Analysis of fracture mode transformation mechanism and mechanical model of rock strata with different thicknesses

The deformation, fracture, and movement mode of rock strata are greatly related to underground pressure, surface subsidence, etc. The fracture modes of the thin rock stratum and thick rock stratum are significantly different. How to uniformly describe the fracture modes of rock strata with different thicknesses and establish a mechanical model is a difficult theoretical problem in rock movement. In this paper, the fracture structures of mining strata in 23 typical working faces are investigated. In addition, the fracture mechanical factors and movement modes of the rock stratum are classified based on fracture mechanics, and the relationship between fracture structure and rock stratum thickness is analyzed. Based on the medium-thick plate theory, the fracture mechanical model of rock strata with different thicknesses is established. The fracture mechanical mechanism and fracture mode of rock strata with different thicknesses are revealed, and the corresponding criteria are given. The breakage and movement laws of rock strata with different thicknesses and fracture modes in the mining process are analyzed by numerical simulation. The research shows that when different mining conditions and different stress boundary conditions act on rock strata with different thicknesses, different fracture modes will occur. With the increase of the rock strata thickness, the shear stress of rock strata increases continuously, and the fracture mechanical mechanism of rock stratum presents the evolution law of tensile fracture, tensile shear fracture, and shear fracture. Also, the corresponding rock mass structures are masonry beam structure, layered fracture, and step voussoir beam respectively. Moreover, the statistical data show that the rock layers with a thickness span ratio greater than 0.5 are more prone to occur shear fractures and form step voussoir beams. Based on the above analysis, a mixed fracture model is proposed aiming at the possible tension shear failure of thick rock strata, and the rock fracture mechanical factors are further subdivided into three types: tensile fracture, tensile shear fracture, and shear fracture. There are seven types of fracture modes in rock strata in total. Tensile fracture often occurs in a thin layer, which will change to a shear fracture when the fault appears. Tensile fracture, tensile shear fracture, and shear fracture are typically fracture modes in a thick layer, in which tensile shear mixed fracture is divided into end tensile shear mixed fracture, layered linkage movement, and layered uncoordinated movement. Further research on the fracture modes of rock strata can provide valuable theoretical support for the control of ground pressure and the prevention of surface subsidence hazards in mining

Theoretical model and verification of “analogous hyperbola (hyperboloid)” for the overall movement of mining rock strata: From two-dimensional “analogous hyperbola” to three-dimensional “analogous hyperboloid” models

Coal mining can cause the deformation, fracture, and movement of overlying strata from bottom to top, leading to surface subsidence and other problems. This is a mechanical process, so it is urgent to develop a movement theoretical model based on the mechanical mechanism of rock fracture. Firstly, this paper reviews some theoretical models of rock movement worldwide, and then focuses on our research progress in the field of overall rock movement theoretical models in recent years. Based on the mechanical analysis of the fracture morphology of different layers of rock and the results of similar simulation tests, an “analogous hyperbola” model for the overall movement of mining induced overlying strata was proposed, the focus of the model was approximately located in the layer of the main key stratum of the overlying strata. Furthermore, the overall model of “analogous hyperbola” inside and outside the strata movement was established, and the expression and physical significance parameter system for the internal and external movement of mining overlying rocks were provided. The evolution law of the “hyperbolic like” model for the overall movement of rock layers was analyzed based on different occurrence conditions of overlying rocks and coal seams. On this basis, further extending the two-dimensional “analogous hyperbola” model to the three-dimensional “analogous hyperboloid” model, the three-dimensional movement model of “analogous hyperboloid” in the whole space of mining overburden was established, which includes “quasi-single-leaf” and “quasi-double-leaf” hyperboloids. This theoretical model is based on the research of many predecessors and scholars in China, from the perspective of systems science, it considers the overall movement law of rock layers. A preliminary theoretical model framework of the “analogous hyperbola (hyperboloid)” theory for the overall movement of mining overburden has been formed, hoping to provide a theoretical guidance for scientific coal mining in China

Transcriptionally active HERV-H retrotransposons demarcate topologically associating domains in human pluripotent stem cells.

