Las nanoestructuras de ZnO y sus aplicaciones como sensor de gas H2S / The ZnO nanostructures and their applications as a H2S gas sensor

RESUMEN Existe un interés global en la detección de gases tóxicos, para la protección del medio ambiente y los seres humanos. Se han desarrollado múltiples estudios enfocados en el uso de sensores de gases basados en óxidos metálicos, como es el óxido de zinc (ZnO), el cual presenta propiedades electrónicas específicas como sensor de gases por ser un semiconductor tipo n y bajo costo de producción. El objetivo de este trabajo fue analizar el uso de nanoestructuras de ZnO, para la fabricación de sensores del gas ácido sulfhídrico (H2S), así como las técnicas de obtención más comunes de dichas estructuras. Las características de las nanoestructuras de óxido de zinc (NE´s-ZnO) varían por efecto del método de obtención, generando diferentes morfologías y tamaño, que impactan en la capacidad de detección de gas (0.5 ppm a 600 ppm) y en el rango de temperatura que se requiere. Los avances en la generación de diversas NE´s-ZnO facilitarán la posibilidad de generar sensores que puedan ser utilizados en detectores portátiles y operen a temperatura ambiente, lo cual es un reto actual.

ABSTRACT There is a global interest in the detection of toxic gases for the protection of the environment and human beings, using low-cost and easy-to-use sensors. Multiple studies have focused on the use of gas detectors based on metal oxides, such as zinc oxide (ZnO), which has specific electronic properties as a gas detector because it is an n-type semiconductor and it has a low production cost. The objective of this work was to analyze the use of ZnO nanostructures for the manufacturing of hydrogen sulfide (H2S) gas sensors, as well as the most common techniques for obtaining these structures. The characteristics of zinc oxide nanostructures (NE´s-ZnO) vary due to the effect of the obtaining method, generating different morphologies and sizes, which impacts gas detection performance (0.5 ppm up to 600 ppm) and in the temperature range that is required. Advances in the design of various NE's-ZnO will have the possibility of generating sensors that can be used in portable detectors and operate at room temperature, which is a current challenge.

Medicinal plant resources in Inner Mongolia autonomous region of China and Mongolia: a comparative study / 中国中药杂志

Inner Mongolia autonomous region of China and Mongolia are the primary regions where Chinese and Mongolian medicine and its medicinal plant resources are distributed. In this study, 133 families, 586 genera, and 1 497 species of medicinal plants in Inner Mongolia as well as 62 families, 261 genera, and 467 species of medicinal plants in Mongolia were collected through field investigation, specimen collection and identification, and literature research. And the species, geographic distribution, and influencing factors of the above medicinal plants were analyzed. The results revealed that there were more plant species utilized for medicinal reasons in Inner Mongolia than in Mongolia. Hotspots emerged in Hulunbuir, Chifeng, and Tongliao of Inner Mongolia, while there were several hotspots in Eastern province, Sukhbaatar province, Gobi Altai province, Bayankhongor province, Middle Gobi province, Kobdo province, South Gobi province, and Central province of Mongolia. The interplay of elevation and climate made a non-significant overall contribution to the diversity of plant types in Inner Mongolia and Mongolia. The contribution of each factor increased significantly when the vegetation types of Inner Mongolia and Mongolia were broadly divided into forest, grassland and desert. Thus, the distribution of medicinal plant resources and vegetation cover were jointly influenced by a variety of natural factors such as topography, climate and interactions between species, and these factors contributed to and constrained each other. This study provided reference for sustainable development and rational exploitation of medicinal plant resources in future.

Development of a semi-empirical method to determine the efficiency of a gamma radiation detector for point sources / Desarrollo de un método semi-empírico para determinar la eficiencia de un detector de radiación gamma para fuentes puntuales

Abstract In the present work, we introduce the theoretical development and a new approach to validate a novel method to calibrate the efficiency of a gamma radiation detector for point sources, which we have named the "Efficiency Extrapolation Method". The method consists in the determination of the detector efficiency using a set of monoenergetic gamma sources, which we will refer to as reference efficiencies. From these values, we will extrapolate the detector efficiency to the complete energy range using the first principle physics of gamma radiation detection theory. Therefore the proposed method corresponds to a semi-empirical one. The determination of reference efficiencies must be done experimentally, but in this work, simulations were performed using FLUKA code. The reference energies will be: 59,54 keV, 661,66 keV and 1 274,54 keV associated to the isotopes 241Am, 137Cs and 22Na respectively. The second part of the method, the extrapolation from the reference energies to the gamma range, will be done over the energies emitted by 152Eu and 133Ba. In general, the results are very good. While the obtained results for energies 53,16 keV and greater than 344,3 keV show an excellent agreement, the results obtained for energies in the middle range are only good.

