The construction of the sh-Lie-algebra of closed bosonic strings

We present a construction of the closed string algebra in terms of Gaussian processes and crossed products. Also we give a purely functional analytical prove of the sh-Lie-structure.     

Rhenium on W(110): Structure and mobility of higher clusters

Rhenium tetramers, pentamers, and larger clusters have been formed on W(110) and examined in the field ion microscope. Tetramers and pentamers exist in different configurations, but an open, ringlike structure predominates at high temperatures. In this configuration none of the component adatoms are in nearest neighbor sites, and the atoms can be individually resolved. The mobility of these open clusters has been explored, and found to be considerably higher than that of tri mers, or of larger aggregates.     

Direct evidence for conduction pathways in a solid electrolyte

The emission of silver ions from the apex of an amorphous electrolyte tip has been investigated by field ion microscopy. The ion emission patterns show discrete nanometer-sized spots. We present evidence that they represent the termination of bulk ion conduction pathways at the solid-vacuum interface. The analysis of the signals from individual emission sites suggests the existence of a network of such pathways in the solid. Auto- and cross-correlation measurements of the currents from individual sites provide quantitative information on the microscopic dynamics of charge transport in solid electrolytes as well as on the lateral extent of the pathway network.     

Lattice steps and adatom binding on W(211)

The role of a lattice step in affecting the binding of adatoms in its vicinity has been explored for tungsten as well as rhenium adatoms on the (211) plane of tungsten. On this plane adatoms are confined to sites in a one-dimensional channel along [1̄11]. From the equilibrium distribution of an adatom over all sites in a channel it is possible to derive the relative free energy of binding at the different sites. Such measurements have been made using a field ion microscope supported by an automated data handling system. Contrary to expectations based on potential calculations using standard pair interactions, atom binding is found to be stronger close to the plane edges rather than in the center, where the number of distant neighbors around the adatom is larger. These edge effects have a surprisingly long range, extending at least over three sites, and are strongly dependent upon the chemical identity of the adatom.     

Liquid crystalline model compounds based on 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA)

3,3',4,4'-Biphenyltetracarboxylic dianhydride (BPDA) was investigated as the central core unit in mesogenic molecules. Of particular interest was whether the BPDA unit could be self-constrained into a trans-conformation, and thus organize into a liquid crystalline phase. Two homologous series of symmetrical substituted model compounds, 3,3',4,4'-biphenyltetracarboxy-N-N'-bis-(4-n- alkylphenyl) diimides and 3,3',4,4'-biphenyltetracarboxy-N-N'-bis-(4-n- alkoxyphenyl)diimides were synthesized. For both series high temperature smectic A phases were observed. To our knowledge these are the first examples of liquid crystalline behaviour observed with BPDA as the mesogenic core.     

Determination of alkylphenols and linear alkylbenzene sulfonates in sediments applying accelerated solvent extraction (ASE)

A time and solvent saving method (accelerated solvent extraction, ASE) for the extraction of anionic surfactants as linear alkylbenzene sulfonates (LAS) and alkylphenols from sediments is presented. The analytes are extracted by methanol at 100 degrees C and 150 atm within 10 min of static and 5 min of dynamic extraction. The presence of methanol and a maximum pressure of 150 atm are essential for the complete extraction of anionic surfactants, whereas the extraction of alkylphenols is independent of both parameters. The extraction of alkylphenolethoxylates yielded only unsatisfactor results. It was demonstrated that the ASE extraction is selective for LAS surfactants, while matrix substances, which are extracted by the methanol extraction and interfere with the target analytes during the HPLC-run, remain in the sample. Thus, a further clean-up procedure of the ASE extract is not necessary.