Optical stability of F centers in potassium chloride “cleavage” and ordinary whiskers

The kinetic characteristics of the optical decoloration of F centers in cleavage whiskers and needle-shaped crystals (ordinary whiskers) are analyzed. The effect of the size of the ordinary and cleavage whiskers on the optical stability of the F centers as well as the initial concentration of the latter is established. The mechanisms underlying the optical breakdown of the F centers are considered on the basis of the kinetic decoloration curves.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 1, pp. 132–135, January, 1976.     

Steroids of the spirostan and furostan series of plants of the Allium genus. XXIII. Structure of cepagenin and of alliospirosides C and D from Allium cepa

Two new steroid glycosides of the spirostan series have been isolated from the fruit ofAllium cepa L. (family Liliaceae): alliospirosides C and D. On the basis of chemical transformations and spectral characteristics it has been established that the aglycon of both glycosides is a new steroid sapogenin — cepagenin — having the structure of (24S,25R)-spirost-5-ene-1β,3β,24-triol. Alliospirosides C and D are cepagenin 1-O-[O-α-L-rhamnopyranosyl-(1→2)α-L-arabinopyranoside] and 1-O-[O-α-L-rhamnopyranosyl-(1→2)-O-β-D-galactopyranoside], respectively.     

Preparation of composite membranes by means of plasma polymerization of tiophene

The structure and the charge transport properties of poly(ethylene terephthalate) track membranes modified in a thiophene plasma were studied. It was found that polymer deposition on the surface of a track membrane via the plasma polymerization of thiophene results in composite membranes that, in the case of the formation of a semipermeable layer, exhibit conductivity asymmetry—rectifying effect—in electrolyte solutions. It was shown that chemical doping with iodine or photo-oxidation of the polymer layer produced in plasma leads to alteration in the electrochemical properties of plasma-modified membranes.     

Specific features of the magnetoreflection of co-based amorphous ribbons in the IR region

The light reflection spectra and the magnetorefractive effect in the cobalt-based amorphous ribbons in the IR spectral region (λ = 2.5–25 μm) are studied. These amorphous alloys are characterized by the magnetoimpedance effect, which is enhanced after thermal and laser annealing. It is found that the magnetoimpedance and magnetorefractive effects correlate with each other. The magnetorefractive effect reveals a feature at λ = 15–20 μm and the change of sign in the wavelength region 20–25 μm. It is shown that, in the first approximation, the optical properties of the amorphous alloys in the IR spectral region can be explained on the basis of a modified Hagen-Rubens relation. It is found that the change in the reflection coefficient of amorphous metal films in the IR spectral region under action of a magnetic field is caused by the change in both their magnetic permeability and conductivity, which is caused by the degree of polarization of localized electronic states at the Fermi level.     

Numerical Modeling of Two-Dimensional Flow of a Nonhomogeneous Fluid in a Confined Domain

The pattern of the two-dimensional vortex flow of a nonhomogeneous fluid in a confined domain is studied using two-dimensional numerical calculations. It is found that in the case of a nonhomogeneous initial density distribution the kinetic energy decay rates are proportional to the square root of viscosity at the active stage of flow restructuring. The correlation functions of the velocity and the density are derived for different moments of time in the inertial range. All these results indicate the choice of the two-dimensional turbulence development scenario in a nonhomogeneous fluid.     

Explosion of the Primer at the End of a Borehole Charge

International Applied Mechanics - The possibilities of controlling the edge effect of the explosion of the conic primer in the lower part of the borehole charge on the level of the bench sole are...     

Low-Temperature Synthesis of Glass-Ceramics with YNbO4:Eu3+ Crystallites

Optics and Spectroscopy - The main aim of this work was to perform low-temperature synthesis of glass-ceramics with YNbO4:Eu3+ crystallites and study the structural and luminescent properties of...     

Magneto-optical recording on the multilayers systems with plasmon excitation

The maximization of the sensitivity of magneto-optical recording media in the short wavelength region is discussed. We show that a combination of the optimized thickness of dielectric and Ag (or CoAg) films can increase the magneto-optic Kerr effect in FeTbCo media by about five times of magnitude in the UV and blue spectral range. It has been shown that the local plasmon excited in the Ag-based films strongly enhances the magneto-optical properties in amorphous FeTbCo magnetic film. The Kerr rotation spectra get the maxima values for the resonance conditions when the local plasmon can be excited in the Ag or CoAg films.     

Raman scattering of light in silicon nanostructures: First-and second-order spectra

First-and second-order Raman scattering spectra in Si nanocrystals have been studied. The shift to lower frequencies and the substantial broadening of first-order Raman scattering lines observed to occur with decreasing nanoparticle size were established to correlate with those in second-order spectra. It is shown that the experimentally observed shifts of peaks and their broadening cannot be predicted based only on the phenomenological model of strong phonon wave function localization. The anharmonic effect originating from the heating of the nanoparticle surface by laser radiation should also be included. Proper fitting of experimental data revealed that the anharmonic constants depend strongly on nanoparticle size. The shape and spectral positions of maxima in second-order Raman scattering spectra have been theoretically described.