Showing papers by "École Normale Supérieure published in 1997"
TL;DR: This chapter presents the basic schemes of VNS and some of its extensions, and presents five families of applications in which VNS has proven to be very successful.
3,572 citations
TL;DR: A new source separation technique exploiting the time coherence of the source signals is introduced, which relies only on stationary second-order statistics that are based on a joint diagonalization of a set of covariance matrices.
Abstract: Separation of sources consists of recovering a set of signals of which only instantaneous linear mixtures are observed. In many situations, no a priori information on the mixing matrix is available: The linear mixture should be "blindly" processed. This typically occurs in narrowband array processing applications when the array manifold is unknown or distorted. This paper introduces a new source separation technique exploiting the time coherence of the source signals. In contrast with other previously reported techniques, the proposed approach relies only on stationary second-order statistics that are based on a joint diagonalization of a set of covariance matrices. Asymptotic performance analysis of this method is carried out; some numerical simulations are provided to illustrate the effectiveness of the proposed method.
2,721 citations
TL;DR: This paper describes a linear matrix inequality (LMI)-based algorithm for the static and reduced-order output-feedback synthesis problems of nth-order linear time-invariant (LTI) systems with n/sub u/ and n/ sub y/) independent inputs (respectively, outputs).
Abstract: This paper describes a linear matrix inequality (LMI)-based algorithm for the static and reduced-order output-feedback synthesis problems of nth-order linear time-invariant (LTI) systems with n/sub u/ (respectively, n/sub y/) independent inputs (respectively, outputs). The algorithm is based on a "cone complementarity" formulation of the problem and is guaranteed to produce a stabilizing controller of order m/spl les/n-max(n/sub u/,n/sub y/), matching a generic stabilizability result of Davison and Chatterjee (1971). Extensive numerical experiments indicate that the algorithm finds a controller with order less than or equal to that predicted by Kimura's generic stabilizability result (m/spl les/n-n/sub u/-n/sub y/+1). A similar algorithm can be applied to a variety of control problems, including robust control synthesis.
1,933 citations
TL;DR: The List of Bacterial Names with Standing in Nomenclature includes, alphabetically and chronologically, the official names of bacteria as published or validated in the International Journal of Systematic Bacteriology.
Abstract: The List of Bacterial Names with Standing in Nomenclature includes, alphabetically and chronologically, the official names of bacteria as published or validated in the International Journal of Systematic Bacteriology. It encompasses 5,569 taxa (as of 31 December 1996) and is available on the Internet (URL: ftp://ftp.cict.fr/pub/bacterio/).
1,114 citations
TL;DR: It is shown that dynamic asters can also be obtained from a homogeneous solution of tubulin and motors, and it is demonstrated that the same final structure can be reached through different assembly ‘pathways’.
Abstract: Cellular structures are established and maintained through a dynamic interplay between assembly and regulatory processes. Self-organization of molecular components provides a variety of possible spatial structures: the regulatory machinery chooses the most appropriate to express a given cellular function. Here we study the extent and the characteristics of self-organization using microtubules and molecular motors as a model system. These components are known to participate in the formation of many cellular structures, such as the dynamic asters found in mitotic and meiotic spindles. Purified motors and microtubules have previously been observed to form asters in vitro. We have reproduced this result with a simple system consisting solely of multi-headed constructs of the motor protein kinesin and stabilized microtubules. We show that dynamic asters can also be obtained from a homogeneous solution of tubulin and motors. By varying the relative concentrations of the components, we obtain a variety of self-organized structures. Further, by studying this process in a constrained geometry of micro-fabricated glass chambers, we demonstrate that the same final structure can be reached through different assembly 'pathways.
772 citations
TL;DR: This article shows that the infomax (information-maximization) principle is equivalent to the maximum likelihood.
Abstract: Algorithms for the blind separation of sources can be derived from several different principles. This article shows that the infomax (information-maximization) principle is equivalent to the maximum likelihood. The application of the infomax principle to source separation consists of maximizing an output entropy.
