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Search Results: 1 - 10 of 27062 matches for " Jean-Fran?ois Dupuy "
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Maximum likelihood estimation in a partially observed stratified regression model with censored data
Amélie Detais,Jean-Franois Dupuy
Mathematics , 2008,
Abstract: The stratified proportional intensity model generalizes Cox's proportional intensity model by allowing different groups of the population under study to have distinct baseline intensity functions. In this article, we consider the problem of estimation in this model when the variable indicating the stratum is unobserved for some individuals in the studied sample. In this setting, we construct nonparametric maximum likelihood estimators for the parameters of the stratified model and we establish their consistency and asymptotic normality. Consistent estimators for the limiting variances are also obtained.
Asymptotic theory for the Cox model with missing time-dependent covariate
Jean-Franois Dupuy,Ion Grama,Mounir Mesbah
Mathematics , 2006, DOI: 10.1214/009053606000000038
Abstract: The relationship between a time-dependent covariate and survival times is usually evaluated via the Cox model. Time-dependent covariates are generally available as longitudinal data collected regularly during the course of the study. A frequent problem, however, is the occurence of missing covariate data. A recent approach to estimation in the Cox model in this case jointly models survival and the longitudinal covariate. However, theoretical justification of this approach is still lacking. In this paper we prove existence and consistency of the maximum likelihood estimators in a joint model. The asymptotic distribution of the estimators is given along with a consistent estimator of the asymptotic variance.
Non parametric estimation of the structural expectation of a stochastic increasing function
Jean-Franois Dupuy,Jean-Michel Loubes,Elie Maza
Mathematics , 2008,
Abstract: This article introduces a non parametric warping model for functional data. When the outcome of an experiment is a sample of curves, data can be seen as realizations of a stochastic process, which takes into account the small variations between the different observed curves. The aim of this work is to define a mean pattern which represents the main behaviour of the set of all the realizations. So we define the structural expectation of the underlying stochastic function. Then we provide empirical estimators of this structural expectation and of each individual warping function. Consistency and asymptotic normality for such estimators are proved.
An Ethnomethodological Perspective on the Conflict between Magistrates and Journalists in Cameroon  [PDF]
Jean-Franois Nguegan, Thomas Essono
Advances in Journalism and Communication (AJC) , 2015, DOI: 10.4236/ajc.2015.34013
Abstract: The report of the magistrate profession to that of a journalist in Cameroon can be studied from the perspective both of the sociology of professions and sociology of the conflict; the actors, who belong to different territories, are usually against the quality, legitimacy and competence required to deal with media information, and judicial control, individual freedom. This relationship is mainly studied in this research in terms of symbolic interactionism, to emphasize first of all on the importance that judges and journalists themselves give to their profession and secondly on the rationality of their game in the construction and the demarcation of their respective territories. This article is a contribution to the study of the discourse of these two groups of professionals who compete with each other.
CIMAvax®EGF vaccine therapy for non-small cell lung cancer: A weighted log-rank tests-based evaluation  [PDF]
Carmen Viada Gonzalez, Jean-Franois Dupuy, Martha Fors López, Patricia Lorenzo Luaces, Tania Crombet-Ramos, Gisela González Marinello, Elia Neninger Vinagera, Beatriz García Verdecia
Modern Chemotherapy (MC) , 2013, DOI: 10.4236/mc.2013.23006
Abstract:

Time-to-event has become one of the primary endpoints of many clinical trials. Comparing treatments and therapies using time-to-event (or “survival”) data requires some care, since survival differences may occur either early or late in the follow-up period, depending on various factors such as the initial potency or the duration of efficacy of the drugs. In this work, we investigate the effect of the CIMAvax?EGF vaccine therapy on the survival of patients with non-small cell lung cancer, using stratified and unstratified weighted log-rank tests. Weighted log-rank tests are designed to identify early and late survival differences between treatments. Using these tests, we conclude that the vaccine is more efficient than the standard therapy among patients less than 60 years of age.

