低场核磁共振短死时间射频线圈与射频开关的设计

本文以核磁共振（NMR）射频线圈振铃信号产生原理为对象进行分析研究,提出了一种适用于低场环境下由环状间隙腔线圈与螺线管线圈构成的收发分离式短死时间射频线圈设计方案,采用优化调谐匹配网络提高发射效率;根据射频线圈方案需求设计了快速切换的射频开关及驱动．在此基础上依据仿真结果制作了短死时间射频线圈,并应用于自主研制的低场9.51 MHz便携式NMR谱仪系统,进行NMR实验,结果显示可将收发切换时间缩短至10 μs以内,验证了该设计方案的可行性．     

基于稀土离子介导石墨烯量子点荧光开关的凝血酶生物传感器

稀土离子(Er3+)可与荧光石墨烯量子点(GQDs)表面的含氧基团发生配位,在Er3+介导下形成高配位数的GQDs/Er3+配合物,引起GQDs聚集而使其荧光减弱.凝血酶(Tb)中的氮和氧等原子可与Er3+发生配位作用,从而与GQDs竞争结合Er3+,减弱了GQDs与Er3+的作用而使其荧光恢复.通过检测GQDs的荧光即可实现对Tb活性的高灵敏分析,构建了基于Er3+介导GQDs荧光开关的Tb传感方法,采用透射电镜、原子力显微镜、红外吸收光谱以及荧光光谱等对传感机理进行了研究.本方法对Tb的检出限低至0.049 nmol/L,其它蛋白质对Tb检测无明显干扰,实际样品中Tb加标回收率为98.0%~105.3%,相对标准偏差为0.6%~4.2%.     

A Competitor-switched Electrochemical Sensor for Detection of DNA

A competitor‐switched electrochemical sensor based on a generic displacement strategy was designed for DNA detection. In this strategy, an unmodified single‐stranded DNA (cDNA) completely complementary to the target DNA served as the molecular recognition element, while a hairpin DNA (hDNA) labeled with a ferrocene (Fc) and a thiol group at its terminals served as both the competitor element and the probe. This electrochemical sensor was fabricated by self‐assembling a dsDNA onto a gold electrode surface. The dsDNA was pre‐formed through the hybridization of Fc‐labeled hDNA and cDNA with their part complementary sequences. Initially, the labeled ferrocene in the dsDNA was far from surface of the electrode, the electrochemical sensor exhibited a "switch‐off" mode due to unfavorable electron transfer of Fc label. However, in the presence of target DNA, cDNA was released from hDNA by target DNA, the hairpin‐open hDNA restored its original hairpin structure and the ferrocene approached onto the electrode surface, thus the electrochemical sensor exhibited a "switch‐on" mode accompanying with a change in the current response. The experimental results showed that as low as 4.4×10⁻¹⁰ mol/L target DNA could be distinguishingly detected, and this method had obvious advantages such as facile operation, low cost and reagentless procedure.     

LC/ESI-MS n and 1H HR-MAS NMR analytical methods as useful taxonomical tools within the genus Cystoseira C. Agardh (Fucales; Phaeophyceae)

Species of the genus Cystoseira are particularly hard to discriminate, due to the complexity of their morphology, which can be influenced by their phenological state and ecological parameters. Our study emphasized on the relevance of two kinds of analytical tools, (1) LC/ESI-MSⁿ and (2) ¹H HR-MAS NMR, also called in vivo NMR, to identify Cystoseira specimens at the specific level and discuss their taxonomy. For these analyses, samples were collected at several locations in Brittany (France), where Cystoseira baccata, C. foeniculacea, C. humilis, C. nodicaulis and C. tamariscifolia were previously reported. To validate our chemical procedure, the sequence of the ITS2 has been obtained for each species to investigate their phylogenetic relationships at a molecular level. Our study highlighted the consistency of the two physico-chemical methods, compared to “classical” molecular approach, in studying taxonomy within the genus Cystoseira. Especially, LC/ESI-MSⁿ and phylogenetic analyses converged into the discrimination of two taxonomical groups among the 5 species. The occurrence of some specific signals in the ¹H HR-MAS NMR spectra and/or some characteristic chemical compounds during LC/ESI-MSⁿ analysis could be regarded as discriminating factors. LC/ESI-MSⁿ and ¹H HR-MAS NMR turned out to be two relevant and innovative techniques to discriminate taxonomically this complex genus.     

