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We present a novel approach to induce charge density waves (CDWs) in metallic MA2Z4materials, resembling the behavior observed in transition metal dichalcogenides (TMDCs). This method leverages the intercalating architecture to maintain the same crystal field and Fermi surface topologies. Our investigation reveals that CDW instability in these materials arises from electron–phonon coupling (EPC) between the dband and longitudinal acoustic (LA) phonons, mirroring TMDC’s behavior. By combining α-MA2Z4with 1H-MX2materials in a predictive CDW phase diagram using critical EPC constants, we demonstrate the feasibility of extending CDW across material families with comparable crystal fields and reveal the crucial role in CDW instability of the competition between ionic charge transfer and electron correlation. We further uncover a strain-induced Mott transition in β2-NbGe2N4monolayer featuring star-of-David patterns. This work highlights the potential of intercalating architecture to engineer CDW materials, expanding our understanding of CDW instability and correlation physics.

Topological phonons in materials are associated with specific atomic lattice vibrations around the terahertz frequency ranges, offering a rich platform for studying various boson-related quasiparticles. Recently, researchers in topological physics have prioritized the search for materials that exhibit topological phonons. This review focuses on topological nodal-point phononic systems in three dimensions. On the one hand, the review highlights the classification, symmetry conditions, material realizations, unique properties, and potential applications of these topological nodal-point systems. On the other hand, it summarizes our guidelines for predicting such materials in three and two dimensions. This review can serve as a scholarly survey of recent developments in topological nodal-point phononic systems over the past 5 years as well as a guide for achieving other and designing new topological nodal-point phononic states in the future. It will undoubtedly benefit academic communities interested in materials science and condensed matter physics.

ABSTRACTOnshore shale oil is difficult to develop due to its special pore structure and low permeability characteristics. Artificial fracturing causes a large amount of fracturing fluid to intrude into the reservoir, resulting in a complex reservoir seepage pattern. Therefore, this paper aims to explore the changes in the reservoir at the macro and micro levels due to the interaction between fracturing fluids and shale oil reservoirs. For this, four rock samples from shale oil reservoirs and two fracturing fluids commonly used in the mine were used. Then, core repulsion, scanning electron microscopy, X-ray diffraction and CT scanning experiments were carried out successively. The following results were derived from our analyses. (1) Permeability of the rock samples was reduced by an average of 24.47% after replacement by fracturing fluid, while the experimental groups with larger fluid-grain sizes and well-developed fracture networks suffered more significant solid-phase damage and fluid-phase trapping. (2) Fracturing fluids have different effects on fractures at different scales; large fractures (>7.71 μm) were widened, while small fractures (<3.47 μm) were shrunk or even plugged. (3) Based on the water-sensitive effect, fracturing fluids can disperse and transport clay minerals, resulting in fluid-phase damage and an average decrease of 14.33% in clay content in the reservoir. (4) Analysis of the digital core model shows that fracturing fluid intrusion and retention can cause solid-phase damage to the reservoir matrix, with 38.14% and 60% damage to the pore and throat channels, respectively. This paper uses a combination of physical experiments and numerical analysis to investigate the interaction mechanism between fracturing fluids and shale oil reservoirs from both microscopic and macroscopic perspectives. Overall, the results of this study provide experimental support for future studies on the seepage characteristics of this type of reservoir and the design of fracturing construction schemes.

Purpose: The High-Energy Photon Source (HEPS) is a 6 GeV storage ring-based light source under construction in Beijing, China. Its accelerator consists of a 6 GeV storage ring, a full-energy booster, an S-band normal-conducting 500 MeV linac, and three transport lines. As the beginning of HEPS, a stable linac is quite important, which needs a qualified waveguide distribution system to transmit microwave power from klystrons to accelerating structures. Methods: Installation and high-power conditioning of the HEPS linac were performed from February to September 2022. The assembly and conditioning of the waveguide distribution system were completed in April and July, respectively. The design of the waveguide distribution system began in 2018 and was finalized at the end of 2020 after multiple iterations. Results: Owing to careful design, fabrication, and assembly preparation, the assembly and conditioning of the system proceeded smoothly and considerable time was saved. Conclusion: The entire process from the design to the ultimate realization of the system is introduced in detail in this paper. Satisfactory measurement results were obtained for some waveguide components.

