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The coal-seam fire is one of the most significant disasters in the coal mining industry in China, affecting the safety of coal production in China. The working-position risk in coal mining has an important impact on the risk of fire occurrence, and thus it would be worthwhile to analyze working-position risks so as to effectively prevent and control coal-seam fires. Based on the kernel density estimation (KDE), this research puts forward an innovative calculation-model and assessment method of the superposition risk of the working position on coal-seam fire accidents. This research aims to evaluate the priority of risk management of working positions in coal-seam fire accidents. In order to achieve this research aim and objectives, this research carried out a statistical analysis of 100 classic cases of coal-seam fire accidents from 2000 to 2022, using the accident-tree-structure importance analysis method. This research contributed to the evaluation of the frequency and severity of various risk factors leading to fire accidents, and the development of the value at risk (VaR) of various risk factors in the coal-seam fire accidents. Integrating all the risk factors involved in each position and their risk values, and building a position-risk calculation model was carried out. In addition, in accordance with the kernel density estimation (KDE), a post-superposition risk model was established. Moreover, ArcGIS software was used to obtain the superimposed risk of posts and build a risk-distribution map. Based on the possibility of post-risk occurrence and the severity of the consequences, a risk-assessment matrix was developed, a post-risk grading standard was established, and risk levels of the working position were divided up in this research. Results indicated that (1) before risk superposition, working-position risks and risk levels are densely distributed, and nearly 80% of risk levels of the working position are focused on Level II and III, without Level I. (2) After risk superposition, the post-risk is affected by the surrounding post-risk, and the risk- and level-distribution is more hierarchical; the number of Level I risks in working positions increased to 12, which were mainly distributed among the comprehensive mining team, comprehensive excavation team and ventilation team, which accords more with the objective and actual production-conditions. The risk-distribution map directly showed that the post-fire risk at the mining face and shaft is higher, a result which will take on a significant guiding role in the effective control and prevention of risk in coal-seam fires in the future. [ABSTRACT FROM AUTHOR]

• No negative effects occurred for SAR (pH 3.5 and pH 4.5). • SAR (pH 2.5) reduced chloroplasts and damaged the outer leaf layers. • SAR (pH 2.5) altered genes related to photosynthesis and various metabolic pathways. • Plants respond to SAR stress by mechanisms of resistance, avoidance, and escape. Tea plants (Camellia sinensis (L.) O. Kuntze), which are typically cultivated in high-elevation mountainous regions in southern China, are severely affected by acid rain. Our recent study indicated that simulated acid rain (SAR) at pH 2.5 produced necrotic spots on the leaf surface, impaired plant development by inhibiting photosynthesis and the antioxidant defense system, and caused metabolic disorders. In contrast, a pH of 4.5 had no toxic effects on tea seedlings. However, molecular-level evidence for these conclusions is still lacking. In this study, we explored the changes in leaf micromorphology under different SAR treatments using electron microscopy, and presented the first case study on the systemic responses of the tea leaf transcriptome to SAR. An examination of leaves using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that SAR (pH 4.5 and pH 3.5) did not impair the epidermis or chloroplast structures, but SAR (pH 2.5) reduced the number of chloroplasts, corroded epicuticular wax and trichomes, and altered stomatal density and size. Transcriptomic analysis revealed that the expression of multiple genes related to photosynthesis and carbohydrate, nitrogen, and sulfur metabolism were altered under SAR. Additionally, epicuticle wax biosynthesis and plant hormone signal transduction pathways were found to significantly influenced by high-acidity SAR. Taken together, our results suggest that tea plant responses to intense SAR stress incorporate three aspects: (1) stress resistance via altering metabolic pathways to enable survival; (2) stress avoidance via restraining uncontrolled non-stomatal gas exchange; and (3) stress escape via redistributing nitrogen from stress damaged leaves. These findings provide valuable insights into plant responses to acid rain stress. [ABSTRACT FROM AUTHOR]

