Determination of stainless steel constituents in plastics

Summary Instrumental neutron activation analysis (INAA), atomic absorption spectrometry (AAS), and X-ray fluorescence analysis (XRF) were tested for the determination of the abrasion effect in plastics processing equipment. As optimal solution measurement of Fe by XRF in cylindrical samples was found.     

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.     

Confined Subspaces: A Schematic Model

 An essential feature of confining systems is the existence of channels into which probability flux can enter only for short spacetime intervals, but where it can never, irrespective of the total energy involved, propagate to asymptotic distances. It is demonstrated in a schematic quantum-mechanical model that this situation, which is unknown in ordinary scattering theory, does arise in a representation obtained through a non-unitary similarity transformation, and therefore involving a nontrivial metric. In the “confined” channels of this representation, propagation is described by Green’s functions having a complex conjugate pair of poles in momentum space instead of the usual real-axis pole. On the asymptotically accessible subspace, the S matrix is unitary, but finite-time unitarity for the total system becomes visible only when using the nontrivial metric. It is suggested that field-theory propagators with complex-conjugate pairs of singularities as obtained in several QCD studies, which seem to contradict finite-time unitarity, can in fact be imbedded into a unitary framework along the line illustrated by this model. A further conjecture is that interacting QCD fields differing from the perturbative ones by a non-unitary similarity transformation form an essential ingredient for a theory of confinement. Received June 17, 1999; accepted for publication August 23, 1999     

Material parameter computation for multi-layered vocal fold models

Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one's livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations.     

High-power sub-10-fs Ti:sapphire oscillators

Received: 10 March 1997/Revised version: 16 April 1997     

A systematic extended iterative solution for quantum chromodynamics

An outline is given of an extended perturbative solution of Euclidean QCD which systematically accounts for a class of nonperturbative effects, while still allowing renormalization by the perturbative counterterms. Euclidean proper verticesΓ are approximated by a double sequenceΓ ^[r,p] , wherer denotes the degree of rational approximation with respect to the spontaneous mass scaleΛ _QCD, nonanalytic in the couplingg ², whilep represents the order of perturbative corrections ing ² calculated fromΓ ^[r,0]-rather than from the perturbative Feynman rulesΓ ^(0)pert-as a starting point. The mechanism allowing the nonperturbative terms to reproduce themselves in the Dyson-Schwinger equations preserves perturbative renormalizability and is intimately tied to the divergence structure of the theory. As a result, it restricts the self-consistency problem for theΓ ^[r,0] rigorously — i.e. without decoupling approximations — to the seven superficially divergent vertices. An interesting aspect of the solution is that rational-function sequences for the QCD propagators contain subsequences describing short-lived elementary excitations. The method is calculational, in that it allows the known techniques of loop computation to be used while dealing with integrands of truly nonperturative content.     

Antisymmetrization effects in alpha-nucleus scattering

Antisymmetrization effects in alpha-nucleus scattering are analyzed with respect to the number of nucleons exchanged between the alpha-particle and the nucleus. It turns out that all exchange contributions are essential to reproduce the results of a completely antisymmetrized calculation. Folding model calculations should, therefore, be viewed with caution at low energies. As an example, the backangle anomaly in elastic alpha-nucleus scattering is discussed.