Deuterium in the Galactic Centre as a result of recent infall of low-metallicity gas

The Galactic Centre is the most active and heavily processed region of the Milky Way, so it can be used as a stringent test for the abundance of deuterium (a sensitive indicator of conditions in the first 1,000 seconds in the life of the Universe). As deuterium is destroyed in stellar interiors, chemical evolution models 1 predict that its Galactic Centre abundance relative to hydrogen is D/H = 5 x 10(-12), unless there is a continuous source of deuterium from relatively primordial (low-metallicity) gas. Here we report the detection of deuterium (in the molecule DCN) in a molecular cloud only 10 parsecs from the Galactic Centre. Our data, when combined with a model of molecular abundances, indicate that D/H = (1.7 +/- 0.3) x 10(-6), five orders of magnitude larger than the predictions of evolutionary models with no continuous source of deuterium. The most probable explanation is recent infall of relatively unprocessed metal-poor gas into the Galactic Centre (at the rate inferred by Wakker(2)). Our measured D/H is nine times less than the local interstellar value, and the lowest D/H observed in the Galaxy. We conclude that the observed Galactic Centre deuterium is cosmological, with an abundance reduced by stellar processing and mixing, and that there is no significant Galactic source of deuterium.

Dissociative Recombination of Protonated Formic Acid: Implications for Molecular Cloud and Cometary Chemistry

At the heavy ion storage ring CRYRING in Stockholm, Sweden, we have investigated the dissociative recombination of DCOOD2+ at low relative kinetic energies, from ~1 meV to 1 eV. The thermal rate coefficient has been found to follow the expression k(T) = 8.43 × 10-7 (T/300)^-0.78 cm3 s-1 for electron temperatures, T, ranging from ~10 to ~1000 K. The branching fractions of the reaction have been studied at ~2 meV relative kinetic energy. It has been found that ~87% of the reactions involve breaking a bond between heavy atoms. In only 13% of the reactions do the heavy atoms remain in the same product fragment. This puts limits on the gas-phase production of formic acid, observed in both molecular clouds and cometary comae. Using the experimental results in chemical models of the dark cloud, TMC-1, and using the latest release of the UMIST Database for Astrochemistry improves the agreement with observations for the abundance of formic acid. Our results also strengthen the assumption that formic acid is a component of cometary ices.

Effect of growth-promoting 17ß estradiol, 19 nortestosterone and dexamethasone on circulating levels of nine potential biomarker candidates in veal calves

The use of screening methods based on the detection of biological effects of growth promoters is a promising approach to assist residue monitoring. To reveal useful effects on protein metabolism, male and female veal calves at 10 weeks of age were treated thrice with a combination of 25 mg 17ß-estradiol 3-benzoate and 150 mg 19-nortestosterone decanoate with 2 weeks intervals and finally once with 4 mg dexamethasone. Hormone-treated calves showed a significant accelerated growth rate over 6 weeks. Plasma samples of treated and control calves were analysed for immunoreactive inhibin (ir-inhibin), osteocalcin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor-binding protein 2 (IGFBP-2), IGFBP-3, luteinzing hormone (LH), follicle-stimulating hormone (FSH) and prolactin using immunoaffinity assays. Hormone treatment did not affect levels of IGF-1, IGFBP-2, IGFBP-3, LH, FSH and prolactin. The concentration of circulating ir-inhibin decreased, however, significantly (P < 0.05) in bull calves upon administration of the sex steroids, whereas it remained unchanged in the female animals. Dexamethasone treatment decreased significantly (P < 0.05) circulating levels of osteocalcin in both female and male animals. Ir-inhibin and osteocalcin were, therefore, considered as candidates for a protein biomarker-based screening assay for detection of abuse of estrogens, androgens and/or glucocorticoids in cattle fattening, which is being developed in the framework of EU research project BioCop

The effects of a volunteer mentoring programme on reading outcomes among eight- to nine-year-old children: A follow up randomized controlled trial

This article presents the findings of a randomized controlled trial evaluation of the effects of a revised version of the volunteer mentoring programme, Time to Read. Participating children received two 30-minute mentoring sessions per week from volunteer mentors who carried out paired reading activities with the children. The current trial involved 512 children aged eight to nine years from 50 primary schools. The programme was found to be effective in improving decoding skills (d=+.15), reading rate (d=+.22) and reading fluency (d=+.14) and there was some evidence of a positive effect in relation to the children’s aspirations for the future (d=+.11). However, no evidence was found of the programme having an effect on reading comprehension or reading confidence and enjoyment of reading. The article concludes by suggesting that mentoring programmes using non-specialist volunteers can be effective in improving foundational reading skills but would appear to be less effective in terms of improving higher-order skills such as comprehension. The article also suggests that such programmes are likely to be most effective if concentrating on core reading activities rather than attempting to address reading outcomes indirectly through improving children’s confidence or wider enjoyment of reading.

Performance models of storage contention in cloud environments

We propose simple models to predict the performance degradation of disk requests due to storage device contention in consolidated virtualized environments. Model parameters can be deduced from measurements obtained inside Virtual Machines (VMs) from a system where a single VM accesses a remote storage server. The parameterized model can then be used to predict the effect of storage contention when multiple VMs are consolidated on the same server. We first propose a trace-driven approach that evaluates a queueing network with fair share scheduling using simulation. The model parameters consider Virtual Machine Monitor level disk access optimizations and rely on a calibration technique. We further present a measurement-based approach that allows a distinct characterization of read/write performance attributes. In particular, we define simple linear prediction models for I/O request mean response times, throughputs and read/write mixes, as well as a simulation model for predicting response time distributions. We found our models to be effective in predicting such quantities across a range of synthetic and emulated application workloads. 

Molecular abundances in the magellanic clouds III. LIRS 36, a star-forming region in the Small Magellanic Cloud

Detections of CO, CS, SO, C2H, HCO+, HCN, HNC, H2CO, and C3H2 are reported from LIRS 36, a star-forming region in the Small Magellanic Cloud. (CO)-O-18, NO, CH3OH, and most notably CN have not been detected, while the rare isotopes (CO)-C-13 and, tentatively, (CS)-S-34 ar,seen. This is so far the most extensive molecular multiline study of an interstellar medium with a heavy element depletion exceeding a factor of four.

THE EFFECT OF VARYING COSMIC-RAY IONIZATION RATES ON DARK CLOUD CHEMISTRY

We investigate the effects of varying the cosmic ray ionization rate in chemical models of dense interstellar clouds. In the absence of such ionization, a scenario which may be applicable to dark cloud cores, we find that chemi-ionization is able to drive a limited ion-neutral chemistry. Models of clouds in starburst galaxies, which may have enhanced cosmic ray fluxes, are also investigated and enable an upper limit to be derived for the cosmic ray ionization rate in M82. The derived value, which is about 700 times the typical value for Galactic molecular clouds, is in good agreement with that necessary to explain the recent observations of C I in this galaxy.