基于晶体管的自动增益控制技术研究

针对传统的自动增益控制方式电路复杂、成本偏高的情况,设计了基于晶体管的自动增益控制方案,包括双晶体管控制方式和单晶体管控制方式,对其工作原理进行了分析。在电路设计环节,推导了基于级联AD603的大动态可变增益放大器(VGA)模型,设计了具体的反馈控制电路。给出了实际电路的测试数据,并对测试结果进行了分析。对这2种控制方式进行了比较,并对特点进行了说明。     

基于AD6652数字下变频模块的实现

提出了数字接收机基于AD6652的宽中频采样结构,使整个系统的灵活性、重构性、适应性得到很大的提升.AD6652采用矩阵输入,输入灵活,减少交叉连接产生的寄生信号,同时可以根据应用的不同在抽取滤波后进行多相合并,增加带宽.通过理论分析和仿真检验表明,该系统性能优良,结构简单,易于实现,具有实际应用价值.     

A test to determine the nature and presence of the memory effect columns packed with the amylose tris(3,5-dimethylphenylcarbamate) stationary phase

Acid/base mobile phase modifiers affect enantioseparations in ways that are not fully understood yet, for the lack of systematic studies. This makes chiral analysis of some pharmaceuticals difficult to reproduce. Once a column has been exposed to a modifier, the selectivity of certain pairs of enantiomers may change, for the better or the worse. We study the behavior of five enantiomeric pairs, three which are highly sensitive to the addition of certain modifiers and two that have little sensitivity to these modifiers. Their use permits the determination of the extent of the memory effect response on individual columns. The selectivity of 4-chlorophenylalanine methyl and ethyl ester, and of ketoprofen improve as a solution of ethanesulfonic acid is percolated through the column. As a result, these pairs are most useful for the determination of the extent of acid memory effect on a column. The selectivity of propranolol HCl and, to a lesser degree, Tröger's base increases as a solution of diisopropylethylamine is percolated through the column. The separation of each one of these five pairs is inversely affected by the percolation of the opposite acid/base solution. We used trans-stilbene oxide (TSO) as a ‘standard’ to determine the column stability because no memory effect is observed for it (its retention, enantioselectivity, and resolution remain constant). Understanding whether a column is under the influence of the memory effect is critical to both the analysis of pharmaceutical ingredients and to the development of preparative purification techniques for racemic mixtures. Thus, columns that were unreliable for method development and method transfer, due to the memory effect and a lack of proper solvent exposure records, can now be used.     

基于质谱检测的相关色谱技术在阿尔茨海默病诊断中的应用

随着世界老年人口的急速增长,阿尔茨海默病发病人数也逐年增多,已成为继心脑血管疾病和恶性肿瘤之后威胁人类健康的“第三大杀手”。疾病的诊断和治疗同等重要,阿尔茨海默病诊断通常依靠典型的临床特征、神经影像技术以及检测疾病相关的生物标志物等。近些年来蛋白质组学和质谱技术迅速发展,可以利用这些技术寻找到与疾病相关的特异性的蛋白质分子作为早期诊断的生物标志物。本文就此进行了综述,主要包括基于蛋白质组学的诊断标志物的筛选和基于质谱检测的色谱技术在阿尔茨海默病诊断中的应用,引用文献34篇。     

宽量程智能射频功率检测系统研究

介绍了一种基于数字衰减器HMC274及功率-电压转换芯片AD8362的新型宽量程射频信号功率检测系统;利用微控制器STC12C5A60S2控制HMC274的衰减值,确保被测信号的功率真值在AD8362的线性转换范围内,从而使量程上限提高了31 dB;并通过GSM模块TC35i和LCD显示模块,分别实现了对功率值的远程和近程检测;经过对900 MHz射频信号的实验测试和数据拟合,功率真值量程扩大到了-50～+40 dB,输出灵敏度为50 mV/dBm。     

