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Subczynski WK Mainali L Camenisch TG Froncisz W Hyde JS 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):142-148
Spin-lattice relaxation times (T?s) of small water-soluble spin-labels in the aqueous phase as well as lipid-type spin-labels in membranes increase when the microwave frequency increases from 2 to 35 GHz (Hyde, et al., J. Phys. Chem. B 108 (2004) 9524-9529). The T?s measured at W-band (94 GHz) for the water-soluble spin-labels CTPO and TEMPONE (Froncisz, et al., J. Magn. Reson. 193 (2008) 297-304) are, however, shorter than when measured at Q-band (35 GHz). In this paper, the decreasing trends at W-band have been confirmed for commonly used lipid-type spin-labels in model membranes. It is concluded that the longest values of T? will generally be found at Q-band, noting that long values are advantageous for measurement of bimolecular collisions with oxygen. The contribution of dissolved molecular oxygen to the relaxation rate was found to be independent of microwave frequency up to 94 GHz for lipid-type spin-labels in membranes. This contribution is expressed in terms of the oxygen transport parameter W=T??1(Air)-T??1(N?), which is a function of both concentration and translational diffusion of oxygen in the local environment of a spin-label. The new capabilities in measurement of the oxygen transport parameter using saturation-recovery (SR) EPR at Q- and W-band have been demonstrated in saturated (DMPC) and unsaturated (POPC) lipid bilayer membranes with the use of stearic acid (n-SASL) and phosphatidylcholine (n-PC) spin-labels, and compared with results obtained earlier at X-band. SR EPR spin-label oximetry at Q- and W-band has the potential to be a powerful tool for studying samples of small volume, ~30 nL. These benefits, together with other factors such as a higher resonator efficiency parameter and a new technique for canceling free induction decay signals, are discussed. 相似文献
65.
通过将单回路镜像对称开口金属环结构印制在高介电常数基板上,实现了一种金属含量比传统负折射材料更少,"双负"通带比全介质负折射材料更宽的负折射材料.分析了高介电常数基板产生负介电常数以及"双负"通带形成的机理,通过仿真实验分析了影响"双负"通带的因素.通过制作样品验证了这一机理实现"双负"的可行性,理论分析与实验结果都表明这种方法可实现较宽频段内的"双负"通带.
关键词:
负折射材料
负介电常数
负磁导率
介质谐振器原理 相似文献
66.
Cas van der AvoortRein van der Hout Joost Hulshof 《Physica D: Nonlinear Phenomena》2011,240(11):913-919
We study the response of a MEMS resonator, driven in an in-plane length-extensional mode of excitation. It is observed that the amplitude of the resulting vibration has an upper bound, i.e., the response shows saturation. We present a model for this phenomenon, incorporating interaction with a bending mode. We show that this model accurately describes the observed phenomena. The in-plane (“trivial”) mode is shown to be stable up to a critical value of the amplitude of the excitation. At this value, a new “bending” branch of solutions bifurcates. For appropriate values of the parameters, a subsequent Hopf bifurcation causes a beating phenomenon, in accordance with experimental observations. 相似文献
67.
基于自再现原理,利用菲涅耳-基尔霍夫衍射积分方程,引入腔镜失调、激光介质上的增益分布以及光阑口径,采用本征矢量法分析了大口径平凹腔薄片激光器的本征模式,并计算了相应的光束质量因子M2.建立了千瓦级薄片激光系统和光纤扫描光斑诊断装置,开展了高功率激光输出特性研究.结果表明,在大口径高功率平凹腔中多个本征模式可同时起振,获... 相似文献
68.
Anatoly I. Fisun 《International Journal of Infrared and Millimeter Waves》1997,18(7):1431-1443
The theoretical and experimental analysis of the open resonator with the reflection diffraction comb grating has been presented.
This resonator has excitation where is close to the monofrequency mode. This results may be used for the elaboration of mm-wave
quasi-optical devices such as generators, mixer, converter, wavemeters and others. 相似文献
69.
A new design of the U-type resonator is described. In this way, a laser beam with symmetrical intensity profile (regarding to a symmetry plane) can be extracted from an active medium that exhibits gain asymmetry along one of the transverse directions. The whole area of the active medium cross-section can be used, and consequently the laser efficiency will be increased. This resonator structure was applied for efficiency power extraction (as a low order TEM modes laser beam) from a DC excited transverse flow CO2 laser with cylindrical geometry. Although the cross-section area of the discharge was entirely used (including the cathode fall region), a symmetrical intensity profile of the laser beam (regarding to the two orthogonal symmetry planes) was obtained in the near field as well as in the far field; the gain asymmetry along the flow direction was compensated by the gas circulation fluidodynamical circuit with two counterflowing discharge channels. A double-U optical resonator was introduced in order to provide a laser beam with axial symmetry.For the practical construction of these two types of optical resonators we have developed two new types of 90° deflection elements: the first one, which does not reverse the image (and which has the properties of the pentaprism), and the second one, which rotates the image with 90° angle. Both elements exhibit good focusability if they are equipped with two concave mirrors. 相似文献
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