Four Lessons in Versatility or How Query Languages Adapt to the Web

Exposing not only human-centered information, but machine-processable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based query language that aims to give shield application builders from much of this complexity: In a single query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C’s GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for querying XML and RDF in the same way. (3) We show that the resulting query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space querying also for many RDF graphs. We believe that Web query languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a “Web of Data”

The Temperature Dependence of P680+ Reduction in Oxygen-Evolving Photosystem II

Original article can be found at: http://pubs.acs.org/journals/bichaw/index.html Copyright American Chemical Society [Full text of this article is not available in the UHRA]Peer reviewe

Resolution of a long lived fluorescence component from D1/D2/ cytochrome b-559 reaction centres

AbstractD1/D2/cytochrome b-559 reaction centres rapidly degrade under continuous illumination. This is a problem in time-resolved spectroscopy experiments. A long lived fluorescence component assigned to radical pair recombination has been reported previously, but contributing to less than 2% of the fluorescence. This letter reports that sample stability is significantly improved under anaerobic conditions. Fluorescence lifetime measurements described here assign 44% of the total fluorescence yield to a 36.5 ± 2.5 ns lifetime

Are the trapping dynamics in Photosystem II sensitive to QA redox potential?

Removal of the manganese complex from photosystem II (PSII) causes a 145 meV shift in the redox potential of the plastoquinone QA [Biochim. Biophys. Acta 1229 (1995) 193; Photosynthetica 27 (1–2) (1992) 89; Biochim. Biophys. Acta 1229 (1995) 202]. Time resolved single photon counting has been used to monitor the time dependent concentrations of the singlet states in intact and manganese depleted BBY-type core particles studied with QA in a fully open state. Surprisingly, no difference is observed between the experimental results obtained from the intact and manganese depleted samples. We demonstrate that this could be indicative of a very deep primary radical pair trap formed in PSII core particles with QA in a fully open state. Alternatively, static inhomogeneity or a possible time-dependence of the QA redox potential via relaxations such as proton motions should be considered