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Search Results: 1 - 10 of 28640 matches for " Jean-Pierre Levraud "
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Volatility Forecasting of Market Demand as Aids for Planning Manufacturing Activities  [PDF]
Jean-Pierre Briffaut, Patrick Lallement
Journal of Service Science and Management (JSSM) , 2010, DOI: 10.4236/jssm.2010.34045
Abstract: The concepts and techniques designed and used for pricing financial options have been applied to assist in scheduling manufacturing activities. Releasing a manufacturing order is viewed as an investment opportunity whose properties are similar to a call option. Its value can be considered as the derivative of the market demand mirrored in the selling price of the manufactured products and changes over time following an Itô process. Dynamic programming has been used to derive the optimal timing for releasing manufacturing orders. It appears advisable to release a manufacturing when the unit selling price come to a threshold P* given by the relation P* = β/(β–1) C with C = unit cost price. β is a parameter whose value depends on the trend parameter α and the volatility σ of the selling price, the discount rate ρ applicable to the capital appreciation relevant to the business context under consideration. The results have been successfully applied to the evolution of the quarterly construction cost index in France over ten years.
Chaos Appearance during Domain Wall Motion under Electronic Transfer in Nanomagnets  [PDF]
Donfack Gildas Hermann, Jean-Pierre Nguenang
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.33022
Abstract:

In this paper, we study the likelihood of chaos appearance during domain wall motion induced by electronic transfer. Considering a time-varying current density theory, we proceed to a numerical investigation of the dynamics. Using the dissipation parameter, amplitude and frequency of current density as control parameters; we show how periodic regime as well as chaotic regime can be exhibited in nanomagnetic systems. Numerical results allow setting up the periodicity and quasi-periodicity of system and chaotic phenomena occurring during magnetization switching process in nanomagnet through electronic transfer.

Traceability in Acceptance Testing  [PDF]
Jean-Pierre Corriveau, Wei Shi
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.610A005
Abstract:

Regardless of which (model-centric or code-centric) development process is adopted, industrial software production ultimately and necessarily requires the delivery of an executable implementation. It is generally accepted that the quality of such an implementation is of utmost importance. Yet current verification techniques, including software testing, remain problematic. In this paper, we focus on acceptance testing, that is, on the validation of the actual behavior of the implementation under test against the requirements of stakeholder(s). This task must be as objective and automated as possible. Our first goal is to review existing code-based and model-based tools for testing in light of what such an objective and automated approach to acceptance testing entails. Our contention is that the difficulties we identify originate mainly in a lack of traceability between a testable model of the requirements of the stakeholder(s) and the test cases used to validate these requirements. We then investigate whether such traceability is addressed in other relevant specification-based approaches.

DNA Nano Devices as a Biased Random Walk Process: A Case Study of Isothermal Ratchet?  [PDF]
Jean-Pierre Aimé, Juan Elezgaray
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.65045
Abstract: Computation and amplification processes based on Networks of Chemical Reactions are at the heart of our understanding of the regulation and error correction of life systems. The recent advances in DNA nanotechnology, with the creation of the modular structures origamis and the development of dynamical networks using the toe hold mediated strand displacement, open fertile areas to construct Hierarchical Cascades of Chemical Reactions with an increasing complexity inspired from systems in biology. DNA strands have the great advantage to design autonomous and homogeneous Networks of Chemical Reactions leaving aside companion chemical reactions as it occurs in biological systems. In the present paper, we use the Fokker Planck equation to extract predictions that address a wider class of systems beyond the case of diluted solutions. We introduce the concept of toehold strength and output strength that leads to an exponential square dependence of the toehold strength divided by the output strength on the escape rate and the probability for the output strand to leave the gate. We highlight the influence of the boundary conditions that may have an important consequence in confined environment when modular structures like origamis are employed.
Origin and Evolution of TRIM Proteins: New Insights from the Complete TRIM Repertoire of Zebrafish and Pufferfish
Pierre Boudinot, Lieke M. van der Aa, Luc Jouneau, Louis Du Pasquier, Pierre Pontarotti, Valérie Briolat, Abdenour Benmansour, Jean-Pierre Levraud
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022022
Abstract: Tripartite motif proteins (TRIM) constitute a large family of proteins containing a RING-Bbox-Coiled Coil motif followed by different C-terminal domains. Involved in ubiquitination, TRIM proteins participate in many cellular processes including antiviral immunity. The TRIM family is ancient and has been greatly diversified in vertebrates and especially in fish. We analyzed the complete sets of trim genes of the large zebrafish genome and of the compact pufferfish genome. Both contain three large multigene subsets - adding the hsl5/trim35-like genes (hltr) to the ftr and the btr that we previously described - all containing a B30.2 domain that evolved under positive selection. These subsets are conserved among teleosts. By contrast, most human trim genes of the other classes have only one or two orthologues in fish. Loss or gain of C-terminal exons generated proteins with different domain organizations; either by the deletion of the ancestral domain or, remarkably, by the acquisition of a new C-terminal domain. Our survey of fish trim genes in fish identifies subsets with different evolutionary dynamics. trims encoding RBCC-B30.2 proteins show the same evolutionary trends in fish and tetrapods: they evolve fast, often under positive selection, and they duplicate to create multigenic families. We could identify new combinations of domains, which epitomize how new trim classes appear by domain insertion or exon shuffling. Notably, we found that a cyclophilin-A domain replaces the B30.2 domain of a zebrafish fintrim gene, as reported in the macaque and owl monkey antiretroviral TRIM5α. Finally, trim genes encoding RBCC-B30.2 proteins are preferentially located in the vicinity of MHC or MHC gene paralogues, which suggests that such trim genes may have been part of the ancestral MHC.
