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As the core unit of backfill mining method, the strength of backfill is an important indicator to ensure safe mining. Na-based bentonite features a high methylene blue adsorption capacity and green compressive strength, making it a high-quality additive for preparing filling materials. However, there are few studies probing into the relationship between the dosage and the strength of the filling materials. This paper analyzes the changes in shear wave velocity, dominant frequency amplitude, amplitude attenuation coefficient, and waveform fractal dimension of filling materials with different Na-based bentonite dosages at different ages through ultrasonic testing technology and uniaxial compression tests. Combined with sensitivity analysis, we selected the most sensitive acoustic parameters to changes in compressive strength. Furthermore, this study establishes a strength prediction model for backfill with different Na-bentonite contents and combining significance testing and comparative analysis. The research findings can serve as a valuable reference for theoretical research and engineering applications related to predicting the uniaxial compressive strength of backfill materials.

This study proposes a finite element model for submerged water jet excavation using a cylindrical nozzle with an aim to determine the depth and diameter of jet orifices during water jet excavation. The model's accuracy was verified through indoor experiments, employing the Lagrangian-Eulerian fluid-solid coupling algorithm. The response surface method was utilized to establish a predictive model for the depth and diameter of jet orifices, which includes the impact of nozzle diameter, jet standoff distance, jet pressure, and their interactions. The construction parameters for jet excavation were optimized using a satisfaction function. Results indicated that for excavation depths of 10 cm, 15 cm, and 20 cm, keeping the stability of the jet orifices to the maximum required higher jet pressure(7.2 MPa), smaller jet standoff distance(1 cm), and an appropriate nozzle diameter(0.928 mm, 1.164 mm, and 1.345 mm). After optimization, the predicted values of jet orifice depth and diameter for the specific target excavation depths showed an error of less than 15 % compared to the experimental values, demonstrating the credibility and reliability of the predictions.

Background: The fenestrated stent technique has been developed for the treatment of aneurysms with branches. However, the hole size and type, which are the key factors for optimal treatment outcomes, are still controversial in clinical application. Therefore, a hemodynamics investigation in terms of the size and type of the hole was performed with the objective of providing evidence for optimization of this technique. Method: Six cases were modeled for comparison: cases 1 and 2 corresponded to suprarenal aortic aneurysm (SRAA) models with no stent and a multilayer stent (MS), respectively; cases 3–6 represented the SRAA models treated with fenestrated stent grafts (FSGs) including a small-sized hole (SSH, 3 ​mm), middle-sized hole (MSH, 6 ​mm), large-sized hole (LSH, 9 ​mm), and multiple holes (MH, which included the features of both the MS and stent graft, 6 ​mm), respectively. The total stent area in cases 4 and 6 was equal to the cross-section of the branch. Results: As opposed to cases 1 and 2, the pressure on the aneurysmal wall reduced more significantly with FSG intervention (cases 3–6), and the area of low wall shear stress (WSS) on the aneurysmal wall was unexpectedly large in case 5 owing to jet flow deflection. The branch flux increased with the increase of the hole size, and normal blood flow in the branch was only observed in case 5. Interestingly, the weakest jet flow was found in case 5. Conclusion: Our findings indicate that the diameter of the hole should be slightly larger than that of the branch to achieve better aneurysm isolation and preserve branch patency.

Clay minerals have a specific adsorption capability for anions, which increases the amount of net negative charge on the surface, leading to the increased adsorption of rare-earth ions in clay minerals and some change from exchangeable to non-exchangeable. Further, anions show a shielding effect on rare-earth ions. The shielding capacity of anions in the leaching agents for rare-earth ions was measured in this study. The relationship between the solid-phase concentration of rare-earth ions shielded and the anion concentration was consistent with the Langmuir model. Based on the Kerr model describing the exchange of rare-earth ions by ammonium ions, an ion-exchange model considering the shielding influence of anions was proposed. The accuracy of the proposed model was higher than that of the Kerr model. When the leaching agent was ammonium sulfate, the calculation accuracy of XW and AY samples was increased by 1.15% and 5.75%, respectively. The improvement in accuracy positively correlated with the proportion of iron oxides, aluminium oxides, and Kaolin. The established ion-exchange model can provide accurate source and sink terms for the numerical simulation of the leaching process of ion-adsorption-type rare-earth ores. [ABSTRACT FROM AUTHOR]

