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When ca. 85% cis films of the semiconducting polymer, polyacetylene, (CH)x, are first doped with bromine and then partly dehydrobrominated at 150°C, substitution of II by Br occurs to yield new semiconducting polymers of general composition [CH1-uBry]x, where y=0.003-0.23. These films have been studied using electron paramagnetic resonance (EPR), dynamic nuclear polarization (DNP), and Raman spectroscopic techniques. EPR results indicate that with an increase in bromine substitution, the linewidth (ΔHpp), g-value, and homogeneity of the samples increase. This is consistent with DNP results which suggest a decrease in the diffusion coefficient of unpaired spins as the bromine substitution level increases. Raman results are consistent with bromine substitution and indicate that essentially no change in conjugation length occurs when H is substituted by Br.

A study of Raman scattering from partially isomerized polyacetylene films with varying cis-trans content is presented. Major differences are discovered in the dispersion of trans-(CH)x Raman bands between pure trans- and cis-rich samples. It is shown that the unusual dispersion of the trans-(CH)x Raman bands in partially isomerized samples cannot arise from a distribution of short chains. These results are discussed in terms of the complex response of the lattice to the presence of photoinjected electron-hole pairs.

Changes in muscle proteins in serum after exercise were studied to evaluate the use of such proteins as indicators of increased muscle membrane vulnerability. Seventy-one women were asked to perform bicycle exercise for 45 min at a moderate load; four proteins (creatine kinase — CK, myoglobin — Mb, aldolase — Ald and pyruvate kinase — PK) were measured in serum up to 24 h after exercise. Twenty-one women were carriers of Duchenne's muscular dystrophy (DMD); these are known to show an elevated serum CK activity at rest, as well as an increased CK response after exercise. Fifty women without a family history of neuromuscular disease were tested to obtain normal values: they showed a small peak (18%) of CK activity 8h after exercise, and an even smaller peak of Mb (9%) 1h after exercise. The mean post-exercise increase for both CK and Mb in the 21 DMD carriers was significantly higher than in controls; the maximum of Mb, on average 70% of baseline levels, was reached 1h after exercise and was higher than that for CK (48%), which was reached 8 h after exercise. It is concluded that myoglobin levels after exercise are a good index of increased vulnerability of the muscle membrane.

When the COVID-19 pandemic hit the U.S. about a year ago, libraries at first acted to slow the spread of the virus. Many locked their doors and sent staffers to [...]