一种基于脱氧核酶的铅离子电致化学发光传感器

本文设计了一种基于脱氧核酶(DNAzyme)检测Pb2+的电致化学发光(Electrocheluminescent,ECL)传感器。将对Pb2+特异性识别的DNAzyme通过金-巯键固定于金电极表面,并与标记有二氧化硅包埋的钌联吡啶(Ru-SNPs)的底物DNA链发生杂交,形成双链DNA(ds-DNA)传感器。Pb2+不存在时,由于Ru-SNPs靠近电极表面,产生强的ECL信号。当Pb2+存在时,DNAzyme催化底物链断裂,Ru-SNPs远离电极表面,导致ECL信号下降。实验结果表明ECL强度与Pb2+浓度在0.2-1.0 nmol/L范围内呈良好的线性关系,检测限可达0.04 nmol/L,其他二价金属离子对其基本无干扰。     

基于MEMS光线引入器的太阳敏感器技术

太阳敏感器是卫星等航天器上的重要姿态测量部件,其原理是测量太阳光线和敏感器本体主轴的夹角,近而确定卫星的指向.随着MEMS技术和高精度图像传感器技术的发展,将MEMS光线引入器阵列和APS(Active Pixel Sensor)图像传感器技术进行组合,在不增加系统的质量和功耗的情况下通过多个成像阵列来降低系统的随机误差,提高成像中心位置的准确性,从而将太阳敏感器的测量精度提高一个量级.同时采用图像预测提取相关算法(Future Extraction and Image Corre-lation-FEIC),提高了系统的鲁棒性,在部分小孔受到堵塞等干扰情况下,依然保证系统正常工作,精度上基本上不受影响.传统的太阳敏感器一般采用单孔式光线引入器和CCD等方案来实现的,精度比较低.这种新设计思路和实现方法为太阳敏感器系统的可靠性提供了重要保障.     

Triggered polycatenated DNA scaffolds for DNA sensors and aptasensors by a combination of rolling circle amplification and DNAzyme amplification

The concept of triggered polycatenated DNA scaffolds has been elegantly introduced into ultrasensitive biosensing applications by a combination of rolling circle amplification (RCA) and DNAzyme amplification. As compared to traditional methods in which one target could only initiate the formation of one circular template for RCA reaction, in the present study two species of linear single-stranded DNA (ssDNA) monomers are self-assembled into mechanically interlocked polycatenated nanostructures on capture probe-tagged magnetic nanoparticles (MNPs) only upon the introduction of one base mutant DNA sequence as initiator for single-nucleotide polymorphisms (SNPs) analysis. The resultant topologically polycatenated DNA ladder is further available for RCA process by using the serially ligated circular DNA as template for the synthesis of hemin/G-quadruplex HRP-mimicking DNAzyme chains, which act as biocatalytic labels for the luminol-H(2)O(2) chemiluminescence (CL) system. Notably, the problem of high background induced by excess hemin itself is circumvented by immobilizing the biotinylated RCA products on streptavidin-modified MNPs via biotin-streptavidin interaction. Similarly, a universal strategy is contrived by substitutedly employing aptamer as initiator for the construction of polycatenated DNA scaffolds to accomplish ultrasensitive detection of proteins based on structure-switching of aptamer upon target binding, which is demonstrated by using thrombin as a model analyte in this study. Overall, with two successive amplification steps and one magnetic separation procedure, this flexible biosensing system exhibits not only high sensitivity and specificity with the detection limits of SNPs and thrombin as low as 71 aM and 6.6 pM, respectively, but also excellent performance in real human serum assay with no PCR preamplification for SNPs assay. Given the unique and attractive characteristics, this study illustrates the potential of DNA nanotechnology in bioanalytical applications for both fundamental and practical research.     

An electric sensor based on the electrogyration effect in a lead tungstate crystal

We present original results of an investigation of the specific features of optical electrochirality (electrogyration) in a lead tungstate crystal. Since this crystal exhibits neither the Pockels effect nor the inverse piezoelectric effect, the electrogyration effect can be used to create a fast-response electric sensor for remote monitoring of high-speed processes in high-voltage electric networks. A fiber-optic sensor prototype has been manufactured using optical elements intended for fiber communications.     

Electrochemical biosensor for detection of adenosine based on structure-switching aptamer and amplification with reporter probe DNA modified Au nanoparticles

In the present study, an electrochemical sensing strategy for highly sensitive detection of small molecules was developed based on switching structures of aptamers from DNA/DNA duplex to DNA/target complex. A gold electrode was first modified with gold nanoparticles (AuNPs), and thiolated capture probe was immobilized onto the electrode via sulfur-gold affinity. Then, a "sandwich-type" strategy was employed, which involved a linker DNA containing antiadenosine aptamer sequence and reporter DNA loaded on AuNPs. In the presence of adenosine, the aptamer part bound with adenosine and folded to the complex structure. As a result, the reporter probes together with AuNPs were released into solution and reduced a decrease in peak current. With the enhancement effect of AuNPs, a detection limit as low as 1.8 x 10(-10) M for adenosine was achieved. The sensor exhibited excellent selectivity against other nucleosides and could be used to detect adenosine from real human serum samples.     

