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排序方式: 共有456条查询结果,搜索用时 62 毫秒
51.
J.G.H. de Groot T. Hansl M. Holder J. Knobloch J. May P. Palazzi A. Para F. Ranjard A. Savoy-Navarro D. Schlatter J. Steinberger W. von Rüden H. Wahl F. Eisele K. Kleinknecht H. Lierl H.J. Willutzki F. Dydak F.L. Navarria 《Physics letters. [Part B]》1979,86(1):103-107
290 events of the type νFe→μ?μ?X and 53 events from the reaction and muon momenta pμ>6.5GeV/c have been observed in the CDHS detector. After subtracting the background from charged-current processes with one π or K meson of the hadronic shower decaying into , we obtain for neutrinos a rate of prompt like- sign dimuon production of (3.4±1.8)×10?5 relative to the rate of charged-current events with the same cuts, or (4.1 ± 2.2)% relative to the prompt μ?μ+ rate, and for antineutrinos the corresponding relative rates (4.3±2.3)×10?5 and (4.2 ± 2.3)%. A possible explanation for the events is charm pair production at a level of 10?3 relative to all charged-current reactions. 相似文献
52.
J. de Groot 《Mathematische Annalen》1959,138(1):80-102
53.
J. H. de Groot A. J. Nijenhuis P. Bruin A. J. Pennings R. P. H. Veth J. Klompmaker H. W. B. Jansen 《Colloid and polymer science》1990,268(12):1073-1081
Porous biodegradable poly(urethanes) for reconstructing menisci have been prepared using two different combinations of techniques: freeze-drying/salt-leaching and in-situ polymerization/salt-leaching. Using these methods, homogenous porous materials with a controllable and reproducible morphology can be prepared. The materials were made of three different poly(urethanes): a methylenediphenyldiisocyanate-based polyurethane, a lysine diisocyanate-based poly(urethane), and a poly(-caprolactone)-based poly(urethane). The compressive stress-strain behavior of the Estane foams was determined. Foams made by the freeze-drying/salt-leaching technique implanted in dogs showed healing and good ingrowth of fibrocartilaginous tissue. 相似文献
54.
The intensities of the CH out-of-plane bending (v7) and CH stretch (v1) vibrations of ethylene adsorbed on Ag(l 10) precovered with oxygen have been measured in EELS as a function of beam energy from 2 to 20 eV. The energy dependence of the v7 vibration is satisfactorily described by the dipole approximation. For the v1 vibration, which is purely dipole forbidden, an entirely different energy dependence is found, with a maximum intensity at a beam energy of 2 eV. Comparison of the EEL intensities observed experimentally with those predicted from the dipole moments of the free molecule confirms the conclusion that the molecular plane of chemisorbed ethylene is parallel to the surface. 相似文献
55.
E. H. de Groot G. J. Gounaris D. Schildknecht 《Zeitschrift fur Physik C Particles and Fields》1980,5(2):127-146
We examine a class of gauge theories based on U(1)×SU(2)×G allowing for an arbitrary number of gauge bosons, while retaining the lowq 2 four fermion interaction of the standard model. Measurable consequences fore + e ?→μ + μ ? ande + e ?→e + e ? at presently available as well as LEP energies are presented. Implications of the recently determined QED cut-offΛ ? ? 100 GeV on gauge boson properties and the anomalous magnetic moment of the muon are pointed out. 相似文献
56.
From the week interaction and the relativistic generalization of the quantum transport equation the volume viscosity of a degenerate massive neutrino gas is derived as a function of the density and the neutrino mass. 相似文献
57.
Vankó G Neisius T Molnar G Renz F Karpati S Shukla A de Groot FM 《The journal of physical chemistry. B》2006,110(24):11647-11653
We report X-ray emission spectra of Fe(III), Fe(II), and Co(II) spin-crossover compounds in their high-spin and low-spin forms. It is shown that all X-ray emission features are sensitive to the spin state. Variations of the Kbeta and the Kalpha emission line shapes, which are in agreement with theory, can be used as quantitative probes of the spin state; it is suggested that with appropriate reference experiments one can extract the spin momentum for a general case. Resonant X-ray emission spectra unveil details of the redistribution of electrons on the 3d levels associated with the spin-state change by revealing features at the X-ray absorption preedge not accessible through standard absorption measurements. 相似文献
58.
Heersche HB de Groot Z Folk JA Kouwenhoven LP van der Zant HS Houck AA Labaziewicz J Chuang IL 《Physical review letters》2006,96(1):017205
We measure transport through gold grain quantum dots fabricated using electromigration, with magnetic impurities in the leads. A Kondo interaction is observed between dot and leads, but the presence of magnetic impurities results in a gate-dependent zero-bias conductance peak that is split due to a RKKY interaction between the spin of the dot and the static spins of the impurities. A magnetic field restores the single Kondo peak in the case of an antiferromagnetic RKKY interaction. This system provides a new platform to study Kondo and RKKY interactions in metals at the level of a single spin. 相似文献
59.
Beale AM Grandjean D Kornatowski J Glatzel P de Groot FM Weckhuysen BM 《The journal of physical chemistry. B》2006,110(2):716-722
A CrAPO-5 molecular sieve has been investigated with X-ray absorption spectroscopy (EXAFS-XANES) as dehydrated material and after loading with water and ammonia to unravel the coordination geometries of Cr3+ in the framework of a microporous crystalline aluminophosphate, more particularly of the AFI-type. A comparison of the XANES data, a preedge analysis with crystal field multiplet calculations and EXAFS data, pointed toward the presence of framework Cr3+ which, on dehydration, takes on a distorted tetrahedral coordination state. Due to the 3d3 configuration of Cr3+, this unusual tetrahedral coordination environment strongly tends to transform into the more stable 6-fold coordination geometry by binding two extraframework water molecules during hydration. In the presence of ammonia, tetrahedral Cr3+ readily transforms into a 5-fold coordination geometry by binding one ammonia molecule. Therefore, depending on the environmental conditions, the Cr3+ ions can occur in a 4-, 5-, or 6-fold coordination. This observation underlines the flexibility of transition metal ions, such as Cr3+, to cope with unusual coordination geometries in inorganic hosts, making them interesting as potential active sites in heterogeneous catalysis. 相似文献
60.
Safonova OV Tromp M van Bokhoven JA de Groot FM Evans J Glatzel P 《The journal of physical chemistry. B》2006,110(33):16162-16164
High-energy-resolution fluorescence detection (HERFD) X-ray spectroscopy is presented as a new tool for the identification of the bonding sites of reactants in supported metal catalysts. The type of adsorption site of CO on an alumina-supported platinum catalyst and the orbitals involved in the bonding are identified. Because X-ray absorption spectroscopy (XAS) is element-specific and can be used under high pressures and temperatures, in situ HERFD XAS can be applied to a swathe of catalytic systems, including alloys. 相似文献