Relaxation dynamics of an unlike spin pair system

Redfield master equation was applied to study the dynamics of an ensemble of interacting pair of unlike spins at room temperature. This spin quantum system is a workbench quantum model to analyze the relaxation dynamics of a heteronuclear two-level spin system interacting by a pure dipole-dipole coupling. Expressions for the density matrix elements and their relaxation rate constants of each coherence order were computed. In addition, the solutions were evaluated considering three initial quantum states, and the theoretical predictions, such as multi-exponential evolutions and enhancement, are behaviors that the solutions preserve and agree with previous studies performed for magnetization time evolutions. Moreover, the solutions computed to predict the dynamics of the longitudinal magnetization avoid the disagreement reported by I. Solomon

ProBiota | Serie Documentos | Un congreso para el Bicentenario : Juanito de las pampas y el primer congreso de Limnología

–El agua es vida –dijo Jack Vallentyne mirando a los ojos a un desconcertado “Palito” Ortega, gobernador de Tucumán por aquel entonces. Luego se sentó y creó un instante por lo menos curioso, según recuerda Hurlbert (2011) de aquel caluroso día de septiembre de 1994 en casa de gobierno. Aquella visita protocolar se hizo dentro del primer Congreso argentino de Limnología, después de una serie de reuniones previas en La Plata. Aclaremos que la Limnología es una rama (si cabe) de la Ecología que se encarga del estudio de los ecosistemas acuáticos continentales. Ahora, volvamos a “Juanito de las pampas” como tituló Hurlbert el párrafo final de sus recuerdos sobre Jack Vallentyne (alias Johnny Biosphere) en ocasión de su encuentro en esta reunión científica. No encontré muchos otros aquí en Tucumán que habiendo estado en aquella reunión, recordaran aquel momento singular. Mucho menos alguna foto que inmortalizara aquella visita…Facultad de Ciencias Naturales y Muse

ProBiota | Serie Documentos | Un congreso para el Bicentenario : Juanito de las pampas y el primer congreso de Limnología

–El agua es vida –dijo Jack Vallentyne mirando a los ojos a un desconcertado “Palito” Ortega, gobernador de Tucumán por aquel entonces. Luego se sentó y creó un instante por lo menos curioso, según recuerda Hurlbert (2011) de aquel caluroso día de septiembre de 1994 en casa de gobierno. Aquella visita protocolar se hizo dentro del primer Congreso argentino de Limnología, después de una serie de reuniones previas en La Plata. Aclaremos que la Limnología es una rama (si cabe) de la Ecología que se encarga del estudio de los ecosistemas acuáticos continentales. Ahora, volvamos a “Juanito de las pampas” como tituló Hurlbert el párrafo final de sus recuerdos sobre Jack Vallentyne (alias Johnny Biosphere) en ocasión de su encuentro en esta reunión científica. No encontré muchos otros aquí en Tucumán que habiendo estado en aquella reunión, recordaran aquel momento singular. Mucho menos alguna foto que inmortalizara aquella visita…Facultad de Ciencias Naturales y Muse

Turbulencia empresarial en Colombia : sector de seguros

En el año 2010, la Facultad de Administración de la Universidad del Rosario puso en marcha un proyecto de investigación donde se exploraba el fenómeno de la turbulencia empresarial. En este momento han sido publicados más de 15 documentos donde se realiza la descripción de lo ocurrido en igual número de sectores. En este número se realiza un análisis del sector asegurador, actividad empresarial que contribuye de manera significativa a la economía del país. El trabajo ha sido realizado de manera conjunta por los profesores Natalia Malaver y Hugo Rivera de la asignatura Estrategia de empresa I, con estudiantes del pregrado de la Facultad, quienes se motivaron por encontrar respuestas a la forma como algunas empresas del sector enfrentan la turbulencia sectorial. La estructura del documento incluye una breve descripción del sector; luego un análisis de la turbulencia, y un estudio sectorial realizado aplicando la metodología del Análisis Estructural de Sectores Estratégicos (AESE) desarrollada por el grupo de investigación en perdurabilidad empresarial de la Facultad de Aministración de la Universidad del Rosario

Characterization of MSB Synapses in Dissociated Hippocampal Culture with Simultaneous Pre- and Postsynaptic Live Microscopy

Multisynaptic boutons (MSBs) are presynaptic boutons in contact with multiple postsynaptic partners. Although MSB synapses have been studied with static imaging techniques such as electron microscopy (EM), the dynamics of individual MSB synapses have not been directly evaluated. It is known that the number of MSB synapses increases with synaptogenesis and plasticity but the formation, behavior, and fate of individual MSB synapses remains largely unknown. To address this, we developed a means of live imaging MSB synapses to observe them directly over time. With time lapse confocal microscopy of GFP-filled dendrites in contact with VAMP2-DsRed-labeled boutons, we recorded both MSBs and their contacting spines hourly over 15 or more hours. Our live microscopy showed that, compared to spines contacting single synaptic boutons (SSBs), MSB-contacting spines exhibit elevated dynamic behavior. These results are consistent with the idea that MSBs serve as intermediates in synaptic development and plasticity

