Desarrollo de un modelo estequiométrico para el cálculo del número TC en aplicaciones cuantitativas

Las imágenes de Tomografía Computarizada (TC) son empleadas de forma cuantitativa en diferentes aplicaciones, entre otras, el cálculo de la dosis absorbida en tratamientos de radioterapia, la corrección de la atenuación en imágenes de emisión en equipos híbridos SPECT/CT y PET/CT, o la cuantificación del contenido mineral en hueso y caracterización tisular. Estas aplicaciones son posibles porque una imagen de TC está formada a partir de una magnitud física definida de forma precisa: el coeficiente de atenuación lineal. El valor mostrado en cada píxel (número TC) es el coeficiente de atenuación lineal del material en esa posición relativo al del agua, expresado en unidades Hounsfield (HU). El número TC se introdujo históricamente para que fuera independiente de la máquina en cuestión. Las diferencias en el número TC de los tejidos son un problema para las aplicaciones cuantitativas ya que dificultan las comparaciones entre escáneres diferentes e implican un proceso de calibración individualizado. Estas variaciones se producen porque los haces de rayos X empleados son polienergéticos. Las diferencias de atenuación entre las energías dan lugar a que el espectro del haz emergente detectado por la matriz de detectores sea dependiente de la proyección, efecto denominado endurecimiento del haz. El coeficiente de atenuación medido por el escáner es el correspondiente a la energía efectiva del haz, definida como aquella para la cual el coeficiente de atenuación lineal del agua es igual al medido por el escáner. Desde los comienzos de la utilización clínica de la TC se ha propuesto que los estudios cuantitativos con números TC estén conectados con el valor de la energía efectiva implicada; de ahí la importancia de contar con un método adecuado para poder determinar la energía efectiva de un haz para cada condición particular. El espectro detectado y los detalles de la corrección por endurecimiento del haz en los actuales escáneres son, en principio, desconocidos, por lo que el cálculo de la energía efectiva a partir de la definición del párrafo anterior es inviable. Existe una definición empírica propuesta por varios autores que permite medirla: es la energía que produce máxima correlación lineal entre los números TC medidos y los coeficientes de atenuación para un conjunto de materiales. Sin embargo, al no contar con una expresión paramétrica para el número TC su aplicación no es sencilla. Estos problemas han motivado la utilización de métodos alternativos para la calibración de los escáneres TC que se describen a continuación..

Hybrid classical-quantum formulations ask for hybrid notions

We reappraise some of the hybrid classical-quantum models proposed in the literature with the goal of retrieving some of their common characteristics. In particular, first, we analyze in detail the Peres-Terno argument regarding the inconsistency of hybrid quantizations of the Sudarshan type. We show that to accept such hybrid formalism entails the necessity of dealing with additional degrees of freedom beyond those in the straight complete quantization of the system. Second, we recover a similar enlargement of degrees of freedom in the so-called statistical hybrid models. Finally, we use Wigner's quantization of a simple model to illustrate how in hybrid systems the subsystems are never purely classical or quantum. A certain degree of quantumness (classicality) is being exchanged between the different sectors of the theory, which in this particular unphysical toy model makes them undistinguishable.Comment: 13 pages, 3 figures (minor changes to match the published version

Toward sustainable management: 2D modelling of a self-cleaning system to improve geometry in front of the flushing gate

This paper aims to show how numerical modelling based on 2D SWE can be used to analyze the cleaning effectiveness of flushing waves in storm tanks. The case study under consideration is an existing storm tank located in Badalona, a municipality of Barcelona, Spain. Storm tank cleaning systems are critical features that must be carefully addressed. If not appropriately addressed, operation and maintenance work costs can drastically increase. There are numerous currently available technologies for cleaning storage tanks. However, no specific guide on this field has been identified. References are provided by the manufacturers through their commercial catalogues. Generally, this information is not based on experimental or numerical experiences or results have not been published in the literature of scientific papers. In this study, a public domain software (IBER) was used to develop 2D hydraulic analysis of the selected tank. The results obtained show how the phenomenon of recirculation is acting in some areas of the lane. This implies a dissipation of energy, thus causing difficulties in terms of cleaning procedures. Furthermore, two new scenarios have been tested to determine how a different lane width might affect hydrodynamic behavior. A newly suggested geometry for the existing lane of the tank is proposed by using the numerical modeling software. The proposed geometry in the current pilot tank achieves higher velocities and avoids recirculation areas. The results demonstrate that numerical modelling of these types of processes is possible with the computer models available (commercial codes) and can be used to optimize cleaning system designPeer ReviewedPostprint (published version

Comunidades de aprendizaje móvil, Mastery Learning y el problema 2 sigma como estrategias para el conocimiento previo en la resolución de actividades

