Nonsequential Double Ionization with Polarization-gated Pulses

We investigate laser-induced nonsequential double ionization by a polarization-gated laser pulse, constructed employing two counter-rotating circularly polarized few cycle pulses with a time delay $T_{d}$. We address the problem within a classical framework, and mimic the behavior of the quantum-mechanical electronic wave packet by means of an ensemble of classical electron trajectories. These trajectories are initially weighted with the quasi-static tunneling rate, and with suitably chosen distributions for the momentum components parallel and perpendicular to the laser-field polarization, in the temporal region for which it is nearly linearly polarized. We show that, if the time delay $T_{d}$ is of the order of the pulse length, the electron-momentum distributions, as functions of the parallel momentum components, are highly asymmetric and dependent on the carrier-envelope (CE) phase. As this delay is decreased, this asymmetry gradually vanishes. We explain this behavior in terms of the available phase space, the quasi-static tunneling rate and the recollision rate for the first electron, for different sets of trajectories. Our results show that polarization-gating technique may provide an efficient way to study the NSDI dynamics in the single-cycle limit, without employing few-cycle pulses.Comment: 17 pages, 6 figure

Nanotoxicologia aliada à avaliação de riscos ambientais: uma estratégia para avaliações de segurança das nanotecnologias no Brasil.

As mesmas propriedades que tornam as nanopartículas interessantes para aplicações, também as tornam acessíveis a locais anteriormente inacessíveis em sistemas vivos, com conseqüências potencialmente significativas para a nanosegurança. As principais recomendações para a avaliação do risco-benefício e de gerenciamento de risco lidam com aplicações de máximo risco da nanotecnologia, questões de curto e longo prazo, além de modelos de regulamentação global para a nanotecnologia. A avaliação do potencial impacto biológico dos nanomateriais se tornou de grande importância nos últimos anos, pois o rápido ritmo de desenvolvimento da nanotecnologia não foi acompanhado por uma investigação completa de sua segurança

Comércio de iscas vivas no Pantanal de Mato Grosso do Sul, SCPESCA/MS, 2005.

O monitoramento pelo SCPESCA/MS constitui um exemplo gratificante de parceria entre instituições que atuam junto à pesca no Pantanal. O Sistema, que não seria possível sem esse esforço conjunto, gera resultados como a descrição anual da pesca e vem formando um grande banco de dados sobre a atividade, constituindo uma fonte importante de informações e conhecimentos para subsidiar a gestão dos recursos pesqueiros da região. Este estudo aborda o comércio de iscas vivas registrado pelo Sistema de Controle da Pesca de Mato Grosso do Sul (SCPESCA/MS) em 2005. Trata-se do comércio no atacado, realizado por intermediários entre municípios e entre Estados, pois a venda local (no atacado ou varejo) é feita diretamente entre as partes e não é contabilizada pelo Sistema.bitstream/CPAP-2010/57289/1/BP90.pd

Ionospheric response to the 2009 sudden stratospheric warming over the equatorial, low, and middle latitudes in the South American sector

The present study investigates the ionospheric total electron content (TEC) and F-layer response in the Southern Hemisphere equatorial, low, and middle latitudes due to major sudden stratospheric warming (SSW) event, which took place during January-February 2009 in the Northern Hemisphere. In this study, using 17 ground-based dual frequency GPS stations and two ionosonde stations spanning latitudes from 2.8°N to 53.8°S, longitudes from 36.7°W to 67.8°W over the South American sector, it is observed that the ionosphere was significantly disturbed by the SSW event from the equator to the midlatitudes. During day of year 26 and 27 at 14:00 UT, the TEC was two times larger than that observed during average quiet days. The vertical TEC at all 17 GPS and two ionosonde stations shows significant deviations lasting for several days after the SSW temperature peak. Using one GPS station located at Rio Grande (53.8°S, 67.8°W, midlatitude South America sector), it is reported for the first time that the midlatitude in the Southern Hemisphere was disturbed by the SSW event in the Northern Hemisphere.Fil: Fagundes, P. R.. Universidade do Vale do Paraíba; BrasilFil: Goncharenko, L. P.. Massachusetts Institute of Technology; Estados UnidosFil: De Abreu, A. J.. Universidade do Vale do Paraíba; BrasilFil: Venkatesh, K.. Universidade do Vale do Paraíba; BrasilFil: Pezzopane, M.. Istituto Nazionale Di Geofisica E Vulcanologia; ItaliaFil: De Jesus, R.. Universidade do Vale do Paraíba; BrasilFil: Gende, Mauricio Alfredo. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Coster, A. J.. Massachusetts Institute of Technology; Estados UnidosFil: Pillat, V. G.. Universidade do Vale do Paraíba; Brasi

