ABSTRACT
Objective:A two-dimensional (2D) in-house-built scintillator detection system (SDS) was utilized for quality assurance of the active spot scanning proton and heavy ion accelerator, aiming to establish a rapid detection method and provide reference for the quality of proton and heavy ion beam (spot position, spot size, virtual source-to-axis distance, profile depth dose distribution and beam range).Methods:The SDS consisted of a ceramic gadolinium-sulfoxylate phosphor-scintillating screen, a mirror and a commercial digital camera. The dose distribution image was obtained based on scintillator, mirror reflector and optical signal acquisition device to transform the proton and heavy ion beam into visible light through sulfur gadolinium oxide scintillator and collect visible light information to meet the clinical requirements for the quality of proton and heavy ion beam.Results:The deviation of spot position measured by multifilament proportional chamber and the SDS was less than 1mm. The differences of beam spot size measured by multifilament proportional chamber and the SDS were (1.40±0.59)mm for protons, and (0.5±0.08)mm for carbon ions. For 429.25MeV/u carbon, the virtual source-to-axis distance (V SAD) at the x-and y-axes was 751.8cm and 805.6cm. And difference between physical distance and virtual source-to-axis distance was less than 1%. The range of 287.5MeV/u carbon measured by SDS was 160mm. Conclusions:The in-house-built scintillator detector can measure beam spot position and size, virtual source, depth distribution curve and range, which can be used as an effective tool for quality assurance control of proton and heavy ion therapy.
ABSTRACT
Hermit crabs (Anomura: Paguroidea) distribution patterns in the Colombian Caribbean Sea. Hermit crabs represent the marine life in the Colombian Caribbean, and are important for the dynamic equilibrium maintenance in ecosystems, the ecological interactions and their impact on food web stability. Generally, in order to come up with some conservation strategies, strong bio-geographical information is needed for policies definition. With this aim, this study analyzed the distribution patterns of hermit crabs in the Colombian Caribbean Sea, through classification and spatial ordination multivariate analyses, using historical records from years 1916 to 2006. Besides, the world distribution of Colombian species and their geographic affinity in the Caribbean and Western Atlantic were identified. The results show deep differences between coastal and continental slope faunas, and latitudinal differences in the assemblages, with the identification of three groups: Northeast, Center and Southwest. The differences in faunal composition that support these three groups were determined. Based on maps of the Colombian marine ecosystems, it was found that the main factors affecting the distribution of hermit crabs were the Caribaná slope (depth), water-mass temperature, Guajira sea-grass beds, and particular conditions of “Coralline Archipelagos” and “Darién” eco-regions. Colombian hermit crab fauna is more related to the North Atlantic and the Antilles, than to the South Atlantic and the Gulf of Mexico. Additionally, geographical sub-provinces in which Colombia is included, these were found as transition zones among Northern and Austral subprovinces of the Greater Caribbean.
Los cangrejos ermitaños son un grupo representativo de la fauna marina del Caribe colombiano, además, son importantes en el mantenimiento del equilibrio dinámico, en los ecosistemas por sus interacciones ecológicas y también por el impacto en la estabilidad de las redes tróficas. Sus patrones de distribución se identificaron mediante análisis multivariados de clasificación y ordenación espacial, se usaron registros históricos desde 1916 hasta el 2006. Los resultados indican diferencias por profundidad entre la fauna costera y la del talud continental y diferencias en la distribución latitudinal, en donde se encontraron tres grupos: Noreste, Centro y Suroeste, sustentados por diferencias en la composición faunística. Con base en los mapas de ecosistemas marinos de Colombia, se determinó que los principales factores que afectan su distribución son la influencia del talud Caribaná (profundidad), la temperatura de las masas de agua, las praderas de pastos marinos de la Guajira y las condiciones particulares de las ecorregiones Archipiélagos coralinos y Darién. Se identificó la distribución mundial de las especies colombianas y su afinidad geográfica, y se encontró mayor afinidad con el Atlántico norte y las Antillas que con el Atlántico sur y el Golfo de México, asimismo, las subprovincias geográficas que incluyen a Colombia son zonas de transición dentro de la subprovincias septentrionales y australes del Gran Caribe.