Resumen En el presente trabajo presentamos el desarrollo teórico y un nuevo enfoque para validar un nuevo método para calibrar la eficiencia de un detector de radiación gamma para fuentes puntuales, al cual hemos llamado el método de extrapolación de la eficiencia. El método consiste en la determinación de la eficiencia del detector usando un conjunto de fuentes gamma monoenergéticas, a las cuales llamaremos eficiencias de referencia. Desde estos valores, extrapolaremos la eficiencia del detector al rango completo de energías usando la física de primeros principios de la teoría de detección de radiación gamma. Por lo tanto el método propuesto corresponde a un método semiempírico. La determinación de las eficiencias de referencia debe hacerse experimentalmente, pero en este trabajo, se realizaron simulaciones usando el código FLUKA. Las energías de referencia serán: 59,54 keV, 661,65 keV y 1 274,54 keV asociadas a los isótopos 241 Am, 137Cs y 22Na respectivamente. La segunda parte del método, la extrapolación desde las energías de referencia hacia el rango gamma de las energías, será realizada sobre las energías emitidas por los isótopos 152Eu y 133Ba. En general, los resultados son muy buenos. Mientras que los resultados obtenidos para las energías de 53,16 keV y mayores que 344,3 keV muestran un excelente acuerdo, los resultados obtenidos para las energías del rango intermedio son solo buenas.

Analysis of radiation effects on some properties of GaAs:Cr and Si sensors exposed to a 22 MeV electron beam / Análisis de los efectos de la radiación en algunas propiedades de sensores de GaAs:Cr y Si expuestos a un haz de electrones de 22 MeV

Abstract Nowadays, the experiments related to High Energy Physics and others fields demand the use of detectors with greater radiation resistance, and the novel material GaAs:Cr has demonstrated excellent radiation hardness compared with other semiconductors. On the basis of evidence obtained in the JINR experiment with the use of 22 MeV electrons beam generated by the LINAC-800 accelerator, an analysis of electron radiation effects on GaAs:Cr and Si detectors is presented. The measured I-V characteristics showed a dark current increase with dose, and an asymmetry between the two branches of behaviors for all detectors. Analyzing the MIP spectra and CCE dose dependence measurements a deterioration process of detectors collection capacity with dose increase was found, although behaviors are somewhat different according to the detector type. The detailed explanation of these effects from the microscopic point of view appears in the text, and are generally linked to the generation of atomic displacement, vacancies and other radiation defects, modifying the energy levels structure of the target material. These changes affect the lifetime and concentration of the charge carriers, and other characteristics of the target material.

Resumen Actualmente, los experimentos relacionados con la física de altas energías y otros campos, demandan el uso de detectores con mayor resistencia a las radiaciones y el novedoso material GaAs:Cr ha demostrado poseer una excelente fortaleza comparado con otros semiconductores. En base a las evidencias obtenidas en el experimento del IUIN con el uso de un haz de electrones de 22 MeV generado por el acelerador LINAC-800, se presenta un análisis de los efectos de la radiación en detectores de Si y GaAs:Cr. Las características I-V medidas mostraron un incremento de la corriente de fuga con la dosis y una asimetría entre las dos ramas de estos comportamientos para todos los detectores. Analizando las mediciones de los espectros MIP y la dependencia de la CCE con la dosis, fue encontrado un proceso de deterioro de la capacidad de detección de los detectores con el aumento de la dosis, sin embargo, los comportamientos son diferentes de acuerdo al tipo de detector. La explicación detallada de estos efectos desde el punto de vista microscópico aparece en el texto, los cuales están relacionados generalmente con la generación de desplazamientos atómicos, vacancias y otros defectos producto de la radiación, modificando la estructura de los niveles energéticos en el material sensor. Estos cambios afectan el tiempo de vida y la concentración de los portadores de carga, así como otras características del material.

