Attachment of Salmonella typhimurium to Poultry Skin as Related to Cell Viability

³H-labeled S. typhimurium cells inactivated by gamma-radiation (⁶⁰Co) and by formaldehyde (5%) were used to determine if cell viability affected attachment to poultry skin. Both gamma-irradiated and formal-dehyde-treated cells attached like live cells. There was no difference in attachment between cells grown in a chemically defined medium (SCDM) or in brain heart infusion broth (BHI). Live and gamma-irradiated cells and BHI-grown and SCDM-grown cells had similar surface hydrophobicity. Live and gamma-irradiated cells had similar cell surface charges, whereas BHI and SCDM-grown cells had different surface charges. Differences in cell surface charge did not affect attachment rate.     

Clay-Particle Dispersion by Ultrasons

The dispersion of 1.0% kaolin suspensions in water was studied utilizing ultrasonic vibrational energy. The effect of time of exposure to ultra-sons was examined microscopically and turbidi-metrically by means of a spectrophotometer. Complete deagglomeration and dispersion were accomplished in 10 minutes of exposure to ultra-sons without any apparent deleterious effects on the primary particle size of the kaolin. The effects of two accepted methods of dispersion were compared with the ultrasonic method.     

Aspects of surface and environment protection in German mining areas

Hard coal mining in the German Ruhr district has a tradition of more than 200 years. Starting in the south near the river Ruhr with mining of seams near to the surface, mining wandered to the north with coal seams deeper and deeper. In the same way all environmental effects of mining wandered from south to north, as there are abandoned mining sites, contaminated areas, burning mining dumps, subsided areas and gas accesses at day ground. This all happened in a very high populated area with more than four million inhabitants. Therefore Germany has a long tradition in solving environmental problems of mining activities. The very good interaction of mine authority, mining companies and the mine workers' union is the main reason why the problems of decreasing mining activities in Germany were solved without economic, environmental or social hazards.     

A City Metaphor to Support Navigation in Complex Information Spaces

A major problem in modern information systems is to locate information and to re-find information one has seen before. Systems like the World Wide Web are heavily interlinked, but do not show structures that help users to navigate the information it contains. The use of appropriate navigation metaphors can help to make the structure of modern information systems easier to understand and therefore easier to use.We propose a conceptual user interface metaphor based on the structure of a city. Cities are very complex spatial environments and people know how to get information, how to reach certain locations in a city, and how to make use of the available infrastructure, etc. Cities provide a rich set of navigational infrastructure that lends itself to creating sub-metaphors for navigational tools. A city metaphor makes this existing knowledge about a structured environment available to the user of a computerized information system.We first focus on several properties necessary for future user interfaces (or user interface metaphors) that will distinguish them from current systems, like the richness of information or the use of visualizations to show the structure of information spaces. We also describe the strengths and problems of spatial user-interface metaphors. Then we present the structure of the information city metaphor, its structuring and navigation metaphors and what we see as its main advantages and problems. We further outline a few scenarios of how an Information City might work. Finally, we compare implementing this metaphor using either a textual or a graphical virtual environment or a combination.     

Observation of the loss of the hydroxyapatite sixfold symmetry in a human fetal tooth enamel crystal

A deviation from the hydroxyapatite hexagonal symmetry of a human tooth enamel crystal observed by high-resolution electron microscopy is reported. This symmetry deviation is characterized by: (1) ‘preferential’ planes that can be indexed as (100) with an intensity that differs from the (300) and the other {100} hexagonal equivalent planes; and (2) streaking of higher order reflections in the optical diffractogram of the image of the crystal. Computer simulations show that similar ‘preferential’ planes can also be observed at specific crystal tilt angles (and/or beam tilt and/or objective aperture misalignment) and at crystal thickness/microscope defocus values in images of hydroxyapatite crystals observed along the [0001] or [] zone axes. The streaking of higher order reflections in the optical diffractogram is related to a deformation of the crystal itself and does indeed show a symmetry deviation of the crystal under observation.     

Calibration of a wide-field frequency-domain fluorescence lifetime microscopy system using light emitting diodes as light sources

High brightness light emitting diodes are an inexpensive and versatile light source for wide‐field frequency‐domain fluorescence lifetime imaging microscopy. In this paper a full calibration of an LED based fluorescence lifetime imaging microscopy system is presented for the first time. A radio‐frequency generator was used for simultaneous modulation of light emitting diode (LED) intensity and the gain of an intensified charge coupled device (CCD) camera. A homodyne detection scheme was employed to measure the demodulation and phase shift of the emitted fluorescence, from which phase and modulation lifetimes were determined at each image pixel. The system was characterized both in terms of its sensitivity to measure short lifetimes (500 ps to 4 ns), and its capability to distinguish image features with small lifetime differences. Calibration measurements were performed in quenched solutions containing Rhodamine 6G dye and the results compared to several independent measurements performed with other measurement methodologies, including time correlated single photon counting, time gated detection, and acousto optical modulator (AOM) based modulation of excitation sources. Results are presented from measurements and simulations. The effects of limited signal‐to‐noise ratios, baseline drifts and calibration errors are discussed in detail. The implications of limited modulation bandwidth of high brightness, large area LED devices (～40 MHz for devices used here) are presented. The results show that phase lifetime measurements are robust down to sub ns levels, whereas modulation lifetimes are prone to errors even at large signal‐to‐noise ratios. Strategies for optimizing measurement fidelity are discussed. Application of the fluorescence lifetime imaging microscopy system is illustrated with examples from studies of molecular mixing in microfluidic devices and targeted drug delivery research.     

Sensitivity analysis of pulse-frequency-modulated control using a linearized model†

The paper discusses the sensitivity of pulse-frequency modulated (PFM) control systems with respect to changes in the plant and controller parameters. The investigations of the sensitivity behaviour of non-linear PFM control systems are carried out using a linearized approach for the PFM controller, as proposed by Frank and Dillmann. The goal of this paper is to study the effectiveness of this method as applied to the investigation of an unstable plant. The sensitivity functions of the PFM system and the corresponding continuous equivalent systems are evaluated by considering parameter changes in the actual plant. The limitations of this method are pointed out.     

Identification of change structure in statistical process control

In order to diagnose properly quality problems that occur in manufacturing the diagnostician, be it human or computer, must be privy to various sources of information about the process and its behaviour. This paper describes how neural networks and Bayesian discriminant function techniques can be used to provide knowledge of how a product characteristic changed, i.e. shift in mean or variability, when so noted by the control chart application. Such information is useful because there usually exists some underyling knowledge about the physical phenomena in question that relates the behaviour of the observed characteristic to its processing variables. When a change in the process is detected by the appropriate statistical method, a feature vector of process-related statistics is used to identify the change structure as a shift in mean or variance. This paper addresses various issues concerned with this problem, namely: process change detection, feature vector selection, training patterns, and error rates. Simulation experiments are used to test various hypotheses and also compare the effectiveness of the two proposed approaches against two simpler heuristics. Results show the neural network and quadratic discriminant function approaches to be fairly similar, with a success rate of 94% and both to be superior to the simpler heuristic approaches.