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31.
Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
32.
KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
33.
Abbasi RU Abu-Zayyad T Amann JF Archbold G Bellido JA Belov K Belz JW Bergman DR Cao Z Clay RW Cooper MD Dai H Dawson BR Everett AA Fedorova YA Girard JH Gray RC Hanlon WF Hoffman CM Holzscheiter MH Hüntemeyer P Jones BF Jui CC Kieda DB Kim K Kirn MA Loh EC Manago N Marek LJ Martens K Martin G Matthews JA Matthews JN Meyer JR Moore SA Morrison P Moosman AN Mumford JR Munro MW Painter CA Perera L Reil K Riehle R Roberts M Sarracino JS Sasaki M Schnetzer SR Shen P Simpson KM Sinnis G Smith JD 《Physical review letters》2004,92(15):151101
We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources. 相似文献
34.
J. M. A. De Mendonça A. V. Bellido 《Journal of Radioanalytical and Nuclear Chemistry》1986,98(1):75-81
The chemical consequences of (n,2n) reactions on crystalline sodium iodates and sodium periodates, containing127I or127I+129I, were investigated measuring the initial yields and the post irradiation thermal annealing yields at 90°C for three separated fractions: I+Io, IO
3
–
and IO
4
–
. The results show different effects for each system and neither isotope effect nor qualitative differences on thermal annealing were observed. The influence of the nuclear reaction type, of the hot-atom's nature and of the structural and chemical environment are discussed. 相似文献
35.
Lifetimes of high spin states up to {
}=22+ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in 72, 74Se. The Q
t values derived from these measurements indicate that prolate shape stabilizes for 72Se, while a triaxial shape develops for 74Se at higher spins. Comparison of the observed trend in Q
t with spin for 72, 74Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency. 相似文献
36.
37.
Bellido E Cardona-Serra S Coronado E Ruiz-Molina D 《Chemical communications (Cambridge, England)》2011,47(18):5175-5177
Femptolitre droplets deposited on surfaces assisted by an AFM tip are used as reactor vessels to fabricate arrays of nanoarchitectures ranging from single-crystals of metal-organic frameworks to hollow capsules of magnetic polyoxometalates. 相似文献
38.
In this note, we deal with finding the shape of distributed piezoelectric modal sensors for circular plates with polar symmetric boundary conditions. The problem is treated by an optimization approach, where a binary function is used to model the design variable: the polarization profile of the piezoelectric layer. The numerical procedure proposed here allows us to find polarization profiles which take on two values only, i.e. either positive or negative polarization, that isolate particular vibration modes in the frequency domain. 相似文献
39.
Anne Bellido Jean-Pierre Dedieu Jean-Claude Yakoubsohn 《Annali dell'Universita di Ferrara》1991,37(1):65-83
Résumé Nous montrons que, en général, il existe au plus huit octaèdres différents dont les longueurs des arêtes sont données. Nous
donnons un exemple pour lequel ce nombre huit est atteint.
Logiciels de Calculus formels utilisés:Maple. CoCOA: Alessandro Giovini, Gianfranco Niesi, Department of Mathematics, University of Genova, viale Leon Battista Alberti 4, 16132 Genova, Italy. 相似文献
We prove that, in general, there are at the most eight distinct octahedrons with given edge-lengths. We also give an example for which this number is reached.
Logiciels de Calculus formels utilisés:Maple. CoCOA: Alessandro Giovini, Gianfranco Niesi, Department of Mathematics, University of Genova, viale Leon Battista Alberti 4, 16132 Genova, Italy. 相似文献
40.
The group theory for nonrigid molecules is used for studying the internal dynamics of the two equivalent C3v rotor “bent” molecules. Special emphasis is given to the deduction of the symmetry basis vectors which represent in box form the Hamiltonian operator. It is shown that these basis vectors may be advantageously employed in order to simplify the resolution of the two-rotor equation. The procedure is applied to the acetone molecule. It is found that the lowest solutions are clustered into groups of four. The four lowest levels are related to vibrational states, the upper 64 to vibro–rotational states, in which the rotors are rotating in a restricted manner. Only few states show some cogwheel effect. Internal rotation contributions to the principal thermodynamic parameters of acetone are also computed. 相似文献