Nanoenergetic Materials for MEMS: A Review

New energetic materials (EMs) are the key to great advances in microscale energy-demanding systems as actuation part, igniter, propulsion unit, and power. Nanoscale EMs (nEMs)particularly offer the promise of much higher energy densities, faster rate of energy release, greater stability, and more security sensitivity to unwanted initiation). nEMs could therefore give response to microenergetics challenges. This paper provides a comprehensive review of current research activities in nEMs for microenergetics application. While thermodynamic calculations of flame temperature and reaction enthalpies are tools to choose desirable EMs, they are not sufficient for the choice of good material for microscale application where thermal losses are very penalizing. A strategy to select nEM is therefore proposed based on an analysis of the material diffusivity and heat of reaction. Finally, after a description of the different nEMs synthesis approaches, some guidelines for future investigations are provided

Precambrian protoliths and Early Paleozoic magmatism in the French Massif Central: U–Pb data and the North Gondwana connection in the west European Variscan belt

International audienceU–Pb geochronological data were collected on zircon by LA-MC-ICP-MS on orthogneiss and paragneiss from the Limousin area in the French Massif Central (FMC), in order to investigate the connection between the west European Variscan belt and the northern margin of Gondwana. Fifteen samples were collected in the four main tectonostratigraphic units of the FMC, namely: the Para-Autochthonous Unit, the Lower Gneiss Unit (LGU), the Upper Gneiss Unit (UGU) and the Thiviers–Payzac Unit. Orthogneiss yield intrusion age between 521 ± 7 and 446 ± 6 Ma. Considering all the results from both magmatic and metasedimentary samples, two peaks at 531 and 473 Ma are recognized. Rifting processes taking place along the North Gondwana margin during the Lower Paleozoic went on until the end of the Ordovician, as suggested by the magmatic event recorded around 450 Ma. Several maximum depositional ages were ascertained in the metasedimentary formations of the FMC, as determined by the youngest detected detrital zircon crystal, ranging from 604 ± 16 Ma for metasediments of the Para-Autochthonous unit, 573 ± 12 Ma for the LGU, 564 ± 9 Ma for the Thiviers–Payzac Unit, and 523 ± 4 Ma in the UGU. Minimum depositional ages are given by magmatic emplacement ages obtained in the crosscutting orthogneiss. There is some evidence for a decrease of this maximum age upwards in the tectonostratigraphy. Detrital zircon in metasedimentary formations and inherited zircon in orthogneiss display a wide spectrum of ages with significant peaks at around 590 Ma and 560 Ma. Archean, Paleoproterozoic and Neoproterozoic detrital zircons suggest a West African craton source of the sedimentation. The large amount of Neoproterozoic and Lower Paleozoic ages obtained in this study suggests that these periods played a significant role in the continental crustal growth history of Western Europe

Étude de cas sur la représentation des médias dans le matériel pédagogique en éducation aux médias destiné aux enfants du second cycle du primaire

Ce mémoire porte sur l'éducation aux médias, spécifiquement pour les élèves du second cycle du cours primaire au Québec. La relation qu'entretiennent les enfants avec les médias est régulièrement le sujet de controverses, générant craintes et pessimisme, mais permettant aussi l'expression positive de la capacité des écoliers de comprendre le sens des messages médiatiques véhiculés. Les enfants seront éventuellement des citoyens dont les décisions et les actions auront un impact dans l'arène sociale. Or, la compréhension des enjeux médiatiques au coeur de la démocratie constitue un avantage certain pour toute personne à qui ce rôle participatif est dévolu. Le Ministère de l'Éducation du Québec a publié en 2001 son Programme de formation de l'école québécoise. Ce programme, issu de la réforme de l'éducation, instaure des domaines d'apprentissage, dont l'un est intitulé «Les Médias». À travers l'enseignement des matières de base, les enseignants sont ainsi invités à traiter des médias auprès de leurs élèves. Plus précisément, nous questionnons la représentation des médias qui est faite dans le matériel pédagogique qui est distribué aux enfants. En effet, afin que les écoliers se construisent une idée juste des possibilités des médias et de leurs limites, les connaissances qui leur sont transmises à leur égard devraient être exemptes de préjugés. Pour ce faire, nous avons opté pour une étude de cas. Le matériel didactique produit par la maison d'édition Grand Duc-HRW pour les élèves du second cycle du primaire nous a servi de base. Nous avons procédé à une analyse de discours et à une analyse de contenu afin d'y relever les éléments présents et absents, relatifs aux médias.\ud En somme, nous avons découvert que les textes destinés aux enfants s'avèrent relativement affranchis d'idées préconçues, à l'exception du média télévisuel, sujet à de nombreuses critiques principalement dirigées contre sa consommation, jugée excessive. La responsabilité individuelle occupe, à notre avis, une place importante quant à la vision que chacun développe sur l'univers médiatique: nous ne croyons pas que les médias soient aliénants au point de retirer aux lecteurs et aux spectateurs leur autonomie et leur capacité de réflexion, ces capacités s'avérant des gages certains d'une vie citoyenne et démocratique saine et équilibrée. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Médias, Éducation aux médias, Québec, Enfants, Responsabilité, Analyse de discours, Analyse de contenu

Geology of the Zicavo Metamorphic Complex, southern Corsica (France)

