排序方式: 共有49条查询结果,搜索用时 31 毫秒
21.
Microwave propagation in two-dimensional dielectric lattices 总被引:1,自引:0,他引:1
McCall SL Platzman PM Dalichaouch R Smith D Schultz S 《Physical review letters》1991,67(15):2017-2020
22.
We show that the rather peculiar behavior of position lifetimes in cold, dense helium vapor are not inconsistent with some very simple ideas regarding the localization of carriers in random systems. 相似文献
23.
24.
Alan Rigter Jan Priem Drophatie Timmers-Parohi Jan PM Langeveld Fred G van Zijderveld Alex Bossers 《BMC biochemistry》2009,10(1):29-16
Background
Molecular mechanisms underlying prion agent replication, converting host-encoded cellular prion protein (PrPC) into the scrapie associated isoform (PrPSc), are poorly understood. Selective self-interaction between PrP molecules forms a basis underlying the observed differences of the PrPC into PrPSc conversion process (agent replication). The importance of previously peptide-scanning mapped ovine PrP self-interaction domains on this conversion was investigated by studying the ability of six of these ovine PrP based peptides to modulate two processes; PrP self-interaction and conversion. 相似文献25.
26.
Reiter G Burnham C Homouz D Platzman PM Mayers J Abdul-Redah T Moravsky AP Li JC Loong CK Kolesnikov AI 《Physical review letters》2006,97(24):247801
The momentum distribution of the protons in ice Ih, ice VI, high density amorphous ice, and water in carbon nanotubes has been measured using deep inelastic neutron scattering. We find that at 5 K the kinetic energy of the protons is 35 meV less than that in ice Ih at the same temperature, and the high momentum tail of the distribution, characteristic of the molecular covalent bond, is not present. We observe a phase transition between 230 and 268 K to a phase that does resemble ice Ih. Although there is yet no model for water that explains the low temperature momentum distribution, our data reveal that the protons in the hydrogen bonds are coherently delocalized and that the low temperature phase is a qualitatively new phase of ice. 相似文献
27.
28.
Neutron Compton scattering measurements presented here of the momentum distribution of hydrogen in KH2PO4 just above and well below the ferroelectric transition temperature are sufficiently sensitive to show clearly that the proton is coherent over both sites in the high temperature phase, a result that invalidates the commonly accepted order-disorder picture of the transition. The Born-Oppenheimer potential for the hydrogen, extracted directly from data for the first time, is consistent with neutron dif-fraction data, and the vibrational spectrum is in substantial agreement with infrared absorption measurements. The measurements are sensitive enough to detect the effect of surrounding ligands on the hydrogen bond, and can be used to study the systematic effect of the variation of these ligands in other hydrogen bonded systems. 相似文献
29.
We report high-resolution inelastic x-ray scattering measurements in the metallic liquid Li(NH3)4, which to a good approximation can be treated as a dilute alkali metal. We see a well-defined excitation out to large momentum transfers. This excitation shows a strong softening at wave vectors near the first peak in the structure factor, which occurs near twice the Fermi momentum. 相似文献
30.
We consider the effect of electron correlations on tunneling from a 2D electron layer in a magnetic field parallel to the layer. A tunneling electron can exchange its momentum with other electrons, which leads to an exponential increase of the tunneling rate compared to the single-electron approximation. The effect depends on the interrelation between the dynamics of tunneling and momentum exchange. The results explain and provide a no-parameter fit to the data on electrons on helium. We also discuss tunneling in semiconductor heterostructures. 相似文献