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Purpose: The research focuses on the related measurement and shielding works for solving the spatial electromagnetic radiation and interference problems of the BEPCII Linac. Methods: The radiation frequency and intensity can be determined by using a set of antennas connected with a spectrum analyser. Results: The source of the radiation is located on the cable connectors of some device panels. The radiation intensity is significantly reduced after wrapping the connectors with the radiation shielding tape. Conclusions: The entire research process includes the selection of a domestically made ultra-wideband antenna, the proposal of the measurement methods, the locating of the radiation source, the performance measurement of the radiation shielding tape and the shielding of the radiation. It provides a whole set of feasible solutions for similar problems in accelerators.

ABSTRACTPolygonatum sibiricumpolysaccharides (PSP) can decrease the levels of fasting blood glucose, total cholesterol, and triglyceride (TG) in hyperlipidemic and diabetic animals. It can also reduce inflammatory cytokines and promote glucose uptake in adipocytes. However, the underlying molecular mechanisms of PSP in improving insulin resistance (IR) in skeletal muscle remain unclear. In this study, palmitic acid (PA) induced an IR model in L6 myotubes. After treatment, cell proliferation was measured using the CCK8. miR-340-3p, glucose transporter 4 (GLUT-4), and interleukin-1 receptor-associated kinase 3 (IRAK3) expression was measured by qRT-PCR. IRAK3 protein levels were measured by Western blotting. Glucose in the cell supernatant, TG concentration in L6 myotubes, and the levels of IL-1β, IL-6, and TNF-α were measured by an ELISA. We found that cell survival, glucose uptake, and GLUT-4 expression in L6 myotubes were significantly suppressed, while lipid accumulation and inflammatory factor levels were enhanced by PA stimulation. Furthermore, PSP treatment markedly alleviated these effects. Interestingly, PSP also significantly reduced the upregulated expression of miR-340-3p in the L6 myotube model of IR. Furthermore, overexpression of miR-340-3p reversed the beneficial effects of PSP in the same IR model. miR-340-3p can bind to the 3′-untranslated regions of IRAK3. Additionally, PA treatment inhibited IRAK3 expression, whereas PSP treatment enhanced IRAK3 expression in L6 myotubes. Additionally, miR-340-3p also inhibited IRAK3 expression in L6 myotubes. Taken together, PSP improved inflammation and glucose uptake in PA-treated L6 myotubes by regulating miR-340-3p/IRAK3, suggesting that PSP may be suitable as a novel therapeutic agent for IR.

Ricin toxin A subunit (RTA) is the catalytic subunit of ricin, which depurinates an adenine from the sarcin/ricin loop in eukaryotic ribosomes. There are no approved inhibitors against ricin. We used a new strategy to disrupt RTA–ribosome interactions by fragment screening using surface plasmon resonance. Here, using a structure-guided approach, we improved the affinity and inhibitory activity of small-molecular-weight lead compounds and obtained improved compounds with over an order of magnitude higher efficiency. Four advanced compounds were characterized by X-ray crystallography. They bind at the RTA–ribosome binding site as the original compound but in a distinctive manner. These inhibitors bind remotely from the catalytic site and cause local conformational changes with no alteration of the catalytic site geometry. Yet they inhibit depurination by ricin holotoxin and inhibit the cytotoxicity of ricin in mammalian cells. They are the first agents that protect against ricin holotoxin by acting directly on RTA.

The purpose of this study is to establish an elastic–plastic damage constitutive model of shale and simulate the elastic–plastic damage characteristics of shale under stress. Based on the unified strength theory and the mechanics of shale rock samples characterized in laboratory tests, a new elastic–plastic damage constitutive model for shale is established by introducing compression factors and damage variables. The main considerations include the compressibility of primary fractures and pores in the shale core, and the formation of secondary cracks in the rock matrix under stress. A fully implicit backward Euler regression mapping algorithm has been used to solve the model, and the numerical simulation results are in good agreement with the experimental results. The results show that the model established in this paper can accurately simulate the elastic–plastic damage characteristics of shale under stress, and that it provides a new numerical simulation method for describing the elastic–plastic damage in shale.

