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Background and Objectives: To estimate the clinical outcomes of uniportal and biportal full-endoscopic spine surgery for the treatment of lumbar degenerative disease (LDD), and to provide the latest evidence for clinical selection. Materials and Methods: Relevant literatures published in PubMed, Web of Science, Embase, CNKI, and WanFang Database before 21 November 2021 were searched systematically. Two researchers independently screened the studies, extracted data, and evaluated the risk of bias of the included studies. The systematic review and meta-analysis were performed using the Review Manager software (version 5.4; The Cochrane Collaboration). Results: A total of seven studies were included in this meta-analysis, including 198 patients in a uniportal endoscopy group and 185 patients in a biportal endoscopy group. The results of this meta-analysis demonstrated that the biportal endoscopy group experienced less intraoperative estimated blood loss (WMD = −2.54, 95%CI [−4.48, −0.60], p = 0.01), while the uniportal endoscopy group displayed significantly better recovery results in Visual Analog Scale (VAS) assessments of the back within 3 days of surgery (WMD = 0.69, 95%CI [0.02, 1.37], p = 0.04). However, no significant differences in operation time, length of hospital stay, complication rates, Oswestry Disability Index (ODI) (within 3 months), ODI (last follow-up), VAS for back (within 3 months), VAS for back (last follow-up), and VAS for leg (within 3 days, within 3 months, last follow-up) were identified between the two groups. Conclusions: According to our meta-analysis, patients who underwent the uniportal endoscopic procedure had more significant early postoperative back pain relief than those who underwent the biportal endoscopic procedure. Nevertheless, both surgical techniques are safe and effective.

A restructuring method for least square (LS) channel est ation using cyclic-prefix frequency sequences (CPFS) in orthogonal frequency division multiplexing (OFDM) system was proposed. The restructuring method was based on the relationship of CPFS and comb-pilots which made a higher LS channel estimation precision. Specifically, the relationship used a convex optimization model, the model was set up using total sub carriers as variable and mi-nimized mean square error (MSE) as the principle to generate constraint, where further the optimized restructuring result using Lagrange method was derived. Simulations verify that under the restructured total sub carriers CPFS can enhance the LS channel estimation precision.

Channel estimation problem is one of the key technical issues in sparse frequency-selective fading multiple-input multiple-output (MIMO) communication systems using orthogonal frequency division multiplexing (OFDM) scheme. To estimate sparse MIMO channels, sparse invariable step-size normalized least mean square (ISS-NLMS) algorithms were applied to adaptive sparse channel estimation (ACSE). It is well known that step-size is a critical parameter which controls three aspects: algorithm stability, estimation performance, and computational cost. However, traditional methods are vulnerable to cause estimation performance loss because ISS cannot balance the three aspects simultaneously. In this paper, we propose two stable sparse variable step-size NLMS (VSS-NLMS) algorithms to improve the accuracy of MIMO channel estimators. First, ASCE is formulated in MIMO-OFDM systems. Second, different sparse penalties are introduced to VSS-NLMS algorithm for ASCE. In addition, difference between sparse ISS-NLMS algorithms and sparse VSS-NLMS ones is explained and their lower bounds are also derived. At last, to verify the effectiveness of the proposed algorithms for ASCE, several selected simulation results are shown to prove that the proposed sparse VSS-NLMS algorithms can achieve better estimation performance than the conventional methods via mean square error (MSE) and bit error rate (BER) metrics.

