Zur Entstehung von Oberflächenladungen im Zusammenhang mit Ionentransport- und Sekundärelektronenemissionserscheinungen

Surface charges at the glassy or metallized but isolated inner walls of differently sized diodes are investigated as dependent upon different conditions (vacuum, inner geometry, electric operational conditions). For this purpose, a special condenser discharge method is used which gives the opportunity to study under well known conditions the temporal behaviour of those surface charges caused by electrical fields from outside the tube changing with time. One gets informations concerning the transport of positive ions and of electrons within such tubes in respect to the different kinds of wall material. The conditions are given for origin and maintenance of a stable positive wall potential above 150 V. In this case, the ratio of the electron current from the cathode to the wall and to the anode respectively comes out as ascending from 0.3 to 0.7 for a variation of the anode current from 200 to 900 μA, as one finds by comparing observations of a desorption effect stimulated by the electron current to the wall.     

High-performance liquid chromatography of lactose with evaporative light scattering detection, applied to determine fine particle dose of carrier in dry powder inhalation products

A method for quantification of the fine particle dose of lactose is described, using a hydrophilic interaction chromatography (HILIC) method and evaporative light scattering detection. The HILIC method used an aminopropyl column and a mobile phase consisting of acetonitril/water (80/20, v/v) for isocratic elution. Sensitive chromatography was obtained using a low concentration of water in the extraction solvent. The detection limit (RSD<10%) at an injection volume of 10 microL is 10 microg/mL. Linearity was obtained in the range of 10-80 microg/mL (R(2)>0.99). A relative standard deviation (RSD) of 0.5% (N=6) demonstrated good precision of the optimized method.     

A posteriori control of modelling errors in linear elasticity

The concept of adaptive error control for finite element Galerkin discretizations has more recently been extended from the pure treatment of the discretization errors [1], [2] also to the control of modelling errors [4], [5]. These techniques can be employed for a rigorous justification of the local choice of the model out of a given hierarchy with increasing complexity. In the present paper the concept is exemplified by a hierarchy of linear-elastic models, consisting of a basic model with constant E modulus and an improved model with oscillating E modulus. Significant reduction of the computational complexity can be achieved by a proper choice of the model in different subdomains, automatically chosen by the error estimators. Several error indicators are investigated in the context of goal oriented error estimation. Their efficiency is compared by means of finite element simulations [3] of an elementary example. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ein Kommutativitätskriterium für unendliche auflösbare Gruppen

Ohne Zusammenfassung     

Dielectric spectroscopy on aqueous solutions of some zwitterionic amino acids

The complex (electric) permittivity of aqueous solutions of dipolar solutes has been measured as a function of frequency between 1 MHz and 40 GHz. Solutes are the isomers DL-2-aminobutyric acid, DL-3-aminobutyric acid, and 4-aminobutyric acid, and also 6-aminohexanoic acid. The measured dielectric spectra show two dispersion/dielectric loss regions, one due to the orientational diffusion of the solute molecules the other one due to the dielectric relaxation of the solvent water. A relaxation spectral function based on a model of the solutions has been fitted to the measured frequency dependence of the complex permittivity. The values for the electric dipole moment and reorientation time of the zwitterionic part of the solute particles derived by this analysis from the measurements fairly agree with theoretical predictions. Quite remarkably, the dipole moment in solution of 4-aminobutyric acid and 6-aminohexanoic acid up to remarkably high solute concentrations is nearly constant. A noteworthy result for the hydration water of the amino acids is, that its relaxation time is almost independent of the solute dipole moment.     

New Synthetic Route to Polyhedral Organylsilsesquioxanes

Hydrosilation of methylenecyclohexane and hex-1-ene by octa(hydridosilsesquioxane) catalysed by hexachloroplatinic acid is a new route to polyhedral organylsilsesquioxanes. Quantitative yield of octa(cyclohexylmethylsilsesquioxane) is reached. This reaction opens a vast field of yet unknown polyhedral silsesquioxanes.