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Tetracyclines (TCs) are the most commonly antimicrobial agents that used in livestock production worldwide. It is important to supervise tetracyclines residues in food for environmental monitoring and food safety. In this study, a novel, label-free chemiluminescence (CL) assay without antibody was established. Fe3O4 NPs could facilitate the CL interaction between luminol and H2O2. Interestingly, TCs could enhance the catalytic ability of Fe3O4 NPs and result in a further amplification of the CL intensity. The CL intensity varied linearly with the concentration of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), and ranging from 10–2400, 10–2800, and 5–2100 nmol/L, respectively; The limits of detection were 4 nmol/L for TC, 6 nmol/L for OTC, and 2 nmol/L for CTC. This CL strategy was applied successfully in testing three TCs residues in milk, eggs and honey samples with more sensitive results, which provided an alternative strategy for monitoring the correct use of TCs.

Building on a theoretical model of decision-making under risk and uncertainty, this paper examines how Chinese college students made decisions about international moblity or immobility during the COVID-19 pandemic. The paper finds that among the 118 interviewees, most continued to choose to study abroad, whilst some gave up after getting offers from prestigious Western universities. We further analysed the divergent patterns of two choices which can be explained by resilience to risks and uncertainties and lack of thereof. For those who have given up studying abroad, the symbolic capital and labor market advantages brought by degrees (especially master degrees) from Western universities have become uncertain and offset by the risk of the epidemic. These findings suggest that, in addition to safety, college students will prefer certainty more than before when choosing whether to go abroad and the study abroad landscape may change based on this mindset.