基于压电免疫凝聚的霍乱毒素检测

考察了压电免疫凝聚方法对霍乱毒素的检测:金电极表面自吸附的霍乱毒素抗体和检测池中自由分布的霍乱毒素抗体在霍乱毒素出现时发生凝聚,形成网状交联结构,改变了溶液体系的密度和粘度,产生频率响应.实验结果验证了压电免疫凝聚原理的正确性.且显示本方法具有操作简便,组装步骤少,对霍乱毒素检测具有较明显的线性范围(2～4 mg/L)和较低的检测限(1.65 mg/L)及较好的选择性.有望用于霍乱毒素的快速检测.     

基于等离子体聚合膜的压电免疫传感器检测HSA抗体的活性

先在石英晶振(QCM)上沉积正丁胺等离子体聚合膜(PPF),再自组装一层聚电解质,得到一个可吸附固定人血清白蛋白(HSA)和易于晶振再生的界面,构造了一种简便、快速、准确、可逆的测定HSA抗体的压电免疫传感器,用于免标记和非纯化的条件下实时检测白蛋白抗体的活性(效价),极大地简化了传统检测方法中需标记和纯化抗体的繁琐步骤.探讨了晶振包被白蛋白时溶液的pH值、离子强度和白蛋白浓度以及免疫反应温度等条件的影响;考察了传感器的响应性能和再生性能,并与文献上表面等离子共振法(SPR)进行了比较.结果表明,该压电传感技术能较好地满足生化实验室直接检测抗体活性(效价)的要求,也是鉴定抗体类型、筛选杂交瘤以及筛选特效性药物的一种实用装置.     

石英晶体谐振频率测量系统

在石英晶振的生产过程中,切割后的晶振片需要对其共振频率进行快速测量,并通过机械手按频率分选。本文介绍了一种结合单片机、直接数字频率合成器(DDS)和增益鉴相器的简单石英晶振共振频率检测系统,利用晶振阻抗随激励信号频率而变化的特性,在100ms内测得其共振频率,控制成本的同时保证了一定的测量精度。     

玻璃体系对铜浆性能的影响

本文采用熔融-水淬法制备了SiO2-B2O3-Bi2O3、SiO2-B2O3-ZnO和SiO2-B2O3-CaO 3种体系的无铅玻璃粉,根据玻璃粉的XRD和差热分析结果,分析并讨论了玻璃析晶、成玻化程度及玻璃转化温度Tg对铜浆性能的影响,并通过SEM观察了铜膜的表面形貌,验证了以上分析。结果表明:SiO2-B2O3-CaO体系的无铅玻璃粉具有良好的成玻性和合适的玻璃转化温度,采用该体系作为铜浆的玻璃相,铜浆性能较好。     

智能电能表用晶振检测方法研究

智能电能表主要用途是计量电能,是供用电之间结算电费的依据。电能计量的关键参数之一是时间,而智能电能表内置晶振是产生时间的关键元件,其准确性和可靠性直接关系到智能电能表的计量是否公平、公正和准确。本文收集了国内外同晶振检测相关的标准,针对晶振的特性确定了电参数、机械特性参数和环境温度参数的检测方法,并对不同厂家的晶振进行了测试分析,验证了检测方法的正确性和实施性。     

基于酪胺电聚合膜和纳米金自组装界面的甲状腺激素压电免疫传感器的研究

本文提出了一种结合酪胺聚合膜和纳米金为界面的甲状腺激素压电免疫传感器.先在晶振表面电聚合一层酪胺聚合膜,然后通过聚酪胺一端的氨基和纳米金之间的作用力在聚合膜表面自组装一层纳米金,再在纳米金上固定T4抗体,实现对T4的检测.考察了一些实验条件,如免疫反应时间,抗体浓度等对传感器响应性能的影响,该传感器对T4在1.0～97.7 μg/dL范围具有很好的线性响应,并将此传感器与采用戊二醛交联法和半胱氨吸附界面的传感器进行了比较.     