Synthesis and spectroscopic characterization of red-shifted spironaphthoxazine based optical switch probes

Spironaphthoxazine (NISO) is an efficient optical switch probe that has applications in high contrast detection of Förster resonance energy transfer (FRET) using optical lock-in detection (OLID). NISO exists in two distinct states, spiro (SP) and merocyanine (MC), that can be independently controlled by using alternate irradiation with near ultraviolet and visible light. Unfortunately, the SP-state of NISO has an absorption centered at 350 nm, which may lead to phototoxic effects when manipulating the probe within a living cell. To overcome this problem we introduce new, red-shifted amino-substituted NISO probes compared to NISO that undergo an efficient SP to MC transition in response to irradiation by using 405-nm light, which is less damaging to living cells. This study details the synthesis of amino-substituted NISO and their N-hydroxysuccinimide ester and maleimide derivatives and their use in generating covalent attached protein conjugates. This study also presents a characterization of the spectroscopic and optical switching properties of these red-shifted NISO probe in solution.     

一种基于厚膜技术的浮动板调制器的设计

本文设计了一种基于厚膜技术的浮动板调制器,通过试验证明,该调制器具有结构简单、可靠性高、输出波形好,通用性强等优点。     

新型低压无功补偿器的设计

主要介绍了基于ATT7022B和ST-SRC或ST-SRCS-4智能开关的新型无功补偿统。该控制器通过高精度多功能三相电能专用计量芯片ATT7022B实时检测电网的电压、电流、功率因数、无功电流和无功功率,并有CAN总线通信接口。ST-SRC或ST-SRCS-4智能开关可在电压或电流过零点时动作,并可以通过CAN总线接口与和无功补偿控制器进行通信,最终使电容器组按一定的规律进行投切,最终实现无功补偿。     

Redox‐induced configuration conversion for thioacetamide dimer can function as a molecular switch

The electronic switching properties of thioacetamide dimer (TAD) were investigated using the nonequilibrium Green's function method combined with density functional theory for design of a novel molecular switch. The H‐bonded TAD can be converted upon hole‐trapping to a three‐electron (3e)‐bonded configuration with a S∴S linkage which could provide a more favorable channel for charge transfer than the before. The redox‐induced configuration conversion between the H‐bonded and the 3e‐bonded TADs could govern the charge migration through the molecular junction with a considerable difference in conduction currents. The calculated I–V characteristic curves of two configurations exhibit a switching behavior with an On‐Off ratio in a range of about 4.3–7.6 within the applied voltages. Clearly, this hypothetical scheme provides a potential way to explore the novel conformation‐dependent molecular switch. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Development of a switchable multidimensional/comprehensive two-dimensional gas chromatographic analytical system

In this study, a new system for analysis using a dual comprehensive two-dimensional gas chromatography/targeted multidimensional gas chromatography (switchable GC × GC/targeted MDGC) analysis was developed. The configuration of this system not only permits the independent operation of GC, GC × GC and targeted MDGC analyses in separate analyses, but also allows the mode to be switched from GC × GC to targeted MDGC any number of times through a single analysis. By incorporating a Deans switch microfluidics transfer module prior to a cryotrapping device, the flow stream from the first dimension column can be directed to either one of two second dimension columns in a classical heart-cutting operation. Both second columns pass through the cryotrap to allow solute bands to be focused and then rapidly remobilized to the respective second columns. A short second column enables GC × GC operation, whilst a longer column is used for targeted MDGC. Validation of the system was performed using a standard mixture of compounds relevant to essential oil analysis, and then using compounds present at different abundances in lavender essential oil. Reproducibility of retention times and peak area responses demonstrated that there was negligible variation in the system over the course of multiple heart-cuts, and proved the reliable operation of the system. An application of the system to lavender oil, as a more complex sample, was carried out to affirm system feasibility, and demonstrate the ability of the system to target multiple components in the oil. The system was proposed to be useful for study of aroma-impact compounds where GC × GC can be incorporated with MDGC to permit precise identification of aroma-active compounds, where heart-cut multidimensional GC-olfactometry detection (MDGC-O) is a more appropriate technology for odour assessment.     

基于FPGA的多路视频通道控制

根据织布机告警系统的需求,提出一种开关设计思想,阐述开关设计过程中遇到的问题以及解决方法。首先在FPGA中设计一个开关控制信号,利用这个信号结合双口RAM中的编码数据识别两个拨动开关状态．从而达到控制多路视频通道的目的,使本告警系统更方便的应用于实际工业中。介绍整个控制系统的工作原理,给出硬件结构图和软件设计过程,然后利用QnartusⅡ中的SignalTapⅡLogic Analyzer工具对控制信号进行实时采样分析．最后在织布机告警系统中成功实现视频通道控制功能。