Search results for "Elastic"
showing 10 items of 2162 documents
Coupled rotational and translational modes in the mixed molecular crystal KBr1?x (CN) x
1980
TheE g andT 2g acoustic phonon modes of the molecular crystals KBr0.96(CN)0.04 and KBr0.86(CN)0.14 have been investigated by inelastic neutron scattering at 6, 90 and 300 K. Clear resonances due to mode-mode coupling to molecular excitations were observed. In complementary ultrasonic experiments the elastic constants were found to pass through minima as a function of temperature. The results were quantitavely explained by a model which assumes simple forms of the molecular excitation spectrum. An alternative interpretation, though being only qualitative, postulates a freezing of the CN molecules into a glass-like phase.
Crystal Fields in Pr-Hydrides
1977
Inelastic neutron scattering was used to determine the crystal field splittings of PrD2 and PrD2.5. For the PrD2 crystal field at the Pr-site is cubic and can be explained by a negative charge of the hydrogen. The splitting observed for PrD2.5 can be described assuming a well defined short range order caused by a mer-configuration of the half filled octahedral hydrogen sites leading to an orthorhombic crystal field. The structure and the paramagnetic susceptibility of the Pr-hydrides are discussed on this basis.
Crystal field splitting of some rare earth intermetallic compounds with Cu3Au structure
1980
Inelastic neutron scattering studies were performed in the paramagnetic phases of several rare earth compounds that crystallize in the cubic Cu3Au structure: ErPb3, ErTl3, ErIn3, HoPb3, HoTl3, HoIn3, PrSn3, PrPb3, PrTl3, PrIn3, CeIn3, La1−c Pr c Tl3, and Pr(In0.5Tl0.5)3. The energies, widths and intensities of the crystal field excitations are determined and discussed in terms of interactions between the rare earth ions. Variations of the crystal field parameters are observed across the series.
Crystal Electric Fields in Rare-Earth Al2 Compounds
1977
Neutron time-of-flight measurements have been performed on REAl2 compounds (RE = Pr, Ho, Er, Tm) in the paramagnetic region. Resolved crystal field transitions are observed in ErAl2 and TmAl2. We deduce crystal field parameters (x = 0.16, W = -0.030 meV) and (x = -0.28, W = +0.040 meV) for ErAl2 and TmAl2 respectively.
Structure, phase transitions and molecular motions in ferroelastic (C4H8NH2)SbCl6·(C4H8NH2)Cl
2002
The crystal structure at 293 K of the new pyrrolidinium chloroantimonate (V) analogue, (C4H8NH2)SbCl6(C4H8NH2)Cl, has been determined by x-ray diffraction as monoclinic, space group P21/c, Z = 8. The crystal is built up of isolated SbCl6- anions, two types of inequivalent pyrrolidinium cation and isolated Cl- ions. It undergoes five solid-solid phase transitions: at 351/374 K of first-order type (cooling/heating, respectively), at 356 and 152 K second order and at 135/141 and 105/134 K first order, detected by differential scanning calorimetry, dilatometric and dielectric measurements. The ferroelastic domain structure appears between 152 and 135 K. The proton nuclear magnetic resonance sec…
Solid state NMR studies of gels derived from low molecular mass gelators
2016
The emergence of NMR crystallography provides a unique opportunity to study solids, gels and xerogels, thereby providing ample information to elucidate molecular packing in the native gel. This review details the importance as well as the application of solid state NMR spectroscopy combined with other analytical tools to study gels derived from low molecular mass organo- and hydrogelators.
Determination of Zircaloy -4 Radiocristallographic Elastic Constants from Room Temperature to 300°C
2000
A new experimental apparatus, allowing the determination of radiocristallographic elastic constants (REC) as a function of the temperature is presented. The material studied the zirconium alloy Zircaloy-4, showing low elastic anisotropy, an isotropic treatment of the problem is possible. As a consequence, the classical sin 2 ψ method is used to determine the REC from room temperature to 300°C.
Limits of Sobolev homeomorphisms
2017
Let X; Y subset of R-2 be topologically equivalent bounded Lipschitz domains. We prove that weak and strong limits of homeomorphisms h: X (onto)-> Y in the Sobolev space W-1,W-p (X, R-2), p >= 2; are the same. As an application, we establish the existence of 2D-traction free minimal deformations for fairly general energy integrals. Peer reviewed
Acquisition of Structure-guiding and Structure-forming Properties during Maturation from the Pro-silicatein to the Silicatein Form
2012
Silicateins are the key enzymes involved in the enzymatic polycondensation of the inorganic scaffold of the skeletal elements of the siliceous sponges, the spicules. The gene encoding pro-silicatein is inserted into the pCold TF vector, comprising the gene for the bacterial trigger factor. This hybrid gene is expressed in Escherichia coli and the synthesized fusion protein is purified. The fusion protein is split into the single proteins with thrombin by cleavage of the linker sequence present between the two proteins. At 23 °C, the 87 kDa trigger factor-pro-silicatein fusion protein is cleaved to the 51 kDa trigger factor and the 35 kDa pro-silicatein. The cleavage process proceeds and res…
Collisional Broadening, Line Shifting, and Line Mixing in the Stimulated Raman 2-v2 Q-Branch of CH4
1991
0021-9606; Self-, argon-, and helium-broadening coefficients have been measured for 13 lines in the 2v2 Raman Q branch of CH4 using stimulated inverse Raman spectroscopy. The linewidths clearly show the symmetry-state dependence characteristic of pressure broadening, and inelastic processes in general, involving spherical-top molecules. Pressure-induced line shifts have also been measured for these features in pure methane. The pressure-shift coefficients do not display the symmetry-state dependence found for the linewidths. By applying the Rosenkranz perturbation treatment to a pair of collisionally mixed lines, we have been able to obtain an estimate of individual state-to-state contribut…