An efficient electrochemical biosensor for silver ion detection using hydrogen peroxide as a redox indicator

Conference Name:2014 International Conference on Materials Science and Computational Engineering, ICMSCE 2014. Conference Address: Qingdao, China. Time:May 20, 2014 - May 21, 2014.Engineering of Qingdao University; et al; Institute for Computational Science and; Laboratory of Qingdao University; New fiber materials and modern textile State KeyThe strong and specific binding of two DNA cytosine bases by silver ion (C-Ag+-C) was applied to develop an efficient electrochemical biosensor for the detection of silver ion in aqueous solution. As a redox indicator, the hydrogen peroxide worked to generate a readable electrochemical signal. Thiolated short oligonucleotide strands containing 5 cytosine bases served as probe and self-assembled via Au-S bonding on gold electrode. In the presence of Ag+, the specific coordination between Ag+ and cytosine bases resulted in more stable and porous arrangement of oligonucleotide strands. Hydrogen peroxide could adsorb onto the surface of gold electrode and produce an electrochemical signal. The cyclic voltammetry shows a linear correlation between the signal and the concentration of Ag+ over the range 0-0.2 μM (R2 = 0.9955) with a detection limit of 30 nM. The length of probe DNA has no significant impact on the sensor performance. This biosensor is simple, economical and reusable with good sensitivity and selectivity. We also validated the practicality for the determination of Ag+ in real water samples. ? (2014) Trans Tech Publications, Switzerland

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Early-Warning Method of Train Running Safety of a High-Speed Railway Bridge Based on Transverse Vibration Monitoring

Making use of long-term transverse vibration monitoring data of DaShengGuan Bridge, the early-warning method of train running safety of the high-speed railway bridge is established by adopting principal component analysis (PCA) method. Firstly, the root mean square (RMS) of the transverse acceleration of the main girder is used as the monitoring parameter for the train running safety. The correlation model between the RMS values measured from different positions is further adopted as the evaluating model for the train running safety. Finally, the effects of the environmental changes on the evaluating model are eliminated using the PCA method and the warning index for the train running safety is further constructed. The analysis results show that the correlation between the RMS values of the accelerations from different measuring positions on the main girder can be analyzed by a quadratic polynomial fitting model. The PCA method can effectively remove the environmental effects on the quadratic polynomial fitting model. The proposed warning method provides a good capability for detecting the abnormal changes of the measured transverse accelerations and hence it is suitable for early-warning of the train running safety