To understand the deteriorate characteristics of granite in cold regions, the influences of freeze–thaw cycles on the mechanical properties need to be investigated. The rock specimens (biotite ...granite from Tibet in China) were frozen and thawed in a temperature and humidity controlled container where the temperature varied from +
40 to −
40
°C and the humidity was kept at 100% continuously. The freeze–thaw tests were conducted for one cycle including 4
h of freezing and 4
h of thawing, and the number of cycles was from 0 to 150. The deterioration of the specimens was examined by the changes of strength, deformation characteristics, elastic modulus, cohesive strength and internal frictional angle in a series of uniaxial and triaxial compression tests. The experimental results show that (1) the axial strain corresponding to the peak stress increases with an increasing of confining pressure and freeze–thaw cycles; (2) The compressive strength decayed exponentially with the number of freeze–thaw cycles, as well as elastic modulus and cohesive strength; (3) the internal frictional angle remained constant in the process of freeze–thaw cycles; (4) The interrelation among compressive strength, confining pressure and number of cycles can be described by Mohr–Coulomb strength criterion.
► The compressive strength, deformation characteristics and elastic modulus are decreased with increasing number of freeze–thaw cycles; ► Several exponential decay function models are proposed to describe their relationships; ► A formulation is proposed to describe the relationship between triaxial compressive strength and the number of freeze–thaw cycles; ► The influence of the number of freeze–thaw cycles on the compressive strength is correctly described by the proposed formulation.
•Bubble–bubble interaction can suppress or enlarge the radial pulsations of bubbles.•The suppression or enlargement depends on the ultrasound parameters, the radii, the distances and the bubble ...number.•The frequency response curve of expansion ratio decreases and shifts to left due to bubble–bubble interaction.•The larger the coupling strength is, the more the left-shifting is.
Using a model that with or without considering the interaction between bubbles through the radiated pressure waves, numerical simulations of cavitation bubbles have been performed in order to study the effect of the bubble–bubble interaction on radial pulsations of bubbles. Comparing the results obtained by with or without considering the bubble–bubble interaction, it is suggested that the suppression or enlargement property of expansion ratios of bubbles due to the bubble–bubble interaction largely depends on the ultrasound parameters, the ambient bubble radii, the distances between bubbles and the number of bubbles (in multi-bubble environment, the last two aspects can be expressed using the coupling strength). The frequency response curve of expansion ratio decreases and shifts to left due to the bubble–bubble interaction and the larger the coupling strength is, the more the left-shifting is.
N(6)-methyladenosine (m(6)A) is the most prevalent and reversible internal modification in mammalian messenger and noncoding RNAs. We report here that human methyltransferase-like 14 (METTL14) ...catalyzes m(6)A RNA methylation. Together with METTL3, the only previously known m(6)A methyltransferase, these two proteins form a stable heterodimer core complex of METTL3-METTL14 that functions in cellular m(6)A deposition on mammalian nuclear RNAs. WTAP, a mammalian splicing factor, can interact with this complex and affect this methylation.
•A coupled hydromechanmical hydraulic fracturing model based on the Perdidynamics is established, which can simulate the hydraulic fracturing problem with arbitrary fracture network.•The problem of ...tracing macro fractures in the PD model is solved.•Failure criterion of rock mass shear failure based on PD.•A method for calculating the contact, friction and cohesion force on the fracture surface in PD model is proposed.•A model for judging and recording the connectivity of fracture networks.
A coupled hydromechanical model based on peridynamics is proposed to simulate the hydraulic fracturing in a complex fracture network. The proposed method is validated by comparing the numerical results with the analytical and experimental solution. Then, the influence of the crustal stress distribution, the friction force acting on the natural fracture (NF) surface and the NF network on hydraulic fracture (HF) propagation are investigated. The simulation results reveal that the crustal stress ratio mainly affects the HF propagation direction. When HFs and NFs are connected, the induced stress caused by the opening of NFs deflects the propagation direction of new fractures. The friction force on NF surface is an important factor affecting the interaction between HFs and NFs.