The accurate prediction of the vertical extent of water-conducting fracture (WCF) zones in weakly cemented strata is particularly significant in preventing and controlling water hazards in western coal mines. The evolution of fractures in weakly cemented strata affected by mining disturbances was comprehensively analyzed by physical similarity models, numerical simulations, and field investigations. Results indicated that the development progress of water-conducting fractures can be divided into three phases: initial slow generation, subsequent rapid development, and eventual stabilization. The numerical simulation results revealed that in the initial stage of working face mining, the development of the plastic zone is limited, and there is minimal failure in the overlying strata; therefore, fractures are slowly produced without penetrating through the strata. When the plastic zone fully encompasses the entire main roof, it triggers severe shear failure in the overlying strata, resulting in rapid fracture propagation and penetration. Once the fracture height reaches a stable state, there is no further increase in the maximum vertical displacement of key strata, indicating the extensive collapse and compaction of the overburden as well as the stabilization of the fracture heights. A modified prediction equation for WCF in weakly cemented strata was obtained by correcting the traditional empirical formula based on field investigations. This modified prediction equation enhances the accuracy in predicting fracture heights and provides a theoretical reference to address the issue of the inaccurate prediction of the water-conducting fracture height in western mine rock strata. [ABSTRACT FROM AUTHOR]

This article establishes a circuit model with which to analyze the difficulty of auto-gain control driving for low-Q micromechanical gyroscopes at room temperature and normal pressure. It also proposes a driving circuit based on frequency modulation to eliminate the same-frequency coupling between the drive signal and displacement signal using a second harmonic demodulation circuit. The results of the simulation indicate that a closed-loop driving circuit system based on the frequency modulation principle can be established within 200 ms with a stable average frequency of 4504 Hz and a frequency deviation of 1 Hz. After the system was stabilized, the root mean square of the simulation data was taken, and the frequency jitter was 0.0221 Hz. [ABSTRACT FROM AUTHOR]

Without a reliable design method for the leaching and seepage step of in situ leaching (ISL), problems such as low comprehensive resource recovery rate and frequent geological disasters such as landslides are prominent. This study established a simplified "liquid injection-collection" plane model of ISL with a linear barefoot type rare earth mine as the research object. The steady seepage line equation was derived based on groundwater dynamics and the Dupuit assumption. Then, engineering verification and calculation error analysis were performed. The seepage line equation is expressed as a piecewise function, where the seepage line in the liquid injection area is the upper half of the ellipse line, and the one in the non-liquid injection area is a parabola. The calculation error increases along the flow field direction. The seepage gradient, bedrock gradient, liquid injection range, and relative permeability coefficient have limited influence on the calculation error of the equation. The seepage line equation can be fairly applied in ISL. The seepage line equation can provide a theoretical basis for the "prior prediction (design)" of the "liquid injection/collection" leaching and seepage process in ISL. [ABSTRACT FROM AUTHOR]

Ion-adsorption-type rare-earth ores (IATREOs) that have experienced granite weathering have good permeability, and their leaching process involves the solute transport problem, which is dominated by convection. Because of the oscillation and dispersion errors of existing numerical methods for solving the convective-dominated solute transport equation, the results have low precision in the twin leaching process. In this paper, the convection–dispersion equation is decoupled into the dispersion equation, the convection equation, and the source-sink equation; the Crank–Nicolson and implicit difference methods are used to solve the dispersion equation and the source-sink equation, respectively. The solution of the convection equation is achieved on the basis of its physical interpretation. Therefore, a decoupling method for the convective-dominated solute transport equation is established. In comparison to the two examples with analytical solutions, the calculation errors of the method established in this paper are less than 2.00%, and it can solve the oscillation and dispersion problems. The rationality of the method is further demonstrated through the column leaching experiment of IATREOs. In comparison to the test results, the coefficients of determination of the breakthrough curves of rare-earth ions and ammonium ions calculated by the proposed method are all greater than 0.850, and the peak concentration error of rare-earth ions is less than 7.00%. This indicates that the proposed method can simulate the leaching process well. Furthermore, by combining the multiple/half method and the dichotomy method, an optimization method for determining the leaching agent amount was established to analyze the relationship between the leaching agent and the ratio of dispersion to pillar length. The results can provide a solution that can be used to mine IATREOs from experience to theory. [ABSTRACT FROM AUTHOR]

