Search

International audience; Graphene (Gr) is known to be an excellent barrier preventing atoms and molecules to diffuse through it. This is due to the carbon atom arrangement in a two-dimensional (2D) honeycomb structure with a very small lattice parameter thus forming an electron cloud that prevents atoms and molecules crossing. Nonetheless at high temperature of annealing, intercalation of atoms through graphene occurs, opening the path for formation of vertical heterojunctions formed of two-dimensional layers. In this paper, we report on the ability of silicon atoms to penetrate the graphene network, fully epitaxially grown on a Ni(111) surface, even at room temperature. Our scanning tunneling microscopy (STM) shows that defects like vacancies and dislocations of the graphene lattice favor the Si intercalation below the Gr layer forming two-dimensional, flat and disordered islands. Ab-initio molecular dynamics calculations confirm that Gr defects are necessary for Si intercalation at room temperature and show that a hypothetical intercalated silicene layer cannot be stable for more than 8 ps and that the corresponding Si atoms completely lose their in-plane order resulting in a random planar distribution and form strong covalent bonds with Ni atoms.

Clostridium difficile is a major cause of antibiotic associated diarrhea. Recently, we have shown that effective protection can be mediated in hamsters through the inclusion of specific recombinant fragments from toxin A and B in a systemically delivered vaccine. Interestingly while neutralizing antibodies to the binding domains of both toxin A and B are moderately protective, enhanced survival is observed when fragments from the glucosyltransferase region of toxin B replace those from the binding domain of this toxin. In this addendum, we discuss additional information that has been derived from such vaccination studies. This includes observations on efficacy and cross-protection against different ribotypes mediated by these vaccines and the challenges that remain for a vaccine which prevents clinical symptoms but not colonization. The use and value of vaccination both in the prevention of infection and for treatment of disease relapse will be discussed.

Surface chemical composition and topography of Pt-SnO2 thin films grown by radiofrequency (rf) reactive sputtering on two different Al2O3 substrates (rough and mechanically polished) were investigated by x-ray photoemission spectromicroscopy (XPSM) and atomic force microscopy (AFM). XPSM measurements showed, for both substrates, a homogeneous chemical composition of the Pt-SnO2 films. The only difference was the observation of different charging in different areas of the film grown on rough alumina substrates, due, presumably, to a non-continuous Pt-SnO2 film. AFM showed large topographical variations (several hundred nanometres) for the Pt-SnO2 film grown on a rough alumina substrate, due to structures already present on the substrate. The estimated roughness of the sensor was 20% larger for the Pt-SnO2 film grown on a rough alumina substrate. The response to carbon monoxide was 30% higher for the sensor grown on rough alumina than that on polished alumina, reflecting the larger exposed sensor area.

Chlamydia are intracellular bacteria associated to serious human disease. A vaccine has proved difficult to obtain so far, and current opinions agree that multi-antigen combinations may be required to induce optimal protective responses. In order to identify new potential vaccine candidates, we recently screened the Chlamydia pneumoniae (Cpn) genome and described 53 recombinant proteins which elicited antibodies binding to purified Cpn cells.We now report that six proteins in this group can also induce in vitro neutralizing antibodies. Antibody specificity for the corresponding antigens was assessed by immunoblot analysis of 2DE Cpn protein maps. Furthermore, four of the six in vitro neutralizing antigens (Pmp2, Pmp10, OmpH-like and enolase) could inhibit Cpn dissemination in a hamster model. The results show that these Cpn proteins are immunoaccessible in infectious EBs, and recommend further investigation on their value as vaccine components.