With the intensification of people’s production and life behaviors, the systemic risks of water, energy and food in the Yangtze River Basin have become increasingly prominent, which has become a ...bottleneck for sustainable development of social, economic and ecological in the basin. Therefore, studying the symbiotic coordination between water, energy and food is of great significance to promoting regional sustainable development. First, from the perspective of water–energy–food symbiosis, with the water–energy–food ecosystem conceptual model as the nexus, the two-step measurement model of the symbiotic index and the symbiotic level index is used to study the water–energy–food symbiosis of the Yangtze River. Then, we use the BP-DEMATEL-GTCW model to identify the key influencing factors that affect the symbiotic security of the water–energy–food ecosystem. In this research, it is found that the average value of the symbiotic degree of the water–energy–food ecosystem of the 11 provinces or municipalities in the Yangtze River Basin only reached the risk grade. It can also be seen from the identification results of key influencing factors that energy microsystem-related indicators have a greater impact on the symbiotic development of the entire WEF ecosystem. Therefore, special attention needs to be paid to increasing energy sources and reducing expenditure. Relevant departments need to effectively develop primary energy production and expand energy-saving investment through multiple channels to expand energy self-sufficiency and ultimately promote the coordinated and effective development of water, energy and food in the Yangtze River Basin.
Staphylococcus aureus, a major human pathogen, has been the cause of serious infectious diseases with a high mortality rate. Although genetics is a key means to study S. aureus physiology, such as ...drug resistance and pathogenesis, genetic manipulation in S. aureus is always time-consuming and labor-intensive. Here we report a CRISPR/Cas9 system (pCasSA) for rapid and efficient genome editing, including gene deletion, insertion, and single-base substitution mutation in S. aureus. The designed pCasSA system is amenable to the assembly of spacers and repair arms by Golden Gate assembly and Gibson assembly, respectively, enabling rapid construction of the plasmids for editing. We further engineered the pCasSA system to be an efficient transcription inhibition system for gene knockdown and possible genome-wide screening. The development of the CRISPR/Cas9-mediated genome editing and transcription inhibition tools will dramatically accelerate drug-target exploration and drug development.
BackgroundThe incidence of hypertension has been increasing in the past decade. Little is known regarding the relationship between hypertension and human development index (HDI). ObjectivesThe ...objective is to identify the relationship between the prevalence of hypertension and human development index (HDI). MethodsAn ecological study was conducted. The data from World Health Organization reports and United Nations Development Programme reports for 182 countries, including the HDI values, rates of tobacco use, physical inactivity, alcohol use, and salt intake. The Generalized Additive Models were implemented to assess the association between the prevalence of hypertension and the HDI. ResultsAmong 182 countries, the prevalence of hypertension ranged from 13% to 41%. The highest HDI value was 0.949 and the lowest was 0.352. In model 1, statistically significant associations were found in three populations, the largest R2 was 0.245. In model 2, the largest R2 was 0.485. In linear part, there was negative relationship in female population, while HDI was associated with prevalence of hypertension in all three populations, which was explained by spline function. The curve indicated that there were three intervals from low to high HDI. From 0 to 0.6 and 0.8 to 1, an evident decreasing trend of prevalence was found, while the rate increased when HDI was in the interval of 0.6 to 0.8. ConclusionsIn this study, we identified the association between the prevalence of hypertension and the HDI and the underlying pattern of the relationship. The findings will aid the planning of hypertension control priorities and provide suggestions for interventions.
Geotechnical instability and failure are closely related to the hydro-mechanical coupled behavior of fractured rocks, and the existing studies often regard the fracture seepage as linear Darcy flow. ...Due to the neglect of non-Darcy effect caused by rough rock wall and high flow velocity, the estimated rock deformation and seepage flow can lead to incorrect assessment of geotechnical risks. Hence, this study proposed an efficient and robust hydro-mechanical (HM) coupled model to consider non-Darcy flow in complex fracture networks. The fractured rock mass's mechanical response, including the fracture surface's frictional contact, was calculated using the XFEM solver, and the widely used Forchheimer's law was adopted to describe the non-Darcy flow along the fractures. The fracture segments cut by mechanical element edges are considered one-dimensional flow elements, and the Newton-Raphson iteration method is adopted to solve the Forchheimer equation directly. To consider the influence of fracture deformation on the conductivity of fractures, the Barton-Bandis model was adopted to determine the hydraulic aperture of the fractures when the fracture was closed. Subsequently, a staggering Newton-Raphson method can be developed to decouple the fracture deformation and fluid flow process. Experimental results were adopted to validate the accuracy of the numerical model, and several numerical cases were used to illustrate the efficiency and robustness of the proposed model. The effects of inlet pressure, confining stress, and non-Darcy effect on the HM-coupled behavior of fractured rock were investigated. Numerical results suggested that the distribution of fluid pressure and failure process of rock mass based on Darcy assumption could be dramatically changed after considering the nonlinear seepage behavior.
