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Search Results: 1 - 10 of 6921 matches for " Stéphane Roche "
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La diffusion spatiale des technologies de l'information géographique en France
Stéphane Roche,Jean-Baptiste Humeau
Mappemonde , 1999,
Abstract: La diffusion des technologies de l'information géographique sur le territoire fran ais s'inscrit dans les modèles classiques centre-périphérie de diffusion des innovations technologiques. Pourtant, au-delà de ces grandes dynamiques nationales, la distribution spatiale des TIG reflète les caractéristiques institutionnelles, culturelles et spatiales spécifiques d'un secteur géomatique en plein développement.
Of Bits and Bugs — On the Use of Bioinformatics and a Bacterial Crystal Structure to Solve a Eukaryotic Repeat-Protein Structure
Almut Graebsch,Stéphane Roche,Dirk Kostrewa,Johannes S?ding,Dierk Niessing
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013402
Abstract: Pur-α is a nucleic acid-binding protein involved in cell cycle control, transcription, and neuronal function. Initially no prediction of the three-dimensional structure of Pur-α was possible. However, recently we solved the X-ray structure of Pur-α from the fruitfly Drosophila melanogaster and showed that it contains a so-called PUR domain. Here we explain how we exploited bioinformatics tools in combination with X-ray structure determination of a bacterial homolog to obtain diffracting crystals and the high-resolution structure of Drosophila Pur-α. First, we used sensitive methods for remote-homology detection to find three repetitive regions in Pur-α. We realized that our lack of understanding how these repeats interact to form a globular domain was a major problem for crystallization and structure determination. With our information on the repeat motifs we then identified a distant bacterial homolog that contains only one repeat. We determined the bacterial crystal structure and found that two of the repeats interact to form a globular domain. Based on this bacterial structure, we calculated a computational model of the eukaryotic protein. The model allowed us to design a crystallizable fragment and to determine the structure of Drosophila Pur-α. Key for success was the fact that single repeats of the bacterial protein self-assembled into a globular domain, instructing us on the number and boundaries of repeats to be included for crystallization trials with the eukaryotic protein. This study demonstrates that the simpler structural domain arrangement of a distant prokaryotic protein can guide the design of eukaryotic crystallization constructs. Since many eukaryotic proteins contain multiple repeats or repeating domains, this approach might be instructive for structural studies of a range of proteins.
WikiGIS Basic Concepts: Web 2.0 for Geospatial Collaboration
Stéphane Roche,Boris Mericskay,Wided Batita,Matthieu Bach,Mathieu Rondeau
Future Internet , 2012, DOI: 10.3390/fi4010265
Abstract: With the emergence of Web 2.0, new applications arise and evolve into more interactive forms of collective intelligence. These applications offer to both professionals and citizens an open and expanded access to geographic information. In this paper, we develop the conceptual foundations of a new technology solution called WikiGIS. WikiGIS’s strength lies in its ability to ensure the traceability of changes in spatial-temporal geographic components (geometric location and shape, graphics: iconography and descriptive) generated by users. The final use case highlights to what extent WikiGIS could be a relevant and useful technological innovation in Geocollaboration.
Interest of major serum protein removal for Surface-Enhanced Laser Desorption/Ionization – Time Of Flight (SELDI-TOF) proteomic blood profiling
Stéphane Roche, Laurent Tiers, Monique Provansal, Marie-Thérèse Piva, Sylvain Lehmann
Proteome Science , 2006, DOI: 10.1186/1477-5956-4-20
Abstract: We used a serum depletion scheme using chicken antibodies against various abundant proteins to realized a pre-fractionation of serum prior to SELDI-TOF profiling. Depletion of major serum proteins by immunocapture was confirmed by 1D and 2D gel electrophoresis. SELDI-TOF analysis of bound and unbound (depleted) serum fractions revealed that this approach allows the detection of new low abundant protein peaks with satisfactory reproducibility.The combination of immunocapture and SELDI-TOF analysis opens new avenues into proteomic profiling for the discovery of blood biomarkers.Human serum and plasma have an important clinical value for identification and detection of biomarkers. However, the analysis of these biological fluids is analytically challenging due to the high dynamic concentration range (over 10 orders of magnitude) of constituent protein/peptide species [1]. In addition, the few most abundant blood proteins constitute 95% of the bulk mass of proteins but they