Statistical estimate of the deformation of a light pulse in the location of plane stratified clouds

The study of clouds in the lower atmosphere by means of laser location (lidar) started in the second half of the sixties. The first investigations in this direction by Ligda [1] and Collis [2–5] indicated the extensive prospects of optical probe systems in studying the structure and dynamics of clouds. The powerful lasers used in these systems (lasers with pulses as short as 10^–9 sec) help in identifying the upper and lower boundaries and the spatial inhomogeneity of clouds of fairly low density with the resolution necessary for projector probing. As in the case of radar, methods of studying atmospheric objects with lidars are based on an analysis of the information included in the reflected signal. The reflected signal in these cases is formed by the back-scattering of light on diffuse interaction with atmospheric inhomogeneities. The different meteorological nature (shower, fog, haze, etc.) and internal structure of the inhomogeneities reflect differently on the parameters of the signal. In general the intensity, the state of polarization, the shape of the envelope of the pulse, and the energy and frequency spectrum all vary. However, the extraction and analysis of the information contained in these changes in order to solve the inverse problem present an extremely complicated problem, as yet only solved in individual simple cases. In problems relating to the laser probing of clouds and mists, one of the most informative and easily-analyzed characteristics is the degree of deformation of the initial pulse by reason of the repeated scattering of photons. A number of preliminary estimates establishing a relationship between the parameters of the cloud layer and the shape of the reflected light pulse were presented in [6–9]. In [6, 9], in particular, the authors estimated the time characteristics of a diffusely-reflected light signal by the method of statistical tests [10], which is particularly suitable for solving multidimensional problems of atmospheric optics [11]. The algorithm of the Monte Carlo method proposed in [6, 9] and used in the present investigation enables us to allow for the complicated boundary conditions arising in the propagation of a divergent, spatially-limited light beam in a layer-like inhomogeneous scattering medium, and also the transient nature of the process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 50–53, February, 1973.     

Synthesis of (S)-proline derivatives with an alkylated N-benzyl substituent. Benzylation of (S)-indoline-2-carboxylic acid

The synthesis is reported of (S)-proline derivatives which contain a 2,4,6-trimethyl-, 4-tert-butyl-, or pentamethylbenzyl substituent on the nitrogen atom. Under similar conditions the benzylation of indoline-2-carboxylic acid was unsuccessful. Treatment of indoline-2-carboxylic acid with benzyl chloride in the presence of KOH in dimethylacetamide gave the benzyl ester of N-benzylindoline-2-carboxylic acid which is unstable on light.Laboratory of Biomembranes, University of South Bohemia, Branisovska 31, Ceske Budejovice 37005 Czech Republic. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 625–628, May, 2000.     

Self-oscillations of spins in a nanodimensional spin waveguide with localized sources of spin-polarized current

Spin oscillations and their phase synchronization are discovered in a spin 1D waveguide (nanowire) after the local injection of a spin-polarized current in the vertical (perpendicular) geometry of magnetization. The mode composition of nonlinear spin self-oscillations is analyzed for a single nano-oscillator using the effect of spin transfer torque with regard to spin wave runaway over the 1D waveguide and synchronized spin self-oscillations at current pumping by two nano-oscillators. It is shown specifically that, along with simple (“nontopological”) oscillation modes, in which singular points in the oscillation amplitude spatial distribution are absent, the 1D waveguide may support modes with pole-type singular points inside the current pumping domain, which are characteristic of the geometry of a precessing 2π-domain boundary. A diagram for frequency- and current-detuning-synchronized spin self-oscillations that are excited by two spin nano-oscillators in the 1D spin waveguide is constructed.     

Acetylation of α- and β-cyclodextrines

Applying acetyl chloride and versatile bases and solvents per- and regioacetylated derivatives of α- and β-cyclodextrines were prepared. Conditions were established for performing regiodirected acetylation of the primary hydroxy groups of α- and β-cyclodextrines in the presence of free secondary hydroxy groups.     

Synthesis of 1-Aryl-4-azolylbutanones

A convenient method was developed for the synthesis of substituted 4-azolyl-1-arylbutanones from the available γ-chlorobutyrophenones by successive stages of transformation into ketals, alkylation of sodium imidazolate or 1,2,4-triazolate by the ketals in DMF, and removal of the ketal protection. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1161–1167, August, 2005.     

Observation of laser-induced local modification of magnetic order in transition metal layers

Laser-induced local modifications of magnetic order in thin Fe-Cr layers were investigated. Local modification in the layers were induced by interfering laser beams. The results of the study give evidence for the formation of submicron-sized anisotropically shaped ferromagnetic regions with a well-defined direction of the easy magnetic axis in the interference maxima at the modification threshold. It was also found that the magnetic anisotropy of a medium is drastically reduced with changing the shapes of these local regions and distances between them. This may be due to the strengthening of the interaction between the regions through the paramagnetic matrix.     

Preparation of 4-(azol-1-yl)butyric acids by the interaction of azoles with γ-butyrolactone

The interaction of salts of imidazole, 1,2,4-triazole, benzimidazole, and 2-benzylbenzimidazole with γ-butyrolactone has been studied. Ab initio quantum-chemical calculations showed a preference for N-alkylation on interaction of azolates with γ-butyrolactone. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6. pp. 910–916, June, 2007.     

Copolymerization in N-vinylcaprolactam-N-vinylpyrrolidone and N,N-diethylacrylamide-N,N-dimethylacrylamide systems: The effect of composition and spatial structure of copolymers on their thermal sensitivity

Factors that affect the temperature-responsive properties of water-soluble polymers were revealed by studying the copolymerization of two pairs of monomers: N-vinylcaprolactam-N-vinylpyrrolidone and N,N-diethylacrylamide-N,N-dimethylacrylamide. In each pair, the first monomer forms a temperature-responsive polymer and the second gives a polymer soluble in water up to the boiling point. It was found that in all cases, the addition of the second (more hydrophilic) monomer resulted in a monotonous increase in the phase separation temperature in an aqueous copolymer solution, with the temperature rise being comparatively slow in the initial stage and sharply accelerating after the addition of more than 40–50 mol % second monomer. The phase-separation temperature versus copolymer composition curves for N,N-diethylacrylamide-N,N-dimethylacrylamide copolymers of iso-and heterotactic structure synthesized via anionic polymerization are rather similar. At the same time, the copolymers of both types prepared via radical polymerization are characterized by steeper curves, a pattern that may be due to a high content of the syndiotactic structure, however, changes in the copolymer spatial structure have a lesser effect on the phase separation temperature than the presence of units of a more hydrophilic monomer. The addition of a relatively low amount (20–25 mol %) of a less hydrophilic monomer imparts temperature sensitivity to polymers, such as polyvinylpyrrolidone or polydimethylacrylamide, which do not possess this property in the pure form.     

Features of the low-temperature specific heat in underdoped YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6 + <Emphasis Type="Italic">x</Emphasis></Subscript> single crystals

The behavior of the low-temperature specific heat C(T) for YBa₂Cu₃O_{6 + x} single crystals with the doping level corresponding to the normal phase has been studied by the relaxation technique at different values of the applied magnetic field. It has been found that the C(T)/T plot exhibits such an anomaly as a steep increase with decreasing temperature from T about 4 K down to T ≤ 2 K (the minimum temperature value accessible in the experiment). The applied magnetic field as high as 9 T inverts this anomaly and leads to a sharp drop in C(T)/T during cooling within the same temperature range. A model involving the Schottky-type centers formulated in this work and the data on spin correlation functions has allowed us to calculate the temperature dependence of the specific heat, which fits the experimental curves quite well.