Electron and Phonon Thermal Waves in Semiconductors: an Application to Photothermal Effects

The electron and phonon temperature distribution function are calculated in semiconductors. We solved the coupled one-dimensional heat-diffussion equations in the linear approximation in which the physical parameters on the sample are independent of the temperature. We also consider the heat flux at the surface of the semiconductor as a boundary condition for each electron and phonon systems instead of using a fixed temperature. From this, we obtain an expression for electron and phonon temperature respectively. The characterization of the thermal waves properties is duscussed and some practical procedures for this purpose provide us information about the electron and phonon thermal parameters.Comment: 12 pages, amstex and amssymb macro package (LaTeX2e edition

Metodologia para la evaluacion de sistemas de refrigeracion industrial

Este articulo muestra una metodología que puede ser usada en diferentes sistemas de refrigeración. En este trabajo fue aplicada en un combinado cárnico de la Republica de Cuba con resultados satisfactorios, es confiable y precisa

Metodologia para la evaluacion de sistemas de refrigeracion industrial

Este articulo muestra una metodología que puede ser usada en diferentes sistemas de refrigeración. En este trabajo fue aplicada en un combinado cárnico de la Republica de Cuba con resultados satisfactorios, es confiable y precisa

Estimación de los términos de transferencia de masa en la recuperación de licopeno empleando aceite de Moringa oleifera Lam como solvente

The aim of this work was to assess the terms associated with mass transfer in the lycopene recovery from the waste of a tomato canning plant. Moringa oleifera Lam oil was employed as solvent. An ultrasonic extraction was carried out on skin and seeds. The operational variables were temperature (skin: 45, 60, 75, 90 ºC; seed: 45, 60, 75 ºC), matrix/solvent ratio (m/v) (1:20, 1:25, 1:30), particle size (skin: < 1, 1-2, > 3.15 mm; seed: < 1, 1-2, > 2 mm) and extract separation method (filtration and centrifugation). Kinetic constant, lycopene concentration on the solid surface, volumetric coefficient of mass transfer and effective diffusivity were determined. The more the kinetic constant increased, the higher the volumetric coefficient of mass transfer was. Effective diffusivity increased with temperature. Activation energy values suggest a possible deterioration of lycopene at temperatures higher than the optimum. The use of M. oleifera oil as solvent should increase the biological value of the lycopene extracts.El objetivo del presente trabajo fue evaluar los términos asociados a la transferencia de masa en la extracción de licopeno a partir del residuo de la industria de conservas de tomate. Como solvente se utilizó aceite de Moringa oleífera Lam. Se realizó una extracción ultrasónica sobre piel y semillas. Las variables operacionales investigadas fueron, temperatura (piel: 45, 60, 75, 90 ºC; semillas: 45, 60, 75 ºC), relación soluto/solvente (m/v) (1:20, 1:25, 1:30), tamaño de partícula (piel: <1, 1-2, >3.15 mm; semilla: <1, 1-2, >2 mm) y métodos de separación del extracto (filtración y centrifugación). Se determinaron la constante cinética, la concentración de licopeno en la superficie del sólido, el coeficiente volumétrico de transferencia de masa y la difusividad efectiva. A mayor contante cinética, mayor coeficiente volumétrico de transferencia de masa. La difusividad efectiva aumentó con la temperatura. Los valores de energía de activación sugieren un posible deterioro del licopeno a temperaturas superiores a las óptimas. El uso del aceite de M. oleífera como solvente debe incrementar el valor biológico de los extractos de licopeno

Voxel model in BNCT treatment planning: Performance analysis and improvements

In recent years, many efforts have been made to study the performance of treatment planning systems in deriving an accurate dosimetry of the complex radiation fields involved in boron neutron capture therapy (BNCT). The computational model of the patient's anatomy is one of the main factors involved in this subject. This work presents a detailed analysis of the performance of the 1 cm based voxel reconstruction approach. First, a new and improved material assignment algorithm implemented in NCTPlan treatment planning system for BNCT is described. Based on previous works, the performances of the 1 cm based voxel methods used in the MacNCTPlan and NCTPlan treatment planning systems are compared by standard simulation tests. In addition, the NCTPlan voxel model is benchmarked against in-phantom physical dosimetry of the RA-6 reactor of Argentina. This investigation shows the 1 cm resolution to be accurate enough for all reported tests, even in the extreme cases such as a parallelepiped phantom irradiated through one of its sharp edges. This accuracy can be degraded at very shallow depths in which, to improve the estimates, the anatomy images need to be positioned in a suitable way. Rules for this positioning are presented. The skin is considered one of the organs at risk in all BNCT treatments and, in the particular case of cutaneous melanoma of extremities, limits the delivered dose to the patient. Therefore, the performance of the voxel technique is deeply analysed in these shallow regions. A theoretical analysis is carried out to assess the distortion caused by homogenization and material percentage rounding processes. Then, a new strategy for the treatment of surface voxels is proposed and tested using two different irradiation problems. For a parallelepiped phantom perpendicularly irradiated with a 5 keV neutron source, the large thermal neutron fluence deviation present at shallow depths (from 54% at 0 mm depth to 5% at 4 mm depth) is reduced to 2% on average. Reassigning fluence values in the case of this phantom in angular position produced the maximum deviation in the thermal fluence to decrease from 140% to 23% at the surface of the phantom. Thus, even for the largest deviations, obtained by intentionally placing the phantom in the most disadvantageous position with respect to the voxel grid, the reassignment shows very good performance. Since these results substantially improve the performance of the 1 cm based voxel model in surface boundary regions, the proposed strategy will be implemented in future versions of the NCTPlan code.Fil: González, Sara Josefina. Comisión Nacional de Energía Atómica; Argentina. United Automobile Insurance Company; ArgentinaFil: Carando, Daniel Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentina. Universidad de San Andrés; ArgentinaFil: Santa Cruz, Gustavo Alberto. Comisión Nacional de Energía Atómica; Argentina. United Automobile Insurance Company; ArgentinaFil: Zamenhof, Robert G.. Tufts-New England Medical Center; Estados Unido

