Bastien J.-S.,UniversiteLaval |
Fortin D.,UniversiteLaval |
Wilmshurst J.F.,Western and Northern Service Center |
Ecology | Year: 2011
Developing tools that help predict animal distribution in the face of environmental change is central to understanding ecosystem function, but it remains a significant ecological challenge. We tested whether a single foraging currency could explain bison (Bison bison) distribution in dissimilar environments: a largely forested environment in Prince Albert National Park (Saskatchewan, Canada) and a prairie environment in Grasslands National Park (Saskatchewan, Canada). We blended extensive behavioral observations, relocations of radio-collared bison, vegetation surveys, and laboratory analyses to spatially link bison distribution in the two parks and expected gains for different nutritional currencies. In Prince Albert National Park, bison were more closely associated with the distribution of plants that maximized their instantaneous energy intake rate (IDE) than their daily intake of digestible energy. This result reflected both bison's intensity of use of individual meadows and their selection of foraging sites within meadows. On this basis, we tested whether IDE could explain the spatial dynamics of bison reintroduced to Grasslands National Park. As predicted, bison distribution in this park best matched spatial patterns of plants offering rapid IDE rather than rapid sodium intake, phosphorus intake, or daily intake of digestible energy. Because the two study areas have very different plant communities, a phenomenological model of resource selection developed in one area could not be used to predict animal distribution in the other. We were able, however, to successfully infer the distribution of bison from their foraging objective. This consistency in foraging currency across ecosystems and populations provides a strong basis for forecasting animal distributions in novel and dynamic environments. © 2011 by the Ecological Society of America.
Aryanpour G.,UniversiteLaval |
Mashl S.,Michigan Technological University |
Warke V.,Bodycote Hot Isostatic Pressing Inc.
Powder Metallurgy | Year: 2013
A constitutive model is proposed for the densification of metal powder during hot isostatic pressing. The model considers an inelastic deformation resulting from time dependent (viscoplastic) and time independent (plastic) mechanisms during loading. With employing the Abouaf's formalism for viscoplastic part, the paper is focused mainly on the plasticity contribution including the hardening effects of both relative density and the equivalent plastic strain. The proposed plastic-viscoplastic model is summarised to an equation expressing the densification rate under hydrostatic loading. The gas atomised 316LN stainless steel powder was used in this study. Model parameters necessary for simulation of HIP process during a given pressure ramp at constant temperature are identified using previously published data. The identified model is then verified using experimental data obtained from HIP trials performed at another fixed temperature but with varied pressure ramp rates. A good agreement was found between the model prediction and the experimental results. © 2013 Institute of Materials, Minerals and Mining.
Boivin M.,UniversiteLaval |
Brendgen M.,University of Quebec at Montréal |
Vitaro F.,University of Montréal |
Forget-Dubois N.,UniversiteLaval |
And 5 more authors.
Development and Psychopathology | Year: 2013
Early disruptive behaviors, such as aggressive and hyperactive behaviors, known to be influenced by genetic factors, have been found to predict early school peer relation difficulties, such as peer rejection and victimization. However, there is no consensus regarding the developmental processes underlying this predictive association. Genetically informative designs, such as twin studies, are well suited for investigating the underlying genetic and environmental etiology of this association. The main goal of the present study was to examine the possible establishment of an emerging gene-environment correlation linking disruptive behaviors to peer relationship difficulties during the first years of school. Participants were drawn from an ongoing longitudinal study of twins who were assessed with respect to their social behaviors and their peer relation difficulties in kindergarten and in Grade 1 through peer nominations measures and teacher ratings. As predicted, disruptive behaviors were concurrently and predictively associated with peer relation difficulties. Multivariate analyses of these associations indicate that they were mainly accounted for by genetic factors. These results emphasize the need to adopt an early and persistent prevention framework targeting both the child and the peer context to alleviate the establishment of a negative coercive process and its consequences. © 2013 Cambridge University Press.
