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11.
12.
Simic-Milosevic V Mehlhorn M Rieder KH Meyer J Morgenstern K 《Physical review letters》2007,98(11):116102
A scanning tunneling microscope operating at 5 K is used to induce the isomerization of single chloronitrobenzene molecules on Cu(111) and verify the reaction. The threshold voltage of (227+/-7) mV for this reaction is explained based on electron-induced vibrational heating. We propose that the isomerization is initiated by simultaneous excitation of two vibrational molecular modes via inelastically tunneling electrons. This excitation results in a shift of the distribution probability of chlorine and hydrogen positions, which facilitates their mutual exchange. 相似文献
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K-H Wang 《The Journal of the Operational Research Society》1997,48(9):936-942
In this paper we deal with a single removable service station queueing system with Poisson arrivals and Erlang distribution service times. The service station can be turned on at arrival epochs or off at departure epochs. While the service station is working, it is subject to breakdowns according to a Poisson process. When the station breaks down, it requires repair at a repair facility, where the repair times follow the negative exponential distribution. Conditions for a stable queueing system, that is steady-state, are provided. The steady-state results are derived and it is shown that the probability that the service station is busy is equal to the traffic intensity. Following the construction of the total expected cost function per unit time, we determine the optimal operating policy at minimum cost. 相似文献
15.
Wave-number spectra of magnetic field fluctuations are directly determined in the terrestrial foreshock region (upstream of a quasiparallel collisionless shock wave) using four-point Cluster spacecraft measurements. The spectral curve is characterized by three ranges reminiscent of turbulence: energy injection, inertial, and dissipation range. The spectral index for the inertial range spectrum is close to Kolmogorov's slope, -5/3. On the other hand, the fluctuations are highly anisotropic and intermittent perpendicular to the mean magnetic field direction. These results suggest that the foreshock is in a weakly turbulent and intermittent state in which parallel propagating Alfvén waves interact with one another, resulting in the phase coherence or the intermittency. 相似文献
16.
Achterberg A Ackermann M Adams J Ahrens J Andeen K Atlee DW Bahcall JN Bai X Baret B Bartelt M Barwick SW Bay R Beattie K Becka T Becker JK Becker KH Berghaus P Berley D Bernardini E Bertrand D Besson DZ Blaufuss E Boersma DJ Bohm C Bolmont J Böser S Botner O Bouchta A Braun J Burgess C Burgess T Castermans T Chirkin D Christy B Clem J Cowen DF D'Agostino MV Davour A Day CT De Clercq C Demirörs L Descamps F Desiati P Deyoung T Diaz-Velez JC Dreyer J Dumm JP Duvoort MR Edwards WR Ehrlich R 《Physical review letters》2006,97(22):221101
On 27 December 2004, a giant gamma flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: 0.05(0.5) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the gamma flux and 0.4(6.1) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the high-energy neutrino flux. 相似文献
17.
Müller KH 《The Journal of chemical physics》2008,129(4):044708
The room temperature thermoelectric properties of a three-dimensional array of molecular junctions are calculated. The array is composed of n-doped silicon nanoparticles where the surfaces are partially covered with polar molecules and the nanoparticles are bridged by trans-polyacetylene molecules. The role of the polar molecules is to reduce the band bending in the n-doped silicon nanoparticles and to shift the electronic resonances of the bridging molecules to the nanoparticle conduction band edges where the molecular resonances act as electron energy filters. The transmission coefficients of the bridging molecules that appear in the formulas for the Seebeck coefficient, the electrical conductance, and the electronic thermal conductance, are calculated using the nonequilibrium Green's function technique. A simple tight-binding Hamiltonian is used to describe the bridging molecules, and the self-energy term is calculated using the parabolic conduction band approximation. The dependencies of the thermoelectric properties of the molecular junctions on the silicon doping concentration and on the molecule-nanoparticle coupling are discussed. The maximal achievable thermoelectric figure of merit ZT of the array is estimated as a function of the phononic thermal conductance of the bridging molecules and the doping of the nanoparticles. The power factor of the array is also calculated. For sufficiently small phononic thermal conductances of the bridging molecules, very high ZT values are predicted. 相似文献
18.
J Benlliure S Steinhäuser C Böckstiegel A Grewe H-G Clerc A heinz M de Jong A R Junghans J Müller K-H Schmidt M Pfützner 《Pramana》1999,53(3):637-646
Nuclear fission from excitation energies around 11 MeV was studied at GSI, Darmstadt for 76 neutron-deficient actinides and
pre-actinides by use of relativistic secondary beams. The characteristics of multimodal fission of nuclei around 226Th are systematically investigated and related to the influence of shell effects on the potential-energy and on the level
density between saddle point and scission. A systematic view on the large number of elemental yields measured gave rise to
a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of
pair breaking in fission. 相似文献
19.
T. Döppner S. Teuber M. Schumacher J. Tiggesbäumker K.H. Meiwes-Broer 《Applied physics. B, Lasers and optics》2000,71(3):357-360
Clusters of heavy metal atoms in strong femtosecond laser-light fields undergo multi-ionization with the loss of hundreds
of electrons. The cross section largely exceeds that of corresponding isolated atoms, which leads in the case of PbN to a complete ionization of the 4f shell with a light intensity of 1.2×1015 W/cm2. Experimental investigations on Pb and Pt clusters with variable pulse widths and, for the first time, with the pump&probe
technique give insight into the dynamics of the coupling of electromagnetic radiation into the clusters. Both approaches support
the picture according to which, after an initial charging, the clusters expand due to Coulomb forces. This expansion is accompanied
by a reduction of the electron density and at the same time by an increase of the optical sensitivity. Once the plasmon energy
of the diluted nanoplasma approaches the photon energy, the charging efficiency increases significantly. The experimental
observations are confirmed by random-phase approximation (RPA) calculations of the optical response, including molecular-dynamics
simulations of the expanding systems.
Received: 11 November 1999 / Published online: 13 July 2000 相似文献
20.