Effect of the susceptibility on the magnetic phase diagrams of a ferrimagnet with magnetic instability

The magnetic phase diagrams of a two-sublattice ferrimagnet with a magnetically unstable subsystem are calculated taking account of the susceptibility. Analytic expressions are obtained for the phase-transition fields and critical values of the parameters of the ferrimagnet. The evolution of the magnetic phase diagrams as the susceptibility of the unstable sublattice increases is analyzed.     

Enhancement of the quantum characteristics of light from an inversionless three-level Λ-laser in cascade schemes

We show that when a three-level laser is excited by Poisson light the lasing remains sub-Poisson, as asserted by H. Ritsch, M. A. M. Marte, and P. Zoller [Europhys. Lett. 19, 7 (1992)], only if there is no reciprocal action on the exciting laser (weak coupling). In cascade schemes in which each three-level Λ-laser excites each succeeding Λ-laser with its light, any desired degree of shot-noise suppression can be achieved. Zh. éksp. Teor. Fiz. 114, 1971–1992 (December 1998)     

On variable stepsize Runge-Kutta approximations of a Cauchy problem for the evolution equation

We consider a Cauchy problem for the sectorial evolution equation with generally variable operator in a Banach space. Variable stepsize discretizations of this problem by means of a strongly A(φ)-stable Runge-Kutta method are studied. The stability and error estimates of the discrete solutions are derived for wider families of nonuniform grids than quasiuniform ones (in particular, if the operator in question is constant or Lipschitz-continuous, for arbitrary grids).     

“Horizontal” and “vertical” quantum-dot molecules

An analysis is made of a two-electron system of two adjacent quantum dots (QD) with a two-dimensional parabolic lateral confining potential, and of two coupled or double, spatially separated QDs (a “horizontal” and a “vertical” QD molecule), and of their behavior in an external transverse magnetic field. The ground-state energies and energy spectra of the system have been determined by various methods (Heitler-London, molecular-orbital, variational approach, and numerical diagonalization of Hamiltonian), with inclusion of electron-electron interaction, and for a broad range of confining-potential steepness, QD-center spacing (interlayer distance), and external magnetic field. Fiz. Tverd. Tela (St. Petersburg) 40, 2127–2133 (November 1998)     

Response of a YBaCuO/MgO bolometer structure at high levels of laser excitation. Nonlinear model and experiment

A nonlinear model is developed for the photoresponse of a bolometric structure taking into account the temperature dependences of the thermal constants of the YBaCuO/MgO structure and its boundary thermal resistance. The model also allows for the specific form of the currentvoltage characteristic of YBaCuO and the heat release from the transport current flow. A comparison between the experimental data and the model showed that the nonlinear thermal model accurately describes the temporal characteristics of the photoresponse. Fiz. Tverd. Tela (St. Petersburg) 40, 191–194 (February 1998)     

Stress state of infinite medium with elastic paraboloidal inclusion

S. P. Timoshenko Institute of Mechanics, Ukrainian Academy of Sciences, Kiev. Translated from Prikladnaya Mekhanika, Vol. 29, No. 12, pp. 15–21, December, 1993.     

New numerical methods and some applied aspects of the p-regularity theory

The theory of p-regularity is applied to optimization problems and to singular ordinary differential equations (ODE). The special variant of the method of the modified Lagrangian function proposed by Yu.G. Evtushenko for constrained optimization problems with inequality constraints is justified on the basis of the 2-factor transformation. An implicit function theorem is given for the singular case. This theorem is used to show the existence of solutions to a boundary value problem for a nonlinear differential equation in the resonance case. New numerical methods are proposed including the p-factor method for solving ODEs with a small parameter.     

Experimental investigation of highly excited states of the 5,6He and 5,6Li nuclei in the (6Li, 7Be) and (6Li, 7Li) one-nucleon pickup reactions

The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions on ⁶Li and ⁷Li nuclei were investigated in the angular interval 0°–20° in the laboratory system at a ⁶Li energy of 93 MeV. In addition to low-lying states of the ^5,6He and ^5,6Li nuclei, broad structures were observed near the t(³He)+d and t(³He)+t thresholds at the excitation energies of 16.75 (3/2⁺) and ～20 MeV (for ⁵He), 16.66 (3/2⁺) and ～20 MeV (⁵Li), 14.0 and 25 MeV (⁶He), and ～20 MeV (⁶Li). The angular distributions measured in the ⁷Li(⁶Li, ⁷Be)⁶He reaction for transitions to the ground state (0⁺) and excited states at E _x=1.8 MeV (2⁺) and 14.0 MeV of the ⁶He nucleus were analyzed by the finite-range distorted-wave method assuming the 1p-and 1s-proton pickup mechanism. The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions were shown to proceed predominantly through the one-step pickup mechanism, and the broad structures observed at high excitation energies are considered as quasimolecular states of the t(³He)+d and t(³He)+t types.     

卡尔曼滤波紫外光度法同时测定酱油、食醋中的山梨酸和苯甲酸

在酸性条件下，采用乙酸乙酯萃取、Na2HPO4溶液反萃取分离酱汪、食醋中的山梨酸、苯甲酸，卡尔曼滤波法计算结果，并与比值导数波谱法进行比较。结果表明，卡尔曼滤波法较地数波谱法有较高准确度和精密度，并能监测干扰物质存在与否。用于实际样品分析有更高的可靠性。     

Investigation of metal-containing carbon nanostructures prepared from functional polymers

Metal-containing carbon nanostructures are prepared by heating poly(vinyl alcohol) in mineral media with a lamellar structure at a temperature below 300°C. It is demonstrated that three possible types of nanostructures can be formed, namely, multilayer carbon nanotubes, spherical carbon nanoparticles, and finely crystalline carbon structures. According to the data of transmission electron microscopy, the nanotube size falls in the range from 50 to 300 nm and the nanotubes themselves have a stranded structure.