Marginally Stable Nuclear Burning

Thermonuclear X-ray bursts result from unstable nuclear burning of the material accreted on neutron stars in some low mass X-ray binaries (LMXBs). Theory predicts that close to the boundary of stability oscillatory burning can occur. This marginally stable regime has so far been identified in only a small number of sources. We present Rossi X-ray Timing Explorer (RXTE) observations of the bursting, high- inclination LMXB 4U 1323-619 that reveal for the first time in this source the signature of marginally stable burning. The source was observed during two successive RXTE orbits for approximately 5 ksec beginning at 10:14:01 UTC on March 28, 2011. Significant mHz quasi- periodic oscillations (QPO) at a frequency of 8.1 mHz are detected for approximately 1600 s from the beginning of the observation until the occurrence of a thermonuclear X-ray burst at 10:42:22 UTC. The mHz oscillations are not detected following the X-ray burst. The average fractional rms amplitude of the mHz QPOs is 6.4% (3 - 20 keV), and the amplitude increases to about 8% below 10 keV.This phenomenology is strikingly similar to that seen in the LMXB 4U 1636-53. Indeed, the frequency of the mHz QPOs in 4U 1323-619 prior to the X-ray burst is very similar to the transition frequency between mHz QPO and bursts found in 4U 1636-53 by Altamirano et al. (2008). These results strongly suggest that the observed QPOs in 4U 1323-619 are, like those in 4U 1636-53, due to marginally stable nuclear burning. We also explore the dependence of the energy spectrum on the oscillation phase, and we place the present observations within the context of the spectral evolution of the accretion-powered flux from the source

A search for the near-infrared counterpart of the eclipsing millisecond X-ray pulsar Swift J1749.4-2807

Swift J1749.4-2807 is a transient accreting millisecond X-ray pulsars, the first that displayed X-ray eclipses. Therefore it holds a great potential for accurate mass measurements in a low mass X-ray binary system. The determination of the companion star radial velocity would make it possible to fully resolve the system and to accurately measure the mass of the neutron star based on dynamical measurements. Unfortunately, no optical/NIR counterpart has been identified to date for this system, either in outburst or in quiescence. We performed a photometric study of the field of Swift J1749.4-2807 during quiescence in order to search for the presence of a variable counterpart. The source direction lies on the Galactic plane, making any search for its optical/NIR counterpart challenging. To minimize the effects of field crowding and interstellar extinction, we carried out our observations using the adaptive optics near-infrared imager NACO mounted at the ESO Very Large Telescope. From the analysis of Swift X-ray data obtained during outburst, we derived the most precise (1.6" radius) position for this source. Due to the extreme stellar crowding of the field, 41 sources are detected in our VLT images within the X-ray error circle, with some of them possibly showing variability consistent with the expectations. We carried out the first deep imaging campaign devoted to the search of the quiescent NIR counterpart of Swift J1749.4-2807. Our results allow to provide constraints on the nature of the companion star of this system. Furthermore, they suggest that future phase-resolved NIR observations (performed with large aperture telescopes and adaptive optics) covering the full orbital period of the system are likely to identify the quiescent counterpart of Swift J1749.4-2807, through the measure of its orbital variability, opening the possibility of dynamical studies of this unique source.Comment: 5 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Factores de riesgos clinicas y epidemiologicos que influyen en el desarrollo de hipertension arterial en pacientes diabeticos, atendidos en el centro de salud Lacayo Farfan, durante el año 2015

En el mundo hay más de 347 millones de personas con diabetes. Se calcula que en 2004 fallecieron 3,4 millones de personas como consecuencias del exceso de azúcar en la sangre. En Nicaragua este es un problema de salud pública que cada día va en aumento. El presente trabajo está dirigido al estudio y análisis de los principales factores de riesgo clínico y epidemiológico que influyen en el desarrollo de la hipertensión arterial en pacientes diabéticos del Centro de Salud Lacayo Farfán del municipio de Matagalpa durante el año 2013 enfocando también la dificultad para el manejo y control de las descompensaciones. Es un estudio de casos y controles y cuyo método de recolección de información fueron entrevistas dirigidas al paciente y fichas llenadas con el expediente clínico. Durante el desarrollo del trabajo encontramos como principal factor de riesgo para desarrollar hipertensión arterial de los pacientes diabéticos, es la presencia de antecedentes genéticos asociado a los hábitos de vida poco saludables y que estos conlleva a la aparición de sobrepeso u obesidad en estos pacientes. Como dato relevante encontramos que estos pacientes son manejados principalmente con beta bloqueadores (Atenolol) a pesar que las guías internacionales proponen otro manejo. Por lo tanto concluimos que para mejorar la atención adecuada de los pacientes, se debe realizar controles periódicos, impartir charlas periódicas sobre el cuido personal, la medicación adecuada y procurar una vida sana a base de una alimentación sana y actividad física cotidian

