Esterification in reactive extrusion

A condensation type reaction has been studied for reactive extrusion in a twin-screw extruder. The esterification reaction is to graft a nonylphenyl-ethoxylate (NP8) onto a pre-maleated ethylene-propylene (EPR_MA). The kinetics were initially characterized in the static mixture using a thermally controlled call in a FTIR spectrometer. These were then used to predict the conversion along the length of the extruder screws, having determined the residence time distribution at various sampling locations. A reasonable fit with the data was obtained, although the kinetics seem to be slightly faster in the flowing medium than those predicted. Over short screw distances, the equilibrium rapidly approached equilibrium. Moreover, the NP8 was shown to penetrate the EPR_MA within screw distance of less than 1.3 L/D, despite using conveying elements known for their minimal mixing capacity. Within the molten medium, a mixing model showed that obtaining the expected conversion in a product does not imply that the reactants in the product have in fact been well mixed.     

Temperature resistance coefficient of composite resistive materials in the mixed-structure approximation

A method of calculating the temperature resistance coefficient and its temperature dependence for resistive materials in the approximation of a matrix-statistical structure is outlined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 477–481, September, 1985.     

Lens antennas for mobile broadband systems in the millimetre-waverange

An improved antenna for a wireless mobile broadband system (e.g. as realised by Bosch as a demonstrator) is proposed. By means of a shaped dielectric lens the radiation pattern of a primary antenna (e.g. a short helical structure) can be shaped to optimise the power distribution across an indoor cell. The calculated performance of lenses designed for the 30 and 60 GHz bands by using geometric optics shows good agreement with measured results     

Algorithms and software tools for ordering clone libraries: application to the mapping of the genome of Schizosaccharomyces pombe

A complete set of software tools to aid the physical mapping of a genome has been developed and successfully applied to the genomic mapping of the fission yeast Schizosaccharomyces pombe. Two approaches were used for ordering single-copy hybridisation probes: one was based on the simulated annealing algorithm to order all probes, and another on inferring the minimum-spanning subset of the probes using a heuristic filtering procedure. Both algorithms produced almost identical maps, with minor differences in the order of repetitive probes and those having identical hybridisation patterns. A separate algorithm fitted the clones to the established probe order. Approaches for handling experimental noise and repetitive elements are discussed. In addition to these programs and the database management software, tools for visualizing and editing the data are described. The issues of combining the information from different libraries are addressed. Also, ways of handling multiple-copy probes and non-hybridisation data are discussed.     

Schrifttumsberichte

Ohne Zusammenfassung     

Verkleinerung verfahrenstechnischer Versuchsanlagen — was ist erreichbar?

Scale-down of chemical engineering pilot plant – what is attainable? The use of fully automated experimental laboratory-scale plantoffer interesting possibilities for assessment of the economic operation and technical feasibility of new or modified processes. An important condition for the success of this kind of experimental approach is the availability of miniaturized equipment, machines, and sensors. The goal of such experimental plant can be both the process engineering development of individual process steps and also integrated running to model complete processes. Moreover, questions of scale-up can be studied and typical quantities can be provided. The state of the art is reported with the aid of selected examples of equipment and mechanical components and measurement and control units.     

Bestimmung des Endotoxin-Gehalts in Eiprodukten mit Hilfe eines miniaturisierten chromogenen Limulus-Tests

Zusammenfassung Die Eignung eines chromogenenLimulus-Tests zur Bestimmung des Endotoxin-Gehalts in Eiprodukten wurde gepruft. Dabei zeigte die Analyse verschieden stark bakteriell belasteter Volleimassen eine deutliche Korrelation zwischen Endotoxin-Konzentration und Gesamtkeimzahl (6 x 10⁴ cfu x ng^–1 Endotoxin) Bowie der Anzahl vonEnterobacteriaceen (7x10² cfu x ng^–1 Endotoxin). Vergleichbare Ergebnisse konnten auch mit Eigelb- und Eiweilßproben erzielt werden. Der Endotoxin-Nachweis wurde durch Hitzebehandlung (65 °C, 60 min) nicht beeinflußt. Endotoxinfreies steriles Volleimaterial hatte bis zu einer Konzentration im Testansatz von 10 mg x ml^–1 keinen Einfluß auf das Mcßergebnis. Im vorliegenden Bericht wird eine miniaturisierte Version des Testverfahrens vorgestellt, die im Mikro titerplatten-System durchgeführt werden kann.

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Determination of endotoxin in egg products with a miniaturized chromogenic Limulus test

Summary A chromogenicLimulus amoebocyte lysate assay was applied to monitor endotoxin concentration in egg products. Analysis of differently contaminated whole egg probes revealed a strong correlation of endotoxin concentration to total bacterial count 6 x 10⁴ cfu x ng^–1, where cfu=colony-forming unit) as well as to number ofEnterobacteriaceae (1 ng/7 x 10² cfu). Similar relations were also found for egg white and egg yolk probes. A significant influence of heat pretreatment of egg probes (65° C, 60 min) on endotoxin detection could be excluded. Up to a concentration of 10 mg x µl^–1 endotoxin-free whole egg material did not interfere with the test system. A miniaturized version of the chromogenicLimulus test, which can be carried out in microtiter plates, is described.

     

WDM Ethernet passive optical networks

WDM EPONs not only allow for cautious pay-as-you-grow upgrades of single-channel TDM EPONs but also avoid linearly increasing polling cycle times for an increasing number of ONUS. In this article, we first provide a comprehensive overview of the state of the art of TDM EPONs and recently reported dynamic bandwidth allocation algorithms, including decentralized scheduling schemes. After reviewing previous work on WDM EPONs, we address the requirements of WDM upgraded EPONs and make recommendations on an evolutionary WDM upgrade at the architecture, protocol, and dynamic bandwidth allocation algorithm levels, taking backward compatibility with MPCP and future-proofness against arbitrary WDM ONU structures into account. We describe and compare online and offline scheduling paradigms for WDM EPONs. Our simulation results indicate that online scheduling can achieve lower delays, especially at high loads. We outline areas of future research on WDM EPONs.