appear as external particles. While such ghost contributions
cancel in the cross section asymmetry A_{LL} and thus were not listed in our
previous paper, they do contribute to the absolute cross sections. For
completeness and the reader's convenience, they are provided in this addendum.Comment: 5 page
QCD Physics with ZEUS and H1 at HERA
A review is presented of recent results in QCD from the H1 and ZEUS
experiments at HERA, emphasizing the use of higher order calculations to
describe the data.Comment: 12 pages, 15 figures, invited review paper for Mod. Phys. Lett
Geo-additive models of Childhood Undernutrition in three Sub-Saharan African Countries
We investigate the geographical and socioeconomic determinants of childhood undernutrition in Malawi, Tanzania and Zambia, three neighboring countries in Southern Africa using the 1992 Demographic and Health Surveys. We estimate models of undernutrition jointly for the three countries to explore regional patterns of undernutrition that transcend boundaries, while allowing for country-specific interactions. We use semiparametric models to flexibly model the effects of selected so-cioeconomic covariates and spatial effects. Our spatial analysis is based on a flexible geo-additive model using the district as the geographic unit of anal-ysis, which allows to separate smooth structured spatial effects from random effect. Inference is fully Bayesian and uses recent Markov chain Monte Carlo techniques. While the socioeconomic determinants generally confirm what is known in the literature, we find distinct residual spatial patterns that are not explained by the socioeconomic determinants. In particular, there appears to be a belt run-ning from Southern Tanzania to Northeastern Zambia which exhibits much worse undernutrition, even after controlling for socioeconomic effects. These effects do transcend borders between the countries, but to a varying degree. These findings have important implications for targeting policy as well as the search for left-out variables that might account for these residual spatial patterns
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