The ternary system LiCl–SrCl2–H2O and the quaternary system KCl–LiCl–SrCl2–H2O at 308 K were investigated using the isothermal dissolution equilibrium method. According to the obtained experimental results, the phase diagrams of the two systems listed above were plotted separately. The results show that both systems belong to hydrate I-type cosaturated systems at 308 K, and there are no double salts or solid solution formation. Lithium chloride has strong salting-out effect on strontium chloride and potassium chloride. There are two invariant points, three univariate curves, and three crystallization zones of SrCl2·6H2O, SrCl2·2H2O, and LiCl·H2O in the ternary system LiCl–SrCl2–H2O at 308 K. The equilibrium phase diagram of the quaternary system KCl–LiCl–SrCl2–H2O at 308 K consists of two invariant points, five univariant curves, and four crystallization zones, which correspond to SrCl2·6H2O, SrCl2·2H2O, LiCl·H2O, and KCl. These results can provide solubility data for the development and utilization of the underground brine in the Sichuan Basin of China.

Shiga toxin 2a (Stx2a) is the virulence factor of Escherichia coli(STEC), which is associated with hemolytic uremic syndrome, the leading cause of pediatric kidney failure. The A1 subunit of Stx2a (Stx2A1) binds to the conserved C-terminal domain (CTD) of the ribosomal P-stalk proteins to remove an adenine from the sarcin–ricin loop (SRL) in the 28S rRNA, inhibiting protein synthesis. There are no antidotes against Stx2a or any other ribosome-inactivating protein (RIP). The structural and functional details of the binding of Stx2A1 to the P-stalk CTD are not known. Here, we carry out a deletion analysis of the conserved P-stalk CTD and show that the last eight amino acids (P8) of the P-stalk proteins are the minimal sequence required for optimal affinity and maximal inhibitory activity against Stx2A1. We determined the first X-ray crystal structure of Stx2A1 alone and in complex with P8 and identified the exact binding site. The C-terminal aspartic acid of the P-stalk CTD serves as an anchor, forming key contacts with the conserved arginine residues at the P-stalk binding pocket of Stx2A1. Although the ricin A subunit (RTA) binds to the P-stalk CTD, the last aspartic acid is more critical for the interaction with Stx2A1, indicating that RIPs differ in their requirements for the P-stalk. These results demonstrate that the catalytic activity of Stx2A1 is inhibited by blocking its interactions with the P-stalk, providing evidence that P-stalk binding is an essential first step in the recruitment of Stx2A1 to the SRL for depurination.

The effects of Sn content on microstructure and tensile properties of as-cast and as-extruded Mg−8Li−3Al− (1,2,3)Sn (wt.%) alloys were investigated by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and tensile test. It is found that, as-cast Mg−8Li−3Al−(1,2,3)Sn alloys consist of α-Mg+β-Li duplex matrix, MgLiAl2and Li2MgSn phases. Increasing Sn content leads to grain refinement of α-Mg dendrites and increase in content of Li2MgSn phase. During hot extrusion, complete dynamic recrystallization (DRX) takes place in β-Li phase while incomplete DRX takes place in α-Mg phase. As Sn content is increased, the volume fraction of DRXed α-Mg grains is increased and the average grain size of DRXed α-Mg grains is decreased. Increasing Sn content is beneficial to strength but harmful to ductility for as-cast Mg−8Li−3Al−(1,2,3)Sn alloys. Tensile properties of Mg−8Li−3Al− (1,2,3)Sn alloys are improved significantly via hot extrusion and Mg−8Li−3Al−2Sn alloy exhibits the best tensile properties.