The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies

We present Keck/OSIRIS adaptive optics observations with 150-400 pc spatial sampling of 7 turbulent, clumpy disc galaxies from the DYNAMO sample ($0.07<z<0.2$). DYNAMO galaxies have previously been shown to be well matched in properties to main sequence galaxies at $z\sim1.5$. Integral field spectroscopy observations using adaptive optics are subject to a number of systematics including a variable PSF and spatial sampling, which we account for in our analysis. We present gas velocity dispersion maps corrected for these effects, and confirm that DYNAMO galaxies do have high gas velocity dispersion ($\sigma=40-80$\kms), even at high spatial sampling. We find statistically significant structure in 6 out of 7 galaxies. The most common distance between the peaks in velocity dispersion and emission line peaks is $\sim0.5$~kpc, we note this is very similar to the average size of a clump measured with HST H$\alpha$ maps. This could suggest that the peaks in velocity dispersion in clumpy galaxies likely arise due to some interaction between the clump and the surrounding ISM of the galaxy, though our observations cannot distinguish between outflows, inflows or velocity shear. Observations covering a wider area of the galaxies will be needed to confirm this result.Comment: Accepted for publication in MNRA

Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1

Aql X-1 is a prolific transient neutron star low-mass X-ray binary that exhibits an accretion outburst approximately once every year. Whether the thermal X-rays detected in intervening quiescent episodes are the result of cooling of the neutron star or due to continued low-level accretion remains unclear. In this work we use Swift data obtained after the long and bright 2011 and 2013 outbursts, as well as the short and faint 2015 outburst, to investigate the hypothesis that cooling of the accretion-heated neutron star crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that the X-ray light curves and measured neutron star surface temperatures are consistent with the expectations of the crust cooling paradigm. By using a thermal evolution code, we find that ~1.2-3.2 MeV/nucleon of shallow heat release describes the observational data well, depending on the assumed mass-accretion rate and temperature of the stellar core. We find no evidence for varying strengths of this shallow heating after different outbursts, but this could be due to limitations of the data. We argue that monitoring Aql X-1 for up to ~1 year after future outbursts can be a powerful tool to break model degeneracies and solve open questions about the magnitude, depth and origin of shallow heating in neutron star crusts.Comment: 14 pages, 5 figures, 3 tables, accepted to MNRA

Discovery of a Second Transient Low-Mass X-ray Binary in the Globular Cluster NGC 6440

We have identified a new transient luminous low-mass X-ray binary, NGC 6440 X-2, with Chandra/ACIS, RXTE/PCA, and Swift/XRT observations of the globular cluster NGC 6440. The discovery outburst (July 28-31, 2009) peaked at L_X~1.5*10^36 ergs/s, and lasted for <4 days above L_X=10^35 ergs/s. Four other outbursts (May 29-June 4, Aug. 29-Sept. 1, Oct. 1-3, and Oct. 28-31 2009) have been observed with RXTE/PCA (identifying millisecond pulsations, Altamirano et al. 2009a) and Swift/XRT (confirming a positional association with NGC 6440 X-2), with similar peak luminosities and decay times. Optical and infrared imaging did not detect a clear counterpart, with best limits of V>21, B>22 in quiescence from archival HST imaging, g'>22 during the August outburst from Gemini-South GMOS imaging, and J>~18.5$ and K>~17 during the July outburst from CTIO 4-m ISPI imaging. Archival Chandra X-ray images of the core do not detect the quiescent counterpart, and place a bolometric luminosity limit of L_{NS}< 6*10^31 ergs/s (one of the lowest measured) for a hydrogen atmosphere neutron star. A short Chandra observation 10 days into quiescence found two photons at NGC 6440 X-2's position, suggesting enhanced quiescent emission at L_X~6*10^31 ergs/s . NGC 6440 X-2 currently shows the shortest recurrence time (~31 days) of any known X-ray transient, although regular outbursts were not visible in the bulge scans before early 2009. Fast, low-luminosity transients like NGC 6440 X-2 may be easily missed by current X-ray monitoring.Comment: 13 pages (emulateapj), 8 (color) figures, ApJ in press. Revised version adds 5th outburst (Oct./Nov. 2009), additional discussion of possible causes of short outburst recurrence time

Probing the effects of a thermonuclear X-ray burst on the neutron star accretion flow with NuSTAR

