1,925 research outputs found

    On the Excitation and Formation of Circumstellar Fullerenes

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    We compare and analyze the Spitzer mid-infrared spectrum of three fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds; Tc1, SMP SMC16, and SMP LMC56. The three planetary nebulae share many spectroscopic similarities. The strongest circumstellar emission bands correspond to the infrared active vibrational modes of the fullerene species C60 and little or no emission is present from Polycyclic Aromatic Hydrocarbons (PAHs). The strength of the fullerene bands in the three planetary nebulae is very similar, while the ratio of the [NeIII]15.5um/[NeII]12.8um fine structure lines, an indicator of the strength of the radiation field, is markedly different. This raises questions about their excitation mechanism and we compare the fullerene emission to fluorescent and thermal models. In addition, the spectra show other interesting and common features, most notably in the 6-9um region, where a broad plateau with substructure dominates the emission. These features have previously been associated with mixtures of aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this band, which is likely related to the fullerene formation mechanism, and compare it with modeled Hydrogenated Amorphous Carbon that present emission in this region.Comment: 13 pages, 2 tables, 7 figures, Accepted for publication in Ap

    Reconstrucción de rotura crónica de tendón distal del bíceps braquial: a propósito de un caso

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    Las roturas inveteradas o crónicas del tendón distal del bíceps braquial son infrecuentes. Su tratamiento supone un reto importante por el grado de retracción y deficiente calidad del tendón y músculo lesionados, que en ocasiones obligan al empleo de injertos para tratar de restaurar la anatomía y mejorar los resultados funcionales. La tasa de complicaciones en las reparaciones de roturas crónicas es mayor con respecto a las reparaciones de lesiones agudas. Presentamos el caso de una reparación quirúrgica de una rotura crónica de 3 meses de evolución mediante la utilización de aloinjerto liofilizado de Aquiles.Chronic or inveterate disruptions of the distal biceps brachii are uncommon. Treatment remains a major challenge by shrinkage and poor quality of the injured tendon and muscle, which sometimes require the use of grafts to try to restore the anatomy and improve the functional outcomes. The rate of complications in surgical treatment of chronic tears is more than the repairs of acute injuries. We report the case of a surgical reconstruction of a chronic tear three months of evolution using lyophilized Achilles allograft

    Herpetofauna en dos sitios en el municipio de Soto la Marina, Tamaulipas, México

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    We conducted a herpetofaunal study from November 2009 to July 2010 on the ranches El Herradero and San Jose de los Leones, both in the municipality of Soto la Marina, in the centraleastern part of the state of Tamaulipas, northeastern Mexico. Their location corresponds to a peninsula surrounded by the Laguna Madre. The objectives were to conduct a herpetological inventory and to determine the distribution of the species in the plant communities and the status of each species following the criteria of the NOM-059-SEMARNAT-2010. The information will be useful in delineating an area to set aside for conservation easement for the species. We followed the transect method described by Campbell & Christman (1982). We recorded 17 species: one anuran, one crocodile, six turtles, three lizards and six snakes. Of these, eight are new records for the municipality of Soto la Marina, 10 species are at risk, six are of special concern, three are threatened, and one is endangered. The ranches contain 34.69% of the herpetofauna species present in the municipality.Se realizó un estudio herpetofaunístico en los ranchos El Herradero y San José de los Leones ambos ubicados en el municipio de Soto la Marina, en la porción central-oriental del estado de Tamaulipas al Noreste de México. Estos predios se ubican en una forma de península rodeada por agua perteneciente a la Laguna Madre. Los objetivos fueron: realizar un inventario herpetológico, determinar la asociación de la herpetofauna con las comunidades vegetales y determinar el estatus de cada una de las especies de acuerdo a la NOM-059-SEMARNAT-2010. Lo anterior con la finalidad de que el área ocupada por los ranchos sea para establecer sitios de conservación como servidumbre ecológica de especies. Se siguió el muestreo de transectos descrito por Campbell & Christman (1982). El estudio se realizó desde noviembre de 2009 hasta julio de 2010. Se registraron 17 especies: un anuro, seis tortugas, un cocodrilo, tres lagartijas y seis serpientes. De estos, ocho son nuevos reportes para el municipio de Soto la Marina, y de acuerdo con la NOM-059-SEMARNAT-2010 se reportaron 10 especies donde seis se encuentran Sujetas a Protección Especial, tres se encuentran Amenazadas y una en Peligro de Extinción. Los ranchos cuentan con 34.69% de las especies de herpetofauna presente en el municipio