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

A proposal for the withdrawal of inhaled corticosteroids in the clinical practice of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease; Exacerbations; Inhaled corticosteroidsMalaltia pulmonar obstructiva crònica; Empitjorament; Corticoesteroides inhalatsEnfermedad pulmonar obstructiva crónica; Empeoramiento; Corticoesteroides inhaladosAccording to the current clinical practice guidelines for chronic obstructive pulmonary disease (COPD), the addition of inhaled corticosteroids (ICS) to long-acting β2 agonist therapy is recommended in patients with moderate-to-severe disease and an increased risk of exacerbations. However, ICS are largely overprescribed in clinical practice, and most patients are unlikely to benefit from long-term ICS therapy.Evidence from recent randomized-controlled trials supports the hypothesis that ICS can be safely and effectively discontinued in patients with stable COPD and in whom ICS therapy may not be indicated, without detrimental effects on lung function, health status, or risk of exacerbations. This article summarizes the evidence supporting the discontinuation of ICS therapy, and proposes an algorithm for the implementation of ICS withdrawal in patients with COPD in clinical practice.Given the increased risk of potentially serious adverse effects and complications with ICS therapy (including pneumonia), the use of ICS should be limited to the minority of patients in whom the treatment effects outweigh the risks

Agenesia lumbosacra

La agenesia lumbosacra es una malformación congénita muy rara que forma parte del síndrome de regresión caudal; su incidencia es de un caso por cada 25,000 nacidos vivos y es más frecuente en los hijos de madres diabéticas. Se comunica el caso de un neonato masculino de dos días de vida extrauterina atendido en el Hospital Universitario Dr. José Eleuterio González, con malformaciones en el segmento corporal inferior. Con el estudio radiográfico se comprobó el diagnóstico de agenesia lumbosacra. La familia desconocía los tipos de malformaciones o enfermedades hereditarias en su árbol genealógico; el estudio de cariotipo no demostró alteraciones (46 XY), al igual que la determinación de hemoglobina glucosilada a la madre. En el ecocardiograma se identificó foramen oval permeable y miocardiopatía hipertrófica sin repercusión hemodinámica. Debido a su complejidad clínica, el tratamiento para la agenesia lumbosacacra debe abordarse con un equipo médico multidisciplinario para identificar cualquier alteración anatómica y funcional

Integrating clinical research in an operative screening and diagnostic breast imaging department: First experience, results and perspectives using microwave imaging.

Clinical research is crucial for evaluating new medical procedures and devices. It is important for healthcare units and hospitals to minimize the disruptions caused by conducting clinical studies; however, complex clinical pathways require dedicated recruitment and study designs.This work presents the effective introduction of novel microwave breast imaging (MBI), via MammoWave apparatus, into the clinical routine of an operative screening and diagnostic breast imaging department for conducting a multicentric clinical study. Microwave breast imaging, using MammoWave apparatus, was performed on volunteers coming from different clinical pathways. Clinical data, comprising demographics and conventional radiologic reports (used as reference standard), was collected; a satisfaction questionnaire was filled by every volunteer. Microwave images were analyzed by an automatic clinical decision support system, which quantified their corresponding features to discriminate between breasts with no relevant radiological findings (NF) and breasts with described findings (WF). Conventional breast imaging (DBT, US, MRI) and MBI were performed and adapted to assure best clinical practices and optimum pathways. 180 volunteers, both symptomatic and asymptomatic, were enrolled in the study. After microwave images' quality assessment, 48 NF (15 dense) and 169 WF (88 dense) breasts were used for the prospective study; 48 (18 dense) breasts suffered from a histology-confirmed carcinoma. An overall sensitivity of 85.8 % in breasts lesions' detection was achieved by the microwave imaging apparatus. An optimum recruitment strategy was implemented to assess MBI. Future trials may show the clinical usefulness of microwave imaging, which may play an important role in breast screening. [Abstract copyright: © 2023 The Authors.