Search

In order to judge the mildew degree of wheat seeds quickly and accurately, this study proposed a qualitative analysis method for moldy wheat using terahertz time-domain (THz-TDS) spectroscopy combined with support vector (SVM), random forest (RF) or extreme learning machine (ELM). According to the content of aflatoxin B1 (AFB1), wheat seeds were classified into four types: normal, slight mildew, moderate mildew and severe mildew. Spectral data in the band of 0.1–4.0 THz were obtained using a CCT-1800 THz spectrometer. The effects of different spectral pretreatment methods on the results discrimination were examined, and three dimensionality reduction methods, principal component analysis (PCA), linear discriminant analysis (LDA), and t-distributed stochastic neighbor embedding (t-SNE), were used to reduce the dimension of spectral data. LDA was found to be the best method. Finally, a model based on SVM, RF or ELM was constructed. The SVM model had the best classification effect. When polynomial kernel function was chosen and error penalty coefficient was 1, the accuracy of discrimination was 98.61% and the root mean square error of prediction was 0.142 9. This study confirms that THz spectroscopy can be applied for accurate detection of wheat mildew, which can provide a detection approach for food safety and grain storage and detection.

Meaning in life refers to an individual's capacity to understand and grasp the meaning of their own existence, as well as being aware of the goals, tasks, or missions in their personal life. Previous studies have found that college students lack meaning in life, but physical exercise can enhance it. In this study, 3,196 college students completed self-report questionnaires to assess self-efficacy, life satisfaction, physical exercise, and meaning in life. The results revealed that the physical exercise not only influenced an individual's perceived meaning in life directly, but also influenced it through self-efficacy. Furthermore, it confirmed the chain mediating role of self-efficacy and life satisfaction, whereby engaging in physical exercise can ultimately impact meaning in life through self-efficacy and life satisfaction. This discovery can help educators create interventions to improve college students' physical exercise engagement and overall life satisfaction. [ABSTRACT FROM AUTHOR]

Transverse spin, a spin component with unique characteristics, provides a new dimension for plenty of applications, such as optical trapping, imaging, and communication. Here, we analyze the pure transverse spin in the Bessel beam, which is solely present in the azimuthal direction. Based on a single layer dielectric metasurface, we efficiently generate Bessel beams with pure transverse spin in a compact optical system. As designed, the transverse spin is flexibly tunable by converting the polarization of the incident light. Furthermore, in the scattered Bessel beam, the local electromagnetic field oscillates around the transverse axis, which is perpendicular to the beam propagation. At certain positions, the local polarization ellipse degenerates into a perfect circle, resulting in a ring-periodic distribution of circularly polarized points (C points) in the beam. This suggests that the local polarization demonstrates a nontrivial periodic structure. This work deepens our understanding of spin-related physics and opens a new avenue for the study and application of transverse spins in ultracompact, flat, multifunctional nanophotonic platforms.