COMBUSTION DRIVEN ATOMIC FLUORINE GENERATORS FOR DF CHEMICAL LASERS

Des foyers de combustion conventionnels à haute pression délivrant du fluor atomique pour des lasers chimiques à DF ont été réalisés et essayés. Une méthode pour déterminer la production de fluor atomique est présentée ; elle permet aussi la sélection des combustibles dans le cas d'une détente figée isentropique et avec ou sans pertes de chaleur dans le foyer. Des valeurs sont présentées pour une mole de produits finals et une fraction molaire de diluent de 0,75. Les meilleures conditions de richesse pour différents systèmes combustible/comburant/diluant sont déterminées dans le cas adiabatique et dans le cas réel. De bonnes corrélations ont été obtenues entre le maximum de puissance laser et le maximum de production de fluor atomique à un bon niveau de puissance spécifique.Conventional high pressure combustors delivering atomic fluorine for DF chemical lasers have been designed and tested. A method for routine estimation of the output F atom mass flow rate is presented. It also provides means to select fuels from the computation of the theoretical maximum atomic production for various input chemical compositions assuming frozen isentropic expansion and with or without heat losses in the combustor. The values are presented for one mole of combustion products including the diluent and for a .75 typical value of the molar fraction of diluent. The best equivalence ratio for various fuel/oxidizer/diluent system is calculated for adiabatic conditions and for the effective conditions of heat losses. Good correlations have been obtained between the maximum laser power and the predicted best conditions of atomic fluorine production at good overall laser power

Potential IF chemical laser

Paru dans : 8th G. C. L., Madrid (Spain), September 10-14, 1990Available at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1990 n.121 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Microbial Diversity and Processes in Lake Kivu (East Africa)

Lake Kivu is a deep meromictic and oligotrophic tropical African lake with a permanent thermal- and haline stratification with huge accumulations of dissolved CO2 and CH4 (ca. 300 km3 and 60 km3, respectively) in the deep anoxic monimolimnion (from 60 o 480 m depth). Although there are a wealth of information on the ecology of small eukaryotes and their trophic role on Kivu, available information on prokaryotic planktonic assemblages is scarce. Molecular analysis of archaeal and bacterial communities showed a vertical segregation imposed by the permanent redoxcline. In relation to Bacteria, Actinobacteria, Betaproteobacteria, Green Sulfur Bacteria and Bacteroidetes were the most commonly retrieved groups. For Archaea, a marked dominance of Thaumarchaeota and Crenarchaeota (75% of all archaeal OTUs) over Euryarchaeota was observed. In the anoxic hypolimnion, Euryarchaoeta (Methanosarcinales and Methanocellales) lineages together with Miscellaneous Crenarchaeotic Group phylotypes were mainly recovered. In turn, Thaumarchaeota phylotypes were recovered in oxic and suboxic waters. CARDFISH analyses over the first 100 m revealed the dominance of Bacteria (51.4% – 95.7% of DAPI-stained cells), especially Actinobacteria (epilimnion), Betaproteobacteria (oxic-anoxic interface) and Bacteroidetes (upper hypolimnion), over Archaea (1.0% – 4.5%; maximum abundances at the oxic-anoxic interface). In turn, flow cytometry evidenced the dominance of HNA cells in the euphotic layer, whereas the proportion of LNA cells increased with depth. HNA and LNA populations were still observed in the anoxic hypolimnion suggesting facultative or strict anaerobic metabolisms. The detection of distinct depth maxima of nitrate, nitrite, archaeal amoA and Marine Thaumarchaeota 16S gene copy numbers together with regularly detection of deep maxima of 3H-Thymidine uptake, and the presence of low-light adapted GSB species point towards a strong link of N, C, and S cycles in the redoxcline of Lake Kivu

Carbon cycling in a large, meromictic tropical lake (Lake Kivu, East Africa): insights from seasonal monitoring of biogeochemical depth profiles

audience: researcher, professional, studen

Diversity and Processes in Lake Kivu (East Africa)

info:eu-repo/semantics/nonPublishe