Assessing the Impact of Bycatch on Dolphin Populations: The Case of the Common Dolphin in the Eastern North Atlantic
Laura Mannocci, Willy Dabin, Emmanuelle Augeraud-Véron, Jean-Franois Dupuy, Christophe Barbraud, Vincent Ridoux
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032615
Abstract: Fisheries interactions have been implicated in the decline of many marine vertebrates worldwide. In the eastern North Atlantic, at least 1000 common dolphins (Delphinus delphis) are bycaught each year, particularly in pelagic pair-trawls. We have assessed the resulting impact of bycatch on this population using a demographic modeling approach. We relied on a sample of females stranded along the French Atlantic and western Channel coasts. Strandings represent an extensive source of demographic information to monitor our study population. Necropsy analysis provided an estimate of individual age and reproductive state. Then we estimated effective survivorship (including natural and human-induced mortality), age at first reproduction and pregnancy rates. Reproductive parameters were consistent with literature, but effective survivorship was unexpectedly low. Demographic parameters were then used as inputs in two models. A constant parameter matrix proposed an effective growth rate of ?5.5±0.5%, corresponding to the current situation (including bycatch mortality). Subsequently, deterministic projections suggested that the population would be reduced to 20% of its current size in 30 years and would be extinct in 100 years. The demographic invariant model suggested a maximum growth rate of +4.5±0.09%, corresponding to the optimal demographic situation. Then, a risk analysis incorporating Potential Biological Removal (PBR), based on two plausible scenarii for stock structure suggested that bycatch level was unsustainable for the neritic population of the Bay of Biscay under a two-stock scenario. In depth assessment of stock structure and improved observer programs to provide scientifically robust bycatch estimates are needed. Effective conservation measures would be reducing bycatch to less than 50% of the current level in the neritic stock to reach PBR. Our approach provided indicators of the status and trajectory of the common dolphin population in the eastern North Atlantic and therefore proved to be a valuable tool for management, applicable to other dolphin populations.
Large-scale RNAi screens identify novel genes that interact with the C. elegans retinoblastoma pathway as well as splicing-related components with synMuv B activity
Julian Ceron, Jean-Franois Rual, Abha Chandra, Denis Dupuy, Marc Vidal, Sander van den Heuvel
BMC Developmental Biology , 2007, DOI: 10.1186/1471-213x-7-30
Abstract: We used the ORFeome RNAi library to identify genes that interact with C. elegans lin-35 Rb and identified 57 genes that showed synthetic or enhanced RNAi phenotypes in lin-35 mutants as compared to rrf-3 and eri-1 RNAi hypersensitive mutants. Based on characterizations of a deletion allele, the synthetic lin-35 interactor zfp-2 was found to suppress RNAi and to cooperate with lin-35 Rb in somatic gonad development. Interestingly, ten splicing-related genes were found to function similar to lin-35 Rb, as synMuv B genes that prevent inappropriate vulval induction. Partial inactivation of specific spliceosome components revealed further similarities with lin-35 Rb functions in cell-cycle control, transgene expression and restricted expression of germline granules.We identified an extensive series of candidate lin-35 Rb interacting genes and validated zfp-2 as a novel lin-35 synthetic lethal gene. In addition, we observed a novel role for a subset of splicing components in lin-35 Rb-controlled processes. Our data support novel hypotheses about possibilities for anti-cancer therapies and multilevel regulation of gene expression.The retinoblastoma gene (Rb) was the first tumor suppressor gene to be genetically identified and cloned, based on germline mutations in familial cases of retinoblastoma [1]. Since, deregulation of the Rb pathway has been found to be a general aspect of a wide variety of human cancers, with ~80% of all sporadic cancers containing alterations in Rb or its regulatory components [2,3]. The frequency of mutations in the Rb gene itself varies greatly between different tumor types, which likely relates to expression levels of other members of the Rb family (p130 and p107) that are closely related in structure and show partly redundant functions in vivo [4].Proteins of the pRb family function as transcriptional repressors to control cell division, differentiation and death [[5], and citations herein]. To control cell proliferation, pRb family members inh