Esta experiencia es parte de una investigación sobre el futuro de las tecnologías dentro y fuera del salón de clase; se basa en una investigación acción, con la finalidad de planificar, actuar, observar y reflexionar, con el fin de transformar la situación de partida e innovar en nuevos espacios de enseñanza-aprendizaje e indagar estrategias mediadas por tecnologías para la resolución de actividades planteadas a los participantes del curso La web: un espacio para el aprendizaje de la edición UPEL- IMPM-Táchira, llevado a cabo durante junio, julio y agosto de 2016. A partir de una comunidad de aprendizaje móvil (WhatsApp), los participantes alcanzaron un alto nivel de aprendizaje según lo refiere el Mastery Learning, obteniendo un 90% de conocimientos previos, antes de continuar con la información subsiguiente, a través del apoyo de tutorías (Problema 2 Sigma), realizadas de manera síncrona mediante Hangouts. La puesta en marcha de discusiones grupales en una comunidad de aprendizaje móvil, con herramientas como WhatsApp, apoyado en Facebook y tutoría en línea, se implementa como estrategia anticipada a la resolución de actividades en cada unidad temática, para lograr una mayor comprensión de los contenidos al llegar con un 90% de conocimientos previos que permitan afrontar y realizar las actividades planteadas. Se logró, un aprendizaje personalizado, adaptativo y flexible, al realizar análisis del aprendizaje luego de cuatro semanas dentro del aula virtual, con la propuesta de otras tutorías en línea, para aquellos participantes con actividades atrasadas, obteniéndose un 85% de recuperación para una finalización exitosa del curso

Tendencias tecnológicas en educación

Esta infografía recopila los informes de tres Instituciones que han analizado las tendencias, en diferentes ámbitos, que marcarán el futuro de la educación en el mundo

Retrieval of bilingual Spanish-English information by means of a standard automatic translation system

This paper describes our participation in bilingual retrieval (queries in Spanish on documents in English), by means of an information retrieval system based on the vector model. The queries, formulated in Spanish, were translated into English by means of a commercial automatic translation system; the terms extracted from the resulting translations were filtered in order to get rid of empty words and then they were normalised by stemming. Results are poorer than those obtained through monolingual retrieval with the original queries in English slightly above 15%

Cooling Average Potential of Evaporative Cooling System in Dry Warm Climate

AbstractThe high summer temperatures, high solar radiation and common inadequate thermal design of buildings obliges the occupants to recur to the use cooling equipment such as evaporative air-conditioning to achieve acceptable levels of habitability. Evaporative cooling systems require considerable electric energy and a significant constant clean water supply during operation. Therefore, this paper presents the results of a field study aims to quantify in this kind of weather, the potential cooling means having the following strategies: indirect evaporative cooling and shading devices; indirect evaporative cooling, shading devices and thermal mass; indirect evaporative cooling, solar protection, thermal mass and nocturnal radiative cooling; indirect evaporative cooling, thermal insulation and nocturnal radiative cooling; and finally indirect evaporative cooling, thermal insulation, thermal mass and nocturnal radiative cooling. The method consisted of measuring the reduction in air temperature is achieved with each of these cooling strategies, applied in three research modules of same construction features, orientation and dimensions during the summer 2012.Then quantified the cooling average potential by the method proposed by Dr. Eduardo Gonzalez (1989). Finally registration was the water consumption with each of these strategies and estimated required consumption by direct evaporative cooling to achieve the same cooling potential. The results obtained indicate that the IEC/TI/NRC had cooling potential of 822.89 Wh/m2day, followed IEC/SP with 764.19 Wh/m2day and finally IEC/SP+TM 568.60 Wh/m2day

Testing for deterministic components in vector seasonal time series

Certain locally optimal tests for deterministic components in vector time series have associated sampling distributions determined by a linear combination of Beta variates. Such distributions are nonstandard and must be tabulated by Monte Carlo simulation. In this paper, we provide closed form expressions for the mean and variance of several multivariate test statistics, moments that can be used to approximate unknown distributions. In particular, we find that the two-moment Inverse Gaussian approximation provides a simple and fast method to compute accurate quantiles and p-values in small and asymptotic samples. To illustrate the scope of this approximation we review some standard tests for deterministic trends and/or seasonal patterns in VARIMA and structural time series models

Engineered Salmonella allows real-time heterologous gene expression monitoring within infected zebrafish embryos

Short communication.Microbial host–pathogen interactions have been traditionally well studied at genetic and physiological levels, but cell-resolution analyses have been particularly scarce. This has been especially remarkable for intracellular parasites for two major reasons: first, the inherent loss of bacteria traceability once infects its hosts; second and more important, the limited availability of genetic tools that allow a tight regulated expression of bacterial virulence genes once inside the host tissues. Here we present novel data supporting the use of zebrafish embryos to monitor Salmonella enterica serovar Thyphimurium infection. Intravenous infection of Salmonella can be easily monitored using in vivo fluorescence that allows the visualization of free-swimming bacteria through the circulatory system. Moreover, we have engineered Salmonella to voluntarily activate heterologous gene expression at any point during infection once inside the zebrafish macrophages using a salicylate-based expression system. This approach allows real-time cell-resolution in vivo monitoring of the infection. All together, this approach paves the road to cell-based resolution experiments that would be harder to mimic in other vertebrate infection models.his work was funded by grants BFU2010-14839, CSD2007-00008, CSD2007-00005 and Proyectos de Excelencia CVI-3488 and P07-CVI-02518 from the Spanish and Andalusian Governments, respectively. Jose Luis Royo holds a JAE DOC contract from the Spanish National Research Council (CSIC).Peer reviewe