Numerical manifold method for thermo-mechanical coupling simulation of fractured rock mass

As a calculation method based on the Galerkin variation,the numerical manifold method(NMM)adopts a double covering system,which can easily deal with discontinuous deformation problems and has a high calculation accuracy.Aiming at the thermo-mechanical(TM)coupling problem of fractured rock masses,this study uses the NMM to simulate the processes of crack initiation and propagation in a rock mass under the influence of temperature field,deduces related system equations,and proposes a penalty function method to deal with boundary conditions.Numerical examples are employed to confirm the effectiveness and high accuracy of this method.By the thermal stress analysis of a thick-walled cylinder(TWC),the simulation of cracking in the TWC under heating and cooling conditions,and the simulation of thermal cracking of the SwedishÄspöPillar Stability Experiment(APSE)rock column,the thermal stress,and TM coupling are obtained.The numerical simulation results are in good agreement with the test data and other numerical results,thus verifying the effectiveness of the NMM in dealing with thermal stress and crack propagation problems of fractured rock masses.

Rock mass quality classification based on deep learning:A feasibility study for stacked autoencoders

Objective and accurate evaluation of rock mass quality classification is the prerequisite for reliable sta-bility assessment.To develop a tool that can deliver quick and accurate evaluation of rock mass quality,a deep learning approach is developed,which uses stacked autoencoders(SAEs)with several autoencoders and a softmax net layer.Ten rock parameters of rock mass rating(RMR)system are calibrated in this model.The model is trained using 75%of the total database for training sample data.The SAEs trained model achieves a nearly 100%prediction accuracy.For comparison,other different models are also trained with the same dataset,using artificial neural network(ANN)and radial basis function(RBF).The results show that the SAEs classify all test samples correctly while the rating accuracies of ANN and RBF are 97.5%and 98.7%,repectively,which are calculated from the confusion matrix.Moreover,this model is further employed to predict the slope risk level of an abandoned quarry.The proposed approach using SAEs,or deep learning in general,is more objective and more accurate and requires less human inter-vention.The findings presented here shall shed light for engineers/researchers interested in analyzing rock mass classification criteria or performing field investigation.

Rectified transport of a single vibration-driven vehicle in the asymmetric channel

The rectification transport of a single vibration-driven self-propelled vehicle in a two-dimensional left–right asymmetric channel was experimentally investigated. The rectification efficiency of the vehicle moving from the center to the exit was statistically obtained for the range of channel widths, inter-channel asymmetry degrees, and platform tilt angles.The trajectory of its movement was also analyzed. It was found that the structure of the channel provides the main influence. Different channel shapes lead to different ranges of unfavorable widths, and transport efficiency decreases when the asymmetry diminishes—the two channels converge. The addition of external gravity does not counteract the structural limitations, but only affects the probability of departure.

吲哚菁绿荧光成像在全腹腔镜远端胃癌根治术中的应用

目的:探讨吲哚菁绿(indocyanine green,ICG)荧光成像技术在全腹腔镜远端胃癌根治术中肿瘤定位及淋巴结清扫方面的应用价值。方法:回顾性收集2017年8月至2019年8月北京大学肿瘤医院收治的经胃镜及病理确诊的126例远端胃癌患者临床病理资料。其中62例患者在ICG标记近红外荧光腹腔镜下完成手术(观察组),64例行常规腹腔镜手术(对照组)。评估对比术前ICG标记与术中内镜定位的效果;对比两组淋巴结清扫与检获情况。结果:T1~2期观察组患者术中标本测量近端切缘距离(4.92±1.65)cm与对照组(4.76±1.66)cm相比差异无统计学意义(P=0.671)。T3~4期观察组患者第二站淋巴结清扫数目为(11.09±6.19)枚,高于对照组(8.89±4.35)枚(P=0.049);观察组破损淋巴结检出数量(0.74±0.46)枚少于对照组(1.27±1.22)枚(P=0.009)。结论:T1~2期胃癌患者行术前ICG标记可精准判断肿瘤边界,其肿瘤定位效果与术中胃镜相当,全腹腔镜手术时可指导选择合适的切除线。ICG在T3~4期胃癌的淋巴导航作用可指导术中更精细、完整、彻底地清扫淋巴结,增加淋巴结清扫数量,减少术中淋巴结的破损。

