Essai de synthèse sur la métallogénie du Pérou

Les ressources minières du Pérou sont associées aux cycles orogéniques précambriens, paléozoïques et surtout andin. Aux cycles précambriens sont associés principalement des indices de Ni et Cr dans des roches ultrabasiques en Cordillère Orientale. Aux cycles paléozoïques sont associées des minéralisations aurifères en filons et en mantos et amas stratiformes volcanogènes ainsi que des minéralisations polymétalliques filoniennes liées à l'activité magmatique éohercynienne et tardihercynienne. Au cycle andin est associé l'ensemble des minéralisations à caratère économique de Cu, Zn, Pb, Ag, Sn, W... Les gisements andins sont groupés en provinces métallogéniques parrallèles à la chaine mais généralement limitées à un segment de celle-ci. Cette segmentation, à laquelle la province jurassique des gisements filoniens hypothermaux ou pyrométasomatiques de Fe de la côte n'obéit pas, joue pour de nombreuses caratéristiques de la chaîne autres que métallogéniques et est interprétée comme résultant en grande partie d'une structuration pré-mésozoïque de la bordure ouest du continent sud-américain. La distribution des provinces métallogéniques andines est alors interprétée comme résultante de l'influence, différente selon les segments et selon les époques, de la croûte continentale sur l'évolution et la mise en place de magmas calcoalcalins potentiellement métallogéniques

Strike-slip faulting, thrusting and related basins in the Cenozoic evolution of the Southern branch of the Bolivian orocline

The evolution of the Cenozoic deformation of the Cordillera Oriental and of the contact zone with the Altiplano in southern Bolivia is well documented in the Tupiza, Nazareno and Estarca basins. The tectonic evolution started at about 29 Ma. The period between 29 and about 22-21 Ma is marked by developement of a pull-apart basin related to N-S trending left-lateral strike-slip faulting. During this period, initial deposition consisted of andesitic lavas and detrital sediments (breccias ; matrix-supported red conglomerats ; sands and silts...) of the Catati and Tupiza Formation, deposited in alluvial fan and flood plain environments. From 21 to 20 Ma, the tectonic setting evolved to N-S oriented thrusts, which had a dextral component. This event caused the Tupiza basin to evolve into a full-ramp basin, and triggered the developement of two piggy-back basins : Nazareno and Estarca. Both basins record detrital deposition (Nazareno Formation) in an alluvial fan environment. At 10-9 Ma, deformation in this area stopped allowing peneplanation during which time the San Juan de Oro erosional surface was formed and the fluvial conglomerates of the Oploca Formation were deposited. This segment of the Andes was then tectonically transported to the east, while uplift due to thrusting continued in the eastern Andean front and in the Subandean zone. (Résumé d'auteur

Modélisation des données d'enquêtes cas-cohorte par imputation multiple (Application en épidémiologie cardio-vasculaire.)

