High-energy ion emission from cooled deuterium clusters in 20 TW laser fields

High-energy ion emission from intense-ultrashort (30fs) laser-pulse- cooled deuterium-cluster (80K) interaction is measured. The deuterium ions have an average energy 20keV, which greatly exceeds Zweiback's expectation [Phys. Rev. Lett. 84 (2000) 2634]. These fast deuterium ions can be used to drive fusion and have a broad prospect.

Flood risk management: What are the main drivers of prevention?

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A scaling law of photoionization in few-cycle regime

In this paper, a scaling law of photoionization of atoms irradiated by intense, few- cycle laser pulses is established. The scaling law sets a relation to the phase- dependent ionization with the kinetic energy of photoelectrons, the duration and peak intensity of short pulses, and the ionization potential of the target atoms. We find that it will be advantageous to manifest the phase- dependent photoionization by choosing the target atoms with larger ionization potential, using laser with smaller carrier- frequency, and increasing the pulse intensity. (c) 2007 Optical Society of America.

Generation of 5 fs, 0.7 mJ pulses at 1 kHz through cascade filamentation

Two-cycle optical pulses with duration of 5 fs and energy of 0.7 mJ have been generated at 1 kHz by compressing the 38 fs laser pulses from a carrier-envelope phase (CEP) controlled Ti:sapphire laser system through a cascade filamentation compression technique. A simple and effective method is developed to suppress multiple filament formation and stabilize a single filament by inserting a soft aperture with an appropriate diameter into the driving laser beam prior to focusing, resulting in an excellent compressed beam quality. The good beam quality and potentially higher peak power make this ultrashort laser pulse source a significant tool for high-field physics applications. (C) 2007 Optical Society of America.

The Madden-Julian Oscillation : observation, modeling, and theory

The Madden-Julian Oscillation (MJO) is a pattern of intense rainfall and associated planetary-scale circulations in the tropical atmosphere, with a recurrence interval of 30-90 days. Although the MJO was first discovered 40 years ago, it is still a challenge to simulate the MJO in general circulation models (GCMs), and even with simple models it is difficult to agree on the basic mechanisms. This deficiency is mainly due to our poor understanding of moist convection—deep cumulus clouds and thunderstorms, which occur at scales that are smaller than the resolution elements of the GCMs. Moist convection is the most important mechanism for transporting energy from the ocean to the atmosphere. Success in simulating the MJO will improve our understanding of moist convection and thereby improve weather and climate forecasting.

We address this fundamental subject by analyzing observational datasets, constructing a hierarchy of numerical models, and developing theories. Parameters of the models are taken from observation, and the simulated MJO fits the data without further adjustments. The major findings include: 1) the MJO may be an ensemble of convection events linked together by small-scale high-frequency inertia-gravity waves; 2) the eastward propagation of the MJO is determined by the difference between the eastward and westward phase speeds of the waves; 3) the planetary scale of the MJO is the length over which temperature anomalies can be effectively smoothed by gravity waves; 4) the strength of the MJO increases with the typical strength of convection, which increases in a warming climate; 5) the horizontal scale of the MJO increases with the spatial frequency of convection; and 6) triggered convection, where potential energy accumulates until a threshold is reached, is important in simulating the MJO. Our findings challenge previous paradigms, which consider the MJO as a large-scale mode, and point to ways for improving the climate models.

Temporal confinement and enhancement of high-order harmonic emission with a synthesized laser field

We demonstrated that a synthesized laser field consisting of an intense long (45 fs, multi-optical-cycle) laser pulse and a weak short (7 fs, few-optical-cycle) laser pulse can control the electron dynamics and high-order harmonic generation in argon, and generate extreme ultraviolet supercontinuum towards the production of a single strong attosecond pulse. The long pulse offers a large amplitude field, and the short pulse creates a temporally narrow enhancement of the laser field and a gate for the highest energy harmonic emission. This scheme paves the way to generate intense isolated attosecond pulses with strong multi-optical-cycle laser pulses.

