Errors in the determination of mass transfer in gas-liquid dispersions

Mass transfer behaviour of gas-liquid dispersions is usually characterized by the volumetric mass transfer coefficient β_La. For its experimental determination various methods exist which can be grouped into stationary and instationary (dynamic) methods. Very often volumetric mass transfer coefficients published in literature show surprisingly large scattering and divergence which cannot be explained by differences in properties of the systems. In order to find possible causes for these inconsistencies in experimental results, the two types of methods have been subjected to an analysis of errors. It is shown that deviations of real from assumed mixing behaviour in both phases as well as rather small errors in the concentration of the liquid phase may result in deviations up to a factor of 5–10. This may also be the case in the evaluation of results obtained by the dynamic method, if the approximations used are too rigorous. The limits of applicability of the two methods are discussed.     

Trend-specific clustering for micro mass production of linked parts

In micro production, small tolerances, as well as size effects increase the requirement for a fast, precise, and reliable methodology that enhances the output of assemblies. In contrast to conventional approaches, a widening of the tolerance field enables an overall improvement of the output of a process chain while assuring functionality of parts. Therefore, the consideration of trends for building sections is essential for increasing the outcome by identifying sections that can be matched. This paper presents the Linked Parts Clustering Algorithm for the identification of trend-specific clusters in linked parts and demonstrates the area of application.     

Imbedded Nanocrystals of CsPbBr3 in Cs4PbBr6: Kinetics,Enhanced Oscillator Strength,and Application in Light‐Emitting Diodes

Solution‐grown films of CsPbBr₃ nanocrystals imbedded in Cs₄PbBr₆ are incorporated as the recombination layer in light‐emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr₃ and the nanoinclusion composite are measured and analyzed, indicating second‐order kinetics in extended and mainly first‐order kinetics in the confined CsPbBr₃, respectively. Analysis of absorption strength of this all‐perovskite, all‐inorganic imbedded nanocrystal composite relative to pure CsPbBr₃ indicates enhanced oscillator strength consistent with earlier published attribution of the sub‐nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr₃ in melt‐grown CsBr host crystals and CsPbBr₃ evaporated films.     

Electrodiffusional direction-specific probe for measuring local velocity of aerated aqueous systems

A three-segment direction specific probe based on the electrodiffusion measuring technique was used to measure local liquid velocities in gas-liquid flow. Dissolved oxygen was employed as depolarizer instead of the usually applied redox system ferro-ferricyanide in water. The concentration of the auxiliary electrolyte K₂SO₄ was so low that coalescence behaviour of the gas-liquid system was not influenced. It was possible to measure liquid velocities up to ca 100cm s^–1. The probe showed satisfying sensitivity to flow direction. Furthermore, unequivocal discrimination between signals from the liquid and gas phases was achieved.Notation a _ij,b _ij Fourier coefficients - D diameter (cm) - E potential (V) - I _i single segment current (A) - k number of probe segment - Re Reynolds number - Sc Schmidt number - Sh Sherwood number - t time (s) - T temperature (°C) - u, v liquid velocity (ms^–1) - flow angle (°) This paper was presented at the Workshop on Electrodiffusion Flow Diagnostics, CHISA, Prague, August 1990.     

IQ technology: an automated, high-throughput screening assay for kinase, phosphatase, and protease targets

IQ^® Technology, a homogeneous, universal-detection platform, originally designed for high-throughput screening (HTS) of kinases and phosphatases, has now been applied to protease screening. Representative enzymes from the major classes of proteases have been assayed in the IQ^® format. Enzyme activity and compound inhibition data are presented for such enzymes as Trypsin, Matrix Metalloproteinase 3 (MMP-3) and Calpain 1. The technology has been tested in 96- to 384- to 1536-well microplate formats and is universally suited for automated screening. IQ^® Technology is a direct, noncompetitive assay that does not require antibodies or radioisotopes. Fluorophore-labeled peptides are used as enzyme substrates. Kinase or phosphatase activity is quantified by direct measurement of the phosphorylation state of the substrate. For protease activity, cleavage is quantified with a peptide substrate containing a phospho-residue distal to the fluorphore. Cleavage of the substrate liberates the fluorphore-labeled terminus from the terminus containing the phospho-residue. Protease activity is measured by the change in fluorescence intensity that occurs when a proprietary compound binds specifically to phosphoryl groups on peptides and quenches the fluorescence. IQ^® Technology can be used with any peptide sequence and is insensitive to high concentrations of ATP and substrate. The IQ^® Technology has been validated against a large number of detergents, organics, and other reagents found in reaction mixtures and has been optimized for HTS applications exhibiting representative Z' values of 0.7.     

Therapists' emotional reactions to substance abusers: A new questionnaire and initial findings.

Developed and tested the Ratings of Emotional Attitudes to Clients by Treaters (REACT) scale. The REACT was administered to 52 therapists and 140 cocaine-dependent outpatients, at sessions 2, 5, and 24 of psychotherapy. It was found to have high internal consistency at each time point, moderately high convergent validity with therapists' (but not patients') therapeutic alliance ratings, and a factor structure that appeared to meaningfully derive 4 factors: "therapist in conflict with self," "therapist focused on own needs," "positive connection," and "therapist in conflict with the patient." Therapists' emotional responses were found to become more negative over the course of treatment, and, when compared by theoretical orientation, were found more positive for 12-step drug counselors than for cognitive or supportive-expressive therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptation to the driver as part of a driver monitoring and warning system

Different contrast agents have been clinically used in MR imaging of the liver including extracellular gadolinium chelates, contrast agents targeted to the macrophage-monocytic phagocytic system (MMPS), hepatobiliary contrast agents, and blood-pool contrast agents. Extracellular gadolinium chelates are optimally used for characterization of focal hepatic lesions, whereas hepatobiliary and MMPS-targeted contrast agents are optimally used for detection and preoperative evaluation. The present review portrays these contrast agents and discusses their advantages and shortcomings.     

Physikalisch-chemische Trennverfahren in der Biotechnologie

Physicochemical separation processes in biotechnology. A number of special features of the work-up of products of biotechnological processes play a decisive role in selection of a separation process. Thus the products generally have to be isolated from dilute aqueous solutions. Moreover, the substances to be isolated are generally sensitive to external influences such as temperature or pH value and have to be isolated from mixtures with chemically similar compounds. Demands for greater selectivity of separation are met by processes based on differences in molecular structure of the substances to be separated. These include separation methods which have practically no significance in chemical engineering, e. g. chromatographic, membrane, and electrophoretic processes. The development of industrially utilizable processes to exploit the high separation efficiency of the physicochemical techniques requires close collaboration between process engineers and chemists.