Search results for "upe"
showing 10 items of 7447 documents
Raman scattering study of the anharmonic effects in CeO2−ynanocrystals
2007
We have studied the temperature dependence of the F2g Raman mode phonon frequency and broadening in CeO2−y nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for…
Vibrational properties of ZnTe at high pressures
2002
Raman spectra of ZnTe were measured under hydrostatic pressures up to 15 GPa at T = 300 K. Results for the frequencies of first- and second-order Raman features of the zincblende phase (0-9.5 GPa) are used to set up a rigid-ion model of the phonon dispersion relations under pressure. Calculated phonon densities of states, mode Gruneisen parameters and the thermal expansion coefficient as a function of pressure are discussed. The effect of pressure on the widths and intensities of Raman spectral features is considered. Raman spectra of high-pressure phases of ZnTe are reported. These spectra indicate the possible existence of a new phase near 13 GPa, intermediate between the cinnabar and ort…
First-principles phonon calculations of Fe4+impurity in SrTiO3
2012
The results of hybrid density functional theory calculations on phonons in Sr(Fe(x)Ti(1-x))O(3) solid solution within the formalism of a linear combination of atomic orbitals are presented. The phonon density of states (DOS) calculated for 6.25% Fe(4+) impurities is reported and defect-induced phonon modes are identified. Based on our calculations and group-theoretical analysis, we suggest for the first time an interpretation of experimentally observed Raman- and IR-active modes.
β-process of supercooled o-terphenyl: a comparison of dielectrical and NMR data guided by mode-coupling theory
1990
Abstract According to predictions of mode-coupling theory of the liquid-glass transition, a Cole-Cole dynamical susceptibility is applied to the β-relaxation of supercooled o -terphenyl as studied by 2 H NMR spin-lattice relaxation and by dielectrical relaxation. A temperature-dependent amplitude (1- f ) is assumed for the β-process which yields a description of the NMR data consistent with the dielectrical data. The plateau value f separating the α- and β-processes in the two-step correlation function reveals a similar temperature dependence as compared to the Debye-Waller factor.
Hybrid Materials Based on Polyoxometalates with Solid State Properties
2003
Molecular materials with cooperative physical properties constitute one of the most active focus of interest in contemporary materials science. An attractive chemical feature of these materials derives from the possibility of building them from molecular bricks using the advantages provided by molecular chemistry and the knowledge achieved over the last 20 years in the so-called molecular engineering. From the point of view of the physical properties, it is well known that molecular materials can exhibit the properties typically associated with the inorganic network solids, as for example metallic conductivity and superconductivity [1], ferromagnetism [2] and non-linear optics [3].
An investigation on the relationship between the occurrence of CMV DNAemia and the development of invasive aspergillosis in the allogeneic stem cell …
2013
Cytomegalovirus (CMV) infection might increase the risk of fungal superinfection in allogeneic stem cell transplant patients. The potential association between the occurrence of CMV DNAemia and the development of invasive aspergillosis in this clinical setting was investigated. The current retrospective observational study included 167 patients undergoing T cell-replete allogeneic stem cell transplantation. Virological monitoring of active CMV infection was performed by the pp65 antigenemia assay and/or by a plasma real-time PCR assay. A total of 109 out of 167 patients developed CMV DNAemia. Twenty-three patients had proven (n = 4) or probable (n = 19) invasive aspergillosis. The occurrenc…
Le rôle des dames dans les maisons fortes de Bourgogne, du XIIIe au XVIe siècle
2004
International audience
Exact Mechanical Hierarchy of Non-Linear Fractional-Order Hereditariness
2020
Non-local time evolution of material stress/strain is often referred to as material hereditariness. In this paper, the widely used non-linear approach to single integral time non-local mechanics named quasi-linear approach is proposed in the context of fractional differential calculus. The non-linear model of the springpot is defined in terms of a single integral with separable kernel endowed with a non-linear transform of the state variable that allows for the use of Boltzmann superposition. The model represents a self-similar hierarchy that allows for a time-invariance as the result of the application of the conservation laws at any resolution scale. It is shown that the non-linear spring…
Potential for cascading impacts of environmental change and policy on indigenous culture.
2022
AbstractGlobal environmental and societal changes threaten the cultures of indigenous peoples and local communities (IPLC). Despite the importance of IPLC worldviews and knowledge to sustaining human well-being and biodiversity, risks to these cultural resources are commonly neglected in environmental governance, in part because impacts can be indirect and therefore difficult to evaluate. Here, we investigate the connectivity of values associated with the relationship Ngātiwai (a New Zealand Māori tribe) have with their environment. We show that mapping the architecture of values-environment relationships enables assessment of how deep into culture the impacts of environmental change or pol…
Towards human cell simulation
2019
The faithful reproduction and accurate prediction of the phe-notypes and emergent behaviors of complex cellular systems are among the most challenging goals in Systems Biology. Although mathematical models that describe the interactions among all biochemical processes in a cell are theoretically feasible, their simulation is generally hard because of a variety of reasons. For instance, many quantitative data (e.g., kinetic rates) are usually not available, a problem that hinders the execution of simulation algorithms as long as some parameter estimation methods are used. Though, even with a candidate parameterization, the simulation of mechanistic models could be challenging due to the extr…