520 research outputs found
La formalisation des droits sur la terre dans les pays du Sud : dépasser les controverses et alimenter les stratégies
Les investissements privés dans les terres s’accélèrent avec des interrogations sur leurs impacts économiques et fonciers pour les populations. Les appels pour améliorer la gouvernance foncière se multiplient. De nombreuses institutions internationales et agences de développement appuient la mise en oeuvre de politiques et de programmes de formalisation des droits fonciers, censés apporter des réponses aux défis du développement. Mais que signifie la formalisation des droits fonciers dans des contextes de pluralité des normes ? Quelle est la gamme des options ? Que sait-on des résultats de ces politiques ? Mobilisant les acquis de la recherche et les travaux des membres du Comité technique « Foncier et développement » et de ses partenaires, ce document met en avant les enjeux politiques de la formalisation des droits fonciers, identifie les conditions pour réussir des politiques durables et inclusives de formalisation, et propose des pistes d’actions dont peuvent se saisir les acteurs de politiques et leurs partenaires pour enrichir leurs démarches et leurs stratégies
Liquid Transport Due to Light Scattering
Using experiments and theory, we show that light scattering by
inhomogeneities in the index of refraction of a fluid can drive a large-scale
flow. The experiment uses a near-critical, phase-separated liquid, which
experiences large fluctuations in its index of refraction. A laser beam
traversing the liquid produces a large-scale deformation of the interface and
can cause a liquid jet to form. We demonstrate that the deformation is produced
by a scattering-induced flow by obtaining good agreements between the measured
deformations and those calculated assuming this mechanism.Comment: 4 pages, 5 figures, submitted to Physical Review Letters v2: Edited
based on comments from referee
Vasopressin/serotonin interactions in the anterior hypothalamus control aggressive behavior in golden hamsters
Studies in several species of rodents show that arginine vasopressin (AVP) acting through a V1A receptor facilitates offensive aggression, i.e., the initiation of attacks and bites, whereas serotonin (5-HT) acting through a 5-HT1B receptor inhibits aggressive responding. One area of the CNS that seems critical for the organization of aggressive behavior is the basolateral hypothalamus, particularly the anterior hypothalamic region. The present studies examine the neuroanatomical and neurochemical interaction between AVP and 5-HT at the level of the anterior hypothalamus (AH) in the control of offensive aggression in Syrian golden hamsters. First, specific V1A and 5-HT1B binding sites in the AH are shown by in vitro receptor autoradiography. The binding for each neurotransmitter colocalizes with a dense field of immunoreactive AVP and 5-HT fibers and putative terminals. Putative 5-HT synapses on AVP neurons in the area of the AH are identified by double-staining immunocytochemistry and laser scanning confocal microscopy. These morphological data predispose a functional interaction between AVP and 5-HT at the level of the AH. When tested for offensive aggression in a resident/intruder paradigm, resident hamsters treated with fluoxetine, a selective 5-HT reuptake inhibitor, have significantly longer latencies to bite and bite fewer times than vehicle-treated controls. Conversely, AVP microinjections into the AH significantly shorten the latency to bite and increase biting attacks. The action of microinjected AVP to increase offensive aggression is blocked by the pretreatment of hamsters with fluoxetine. These data suggest that 5-HT inhibits fighting, in part, by antagonizing the aggression-promoting action of the AVP system
Stretching and squeezing of sessile dielectric drops by the optical radiation pressure
We study numerically the deformation of sessile dielectric drops immersed in
a second fluid when submitted to the optical radiation pressure of a continuous
Gaussian laser wave. Both drop stretching and drop squeezing are investigated
at steady state where capillary effects balance the optical radiation pressure.
A boundary integral method is implemented to solve the axisymmetric Stokes flow
in the two fluids. In the stretching case, we find that the drop shape goes
from prolate to near-conical for increasing optical radiation pressure whatever
the drop to beam radius ratio and the refractive index contrast between the two
fluids. The semi-angle of the cone at equilibrium decreases with the drop to
beam radius ratio and is weakly influenced by the index contrast. Above a
threshold value of the radiation pressure, these "optical cones" become
unstable and a disruption is observed. Conversely, when optically squeezed, the
drop shifts from an oblate to a concave shape leading to the formation of a
stable "optical torus". These findings extend the electrohydrodynamics approach
of drop deformation to the much less investigated "optical domain" and reveal
the openings offered by laser waves to actively manipulate droplets at the
micrometer scale
Between supply and demand: the limits to participatory development in South Africa
Much of the focus in the literature on participatory development has been on the
demand side and on the extent to which citizens succeed in pressuring the state to
deliver basic services. Less attention has been focused on the supply side of participatory
development, namely on how state institutions give effect to development policies.
Post-Apartheid South Africa is replete with policies and legislation supporting participatory
processes and yet in practice this has seldom lived up to the ideals espoused.
This article examines the delivery of public housing in poor communities in three
municipalities in South Africa and argues that there is a mismatch between how the
formulators of policy understand participation and how it is interpreted by beneficiary
communities and local officials. It concludes that considerably more attention needs to
be focused on why officials fail to translate national policies into action if participatory
democracy is to attain any legitimacy in the population at large.Web of Scienc
Structure of laponite-styrene precursor dispersions for production of advanced polymer-clay nanocomposites
One method for production of polymer-clay nanocomposites involves dispersal of surface-modified clay in a polymerisable monomeric solvent, followed by fast in situ polymerisation. In order to tailor the properties of the final material we aim to control the dispersion state of the clay in the precursor solvent. Here, we study dispersions of surface-modified Laponite, a synthetic clay, in styrene via large-scale Monte-Carlo simulations and experimentally, using small angle X-ray and static light scattering. By tuning the effective interaction between simulated laponite particles we are able to reproduce the experimental scattering intensity patterns for this system, with good accuracy over a wide range of length scales. However, this agreement could only be obtained by introducing a permanent electrostatic dipole moment into the plane of each Laponite particle, which we explain in terms of the distribution of substituted metal atoms within each Laponite particle. This suggests that Laponite dispersions, and perhaps other clay suspensions, should display some of the structural characteristics of dipolar fluids. Our simulated structures show aggregation regimes ranging from networks of long chains to dense clusters of Laponite particles, and we also obtain some intriguing ‘globular’ clusters, similar to capsids. We see no indication of any ‘house-of-cards’ structures. The simulation that most closely matches experimental results indicates that gel-like networks are obtained in Laponite dispersions, which however appear optically clear and non-sedimenting over extended periods of time. This suggests it could be difficult to obtain truly isotropic equilibrium dispersion as a starting point for synthesis of advanced polymer-clay nanocomposites with controlled structures
Test methodologies for determining high temperature material properties of thin walled tubes
This report presents briefly the test methods used, within the in the EERA JPNM Pilot Project TASTE, for defining the tensile and creep material properties relevant to the integrity of nuclear fuel claddings. These properties are challenging to extract from thin walled tubes since the standard test methods use test specimen that require minimum material thicknesses in the order of 10 mm or more. In consequence the thin walled material properties are acquired through a number of testing techniques and evaluation methodologies suitable for the thin walled product form. In this report the different test methods and their data assessment requirements are briefly described. The test methods evaluated here comprises of sub-size (curved specimen) tensile testing (ST) of the cladding tube, micro specimen (dog-bone) tensile testing (MT), Small Punch testing (SP), Segmented Expanding Cone Mandrel tests (SCM), the ring tension (RT) and ring compression (RC) tests and internal pressure testing (IP).JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes
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