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Dispersive two-beam Fourier interferograms of N2-gas in the visible wave number range are calculated numerically for nonabsorbing as well as absorbing gas and compared with experiment. Some problems of inverse Fourier transformation of dispersive interferograms are also discussed. 相似文献
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We report high-resolution opto-acoustic spectroscopy of v = 0 → 1 vibrational rotational transitions of 15NO using a low field spin flip Raman laser as the source of tunable infrared radiation. Fifteen transitions belonging to the 2Σ thirteen transitions belonging to 2Π state have been measured and we report the Λ-doubling for the 2Π tran sitions. A preliminary analysis of the Λ-doubling parameters is given. 相似文献
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Direct evaluation of the subgrid scale scalar flux in turbulent premixed flames with conditioned dual-plane stereo PIV 总被引:1,自引:0,他引:1
Sebastian Pfadler Johannes Kerl Frank Beyrau Alfred Leipertz Amsini Sadiki Jrg Scheuerlein Friedrich Dinkelacker 《Proceedings of the Combustion Institute》2009,32(2):1723-1730
With the dual-plane stereo PIV technique the instantaneous three-dimensional resolved rate-of-strain tensor is directly measured in turbulent premixed flames. Simultaneously, also the instantaneous subgrid scale (SGS) scalar flux is measured with fine resolution, where for the latter term the conditioned particle image velocimetry (CPIV) technique is applied. The subgrid resolution reaches 118 μm, allowing a 9 × 9 resolution of a subgrid filter with width Δ = 1 mm. This combined measurement approach allows the a-priori comparison of models for the SGS scalar flux term with direct measurements which is important for large eddy simulation methods in turbulent premixed flames. Two different flame conditions of a premixed V-shaped turbulent flame are investigated where the turbulence intensity is varied by a factor of nearly three. The instantaneous radial and axial SGS fluxes are compared with the following three models: gradient model with Smagorinsky approach for the turbulent viscosity, Clark model, and extended gradient model with an anisotropy term. None of these models shows a good correlation with the directly measured flux. The anisotropy term alone (being nearly similar to the Clark model) shows, however, a right trend behaviour. An analysis of the data indicates a significant dependency of the experimentally determined SGS flux on the Favre averaged reaction progress (spatially averaged over the SGS area). A relatively simple closure for the SGS flux, which describes the dilatation due to the gasdynamic expansion, and which is a function proportional to , shows a rather good correlation with direct measurement for some of the components. A successful SGS scalar flux model for premixed turbulent flames most likely needs to include at least two different effects. 相似文献
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Isotopic and ultratrace analysis of uranium by double-focusing sector field ICP mass spectrometry 总被引:1,自引:0,他引:1
W. Kerl J. S. Becker H.-J. Dietze W. Dannecker 《Analytical and bioanalytical chemistry》1997,359(4-5):407-409
An analytical method for the ultratrace and isotopic analysis of uranium in radioactive waste samples using a double-focusing
sector field ICP mass spectrometer is described. In high-purity water a detection limit for uranium in the lowest fg/mL range
has been achieved. Under optimum experimental conditions (235U/238U ≈ 1), the precision in 235U/238U isotopic ratio determinations has been determined as 0.07% RSD. With the isotopic standard U-020 (235U/238U = 0.0208) a precision of 0.23% RSD at the 100 pg/mL level using ultrasonic nebulization has been achieved. With 234U/238U isotopic ratios of down to 10–5, the values obtained by double-focusing sector field ICP-MS and alpha spectrometry were in agreement.
Received: 27 February 1997 / Revised: 10 Juni 1997 / Accepted: 12 June 1997 相似文献
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Thomas Kerl Florian Berger Prof. Dr. Hans‐Günther Schmalz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2935-2938
The first total synthesis of houttuynoid B, a powerful antiviral flavonoid glycoside from the Chinese plant Houttuynia cordata, is described. In a key step, a Baker–Venkataraman rearrangement employing an already glycosylated substrate was used to efficiently set up the fully functionalized carbon skeleton. The required benzofuran building block was prepared through a domino Sonogashira coupling/5‐endo‐dig cyclization and converted into a stable 1‐hydroxybenzotriazole‐derived active ester prior to linking with a galactosylated hydroxyacetophenone unit. The elaborated synthesis requires only nine steps (11 % overall yield) along the longest linear sequence and paves the way for the preparation of structurally related compounds for further biological evaluation. 相似文献
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M. Hamester D. Wiederin J. Wills W. Kerl C. B. Douthitt 《Analytical and bioanalytical chemistry》1999,364(5):495-498
A single collector double focusing sector field ICP-MS is evaluated for the determination of isotope ratios. Spectral interferences
(e.g. 40Ar23Na on 63Cu) can lead to calculation of inaccurate ratios. The use of high resolution enables such interferences to be separated from
the isotopes of interest. External reproducibilities of < 0.02% are shown for uninterfered isotopes (measured at low resolution
R = 300) and < 0.1% for interfered isotopes which required the use of medium (R = 4000) and high resolution (R = 10000).
Received: 11 January 1999 / Revised: 8 April 1999 / Accepted: 11 April 1999 相似文献