The performance characteristics of the Hamamatsu R928 side‐window photomultiplier tube have been evaluated in the picosecond time domain. This phototube is proposed as an attractive solution to the problem of high time resolution when a sync‐pumped dye laser is combined with the single‐photon time correlation method for determining fluorescence lifetimes and measuring time‐resolved emission spectra and polarization anisotropy. It combines excellent timing characteristics in the single‐photon mode and a small‐to‐negligible wavelength effect with high gain, low noise, and low cost. Twice the resolution previously reported has been obtained.

Performance characteristics of a small side-window photomultiplier in laser single-photon fluorescence decay measurements

Supersymmetry in the picric acid and pyrazole structural classes

The systematics of heterocycles, their place in organic chemistry, and their significance for theory and practice are discussed. Problems of the chemistry of heterocycles are discussed on the examples of systems with various types of conjugation and ring sizes. The focus is on the principles of synthesis of heterocycles, in particular, those based on acetylene, various C3 fragments, carbon disulfide, and maleic anhydride. Individual sections of the survey are devoted to the role of heterocycles in biosynthesis, as well as certain problems common to the chemistry of heterocycles, biochemistry, and macromolecular chemistry.

Aspects and prospects of the chemistry of organic heterocycles (review). Part I

X-Ray diffraction of the title compound shows that the molecule is planar. The bond lengths of the central cyclopenta[b]pyran system indicate pronounced bond alternation and hence little aromatic character. The results of ωβ-calculations are in good agreement with the experimental bond distances.

Fred W. Clark

Papers

pseudo-Azulenes. Part 7. Crystal and molecular structure of benzo-[b]indeno[1,2-e]pyran