Dichroïsme linéaire sous contrainte des ions Ag- et Cu- dans KCl et NaCl

We report on an investigation of the room-temperature stress induced linear dichroism of Ag- in KCl, NaCl and NaCl/Ca2+, as well as that of Cu- in the same matrices and in KCl/Ca2+. It follows from the analysis of our data by the method of moments that Ag- in KCl and NaCl shows many ressemblances with the F-center in alkali halides, whereas Cu- in NaCl behaves like the already studied Tl+ isoelectronic ion. The response of the Cu -/KCl system to an uniaxial stress is quite different from that of the above systems. We tentatively suggest this to be due to an off-center position of the copper ion along the axes in the lattice.Nous avons étudié le dichroïsme linéaire sous contrainte de l'ion Ag- dans KCl, NaCl et NaCl/Ca2+, et de l'ion Cu- dans KCl, NaCl, KCl/Ca2+ et NaCl/Ca2+ à température ordinaire. Nous avons analysé les résultats obtenus à l'aide de la méthode des moments. Cette étude montre que les systèmes Ag- dans KCl et NaCl ont un comportement analogue à celui des centres F dans les halogénures alcalins tandis que Cu- dans NaCl apparaît semblable aux ions isoélectroniques déjà étudiés (Tl+ , In+). Le système Cu-/KCl, par contre, apparaît comme notablement différent des précédents du point de vue de son comportement sous l'influence d'une contrainte. Nous en concluons que le processus de couplage avec les distorsions dynamiques doit être différent, ceci étant dû probablement au fait que l'ion Cu- se trouve légèrement excentré dans le réseau suivant

Simulation of the Planck-HFI thermal control system

International audienceThe core of the High Frequency Instrument (HFI) on-board the Planck satellite consists of 52 bolometric detectors cooled at 0.1 Kelvin. In order to achieve such a low temperature, the HFI cryogenic architecture consists in several stages cooled using different active coolers. These generate weak thermal fluctuations on the HFI thermal stages. Without a dedicated thermal control system these fluctuations could produce unwanted systematic effects, altering the scientific data. The HFI thermal architecture allows to minimise these systematic effects, thanks to passive and active control systems described in this paper. The passive and active systems are used to damp the high and low frequency fluctuations respectively. The results of the simulation of these active and passive control systems are presented here. These simulations based on the use of thermal transfer functions for the thermal modelling can then be used for finding the optimal working point of the HFI PID active thermal control system

Inactivation of the protein phosphatase 2A regulatory subunit A results in morphological and transcriptional defects in Saccharomyces cerevisiae.

We have determined that TPD3, a gene previously identified in a screen for mutants defective in tRNA biosynthesis, most likely encodes the A regulatory subunit of the major protein phosphatase 2A species in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence of the product of TPD3 is highly homologous to the sequence of the mammalian A subunit of protein phosphatase 2A. In addition, antibodies raised against Tpd3p specifically precipitate a significant fraction of the protein phosphatase 2A activity in the cell, and extracts of tpd3 strains yield a different chromatographic profile of protein phosphatase 2A than do extracts of isogenic TPD3 strains. tpd3 deletion strains generally grow poorly and have at least two distinct phenotypes. At reduced temperatures, tpd3 strains appear to be defective in cytokinesis, since most cells become multibudded and multinucleate following a shift to 13 degrees C. This is similar to the phenotype obtained by overexpression of the protein phosphatase 2A catalytic subunit or by loss of CDC55, a gene that encodes a protein with homology to a second regulatory subunit of protein phosphatase 2A. At elevated temperatures, tpd3 strains are defective in transcription by RNA polymerase III. Consistent with this in vivo phenotype, extracts of tpd3 strains fail to support in vitro transcription of tRNA genes, a defect that can be reversed by addition of either purified RNA polymerase III or TFIIIB. These results reinforce the notion that protein phosphatase 2A affects a variety of biological processes in the cell and provide an initial identification of critical substrates for this phosphatase

A liquid hexavalent combined vaccine against diphtheria, tetanus, pertussis, poliomyelitis, Haemophilus influenzae type B and hepatitis B: review of immunogenicity and safety

To reduce the number of injections needed to comply with paediatric vaccination requirements, a liquid, hexavalent vaccine (DTaP-IPV-PRP-T-HBs; Hexavac((R)); Aventis Pasteur MSD) has been developed for primary and booster vaccination of infants and toddlers. In extensive clinical studies, Hexavac((R)) has been shown to be highly immunogenic. Seroconversion or seroprotective titres of antibodies against all antigens were achieved in the majority of infants following a primary series of three doses administered at 1-2-month intervals from 2 months of age. Hexavac((R)) also induced immunologic memory, as evidenced by the anamnestic response to booster vaccination at 12-18 months of age. These responses were comparable with those seen following concomitant administration of Pentavac(TM) (DTaP-IPV//PRP-T) and monovalent hepatitis B vaccine (H-B-Vax(TM) II), and were also within the ranges observed for other relevant licensed vaccines. Clinical studies comparing the immunogenicity of Hexavac((R)) administered at either 2, 3 and 4 months or 2, 4 and 6 months demonstrated that it can be used by either vaccination schedule. A further study also supported the use of primary doses of Hexavac((R)) at 3 and 5 months with a booster at 12 months of age. Hexavac((R)) demonstrated a good reactogenicity and tolerability profile. The most frequently reported adverse events after both primary and booster doses were local reactions of redness and swelling/induration and a systemic response of mild fever, irrespective of the vaccine used for priming. Hexavac((R)) provided immunity against six important childhood diseases with a single injection at each visit. (C) 2003 Elsevier Ltd. All rights reserved