Les altérites : l'épiderme de la Terre.

Les phénomènes d'altération supergène (météoriques) comptent parmi les processus les plus importants qui modifient la surface de notre planète. Les altérations sont le résultat des interactions entre géosphère, biosphère, hydrosphère et atmosphèr

Recognizing pedogenic features in Paleogene sandstones and silcretes in Belgium: a key-feature for paleoenvironmental and sourcing material studies

International audienceA few sandstones occurring in Belgium, especially those from Paleogene strata, share many common features with pedogenic and groundwater silcretes documented in the Paris Basin in France, in South Africa and in Australia (e.g. Thiry, 1999; Summerfield, 1983; Webb & Golding, 1998,). Here we present a review of the criteria that may be used to assess the pedogenic (or "groundwater") origin for sandstones and silcretes. At field scale, pedogenic features in silcrete often consist in the development of vertical (columnar) or nodular structures and/or layers (horizons) due to vetical percolation (illuviation) and transformation of materials in the profile porosity and cracks. Groundwater silcrete often exhibit a typical mammilated surface (e.g. Nash & Ullyot, 2007). Root and rootlet casts, sometimes with silicified root or wood material, also indicate that the rock evolved at the surface or near-surface. At microscopic scale, illuviation of silt and clays in the vadose or water-table environment results in the formation of a series of finely-laminated coatings and infillings. These pedofeatures consist in "typic", "crescent", "capping", "pendent", "micropan" and "crust" coatings (Bullock et al., 1985). Irregular rounded structures or "glaebules" also develop as well as micro-columnar or prismatic textures. Many of them have been observed in pedogenic silcretes around the world (e.g. Thiry, 1999) but also in Paleogene silcrete in Belgium (e.g. Veldman et al., in review). Of particular importance is the concentration of fine-grained titanium-oxides in pedogenic silcrete. These Ti-oxides most probably originated from the weathering of clay material and were concentrated via the same pedogenic processes which concentrated silica in the silcrete profile (Thiry, 1997). In sandstones with a pure sand matrix, where no or few fine-grained material is available for illuviation, assessing the pedogenic origin for the silicification is much more difficult based solely on microtextural observations. New perspectives may arise from trace-element analysis in the quartz cement overgrowing the grains. For example, combining cathodoluminescence imaging (CL) and electron microprobe analysis (EPMA) allowed the detec on of abnormally-high concentration of Al and K in the quartz cement relative to the quartz grains in the Grandglise Thanetian sandstone in the Mons Basin (figure). This suggests that first the weathering of glauconite, which is actually observed here, is the likely source for silica and secondly, the evidence for aluminum migration would indicate strongly acidic conditions in the pore fluids

Accompagnement virtuel personnalisé: motivation et réussite scolaire

Titre de l'écran-titre (visionné le 21 juin 2007)Également disponible en format papierMédiagraphi

Accompagnement virtuel personnalisé motivation et réussite scolaire : rapport de recherche PREP /

Titre de l'écran-titre (visionné le 21 juin 2007)Également disponible en format papierMédiagraphi

Outils virtuels et qualité de la langue

La présente recherche a été subventionnée par le ministère de l'Éducation, du Loisir et du Sport dans le cadre du Programme d'aide à la recherche sur l'enseignement et l'apprentissage (PAREA 2009-2011)PA-2009-003Titre de l'écran-titre (visionné le 8 nov. 2011

Evaluation of intensive versus standard blood pressure reduction and association with cognitive decline and dementia : a systematic review and metaAnalysis

