La repoblació del conill de bosc incrementa la sarna

Les malalties víriques, la caça intensiva i les noves pràctiques agrícoles han comportat que el conill de bosc de la Península Ibèrica sigui una espècie "gairebé amenaçada". Però, segons un estudi d'investigadors del Departament de Medicina i Cirurgia Animal de la UAB, la repoblació de conills que es duu a terme a molts llocs de la Península introdueix noves malalties en les poblacions receptores, com la sarna sarcòptica que perfora l'epidermis de més de cent espècies de mamífers, inclòs l'home. A la vista d'aquests resultats, els investigadors recomanen un estricte control sanitari dels conills alliberats.Las enfermedades víricas, la caza intensiva y las nuevas prácticas agrícolas han supuesto que el conejo de monte de la Península Ibérica sea una especie "casi amenazada". Pero, según un estudio de investigadores del Departamento de Medicina y Cirugía Animal de la UAB, la repoblación de conejos que se lleva a cabo en muchos lugares de la Península introduce nuevas enfermedades en las poblaciones receptoras, como la sarna sarcóptica que perfora la epidermis de más de cien especies de mamíferos, incluído el hombre. A la vista de estos resultados, los investigadores recomiendan un estricto control sanitario de los conejos liberados

Nature and Nurture in Dark Matter Halos

Cosmological simulations consistently predict specific properties of dark matter halos, but these have not yet led to a physical understanding that is generally accepted. This is especially true for the central regions of these structures. Recently two major themes have emerged. In one, the dark matter halo is primarily a result of the sequential accretion of primordial structure (ie `Nature'); while in the other, dynamical relaxation (ie `Nurture') dominates at least in the central regions. Some relaxation is however required in either mechanism. In this paper we accept the recently established scale-free sub-structure of halos as an essential part of both mechanisms. Consequently; a simple model for the central relaxation based on a self-similar cascade of tidal interactions, is contrasted with a model based on the accretion of adiabatically self-similar, primordial structure. We conclude that a weak form of this relaxation is present in the simulations, but that is normally described as the radial orbit instability.Comment: 25 pages, 3 figures, fig with parts 1 to d, fig 3 with parts a to

Negative ions formed in N₂/CH₄/Ar discharge – a simulation of Titan's atmosphere chemistry

The formation of negative ions produced in a negative point-to-plane corona discharge fed by a Ar/N2//CH4/ gas mixture has been studied using mass spectrometry. The measurements were carried out in flowing regime at ambient temperature and a reduced pressure of 460 mbar. The CN ? anion has been found to be the most dominant negative ion in the discharge and is believed to be the precursor of heavier negative ions such as C3/N ? and C5/N ? . The most likely pathway for the formation of such molecular anions is H-loss dissociative electron attachment to HCN, H3/CN and H5/CN formed in the discharge. These same anions have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere and hence assist in the interpretation of results from the Cassini Huygens space mission

Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario

We present an entirely analytic model for a preheated, polytropic intergalactic medium in hydrostatic equilibrium within a NFW dark halo potential in which the evolution of the halo structure between major merger events proceeds inside-out by accretion. This model is used to explain, within a standard $\Lambda$CDM cosmogony, the observed X-ray properties of nearby relaxed, non-cooling flow groups and clusters of galaxies. We find that our preferred solution to the equilibrium equations produces scaling relations in excellent agreement with observations, while simultaneously accounting for the typical structural characteristics of the distribution of the diffuse baryons. In the class of preheating models, ours stands out because it offers a unified description of the intrahalo medium for galaxy systems with total masses above \sm 2\times 10^{13}\msun, does not produce baryonic configurations with large isentropic cores, and reproduces faithfully the observed behavior of the gas entropy at large radii. All this is achieved with a moderate level of energy injection of about half a keV, which can be easily accommodated within the limits of the total energy released by the most commonly invoked feedback mechanisms, as well as with a polytropic index of 1.2, consistent with both many observational determinations and predictions from high-resolution gas-dynamical simulations of non-cooling flow clusters. More interestingly, our scheme offers a physical motivation for the adoption of this specific value of the polytropic index, as it is the one that best ensures the conservation after halo virialization of the balance between the total specific energies of the gas and dark matter components for the full range of masses investigated.Comment: 18 pages, 11 figures, accepted for publication in the Astrophysical Journa

Kinematics of planet-host stars and their relation with dynamical streams in the solar neighbourhood

We present a detailed study on the kinematics of metal-rich stars with and without planets, and their relation with the Hyades, Sirius and Hercules dynamical streams in the solar neighbourhood. Accurate kinematics have been derived for all the stars belonging to the CORALIE planet search survey. We used precise radial velocity measurements and CCF parameters from the CORALIE database, and parallaxes, photometry and proper motions from the HIPPARCOS and Tycho-2 catalogues. The location of stars with planets in the thin or thick discs has been analysed using both kinematic and chemical constraints. We compare the kinematic behaviour of known planet-host stars to the remaining targets belonging to the volume-limited sample, in particular to its metal-rich population. The high average metallicity of the Hyades stream is confirmed. The planet-host targets show a kinematic behaviour similar to that of the metal-rich comparison subsample, rather than to that of the comparison sample as a whole, thus supporting a primordial origin for the metal excess observed in stars with known planetary companions. According to the scenarios proposed as an explanation for the dynamical streams, systems with giant planets could have formed more easily in metal-rich inner Galactic regions and then been brought into the solar neighbourhood by dynamical streams.Comment: 14 pages, 12 figures, accepted for publication in A&A (28 August 2006