    A Hybrid Coral Reefs Optimization – Variable Neighborhood Search Approach for the Unequal Area Facility Layout Problem

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    The Unequal Area Facility Layout Problem (UA-FLP) is a relevant optimization problem related to industrial design, that deals with obtaining the most effective allocation of facilities, that make up the rectangular manufacturing plant layout. The UA-FLP is known to be a hard optimization problem, where meta-heuristic approaches are a good option to obtain competitive solutions. Many of these computational approaches, however, usually fall into local optima, and suffer from lack of diversity in their population, mainly due to the huge search spaces and hard fitness landscapes produced by the traditional representation of UA-FLP. To solve these issues, in this paper we propose a novel hybrid meta-heuristic approach, which combines a Coral Reefs Optimization algorithm (CRO) with a Variable Neighborhood Search (VNS) and a new representation for the problem, called Relaxed Flexible Bay Structure (RFBS), which simplifies the encoding and makes its fitness landscape more affordable. Thus, the use of VNS allows more intensive exploitation of the searching space with an affordable computational cost, as well as the RFBS allows better management of the free space into the plant layout. This combined strategy has been tested over a set of UA-FLP instances of different sizes, which have been previously tackled in the literature with alternative meta-heuristics. The tests results show very good performance in all cases

    A novel multi-objective Interactive Coral Reefs Optimization algorithm for the Unequal Area Facility Layout Problem

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    The Unequal Area Facility Layout Problem (UA-FLP) has been widely analyzed in the literature using several heuristics and meta-heuristics to optimize some qualitative criteria, taking into account different restrictions and constraints. Nevertheless, the subjective opinion of the designer (Decision Maker, DM) has never been considered along with the quantitative criteria and restrictions. This work proposes a novel approach for the UA-FLP based on an Interactive Coral Reefs Optimization (ICRO) algorithm, which combines the simultaneous consideration of both quantitative and qualitative (DM opinion) features. The algorithm implementation is explained in detail, including the way of jointly considering quantitative and qualitative aspects in the fitness function of the problem. The experimental part of the paper illustrates the effect of including qualitative aspects in UA-FLP problems, considering three different hard UA-FLP instances. Empirical results show that the proposed approach is able to incorporate the DM preferences in the obtained layouts, without affecting much to the quantitative part of the solutions

    Rotura bilateral y simultánea del tendón de Aquiles

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    La rotura bilateral y simultánea del tendón de Aquiles es un hecho excepcional. La producción de esta lesión en una persona joven, sin antecedentes patológicos ni de administración de ciertos medicamentos es aún más excepcional. El tratamiento quirúrgico y un adecuado proceso de seguimiento y rehabilitación contribuyen a una buena recuperación y pronóstico en los individuos jóvenes y activos con roturas del tendón de Aquiles. Se presenta un caso clínico de una mujer de 21 años tratada quirúrgicamente con buen resultado.The bilateral and simultaneous rupture of Achilles tendon is an excepcional situation. The production of this injury in a young person, without history pathological or administration of certain drugs is even more exceptional. The surgical treatment and a proper process of following-up and rehabilitation help to a good recovery and prognosis in young and active people with Achilles tendon ruptures

