oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 9 )

2018 ( 14 )

2017 ( 13 )

2016 ( 38 )

Custom range...

Search Results: 1 - 10 of 12053 matches for " Torres Brizuela "
All listed articles are free for downloading (OA Articles)
Page 1 /12053
Display every page Item
Sensitivity of main downdraft features to vertical wind shear and ice-phase in a microburst-producing thunderstorm
TORRES BRIZUELA, M;NICOLINI, M;
Atmósfera , 2008,
Abstract: this paper presents results from numerical simulations of a severe storm producing a microburst, using a convective numerical model. the numerical experiments are done in order to understand the role of the environmental vertical wind profile and/or the ice phase in organizing cloud dynamics and the strength of the microburst. three particular downdraft types (the mid level, the penetrative and the precipitation related) and their relationship with cloud microphysics and the environmental wind profile are analyzed. to accomplish this objective, a well documented storm developed on 20 july 1986 over northern alabama (usa), is used as case study. similar environmental conditions to those that characterize this event have been observed prior to thunderstorms that produce severe low-level winds over northeastern argentina. model results show a good representation of the observed main storm features during the different cloud stages for the control its weak magnitude, in the genesis and support of the mid-level downdraft. the inclusion of the ice phase provides additional buoyancy that promotes a stronger updraft and vertical growth and reduces the loading contribution related to supercooled raindrops to the mid-level downdraft. melting provides an additional cooling that reinforces both the low-level precipitation related downdraft and the divergent outflow velocity differential in the microburst.
Fibrilación atrial en los adultos mayores
Brizuela-Torres,Jorge; Morales-Martínez,Fernando;
Acta Médica Costarricense , 2009,
Abstract: atrial fibrillation is the most prevalent arrhythmia in the elderly. its frequency increases with age, being 1.5% from 50 to 59 years old and 10% from 80 to 89 years old. non valvular atrial fibrillation increases 5 fold the risk of suffering an stroke and causes 15% of strokes in the usa. atrial fibrillation management focuses in the prevention of thromboembolic phenomena and heart rate and rhythm control. anticoagulation, when indicated, has demonstrated to be the main tool in the prevention of these events. nevertheless, although bleeding complications are more frequent in this population and increase with age, anticoagulation benefits are greater than the risks. heart rate control is better than rhythm control regarding cerebrovascular accidents and mortality. age by itself is not a contraindication to offer optimal therapy. functional, mental and social status, must be taken into account as well as physiological aspects of aging when it comes to prescribing medications. if symptoms persist in spite of adequate treatment, invasive strategies have demonstrated to be of benefit, however studies in elderly population are lacking.
Fibrilación atrial en los adultos mayores Atrial Fibrillation in the Elderly
Jorge Brizuela-Torres,Fernando Morales-Martínez
Acta Médica Costarricense , 2009,
Abstract: La fibrilación atrial es la taquiarritmia más prevalente en los adultos mayores. La frecuencia de dicha arritmia aumenta con la edad, presentándose en un 1.5% de los 50 a 59 a os a 10% de los 80 a 89 a os. La fibrilación atrial no valvular incrementa el riesgo de sufrir un evento cerebrovascular isquémico cardioembólico en 5 veces y causa el 15% de todos los accidentes cerebrovasculares isquémicos en Estados Unidos de América. El manejo de la fibrilación atrial se enfoca, principalmente, en la prevención de los fenómenos tromboembólicos y en el control de la frecuencia y ritmo cardiaco. La anticoagulación, cuando está indicada, ha demostrado ser la principal herramienta en la prevención de dichos eventos. Sin embargo, aunque las complicaciones hemorrágicas son más frecuentes, en esta población, y aumentan con la edad, sobrepasa por mucho, el beneficio al riesgo. El control de la frecuencia cardiaca ha demostrado ser igual o mejor que el control del ritmo en cuanto a prevención de eventos cerebrovasculares y mortalidad en estos pacientes. La edad cronológica por sí sola, no es contraindicación alguna para ofrecer una terapia óptima. Debe tomarse en cuenta el estado funcional, cognitivo y social, así como aspectos fisiológicos del envejecimiento con respecto a la prescripción de medicamentos. Cuando, a pesar del tratamiento adecuado, la sintomatología persiste, las estrategias invasivas han demostrado ser beneficiosas, pero faltan estudios que involucren a individuos mayores. Atrial fibrillation is the most prevalent arrhythmia in the elderly. Its frequency increases with age, being 1.5% from 50 to 59 years old and 10% from 80 to 89 years old. Non valvular atrial fibrillation increases 5 fold the risk of suffering an stroke and causes 15% of strokes in the USA. Atrial fibrillation management focuses in the prevention of thromboembolic phenomena and heart rate and rhythm control. Anticoagulation, when indicated, has demonstrated to be the main tool in the prevention of these events. Nevertheless, although bleeding complications are more frequent in this population and increase with age, anticoagulation benefits are greater than the risks. Heart rate control is better than rhythm control regarding cerebrovascular accidents and mortality. Age by itself is not a contraindication to offer optimal therapy. Functional, mental and social status, must be taken into account as well as physiological aspects of aging when it comes to prescribing medications. If symptoms persist in spite of adequate treatment, invasive strategies have demonstrated to be of benefit, ho
