Electron-beam treatment of aromatic hydrocarbons that can be air-stripped from contaminated groundwater. 2. Gas-phase studies

The electron-beam (EB) degradation of volatile aromatics (benzene, toluene, ethylbenzene, xylenes: BTEX) in groundwater strip gas, which in the present work has been modeled by the introduction of the desired aromatic(s) to a stream of air or another gas, such as oxygen, is initiated essentially by the addition of *OH radicals to the aromatic ring, giving rise to hydroxycyclohexadienyl radicals, which form the corresponding peroxyl radicals upon addition of oxygen. As studied in some detail with benzene as a BTEX representative, various reactions of these lead to numerous oxidation products in a cascade of reactions, including the decomposition of products under the prevailing conditions of high turnover of the initial aromatic. Importantly, hydroxycyclohexadienylperoxyl radical formation is partly reversible, and the reactions of the hydroxycyclohexadienyl radicals, which thus have a significant presence in these systems, must therefore also be taken into consideration. In the gas phase, in contrast to the aqueous phase (see Part 1), the reactions of the hydroxycyclohexadienyl radicals lead to oligomeric products that appear to contribute, in addition to ionic clusters, to nucleation for the aerosols observed. Various nitrated products, among them nitrophenols, are observed when air is used for the stripping. However, these studies did not clear the pilot plant stage, since BTEX degradation using a bioreactor carried out in parallel was so successful that the EB technology was judged to be noncompetitive. As for the latter, expensive equipment consisting of a stripper, the EB machine, and an aerosol precipitator would be required. The condensed aerosols are biorefractory and would require further treatment for detoxification.     

Linear multiobjective maxmin optimization and some Pareto and lexmaxmin extensions

Summary This is a lexmaxmin extension of some results on linear maxmin programming recently obtained by Posner and Wu, Kaplan, Gupta and Arora, and Kabe. The findings of these authors will be combined with previous results by the author of the present paper to give further insight into the interrelation between optimization with respect to maxmin, Pareto, and lexmaxmin.

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Zusammenfassung Diese Arbeit enthält Lexmaxmin-Erweiterungen einiger jüngerer Ergebnisse von Posner und Wu, von Kaplan, von Gupta und Arora und von Kabe über lineare Maxmin-Probleme. Die Beobachtungen der genannten Autoren werden mit früheren Ergebnissen des Autors der vorliegenden Arbeit mit dem Ziel vereint, weitere Einsichten in den Zusammenhang zwischen Maxmin-, Pareto- und Lexmaxmin-Optimierung zu vermitteln.

     

Reconfigurable optoelectronic wavelength translation based on anintegrated electroabsorption modulated laser array

Reconfigurable optoelectronic wavelength conversion to 11 100-GHz spaced wavelengths is achieved using a wavelength selectable laser array with an integrated electroabsorption (EA) modulator at a bit rate of 2.5 Gb/s. Wide dynamic range at the input from -24.2 to -6.5 dBm is achieved and uniform back-to-back transmission performance is measured for all wavelengths     

Towards a medically approved technology for alginate-based microcapsules allowing long-term immunoisolated transplantation

The concept of encapsulated-cell therapy is very appealing, but in practice a great deal of technology and know-how is needed for the production of long-term functional transplants. Alginate is one of the most promising biomaterials for immunoisolation of allogeneic and xenogeneic cells and tissues (such as Langerhans islets). Although great advances in alginate-based cell encapsulation have been reported, several improvements need to be made before routine clinical applications can be considered. Among these is the production of purified alginates with consistently high transplantation-grade quality. This depends to a great extent on the purity of the input algal source as well as on the development of alginate extraction and purification processes that can be validated. A key engineering challenge in designing immunoisolating alginate-based microcapsules is that of maintaining unimpeded exchange of nutrients, oxygen and therapeutic factors (released by the encapsulated cells), while simultaneously avoiding swelling and subsequent rupture of the microcapsules. This requires the development of efficient, validated and well-documented technology for cross-linking alginates with divalent cations. Clinical applications also require validated technology for long-term cryopreservation of encapsulated cells to maintaining a product inventory in order to meet end-user demands. As shown here these demands could be met by the development of novel, validated technologies for production of transplantation-grade alginate and microcapsule engineering and storage. The advances in alginate-based therapy are demonstrated by transplantation of encapsulated rat and human islet grafts that functioned properly for about 1 year in diabetic mice.