Search

One of the major challenges in population economics is accurately predicting population size. Incorrect predictions can lead to ineffective population control policies. Traditional differential models assume a smooth change in population, but this assumption is invalid when measuring population on a small-time scale. To address this change, we developed two-scale fractal population dynamics that can accurately predict population size with minimal experimental data. The Taylor series method is used to reveal the population’s dynamical properties, and the Padé technology is adopted to accelerate the convergence rate. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional self-consistent fluid model was developed in atmospheric helium for dielectric barrier discharge excited by microsecond voltage pulses, in which a dielectric sheet with micropore is inserted in the interelectrode gap. It demonstrates that the discharge generated in dielectric micropore is in the form of propagating ionization wave, which reaches the plasma density of 1.32 × 1020 m−3 and the mean electron energy of 17.70 eV. The transverse electric field perpendicular to the applied longitudinal electric field in dielectric micropore is found to play an important role on the electron acceleration and generation, which is induced by the space charges in the micropore. The migration fluxes of electron and ions driven by electric field and diffusion explains the formation of transverse electric field and sheath regions above the dielectric surfaces. [ABSTRACT FROM AUTHOR]

In this paper, we prove the uniqueness and H 2 -regularity of solution u for a semi-linear elliptical equation with a 2 m − 1 polynomial nonlinearity under the stability and uniqueness conditions. Moreover, we design the finite element method based on P 1 -element for the semi-linear elliptical equation and prove the existence and uniqueness of the finite element solution u h by the finite element Oseen iterative method under the stability and uniqueness condition. Next, we prove the existence and uniqueness of the solution u for the semi-linear elliptical equation by the finite element solution u h under the stability and uniqueness conditions. Furthermore, we provide the H 1 − L 2 optimal error estimates of the finite element solution u h with respect to the exact solution u for the semi-linear elliptical equation under the stability and uniqueness conditions. Finally, some numerical tests are presented to show the efficiency of the proposed method for the semi-linear elliptical equation with a 2 m − 1 polynomial nonlinearity. [ABSTRACT FROM AUTHOR]

Because microbial corrosion is one of the major threats to the service life of buried pipeline steel, it is very important to predict the service life of X90 pipeline steel in a microbial corrosion environment. In this study, the hoop stress of pipeline steel is determined according to the calculation of the corrosion rate. The calculation model of stress intensity factor is obtained by comparing and selecting the M-parameter model method and Ballellle method, considering normal distribution and 3σ. The calculation method of ductile crack arrest reliability is obtained according to the criterion, and the variation of stress intensity factor and reliability of X90 pipeline steel with the increase in service life under different microbial corrosion rates is obtained. The ductile crack failure analysis using American Standard dot 49 CFR Part 192 is compared with the prediction results of strength check failure analysis using national standards GB 50251, GBT 34275, and GB150. The prediction results show that the ductile crack failure risk probability of X90 Pipeline Steel is higher than that of strength failure. For the ductile crack failure mode, the prediction of the failure life of pipeline steel with 8 steel pipes is slightly stricter than that with 5 steel pipes. [ABSTRACT FROM AUTHOR]

The capacity of soil to store carbon (C) and emit carbon dioxide (CO2) into the atmosphere primarily depends on soil management practices. It is essential to understand the impact of management strategies on the soil organic carbon (SOC) content and labile organic carbon (LOC) fraction. The impacts of 24‑year-long organic and inorganic nitrogen (N) treatments on SOC, KMnO4-oxidizable organic carbon and its fractions (highly labile organic carbon (HLOC), moderately labile organic carbon (MLOC), low labile organic carbon (LLOC) and nonlabile organic carbon (NLOC)), and a carbon management index (CMI) were investigated under a continuous maize cultivation system in a long-term experiment in Guizhou, Southwest China. Six fertilizer treatments were included: no fertilizer input (CK), chemical fertilizer alone (NPK), 25% N through farmyard manure (FYM) plus 75% N through chemical fertilizer (1/4N-M+3/4N-CF), 50% N through FYM plus 50% N through chemical fertilizer (1/2N-M+1/2N-CF), FYM plus chemical fertilizer (MNPK) and FYM alone (M). We used the LOC content and CMI value to assess the effects of long-term combinations of FYM and chemical fertilizers at different rates on the SOC pool in various soil layers (0–20, 20–40, 40–60, 60–80, 80–100 cm) and to identify the most suitable integrated treatment. The results showed that the application of organic fertilizer generally increased the SOC content, the LOC fraction, and the CMI values in different layers, especially the surface layer, compared to the CK and NPK fertilization treatments. The SOC content and LOC fraction decreased with increasing soil depth. The significant relationship between the LOC fraction, CMI value, LOC available ratio of carbon (LOC-AR), and soil parameters showed that these values can be used to sensitively assess soil quality and SOC changes in the system. Considering the comprehensive effects on the SOC content, LOC fraction, CMI value, AR value, etc., the 1/4N-M+3/4N-CF and 1/2N-M+1/2N-CF treatments showed the greatest influence on carbon sequestration and soil productivity; therefore, these could be the best options for maize cropping systems in this region. [ABSTRACT FROM AUTHOR]

