1,155 research outputs found
Conséquences écologiques et évolutives de la chasse chez l'ours brun (Ursus arctos) scandinave
La planĂšte Terre fait face Ă sa sixiĂšme extinction massive des espĂšces. Cette fois, lâHomme (Homo sapiens) est considĂ©rĂ© comme la cause principale de ce phĂ©nomĂšne. Une des menaces les plus importantes qui pĂšsent sur la survie des populations animales est la surexploitation, telle que la pĂȘche et la chasse. Lâexploitation diminue la survie des classes dâĂąges et de sexes qui sont rĂ©coltĂ©es, mais elle peut Ă©galement induire des effets Ă©cologiques et Ă©volutifs sur les populations sauvages. Bien que les effets Ă©cologiques et Ă©volutifs de la rĂ©colte puissent influencer le taux de croissance de la population, ils sont peu documentĂ©s et quantifiĂ©s dans la littĂ©rature scientifique et sont rarement pris en compte lors de la gestion des populations exploitĂ©es. Cette thĂšse a donc comme objectif principal de quantifier les effets Ă©cologiques et Ă©volutifs de la chasse chez une population de grand carnivore ; lâours brun (Ursus arctos) scandinave. Cette population est suivie de maniĂšre longitudinale depuis 1985 par le Scandinavian Brown Bear Project. Ce projet de recherche cumule des informations, entre autres, sur lâĂąge, le sexe, la reproduction, la survie et le comportement des ours bruns, ce qui en fait une des bases de donnĂ©es des plus complĂštes au monde chez un grand carnivore.
Dans un premier temps, jâai Ă©valuĂ© les effets Ă©cologiques de la chasse. La chasse peut dĂ©stabiliser la structure spatiale et sociale dâune population rĂ©coltĂ©e et ainsi augmenter la probabilitĂ© dâobserver de lâinfanticide sexuellement sĂ©lectionnĂ©. Par consĂ©quent, la chasse a le potentiel de diminuer la survie juvĂ©nile mĂȘme si cette classe dâĂąge nâest pas directement visĂ©e par la rĂ©colte. En combinant des informations sur la survie juvĂ©nile et la localisation des mĂąles rĂ©coltĂ©s Ă la chasse, jâai mis en Ă©vidence une diminution de la survie dâune portĂ©e dâune femelle lorsquâun mĂąle Ă©tait tuĂ© Ă proximitĂ© (Chapitre deux). De plus, jâai montrĂ© que la mortalitĂ© dâun mĂąle Ă la chasse rĂ©sulte en une restructuration spatiale qui perdure pendant deux annĂ©es (Chapitre trois). Les rĂ©sultats obtenus suggĂšrent que la chasse a des effets Ă©cologiques Ă long terme qui peuvent influencer la viabilitĂ© des populations.
Dans un deuxiĂšme temps, jâai Ă©valuĂ© les consĂ©quences Ă©volutives potentielles de la chasse. Jâai dĂ©butĂ© en montrant quâil existe de la variabilitĂ© comportementale en sĂ©lection dâhabitat chez lâours brun (Chapitre quatre), soit une des conditions de lâĂ©volution par sĂ©lection naturelle. Ensuite, jâai colligĂ© de lâinformation issue de la littĂ©rature scientifique afin de montrer que les comportements des animaux peuvent influencer leur vulnĂ©rabilitĂ© Ă la rĂ©colte, que ce soit la pĂȘche ou la chasse (Chapitre cinq). Ensuite, jâai montrĂ© que les chasseurs peuvent induire des pressions sĂ©lectives sur le comportement des ours, soit la deuxiĂšme condition de lâĂ©volution par sĂ©lection naturelle (Chapitre six). Bien que je nâaie pas quantifiĂ© lâhĂ©ritabilitĂ© comportementale dans cette thĂšse, les rĂ©sultats des chapitres quatre, cinq et six suggĂšrent nĂ©anmoins quâil pourrait y avoir de lâĂ©volution induite par la rĂ©colte pour les traits comportementaux hĂ©ritables.
