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941.
F. A. Theopold E. Gerdau R. Hollatz H. Riege R. Rüffer R. Van Staa 《Hyperfine Interactions》1986,29(1-4):1555-1558
Construction and use of a function generator are presented. The flexible outline allows a high precision control for all required
velocity profiles. 相似文献
942.
943.
944.
Yves Van Ingelgem Els Tourwé Orlin Blajiev Rik Pintelon Annick Hubin 《Electroanalysis》2009,21(6):730-739
Electrochemical impedance spectroscopy (EIS) is a powerful technique to study electrochemical processes and to perform screening tasks. Recently an integrated measuring and modeling methodology for EIS based on a multisine excitation signal was developed. A key issue in this methodology is the data analysis, allowing us to rapidly quantify the reliability of the measured data. In this paper, a comparison is made between classical single‐sine and the proposed multisine measurements on the same system. The fitting of the impedance data obtained by single‐or multisine excitation and using different weighting factors is also discussed. In addition to the advantages reported in earlier work, it is concluded that, of all investigated frequencies, the odd random phase multisine excitation yields the highest quality data in the shortest measurement time. 相似文献
945.
Christopher M. Leavitt Jos Oomens Ryan P. Dain Jeffrey Steill Gary S. Groenewold Michael J. Van Stipdonk 《Journal of the American Society for Mass Spectrometry》2009,20(5):772-782
Anionic group II metal nitrate clusters of the formula [M2(NO3)5]−, where M2 = Mg2, MgCa, Ca2, and Sr2, are investigated by infrared multiple photon dissociation (IRMPD) spectroscopy to obtain vibrational spectra in the mid-IR
region. The IR spectra are dominated by the symmetric and the antisymmetric nitrate stretches, with the latter split into
high and low-frequency components due to the distortion of nitrate anion symmetry by interactions with the cation. Density
functional theory (DFT) is used to predict geometries and vibrational spectra for comparison to the experimental spectra.
Calculations yield two stable isomers: the first one contains two terminal nitrate anions on each cation and a single bridging
nitrate (“mono-bridging”), while the second structure features a single terminal nitrate on each cation with three bridging
nitrate ligands (“tri-bridging”). The tri-bridging isomer is calculated to be lower in energy than the mono-bridging one for
all species. Theoretical spectra of the tri-bridging structure provide a better qualitative match to the experimental infrared
spectra of [Mg2(NO3)5]− and [MgCa(NO3)5]−. However, the profile of the low-frequency ν
3 band for the Mg2 complex suggests a third possible isomer not predicted by theory. The IRMPD spectra of the Ca2 and Sr2 complexes are better reconciled by a weighted summation of the spectra of both isomers suggesting that a mixture of structures
is present. 相似文献
946.
947.
F. De Corte M. Dejaeger S. M. Hossain D. Vandenberghe A. De Wispelaere P. Van den Haute 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(3):659-663
Summary Recently, in our laboratory an intercomparison was made of methods for the annual radiation dose determination (assessed from direct radiation counting and/or from the measurement of the K, Th and U contents) applied to luminescence dating of loess and sand sediment, whereby the emphasis was put on their precision and accuracy. Although these properties are important, the duration of the measurement is also a practically relevant aspect. Indeed, direct alpha, beta and gamma-counting can last a week or more, and the determination of K, Th and U via NAA can take up to three weeks to enable proper gamma-ray spectrometry of the long-lived 233 Th/233Pa. Therefore, in the present work the performance of k0-based epiCd-NAA (ENAA, with irradiation under a cadmium cover) when applied to sediments is compared to k0-NAA. As concluded, with the use of k0-ENAA the analysis turnaround time could be considerably reduced from ~3 weeks to ~ 2.5days, while maintaining satisfactory accuracy, precision and determination sensitivity. 相似文献
948.
Brajendra K. Singh Christian V. Stevens Davy R.J. Acke Erik V. Van der Eycken 《Tetrahedron letters》2009,50(1):15-4274
A continuous flow procedure has been elaborated for the copper(II)-mediated N- and O-arylation of a range of compounds with arylboronic acids using a commercial microreactor setup. The compounds could be continuously generated in good yields paving the way for efficient scalability. 相似文献
949.
Oscar J. Pozo Koen Deventer Peter Van Eenoo Robert Rubens Frans T. Delbeke 《Biomedical chromatography : BMC》2009,23(8):873-880
Testosterone undecanoate (T‐C11) can be used by athletes in order to improve performance. After oral intake, T‐C11 is rapidly metabolized, hampering discrimination between exogenous and endogenous testosterone. A possible alternative is to detect the intact ester in hair. A method based on liquid chromatography–tandem mass spectrometry was developed for the determination of T‐C11 in hair. The sample procedure consisted of digestion of 200 mg of pulverized hair with tris(2‐carboxyethyl)phosphine hydrochloride and liquid–liquid extraction with n‐pentane. Several parameters such as the mobile phase, the ionization source and the washing step were optimized. The method was validated at different spiked levels obtaining satisfactory values for accuracy (between 92 and 102%) with relative standard deviations lower than 7% and a limit of detection of 0.2 ng/g. The applicability of the method was checked by the analysis of three samples from patients using T‐C11. A peak for the analyte was detected in all samples with concentrations between 0.4 and 8.4 ng/g. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
950.
G. Reusen V. R. Bom P. Decrock P. Dendooven M. Huyse R. W. Hollander P. Van Duppen J. Vanhorenbeeck J. Wauters 《Zeitschrift für Physik A Hadrons and Nuclei》1990,336(4):381-386
Theβ-strength function of104Cd is studied in theβ +/EC decay of mass-separated104In. The determination of theβ + feeding and theβ +/β +EC ratio is the result of the simultaneous measurement of beta and gamma rays in one semiconductor beta-spectrometer. Information on the strength function near theQ EC value is obtained from the detection of high-energyγ rays. The total observedβ strength amounts up to 10% of the Extreme Single-Particle Shell Model value. A strong enhancement in theβ +/EC feeding to a group of levels around 5.6 MeV shows the influence of the Gamow-Teller Resonance. 相似文献