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21.
Clauwaert KM Van Bocxlaer JF Major HJ Claereboudt JA Lambert WE 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
22.
U. Kleineberg G. Haindl A. Hütten G. Reiss E.M. Gullikson M.S. Jones S. Mrowka S.B. Rekawa J.H. Underwood 《Applied Physics A: Materials Science & Processing》2001,73(4):515-519
The local surface oxidation of the permalloy surface layer in Py/Cu GMR multilayers on a micron lateral scale has been analyzed
by means of a microspot-X-ray absorption spectromicroscope utilizing synchrotron radiation from the Advanced Light Source
bending magnet beamline 6.3.2. Additionally, the GMR multilayer samples prepared by dc magnetron sputtering have been analyzed
by cross-sectional transmission electron microscopy, hard X-ray reflection and magnetoresistance measurements. The formation
of a passivating iron-oxide layer on the sample surface was identified by X-ray absorption near edge structure spectroscopy
(XANES) near the Fe-2p edge while no indication for nickel-oxide formation could be found. Small micron-size pits of reduced
iron-oxide concentration could be identified by XANES microscopy while the corresponding nickel distribution appeared to be
homogeneous. The results are explained in terms of a local breakdown of the passivating oxide layer.
Received:16 October 2000 / Accepted: 4 December 2000 / Published online: 21 March 2001 相似文献
23.
Hau-Riege SP Chapman HN Krzywinski J Sobierajski R Bajt S London RA Bergh M Caleman C Nietubyc R Juha L Kuba J Spiller E Baker S Bionta R Sokolowski Tinten K Stojanovic N Kjornrattanawanich B Gullikson E Plönjes E Toleikis S Tschentscher T 《Physical review letters》2007,98(14):145502
At the recently built FLASH x-ray free-electron laser, we studied the reflectivity of Si/C multilayers with fluxes up to 3 x 10(14) W/cm2. Even though the nanostructures were ultimately completely destroyed, we found that they maintained their integrity and reflectance characteristics during the 25-fs-long pulse, with no evidence for any structural changes over lengths greater than 3 A. This experiment demonstrates that with intense ultrafast pulses, structural damage does not occur during the pulse, giving credence to the concept of diffraction imaging of single macromolecules. 相似文献
24.
Kaiser AM Gray AX Conti G Son J Greer A Perona A Rattanachata A Saw AY Bostwick A Yang S Yang SH Gullikson EM Kortright JB Stemmer S Fadley CS 《Physical review letters》2011,107(11):116402
Standing-wave-excited photoemission is used to study a SrTiO3/LaNiO3 superlattice. Rocking curves of core-level and valence band spectra are used to derive layer-resolved spectral functions, revealing a suppression of electronic states near the Fermi level in the multilayer as compared to bulk LaNiO3. Further analysis shows that the suppression of these states is not homogeneously distributed over the LaNiO3 layers but is more pronounced near the interfaces. Possible origins of this effect and its relationship to a previously observed metal-insulator-transition in ultrathin LaNiO3 films are discussed. 相似文献
25.
Natsume Y Kohno T Minakata T Konishi T Gullikson EM Muramatsu Y 《The journal of physical chemistry. A》2012,116(6):1527-1531
The chemical states of organic semiconductors were investigated by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS) and first-principles calculations. The organic semiconductors, pentacene (C(22)H(14)) and pentacenequinone (C(22)H(12)O(2)), were subjected to TEY-XAS and the experimental spectra obtained were compared with the 1s core-level excited spectra of C and O atoms, calculated by a first-principles planewave pseudopotential method. Excellent agreement between the measured and the calculated spectra were obtained for both materials. Using this methodology, we examined the chemical states of the aged pentacene, and confirmed that both C-OH and C═O chemical bonds are generated by exposure to air. This result implies that not only oxygen but also humidity causes pentacene oxidation. 相似文献