Finalement, jâai comparĂ©, pour la mĂȘme population, les donnĂ©es du suivi longitudinal du Scandinavian Brown Bear Project aux donnĂ©es du registre dâabattages de chasse. Jâai mis en lumiĂšre que les donnĂ©es de registre dâabattages de chasse peuvent ĂȘtre biaisĂ©es par rapport Ă des donnĂ©es issues dâun suivi longitudinal, et ce, mĂȘme dans un systĂšme dâĂ©tude oĂč la chasse est considĂ©rĂ©e comme peu sĂ©lective (Chapitre sept). Cette conclusion est importante pour la gestion, la conservation et lâĂ©tude des effets Ă©cologiques et Ă©volutifs de la chasse qui utilisent souvent les donnĂ©es dans les registres dâabattages de chasse. En effet, ces donnĂ©es constituent souvent une des seules sources dâinformations disponibles pour plusieurs espĂšces exploitĂ©es. Bien que les donnĂ©es de registres dâabattages de chasse soient souvent abondantes, elles devraient ĂȘtre utilisĂ©es de maniĂšre prudente dans les dĂ©cisions de gestion et de conservation considĂ©rant quâelles sont souvent biaisĂ©es.
Les rĂ©sultats de cette thĂšse ont permis de quantifier certains effets Ă©cologiques et Ă©volutifs de la rĂ©colte et de souligner lâimportance de ces effets pour la viabilitĂ© Ă long terme des populations exploitĂ©es. Mieux documenter les effets des activitĂ©s anthropiques est primordial afin de pouvoir dĂ©cider des actions Ă poser pour rĂ©duire ces effets dans une Ăšre oĂč lâHomme est la principale menace Ă la biodiversitĂ© de la planĂšte
Tests d'association génétique pour des durées de vie en grappes
Tableau dâhonneur de la FacultĂ© des Ă©tudes supĂ©rieures et postdoctorales, 2015-2016Les outils statistiques dĂ©veloppĂ©s dans cette thĂšse par articles visent Ă dĂ©tecter de nouvelles associations entre des variants gĂ©nĂ©tiques et des donnĂ©es de survie en grappes. Le dĂ©veloppement mĂ©thodologique en analyse des durĂ©es de vie est aujourd'hui ininterrompu avec la prolifĂ©ration des tests d'association gĂ©nĂ©tique et, de façon ultime, de la mĂ©decine personnalisĂ©e qui est centrĂ©e sur la prĂ©vention de la maladie et la prolongation de la vie. Dans le premier article, le problĂšme suivant est traitĂ© : tester l'Ă©galitĂ© de fonctions de survie en prĂ©sence d'un biais de sĂ©lection et de corrĂ©lation intra-grappe lorsque l'hypothĂšse des risques proportionnels n'est pas valide. Le nouveau test est basĂ© sur une statistique de type CramĂ©rvon Mises. La valeur de p est estimĂ©e en utilisant une procĂ©dure novatrice de bootstrap semiparamĂ©trique qui implique de gĂ©nĂ©rer des observations corrĂ©lĂ©es selon un devis non-alĂ©atoire. Pour des scĂ©narios de simulations prĂ©sentant un Ă©cart vis-Ă -vis l'hypothĂšse nulle avec courbes de survie qui se croisent, la statistique de Cramer-von Mises offre de meilleurs rĂ©sultats que la statistique de Wald du modĂšle de Cox Ă risques proportionnels pondĂ©rĂ©. Le nouveau test a Ă©tĂ© utilisĂ© pour analyser l'association entre un polymorphisme nuclĂ©otidique (SNP) candidat et le risque de cancer du sein chez des femmes porteuses d'une mutation sur le gĂšne suppresseur de tumeur BRCA2. Un test d'association sequence kernel (SKAT) pour dĂ©tecter l'association entre un ensemble de SNPs et des durĂ©es de vie en grappes provenant d'Ă©tudes familiales a Ă©tĂ© dĂ©veloppĂ© dans le deuxiĂšme article. La statistique de test proposĂ©e utilise la matrice de parentĂ© de l'Ă©chantillon pour modĂ©liser la corrĂ©lation intra-famille rĂ©siduelle entre les durĂ©es de vie via une copule gaussienne. La procĂ©dure de test fait appel Ă l'imputation multiple pour estimer la contribution des variables rĂ©ponses de survie censurĂ©es Ă la statistique du score, laquelle est un mĂ©lange de distributions du khi-carrĂ©. Les rĂ©sultats de simulations indiquent que le nouveau test du score de type noyau ajustĂ© pour la parentĂ© contrĂŽle de façon adĂ©quate le risque d'erreur de type I. Le nouveau test a Ă©tĂ© appliquĂ© Ă un ensemble de SNPs du locus TERT. Le troisiĂšme article vise Ă prĂ©senter le progiciel R gyriq, lequel implante une version bonifiĂ©e du test d'association gĂ©nĂ©tique dĂ©veloppĂ© dans le deuxiĂšme article. La matrice noyau identical-by-state (IBS) pondĂ©rĂ©e a