Frequency measuring system using mirror gap stabilized Fabry-Perot interferometer

The mirror gap of a Fabry-Perot interferometer was stabilized with two laser diodes; one locked to the line frequency 385,243,555.14445 MHz of the F=3<--1 in 5D(3/2)<--5S(1/2) (87Rb) and the other to the 385,284,566.3663 MHz of the F=4<--2 in 5D(5/2)<--5S(1/2) (87Rb) [Opt. Commun. 102 (1993) 432]. The length of the mirror gap was adjusted to generate the zero-cross points simultaneously at both of the two line positions. The fringe signals obtained from an interferometer thus stabilized can be used as frequency markers having accuracies of the order of 10(10) depending on the finesse of the interferometer used. Based on measurement using Cs D1 hyperfine lines reported by Udem et al. [Phys. Rev. Lett. 82 (1999) 3568], the uncertainty of markers in the region 50 THz apart from the reference lines is +/- 5 MHz.     

Electronic effect on the regioselectivity in the ring opening of para-substituted phenyloxiranes by acetylides

The electronic effect on the regioselectivity in the alkynylation of phenyloxiranes was investigated using three kinds of metal acetylides. BF₃ mediated lithium acetylide provided either the α- or β-alkynylated products by controlling the effect of the para-substituents of the phenyloxiranes. LiClO₄ mediated lithium acetylide and titanium acetylide, on the other hand, afforded predominantly the β- and α-products, respectively.     

Synthesis and self-aggregation of cyclic alkynes containing helicene

[structure: see text]. All stereoisomers of a cyclic alkyne containing three helicene units, 1,12-dimethylbenzo[c]phenanthrene, are synthesized using a building block. Isomeric [3 + 3]cycloalkynes aggregate in organic solvents. Vapor pressure osmometry reveals dimer formation of (M,M,M)-[3 + 3]cycloalkynes in chloroform and benzene at concentrations above 2 mM. No higher aggregation is observed. The chirality of helicenes plays an important role in self-aggregation, and diastereomeric (M,P,M)-[3 + 3]cycloalkyne forms a dimer only above 15 mM. Aggregation of racemic (M,M,M)-[3 + 3]cycloalkyne or (M,P,M)-[3 + 3]cycloalkyne is much weaker than that of a single enantiomer.     

Synthesis of photoreactive polyimide having indan structure

Polyimide containing an indan unit and alkyl moiety with a high molecular weight was prepared from 5,7‐diamino‐1,1,4,6‐tetramethylindan and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride. This polyimide was amorphous and soluble in common organic solvents, such as tetrahydrofuran, chloroform, and cyclopentanone. Thermogravimetry of the polyimide showed good thermal stability, indicating that a 10% weight loss of the polyimide was observed at 500 °C in nitrogen. The glass‐transition temperature of the polyimide was not observed by DSC measurement between room temperature and 400 °C at a heating rate of 10 °C/min (Apparatus: DSC3100 MAC Science Co., Ltd.). Transparency of the polyimide at 365 nm was 80%. The polyimide acted as a photosensitive resist of negative type by UV radiation. The resist had a sensitivity of 31 mJ/cm² and a contrast of 2.3 when it was developed with cyclopentanone at room temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 423–428, 2002     

Dipole moments of (styrene-p-chlorostyrene) triblock copolymers in solutions

(Styrene-p-chlorostyrene) triblock copolymers of the ABA and BAB types (A—polystyrene; B—poly-p-chlorostyrene) were prepared by anionic polymerization and their conformational behaviours in solutions were studied from measurements of the dipole moments. Two solvents, toluene and cumene, were used for the study; toluene is a good solvent for both polystyrene and poly-p-chlorostyrene whereas cumene is a selective solvent, good for polystyrene but poor for poly-p-chlorostyrene. It was found that the dipole moments of the block copolymers measured in toluene are the same for the ABA and BAB copolymers; in cumene however the dipole moment of the BAB copolymer is smaller than that of the ABA copolymer. The results give an additional support to our previous conclusion that the conformation of the block copolymers in a good solvent such as toluene could be approximated with a pseudo-random coil form; in a selective solvent, however, some anomalies take place in the conformation of the block copolymers, as deduced from intrinsic viscosity, osmotic pressure and light scattering measurements.     

Synthesis of aromatic polyamides by 1-hydroxybenzotriazole-catalyzed polycondensation of active aromatic diesters with aromatic diamines

Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed.     

Synthesis and antifungal activities of a series of (1,2-disubstituted vinyl)imidazoles.

A series of vinylimidazoles containing a hetero atom such as sulfur or oxygen at a beta-position of the vinyl group was prepared and the antifungal activities were tested. It was found that sulfur-substituted derivatives such as (E)-1-[2-(methylthio)-1-[2-(pentyloxy)phenyl]ethenyl]-1H-imidazole (5a-5) and (E)-1-[1-[2-(hexyloxy)phenyl]-2-(methylthio)ethenyl]-1H-imidazole (5a-6) showed excellent antifungal activities against dermatophytes and yeast cells. The stereochemistry of the hydrochloride salt of 5a-5 was determined by X-ray crystallography. The structure-activity relationships were discussed.