Monte Carlo simulation of the radiation transport in chromium compensated gallium arsenide detectors / Simulación por Monte Carlo del transporte de las radiaciones en detectores dearseniuro de galio compensado con cromo

Abstract Some results obtained with the use of Monte Carlo mathematical simulation of radiation transport in Timepix hybrid detectors based on chromium compensated gallium arsenide are presented in this contribution. The MCNPX, GEANT4, SRIM and MCCM code systems were used for this purpose. The in-depth profiles of the deposited energy by the incident photons within the sensor active volume, the shapes and dimensions of the generated charge carriers clouds for different incident energies and specific geometrical conditions were obtained and presented. The 22Ne ions ranges in the target material for two different energies and the contributions of each energy loss channel were also determined. Finally, for a selected detector irradiated with photons of different energies, the displacement cross sections for each chemical element in the active material, as well as the number of displacements per atoms produced for each atomic species were calculated.

Resumen En este trabajo se presentan algunos de los resultados obtenidos con el uso de la modelación matemática por Monte Carlo del transporte de radiación en detectores híbridos Timepix basados en el arseniuro de galio compensado con cromo. Se emplearon para este propósito los sistemas de códigos MCNPX, GEANT4, SRIM y MCCM. Fueron obtenidos los perfiles en profundidad de la energía depositada por la radiación incidente dentro del volumen activo del sensor, las formas y dimensiones de las nubes de portadores de cargas generados por fotones incidentes de diferentes energías y condiciones geométricas específicas. También se determinaron los alcances de los iones de 22Ne de dos energías diferentes en el material blanco y las contribuciones de cada canal de pérdida de energía. Finalmente, para un detector seleccionado irradiado con fotones de diferentes energías se calcularon las secciones eficaces de desplazamiento para cada elemento químico en el material activo, así como el número de desplazamientos por átomos producidos para cada especie atómica.

Study of charge sharing effect and energy resolution of the Timepix hybrid detector based on gallium arsenide compensated with chromium / Estudio del efecto de compartición de cargas y la resolución energética del detector híbrido Timepix de arseniuro de galio compensado con cromo

Abstract Among the latest ionizing radiation detectors, those based on chromium compensated gallium arsenide (GaAs:Cr) are ones of the most competitive for many applications due to their high Z and strong resistance to radiation damage. They have been used in high energy physics research, medical visualization and spatial technologies, geological prospecting, among other advanced fields. The object of this work is a 900 µm GaAs:Cr detector with Timepix readout technology. Some detector characteristics for three experimental conditions were measured and studied by using the X-rays from a synchrotron and an X-ray tube provided with different materials for obtaining the corresponding fluorescence photons. A complex function was used to decompose the differential spectra into the most important contributions involved. As an additional tool for the research, the mathematical modeling of the mobility of charge carriers generated by radiation within the active volume of the detector was used. The results of these charge sharing effect studies showed a noticeable prevalence in the detector of this effect, changing its contribution according to the experiment characteristics. The detector was calibrated for the planned experiments and the energy resolution was determined. From the analysis of all the obtained results and their comparison with those reported in literature, it was confirmed that the detector has a marked charge-sharing effect between neighboring pixels, being its performance more impaired as the energy of incident photons increases.

Resumen Entre los últimos detectores de radiación ionizante, los basados ​​en arseniuro de galio compensado con cromo (GaAs: Cr) son de los más competitivos para muchas aplicaciones debido a su alto Z y fuerte resistencia al daño de la radiación. Se han utilizado en investigación de física de alta energía, visualización médica y tecnologías espaciales, prospección geológica, entre otros campos avanzados. El objeto de este trabajo es un detector de GaAs: Cr de 900 µm con tecnología de lectura Timepix. Algunas características del detector para tres condiciones experimentales se midieron y estudiaron utilizando rayos X de un sincrotrón y un tubo de rayos X provisto de diferentes materiales para obtener los fotones de fluorescencia correspondientes. Se utilizó una función compleja para descomponer los espectros diferenciales en las contribuciones más importantes involucradas. Como herramienta adicional para la investigación, se utilizó el modelado matemático de la movilidad de los portadores de carga generados por la radiación dentro del volumen activo del detector. Los resultados de estos estudios de efecto de carga compartida mostraron una prevalencia notable en el detector de este efecto, cambiando su contribución según las características del experimento. El detector se calibró para los experimentos planificados y se determinó la resolución de energía. A partir del análisis de todos los resultados obtenidos y su comparación con los reportados en la literatura, se confirmó que el detector tiene un marcado efecto de reparto de carga entre píxeles vecinos, y su rendimiento se ve más afectado a medida que aumenta la energía de los fotones incidentes.

