Pincer ligands based on α-amino acids: III. New ligands based on 4-substituted phenols and their copper complexes. Enantioselective recognition of tyrosine

Reactions of L-methionine, L-serine, and L-valine with 5-substituted-2-hydroxybenzene-1,3-dicarbaldehydes gave a series of chiral Schiff base pincer ligands which were reduced to the corresponding diamines. The new Schiff base ligands reacted with copper(II) chloride to form dinuclear copper complexes which were found to be capable of recognizing tyrosine enantiomers in aqueous solution. The structure of the complexes was determined on the basis of their spectral parameters.     

Edge diffraction of a Laguerre light beam

The phenomenon of transverse diffusion of ray amplitude along two principal orthogonal directions on the cylindrical surface of a diffracted boundary wave is observed in the diffraction of a Laguerre laser beam by the straight sharp edge of a planar safety-razor blade.     

Classical demonstration experiments on electricity and magnetism at the faculty of physics of Moscow State University

Lecture demonstrations are the most important phenomenological component of the general physics course. Many of them have been undeservedly forgotten or replaced with virtual experiments. In this paper, a number of experiments are considered, which most clearly illustrate the magnetic action of an electric current, interaction of currents, properties of magnets, phenomenon of electromagnetic induction, and principles of transformer operation.     

Electromagnetic waves in isotropic and gyrotropic media

Maxwell’s equations are considered for waves in transparent inhomogeneous anisotropic and gyrotropic media with time dispersion. A uniaxial inhomogeneous crystal is taken for an anisotropic medium and an isotropic heterogeneous medium in a constant electric field for a gyrotropic medium. The solutions for flat-layered and cylindrical media are presented in terms of Hertz potentials. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 82–86, March, 2008.     

Special features of the effect of cellular structure on the mechanical properties of foamed plastics

On the basis of the cell model proposed the mechanical characteristics of high-density foamed plastics are calculated. Assuming the general application of the foaming mechanism and the formation of macrostructure, the principle of structural-mechanical superposition of foamed plastics is established. This enables the equivalence of changes in their strength and elastic properties to be indicated over a wide range of variation of the stiffness of the polymer base and the apparent density of the foamed material.Scientific-Research Institute for Synthetic Resins, Vladimirsk. Translated from Mekhanika Polimerov, No. 6, pp. 976–981, November–December, 1972.     

Nuclear-matter distributions of halo nuclei from elastic proton scattering in inverse kinematics

Proton-nucleus elastic scattering at intermediate energies, a well-established method for probing nuclear-matter density distributions of stable nuclei, was applied for the first time to exotic nuclei. This method is demonstrated to be an effective means for obtaining accurate and detailed information on the size and radial shape of halo nuclei. Absolute differential cross-sections for small-angle scattering were measured at energies near 700 MeV/u for the neutron-rich helium isotopes ⁶He and ⁸He, and more recently for the lithium isotopes ⁶Li, ⁸Li, ⁹Li and ¹¹Li, using He and Li beams provided by the fragment separator FRS at GSI Darmstadt. Experiments were performed in inverse kinematics using the hydrogen-filled ionization chamber IKAR which served simultaneously as target and recoil-proton detector. For deducing nuclear-matter distributions, differential cross-sections calculated with the aid of the Glauber multiple-scattering theory, using various parametrizations for the nucleon density distributions as input, were fitted to the experimental cross-sections. The results on nuclear-matter radii and matter distributions are presented, and the significance of the data for a halo structure is discussed. Nuclear-matter distributions obtained for ⁶He and ⁸He conform with the concept that both nuclei compose of α-particle like cores and significant neutron halos. The matter distribution in ¹¹Li exhibits, as expected from previous reaction cross-section studies with nuclear targets, the by far most extended halo component of all nuclei being investigated. In addition the present data allow a quantitative comparison of the structure of the He and Li isobares of either the mass number A = 6 or A = 8. The measured differential cross-sections have also been used for probing density distributions as predicted from various microscopic calculations. A few examples are presented. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: p.egelhof@gsi.de     

Early onset of ground state deformation in neutron deficient polonium isotopes

In-source resonant ionization laser spectroscopy of the even-A polonium isotopes (192-210,216,218)Po has been performed using the 6p(3)7s (5)S(2) to 6p(3)7p (5)P(2) (λ=843.38 nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in (200-210)Po with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.     

Synthesis of 1,3,5-tribromo- and triiodophloroglucinol tris(triflates)

A method for the preparative synthesis of 1,3,5-tribromophloroglucinol and 1,3,5-triiodophloroglucinol tris(triflates) was suggested. This synthesis was shown to be extremely sensitive to reaction temperature conditions.     

Synthesis and antioxidant activity of modified sterically hindered phenols

Salicylaldehyde derivatives containing sterically hindered phenol fragments were synthesized. The compounds obtained are capable to offer protection against UV radiation.     

Spectral-kinetic characteristics of crystals and nanoceramics based on BaF<Subscript>2</Subscript> and BaF<Subscript>2</Subscript>: Ce

Optical characteristics of BaF₂ and BaF₂: Ce single crystals and nanoceramic materials prepared from these single crystals by uniaxial hot pressing have been studied. It has been shown that the introduction of Ce₃₊ ions into BaF₂ hardly affects the ultrafast (∼0.9 ns) luminescence component. The integrated luminescence intensity of the BaF₂: Ce nanoceramics is higher than that of the corresponding single crystal and considerably higher that the intensity of the undoped BaF₂ crystal. It has been demonstrated that the slow (several hundred nanoseconds) component of the luminescence decay of BaF₂: Ce is due to the energy transfer from excitons to Ce³⁺ ions.