968 research outputs found
Simulations of magnetic and magnetoelastic properties of Tb2Ti2O7 in paramagnetic phase
Magnetic and magnetoelastic properties of terbium titanate pyrochlore in
paramagnetic phase are simulated. The magnetic field and temperature
dependences of magnetization and forced magnetostriction in Tb2Ti2O7 single
crystals and polycrystalline samples are calculated in the framework of
exchange charge model of crystal field theory and a mean field approximation.
The set of electron-deformation coupling constants has been determined.
Variations of elastic constants with temperature and applied magnetic field are
discussed. Additional strong softening of the crystal lattice at liquid helium
temperatures in the magnetic field directed along the rhombic symmetry axis is
predicted.Comment: 13 pages, 4 figures, 2 table
Topochemical differences in the amount of RNA in the motoneurons of the spinal chord in hypoxia and hypokinesia
Reactions to hypoxia and hypoknesia were compared by measuring charges in the amount of ribonucleic acid (RNA) in the cytoplasm of neurons of the intumescentia cervicalis and lumbalis. Animals were subjected to hypoxia, hypokinesia and both combined and a control group to neither. A total of two groups of motoneurons were compared, one innervating the respiratory musculature, the other the musculature of the lower extremities, so that hypoxic hypoxia would probably affect the first group primarily and hypokinesia the second. Results indicate that neither affect the amount of RNA in the neurons of the first group but a significant increase is noted in neurons of the second group. Other significant results are reported
Space-Time Complexity in Hamiltonian Dynamics
New notions of the complexity function C(epsilon;t,s) and entropy function
S(epsilon;t,s) are introduced to describe systems with nonzero or zero Lyapunov
exponents or systems that exhibit strong intermittent behavior with
``flights'', trappings, weak mixing, etc. The important part of the new notions
is the first appearance of epsilon-separation of initially close trajectories.
The complexity function is similar to the propagator p(t0,x0;t,x) with a
replacement of x by the natural lengths s of trajectories, and its introduction
does not assume of the space-time independence in the process of evolution of
the system. A special stress is done on the choice of variables and the
replacement t by eta=ln(t), s by xi=ln(s) makes it possible to consider
time-algebraic and space-algebraic complexity and some mixed cases. It is shown
that for typical cases the entropy function S(epsilon;xi,eta) possesses
invariants (alpha,beta) that describe the fractal dimensions of the space-time
structures of trajectories. The invariants (alpha,beta) can be linked to the
transport properties of the system, from one side, and to the Riemann
invariants for simple waves, from the other side. This analog provides a new
meaning for the transport exponent mu that can be considered as the speed of a
Riemann wave in the log-phase space of the log-space-time variables. Some other
applications of new notions are considered and numerical examples are
presented.Comment: 27 pages, 6 figure
Structural and Magnetic Investigations of Single-Crystals of the Neodymium Zirconate Pyrochlore, Nd2Zr2O7
We report structural and magnetic properties studies of large high quality
single-crystals of the frustrated magnet, NdZrO. Powder x-ray
diffraction analysis confirms that NdZrO adopts the pyrochlore
structure. Room-temperature x-ray diffraction and time-of-flight neutron
scattering experiments show that the crystals are stoichiometric in composition
with no measurable site disorder. The temperature dependence of the magnetic
susceptibility shows no magnetic ordering at temperatures down to 0.5 K. Fits
to the magnetic susceptibility data using a Curie-Weiss law reveal a
ferromagnetic coupling between the Nd moments. Magnetization versus field
measurements show a local Ising anisotropy along the axes of the
Nd ions in the ground state. Specific heat versus temperature
measurements in zero applied magnetic field indicate the presence of a thermal
anomaly below K, but no evidence of magnetic ordering is observed down
to 0.5 K. The experimental temperature dependence of the single-crystal bulk dc
susceptibility and isothermal magnetization are analyzed using crystal field
theory and the crystal field parameters and exchange coupling constants
determined.Comment: 10 pages, 6 figures, 4 tables. Accepted for publication in Physical
Review
Coherent states and related quantizations for unbounded motions
We build coherent states (CS) for unbounded motions along two different
procedures. In the first one we adapt the Malkin-Manko construction for
quadratic Hamiltonians to the motion of a particle in a linear potential. A
generalization to arbitrary potentials is discussed. The second one extends to
continuous spectrum previous constructions of action-angle coherent states in
view of a consistent energy quantization
Supersymmetry of the Nonstationary Schr\"odinger equation and Time-Dependent Exactly Solvable Quantum Models
New exactly solvable quantum models are obtained with the help of the
supersymmetric extencion of the nonstationary Schr/"odinger equation.Comment: Talk at the 8th International Conference "Symmetry Methods in
Physics". Dubna, Russia, 28 July - 2 August, 199
Supersymmetry of a Nonstationary Pauli Equation
The supersymmetry of the electron in both the nonstationary magnetic and
electric fields in a two-dimensional case is studied. The supercharges which
are the integrals of motion and their algebra are established. Using the
obtained algebra the solutions of nonstationary Pauli equation are generated.Comment: 12 pages, Late
Coherent states of non-relativistic electron in magnetic-solenoid field
We construct coherent states of a nonrelativistic electron in the
magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field
and a collinear uniform magnetic field. In the problem under consideration
there are two kind of coherent states, the first kind corresponds to classical
trajectories which embrace the solenoid and the second one to trajectories
which do not. Mean coordinates in the constructed coherent states are moving
along classical trajectories, the coherent states maintain their form under the
time evolution, and represent a complete set of functions, which can be useful
in semi classical calculations. In the absence of the Aharonov-Bohm filed these
states are reduced to the well-known in the case of uniform magnetic field
Malkin-Man'ko coherent states.Comment: 11 pages, version accepted for publication in J. Phys. A, 3 figures
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Batch drying in sintering
An adapted mathematical model of sintering permits analysis of the thermophysical characteristics of batch drying, primarily in the main sintering period. Over the whole length of the sintering machine, most of the bed volume corresponds to equilibrium moisture content, which may be higher or lower than the initial value. The temperature of the gas entering the drying zone is calculated, and its dependence on the parameters of the batch and gas is determined. © 2013 Allerton Press, Inc
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