Finite element study of hyperstructure systems with modular light‐frame construction in high‐rise buildings

To answer both the growth of the world's urban population and the climate changes, new structural systems with high prefabrication levels and renewable materials need to be developed. A novel structural system that could enable the use of modular light‐frame construction in high‐rise buildings was modeled and analyzed. This system was achieved by having a hyperstructure carrying the loads of four‐story light‐frame superposed substructures. Two 20‐story hyperstructures, one using glulam and another one using reinforced concrete, were designed according to the 2015 National Building Code of Canada and compared. A simplified model for the light‐frame modules according to the CSA O86‐19 was proposed. The interaction between both systems and the impact on the substructures were analyzed. The results of the response spectrum analysis and dynamic wind analysis show that, with a glulam hyperstructure, modules could be connected to the columns and the floors or only to the floors. With a concrete hyperstructure, the modules must be connected to the columns and the cores. For both systems, the design of shearwalls on the short side of the modules is governed by the lateral deformation imposed by seismic forces, while the design of shearwalls on the long side of the modules is governed by the vertical deformation of the primary beams under gravity loads. Standard shearwall assemblies are sufficient to resist the shear induced by gravitational, wind and seismic loads. The analysis indicates that the system could be viable, but more research should be especially performed on the connections between the substructures and the hyperstructure

Holocene Evolution of Lakes in the Bluefish Basin, Northern Yukon, Canada

This study documents the Holocene evolution of lakes located in the Bluefish Basin, northern Yukon, on the basis of lake lithology, distribution of plant macrofossils, and radiocarbon dating of the basal organic material in sediment cores obtained from former lake basins. Basal organic matter from former lake basins is radiocarbon-dated to the late Holocene (< 3770 yr. BP), whereas the 14C ages from the polygonal peat plateaus (~2 m thick) that surround most of the former lake basins cluster in the early Holocene (between 11 435 and 8200 yr. BP). Plant macrofossil distribution in four out of five cores obtained in former lake basins indicates a transition from emergent aquatic vegetation to wetland and terrestrial-type vegetation, suggesting a gradual decline in water levels. The fifth core analyzed for macrofossils showed evidence of sudden lake drainage. The absence of 14C ages from the middle Holocene (7000 to 4000 yr. BP) suggests that the lakes had a greater spatial coverage and water levels during that period, a conclusion supported by the greater surface area occupied by the former lake basins relative to modern lakes and by the fact that the middle Holocene was a wet period in northern Yukon. The gradual decrease in water levels during the late Holocene could be attributed to partial drainage of lakes, increased evaporation under a drier climate, or a combination of both. Acomparison with other regional climate records indicates a change toward drier climate conditions around 4500 yr. BP as a result of a reconfiguration in large-scale atmospheric circulation patterns, suggesting a climate-driven change in hydrological conditions.La présente étude retrace l’évolution des lacs de l’Holocène situés dans le bassin Bluefish, dans le nord du Yukon. Elle s’appuie sur la lithologie des lacs, la répartition des macrofossiles de plantes et la datation par le radiocarbone des matières organiques de base se trouvant dans les carottes de sédiments provenant d’anciens bassins lacustres. La datation par le radiocarbone de la matière organique de base d’anciens bassins lacustres fait remonter cette matière à l’Holocène supérieur (< 3 770 ans avant le présent), tandis que la datation par le radiocarbone des plateaux de tourbe polygonaux (~2 m d’épaisseur) qui entourent la plus grande partie du groupement d’anciens bassins lacustres remonte à l’Holocène inférieur (entre 11 435 et 8 200 ans avant le présent). La répartition des macrofossiles de plantes dans quatre des cinq carottes provenant des anciens bassins lacustres laisse voir une transition allant d’une végétation aquatique émergente à une végétation de zone humide et de type terrestre, ce qui attesterait du déclin graduel des niveaux d’eau. Dans la cinquième carotte, les macrofossiles présentaient des preuves d’un assèchement lacustre soudain. L’absence de datation par le radiocarbone de l’Holocène moyen (de 7 000 à 4 000 ans avant le présent) laisse entrevoir que les lacs s’étendaient sur de plus grandes aires et que les niveaux d’eau étaient plus élevés pendant cette période, conclusion qui est appuyée par la plus grande surface occupée par les anciens bassins lacustres relativement aux lacs contemporains et par le fait que l’Holocène moyen était une période humide dans le nord du Yukon. La diminution graduelle des niveaux d’eau pendant l’Holocène supérieur pourrait être attribuée à l’assèchement partiel des lacs, à l’évaporation accrue lors d’un climat plus sec ou à une combinaison des deux. La comparaison avec d’autres relevés climatologiques régionaux indique un changement s’orientant vers des conditions climatiques plus sèches environ 4 500 ans avant le présent, changement découlant de la reconfiguration de la circulation atmosphérique à grande échelle, ce qui laisse entendre que les conditions hydrologiques auraient évolué en raison du climat

