The effect of phase difference of subpicosecond IR laser pulses propagating in a GaAs/ZnTe periodic structure on the efficiency of generation of the sum and difference frequencies radiations

The results of theoretical research and numerical simulation of the nonlinear interaction process of mutually orthogonal and linearly polarized IR subpicosecond laser pulses with the one-dimensional periodic structure of the GaAs/ZnTe are presented. In particular, the interaction of such pulses with the equal amplitude electric field of 70.71 MV/m, with the duration of 333 fs at the central wavelength λ₀ = 10 μm, with the periodic structure of the GaAs and the ZnTe with the thickness of layers equal to λ₀/2n_GaAs = 1.527 μm and λ0/4n_ZnTe = 0.931 μm, respectively, and with the number of periods equal to 100 is considered. It is shown that the efficiency of generation of sum and difference frequencies is proportional to the phase difference of the interacting IR pump pulses.     

The performance of the jet identification and reconstruction in heavy ions collisions with CMS detector

A jet reconstruction algorithm is developed for events with a high particle density in the calorimetric system. The performance of the reconstruction of hard QCD jets with initial parton energies 50–300 GeV is studied in central Pb–Pb collisions with a modified cone jet finder which includes an algorithm for event-by-event background subtraction. The heavy ion background is simulated using the HIJING Monte Carlo generator with . Results on the achieved jet reconstruction efficiency, purity, energy and spatial resolution are presented.     

Wave nonreciprocity in inhomogeneous gyrotropic media and multilayer systems: I. Inhomogeneous gyrotropic media

The propagation of electromagnetic waves in naturally (or structurally) gyrotropic inhomogeneous media is considered. A new mechanism of wave nonreciprocity is found, which is caused by the simultaneous presence of a gradient of one of the parameters of a medium and natural (or structural) gyrotropy. The problem of light transmission through a layer of a naturally gyrotropic inhomogeneous medium of finite thickness is solved by the method of addition of layers. Specific features of this nonreciprocity are considered. It is shown that such a system can operate as a one-sided reflector at certain angles of incidence of light. The mechanisms of enhancement of the nonreciprocity effects are investigated. It is shown that multiple reflections in a layer of finite thickness and diffraction of light by periodic inhomogeneities of a medium increase the nonreciprocity effects by several (from 2 to 5) orders of magnitude. This phenomenon, in turn, opens new fields of application of the nonreciprocity effects. Another interesting manifestation of wave nonreciprocity is revealed, which consists in asymmetry of the curve R(?):R(?)≠R(??) (R is the reflectance and ? is the angle of incidence).     

X-Ray structural investigation of 1,3,6-trichloro-3,6-dimethylcycloheptanecarbonitrile and 2,5-dimethyl-2,5-dichlorohexane — Products of the reaction of 2,5-dimethyl-1,5-hexadiene with trichloroacetonitrile

Addition of trichloroacetonitrile to 2,5-dimethyl-1,5-hexadiene in the presence of cuprous amine complexes is studied. Single crystal X-ray diffraction unambiguously proves that the main product is a racemic mixture of the cyclic symmetric nitrile: (1r,3R,6S)-and (1r,3S,6R)-1,3,6-trichloro-3,6-dimethylcycloheptanecarbonitrile. Established relative configuration of the product confirms the ring closure mechanism suggested before. Also, a side product 2,5-dimethyl-2,5-dichlorohexane is isolated (the product of hydrochlorination of the starting alkadiene). Low-temperature (190 K) structural examination of this centrosymmetrical molecule indicates that the unit cell comprises one molecule.     

Study on cyanobiphenyl nematic doped by silver nanoparticles

We study the effects of doped (1%wt and 2%wt) silver nanoparticles on material properties of nematic liquid crystal: 4-pentyl-4′-cyanobiphenyl. Using differential scanning calorimetry, electrical and dielectric measurements methods, we show that the doped NPs do not affect the nematic’s phase clearing point, lower the dielectric anisotropy, viscosity, switching-off time, and increase the threshold voltage and elasticity of the nematic. We report that the doped materials temperature behaviour of Frederick’s transition threshold voltage and switching-off time, deviates from the expected behaviour for pristine nematics. To explain this anomalous behaviour, we perform data analysis of the governing Frederick’s transition material parameters of studied samples. We show that the elastic parameter of doped samples is not following the predictions of Maier–Saupe theory, which is valid for conventional nematics. We report that the doped samples temperature behaviour of the elastic parameter follows the predictions of the Gelbart and Ben-Shaul theory.     

Some aspects of copolymerization of dienes under the influence of π-allyl complexes of nickel

π-Allyl complexes of nickel induce stereospecific homopolymerization of cyclohexadiene-1,3 and 2,3-dimethylbutadiene with the formation of crystalline polymers. These polymers consist of 1,4-monomer units in cis-configuration for polycyclohexadiene and in trans-configuration for poly-2,3-dimethylbutadiene. Peculiarities of copolymerization of cyclohexadiene-1,3 with butadiene and isoprene and of 2,3-dimethylbutadiene with butadiene under the influence of various π-allyl complexes of nickel are studied. By i.r.- and NMR-spectroscopy and radiochemical methods, the composition of copolymers for the above pairs of monomers are determined and the reactivity ratios are found. Influence of the monomers on the microstructure of the chain in copolymerization is established; the mechanism of this phenomenon is discussed.