Crossbar demultiplexers for nanoelectronics based on n-hot codes

Demultiplexers are expected to be key components in interfacing submicrometer-scale and nano-scale electronic circuits. Designing them is challenging because most nanoarchitectures are limited to simple regular structures, such as crossbars, and nanoelectronic circuits in general are likely to be plagued with relatively high hard-defect and soft-error rates. Previous work has shown how linear codes can be used to design defect-tolerant demultiplexers using resistor or diode crossbars. We extend those results with nonlinear codes, constructing resistor and diode crossbar-based demultiplexers that have better electrical characteristics and defect tolerance for a given area of the nano substrate, at the cost of more complex address encoding circuitry.     

Resistor-logic demultiplexers for nanoelectronics based on constant-weight codes

The voltage margin of a resistor-logic demultiplexer can be improved significantly by basing its connection pattern on a constant-weight code. Each distinct code determines a unique demultiplexer, and therefore a large family of circuits is defined. We consider using these demultiplexers for building nanoscale crossbar memories, and determine the voltage margin of the memory system based on a particular code. We determine a purely code-theoretic criterion for selecting codes that will yield memories with large voltage margins, which is to minimize the ratio of the maximum to the minimum Hamming distance between distinct codewords. For the specific example of a 64 × 64 crossbar, we discuss what codes provide optimal performance for a memory.     

Electrochemical sensor for ranitidine determination based on carbon paste electrode modified with oxovanadium (IV) salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicyllideneiminato)oxovanadium (IV) complex ([VO(salen)]) as well as its application for ranitidine determination are described. The electrochemical behavior of the modified electrode for the electroreduction of ranitidine was investigated using cyclic voltammetry, and analytical curves were obtained for ranitidine using linear sweep voltammetry (LSV) under optimized conditions. The best voltammetric response was obtained for an electrode composition of 20% (m/m) [VO(salen)] in the paste, 0.10 mol L^? 1 of KCl solution (pH 5.5 adjusted with HCl) as supporting electrolyte and scan rate of 25 mV s^? 1. A sensitive linear voltammetric response for ranitidine was obtained in the concentration range from 9.9 × 10^? 5 to 1.0 × 10^? 3 mol L^? 1, with a detection limit of 6.6 × 10^? 5 mol L^? 1 using linear sweep voltammetry. These results demonstrated the viability of this modified electrode as a sensor for determination, quality control and routine analysis of ranitidine in pharmaceutical formulations.     

Electrochemical method for quantitative determination of trace amounts of lead

An ultrasensitive chronoamperometric method for quantitative determination of trace amounts of lead (down to 20 ppb) in acidic solutions is proposed in this paper. The method is based on observations that a complete underpotentially deposited (UPD) lead layer inhibits the electroreduction of nitrate on a bare Cu(111) electrode. To asses the limits of the method, both the electroreduction of nitrate and UPD of lead monolayer on copper single (111) and polycrystalline electrodes in perchloric acidic solution are studied by means of cyclic voltammetry, chronoamperometry, and rotating disk electrode (RDE) experiments. It is found that an inexpensive polycrystalline copper electrode is sensitive enough for analytical detection of lead traces in electrolytes down to 1 x 10(-8) M. Analytical results obtained by the proposed method in 2 orders of magnitude concentration range are compared to atomic absorption spectroscopy measurements to evaluate and assess the sensitivity of the employed experimental protocol. The excellent match between both analytical approaches validates the applicability of the proposed method.     

Electrochemical sensor for measurement of urea and creatinine in serum based on ac impedance measurement of enzyme-catalyzed polymer transformation.

Enzyme-catalyzed polymer transformation with electrochemical ac impedance detection has been employed for the measurement of urea and creatinine in serum samples. A polymer, based on poly(methylvinyl ether)/maleic anhydride modified by esterification with n-octanol, which is stable at pH 7.4 and which is transformed rapidly in response to alkaline pH changes, was linked to enzymatic reactions between urease and urea or creatinine deiminase and creatinine to produce a disposable sensor system. The polymer was screen-printed onto interdigitated screen-printed carbon electrodes and the electrodes overlaid with absorbent pads containing the relevant enzyme. Application of serum samples, "spiked" with either urea or creatinine, resulted in rapid polymer transformation, and resultant changes in the capacitance of the polymer-coated electrodes were analyte-concentration dependent. Additional information on the mechanisms of polymer transformation was obtained from dynamic quartz crystal microbalance measurements.     

