Brazilian Atlantic Forest Lato Sensu: The Most Ancient Brazilian Forest, And A Biodiversity Hotspot, Is Highly Threatened By Climate Change.

After 500 years of exploitation and destruction, the Brazilian Atlantic Forest has been reduced to less the 8% of its original cover, and climate change may pose a new threat to the remnants of this biodiversity hotspot. In this study we used modelling techniques to determine present and future geographical distribution of 38 species of trees that are typical of the Brazilian Atlantic Forest (Mata Atlântica), considering two global warming scenarios. The optimistic scenario, based in a 0.5% increase in the concentration of CO2 in the atmosphere, predicts an increase of up to 2 °C in the Earth's average temperature; in the pessimistic scenario, based on a 1% increase in the concentration of CO2 in the atmosphere, temperature increase may reach 4 °C. Using these parameters, the occurrence points of the studied species registered in literature, the Genetic Algorithm for Rule-set Predictions/GARP and Maximum entropy modeling of species geographic distributions/MaxEnt we developed models of present and future possible occurrence of each species, considering Earth's mean temperature by 2050 with the optimistic and the pessimistic scenarios of CO2 emission. The results obtained show an alarming reduction in the area of possible occurrence of the species studied, as well as a shift towards southern areas of Brazil. Using GARP, on average, in the optimistic scenario this reduction is of 25% while in the pessimistic scenario it reaches 50%, and the species that will suffer the worst reduction in their possible area of occurrence are: Euterpe edulis, Mollinedia schottiana, Virola bicuhyba, Inga sessilis and Vochysia magnifica. Using MaxEnt, on average, in the optimistic scenario the reduction will be of 20% while in the pessimistic scenario it reaches 30%, and the species that will suffer the worst reduction are: Hyeronima alchorneoides, Schefflera angustissima, Andira fraxinifolia and the species of Myrtaceae studied.70697-70

À la recherche d’une « démocratie technique ». Enseignements de la conférence citoyenne sur les OGM en France

This article presents an analysis of the consensus conference on GMO’s held in France in 1998. Centred on the experience of the citizen panel, it also discusses criticisms expressed by various actors in France about this conference, most of which related to the lack of representativeness of a panel of citizens with no prior knowledge or interest in the issue at stake. Our analysis of the deliberations and report of the panel reveals the reflexive endeavour undertaken by these citizens with respect to their own role and representativeness. We show how the members of the panel addressed, from the start, the issue of their role in relation to that of the experts and in the decision-making process; how they constructed their collective identity on the basis of their own definition of their role and how this in turn determined how they interacted with the experts and stakeholders invited to the public conference and the nature of their recommendations. We argue that the work conducted by the citizen panel inaugurates a new form of active representation, which is of a very different nature to representation by elected politicians and to “figurative” representation by professional institutions, trade unions and other non-governmental organisations. This novel form of representation enables the exploration of scientific and technical aspects together with social aspects, from the perspective of “ordinary citizens”. It is indeed the “ordinary” character of the panel members that is relevant, because the essence of the operation is to inform decision-makers about the views of those who do not speak out and who do not feel represented by political parties, trade unions, or environmental and consumer NGOs. The article demonstrates how these cognitive and political processes were intrinsically intermeshed in the activities of the panel. The extent and nature of this socio-technical exploration was, however, constrained by some aspects of the consensus conference method itself and we discuss ways in which these could be overcome. On the basis of this analysis, the article addresses two more general issues: the relationship between this type of participatory technology assessment initiative and NGO mobilisations and the link with decision-making processes

Exponential decay for the damped wave equation in unbounded domains

We study the decay of the semigroup generated by the damped wave equation in an unbounded domain. We first prove under the natural geometric control condition the exponential decay of the semigroup. Then we prove under a weaker condition the logarithmic decay of the solutions (assuming that the initial data are smoother). As corollaries, we obtain several extensions of previous results of stabilisation and control

Diffusion in pores and its dependence on boundary conditions

We study the influence of the boundary conditions at the solid liquid interface on diffusion in a confined fluid. Using an hydrodynamic approach, we compute numerical estimates for the diffusion of a particle confined between two planes. Partial slip is shown to significantly influence the diffusion coefficient near a wall. Analytical expressions are derived in the low and high confinement limits, and are in good agreement with numerical results. These calculations indicate that diffusion of tagged particles could be used as a sensitive probe of the solid-liquid boundary conditions.Comment: soumis \`a J.Phys. Cond. Matt. special issue on "Diffusion in Liquids, Polymers, Biophysics and Chemical Dynamics

Nonessential role of beta3 and beta5 integrin subunits for efficient clearance of cellular debris after light-induced photoreceptor degeneration