In the in situ leaching process of ionic rare earth ore, high-pressure moving water jet technology has been applied to improve floor leakage problems. However, it has been found that the morphology of the erosion surface formed by a moving water jet cannot be accurately predicted. The range of the erosion surface has an important influence on the stability of liquid collection engineering and the liquid collection rate of rare earth resources, which is an important basis for the design of liquid collection engineering. To study this, soil-breaking tests using high-pressure moving water jets for a Pingnan mine were conducted. The influences of jet pressure and nozzle moving speed on soil-breaking morphology were analysed. The mechanism of erosion surface formation was revealed by erosion theory, and a method of predicting the erosion surface geometry based on jet pressure and nozzle speed is proposed. The results show that, in the jet pressure range of 5~10 MPa, with increases in jet pressure and decreases in nozzle speed, the geometric shape of the erosion surface tends to expand, and these parameters have no effect on the morphological characteristics of the erosion surface. In the soil-breaking process, the erosion speed decreases with increases in jet distance. As the nozzle speed becomes greater, the degree of the attenuation of erosion speed at a given jet pressure also becomes greater. Soil-breaking depth has a quadratic relationship with jet pressure and a 0.5 power function relationship with nozzle speed. The geometry of the erosion surface has self-similarity and can be divided into straight and curved sections. Accordingly, an empirical formula of the erosion surface geometric shape is proposed. The error of predicting the soil-breaking depth is less than 11%, which can provide a reference for engineering applications. [ABSTRACT FROM AUTHOR]

It is preliminarily acknowledged that multilayer stent (MS) is a promising alternative technology in the treatment of visceral branched aneurysms, but hemodynamic consequences of eccentricity in such aneurysms with MS are less examined. In this work, we performed a time-dependent simulation of branched aneurysms of various eccentricities with different stent layers, and thrombosis-related parameters, such as time-averaged wall shear stress (TAWSS), oscillating shear index (OSI), and relative residence time (RRT), were also analyzed. Our results revealed that MS can generally restore laminar flow inside the stent, and allow proper perfusion to vital organs while also fostering a relatively secluded hemodynamic environment for thrombosis formation. Particularly, a flow in the aneurysm sac communicating between the main artery and side branch forms at early systole. However, MS fails to completely eliminate detrimental flow impingement after peak systole, which may hinder aneurysm recovery, especially in the cases of eccentric aneurysms. Therefore, saccular aneurysms should be treated with more caution than fusiform aneurysms. And further therapeutic attempts to keep both perfusion in the proximal region of the aneurysm and isolation in the distal region of the aneurysm should be considered. [ABSTRACT FROM AUTHOR]

Objective: To study the hemodynamic response to lower leg heating intervention (LLHI) inside the abdominal and iliac arterial segments (AIAS) of young sedentary individuals. Methods: A Doppler measurement of blood flow was conducted for 5 young sedentary adults with LLHI. Heating durations of 0, 20, and 40 min were considered. A lumped parameter model (LPM) was used to ascertain the hemodynamic mechanism. The hemodynamics were determined via numerical approaches. Results: Ultrasonography revealed that the blood flow waveform shifted upwards under LLHI; in particular, the mean flow increased significantly (p < 0.05) with increasing heating duration. The LPM showed that its mechanism depends on the reduction in afterload resistance, not on the inertia of blood flow and arterial compliance. The time-averaged wall shear stress, time-averaged production rate of nitric oxide, and helicity in the external iliac arteries increased more significantly than in other segments as the heating duration increased, while the oscillation shear index (OSI) and relative residence time (RRT) in the AIAS declined with increasing heating duration. There was a more obvious helicity response in the bilateral external iliac arteries than the OSI and RRT responses. Conclusion: LLHI can effectively induce a positive hemodynamic environment in the AIAS of young sedentary individuals. [ABSTRACT FROM AUTHOR]