Yamashita S.,University of Iowa |
Tai P.,University of Iowa |
Charron J.,UniversiteLaval |
Ko C.,University of Kentucky |
Ascoli M.,University of Iowa
Molecular Endocrinology | Year: 2011
MAPK kinase (MEK)1 and MEK2 were deleted from Leydig cells by crossing Mek1f/f;Mek2-/- and Cyp17iCre mice. Primary cultures of Leydig cell from mice of the appropriate genotype (Mek1f/f; Mek2-/-;iCre+) show decreased, but still detectable, MEK1 expression and decreased or absent ERK1/2 phosphorylation when stimulated with epidermal growth factor, Kit ligand, cAMP, or human choriogonadotropin (hCG). The body or testicular weights of Mek1f/f;Mek2-/-;iCre+ mice are not significantly affected, but the testis have fewer Leydig cells. The Leydig cell hypoplasia is paralleled by decreased testicular expression of several Leydig cell markers, such as the lutropin receptor, steroidogenic acute regulatory protein, cholesterol side chain cleavage enzyme, 17α- hydroxylase, and estrogen sulfotransferase. The expression of Sertoli or germ cell markers, as well as the shape, size, and cellular composition of the seminiferous tubules, are not affected. cAMP accumulation in response to hCG stimulation in primary cultures of Leydig cells from Mek1f/f; Mek2-/-;iCre+ mice is normal, but basal testosterone and testosterone syntheses provoked by addition of hCG or a cAMP analog, or by addition of substrates such as 22-hydroxycholesterol or pregnenolone, are barely detectable. The Mek1f/f;Mek2-/-;iCre+ males show decreased intratesticular testosterone and display several signs of hypoandrogenemia, such as elevated serum LH, decreased expression of two renal androgen-responsive genes, and decreased seminal vesicle weight. Also, in spite of normal sperm number and motility, the Mek1f/f;Mek2-/-;iCre+ mice show reduced fertility. These studies show that deletion of MEK1/2 in Leydig cells results in Leydig cell hypoplasia, hypoandrogenemia, and reduced fertility. © 2011 by The Endocrine Society.
Bilcke J.,University of Antwerp |
Beutels P.,University of Antwerp |
Brisson M.,UniversiteLaval |
Brisson M.,University of Québec |
Jit M.,Public Health England
Medical Decision Making | Year: 2011
Accounting for uncertainty is now a standard part of decision-analytic modeling and is recommended by many health technology agencies and published guidelines. However, the scope of such analyses is often limited, even though techniques have been developed for presenting the effects of methodological, structural, and parameter uncertainty on model results. To help bring these techniques into mainstream use, the authors present a step-by-step guide that offers an integrated approach to account for different kinds of uncertainty in the same model, along with a checklist for assessing the way in which uncertainty has been incorporated. The guide also addresses special situations such as when a source of uncertainty is difficult to parameterize, resources are limited for an ideal exploration of uncertainty, or evidence to inform the model is not available or not reliable. Methods for identifying the sources of uncertainty that influence results most are also described. Besides guiding analysts, the guide and checklist may be useful to decision makers who need to assess how well uncertainty has been accounted for in a decision-analytic model before using the results to make a decision.
Bier N.,Laval University |
Bier N.,Université de Sherbrooke |
Macoir J.,Laval University |
Journal of Clinical and Experimental Neuropsychology | Year: 2010
The purpose of this article is to present current evidence regarding the role of semantic memory in everyday actions. First we describe key models of everyday actions. We then discuss current evidence regarding the role of semantic memory in everyday actions. We reviewed articles reporting on the execution and representation of everyday actions in populations with semantic-memory deficits and single-object use in patients with semantic dementia. Although the evidence is sparse, the general conclusion of this review is that semantic memory seems necessary to support everyday actions. Finally, future challenges and research perspectives are discussed. © 2009 Psychology Press.
Souchay G.,UniversiteLaval |
Souchay G.,Montpellier University |
Souchay G.,Swiss Ornithological Institute |
Gauthier G.,UniversiteLaval |
Pradel R.,Montpellier University
Ecology | Year: 2014
Breeding propensity, i.e., the probability that a mature female attempts to breed in a given year, is a critical demographic parameter in long-lived species. Life-history theory predicts that this trait should be affected by reproductive trade-offs so that the probability of future reproduction should depend on the current reproductive investment. However, breeding propensity is one of the most difficult parameters to estimate because nonbreeders are often absent from the breeding area, thereby requiring the inclusion of unobservable states in the analysis. We developed a new methodological approach by integrating a robust design sampling scheme within the multi-event capture-recapture framework. Our new model accounted for uncertainty in state assignation while allowing for departure of individuals between secondary sampling occasions. We applied this model to a long-term data set of female Greater Snow Geese (Chen caerulescens atlantica) to estimate breeding propensity and to investigate potential reproductive costs. We combined resightings during the nesting stage and recapture at the end of the breeding season to estimate breeding propensity and nesting success, and added recoveries to improve survival probability estimates. We found that both breeding propensity and nesting success depended upon breeding status in the previous year, though not survival. Successful breeders had a lower breeding propensity than failed breeders in the following year, but a higher nesting success. Individuals absent from the breeding colony had a low breeding propensity, but a high nesting success the following year. Our results suggest a cost of reproduction on breeding propensity in the next year, but once females decide to breed, nesting success is likely driven by individual quality. An added benefit of our model is that, unlike previous models with unobservable states, all parameters were identifiable when survival and breeding probabilities were fully state dependent. Our new multi-event framework is a flexible tool that can be applied to a large range of species to estimate breeding propensity and to investigate reproductive trade-offs. © 2014 by the Ecological Society of America.
