Effect of low-cycle-fatigue damage on the strength and ductility of structural steel

It is found that the residual stresses and strains at a welding connection may cause material yielding in tension. Structural components, such as a ship in service experience continuous fatigue load cycles due to cyclic stress in addition to residual stresses and other locked-in stresses. Thus, there is a build up of fatigue damage. Currently, structures are designed for fatigue and strength. However, the strength design is undertaken assuming they are virgin structures. Therefore, no interaction between fatigue damage and strength is considered. In reality, structural components such as a ship in service for a considerable period of time will have accumulated damage due to fatigue load cycles and this may interact with the mechanical properties such as strength and ductility of the material. Thus, an interaction between fatigue damage and the mechanical properties of structural steel should be considered for safer structural designs. Since, the residual stress alone can cause yielding of steel at welded connections; cyclic stress is expected to produce low-cycle-fatigue locally at these connections. This study was, therefore, undertaken to understand the effect of low-cycle-fatigue damage on the mechanical properties such as strength and ductility of structural steel

The Relationship between Mobile Learning and Academic Achievement in a Community College System Online Environment

This study poses the question: Is there a relationship between student use of mobile technology in an online environment and student achievement expressed by final grades? The purpose of this study is to examine the relationship between mobile learning (m-learning) using mobile technology and academic achievement in terms of final grades in an online environment. The literature on m-learning indicates the freedom and flexibility of the m-learner constitutes a new paradigm in education. The untethered nature of m-learning means students can access course content anywhere, anytime. Studies have focused on the use of specific technologies in learning environments; this study uses a bivariate correlation method to cut across disciplines and measure the magnitude of mobile technology use as a function of degree of access to course materials while mobile. The degree of mobility and GPA were captured through an anonymous survey with analysis designed to discover the relationship between the variables. This study fills an important gap in assessing the impact of m-learning on academic achievement. Overall results did not show a significant relationship between m-learning and academic achievement. Results indicate that a larger study to include location context and quality of institutional support for mobility would better understand the impact of m-learning on academic achievement in the online environment

Historique des feux au nord du Témiscamingue, Québec

L'historique des feux a été reconstruit pour une superficie de 2500 km2 à l'interface de la forêt boréale et de la forêt feuillue septentrionale du sud-ouest du Québec. L'objectif primaire de ce projet était de récolter les données de base nécessaires à la description du régime de feux naturels, dans un contexte de remplacement des peuplements après incendies sévères pour la région du Témiscamingue. Cette description du régime des feux constitue également l'étape initiale pour le développement d'un scénario d'aménagement forestier basé sur le régime des perturbations naturelles pour cette même région. Les buts secondaires étaient d'évaluer les effets de différentes échelles spatio-temporelles sur la fréquence des feux, en déterminant le rôle des facteurs explicatifs aux échelles locale, paysagère et régionale. Un dispositif d'échantillonnage aléatoire, utilisant la dendrochronologie conjointement avec les archives gouvernementales et les photos aériennes, a été utilisé pour décrire le cycle de feu dans le contexte du modèle exponentiel négatif. Les éléments physiographiques ne présentent pas localement d'influence sur la fréquence des feux. Cependant, les patrons d'utilisation des terres associées à la colonisation affectent significativement la fréquence des feux à l'échelle du paysage. Un changement temporel dans la fréquence des feux a été aussi détecté et coïncide avec la période de colonisation Euro-canadienne, ainsi qu'avec des années de sécheresse extrême pour le site d'étude. De plus, une période sans feu a été récemment identifiée et associée à la suppression du feu et aux changements climatiques. Les cycles estimés (-190 à 300 ans) pour la section sud-est du site d'étude seraient représentatifs des cycles naturels due à une moins grande influence humaine. Les longs cycles de feu observés sont responsables d'une proportion élevée de forêts anciennes dont la dynamique est surtout contrôlée par des perturbations secondaires (trouées, épidémies d'insectes). Par conséquent, un régime d'aménagement forestier équienne à rotation courte qui serait inspiré du régime des feux est à remettre en question pour ce secteur. Des pratiques sylvicoles plus diversifiées s'inspirant à la fois d'une fréquence faible des feux et surtout de la présence des perturbations secondaires serait plus en accord avec une approche d'aménagement s'inspirant des perturbations naturelles

Contribution of Gypsum-board Sheathing to the Compressive Resistance of Wood Studs Subjected to Gravitational Loads

