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The causal character of the zero-areal-radius (R=0) singularity in spherically symmetric spacetimes is studied. By using the techniques of the qualitative behaviour of dynamic systems, we are able to present the most comprehensive scheme so far to try to find out their causal characterization, taking into account and analyzing, the possible limitations of the approach. We show that, with this approach, the knowledge of the scalar invariant $m\equiv R(1-g^{\mu\nu}\partial_\mu R\partial_\nu R)/2$ suffices to characterize the singularity. We apply our results to the study of the outcome of Black Hole evaporation and show different possibilities. In this way, we find that a persistent naked singularity could develop in the final stages of the evaporation and we show its distinctive features. Likewise, we study the options for the generation of naked singularities in the collapse of an object (such as a star) as a means of violating the cosmic censorship conjecture. more...

"In spite of ~130 years of geologic research in Mexico, much remains pending e.g. only 1/3 of this country’s territory is mapped in detail [i.e., scale 1:50000], the formal stratigraphic differentiation of the continental sedimentary Cenozoic is barely started, discriminating the depositional systems that make up basic units is even less pursued. Towards filling this gap, the detailed Cenozoic lithostratigraphy of a graben fill in central-east Mexico is reviewed, a new Miocene formation is proposed, and its importance in understanding the regional geologic evolution is discussed. The study area lies in San Luis Potosí State, within the Sierra Madre Oriental Morphotectonic Province [SMO], between 22°11’- 22°19’ N Lat. and 100°30’-100°39’ W Long., and 1295 – 2025 masl. The ~1200 m thick Tertiary sedimentary sequence is preserved in the N-S trending Peotillos-Tolentino Graben, which is bound by horsts of folded and faulted Cretaceous carbonate units; it includes a Paleogene volcanic succession formed by an andesitic-basaltic lavic stack intertongued/overlain by a rhyolitic ash flow-tuff sheet, which non-conformably underlies the new unit, a Late Miocene, ~1100 m thick, fluvio-lacustrine, largely calcilithitic, 15° – 20° NE dipping, peneplained sequence, in turn unconformably overlain by a Quaternary, ~40 m thick, calcilithitic-volcarenitic blanket; locally overlain by mafic lavic/pyroclastic rocks. The new formation was deposited in a subsiding basin, under humid to subhumid conditions allowing erosion of large clastics volumes, and the development of an axial fluvial network, capable of transporting/depositing such volumes. Nevertheless, floodplain calcisols and calcretes indicate periods of dry conditions. The ~1100 m thick, largely fluvial stratal pile thus formed, records cyclic superimposing of such network’s systems during Late Miocene time; this in turn, denotes stability of the tectono-sedimentary-climatic conditions. Subsequently, faulting, erosion and finally peneplanation took place. In the Quaternary, clastic sedimentation was reestablished. The holistic approach used to study the Peotillos-Tolentino Graben and its sedimentary fill, could be applied to the other post-orogenic basins of the Sierra Madre Oriental that bear Cenozoic clastic sequences, probably resulting from similar processes, to identify and characterize such processes, thus contributing to a better understanding of the Cenozoic geologic makeup and evolution of this province." more...

We provide a general formalism that allows to analyze the phenomenon of tunneling in arbitrary spacetimes. We show that a flux of particles produced by tunneling through general marginally trapped surfaces may be perceived by some privileged observers. We discuss how this particle perception can be related to Hawking/Unruh radiation in specific cases. Our approach naturally leads to an expression for the effective surface gravity of marginally trapped surfaces. The procedure is applicable to general astrophysical and cosmological dynamical situations. Some practical examples for known and new cases are provided., 24 pages, 2 figures. Section 4.2, concerning the analysis of the Kerr-Vaidya solution, has been rewritten, correcting mistakes in previous versions. The corrected calculations do support our claims. A corrigendum has also been sent to CQG. New references added. Some of the mistakes in previous versions are actually common and spread in the literature on the Kerr-Vaidya solution more...

Different proposals for regular rotating black hole spacetimes have appeared recently in the literature. However, a rigorous analysis and proof of the regularity of this kind of spacetimes is still lacking. In this note we analyze rotating Kerr-like black hole spacetimes and find the necessary and sufficient conditions for the regularity of all their second order scalar invariants polynomial in the Riemann tensor. We also show that the regularity is linked to a violation of the weak energy conditions around the core of the rotating black hole., Comment: 10 p more...

The San Luis Potosi volcanic field, is located in the southeastern of the Mesa Central, mainly formed by a sequence of lavas and pyroclastic flows with ages between the Middle Eocene until the Quaternary. Generally in the San Luis Potosi Volcanic Field there are five mainly volcanic stages; the first one restringed to the middle Eocene with the emission of andesitic lavas; the second stage is the more...

