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811.
A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive. 相似文献
812.
813.
The fluorescence quenching of the Y-BPMPHD-CTMAB by nucleic acids is reported. It is considered that the Y-BPMPHD-CTMAB can form a large complex with nucleic acid through the electrostatic attraction in the pH range of 4.2-6.8. Under optimal conditions, the difference of fluorescence intensity between the system without and with nucleic acids is proportional to the concentration of nucleic acids over the range of 4.5 x 10(-8)-1.2 x 10(-5) g/mL for fsDNA and 3.2 x 10(-8)-3.0 x 10(-5) g/mL for yRNA, respectively. The detection limits are 14.0 ng/mL for fsDNA and 21.0 ng/mL for yRNA. The method is applied for the determination of nucleic acids in actual sample, and the result obtained is satisfactory. 相似文献
814.
Chunjie Wang 《Journal of Mathematical Analysis and Applications》2004,296(1):262-264
Let be the Bergman space over the open unit disk in the complex plane. Korenblum conjectured that there is an absolute constant c∈(0,1), such that whenever |f(z)|?|g(z)| () in the annulus c<|z|<1, then ‖f‖?‖g‖. In 1999 Hayman proved Korenblum's conjecture. But the sharp value of c (we use γ to denote this sharp value) is still unknown. In this paper we give an upper bound on γ, that is, γ<0.67795, which improves an earlier result of the author. 相似文献
815.
Xia JS Pan W Vicente CL Adams ED Sullivan NS Stormer HL Tsui DC Pfeiffer LN Baldwin KW West KW 《Physical review letters》2004,93(17):176809
At a very low-temperature of 9 mK, electrons in the second Landau level of an extremely high-mobility two-dimensional electron system exhibit a very complex electronic behavior. With a varying filling factor, quantum liquids of different origins compete with several insulating phases leading to an irregular pattern in the transport parameters. We observe a fully developed nu=2+2/5 state separated from the even-denominator nu=2+1/2 state by an insulating phase and a nu=2+2/7 and nu=2+1/5 state surrounded by such phases. A developing plateau at nu=2+3/8 points to the existence of other even-denominator states. 相似文献
816.
817.
Local convective heat flux in turbulent thermal convection is obtained from simultaneous velocity and temperature measurements in an aspect-ratio-one convection cell filled with water. It is found that fluctuations of the vertical heat flux are highly intermittent and are determined primarily by the thermal plumes in the system. The experiment reveals a unique mechanism for the heat transport in turbulent convection. 相似文献
818.
We report the first experimental observation of the inverse energy cascade correlated with the generation of large turbulent structures. Spectral energy is nonlinearly transferred from the unstable region of the spectrum into large coherent structures and into broadband turbulence in agreement with theoretical expectations. These results are obtained by producing plasma in the H-1 heliac whose parameters allow a single-field, Hasegawa-Mima-type model to be used for the spectral energy transfer analysis. 相似文献
819.
The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties
were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural
analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical
measurement showed a minimum ohmic contact resistance of 3×10-4 Ω cm2. The dominant current mechanism was found to be thermionic emission with a barrier height of Φb, of 0.09 V by comparing the experimental data with different theoretical models.
Received: 14 December 2001 / Accepted: 4 April 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +86-21/6226-4397, E-mail: zhoujian999@163.net 相似文献
820.