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Search Results: 1 - 10 of 62715 matches for " David Ramos "
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Sobre la diversión de los falsos amigos On the diversion of false friends
David Martínez-Ramos
Revista Colombiana de Cirugía , 2010,
Abstract:
Mechanisms of Gene Duplication and Translocation and Progress towards Understanding Their Relative Contributions to Animal Genome Evolution
Olivia Mendivil Ramos,David E. K. Ferrier
International Journal of Evolutionary Biology , 2012, DOI: 10.1155/2012/846421
Abstract: Duplication of genetic material is clearly a major route to genetic change, with consequences for both evolution and disease. A variety of forms and mechanisms of duplication are recognised, operating across the scales of a few base pairs upto entire genomes. With the ever-increasing amounts of gene and genome sequence data that are becoming available, our understanding of the extent of duplication is greatly improving, both in terms of the scales of duplication events as well as their rates of occurrence. An accurate understanding of these processes is vital if we are to properly understand important events in evolution as well as mechanisms operating at the level of genome organisation. Here we will focus on duplication in animal genomes and how the duplicated sequences are distributed, with the aim of maintaining a focus on principles of evolution and organisation that are most directly applicable to the shaping of our own genome. 1. Introduction New genes constitute some of the major raw material for the evolution of biodiversity. They do not arise out of thin air. Some instances of new gene evolution from previously non-coding sequence have now been discovered [1, 2]. Also, new genes can be formed by shuffling of pre-existing nucleotide sequences. The relatively recent discovery of large numbers of taxonomically restricted genes also demands a closer investigation of their mode(s) of origin [3]. Nevertheless, a major mechanism for the generation of new genes is via duplication. Such duplicates are called paralogues, to reflect their homologous relationship being due to a duplication event rather than a speciation event (see Figure 1). Figure 1: Overview of the current terminology. The different panels represent term(s) for duplicated genes. (a) Orthologues. The square blue arrows represent an orthologous relationship between the two genes. (b) Paralogues. The square green arrows represent paralogous relationships between the genes. (c) Proto-orthologue. The square red arrow represents the pro-orthologue relationship of gene a/b from Branchiostoma floridae to gene a from Mus musculus. (d) Semi-orthologue. The square orange arrow represents the semi-orthologous relationship of gene a of Mus musculus to gene a/b from Branchiostoma floridae. (e) Inparalogues and Outparalogues. The square yellow arrows represent the outparalogous relationship in which human and mouse a genes are outparalogous to human and mouse b genes. As a set, genes a and b from mouse and human represents coorthologues. The square purple arrows represent the inparalogous relationship
Preparation and Characterization of Directionally Freeze-cast Copper Foams
Aurelia I. Cuba Ramos,David C. Dunand
Metals , 2012, DOI: 10.3390/met2030265
Abstract: Because of their excellent thermal and electric conductivities, copper foams are ideally suited for applications such as heat exchangers, catalyst supports and EMI-shields. Here, we demonstrate the preparation of copper with ~80% aligned, elongated, interconnected pores via directional freeze casting, a well established processing technique for porous ceramics. First, an aqueous slurry of 40?80 nm cupric oxide powders was directionally solidified, resulting in a preform consisting of elongated, aligned dendrites of pure ice separated by interdendritic ice walls with high oxide powder content. Oxide rather than metallic nanometric particles are used, as the latter would oxidize rapidly and uncontrollably when suspended in the aqueous solution used during directional casting. The preforms were then freeze-dried to sublimate the ice and sintered in a hydrogen-bearing atmosphere to reduce the copper oxide to metallic copper particles and densify these copper particles. Microstructural analysis of the copper foams shows that three types of porosities are present: (i) aligned, elongated pores replicating the ice dendrites created during the freeze-casting process; (ii) micro-porosity in the partially sintered copper walls separating the elongated pores; and (iii) cracks in these copper walls, probably created because of shrinkage associated with the reduction of the oxide powders.
