A comparative study of the field emission properties of aligned carbon nanostructures films, from carbon nanotubes to diamond

International audienceThe electron field emission properties of different graphitic and diamond-like nanostructures films are compared. They are prepared in the same CVD chamber on SiO{2}/Si(100) and Si(100) flat surfaces, respectively. These nanostructures are thoroughly characterized by scanning electron emission (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Films of dense aligned carbon nanotubes by far display the lowest threshold fields around few V/μ m and the largest emission currents. Carbon nanofibers, with platelet arrangement of the graphitic planes parallel to the substrate, exhibit higher emission thresholds around 10 V/μ m. Diamond nanostructures, either modified through ammonia incorporation within the gas phase or not, exhibit the largest emission threshold around 25 V/μ m. The high enhancement factors, deduced from the Fowler-Nordheim plots, can explain the low emission thresholds whereas limitations to the electron transport ever occur through different processes (i) surface modifications of the surface, as the transformation of the SiO{2} barrier layer into SiN{x} in the presence of ammonia evidenced by XPS; (ii) different orientation of the graphitic basal planes relative to the direction of electron transport (carbon nanofiber) and (iii) presence of a graphitic nest at the interface of the carbon nanostructure and the substrate, observed when catalyst is deposited through mild evaporation

Deux etudes biochimiques de la cellule stressee chez les mammiferes: acceleration de l'echange du phosphate sur la proteine de choc thermique HSP90; stimulation des activites proteine-kinases de type cdc2 et RNA polymerase II CTD-kinase

SIGLEINIST T 74876 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Introduction to chromosome dynamics in mitosis.

International audienceTo ensure that the genetic information, replicated in the S-phase of the cell cycle, is correctly distributed between daughter cells at mitosis, chromatin duplication and chromosome segregation are highly regulated events. Since the early 1980's, our knowledge of the mechanisms governing these two events has greatly increased due to the use of genetic and biochemical approaches. We present here, first, an overview of the replication process, highlighting molecular aspects involved in coupling replication with chromatin dynamics in mitosis. The second part will present the current understanding of chromosome condensation and segregation during mitosis in higher eukaryotes. Finally, we will underline the links that exist between replication and mitosis

Contribution of hCAP-D2, a Non-SMC Subunit of Condensin I, to Chromosome and Chromosomal Protein Dynamics during Mitosis

Condensins are heteropentameric complexes that were first identified as structural components of mitotic chromosomes. They are composed of two SMC (structural maintenance of chromosomes) and three non-SMC subunits. Condensins play a role in the resolution and segregation of sister chromatids during mitosis, as well as in some aspects of mitotic chromosome assembly. Two distinct condensin complexes, condensin I and condensin II, which differ only in their non-SMC subunits, exist. Here, we used an RNA interference approach to deplete hCAP-D2, a non-SMC subunit of condensin I, in HeLa cells. We found that the association of hCAP-H, another non-SMC subunit of condensin I, with mitotic chromosomes depends on the presence of hCAP-D2. Moreover, chromatid axes, as defined by topoisomerase II and hCAP-E localization, are disorganized in the absence of hCAP-D2, and the resolution and segregation of sister chromatids are impaired. In addition, hCAP-D2 depletion affects chromosome alignment in metaphase and delays entry into anaphase. This suggests that condensin I is involved in the correct attachment between chromosome kinetochores and microtubules of the mitotic spindle. These results are discussed relative to the effects of depleting both condensin complexes

Compromis entre alimentation et risque de prédation chez les canards hivernants (Une approche multi-échelles)

Les stratégies comportementales réalisées par les canards de surface hivernants (colvert Anas platyrhynchos et sarcelle d hiver A.crecca) en fonction des ressources et du risque de prédation ont été étudiées sur trois sites: l estuaire de la Seine, le marais de Moëze-Oléron et les étangs de Brenne. Les décisions d alimentation dépendent étroitement de la densité de ressources présente avec l existence d une densité critique à 15 g/m . Le pâturage ou la tonte vont diminuer le stock de graines disponible et influencer la capacité d accueil. Le suivi d individus équipés d émetteurs aura permis de montrer que la décision de quitter les zones protégées pour s alimenter sur des zones plus risquées (chassées) est fonction de la taille des individus. Le marquage de colverts d élevage lâchés en Brenne aura permis de montrer que la pression de chasse est la cause principale de mouvement où les individus de plus petite taille vont quitter leur lieu de lâcher et ainsi augmenter leur survie.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Multiple roles of Condensins: a complex story.

International audienceCondensins are pentameric complexes that were initially described as being involved in the dynamics of chromosomes during mitosis. It has been recently established that two related complexes (Condensin I and Condensin II) contribute to this process. An increasing sum of studies, using different approaches in various organisms, leads to the paradigm that Condensins are required for the correct segregation of replicated chromosomes by cooperating somehow with Topoisomerase II in sister chromatid resolution. Depending on species and/or experimental studies, these complexes also contribute to some aspects of the assembly and compaction of mitotic chromosomes. Recent studies provided evidences that Condensins and related complexes also function in non-mitotic processes such as replication and transcription. Biochemical studies have highlighted mechanistic aspects of Condensin function and initiated a fine functional dissection of core and regulatory subunits. However, the exact contribution of each subunit remains largely elusive as well as the functional interplay between Condensin I and Condensin II