Contemporary (1951–2001) Evolution of Lakes in the Old Crow Basin, Northern Yukon, Canada: Remote Sensing, Numerical Modeling, and Stable Isotope Analysis

This study reports on changes in the distribution, surface area, and modern water balance of lakes and ponds located in the Old Crow Basin, northern Yukon, over a 50-year period (1951–2001), using aerial photographs, satellite imagery, a numerical lake model, and stable O-H isotope analysis. Results from the analysis of historical air photos (1951 and 1972) and a Landsat-7 Enhanced Thematic Mapper (ETM+) image (2001) show an overall decrease (-3.5%) in lake surface area between 1951 and 2001. Large lakes typically decreased in extent over the study period, whereas ponds generally increased. Between 1951 and 1972, approximately 70% of the lakes increased in extent; however, between 1972 and 2001, 45% decreased in extent. These figures are corroborated by a numerical lake water balance simulation (P-E index) and stable O-H isotope analysis indicating that most lakes experienced a water deficit over the period 1988–2001. These observed trends towards a reduction in lake surface area are mainly attributable to a warmer and drier climate. The modern decrease in lake levels corresponds well to changes in regional atmospheric teleconnection patterns (Arctic and Pacific Decadal oscillations). In 1977, the climate in the region switched from a predominantly cool and moist regime, associated with the increase in lake surface area, to a hot and dry one, thus resulting in the observed decrease in lake surface area. Although some lakes may have drained catastrophically by stream erosion or bank overflow, it is not possible to determine with certainty which lakes experienced such catastrophic drainage, since an interval of two decades separates the two air photo mosaics, and the satellite image was obtained almost30 years after the second mosaic of air photos.La présente étude fait état des changements caractérisant la répartition, l’étendue et le bilan hydrique contemporain des lacs et des étangs situés dans le bassin Old Crow, dans le nord du Yukon, sur une période de 50 ans (1951–2001). L’étude s’est appuyée sur des photographies aériennes, l’imagerie satellitaire, un modèle numérique des lacs et l’analyse des isotopes stables O-H. D’après les résultats de l’analyse des photos aériennes historiques (1951 et 1972) et d’une image par capteur ETM+ (Enhanced Thematic Mapper) de Landsat-7 (2001), il y a eu rétrécissement général ( 3,5 %) de la surface des lacs entre 1951 et 2001. D’un point de vue général, l’étendue des grands lacs a diminué au cours de la période visée par l’étude, tandis que celle des étangs a augmenté. Entre 1951 et 1972, l’étendue d’environ 70 % des lacs s’est accrue, mais entre 1972 et 2001, l’étendue de 45 % des lacs a diminué. Ces données ont été corroborées au moyen de la simulation numérique du bilan hydrique des lacs (indice P-E) et de l’analyse des isotopes stables O-H, qui ont laissé entrevoir que la plupart des lacs ont enregistré un déficit en eau au cours de la période allant de 1988 à 2001. Les tendances de réduction de la surface des lacs qui ont été observées sont principalement attribuables à un climat plus chaud et plus sec. La diminution contemporaine du niveau des lacs correspond bien aux changements caractérisant les modèles régionaux de téléconnexion atmosphérique (oscillations décadaires arctiques et pacifiques). En 1977, le climat de la région est passé d’un régime à prédominance fraîche et humide (associé à l’augmentation de la surface des lacs de la région) à un régime chaud et sec, ce qui s’est traduit par la diminution de la surface des lacs qui a été observée. Bien que certains lacs puissent avoir été drainés de manière catastrophique en raison de l’érosion des cours d’eau ou du débordement des rives, il est impossible de déterminer avec certitude quels lacs ont été la cible d’un assèchement si catastrophique puisqu’un intervalle de deux décennies sépare les deux mosaïques de photographies aériennes, et que l’image satellitaire a été obtenue presque une trentaine d’années après la deuxième mosaïque de photo aérienne

Faunal and Archaeological Remains as Evidence of Climate Change in Freezing Caverns, Yukon Territory, Canada

Animal and plant remains, some associated with prehistoric artifacts, were collected in freezing caverns (glacières) of northern Yukon Territory. Radiocarbon dates show that the oldest remains are Middle Wisconsinan ca. 38 000 BP). The absence of material of Late Wisconsinan age likely indicates that the caves were infilled by ice during this cold period. Climate warming and ice melting during the Holocene allowed animals and prehistoric hunters to regularly visit these caves. Ice plugs were evidently smaller during the early Holocene than they are now.Des restes d'animaux et de plantes, parfois associés à des vestiges préhistoriques, ont été récoltés dans des glacières du nord du Territoire du Yukon. Leur âge radiocarbone indique que les plus anciens vestiges datent du Wisconsinien moyen (v. 38 000 BP). L'absence de matériel contemporain du Wisconsinien supérieur semble indiquer que pendant cette période froide les cavernes étaient comblées par de la glace. Au cours de l'Holocène, le réchauffement du climat et la fonte subséquente des glaces ont permis aux animaux et aux chasseurs préhistoriques de visiter les cavernes sur une base régulière. Les bouchons de glace étaient de toute évidence moins développés au début de l'Holocène qu'ils ne le sont aujourd'hui

