Conception d'une chambre de diffraction RX haute température pour l'étude de l'adsorption d'un gaz par un solide sous haute pression

Le caractère original et innovateur de la chambre d'analyse qui est présentée dans ce travail repose sur son champ d'utilisation large, en particulier dans le domaine de l'adsorption sous haute pression d'un gaz condensable. Cette chambre qui a été spécialement conçue au Laboratoire de Recherches sur la Réactivité des Solides de l'Université de Bourgogne est susceptible d'opérer dans des domaines étendus de pression et de température, respectivement (10-4-104) hPa et (20 - 350) °C. Un doigt de gant en béryllium monté sur un passage électrique assure l'étanchéité de l'enceinte réactionnelle ; l'échantillon est chauffé par conduction. La chambre qui est placée dans une enceinte externe (équipée d'une fenêtre hémi-cylindrique en kapton) maintenue sous un vide dynamique de 10-4 hPa pour s'affranchir de toute oxydation du béryllium et de toutes émanations éventuelles de gaz condensable est installée sur un goniomètre à axe horizontal muni d'un compteur à localisation courbe INEL CPS 120. L'ensemble du dispositif est connecté d'une part à une ligne de vide, d'autre part à une réserve de gaz. Un exemple d'utilisation de la chambre est présenté dans le cas de l'adsorption et la désorption sous 5 x 103 hPa de l'isopentane par la zéolite 5A.The originality of the present new X-ray reactor chamber is based on its wide range of use for studying solid-gas reactions, especially for condensable gases under high pressure. This chamber constructed in the Laboratory of Research on the Reactivity of Solids of the University of Burgundy, permits studies at wide pressure and temperature ranges from 10-4 hPa to 104 hPa and from room temperature to 350 °C respectively. A beryllium tube mounted on a feedthrough ensures the tightness of the reactor chamber. The sample is heated by conduction. The chamber which is set into an external tight container is fixed on an horizontal axis goniometer connected to a curved X ray position sensitive detector INEL CPS 120. During the experiments a continuous vacuum of approximately 10-4 is imposed into the external container equiped with a semi-cylindrical kapton window, to prevent any oxidation of beryllium and any casual outflow of the condensable gas. The X-ray reactor chamber is connected on one side to vacuum and on the other side to a gas reserve. One application of the X-ray reactor chamber is shown from the study of the adsorption and desorption of isopentane on a zeolite 5A under 5 x 103 hPa

Value-Based File Retention: File Attributes as File Value and Information Waste Indicators

Several file retention policy methods propose that a file retention policy should be based on file value. Though such a retention policy might increase the value of accessible files, the method to arrive at such a policy is underresearched. This article discusses how one can arrive at a method for developing file retention policies based on the use values of files. The method’s applicability is initially assessed through a case study at Capgemini, Netherlands. In the case study, we hypothesize that one can develop a file retention policy by testing causal relations between file attributes (as used by file retention methods) and the use value of files. Unfortunately, most file attributes used by file retention methods have a weak correlation with file value, resulting in the conclusion that these methods do not well select out high- and low-value files. This would imply the ineffectiveness of the used attributes in our study or errors in our conceptualization of file value. We continue with the last possibility and develop indicators for file utility (with low utility being waste). With this approach we were able to detect waste files, in a sample of files, with an accuracy of 80%. We therefore not only suggest further research in information waste detection as part of a file retention policy, but also to further explore other file attributes that could better predict file value and file utility

Asymmetric conformational changes in a GPCR dimer controlled by G-proteins

G-protein-coupled receptors (GPCRs) are key players in cell communication. Although long considered as monomeric, it now appears that these heptahelical proteins can form homo- or heterodimers. Here, we analyzed the conformational changes in each subunit of a receptor dimer resulting from agonist binding to either one or both subunits by measuring the fluorescent properties of a leukotriene B(4) receptor dimer with a single 5-hydroxytryptophan-labeled protomer. We show that a receptor dimer with only a single agonist-occupied subunit can trigger G-protein activation. We also show that the two subunits of the receptor dimer in the G-protein-coupled state differ in their conformation, even when both are liganded by the agonist. No such asymmetric conformational changes are observed in the absence of G-protein, indicating that the interaction of the G-protein with the receptor dimer brings specific constraints that prevent a symmetric functioning of this dimer. These data open new options for the differential signaling properties of GPCR dimers

Real-Time Detection of Covert Channels in Highly Virtualized Environments

Part 3: INFRASTRUCTURE SECURITYInternational audienceDespite extensive research, covert channels are a principal threat to information security. Covert channels employ specially-crafted content or timing characteristics to transmit internal information to external attackers. Most techniques for detecting covert channels model legitimate network traffic. However, such an approach may not be applicable in dynamic virtualized environments because traffic for modeling normal activities may not be available.This paper describes Observer, a real-time covert channel detection system. The system runs a secure virtual machine that mimics the vulnerable virtual machine so that any differences between two virtual machines can be identified in real time. Unlike other detection systems, Observer does not require historic data to construct a model. Experimental tests demonstrate that Observer can detect covert channels with a high success rate and low latency and overhead