'Com Quem Os Filhos Ficarão?' Representações Sociais da Guarda Após a Separação Conjugal

Este trabalho objetivou investigar as representações sociais da guarda de filhos em caso de separação conjugal e teve como base a Teoria das Representações Sociais de Serge Moscovici. Compartilhar a criação dos filhos é uma tarefa inerente ao poder familiar e é exercida na constância do casamento ou da união estável. O tema se torna controverso quando há ruptura conjugal e surge a necessidade de discutir com quem os filhos ficarão. No Brasil, na maior parte dos casos, a guarda é entregue à mãe, pois parte-se do princípio de que é natural que os filhos sejam criados pelas mães, com o auxílio dos pais. Contudo, a relativização dessa concepção naturalista da maternidade ganhou destaque com a edição da lei que instituiu a guarda compartilhada no ordenamento jurídico brasileiro em 2008. Para averiguar o que pensam sobre essa nova possibilidade, foram escolhidos 30 sujeitos moradores da Grande Vitória/ES, com curso superior e idade média de 40 anos, sendo 15 mães e 15 pais de filhos menores de idade. Os instrumentos utilizados foram uma entrevista e um questionário, abordando os seguintes temas: reflexão e decisão acerca da separação, concretização da separação, vida após a separação, e guarda de filhos. As respostas foram gravadas em áudio e transcritas. Os dados foram analisados por meio de análise de conteúdo temática. Os resultados principais indicam que, na fase de reflexão e decisão acerca da separação, o bem-estar psicológico dos filhos foi a preocupação referida com maior frequência pelos sujeitos e que a reação dos filhos influencia a decisão sobre a separação do casal. Na fase de concretização da separação, para a maior parte dos sujeitos, os filhos devem ficar com a mãe quando o casal se separa, e considera que a opinião dos filhos influencia na decisão dos pais sobre a guarda e a visitação. Na fase após a separação, as preocupações mais referidas pelos sujeitos foram o bem-estar psicológico dos filhos e participar ativamente da vida dos filhos. Os elementos que compuseram a representação social de guarda unilateral foram guarda materna, exclusividade de um genitor e exclusão do outro, e desacordo entre os ex-cônjuges. Na representação social de guarda compartilhada os elementos encontrados foram igualdade de convívio entre genitores e filhos, divisão de responsabilidades sobre os filhos entre os genitores, acordo e/ou amizade entre os genitores, além de diversidade de ambientes, que invoca tanto a noção de fonte de aprendizado para os filhos quanto a possibilidade de haver confusão na educação. Os resultados indicam que a preferência pela guarda unilateral e a resistência à guarda compartilhada relacionam-se com as representações sociais da maternidade e da paternidade, as quais tomam a figura materna como central na criação dos filhos. Palavras-chave: parentalidade

Highly Conducting pi-Conjugated Molecular Junctions Covalently Bonded to Gold Electrodes

We measure electronic conductance through single conjugated molecules bonded to Au metal electrodes with direct Au-C covalent bonds using the scanning tunneling microscope based break-junction technique. We start with molecules terminated with trimethyltin end groups that cleave off in situ resulting in formation of a direct covalent sigma bond between the carbon backbone and the gold metal electrodes. The molecular carbon backbone used in this study consist of a conjugated pi-system that has one terminal methylene group on each end, which bonds to the electrodes, achieving large electronic coupling of the electrodes to the pi-system. The junctions formed with the prototypical example of 1,4-dimethylenebenzene show a conductance approaching one conductance quantum (G0 = 2e2/h). Junctions formed with methylene terminated oligophenyls with two to four phenyl units show a hundred-fold increase in conductance compared with junctions formed with amine-linked oligophenyls. The conduction mechanism for these longer oligophenyls is tunneling as they exhibit an exponential dependence of conductance with oligomer length. In addition, density functional theory based calculations for the Au-xylylene-Au junction show near-resonant transmission with a cross-over to tunneling for the longer oligomers.Comment: Accepted to the Journal of the American Chemical Society as a Communication

Experimental observation of transient δ18O interaction between snow and advective airflow under various temperature gradient conditions

Stable water isotopes (δ18O) obtained from snow and ice samples of polar regions are used to reconstruct past climate variability, but heat and mass transport processes can affect the isotopic composition. Here we present an experimental study on the effect of airflow on the snow isotopic composition through a snow pack in controlled laboratory conditions. The influence of isothermal and controlled temperature gradient conditions on the δ18O content in the snow and interstitial water vapour is elucidated. The observed disequilibrium between snow and vapour isotopes led to the exchange of isotopes between snow and vapour under non-equilibrium processes, significantly changing the δ18O content of the snow. The type of metamorphism of the snow had a significant influence on this process. These findings are pertinent to the interpretation of the records of stable isotopes of water from ice cores. These laboratory measurements suggest that a highly resolved climate history is relevant for the interpretation of the snow isotopic composition in the field

