240 research outputs found
Enhancement of microalgae anaerobic digestion by thermo-alkaline pretreatment with lime (CaO)
The aim of this study was to evaluate for the first time the effect of a thermo-alkaline pretreatment with lime (CaO) on microalgae anaerobic digestion. The pretreatment was carried out by adding different CaO doses (4 and 10%) at different temperatures (room temperature (25 °C), 55 and 72 °C). The exposure time was 4 days for pretreatments at 25 °C, and 24 h for pretreatments at 55 and 72 °C. Following, a biochemical methane potential test was conducted with pretreated and untreated microalgae. According to the results, the pretreatment enhanced proteins solubilisation by 32.4% and carbohydrates solubilisation by 31.4% with the highest lime dose and temperature (10% CaO and 72 °C). Furthermore, anaerobic digestion kinetics were improved in all cases (from 0.08 to 0.14 day- 1 for untreated and pretreated microalgae, respectively). The maximum biochemical methane potential increase (25%) was achieved with 10% CaO at 72 °C, in accordance with the highest biomass solubilisation. Thus, lime pretreatment appears as a potential strategy to improve microalgae anaerobic digestion.Peer ReviewedPostprint (author's final draft
Spin and recombination dynamics of excitons and free electrons in p-type GaAs : effect of carrier density
Carrier and spin recombination are investigated in p-type GaAs of acceptor
concentration NA = 1.5 x 10^(17) cm^(-3) using time-resolved photoluminescence
spectroscopy at 15 K. At low pho- tocarrier concentration, acceptors are mostly
neutral and photoelectrons can either recombine with holes bound to acceptors
(e-A0 line) or form excitons which are mostly trapped on neutral acceptors
forming the (A0X) complex. It is found that the spin lifetime is shorter for
electrons that recombine through the e-A0 transition due to spin relaxation
generated by the exchange scattering of free electrons with either trapped or
free holes, whereas spin flip processes are less likely to occur once the
electron forms with a free hole an exciton bound to a neutral acceptor. An
increase of exci- tation power induces a cross-over to a regime where the
bimolecular band-to-band (b-b) emission becomes more favorable due to screening
of the electron-hole Coulomb interaction and ionization of excitonic complexes
and free excitons. Then, the formation of excitons is no longer possible, the
carrier recombination lifetime increases and the spin lifetime is found to
decrease dramatically with concentration due to fast spin relaxation with free
photoholes. In this high density regime, both the electrons that recombine
through the e-A0 transition and through the b-b transition have the same spin
relaxation time.Comment: 4 pages, 5 figure
Room temperature Giant Spin-dependent Photoconductivity in dilute nitride semiconductors
By combining optical spin injection techniques with transport spectroscopy
tools, we demonstrate a spin-photodetector allowing for the electrical
measurement and active filtering of conduction band electron spin at room
temperature in a non-magnetic GaAsN semiconductor structure. By switching the
polarization of the incident light from linear to circular, we observe a Giant
Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of
an external magnetic field. We show that the GSP is due to a very efficient
spin filtering effect of conduction band electrons on Nitrogen-induced Ga
self-interstitial deep paramagnetic centers.Comment: 4 pages, 3 figure
Transient colonization of the airways by unusual Aspergillus species in two cystic fibrosis patients
Date du colloque : 06/2009</p
Durée de la survie des Brucella dans le fromage de Roquefort
CarrĂšre Louis, LafenĂȘtre Henri, Quatrefages H., De Noronha Fernando. DurĂ©e de la survie des Brucella dans le fromage de Roquefort. In: Bulletin de l'AcadĂ©mie VĂ©tĂ©rinaire de France tome 113 n°8, 1960. pp. 469-473
Efficacité comparée de cinq vaccins antibrucelliques chez la Brebis
LafenĂȘtre Henri, CarrĂšre Louis, Cortez A., Vollhardt Yves, Quatrefages H. EfficacitĂ© comparĂ©e de cinq vaccins antibrucelliques chez la brebis. In: Bulletin de l'AcadĂ©mie VĂ©tĂ©rinaire de France tome 115 n°8, 1962. pp. 319-324
Ăvolution de quelques agglutinines vaccinales brucelliques chez la brebis
â Les brebis vaccinĂ©es avec le vaccin Renoux prĂ©sentent pendant un an au moins une sĂ©ro-agglutination positive qui ne permet pas de les distinguer des animaux infectĂ©s ; â La mĂȘme conclusion sâapplique aux brebis vaccinĂ©es avec la B.19, bien que le taux dâagglutination soit nettement plus faible que dans le cas prĂ©cĂ©dent et reprĂ©sente plutĂŽt une suspicion quâune positivitĂ©. â Pour soupçonner lâexistence dâune infection brucellique chez les brebis vaccinĂ©es avec les trois autres vaccins, il faut constater une rĂ©action positive ( + + au 1/20) non point sur un ou deux sujets isolĂ©s, qui peuvent figurer parmi ceux qui conservent en permanence les agglutinines vaccinales, mais sur un groupe de sujets reprĂ©sentant 10% ou mieux 15% de lâeffectif total du trou peau, Ă condition que cette constatation soit faite dans un dĂ©lai post-vaccinal supĂ©rieur Ă 2 mois pour le vaccin Dubois, 3 mois pour le B.112 et 4 mois pour le nĂ©o-brucel. Cette suspicion devient presque une certitude si, lâĂ©preuve Ă©tant recommencĂ©e au bout de 3 Ă 4 semaines, les taux dâagglutination constatĂ©s sont supĂ©rieurs aux taux prĂ©cĂ©dents. On pourra peut-ĂȘtre nous reprocher de nâavoir pas fait porter notre expĂ©rience sur tous les vaccins antibrucelliques susceptibles dâĂȘtre utilisĂ©s dans la pratique ; nous nous sommes volontairement limitĂ©s Ă ceux qui ont fait lâobjet, au moment de leur mise au point, de contrĂŽles scientifiques publiĂ©s. Nous avons Ă©galement laissĂ© de cĂŽtĂ© certains vaccins multivalents qui renferment des brucella Ă titre accessoire, et au" sujet desquels il serait souhaitable que ces bactĂ©ries soient Ă©liminĂ©es, car elles peuvent aussi, par les agglutinines quâelles provoquent, constituer un obstacle pour les opĂ©rations de prophylaxie. Il est Ă peine besoin de souligner enfin que lâapprĂ©ciation de lâinfection dans un troupeau, basĂ©e sur lâĂ©volution des agglutinines vaccinales, suppose la connaissance de la date de la vaccination et de la nature du vaccin utilisĂ©, câest-Ă -dire le contrĂŽle des vaccinations par le Directeur des Services VĂ©tĂ©rinaires
Les limites de la protection vaccinale antibrucellique chez la brebis
LafenĂȘtre Henri, CarrĂšre Louis, Cortez A., Vollhardt Yves, Quatrefages H. Les limites de la protection vaccinale antibrucellique chez la Brebis. In: Bulletin de l'AcadĂ©mie VĂ©tĂ©rinaire de France tome 117 n°3, 1964. pp. 117-121
Vaccins anti-brucelliques tuĂ©s et allergie dans lâespĂšce ovine
LafenĂȘtre Henri, CarrĂšre Louis, Petitdidier M., Vollhardt Yves, Quatrefages H. Vaccins anti-brucelliques tuĂ©s et allergie dans lâespĂšce ovine. In: Bulletin de l'AcadĂ©mie VĂ©tĂ©rinaire de France tome 117 n°4, 1964. pp. 189-191
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