Globalizations | Year: 2011
Inquiries into global discipline and dissent are apt to carry thinking from the most situated and specific instances of power and counter-power to broad structural orders, in a manner that is remarkably independent of political mediation and thus respectful of the ways in which actually existing human beings negotiate lives sutured at the intersection of the local and the global. This article is part of a broader theoretical project that is informed by historical research on a wide variety of movements of resistance against world ordering-from slave revolts at the beginning of the nineteenth century, to coolies uprisings in the twentieth, to gas and water wars at the beginning of the twenty-first. In it, I come to distinguish between two modes of relation to the world economy. In creative dislocation, situated life gets resolved before being carried off, neat and bereft of possibilities, into the global. In the process, a putative subject gets made that carries a reified sense of itself. In the dialectics of presence, the unresolved lot of situated life gets taken whole to the world economy. Wars of position give way to wars of movement. Dialectically, positions come to be charged with a sense of context and possibilities. World-historical subjects sometimes make themselves for a while, from conditions that were not of their choosing. © 2011 Copyright Taylor and Francis Group, LLC.
Turcotte B.,UniversiteLaval |
Morse B.,UniversiteLaval |
Hydrological Processes | Year: 2012
This paper examines the controlling influence of snow and rain on river ice processes in creeks and streams. Winter precipitation (in the form of rain and snow) has been observed to affect river ice processes and channel parameters of low and high gradient channels in unsuspected ways that can have significant impacts on channel hydraulics, hydrology and habitat. On a low gradient stream, a snowfall event initiated the development of an ice cover by creating unconsolidated snow slush bridges that eventually froze in place. Afterward, both snowfalls and rainfalls in alternation with cold spells dramatically increased the thickening rate of the ice cover well beyond that predicted by classic equations. In a smaller low-gradient agricultural creek, wind-blown snow impeded the formation of an ice cover by insulating the flow from cold atmospheric conditions. On steep channels (of different sizes and morphologies), anchor snow slush has been seen to accumulate on the bed substrate. As opposed to anchor ice, anchor snow slush is not believed to require supercooling water conditions to form nor to stay in place. Finally, in a steep headwater creek, a rain-on-snow event generated a snow slush flow and multiple snow slush jams. This phenomenon was seen to divert most of the water out of the channel into another watershed and concomitantly signalled a mid-winter breakup in the greater watershed downstream. These observations suggest that the role of precipitation on small channel winter ice morphology and water flows, levels and currents has been severely underestimated and that any ecological winter studies, hydraulic structure designs and river modelling efforts need to include processes that are sometimes dominated by rain, slush and snow. © 2012 John Wiley & Sons, Ltd.
Moreira W.,UniversiteLaval |
Leprohon P.,UniversiteLaval |
Cell Death and Disease | Year: 2011
The control of the protozoan parasite Leishmania relies on few drugs with unknown cellular targets and unclear mode of action. Several antileishmanials, however, were shown to induce apoptosis in Leishmania and this death mechanism was further studied in drug-sensitive and drug-resistant Leishmania infantum. In sensitive parasites, antimonials (SbIII), miltefosine (MF) and amphotericin B (AMB), but not paromomycin (PARO), triggered apoptotic cell death associated with reactive oxygen species (ROS). In contrast, Leishmania mutants resistant to SbIII, MF or AMB not only failed to undergo apoptosis following exposure to their respective drugs, but also were more tolerant towards apoptosis induced by other antileishmanials, provided that these killed Leishmania via ROS production. Such tolerance favored the rapid acquisition of multidrug resistance. PARO killed Leishmania in a non-apoptotic manner and failed to produce ROS. PARO resistance neither protected against drug-induced apoptosis nor provided an increased rate of acquisition of resistance to other antileishmanials. However, the PARO-resistant mutant, but not SbIII-, MF- or AMB-resistant mutants, became rapidly cross-resistant to methotrexate, a model drug also not producing ROS. Our results therefore link the mode of killing of drugs to tolerance to cell death and to a facilitated emergence of multidrug resistance. These findings may have fundamental implications in the field of chemotherapeutic interventions. © 2011 Macmillan Publishers Limited All rights reserved.