Elastic thick shells in general relativity

It is shown that exact spherically symmetric solutions to Einstein's field equations exist such that, over an open region of the spacetime, they are singularity free, satisfy the dominant energy condition, represent elastic matter with a well-defined constitutive function, and are such that elastic perturbations propagate causally. Two toy models are then built up in which a thick elastic, spherically symmetric shell with the above properties, separates two Robertson-Walker regions corresponding to different values of the curvature k in the first model and to the same value of k in the second model. The junction conditions (continuity of the first and second fundamental forms) are shown to be exactly satisfied across the corresponding matching spherical surfaces.- The authors are grateful to Prof. Raul Vera, from the Universidad del Pais Vasco/Euskal Herriko Unibersitatea, for helpful discussions and suggestions. One of the authors (J. C.) acknowledges financial support from the Spanish Ministerio de Economia y Competitividad through Grants No. FPA2013-41042-P and No. FPA2016-76821-P, and also acknowledges the warm hospitality, and partial financial support, from the University do Minho, where the present version of this manuscript was prepared. The research of I. B. and E. V. was partially financed by Portuguese Funds through FCT (Fundacao para a Ciencia e Tecnologia) within the Project No. UID/MAT/00013/2013. I. B. is grateful for support from FCT, through the Project No. PEstOE/MAT/UI0013/2014 and also expresses her gratitude for the hospitality at the Universitat de les Illes Balears

Busca usando sinônimos no Ainfo-Consulta.

O foco deste trabalho é na expansão de consultas com termos obtidos por meio do Thesaurus Brasileiro de Agricultura - Thesagro (BRASIL, 1999) para melhorar os resultados do Ainfo-Consulta

General spherically symmetric elastic stars in Relativity

The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modeling of star interiors possessing elastic properties such as theones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6].Comment: 23 page

Dynamical Mass Constraints on Low-Mass Pre-Main-Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 Msun Primary and an 0.7 Msun Secondary

We report the discovery of a double-lined, spectroscopic, eclipsing binary in the Orion star-forming region. We analyze the system spectroscopically and photometrically to empirically determine precise, distance-independent masses, radii, effective temperatures, and luminosities for both components. The measured masses for the primary and secondary, accurate to ~1%, are 1.01 Msun and 0.73 Msun, respectively; thus the primary is a definitive pre-main-sequence solar analog, and the secondary is the lowest-mass star yet discovered among pre-main-sequence eclipsing binary systems. We use these fundamental measurements to test the predictions of pre-main-sequence stellar evolutionary tracks. None of the models we examined correctly predict the masses of the two components simultaneously, and we implicate differences between the theoretical and empirical effective temperature scales for this failing. All of the models predict the observed slope of the mass-radius relationship reasonably well, though the observations tend to favor models with low convection efficiencies. Indeed, considering our newly determined mass measurements together with other dynamical mass measurements of pre-main-sequence stars in the literature, as well as measurements of Li abundances in these stars, we show that the data strongly favor evolutionary models with inefficient convection in the stellar interior, even though such models cannot reproduce the properties of the present-day Sun.Comment: Accepted by Ap

A raça Valdostana: uma nova opção para linha materna.

Origem e distribuição geográfica. Características da raça. Características produtivas. Características reprodutivas. Avaliação preliminares. Avaliações futuras.bitstream/item/132424/1/COT-59.pdf.pdfCNPGC

The Einstein field equations for cylindrically symmetric elastic configurations

In the context of relativistic elasticity it is interesting to study axially symmetric space-times due to their significance in modeling neutron stars and other astrophysical systems of interest. To approach this problem, here, a particular class of these space-times is considered. A cylindrically symmetric elastic space-time configuration is studied, where the material metric is taken to be flat. The components of the energy-momentum tensor for elastic matter are written in terms of the invariants of the strain tensor, here chosen to be the eigenvalues of the pulled-back material metric. The Einstein field equations are presented and a condition confirming the existence of a constitutive function is obtained. This condition leads to special cases, in one of which a new system for the metric functions and an expression for the constitutive function are deduced. The new system depends on a particular function, which builds up the constitutive equation.IB and EGLRV acknowledge financial support from FCT and CMAT. They also express their thanks and gratitude for the hospitality at the Universitat de les Illes Balears