Guide to identifying alert thresholds for heat waves in Canada based on evidence

Among natural-disaster risks, heat waves are responsible for a large number of deaths, diseases and economic losses around the world. As they will increase in severity, duration and frequency over the decades to come within the context of climate change, these extreme events constitute a genuine danger to human health, and heat-warning systems are strongly recommended by public health authorities to reduce this risk of diseases and of excessive mortality and morbidity. Thus, evidence-based public alerting criteria are needed to reduce impacts on human health before and during persistent hot weather conditions.\ud The goal of this guide is to identify alert thresholds for heat waves in Canada based on evidence, and to propose an approach for better defining heat waves in the Canadian context in order to reduce the risks to human health and contribute to the well-being of Canadians. This guide is the result of the collaboration among various research and public institutions working on: 1) meteorological and climate aspects, i.e. the Meteorological Service of Canada (MSC, Environment and Climate Change Canada), and the ESCER centre at the Université du Québec à Montréal, and 2) public health, i.e. Health Canada and the Institut National de Santé Publique du Québec

An essential function of the mitogen‐activated protein kinase Erk2 in mouse trophoblast development

The closely related mitogen-activated protein kinase isoforms extracellular signal-regulated kinase 1 (ERK1) and ERK2 have been implicated in the control of cell proliferation, differentiation and survival. However, the specific in vivo functions of the two ERK isoforms remain to be analysed. Here, we show that disruption of the Erk2 locus leads to embryonic lethality early in mouse development after the implantation stage. Erk2 mutant embryos fail to form the ectoplacental cone and extra-embryonic ectoderm, which give rise to mature trophoblast derivatives in the fetus. Analysis of chimeric embryos showed that Erk2 functions in a cell-autonomous manner during the development of extra-embryonic cell lineages. We also found that both Erk2 and Erk1 are widely expressed throughout early-stage embryos. The inability of Erk1 to compensate for Erk2 function suggests a specific function for Erk2 in normal trophoblast development in the mouse, probably in regulating the proliferation of polar trophectoderm cells

Conceptual Links between Two Mad Cow Crises: The Absence of Paradigmatic Change and Policymaking Implications

On March 20, 1996, a day known as Black Wednesday to the British beef industry, the British Secretary of State of Health announced that a possible link existed between BSE and the Creutzfeldt-Jakob disease (vCJD), the human variant of mad cow. Seven years later, a somewhat comparable fate struck the Canadian beef industry. In May 2003, the discovery of the first native North American case of BSE in Canada deflated the prospects of the industry across the country, consequently creating environmental uncertainty. This paper conceptually analyses the events that occurred in Britain by considering the beef industry as a political economy. The authors find that socio-political structures, driven by power and dependency relations, socio-political processes, and driven by cooperation and conflicts within a marketing channel greatly influenced channel members' behaviors during this crisis. In addition, even though some changes were made, the authors believe that, based on the conceptual analysis of the first year following this critical event, Canadian beef industry leaders and government alike did not learn sufficiently from the unfortunate events that occurred in Britain in 1996, even if some stakeholders believed that they had

Conceptual Links between Two Mad Cow Crises: The Absence of Paradigmatic Change and Policymaking Implications

On March 20, 1996, a day known as Black Wednesday to the British beef industry, the British Secretary of State of Health announced that a possible link existed between BSE and the Creutzfeldt-Jakob disease (vCJD), the human variant of mad cow. Seven years later, a somewhat comparable fate struck the Canadian beef industry. In May 2003, the discovery of the first native North American case of BSE in Canada deflated the prospects of the industry across the country, consequently creating environmental uncertainty. This paper conceptually analyses the events that occurred in Britain by considering the beef industry as a political economy. The authors find that socio-political structures, driven by power and dependency relations, socio-political processes, and driven by cooperation and conflicts within a marketing channel greatly influenced channel members' behaviors during this crisis. In addition, even though some changes were made, the authors believe that, based on the conceptual analysis of the first year following this critical event, Canadian beef industry leaders and government alike did not learn sufficiently from the unfortunate events that occurred in Britain in 1996, even if some stakeholders believed that they had.BSE, food safety policies, food marketing, food distribution, crisis management, Agricultural and Food Policy, Livestock Production/Industries,