Application of quartz crystal nanobalance in conjunction with a net analyte signal based method for simultaneous determination of leucine, isoleucine and valine

The aim of the present investigation was to develop a biosensor for the detection of amino acids, Leucine, Isoleucine and Valine based on a quartz crystal nanobalance. leucine (Leu), isoleucine (Ile), and valine (Val) were selectively determined by quartz crystal nanobalance (QCN) sensor in conjunction with net analyte signal (NAS)-based method called HLA/GO. An orthogonal design was applied for the formation of calibration and prediction sets including Leu, Ile and Val compounds. The selection of the optimal time range involved the calculation of the net analyte sig-nal regression plot in any considered time window for each test sample. The searching of a region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of PRESS value was carried out by applying a moving window strategy. On the base of obtained results, the differences on the adsorption profiles in the time range between 1 and 300 s were used to determine mixtures of compounds by HLA/GO method. The results showed that the method was successfully applied for the determina-tion of Leu, Ile and Val.

Interactions between Phospholipid Monolayers (DPPC and DMPC) and Anesthetic Isoflurane Observed by Quartz Crystal Oscillator

The interactions of phospholipid monolayers (dipalmitoyl phosphatidyl choline;DPPC and dimyristoyl phosphatidyl choline;DMPC) with volatile anesthetic isoflurane were investigated using quartz crystal microbalance (QCM) and quartz crystal impedance (QCI) methods. The quartz crystal oscillator was attached horizontally on the surface of DPPC and DMPC monolayer formed on the water surface. Physisorption of isoflurane hydrate at the DPPC monolayer surface was monitored in terms of frequency and resistance change of quartz crystal on addition of anesthetics isoflurane. Both frequency and resistance change showed the elastic nature of DPPC monolayer. Measurement of DMPC monolayer-isoflurane hydrate revealed the expandable nature of DMPC monolayer. Variation of frequency and impedance of DPPC and DMPC monolayer on addition of isoflurane which proved a two-step change has occurred at monolayer surface at isoflurane concentration of ≤8 mM that has been attributed to isoflurane aggregation at monolayer/water interface. Isoflurane hydrates formed in the process have capability to affect the interfacial properties of monolayer such as existence of structured water.

Start-Up Acceleration of Quartz Crystal Oscillator Using Active Inductance Double Resonance and Embedded Triggering Circuit

Low-frequency double-resonance quartz crystal oscillator was developed with active inductance circuit aiming the start-up of stable oscillation of tuning fork-type quartz crystal resonator at 32.768 kHz within 0.37 ms. The initial oscillation is triggered by a part of crystal oscillator forming a CR oscillator. The negative resistance ranges to 4 MΩ at gmf of 4.1 μA/V. In a limited frequency range, the circuit shows negative reactance Ccci = -3.4 pF equivalent to inductance Lcc = 9.8 H. The Allan standard deviation indicated 10-11 to 10-10, showing high stability comparable to general quartz crystal oscillator.

Estimation of Copper, Silver and Gold Coverages on the Iridium Field Emitter Tip Surface

The work described in this paper is a study of the estimation of copper, silver and gold coverages on the iridium field emitter tip surface. The study has been carried out by using a simple field emission microscope designed especially for the purpose of the adsorbate coverage calibration. It was equipped with an iridium field emitter tip. On one side of the microscope was the vapor source 12.5 cm from the tip, and on the other side 16.2 cm from the source was a quartz crystal oscillator. The crystal leads were spot welded to a two-pin tungsten-glass press-seal. In front of the crystal, a nickel shield was mounted in which there was a circular hole of an area of 0.0804 cm2, slightly smaller than the surface of the crystal, to prevent shorting of the conducting ends of the crystal which would be brought about by the condensed metal. The sensing crystal inside the microscope was driven by a small circuit placed just outside the microscope. The driving circuit was in turn connected to another circuit which comprised a frequency comparator unit which could read the frequency of the quartz crystal oscillator before and after the deposition of the adsorbate and gave a direct digital reading of ?(f is the resonance frequency of the crystal before the deposition of the adsorbate and Δf is the difference in the frequency of the oscillator after and before the deposition of the adsorbate on the crystal). The mass added to either side of the crystal alters its resonant frequency. The frequency shift obtained for a certain thickness of the deposited film depends on the density of the deposited film [1] [2].

