Showing papers by "University of Nice Sophia Antipolis published in 2004"

Frobenius Algebras and 2-D Topological Quantum Field Theories

Abstract: 1. Cobordisms and TQFTs 2. Frobenius algebras 3. Monoids and monoidal categories Appendix. Vocabulary from category theory.

Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis

Abstract: The evolution of life on Earth is marked by catastrophic extinction events, one of which occurred ca. 200 Ma at the transition from the Triassic Period to the Jurassic Period (Tr-J boundary), apparently contemporaneous with the eruption of the world's largest known continental igneous province, the Central Atlantic magmatic province. The temporal relationship of the Tr-J boundary and the province's volcanism is clarified by new multidisciplinary (stratigraphic, palynologic, geochronologic, paleomagnetic, geochemical) data that demonstrate that development of the Central Atlantic magmatic province straddled the Tr-J boundary and thus may have had a causal relationship with the climatic crisis and biotic turnover demarcating the boundary.

Physiological and Functional Responses to Low-Moderate Versus High-Intensity Progressive Resistance Training in Frail Elders

Abstract: Background. The purpose of this efficacy study was to measure the dose–response effect of a free weight-based resistance training program by comparing the effects of two training intensities (low-moderate and high) of the knee extensor (KE) muscles on muscle function, functional limitations, and self-reported disability. Methods. The authors conducted a single-blinded, randomized, placebo-controlled trial. Twenty-two institutionalized elders (mean age, 81.5 years) were assigned to either high-intensity strength training (HI; n = 8), low-moderate intensity strength training (LI; n = 6), or weight-free placebo-control training (PC; n = 8). The HI group trained at 80% of their 1-repetition maximum and the LI group trained at 40%. All groups performed 3 sets of 8 repetitions, 3 times per week for 10 weeks. Outcome measures included KE maximal strength, KE endurance, and functional performance as assessed by 6-minute walking, chair-rising, and stair-climbing tests, and by self-reported disability. Results. KE strength and endurance, stair-climbing power, and chair-rising time improved significantly in the HI and LI groups compared with the PC group. Six-minute walking distance improved significantly in the HI group but not in the LI group compared with the PC group. Changes observed in HI were significantly different from those observed in the LI group for KE strength and endurance and the 6-minute walking test, with a trend in the same direction for chair-rising and stair-climbing. Changes in strength were significantly related to changes in functional outcomes, explaining 37% to 61% of the variance. Conclusions. These results show strong dose–response relationships between resistance training intensity and strength gains, and between strength gains and functional improvements after resistance training. Low-moderate intensity resistance training of the KE muscles may not be sufficiently robust from a physiologic perspective to achieve optimal improvement of functional performance. Supervised HI, free weight-based training for frail elders appears to be as safe as lower intensity training but is more effective physiologically and functionally.

Phylogenetic relationships among marine Alteromonas-like proteobacteria: emended description of the family Alteromonadaceae and proposal of Pseudoalteromonadaceae fam. nov., Colwelliaceae fam. nov., Shewanellaceae fam. nov., Moritellaceae fam. nov., Ferrimonadaceae fam. nov., Idiomarinaceae fam. nov. and Psychromonadaceae fam. nov.

Abstract: The phylogenetic relationships among marine Alteromonas-like bacteria of the genera Alteromonas, Pseudoalteromonas, Glaciecola, Thalassomonas, Colwellia, Idiomarina, Oceanimonas, Oceanisphaera, Shewanella, Moritella, Ferrimonas, Psychromonas and several other genera of the ‘Gammaproteobacteria’ were studied. Results of 16S rRNA gene sequence analyses revealed that some members of these genera formed several coherent groups at the family level. Characteristic signature oligonucleotides for studied taxa were defined. Signature positions are divided into three classes: (i) single compensatory mutations, (ii) double compensatory mutations and (iii) mutations affecting nucleotides not paired in the secondary structure. The 16S rRNA gene sequence similarity level within genera was 93 % or above. This value can be a useful additional criterion for genus discrimination. On the basis of this work and previous polyphasic taxonomic studies, the circumscription of the family Alteromonadaceae is limited to the genera Alteromonas and Glaciecola and the creation is proposed of the families Pseudoalteromonadaceae fam. nov. to accommodate bacteria of the genera Pseudoalteromonas and Algicola gen. nov. (formerly Pseudoalteromonas bacteriolytica) and Colwelliaceae fam. nov. to accommodate bacteria of the genera Colwellia and Thalassomonas. Bacteria of the genera Oceanimonas and Oceanisphaera formed a robust cluster and shared common signature oligonucleotides. Because of deep branching and lack of association with any other genus, the following families are proposed that include single genera: Idiomarinaceae fam. nov., Psychromonadaceae fam. nov., Moritellaceae fam. nov., Ferrimonadaceae fam. nov. and Shewanellaceae fam. nov. Finally, this study also revealed that [Hyphomicrobium] indicum should be reclassified as Photobacterium indicum comb. nov.

