Variante Einer Neuen Sphärometrischen Methode

Ohne Zusammenfassung

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An effective and mild method for the conversion of oximes to secondary nitro compounds

A mild and efficient process for the conversion of cyclic ketones to saturated nitro compounds, as outlined below, is described.     

The role of coating densities in X-ray microanalysis

Densities of gold and carbon coatings prepared by standard methods of vacuum evaporation and magnetron sputtering were measured using grazing incidence X-ray reflection. The densities of magnetron sputtered layers were practically identical to that of the bulk material whereas vacuum evaporated carbon exhibited a density decrease by 9%. Calculations suggest that the real density of coatings is one of the parameters which must be taken into account when performing quantitative electron probe X-ray measurements, namely under the conditions disabling precise direct measurement of the mass thickness.     

Brilliant Sm, Eu, Tb, and Dy chiral lanthanide complexes with strong circularly polarized luminescence

The synthesis, characterization, and luminescent behavior of trivalent Sm, Eu, Dy, and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g(lum), recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.     

The CuPL defect and the Cus1Cui3 complex

The Cu_PL defect is characterized by intense photoluminescence (PL) emission with a 1014 meV zero-phonon line and has since long been called the ‘copper-pair’ defect. However, recent PL studies in isotopically pure ²⁸Si samples show clear evidence for four Cu atoms in this defect. This defect is one of a family of complexes that contain four (sometimes five) metal impurities. No complex containing two or three metal impurities (at least one of which is a transition metal) has been reported. We have performed systematic calculations of a priori possible Cu₄ complexes, including the Cu_s1Cu_i3 complex proposed by Shirai et al. [18]. This complex has the lowest formation energy of all the Cu₄ defects. We have studied its properties using first-principle theory. In addition to the structures, binding energies, and vibrational spectra, we studied the formation pathway in an attempt to figure out why smaller (or larger) complexes do not form. We find that Cu_s1Cu_in with n=0, 1 or 2 continue to trap Cu_i⁺ if the Fermi level is midgap, and that the process stops when n=3. © 2011 Elsevier Science. All rights reserved     

Tree-Code Based Improvement of Computational Performance of the X-ray-Matter-Interaction Simulation Tool XMDYN

In this work, we report on incorporating for the first time tree-algorithm based solvers into the molecular dynamics code, XMDYN. XMDYN was developed to describe the interaction of ultrafast X-ray pulses with atomic assemblies. It is also a part of the simulation platform, SIMEX, developed for computational single-particle imaging studies at the SPB/SFX instrument of the European XFEL facility. In order to improve the XMDYN performance, we incorporated the existing tree-algorithm based Coulomb solver, PEPC, into the code, and developed a dedicated tree-algorithm based secondary ionization solver, now also included in the XMDYN code. These extensions enable computationally efficient simulations of X-ray irradiated large atomic assemblies, e.g., large protein systems or viruses that are of strong interest for ultrafast X-ray science. The XMDYN-based preparatory simulations can now guide future single-particle-imaging experiments at the free-electron-laser facility, EuXFEL.