15 research outputs found
La longue marche de la formation documentaire
Des années 1980 à aujourd’hui, l’enseignement documentaire dans le supérieur s’est généralisé et a évolué de la simple formation aux outils à l’apprentissage de l’autonomie dans la société de la connaissance
Instabilities in crystal growth by atomic or molecular beams
The planar front of a growing a crystal is often destroyed by instabilities.
In the case of growth from a condensed phase, the most frequent ones are
diffusion instabilities, which will be but briefly discussed in simple terms in
chapter II. The present review is mainly devoted to instabilities which arise
in ballistic growth, especially Molecular Beam Epitaxy (MBE). The reasons of
the instabilities can be geometric (shadowing effect), but they are mostly
kinetic or thermodynamic. The kinetic instabilities which will be studied in
detail in chapters IV and V result from the fact that adatoms diffusing on a
surface do not easily cross steps (Ehrlich-Schwoebel or ES effect). When the
growth front is a high symmetry surface, the ES effect produces mounds which
often coarsen in time according to power laws. When the growth front is a
stepped surface, the ES effect initially produces a meandering of the steps,
which eventually may also give rise to mounds. Kinetic instabilities can
usually be avoided by raising the temperature, but this favours thermodynamic
instabilities. Concerning these ones, the attention will be focussed on the
instabilities resulting from slightly different lattice constants of the
substrate and the adsorbate. They can take the following forms. i) Formation of
misfit dislocations (chapter VIII). ii) Formation of isolated epitaxial
clusters which, at least in their earliest form, are `coherent' with the
substrate, i.e. dislocation-free (chapter X). iii) Wavy deformation of the
surface, which is presumably the incipient stage of (ii) (chapter IX). The
theories and the experiments are critically reviewed and their comparison is
qualitatively satisfactory although some important questions have not yet
received a complete answer.Comment: 90 pages in revtex, 45 figures mainly in gif format. Review paper to
be published in Physics Reports. Postscript versions for all the figures can
be found at http://www.theo-phys.uni-essen.de/tp/u/politi
Mettre en œuvre un service de questions-réponses en ligne
En quelques années, les bibliothèques françaises ont développé des services de questions-réponses en ligne. Beaucoup d'établissements en sont encore à la phase de réflexion, d'autres démarrent, des réseaux s'élaborent. Dans le contexte actuel du repérage, de la sélection et de la validation de l'information pléthorique disponible sur Internet, les services de questions-réponses en ligne ont un rôle primordial à jouer. En effet, ils valorisent l'offre des bibliothèques dans le contexte du développement des services aux publics et des services à distance. Leur mise en place interroge le professionnel sous de multiples facettes : organisation du travail, politique de services, choix des outils… Ces différents aspects sont abordés, s'appuyant sur des expériences françaises et étrangères, qu'elles soient locales, coopératives et/ou collaboratives. Un éventail d'offres existe aujourd'hui, selon les objectifs, les besoins, les publics, les moyens mis à disposition et les technologies choisies. Le plan s'articule autour de quatre parties pragmatiques et opératoires : construire le projet, développer un savoir-répondre, organiser et travailler au sein d'une équipe et, enfin, adapter le service à l'environnement et à la nature de ses publics. Cet ouvrage collectif, coordonné par Claire Nguyen, se veut un guide utile à tous les professionnels qui veulent créer, maintenir ou faire évoluer un service de questions-réponses à distance
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
8. Le service Questions ? Réponses ! de l’ENSSIB
• Service Questions ? Réponses ! http://www.enssib.fr/questionsreponses/ Ouvert en octobre 2007, le service Question ? Réponses ! est un service de questions-réponses en ligne spécialisé dans les sciences de l’information et des bibliothèques. Il répond à une forte demande, puisque la Bpi et Le GdS recevaient déjà un grand nombre de questions relevant de ce domaine. Ce sont les bibliothécaires de l’école qui répondent, dans un délai de 3 jours ouvrés. Les réponses alimentent une base de con..