In this paper, we propose and analyze a new finite element method for a semilinear elliptical problem with small viscosity. Firstly, we prove the existence and uniqueness of solution for its variational problem. Then, we obtain the stability and convergence of the corresponding finite element Galerkin approximation. Furthermore, we derive the optimal error estimates in the L 2 and H 1 norms for the finite element approximations respectively. Finally, several numerical experiments are provided to confirm the above theoretical results. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the clinical feasibility of early 30-minute dynamic 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) positron emission tomography (PET) scanning protocol for patients with lung lesions in comparison to the standard 65-minute dynamic FDG-PET scanning as a reference. Methods: Dynamic 18F-FDG PET images of 146 patients with 181 lung lesions (including 146 lesions confirmed by histology) were analyzed in this prospective study. Dynamic images were reconstructed into 28 frames with a specific temporal division protocol for the scan data acquired 65 min post-injection. Ki images and quantitative parameters Ki based on two different acquisition durations [the first 30 min (Ki-30 min) and 65 min (Ki-65 min)] were obtained by applying the irreversible two-tissue compartment model using in-house Matlab software. The two acquisition durations were compared for Ki image quality (including visual score analysis and number of lesions detected) and Ki value (including accuracy of Ki, the value of differential diagnosis of lung lesions and prediction of PD-L1 status) by Wilcoxon's rank sum test, Spearman's rank correlation analysis, receiver operating characteristic (ROC) curve, and the DeLong test. The significant testing level (alpha) was set to 0.05. Results: The quality of the Ki-30 min images was not significantly different from the Ki-65 min images based on visual score analysis (P > 0.05). In terms of Ki value, among 181 lesions, Ki-65 min was statistically higher than Ki-30 min (0.027 ± 0.017 ml/g/min vs. 0.026 ± 0.018 ml/g/min, P < 0.05), while a very high correlation was obtained between Ki-65 min and Ki-30 min (r = 0.977, P < 0.05). In the differential diagnosis of lung lesions, ROC analysis was performed on 146 histologically confirmed lesions, the area under the curve (AUC) of Ki-65 min, Ki-30 min, and SUVmax was 0.816, 0.816, and 0.709, respectively. According to the Delong test, no significant differences in the diagnostic accuracies were found between Ki-65 min and Ki-30 min (P > 0.05), while the diagnostic accuracies of Ki-65 min and Ki-30 min were both significantly higher than that of SUVmax (P < 0.05). In 73 (NSCLC) lesions with definite PD-L1 expression results, the Ki-65 min, Ki-30 min, and SUVmax in PD-L1 positivity were significantly higher than that in PD-L1 negativity (P < 0.05). And no significant differences in predicting PD-L1 positivity were found among Ki-65 min, Ki-30 min, and SUVmax (AUC = 0.704, 0.695, and 0.737, respectively, P > 0.05), according to the results of ROC analysis and Delong test. Conclusions: This study indicates that an early 30-minute dynamic FDG-PET acquisition appears to be sufficient to provide quantitative images with good-quality and accurate Ki values for the assessment of lung lesions and prediction of PD-L1 expression. Protocols with a shortened early 30-minute acquisition time may be considered for patients who have difficulty with prolonged acquisitions to improve the efficiency of clinical acquisitions. [ABSTRACT FROM AUTHOR]

Abstract By boundary element method, we present a numerical iterative process for solving a free third boundary problem modeling tumor growth with spectral accuracy. The piecewise quadratic curves are fitted to maintain local smoothness of the boundary at every node. The double-layer and single-layer potentials with weakly singular kernels are evaluated with spectral accuracy. The method of characteristics is employed to transform interfacial velocity PDE into discrete ODEs. The numerical integral formula for weakly singular operator with logarithmic singularity is deduced and the convergence and error are presented. The nonradially symmetric solutions of the free boundary problem on a perturbed boundary are provided to test the accuracy and effectiveness of the numerical method. [ABSTRACT FROM AUTHOR]

