Self-diffusion in melts of statistical copolymers: The effect of changes in microstructural composition

We have used nuclear reaction analysis to measure diffusion coefficients D in couples consisting of hydrogenated polybutadienes of structure (C₂H₃(C₂H₅))_x(C₄H₈)_1?x and their partly deuterated counterparts. The 1,2- and 1,4-olefinic isomers are randomly distributed along the chains and the mean vinyl fraction x varies between 0.38 and 0.94. We find that the effective monomeric mobility D₀ [defined by D = D₀(N_e/N²) for each copolymer, where N is the backbone length and N_e the entanglement spacing] decreases monotonically with increasing vinyl content x. Over the range of microstructures and temperatures T (?14?40°C) investigated we find log(D₀/T) varies smoothly with (T ? T_g), where T_g is the glass transition temperature of the respective melts. An analysis of our data in terms of a simple activated rate process model suggests that D₀ is controlled by thermally activated hopping of segments whose effective volume is close to that of the respective statistical segment lengths of the copolymeric chains. ©1995 John Wiley & Sons, Inc.     

Gegenbeispiele zur Interpolationstheorie der nuklearen und absolutsummierenden Operatoren

Ohne Zusammenfassung     

Abtrennung von wismut durch chloroformextraktion mit n-benzoyl-α-aminobuttersäure

Extractive separation of bismuth in nitric acid solutions from many metal ions is possible after simple pH adjustment. A specially designed separating funnel is useful. Alloys and pharmaceutical preparations are easily analyzed.     

Integrierte Verkaufs-, Produktions- und Investitionsplanung

Zusammenfassung In vorliegendem Aufsatz wird ein Erfahrungsbericht über die Entwicklung und den Einsatz komplexer Unternehmensplanungssysteme gegeben.

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Summary In this paper the development and implementation of a complex planning system is presented and the resulting experience is shown.

     

Rescattering of ultralow-energy electrons for single ionization of Ne in the tunneling regime

Electron emission for single ionization of Ne by 25 fs, 1.0 PW/cm(2) laser pulses at 800 nm has been investigated in a kinematically complete experiment using a "reaction microscope." Mapping the complete final state momentum space with high resolution, a distinct local minimum is observed at P(e parallel )=0, where P(e parallel ) is the electron momentum parallel to the laser polarization. Whereas tunneling theory predicts a maximum at zero momentum, our findings are in good agreement with recent semiclassical predictions which were interpreted to be due to "recollision."     

High precision wavelength measurements of QED-sensitive forbidden transitions in highly charged argon ions

We present the results of an experimental study of magnetic dipole (M1) transitions in highly charged argon ions (Ar X, Ar XI, Ar XIV, Ar XV) in the visible spectral range using an electron beam ion trap. Their wavelengths were determined with, for highly charged ions, unprecedented accuracy up to the sub-ppm level and compared with theoretical calculations. The QED contributions, calculated in this Letter, are found to be 4 orders of magnitude larger than the experimental error and are absolutely indispensable to bring theory and experiment to a good agreement. This method shows great potential for the study of QED effects in relativistic few-electron systems.     

Electron correlations observed through intensity interferometry

Intensity interferometry was applied to study electron correlations in doubly ionizing ion-atom collisions. In this method, the probability to find two electrons emitted in the same double ionization event with a certain momentum difference is compared to the corresponding probability for two uncorrelated electrons from two independent events. The ratio of both probabilities, the so-called correlation function, is found to sensitively reveal electron correlation effects, but it is rather insensitive to the collision dynamics.