    Mitochondrial echoes of first settlement and genetic continuity in El Salvador

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    Background: From Paleo-Indian times to recent historical episodes, the Mesoamerican isthmus played an important role in the distribution and patterns of variability all around the double American continent. However, the amount of genetic information currently available on Central American continental populations is very scarce. In order to shed light on the role of Mesoamerica in the peopling of the New World, the present study focuses on the analysis of the mtDNA variation in a population sample from El Salvador. Methodology/Principal Findings: We have carried out DNA sequencing of the entire control region of the mitochondrial DNA (mtDNA) genome in 90 individuals from El Salvador. We have also compiled more than 3,985 control region profiles from the public domain and the literature in order to carry out inter-population comparisons. The results reveal a predominant Native American component in this region: by far, the most prevalent mtDNA haplogroup in this country (at ~90%) is A2, in contrast with other North, Meso- and South American populations. Haplogroup A2 shows a star-like phylogeny and is very diverse with a substantial proportion of mtDNAs (45%; sequence range 16090–16365) still unobserved in other American populations. Two different Bayesian approaches used to estimate admixture proportions in El Salvador shows that the majority of the mtDNAs observed come from North America. A preliminary founder analysis indicates that the settlement of El Salvador occurred about 13,400±5,200 Y.B.P.. The founder age of A2 in El Salvador is close to the overall age of A2 in America, which suggests that the colonization of this region occurred within a few thousand years of the initial expansion into the Americas. Conclusions/Significance: As a whole, the results are compatible with the hypothesis that today's A2 variability in El Salvador represents to a large extent the indigenous component of the region. Concordant with this hypothesis is also the observation of a very limited contribution from European and African women (~5%). This implies that the Atlantic slave trade had a very small demographic impact in El Salvador in contrast to its transformation of the gene pool in neighbouring populations from the Caribbean facade

    Influencia de la composición petrológica y procedencia en la albitización de las areniscas sinrift del Cretácico inferior, Cuenca del Maestrazgo, Cadena Ibérica

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    Lower Cretaceous sandstones from the Maestrat Basin are characterized by differences in detrital composition, provenance and degree of albitized feldspars (partial to complete). Petrological composition of Lower Cretaceous sandstones revealed a mixed provenance from plutonic and metamorphic source areas. A progressively major influence of granitic source rocks was detected from the lowermost Mora petrofacies toward the uppermost El Castellar and Camarillas petrofacies. Albitization of detrital feldspars occurred in all the studied sandstones, but feldspars were completely albitized in the lowermost Mora Fm. and only partially albitized in the overlying Castellar and Camarillas formations. However, all the Lower Cretaceous sandstones underwent, approximately, the same burial and thermal conditions (119-134ºC; based on vitrinite reflectance and thermal modelling). The decrease in replacive albite/detrital feldspars ratio from the lowermost Mora Fm. toward the uppermost Camarillas Fm. was related to differences in detrital composition and provenance of sandstones. Albitization was pervasive in the Mora Fm. sandstones because of its dominant metamorphic source areas, which implies a relative low abundance of K-feldspar compared to plagioclase. In contrast, the abundance of K-feldspars in Castellar and Camarillas formations prevented the complete albitization of feldspars. Thus, differences in original composition and provenance of sandstones influenced significantly the different degree of albitization for comparable burial and thermal rates.Las areniscas del Cretácico inferior de la Cuenca del Maestrazgo presentan diferencias en su composición detrítica, procedencia y grado de albitización de los feldespatos. La composición petrológica indica una mezcla de aportes de rocas metamórficas (dominantes en la Fm. Mora, Berriansiense-Valanginiense) y plutónicas (progresiva mayor contribución hacia las fms. Castellar y Camarillas, Valanginiense-Barremiense). La albitización de los feldespatos detríticos se observa en todas las areniscas, pero sólo la Fm. Mora presenta feldespatos completamente albitizados, mientras que las fms. Castellar y Camarillas la albitización es parcial. Uno de los factores que controla el proceso de albitización es la temperatura, sin embargo, todas las areniscas del Cretácico inferior estuvieron sometidas a condiciones de enterramiento y temperatura similares (119-134ºC; basadas en reflectancia de vitrinitas y modelización térmica). La disminución de grado de albitización hacia las fms. Castellar y Camarillas estaría relacionada con las diferencias en composición y procedencia de las areniscas. La albitización fue completa en la Fm. Mora debido a la mayor presencia de aportes de rocas metamórficas, lo que implica una mayor abundancia de plagioclasas. Por el contrario, la mayor abundancia de feldespato-K en las fms. Castellar y Camarillas impidió la completa albitización de los feldespatos. Por tanto, las diferencias en la composición y procedencia de las areniscas influyeron significativamente en el grado de albitización de los feldespatos en condiciones similares de enterramiento y temperaturaDepto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEMinisterio de Educación y Ciencia (MEC)pu
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