Investigation of gamma-ray sensitivity of neutron detectors based on thin converter films

Currently, many detector technologies for thermal neutron detection are in development in order to lower the demand for the rare 3He gas. Gas detectors with solid thin film neutron converters readout by gas proportional counter method have been proposed as an appropriate choice for applications where large area coverage is necessary. In this paper, we investigate the probability for gamma-rays to generate a false count in a neutron measurement. Simulated results are compared to measurement with a 10B thin film prototype and a 3He detector. It is demonstrated that equal gamma-ray rejection to that of 3He tubes is achieved with the new technology. The arguments and results presented here are also applicable to gas detectors with converters other than solid 10B layers, such as 6Li layers and 10BF3 gas.Comment: Submitted to Journal of Instrumentatio

Diseño e instalación de sistema de generación eléctrica por movimiento circular uniforme

El objetivo de este proyecto es exponer las características , diseño e implementación de un sistema de generación eléctrica utilizando el principio básico del funcionamiento de la bicicleta, este sistema de generación ya ha sido desarrollado anteriormente en algunas regiones de Colombia pero sin el enfoque que se le dará en la construcción de este proyecto, en algunos lugares del mundo existen empresas como lo es WE WATT que desarrolla sistemas de generación eléctrica renovable, más sin embargo los costos de adquisición son muy elevados. Luego de realizar una investigación sobre las principales propiedades del diseño del sistema de generación eléctrica por movimiento circular uniforme se implementó diferente software de diseño mecánico y eléctrico para garantizar el buen funcionamiento y eficiencia del sistema

Global trends in exposure to light pollution in natural terrestrial ecosystems

This is a freely-available open access publication. Please cite the published version which is available via the DOI link in this record.The rapid growth in electric light usage across the globe has led to increasing presence of artificial light in natural and semi-natural ecosystems at night. This occurs both due to direct illumination and skyglow - scattered light in the atmosphere. There is increasing concern about the effects of artificial light on biological processes, biodiversity and the functioning of ecosystems. We combine intercalibrated Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS) images of stable night-time lights for the period 1992 to 2012 with a remotely sensed landcover product (GLC2000) to assess recent changes in exposure to artificial light at night in 43 global ecosystem types. We find that Mediterranean-climate ecosystems have experienced the greatest increases in exposure, followed by temperate ecosystems. Boreal, Arctic and montane systems experienced the lowest increases. In tropical and subtropical regions, the greatest increases are in mangroves and subtropical needleleaf and mixed forests, and in arid regions increases are mainly in forest and agricultural areas. The global ecosystems experiencing the greatest increase in exposure to artificial light are already localized and fragmented, and often of particular conservation importance due to high levels of diversity, endemism and rarity. Night time remote sensing can play a key role in identifying the extent to which natural ecosystems are exposed to light pollution.European Research Council/ European Union’s Seventh Framework Programme (FP7/2007–2013

Spatial patterns of Anchoveta (Engraulis ringens) eggs and larvae in relation to p CO 2 in the Peruvian upwelling system

Large and productive fisheries occur in regions experiencing or projected to experience ocean acidification. Anchoveta (Engraulis ringens) constitute the world's largest single-species fishery and live in one of the ocean's highest pCO2 regions. We investigated the relationship of the distribution and abundance of Anchoveta eggs and larvae to natural gradients in pCO2 in the Peruvian upwelling system. Eggs and larvae, zooplankton, and data on temperature, salinity, chlorophyll a and pCO2 were collected during a cruise off Peru in 2013. pCO2 ranged from 167-1392 µatm and explained variability in egg presence, an index of spawning habitat. Zooplankton abundance explained variability in the abundance of small larvae. Within the main spawning and larva habitats (6-10°S), eggs were found in cool, low-salinity, and both extremely low (less than 200 µatm) and high (more than 900 µatm) pCO2 waters, and larvae were collected in warmer, higher salinity, and moderate (400-600 µatm) pCO2 waters. Our data support the hypothesis that Anchoveta preferentially spawned at high pCO2 and these eggs had lower survival. Enhanced understanding of the influence of pCO2 on Anchoveta spawning and larva mortality, together with pCO2 measurements, may enable predictions of ocean acidification effects on Anchoveta and inform adaptive fisheries management

