Stress compensation by gap monolayers for stacked InAs/GaAs quantum dots solar cells

In this work we report the stacking of 10 and 50 InAs quantum dots layers using 2 monolayers of GaP for stress compensation and a stack period of 18 nm on GaAs (001) substrates. Very good structural and optical quality is found in both samples. Vertical alignment of the dots is observed by transmission electron microscopy suggesting the existence of residual stress around them. Photocurrent measurements show light absorption up to 1.2 μm in the nanostructures together with a reduction in the blue response of the device. As a result of the phosphorus incorporation in the barriers, a very high thermal activation energy (431 meV) has also been obtained for the quantum dot emission

Microhabitat heterogeneity promotes soil fertility and ground-dwelling arthropod diversity in Mediterranean wood-pastures

P. 192-201Mediterranean wood-pastures are extensive agroforestry systems that hold great ecological, social and cultural values, which consist of mixtures of grassland, scattered trees and shrubs, primarily used for livestock grazing. For centuries, low-intensity management in these landscapes has resulted in multiple microhabitats that favour biodiversity and are considered key elements for the long-term persistence of wood-pastures. However, the relative contribution of each microhabitat type to wood-pasture biodiversity and functioning remains poorly studied. We investigated the impact that different wood-pasture microhabitats have on soil chemical fertility and the decomposition food web. We analysed the two main microhabitats that make wood-pastures up – open grasslands and isolated trees – and three additional “litter-trapping” microhabitats – shrubs scattered in the grassland matrix, canopied shrubs and piles of pruning debris—in terms of soil chemical properties (organic matter content, total N, C:N ratio, available P, and exchangeable base cations), collembolan and dipteran (mostly detritivores) abundance, and carabid (seed-eaters and predators) and staphylinid (mostly predators) beetle abundance, body size, biomass, species richness and composition. Grasslands were the most different microhabitats, with the lowest soil nutrient content and particular carabid and staphylinid species composition. Trees had the highest soil fertility levels and abundance of Diptera and staphylinids, and held unique staphylinid assemblages. “Litter-trapping” microhabitats had medium to high soil nutrient values and shared a distinct staphylinid assemblage compared to grasslands and trees. Besides, scattered shrubs provided shelter for large-sized carabid and staphylinid predators, while canopied shrubs held the highest carabid abundance and biomass. “Litter-trapping” microhabitats retained tree leaves that would otherwise be lost to the wood-pasture, recovering nutrients to the system, and provided new habitat, shelter and food for detritivores and unique predator assemblages. “Litter-trapping” microhabitats thus enhanced soil fertility and the decomposition process, at the same time as increased the abundance and diversity of the communities of ground-dwelling detritivores and predators inhabiting wood-pastures. These findings confirmed that microhabitat heterogeneity resulting from low-intensity management is essential to maintain both the primary production and the biodiversity conservation value of wood-pastures.S

Slope-shelf faunal link and unreported diversity off Nova Scotia: Evidence from polychaete data

Deep-water sedimentary habitats off Nova Scotia have only rarely been explored. The topographically and oceanographically complex shelf of Nova Scotia harbours two interesting topographic features, Emerald Basin, a sedimentary habitat reaching greater depths (max of 270 m) than the surrounding shelf and the Gully, the largest canyon in NW Atlantic. Emerald Basin is exposed to upwellings of slope water and harbours predominantly deep-sea hexactinellid sponges. Such distributional pattern resembles “deep-water emergence”. In this study an abundant benthic group, the polychaetes, were selected to test for such deep-water faunal link. Qualitative boxcores were collected from Emerald Basin (180 m depth, N = 5) and the adjacent Gully Canyon (1600 m, N = 3). At species level, there was no overlap in distribution between Emerald Basin (N = 73, S=29) and Gully Canyon (N = 351, S = 60) fauna based on morphological assessment of all specimens and molecular analysis (COI and 16S markers) of selected morphotypes. In an alternative approach, Multivariate analysis (nMDS, Cluster Analysis) of incidence data for polychaete genera (N = 179) from 24 Atlantic sites (5–1600 m) was carried out. These results showed a greater similarity of Emerald Basin polychaetes to bathyal sites (400–1000 m), particularly the 680 m site off Nova Scotia rather than shelf sites (5–80 m), including those on the Nova Scotia shelf. Thus, at 1600 m, the Gully Canyon samples were likely “too deep” for our comparative purposes and depths of ≺1000 m should be targeted in the future. Our data also provide the first published assessment of polychaete diversity from the Gully Canyon, suggesting the presence of a diverse assemblage (S = 60). Unusually for a deep-sea site, the Gully Canyon polychaetes are mostly known taxa with wider distribution across bathyal NW Atlantic. Additionally, our molecular data provide an interesting insights into the distribution of several polychaete species commonly found in deep-sea (e.g Aurospio dibranchiata Maciolek, 1981; Ophelina abranchiata Støp-Bowitz, 1948) suggesting wide geographical distribution for some but revealing species complexes for others

