Structure and Properties of Exotic Nano- and Mesodiamonds with Pentagonal Symmetry

Russian Physics Journal - A comprehensive critical survey of structures of exotic nano-, meso- and microdiamonds with dodecahedral and icosahedral symmetry (N/MDPS) is presented. Due to their high...     

Bias voltage dependence of tunneling magnetoresistance in granular C60–Co films with current-perpendicular-to-plane geometry

Voltage-dependence of the tunneling magnetoresistance effect in the granular C₆₀–Co films has been investigated for the samples with the current-perpendicular-to-plane geometry. The transport measurements under this geometry demonstrate that the granular C₆₀–Co films show an unusual exponential bias voltage dependence of the magnetoresistance ratio down to zero voltage. Small characteristic energies of less than 10's meV are derived from the temperature dependences of the characteristic voltage in the exponential relationship. Considering the magnitudes of the voltage drop between Co nanoparticles and also the effect of cotunneling on the energy values, the characteristic energies for the voltage-induced degradation of the spin polarization are found to show a satisfactory agreement with that for the thermally-induced one. It can be reasonably expected that the onset of magnetic disorder to the localized d-electron spins at the interface region of the C₆₀-based matrix (C₆₀–Co compound) with Co nanoparticles leading to the unusual voltage and temperature dependence of the magnetoresistance ratio and the spin polarization at low temperatures.     

Multidimensional models of traveling waves and nonlinear modes in cylindrical shells

The nonlinear dynamic deformation of a cylindrical shell is modeled taking into account several conjugate vibration modes. Two types of motion are considered: nonlinear normal modes and traveling waves     

Hypothesis of Hemoprotein Sensor Confirmed by Ab initio Quantum-Chemical Method

The nature of the chemical bond of complexes of iron and cobalt porphyrinates with ligands is studied by the quantum-chemical method in the Hartree–Fock self-consistent field approximation using the 3-21G basis set. The addition of oxygen molecule to the MP and MPIm complexes (M = Fe, Co; Im is imidazole) is established to be more favorable than water addition. However, imidazole, which is the second ligand in the MPImO₂ and MPImH₂O complexes (M = Fe, Co), increases the M–O₂ and M–H₂O binding energies for iron, but decreases them for cobalt. The Co atom is bound with the porphyrin ring more strongly than the iron atom due to the larger total overlap of the atomic orbitals. The calculations of the binding energy in the complexes demonstrate similar changes in the structures of the spatial conformation of the deoxy form (FeP + H₂O) of iron porphyrinate and the oxy form (CoP + O₂) of cobalt porphyrinate. This is an argument in favor of the hypothesis of hemoprotein sensor of partial oxygen stress in tissues.     

On interaction of vibrating beam with essentially nonlinear absorber

The paper deals with interaction of elastic beam with essentially nonlinear vibration absorber. Forced vibrations of the beam are described by 2DOF model. We treat the motions favorable for vibration absorption as nonlinear modes in a configuration space and compute them by a modification of Rausher method. Stability of these modes is analyzed numerically with the help of the Floquet theory.     

On the nonlinear normal modes of free vibration of piecewise linear systems

A modification of the Shaw–Pierre nonlinear normal modes is suggested in order to analyze the vibrations of a piecewise linear mechanical systems with finite degrees of freedom. The use of this approach allows one to reduce to twice the dimension of the nonlinear algebraic equations system for nonlinear normal modes calculations in comparison with systems obtained by previous researchers. Two degrees of freedom and fifteen degrees of freedom nonlinear dynamical systems are investigated numerically by using nonlinear normal modes.     

Free linear vibrations of thin axisymmetric parabolic shells

The Rayleigh–Ritz method is used to minimize the energy functional in order to calculate eigenfrequencies of parabolic shells. The properties of eigenfrequencies and eigenmodes of different heights parabolic shells are analyzed numerically.     

Possible differences between the surface and bulk structure of glasses

Changes in cation co-ordination at glass surfaces (indicating an increase of the oxygen-to-cation ratio within the topmost superficial layers) are evidenced by comparing data acquired by spectroscopic techniques of different excitation depth. Based on these experimental results, a theoretical model is developed that predicts structural discrepancies between surface and bulk structure. Such reconstructed surfaces are of great importance for all kind of surface-related crystallization phenomena.