Equivalence of the boson peak in glasses to the transverse acoustic van Hove singularity in crystals.

We compare the atomic dynamics of the glass to that of the relevant crystal. In the spectra of inelastic scattering, the boson peak of the glass appears higher than the transverse acoustic (TA) singularity of the crystal. However, the density of states shows that they have the same number of states. Increasing pressure causes the transformation of the boson peak of the glass towards the TA singularity of the crystal. Once corrected for the difference in the elastic medium, the boson peak matches the TA singularity in energy and height. This suggests the identical nature of the two features.

Phonon mechanism of the magnetostructural phase transition in MnAs.

Density functional theory was used to study structural and dynamical changes related to the magnetostructural phase transition in MnAs. The soft mode inducing the transition from the high-symmetry hexagonal to the low-symmetry orthorhombic phase was revealed. A giant coupling between the soft mode and magnetic moments was found and its crucial role in the magnetostructural transition was established. The estimated phonon contribution to the total entropy change has the opposite sign to the magnetic entropy change.

DFT study of structure stability and elasticity of wadsleyite II.

The structure and stability properties of wadsleyite II as the new phase of Mg(2)SiO(4) has been studied at high pressure by the DFT method. The pressure range corresponds to the transition zone in the Earth. At zero pressure the calculated lattice parameters of the wadsleyite II structure are a=5.749 Å, b=28.791 Å and c=8.289 Å with the density ρ=3406 kg m(-3). The third order Birch-Murnaghan equation of state has been determined for the structure with isothermal bulk moduli K(T)=160.1 GPa and K(T)'=4.3 at a pressure range up to 50 GPa. The elasticity tensor coefficients C(ij)(P), as well as the compressional and shear wave velocities and their pressure derivatives, have been calculated using the deformation method at a range of pressures up to 25 GPa. The results agree with the experimental data and structure properties of the wadsleyite II model. The properties of the wadsleyite II phase are very close to the wadsleyite phase.

Probing the coulomb interaction of the unconventional superconductor by phonon spectroscopy.

The phonon dispersion curves of the superconductor PuCoGa(5) were studied by inelastic x-ray scattering at room temperature. The experimental data agree well with ab initio lattice dynamics calculations. An accurate description of the phonon spectrum is obtained only when a local Coulomb repulsion U approximately equal 3 eV among 5f electrons is taken into account.

Chemotaxis of Amoeba proteus in the developing pH gradient within a pocket-like chamber studied with the computer assisted method.

A new "U" shaped, pocket-like chamber was used to observe the chemotactic responses of individual cells. This method permits monitoring of both the development of the concentration gradient of a tested substance and cell locomotion. We investigated the chemotactic responses of Amoeba proteus and observed that the amoebae moved in positively and negatively developing [H+] gradients towards the solution of lower pH in a pH range 5.75-7.75. The chemotactic response of amoebae to [H+] gradients required the presence of extracellular calcium ions. It was blocked and random locomotion was restored by the replacement of calcium with magnesium in the cell medium. Time-lapse video recording and data processing were accomplished with computer-assisted methods. This made it possible to compare selected methods of data presentation and analysis for cells locomoting in isotropic and anisotropic conditions. The cell trajectories were determined and displayed in circular diagrams, lengths of cell tracks and final cell displacements were estimated and a few parameters characterizing cell locomotion were computed.