Chemical Sensors and Computer-Aided Analytical Chemistry

A simplified thermodynamic model of potentiometric and optical ion sensor membranes allows to improve their properties and the measurement of complex formation constants in membrane phases. The simultaneous optical and potentiometric investigation of sensing films revealed diffusion-related long-term drifts. The lower detection limit of ion-selective electrodes was shifted from the micromolar to the picomolar range, thus allowing many new applications especially in environmental and biological trace metal analysis. Also, various prediction methods of spectroscopic and other physical data from chemical structures have been created which allow a fast compatibility check between structures and molecular spectra. Furthermore, programs are being developed for automatic spectra interpretation

The excitation of unstable perturbations in a laminar friction layer

With the aid of the method of small oscillations which was used successfully in the investigation of the stability of laminar velocity distributions in the presence of two-dimensional perturbations, the excitation of the unstable perturbations for the Hartree velocity distributions occurring in plane boundary-layer flow for decreasing and increasing pressure is calculated as a supplement to a former report. The results of this investigation are to make a contribution toward calculation of the transition point on cylindrical bodies

The stability of laminar flow past a sphere

As a contribution to the problem of turbulence on a surface of rotation, the method of small oscillation is applied to the flow past a sphere. It was found that the method developed for two-dimensional flow is applicable without modifications. The frictional layer in the vicinity of the stagnation point of a surface of rotation is less stable against small two-dimensional disturbances than in the stagnation point itself, as proved from an analysis of the velocity distribution made by Homann

Theoretical solution of profile drag

After a survey of the customary procedures for appraising the profile drag in which pressure drag was discounted and the methods for computing the laminar and turbulent friction flow, the author proposes a method by which the pressure drag can be computed with the aid of the displacement thickness of the frictional layer. The method is restricted to the case where the effects, caused by separation of frictional layer, are small. Then the total profile drag can be expressed solely by quantities derived from the velocity distribution in the frictional layer immediately at the trailing edge

A polypyrrole-based solid-contact Pb2+-selective PVC-membrane electrode with a nanomolar detection limit

Ion-selective electrodes (ISE) based on conventional plasticized PVC membranes with solid inner contact (SC) have so far had unsatisfactory lower detection limits. Here it is shown that electropolymerization of pyrrole in the presence of potassium hexacyanoferrate(II)/(III) on Pt results in adequate inner contact for SC-ISE. The nanomolar lower detection limit achieved with the Pb2+-selective PVC membranes investigated is comparable with values obtained with optimized internal solutions of liquid-contact IS

Calibration Tunnel for High Speed

For the nvestigation of measuring instruments at higher speeds up to a Mach number 0.7 a tunnel with closed test section was built in 1942 which was as simple and cheap as possble. The blower was a radial blower with straight sheet vanes of 800-millimeter diameter the tips of which were bent backward a little. The blower sucks the air through a honeycomb of diameter 1.2 neter with wide meshes. The air is then accelerated in a short cone with smooth transition to the test section. The cylindrical test section of 200-milimeter diameter has two windows (which are displaced 180 deg from each other. The instruments may be introduced and observed through and observed through these windows. . The cross section is then enlarged by a straight diffuser 3.5 meters long and reaches the ninefold cross section. The air flows back into the room through a disk diffuser of 2-meter diameter. The maximum speed in the jet is 250 m/s for a drive power of 35 kT., if there are no installations in the jet. The velocity is determined by pressure holed along the test section

Deformation an sarmatischen Sedimenten (St. Margarethen / Burgenland)

Im Sarmatium und Pannonium des Eisenstädter-Sopron-Beckens zeigen sich, aufgrund extensioneller Bruchtektonik im Rahmen der alpinen Orogenese, eine Reihe von Störungen, welche variablen Versatz von wenigen Zentimetern bis hin zu mehreren Metern aufweisen. Diese deformierten Sedimente befinden sich in der Hangendscholle einer großen Hauptstörung. In der Liegendscholle unter der Hauptstörung mit einem Versatz von mehreren Zehnermetern befinden sich Sedimente des Badeniums. Eine vertikale, in einer Kiesgrube sehr gut aufgeschlossenen, Wand bot die Gelegenheit diese Störungen, auch mit Hilfe eines Laserscanners vom Institut für Photogrammetrie und Fernerkundung (TU-Wien), detailliert zu vermessen und in einem 3D Visualisierungsprogramm darzustellen. Da der Versatz an den Störungen einen starken Versetzungsgradienten aufweist und sich an den angrenzenden Schichten gegen Null bewegt stellte sich die Frage wie sich dieser starke Gradient in Form einer Reduktion der Porosität in den angrenzenden Schichten widerspiegelt. Dazu wurde im Rahmen dieser Arbeit eine herkömmliche und eine computerunterstützte Methode verwendet und quantitativ gegenübergestellt. Weiters wurde der extensionelle Versatz und die damit verbundene Deformation der Sedimente mit einem eigens entwickelten Computerprogramm bilanziert. Dieses Programm beruht auf einer kinematischen Methode, welche das Modell einer listrischen Abschiebung voraussetzt. Die Schwierigkeit unter diesen Annahmen die natürlichen Geometrien nachzumodellieren lässt den Schluss zu, dass es sich bei diesem Abschiebungssystem um keine listrische Störung, sondern um eine planare Abschiebung mit einem starken Versetzungsgradienden handelt.A range of faults formed in the Eisenstadt-Sopron Basin during the Sarmatian and Pannonian, with displacements varying from a few centimetres to several metres, due to extensional tectonics related to the Alpine Orogeny. Sarmatian sediments lying in the hanging-wall of a large-scale normal fault in a quarry in the St Margareten area of Burgenland, show several minor synthetic faults. In the footwall, under the main fault-surface, along which a displacement of several tens of metres occurred, sediments of Badenian age crop out. A very well-exposed vertical face within the quarry exhibits the geometrical relationships between the minor faults and the adjacent bedding. These were measured in detail, using laser-scanning equipment from the Institute of Photogrammetry and Remote Sensing (TU Vienna), and subsequently displayed in a 3D graphics program (GOCAD). Since the displacement along these fault shows a large gradient that goes to zero at the beds bordering the ends of the faults, the question arose as to whether the gradient could have developed through a reduction in the porosity of the beds cut by the fault. As a part of the project, conventional and computer-aided methods to determine porosity were utilised and quantitatively compared. Both methods showed a very rapid porosity reduction directly adjacent to the fault surface. The extensional offset and associated deformation of the sediments adjacent to the major fault was balanced with a self-written computer program. The program was based on a kinematic model that presumed that the fault had a listric geometry. Difficulties in modelling the real geometry, as a result of this assumption, led to the conclusion that the fault system was not listric but planar, with a steep displacement gradient