Synthesen von neuen Tetracyclinderivaten mit antibakterieller Wirkung bei tetracyclinresistenten Keimen

The syntheses of N(b)-cycloheptatrienyltetracyclines and N(b)-cycloheptyltetracyclines are reported. The type of substitution at N(b) of tetracyclines is correlated with the antibacterial activity against tetracycline resistant strains.     

Resolution enhancement of pHe+ atomic line profiles measured with a pulsed dye laser and a Fizeau wavelength meter

A Fizeau wavelength meter was used to compensate for fluctuations in the longitudinal mode structure and wavelength of a pulsed dye laser. The average laser linewidth was effectively narrowed by selection of laser pulses with a single longitudinal mode. These techniques were recently employed to measure some atomic transition wavelengths in pHe+ to fractional precisions greater than 1 part in 10(7). The wavelengths were absolutely calibrated against iodine or tellurium lines by absorption spectroscopy or against neon or argon lines by optogalvanic spectroscopy.     

Group contribution analysis of the damping behavior of homopolymers,statistical copolymers,and interpenetrating polymer networks based on acrylic,vinyl, and styrenic mers

The integral of loss modulus versus temperature plots in the vicinity of the glass transition temperature (loss area, LA) was characterized for various homopolymers, statistical copolymers, and interpenetrating polymer networks (IPNs), based on acrylics, vinyls, and styrenic mers. The quantity LA was found to be a molecular characteristic, governed by the structure of the individual mers. The LA of both IPNs and statistical copolymers obeys an additive relation of the component polymers. A group contribution analysis for LA was developed in which each moiety contributes a specific value to LA. A table derived via this group-contribution analysis permits the prediction of LA values. The results show that backbone motions and the moieties attached directly to the backbone contribute the most to the damping peak, and that long side chains act as diluents.     

Enantiomerentrennung von N-Acylaminos?uren ohne vorherige Derivatisierung

Ohne Zusammenfassung

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Separation of enantiomeric N-acylamino acids without preceding derivatisation