拜耳法Na-S-Fe-H_(2)O系热力学分析

构建Na−S−Fe−H_(2)O系热力学图,分析拜耳法生产过程中硫和铁的行为。溶出后,铁最可能以Fe_(3)O_(4)和Fe_(2)O_(3)的形式进入赤泥,部分铁以Fe(OH)_(3)^(−)、HFeO_(2)^(−)、Fe(OH)_(4)^(−)和Fe(OH)_(4)^(2−)的形式转入液相。硫的优势物种是S^(2−),其次是SO_(4)^(2−),然后是SO_(3)^(2−)和S_(2)O_(3)^(2−)。热力学分析结果与实验测得的溶液中铁和硫的形态分布一致。当温度降低时,硫和铁会结合析出。控制低电位和降低温度均有利于将硫和铁从溶液中脱除。XRD谱表明,NaFeS_(2)·2H_(2)O、FeS和FeS_(2)广泛存在于赤泥以及黄铁矿和高硫铝土矿溶出液的析出物中。热力学分析可用于指导拜耳法同步除硫和铁。

CTHRC1增强结直肠癌细胞侵袭能力促进结直肠癌转移的机制研究

目的:探讨胶原三股螺旋重叠蛋白1(collagen triple helix repeat containing 1,CTHRC1)对结直肠癌细胞生物学特性的影响及可能的调控机制。方法:采用实时定量PCR技术检测上调或抑制miR-520d-5P的表达,探讨其对基因CTHRC1的调控作用,双荧光素酶实验验证miR-520d-5P与基因CTHRC1的3'UTR区之间是否相互结合。采用Western blot法检测6株不同结直肠癌细胞系及临床结直肠癌配对标本中基因CTHRC1的蛋白表达水平。构建稳定转染基因CTHRC1的结直肠癌细胞系;CCK-8、Transwell等方法检测稳定转染目的基因后结直肠癌细胞的增殖、侵袭能力的变化。结果:在配对结直肠癌患者组织中发现,正常组织中miR-520d-5P的表达高于癌组织(P<0.001),基因CTHRC1的表达趋势相反(P<0.001),且两者的表达呈负相关。通过miR-520d-5P模拟类似物mimics及抑制物inhibitor的瞬时转染实验发现其对基因CTHRC1的蛋白表达有负向调节作用。双荧光素酶实验验证miR-520d-5P与CTHRC1的3'UTR之间存在相互结合。稳定转染基因CTHRC1后,细胞的增殖能力下降,但侵袭能力提高,差异具有统计学意义(P<0.05)。在配对结直肠癌标本中,原发癌组织中基因CTHRC1的蛋白表达水平高于正常组织(P=0.003)。结论:miR-520d-5P对基因CTHRC1蛋白表达具有负调控作用。基因CTHRC1可以增强结直肠癌细胞的侵袭能力,抑制结直肠癌细胞的增殖能力,且与miR-520d-5P具有临床相关性。

Comparison of microendoscopic discectomy and open discectomy for single-segment lumbar disc herniation

BACKGROUND Lumbar disc herniation is a common disease.Endoscopic treatment may have more advantages than traditional surgery.AIM To compare the clinical efficacy and safety of microendoscopic discectomy(MED)and open discectomy with lamina nucleus enucleation in the treatment of singlesegment lumbar intervertebral disc herniation.METHODS Ninety-six patients who were operated at our hospital were selected for this study.Patients with single-segment lumbar disc herniation were admitted to the hospital from March 2018 to March 2019 and were randomly divided into the observation group and the control group with 48 cases in each group.The former group underwent lumbar discectomy and the latter underwent laparotomy and nucleus pulpectomy.Surgical effects were compared between the two groups.RESULTS In terms of surgical indicators,the observation group had a longer operation time,shorter postoperative bedtime and hospital stay,less intraoperative blood loss,and smaller incision length than the control group(P<0.05).The excellent recovery rate did not differ significantly between the observation group(93.75%)and the control group(91.67%).Visual analogue scale pain scores were significantly lower in the observation group than in the control group at 1 d,3 d,1 mo,and 6 mo after surgery(P<0.05).The incidence of complications was significantly lower in the observation group than in the control group(6.25%vs 22.92%,P<0.05).CONCLUSION Both MED and open discectomy can effectively improve single-segment lumbar disc herniation,but MED is associated with less trauma,less bleeding,and a lower incidence of complications.

