Effect of pressure on Hydrogen/Oxygen coupled flame-wall interaction

The design and optimization of liquid-fuel rocket engines is a major scientific and technological challenge. One particularly critical issue is the heating of solid parts that are subjected to extremely high heat fluxes when exposed to the flame. This in turn changes the injector lip temperature, leading to possibly different flame behaviors and a fully coupled system. As the cham- ber pressure is usually much larger than the critical pressure of the mixture, supercritical flow behaviors add even more complexity to the thermal prob- lem. When simulating such phenomena, these thermodynamic conditions raise both modeling and numerical specific issues. In this paper, both sub- critical and supercritical Hydrogen/Oxygen one-dimensional, laminar flames interacting with solid walls are studied by use of conjugate heat transfer simulations, allowing to evaluate the wall heat flux and temperature, their impact on the flame as well as their sensitivity to high pressure and real gas thermodynamics up to 100 bar where real gas effects are important. At low pressure, results are found in good agreement with previous studies in terms of wall heat flux and quenching distance, and the wall stays close to isothermal. On the contrary, due to important changes of the fluid trans- port properties and the flame characteristics, the wall experiences significant heating at high pressure condition and the flame behavior is modified

NA activity as marker for airborne virus detection

Viruses offer a limited range of targets for their detection. To date, PCR and RT-PCR have been widely used for detection of viruses. In the case of environmental air sampling, the ability to detect a broad range of viruses would constitute a significant advantage for preventing outbreaks of airborne-transmitted viral infections. Given that neuraminidase is found on some respiratory virus species of medical or agricultural importance, this enzyme could theoretically be used to detect several different airborne viruses in a single assay. The aim of the present study was to evaluate the potential of neuraminidase activity as a marker for rapid detection of airborne viruses. We first validated the use of a low-pathogenic strain of Newcastle disease virus (NDV) as a model airborne virus. Our findings revealed that neuraminidase activity-based assays are almost as sensitive as RT-PCR assays currently used for detection of NDV. We also validated the utilization of a neuraminidase substrate specific to viral neuraminidase. Experiments conducted in a controlled chamber demonstrated that the neuraminidase activity is preserved after aerosolization, air sampling using impingement and handling. Finally, we tested our method with swine barn air samples. Our results demonstrate that neuraminidase activity-based assays are suitable for detection of viruses in air samples

Detection and quantification of airborne norovirus during outbreaks in healthcare facilities

Background. Noroviruses are responsible for at least 50% of all gastroenteritis outbreaks worldwide. Noroviruses GII can infect humans via multiple routes including direct contact with an infected person, fecal matter, or vomitus, and contact with contaminated surfaces. Although norovirus is an intestinal pathogen, aerosols could, if inhaled, settle in the pharynx and later be swallowed. The aims of this study were to investigate the presence of norovirus GII bioaerosols during gastroenteritis outbreaks in healthcare facilities and to study the in vitro effects of aerosolization and air sampling on the noroviruses using murine norovirus as a surrogate. Methods. A total of 48 air samples were collected during norovirus outbreaks in 8 healthcare facilities. Samples were taken 1 m away from each patient, in front of the patient's room and at the nurses' station. The resistance to aerosolization stress of murine norovirus type 1 (MNV-1) bioaerosols was also tested in vitro using an aerosol chamber. Results. Norovirus genomes were detected in 6 of 8 healthcare centers. The concentrations ranged from 1.35 × 101 to 2.35 × 103 genomes/m3 in 47% of air samples. MNV-1 preserved its infectivity and integrity during in vitro aerosol studies. Conclusions. Norovirus genomes are frequently detected in the air of healthcare facilities during outbreaks, even outside patients' rooms. In addition, in vitro models suggest that this virus may withstand aerosolization

Identification of dichloroacetic acid degrading Cupriavidus bacteria in a drinking water distribution network model

Aims: Bacterial community structure and composition of a drinking water network were assessed to better understand this ecosystem in relation to haloacetic acid (HAA) degradation and to identify new bacterial species having HAA degradation capacities. Methods and Results: Biofilm samples were collected from a model system, simulating the end of the drinking water distribution network and supplied with different concentrations of dichloroacetic and trichloroacetic acids at different periods over the course of a year. The samples were analysed by culturing, denaturing gradient gel electrophoresis (DGGE) and sequencing. Pipe diameter and HAA ratios did not impact the bacterial community profiles, but the season had a clear influence. Based on DGGE profiles, it appeared that a particular biomass has developed during the summer compared with the other seasons. Among the bacteria isolated in this study, those from genus Cupriavidus were able to degrade dichloroacetic acid. Moreover, these bacteria degrade dichloroacetic acid at 18°C but not at 10°C. Conclusions: The microbial diversity evolved throughout the experiment, but the bacterial community was distinct during the summer. Results obtained on the capacity of Cupriavidus to degrade DCAA only at 18°C but not at 10°C indicate that water temperature is a major element affecting DCAA degradation and confirming observations made regarding season influence on HAA degradation in the drinking water distribution network. Significance and Impact of the Study: This is the first demonstration of the HAA biodegradation capacity of the genus Cupriavidu

