Observation of self-generation of dark envelope solitons for spin waves in ferromagnetic films

We have performed experiments in which self-generation of dark envelope solitons for spin waves at microwave frequencies were obtained. Stable self-generation of dark solitons was observed in a ring consisting of tangentially magnetized yttrium iron garnet film and a microwave signal amplifier. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 3, 229–233 (10 August 1998)     

Polymorphism of biperiodic stripe domain structures

Magnetic-field-induced polymorphism of biperiodic stripe domain structures of films with a positive anisotropy constant and easy axis parallel to the normal to the surface is studied. A symmetry classification of the observed types of domain structures is performed, and the phase diagram of the films in the (H _⊥, H _∥) plane, where H _⊥ and H _∥ are, respectively, the components of the magnetic field vector perpendicular and parallel to the normal to the surface, is determined. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 701–706 (10 May 1998)     

Low noise optical receiver with multi-octave bandwidth

Optical and Quantum Electronics - A new approach for the design and construction of low noise broadband optical receivers is presented utilizing distributed amplification based on hybrid integrated...     

Second-approximation shear theory for shallow layered shells and plates

Analysis of a second-approximation refined shear model for shallow layered composite shells and plates with a substantially inhomogeneous structure over the thickness is presented. The tangential displacements and corresponding normal stresses are expressed in the form of a polynomial of the fith degree in the transverse coordinate and contain squared rigidity characteristics. In this way, the accuracy of results and practical coincidence with the 3D solutions is ensured. Based on the refined model, a theory of shallow layered shells is developed. A system of resolving equations of sixteenth power together with appropriate boundary conditions was obtained and solved analytically. It is shown that the area of application of the formed model is extended as compared with the model of the first approximation. The model proposed allows us to examine the stress-strain state of layered composite structures of substantially different thickness and physical-mechanical characteristics of the layers, including the possibility of simulating relatively large shear deformations of rigid layers separated by a low-modulus thin interlayer pliable to transverse shear.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian Transport University, Kiev, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 3, pp. 363–370, May–June, 1998.     

Asymptotic behavior of neutron small-angle multiple scattering spectra

The asymptotic behavior of the spectra for large values of the scattering vector for the case of elastic multiple small-angle neutron scattering (SANS) is investigated theoretically and experimentally. An expansion of the spectrum in terms of the reciprocal of the magnitude of the momentum transfer is obtained taking account of the influence of the instrumental line. It is shown that, to within some factor, the leading term of the expansion is identical to the differential single-scattering cross section averaged over a statistical ensemble of particles; several subsequent terms in the expansion are calculated and the range of applicability of the resulting expressions is determined. The asymptotic behavior of the multiple SANS spectrum is measured, using a two-crystal neutron spectrometer, for samples of an HTSC ceramic, the alloy Fe-Ni, and Al powder. The agreement between the experimental results and the theoretical predictions is analyzed. Zh. éksp. Teor. Fiz. 114, 2194–2203 (December 1998)     

Phase transitions in silicon single crystals resulting from directional plastic deformation

The formation of polytypic modifications is observed in dislocation-free silicon single crystals under directional plastic deformation. It is shown that the deformation-stimulated phase appears on the surface of the sample in the form of small grains ranging from several hundred to several thousand angstroms in size. A twin structure in the individual grains is observed. Fiz. Tverd. Tela (St. Petersburg) 40, 746–749 (April 1998)     

Determination of the surface potential of a dielectric layer on a target bombarded by an ion beam

The electric field at the surface of a charge spot created by an ion beam on a dielectric coating of a target is calculated. An expression is obtained which relates the surface potential of the insulator to the potential of the collector corresponding to saturation of the collector secondary-electron current. It permits determination of the potential drop across the oxide layer of a cold cathode without introducing complications in the construction of the experimental apparatus. Zh. Tekh. Fiz. 68, 126–128 (September 1998)     

Phenomenological πN→ππN amplitude and the modelling of the Olsson–Turner and Chew–Low approaches

The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P _Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics. Received: 10 December 1997     

Statistical mechanics of warm and cold unfolding in proteins

We present a statistical mechanics treatment of the stability of globular proteins which takes explicitly into account the coupling between the protein and water degrees of freedom. This allows us to describe both the cold and the warm unfolding, thus qualitatively reproducing the known thermodynamics of proteins. Received: 19 March 1998 / Revised and Accepted: 25 May 1998