Sensitivity of the stress response function to packing preparation

A granular assembly composed of a collection of identical grains may pack under different microscopic configurations with microscopic features that are sensitive to the preparation history. A given configuration may also change in response to external actions such as compression, shearing etc. We show using a mechanical response function method developed experimentally and numerically, that the macroscopic stress profiles are strongly dependent on these preparation procedures. These results were obtained for both two and three dimensions. The method reveals that, under a given preparation history, the macroscopic symmetries of the granular material is affected and in most cases significant departures from isotropy should be observed. This suggests a new path toward a non-intrusive test of granular material constitutive properties.Comment: 15 pages, 11 figures, some numerical data corrected, to appear in J. Phys. Cond. Mat. special issue on Granular Materials (M. Nicodemi Editor

Improved count rate corrections for highest data quality with PILATUS detectors

A Monte Carlo simulation is presented, which computes the rate correction factors taking into account the detector settings and the time structure of the X-ray beam. The results show good agreement with experimentally determined correction factors

Observation of squeezed light from one atom excited with two photons

Single quantum emitters like atoms are well-known as non-classical light sources which can produce photons one by one at given times, with reduced intensity noise. However, the light field emitted by a single atom can exhibit much richer dynamics. A prominent example is the predicted ability for a single atom to produce quadrature-squeezed light, with sub-shot-noise amplitude or phase fluctuations. It has long been foreseen, though, that such squeezing would be "at least an order of magnitude more difficult" to observe than the emission of single photons. Squeezed beams have been generated using macroscopic and mesoscopic media down to a few tens of atoms, but despite experimental efforts, single-atom squeezing has so far escaped observation. Here we generate squeezed light with a single atom in a high-finesse optical resonator. The strong coupling of the atom to the cavity field induces a genuine quantum mechanical nonlinearity, several orders of magnitude larger than for usual macroscopic media. This produces observable quadrature squeezing with an excitation beam containing on average only two photons per system lifetime. In sharp contrast to the emission of single photons, the squeezed light stems from the quantum coherence of photon pairs emitted from the system. The ability of a single atom to induce strong coherent interactions between propagating photons opens up new perspectives for photonic quantum logic with single emittersComment: Main paper (4 pages, 3 figures) + Supplementary information (5 pages, 2 figures). Revised versio

Polarimetric X-band weather radar measurements in the tropics: radome and rain attenuation correction

A polarimetric X-band radar has been deployed during one month (April 2011) for a field campaign in Fortaleza, Brazil, together with three additional laser disdrometers. The disdrometers are capable of measuring the raindrop size distributions (DSDs), hence making it possible to forward-model theoretical polarimetric X-band radar observables at the point where the instruments are located. This setup allows to thoroughly test the accuracy of the X-band radar measurements as well as the algorithms that are used to correct the radar data for radome and rain attenuation. For the campaign in Fortaleza it was found that radome attenuation dominantly affects the measurements. With an algorithm that is based on the self-consistency of the polarimetric observables, the radome induced reflectivity offset was estimated. Offset corrected measurements were then further corrected for rain attenuation with two different schemes. The performance of the post-processing steps was analyzed by comparing the data with disdrometer-inferred polarimetric variables that were measured at a distance of 20 km from the radar. Radome attenuation reached values up to 14 dB which was found to be consistent with an empirical radome attenuation vs. rain intensity relation that was previously developed for the same radar type. In contrast to previous work, our results suggest that radome attenuation should be estimated individually for every view direction of the radar in order to obtain homogenous reflectivity fields.FAPESP [2009/15235-8

The Influence of Molecular Adsorption on Elongating Gold Nanowires

Using molecular dynamics simulations, we study the impact of physisorbing adsorbates on the structural and mechanical evolution of gold nanowires (AuNWs) undergoing elongation. We used various adsorbate models in our simulations, with each model giving rise to a different surface coverage and mobility of the adsorbed phase. We find that the local structure and mobility of the adsorbed phase remains relatively uniform across all segments of an elongating AuNW, except for the thinning region of the wire where the high mobility of Au atoms disrupts the monolayer structure, giving rise to higher solvent mobility. We analyzed the AuNW trajectories by measuring the ductile elongation of the wires and detecting the presence of characteristic structural motifs that appeared during elongation. Our findings indicate that adsorbates facilitate the formation of high-energy structural motifs and lead to significantly higher ductile elongations. In particular, our simulations result in a large number of monatomic chains and helical structures possessing mechanical stability in excess of what we observe in vacuum. Conversely, we find that a molecular species that interacts weakly (i.e., does not adsorb) with AuNWs worsens the mechanical stability of monatomic chains.Comment: To appear in Journal of Physical Chemistry