XPS analysis of β-AlF3 phases with Al successively substituted by Mg to be used for heterogeneously catalyzed Cl/F exchange reactions

A new method of static charge referencing was applied in a XPS study of β-AlF₃ phases with aluminum successively substituted by magnesium. This class of compounds is characterized by strong Lewis acid sites, which are assumed to be the catalytically active sites for Cl/F exchange reactions. In order to adjust their strengths Mg was introduced into the β-AlF₃ lattice. At low amounts of Mg the resulting samples were found to be highly catalytically active in Cl/F exchange reactions. 20 nm gold particles were deposited on the sample surface to provide a static charge reference. With the help of this procedure binding energies (BE) of photo peaks as well as kinetic energies (KE) of Auger electron emission peaks are presented in relation to the Au4f_7/2 BE reference. Furthermore, a detailed analysis of the relaxation behavior of the Mg nucleus lead to the conclusion that, at low Mg contents, strong Lewis acidic Mg cations in Mg_xF_y clusters act as the catalytically active sites. At high Mg contents, small MgF₂ like crystallites are formed in the disturbed β-AlF₃ lattice, which are catalytically inactive as MgF₂.     

Characterization of covalently bonded and adsorbed polymer coatings on silica, alumina and zirconia by means of physico-chemical and chromatographic methods

Polymer coatings on porous silica, alumina and zirconia were prepared by covalent bonding of a copolymer of styrene and vinylsilane on the oxidic surface with or without subsequent cross-linking of the immobilized polymeric layer. Polybutadiene and polychloromethylstyrene were adsorbed on the surface of porous alumina without covalent bonding and were cross-linked after deposition. Analysis of the pore structure of coated oxides by means of nitrogen adsorption, mercury porosimetry and inverse size-exclusion chromatography revealed different polymer distributions across the modified surface and different changes of the porosity of the initial oxides depending on the method of polymer immobilization. By covalent bonding of the copolymer of styrene and vinylsilane to alumina and zirconia with subsequent cross-linking the modifying polymeric layer, highly hydrolytic stable packings were synthesized and their application in separations with aggressive eluents were demonstrated.     

Three-dimensional pictures of industrial scenes applying an optical radar

For small scale ranging, a light beam, modulated with a wavelength typical for radio waves, is a suitable means of scanning. The ranging beam can be focussed to illuminate only a small spot. The diffuse reflection on the spot ensures that an echo appears. By applying phase comparison techniques to the ranging and echo beam the optical path length and thus the height of the illuminated surface element can be determined. By systematically deflecting the beam and thereby scanning the scene, a discrete height map is obtained. The realisation of such a small scale ‘optical radar’ is described, the main elements of which are a semiconductor diode laser for emission, an avalanche photo diode for detection, and a two-dimensional beam deflection mechanics for scanning. The typical performance is taking a picture of a volume of about 0·5 m × 0·5 m × 0·5 m within 1s, consisting of about 64 000 pixels.     

Magnetic resonance imaging in human lymphedema: comparison with lymphangioscintigraphy.

Magnetic resonance (MR) imaging and isotope lymphography (lymphangioscintigraphy, LAS) was done in 32 patients with peripheral lymphedema (19 primary and 13 secondary). MRI characteristically showed diffuse dermal and subcutaneous edema, a nonedematous, occasionally hypertrophied skeletal muscle compartment, variability in regional lymph node size and appearance depending on the underlying clinical disorder, serpiginous "channels" or "lakes" consistent with dermal collateral lymphangiectasis and sequestered lymph, and increased subcutaneous fat. In contrast, LAS showed dermal diffusion ("backflow"), cross-over with retrograde tracer backflow (reflux), delayed tracer transport, and depending on the cause of lymphedema (i.e., primary or secondary), discrete or poorly defined lymph trunks (tracer "bands") and delayed or nonvisualization of regional lymph nodes. Although not a first-line clinical test, MR particularly in conjunction with LAS noninvasively provides accurate anatomical definition of the peripheral lymphatic system. In contradistinction to LAS, MR can visualize lymph trunks, nodes, and soft tissues proximal to sites of lymphatic obstruction. Together these imaging modalities may substitute for conventional oil contrast lymphography in the evaluation of the pathogenesis and evolution of most lymphologic disorders.     

Separation studies of amino acids,proteins and enzymes on bonded 1,2-dihydroxy-, 1,2-hydroxylamino-and amino silica packings

Summary 1,2-dihydroxy-3-propoxypropyl (HPPS), 1-amino-2-hydroxy-3-propoxypropyl (AHPS) and 1-aminoethyl-3-aminopropyl (AEAPS) silica were synthesized by means of both a surface modification procedure (I) and a bulk modification procedure (II). Method (I) gave a surface concentration, , of functional groups of 2–3 mole/m², whereas method (II) gave values up to 5 mole/m². Retention times, peak asymmetries and plate heights of thiamine and ascorbic acid eluted with aqueous buffer solutions ranging from pH 5.3 to 9.2 gave only a±5% variation over periods of 12 hours and more.The recoveries of selected enzymes and proteines examined under static and dynamic conditions were between 60% and 100% depending on the functional group of the packing and on the solute. With HPPS silica, which showed the least adsorption and denaturing effects, separation of biopolymers depended on a size exclusion effect in the relative molecular mass range 10,000 to 80,000 and could be achieved within 10 min.A part of the paper was presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Febr. 28 to March 4, 1977, Cleveland, Ohio, U.S.A.     

Hydrodynamic chromatography of macromolecules on 2 μm non-porous spherical silica gel packings

Chromatographia - Non-porous spherical 2μm silica gel particles have been tested as packing for hydrodynamic chromatography of macromolecules (HDC). Columns packed with these particles in...     

Investigation of the porosity of silica and alumina with chemically bonded polystyrene

The effect of modification of porous silica and alumina with a copolymer of styrene and vinylsilane on the porosity of oxides have been investigated by means of low temperature nitrogen sorption. Only small changes of the specific surface area and of the specific pore volume were observed on modification of oxides with non-cross-linked copolymer. The specific surface area significantly increased after the cross-linking of the deposited polymeric layer while the specific pore volume remains almost unaffected. A broad hysteresis loop appears in the nitrogen sorption isotherm for the alumina modified with the cross-linked polymer. The porosity of oxides modified by chemisorption method differed strongly from that observed for composites modified by physisorption of polymer.     

Ueber die gerichtliche Chemie des Sulfonals

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