PURPOSE: During light-induced photoreceptor degeneration, large amounts of cellular debris are formed that must be cleared from the subretinal space. The integrins alphavbeta5 and alphavbeta3 are involved in the normal physiological process of phagocytosis in the retina. This study was conducted to investigate the question of whether the lack of beta5 and/or beta3 integrin subunits might influence the course of retinal degeneration and/or clearance of photoreceptor debris induced by acute exposure to light. METHODS: Wild-type, beta5(-/-) and beta3(-/-) single-knockout, and beta3(-/-)/beta5(-/-) Ccl2(-/-)/beta5(-/-) double-knockout mice were exposed to 13,000 lux of white light for 2 hours to induce severe photoreceptor degeneration. Real-time PCR and Western blot analysis were used to analyze gene and protein expression, light- and electron microscopy to judge retinal morphology, and immunofluorescence to study retinal distribution of proteins. RESULTS: Individual or combined deletion of beta3 and beta5 integrin subunits did not affect the pattern of photoreceptor cell loss or the clearance of photoreceptor debris in mice compared with that in wild-type mice. Invading macrophages may contribute to efficient phagocytosis. However, ablation of the MCP-1 gene did not prevent macrophage recruitment. Several chemokines in addition to MCP-1 were induced after light-induced damage that may have compensated for the deletion of MCP-1. CONCLUSIONS: Acute clearance of a large amount of cellular debris from the subretinal space involves invading macrophages and does not depend on beta3 and beta5 integrins

Energy and position resolution of a CdZnTe gamma-ray detector with orthogonal coplanar anodes

We report on the simulation, construction and performance of prototype CZT imaging detectors employing orthogonal coplanar anodes. These detectors employ a novel electrode geometry with non-collecting anode strips in 1D and collecting anode pixels, interconnected in rows, in the orthogonal dimensions. These detectors retain the spectroscopic and detection efficiency advantages of single carried charge sensing devices as well as the principal advantage of conventional strip detectors with orthogonal anode and cathode strips, i.e. an N X N array of imagin pixels are realized with only 2N electronic channels. Charge signals induced on the various electrodes of a prototype detector with 8 X 8 unit cells are in good agreement with the simulations. The position resolution is about 1 mm in the direction perpendicular to the pixel lines while it is of the order of 100 micrometers in the other direction. Energy resolutions of 0.9 percent at 662 keV, 2.6 percent at 122 keV and 5.7 percent at 60 keV have been obtained at room temperature

On the limits of Brans-Dicke spacetimes: a coordinate-free approach

We investigate the limit of Brans-Dicke spacetimes as the scalar field coupling constant omega tends to infinity applying a coordinate-free technique. We obtain the limits of some known exact solutions. It is shown that these limits may not correspond to similar solutions in the general relativity theory.Comment: LaTeX, 16 pp, report DF/UFPB/02-9

Linear superposition in nonlinear wave dynamics

We study nonlinear dispersive wave systems described by hyperbolic PDE's in R^{d} and difference equations on the lattice Z^{d}. The systems involve two small parameters: one is the ratio of the slow and the fast time scales, and another one is the ratio of the small and the large space scales. We show that a wide class of such systems, including nonlinear Schrodinger and Maxwell equations, Fermi-Pasta-Ulam model and many other not completely integrable systems, satisfy a superposition principle. The principle essentially states that if a nonlinear evolution of a wave starts initially as a sum of generic wavepackets (defined as almost monochromatic waves), then this wave with a high accuracy remains a sum of separate wavepacket waves undergoing independent nonlinear evolution. The time intervals for which the evolution is considered are long enough to observe fully developed nonlinear phenomena for involved wavepackets. In particular, our approach provides a simple justification for numerically observed effect of almost non-interaction of solitons passing through each other without any recourse to the complete integrability. Our analysis does not rely on any ansatz or common asymptotic expansions with respect to the two small parameters but it uses rather explicit and constructive representation for solutions as functions of the initial data in the form of functional analytic series.Comment: New introduction written, style changed, references added and typos correcte

High-level feature detection from video in TRECVid: a 5-year retrospective of achievements

Successful and effective content-based access to digital video requires fast, accurate and scalable methods to determine the video content automatically. A variety of contemporary approaches to this rely on text taken from speech within the video, or on matching one video frame against others using low-level characteristics like colour, texture, or shapes, or on determining and matching objects appearing within the video. Possibly the most important technique, however, is one which determines the presence or absence of a high-level or semantic feature, within a video clip or shot. By utilizing dozens, hundreds or even thousands of such semantic features we can support many kinds of content-based video navigation. Critically however, this depends on being able to determine whether each feature is or is not present in a video clip. The last 5 years have seen much progress in the development of techniques to determine the presence of semantic features within video. This progress can be tracked in the annual TRECVid benchmarking activity where dozens of research groups measure the effectiveness of their techniques on common data and using an open, metrics-based approach. In this chapter we summarise the work done on the TRECVid high-level feature task, showing the progress made year-on-year. This provides a fairly comprehensive statement on where the state-of-the-art is regarding this important task, not just for one research group or for one approach, but across the spectrum. We then use this past and on-going work as a basis for highlighting the trends that are emerging in this area, and the questions which remain to be addressed before we can achieve large-scale, fast and reliable high-level feature detection on video