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91.
We present a novel fast fabrication method for making optical waveguides by using a photoaligning and a liquid-crystal polymer. A difference in the refractive indices in the core and cladding regions is achieved by use of polarized UV light to align the polymer chains differently. A refractive-index difference of Deltan = 0.07 was achieved. The propagation loss in a channel waveguide is 4 dB/cm at a wavelength of 1.55 microm. The fabrication method has only a few processing steps and yields short fabrication times. The waveguide structures offer possibilities for generating devices with new applications related to the polarization of the guided light. 相似文献
92.
A New and Simple Method for the Synthesis of Spirocyclic la-Quinolines The reaction of anilines with (+)-(R)-pulegone in toluene at temperatures between 125 and 150° with 4-toluenesulfonic acid or I2 as catalysts leads to diastereoisomeric mixtures of spiro[cyclohexane-1,2′(1′H)-quinoline] derivatives (see 1–4 , Scheme 1; Table). The diastereoisomers are separated by column chromatography, and the structure of the single isomers is determined by NMR-spectroscopic methods. A reaction mechanism proceeding via several 6π-electrocyclic rearrangements and H-shifts is proposed for the formation of 1H-quinolines 1–4 (Scheme 2). This mechanism is in accordance with the results of the reaction of 2-isopropenylaniline with 3-methylcyclohexanone which leads to a stereoisomeric mixture of 3,4′-dimethylspiro[cyclohexane-1,2′(1H)-quinolines] (Scheme 3). 相似文献
93.
Photochemical nitrogen elimination of 1,2,3-thiadiazoles leads to primary fragments ( 1 , X = S), which are able to cyclize to thiirenes ( 2 , X = S). An exception is found for bicyclic systems like 4 . These results, gained by isotope labelling experiments are related to the oxirene formation of α-oxocarbenes. 相似文献
94.
Structure Elucidation of Elaiophylin: Spectroscopy and Chemical Degradation The structure of the antibiotic elaiophylin (azalomycin B) was elucidated by extended spectroscopic investigations and chemical degradation. Elaiophylin ( 26 ) is a macrodiolide with a 16membered dilactone ring. The synthesis of 7-acetoxy-6-ethyl-3-octanone ( 14 ), the acetyl derivative of an important degradation product, is described. 相似文献
95.
An autonomous fourth order model of vocal fold vibrations is proposed. Each fold is represented by a lower and upper mass, and the aerodynamic forces are derived from a modified Bernoulli equation. The model exhibits many features of normal phonation in a wide parameter region. At the borderlines of this region coexistence of limit cycles, period-doubling and chaos are observed. Implications for an understanding of pathological voices are discussed. 相似文献
96.
97.
E. Bucher S. Schulz M. Ch. Lux-Steiner P. Munz U. Gubler F. Greuter 《Applied Physics A: Materials Science & Processing》1986,40(2):71-77
The work function of 13 polycrystalline transition metal suicides was measured by photoemission in uhv. Their values are discussed in relationship to their Schottky barrier heights on n-Si. While there appears to be a weak correlation for a certain group of transition metal suicides, the values of the 5d-noble metal suicides including some of the lattice matched Ni suicides appear to be completely uncorrelated. Experimental values of work functions are compared to the values proposed previously by Freeouf. 相似文献
98.
Gerhard Buchbauer Hanspeter Kählig Helmut Spreitzer Walpurga Wegscheider 《Monatshefte für Chemie / Chemical Monthly》1991,122(12):1089-1095
Summary The separation of a complex mixture of a fragrance material into its isomers is described. Instead of an odour of sandalwood the mixture exhibits mainly a mushroom odour but also the pure isomers show other organoleptic qualities. The structure of two isomers could be ascertained mainly by13C- and1H-NMR-measurements, for two isomers a structure proposal is given.
Herrn Prof. Dr. Wilhelm Fleischhacker mit den besten Wünschen zum 60. Geburtstag gewidmet 相似文献
99.
Müller MG Hardy EH Vogt PS Bratschi C Kirchner B Huber H Searles DJ 《Journal of the American Chemical Society》2004,126(14):4704-4710
An approach is presented that allows NMR relaxation rates to be determined for a complex mixture, and it is applied to a dimethyl sulfoxide/water solution. This approach is novel for such systems, having only been used for simple systems such as atomic liquids or atomic ions in liquids until now. It involves use of a predetermined, quantum mechanical, multidimensional property surface in a simulation. The results are used in conjunction with the simulated rotational correlation time to calculate the deuteron quadrupole coupling constant (DQCC), in an analogous approach to the one used by experimentalists, and to examine the surprising experimental findings for the composition dependence of the DQCC in the dimethyl sulfoxide/water mixture. Experiments have suggested that the DQCC for a mixture of 5% dimethyl sulfoxide in water is close to the DQCC of ice, whereas its value increases to a value close to the gas value with further dilution.(1) The results are further critically analyzed using combinations of different experimental and theoretical results from the literature. 相似文献
100.
Hanspeter Kählig Peter Paul Nimmerrichter Wolfgang Robien 《Monatshefte für Chemie / Chemical Monthly》1993,124(1):71-75
Summary Treatment of abietic acid methylester with Hg(OAc)2/MeOH produces a dimethoxy derivative. The determination of the configuration at C-7 of this product by means of 1D- and 2D-NMR-spectroscopic methods is described. The results are verified by application of17O-NMR spectroscopy and comparison with well-established stereochemical dependencies of17O chemical shifts.
17O-NMR-Spectroskopie zur stereochemischen Analyse. Anwendung auf ein Diterpen-Derivat
Zusammenfassung Umsetzung von Abietinsäuremethylester mit Hg(OAc)2/MeOH führt zu einem Dimethoxyderivat. Die Bestimmung der Konfiguration am Zentrum C-7 erfolgt durch Anwendung von 1D- und 2D-NMR-Methoden. Die Resultate konnten durch17O-NMR-Spektroskopie aufgrund der bekannten stereochemischen Verschiebungsabhängigkeit bestätigt werden.相似文献