Geometric aspects of nonholonomic field theories

A geometric model for nonholonomic Lagrangian field theory is studied. The multisymplectic approach to such a theory as well as the corresponding Cauchy formalism are discussed. It is shown that in both formulations, the relevant equations for the constrained system can be recovered by a suitable projection of the equations for the underlying free (i.e. unconstrained) Lagrangian system.Comment: 29 pages; typos remove

Neutral perfect fluids of Majumdar-type in general relativity

We consider the extension of the Majumdar-type class of static solutions for the Einstein-Maxwell equations, proposed by Ida to include charged perfect fluid sources. We impose the equation of state $\rho+3p=0$ and discuss spherically symmetric solutions for the linear potential equation satisfied by the metric. In this particular case the fluid charge density vanishes and we locate the arising neutral perfect fluid in the intermediate region defined by two thin shells with respective charges $Q$ and $-Q$. With its innermost flat and external (Schwarzschild) asymptotically flat spacetime regions, the resultant condenser-like geometries resemble solutions discussed by Cohen and Cohen in a different context. We explore this relationship and point out an exotic gravitational property of our neutral perfect fluid. We mention possible continuations of this study to embrace non-spherically symmetric situations and higher dimensional spacetimes.Comment: 9 page

Non-perturbative scalar gauge-invariant metric fluctuations from the Ponce de Leon metric in the STM theory of gravity

We study our non-perturbative formalism to describe scalar gauge-invariant metric fluctuations by extending the Ponce de Leon metric.Comment: accepted in Eur. Phys. J.

Discrete Nonholonomic Lagrangian Systems on Lie Groupoids

This paper studies the construction of geometric integrators for nonholonomic systems. We derive the nonholonomic discrete Euler-Lagrange equations in a setting which permits to deduce geometric integrators for continuous nonholonomic systems (reduced or not). The formalism is given in terms of Lie groupoids, specifying a discrete Lagrangian and a constraint submanifold on it. Additionally, it is necessary to fix a vector subbundle of the Lie algebroid associated to the Lie groupoid. We also discuss the existence of nonholonomic evolution operators in terms of the discrete nonholonomic Legendre transformations and in terms of adequate decompositions of the prolongation of the Lie groupoid. The characterization of the reversibility of the evolution operator and the discrete nonholonomic momentum equation are also considered. Finally, we illustrate with several classical examples the wide range of application of the theory (the discrete nonholonomic constrained particle, the Suslov system, the Chaplygin sleigh, the Veselova system, the rolling ball on a rotating table and the two wheeled planar mobile robot).Comment: 45 page

Program of genetic management of the hispano-arabe horse breed

The Hispano-Arabe horse breed could be considered as a synthetic breed formed in Spain at least two centuries ago, because the farmer intention of create a breed for working and sport according the necessities of the epoch. Today the breed is officially recognized as autochthons breed of especial protection, due to their few effectives. In this communication we are presenting the program for the genetic management of the breed in development in an interdisciplinary and inter-institutional manner. The program has the following parts: Design and initiation of a program of improvement and conservation; Creation of a germplasm bank for the principal reproducers; Study of the genetic structure of the breed using DNA microsatellite markers; Technical formation and divulgation of the breed. The program and the work developed by the moment are described.El caballo Hispano-Árabe puede considerarse una raza sintética formada en España desde hace más de dos siglos por la intención de los ganaderos de contar con una raza de trabajo y deporte adecuada a las necesidades de la época. Hoy en día está reconocido oficialmente como una raza autóctona de protección especial, debido a sus escasos efectivos. En esta comunicación se presenta el programa de gestión genética de la raza, el cual se está desarrollando de manera interdisciplinar e inter-institucional. Consta de los siguientes apartados: Diseño y puesta en marcha de un programa de mejora y de conservación; Creación de un banco de germoplasma de los reproductores destacados; Estudio de la estructura genética de la raza utilizando marcadores microsatélites del ADN; Formación técnica y divulgación de la raza. Se describen el programa y las actuaciones desarrolladas hasta el momento

Capillary Condensation and Interface Structure of a Model Colloid-Polymer Mixture in a Porous Medium

We consider the Asakura-Oosawa model of hard sphere colloids and ideal polymers in contact with a porous matrix modeled by immobilized configurations of hard spheres. For this ternary mixture a fundamental measure density functional theory is employed, where the matrix particles are quenched and the colloids and polymers are annealed, i.e. allowed to equilibrate. We study capillary condensation of the mixture in a tiny sample of matrix as well as demixing and the fluid-fluid interface inside a bulk matrix. Density profiles normal to the interface and surface tensions are calculated and compared to the case without matrix. Two kinds of matrices are considered: (i) colloid-sized matrix particles at low packing fractions and (ii) large matrix particles at high packing fractions. These two cases show fundamentally different behavior and should both be experimentally realizable. Furthermore, we argue that capillary condensation of a colloidal suspension could be experimentally accessible. We find that in case (ii), even at high packing fractions, the main effect of the matrix is to exclude volume and, to high accuracy, the results can be mapped onto those of the same system without matrix via a simple rescaling.Comment: 12 pages, 9 figures, submitted to PR

