42 research outputs found
Au-delĂ du confinement, la lutte continue
Pour ne pas ĂȘtre de ceux qui se taisent, pour tĂ©moigner en faveur de ces pestifĂ©rĂ©s, pour laisser du moins un souvenir de lâinjustice et de la violence qui leur avait Ă©tĂ© faites, et pour dire simplement ce quâon apprend au milieu des flĂ©aux, quâil y a dans les hommes plus de choses Ă admirer que de choses Ă mĂ©priser. Albert Camus, La Peste La crise sanitaire quâa engendrĂ© le Coronavirus-19 nous oblige Ă comprendre quelles sont nos prioritĂ©s. Dans ce contexte de repli sur lâessentiel, oĂč toute..
Spectroscopic evidence for strong correlations between local superconducting gap and local Altshuler-Aronov density-of-states suppression in ultrathin NbN films
Disorder has different profound effects on superconducting thin films. For a
large variety of materials, increasing disorder reduces electronic screening
which enhances electron-electron repulsion. These fermionic effects lead to a
mechanism described by Finkelstein: when disorder combined to electron-electron
interactions increases, there is a global decrease of the superconducting
energy gap and of the critical temperature , the ratio
/ remaining roughly constant. In addition, in most films an
emergent granularity develops with increasing disorder and results in the
formation of inhomogeneous superconducting puddles. These gap inhomogeneities
are usually accompanied by the development of bosonic features: a pseudogap
develops above the critical temperature and the energy gap
starts decoupling from . Thus the mechanism(s) driving the appearance of
these gap inhomogeneities could result from a complicated interplay between
fermionic and bosonic effects. By studying the local electronic properties of a
NbN film with scanning tunneling spectroscopy (STS) we show that the
inhomogeneous spatial distribution of is locally strongly correlated
to a large depletion in the local density of states (LDOS) around the Fermi
level, associated to the Altshuler-Aronov effect induced by strong electronic
interactions. By modelling quantitatively the measured LDOS suppression, we
show that the latter can be interpreted as local variations of the film
resistivity. This local change in resistivity leads to a local variation of
through a local Finkelstein mechanism. Our analysis furnishes a purely
fermionic scenario explaining quantitatively the emergent superconducting
inhomogeneities, while the precise origin of the latter remained unclear up to
now.Comment: 11 pages, 4 figure
Direct observation of homogeneous cavitation in nanopores
We report on the evaporation of hexane from porous alumina and silicon
membranes. These membranes contain billions of independent nanopores tailored
to an ink-bottle shape, where a cavity several tens of nanometers in diameter
is separated from the bulk vapor by a constriction. For alumina membranes with
narrow enough constrictions, we demonstrate that cavity evaporation proceeds by
cavitation. Measurements of the pressure dependence of the cavitation rate
follow the predictions of the bulk, homogeneous, classical nucleation theory,
definitively establishing the relevance of homogeneous cavitation as an
evaporation mechanism in mesoporous materials. Our results imply that porous
alumina membranes are a promising new system to study liquids in a deeply
metastable state.Comment: 14 pages , 4 figures. Source files also contain Supplemental Material
(Doebele_HomogeneousCavitationMembranes_SM.pdf
Frontal sinus variation in large samples of extant species of the genera Pan, Gorilla and Homo
Frontal pneumatisation is not present in all primates, and among extant species, ethmoidally-derived frontal sinuses are present only in the genera Pan, Gorilla and Homo. A simple and repeatable method is described here to quantify variation in the shape, size and bilateral variation of the frontal sinuses. This has allowed the first large study of these variables, including analyses of large samples of P. paniscus, P. troglodytes, G. gorilla and of several geographically diverse populations of H. sapiens. Frontal sinus shape and size are potential phylogenetic markers in primate systematics. We suggest that, in contrast to an allometric relationship between endocranial and frontal sinus form in Pan and Gorilla, H. sapiens is autapomorphic in having highly variable, supero-inferiorly large frontal sinuses, whose size is unrestricted by variation in cranial form. However, we also describe differences in frontal pneumatisation between those taxa. H. sapiens differs from the other taxa in having relatively smaller frontal sinuses that are more variable in shape and size. In P. troglodytes, P. paniscus and G. gorilla, the shape and size of frontal pneumatisation correlates positively with the overall size of the braincase. This suggests that the large space available in the bone structures of the non-human primates analysed allows the sinuses to develop under only slight constraint (if any) from surrounding structures. In H. sapiens, a significant correlation is observed between the asymmetry in the anterior extension of the frontal lobes of the brain and the shape and extension of the frontal sinuses. We suggest that the more vertical orientation of the H. sapiens frontal bone, its reduced thickness, the reduction of the supraorbital tori and the increased influence of the frontal lobes appear to have modified the integration between the skull, brain and sinuses in the frontal region in our species compared to our nearest extant relatives. Our results reduce the possibility of a strong functional origin for the variation in size and shape of the frontal sinuses in the primates analysed
De la LRU Ă la LPPR
Marie Cuillerai est philosophe, professeure Ă lâuniversitĂ© de Paris et directrice du Laboratoire du changement social et politique (LCSP). Elle travaille sur les pratiques et thĂ©ories Ă©conomiques hĂ©tĂ©rodoxes, alternatives ou utopiques. Son travail sâancre dans la philosophie contemporaine, en dialogue avec la sociologie et lâanthropologie politique. Jâai rencontrĂ© Marie Cuillerai en pleine mobilisation contre la LPPR, pendant un jury de soutenance de thĂšse quâelle prĂ©sidait. Les quelques heu..
Pour un monde meilleur
Les ReprĂ©sentants du Peuple Français, constituĂ©s en AssemblĂ©e Nationale, considĂ©rant que lâignorance, lâoubli ou le mĂ©pris des droits de lâHomme sont les seules causes des malheurs publics et de la corruption des Gouvernements, ont rĂ©solu dâexposer, dans une DĂ©claration solennelle, les droits naturels, inaliĂ©nables et sacrĂ©s de lâHomme, afin que cette DĂ©claration, constamment prĂ©sente Ă tous les Membres du corps social, leur rappelle sans cesse leurs droits et leurs devoirs ; afin que les act..
à propos de la réforme de la retraite
Dans les textes qui paraissent sur la rĂ©forme de la retraite, il nâest guĂšre fait rĂ©fĂ©rence Ă la perspective historique dans laquelle se situe la retraite en France. Elle est trĂšs diffĂ©rente de celle qui a prĂ©valu aux Ătats-Unis oĂč la DĂ©claration des droits, dĂšs 1787, privilĂ©giait lâindividu, dĂ©tenteur de droits pour lui seul. Or, contrairement Ă lâinterprĂ©tation que faisait Marx des droits de lâHomme, qui aurait privilĂ©giĂ© lâindividu bourgeois, la DĂ©claration française de 1789 (dite universe..
Une AG (pas) ordinaire ?
La lutte contre la rĂ©forme des retraites a commencĂ© en dĂ©cembre Ă lâuniversitĂ© Paris 8, celle contre la LPPR autour du 20 janvier, au dĂ©but du second semestre. De quelques AG mises en place en dĂ©cembre, on est passĂ© Ă une grande mobilisation en janvier oĂč la plupart des dĂ©partements, aprĂšs sâĂȘtre rĂ©unis en assemblĂ©e gĂ©nĂ©rale, se sont dĂ©clarĂ©s en grĂšve. Les AG de dĂ©partements â rĂ©unissant ou non les Ă©tudiant.es et les enseignant.es titulaires et vacataires â se sont ensuite tenues chaque semai..