On the law of approach to saturation in manganese-magnesium ferrite

The law of approach to saturation is studied for three differently porous samples of polycrystalline sintered Mn-Mg ferrite. Such an internal fieldH is sought that the dependenceI=I _s(1–a/H ²) might be satisfied. The changes which occu rin such a dependence, if the fieldH is changed by a certain multiple of the magnetization, ere investigated by calculation. Relations are derived for this case, which are satisfied very well by the experimental values. The properties of the effective anisotropy constants ara dealt with and, on the basis of temperature measurements, these constants are ascribed with very great probability to the internal form anisotropy.

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- Mn-Mg- . , I= I_S(1-a/H²). , , . , . .

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Reported on in the form of preliminary results in the Institute of Semi-conductors, Academy of Sciences, USSR, in Leningrad on 17. 10. 1960.

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In conclusion the author would like to thank Dr. S. Krupika, C. Sc., K. Závta, C. Sc., grad. phys. R. Gerber and grad. phys. E. Kratochvílová for valuable discussions and A. Hadincová for help in the measurements and for carefully making the numerical calculations and graphs.     

Abelian groups and the Weyl approach to kinematics nonlocal function-algebras

This paper is motivated by the Weyl-Wigner-Moyal approach to quantum mechanics [8], [12]. The nonlocal multiplication of phase space functions is generalized to functions over locally compact Abelian groups or over homogeneous spaces of such groups. It is shown that such nonlocal algebras of functions are closely related to the ray-representations of the corresponding dual groups. An arbitrary continuous solution of the factor- equation on ? gives rise to some translationally invariant nonlocal algebra over G or over its homogeneous space. This enables us to find the group-theoretical interpretation of the well-known symmetrization rules (e.g. the standard, antistandard and Weyl rules [2]). Some properties of the nonlocal products are studied (e.g. the existence of the identity). It should be noted that some of our results (e.g. the theory of weighted convolutions of measures) are valid in the non-Abelian cases, as well, and they generalize some ideas of Edwards and Lewis [14]. When working with the Fourier analysis on the locally compact Abelian groups, we mostly use the language of W. Rudin's book [10].     

Information-theoretic approach to single-particle and two-particle interference in multipath interferometers

We propose entropic measures for the strength of single-particle and two-particle interference in interferometric experiments where each particle of a pair traverses a multipath interferometer. Optimal single-particle interference excludes any two-particle interference, and vice versa. We report an inequality that states the compromises allowed by quantum mechanics in intermediate situations, and identify a class of two-particle states for which the upper bound is reached. Our approach is applicable to symmetric two-partite systems of any finite dimension.     

Law describing the approach to saturation of porous anisotropic materials

A law is obtained for the approach to saturation with respect to magnetization for anisotropic magnetic materials with inhomogeneous saturation magnetization. In the calculation, the spin-wave formalism is used. The effect of an inhomogeneous exchange interaction on the approach to saturation is taken into account. The relations obtained are generalizations of the already known Neel and Holstein-Primakov formulas.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 32–38, August, 1979.     

A sensitivity analysis approach to optical parameters of scintillation detectors

In this study, an extended version of the Monte Carlo light transport code, PHOTRACK, has been used for a sensitivity analysis to estimate the importance of different wavelength-dependent parameters in the modelling of light collection process in scintillators.     

Recoil effect and kinematics of the molecular states approach to heavy-ion transfer reactions

The kinematic properties of the adiabatic representation of the total wave function which can be useful to demonstrate the molecular features in the heavy-ion transfer reactions are discussed. The matrix transformation of the adiabatic Hamiltonian which simplifies its asymptotic form is then constructed. This allows one to treat the recoil effect in the form of a simple matrix transformation of the adiabatic S-matrix.     

A theoretical approach to saturation effects in lasers

Exact numerical solution of a one-dimensional three-level lasing system (homogeneously broadened) is used to establish the relevance of spatially independent rate equations. It is shown that these equations can be applied not only for unsaturated lasing media but also for highly saturated media. However the loss term and the correlation term have to be modified.     

Heuristic approach to non-abelian quantum kinematics and dynamics in configuration spacetime

New plausible kinematic foundations of quantum dynamics are discussed in a heuristic manner in which the quantum rule stems directly from the non-Abelian configuration symmetries of a system. Upon quantizing the ‘complete’ configuration symmetry group itself, irreducible generalized configuration-state representations can be calculated, whose transition amplitudes yield the propagation kernel. These states results from solving a set of ‘generalized Schrödinger equations’ corresponding to the superselection rules dictated by the quantized group. The propagation kernel of the system is thus obtained as an invariant Hurwitz integral, defined over the manifold of the complete symmetry group. A heuristic argument is given in favor of this approach to non-Abelian quantum kinematics, in which sums over physical world lines are evaluated instead of sums over arbitrary paths, for obtaining the propagation kernel of quantum systems having a classical Lagrangian analog. The attained quantum kinematic formalism, however, is completely general and does not depend on this particular interpretation. Nevertheless, the heuristic argument strongly suggests that non-Abelian quantum kinematics contains the formalism of standard nonrelativistic quantum mechanics as a very special case. No examples of the issues involved are presented in this paper.     

