Discurso inaugural que en la solemne apertura del curso de 1861 a 1862, pronunció en la Universidad Literaria de Valladolid, el doctor Félix Pérez Martín

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Hybrid SGP4 orbit propagator

Two-Line Elements (TLEs) continue to be the sole public source of orbiter observations. The accuracy of TLE propagations through the Simplified General Perturbations-4 (SGP4) software decreases dramatically as the propagation horizon increases, and thus the period of validity of TLEs is very limited. As a result, TLEs are gradually becoming insufficient for the growing demands of Space Situational Awareness (SSA). We propose a technique, based on the hybrid propagation methodology, aimed at extending TLE validity with minimal changes to the current TLE-SGP4 system in a non-intrusive way. It requires that the institution in possession of the osculating elements distributes hybrid TLEs, HTLEs, which encapsulate the standard TLE and the model of its propagation error. The validity extension can be accomplished when the end user processes HTLEs through the hybrid SGP4 propagator, HSGP4, which comprises the standard SGP4 and an error corrector.Comment: 18 pages, 4 figure

Glycopeptide resistance in enterococci

The selective pressure resulting from the extensive use of antibiotics over the last 50 years has led to the emergence of bacterial resistance and to the dissemination of resistance genes among pathogenic microorganisms. Consequently, we are now at serious risk of suffering intractable, life-threatening infections. The progressive emergence and rapid dissemination of resistance to glycopeptides, the last resort for treating nosocomial infections with enterococci resistant to usual antibiotics, constitute one of the most dramatic examples of such resistance. Enterococci are normal human commensals, but are also a frequent cause of nosocomial urinary tract infections and nosocomial bacteremia. Enterococcus faecalis causes 80 to 90% of human enterococcal infections, while Enterococcus faecium accounts for most of the remainder. During the last decade, our understanding of the genetics and biochemical basis of resistance to glycopeptides has increased greatly. Furthermore, the application of molecular methods for the diagnosis of glycopeptide-resistant enterococci has provided new insights into the epidemiology of enterococcal infections

Structural modelling of medieval walls

International Seminar on Structural Analysis of Historical Constructions (3º 2001 Guimaraens)Sistemas constructivos medievales a menudo involucrados la construcción de múltiples capas paredes formadas por dos caras de sillería o mampostería con un relleno central que consiste en escombros ligada con mortero, generalmente cal-basado. Se trata de una construcción simple y eficiente sistema que se siguió utilizando en los siglos posteriores. Sin embargo, el modelado estructural de este tipo de pared no es fácil de lograr. Los dos pared caras no están vinculados rígidamente y, por otro lado, las bóvedas son normalmente compatibles sólo en el la cara interna, lo que resulta en la eficiencia reducida de la unidad de pared. Modelos comunes de elementos finitos no son capaces de resolver muchos de los problemas que surgen cuando se aplican a una monumental construcción. En este trabajo se aborda el problema y propone varias posibilidades de solución con diferentes tipos de elementos .. También proporciona dos ejemplos de monumentos góticos en Galicia (España) en el que comportamiento estructural se ha estudiado el uso de algunos de estos modelos de cálculo: las iglesias de Guimaraens y Cambados.[Abstract]Medieval construction systems usually involved the construction of multi-layer walls formed by two faces of ashlar work or masonry with a central infilling consisting of rubble bound with mortar, generally lime-based. It is a simple and efficient construction system which continued to be used in subsequent centuries. Nevertheless, structural modelling of this type of wall is not easy to achieve. The two wall faces are not rigidly bound and on the other hand, vaults are normally supported only on the intemal face, resulting in reduced efficiency of the wall unit. Common models of finite elements are unable to solve many of the problems that arise when they are applied to a monumental construction. This paper tackles the problem and puts forward various possibilities of solution with different element types.. It also provides two examples of Gothic monuments in Galicia (Spain) in which structural behaviour was studied using some of these calculation models: the churches of Guimarei and Cambados

Physical and chemical properties in relation to soil porosity: The influence of the natural wetting-drying cycle. III. Porosity and clay fraction

En el presente trabajo se presentan y discuten los resultados del análisis mineralógico de las arcillas de ocho perfiles patrones representativos de diversos suelos de interés agronómico. La composición mineralógica se estudia en relación con diversas fracciones de porosidad.In the present paper results from day mineralogical analyses of eight representative agronomically useful soil pro files are presented and discussed. Soil clay content and mineralogical composition are studied in relation to various soil pore-size ranges