The continuous change in solution concentration in ore pores during in situ mineral leaching influences the stability of ore aggregate. In this study, influences of the concentration of ammonium sulfate ((NH4)2SO4) solution on the interaction forces between ore particles were calculated. On this basis, the mechanism by which (NH4)2SO4 solution concentration influences the stability of ore aggregate was analyzed. Furthermore, an empirical formula for estimating the critical (NH4)2SO4 solution concentration for aggregation and dispersion of ore body aggregates with different grain composition was proposed. Some major conclusions were drawn. First, for ore bodies with an initial particle size of less than 0.075 mm, the interaction force between particles was net attraction, with the distance range of this force increasing as the concentration of (NH4)2SO4 solution increased from ≤0.001 to 0.16 mol·L−1, aggregation of ore particles occurring within this distance range. Secondly, for ore bodies with initial particle size of less than 0.075 mm, the interaction force between particles was net attraction, but with the distance range of this force decreasing when the (NH4)2SO4 solution concentration increased from 0.16 to 0.28 mol·L−1, dispersion of ore particles occurring beyond this distance range. Thirdly, for ore bodies with particle sizes of less than 0.038, 0.075 and 0.1 mm, the cation exchange capacity (CEC) was 9.13, 8.96, and 8.8 cmol·kg−1, respectively, and the critical (NH4)2SO4 solution concentration affecting the aggregation and dispersion of ore bodies was 0.12, 0.16, and 0.20 mol·L−1, respectively. [ABSTRACT FROM AUTHOR]

The adsorption behavior of NH4+ and Mg2+ at kaolinite surfaces was investigated by using molecular dynamics (MD) simulations, considering the factors such as ion concentration, NH4+/Mg2+ mixing ratio, and layer charge of kaolinite. The results showed that the increase in ion concentration did not affect the adsorption modes of NH4+ and Mg2+ ions but promote the increase in the adsorption capacity. The total adsorption capacities of Mg2+ and NH4+ were 3.25 × 10−6 and 2.85 × 10−6 μmol·mm−2 at the ion concentration of 1.5 mol·L−1, respectively. When NH4+ and Mg2+ were co‐adsorbed, they could inhibit the adsorption of each other at the surface of kaolinite, except that the inner‐sphere (IS) adsorption of NH4+ at aluminum hydroxyl (Al–OH) surface could be enhanced by the presence of Mg2+. Both NH4+ and Mg2+ tended to adsorb at the siloxane (Si–O) surface of kaolinite rather than Al–OH surface. When layer charge occurred in kaolinite, a small number of Mg2+ began to adsorb in the IS complexes at 1.7 and 2.3 Å above the Al and O atoms of the lattice‐substituted tetrahedra of the Si–O surface, and at 1.7 Å above the hexahedra of the Al–OH surface. However, most of NH4+ were adsorbed in IS complexes at 1.7 Å above the center of the oxygen six‐membered ring of the Si–O surface and above the hexahedron of the Al–OH surface. The adsorption capacity of Mg2+ changed little with the increase of layer charge density, while the IS and total adsorption capacity of NH4+ increased significantly. [ABSTRACT FROM AUTHOR]

The residual and release of ammonium in ion-adsorption rare earth tailings and soil are related to the interaction of NH 4 + with clay minerals. Molecular dynamics simulations were used to study the adsorption and diffusion of NH 4 + on the external surface of smectite. The factors, such as layer charge position (octahedral and tetrahedral substitution) and charge density (0.5, 1.0 and 1.5 e⋅uc−1, where uc denotes unit cell), initial NH 4 + concentration (from 0.64 to 1.60 mol⋅L−1), and anion types (Cl−, NO 3 − and SO 4 2−) were considered. The results of NH 4 + adsorption on the external surface were also compared with that in the interlayer. The layer charge of smectite significantly affected the interaction between NH 4 + and smectite. With increasing charge density, the major NH 4 + surface complexes were changed from outer-sphere to inner-sphere, resulting in increased adsorption density and stability, which was verified by calculated hydration structure and adsorption free energies. The inner-sphere NH 4 + complexes were located above the centers of the hexagonal rings and the Si tetrahedras for montmorillonite at a charge density of 1.0 e⋅uc−1, while only located in the vicinity of tetrahedral substitutions for beidellite. NO 3 − promoted the adsorption of NH 4 + as inner-sphere complexes relative to Cl− and SO 4 2−. As the water content in the interlayer increased, the confinement effect weakened and the mobility of NH 4 + increased, and the NH 4 + adsorption in the interlayer exhibited similar characteristics to that on the external surface at a water content of 10 H 2 O⋅uc−1. [Display omitted] • The inner-sphere complexes of NH 4 + on smectite external surface vary with the charge location. • With increasing charge density, the major NH 4 + complexes are changed from outer- to inner-sphere. • Increasing of NH 4 + concentration increase adsorption amount rather than change adsorption pattern. • NO 3 − promote the adsorption of NH 4 + as inner-sphere complexes relative to Cl− and SO 4 2−. • NH 4 + in the interlayer have similar adsorption features to on external surface at 10 H 2 O⋅uc−1. [ABSTRACT FROM AUTHOR]

