Effects of reaction parameters on the preparation of thick silica gel films by an interfacial polymerization. 1. Effects of pH and type of catalyst

The polymerization of different silicon precursors at the interface of two immiscible liquids (organic and inorganic phase) led to the formation of thick (up to 40 m) and crack-free silica gel films. The pH of the inorganic phase and the type of catalyst strongly governed the rate of film formation along with the gel film properties. The preparation of thick and crack-free gel films within 24 hours of reaction time was possible for both acid-catalyzed and base-catalyzed systems in the vicinity of pH=2 and 11, respectively. The use of acetic acid as an catalyst led to gel films with a weight eight times higher than those prepared using HCl and HNO₃ catalysts. The weight of formic acid-catalyzed gel films was four times higher, and the weight of citric acid-catalyzed gel films was twice as high as the mineral acid-catalyzed gel films, respectively.     

Verschlüsselungstheorie für symmetrische Kanäle

Zusammenfassung Es ist das Ziel dieser Arbeit, einige bisher nur für den binÄr-symmetrischen Kanal (BSC) aufgestellte SÄtze auf sogenannte symmetrische KanÄle zu übertragen. Diese symmetrischen KanÄle, die wir in Abschnitt III definieren werden, stellen eine Verallgemeinerung des BSC dar. In Abschnitt I wird der Begriff des Schlüssels und des linearen Schlüssels eingeführt und seine wichtigsten Eigenschaften angeführt. Abschnitt II bringt den Hauptsatz der Informationstheorie in einer Form, die für die Kodierungstheorie besonders geeignet ist. In Abschnitt III wird die KapazitÄt des in diesem Abschnitt definierten symmetrischen Kanals berechnet. Gleichzeitig wird die von Slepian entdeckte Möglichkeit, lineare Schlüssel einfach zu ver- und entschlüsseln, auf den symmetrischen Kanal erweitert. In Abschnitt IV wird der Eliassche Satz, nach dem man im Hauptsatz das Wort Schlüssel durch linearen Schlüssel oder sogar gleitenden linearen Schlüssel ersetzen darf, auf den symmetrischen Kanal verallgemeinert. Die Arbeit schlie\t in Abschnitt V mit einigen Bemerkungen über optimale Schlüssel, Irrtum-verbessernde Schlüssel und deren EntschlüsselungHerrn Prof. Dr. K. Krickeberg (Heidelberg), der das Thema dieser Arbeit angeregt hat und mich bei der Abfassung dieser Arbeit mit zahlreichen RatschlÄgen unterstützt hat, bin ich zu gro\em Dank verpflichtet. Au\erdem schulde ich Herrn Prof. Dr. K. Jacobs (Göttingen) Dank für die Durchsicht dieses Manuskripts und einige Verbesserungsvorschläge.     

Is the madison convention really convenient at low energies? : The reaction

It is shown that s-wave induced reactions with polarized particles can be described much more conveniently in new coordinates. Even with higher partial waves, cross sections can be fitted with less parameters than in conventional expansions.     

Shrinkage estimation in the frequency domain of multivariate time series

In this paper on developing shrinkage for spectral analysis of multivariate time series of high dimensionality, we propose a new nonparametric estimator of the spectral matrix with two appealing properties. First, compared to the traditional smoothed periodogram our shrinkage estimator has a smaller L₂ risk. Second, the proposed shrinkage estimator is numerically more stable due to a smaller condition number. We use the concept of “Kolmogorov” asymptotics where simultaneously the sample size and the dimensionality tend to infinity, to show that the smoothed periodogram is not consistent and to derive the asymptotic properties of our regularized estimator. This estimator is shown to have asymptotically minimal risk among all linear combinations of the identity and the averaged periodogram matrix. Compared to existing work on shrinkage in the time domain, our results show that in the frequency domain it is necessary to take the size of the smoothing span as “effective sample size” into account. Furthermore, we perform extensive Monte Carlo studies showing the overwhelming gain in terms of lower L₂ risk of our shrinkage estimator, even in situations of oversmoothing the periodogram by using a large smoothing span.     

Radiation curable materials – principles and new perspectives

Increasing environmental concerns and the ensuing legislation to cut emissions of volatile organic compounds (VOCs) have been major driving forces behind the development of radiation cured coatings over the past 25 years. Today radiation cured coatings are known for their good overall performance and their excellent resistance against chemical and physical surface damages. Advanced photoinitiator systems allow the light stabilisation of UV‐curable formulations and the outdoor application of the coating. The rapid curing, combined with the possibility of immediate processing of the coated objects opens the way for radiation curing – in 100%‐, water based‐, and dual cure systems as well as for radiation curable powder coatings – for a wide variety of application.