Vacuum Cerenkov radiation

Within the classical Maxwell-Chern-Simons limit of the standard-model extension, the emission of light by uniformly moving charges is studied confirming the possibility of a Cerenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions.     

The NOνA experiment

NOνA is a long-baseline neutrino experiment designed to study ν _μ →ν _e and $\overline \nu_{\mu} \to \overline \nu_e $ oscillations. It will measure the neutrino mixing angles θ ₁₃ and θ ₂₃ with high precision, probe the neutrino mass hierarchy, and search for CP violation in neutrino oscillations. The experiment consists of two detectors. The Near Detector will be located at Fermilab close to the source of the neutrino beam. The Far Detector is being built at Ash River in northern Minnesota. It is positioned 14 mrad off the neutrino beam axis where the neutrinos have an energy distribution with a narrow peak around 2 GeV, and where the transition probability of ν _μ →ν _e is close to its maximum.     

Unusual nucleation and growth of γ′ iron nitride upon nitriding Fe–4.75 at.% Al alloy

The influence of substitutionally dissolved Al in ferritic Fe–4.75 at.% Al alloy on the nucleation and growth of γ′ iron nitride (Fe₄N_{1? x} ) was investigated upon nitriding in NH₃/H₂ gas mixtures. The nitrided specimens were characterised employing optical microscopy, scanning electron microscopy, transmission electron microscopy, electron probe microanalysis and X-ray diffraction. As compared to the nitriding of pure ferrite (α-Fe), where a layer of γ′ develops at the surface, upon nitriding ferritic Fe–4.75 at.% Al an unusual morphology of γ′ plates develops at the surface, which plates deeply penetrate the substrate. In the diffusion zone, nano-sized precipitates of γ′ and of metastable, cubic (NaCl-type) AlN occur, having, with the ferrite matrix, a Nishiyama–Wassermann orientation relationship and a Bain orientation relationship, respectively. The γ′ plates contain a high density of stacking faults and fine ε iron nitride (Fe₂N_{1? z} ) precipitates, although the formation of ε iron nitride is not expected for the employed nitriding parameters. On the basis of dedicated nitriding experiments it is shown that the unusual microstructural development is a consequence of the negligible solubility of Al in γ′ and the obstructed precipitation of the thermodynamically stable, hexagonal (wurtzite-type) AlN in ferrite.     

Towards a finite element simulation of coating by means of thermal spraying

Metal sheet forming processes like deep drawing are applied in order to produce carriage parts in mass production. Therefore, forming tools are required that are well protected against wear. For such forming tools, wear resistant surfaces are, e.g., produced by thermal spraying of hard material coatings. The thermal spraying process itself is a highly transient thermo-mechanical process. In order to gain a better understanding of the heat input and transfer during thermal spraying, a simulation framework for thermal spraying processes is presented. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A General and Highly Selective Palladium‐Catalyzed Hydroamidation of 1,3‐Diynes

A chemo‐, regio‐, and stereoselective mono‐hydroamidation of (un)symmetrical 1,3‐diynes is described. Key for the success of this novel transformation is the utilization of an advanced palladium catalyst system with the specific ligand Neolephos. The synthetic value of this general approach to synthetically useful α‐alkynyl‐α, β‐unsaturated amides is showcased by diversification of several structurally complex molecules and marketed drugs. Control experiments and density‐functional theory (M06L‐SMD) computations also suggest the crucial role of the substrate in controlling the regioselectivity of unsymmetrical 1,3‐diynes.     

Formation of “Quasi” Contact or Solvent‐separated Ion Pairs in the Local Environment of Probe Molecules Dissolved in Ionic Liquids

The change from “quasi” contact to “quasi” solvent‐separated ion‐pair configuration in the local environment of a probe molecule in ionic liquids depends on the varying interaction strength of the chosen anions. The ion speciation in these Coulomb fluids could be shown by combining infrared spectroscopy, density functional theory calculations, and natural bond orbital analysis using a low‐self‐clustering probe molecule.     

Molecular imprinting of the endogenous neuropeptide Leu5-enkephalin and some derivatives thereof

We have undertaken the molecular imprinting of Leu⁵-enkephalin, and derivatives related to this endogenous neuropeptide, in highly cross-linked methacrylic acid/ethylene dimethacrylate copolymers. The underivatized enkephalin peptide yielded polymers with poor recognition abilities, since the imprinting of this compound had to be performed using dimethyl sulfoxide, which was found to interfere with the imprint inducement, as the solvent of polymerisation. In order to circumvent this problem, the amino- and carboxy-protected derivatives Boc-Leu⁵-enkephalin and Leu⁵-enkephalin anilide, which are soluble in apolar solvents, were investigated as alternative imprint molecules. Both compounds led to polymers which are highly specific for the imprint species. The anilide derivative was shown to be a good substitute for the free peptide since the resultant polymers showed efficient recognition of the parent enkephalin structure.