A Basis for Invariants in Non-Abelian Gauge Theories

An algorithm is described to convert Lorentz and gauge invariant expressions in non--Abelian gauge theories with matter into a standard form, consisting of a linear combination of basis invariants. This algorithm is needed for computer calculations of effective actions. The defining properties of the basis invariants are reported. The number of basis invariants up to mass dimension 16 are presented.Comment: 6 pages, LaTeX, talk presented at the AIHENP-95 workshop, Pisa (Italy), April 1995, revised version of the proceedings contributio

The Complete Solution of the Classical SL(2,R)/U(1) Gauged WZNW Field Theory

We prove that any gauged WZNW model has a Lax pair representation, and give explicitly the general solution of the classical equations of motion of the SL(2,R)/U(1) theory. We calculate the symplectic structure of this solution by solving a differential equation of the Gelfand-Dikii type with initial state conditions at infinity, and transform the canonical physical fields non-locally onto canonical free fields. The results will, finally, be collected in a local B\"acklund transformation. These calculations prepare the theory for an exact canonical quantization.Comment: 20 pages, no figures, LaTeX, uses amsfont

Towards a Reference Architecture for Context-Aware Services

This Chapter describes an infrastructure for multi-modal perceptual systems which aims at developing and realizing computer services that are delivered to humans in an implicit and unobtrusive way. The framework presented here supports the implementation of humancentric context-aware applications providing non-obtrusive assistance to participants in events such as meetings, lectures, conferences and presentations taking place in indoor "smart spaces". We emphasize on the design and implementation of an agent-based framework that supports "pluggable" service logic in the sense that the service developer can concentrate on the service logic independently of the underlying middleware. Furthermore, we give an example of the architecture’s ability to support the cooperation of multiple services in a meeting scenario using an intelligent connector service and a semantic web oriented travel service. The framework was developed as part of the project CHIL (Computers in the Human Interaction Loop). The vision of CHIL was to be able to provide context-aware human centric services which will operate in the background, provide assistance to the participants in the CHIL spaces and undertake tedious tasks in an unobtrusive way. To achieve this, significant effort had to be put in designing efficient context extraction components so that the CHIL system can acquire an accurate perspective of the current state of the CHIL space. However, the CHIL services required a much more sophisticated modelling of the actual event, rather than simple and fluctuating impressions of it. Furthermore, by nature the CHIL spaces are highly dynamic and heterogeneous; people join or leave, sensors fail or are restarted, user devices connect to the network, etc. To manage this diverse infrastructure, sophisticated techniques were necessary that can map all entities present in the CHIL system and provide information to all components which may require it. From these facts, one can easily understand that in addition to highly sophisticated components at an individual level, another mechanism (or a combination of mechanisms) should be present which can handle this infrastructure. The CHIL Reference Architecture for Multi Modal Systems lies in the background, and provides the solid, high performance and robust backbone for the CHIL services. Each individual need is assigned to a specially designed and integrated layer which is docked to the individual component, and provides all the necessary actions to enable the component to be plugged in the CHIL framework

The MX beamlines BL14.1-3 at BESSY II

The Macromolecular Crystallography (MX) group at the Helmholtz-Zentrum Berlin (HZB) is operating three state-of-the-art synchrotron beamlines for MX at BESSY II in Berlin (Heinemann et al., 2003; Mueller et al., 2012, 2015). The radiation source for all three beamlines BL14.1-3 is a superconducting 7T-wavelength shifter. Currently, the three beam lines are the most productive stations for MX in Germany, with about 250 PDB depositions per year and over 1500 PDB depositions in total (Status 10/2015). BL14.1 and BL14.2 are energy tuneable in the range 5.5-15.5 keV, while beam line BL14.3 is a fixed-energy side station operated at 13.8 keV. The HZB-MX beamlines are in regular user operation providing close to 200 beam days per year and about 600 user shifts to approximately 100 research groups across Europe. Additional user facilities include office space adjacent to the beam lines, a sample preparation laboratory, a biology laboratory (safety level 1) and high-end computing resources

Influence of hydroxyethyl starch (6% HES 130/0.4) administration on hematology and clinical chemistry parameters

