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排序方式: 共有111条查询结果,搜索用时 31 毫秒
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W. D. Wu A. Keren L. P. Le G. M. Luke B. J. Sternlieb Y. J. Uemura D. C. Johnston B. K. Cho P. Gehring 《Hyperfine Interactions》1994,86(1):615-621
Muon spin relaxation (SR) studies have been performed in the normal spinel LiTi2O4 and the A-15 superconductor V3Si to measure the magnetic penetration depth . The relaxation rate(T) 1/2 in field-cooled measurements shows a sharp increase belowT
c
followed by saturation at low temperatures in both systems. This feature implies an isotropic energy gap without anomalous zeros, and most likelys-wave pairing. The low temperature penetration depth (T 0) is determined to be 2100Å for LiTi2O4 and 1300Å for V3Si respectively. Assuming a clean limit relation –2 n
s
/m
*, we derive the Fermi temperatureT
F
n
s/
2/3
m
* from the relaxation rate and the Sommerfeld constant asT
F
3/4–1/4. Unlike conventional superconductors, both LiTi2O4 and V3Si have a large ratio ofT
c
/T
F
0.01, only slightly smaller than those ratios in more exotic superconductors.We thank C. Ballard and K. Hoyle for technical assistance. Work at Columbia University is supported by NSF Grant No. DMR-89-13784 and Packard Foundation (YJU). Ames Laboratory is operated for the U. S. Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. Work at Ames was supported by the Director for Energy Research, Office of Basic Energy Sciences. 相似文献
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Margherita Modesti Colleen Szeto Renata Ristic WenWen Jiang Julie Culbert Keren Bindon Cesare Catelli Fabio Mencarelli Pietro Tonutti Kerry Wilkinson 《Molecules (Basel, Switzerland)》2021,26(6)
When bushfires occur near grape growing regions, vineyards can be exposed to smoke, and depending on the timing and duration of grapevine smoke exposure, fruit can become tainted. Smoke-derived volatile compounds, including volatile phenols, can impart unpleasant smoky, ashy characters to wines made from smoke-affected grapes, leading to substantial revenue losses where wines are perceivably tainted. This study investigated the potential for post-harvest ozone treatment of smoke-affected grapes to mitigate the intensity of smoke taint in wine. Merlot grapevines were exposed to smoke at ~7 days post-veraison and at harvest grapes were treated with 1 or 3 ppm of gaseous ozone (for 24 or 12 h, respectively), prior to winemaking. The concentrations of smoke taint marker compounds (i.e., free and glycosylated volatile phenols) were measured in grapes and wines to determine to what extent ozonation could mitigate the effects of grapevine exposure to smoke. The 24 h 1 ppm ozone treatment not only gave significantly lower volatile phenol and volatile phenol glycoside concentrations but also diminished the sensory perception of smoke taint in wine. Post-harvest smoke and ozone treatment of grapes suggests that ozone works more effectively when smoke-derived volatile phenols are in their free (aglycone) form, rather than glycosylated forms. Nevertheless, the collective results demonstrate the efficacy of post-harvest ozone treatment as a strategy for mitigation of smoke taint in wine. 相似文献
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S Tal N Keren J Hirschberg I Ohad 《Journal of photochemistry and photobiology. B, Biology》1999,48(2-3):120-126
Site-directed psbA mutants at the tyrosine Y112 position have been generated in Synechocystis PCC6803 cells. The mutation Y112F does not affect photosystem II (PSII) activity as compared with control 4 delta 1K cells. However, the Y112L mutant exhibits a photosynthetically impaired phenotype. PSII activity is not detectable in this mutant when grown at 30 mumol photons m-2 s-1, while low levels of the D1 and D2 proteins and oxygen evolution activity are present in the mutant cells grown at a low light intensity (0.5-1 mumol m-2 s-1). The recombination of the QB-/S2,3 states of PSII in the Y112L mutant cells as detected by thermoluminescence (TL) is altered. The TL signal emission maximum of these cells due to charge recombination of the S2,3/QB- occurs at 20 degrees C as compared to 35-40 degrees C for the wild-type cells, indicating a possible change in the S2,3/Yz equilibrium. The Y112L mutant cells are rapidly photoinactivated and impaired in the recovery of the PSII activity. These results suggest that replacement of the aromatic residue at position Y112 by a hydrophobic amino acid may alter the function of the donor-side activity and affects the degradation and replacement of the PSII core proteins. 相似文献
9.
K. Fradkin-Kashi A. Arie P. Urenski G. Rosenman 《Applied physics. B, Lasers and optics》2000,71(2):251-255
Tunable mid-infrared coherent radiation (3.25-
3.7 μm) is generated by quasi-phase-matched difference frequency generation in a multi-grating periodically-poled RbTiOAsO4 crystal. The spontaneous polarization and coercive field of flux-grown RbTiOAsO4 are determined by polarization switching measurements. The nonlinear interaction enables us to explore the optical and nonlinear
properties of this material in the mid-infrared range, where data is scarce. The measurements are used to derive a mid- infrared
corrected dispersion equation for nz in RbTiOAsO4. This equation is in excellent agreement with previously published measurements of nonlinear interactions in periodically-poled
RbTiOAsO4. The measured wavelength and temperature bandwidths are ≈48 nm cm and ≈29 °C cm, respectively. A relatively high temperature
tuning slope of the phase-matched idler wavelength, -1.27 nm/°C, is measured. This may be useful for realizing temperature-tuned
nonlinear devices.
Received: 30 March 2000 / Revised version: 9 May 2000 / Published online: 30 June 2000 相似文献
10.
I. Mirebeau M. Hennion M.J.P. Gingras A. Keren K. Kojima M. Larkin G.M. Luke B. Nachumi W.D. Wu Y.J. Uemura I.A. Campbell G.D. Morris 《Hyperfine Interactions》1997,104(1-4):343-348
In the amorphous ( Fe1-x Mn_x)75 P16 B_6 Al_3 alloys, muon and neutron depolarization data, combined with the results of small angle neutron scattering, magnetization and Mössbauer spectroscopy, probe the existence of three distinct magnetic transitions at TC, TK and TF (TF < K < C). 相似文献