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Quantum Zeno and anti-Zeno paradoxes 总被引:1,自引:0,他引:1
Continuous observation of a time independent projection operator is known to prevent change of state (the quantum Zeno paradox).
We discuss the recent result that generic continuous measurement of time dependent projection operators will in fact ensure
change of state: an anti-Zeno paradox. 相似文献
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粉粒体两相流的电容层析成象测量 总被引:4,自引:0,他引:4
粉粒体系统中的固相浓度分布的在线测量是十分困难的问题.电容层析成象技术是一种近年来发展起来的非侵入式快速浓度场测量技术.它不干扰流场,不受流动中颗粒浓度、加速度、不透明等因素的制约.本文讨论其测量原理、应用、近期进展、存在的主要问题及其解决的对策. 相似文献
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ac Conductivity measurements are carried out across the metal to insulator transition in NiAl0.7Cr0.7Fe0.6O4. The low frequency data is analyzed using Summerfield scaling theory for hopping conductivity. The exponent of the scaling
behavior has significantly different values in the conducting and insulating regimes. The hopping frequency and the zero frequency
conductivity are found to increase with temperature, slowly in the metallic regime and rapidly in the insulating regime. 相似文献
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DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements
have been reported for the Co1.1−x
Zn
x
Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic
ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained
under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important
role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed. 相似文献
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Nicolas DiCesare Devi P. Adhikari Justin J. Heynekamp Michael D. Heagy Joseph R. Lakowicz 《Journal of fluorescence》2002,12(2):147-154
Spectroscopic and photophysical properties of two fluorescent probes for monosaccharides are presented. Probes are based on the N-phenyl-1,8-naphthalimide structure having the boronic acid group [R-B(OH)2] in ortho in one case, and meta in the other case, positions of the N-phenyl group. Formation of the anionic form of the boronic acid group [R-B(OH)–
3] induced a substantial decrease of the steady-state fluorescence of both compounds. Because no change in the fluorescence lifetime from the neutral to the anionic forms is observed, static quenching resulting from photoinduced electron transfer from the anionic form of the boronic acid is used to explain the decrease of the emission intensity. Both compounds show substantial decreases of their fluorescence intensity in the presence of sugars. In addition, this decrease of the fluorescence intensity is associated with an increase of the fluorescence lifetime for the ortho derivative while no effect on the lifetime is observed for the meta derivative. Both photoinduced electron transfer and steric hindrance are discussed to correlate the observed results. 相似文献
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Boyle Timothy J. Clem Paul G. Rodriguez Mark A. Tuttle Bruce A. Heagy Michael D. 《Journal of Sol-Gel Science and Technology》1999,16(1-2):47-55
We have recently isolated the neo-pentoxide (HOCH2CMe3, ONp) derivatives of Ba, Sr, and Ti as Ba4(ONp)8(HONp)6(py)2, Sr5(O)(ONp)8(Solv)5 (Solv = solvent), and Ti2(ONp)8, respectively. The combination of these precursors were found to be readily soluble in a wide range of solvents and thus were excellent candidates for preparation of barium strontium titanate ((Ba,Sr)TiO3 or BST) thin films using spin-cast deposition techniques. The highest quality BST films for this system were generated from ternary mixtures dissolved in either pyridine or pyridine/toluene. By in situ VT-GIXRD analysis it was determined that the perovskite phase of BST was readily formed at 650°C. The electronic properties of films crystallized at 700°C indicated that the thin films (300 nm) possessed a dielectric constant of 120 (tan = 0.03) with a tunability of 29% at ±10 V. 300 nm films (700°C) which had been generated from a standard BST solution modified with a novel tridentate ligand, had a higher dielectric constant of 180 and a tunability of 35% at ±10 V. The collective characteristics of these precursors offer an attractive alternative to the more complex, less stable sol-gel precursors currently in use. 相似文献
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A ten element matrix of 5- and 6-substituted-(2,3)-naphthalimides was prepared for the appropriate placement of substituents necessary to promote dual fluorescence (DF). As prescribed by our balanced seesaw photophysical model this matrix yielded nine new DF dyes out of a possible ten compounds. From this set of nine DF dyes, 4-fluoronaphthalic amide (37) was selected as a probe for ratiometric detection of DNA and demonstration of panchromatic emission. 相似文献