Mechanical Properties of Materials Based on Graphene C62H20 and Polyethylene (–CH2–CH2–)n

Technical Physics - The mechanical properties of materials based on graphene C62H20 and polyethylene (–CH2–CH2–)n have been studied using the semiempirical PM3 method, and visual...     

Application of dual-frequency liquid crystal for tunable selective filtration of infrared radiation

The novel dual-frequency liquid crystal (DFLC) consisting of 4-n-pentyl-4′-cyanobiphenyl (5CB), 4-hexyloxyphenyl ester 4′-hexyloxy-3-nitrobenzoic acid (C2), and 4-n-pentanoyloxy-benzoic acid-4′-hexyloxyphenyl ester (H22) was developed and its basic dielectric characteristics were determined. Transmission spectra of the Al₂O₃ particles-DFLC system in both the ordinary electrooptical cell and the twist-structure were studied. It was shown that for certain changes in the frequency of the applied electric field, a transmission region maximum of the Al₂O₃ particles-DFLC ordinary cell switches from one wavenumber to the other. While the twist-structure of the system at low frequencies passes the light at the same wavenumbers but it becomes practically opaque at high frequencies. The experimental results are explained by the optical homogeneity of the system in a narrow wavelength interval when the refractive indices of the particle material and the matrix are close, and also by reorientation of the liquid crystal molecules as the frequency of the applied voltage changes.     

On a Sturm–Liouville type problem with retarded argument

In this work, a Sturm–Liouville‐type problem with retarded argument, which contains spectral parameter in the boundary conditions and with transmission conditions at the point of discontinuity are investigated. We obtained asymptotic formulas for the eigenvalues and eigenfunctions. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel type of tunable infrared filters based on the Al2O3 particles - Liquid crystal system

The optical transmission of small aluminum oxide particles in liquid crystal 4-methoxybenzylidene-4′-butylaniline (MBBA) and dual-frequency liquid crystal mixture consisting of 4-n-pentyl-4′-cyanobiphenyl (5CB), 4-hexyloxyphenyl ester 4′-hexyloxy-3-nitrobenzoic acid (C2), 4-n-pentanoyloxy-benzoic acid-4′-hexyloxyphenyl ester (H 22) was studied. It was established that there was a transmission band which was shifted on application of a voltage and depended on temperature. At using the dual-frequency liquid crystal as a matrix, a transmission band maximum switched at changing of the frequency. The experimental results are explained by the optical homogeneity of the system in a narrow wavenumber interval when the refractive indices of the particle material and the matrix are close, and also by re-orientation of the liquid crystal molecules when a voltage is applied.The obtained results can be used in constructing of tunable filters and compact monochromators.     

Disorder-induced Raman scattering of In1−xGaxP in the transverse acoustic phonon region

Raman scattering measurements have been performed on In_1?xGa_xP (0.62?x?1) over the entire frequency range of first and second order scattering. Besides the already known disorder activated band between the LO(Γ) and TO(Γ) modes a new disorder activated band is found in the region of transverse acoustic phonons around 87 cm^-1. The position of the new band shifts only slightly with composition while its strength and line-shape change.     

The second regularized trace of differential operator equation with the semi‐periodic boundary conditions

In this paper, we have obtained the second regularized trace formula for the differential operator equation with the semi‐periodic boundary conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Molecular dynamics of (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone in solution studied by NMR spectroscopy

The formation of hydrogen bonds and the molecular dynamics for molecules (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone, (E)-4-bromoacetophenone thiosemicarbazone have been investigated in solution using NMR. The results confirm the formation of different O-H…O type intramolecular hydrogen bonds in the oxime molecule. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined.     

Clark–Lagerwall effect in the small particles—Ferroelectric liquid crystal system

The smectic C* based on a three-component mixture of liquid crystals (LC) with not mesogene chiral additive and showing ferroelectric properties has been developed. The physical parameters which are responsible for electrooptical effects are defined. The Clark–Lagerwall effect both in the pure smectic C* and with the additive of small particles of the centrosymmetric substance Al₂O₃ and the ferroelectric SrTiO₃ is investigated. It has been shown that time characteristics of a cell with LC-Al₂O₃ are a little bit worsened in comparison with a cell with pure LC. It is caused by increase of the rotational viscosity of the ferroelectric liquid crystal with addition of small particles Al₂O₃. Time characteristics of the Clark–Lagerwall effect in the LC-SrTiO₃ cell essentially surpass time characteristics of the cell with pure LC because the transition from the deformed UP-state to the DOWN-state demands overcoming much lower energy than the transition from the pure UP-condition to the DOWN-state.     

Peculiarities of photoluminescence of porous silicon with luminescent liquid crystal fillers

Photoluminescence spectra of porous silicon filled by luminescent liquid crystals 5CB and H109 were investigated. It was observed that there were photoluminescence bands corresponding to both porous silicon and liquid crystal in experimental spectra. In addition, the band corresponding to porous silicon increases in comparison with photoluminescence of porous silicon without the filler. Experimental results are explained by the radiating and nonradiating energy transfer from liquid crystal to porous silicon.     

Molecular dynamics of 6‐methyl‐2‐phenyl‐2,3‐dihydro‐4H‐chromen‐4‐one and 6‐methyl‐2‐(4‐nitrophenyl)‐2,3‐dihydro‐4H‐chromen‐4‐one (flavanone) derivatives in a solution studied by NMR spectroscopy

Molecular dynamics of benzoxazepin, oxime, pyrazole, and thiosemicarbazone derivatives of some flavanones have been investigated in a solution using NMR. The results confirm the formation of different O–H···O, O–H···N, N···H–N type intramolecular hydrogen bonds in the pyrazole and oxime molecules. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined. Copyright © 2013 John Wiley & Sons, Ltd.