Structural properties of the condensate in two-dimensional mesoscopic systems of strongly correlated excitons

A two-dimensional mesoscopic Bose system of dipoles in a 2D trap is considered using computer simulation by the quantum path-integral Monte Carlo method. The model describes a rarefied system of spatially indirect excitons in a confining potential. Bose condensation in the system and its superfluid and structural properties are studied over a wide range of interparticle spatial correlations, from an almost ideal Bose gas to the regime of a strongly correlated system. It is found that, at strong interparticle spatial correlations, particles in the condensate form a crystal-like structure. In this case, the spatial correlations of particles in the condensate are less pronounced than the correlations of noncondensed particles. The effect of recurrent crystallization is observed in the regime of strong interparticle correlations.     

Iteration scheme for accelerometer unit calibration by a guaranteeing approach

Methods for accelerometer unit calibration are usually based on sufficiently strict requirements on the knowledge of the gravity orientation with respect to the unit (of the order of fractions of an arc minute). But it is not always possible to know the orientation with such high accuracy. In the present paper, we consider an approach to accelerometer unit calibration for whose implementation it suffices to have rough angular information (of the order of tens of arc minutes). We use a guaranteeing approach to calculate optimal schemes calibration experiments and propose an iterative scheme of calibration.     

Features of light attenuation in crystals under violation of the Bouguer law

A computer simulation and measurements of the light transmittance of germanium and paratellurite crystals of different thickness were used to show that, at scattering probabilities of photons comparable to their absorption probabilities, the standard methods for calculating light extinction coefficients on the basis of the Bouguer law lead to rough errors in estimation of the optical quality of a material.     

A retractable structure based on Bricard linkages and rotating rings of tetrahedra

Retractable structures which alter their geometries according to practical requirements are widely used in roof structures of stadiums for their versatility. A retractable structure based on threefold-symmetric Bricard linkages and rotating rings of tetrahedra is proposed and developed in this paper. By replacing each link of a threefold-symmetric Bricard linkage with a tetrahedron, a retractable structure is obtained which can repeatedly open and close by rotating the tetrahedra. The geometric relationship between the retractable structure and the threefold-symmetric Bricard linkage is derived and ranges of main geometric parameters are determined to ensure a continuous and smooth movement in the deployment of the structure. Then the relative displacement of the support and the open rate of the structure, two main parameters concerned in practical applications, are investigated. Preferred ranges of main geometric parameters are proposed and a physical model is manufactured to verify them. A discussion on some possible improvements and modifications of the structure is also presented.     

Chlorination and oxidation products formed from 1,2,4-trimethylbenzene in aqueous solution under the action of chlorine dioxide

Products of the reaction of 1,2,4-trimethylbenzene with chlorine dioxide in aqueous solution were studied. A scheme of 1,2,4-trimethylbenzene transformations was suggested. The influence exerted on the number of the reaction products by the ClO₂ dosage and time of its contact with the substrate was examined.     

Synthesis and characterization of wholly aromatic poly(azomethine)s containing donor–acceptor triphenylamine moieties

N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine was synthesized from N‐(4‐nitrophenyl)‐diphenylamine by the Vilsmeier‐Haack reaction. Soluble aromatic poly(azomethine)s (PAMs) were prepared by the solution polycondensation of N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine and aromatic diamine in N‐methyl‐2‐pyrrolidone (NMP) at room temperature under reduced pressure. All the PAMs are highly soluble in various organic solvents, such as N,N‐dimethylacetamide (DMAc), chloroform (CHCl₃), and tetrahydrofuran (THF). Differential scanning calorimetry (DSC) indicated that these PAMs had glass‐transition temperatures (T_gs) in the range of 170–230 °C, and a 10% weight‐loss temperatures in excess of 490 °C with char yield at 800 °C in nitrogen higher than 60%. These PAMs in NMP solution showed UV‐Vis charge‐transfer (CT) absorption at 405–421 nm and photoluminescence peaks around 462–466 nm with fluorescence quantum efficiency (Φ_F) 0.10–0.99%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of these PAMs can be determined from cyclic voltammograms as 4.86–5.43 and 3.31–3.34 eV, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4921–4932, 2007     

Metal complexes of 2-hetarylindandiones-1,3

The chelate and molecular complexes of 2-(2-benzazolyl, perimidyl)-indandiones-1,3 were synthesized for the first time. The structures of the ligands (tautomeric forms) and complex compounds were determined from the X-ray diffraction, ¹H, ¹³C NMR, and IR data and the quantum-chemical calculations (RHF SCF in 6-31 G** basis).