共查询到19条相似文献，搜索用时 671 毫秒
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利用盐酸多巴酚丁胺对血红蛋白模拟酶催化L-酪氨酸和H2O2体系的抑制作用,建立了酶催化荧光法测定盐酸多巴酚丁胺的新方法。研究了该猝灭反应的最佳实验条件,其猝灭程度与盐酸多巴酚丁胺的浓度呈线性关系。测定的线性范围为5.92×10-7～8.88×10-6mol/L,检出限为1.43×10-9mol/L。对浓度为5.92×10-7mol/L的盐酸多巴酚丁胺溶液进行11次平行测定,其相对标准偏差为3.2%。该方法用于药物中盐酸多巴酚丁胺含量的测定,结果满意。 相似文献
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利用盐酸多巴酚丁胺对血红蛋白模拟酶催化L-酪氨酸和H2O2体系的抑制作用,建立了酶催化荧光法测定盐酸多巴酚丁胺的新方法。研究了该猝灭反应的最佳实验条件,其猝灭程度与盐酸多巴酚丁胺的浓度呈线性关系。测定的线性范围为5.92×10-7~8.88×10-6mol/L,检出限为1.43×10-9mol/L。对浓度为5.92×10-7mol/L的盐酸多巴酚丁胺溶液进行11次平行测定,其相对标准偏差为3.2%。该方法用于药物中盐酸多巴酚丁胺含量的测定,结果满意。 相似文献
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本文研究了维生素 P(V_p)在0.05M NH_4Cl 0.1M KCl 底液中的示波极谱、普通极谱及新极谱(卷积伏安)行为.V p 的导数峰电位为 E_p=-1.54V[VS.Ag/AgCl(sat.),KCl(sat.].导数示波极谱测定 V_p 的检测限为5×10~(-9)M(3ppb),V_p 浓度在1×10~(-8)-8×10~(-4)M(6ppb-500ppm)间与导数峰高成良好的线性关系,可用于定性及定量测定 V_p.卷积伏安法等多种方法的研究证明 V_p 的电极反应属于自动催化过程. 相似文献
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用单扫示波极谱法，青藤碱在0．1mol／LNa_2B_4O_7中有两个还原峰，峰P_1和P_2的电位分别为-1．45V和-1．67V（vs．SCE），峰P_1的峰电流与浓度在0．06～1．8mg／L和20～34．6mg／L范围内有线性关系，检测限为0.02mg／L，用以测定中药膏风藤克总生物碱的含量，结果令人满意．实验证明，青藤碱的电极反应过程为不可逆的四电子过程，并讨论了青藤碱对超氧阴离子自由基（O_2~-）的清除作用。 相似文献
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研究罗红霉素药物的B-Z振荡行为.方法 将不同浓度罗红霉素加入到经典的B-Z振荡体系中,考察其对周期和振幅的影响.结果 罗红霉素对振荡体系产生了明显的扰动,周期和振幅的变化率与所加入罗红霉素的浓度呈良好的线性关系,其浓度分别在6.5×10^-7～1.75×10^-4g/mL和4.0×10^-7～2.3×10^-4g/mL,相关系数分别为0.9955和0.9971;检出限为3.0×10^-8g/mL. 结论 建立了一种简便的罗红霉素化学振荡的电化学方法,对其临床用药具一定的指导意义. 相似文献
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研究表明被测物H2O2的浓度一定时,用电流-曲线,CdS量子点（CdS QDs）修饰电极在光照时与不被光照时电流大小有明显的差异。CdS QDs修饰电极在光照条件下有明显的促进电流增大作用,并且容易受到pH的影响,在pH=4最有利于增大电流。pH=4时被检测物H2O2浓度在3×10^-7到4×10^-6成很好的线性关系,可用于H2O2低浓度的检测。 相似文献
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实现了一种应用于WiMAX无线接收机中频部分的单级可变增益放大器.由于采用电流平方技术,该结构能以较少的级联数,实现系统所需的固定增益变化范围,以达到降低总功耗的目的.该电路采用0.13μm CMOS工艺进行流片,总面积为0.6×0.4 mm2.测试结果表明,当控制电压从0.5 V变化到1 V时,VGA的增益变化范围为-20～25 dB,其3 dB带宽大于15 MHz,IIP3为-21～5 dBm,在1.2 V电源电压下功耗为3.6 mW. 相似文献
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用蒙脱石与Ｎａｆｉｏｎ制备了阳离子染料中性红化学修饰电极（ＣＭＥ）．两种ＣＭＥ在支持电解质溶液中有相似的循环伏安行为．蒙脱石ＣＭＥ的峰电流随膜厚增加而增加，而ＮａｆｉｏｎＣＭＥ的峰电流随膜厚增加有所降低．阳离子染料在蒙脱石膜内的扩散系数比在Ｎａｆｉｏｎ膜中的扩散系数大一个数量级．阴离子电活性物以及不同的制备方法对两种ＣＭＥ的电化学响应有不同的影响．两种ＣＭＥ在性质上的差异反映了两种膜的微结构与通透性等方面的差别．蒙脱石用作制备化学修饰电极的表面层材料有一定吸引力． 相似文献
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Through the use of nonpolar viscoelasticity theory, the problem of traveling loads with time dependent magnitude variability is considered. Employing a moving Lagrangian observer, a quadratic form is developed to ascertain potential time dependent magnitude variability induced shifts, bifurcations and wavelength interdependencies in the critical speeds associated with Rayleigh, plane and transverse wave phenomena. In terms of the moving Lagrangian formulation, a solution is developed which enables the characterization of response behavior in the various sub, trans and supercritical speed ranges associated with each of the different wave types. Based on the solution, the results of several numerical experiments are presented. These demonstrate various aspects of the foregoing phenomena. 相似文献
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Electroosmotic flow that involves one fluid displacing another fluid is commonly encountered in various microfludic applications and experiments, for example, current monitoring technique to determine zeta potential of microchannel. There is experimentally observed anomaly in such flow, namely, the displacement time is flow direction dependent, i.e., it depends if it is a high concentration fluid displacing a low concentration fluid, or vice versa. Thus, this investigation focuses on the displacement flow of two fluids with various concentration differences. The displacement time was determined experimentally with current monitoring method. It is concluded that the time required for a high concentration solution to displace a low concentration solution is smaller than the time required for a low concentration solution to displace a high concentration solution. The percentage displacement time difference increases with increasing concentration difference and independent of the length or width of the channel and the voltage applied. Hitherto, no theoretical analysis or numerical simulation has been conducted to explain this phenomenon. A numerical model based on finite element method was developed to explain the experimental observations. Simulations showed that the velocity profile and ion distribution deviate significantly from a single fluid electroosmotic flow. The distortion of ion distribution near the electrical double layer is responsible for the displacement time difference for the two different flow directions. The trends obtained from simulations agree with the experimental findings. 相似文献
