Sand-fixing effect and compound change of nylon checkerboard sand barrier.

Grid-based sand-fixing protection barriers have been widely used to solve linear engineering problems in sandy areas. Their placement directly affects the combined change law of wind speed weakening and sand sediment in the sand barrier. It also affects the cost of sand control and the selected structure of the protection system. Therefore, quantifying the effect of different sand barriers is important. We installed nylon mesh checkerboard sand-fixing barriers of three heights and three sizes on the windward side of the highway in the Ulanbuhe Desert, China. By using anemometer and sand collecting instrument, through comparing and observing air flow changes, windproof efficiency, and sand sediment inside the sand barrier, it is found that height had more influence on the protective benefit of a sand barrier than did the mesh specification. The protective effect at the boundary of a sand barrier resulted from compound superposition. The model for calculating a suitable sand barrier protection width was affected by sand-driving wind speed, open field wind speed, sand barrier unit side length, height, and actual protection demand. Sand barriers of 1 × 1 m (It is the grid size of the mesh.) at 20-cm height, 1 × 1 m and 1.5 × 1.5-m at 30-cm height could be laid over a wide area. Different collocation patterns can be selected according to the dominant wind direction. The results can provide basic data and theoretical support for sand barrier protection system.

Electrochemical aptasensor based on electrodeposited poly(3,4-ethylenedioxythiophene)-graphene oxide coupled with Au@Pt nanocrystals for the detection of 17ß-estradiol.

An electrochemical aptasensor is reported for the sensitive and specific monitoring of 17ß-estradiol (E2) based on the modification of electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT)-graphene oxide (GO) coupled with Au@Pt nanocrystals (Au@Pt). With excellent conductivity, chemical stability and active sites, the PEDOT-GO nanocomposite film was firstly in situ polymerized on the glassy carbon electrode by cyclic voltammetry. Subsequently, one-step synthesized Au@Pt were decorated on the conductive polymer, providing a platform for immobilizing the aptamer and enhancing the detecting sensitivity. With the addition of E2, since the interfacial electron transfer process was retarded by the E2-aptamer complex, the differential pulse voltammetry signal decreased gradually. Under optimum conditions, the calibration curve of E2 exhibited a linear range between 0.1 pM and 1 nM, with a low detection limit (S/N = 3) of 0.08 pM. The developed aptasensor showed admiring selectivity, stability, and reproducibility. It was tested in human serum, lake water and tap water samples after low-cost and simple pretreatment. Consequently, the developed platform could provide a new design thought for ultrasensitive detection of E2 in clinical and environmental samples.