Chromatin architecture has been implicated in cell type-specific gene regulatory programs, yet how chromatin remodels during development remains to be fully elucidated. Here, by interrogating chromatin reorganization during human pluripotent stem cell (hPSC) differentiation, we discover a role for the primate-specific endogenous retrotransposon human endogenous retrovirus subfamily H (HERV-H) in creating topologically associating domains (TADs) in hPSCs. Deleting these HERV-H elements eliminates their corresponding TAD boundaries and reduces the transcription of upstream genes, while de novo insertion of HERV-H elements can introduce new TAD boundaries. The ability of HERV-H to create TAD boundaries depends on high transcription, as transcriptional repression of HERV-H elements prevents the formation of boundaries. This ability is not limited to hPSCs, as these actively transcribed HERV-H elements and their corresponding TAD boundaries also appear in pluripotent stem cells from other hominids but not in more distantly related species lacking HERV-H elements. Overall, our results provide direct evidence for retrotransposons in actively shaping cell type- and species-specific chromatin architecture

Association Between Greenness Surrounding Schools and Kindergartens and Attention-Deficit/Hyperactivity Disorder in Children in China

IMPORTANCE Few studies have investigated the association between greenness and childhood attention-deficit/hyperactivity disorder (ADHD). OBJECTIVE To evaluate the association between greenness surrounding schools or kindergartens and symptoms of ADHD in children. DESIGN, SETTING, AND PARTICIPANTS This population-based cross-sectional study was performed between April 2012 and January 2013 in 7 cities in northeastern China. This analysis included 59 754 children (aged 2-17 years) from 94 schools and kindergartens, who had resided in the study area for 2 years or longer. Data were analyzed from April 15, 2019, to October 10, 2019. EXPOSURES Greenness surrounding each child's school or kindergarten was estimated using 2 satellite image-derived vegetation indexes: the normalized difference vegetation index and the soil-adjusted vegetation index. MAIN OUTCOMES AND MEASURES Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) scales were used to measure ADHD symptoms (9 inattention symptoms and 9 hyperactivity-impulsivity symptoms). Parents or guardians rated the frequency of each of 18 ADHD symptoms during the preceding 6 months. Children with 6 or more symptoms of either inattention or hyperactivity-impulsivity were defined as having ADHD symptoms. Generalized linear mixed models were applied to estimate the association between greenness and ADHD symptoms. RESULTS The mean (SD) age of the 59 754 study participants was 10.3 (3.6) years, and 29 494 (49.4%) were girls. A total of 2566 participants (4.3%) had ADHD symptoms. Greenness levels differed substantially across schools and kindergartens. The normalized difference vegetation index within 500 m of a school or kindergarten ranged from -0.09 to 0.77. Greater greenness levels were associated with lower odds of ADHD symptoms. In covariate-adjusted models, a 0.1-unit increase in normalized difference vegetation index or soil-adjusted vegetation index within 500mof a school or kindergarten was significantly associated with lower odds of ADHD symptoms (odds ratios, 0.87 [95% CI, 0.83-0.91] and 0.80 [95% CI, 0.74-0.86], respectively;P < .001 for both). The associations were robust in a series of sensitivity analyses. CONCLUSIONS AND RELEVANCE These findings suggest that there may be a beneficial association between school-based greenness and ADHD symptoms in Chinese children. Future longitudinal and mechanistic studies are needed to confirm the findings of this cross-sectional analysis and further explore potential mechanisms of this association

Maternal exposure to ambient air pollution and congenital heart defects in China

Background: Evidence of maternal exposure to ambient air pollution on congenital heart defects (CHD) has been mixed and are still relatively limited in developing countries. We aimed to investigate the association between maternal exposure to air pollution and CHD in China.Method: This longitudinal, population-based, case-control study consecutively recruited fetuses with CHD and healthy volunteers from 21 cities, Southern China, between January 2006 and December 2016. Residential address at delivery was linked to random forests models to estimate maternal exposure to particulate matter with an aerodynamic diameter of ≤1 µm (PM1), ≤2.5 µm, and ≤10 µm as well as nitrogen dioxides, in three trimesters. The CHD cases were evaluated by obstetrician, pediatrician, or cardiologist, and confirmed by cardia ultrasound. The CHD subtypes were coded using the International Classification Diseases. Adjusted logistic regression models were used to assess the associations between air pollutants and CHD and its subtypes.Results: A total of 7055 isolated CHD and 6423 controls were included in the current analysis. Maternal air pollution exposures were consistently higher among cases than those among controls. Logistic regression analyses showed that maternal exposure to all air pollutants during the first trimester was associated with an increased odds of CHD (e.g., an interquartile range [13.3 µg/m3] increase in PM1 was associated with 1.09-fold ([95% confidence interval, 1.01-1.18]) greater odds of CHD). No significant associations were observed for maternal air pollution exposures during the second trimester and the third trimester. The pattern of the associations between air pollutants and different CHD subtypes was mixed.Conclusions: Maternal exposure to greater levels of air pollutants during the pregnancy, especially the first trimester, is associated with higher odds of CHD in offspring. Further longitudinal well-designed studies are warranted to confirm our findings

