Two Asteraceae species, Clibadium surinamense L. and Montanoa grandiflora D.C., were analyzed to determine the composition of the essential oil and to search for phototoxic compounds. Three parts of the plants were studied, inflorescence, stems and leaves. Intra and interspecific differences were found in the essential oil composition, which was determined by gas chromatography. In the chromato...

Photoexcited states in trans polyacetylene lt-(CH), l and in ulkoxy derivatives of poly(puraphenylenevinylene) (PPV) have been studied by the technique of absorption detected magnetic resonance. In addition to the stable charged photoexcitations, which are charged solitons in t-(CH), and bipolarons in PPV, we clearly identify neutral photoexcitations with nonzero spins. In t-(CH), these are spi...

The tight binding Hamiltonian of Su, Schrieffer, and Heeger has been used to describe the physical properties of the polyacetylene chain. The chain temperature is calculated from the potential energy which is directly related to the CH group displacement. Two different forms of the displacements have been considered: random and Gaussian. The third harmonic generation susceptibility spectra have...

A numerical model was used to study methane photochemistry in the stratosphere of Neptune. The observed mixing ratio of methane, 2%, forces photolysis to occur near the CH4 homopause. For an assumed nominal value of the eddy mixing coefficient of 106 cm 2 sec -1 at the CH4 homopause, the predicted average mixing ratios of CzH6 and C2Hz, 1.5 x 10 -6 and 6 x 10 -7, respectively, agree well with o...

Drug-resistant tuberculosis threatens to undermine global control programs by limiting treatment options. New antimicrobial drugs are required, derived from new chemical classes. Natural products offer extensive diversity and inspiration for synthetic chemistry. Here, we isolate, synthesize test a library of 52 natural compounds activity against Mycobacterium . We identify seven as antimycobact...