飞机刹车半实物仿真机轮速度信号模拟装置的设计

受器件老化、随机噪声等因素影响,晶振频率变化较复杂。以GPS秒脉冲作为测量标准,构建了晶振频率随时间变化的测量系统,通过对测量数据进行一元回归统计处理,分离出了晶振实际频率与其标称频率的相对偏差及晶振的各种随机误差,并分析了这两种误差对晶振准确度及稳定度的影响。该方法可为频率源误差测量分析提供借鉴作用。     

晶振频率偏差补偿的无线传感器网络时间同步算法

节点间存在的晶振频率偏差是引起时间漂移的最主要原因,针对这个问题,本文提出一种基于晶振频率偏差补偿的时间同步算法,该算利用相邻两次同步过程中记录的时间估算出了与时间基准节点间的晶振频率偏差,并根据晶振频率偏差和双向报文交换模型对时间偏移进行了补偿.试验结果表明,该算法大大提高了同步精度.     

基于胱胺自组装膜和SiO2纳米颗粒增强效应的日本血吸虫压电免疫传感器的研究

提出了一种基于胱胺自组装膜和SiO2纳米颗粒增强效应的生物分子固定法,并将之用于日本血吸虫压电免疫传感器的研究.所制备的SiO2纳米颗粒具有生物亲和性高和比表面积大等优良理化性能,经表面功能化后可高效键合日本血吸虫抗原(SjAg)分子,制得敏化的SjAg@SiO2颗粒.将SjAg@SiO2固定于修饰了胱胺自组装膜的石英晶体表面,发展了一种新型压电免疫传感器,用于日本血吸虫抗体(SjAb)的检测.实验结果表明,SiO2颗粒的纳米三维(3D)空间结构有利于所固定的抗原对抗体的识别,进而获得了对目标物SjAb的高灵敏检测.所研制的传感器检测感染兔血清样中SjAb浓度的线性范围为0.6～22.7 μg/mL,检测下限为0.4 μg/mL(S/N=3).此外,临床实际样品的分析结果表明,该免疫传感技术的分析检测能力与经典酶联免疫法(ELISA)相接近,可望用于血吸虫病临床生化诊断、现场筛查和疫情监控等.     

基于壳聚糖包埋二氧化硅-亚甲基蓝纳米复合物的电流型癌胚抗原免疫传感器的研究

合成了一种新型的SiO2-亚甲基蓝(SiO2-MB)纳米复合物.SiO2-MB纳米复合物具有不同于一般的纳米SiO2的性质,它能将MB的电子转移到电极表面,而且更重要的是减小了MB的渗漏.SiO-MB纳米复合物作为免疫传感器的媒介体使用,并采用壳聚糖(CS)包埋此复合物形成CS-SiO2-MB复合膜滴涂于洁净的玻碳电极(GCE)表面,然后在复合膜的表面固定纳米金(nano-Au)并吸附癌胚抗体(anti-CEA),制备出了性能良好的电流型免疫传感器.通过循环伏安考察了电极的电化学特性,并采用透射电子显微镜(TEM)对SiO2-MB纳米复合物的微观结构进行了表征.在最优条件下,该传感器在癌胚抗原(CEA)浓度为1～80 ng/mL范围内有良好的线性关系,检测下限为0.3 ng/mL(3倍信噪比).而且,该传感器制作简单,检测快速,稳定性较好.     

Multi-scale molecular dynamics study of cholera pentamer binding to a GM1-phospholipid membrane

The AB₅ type toxin produced by the Vibrio cholerae bacterium is the causative agent of the cholera disease. The cholera toxin (CT) has been shown to bind specifically to GM1 glycolipids on the membrane surface. This binding of CT to the membrane is the initial step in its endocytosis and has been postulated to cause significant disruption to the membrane structure. In this work, we have carried out a combination of coarse-grain and atomistic simulations to study the binding of CT to a membrane modelled as an asymmetrical GM1-DPPC bilayer. Simulation results indicate that the toxin binds to the membrane through only three of its five B subunits, in effect resulting in a tilted bound configuration. Additionally, the binding of the CT can increase the area per lipid of GM1 leaflet, which in turn can cause the membrane regions interacting with the bound subunits to experience significant bilayer thinning and lipid tail disorder across both the leaflets.     

