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A powerful way to measure the mass distribution in elliptical galaxies is to study systems with a central disk of ionized gas. Such disks occur in a small fraction (perhaps 10–20%) of nearby ellipticals, and the gas is generally believed to have been accreted from outside the galaxy as the result of a merger or interaction. Once the gas disk has settled into a principal plane of the stellar figure, measurements of its orientation and kinematics set strong constraints on the shape and orientation of the galaxy and allow us to derive M/L as a function of radius. Indeed, the observations discussed here were made at the ESO/MPI 2.2-m telescope as part of our ESO KEY-PROGRAMME, in which we aim to determine the mass-to-light ratios of nearby elliptical galaxies and examine the evidence for dark matter.
The Dark Energy Survey is undertaking an observational programme imaging 1/4 of the southern hemisphere sky with unprecedented photometric accuracy. In the process of observing millions of faint stars and galaxies to constrain the parameters of the dark energy equation of state, the Dark Energy Survey will obtain pre-discovery images of the regions surrounding an estimated 100 gamma-ray bursts over 5 yr. Once gamma-ray bursts are detected by, e.g., the Swift satellite, the DES data will be extremely useful for follow-up observations by the transient astronomy community. We describe a recently-commissioned suite of software that listens continuously for automated notices of gamma-ray burst activity, collates information from archival DES data, and disseminates relevant data products back to the community in near-real-time. Of particular importance are the opportunities that non-public DES data provide for relative photometry of the optical counterparts of gamma-ray bursts, as well as for identifying key characteristics (e.g., photometric redshifts) of potential gamma-ray burst host galaxies. We provide the functional details of the DESAlert software, and its data products, and we show sample results from the application of DESAlert to numerous previously detected gamma-ray bursts, including the possible identification of several heretofore unknown gamma-ray burst hosts.
We present a combined theoretical and experimental study of the adsorption of two pairs
of organic isomers, (i) acetic acid AA (CH3COOH) and methyl
formate MF (HCOOCH3), and (ii) ethanol EtOH
(CH3CH2OH) and dimethyl ether DME (CH3OCH3),
onto crystalline water ice surfaces at low temperatures. Both approaches show that, for
each pair, the most stable isomer from a thermodynamical point of view,
i.e. AA and EtOH, is
also the one which is the more tightly bound to the water ice surface compared to the less
stable isomers (MF and DME). This finding, which can be explained by the ability of AA or
EtOH to efficiently interact with the ice surface via hydrogen bondings, may have
important consequences in an astrophysical context, since it could explain why the most
stable isomer is not the most abundant observed in the interstellar gas phase.
The World Heritage Site of Wanar in Senegal features 21 stone circles, remarkable not least because they were erected in the twelfth and thirteenth century AD, when Islam ruled the Indian Ocean and Europe was in its Middle Ages. The state of preservation has benefited the exemplary investigation currently carried out by a French-Senegalese team, which we are pleased to report here. The site began as a burial ground to which monumental stones were added, perhaps echoing the form of original funerary houses. Found in a neighbouring field were scoops left from the cutting out of the cylindrical monoliths from surface rock. While the origins of Wanar lie in a period of state formation, the monuments are shown to have had a long ritual use. The investigation not only provides a new context for one of the most important sites in West Africa but the precise determination of the sequence and techniques used at Wanar offers key pointers for the understanding of megalithic structures everywhere.
The objective was to study the multidimensional nature of the relationship between adult obesity (OB) and socio-economic status (SES), using comprehensive indices of SES taken separately or synthesised in an overall index. A nationally representative sample of adults aged 18–79 years was taken from the French second National Individual Survey on Food Consumption (INCA 2) dietary survey (2006–07). Weight and height were measured and OB defined as BMI ≥ 30 kg/m2. SES variables were reported in questionnaires and included occupation, education and characteristics of household wealth. Composite indices of SES (household wealth and overall SES indices) were computed by correspondence analysis, and relationships with OB were investigated with logistic regression analysis. In total, 11·8 (95 % CI 10·1, 13·4) % of French adults were obese, without significant difference by sex. While no significant relationship was observed in men, all SES indicators were inversely correlated to OB in women. Both education and the household wealth index were retained in the stepwise multivariate model, confirming that different socio-economic variables are not necessarily proxies of each other regarding the OB issue. On the other hand, ‘controlling for SES’ while including several measures of SES in multivariate models may lead to collinearity, and thus over-adjustment. A more integrative approach may be to derive a synthetic index by including the SES factors available in a given study. Beyond this methodological perspective, understanding how OB is related to the different dimensions of SES should help to target the more vulnerable groups and increase the effectiveness of prevention.
We characterized two samples consisting of photoresist layers on silicon with square arrays of square holes by spectroscopic ellipsometry (SE) and Mueller matrix polarimetry (MMP). Hole lateral dimensions and depths were determined by fitting either SE data taken in conventional planar geometry or MMP data in general conical diffraction configurations. A method for objective determination of the optimal measurement conditions based on sensitivity and parameter correlations is presented. When applied to MMP, this approach showed that for one of the samples the optimal incidence angle was 45°, much below the widely used 70° value. The robustness of the dimensional characterisation based on MMP is demonstrated by the high stability of the results provided by separated fits of the data taken at different azimuthal angles.
Many astrophysical problems, ranging from structure formation in cosmology to dynamics of elliptical galaxies, refer to slow processes of evolution of essentially collisionless self-gravitating systems. To determine the relevant quasi-equilibrium configuration at time t from given initial conditions, such slow evolution is often approximated in terms of adiabatic evolution. Here we focus on the slow process of evolution induced by dynamical friction of a spherical stellar system (the host galaxy) on a minority component of “satellites” (distributed in a spherical shell), to determine to what extent an adiabatic description might be applied.
When two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between
them. Selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e.
competitive processes to gain control of the intermediate host. The evidence for both phenomena depends largely on the
study of the relative competitive abilities of parasites within their common intermediate host. We studied the effects of
simultaneous infection by a fish acanthocephalan parasite, Pomphorhynchus laevis, and a bird acanthocephalan parasite,
Polymorphus minutus, on the behaviour of their common intermediate host, the amphipod Gammarus pulex. We compared
the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring
a single parasite species and uninfected ones under controlled conditions. Compared to uninfected gammarids that were
photophobic and tended to remain at the bottom of the water column, P. laevis-infected gammarids were attracted to light,
whereas P. minutus-infected individuals showed a modified vertical distribution and were swimming closer to the water
surface. The effects of both P. laevis and P. minutus appeared to be dependent only on their presence, not on their intensity.
Depending on the behavioural trait under study, however, the outcome of the antagonism between P. laevis and P. minutus
differed. The vertical distribution of gammarids harbouring both parasites was half-way between those of P. laevis- and
P. minutus-infected individuals, whereas P. laevis was able to induce altered reaction to light even in the presence
of P. minutus. We discuss our results in relation to the occurrence of active avoidance or hijacking between conflicting
manipulative parasites and provide some recommendations for future research.
Neodymium- or erbium-doped silica films are deposited on single crystal silicon substrates using a sol-gel process and a spin-coating technique. These glasses are doped with neodymium or erbium in various Nd/Si or Er/Si atomic ratios up to 8% using neodymium nitrate or erbium nitrate as precursor. A preparation method of such films is described. Film rare earth concentration measured by Rutherford Backscattering Spectroscopy (RBS) is the same as in the initial liquid solution. Film thickness and refractive index are obtained by variable angle spectroscopic ellipsometry. We have shown that both RBS analysis and spectroscopic ellipsometry are powerful tools to control rare earth doping level and optical properties of the silica films.
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