Background: Chinese topography appears a three-rung ladder-like distribution of decreasing elevation from northwest to southeast, which is divided by two sloping edges. Previous studies have reported that prevalence of thyroid diseases differed by altitude, and geographical factors were associated with thyroid disorders. To explore the association between three-rung ladder-like regions and thyroid disorders according to unique Chinese topographic features, we conducted an epidemiological cross-sectional study from 2015–2017 that covered all 31 mainland Chinese provinces. Methods: A total of 78,470 participants aged ≥ 18 years from a nationally representative cross-sectional study were included. Serum thyroid peroxidase antibody, thyroglobulin antibody, and thyroid-stimulating hormone levels; urine iodine concentration; and thyroid volume were measured. The three-rung ladder-like distribution of decreasing elevation from northwest to southeast in China was categorized into three topographic groups according to elevation: first ladder, > 3000 m above sea level; second ladder, descending from 3000—500 m; and third ladder, descending from 500 m to sea level. The third ladder was further divided into groups A (500–100 m) and B (< 100 m). Associations between geographic factors and thyroid disorders were assessed using linear and binary logistic regression analyses. Results: Participants in the first ladder group were associated with lower thyroid peroxidase (β = -4.69; P = 0.00), thyroglobulin antibody levels (β = -11.08; P = 0.01), and the largest thyroid volume (β = 1.74; P = 0.00), compared with the other groups. The second ladder group was associated with autoimmune thyroiditis (odds ratio = 1.30, 95% confidence interval [1.18–1.43]) and subclinical hypothyroidism (odds ratio = 0.61, 95%confidence interval [0.57–0.66]) (P < 0.05) compared with the first ladder group. Group A (third ladder) (500–100 m) was associated with thyroid nodules and subclinical hypothyroidism (P < 0.05). Furthermore, group B (< 100 m) was positively associated with autoimmune thyroiditis, thyroid peroxidase and thyroglobulin antibody positivity, and negatively associated with overt hypothyroidism, subclinical hypothyroidism, and goiter compared with the first ladder group(P < 0.05). Conclusion: We are the first to investigate the association between different ladder regions and thyroid disorders according to unique Chinese topographic features. The prevalence of thyroid disorders varied among the three-rung ladder-like topography groups in China, with the exception of overt hyperthyroidism. [ABSTRACT FROM AUTHOR]

Curved composite twin-girder bridges are suitable for mountainous areas, due to their advantages of light self-weight, excellent mechanical performance, and fewer construction requirements. It has been found that many composite twin-girder bridges collapsed due to fatigue failure. However, the literature review showed no relevant studies on the fatigue performance of curved composite twin-girder bridges. Because of this, the specimen of 1:2 scale curved composite twin-girder bridge in accordance with the design scheme of Xizhen Bridge in China was designed and tested. Three possible fatigue details were selected: cruciform connections, transverse attachments, and transverse splices named Class I, Class II, and Class III. For the test data of nominal stress (NS), equations were proposed to convert the strain value into the internal force of the fatigue detail position. The stress caused by torsion accounts for 2.8% of the total stress, which is almost negligible. The fatigue evaluation process based on the hot spot stress (HSS) S-N curve method is presented. The HSS method is more conservative than the NS S-N curve method in predicting the fatigue life of complex structures with high-stress concentrations. [ABSTRACT FROM AUTHOR]

Abstract: We aimed to examine the association between sleep duration and impaired cognitive function in different cognitive domains in Chinese community-dwelling older adults. A total of 1591 participants (≥60 years) were divided into five groups: ≤6 hours (very short sleep duration), >6 to 7 hours (short sleep duration), ≥7 to 8 hours (moderate sleep duration), >8 to 9 hours (moderately long sleep duration), and >9 hours (long sleep duration), according to sleep duration. Cognitive function was assessed using the Mini-Mental State Examination. Long sleep duration significantly increased the likelihood of cognitive impairment. In addition to attention, long sleep duration was negatively related to poorer global cognition and other cognitive domain functions. With the stratification of age groups, long sleep duration was negatively associated with other cognitive domain functions except delayed recall in older elderly (≥75 years) people, but not in younger elderly (60-74 years) people. Long sleep duration was associated with higher rates of cognitive impairment, poorer global cognition, and declined orientation, memory, language ability, and executive function in Chinese community-dwelling older adults, which was more significant in older elderly people. [ABSTRACT FROM AUTHOR]