Electron paramagnetic resonance and optical absorption spectra of Cr ions in cadmium phosphate glass

EPR and optical absorption investigations of chromium doped cadmium phosphate glass are carried out. Crystal field, spin-Hamiltonian and bonding parameters are evaluated. From the results and analyses of the EPR and optical studies, the site symmetry of Cr³⁺ ion in the glass is ascribed to a distorted octahedron. The bonding parameters suggest the ionic nature of Cr³⁺ ion with the ligands.     

Sulfur Concentration in Nanoporous Alumina Membrane

Nanoporous alumina membrane prepared by anodic oxidation using sulfuric acid electrolyte was subjected to TG-DTA and X-ray Photoelectron Spectroscopy (XPS or ESCA) to further study the distribution of sulfur. In XPS study, Ar⁺ ion bombardment was performed on the sample to etch the surface at a rate of 3 nm min^-1. As a result, sulfur was found to be concentrated within a depth of 3nm from the surface. The S content of the surface was found to be 2.7±0.5 wt%, and that at a depth of ca. 3 nm and ca. 10 nm was found to be as low as about 0.6±0.11 wt% (5.37±1.0 wt%→ 1.26±0.2wt% SO₂). In TG-DTA, the mass loss of 7.3% was in fair agreement with that calculated on XPS results (7.1±1.2%). This revised version was published online in July 2006 with corrections to the Cover Date.     

A fiberwise analogue of the Borsuk-Ulam theorem for sphere bundles over a 2-cell complex II

We describe a finite complex B as I-trivial if there does not exist a Z₂-map from Si−1 to S(α) for any vector bundle α over B and any integer i with i>dimα. We prove that the m-fold suspension of projective plane FP² is I-trivial if and only if m≠0,2,4 for F=C, m≠0,4 for F=H. In the case where F is the Cayley algebra, the m-fold suspension is shown to be I-trivial for every m>0.     

Mass spectrometric analysis of low molecular mass polyesters by laser desorption/ionization on porous silicon

A low molecular mass polyester was analyzed by desorption/ionization on porous silicon (DIOS) mass spectrometry. The results were compared with those of matrix-assisted laser desorption ionization (MALDI) mass spectrometry using matrixes of alpha-cyano-4-hydroxycinnamic acid (CHCA) and 10,15,20-tetrakis(pentafluorophenyl)porphyrin (F20TPP). The CHCA matrix was not suitable for characterization of low molecular mass components of the polyester because the matrix-related ions interfered with the component ions. On the other hand, the F20TPP matrix showed no interference because no matrix-related ions appeared below m/z 822. However, the solvent selection for determining optimal conditions of sample preparation was limited, because F20TPP does not dissolve readily in any of the available organic solvents. In the DIOS spectra, the polymer ions were observed at high sensitivity without a contaminating ion. No matrix is needed for DIOS spectra of low molecular mass polyesters, facilitating sample preparation and selectivity of a precursor ion in post-source decay measurements.     

Synthesis and photoinduced memory effect of poly[2-N-carbazolylethyl acrylate-co-2-(3,5-dinitrobenzoyloxy) ethyl methacrylate]

Copolymers containing an intramolecular electron donor-acceptor (EDA) complex were synthesized by free radical copolymerization of 2-N-carbazolylethyl acrylate and 2-(3,5-dinitrobenzoyloxy)ethyl methacrylate. Glass transition temperatures show a positive deviation from the weight-average values of copolymers, indicating the presence of the specific EDA interaction in copolymers in the solid state. Photoinduced “memory effect,” which is defined as the percentage of the difference of the surface potential given by corona charging before and after irradiation of light on polymer films, was 30% for the copolymer with 5 mol% of acceptor content. Memory effect increased to 70% for a 8 μm film by doping with 2 wt% of trichloroacetic acid (TCAA), and leveled off at 5 wt% of TCAA content. Memory effect was also enhanced by increasing the thickness of polymer films and irradiation time. The largest value of memory effect (85%) was obtained from the film of the copolymer with 5 mol% acceptor content doped with 1 wt% TCAA and with thickness larger than 14 μm.     

Synthesis and properties of new crystalline poly(arylene ether nitriles)

Crystalline poly(arylene ether nitrile) could be prepared by the polycondensation of 2,6-dihalobenzonitrile with resorcinol at 200°C in N-methylpyrrolidone in the presence of sodium carbonate. A reaction temperature of at least 200°C was necessary to attain high molecular weight polymer. Spectral data indicated that the polymer had the structure of a poly(meta-phenylene ether) with pendent nitrile groups on every other phenylene unit. Despite this structure, the crystallinity and the crystallization rate of the polymer were greater than those of the corresponding polymer with a para-linked structure. The glass transition temperature and the melting temperature of the polymer were almost the same as those of poly(etheretherketone) (PEEK^TM). A series of other new poly(arylene ether nitriles) were also examined. The polymers derived from 4,4′-biphenol, dihydroxytetra-phenylmethane, dihydroxydiphenylsulfone, and 1,5-isoquinolinediol had high glass transition temperatures. The poly(arylene ether nitriles) exhibited excellent tensile strength compared with the corresponding ketone- or sulfone-containing polymers. Comparing the three different kinds of polymers containing the same bisphenol units, the order of glass transition temperature was found to be sulfone- > nitrile- > ketone-containing polymers, while the order of tensile strength was nitrile- > ketone- > sulfone-containing polymers. The excellent mechanical properties are attributable to dipole-dipole interactions of nitrile groups. © 1993 John Wiley & Sons, Inc.     

POLYETHYLENE GLYCOL-MODIFIED HEMATOPORPHYRIN AS PHOTOSENSITIZER

Abstract— Hematoporphyrin, having two carboxylic groups, was coupled with α-(3-aminopropyl)-ω-methoxypoly(oxyethylene), PEG-NH₂, through acid-amide bond formed with carbodtimide. PEG-modified hematoporphyrin was readily soluble not only in neutral aqueous solution but also in organic solvents. Its absorption spectrum showed a sharp band at 376 nm in neutral aqueous solution and at 403 nm in benzene. Modified hematoporphyrin acted as a photosensitizer; imidazole and indole were photooxidized in organic solvents such as benzene or chloroform, and uric acid was also photooxidized in neutral aqueous solution.