Darstellung und Molekülstrukturen von oligofunktionalen Dirheniumcarbonylderivaten aus Dirheniumnonacarbonylphosphan

Preparation and Molecular Structures of Oligofunctional Dirhenium Carbonyl Derivatives from Dirhenium Nonacarbonylphosphane Starting with dirheniumdecacarbonyl, one CO-Ligand was eliminated oxidatively and substituted by the labile acetonitrile ligand. As an intermediate eq-Re₂(CO)₉NCCH₃ was received. The reaction of this labilised carbonyl with tris(trimethylsilyl)phosphine and subsequent methanolysis gave ax-Re₂(CO)₉PH₃, which was isolated and characterized for the first time. Photochemical and thermal reaction of ax-Re₂(CO)₉PH₃ led to the new bi- and trinuclear complexes Re₂(μ-H)(μ₃-PHRe(CO)₅)(CO)₈, Re₂(μ-PH₂)₂(CO)₈ and Re₂(μ-H) · (μ-PH₂)(CO)₈, which were characterized by IR-, ¹H- and ³¹P-NMR spectroscopy. The structures of ax-Re₂(CO)₉PH₃, Re₂(μ-H)(μ₃-PHRe(CO)₅)(CO)₈ and Re₂(μ-PH₂)₂(CO)₈ were confirmed by single-crystal X-ray analysis. ax-Re₂(CO)₉PH₃ has a very short Re? P bond length of 228(2) pm.     

Application of enzyme-field effect transistor sensor arrays as detectors in a flow-injection analysis system for simultaneous monitoring of medium components. Part II. Monitoring of cultivation processes

Glucose, maltose, sucrose, lactose, ethanol and urea concentrations were monitored simultaneously during the cultivation of Escherichia coli and Saccharomyces cerevisiae by means of enzyme field effect transistors (EnFETs) applying glucose dehydrogenase (GDH), maltase (MAL)/GDH, invertase (INV)/GDH, β-galactosidase (β-GAL)/galactosedehydrogenase (GALDH), alcoholdehydrogenase (ADH)/aldehydedehydrogenase (ALDH), and urease. These enzymes were (co)immobilized on the pH sensitive gates of an eight-FET array. The FET array was integrated in a commercial FIA system.     

Siderophore Transport in Mycobacteria Analyzed by Mössbauer Spectroscopy: Possible Routes to Novel Antibiotics against These Organisms?

Iron uptake of the ⁵⁷Fe-siderophores ferricrocin, rhizoferrin and citrate in M. smegmatis was analyzed by in situ Mössbauer spectroscopy. Siderophore dependent uptake and metabolic utilization patterns of ⁵⁷Fe were found. Rhizoferrin is accumulated in the organism and, therefore, represents a suitable candidate for the synthesis of novel siderophore-antibiotics conjugates.     

Induced smectic C* phases

Induced ferroelectric S*_C phases are formed by non-chiral S_C host phases doped with chiral dipolar guest molecules. In those mixtures the spontaneous polarization P_s and the tilt angle Θ has been investigated as a function of the mole fraction x_G of the chiral dopant. In most cases the reduced polarization P₀ = P_S/ sin Θ has been found to depend linearly on x_G. The polarization power which is defined by δ_P=(∂P₀/∂x_G)ΔT is discussed in terms of the molecular structure of the chiral dopants. There are systems in which P₀(x_G) deviates positively from linearity. This behaviour can be understood by considering a local field correction to P₀. By assuming a local field of Lorentz type a theoretical relation for P₀(x_G) has been derived which explains the experimental results. The effect of a local field is considerable if the transverse dipole moment and the polarizability of the chiral dopant are large.     

MITATT mode in DDR heterostructure Impatt

Large signal characterisation of double heterostructure DDR Impatt diode has been carried out in the millimeter-wave range considering the MITATT mode of operation. The structure of the device is p⁺-p₂-p₁-n₁-n₂-n⁺ where impact ionisation and tunneling takes place in the p₁-n₁ region. In this study we have considered two well-known heterostructures, e.g., InP/GaInAs/InP and InP/InGaAsP/InP and one nonconventional structure GaAs/InP/GaAs. The theoretical results of the performances of these devices as regards of output power, efficiency, and negative conductance revealed that the structures are quite promising as the source of power in the millimeter-wave range. The analysis may be used for other mm wave DDR heterostructure Impatts.     

On a new class of function systems of Faber-Schauder type

In this paper, we introduce a new class of function systems generalizing the classical Faber-Schauder system. Under the condition that the generating sequence is bounded, we show that systems of such a class constitute bases in the space of continuous functions and prove some properties of series expansions of functions in these systems.     

Fluctuation measurements in a supersonic boundary layer implying in-situ calibration of the hot-wire anemometer

A calibration technique for the constant-temperature hot-wire anemometer is presented, which is based on traversing the probe through the boundary layer of a flat plate while simultaneously performing fluctuation measurements. The free stream Mach number was M = 2.54, and the Reynolds number Re_d, based on wire diameter, ranged from 9 to 23. A comparison of the sensitivity values obtained with the aid of such a calibration procedure — under the condition of neglecting low temperature loadings (t<0.6) — agrees well with sensitivities determined with free-stream data-The use of a modified transfer function for correcting the power spectra of flow perturbations revealed a conformity of wide parts of the corrected spectra with the Kolmogorov decay. The fluctuation levels of total temperature and mass flux were computed for the boundary layer of a flat plate. This work was presented at the International Conference on the Methods of Aerophysical Research ICMAR 2007, which was held in Novosibirsk on 5–10 February 2007.     

Mg 2p shallow core-level and local atomic structure of i-ZnMgRE quasicrystals

We present a detailed analysis of the Mg 2p shallow core-levels measured on icosahedral single-grain ZnMgY, ZnMgHo, and ZnMgEr quasicrystals during a photoelectron microscopy study. The synchrotron radiation photoemission measurements were performed on in situ cleaved samples at a pressure of 10⁻¹⁰ mbar and at low temperature, typically 90-150 K. The Mg 2p photoemission lines are essentially broadened as compared to those of the Mg 2p spin-orbit doublet recorded on the Zn₂Mg crystalline Laves phase. The broadening is associated to the coordination shifts of the Mg 2p level due to the inequivalent magnesium sites in the quasicrystalline lattice. The coordination shifts are calculated on the basis of i-ZnMg(Ho, Y) atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts obtained are up to 0.2 eV. The Mg 2p experimental spectral intensity is nicely reproduced by a superposition of coordination-shifted Mg 2p spin-orbit doublets.