Gamma-ray absorption and the origin of the gamma-ray flare in Cygnus X-1

The high-mass microquasar Cygnus X-1, the best-established candidate for a stellar-mass black hole in the Galaxy, has been detected in a flaring state at very high energies (VHE), E > 200 GeV, by the Atmospheric Cherenkov Telescope MAGIC. The flare occurred at orbital phase 0.91, where phase 1 is the configuration with the black hole behind the companion high-mass star, when the absorption of gamma-ray photons by photon-photon annihilation with the stellar field is expected to be highest. We aim to set up a model for the high-energy emission and absorption in Cyg X-1 that can explain the nature of the observed gamma-ray flare. We study the gamma-ray opacity due to pair creation along the whole orbit, and for different locations of the emitter. Then we consider a possible mechanism for the production of the VHE emission. We present detailed calculations of the gamma-ray opacity and infer from these calculations the distance from the black hole where the emitting region was located. We suggest that the flare was the result of a jet-clump interaction where the decay products of inelastic proton-proton collisions dominate the VHE outcome. We are able to reproduce the spectrum of Cyg X-1 during the observed flare under reasonable assumptions. The flare may be the first event of jet-cloud interaction ever detected at such high energies.Comment: 9 pages, 7 figure

Genetic Evolution of a Helicobacter pylori Acid-Sensing Histidine Kinase and Gastric Disease

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, which develops within a hypochlorhydric environment. We sequentially isolated H. pylori (strain J99) from a patient who developed corpus-predominant gastritis and hypochlorhydia over a 6-year interval. Archival J99 survived significantly better under acidic conditions than recent J99 strains. H. pylori arsRS encodes a 2-component system critical for stress responses; recent J99 isolates harbored 2 nonsynonymous arsS mutations, and arsS inactivation abolished acid survival. In vivo, acid-resistant archival, but not recent J99, successfully colonized high-acid-secreting rodents. Thus, genetic evolution of arsS may influence progression to hypochlorhydia and gastric cancer

The relationship between capacities and entrepreneurial intention in secondary school students

Education in entrepreneurship is a key factor in intentions to create companies. Given that adolescence is an ideal stage to acquire knowledge, secondary schools and universities are tasked with the challenge of offering educational programs. This study identifies potential entrepreneurs from among 897 secondary school’s students and analyzes their entrepreneurial skills in motivation, risk, dedication, empathetic and communication. Results indicate that there is a high percentage of potential entrepreneurs among secondary school and that entrepreneurship is not limited to a specific field, but rather it is recognized as a future employment option regardless of the studies students want to pursue

Spectral energy distribution of the gamma-ray microquasar LS 5039

The microquasar LS 5039 has recently been detected as a source of very high energy (VHE) $\gamma$-rays. This detection, that confirms the previously proposed association of LS 5039 with the EGRET source 3EG~J1824$-$1514, makes of LS 5039 a special system with observational data covering nearly all the electromagnetic spectrum. In order to reproduce the observed spectrum of LS 5039, from radio to VHE $\gamma$-rays, we have applied a cold matter dominated jet model that takes into account accretion variability, the jet magnetic field, particle acceleration, adiabatic and radiative losses, microscopic energy conservation in the jet, and pair creation and absorption due to the external photon fields, as well as the emission from the first generation of secondaries. The radiative processes taken into account are synchrotron, relativistic Bremsstrahlung and inverse Compton (IC). The model is based on a scenario that has been characterized with recent observational results, concerning the orbital parameters, the orbital variability at X-rays and the nature of the compact object. The computed spectral energy distribution (SED) shows a good agreement with the available observational data.Comment: 8 pages, 3 figures, submitted to A&A, revised vesion accounting for referee comments, small improvements of the results due to better calculation

Low X-ray Luminosity Galaxy Clusters. III: Weak Lensing Mass Determination at 0.18 << z << 0.70

