Quantum Electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell's equations due to vacuum polarization. Our multidimensional solver reproduced in one dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of counter-propagating configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities

Beam loading in the nonlinear regime of plasma-based acceleration

A theory that describes how to load negative charge into a nonlinear, three-dimensional plasma wakefield is presented. In this regime, a laser or an electron beam blows out the plasma electrons and creates a nearly spherical ion channel, which is modified by the presence of the beam load. Analytical solutions for the fields and the shape of the ion channel are derived. It is shown that very high beam-loading efficiency can be achieved, while the energy spread of the bunch is conserved. The theoretical results are verified with the Particle-In-Cell code OSIRIS.Comment: 5 pages, 2 figures, to appear in Physical Review Letter

Entanglement and the nonlinear elastic behavior of forests of coiled carbon nanotubes

Helical or coiled nanostructures have been object of intense experimental and theoretical studies due to their special electronic and mechanical properties. Recently, it was experimentally reported that the dynamical response of foamlike forest of coiled carbon nanotubes under mechanical impact exhibits a nonlinear, non-Hertzian behavior, with no trace of plastic deformation. The physical origin of this unusual behavior is not yet fully understood. In this work, based on analytical models, we show that the entanglement among neighboring coils in the superior part of the forest surface must be taken into account for a full description of the strongly nonlinear behavior of the impact response of a drop-ball onto a forest of coiled carbon nanotubes.Comment: 4 pages, 3 figure

All-optical trapping and acceleration of heavy particles

A scheme for fast, compact, and controllable acceleration of heavy particles in vacuum is proposed, in which two counterpropagating lasers with variable frequencies drive a beat-wave structure with variable phase velocity, thus allowing for trapping and acceleration of heavy particles, such as ions or muons. Fine control over the energy distribution and the total charge of the beam is obtained via tuning of the frequency variation. The acceleration scheme is described with a one-dimensional theory, providing the general conditions for trapping and scaling laws for the relevant features of the particle beam. Two-dimensional, electromagnetic particle-in-cell simulations confirm the validity and the robustness of the physical mechanism.Comment: 10 pages, 3 figures, to appear in New Journal of Physic

Representações sociais sobre a organização espacial no Assentamento Mato Grande, Corumbá, Mato Grosso do Sul.

O estudo tem como propósito analisar as representações de agricultoras, esposas de assentados, em relação à organização espacial na conformação do Assentamento Mato Grande, em Corumbá, MS. O assentamento rural foi criado em 1988, e foram assentadas 50 famílias, sendo 25 delas oriundas do Estado do Paraná e outras 25 da Cidade de Corumbá. No intuito de se verificar a compreensão que um grupo de agricultoras tem em relação à distribuição espacial do assentamento foi utilizada a técnica do mapeamento participativo da comunidade onde as agricultoras desenharam o assentamento e suas representações, focando em especial na localização e disponibilidade da palmeira bocaiuva, com potencial econômico. Observou-se que o grupo tem o conhecimento do dos recursos naturais, e da distribuição e ocorrência de grupos da palmeira. Problemas de gestão d'água, individualismo e disputas internas entravam o desenvolvimento social e econômico do assentamento. The aim of this study is analyze the representations of women, wives of land reform farmers in relation to the space organization in the conformation of the land reform settlement Mato Grande, in Corumba, MS. The land reform settlement was created in 1988 and is composed by 50 families, 25 of them originated from the State of Parana and 25 from the Corumba County.In order to study the farmer's women understanding of space organization of the settlement it was used the participatory mapping technique, where the farmer women themselves drew the settlement space and its representations, focusing in particular on the location and availability of bocaiuva palm tree, which has economic potential. It was observed that the group has the knowledge of the natural resources, and the distribution and occurrence of palm tree groups. Water management problems, individualism and internal disputes hinder social and economic development of the settlement.Título em inglês: Social representations about the space organization in Mato Grande Land Reform Settlement, Corumbá, Mato Grosso do Sul

One-to-one full scale simulations of laser wakefield acceleration using QuickPIC

We use the quasi-static particle-in-cell code QuickPIC to perform full-scale, one-to-one LWFA numerical experiments, with parameters that closely follow current experimental conditions. The propagation of state-of-the-art laser pulses in both preformed and uniform plasma channels is examined. We show that the presence of the channel is important whenever the laser self-modulations do not dominate the propagation. We examine the acceleration of an externally injected electron beam in the wake generated by 10 J laser pulses, showing that by using ten-centimeter-scale plasma channels it is possible to accelerate electrons to more than 4 GeV. A comparison between QuickPIC and 2D OSIRIS is provided. Good qualitative agreement between the two codes is found, but the 2D full PIC simulations fail to predict the correct laser and wakefield amplitudes.Comment: 5 pages, 5 figures, accepted for publication IEEE TPS, Special Issue - Laser & Plasma Accelerators - 8/200

Avaliação do perfil fenotípico de caprinos brasileiros e africanos.

Resumo: Objetivou-se diferenciar populações caprinas brasileiras e cabo-verdianas (n=1084) por meio de descritores biométricos e comparação com raças comerciais. Foram avaliadas sete características de fêmeas adultas, através da estatística descritiva, análise de variância, teste de multicolinearidade, distância generalizada de Mahalanobis (D2) e algoritmo UPGMA. Após o teste de multicolinearidade foi identificada e descartada a variável profundidade torácica. O maior valor da D2 foi entre as populações Nambi e Mambrina (D2=93,78), e a menor D2 foi entre as cabras cabo-verdianas de Santo Antão e São Vicente (D2=0,41). O dendrograma colocou as raças Mambrina e Anglo-Nubiana a parte das demais. As cabras de Cabo Verde ficaram mais próximas das brasileiras de núcleos de conservação. As caboverdianas se agruparam segundo Barlavento e Sotavento. A eficácia da manutenção dos caprinos brasileiros em rebanhos de conservação nos faz preconizar tais iniciativas como ferramenta eficaz de manutenção dos recursos genéticos para potencial uso sustentável. Evaluation of the phenotypic profile of Brazilian and African goats. Abstract: The work aims was differentiate Brazilian goats populations of Cape Verdean (n = 1084) using biometric descriptors and comparison with commercial breeds. It was measured seven characteristics of female adult goats by using descriptive statistics, analysis of variance test multicollinearity, Mahalanobis distance (D2) and UPGMA algorithm. After testing of multicollinearity was identified and discarded the thoracic depth variable. The maximum value of D2 was between populations Nambi and Mambrina (D2 = 93.78), and the lower D2 was between the Cape Verdean goats of Santo Antão and São Vicente (D2 = 0.41). The dendrogram put the breeds Mambrina and Anglo-Nubian part of others. The goats of Cape Verde were closer to the Brazilian conservation nuclei. The Cape Verdean were made a group was Barlavento and Sotavento. The maintenance efficiency of the Brazilian goat herds conservation makes us valuate such initiatives as an effective tool for maintenance of genetic resources for potential use sustainable

GnRH use in different times on estrus synchronization and ovulation in Santa Inês ewes.

Proceedings of the 28th Annual Meeting of the Brazilian Embryo Technology Society (SBTE), August, 2014, Natal, RN, Brazil. Abstracts

Quantum electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell’s equations due to vacuum polarization. Our multidimensional solver reproduced in one-dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of laser configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities.info:eu-repo/semantics/publishedVersio