Importance: Optimal blood pressure (BP) targets for the prevention of cognitive impairment remain uncertain. Objective: To explore the association of intensive (i.e. lower than usual) BP reduction compared to guidelines on the incidence of cognitive decline and dementia in adults with hypertension. Data Sources and Study Selection: We conducted a systematic review and meta-analysis of randomized controlled trials that evaluated the association of intensive systolic BP lowering on cognitive outcomes by searching MEDLINE, Embase, CENTRAL, Web of Science, CINAHL, PsycINFO, ICTRP and ClinicalTrials.gov for data up to October 27, 2020. Data Extraction and Synthesis: Data screening and extraction were performed independently by two reviewers based on PRISMA guidelines. The risk of bias was assessed using the Cochrane risk-of-bias 2 tool. We used random-effects models using the inverse variance method for our pooled analyses. We evaluated the presence of potential heterogeneity with the I2 index. Main Outcomes and Measures: Our primary outcome was cognitive decline. Secondary outcomes included the incidence of dementia, mild cognitive impairment (MCI), cerebrovascular events, serious adverse events, and all-cause mortality. Results: From 7,755 citations, we identified sixteen publications from five trials (17,396 participants, mean age 65.7 years, 60.5% males) and two additional ongoing trials. All five trials included in quantitative analyses were considered at unclear to high risk of bias. The mean followup duration was 3.3 years (range 2.0 to 4.7 years). Intensive BP reduction was not significantly associated with global cognitive performance (SMD 0.01, 95% CI -0.04 to 0.06, I2 = 0%, four trials, 5,246 patients), incidence of dementia (RR 1.09, 95% CI 0.32 to 3.67, I2 = 27%, two trials, 9,444 patients) or incidence of MCI (RR 0.91, 95% CI 0.73 to 1.14, I2 = 74%, two trials, 10,774 patients) when compared to standard treatment. However, we found a reduction of cerebrovascular events in the intensive arm (RR 0.79, 95% CI 0.67-0.93, I2 = 0%, five trials, 17,396 patients) without an increased risk of serious adverse events or mortality. Conclusions and Relevance: We did not detect a significant association between BP reduction and lower risk of cognitive decline, dementia or MCI. The certainty of this evidence is low due to the limited sample size, the risk of bias of included trials and the observed statistical heterogeneity. Hence, current available evidence does not justify the use of lower BP targets for the prevention of cognitive decline and dementi

Exploiting Mitochondrial Dysfunction for Effective Elimination of Imatinib-Resistant Leukemic Cells

Challenges today concern chronic myeloid leukemia (CML) patients resistant to imatinib. There is growing evidence that imatinib-resistant leukemic cells present abnormal glucose metabolism but the impact on mitochondria has been neglected. Our work aimed to better understand and exploit the metabolic alterations of imatinib-resistant leukemic cells. Imatinib-resistant cells presented high glycolysis as compared to sensitive cells. Consistently, expression of key glycolytic enzymes, at least partly mediated by HIF-1α, was modified in imatinib-resistant cells suggesting that imatinib-resistant cells uncouple glycolytic flux from pyruvate oxidation. Interestingly, mitochondria of imatinib-resistant cells exhibited accumulation of TCA cycle intermediates, increased NADH and low oxygen consumption. These mitochondrial alterations due to the partial failure of ETC were further confirmed in leukemic cells isolated from some imatinib-resistant CML patients. As a consequence, mitochondria generated more ROS than those of imatinib-sensitive cells. This, in turn, resulted in increased death of imatinib-resistant leukemic cells following in vitro or in vivo treatment with the pro-oxidants, PEITC and Trisenox, in a syngeneic mouse tumor model. Conversely, inhibition of glycolysis caused derepression of respiration leading to lower cellular ROS. In conclusion, these findings indicate that imatinib-resistant leukemic cells have an unexpected mitochondrial dysfunction that could be exploited for selective therapeutic intervention

