Spike detection and sorting: combining algebraic differentiations with ICA

International audienceA new method for action potentials detection is proposed. The method is based on a numerical differentiation, as recently intro- duced from operational calculus. We show that it has good performance as compared to existing methods. We also combine the proposed method with ICA in order to obtain spike sorting

Longitudinal measurement of the developing grey matter in preterm subjects using multi-modal MRI.

Preterm birth is a major public health concern, with the severity and occurrence of adverse outcome increasing with earlier delivery. Being born preterm disrupts a time of rapid brain development: in addition to volumetric growth, the cortex folds, myelination is occurring and there are changes on the cellular level. These neurological events have been imaged non-invasively using diffusion-weighted (DW) MRI. In this population, there has been a focus on examining diffusion in the white matter, but the grey matter is also critically important for neurological health. We acquired multi-shell high-resolution diffusion data on 12 infants born at ≤28weeks of gestational age at two time-points: once when stable after birth, and again at term-equivalent age. We used the Neurite Orientation Dispersion and Density Imaging model (NODDI) (Zhang et al., 2012) to analyse the changes in the cerebral cortex and the thalamus, both grey matter regions. We showed region-dependent changes in NODDI parameters over the preterm period, highlighting underlying changes specific to the microstructure. This work is the first time that NODDI parameters have been evaluated in both the cortical and the thalamic grey matter as a function of age in preterm infants, offering a unique insight into neuro-development in this at-risk population

Electromagnetic Properties of Kerr-Anti-de Sitter Black Holes

We examine the electromagnetic properties of Kerr-anti-de Sitter (Kerr-AdS) black holes in four and higher spacetime dimensions. Assuming that the black holes may carry a test electric charge we show that the Killing one-form which represents the difference between the timelike generators in the spacetime and in the reference background can be used as a potential one-form for the associated electromagnetic field. In four dimensions the potential one-form and the Kerr-AdS metric with properly re-scaled mass parameter solve the Einstein-Maxwell equations, thereby resulting in the familiar Kerr-Newman-AdS solution. We solve the quartic equation governing the location of the event horizons of the Kerr-Newman-AdS black holes and present closed analytic expressions for the radii of the horizons. We also compute the gyromagnetic ratio for these black holes and show that it corresponds to g=2 just as for ordinary black holes in asymptotically flat spacetime. Next, we compute the gyromagnetic ratio for the Kerr-AdS black holes with a single angular momentum and with a test electric charge in all higher dimensions. The gyromagnetic ratio crucially depends on the dimensionless ratio of the rotation parameter to the curvature radius of the AdS background. At the critical limit, when the boundary Einstein universe is rotating at the speed of light, it tends to g=2 irrespective of the spacetime dimension. Finally, we consider the case of a five dimensional Kerr-AdS black hole with two angular momenta and show that it possesses two distinct gyromagnetic ratios in accordance with its two orthogonal 2-planes of rotation. In the special case of two equal angular momenta, the two gyromagnetic ratios merge into one leading to g=4 at the maximum angular velocities of rotation.Comment: Typos corrected; 31 pages, REVTe

Ciclo reprodutivo de machos e fêmeas de jacaré-do-Pantanal, Caiman crocodilus yacare.

A reprodução dos crocodilianos, tanto em condições naturais como em cativeiro, tem recebido considerável atenção, particularmente devido a suas aplicações no manejo. entretanto, muitas das informações disponíveis são relacionadas à produção de ninhos, duração do período de postura, tamanho de ovos e filhotes e sua relação com tamanho das fêmeas (Greer, 1975; Thorbjarnarson, 1994, 1996; Campos & Magnusson, 1995). Além dos estudos com aligátores (por ex. Joanen & McNease, 1980; lance, 1987, 1989; Guillette & Milnes, 2000; Uribe & Guillette, 2000), e uns poucos trabalhos com outras espécies como Crocodylus niloticus (Graham, 1968; Kofron, 1990) ou Caiman crocodilus (Thorbjarnarson, 1994), existem poucas informações sobre a estrutura e função das gônadas dos crodilianos. Nas espécies estudadas, nas atividades das gônadas têm mostrado um ciclo sazonas, relacionado com os fatores ambientais, como temperatura e nível d'água. A produção de hormônios pode variar entre espécies e sua relação com a espermatogênese pode não ser consistente, entretanto, o desenvolvimento folicular e ovidutal parecem ser associados com os hormônios sexuais esteróides (Lance, 1987; Kofron, 1990; Guillette & Milnes, 2000). A biologia reprodutiva do jacaré-do-Pantanal, Caiman crocodilus yacare, foi estudado por vários autores (Crasharw e Shaller, 1980; Cintra, 1988; Campos, 1993, Campos & Magnusson, 1995; Aleixo & Maciel, 1998), no entanto, não existem estudos da função endócrina das gônadas dos machos e fêmeas. Este Comunicado Técnico tem o objetivo de preencher essa lacuna dos conhecimentos da vitologênese e espermatogênese do jacaré-do-Pantanal.bitstream/item/79546/1/COT51.pd

