STUDIES ON PLANT BILE PIGMENTS.

The (4 Z, 10 2, 15Ej-2,3-dihydrobilindione 4, along with the fully unsaturated (E, 2, Z)-analogue 8, has been prepared from the corresponding (Z, Z, Z)-isomer by a variation of Falk's method (Falk et ul., 1980). The photochemical and acid-catalyzed back-reactions have been studied by UV-vis and 'H-NMR spectroscopy

Pseudoreceptor-based pocket selection in a molecular dynamics simulation of the histamine H4 receptor

There is a renewed interest in pseudoreceptor models which enable computational chemists to bridge the gap of ligand- and receptor-based drug design. We developed a pseudoreceptor model for the histamine H4 receptor (H4R) based on five potent antagonists representing different chemotypes. Here we present the selection of potential ligand binding pockets that occur during molecular dynamics (MD) simulations of a homology-based receptor model. We present a method for prioritizing receptor models according to their match with the consensus ligand-binding mode represented by the pseudoreceptor. In this way, ligand information can be transferred to receptor-based modelling. We use Geometric Hashing to match three-dimensional points in Cartesion space. This allows for the rapid translation- and rotation-free comparison of atom coordinates, which also permits partial matching. The only prerequisite is a hash table, which uses distance triplets as hash keys. Each time a distance triplet occurring in the candidate point set which corresponds to an existing key, the match is represented by a vote of the respective key. Finally, the global match of both point sets can be easily extracted by selection of voted distance triplets. The results revealed a preferred ligand-binding pocket in H4R, which would not have been identified using an unrefined homology model of the protein. The key idea was to rely on ligand information by pseudoreceptor modelling

Free Riding and Collective Action: An Experiment in Public Microeconomics

The well-known free-rider hypothesis is examined experimentally to see (i) whether individuals behave systematically as free riders when systematic incentives to do so are created, and (ii) the extent to which free riding actually occurs. Though the experiment's participants behaved in accordance with the hypothesis, the quantitative extent to which such behavior occurred was rather modest. From this it may be concluded that the free-rider hypothesis as presently stated indicates an incompleteness in standard public microeconomics rather than providing a description of the real worl

On Multiple Einstein Rings

A number of recent surveys for gravitational lenses have found examples of double Einstein rings. Here, we investigate analytically the occurrence of multiple Einstein rings. We prove, under very general assumptions, that at most one Einstein ring can arise from a mass distribution in a single plane lensing a single background source. Two or more Einstein rings can therefore only occur in multi-plane lensing. Surprisingly, we show that it is possible for a single source to produce more than one Einstein ring. If two point masses (or two isothermal spheres) in different planes are aligned with observer and source on the optical axis, we show that there are up to three Einstein rings. We also discuss the image morphologies for these two models if axisymmetry is broken, and give the first instances of magnification invariants in the case of two lens planes.Comment: MNRAS, in press (extra figure included

Report No. 18: Umsetzung des Workfare-Ansatzes im BMWi-Modell für eine existenzsichernde Beschäftigung

Abschlussbericht Projekt 53/07 des Bundesministeriums für Wirtschaft und Technologie, Bonn 2008 (94 Seiten)

Geometry of Universal Magnification Invariants

Recent work in gravitational lensing and catastrophe theory has shown that the sum of the signed magnifications of images near folds, cusps and also higher catastrophes is zero. Here, it is discussed how Lefschetz fixed point theory can be used to interpret this result geometrically. It is shown for the generic case as well as for elliptic and hyperbolic umbilics in gravitational lensing.Comment: RevTEX4, 13 pages, submitted to J. Math. Phy

Report No. 20: Bald erstmals weniger als 3 Mio. Arbeitslose in Deutschland

Bericht im Auftrag der Initiative Neue Soziale Marktwirtschaft, Bonn 2008 (18 Seiten)

Oculomotor capture by search-irrelevant features in visual working memory: on the crucial role of target–distractor similarity

Foerster RM, Schneider WX. Oculomotor capture by search-irrelevant features in visual working memory: on the crucial role of target–distractor similarity. Attention, Perception, & Psychophysics. 2020;82:2379–2392.When searching for varying targets in the environment, a target template has to be maintained in visual working memory (VWM). Recently, we showed that search-irrelevant features of a VWM template bias attention in an object-based manner, so that objects sharing such features with a VWM template capture the eyes involuntarily. Here, we investigated whether target–distractor similarity modulates capture strength. Participants saccaded to a target accompanied by a distractor. A single feature (e.g., shape) defined the target in each trial indicated by a cue, and the cue also varied in one irrelevant feature (e.g., color). The distractor matched the cue’s irrelevant feature in half of the trials. Nine experiments showed that target–distractor similarity consistently influenced the degree of oculomotor capture. High target–distractor dissimilarity in the search-relevant feature reduced capture by the irrelevant feature (Experiments 1, 3, 6, 7). However, capture was reduced by high target–distractor similarity in the search-irrelevant feature (Experiments 1, 4, 5, 8). Strong oculomotor capture was observed if target–distractor similarity was reasonably low in the relevant and high in the irrelevant feature, irrespective of whether color or shape were relevant (Experiments 2 and 5). These findings argue for involuntary and object-based, top-down control by VWM templates, whereas its manifestation in oculomotor capture depends crucially on target–distractor similarity in relevant and irrelevant feature dimensions of the search object