The phase equilibria of the ternary system NaCl–SrCl2–H2O at 273 and 308 K and quaternary system LiCl–NaCl–SrCl2–H2O at 308 K were measured by the isothermal dissolution equilibrium method. The phase diagrams of the ternary system at two temperatures both contain one invariant point, two univariant curves, and two crystallization fields (SrCl2·6H2O and NaCl). The phase equilibria of this ternary system were also compared and discussed at different temperatures. The phase diagram of the quaternary system LiCl–NaCl–SrCl2–H2O at 308 K consists of two invariant points, five univariant curves, and four crystallization fields (which are corresponding to SrCl2·6H2O, SrCl2·2H2O, LiCl·H2O, and NaCl). The Pitzer model known as an ion-interaction model has been successfully used to calculate the solubilities of salts in water–salt systems with an experimental accuracy. Based on the Pitzer model parameters from the literatures, the Pitzer model was used to predict the solubilities of salts in the ternary system NaCl–SrCl2–H2O at 273 and 308 K. The comparisons show that the calculated results are in good agreement with those of experiment.

To explore the optimal thermal effect parameter combination of An-pressing manipulation based on the pressing force, time and frequency, and to compare the thermal effect differences between the rhythmic and the continuous An-pressing manipulations. Three levels of light, moderate and heavy pressing forces were determined according to the An-pressing forces of the clinical tuina physicians; the pressing time and frequency parameters were determined according to the literatures about An-pressing manipulation. The volunteers were stimulated by the homemade An-pressing manipulation stimulator on the right Xinshu (BL 15), and then the three-factor and three-level orthogonal tests were carried out according to the test sequence specified by the L9(34) orthogonal table, and the temperature before and after pressing was recorded by an infrared thermal imaging system to screen the best parameters for the thermal effect of the An-pressing manipulation, thus to determine the optimal pressing parameters. The optimal parameters were then used for both continuous and rhythmic An-pressing manipulations to stimulate the bilateral Xinshu (BL 15). The temperature changes after pressing and the duration of the thermal effect (temperature difference ≤0.5 °C on both sides) were recorded by the infrared thermal imaging system, to explore the differences in the thermal effects of different An-pressing manipulations. Among the three factors of pressing force, time and frequency, the influences of different pressing forces on temperature were significantly different (F=32.843, P=0.030), and the influence of 2.5 kg pressing force was the most significant; the effects of different pressing time on temperature were significantly different (F=54.102, P=0.018), and the pressing time of 7.5 min was the most significant; the influences of different pressing frequencies on temperature were not statistically significant (F=2.181, P=0.314), though the influence of 10 times/min pressing frequency was the largest. The influences on temperature difference of the rhythmic and the continuous An-pressing manipulations were significantly different (P=0.031 on the left side and P=0.045 on the right side), but there was no statistical difference in the duration of the thermal effect (P=0.690). The An-pressing manipulation parameters that significantly affect the temperature difference are pressing force and time. The optimal combination of thermal effect parameters is pressing force of 2.5 kg, time of 7.5 min, and frequency of 10 times/min. The local thermal effect of the rhythmic An-pressing manipulation is significantly greater than of the continuous An-pressing manipulation. 从力度、 时间和频率三方面探索按法热效应的最佳参数组合, 并据此比较节律性按法和持续性按 法热效应的差异. 以临床推拿医生按法力量值, 确定力度轻、中、重三个水平; 参考有关按法的文献, 确定时间和频率参数. 用自制按法刺激器对志愿者右侧心俞穴进行按法刺激, 然后按照L9(34)正交表规定的试验顺序进行三因素三水平的正交试验, 并以红外热像仪记录按压前后温度, 对按法热效应最佳参数进行筛选, 以确定最佳操作参数. 再以此为参数, 分别以节律性按法和持续性按法刺激双侧心俞穴, 用红外热像仪记录按压前后温度变化以及热效应持续时间(两侧温差⩽0.5 ℃的时间), 探索按法不同刺激方式热效应的差异. 在力量、操作时间和频率三个因素中, 不同力量对温差的影响有显著性差异(F=32.843, P=0.030), 2.5 kg 的力量影响最显著; 不同操作时间对温差的影响有显著性差异(F=54.102, P=0.018), 7.5 min 的操作时间影响最显著; 频率对温差 的影响无统计学意义 (F=2.181, P=0.314), 右侧P=0.045), 但对热效应持续时间的影响无统计学差异(P=0.690)。 对温差影响显著的按法参数为力量与操作时间. 最佳热效应参数组合为力量2.5 kg, 操作时间7.5 min, 频率10 次/分. 节律性按法的局部热效应比持续性按法显著.