Les estimateurs pondérés généralement utilisés pour analyser les enquêtes cas-cohorte ne sont pas pleinement efficaces. Or, les enquêtes cas-cohorte sont un cas particulier de données incomplètes où le processus d'observation est contrôlé par les organisateurs de l'étude. Ainsi, des méthodes d'analyse pour données manquant au hasard (MA) peuvent être pertinentes, en particulier, l'imputation multiple, qui utilise toute l'information disponible et permet d'approcher l'estimateur du maximum de vraisemblance partielle.Cette méthode est fondée sur la génération de plusieurs jeux plausibles de données complétées prenant en compte les différents niveaux d'incertitude sur les données manquantes. Elle permet d'adapter facilement n'importe quel outil statistique disponible pour les données de cohorte, par exemple, l'estimation de la capacité prédictive d'un modèle ou d'une variable additionnelle qui pose des problèmes spécifiques dans les enquêtes cas-cohorte. Nous avons montré que le modèle d'imputation doit être estimé à partir de tous les sujets complètement observés (cas et non-cas) en incluant l'indicatrice de statut parmi les variables explicatives. Nous avons validé cette approche à l'aide de plusieurs séries de simulations: 1) données complètement simulées, où nous connaissions les vraies valeurs des paramètres, 2) enquêtes cas-cohorte simulées à partir de la cohorte PRIME, où nous ne disposions pas d'une variable de phase-1 (observée sur tous les sujets) fortement prédictive de la variable de phase-2 (incomplètement observée), 3) enquêtes cas-cohorte simulées à partir de la cohorte NWTS, où une variable de phase-1 fortement prédictive de la variable de phase-2 était disponible. Ces simulations ont montré que l'imputation multiple fournissait généralement des estimateurs sans biais des risques relatifs. Pour les variables de phase-1, ils approchaient la précision obtenue par l'analyse de la cohorte complète, ils étaient légèrement plus précis que l'estimateur calibré de Breslow et coll. et surtout que les estimateurs pondérés classiques. Pour les variables de phase-2, l'estimateur de l'imputation multiple était généralement sans biais et d'une précision supérieure à celle des estimateurs pondérés classiques et analogue à celle de l'estimateur calibré. Les résultats des simulations réalisées à partir des données de la cohorte NWTS étaient cependant moins bons pour les effets impliquant la variable de phase-2 : les estimateurs de l'imputation multiple étaient légèrement biaisés et moins précis que les estimateurs pondérés. Cela s'explique par la présence de termes d'interaction impliquant la variable de phase-2 dans le modèle d'analyse, d'où la nécessité d'estimer des modèles d'imputation spécifiques à différentes strates de la cohorte incluant parfois trop peu de cas pour que les conditions asymptotiques soient réunies.Nous recommandons d'utiliser l'imputation multiple pour obtenir des estimations plus précises des risques relatifs, tout en s'assurant qu'elles sont analogues à celles fournies par les analyses pondérées. Nos simulations ont également montré que l'imputation multiple fournissait des estimations de la valeur prédictive d'un modèle (C de Harrell) ou d'une variable additionnelle (différence des indices C, NRI ou IDI) analogues à celles fournies par la cohorte complèteThe weighted estimators generally used for analyzing case-cohort studies are not fully efficient. However, case-cohort surveys are a special type of incomplete data in which the observation process is controlled by the study organizers. So, methods for analyzing Missing At Random (MAR) data could be appropriate, in particular, multiple imputation, which uses all the available information and allows to approximate the partial maximum likelihood estimator.This approach is based on the generation of several plausible complete data sets, taking into account all the uncertainty about the missing values. It allows adapting any statistical tool available for cohort data, for instance, estimators of the predictive ability of a model or of an additional variable, which meet specific problems with case-cohort data. We have shown that the imputation model must be estimated on all the completely observed subjects (cases and non-cases) including the case indicator among the explanatory variables. We validated this approach with several sets of simulations: 1) completely simulated data where the true parameter values were known, 2) case-cohort data simulated from the PRIME cohort, without any phase-1 variable (completely observed) strongly predictive of the phase-2 variable (incompletely observed), 3) case-cohort data simulated from de NWTS cohort, where a phase-1 variable strongly predictive of the phase-2 variable was available. These simulations showed that multiple imputation generally provided unbiased estimates of the risk ratios. For the phase-1 variables, they were almost as precise as the estimates provided by the full cohort, slightly more precise than Breslow et al. calibrated estimator and still more precise than classical weighted estimators. For the phase-2 variables, the multiple imputation estimator was generally unbiased, with a precision better than classical weighted estimators and similar to Breslow et al. calibrated estimator. The simulations performed with the NWTS cohort data provided less satisfactory results for the effects where the phase-2 variable was involved: the multiple imputation estimators were slightly biased and less precise than the weighted estimators. This can be explained by the interactions terms involving the phase-2 variable in the analysis model and the necessity of estimating specific imputation models in different strata not including sometimes enough cases to satisfy the asymptotic conditions. We advocate the use of multiple imputation for improving the precision of the risk ratios estimates while making sure they are similar to the weighted estimates.Our simulations also showed that multiple imputation provided estimates of a model predictive value (Harrell's C) or of an additional variable (difference of C indices, NRI or IDI) similar to those obtained from the full cohort.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

EXPERIMENTOS DE SEDIMENTAÇÃO EM BATELADA E PROJETO DE UM DECANTADOR CONTÍNUO INDUSTRIAL

Para ocorrer a separação de líquidos e sólidos, algumas técnicas são utilizadas. Dentre elas estão a sedimentação, decantação, centrifugação, filtração e evaporação. No experimento realizado, utilizamos a técnica de sedimentação com o auxílio dos agentes coagulantes sulfato de alumínio e o sulfato férrico. Na realização inicial do planejamento do experimento, foram diluídas 25 gramas de carbonato de cálcio em 500 mL de água em um Becker durante 5 minutos. Para a amostra inicial não foi utilizado coagulante, podendo assim observar o efeito da sedimentação sem o auxílio de coagulante. Em seguida, a solução foi despejada em uma proveta de 500 mL e, assim, iniciou-se a contagem do cronômetro. As próximas amostragens foram realizadas com o auxílio dos coagulantes, sulfato dealumínio e sulfato férrico, onde foi seguido o mesmo procedimento, adicionando 2,5 mL de coagulante em cada amostra de carbonato de cálcio com ajuste de pH entre 7,5 e 8,0 utilizando uma solução de HCl a 15% (w/w). Após a realização dos experimentos e da contagem do tempo de sedimentação de cada amostra, foi calculada a área de um sedimentador contínuo em escala industrial, utilizando o método proposto por FOUST, concluindo assim, que o coagulante utilizado para escala industrial ideal é o sulfato de alumínio