Novel connection between newborn granule neurons and the hippocampal CA2 field

© 2014 Elsevier Inc. Newborn neurons are continuously added to the hippocampal dentate gyrus (DG) throughout life. Mature and immature granule neurons are believed to send their axonal projections exclusively to the hippocampal CA3 field. However, recent data point to an alternative trisynaptic circuit, involving a direct axonal projection from mature granule neurons to the CA2 field. Whether this circuit takes place only in mature granule neurons or, on the contrary, whether immature granule neurons also contribute to this novel connection is unknown. We used various retroviral vectors to show that immature granule neurons send axonal processes to and establish synaptic contacts with CA2 pyramidal neurons and that axonal growth follows a similar time course to that described for CA3 innervation. In addition, we provide experimental evidence demonstrating that the pathway connecting newborn granule neurons and the CA2 field can be modulated by physiological and deleterious stimuli.Spanish Ministry of Health (SAF 2006-02424, BFU-2008-03980, BFU-2010-21507), the Comunidad de Madrid (SAL/0202/2006), the Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED, ISCIII) (CB401), and the Fundación R. ArecesPeer Reviewe

Rgf1p (Rho1p GEF) is required for double-strand break repair in fission yeast

Datos de investigación en: http://hdl.handle.net/10366/146281[EN]Rho GTPases are conserved molecules that control cytoskeletal dynamics. These functions are expedited by Rho GEFs that stimulate the release of GDP to enable GTP binding, thereby allowing Rho proteins to initiate intracellular signaling. How Rho GEFs and Rho GTPases protect cells from DNA damage is unknown. Here, we explore the extreme sensitivity of a deletion mutation in the Rho1p exchange factor Rgf1p to the DNA break/inducing antibiotic phleomycin (Phl). The Rgf1p mutant cells are defective in reentry into the cell cycle following the induction of severe DNA damage. This phenotype correlates with the inability of rgf1Δ cells to efficiently repair fragmented chromosomes after Phl treatment. Consistent with this observation Rad11p (ssDNA binding protein, RPA), Rad52p, Rad54p and Rad51p, which facilitate strand invasion in the process of homology-directed repair (HDR), are permanently stacked in Phl-induced foci in rgf1Δ cells. These phenotypes are phenocopied by genetic inhibition of Rho1p. Our data provide evidence that Rgf1p/Rho1p activity positively controls a repair function that confers resistance against the anti-cancer drug Phl.CICYT, Spain [BFU2011-24683/BMC]; Junta de Castilla y León [SA073U14]. Funding for open access charge: MINECO

Un nuevo rastro lacustre enigmático en el Mioceno superior de la Sierra de las Cabras (Jumilla, Murcia, España)

A new fossil trackway is described in the upper lacustrine Miocene in the Prebetic Zone of the Iberian Peninsula, in town (Murcia region) called Aenigmatichnus jumillensis nov. ichnogen. nov. ichnosp. This trackway consists of a made up of sets of three tracks or triads, which are subparallel to each other, arranged in alternate groups. Each track presents a depression formed by a central body that is three times as long as it is wide, with straight or slightly curved walls, with shorter bodies placed at the ends, one of the ends being shorter and more pronounced than the opposite, which is longer stretched. All the biomechanical possibilities compatible with an anatomical design that could leave the impression of alternate triads of tracks are analysed. The supports are only from the extremities on one side of the organism (left or the displacement being by translation. It is concluded that it had to be a large arthropod (metre scale), with a hexapod decapod (less probably octopod), which had to be dragged laterally by a current in a very shallow lake or wetland environment. To date, no fossil organism is known, nor its current equivalent, that corresponds to these characteristics.Se describe una nueva pista fósil en el Mioceno superior lacustre de la Zona Prebética de la Península Ibérica, en la localidad de Jumilla (Región de Murcia) denominada Aenigmatichnus jumillensis nov. ichnogen. nov. ichnosp. Esta pista presenta un patrón que está formado por conjuntos de tres huellas o tríadas, subparalelas entre sí, y dispuestas en grupos alternos. Cada huella presenta una depresión formada por un cuerpo central que es tres veces más largo que ancho, con las paredes rectas o ligeramente curvadas. Presenta también dos cuerpos más cortos situados en los extremos, siendo uno de ellos más corto y pronunciado que el opuesto, que es más largo y estirado. Se analizan todas las posibilidades biomecánicas compatibles con un diseño anatómico que pudiera dejar la impresión de tres apéndices alternos. Los apoyos son sólo de las extremidades de un lado del organismo (izquierda o derecha), siendo el desplazamiento por traslación. Se concluye que tuvo que tratarse de un artrópodo de gran tamaño (escala métrica), ya fuera un hexápodo o decápodo (menos probablemente octópodo), que tuvo que ser arrastrado lateralmente por una corriente en un entorno lacustre o humedal muy poco profundo. Hasta la fecha, no se conoce ningún organismo fósil, ni su equivalente actual, que responda a estas característicasFunding for open access publishing: Universidad de Huelva/ CBUA. Funding for open access charge: Universidad de Huelva/CBUA. Thanks to Nicholas Minter an anonymous reviewer for comments and suggestions, which improved the manuscript. This study has been partially supported by the project PID2019- 104625RB-100 of the Ministry of Science and Innovation, State Research Agency, and by the Junta de Andalucía to the Research Group RNM276 of the CCTH of the University of Huelva