Thermal Expansion in the Zr and 1-, 2-valent Complex Phosphates of NaZr2(PO4)3 (NZP) Structure

A_5–4xZr_xZr(PO₄)₃ (A=Na, K;0≤x≤1.25), Na_1-xCd_0.5xZr₂(PO₄)₃ (0≤x≤1), Na_5–xCd_0.5xZr(PO₄)₃ (0≤x≤4) compositions which belong to the NZP structural family were synthesized using the sol-gel method. The lattice thermal expansion of members of these rows were determined up to 600°C by high-temperature X-ray diffractometry. The axial thermal expansion coefficients change from -5.8·10^-6to 7.5·10^-6 °C^-1 (α_a) and from 2.6·10^–6 to 22·10^–6 °C^-1 (α_c). These results, in addition to those for other NZP compounds allow us to explain their low thermal expansion. The mechanism can be attributed to strongly bonded three-dimensional network structure, the existence of structural holes capable to damp some of the thermal vibrations and anisotropyin the thermal expansion of the lattice. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diagnostics of a strong magnetic field using spectropolarimetry of the decaying emission

A method for diagnostics of a magnetic field is suggested. The method is based on spectropolarimetry of the decaying emission of an ensemble of particles whose angular momenta were ordered by pulsed axially symmetric perturbation.     

About the Depolarization Tensor

It is suggested that the concept of the depolarization tensor usually introduced for an ellipsoid be generalized to arbitrary regions of space. It is demonstrated that the class of problems for which this concept is useful is sufficiently wide. Examples of calculations of the depolarization tensor for various 3D and 2D figures are presented.     

Spherical magnetic multipole moments system of currents

Concepts of spherical magnetic multipoles that represent distributions of electric currents over a spherical surface are introduced. Vector potentials of magnetic multipoles meet solenoidal- and harmonic-field conditions outside of the spherical surface and are continuous on it. Within the sphere, the vector potential of currents flowing outside of it is represented by the sum of vector potentials of basis magnetic multipoles with coefficients expressed by spherical multipole moments of system of currents. This expansion of the vector potential is in many respects analogous to the multipole expansion known from electrostatics. The first three terms of the expansion represent components of the well-known magnetic moment, the next five terms represent components of the magnetic quadrupole moment, etc. Possible applications of the magnetic spherical multipole technique are discussed. Krasnoyarsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 66–72, October, 1999.     

Synchronization in a Network of Spiking Neural Oscillators with Plastic Connectivity

Radiophysics and Quantum Electronics - Synchronization of neural activity plays an important role for processing of information in the brain. In this work, we study the dynamics of a neural network...     

Effect of a Carbon Promoter on the Properties of a Co/MgAlO4 Catalyst for Fischer–Tropsch Synthesis

Kinetics and Catalysis - The influence of carbon on the genesis of the active phase of cobalt in aluminum–magnesium spinel supported catalysts on their catalytic properties in the synthesis...     

Interference of atom,and atomic spatial lattices in light fields

A scheme is proposed to observe interference of atoms by using a weakly coherent atomic beam scattered at two standing light waves. It is shown that atoms can transfer spatial coherence over rather large distances.     

Dynamics of excitation pulses in two coupled nerve fibers

In this paper, we study the phenomena of interaction of traveling pulses in a system of two coupled nerve fibers. Each fiber is modeled by a discrete chain of mutually coupled Fitz Hugh-Nagumo excitable elements. The interaction among the fibers can be distributed, homogeneous, and also localized at certain points in space. In the case of homogeneous interaction, we show the possibility of interfiber synchronization of pulses. For localized interactions, we study the dynamics of point and two-point contacts, allowing us to perform effective control over the propagation of excitation along the coupled fibers. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1593–1603, December, 1998.     

Thermal Expansion of Mixed Zirconium Phosphates

A series of framework phosphates with varied ratio of cations Na_5-2x B _x ^IIZr(PO₄)₃, B^II = Mg, Ca, Sr, Ba (0 x 2) and Na_5-3x Fe _x Zr(PO₄)₃ (0 x 1.33) were synthesized and studied under heating. The coefficients of thermal expansion along crystal axes _a and _c were calculated, and their dependences on the cationic composition (nature and concentration) and on the occupancy of out-of-framework structural positions were established.