Gypsum board is the most commonly used sheathing material in Canadian residential construction. Current Canadian standards recognize the role of gypsum-board sheathing in bracing studs to prevent weak-axis buckling and in resisting in-plane shear, but do not recognize its potential contribution to axial compressive resistance of a sheathed wall. The research in this thesis, therefore, investigates this contribution for light-frame wood stud walls sheathed with gypsum-board on both sides of the stud. The axial compressive resistance of bare and gypsum-board sheathed studs were computed using new finite element models that account for the nonlinear wood stress-strain relationship and nonlinear shear load-slip response of gypsum-board-to-stud fastener connections. These models were validated using full-scale test data for 100 bare and 19 sheathed studs, and with an idealized responses of fastener connections derived using test data from 283 monotonic and 15 load-reversal tests. The strength distributions of the axial capacities of bare and sheathed studs were quantified by conducting Monte Carlo simulations using these models. As a result, it was determined that gypsum-board sheathing increases the axial compressive resistance of wood studs by a factor of 1.05 to 1.56, depending on the stud size, stud length, gypsum-board thickness, and fastener spacing. A modification factor that conforms to the current CAN/CSA-086-09 equations (CWC, 2009) to account for the strength increment provided by the gypsum-board sheathing was then derived as a function modulus of elasticity of the wood for various stud sizes and lengths, gypsum-board thicknesses, and fastener spacings. The revised equation was used to compute the factored axial compressive resistance of 2400 and 3600 mm long gypsum-board-sheathed 38x89 and 38x140 mm wood studs. A total of 15 additional stud designs are recommended to be included in Part 9 “Housing and Small Buildings” of National Building Code of Canada (NRC, 2010) when the extra strength provided by 12.7 mm or 15.9 mm gypsum-board sheathing, with a maximum fastener spacing of 300 mm, is accounted for

The SspA subtilisin-like protease of Streptococcus suis triggers a pro-inflammatory response in macrophages through a non-proteolytic mechanism

<p>Abstract</p> <p>Background</p> <p><it>Streptococcus suis </it>is a major swine pathogen worldwide that causes meningitis, septicemia, arthritis, and endocarditis. Using animal models, a surface-associated subtilisin-like protease (SspA) has recently been shown to be an important virulence factor for <it>S. suis</it>. In this study, we hypothesized that the <it>S. suis </it>SspA subtilisin-like protease may modulate cytokine secretion by macrophages thus contributing to the pathogenic process of meningitis.</p> <p>Results</p> <p>Phorbol 12-myristate 13-acetate-differentiated U937 macrophages were stimulated with recombinant SspA prior to monitor cytokine secretion by ELISA. Our results indicated that the recombinant SspA was able to dose-dependently induce IL-1β, IL-6, TNF-α, CXCL8 and CCL5 secretion in macrophages. The heat-inactivated protease was still able to induce cytokine secretion suggesting a non-proteolytic mechanism of macrophage activation. Using specific kinase inhibitors, evidence were bought that cytokine secretion by macrophages stimulated with the recombinant SspA involves the mitogen-activated protein kinase signal transduction pathway. While stimulation of macrophages with low concentrations of recombinant SspA was associated to secretion of high amounts of CCL5, the use of recombinant SspA at a high concentration resulted in low amounts of CCL5 detected in the conditioned medium. This was found to be associated with a proteolytic degradation of CCL5 by SspA. The ability of SspA to induce cytokine secretion in macrophages was confirmed using a mutant of <it>S. suis </it>deficient in SspA expression.</p> <p>Conclusion</p> <p>In conclusion, this study identified a new mechanism by which the <it>S. suis </it>SspA may promote central nervous system inflammation associated with meningitis.</p

Histoire de l’art et anthropologie, 6. Le modèle, la copie

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Porphyromonas gingivalis Gingipains Trigger a Proinflammatory Response in Human Monocyte-derived Macrophages Through the p38α Mitogen-activated Protein Kinase Signal Transduction Pathway

Porphyromonas gingivalis, the major etiologic agent of chronic periodontitis, produces a broad spectrum of virulence factors, including Arg- and Lys-gingipain cysteine proteinases. In this study, we investigated the capacity of P. gingivalis gingipains to trigger a proinflammatory response in human monocyte-derived macrophages. Both Arg- and Lys-gingipain preparations induced the secretion of TNF-α and IL-8 by macrophages. Stimulation of macrophages with Arg-gingipain A/B preparation at the highest concentration was associated with lower amounts of cytokines detected, a phenomenon likely related to proteolytic degradation. The inflammatory response induced by gingipains was not dependent of their catalytic activity since heat-inactivated preparations were still effective. Stimulating macrophages with gingipain preparations was associated with increased levels of phosphorylated p38α MAPK suggesting its involvement in cell activation. In conclusion, our study brought clear evidence that P. gingivalis Arg- and Lys-gingipains may contribute to the host inflammatory response, a critical factor in periodontitis-associated tissue destruction

Combined detailed and quasi steady-state time simulations for large-disturbance analysis

peer reviewedThis paper deals with the simulation of long-term power system responses to large disturbances in the presence of discrete events. A method combining detailed and quasi steady-state time simulations is presented, the former being used for accuracy and the latter for ef ciency reasons. Detailed time simulation is used to analyze the short-term period following a large disturbance and identify the discrete controls triggered. Next, quasi steady-state simulation is used to simulate the same time interval with the discrete controls imposed as external events, before letting the system evolve as usual in the long term. This simple method has been successfully tested on the Hydro-Québec system