Phase-matching control of high-order harmonic generation in a two-color laser field

The phase-matching condition of high-order harmonic generation driven by intense few-cycle pulses could be controlled by adding second-harmonic pulses to change the ionization fraction of the gaseous medium. The harmonic generation efficiency could be improved by moving the phase-matching point with an all-optical control of the ionization fraction or a proper change of the confocal parameter. A specific order of harmonics could be easily controlled to reach phase matching at a fixed higher gas pressure by adding second-harmonic pulses with a suitable intensity. Such an all-optical phase-matching control was demonstrated to be dependent upon the temporal delay between the fundamental-wave and second harmonic pulses.

Generation of strong quasistatic magnetic fields in interactions of ultraintense and short laser pulses with overdense plasma targets

An analytical fluid model is proposed for the generation of strong quasistatic magnetic fields during normal incidence of a short ultraintense Gaussian laser pulse with a finite spot size on an overdense plasma. The steepening of the electron density profile in the originally homogeneous overdense plasma and the formation of electron cavitation as the electrons are pushed inward by the laser are included self-consistently. It is shown that the appearance of the cavitation plays an important role in the generation of quasistatic magnetic fields: the strong plasma inhomogeneities caused by the formation of the electron cavitation lead to the generation of a strong axial quasistatic magnetic field B-z. In the overdense regime, the generated quasistatic magnetic field increases with increasing laser intensity, while it decreases with increasing plasma density. It is also found that, in a moderately overdense plasma, highly intense laser pulses can generate magnetic fields similar to 100 MG and greater due to the transverse linear mode conversion process.

Generation of an extreme ultraviolet supercontinuum in a two-color laser field

We theoretically investigate the high-order harmonic generation in a helium atom with a two-color optical field synthesized by an intense 6 fs pulse at 800 nm and a relatively weak 21.3 fs pulse at 400 nm. When the frequency-doubled pulse is properly time shifted with respect to the fundamental pulse, an ultrabroad extreme ultraviolet supercontinuum spectrum with a 148 eV spectral width can be generated which directly creates an isolated 65 as pulse even without phase compensation. We explain this extraordinary phenomenon by analyzing maximum electron kinetic energies at different return times.

低密度大尺寸团簇形成的诊断研究

利用线性啁啾散射光谱测量法,研究了背压对团簇尺寸的影响以及团簇形成过程中尺寸的变化过程.同时发现低密度大尺寸团簇的形成,可以作为相关实验需要的干净且重要的团簇靶.

Estudo da expressão e participação de osteopontina durante a interação taquizoíto de Toxoplasma gondii célula hospedeira.

Toxoplasma gondii é um parasito do filo Apicomplexa que infecta uma grande variedade de hospedeiros, incluindo os humanos. O parasito invade a célula hospedeira por penetração ativa, com a participação das proteínas de suas organelas secretoras durante esse processo. Até o momento, somente um número limitado de proteínas secretoras tem sido descoberto, além disso, as moléculas efetoras envolvidas na invasão e sobrevivência do parasito não estão completamente compreendidas. A osteopontina (OPN) é uma glicofosfoproteína adesiva secretada, multifuncional, que contém o domínio arginina-glicina-ácido aspártico (RGD) de ligação à integrina, que está envolvida em uma variedade de eventos fisiológicos e patológicos, incluindo sinalização e sobrevivência celular. Pela primeira vez, nós demonstramos pelas técnicas de imunofluorescência e imunocitoquímica ultraestrutural que há uma intensa marcação para uma proteína OPN-like nos grânulos densos de taquizoítos de T. gondii extracelulares. O western blotting e o RT-PRC confirmaram a expressão de OPN-like nos taquizoítos. Nossos resultados também mostram que após a invasão dos macrófagos, a proteína OPN-like está localizada na membrana do vacúolo parasitóforo. Esses dados sugerem que os grânulos densos secretam uma proteína OPN-like, e nós podemos especular que essa proteína participa durante o processo de interação do parasito com as células hospedeiras. .

