4,103 research outputs found

    Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores

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    We study the origin of large abundances of complex organic molecules in the Galactic center (GC). We carried out a systematic study of the complex organic molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The CH3OH abundance between clouds varies by nearly two orders of magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex organic molecules relative to that of CH3OH is basically independent of the CH3OH abundance, with variations of only a factor 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH3OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx, natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in A&A 2006. version 2. relocated figures and tables. Language editor suggestions. added reference

    Two Distinct, Geographically Overlapping Lineages of the Corallimorpharian Ricordea Florida (Cnidaria: Hexacorallia: Ricordeidae)

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    We examined the genetic variation of the corallimorpharian Ricordea florida; it is distributed throughout the Caribbean region and is heavily harvested for the marine aquarium trade. Eighty-four distinct individuals of R. florida were sequenced from four geographically distant Caribbean locations (Curaçao, Florida, Guadeloupe, and Puerto Rico). Analysis of the ribosomal nuclear region (ITS1, 5.8S, ITS2) uncovered two geographically partially overlapping genetic lineages in R. florida, probably representing two cryptic species. Lineage 1 was found in Florida and Puerto Rico, and Lineage 2 was found in Florida, Puerto Rico, Guadeloupe, and Curaçao. Because of the multi-allelic nature of the ITS region, four individuals from Lineage 1 and six from Lineage 2 were cloned to evaluate the levels of hidden intra-individual variability. Pairwise genetic comparisons indicated that the levels of intra-individual and intra-lineage variability (\u3c1%) were approximately an order of magnitude lower than the divergence (~9%) observed between the two lineages. The fishery regulations of the aquarium trade regard R. florida as one species. More refined regulations should take into account the presence of two genetic lineages, and they should be managed separately in order to preserve the long-term evolutionary potential of this corallimorpharian. The discovery of two distinct lineages in R. florida illustrates the importance of evaluating genetic variability in harvested species prior to the implementation of management policies

    Internal and relative motions of the Taurus and Ophiuchus star-forming regions

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    We investigate the internal and relative motions of the Taurus and Ophiuchus star-forming regions using a sample of young stars with accurately measured radial velocities and proper motions. We find no evidence for expansion or contraction of the Taurus complex, but a clear indication for a global rotation, resulting in velocity gradients, this suggests a common origin, possibly related to that of Gould's Belt.Comment: 2 figure

    Causal illusion as a cognitive basis of pseudoscientific beliefs

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    Causal illusion has been proposed as a cognitive mediator of pseudoscientific beliefs. However, previous studies have only tested the association between this cognitive bias and a closely related but different type of unwarranted beliefs, those related to superstition and paranormal phenomena. Participants (n = 225) responded to a novel questionnaire of pseudoscientific beliefs designed for this study. They also completed a contingency learning task in which a possible cause, infusion intake, and a desired effect, headache remission, were actually non‐contingent. Volunteers with higher scores on the questionnaire also presented stronger causal illusion effects. These results support the hypothesis that causal illusions might play a fundamental role in the endorsement of pseudoscientific beliefs

    Kardar-Parisi-Zhang universality in first-passage percolation: the role of geodesic degeneracy

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    We have characterized the scaling behavior of the first-passage percolation (FPP) model on two types of discrete networks, the regular square lattice and the disordered Delaunay lattice, thereby addressing the effect of the underlying topology. Several distribution functions for the link-times were considered. The asymptotic behavior of the fluctuations for both the minimal arrival time and the lateral deviation of the geodesic path are in perfect agreement with the Kardar-Parisi-Zhang (KPZ) universality class regardless of the type of the link-time distribution and of the lattice topology. Pre-asymptotic behavior, on the other hand, is found to depend on the uniqueness of geodesics in absence of disorder in the local crossing times, a topological property of lattice directions that we term geodesic degeneracy. This property has important consequences on the model, as for example the well-known anisotropic growth in regular lattices. In this work we provide a framework to understand its effect as well as to characterize its extent.We acknowledge fruitful conversations with E. Korutcheva. This work has been supported by MINECO/FEDER (Spain/EU) grants FIS2015-66020-C2-1-P and FIS2015-69167-C2-1-P

    La estimación de un indicador de brecha del producto a partir de encuestas y datos reales

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    Una estimación adecuada de la brecha del producto es un requisito indispensable para la conducción de la política monetaria bajo el régimen de inflación objetivo. Por esta razón, en la literatura y al interior del Banco de la República, se trabaja con una gran variedad de mediciones a partir de técnicas alternativas. Desafortunadamente, como la brecha del producto es una variable no observable, siempre hay gran incertidumbre sobre cualquier estimación. Para sobreponerse a este problema, en el Departamento de Inflación se siguen regularmente una amplia gama de indicadores, en especial encuestas de opinión empresarial y datos de actividad, para mejorar la comprensión de la situación de la economía en el ciclo y para identificar posibles presiones de demanda. Aunque en principio parece razonable y adecuado contar con gran cantidad de medidas y monitorear diversas fuentes de información complementarias, en la práctica resulta problemático poder resumir de manera eficiente la información disponible en una sola medida que pueda ser utilizada para producir pronósticos de inflación y recomendaciones de política. Hasta hace poco, la reducción de la información se hacía a partir del juicio de los expertos sobre los pesos relativos que se asignaban para cada medición y para la información proveniente de encuestas. Lo cual potencialmente podía conducir a un problema de variables omitidas y a sesgar cualquier estimación. Para resolver este problema en este trabajo se estima un indicador de brecha del producto como el factor no observado entre los datos disponibles. Dicho factor se estima utilizando componentes principales estáticos, el cual debe resumir la información contenida en los datos mientras que excluye cualquier error presente en las medidas originales. La calidad del indicador se evalúa posteriormente a partir de su capacidad predictiva de la inflación básica de bienes no transables en Colombia, mediante una Curva de Phillips híbrida. Los resultados sugieren, como se esperaba, que el indicador de brecha del producto es superior a cualquiera de las medidas individuales para señalar presiones de demanda, puesto que combina de manera eficiente la información de varias fuentes. Adicionalmente se encuentra, que los pronósticos fuera de muestra se pueden mejorar si se excluyen para la estimación del indicador aquellas medidas que provienen de filtros estadísticos. Lo cual reafirma la importancia de seguir fuentes alternativas de información, en especial de encuestas de opinión industrial, a pesar de que la industria tan sólo pesa un 15% del PIB en Colombia.Brecha del producto, componentes principales, Curva de Phillips, Colombia.

    Landmark vs. geometry learning: Explaining female rats' selective preference for a landmark

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    Rats were trained in a triangular-shaped pool to find a hidden platform, whose location was defined in terms of two sources of information, a landmark outside the pool and a particular corner of the pool. Subsequent test trials without the platform pitted these two sources of information against one another. In Experiment 1 this test revealed a clear, although selective, sex difference. As in previous experiments, females spent more time in an area of the pool that corresponded to the landmark, but here only when it was a cone but not when it was a pyramid. Males, on the other hand, always spent more time in the distinctive corner of the pool. Experiments 2 and 3 were only with female rats. In Experiment 2 two identical shaped cylinders were used as landmark cues (one plain white and the other vertically patterned with four different patterns). The results of the preference test revealed that only the females trained and tested with the plain cylinder spent more time in the area of the pool that corresponded to the landmark than in the distinctive corner of the pool. Finally, Experiment 3 replicated the results of Experiment 2 while eliminating an alternative explanation in terms of differential contrast between the two cylinders and the black curtain
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