Sistemas Operativos

Documento PDF, 98 páginasGuía de estudio para el curso Sistemas Operativos, código 0881, que se imparte en el programa de Ingeniería Informática de la UNED.Universidad Estatal a Distancia de Costa Ric

Los seguros y el TLC Costa Rica y los Estados Unidos

Trabajo final de graduación de 29 páginas en formato pdfLa Región Centroamericana cuenta con una amplia historia de negociaciones de tratados comerciales; no obstante, la firma del Tratado de Libre Comercio entre Estados Unidos y Centroamérica (CAFTA) es un tema sumamente relevante para el desarrollo del país, si se considera la importancia de la potencia comercial con la cual se realiza la negociación: Estados Unidos, el principal exportador e importador a nivel mundial. La particularidad recién descrita advierte sobre la necesidad de analizar y comprender con profundidad las posibles implicaciones que este tratado tiene para nuestro país. En este contexto, el presente trabajo desarrolla uno de los temas más sensibles que se negociaron en ese proceso: los seguros. Una vez más, el Instituto Nacional de Seguros vuelve a estar en la mira, en esta oportunidad con los planes políticos para privatizarlo, en el renglón que concierne a los seguros y en esta ocasión amparados bajo el Tratado de Libre Comercio entre Centroamérica y los Estados Unidos que les ha proporcionado una excusa para hacerlo. El Instituto Nacional de Seguros ha sido la institución del estado costarricense, encargada de producir, comercializar y administrar todo lo relativo a pólizas de seguros, para proteger los bienes, los intereses financieros, la salud y hasta la vida de la colectividad nacional. El éxito en su gestión administrativa queda establecido por la solidez financiera que presenta, por el visible crecimiento en la cobertura geográfica –lo que le ha permitido tener presencia física en la mayoría de las poblaciones estratégicas del país—y por la confianza que genera entre grandes compañías aseguradoras del mundo, muchas de las cuales re-aseguran al INS. El objetivo del presente ensayo, además del académico, es dar a conocer, en lo que al Instituto Nacional de Seguros concierne, que la aplicación de las normas, en la forma planteada en el marco del TLC, acaba con el octogenario monopolio de los seguros o al menos lo debilita peligrosamente. El peligro radica en la extinción paulatina del papel solidario y social que brinda el INS. La opinión de los expertos alrededor de este TLC que llama poderosamente la atención es sobre las implicaciones negativas que estas medidas tienen para la sociedad costarricense.Universidad Estatal a Distancia de Costa Ric

Analytic solutions to the accretion of a rotating finite cloud towards a central object - II. Schwarzschild spacetime

We construct a general relativistic model for the accretion flow of a rotating finite cloud of non-interacting particles infalling onto a Schwarzschild black hole. The streamlines start at a spherical shell, where boundary conditions are fixed, and are followed down to the point at which they either cross the black hole horizon or become incorporated into an equatorial thin disc. Analytic expressions for the streamlines and the velocity field are given, in terms of Jacobi elliptic functions, under the assumptions of stationarity and ballistic motion. A novel approach allows us to describe all of the possible types of orbit with a single formula. A simple numerical scheme is presented for calculating the density field. This model is the relativistic generalisation of the Newtonian one developed by Mendoza, Tejeda, Nagel, 2009 and, due to its analytic nature, it can be useful in providing a benchmark for general relativistic hydrodynamical codes and for exploring the parameter space in applications involving accretion onto black holes when the approximations of steady state and ballistic motion are reasonable ones.Comment: 12 pages, 6 figures, references and minor changes added to match version accepted for publication in MNRA

Studying the Variation of the Fine Structure Constant Using Emission Line Multiplets

As an extension of the method by Bahcall et al. (2004) to investigate the time dependence of the fine structure constant, we describe an approach based on new observations of forbidden line multiplets from different ionic species. We obtain optical spectra of fine structure transitions in [Ne III], [Ne V], [O III], [OI], and [SII] multiplets from a sample of 14 Seyfert 1.5 galaxies in the low-z range 0.035 < z < 0.281. Each source and each multiplet is independently analyzed to ascertain possible errors. Averaging over our sample, we obtain a conservative value alpha^2(t)/\alpha^2(0) = 1.0030+-0.0014. However, our sample is limited in size and our fitting technique simplistic as we primarily intend to illustrate the scope and strengths of emission line studies of the time variation of the fine structure constant. The approach can be further extended and generalized to a "many-multiplet emission line method" analogous in principle to the corresponding method using absorption lines. With that aim, we note that the theoretical limits on emission line ratios of selected ions are precisely known, and provide well constrained selection criteria. We also discuss several other forbidden and allowed lines that may constitute the basis for a more rigorous study using high-resolution instruments on the next generation of 8 m class telescopes.Comment: 20 pages, 4 figures, sumbitted to A

How good are the Garvey-Kelson predictions of nuclear masses?

