277 research outputs found

    Preliminary synthesis : IDRC-supported research on large-scale land acquisitions in Africa; using action research to build greater accountability

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    French version available in IDRC Digital Library: Synthèse préliminaire des travaux subventionnés par le CRDI sur les acquisitions foncières à grande échelle en Afrique : utiliser la recherche-action pour accroître la reddition de comptesThis report presents a preliminary synthesis of existing findings emerging from IDRC-supported projects on large-scale land acquisitions and accountability in Africa. Two-thirds of foreign land deals take place in developing countries with serious hunger problems and in countries with the weakest land rights protection laws. Investments to date have served to highlight existing weaknesses in the management and governance of agricultural lands and local communities. A summit of all the research teams investigating the conditions for promoting greater accountability, legitimacy and access to justice around land investment processes and the broader network of IDRC land partners met in Dakar (2015)

    Dark Matter Direct Detection with Non-Maxwellian Velocity Structure

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    The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted dark matter - nucleon scattering rates in direct detection experiments, especially for dark matter models in which the scattering is sensitive to the high velocity tail of the distribution, such as inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for experiments that require high energy recoil events, such as many directionally sensitive experiments. Here we determine the velocity distribution functions from two of the highest resolution numerical simulations of Galactic dark matter structure (Via Lactea II and GHALO), and study the effects for these scenarios. For directional detection, we find that the observed departures from Maxwell-Boltzmann increase the contrast of the signal and change the typical direction of incoming DM particles. For iDM, the expected signals at direct detection experiments are changed dramatically: the annual modulation can be enhanced by more than a factor two, and the relative rates of DAMA compared to CDMS can change by an order of magnitude, while those compared to CRESST can change by a factor of two. The spectrum of the signal can also change dramatically, with many features arising due to substructure. For LDM the spectral effects are smaller, but changes do arise that improve the compatibility with existing experiments. We find that the phase of the modulation can depend upon energy, which would help discriminate against background should it be found.Comment: 34 pages, 16 figures, submitted to JCAP. Tables of g(v_min), the integral of f(v)/v from v_min to infinity, derived from our simulations, are available for download at http://astro.berkeley.edu/~mqk/dmdd

    Dependence of direct detection signals on the WIMP velocity distribution

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    The signals expected in WIMP direct detection experiments depend on the ultra-local dark matter distribution. Observations probe the local density, circular speed and escape speed, while simulations find velocity distributions that deviate significantly from the standard Maxwellian distribution. We calculate the energy, time and direction dependence of the event rate for a range of velocity distributions motivated by recent observations and simulations, and also investigate the uncertainty in the determination of WIMP parameters. The dominant uncertainties are the systematic error in the local circular speed and whether or not the MW has a high density dark disc. In both cases there are substantial changes in the mean differential event rate and the annual modulation signal, and hence exclusion limits and determinations of the WIMP mass. The uncertainty in the shape of the halo velocity distribution is less important, however it leads to a 5% systematic error in the WIMP mass. The detailed direction dependence of the event rate is sensitive to the velocity distribution. However the numbers of events required to detect anisotropy and confirm the median recoil direction do not change substantially.Comment: 21 pages, 7 figures, v2 version to appear in JCAP, minor change

    A Bayesian view of the current status of dark matter direct searches

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    Bayesian statistical methods offer a simple and consistent framework for incorporating uncertainties into a multi-parameter inference problem. In this work we apply these methods to a selection of current direct dark matter searches. We consider the simplest scenario of spin-independent elastic WIMP scattering, and infer the WIMP mass and cross-section from the experimental data with the essential systematic uncertainties folded into the analysis. We find that when uncertainties in the scintillation efficiency of Xenon100 have been accounted for, the resulting exclusion limit is not sufficiently constraining to rule out the CoGeNT preferred parameter region, contrary to previous claims. In the same vein, we also investigate the impact of astrophysical uncertainties on the preferred WIMP parameters. We find that within the class of smooth and isotropic WIMP velocity distributions, it is difficult to reconcile the DAMA and the CoGeNT preferred regions by tweaking the astrophysics parameters alone. If we demand compatibility between these experiments, then the inference process naturally concludes that a high value for the sodium quenching factor for DAMA is preferred.Comment: 37 pages, 14 figures and 7 tables. Replacement for matching the version accepted for publicatio

    Vertical distribution and migration of fish larvae in the NW Iberian upwelling system during the winter mixing period: implications for cross-shelf distribution

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    The vertical distribution and vertical migrations of fish larvae and implications for their cross-shelf distribution were investigated in the northern limit of the NE Atlantic upwelling region during the late winter mixing period of 2012. The average positive values of the upwelling index for February and March of this year were far from normal, although the average hydrographic conditions during the period of study were of downwelling and the water column was completely mixed. Fish larvae, most in the preflexion stage, were concentrated in the upper layers of the water column and their distribution was depth stratified, both day and night. However, the larval fish community was not structured in the vertical plane and fish larvae did not show significant diel vertical migration (DVM), although five species showed ontogenetic vertical migration. In regions of coastal upwelling and in the absence of DVM, the location of fish larvae in the water column is crucial for their cross-shelf distribution. Thus, the cross-shelf distribution of the six most abundant species collected in this study can be explained by the surface onshore flow associated with coastal downwelling, retaining larvae of the coastal spawning species with a relatively shallow distribution in the shelf region and transporting larvae of slope spawning species onto the shelf. The wide vertical distribution shown by larvae of the offshore spawning species could be an adaptation of these species to ensure that some larvae reach the inshore nursery areasPlan Nacional de I+D+i (CRAMERCTM2010- 21856-CO3-02), Junta de Galicia (ECOPREGA-10MMA602021PR), Principado de Asturias (GRUPIN14-144)Postprint2,044

    Chromosomal localization of 15 ion channel genes

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    Several human Mendelian diseases, including the long-QT syndrome, malignant hyperthermia, and episodic ataxia/myokymia syndrome, have recently been demonstrated to be due to mutations in ion channel genes. Systematic mapping of ion channel genes may therefore reveal candidates for other heritable disorders. In this study, the GenBank and dbEST databases were used to identify members of several ion channel families (voltage-gated calcium and sodium cardiac chloride, and all classes of potassium channels). Genes and ESTs without prior map localization were identified based on GDB and OWL database information and 15 genes and ESTs were selected for mapping. Of these 15, only the serotonin receptor 5HT3R had been previously mapped to a chromosome. A somatic cell hybrid panel (SCH) was screened with an STS from each gene and, if necessary, the results verified by a second SCH panel. For three ESTs, rodent derived PCR products of the same size as the human STS precluded SCH mapping. For these three, human Pl clones were isolated and the genomic location was determined by metaphase FISH. These genes and ESTs can now be further evaluated as candidate genes for inherited cardiac, neuromuscular, and psychiatric disorders mapped to these chromosomes. Furthermore, the ESTs developed in this study can be used to isolate genomic clones, enabling the determination of each transcript's genomic structure and physical map location. This approach may also be applicable to other gene families and may aid in the identification of candidate genes for groups of related heritable disorders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45548/1/11188_2006_Article_BF02369898.pd
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