A Novel Environment Characterization Metric for Clustered MIMO Channels

In this work we introduce a novel metric for characterizing the double-directional propagation environment and use this metric to assess the performance of a SAGE parameter estimator for MIMO channels. Using the IlmProp, a geometry-based MIMO channel modeling tool, we construct synthetic channels for three different scenarios showing: (i) well separated clusters containing dense propagation paths, and single-bounce scattering; (ii) partly overlapping clusters containing widely spread propagation paths, and single-bounce scattering; (iii) unclustered multipath components (“rich scattering”), and double-bounce-only scattering. We model the scatterers and the receiver in the environment as fixed, but the transmitter as moving. The Initialization and Search-Improved SAGE (ISIS) estimation tool is used to extract the propagation paths from the constructed channels. Both true and estimated paths are fed to the new system-independent metric which genuinely reflects the structure of the channel and the compactness of the propagation paths. We use this metric to decide on the accuracy of the channel estimator. The results show a convincing agreement between true and estimated paths.     

Über Zeitkonstanten von Kondensatoren

Zusammenfassung Bei hinreichend langer Trocknung und Bernsteinisolation lassen sich mit Luftkondensatoren Zeitkonstanten erreichen, die in der Größenordnung 10⁷ s bzw. 10³ s/pF liegen. Die physikalischen Ursachen der Entladung werden näher untersucht. Praktisch erfolgt die Entladung nur über die Bernsteinisolation; die Leitfähigkeit der Luft ist zu vernachlässigen. Maßgebend für die Entladung ist das Verhältnis Volumen zur Kapazität. Hohe Zeitkonstanten lassen sich erreichen, wenn das Verhältnis Volumen zur Kapazität klein ist. Kondensatoren mit sehr hohen Zeitkonstanten finden ihre Anwendung, z. B. wenn ein aufgeladener Kondensator als Vergleichsspannungsquelle dienen soll, bei der elektrischen Kurzzeitmèssung als Zeittransformator oder zur Messung sehr hoher Widerstände von der Größenordnung 10¹⁰ bis 10¹⁵ nach dem Kondensatorentladungsverfahren. Über eine weitere Anwendung wird demnächst berichtet werden.Die vorliegende Untersuchung wurde von Herrn Prof. Dr.-Ing. E. h. Dr.-Ing. W. Rogowski angeregt, dem ich für seine vielseitige Unterstützung zu großem Dank verpflichtet bin. Der Deutschen Forschungsgemeinschaft danke ich für die Mittel zur Durchführung der Arbeit.     

On the Dieudonné Theorem in Reflexive Banach Spaces

The converse part of the Dieudonné theorem on the closedness of the difference of two closed convex sets is establish. It is proved that, in a reflexive Banach setting, the sufficient conditions given by Dieudonné when applied for the weak topology, are also necessary.     

Vermischungsvorgänge beim Stranggießen

Die Untersuchung stationärer und instationärer Zustände beim Sequenzgießen auf einer Brammenstranggießanlage hat Informationen über die wichtigsten Einflußparameter auf den Ablauf der Vermischungsvorgänge geliefert. Je nach betrieblichen Gegebenheiten und Erfordernissen können Gießstrategien zur Abflachung oder Aufrichtung der vermischungsbedingten Konzentrationsverläufe im festen Strang angewendet werden. Die modellmäßige Beschreibung der Mischvorgänge wurde unter vereinfachenden Annahmen und erster Näherung nach dem Konzept der Kaskade mit seriellen Mischzellen vorgenommen. Es ist zu erwarten, daß die Mischvorgänge beim Stranggießen in Zukunft wegen steigender Ansprüche an die Gleichmäßigkeit des Produktes im Mittelpunkt von Entwicklungsarbeiten stehen werden.     

Magnetostatic wave devices for UHF band applications

Magnetostatic surface wave (MSSW) devices made with pure and gallium-substituted yttrium-iron garnet (Ga:La-YIG) films are described. These devices include nondispersive and dispersive delay lines, band-pass filters, oscillators, and resonators. By controlling the magnitude of the bias magnetic field and the temperature of operation, it is possible to tune these devices over a wide frequency range extending from 0.3 to 4 GHz and from 3 to 18 GHz using Ga:La-YIG and pure YIG films, respectively.These devices could be used in pulse compression radar, microscan receivers, complicated Fourier transform processors, and fundamental oscillator circuits. In this paper, we briefly show results for pure YIG devices tunable in C and X bands and discuss, in detail, the performance of the Ga:La-YIG devices for UHF applications.     

The Tyrosine Gate of the Bacterial Lectin FimH: A Conformational Analysis by NMR Spectroscopy and X‐ray Crystallography

Urinary tract infections caused by uropathogenic E. coli are among the most prevalent infectious diseases. The mannose‐specific lectin FimH mediates the adhesion of the bacteria to the urothelium, thus enabling host cell invasion and recurrent infections. An attractive alternative to antibiotic treatment is the development of FimH antagonists that mimic the physiological ligand. A large variety of candidate drugs have been developed and characterized by means of in vitro studies and animal models. Here we present the X‐ray co‐crystal structures of FimH with members of four antagonist classes. In three of these cases no structural data had previously been available. We used NMR spectroscopy to characterize FimH–antagonist interactions further by chemical shift perturbation. The analysis allowed a clear determination of the conformation of the tyrosine gate motif that is crucial for the interaction with aglycone moieties and was not obvious from X‐ray structural data alone. Finally, ITC experiments provided insight into the thermodynamics of antagonist binding. In conjunction with the structural information from X‐ray and NMR experiments the results provide a mechanism for the often‐observed enthalpy–entropy compensation of FimH antagonists that plays a role in fine‐tuning of the interaction.     

From the ganglioside GQ1balpha to glycomimetic antagonists of the myelin-associated glycoprotein (MAG)

The tetrasaccharide 4, a substructure of ganglioside GQ1balpha, shows a remarkable affinity for the myelin-associated glycoprotein (MAG) and was therefore selected as starting point for a lead optimization program. In our search for structurally simplified and pharmacokinetically improved mimics of 4, antagonists with modifications of the core disaccharide Galbeta(1-3)GalNAc, as well as the terminal alpha(2-3)- and the internal alpha(2-6)-linked neuraminic acid were synthesized and tested in target-based binding assays. Compared to the reference tetrasaccharide 4, the most potent antagonist 17 exhibits a 360-fold improved affinity. Furthermore, pharmacokinetic parameters such as stability in the cerebrospinal fluid, logD and permeation through the BBB indicate the drug-like properties of antagonist 17.