基于QCM液体密度响应模型测量油品含水率研究

油田开发中一直存在高含水率和低含水率测量不准确的问题,新型可再生的生物柴油,同样需要控制含水率以保证热值和稳定性。文中提出一种基于石英晶体微天平(QCM)液体密度响应模型的油品含水率测量方法,通过5组标准甘油溶液进行模型验证,结果表明,实验值与理论值的误差小于5%,并且在低含水量和高含水量2种情况下,误差幅度小于1%。重复性实验验证了模型的有效性。现场测量实验结果证实了模型的适用性。

石英晶体振荡法测量气体中痕量水的不确定度评定

用氮气中水气体标准物质和内置水分发生器分别校准仪器,测量氮气中痕量水,并对测定结果的不确定度进行评定。不确定度来源主要包括单点线性校准、测量随机效应、影响准确测量的仪器参数和氮气中水气体标准物质4个方面,合成得到相对示值误差的扩展不确定度。当测试点的摩尔分数分别为4.3、51.8、99.7μmol/mol时,采用标准气体校准时相对示值误差的扩展不确定度分别为5.5%、4.4%、5.2%,采用水分发生器校准时相对示值误差的扩展不确定度分别为6.1%、4.8%、6.3%。在测量区间1~100μmol/mol范围内,离校准点越远,单点线性校准引入的不确定度越大,校准曲线的精确度和可信度越差;测试点量值越大,外部物理条件引入的不确定度就越大;不同校准途径对相对示值误差不确定度的影响不大。

加热电流对恒温晶振温度稳定性的影响

通信技术的发展对恒温晶振的小型化需求越来越高。在设计一款小尺寸的恒温晶振时发现,环境温度从-40℃到85℃时,频率曲线一致向上,难以满足±3×10^(-9)频率温度稳定度要求。经分析表明,晶振的加热电流随环境温度而变化,在通过低电导率的接地引线时引起晶振PCB内的地电压波动,进而导致变容管的偏置电压发生变化。采用双地法和补偿法解决了加热电流引起的地电压波动对恒温晶振温度稳定性的影响。

深紫外高透过石英晶体的生长和光学性能表征

照明系统是光刻机的重要组成部分,其主要功能是对激光光束进行扩束、整形和匀光。石英晶体x晶向具有本征双折射特点,以其原理制作的偏振装置可实现对光束偏振态的控制,配合离轴照明,能够进一步提高光刻机照明系统的分辨率和成像质量。受传统石英晶体生长工艺和晶体自范性限制,用于偏振装置的大口径石英波片(>ϕ50 mm)一直是石英晶体研究的难题。本文利用平行定向生长水热工艺,系统调整温度、压力、矿化剂种类和浓度、节流挡板开孔率等参数,成功合成了可用于193 nm波长的高透过率石英单晶,并加工出已知报道的最大尺寸ϕ160 mm石英波片坯料。实验过程中使用改进的框架籽晶法淘汰了可遗传腐蚀隧道缺陷,通过优化原料配比进一步降低Al^(3+)、Na^(+)等微量元素含量,控制升温曲线实现籽晶界面晶格匹配,从而淡化籽晶外延区域均匀性差异。对单晶样品进行微量元素含量、内透过率、双折射性能和光学均匀性表征,结果表明,石英晶体微量元素总含量控制在7×10^(-6)以内,内透过率达到99.80%/mm,双折射率差不均匀性低于0.0297%,ϕ140 mm有效通光口径内光学均匀性PV值达到3.9×10^(-6)。

普通晶体振荡器的关键工序研究

普通晶体振荡器(SPXO)是用量最大的石英晶体器件,其关键生产工序控制对于保障其质量与可靠性具有重要的意义。因此,对SPXO的关键工序进行了研究。首先,介绍了SPXO的结构和加工工序;然后,从中找出3个关键工序,即:被银前的清洗工序、点胶工序和微调工序;最后,介绍了一些由于关键工序未得到有效控制而导致的失效案例和失效分析过程,以使相关研究者更深刻地了解和掌握这些关键工序,从而有效地提高SPXO的总体质量,降低SPXO的失效率。

Analyzing the response of a contactless conductivity detector in capillary electrophoresis by a resonant method

We report a resonant method to measure the wall capacitance（C_w） and solution resistance（R_S） in a capacitively coupled contactless conductivity detector（C^4D）.Under the typical operating conditions in capillary electrophoresis（I.D.50μm,O.D. 360μm,electrode length of 4 mm,electrode gap of 1 mm,frequency of 200 kHz）,the values of C_w measured in 1 and 20 mmol/L NaCl solutions are 2.8 and 32 fF,which are only 1.1%and 12%of prediction by the equation in references,respectively.The value of R_S is less than the prediction in solutions withκ〈0.02 S/m.The response current of C^4D is due to the change in C_w because the total impedance of a C^4D is composed mainly by the impedance from C_w.

