IV. Referate

Ohne Zusammenfassung     

On an analogy to the area–velocity relation of gasdynamics in slender vortices

Inviscid compressible flow in a slender longitudinal vortex with the axis parallel to the main flow direction is discussed. The Euler equations for steady, axially symmetric flow are simplified for the neighbourhood of the axis of the vortex. The resulting relations, expressing the angular velocity in terms of the axial mass flow, when recast and integrated, represent an analogy to the area–velocity and the area-Mach number relation of one-dimensional gasdynamics. By restricting the analysis to the flow in a Rankine vortex with constant stagnation enthalpy, the static pressure on the axis can be related to the free-stream pressure far away from the axis and the maximum value of the azimuthal velocity. The influence of a radial wake-like distribution of the axial velocity component on the axial pressure is discussed. Its dependence on variable external boundary conditions is given. A condition is formulated, which has to be satisfied for the formation of a free stagnation point on the axis.     

Referate

Ohne Zusammenfassung     

Referate

Ohne Zusammenfassung     

Referate

Ohne Zusammenfassung     

IV. Referate

Ohne Zusammenfassung     

ESBL-producing E. coli in Austrian sewage sludge

The aim of this study was to investigate the degree of contamination of sewage sludge with ESBL-producing Escherichia coli strains and the effectiveness of different sewage sludge treatment methods.Monthly sewage sludge samples were collected between January and September 2009 in 5 different sewage treatment plants and tested for the presence of ESBL E. coli. In addition, the number of colony forming units (CFU) of E. coli and coliform bacteria before and after the different sludge treatment methods (aerobic/anaerobic digestion, lime stabilization, and thermal treatment) was investigated.Of the 72 sewage sludge samples investigated, ESBL-positive E. coli were found in 44 (61.1%) sewage sludge samples. The classification of β-lactamase groups was carried out in 15 strains resulting in the detection of 2 different groups (CTX-M and TEM) of bla genes. All 15 of them had a CTX-M gene and 4 of these strains furthermore carried a TEM gene.With regard to the CFU of E. coli and coliform bacteria, thermal treatment and lime stabilization following dehydration sufficiently reduced pathogen concentrations. The plants using merely stabilization and dehydration showed an increase of E. coli and coliform bacteria and thus also an increase in ESBL-producing E. coli.     

Aerobic Oxidative Coupling of o‐Xylene: Discovery of 2‐Fluoropyridine as a Ligand to Support Selective Pd‐Catalyzed C?H Functionalization

An improved method for the direct oxidative coupling of o‐xylene could provide streamlined access to an important monomer used in polyimide resins. The use of 2‐fluoropyridine as a ligand has been found to enable unprecedented levels of chemo‐ and regioselectivity in this palladium‐catalyzed aerobic oxidative coupling reaction. Preliminary insights have been obtained into the origin of the effectiveness of 2‐fluoropyridine as a ligand.     

Screening method for nitroaromatic compounds in water based on solid-phase microextraction and infrared spectroscopy

A new method is described for determining nitroaromatic compounds in water that combines solid-phase microextraction (SPME) and infrared (IR) spectroscopy. In this method, the compounds are extracted from a 250-mL volume of water into a small square (3.2 cm x 3.2 cm x 61.2 microm thick) of silicone polycarbonate copolymer film (MEM-213). Five nitroaromatic compounds, including 2,4,6-trinitrotoluene (TNT), were chosen to evaluate the SPME/IR procedure. Quantitation limits for the five test compounds range from 50 microg/L for TNT to 400 microg/L for nitrobenzene. Precision values, determined at aqueous concentrations of four times the quantitation limit, range from 4 to 7%, and linear dynamic ranges extend to the maximum limit of the IR instrumentation. The potential of this SPME/IR method for determining nitroaromatics in natural water samples was also investigated by extracting "real world" soil samples contaminated with TNT. Results obtained from the SPME/ IR determination of the diluted extracts were in reasonable agreement with those obtained from dichloromethane extraction followed by gas chromatographic analysis.     

Probing the pore space of geothermal reservoir sandstones by Nuclear Magnetic Resonance

Pulsed-Field-Gradient–Nuclear Magnetic Resonance (PFG–NMR) is an interesting method to determine microscopic but volumetrically averaged properties of pore space. In the present paper a number of sandstone samples, taken from drill cores of geothermal wells in North Germany, have been investigated. The time-dependent self-diffusion of water molecules in their confined geometry is used to probe the pore space. The short-time behaviour of the self-diffusion coefficient (anomalous diffusion) in the porous matrix allows the determination of the surface-to-pore volume ratio S/V_p. At long diffusion times, molecules scout the tortuosity of the interconnected pore space of the sandstones. The NMR results were compared with data from petrographic image analysis (PIA), adsorption experiments and electric conductivity measurements. The PFG–NMR measurements give surface-to-pore volume ratios S/V_p that are comparable to those estimated with the petrographic image analysis. The tortuosities match in most cases data from conductivity measurements, so the PFG–NMR is regarded as an appropriate tool to determine this quantity. The results are not influenced by the adherence of ‘scout-molecules’ to the pore walls. The surface-to-pore volume ratios and tortuosities were used to calculate permeabilities of the systems of interest, which were in good agreement with measured core-plug permeabilities. Results of additional NMR relaxation experiments are used to obtain adsorption isotherms for cations at active surface sites.