Effective single-band Hamiltonian for electron-phonon coupling in cuprate superconductors

We derive an effective single-band Hubbard type Hamiltonian for CuO₂ planes. The Hamiltonian includes both electron-electron repulsion and electron-phonon coupling to oxygen vibrational modes. We start with first-principles density functional theory parameters and then map onto a single-band model. Unlike previous mappings to a single-band Hamiltonian, ours explicitly preserves the Fermi surface shape and matrix elements of the many-band Hamiltonian. We consider both in-plane oxygen breathing modes as well as out-of-plane tilting modes. The latter modes have a quadratic electron-phonon coupling, and are also highly anharmonic in La₂CuO₄ based superconductors. The coupling to breathing modes is too small to account for highT _c, while the coupling to quadratic modes is much stronger even though they would be neglected in a standard Migdal-Eliashberg approach to superconductivity.     

In situ analysis of three-dimensional electrolyte convection evolving during the electrodeposition of copper in magnetic gradient fields

A novel three-dimensional particle tracking velocimetry technique was used to examine the flow during electrodeposition of Cu. For the first time electrode-normal, circumferential, and radial velocities were spatially resolved during deposition in superimposed low and high magnetic gradient fields. In this way the complex interaction of magnetic field gradient force and Lorentz force induced convective effects could be measured and analyzed. Magnetic field gradient force induced electrolyte flow was detected only in high gradient magnetic fields, and it was found to be directed toward regions of gradient maxima. Since this electrode-normal flow causes enhanced transport of Cu(2+) ions from the bulk electrolyte to those regions of the working electrode where maxima of magnetic gradients are present, a structured deposit is formed during diffusion-limited electrodeposition. Lorentz force driven convection was observed during deposition in the low and the high magnetic gradient experiments. The overall fluid motion and the convection near the working electrode were determined experimentally and discussed with regard to the acting magnetic forces and numerical simulations.     

The Key Enzyme of the Sialic Acid Metabolism Is Involved in Embryoid Body Formation and Expression of Marker Genes of Germ Layer Formation

The bi-functional enzyme UDP-N-acetyl-2-epimerase/N-acetylmannosamine kinase (GNE) is the key enzyme of the sialic acid biosynthesis. Sialic acids are negatively charged nine carbon amino sugars and are found on most glycoproteins and many glycolipids in terminal positions, where they are involved in a variety of biological important molecular interactions. Inactivation of the GNE by homologous recombination results in early embryonic lethality in mice. Here, we report that GNE-deficient embryonic stem cells express less differentiation markers compared to wild-type embryonic stem cells. As a result, GNE-deficient embryonic stem cells fail to form proper embryoid bodies (EB) within the first day of culture. However, when culturing these cells in the presence of sialic acids for three days, also GNE-deficient embryonic stem cells form normal EBs. In contrast, when culturing these cells in sialic acid reduced medium, GNE-deficient embryonic stem cells proliferate faster and form larger EBs without any change in the expression of markers of the germ layers.     

Der Verdacht der Simulation

The Suspicion of Simulation. A Psychiatric Case History between Appropriation and Disciplinary Action at the End of the 19th Century. This case history explores how the question of agency was dealt with historically in two developing, normative orders of deviant behaviour. Examining the institutional career of the supposed adulterer, marriage swindler, and craft baker, we can trace the different observation regimes and systems of knowledge acquisition in the prison and in psychiatry. In both institutions there was talk of simulated madness; the explanations, however, were different. For the prison doctors and civil servants, the baker was a criminal; his deviant behaviour was a matter of consciously planned-out deception. For the examining psychiatrist, on the other hand, he was mentally ill and could not be held responsible for his own behaviour.     

Electrochemical corrosion behavior of carbon-based thin films in chloride ions containing electrolytes

Commercially available carbon-based thin films consisting of single layers of amorphous diamond-like carbon or multilayers of crystalline TiAlN or CrN with diamond-like carbon top coatings were evaluated in relation to their electrochemical corrosion behavior in chloride ions containing electrolytes. The hardened working steel (an alloy of 0.9% C, 4.1% Cr, 4.9% Mo, 1.8% V, 6.4% W) was used as a substrate material.The potentiodynamic corrosion behavior of coated samples was tested in 3.5 wt.% NaCl solution and Hank's balanced body solution, HBBS (0.89 wt.% NaCl, further chlorides, sulfates, carbonates and phosphates). The multi-layers TiAlN + a-C:H:W and CrN + a-C:H:W exhibited only a minor improvement in corrosion resistance. Single layers of amorphous diamond-like carbon coating without hydrogen (a-C) spall off during the corrosion tests in chloride containing media. A minor improvement of the corrosion resistance is possible. The a-C:H and the a-C:H:Si, which contain hydrogen, showed the best corrosion resistance with a 100 times lower corrosion current density.     

Noncovalent, site-specific biotinylation of histidine-tagged proteins

Site-specific conjugation of proteins to surfaces, spectroscopic probes, or other functional units is a key task for implementing biochemical assays. The streptavidin-biotin interaction has proven a highly versatile tool for detection, quantification, and functional analysis of proteins. We have developed an approach for site-specific reversible biotinylation of recombinant proteins through their histidine tag using biotin conjugated to the multivalent chelator trisnitrilotriacetic acid (BTtris-NTA). Stable binding of BTtris-NTA to His-tagged proteins was demonstrated, which is readily reversed by addition of imidazole, enabling versatile conjugation schemes in solution as well as at interfaces. Gel filtration experiments revealed that His-tagged proteins bind to streptavidin doped with BTtris-NTA in a 2:1 stoichiometry. Furthermore, an increased binding affinity toward His-tagged proteins was observed for BTtris-NTA linked to streptavidin compared to tris-NTA in solution and on surfaces. These results indicate an efficient cooperative interaction of two adjacent tris-NTA moieties with a single His-tag, yielding an extremely tight complex with a lifetime of several days. We demonstrate several applications of BTtris-NTA including multiplexed capturing of proteins to biosensor surfaces, cell surface labeling, and Western blot detection. The remarkable selectivity of the His-tag-specific biotinylation, as well as the highly stable, yet reversible complex provides the basis for numerous further applications for functional protein analysis.