为了解决甘油合成碳酸甘油酯产率较低及反应完成后催化剂的回收问题，制备磁性水滑石LDH-Fe3O4，以KNO3为活性组分前驱体对其改性制备磁性固体碱催化剂K2O/LDO-γ-Fe2O3，对KNO3的负载量进行考察，对K2O/LDO-γ-Fe2O3进行X射线衍射、 扫描电子显微镜、 CO2程序升温脱附、BET及磁化强度表征，采用单因素试验对K2O/LDO-γ-Fe2O3催化甘油酯交换合成碳酸甘油酯的工艺条件进行了优化，并对K2O/LDO-γ-Fe2O3的重复使用性能进行了考察。结果表明：KNO3负载提供了大量的碱性位点，有利于催化剂催化活性的提高，KNO3的最佳负载量为10%（以LDH-Fe3O4质量计），K2O/LDO-γ-Fe2O3的饱和磁化强度为10.47 emu/g；K2O/LDO-γ-Fe2O3催化酯交换最佳反应条件为反应温度100 ℃、反应时间2 h、催化剂用量3%（以甘油质量计）、甘油与碳酸二甲酯物质的量比1∶ 2，在此条件下碳酸甘油酯产率为92.12%；催化剂重复使用5次后碳酸甘油酯产率高达89.35%，相比镁铝水滑石，K2O/LDO-γ-Fe2O3催化反应时间短，反应试剂用量少。K2O/LDO-γ-Fe2O3催化剂具有磁性，可在外加磁场作用下与反应体系分离，并且在数次循环使用中保持较高的活性，经济成本降低，在工业生产碳酸甘油酯中有很好的应用前景。In order to solve the problems of the low yield of glycerol carbonate synthesized with glycerol and the recovery of the catalyst after the reaction, the magnetic hydrotalcite LDH-Fe3O4 was prepared and modified by KNO3 as the active component precursor to prepare magnetic solid base catalyst K2O/LDO-γ-Fe2O3.The KNO3 loading amount of the catalyst was studied.The K2O/LDO-γ-Fe2O3 was characterized by X-ray diffraction, scanning electron microscopy, CO2-TPD, BET and magnetization intensity. The process conditions of the K2O/LDO-γ-Fe2O3-catalyzed transesterification of glycerol for the synthesis of glycerol carbonate were optimized using single factor experiment. The reusability of K2O/LDO-γ-Fe2O3 was investigated. The results showed that KNO3 provided a large number of alkaline sites, which facilitated the catalytic activity of the catalyst,and the optimal loading amount was 10%(based on the mass of LDH-Fe3O4). The saturation magnetization intensity of K2O/LDO-γ-Fe2O3 was 10.47 emu/g. The optimal transesterification conditions were as follows: reaction temperature 100 ℃, reaction time 2 h, catalyst dosage 3%(based on the mass of glycerol), and molar ratio of glycerol to dimethyl carbonate 1∶ 2. Under the optimal conditions, the glycerol carbonate yield was 92.12%. The yield of glycerol carbonate reached 89.35% after five repetitions of the catalyst. The K2O/LDO-γ-Fe2O3 catalytic reaction time was shorter and the amount of reaction reagent was less than that of Mg-Al hydrotalcite. In conclusion, the magnetic catalyst prepared is magnetic and can be separated from the reaction system under the action of an applied magnetic field, and can maintain high activity in several cycles with reduced economic costs,and has a good application prospect in industrial production of glycerol carbonate.

Huge numbers of induced unpropped (IU) fractures are generated near propped fractures during hydraulic fracturing in shale gas reservoirs. But it is still unclear how their fracture space and conductivity evolve under in-situ conditions. This paper prepares three types of samples, namely, manually split vertical/parallel to beddings (MSV, MSP) and parallel natural fractures (NFP), to represent the varied IU fractures as well as their surface morphology. Laser scan and reconstruction demonstrate that the initial fracture spaces of MSVs and MSPs are limited as the asperities of newly created surfaces are well-matched, and the NFPs have bigger space due to inhomogeneous geological corrosion. Surface slippage and consequent asperity mismatch increase the fracture width by several times, and the increase is proportional to surface roughness. Under stressful conditions, the slipped MSVs retain the smallest residual space and conductivity due to the newly sharp asperities. Controlled by the bedding structures and clay mineral hydrations, the conductivity of MSPs decreases most after treated with a fracturing fluid. The NFPs remain the highest conductivity, benefitting from their dispersive, gentle, and strong asperities. The results reveal the diverse evolution trends of IU fractures and can provide reliable parameters for fracturing design, post-fracturing evaluation, and productivity forecasting. [ABSTRACT FROM AUTHOR]

