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Search Results: 1 - 10 of 8321 matches for " Michel Baranger "
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A Semiclassical Calculation of Scars for a Smooth Potential
Daniel Provost,Michel Baranger
Physics , 1993, DOI: 10.1103/PhysRevLett.71.662
Abstract: Bogomolny's formula for energy-smoothed scars is applied for the first time to a non-specific, non-scalable Hamiltonian, a 2-D anharmonic oscillator. The semiclassical theory reproduces well the exact quantal results over a large spatial and energy range.
Kolmogorov-Sinai entropy-rate vs. physical entropy
Vito Latora,Michel Baranger
Physics , 1998, DOI: 10.1103/PhysRevLett.82.520
Abstract: This paper elucidates the connection between the KS entropy-rate kappa and the time evolution of the physical or statistical entropy S. For a large family of chaotic conservative dynamical systems including the simplest ones, the evolution of S(t) for far-from-equilibrium processes includes a stage during which S is a simple linear function of time whose slope is kappa. The paper presents numerical confirmation of this connection for a number of chaotic symplectic maps, ranging from the simplest 2-dimensional ones to a 4-dimensional and strongly nonlinear map.
Generalization of the Peres criterion for local realism through nonextensive entropy
Constantino Tsallis,Seth Lloyd,Michel Baranger
Physics , 2000,
Abstract: A bipartite spin-1/2 system having the probabilities $\frac{1+3x}{4}$ of being in the Einstein-Podolsky-Rosen entangled state $|\Psi^-$$> \equiv \frac{1}{\sqrt 2}(|$$\uparrow>_A|$$\downarrow>_B$$-|$$\downarrow>_A|$$\uparrow>_B)$ and $\frac{3(1-x)}{4}$ of being orthogonal, is known to admit a local realistic description if and only if $x<1/3$ (Peres criterion). We consider here a more general case where the probabilities of being in the entangled states $|\Phi^{\pm}$$> \equiv \frac{1}{\sqrt 2}(|$$\uparrow>_A|$$\uparrow>_B \pm |$$\downarrow>_A|$$\downarrow>_B)$ and $|\Psi^{\pm}$$> \equiv \frac{1}{\sqrt 2}(|$$\uparrow>_A|$$\downarrow>_B \pm |$$\downarrow>_A|$$\uparrow>_B)$ (Bell basis) are given respectively by $\frac{1-x}{4}$, $\frac{1-y}{4}$, $\frac{1-z}{4}$ and $\frac{1+x+y+z}{4}$. Following Abe and Rajagopal, we use the nonextensive entropic form $S_q \equiv \frac{1- Tr \rho^q}{q-1} (q \in \cal{R}; $$S_1$$= -$ $Tr$ $ \rho \ln \rho)$ which has enabled a current generalization of Boltzmann-Gibbs statistical mechanics, and determine the entire region in the $(x,y,z)$ space where local realism is admissible. For instance, in the vicinity of the EPR state, classical realism is possible if and only if $x+y+z<1$, which recovers Peres' criterion when $x=y=z$. In the vicinity of the other three states of the Bell basis, the situation is identical. A critical-phenomenon-like scenario emerges. These results illustrate the computational power of this new nonextensive-quantum-information procedure.
Can the benefits of cannabinoid receptor stimulation on neuroinflammation, neurogenesis and memory during normal aging be useful in AD prevention?
Yannick Marchalant, Kevin Baranger, Gary L Wenk, Michel Khrestchatisky, Santiago Rivera
Journal of Neuroinflammation , 2012, DOI: 10.1186/1742-2094-9-10
Abstract: The growing number of medical benefits of cannabinoids, such as their ability to regulate age-related processes like neuroinflammation, neurogenesis and memory, raise the question of their potential role as a preventive treatment of AD.To test this hypothesis, epidemiological studies on long term, chronic cannabinoid users could enlighten us on the potential benefits of these compounds in normal and pathological ageing processes. Systematic pharmacological (and thus more mechanistic) investigations using animal models of Alzheimer's disease that have been developed would also allow a thorough investigation of the benefits of cannabinoid pharmacotherapy in the pathogenesis of Alzheimer's disease.The chronic administration of non-selective cannabinoids may delay the onset of cognitive deficits in AD patients; this will dramatically reduce the socio-economic burden of AD and improve the quality of life of the patients and their families.Alzheimer's disease (AD) is the most common neurodegenerative disease and accounts for the majority of diagnosed dementia after age 60. Currently available drugs only produce temporary relief from some cognitive symptoms without delaying, stopping or reversing the neuropathology. Due to poor efficacy of current treatments and the likely delay to implement future safe and efficacious treatments, there is an opportunity to develop preventive approaches based on currently available knowledge regarding the pathogenesis of AD. Neuroinflammation has attracted growing attention due to its slow progression and chronic nature, particularly during normal aging, as well as its involvement in various neurodegenerative diseases [1]. Neuroinflammation has thus been targeted by numerous pharmacological agents [1-4]. Elderly patients (65 years and older) treated with non-steroidal anti-inflammatory drugs (NSAIDS) for 24 months exhibited a surprisingly lower prevalence of developing AD years later (follow up of 8 years, [5]). Subsequent clinical trials
Argentine social anthropology and sociology: Disciplinary identities in four conferences Antropología social y sociología argentinas: Identidades disciplinares en cuatro congresos Antropologia social e sociologia da Argentina: identidades disciplinares em quatro congressos
Denis Baranger
Revista Latinoamericana de Metodología de las Ciencias Sociales , 2011,
