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21.
Clement Levard F. Marc Michel Yingge Wang Yongseong Choi Peter Eng Gordon E. Brown Jr 《Journal of synchrotron radiation》2011,18(6):871-878
Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag‐Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag‐Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag+ from oxidation/dissolution of Ag‐Nps may strongly impact ecosystems. In this context, Ag‐Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl? in solution] has been investigated. A combination of synchrotron‐based X‐ray standing‐wave fluorescence yield‐ and X‐ray diffraction‐based experiments on a sample consisting of an approximately single‐particle layer of Ag‐Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag‐Nps–PAA interface were characterized with a high spatial resolution using this new approach. 相似文献
22.
M. A. Mironov P. A. Pyatakov I. I. Konopatskaya G. T. Clement N. I. Vykhodtseva 《Acoustical Physics》2009,55(4-5):567-574
One of the possible mechanisms that may underlie ultrasound-induced damage of soft solids is discussed. The model of three-wave interaction in a solid is used to consider shear wave generation by a longitudinal sound wave in a solid with a small shear modulus. Numerical estimates are obtained for the excitation threshold of the shear wave in biological tissues. Since the wavelength of ultrasound-generated shear waves is small, the shear stresses may be sufficient to destroy the structure of biological tissue. Results of model experiments are presented. 相似文献
23.
D. T. Khoa W. von Oertzen Amand Faessler
M. Ermer
H. Clement 《Physics letters. [Part B]》1991,260(3-4):278-284The real optical potential for 16O+16O system is calculated within a generalized version of the double-folding model with the Pauli knock-on exchange effects between the projectile nucleons and the target nucleons taken into account from first principle. The elastic scattering data at Elab=350 MeV supplemented by the new measurement at larger angles seem to be the first case in heavy-ion scattering where one can test the reliability of different theoretical heavy-ion optical potentials. Predictions are made for the elastic scattering of 16O+16O at laboratory energies of 240–480 MeV to illustrare the energy dependence of the rainbow structure which has been clearly observed in experiment at 350 MeV. 相似文献
24.
R.D. Felder T.M. Williams G.S. Mutchler I. Duck J. Hudomalj-Gabitzsch M. Furic D. Mann N.D. Gabitzsch J.M. Clement G.C. Phillips T.R. Witten E.V. Hungerford M. Warneke B.W. Mayes L.Y. Lee J.C. Allred 《Nuclear Physics A》1977,280(2):308-324
Neutron-proton final state interactions (FSI) were observed in the deuteron breakup reaction 2H(p, 2p)n-via a kinematically complete experiment at incident proton energies of 585 and 800 MeV. Kinematic conditions were chosen which allowed the final state proton and neutron to have small relative energies; data were taken at four proton c.m. scattering angles at 800 MeV, ranging from 71° to 119° and at 94° and 106° at 585 MeV. The data are analyzed in terms of the Goldberger-Watson formalism for final state interactions, and the individual contributions of the 1S0 and 3S1 np states are determined. The ratio is large, as expected from some reaction models. The ratio of 3S1 (almost elastic) to pd elastic cross sections is in good agreement with FSI analysis. 相似文献
25.
The photo reaction which contributes appreciably to the nuclear photo effect for photon energies between 16 and 35 MeV is studied in the framework of the unified theory of nuclear reactions based on cluster representations. 相似文献
26.
Enhanced ultrasound transmission through the human skull using shear mode conversion 总被引:2,自引:0,他引:2
Clement GT White PJ Hynynen K 《The Journal of the Acoustical Society of America》2004,115(3):1356-1364
A new transskull propagation technique, which deliberately induces a shear mode in the skull bone, is investigated. Incident waves beyond Snell's critical angle experience a mode conversion from an incident longitudinal wave into a shear wave in the bone layers and then back to a longitudinal wave in the brain. The skull's shear speed provides a better impedance match, less refraction, and less phase alteration than its longitudinal counterpart. Therefore, the idea of utilizing a shear wave for focusing ultrasound in the brain is examined. Demonstrations of the phenomena, and numerical predictions are first studied with plastic phantoms and then using an ex vivo human skull. It is shown that at a frequency of 0.74 MHz the transskull shear method produces an amplitude on the order of--and sometimes higher than--longitudinal propagation. Furthermore, since the shear wave experiences a reduced overall phase shift, this indicates that it is plausible for an existing noninvasive transskull focusing method [Clement, Phys. Med. Biol. 47(8), 1219-1236 (2002)] to be simplified and extended to a larger region in the brain. 相似文献
27.
Supershell structure in alkali metal nanowires 总被引:1,自引:0,他引:1
Nanowires are formed by indenting and subsequently retracting two pieces of sodium metal. Their cross section gradually reduces upon retraction and the diameters can be obtained from the conductance. In previous work we have demonstrated that when one constructs a histogram of diameters from large numbers of indentation-retraction cycles such histograms show a periodic pattern of stable nanowire diameters due to shell structure in the conductance modes. Here, we report the observation of a modulation of this periodic pattern, in agreement with predictions of a supershell structure. 相似文献
28.
Ulrich Girreser Ullvi Bluhm Bernd Clement Dieter Heber 《Magnetic resonance in chemistry : MRC》2013,51(11):714-721
The NMR spectroscopic data of a series of thirty‐four 3‐acylpyrido[1,2‐a]pyrimidinium salts are analyzed, which were prepared as either perchlorates or chlorides. Methyl group substituted 3‐aroyltetrahydropyrido[1,2‐a]pyrimidines with the methyl substituent in positions 6, 8 and 9 as well as both in positions 6 and 8 were investigated bearing various aroyl substituents. Unequivocal assignment of all resonances was achieved via two‐dimensional 1H,1H‐COSY measurements, 1H,13C and 1H,15N HSQC as well as HMBC experiments, and important diagnostic CH and NH couplings in the heteroaromatic ring system are evaluated. The influence of the methyl substituents was analyzed on the proton, carbon and nitrogen shifts. A significant effect of the counter ion on some chemical shifts of the nuclei under discussion of the pyridopyrimidines is found, allowing the indirect detection of the anion, which is confirmed by direct measurement of the 35Cl nucleus of the perchlorates. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
29.
30.
Jusang Park Han-Bo-Ram Lee Doyoung Kim Jaehong Yoon Clement Lansalot Julien Gatineau Henri Chevrel Hyungjun Kim 《Journal of Energy Chemistry》2013,22(3):403-407
Cobalt (Co) thermal or plasma enhanced atomic layer deposition (PE-ALD) was investigated using a novel metal organic precursor, Co(MeCp)2, and NH3 or H2 or their plasma as a reactant. The growth characteristics, electrical and microstructural properties were investigated. Especially, PE-ALD produced Co thin films at low growth temperature down to 100 °C. Interestingly, the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300 °C. The growth characteristics and films properties of PE-ALD Co using bis(η-methylcyclopentadienyl) Co(II) (Co(MeCp)2) was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt (II) (CoCp2) and cyclopentadienyl isopropyl acetamidinato-cobalt (Co(CpAMD)). 相似文献