Assemblage par soudage diffusion de deux superalliages. Aspects diffusionnels et microstructuraux au niveau du joint

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Les dessins de machines à l’Ecole polytechnique (1794-1850), iconographie commentée

Cet ensemble de reproductions - planches imprimées et dessins d’élèves - choisies dans les Archives conservées à la Bibliothèque centrale, permet de se faire une idée de ce que fut le « cours de Machines » de l’Ecole polytechnique entre 1794 et 1850. La mise en place d’un cours autonome n’aboutit qu’en 1806, dans le cadre de la Géométrie. Il rejoint les Applications de l’Analyse après 1817, et devient « cours de Machines et d’Hydraulique » en 1839. Pour finir, cet enseignement sera rattaché à..

Première partie – La genèse d’un enseignement : 1794 - 1806

Avec la Révolution française s’ouvre un débat sur l’enseignement scientifique et technique. Les projets sont nombreux et concernent tous les niveaux. Mais le fait le plus marquant de cette période est sans doute la fondation en 1794 de l’Ecole centrale des travaux publics, destinée à remplacer les deux écoles d’ingénieurs créées au milieu du XVIIIe siècle : celle des Ponts et Chaussées (à Paris) et celle du Génie (à Mézières). L’Ecole est rebaptisée Ecole polytechnique dès 1795 et sa mise en ..

Deuxième partie - Le cours de Hachette : 1806 - 1816

La loi d’organisation de l’Ecole prescrit un cours d’application de la géométrie descriptive aux éléments des machines. Mais on lit dans le procès-verbal de la séance du Conseil d’instruction du 25 juin 1800 que « vu l’absence du citoyenMonge, qui s’était chargé de faire un cours sur les Eléments des Machines, le Conseil arrête que ce Cours n’aura pas lieu cette année (...) ». Un nouveau projet est élaboré pour l’année suivante ; Monge repart en Italie et le cours de Machines est encore ajou..

Le cours de Machines de l’Ecole polytechnique, de sa création jusqu’en 1850

La création de l’Ecole centrale des travaux publics et les débuts de l’Ecole polytechnique sont relativement bien connus. Le « cours de Machines » l’est beaucoup moins ; il n’a pas encore été étudié pour lui-même, bien qu’il présente un intérêt certain : cet enseignement est le premier du genre. La consultation des Archives de l’Ecole permet d’en suivre la mise en œuvre, dans le détail de son déroulement, et de corriger l’impression de confusion, voire les contradictions qui ressortent de cer..

Troisième partie - Les Machines, cours d’application : 1817 – 1850

La Restauration et la remise en ordre de l’enseignement de l’Ecole La chute de l’Empire et la Restauration de la monarchie s’accompagnent d’un certain nombre de changements à l’Ecole polytechnique. A la suite de manifestations des élèves, ceux-ci sont licenciés le 14 avril 1816. L’Ecole est rouverte le 17 janvier 1817 et le Conseil de perfectionnement, maintenant constitué de personnalités extérieures et présidé par un Pair de France, réorganise l’enseignement. Le nouveau régime sanctionne au..

Computational identification of transcriptionally co-regulated genes, validation with the four ANT isoform genes.

International audienceABSTRACT: BACKGROUND: The analysis of gene promoters is essential to understand the mechanisms of transcriptional regulation required under the effects of physiological processes, nutritional intake or pathologies. In higher eukaryotes, transcriptional regulation implies the recruitment of a set of regulatory proteins that bind on combinations of nucleotide motifs. We developed a computational analysis of promoter nucleotide sequences, to identify co-regulated genes by combining several programs that allowed us to build regulatory models and perform a crossed analysis on several databases. This strategy was tested on a set of four human genes encoding isoforms 1 to 4 of the mitochondrial ADP/ATP carrier ANT. Each isoform has a specific tissue expression profile linked to its role in cellular bioenergetics. RESULTS: From their promoter sequence and from the phylogenetic evolution of these ANT genes in mammals, we constructed combinations of specific regulatory elements. These models were screened using the full human genome and databases of promoter sequences from human and several other mammalian species. For each of transcriptionally regulated ANT1, 2 and 4 genes, a set of co-regulated genes was identified and their over-expression was verified in microarray databases. CONCLUSIONS: Most of the identified genes encode proteins with a cellular function and specificity in agreement with those of the corresponding ANT isoform. Our in silico study shows that the tissue specific gene expression is mainly driven by promoter regulatory sequences located up to about a thousand base pairs upstream the transcription start site. Moreover, this computational strategy on the study of regulatory pathways should provide, along with transcriptomics and metabolomics, data to construct cellular metabolic networks

Placebo analgesia persists during sleep : an experimental study

Although placebo analgesia is a well-recognized phenomenon with important clinical implications, the possibility that placebo effects occur during sleep has received little attention. This experimental study examined whether responsiveness to acute heat pain stimuli applied during sleep could be reduced following a placebo conditioning procedure administered before sleep. Healthy individuals (n = 9) underwent polysomnographic recordings for one habituation night followed by one placebo analgesia night and one control night in counterbalanced order. Conditioning induced robust analgesia expectations before the placebo night. In the morning after the placebo night, participants reported less nocturnal pain, anxiety, and associated sleep disturbance (all p's < 0.05) compared to the control night. Furthermore, placebo induction produced a 10% reduction in brain arousals evoked by noxious stimuli during rapid-eye-movement (REM) sleep (p = 0.03), consistent with our previous findings suggesting that analgesia expectations are reprocessed during REM sleep. In contrast, arousals increased by 14% during slow wave sleep (SWS) (p = 0.02). In the morning after the last recording night, placebo testing administered as a manipulation check confirmed that typical placebo analgesic responses were produced during waking (p's < 0.05). These results suggest that analgesia expectations developed before sleep reduced nocturnal pain perception and subjective sleep disturbances and activated brain processes that modulate incoming nociceptive signals differentially according to sleep stage. These results need to be replicated in future studies exploring how analgesia expectations may be reactivated during different sleep stages to modulate nociceptive responses

Assessing the sensitivity and representativeness of the Belgian Sentinel Network of Laboratories using test reimbursement data.

BACKGROUND: The Belgian Sentinel Network of Laboratories (SNL) was created in 1983 in order to monitor trends in infectious diseases. Given the evolution of the surveillance system, such as the waivers, fusions and adhesions of laboratories over time, it is important to evaluate whether the SNL is still fit for purpose. This study aims to evaluate aspects of the sensitivity and representativeness of the SNL by means of a test coverage analysis. METHODS: We estimated test coverage of the SNL using the ratio of reimbursed tests performed by participating laboratories to the total number of tests performed between 2007 and 2012, for 12 (groups of) pathogens. We further evaluated the geographical difference coverage of the SNL at regional and provincial levels. RESULTS: We found that test coverage of the SNL was stable over time and close to, or greater than, 50 % for the 12 (groups of) pathogens studied. These results hold for the three regions of Belgium but not for all provinces. We showed that some provinces had a low test coverage for some pathogens and that test coverage was more variable over time at provincial level. CONCLUSIONS: This sensitivity and representativeness study based on test coverage suggests that the SNL is capable to describe trend and to monitor changes in the 12 (groups of) pathogens studied both at national and regional levels. Therefore, the SNL is useful to contribute to estimate the burden of disease and to inform preventive measures. It should however be reinforced to allow to be used as an alert system at provincial level