Methane adsorption is a critical assessment of the gas storage capacity (GSC) of shales with geological conditions. Although the related research of marine shales has been well-illustrated, the methane adsorption of marine-continental transitional (MCT) shales is still ambiguous. In this study, a method of combining experimental data with analytical models was used to investigate the methane adsorption characteristics and GSC of MCT shales collected from the Qinshui Basin, China. The Ono-Kondo model was used to fit the adsorption data to obtain the adsorption parameters. Subsequently, the geological model of GSC based on pore evolution was constructed using a representative shale sample with a total organic carbon (TOC) content of 1.71%, and the effects of reservoir pressure coefficient and water saturation on GSC were explored. In experimental results, compared to the composition of the MCT shale, the pore structure dominates the methane adsorption, and meanwhile, the maturity mainly governs the pore structure. Besides, maturity in the middle-eastern region of the Qinshui Basin shows a strong positive correlation with burial depth. The two parameters, micropore pore volume and non-micropore surface area, induce a good fit for the adsorption capacity data of the shale. In simulation results, the depth, pressure coefficient, and water saturation of the shale all affect the GSC. It demonstrates a promising shale gas potential of the MCT shale in a deeper block, especially with low water saturation. Specifically, the economic feasibility of shale gas could be a major consideration for the shale with a depth of <800 m and/or water saturation >60% in the Yushe-Wuxiang area. This study provides a valuable reference for the reservoir evaluation and favorable block search of MCT shale gas. [ABSTRACT FROM AUTHOR]

With continuous hydrocarbon exploration extending to deeper basins, the deepest industrial oil accumulationwas discovered below 8,200 m, revealing a new exploration field. Hence, the extent to which oil exploration can be extended, and the prediction of the depth limit of oil accumulation (DLOA), are issues that have attracted significant attention in petroleum geology. Since it is difficult to characterize the evolution of the physical properties of the marine carbonate reservoir with burial depth, and the deepest drilling still cannot reach the DLOA. Hence, the DLOA cannot be predicted by directly establishing the relationship between the ratio of drilling to the dry layer and the depth. In this study, by establishing the relationships between the porosity and the depth and dry layer ratio of the carbonate reservoir, the relationships between the depth and dry layer ratio were obtained collectively. The depth corresponding to a dry layer ratio of 100% is the DLOA. Based on this, a quantitative prediction model for the DLOA was finally built. The results indicate that the porosity of the carbonate reservoir, Lower Ordovician in Tazhong area of Tarim Basin, tends to decrease with burial depth, and manifests as an overall low porosity reservoir in deep layer. The critical porosity of the DLOA was 1.8%, which is the critical geological condition corresponding to a 100% dry layer ratio encountered in the reservoir. The depth of the DLOA was 9,000 m. This study provides a new method for DLOA prediction that is beneficial for a deeper understanding of oil accumulation, and is of great importance for scientific guidance on deep oil drilling. [ABSTRACT FROM AUTHOR]

A full-length cDNA library from leaf and root tissues of cassava (Manihot esculenta) Arg7 and one accession of its wild ancestor W14 (M. esculenta ssp. flabellifolia) has been constructed. The library is comprised of four sub-libraries, containing 32640 recombinant clones, 6028 cDNA clones from their 5′ ends, and 128 clones from the 3′ ends were sequenced. In total, 5013 high-quality expressed sequence tags (ESTs) and 1259 unigenes were obtained. Of these, 746 unigenes were identified by their sequence homologies to ESTs from model plants, and 323 unigenes were mapped onto 114 different KEGG pathways. From these, 24 differentially expressed genes involved in starch metabolism and photosynthesis were identified and five of them were selected to compare their expression level between Arg7 and W14. Notably, Arg7 has a higher net photosynthesis rate in leaves, higher ribulose-1,5-bisphosphate carboxy-lase oxygenase activities in leaves, and higher AGPase activity in roots. This resource is the first EST collection from wild cassava and should be of value for gene discovery, genome annotation and studies of Manihot evolution.