3-D Tunnel Seismic Advance Prediction Method with Wide Illumination and High-Precision

Tunnel seismic advance prediction can effectively reduce the construction risk during tunnel excavation.Compared with the 2-D method,the 3-D method is more conducive to describing the spatial characteristics of the geological body by adding the seismic data in the vertical direction.However,some drawbacks still need improvement in the current 3-D tunnel seismic prediction method.(1)The geometry is complex,which is destructiveness,high cost,and time-consuming,and will delay the tunnel construction schedule.(2)Illumination of the anomalous body is insufficient,and the precision of migration imaging is low.(3)Shot points are far away from the tunnel face,the energy loss at the shot points is more serious.(4)The received signals at the tunnel wall have the surface wave with strong energy when the shot points are placed on the tunnel wall.(5)The geometry is not linear,so the directional filtering method cannot be used to extract the reflection wave.To overcome the drawbacks of the current prediction method,a new 3-D symmetrical tunnel seismic prediction method is proposed.Six geophones are installed on the tunnel wall,two on the left side,two on the right side,and two on the top side.Twenty-four shot points are placed on the tunnel face and near both sides of the tunnel wall,twelve shot points on the left side and twelve shot points on the right side.The shot points will move along with the forward excavation of the tunnel.The wavefield analysis,illumination statistics,and 3-D reverse time migration imaging are used to evaluate the proposed method.The result of modeled data indicates that the proposed 3-D geometry has some advantages:(1)the geometry is simple and the geophone installation time is short;(2)it has high illumination energy,wide illumination range,and can improve the prediction distance and imaging accuracy;(3)the proposed 3-D method can better estimate the velocity of surrounding rock and is more conducive to extracting the reflection wave with high resolution.

Clinical applications of stem cell-derived exosomes

Although stem cell-based therapy has demonstrated considerable potential to manage certain diseases more successfully than conventional surgery,it nevertheless comes with inescapable drawbacks that might limit its clinical translation.Compared to stem cells,stem cell-derived exosomes possess numerous advantages,such as non-immunogenicity,non-infusion toxicity,easy access,effortless preservation,and freedom from tumorigenic potential and ethical issues.Exosomes can inherit similar therapeutic effects from their parental cells such as embryonic stem cells and adult stem cells through vertical delivery of their pluripotency or multipotency.After a thorough search and meticulous dissection of relevant literature from the last five years,we present this comprehensive,up-to-date,specialty-specific and disease-oriented review to highlight the surgical application and potential of stem cell-derived exosomes.Exosomes derived from stem cells(e.g.,embryonic,induced pluripotent,hematopoietic,mesenchymal,neural,and endothelial stem cells)are capable of treating numerous diseases encountered in orthopedic surgery,neurosurgery,plastic surgery,general surgery,cardiothoracic surgery,urology,head and neck surgery,ophthalmology,and obstetrics and gynecology.The diverse therapeutic effects of stem cells-derived exosomes are a hierarchical translation through tissue-specific responses,and cell-specific molecular signaling pathways.In this review,we highlight stem cell-derived exosomes as a viable and potent alternative to stem cell-based therapy in managing various surgical conditions.We recommend that future research combines wisdoms from surgeons,nanomedicine practitioners,and stem cell researchers in this relevant and intriguing research area.

Genetic Mechanism of Water-Rich Landslide Considering Antecedent Rainfalls:A Case Study of Pingyikou Landslide in Three Gorges Reservoir Area

Water-rich slope,which could easily fail after prolonged or heavy rain,is very sensitive to rainfall.Pingyikou Landslide is a typical water-rich slope located in the Three Gorges Reservoir area of China.It was unstable because of the continuous rainfall that occurred from September to October 2017.To understand the deformation process and genetic mechanism of the landslide,the geomorphological features,geological characteristics,hydrological conditions,and rainfall characteristics were systematically studied by a detailed field investigation of the slope and monitoring of rainfall,water level,and displacement.In addition,the influence of different initial conditions on the stability of the slope was also studied through numerical simulation using measured rainfall data on the basis of which,the effect of antecedent rainfall on slope stability was studied by unsaturated seepage analysis method.The results show that the deformation of slope is strongly correlated with the rainfall and groundwater level,and this landslide is a typical rainfall-induced landslide.In the analysis of genetic mechanism of the same type of landslide,a maximum initial pore water pressure of -25 kPa as the initial condition is reasonable.And the antecedent rainfall has a greater effect on the stability of the slope,more than 10 days of antecedent rainfall should be considered when designing and controling the slope.

