6,702 research outputs found
A survey of recent introduction events, spread and mitigation efforts of mynas (Acridotheres sp.) in Spain and Portugal
Un estudio sobre los recientes episodios de introducción, la propagación y las iniciativas de mitigación de los minás (Acridotheres sp.) en España y Portugal
El miná común, Acridotheres tristis, está catalogado entre las 100 especies más invasoras del mundo. En el presente artÃculo combinamos las observaciones ya existentes con un estudio de campo para determinar los procesos de invasión de tres especies de minás en España y Portugal. Los resultados sugieren que hubo al menos 22 introducciones accidentales e independientes desde comienzos de los años 90 en la penÃnsula ibérica y en tres archipiélagos. Si bien el miná oscuro (A. ginginianus) no ha llegado a establecerse, hay poblaciones reproductoras de miná común en cuatro islas. Las iniciativas de erradicación permitieron eliminar esas poblaciones insulares, pero la especie se mantiene en el estuario del Tajo (Portugal). En esta región existe también una población reproductora de miná crestado (A. cristatellus), que ha crecido exponencialmente en la última década. Es necesario combinar las campañas de erradicación con acciones preventivas, cuyo objetivo sea detener el comercio de estas especies en Europa, para evitar nuevas introducciones accidentales.The common myna Acridotheres tristis is listed among the world’s 100 worst invasive alien species. We combined previous records with a field survey to update the extent and fate of myna introductions in Spain and Portugal. Results suggest that there have been at least 22 independent accidental introductions of three myna species throughout the Iberian peninsula and three archipelagos since the early 1990s. While bank mynas (A. ginginianus) did not become established elsewhere, common mynas reached breeding populations on four islands. Eradication efforts allowed the extirpation of these breeding island populations, but common mynas continue to breed in the Tagus Estuary (continental Portugal). In this region, there is also a breeding population of crested mynas (A. cristatellus), which was undergone an exponential population growth in the last decade. To avoid further accidental introductions, eradication campaigns should be combined with preventive actions aiming to stop the trade of these species in Europe.Un estudio sobre los recientes episodios de introducción, la propagación y las iniciativas de mitigación de los minás (Acridotheres sp.) en España y Portugal
El miná común, Acridotheres tristis, está catalogado entre las 100 especies más invasoras del mundo. En el presente artÃculo combinamos las observaciones ya existentes con un estudio de campo para determinar los procesos de invasión de tres especies de minás en España y Portugal. Los resultados sugieren que hubo al menos 22 introducciones accidentales e independientes desde comienzos de los años 90 en la penÃnsula ibérica y en tres archipiélagos. Si bien el miná oscuro (A. ginginianus) no ha llegado a establecerse, hay poblaciones reproductoras de miná común en cuatro islas. Las iniciativas de erradicación permitieron eliminar esas poblaciones insulares, pero la especie se mantiene en el estuario del Tajo (Portugal). En esta región existe también una población reproductora de miná crestado (A. cristatellus), que ha crecido exponencialmente en la última década. Es necesario combinar las campañas de erradicación con acciones preventivas, cuyo objetivo sea detener el comercio de estas especies en Europa, para evitar nuevas introducciones accidentales
Control of quantum interference in the quantum eraser
We have implemented an optical quantum eraser with the aim of studying this
phenomenon in the context of state discrimination. An interfering single photon
is entangled with another one serving as a which-path marker. As a consequence,
the visibility of the interference as well as the which-path information are
constrained by the overlap (measured by the inner product) between the
which-path marker states, which in a more general situation are non-orthogonal.
In order to perform which-path or quantum eraser measurements while analyzing
non-orthogonal states, we resort to a probabilistic method for the unambiguous
modification of the inner product between the two states of the which-path
marker in a discrimination-like process.Comment: Submitted to New Journal of Physics, March 200
Generalized commutation relations and Non linear momenta theories, a close relationship
A revision of generalized commutation relations is performed, besides a
description of Non linear momenta realization included in some DSR theories. It
is shown that these propositions are closely related, specially we focus on
Magueijo Smolin momenta and Kempf et al. and L.N. Chang generalized
commutators. Due to this, a new algebra arises with its own features that is
also analyzed.Comment: accepted version in IJMP
Influencia de las condiciones experimentales en la determinación de S, Cl, Br y I en agua por espectrometrÃa de masas de alta resolución (HR-ICP-MS)
A systematic study was undertaken to optimize a method to determine S, Cl, Br and I in water by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The sample composition and preparation conditions (the total dissolved solids -TDS-, the total organic compounds -TOC- and the addition of nitric acid) were evaluated to assess the sample matrix influence. Furthermore, the effect of instrumental parameters (carrier gas flow rate, sample flow rate, radiofrequency -RF- power and analyzer resolution) was also studied to minimize the
contribution of polyatomic species, and to establish the required resolution. Low, medium or high resolutions were compared in terms of background level and sensitivity. After optimization, a multivariate robustness test was carried out by means of a Placket-Burman design. This method was applied to samples of the Llobregat and Ter rivers which are used for the drinking water system of the Metropolitan Area of Barcelona (~4.5 million inhabitants), Catalonia, northeast Spain.Este estudio fue financiado a través del Proyecto QUECA del Ministerio de EconomÃa y Competitividad de España (CGL2011-23307) y el Proyecto PICT-2013-1259 (FONCyT, Argentina). Los análisis se realizaron en el Laboratorio de GeoquÃmica labGEOTOP en el ICTJA CSIC, infraestructura cofinanciada por FEDER-UE(Ref. CSIC08-4E-001).Peer Reviewe
