The importance of OH radical–neutral low temperature tunnelling reactions in interstellar clouds using a new model

Recent laboratory experiments using a pulsed Laval nozzle apparatus have shown that reactions between a neutral molecule and the radical OH can occur efficiently at low temperatures despite activation energy barriers if there is a hydrogen-bonded complex in the entrance channel which allows the system to tunnel efficiently under the barrier. Since OH is a major radical in the interstellar medium, this class of reactions may well be important in the chemistry that occurs in the gas phase of interstellar clouds. Using a new gas-grain chemical network with both gas-phase reactions and reactions on the surfaces of dust particles, we studied the role of OH–neutral reactions in dense interstellar clouds at 10, 50, and 100 K. We determined that at least one of these reactions can be significant, especially at the lowest temperatures studied, where the rate constants are large. It was found in particular that the reaction between CH3OH and OH provides an effective and unambiguous gas-phase route to the production of the gaseous methoxy radical (CH3O), which has been recently detected in cold, dense interstsellar clouds. The role of other reactions in this class is explored

High prevalence of PRPH2 in autosomal dominant retinitis pigmentosa in france and characterization of biochemical and clinical features.

PURPOSE: To assess the prevalence of PRPH2 in autosomal dominant retinitis pigmentosa (adRP), to report 6 novel mutations, to characterize the biochemical features of a recurrent novel mutation, and to study the clinical features of adRP patients. DESIGN: Retrospective clinical and molecular genetic study. METHODS: Clinical investigations included visual field testing, fundus examination, high-resolution spectral-domain optical coherence tomography (OCT), fundus autofluorescence imaging, and electroretinogram (ERG) recording. PRPH2 was screened by Sanger sequencing in a cohort of 310 French families with adRP. Peripherin-2 protein was produced in yeast and analyzed by Western blot. RESULTS: We identified 15 mutations, including 6 novel and 9 previously reported changes in 32 families, accounting for a prevalence of 10.3% in this adRP population. We showed that a new recurrent p.Leu254Gln mutation leads to protein aggregation, suggesting abnormal folding. The clinical severity of the disease in examined patients was moderate with 78% of the eyes having 1-0.5 of visual acuity and 52% of the eyes retaining more than 50% of the visual field. Some patients characteristically showed vitelliform deposits or macular involvement. In some families, pericentral RP or macular dystrophy were found in family members while widespread RP was present in other members of the same families. CONCLUSIONS: The mutations in PRPH2 account for 10.3% of adRP in the French population, which is higher than previously reported (0%-8%) This makes PRPH2 the second most frequent adRP gene after RHO in our series. PRPH2 mutations cause highly variable phenotypes and moderate forms of adRP, including mild cases, which could be underdiagnosed

Small magellanic cloud be stars: color-magnitude relations and mass-loss

We present an analysis of optical lightcurves of Small Magellanic Cloud (SMC) Be-type stars. Observations show that (1) optical excess flux is correlated with near-IR excess flux indicating a similar mechanism and (2) the lightcurves can trace out “loops” in a colour-magnitude diagram. A simple model for the time dependence of bound-free and free-free (bf-ff) emission produced by an outflowing circumstellar disk gives reasonable fits to the observations

the remarkable light and colour variability of Small Magellanic cloud Be stars

Aims. The purpose of this study is to investigate the distributions of the isomeric molecules HCN and HNC and estimate their abundance ratio in the protostellar core Cha-MMS1 located in Chamaeleon i. Methods. The core was mapped in the J = 1−0 rotational lines of HCN, HNC, and HN13C. The column densities of H13CN, HN13C, H15NC and NH3 were estimated towards the centre of the core. Results. The core is well delineated in all three maps. The kinetic temperature in the core, derived from the NH3 (1, 1) and (2, 2) inversion lines, is 12.1 ± 0.1 K. The HN13C/H13CN column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN13C/H15NC column density ratio is ∼7. In case no 15N fractionation occurs in HNC (as suggested by recent modelling results), the HNC/HN13C abundance ratio is in the range 30−40, which indicates a high degree of 13C fractionation in HNC. Assuming no differential 13C fractionation the HCN and HNC abundances are estimated to be ∼7 × 10−10 and ∼2 × 10−9, respectively, the former being nearly two orders of magnitude smaller than that of NH3. Using also previously determined column densities in Cha-MMS1, we can put the most commonly observed nitrogenous molecules in the following order according to their fractional abundances: χ(NH3) > χ(HC3N) > χ(HNC) > χ(HCN) > χ(N2H+). Conclusions. The relationships between molecular abundances suggest that Cha-MMS1 represents an evolved chemical stage, experiencing at present the “late-time” cyanopolyyne peak. The possibility that the relatively high HNC/HCN ratio derived here is only valid for the 13C isotopic substitutes cannot be excluded on the basis of the present and other available data

Small magellanic cloud be stars: color-magnitude relations and mass-loss

We present an analysis of optical lightcurves of Small Magellanic Cloud (SMC) Be-type stars. Observations show that (1) optical excess flux is correlated with near-IR excess flux indicating a similar mechanism and (2) the lightcurves can trace out “loops” in a colour-magnitude diagram. A simple model for the time dependence of bound-free and free-free (bf-ff) emission produced by an outflowing circumstellar disk gives reasonable fits to the observations

ExELS: an exoplanet legacy science proposal for the ESA Euclid mission. II. Hot exoplanets and sub-stellar systems

International audienc

Realising a single labour market for researchers: Report of the ERA Expert Group

It has become increasingly evident that a more concerted strategy is necessary to address the human resources needs of the European Research Area (ERA). Such a strategy should establish realistic goals and develop clear methods for their implementation. The present Report addresses the Policy Options that the Expert Group 'Realising a single labour market for researchers' (EG Researchers) has identified in order to ensure more attractive careers for researchers and to progressively eliminate the obstacles hampering their mobility. We have chosen an architectural image in order to highlight the complementary nature of the components of the tetrahedral structure that we have conceived. For each of the proposed four cornerstones we identify the obstacles and hindrances that, in our view, continue to hamper the development of ERA, and provide some 'case studies' in order to illustrate our concerns. We then provide Policy Options, some of which have already been successfully tested and could therefore be generalised almost immediately, others could be implemented progressively. The recommendations in this report are addressed to all bodies in receipt of public funds for research. This is meant to include the funding agencies who disburse funds and those who receive them, in the public and private sector (universities, research centres and companies). All must take individual and collective responsibility for the implementation of the recommendations; in our opinion they will determine whether Europe does indeed become a single labour market for researchers. We believe that the European Commission can take the lead by implementing the recommendations in the Seventh Framework Programme