Computer-algebra calculations and measurements on AB spin systems for double-spin-echo sequences

The time evolution of the density operator of an AB spin system during a double-spin-echo pulse sequence is evaluated analytically by a computer-algebra system. The computer-algebra system allows one to generate the extensive formulas describing the density operator and yields an expression for the integral of the spectral signals. The simulation of spectra for arbitrary sequence timings can be easily performed by this new tool without risking errors that might occur in conventional calculations. The computer-algebra method can be extended straightforward to other pulse angles and types of sequences. The double-spin-echo pulse sequence is used in the point-resolved spectroscopy (PRESS) method which is often applied for volume selective examinationsin vivo. For verification of the results generated by the computer-algebra system,¹H spectra from a half-liter spherical sample with an aqueous solution that was 0.1 M in sodium citrate and 0.1 M in sodium acetate were recorded after 90°-180°-180° double-spin-echo pulse sequences on a 1.5-T whole-body unit. The measured behavior of the citrate AB spin system corresponds very well with the theoretical predictions. Thus, the theory provides the basis for the optimization of sequence timings for double-spin-echo measurements with high signal gain from AB systems as, for example, citrate. In addition, the theoretically predicted signal modulations could be fitted to the experimental data, providing the transverse relaxation time of the AB-coupled protons.     

Microgravity materials and life sciences research applications of digital holography

We investigate the utility of digital holographic interferometry for analyzing gravity-dependent mass transport phenomena as applicable to materials and life science research topics. Digital holography is useful for measurement of parameters that introduce phase changes in light traversing the material of interest, such as temperature or concentration variations in an aqueous environment. We have constructed, tested, and verified a compact, portable digital holographic monitor (DHM) suitable for characterization of transparent samples. It has proved useful for the study of systems such as protein crystal growth solutions and has been proposed for further application into studies involving microbial metabolism. The DHM is also sufficiently rugged for field operation in challenging environments a s may be encountered in a spacecraft or industrial setting. We discuss some system capabilities and limitations.     

Modellversuche zur Blaufleckigkeit von Kartoffelknollen

Zusammenfassung In Modelluntersuchungen zur Blaufleckigkeit konnte an der SorteGRATA gezeigt werden, daß in den Druckstellen der Knollen die Aktivität der Phenylalaninammoniumlyase und Saccharase sowie der Gehalt an Gesamtphenolen stark erhöht sind. Polyphenoloxydaseaktivität und Chlorogensduregehalt sind dagegen vermindert. Der Gehalt einzelner freier Aminosäuren in den geschlagenen Knollen ist ebenfalls verändert: Prolin nimmt stark zu, Valin, Lysin, Histidin und Arginin, Phenylalanin und Tyrosin nehmen mehr oder minder ab.[/p]

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Model experiments on black spots of potatoe-tubers

Summary In model experiments with the variety Grata it could be demonstrated that the activity of phenylalaninammoniumlyase and saccharase as well as the content of total phenols are severely increased in the black spots of potatoe tubers. However, polyphenoloxidase activity and the chlorogenic acid content were reduced. The content of several free amino acids in the black spots was also changed: proline defenitely increased, valine, lysine, histidine, arginine, phenylalanine and tyrosine decerased more or less.[/p]

     

Determination of polymer crystallinity from proton solid-echo NMR measurements

Summary The decomposition of the solid-echo curves of crystalline polymers into the crystalline and the amorphous component is discussed. The crystalline component is experimentally determined by using a special method of measurement. The amorphous component is assumed to correspond to a distribution of correlation times.Presented at the 22nd Microsymposium Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, CSSR, July 20–23, 1981The author thanks Dr. H. Haberkorn for the determination of the x-ray crystallinities.     

Ein neuer Weg zur quantitativen Erfassung der Vorgänge beim kontrollierten Walzen

Qualitative Ableitung der Größe ?addierte Endverformung“ und ihre quantitative Beschreibung über temperaturabhängige Additionskoeffizienten. Vorausberechnung von Streckgrenze und Festigkeit aus dem Stichplan. Berechnung eines Übergangspunktes der Kristallinität und hieraus Konstruktion der Kerbschlagzähigkeitskurve.