Examination of the local structure in composite and low dimensional semiconductor by X-ray Absorption Spectroscopy

X-ray absorption methods have been successfully used to obtain quantitative information about local atomic composition of two different materials. X-ray Absorption Near Edge Structure analysis and X-Ray Photoelectron Spectroscopy allowed us to determine seven chemical compounds and their concentrations in c-BN composite. Use of Extended X-ray Absorption Fine Structure in combination with Transmission Electron Microscopy enabled us to determine the composition and size of buried Ge quantum dots. It was found that the quantum dots consisted out of pure Ge core covered by 1-2 monolayers of a layer rich in Si

Coronaviruses fusion with the membrane and entry to the host cell

Introduction. Coronaviruses (CoVs) are positive-strand RNA viruses with the largest genome among all RNA viruses. They are able to infect many host, such as mammals or birds. Whereas CoVs were identified 1930s, they became known again in 2003 as the agents of the Severe Acute Respiratory Syndrome (SARS). The spike protein is thought to be essential in the process of CoVs entry, because it is associated with the binding to the receptor on the host cell. It is also involved in cell tropism and pathogenesis. Receptor recognition is the crucial step in the infection. CoVs are able to bind a variety of receptors, although the selection of receptor remains unclear. Coronaviruses were initially believed to enter cells by fusion with the plasma membrane. Further studies demonstrated that many of them involve endocytosis through clathrin-dependent, caveolae-dependent, clathrin-independent, as well as caveolae-independent mechanisms. Objectives. The aim of this review is to summarise current knowledge about coronaviruses, focussing especially on CoVs entry into the host cell. Advances in understanding coronaviruses replication strategy and the functioning of the replicative structures are also highlighted. The development of host-directed antiviral therapy seems to be a promising way to treat infections with SARS-CoV or other pathogenic coronaviruses. There is still much to be discovered in the inventory of pro-and anti-viral host factors relevant for CoVs replication. The latest pandemic danger, originating from China, has given our previously prepared work even more of topicality

23. Albert le Grand et Roger Bacon, inventions et découvertes

PRESSE À IMPRIMER. Détail de la planche XIV extraite du chapitre « Imprimerie » de l’Encyclopédie de Diderot & d’Alembert (volume 7 de 1769). Tous les écrivains distingués du xiiie siècle ont appartenu aux ordres mendiants ; et on ne doit pas s’en étonner, car c’était seulement dans les monastères que les hommes qui avaient le goût de l’étude pouvaient s’y livrer tranquillement, et trouver toutes les facilités dont ils avaient besoin. Souvent le chef d’un couvent avait sous ses ordres plusie..