A retrofitting framework for pre-Northridge steel moment-frame buildings

In the 1994 M_w 6.7 Northridge and 1995 M_w 6.9 Kobe earthquakes, steel moment-frame buildings were exposed to an unexpected flaw. The commonly utilized welded unreinforced flange, bolted web connections were observed to experience brittle fractures in a number of buildings, even at low levels of seismic demand. A majority of these buildings have not been retrofitted and may be susceptible to structural collapse in a major earthquake.

This dissertation presents a case study of retrofitting a 20-story pre-Northridge steel moment-frame building. Twelve retrofit schemes are developed that present some range in degree of intervention. Three retrofitting techniques are considered: upgrading the brittle beam-to-column moment resisting connections, and implementing either conventional or buckling-restrained brace elements within the existing moment-frame bays. The retrofit schemes include some that are designed to the basic safety objective of ASCE-41 Seismic Rehabilitation of Existing Buildings.

Detailed finite element models of the base line building and the retrofit schemes are constructed. The models include considerations of brittle beam-to-column moment resisting connection fractures, column splice fractures, column baseplate fractures, accidental contributions from ``simple'' non-moment resisting beam-to-column connections to the lateral force-resisting system, and composite actions of beams with the overlying floor system. In addition, foundation interaction is included through nonlinear translational springs underneath basement columns.

To investigate the effectiveness of the retrofit schemes, the building models are analyzed under ground motions from three large magnitude simulated earthquakes that cause intense shaking in the greater Los Angeles metropolitan area, and under recorded ground motions from actual earthquakes. It is found that retrofit schemes that convert the existing moment-frames into braced-frames by implementing either conventional or buckling-restrained braces are effective in limiting structural damage and mitigating structural collapse. In the three simulated earthquakes, a 20% chance of simulated collapse is realized at PGV of around 0.6 m/s for the base line model, but at PGV of around 1.8 m/s for some of the retrofit schemes. However, conventional braces are observed to deteriorate rapidly. Hence, if a braced-frame that employs conventional braces survives a large earthquake, it is questionable how much service the braces provide in potential aftershocks.

Lynx1 Modulation of Nicotinic Acetylcholine Receptors

Nicotinic receptors are the target of nicotine in the brain. They are pentameric ion channels. The pentamer structure allows many combinations of receptors to be formed. These various subtypes exhibit specific properties determined by their subunit composition. Each brain region contains a fixed complement of nicotinic receptor subunits. The midbrain region is of particular interest because the dopaminergic neurons of the midbrain express several subtypes of nicotinic receptors, and these dopaminergic neurons are important for the rewarding effects of nicotine. The α6 nicotinic receptor subunit has garnered intense interest because it is present in dopaminergic neurons but very few other brain regions. With its specific and limited presence in the brain, targeting this subtype of nicotinic receptor may prove advantageous as a method for smoking cessation. However, we do not fully understand the trafficking and membrane localization of this receptor or its effects on dopamine release in the striatum. We hypothesized that lynx1, a known modulator of other nicotinic receptor subtypes, is important for the proper function of α6 nicotinic receptors. lynx1 has been found to act upon several classes of nicotinic receptors, such as α4β2 and α7, the two most common subtypes in the brain. To determine whether lynx1 affects α6 containing nicotinic receptors we used biochemistry, patch clamp electrophysiology, fast scan cyclic voltammetry, and mouse behavior. We found that lynx1 has effects on α6 containing nicotinic receptors, but the effects were subtle. This thesis will detail the observed effects of lynx1 on α6 nicotinic receptors.