Análisis del entorno sinóptico asociado con eventos de Bow-Echo en la Provincia de Buenos Aires
Torres Brizuela,Marcela; Vidal,Ricardo; García Skabar,Yanina; Nicolini,Matilde; Vidal,Luciano;
Meteorologica , 2011,
Abstract: during the morning hours on october 21 2008, three convective lines developed over the buenos aires province, and were captured by the meteorological radars located at ezeiza and pergamino. the spatial structure and temporal evolution of the reflectivity field of these convective systems present the attributes of the particular convective system referred to as a “bow-echo”. ezeiza doppler radar images, captured winds stronger than 20 m.s-1 behind these arc lines, a phenomenon that frequently characterizes the presence of a bow-echo. the main objective of this study is to understand the synoptic weather conditions accompanying the occurrence of these bow echo events to enhance the weather forecasting of these systems. on this particular case the specific humidity field over the northern part of the buenos aires province (q≥ 12-14 g.kg-1) and also the environmental vertical wind shear values below 700 hpa meet the required conditions to develop a bow-echo event, although the available surface level cape values do not promote this event.
Análisis del entorno sinóptico asociado con eventos de Bow-Echo en la Provincia de Buenos Aires Synoptic Environment Analysis Associated With Bow - Echo Events In The Province Of Buenos Aires
Marcela Torres Brizuela,Ricardo Vidal,Yanina García Skabar,Matilde Nicolini
Meteorologica , 2011,
Abstract: Durante la madrugada del día 21 de Octubre de 2008 se desarrollaron tres líneas convectivas en la provincia de Buenos Aires, captadas por los radares meteorológicos de las localidades de Ezeiza y Pergamino. La estructura espacial y evolución temporal del campo de reflectividad de estos sistemas, configuración de línea en arco, responde al modo convectivo conocido con el nombre de “bow-echo”. La imagen doppler del radar de Ezeiza registró un fenómeno típico en la parte posterior de estas líneas en arco: los vientos intensos mayores a 20 m.s-1. El objetivo principal de este estudio es comprender las condiciones sinópticas que acompa aron la ocurrencia de estos sistemas para poder contribuir al pronóstico de su ocurrencia. En este evento las condiciones de humedad especifica en la zona del norte de la provincia de Buenos Aires (q≥ 12-14 g.kg-1), así como la de cortante vertical del viento por debajo del nivel de 700 hPa (Us>15 m.s-1) coinciden en indicar al entorno como favorable al desarrollo del mismo, aunque no así los valores disponibles de CAPE evaluados para parcelas que se elevan desde superficie. During the morning hours on October 21 2008, three convective lines developed over the Buenos Aires province, and were captured by the meteorological radars located at Ezeiza and Pergamino. The spatial structure and temporal evolution of the reflectivity field of these convective systems present the attributes of the particular convective system referred to as a “bow-echo”. Ezeiza doppler radar images, captured winds stronger than 20 m.s-1 behind these arc lines, a phenomenon that frequently characterizes the presence of a bow-echo. The main objective of this study is to understand the synoptic weather conditions accompanying the occurrence of these bow echo events to enhance the weather forecasting of these systems. On this particular case the specific humidity field over the northern part of the Buenos Aires province (q≥ 12-14 g.kg-1) and also the environmental vertical wind shear values below 700 hPa meet the required conditions to develop a bow-echo event, although the available surface level CAPE values do not promote this event.
Statistical moments for classical and quantum dynamics: formalism and generalized uncertainty relations
David Brizuela
Physics , 2014, DOI: 10.1103/PhysRevD.90.085027
Abstract: The classical and quantum evolution of a generic probability distribution is analyzed. To that end, a formalism based on the decomposition of the distribution in terms of its statistical moments is used, which makes explicit the differences between the classical and quantum dynamics. In particular, there are two different sources of quantum effects. Distributional effects, which are also present in the classical evolution of an extended distribution, are due to the fact that all moments can not be vanishing because of the Heisenberg uncertainty principle. In addition, the non-commutativity of the basic quantum operators add some terms to the quantum equations of motion that explicitly depend on the Planck constant and are not present in the classical setting. These are thus purely-quantum effects. Some particular Hamiltonians are analyzed that have very special properties regarding the evolution they generate in the classical and quantum sector. In addition, a large class of inequalities obeyed by high-order statistical moments, and in particular uncertainty relations that bound the information that is possible to obtain from a quantum system, are derived.
Classical versus quantum evolution for a universe with a positive cosmological constant
David Brizuela
Physics , 2015, DOI: 10.1103/PhysRevD.91.085003