A COVID-19 Risk Score Combining Chest CT Radiomics and Clinical Characteristics to Differentiate COVID-19 Pneumonia From Other Viral Pneumonias

With the continued transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) throughout the world, identification of highly suspected COVID-19 patients remains an urgent priority. In this study, we developed and validated COVID-19 risk scores to identify patients with COVID-19. In this study, for patient-wise analysis, three signatures, including the risk score using radiomic features only, the risk score using clinical factors only, and the risk score combining radiomic features and clinical variables, show an excellent performance in differentiating COVID-19 from other viral-induced pneumonias in the validation set. For lesion-wise analysis, the risk score using three radiomic features only also achieved an excellent AUC value. In contrast, the performance of 130 radiologists based on the chest CT images alone without the clinical characteristics included was moderate as compared to the risk scores developed. The risk scores depicting the correlation of CT radiomics and clinical factors with COVID-19 could be used to accurately identify patients with COVID-19, which would have clinically translatable diagnostic and therapeutic implications from a precision medicine perspective

Comparative transcriptomics and proteomics analysis of citrus fruit, to improve understanding of the effect of low temperature on maintaining fruit quality during lengthy post-harvest storage

Fruit quality is a very complex trait that is affected by both genetic and non-genetic factors. Generally, low temperature (LT) is used to delay fruit senescence and maintain fruit quality during post-harvest storage but the molecular mechanisms involved are poorly understood. Hirado Buntan Pummelo (HBP; Citrus grandis × C. paradis) fruit were chosen to explore the mechanisms that maintain citrus fruit quality during lengthy LT storage using transcriptome and proteome studies based on digital gene expression (DGE) profiling and two-dimensional gel electrophoresis (2-DE), respectively. Results showed that LT up-regulated stress-responsive genes, arrested signal transduction, and inhibited primary metabolism, secondary metabolism and the transportation of metabolites. Calcineurin B-like protein (CBL)–CBL-interacting protein kinase complexes might be involved in the signal transduction of LT stress, and fruit quality is likely to be regulated by sugar-mediated auxin and abscisic acid (ABA) signalling. Furthermore, ABA was specific to the regulation of citrus fruit senescence and was not involved in the LT stress response. In addition, the accumulation of limonin, nomilin, methanol, and aldehyde, together with the up-regulated heat shock proteins, COR15, and cold response-related genes, provided a comprehensive proteomics and transcriptomics view on the coordination of fruit LT stress responses

Global variation in diabetes diagnosis and prevalence based on fasting glucose and hemoglobin A1c

Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) are both used to diagnose diabetes, but these measurements can identify different people as having diabetes. We used data from 117 population-based studies and quantified, in different world regions, the prevalence of diagnosed diabetes, and whether those who were previously undiagnosed and detected as having diabetes in survey screening, had elevated FPG, HbA1c or both. We developed prediction equations for estimating the probability that a person without previously diagnosed diabetes, and at a specific level of FPG, had elevated HbA1c, and vice versa. The age-standardized proportion of diabetes that was previously undiagnosed and detected in survey screening ranged from 30% in the high-income western region to 66% in south Asia. Among those with screen-detected diabetes with either test, the age-standardized proportion who had elevated levels of both FPG and HbA1c was 29-39% across regions; the remainder had discordant elevation of FPG or HbA1c. In most low- and middle-income regions, isolated elevated HbA1c was more common than isolated elevated FPG. In these regions, the use of FPG alone may delay diabetes diagnosis and underestimate diabetes prevalence. Our prediction equations help allocate finite resources for measuring HbA1c to reduce the global shortfall in diabetes diagnosis and surveillance