基于Spinal码的编码协作

针对5G的高速率传输需求,研究了基于Spinal码的编码协作。基于Spinal码的无速率性,提出了直接选用不同通道内所有编码符号实现编码协作的CC-SPSC方案。在此方案基础上,考虑基站在设备条件和中心调度方面的优势,引入以基站为控制核心的策略,提出了CC-SPSC-BSC-AL方案和CC-SPSC-BSC-SR方案。仿真结果表明,所提方案在模拟信道和数字信道下均有显著的误码率性能提升,尤其是CC-SPSC和CC-SPSC-BSCSR方案,分别在模拟信道和数字信道下的应用优势突出。     

Bifunctional colorimetric oligonucleotide probe based on a G-quadruplex DNAzyme molecular beacon

A label-free bifunctional colorimetric oligonucleotide probe for DNA and protein detection has been developed on the basis of a novel catalytic molecular beacon consisting of two hairpin structures and a split G-quadruplex DNAzyme in the middle. The two loops of this molecular beacon consist of thrombin aptamer sequence and the complementary sequence of target DNA, which are utilized to sense single-stranded DNA and thrombin. The G-quadruplex DNAzyme can effectively catalyze the H(2)O(2)-mediated oxidation of 3,3',5,5'-tetramethylbenzidine sulfate to generate colorimetric signal. Upon addition of the target, the DNA or protein combines with one loop of the hairpin structures, and meanwhile drives the middle G-quadruplex DNAzyme to dissociate. This results in a decrease of catalytic activity, enabling the separate analysis of DNA and thrombin.     

Electrochemical migration of lead free solder joints

Electrochemical migration (ECM) tests on lead bearing and lead free solder joints on Cu lamination on FR-4 board were conducted by applying constant voltage. This paper first studied the ECM of the soldered joints under distilled water after removing the fluxes. In addition, conditions under high temperature and high humidity were also set up to investigate the changes of the initial surface insulation resistance (SIR) with the residues of no clean fluxes. It is found under distilled water that dendrites of the solder joints take on different morphologies with the different migration elements. For the joints of Sn-37Pb and Sn-36Pb-2Ag solders, the main migration element is Pb. While that of Sn-3.5Ag and Sn-4Ag-0.5Cu solders, it is Cu that usually migrates and forms dendrites due to the poor wettability of the solder paste leads to part exposure of Cu substrate at the wetting brim. For Sn-3Ag-0.5Cu solder joints, Sn leads the migration. While for Sn-Zn-Bi solder joints, it is always Zn to migrate which means Zn is more mobile than Cu. The investigation on SIR shows the fluxes have great effect on the migration behavior. The failure time of the joints with the same solder alloy compositions have different failure time due to the different fluxes. The effect of the wettability and the role of Cu substrate on the ECM behavior of the solder joints are discussed in detail.     

基于校验式判决的LDPC码编码的HARQ协议

针对RB-HARQ协议系统开销巨大的问题,提出一种基于校验式判决的HARQ协议.该协议根据不成立的校验式与错误比特之间的关系,将一部分不成立的校验式的序号通过反馈信道反馈给发射机,发射机按照一定的规则将这些校验式所包含的某些比特确定为重传比特,重新发送给接收端,接收端将重传的比特与先前发送的码字进行最大比合并,最后进行译码.数值仿真结果表明,由于只需要反馈一部分校验式的序号,该协议能够有效降低系统的开销,其吞吐量性能能够接近RB-HARQ协议.     

Computer-Readable DNAzyme Assay on Disc for ppb-Level Lead Detection

A method for the convenient detection of lead at the parts-per-billion (ppb)-level has been developed; it uses a conventional compact disc (CD) as the platform for preparing DNAzyme assays and an unmodified optical drive of ordinary desktop/laptop computers as the readout device. In particular, by immobilization of Pb(2+)-specific DNAzyme sensing constructs on the "transparent side" of a conventional CD-R via mild surface reactions, the Pb(2+) concentration can be determined by a free diagnostic program that checks the error distribution on the CD (i.e., it extracts the number of errors in a prerecorded audio file). The reading errors increase monotonically over a wide range of Pb(2+) concentrations (from 10 nM to 1 mM), and the selectivity is confirmed by testing several other divalent cations (Zn(2+), Ba(2+), Mg(2+), Ca(2+), Cu(2+), and Hg(2+)).     

