Triggered star formation in a molecular shell created by a SNR?

We present a study of a new molecular shell, G126.1-0.8-14, using available multiwavelegth Galactic plane surveys and optical Gemini observations. A well defined shell-like structure is observed in the CO(1--0) line emission at (l,b) = (126.1, -0.8), in the velocity range --10.5 to --15.5 km/s. The HI, emission shows a region of low emissivity inside G126.1-0.8-14, while radio continuum observations reveal faint non-thermal emission possibly related to this shell. Optical spectra obtained with Gemini South show the existence of B-type stars likely to be associated with G126.1-0.8-14. An estimate of the stellar wind energy injected by these stars show that they alone can not be able to create such a structure. On the other hand, one supernova explosion would provide enough energy to generate the shell. Using the MSX, IRAS, and WISE Point Source Catalogues we have found about 30 young stellar objects candidates, whose birth could have been triggered by the expansion of G126.1-0.8-14. In this context, Sh2-187 could be a consequence of the action on its surroundings of the most massive (and thus most evolve) of the stars formed by the expanding molecular shell.Comment: 13 pages, 10 figures, accepted in MNRA

Two-particle quantum correlations in stochastically-coupled networks

Quantum walks in dynamically-disordered networks have become an invaluable tool for understanding the physics of open quantum systems. In this work, we introduce a novel approach to describe the dynamics of indistinguishable particles in noisy quantum networks. By making use of stochastic calculus, we derive a master equation for the propagation of two non-interacting correlated particles in tight-binding networks affected by off-diagonal dynamical disorder. We show that the presence of noise in the couplings of a quantum network creates a pure-dephasing-like process that destroys all coherences in the single-particle Hilbert subspace. Remarkably, we find that when two or more correlated particles propagate in the network, coherences accounting for particle indistinguishability are robust against the impact of noise, thus showing that it is possible, in principle, to find specific conditions for which many indistinguishable particles can traverse dynamically-disordered systems without losing their ability to interfere. These results shed light on the role of particle indistinguishability in the preservation of quantum coherence in dynamically-disordered quantum networks.Comment: 15 pages, 4 figure

Síndrome de las plaquetas pegajosas, la condición de trombofilia heredada más frecuente en pacientes mexicanos

Antecedentes: el síndrome de las plaquetas pegajosas supone trastornos en la agregabilidad de las plaquetas, caracterizados por incremento anormal de las mismas y tendencia a fenómenos vasoclusivos, arteriales y venosos. El mecanismo patogénico no se conoce; su existencia sólo puede determinarse con las pruebas de agregación plaquetaria. Su prevalencia tampoco se conoce pero hay datos que sugieren que es frecuente. Algunos autores opinan que es responsable de 20% de las trombosis arteriales inexplicables y de 13% de las venosas en las que no es posible identificar una causa. Objetivos: revisar la información disponible sobre el síndrome de las plaquetas pegajosas y su trascendencia en México. Conclusiones: el síndrome de las plaquetas pegajosas es la condición de trombofi lia más frecuente en México. Existen pocos reportes de la evaluación clínica de pacientes mexicanos, lo que hace imperativo realizar estudios prospectivos rigurosos para establecer su magnitud

Do broadband and Information and Communication Technologies (ICTS) have a positive impact on school performance? : evidence for CHILE

Spanish version available in IDRC Digital Library: Tienen la banda ancha y las TIC un impacto positivo en el rendimiento escolar? : evidencia sobre ChileEven though connectivity actually generates a greater degree of efficiency in the teaching-learning process, test results can fall due to the fact that students can be distracted by having internet access. Access to internet at home shows in general a negative impact upon performance, but having a computer available at home has a positive and significant impact. Traditional evaluation techniques for impact evaluation of ICT in the Classroom programs were used, but results do not identify a significant impact of these programs, either separately or jointly

Factores que afectan algunas de las pruebas del tamiz neonatal

Introducción: los métodos analíticos del tamiz metabólico, adaptados al estudio de sangre impregnada en un papel fi ltro, pueden afectarse por factores externos que alteran falsamente los resultados. Objetivo: identificar los factores que afectan las pruebas y el control de calidad del tamiz neonatal. Material y métodos: se realizó análisis retrospectivo y observacional, desde junio del 2002 hasta octubre del 2004, y se estudió el tamiz neonatal de 632 pacientes para identificar los factores que alteran los resultados y determinar cuáles son las pruebas más susceptibles. Se evaluó la calidad de la muestra, y las condiciones de almacenamiento y transporte. Resultados: entre los 632 estudios, en 42 pacientes (6.6%) estuvieron alterados uno o varios de los analitos; en 11 de estos últimos (1.7% del total y 26% de los estudios con resultados anormales) se comprobó un defecto metabólico y en los restantes 31 alguna interferencia. Las pruebas más susceptibles al efecto de la interferencia fueron glucosa-6-fosfato deshidrogenasa (13 casos), uridil galactosa transferasa (nueve casos) y tripsinógeno inmunoreactivo (cinco casos). Las causas más frecuentes de interferencia fueron muestras mal conservadas y administración de medicamentos anticonvulsivantes (ácido valproico). Discusión: la elevada frecuencia de resultados falsos positivos en el tamiz neonatal hace imperativo establecer acciones preventivas para disminuir el número de muestras rechazadas y obliga a descartar las fuentes comunes de interferencia antes de emitir algún diagnóstico presuntivo