The assumption of constant reservoir permeability is not strictly applicable to reservoirs where rock properties undergo changes, such as stress-sensitive porous media. Most researches on the permeability stress sensitivity mainly concentrated on experimental approach, physical modeling or pressure transient analysis, whereas rate transient analysis does not attract much attention. Based on source/sink function method, this paper develops a seepage model of multi-fractured horizontal well incorporating stress-sensitive permeability. The model is semi-analytically solved by fracture discretization, Pedrosa’s transformation, perturbation theory, and integration transformation method. Not only pressure transient analysis, but also rate transient analysis is separately performed with relevant parameters. The model presented here can provide some insights into well dynamic forecasting during exploiting such reservoirs, and contribute to establish the theoretical basic for transient analysis efficiently.

The mean activity coefficient of NaCl in NaCl–SrCl2–H2O was measured at 308 K by the electromotive force method. The total ion strength range of the mixed solution was 0.0100–1.0000 mol·kg–1, and the ion intensity fraction of ybof SrCl2, i.e., yb= (0.8, 0.6, 0.4, 0.2, 0). A liquid-free electrochemical cell (Na-ISE | NaCl(m1) SrCl2(m2)| Cl-ISE) was used to determine the electromotive force of a NaCl single salt and mixed solution. According to experimental data, the activity coefficient diagrams were drawn. The experimental results show that the measured activity coefficients are accurate and reliable, and the average activity coefficient of NaCl decreases with the increase of the ion strength of SrCl2. Using the measured average activity coefficient of NaCl, the parameters of the mixed ion action of the Pitzer equation θNa+·Sr2+and φNa+·Cl–·Sr2+are fitted. Furthermore, the Pitzer equation is used to calculate the average activity coefficents of SrCl2, the water activities aw, osmotic coefficients Φ, and Gibbs free energies GEof the mixed system.

In this work, we investigated some thermodynamic properties of the NaCl–CuCl2–H2O ternary system. We designed a cell without liquid junction as follows: Na-ISE | NaCl (m1), CuCl2(m2) | Cl-ISE, which was used to study the mean activity coefficients of NaCl in the NaCl–CuCl2–H2O system at 298.15 K by the electromotive force method. In this system, the total ionic strength Iranges from 0.01 up to 1.00 mol·kg–1for different ionic strength fractions ybof CuCl2, i.e., yb= (0.0, 0.2, 0.4, 0.6, 0.8). The results show that the Na-ISE and Cl-ISE have a good Nernst effect. The mean activity coefficients of NaCl in the ternary system were calculated using the Nernst equation. The Pitzer ion interaction parameters θNa,Cuand ψNa,Cu,Clwere fitted by Pitzer model with experimental results in this work. In addition, the osmotic coefficients, the solvent activities, and the excess Gibbs free energies of the ternary system were also calculated.

The underground brine of the Sichuan Basin is rich in liquid mineral resources such as strontium and potassium. In order to realize the comprehensive utilization of resources and utilize the underground brine reasonably and effectively, the stable phase equilibria of the quinary system NaCl–KCl–MgCl2–SrCl2–H2O (saturated with NaCl) at 373 K were investigated by the isothermal dissolution equilibrium method. On the basis of the experimental results, the phase diagram of this quinary system was drawn. Complex salt KCl·MgCl2·6H2O (Car) was generated in the quinary system NaCl–KCl–MgCl2–SrCl2–H2O (saturated with NaCl), and there was no solid solution formation. The dry salt phase diagram of this quinary system contains three invariant points, seven univariant curves, and five crystallization regions (where the solid phases are KCl, MgCl2·6H2O, SrCl2·2H2O, SrCl2·H2O, and KCl·MgCl2·6H2O under the condition of NaCl saturation). These results can provide basic phase equilibrium data for the development and utilization of the underground brine in the Sichuan Basin.

