Assessing the performance of German <Emphasis Type="Italic">Bundesliga</Emphasis> football players: a non-parametric metafrontier approach

This article presents a novel model for evaluating the performance of field players in football. Based upon Data Envelopment Analysis (DEA), we employ a non-concave metafrontier approach that permits estimation of players’ efficiency scores under consideration of their playing positions. The model is applied to a data set of Germany’s premier league football players covering the playing seasons 2002/03 to 2008/09. The results reveal a clear positive relationship between a team’s average player efficiency score and its rank in the league table at the end of the season. In addition, the metafrontier approach is used to identify a footballer’s optimal playing position in the team and to quantify the performance increase from moving to that position.     

Hydrogen absorption and desorption properties of a novel ScNiAl alloy

A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen reversibly. In this compound, hydrogen absorption is a two-step process; solid solution of hydrogen at temperatures below 180°C and decomposition into ScH₂ and NiAl at higher temperatures. Detailed analysis of the hydrogen absorption/desorption has been performed using in situ synchrotron radiation powder X-ray diffraction and thermal desorption spectroscopy. The apparent activation energy for hydrogen desorption was determined to be 182 kJ/mol and the material is stable during cycling.     

Analysis of Organochlorine Pesticides by Solid-Phase Microextraction followed by Gas Chromatography-Mass Spectrometry

Solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was optimized for the analysis of hexachlorocyclohexanes, DDD, DDE, DDT and other organochlorine pesticides in aqueous samples. Higher extraction efficiency was observed with the SPME fibre coated with 100 µm polydimethylsiloxane than with the fibres coated with 85 µm polyacrylate or 65 µm polydimethylsiloxane/divinylbenzene. Equilibration times were longer than 60 min, except for the hexachlorocyclohexanes, in spite of rapid stirring of the sample. However, precise quantitative analysis could be performed also under non-equilibrium conditions: i.e. repeatability standard deviations below 20%. Salt addition had a positive effect on the response for the hexachlorocyclohexanes, whereas the extraction of the other analytes was affected negatively. The pH of the sample solution did not influence the extraction efficiency. The desorption was performed for 5 min at 275°C directly in the GC injector. At shorter desorption times or lower temperatures a significant carry-over was observed for the heavier analytes. Generally, detection limits in the ng/L range were obtainable.     

Single switch surface hopping for a model of pyrazine

The single switch trajectory surface hopping algorithm is tested for numerical simulations of a two-state three-mode model for the internal conversion of pyrazine through a conical intersection of potential energy surfaces. The algorithm is compared to two other surface hopping approaches, namely, Tully's method of the fewest switches [J. Chem. Phys. 93, 1061 (1990)] and the method by Voronin et al. [J. Phys. Chem. A 102, 6057 (1998)]. The single switch algorithm achieves the most accurate results. Replacing its deterministic nonadiabatic branching condition by a probabilistic accept-reject criterion, one obtains the method of Voronin et al. without momentum adjustment. This probabilistic version of the single switch approach outperforms the considered algorithms in terms of accuracy, memory requirement, and runtime.     

Determination of D/L-amino acids by zero needle voltage electrospray ionisation

Ion formation may be made more efficient than in normal electrospray ionization (ESI) for certain classes of compounds, such as the polar amino acids Glu, Asn, His, Ser, Asp, Arg, Tyr and Lys, by adjusting the voltage of a normal ESI interface needle to zero voltage. For aspartic acid (Asp) the gain in signal-to-noise (S/N) ratio of the liquid chromatography/mass spectrometry (LC/MS) chromatograms obtained in the selective ion monitoring (SIM) mode (m/z 134) with zero needle potential was 40-50 times higher than detection at 4 kV. Ion formation at zero potential is likely to follow a mechanism related to sonic spray ionization. The utility of the zero needle voltage ESI was illustrated by determining the age of a human tooth by the aspartic acid epimerization method. The procedure involved separating the D- and L-aspartic acid of a tooth extract on a chiral HPLC column and detection by zero voltage ESI-MS3.     

Application of membrane inlet mass spectrometry for online and in situ analysis of methane in aquatic environments

A method is presented for the online measurement of methane in aquatic environments by application of membrane inlet mass spectrometry (MIMS). For this purpose, the underwater mass spectrometer Inspectr200-200 was applied. A simple and reliable volumetric calibration technique, based on the mixing of two end member concentrations, was used for the analysis of CH₄ by MIMS. To minimize interferences caused by the high water vapor content, permeating through the membrane inlet system into the vacuum section of the mass spectrometer, a cool-trap was designed. With the application of the cool-trap, the detection limit was lowered from 100 to 16 nmol/L CH₄. This allows for measurements of methane concentrations in surface and bottom waters of coastal areas and lakes. Furthermore, in case of membrane rupture, the cool-trap acts as a security system, avoiding total damage of the mass spectrometer by flushing it with water. The Inspectr200-200 was applied for studies of methane and carbon dioxide concentrations in coastal areas of the Baltic Sea and Lake Constance. The low detection limit and fast response time of the MIMS allowed a detailed investigation of methane concentrations in the vicinity of gas seepages.     

Bonding modes of stanna-closo-dodecaborate: eta1(Sn) to eta3(BH) rearrangement reactions in zwitterionic stanna-closo-dodecaborate ruthenium complexes

Reaction of the stanna-closo-dodecaborate salt [Bu3MeN]2[SnB11H11] with the dimeric ruthenium complex [Ru2(mu-Cl)3(triphos)2]Cl (triphos = {MeC(CH2PPh2)3}) in refluxing acetonitrile yields the zwitterionic compound [Ru(SnB11H11)(MeCN)2(triphos)] (4) which has been characterized by single-crystal X-ray diffraction analysis and solid-state NMR spectroscopy. Refluxing the zwitterion in acetone leads to an eta1(Sn) to eta3(BH) rearrangement with formation of [Ru(SnB1)H11)(triphos)] (5) whose structure has been confirmed by X-ray diffraction and multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, two isomeric zwitterions fac- and mer-[Ru(SnB11H11)(dppb)(MeCN)3] (6a, 6b) and their rearrangement reactions as well as their NMR properties are described.     

Applications of Rosenbrock-type methods to the p-version of finite elements

In quasistatic solid mechanics the spatial as well as the temporal domain need to be discetized. For the spatial discretization usually elements with linear shape functions are used even though it has been shown that generally the p-version of the finite elemente method yields more effective discretizations, see e.g. [1], [2]. For the temporal discretization diagonal-implicit, see e.g. [4], and especially linear-implicit Runge-Kutta schemes, see e.g. [5], [6], have for smooth problems proven to be superior to the frequently applied Backward-Euler scheme (BE). Thus an approach combining the p-version of the finite element method with linear-implicit Runge-Kutta schemes, so-called Rosenbrock-type methods, is presented. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anisotropic finite strain hyperelasticity based on the multiplicative decomposition of the deformation gradient

In this contribution a new constitutive model for transversely isotropic materials is presented. The proposed model is based on the multiplicative decomposition of the deformation gradient into one part containing the deformation only in the direction of anisotropy and another part describing the remaining deformation. This clear assignment leads to a decoupling of the stress-state. The model is investigated analytically in view of simple tension. Moreover, an inhomogenous deformation is solved using a finite elements simulation. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)