Excimer dynamics in poly(N-vinylcarbazole) films

Using a mode-locked Nd³⁺: YAG laser and a streak camera, the formation process of excimers in poly(N-vinylcarbazole) film was directly measured to be quite rapid (<100 ps). The excimer—excimer interaction in polymer film was demonstrated for the first time, and compared with the S₁-S₁ annihilation process of molecular crystals.     

A new determination of the absolute configuration of the chiral amine

A new method for assignment of the absolute configuration of the asymmetric carbon atom attached to an amino or imino group using rac.-3-hexadecanoyl-4-methoxycarbonyl-1,3-thiazolidine-2-thione (rac.-HDMTT) ($\text{4}$) is described.     

The structure of prostaglandin B1 dimer

Dimeric derivatives of prostaglandin B₁ were prepared under alkaline conditions and the structures were determined by NMR spectroscopies.     

On the kernel of the Magnus representation of the Torelli group

From our previous paper, it is known that the Magnus representation of the Torelli group is not faithful. In this paper, we characterize the kernel of its representation for a certain kind of elements.

     

Separation and determination of purpurea glycosides in Digitalis purpurea leaves by micro-HPLC

A micro high-performance liquid chromatographic (micro-HPLC) method was developed for the determination of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin in Digitalis purpurea leaves. The extract of dry leaf powder was applied to a Sep-Pak silica cartridge followed by preparative thin-layer chromatography prior to micro-HPLC analysis. The analysis was performed on an ODS micro column, using acetonitrile-methanol-water (21:20:45) and ultraviolet detection (220 nm). The amounts of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin per 100 mg of dry leaf powder were estimated to be 52.6, 50.7, and 108.6 μg, respectively.     

Polymerization of propylene carbonate

Polymerization of propylene carbonate was carried out at 120–180°C mainly with the use of diethylzinc catalyst. The polymer was a pale-yellow, viscous material of relatively low molecular weight (1000–4000). From the spectroscopic analysis of the polymer and its hydrolyzed product, the polymer was determined to have the structure where x ? 0.50, y ? 0.25, and z ? 0.25. This strongly suggested that the polymerization of propylene carbonate proceeded via 2,7-dimethyl-1,4,6,9-tetraoxaspiro[4,4]nonane (DTN) as an intermediate compound. Hence, DTN was synthesized and polymerized with the use of diethylzinc catalyst. The structure of the polymer thus prepared coincided exactly with that of the polymer from propylene carbonate. From these, a plausible mechanism of the polymerization was developed.     

Numerical algorithms for the Moore-Penrose inverse of a matrix: Direct methods

Summary Direct methods for computing the Moore-Penrose inverse of a matrix are surveyed, classified and tested. It is observed that the algorithms using matrix decompositions or bordered matrices are numerically more stable.