Abstract: This paper deals with social anthropology and sociology in their current state in Argentina. Beginning with a commentary about the relationship between those disciplines, and on their institutionalization in Argentina since 1957, then is performed a Principal Component Analysis [PCA] on the presentations at four scientific meetings, concerning the structure of their theoretical and methodological framework, as one of the main dimensions of the differentiation of disciplines. The results show an overlap of references important enough as to conceive that the reasons for the difference between those disciplines are hardly related to epistemology, methodology or theory. Finally, drawing on ideas from Abbott and Passeron, is discussed the possibility of a single community of social scientists En este artículo se toman como objeto la antropología social y la sociología argentinas en su estado actual. Comenzando por un comentario general sobre la relación entre estas disciplinas y sobre su institucionalización en Argentina desde 1957, se pasa luego a la descripción de una de las hipotéticas dimensiones de su diferenciación basada en un análisis de componentes principales (ACP) sobre las ponencias presentadas en cuatro reuniones científicas en cuanto a la estructura de sus referentes teóricos y metodológicos. Los resultados muestran una superposición de referencias lo suficientemente importante como para asentar la idea de que las razones para la diferenciación entre estas disciplinas están lejos de obedecer a factores vinculados ala epistemología, la metodología o la teoría. Finalmente, retomando ideas de Abbott y Passeron, se argumenta sobre una posible comunidad única de cientistas sociales no disponible
Area-Specific Alterations of Synaptic Plasticity in the 5XFAD Mouse Model of Alzheimer’s Disease: Dissociation between Somatosensory Cortex and Hippocampus
Nadine Crouzin, Kevin Baranger, Mélanie Cavalier, Yannick Marchalant, Catherine Cohen-Solal, Fran?ois S. Roman, Michel Khrestchatisky, Santiago Rivera, Fran?ois Féron, Michel Vignes
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0074667
Abstract: Transgenic mouse models of Alzheimer’s disease (AD) that overproduce the amyloid beta peptide (Aβ) have highlighted impairments of hippocampal long-term synaptic plasticity associated with the progression of the disease. Here we examined whether the characteristics of one of the hallmarks of AD, i.e. Aβ deposition, in both the somatosensory cortex and the hippocampus, correlated with specific losses of synaptic plasticity in these areas. For this, we evaluated the occurrence of long-term potentiation (LTP) in the cortex and the hippocampus of 6-month old 5xFAD transgenic mice that exhibited massive Aβ deposition in both regions but with different features: in cortical areas a majority of Aβ deposits comprised a dense core surrounded by a diffuse corona while such kind of Aβ deposition was less frequently observed in the hippocampus. In order to simultaneously monitor synaptic changes in both areas, we developed a method based on the use of Multi-Electrode Arrays (MEA). When compared with wild-type (WT) mice, basal transmission was significantly reduced in both areas in 5xFAD mice, while short-term synaptic plasticity was unaffected. The induction of long-term changes of synaptic transmission by different protocols revealed that in 5xFAD mice, LTP in the layer 5 of the somatosensory cortex was more severely impaired than LTP triggered in the CA1 area of the hippocampus. We conclude that cortical plasticity is deficient in the 5xFAD model and that this deficit could be correlated with the proportion of diffuse plaques in 5xFAD mice.
Grupo escolar Les Eguerets . Ciudad nueva de Cergy Pontoise. Francia
Baranger, Alain Philippe
Informes de la Construccion , 1984,
Abstract: On a terrain of 9,500 m2, situated on the plateau occupied by the district of Versants de l'Hautil, of the new city of Cergy-Pontolse, this scholastic group has been constructed, consisting of ten classes for primaries, five for infants and five dwellings of 4 rooms, apart from the usual annexes of a construction of these characteristics: library multi-purpose hall, restaurant with kitchen, workshops for manual activities, sports zones, courtyards and playgrounds. Its dominant situation has been reinforced with the type of construction employed, on the basis of a modular metal structure which supports a series of roofs at two water of distinct rythms. En un terreno de 9,500 m2, situado en la meseta ocupada por el barrio de los Versants de l'Hautil de la nueva ciudad de Cergy Pontoise, se ha levantado este grupo escolar constituido por diez clases destinadas a primaria, cinco a párvulos y cinco a viviendas de 4 habitaciones, amén de los anexos propios de una construcción de estas características: biblioteca, sala polivalente, restaurante con cocina, talleres de actividades manuales, zonas deportivas, patios y jardines de recreo. Su situación dominante se ha reforzado con el tipo de construcción empleado, a base de una estructura modular metálica que soporta una serie de tejados a dos aguas de distintos ritmos. Se pretendía que las actividades de la escuela participaran en la animación de la calle peatonal de acceso, lo que se ha conseguido mediante fachadas fuertemente acristaladas que dejan ver gran parte del interior. En esta escuela se ha querido salir al paso de las sucesivas alternativas pedagógicas, procurando espacios de muy variada índole, acordes con las distintas tendencias.