The EXOTIC project at INFN-LNL / El proyecto EXOTIC en INFN-LNL

Abstract The low-energy light radioactive ion beam in-flight facility EXOTIC and the associated experimental set-up,operational at Legnaro National Laboratories of the National Institute of Nuclear Physics (LNL-INFN, Italy) and designed for nuclear physics and nuclear astrophysics experiments, were described. The outline of the experimental program carried out employing the produced radioactive ion beams was presented and the perspectives of the EXOTIC project were discussed.

Resumen Se describe la instalación EXOTIC de haz de iones radioactivos ligeros de baja energía en vuelo y la configuración experimental asociada, en operación en el Laboratorio Nacional de Legnaro del Instituto Nacional de Física Nuclear (LNL-INFN, Italia) y diseñada para experimentos de física nuclear y astrofísica nuclear. Se presenta el esquema del programa experimental llevado a cabo empleando los haces iónicos radioactivos producidos y se discuten las perspectivas del proyecto EXOTIC.

The “Warm Zone” Cases: Environmental Monitoring Immediately Outside the Fire Incident Response Arena by Firefighters

Hazardous work zones (i.e., hot, warm, and cold) are typically established by emergency response teams during hazardous materials (HAZMAT) callsbut less consistently for fire responses to segment personnel and response activities in the immediate geographic area around the fire. Despite national guidelines, studies have documented the inconsistent use of respiratory protective equipment by firefighters at the fire scene. In this case-series report, we describe warm zone gas levels using multigas detectors across five independent fire incident responses all occurring in a large South Florida fire department. Multigas detector data collected at each fire response indicate the presence of sustained levels of volatile organic compounds in the “warm zone” of each fire event. These cases suggest that firefighters should not only implement strategies for multigas detector use within the warm zone but also include respiratory protection to provide adequate safety from toxic exposures in the warm zone.

Estimation of the Optimal CA-CFAR Threshold Multiplier in Pareto Clutter with Known Parameters

The performance of the CA-CFAR processor is affected by certain clutter variations. Although problems caused by sudden clutter changes have already been corrected in multiple CFAR proposals, the influence of slow statistical variations in the background signal is often ignored. To solve this problem, the authors estimated the optimal CA-CFAR threshold multiplier values necessary to adapt the processor to the clutter slow statistical changes. The application of the results guarantees that the operational false alarm probability of the processor will only exhibit a small deviation from the value conceived in the design. The clutter was simulated with a Pareto distribution with a known fluctuating shape parameter according to recent papers that strongly suggest the use of this distribution. The current research completes an important step in the design of an adaptive detector that operates without a priori knowledge of the shape parameter In addition, the authors provide mathematical expressions that allow the direct application of the results in the design of radar detectors.

El desempeño del procesador CA-CFAR es afectado por ciertas variaciones del clutter Mientras que los problemas causados por los cambios repentinos del clutter han sido corregidos por múltiples propuestas CFAR, se ignora frecuentemente la influencia de las variaciones estadísticas lentas de la señal de fondo. Para resolver este problema, los autores estimaron los valores óptimos del multiplicador del umbral CA-CFAR necesarios para adaptar el procesador a los cambios estadísticos lentos, garantizando por tanto que la probabilidad de falsa alarma del detector exhibirá solamente una ligera desviación con respecto al valor concebido en el diseño. El clutter fue simulado con una distribución Pareto con parámetro de forma conocido de antemano, de acuerdo a publicaciones recientes que sugieren fuertemente el uso de esta distribución. La investigación actual completa un paso importante en el diseño de detectores adaptativos que operan sin el conocimiento a priori del parámetro de forma. Adicionalmente, los autores proporcionan expresiones matemáticas que permiten la aplicación directa de los resultados en el diseño de detectores de radar.

