Las dorsales continentales.

Gustavo A. Tirado F. (biografía): Nació en Valverde, República Dominicana. Ingeniero agrónomo, Escuela Superior de Agricultura, Saltillo, Coahuila, México. Maestría en Suelos y Recursos Naturales, Centro Tropical de Investigación y Enseñanza, Turrialba, Costa Rica. Posgrados en Suelos y Recursos Naturales, Universidad de Carolina del Norte y Texas A&M University, Estados Unidos; Posgrado en Manejo de Imágenes de Satélite para los Recursos Naturales, Centro Espacial San Miguel, Buenos Aires, Argentina; Posgrado en Manejo Integrado y Análisis de Cuencas Hidrográficas (Watershed Management), Cornell University, Ithaca, Nueva York. Ministerio de Agricultura, director de la Escuela de Agronomía y del Depto. de Recursos Naturales; profesor de Suelos, Foresta, Riego y Drenaje, Hidráulica Agrícola, Conservación de Suelos y Construcciones Rurales, de la Unphu; y de Ecología, de Unapec. Representante del país en eventos en México, Venezuela, Brasil, Argentina y en la FAO, en Italia. Ha publicado varios artículos sobre suelos, recursos naturales, y ciencia y tecnología. Es autor del libro Los suelos de la República Dominicana y prepara otros dos libros sobre recursos naturales.Las dorsales oceánicas son cordilleras submarinas, que se forman tras el desplazamiento de las placas tectónicas en el fondo marino. Gracias a las dorsales podemos conocer la evolución de nuestro planeta, y sobretodo el futuro inmediato del mismo. Hoy día de hecho, sabemos que, gracias a la ciencia y su aporte al conocimiento, nuestros continentes, son el resultado de la disgregación o desplazamiento de las placas. En este trabajo por supuesto el objetivo fundamental del autor es que conozcamos la funcion de las dorsales oceánico, así como explicarnos como las placas tectónicas intervienen en los procesos geológicos del planeta, en adición a esto mostrarnos la importancia y papel que cumple el magma en la corteza marina

Nuestros suelos : al mar

Gustavo A. Tirado (biografía): Nació en Valverde, República Dominicana. Es ingeniero agrónomo y tiene una maestría en suelos y recursos naturales. Fue director del Departamento de Recursos Naturales de la Universidad Nacional Pedro Henríquez Ureña (UNPHU) y es profesor de Ecología en UNAPEC. Publicó Los suelos de la República Dominicana.En todo el mundo el suelo está expuesto permanentemente a la erosión o desgaste: por la vía del aire, o por la vía del agua. El principal problema que presentan los suelos es el manejo que hacemos los humanos. Por esto, el resultado del mal manejo de las características físicas y químicas del suelo se convierte en una mayor exposición a los agentes erosivos. Por esa razón estamos obligados a preservar nuestros suelos, ya que son la base de la alimentación de todos los seres vivos; en especial de los humanos, que lo hacemos directa o indirectamente de los cultivos producidos en los suelos

Los volcanes de la República Dominicana

Gustavo A. Tirado F. (biografía): Se tituló de Ingeniero agrónomo en la Escuela Superior de Agricultura, Saltillo, Coahuila, México. Maestría en Suelos y Recursos Naturales, Centro Tropical de Investigación y Enseñanza, Turrialba, Costa Rica. Posgrados en Suelos y Recursos Naturales, Universidad de Carolina del Norte y Texas A&M University, Estados Unidos; Posgrado en Manejo de Imágenes de Satélite para los Recursos Naturales, Centro Espacial San Miguel, Buenos Aires, Argentina; Posgrado en Manejo Integrado y Análisis de Cuencas Hidrográficas (Watershed Management), Cornell University, Ithaca, Nueva York. Ministerio de Agricultura, director de la Escuela de Agronomía y del Depto. de Recursos Naturales; profesor de Suelos, Foresta, Riego y Drenaje, Hidráulica Agrícola, Conservación de Suelos y Construcciones Rurales, de la Unphu; y de Ecología, de Unapec. Representante del país en eventos en México, Venezuela, Brasil, Argentina y en la FAO, en Italia. Ha publicado varios artículos sobre suelos, recursos naturales, y ciencia y tecnología. Es autor del libro Los suelos de la República Dominicana y prepara otros dos libros sobre recursos naturales.Este trabajo explica la importancia de los volcanes, su formación, así como el papel que cumplen en la modificación de la corteza terrestre y como inciden en la creación de nuevas superficies. Hace un recuento de los tipos de volcanes y sus características.Universidad APE

Cached Geometry Manager for View-dependent LOD Rendering

The new generation of commodity graphics cards with significant on-board video memory has become widely popular and provides high-performance rendering and flexibility. One of the features to be exploited with this hardware is the use of the on-board video memory to store geometry information. This strategy significantly reduces the data transfer overhead from sending geometry data over the (AGP) bus interface from main memory to the graphics card. However, taking advantage of cached geometry is not a trivial task because the data models often exceed the memory size of the graphics card. In this paper we present a dynamic Cached Geometry Manager (CGM) to address this issue. We show how this technique improves the performance of real-time view-dependent level-of-detail (LOD) selection and rendering algorithms of large data sets. Alternative caching approaches have been analyzed over two different view-dependent progressive mesh (VDPM) frameworks: one for rendering of arbitrary manifold 3D meshes, and one for terrain visualization

