Transition from Diffusive to Localized Regimes in Surface Corrugated Optical Waveguides

Exact calculations of the transmittance of surface corrugated optical waveguides are presented. The elastic scattering of diffuse light or other electromagnetic waves from a rough surface induces a diffusive transport along the waveguide axis. As the length of the corrugated part of the waveguide increases, a transition from the diffusive to the localized regime is observed. This involves an analogy with electron conduction in nanowires, and hence, a concept analogous to that of ``resistance'' can be introduced. We show an oscillatory behavior of both the elastic mean free path and the localization length versus the wavelength.Comment: 3 pages, REVTEX, 3 PS figure

Intensity Distribution of Modes in Surface Corrugated Waveguides

Exact calculations of transmission and reflection coefficients in surface randomly corrugated optical waveguides are presented. As the length of the corrugated part of the waveguide increases, there is a strong preference to forward coupling through the lowest mode. An oscillating behavior of the enhanced backscattering as a function of the wavelength is predicted. Although the transport is strongly non isotropic, the analysis of the probability distributions of the transmitted waves confirms in this configuration distributions predicted by Random Matrix Theory for volume disorder

Identificação de animais influentes na população de touros da raça Nelore padrão com sêmen em central de inseminação.

Conhecendo os animais influentes de uma raça é possível selecionar animais de modo a evitar estreitamento da base genética. Enquanto o parentesco é suficiente para avaliar a influência dos animais fundadores, para os demais animais é preciso eliminar o parentesco colateral, de forma a avaliar a contribuição direta do ancestral na população. O objetivo deste trabalho foi identificar indivíduos influentes, mesmo entre os animais não-fundadores, em reprodutores da raça Nelore Padrão com sêmen comercializado em centrais de inseminação, entre os anos de 2008 e 2009. Para tanto foi utilizada a genealogia de 642 touros Nelore padrão com sêmen em central de inseminação

Severe acute respiratory syndrome coronavirus E protein transports calcium ions and activates the NLRP3 inflammasome

Severe acute respiratory syndrome coronavirus (SARS-CoV) envelope (E) protein is a viroporin involved in virulence. E protein ion channel (IC) activity is specifically correlated with enhanced pulmonary damage, edema accumulation and death. IL-1β driven proinflammation is associated with those pathological signatures, however its link to IC activity remains unknown. In this report, we demonstrate that SARS-CoV E protein forms protein–lipid channels in ERGIC/Golgi membranes that are permeable to calcium ions, a highly relevant feature never reported before. Calcium ions together with pH modulated E protein pore charge and selectivity. Interestingly, E protein IC activity boosted the activation of the NLRP3 inflammasome, leading to IL-1β overproduction. Calcium transport through the E protein IC was the main trigger of this process. These findings strikingly link SARS-CoV E protein IC induced ionic disturbances at the cell level to immunopathological consequences and disease worsening in the infected organism

Severe Acute Respiratory Syndrome Coronavirus Envelope Protein Ion Channel Activity Promotes Virus Fitness and Pathogenesis

Deletion of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) envelope (E) gene attenuates the virus. E gene encodes a small multifunctional protein that possesses ion channel (IC) activity, an important function in virus-host interaction. To test the contribution of E protein IC activity in virus pathogenesis, two recombinant mouse-adapted SARSCoVs, each containing one single amino acid mutation that suppressed ion conductivity, were engineered. After serial infections, mutant viruses, in general, incorporated compensatory mutations within E gene that rendered active ion channels. Furthermore, IC activity conferred better fitness in competition assays, suggesting that ion conductivity represents an advantage for the virus. Interestingly, mice infected with viruses displaying E protein IC activity, either with the wild-type E protein sequence or with the revertants that restored ion transport, rapidly lost weight and died. In contrast, mice infected with mutants lacking IC activity, which did not incorporate mutations within E gene during the experiment, recovered from disease and most survived. Knocking down E protein IC activity did not significantly affect virus growth in infected mice but decreased edema accumulation, the major determinant of acute respiratory distress syndrome (ARDS) leading to death. Reduced edema correlated with lung epithelia integrity and proper localization of Na+ /K+ ATPase, which participates in edema resolution. Levels of inflammasome-activated IL-1b were reduced in the lung airways of the animals infected with viruses lacking E protein IC activity, indicating that E protein IC function is required for inflammasome activation. Reduction of IL-1b was accompanied by diminished amounts of TNF and IL-6 in the absence of E protein ion conductivity. All these key cytokines promote the progression of lung damage and ARDS pathology. In conclusion, E protein IC activity represents a new determinant for SARS-CoV virulence

