23,399 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
Teenage Pregnancy in Mexico: Evolution and Consequences
We analyze the consequences of a teenage pregnancy event in the short- and long-run in Mexico. Using longitudinal and cross-section data, we match females who got pregnant and those that did not based on a propensity score. Several balancing tests and specifications indicate that the main assumptions to estimate the average treatment effect on the treated using a propensity score are satisfied. In the short-run, we find that a teenage pregnancy causes a decrease of 0.6-0.8 years of schooling, lower attendance to school, less hours of work and a higher marriage rate. At the household level, we do not find any effect in parental hours of work or income per capita. In the long-run, we find a loss in years of education of 1-1.2 and a higher probability of being married, but also higher probability of being separated or divorced. We also find that household income per capita is lower at least in the long-run.teenage, pregnancy, labor outcomes, propensity score, matching
Impact of internal bremsstrahlung on the detection of gamma-rays from neutralinos
We present a detailed study of the effect of internal bremsstrahlung photons
in the context of the minimal supersymmetric standard models and their impact
on gamma-ray dark matter annihilation searches. We find that although this
effect has to be included for the correct evaluation of fluxes of high energy
photons from neutralino annihilation, its contribution is relevant only in
models and at energies where the lines contribution is dominant over the
secondary photons. Therefore, we find that the most optimistic supersymmetric
scenarios for dark matter detection do not change significantly when including
the internal bremsstrahlung. As an example, we review the gamma-ray dark matter
detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC
stereoscopic system and the CTA project. Though the flux of high energy photons
is enhanced by an order of magnitude in some regions of the parameter space,
the expected fluxes are still much below the sensitivity of the instruments.Comment: 5 pages, twocolumn format, 3 figures:3 references added, accepted as
Brief Report in PR
Rotational velocities of A-type stars II. Measurement of vsini in the northern hemisphere
This work is the second part of the set of measurements of vsini for A-type
stars, begun by Royer et al. (2002). Spectra of 249 B8 to F2-type stars
brighter than V=7 have been collected at Observatoire de Haute-Provence (OHP).
Fourier transforms of several line profiles in the range 4200--4600 A are used
to derive vsini from the frequency of the first zero. Statistical analysis of
the sample indicates that measurement error mainly depends on vsini and this
relative error of the rotational velocity is found to be about 5% on average.
The systematic shift with respect to standard values from Slettebak et al.
(1975), previously found in the first paper, is here confirmed. Comparisons
with data from the literature agree with our findings: vsini values from
Slettebak et al. are underestimated and the relation between both scales
follows a linear law: vsini(new) = 1.03 vsini(old) + 7.7. Finally, these data
are combined with those from the previous paper (Royer et al. 2002), together
with the catalogue of Abt & Morrell (1995). The resulting sample includes some
2150 stars with homogenized rotational velocities.Comment: 16 pages, includes 13 figures, accepted in A&
When the Milky Way turned off the lights: APOGEE provides evidence of star formation quenching in our Galaxy
Quenching, the cessation of star formation, is one of the most significant
events in the life cycle of galaxies. We show here the first evidence that the
Milky Way experienced a generalised quenching of its star formation at the end
of its thick disk formation 9 Gyr ago. Elemental abundances of stars
studied as part of the APOGEE survey reveal indeed that in less than 2
Gyr the star formation rate in our Galaxy dropped by an order-of-magnitude.
Because of the tight correlation between age and alpha abundance, this event
reflects in the dearth of stars along the inner disk sequence in the
[Fe/H]-[/Fe] plane. Before this phase, which lasted about 1.5 Gyr, the
Milky Way was actively forming stars. Afterwards, the star formation resumed at
a much lower level to form the thin disk. These events are very well matched by
the latest observation of MW-type progenitors at high redshifts. In late type
galaxies, quenching is believed to be related to a long and secular exhaustion
of gas. In our Galaxy, it occurred on a much shorter time scale, while the
chemical continuity before and after the quenching indicates that it was not
due to the exhaustion of the gas. While quenching is generally associated with
spheroids, our results show that it also occurs in galaxies like the Milky Way,
possibly when they are undergoing a morphological transition from thick to thin
disks. Given the demographics of late type galaxies in the local universe, in
which classical bulges are rare, we suggest further that this may hold true
generally in galaxies with mass lower than or approximately , where
quenching could be directly a consequence of thick disk formation. We emphasize
that the quenching phase in the Milky Way could be contemporaneous with, and
related to, the formation of the bar. We sketch a scenario on how a strong bar
may inhibit star formation.Comment: 17 pages, 8 figures. Published versio
A survey for water maser emission towards planetary nebulae. New detection in IRAS 17347-3139
We report on a water maser survey towards a sample of 27 planetary nebulae
(PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well
as the Very Large Array (VLA). Two detections have been obtained: the already
known water maser emission in K 3-35, and a new cluster of masers in IRAS
17347-3139. This low rate of detections is compatible with the short life-time
of water molecules in PNe (~100 yr). The water maser cluster at IRAS 17347-3139
are distributed on a ellipse of size ~ 0.2" x 0.1", spatially associated with
compact 1.3 cm continuum emission (simultaneously observed with the VLA). From
archive VLA continuum data at 4.9, 8.4, and 14.9 GHz, a spectral index alpha =
0.76 +- 0.03 is derived for this radio source, which is consistent with either
a partially optically thick ionized region or with an ionized wind. However,
the latter scenario can be ruled out on mass-loss considerations, thus
indicating that this source is probably a young PN. The spatial distribution
and the radial velocities of the water masers are suggestive of a rotating and
expanding maser ring, tracing the innermost regions of a torus formed at the
end of the AGB phase. Given that the 1.3 cm continuum emission peak is located
near one of the tips of the major axis of the ellipse of masers, we speculate
on a possible binary nature of IRAS 17347-3139, where the radio continuum
emission could belong to one of the components and the water masers would be
associated with a companion.Comment: Accepted by The Astrophysical Journal. 25 pages, 6 figure
Excited lepton triplet contribution to electroweak observables at one loop level
In this paper, we present the one-loop radiative corrections to the
electroweak precision observable coming from the
multiplet excited leptons. We have calculated the couplings of the exotic
lepton triplet to the vector bosons and ordinary leptons using effective
Lagrangian approach. These couplings are then used to estimate the excited
lepton triplet contribution to the parameter. The mass degenerate
excited lepton contribution to is small and can be neglected.
However, if the excited leptons are non-degenerate, their contribution can be
large which can result in more stringent constraints on the excited fermion
parameter space compared to the constraints from present experimental searches
and perturbative unitarity condition
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