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961.
We describe a new class of nanoscale structured metals wherein the effects of quantum confinement are combined with dispersive metallic electronic states to induce modifications to the fundamental low-energy microscopic properties of a three-dimensional metal: the density of states, the distribution of Fermi velocities, and the collective electronic response. 相似文献
962.
We study the observability for a lepton flavor-changing decay of a Higgs boson h--> mutau at Hadron colliders. Flavor-changing couplings of a Higgs boson exist at tree level in models with multiple Higgs doublets. The hmutau coupling is particularly motivated by the favorable interpretation of nu(mu)-nu(tau) oscillation. We find that at the Tevatron run II the unique mutau signature could serve as the Higgs discovery channel, surpassing expectations for Higgs boson searches in the SM and in a large parameter region of the MSSM. The sensitivity will be greatly improved at the LHC, beyond the coverage at a muon collider Higgs factory. 相似文献
963.
Han SI Marseille O Gehlen C Blümich B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,152(1):87-94
Pipe flow of blood in tubes of 1 and 7 mm inner diameter, respectively, was investigated employing two-dimensional NMR velocity imaging and PFG propagator measurements at different Reynolds numbers between 10 and 3500. The results are compared to flow of a water/glycerol mixture of matching viscosity under identical conditions. The transition from laminar to turbulent flow is observed by both a flattening of the velocity profile and a change of the propagator shape. For blood flow this transition is found to be shifted toward higher Reynolds numbers as compared to the transition of the water/glycerol mixture. This observation is in agreement with predictions from hydraulic measurements and is a consequence of the non-Newtonian flow characteristics of blood as a suspension of erythrocytes and plasma. Likewise, a deviation from the laminar flow condition is observed for blood at low Reynolds numbers between 10 and 100. This phenomenon is unknown for Newtonian liquids and is explained by the onset of a geometrical arrangement of the erythrocytes, the so-called rouleaux effect. 相似文献
964.
促性腺激素诱导休情期母貂发情的结果表明,激素处理后,母貂均表现出不同程度的发情征状外阴肿胀、卵巢和子宫增重、血液雌二醇和孕酮水平升高;发情高潮时,卵巢和子宫质量达最大值,孕酮水平上升,雌二醇水平下降,这是母貂发情旺期的特征.对各组激素作用的比较,确认HCG是诱导休情期母貂发情的最佳激素. 相似文献
965.
We present time-domain transmission imaging of an opaque structure in pork-fat tissue obtained with a terahertz (THz) field sampling technique. Compared with imaging with near-infrared pulses, the terahertz sampling technique shows significantly enhanced contrast, as a result of low scattering. For enhanced spatial resolution, we show mid-infrared THz imaging of onion cells. Water absorption of THz pulse in muscle tissues is discussed. 相似文献
966.
Use of the organic crystal DAST for terahertz beam applications 总被引:2,自引:0,他引:2
We report the use of the organic crystal DAST as a freely propagating electromagnetic-wave sensor at terahertz (THz) frequency. We also report the result of using a DAST crystal as a mid-IR THz emitter. Compared with the optical rectification from our best ZnTe emitter, that obtained by use of DAST demonstrates a sixfold enhancement of radiation at 7-20 THz. 相似文献
967.
Han S Gemmell SJ Helmer KG Grigg P Wellen JW Hoffman AH Sotak CH 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,144(2):217-227
Water diffusion measurements were performed on rabbit Achilles tendons during static tensile loading and tendons in an unloaded state. The apparent diffusion coefficient (ADC) was measured along two directions: parallel and perpendicular to the long axis of the tendon. Tendons were studied after being prepared in two ways: (a) after being stored frozen in phosphate-buffered saline (PBS) and (b) freshly isolated. Statistically significant directional anisotropy was observed in the ADC in all tendons. The ADC was significantly greater in the direction parallel to the long axis of the tendon than in the perpendicular direction. The anisotropy is attributed to the greater restrictions seen by the water molecules in the perpendicular direction and is consistent with the known geometry of the tendon. Storage in PBS caused tendons to swell. This increased the ADC measured along both directions and reduced the anisotropy. The existence of anisotropy in the ADC was not related to the orientation of the specimen in the magnet. The ADC increased along both directions following the application of a 5-N tensile load; the increase was greatest along the perpendicular axis of the tendon. In order to determine whether load-related changes in the ADC reflected changes in interfibrilar spacing, we used electron microscopy to measure load-related changes in fibril spacing. Load-related changes in fiber spacing could not account for the observed changes in the ADC. The increase in ADC caused by loading was attributed to the extrusion of tendon water into a bulk phase along the outside surface of the tendon. In PBS-stored samples, enough fluid was extruded that it could be visualized. The transient response of the ADC to a 5-N tensile load was also studied. The absolute ADC in both directions increased with loading and recovered to baseline upon unloading. The transient changes in ADC, for both loading and unloading, had a mean time constant of approximately 15 min. The magnitude of the load-induced transient ADC changes was comparable to that seen in the static-loading experiments. 相似文献
968.
969.
970.