The effect of extrusion ratio on microstructure and mechanical properties of as-extruded Mg-6Sn-2Zn-1Ca (TZX621) (mass fraction, %) alloy was investigated. It is found that incomplete dynamic recrystallization (DRX) took place in as-extruded TZX621 alloy. As the extrusion ratio was increased from 6 to 16, both fraction of un-DRXed grains and average size of DRXed grains in as-extruded TZX621 alloy decreased and the basal texture was weakened. Coarse CaMgSn phase was broken into particles and fine Mg2Sn phase precipitated from α-Mg matrix during hot extrusion. Yield strength, ultimate tensile strength and elongation of as-extruded TZX621 alloy with extrusion ratio of 16 reached 226.9 MPa, 295.6 MPa and 18.1%, which were improved by 36.0%, 17.7% and 13.5%, respectively, compared to those of as-extruded TZX621 alloy with extrusion ratio of 6.

Most researches of the threshold pressure gradient in tight gas reservoirs are experimental and mainly focus on the transient pressure response, without paying much attention to the transient rate decline. This paper establishes a dual-porosity rate transient decline model for the horizontal well with consideration of the threshold pressure gradient, which represents the non-Darcy flow in a fracture system. The solution is obtained by employing the Laplace transform and the orthogonal transform. The bi-logarithmic type curves of the dimensionless production rate and derivative are plotted by the Stehfest numerical inversion method. Seven different flow regimes are identified and the effects of the influence factors such as the threshold pressure gradient, the elastic storativity ratio, and the cross flow coefficient are discussed. The presented research could interpret the production behavior more accurately and effectively for tight gas reservoirs.

Herein, in order to detect hydroquinone (HQ) and catechol (CC) simultaneously, an electrochemical sensor with good selectivity and sensitivity was developed. It is constructed by electrodeposition of carbon nanodots (CDs) on the surface of multi-walled carbon nanotubes (MWNTs) doped glassy carbon electrode. First, the experimental parameter was optimized. The electrochemical behavior was then evaluated by electrochemical impedance spectroscopy and cyclic voltammetry. The linear range for HQ and CC was 0.1-200 μM, and the detection limit was 0.03 μM. Incorporated the large surface area and fast charge transfer of MWNTs and CDs with electrodeposition technology's stability, high excellent selectivity, sensitivity, stability and good reproducibility was exhibited by the fabricated sensor. Furthermore, the electrode was successfully used to determine the concentration of HQ and CC in tap water, and thus exhibited potential applications environment monitoring.

The surface properties of a series of 1-alkyl-3-methylimidazolium (AMIM)-based ionic liquids (ILs) were characterized using an inverse gas chromatography technique at temperatures from 343.15 to 373.15 K. Nine polar and nonpolar probe solvents were used to investigate the surface properties, which included the Lewis acid–base constants, adsorption free energy, enthalpy adsorption, and dispersive component of the surface free energy (rsd). Furthermore, the effects of the alkyl chain length of the cation and the different anions on the surface properties were also studied. The results indicated that all of the investigated ILs were Lewis amphoteric material with low rsdvalues. When the anion was kept as [PF6]−, rsdof the series of AMIM-based ILs linearly decreased as the alkyl chain length was increased in the imidazolium cation, and the basicity also decreased as the alkyl chain length was increased.

The microstructure and mechanical properties of magnesium (Mg) alloys are significantly influenced by the casting process. In this paper, a comparative study on microstructure and mechanical properties at ambient and elevated temperatures of AZ91-2wt.% Ca (AZX912) Mg alloy samples prepared by gravity casting (GC), squeeze casting (SC) and rheo-squeeze casting (RSC), respectively, was carried out. The results show that α-Mg grains in SC and RSC samples are significantly refined compared to the GC sample. The average secondary dendritic arm spacing of AZX912 alloy samples decreases in the order of GC, SC and RSC. As testing temperature increases from 25 °C to 200 °C, strength of AZX912 alloy samples is reduced, while their elongation is increased continuously. Compared to GC and SC processes, RSC process can improve the mechanical properties of AZX912 alloy at both ambient and elevated temperatures. The enhancement of mechanical properties of RSC sample over GC and SC samples mainly results from grain refinement in the as-cast microstructure of AZX912 alloy.

