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showing 10 items of 6843 documents
Numerical Study of the semiclassical limit of the Davey-Stewartson II equations
2014
We present the first detailed numerical study of the semiclassical limit of the Davey–Stewartson II equations both for the focusing and the defocusing variant. We concentrate on rapidly decreasing initial data with a single hump. The formal limit of these equations for vanishing semiclassical parameter , the semiclassical equations, is numerically integrated up to the formation of a shock. The use of parallelized algorithms allows one to determine the critical time tc and the critical solution for these 2 + 1-dimensional shocks. It is shown that the solutions generically break in isolated points similarly to the case of the 1 + 1-dimensional cubic nonlinear Schrodinger equation, i.e., cubic…
Effects of high-pressure on the structural, vibrational, and electronic properties of monazite-type PbCrO4
2012
We have performed an experimental study of the crystal structure, lattice dynamics, and optical properties of PbCrO 4 (the mineral crocoite) at ambient and high pressures. In particular, the crystal structure, Raman-active phonons, and electronic band gap have been accurately determined. X-ray-diffraction, Raman, and optical absorption experiments have allowed us also to completely characterize two pressure-induced structural phase transitions. The first transition is from a monoclinic structure to another monoclinic structure. It maintains the symmetry of the crystal but has important consequences in the physical properties; among others, a band-gap collapse is induced. The second one invo…
État des lieux et évaluation de la surveillance des Staphylococcus aureus résistants à la méticilline (SARM) : PMSI versus surveillance Raisin
2013
Abstract Background The surveillance of methicillin-resistant Staphylococcus aureus (MRSA) is a national priority. The rate of MRSA infections is one of six indicators tracked by the Department of Health. Since 2002, the French institute for public health surveillance (InVS) has monitored MRSA infections to estimate incidence density. Today, the use of the French administrative database (PMSI) could facilitate this surveillance. The aim of this study was to compare MRSA incidence density computed at a national level using PMSI databases with the results from the InVS taken as the reference. Methods PMSI databases for the years 2006 to 2009 were used. The reference results were those publish…
The interaction of language and thought in children's language acquisition: a crosslinguistic study
1997
The purpose of this research was to investigate the potential interaction of conceptual representations and linguistic systems in the process of language acquisition. Language–thought interactions were studied in 80 American, 48 Finnish and 48 Polish preschool children. The research focused on the conceptual and linguistic development of space and time. The spatial and temporal conceptual tasks were designed to measure the transition from experiential to inferential knowledge of space/time representations. In the linguistic domain, comprehension and production tests were used to evaluate the children's capacity to understand mono- and bi-referential location in space and time, where mono-re…
High prevalence of oral potentially malignant disorders and risk factors in a semi-urban brazilian city: a population-based cross-sectional study
2021
Background Oral Potentially Malignant Disorders (OPMDs) are defined as lesions with a greater likelihood of progressing to cancer. Population-based studies that evaluate the prevalence of OPMDs are scarce in Brazil. The aim of the present study was to determine the prevalence of OPMDs and associated risk factors in a semi-urban Brazilian population. Material and Methods This is a cross-sectional study, whose universe included individuals aged 40 years or older residing in a medium-sized city of northeastern Brazil. Data collection was divided into two steps: interview and oral examination. The outcome variable was the presence of OPMDs. The predictor variables were sociodemographic characte…
<title>Manifestation of structural features in Raman spectra of LiNbO<formula><inf><roman>3</roman></inf></for…
2008
Raman studies of ostensibly pure congruent, close to stoichiometric and stoichiometric lithium niobate single crystals and single crystals of lithium niobate containing admixture of Gd3+, Y+, and Mg2+ are reported. The authors have revealed weak Raman bands anomalously narrowing at changes of crystal composition disordering the cation sublattice and discuss the results with regard to evidence of anomalous ordering of structural units of the cation sublattice occurring at disordering of the cation sublattice as a whole.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Crystal Field Excitations in CeAgl−xInx Compounds
1982
The substitution of the monovalent Ag for the trivalent In in LaAgl−xInx and CeAgl−xInx offers the possibility of influencing the conduction electron system in these compounds. The strong dependence of the spin susceptibility of La-systems on the In-concentration1 was interpreted by band calculations which suggest that the Fermi level is pushed into a region of a high 5d-eg-band density of states2. Furthermore, CeAgl−xInx is one of the rare 4f systems where a structural phase transition (from cubic to tetragonal) occurs prior to magnetic ordering. The ferromagnetic Curie temperature TC is roughly independent of x whereas the structural transition temperature Ts rises from 15 K for CeAg to a…
Average Structure vs. Real Structure: Molecular Dynamics Studies of Silica
2003
The microscopic structure of a crystal and thermal fluctuations of the atoms constituting the crystal are intimately connected with the macroscopic elastic properties including mechanical stability. In some cases, however, the picture is more complex than that which is drawn in text books on solid state physics. (i) The instantaneous microscopic structure can deviate in a non-Gaussian way from the average structure even when domain disorder and/or crystal defects are absent. Quasi harmonic approximations may then turn out to be meaningless. (ii) The crystal is subject to external pressures that are sufficiently large in order to render the definition of elastic constants non unique. These t…
Metallophilic interactions in polymeric group 11 thiols
2016
Three polymeric group 11 transition metal polymers featuring metallophilic interactions were obtained directly via self-assembly of metal ions and 4-pyridinethiol ligands. In the cationic [Cu2(S-pyH)4]n2+ with [ZnCl4]n2− counterion (1) and in the neutral [Ag(S-py) (S-pyH)]n (2) 4-pyridinethiol (S-pyH) and its deprotonated form (S-py) are coordinated through the sulfur atom. Both ligands are acting as bridging ligands linking the metal centers together. In the solid state, the gold(I) polymer [Au(S-pyH)2]Cl (3) consists of the repeating cationic [Au(S-pyH)2]+ units held together by aurophilic interactions. Compound 1 is a zig-zag chain, whereas the metal chains in the structures of 2 and 3 a…
(5R)-5-[(1R)-2,2-Dichloro-1-methylcyclopropyl]-2-methylcyclohex-2-en-1-one
2011
The title compound, C(11)H(14)Cl(2)O, was synthesized by the reaction of a dichloro-methane solution of (R)-carvone and potassium tert-butano-late in the presence of a catalytic amount of benzyl-triethyl-ammonium chloride in chloro-form. The cyclo-hexene ring adopts a half-boat conformation. The cyclo-propyl ring is unsymmetrical, the shortest C-C bond being distal to the alkyl-substituted C atom. The crystal packing is stabilized only by van der Waals inter-actions.