Finite arithmetical affine complete algebras having no proper subalgebras

Presented by E. Fried.     

Dark and photomagnetoresistance in semi-magnetic semiconductors

Summary Magnetic-field dependence of electron mobility and photoconductivity in semi-magnetic semiconductors are studied both theoretically and experimentally. The electron relaxation times due to various scattering mechanisms are calculated paying special attention to spin disorder and alloy scatterings. The calculated mobility in Cd_1−c Mn _c Te is compared with experimental photomagnetoresistance (PMR) results. It is concluded that the magnetic-field-dependent mobility may contribute significantly to PMR at high Mn concentrations and low temperatures. Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982.     

Tolokonnikov’s Lemma for Real H ∞ and the Real Disc Algebra

We prove Tolokonnikov’s Lemma and the inner-outer factorization for the real Hardy space , the space of bounded holomorphic (possibly operator-valued) functions on the unit disc all of whose matrix-entries (with respect to fixed orthonormal bases) are functions having real Fourier coefficients, or equivalently, each matrix entry f satisfies for all z ∈ . Tolokonnikov’s Lemma for means that if f is left-invertible, then f can be completed to an isomorphism; that is, there exists an F, invertible in , such that F = [ f f _c ] for some f _c in . In control theory, Tolokonnikov’s Lemma implies that if a function has a right coprime factorization over , then it has a doubly coprime factorization in . We prove the lemma for the real disc algebra as well. In particular, and are Hermite rings. The work of the first author was supported by Magnus Ehrnrooth Foundation. Received: December 5, 2006. Revised: February 4, 2007.     

Choice of Reference Electrode is Critical for Potentiometric Whole Cell‐based Sensor

Cells have a net negative outer charge which gives rise to a potential difference in a potentiometric set up. Here, Triton X‐100 was used as a model toxin and the cell death was monitored by the potential change, noticed as decrease in negativity. Hence, cytotoxicity can be tested in vitro and real‐time using potentiometry. However, silver ions (Ag⁺) and/or silver chloride ions (AgCl₂)^?1 lead to cell death when we used the standard Ag/AgCl reference electrode with 3 M NaCl as filling solution. Our further experimentation showed that PBS as filling solution was biocompatible and also gave stable potentiometric profiles.     

A new approach to construct a fused 2-ylidene chromene ring: highly regioselective synthesis of novel chromeno quinoxalines

Regioselective construction of a fused 2-ylidene chromene ring was achieved for the first time by using AlCl(3)-induced C-C bond formation followed by Pd/C-Cu mediate coupling-cyclization strategy. A number of chromeno[4,3-b]quinoxaline derivatives were prepared by using this strategy. Single crystal X-ray diffraction study of a representative compound e.g. 6-(2,2-dimethylpropylidene)-4-methyl-6H-chromeno[4,3-b]quinoxalin-3-ol confirmed the presence of an exocyclic C-C double bond with Z-geometry. The crystal structure analysis and hydrogen bonding patterns of the same compound along with its structure elaboration via propargylation followed by Sonogashira coupling of the resulting terminal alkyne is presented. A probable mechanism for the formation of 2-ylidene chromene ring is discussed. Some of the compounds synthesized showed anticancer properties when tested in vitro.     

Lcao-Gáspár-Kohn-Sham energy bands of trans-polyacetylene-chain

The band structure of the dimerised trans-polyacetylene-chain ($\text{d}{}_{\mathrm{<mtext>CC</mtext>}}\text{= 1.35}\text{A}\text{?}$, $\text{d}{}_{\mathrm{<mtext>CC</mtext>}}\text{= 1.46}\text{A}\text{?}$, $\text{?}\text{CCC}\text{= 120°}$, $\text{d}{}_{\mathrm{<mtext>CH</mtext>}}\text{= 1.09}\text{A}\text{?}\text{)}$ is calculated with the (parameter-free, non-self-consistent) linear-combination-of-atomic-orbitals method using the Gáspár-Kohn-Sham (GKS) potential for the exchange and correlation. The calculated dimerisation gap of 1.6 eV agrees closely with experiment and also with other GKS calculations when the degree of dimerisation is taken into account. The calculated density of states agrees closely with the X-ray photoemission spectrum of Brundle.     

Metal binding characteristics of a laterally nonsymmetric aza cryptand upon functionalization with a pi-acceptor group

The laterally nonsymmetric aza cryptand synthesized by condensing tris(2-aminoethyl)amine (tren) with tris[[2-(3-(oxomethyl)phenyl)oxy]ethyl]amine readily forms mononuclear inclusion complexes with both transition and main-group metal ions. In these complexes, the metal ion occupies the tren-end of the cavity making bonds with the three secondary amino and the bridgehead N atoms. When a strong pi-acceptor group such as 2,4-dinitrobenzene is attached to one of the secondary amines, the binding property of the cryptand changes drastically. When perchlorate or tetrafluoroborate salts of Ni(II), Cu(II), Zn(II), or Cd(II) are used, the metal ion enters the cavity which can be monitored by the hypsochromic shift of the intramolecular charge-transfer transition from the donor amino N atom to the acceptor dinitrobenzene. However, in the presence of coordinating ions such as Cl(-), N(3)(-), and SCN(-), the metal ion comes out of the cavity and binds the cryptand outside the cavity at a site away from the dinitrobenzene moiety. Four such complexes are characterized by X-ray crystallography. Thus, a metal ion can translocate between inside and outside of the cryptand cavity depending upon the nature of the counter anion.     

Monitoring ultrathin film photopolymerization of tetra‐alkylepoxyporphyrin by UV‐Vis spectroscopy

Cationic photopolymerization is a convenient in situ polymerization method for organic thin film preparation. In this work, the polymerization mechanisms is applied for highly viscous cross‐linking monomers, using tetra‐alkylepoxyporphyrin (TAEP) as a case study. By comparing the UV‐Vis spectra of the polymerized sample before and after the unreacted monomers have been dissolved, it is possible to estimate the polymerization yield. An IR spectrum of a reference thick film confirms full polymerization. Scanning fluorescence lifetime microscopy and AFM show the uniformity of the polymer. It was shown that photopolymerization is highly dependent on the substrate nature and requires at best case a 10 min illumination at 90 °C. Thermal polymerization of the same sample requires 10 min heating at 150 °C in dark. It was also shown that TAEP works as a self‐sensitizer for cationic photopolymerization. The proposed method is a mild and versatile technique for in situ preparation of thin polymeric films directly from chromophore monomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6095–6103, 2009