Novel functional oligonucleotides, especially DNAzymes with RNA-cleavage activity, evoke current research interest increasingly due to their potential applications in therapeutics and sensors. One of the most attention-attracting is the lead-specific DNAzyme, which is composed of an enzyme strand 17E and a substrate strand 17S, addition of Pb2+ enables the DNAzyme to cleave its substrate. In this study, we took advantage of the unique optical properties of a water-soluble cationic polythiophene (PT) and designed a fluorometric sensing assay for the detection of Pb2+. A simple "mix-and-detect" approach enabled the detection of Pb2+ within 20 minutes due to the distinguishable optical properties of PT-dsDNA and PT-ssDNA. As low as 10 nMPb(2+) could be detected with a detection range from 10 nM to 100 mu M via this method. Furthermore, this method was highly selective and only minimally perturbed by nonspecific metal ions. Since common steps such as modification and separation could be successfully avoided, this simple, sensitive, specific, and cost-effective approach showed great potential applications in environmental monitoring, waste management and clinical toxicology.

The quenching mechanism of the fluorescence of quantum dots by abscisic acid has been systematically investigated. The quenching constant K SV = 5.1 × 1011 / M was obtained under the optimized condition. On the basis of that, a very sensitive method for the determination of abscisic acid has been developed. The linear equation was F 0/F = 0.9309 + 0.5072 C (pmol/L) and its linear range was 0.2–3.0 pmol/L with a correlation coefficient of 0.9939. The limit of detection was 0.09 pmol/L.

The interaction between the water-soluble cation fluorescent conjugated polymer ( WCFP) and adenosine adenosine triphosphate( ATP) was studied with fluorescence spectra. It was found that the fluorescence of WCFP was quenched by ATP. Based on this, a novel fluorimetric method has been developed for the determination of ATP. In 0.05 mol/L Tris-HCl buffer ( pH 7.4), the linear relationship for the determination of ATP was 8.0 x 10(-8) -1.0 x 10(-5) mol/L with a detection limit of 2.0 x 10(-8) mol/L. The method is simple, practical and selective. It has been applied for the determination of ATP in tablets and crucian fish with satisfactory results. The relative standard deviation was 2.2% - 6.9% for 5 parallel determinations of ATP samples, and the recoveries were 93.6% - 105.6%.

Water-soluble fluorescent conjugated polymers can be used as an optical platform in highly sensitive DNA sensors. Here we report a simple label-free DNA sensor using poly(3-alkoxy-4-methylthiophene) to recognize and detect different oligonucleotide targets related to the YMDD gene mutation of hepatitis B virus. The concentration of surfactant Triton X-100, NaCl, the oligonucleotide capture probe and the oligonucleotide hybridization conditions have a great impact on fluorescence intensity. Under the optimum conditions, two types of oligonucleotide targets involving YMDD gene mutation of hepatitis B virus were successfully recognized. Moreover, there was a linear relationship between fluorescence intensity and the concentration of oligonucleotide target. The detection limit of the wild-type hepatitis B virus target is 88 pmol L(-1).

In this contribution, we designed a fluorescent thiophene copolymer to detect insertion/deletion mutation in DNA by doping aldehyde group in the main chain. The fluorescence of the copolymer could be dramatically quenched on the addition of single-stranded DNA (ssDNA) via strong electrostatic interactions and electronic/energy transfer. Although the complementary ssDNA made the fluorescence recover, the hydrogen bonds and chemical coupling also played a significant role between the unpaired bases and aldehyde group, which could differentiate the subtle differences in such mutant DNA. The influence of buffer pH, concentration of NaCl, heating time and the temperature was systemically investigated and the proposed method was then successfully applied to detect real sample. With the respect to the linearity, limit of detection precision, specificity, this procedure could provide sensitive methodologies for the rapid detection and identification of nucleic acids.

A new rapid polymerization method with high polymerization yield was developed to prepare the water-soluble fluorescent conjugated polymer poly(5-methoxy-2-propyloxy sulfonate phenylene vinylene) (MPS-PPV) in the solution of NaOH/C2H5OH/DMF. The regulation of the fluorescence emission wavelength was realized by changing the concentration of NaOH. The polymer was characterized by elemental analysis and infrared absorption spectrum. The molecular weight was measured by static light scattering experiments. The fluorescence spectra and UV-Vis spectra of MPS-PPV under different polymerization conditions were also explored. The effect of hydrogen peroxide on the fluorescence intensity and wavelength of MPS-PPV was studied, which will provide guidelines to develop the novel fluorescence polymer-based sensors.

