Temperature Dependence of Transport Coefficients in Liquid and Amorphous Metals

We apply the muffin-tin effective medium approximation to calculate the temperature dependence of the resistivity and of the thermopower of amorphous and liquid metals. The results show unambiguously that a large resistivity is accompanied by a negative temperature coefficient, in agreement with the experimental situation. This behavior is shown to result from a pseudo-gap which opens in the 1-particle spectrum due to strong scattering at the quasi zone boundary. In turn the thermopower is found to have non-trivial density and temperature dependences.Comment: 9 pages, 9 Postscript figure

Controlling the Biological Invasion of a Commercial Fishery by a Space Competitor: A Bioeconomic Model with Reference to the Bay of St-Brieuc Scallop Fishery

This paper presents a bioeconomic model of a commercial fishery facing biological invasion by an alien species acting as a space competitor for the native species. The model is illustrated in a case study of the common scallop fishery of the Bay of St-Brieuc (France), where biological invasion by a slipper-limpet (Crepidula fornicata) is now addressed by a control program. First we present the model, which combines the dynamics of the two competing stocks. We then use the model to analyze the equilibrium of the fishery under various assumptions concerning invasive species control, and to assess the social cost of the invasion. Finally we propose a set of dynamic simulations concerning the ongoing program, emphasizing the influence of its starting date on its overall economic results.aquatic invasive species, biological invasion control, common scallop, ecosystemic fisheries management, plurispecies bioeconomic modeling, slipper-limpet, Resource /Energy Economics and Policy,

Creation of new tissue priors for automated delineation of basal ganglia in magnetic resonance imaging

The advent of magnetic resonance (MR) imaging has brought to the field of neurosciences the stupendous ability of in-vivo study of the human brain's tissular properties. More recent developments in the field of computational anatomy have led to automated approaches of volumetric assessment of the brain in voxel-based morphometry (VBM). VBM has provided significant understanding about physiopathology of brain diseases, including psychiatric and neurodegenerative diseases (NDDs). VBM performs tissue classification using algorithms that rely on contrast between tissues and probabilistic maps, termed tissue priors. These algorithms have provided accurate and satisfying study of the human cortex. However, tissue classification of deep gray matter such as the basal ganglia has been found to be largely unreliable. Conventional T1-weighted MR imaging provides lower contrast for deep gray matter than the cortical gray matter. The main reason for this contrast bias is the higher iron concentration in those structures. Moreover, iron deposits increase in the normal ageing adult and reach pathological concentrations in a wide number of neurological disorders including NDDs. Accurate assessment is thus challenged for subcortical structures in both health and disease. Recently, quantitative MR imaging (qMRI) has been developed to allow quantitative assessment of tissular microstructure of the brain. Those new sequences, such as magnetization transfer saturation (MT) and effective transverse relaxation rate (R2*) parameter maps, provide better contrast by displaying quantitative surrogates for myelin and iron respectively. MT parameter maps have shown to overcome high iron content sensitivity and to be highly suitable for automated delineation of the basal ganglia. Although MT parameter maps provide sufficient contrast, current tissue priors remain insufficient to provide satisfying tissue classification. In this work, we created robust and accurate tissue priors for deep gray matter

On the ferromagnetic character of (LaVO3_3)m_m/SrVO3_3 superlattices

The experimental observation that vanadate superlattices (LaVO$_3$)$_m$/SrVO$_3$ show ferromagnetism up to room temperature [U.\ L\"uders {\it et al.}, Phys.\ Rev.\ B {\bf 80}, 241102R (2009)] is investigated by means of density functional theory. First, the influence of the density functional on the electronic and magnetic structure of bulk ${\rm LaVO_3}$ is discussed. Second, the band structure of a (LaVO$_3$)$_m$/SrVO$_3$ slab for $m=5$ and 6 is calculated. Very different behaviors for odd and even values of $m$ are found: In the odd case lattice relaxation results into a buckling of the interface VO$_2$ layers that leads to spin-polarized interfaces. In the even case a decoupling of the interface VO$_2$ layers from the LaO layers is obtained, confining the interface electrons into a two-dimensional electron gas. The orbital reconstruction at the interface due to the lattice relaxation is discussed.Comment: 8 pages, 7 figure