基于金纳米颗粒免疫凝集的压电传感技术快速检测人血清免疫球蛋白IgG

发展了一种利用金纳米颗粒免疫凝集的压电传感技术用于人血清免疫球蛋白IgG的简单、快速、高灵敏检测.以金纳米颗粒替代传统胶乳标记羊抗人IgG诊断血清(抗IgG),利用石英晶体微天平(QCM)直接灵敏响虚因金纳米颗粒免疫凝集而引起溶液的非质量参数(密度、粘度等)的变化.考察了pH值、离子强度和抗IgG-金纳米颗粒浓度对免疫凝集反应的影响,并进行了质控实验.结果表明,该传感技术毋需固定活性组分,可快速榆测浓度下限0.38μg/mL的免疫球蛋白IgC.定量能力与经典ELISA法相接近,可基本满足临床疾病诊断的生化检测要求.     

Au纳米粒子修饰纳米片状结构衬底的SERS研究

通过电化学共沉积和化学脱合金处理在金属W片上制备了纳米片状基底,将Au纳米粒子通过等离子溅射到纳米片状基底上得到表面增强拉曼散射(SERS)衬底。采用扫描电子显微镜(FE-SEM)、能谱仪(EDX)对复合纳米衬底进行表征,罗丹明6G作为探测分子对SERS衬底的拉曼表面增强效果进行检测。通过实验发现:三维空间结构的纳米片状结构具有拉曼表面增强效应,溅射Au纳米颗粒得到的Au纳米片衬底信号增强效果显著。     

Direct Fabrication of Nanoscale Light Emitting Diode on Silicon Probe Tip for Scanning Microscopy

We have fabricated a silicon microprobe integrated with a nanometer-sized light emitting diode (Nano-LED) on the tip. This paper describes the fabrication procedure and preliminary topographic testing results. The silicon probe with electrode pattern was made by wet-etching a silicon-on-insulator wafer using oxide as the mask. Subsequently, the probe tip was cut using a focused ion beam (FIB) to form a 150 nm-wide gap. Semiconductor nanoparticles (CdSe/ZnS core-shell nanoparticles) were electrostatically trapped and excited within the electrode gap made on the probe tip. The LED-tip is approximately 150 nm 150 nm. The nano-LED light intensity and current were measured as a function of the driving voltage up to 25 V. In addition to the electroluminescence peaks from the CdSe particles, possible emission from silicon dioxide doped in the FIB milling process was also observed in the measured spectra. Basic mechanical characteristics of the silicon probe were measured by mounting the probe on a tuning fork in a standard near-field scanning optical microscopy (NSOM) set up. It was observed that the drag force reduces the probe oscillation as the vibrating tip approached the near-field of the sample surface. The topographic images of a chromium test pattern on a glass substrate were successfully acquired by keeping the probe tip within roughly 5 nm from the sample surface. Although the probe tip shape and the location of the Nano-LED are yet to be further optimized before realizing near-field optical scanning experiment, the result showed its great promise as a new type of NSOM tip with the ldquoon-proberdquo light-source.     

Fiber-optic chemical and biochemical probes based on localized surface plasmon resonance

A novel reflection-based localized surface plasmon resonance fiber-optic probe for chemical and biochemical sensing is reported. The sensor is based on intensity measurement of the internal reflected light at a fixed wavelength from an optical fiber where the extinction cross-section of self-assembled gold nanoparticles on the unclad portion of the optical fiber changes with different refractive index of the environment near the gold surface. The reflection-based localized surface plasmon resonance fiber-optic probe has been shown to be capable of direct sensing of the “spectroscopically silent” Ni²⁺ ion and label-free detection of streptavidin and staphylococcal enterotoxin B at the picomolar level.     

Surface plasmon resonance of metal nanoparticles for interface characterization

This paper demonstrates three cases of simple analytical classical Maxwell-Garnett model to estimate the size and concentration of silver and gold nanoparticles and their interface. The examples show that the model can satisfactorily interpret the spectral properties of ISTC and, in particular, to determine the presence and thickness of the shell on the surface of metallic nanoparticles in colloidal solution, and their interface in porous glass and complex colloidal solutions. The results can be used to study the optical properties of heterogeneous systems with metal nanoparticles, including the evolution of biological systems in vivo and the type of interaction precious metal nanoparticles with biological objects. The text was submitted by the authors in English.     

