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991.
992.
Felix Sedlmeier Yann von Hansen Liang Mengyu Dominik Horinek Roland R. Netz 《Journal of statistical physics》2011,145(2):240-252
The dynamics of single water molecules in bulk and at interfaces is studied by means of molecular dynamics simulations. We
use a recently developed stochastic method based on the Fokker-Planck equation to disentangle the contributions of the free
energy and diffusivity profiles on the local dynamics. The strong variations found in the diffusivity profiles are crucial
for accurately modeling the water kinetics. A comparison of hydrophobic and hydrophilic substrates and solutes yields significant
differences in the diffusivities, which can be attributed to the presence of hydrogen bonds. 相似文献
993.
The phase diagram of the superconducting high-T(c) cuprates is governed by two energy scales: T*, the temperature below which a gap is opened in the excitation spectrum, and T(c), the superconducting transition temperature. The way these two energy scales are reflected in the low-temperature energy gap is being intensively debated. Using Zn substitution and carefully controlled annealing we prepared a set of samples having the same T* but different T(c)'s, and measured their gap using angle-resolved photoemission spectroscopy (ARPES). We show that T(c) is not related to the gap shape or size, but it controls the size of the coherence peak at the gap edge. 相似文献
994.
Brugnera L Hoffmann DJ Siegel T Frank F Zaïr A Tisch JW Marangos JP 《Physical review letters》2011,107(15):153902
We demonstrate control of short and long quantum trajectories in high harmonic emission through the use of an orthogonally polarized two-color field. By controlling the relative phase ? between the two fields we show via classical and quantum calculations that we can steer the two-dimensional trajectories to return, or not, to the core and so control the relative strength of the short or long quantum trajectory contribution. In experiments, we demonstrate that this leads to robust control over the trajectory contributions using a drive field from a femtosecond laser composed of the fundamental ω at 800 nm (intensity ~1.2×10(14) W?cm(-2)) and its weaker orthogonally polarized second harmonic 2ω (intensity ~0.3×10(14) W?cm(-2)) with the relative phase between the ω and 2ω fields varied simply by tilting a fused silica plate. This is the first demonstration of short and long quantum trajectory control at the single-atom level. 相似文献
995.
We develop a scattering theory of current-induced forces exerted by the conduction electrons of a general mesoscopic conductor on slow "mechanical" degrees of freedom. Our theory describes the current-induced forces both in and out of equilibrium in terms of the scattering matrix of the phase-coherent conductor. Under general nonequilibrium conditions, the resulting mechanical Langevin dynamics is subject to both nonconservative and velocity-dependent Lorentz-like forces, in addition to (possibly negative) friction. We illustrate our results with a two-mode model inspired by hydrogen molecules in a break junction which exhibits limit-cycle dynamics of the mechanical modes. 相似文献
996.
Schottky-type grain boundaries in CCTO ceramics 总被引:1,自引:0,他引:1
In this work we studied electrical barriers existing at CaCu3Ti4O12 (CCTO) ceramics using dc electrical measurements. CCTO pellets were produced by solid state reaction method and X-ray diffractograms showed which single phase polycrystalline samples were obtained. The samples were electrically characterized by dc and ac measurements as a function of temperature, and semiconductor theory was applied to analyze the barrier at grain boundaries. The ac results showed the sample’s permittivity is almost constant (104) as function of temperature at low frequencies and it changes from 100 to 104 as the temperature increases at high frequencies. Using dc measurements as a function of temperature, the behavior of barriers was studied in detail. Comparison between Schottky and Poole-Frenkel models was performed, and results prove that CCTO barriers are more influenced by temperature than by electric field (Schottky barriers). Besides, the behavior of barrier width as function of temperature was also studied and experimental results confirm the theoretical assumptions. 相似文献
997.
Steffen Berger Sergiu P. Albu Felix Schmidt-Stein Helga Hildebrand Patrik Schmuki John S. Hammond Dennis F. Paul Stefan Reichlmaier 《Surface science》2011,605(19-20):L57-L60
High resolution Scanning Auger Electron Spectroscopy (AES) is used to demonstrate the compositional variation across self-organized TiO2 nanotube layers grown in fluoride containing ethylene glycol electrolytes. The analysis results show a distinct fluoride rich layer in between the TiO2 nanotubes and particularly in the triple points of the hexagonally ordered nanotubular arrays. AES analysis further revealed that extended e-beam exposure leads to a decrease in the fluoride signal (electron beam induced decomposition of fluoride species). The proof of the existence of a fluoride rich layer located between the tube walls strongly supports fluoride dissolution as the reason for a transition from a porous to a tubular morphology. 相似文献
998.
Galinski H Ryll T Schlagenhauf L Rechberger F Ying S Gauckler LJ Mornaghini FC Ries Y Spolenak R Döbeli M 《Physical review letters》2011,107(22):225503
The application of focused ion beam (FIB) nanotomography and Rutherford backscattering spectroscopy (RBS) to dealloyed platinum-aluminum thin films allows for an in-depth analysis of the dominating physical mechanisms of nanoporosity formation during the dealloying process. The porosity formation due to the dissolution of the less noble aluminum in the alloy is treated as result of a reaction-diffusion system. The RBS and FIB analysis yields that the porosity evolution has to be regarded as superposition of two independent processes, a linearly propagating diffusion front with a uniform speed and a slower dissolution process in regions which have already been passed by the diffusion front. The experimentally observed front evolution is captured by the Fisher-Kolmogorov-Petrovskii-Piskounov (FKPP). The slower dissolution is represented by a zero-order rate law which causes a gradual porosity in the thin film. 相似文献
999.
Recently evidence has emerged for enormous features in the γ-ray sky observed by the Fermi-LAT instrument: bilateral "bubbles" of emission centered on the core of the Galaxy and extending to around ± 10 kpc from the Galactic plane. These structures are coincident with a nonthermal microwave "haze" and an extended region of x-ray emission. The bubbles' γ-ray emission is characterized by a hard and relatively uniform spectrum, relatively uniform intensity, and an overall luminosity 4×10(37) erg/s, around 1 order of magnitude larger than their microwave luminosity while more than order of magnitude less than their x-ray luminosity. Here we show that the bubbles are naturally explained as due to a population of relic cosmic ray protons and heavier ions injected by processes associated with extremely long time scale (? 8 Gyr) and high areal density star formation in the Galactic center. 相似文献
1000.
Austin DR Witting T Arrell CA Frank F Wyatt AS Marangos JP Tisch JW Walmsley IA 《Optics letters》2011,36(10):1746-1748
We present a technique for frequency-resolved wavefront characterization of high harmonics based on lateral shearing interferometry. Tilted replicas of the driving laser pulse are produced by a Mach-Zehnder interferometer, producing separate focii in the target. The interference of the resulting harmonics on a flat-field extreme ultraviolet spectrometer yields the spatial phase derivative. A comprehensive set of spatial profiles, resolved by harmonic order, validate the technique and reveal the interplay of single-atom and macroscopic effects. 相似文献