Abstract A finite element method based on P 1 -element for the 3D semilinear elliptic boundary value problem with small viscosity is considered. The existence, uniqueness and uniform optimal H 1 and suboptimal L 2 error estimates of the finite element solution are provided, where 0 < ν < < 1 ≤ β. Also, the numerical tests are made to show the efficiency of the error estimates of the finite element solution for the 3D semilinear elliptic boundary value problem with small viscosity. [ABSTRACT FROM AUTHOR]

In the mathematical model of tumor growth, the initial boundary surface of the three dimensional tumor domain is known, but the tumor domain and its boundary surface change over time in a way that is unknown in advance. People are concerned whether the tumor is likely to spread or shrink and how the tumor will change. In this article, by the boundary element method, the free boundary problem in the three-dimensional tumor domain will be solved via the integration on a two-dimensional boundary surfaces (at the expense of singularity in the Green’s functions). We will numerically compute and graphically show the changing boundary surfaces of the three dimensional tumor domain over time. We will numerically analyze the trend of tumor growth with varying proliferation rate μ . Our numerical approach Professor Bei Hu proposed is new and our numerical experiments contribute to the prediction of tumor growth in clinical medicine. [ABSTRACT FROM AUTHOR]

SMARCA4-deficient non-small cell lung cancer (NSCLC) is a more recently recognized subset of NSCLC. We describe the 18F-fluorodeoxyglucose (FDG) PET/CT findings in a rare case of SMARCA4-deficient NSCLC and response to therapy. A 45-year-old male patient with a history of heavy smoking (10 years) underwent an 18F-fluorodeoxyglucose (FDG) PET/CT dynamic (chest) + static (whole-body) scan for diagnosis and pre-treatment staging. 18F-FDG PET/CT showed an FDG-avid mass in the upper lobe of the left lung (SUVmax of 22.4) and FDG-avid lymph nodes (LN) in the left pulmonary hilar region (SUVmax of 5.7). In addition, there were multiple metastases throughout the body, including in the distant LNs, adrenal glands, bone, left subcutaneous lumbar region, and brain. Pathological findings confirmed SMARCA4-deficient NSCLC. After four cycles of chemotherapy and immune checkpoint inhibitors (ICI), the patient underwent again an 18F-FDG PET/CT scan (including a dynamic scan) for efficacy evaluation. We report a case that deepens the understanding of the 18F-FDG PET/CT presentation of SMARCA4-deficient NSCLC as well as dynamic imaging features and parametric characteristics. [ABSTRACT FROM AUTHOR]

To treat the osteoporosis and regulate the biological behaviors of both osteoblasts and osteoclasts, we prepared a natural polysaccharide-derived nanocomposite, containing alendronate-grafted hyaluronate (HA-Aln) and bone morphogenetic protein 2 (BMP-2) and investigated its synergistic regulation on the behaviors of osteoblasts and osteoclastsin vitro. The HA-Aln/BMP-2 nanocomposite was fabricated through the electrostatic interactions between the HA-Aln molecule and BMP-2 molecule. Here, BMP-2 was used to improve the osteoblast-mediated bone formation. Alendronate (Aln), a targeting ligand to bone matrix, was used to inhibit the osteoclast-mediated bone resorption.In vitroresults showed that HA-Aln/BMP-2 nanocomposite could effectively maintain the bioactivity of loaded drugs. The osteoblasts that treated with the HA-Aln/BMP-2 nanocomposite presented a higher level of cell motility, alkaline phosphatase (ALP) activity, mineralization capacity, and osteoblast-related gene expressions (runt-related transcription factor 2, osterix, ALP, collagen type I, osteocalcin, and osteopontin), as compared to that of control group. Besides, the RAW264.7 cells that were treated with HA-Aln/BMP-2 nanocomposite showed a lower level of osteoclastic differentiation. Overall, the HA-Aln/BMP-2 nanocomposite exhibits promising potential as an efficient carrier for co-delivery of anti-osteoporotic drug and growth factors to promote osteoblastic differentiation and bone formation while suppressing osteoclastic activity. [ABSTRACT FROM AUTHOR]