A regulação política da sexualidade no âmbito da família por saberes e instituições médicas brasileiras : 1838-1940

Esta tese tem como objeto a regulação política da sexualidade no âmbito da família por saberes e instituições médicas brasileiras (1838-1940). Orienta-se pelo interesse em analisar continuidades e descontinuidades na construção de objetos, estratégias e táticas políticas direcionados para a regulação higiênica e eugênica do casamento e da sexualidade infantil. De inspiração foucaultiana, inscreve-se no campo da história dos saberes e está subsidiada por um conjunto heterogêneo de documentos (teses, artigos de periódicos, livros, anais etc.) circunscritos, majoritariamente, ao campo da medicina. Analisa a constituição de uma defesa higiênica dos casamentos no pensamento médico novecentista, voltada para remanejamentos das figuras de esposa e marido na nova configuração de família que começava a se esboçar no Brasil, contrastando-a com a regulação católica da moral sexual colonial. Em seguida, descreve a visibilidade higiênica que a medicina dará a infância no século XIX, problematizando especificamente o interesse pelo tema da masturbação, que articula simultaneamente a família, centrada na figura da mãe, e a escola na convocação de zelar pela criança. Partindo das contradições sociais que se apresentaram na construção do projeto liberal nacional a partir da década de 1870, discute a apropriação do discurso da degenerescência pelo saber médico-psiquiátrico brasileiro, que propiciou uma leitura da brasilidade marcada pelo excesso sexual e pela condição degenerada da miscigenação, a fim de pensar as condições de possibilidade para a emergência do projeto de eugenia matrimonial institucionalizado nas primeiras décadas do século XX e toma como táticas a campanha pela compulsoriedade do exame pré-nupcial, o combate aos casamentos consanguíneos, o controle do contágio venéreo e o aconselhamento sexual dos casais. Analisa a campanha de educação sexual, cuja pretensão de instituir uma sciencia sexual no Brasil, de legitimidade controversa, tinha como horizonte viabilizar uma profilaxia sexual que mitigasse a produção da criminalidade, das perversões sexuais e das doenças nervosas, bem como os desajustes familiares, a partir da fabricação de um novo objeto, qual seja, a sexualidade infantil, no qual incidirá uma nova pedagogia. Nesse particular, aponta particularidades discursivas da difusão das idéias freudianas entre higienistas brasileiros. Finalmente, sinaliza a constituição da higiene mental da criança como um novo domínio para a psiquiatria brasileira, que tomou a intensa circulação afetiva intrafamiliar como ponto de ancoragem para um projeto de normalização social, ainda centrado na eugenia, mas já atravessado por uma psicologia da adaptação.

A obrigação de extraditar para a repressão do terrorismo: a prática brasileira à luz do direito penal transnacional

O combate efetivo ao flagelo secular do terrorismo, ainda que possa se revestir de muitas formas, não prescinde da repressão penal de seus autores. Em vista da maciça internacionalização do terrorismo, a partir do Século XX, a cooperação jurídica internacional em matéria penal (aí incluída a extradição) consolida-se como instrumento de essencial importância para a repressão do terrorismo pela comunidade internacional, com a vantagem de resguardar o domínio do direito e, por conseguinte, de assegurar a paz e a segurança internacionais. A evolução do tratamento do crime de terrorismo pelo direito penal transnacional influenciada pelo direito da segurança coletiva, especialmente a partir dos atentados de 11 de setembro de 2001 exerceu expressivo impacto no direito extradicional. O entendimento desse efeito é fundamental para extrair-se do instituto da extradição todo o seu potencial para a repressão penal do terrorismo. Desde que presentes determinados requisitos, uma conduta de caráter terrorista à luz de parâmetros internacionais gera a obrigação estatal de extraditar ou processar seu autor, mesmo na ausência de tratado. Além disso, a extradição exercida ou não em decorrência de obrigação convencional tem seus princípios afetados pela obrigação internacional de repressão do terrorismo, particularmente no que se refere a questões como extraditabilidade, extradição por crimes políticos e extradição de refugiados. O direito brasileiro apresenta algumas vulnerabilidades para o cumprimento da obrigação aut dedere aut iudicare e a prática judicial brasileira relativa à extradição de acusados de atos de terrorismo poderia reportar-se mais ao direito internacional, com vistas a evitar o risco de violação de obrigações internacionais pelo Brasil.