Quality of social networks and educational investment decisions

All individuals belong to a social network with certain quality level. This paper analyzes the role of the quality of the social network in the educational decision making process. We propose a measure for quality of network based on the schooling level and the labor position of the members of the net. Our analysis compares individuals who are similar in at least two characteristics: socioeconomic level and intellectual ability. Although they belong to the same type of community (poor), they differ in the composition of their social network. The higher the quality of the network, the higher the probability of investing in education. Hence, socially disadvantaged and equally intelligent individuals may end up acquiring different schooling levels.

Sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride photocatalyst: insights from first principles

We present here results of our first principles studies of the sulfur doping effects on the electronic and geometric structures of graphitic carbon nitride (g-C3N4). Using the Ab initio thermodynamics approach combined with some kinetic analysis, we reveal the favorable S-doping configurations By analyzing the valence charge densities of the doped and un-doped systems, we find that sulfur partially donates its px- and py- electrons to the system with some back donation to the S pz-states. To obtain accurate description of the excited electronic states, we calculate the electronic structure of the systems using the GW method. The band gap width calculated for g-C3N4 is found to be equal to 2.7 eV that is in agreement with experiment. We find the S doping to cause a significant narrowing the gap. Furthermore, the electronic states just above the gap become occupied upon doping that makes the material a conductor. Analysis of the projected local densities of states provides insight into the mechanism underlying such dramatic changes in the electronic structure of g-C3N4 upon the S doping. Based on our results, we propose a possible explanation for the S doping effect on the photo-catalytic properties of g-C3N4 observed in the experiments

First principles studies of the size and shape effects on reactivity of the Se modified Ru nanoparticles

We present here the results of our density-functional-theory-based calculations of the electronic and geometric structures and energetics of Se and O adsorption on Ru 93- and 105-atom nanoparticles. These studies have been inspired by the fact that Se/Ru nanoparticles are considered promising electrocatalysts for the oxygen reduction reaction (ORR) on the direct methanol fuel cell cathodes and the oxygen binding energy is a descriptor for the catalyst activity towards this reaction. We find the character of chemical bonding of Se on a flat nanoparticle facet to be ionic, similar to that obtained earlier for the Se/Ru(0001) surface, while in the case of a low coordinated Ru configuration there is an indication of some covalent contribution to the bonding leading to an increase in Se binding energy. Se and O co-adsorbed on the flat facet, both accept electronic charge from Ru, whereas the adsorption on low-coordinated sites causes more complicated valence charge redistribution. The Se modification of the Ru particles leads to weakening of the oxygen bonding to the particle. However, overall, O binding energies are found to be higher for the particles than for Se/Ru(0001). High reactivity of the Se/Ru nanoparticles found in this work is not favorable for ORR. We thus expect that larger particles with well-developed flat facets are more efficient ORR catalysts than small nanoparticles with a large fraction of under-coordinated adsorption sites

Different channels of impact of education on poverty: an analysis for Colombia

This paper analyses pecuniary and non-pecuniary effects of education on poverty. Two are the main contributions: first, the pecuniary analysis employs the recently developed technique of instrumental variable quantile regression, very helpful method when one is interested in the lowest or highest extremes of the distribution function of the dependent variable. In fact, quantile regression offers coefficient estimations for any conditional quantile. The second contribution derives from our purpose to highlight the non-pecuniary returns to education: resources invested in education bring future returns to individuals, not only reflected in monetary earnings, but also in higher levels of satisfaction of basic needs.education, poverty, quantile regression, Colombia

Unbalanced groups in nonparametric survival tests

It is fairly common to find medical examples with survival data with unequal sample size among the groups. There are several tests for those cases, but in practice, the use of one test instead of another is done without justifying the election. Sometimes, the choice of one test or another can lead to different conclusions, so it is important to have some guidelines to help to choose the suitable test in unbalanced groups. The computation of the tests is done with the statistical software (BMDP, SAS, SPSS, Stata, Statgraphics, and S-Plus). However the commercial software only covers tests for the family of the weigthed tests, none of the score tests, and the nomenclature is not unified, using different names for the same test. We perform several simulations to give some pieces of advice for picking out the right test. Due to the fact that there are situations where it is advisable to use a test from the family of the score tests against a weighted one, we have developed a new software in JavaScript for Internet that computes score and weighted tests versions (10 tests) that unifies the nomenclature (this software is available from the authors upon request). We include real examples where we apply, using the new JavaScript programs, the recommendations suggested by the simulations

Differentes canais de impacto da educação na pobreza

O artigo analisa os efeitos monetários e os não-monetários do nível de escolaridade do chefe de família na situação de pobreza. Propomos que o rendimento da escolaridade não seja pensado como um simples número– usualmente o coefi ciente de escolaridade em uma equação da renda–mas como um conjunto de elementos cuja extensão depende da quantidade de dimensões de pobreza identifi cadas. A análise monetária usa a técnica de Regressão Quantil, muito útil especialmente quando estamos interessados nos extremos da função de distribuição das rendas. Nossos resultados mostram diferenças entre os quantis dos retornos. Também encontrámos interessantes desigualdades conforme o sexo e a localização urbana-rural. Explorando os retornos não pecuniários, descobrimos que a educação do chefe de família infl uencia positivamente a saúde familiar e as condições de habitação.