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Search Results: 1 - 10 of 471857 matches for " S. Doucet and N. Letourneau "
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Coping and Suicidal Ideations in Women with Symptoms of Postpartum Depression
S. Doucet and N. Letourneau
Clinical Medicine Insights: Reproductive Health , 2012,
Abstract: Objective: To explore the relationship between coping mechanisms and suicidal ideations among women who experience symptoms of postpartum depression. Design: This exploratory descriptive study used secondary data from a study of women who experienced symptoms of postpartum depression. Participants: Convenience and purposive sampling were used to obtain the community sample of 40 women who experienced symptoms of postpartum depression. Methods: Binary logistic regression was employed to explore emotion-focused coping, avoidance-focused coping, problem-focused coping, and religious coping as predictors of suicidal ideations. Results: Approximately 27% of the sample reported suicidal ideations within the past seven days. The results showed that lower levels of emotion-focused coping and higher levels of avoidance-focused and religious coping predicted suicidal ideations in participants. Problem-focused coping did not predict suicidal ideations. Conclusion: Overall, our findings provide support for the importance of coping mechanisms as predictors of suicidal ideations among women who experience symptoms of postpartum depression. The results illustrate the need for health professionals to conduct routine assessments on coping strategies and thoughts of suicide when caring for postpartum women, as well as the need to integrate coping approaches in the prevention and treatment of suicidal ideations.
Consensus in the Wasserstein Metric Space of Probability Measures
Adrian N. Bishop,Arnaud Doucet
Mathematics , 2014,
Abstract: Distributed consensus in the Wasserstein metric space of probability measures is introduced in this work. Convergence of each agent's measure to a common measure value is proven under a weak network connectivity condition. The common measure reached at each agent is one minimizing a weighted sum of its Wasserstein distance to all initial agent measures. This measure is known as the Wasserstein barycentre. Special cases involving Gaussian measures, empirical measures, and time-invariant network topologies are considered, where convergence rates and average-consensus results are given. This algorithm has potential applicability in computer vision, machine learning and distributed estimation, etc.
What Risk Assessments of Genetically Modified Organisms Can Learn from Institutional Analyses of Public Health Risks
S. Ravi Rajan,Deborah K. Letourneau
Journal of Biomedicine and Biotechnology , 2012, DOI: 10.1155/2012/203093
Abstract: The risks of genetically modified organisms (GMOs) are evaluated traditionally by combining hazard identification and exposure estimates to provide decision support for regulatory agencies. We question the utility of the classical risk paradigm and discuss its evolution in GMO risk assessment. First, we consider the problem of uncertainty, by comparing risk assessment for environmental toxins in the public health domain with genetically modified organisms in the environment; we use the specific comparison of an insecticide to a transgenic, insecticidal food crop. Next, we examine normal accident theory (NAT) as a heuristic to consider runaway effects of GMOs, such as negative community level consequences of gene flow from transgenic, insecticidal crops. These examples illustrate how risk assessments are made more complex and contentious by both their inherent uncertainty and the inevitability of failure beyond expectation in complex systems. We emphasize the value of conducting decision-support research, embracing uncertainty, increasing transparency, and building interdisciplinary institutions that can address the complex interactions between ecosystems and society. In particular, we argue against black boxing risk analysis, and for a program to educate policy makers about uncertainty and complexity, so that eventually, decision making is not the burden that falls upon scientists but is assumed by the public at large.
Chimeric β-Lactamases: Global Conservation of Parental Function and Fast Time-Scale Dynamics with Increased Slow Motions
Christopher M. Clouthier, Sébastien Morin, Sophie M. C. Gobeil, Nicolas Doucet, Jonathan Blanchet, Elisabeth Nguyen, Stéphane M. Gagné, Joelle N. Pelletier
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0052283
Abstract: Enzyme engineering has been facilitated by recombination of close homologues, followed by functional screening. In one such effort, chimeras of two class-A β-lactamases – TEM-1 and PSE-4 – were created according to structure-guided protein recombination and selected for their capacity to promote bacterial proliferation in the presence of ampicillin (Voigt et al., Nat. Struct. Biol. 2002 9:553). To provide a more detailed assessment of the effects of protein recombination on the structure and function of the resulting chimeric enzymes, we characterized a series of functional TEM-1/PSE-4 chimeras possessing between 17 and 92 substitutions relative to TEM-1 β-lactamase. Circular dichroism and thermal scanning fluorimetry revealed that the chimeras were generally well folded. Despite harbouring important sequence variation relative to either of the two ‘parental’ β-lactamases, the chimeric β-lactamases displayed substrate recognition spectra and reactivity similar to their most closely-related parent. To gain further insight into the changes induced by chimerization, the chimera with 17 substitutions was investigated by NMR spin relaxation. While high order was conserved on the ps-ns timescale, a hallmark of class A β-lactamases, evidence of additional slow motions on the μs-ms timescale was extracted from model-free calculations. This is consistent with the greater number of resonances that could not be assigned in this chimera relative to the parental β-lactamases, and is consistent with this well-folded and functional chimeric β-lactamase displaying increased slow time-scale motions.
