29Si–1H IMPACT HMBC: a suitable tool for analyzing silylated derivatives

A modified version of the IMPACT heteronuclear multiple bond correlation (HMBC) has allowed the characterization of an organosilane and a tetrasilylated yttrium complex. With the help of this sequence, an average gain in sensitivity close to 2 has been obtained compared with the standard HMBC experiment for disilanes as well as for yttrium complexes containing silylated ligands. This modified version of this long‐range correlation experiment opens the way for following kinetics in the range of a fraction of a minute and to study by NMR low concentrated samples and low abundant nuclei. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimal Data Selection for Piezoelectric Material Characterization

In the simulation and design of piezoelectric transducers the exact knowledge of the entries in the material tensors - the elastic, dielectric and piezoelectric coupling coefficients - is an important prerequisite. Our task is the identification of these coefficients from indirect measurements, namely electric impedance data at different frequencies. This leads to a parameter identification problem for a system of coupled PDEs, which we solve by regularized Newton iterations. A crucial issue is the selection of frequencies at which measurements are taken. Here, we discuss the problem of choosing these frequencies in an optimal way to preserve efficiency of our identification scheme while improving reliability of the reconstruction results. For this purpose, we formulate this task as an optimization problem with PDE constraints and propose two approaches for its solution. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Meson production in p + d reactions

Total and differential cross sections for the reactions p + d → ³He + m ⁰ with m=π, η and p + d → ³H+π⁺ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied. Representing the GEM Collaboration     

Waterpipe smoke: A considerable source of human exposure against furanic compounds

Smoking of waterpipes became increasingly popular in the Western hemisphere in recent years. Yet, up to now only little is known about the health hazards and on the composition of waterpipe smoke. To obtain more information on the ingredients present in waterpipe smoke we utilized two different approaches. Based on headspace-solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME–GC–MS) instrumentation we identified new compounds present in the waterpipe smoke. Additional reversed-phase-high performance liquid chromatography–diode array detection (RP-HPLC–DAD) then led us to perform reliable quantification of the newly detected chemical species. Upon identification of a range of different furanic compounds such as 5-(hydroxymethyl)-2-furaldehyde (HMF), 2-furaldehyde, and others, we developed an easy-to-perform and fast RP-HPLC–DAD method to quantify these compounds in the complex matrix of waterpipe smoke. The detection limits range from 0.04 μg for HMF to 7.1 μg for 3-furan methanol per smoking session. Linearity, intra- and inter-day precision and recovery were determined and proved excellent. We analyzed 5 waterpipe tobacco brands and found up to 62.3 ± 11 mg of HMF generated during one waterpipe smoking session. The applied smoking protocol comprised 171 puffs of 530 mL each and 2.6 s duration every 20 s. Our results reveal that waterpipe smoking constitutes a major source of HMF exposure. Furthermore, we found a distinct filter effect of the bowl water for all furanic compounds investigated except HMF.     

BINAP: rhodium–diolefin complexes in asymmetric hydrogenation

The complexes [Rh((S)-BINAP)(COD)]BF₄ 1, [Rh((S)-BINAP)(NBD)]BF₄ 2, [Rh((R)-BINAP)(COD)]OTf 3, [Rh((R)-BINAP)(NBD)]OTf 4, and [Rh((R)-BINAP)(COD)]BArF 5 were synthesized, and 1–4 were analyzed by single crystal X-ray crystallography. The transformation of these precatalysts into hydrogenation-active species was investigated as well as the hydrogenation of prochiral olefins. In particular, this series of transformations was investigated with regard to solvent and counterions.     

Visualization of the gas flow in fuel cell bipolar plates using molecular flow seeding and micro-particle image velocimetry

Main components of proton exchange membrane fuel cells are bipolar plates that electrically connect the electrodes and provide a gas flow to the membrane. We investigate the flow in the channel structures of bipolar plates. Flow seeding is used to visualize the propagating and mixing gas stream. It is shown that a part of the gas is transported perpendicularly to the channel structure. An analysis of the diffusion compared with the convection shows different transport behavior for both flow directions. Additionally, the convective flow field is investigated in detail near the channel wall using Micro-PIV in a Reynolds-number-scaled liquid fluid system. For a more exact comparison of the experimental setups, flow seeding in both gas and liquid systems is performed.