GeSn/Ge heterostructure short-wave infrared photodetectors on silicon

status: publishe

Results of an international phosphorus digestibility ring test with broiler chickens

The objective of this ring test was to investigate the prececal phosphorus (P) digestibility of soybean meal (SBM) in broiler chickens using the trial protocol proposed by the World's Poultry Science Association. It was hypothesized that prececal P digestibility of SBM determined in the collaborating stations is similar. Three diets with different inclusion levels of SBM were mixed in a feed mill specialized in experimental diets and transported to 17 collaborating stations. Broiler chicks were raised on commercial starter diets according to station-specific management routine. Then they were fed the experimental diets for a minimum of 5 d before content of the posterior half of the ileum was collected. A minimum of 6 experimental replicates per diet was used in each station. All diets and digesta samples were analyzed in the same laboratory. Diet, station, and their interaction significantly affected (P < 0.05) the prececal digestibility values of P and calcium of the diets. The prececal P digestibility of SBM was determined by linear regression and varied among stations from 19 to 51%, with significant differences among stations. In a subset of 4 stations, the prececal disappearance of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate)-P; InsP6-P) also was studied. The prececal InsP6-P disappearance correlated well with the prececal P digestibility. We hypothesized that factors influencing InsP6 hydrolysis were main contributors to the variation in prececal P digestibility among stations. These factors were probably related to the feeding and housing conditions (floor pens or cages) of the birds in the pre-experimental phase. Therefore, we suggest that the World's Poultry Science Association protocol for the determination of digestible P be should extended to the standardization of the pre-experimental period. We also suggest that comparisons of P digestibility measurements among studies are made only with great caution until the protocol is more refined

La decisione di significare. Il libro 'Gamma' della 'Metafisica', testo critico, commentario

Traduzione dal greco all'italiano di S. Maso. Saggio introduttivo di B.Cassin. Edizione del testo greco di B. Cassin e M. Narc

Sb-based laser sources grown by molecular beam epitaxy on silicon substrates

International audienc

Sistemas de lagunaje como tecnología alternativa para el tratamiento de aguas residuales: vigencia de esta técnica en Costa Rica

Los sistemas de lagunaje son una tecnología ampliamente utilizada a nivel mundial para para el tratamiento de las aguas residuales, especialmente en pequeñas poblaciones y zonas rurales. Actualmente el reto en su funcionamiento consiste en maximizar la eficiencia para recibir cargas altas y potenciar el aprovechamiento biotecnológico de las algas que proliferan en este tipo de sistemas. En el presente estudio se presenta el análisis de un sistema de lagunas para el tratamiento de aguas residuales, ubicado en Costa Rica, que recibe aguas residuales domésticas. El sistema se estudió en cuanto a la remoción individual de contaminantes en cada una de las lagunas que lo componen y se identificaron los principales tipos de algas presentes en las aguas residuales dentro de la misma. Se observó una remoción alta especialmente de materia orgánica y la presencia de algas con un papel relevante a nivel de su aprovechamiento biotecnológico.Wastewater treatment ponds are a sanitation technology used worldwide especially in small towns and rural areas. The current challenge in its operation is to maximize efficiency, to receive high loads and enhance the biotechnological use of the algae that proliferate in this type of system. This study presents the analysis of a domestic wastewater treatment pond, located in Costa Rica. The system was studied in terms of the individual removal of contaminants in each of the ponds and the main types of algae present in wastewater. It was observed a high removal especially of organic matter and the presence of algae with a relevant biotechnological use.Universidad Nacional, Costa RicaEscuela de Ciencias BiológicasEscuela de Químic

Brief Assessment of the Presence of Diatoms and Their Relationship with Some Physical and Chemical Parameters in the Pirro River, Heredia, Costa Rica

La evaluación de la calidad de agua en ecosistemas fluviales en áreas urbanas en el trópico, basada en la utilización de diatomeas, es escasa. Este estudio exploratorio pretendió establecer la composición y riqueza de especies de diatomeas en relación con los parámetros físicos químicos como elemento base para un monitoreo de la microcuenca urbana del río Pirro, Heredia, Costa Rica. Los materiales se colectaron en la parte alta, media y baja del río durante la época seca, lluviosa y de transición. Se analizó el pH, el oxígeno disuelto, la conductividad, la temperatura y la composición de diatomeas raspando una superficie de 20 cm x 20 cm de rocas. Se observaron 18 especies de diatomeas con poca abundancia, con presencia de Navicula seminulum, N. minima y N. cryptotenella que son indicadoras de condiciones moderadas de contaminación y del género Nitzschia que presenta especies tolerantes a contaminantes. La mayor diversidad de especies de diatomeas ocurrió en la época lluviosa y se observaron diferencias significativas entre las épocas del muestreo y la riqueza de especies. Se concluye, con base en la presencia de especies, que el río Pirro presenta condiciones sanitarias malas y que el cauce bajo es el sitio más afectado por la contaminación. Pero es necesario aumentar la información en esta temática.The assessment of water quality in river ecosystems located in urban areas in the tropics based on the use of diatoms is scarce. This exploratory study aimed to establish the composition and species richness of diatoms in relation to physicochemical parameters as base element for monitoring the Pirro urban micro-watershed river in Heredia, Costa Rica. Materials were collected in the upper, middle, and lower river during dry, rainy, and transitional seasons. Dissolved oxygen, pH, conductivity, temperature, and composition diatomaceous were evaluated by scraping an area of 20 cm x 20 cm rocks. 18 diatom species with low abundance such as Navicula seminulum, N. minimum and N. cryptotenella were observed. These are indicatives of moderate conditions of pollution; others kinds, such as Nitzschia, display tolerant species to contaminants. The greatest diversity of species of diatoms occurred in the rainy season, and significant differences between sampling season and species richness were observed. In conclusion, Pirro river has poor sanitary conditions based on the presence of many different species, and the low channel of the river is the most affected by pollution. However, it is necessary to boost the information on this subject.Universidad Nacional, Costa RicaEscuela de Ciencias Biológica