Quasar-galaxy and AGN-galaxy cross-correlations

We compute quasar-galaxy and AGN-galaxy cross-correlation functions for samples taken from the \cite{VCV98} catalog of quasars and active galaxies, using tracer galaxies taken from the Edinburgh/Durham Southern Catalog. The sample of active galaxy targets shows positive correlation at projected separations $r_p < 6 h^{-1} Mpc$ consistent with the usual power-law. On the other hand, we do not find a statistically significant positive quasar-galaxy correlation signal except in the range $3 h^{-1} Mpc < r_p < 6 h^{-1} Mpc$ where we find similar AGN-galaxy and quasar-galaxy correlation amplitudes. At separations $r_p<3 h^{-1} Mpc$ a strong decline of quasar-galaxy correlations is observed, suggesting a significant local influence of quasars in galaxy formation. In an attempt to reproduce the observed cross-correlation between quasars and galaxies, we have performed CDM cosmological hydrodynamical simulations and tested the viability of a scenario based on the model developed by \cite{silkrees98}. In this scheme a fraction of the energy released by quasars is considered to be transferred into the baryonic component of the intergalactic medium in the form of winds. The results of the simulations suggest that the shape of the observed quasar-galaxy cross-correlation function could be understood in a scenario where a substantial amount of energy is transferred to the medium at the redshift of maximum quasar activity.Comment: 11 pages, 9 figures. Accepted for publication in Ap

Correlation Function of Galaxy Groups

We use the Updated Zwicky Catalog of galaxies (Falco et al. 1999) to generate a catalog of groups, by means of a friend-of-friend algorithm. The correlation length of the total sample is well fitted with a power law $\xi(r)=(r/r_0)^\gamma$ with parameters $r_0=9.0 \pm 0.4 h^{-1}Mpc$ and $\gamma = -1.67 \pm 0.09$ for values of $r<70 h^{-1} Mpc$. Three subsamples defined by the range of group virial masses ${\cal M}$ were used to have their clustering properties examined throughout the autocorrelation function. We find an increase of the amplitude of the correlation function according to the group masses which extends the results of the $r_0-d_c$ relation for galaxy systems at small $d_c$. For completeness we have also analyzed a sample of groups obtained from the Southern Sky Redshift Survey (da Costa et al.1998) in the range of virial masses $5\times10^{12}M_{\odot}<{\cal M}<4\times10^{14}M_{\odot}$ to compare the results with those obtained from GUZC.Comment: 9 figures, accepted for publication in Ap

Predicción de amputación mediante MESS (Mangled Extremity Severity Score) en pacientes con lesión traumática vascular grave

En este estudio retrospectivo y ciego se analizan las historias clínicas de 60 pacientes (63 miembros inferiores), que ingresaron en nuestro hospital desde 1978 a 1992 a causa de una lesión traumática vascular grave; en este grupo no se incluyeron los pacientes con traumatismo vascular localizado por encima de la cadera o debajo del tobillo. El objetivo del estudio ha sido investigar si el MESS (Mangled extremity severity score) es un sistema útil para decidir entre la amputación precoz o el intento de reconstrucción en este tipo de pacientes. De 36 miembros que terminaron en amputación, 34 tuvieron un MESS de 7 o más, demostrando una sensibilidad del test del 94,4%. De 27 miembros que se salvaron, 22 tuvieron un MESS de 6 o menos, demostrando una especificidad del 81,4%. Así pues, el MESS es un test útil para predecir la necesidad o no de amputar un miembro con lesión vascular traumática grave, pero no es absolutamente fiable. Parece más fiable cuando se aplica a pacientes con traumatismo vascular grave que cuando se aplica a pacientes con traumatismo, tengan o no lesión vascular.60 patients (63 limbs) suffering from a severe vascular injury of the lower extremities between 1978-1992 have been retrospectively reviewed. Those cases wherein vascular injury was located above the hip level or under the ankle level were not included. The aim of this study was to investígate whether the Mangled Extremity Severity Score (MESS) is a useful test to decide between limb salvage or early amputation in this type of patients. Among 36 amputated limbs. 34 had a score equal or greater than 7, the rate of sensitivity of the test was 94,4%. Among 27 salvaged limbs, 22 had a score equal or lower than 6, showing a rate of specificity of 81,4%. The MESS seems to be a very useful test for prediction of limb salvage versus amputation with severe vascular injury, although it is not totally reliable. It seems better when applied to patients with vascular injury, rather than to those with mangled extremity, with or without vascular injury