Whole-Body Analysis of a Viral Infection: Vascular Endothelium is a Primary Target of Infectious Hematopoietic Necrosis Virus in Zebrafish Larvae
Marion Ludwig equal contributor,Nuno Palha equal contributor,Corinne Torhy,Valérie Briolat,Emma Colucci-Guyon,Michel Brémont,Philippe Herbomel,Pierre Boudinot,Jean-Pierre Levraud
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1001269
Abstract: The progression of viral infections is notoriously difficult to follow in whole organisms. The small, transparent zebrafish larva constitutes a valuable system to study how pathogens spread. We describe here the course of infection of zebrafish early larvae with a heat-adapted variant of the Infectious Hematopoietic Necrosis Virus (IHNV), a rhabdovirus that represents an important threat to the salmonid culture industry. When incubated at 24°C, a permissive temperature for virus replication, larvae infected by intravenous injection died within three to four days. Macroscopic signs of infection followed a highly predictable course, with a slowdown then arrest of blood flow despite continuing heartbeat, followed by a loss of reactivity to touch and ultimately by death. Using whole-mount in situ hybridization, patterns of infection were imaged in whole larvae. The first infected cells were detectable as early as 6 hours post infection, and a steady increase in infected cell number and staining intensity occurred with time. Venous endothelium appeared as a primary target of infection, as could be confirmed in fli1:GFP transgenic larvae by live imaging and immunohistochemistry. Disruption of the first vessels took place before arrest of blood circulation, and hemorrhages could be observed in various places. Our data suggest that infection spread from the damaged vessels to underlying tissue. By shifting infected fish to a temperature of 28°C that is non-permissive for viral propagation, it was possible to establish when virus-generated damage became irreversible. This stage was reached many hours before any detectable induction of the host response. Zebrafish larvae infected with IHNV constitute a vertebrate model of an hemorrhagic viral disease. This tractable system will allow the in vivo dissection of host-virus interactions at the whole organism scale, a feature unrivalled by other vertebrate models.
A large new subset of TRIM genes highly diversified by duplication and positive selection in teleost fish
Lieke M van der Aa, Jean-Pierre Levraud, Malika Yahmi, Emilie Lauret, Valérie Briolat, Philippe Herbomel, Abdenour Benmansour, Pierre Boudinot
BMC Biology , 2009, DOI: 10.1186/1741-7007-7-7
Abstract: We describe here a large new subfamily of TRIMs in teleosts, called finTRIMs, identified in rainbow trout as virus-induced transcripts. FinTRIMs are formed of nearly identical RING/B-box regions and C-termini of variable length; the long variants include a B30.2 domain. The zebrafish genome harbors a striking diversity of finTRIMs, with 84 genes distributed in clusters on different chromosomes. A phylogenetic analysis revealed different subsets suggesting lineage-specific diversification events. Accordingly, the number of fintrim genes varies greatly among fish species. Conserved syntenies were observed only for the oldest fintrims. The closest mammalian relatives are trim16 and trim25, but they are not true orthologs. The B30.2 domain of zebrafish finTRIMs evolved under strong positive selection. The positions under positive selection are remarkably congruent in finTRIMs and in mammalian antiviral TRIM5α, concentrated within a viral recognition motif in mammals. The B30.2 domains most closely related to finTRIM are found among NOD-like receptors (NLR), indicating that the evolution of TRIMs and NLRs was intertwined by exon shuffling.The diversity, evolution, and features of finTRIMs suggest an important role in fish innate immunity; this would make them the first TRIMs involved in immunity identified outside mammals.Newly discovered players in the antiviral immunity field are the proteins belonging to the tripartite motif (TRIM) family. The TRIM proteins are characterized by a tripartite motif that comprises from the N- to C-terminus, a RING zinc finger domain, one or two B-boxes and a coiled-coil domain. They are therefore also known as RBCC proteins [1]. The RING finger and B-box are cysteine-rich domains and both domains bind zinc atoms, suggesting interaction with other proteins, RNA and DNA [2-5]. They are usually encoded as a single exon, and together form the 'RBB' region. In addition, the RING finger has E3 ubiquitin ligase activity [6]. The coiled-coil reg
The Zebrafish as a New Model for the In Vivo Study of Shigella flexneri Interaction with Phagocytes and Bacterial Autophagy
Serge Mostowy ,Laurent Boucontet,Maria J. Mazon Moya,Andrea Sirianni,Pierre Boudinot,Michael Hollinshead,Pascale Cossart,Philippe Herbomel,Jean-Pierre Levraud,Emma Colucci-Guyon
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003588
Abstract: Autophagy, an ancient and highly conserved intracellular degradation process, is viewed as a critical component of innate immunity because of its ability to deliver cytosolic bacteria to the lysosome. However, the role of bacterial autophagy in vivo remains poorly understood. The zebrafish (Danio rerio) has emerged as a vertebrate model for the study of infections because it is optically accessible at the larval stages when the innate immune system is already functional. Here, we have characterized the susceptibility of zebrafish larvae to Shigella flexneri, a paradigm for bacterial autophagy, and have used this model to study Shigella-phagocyte interactions in vivo. Depending on the dose, S. flexneri injected in zebrafish larvae were either cleared in a few days or resulted in a progressive and ultimately fatal infection. Using high resolution live imaging, we found that S. flexneri were rapidly engulfed by macrophages and neutrophils; moreover we discovered a scavenger role for neutrophils in eliminating infected dead macrophages and non-immune cell types that failed to control Shigella infection. We observed that intracellular S. flexneri could escape to the cytosol, induce septin caging and be targeted to autophagy in vivo. Depletion of p62 (sequestosome 1 or SQSTM1), an adaptor protein critical for bacterial autophagy in vitro, significantly increased bacterial burden and host susceptibility to infection. These results show the zebrafish larva as a new model for the study of S. flexneri interaction with phagocytes, and the manipulation of autophagy for anti-bacterial therapy in vivo.
