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81.
Chéty-Gimondo R Aubriet F Millon E Muller JF 《Rapid communications in mass spectrometry : RCM》2004,18(23):2939-2945
The ions generated by laser ablation (LA) of calcium and gadolinium oxoborate GdCa4O(BO3)3 (GdCOB) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS), a powerful tool for the characterization of ionic species produced by laser interaction with solid material. In order to better understand the matter transfer and the mechanism of thin film growth by pulsed-laser deposition (PLD), cationic and anionic clusters generated by UV laser ablation of GdCOB bulk material were studied. Laser ablation of GdCOB leads to the formation of various cluster ions which result from association of CaO, BO and B2O3 building blocks (BB) with different charge carriers (CC): H+, BO+, GdO+ in positive ion mode, and BO2-, OK-, OH-, Cl-, WO3- in negative ion mode. LA-FTICRMS investigations allow us to assign a valence state to each metallic atom included in each BB. A +II chemical state may be associated with calcium and +II and +III ones to boron. UV laser ablation of GdCOB therefore induces reduction processes of boron species in the gas phase. The oxygen reactive atmosphere used during PLD experiments allows the growth of stoichiometric thin films by fixation of oxygen on the ablated species. 相似文献
82.
K. A. Aniol M. B. Epstein E. Gama D. J. Margaziotis W. Bertozzi J. P. Chen D. Dale R. E. J. Florizone S. Gilad A. J. Sarty J. A. Templon S. P. Van Verst J. Zhao Z. -L. Zhou P. Bartsch W. U. Boeglin R. Boehm M. O. Distler I. Ewald J. M. Friedrich J. M. Friedrich R. Geiges P. Jennewein M. Kahrau K. W. Krygier A. Liesenfeld H. Merkel K. Merle U. Muller R. Neuhausen E. A. J. M. Offermann Th. Pospischil G. Rosner H. Schmieden A. Wagner Th. Walcher M. Kuss A. Richter G. Schrieder K. Bohinc M. Potokar S. Širca J. M. Udias Javier R. Vignote R. Schiavilla 《The European Physical Journal A - Hadrons and Nuclei》2004,22(3):449-454
We have measured the 4He(e, ep)3H reaction at missing momenta of 130-300 MeV/c using the three-spectrometer facility at the Mainz microtron MAMI. Data were taken in perpendicular kinematics to allow us to determine the response function RLT and the asymmetry term ATL. The data are compared to both relativistic and non-relativistic calculations. 相似文献
83.
Oxidation of single- or double-stranded DNA containing a 7,8-dihydro-8-oxoguanosine lesion with the one-electron oxidant Na2IrCl6 in the presence of spermine led to formation of a covalent adduct that was analyzed by gel electrophoresis, HPLC, ESI-MS, and UV-vis. The adduct was labile to heat, exhibiting a t1/2 of 12 h at 37 degrees C, and the ultimate hydrolysis product was characterized as a deoxyribosylurea lesion. Data from model studies with 1,3-diaminopropane vs 1,4-diaminobutane are consistent with initial formation of a C5 spermine adduct from a dehydro-8-oxoguanosine intermediate, followed by rearrangement to a spiroaminal subject to slow hydrolysis at C4 of the purine. Spermine adducts could also be formed from oxidation of the analogous G-containing oligomer from reaction with singlet oxygen, albeit in lower yield. These results are surprising in light of the traditional view that spermine is radioprotective against DNA oxidation. 相似文献
84.
Dinu LC Muller HG Kazamias S Mullot G Augé F Balcou P Paul PM Kovacev M Breger P Agostini P 《Physical review letters》2003,91(6):063901
The absolute timing of the high-harmonic attosecond pulse train with respect to the generating IR pump cycle has been measured for the first time. The attosecond pulses occur 190+/-20 as after each pump field maxima (twice per optical cycle), in agreement with the "short" quantum path of the quasiclassical model of harmonic generation. 相似文献
85.
Voyles PM Chadi DJ Citrin PH Muller DA Grazul JL Northrup PA Gossmann HJ 《Physical review letters》2003,91(12):125505
Electron channeling experiments performed on individually scanned, single columns of atoms show that in highly n-type Si grown at low temperatures the primary electrically deactivating defect cannot belong to either the widely accepted class of donor-vacancy clusters or a recently proposed class of donor pairs. First-principles calculations suggest a new class of defects consisting of two dopant donor atoms near a displaced Si atom, which forms a vacancy-interstitial pair. These complexes are consistent with the present experimental results, the measured open volume of the defects, the observed electrical activity as a function of dopant concentration, and the enhanced diffusion of impurities in the presence of deactivated dopants. 相似文献
86.
[reaction: see text] Further oxidation of the common DNA lesion 8-oxo-7,8-dihydroguanosine by one-electron oxidants such as IrCl6(2-), Fe(CN)6(3-), or SO4-* leads to two major products, depending upon reaction conditions. In nucleosides at pH 7, 22 degrees C, the principal product is shown herein to be a spiroiminodihydantoin nucleoside, as a diastereomeric mixture, that can be characterized by NMR, ESI-MS/MS, and independent synthesis. 相似文献
87.
88.
Fera A Dolbnya IP Grubel G Muller HG Ostrovskii BI Shalaginov AN de Jeu WH 《Physical review letters》2000,85(11):2316-2319
Coherent dynamic x-ray scattering has been used to study the thermally excited layer fluctuations in freely suspended smectic films of the compound 4O.8. Using 8-keV x rays and films with a thickness around 0.3 &mgr;m we resolve relaxation times down to a few &mgr;s. A combination of damped and oscillatory behavior is observed for the layer undulations, which can be attributed to inertial effects. These are due to the surface contribution to the free energy which cannot be disregarded for thin films. 相似文献
89.
A classical and quantum mechanical generalized second law of thermodynamics in cosmology implies constraints on the effective equation of state of the universe in the form of energy conditions, obeyed by many known cosmological solutions, forbids certain cosmological singularities, and is compatible with entropy bounds. This second law is based on the conjecture that causal boundaries and not only event horizons have geometric entropies proportional to their area. In string cosmology the second law provides new information about nonsingular solutions. 相似文献
90.
The effects of viscous heating on the stability of Taylor-Couette flow were investigated through flow visualization experiments for Newtonian and viscoelastic fluids. For highly viscous Newtonian fluids, viscous heating drives a transition to a new, oscillatory mode of instability at a critical Reynolds number significantly below that at which the inertial transition is observed in isothermal flows. The effects of viscous heating may explain the discrepancies between the observed and predicted critical conditions and the symmetry of the disturbance flow for viscoelastic instabilities. 相似文献