Sequence distribution of repeating units of copolyamides by interfacial or solution methods

The sequence distribution of repeating units of copolyamides from different diamines with isophthaloyl or terephthaloyl chlorides and dithiophenyl adipate have been investigated either by interfacial or solution methods to aim at the sequence control of the copolyamides by solvents. Copolycondensation of dithiophenyl adipate and isophthaloyl chloride with m-xylylenediamine in various solvents yielded copolyamides having different compositions of repeating units. Aprotic polar solvents produced random copolyamides having the same compositions as feed ratios of the comonomers, while nonpolar solvents yielded copolyamides rich in isophthaloyl units. Also the sequence distribution of the copolyamides from m- and p-phenylenediamines with isophthaloyl chloride was affected by solvents; nonpolar solvents produced copolyamides having a less-random and block character of the repeating units either by interfacial or solution methods.     

Vinyl polymerization. 351. Polymerization of methyl methacrylate initiated with α-amylase and copper(II) ion in water

The polymerization of MMA initiated by a system of α-amylase, cupric chloride, and water was carried out. The effects of the amounts of water, copper(II) ion, and MMA on the conversion of MMA were studied. The overall activation energy was estimated to be 55 kJ/mole. Urea, known as a denaturing agent for protein, was found to increase the rate of polymerization and efficiency of grafting onto α-amylase.     

Bispectrum Analysis of One-Dimensional Regular Fractals with Additive Random Noise

The bispectrum of the Cantor set that is a typical regular fractal is calculated and its fractalities are shown. A relation between the bispectrum and the fractal dimension of the object is elucidated. Effects of additive random noise on the scaling property of the bispectrum are compared with those of the corresponding power spectrum.     

Estimation of HRTFs on the horizontal plane using physical features

Sound localization can be controlled by using head related transfer functions (HRTFs), which are related to the size of the head, the ears and so on. Since HRTFs are characterized by source directions and subjects, it is necessary to conduct measurements in all directions for all subjects. However, such measurement is expensive and time-consuming. In this paper, we propose a simpler and more useful method that investigates the relationship between HRTFs and physical size by multiple regression analysis. The estimated HRTFs are evaluated by objective and subjective measures. For objective results, the average spectral distortion score is 4.0 dB in a bandwidth ranging from 0 to 8 kHz. Subjective results indicate no significant difference between the measured and the estimated HRTFs in that frequency range. These results support the hypothesis that the proposed method is effective for estimating HRTFs.     

Palladium-catalyzed highly regio- and stereoselective synthesis of 4-alkylidene-4H-3,1-benzoxazines from N-acyl-o-alkynylanilines

The highly regio- and stereoselective 6-exo-dig mode cyclization of N-acyl-o-alkynylanilines producing 4-alkylidene-3,1-benzoxazines occurred unpredictably by use of a proper catalyst [Pd(OAc)(2)] and an effective additive (acetic acid) under suitable reaction conditions.     

4-Carbomethoxybenzaldehyde as a highly sensitive pre-column fluorescence derivatization reagent for 9,10-phenanthrenequinone

9,10-Phenanthrenequinone (PQ) is harmful environmental pollutant that is detected in airborne particulates. The measurement of PQ in the air should be necessary to evaluate the potential adverse effects of PQ on human health. We have recently developed a determination method for PQ based on the fluorescence derivatization of PQ using benzaldehyde and ammonium acetate as a reagent. In this study, in order to obtain more sensitive and selective fluorescence derivatization reaction, we measured the fluorescence of the reaction mixture of PQ with 21 kinds of aromatic aldehydes in the presence of ammonium acetate. Among the tested aldehydes, 4-carbomethoxybenzaldehyde was found to be the best reagent in regard to fluorescence intensity and emission wavelength maximum. Based on the fluorescence derivatization with 4-carbomethoxybenzaldehyde, a highly sensitive chromatographic method was developed for the determination of PQ with the detection limit (S/N=3) of 1.2 fmol/injection.     

Temperature dependence of multilayering at the free surface of ionic liquids probed by X-ray reflectivity measurements

The effect of the temperature on the surface layering of ionic liquids has been studied for two ionic liquids, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide([TOMA(+)][C(4)C(4)N(-)]) and trihexyltetradecylphosphonium bis(nonafluorobutanesulfonyl)amide ([THTDP(+)][C(4)C(4)N(-)]), using X-ray reflectivity measurements at 285, 300, and 315 K. Both [TOMA(+)][C(4)C(4)N(-)] and [THTDP(+)][C(4)C(4)N(-)] develop multilayers at the surface. The structure of the multilayers at the [TOMA(+)][C(4)C(4)N(-)] surface shows little temperature-dependent change, whereas that at the [THTDP(+)][C(4)C(4)N(-)] surface clearly becomes diffused with increasing temperature. The different temperature dependence seems to be related to the difference in the recently reported ultraslow dynamics of the interfacial structure of [TOMA(+)][C(4)C(4)N(-)] and [THTDP(+)][C(4)C(4)N(-)] at the ionic liquid|water interface.     

Orange and yellow crystals of copper(I) complexes bearing 8-(diphenylphosphino)quinoline: a pair of distortion isomers of an intrinsic tetrahedral complex

The tetrafluoroborate salt of bis{8-(diphenylphosphino)quinoline}copper(I), [Cu(Ph(2)Pqn)(2)]BF(4), afforded orange prismatic (2O) or yellow columnar (2Y) crystals, dependent on the solvent and concentration of the recrystallization solution used. X-ray analysis revealed that crystals of 2O and 2Y had the same composition and exhibited different crystal systems: 2O was triclinic, with space group P ?1 and Z = 2, and 2Y was monoclinic with space group P2(1)/c and Z = 4. In these crystals, the tetrahedral copper(I) complex exhibited a strong "rocking distortion" toward a trigonal pyramidal coordination geometry (by a slide translation of one of the unsymmetrical bidentate chelating ligands along the tetrahedral edge). In addition, both the 2O and 2Y complexes showed a "flattening distortion", meaning that the dihedral angle between the two chelate planes were off-perpendicular and oriented toward opposite directions, which resulted in a pair of distortion isomers: syn clinal (sc: 2O) and anti clinal (ac: 2Y). (31)P CP-MAS NMR spectroscopy indicated that 2O and 2Y could be distinguished. Both isomers exhibited inequivalent P atoms, but a larger difference in chemical shift was observed in 2Y. TD-DFT calculations reproduced the difference in spectra between the orange- and yellow-colored complexes, which originated from metal-to-ligand charge-transfer transitions.