In this contribution, a simple and sensitive method for l-cysteine detection was established based on the increment of the fluorescence intensity of mercaptoacetic acid-capped CdSe/ZnS quantum dots (QDs) in aqueous solution. Meanwhile, the fluorescence characteristics and the optimal conditions were investigated in detail. Under the optimized conditions, the linear range of QDs fluorescence intensity versus the concentration of l-cysteine was 10–800nmolL−1, with a correlation coefficient (R) of 0.9969 and a limit of detection (3σ black) of 3.8nmolL−1. The relative standard deviation (R.S.D.) for 0.5μmolL−1l-cysteine was 1.1% (n=5). There was no interference to coexisting foreign substances including common ions, carbohydrates, nucleotide acids and other 19 amino acids. The proposed method possessed the advantages of simplicity, rapidity and sensitivity. Synthetic amino acid samples, medicine sample together with human urine samples were analyzed by the methodology and the results were satisfying.

A layer-by-layer surface decoration technique has been developed to anchor quantum dots (QDs) onto a gold substrate and an in situ surface plasmon resonance technique has been used to study interactions between the QDs and different proteins. Direct observation of the binding of the protein onto the QDs and the kinetics of the adsorption and dissociation of different proteins on the QDs has been achieved. This would be helpful for the identification of particle-associated proteins and may offer a fundamental prerequisite for nanobiology, nanomedicine and nanotoxicology. The combination of the novel layer-by-layer surface modification method and in situ surface plasmon resonance would be powerful in studying biological systems such as DNA and cells.

The wide applications of Ru(Ⅱ)complexes,such as [Ru(bipy)2dppz]2+ and [Ru(phen)2dppz]2+,served as molecular light switches for nucleic acid were reviewed.The applications included the trace DNA detection,gene sequence analysis,triple helix of DNA detection,DNA imaging,interaction study,ATP detection,protein analysis,quantum dots biological effect,electroanalytical probe and humidity sensing.The nucleic acid molecular light switches showed the potential advantages of low cost,simplicity,high speed,stability and environment-friendly.With the development of aptamer,it would be more important for the basic research in life science,food safety and medicine diagnosis.55 references were cited.

The models of conventional wind turbines with an asynchronous generator and power system are developed in DIgSILENT/Power Factory. Based on the model, the impacts of wind turbines with an asynchronous generator on the small-signal stability and damping characteristics of power system are analysed. An improved pitch control scheme is presented by introducing a frequency deviation signal into the control system. When low frequency oscillation happens, the wind turbine output is regulated to correlate with system oscillation frequencies. Both frequency domain analysis and time domain simulation results demonstrate that the improved pitch control methods significantly improve the damping characteristics of power system. Therefore the power oscillations are mitigated and the system dynamic stability is enhanced effectively in the system.

The models of the wind turbine generator and power system are established with power system analysis software DIgSILENT / Power Factory,including fixed speed-wind turbine generator and variable-speed wind turbine doubly-fed induction generator(VSWT-DFIG).The 3-phase symmetrical short circuit fault near wind farm is set for theriotic and simulative study.The short circuit waveforms are compared between wind turbine generators and synchronous generator with same capacity.The short-circuit busbar currents near wind farm are calculated before and after its connection to grid.Its incremental percents is also calculated to evaluate the contribution of wind farm to system short curcuit current.The results demonstrate that the influence of wind farm on the short-circuit current of nearby node must be considered in selecting the electrical devices near wind farm and calculating their thermal stabilities.

A power system stabilizing technology is introduced into the wind turbine with a doubly fed induction generator(DFIG),by use of the slip signal as feedbacks into the rotor side converter control model.During the power oscillation of a power system,a damping active power is injected into the network from the DFIG machine via regulating the rotor excitation voltage angle.This will improve the overall system damping characteristic.A testing system including a wind farm is established in DIgSILENT/Power Factory.The eigenvalue analysis and time response simulation studies are conducted with and without the proposed control model.The results illustrate those wind turbines using the proposed controller can improve the system damping.The power oscillations are restrained and the dynamic stability enhanced.