Ă©tĂ© ajoutĂ©e, les tests d'association gĂ©nĂ©tique actuellement disponibles pour des variables rĂ©ponses d'Ăąge d'apparition ont Ă©tĂ© briĂšvement revus de pair avec les logiciels les accompagnant, l'implantation du progiciel a Ă©tĂ© dĂ©crite et illustrĂ©e par des exemples.The statistical tools developed in this manuscript-based thesis aim at detecting new associations between genetic variants and clustered survival data. Methodological development in lifetime data analysis is today ongoing with the proliferation of genetic association testing and, ultimately, personalized medicine which focuses on preventing disease and prolonging life. In the first paper, the following problem is considered: testing the equality of survival functions in the presence of selection bias and intracluster correlation when the assumption of proportional hazards does not hold. The new proposed test is based on a CramĂ©r-von Mises type statistic. The p-value is approximated using an innovative semiparametric bootstrap procedure which implies generating correlated observations according to a non-random design. For simulation scenarios of departures from the null hypothesis with crossing survival curves, the Cramer-von Mises statistic clearly outperformed the Wald statistic from the weighted Cox proportional hazards model. The new test was used to analyse the association between a candidate single nucleotide polymorphism (SNP) and breast cancer risk in women carrying a mutation in the BRCA2 tumor suppressor gene. A sequence kernel association test (SKAT) to detect the association between a set of genetic variants and clustered survival outcomes from family studies is developed in the second manuscript. The proposed statistic uses the kinship matrix of the sample to model the residual intra-family correlation between survival outcomes via a Gaussian copula. The test procedure relies on multiple imputation to estimate the contribution of the censored survival outcomes to the score statistic which is a mixture of chi-square distributions. Simulation results show that the new kinship-adjusted kernel score test controls adequately for the type I error rate. The new test was applied to a set of SNPs from the TERT locus. The third manuscript aims at presenting the R package gyriq which implements an enhanced version of the genetic association test developed in the second manuscript. The weighted identical-by-state (IBS) kernel matrix is added, genetic association tests and accompanying software currently available for age-at-onset outcomes are briefly reviewed, the implementation of the package is described, and illustrated through examples
Efficient reduction of neointimal hyperplasia in double injured rabbit carotid arteries by cholesterol-conjugated antisense C-mycoligonucleotides
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Are VNTR co-localizing with breast cancer-associated SNPs?
PURPOSE:
Several common genetic variants (single-nucleotide polymorphisms, SNPs) have been shown to be associated with breast cancer (BC) risk in the general population, and to modify BC risk for BRCA1 and BRCA2 mutation carriers. Co-localization of variable number of tandem repeats (VNTRs) with these BC-associated SNPS has not been comprehensively studied.
METHODS:
Cross referencing of genome-wide VNTRs with the known BC genome-wide association studies (GWAS) SNPs significantly associated with increased risk for developing breast cancer was carried out. Analysis was based on the overlap between the VNTRs and 10-kb windows around these BC-susceptibility SNPs.
RESULTS:
Cross referencing of the 1.2 million TR with the 161 known BC-associated SNPs in the general population led to 690 matches. Of those, in 17 VNTRs, the SNP was within the VNTR. Analysis restricted to loci known to modify BC penetrance in BRCA1 (n = 31) and BRCA2 (n = 33) mutation carriers led to 139 and 170 co-localization matches, respectively. For these, none of the SNPs were within the VNTR. The distances between the SNPs and the VNTRs were not significantly different from what was expected to occur by chance alone (p = 0.61; p = 0.44; p = 0.25, respectively).
