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131.
132.
Swegle J.A. Anderson R.A. Camacho J.F. Poole B.R. Rhodes M.A. Rosenbury E.T. Shaeffer D.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(6):714-724
A relativistic backward-wave oscillator (BWO) operating at a frequency near 8 GHz has been built. The parameters of the 60-ns electron beam driving this microwave source are varied over the ranges 0.8-1.5 MV and 2-10 kA. Several different annular cathodes for launching the electron beam are tried, varying the outer radius and shape. The axial magnetic field guiding the beam through the BWO is varied between 0.6 and 3 T. The power transfer downstream to an output waveguide is investigated as a function of the shape of the transition from the BWO to the waveguide. The scaling of the output power and frequency with these variations is discussed. Time-resolved measurements of 2-ns-long segments of the microwave output are shown. In observations of the microwave signal, it is found that the frequency shifts as the output power envelope passes through a sharp dip. It is proposed that this shift corresponds to a change in the longitudinal operating mode of the BWO 相似文献
133.
Cytochrome P450 enzymes are the predominant mediators of phase I metabolism of exogenous small molecules. As a result of their extensive role in metabolism of xenobiotics, drug compounds, and endogenous compounds, as well as their wide tissue distribution, significant drug discovery resources are spent to avoid interacting with this class of enzymes. Here we review historical and recent in silico modeling of 7 cytochrome P450 enzymes of particular interest, specifically CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. For each we provide a brief biological background including known inhibitors, substrates, and inducers, as well as details of computational modeling efforts and advances in structural biology. We also provide similar details for 3 nuclear receptors known to regulate gene expression of these enzyme families. 相似文献
134.
Motivated by isotropic fully developed turbulence, we define a theory of symmetric matrix valued isotropic Gaussian multiplicative chaos. Our construction extends the scalar theory developed by J.P. Kahane in 1985. 相似文献
135.
Metal speciation has become one of the most important areas of concern for today's analysts. Metal complexes can be more readily assimilated by living systems than inorganic forms of the same metals. Conventional atomic absorption spectroscopy is the most widely used technique for the determination of trace metals. By using atomic absorption spectroscopy in conjunction with accelerated electroplating it is possible to distinguish between ionic metal and organically bound or complexed metals in solution. 相似文献
136.
The objective of this work is to provide a correlation between the heat transfer coefficient and the Nusselt Number with the flow Reynolds number for a truncated cylindrical probe in cross-flow, a configuration that has not previously been well defined. In the experiment, thermally stabilized, dry air was discharged into the test section across a heated probe that was instrumented with thermocouples and exhausted to atmosphere. Experimental data were recorded for several run conditions. A correlation between the probe heat transfer coefficient and the Reynolds number was developed with a calculated uncertainty of 1.24%. 相似文献
137.
E. J. Rhodes 《Radiation measurements》2000,32(5-6):595-602
The conclusions of Rhodes and Pownall (Rhodes, E.J., Pownall, L., 1994. Zeroing of the OSL signal in quartz from young glaciofluvial sediments. Radiation Measurements 23, 329–333) were somewhat discouraging for the prospects of using quartz OSL for dating glacigenic sediments, while the more detailed study of Rhodes and Bailey (Rhodes, E.J., Bailey, R.M., 1997. The effect of thermal transfer on the zeroing of the luminescence of quartz from recent glaciofluvial sediments. Quaternary Science Reviews (Quaternary Geochronology) 16, 291–298) provided more encouragement. Specifically, the latter authors were able to account for the relatively high De values observed for recent glacigenic (dominantly glaciofluvial) sediments in terms of an anomalously high thermal transfer effect, rather than simply insufficient bleaching prior to deposition. In other locations, the OSL of quartz from glacigenic material appears to provide reliable age estimates, and does not suffer from these effects (Owen, L.A., Richards, B., Rhodes, E.J., Cunningham, W.D., Windley, B.F., Badamgarav, J., Dorjnamjaa, D., 1998. Relic permofrost structures in the Gobi of Mongolia: age and significance. Journal of Quaternary Science 13 (16), 539–548; Richards, B.W., Owen, L.A., Rhodes, E.J., 2000. Timing of Late Quaternary glaciations in the Himalayas of northern Pakistan. Journal of Quaternary Science 15, 283–297). In this paper, laboratory bleached samples from both the above studies are remeasured, using an experimental design to correct for OSL sensitivity changes, which has some similarities to the single aliquot regenerative dose (SAR) protocol of Murray and Wintle (Murray A.S., Wintle A.G., 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32, 57–73). Clear evidence of thermal transfer OSL signals, generated during the preheating procedure, is presented. Further measurements, using the full SAR protocol, demonstrate that the source of this charge is related to natural dosing. For one sample, the apparent effect is subtracted effectively by the SAR protocol. Another sample studied in detail shows a striking relationship between the thermally transferred OSL signal and the total TL observed during the ramping of the preceding preheat treatment. 相似文献
138.
A readily available source of ultrapure water is a basic requirement in most analytical work. The earliest requirement for ultrapure water was in electrochemical research1. In recent years, nuclear reactors, semiconductor and electronic industries require very pure water2,3. Ultrapure water is needed to prepare standards whenever the determination of ultratrace (ppb) concentrations of metals is required. 相似文献
139.
140.
In this paper a second order semilinear parabolic PDE with rapidly oscillating coefficients is homogenized. The novelty of our result lies in the fact that we allow the second order part of the differential operator to be degenerate in some part of Rd. 相似文献