In this study, we investigated the Zicavo Metamorphic Complex (southern Corsica), which ispart of the innermost Axial Zone of the Corsica-Sardinia Variscan belt. To better evaluate itsgeological and structural outline, a 1:5000 geological map, coupled with new structural/microstructural and petrographic data, is presented. The complex is formed by threetectonic units, from bottom to top: (i) an Orthogneiss Unit, (ii) a Leptyno-Amphibolite Unit,and (iii) a Micaschist Unit. They are separated by ductile shear zones with a top-to-the-SEsense of shear. They underwent a polyphase deformation and polymetamorphic history,with a shortening stage in the amphibolite facies, responsible for the main structures andshearing, followed by an exhumation phase

Middle Carboniferous crustal melting in the Variscan Belt: New insights from U-Th-Pbtot. monazite and U-Pb zircon ages of the Montagne Noire Axial Zone (southern French Massif Central)

International audienceIn France, the Devonian-Carboniferous Variscan orogeny developed at the expense of continental crust belonging to the northern margin of Gondwana. A Visean-Serpukhovian crustal melting has been recently documented in several massifs. However, in the Montagne Noire of the Variscan French Massif Central, which is the largest area involved in this partial melting episode, the age of migmatization was not clearly settled. Eleven U-Th-Pbtot. ages on monazite and three U-Pb ages on associated zircon are reported from migmatites (La Salvetat, Ourtigas), anatectic granitoids (Laouzas, Montalet) and post-migmatitic granites (Anglès, Vialais, Soulié) from the Montagne Noire Axial Zone are presented here for the first time. Migmatization and emplacement of anatectic granitoids took place around 333-326Ma (Visean) and late granitoids emplaced around 325-318Ma (Serpukhovian). Inherited zircons and monazite date the orthogneiss source rock of the Late Visean melts between 560Ma and 480Ma. In migmatites and anatectic granites, inherited crystals dominate the zircon populations. The migmatitization is the middle crust expression of a pervasive Visean crustal melting event also represented by the "Tufs anthracifères" volcanism in the northern Massif Central. This crustal melting is widespread in the French Variscan belt, though it is restricted to the upper plate of the collision belt. A mantle input appears as a likely mechanism to release the heat necessary to trigger the melting of the Variscan middle crust at a continental scale

Electron microprobe monazite geochronology : a tool for evaluating magmatic ages with examples from Variscan Massif Central migmatites and granotoids, France.

U–Th–Pb dating of monazite with the electron probe microanalyser (EPMA) is increasingly documented as a reliable geochronological method offering high spatial resolution. This method has been applied on monazite from the Cévennes migmatites and granitoids from the southeast of the French Massif Central. Measurements were performed on separated grains after systematic back-scattered electron (BSE) imaging. Monazites from migmatites record two main ages: (i) a protolith age of about 550–543 Ma obtained on inherited cores, and (ii) a migmatization event between 329 ± 5 and 323 ± 3 Ma recorded by monazite rims and all other monogenetic grains. Monazite from the peraluminous Rocles pluton yields a 318 ± 3 Ma age. Finally, three granite dykes are dated at 333 ± 6, 318 ± 5 and 311 ± 5 Ma; the older dyke is the most deformed of them and is interpreted as linked to the migmatization event; the two other dykes are geochronologically, petrologically and structurally coeval with the Rocles pluton. The data constrain the timing of crustal melting following Variscan thickening in the northern Cévennes area. Migmatization of Ordovician protoliths took place at 329–323 Ma and was shortly followed by intrusion of leucogranite at 318–311 Ma. The study shows that EPMA dating of monazite can be successfully used to resolve a close succession of regional melting events

The South Millevaches Middle Carboniferous crustal melting and its place in the French Variscan Belt

International audienceSeveral episodes of crustal melting are now well identified in the Variscan French Massif Central. Middle Devonian (ca 385-375 Ma) migmatites are recognized in the Upper and Lower Gneiss Units involved in the stack of nappes. Late Carboniferous migmatites (ca 300 Ma) are exposed in the Velay Massif only wilst and Middle Carboniferous migmatites crop out in the Para-Autochthonous Unit and Southern Fold-and-Thrust Belt. In the SW part of the Massif Central, the South Millevaches massif exposes migmatites developed at the expense of ortho- and paragneiss. Theform kilometer-sized septa within the foliated Goulles leucogranitic pluton, which is in turn intruded by the non-foliated Glény two micas granite pluton. Monazite grains extracted from these three rock-types have been dated by the EPMA chemical method. Three samples of migmatite yield a late Visean age (ca 337-328 Ma), the Goulles and Glény granitic plutons yield ages at 324-323 Ma and 324-318 Ma, respectively. These new results enlarge the evidence of a Middle Carboniferous crustal melting imprint that, up to now was only reported in the eastern part of the French Massif Central, in the northern Cévennes and in the Montagne Noire axial zone. At the scale of the French Variscan massifs, the Visean crustal melting event is conspicuously developed since it is recognized from the Massif Armoricain (Vendée and south coast of Brittany) to the Central Vosges. This episode is synchronous with the huge thermal event responsible for the “Tuffs anthracifères” magmatism of the northern Massif Central and Vosges, and took place immediately after the last thickening phase recorded both in Montagne Noire and Ardennes, this is on the southern and northern outer zones of the Variscan Belt, respectively. However, the geodynamic significance of this major event is not fully understood yet