4,778 research outputs found
Four dimensional R^4 superinvariants through gauge completion
We fully compute the N=1 supersymmetrization of the fourth power of the Weyl
tensor in d=4 x-space with the auxiliary fields. In a previous paper, we showed
that their elimination requires an infinite number of terms; we explicitely
compute those terms to order \kappa^4 (three loop). We also write, in
superspace notation, all the possible N=1 actions, in four dimensions, that
contain pure R^4 terms (with coupling constants). We explicitely write these
actions in terms of the \theta components of the chiral density \epsilon and
the supergravity superfields R, G_m, W_{ABC}. Using the method of gauge
completion, we compute the necessary \theta components which allow us to write
these actions in x-space. We discuss under which circumstances can these extra
R^4 correction terms be reabsorbed in the pure supergravity action, and their
relevance to the quantum supergravity/string theory effective actions.Comment: 20 pages, no figures. Sec. 3 clarified; typos correcte
Extração de palavras-chave e taxonomias de tópicos para a BDPA.
Este trabalho refere-se ao desenvolvimento de técnicas e ferramentas baseadas em extração de informação e mineração de textos para análise automatizada de conteúdo de campos dos registros existentes na Base de Dados de Pesquisa Agropecuária (BDPA). A princípio, os objetivos são chegar a uma taxonomia de tópicos inicial para sub-bases da Produção Científica da Embrapa (ProdEMB) e o estudo e identificação de campos faltantes nos registros da BDPA
Aplicativo para análise de componentes principais.
Análise por componentes principais. Entrada de dados para o aplicativo: Procedimento. Opções do aplicativo. Especificação de algoritmos: Descrição de método. Cálculo usando a matriz de variâncias e covariâncias(S). Cálculo usando a matriz de correlação (R). Cálculo usando a Matriz Parcial.bitstream/item/76655/1/CNPTIA-COM.TEC.-6-99.pd
Variação da habilidade combinatória em população restauradora para o desenvolvimento de linhagens R em arroz.
O objetivo deste trabalho foi avaliar test crosses de uma população desenvolvida para a criação de linhagens R genitoras de híbridos, do Programa Arroz Híbrido Embrapa-Cirad
Aplicativo para análise de correspondência.
Análise de correspondência. Descrição do aplicativo. Entrada de dados. Seleção de variáveis. Opções do aplicativo. Algoritmo.bitstream/item/76674/1/CNPTIA-COM.TEC.-5-99.pd
Tutorial TaxTools.
A ferramenta TaxTools foi desenvolvida pelo Laboratório de Inteligência Computacional (Labic) do Instituto de Ciência Matemática e de Computação (ICMC) da Universidade de São Paulo (USP), campus de São Carlos, SP, com o objetivo de auxiliar no processo de mineração de textos. Atualmente, ela tem sido mantida e evoluída pelo Laboratório de Inteligência Computacional (LabIC) da Embrapa Informática Agropecuária. Esse tutorial abrange apenas as opções disponíveis na TaxTools, que completam o processo de obtenção de uma taxonomia de tópicos (MOURA et al., 2008); como clusterização, cálculos de medidas intercluster e de joinability, métodos de podas, métodos de visualização de resultados e algumas opções auxiliares.bitstream/item/30572/1/doc104.pd
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Differential mesenteric fat deposition in bovines fed on silage or concentrate is independent of glycerol membrane permeability
© The Animal Consortium 2011In the meat industry, the manipulation of fat deposition in cattle is of pivotal importance to improve production efficiency, carcass composition and ultimately meat quality. There is an increasing interest in the identification of key factors and molecular mechanisms responsible for the development of specific fat depots. This study aimed at elucidating the influence of breed and diet on adipose tissue membrane permeability and fluidity and their interplay on fat deposition in bovines. Two Portuguese autochthonous breeds, Alentejana and Barrosã, recognized as late- and early-maturing breeds, respectively, were chosen to examine the effects of breed and diet on fat deposition and on adipose membrane composition and permeability. Twenty-four male bovines from these breeds were fed on silage-based or concentrate-based diets for 11 months. Animals were slaughtered to determine their live slaughter and hot carcass weights, as well as weights of subcutaneous and visceral adipose depots. Mesenteric fat depots were excised and used to isolate adipocyte membrane vesicles where cholesterol content, fatty acid profile as well as permeability and fluidity were determined. Total accumulation of neither subcutaneous nor visceral fat was influenced by breed. In contrast, mesenteric and omental fat depots weights were higher in concentrate-fed bulls relative to silage-fed animals. Membrane fluidity and permeability to water and glycerol in mesenteric adipose tissue were found to be independent of breed and diet. Moreover, the deposition of cholesterol and unsaturated fatty acids, which may influence membrane properties, were unchanged among experimental groups. Adipose membrane lipids from the mesenteric fat depot of ruminants were rich in saturated fatty acids, and unaffected by polyunsaturated fatty acids dietary levels. Our results provide evidence against the involvement of cellular membrane permeability to glycerol on fat accumulation in mesenteric fat tissue of concentrate-fed bovines, which is consistent with the unchanged membrane lipid profile found among experimental groups.This study was supported by Fundação para a Ciência e a Tecnologia (FCT) through grant PTDC/CVT/2006/66114 and individual fellowships to Ana P. Martins (SFRH/BD/2009/65046), Ana S. H. Costa (SFRH/BD/2009/61068) and Susana V. Martins (SFRH/BPD/2009/63019). Paula A. Lopes is a researcher from the program ‘‘Ciência 2008’’ from FC
Design and Development of an Adhesive Joint Testing Apparatus for Mixed-Mode Evaluation
The present work is dedicated to the development and design of a load jig inspired in theproposed solution by Fernlund and Spelt in order to characterize fracture of bonded joints undermixed-mode I+II loading. The jig allows for easy alteration of the mode-mixity and permits coveringthe full range of mixed-mode I+II combinations. A data reduction scheme based on specimencompliance, beam theory and crack equivalent concept is proposed to overcome several difficultiesinherent to the test analysis. The development was based in a design methodology using numericalvalidation based on experimental data obtained with a Dual Loading Frame from Virginia Tech. Thismethodology is presented and then validated with the experimental application of the jig
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