Impacto de la eliminación de barreras fluviales sobre el estado ecológico en la parte española de la demarcación hidrográfica del Tajo

La eliminación de barreras fluviales se postula como una actuación de especial relevancia para la mejora del estado ecológico de los ríos. Estas estructuras producen la fragmentación del ecosistema y la pérdida de continuidad fluvial, y repercuten negativamente sobre la hidromorfología, la calidad fisicoquímica del agua y, consecuentemente, sobre las comunidades biológicas. La Confederación Hidrográfica del Tajo lo considera como un tema importante en la consecución de los objetivos medioambientales establecidos por la Directiva Marco del Agua. Este trabajo tiene como objetivo evaluar el impacto de la eliminación de barreras fluviales sobre el estado ecológico en la parte española de la Demarcación Hidrográfica del Tajo. Para ello, se han identificado la tipología y distribución de los ríos en el territorio, las barreras eliminadas y las estaciones foronómicas y de control de la calidad aguas abajo de las mismas. Se ha analizado el valor de los indicadores de calidad referidos en la legislación vigente para evaluar el estado ecológico en esas estaciones, antes y después de ser demolidas dichas barreras. Los resultados muestran que, a pesar de observar variaciones en algunos indicadores a nivel individual, la mayoría de los tramos fluviales estudiados (agrupados en cinco casos de estudio) no experimentaron cambios importantes en el estado ecológico global antes y después de las actuaciones. Sin embargo, sí mejora la continuidad fluvial y la eliminación de la barrera podría contribuir a la recuperación de las comunidades biológicas y a la mejora de la calidad fisicoquímica del agua. Es necesario abordar un monitoreo exhaustivo en futuras actuaciones y enfocar los esfuerzos en aquellas barreras cuyo impacto sobre los ríos sea mayor.The removal of river barriers is postulated as an action of special relevance in order to improve the river ecological status. These structures result in ecosystem fragmentation and loss of river continuity, and they negatively affect hydromorphology, physicochemical quality of water, and consequently, the biological communities. The Tagus River Basin Authority includes it as an important issue to achieve the environmental objectives established by the Water Framework Directive. The aim of this work is to assess the impact of the removal of rivers barriers on the ecological status in the Spanish part of the Tagus River Basin District. To achieve it, the typology and distribution of the rivers in the territory, the eliminated barriers, and the stream gauging and quality control stations, downstream of those barriers have been identified. The quality indicators values referred in the current legislation before and after the demolition of the barriers have been analysed, thus assessing the ecological status in these stations. The results reveal that, despite some individual parameters show certain variations, most of the fluvial sections studied (grouped in five study cases) did not experience significant changes in its global ecological status before and after the actions. However, river continuity improves and the removal could contribute to the biological communities recovery and to the improvement of the physicochemical quality of the water. It is necessary to address an exhaustive monitoring in future actions and focus the efforts on those barriers whose impact on rivers is greater.Grado en Ciencias Ambientale

Some Like It Fat: Comparative Ultrastructure of the Embryo in Two Demosponges of the Genus Mycale (Order Poecilosclerida) from Antarctica and the Caribbean

0000-0002-7993-1523© 2015 Riesgo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License [4.0], which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article

Propuesta de sistema contable basada en la teoría general de sistemas para mejorar el control de los registros contables en Transportes Fenix, de Chiclayo - 2010