Observational evidence has been accumulating that thermonuclear X-ray bursts ignited on the surface of neutron stars influence the surrounding accretion flow. Here, we exploit the excellent sensitivity of NuSTAR up to 79 keV to analyze the impact of an X-ray burst on the accretion emission of the neutron star LMXB 4U 1608-52. The ~200 s long X-ray burst occurred during a hard X-ray spectral state, and had a peak intensity of ~30-50 per cent of the Eddington limit with no signs of photospheric radius expansion. Spectral analysis suggests that the accretion emission was enhanced up to a factor of ~5 during the X-ray burst. We also applied a linear unsupervised decomposition method, namely non-negative matrix factorization (NMF), to study this X-ray burst. We find that the NMF performs well in characterizing the evolution of the burst emission and is a promising technique to study changes in the underlying accretion emission in more detail than is possible through conventional spectral fitting. For the burst of 4U 1608-52, the NMF suggests a possible softening of the accretion spectrum during the X-ray burst, which could potentially be ascribed to cooling of a corona. Finally, we report a small (~3 per cent) but significant rise in the accretion emission ~0.5 h before the X-ray burst, although it is unclear whether this was related to the X-ray burst ignition.Comment: 10 pages, 10 figures, 1 table, to appear in MNRA

Propuesta de calidad en el servicio: una perspectiva del proceso de admisión del ITESO

Ante el crecimiento acelerado de la oferta educativa de nivel superior privado en México, las universidades se han visto en la necesidad de crear estrategias de innovación que les permitan diferenciarse con el objetivo de lograr una mayor captación de alumnado. Actualmente el ITESO, la universidad Jesuita de Guadalajara, desde su oficina de admisión se encuentra en la búsqueda de nuevas oportunidades de mejora en sus servicios. Por lo anterior, el presente trabajo se propone: desarrollar una propuesta de mejora en la calidad del servicio de la oficina de admisión del ITESO, específicamente en su área de atención, e identificar los puntos de contacto claves y aumentar la eficiencia en la captación y retención de aspirantes durante el proceso de admisión; establecer la línea base de calidad del proceso de admisión; identificar las actividades que no agregan valor; detectar en qué parte del trámite los aspirantes abandonan el proceso de admisión y las razones principales para hacerlo; redefinir las estrategias utilizadas para lograr la retención de los aspirantes; replicar el proyecto en áreas que estén involucradas directamente en el proceso de admisión del aspirante.ITESO, A.C

Development of a Standard Methodology for Documenting Processes in an Organization

The application of process management in our country has been extended throughout the last decade; improvement in management, high performance levels, reduction of operation times, optimization of resources and obtaining of quality certifications are among the main reasons why both public and private organizations seek to implement it. However, despite being an implicit activity within the change of management model to the process approach and even the improvement of the functional administrative model, the documentation of processes becomes an uncomfortable, complex and time-consuming task that often generates nervousness and distrust in workers. Diversity of criteria and the lack of an adequate methodology with effective tools makes it difficult to achieve the expected results. This article presents in detail the steps, their sequence and instruments used that allow an organization to raise the information of its processes and document them. As a result of different research projects developed over several years, the methodology of process mapping allowed for the documentation of all the activities of different administrative units of the Escuela Superior Politécnica de Chimborazo and not only to comply with the laws and regulations but also to improve their management. In the last application, it contributed to the development of the documentary structure of a quality management system that allowed an academic unit to achieve international quality certification. Keywords: management, processes, process documentation, process manual. Resumen Escuela Superior Politécnica de Chimborazo, Riobamba, Ecuador *E-mail: [email protected] La aplicación de la gestión de procesos en nuestro país se ha ido extendiendo a lo largo de la última década; mejoras en la gestión, altos niveles de rendimiento, reducción de tiempos de operaciones, optimización de recursos y obtenciones de certificaciones de calidad son entre otros los principales motivos por los cuales organizaciones tanto públicas como privadas buscan implementarla. Sin embargo y a pesar de ser una actividad implícita dentro del cambio de modelo de gestión hacia el enfoque de procesos e incluso del mejoramiento del modelo administrativo funcional, la documentación de los procesos se convierte en una labor incomoda, compleja y con un alto consumo de tiempo que suele generar nerviosismo y desconfianza en los trabajadores. Diversidad de criterios y la falta de una metodología adecuada con instrumentos eficaces complica cumplir los resultados esperados. El presente artículo presenta a detalle los pasos, su secuencia e instrumentos utilizados que le permiten a una organización levantar la información de sus procesos y documentarlos. Resultado de diferentes proyectos de investigación desarrollados a los largo de varios años, la metodología de levantamiento de procesos permitió documentar todas las actividades de distintas unidades administrativas de la Escuela Superior Politécnica de Chimborazo y no solo cumplir lo establecido el leyes y reglamentos sino también mejorar su gestión, en la última aplicación contribuyó a elaborar la estructura documental de un sistema de gestión de la calidad que logró que una unidad académica alcance una certificación internacional de calidad. Palabras claves: gestión, procesos, documentación de procesos, manual de procesos