The Critical Role of Water at the Gold-titania Interface in Catalytic CO Oxidation
We provide direct evidence of a water-mediated reaction mechanism for room-temperature CO oxidation over Au/TiO2 catalysts. A hydrogen/deuterium kinetic isotope effect of nearly 2 implicates O-H(D) bond breaking in the rate-determining step. Kinetics and in situ infrared spectroscopy experiments showed that the coverage of weakly adsorbed water on TiO2 largely determines catalyst activity by changing the number of active sites. Density functional theory calculations indicated that proton transfer at the metal-support interface facilitates O2 binding and activation; the resulting Au-OOH species readily reacts with adsorbed Au-CO, yielding Au-COOH. Au-COOH decomposition involves proton transfer to water and was suggested to be rate determining. These results provide a unified explanation to disparate literature results, clearly defining the mechanistic roles of water, support OH groups, and the metal-support interface
Effects of Short-Range Correlations in (e,e'p) reactions and nuclear overlap functions
A study of the effects of short-range correlations over the (e,e'p) reaction
for low missing energy in closed shell nuclei is presented. We use correlated,
quasi-hole overlap functions extracted from the asymptotic behavior of the
one-body density matrix, containing central correlations of Jastrow type, up to
first-order in a cluster expansion, and computed in the very high asymptotic
region, up to 100 fm. The method to extract the overlap functions is checked in
a simple shell model, where the exact results are known. We find that the
single-particle wave functions of the valence shells are shifted to the right
due to the short-range repulsion by the nuclear core. The corresponding
spectroscopic factors are reduced only a few percent with respect to the shell
model. However, the (e,e'p) response functions and cross sections are enhanced
in the region of the maximum of the missing momentum distribution due to
short-range correlations.Comment: 45 pages, 15 figure
Direct finite element simulation of turbulent flow for marine based renewable energy
In this article we present a computational framework for simulation of
turbulent flow in marine based renewable energy applications. In
particular, we focus on floating structures and rotating
turbines. This work is an extension to multiphase turbulent flow, of
our existing framework of residual based turbulence modeling for
single phase turbulent incompressible flow. We illustrate the
framework in four examples: a regular wave test where we compare
against an exact solution, the standard MARIN wave impact benchmark
with experimental validation data, a vertical axis turbine with
complex geometry from an existing turbine, and finally a prototype
simulation of decay test in a coupled moving boundary rigid-body and
two-phase fluid simulation.IEA-OES Task 1
Mineralogical characterization of silica sinters from the El Tatio geothermal field, Chile
11 páginas.Silica sinters, deposited from alkali chloride waters in the El Tatio geothermal field in northern Chile (22°20'S, 68°01'W), have been characterized by XRD, SEM, TG-DTA, and FTIR. The dominant silica phase is opal-A. Minor contents of opal-A/-CT and opal-CT are also present together with halite (NaCl), sylvite (KCl), and realgar (AsS). Accessory phases include teruggite [Ca4MgAs2B12O22(OH)12·12(H2O)], sassolite (H3BO3), and detrital quartz (SiO2). FWHM values reflect the immature nature of the studied opal-A. DTA heating experiments of opal-A show cristobalite crystallization at ~1000 °C, whereas DTA cooling experiments show the β -alfacristobalite transformation at ~200 °C. The total weight loss is related to changes in the sinter microtextures, mineral phases, and organic matter contents. FTIR spectra show the effects of silica maturation as consequence of the loss of trapped and absorbed water attached to silanols.Peer reviewe
Top Quark Physics at the Tevatron
We review the field of top-quark physics with an emphasis on experimental
techniques. The role of the top quark in the Standard Model of particle physics
is summarized and the basic phenomenology of top-quark production and decay is
introduced. We discuss how contributions from physics beyond the Standard Model
could affect top-quark properties or event samples. The many measurements made
at the Fermilab Tevatron, which test the Standard Model predictions or probe
for direct evidence of new physics using the top-quark event samples, are
reviewed here.Comment: 50 pages, 17 figures, 2 tables; version accepted by Review of Modern
Physic
Biexciton oscillator strength
Our goal is to provide a physical understanding of the elementary coupling
between photon and biexciton and to derive the physical characteristics of the
biexciton oscillator strength, following the procedure we used for trion.
Instead of the more standard two-photon absorption, this work concentrates on
molecular biexciton created by photon absorption in an exciton gas. We first
determine the appropriate set of coordinates in real and momentum spaces to
describe one biexciton as two interacting excitons. We then turn to second
quantization and introduce the "Fourier transform in the exciton sense" of the
biexciton wave function which is the relevant quantity for oscillator strength.
We find that, like for trion, the oscillator strength for the formation of one
biexciton out of one photon plus a \emph{single} exciton is extremely small: it
is one biexciton volume divided by one sample volume smaller than the exciton
oscillator strength. However, due to their quantum nature, trion and biexciton
have absorption lines which behave quite differently. Electrons and trions are
fermionic particles impossible to pile up all at the same energy. This would
make the weak trion line spread with electron density, the peak structure only
coming from singular many-body effects. By contrast, the bosonic nature of
exciton and biexciton makes the biexciton peak mainly rise with exciton
density, this rise being simply linear if we forget many-body effects between
the photocreated exciton and the excitons present in the sample
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