Poly(alkyl α-chloroacrylates). IV. Tacticity analysis from 300 MHz proton magnetic resonance spectra

300 MHz proton magnetic resonance spectroscopy was applied to the determination of triad structures of three poly(alkyl α-chloroacrylates) of widely varying stereoregularities. Assignments and quantitative analyses were made for all of the tetrad peaks in the backbone methylene resonance of poly(methyl α-chloroacrylate), poly(ethyl α-chloroacrylate), and poly(isopropyl α-chloroacrylate). In addition the methyl singlet peaks of poly(methyl α-chloroacrylate), the methyl triplet peaks of poly(ethyl α-chloroacrylate) which had not been amenable previously to resolution at 220 MHz, and the methyl doublet peaks of poly(isopropyl α-chloroacrylate) were resolved, and the triad values which were obtained from these pendant ester group resonances compared favorably with triad values calculated from experimental tetrad values. As a demonstration of the internal agreement of the triad and tetrad peaks assignments, statistical calculations of the stereochemical structures of the actic and syndiotactic polymers were generally described well or to a first approximation by random selection statistics (Bernoullian) while the stereochemical statistics of the moderately to highly isotactic polymers were consistent with a nonrandom statistical process (first-order Markovian), as expected.     

The Δ-nucleus spin-orbit interaction in π-nucleus scattering

The role of the Δ-nucleus spin-orbit interaction in π-nucleus scattering is studied within the isobar-hole formalism. Due to the peripheral nature of the π-nucleus interaction, elastic scattering is very sensitive to the presence of such an L-S term. We report results for pion scattering on light nuclei in the resonance region. The systematics of the phenomenological Δ-nucleus optical potential are discussed.     

Über die Einführung einer absoluten Polarität in die projektive und affine Geometrie des Raumes

Ohne Zusammenfassung     

Über die Bedeckung ebener Punktmengen durch solche kleineren Durchmessers

Ohne ZusammenfassungHerrn Professor J. Lense zum 65. Geburtstag gewidmet     

Bilder lokaler Aufladungen im Elektronen-Spiegelmikroskop

Two characteristic types of spots which are frequently found in electron mirror microscope images are interpreted as caustic cross sections caused by local surface charges. Negative charges produce dark circular spots with a bright edge while the caustic cross sections produced by positive charges are of the type well known from the caustic surfaces of electron lenses suffering from spherical aberration and astigmatism. The bright edge in the negative caustic is accompanied by a second edge which in all practical cases is much less intense and consequently invisible.