844 resultados para Expanded Bed Chromatography
Resumo:
Se analiza como se trata el tema del desplazamiento, cuestión clave en la literatura post-colonial, en dos historias cortas de las escritoras caribeñas Merle Collin y Maureen Ismay, principalmente a través de la problemática de género, raza, y la relación madre-hija, metrópoli-colonia, así como la cuestión linguística.
Resumo:
Descubre quince maneras de ir a la cama en esta colección de poemas, que muestra los múltiples enredos, batallas, juegos y sorpresas en torno a la rutina diaria de acostarse.
Resumo:
Varias historietas de humor absurdo sobre la cama. Cuando un niño se despierta en su cama, comprueba que a ésta le han crecido alas y puede volar. El niño en su cama sobrevuela tejados y calles. Llega tan lejos que, desde el cielo ve los barcos de pesca cruzando el mar.
Resumo:
A Molly le encanta jugar. Juega a caballo. Juega a hacer un dinosaurio. Así que cuando su madre dice: Molly, ordena, ella nunca tiene tiempo para hacerlo, pero todo termina siempre limpio y ordenado. Es magia, o hay un pulpo que le gusta la casa y que vive bajo la cama. Molly está decidida a averiguarlo.
Resumo:
Historia de una niña haciendo lo mejor que puede en un implacable mundo donde las cosas nunca son realmente como deberían ser. Elsa y su familia vivían en una hermosa casa, pero su padrastro perdió su puesto de trabajo y ahora viven en una habitación familiar en el Royal Hotel. Lo que significa que ella, mamá, Mack, y su hermana pequeña Pippa y Hank están abarrotados en la habitación y esto realmente llega a atacar los nervios. Ella cuenta chistes y hace bromas todo el tiempo, para intentar hacer reír a la gente, aunque no siempre es fácil. Pero cuando ocurre un desastre en el hotel, Elsa tiene la oportunidad de ser una verdadera estrella. Para ocho a diez años.
Resumo:
Se basa en una canción tradicional. Cuenta cómo un niño llega a abordar el problema de dormir con demasiados juguetes. El texto permite a los niños seguir la rima fácilmente. Para aprender los primeros números y contar hasta diez. Para identificar a los animales de peluche e imitar sus sonidos. Para la lectura en grupo, individual o en parejas.
Resumo:
Se basa en una canción tradicional. Cuenta cómo un niño llega a abordar el problema de dormir con demasiados juguetes. El texto permite a los niños seguir la rima fácilmente. Para aprender los primeros números y contar hasta diez. Para identificar a los animales de peluche e imitar sus sonidos. Para la lectura en grupo, individual o en parejas.
Resumo:
Aquatic sediments often remove hydrophobic contaminants from fresh waters. The subsequent distribution and concentration of contaminants in bed sediments determines their effect on benthic organisms and the risk of re-entry into the water and/or leaching to groundwater. This study examines the transport of simazine and lindane in aquatic bed sediments with the aim of understanding the processes that determine their depth distribution. Experiments in flume channels (water flow of 10 cm s(-1)) determined the persistence of the compounds in the absence of sediment with (a) de-ionised water and (b) a solution that had been in contact with river sediment. In further experiments with river bed sediments in light and dark conditions, measurements were made of the concentration of the compounds in the overlying water and the development of bacterial/algal biofilms and bioturbation activity. At the end of the experiments, concentrations in sediments and associated pore waters were determined in sections of the sediment at 1 mm resolution down to 5 mm and then at 10 mm resolution to 50 mm depth and these distributions analysed using a sorption-diffusion-degradation model. The fine resolution in the depth profile permitted the detection of a maximum in the concentration of the compounds in the pore water near the surface, whereas concentrations in the sediment increased to a maximum at the surface itself. Experimental distribution coefficients determined from the pore water and sediment concentrations indicated a gradient with depth that was partly explained by an increase in organic matter content and specific surface area of the solids near the interface. The modelling showed that degradation of lindane within the sediment was necessary to explain the concentration profiles, with the optimum agreement between the measured and theoretical profiles obtained with differential degradation in the oxic and anoxic zones. The compounds penetrated to a depth of 40-50 rum over a period of 42 days. (C) 2004 Society of Chemical Industry.
Resumo:
Bed-sediments are a sink for many micro-organic contaminants in aquatic environments. The impact of toxic contaminants on benthic fauna often depends on their spatial distribution, and the fate of the parent compounds and their metabolites. The distribution of a synthetic pyrethroid, permethrin, a compound known to be toxic to aquatic invertebrates, was studied using river bed-sediments in lotic flume channels. trans/cis-Permethrin diagnostic ratios were used to quantify the photoisomerization of the trans isomer in water. Rates were affected by the presence of sediment particles and colloids when compared to distilled water alone. Two experiments in dark/light conditions with replicate channels were undertaken using natural sediment, previously contaminated with permethrin, to examine the effect of the growth of an algal biofilm at the sediment-water interface on diffusive fluxes of permethrin into the sediment. After 42 days, the bulk water was removed, allowing a fine sectioning of the sediment bed (i.e., every mm down to 5 mm and then 5-10 mm, then every 10 mm down to 50 mm). Permethrin was detected in all cases down to a depth of 5-10 mm, in agreement with estimates by the Millington and Quirk model, and measurements of concentrations in pore water produced a distribution coefficient (K-d) for each section, High K-d's were observed for the top layers, mainly as a result of high organic matter and specific surface area. Concentrations in the algal biofilm measured at the end of the experiment under light conditions, and increases in concentration in the top 1 mm of the sediment, demonstrated that algal/bacterial biofilm material was responsible for high K-d's at the sediment surface, and for the retardation of permethrin diffusion. This specific partition of permethrin to fine sediment particles and algae may enhance its threat to benthic invertebrates. In addition,the analysis of trans/cis-permethrin isomer ratios in sediment showed greater losses of trans-permethrin in the experiment under light conditions, which may have also resulted from enhanced biological activity at the sediment surface.
Resumo:
The beds of active ice streams in Greenland and Antarctica are largely inaccessible, hindering a full understanding of the processes that initiate, sustain and inhibit fast ice flow in ice sheets. Detailed mapping of the glacial geomorphology of palaeo-ice stream tracks is, therefore, a valuable tool for exploring the basal processes that control their behaviour. In this paper we present a map that shows detailed glacial geomorphology from a part of the Dubawnt Lake Palaeo-Ice Stream bed on the north-western Canadian Shield (Northwest Territories), which operated at the end of the last glacial cycle. The map (centred on 63 degrees 55 '' 42'N, 102 degrees 29 '' 11'W, approximate scale 1:90,000) was compiled from digital Landsat Enhanced Thematic Mapper Plus satellite imagery and digital and hard-copy stereo-aerial photographs. The ice stream bed is dominated by parallel mega-scale glacial lineations (MGSL), whose lengths exceed several kilometres but the map also reveals that they have, in places, been superimposed with transverse ridges known as ribbed moraines. The ribbed moraines lie on top of the MSGL and appear to have segmented the individual lineaments. This indicates that formation of the ribbed moraines post-date the formation of the MSGL. The presence of ribbed moraine in the onset zone of another palaeo-ice stream has been linked to oscillations between cold and warm-based ice and/or a patchwork of cold-based areas which led to acceleration and deceleration of ice velocity. Our hypothesis is that the ribbed moraines on the Dubawnt Lake Ice Stream bed are a manifestation of the process that led to ice stream shut-down and may be associated with the process of basal freeze-on. The precise formation of ribbed moraines, however, remains open to debate and field observation of their structure will provide valuable data for formal testing of models of their formation.