A beam-beam monitoring detector for the MPD experiment at NICA

The Multi-Purpose Detector (MPD) is to be installed at the Nuclotron Ion Collider fAcility (NICA) of the Joint Institute for Nuclear Research (JINR). Its main goal is to study the phase diagram of the strongly interacting matter produced in heavy-ion collisions. These studies, while providing insight into the physics of heavy-ion collisions, are relevant for improving our understanding of the evolution of the early Universe and the formation of neutron stars. In order to extend the MPD trigger capabilities, we propose to include a high granularity beam-beam monitoring detector (BE-BE) to provide a level-0 trigger signal with an expected time resolution of 30 ps. This new detector will improve the determination of the reaction plane by the MPD experiment, a key measurement for flow studies that provides physics insight into the early stages of the reaction. In this work, we use simulated Au+Au collisions at NICA energies to show the potential of such a detector to determine the event plane resolution, providing further redundancy to the detectors originally considered for this purpose namely, the Fast Forward Detector (FFD) and the Hadron Calorimeter (HCAL). We also show our results for the time resolution studies of two prototype cells carried out at the T10 beam line at the CERN PS complex.Comment: 16 pages, 12 figures. Updated to published version with added comments and correction

First bounds on the high-energy emission from isolated Wolf-Rayet binary systems

High-energy gamma-ray emission is theoretically expected to arise in tight binary star systems (with high mass loss and high velocity winds), although the evidence of this relationship has proven to be elusive so far. Here we present the first bounds on this putative emission from isolated Wolf-Rayet (WR) star binaries, WR 147 and WR 146, obtained from observations with the MAGIC telescope.Comment: (Authors are the MAGIC Collaboration.) Manuscript in press at The Astrophysical Journal Letter

Evaluación preliminar de la diversidad genética del leoncillo Callithrixpygmaea (Primates: Cebidae: Callithrichinae) mediante microsatélites (SSR: Short Sequence Repeat)

The pygmy marmoset (Callithrix pygmaea) is one of the most specialized Ecuadorian pri­mate species. Its high specialization in habitat and diet, and the increase of human activities in the Amazon region may cause pygmy marmosets to go through population bottle necks, losing genetic diversity. To estimate the magnitude of this threat, since 2008 we carried out a pilot study for evaluating the genetic diversity of four wild groups of this species in a population located on the margins of the Aguarico river. For the genetic analyses we used 50 fecal samples collected from September 2008 to February 2009; 50% of the samples belonged to group P4, groups P1, P2 and P5 provided the remaining 50%. We extracted DNA from the feces using the QLAamp DNA Stool Mini Kit (QIAGEN). With PCR we amplified 9 microsatellite primers reported for a related species of Callitrichinae. DNA bands were visualized in polyacrylamide (6 %) and urea (5M) gels. Statistical analyses we­re carried out with GenAlEx 6 software. Three to eight alleles were found per locus. The Hardy-Weinberg equilibrium test suggested that inbreeding may be occurring in group P4. Expected heterocigocity in groups P1 and P2 is 0.5, while in group P4 ranges from 05. to 0.836. Nei’s genetic distance between groups P1 and P2 is 1.211, whereas group P4 differs 0.612 and 0.485 from groups P2 and P1, respectively. This is the first study of this type for this species in Ecuador and elsewhere, the results point out the need to evaluate human impact on the genetic diversity of Ecuadorian species.El leoncillo (Callithrix pygmaea) es uno de los primates ecuatorianos con mayor grado de especialización de hábitat y de dieta. Esta alta especialización y la intensificación de las actividades humanas en la Amazonia ecuatoriana podrían causar que las poblaciones del leoncillo atraviesen por cuellos de botella y pierdan su diversidad genética. Con el fin de estimar la magnitud de esta amenaza, desde el año 2008, se realizó un estudio piloto para evaluar el nivel de variabilidad genética de cuatro grupos de esta especie de una población a orillas del rio Aguarico. Para la realización del análisis genético se utilizó un total de 50 muestras de heces, colectadas durante el periodo de septiembre 2008 y febrero 2009; el 50% de las muestras correspondió al grupo P4, los grupos P1, P2 y P5 aportaron con el restante 50%. A partir de estas muestras se extrajo ADN con el kit QIAamp DNA Stool Mini Kit (QIAGEN). Mediante la técnica de PCR se amplificaron nueve primers de mi­crosatélites reportados para otra especie de Callitrichinae. La visualización de bandas se realizó en geles denaturantes de poliacrilamida al 6% y Urea 5M. El análisis estadístico fue realizado con el programa GenAlEx 6. Los resultados obtenidos muestran que existen de 3 a 8 alelos/locus, la prueba de equilibrio Hardy-Weinberg sugiere que en el grupo P4 puede estar sucediendo endogamia, la heterocigocidad esperada en los grupos P1 y P2 tiene valores de 0.5, mientras que los valores del grupo P4 varían de 0.5 a 0.836. La distancia genética de Nei entre los grupos P1 y P2 es de 1.211, mientras que el grupo P4 difiere 0.612 y 0.485 con respecto de los grupos P2 y P1. Este estudio es pionero en este campo y evidencia la necesidad de continuar con investigaciones para evaluar el impacto humano sobre la diversidad genética en esta y otras especies ecuatorianas

Observation of Pulsed Gamma-rays Above 25 GeV from the Crab Pulsar with MAGIC

One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov (MAGIC) telescope to 25 GeV. In this configuration, we detected pulsed gamma-rays from the Crab pulsar that were greater than 25 GeV, revealing a relatively high cutoff energy in the phase-averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar-cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot-gap scenario.Comment: Slight modification of the analysis: Fitting a more general function to the combined data set of COMPTEL, EGRET and MAGIC. Final result and conclusion is unchange