Tienen la banda ancha y las TIC un impacto positivo en el rendimiento escolar? : evidencia sobre Chile

Versión en inglés disponible en la Biblioteca Digital del IDRC: Do broadband and Information and Communication Technologies (ICTS) have a positive impact on school performance? : evidence for CHILEEn este artículo se estudia el impacto de la conectividad a banda ancha y del uso de tecnologías de la información y la comunicación (TIC) con fines pedagógicos en la calidad de la educación de los estudiantes del ciclo básico de establecimientos educacionales subvencionados (EES) de Chile. Para ello, se estima el impacto de dos iniciativas del Ministerio de Educación (MINEDUC), “Fondos para banda ancha” (2006-2010) y “TIC en aula” (2007-2011) sobre el rendimiento de los estudiantes en las pruebas nacionales estandarizadas de Lenguaje y Matemáticas establecidas por el Sistema de Medición de Calidad de la Educación (SIMCE), disponible desde 1998. La unidad de observación es el estudiante y se analiza el efecto individual, conjunto y focalizado de los programas mencionados sobre cohortes que rinden las evaluaciones en dos momentos del tiempo. La muestra de estudio excluyó EES pertenecientes al grupo socioeconómico alto y, en el caso de “TIC en aula”, se trabajó solo con los municipalizados. Los resultados muestran que los programas no tienen efectos significativos en el rendimiento, ni individual ni conjuntamente, pero sí fue posible identificar efectos positivos de “TIC en aula” en grupos específicos en Lenguaje, no así en Matemáticas

Quantum Noise Limits for Nonlinear, Phase-Invariant Amplifiers

Any quantum device that amplifies coherent states of a field while preserving their phase generates noise. A nonlinear, phase-invariant amplifier may generate less noise, over a range of input field strengths, than any linear amplifier with the same amplification. We present explicit examples of such nonlinear amplifiers, and derive lower bounds on the noise generated by a nonlinear, phase-invariant quantum amplifier.Comment: RevTeX, 6 pages + 4 figures (included in file; hard copy sent on request

An implicit unsteady hydraulic solver for suspended cuttings transport in managed pressure wells

We present a simulation tool for transient events in complex hydraulic networks. The code includes modelling of the transport of suspended cuttings in near-vertical wells. An unstructured finite volume formulation with implicit time integration has been chosen. The unconditional stability of the integrator makes the method suitable for the simulation of transient events over a wide range of characteristic timescales. It handles both very fast transients (e.g. fluid hammer events) and the long-term evolution of the well (e.g. hole cleaning operations). The software has been developed to address the need of the oil industry for a robust and efficient predictive tool allowing effective well control in managed pressure drilling operations. The physical modelling follows the standard practices accepted by the industry (e.g. mud rheology computations). The mathematical foundation of the algorithm is described followed by validation cases that illustrate its capabilities and accuracy. Finally, a practical industrial application example is provided to demonstrate the real-world performance of the software.Peer ReviewedPostprint (author's final draft

Two-particle quantum correlations in stochastically-coupled networks

Quantum walks in dynamically-disordered networks have become an invaluable tool for understanding the physics of open quantum systems. Although much work has been carried out considering networks affected by diagonal disorder, it is of fundamental importance to study the effects of fluctuating couplings. This is particularly relevant in materials science models, where the interaction forces may change depending on the species of the atoms being linked. In this work, we make use of stochastic calculus to derive a master equation for the dynamics of one and two non-interacting correlated particles in tight-binding networks affected by off-diagonal dynamical disorder. We show that the presence of noise in the couplings of a quantum network creates a pure-dephasing-like process that destroys all coherences in the single-particle Hilbert subspace. Moreover, we show that when two or more correlated particles propagate in the network, coherences accounting for particle indistinguishability are robust against the impact of off-diagonal noise, thus showing that it is possible, in principle, to find specific conditions for which many indistinguishable particles can traverse stochastically-coupled networks without losing their ability to interfere. © 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft

Using community phylogenetics to assess phylogenetic structure in the fitzcarrald region of Western Amazonia

© 2020 The Authors. Di versity and Distributions Published by SBI. Here we explore the use of community phylogenetics as a tool to document patterns of biodiversity in the Fitzcarrald region, a remote area in Southwestern Amazonia. For these analyses, we subdivide the region into basin-wide assemblages encompassing the headwaters of four Amazonian tributaries (Urubamba, Yuruá, Purús and Las Piedras basins), and habitat types: river channels, terra firme (non-floodplain) streams, and floodplain lakes. We present a robust, well-documented collection of fishes from the region including 272 species collected from 132 field sites over 63 field days and four years, comprising the most extensive collection of fishes from this region to date. We conduct a preliminary community phylogenetic analysis based on this collection and recover results largely statistically indistinguishable from the random expectation, with only a few instances of phylogenetic structure. Based on these results, and of those published in other recent biogeographic studies, we conclude that the Fitzcarrald fish species pool accumulated over a period of several million years, plausibly as a result of dispersal from the larger species pool of Greater Amazonia