739 citations
TL;DR: Evidence suggesting that the NR ethylene perception and transduction pathway is specific to a defined set of genes expressed in ripening climacteric fruit and that a distinct ETR pathway regulates other ethylene-regulated genes in both immature and ripening Climacteric Fruit as well as in non-climacteric fruits is discussed.
Abstract: The latest advances in our understanding of the relationship between ethylene and fruit ripening are reviewed. Considerable progress has been made in the characterisation of genes encoding the key ethylene biosynthetic enzymes, ACC synthase (ACS) and ACC oxidase (ACO) and in the isolation of genes involved in the ethylene signal transduction pathway, particularly those encoding ethylene receptors (ETR). These have allowed the generation of transgenic fruit with reduced ethylene production and the identification of the Nr tomato ripening mutant as an ethylene receptor mutant. Through these tools, a clearer picture of the role of ethylene in fruit ripening is now emerging. In climacteric fruit, the transition to autocatalytic ethylene production appears to result from a series of events where developmentally regulated ACO and ACS gene expression initiates a rise in ethylene production, setting in motion the activation of autocatalytic ethylene production. Differential expression of ACS and ACO gene family members is probably involved in such a transition. Finally, we discuss evidence suggesting that the NR ethylene perception and transduction pathway is specific to a defined set of genes expressed in ripening climacteric fruit and that a distinct ETR pathway regulates other ethylene-regulated genes in both immature and ripening climacteric fruit as well as in non-climacteric fruit. The emerging picture is one where both ethylene-dependent and -independent pathways coexist in both climacteric and non-climacteric fruits. Further work is needed in order to dissect the molecular events involved in individual ripening processes and to understand the regulation of the expression of both ethylene-dependent and -independent genes.
735 citations
TL;DR: Whether high mutation rates might play an important role in adaptive evolution is considered, as models of large, asexual, clonal populations adapting to a new environment show that strong mutator genes can accelerate adaptation, even if the mutator gene remains at a very low frequency.
Abstract: that the mutation rate has evolved to be as low as possible, limited only by the cost of error-avoidance and error-correction mechanisms. But up to one per cent of natural bacterial isolates are 'mutator' clones that have high mutation rates 4-6 . We consider here whether high mutation rates might play an important role in adaptive evolution. Models of large, asexual, clonal populations adapting to a new environment show that strong mutator genes (such as those that increase mutation rates by 1,000-fold) can accelerate adaptation, even if the mutator gene remains at a very low frequency (for example, 10 2 5 ). Less potent mutators (10 to 100-fold increase) can become fixed in a fraction of finite populations. The parameters of the model have been set to values typical for Escherichia coli cultures, which behave in a manner similar to the model in long-term adaptation experiments 7 . Early models of the evolution of the mutation rate were based on group selection for an optimal compromise between adaptability and adaptedness 2,3 . However, later models, incorporating mutators and antimutators (modifiers of the mutation rate) showed that a mutator can reduce individual fitness while increasing the prob- ability for an adaptive mutation to appear in the population. The prediction of these models was that a minimal mutation rate would be selected in a stable environment (reduction principle 8 ), whereas in an oscillating environment, infinite populations at equilibrium
706 citations
TL;DR: It is shown that two types of inhibitory neurons in the cerebellar cortex fire spontaneously and regularly in the absence of synaptic input but generate an irregular firing pattern in the presence of tonic synaptic inhibition, suggesting that the time window for synaptic integration is a dynamic variable modulated by the level of Tonic inhibition.
679 citations
TL;DR: The majority of Japanese even today believe that the politico-cultural universe of the Edo period was fundamentally determined by the closure of the country as mentioned in this paper, and they also think that the opening of Japan can be reduced to the development of exchanges with the West, following the birth of the Meiji regime.