Recognition of essential purines by the U1A protein
Yulia Benitex, Anne M Baranger
BMC Biochemistry , 2007, DOI: 10.1186/1471-2091-8-22
Abstract: In this paper we have investigated the origins of specificity of the N terminal RRM of the U1A protein for stem loop 2 (SL2) of U1 snRNA by substituting modified bases for essential purines in SL2 RNA. In one series of modified bases, hydrogen bond donors and acceptors were replaced by aliphatic groups to probe the importance of these functional groups to binding. In a second series of modified bases, hydrogen bond donors and acceptors were incorrectly placed on the purine bases to analyze the origins of discrimination between cognate and non-cognate RNA. The results of these experiments show that three different approaches are used by the U1A protein to gain specificity for purines. Specificity for the first base in the loop, A1, is based primarily on discrimination against RNA containing the incorrect base, specificity for the fourth base in the loop, G4, is based largely on recognition of the donors and acceptors of G4, while specificity for the sixth base in the loop, A6, results from a combination of direct recognition of the base and discrimination against incorrectly placed functional groups.These investigations identify different roles that hydrogen bond donors and acceptors on bases in both cognate and non-cognate RNA play in the specific recognition of RNA by the U1A protein. Taken together with investigations of other RNA-RRM complexes, the results contribute to a general understanding of the origins of RNA-RRM specificity and highlight, in particular, the contribution of steric and electrostatic repulsion to binding specificity.The RRM is one of the most common RNA-binding domains [1-3] and is found in proteins that participate in all steps of gene expression and RNA processing [4,5]. The RRM is approximately 100 amino acids and forms a general single-stranded RNA binding scaffold comprised of a four-stranded anti-parallel β-sheet flanked by two α-helices [6]. RRMs bind RNAs of different sequences and in many different structural contexts. In general, RR
Mesoscopic Tunneling Magnetoresistance
Gonzalo Usaj,Harold. U. Baranger
Physics , 2000, DOI: 10.1103/PhysRevB.63.184418
Abstract: We study spin-dependent transport through ferromagnet/normal-metal/ferromagnet double tunnel junctions in the mesoscopic Coulomb blockade regime. A general transport equation allows us to calculate the conductance in the absence or presence of spin-orbit interaction and for arbitrary orientation of the lead magnetizations. The tunneling magnetoresistance (TMR), defined at the Coulomb blockade conductance peaks, is calculated and its probability distribution presented. We show that mesoscopic fluctuations can lead to the optimal value of the TMR.
Spin and e-e interactions in quantum dots: Leading order corrections to universality and temperature effects
Gonzalo Usaj,Harold U. Baranger
Physics , 2002, DOI: 10.1103/PhysRevB.66.155333
Abstract: We study the statistics of the spacing between Coulomb blockade conductance peaks in quantum dots with large dimensionless conductance g. Our starting point is the ``universal Hamiltonian''--valid in the g->oo limit--which includes the charging energy, the single-electron energies (described by random matrix theory), and the average exchange interaction. We then calculate the magnitude of the most relevant finite g corrections, namely, the effect of surface charge, the ``gate'' effect, and the fluctuation of the residual e-e interaction. The resulting zero-temperature peak spacing distribution has corrections of order Delta/sqrt(g). For typical values of the e-e interaction (r_s ~ 1) and simple geometries, theory does indeed predict an asymmetric distribution with a significant even/odd effect. The width of the distribution is of order 0.3 Delta, and its dominant feature is a large peak for the odd case, reminiscent of the delta-function in the g->oo limit. We consider finite temperature effects next. Only after their inclusion is good agreement with the experimental results obtained. Even relatively low temperature causes large modifications in the peak spacing distribution: (a) its peak is dominated by the even distribution at kT ~ 0.3 Delta (at lower T a double peak appears); (b) it becomes more symmetric; (c) the even/odd effect is considerably weaker; (d) the delta-function is completely washed-out; and (e) fluctuation of the coupling to the leads becomes relevant. Experiments aimed at observing the T=0 peak spacing distribution should therefore be done at kT<0.1 Delta for typical values of the e-e interaction.
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