Microprocessing of liquid plugs for bio/chemical analyses

A microfluidic device and operation to handle liquid plugs for biochemical analyses were developed for efficient handling of plugs of many solutions. A major part of the device was a T-junction consisting of a main flow channel and a handling flow channel. Unit operations including attachment of plugs, division of a plug, sorting of plugs, and formation of plugs of various lengths enabled controlled sequential reactions in a microflow channel. Rapid mixing could easily be achieved by moving a plug formed by merging two plugs back and forth. The device could be used for efficient characterization of performance in bio/chemical sensing. In experiments using L-glutamate oxidase, plugs containing an enzyme or a substrate were formed, mixed sequentially, and the intensity of fluorescence from plugs of different concentrations of L-glutamate or pHs could be measured simultaneously. Cross-contamination of plugs by neighboring plugs poses a problem in using the same flow channel repeatedly. However, the influence could be minimized by using a cleansing plug placed between them in a sufficiently hydrophobic flow channel and by processing the plugs at a low velocity. The device can be a critical component for microprocessing in various bio/chemical analyses.     

Automatic electrochemical micro-pH-stat for biomicrosystems

A microelectrochemical pH-stat with an automatic feedback function was fabricated. The operation of the device is based on the nonstandard use of an electrochemical three-electrode system with a pH-sensitive reference electrode, a Ag/AgCl working electrode, and an iridium auxiliary electrode that functions as an actuator to adjust the solution pH. The combination of the electrodes caused a negative feedback in response to a pH change. The shift of the potential of the pH-sensitive reference electrode caused an overpotential on the Ag/AgCl working electrode, which then caused a significant current increase. This led to the electrolysis of water on the auxiliary electrode and the rapid recovery of the pH. The negative feedback function to stabilize the initial state could be confirmed for changes to both the acidic and basic directions. The performance of the pH-stat was characterized in the titration of acetic acid or ammonia. The charge generated in the feedback process changed linearly with respect to the concentration. The pH-stat was also used in the determination of urea by urease and that of the activities of trypsin and pepsin while maintaining the optimum pH for the enzymes. The pH to be fixed could be changed by changing the working electrode potential. Moreover, the two pH-stats could be used to form a pH gradient in a microflow channel by fixing the pH values at two positions.     

Influence of nanometric holes on the sensitivity of a waveguide-mode sensor: label-free nanosensor for the analysis of RNA aptamer-ligand interactions

Evanescent-field-coupled (EFC) waveguide-mode sensors can be used to detect nucleic acids or proteins from the changes in the local index of refraction upon adsorption of the target molecule on a waveguide surface. We recently described an EFC waveguide-mode sensor in which nanometric holes on a waveguide film resulted in an improved sensitivity in the analysis of the interactions of biomolecules. In the present study, we have shown that sensitivity depends upon the diameter of the holes, where increase in diameter of holes increases spectral shift resulting in an improved sensitivity. Using this improved EFC waveguide-mode sensor, we could detect interactions between RNA and a small ligand, cyanocobalamin (vitamin B 12), and between RNA and a protein (human coagulation factor IXa). These two interactions were monitored on surfaces modified with biotin-streptavidin-biotin and N-(2-trifluoroethanesulfonatoethyl)- N-(methyl)triethoxysilylpropyl-3-amine, respectively.     

Preparation of ethyl magnesium bromide for regiospecific analysis of triacylglycerols

This paper presents a procedure for preparation of a Grignard reagent, ethyl magnesium bromide, used for partial deacylation of triacylglycerols (TAG) in their regiospecific analysis. Magnesium turnings were reacted with ethereal solution of bromoethane in a screw-capped test tube to synthesize 2 mL of 1 M ethyl magnesium bromide. Continuously stirred with a vortex mixer, the reaction smoothly proceeded at room temperature. Regiospecific analysis of 1,3-distearoyl-2-oleoylglycerol using this product showed that fatty acid compositions of the sn-1(3) and sn-2 positions were contaminated by less than 2 mol% of fatty acids migrated from isomeric positions. The analyses of lard and cod liver/mackerel oil TAG showed typical distribution patterns of 16:0, 22:5n-3 and 22:6n-3 in pig and fish depot TAG. These results confirmed the view that the freshly prepared reagent is usable for regiospecific analysis of TAG.     

