On the trimerization of cyanoacetylene: mechanism of formation of tricyanobenzene isomers and laboratory detection of their radio spectra

In support of a deeper understanding of the chemistry of cyanoacetylene--a known constituent of planetary atmospheres and interstellar space--theoretical and experimental studies address the chemical mechanism of dimerization and trimerization, and provide high-resolution rotational spectra of two of the trimeric products, 1,2,3- and 1,2,4-tricyanobenzene. Analysis of the rotational spectra is particularly challenging because of quadrupolar coupling from three (14)N nuclei. The laboratory rotational spectra provide the basis for future searches for these polar aromatic compounds in interstellar space by radio astronomy.     

Standardization in allergen determination

An overview is given of sensitization and allergic reaction on food, along with minimal eliciting doses for selected allergens (milk, egg, peanut), followed by the legislative situation in the European Community, the USA, Canada, Australia/New Zealand and Japan. The main focus of the paper discusses methods for food allergen determination (chromatography, DNA-based, antibody-based) and their limitations. Special emphasis is given on antibody-based systems, which are at the moment the most advanced and validated methods available. Examples are given of the current status of standardization for egg, milk, nuts, prolamins, glutelins and for clinical validated reference samples from the EU project EuroPrevall. Recommendations for ongoing activities are also included.     

Computational homogenization and parameter-identification for heterogeneous inelastic materials

The aim of this paper is to describe a method for identifying micro material parameters using only macroscopic experimental data. The FE² method is used to model the behavior of the complex materials with heterogeneous micro-structure. The resulting least squares problem is minimized using gradient-based optimization algorithms, where the gradient information is derived analytically within the discretized scheme. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A 43Ca and 13C NMR study of the chemical interaction between poly(ethylene-vinyl acetate) and white cement during hydration

⁴³Ca and ¹³C NMR methods were used to study the chemical interaction of poly(ethylene–vinyl acetate) (PEVAc) admixture in commercial-grade white cement. From ⁴³Ca NMR it is shown both that PEVAc induces modest changes in the hydrated cement structure, and that hydrated commercial cement is significantly more complex than models that have been used for its structure in past work. The ¹³C NMR results show that the PEVAc hydrolysis occurs early in the cement hydration acceleration period, with a rate well-fit by an exponential decay using a time constant of 6±1 days.     

Operation of a Raman laser in bulk silicon

A Raman laser based on a bulk silicon single crystal with 1.127 μm emission wavelength is demonstrated. The Si crystal with 30 mm length was placed into an external cavity and pumped by a Q-switched Nd:YAG master oscillator power amplifier system. Strong defocusing of the pump and Raman laser beam by free carriers was compensated by an intracavity lens. Raman laser operation with a pulse duration of 2.5 ns was identified by a Raman laser threshold significantly lower than the single-pass stimulated Raman-scattering threshold. Linear absorption losses of the 1.06415 μm pump radiation are strongly reduced by cooling the Si crystal to a temperature of 10 K.     

Understanding the Buoy Effect of Surface-Enriched Pt Complexes in Ionic Liquids: A Combined ARXPS and Pendant Drop Study**

Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C₄C₁Im][PF₆] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our previous angle-resolved X-ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5 %_mol down to 1 %_mol and present complementary surface tension pendant drop (PD) measurements under ultraclean vacuum conditions. This combination allows for connecting the microscopic information on the IL/gas interface derived from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1 %_mol. It also displays a strong temperature dependence, which was not observed for 5 %_mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy-complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of IL-based catalyst systems with large contact areas to the surrounding reactant/product phase, such as in supported IL phase (SILP) catalysis.     

A Fast and Efficient Track to Allosteric Modulators of Muscarinic Receptors: Microwave-Assisted Syntheses

By using microwave irradiation bisammonium-and bispyridinium-type allosteric modulators of muscarinic receptors can be obtained fast and efficiently.     

Factorization of the (relative) Chern character through Lie algebra homology

Karoubi's relative Chern character is constructed as a chain map factoring through Lie algebra chains.This is part of the author's doctoral thesis, Stanford University 1990.