Establishment of a Real-Time PCR-Based Approach for Accurate Quantification of Bacterial RNA Targets in Water, Using Salmonella as a Model Organism

Abstract: Quantitative PCR (Q-PCR) is a fast and efficient tool to quantify target genes. In eukaryotic cells, quantitative reverse transcription-PCR (Q-RT-PCR) is also used to quantify gene expression, with stably expressed housekeeping genes as standards. In bacteria, such stable expression of housekeeping genes does not occur, and the use of DNA standards leads to a broad underestimation. Therefore, an accurate quantification of RNA is feasible only by using appropriate RNA standards. We established and validated a Q-PCR method which enables the quantification of not only the number of copies of target genes (i.e., the number of bacterial cells) but also the number of RNA copies. The genes coding for InvA and the 16S rRNA of Salmonella enterica serovar Typhimurium were selected for the evaluation of the method. As DNA standards, amplified fragments of the target genes were used, whereas the same DNA standards were transcribed in vitro for the development of appropriate RNA standards. Salmonella cultures and environmental water samples inoculated with bacteria were then employed for the final testing. Both experimental approaches led to a sensitive, accurate, and reproducible quantification of the selected target genes and RNA molecules by Q-PCR and Q-RT-PCR. It is the first time that RNA standards have been successfully used for a precise quantification of the number of RNA molecules in prokaryotes. This demonstrates the potential of this approach for determining the presence and metabolic activity of pathogenic bacteria in environmental samples.

Querying the Semantic Web with Corese search engine

Abstract: This paper presents an ontology-based approach for web querying, using semantic metadata. We propose a query language based on ontologies and emphasize its ability to express approximate queries, useful for an efficient information retrieval on the web. We present the Corese search engine dedicated to RDF(S) metadata and illustrate it through several real-world applications.

High-quality asynchronous heralded single-photon source at telecom wavelength

Abstract: We report on the experimental realization and characterization of an asynchronous heralded single-photon source based on spontaneous parametric down-conversion. Photons at 1550 nm are heralded as being inside a single-mode fibre with more than 60% probability, and the multi-photon emission probability is reduced by a factor of up to more than 500 compared to Poissonian light sources. These figures of merit, together with the choice of telecom wavelength for the heralded photons, are compatible with practical applications needing very efficient and robust single-photon sources.

Isoconversional Approach to Evaluating the Hoffman–Lauritzen Parameters (U* and Kg) from the Overall Rates of Nonisothermal Crystallization

Abstract: An equation has been derived that correlates the temperature coefficient of the growth rate with the temperature dependence of the effective activation energy of the overall crystallization rate, which can be measured by differential scanning calorimetry. The dependence is evaluated by using an advanced isoconversional method and is parameterized in terms of the Hoffman-Lauritzen equation. The parameters obtained for the nonisothermal crystallization of the poly(ethylene terephthalate) melt are consistent with the parameters reported for isothermal crystallization.

Quantum monte carlo simulations of confined bosonic atoms in optical lattices

Abstract: We study static properties of ultra-cold bosonic atoms in two-dimensional optical lattices by quantum Monte Carlo simulations of the bosonic Hubbard model in parabolic confinement potentials. Our focus is on local probes identifying Mott-insulating and superfluid regions, which can coexist in the inhomogenous environment of the trap. By proposing an effective ladder model for the boundary region between the two phases we can show clear evidence for the absence of true quantum critical behavior and explain the absence of critical slowing down at the quantum phase transition in a harmonic trap.

