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991.
In this paper properties and construction of designs under a centered version of the -discrepancy are analyzed. The theoretic expectation and variance of this discrepancy are derived for random designs and Latin hypercube designs. The expectation and variance of Latin hypercube designs are significantly lower than that of random designs. While in dimension one the unique uniform design is also a set of equidistant points, low-discrepancy designs in higher dimension have to be generated by explicit optimization. Optimization is performed using the threshold accepting heuristic which produces low discrepancy designs compared to theoretic expectation and variance.
992.
High-performance capillary electrophoresis with electrochemical detection was employed to analyse active ingredients of Rhododendron dauricum L., an important crude herb frequently used in Chinese medicines. Farrerol, quercetin, syringic acid, vanillic acid, 4-hydroxybenzoic acid, protocatechuic acid are major important active ingredients. Operated in a wall-jet configuration, a 300-microm diameter carbon-disk electrode was used as the working electrode, which exhibits a good response at +950 mV (vs. saturated calomel electrodes) for six analytes. Under the optimum conditions, the analytes were baseline separated within 16 min in a borax buffer (pH 8.7). Notably, excellent linearity was obtained over two orders of magnitude with detection limits (S/N=3) ranged from 9 x 10(-7) to 3.0 x 10(-6) M for all analytes. This method was successfully used in the analysis of Rhododendron dauricum L. with relatively simple extraction procedures, and the assay results were satisfactory. 相似文献
993.
Liao JH Chen CT Chou HC Cheng CC Chou PT Fang JM Slanina Z Chow TJ 《Organic letters》2002,4(18):3107-3110
[structure: see text] A push-pull conjugated molecule, 2,7-bis(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine (BPN), has been designed to bind selectively with octyl glucopyranoside (OGU). The BPN/OGU quadruple hydrogen-bonding complex adopts a rigid BPN conformation in which the proton donor (d) and acceptor (a) relays (daad) are resonantly conjugated through the ethynyl bridge, inducing pi-electron delocalization, i.e., a charge transfer effect. The excellent photophysical properties make BPN a highly sensitive probe for monitoring glucopyranoside to a detection limit of approximately 100 pM. 相似文献
994.
Krokovny P Abe K Abe K Abe T Adachi I Ahn BS Aihara H Akatsu M Asano Y Aso T Aulchenko V Aushev T Bakich AM Ban Y Banas E Bay A Bedny I Behera PK Bizjak I Bondar A Bozek A Bracko M Brodzicka J Browder TE Casey BC Chang P Chao Y Chen KF Cheon BG Chistov R Choi SK Choi Y Danilov M Dong LY Drutskoy A Eidelman S Eiges V Enari Y Everton CW Fang F Fukunaga C Gabyshev N Garmash A Gershon T Golob B Gordon A Guo R Haba J Hanagaki K Handa F Harada Y Hayashii H Hazumi M Heenan EM Higuchi T Hinz L Hojo T 《Physical review letters》2002,89(23):231804
We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|. 相似文献
995.
We have studied the enhancement of spontaneous emission rates for InAs quantum dots embedded in GaAs microdisks in a time-resolved photoluminescence experiment. Inhomogeneous broadening of the quantum dot energy levels and random spatial distribution of the quantum dots in a microdisk lead to a broad distribution of the spontaneous emission rates. Using a nonnegative least-norm algorithm, we extract the distribution of spontaneous emission rates from the temporal decay of emission intensity. The maximum spontaneous emission enhancement factor exceeds 10. 相似文献
996.
The time-of-flight mass spectrum (TOFMS) relative to the resonant two-photon ionization of gas phase p- dichlorobenzene was obtained in the wavelength range of 240 - 250 nm by a home-made system. A special design was made to reduce the effect of memory on the inner wall of the sample inlet system suitable for the investigation of semi-volatile organic compound. In this wavelength range, p-dichlorobenzene molecules firstly absorbed one photon to be excited from the ground state ^1Ag(So) to the first excited state ^1B2u (S1), then absorbed another photon to be ionized. The relationship between the signal intensity of p-dichlorobenzene molecular ion C6H4^35Cl2^+ at 248-nm wavelength and the laser power was given. The 1.52 power index of C6H4^35Cl2^+ was a typical identification of the 3/2 power law. The relationship between the ion signal intensity of C6H4^35Cl2^+ and the sample concentration was close to a linear one in the ppm(V/V) range, which led to a detection limit of 125 ppb(V/V) for p-dichlorobenzene. 相似文献
997.
We introduce the graded version of the antisimple radical S, the graded antisimple radical SG. When |G| < , we show that SG = Sref = SG, where Sref denotes the reflected antisimple radical and SG denotes the restricted antisimple radical. 相似文献
998.
环境水中微量硫酸根离子的流动注射分光光度法测定 总被引:2,自引:0,他引:2
本文报道了以二甲基磺基偶氮Ⅲ为试剂,硫酸根离子与试剂-钡离子的络合物发生反应测定了水中低含量的硫酸根离子,方法适合于环境水中低浓度的硫酸根离子的检测。 相似文献
999.
本文在分析影响预测准确原因的基础上.指出预测工作必须定量与定性相结合.针对地区电力消费需求的特点,提出了适宜于定性分析的四个预测模型.运用上述模型,实际预测结果令人满意。 相似文献
1000.
用三次B样条函数配点法,求得在矩形波冲击下具有立方非线性产品包装的冲击谱。讨论了软、硬非线性及外界激励幅值对产品损坏边界的影响。提出用损坏边界曲面来描述非线性产品包装的安全区域,并作出了相应的损坏边界曲面. 相似文献