Abstract: The majority of Japanese even today believe that the politico-cultural universe of the Edo period was fundamentally determined by the closure of the country. They also think that the opening of Japan can be reduced to the development of exchanges with the West, following the birth of the Meiji regime. It is hard for them to imagine that Japan developed in relation with other Asian countries, since they are hardly used to appreciating Asian cultures.
665 citations
TL;DR: In this paper, a pair of atoms were prepared in an entangled state of the Einstein-Podolsky-Rosen (EPR) type by the exchange of a single photon between the atoms in a high $Q$ cavity.
Abstract: Pairs of atoms have been prepared in an entangled state of the Einstein-Podolsky-Rosen (EPR) type. They were produced by the exchange of a single photon between the atoms in a high $Q$ cavity. The atoms, entangled in a superposition involving two different circular Rydberg states, were separated by a distance of the order of 1 cm. At variance with most previous EPR experiments, this one involves massive particles. It can be generalized to three or more atoms and opens the way to new tests of nonlocality in mesoscopic quantum systems.
TL;DR: GFP reporters consist of wild‐type GFP or GFP‐S65T coding sequences, lacking the ATG, fused to the S. cerevisiae ADH1 terminator and PCR‐synthesized 2·4 kb‐long double modules flanked by 40 bp‐long guide sequences were successfully targeted to the carboxy‐terminus of a number of S. Cerevisiae genes.
Abstract: We have fused the open reading frames of his3-complementing genes from Saccharomyces kluyveri and Schizosac-charomyces pombe to the strong TEF gene promotor of the filamentous fungus Ashbya gossypii. Both chimeric modules and the cognate S. kluyveri HIS3 gene were tested in transformations of his3 S. cerevisiae strains using PCR fragments flanked by 40 bp target guide sequences. The 1.4 kb chimeric Sz. pombe module (HIS3MX6) performed best. With less than 5% incorrectly targeted transformants, it functions as reliably as the widely used geniticin resistance marker kanMX. The rare false-positive His+ transformants seem to be due to non-homologous recombination rather than to gene conversion of the mutated endogenous his3 allele. We also cloned the green fluorescent protein gene from Aequorea victoria into our pFA-plasmids with HIS3MX6 and kanMX markers. The 0.9 kb GFP reporters consist of wild-type GFP or GFP-S65T coding sequences, lacking the ATG, fused to the S. cerevisiae ADH1 terminator. PCR-synthesized 2.4 kb-long double modules flanked by 40-45 bp-long guide sequences were successfully targeted to the carboxy-terminus of a number of S. cerevisiae genes. We could estimate that only about 10% of the transformants carried inactivating mutations in the GFP reporter.
TL;DR: In this article, a survey of clustering from a mathematical programming viewpoint is presented, focusing on solution methods, i.e., dynamic programming, graph theoretical algorithms, branch-and-bound, cutting planes, column generation and heuristics.
Abstract: Given a set of entities, Cluster Analysis aims at finding subsets, called clusters, which are homogeneous and/or well separated. As many types of clustering and criteria for homogeneity or separation are of interest, this is a vast field. A survey is given from a mathematical programming viewpoint. Steps of a clustering study, types of clustering and criteria are discussed. Then algorithms for hierarchical, partitioning, sequential, and additive clustering are studied. Emphasis is on solution methods, i.e., dynamic programming, graph theoretical algorithms, branch-and-bound, cutting planes, column generation and heuristics.
TL;DR: A brief introduction to the biology of the immune system is provided and a number of immunological problems in which the use of physical concepts and mathematical methods has increased the authors' understanding are discussed.