The orphan receptor Rev-erbα gene is a target of the circadian clock pacemaker

Abstract: Rev-erbα is a ubiquitously expressed orphan nuclear receptor which functions as a constitutive transcriptional repressor and is expressed in vertebrates according to a robust circadian rhythm. We report here that two Rev-erbα mRNA isoforms, namely Rev-erbα1 and Rev-erbα2, are generated through alternative promoter usage and that both show a circadian expression pattern in an in vitro system using serum-shocked fibroblasts. Both promoter regions P1 (Rev-erbα1) and P2 (Rev-erbα2) contain several E-box DNA sequences, which function as response elements for the core circadian-clock components: CLOCK and BMAL1. The CLOCK–BMAL1 heterodimer stimulates the activity of both P1 and P2 promoters in transient transfection assay by 3–6-fold. This activation was inhibited by the overexpression of CRY1, a component of the negative limb of the circadian transcriptional loop. Critical E-box elements were mapped within both promoters. This regulation is conserved in vertebrates since we found that the CLOCK–BMAL1 heterodimer also regulates the zebrafish Rev-erbα gene. In line with these data Rev-erbα circadian expression was strongly impaired in the livers of Clock mutant mice and in the pineal glands of zebrafish embryos treated with Clock and Bmal1 antisense oligonucleotides. Together these data demonstrate that CLOCK is a critical regulator of Rev-erbα circadian gene expression in evolutionarily distant vertebrates and suggest a role for Rev-erbα in the circadian clock output.

Combinatorial operad actions on cochains

Abstract: A classical E-infinity operad is formed by the bar construction of the symmetric groups. Such an operad has been introduced by M. Barratt and P. Eccles in the context of simplicial sets in order to have an analogue of the Milnor FK-construction for infinite loop spaces. The purpose of this article is to prove that the associative algebra structure on the normalized cochain complex of a simplicial set extends to the structure of an algebra over the Barratt-Eccles operad. We also prove that differential graded algebras over the Barratt-Eccles operad form a closed model category. Similar results hold for the normalized Hochschild cochain complex of an associative algebra. More precisely, the Hochschild cochain complex is acted on by a suboperad of the Barratt-Eccles operad which is equivalent to the classical little squares operad.

Equilibrium and Non-Equilibrium Statistical Thermodynamics

Abstract: This graduate-level text gives a self-contained exposition of fundamental topics in equilibrium and nonequilibrium statistical thermodynamics. The text follows a balanced approach between the macroscopic (thermodynamic) and microscopic (statistical) points of view. The first half of the book deals with equilibrium thermodynamics and statistical mechanics. In addition to standard subjects, the reader will find a detailed account of broken symmetries, critical phenomena and the renormalization group, as well as an introduction to numerical methods. The second half of the book is devoted to nonequilibrium phenomena, first following a macroscopic approach, with hydrodynamics as an important example. Kinetic theory receives a thorough treatment through analysis of the Boltzmann-Lorentz model and the Boltzmann equation. The book concludes with general nonequilibrium methods such as linear response, projection method and the Langevin and Fokker-Planck equations, including numerical simulations. This advanced textbook will be of interest to graduate students and researchers in physics.

Brain perfusion correlates of the apathy inventory dimensions of Alzheimer's disease.

