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排序方式: 共有105条查询结果,搜索用时 9 毫秒
1.
U. Wannagat K. -P. Giesen H. -H. Falius 《Monatshefte für Chemie / Chemical Monthly》1973,104(5):1444-1452
Compounds I-X of the sixmembered ring system PSi2N2O with phosphorus in different oxidation and bond numbers, collected in Schema 1, have been prepared for the first time and confirmed in their structure by elemental analysis as well as by infrared and1H- and31P-spectroscopy.
Mit Auszügen aus der DissertationK. P. Giesen, Techn. Univ. Braunschweig 1972. 相似文献
Mit Auszügen aus der DissertationK. P. Giesen, Techn. Univ. Braunschweig 1972. 相似文献
2.
3.
Mostafa Mesgar Dr. Payam Kaghazchi Prof. Dr. Timo Jacob Dr. Ernesto Pichardo‐Pedrero Dr. Margret Giesen Dr. Ernesto Pichardo‐Pedrero Dr. Margret Giesen Prof. Dr. Harald Ibach Dr. Noelia B. Luque Prof. Dr. Wolfgang Schmickler 《Chemphyschem》2013,14(1):233-236
Motivated by experimental studies of two‐dimensional Ostwald ripening on Au(100) electrodes in chlorine‐containing electrolytes, we have studied diffusion processes using density functional theory. We find that chlorine has a propensity to temporary form AuCl complexes, which diffuse significantly faster than gold adatoms. With and without chlorine, the lowest activation energy is found for the exchange mechanism. Chlorine furthermore reduces the activation energy for the detachment from kink sites. Kinetic Monte Carlo simulations were performed on the basis of extensive density functional theory calculations. The island‐decay rate obtained from these Monte Carlo simulations, as well as the decay rate obtained from the theoretical activation energies and frequency factors when inserted into analytical solutions for Ostwald ripening, are in agreement with experimental island‐decay rates in chlorine‐containing electrolytes. 相似文献
4.
Gregor Giesen Peter M. Topping 《Calculus of Variations and Partial Differential Equations》2010,38(3-4):357-367
We show uniqueness of Ricci flows starting at a surface of uniformly negative curvature, with the assumption that the flows become complete instantaneously. Together with the more general existence result proved in [10], this settles the issue of well-posedness in this class. 相似文献
5.
240-fs pulses with 22-W average power from a mode-locked thin-disk Yb:KY(WO(4))(2) laser 总被引:3,自引:0,他引:3
Brunner F Südmeyer T Innerhofer E Morier-Genoud F Paschotta R Kisel VE Shcherbitsky VG Kuleshov NV Gao J Contag K Giesen A Keller U 《Optics letters》2002,27(13):1162-1164
We demonstrate what is to our knowledge the first passively mode-locked thin-disk Yb:KY(WO(4))(2) laser. The laser produces pulses of 240-fs duration with an average power of 22 W at a center wavelength of 1028 nm. At a pulse repetition rate of 25 MHz, the pulse energy is 0.9microJ , and the peak power is as high as 3.3 MW. The beam quality is very close to the diffraction limit, with M(2)=1.1 . 相似文献
6.
B.?Giesen H.?Wiggers A.?Kowalik P.?RothEmail author 《Journal of nanoparticle research》2005,7(1):29-41
The formation and growth of silicon-nanoparticles from silane in a microwave reactor was investigated. Experiments were performed for the following conditions: precursor concentration 380–2530 ppm, pressures of 20–30 mbar, microwave powers 120–300 W. The formed particles were examined in-situ with a particle mass spectrometer. Additionally, particles were collected on grids and analyzed by transmission electron microscopy, X-ray diffraction, and by determining the specific surface area by BET. The particle size was found to be in the range of 5–8 nm in diameter. A simple model was used to simulate the particle formation processes taking place inside the reactor. The microwave energy coupled into the reactor flow was treated as a spatially distributed energy source resulting in a local temperature increase. The particles were assumed to have a monodisperse size distribution. To allow an approximation of their shape they were characterized by their volume and surface area. The model takes nucleation, convection, coagulation, and coalescence into account. The fluid flow inside the microwave reactor was simulated with the commercial CFD-code Fluent. 相似文献
7.
M.H.?NiemzEmail author A.?Kasenbacher M.?Strassl A.?B?cker A.?Beyertt D.?Nickel A.?Giesen 《Applied physics. B, Lasers and optics》2004,79(3):269-271
Caries – the most frequent cause for dental surgery – still is mainly treated with conventional mechanical drills, although lasers have meanwhile been successfully applied to various clinical disciplines. Since ultrashort laser pulses with sufficient pulse energies have only been available at low repetition rates (< 1 kHz) in recent decades, solely continuous wave radiation or pulse durations longer than thermal diffusion processes were applied with the result of severe thermal damage and pain. In this report we present results on dental tissue ablation obtained with a novel thin disk Yb:KYW regenerative amplifier system that does not require chirped pulse amplification (CPA). We show that femtosecond laser pulses provide us with todays optimal tool to treat dental decay in an acceptable time, in an excellent quality, and with unsurpassed caries selectivity. The superior quality is a result of the non-thermal laser-tooth interaction. All our results are based on environmental scanning electron microscopy. PACS 42.62.–b; 06.60.Jn; 82.80.–d 相似文献
8.
Trinczek M Gorelov A Melconian D Alford WP Asgeirsson D Ashery D Behr JA Bricault PG D'Auria JM Deutsch J Dilling J Dombsky M Dubé P Eaton S Fingler J Giesen U Gu S Häusser O Jackson KP Lee B Schmid JH Stocki TJ Swanson TB Wong W 《Physical review letters》2003,90(1):012501
A new technique, full neutrino momentum reconstruction, is used to set limits on the admixture of heavy neutrinos into the electron neutrino. We measure coincidences between nuclear recoils and positrons from the beta decay of trapped radioactive atoms and deduce the neutrino momentum. A search for peaks in the reconstructed recoil time-of-flight spectrum as a function of positron energy is performed. The admixture upper limits range from 4 x 10(-3) to 2 x 10(-2) and are the best direct limits for neutrinos (as opposed to antineutrinos) for the mass region of 0.7 to 3.5 MeV. 相似文献
9.
A.V. Potapov L.A. Surin S. Schlemmer T.F. Giesen 《Journal of Molecular Spectroscopy》2011,270(2):116-119
The pure rotational spectrum of the Ne–CO van der Waals complex has been measured in the frequency range of 208–230 GHz by using the Cologne supersonic jet spectrometer for terahertz applications (SuJeSTA). Eleven new transitions were assigned as belonging to two R- and two Q-branches of the K = 2–1 subband detected for the first time in the ground vibrational state of CO (νCO = 0). Improved molecular parameters of the Ne–CO complex were obtained which allowed for a sensitive test of the available intermolecular potential energy surfaces of the Ne–CO system. 相似文献
10.
J. Giesen 《Discrete and Computational Geometry》2000,24(4):577-603
We give necessary and sufficient regularity conditions under which the curve reconstruction problem is solved by a traveling
salesman tour or path, respectively. For the proof we have to generalize a theorem of Menger [12], [13] on arc length.
Received May 17, 1999, and in revised form February 22, 2000. {\it Online publication August\/} 11, 2000. 相似文献