Assessment of the risk of Hepatitis E virus occurrence in pork carcasses at slaughter in the UK

Hepatitis E virus (HEV) is a RNA virus of the genus Hepevirus. HEV genotype 3 is zoonotic and pigs are the main reservoir. This genotype has been identified in the United Kingdom, in sporadic locally-acquired cases without recent history of foreign travel to endemic countries. The number of HEV-confirmed human cases in the UK has increased significantly, from 124 cases in 2003 to 661 in 2013. Non-travel cases now account for the majority (69%) of cases observed annually in the UK. Our aim was to assess the risk of HEV occurrence in pork carcases at slaughter in the UK. We performed a quantitative exposure assessment using Monte Carlo simulation to estimate the number of carcasses contaminated with HEV produced in a high throughput porcine abattoir during one year. The input data used were: a) true prevalence in British pigs, b) probability of viral shedding in bile and faeces c) number of pig carcases with bile and/or faecal contamination detected during post-mortem inspection. The following assumptions were made when data were unavailable: a) sensitivity and specificity of the RP-PCR diagnostic test; b) meat from viraemic pigs was considered HEV-positive; c) visual faecal and bile contamination only considered since microscopic contamination would not be detected through visual inspection. We estimated through our model that 175,152 (2.4%) of carcases produced in high throughput abattoirs would be infected with HEV in one year period. The number of viraemic pigs slaughtered at the abattoir was the largest driver of the uncertainty in carcass contamination. Variations in this parameter would change the output from 62,982 carcasses up to 306,320. Mitigation strategies at farm level should be explored, as it appears that control at this level would likely result in a higher reduction in HEV contamination in pork meat

Does Low Frequency X-ray QPO Behavior in GRS 1915+105 Influence Subsequent X-ray and Infrared Evolution?

Using observations with the Rossi X-ray Timing Explorer, we examine the behavior of 2-10 Hz quasi-periodic oscillations (QPOs) during spectrally-hard dips in the x-ray light curve of GRS 1915+105 that are accompanied by infrared flares. Of the twelve light-curves examined, nine are beta-class and three are alpha-class following the scheme of Belloni et al. (2000). In most cases, the QPO frequency is most strongly correlated to the power law flux, which partially contradicts some earlier claims that the strongest correlation is between QPO frequency and blackbody flux. Seven beta-class curves are highly correlated to blackbody features. In several cases, the QPO evolution appears to decouple from the spectral evolution. We find that beta-class light-curves with strong correlations can be distinguished from those without by their ``trigger spike'' morphology. We also show that the origin and strength of the subsequent infrared flare may be causally linked to the variations in QPO frequency evolution and not solely tied to the onset of soft x-ray flaring behavior. We divide the twelve alpha- and beta-class light-curves into three groups based on the evolution of the QPO, the morphology of the trigger spike, and the infrared flare strength. An apparent crossover case leads us to conclude that these groups are not unique modes but represent part of a continuum of accretion behaviors. We believe the QPO behavior at the initiation of the hard dip can ultimately be used to determine the terminating x-ray behavior, and the following infrared flaring behavior.Comment: 29 pages, 9 figures, to be published in Ap

Gamma-ray bursts: afterglows from cylindrical jets

Nearly all previous discussion on beaming effects in GRBs have assumed a conical geometry. However, more and more observations on relativistic jets in radio galaxies, active galactic nuclei, and "microquasars" in the Galaxy have shown that many of these outflows are not conical, but cylindrical, i.e., they maintain constant cross sections at large scales. Thus it is necessary to discuss the possibility that GRBs may be due to highly collimated cylindrical jets, not conical ones. Here we study the dynamical evolution of cylindrical jets and discuss their afterglows. Both analytical and numerical results are presented. It is shown that when the lateral expansion is not taken into account, a cylindrical jet typically remains to be highly relativistic for \sim 10^8 - 10^9 s. During this relativistic phase, the optical afterglow decays as \propto t^{-p/2} at first, where p is the index characterizing the power-law energy distribution of electrons. Then the light curve steepens to be \propto t^{-(p+1)/2} due to cooling of electrons. After entering the non-relativistic phase (i.e., t > 10^{11} s), the afterglow is \propto t^{-(5p-4)/6}. But if the cylindrical jet expands laterally at co-moving sound speed, then the decay becomes \propto t^{-p} and \propto t^{-(15p-21)/10} - t^{-(15p-20)/10} in the ultra-relativistic and non-relativistic phase respectively. Note that in both cases, the light curve turns flatter after the relativistic-Newtonian transition point, which differs markedly from the behaviour of a conical jet. It is suggested that some GRBs with afterglows decaying as t^{-1.1} - t^{-1.3} may be due to cylindrical jets, not necessarily isotropic fireballs.Comment: 19 pages(use mn.sty), 9 eps figures, MNRAS accepte