Abstract: Background Apathy is defined as a lack of motivation in behavior, cognition and affect. This syndrome is frequent in various neuropsychiatric diseases but little is known about its pathophysiology. Objectives The aim of this study was to investigate the metabolic correlates of the behavioral, cognitive and emotional, aspects of apathy in Alzheimer's disease (AD). Method< Thirty AD patients were included. Lack of initiative, lack of interest and of emotional blunting were assessed with the Apathy Inventory (IA), a tool designed to provide a separate assessment of the behavioral, cognitive and emotional, aspects of apathy. Brain perfusion was measured by 99mTc-labeled bicisate (ECD) single photon emission tomography. Results The Statistical Parametric Mapping software provides negative correlation between IA total score and brain perfusion in left and right superior orbito-frontal gyrus, and to a lesser extent in left middle frontal gyrus (BA10). Lack of initiative score was negatively correlated with perfusion in right anterior cingulate cortex. Lack of interest score was negatively correlated with perfusion in right middle orbitofrontal gyrus). Emotional blunting score correlated negatively with in left superior dorsolateral prefrontal cortex activity. Conclusion These results underline that the cognitive, behavioral and affective components of motivation are mediated by different fronto-sub-cortical circuits and are differently lateralized. In particular, left prefrontal hypoperfusion is involved in emotional blunting, as it was often demonstrated in depressive disorders. These distinct components of apathy may be targeted by different therapeutic means, in which dopaminergic enhancement might play a major role. Copyright © 2004 John Wiley & Sons, Ltd.

Hazard rate for credit risk and hedging defaultable contingent claims

Abstract: We provide a concise exposition of theoretical results that appear in modeling default time as a random time, we study in details the invariance martingale property and we establish a representation theorem which leads, in a complete market setting, to the hedging portfolio of a vulnerable claim. Our main result is that, to hedge a defaultable claim one has to invest the value of this contingent claim in the defaultable zero-coupon.

The Importance of Organizational Justice in Personnel Selection: Defining when Selection Fairness Really Matters

Abstract: The purpose of this paper is to examine the usefulness of the organizational justice approach to applicant reactions We begin with an overview of the research relating the fairness of selection procedures ("selection fairness") to individual and organizational outcomes Next we propose boundary conditions defining when fairness should matter, the appropriate outcomes to examine in applicant reactions research, and methodological issues limiting the contribution of much of the current literature We then consider a range of questions that remain to be addressed and new issues such as high-tech testing Finally, we propose a series of applied questions and recommendations based on both theory and empirical research

Theoretical modelling of S-band thulium-doped silica fibre amplifiers

Abstract: A comprehensive numerical model of a thulium-doped silica-based fibre amplifiers is presented. The model is spectrally and spatially resolved and is general in terms of pumping scheme used. The application of the model for predicting the S-band amplifier performance and for optimization of amplifier parameters is shown. For optimized Tm-doped fibre with 3H4 level lifetime of 45 μs, which is the maximum value in the Tm-doped silica fibres prepared by the authors, above 20 dB of gain with 2000 mW pump power at the 1050 nm pump band can be expected according to the simulations.

Postextinction infusion of a mitogen-activated protein kinase inhibitor into the medial prefrontal cortex impairs memory of the extinction of conditioned fear.

Abstract: We investigated whether postextinction training infusion of PD098059, a selective inhibitor of mitogen-activated protein kinase (MAPK) activation, into the medial prefrontal cortex, would impair retention of extinction learning in rats. We found that immediate, but not late (2 or 4 h), postextinction infusion of PD098059 provoked a full return of conditioned freezing. These results suggest that activation of prefrontal MAPK in early stages of postextinction training participates in processes that protect against spontaneous recovery of aversive responses.

The Importance of Organizational Justice in Personnel Selection: Defining When Selection Fairness Really Matters

Abstract: The purpose of this paper is to examine the usefulness of the organizational justice approach to applicant reactions. We begin with an overview of the research relating the fairness of selection procedures (“selection fairness”) to individual and organizational outcomes. Next we propose boundary conditions defining when fairness should matter, the appropriate outcomes to examine in applicant reactions research, and methodological issues limiting the contribution of much of the current literature. We then consider a range of questions that remain to be addressed and new issues such as high-tech testing. Finally, we propose a series of applied questions and recommendations based on both theory and empirical research.