Broadly neutralizing antibodies and appropriate immunogens are critical for preexposure prophylaxis and therapeutic HIV vaccines. In this study, we aimed to explore effective antibodies against the genetically diverse HIV-1 strains by investigating the roles of human CD4 D1D2 domain and nonvariable immugens. The human CD4 D1D2 domain and the chimeric protein of mouse D1 domain/human D2 domain were expressed in Sf9 insect cells and purified by gel-filtration chromatography. The human CD4 D1D2 domain potently inhibited the infection of 77.8% HIV-1 pseudoviruses, including the clades AE, B' and BC, with less than 20 μg/mL of IC50. pcDNA3.1-mhD1D2m and pcDNA3.1-mhD2m plasmids were used for the production of mouse anti-human CD4 polyclonal antibodies. The neutralizing activities of the polyclonal antibodies were determined by using pseudotyped HIV-1 viruses. The antibodies induced by plasmids containing human CD4 D1D2 domain were able to potently inhibit all pseudotyped HIV-1 strains. The antibodies from mhD1D2m-immunized mice also showed strong binding capacity to CD4 expressed on the surface of TZM-bl cells. The potent and broad inhibitory activity of antibodies against the human CD4 D1D2 domain may be used to develop effective passive immunization agent to control the spread of HIV infection. [ABSTRACT FROM AUTHOR]

The interaction of ammonium ions (NH 4 +) with clay is closely associated with many geochemistry, engineering, and environment issues. Molecular dynamics (MD) simulations were performed to investigate to the structure, energetics, and dynamics properties of ammonium-montmorillonite (NH 4 -Mt) at different hydration levels. The simulation results show that the layer spacing, immersion and hydration energy, atomic density, coordination number, self-diffusion coefficient and residence time of NH 4 -Mt vary with the water contents. The one-layer hydrate is the most energetically favorable at the water content of 5 H 2 O/uc but up to three-layer hydrate of NH 4 -Mt can potentially be formed at the high water content (13 H 2 O/uc). As the water content increases, some NH 4 + ions which adsorbed in inner-sphere (IS) complexes at low hydration level can change to outer-sphere (OS) complexes, and further to random ions in a diffuse aqueous layer, with the interaction between NH 4 + ions and basal surfaces becoming weaker. The H-bonding of N-H n ···O s , donated by hydrogen atoms of NH 4 + to surface oxygen atoms, contributes to the adsorption of NH 4 + ions besides the electrostatic attraction. NH 4 + ions in inner-sphere complexes can reside above the hexagonal cavities longer and have more stable hydration shell at the low hydration level. Unlabelled Image • Monolayer hydrate is the most energetically favorable for NH 4 -Mt. • H-bonds between NH 4 + and Mt. contribute to the adsorption of NH 4 +. • Interaction between NH 4 + and Mt. weakens as the water content increases. • NH 4 + in IS complexes reside above surface cavity longer at low water content. [ABSTRACT FROM AUTHOR]

The role of DNA topoisomerase III (Topo III) in bacterial cells has proven elusive. Whereas eukaryotic Top IIIa homologs are clearly involved with homologs of the bacterial DNA helicase RecQ in unraveling double Holliday junctions, preventing crossover exchange of genetic information at unscheduled recombination intermediates, and Top IIIβ homologs have been shown to be involved in regulation of various mRNAs involved in neuronal function, there is little evidence for similar reactions in bacteria. Instead, most data point to Topo III playing a role supplemental to that of topoisomerase IV in unlinking daughter chromosomes during DNA replication. In support of this model, we show that Escherichia coli Topo III associates with the replication fork in vivo (likely via interactions with the single-stranded DNA-binding protein and the β clamp-loading DnaX complex of the DNA polymerase III holoenzyme), that the DnaX complex stimulates the ability of Topo III to unlink both catenated and precatenated DNA rings, and that ΔtopB cells show delayed and disorganized nucleoid segregation compared to that of wild-type cells. These data argue that Topo III normally assists topoisomerase IV in chromosome decatenation by removing excess positive topological linkages at or near the replication fork as they are converted into precatenanes. [ABSTRACT FROM AUTHOR]