represent less than 0.1% of the total number of proteins. These high abundant proteins, and in particular albumin, produce large signals in most proteomics approaches and they mask or interfere with the detection of the other low amount protein components. This situation explains why the discovery of new proteins or peptides biomarkers in blood is challenging. To minimize these problems, proteomics techniques are constantly improving to provide a wider range and an optimized detection of low concentration candidates [2,3]. Many methods rely on a multidimensional separation scheme combining for example multidimensional chromatography or electrophoresis and mass spectrometry (MS) [4,5]. This is the case of the Surface-Enhanced Laser Desorption/Ionization – Time Of Flight (SELDI-TOF) method [6,7] that relies on MS to detect proteins and peptides initially selected by binding to various chromatographic surfaces (anionic, cationic, IMAC, hydrophobic). SELDI-TOF therefore focuses on a particular subset of
Proteomic analysis of mare follicular fluid during late follicle development
Somayyeh Fahiminiya, Valérie Labas, Stéphane Roche, Jean-Louis Dacheux, Nadine Gérard
Proteome Science , 2011, DOI: 10.1186/1477-5956-9-54
Abstract: Follicular fluid samples were collected from ovaries at three different stages of follicle development (early dominant, late dominant and preovulatory). Blood samples were also collected at each time. The proteomic analysis was carried out on crude, depleted and enriched follicular fluid by 2D-PAGE, 1D-PAGE and mass spectrometry.Total of 459 protein spots were visualized by 2D-PAGE of crude mare follicular fluid, with no difference among the three physiological stages. Thirty proteins were observed as differentially expressed between serum and follicular fluid. Enrichment method was found to be the most powerful method for detection and identification of low-abundance proteins from follicular fluid. Actually, we were able to identify 18 proteins in the crude follicular fluid, and as many as 113 in the enriched follicular fluid. Inhibins and a few other proteins involved in reproduction could only be identified after enrichment of follicular fluid, demonstrating the power of the method used. The comparison of proteins found in mare follicular fluid with proteins previously identified in human, porcine and canine follicular fluids, led to the identification of 12 common proteins and of several species-specific proteins.This study provides the first description of mare follicular fluid proteome during the late follicle development stages. We identified several proteins from crude, depleted and enriched follicular fluid. Our results demonstrate that the enrichment method, combined with 2D-PAGE and mass spectrometry, can be successfully used to visualize and further identify the low-abundance proteins in the follicular fluid.Follicular fluid accumulates into the follicle antrum starting with the early stage of follicle development. Plenty of evidence suggests that follicular fluid proteins originate from two sources: blood and surrounding somatic cell layers (granulosa and theca cells) (Figure 1). Earlier studies showed that the "blood-follicle barrier" is permeable for
Characterization of Monomeric Intermediates during VSV Glycoprotein Structural Transition
Aurélie A. Albertini,Cécile Mérigoux,Sonia Libersou,Karine Madiona,Stéphane Bressanelli,Stéphane Roche,Jean Lepault,Ronald Melki,Patrice Vachette,Yves Gaudin
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1002556
Abstract: Entry of enveloped viruses requires fusion of viral and cellular membranes, driven by conformational changes of viral glycoproteins. Crystal structures provide static pictures of pre- and post-fusion conformations of these proteins but the transition pathway remains elusive. Here, using several biophysical techniques, including analytical ultracentrifugation, circular dichro?sm, electron microscopy and small angle X-ray scattering, we have characterized the low-pH-induced fusogenic structural transition of a soluble form of vesicular stomatitis virus (VSV) glycoprotein G ectodomain (Gth, aa residues 1–422, the fragment that was previously crystallized). While the post-fusion trimer is the major species detected at low pH, the pre-fusion trimer is not detected in solution. Rather, at high pH, Gth is a flexible monomer that explores a large conformational space. The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases. Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification. Solution studies are complemented by electron micrographs of negatively stained viral particles in which monomeric ectodomains of G are observed at the viral surface at both pH 7.5 and pH 6.7. We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.
Pricing and Hedging in Stochastic Volatility Regime Switching Models  [PDF]
Stéphane Goutte
Journal of Mathematical Finance (JMF) , 2013, DOI: 10.4236/jmf.2013.31006
Abstract:

