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Binh P.H.,INSA Toulouse | Binh P.H.,Institute of Material Science | Renucci P.,INSA Toulouse | Truong V.G.,INSA Toulouse | Marie X.,INSA Toulouse
Electronics Letters | Year: 2012

A new pulse-shaping circuit has been designed to increase the performances of large signal modulation of light emitting diodes. It is simply based on a parallel Schottky-capacitance circuit in series with the light emitter. The peak power of the generated optical pulse is shown to be significantly improved compared to the classical resistance-capacitance peaking circuit for sub-nanosecond pulsewidths. © 2012 The Institution of Engineering and Technology.

Parhi N.,P.A. College | Rout G.C.,Fakir Mohan University | Behera S.N.,Institute of Material Science
Indian Journal of Physics | Year: 2010

We present here a theoretical study of the effect of Jahn-Teller(J-T) distortion on the self-energy of electrons in the CMR manganites. The model consists of the itinerant eg electrons distorted by J-T effect and the localized t2g core electrons carrying strong ferromagnetism due to Hund's rule. The phonon interacts with the eg electrons as well as the J-T distorted eg band. The electron Green's functions are calculated by Zubarev's technique. The electron self-energy which carries all the information of the model is calculated from the Green's function. The effect of J-T distortion, magnetism on the frequency and temperature dependent dynamic selfenergy is presented in this paper. The results are discussed. © 2010 IACS.

Dotsika E.,Institute of Material Science | Dotsika E.,CNR Institute of Geosciences and Earth Resources
Journal of Volcanology and Geothermal Research | Year: 2012

Thermal and cold water samples were collected from the island of Samothraki, in the northern part of the Aegean Sea. Isotopic (δD, δ 18O, δ 34S SO4, δ 34S S2-, δ 18O SO4) and chemical analyses (major ions, Br, B, Li, SiO 2) were performed in most of them. The study of ionic and isotopic contents shows that, the thermal waters of Samothraki Island are mainly locally fed groundwater that changes, chemically and isotopically, during its circulation within a major fracture zone reaching great depths. More specifically, the evaluation of the entire dataset indicates that water-rock reactions and mixing with brines are the principal sources of the isotopic and salinity fingerprint of these waters.The isotopic [δ 18O (SO 4 2--H 2O)] and chemical geothermometers applied on the waters of the thermal springs, suggest the probable existence of a geothermal reservoir of high enthalpy. The temperature attributed to this deep geothermal field is higher than 220°C. © 2012 Elsevier B.V.

Georgakilas V.,Institute of Material Science | Bourlinos A.B.,Institute of Material Science | Zboril R.,Palacky University | Steriotis T.A.,Institute of Physical Chemistry | And 4 more authors.
Chemical Communications | Year: 2010

Graphene sheets derived from dispersion of graphite in pyridine were functionalised by the 1,3 dipolar cycloaddition of azomethine ylide. The organically modified graphene sheets are easily dispersible in polar organic solvents and water, and they are extensively characterised using several spectroscopic and microscopy techniques. © 2010 The Royal Society of Chemistry.

Schaller J.,TU Dresden | Schaller J.,Institute of General Ecology and Environmental Protection | Brackhage C.,TU Dresden | Brackhage C.,Institute of General Ecology and Environmental Protection | And 4 more authors.
Science of the Total Environment | Year: 2011

The focus of this article is to combine two main areas of research activities in freshwater ecosystems: the effect of inorganic pollutants on freshwater ecosystems and litter decomposition as a fundamental ecological process in streams.The decomposition of plant litter in aquatic systems as a main energy source in running water ecosystems proceeds in three distinct temporal stages of leaching, conditioning and fragmentation. During these stages metals and metalloids may be fixed by litter, its decay products and the associated organisms. The global-scale problem of contaminated freshwater ecosystems by metals and metalloids has led to many investigations on the acute and chronic toxicity of these elements to plants and animals as well as the impact on animal activity under laboratory conditions. Where sorption properties and accumulation/remobilization potential of metals in sediments and attached microorganisms are quite well understood, the combination of both research areas concerning the impact of higher trophic levels on the modification of sediment sorption conditions and the influence of metal/metalloid pollution on decomposition of plant litter mediated by decomposer community, as well as the effect of high metal load during litter decay on organism health under field conditions, has still to be elucidated. So far it was found that microbes and invertebrate shredder (species of the genera Gammarus and Asellus) have a significant influence on metal fixation on litter. Not many studies focus on the impact of other functional groups affecting litter decay (e.g. grazer and collectors) or other main processes in freshwater ecosystems like bioturbation (e.g. Tubifex, Chironomus) on metal fixation/release. © 2011 Elsevier B.V.

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