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941.
The softening of the IR active 300 cm−1 phonon mode in Tl-2223 superconductor, aroundT
c has been explained by considering a sixth order polarization potential at the off-center oxygen ion site in the Tl-O plane,
and by using a nonlinear lattice dynamical theory. The present theory explains, more or less satisfactorily, the unusual temperature
dependence of oxygen ion vibration and frequency shifts at higher temperature. The existence of strong nonlinear electron-phonon
interaction atT
c has been emphasized. 相似文献
942.
Summary The optogalvanic signal (OGS) induced in a uranium-neon hollow-cathode discharge was measured as a function of the laser power
density for the 0→16900 cm−1 (591.5 nm) uranium transition. Theoretical relations derived by solving a two-level system rate equations showed the OGS
dependence on the laser photon flux, for a modulated c.w. light and for stimulated transitions starting from the ground state.
A fitting of the theoretical relations to the experimental measurements allowed the determination of the σ0 τ product, that is, the saturation parameter of the transition. The results showed good agreement between the σ0 τ values obtained by the optogalvanic and the usual optical absorption processes. 相似文献
943.
944.
Static dielectric constants and refractive indices of 2-butoxyethanol-n-hexane and-n-heptane mixtures were measured at 30 and 40°C and the various dielectric excess functionsviz. dielectric constants, molar polarizations, and orientation polarizations were evaluated. The excess dielectric constants and molar polarizations were found to be unsymmetrical and negative over the entire range of mole fraction. The trend in the variation of excess orientation polarization has shown three characteristic regions. The excess functions were smoothed through a variable degree polynomial. The results show the dominance of dipole-dipole interactions in the butoxyethanol deficient regions and weak specific interactions with unlike alkane molecules at higher butoxyethanol mole fractions. 相似文献
945.
The question of a possible container shape dependence of the sedimentation velocity in a homogeneous suspension is reexamined. To this end we develop a statistical theory of suspensions based on low-Reynolds-number hydrodynamics of spherical particles in a container. It is shown, to first order in the volume fraction, that in an arbitrary vessel the relative sedimentation velocity is shape independent, but that at the same time shape-dependent convection occurs. The theory forms a bridge between earlier calculations for special geometries by Beenakker and Mazur and a phenomenological theory recently proposed by Nozières.This paper is dedicated to N. G. van Kampen. 相似文献
946.
Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》1996,59(1):111-116
The conditions for the occurrence of critical phenomena in multi-component adsorption layers are discussed for the case of lateral interactions and clustering of adsorbed molecules. It is demonstrated, that the critical temperature.i.e. the temperature below which surface phase transformation can occur, is independent of the size of clusters. 相似文献
947.
Guido Barone Giuseppina Castronuovo Pompea Del Vecchio Vittorio Elia Maria Teresa Tosto 《Journal of solution chemistry》1988,17(10):925-936
The excess enthalpies of ternary aqueous solutions of biuret with four aliphatic alcohols or four isomeric pentoses have been determined by flow microcalorimetry at 25°C. The coefficients of the virial expansion of the excess enthalpies have been evaluated and compared with those already reported for urea and thiourea with the same alcohols and pentoses used here. For biuret-alcohol systems, the cross coefficients are positive and depend on the length and branching of the alkyl chain of the alcohols. On the contrary, they are negative for biuret-pentose systems. Hence, biuret, as urea and thioura, is able to differentiate the behavior of families of solutes characterized by the same functional groups. The results are interpreted in terms of the relative stabilities of the hydration cospheres of predominantly hydrophobic or predominantly hydrophilic cosolutes. However, hypotheses about the hydration cospheres of the saccharides, which are more complex than those used previously, seem to be necessary to rationalize their complete behavior in water. 相似文献
948.
The critical behavior of the layer magnetizations and local susceptibilities of theD-vector lattice models with Kac-type ferromagnetic interactions for a semi-infinite system is studied. These local quantities behave less singularly than the bulk ones, showing that this is not peculiar to the two-dimensional Ising model. Moreover, the limiting form (at the critical point) of the magnetization profile can be obtained, which, when properly scaled, satisfies the minimum condition in the Landau theory for a semi-infinite continuous system. Landau-type critical behavior is thus recovered. 相似文献
949.
950.
Electrospray ionization mass spectrometry (ESI-MS) was used to investigate noncovalent complexes formed between four novel polyamides containing N-methylpyrrole (Py) and N-methylimidazole (Im), and human telomeric DNA. Of the four polyamides investigated, PyPyPygammaImImImbetaDp (3) had the highest binding affinity towards the duplex d(TTAGGGTTAGGG/CCCTAACCCTAA) (D1). Results of competition analysis showed that the polyamides had binding affinities with D1 in the order PyPyPygammaImImImbetaDp (3)>PyPyPyPygammaPyImImPybetaDp (4)>PyPyPybetaImImImbetaDp (2)>ImImImbetaDp (1). MS/MS spectra confirmed that binding between D1 and the hairpin polyamides is more stable than that with the three-ring polyamides. By contrast, in the case of single-stranded d(TTAGGGTTAGGG)(D2), the binding order changes to ImImImbetaDp (1)>PyPyPygammaImImImbetaDp (3)>PyPyPybetaImImImbetaDp (2). 相似文献