Electrochemical sensor for uric acid based on a molecularly imprinted polymer brush grafted to tetraethoxysilane derived sol-gel thin film graphite electrode

Determination of uric acid in human serum and urine is useful to provide treatment guidelines to hyperuricemic patients. An electrochemical sensor was developed for selective and quantitative recognition of uric acid by using a preanodised sol-gel coated graphite electrode with a molecularly imprinted polymer brush of poly(melamine–co-chloranil) grafted to its exterior surface. During a preconcentration step at (+ 2.0 V versus saturated calomel electrode), the encapsulated analyte recapture involved hydrophobically induced hydrogen-bondings in outwardly exposed MIP cavities in aqueous environment (pH 7.0), instantly oxidised as dications, and then cathodically stripped off as corresponding lactam responding differential pulse, cathodic stripping voltammetric signal. The uric acid was selectively detected without any cross reactivity in the windows of 14.56–177.42 µg mL^? 1 (aqueous medium), 4.78–106.96 µg mL^? 1 (blood serum), and 7.81–148.42 µg mL^? 1 (urine) indicating detection limits in the range of 3.71–4.10 µg mL^? 1 (3σ, RSD = 1.9%).     

Improved identification schemes based on error-correcting codes

As it is often the case in public-key cryptography, the first practical identification schemes were based on hard problems from number theory (factoring, discrete logarithms). The security of the proposed scheme depends on an NP-complete problem from the theory of error correcting codes: the syndrome decoding problem which relies on the hardness of decoding a binary word of given weight and given syndrome. Starting from Stern’s scheme [18], we define a dual version which, unlike the other schemes based on the SD problem, uses a generator matrix of a random linear binary code. This allows, among other things, an improvement of the transmission rate with regards to the other schemes. Finally, by using techniques of computation in a finite field, we show how it is possible to considerably reduce:

- the complexity of the computations done by the prover (which is usually a portable device with a limited computing power).

- the size of the data stored by the latter.

     

Ultrasensitive electrochemical detection of proteins by amplification of aptamer-nanoparticle bio bar codes

An ultrasensitive label-free bioelectrochemical method for rapid determination of thrombin has been developed by directly detecting the redox activity of adenine (A) nucleobases of anti-thrombin aptamer using a pyrolytic graphite electrode. The bioelectrochemical protocol involves a sandwich format. Thrombin, captured by immobilzed anti-thrombin antibody on microtiter plates, is detected by anti-thrombin aptamer-Au nanoparticle bio bar codes. A systematic optimization of the parameters has been carried out via ELAA (enzyme linked aptamer assay) performance. The adenine nucleobases were released by acid or nuclease from Au nanoparticles bound on microtiter plates. Differential pulse voltammetry was employed to investigate the electrochemical behaviors of the purine nucleobases. Well-defined adenine signal was observed at about 0.85 V in pH 5.9 acetate buffer. Because the nanoparticle carries a large number of aptamers per thrombin binding event, there is substantial amplification and thrombin can be detected at a very low level of detection (0.1 ng/mL). This method has been used to detect thrombin in complex matrix such as fetal calf serum with minimum background interference.     

Colorimetric and ultrasensitive bioassay based on a dual-amplification system using aptamer and DNAzyme

Rapid detection of ultralow amount of biomarkers in a biologically complex mixture remains a major challenge. Herein, we report a novel aptamer-based protein detection assay that integrates two signal amplification processes, namely, polymerase-mediated rolling-circle amplification (RCA) and DNA enzyme-catalyzed colorimetric reaction. The target biomarker is captured in a sandwich assay by primary aptamer-functionalized microbeads (MBs) and a secondary aptamer that is connected to a RCA primer/circular template complex. RCA reaction, which amplifies the single biomarker binding events by a factor of hundreds to thousands (the first amplification) produces a long DNA molecule containing multiple DNAzyme units. The peroxidase-like DNAzyme catalyzes the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (the second amplification), which generates a blue-green colorimetric signal. This new biosensing platform permits the ultrasensitive, label-free, colorimetric detection of biomarker in real time. Using platelet-derived growth factor B-chain (PDGF-BB) as a model system, we demonstrated that our assay can detect a protein marker specifically in a serum-containing medium, at a concentration as low as 0.2 pg/mL in ～2 h, which rivals traditional assays such as ELISA. We anticipate this simple methodology for biomarker detection can find utility in point-of-care applications.     

基于混合蒙特卡罗箱方法的移动感知网节点定位方法

通过将机器人领域的蒙特卡罗定位方法(Monte-Carlo localization,MCL)引入到移动感知网的节点定位,提出了一种混合蒙特卡罗箱方法(mixture Monte-Carlo Box,Mixture-MCB).该方法采用混合采样的方式提高采样的成功率,有效地解决了传统蒙特卡罗方法的粒子耗散问题.与其他现有方法相比,该方法不仅计算简单,定位精度高,而且对于环境参数的改变具有较强的鲁棒性,因此适用于由计算能力较弱的节点构成的大规模移动感知网.仿真实验对算法的计算复杂度、定位精度和鲁棒性进行了分析并与其他方法进行了比较,结果表明,该方法是可行而有效的.