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1.
Experimental research on the improvement of the sensitivity and time resolution of pulsed magnetic resonance spectrometers
is discussed. It is shown that application of a time-variable feedback of a signal to the input of the receiver amplifier
can decouple, the “fixed” relationship between the quality factorQ and the ringdown time of the resonance system. Experiments were performed with low-frequency, radio-frequency and microwave
pulse-type magnetic resonance receivers. Modifications of an S/C-band electron spin echo modulation spectrometer carried out
to check the “time-variable feedback” performance are described. It is demonstrated that the application of a time-variable
feedback can significantly reduce the ringdown time and improve the recovery properties of the magnetic resonance receiver
system. It is also demonstrated that the time-variable feedback can improve the overall receiver sensitivity due to the fact
that the working bandwidth of the resonance system can be optimized separately for the transmitting and the receiving mode.
Signal values could be increased at least three times and the signal-to-noise ratio about 1.5–2 times. The largest improvement
is achieved with the initially overcoupled resonator. Experimental spectra of test samples for different settings of the time-variable
feedback are shown. 相似文献
2.
The solid solubility in the systems Y2O2S---La2O2S, Y2O2S---Gd2O2S, and Gd2O2S---La2O2S has been investigated. Solid solutions of all compounds, throughout the whole composition range, were readily obtained, using coprecipitated oxalates and a polysulfide flux. 相似文献
3.
自由曲面光学产品设计、制造与检测的工艺流程,通常采取试凑法逐次逼近。由于加工 检测 再加工,循环往复,既费时,成本又高,产生了瓶颈问题。为了解决此弊端,本文运用虚拟制造技术,提出光学虚拟制造的基本构想,即虚拟制造系统结构模型,给出光学系统虚拟原型的构成和光学系统成像质量虚拟检测系统的构成,讨论光学成像质量的仿真检测以及敏度分析方法。研究结果表明:运用虚拟制造与检测技术,可缩短研发周期,降低成本,优化工艺并提高产品质量。 相似文献
4.
5.
There are consistently estimable parameters of interest whose semiparametric Fisher information vanishes at some points of the model in question. Here we investigate how bad this is for estimation. 相似文献
6.
7.
Klaassen T Kasel D Harlfinger S Fuhr U 《Rapid communications in mass spectrometry : RCM》2004,18(15):1675-1680
A reliable and easy to use liquid chromatography/tandem mass spectrometry (LC/MS/MS) method without the use of sample extraction was developed for the simultaneous quantification of urinary concentrations of mephenytoin, a standard phenotyping substrate for the cytochrome P450 enzyme CYP2C19, and its phase I metabolites 4'-hydroxymephenytoin and nirvanol. Fifty microL of urine were diluted with a buffered beta-glucuronidase solution and incubated at 37 degrees C for 6 h followed by addition of methanol, containing the internal standard 4'-methoxymephenytoin. The chromatographic separation was achieved using a 100 x 3 mm, 5 micro Thermo Electron Aquasil C18 column with a gradient flow, increasing the organic fraction (acetonitrile/methanol 50:50) of the mobile phase from 10 to 90%. Quantification by triple-stage mass spectrometry (TSQ Quantum, Thermo Electron) was accomplished by negative electrospray ionization in the selected reaction monitoring mode. Linearity was observed for all substances in the concentration range 15-10 000 ng/mL. The lower limit of quantification (LLOQ) was 20 ng/mL for 4'-hydroxymephenytoin and 30 ng/mL for nirvanol and mephenytoin, respectively. Intra- and inter-day inaccuracy did not exceed 9.5% for all substances from LLOQ to 10 000 ng/mL. Intra- and inter-day precision were in the range of 0.8-10.5%. The method was validated according to international ICH and FDA guidelines and successfully applied for phenotyping of Caucasian male volunteers who received an oral dose of 50 mg mephenytoin. 相似文献
8.
R.Kh. Zhukavin D.M. Gaponova A.V. Muravjov E.E. Orlova V.N. Shastin S.G. Pavlov H.-W. Hübers J.N. Hovenier T.O. Klaassen H. Riemann A.F.G. van der Meer 《Applied physics. B, Lasers and optics》2003,76(5):613-616
Terahertz stimulated emission of phosphorus donors in silicon optically excited by radiation from the free-electron laser
FELIX has been studied. It is found that a spectral line of the Si:P laser emission depends on pump frequency. Stimulated
emission arises on the 2p0→1s(E) intra-centre transition (21.2 meV) under resonant pumping of the 2p0 state and on the 2p0→1s(T2) transition (22.3 meV) under pumping of the 2p± or higher odd-parity donor states. The line shift is attributed to the Auger redistribution of the 1s(E)- and 1s(T2)-state populations.
Received: 7 November 2002 / Revised version: 7 April 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-30/6705-55-07, E-mail: sergeij.pavlov@dlr.de
RID="**"
ID="**"On leave from: The Institute for Physics of Microstructures, Nizhny Novgorod, Russia 相似文献
9.
P. R. Orella J. A. Klaassen M. T. François und N. Laffitte 《Fresenius' Journal of Analytical Chemistry》1938,113(1-2):79-80
Ohne Zusammenfassung 相似文献
10.
In service systems, in order to balance the server’s idle times and the customers’ waiting times, one may fix the arrival times of the customers beforehand in an appointment schedule. We propose a procedure for determining appointment schedules in such a D/G/1-type of system by sequentially minimizing the per-customer expected loss. Our approach provides schedules for any convex loss function; for the practically relevant cases of the quadratic and absolute value loss functions appealing closed-form results are derived. Importantly, our approach does not impose any conditions on the service time distribution; it is even allowed that the customers’ service times have different distributions. 相似文献