Characterization of dimyristoylphosphatidylcholine liposome aggregates induced by dextran sulfate and La3+ by fluorescence spectroscopy

The addition of dextran sulfate (DS) to DMPC vesicles in the presence of di- and trivalent cations leads to a strong aggregation, resulting in a stack-like arrangement of the opposing membrane surfaces as shown by freeze-fracture electron microscopy. The strong aggregation is connected with a lipid mixing process, especially in the presence of La³⁺ (measured by the NBD/Rh assay). The extent of lipid mixing depends on the molecular weight of DS and size of the DMPC vesicles. Additionally, a decrease in the surface dielectric constant of DMPC vesicles [measured by the emission shift of the fluorescent probe, dansylphosphatidyl-ethanolamine (DPE)] was observed. A direct dependence on the molecular weight (MW) of DS exists: the higher their MW, the higher the blue emission shift of the DPE probe. The results are discussed in terms of the theory proposed by Ohki and Arnold, which connects the decrease of the surface dielectric constant with the interaction parameters of phospholipid membranes.     

Investigation of phase transformations in thermal processing of phosphate rock

The reaction mechanism of the hydrothermal sintering processing of hydroxyfluorapatite (HFA) was studied. Samples from an industrial rotary kiln and laboratory-made samples were investigated by thermal, X-ray and chemical analysis. It was found that HFA decomposes by a solid-solid reaction with Ca-Mg-phosphates and by interaction with fused clinker. Apatite decomposition is not accompanied by fluorine evaporation; it merely creates the main precondition for fluorine evolution from clinker.

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Zusammenfassung Es wurde der Reaktionsmechanismus des hydrothermischen Sinterverfahrens von Hydroxyfluorapatit (HFA) untersucht. Proben aus einem Industriedrehofen und aus dem Labor wurden mittels Thermo-, röntgenographischer und chemischer Analyse untersucht. Es wurde gefunden, da\ HFA durch eine Feststoffreaktion mit Ca-Mg-Phosphaten und mittels einer Wechselwirkung mit geschmolzener Schlacke zerfÄllt. Die Zersetzung von Apatit wird von keiner Abdampfung von Fluor begleitet; es schafft lediglich die Hauptvoraussetzung für die Freisetzung von Fluor aus Schlacke.

     

Thermal Modelling of Edge-Cooled Single Disc Gyrotron Windows Using a One-Dimensional Finite Difference Computer Code

A one - dimensional finite - difference computer code has been developed and shown to be quite effective in thermal design and analysis of various plane edge-cooled single - disc windows for gyrotrons with Gaussian rf beam output. The program has a modular structure and is flexible enough to suit specific requirements of users; it can handle nonlinearity. Results obtained for various CVD diamond window cases compare well with the experiment and with the results obtained using ABACUS, a well-established 3-D Finite Element code. Results indicate that a CVD diamond disc with 94 mm diameter and edge cooled by water at 293 K will ensure the passage of 1 MW CW at 140 GHz. A fused quartz window, with 60 mm diamter and operating at 165 GHZ on a 1.5 MW pulsed coaxial gyrotron has also been analysed for its transient characteristics and results are presented.     

The Use of Miniature Disc Bend Tests with Plastic Materials

The use of miniaturised disc bend tests, a method that is commonly used with metallic materials, is assessed for use with polymeric materials. The test method uses the indention force/displacement characteristics for a hemispherical-ended punch forced onto a small disc of the test material. Characterisation tests were performed using acetal, PMMA and polypropylene, under a range of different test rates and temperatures. These were compared with conventional tensile tests under the same conditions. Although no quantitative comparison between the two methods has been formulated, good qualitative agreement was found for all materials, including a wider comparison with nine materials. The advantages of the disc bend test are that smaller amounts of material are needed, the sample preparation is easier, the test is often easier to perform, it shows ductile–brittle transitions more sharply and is a very convenient method of performing environmental stress cracking tests.     

A Comparison of Evolution Strategies with Other Direct Search Methods in the Presence of Noise

Evolution strategies are general, nature-inspired heuristics for search and optimization. Due to their use of populations of candidate solutions and their advanced adaptation schemes, there is a common belief that evolution strategies are especially useful for optimization in the presence of noise. Empirical evidence as well as a number of theoretical findings with respect to the performance of evolution strategies on a class of spherical objective functions disturbed by Gaussian noise support that belief. However, little is known with respect to the capabilities in the presence of noise of evolution strategies relative to those of other direct optimization strategies.In the present paper, theoretical results with respect to the performance of evolution strategies in the presence of Gaussian noise are summarized and discussed. Then, the performance of evolution strategies is compared empirically with that of several other direct optimizationstrategies in the noisy, spherical environment that the theoretical results have been obtained in. Due to the simplicity of that environment, the results are easily interpretable and can serve to reveal the respective strengths and weaknesses of the algorithms. It is seen that for low levels of noise, most of the strategies exhibit similar degrees of efficiency. For higher levels of noise, their step length adaptation scheme affords evolution strategies a greater degree of robustness than the other algorithms tested.     

Reply to Cooperstock and Faraoni

We reply to the comments made by Cooperstock and Faraoni concerning (1+1)-dimensional gravity.     

Multi-channel laser doppler velocimetry (LDV) and digital image processing (DIP) in fluvial hydromechanics

Recent efforts in fluvial hydromechanics aim at the capability of reliably predicting fluvial flow, turbulence and mass transport by means of multi-dimensional hydrodynamic numerical models. For this purpose, most detailed and highly accurate experimental data are needed in order to calibrate and verify the simulation tools. An optimum, but so far non-existing measurement technique would provide the complete state-space representation of the investigated water body at a high spatial and temporal resolution. While this is far from being available, already well established optical methods, such as Laser Doppler Velocimetry (LDV) and Digital Image Processing (DIP), seem to bear the potential for coming close to the optimum if applied in effective combination. Within this paper, several corresponding applications of LDV and DIP to the investigation of compound open-channel flow are described and discussed regarding their characteristic results, advantages and disadvantages as well as possible future improvements.