Wave induced vibrations of gravity platforms: a stochastic theory

This paper presents a consistent stochastic method to evaluate wave induced vibrations of offshore platforms with special emphasis on gravity type structures. The wavy sea surface is idealized as a stationary and homogeneous stochastic Gaussian (or semi-Gaussian) field. The wave loading processes are treated by applying the concepts of probabilistic potential theory and the stochastic linearization method. The structure is modelled according to the finite element method using boundary spring-dashpot elements to idealize the soil-foundation system. The linearized equations of motion are solved by the frequency response method accounting properly for the temporal and spatial structure of waves as well as for time dependent system function. Numerical results for a 170m high concrete platform are presented including a parametric study of effects due to the shape of the wave spectral density.     

On a method of measuring diffusion coefficients of solid materials

In a certain method for measuring diffusion coefficients of solid materials a circular cylindrical sample of the material is clamped between annular rings and the difference in concentration between the end surfaces and the flux through the sample are measured. In order that the diffusion coefficient can be determined from these data a certain factor which depends on the geometry of the sample must be known. In this note two complementary variational principles are derived and used to obtain precise upper and lower bounds for this factor.

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Zusammenfassung Bei einem Verfahren zur Messung von Diffusionskoeffizienten von Feststoffen wird eine zirkulärzylindrische Stoffprobe zwischen zwei ringförmingen Haltern eingespannt. Der Konzentrationsunterschied zwischen den Endflächen und dem Flux werden gemessen.Um bei diesem Verfahren den Koeffizient bestimmen zu können, muss ein Faktor, der von der Geometrie der Einspannungsvorrichtung abhängt, bekannt sein. In dieser Arbeit werden zwei komplementäre Variationsprinzipien hergeleitet, die dann anschliessend für die Berechnung von genauen oberen und unteren Schranken dieses Faktors angewandt werden.

     

Glueball mass calculations on an array of computers

We have calculated the mass of the 0⁺ glueball in SU(2) pure gauge theory in 4 dimensions, with very high statistics. The computation was done on an array of microprocessors with nearest-neighbor connections which run concurrently. We discuss, in detail, the implementation of the pure gauge algorithm for SU(2) and SU(3) and also the algorithm for calculating arbitrarily shaped Wilson loops on the array. The extension of these algorithms to the inclusion of dynamical fermions is also discussed. Finally, we present the results of our variational calculation of glueball masses which are in agreement with published results.     

Die Konstitutionsabhängigkeit und die benzolinduzierten Effekte der chemischen Verschiebungen der Methoxyprotonen einiger Carbonsäuremethylester

The Chemical shifts of the methoxyprotons in about 60 methyl esters of carboxylic acids were obtained in CCl₄ and C₆D₆, and their dependence on constitution and solvent are discussed. It was shown that the values of a certain molecule could be assumed to be composed additively of a number of parameters which characterise the substituents.     

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Manganese‐catalyzed C?H bond activation chemistry is emerging as a powerful and complementary method for molecular functionalization. A highly reactive seven‐membered Mn^I intermediate is detected and characterized that is effective for H‐transfer or reductive elimination to deliver alkenylated or pyridinium products, respectively. The two pathways are determined at Mn^I by judicious choice of an electron‐deficient 2‐pyrone substrate containing a 2‐pyridyl directing group, which undergoes regioselective C?H bond activation, serving as a valuable system for probing the mechanistic features of Mn C?H bond activation chemistry.     

A semi‐quantitative approach for the rapid screening and mass profiling of naphthenic acids directly in contaminated aqueous samples

We report the use of a direct sampling, online analytical approach for the determination of acid extractable naphthenic acids in complex aqueous samples, known as condensed phase membrane introduction mass spectrometry (CP‐MIMS). The technique employs a capillary hollow fibre semi‐permeable membrane probe configured for immersion into a pH adjusted sample. A continuously flowing methanol acceptor phase transfers naphthenic acids to an electrospray ionization source, operated in negative ion mode, whereupon they are analysed by mass spectrometry as [M–H]^? ions. High‐resolution mass spectrometry is used to characterize the influence of sample pH on membrane transport of multiple components of complex naphthenic acid mixtures. We demonstrate the use of CP‐MIMS for semi‐quantitative analysis of real‐world samples using selected ion monitoring and full scan mass spectra at unit mass resolution. The technique has also been employed to continuously monitor the temporal evolution in the mass profile and concentrations of individual naphthenic acid isomer classes in heterogeneous solutions during adsorption processes. Copyright © 2015 John Wiley & Sons, Ltd.