3,823 research outputs found

    Characterization of abiotic coaditions affecting vegetation distribution in the river plate coastal plain, Argentina

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    The river Plate coastal plain is located in northeastern Buenos Aires province, where geological events such as sea transgressions and regressions in the Holocene have produced a stratigraphic column with marine-estuarine, fluviatile and continental sediments, as well as a variety of landforms and soils. The aim of this paper is to describe these different coastal settings and their influence in the distribution of plant communities

    Shell-like structures in our cosmic neighbourhood

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    Signatures of the processes in the early Universe are imprinted in the cosmic web. Some of them may define shell-like structures characterised by typical scales. We search for shell-like structures in the distribution of nearby rich clusters of galaxies drawn from the SDSS DR8. We calculate the distance distributions between rich clusters of galaxies, and groups and clusters of various richness, look for the maxima in the distance distributions, and select candidates of shell-like structures. We analyse the space distribution of groups and clusters forming shell walls. We find six possible candidates of shell-like structures, in which galaxy clusters have maxima in the distance distribution to other galaxy groups and clusters at the distance of about 120 Mpc/h. The rich galaxy cluster A1795, the central cluster of the Bootes supercluster, has the highest maximum in the distance distribution of other groups and clusters around them at the distance of about 120 Mpc/h among our rich cluster sample, and another maximum at the distance of about 240 Mpc/h. The structures of galaxy systems causing the maxima at 120 Mpc/h form an almost complete shell of galaxy groups, clusters and superclusters. The richest systems in the nearby universe, the Sloan Great Wall, the Corona Borealis supercluster and the Ursa Major supercluster are among them. The probability that we obtain maxima like this from random distributions is lower than 0.001. Our results confirm that shell-like structures can be found in the distribution of nearby galaxies and their systems. The radii of the possible shells are larger than expected for a BAO shell (approximately 109 Mpc/h versus approximately 120 Mpc/h), and they are determined by very rich galaxy clusters and superclusters with high density contrast while BAO shells are barely seen in the galaxy distribution. We discuss possible consequences of these differences.Comment: Comments: 9 pages, 10 figures, Astronomy and Astrophysics, in pres

    Cyanobacterial biomass pigments as natural sensitizer for tio2 thin films

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    In this work, we studied the effect of TiO2 sensitization with dry biomass extracted of cyanobacteria on the degradation of methylene blue dye (AM). Cyanobacterial cultures isolated from water samples were collected from the swamp of Malambo in Colombia; two main genera of cyanobacteria were identified, and they were cultivated with BG-11 culture medium. The concentrations of chlorophyll a in the exponential and stationary phases of growth were measured; the phycobilin content was quantified by spectrophotometry. Thin films of TiO2 were deposited by a doctor blade method, and they were sensitized by wet impregnation. Furthermore, a methylene blue (MB) photodegradation process was studied under visible light irradiation on the cyanobacterial biomass sensitized TiO2 material (TiO2/sensitizer); besides, the pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. The results showed that the BG-11+ treatment reported a higher amount of dry biomass and phycobiliproteins. After the sensitization process, the TiO2/sensitizer thin films showed a significant red shift in the optical activity; besides the thin film roughness decreasing, the TiO2/sensitizer showed photocatalytic activity of 23.2% under visible irradiation, and besides, the kinetic () constant for TiO2/sensitizer thin films was 3.1 times greater than the value of TiO2 thin films. Finally, results indicated that cyanobacterial biomass is a suitable source of natural sensitizers to be used in semiconductor sensitization.Universidad del Atlántico, Universidad de la Costa, Institución Universitaria Politécnico Gran Colombiano, Universidad Central, Universidad Minuto de Dios, Pontificia Universidad Católica de Chile, Millennium Nuclei on Catalytic Processes towards Sustainable Chemistry

    Aprendizaje del Fibrobroncoscopio del Servicio de Anestesiología del Hospital Universitario de Getafe: Programa de aprendizaje

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    Las complicaciones más severas en Anestesiología son las relacionadas con la Vía Aérea, y una dificultad de intubación o ventilación del paciente originan una gran mórbida/mortalidad. En los últimos años, para mejorar la seguridad del paciente en este campo, ha habido una evolución muy importante en el manejo de la Vía Aérea Difícil (VAD). Las Sociedades internacionales más prestigiosas de este campo aconsejan en sus últimos trabajos y guías (ASA [Sociedad Americana de Vía Aérea Difícil] en el algoritmo del 2013, y la DAS [Difficult Airway Society] en el NAP4 y las guías de 2015….) aconsejan que todos los miembros del servicio de Anestesiología sean capaces de poder realizar una intubación con Fibroscopio (FOB) en paciente despierto cuando se precise. Es decir, en aquellos pacientes que tienen una intubación difícil conocida, y en los que administrarles anestesia general para realizar una intubación, perdiendo la respiración espontanea, supone un riesgo muy importante para ellos

    Intraoperative goal directed hemodynamic therapy in noncardiac surgery: a systematic review and meta-analysis