O desempenho do processador CA-CFAR está afectada por certas variações da desordem. Enquanto os problemas causados por mudanças bruscas de lixo foram corrigidos para múltiplas propostas CFAR, é muitas vezes ignorado a influ-ência de variações estatísticas lento do sinal de fundo. Para resolver esse problema, os autores estimaram os valores ideais do limiar necessário multiplicador CA-CFAR para adaptar o processador para retardar alterações estatísticas, garantizando, portanto, a probabilidade de falsa detector de alarme apenas um ligeiro desvio da valor concebido no design. A desordem foi simulado com um parâmetro de distribuição de Pareto conhecidos na maneira previamente, de acordo com publicações recentes que sugerem fortemente a utilização desta distribuição. A investigação actual complete um passo importante na concepção de detectores adaptativas que operam sem conhecimento a priori do parâmetro de forma. Addi-cionalmente, os autores fornecem expressões matemáticas que permitem a aplicação direta dos resultados do projeto de detectores de radar.

Detection and analysis of effect of geographical environmental factors on spatial distribution of artemisinic acid in Artemisia annua / 中国中药杂志

Dao-di herbs are preferred by long-term clinical application of Chinese medicine, they are produced in a specific area and affected by the specific production and processing methods. Dao-di herbs have a high reputation, compared with other regions produced by the same kind of herbs with good quality, good efficacy and stable quality characteristics. Geo-herbal is a unique concept that has been formed by the history of Chinese civilization for thousands of years and the history of Chinese medicine. According to the definition of geo-herbal, it can be seen that there are some differences in the quality and efficacy of the same kind of medicinal herbs in different regions, and there is some similarity in the specific area. In this study, based on the content of artemisinic acid in sampling points and its potential environmental factors, the effects of geographical environment factors on the spatial distribution of artemisinic acid content in Artemisia annua were studied by using the geophysical model. The results show that the spatial distribution of artemisinic acid content is the result of a combination of multiple factors. The effects of environmental factors on the spatial distribution of artemisinic acid were in the order of soil type (0.233)> radiation (0.208)> vegetation type (0.192)> elevation (0.171)> sunshine (0.170)> annual mean temperature (0.153) >annual precipitation (0.111)> slope (0.110)> relative humidity. Among them, the soil type and the amount of radiation are the main influencing factors, and the main influencing area is in the soil type as the initial soil and the average annual radiation of 1 200-1 400 kWh•m⁻². The main influencing factors selected in this study can be used to monitor the spatial distribution of artemisinic acid by remote sensing technology, so as to provide the theoretical basis for the cultivation of A. annua.

A comparative study of measurement of small field data and calculation based on Monte Carlo method / 中华放射肿瘤学杂志

Objective To compare the relative dose of small fields measured by clinically common detectors and those obtained from Monte Carlo simulation in order to obtain the accurate measurement method, and to modify the inappropriate detectors.Methods The percentage depth-dose distribution curve and profile (flatness and symmetry) curves were collected at 2 cm×2 cm, 3 cm×3 cm, and 4 cm×4 cm under 6-MV X-ray of Trilogy linear accelerator by CC13, PFD, SFD, and blue phantom.The results were compared with the stimulation results from Monte Carlo method (the current gold standard).The correction factors for the detectors with large error were calculated to provide reference data for clinical practice.Results The results measured by SFD detector were most close to the results from Monte Carlo simulation.The measurement errors of CC13 and PFD detectors were large.The correction factor in the penumbra for CC13 and PFD detector was 0.664-1.499.Conclusions SFD detector is better than CC13 and PFD detector in the measurement of small fields, but CC13 and PFD detector can provide reference data for clinical practice after the corresponding correction.

Determination of 20(R)-25-OH-PPT in different parts of species in Panax Linn. by HPLC-ELSD methods / 中草药

