Dosimetric characterization of a brachytherapy applicator using MCNP5 modelisation and in-phantom measurements

[EN] A gynaecological applicator consisting of a metallic intra-uterine tube with a plastic vaginal applicator and an HDR Ir-192 source have been simulated with MCNP5 (Monte Carlo code). A solid phantom has been designed to perform measurements around the applicator with radiochromic films. The isodose curves obtained are compared with curves calculated with the F4MESH tally of MCNP5 with a good agreement. A pinpoint ionization chamber has been used to evaluate dose at some reference points. (c) 2009 Elsevier Ltd. All rights reserved.Gerardy, I.; Ródenas Diago, J.; Van Dycke, M.; Gallardo Bermell, S.; Ceccolini, E. (2010). Dosimetric characterization of a brachytherapy applicator using MCNP5 modelisation and in-phantom measurements. Applied Radiation and Isotopes. 68(4):735-737. doi:10.1016/j.apradiso.2009.10.018S73573768

Correlations between Elastic, Calorimetric, and Polar Properties of Ferroelectric PbSc0.5Ta0.5O3 (PST)

Calorimetric, elastic, and polar properties of ferrolectric lead scandium tantalate PbSc0.5Ta0.5O3 (PST) with 65% cation order have been investigated in the vicinity of the paraelectric-ferroelectric transition at Ttrans = 295K. Comparison of temperature dependencies of the excess specific heat and elastic properties indicate that both anomalies stem from ther- mal fluctuations of order parameters in three dimensions. These fluctuations are consistent with tweed microstructure. This transition is driven by several coupled thermodynamic order parameters, as evidenced by a strongly non-linear scaling of the excess entropy with the squared ferroelectric polarization.National Natural Science Foundation of China (51850410520, 51320105014 and 51621063

Espectrómetro de doble paso, simple y económico, para analizar radiación láser

En distintas épocas, antes y después del advenimiento del láser, se han diseñado espectrómetros ópticos para incrementar la dispersión con la cual se desea analizar la radiación o bien para reducir lo más posible la luz difundida en los elementos dispersivos, prismas o redes de difracción. Una vez que el láser pasó a ser una eficaz herramienta de laboratorio, varios campos de la óptica encontraron la oportunidad de lograr desarrollos sensacionales. La holografía y la espectroscopia de la radiación dispersada por la materia, constituyen ejemplos notables de aquellos campos de la óptica en los que el láser provocó una situación de avance sin precedentes. En el caso de los estudios de la radiación dispersada por la materia, fue necesario el diseño de espectrómetros especiales para detectar, por ejemplo, las débiles señales Stokes y anti-Stokes, excitadas por láseres diversos, en gases, líquidos o sol idos. Los espectrómetros ópticos o monocromadores usados en la investigación del efecto Raman, pueden clasificarse en tres tipos: a) los monocromadores de doble paso; b) los monocromadores duales y c) los monocromadores en tándem

Wilson maxillary curve analyzed by cbct a study on normocclusion and malocclusion individuals

The anatomy of dental compensation curve in the frontal plane described by George H. Wilson is one of the occlusal determinants of orthodontic treatment. However, there is few published comparing malocclusion and normocclusion individuals. Objectives: The aim of this study is to compare the curve of Wilson at first and second maxillary molars, normocclusion pattern and malocclusion pattern, with and without bilateral posterior crossbite, using angular references in CBCT studies. Material and Methods: We analyzed 10 cases of malocclusion with bilateral posterior crossbite, 10 cases of malocclusion without bilateral posterior crossbite and 10 cases with non orthodontic normocclusion (patients who underwent cone beam study for other reasons than orthodontic). All of them were adults, more than 19 years. Angular variables from left and right axis (line connecting the occlusal and furcation groove) of first and second molars towards a perpendicular to the frontal palate were measured. There was carried out an Anova test, Bonferroni analysis and Levene's statistics. Results: The descriptive analysis of the results shows an average values of total maxillary curve of Wilson for first molars (sum of left and right angle) of 8.1° for normocclusion group, 0.4° for the malocclusion pattern with bilateral posterior crossbite and 16.9° for the malocclusion pattern without this alteration. The mean differences was statistical significant (P<0,042) between between malocclusion pattern groups with and without crossbite . Conclusion: The curve of Wilson, measured at maxillary first molars in patients with bilateral posterior crossbite is more concave than the other groups, suggesting no dentoalveolar compensations

Performance of the reconstruction algorithms of the FIRST experiment pixel sensors vertex detector