Summary Many essential cellular processes, such as gene control, employ elaborate mechanisms involving the coordination of large, multi-component molecular assemblies. Few structural biology tools presently have the combined spatial-temporal resolution and molecular specificity required to capture the movement, conformational changes, and subunit association-dissociation kinetics, three fundamental elements of how such intricate molecular machines work. Here, we report a 3D single-molecule super-resolution imaging study using modulation interferometry and phase-sensitive detection that achieves <2 nm axial localization precision, well below the few-nanometer-sized individual protein components. To illustrate the capability of this technique in probing the dynamics of complex macromolecular machines, we visualize the movement of individual multi-subunit E. coli RNA polymerases through the complete transcription cycle, dissect the kinetics of the initiation-elongation transition, and determine the fate of σ 70 initiation factors during promoter escape. Modulation interferometry sets the stage for single-molecule studies of several hitherto difficult-to-investigate multi-molecular transactions that underlie genome regulation. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of g-C 3 N 4 /TiO 2 heterostructure are investigated using spin-polarized DFT+ U calculations. The equilibrium spacing (1.94 Å) and binding energy (24 meV/Å 2 ) show that g-C 3 N 4 /TiO 2 is a van der Waals heterostructure. And the calculated band gap of g-C 3 N 4 /TiO 2 is significantly reduced compared with TiO 2 . Therefore, the visible light response of g-C 3 N 4 /TiO 2 heterostructure is remarkably improved. Besides, the predicted type II band alignment would ensure that the electrons can migrate from g-C 3 N 4 monolayer to anatase TiO 2 (101) surface, which leads oxidation and redox reactions can occur on g-C 3 N 4 and TiO 2 , respectively. Finally, a built-in electric field within the interface region will be set. Above processes can benefit the separation of photoexcited carriers and enhance the hydrogen-evolution activity. In addition, compared with TiO 2 , g-C 3 N 4 /TiO 2 with higher conduction band minimum energy can effectively produce higher-energy electrons to reduce hydrogen ions. Moreover, the influence of composite distance and the number of g-C 3 N 4 layers are also investigated systematically. The results indicate that the optical absorption is enhanced over the whole spectrum with the increase of the number of g-C 3 N 4 layers. Similar visible light enhancing is also found when the composite distance is decreased. [ABSTRACT FROM AUTHOR]

Transforming the vast knowledge from genetics, biochemistry, and structural biology into detailed molecular descriptions of biological processes inside cells remains a major challenge—one in sore need of better imaging technologies. For example, transcription involves the complex interplay between RNA polymerase II (Pol II), regulatory factors (RFs), and chromatin, but visualizing these dynamic molecular transactions in their native intracellular milieu remains elusive. Here, we zoom into single tagged genes using nanoscopy techniques, including an active target-locking, ultra-sensitive system that enables single-molecule detection in addressable sub-diffraction volumes, within crowded intracellular environments. We image, track, and quantify Pol II with single-molecule resolution, unveiling its dynamics during the transcription cycle. Further probing multiple functionally linked events—RF-chromatin interactions, Pol II dynamics, and nascent transcription kinetics—reveals detailed operational parameters of gene-regulatory mechanisms hitherto-unseen in vivo. Our approach sets the stage for single-molecule studies of complex molecular processes in live cells. • Real-time single-molecule detection in high-background, crowded cellular locales • Imaging and tracking Pol II at single genes during the transcription cycle • Organization, dynamics, and interdependencies of enhancer-bound regulatory factors • Dissection of enhancer mechanisms at the endogenous Pou5f1 and Nanog Key limitations of imaging single copies of highly abundant factors at specific intracellular sites of activity are overcome by an active target-locking system that achieves long-term tracking at single-molecule resolution. [ABSTRACT FROM AUTHOR]