We consider general regime switching stochastic volatility models where both the asset and the volatility dynamics depend on the values of a Markov jump process. Due to the stochastic volatility and the Markov regime switching, this financial market is thus incomplete and perfect pricing and hedging of options are not possible. Thus, we are interested in finding formulae to solve the problem of pricing and hedging options in this framework. For this, we use the local risk minimization approach to obtain pricing and hedging formulae based on solving a system of partial differential equations. Then we get also formulae to price volatility and variance swap options on these general regime switching stochastic volatility models.

 

Analysis of Relationships between Port Activity and Other Sectors of the Economy: Evidence from Cote d’Ivoire  [PDF]
Nomel Paul Stéphane Essoh
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.33042
Abstract:

This research paper aims to study the correlation between the port activity and the activity of the different services sectors. By comparing trends between them and analyzing the causality relationships between the port traffic and the other economic sectors, our study tends to present how the activity of the port of Abidjan could have a decisive effect on the local economy. To meet our objectives, correlation analysis and statistical test tools Eviews and other techniques have been run with data provided by local agencies and port authority. By doing so, our research study finds that there is existing correlation between port activity and activity generated by the other services sectors and its contribution can accelerate the economic growth.

Cote d’Ivoire’s Commodities Export and Shipping: Challenges for Port Traffic and Regional Market Size  [PDF]
Nomel P. Stéphane Essoh
American Journal of Industrial and Business Management (AJIBM) , 2014, DOI: 10.4236/ajibm.2014.45031
Abstract:

The global integration with the growth of the world population generated a constant need of goods where trade took place with both inputs and ready-made products. Although this global need has led to a diversification of exports of goods, it still requires special commodities from tropical Africa and trade partners in West Africa that may supply more their specialized products which can be moved in cargo between destinations. This paper identifies especially Cote d’Ivoire’s commodities export and shipping market structure with its main agricultural products which makes him the world’s dominant producer and exporter of cocoa beans. It develops the importance of export crops structure for local economy driven by the international demand for cocoa beans. And it finally could indicate in our future study whether the possibility of pricing power and export taxes affecting the shipping market has a decisive impact on the port traffic and accelerates growth.

Recent Emergence of Dengue Virus Serotype 4 in French Polynesia Results from Multiple Introductions from Other South Pacific Islands
Van-Mai Cao-Lormeau, Claudine Roche, Maite Aubry, Anita Teissier, Stéphane Lastere, Elise Daudens, Henri-Pierre Mallet, Didier Musso, John Aaskov
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029555
Abstract: Background Infection by dengue virus (DENV) is a major public health concern in hundreds of tropical and subtropical countries. French Polynesia (FP) regularly experiences epidemics that initiate, or are consecutive to, DENV circulation in other South Pacific Island Countries (SPICs). In January 2009, after a decade of serotype 1 (DENV-1) circulation, the first cases of DENV-4 infection were reported in FP. Two months later a new epidemic emerged, occurring about 20 years after the previous circulation of DENV-4 in FP. In this study, we investigated the epidemiological and molecular characteristics of the introduction, spread and genetic microevolution of DENV-4 in FP. Methodology/Principal Findings Epidemiological data suggested that recent transmission of DENV-4 in FP started in the Leeward Islands and this serotype quickly displaced DENV-1 throughout FP. Phylogenetic analyses of the nucleotide sequences of the envelope (E) gene of 64 DENV-4 strains collected in FP in the 1980s and in 2009–2010, and some additional strains from other SPICs showed that DENV-4 strains from the SPICs were distributed into genotypes IIa and IIb. Recent FP strains were distributed into two clusters, each comprising viruses from other but distinct SPICs, suggesting that emergence of DENV-4 in FP in 2009 resulted from multiple introductions. Otherwise, we observed that almost all strains collected in the SPICs in the 1980s exhibit an amino acid (aa) substitution V287I within domain I of the E protein, and all recent South Pacific strains exhibit a T365I substitution within domain III. Conclusions/Significance This study confirmed the cyclic re-emergence and displacement of DENV serotypes in FP. Otherwise, our results showed that specific aa substitutions on the E protein were present on all DENV-4 strains circulating in SPICs. These substitutions probably acquired and subsequently conserved could reflect a founder effect to be associated with epidemiological, geographical, eco-biological and social specificities in SPICs.
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