The pulse compressor plays an important role in accelerators by enhancing the RF peak power. An S-band (2856 MHz) spherical cavity pulse compressor consisting of a special 3 dB coupler and a single spherical energy storage cavity has been developed in Institute of High Energy Physics. The special 3 dB coupler converts the $$\hbox {TE}_{10}$$ TE10 mode in rectangular waveguide to two polarization degenerated $$\hbox {TE}_{11}$$ TE11 modes in cylindrical waveguide. It is also a circular polarizer and its general scattering matrix is given for the first time. The magnitude and the phase difference of the two $$\hbox {TE}_{11}$$ TE11 modes are −3.016, −3.005 dB and 90.02$$^\circ $$ ∘ in HFSS, while it is −3.01, −3.01 dB and 89.79$$^\circ $$ ∘ in CST. The simulated S parameters show agreement with the general scattering matrix. The $$\hbox {TE}_{114}$$ TE114 mode with an unloaded Qfactor of 190,000 has been chosen to resonate in the spherical cavity. An energy multiplication factor of 1.75 and a peak power gain of 5.75 were obtained for the whole pulse compressor, which agrees with the design requirements. A good pulse compression performance is also proved by the CST time-domain simulation. In addition, the scheme for tuning and detuning is designed and given in detail. Compared to the traditional SLED type, the spherical cavity pulse compressor uses only one spherical cavity to realize the pulse compression, which makes it compact as a whole.

To determine how fracture–vuggy structure, pressure, and injection–production mode influence displacement efficiency in the water flooding process in fracture–vuggy reservoirs, two types of models were built based on the characteristic of such reservoir: two fracture models with different fracture apertures and two fracture–vuggy models with different sizes of vugs. A series of two-phase fluid flow experiments was conducted to study oil and water distribution as well as flow pattern in the water flooding process. Results show that displacement efficiency is significantly influenced by injection–production mode and injection pressure. By contrast, its relationship with the size of vugs is insignificant. Under the same injection–production mode, high-to-low recovery that corresponds to model type includes the small fracture, large fracture, small vug, and large vug models. Under the same pore volume multiple, high-to-low recovery that corresponds to model includes the small fracture, small vug, large fracture, and large vug models.

The rheo-squeeze casting (RSC) process is a newly-developed casting process for high-performance components. In order to further improve the mechanical properties of magnesium alloys, AZ91-2wt.%Ca (AZX912) alloy was prepared by the RSC process and then subjected to heat treatment. The microstructure evolution and mechanical properties of AZX912 alloy during heat treatment were investigated. It was found that during solid solution treatment at 410 °C, β-Mg17Al12phase with low melting point dissolves into α-Mg matrix, while the connected network-like Al2Ca phase with high melting point tends to separate gradually, and the tips of Al2Ca phase is partially spheroidized. With the increase of solid solution time, the yield strength (YS) of AZX912 alloy decreases gradually while the ultimate tensile strength (UTS) and elongation to failure (Ef) increase continuously. Isothermal ageing at 225 °C promotes the precipitation of β-Mg17Al12phase in the matrix of AZX912 alloy. The hardness reaches the peak after ageing for 96 h and the increase in hardness is about 24.8%. The precipitation of β-Mg17Al12phase during ageing treatment is beneficial to YS but harmful to Ef. The mechanism of microstructure evolution during heat treatment and its effect on mechanical properties are discussed.