Slider block friction model for landslides: Application to Vaiont and La Clapière landslides

Abstract: [1] Accelerating displacements preceding some catastrophic landslides have been found to display a finite time singularity of the velocity v ∼1/(tc − t) [Voight, 1988a, 1988b]. Here we provide a physical basis for this phenomenological law based on a slider block model using a state- and velocity-dependent friction law established in the laboratory. This physical model accounts for and generalizes Voight's observation: Depending on the ratio B/A of two parameters of the rate and state friction law and on the initial frictional state of the sliding surfaces characterized by a reduced parameter Xi, four possible regimes are found. Two regimes can account for an acceleration of the displacement. For B/A > 1 (velocity weakening) and Xi 1. In this case, the acceleration of the displacement evolves toward a stable sliding with a constant sliding velocity. The two other cases (B/A 1 and Xi > 1) give a deceleration of the displacement. We use the slider block friction model to analyze quantitatively the displacement and velocity data preceding two landslides, Vaiont and La Clapiere. The Vaiont landslide was the catastrophic culmination of an accelerated slope velocity. La Clapiere landslide was characterized by a peak of slope acceleration that followed decades of ongoing accelerating displacements succeeded by a restabilization. Our inversion of the slider block model in these data sets shows good fits and suggests a classification of the Vaiont landslide as belonging to the unstable velocity-weakening sliding regime and La Clapiere landslide as belonging to the stable velocity-strengthening regime.

Aquiflexum balticum gen. nov., sp. nov., a novel marine bacterium of the Cytophaga-Flavobacterium-Bacteroides group isolated from surface water of the central Baltic Sea.

Abstract: A bacterial isolate from the Baltic Sea, BA160T, was characterized for its physiological and biochemical features, fatty acid profile, G+C content and phylogenetic position based on 16S rRNA gene sequences. The strain was isolated from the surface water of the central Baltic Sea during the decay of a plankton bloom. Phylogenetic analyses of the 16S rRNA gene sequence revealed a clear affiliation with the family ‘Flexibacteraceae’, and showed the closest phylogenetic relationship with the species Belliella baltica and Cyclobacterium marinum. The G+C content of the DNA was 38·4 mol%. The strain was red-coloured due to carotenoids, Gram-negative, rod-shaped, and catalase- and oxidase-positive. Growth was observed at salinities from 0 to 6 %, with an optimum around 1·5 %. Temperature for growth ranged from 4 to 40 °C, with an optimum around 30 °C. The fatty acids were dominated by branched-chain fatty acids (>87 %), with a high abundance of iso-C15 : 0 (23 %) and anteiso-C15 : 0 (19 %). According to its morphology, physiology, fatty acid composition, G+C content and 16S rRNA gene sequence, strain BA160T is considered to represent a new genus of the family ‘Flexibacteraceae’. Due to its aquatic origin, the name Aquiflexum balticum gen. nov, sp. nov. is suggested for the type species (type strain, BA160T=DSM 16537T=LMG 22565T=CIP 108445T) of the new genus.

The cover of living and dead corals from airborne remote sensing

Abstract: Trends in coral cover are widely used to indi- cate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m 2 pixels and 6 spectral bands with 0.25-m 2 pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral res- olution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead Porites (total colony mortality within 6 months), old dead (>6 months) Porites, Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562-580 nm. However, partially dead and recently dead Poritescolonies could not be distinguished from an airborne platform. Spectral dif- ferences among substrata are then exploited to predict the cover of reef substrata in ten 25-m 2 plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01- m 2 grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m 2 quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of Porites spp.). At the scale of the reef (all ten 25-m 2 quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living Porites, recently dead Porites and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods re- quired 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Re- mote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m 2 of reef, which represents 3,700 plots of 25 m 2 each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m 2 and 0.25-m 2 image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6-1.8 times greater in 0.25-m 2 pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, provid- ing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey).

Blind identification and source separation in 2/spl times/3 under-determined mixtures

Abstract: Under-determined mixtures are characterized by the fact that they have more inputs than outputs, or, with the antenna array processing terminology, more sources than sensors. The problem addressed is that of identifying and inverting the mixture, which obviously does not admit a linear inverse. Identification is carried out with the help of tensor canonical decompositions. On the other hand, the discrete distribution of the sources is utilized for performing the source extraction, the under-determined mixture being either known or unknown. The results presented in this paper are limited to two-dimensional (2-D) mixtures of three sources.