VISUALIZACIóN INTERNA DE NUDOS EN ROLLIZOS DE MADERA DE PINUS RADIATA D. DON UTILIZANDO RAYOS-X
Aguilera,Cristhian; Ramos,Mario; Salinas,David;
Maderas. Ciencia y tecnología , 2002, DOI: 10.4067/S0718-221X2002000200010
Abstract: internal structure of wood permits to know different qualities of the raw material. this knowledge can yield utilities up to 10 times for turning one log into optimum wood. differences of density in the structures that compound wood (heartwood, sapwood, knots) make possible that with a computerized tomography, these structures are clearly recognized and differenced. the collection of images from the ct must be treated to see the log as a volume and difference defects in it. volume rendering (vr) allows to generate a 3d image from 2d images. the objective of this article is introduce the progresses in the visualization of knots in logs of pinus radiata d. don grown in chile. for this, 2d images acquired with a x-ray tomograph are used. here, it introduces methods and preliminary results to visualize with vr a commercial diameter log. the results show that it is possible simulate solid of the log and see how the knotty cylinder of the log behaves
Aproximación crítica a los trastornos somatomorfos en ni os Critical Approach to Somatomorphic Disorders in Children
Juan David Ramos Guevara,Rafael Vásquez
Revista Colombiana de Psiquiatría , 2012,
Abstract: Los trastornos somatomorfos tienen en común manifestaciones somáticas que no tienen explicación médica y que pueden producir una alteración de la vida diaria. En ni os, existen dificultades de evaluación por el reporte u observación de síntomas debido a su edad, a la influencia parental y a los factores asociados. El objetivo de este trabajo es reconocer las dificultades diagnósticas y las herramientas clínicas que permitan la aproximación a los trastornos somatomorfos en ni os. Se realizó una búsqueda sistemática de la información publicada en los últimos diez a os sobre el tema. La evolución histórica del concepto de somatización ha generado dificultades en su abordaje. Algunas signos pueden hacer sospechar un trastorno somatomorfo; sin embargo, existen muy pocas herramientas de evaluación en ni os. Actualmente, dichas herramientas se basan solamente en listas de síntomas y no responden por completo a todos los interrogantes. Los trastornos somatomorfos o síntomas somáticos en ni os son un campo con un vacío aún por llenar. Somatomorphic disorders have common somatic manifestations without medical explanation, that can affect daily life. There are evaluation difficulties regarding symptom report or observation in children due to their age, parental influence and associated factors. The aim of this work is to acknowledge diagnosis difficulties and clinic tools to approach somatomorphic disorders in children. A systematic search in the information published for the last ten years was carried out. Historical evolution of the concept of somatization has generated difficulties to approach this issue. Some signs could indicate a somatomorphic disorder; however, there are very little evaluating tools for children. Currently, said tools are only based on lists of symptoms without fully answering to all questions. Somatomorphic disorders or somatic symptoms in children are still a gap to be closed.
VISUALIZACIóN INTERNA DE NUDOS EN ROLLIZOS DE MADERA DE PINUS RADIATA D. DON UTILIZANDO RAYOS-X INTERNAL VISUALIZATION OF KNOTS IN RADIATA PINE LOGS USING X-RAYS
Cristhian Aguilera,Mario Ramos,David Salinas
MADERAS : Ciencia y Tecnología , 2002,
Abstract: Visualizar la estructura interna de las trozas, permite conocer la calidad y destino óptimo de la materia prima, generando ganancias de hasta 10 veces, al identificar el destino de las trozas. Las diferencias de densidad en las estructuras que componen la madera hacen posible que en una Tomografía Computarizada (TC) estas estructuras sean reconocibles y claramente diferenciadas. La colección de imágenes de TC debe ser tratada para poder visualizar el interior de la troza y diferenciar los defectos en esta. El Rendering Volumétrico (RV) nos permite, por otro lado, a partir de una colección de imágenes 2D, generar una visualización del volumen en 3D. El objetivo de este artículo es presentar los avances en la visualización de nudos en trozos de Pinus radiata D. Don crecido en Chile. Para ello se utilizan imágenes tomadas con un tomógrafo de rayos-X. Se presenta aquí la metodología desarrollada para obtener la visualización y los resultados preliminares de la visualización interna. Se realizó un ensayo destructivo en las trozas, obteniéndose índices de exactitud que se contrastaron con la TC y con la reconstrucción hecha por RV. Los resultados indican que es posible disponer de una simulación de la troza y en particular observar como se comporta el cilindro nudoso Internal structure of wood permits to know different qualities of the raw material. This knowledge can yield utilities up to 10 times for turning one log into optimum wood. Differences of density in the structures that compound wood (heartwood, sapwood, knots) make possible that with a Computerized Tomography, these structures are clearly recognized and differenced. The collection of images from the CT must be treated to see the log as a volume and difference defects in it. Volume Rendering (VR) allows to generate a 3D image from 2D images. The objective of this article is introduce the progresses in the visualization of knots in logs of Pinus radiata D. Don grown in Chile. For this, 2D images acquired with a X-Ray tomograph are used. Here, it introduces methods and preliminary results to visualize with VR a commercial diameter log. The results show that it is possible simulate solid of the log and see how the knotty cylinder of the log behaves
Motivos para a cria o de universidades corporativas – estudo de casos.