ABSTRACTThe A1 subunits of Shiga toxin 1 (Stx1A1) and Shiga toxin 2 (Stx2A1) interact with the conserved C termini of ribosomal-stalk P-proteins to remove a specific adenine from the sarcin/ricin loop. We previously showed that Stx2A1 has higher affinity for the ribosome and higher catalytic activity than Stx1A1. To determine if conserved arginines at the distal face of the active site contribute to the higher affinity of Stx2A1 for the ribosome, we mutated Arg172, Arg176, and Arg179 in both toxins. We show that Arg172 and Arg176 are more important than Arg179 for the depurination activity and toxicity of Stx1A1 and Stx2A1. Mutation of a single arginine reduced the depurination activity of Stx1A1 more than that of Stx2A1. In contrast, mutation of at least two arginines was necessary to reduce depurination by Stx2A1 to a level similar to that of Stx1A1. R176A and R172A/R176A mutations eliminated interaction of Stx1A1 and Stx2A1 with ribosomes and with the stalk, while mutation of Arg170 at the active site reduced the binding affinity of Stx1A1 and Stx2A1 for the ribosome, but not for the stalk. These results demonstrate that conserved arginines at the distal face of the active site are critical for interactions of Stx1A1 and Stx2A1 with the stalk, while a conserved arginine at the active site is critical for non-stalk-specific interactions with the ribosome. Arginine mutations at either site reduced ribosome interactions of Stx1A1 and Stx2A1 similarly, indicating that conserved arginines are critical for ribosome interactions but do not contribute to the higher affinity of Stx2A1 for the ribosome.

Measuring deep brain neural activities with a microelectrode is of greatest importance in uncovering the mechanism of various brain disorders. In this operation, a microelectrode needs to be accurately inserted into deep the brain. However, a microelectrode of high flexibility would bend at encountering a layer of tough tissue during insertion, which would lead to deflection and impaired targeting accuracy. To deal with this problem, a rotational insertion method has been developed in this paper for deflection-free insertion. Rotation helps generate a dynamic anti-bending force to prevent buckling, and this force becomes larger with the increase of rotational speed. Thus, by controlling the rotational speed at which insertion is carried out, deflection-free insertion of a microelectrode deep into brain can be realized. The effectiveness of this method has been experimentally confirmed.

Rupture often happens when high-speed thin steel plate roller endures exchanging stress. Based on fuzzy theory, the paper discusses the fuzzy reliability design of roller with random variables and fuzzy variables, puts forward a basic method of digital simulation, and furthermore takes actions to improve the reliability of the rollers.

Genetic Algorithms is a new method, which has good robustness in optimization design for complex system. In this paper, we make the mathematical model of optimization design for the main-axis in big power inverted umbrella aeration machine by studying Genetic Algorithms. Using coding method, we complete the optimization design of the main-axis in big power inverted umbrella aeration machine.

ABSTRACTShiga toxin (Stx)-producing Escherichia coli(STEC) infections can lead to life-threatening complications, including hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS), which is the most common cause of acute renal failure in children in the United States. Stx1 and Stx2 are AB5 toxins consisting of an enzymatically active A subunit associated with a pentamer of receptor binding B subunits. Epidemiological evidence suggests that Stx2-producing E. colistrains are more frequently associated with HUS than Stx1-producing strains. Several studies suggest that the B subunit plays a role in mediating toxicity. However, the role of the A subunits in the increased potency of Stx2 has not been fully investigated. Here, using purified A1 subunits, we show that Stx2A1 has a higher affinity for yeast and mammalian ribosomes than Stx1A1. Biacore analysis indicated that Stx2A1 has faster association and dissociation with ribosomes than Stx1A1. Analysis of ribosome depurination kinetics demonstrated that Stx2A1 depurinates yeast and mammalian ribosomes and an RNA stem-loop mimic of the sarcin/ricin loop (SRL) at a higher catalytic rate and is a more efficient enzyme than Stx1A1. Stx2A1 depurinated ribosomes at a higher level in vivoand was more cytotoxic than Stx1A1 in Saccharomyces cerevisiae. Stx2A1 depurinated ribosomes and inhibited translation at a significantly higher level than Stx1A1 in human cells. These results provide the first direct evidence that the higher affinity for ribosomes in combination with higher catalytic activity toward the SRL allows Stx2A1 to depurinate ribosomes, inhibit translation, and exhibit cytotoxicity at a significantly higher level than Stx1A1.