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Die Kombination einer Membran mit einer katalytischen Reaktion in einem Membranreaktor ist eines der Konzepte multifunktionaler Reaktoren zur Prozessintensivierung. Eine industriell besonders interessante Anwendung ist dabei die Darstellung von Synthesegas durch partielle Oxidation von Methan zu Kohlenmonoxid und Wasserstoff, wobei der Sauerstoff durch eine gemischtleitende Perowskit-Membran aus Luft zudosiert wird. Es ist gelungen, entsprechende Perowskit-Membranen als Hohlfasern mit einer volumenbezogenen Membranfläche von bis zu 500 m2/m3 durch einen ökonomischen Spinnprozess zu entwickeln. Unter Laborbedingungen konnten langzeitstabil Synthesegas (CO, H2) mit einer CO-Selektivität von 95 % bei 95 % CH4-Umsatz erzeugt und die Ergebnisse durch eine detaillierte mathematische Modellierung beschrieben werden.

Für die Entfernung von VOC (volatile organic compounds) aus der Luft von Fertigungsstätten werden vielfach mikroporöse Adsorbentien eingesetzt. Die gereinigte Luft wird rezyklisiert. Für die mit VOC beladenen Adsorbentien wird ein Regenerierungsweg für den mehrfachen Gebrauch gesucht. Bei der Regenerierung sollen die VOC möglichst vollständig desorbiert werden und mit einer geringen Gasmenge in einer katalytischen Verbrennung zu CO2 und H2O umgewandelt werden. Die Wirtschaftlichkeit der Luftreinigung wird wesentlich bestimmt durch die Sorptionskapazität des Adsorbens, die erforderliche Energie für die thermische Regenerierung und die Menge des Spülgases bei der Regenerierung. In dieser Arbeit wird der Einsatz von Typ X-Zeolithpulver in der Luftreinigung einer Lackiererei beschrieben und dessen Regenerierung im Labor mittels DTA/TG und Isothermenmessung der Schlüsselkomponenten untersucht. Ferner wurde die Regenerierung des beladenen Zeoliths in einem Labor-Drehrohrofen unter Variation der Betriebsparameter untersucht und anschließend mit ausgewählten Parametern in einem kleintechnischen Drehrohrofen durchgeführt. Die Verfahrensvarianten werden diskutiert.

Novel hydrophilic SiOxmodified alumina membranes with high separation factors and flux rates have been prepared for the separation of water from organic solvents. For the preparation of the membranes, SiOxnetworks are deposited inside the γ‐Al2O3layer of a commercial ultrafiltration membrane by hydrolysis of tetraethylorthosilicate in autoclaves at 250 °C. The transport resistances of the individual membrane layers for the permeation flux are described by a model. The membranes are stable towards solvents to temperatures of at least 150 °C. Pervaporation studies show that water can be separated from solvents such as acetonitrile, tetrahydrofurane, 2‐propanol, ethyl alcohol, dimethylsulfoxide, N, N‐dimethylformamide, and phenol. The separation performance of the membranes allows their use in technical separation processes, especially for the removal of water.

Molecular sieve membranes are characterized by their high thermal and chemical resistance and by their monodisperse micropore system. Mixtures can be separated by their molecular size as well as by adsorptive interactions and differences in the diffusion coefficients. In this paper, techniques for a reproducible preparation of large area tubular zeolite membranes together with ways for their regeneration and repair are shown. The separation figures demonstrate the efficiency of the molecular sieve membranes developed. Potential application fields are discussed.

Molekularsieb-Membranen zeichnen sich durch ihre hohe thermische und chemische Beständigkeit und ihr monodisperses mikroporöses Porensystem aus. Stoffgemische werden nach der Molekülgröße oder nach ihrer Adsorptions- und Diffusions-Wechselwirkung getrennt. Es werden Wege zur reproduzierbaren Herstellung großflächiger Membranen und zu ihrer Regenerierung und Reparatur gezeigt. Die Trennbeispiele demonstrieren die Leistungsfähigkeit der Membranen. Künftige Einsatzgebiete lassen sich aus der Darstellung der Entwicklungstrends ableiten.

AIMS: Ultrafast detector technology enables bolus-triggered application of contrast media. In a prospective study we investigated the benefit of this new method with the intention of optimizing enhancement during examination of the chest and abdomen.