String-Loop Corrected Magnetic Black Holes

We discuss the form of the string-loop-corrected effective action obtained by compactification of the heterotic string theory on the manifold $K3\times T^2$ or on its orbifold limit and the loop-corrected magnetic black hole solutions of the equations of motion. Effective 4D theory has N=2 local supersymmetry. Using the string-loop-corrected prepotential of the N=2 supersymmetric theory, which receives corrections only from the string world sheets of torus topology, we calculate the loop corrections to the tree-level gauge couplings and solve the loop-corrected equations of motion. At the string-tree level, the effective gauge couplings decrease at small distances from the origin, and in this region string-loop corrections to the gauge couplings become important. A possibility of smearing the singularity of the tree-level supersymmetric solution with partially broken supersymmetry by quantum corrections is discussed.Comment: Improved version. Mixing of the dilaton with other moduli properly taken into account. Explanatory notes adde

Gaugino Condensation in N=1 Supergravity Models with Multiple Dilaton-Like Fields

We study supersymmetry breaking by hidden-sector gaugino condensation in N=1 D=4 supergravity models with multiple dilaton-like moduli fields. Our work is motivated by Type I string theory, in which the low-energy effective Lagrangian can have different dilaton-like fields coupling to different sectors of the theory. We construct the effective Lagrangian for gaugino condensation and use it to compute the visible-sector gaugino masses. We find that the gaugino masses can be of order the gravitino mass, in stark contrast to heterotic string models with a single dilaton field.Comment: LaTeX, 17 pages, 2 eps figure

Fake Supergravity and Domain Wall Stability

We review the generalized Witten-Nester spinor stability argument for flat domain wall solutions of gravitational theories. Neither the field theory nor the solution need be supersymmetric. Nor is the space-time dimension restricted. We develop the non-trivial extension required for AdS-sliced domain walls and apply this to show that the recently proposed "Janus" solution of Type IIB supergravity is stable non-perturbatively for a broad class of deformations. Generalizations of this solution to arbitrary dimension and a simple curious linear dilaton solution of Type IIB supergravity are byproducts of this work.Comment: 37 pages, 3 figures, v2: minor corrections, references and acknowledgments adde

Behavioural patterns behind the demise of the commons across different cultures

Common-pool resources require a dose of self-restraint to ensure sustainable exploitation, but this has often proven elusive in practice. To understand why, and characterize behaviours towards ecological systems in general, we devised a social dilemma experiment in which participants gain profit from harvesting a virtual forest vulnerable to overexploitation. Out of 16 Chinese and 15 Spanish player groups, only one group from each country converged to the forest's maximum sustainable yield. All other groups were overzealous, with about half of them surpassing or on the way to surpass a no-recovery threshold. Comp utational-statistical analyses attribute such outcomes to an interplay between three prominent player behaviours, two of which are subject to decision-making "inertia" that causes near blindness to the resource state. These behaviours, being equally pervasive among players from both nations, imply that the commons fall victim to behavioural patterns robust to confounding factors such as age, education and culture

Milled rice quality evaluation during storage under different temperature conditions.

Most of Brazilian consumers prefer to eat soft and fluffy cooked rice, especially when it is stored under refrigeration and re-heated. After harvest, some rice varieties, mainly from lowland system, need some weeks or months to reach the desirable cooking grain quality and normally the chemical and sensory analyses take place right after harvest. In order to check the home storage conditions effect on rice quality traits, five lowland varieties were cultivated in the same field at Embrapa Rice and Beans experimental station and harvested at the recommended point. The rice paddy was dehulled and milled and the milling degree was kept uniform

Single vortex structure in two models of iron pnictide s±s^\pm superconductivity

The structure of a single vortex in a FeAs superconductor is studied in the framework of two formulations of superconductivity for the recently proposed sign-reversed $s$ wave ($s^\pm$) scenario: {\it (i)} a continuum model taking into account the existence of an electron and a hole band with a repulsive local interaction between the two; {\it (ii)} a lattice tight-binding model with two orbitals per unit cell and a next-nearest-neighbour attractive interaction. In the first model, the local density of states (LDOS) at the vortex centre, as a function of energy, exhibits a peak at the Fermi level, while in the second model such LDOS peak is deviated from the Fermi level and its energy depends on band filling. An impurity located outside the vortex core has little effect on the LDOS peak, but an impurity close to the vortex core can almost suppress it and modify its position.Comment: 17 pages, 15 figures. Accepted for publication in New Journal of Physic