One-dimensional modelling of DBDs in NeXe mixtures for excimer lamps

International audienceDielectric barrier discharges (DBDs) are a promising technology for high-intensity sources of specific UV and VUV radiation. In this work, the microdischarge dynamics in DBDs for Ne−Xe mixtures under the close conditions of excimer lamp working has been investigated. The computer model including the cathode fall, the positive column and the dielectric is composed of two coupled sub-models. The first submodel describes the electrical properties of the discharge and is based on a fluid, two-moments description of electron and ion transport coupled with Poisson's equation during the discharge pulse. The second submodel, based on three main modules: a plasma chemistry module, a circuit module and a Boltzmann equation module, with source terms deduced from the electric model, describes the time variations of charged and excited species concentrations and the UV photon emission. The use of the present description allows a good resolution near the sheath at high pressure and it predicts correctly the waveform of the discharge behavior. The effects of operation voltage, dielectric capacitance, gas mixture composition, gas pressure, as well as the secondary electron emission by ion at the cathode on the discharge characteristics and the 173 nm photon generation have been investigated and discussed

Abundant Zoophycos and Chondrites from the Messinian (Upper Miocene) of northwestern Algeria

© 2020 Elsevier Ltd The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). The upper part of the Diatomaceous Formation is intercalated by four diatomaceous beds rich in Zoophycos and Chondrites. Both these traces were produced by the members of endo-benthonic fauna adapted to nutrient exploitation within sediments. In the Diatomaceous Formation, larger dark-coloured Chondrites targionii cross-cuts smaller C. intricatus, which could indicate ecological succession perhaps due to conditions getting less oxygenated and causing the need for larger burrows. Size increase of Zoophycos upwards in the section may indicate that environment became less stressed, shallower and likely had a higher nutrient content or alternatively there was a change in the trace-maker biological affinity. The depositional environment shows some evidence of low-oxygenated to dysoxic conditions, because abundant Chondrites occurs without any other trace fossils with the exception of Zoophycos. Chondrites trace-makers likely maintained a connection to oxygenated water but penetrate into anoxic sediments rich in sulfides or ammonium that are required for microbe-breeding and feeding. Most likely studied Zoophycos-Chondrites and pure Zoophycos associations of the Upper Member of the Diatomaceous Formation are of deeper shelf origin. The diatomaceous volcanic ash beds of the upper part of the formation are intensively bioturbated by a horizontal network of large-size Thalassinoides, which represents domichnial and fodinichnial structures, and suggesting an enough oxygenated environment with sufficient nutrients. Thalassinoides level likely represents shallower water conditions (shallow shelf) than the underlying levels characterised with Zoophycos-Chondrites and Zoophycos associations

Surgery for treating Lesions of the Facial Nerve

ZusammenfassungUrsachen für eine Läsion mit nachfolgender Lähmung des N. facialis sind vielfältig, von der idiopathischen Fazialisparese bis hin zur Destruktion des Nervs durch einen malignen Tumor. Eine Indikation zur chirurgischen Intervention besteht immer dann, wenn die Wahrscheinlichkeit einer spontanen Heilung mit gutem funktionellen Ergebnis gering oder gar nicht vorhanden ist, und eine medikamentöse Behandlung nicht möglich oder auch der chirurgischen Therapie unterlegen ist.</jats:p

Theoretical Kinetics Investigation of Krypton Dielectric Barrier Discharge for UV Lamp

International audienceThis work presents an electric and kinetic study of homogeneous dielectric barrier discharge (DBD) in pure krypton (Kr). The electrical characterization and kinetic analyses of the DBD in Kr are performed. The plasma formation in DBD, excited by sinusoidal voltage at high pressure, was studied. The discharge development, with homogeneous model approach and using extended kinetic scheme, is simulated. The study is based on a spatial homogeneity model including the plasma chemistry, the electrical circuit and the Boltzmann equations’. The temporal variations of discharge voltage, dielectrics voltage, discharge current, electric field and species concentrations are calculated. The plasma kinetics is discussed with the aim to finding the optimal efficiency. The photon generation, under typical operating conditions, was investigated and discussed. The effect of some parameters on the excilamp like pressure, applied voltage, and frequency are investigated in order to identify the optimal parameters for maximum luminous efficiency in the UV range

The Upper Jurassic Faïdja Formation (Northwestern Algeria): Sedimentology, biostratigraphy and ichnology

© 2020 Elsevier Ltd The Faïdja Formation displays mixed siliciclastic-carbonate deposits distributed in three members, which are organised from bottom to top as follows: the Clayey Sandstone Faïdja Member; the Clayey Limestone Bel Aoura Member and the Sandy Claystone Douaouda Member. Sedimentological data indicate the evolution of a subsiding marine environment from the shelf edge to the lower shoreface, sporadically dominated by storms. New age based on recently collected ammonite fauna allowed us to update the age of the Faïdja Formation as Early-Late Kimmeridgian. Ichnological analysis reveals the occurrence of abundant and diverse invertebrate trace fossils, grouped in four ichnoassociations. Ichnoassociation -A- coincides with the lowermost part of the Clayey Sandstone Faïdja Member; it is distinguished by a combination of pre-graphoglyptids and post-depositional traces, ascribed to the distal Cruziana ichnofacies transitional to the Nereites ichnofacies, which indicates a lower offshore zone to shelf edge environment characterised by a low-oxygenated period (anoxic event), frequent storm events and nutrient frequency. Ichnoassociation -B- occupies the middle and upper parts of the Clayey Sandstone Faïdja Member, it is characterised by an abundance of post-depositional traces, corresponding to the archetypal Cruziana ichnofacies that indicates a lower to transitional offshore environment with short phases of low hydrodynamic energy. Ichnoassociation -C- corresponds to the Clayey Limestone Bel Aoura Member that coincides with a drastic facial change and depositional conditions; this association documents a proximal Cruziana ichnofacies, and indicates an upper to transitional offshore zone as a depositional environment. Finally, ichnoassociation -D- coincides with the Sandy Claystone Douaouda Member; it is ascribed to the proximal Cruziana ichnofacies, indicating a lower shoreface environment. The combined sedimentological and ichnological data indicates a relatively subsiding platform with shallowing upwards corresponding to distal, archetypal and proximal Cruziana ichnofacies, respectively