Final Master\u27s Portfolio

Jonathan G. Correa\u27s Master\u27s Portfoli

Efectos de una zona urbana sobre la comunidad de macroinvertebrados bentónicos de un ecosistema fluvial del sur de Chile

Un cuerpo de agua dulce saludable puede proveer de numerosos beneficios a la sociedad, aunque actualmente la degradación de este tipo de ecosistemas se ha visto incrementada por el establecimiento de centros urbanos en sus riberas. En este estudio analizamos el efecto espacial de estas zonas sobre la calidad del agua, utilizando la comunidad de macroinvertebrados bentónicos como bioindicadores de contaminación fluvial en el canal Gibbs de la comuna de Temuco (38° 46' S 72° 38' W). Los muestreos fueron realizados en la época de primavera en seis sitios. El macrozoobentos estuvo compuesto por un total de 15 taxones, correspondientes a organismos tolerantes a condiciones de anoxia y a altas concentraciones de materia orgánica, tales como anfípodos (RyaleIla), dípteros (Quironomidae) y oligoquetos (Oligochaeta). Hubo una marcada diferencia en la composición y abundancia de taxones entre las zonas pre-urbana, urbana y post-urbana (ANOS1M R Global = 0.882; P = 0.001), tendencia que también fue registrada por los parámetros fisicoquímicos (ANOS1M R Global = 0.498; p = 0.001), de los cuales el pH, sólidos suspendidos totales y oxígeno disuelto son los que mejor explicaron los patrones observados en el macrozoobentos. Los resultados obtenidos con el índice biótico de familias (ChIBF) fueron similares a los registrados en las partes bajas de las cuencas del Sur de Chile y la comunidad de invertebrados demostró ser sensible a perturbaciones de origen antrópico.A healthy body of freshwater can provide numerous benefits to the society, although currentIy, the degradation of such ecosys­tems has been increased due to the establishment of urban areas along its riverbanks. In this study we analyzed the spatial effect of these zones on the water quality, using the benthonic macroinvertebrate communities as bioindicators of fluvial con­tamination in the Gibbs channel ofthe Temuco commune (38°46'S n038'W). The samplings were performed in spring, in six sites. The macrozoobentos was composed by a total of 15 taxa, corresponding to organisms tolerant to anoxic conditions and high concentrations of organic matter, such as amphipods (Hyalella), dipterans (Quironomidae), and oligochaetes (Oligochae­ta). There was a marked difference in the composition and abundance of taxa between the pre-urban, urban, and post-urban areas (ANOSIM Global R = 0.882,p = 0.001) tendency that was also recorded by the physicochemical parameters (ANOS 1M Global R = 0.498, p = 0.001), of which pR, total suspended solids, and dissolved oxygen are those that best explained the patterns observed in the macrozoobentos. The results obtained with the biotic family index (ChIBF) were similar to those registered in the lower parts of the basins of southern Chile and the invertebrate community was shown to be sensitive to anthropogenic disturbances

Deep-coverage whole genome sequences and blood lipids among 16,324 individuals.

Large-scale deep-coverage whole-genome sequencing (WGS) is now feasible and offers potential advantages for locus discovery. We perform WGS in 16,324 participants from four ancestries at mean depth >29X and analyze genotypes with four quantitative traits-plasma total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and triglycerides. Common variant association yields known loci except for few variants previously poorly imputed. Rare coding variant association yields known Mendelian dyslipidemia genes but rare non-coding variant association detects no signals. A high 2M-SNP LDL-C polygenic score (top 5th percentile) confers similar effect size to a monogenic mutation (~30 mg/dl higher for each); however, among those with severe hypercholesterolemia, 23% have a high polygenic score and only 2% carry a monogenic mutation. At these sample sizes and for these phenotypes, the incremental value of WGS for discovery is limited but WGS permits simultaneous assessment of monogenic and polygenic models to severe hypercholesterolemia