The white andalusian goat breed: characterization and conservation

The Blanca Serrana Andaluza goat breed is one of the most ancient in the Iberian Peninsula and for its origin the only one showing the influence of African branches; its meat aptitude, its size and its adaptation to hard conditions has always located this breed in the most marginal areas of Andalusia, usually zones without use for agriculture and other farming activities. Presently three main causes of endangering are over the breed; the first is the diminution of the census; the second is the competence by feeding areas with hunting species, specially deers, and finally the most important cause is the cross-breeding with the Blanca Celtibérica goat breed, shorter animal with low adaptability. In opposite of this situation, we are using the advantages presented by the scarce census of the breed, one of them is that the existing farms belong to young farmers very sensitized for the conservation and the improvement of traditional extensive management systems, what is favouring the creation of a breeders association. We have also started the characterization of the breed by mean of molecular markers, as a fundamental tool for the populational definitions, specially in situation like this one with clear crossbreeding with other breeds.La cabra Blanca Serrana Andaluza es una de las más antiguas de la península Ibérica y por origen, la única con marcada influencia de troncos africanos, su aptitud cárnica, envergadura y adaptación a las condiciones adversas ha situado siempre su área de explotación en las zonas más marginales de Andalucía, zonas de montaña, no aptas para cultivos u otras ganaderías como bovinas, ovinas y caprinas lecheras. En la actualidad tres grandes amenazas se ciernen sobre esta raza, por un lado, la imparable disminución de sus censos, por otro, la competencia con las especies cinegéticas, fundamentalmente ciervos, por las zonas de pastoreo, y por último, la amenaza más peligrosa pues es menos visible y más destructiva, el cruce con animales de la raza Blanca Celtibérica, de menor envergadura y e inferior aptitud para zonas de monte cerrado. Ante esta situación, se aprovechan las ventajas que presentan los escasos efectivos de la raza, una de ellas, es que los rebaños que no han sido sacrificados, han ido pasando a manos de ganaderos y ganaderas jóvenes y, en gran parte de las ocasiones, con sensibilidad a los temas conservacionistas y a la mejora de los sistemas de explotación tradicionales, extensivos, lo que ha favorecido la creación de una asociación. También para defensa de los intereses de la raza, se ha comenzando por su caracterización, que en estos momentos se está desarrollando, mediante el uso de marcadores moleculares, pues es una herramienta fundamental en la definición de poblaciones, sobre todo en situaciones de cruce de individuos con otras razas

Analisis and tools for performance prediction

We present an analytical model that extends BSP to cover both oblivious synchronization and group partitioning. There are a few oversimplifications in BSP that make difficult to have accurate predictions. Even if the numbers of individual communication or computation operations in two stages are the same, the actual times for these two stages may differ. These differences are due to the separate nature of the operations or to the particular pattern followed by the messages. Even worse, the assumption that a constant number of machine instructions takes constant time is far from the truth. Current memory hierarchies imply that memory access vary from a few cycles to several thousands. A natural proposal is to associate a different proportionality constant with each basic block, and analogously, to associate different latencies and bandwidths with each “communication block”. Unfortunately, to use this approach implies that the evaluation parameters not only depend on given architecture, but also reflect algorithm characteristics. Such parameter evaluation must be done for every algorithm. This is a heavy task, implying experiment design, timing, statistics, pattern recognition and multi-parameter fitting algorithms. Software support is required. We have developed a compiler that takes as source a C program annotated with complexity formulas and produces as output an instrumented code. The trace files obtained from the execution of the resulting code are analyzed with an interactive interpreter, giving us, among other information, the values of those parameters.Eje: Programación concurrenteRed de Universidades con Carreras en Informática (RedUNCI

Influence of cardiovascular condition on retinal and retinal nerve fiber layer measurements

Objective To assess changes in the retinal nerve fiber layer (RNFL) and macula in subjects with cardiovascular risk factors or subclinical ischemia. Design Prospective and observational study. Methods A total of 152 healthy men underwent cardiovascular examination, including quantification of subclinical atheroma plaques by artery ultrasound scans, blood analysis, and a complete ophthalmic evaluation, including spectral-domain optical coherence tomography. The variables registered in cardiovascular examination were quantification of classic major risk factors, subclinical atheroma plaques by artery ultrasound scans, and analytical records. The ophthalmic evaluation registered RNFL and macular thickness. Results Mean subject age was 51.27±3.71 years. The 40 subjects without classic cardiovascular risk factors did not show differences in RNFL and macular thicknesses compared with the 112 subjects with at least one risk factor (except in sector 9 that showed higher thicknesses in subjects with 1 risk factor). Comparison between the group of subjects with and without atheroma plaques revealed no differences in RNFL and macular thicknesses. The sub-analysis of subjects with subclinical atheroma plaques in the common carotid artery revealed a significant reduction in central macular thickness in the left eye compared with the right eye (p = 0.016), RNFL in the superior quadrant (p = 0.007), and the 11 o’clock sector (p = 0.020). Comparison between smokers and nonsmokers revealed that smokers had significant thinning of the central macular thickness (p = 0.034), the nasal RNFL quadrant (p = 0.006), and the 3 and 5 o’clock sectors (p = 0.016 and 0.009). Conclusions Classic cardiovascular risk factors do not cause RNFL or macular thickness reduction, but tobacco smoking habit reduces nasal RNFL thickness. Subclinical atherosclerosis in the common carotid artery associates a reduction in central macular and nasal RNFL quadrant thicknesses in the left eye compared with the right eye