Los indicadores biológicos

Los indicadores biológicos sintetizan información del medio que habitan, por lo tanto su aporte al diagnóstico de la calidad ambiental de los ecosistemas acuáticos resulta un complemento indispensable de otros tipos de mediciones como las que brindan los parámetros físico-químicos. Su uso como biomonitores puede ser considerado, además de una herramienta de evaluación ambiental, un potente medio de comunicación. En este capítulo se expone el empleo de distintos niveles de organización biológica que se pueden utilizar para evaluar las consecuencias de un impacto natural o antropogénico en un cuerpo de agua. Se presentan desde indicadores de cambios moleculares y bioquímicos hasta los que involucran la estructura y funcionamiento del ecosistema. Se exponen las ventajas y desventajas del uso de los principales grupos de organismos acuáticos que se pueden emplear en el monitoreo, los principales métodos de evaluación biológica y las escalas temporales en el empleo de indicadores biológicos.Instituto de Limnología "Dr. Raúl A. Ringuelet

Teleseisms monitoring using chirped-pulse φOTDR

Monitoring of seismic activity around the word is a topic of high interest for the analysis and understanding of deep Earth dynamics. However, the deployment of a homogeneous network of seismic stations both onshore and offshore poses a strong economic challenge that makes this solution practically inviable. Using the pre-existing fiber optical network for seismic monitoring arises as an excellent solution with important advantages in terms of ubiquity and cost. In this communication, we present the detection of an M8.2 earthquake occurred in Fiji Island using distributed acoustic sensing based on chirped-pulse φOTDR. Two sensors were placed simultaneously at two different locations at >9,000 km from the earthquake epicenter: a metropolitan area and a submarine environment. The recorded data is postprocessed using a 2D linear filter to cancel out environmental noise. The resulting signals are compared with the signals acquired by nearby seismometers. The attained good matching between the recorded data and the seismometer data shows the strong potential of the use of the already-deployed communication fiber network for teleseism monitoring

Distributed acoustic sensing for seismic activity monitoring

Continuous, real-time monitoring of surface seismic activity around the globe is of great interest for acquiring new insight into global tomography analyses and for recognition of seismic patterns leading to potentially hazardous situations. The already-existing telecommunication fiber optic network arises as an ideal solution for this application, owing to its ubiquity and the capacity of optical fibers to perform distributed, highly sensitive monitoring of vibrations at relatively low cost (ultra-high density of point sensors available with minimal deployment of new equipment). This perspective article discusses early approaches on the application of fiber-optic distributed acoustic sensors (DASs) for seismic activity monitoring. The benefits and potential impact of DAS technology in these kinds of applications are here illustrated with new experimental results on teleseism monitoring based on a specific approach: the so-called chirped-pulse DAS. This technology offers promising prospects for the field of seismic tomography due to its appealing properties in terms of simplicity, consistent sensitivity across sensing channels, and robustness. Furthermore, we also report on several signal processing techniques readily applicable to chirped-pulse DAS recordings for extracting relevant seismic information from ambient acoustic noise. The outcome presented here may serve as a foundation for a novel conception for ubiquitous seismic monitoring with minimal investment

Distributed acoustic sensing for seismic activity monitoring

Continuous, real-time monitoring of surface seismic activity around the globe is of great interest for acquiring new insight into global tomography analyses and for recognition of seismic patterns leading to potentially hazardous situations. The already-existing telecommunication fiber optic network arises as an ideal solution for this application, owing to its ubiquity and the capacity of optical fibers to perform distributed, highly sensitive monitoring of vibrations at relatively low cost (ultra-high density of point sensors available with minimal deployment of new equipment). This perspective article discusses early approaches on the application of fiber-optic distributed acoustic sensors (DASs) for seismic activity monitoring. The benefits and potential impact of DAS technology in these kinds of applications are here illustrated with new experimental results on teleseism monitoring based on a specific approach: the so-called chirped-pulse DAS. This technology offers promising prospects for the field of seismic tomography due to its appealing properties in terms of simplicity, consistent sensitivity across sensing channels, and robustness. Furthermore, we also report on several signal processing techniques readily applicable to chirped-pulse DAS recordings for extracting relevant seismic information from ambient acoustic noise. The outcome presented here may serve as a foundation for a novel conception for ubiquitous seismic monitoring with minimal investment