Trace and surface analysis of ceramic layers of solid oxide fuel cells by mass spectrometry

For the trace analysis of impurities in thick ceramic layers of a solid oxide fuel cell (SOFC) sensitive solid-state mass spectrometric methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and radiofrequency glow discharge mass spectrometry (rf-GDMS) have been developed and used. In order to quantify the analytical results of LA-ICP-MS, the relative sensitivity coefficients of elements in a La(0.6)Sr(0.35)MnO(3) matrix have been determined using synthetic standards. Secondary ion mass spectrometry (SIMS) - as a surface analytical method - has been used to characterize the element distribution and diffusion profiles of matrix elements on the interface of a perovskite/Y-stabilized ZrO(2) layer. The application of different mass spectrometric methods for process control in the preparation of ceramic layers for the SOFC is described.     

Zur gas-chromatographisch-massenspektrometrischen Bestimmung von Steroidhormonen in Körperflüssigkeiten unter Verwendung eines Multiple Ion Detectors (Fragmentographie)

The quantitative determination of small amounts of steroids in body fluids by physical-chemical methods (gas chromatography, double isotope derivative dilution) requires a considerable amount of time and effort. The use of the combination gas chromatography-mass spectrometry provides a simple method which is highly specific and sensitive. The mass spectrometer can be used as a specific detector for gas chromatography; this is achieved by adjusting to a suitablem/e value. By means of the multiple ion detector, it is possible to record several masses simultaneously. The applicability of this method is demonstrated by the determination of the following steroid hormones: testosterone in plasma, aldosterone in urine, oestradiol-17β and oestrone in plasma. For the determination of oestrogens, the use of the corresponding dideutero compounds as standards offers a special advantage. Preliminary experiments showed that the lower limits of detection are 1 ng for aldosterone and testosterone, and 0.05 ng for oestradiol-17β and oestrone.     

Quantitative determination of element distributions in silicon based thin film solar cells using SNMS

The determination of elemental distributions in thin film solar cells based on amorphous silicon using electron beam SNMS is possible by quantifying the measured ion intensities. The relative sensitivity factors (RSFs) for all elements measured have to be known. The RSFs have been determined experimentally using implantation and bulk standards with known concentrations of the interesting elements. The measured RSFs have been compared with calculated RSFs. The model used for the calculation of the RSFs takes into account the probability for electron impact ionization and the dwell time of the neutrals inside the postionization region. The comparison between measured and calculated RSF shows, that this model is capable to explain the RSFs for most elements. Differences between calculated and measured values can be explained by the formation of hydride and fluoride molecules (in case of H and F) and influences of the angular distribution of the sputtered neutrals in case of Al. The experimentally determined RSFs have been used for a quantification of depth profiles of the i-, buffer-, p- and front contact layers of a-Si solar cells.     

A universality theorem for ratios of random characteristic polynomials

We consider asymptotics of ratios of random characteristic polynomials associated with orthogonal polynomial ensembles. Under some natural conditions on the measure in the definition of the orthogonal polynomial ensemble we establish a universality limit for these ratios.     

Biorelevant Phosphonic Acids - Protonation and Complexformation Equilibria

Abstract

Various methods of NMR- and PC-controlled titrations were developed in our laboratories. In addition to the by now well-investigated ³¹P- we applied ¹³C-, ¹H-, ¹⁹F- and ¹¹³Cd-NMR controlled titrations. Here we report about the methodical progress and results obtained from acylphophonic acids and corresponding hydroxyimino derivatives - as shown below - which gained interests as potentially anti-viral agents:     

High resolution spectroscopy of (lambda)(12)B by electroproduction

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.     

Oscillatory motions of a prestrained compliant membrane caused by fluid–membrane interaction

Flow over a compliant membrane is a complex problem where the interaction between fluid and membrane determines the nature of the aerodynamic characteristics of the membrane wing. This investigation is concerned with the deformation and oscillatory motion of a membrane under aerodynamic loading. The approach is computational, but the analytical solution is also presented for a constant pressure loading. The computational results are compared with the experimental data available in the literature as well as with the present analytical solution. In this study, the values of Reynolds number are 38 416 and 141 500, and the angle of attack and prestrain range from 10° to 40° and from 0 to 0.074, respectively. This range of parameters makes the outcome of the investigation more relevant to applications involving the flight of micro air vehicles and the membrane wings of flying mammals such as bats. The computations indicate a mostly asymmetric deflection with the point of maximum camber located nearly at 40% of the chord length from the leading edge. The deflection is decreased with prestrain, and it is increased with Reynolds number. Moreover, the lift coefficient generally increases with the angle of attack. However, for Re=141 500, it increases first to a peak at 20–30° angle of attack, and then decreases. The drag coefficient is much higher than that of conventional airfoils. The membrane oscillates in the streamwise and vertical directions. The largest amplitude of oscillations is observed at 40° for Re=38 416. The oscillations are caused by the oscillatory nature of the flow due to fluid–membrane interaction and the formation of the leading edge and trailing edge vortices. Compared with a rigid membrane of the same camber, the compliant membrane has a smaller recirculation region which may lead to a delayed stall.