Les vidéotransmissions interactives du CNED - Centre National d'Enseignement à Distance

At first the Direct Broadcasting by Satellite is presented and its working principle compared to the one of minowaves beams. The satellite scenery is summarily described : geostationnary satellite characteristics, and satellite classification according to their mission and to their power. Then the configuration of a hub station is described, and finally some pieces of advise are given about the choice of a configuration according to the planned use. In broadcasting more than one hundred and twenty hours of live programmes during the 93 -94 school year, the C.N.E.D (Centre National d'Enseignement à Distance = National Center for teaching and training through correspondence and television) has settled a wilful policy to integrate interactive videopro grammes (VTI = VidéoTransmissions Interactives) among its educational aids for both teaching and training. Schoolchildren have been involved in such programmes since 1991. New programmes have been broadcasted this year for students registered with the CNED, and also for law students in France and abroad. All these different programmes for different audiences are based on the same concept : live video programmes broadcasted by satellite which combine presentations with dialogues between the audience and the contributors. An evaluation of the practice shows the importance of a thorough preparation and demonstrates that VT1 gains its true value when it is supported by mediators and integrated within consistent processes of teaching and training : thus, motivation, social and cultural relationship are achieved. To know its audiences and their needs better, to improve the rigour and the professionalism of its teaching staajf, as well as its technical teams, are the objectives assigned to the CNED, in order to succeed in widening its range of teaching and training aids efficiently. programmes since 1991. New programmes have been broadcasted this year for students registered with the CNED, and also for law students in France and abroad. All these different programmes for different audiences are based on the same concept : live video programmes broadcasted by satellite which combine presentations with dialogues between the audience and the contributors. An evaluation of the practice shows the importance of a thorough preparation and demonstrates that VT1 gains its true value when it is supported by mediators and integrated within consistent processes of teaching and training : thus, motivation, social and cultural relationship are achieved. To know its audiences and their needs better, to improve the rigour and the professionalism of its teaching staajf, as well as its technical teams, are the objectives assigned to the CNED, in order to succeed in widening its range of teaching and training aids efficiently.On présente pour commencer la Télévision Directe par Satellite en comparant son principe à celui des faisceaux hertziens et en décrivant sommairement le paysage satellitaire : caractéristiques des satellites géostationnaires et classification en fonction de leurs missions ou de leurs puissances. Puis, après avoir résumé la constitution d'une station à antenne parabolique, on donne quelques conseils sur le choix des équipements suivant l'utilisation prévue. Avec plus de 120 heures d'émissions diffusées en direct sur l'année scolaire 93/94, le CNED s'est lancé dans une politique volontariste d'intégration des vidéotransmissions interactives (VTI) parmi ses supports deformation à distance. Concerné dès 1991, le public scolaire est depuis cette année rejoint par les inscrits du CNED et des étudiants en droit, en France et à l'étranger. Séries différentes pour publics différents mais un même concept : celui du direct transmis par satellite associant exposé et dialogue entre le public et les intervenants. L'évaluation des usages montre l'importance d'une préparation de qualité et démontre que la VTI ne prend toute sa valeur que relayée sur place par un médiateur et intégrée dans une démarche cohérente de formation : l'ouverture sociale et culturelle, la motivation sont alors au rendez-vous. Mieux connaître ses publics et leurs besoins, accroître la rigueur et le professionnalisme de ses équipes tant pédagogiques que techniques, tels sont les objectifs fixés par le CNED pour réussir un élargissement efficace de ses supports de formation.Duchaine Pierre-Jean, Bellet Jean-Claude. Les vidéotransmissions interactives du CNED - Centre National d'Enseignement à Distance. In: Sciences et techniques éducatives, volume 1 n°2, 1994. pp. 237-259

Les vidéotransmissions interactives du CNED

Partie 2 (p. 223-236) : http://www.epi.asso.fr/revue/76som.htm#b76p223<br /><br />Sommaires des numéros :<br />http://archive-edutice.ccsd.cnrs.fr/edutice-00000863<br />http://archive-edutice.ccsd.cnrs.fr/edutice-00000864En Février 1991, le centre CNED de Poitiers-Futuroscope réalisait la première vidéotransmission interactive (VTI) à destination d'établissements scolaires ; de septembre 1993 à juin 1994, près de 150 heures de direct seront diffusées par satellite sur le territoire national et vers l'étranger. La maîtrise technologique de l'outil, une meilleure appréhension de ses spécificités pédagogiques ont permis cette montée en charge. Toutefois, le développement des vidéotransmissions interactives pour des publics très divers, même si l'objectif général commun est celui de la formation, et l'utilisation de ces émissions comme des outils à part entière de l'EAD ne peuvent se mettre en perspective que précédés d'une réflexion de fond sur les contraintes et les apports des VTI, leur impact et la pertinence de leur mise en place dans telle ou telle action de formation. <br /><br />Cet article se veut une photographie des pratiques du CNED dans ce domaine, de ses interrogations et de ses perspectives. <br />1re partie [b75p217]<br />2e partie [b76p223

Nouvelle relation de l'apparition miraculeuse de la sainte Vierge à deux petits bergers sur une montagne de la Salette... / par M. l'abbé Duchaine,...

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