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51.
Johann Günter Krieg 《Zeitschrift für Physik A Hadrons and Nuclei》1967,205(5):425-439
This paper realizes an idea ofRedfield in a general and quantitative manner: Charged point defects produce local electric fields in a crystal which cause a change in the absorption-constant compared with the absorption-constant of an undisturbed crystal (Franz-Keldysh-effect). Thus one gets a tail in the absorption constant decreasing from the ideal intrinsic absorption edge towards longer wave-lengths. Applying an external fieldF one finds an additional, frequency-dependent absorptionconstantΔα. Its magnitude and spectral distribution depend on the concentration of defects. For external fields smaller than the internal onesΔα∝ F 2 holds at all frequencies. The results are compared with those found byFranz. 相似文献
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The synthesis of five eight-electron-ligands, two six-electron-ligands and one four-electron-ligand for transition metals is described. These heterocycles contain in each case arsenic and sulfur as heteroatoms, and additionally oxygen in one case. 相似文献
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Dreer S Wilhartitz P Piplits K Mayerhofer K Foisner J Hutter H 《Analytical and bioanalytical chemistry》2004,379(4):599-604
Gate oxynitride structures of TFT-LCDs were investigated by SIMS, and successful solutions are demonstrated to overcome difficulties arising due to the charging effects of the multilayer systems, the matrix effect of the method, and the small pattern sizes of the samples. Because of the excellent reproducibility achieved by applying exponential relative sensitivity functions for quantitative analysis, minor differences in the barrier gate-oxynitride composition deposited on molybdenum capped aluminium-neodymium metallisation electrodes were determined between the centre and the edge of the TFT-LCD substrates. No differences were found for molybdenum-tungsten metallisations. Furthermore, at the edge of the glass substrates, aluminium, neodymium, and molybdenum SIMS depth profiles show an exponential trend. With TEM micrographs an inhomogeneous thickness of the molybdenum capping is revealed as the source of this effect, which influences the electrical behaviour of the device.The production process was improved after these results and the aging behaviour of TFT-LCDs was investigated in order to explain the change in control voltage occurring during the lifetime of the displays. SIMS and TEM show an enrichment of neodymium at the interface to the molybdenum layer, confirming good diffusion protection of the molybdenum barrier during accelerated aging. The reason for the shift of the control voltage was finally located by semi-quantitative depth profiling of the sodium diffusion originating from the glass substrate. Molybdenum-tungsten was a much better buffer for the highly-mobile charge carriers than aluminium-neodymium. Best results were achieved with PVD silicon oxynitride as diffusion barrier and gate insulator deposited on aluminium-neodymium metallisation layers. 相似文献
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Ihling C Berger K Höfliger MM Führer D Beck-Sickinger AG Sinz A 《Rapid communications in mass spectrometry : RCM》2003,17(12):1240-1246
Fourier transform ion-cyclotron resonance (FTICR) mass spectrometry offers several advantages for the analysis of biological samples, including excellent mass resolution, ultra-high mass measurement accuracy, high sensitivity, and wide mass range. We report the application of a nano-HPLC system coupled to an FTICR mass spectrometer equipped with nanoelectrospray source (nano-HPLC/nano-ESI-FTICRMS) for proteome analysis. Protein identification in proteomics is usually conducted by accurately determining peptide masses resulting from enzymatic protein digests and comparing them with theoretically digested protein sequences from databases. A tryptic in-solution digest of bovine serum albumin was used to optimize experimental conditions and data processing. Spots from Coomassie Blue and silver-stained two-dimensional (2D) gels of human thyroid tissue were excised, in-gel digested with trypsin, and subsequently analyzed by nano-HPLC/nano-ESI-FTICRMS. Additionally, we analyzed 1D-gel bands of membrane preparations of COS-6 cells from African green monkey kidney as an example of more complex protein mixtures. Nano-HPLC was performed using 1-mm reverse-phase C-18 columns for pre-concentration of the samples and reverse-phase C-18 capillary columns for separation, applying water/acetonitrile gradient elution conditions at flow rates of 200 nL/min. Mass measurement accuracies smaller than 3 ppm were routinely obtained. Different methods for processing the raw data were compared in order to identify a maximum number of peptides with the highest possible degree of automation. Parallel identification of proteins from complex mixtures down to low-femtomole levels makes nano-HPLC/nano-ESI-FTICRMS an attractive approach for proteome analysis. 相似文献
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Shankaramma SC Moehle K James S Vrijbloed JW Obrecht D Robinson JA 《Chemical communications (Cambridge, England)》2003,(15):1842-1843
Macrocyclic peptidomimetics having a mixed peptide-peptoid backbone have been synthesized and shown to possess antibiotic activity against gram-positive and -negative bacteria with a low hemolytic activity against human erythrocytes; one is shown to adopt a regular beta-hairpin conformation by NMR in aqueous solution. 相似文献
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