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We consider 4-dimensional flexible projective planes with the following properties: The collineation group is a 6-dimensional solvable Lie group which fixes some flag ∞ ∈ W. Furthermore, the collineation group has a 1-dimensional orbit both on W and on the pencil of lines through {∞}. We show that there are three different families of planes with these properties. 相似文献
824.
Berger Oliver Heinzelmann Robert Stöhr Andreas Jäger Dieter Huang Xuan Seeds Alwyn 《Optical and Quantum Electronics》1999,31(9-10):1031-1045
A dynamic model for the design of multi-section semiconductor lasers is developed based on the Transmission Line Method. The different building blocks of this model are presented and the model is evaluated for a tunable two-section laser device. 相似文献
825.
Dieter Fischer Petra Pötschke Harald Brünig Andreas Janke 《Macromolecular Symposia》2005,230(1):167-172
The superior association of the inherent good mechanical and electrical properties makes carbon nanotubes (CNT) exceptionally interesting for the production of composite fibers of thermoplastic polymers with CNT. Alignment of the CNT in the polymer fiber is important for improved mechanical properties. Especially the production of fibers makes it necessary to get a controlled orientation and/or alignment of the CNT. We applied transmission electron microscopy (TEM) and polarized Raman microscopy to quantify multiwalled carbon nanotubes (MWNT) orientation, alignment and crystallinity in polycarbonate (PC). The evaluation of the Raman measurements provided an improved alignment orientation of the MWNT in the fibers with increasing take-up velocity during melt spinning and that the crystal structure of the MWNT is not changed through melt spinning. 相似文献
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Raman spectroscopy, which does not require a time‐consuming sample preparation, is described as an analytical tool for the high‐throughput characterization of polyethylenes. The content of comonomer and the amount of methyl groups per 1 000 carbon atoms of polyethylenes can be predicted from Raman spectra using multivariate data analysis. In addition, macroscopic properties, such as density and elastic modulus as well as yield stress, can be derived from Raman spectra.
828.
Dieter Schrenk 《Chemie in Unserer Zeit》2003,37(2):140-146
Food contains a variety of compounds of natural origin that may be harmful when consumed too frequently or at a very high dose level or under inappropriate conditions. Examples for such constituents include the glucosinolates in cabbage or tyrpsin inhibitors in raw beans. Other constituents such as vicin in broad beans or glycyrrhizic acid in liquorice may be harmful for a subpopulation only, e.g., in patients suffering from high blood pressure or in individuals bearing certain genetic defects of metabolism. Furthermore, food may contain compounds which have been added by purpose (legal food additives) such as emulsifiers, preservatives, synthetic colors etc. These compounds are under strict regulation and their safety has been tested rigorously. Contaminants in food such as dioxins, pesticides, drug residues etc. may originate from illegal or inappropriate production or treatment. At lower levels they may reflect background contamination, e.g., in the environment. Finally, nutritional supplements and ingredients of ‘functional food’ require special toxicological testing and evaluation since not all compounds considered as ‘healthy’ in certain concentrations are also beneficial or safe when consumed at higher doses. 相似文献
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