Human lung fibroblasts may modulate dendritic cell phenotype and function: results from a pilot in vitro study

International audienceAbstractIn human lung fibrotic lesions, fibroblasts were shown to be closely associated with immature dendritic cell (DC) accumulation. The aim of the present pilot study was to characterize the role of pulmonary fibroblasts on DC phenotype and function, using co-culture of lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) and from control patients, with a DC cell line MUTZ-3. We observed that co-culture of lung control and IPF fibroblasts with DCs reduced the expression of specific DC markers and down-regulated their T-cell stimulatory activity. This suggests that pulmonary fibroblasts might sustain chronic inflammation in the fibrotic lung by maintaining in situ a pool of immature DCs

Centre de recherches sur les mondes américains

François-Xavier Guerra, professeur à l’Université de Paris-ICarmen Salazar-Soler, chargée de recherche au CNRSJean-Michel Sallman, professeur à l’Université de Paris-X L’Euro-Amérique : un espace culturel commun Le séminaire de l’UMR 8565, qui a eu lieu pour la troisième année consécutive autour de la question des « circulations » - des personnes (1998-1999) et des choses (1999-2000) - a réuni en 2000-2001 une trentaine de personnes à chacune de ses sept séances. Organisé par François-Xavier ..

Summary report of MINSIS workshop in Madrid

Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard {\mu} - {\tau} flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal.Comment: Proceedings of the MINSIS Workshop, Dec 10-11, 2009 in Madrid. 15 pages late

Development Of A Prototype Of Video Synchronisation For Relocalization Of Biopsy Sites During Endoscopic Evaluation Of Barrett's Oesophagus: Preliminary Experimental And Clinical Study

International audienceINTRODUCTION: The prevalence of Barrett's oesophagus (BE) is 5 to 6% in the general population, with a progression from dysplasia to adenocarcinoma 0.6 to 0.7 patient-years. Hence, endoscopic surveillance is justified to detect early lesions accessible to endoscopic treatment. However, the relocalisation of lesions detected by biopsies may be difficult during follow-up endoscopies. The purpose of this study was to evaluate the prototype of a magnetic probe for accurate location of the position of the endoscope, allowing the relocalisation of this position in a subsequent endoscopy. We report the results of a feasibility study in pigs and the use of this device in two patients with BE. AIMS & METHODS: The system consists of an electromagnetic (EM) field transmitter and an EM probe constituting the electromagnetic tracking system (EMS) (NDI, Aurora). The EM probe is inserted through the operating channel of a double channel gastroscope. The EM field generator is positionned on the patient chest wall. The system also includes a new software developed at IHU/IRCAD, which performs simultaneous recording of the video from the endoscope alongwith its corresponding position, as measured by the EMS. During a second endoscopy, this software allows automatic synchronization of the recorded video to provide relocalisation of the endoscope in front of previous biopsy sites in the oesophagus. The system was tested in 5 anesthetized pigs. During the first endoscopy, ten markings were performed by argon plasma electrocoagulation (ERBE Tübingen, Germany) in the distal esophagus. The position of each marking was recorded by the system. A second operator to then performed a blind endoscopy on the same pigs and was asked to follow the system implicitly as a guide to relocate the markings. In 2 patients with BE, the system was then tested to facilitate relocalization of the biopsy sites. RESULTS: Ten markings were made in the distal oeosphagus of 5. After withdrawal of the endoscope the second operator found 48 of the 50 markings (96%) using the guidance provided by the system. The positioning of the endoscope provided by the EMS system was within a 2mm range from the initial positionning. In the evaluation of BE patients, the system relocalized the biospy sites within a range of 3mm. CONCLUSION: This preliminary study shows the feasibility of the EMS prototype to relocalize the endoscope in the oesophagus within an acceptable range. The clinical usefulness of this system should be evaluated further during the follow-up of patients with BE