Modeling of Planck-high frequency instrument bolometers using non-linear effects

Abstract The Planck satellite, which is planned to be launched in 2007, is dedicated to surveying the Cosmic Microwave Background (CMB) to a high precision. Aboard this mission, the High-Frequency Instrument (HFI) will use 52 NTD Ge spiderweb bolometers made by Caltech-JPL and cooled to 100 mK by a dilution cooler. In this paper, we present a model of these detectors that includes non-linear effects seen in NTD Ge thermometers: electron-phonon decoupling and electrical field effect. We show that this model leads to consider only electrical field effect. Furthermore, the optical characterization of the HFI bolometers clearly shows a non-ideal behavior that is explained by non-linear effects in the thermometer. We finally show that these effects have to be taken into account for optimized CMB observations and to fully understand the physics of semi-conducting bolometers. r 2005 Elsevier B.V. All rights reserved. PACS: 95.55.J

Potential of lactic acid bacteria to interact with Salmonella through nutritional competition in dairy-like media

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Reduced growth of Listeria monocytogenes in two model cheese microcosms is not associated with individual microbial strains

Two model antilisterial microbial communities consisting of two yeasts, two Gram positive and two Gram negative bacteria, and originating from Livarot cheese smear were previously designed. They were used in the present study to analyse the impact of microbial population dynamics on growth of Listeria monocytogenes in cheese microcosm. Specific culture media and PCR primers were developed for simultaneous culture-dependent and real-time PCR quantification of strains belonging to Marinomonas sp., Paenibacillus sp., Staphylococcus equorum, Arthrobacter arilaitensis, Pseudomonas putida, Serratia liquefaciens, Candida natalensis, and Geotrichum candidum, in cheese microcosms. All strains were enumerated after 3, 5, 8 and 14 days at 15 C. They established well at high counts in all cheese microcosms. Growth dynamics for all strains in presence of L. monocytogenes WSLC 1685 were compared to those of microbial communities obtained by omitting in turn one of the six members of the initial community. The growth of the microbial strains was neither markedly disturbed by Listeria presence nor by the removal of each strain in turn. Furthermore, these communities had a significant reducing effect on growth of L. monocytogenes independently of pH, as confirmed by mathematical modelling. A barrier effect was observed, that could be explained by specific competition for nutrients

Viandes sous vide : utilise-t-on les bons indicateurs microbiologiques ?

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Viandes sous vide : utilise-t-on les bons indicateurs microbiologiques ?

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Viande de bœuf sous vide : vers une approche analytique plus adaptée du critère flore lactique

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