The Garvey-Kelson relations are used in an iterative process to predict nuclear masses in the neighborhood of nuclei with measured masses. Average errors in the predicted masses for the first three iteration shells are smaller than those obtained with the best nuclear mass models. Their quality is comparable with the Audi-Wapstra extrapolations, offering a simple and reproducible procedure for short range mass predictions. A systematic study of the way the error grows as a function of the iteration and the distance to the known masses region, shows that a correlation exists between the error and the residual neutron-proton interaction, produced mainly by the implicit assumption that $V_{np}$ varies smoothly along the nuclear landscape.Comment: 10 pages, 18 figure

The homeologous Zea mays gigantea genes: characterization of expression and novel mutant alleles

The two homeologous Zea mays gigantea (gi) genes, gi1 and gi2, arose from the last genome duplication event in the maize lineage. Homologs of these genes in other species are required for correct circadian rhythms and proper regulation of growth and development. Here we characterized the expression of these two maize gi genes. Although gi1 and gi2 shared comparable 24-hour rhythmic expression profiles, gi1 levels were consistently higher than gi2. Furthermore, short day photoperiods repressed gi2 expression. The transcriptional unit for gi1 is established based on 5’-RACE analysis. Two independent mutant alleles for gi1 are described that are caused by transposons of the Mutator (Mu) class inserted into the 5’-end of the gene. The type of Mu element and position of the transposon in gi1 was different for each gi1 allele. Mutant plants had a marked reduction in gi1 expression and carried transcripts interrupted by the Mu element. Together, these results provide a deeper understanding of the gi genes in maize. In addition, the novel gi1 mutant alleles described here will be valuable tools to study gi1 function in maize, as well as the role of circadian clock regulation in maize metabolism, growth, and development

Plant proteases

Plant proteases are involved in most aspects of plant physiology and development, playing key roles in the generation of signaling molecules and as regulators of essential cellular processes such as cell division and metabolism. They take part in important pathways like protein turnover by the degradation of misfolded proteins and the ubiquitin-proteasome pathway, and they are responsible for post-translational modifications of proteins by proteolysis at highly specific sites. Proteases are also implicated in a great variety of environmentally controlled processes, including mobilization of storage proteins during seed germination, development of seedlings, senescence, programmed cell death and defense mechanisms against pests and pathogens. However, in spite of their importance, little is known about the functions and mode of actions of specific plant proteases. This Research Topic aims to collect contributions covering diverse aspects of plant proteases research, including: • Plant proteases biological role and functional characterization • Process regulation by plant proteases and their inhibitors • Development of strategies to monitor and alter plant proteases activity • Elucidation of the biochemistry of specific protease families • Novel technologies to study proteases and identify their natural substrates • New methods that can be used to track and inhibit protease activity at the molecular level and their biotechnological applications • Recent advances in the use of structural biology to study individual proteases and proteases that are part of larger complexes We encourage all scientists engaged in plant proteases research to participate this Research Topic. Original research articles and reviews are welcome

Behavior of early warnings near the critical temperature in the two-dimensional Ising model

Among the properties that are common to complex systems, the presence of critical thresholds in the dynamics of the system is one of the most important. Recently, there has been interest in the universalities that occur in the behavior of systems near critical points. These universal properties make it possible to estimate how far a system is from a critical threshold. Several early-warning signals have been reported in time series representing systems near catastrophic shifts. The proper understanding of these early-warnings may allow the prediction and perhaps control of these dramatic shifts in a wide variety of systems. In this paper we analyze this universal behavior for a system that is a paradigm of phase transitions, the Ising model. We study the behavior of the early-warning signals and the way the temporal correlations of the system increase when the system is near the critical point.Comment: 20 pages, 8 figures, Submitted to PLOS ONE on Oct. 20th 2014. PONE-D-14-4718

Hot Filament Chemical Vapor Deposition: Enabling the Scalable Synthesis of Bilayer Graphene and Other Carbon Materials

The hot filament chemical vapor deposition (HFCVD) technique is limited only by the size of the reactor and lends itself to be incorporated into continuous roll-to-roll industrial fabrication processes. We discuss the HFCVD reactor design and the interplay between the reactor parameters, such as filament and substrate temperatures, filament-to-substrate distance, and total pressure. Special attention is given to the large-area synthesis of bilayer graphene on copper, which is successfully grown by HFCVD with transmittance greater than 90% in the visible region and no gaps. We also discuss the HFCVD synthesis of carbon nanotubes, microcrystalline diamond, and nanocrystalline diamond

Shaping point- and mirror-symmetric proto-planetary nebulae by the orbital motion of the central binary system

We present 3D hydrodynamical simulations of a jet launched from the secondary star of a binary system inside a proto-planetary nebula. The secondary star moves around the primary in a close eccentric orbit. From the gasdynamic simulations we compute synthetic [NII] 6583 emission maps. Different jet axis inclinations with respect to the orbital plane, as well as different orientations of the flow with respect to the observer are considered. For some parameter combinations, we obtain structures that show point- or mirror-symmetric morphologies depending on the orientation of the flow with respect to the observer. Furthermore, our models can explain some of the emission distribution asymmetries that are summarized in the classification given by Soker & hadar (2002).Comment: 15 pages, 3 figures, 2 tables, Accepted in Apj Letter