This is the third of a series of papers of low X-ray luminosity galaxy clusters. In this work we present the weak lensing analysis of eight clusters, based on observations obtained with the Gemini Multi-Object Spectrograph in the $g'$, $r'$ and $i'$ passbands. For this purpose, we have developed a pipeline for the lensing analysis of ground-based images and we have performed tests applied to simulated data. We have determined the masses of seven galaxy clusters, six of them measured for the first time. For the four clusters with availably spectroscopic data, we find a general agreement between the velocity dispersions obtained via weak lensing assuming a Singular Isothermal Sphere profile, and those obtained from the redshift distribution of member galaxies. The correlation between our weak lensing mass determinations and the X-ray luminosities are suitably fitted by other observations of the $M-L_{X}$ relation and models

A broadband leptonic model for gamma-ray emitting microquasars

Observational and theoretical studies point to microquasars (MQs) as possible counterparts of a significant fraction of the unidentified gamma-ray sources detected so far. At present, a proper scenario to explain the emission beyond soft X-rays from these objects is not known, nor what the precise connection is between the radio and the high-energy radiation. We develop a new model where the MQ jet is dynamically dominated by cold protons and radiatively dominated by relativistic leptons. The matter content and power of the jet are both related with the accretion process. The magnetic field is assumed to be close to equipartition, although it is attached to and dominated by the jet matter. For the relativistic particles in the jet, their maximum energy depends on both the acceleration efficiency and the energy losses. The model takes into account the interaction of the relativistic jet particles with the magnetic field and all the photon and matter fields. Such interaction produces significant amounts of radiation from radio to very high energies through synchrotron, relativistic Bremsstrahlung, and inverse Compton (IC) processes. Variability of the emission produced by changes in the accretion process (e.g. via orbital eccentricity) is also expected. The effects of the gamma-ray absorption by the external photon fields on the gamma-ray spectrum have been taken into account, revealing clear spectral features that might be observed. This model is consistent to the accretion scenario, energy conservation laws, and current observational knowledge, and can provide deeper physical information of the source when tested against multiwavelength data.Comment: 15 pages, 12 figures, A&A, in press (text and plots improved after minor corrections in calculations, text improved also by referee comments

High-energy emission from jet-clump interactions in microquasars

High-mass microquasars are binary systems consisting of a massive star and an accreting compact object from which relativistic jets are launched. There is considerable observational evidence that winds of massive stars are clumpy. Individual clumps may interact with the jets in high-mass microquasars to produce outbursts of high-energy emission. Gamma-ray flares have been detected in some high-mass X-ray binaries, such as Cygnus X-1, and probably in LS 5039 and LS I+61 303. We predict the high-energy emission produced by the interaction between a jet and a clump of the stellar wind in a high-mass microquasar. Assuming a hydrodynamic scenario for the jet-clump interaction, we calculate the spectral energy distributions produced by the dominant non-thermal processes: relativistic bremsstrahlung, synchrotron and inverse Compton radiation, for leptons, and for hadrons, proton-proton collisions. Significant levels of emission in X-rays (synchrotron), high-energy gamma rays (inverse Compton), and very high-energy gamma rays (from the decay of neutral pions) are predicted, with luminosities in the different domains in the range ~ 10^{32}-10^{35} erg/s. The spectral energy distributions vary strongly depending on the specific conditions. Jet-clump interactions may be detectable at high and very high energies, and provide an explanation for the fast TeV variability found in some high-mass X-ray binary systems. Our model can help to infer information about the properties of jets and clumpy winds by means of high-sensitivity gamma-ray astronomy.Comment: Accepted for publication in A&A (10 pages, 8 figures

New records of Ascomycota in the Northwestern Argentinean Yungas

We report new records for nine species of ascomycetes from the Yungas of northwestern Argentina. Capronia nigerrima, Capronia pulcherrima and Rosellinia dingleyae are new records for South America. Byssosphaeria rhodomphala, Camarops tubulina, Cercophora ambigua, Chaetosphaerella phaeostroma, Tubeufia, cylindrothecia are new species for Argentina, and Togninia minima is a new record for the biome.Fil: Gallo, María Cecilia Fátima. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucuman. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Miguel Lillo; ArgentinaFil: Robledo, Gerardo Lucio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); ArgentinaFil: Romero, Andrea Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Plantas Tóxicas y Medicinales, Metabolismo de Compuestos Sintéticos y Naturales - Hongos que Intervienen en la Degradación Biológica; ArgentinaFil: Catania, Myriam del V.. Fundación Miguel Lillo; Argentin

