Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds

In utilizing the advantages of extinction measurements in micron and especially submicron particle characterization, the properties of a multiple wavelength extinction technique have been the subject of extended theoretical studies. Furthermore, an experimental set-up was designed which provides high flexibility owing to its modular design. The performance of the technique described is demonstrated by a large variety of applications in aerosol and combustion research and in large-scale industrial systems. It was found to be a reliable tool in characterizing dense particulate systems.     

Die gravimetrische Phosphorbestimmung in wolframhaltigen St?hlen

Zusammenfassung Einige der üblichen Methoden zur Phosphorbestimmung in wolframlegierten Stählen werden unter Anwendung von ¹⁸⁵W und ³²P einer Nachprüfung unterzogen. Dabei erweisen sich die Phosphorverluste durch Adsorption an dem Wolframsäureniederschlag als gering, so daß sie bei weniger anspruchsvollen Bestimmungen unberücksichtigt bleiben können. Erheblich größer sind dagegen die Fehler, die durch Mitfällung von Wolframsäure mit dem Ammoniummolybdatophosphatniederschlag entstehen können. Es werden zwei Methoden angegeben, nach denen eine quantitative Abtrennung des Wolframs und damit eine sichere Bestimmung des Phosphors möglich ist.Herr Prof. Dr.-Ing. K. Schwabe ermöglichte es uns freundlicherweise, die Untersuchungen mit radioaktivem Wolfram und Phosphor im Zentralinstitut für Kernphysik Rossendorf, Bereich Radiochemie, durchzuführen. Ihm sei auch an dieser Stelle herzlichst gedankt.     

Modification of Branched Poly(ethylene imine) with d-Fructose for Selective Delivery of siRNA into Human Breast Cancer Cells

Branched poly(ethylene imine) (bPEI) is frequently used in RNA interference (RNAi) experiments as a cationic polymer for the delivery of small interfering RNA (siRNA) because of its ability to form stable polyplexes that facilitate siRNA uptake. However, the use of bPEI in gene delivery is limited by its cytotoxicity and a need for target specificity. In this work, bPEI is modified with d- fructose to improve biocompatibility and target breast cancer cells through the overexpressed GLUT5 transporter. Fructose-substituted bPEI (Fru−bPEI) is accessible in three steps starting from commercially available protected fructopyranosides and bPEI. Several polymers with varying molecular weights, degrees of substitution, and linker positions on d- fructose (C1 and C3) are synthesized and characterized with NMR spectroscopy, size exclusion chromatography, and elemental analysis. In vitro biological screenings show significantly reduced cytotoxicity of 10 kDa bPEI after fructose functionalization, specific uptake of siRNA polyplexes, and targeted knockdown of green fluorescent protein (GFP) in triple-negative breast cancer cells (MDA-MB-231) compared to noncancer cells (HEK293T).     

Application of fluid opacity for determining the phase behavior of binary mixtures near their critical loci – CO2 plus ethane and CO2 plus propane

The rapid determination of critical data of binary mixtures of carbon dioxide plus propane and carbon dioxide plus ethane has been carried out using the opalescence effect of pure substances or mixtures near their critical loci. The experiments have been performed applying a heatable stainless-steel vessel equipped with two sapphire windows for optical observation of changes of state. The initial two-phase mixture is continuously heated and pressurized. The vessel content increasingly becomes opalescent and the critical point is characterized by a total opacity. Beyond this point the fluid instantly becomes clear; the one-phase supercritical state is reached. Received: 17 December / Revised: 24 February 1999 / Accepted: 26 February 1999     

Radiometrische Schwefelbestimmung nach dem Entwicklungsverfahren

Zusammenfassung Unter Beibehaltung des Entwicklungsverfahrens wird eine Schwefelbestimmung in unlegiertem Stahl, Roh- und Gu\eisen ausgearbeitet, die sich durch Schnelligkeit und Sicherheit auszeichnet. Die Absorptionslösung wird durch Zusatz von ¹¹⁵Cd markiert und die RestaktivitÄt der Lösung nach Abtrennung von CdS bestimmt. Minderbefunde, die sich durch die grö\ere Löslichkeit von CdS in der essigsauren Absorptionsflüssigkeit ergeben, können durch einen experimentell ermittelten Korrekturwert eliminiert werden.

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Summary Based on the escapement method a rapid and safe determination of sulphur in non-alloy steel, pig iron and cast iron has been worked out. The absorbent solution is labeled by addition of ¹¹⁵Cd and residual activity is measured after separation of CdS. Tow low results may be found due to the increased solubility of CdS in the acetic acid absorbent solution, but can be improved by an experimental correction value.