Miscibility of Hydrocarbon and Fluorocarbon Surfactants in Adsorbed Film and Micelle

We investigated the miscibility of nonionic hydrocarbon and fluorocarbon surfactants in the adsorbed film and the micelle by surface tension measurements of the aqueous solution. The combination of tetraethyleneglycol monodecyl ether (C10E4) and tetraethyleneglycol mono-1,1,7-trihydrododecafluoroheptyl ether (FC7E4) was chosen because they have the same hydrophilic groups and about the same surface activity. The extent of nonideal mixing was estimated quantitatively in terms of the excess Gibbs energy in the adsorbed film g(H,E) and that in the micelle g(M,E). The excess area per adsorbed molecule, A(H,E), was also evaluated and discussed. The ionic hydrocarbon and fluorocarbon mixed surfactant systems, lithium dodecyl sulfate (LiDS)/lithium perfluorooctane sulfonate (LiFOS) and lithium tetradecyl sulfate (LiTS)/LiFOS systems are also investigated from the standpoint of excess Gibbs energy and excess area. It is also clearly shown that the regular solution approach does not fit in the systems that contain ionic species. Copyright 2001 Academic Press.     

A new shoulder in luminescence spectra due to the triplet excitons in AgBr

Magneto-optical measurements of pure AgBr have been extended to cover the luminescence study. A new and intrinsic shoulder in luminescence spectra supposed to be due to “the indirect allowed triplet excitons” has been found, for the first time, for zone refined AgBr crystals at high magnetic fields up to 50 kOe.     

Revised structure of diastereomeric 3,8-di-t-butylspiro[4,4]nonane-1,6-diones

The recently assigned diastereomeric configuration of 3,8-di-t-butylspiro[4.4]nonane-1,6-dione has been revised based on the X-ray analysis.     

The synthesis of optically active pyridyl alcohols from the corresponding racemates by Catharanthus roseus cell cultures

A novel method for producing optically active pyridyl alcohols 1a-f from the corresponding racemates was developed. When racemic 3-pyridylphenylmethanol 1b is reacted with Catharanthus roseus cell cultures, (−)-1b is obtained in 96% yield with 100 %ee.     

Relationship between physicochemical characteristics and functional properties of chitosan

In order to select an ideal chitosan (CS) species as a material for implantation vehicle to control drug release in the body, the relationship between physicochemical characteristics (including molecular weight, degree of deacetylation, and viscosity) and functional properties (including ability to form spherical gel, control of drug release from CS gel, and biodegradation of CS) was investigated for various CS. The ease of spherical gel formation in aqueous amino acid solution or aqueous solution containing metal ions was affected mainly by viscosity of the CS solution. Drug diffusion rate from the CS gel was controlled by density of the gel matrix structure, which was governed by viscosity of the CS solution prior to gelation. Biodegradation of CS tended to vary with degree of deacetylation. However, linear relationships for these trends were not observed, and the possibility that characteristics other than CS molecular weight, degree of deacetylation, and viscosity of the CS solution, such as distribution of acetamide groups in the CS molecule affect functional properties of CS, was also indicated. These observations demonstrate that CS functions are affected by various CS characteristics and that investigation of individual CS characteristics is important for the selection of the appropriate CS as a material for drug delivery vehicles.     

The birch reduction of heterocyclic compounds. III. Birch reduction-elimination reaction of 2- and 3-furancarboxylic acid derivatives

The Birch reduction of 2-(1-alkoxyalkyl)furan-3-carboxylic acids 1a-f gave 2-alkyl-3-furancarboxylic acids 2a-f with loss of the alkoxyl group in excellent isolated yields.     

Oxidation reaction of [Ni(1,4,7-triazacyclononane)(2)](2+) by [Fe(o-phenanthroline)(3)](3+) in aqueous acidic solution at elevated pressures: determination of the activation and reaction volumes for the Ni(iii)/(ii) couple

The reaction volume corresponding to the self-exchange process of the [Ni(tacn)(2)](3+/2+) couple was determined in aqueous acidic solution. Theoretical equations on the basis of the Mean Spherical Approximation were proposed for the estimation of reaction volumes for M(n+/(n- 1)+) couples in solution, and the calculated reaction volumes were compared with the experimentally estimated values. The activation volume for the [Ni(tacn)(2)](3+/2+) couple was determined in the acidic condition from the cross reaction of [Ni(tacn)(2)](2+) and [Fe(o-phen)(3)](3+) at elevated pressures. The agreement of the experimentally estimated activation volume for the [Ni(tacn)(2)](3+/2+) couple, -8.2 +/- 2.4 cm(3) mol(-1), with the theoretically calculated value, -7.5 cm(3) mol(-1), within the allowed uncertainty (+/-1 cm(3) mol(-1)) indicates that the electron self-exchange reaction of this redox couple obeys the Marcusian behavior in aqueous acidic solution.     

FORMATION OF NON-VIABLE SPORES OF DICTYOSTELIUM DISCOIDEUM BY UV-IRRADIATION AND CAFFEINE

Abstract We have characterized the spores formed from amoeboid cells of the wild type strain of Dictyostelium discoideum after UV-irradiation. Cell differentiation in the presence of caffeine after a fluence of 300 J/m² resulted in a population of spores which was 98% non-viable. The UV-irradiation did not affect the conversion of the spores to swollen spores but did affect the conversion of swollen spores to amoeboid cells. When the germination of the spores was done without caffeine, we detected only a small effect on conversion of swollen spores to amoeboid cells and on the beginning of growth. On the other hand, in the presence of caffeine, the spores had a remarkable delay in both. It was also shown that few, if any, pyrimidine dimers exist in the DNA of the non-viable spores. Possible mechanisms of formation of non-viable spores are discussed.     

Catalytic C-C bond cleavage and C-Si bond formation in the reaction of RCN with Et3SiH promoted by an iron complex

Catalytic C-C bond cleavage of acetonitrile and C-Si bond formation have been attained in the photoreaction of MeCN with Et3SiH in the presence of an iron complex, Cp(CO)2FeMe. This catalytic system can be applied for arylnitrile C-C bond cleavage.     

STM observation of alkyl-chain-assisted self-assembled monolayers of pyridine-coordinated porphyrin rhodium chlorides

Alkyl-chain-assisted self-assembled monolayers of pyridine-coordinated porphyrin rhodium chlorides were observed at the solid-liquid interface by scanning tunneling microscopy (STM). The resolved images at a molecular level were obtainable in the pure solution of pyridine-coordinated porphyrin rhodium chloride with four triacontyl groups [Rh(C300PP)(Cl)(Py)]. In the case of pyridine-coordinated porphyrin rhodium chloride with four octadecyl groups [Rh(C18OPP)(Cl)(Py)], the STM images were not obtainable in the pure solution of Rh(C18OPP)(Cl)(Py) but obtainable in the mixture containing Rh(C18OPP)(Cl)(Py) and free porphyrin C18OPP. On the basis of the mixed self-assembled monolayer analysis, the apparent difference in the adsorption free energy between Rh(CnOPP)(Cl)(Py) and CnOPP (deltaGapp) was calculated. The calculated deltaGapp values for C18OPP and C30OPP mixed systems were quite different. The disadvantage of the adsorption free energy of Rh(C18OPP)(Cl)(Py) makes it difficult to obtain molecularly resolved images of Rh(C18OPP)(Cl)(Py), and the large adsorption energy due to the long alkyl chains enabled us to obtain molecularly resolved images of Rh(C30OPP)(Cl)(Py).