• The optimal convergence rate of L 2 -error for the velocity is completely proven. • The corresponding algorithm of our method is simple to be implemented by codes. • The remarkable advantage of our method is demonstrated via adequate numerical experiments. In this work, we develop a high-order pressure-robust method for the rotation form of the incompressible Navier–Stokes equations. The original idea is to change the velocity test functions in the discretization of trilinear and right hand side terms by using an H (div) -conforming velocity reconstruction operator. In order to match the rotation form and ease error analysis, a skew-symmetric discrete trilinear form containing the reconstruction operator is proposed, in which not only the velocity test function is changed. The corresponding well-posed discrete weak formulation stems straight from the classical inf-sup stable mixed conforming high-order finite elements, and it is proved to achieve the pressure-independent velocity errors. Optimal convergence rates of H 1 , L 2 -error for the velocity and L 2 -error for the Bernoulli pressure are completely established. Adequate numerical experiments are presented to demonstrate the theoretical results and remarkable performance of the proposed method. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD)-related brain deterioration is linked to the type 2 diabetes mellitus (T2DM) features hyperglycemia, hyperinsulinemia, and insulin resistance. Hypoxia as a common risk factor for both AD and T2DM. Hypoxia-inducible factor-1 alpha (HIF-1α) acts as the main regulator of the hypoxia response and may be a key target in the comorbidity of AD and T2DM. HIF-1α expression is closely related to hyperglycemia, insulin resistance, and inflammation. Tissue oxygen consumption disrupts HIF-1α homeostasis, leading to increased reactive oxygen species levels and the inhibition of insulin receptor pathway activity, causing neuroinflammation, insulin resistance, abnormal Aβ deposition, and tau hyperphosphorylation. HIF-1α activation also leads to the deposition of Aβ by promoting the abnormal shearing of amyloid precursor protein and inhibiting the degradation of Aβ, and it promotes tau hyperphosphorylation by activating oxidative stress and the activation of astrocytes, which further exasperates AD. Therefore, we believe that HIF-α has great potential as a target for the treatment of AD. Importantly, the intracellular homeostasis of HIF-1α is a more crucial factor than its expression level. [Display omitted] [ABSTRACT FROM AUTHOR]

The investigation of the fragmentation law of granular fertilisers in side-deep fertilisation devices is crucial for optimizing machinery. In this paper, Hertz-Mindlin with Bonding was used to establish a granular fertiliser model with breakage properties. The single-factor and central composite tests were carried out with the screw pitch, screw speed, and Y-shaped mouth angle selected as the test factors, and the broken bond rate as the evaluation index to indicate the fragmentation rate of the granular fertilisers. The result indicated a positive correlation between broken bond rate and screw speed in the range of 100–300 rpm, as well as a negative correlation between broken bond rate and screw pitch in the range of 18–38 mm and the Y-shaped mouth angle in the range of 25–45°. Moreover, during the reduction in screw pitch from 33 to 23 mm, the increment of broken bond rate caused by screw pitch was increased due to the higher screw speed and decreased due to the larger Y-shaped mouth angle. The key factors, in order of importance, are the screw pitch, screw speed, and Y-shaped mouth angle. In addition, the verification test was carried out in the range of 100–300 rpm and the test results showed a similar response trend to the simulation results, indicating that the fragmentation law obtained by the simulation is reliable. These research findings can provide a reference for the optimization of the side-deep fertilisation devices. • The fragmentation rate is researched based on the side-deep fertilization device. • The Hertz-Mindlin with Bonding contact model of granular fertilizer is established. • Single-factor and central composite tests and physical experiments are conducted. • The influence law of key parameters on granular fertilizer crushing are revealed. [ABSTRACT FROM AUTHOR]

The discharge characteristics and mechanism of pulse modulated radio frequency (RF) atmospheric pressure glow discharge (APGD) are studied using a two-dimensional self-consistent numerical fluid model. The ignition of an RF discharge burst is demonstrated by the increase in RF current amplitude and evolution of the discharge spatial profile from a bell shape to a double-hump shape. With a time interval of 80 µs between two consecutive RF discharge bursts, the electron dissipation after an RF discharge burst is shown, whose reduction slope changes from 1.7 × 1022 m−3s−1 to 9.1 × 1019 m−3s−1 with a time delay. The corresponding electron dissipation mechanism is proposed to be the electron loss due to reactions in the discharge bulk and the drift of electrons across the discharge gap, which explains the continuum and discrete operation modes in pulse modulated RF APGD. [ABSTRACT FROM AUTHOR]