Background: The chemical inertness of hydroxyethyl starch (HES) might cause interferences of the colloid with a variety of laboratory tests. We aimed to evaluate potential influences of HES 130/0.4, the newest HES type, on several common hematology and clinical chemistry parameters. Methods and results: A convenient sample of 25 patients scheduled for rheological therapy with 500 mL 6% HES 130/0.4 was evaluated. Blood samples were drawn before and after colloid application. Comparing pre- and post-infusion values of a battery of laboratory tests (i.e., hematology and hemostasis parameters, electrolytes, enzymes, kidney and metabolic parameters, lipids, etc.) in time course, a median difference greater than the reference change value for a specific parameter was considered clinically relevant. Among all parameters tested, only serum amylase activity displayed a clinically relevant difference between pre- and post-infusion values (median increase of 85% due to HES administration). By applying in vitro experiments, we demonstrated that serum amylase values obtained in the samples diluted in a 1:1 ratio with HES 130/0.4 and in samples diluted in a 1:1 ratio with 0.9% NaCl displayed a negligible median difference of 3%. Conclusions: The in vivo effect of HES 130/0.4 administration on serum amylase activity observed in our study was pharmacological (real) in nature. With the exception of the influence of HES 130/0.4 on amylase activity, the effects of HES 130/0.4 on other parameters tested in this study can be interpreted as having no clinical relevance

The Rev/Rex homolog HERV-K cORF multimerizes via a C-terminal domain

AbstractExpression of human endogenous retrovirus K (HERV-K) is associated with germ-cell neoplasia. HERV-K encodes a protein of the Rev/Rex family, cORF, that supports cellular transformation and binds the promyelocytic leukemia zinc finger (PLZF) protein implicated in spermatogenesis. Rev/Rex function invariably depends on multimerization. Here we show that cORF likewise self-associates to form higher-order oligomers. Amino acids (aa) 47–87 in cORF are sufficient, aa 75–87 essential for self-association. Consistently, this domain is predicted to form a hydrophobic α-helix that may represent an oligomerization interface. The existence of a dimerization-competent cORF mutant lacking PLZF-binding activity (cORF47–87) suggests a way of dominant negative inhibition of the proposed tumor susceptibility factor cORF

A silent H-bond can be mutationally activated for high-affinity interaction of BMP-2 and activin type IIB receptor

BACKGROUND: Bone morphogenetic proteins (BMPs) are key regulators in the embryonic development and postnatal tissue homeostasis in all animals. Loss of function or dysregulation of BMPs results in severe diseases or even lethality. Like transforming growth factors β (TGF-βs), activins, growth and differentiation factors (GDFs) and other members of the TGF-β superfamily, BMPs signal by assembling two types of serine/threonine-kinase receptor chains to form a hetero-oligomeric ligand-receptor complex. BMP ligand receptor interaction is highly promiscuous, i.e. BMPs bind more than one receptor of each subtype, and a receptor bind various ligands. The activin type II receptors are of particular interest, since they bind a large number of diverse ligands. In addition they act as high-affinity receptors for activins but are also low-affinity receptors for BMPs. ActR-II and ActR-IIB therefore represent an interesting example how affinity and specificity might be generated in a promiscuous background. RESULTS: Here we present the high-resolution structures of the ternary complexes of wildtype and a variant BMP-2 bound to its high-affinity type I receptor BMPR-IA and its low-affinity type II receptor ActR-IIB and compare them with the known structures of binary and ternary ligand-receptor complexes of BMP-2. In contrast to activin or TGF-β3 no changes in the dimer architecture of the BMP-2 ligand occur upon complex formation. Functional analysis of the ActR-IIB binding epitope shows that hydrophobic interactions dominate in low-affinity binding of BMPs; polar interactions contribute only little to binding affinity. However, a conserved H-bond in the center of the type II ligand-receptor interface, which does not contribute to binding in the BMP-2 – ActR-IIB interaction can be mutationally activated resulting in a BMP-2 variant with high-affinity for ActR-IIB. Further mutagenesis studies were performed to elucidate the binding mechanism allowing us to construct BMP-2 variants with defined type II receptor binding properties. CONCLUSION: Binding specificity of BMP-2 for its three type II receptors BMPR-II, Act-RII and ActR-IIB is encoded on single amino acid level. Exchange of only one or two residues results in BMP-2 variants with a dramatically altered type II receptor specificity profile, possibly allowing construction of BMP-2 variants that address a single type II receptor. The structure-/function studies presented here revealed a new mechanism, in which the energy contribution of a conserved H-bond is modulated by surrounding intramolecular interactions to achieve a switch between low- and high-affinity binding