51,241 research outputs found
Child health in rural Colombia: determinants and policy interventions
In this paper we study the determinants of child anthropometrics on a sample of poor Colombian
children living in small municipalities. We focus on the influence of household consumption, and
public infrastructure. We take into account the endogeneity of household consumption using two
different sets of instruments: household assets and municipality average wage. We find that household
consumption is an important determinant of child health. The importance of the effect is confirmed by
the two different sets of instruments. We find that using ordinary least squares would lead to conclude
that the importance of household consumption is much smaller than the instrumental variable
estimates suggest. The presence of a public hospital in the municipality positively influences child
health. The extent of the piped water network positively influences the health of children if their
parents have at least some education. The number of hours of growth and development check-ups is
also an important determinant of child health. We find that some of these results only show up once
squared and interaction terms have been included in the regression. Overall, our estimates suggest that
both public and private investments are important to improve child health in poor environments
Sizes of Confirmed Globular Clusters in NGC 5128: A Wide-Field High-Resolution Study
Using Magellan/IMACS images covering a 1.2 x 1.2 sq. degree FOV with seeing
of 0.4"-0.6", we have applied convolution techniques to analyse the light
distribution of 364 confirmed globular cluster in the field of NGC 5128 and to
obtain their structural parameters. Combining these parameters with existing
Washington photometry from Harris et al. (2004), we are able to examine the
size difference between metal-poor (blue) and metal-rich (red) globular
clusters. For the first time, this can be addressed on a sample of confirmed
clusters that extends to galactocentric distances about 8 times the effective
radius, R, of the galaxy. Within 1 R, red clusters are about
30% smaller on average than blue clusters, in agreement with the vast majority
of extragalactic globular cluster systems studied. As the galactocentric
distance increases, however, this difference becomes negligible. Thus, our
results indicate that the difference in the clusters' effective radii, r,
could be explained purely by projection effects, with red clusters being more
centrally concentrated than blue ones and an intrinsic r--R
dependence, like the one observed for the Galaxy.Comment: 4 figures, accepted for publication in ApJ
Soft masses in superstring models with anomalous U(1) symmetries
We analyze the general structure of soft scalar masses emerging in
superstring models involving anomalous U(1) symmetries, with the aim of
characterizing more systematically the circumstances under which they can
happen to be flavor universal. We consider both heterotic orbifold and
intersecting brane models, possibly with several anomalous and non-anomalous
spontaneously broken U(1) symmetries. The hidden sector is assumed to consist
of the universal dilaton, Kahler class and complex structure moduli, which are
supposed to break supersymmetry, and a minimal set of Higgs fields which
compensate the Fayet-Iliopoulos terms. We leave the superpotential that is
supposed to stabilize the hidden sector fields unspecified, but we carefully
take into account the relations implied by gauge invariance and the constraints
required for the existence of a metastable vacuum with vanishing cosmological
constant. The results are parametrized in terms of a constrained Goldstino
direction, suitably defined effective modular weights, and the U(1) charges and
shifts. We show that the effect induced by vector multiplets strongly depends
on the functional form of the Kahler potential for the Higgs fields. We find in
particular that whenever these are charged matter fields, like in heterotic
models, the effect is non-trivial, whereas when they are shifting moduli
fields, like in certain intersecting brane models, the effect may vanish.Comment: 35 pages, LaTe
Biodiversity study of Southern Biscayne Bay and Card Sound 1968-1973
A multi-disciplinary investigation was conducted in southern Biscayne Bay and Card Sound from 1968 to 1973. The purpose of the investigation was to conduct an integrated study of the ecology of southern Biscayne Bay with special emphasis on the effects of the heated effluent from the Turkey Point fossil fuel power plant, and to predict the impact of additional effluent from the planned conversion of the plant to nuclear fuel. The results of this investigation have been discussed in numerous publications. This report contains the unpublished biology data that resulted from the investigation. (PDF contains 44 pages
Ambipolar Filamentation of Turbulent Magnetic Fields : A numerical simulation
We present the results of a 2-D, two fluid (ions and neutrals) simulation of
the ambipolar filamentation process, in which a magnetized, weakly ionized
plasma is stirred by turbulence in the ambipolar frequency range. The higher
turbulent velocity of the neutrals in the most ionized regions gives rise to a
non-linear force driving them out of these regions, so that the initial
ionization inhomogeneities are strongly amplified. This effect, the ambipolar
filamentation, causes the ions and the magnetic flux to condense and separate
from the neutrals, resulting in a filamentary structure.Comment: 8 pages, 6 figures, accepted for publication in A&
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