Morphology and protonic conductivity of the polyurethanes with acid groups in the flexible segment

Thermal transitions, morphology and electric conductivity of polyurethanes that contain acid (COOH) groups bound to their polyether (poly(tetramethylene oxide)) chains and hard urethane segments of various length have been studied by means of calorimetry, wide- and small-angle X-ray scattering and a.c. conductivity in wide range of frequencies (0.1 Hz–1 MHz) and temperature (−100 to 100°C). It was shown that the polyurethanes are basically microphase-separated systems whose polyether-rich matrix contain from 20 to 25% of the hard urethane fragments. The protonic conductivity of the materials decreases with decreasing the polyether phase in the system.     

Effect of cooperative interactions in optical ensembles on the threshold characteristics of lasing in the case of coherent optical pumping

The dependence of the threshold pump energy of dye lasers on the quantum yield of fluorescence of active solutions in the case of laser excitation was studied. The rate of increase in the threshold pump energy was found to be considerably lower than the rate of decrease in quantum yield. The results were interpreted in terms of the development of the cooperative interaction between active centers in the high-intensity coherent pump field.

     

Zero field muon spin relaxation rate in the superconducting state of Nb3Al

It was shown that at T=12 k the dipole relaxation of a positive muon in Nb₃Al in the zero external magnetic field is well described by the Kubo-Toyabe function for the static distrubution of the dipole magnetic fields in the absence of muon diffusion. The superconducting state of Nb₃Al was used for eliminating the background from muons stopped in the cryostat walls.     

Oxidation of molecular nitrogen with hydrogen peroxide

Russian Chemical Bulletin -     

High-peak-power diode-pumped Nd:YAG laser with a Brillouin phase-conjugation--pulse-compression mirror

We demonstrate stimulated Brillouin scattering compression of diode-pumped Nd:YAG laser pulses with a 3-ns duration into 350-ps pulses at a pulse-repetition rate of 100 Hz for what is believed to be the first time. The output pulse energy was 6.5 mJ, with a beam-quality factor M(2) of 1.15, and after final amplification the energy reached 36 mJ, with M(2) of 2.5.