Hadrontherapy treatments use charged particles (e.g. protons and carbon ions) to treat tumors. During a therapeutic treatment with carbon ions, the beam undergoes nuclear fragmentation processes giving rise to significant yields of secondary charged particles. An accurate prediction of these production rates is necessary to estimate precisely the dose deposited into the tumours and the surrounding healthy tissues. Nowadays, a limited set of double differential carbon fragmentation cross-section is available. Experimental data are necessary to benchmark Monte Carlo simulations for their use in hadrontherapy. The purpose of the FIRST experiment is to study nuclear fragmentation processes of ions with kinetic energy in the range from 100 to 1000 MeV/u. Tracks are reconstructed using information from a pixel silicon detector based on the CMOS technology. The performances achieved using this device for hadrontherapy purpose are discussed. For each reconstruction step (clustering, tracking and vertexing), different methods are implemented. The algorithm performances and the accuracy on reconstructed observables are evaluated on the basis of simulated and experimental data

Estudio del período de vibración de puentes con vigas de acero en Panamá

In this article the main frequency of vibration obtained in 31 spans of steel beam bridges are presented, and studied together with other 25 steel beam bridges vibration frequencies presented in previous studies. An equation that estimates the main period of vibration as a function of the span length of these bridges is presented. Additionally, matching of frequency of vibration in adjacent spans with different lengths was observed in some non-continuous-beam multi-span bridges; this phenomena is considered to be related to forced vibration in the shorter spans caused by the natural vibration of the longest spans. In addition, an equation to estimate an upper bound period of vibration as a reference to identify atypical bridges, whose vibration periods are considerably far from the trend.En este artículo se presenta la frecuencia de vibración principal de 31 luces de puentes de viga de acero, y se estudian en conjunto con la frecuencia de vibración de otras 25 luces de puentes de acero presentadas en estudios anteriores. Se presenta una ecuación que estima el período de vibración principal en función de la longitud de la luz estudiada. En algunos puentes se observó una sincronización de la frecuencia de vibración en tramos adyacentes (los cuales presentan diferentes longitudes entre ellos) en puentes de varias luces con vigas no continuas; se propone que este fenómeno está relacionado con la vibración forzada en los tramos más cortos, causada​ por la vibración natural de las luces adyacentes más largas. Además, una ecuación para estimar el período de vibración que se puede utilizar como límite superior, una referencia para identificar puentes atípicos, cuyos períodos de vibración son considerablemente mayores a la tendenci

Influence of the electric field on the latent heat of the ferroelectric phase transition in KDP

The specific heat, heat flux (DTA trace) and dielectric constant of KDP ferroelectric crystal have been measured simultaneously for various electric fields with a conduction calorimeter. The specific heat presents a strong anomaly but these simultaneous measurements allow us to evaluate the latent heat accurately. Latent heat decreases with field and the value of critical electric field --that where latent heat disappears-- is estimated to be (0.44\pm0.03) kV/cm. Incidentally, we have measured simultaneously the dielectric permittivity which suggests that latent heat is developed as domains are growing.Comment: 7 pages, 6 figures, ReVTeX, twocolumn format, to appear in J. Phys. Cond. Matte

La comunicación en entornos simulados para el aprendizaje

El propósito de esta investigación es describir de qué manera los entornos virtuales de aprendizaje que integran simulaciones 3D favorecen la comunicación, interacción y colaboración de los estudiantes. Esta investigación utiliza una metodología cualitativa basada en la observación sistémica. Los resultados muestran que los estudiantes a partir de la experiencia en entornos de simulación 3D, pasan a ser agentes activos en la construcción de su proceso de aprendizaje. Los entornos de simulación 3D con mediación pedagógica favorecen la comunicación e interacción de los estudiantes en el contexto de la secuencia pedagógica planteada promoviendo el aprender de los estudiantes y generando dos tipos de comunicación: interacción entre participante y objeto 3D, e interacción entre participantes que se desarrolla más espontáneamente y en mayor cantidad

Mesiodistal sizes and intermaxillary tooth-size ratios of two populations; Spanish and Peruvian. A comparative study

