Ordered mesoporous silica materials in liquid chromatography : synthesis and application

This research work describes the synthesis and application of ordered mesoporous silica materials in liquid chromatography. For this purpose spherical particles and thick layers were developed. In a first part the synthesis and the particle properties were investigated. Spray drying was used as a fast technique to produce sufficient quantities of spherical ordered mesoporous particles. After the proces was optimized adequate amounts of both an organosilica and a pure silica material were packed and chromatographically evaluated. The ordered porosity as it seems has a profound influence on the retention of analytes as it more than triples. The second and final part describes the synthesis of a thick layer on the inner lining of a fused silica capillary. This open tubular column was evaluated in capillary electro chromatography where various mixtures were succesfully base separated

Atomic layer deposition-based tuning of the pore size in mesoporous thin films studied by in situ grazing incidence small angle x-ray scattering

Atomic layer deposition (ALD) enables the conformal coating of porous materials, making the technique suitable for pore size tuning at the atomic level, e.g., for applications in catalysis, gas separation and sensing. It is, however, not straightforward to obtain information about the conformality of ALD coatings deposited in pores with diameters in the low mesoporous regime (< 10 nm). In this work, it is demonstrated that in situ synchrotron based grazing incidence small angle x-ray scattering (GISAXS) can provide valuable information on the change in density and internal surface area during ALD of TiO2 in a porous titania film with small mesopores (3-8 nm). The results are shown to be in good agreement with in situ x-ray fluorescence data representing the evolution of the amount of Ti atoms deposited in the porous film. Analysis of both data sets indicates that the minimum pore diameter that can be achieved by ALD is determined by the size of the Ti-precursor molecule

Zum Einsatz des Deutschen Sprachdiploms der Kultusministerkonferenz (erste Stufe) an Schulen in Deutschland: Ein Problemaufriss

Neuerdings kommt das für Deutschlernende an Schulen im Ausland entwickelte Deutsche Sprachdiplom (DSD) der Kultusministerkonferenz (erste Stufe) auch im Inland zum Einsatz. Allerdings wurde die Validität dieser Testverwendung noch nicht nachgewiesen. Basierend auf einem verbreiteten Validierungsmodell diskutiert dieser Artikel Potenziale und Herausforderungen des DSD-Einsatzes im Inland. Es wird gezeigt, dass positive Konsequenzen erhofft werden, deren Nachweis jedoch noch aussteht; nicht intendierte Folgen werden kaum thematisiert. Ferner zeigt sich eine große Heterogenität der Einsatzzwecke. Der Beitrag bespricht dann das im Spannungsfeld von kommunikativer und bildungssprachlicher Kompetenz angesiedelte Testkonstrukt und diskutiert die Rolle des Gemeinsamen europäischen Referenzrahmens. Modelltestanalysen zeigen ferner, dass Testinhalte teils ethisch problematisch sind. Insgesamt verweist der Beitrag auf den Bedarf einer umfassenden Validierungsanstrengung für die neue Verwendung des DSD I

Isomeric periodic mesoporous organosilicas with controllable properties

The synthesis procedure for isomeric periodic mesoporous organosilicas with E-configured ethenylene bridges was investigated using the homemade pure E-isomer of 1,2-bis(triethoxysilyl)ethene. The pH, aging temperature and the presence of cosolvents played a key role in obtaining well-ordered mesoporous materials with controllable properties and morphologies. By fine-tuning the reaction mixture acidity, PMOs with high surface areas and pore volumes could be attained. By selecting various alcohols as cosolvents and optimizing the alcohol concentration, PMOs with crystal-like disc shaped, fibrous and spherical particle morphologies were obtained. The synthesis temperature of these ethenylene-bridged PMOs influences the pore size, structure, connectivity and volume

A random map implementation of implicit filters

Implicit particle filters for data assimilation generate high-probability samples by representing each particle location as a separate function of a common reference variable. This representation requires that a certain underdetermined equation be solved for each particle and at each time an observation becomes available. We present a new implementation of implicit filters in which we find the solution of the equation via a random map. As examples, we assimilate data for a stochastically driven Lorenz system with sparse observations and for a stochastic Kuramoto-Sivashinski equation with observations that are sparse in both space and time