Sylvia Constant Vergara,David Ricardo Moreira Ramos
Revista de Administra??o Mackenzie , 2002,
Abstract: As universidades corporativas apresentam-se como uma recente e importante estratégia das organiza es, no sentido de potencializar o desenvolvimento de seus funcionários e assim contribuir para a cria o ou manuten o de vantagem competitiva. Esse artigo apresenta e analisa os resultados de uma pesquisa de campo realizada em cinco empresas brasileiras líderes em seu ramo de negócio, que disp em de uma universidade corporativa. Buscou-se identificar os motivos para a sua cria o e suas formas de atua o, por meio de entrevistas realizadas com seus principais executivos. Como conclus o, os autores apontam que as universidades corporativas estudadas surgiram para cobrir lacunas percebidas nos tradicionais programas de treinamento e desenvolvimento, que utilizam, predominantemente, o tradicional método presencial de ensino, que têm, em geral, caráter doutrinário e que buscam alinhar suas práticas com a gest o por competências e a gest o do conhecimento.
Existence and multiplicity results for nonlinear elliptic problems in $R^N$ with an indefinite functional
David G. Costa,Yuxia Guo,Miguel Ramos
Electronic Journal of Differential Equations , 2002,
Abstract: We prove the existence of a nontrivial solution for the nonlinear elliptic problem $-Delta u=lambda h(x)u + a(x)g(u)$ in $R^N$, where $g$ is superlinear near zero and near infinity, $a(x)$ changes sign, $lambda $ is positive, and $h(x)geq 0$ is a weight function. For $g$ odd, we prove the existence of an infinite number of solutions.
Entanglement and Applications of Pure Fourpartite of Qubit States
David Sena Oliveira,Rubens Viana Ramos
Physics , 2009,
Abstract: In this work we study the entanglement of pure fourpartite of qubit states. The analysis is realized through the comparison between two different entanglement measures: the Groverian entanglement measure and the residual entanglement measured with negativities. Furthemore, we discuss some applications of four-way entangled fourpartite states.
Energy evolution of the moments of the hadron distribution in QCD jets including NNLL resummation and NLO running-coupling corrections
Redamy Perez-Ramos,David d'Enterria
Physics , 2013, DOI: 10.1007/JHEP08(2014)068
Abstract: The moments of the single inclusive momentum distribution of hadrons in QCD jets, are studied in the next-to-modified-leading-log approximation (NMLLA) including next-to-leading-order (NLO) corrections to the alpha_s strong coupling. The evolution equations are solved using a distorted Gaussian parametrisation, which successfully reproduces the spectrum of charged hadrons of jets measured in e+e- collisions. The energy dependencies of the maximum peak, multiplicity, width, kurtosis and skewness of the jet hadron distribution are computed analytically. Comparisons of all the existing jet data measured in e+e- collisions in the range sqrt(s)~2-200 GeV to the NMLLA+NLO* predictions allow one to extract a value of the QCD parameter Lambda_QCD, and associated two-loop coupling constant at the Z resonance alpha_s(m_Z^2)= 0.1195 +/- 0.0022, in excellent numerical agreement with the current world average obtained using other methods.
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