IMPACT OF INTERACTION P AND Zn ON BIOFORTIFICATION OF BEAN

INTRODUCTION: A large part of the world population has low levels of micronutrients, especially pregnant women and children in developing countries. Zinc (Zn) is a micronutrient, performing many functions in the organism. Biofortifcation aims to increase the concentration of certain mineral in parts consumed of the cultivated plants. The crops of most interest are those that constitute the basic diet for the majority of the population, including beans. Two main strategies are used in biofortification, selection of cultivars more favorable to biofortification and increase the micronutrient dose. Biofortification of bean with Zn is difficult due to interaction with phosphorus (P). The decrease in zinc absorption caused by phosphorus depends on soil atributes such as pH, cation exchange capacity and direct reaction with Zn and subsequent precipitation. The increase of the dose of Zn can reduce the absorption of iron by plants by competitve inhibition. This study aimed to evaluate the interaction between P and Zn about biofortication in two bean cultivars, evaluating the concentration of Zn and iron in the grain and production

IMPACT OF INTERACTION P AND Zn ON BIOFORTIFICATION OF BEAN

INTRODUCTION: A large part of the world population has low levels of micronutrients, especially pregnant women and children in developing countries. Zinc (Zn) is a micronutrient, performing many functions in the organism. Biofortifcation aims to increase the concentration of certain mineral in parts consumed of the cultivated plants. The crops of most interest are those that constitute the basic diet for the majority of the population, including beans. Two main strategies are used in biofortification, selection of cultivars more favorable to biofortification and increase the micronutrient dose. Biofortification of bean with Zn is difficult due to interaction with phosphorus (P). The decrease in zinc absorption caused by phosphorus depends on soil atributes such as pH, cation exchange capacity and direct reaction with Zn and subsequent precipitation. The increase of the dose of Zn can reduce the absorption of iron by plants by competitve inhibition. This study aimed to evaluate the interaction between P and Zn about biofortication in two bean cultivars, evaluating the concentration of Zn and iron in the grain and production

Glycyrrhizic acid and its hydrolyzed metabolite 18β-glycyrrhetinic acid as specific ligands for targeting nanosystems in the treatment of liver cancer

Glycyrrhizic acid and its hydrolyzed metabolite 18β-glycyrrhetinic acid, obtained from the plant Glycyrrhiza glabra, have numerous pharmacological activities, such as anti-inflammatory, anti-ulcerative, antiallergic, immunomodulatory, antiviral, antitumor, hepatoprotective, and antioxidant effects, and others. In addition to the pharmacological activities, in the 1980s, an interaction and uptake of these molecules by the liver was verified, which was later confirmed by other studies through the discovery of specific receptors in the hepatocytes. The presence of these specific receptors in the liver led to vectorization and delivery of drugs, by the introduction of glycyrrhizic acid or glycyrrhetinic acid on the surface of nanosystems, for the treatment of liver diseases. This review describes experimental evidence of vectorization by conjugating glycyrrhizic acid or glycyrrhetinic acid to nanosystems and delivery of antitumor drugs for the treatment of liver cancer and also describes the techniques used to perform this conjugation. We have shown that due to the existence of specific receptors for these molecules, in addition to the targeting of nanosystems to hepatocytes, nanosystems having glycyrrhizic acid or glycyrrhetinic acid on their surface had the same therapeutic effect in a significantly lower dose compared to the free drug and unconjugated nanosystems, with consequent reduction of side effects and toxicity

Spherically symmetric elasticity in relativity

The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modelling of star interiors possessing elastic properties such as the ones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6].JC acknowledges financial support from MEC through grant No.: HP2006-0074. Partial financial support from (MEC) through grant FPA-2007-60220 and from the Govern de les Illes Balears is also acknowledged. IB and EGLRV acknowledge financial support from (CRUP) through grant No.: E-89/07 and from FCT and CMAT