Forum / Kolumne

Hinter den Lehrbüchern die vorlesende Forscherpers?nlichkeit, hinter dem Prospekt der Rat des erfahrenen Fachverk?ufers.     

Thermoelektrische analyse (TEA), eine neue Methode zum gleichzeitigen Studium elektrischer und thermischer Eigenschaften von Polymeren

A new method for the simultaneous study of electrical and thermal properties of polymers is proposed. The thermal electrical analysis (TEA) combines the existing techniques of DSC (or DTA) with the electrical method of thermally stimulated discharge (TSD). TEA measurements were carried out with copolymers of methyl methacrylate (PMMA). The molecular origin of the TSD-current at the lower temperature side of the α₁-relaxation process (glass transition T_g of the PMMA) is related to the disorientation of small polar segments of the comonomer (α₂-relaxation) in the main chain of the PMMA. It can be shown that the TSD-current of the α₂-relaxation (T > 80°C) increases with increasing comonomer content. This supports the molecular interpretation of the α₂-process which is not reflected in the DSC. At higher temperatures frozen in dipoles regain their mobility and show a TSD peak at that temperature which corresponds to the T_g of the PMMA. The TSD ρ-peak at T>T_g can be attributed to trapped space charges which regain their freedom of motion. The results demonstrate the high resolution and resolving power of the TEA-method. TEA is recommended as an analyzing tool to investigate the relationship between the depolarization of dipoles, carrier transport, trapping of real charges and thermal transitions of polymers.     

Quantification of microvessels in canine lymph nodes

Quantification of microvessels in tumors is mostly based on counts of vessel profiles in tumor hot spots. Drawbacks of this method include low reproducibility and large interobserver variance, mainly as a result of individual differences in sampling of image fields for analysis. Our aim was to test an unbiased method for quantifying microvessels in healthy and tumorous lymph nodes of dogs. The endothelium of blood vessels was detected in paraffin sections by a combination of immunohistochemistry (von Willebrand factor) and lectin histochemistry (wheat germ agglutinin) in comparison with detection of basal laminae by laminin immunohistochemistry or silver impregnation. Systematic uniform random sampling of 50 image fields was performed during photo-documentation. An unbiased counting frame (area 113,600 microm(2)) was applied to each micrograph. The total area sampled from each node was 5.68 mm(2). Vessel profiles were counted according to stereological counting rules. Inter- and intraobserver variabilities were tested. The application of systematic uniform random sampling was compared with the counting of vessel profiles in hot spots. The unbiased estimate of the number of vessel profiles per unit area ranged from 100.5 +/- 44.0/mm(2) to 442.6 +/- 102.5/mm(2) in contrast to 264 +/- 72.2/mm(2) to 771.0 +/- 108.2/mm(2) in hot spots. The advantage of using systematic uniform random sampling is its reproducibility, with reasonable interobserver and low intraobserver variance. This method also allows for the possibility of using archival material, because staining quality is not limiting as it is for image analysis, and artifacts can easily be excluded. However, this method is comparatively time-consuming.     

Didaktik für Profs und Mathetik für Studis!

Ohne Zusammenfassung     

Sport – dank Technologie

Ohne Zusammenfassung     

Efficient similarity-based operations for data integration

Dealing with discrepancies in data is still a big challenge in data integration systems. The problem occurs both during eliminating duplicates from semantic overlapping sources as well as during combining complementary data from different sources. Though using SQL operations like grouping and join seems to be a viable way, they fail if the attribute values of the potential duplicates or related tuples are not equal but only similar by certain criteria. As a solution to this problem, we present in this paper similarity-based variants of grouping and join operators. The extended grouping operator produces groups of similar tuples, the extended join combines tuples satisfying a given similarity condition. We describe the semantics of this operator, discuss efficient implementations for the edit distance similarity and present evaluation results. Finally, we give examples of application from the context of a data reconciliation project for looted art.     

Schlangenbeschwörer

Alpha Versionen sind Lehrbücher, Gesetze, Produkthochglanzprospekte, Aktienneuemissionsanzeigen, Regierungserklärungen. Dahinter ist das Reale. Hinter den Lehrbüchern die vorlesende Forscherpersönlichkeit, hinter dem Prospekt der Rat des erfahrenen Fachverkäufers. Alpha Versionen meiden Urteile, Meinungen und Leidenschaftlichkeit. Diese Kolumne ist kompromißlos beta.