Foamed concrete has a good energy absorption capability and can be used as seismic isolation material for tunnels. This study aims to investigate the mechanical properties and associated seismic ...isolation effects of foamed concrete layer in rock tunnel. For this, a series of uniaxial/triaxial compression tests was conducted to understand the effects of concrete density, confining stress and strain rate on the mechanical properties of foamed concrete. The direct shear tests were also performed to investigate the effects of concrete density and normal stress on the nonlinear behaviors of foamed concrete layer-lining interface. The test results showed that the mechanical properties of foamed concrete are significantly influenced by the concrete density. The foamed concrete also has high volumetric compressibility and strain-rate dependence. The peak stress, residual stress, shear stiffness and residual friction coefficient of the foamed concrete layer-lining interface are influenced by the foamed concrete density and normal stress applied. Then, a crushable foam constitutive model was constructed using ABAQUS software and a composite exponential model was also established to study the relationship between shear stress and shear displacement of the interface, in which their parameters were fitted based on the experimental results. Finally, a parametric analysis using the finite element method (FEM) was conducted to understand the influence of foamed concrete layer properties on the seismic isolation effect, including the density and thickness of the layer as well as the shear stiffness and residual friction coefficient of the interface. It was revealed that lower density and greater thickness in addition to smaller shear stiffness or residual friction coefficient of the foamed concrete layer could yield better seismic isolation effect, and the influences of the first two tend to be more significant.
RNA molecules can attach to chromatin. It remains difficult to know what RNAs are associated with chromatin and where the genomic target loci of these RNAs are. Here, we present MARGI (mapping ...RNA-genome interactions), a technology to massively reveal native RNA-chromatin interactions from unperturbed cells. The gist of this technology is to ligate chromatin-associated RNAs (caRNAs) with their target genomic sequences by proximity ligation, forming RNA-DNA chimeric sequences, which are converted to a sequencing library for paired-end sequencing. Using MARGI, we produced RNA-genome interaction maps for human embryonic stem cells (ESCs) and human embryonic kidney (HEK) cells. MARGI revealed hundreds of caRNAs, including previously known XIST, SNHG1, NEAT1, and MALAT1, as well as each caRNA’s genomic interaction loci. Using a cross-species experiment, we estimated that approximately 2.2% of MARGI-identified interactions were false positives. In ESCs and HEK cells, the RNA ends of more than 5% of MARGI read pairs were mapped to distal or inter-chromosomal locations as compared to the locations of their corresponding DNA ends. The majority of transcription start sites are associated with distal or inter-chromosomal caRNAs. Chromatin-immunoprecipitation-sequencing (ChIP-seq)-reported H3K27ac and H3K4me3 levels are positively correlated, while H3K9me3 is negatively correlated, with MARGI-reported RNA attachment levels. The MARGI technology should facilitate revealing novel RNA functions and their genomic target regions.
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•MARGI globally profiles native RNA-chromatin interactions•Two variations of MARGI interrogate proximity-based and direct interactions•The majority of transcription start sites are associated with interacting RNAs•RNA attachment is positively correlated with active histone marks in promoters
Sridhar et al. develop a technology to map global RNA-chromatin interactions in unperturbed cells. They discover hundreds of chromatin-associated RNAs. They find that the majority of known transcription start sites are associated with chromatin-associated RNAs, suggesting that this phenomenon is more widespread than previously thought.
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