Experimental observation of flow fields around active Janus spheres

The phoretic mechanisms at stake in the propulsion of asymmetric colloids have been the subject of debates during the past years. In particular, the importance of electrokinetic effects on the motility of Pt-PS Janus sphere was recently discussed. Here, we probe the hydrodynamic flow field around a catalytically active colloid using particle tracking velocimetry both in the freely swimming state and when kept stationary with an external force. Our measurements provide information about the fluid velocity in the vicinity of the surface of the colloid, and confirm a mechanism for propulsion that was proposed recently. In addition to offering a unified understanding of the nonequilibrium interfacial transport processes at stake, our results open the way to a thorough description of the hydrodynamic interactions between such active particles and understanding their collective dynamics

Distinct Behaviour of the Homeodomain Derived Cell Penetrating Peptide Penetratin in Interaction with Different Phospholipids

Penetratin is a protein transduction domain derived from the homeoprotein Antennapedia. Thereby it is currently used as a cell penetrating peptide to introduce diverse molecules into eukaryotic cells, and it could also be involved in the cellular export of transcription factors. Moreover, it has been shown that it is able to act as an antimicrobial agent. The mechanisms involved in all these processes are quite controversial.In this article, we report spectroscopic, calorimetric and biochemical data on the penetratin interaction with three different phospholipids: phosphatidylcholine (PC) and phosphatidylethanolamine (PE) to mimic respectively the outer and the inner leaflets of the eukaryotic plasma membrane and phosphatidylglycerol (PG) to mimic the bacterial membrane. We demonstrate that with PC, penetratin is able to form vesicle aggregates with no major change in membrane fluidity and presents no well defined secondary structure organization. With PE, penetratin aggregates vesicles, increases membrane rigidity and acquires an α-helical structure. With PG membranes, penetratin does not aggregate vesicles but decreases membrane fluidity and acquires a structure with both α-helical and β–sheet contributions.These data from membrane models suggest that the different penetratin actions in eukaryotic cells (membrane translocation during export and import) and on prokaryotes may result from different peptide and lipid structural arrangements. The data suggest that, for eukaryotic cell penetration, penetratin does not acquire classical secondary structure but requires a different conformation compared to that in solution

Les homologations d'huiles pour moteurs thermiques dans l'administration des PTT

L'Administration des PTT, qui dispose d'un parc automobile de plus de 50000 véhicules, a cherché à définir les exigences de graissage de ses moteurs afin de pouvoir acquérir, à un prix raisonnable, une huile de qualité bien adaptée à ses besoins. La variété des types de véhicules (essence et Diesel), des services (route et ville, plaine et montagne) et des conditions climatiques (totalité du territoire français) a nécessité une étude approfondie - à laquelle l'Institut Français du Pétrole a pris une large part - qui a abouti à la définition d'une huile type et d'essais pratiques sur véhicules très significatifs, objets d'un cahier des charges PTT présentant un intérêt général pour les autres grandes administrations ou services importants. Le présent article expose les motivations et les clauses du cahier des charges ainsi que les résultats des essais d'homologation de la dernière consultation

Are nicotinoids protonated on the pyridine or the amino nitrogen in the gas phase?

0894-323

Expression and role of cubilin in the internalization of nutrients during the peri-implantation development of the rodent embryo

Histiotrophic nutrition is essential during the peri-implantation development in rodents, but little is known about receptors involved in protein and lipid endocytosis derived from the endometrium and the uterine glands. Previous studies suggested that cubilin, a multiligand receptor for vitamin, iron, and protein uptake in the adult, might be important in this process, but the onset of its expression and function is not known. In this study, we analyzed the expression of cubilin in the pre- and early post-implantation rodent embryo and tested its potential function in protein and cholesterol uptake. Using morphological and Western blot analysis, we showed that cubilin first appeared at the eight-cell stage. It was expressed by the maternal-fetal interfaces, trophectoderm and visceral endoderm, but also by the future neuroepithelial cells and the developing neural tube. At all these sites, cubilin was localized at the apical pole of the cells exposed to the maternal environment or to the amniotic and neural tube cavities, and had a very similar distribution to megalin, a member of the LDLR gene family and a coreceptor for cubilin in adult tissues. To analyze cubilin function, we followed endocytosis of apolipoprotein A-I and HDL cholesterol, nutrients normally present in the uterine glands and essential for embryonic growth. We showed that internalization of both ligands was cubilin dependent during the early rodent gestation. In conclusion, the early cubilin expression and its function in protein and cholesterol uptake suggest an important role for cubilin in the development of the peri-implantation embryo

Electron and hole mobility in silicon at large operating temperatures. I. Bulk mobility

In this paper, an experimental investigation on high-temperature carrier mobility in bulk silicon is carried out with the aim of improving our qualitative and quantitative understanding of carrier transport under ESD events. Circular van der Pauw patterns, suitable for resistivity and Hall measurements, were designed and manufactured using both the n and players made available by the BCD-3 smart-power technology. The previous measurements were carried out using a special measurement setup that allows operating temperatures in excess of 400 °C to be reached within the polar expansions of a commercial magnet. A novel extraction methodology that allows for the determination of the Hall factor and drift mobility against impurity concentration and lattice temperature has been developed. Also, a compact mobility model suitable for implementation in device simulators is worked out and implemented in the DESSIS© code. Comparisons with the mobility models by Masetti and Klaassen are shown in the temperature range between 25 and 400 °C

Amphimedonoic acid and psammaplysene E, novel brominated alkaloids from Amphimedon sp.

International audienceExamination of the CH2Cl2-MeOH (1:1) extract from the Madagascan sponge Amphimedon sp. highlighted two new brominated alkaloids, amphimedonoic acid (1) and psammaplysene E (2), along with the known 3,5-dibromo-4-methoxybenzoic acid (3). Their structures were elucidated by 1D and 2D NMR spectroscopy and HRESIMS data