Objective: For making full use of our country's rich ginseng resources to look for 25-OH-PPT\ and provide the scientific basis for the innovation and development of ginsenoside hypoglycemic activity. Methods: Using chromatographic column Agilent C18 (250 mm × 4.6 mm, 5 μm); mobile phase was CH3OH-H2O (70:30); Column temperature was 35 ℃; Flow rate was 1.0 mL/min; the boiling chamber temperature of ELSD was 87 ℃; Flow rate of carrier gas was 2.20 L/min; injection volume was 10 μL. Using acetone as the solvent and ultrasonic extraction to extract the medicinal materials, then using the HPLC-ELSD method to determine the contents of 20(R)-25-OH-PPT in different parts of plants in Panax ginseng. Results: 20(R)-25-OH-PPT had a good linear relationship when the concentration was 0.001-0.05 mg/mL. The 20(R)-25-OH-PPT contents in gingseng cauline leaf, gingseng root, gingseng fruit, gingseng flower, cauline leaf of American ginseng, root of American ginseng, and the basal part of stem of P. notoginseng were 3.74%, 2.59%, 0.40%, 2.37%, 0.68%, 0.22%, and 0.39%. The recovery rates were 98.54%, 97.54%, 100.35%, 101.46%, 97.46%, 99.14%, and 99.38%. Conclusion :25(R)-OH-PPT exists in different parts of P. ginseng, and it can be an important basis for the use and development of ginsenoside with hypoglycemic activity.

Monte Carlo simulation of the efficiency response of a well-type HPGe detector at 46.54 keV / Simulación por Monte Carlo de la respuesta en eficiencia de un detector HPGe tipo pozo a la energía de 46.54 keV

In this paper, we used the Monte Carlo simulations method in a well-type HPGe detector using directly the manufacturer supplied data in order to simulate the effi ciency response at 46.54 keV. The efficiency values were calculated as a function of the fi lling height of the sample into the measurement geometry and results were found in good agreement with experimental data. The main deviations were less than 2.5 % with a mean of 0.9 %, which is totally satisfactory for the purposes of environmental samples measurements. We also present a brief discussion about the response of the detector to different values of its geometric parameters.

En el trabajo se utilizaron los métodos de simulación por Monte Carlo en un detector HPGe tipo pozo, usando directamente los parámetros del fabricante para simular la respuesta en eficiencia a la energía de 46.54 keV. Los valores de efi ciencia se calcularon en función de la altura de la muestra en la geometría de medición y los resultados se correspondieron con los valores experimentales. Las mayores diferencias fueron menores que el 2.5 % con un promedio de 0.9 %, lo que es totalmente satisfactorio para la medición de muestras ambientales. Se presentó una breve discusión sobre la respuesta del detector para diferentes parámetros geométrico.

Aplicación de un modelo de un acelerador Elekta Precise basado en Monte Carlo para la evaluación de la respuesta de detectores de estado sólido / Application of an Elekta Precise lineal accelerator model based on Monte Carlo to evaluate the solid state detectors response

En el trabajo se realizó el análisis de la respuesta de diferentes detectores de estado sólido a partir de un modelo de Monte Carlo de un acelerador lineal Elekta Precise, para los haces de energías de 6 MV y 15 MV. Para ello se realizaron simulaciones con el código EGSnrc. Se calculó la dosis depositada en un maniquí de agua voxelizado con su superficie a 100 cm de la fuente, empleando los valoresóptimos de energía media y FWHM del haz primario de electrones para este modelo. A partir de la dosis depositada en el maniquí se construyeron las curvas de dosis en profundidad y perfiles de dosis a diferentes profundidades. Las curvas se compararon con valores medidos para cada detector empleado en un arreglo experimental similar a la simulación realizada, aplicando criterios de aceptabilidad basados en intervalos de confianza. De forma adicional se analizó para cada caso la dosis en función del tamaño de campo. Se obtuvo una buena correspondencia entre las simulaciones y las mediciones, encontrándose todos los resultados dentro de los márgenes de tolerancia.

The evaluation of the solid state detectors response based on a Monte Carlo model of an Elekta Precise lineal accelerator, was done in this work for the beam energies of 6 y 15 MV. Simulations were performed using the EGSnrc code. Employing the optimal values of mean energy and FWHM from the primary electron beam, deposited dose in a voxelized water phantom at 100 cm of source to surface distance was calculated. Depth dose curves and lateral dose profi les were obtained. Comparison between simulations and the experimental values obtained for each detector, were done using acceptability criteria based on confi dence limits. Additionally outputs factors were analyzed in each one of the study cases. Good agreement between simulations and measurements were reached.

