Synthesis of new racemic and optically active N‐phosphonoalkyl bicyclic β‐amino acids via the kabachnik–fields reaction as potential biologically active compounds

Novel racemic and optically active constrained N‐phosphonoalkyl bicyclic β‐amino acids have been synthesized via the Kabachnik–Fields reaction of the (RS) or (R)‐1‐aminobicyclo[2.2.2]octane‐2‐carboxylic acids with paraformaldehyde and benzaldehyde, and the dimethyl‐H‐phosphonate. The structure of obtained compounds was characterized by NMR (¹H, ¹³C, and ³¹P), LC/MS, and X‐ray diffraction analyses. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:123–130, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20759     

A relaxation method for solving systems with infinitely many linear inequalities

The problem of finding a feasible solution to a linear inequality system arises in numerous contexts. We consider solving linear semi-infinite inequality systems via an extension of the relaxation method for finite linear inequality systems. The difficulties are discussed and a convergence result is derived under fairly general assumptions on a large class of linear semi-infinite inequality systems.     

Four Mutually Orthogonal Latin Squares of Order 14

The paper gives example of orthogonal array OA(6, 14) obtained from a difference matrix . The construction is equivalent to four mutually orthogonal Latin squares (MOLS) of order 14. © 2012 Wiley Periodicals, Inc. J. Combin. Designs 20: 363–367, 2012     

Chiral amine-induced stereoselectivity in trans-β-lactam formation via Staudinger cycloaddition

A series of chiral trans-β-lactams was obtained via Staudinger cycloaddition with low to moderate diastereoselectivity (up to 54% de) induced by a chiral amine component of the imine. It was shown that the direct connection of nitrogen to a chiral centre is crucial to induce chirality; moderate asymmetric induction was achieved by using isomeric 1-phenylethylamines, which are among the cheapest chiral sources on the market, while low diastereoselectivity was obtained from 3-aminomethylpinane, where the chiral centres are distant from nitrogen by a methylene group. It was shown, that an increase of the reaction temperature from 110 °C to 140 °C led to commensurable results but speeded-up the transformation significantly. The absolute configurations of phenylethylamine derivatives were determined by X-ray analysis of selected samples.     

Single crystals growth and absorption spectra of Cr-doped Al2−xInx(WO4)3 solid solutions

The growth conditions of pure and Cr³⁺-doped Al_2−xIn_x(WO₄)₃ single crystals, using top-seeded solution growth (TSSG) technique, have been studied. A series of experiments have been performed at different In concentrations, x=0.0, 0.3, 0.6 and 1.0, as well as at different concentrations of Cr³⁺ (0.0, 0.1, 0.2, 0.5 and 1.0) in at% with respect to the initial total concentration of Al and In in the starting solutions. The basic parameters of the crystal growth are varied over a wide range: seed orientation, speed of rotation, axial and radial temperature differences in the solution and the solution cooling rate. The investigated relations between the basic defects in the crystals and these parameters result in determination of the optimal conditions for growth of defect-free crystals. Distribution coefficients of Al, In and Cr have been determined, so the growth of crystals with given compositions is possible. Values of Dq/B (crystal field strength) for the various crystal compositions are calculated from the optical absorption spectra. The calculated values show that the discussed solid solutions have weak crystal field and are suitable for media with broadband emission spectra.     

Self-compression and controllable guidance of multi-millijoule femtosecond laser pulses

Self-compression of multi-millijoule femtosecond laser pulses and dramatic increase of the peak intensity are found in pressurized helium and neon within a range of intensity in which the ionization modification of the material parameters by the pulse is negligible. The pulse propagation is studied by the (3 + 1)-dimensional nonlinear Schrödinger equation including basic lowest order optical processes - diffraction, second order of dispersion, and third order of nonlinearity. Smooth and well controllable pulse propagation dynamics is found. Construction of compressed pulses of controllable parameters at given space target point by a proper chose of the pulse energy and/or gas pressure is predicted.     

Computer models in room acoustics: The ray tracing method and the auralization algorithms

Computer algorithms are described for constructing virtual acoustic models of various rooms that should satisfy some specific sound quality criteria. The algorithms are based on the ray tracing method, which, in the general case, allows calculation of the amplitude of an acoustic ray that survived multiple reflections from arbitrary curved surfaces. As a result, calculations of room acoustics are reduced to tracing the trajectories of all the acoustic rays in the course of their propagation with multiple reflections from reflecting surfaces to the point of their complete decay. For this approach to be used, the following physical properties of a room should be known: the geometry of the reflecting surfaces, the absorption and diffusion coefficients on each of these surfaces, and the decay law for rays propagating in air. The proposed models allow for the solution of the important problem of architectural acoustics called the auralization problem, i.e., to predict how any given audio segment will sound in any given hall on the basis of computer simulation alone, without any full-scale testing in specific halls.