Microbial perchlorate reduction: A precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis

Perchlorate-reducing bacteria fractionate chlorine stable isotopes giving a powerful approach to monitor the extent of microbial consumption of perchlorate in contaminated sites undergoing remediation or natural perchlorate containing sites. This study reports the full experimental data and methodology used to re-evaluate the chlorine isotope fractionation of perchlorate reduction in duplicate culture experiments of Azospira suillum strain PS at 37 degrees C (Delta Cl-37(Cr)--ClO4-) previously reported, without a supporting data set by Coleman et al. [Coleman, M.L., Ader, M., Chaudhuri, S., Coates,J.D., 2003. Microbial Isotopic Fractionation of Perchlorate Chlorine. Appl. Environ. Microbiol. 69, 4997-5000] in a reconnaissance study, with the goal of increasing the accuracy and precision of the isotopic fractionation determination. The method fully described here for the first time, allows the determination of a higher precision Delta Cl-37(Cl)--ClO4- value, either from accumulated chloride content and isotopic composition or from the residual perchlorate content and isotopic composition. The result sets agree perfectly, within error, giving average Delta Cl-37(Cl)--ClO4- = -14.94 +/- 0.15%omicron. Complementary use of chloride and perchlorate data allowed the identification and rejection of poor quality data by applying mass and isotopic balance checks. This precise Delta Cl-37(Cl)--ClO4-, value can serve as a reference point for comparison with future in situ or microcosm studies but we also note its similarity to the theoretical equilibrium isotopic fractionation between a hypothetical chlorine species of redox state +6 and perchlorate at 37 degrees C and suggest that the first electron transfer during perchlorate reduction may occur at isotopic equilibrium between art enzyme-bound chlorine and perchlorate. (C) 2008 Elsevier B.V. All rights reserved.

Galactic cosmic ray hazard in the unusual extended solar minimum between solar cycle 23 and 24

Galactic cosmic rays (GCRs) are extremely difficult to shield against and pose one of the most severe long-term hazards for human exploration of space. The recent solar minimum between solar cycles 23 and 24 shows a prolonged period of reduced solar activity and low interplanetary magnetic field strengths. As a result, the modulation of GCRs is very weak, and the fluxes of GCRs are near their highest levels in the last 25 years in the fall of 2009. Here we explore the dose rates of GCRs in the current prolonged solar minimum and make predictions for the Lunar Reconnaissance Orbiter (LRO) Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is now measuring GCRs in the lunar environment. Our results confirm the weak modulation of GCRs leading to the largest dose rates seen in the last 25 years over a prolonged period of little solar activity.

Prosodie et Syndrome de Williams : une étude inter-langue

L’objectif de l’étude est de mieux cerner les particularités acoustiques de la prosodie d’enfants porteurs du SW de langue maternelle anglaise et de langue maternelle française. Des productions spontanées ont été recueillies à l’aide de la tâche de narration « Grenouille, où es-tu ? » (Mayer, 1969). La prosodie des enfants SW est comparée à celle de deux groupes typiques, un de même âge chronologique et un de même âge développemental que le groupe avec SW La population se compose de 1. 7 enfants SW de langue française âgés entre 6 ans et 13 ans 7 mois, appariés à deux groupes typiques et 2. 13 enfants SW de langue anglaise âgés entre 6 ans et 13 ans 11 mois, appariés à deux groupes typiques. Notre analyse porte sur un paramètre acoustique de la prosodie des enfants avec SW : la Variation de la Fréquence Fondamentale. Les résultats sont discutés sur les points suivants : 1. les différences et similitudes entre les profils prosodiques des enfants avec SW et des enfants typiques de même âge chronologique ou développemental, en langue anglaise et en langue française, 2. les différences entre les enfants avec SWde langue maternelle anglaise et les enfants avec SWde langue maternelle française et 3. le développement prosodique observé chez les enfants avec SW. (For English abstract see "Additional Information")

L'environnement auditif au travail

À haute intensité, les deux principales sources d'inconfort physique au travail sont la chaleur et le bruit (Pellerin & Candas, 2003). Même à des intensités modérées et faibles, le bruit affecte les performances cognitives, y compris dans les tâches de bureau courantes, mais il le fait de plusieurs manières différentes selon la nature du bruit (par exemple, discours vs. non-discours, intensité sonore, variabilité et prévisibilité etc.) et le type de tâche dans laquelle l'individu ou le groupe est engagé. Il est un peu surprenant, donc, que les individus expriment souvent une préférence pour travailler dans des conditions de bruit modérées (Schlittmeier & Hellbrück, 2009). Les multiples formes de perturbation auditive nuisant aux performances cognitives sont examinées et comparées avec leurs avantages potentiels dans le cadre du travail, résultant du traitement du bruit de fond en termes de sens du lieu, d'apprentissage fortuit des régularités dans le monde auditif, et de commutation intelligente de l'attention.

Vegetation history, human impact and climate change during prehistory: an island perspective of the isles of Tiree, Coll and north-west Mull

Results of extensive site reconnaissance on the Isles of Tiree, Coll and north-west Mull, Inner Hebrides are presented. Pollen-stratigraphic records were compiled from a profile from Glen Aros, north-west Mull and from two profiles on Coll located at Loch an t-Sagairt and Caolas an Eilean. Quantification of microscopic charcoal provided records that were used to facilitate a preliminary evaluation of the causal driving mechanisms of vegetation change. Bayesian modelling of radiocarbon dates was used to construct preliminary chronological frameworks for these records. Basal sedimentary deposits at Glen Aros contain pollen records that correspond with vegetation succession typical of the early Holocene dating to c. 11,370 cal BP. Woodland development is a key feature of the pollen records dating to the early Holocene, while records from Loch an t-Sagairt show that blanket mire communities were widespread in north-west Coll by c. 9800 cal BP. The Corylus-rise is dated to c. 10,710 cal BP at Glen Aros and c. 9905 cal BP at Loch an t-Sagairt, with records indicating extensive cover of hazel woodland with birch. All of the major arboreal taxa were recorded, though Quercus and Ulmus were nowhere widespread. Analysis of wood charcoal remains from a Mesolithic site at Fiskary Bay, Coll indicate that Salix and Populus are likely to be under-represented in the pollen records. Reconstructed isopoll maps appear to underplay the importance of alder in western Scotland during the mid-Holocene. Alder-rise expansions in microscopic charcoal dating to c. 7300 cal BP at Glen Aros and c. 6510 to 5830 cal BP on Coll provide records of significance to the issue of human-induced burning related to the expansion of alder in Britain. Increasing frequencies in microscopic charcoal are correlated with mid-Holocene records of increasing aridity in western Scotland after c. 7490 cal BP at Glen Aros, 6760 cal BP at Loch an t-Sagairt and 6590 cal BP at Caolas an Eilean, while several phases of increasing bog surface wetness were detected in the Loch an t-Sagairt archive during the Holocene. At least five phases of small-scale woodland disturbance during the Mesolithic period were identified in the Glen Aros profile dating to c. 11,650 cal BP, 9300 cal BP, 7840 cal BP, 7040 cal BP and 6100 cal BP. The timing of the third phase is coincident with evidence of Mesolithic settlement at Creit Dhu, north-west Mull. Three phases of small-scale woodland disturbance were detected at Loch an t-Sagairt dating to c. 9270 cal BP, 8770 cal BP and 8270 cal BP, all of which overlap chronologically with evidence of Mesolithic activity at Fiskary Bay, Coll. A number of these episodes are aligned chronologically with phases of Holocene climate variability such as the 8.2 K event.