Abstract: A homogeneous and isotropic cosmological model with a positive cosmological constant is considered. The matter sector is given by a massless scalar field, which can be used as an internal time to deparametrize the theory. The idea is to study and compare the evolutions of a quantum and a classical probability distribution by performing a decomposition of both distributions in their corresponding moments. For the numerical analysis an initial peaked Gaussian state in the volume will be chosen. Furthermore, in order to check the robustness of certain results, as initial state both a slightly deformed Gaussian, as well as another completely different state, will also be studied. Differences and similarities between classical and quantum moments are pointed out. In particular, for a subset of moments classical and quantum evolutions are quite similar, but certain variables show remarkable differences.
Classical and quantum behavior of the harmonic and the quartic oscillators
David Brizuela
Physics , 2014, DOI: 10.1103/PhysRevD.90.125018
Abstract: In a previous paper a formalism to analyze the dynamical evolution of classical and quantum probability distributions in terms of their moments was presented. Here the application of this formalism to the system of a particle moving on a potential is considered in order to derive physical implications about the classical limit of a quantum system. The complete set of harmonic potentials is considered, which includes the particle under a uniform force, as well as the harmonic and the inverse harmonic oscillators. In addition, as an example of anharmonic system, the pure quartic oscillator is analyzed. Classical and quantum moments corresponding to stationary states of these systems are analytically obtained without solving any differential equation. Finally, dynamical states are also considered in order to study the differences between their classical and quantum evolution.
Quantum back-reaction in a universe with positive cosmological constant
David Brizuela
Physics , 2011, DOI: 10.1088/1742-6596/360/1/012026
Abstract: Semiclassical techniques have proven to be a very powerful method to extract physical effects from different quantum theories. Therefore, it is expected that in the near future they will play a very prominent role in the context of quantum gravity. In this work we develop systematic tools to derive semiclassical approximations for any quantum theory with one degree of freedom. In our approach, the wave function is decomposed in terms of an infinite set of moments, which encode the complete quantum information of the system. Semiclassical regimes can then be properly described by truncation of this infinite system. The use of efficient computer algebra tools allows us to compute the equations of motion up to a very high order. In this way, we can study very precisely the quantum back reaction of the system as well as the convergence of the method with the considered order. Finally, these tools are applied to the particular case of a homogeneous universe filled with a massless scalar field and positive cosmological constant, which provide interesting physical results.
Aplicaciones diagnósticas y terapéuticas de la colangiopancreatografía retrógrada endoscópica
Raúl A Brizuela Quintanilla,Julián Ruiz Torres,Carlos Fábregas Rodríguez,Rolando Martínez López
Revista Cubana de Medicina Militar , 2000,
Abstract: Se evaluó el trabajo realizado durante 19 meses, desde mayo de 1997 hasta diciembre de 1998, en 586 pacientes (230 hombres y 356 mujeres) compuesto por diferentes grupos de edades, a los cuales se les indicó colangiopancreatografía retrógrada endoscópica (CPRE). El grupo de mayor incidencia fue el de 40 a 79 a (70 %). Del total de 586 pacientes se realizaron CPRE a 544 (92,8 %), de ellas 255 (46,8 %) fueron diagnósticas y 289 (53,2 %) terapéuticas. La principal causa que motivó la indicación de la CPRE fue la sospecha de enfermedad benigna de la vía biliar principal (VBP) en el 57,3 % de los pacientes y el principal diagnóstico lo fue la litiasis biliar (30 %), seguida de la obstrucción maligna de la VBP (22 %). Los procederes terapéuticos más realizados fueron la esfinterotomía endoscópica (218), la extracción de cálculos de la vía biliar (106) y la colocación de endoprótesis en la VBP (116). Hubo 10 complicaciones (1,8 %), 5 sangramientos ligeros, 2 perforaciones, 2 pancreatitis y una colangitis. Todas se resolvieron mediante tratamiento médico y endoscópico. No se reportaron fallecimientos. Se muestra la utilidad diagnóstica y terapéutica de la CPRE con un mínimo de riesgo y complicaciones para los pacientes que necesitaron este proceder, así como la experiencia alcanzada por el grupo en la realización de éste. The work carried out from May 1997 to December 1998, that is, for 19 months in the treatment of 586 patients (230 men and 356 women) who were performed endoscopic retrograde cholangiopancreatography (ERCP) was assessed in this paper. This group comprised several age groups, being the predominant the 40-79 years-old group (70%). Of 586 patients, 544 underwent ERCP (92.8%) of which 255 (46.8%) were diagnostic and 289 (53.2%) therapeutical. The principal reason for performing ERCP was suspicion of benign main biliary duct disease (MBD) in 57.3% of the patients and the main diagnosis was biliary lithiasis (30%) followed by malignant obstruction in MBD (22%). The most used therapeutic procedures were endoscopic sphinterotomy (218), the extraction of biliary stones (106) and endoscopic biliary prosthesis in MBD (116). There were ten cases with complications (1.8%), 5 cases with bleeding, 2 with perforations, 2 with pancreatitis and one with cholangitis. All these problems were solved by medical and endoscopic treatment. No death was recorded. The diagnostic and therapeutic usefulness of ERCP with minimum risks and complications for patients in need of such technique was proved. Also the experience gained by the medical team in performing ERCP was sh
Page 1 /12053
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.