Assessment of the potential energy hypersurfaces in thymine within multiconfigurational theory: CASSCF vs. CASPT2

The present study provides new insights into the topography of the potential energy hypersurfaces (PEHs) of the thymine nucleobase in order to rationalize its main ultrafast photochemical decay paths by employing two methodologies based on the complete active space self-consistent field (CASSCF) and the complete active space second-order perturbation theory (CASPT2) methods: (i) CASSCF optimized structures and energies corrected with the CASPT2 method at the CASSCF geometries and (ii) CASPT2 optimized geometries and energies. A direct comparison between these strategies is drawn, yielding qualitatively similar results within a static framework. A number of analyses are performed to assess the accuracy of these different computational strategies under study based on a variety of numerical thresholds and optimization methods. Several basis sets and active spaces have also been calibrated to understand to what extent they can influence the resulting geometries and subsequent interpretation of the photochemical decay channels. The study shows small discrepancies between CASSCF and CASPT2 PEHs, displaying a shallow planar or twisted 1(ππ*) minimum, respectively, and thus featuring a qualitatively similar scenario for supporting the ultrafast bi-exponential deactivation registered in thymine upon UV-light exposure. A deeper knowledge of the PEHs at different levels of theory provides useful insight into its correct characterization and subsequent interpretation of the experimental observations. The discrepancies displayed by the different methods studied here are then discussed and framed within their potential consequences in on-the-fly non-adiabatic molecular dynamics simulations, where qualitatively diverse outcomes are expected

Ellipsoidal configurations in the de Sitter spacetime

The cosmological constant $\Lambda$ modifies certain properties of large astrophysical rotating configurations with ellipsoidal geometries, provided the objects are not too compact. Assuming an equilibrium configuration and so using the tensor virial equation with $\Lambda$ we explore several equilibrium properties of homogeneous rotating ellipsoids. One shows that the bifurcation point, which in the oblate case distinguishes the Maclaurin ellipsoid from the Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that, the cosmological constant allows triaxial configurations of equilibrium rotating the minor axis as solutions of the virial equations. The significance of the result lies in the fact that minor axis rotation is indeed found in nature. Being impossible for the oblate case, it is permissible for prolate geometries, with $\Lambda$ zero and positive. For the triaxial case, however, an equilibrium solution is found only for non-zero positive $\Lambda$. Finally, we solve the tensor virial equation for the angular velocity and display special effects of the cosmological constant there.Comment: 15 pages, 11 figures, published in Class. Quant. Grav. References adde

In-situ formation of solidified hydrogen thin-membrane targets using a pulse tube cryocooler

An account is given of the Central Laser Facility's work to produce a cryogenic hydrogen targetry system using a pulse tube cryocooler. Due to the increasing demand for low Z thin laser targets, CLF (in collaboration with TUD) have been developing a system which allows the production of solid hydrogen membranes by engineering a design which can achieve this remotely; enabling the gas injection, condensation and solidification of hydrogen without compromising the vacuum of the target chamber. A dynamic sealing mechanism was integrated which allows targets to be grown and then remotely exposed to open vacuum for laser interaction. Further research was conducted on the survivability of the cryogenic targets which concluded that a warm gas effect causes temperature spiking when exposing the solidified hydrogen to the outer vacuum. This effect was shown to be mitigated by improving the pumping capacity of the environment and reducing the minimum temperature obtainable on the target mount. This was achieved by developing a two-stage radiation shield encased with superinsulating blanketing; reducing the base temperature from 14 0.5 K to 7.2 0.2 K about the coldhead as well as improving temperature control stability following the installation of a high-performance temperature controller and sensor apparatus. The system was delivered experimentally and in July 2014 the first laser shots were taken upon hydrogen targets in the Vulcan TAP facility.</p