Abstract: The immune system is a complex system of cells and molecules that can provide us with a basic defense against pathogenic organisms. Like the nervous system, the immune system performs pattern recognition tasks, learns, and retains a memory of the antigens that it has fought. The immune system contains more than 10{sup 7} different clones of cells that communicate via cell-cell contact and the secretion of molecules. Performing complex tasks such as learning and memory involves cooperation among large numbers of components of the immune system and hence there is interest in using methods and concepts from statistical physics. Furthermore, the immune response develops in time and the description of its time evolution is an interesting problem in dynamical systems. In this paper, the authors provide a brief introduction to the biology of the immune system and discuss a number of immunological problems in which the use of physical concepts and mathematical methods has increased our understanding. {copyright} {ital 1997} {ital The American Physical Society}
TL;DR: In this paper, the authors identify some of the main issues in freight transportation planning and operations, and present appropriate Operations Research models and methods, as well as computer-based planning tools.
TL;DR: In this paper, the authors studied the integrable structures in Conformal Field Theory (CFT) and showed how to construct the operators ${\bf Q}_{\pm}(\lambda)$ which act in the highest weight Virasoro module and commute for different values of the parameter λ.
Abstract: This paper is a direct continuation of [1] where we began the study of the integrable structures in Conformal Field Theory. We show here how to construct the operators ${\bf Q}_{\pm}(\lambda)$ which act in the highest weight Virasoro module and commute for different values of the parameter λ. These operators appear to be the CFT analogs of the Q - matrix of Baxter [2], in particular they satisfy Baxter's famous T- Q equation. We also show that under natural assumptions about analytic properties of the operators as the functions of λ the Baxter's relation allows one to derive the nonlinear integral equations of Destri-de Vega (DDV) [3] for the eigenvalues of the Q-operators. We then use the DDV equation to obtain the asymptotic expansions of the Q - operators at large λ; it is remarkable that unlike the expansions
of the T operators of [1], the asymptotic series for Q(λ) contains the “dual” nonlocal Integrals of Motion along with the local ones. We also discuss an intriguing relation between the vacuum eigenvalues of the Q - operators and the stationary transport properties in the boundary sine-Gordon model. On this basis we propose a number of new exact results about finite voltage charge transport through the point contact in the quantum Hall system.
TL;DR: Although all of the mice injected with homogenate from BSE-infected cattle brain exhibited neurological symptoms and neuronal death, more than 55 percent had no detectable PrPres, suggesting that a further unidentified agent may actually transmit BSE.
Abstract: The agent responsible for transmissible spongiform encephalopathies (TSEs) is thought to be a malfolded, protease-resistant version (PrPres) of the normal cellular prion protein (PrP). The interspecies transmission of bovine spongiform encephalopathy (BSE) to mice was studied. Although all of the mice injected with homogenate from BSE-infected cattle brain exhibited neurological symptoms and neuronal death, more than 55 percent had no detectable PrPres. During serial passage, PrPres appeared after the agent became adapted to the new host. Thus, PrPres may be involved in species adaptation, but a further unidentified agent may actually transmit BSE.
TL;DR: The hypothesis that first language acquisition relies on a dedicated left-hemispheric cerebral network, while late second language acquisition is not necessarily associated with a reproducible biological substrate is supported.
Abstract: Functional magnetic resonance imaging was used to assess inter-subject variability in the cortical representation of language comprehension processes. Moderately fluent French-English bilinguals were scanned while they listened to stories in their first language (L1 = French) or in a second language (L2 = English) acquired at school after the age of seven. In all subjects, listening to L1 always activated a similar set of areas in the left temporal lobe, clustered along the left superior temporal sulcus. Listening to L2, however, activated a highly variable network of left and right temporal and frontal areas, sometimes restricted only to right-hemispheric regions. These results support the hypothesis that first language acquisition relies on a dedicated left-hemispheric cerebral network, while late second language acquisition is not necessarily associated with a reproducible biological substrate. The postulated contribution of the right hemisphere to L2 comprehension is found to hold only on average, individual subjects varying from complete right lateralization to standard left lateralization for L2.
TL;DR: In this paper, the authors examined the effects of music on consumers' reactions to waiting for services and found that regardless of its valence, music ameliorated emotional evaluation of the service environment which in turn positively affects approach behavior towards the service organization.
