Seed polymerization of tetraethyl orthosilicate in the presence of anionic and cationic polystyrene colloidal spheres

Kinetic analyses are made for the seed polymerization of tetraethyl orthosilicate (TEOS) in the presence of anionic and cationic polystyrene colloidal sphere seeds by turbidity and dynamic light-scattering measurements. Transmission-electron microscopy pictures of the spheres formed are also used. The seed polymerization of TEOS is difficult to take place on the surface of anionic polystyrene spheres (44–212 nm in diameter). On the other hand, the reaction proceeds easily on the cationic polystyrene spheres. Hairy and soft surfaces of polystyrene spheres will disturb the seed polymerization. Furthermore, the electrostatic attraction between the anionic hydrolytic products of TEOS molecules and cationic polystyrene spheres plays an important role for the seed polymerization.     

Powder-neutron diffraction studies of geometric isotope and hydrogen-bonding effects in β-CrOOH

Powder-neutron diffraction studies have been done on β-CrOOH and β-CrOOD to confirm whether or not the reported exceptionally large geometric isotope effect is real, and also to study hydrogen-bonding effects in β-CrOOH compared to the prototype CrO₂. The R(O?O) distance in the H-compound at room temperature is confirmed to be 2.472(3) Å, but in the D-compound it is significantly shorter, 2.518(3) Å, than in the earlier work. The resulting magnitude of the geometric isotope effect, 0.046(4) Å, is thus not as exceptionally large as earlier reported, but is still within the maximum range. Structural comparison with CrO₂ clarified the hydrogen-bonding effect in β-CrOOH: the formation of hydrogen bonds brings CrO₆ closer to a regular octahedron.     

Production of an Intense, Well-Collimated Submillimeter Wave Beam and Its Application to Plasma Scattering Measurements

Intense submillimeter wavelength radiation (f=354 GHz, P=110 W) from Gyrotron FU II is converted into a well-collimated, linearly-polarized beam by a quasi-optical transmission line consisting of a quasi-optical antenna and several mirrors. The observed focusing of the beam agrees with calculations based on the Huygens equation. We have used this intense beam to study low frequency density fluctuations by plasma scattering in Compact Helical System (CHS) plasmas at the National Institute for Fusion Science.     

Phasen?nderungen des Polyionen-Komplexes zwischen Polymethacryls?ure und einem Polykation, das Ladungen in der Hauptkette enth?lt

Ohne Zusammenfassung     

Selektive Adsorption von Metallionen an Poly(4-vinylpyridin)-Harzen, in denen die Liganden-Kette durch Vernetzung immobilisiert ist

Ohne Zusammenfassung     

Asymmetric problem of a semi-infinite body having a hemispherical pit under uniaxial tension

This paper presents an asymmetric solution for the stress distributions around a hemispherical pit at a plane surface of a semi-infinite body under uniaxial tension. In this analysis, eight stress functions were chosen so as to fulfill the boundary conditions automatically, both at the plane surface and at infinity. On the other hand, the remaining boundary conditions at the surface of the pit were satisfied with the aid of the half-range expansion technique. Numerical results are given for the variations around the pit and along the z-axis and compared with the corresponding results under biaxial tension.     

Electrochemical and ferromagnetic couplings in 4,4',4' '-(1,3,5-benzenetriyl)tris(phenoxyl) radical formation

4,4',4' '-(1,3,5-Benzenetriyl)tris(2,6-di-tert-butylphenol) was prepared by the cross-coupling of 1,3,5-tribromobenzene and [4-(trimethylsiloxy)phenyl]magnesium bromide. X-ray analysis of the single crystal showed a propeller-like structure with a mean dihedral angle of 39 degrees between the hydroxyphenyl and the core benzene. The phenoxyl mono-, di-, and triradicals were generated by the electrochemical oxidation of the trianion. A stepwise radical formation was revealed by a differential pulse voltammogram, electrolytic ESR spectroscopy, and a comproportionation reaction between the radicals, which was discussed as an effect of the pi-conjugated but non-Kekulé-type coupler. The quartet and triplet ground state for the tri- and diradical, respectively, were confirmed by a SQUID measurement.