Applications of the cavity ring-down technique to a large area rf-plasma reactor

Dans une Inde presque encore aux trois quarts rurale, culture des villes et culture des champs peuvent sembler antagonistes: pourtant, le regard contempteur des citadins, l'agressivité en retour d'un "villagisme" dont les idéaux gandhiens ont été largement pervertis et qui s'appuie sur la dénonciation d'un contestable "parti-pris urbain", aussi bien que l'attachement des ruraux à leur village, ne doivent pas faire oublier la complémentarité des deux économies urbaine et rurale: une réalité économique dont rendent compte même les manuels scolaires du primaire. En fait, les paysans qui migrent en ville parviennent à passer d'une culture à l'autre sans trop de difficultés : sans doute parce que la ville ne représente guère pour eux un milieu beaucoup plus étranger que ne l'est un village différent du leur, ou une caste autre. (Résumé d'auteur

Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution

The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201

Retention and diffusion of radioactive and toxic species on cementitious systems: Main outcome of the CEBAMA project

Cement-based materials are key components in radioactive waste repository barrier systems. To improve the available knowledge base, the European CEBAMA (Cement-based materials) project aimed to provide insight on general processes and phenomena that can be easily transferred to different applications. A bottom up approach was used to study radionuclide retention by cementitious materials, encompassing both individual cement mineral phases and hardened cement pastes. Solubility experiments were conducted with Be, Mo and Se under high pH conditions to provide realistic solubility limits and radionuclide speciation schemes as a prerequisite for meaningful adsorption studies. A number of retention mechanisms were addressed including adsorption, solid solution formation and precipitation of radionuclides within new solid phases formed during cement hydration and evolution. Sorption/desorption experiments were carried out on several anionic radionuclides and/or toxic elements which have received less attention to date, namely: Be, Mo, Tc, I, Se, Cl, Ra and 14C. Solid solution formation between radionuclides in a range of oxidation states (Se, I and Mo) with the main aqueous components (OH−, SO4 −2, Cl−) of cementitious systems on AFm phases were also investigated

Genome-Wide Association Study Identifies Risk Loci for Cluster Headache

OBJECTIVE: To identify susceptibility loci for cluster headache and obtain insights into relevant disease pathways. METHODS: We carried out a genome-wide association study, where 852 UK and 591 Swedish cluster headache cases were compared with 5,614 and 1,134 controls, respectively. Following quality control and imputation, single variant association testing was conducted using a logistic mixed model, for each cohort. The two cohorts were subsequently combined in a merged analysis. Downstream analyses, such as gene-set enrichment, functional variant annotation, prediction and pathway analyses, were performed. RESULTS: Initial independent analysis identified two replicable cluster headache susceptibility loci on chromosome 2. A merged analysis identified an additional locus on chromosome 1 and confirmed a locus significant in the UK analysis on chromosome 6, which overlaps with a previously known migraine locus. The lead single nucleotide polymorphisms were rs113658130 (p = 1.92 x 10-17 , OR [95%CI] = 1.51 [1.37-1.66]) and rs4519530 (p = 6.98 x 10-17 , OR = 1.47 [1.34-1.61]) on chromosome 2, rs12121134 on chromosome 1 (p = 1.66 x 10-8 , OR = 1.36 [1.22-1.52]) and rs11153082 (p = 1.85 x 10-8 , OR = 1.30 [1.19-1.42]) on chromosome 6. Downstream analyses implicated immunological processes in the pathogenesis of cluster headache. INTERPRETATION: We identified and replicated several genome-wide-significant associations supporting a genetic predisposition in cluster headache in a genome-wide association study involving 1,443 cases. Replication in larger independent cohorts combined with comprehensive phenotyping, in relation to e.g. treatment response and cluster headache subtypes, could provide unprecedented insights into genotype-phenotype correlations and the pathophysiological pathways underlying cluster headache

Bioactivity, biocompatibility and antimicrobial properties of a chitosan-mineral composite for periodontal tissue regeneration

A composite membrane of the polymer, chitosan, and the silver-exchanged mineral phase, tobermorite, was prepared by solvent casting and characterised by scanning electron microscopy and Fourier transform infrared spectroscopy. The in vitro bioactivity, cytocompatibility and antimicrobial activity of the composite were evaluated with respect to its potential application as a guided tissue regeneration (GTR) membrane. The in vitro bioactivity was verified by the formation of hydroxyapatite on the surface of the membrane in simulated body fluid and its cytocompatibility was established using MG63 human osteosarcoma cells. The presence of silver ions conferred significant antimicrobial activity against S. aureus, P. aeruginosa and E. coli. The findings of this investigation have indicated that the chitosansilver-tobermorite composite is a prospective candidate for GTR applications

Densification of the interlayer spacing governs the nanomechanical properties of calcium-silicate-hydrate

Calciuam-silicate-hydrate (C-S-H) is the principal binding phase in modern concrete. Molecular simulations imply that its nanoscale stiffness is 'defect-driven', i.e., dominated by crystallographic defects such as bridging site vacancies in its silicate chains. However, experimental validation of this result is difficult due to the hierarchically porous nature of C-S-H down to nanometers. Here, we integrate high pressure X-ray diffraction and atomistic simulations to correlate the anisotropic deformation of nanocrystalline C-S-H to its atomic-scale structure, which is changed by varying the Ca-to-Si molar ratio. Contrary to the 'defect-driven' hypothesis, we clearly observe stiffening of C-S-H with increasing Ca/Si in the range 0.8 ≤ Ca/Si ≤ 1.3, despite increasing numbers of vacancies in its silicate chains. The deformation of these chains along the b-axis occurs mainly through tilting of the Si-O-Si dihedral angle rather than shortening of the Si-O bond, and consequently there is no correlation between the incompressibilities of the a- and b-axes and the Ca/Si. On the contrary, the intrinsic stiffness of C-S-H solid is inversely correlated with the thickness of its interlayer space. This work provides direct experimental evidence to conduct more realistic modelling of C-S-H-based cementitious material