CONCLUSION:
There is no evidence that VNTRs co-localize with currently reported SNP tagged BC GWAS loci
Teaching Sodium Fast Reactor Technology and Operation for the Present and Future Generations of SFR Users
International audienceThis paper provides a description of the education and training activities related to sodium fast reactors, carried out respectively in the French Sodium and Liquid Metal School (ESML) created in 1975 and located in France (at the CEA Cadarache Research Centre), in the Fast Reactor Operation and Safety School (FROSS) created in 2005 at the Phenix plant, and in the Institut National des Sciences et Techniques Nucle'aires (INSTN). It presents their recent developments and the current collaborations throughout the world with some other nuclear organizations and industrial companies. Owing to these three entities, CEA provides education and training sessions for students, researchers, and operators involved in the operation or development of sodium fast reactors and related experimental facilities. The sum of courses provided by CEA through its sodium school, FROSS, and INSTN organizations is a unique valuable amount of knowledge on sodium fast reactor design, technology, safety and operation experience, decommissioning aspects and practical exercises. It is provided for the national demand and, since the last ten years, it is extensively opened to foreign countries. Over more than 35 years, the ESML, FROSS, and INSTN have demonstrated their flexibility in adapting their courses to the changing demand in the sodium fast reactor field, operation of PHENIX and SUPERPHENIX plants, and decommissioning and dismantling operations. The results of this ambitious and constant strategy are first sharing of knowledge obtained from experimental studies carried out in research laboratories and operational feedback from reactors, secondly standardized information on safety, and finally the creation of a ''sodium community'' that debates, shares the knowledge, and suggests new tracks for a better definition of design and operating rules
Influence of young black spruce plantations on moose winter distribution
Logging in the boreal forest may benefit moose by increasing food availability. However, the influence of tree plantations on moose behavior, especially on moose spatial ecology, is poorly understood. We assessed the impacts of black spruce plantations on moose winter distribution at a landscape scale in the BasâSaintâLaurent region (QuĂ©bec, Canada). We used winter aerial surveys to examine relationships among plantation characteristics and other habitat variables known to affect moose distribution. The total area of plantations positively influenced moose abundance, but highly aggregated plantations resulted in fewer moose. Moose abundance was also positively associated with food availability and the density of edges between stands providing cover and stands offering high food availability, but moose abundance was negatively associated with road density. Although plantation characteristics were less influential than habitat variables related to foraging and predator avoidance, we demonstrate that the area of black spruce plantations and their configuration should be considered in moose management. We conclude that an integrated management strategy is needed to find a balance between overdeveloped road networks (needed to join homogeneously distributed plantations) and agglomerated plantations in order to mitigate impacts on moose winter distribution. © 2012 The Wildlife Society
Behavioural strategies towards human disturbances explain individual performance in woodland caribou
Behavioural strategies may have important fitness, ecological and evolutionary consequences. In woodland caribou, human disturbances are associated with higher predation risk. Between 2004 and 2011, we investigated if habitat selection strategies of female caribou towards disturbances influenced their calfâs survival in managed boreal forest with varying intensities of human disturbances. Calf survival was 53 % and 43 % after 30 and 90 days following birth, respectively, and 52 % of calves that died were killed by black bear. The probability that a female lose its calf to predation was not influenced by habitat composition of her annual home range, but decreased with an increase in proportion of open lichen woodland within her calving home range. At the local scale, females that did not lose their calf displayed stronger avoidance of high road density areas than females that lost their calf to predation. Further, females that lost their calf to predation and that had a low proportion of â€5-year-old cutovers within their calving home range were mostly observed in areas where these young cutovers were locally absent. Also, females that lost their calf to predation and that had a high proportion of â€5-year-old cutovers within their calving home range were mostly observed in areas with a high local density of â€5-year-old cutovers. Our study demonstrates that we have to account for human-induced disturbances at both local and regional scales in order to further enhance effective caribou management plans. We demonstrate that disturbances not only impact spatial distribution of individuals, but also their reproductive success
Experimental database of mixed-mode crack propagation tests performed on mortar specimens with a hexapod and full-field measurements. Part II: interactive loading
International audienceThis second paper presents a series of 4 crack propagation tests with the same experimental protocol as in a companion paper, but with some significant loading modifications. The first difference is that the loading is composed of in-plane rotation in addition to tension and shear translations. The second difference is that the loading is manually changed during the tests, depending on the crack tip location. This leads to tests with several bifurcations, and/or different loading ratios during the same test. One of them leads to mode I+II, and then mode I+III crack propagation. Some tests end with instabilities while others are controlled to be stable up to the complete failure of the specimen. In some cases, crack closure and friction between the crack faces occur
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