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151.
Seiichi Nakamura Jun Inagaki Tomohiro Sugimoto Yasuyuki Ura Shunichi Hashimoto 《Tetrahedron》2002,58(52):10375-10386
An efficient, highly stereoselective synthesis of the C10–C31 (BCDEF ring) portion of pinnatoxin A has been achieved utilizing tandem double hemiketal formation/intramolecular hetero-Michael addition to construct the 6,5,6-dispiroketal (BCD ring) system and subsequent intramolecular ketalization to form the 5,6-bicycloketal (EF ring) system as key steps. 相似文献
152.
In pH 6.0-11.2 Britton-Robinson buffer solution, binding of heparin with crystal violet (CV) can result in a significant enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering, such as frequency doubling scattering (FDS) and second-order scattering (SOS). Their maximum scattering wavelengths, λex/λem, appear at 492 nm/492 nm for RRS, 984 nm/492 nm for FDS and 492 nm/984 nm for SOS, respectively. The optimum conditions of the reaction, the influencing factors and the relationship between the three scattering intensities and the concentration of heparin have been investigated. New methods for the determination of trace amounts of heparin based on the RRS, FDS and SOS methods have been developed. The methods exhibit high sensitivities, the detection limit for heparin is 2.9 ng ml−1 for the RRS method, 3.5 ng ml−1 for the FDS method and 3.3 ng ml−1 for the SOS method. The methods have good selectivity and were applied to the determination of heparin in heparin sodium injection samples with satisfactory results. 相似文献
153.
E. C. C. Vasconcellos A. Scalabrin F. R. Petersen K. M. Evenson 《International Journal of Infrared and Millimeter Waves》1981,2(3):533-539
Twenty-four new submillimeter laser lines in fully deuterated methyl alcohol (CD3OD) in the wavelength range from 52 to 328 m have been obtained in a Fabry-Perot FIR resonator by optically pumping the methanol with a cw CO2 laser. We have made accurate wavelength measurements and have determined the relative polarization of most of the known CD3OD laser lines. The frequencies of 13 of the strongest lines were also measured.Contribution of the U.S. Government, not subject to copyright. 相似文献
154.
Immunoanalytical methods at a very low limit of detection (LOD) and a low limit of quantification (LOQ) are becoming more and more important for environmental analysis and especially for monitoring drinking water quality. Biosensors have suitable characteristics such as efficiency in allowing very fast, sensitive, and cost-effective detection. Here we describe a fully automated immunoassay for estrone with a LOD below 0.20 ng L–1 and a LOQ below 1.40 ng L–1. In contrast to common analytical methods such as GC-MS or HPLC-MS, the biosensor used requires no sample pre-treatment and pre-concentration. The basis of our sensitive assay is the antibody with a high affinity constant towards estrone. The very low amount of antibody per sample results in low validation parameters (LOD, LOQ, and IC50), but this assay for estrone represents the current device-related limitation of the River Analyser (RIANA). 相似文献
155.
A one-dimensional system of hard-rod particles with rotational-like internal degrees of freedom is considered. Particles interact with each other through the infinite-range, infinitely weak attractive Kac potential, and through a nearest-neighbor short-range potential. The latter depends also on the internal states of the interacting particles. Exact results for thermodynamic properties and for some correlation functions are obtained. It is found that the considered system exhibits several first-order transitions between phases with different rotational structure, i.e., with different ordering with respect to the internal degrees of freedom. The calculated equation of state seems to suggest that in the solutions of liquid-crystalline substances in neutral solvents there may exist regions in which the coefficient of thermal expansion is negative—an effect similar to that well known in liquid water. 相似文献
156.
使用PSD作为大口径光学元件表面加工质量的评价参数,针对不同的波前调制进行了初步的模拟计算,得到了不同调制频率和不同调制深度情况下的PSD曲线变化情况。当调制频率不同时,PSD曲线的突变部分会发生相应的频移,调制频率高则突变发生在空间频率较高的频段,同时PSD峰值不变。相对应调制深度不同时,PSD曲线的突变部份峰值发生变化,调制深度大则峰值大,与此同时峰值出现的位置不会发生变化。计算和分析结果表明PSD分析结果能够在频率域反应出元件表面受到的不同程度的调制信息。 相似文献
157.
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159.
Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature 下载免费PDF全文
In order to investigate of cobalt-doped interracial polyvinyl alcohol (PVA) layer and interface trap (Dit) effects, A1/p- Si Schottky barrier diodes (SBDs) are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance (Rs), and interfacial layer. Both the real and imaginary parts of dielectric constant (er and err) and electric modulus (Mr and Mrr), loss tangent (tan~), and AC electrical conductivity (aac) are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance (C) and conductance (G/w) values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si (MPS) type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance (CLF-CHF) method. 相似文献
160.
This paper presents the influence of a concentrated mass location on the natural frequencies of a cracked double-beam. The double-beam consists of two different beams connected by an elastic medium. The concentrated mass is located on the main beam. The relationship between the natural frequency and the location of concentrated mass is established and called “Frequency–Mass Location” (FML). The numerical simulations show that when there is a crack, the frequency of the double-beam changes irregularly when the concentrated mass is attacked at the crack position. This irregular change can be amplified by the wavelet transform and this is useful for crack detection: the crack location can be detected by the location of peaks in the wavelet transform of the FML. Finite element model for the cracked double-beam carrying a concentrated mass is presented and numerical simulations are also provided. 相似文献