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Context. The determination of the gaseous water abundances in different intestellar environments is crucial for understanding the oxygen chemistry and its role in the molecular cloud evolution.

Aims.We propose a new description of astronomical dust emission in the spectral region from the far-infrared to millimeter wavelengths.

We present a compilation of PRONAOS-based results concerning the temperature dependence of the dust submillimeter spectral index, including data from Galactic cirrus, star-forming regions, dust associated to a young stellar object, and a spiral galaxy. We observe large variations of the spectral index (from 0.8 to 2.4) in a wide range of temperatures (11 to 80 K). These spectral index variations follow a hyperbolic-shaped function of the temperature, high spectral indices (1.6–2.4) being observed in cold regions (11–20 K) while low indices (0.8–1.6) are observed in warm regions (35–80 K). Three distinct effects may play a role in this temperature dependence: one is that the grain sizes change in dense environments, another is that the chemical composition of the grains is not the same in different environments, a third one is that there is an intrinsic dependence of the dust spectral index on the temperature due to quantum processes. This last effect is backed up by laboratory measurements and could be the dominant one.

Using the Odin satellite, we have mapped the submillimeter emission from the $1_{10}{-}1_{01}$transition of ortho-water in the W3 star-forming region. A $5\arcmin\times 5\arcmin$map of the W3 IRS4 and W3 IRS5 region reveals strong water lines at half the positions in the map. The relative strength of the Odin lines compared to previous observations by SWAS suggests that we are seeing water emission from an extended region. Across much of the map the lines are double-peaked, with an absorption feature at –39 km?s-1; however, some positions in the map show a single strong line at –43 km?s-1. We interpret the double-peaked lines as arising from optically thick, self-absorbed water emission near the W3 IRS5, while the narrower blue-shifted lines originate in emission near W3 IRS4. In this model, the unusual appearance of the spectral lines across the map results from a coincidental agreement in velocity between the emission near W3 IRS4 and the blue peak of the more complex lines near W3 IRS5. The strength of the water lines near W3 IRS4 suggests we may be seeing water emission enhanced in a photon-dominated region.

We map a 50$' \times 30'$area in and around the M 17 molecular complex with the French submillimeter balloon-borne telescope PRONAOS, in order to better understand the thermal emission of cosmic dust and the structure of the interstellar medium. The PRONAOS-SPM instrument has an angular resolution of about 3', corresponding to a size of 2 pc at the distance of this complex, and a high sensitivity up to 0.8 MJy/sr. The observations are made in four wide submillimeter bands corresponding to effective wavelengths of 200 ${\mu}{\rm m}$, 260 ${\mu}{\rm m}$, 360 ${\mu}{\rm m}$and 580 ${\mu}{\rm m}$. Using an improved map-making method for PRONAOS data, we map the M 17 complex and faint condensations near the dense warm core. We derive maps of both the dust temperature and the spectral index, which vary over a wide range, from about 10 K to 100 K for the temperature and from about 1 to 2.5 for the spectral index. We show that these parameters are anticorrelated, the cold areas (10–20 K) having a spectral index around 2, whereas the warm areas have a spectral index between 1 and 1.5. We discuss possible causes of this effect, and we propose an explanation involving intrinsic variations of the grain properties. Indeed, to match the observed spectra with two dust components having a spectral index equal to 2 leads to very large and unlikely amounts of cold dust. We also give estimates of the column densities and masses of the studied clumps. Three cold clumps (14–17 K) could be gravitationally unstable.

The progress in micro electronic and the avaibility to develop custom electronic chips allow to realize a new kind of 2D detectors, the pixel detectors. They can be considered as an array of photon counters with a size of some tenth of millimeters. They allow to obtain images with a higher dynamical range allowing to study complex diffraction systems including weak diffusion.

Anomalous Xray scattering experiments on glassy GexSe1−xsemiconductors have been carried out at energies close to the Ge and Se K edges in a wide concentration range from x  0.15 to 0.333 across the rigidity percolation threshold composition of x  0.20. The total structure factors, SQ, show considerable variation with xin both the position and intensity of the prepeak at about 10 nm−1, while in the remaining Qrange, it stays almost unchanged. The differential structure factors, ΔiSQ, comprise characteristic features, depending on the absorption edges. Comparing them suggests that the prepeak indicating the existence of intermediaterange order IRO purely originates from the GeGe partial correlations. In contrast to the SQ, the prepeak in ΔGeSQ changes very slightly with varying xdown to x ∼ 0.20, suggesting that the prepeak height in SGeGeQ largely enhances with decrease in the Ge concentration, in particular at the the rigidity percolation threshold composition. However, a sudden decrease and a shift of the Qposition are seen at the Ge concentration less than the stiffness transition composition, which may relate to the sudden decrease of the GeSe4–GeSe4connections in the floppy region of this glassy system.

