Excitable Media Seminar

The simulation data presented here, and the conceptual framework developed for their interpretation are, both, in need of substantial refinement and extension. However, granting that they are initial pointers of some merit, and elementary indicators of general principles, several implications follow: the activity patterns of neurons and their assemblies are\ud interdependent with the extracellular milieu in which they are embedded, and to whose time varying composition they contribute. The complexity of this interdependence in the temporal dimension forecloses any time and context invariant relation between what the experimenter may consider stimulus input and its representation in neural activity. Hence, ideas of coding by (quasi)-digital neurons are called in question by the mutual interdependence of neurons and their\ud humoral milieu. Instead, concepts of 'mass action' in the Nervous system gain a new perspective: this time augmented by including the chemical medium surrounding neurons as part of the dynamics of the system as a whole. Accordingly, a meaningful way to describe activity in a neuron assembly would be in terms of a state space in which it can move along an infinite number of trajectories.\u

Speciation and phylogeography in the cosmopolitan marine moon jelly, Aurelia sp.

Background: The cosmopolitan moon jelly Aurelia is characterized by high degrees of morphological and ecological plasticity, and subsequently by an unclear taxonomic status. The latter has been revised repeatedly over the last century, dividing the genus Aurelia in as many as 12 or as little as two species. We used molecular data and phenotypic traits to unravel speciation processes and phylogeographic patterns in Aurelia. Results: Mitochondrial and nuclear DNA data (16S and ITS-1/5.8S rDNA) from 66 world-wide sampled specimens reveal star-like tree topologies, unambiguously differentiating 7 (mtDNA) and 8 (ncDNA) genetic entities with sequence divergences ranging from 7.8 to 14% (mtDNA) and 5 to 32% (ncDNA), respectively. Phylogenetic patterns strongly suggest historic speciation events and the reconstruction of at least 7 different species within Aurelia. Both genetic divergences and life history traits showed associations to environmental factors, suggesting ecological differentiation forced by divergent selection. Hybridization and introgression between Aurelia lineages likely occurred due to secondary contacts, which, however, did not disrupt the unambiguousness of genetic separation. Conclusions: Our findings recommend Aurelia as a model system for using the combined power of organismic, ecological, and molecular data to unravel speciation processes in cosmopolitan marine organisms. © 2002 Schroth et al; licensee BioMed Central Ltd. Verbatim copying and redistribution of this article are permitted in any medium for any non-commercial purpose, provided this notice is preserved along with the article's original URL: http://www.biomedcentral.com/1471-2148/2/

Preference SQL - Design, Implementation, Experiences

Current search engines can hardly cope adequately with complex preferences. The biggest problem of search engines directly implemented with standard SQL is that SQL does not directly understand the notion of preferences. Preference SQL extends standard SQL by a preference model based on strict partial orders, where preference queries behave like soft selection constraints. A variety of built-in base preference types and the powerful Pareto accumulation operator to construct complex preferences, combined with the adherence to declarative SQL programming style, guarantees great programming productivity. The current Preference SQL optimizer does an efficient re-writing into standard SQL, including a high-level implementation of the skyline operator for Pareto-optimal sets. This pre-processor approach enables a seamless application integration, making reference SQL available on a broad variety of SQL platforms including IBM DB2, Oracle, Microsoft SQL Server and Sybase. The benefits of Preference SQL technology comprise cooperative query answering and smart customer advice, leading to a higher e-customer satisfaction and shorter development times of personalized search engines for the e-service provider. We report experiences with practical applications ranging from m-commerce and comparison shopping to a large-scale performance test with real data. Several search engines of commercial B2C portals are powered by Preference SQL

Client-server optimization for multimedia document exchange

The success of the World Wide Web is boosting the development of multimedia database systems and their integration into the internet. For the documents stored and exchanged in the Web there is a variety of multimedia data formats differing in aspects such as resolution, sampling rate, and compression. Furthermore there is a large heterogeneity of Web browsers, the data formats they support, and their network access. Thus storage servers have to store and proxy servers have to transfer many different formats. However, the data formats are not independent from each other but interrelated by conversion tools. There is a large number of alternatives for storage and proxy servers to store some formats or to transfer them via the network and to compute the remaining ones by applying conversion tools. To determine an optimal choice is a nontrivial optimization problem and is subject to changes of the parameters such as query profile, available disk storage, and network bandwidth. We examine the outlined optimization problem in the context of object-oriented databases and illustrate our approach by a practical application

Die Röntgenstrukturen der Glutamatdehydrogenase von Plasmodium falciparum und der Liponamiddehydrogenase von Trypanosoma cruzi. Zielmoleküle für das strukturbasierte Design neuer antiparasitärer Wirkstoffe

In der vorliegenden Arbeit wurden die Kristallstrukturen der Glutamatdehydrogenase des Malariaerregers Plasmodium falciparum und der Liponamiddehydrogenase von Trypanosoma cruzi, dem Erreger der Chagas-Krankheit, aufgeklärt. Beide Enzyme sind validierte bzw. mögliche Zielmoleküle für das rationale Design neuer antiparasitärer Wirkstoffe. Durch die erfolgte Strukturaufklärung besteht nun die Möglichkeit, die Enzyme mit Methoden des computergestützten Drug Designs weiter zu bearbeiten