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采用GPS技术对各种车辆实施监控、调度管理是一个新的研究热点。现提出了基于ARM的嵌入式GPS定住系统设计方案。整个设计被划分为软件和硬件两个部分,其中硬件部分主要完成设备的通信以及接收和发送对执行机构的控制信号。通过软件方式控制信号的接收、识别、编码、发送、执行等具体操作。 相似文献
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针对矿用直流架线电机车在调速过程中采用落后的直流电机方式及浪费大量电能的问题,提出了一种由交流异步电动机拖动电机车的调速系统方案。逆变器采用电压空间矢量控制方式,利用单片机生成PWM波,优化了系统的调速性能。 相似文献
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在艺术开放的今天,在中外各种文化大汇合的时代,民族民间文化的觉醒使每一个艺术家完全可以清晰地审视各种造型观念和方式,真诚而自由的决定审美创造的取向,达到能够驾驭多种审美造型观念的自在状态,真正创造出自己独具个性的具有鲜明民族风格的山峰,屹立于艺术的群巅之中。 相似文献
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In this paper the scattering of plane electromagnetic waves from eccentrically coated metallic spheres is considered. Inhomogeneous, surface, singular integral equations are used to formulate the problem. Their solution is obtained in terms of spherical vector wave functions in conjunction with related addition theorems. Analytical, closed-form results are obtained in the case of small eccentricities kd, where d is the distance between the two centers and k the wave number of the dielectric coating. Thus the scattered field and the various scattering cross-sections of the problem are given by expressions of the form: S(d) = S(0)[1+g’(kd)+g”(kd)2+0(kd)3]. Numerical and graphical results for various values of the parameters are also discussed. 相似文献
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Microfluidic paper-based analytical devices (μPADs) are a promising solution for a wide range of point-of-care applications. The feasibility of inducing ion concentration polarization (ICP) on μPADs has thus far attracted little attention. Accordingly, this study commences by demonstrating the ICP phenomenon in a μPAD with a Nafion ion-selective membrane. We are the first to measure the current-voltage curve on a Nafion-coated μPAD in order to indicate that the ion depletion occurs and the ICP is triggered when the current reaches the limiting current. The ICP effect is then exploited to preconcentrate fluorescein on μPADs incorporating straight and convergent channels. By an optimal geometric design, it is shown that the convergent channel results in a greater preconcentration effect than the straight channel. Specifically, a 20-fold enhancement in the sample concentration is achieved after 130 s given an initial concentration of 10?5 M and an external potential of 50 V. By contrast, the straight channel yields only a 10-fold improvement in the concentration after 180 s. Further, the practical feasibility of the proposed convergent-channel μPAD is demonstrated using fluorescein isothiocyanate labeled bovine serum albumin. The experimental results show that a 15-fold enhancement of the initial sample concentration (10?5 M) is obtained after 120 s given an external potential of 50 V. 相似文献
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James G. Taylor 《Journal of The Franklin Institute》1978,306(2):195-208
Two approximations are developed to the solution of an important nonlinear, nonautonomous second-order differential equation that arises in various fields of science and technology such as operations research, mathematical ecology and epidemiology. The origin of the second-order differential equation from a system of two nonlinear first-order differential equations modelling, for example, Lanchester-type combat between two homogeneous military forces is discussed. Extension of our results to a more general system of nonlinear first-order differential equations is indicated. Error bounds that do not require that the exact solution be known are developed. Some connections between our results and those for the Liouville-Green (or WKB) approximation to the solution of the linear second-order equation are indicated. 相似文献