Lymphocyte blast transformation of 23 melanoma patients was compared to that of 22 healthy persons after stimulation with the mitogens PHA, ConA, and PWM. Transformation rate of lymphocytes in microcultures was measured following 3H-Thymidin uptake in a Liquid-Scintillation-Counter. Calculations were based on analyses of variance. There was no significant difference in blastogenetic response between the 2 groups (patients and controls), but there were differences between the used mitogens.

Translational diffusion of molecules in one-dimensional channel systems has been measured by quasi-elastic neutron scattering. The scattering function for a single-file diffusion model has been derived in order to differentiate this transport model from normal 1D diffusion. In the AlPO4-5 structure, ordinary 1D diffusion is observed for methane and ethane, whatever the loading, which indicates that the molecules are able to pass each other. The diffusion coefficients for both molecules are on the order of 10^-9 m² s^-1. On the other hand, a quite different regime is obtained by varying cyclopropane concentration in the same structure. At low loading, normal 1D diffusion is observed because the molecules can be considered as isolated, but at higher concentration cyclopropane is found to follow single-file diffusion. However, the mobility is too small to be determined. In the less open channel system of ZSM-48, ordinary 1D diffusion is found for small methane concentration, the diffusion coefficient being 2.5 × 10^-9 m² s^-1, at 155 K. At medium loading, single-file diffusion is observed with a mobility factor of 2 × 10^-12 m² s^-1/2. This is the first time that this technique has provided experimental evidence of single-file diffusion in zeolites.

Cefetamet pivoxil was investigated in an open, randomized comparative study involving a total of 37 children with acute pyelonephritis, whose ages ranged from 2 to 14 years. The patients received either 10 mg/kg (n= 18) or 20 mg/kg (n= 8) cefetamet pivoxil twice daily, or 30–50 mg/kg amoxycillin/clavulanic acid three times daily (n= 11) for a period of 7–10 days. Escherichia coliwas the main causative agent isolated in 28 (75.7%) of the patients; other pathogens included Proteus mirabilis(three patients), Proteusspecies (one patient), Klebsiella pneumoniae(two patients), Pseudomonas diminuta(one patient) and mixed infections (three patients). No differences in the overall treatment outcome could be observed between the treatment regimens used and, at the end of treatment, all pathogens were eradicated with neither relapse, nor persistence of the isolated pathogen, nor reinfection occurring. The clinical signs and symptoms had subsided in all patients at treatment end and the tolerability of the trial drugs was found to be satisfactory with no premature treatment withdrawal required. It is concluded that cefetamet pivoxil in the standard twice-daily dose of 10 mg/kg was equally effective and as well tolerated as 20 mg/kg cefetamet pivoxil given twice daily or 30–50 mg/kg amoxycillin/clavulanic acid given three times daily.

Temperature gradient driven Marangoni flow has been investigated experimentally in circular disks of molten NaNO3. 1.5 mm high by 7 mm diameter. Flow velocities were evaluated from motion picture film and temperatures were determined with a miniature thermocouple. The results are compared to an order of magnitude analysis and agreement is reasonably good.

Molecular self-diffusion is studied for several probe molecules in a sample series of Merck silica gels. The fractal interpretation of the pore size distributions from N₂ desorption measurements indicate that both the micro- and mesopore regions can be described as fractal regions. By varying the observation time in the PFG NMR experiment, the relationship between the mean square displacements and the diffusion time is analyzed to trace the occurrence of anomalous self-diffusion in fractal regions. A model for the structure-related self-diffusion in silica gel is proposed. Copyright 1993, 1999 Academic Press

Adsorption measurements of hydrocarbons and water have been performed on ZSM 5 (Si/Al=30) and on two samples prepared from this by dealumination. The properties of the highly dealuminated sample agree essentially with those of silicalite obtained by direct synthesis.

No abstract.

Single‐crystal LaB6 cathodes were prepared by arc float zone refining and their stoichiomerty and impurity level have been determined. The brightnesses of cathodes were evaluated in a SEM modified to allow insitu measurement of the cathode tip temperature. Three crystallographic orientations were evaluated and the relative brightness was found to follow the order (100)≳(321)≳(110) with the value for the (100) orientation being around 106 A/cm2 sr at 1900 °K.