Modélisation locale en imagerie par résonance magnétique de diffusion : de l'acquisition comprimée au connectome

L’imagerie par résonance magnétique pondérée en diffusion est une modalité d’imagerie médicale non invasive qui permet de mesurer les déplacements microscopiques des molécules d’eau dans les tissus biologiques. Il est possible d’utiliser cette information pour inférer la structure du cerveau. Les techniques de modélisation locale de la diffusion permettent de calculer l’orientation et la géométrie des tissus de la matière blanche. Cette thèse s’intéresse à l’optimisation des métaparamètres utilisés par les modèles locaux. Nous dérivons des paramètres optimaux qui améliorent la qualité des métriques de diffusion locale, de la tractographie de la matière blanche et de la connectivité globale. L’échantillonnage de l’espace-q est un des paramètres principaux qui limitent les types de modèle et d’inférence applicable sur des données acquises en clinique. Dans cette thèse, nous développons une technique d’échantillonnage de l’espace-q permettant d’utiliser l’acquisition comprimée pour réduire le temps d’acquisition nécessaire

Rotary Driven Pipe Piles for a 14-Story Building in New York City

Rotary driven pipe piles are a unique solution for foundation construction in constrained urban areas. These piles consist of a closedend, steel casing with sacrificial drill tip. The casing and drill tip are rotated into the ground using a fixed-mast drill rig. Three hundred sixty two 12.75-inch diameter, rotary driven pipe piles were installed to support a 14-story building in the upper east side of Manhattan. The soils consisted of uncontrolled fill, organic silts, and peat over stiff, saturated, varved silts and clays. A novel mathematical relationship between capacity, installation crowd, and torque was used to develop initial pile installation criteria. A simple discrete element model showed the piles would exhibited considerable freeze. This was verified by successive torque readings over time. Four compression, one tension, and one lateral load test were performed. Torque measurements, load test results, and installation observations are presented. All piles performed exceptionally well during the test program in terms of total pile head deflection. Overall, field measurements matched predictions. Careful coordination and communication between all parties allowed pile installation to proceed rapidly; the foundation was completed on schedule and budget. Each pile was fitted with a geothermal conduit loop to create ‘energy piles’, which will be instrumented for future case study research

Impact of residential schooling and of child abuse on substance use problem in Indigenous Peoples

Residential schools were the institutions, in operation from the 19th century to the late 20th century, which Indigenous children in Canada were forced to attend. The literature shows that many young people who attended these institutions were victims of neglect and abuse. Negative psychological effects resulting from child abuse have been amply documented. However, very few studies on this subject have been carried out among Canada's Indigenous peoples. The objective of this cross-sectional study is to evaluate, for an Indigenous population in Quebec (Canada), the impact of residential schooling as well as self-reported experiences of sexual and physical abuse during childhood on the development of alcohol and drug use problems in adulthood. A total of 358 Indigenous participants were interviewed (164 men [45.8%] and 194 women [54.2%]). Alcohol abuse was evaluated using the Michigan Alcoholism Screening Test (MAST). Drug abuse was assessed with the Drug Abuse Screening Test-20 (DAST). Child abuse and residential schooling were assessed with dichotomous questions (yes/no). Among the participants, 28.5% (n = 102) had attended residential schools, 35.2% (n = 121) reported having experienced sexual abuse, and 34.1% (n = 117) reported having experienced physical abuse before adulthood. Results of the exact logistic regression analyses indicated that residential school attendance was linked to alcohol problems, while child abuse was related to drug use problems. The results of this study highlight the importance of considering the consequences of historical traumas related to residential schools to better understand the current situation of Indigenous peoples in Canada

Ensemble Average Propagator Reconstruction via Compressed Sensing: Discrete or Continuous Bases ?

International audienceIn this work, we propose to compare the sparsity of two classes of representations for the EAP : The discrete representations, via the Haar, Daubechie-Cohen-Fauveau (DCF) 5-3, DCF 9-7 wavelets bases , and the continuous representations, via Spherical Polar Fourier (SPF) and 3D-SHORE bases

Regional environmental change versus local signal preservation in Holocene thermokarst lake sediments: A case study from Herschel Island, Yukon (Canada)

Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future

Patterns of belowground overyielding and fine-root biomass in native and exotic angiosperms and gymnosperms