The accumulation of liquid in gas wells has become a prevalent problem in the middle and later stages of gas well development with different wellbore structures, which seriously affects the production efficiency of gas wells. To precisely forecast the generation time of liquid accumulation in gas wells and timely adopt drainage gas production technology, the literatures on gas critical liquid‐carrying flow calculation models for vertical wells, inclined wells and horizontal wells were analyzed and summarized. The results show that the research on the calculation models for gas critical liquid‐carrying flow rate in vertical and inclined wells is relatively mature. However, because of the unique wellbore structure of horizontal wells, the gas‐liquid two‐phase flow pattern and distribution of droplets and liquid‐film are complex, leading to a lack of understanding of gas liquid carrying mechanism throughout the whole wellbore of existing horizontal wells, and we established a calculation model of gas critical liquid‐carrying flow rate in horizontal wells considers single factors. Based on the above summary and analysis, the research direction of the calculation model for gas critical liquid‐carrying flow rate in the entire wellbore of horizontal wells is pointed out. Combining the gas liquid‐carrying test of entire wellbore of the horizontal well, considering the distribution form of droplets and liquid‐film, the aggregation and fission between droplets, and the energy exchange between gas and liquid, the gas liquid‐carrying mechanism of the entire wellbore of horizontal well is revealed, clarifying the most easy to liquid‐accumulating well sections in the whole horizontal well, and a calculation model of gas critical liquid‐carrying flow rate of horizontal well considering multiple factors is established, providing crucial theoretical foundation and technical support for the drainage and gas recovery of a horizontal well. [ABSTRACT FROM AUTHOR]

To address the problem of high adsorption of coalbed methane (CBM), a hydraulic cavitation tool for CBM production enhancement was designed based on the mechanism of cavitation wave promoting CBM production enhancement. To achieve the best cavitation performance and generate high-intensity cavitation waves to promote CBM desorption, the influence of inlet flow rate and upper and lower nozzle diameter ratio on cavitation performance was investigated by CFD technique and cavitation jet experiment. The simulation and experimental results show that as the inlet flow rate increases, the cavitation effect in the oscillation chamber increases, and the throttling pressure difference increases, so the throttling pressure difference is used to characterize the cavitation performance of the cavitation tool. The cavitation performance of the cavitation tool is analyzed when the upper and lower nozzle diameter ratio is from 1.5 to 3 and the inlet flow rate is from 2 to 10 m3/h. When the upper and lower nozzle diameter ratio is 2, the inlet flow rate is 6 m3/h, the throttling pressure difference increases by 73.2%, the value of vapor volume fraction increases by 77.7%, the cavitation effect no longer increases, achieving optimal cavitation performance. As a result, the high-intensity cavitation waves generated by the cavitation tool can continuously propagate in the formation, play a continuous oscillating effect on the coal seam, and can significantly increase the gas production of coalbed methane. The research results can provide new ideas for the development of CBM production enhancement tools. [ABSTRACT FROM AUTHOR]

Background: Dynamic positron emission tomography (PET) images are useful in clinical practice because they can be used to calculate the metabolic parameters (Ki) of tissues using graphical methods (such as Patlak plots). Ki is more stable than the standard uptake value and has a good reference value for clinical diagnosis. However, the long scanning time required for obtaining dynamic PET images, usually an hour, makes this method less useful in some ways. There is a tradeoff between the scan durations and the signal-to-noise ratios (SNRs) of Ki images. The purpose of our study is to obtain approximately the same image as that produced by scanning for one hour in just half an hour, improving the SNRs of images obtained by scanning for 30 min and reducing the necessary 1-h scanning time for acquiring dynamic PET images. Methods: In this paper, we use U-Net as a feature extractor to obtain feature vectors with a priori knowledge about the image structure of interest and then utilize a parameter generator to obtain five parameters for a two-tissue, three-compartment model and generate a time activity curve (TAC), which will become close to the original 1-h TAC through training. The above-generated dynamic PET image finally obtains the Ki parameter image. Results: A quantitative analysis showed that the network-generated Ki parameter maps improved the structural similarity index measure and peak SNR by averages of 2.27% and 7.04%, respectively, and decreased the root mean square error (RMSE) by 16.3% compared to those generated with a scan time of 30 min. Conclusions: The proposed method is feasible, and satisfactory PET quantification accuracy can be achieved using the proposed deep learning method. Further clinical validation is needed before implementing this approach in routine clinical applications. [ABSTRACT FROM AUTHOR]

