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BackgroundDue to widespread SARS-CoV-2 infection, an emergency homeschooling plan was rigorously implemented throughout China. ObjectiveThis study aimed to investigate the experiences and attitudes of elementary school students and their parents (two generations from the same family) toward online learning in China during the pandemic. MethodsA 16-item questionnaire was distributed at the 10-day and 40-day marks after the start of the first online course to 867 parent-child pairs and 141 parent-child pairs, respectively. The questionnaire was comprised of questions pertaining to course and homework completeness, effectiveness, reliability, and abundance as well as the students’ enthusiasm for taking part in online classes and their satisfaction with the courses. ResultsOur findings indicate that 90.7% (786/867) of students exhibited high or moderate enthusiasm for participating in online classes. However, most students performed poorly in online learning classes and after-school homework. With regard to satisfaction, parents' and students' average scores were 7.35 and 7.25, respectively (10-point scoring system). During the second stage of this study, parents' positive evaluations for online learning declined, including those for the effectiveness and reliability of the courses. Furthermore, the proportion of students who completed the courses and homework on time decreased; this difference proved statistically significant (P=.047). The parents’ and students’ overall satisfaction with online learning also declined during the second stage (parents: 7.21; students: 7.23); however, the difference in overall satisfaction between the two stages was not statistically significant (parents: P=.53; students: P=.60). Several of the parents (315/867, 36.2%) indicated that assisting with and supervising the students’ online learning resulted in increased stress. Further, 36% of parents expressed dissatisfaction with or provided suggestions for online learning; most parents and students hoped to return to face-to-face classes (parents: 823/867, 94.9%; students: 811/867, 93.5%). Finally, our results presented the following six main issues that parents were the most concerned about: (1) disappointment regarding timely interaction in courses; (2) apprehensiveness about students’ understanding of the course; (3) the increased burden of annoying adult responsibilities; (4) concern about children's eyesight; (5) the idea that teachers’ explanations were not detailed enough; and (6) concerns about the decline of students' interest in and attention toward online courses. ConclusionsOnline learning can prevent the spread of infectious diseases while still allowing elementary school students to attain knowledge. However, in our study, children’s completion of the courses and homework were not satisfactory. Furthermore, their parents often experienced stress and had many concerns and complaints. Measures such as increasing the interactivity of the courses and prohibiting teachers from assigning tasks to parents could improve the effectiveness of these courses and the mental health of parents and students.

Elastic metamaterials with double negativity can manipulate the propagation of elastic waves at sub-wavelength scales by inducing multiple resonances to achieve different negative effective parameters. Numerous efforts have been made to control the dynamic behavior by directly tuning the frequency range of double negativity in elastic metamaterials. This study examines the impact of tensile loads on double negativity in relation to ligament inclination angle. The findings will aid in the direct tunability of double negativity in single-phase chiral metamaterials. The study examines a simple single-phase four-ligament chiral unit with low-order double negativity. The presence of double negativity was verified through band structure analysis and calculation of the four effective dynamic parameters. Additionally, the effects of two geometrical factors on the frequency ranges of negative parameters were investigated through parametric scanning. The results indicate that the frequency range of double negativity reaches its maximum at a ligament inclination angle of around 45° and disappears as the angle approaches 65°. Given that the ligament inclination angle of the unit cells can be easily altered by external tension, this intriguing outcome is leveraged to achieve the emergence and vanishing of double negativity. This characteristic is confirmed through the examination of negative refraction phenomena via simulation examples. [ABSTRACT FROM AUTHOR]

BackgroundSuicide is one of the serious public health problems worldwide. The relationship between suicide and neutrophil-to-lymphocyte ratio （NLR） may vary in different regions and different age. It is necessary to further investigate the relationship between NLR and suicidal ideation in Chinese children and adolescents with depression.ObjectiveTo explore the correlation between NLR and suicidal ideation in children and adolescents with depression， so as to provide clues for exploring the biomarkers of suicide.MethodsA retrospective analysis of 536 children and adolescents with depression who were hospitalized in the Third People's Hospital of Fuyang from January 2020 to December 2022 and met the diagnostic criteria of the International Classification of Diseases， tenth edition （ICD-10） was performed. Patients were divided into two groups according to whether they reported suicidal ideation. Demographic data， discharge diagnosis， Hamilton Depression Scale-17 item （HAMD-17） score and hematological test data （neutrophil counts， lymphocyte counts） on the second day were collected from medical records. Receiver operating characteristic （ROC） curve was used to determine the optimal cut-off point of NLR for predicting suicidal ideation in children and adolescents with depression， and binary Logistic regression was used to analyze the risk factors for suicidal ideation.ResultsAmong the 536 patients， 429 cases （80.04%） had no suicidal ideation， and 107 cases （19.96%） had suicidal ideation. Compared with patients without suicidal ideation， the HAMD-17 score ［（25.28±8.86） vs. （21.21±8.46）， F=19.400， P