Exponential decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast

To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that the micro-fracture activity decay law after multistage stress loading and blasting disturbance conforms to the ED model,in which the sum of A and n represents the number of initial micro-fracture events,and n represents the level of background micro-fracture events.The ED model can describe the number of initial micro-fracture events with a deviation less than 10%.The ED model outperforms the traditional aftershock models in describing the micro-fracture event decay law in the three cases considered.The ED model can provide a reference for selecting the blasting interval in mines,which is of great significance to maintain the stability of the surrounding rock and ensure safe production in metal mines.

Label-free fluorescent strategy for sensitive detection of tetracycline based on triple-helix molecular switch and G-quadruplex

In this assay, a label-free fluorescent sensing platform based on triple-helix molecular switch（THMS） and G-quadruplex was developed for the detection of tetracycline. We demonstrated this approach by using THMS, which consists of a central section with a shortened 8-mer aptamer sequence with high affinity to tetracycline and flanked by two arm segments. G-rich oligonucleotide can specifically bind to thioflavin T（Th T） as a signal transduction probe（STP）. In the absence of tetracycline, THMS remains stable, the fluorescence of background is low. By the addition of target tetracycline, the aptamer-target binding results in the formation of a structured aptamer-target complex, which disassembles the THMS and releases the STP. The free STP self-assembles into G-quadruplex and specifically binds to Th T which generates a obvious fluorescence enhancement. Using the triple-helix molecular switch, the developed aptamer-based fluorescent sensing platform showed a linear relationship with the concentration of tetracycline ranging from 0.2 to 20.0 nmol/L. The detection limit of tetracycline was determined to be970.0 pmol/L. The assay avoids complicated modifications or chemical labeling, making it simple and cost-effective. So, it is expected that this aptamer-based fluorescent assay could be extensively applied in the field of food safety inspection.