Jet flows are ubiquitous in nature and laboratories. For example, helium and argon jets into ambient air are commonly used to produce atmospheric plasma jets. The jets before and after discharge both are typical multicomponent flows. This study reports on the implementation of a numerical solver based on the graphic processing units to model multicomponent mixture gas flows. To this end, two- and three-dimensional Jacobian matrices for the multicomponent Euler equations were obtained to reconstruct numerical fluxes and build a total variation diminishing scheme. The two-dimensional early-stage mass transfer of gas jets was studied for three mixture gases: He/air, Ar/air, and N2/air to numerically verify the steady functioning of the numerical solver despite the high mass fraction gradients. The mass fraction distribution of helium in ambient air exhibited more complex substructures than those of argon and nitrogen in ambient air. Using the watershed method, self-generated bullets were extracted from the mass fraction distributions of the helium jet. The proposed numerical solver implemented in this study is expected to provide a better understanding of gas jet dynamics, and the Jacobian matrices can provide a mathematical foundation for constructing potential higher schemes. [ABSTRACT FROM AUTHOR]

Nowadays, there has been a rapid expansion of tea plantations in the mountainous areas of southwest China. However, little research has focused on the pollution problems caused by the losses of nitrogen and phosphorus from tea plantations in this area. Therefore, a field experiment was conducted using the runoff plots in situ monitoring method following farmers' conventional management from 2018 to 2020 in Guizhou Province, southwest China. The characteristics of nitrogen and phosphorus losses from tea plantation in the mountainous area were clarified, and the effect of rainfall intensity on the nitrogen and phosphorus losses were explored. 298 natural rainfall events with a total rainfall of 2258 mm were observed during the 2-year observation period, and erosive rainfall accounted for 78.1% of the total rainfall. The total surface runoff amount was 72 mm, and the surface runoff coefficient was 3.19%. The total nitrogen (TN) and total phosphorus (TP) concentrations in the surface runoff ranged from 0.68 to 14.86 mg·L−1 and 0.18 to 2.34 mg·L−1, respectively. The TN and TP losses from tea plantations were 1.47 kg N ha−1 yr−1 and 0.210 kg P ha−1 yr−1. Rainfall intensity directly and significantly affected the surface runoff and nitrogen and phosphorus loss. Where 72.6% of the cumulative rainfall, 92.5% of the total surface runoff amounts, 87.4% of total nitrogen loss, and 90.5% of total phosphorus loss were observed in rainfall events above 10 mm. Taken together, the results provide scientific guidance for quantifying the characteristics of nutrient loss in subtropical mountain tea plantations. [ABSTRACT FROM AUTHOR]

Downhole throttling technology is of great significance to the stable production of natural gas. Downhole throttle is widely used by major oil and gas fields. In view of the frequent failure of downhole throttle, downhole throttling mechanism and relevant literature on downhole throttle failure were studied and analyzed. It is concluded that: (1) structural failure of downhole throttle mainly occurs in the rubber cylinder, slip and throttle nozzle; (2) under the condition of satisfying the strength of slip and rubber cylinder, it is necessary to further study and analyze the problem that jamming of slip and inability of rubber cylinder to rebound effectively by using new soluble materials; (3) for the traditional throttle nozzle with fixed diameter, it is necessary to salvage the throttle when replacing it, which is time-consuming, tedious, costly and easy to lead to throttle failure. Under the premise of not changing normal operating environment, it is the future research direction to adjust the diameter of throttle nozzle effectively, conveniently and intelligently according to real-time downhole temperature and pressure conditions; (4) the large amount of sand produced from the wellbore is the main cause of failure of downhole throttle salvaging operation. The problems that throttle salvaging failure and erosion of throttle anti-sand screen tube are caused by wellbore sand production have been well researched in the innovation of throttle salvaging tools. It is necessary to further study the anti-sand screen tube, multistage anti-sand and anti-sand structure. It points out the direction of further research on downhole throttle. [ABSTRACT FROM AUTHOR]

• A facile green strategy is developed to synthesize the MnO-based anode materials. • MOF derived carbon matrix and graphene greatly enhance the conductivity. • The MnO@rGO shows high reversible capacity and superior electrochemical stability. Although metal-organic frameworks (MOFs) derived MnO-based materials exhibit high reversible capacity over commercial anode materials, their practical application is still impeded due to the drawbacks of conventional synthetic methods, such as environmental hazards and economic costs. Herein, we report a facile and eco-friendly water-based route for the in-suit synthesis of Mn-MOF precursors, which are applied to prepare MnO and MnO@rGO anode materials through one-step pyrolysis. When fabricated as anode for Lithium-ion batteries (LIBs), MnO@rGO composite achieves superior electrochemical performance in comparison to pristine MnO. Exceedingly, it retains high reversible capacity of 920 mAh g−1 even at 2000 mA g−1 after 160 cycles, which is around 1.8 times of pristine MnO. [ABSTRACT FROM AUTHOR]