基于晶体振荡器的高性能守时方法研究

高精度的授时系统因恒温晶振的实际值和标称值存在一定的偏差,基于高精度恒温晶体振荡器对存储的脉冲数进行均值计算,模拟出高精度的脉冲信号,能够达到1 h以内的守时误差低于250 ns,能够满足授时系统的守时要求。文章针对晶体振荡器的老化参数进行拟合,通过模型对晶振守时方法进行实验,确保晶振守时能够保持在每天500 ns,以此来提升晶体振荡器的保持能力。

石英晶体振荡法监控膜厚研究

给出了石英晶体振荡法监控膜厚的基本原理 ,在相同的工艺条件下分别用光电极值法和石英晶体振荡法监控膜厚 ,对制备的增透膜的反射光谱曲线进行了比较 ,并对石英晶体振荡法的监控结果做了误差分析 结果表明 :石英晶体振荡法不仅膜厚监控精度高 ,而且能监控沉积速率 ,获得稳定的膜层折射率 。

阴极蒸发动态测试研究

为了实现阴极蒸发定量测量,本文发展了一种基于石英晶体振荡原理的动态测试方法。研究表明,在选用高质量石英晶振片和对其进行强制冷却的情况下,既使晶振片近距离承受阴极的高温热辐射,晶振片频率降低趋势仍与阴极蒸发物增加的趋势保持良好的一致性,将单位时间的频率降低量代入公式计算,便可获得阴极蒸发的动态速率。与静态方法相比,这一方法可以提供阴极在蒸发之初的关键信息,因而可以更好地用于指导低蒸发覆膜钡钨阴极的制备。

石英晶体微天平传感器在油品粘度中的应用研究

利用石英晶体微天平传感器开发了一种新的油品粘度监测方法 ,阐明了石英晶体微天平传感器在油品粘度监测中应用的基本原理 ,研制了适合油液环境的传感器探头以及振荡电路 .实验结果表明 ,传感器的频移值与润滑油粘度的平方根值有良好的线性关系 ,利用石英晶体微天平传感器对油品粘度进行监测是很灵敏的 。

石英晶体振荡器的集成化设计

在分析典型的分立式共射共基晶体振荡器原理的基础上,通过建立电路模型,设计一种集成化的石英晶体振荡器.采用电压源电路作为缓冲放大器的基极偏置,去掉容值较大的旁路电容,振荡电路与缓冲放大器电路共用偏置分压电阻,缩短电路起振时间,减小电路版图面积.基于特征尺寸为0.35μm的chrt.35dg_sige工艺库,利用Cadence中的spectre仿真工具对电路进行仿真.结果显示:当电源电压为2.7V时,振荡频率为12.8MHz,起振时间约为1.3ms,输出波形的峰峰值约为0.8V,单边带相位噪声1kHz处为-142dBc/Hz,10kHz处为-150dBc/Hz,整个电路的直流功耗小于2.7mW.

用“负阻”概念设计石英晶体Colpitts振荡电路

由“负阻”概念分析推导出Colpitts石英晶体振荡电路的相位平衡条件和振幅平衡条件,并设计具体振荡电路,给出了实际电路参数。

石英晶体板高频振动的三维有限元分析

通过建立石英晶体板的三维模型,运用有限元分析软件ANSYS获得了石英晶体板厚度剪切振动的振动频率和位移云图。验证了数值计算结果的收敛性并提出了避免振动模态强烈耦合的石英晶体板最佳长厚比的选取方法。模型分析过程中发现,六面体网格比四面体网格易观察到石英晶体板的厚度剪切振动。

压电石英晶体振荡频率检测平台的建立及应用

目的 构建一种 2× 5型压电石英微阵列振荡频率检测平台。方法 利用基频 1 0MHz的 2× 5型石英晶体微阵列作为传感换能器件 ,自行设计自激式振荡频率检测仪、频率分析软件PESA2 .0 ,与计算机连接组成压电石英晶体传感器检测平台 ,并应用于气、液相检测。结果 石英晶体微阵列在气、液相起振能力强 ,并获得稳定振荡 ,气相稳定度可达± 1Hz ,液相≤ 2Hz。消除了温度、电离辐射、机械震动等因素的干扰 ;实现了频率信号检测的自动化、微机化和自能化。结论 该检测平台具有检测频率稳定、自动化和智能化程度较高、能实时检测等优点 ,是一种新型压电晶体振荡频率检测共用平台 。

光控-晶控相结合的膜厚监控法对滤光片膜厚的研究

针对光电极值法和石英晶振法各自的弊端,结合两种方法提出了光控-晶控膜厚监控法.在相同工艺条件下,分别使用这三种方法监控905nm窄带滤光片（规整膜系）和830nm截止滤光片（非规整膜系）的膜厚,对制备的滤光片的透射率光谱曲线进行比较.结果表明,光控-晶控膜厚监控法除了各项指标都符合要求外,在曲线通带处获得的平均透过率值比光电极值法和石英晶振法获得的平均透过率值提高了3%～6%,且与理论光谱基本吻合,光谱特性最好.该方法不仅对规整和非规整膜系都能进行监控,且能有效降低膜厚误差,提高光谱特性.

高频高精度石英晶体元件电参数测量技术研究

在介绍π网络法石英晶体元件电参数测量原理的基础上，设计了一种频率高达200MHz的石英晶体元件电参数测量系统，分析了石英晶体元件和π网络的等效电路，采用自动网络分析方法计算出石英晶体元件的阻抗，并依次消除了系统误差和测量误差。实验证明，在1～200MHz频率范围内，系统对串联谐振频率测量误差在±1×10^-4以内，重复测量一致性在±0．5×10^6以内。