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Fermented foods are rich in protein and free amino acids, which are decarboxylated by microbial amino acid decarboxylase to produce biogenic amines. Excessive ingestion of biogenic amines poses a threat to human health. Tyramine, a biogenic amine having high toxicity, is present in fermented foods in large quantities, so developing safe and effective methods to control tyramine is of practical significance for improving the safety of fermented foods. In this article, the physiological functions, harms and limit standard of tyramine in fermented foods are described with an emphasis on the formation mechanism and control methods of tyramine, so as to provide theoretical references for further improving the safety of fermented foods.

【Objective】In order to solve the problem that it is difficult to make the temperature sensor of the Photonic Crystal Fiber (PCF) with Surface Plasma Resonance (SPR), a D-structure PCF temperature sensor is proposed. The micro-structure and arrangement of the air hole are also designed. The method of coating the polishing surface of the optical fiber with gold layer is used to stimulate the SPR of the optical fiber.【Methods】Ethanol is used as a temperature-sensitive material, and the temperature-sensitive effect is used as the temperature sensing mechanism to achieve the effect of temperature sensing. The finite element analysis method is used to simulate the thickness of the gold layer and the size of the elliptical air hole of the fiber respectively. The coupling characteristics between the core mode and the surface plasma mode are analyzed under different conditions, and the structure of the sensor is optimized.【Results】The temperature characteristics of the sensor are simulated. In the range of -80~80 ℃, the sensitivity of the sensor is 3.4 nm /℃, and the linearity is better than 0.969 63.【Conclusion】The temperature sensor designed in this paper has a wide temperature detection range, satisfactory sensitivity, and linearity, which can be used for real-time temperature monitoring in industrial, agricultural, and medical fields.

Objective To verify the function of exosomes from 293T cells over-expressing membrane-localized IL-3 in vitro, so as to lay a foundation for in vivo function verification in animal models of Alzheimer′s disease. Methods Using the patented structure of the group, a recombinant IL-3 lentiviral vector was constructed and virus-infected 293T cells were packaged. Stable cell strain over-expressing IL-3 was screened. The membrane localization of IL-3 was verified by flow cytometry and immuno-fluorescence. Il-3-exosomes were purified by ultra filtration centrifugation, the exosmic morphology was observed by transmission electron microscope, the size distribution and concentration of exosomes were detected by nano-flow analysis, and the expression of IL-3 and exosome related marker proteins were detected by Western blot. The effect of BV-2 on the phagocytosis of Aβ amyloid was detected by immuno-fluorescence. Results Through vector construction, virus infection, screening and verification of puromycin, 293T cell strain with stable over-expression membrane-anchored IL-3 was obtained. The purified exosomes were collected and the structures of double-layer membrane vesicles with a diameter of 50-100 nm were observed under transmission electron microscope. Western blot results proved the presence of CD63, ALIX, TSG101 and other exosome marker proteins and these molecules were rich in IL-3 as compared with the control, that suggested the successful purification of IL-3-exosomes. The results of immuno-fluorescence assay showed that IL-3-exosomes promoted the phagocytosis of Aβ amyloid by BV-2 cells in vitro. Conclusions The gene modified 293T cell exosomes membrane-anchored expression of IL-3 can play a role of both IL-3 and exosomes in vitro, which promote the phagocytosis of microglia, there for provides a new idea for the clinical treatment of Alzheimer′s disease.

Within the COVID-19 pandemic and the new normal period, online learning has become one of the main options for learning. Previous studies on self-regulated learning have shown that it was a better predictor of online learning effectiveness. However, this discussion has not been extended to the situation of the COVID-19 pandemic. To address this gap, this study aims to explore the relationship between the three stages of self-regulated learning (SRL) and learning ineffectiveness (LI). Data of 370 high school students were collected during the period of COVID-19. Structural equation modeling was used to perform confirmatory factor analysis on the data. Findings show that the preparatory stage was positively related to the stages of performance and appraisal, and the performance stage was positively related to the appraisal stage; on the other hand, the stages of performance and appraisal were negatively related to learning ineffectiveness. In addition, the preparatory stage had no direct relation to learning ineffectiveness, but the preparatory stage was correlated with learning ineffectiveness, mediated by the stages of performance and appraisal. These results suggest that better performance in the three stages of self-regulated learning decrease learners' perceived online learning ineffectiveness. This understanding can have implications for global education.