Spectra and Symmetry in Nuclear Pairing

We apply the algebraic Bethe ansatz technique to the nuclear pairing problem with orbit dependent coupling constants and degenerate single particle energy levels. We find the exact energies and eigenstates. We show that for a given shell, there are degeneracies between the states corresponding to less and more than half full shell. We also provide a technique to solve the equations of Bethe ansatz.Comment: 15 pages of REVTEX with 2 eps figure

Proactive coping style in early emerging rainbow trout carries a metabolic cost with no apparent return

The timing with which salmonid larvae emerge from their gravel nests is thought to be correlated with a particular suite of behavioural and physiological traits that correspond to the stress coping style of the individual. Among these traits, aggressiveness, dominance and resilience to stress, are potentially interesting to exploit in aquaculture production. In the present study a series of experiments were performed, with the purpose of characterising behavioural, metabolic and production related traits in rainbow trout juveniles from different emergence fractions. Newly hatched rainbow trout were sorted according to their emergence time from an artificial nest. The early, middle, and late fractions were retained and assessed for their physiological response to stress, growth performance, metabolism, fasting tolerance, and potential for compensatory growth. The early emerging fraction showed proactive behavioural traits; they were faster to reappear following startling, showed a reduced cortisol response following stress,and a reduced metabolic cost of recovery. Emergence time was not correlated with any differences in standard or maximum metabolic rates, but was however, correlated with higher routine metabolic rates, as demonstrated by significantly bigger weight losses during fasting in the early emerging group. Growth rates and feed conversion efficiencies were not significantly different when fish were co-habitated under a restrictive feeding regime, suggesting that early emerging fish are not able to monopolize food resources. The intermediate emerging group, which makes up the bulk of a population and is often ignored, appears to possess the best growth performance traits, possibly because they do not expend excessive energy on dominance behaviour such as the early emerging group, while they are also not overly timid or stress prone such as the late emerging group

Efeito de inoculantes micorrízicos na produção de mudas de banana.

A inoculação de plantas com fungos micorrízicos arbusculares vem sendo adotada como alternativa à dependência de fertilizantes fosfatados durante a fase de crescimento de mudas. Além disso, inoculantes micorrizados também tem sido associados a uma melhor condição de crescimento de explantes micropropagados durante a fase de aclimatação. O desafio é a natureza biotrófica obrigatória dos fungos micorrízicos arbusculares, os quais completam seu ciclo apenas em raízes de culturas vivas

Análise integrada dos critérios de segurança ambiental dos nanoprodutos.

Resumo: As situações de risco potencial de um nanoproduto são cada vez mais multifacetadas. A triagem para a execução de novos testes pode seguir a árvore (decisões sim/não) considerando as informações anterior- mente conhecidas e os dados obtidos em testes a respeito do comportamento no ambiente, as caracteris- ticas e a novidade do nanoproduto. A sequência de passos avaliados com a árvore de decisão dependerá do estado da arte da metodologia de avaliação de risco e das características de cada caso em estudo. Abstract: The potential risk of nanoproducts is increasingly multifaceted. Screening for the implementation of new tests can follow the decision tree (decision yes/no) considering the previously known information and data from tests about the behavior in the environment, the characteristics and the novelty o f nano- product. The sequence of steps evaluated by the decision tree will depend on the methodology state of the art for risk assessment and the characteristics of each case study