变形镜驱动器参数自动标定系统的设计

变形镜驱动器各通道的offset参数和gain参数直接影响到变形镜驱动器输出电压的精度,采用人工方式对其进行标定,不仅效率低,费时费力,而且参数的一致性也无法得到保证。为此,首先设计了AD采集器,其内部仅含一片24bit的高精度AD采集芯片,其并行的16端子输入接口通过继电器与采集芯片相连,内含的微处理器负责完成输入通道切换、采集时序控制和采集数据上传等功能;同时,还设计了上位机应用程序,实现了对变形镜驱动器以及AD采集器通信链路检查、标定过程控制参数设置、采集通道切换以及数据处理等相关操作命令和状态数据的收发,使得变形镜驱动器、AD采集器和上位机组成一套驱动器参数自动标定系统。结果表明,该系统不仅使得一套变形镜驱动器参数标定时间由原来的两个工作日缩短到2小时左右,而且提高了参数标定精度和一致性,其96通道零电压的最大误差由18.2mV降为13.5mV,均方差由原来的6.2mV降低为4.3mV,其输出最高电压120.000V的最大误差由23.4mV降为17.5mV,均方差由原来的10.1mV降低为8.3mV。     

Isoprenoid quantitation in human brain tissue: a validated HPLC–fluorescence detection method for endogenous farnesyl- (FPP) and geranylgeranylpyrophosphate (GGPP)

Farnesyl- and geranylgeranylpyrophosphate (FPP and GGPP) are isoprenoid intermediates in the mevalonate pathway. They play a crucial role in cell survival, growth and differentiation due to their attachment (isoprenylation) to small GTPases (Ras, Rho, etc.). Isoprenoid formation seems to be tightly regulated within the mevalonate pathway and its perturbation has been linked to certain diseases (e.g., cancer, Alzheimer's disease), but tissue levels are unknown. It is therefore of the utmost importance to quantify these isoprenoids in diseased tissue or in tissue after drug administration. The current work describes an isolation procedure utilizing a combination of Extrelut(R) liquid/liquid and reversed-phase solid-phase extraction (SPE) for homogenized human frontal cortex tissue. In addition, after a careful validation of an HPLC-fluorescence method, this assay allowed the determination of nanomolar concentrations of endogenous FPP and GGPP levels (4.5 and 10.6 ng/mg protein, respectively) in human brain tissue. The method is selective, precise (<15% RSD), accurate (<15% relative error) and sensitive over a linear range of 10-400 ng/mL for FPP and 50-1000 ng/mL for GGPP according to the current FDA criteria for bioanalytical method validation. Overall, this new method introduces the ability to simultaneously quantify FPP and GGPP in human brain tissue, and is potentially applicable to several other tissues and species.     

SPR生物传感器测定Aβ(1-40)与Cu(Ⅱ)结合的探索

采用表面等离子共振(SPR)生物传感器,分别固定Aβ及其单克隆抗体于传感芯片表面,实时监测Aβ与Cu(Ⅱ)混合前后与Aβ单抗体特异的结合过程,及Cu(Ⅱ)与Aβ亲和结合及解离情况.结果显示:Cu(Ⅱ)影响Aβ与Aβ单抗体的特异结合能力,加入Cu(Ⅱ)后Aβ不能与Aβ单抗体起特异免疫结合反应;Aβ与Cu(Ⅱ)的结合过程为快结合快解离的动力学过程.     

Liquid chromatographic separation and thermodynamic investigation of stereoisomers of darunavir on Chiralpak AD‐Hcolumn

Liquid chromatographic separation of stereoisomers of darunavir on Chiralpak AD‐H, a column containing the stationary phase coated with amylose tris(3,5‐dimethylphenylcarbamate) as a chiral selector, was studied under normal‐phase conditions at different temperatures between 20 and 50°C. The effect of quality and quantity of different polar organic modifiers viz: methanol, ethanol, 1‐propanol, and 2‐propanol in the mobile phase as well as column temperature on retention, separation, and resolution was investigated and optimized. The optimum separation was accomplished using a mobile phase composed of n‐hexane/ethanol/diethyl amine (80:20:0.1 v/v/v) at 40°C. Apparent thermodynamic parameters ΔH⁰ and ΔS* were derived from the Van't Hoff plots (lnk′ versus 1/T) and used to explain the strength of interactions between the stereoisomers and amylose tris(3,5‐dimethylphenylcarbamate) coated chiral stationary phase.     

AD7793在高精度温控设备中的应用

文章介绍了Σ-Δ型ADC转换器AD7793的特点、工作原理和应用,其中包括ADC的接口电路设计、PCB设计以及MCU通过SPI接口对AD7793进行初始化配置等,同时给出了温控设备的实测结果。