1,729 research outputs found
Hacia una mejor educación rural: impacto de un programa de intervención a las escuelas en Colombia
Utilizando información censal de las sedes educativas rurales de Colombia el presente trabajo evalúa el impacto que tuvo el Programa de Educación Rural -PER - en las tasas de eficiencia (cobertura, reprobación, aprobación y deserción) y calidad de la educación en las sedes en donde se aplicó. A través de la implementación de modelos educativos flexibles adaptados a las necesidades de la comunidad, el programa logró efectos positivos en las medidas de eficiencia y calidad de las sedes tratadas. Los resultados son robustos a distintas metodologías de estimación y grupos de control y evidencian que programas de intervención dirigidos a la oferta (escuelas) pueden mejorar sustancialmente la eficiencia y calidad de la educación en las zonas rurales. Se encuentra, en adición, que el efecto del PER sobre los indicadores de eficiencia de las sedes educativas rurales se da a través de la calidad tanto del material educativo y de la capacitación en los modelos pedagógicos como de las mejoras en la gestión y administración de la institución educativa.Educación rural, evaluación de impacto, diferencias endiferencias, matching estimators.
Aspectos epidemiológicos de la fotosensibilización hepatotóxica asociada al pastoreo de Brachiaria decumbens en los Llanos Orientales de Colombia.
Se describen las características clínicas y epidemiológicas de 43 casos del síndrome de fotosensibilización en bovinos, asociado al consumo de Brachiaria decumbens, los cuales ocurrieron durante un período de 4 años. El síndrome se presenta con preferencia en animales jóvenes, hasta los 24 meses de edad y en épocas de transición lluvias-sequía o viceversa. Se reconocen 2 cuadros clínicos, uno con edemas y el otro con necrosis de piel. Las lesiones macro y microscópicas corresponden a una afección hepatotóxica. La observación de un brote en ovinos de la región en similares circunstancias e idéntico proceso clínico, establece una semejanza del síndrome con el eczema facial de las ovejas en Nueva Zelandi
Numerical atomic orbitals for linear scaling
The performance of basis sets made of numerical atomic orbitals is explored
in density-functional calculations of solids and molecules. With the aim of
optimizing basis quality while maintaining strict localization of the orbitals,
as needed for linear-scaling calculations, several schemes have been tried. The
best performance is obtained for the basis sets generated according to a new
scheme presented here, a flexibilization of previous proposals. The basis sets
are tested versus converged plane-wave calculations on a significant variety of
systems, including covalent, ionic and metallic. Satisfactory convergence
(deviations significantly smaller than the accuracy of the underlying theory)
is obtained for reasonably small basis sizes, with a clear improvement over
previous schemes. The transferability of the obtained basis sets is tested in
several cases and it is found to be satisfactory as well.Comment: 9 pages with 2 encapsulated postscript figures, submitted to Phys.
Rev.
The dark matter environment of the Abell 901/902 supercluster: a weak lensing analysis of the HST STAGES survey
We present a high resolution dark matter reconstruction of the z=0.165 Abell
901/902 supercluster from a weak lensing analysis of the HST STAGES survey. We
detect the four main structures of the supercluster at high significance,
resolving substructure within and between the clusters. We find that the
distribution of dark matter is well traced by the cluster galaxies, with the
brightest cluster galaxies marking out the strongest peaks in the dark matter
distribution. We also find a significant extension of the dark matter
distribution of Abell 901a in the direction of an infalling X-ray group Abell
901alpha. We present mass, mass-to-light and mass-to-stellar mass ratio
measurements of the structures and substructures that we detect. We find no
evidence for variation of the mass-to-light and mass-to-stellar mass ratio
between the different clusters. We compare our space-based lensing analysis
with an earlier ground-based lensing analysis of the supercluster to
demonstrate the importance of space-based imaging for future weak lensing dark
matter 'observations'.Comment: 13 pages, 6 figures and 4 tables. Accepted for publication in MNRA
Global hybrids from the semiclassical atom theory satisfying the local density linear response
We propose global hybrid approximations of the exchange-correlation (XC)
energy functional which reproduce well the modified fourth-order gradient
expansion of the exchange energy in the semiclassical limit of many-electron
neutral atoms and recover the full local density approximation (LDA) linear
response. These XC functionals represent the hybrid versions of the APBE
functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional
correlation functional which uses the localization concept of the correlation
energy density to improve the compatibility with the Hartree-Fock exchange as
well as the coupling-constant-resolved XC potential energy. Broad energetical
and structural testings, including thermochemistry and geometry, transition
metal complexes, non-covalent interactions, gold clusters and small
gold-molecule interfaces, as well as an analysis of the hybrid parameters, show
that our construction is quite robust. In particular, our testing shows that
the resulting hybrid, including 20\% of Hartree-Fock exchange and named hAPBE,
performs remarkably well for a broad palette of systems and properties, being
generally better than popular hybrids (PBE0 and B3LYP). Semi-empirical
dispersion corrections are also provided.Comment: 12 pages, 4 figure
Armed Rollers: Does Nestling’s Vomit Function as a Defence against Predators?