A New Zebrafish Model of Oro-Intestinal Pathogen Colonization Reveals a Key Role for Adhesion in Protection by Probiotic Bacteria
Olaya Rendueles equal contributor,Lionel Ferrières equal contributor,Maxence Frétaud equal contributor,Evelyne Bégaud,Philippe Herbomel,Jean-Pierre Levraud,Jean-Marc Ghigo
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1002815
Abstract: The beneficial contribution of commensal bacteria to host health and homeostasis led to the concept that exogenous non-pathogenic bacteria called probiotics could be used to limit disease caused by pathogens. However, despite recent progress using gnotobiotic mammal and invertebrate models, mechanisms underlying protection afforded by commensal and probiotic bacteria against pathogens remain poorly understood. Here we developed a zebrafish model of controlled co-infection in which germ-free zebrafish raised on axenic living protozoa enabled the study of interactions between host and commensal and pathogenic bacteria. We screened enteric fish pathogens and identified Edwardsiella ictaluri as a virulent strain inducing a strong inflammatory response and rapid mortality in zebrafish larvae infected by the natural oro-intestinal route. Using mortality induced by infection as a phenotypic read-out, we pre-colonized zebrafish larvae with 37 potential probiotic bacterial strains and screened for survival upon E. ictaluri infection. We identified 3 robustly protective strains, including Vibrio parahaemolyticus and 2 Escherichia coli strains. We showed that the observed protective effect of E. coli was not correlated with a reduced host inflammatory response, nor with the release of biocidal molecules by protective bacteria, but rather with the presence of specific adhesion factors such as F pili that promote the emergence of probiotic bacteria in zebrafish larvae. Our study therefore provides new insights into the molecular events underlying the probiotic effect and constitutes a potentially high-throughput in vivo approach to the study of the molecular basis of pathogen exclusion in a relevant model of vertebrate oro-intestinal infection.
Skeletal involvement in the pathogenesis and outcomes of rheumatoid arthritis and osteoarthritis
Jean-Pierre Pelletier
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3571
Abstract: In RA, increased osteoclastic activity is responsible for the development of focal osteopenia/erosion and systemic osteoporosis. The increased osteoclast activity in RA has been demonstrated to be linked to a dysregulation of pathways including cell-cell interactions, cytokines, and the receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) system. Recent studies have shown that joint erosion in RA is linked to a decrease in long-term physical function.Under OA conditions, the subchondral bone is the site of numerous dynamic morphological changes. These changes are associated with a number of local abnormal biochemical pathways related to the altered metabolism of osteoblasts and osteoclasts. At the early stages of the disease process, increased bone loss and resorption is observed with subchondral bone associated with local production of catabolic factors including cathepsin K and MMP-13. Moreover, OA osteoblasts present an abnormal phenotype resulting in increased production of growth hormones and catabolic factors. In addition, factors such as osteoprotegerin (OPG) and RANKL have been found to be expressed and modulated over time in human OA subchondral bone. Their synthesis varies from being reduced in early OA to being increased in the late stages of the disease. This finding may explain that in the early stages of OA, bone remodeling favors resorption and in the more advanced stages of the disease, bone formation is predominant.Magnetic resonance imaging (MRI) studies in knee OA patients have shown that the subchondral bone is frequently the site of signal alterations-bone marrow lesions (BML) - indicative of a great variety of morphological changes. BML and cartilage loss have been linked in several studies. Moreover, studies have identified, in OA patients, a number of risk factors for total knee replacement including BMLs.The paradigms regarding the role of bone lesions in arthritic diseases raise a number of important questions. A comprehensive
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