RESUMEN El presente trabajo de Investigación titulado: PROPUESTA DE SISTEMA CONTABLE BASADA EN LA TEORÍA GENERAL DE SISTEMAS PARA MEJORAR EL CONTROL DE LOS REGISTROS CONTABLES EN “TRANSPORTES FENIX”, DE CHICLAYO, 2010. Se ha realizado en la empresa de transportes de carga interprovincial Transportes Fénix, dedicada a la prestación de servicio de transporte al interior del país (Amazonas, San Martín), en su mayoría son abarrotes y en su retorno transporta frutas, arroz, ganado, madera y maíz. La empresa de Transportes Fénix no esta ajena a los problemas, siendo una de las principales causas, la creciente informalidad en el sector transporte, lo cual no le permite a la empresa percibir los ingresos esperados. Esto asociado a que la empresa no cuenta con un sistema contable, que le permita ver y controlar sus transacciones comerciales cumpliendo con objetivos trazados. Nuestra investigación esta comprendida en el área contable, con el fin de contestar la interrogante ¿De qué manera la propuesta de un sistema contable influye en un mejoramiento de los Registros Contables de la Empresa de servicios Transportes Fénix? La metodología empleada para el desarrollo de la investigación: visitas, entrevistas y encuestas a los directivos de la empresa de Transportes Fénix, al personal de servicio que labora en dicha entidad y clientes así como la observación directa, documentos y registros contables obtenidos de la referida institución. El presente trabajo, la propuesta esta basada en que la empresa de Transportes Fénix, cuente con un sistema contable que le permita tener un adecuado control de los registros contables, mediante formatos que logren mejorar el control en el servicio de transporte con la finalidad de lograr los objetivos y satisfacer las necesidades de sus clientes. Hoy en día las empresas necesitan un flujo de datos constantes y precisos para tomar las decisiones correctas que les permita hacerles frente a la intensa competencia a las que están sometidas en un ambiente de globalización para enrumbar la empresa al logro de sus objetivos. La magnitud del valor de la información es incalculable, ya que aquellas empresas que cuentan con la mayor cantidad y calidad de datos, podrán tomar las mejores decisiones, actualmente la información contable es un mecanismo indispensable para realizar una administración efectiva de los recursos con los cuales cuentan.Tesi

Theoretical modelling of quaternary GaInAsSb/GaAs self-assembled quantum dots

Trabajo presentado al "Quantum Dot", celebrado en Nottingham (UK) del 26 al 30 de Abril de 2010.InAs/GaAs quantum dots exposed to Sb after growth exhibit spectral changes. We study in the present paper an idealized nanostructure consisting of a homogeneous distribution of the quaternary GaInAsSb surrounded by a barrier of GaAs. We nd that the valence band o set is a critical parameter in modelling its electronic structure. Depending on this value, we predict a transition from type-I to type-II band alignment at a di erent Sb concentration. The addition of Sb to reduce the transition energy while keeping a type-I alignment is only of bene t at low Sb concentrationThis work was supported by the Spanish MICINN (projects TEC2008-06756-C03-01/02/TEC, CONSOLIDER INGENIO 2010 CSD2006-0019 and CSD2009-00013), the Junta de Andalucía (PAI research groups TEP-120 and TIC-145; project P08-TEP-03516) and Comunidad Autónoma de Madrid S2009ESP-1503.Peer reviewe

A new species of Isodictya (Porifera: Poecilosclerida) from the Southern Ocean

We discovered a new species of Porifera belonging to the genus Isodictya Bowerbank, 1864 during cruises aboard R/V Hesperides in Antarctica. Collected samples are mostly part of the surveys of the Spanish project BENTART whose main objective has been to study the benthic communities inhabiting sea bottoms of Livingston and Deception Island in the South Shetlands archipelago and the Antarctic Peninsula. Isodictya filiformis sp. nov., described here, is characterized by its fragile and thin morphology (very different from other known species in the area) and by having microxeas as additional microscleres. Three specimens were collected from Marguerite Bay, Low Island and Deception Island (Antarctic Peninsula) and one specimen at Peter I Island (Bellingshausen Sea). Its presence in Peter Island is quite relevant as this location is 390 km away from the nearest coast in the Bellingshausen Sea, an area that has scarcely been investigated in the past. However, results from the Bentart 03 Expedition seem to indicate that Peter I Island has a wide variety of benthic organisms, in contrast to the deep adjacent areas of Bellingshausen Sea. Apart from the morphological analyses, we place the new Isodictya species within its phylogenetic context using two nuclear markers (18S rDNA and 28S rDNA) and provide some information about the ecological preferences of the new speciesPostprint1,44