Adipocytes modulate vascular smooth muscle cells migration potential through their secretions  [PDF]
Souhad El Akoum, Isabelle Cloutier, Jean-Franois Tanguay
Journal of Diabetes Mellitus (JDM) , 2013, DOI: 10.4236/jdm.2013.34035
Abstract:

Impairment of vascular smooth muscle cells (VSMC) is recognized as a predisposition factor for atherosclerosis development. We hypothesize that the metabolic syndrome has a direct impact on VSMC migration and phenotypic switching, which may increase the incidence of atherosclerotic events. Aortic VSMC were extracted from 10 weeks old C57BL6 mice and incubated for 24 hr in adipocytes conditioned cell culture medium. Adipocytes were extracted from diabetic C57BL6 male mice fed with either a vegetal or an animal High-Fat-Diet (HFD) for 20 weeks. Migration of VSMC in response to conditioned media stimulations was significantly modulated compared to control. The most extended effects on VSMC were triggered by adipocytes from mice fed with animal HFD. These effects were concurrent with increased leptin concentrations and decreased adiponectin levels in conditioned media. A significant up-regulation of CD36 mRNA level was found in VSMC treated with adipocytes from HFD-fed mice. In conclusion, we have shown that the development of adipocyte-induced VSMC alterations is linked to diet fatty acid composition and the degree of metabolic alterations. The modulation of adipokine secretions in the adipose tissue that is linked to metabolic alterations may alter the physiology of VSMC and thus accelerate the development of metabolic-related vascular diseases.

Universality in Statistical Measures of Trajectories in Classical Billiard Systems  [PDF]
Jean-Franois Laprise, Ahmad Hosseinizadeh, Helmut Kr?ger
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.68132
Abstract: For classical billiards, we suggest that a matrix of action or length of trajectories in conjunction with statistical measures, level spacing distribution and spectral rigidity, can be used to distinguish chaotic from integrable systems. As examples of 2D chaotic billiards, we considered the Bunimovich stadium billiard and the Sinai billiard. In the level spacing distribution and spectral rigidity, we found GOE behaviour consistent with predictions from random matrix theory. We studied transport properties and computed a diffusion coefficient. For the Sinai billiard, we found normal diffusion, while the stadium billiard showed anomalous diffusion behaviour. As example of a 2D integrable billiard, we considered the rectangular billiard. We found very rigid behaviour with strongly correlated spectra similar to a Dirac comb. These findings present numerical evidence for universality in level spacing fluctuations to hold in classically integrable systems and in classically fully chaotic systems.
Oxytocin and Collective Bargaining: Propositions for a New Research Protocol  [PDF]
Jean-Franois Tremblay, Sébastien Rivard, Eric Gosselin
American Journal of Industrial and Business Management (AJIBM) , 2017, DOI: 10.4236/ajibm.2017.77063
Abstract: This paper contributes to collective bargaining research by providing a causal theoretical biological link path between negotiation behaviors and their substantive and relational results. Specifically, the role of oxytocin is described in light of the scientific knowledge that comes from organizational neurosciences, neuroeconomics and, psychology fields. The properties of the hormone, its place in neuroeconomics research and, their links with the psychology of the collective bargaining processes are discussed to determine guidelines for a new experimental protocol meant to study decision-making processes during collective bargaining. In addition, the conceptual model of strategic negotiations serves as a theoretical framework to consolidate the propositions that can be deduced from the results of the interaction processes in collective bargaining according to two dimensions of the outcome of the negotiations. Finally, the parameters of a new experimental protocol derived from the trust game are presented for the first time. This new game presents a more ecological perspective and is developed to offer a better fit with the specific domain of collective bargaining.
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