TL;DR: The separation force signal is shown to be related to the local GC vs. AT content along the molecule, and variations of this content on a typical scale of 100-500 bases are presently detected.
Abstract: We describe the mechanical separation of the two complementary strands of a single molecule of bacteriophage λ DNA. The 3′ and 5′ extremities on one end of the molecule are pulled progressively apart, and this leads to the opening of the double helix. The typical forces along the opening are in the range of 10–15 pN. The separation force signal is shown to be related to the local GC vs. AT content along the molecule. Variations of this content on a typical scale of 100–500 bases are presently detected.
TL;DR: In this article, the p-median problem is studied in the context of cluster analysis where locations of users are then replaced by points in a given space, and several new Variable Neighborhood Search heuristics are proposed.
TL;DR: This work presents a survey of the techniques developed since the mid-1980s to implement replicated services, emphasizing the relationship between replication techniques and group communication.
Abstract: Replication handled by software on off-the-shelf hardware costs less than using specialized hardware. Although an intuitive concept, replication requires sophisticated techniques for successful implementation. Group communication provides an adequate framework. We present a survey of the techniques developed since the mid-1980s to implement replicated services, emphasizing the relationship between replication techniques and group communication.
TL;DR: In this article, the convergence of a generalisation of the quadratic variations of a Gaussian process was studied and a convergent estimator of the local Holder index of the sample paths was proposed.
Abstract: We study the convergence of a generalisation of the quadratic variations of a Gaussian process. We build a convergent estimator of the local Holder index of the sample paths and prove a central limit theorem.
TL;DR: This paper presents navigation strategies within a four-level hierarchical framework based upon levels of complexity of required processing (Guidance, Place recognition-triggered Response, Topological navigation, Metric navigation), and introduces computational models of animal navigation, i.e. of animats.
TL;DR: In this paper, the authors studied the spectral measure of Gaussian Wigner's matrices and proved that it satisfies the large deviation principle and showed that the good rate function which governs this principle achieves its minimum value at Wigners semicircular law.
Abstract: We study the spectral measure of Gaussian Wigner's matrices and prove that it satisfies a large deviation principle. We show that the good rate function which governs this principle achieves its minimum value at Wigner's semicircular law, which entails the convergence of the spectral measure to the semicircular law. As a conclusion, we give some further examples of random matrices with spectral measure satisfying a large deviation principle and argue about Voiculescu's non commutative entropy.
TL;DR: In this article, the authors modeled the 1992 Landers, California, earthquake as the propagation of a spontaneous rupture controlled by a realistic prestress distribution with the use of a three-dimensional finite-difference method.
Abstract: The 1992 Landers, California, earthquake (magnitude 7.3) was modeled as the propagation of a spontaneous rupture controlled by a realistic prestress distribution with the use of a three-dimensional finite-difference method. The dynamic rupture reproduces the general slip pattern used to compute the initial stress distribution and generates near-fault ground motions at the surface similar to observations. The simulated rupture propagates on the fault along a complex path with highly variable speed and rise time, changing the magnitude and pattern of the stress significantly. The method provides the framework to estimate earthquake rupture parameters from recorded seismic and geodetic data.
TL;DR: In this article, the reduction of the bond length alternation (BLA) in the polyenic chain has been investigated, and unprecedented quadratic hyperpolarizabilities (p) have been achieved (up to p(0) =I500 x 10-30esu) by reduction.
Abstract: Donor-acceptor polyenes of various lengths, and that combine aro- matic electron-donating moieties with powerful heterocyclic electron-withdraw- ing terminal groups, have been synthe- sized and characterized as efficient non- linear optical (NLO) chromophores. Their linear and nonlinear optical proper- ties have been investigated, and variations in these properties have been related to ground-state polarization (dipole p) and structure. In particular, unprecedented quadratic hyperpolarizabilities (p) have been achieved (up to p(0) =I500 x 10-30esu) by reduction of the bond- length alternation (BLA) in the polyenic chain. In each series of homologous com-