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151.
S. Riechel U. Lemmer J. Feldmann T. Benstem W. Kowalsky U. Scherf A. Gombert V. Wittwer 《Applied physics. B, Lasers and optics》2000,71(6):897-900
We report on the laser modes in optically pumped solid-state lasers using an electroluminescent organic semiconductor as the
active medium. Mechanically flexible distributed-feedback lasers are fabricated by depositing a thin film of an active material
onto a nano-patterned polyester substrate either via spin-coating of a soluble ladder-type poly(p-phenylene) or via vacuum
co-sublimation of small organic molecules. The different surface texture resulting from the fabrication process causes different
feedback mechanisms. In both lasers higher lateral modes give rise to a broadening of the laser spectra at higher pumping
levels.
Received: 7 August 2000 / Revised version: 12 September 2000 / Published online: 8 November 2000 相似文献
152.
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154.
Hans R. Kricheldorf Gert Schwarz Sigrid Bhme Claus‐Ludolf Schultz 《Journal of polymer science. Part A, Polymer chemistry》2003,41(7):890-904
Bisphenol A was polycondensed with diphosgene in a dichloromethane/aqueous NaOH system. Temperature, time, and molar ratios of the reactants were optimized according to a previously elaborated optimization of the hydrolytic polycondensation of bisphenol A bischloroformate. Five of the following catalysts were examined: triethylamine, 4‐(N,N‐dimethylamino)pyridine (DMAP), ethyldiisopropylamine (EDPA), tetrabutylammonium hydrogen sulfate, and triethylbenzylammonium chloride (TEBA‐Cl). Triethylamine and DMAP accelerated the hydrolysis of diphosgene by formation of a hydrophilic acylammonium salt. Therefore, the molecular weights decreased with higher concentration of these tert‐amines. However, the molecular weights increased (weight‐average molecular weight up to 106) with higher concentrations of tetraalkylammonium salts because these catalysts favor chain growth in the organic phase via “naked” phenoxide ions without catalyzing the hydrolysis of diphosgene. EDPA gave poor results under all circumstances. Cyclic polycarbonates were discovered in all samples. Their fraction increased with the average molecular weight of the samples. When samples prepared with triethylamine or TEBA‐Cl were fractionated, cycles having molar masses up to 15,000 Da were detected by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 890–904, 2003 相似文献
155.
Mathias Wind Ingo Feldmann Norbert Jakubowski Wolf D Lehmann 《Electrophoresis》2003,24(7-8):1276-1280
Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) with (31)P detection has been used for spotting of phosphoproteins after one-dimensional polyacrylamide gel electrophoresis (1-D PAGE) and membrane transfer. By analyzing a mixture of myoglobin, alpha-casein and reduced fibrinogen it is demonstrated that phosphoproteins are specifically recognized by this method. A special washing step was found to be necessary to remove phosphate noncovalently bound to proteins. The (31)P signal was found to contain quantitative information both with respect to relative and absolute amounts of phosphorus present in phosphoproteins. Normalizing the (31)P signal from a single laser ablation trace by the total amount of phosphoprotein applied to the gel, a detection limit of 5 pmol of phosphorus is estimated. 相似文献
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157.
On the Influence of Chemical Transport on the Habit of Crystals The chemical transport of silicon with silicon tetrachloride as transporting agent leads to crystals with octahedral shape. On the other hand in the presence of adsorbable impurities the transported silicon crystallizes in the shape of long needles. Chemical transport reactions of tellurium are successful with iodine or sulphur. The presence of adsorbable transporting agents has considerable influence on the habit of crystals. 相似文献
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159.
Claus Lubbe Yong-Qiang Shen Arnold L. Demain 《Applied biochemistry and biotechnology》1986,12(1):31-35
A simple and rapid chemical assay for cephalosporins is described. It is a simple modification of the colorimetric determination of penicillins in which the narrow spectrum beta-lactamase (penicillinase) is replaced by a broad spectrum beta-lactamase (cephalosporinase) produced by Enterobacter cloacae. The method can be used for assay of fermentation broths as well as for pure cephalosporins. 相似文献
160.
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