Extralevator abdominoperineal excision versus abdominoperineal excision for low rectal cancer: a meta-analysis

Background:Extralevator abdominoperineal excision (ELAPE) has become a popular procedure for low rectal cancer as compared with abdominoperineal excision (APE). No definitive answer has been achieved whether one is superior to the other. This study aimed to evaluate the safety and efficacy of ELAPE for low rectal cancer with meta-analysis.Methods:The Web of Science, Cochrane Library, Embase, and PubMed databases before September 2019 were comprehensively searched to retrieve comparative trials of ELAPE and APE for low rectal cancer. Pooled analyses of the perioperative variables, surgical complications, and oncological variables were performed. Odds ratio (OR) and mean differences (MD) from each trial were pooled using random or fixed effects model depending on the heterogeneity of the included studies. A subgroup analysis or a sensitivity analysis was conducted to explore the potential source of heterogeneity when necessary.Results:This meta-analysis included 17 studies with 4049 patients, of whom 2248 (55.5%) underwent ELAPE and 1801 (44.5%) underwent APE. There were no statistical differences regarding the circumferential resection margin positivity (13.0% vs. 16.2%, OR = 0.69, 95% CI = 0.42-1.14, P = 0.15) and post-operative perineal wound complication rate (28.9% vs. 24.1%, OR = 1.21, 95% CI = 0.75-1.94, P= 0.43). The ELAPE was associated with lower rate of intraoperative perforation (6.6% vs. 11.3%, OR = 0.50, 95% CI = 0.39-0.64, P < 0.001) and local recurrence (8.8% vs. 20.5%, OR = 0.29, 95% CI = 0.21-0.41, P < 0.001) when compared with APE.Conclusions:The ELAPE was associated with a reduction in the rate of intra-operative perforation and local recurrence, without any increase in the circumferential resection margin positivity and post-operative perineal wound complication rate when compared with APE in the surgical treatment of low rectal cancer.

A grid-based clustering algorithm for wild bird distribution

Advanced satellite tracking technologies provide biologists with long-term location sequence data to understand movement of wild birds then to find explicit correlation between dynamics of migratory birds and the spread of avian influenza. In this paper, we propose a hierarchical clustering algorithm based on a recursive grid partition and kernel density estimation （KDE） to hierarchically identify wild bird habitats with different densities. We hierarchically cluster the GPS data by taking into account the following observations： 1） the habitat variation on a variety of geospatial scales; 2） the spatial variation of the activity patterns of birds in different stages of the migration cycle. In addition, we measure the site fidelity of wild birds based on clustering. To assess effectiveness, we have evaluated our system using a large-scale GPS dataset collected from 59 birds over three years. As a result, our approach can identify the hierarchical habitats and distribution of wild birds more efficiently than several commonly used algorithms such as DBSCAN and DENCLUE.

A networked swellable dextrin nanogels loading Bcl2 siRNA for melanoma tumor therapy

In this study, a networked swellable dextrin nanogel （DNG） was developed to achieve stimulated responsive small interfering RNA （siRNA） release for melanoma tumor therapy, siRNA was loaded into multidimensional dextrin nanogels by charge condensation with positive arginine residues modified in the dextrin backbone. Moreover, the networked nanogel was destroyed and loosened based on its bioreducible responsive property to control accelerated siRNA release in a bioreducible intracellular environment, while it remained stable under normal physiological conditions. We demonstrated that DNGs had swellable and disassembly properties under reduced buffer condition by transmission electron microscopy evaluation. The DNGs achieved an endosomal escape followed by selective release of the cargo into the cytosol by glutathione- triggered disassembly according to confocal microscopy observation. Thus, this smart nanogel achieved outstanding luciferase gene silencing efficiency and decreased Bcl2 protein expression in vitro and in vivo based on western blot analysis. Moreover, this nanogel exhibited superior anti-tumor activity for B16F10 xenograft tumors in C57BL/6 mice. These results demonstrate that the networked DNGs are effective for gene condensation and controlled intracellular release for tumor therapy. Overall, these findings suggest that this multidimensional swellable stimuli-responsive dextrin nanogel is an innovative strategy with great promise for gene and drug delivery.

Single-cell transcriptomic analysis reveals dynamic alternative splicing and gene regulatory networks among pancreatic islets

Dear Editor,An increasing number of single-cell RNA-seq(scRNA-seq)studies gained deep insights into the gene expression heterogeneity among individual cells by cell type/state identification(Chen et al.,2019).Alternative splicing(AS)enables genes to generate multiple isoforms through the combination of disparate exons to increase the diversity of transcriptome(Lee and Rio,2015).