Health outcomes of low-dose ionizing radiation exposure among medical workers: a cohort study of the Canadian national dose registry of radiation workers
Jan M. Zielinski, , Michael J. Garner, Pierre R. Band, , Daniel Krewski, Natalia S. Shilnikova, Huixia Jiang, , Patrick J. Ashmore, , Willem N. Sont, , Martha E. Fair, Ernest G. Letourneau, Robert Semenciw
International Journal of Occupational Medicine and Environmental Health , 2009, DOI: 10.2478/v10001-009-0010-y
Abstract: Background: Medical workers can be exposed to low-dose ionizing radiation from various sources. The potential cancer risks associated with ionizing radiation exposure have been derived from cohort studies of Japanese atomic bomb survivors who had experienced acute, high-level exposure. Since such extrapolations are subject to uncertainty, direct information is needed on the risk associated with chronic low-dose occupational exposure to ionizing radiation. Objectives: To determine the occupational doses of ionizing radiation and examine possible associations with mortality rates and cancer incidence in a cohort of medical workers deriving from the National Dose Registry of Canada (NDR) over the period of 1951-1987. Methods: Standardized mortality and incidence ratios (SMR and SIR, respectively) were ascertained by linking NDR data for a cohort of 67 562 medical workers (23 580 males and 43 982 females) with the data maintained by the Canadian Mortality, and Cancer Incidence databases. Dosimetry information was obtained from the National Dosimetry Services. Results: During the follow-up period, 1309 incident cases of cancer (509 in males, 800 in females) and 1325 deaths (823 in males, 502 in females) were observed. Mortality from cancer and non-cancer causes was generally below expected as compared to the general Canadian population. Thyroid cancer incidence was significantly elevated both among males and females, with a combined SIR of 1.74 and 90% CI: 1.40-2.10. Conclusions: The findings confirm previous reports on an increased risk of the thyroid cancer among medical workers occupationally exposed to ionizing radiation. Over the last 50 years, radiation protection measures have been effective in reducing radiation exposures of medical workers to the current very low levels.
Distributed Maximum Likelihood for Simultaneous Self-localization and Tracking in Sensor Networks
Nikolas Kantas,Sumeetpal S. Singh,Arnaud Doucet
Mathematics , 2012, DOI: 10.1109/TSP.2012.2205923
Abstract: We show that the sensor self-localization problem can be cast as a static parameter estimation problem for Hidden Markov Models and we implement fully decentralized versions of the Recursive Maximum Likelihood and on-line Expectation-Maximization algorithms to localize the sensor network simultaneously with target tracking. For linear Gaussian models, our algorithms can be implemented exactly using a distributed version of the Kalman filter and a novel message passing algorithm. The latter allows each node to compute the local derivatives of the likelihood or the sufficient statistics needed for Expectation-Maximization. In the non-linear case, a solution based on local linearization in the spirit of the Extended Kalman Filter is proposed. In numerical examples we demonstrate that the developed algorithms are able to learn the localization parameters.
Définition du profil écologique de l'azobé, Lophira alata, une espèce ligneuse africaine de grande importance : synthèse bibliographique et perspectives pour des recherches futures
Biwolé, AB.,Bourland, N.,Da?nou, K.,Doucet, JL.
Biotechnologie, Agronomie, Société et Environnement , 2012,
Abstract: Definition of the ecological profile of Lophira alata (ekki), a major important African timber species: literature review and perspectives for future studies. Over two decades, labors made in order to promote sustainable management of African tropical forests are tackled to the lack of knowledge about this complex ecosystem. Ecological parameters of timber species are no more studied, this complicates long-term sustainable forest management. This literature review related to the ecology and silviculture of ekki, Lophira alata Banks ex C.F.Gaertn. (Ochnaceae), a main African timber species recorded as "vulnerable" in the IUCN Red List, will serve as a study's case. The planned literature review reveals the doubt about its taxonomy, as well as the lack of understanding concerning its reproductive biology, growth conditions, population dynamics parameters, and the spatial distribution of its genetic diversity. The deficiency of knowledge about its ecological needs and the factors which have historically influenced its population dynamics explain why most silvicultural trails provide hazardous and uncertain results. Remedying these gaps in order to improve its ecological characterization and innovative silvicultural trails, would be a significant contribution to the sustainable management of its populations.
Radiation Hardness and Linearity Studies of CVD Diamonds
T. Behnke,M. Doucet,N. Ghodbane,A. Imhof
Physics , 2002, DOI: 10.1016/S0920-5632(03)91000-0
Abstract: We report on the behavior of CVD diamonds under intense electromagnetic radiation and on the response of the detector to high density of deposited energy. Diamonds have been found to remain unaffected after doses of 10 MGy of MeV-range photons and the diamond response to energy depositions of up to 250 GeV/cm^3 has been found to be linear to better than 2 %. These observations make diamond an attractive detector material for a calorimeter in the very forward region of the detector proposed for TESLA.
The Secretion of Areolar (Montgomery's) Glands from Lactating Women Elicits Selective, Unconditional Responses in Neonates
Sébastien Doucet,Robert Soussignan,Paul Sagot,Benoist Schaal
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0007579
Abstract: The communicative meaning of human areolae for newborn infants was examined here in directly exposing 3-day old neonates to the secretion from the areolar glands of Montgomery donated by non related, non familiar lactating women.
A Backward Particle Interpretation of Feynman-Kac Formulae
Pierre Del Moral,Arnaud Doucet,Sumeetpal S. Singh
Mathematics , 2009,
Abstract: We design a particle interpretation of Feynman-Kac measures on path spaces based on a backward Markovian representation combined with a traditional mean field particle interpretation of the flow of their final time marginals. In contrast to traditional genealogical tree based models, these new particle algorithms can be used to compute normalized additive functionals "on-the-fly" as well as their limiting occupation measures with a given precision degree that does not depend on the final time horizon. We provide uniform convergence results w.r.t. the time horizon parameter as well as functional central limit theorems and exponential concentration estimates. We also illustrate these results in the context of computational physics and imaginary time Schroedinger type partial differential equations, with a special interest in the numerical approximation of the invariant measure associated to $h$-processes.
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