Darstellung komplexer Betriebsschlacken des LD-Verfahrens im Quasidreistoffsystem

Aus der Darstellung der Schlackenzusammensetzungen im Quasidreistoffsystem ist die Lage der Schlacken zur Kalksättigungslinie deutlich zu erkennen. Die Sublanzenschlacken lassen den Schlackenweg während der letzten Blasminuten erkennen, durch Bodenspülung und Nachspülen wird eine geringe Annäherung an die Kalksättigungslinie erreicht. Aus der Lage der Schlacken im Quasidreistoffsystem läßt sich der Einfluß der Temperatur auf den Verlauf der Kalksättigung entlang unterschiedlicher T-X-Schnitte bestimmen.     

A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut fu?r Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s(-1). Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s(-1) and with diameters of between 0.05 μm and 5 μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.     

Improvement of Aglycone π-Stacking Yields Nanomolar to Sub-nanomolar FimH Antagonists

Antimicrobial resistance has become a serious concern for the treatment of urinary tract infections. In this context, an anti-adhesive approach targeting FimH, a bacterial lectin enabling the attachment of E. coli to host cells, has attracted considerable interest. FimH can adopt a low/medium-affinity state in the absence and a high-affinity state in the presence of shear forces. Until recently, mostly the high-affinity state has been investigated, despite the fact that a therapeutic antagonist should bind predominantly to the low-affinity state. In this communication, we demonstrate that fluorination of biphenyl α-d -mannosides leads to compounds with perfect π–π stacking interactions with the tyrosine gate of FimH, yielding low nanomolar to sub-nanomolar K_D values for the low- and high-affinity states, respectively. The face-to-face alignment of the perfluorinated biphenyl group of FimH ligands and Tyr48 was confirmed by crystal structures as well as ¹H,¹⁵N-HSQC NMR analysis. Finally, fluorination improves pharmacokinetic parameters predictive for oral availability.     

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.     

'Publish-subscribe grows up: support for management, visibility control, and heterogeneity

Message-oriented middleware is used to decouple the operation of cooperating applications. Existing approaches have concentrated mainly on scalability issues, but dynamic business processes and the integration of a wide range of data sources and applications, require a middleware that is customizable. The Rebeca publish-subscribe service uses scoping to structure both middleware and applications. It thus offers advanced routing mechanisms to subsystems that need high scalability and it allows for heterogeneous message models that are transparently mapped onto each other.     

Effect of bottom stirring and post stirring on the oxygen distribution between metal and slag at the end of the LD process

Studies concerning the effect of stirring and post-stirring on the oxygen distribution at the end of the LD process show that a post-stirring phase following the end of the blow establishes an oxygen distribution close to equilibrium. The sub-lance tests performed at 90% of the oxygen throughput show in comparison with the post-stirring phase a distinct oxygen deficiency, while the blow end-point measurements show an excess of oxygen.     

cDNA cloning,biochemical and phylogenetic characterization of beta- and beta'-subunits of Candida albicans protein kinase CK2

We have previously reported that Candida albicans protein kinase CK2 is composed of two distinct catalytic (alpha- and alpha'-) and two distinct regulatory (beta- and beta'-) subunits. We report here the isolation of two cDNAs clones, CaCKB1 and CaCKB2, encoding C. albicans beta- and beta'-subunits, respectively. The predicted beta- and beta'-proteins have calculated molecular masses of 34 kDa and 31 kDa and show all major features conserved in beta-subunits of other organisms, including the N-terminal autophosphorylation site, the internal acidic region and a potential metal-binding motif. The deduced amino acid sequence of C. albicans beta-subunit displays 48% identity with that of Saccharomyces cerevisiae and has an unusually long C-terminal acidic region containing a putative autophosphorylation site. C. albicans beta' shows 54% sequence identity with its S. cerevisiae homologue. Semi-quantitative RT-PCR analyses indicate that the mRNAs corresponding to both subunits are present in similar amounts in the yeast and hyphal forms of the fungus. To evaluate the biochemical properties of C. albicans beta- and beta'-subunits, both proteins were expressed in Escherichia coli and purified. Experiments performed in vitro indicate that both recombinant subunits reconstitute a fully functional holoenzyme when incubated with stoichiometric amounts of human recombinant alpha-subunit, as judged by their ability to abolish basal phosphorylation of calmodulin by human recombinant alpha-subunit and the reversion of the inhibitory effect by polylysine. In addition, both regulatory subunits can be phosphorylated by human recombinant alpha subunit. Phylogenetic analysis of beta- and beta'-proteins of C. albicans and other organisms shows that the CKB gene duplication occurred before the split of the ascomycete and basidiomycete lineages.