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排序方式: 共有246条查询结果,搜索用时 15 毫秒
81.
82.
M. Holder J. Knobloch J. May H.P. Paar P. Palazzi D. Schlatter J. Steinberger H. Suter H. Wahl E.G.H. Williams F. Eisele C. Geweniger K. Kleinknecht G. Spahn H.-J. Willutzki W. Dorth F. Dydak V. Hepp F.L. Navarria 《Physics letters. [Part B]》1977,69(3):377-384
On the basis of 315 dimuon events of opposite sign for which the nature (and energy) of the incident neutrino is known, and the momenta and hadronic shower energy are measured, we find a) very similar production by neutrinos and antineutrinos, and therefore confirmation of the GIM model for semileptonic weak interactions, b) energy spectra, excitation functions, angular correlations and transverse momentum distributions which are in remarkable agreement with the hypothesis of charm production and decay, c) evidence against models for which the second muon has a heavy lepton as origin, d) evidence against “bottom” quark production by antineutrinos, e) the amount and the structure function for the strange quark-antiquark sea, and f) an approximate branching ratio, of 0.15 for the muonic decay of the semistable charmed meson. 相似文献
83.
Nanocomposites of lead sulfide and several polymers, especially poly(ethyleneoxide), were prepared by coprecipitation of lead sulfide and polymer, followed by a drying and pressing procedure. Such nanocomposites consist of ca. 90% w/w (or ca. 50% v/v) lead sulfide, of particle dimensions of 2–40 nm. The refractive index of these materials is on the order of 3 and therefore, to the authors' best knowledge, is the highest reported for any polymer composite. 相似文献
84.
85.
Thyveetil MA Coveney PV Greenwell HC Suter JL 《Journal of the American Chemical Society》2008,130(37):12485-12495
Layered double hydroxides (LDHs) have been shown to form staged intermediate structures in experimental studies of intercalation. However, the mechanism by which staged structures are produced remains undetermined. Using molecular dynamics simulations, we show that LDHs are flexible enough to deform around bulky intercalants such as deoxyribonucleic acid (DNA). The flexibility of layered materials has previously been shown to affect the pathway by which staging occurs. We explore three possible intermediate structures which may form during intercalation of DNA into Mg2Al LDHs and study how the models differ energetically. When DNA strands are stacked directly on top of each other, the LDH system has a higher potential energy than when they are stacked in a staggered or interstratified structure. It is generally thought that staged intercalation occurs through a Daumas-Herold or a Rudorff model. We find, on average, greater diffusion coefficients for DNA strands in a Daumas-Herold configuration compared to a Rudorff model and a stage-1 structure. Our simulations provide evidence for the presence of peristaltic modes of motion within Daumas-Herold configurations. This is confirmed by spectral analysis of the thickness variation of the basal spacing. Peristaltic modes are more prominent in the Daumas-Herold structure compared to the Rudorff and stage-1 structures and support a mechanism by means of which bulky intercalated molecules such as DNA rapidly diffuse within an LDH interlayer. 相似文献
86.
Suter MJ 《Analytical and bioanalytical chemistry》2008,390(8):1957-1958
87.
88.
Geometric phases play a central role in a variety of quantum phenomena, especially in condensed matter physics. Recently, it was shown that this fundamental concept exhibits a connection to quantum phase transitions where the system undergoes a qualitative change in the ground state when a control parameter in its Hamiltonian is varied. Here we report the first experimental study using the geometric phase as a topological test of quantum transitions of the ground state in a Heisenberg XY spin model. Using NMR interferometry, we measure the geometric phase for different adiabatic circuits that do not pass through points of degeneracy. 相似文献
89.
Neumayer P Berger RL Divol L Froula DH London RA Macgowan BJ Meezan NB Ross JS Sorce C Suter LJ Glenzer SH 《Physical review letters》2008,100(10):105001
We demonstrate that multiple-ion-species plasmas greatly reduce stimulated Brillouin scattering (SBS) in high-electron temperature inertial confinement fusion hohlraums. Landau damping is increased by adding hydrogen to a CO(2) gas filled hohlraum. We find that the SBS reflectivity decreases monotonically with increasing hydrogen fraction from 18% to 3% with a simultaneous increase of laser beam transmission. Detailed simulations with a 3D laser-plasma interaction code are in agreement with the experimentally observed reduction in backscattered light. 相似文献
90.
M. Suter C. R. Vane S. B. Elston G. D. Alton P. M. Griffin R. S. Thoe L. Williams I. A. Sellin R. Laubert 《Zeitschrift für Physik A Hadrons and Nuclei》1979,289(4):433-434
In the ejected electron spectra from collisions of C2+, O4+ and Si10,11,12+ with argon toms at energies of 2–4 MeV/amu, a series of intense lines has been observed, which originates from doubly excited autoionizing states of Belike projectiles. These lines correspond to electron energies between 2 and 20 eV in the projectile frame. For kinematic reasons these lines can only be detected near the forward direction. 相似文献