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81.
Bartholomy O Credé V van Pee H Anisovich AV Anton G Bantes R Beloglazov Y Bogendörfer R Castelijns R Ehmanns A Ernst J Fabry I Flemming H Fösel A Freiesleben H Fuchs M Funke Ch Gothe R Gridnev A Gutz E Höffgen SK Horn I Hössl J Joosten R Junkersfeld J Kalinowsky H Klein F Klempt E Koch H Konrad M Kopf B Krusche B Langheinrich J Löhner H Lopatin I Lotz J Matthäy H Menze D Messchendorp J Morales C Novinski D Ostrick M Radkov A Reinnarth J Sarantsev AV Schadmand S Schmidt Ch Schmieden H Schoch B 《Physical review letters》2005,94(1):012003
Single pi(0) photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of approximately 98% of 4pi. Differential cross sections dsigma/dOmega have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gammap-->N(*)(Delta(*))-->ppi(0). A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15. 相似文献
82.
Kaon in-medium masses and mean-field potentials are calculated in isotopically symmetric pion matter to one loop of chiral perturbation theory. The results are extended to BNL RHIC temperatures using experimental data on piK scattering phase shifts. The kaon in-medium broadening results in an acceleration of the phi-->K(-)K decay. The increased apparent dilepton branching of the phi mesons, observed recently by the NA50, NA49, and PHENIX Collaborations at RHIC, is interpreted in terms of rescattering of secondary kaons inside the pion matter. 相似文献
83.
K.?KeutelEmail author H.?Fuchs C.?Edelmann 《Applied Physics A: Materials Science & Processing》2004,78(5):687-690
Originally, modified pulsed arc discharge was used for reactive coatings, for example for the deposition of nitrides on different substrate materials. Scientific studies of this process have shown that the droplet emission, in comparison to the direct current (DC) random arc process, is strongly reduced by the operation of a pulsed arc. Recently, the influence of the process parameters on the properties of the thin films produced was investigated. The interesting film properties from our work are the layer structure, the surface roughness and the microhardness. Electrical arc parameters, for example pulse current and pulse frequency, bias voltage and deposition conditions, like pressure, influence the thin-film properties in different ways. The dependence of the layer properties on the different operating parameters of the coating process are demonstrated and discussed. Furthermore, the plasma was investigated by optical emission spectroscopy in respect to composition and ion charge. The results obtained are used to discuss the influence of the operation conditions of the modified pulsed arc process on the properties of the layers produced. PACS 81.15.Ef; 52.25.Jm; 68.47.De; 68.35.Ct 相似文献
84.
3,3,3-Trichloropropyl-1-triphenylphosphonium chloride is conveniently prepared from 2-chloroethanol, triphenylphosphine, and trichloroacetic acid. Deprotonation of this reagent generates 3,3,3-trichloropropyl-1-triphenylphosphorane, which reacts with aldehydes to give trichloromethylated (Z)-olefins, which are useful for the synthesis of (Z)-1,3-enynes, (Z,Z)-1-chloro-1,3-dienes, and 1,3-diynes in high yields and stereospecificities. 相似文献
85.
Dynamic wave-front correction is applied before each shot on a 100-TW, 30-J/300-fs high-power laser facility by use of an adaptive-optics system. This system allows us to increase the repetition rate of high-energy lasers while maintaining excellent and constant beam focusability with a Strehl ratio of >0.75 despite the amplifiers' not being in thermal equilibrium. The best results in terms of the highest Strehl ratio and intensities are obtained when locking the system on wave-front sensing after pulse recompression. 相似文献
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Dimethyldioxirane (DMDO) C-H oxidation of ketone 17 to hemiketal 18 (82%), bis-dehydration to vinyl ether 21 (77%), and DMDO again provides C-23 axial alcohol 23 (99%). Routine processing, including a double-stereoselective Sharpless AD reaction (de >98%), gives alcohols 7 and 32. C-23 deoxy substrate 7 undergoes Suarez hypoiodite oxidative cyclization to (natural) beta spiroketal 34, but compound 32, bearing a C-23 silyl ether, generates unnatural spiroketal 33. [reaction: see text] 相似文献
89.
We present a calculation of the virtual Compton scattering amplitude for the pseudoscalar meson octet in the framework of chiral perturbation theory at O(p 4). We calculate the electromagnetic generalized polarizabilities and compare the results in the real Compton scattering limit to available experimental values. Finally, we give predctions for the differential cross section of electron-meson bremsstrahlung. 相似文献
90.
Dynamic force spectroscopy of conservative and dissipative forces in an Al-Au(111) tip-sample system
The conservative and dissipative interaction between an aluminum tip and a gold (111) surface were investigated using dynamic force spectroscopy in UHV. Complete force vs distance curves and friction coefficient vs distance curves were obtained quantitatively. The force curves were compared to the model by Muller, Yushenko, and Derjaguin, and long and short range interactions were subsequently quantified without fit parameters. A short range conservative interaction was separated from longer range van der Waals forces. The long range behavior of the damping coefficient obeys an inverse power law of third order. 相似文献