The DEAD box RNA helicase (RH) proteins are homologs involved in diverse cellular functions in all of the organisms from prokaryotes to eukaryotes. Nevertheless, there is a lack of conservation in the splicing pattern in the 53 Arabidopsis thaliana (AtRHs), the 32 Caenorhabditis elegans (CeRHs) and the 29 Drosophila melanogaster (DmRHs) genes. Of the 153 different observed intron positions, 4 are conserved between AtRHs, CeRHs, and DmRHs, and one position is also found in RHs from yeast and human. Of the 27 different AtRH structures with introns, 20 have at least one predicted ancient intron in the regions coding for the catalytic domain. In all of the organisms examined, we found at least one gene with most of its intron predicted to be ancient. In A. thaliana, the large diversity in RH structures suggests that duplications of the ancestral RH were followed by a high number of intron deletions and additions. The very high bias toward phase 0 introns is in favor of intron addition, preferentially in phase 0. Results from this comparative study of the same gene family in a plant and in two animals are discussed in terms of the general mechanisms of gene family evolution.

Abstract:: Monolayers of short chiral alcohols at the water surface provide a simple model for chiral interactions between molecules. This paper is focused on alcohols with two particular chain lengths, 2-tridecanol (2C13) and 2-tetradecanol (2C14). Thermodynamic and structural parameters were measured, varying the ratio of left and right enantiomers within monolayers. The evolution of melting temperatures and entropies is not consistent with the formation of a racemate. Grazing X-ray diffraction, revealing the molecular stacking, shows clearly that there is no chiral separation. In these two compounds molecules spontaneously self-assemble at the water surface as a solid solution. The chiral polar head-group is partially screened by the chain thermal disorder of the rotator phase. 2-tridecanol exhibits a hexagonal rotator phase stable in time and independent of temperature. Experiments performed close to the melting point show pre-transitional effects for mixtures different from 50/50. This broadening of the peak can be related to defects in 2D crystals, phenomena already observed for the melting of some 3D systems.

In CdTe/CdZnTe strained quantum wells (QWs) the exciton inhomogeneous linewidth decreases with decreasing QW width. We interpret this unusual behaviour as a manifestation of the fact that the two QW heterointerfaces are increasingly correlated for narrow QWs, resulting in reduced well width fluctuation along the QW plane. Small incidence angle X-ray diffraction experiments confirm this interpretation.

We present an extended X-ray reflectivity study of a Sm-based epitaxial layer buried into CdTe(001) in order to investigate its structure. The measured reflectivity is modelled over a wide range of momentum transfer and the adjustment of the calculated intensity gives quantitative information about the electron density and interplanar distance profiles along the surface normal. Complementary experiments of photoemission spectroscopy allow the interpretation of the in-plane electron density in terms of chemical composition. High resolution electron microscopy shows that the very strong chemical gradients deduced from the model result from an original topology of the layer.

Context. Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detailto identify different moments in a cloud's lifetime.Aims. We study a fragment of the long filament L1506in the Taurus region, which we name L1506C, a core with interesting dust properties observed by the PRONAOS balloon-borne telescope.Methods. To trace the mass content of L1506C and its kinematics, we mapped the dust emission, and the line emission of two key species, C18O and N2H+. We also observed 13CO and C17O. We model the species emission using 1D Monte Carlo models.Results. This cloud is reminiscent of L1498 but also exhibits peculiar features: i) a large envelope emitting solely in 13CO that contains a much smaller core with strong C18O depletion at its centre despite a low maximum opacity (AV~ 20 mag); ii) extremely narrow C18O lines indicating a low, non-measurable turbulence; iii) contraction traced by C18O itself (plus rotation); iv) unexpectedly, the kinematical signature of the external envelope is opposite to that of the core, the 13CO and C18O velocity gradients having opposite directions and the C18O line profile being blue peaked in contrast to the 13CO one which is red peaked. The core is large (r= 3 $\times$104AU) and not very dense (n(H2) ≤5 $\times$104cm-3, possibly less). This core is therefore not yet prestellar.Conclusions. All these properties imply that the core is kinematically detached from its envelope and in the process of forming a prestellar core. This is the first time that the dynamical formation of a prestellar core has been witnessed. The extremely low turbulence could explain the strong depletion of this core despite its relatively low density and opacity in contrast to undepleted cores such as L1521E, which exhibits a turbulence at least 4 times as high.

Context. Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detailto identify different moments in a cloud's lifetime.

We review the submillimetric PRONAOS observations in the direction of the IC 1318a nebular located at the edge of an ionized region in the Cygnus X complex. The extended emission measured in the PRONAOS four broad photometric bands extending from 200 up to 1100 μm enables a full characterization of the interstellar dust big grains component radiating at thermal equilibrium, leading to a temperature and column density mapping.