Ein Verfahren zur Messung der Rauhigkeitsautokorrelationsfunktion von polierten Glasoberflächen mittels Streubildscherung

A Possibility for Measuring the Autocorrelation Function of Surface Roughness by Means of Stray Light Shearing A method for measuring the autocorrelation function of polished surfaces is presented, utilizing interference of two laterally shifted projections of the scattering sample. The systematic error due to the spread function of the optical image is estimated. BK 7 and BaK 4 samples polished by different techniques are investigated.     

Biodegradable Silica Fibers from Sols

Biodegradable silica fibers for reinforcement of medical implants were successfully prepared by sol-gel processing. The spinnable precursor is based on TEOS and shows a characteristic, non-Newtonian rheological behavior in the presence of sol-particles of size 4 to 5 nm. This property suggests a non-covalent, supramolecular structure of the spinnable silica sol.The fibers obtained were characterized using IR, NMR and thermal analysis as well as biological and mechanical testing. The degradation rate of fibers was tested in continuous flow experiments. The results demonstrate a good potential of the fibers for medical applications.     

Investigations of texture formation in geomaterials by neutron diffraction with high pressure chambers

Abstract

This paper suggests a classification of texture in quartzitic rocks. Possible mechanisms of texture formation and their relation to tectonic processes are discussed.

A scheme for the experimental varification of some models describing the evolution of deformation structures in geological materials in dependence on various erxternal conditions (high pressures, temperatures, various loadings, etc.) acting on a sample is proposed.

To investigate “in situ” the mechanisms of texture formation in rocks, high pressure devices are under construction. They will be built of a special T_i ? Z_r alloy, which has zero coherent scattering lenght and therefore is well suited for neutron diffraction investigations. Two different devices are proposed. The first one allows neutron diffraction measurements of sample volumes up to 4 cm³, a hydrostatic pressure of 1, 5 GPa, a temperature of 300° C, and uniaxial compression up to 50 kN. Pressure temperature and axial load are measured inside the chamber. Besides during the experiment, diagrams of load, elastic wave velocities and acoustic emission will be recorded. The second chamber is designed to investigate the mechanisms of texture formation in polycrystal samples (rocks or their imitations) at temperatures up to 800° C and axial compression with a force of up to 150 kN.     

Excitation of the quasi-bound state in 4He by electron scattering at medium momentum transfer

The cross sections of inelastic electron scattering on ⁴He leading to the quasi-bound state (0⁺, ε = 20.1 MeV) were measured in the momentum transfer range 0.8 fm^?2 < q² < 2.4 fm^?2. We found it to be a pure longitudinal transition and give the form factor of this C0transition.     

Methyl barrier to internal rotation and quadrupole coupling constants in S-methylchlorothioformate

Internal rotation A-E splittings have been observed in the ground state for both ³⁵Cl and ³⁷Cl isotopic species of S-methylchlorothioformate. The values $\text{V}{}_3\text{(}{}^{35}\text{Cl}\text{) = 893 ± 20}$ and $\text{V}{}_3\text{(}{}^{37}\text{Cl) = 890 ± 20 cal/mole}$ have been obtained. The anaalysis of the hyperfine structure gave $\text{χ}{}_{\mathrm{aa}}\text{(}{}^{35}\text{Cl}\text{) = ?49.2}$, $\text{χ}{}_{\mathrm{bb}}\text{(}{}^{35}\text{Cl}\text{) = 22.4}$ and $\text{χ}{}_{\mathrm{aa}}\text{(}{}^{37}\text{Cl}\text{) = ?39.0}$, $\text{χ}{}_{\mathrm{bb}}\text{(}{}^{37}\text{Cl) = 18.3 MHz}$. Only the syn-conformation of the methyl group with respect to the carbonyl group has been observed. A partial r₀ structure is given.     

Zur katalytischen Dimerisierung von Propionaldehyd druch Gemischt-Ligand-Nickel(O)-Komplexe

Catalytical Dimerisation of Propione Aldehyde by Mixed Ligand-Nickel(O)Complexes The reaction of carbonyl compounds with mixed ligand-nickel(O) complexes is described with propione aldehyde as an example. A catalytical conversion of propione aldehyde to α-methyl-β-ethyl-acroleine is found in a high yield. This reaction is influenced by neutralligands bonded at the nickel atom. A complexcoordinative mechanism is provided by pattern reactions. An essential intermediate — 2, 2′-bipyridine-α-methyl-β-ethyl-acroleine-nickel(O) — is isolated. The solvatochromic and thermochromic effects of this compound are discussed.     

Effects of poloxamer polydispersity on micellization in water

The poloxamer 284 (Pluronic P94) is a triblock copolymer of poly(ethylene oxide) and poly(propylene oxide). P94 and fractions of P94 obtained after centrifugation at temperatures where solutions contain both dissolved unimers and micelles have been investigated by differential scanning calorimetry, mass spectrometry, and NMR. The results show that the P94 sample is heterogeneous with respect to both chemical composition and molar mass. The first micelles formed, when the temperature is increased, contain poloxamers with a significantly higher propylene oxide content and a higher molar mass in agreement with theoretical predictions. The characteristic temperatures of micellization, sphere-to-rod, and phase separation transitions observed in thermograms are influenced by polydispersity, which results in broader transitions.     

Neutral cyclodextrins as chiral agents for enantiomeric separations of chromanes in capillary electrophoresis

Summary Six different cyclodextrins with varying cavity size and rim substitution were used as chiral agents for the enantiomeric separation of eight chromane compounds or analogues using capillary electrophoresis. It is shown that the cyclodextrin type and concentration have a large influence on the enantiomeric separation obtained for these compounds. A chiral resolution of 1.4 or better could be obtained for all the substances with either substituted heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin or unsubstituted γ-cyclodextrin as the chiral selector. The influence of the γ-cyclodextrin concentration, ionic strength and pH on the chiral separations was also investigated with a multivariate screening design. The detection limit and resolution of the present method allow determinations of the investigated compounds down to a chiral impurity of less than 0.1 % (area/area).