A comprehensive dataset from 594 fracturing wells throughout the Duvernay Formation near Fox Creek, Alberta, is collected to quantify the influences of geological, geomechanical, and operational features on the distribution and magnitude of hydraulic fracturing-induced seismicity. An integrated machine learning-based investigation is conducted to systematically evaluate multiple factors that contribute to induced seismicity. Feature importance indicates that a distance to fault, a distance to basement, minimum principal stress, cumulative fluid injection, initial formation pressure, and the number of fracturing stages are among significant model predictors. Our seismicity prediction map matches the observed spatial seismicity, and the prediction model successfully guides the fracturing job size of a new well to reduce seismicity risks. This study can apply to mitigating potential seismicity risks in other seismicityfrequent regions. [ABSTRACT FROM AUTHOR]

A novel weighted multidimensional scaling estimator is presented for mobile location using time-of-arrival measurements. Results suggest the achievement of the Cramer-Rao lower bound at moderate noise level before the threshold effect occurs.

In this paper we consider mixed finite element methods for second order elliptic problems. In the case of the lowest order Brezzi-Douglas-Marini elements (if d - 2) or Brezzi-Douglas-Durfin-Fortin elements (if d = 3) on rectangular parallelepipeds, we show that the mixed method system, by incorporating certain quadrature rules, can be written as a simple, cell-centered finite difference method. This leads to the solution of a sparse, positive semidefinite linear system for the scalar unknown. For a diagonal tensor coefficient, the sparsity pattern for the scalar unknown is a five point stencil if d = 2, and seven if d = 3. For a general tensor coefficient, it is a nine point stencil, and nineteen, respectively. Applications of the mixed method implementation as finite differences to nonisothermal multiphase, multicomponent flow in porous media are presented. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) and shot peening were performed on 2219 aluminum alloy plates.The residual stresses generated by FSW and shot peening were measured using X-ray diffraction (XRD)， and the distribution characteristics of residual stresses were analyzed.The effects of parameters such as shot diameter， shot material， and spraying distance on the distribution of residual stresses in FSW were studied.Results showed that there was a large residual tensile stress near the weld zone after welding， and the average stress within ±20 mm of the weld center line was as high as 100.9 MPa， while the base metal area far away from the weld was close to zero stress.After shot peening，the distribution of residual stress of sample changed significantly， surface residual stress was manifested as compressive stress， and the value of compressive stress first increased and then decreased with the increase of depth， and finally remained as tensile stress.Increasing the shot diameter could increase the maximum residual compressive stress value and the depth of the residual compressive stress layer.However， when the shot diameter continued to increase to 1.2 mm，the maximum residual compressive stress value no longer increased.The optimal distribution of residual compressive stress could be obtained by selecting the appropriate shot material.The maximum residual compressive stress and the depth of the residual compressive stress layer firstly increased and then decreased with the increase of the spraying distance.

Objective To explore the expression of protein arginine deiminases (PADs) and protein arginine methyltransferases (PRMTs) in hepatocellular carcinoma, and to analyze whether the level of protein citrullination catalyzed by PADs is related to the expression of PRMTs. Methods The mRNA transcription of PADs and PRMTs in hepatoma cells was detected by quantitative PCR and the protein expression of PADs, citrullinated proteins and PRMTs was detected by Western blot. The mRNA correlation between PADs and PRMTs in liver cancer tissues in TCGA database was analyzed by bioinformatics, and the expressions of PADs, citrullinated proteins and PRMTs in liver cancer tissues was detected by immunohistochemistry. Results Compared with normal liver cell LX-2, the mRNA transcription of PAD2 and PRMT1 in Huh7 cells was higher (P＜0.001), and that of PAD4, PRMT1, PRMT5 and PRMT7 in HepG2 cells was higher (P＜0.01). The protein level of PAD2 and PAD4 in HepG2 and Huh7 was significantly higher than those in LX-2 (P＜0.01). The expression level of citrullinated protein in HepG2 and Huh7 was lower than that in LX-2. The expression of PADs and PRMTs in hepatocellular carcinoma was stronger than that in adjacent tissues, and the expression of citrullinated proteins was almost negative. There were positive correlation between PAD2 and all PRMTs in clinical sample database (P＜0.05). Conclusions The expression of PADs is high in hepatocellular carcinoma, whereas the expression of citrullinated proteins is low, which may be affected by the competition of PRMTs enzyme highly expressed in cells.