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn 2 O 3) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn 2 O 3 exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g−1 at 0.1 A g−1, and excellent rate performance of 410.4 mAh g−1 at 2 A g−1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g−1 at 0.1 A g−1 after 380 cycles, and 755 mAh g−1 at 1 A g−1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li+ diffusion distance. [ABSTRACT FROM AUTHOR]

Coiled tubing endures significant pressure and fluid impact throughout the oil and gas production and transportation processes. The abrasive action of sand-carrying liquids against the pipe wall leads to gradual thinning, compromising its ability to bear pressure and tension, ultimately resulting in fractures and leaks. To address this concern, this study conducts liquid–solid two-phase steady-state erosion experiments on coiled tubing flushed with sand-carrying liquids. The experiments choose CT110, TS110 and QT1100 tubing samples, explore various particle properties, fluid factors, and pipeline conditions to investigate the thinning rate caused by erosion. The CT110 coiled tubing exhibits a higher erosion rate when subjected to sand-laden fluid erosion in the experiment. This characteristic proves beneficial in numerical simulations, as it allows for a more pronounced demonstration of the effectiveness of erosion prediction models under equivalent conditions. A predictive model for coiled tubing erosion and thinning has been established by incorporating erosion theory and the discrete phase model. The discrete phase model adeptly comprehends and describes the experimental phenomena associated with sand-carrying fluid erosion. By providing comprehensive experimental data and theoretical analysis, this article facilitates the prediction of the uniform thinning rate of the oil pipe wall and enables the estimation of its service life. [ABSTRACT FROM AUTHOR]

Lodging is a major constraint to maize productivity and harvesting mechanization in the North China Plain. EDAH (contains ethephon and diethyl aminoethyl hexanoate) is a novel growth regulator, which had been proved to enhance maize lodging resistance and increase yield, especially under high plant density. However, lodging still happens when recommended dose of EDAH was foliar sprayed in many previous reports. Therefore, a field experiment with normal dose (T1) and increased dose (T2) of EDAH was conducted to further enhance maize lodging resistance under different plant densities. Results indicated that T2 significantly reduced plant height and ear height, and obviously increased bending strength (P < 0.05), i.e., increasing EDAH dose more obviously enhanced maize lodging resistance. Concurrently, EDAH distinctly inhibited maize growth which resulted in lower leaf area index (LAI) and leaf area duration (LAD) after silking. However, both leaf photosynthetic rate and chlorophyll content during filling stage were not significantly (P > 0.05) changed by EDAH. Consequently, maize grain yields under T1 and T2 were reduced by 3.2–8.5% and 10.9–13.6% under optimized density (7.5 plants m2−) in this study, respectively. Nevertheless, EDAH did not reduce maize yield under high density (9.0 plants m2−) due to relative high LAI (5.3–5.6). We concluded that high dose EDAH further enhanced lodging resistance with reduced grain yield under optimized density, but maintained grain yield under high plant density. Results of this study provided a critical strategy to lower lodging risk and increase maize grain yield. [ABSTRACT FROM AUTHOR]

In view of the failure causes of downhole choke fishing in tight gas wells, taking the choke fishing failure in Daning–Jixian block as representative, the failure causes are summarized through the actual fishing data and phenomena on site. This study analyzes from 11 aspects: (1) the influence of fishing time on throttle fishing; (2) the influence of the running depth of the choke on the fishing success rate of the choke; (3) the influence of gas well effusion on the success rate of choke fishing; (4) the influence of sand production on choke fishing; (5) the influence of restrictor structure on fishing success rate; (6) life analysis of restrictor; (7) type selection of throttle; (8) throttle structure design; (9) choke fishing; (10) choke sand blockage; (11) impact of switching well. This paper analyzes the methods to improve the fishing success rate of a choke and puts forward a reasonable solution to the fishing failure of choke, to ensure the safety of tight gas well construction. [ABSTRACT FROM AUTHOR]