En el noreste de México se han reportado algunos afloramientos de rocas volcánicas Triásicas y Jurásicas, cuyas características petrológicas y geoquímicas demuestran una afinidad de arco que permite relacionarlas a una margen continental activa. Más elementos que apoyan este ambiente tectónico se localizan en los estados de Durango, Zacatecas, San Luis Potosí, Nuevo León y Tamaulipas, en donde una secuencia siliciclástica tipo flysch en la porción occidental y un bloque continental pre-mesozoico en la porción oriental subyacen a la secuencia volcanogénica. En el presente trabajo se propone que las rocas volcánicas Triásicas y Jurásicas, así como algunas capas rojas asociadas que se encuentran en el centro y noreste de México, están relacionadas genéticamente con una margen continental activa y solamente algunas de las secuencias de capas rojas expuestas en el extremo oriental de México estarían relacionadas a estructuras de rift, posiblemente asociadas a la partición de Pangea como se ha propuesto hasta ahora, o en nuestra opinión, relacionadas más bien a cuencas de trasarco, además de las secuencias relacionadas a procesos posteriores, como la transgresión marina del Calloviano-Oxfordiano, asociada a la evolución de la margen pasiva o la apertura del Golfo de México. more...

The mechanism of intestinal fluid loss in SBP intolerance is not known. The possibility of absorptive disturbances was examined in 82 symptomatic infants. Stool composition, oral absorptive tests and mucosal disaccharidases ruled out absorptive impairment in most infants. The possibility of a secretory disturbance was examined in 10 infants by the intestinal perfusion method. 0.142 M NaCl, 5 mM D-glucose (A) and 0.142 M NaCl,5 mM D-galactose (B) were perfuse in the proximal jejunum following soy protein-sucrose feeding. Net water, Na and Cl secretion occurred during perfusion of A and changed to net water and ion absorption during perfusion of B (p < .001). The effect of D-galactose was then tested clinically by substituting lactose for sucrose in the soy formula. Symptoms of intolerance ceased immediately. Re-examination of the water and ion fluxes after 1 mo. of SBP-lactose feeding showed equal rates of absorption during perfusions of A and B. It was postulated that D-galactose, but not D-glucose, inhibited and SBP-mucosal surface interaction underlying the mechanism of fluid loss. This assumption finds support on the known specificity of soybean protein (glycinin) for galactosyl receptors in membrane glycoproteins. more...

A simple protocol to prepare core-shell gold@spin-crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin-crossover [Fe(Htrz)2(trz)](BF4) coordination polymer is reported. The synthesis relies on a two-step approach consisting on a partial surface ligand substitution of the citrate-stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@shell spherical NPs of 19 nm in size exhibiting a narrow distribution in sizes have been obtained, revealing a switchable SCOshell of ca.4 nm. Temperature-dependent charge transport measurements of an electrical device based on assemblies of these Au@SCO NPs display well-defined, reproducible and sharp thermal hysteresis loops in the conductance near room temperature. This device is characterized both, by a large change in conductance upon spin state switching, and a remarkable transition abruptness, as compared with other memory devices based on the pristine SCO NPs. As a result, the sensitivity of the device to the spin transition is dramatically improved, with values for the ON/OFF ratio which are an order of magnitude better than the best ones obtained in previous SCO devices. more...

El comercio minorista ha evolucionado considerablemente durante las últimas décadas. Lo que ha comenzado como una tienda especializada, se ha convertido en un mercado internacional cada vez más competitivo, con una fuerte presencia de los llamados category killers; tiendas con grandes superficies y poca atención personalizada, que son aspectos fundamentales de su estructura de costes orientada al ahorro significativo de estos. Mientras que el mercado español se encuentra concentrado en un solo category killer: la cadena francesa Decathlon, Alemania cuenta con varios de estos category killers. Como estos persiguen un concepto de bajo coste, los pequeños comerciantes se ven cada día más en la necesidad de obtener condiciones ventajosas en la compra de productos de marca. Agrupaciones transempresariales en forma de centrales de compras persiguen este objetivo. En Alemania, ya cuentan con una penetración muy fuerte en el mercado. Sin embargo, en el marco de la globalización y digitalización, aparecen los competidores online tales como Zalando. En vista de los precios decrecientes, en el mercado de artículos deportivos se está viviendo un consumo excesivo. Como las centrales de compras cuentan con muchos costes fijos y procesos largos de suministro, estas ya no representan una solución apta para los denominados small players. Aprovechándose de las nuevas formas de comunicación posibilitadas por las nuevas tecnologías y del auge de las redes sociales, personajes considerados expertos en un sector dado, se están convirtiendo en las nuevas centrales de compras. Creando nuevos factores competitivos tales como el negocio B2B, centrándose en aspectos clave tales como la oferta de descuentos y eliminando y reduciendo los aspectos innecesarios del negocio, estos Social Influencers ofrecen un valor añadido a menor coste., Máster Universitario en Management y Gestión del Cambio (M145) more...