6,682 research outputs found

    The 2008 R-ISEW (regional index of sustainable economic well-being) for all the English regions

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    This report presents new data calculated in 2008 for the years 1994–2006. The latest data, which also includes the updating of several sets of figures which previously had to be estimated for 2005, show that a 10-year increase in R-ISEW since 1994 has come to a halt, and that R-ISEW per capita actually began declining between 2004 and 2006 despite increasing GVA

    The 2010 R-ISEW (regional index of sustainable economic well-being) for all the English regions

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    This is the fourth consecutive report presenting R-ISEW (regional index of sustainable economic well-being) calculations for the nine Government Office Regions (GORs) of England.1 New data available in the summer of 2010 allows a continuous time series from 1994 to 2008 – 15 years. Because of the nature of the data required for the R-ISEW, there is always a two-year lag before results for any given year can be completed

    Analysis of a diffusive effective mass model for nanowires

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    We propose in this paper to derive and analyze a self-consistent model describing the diffusive transport in a nanowire. From a physical point of view, it describes the electron transport in an ultra-scaled confined structure, taking in account the interactions of charged particles with phonons. The transport direction is assumed to be large compared to the wire section and is described by a drift-diffusion equation including effective quantities computed from a Bloch problem in the crystal lattice. The electrostatic potential solves a Poisson equation where the particle density couples on each energy band a two dimensional confinement density with the monodimensional transport density given by the Boltzmann statistics. On the one hand, we study the derivation of this Nanowire Drift-Diffusion Poisson model from a kinetic level description. On the other hand, we present an existence result for this model in a bounded domain

    The 2009 R-ISEW (regional index of sustainable economic well-being) for all the English regions

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    This latest report presents new data calculated in 2009 for the years 1994–2007. The data, which also includes the updating of several sets of figures that previously had to be estimated for 2006, show that a nine-year increase in the English R-ISEW since 1994, began to peter out in 2003, such that total per capita growth between 2003 and 2007 was only 2.4%. Indeed, between 2005 and 2006, per capita R-ISEW fell slightly

    Giant spin-dependent photo-conductivity in GaAsN dilute nitride semiconductor

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    A theoretical and experimental study of the spin-dependent photoconductivity in dilute Nitride GaAsN is presented. The non linear transport model we develop here is based on the rate equations for electrons, holes, deep paramagnetic and non paramagnetic centers both under CW and pulsed optical excitation. Emphasis is given to the effect of the competition between paramagnetic centers and non paramagnetic centers which allows us to reproduce the measured characteristics of the spin-dependent recombination power dependence. Particular attention is paid to the role of an external magnetic field in Voigt geometry. The photoconductivity exhibits a Hanle-type curve whereas the spin polarization of electrons shows two superimposed Lorentzian curves with different widths, respectively related to the recombination of free and trapped electrons. The model is capable of reproducing qualitatively and quantitatively the most important features of photoluminescence and photocurrent experiments and is helpful in providing insight on the various mechanisms involved in the electron spin polarization and filtering in GaAsN semiconductors.Comment: 10 pages, 5 figure

    An effective mass theorem for the bidimensional electron gas in a strong magnetic field

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    We study the limiting behavior of a singularly perturbed Schr\"odinger-Poisson system describing a 3-dimensional electron gas strongly confined in the vicinity of a plane (x,y)(x,y) and subject to a strong uniform magnetic field in the plane of the gas. The coupled effects of the confinement and of the magnetic field induce fast oscillations in time that need to be averaged out. We obtain at the limit a system of 2-dimensional Schr\"odinger equations in the plane (x,y)(x,y), coupled through an effective selfconsistent electrical potential. In the direction perpendicular to the magnetic field, the electron mass is modified by the field, as the result of an averaging of the cyclotron motion. The main tools of the analysis are the adaptation of the second order long-time averaging theory of ODEs to our PDEs context, and the use of a Sobolev scale adapted to the confinement operator

    Room temperature Giant Spin-dependent Photoconductivity in dilute nitride semiconductors

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    By combining optical spin injection techniques with transport spectroscopy tools, we demonstrate a spin-photodetector allowing for the electrical measurement and active filtering of conduction band electron spin at room temperature in a non-magnetic GaAsN semiconductor structure. By switching the polarization of the incident light from linear to circular, we observe a Giant Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of an external magnetic field. We show that the GSP is due to a very efficient spin filtering effect of conduction band electrons on Nitrogen-induced Ga self-interstitial deep paramagnetic centers.Comment: 4 pages, 3 figure

    Potentialités androgénétiques du palmier dattier Phoenix dactylifera L. et culture in vitro d'anthères

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    Genetic potentialities if five male date palm genotypes, and in vitro culture of anthers. The experimental results derived from the study of five date palm (Phoenix dactylifera L.) genotypes indicate that the ability of microspores to divide varies with genotype and culture medium. The highest frequency of microspore division is obtained with the induction medium [Murashige and Skoog (MS 1962) mineral elements, 2,4-dichlorophenoxyacetique (2,4-D), 2-isopentenylaminopurine (2-IP)] containing activated charcoal. The pollinator T106 was considered as the most efficient genotype in our experimentatio

    The role of farmed fish in the diets of the resource-poor in Egypt.

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    The Egyptian aquaculture industry provides more than 100,000 full-time or part-time jobs and produces the country’s least-expensive farmed animal protein. Thus, aquaculture plays an important role in both sustaining livelihoods and improving the diet quality and nutritional health of Egyptians, including a significant proportion of the 25.5% who are resource-poor. Recognizing this dual role, WorldFish has promoted sustainable growth in Egyptian aquaculture for more than 20 years. Through its work, WorldFish has identified a lack of quality data about fish consumption preferences and practices. Eager to fill this knowledge gap, WorldFish partnered with the Environment and Development Group (EDG) to study consumption of fish, red meat and poultry among the resource-poor in Egypt. This study aimed to characterize current consumer preferences for and consumption patterns of animal-source foods, comparing red meat, poultry and fish. The resulting data is meant to contribute to a better understanding of what drives demand for fish among the resource-poor in Egypt, allowing value chain actors to more successfully market their products to this segment of the population
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