Solitons in anharmonic chains with ultra-long-range interatomic interactions

We study the influence of long-range interatomic interactions on the properties of supersonic pulse solitons in anharmonic chains. We show that in the case of ultra-long-range (e.g., screened Coulomb) interactions three different types of pulse solitons coexist in a certain velocity interval: one type is unstable but the two others are stable. The high-energy stable soliton is broad and can be described in the quasicontinuum approximation. But the low-energy stable soliton consists of two components, short-range and long-range ones, and can be considered as a bound state of these components.     

Buried emitter solar cell structures: Decoupling of metallisation geometry and carrier collection geometry of back contacted solar cells

We present a novel solar cell structure, the “buried emitter solar cell”. This concept is designed for decoupling the metallisation geometry from the geometry of the carrier collecting p–n junction in back‐contacted (and in particular back‐junction) solar cells without requiring electrical insulation by dielectric layers. The most prominent features of this device structure are a carrier collecting emitter that covers close to 100% of the total cell area and an effective electrical insulation between emitter and base metallisation via a p⁺–n⁺ junction. The experimental results presented in this paper report a 19.5% efficient “buried emitter solar cell”, where 50% of the solar cell's rear side exhibit a p⁺–n⁺ junction. This preparation technique implies covering a boron‐doped p‐type emitter with an n‐type surface layer that can be efficiently surface‐passivated by thermal oxidation. All structuring of this cell has been performed by laser processing without any photo‐lithography. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Changes in surface stress, morphology and chemical composition of silica and silicon nitride surfaces during the etching by gaseous HF acid

HF acid attack of SiO₂ and Si₃N₄ substrates is analyzed to improve the sensitivity of a sensor based on microcantilever. Ex situ analysis of the etching using XPS, SIMS and AFM show significant changes in the anisotropy and the rate of the etching of the oxides on SiO₂ and Si₃N₄ surface. Those differences influence the kinetic evolution of the plastic bending deflection of the cantilever coated with SiO₂ and Si₃N₄ layer, respectively. The linear dependence between the HF concentration and the Si₃N₄ cantilever bending corresponds to a deep attack of the layer whereas the non-linear behavior observed for SiO₂ layer can be explained by a combination of deep and lateral etching. The cantilever bending is discussed in terms of free surface energy, layer thickness and grain size.     

Gaseous species as reaction tracers in the solvothermal synthesis of the zinc oxide terephthalate MOF-5

Gaseous species emitted during the zinc oxide/zinc hydroxide 1,4-benzenedicarboxylate metal organic framework synthesis (MOF-5, MOF-69c) have been used to investigate the reaction scheme that leads to the framework creation. Changes of the gas-phase composition over time indicate that the decomposition of the solvent diethylformamide occurs at least via two competing reaction pathways that can be linked to the reaction's overall water and pH management. From isotope exchange experiments, we deduce that one of the decomposition pathways leads to the removal of water from the reaction mixture, which sets the conditions when the synthesis of an oxide-based (MOF-5) instead of an hydroxide-based MOF (MOF-69c) occurs. A quantitative account of most reactants and byproducts before and after the MOF-5/MOF-69c synthesis is presented. From the investigation of the reaction intermediates and byproducts, we derive a proposal of a basic reaction scheme for the standard synthesis zinc oxide carboxylate MOFs.     

Fast wheat variety classification by capillary gel electrophoresis-on-a-chip after single-step one-grain high molecular weight glutenin extraction

Wheat variety identification based on one-step single-grain wheat extraction and fast capillary gel electrophoresis-on-a-chip (CGE-on-a-chip) analyses was evaluated for 15 different wheat varieties grown in Austria. The results of the capillary-based separation system were compared to the internationally accepted method from the International Union for the Protection of New Varieties of Plants which is based on time-consuming sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Comparable protein patterns were observed making the CGE-on-a-chip system a promising tool for high-throughput analysis in food control. For the development of a robust method protein extraction, shelf life of wheat extracts and the instrument’s variability were evaluated. It turned out that a one-step single-grain wheat extraction allowed the sample to be stored at 4 °C for up to 4 weeks without losing any valuable protein information. Furthermore, the technical variation of the whole method is very low making the biological variation of the selected wheat grains the only uncertain factor. Additionally, two unsupervised statistical methods (hierarchical cluster analysis and principal component analysis) were used for variety identification. Identification was successful for a reduced data set of 14 samples from five different wheat varieties making the combination of CGE-on-a-chip analysis of one-step single-grain extraction in combination with automatic data evaluation a promising tool for fast wheat differentiation (within a day).     

Modeling and benchmark data set for the inhibition of c-Jun N-terminal kinase-3

The goal of this paper is to present and describe a novel 2D- and 3D-QSAR (quantitative structure-activity relationship) binary classification data set for the inhibition of c-Jun N-terminal kinase-3 with previously unpublished activities for a diverse set of compounds. JNK3 is an important pharmaceutical target because it is involved in many neurological disorders. Accordingly, the development of JNK3 inhibitors has gained increasing interest. 2D and 3D versions of the data set were used, consisting of 313 (70 actives) and 249 (60 actives) compounds, respectively. All compounds, for which activity was only determined for the racemate, were removed from the 3D data set. We investigated the diversity of the data sets by an agglomerative clustering with feature trees and show that the data set contains several different scaffolds. Furthermore, we show that the benchmarks can be tackled with standard supervised learning algorithms with a convincing performance. For the 2D problem, a random decision forest classifier achieves a Matthew's correlation coefficient of 0.744, the 3D problem could be modeled with a Matthew's correlation coefficient of 0.524 with 3D pharmacophores and a support vector machine. The performance of both data sets was evaluated within a nested 10-fold cross-validation. We therefore suggest that the data set is a reasonable basis for generating QSAR models for JNK3 because of its diverse composition and the performance of the classifiers presented in this study.     

Optimization of the labeling yield by determination of the Cu<Superscript>+</Superscript>–acetonitrile complex constant in Cu<Superscript>+</Superscript>-catalyzed nucleophilic exchange reactions in mixed solvent conditions

To apply the Cu⁺-assisted nucleophilic exchange based radioiodination of aromatic compounds for more lipophilic compounds the reaction is carried out in mixed solvent conditions. Due to its physicochemical properties acetonitrile is an attractive solvent. Although acetonitrile forms complexes with Cu⁺ decreasing the labeling yield. This article describes a method for the determination of the complex constant at labeling temperature based on a Lineweaver–Burk approach, relating the reaction rate constant and the concentration of precursor in presence of different amounts of acetonitrile. The method also allows to calculate the adjusted amount of copper salt in order to obtain the same high labeling yield as obtained in absence of acetonitrile.     

Direct C-4 arylation of crotonaldehyde with arenediazonium tetrafluoroborates

Arenediazonium tetrafluoroborates react with crotonaldehyde (2-butenal) in methanol in the presence of catalytic amounts of Pd(OAc)₂ to yield mainly 4,4-dimethoxy-1-butenylarenes. In most of the examples studied, small amounts of an isomeric byproduct were formed, presumably 3,3-dimethoxy-1-methylenepropylarenes. Because crotonaldehyde and arenediazonium salts are cheap and readily available, this reaction is a convenient access to protected 4-arylbutenals.