Introduction: Adequate tooth-size ratios are required to ensure the satisfactory outcome of orthodontic treatment. Consequently, various methods of measuring tooth-size ratios have been developed being the Bolton ratio the most commonly accepted, known and used one. This ratio depending directly on mesiodistal tooth size has been associated with different ethnic backgrounds. Some authors suggest the need for specific standards for every population. Objectives: The objectives of our study were; to measure and to compare mesiodistal tooth sizes and the Anterior and Overall Bolton ratios in two different populations, one Peruvian and the other Spanish with the same digital method. Material and Methods: The sample included 149 individuals composed of two groups; 99 Spanish (mean age 14.19), 65 being females and 34 males and 50 Peruvian (mean age 14.46), 18 being males and 32 females. The mesiodistal sizes of each of the patients were measured using a digital method and the Anterior and Overall Bolton ratios were calculated. Results: Tooth size does indeed involve a strong ethnic component, and the Anterior Bolton ratio is specific for each ethnic group. Conclusions: The conclusions are; tooth sizes of the Peruvian population were greater than those of the Spanish population. The Anterior Bolton ratio of Peruvian individuals was greater than that of the Spanish, whereas no differences were found for Overall Bolton ratio. These differences suggest the need for specific standards for the Spanish and Peruvian population. © Medicina Oral S. L

Eficacia de la alta presión hidrostática como tratamiento cuarentenario para mejorar la calidad de los frutos del mango infestados por la mosca de la fruta Mexicana Anastrepha ludens

High hydrostatic pressure (HPP) has been reported as an alternative quarantine process in fruits infested by Ceratitis capitata Wiedemann, Rhagoletis indifferens Curran and Cydia pomonella (L.). In Mexico and other Latin-American countries, the Mexican fruit fly Anastrepha ludens Loew is one of the most important insects infesting mangoes, citrus, and other fruits. The present study aimed to determine the effect of pressure level and time on the survival of eggs and larvae of the Mexican fruit fly. Eggs and larvae were pressurized at 25, 50, 75, 100, or 150 MPa for 0, 5, 10 or 20 min at 25 8C. Ripe and green mangoes were also pressurized under the same conditions. On pressurized eggs of 1, 2, 3, and 4 days old, their ability to hatch was recorded. On pressurized first, second and third instars, the percentage of survival was registered. Furthermore, third instars were studied for their ability to pupate and to develop adults. The results showed that although most of eggs and larvae died at pressures lower than 100 MPa, some of them were able to survive even at 150 MPa, and a few third instars were able to pupate and to develop to adulthood. Green mangoes were affected by pressures above 75 MPa but they were more resistant than ripe mangoes. HPP treatments seem to be feasible as a quarantine process for mangoes; however, more studies, such as combining HPP with temperature treatments, are needed in order to decrease the pressure level to avoid fruit damageLa alta presión hidrostática ha sido descrita como un proceso de cuarentena alternativa en frutas infestadas por Ceratitis capitata Wiedemann, Rhagoletis indifferens Curran y Cydia pomonella (L.). En México y otros países Latinoamericanos, la mosca de la fruta mexicana Anastrepha ludens Loew es uno de los más importantes insectos que infestan los mangos, cítricos y otras frutas. El presente estudio tuvo como meta determinar el efecto del nivel de presión y tiempo sobre la supervivencia de huevos y larvas de la mosca de la fruta mexicana. Huevos y larvas se presurizaron a 25, 50, 75, 100, y 150 MPa durante 0, 5, 10, y 20 min a 25 8C. Mangos maduros y verdes también se presurizaron bajo las mismas condiciones. En huevos presurizados de uno, dos, tres y cuatro días de vida, se registró su capacidad para eclosionar. En primera, segunda y tercera etapa larvaria presurizada, el porcentaje de supervivencia también se registró. Además, en la tercera etapa larvaria se estudió su capacidad para salir de la crisálida y desarrollar adultos. Los resultados mostraron que aunque la mayoría de los huevos y larvas murieron a presiones por debajo de 100 MPa, algunos de ellos fueron capaces de sobrevivir aun a 150 MPa, y unas pocas larvas de tercera etapa fueron capaces de salir de la crisálida y desarrollar adultos. Los mangos verdes se vieron afectados por las presiones por encima de 75 MPa pero fueron más resistentes que los mangos maduros. Los tratamientos de alta presión hidrostática parecen ser un proceso viable como método cuarentenario para mangos, sin embargo, se necesitan más estudios tales como la combinación de alta presión hidrostática junto con tratamientos térmicos para disminuir los niveles de presión y evitar daños en la frutaThe authors are grateful to Fondo Mixto CONACYT –Gobierno del Estado de Tamaulipas for the financial support of this work (Project TAMPS-2003-C02-15), to CONACYT for the scholarship granted to author Hugo Ernesto CandelarioS