基于氧化石墨烯/金纳米粒子放大电信号的二茂铁标记型溶菌酶适体传感器

设计了一种简单的信号衰减型电化学溶菌酶适体传感器。以氧化石墨烯修饰的玻碳电极为基底（GO/GCE）,通过循环伏安法电沉积金纳米粒子在电极表面,得到AuNPs/GO/GCE。将3’端修饰巯基的单链DNA通过金硫键共价连接于电极上,而在与前者可部分杂交的适体探针链5’端标记上二茂铁甲酸。当目标物溶菌酶与适体探针链发生特异性结合,通过示差脉冲伏安法检测到二茂铁甲酸还原峰电流相应的改变,从而实现对溶菌酶的识别及定量检测。结果表明,该传感器对溶菌酶具有较好的选择性和灵敏度,对于溶菌酶的检测范围为1.08×10-11～1.08×10-8mol/L,检出限达到6.02×10-12mol/L。     

Magnetohydrodynamic three-dimensional flow of nanofluids with slip and thermal radiation over a nonlinear stretching sheet: a numerical study

A numerical simulation for mixed convective three-dimensional slip flow of water-based nanofluids with temperature jump boundary condition is presented. The flow is caused by nonlinear stretching surface. Conservation of energy equation involves the radiation heat flux term. Applied transverse magnetic effect of variable kind is also incorporated. Suitable nonlinear similarity transformations are used to reduce the governing equations into a set of self-similar equations. The subsequent equations are solved numerically by using shooting method. The solutions for the velocity and temperature distributions are computed for several values of flow pertinent parameters. Further, the numerical values for skin-friction coefficients and Nusselt number in respect of different nanoparticles are tabulated. A comparison between our numerical and already existing results has also been made. It is found that the velocity and thermal slip boundary condition showed a significant effect on momentum and thermal boundary layer thickness at the wall. The presence of nanoparticles stabilizes the thermal boundary layer growth.

     

Novel 3D manufacturing method combining microelectrial discharge machining and electrochemical polishing

This paper reports on the potential of microelectrical discharge machining (μEDM) as an innovative method for the fabrication of 3D microdevices. To demonstrate the wide capabilities of μEDM two different microsystems—a microfluidic device for the dispersion of nanoparticles and a star probe for microcoordinate metrology—are presented. To gain optimized process conditions as well as a high surface quality an adequate adaption of the single erosion parameters such as energy, pulse frequency and spark gap has to be carried out and is discussed below. Thus, a surface roughness of R_a?=?80?nm is achieved at the channel bottom. The fabricated stylus elements for the star probe have sphere diameters of 40–200?μm. For further surface quality enhancement a subsequent electrochemical polishing step is investigated. In case of the dispersion micromodule a combined process chain of μEDM-milling and electropolishing has reached a surface improvement above 70%.     

Estimating cholera risk from an exploratory analysis of its association with satellite-derived land surface temperatures

Occurrence and growth of Vibrio cholerae, the causative agent of cholera, is linked to modalities of elevated temperatures and heavy precipitation. Previous studies have employed temperature- and satellite-derived precipitation data to determine the risk of cholera, but predictions were limited because of the coarse spatial resolution of temperature data (about 50 km). Cholera estimation has a severe impact on those in vulnerable regions with marginal civil infrastructure and those suffering additional damage after a natural disaster. In this study, a new remote-sensing data-based algorithm is proposed that includes a pathway to associate coarse-resolution cholera prediction with high-resolution land surface temperature (LST) dataset. The algorithm allows identification and prediction of regions with elevated risk of cholera at least four weeks in advance. Additionally, it employs a hierarchical structure comprising long-term anomalous LST values to determine hot spots of potential Vibrio cholerae. The algorithm was tested in five cholera epidemic regions of Sub-Saharan Africa (Mozambique, Central African Republic, Cameroon, South Sudan, and Rwanda), with realistic accuracy in demarcating regions where human cholera cases had been reported.