The structure group of an alternative algebra

The structure group of an alternative algebra and various canonical subgroups are defined and investigated. Using the principle of triality, natural sets of generators for these groups in the case of octonion algebras are exhibited. Horst Tietz zur Vollendung des achtzigsten Lebensjahres gewidmet     

Synthesis,characterization, and bonding properties of polymeric fullerides AC70.nNH3 (A = Ca,Sr, Ba,Eu, Yb)

Reduction of C70 with alkaline earth and rare earth metals dissolved in liquid ammonia results in metal fulleride solvates AC70.nNH3 (A = Ca, Sr, Ba, Eu, Yb) containing linear polymeric, anionic chains infinity 1 [C70(2-)]. The compounds were characterised by means of Raman spectroscopy and single-crystal structure determination. The accurate crystal structure of [Sr(NH3)8]C70.3NH3, determined with atomic resolution, allowed for a comparison with results of quantum chemical calculations. The nature of the C-C bonds in the fulleride is analysed in detail leading to a model explaining the unexpected polymerisation of C70(2-).     

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside and other glycosidic constituents from apple leaves

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside 1 has been isolated from a methanolic extract of apple (Malus domestica) leaves by XAD-2 adsorption chromatography and subsequent purification by high speed countercurrent chromatography (HSCCC) and HPLC. Under acidic conditions this glycoside gives rise to a number of volatile compounds including 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) 2, which is known as an off-flavor compound in wine. In the course of the study, six additional glycoconjugates were isolated from apple leaves, i.e. roseoside 3, 3-oxo-alpha-ionol beta-D-glucopyranoside 4, benzoic acid beta-D-glucose ester 5, kaempferol 3-O-rhamnoside 6, (+)-syringaresinol beta-D-glucopyranoside 7 and 4-hydroxy-5-(3'-methyl-2'-butenyl)-benzoic acid methylester 3-beta-D-glucopyranoside 8. The latter compound has been isolated for the first time in nature. In order to avoid the 'kerosene-off-flavor' caused by TDN, the methanolic extract has been subjected to yeast fermentation. This treatment reduced the amount of TDN formed and resulted in an improved flavor impression of the methanolic extract.     

Polymer microfluidic devices

Since the introduction of lab-on-a-chip devices in the early 1990s, glass has been the dominant substrate material for their fabrication (J. Chromatogr. 593 (1992) 253; Science 261 (1993) 895). This is primarily driven by the fact that fabrication methods were well established by the semiconductor industry, and surface properties and derivatization methods were well characterized and developed by the chromatography industry among others. Several material properties of glass make it a very attractive material for use in microfluidic systems; however, the cost of producing systems in glass is driving commercial producers to seek other materials. Commercial manufacturers of microfluidic devices see many benefits in employing plastics that include reduced cost and simplified manufacturing procedures, particularly when compared to glass and silicon. An additional benefit that is extremely attractive is the wide range of available plastic materials which allows the manufacturer to choose materials' properties suitable for their specific application. In this article, we present a review of polymer-based microfluidic systems including their material properties, fabrication methods, device applications, and finally an analysis of the market that drives their development.     

Short total synthesis of 8,10-di-O-methylbergenin

[reaction: see text] A short, high-yielding synthesis of the C-glucoside 8,10-di-O-methylbergenin is reported. Key elements of the synthesis are a stereoselective installation of a beta-C-aryl linkage, a palladium(0)-catalyzed aryl carbonylation, and a regioselective lactonization reaction. This pathway should allow access to a host of bergenin analogues.     

Leading off-diagonal correction to the form factor of large graphs

Using periodic-orbit theory beyond the diagonal approximation we investigate the form factor, K(tau), of a generic quantum graph with mixing classical dynamics and time-reversal symmetry. We calculate the contribution from pairs of self-intersecting orbits that differ from each other only in the orientation of a single loop. In the limit of large graphs, these pairs produce a contribution -2tau(2) to the form factor which agrees with random-matrix theory.     

A new physical characterisation of classical systems in quantum mechanics

A physical characterisation of classical systems in quantum mechanics is given in terms of the set of ensembles in contrast to the well-known characterisations concerning the effects or observables: A quantum mechanical system is classical if and only if each two decompositions of every ensemble are compatible.     

Planar nets of Ti atoms comprising squares and rhombs in the new binary antimonide Ti2Sb

The new binary antimonide Ti(2)Sb was found to crystallize in a distorted variant of the La(2)Sb type, which contains a square planar La net with short La-La bonds. In the Ti(2)Sb structure, the corresponding Ti net is deformed to squares and rhombs in order to enhance Ti-Ti bonding, as proven by single-crystal X-ray investigation in combination with the real-space pair distribution function technique utilizing both X-ray and neutron powder diffraction data. Electronic structure calculations revealed a lowering of the total energy caused by the disorder, the major driving force being strengthened Ti-Ti interactions along the diagonal of the Ti(4) rhombs.