Rencontre de Jean Le Moyne, le mauvais contemporain

This dissertation focuses on the work of essayist Jean Le Moyne (1913-1996), mostly known for his collection Convergences, published in 1961. While most critical studies of Le Moyne's work are limited to the twenty-eight essays contained in Convergences, this thesis provides a more complete study of his work by examining his unpublished writings of over fifty years, written between 1937 and 1988. This larger corpus supports a new reading of Le Moyne's life work, as one of the most erudite Catholic French-Canadian thinkers of his generation, as it relates to intellectual history. From this angle, the concept of uchronia allows us to see that over the formative 1950s and 1960s, Le Moyne developed a spiritual conception of humanity and of French-Canadian society that was never fully realized and never adopted by other writers. Despite the changes taking place in Québécois society at the time, faith was still a major influence on Le Moyne's thought. The Resurrection and the Incarnation were sources of inspiration that helped direct his aesthetic inquiries, along with the writings of Teilhard de Chardin and the music of Johann Sebastian Bach. The results of this research show that Jean Le Moyne's work is marked by paradox, particularly in that his largely innovative and progressive discourse is constantly neutralized by the conservatism of his religious discourse. This dissertation analyses the aspirations and limitations of the body of ideas brought forth by an intellectual belonging to a transition generation attempting to redefine the codes of aesthetic discourse, a thinker who proposed himself as a model for the redefined codes but ultimately failed in his quest to propagate them.Cette thèse porte sur l'œuvre de l'essayiste Jean Le Moyne (1913-1996) qui s'est principalement fait connaître, en 1961, par la publication du recueil Convergences. Si les études critiques au sujet de cet auteur se cantonnent habituellement aux 28 essais que contient ce recueil, le corpus de cette thèse couvre la production de Le Moyne de manière plus complète en tenant compte de ses écrits non édités qui ont été rédigés durant une période de plus de cinquante ans, soit entre 1937 et 1988. Cet élargissement du corpus favorise une nouvelle lecture de l'œuvre qui s'attache à la trajectoire de ce penseur catholique canadien-français, parmi les plus influents de sa génération, sous l'angle de l'histoire intellectuelle. Dans cette perspective, l'idée d'uchronie est un concept utile pour montrer que Jean Le Moyne a développé, au cours des années 1950 et 1960, une conception spirituelle de l'homme et de la société canadienne-française qui ne s'est finalement pas réalisée et qui n'a pas été relayée par d'autres auteurs. Malgré les changements qui s'opèrent dans la société québécoise de cette époque, la pensée de Le Moyne reste profondément attachée à la foi. La Résurrection et l'Incarnation sont des sources d'inspiration qui orientent sa réflexion esthétique, tout comme les écrits du Père Teilhard de Chardin et la musique de Jean-Sébastien Bach. Il ressort de l'analyse que l'œuvre de Jean Le Moyne est marquée par la figure du paradoxe, notamment parce que son discours novateur et progressiste à bien des égards est continuellement neutralisé par le conservatisme de son discours religieux. Cette thèse sur Jean Le Moyne fait comprendre les aspirations et les limites de la pensée d'un intellectuel appartenant à une génération de transition qui cherche à renouveler les codes du discours esthétique, qui s'en fait même le modèle, sans pour autant réussir à les propager

Le pouvoir local et les stratégies de réalignement dans les centres urbains du Québec

RÉSUMÉ / SUMMARYLe pouvoir local et les stratégies de réalignement dans les centres urbains du QuébecLes villes-centres des trois régions métropolitaines du Québec, soit Montréal, Québec et Hull, sont soumises à des contraintes structurelles qui limitent et encadrent leurs possibilités d'action. La décroissance économique des années soixante-dix prend des formes précises : stagnation industrielle à Montréal, baisse drastique des investissements commerciaux à Québec et Hull, et forte croissance du secteur des services dans les trois villes-centres.À la faveur d'une scène politique relativement calme, où domine encore l'idéologie du progrès et de la modernité, Montréal, Québec et Hull adoptent certaines stratégies de réalignement au cours des années 1980 : rationalisation administrative et budgétaire, rentabilisation des équipements existants par la densification et la gentrification de l'espace urbain, et enfin réorganisation des rapports sociaux mettant en cause l'État municipal, les groupes économiques et les résidents. Ces stratégies ont pour effet de renouveler l'alliance politique entre les représentants et la petite bourgeoisie locale et les investisseurs dont ils facilitent la réorganisation. Par ailleurs, cette alliance se réalise au détriment du dynamisme des forces populaires à qui l'État local n'offre aucun support.Local Authority and Urban Planning Stratégies in Québec Metropolitan AreasThe central cities of Quebec's three metropolitan regions - Montreal, Quebec and Hull - are subject to overriding forces restricting and defining what they may do. Economic decline during the 1970's assumed a specific profile : industrial stagnation for Montreal, a severe slump in business investment for Quebec and Hull, and striking development of the service sector in all three central cities.In a reasonably tranquil political setting favoring things progressive and new, Montreal, Quebec and Hull have formulated a number of planning strategies thus far in the '80s : management and budgetary accountability, attempts to maximize use of existing installations through concentration and repopulation in the urban area, and restructuring of societal relationships linking municipal authority, business and the public. These strategies have led to a renewed political alliance between spokesmen for an area's small businesses and the investors whose redeployment they promote. As it happens, such alliances develop only at a cost to the dynamism of popular forces receiving no assistance from local authority