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    Background: The goal directed hemodynamic therapy is an approach focused on the use of cardiac output and related parameters as end-points for fluids and drugs to optimize tissue perfusion and oxygen delivery. Primary aim: To determine the effects of intraoperative goal directed hemodynamic therapy on postoperative complications rates. Methods: A meta-analysis was carried out of the effects of goal directed hemodynamic therapy in adult noncardiac surgery on postoperative complications and mortality using Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. A systematic search was performed in Medline PubMed, Embase, and the Cochrane Library (last update, October 2014). Inclusion criteria were randomized clinical trials in which intraoperative goal directed hemodynamic therapy was compared to conventional fluid management in noncardiac surgery. Exclusion criteria were trauma and pediatric surgery studies and that using pulmonary artery catheter. End-points were postoperative complications (primary) and mortality (secondary). Those studies that fulfilled the entry criteria were examined in full and subjected to quantifiable analysis, predefined subgroup analysis (stratified by type of monitor, therapy, and hemodynamic goal), and predefined sensitivity analysis. Results: 51 RCTs were initially identified, 24 fulfilling the inclusion criteria. 5 randomized clinical trials were added by manual search, resulting in 29 randomized clinical trials in the final analysis, including 2654 patients. A significant reduction in complications for goal directed hemodynamic therapy was observed (RR: 0.70, 95% CI: 0.62-0.79, p < 0.001). No significant decrease in mortality was achieved (RR: 0.76, 95% CI: 0.45-1.28, p = 0.30). Quality sensitive analyses confirmed the main overall results. Conclusions: Intraoperative goal directed hemodynamic therapy with minimally invasive monitoring decreases postoperative complications in noncardiac surgery, although it was not able to show a significant decrease in mortality rate

    Shell-like structures in our cosmic neighbourhood

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    Context. Signatures of the processes in the early Universe are imprinted in the cosmic web. Some of them may define shell-like structures characterised by typical scales. Examples of such structures are shell-like systems of galaxies, which are interpreted as a signatures of the baryon acoustic oscillations.Aims. We search for shell-like structures in the distribution of nearby rich clusters of galaxies drawn from the SDSS DR8.Methods. We calculated the distance distributions between rich clusters of galaxies and groups and clusters of various richness, searched for the maxima in the distance distributions and selected candidates of shell-like structures. We analysed the space distribution of groups and clusters that form shell walls.Results. We find six possible candidates of shell-like structures, in which galaxy clusters have the maximum in their distance distribution to other galaxy groups and clusters at a distance of about 120-130 h(-1) Mpc. Another, less probable maximum is found at a distance of about 240 h(-1) Mpc. The rich galaxy cluster A1795, which is the central cluster of the Bootes supercluster, has the highest maximum in the distance distribution of all other surrounding groups and clusters in our rich cluster sample. It lies at a distance of about 120 h(-1) Mpc. The structures of galaxy systems that cause this maximum form an almost complete shell of galaxy groups, clusters, and superclusters. The richest systems in the nearby universe, the Sloan Great Wall, the Corona Borealis supercluster, and the UrsaMajor supercluster, are among them. The probability that we obtain maxima like this from random distributions is lower than 0.001.Conclusions. Our results confirm that shell-like structures can be found in the distribution of nearby galaxies and their systems. The radii of the possible shells are larger than expected for a baryonic acoustic oscillations (BAO) shell (approximate to 109 h(-1) Mpc versus approximate to 120-130 h(-1) Mpc), and they are determined by very rich galaxy clusters and superclusters. In contrast, BAO shells are barely seen in the galaxy distribution. We discuss possible consequences of these differences

    Direct Measurement of Nuclear Dependence of Charged Current Quasielastic-like Neutrino Interactions using MINERvA

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    Charged-current νμ\nu_{\mu} interactions on carbon, iron, and lead with a final state hadronic system of one or more protons with zero mesons are used to investigate the influence of the nuclear environment on quasielastic-like interactions. The transfered four-momentum squared to the target nucleus, Q2Q^2, is reconstructed based on the kinematics of the leading proton, and differential cross sections versus Q2Q^2 and the cross-section ratios of iron, lead and carbon to scintillator are measured for the first time in a single experiment. The measurements show a dependence on atomic number. While the quasielastic-like scattering on carbon is compatible with predictions, the trends exhibited by scattering on iron and lead favor a prediction with intranuclear rescattering of hadrons accounted for by a conventional particle cascade treatment. These measurements help discriminate between different models of both initial state nucleons and final state interactions used in the neutrino oscillation experiments

    First evidence of coherent K+K^{+} meson production in neutrino-nucleus scattering

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    Neutrino-induced charged-current coherent kaon production, νμA→μ−K+A\nu_{\mu}A\rightarrow\mu^{-}K^{+}A, is a rare, inelastic electroweak process that brings a K+K^+ on shell and leaves the target nucleus intact in its ground state. This process is significantly lower in rate than neutrino-induced charged-current coherent pion production, because of Cabibbo suppression and a kinematic suppression due to the larger kaon mass. We search for such events in the scintillator tracker of MINERvA by observing the final state K+K^+, μ−\mu^- and no other detector activity, and by using the kinematics of the final state particles to reconstruct the small momentum transfer to the nucleus, which is a model-independent characteristic of coherent scattering. We find the first experimental evidence for the process at 3σ3\sigma significance.Comment: added ancillary file with information about the six kaon candidate

    Single neutral pion production by charged-current νˉμ\bar{\nu}_\mu interactions on hydrocarbon at ⟨Eν⟩=\langle E_\nu \rangle = 3.6 GeV

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    Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the \minerva detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for νˉe\bar{\nu}_e appearance oscillation experiments. The differential cross sections for π0\pi^0 momentum and production angle, for events with a single observed π0\pi^0 and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the π0\pi^0 kinematics for this process.Comment: 6 pages, 5 figures, submitted to Physics Letters
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