快速计算电网可用输电能力的交流灵敏度方法

在电力市场环境下，可用输电能力(ATC)是反映输电设备可用于能量交易的剩余容量的重要指标。ATC一旦确定后，快速估计出系统参数变化对输电能力的影响具有很大的实际应用价值。文中首先基于连续潮流方法，考虑输电支路的过负荷约束、发电机有功及无功出力约束和节点电压约束，计算出ATC的值；然后推导出ATC对多种运行参数摄动的一阶灵敏度计算模型，运行参数包括节点负荷功率、发电节点端电压以及给定的能量交易，这些灵敏度系数能够很快地计算；最后，使用了IEEE30节点系统的算例来验证文中所提出的方法的有效性和快速性。     

内置CFRP圆管的方钢管高强混凝土中长柱轴压性能试验

目的 研究内置CFRP圆管的方钢管高强混凝土的可行性和必要性,并指出内置CFRP圆管的方钢管高强混凝土应用于建筑物的竖向承重构件中所具有的优越性.方法 通过对7根内置CFRP圆管的方钢管高强混凝土柱和5根方钢管高强混凝土柱承载力的对比试验,探讨了在相同宽度厚度比的情况下,3种CFRP层数和5种长细比对内置CFRP圆管的方钢管高强混凝土柱承载力的影响.结果 CFRP圆管对构件的承栽力的有显著提高,内置一层CFRP管承载力增长5%左右,二层增加12%左右;随着长细比的增加,内置CFRP圆管的方钢管高强混凝土构件承载力有减小的趋势.结论 通过对应变曲线的分析得出宽厚比和CFRP参数的最优组合为2层.     

贵金属催化同时去除碳颗粒和NOx

为系统研究贵金属催化同时去除碳颗粒和NOx的活性及抗硫抗水性能,采用等体积浸渍法制备了一系列贵金属催化剂(Ru/Zr O2、Ag/Zr O2、Rh/Zr O2、Pd/Zr O2、Pt/Zr O2、Ir/Zr O2、Au/Zr O2),研究了富氧条件下其催化去除碳颗粒和NOx的活性,并考察了SO2和H2O对其催化活性的影响.结果表明:在富氧条件下,贵金属的负载提高了碳颗粒和NOx同时去除的活性,其中Ru/Zr O2、Ag/Zr O2和Pd/Zr O2的催化活性较佳;SO2和H2O对Ir/Zr O2催化同时去除碳颗粒和NOx、Pt/Zr O2催化去除碳颗粒、Ru/Zr O2催化去除NOx有促进作用,但对其他贵金属有抑制作用.     

Pace-sync shoes: intuitive walking-pace guidance based on cyclic vibro-tactile stimulation for the foot

We propose a walking guidance method with a sandal-shaped vibration interface and describe two experiments we performed to formulate the design principles of the interface. In the interface, a vibrating motor presents timing information to the foot, and pressure sensors measure walking pace. Our method is a combination of the walking-state monitoring and vibro-tactile feedback to maintain or promote a walking pace. Vibration stimuli with a constant presentation interval are alternately and repeatedly given to the right or left foot of the user according to the measured walking pace, and then the walking pace gradually conforms to the presented interval of the vibration. In the experiments, we specified the effective timing and intervals of the vibration stimuli for efficient inductance of walking pace. The method is applicable for training and coaching in sports and rehabilitation in health care.     

Stereospecific Effects of Oxygen‐to‐Sulfur Substitution in DNA Phosphate on Ion Pair Dynamics and Protein–DNA Affinity

Oxygen‐to‐sulfur substitutions in DNA phosphate often enhance affinity for DNA‐binding proteins. Our previous studies have suggested that this effect of sulfur substitution of both O_P1 and O_P2 atoms is due to an entropic gain associated with enhanced ion pair dynamics. In this work, we studied stereospecific effects of single sulfur substitution of either the O_P1 or O_P2 atom in DNA phosphate at the Lys57 interaction site of the Antennapedia homeodomain–DNA complex. Using crystallography, we obtained structural information on the R_P and S_P diastereomers of the phosphoromonothioate and their interaction with Lys57. Using fluorescence‐based assays, we found significant affinity enhancement upon sulfur substitution of the O_P2 atom. Using NMR spectroscopy, we found significant mobilization of the Lys57 side‐chain NH₃⁺ group upon sulfur substitution of the O_P2 atom. These data provide further mechanistic insights into the affinity enhancement by oxygen‐to‐sulfur substitution in DNA phosphate.     

Helix-helix transition of poly(β-phenylpropyl l-aspartate) embedded in stable helical poly(γ-phenylethyl glutamate) matrix

We studied the helix-helix transition of poly(β-phenylpropyl l-aspartate) (3PLA) embedded in a right-handed α-helical (α_R) poly(γ-phenylethyl l-glutamate) (2PLG) or left-handed α-helical poly(γ-phenylethyl d-glutamate) (2PDG) matrix. Binary mixtures were prepared with 3PLA:2PLG (2PDG) mole fractions of 9:1 to 1:9. In all these mixtures, the 3PLA molecule exhibited helical sense inversion even if dispersed or isolated into the hard-rod matrix, and the inversion rate of the embedded 3PLA molecule was relatively higher than that of the pure system. Thus, it was concluded that the transition occurs in only a limited space and more easily for the isolated molecule. Further, the 3PLA molecule recognized the chiral environment produced by the surrounding polymers. For 3PLA surrounded by a 2PDG matrix, the helix-helix transition temperature was lower and the transition rate on cooling was slower than those for 3PLA surrounded by a 2PLG matrix. This is reasonable since the left-handed matrix helps right-handed to left-handed helical inversion.