Indoor ²²²Rn levels and effective dose estimation of academic staff in İzmir, Turkey / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the annual effective doses from indoor radon received by academic staff in the Faculty building.</p><p><b>METHODS</b>Measurements of indoor radon concentrations were performed in the Arts and Sciences Faculty of Dokuz Eylül University for two surveys of about 1 month duration respectively using the SSNTD (Solid State Nuclear Track Detectors) method with LR115 detectors. Time integrated measurements comprised different locations inside the faculty building: classrooms, toilets, canteen and offices. Homes of academic staff were also tested for radon.</p><p><b>RESULTS</b>The arithmetic mean radon concentration is 161 Bq m-3 with a range between 40 and 335 Bq m-3 in the Faculty. Six offices and three classrooms have a radon concentration above 200 Bq m-3. The results show that the radon concentration in classrooms is generally higher than in offices. Based on the measured indoor radon data, the annual effective doses received by staff in the Faculty were estimated to range from 0.79 to 4.27 mSv, according to UNSCEAR methodology. The annual effective doses received by staff ranged from 0.78 to 4.20 mSv in homes. On average, the Faculty contributed 56% to the annual effective dose.</p><p><b>CONCLUSION</b>Reported values for radon concentrations and corresponding doses are within the ICRP recommended limits for workplaces.</p>

Detectores y aceleradores que curan / Curing detectors and accelerators / Detectores e aceleradores que curam

Los aceleradores y los detectores utilizados en las investigaciones en física de partículas sirven y han servido desde hace más de 100 años para la detección y cura de enfermedades. Gracias a los avances en la física experimental de partículas, se han desarrollado a lo largo de los años aceleradores más potentes y sistemas de detección más precisos y sofisticados. Estos, conjuntamente con los modernos sistemas de cómputo, han permitido aplicaciones hasta hace poco tiempo impensadas en la medicina. En este trabajo se esboza la historia de estos instrumentos, sus principios de funcionamiento y sus ventajas en las aplicaciones médicas, especialmente en el campo de la detección y tratamiento de tumores.

Accelerators and detectors used in particle physics research have been used for more than 100 years for detection and cure of diseases. Thanks to the progress in experimental particle physics, more powerful accelerators and more precise and sophisticated systems have been developed. These, together with modern computation systems have enabled applications in medicine not even thought of until recently. This work outlines the history of these instruments, their working principles and advantages for health applications, especially in the field of tumor detection and treatment.

Os aceleradores e os detectores utilizados nas pesquisas em física de partículas servem e têm servido já faz mais de 100 anos para a detecção e cura de doenças. Devido aos avanços na física experimental de partículas, aceleradores mais potentes e sistemas de detecção mais precisos e sofisticados têm sido desenvolvidos ao longo dos anos. Eles, junto com os modernos sistemas de cômputo, permitiram aplicações até pouco tempo atrás impensadas em medicina. Neste trabalho esboçamos a história destes instrumentos, seus princípios de funcionamento e suas vantagens nas aplicações médicas, especialmente no campo da detecção e tratamento de tumores.

Analysis of international intercomparisons results organized by Japan for integrating 222Rn-220Rn detectors / 中华放射医学与防护杂志

Objective To guarantee the quality of measurenents with the radon-thoron discriminative detectors of our laboratory.Methods LD-P radon-thoron discriminative detector participated in the international intercomparison for integrating radon/thoron detectors organized by National Institute of Radiological Science (NIRS,Japan).Detectors were sent to NIRS for exposure.Radon intercomparison was conducted with radon chamber providing three levels of exposure:low,medium and high levels.Thoron intercomparison was carried out at thoron chamber,which also provided three levels of exposure:low,medium and high levels.Detectors were posted back to our laboratory for etching and analysis after exposure.Then the measured values were submitted to NIRS.Finally the reference values were informed of us.Results The relative percent difference (RPD) between the measured value and the reference value for radon was-13.8％,-14.4％ and-17.1％ at low,medium and high levels respectively,and that of thoron were-14.4％,8.9％ and-3.2％ at three levels respectively.Conclusions Both radon and thoron measurement of our detectors rank asCategory Ⅰ in the 4th international intercomparisons for integrating radon/thoron detectors with the NIRS radon/thoron chambers.

