Dynamical Particle Simulation with Parallel Cache-Aware Domain Decomposition Strategies

The simulation of large particle systems with the Discrete Element Method can be very time consuming. This is due to the necessity for collision detection between the disordered particles. Various methods, originating from different areas such as computer science, are well established and have been used in various applications. For parallel computations the simulation domain needs to be divided into subdomains to be distributed among the different nodes or machines within a supercomputer or a computer-cluster. The strategy for this domain decomposition has a significant influence on the performance of the calculation. In this paper we discuss some aspects of the development of a hierarchical domain decomposition algorithm that provides flexible adaption of the decomposition pattern to the changing structure of the particle system during the simulation. Thus an even load distribution among the different machines can be maintained. Moreover, the same method is also used to deal with the computational bottleneck caused by the presence of unstructured data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurement of the hyperfine structure of antiprotonic helium

This paper discusses the level splitting of the antiprotonic helium atomcule, an exotic atom consisting of a helium nucleus, an electron, and an antiproton which occupies highly excited states with angular momentum of L ≈ 30–35. The observation of a splitting in a laser transition between two levels is presented, and an experiment in preparation at the forthcoming AD facility at CERN is described which aims at directly measuring the level splitting by using a 2-laser microwave triple resonance technique. This experiment has the potential to determine the magnetic moment of the antiproton with higher precision than currently known. This revised version was published online in August 2006 with corrections to the Cover Date.     

SCANNING AUGER ELECTRON SPECTROSCOPIC INVESTIGATIONS OF MAGNETOSTRICTIVE NANOSCALE MULTILAYERS

The characterisation of thin magnetostrictive multilayers in the nanometerscale range [(4,5nmTb₄₀Fe₆₀/9nmFe)×100] demands a surface sensitive analytical technique. A suitable technique is scanning Auger Electron Spectroscopy (AES) to determine the elemental composition, the thickness, the presence of interdiffusion between thin layers, or the presence of contamination at interfaces.Auger sputter depth profiles are obtained by using Xe-Ion bombardment to etch the sample.Sample rotation during sputtering produces shallow craters, minimises roughening and enhances depth resolution. In addition, Auger maps of the craters are used to reveal the separated magnetostrictive Tb₄₀Fe₆₀ layers and soft magnetic Fe layers.     

Quality control of vegetable oil methyl esters used as diesel fuel substitutes: Quantitative determination of mono-, di-, and triglycerides by capillary GC

Vegetable oil methyl esters are increasingly being used as substitutes for petroleum-based diesel fuels. Because the presence of triglycerides and partial glycerides in the fuel as a result of incomplete transesterification of vegetable oils can lead to serious engine problems, continuous quality control of the product is essential. A rapid gas chromatographic method has been developed for the quantitative determination of mono-, di-, and triglycerides in vegetable oil methyl esters. Prior to analysis, mono-, and diglycerides were silylated with N,O-bis(trimethylsilyl)trifluoroacetamide; tridecanoin was used as internal standard. Calibration was performed by analysis of standard solutions containing mono-, di-, and triolein: the calibration plots for mono- and diglycerides showed good linearity, whereas for triglycerides no linearity was observed for triolein concentrations below 0.05 mg/ml. When a non-linear multi level calibration was employed for the quantitation of triglycerides, the method gave excellent quantitative results for mono-, di-, and triglycerides in vegetable oil methyl esters.     

Organoplatinum compounds : III. [Me3PtCl04]4, preparative and structural aspects of a new organoplatinum cluster compound

Several methods for the preparation of Me₃PtClO₄ have been investigated: anhydrous, pure Me₃PtCl0₄ was obtained by treating AgClO₄ with Me₃PtI in dry benzene. The compound issensitive to moisture and explodes on heat or shock treatment. Molecular weight determination indicates a tetrameric structure [Me₃PtClO₄]₄, and spectroscopic data are consistent with this. Preliminary X-ray investigation of a single crystal indicates a crystal symmetry I_4I/amd (Schoenflies: D¹⁹_4h) with four [Me₃PtClO₄]₄ units in a tetragonal cell (a = b = 11.267(5); c = 25.09(1)) and local symmetry D_2d of the [Me₃PtCl0₄]₄ structure.     

Approximation numbers of bounded operators

The theory of ideals of linear operators is well developed and has a lot of applications in theory and practise. The purpose of this paper is to give a first idea of a similar theory for bounded (nonlinear) operators. In view of applications we will not give an abstract (perhaps general nonsense) theory, but an example of a class λ_p of bounded operators with a structure similar to an $\text{L}$-module($\text{L}$ represents the class of all linear operators between Banach spaces), and applications to projection methods for solving equations with λ_p-type operators.     

Holomorphe Differentialformen zu Kongruenzgruppen der Siegelschen Modulgruppe

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