Deeply virtual Compton scattering and saturation approach

We investigate the deeply virtual Compton scattering (DVCS) in the color dipole approach, implementing the dipole cross section through the saturation model, which interpolates successfully between soft and hard regimes. The imaginary and real part of the DVCS amplitude are obtained and the results are compared to the available data. Received: 12 February 2003, Revised: 2 May 2003, Published online: 11 June 2003     

On the kinematics of the torsion of space-time

On a macroscopic level we take general relativity as the appropriate theory of space-time and gravity. We will argue that, on a more microscopic level, in the Compton wavelength regime of elementary particles, there are good reasons for suspecting the presence of a torsion of space-time. A corresponding gaugetheoretical formalism related to the Poincaré group is reviewed, and the kinematical consequences of the presence of a torsion are worked out. In particular we discuss the operational meaning and the measurability of torsion. The dynamics of torsion is left for a forthcoming article.     

The law of approach to saturation in ferromagnets originating from the magnetocrystalline anisotropy

In this paper, we have investigated the approach to saturation in both Co and Fe single crystals by taking into account the field energy and the magnetocrystalline anisotropy energy and numerically solving the nonlinear equations for equilibrium. And by introducing a new approximation rather than Akulov’s approximation, more accurate, approximate analytical solutions for the nonlinear equations for the field above the magnetocrystalline field have been obtained, which are in good agreement with the numerical results. It has been found that the crystal can reach the saturation as it is magnetized by a field along the easy or hard directions while it will follow the law of approach to saturation by the field applied along the non-easy or non-hard directions. The reason is that depending on the applied field angle the magnetocrystalline anisotropy can make the crystal hard or easy to be magnetized. No paramagnetism-like process occurs, and the a/H, b/H² and χH terms all originate from the magnetocrystalline anisotropy. With the application of our theory to real ferromagnetic materials, the experimental observations can be understood.     

Bayesian approach to non-Gaussian field statistics for diffusive broadband terahertz pulses

We develop a closed-form expression for the probability distribution function for the field components of a diffusive broadband wave propagating through a random medium. We consider each spectral component to provide an individual observation of a random variable, the configurationally averaged spectral intensity. Since the intensity determines the variance of the field distribution at each frequency, this random variable serves as the Bayesian prior that determines the form of the non-Gaussian field statistics. This model agrees well with experimental results.     

Simple approach to one-laser, broadband coherent anti-Stokes Raman scattering microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy is emerging as a powerful method for imaging materials and biological systems, partly because of its noninvasiveness and selective chemical sensitivity. However, its full potential for species-selective imaging is limited by a restricted spectral bandwidth. Recent increases in bandwidth are promising but still are not sufficient for the level of robust component discrimination that would be needed in a chemically complex milieu found, for example, in intracellular and extracellular environments. We demonstrate a truly broadband CARS imaging instrument that we use to acquire hyperspectral images with vibrational spectra over a bandwidth of 2500 cm(-1) with a resolution of 13 cm(-1).     

The influence of precipitates on the law of approach to magnetic saturation in amorphous ferromagnets

Within the framework of the micromagnetic theory of Kronmüller and Ulner we have calculated the influence of spherical precipitates on the law of approach to magnetic saturation in amorphous ferromagnets, taking the exchange energy fully into account. It turns out that in most materials the effect of precipitates is very small. Therefore precipitates cannot be responsible for the A/H_ext-term (H_ext denotes the external magnetic field) in the law of approach to saturation previously observed in the amorphous alloy Fe₄₀Ni₄₀P₁₄B₆.     

Laser and absorption saturation measurements of Cr crystals, pumped by broadband pulsed 940 nm radiation

The characteristics of a 940 nm pumped Cr⁴⁺:forsterite laser have been investigated using a pulsed colour centre laser as the excitation source. Laser threshold, slope efficiency and temporal behaviour have been determined for high and low Cr⁴⁺ doped material. 940 nm pumping is found to be more efficient than 532 and 730–770 nm excitation. Discrepancies with 1064 nm pumping are attributed to excited state absorption. Absorption saturation measurements have been used to assess the potential applications of Cr⁴⁺:forsterite, Cr⁴⁺:YAG and Cr⁴⁺: Lu₃A1₅O₁₂ (LuAG) as passive Q-switches for Nd lasers in the 940 nm region.     

On the approach to Maxwellian distribution

The relaxation to equilibrium of a gas governed by the Boltzmann equation is studied for various collision models. For certain initial distributions evidence is presented that it can be characterized by a state in which there is an over-population of high-velocity particles.