Chemical defences against predators are widespread in the animal kingdom although have been seldom reported in birds. Here, we investigate the possibility that the orange liquid that nestlings of an insectivorous bird, the Eurasian roller (Coracias garrulus), expel when scared at their nests acts as a chemical defence against predators. We studied the diet of nestling rollers and vomit origin, its chemical composition and deterrent effect on a mammal generalist predator. We also hypothesized that nestling rollers, as their main prey (i.e. grasshoppers) do from plants, could sequester chemicals from their prey for their use. Grasshoppers, that also regurgitate when facing to a threat, store the harmful substances used by plants to defend themselves against herbivores. We found that nestling rollers only vomit after being grasped and moved. The production of vomit depended on food consumption and the vomit contained two deterrent chemicals (hydroxycinnamic and hydroxybenzoic acids) stored by grasshoppers and used by plants to diminish herbivory, suggesting that they originate from the rollers’ prey. Finally, we showed for the first time that the oral secretion of a vertebrate had a deterrent effect on a model predator because vomit of nestling rollers made meat distasteful to dogs. These results support the idea that the vomit of nestling rollers is a chemical defence against predators.Financial support was provided by the Junta de Andalucía (project P06-RNM-02177) and the Spanish Ministry of Science and Education/FEDER (projects CGL2008-00718 and CGL2011-27561)
Comparative Proteomic Analysis of Serum from Patients with Systemic Sclerosis and Sclerodermatous GVHD. Evidence of Defective Function of Factor H
BACKGROUND: Systemic sclerosis (SSc) is an autoimmune disease characterized by immunological and vascular abnormalities. Until now, the cause of SSc remains unclear. Sclerodermatous graft-versus-host disease (ScGVHD) is one of the most severe complications following bone marrow transplantation (BMT) for haematological disorders. Since the first cases, the similarity of ScGVHD to SSc has been reported. However, both diseases could have different etiopathogeneses. The objective of this study was to identify new serum biomarkers involved in SSc and ScGVHD. METHODOLOGY: Serum was obtained from patients with SSc and ScGVHD, patients without ScGVHD who received BMT for haematological disorders and healthy controls. Bi-dimensional electrophoresis (2D) was carried out to generate maps of serum proteins from patients and controls. The 2D maps underwent image analysis and differently expressed proteins were identified. Immuno-blot analysis and ELISA assay were used to validate the proteomic data. Hemolytic assay with sheep erythrocytes was performed to evaluate the capacity of Factor H (FH) to control complement activation on the cellular surface. FH binding to endothelial cells (ECs) was also analysed in order to assess possible dysfunctions of this protein. PRINCIPAL FINDINGS: Fourteen differentially expressed proteins were identified. We detected pneumococcal antibody cross-reacting with double stranded DNA in serum of all bone marrow transplanted patients with ScGVHD. We documented higher levels of FH in serum of SSc and ScGVHD patients compared healthy controls and increased sheep erythrocytes lysis after incubation with serum of diffuse SSc patients. In addition, we observed that FH binding to ECs was reduced when we used serum from these patients. CONCLUSIONS: The comparative proteomic analysis of serum from SSc and ScGVHD patients highlighted proteins involved in either promoting or maintaining an inflammatory state. We also found a defective function of Factor H, possibly associated with ECs damage
Human antimicrobial protein hCAP18/LL-37 promotes a metastatic phenotype in breast cancer
International audienc
- …