In order not to hinder gas production, we usually hope that the bottom hole effusion can be discharged to the surface with high-pressure natural gas. For the production data of high water content gas wells, the problems of insufficient water content and liquid-carrying capacity affecting gas well production should be considered. Based on the wellbore gas-liquid two-phase pipe flow theory and heat transfer theory, the temperature and pressure coupling prediction model of a high water-bearing gas well is established. Combined with the downhole throttling mechanism and gas-liquid two-phase homogeneous flow theory, the temperature and pressure field distribution model is established. The results show that compared with the Ramey model and Hassan and Kabir model, the temperature and pressure coupling prediction model of high water-bearing gas wells established in this study has the smallest coefficient of variation in the four groups of data tests. Based on this, the effects of different working conditions and choke diameter on downhole throttling characteristics of high water-bearing gas wells are analyzed. The findings of this study are helpful to better predict the wellbore temperature and pressure coupling of high water-bearing gas wells and provide more effective help for the smooth production of gas wells. [ABSTRACT FROM AUTHOR]

Abstract: Background: As cardiovascular diseases have become the leading cause of death in many countries including China, nurses are increasingly required to be abreast of technological advances and the skills necessary to manage this increasing health care problem. Chinese nurses are under pressure to provide skilled electrocardiography monitoring, and be sufficiently skilled to detect myocardial ischemia and infarction, in this large patient population. This presents a challenge for the nursing profession in China, particularly for nurses working in coronary care in a country where advancement has been so rapid, yet little research has been conducted or reported in the literature. Objectives: The two main objectives were: to explore the demographic and educational factors that affect the use of ST-segment monitoring and correct electrode placement by CCU/ICU nurses in China; and to explore the factors both individual and institutional that affect monitoring and lead placement. Methods: A self-administered questionnaire was distributed to nurses in 126 randomly selected tertiary hospitals, which were stratified into three homogeneous regions across China. The instrument examined demographics, information about hospitals, electrocardiogram devices, current practice patterns and perceptions toward monitoring and lead placement. Data from 734 nurses and 59 nurse managers from 59 hospitals were analyzed using t-tests, ANOVA, Chi-square test and logistic regression. Results: Electrocardiogram monitoring was used to detect myocardial ischemia by 43.7% of respondents, and 35.1% selected leads according to electrocardiogram or angiography findings. Most (70%) agreed that monitoring for acute coronary syndrome was important, while 39.2% did so, and 15.7% were able to identify correct placement. Logistic regression revealed a significant relationship between the uses of ST-segment monitoring and number of hospital beds, continuing education and a belief in its use and ease of use. Correct electrode placement was significantly correlated with respondents from university hospitals, hospitals with more acute coronary syndrome admissions and more independent thinking nurses. Conclusions: Despite best practice evidence, less than half of the sample used electrocardiogram monitoring to detect myocardial ischemia and the majority could not identify correct electrode placement, while ST-segment monitoring was not used routinely. This paper highlights the need for improvements in education both in universities and hospitals and discussion addresses conventions in units, which inhibit development of nurses’ skills. [Copyright &y& Elsevier]

The nirS gene encodes nitrite reductase (NIR) and participates in the denitrification of inorganic nitrogen (N) in soils. Although the gene is important in the global cycling of N, little is known about the responses of nirS -denitrifier communities to the substitution of chemical fertilizer by organic materials. Therefore, a field experiment in a vegetable soil was established with only chemical fertilizer (F) and four partially substituted organic materials treatments: straw (SF), mushroom dregs (MF), biochar (BF), and cattle manure (CF). All treatments received equal amounts of total nitrogen, phosphorus, and potassium. Integrated high-throughput absolute abundance quantification (iHAAQ) was used to quantify the abundance of the nirS gene in denitrifier communities. The relations among NIR activity, N fractions and other soil properties were also evaluated. Compared with the F treatment, the substitution with organic materials increased the diversity but reduced the absolute abundance of the nirS gene, particularly in the SF treatment (P < 0.05). The NIR activity increased in F, SF, and BF treatments, with the highest value (8.14 μmol d−1 g−1) in the BF treatment. In a distance-based redundancy analysis, the composition of the nirS -denitrifier community was significantly correlated with the soil C:N ratio. The NIR activity was significantly correlated with soil N:P ratio (r = 0.486, P < 0.05). Overall, the biochar substitution increased the diversity of nirS -denitrifiers and NIR activity. The substitution of chemical fertilizer by various organic materials changed the nirS community, because the changes in soil properties, especially the interaction of carbon and nitrogen, affected different genera of bacterial. • Biochar substitution increased the NIR activity. • NIR activity was correlated with soil N:P ratio. • The nirS -denitrifier community composition showed a significant correlation with soil C:N ratio. [ABSTRACT FROM AUTHOR]