Use of neural networks for the identification of new z>=3.6 QSOs from FIRST-SDSS DR5

We aim to obtain a complete sample of redshift > 3.6 radio QSOs from FIRST sources having star-like counterparts in the SDSS DR5 photometric survey (r<=20.2). We found that simple supervised neural networks, trained on sources with SDSS spectra, and using optical photometry and radio data, are very effective for identifying high-z QSOs without spectra. The technique yields a completeness of 96 per cent and an efficiency of 62 per cent. Applying the trained networks to 4415 sources without DR5 spectra we found 58 z>=3.6 QSO candidates. We obtained spectra of 27 of them, and 17 are confirmed as high-z QSOs. Spectra of 13 additional candidates from the literature and from SDSS DR6 revealed 7 more z>=3.6 QSOs, giving and overall efficiency of 60 per cent. None of the non-candidates with spectra from NED or DR6 is a z>=3.6 QSO, consistently with a high completeness. The initial sample of z>=3.6 QSOs is increased from 52 to 76, i.e. by a factor 1.46. From the new identifications and candidates we estimate an incompleteness of SDSS for the spectroscopic classification of FIRST 3.6<=z<=4.6 QSOs of 15 percent for r<=20.2.Comment: 16 pages, 9 figures accepted for publication in MNRA

MarsLux: HI-Resolution Illumination Maps Generator for Mars

Illumination simulation codes for the Moon's surface have been thoroughly developed during the last years. Despite works done for the Moon, no studies have investigated the relation between sunlight illumination and the Martian surface applying those codes done for the Moon to Mars. The objective of this work is to describe the development of a surface illumination simulation code, called MarsLux, which allows users to make a detailed investigation of the illumination conditions on Mars, based on its topography and the relative position of the Sun. Our code can derive accurate illumination maps, form topographic data, showing areas that are fully illuminated, areas in total shadow, and areas with partial shade, in short computational times. Although the code does not take into account any atmospheric effect, the results proved to be of high accuracy. The maps generated are useful for geomorphological studies, to study gullies, thermal weathering, or mass wasting processes as well as for producing energy budget maps for future exploration missions.Fil: Spagnuolo, Mauro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Carballo, Federico Daniel. Servicio Geologico Minero Argentino; ArgentinaFil: Marco Figuera, R.. Jacobs University Bremen; AlemaniaFil: Rossi, A. P.. Jacobs University Bremen; Alemani

Tomography of high-redshift clusters with OSIRIS

High-redshift clusters of galaxies are amongst the largest cosmic structures. Their properties and evolution are key ingredients to our understanding of cosmology: to study the growth of structure from the inhomogeneities of the cosmic microwave background; the processes of galaxy formation, evolution, and differentiation; and to measure the cosmological parameters (through their interaction with the geometry of the universe, the age estimates of their component galaxies, or the measurement of the amount of matter locked in their potential wells). However, not much is yet known about the properties of clusters at redshifts of cosmological interest. We propose here a radically new method to study large samples of cluster galaxies using microslits to perform spectroscopy of huge numbers of objects in single fields in a narrow spectral range-chosen to fit an emission line at the cluster redshift. Our objective is to obtain spectroscopy in a very restricted wavelength range (~100 A in width) of several thousands of objects for each single 8x8 square arcmin field. Approximately 100 of them will be identified as cluster emission-line objects and will yield basic measurements of the dynamics and the star formation in the cluster (that figure applies to a cluster at z~0.50, and becomes ~40 and ~20 for clusters at z~0.75 and z~1.00 respectively). This is a pioneering approach that, once proven, will be followed in combination with photometric redshift techniques and applied to other astrophysical problems.Comment: 4 pages, 3 figures. Proceedings of "Science with the GTC", Granada (Spain), February 2002, RMxAA in pres

Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field ${\bm H}_a$, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude $H_a$ of the applied magnetic field and its angle of rotation $\alpha_s$ upon the magnetization of the superconductor sample is analyzed. When $H_a$ is smaller than the penetration field $H_P$, the magnetization components, parallel and perpendicular to ${\bm H_a}$, oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, $H_a$, is larger than $H_P$, both magnetization components become constant functions of $\alpha_s$ at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.Comment: 12 pages, 29 figure

Genetic and Molecular Factors in Drug-Induced Liver Injury: A Review

The diagnosis of drug-induced liver injury (DILI) is challenging and based on complex diagnostic criteria. DILI falls into two main categories i) intrinsic 'dose-dependent' Type A reactions ii) 'idiosyncratic' or Type B reactions (which are usually not predictable). Idiosyncratic reactions can be immunoallergic (hypersensitivity), or metabolic, although overlap between categories can occur. The aim of this review is to summarise the general view of underlying mechanisms in DILI and to highlight individual risk factors for developing hepatotoxicity. Polymorphisms of bioactivation/ toxification pathways through CYP450 enzymes (Phase I), detoxification reactions (Phase II) and excretion/transport (Phase III) are explored together with immunological factors that might determine DILI. The importance of establishing a multidisciplinary and multi-centric network to promote the understanding and research in hepatotoxicity is underlined. Challenges such as genetic analyses for association studies and whole genome studies, pharmacogenetic testing and future approaches to study DILI are considered. Knowledge regarding these operational mechanisms could provide further insight for the prospective identification of susceptible patients at risk of developing drug-induced hepatotoxicity.

The absorption spectra of Q1107+487 and Q1442+295

We present the first moderate resolution (approx. 40--120 km/s) spectroscopic observations of the bright (V<16.7) high-redshift QSOs Q1107+487 (z_{em} = 2.965) and Q1442+295 (z_{em} = 2.669) (Sanduleak & Pesch 1989). The relatively high signal to noise reached in the spectra along with an extensive wavelength coverage of the Lyman alpha and the Lyman beta forest allowed us to obtain, through profile fitting, column densities and Doppler parameters of the Lyman clouds towards these QSOs. The spectral coverage of regions longward of the Lyman alpha emission line of the QSOs at the expected wavelengths of CIV 1548,1550 at the redshifts of the Lyman alpha forest allowed us to identify some heavy element absorption systems (hereafter HEASs) towards these QSOs. We have found no Lyman absorption system or HEAS towards these QSOs for which our data allow a deuterium measurement or to provide an interesting upper limit for the D/H ratio. The reason for this is that the Lyman lines with high column density detected towards these QSOs belong to absorption systems showing velocity structure

Symmetric Variational Formulation of BIE for Domain Decomposition Problems in Elasticity – An SGBEM Approach for Nonconforming Discretizations of Curved Interfaces

An original approach to solve domain decomposition problems by the symmetric Galerkin boundary element method is developed. The approach, based on a new variational principle for such problems, yields a fully symmetric system of equations. A natural property of the proposed approach is its capability to deal with nonconforming discretizations along straight and curved interfaces, allowing in this way an independent meshing of non-overlapping subdomains to be performed. Weak coupling conditions of equilibrium and compatibility at an interface are obtained from the critical point conditions of the energy functional. Equilibrium is imposed through local traction (Neumann) boundary conditions prescribed on a subdomain situated at one side of the interface, and compatibility is imposed through local displacement (Dirichlet) boundary conditions prescribed on the other subdomain situated at the opposite side of the interface. No additional unknowns such as Lagrange multipliers are introduced. An SGBEM code for 2D elastic domain decomposition problems has been implemented. The effectiveness of the approach developed is documented by numerical examples involving non-matching linear boundary element meshes at the interfaces, where the accuracy is analyzed by comparing the numerical results obtained versus the analytical solutions and by evaluating the convergence rate of the error in the (discretized) integral L2-norm and maximum-normfor h-refinements of boundary element meshes. Finally, a theoretical analysis of a problem with an interior and an exterior subdomain is introduced to explain the observed behaviour of numerical results