In recent years, gold nanoparticles and water-soluble fluorescent conjugated polymers are promising materials in terms of their potential applications in a variety of fields, ranging from monitoring DNA hybridization to demonstrate the interaction between proteins, or detecting diseased cell, metal ions and small biomolecular. In order to exploit some new properties of the both, many attempts have been devoted to achieve nanoparticle–polymer composite via incorporating metal nanoparticle into polymer or vice versa, however, only few of them are put into practical application. In the present paper, we utilize the “superquenching” property of AuNPs to polythiophene derivatives for detecting aspartic acid (Asp) and glutamic acid (Glu) in pure water, and discuss the factors accounting for fluorescence quenching and recovery via modulating pH. Thus an exceptionally simple, rapid and sensitive method for detecting Asp and Glu is established with a limit of detection (LOD) is 32nM for Asp and 57nM for Glu, the linear range of determination for Asp is 7.5×10−8M to 6×10−6M and 9.0×10−8M to 5×10−6M for Glu. The system is applied to real sample detection and the results are satisfying. Otherwise the composite is very sensitive to pH change of solution, we expect it will be possible to use as pH sensor with wide range in the future.

The measures to enhance transient voltage stability of induction generator based wind farm are studied in this paper. Constant speed wind turbines equipped with induction generator is the most widely used technology in the world so far. The local grid voltage stability will be reduced due to the integration of induction generator based wind farm because the high demand of reactive power absorbed by induction generator. The SVC with its controller model and pitch control model is set up in the power system simulation program DIgSILENT/PowerFactory in this paper. The model validity and the contribution to the transient voltage stability are verified by power system simulation containing large wind farm. Power system simulation results show that the SVC can assist the induction generator restoring the voltage rapidly in the duration of power system large disturbance, ensuring both the voltage stability of the grid and the continuous operation of the wind turbines. They also demonstrate that pitch control of constant speed wind turbines can effectively reduce the wind turbine mechanical power, preventing the wind turbines from over-speeding and transient voltage instability in the duration of power system large disturbance. Finally, it is concluded that the adoption of the SVC and pitch control enhances the transient voltage stability of induction generator based wind farm, ensures the continuous operation of wind turbines and the security and stability of the power network.

A calculation method of maximum wind power which can be integrated into the regional grid based on static security and stability constraints was introduced, and the calculation flow chart was introduced too. Besides the two static security constraints of node voltage and transmission power, the stability constraints were also considered in this method, including static stability constraints and transient stability constraints. The calculation process considered all the constraints was showed as a flow chart. A case study with this method on a project of wind farm integrating was done and some conclusions were produced. With considering the stability constraints, the critical wind power in a regional grid can be evaluated more reasonably.

The mechanical and electrical systems are decoupled and controlled in doubly fed induction generator (DFIG) using double PWM converters. That leads to poor responding performance of DFIG wind turbines generator to the change of the power system frequency. According to its characteristic and scheme, a frequency control loop based on the model of DFIG based wind turbines is proposed and it is implemented in the simulation package of DIgSILENT/PowerFactory. During the deviation of power system frequency, the DFIG based wind turbine with frequency control loop can release (or absorb) a part of the kinetic energy stored in rotor, so as to increase (or decrease) active power injected to power system to realized the frequency control. Validity and practicability are verified by simulation. It lays a foundation for wind farm participating system frequency regulation.

The request for low voltage ride through (LVRT) characteristic can change the cost of wind turbine generator (WTG). It is necessary to design the capability of LVRT in reason. The model and the control strategy of DFIG with LVRT are implemented in the power system simulation tool DIgSILENT/Power Factory. The system simulation is implemented in a regional grid. A method is presented to confirm the special requirement of LVRT of wind turbine generators in the project. The voltage at the wind turbine terminal is calculated during the faults in power systems. The voltage limit of LVRT is presented in terms of different integration schemes. The results suggest that the LVRT capability is confirmed by the connection of Power Systems and wind farm integration schemes. The voltage limit of LVRT should be confirmed in terms of special integration scheme.

In this paper,different conditions for the determination of nilestriol with fluorescent spectrometry were investigated.It was found that β-cyclodextrin could enhance the fluorescence intensity greatly under neutral situation,thus a simple and highly sensitive approach was put forward with the linear range of 2.63×10~(-7)～1.84×10~(-5) mol/L and the detection limit of 9.4×10~(-8) mol/L,which has been successfully applied to the determination of nilestriol in tablets.The results were satisfactory.

[HJ1]The binding characteristics of dapsone(DS) and bovine serum albumin (BSA) were studied by fluorescence and absorption spectroscopy in aqueous solution.DS had a powerful ability to quench the BSA fluorescence via non-radiation energy transfer mechanism.The fluorescence quenching data were analyzed according to Stern-Volmer equation and double-reciprocal equation,from which the reaction distance and the thermodynamic parameters were obtained.

This paper reviewed the progress of the fluorimetry in pharmaceutical analysis in recent years.The present situation of fluorescence spectrum for the reaction of medicine and biomacromolecules such as protein,nucleic acid was introduced in detail,including its mechanism.The future application is pharmaceutical analysis was foreseen.