Modelo de comunicación efectiva para la difusión de los programas y proyectos de inversión pública del departamento de Loreto (Perú)

This investigation has been developed with the general objective of determining an effective communication model for the dissemination of Public Investment Programs and Projects (PIP) of the Department of Loreto, Peru. Theoretically, it was based on effective communication models: empirical - experimental, functionalist and network communication. From the methodological perspective, it was based on a quantitative methodological strategy, at a descriptive level, with a non-experimental, cross-sectional field design, which was supported by surveys applied to the lieutenant governors of the towns located on the borders with Colombia and Brazil. Once the field work was developed, the information was processed, thus generating the descriptive analysis, the discussion of the results and the proposed model. In essence, it was concluded that there are important limitations in the current model of PIP dissemination in the Department of Loreto, weaknesses concerning all elements of communication: dispersed and unprepared senders, uncharacterized receivers, wasted channels, uncoded and non-contextualized messages, unstimulated feedback. In view of which the Model of Effective Communication for the Diffusion of PIPs (MCE-D-PIP) is designed, which proposes the development of a Situational Room for Effective Communication (SSCE-PIP), which allows to enhance the roles of producers, consumers and prosumers of information, through the diversification of channels and a specialized coding of the message, depending on the context: cultural diversity, educational conditions, technological factors, among others.Esta investigación ha sido desarrollada con el objetivo general de determinar un modelo de comunicación efectiva para la difusión de los Programas y Proyectos de Inversión Pública (PIP) del Departamento de Loreto, que ocupa la tercera parte del territorio del Perú, y, dadas sus características geográficas, existe mucha influencia cultural de Colombia y Brasil. Desde la perspectiva metodológica, se basó en un enfoque cuantitativo, de nivel descriptivo, con un diseño de campo, no experimental, transversal, que se apoyó en encuestas aplicadas a los tenientes gobernadores de los poblados ubicados en las fronteras con Colombia y Brasil. Una vez desarrollado el trabajo de campo, se realizó el procesamiento de la información, generando así el análisis descriptivo, la discusión de los resultados y la propuesta de modelo. En esencia, se llegó a la conclusión de que existen importantes limitaciones en el modelo actual de difusión de los PIP en el Departamento de Loreto, debilidades concernientes a todos los elementos de la comunicación: emisores dispersos y no preparados, receptores no caracterizados, canales desaprovechados, mensajes no codificados ni contextualizados, retroalimentación no estimulada. En vista de lo cual se diseña un Modelo de Comunicación Efectiva para la Difusión de los PIP (MCE-D-PIP) que plantea el desarrollo de una Sala Situacional de Comunicación Efectiva (SSCE– PIP), que permita potenciar los roles de productores, consumidores y prosumidores de la información, mediante la diversificación de los canales y una especializada codificación del mensaje, en función del contexto: diversidad cultural, condiciones educativas, factores tecnológicos, entre otros

Polymorphisms of the acid sensing histidine kinase gene arsS in Helicobacter pylori populations from anatomically distinct gastric sites

Phase variation is frequently utilized by bacterial species to affect gene expression such that phenotypic variants are maintained within populations, ensuring survival as environmental or host conditions change. Unusual among Helicobacter pylori phase variable or contingency genes is arsS, encoding a sensory histidine kinase involved in the acid acclimation of the organism. The presence of a 3\u27 homopolymeric cytosine tract of variable length in arsS among Helicobacter pylori strains allows for the expression of various functional ArsS isoforms, differing in carboxy-terminal protein domains. In this study, we analyzed this 3\u27 arsS region via amplified fragment length polymorphism (AFLP) and sequencing analyses for H. pylori populations from 3 different gastric sites of 12 patients. Our data indicate the presence of multiple arsS alleles within each population of H. pylori derived from the gastric antrum, cardia, or corpus of these patients. We also show that H. pylori, derived from the same anatomical site and patient, are predicted to express multiple ArsS isoforms in each population investigated. Furthermore, we identify a polymorphic deletion within arsS that generates another alternate ArsS C-terminal end. These findings suggest that four C-terminal variations of ArsS adds to the complexity of the ArsRS acid adaptation mechanism as a whole and may influence the ability of H. pylori to persist in the gastric niche for decades. (c) 2012 Elsevier Ltd. All rights reserved