The great american navel : le grand roman américain et le langage approprié

Ce mémoire a pour objectif d'analyser le phénomène du Grand Roman Américain comme représentation de l'imaginaire national, en en faisant l'archéologie. Je propose, à partir de ce postulat initial, de procéder à un balayage sociologique des éléments qui entrent en ligne de compte dans la composition formelle et symbolique de certaines oeuvres marquantes ayant eu droit au titre de Grand Roman Américain. Il s'agit d'une sorte d'histoire chronologique de l'expression et de ses représentations littéraires. Opération qui mènera à une analyse approfondie de la prise en charge du langage, de l'espace et du temps comme discours dans Underworld de Don Delillo, parangon de ce qu'est le Grand Roman Américain dans son acception moderne. Underworld jouera le rôle d'un prisme, apte à rendre compte du roman contemporain (pour des notions telles que l'obsession de la mémoire collective et individuelle, l'absorption des mythes fondateurs, la contamination entre culture d'élite et culture de masse) et de ses prédécesseurs (on peut penser à la réactualisation des archétypes, aux intertextes, aux réécritures). Entre une sociologie qui prendrait comme point d'appui une littérature américaine analyste de son environnement, et une sociocritique d'un roman emblématique comme Underworld, ce mémoire cherche aussi à créer un pont entre différentes oeuvres qui pensent et ont pensé l'Amérique à la fois comme un tout préhensible et un concept fuyant, équivoque. Dans un premier temps, il s'agira de proposer une analyse sociologique et historique de l'expression Grand Roman Américain et d'en examiner les corrélats à l'intérieur de l'imaginaire social de l'Amérique. Dans un aller-retour entre la société et le livre qui s'en veut le reflet, je tenterai de dégager les lignes de tensions et les chevauchements, autrement dit les instants d'imprécisions entre la réalité et le mythe, entre le vrai social et le faux livresque. En quoi les oeuvres littéraires qui se réclament du Grand Roman Américain sont-elles révélatrices des ambiguïtés propres à leur milieu? Se consacrer ensuite à l'étude d'Underworld, c'est chercher à investir le coeur de la problématique. Le roman sera abordé sous les deux angles suivants: premièrement, son rapport au langage et au discours (la parole, la voix, l'énonciation). Qu'est-ce que l'Amérique, comment être Américain? Deuxièmement, et par extension, son appartenance au corpus Grand Roman Américain, dans une perspective d'intertextualité qui permettra de bien saisir les enjeux majeurs qui regroupent et recoupent les différentes époques littéraires et les différentes écritures. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Littérature américaine, Imaginaire social, Oralité, Mythes, Idéologies

Combining image analysis, genome wide association studies and different field trials to reveal stable genetic regions related to panicle architecture and the number of spikelets per panicle in rice

Number of spikelets per panicle (NSP) is a key trait to increase yield potential in rice (O. sativa). The architecture of the rice inflorescence which is mainly determined by the length and number of primary (PBL and PBN) and secondary (SBL and SBN) branches can influence NSP. Although several genes controlling panicle architecture and NSP in rice have been identified, there is little evidence of (i) the genetic control of panicle architecture and NSP in different environments and (ii) the presence of stable genetic associations with panicle architecture across environments. This study combines image phenotyping of 225 accessions belonging to a genetic diversity array of indica rice grown under irrigated field condition in two different environments and Genome Wide Association Studies (GWAS) based on the genotyping of the diversity panel, providing 83,374 SNPs. Accessions sown under direct seeding in one environement had reduced Panicle Length (PL), NSP, PBN, PBL, SBN, and SBL compared to those established under transplanting in the second environment. Across environments, NSP was significantly and positively correlated with PBN, SBN and PBL. However, the length of branches (PBL and SBL) was not significantly correlated with variables related to number of branches (PBN and SBN), suggesting independent genetic control. Twenty- three GWAS sites were detected with P ≤ 1.0E-04 and 27 GWAS sites with p ≤ 5.9E−04. We found 17 GWAS sites related to NSP, 10 for PBN and 11 for SBN, 7 for PBL and 11 for SBL. This study revealed new regions related to NSP, but only three associations were related to both branching number (PBN and SBN) and NSP. Two GWAS sites associated with SBL and SBN were stable across contrasting environments and were not related to genes previously reported. The new regions reported in this study can help improving NSP in rice for both direct seeded and transplanted conditions. The integrated approach of high-throughput phenotyping, multi-environment field trials and GWAS has the potential to dissect complex traits, such as NSP, into less complex traits and to match single nucleotide polymorphisms with relevant function under different environments, offering a potential use for molecular breeding