Mixing tree species can lead to more productive forests, but how belowground productivity is affected by mixtures of trees of diverse phylogenetic and eco-evolutionary histories is unclear. Here, we examine how species origin and phylogeny affect belowground productivity in tree communities of varied richness and functional diversity. We measured standing fine-root biomass and annual fine-root production across 41 assemblages of 12 tree species, representing both angiosperms and gymnosperms originating from North America and Europe. Increasing functional diversity of mixtures stimulated overyielding of annual production but did not affect standing biomass. In general, annual productivity of mixtures of species that were less productive in monoculture had neutral (angiosperms) to positive (North American species: +16%) responses to mixing, whereas annual productivity of mixtures of species that were more productive in monoculture had neutral (European species) to negative (gymnosperms: −6%) responses to mixing. These differences translated into angiosperm mixtures overyielding in standing biomass by 16% but no effects of mixing on gymnosperm mixtures. The trends we observed between North American and European species annual production were reversed when considering standing biomass. European mixtures had 14% more standing biomass and North American mixtures had 10% less standing biomass than expected from monocultures. Our study offers a rare examination of the combined roles of origin and phylogeny in forest fine-root productivity, and suggests varied consequences of biodiversity change for forest belowground productivity based on composition. In North America, belowground productivity of young forests composed of angiosperms and native tree species may be more tightly linked to diversity than that of forests dominated by gymnosperms or European species. This suggests that increased diversity may lead to the greatest enhancement of belowground productivity in native, North American forests dominated by angiosperms, but also that declines in diversity may be felt most strongly in these forests as well

Pathways for cross-boundary effects of biodiversity on ecosystem functioning

The biodiversity-ecosystem functioning concept asserts that processes in ecosystems are markedly influenced by species richness and other facets of biodiversity. However, biodiversity-ecosystem functioning studies have been largely restricted to single ecosystems, ignoring the importance of functional links - such as the exchange of matter, energy, and organisms - between coupled ecosystems. Here we present a basic concept and outline three pathways of cross boundary biodiversity effects on ecosystem processes and propose an agenda to assess such effects, focusing on terrestrial-aquatic linkages to illustrate the case. This cross-boundary perspective of biodiversity-ecosystem functioning relationships presents a promising frontier for biodiversity and ecosystem science with repercussions for the conservation, restoration, and management of biodiversity and ecosystems from local to landscape scales.Peer reviewe

Operationalizing the Springfield Innovation Center

DevelopSpringfield is establishing the Springfield Innovation Center (SIC) in the downtown Springfield area. After extensive research, including site visits and interviews with professionals and SIC stakeholders, our team has produced a detailed set of recommendations for operationalizing the Innovation Center. Included are plans to make full use of the center’s kitchen space, implement a makerspace in a building attached to the center, and market the center. Ultimately, these recommendations will serve to promote entrepreneurial activities at the center

Do position and species identity of neighbours matter in 8–15-year-old post harvest mesic stands in the boreal mixedwood?

Neighbourhood competition indices (NCI), where position and species identity of neighbours are known, have been used to investigate growth and competitive interactions among adult trees. In this study, we used NCI in 8–15-year-old stands following clear-cutting in a boreal mixedwood forest of eastern Canada to improve our understanding of early successional forest dynamics. Trees of increasing diameter from the center (≥1 cm) to the edge (≥5 cm) were mapped in twenty-five circular 450m2 plots. Target trees (DBH≥1 cm) were sampled in plot center to determine their annual radial stem growth. For each species, we compared a set of growth models using either a spatially explicit NCI or a non-spatial competition index. Both types of indices estimated a species-specific competition coefficient for each pair of competitor–target species. NCI were selected as the best competition model for all target species although differences in variance explained relative to the non-spatial index were small. This likely indicates that competition occurs at the local level but that the high density and the relative uniformity of these young stands creates similar neighbourhoods for most trees in a given stand. The effective neighbourhood radius for competitors varied among species and was smaller for shade tolerant species. Intraspecific neighbours were the strongest competitors for most species. Aspen (Populus tremuloides) was a weak competitor for all species as opposed to balsam fir (Abies balsamea) which was a strong competitor in all cases. These results are in contradiction with some widely used forest policies in North America (e.g. free-to-grow standards) that consider broadleaf species, such as aspen, as the strongest competitors. For these early successional forests, the decision regarding the use of spatial or non-spatial competition indices should rest on the intended use. For even-age management, spatial indices might not justify their use in highdensity stands but they are needed for the simulation of novel harvest techniques creating complex stand structure