Simulation and evaluation of the absorption edge subtraction technique in energy-resolved X-ray radiography applied to the cultural heritage studies / Simulación y evaluación de la técnica de sustracción del borde de absorción en un sistema radiográfico espectrométrico destinado al estudio del patrimonio cultural

ABSTRACT In this work the mathematical simulation of photon transport in the matter was used to evaluate the potentials of a new energy-resolved X-ray radiography system. The system is intended for investigations of cultural heritage object, mainly painting. The radiographic system uses polychromatic radiation from an X-ray tube and measures the spectrum transmitted through the object with an energy-dispersive X-ray detector on a pixel-by-pixel basis. Manipulation of the data-set obtained allows constructing images with enhanced contrast for certain elements. Here the use of the absorption edge subtraction technique was emphasized. The simulated results were in good agreement with the experimental data.

RESUMEN En este trabajo se utilizó la simulación matemática del transporte de los fotones en la materia para evaluar las potencialidades de un nuevo sistema radiográfico destinado al estudio de obras del patrimonio cultural. Este sistema emplea una fuente de rayos X no monocromática y mide a nivel de píxel el espectro transmitido a través del objeto en estudio con un detector espectrométrico. El procesamiento del conjunto de datos obtenidos permite la construcción de imágenes con contraste realzado para ciertos elementos. En el presente trabajo se enfatizó en el uso de la técnica de sustracción del borde de absorción para el procesamiento de las imágenes. Los resultados de las simulaciones resultaron consistentes con las mediciones experimentales.

Estudio de la eficiencia cuántica de un detector de microbandas de silicio mediante la modelación matemática / Study of silicon microstrips detector quantum efficiency using mathematical simulation

RESUMEN Se presentan los resultados en la aplicación de la simulación matemática para el estudio de la eficiencia cuántica de un detector de silicio cristalino del tipo microbandas, destinado a imagenología médica y al desarrollo de otras aplicaciones como la autenticación y fechado de obras de arte. Se evaluó el efecto de la geometría fuente-detector, de la energía de los rayos X y del grosor de la zona muerta del detector en la eficiencia cuántica de este dispositivo. Los resultados de la simulación se compararon con el pronóstico teórico y con los datos experimentales disponibles, verificándose una adecuada correspondencia. Se concluyó que la configuración frontal es más eficiente para energías incidentes menores a los 17 keV, y que la configuración de borde es la recomendada para aplicaciones que requieran la detección de energías superiores a este valor. También se determinó que la disminución de la zona muerta del detector conduce a un considerable aumento de la eficiencia para cualquier valor de energía en el intervalo de 5 a 100 keV.

ABSTRACT The paper shows the results from the application of mathematical simulation to study the quantum efficiency of a microstrips crystalline silicon detector, intended for medical imaging and the development of other applications such as authentication and dating of cultural heritage. The effects on the quantum efficiency of some parameters of the system, such as the detector-source geometry, X rays energy and detector dead zone thickness, were evaluated. The simulation results were compared with the theoretical prediction and experimental available data, resulting in a proper correspondence. It was concluded that the use of frontal configuration for incident energies lower than 17 keV is more efficient, however the use of the edge-on configuration for applications requiring the detection of energy above this value is recommended. It was also found that the reduction of the detector dead zone led to a considerable increase in quantum efficiency for any energy value in the interval from 5 to 100 keV.

Physical principles of digital radiographic imaging system / 대한구강악안면방사선학회지

Digital radiographic systems allow the implementation of a fully digital picture archiving and communication system (PACS), and provide the greater dynamic range of digital detectors with possible reduction of X-ray exposure to the patient. This article reviewed the basic physical principles of digital radiographic imaging system in dental clinics generally. Digital radiography can be divided into computed radiography (CR) and direct radiography (DR). CR systems acquire digital images using phosphor storage plates (PSP) with a separate image readout process. On the other hand, DR systems convert X-rays into electrical charges by means of a direct readout process. DR systems can be further divided into direct and indirect conversion systems depending on the type of X-ray conversion. While a direct conversion requires a photoconductor that converts X-ray photons into electrical charges directly, in an indirect conversion, light-sensitive sensors such as CCD or a flat-panel detector convert visible light, proportional to the incident X-ray energy by a scintillator, into electrical charges. Indirect conversion sensors using CCD or CMOS without lens-coupling are used in intraoral radiography. CR system using PSP is mainly used in extraoral radiographic system and a linear array CCD or CR sensors, in panoramic system. Currently, the digital radiographic system is an important subject in the dental field. Most studies reported that no significant difference in diagnostic performance was found between the digital and conventional systems. To accept advances in technology and utilize benefits provided by the systems, the continuous feedback between doctors and manufacturers is essential.