Detection of vortex tubes in solar granulation from observations with Sunrise

We have investigated a time series of continuum intensity maps and corresponding Dopplergrams of granulation in a very quiet solar region at the disk center, recorded with the Imaging Magnetograph eXperiment (IMaX) on board the balloon-borne solar observatory Sunrise. We find that granules frequently show substructure in the form of lanes composed of a leading bright rim and a trailing dark edge, which move together from the boundary of a granule into the granule itself. We find strikingly similar events in synthesized intensity maps from an ab initio numerical simulation of solar surface convection. From cross sections through the computational domain of the simulation, we conclude that these `granular lanes' are the visible signature of (horizontally oriented) vortex tubes. The characteristic optical appearance of vortex tubes at the solar surface is explained. We propose that the observed vortex tubes may represent only the large-scale end of a hierarchy of vortex tubes existing near the solar surface.Comment: Astrophysical Journal Letters: Sunrise Special Issue, reveived 2010 June 16; accepted 2010 August

Aqueous Processes and Microbial Habitability of Gale Crater Sediments from the Blunts Point to the Glenn Torridon Clay Unit

A driving factor for sending the Mars Science Laboratory, Curiosity rover to Gale Crater was the orbital detection of clay minerals in the Glen Torridon (GT) clay unit. Clay mineral detections in GT suggested a past aqueous environment that was habitable, and could contain organic evidence of past microbiology. The mission of the Sample Analysis at Mars (SAM) instrument onboard Curiosity was to detect organic evidence of past microbiology and to detect volatile bearing mineralogy that can inform on whether past geochemical conditions would have supported microbiological activity. The objective of this work was to 1) evaluate the depositional/alteration conditions of Blunts Point (BP) to GT sediments 2) search for evidence of organics, and 3) evaluate microbial habitability in the BP, Vera Rubin Ridge (VRR), and GT sedimentary rock

On the Baryon Fractions in Clusters and Groups of Galaxies

We present the baryon fractions of 2MASS groups and clusters as a function of cluster richness using total and gas masses measured from stacked ROSAT X-ray data and stellar masses estimated from the infrared galaxy catalogs. We detect X-ray emission even in the outskirts of clusters, beyond r_200 for richness classes with X-ray temperatures above 1 keV. This enables us to more accurately determine the total gas mass in these groups and clusters. We find that the optically selected groups and clusters have flatter temperature profiles and higher stellar-to-gas mass ratios than the individually studied, X-ray bright clusters. We also find that the stellar mass in poor groups with temperatures below 1 keV is comparable to the gas mass in these systems. Combining these results with individual measurements for clusters, groups, and galaxies from the literature, we find a break in the baryon fraction at ~1 keV. Above this temperature, the baryon fraction scales with temperature as f_b \propto T^0.20\pm0.03. We see significantly smaller baryon fractions below this temperature, and the baryon fraction of poor groups joins smoothly onto that of systems with still shallower potential wells such as normal and dwarf galaxies where the baryon fraction scales with the inferred velocity dispersion as f_b \propto \sigma^1.6. The small scatter in the baryon fraction at any given potential well depth favors a universal baryon loss mechanism and a preheating model for the baryon loss. The scatter is, however, larger for less massive systems. Finally, we note that although the broken power-law relation can be inferred from data points in the literature alone, the consistency between the baryon fractions for poor groups and massive galaxies inspires us to fit the two categories of objects (galaxies and clusters) with one relation.Comment: 21 pages, 5 figures, ApJ in pres

VVV-WIT-04: An extragalactic variable source caught by the VVV Survey

We report the discovery of VVV-WIT-04, a near-infrared variable source towards the Galactic disk located ~0.2 arcsec apart from the position of the radio source PMN J1515-5559. The object was found serendipitously in the near-IR data of the ESO public survey VISTA Variables in the V\'ia L\'actea (VVV). Our analysis is based on variability, multicolor, and proper motion data from VVV and VVV eXtended surveys, complemented with archive data at longer wavelengths. We suggest that VVV-WIT-04 has an extragalactic origin as the near-IR counterpart of PMN J1515-5559. The Ks-band light-curve of VVV-WIT-04 is highly variable and consistent with that of an Optically Violent Variable (OVV) quasar. The variability in the near-IR can be interpreted as the redshifted optical variability. Residuals to the proper motion varies with the magnitude suggesting contamination by a blended source. Alternative scenarios, including a transient event such as a nova or supernova, or even a binary microlensing event are not in agreement with the available data.R.K.S. acknowledges support from CNPq/Brazil through projects 308968/2016-6 and 421687/2016-9. P.W.L. is supported by STFC Consolidated Grant ST/R000905/1. Support for the authors is provided by the BASAL CONICYT Center for Astrophysics and Associated Technologies (CATA) through grant AFB-170002, and the Ministry for the Economy, Development, and Tourism, Programa Iniciativa Cient´ıfica Milenio through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). D.M. acknowledges support from FONDECYT through project Regular #1170121