Search

AbstractThe excavation of tunnels in karstic rocks inevitably intersects with karst caves even with reasonable geological survey and alignment design. The filler in karst caves directly affect the harmfulness of mud inrush geohazards to tunnels. Therefore, it is essential to understand the properties and failure characteristics of the filler in karst caves before treating karst caves. Based on a tunnel mud inrush case in Guangxi Province, China, failure characteristics and mechanism of clay filler in karst cave were analyzed. Besides, geological survey and geological prospecting indicate that the clay filler was formed by the deposition of surface clay entering the karst cave from the cracks of rock mass. The failure evolution process of clay filler was demonstrated based on discrete element method. The numerical simulation results show that excavation induced sliding force and insufficient shearing strength of clay were the mainly triggering of instability of clay filler in the karst cave. Advanced grouting, construction method improving were used to prevent mud inrush from bursting again and achieved satisfactory reinforcement effect. The lessons and analysis results in this case has reference value for the prevention of tunnel mud inrush in karst area.

The mechanism underlying neurogenesis during embryonic spinal cord development involves a specific ligand/receptor interaction, which may be help guide neuroengineering to boost stem cell-based neural regeneration for the structural and functional repair of spinal cord injury. Herein, we hypothesized that supplying spinal cord defects with an exogenous neural network in the NT-3/fibroin-coated gelatin sponge (NF-GS) scaffold might improve tissue repair efficacy. To test this, we engineered tropomyosin receptor kinase C (TrkC)-modified neural stem cell (NSC)-derived neural network tissue with robust viability within an NF-GS scaffold. When NSCs were genetically modified to overexpress TrkC, the NT-3 receptor, a functional neuronal population dominated the neural network tissue. The pro-regenerative niche allowed the long-term survival and phenotypic maintenance of the donor neural network tissue for up to 8 weeks in the injured spinal cord. Additionally, host nerve fibers regenerated into the graft, making synaptic connections with the donor neurons. Accordingly, motor function recovery was significantly improved in rats with spinal cord injury (SCI) that received TrkC-modified NSC-derived neural network tissue transplantation. Together, the results suggested that transplantation of the neural network tissue formed in the 3D bioactive scaffold may represent a valuable approach to study and develop therapies for SCI.

In tunnel construction, the difficulty of ventilation gradually increases with the increase of ventilation distance, which endangers construction safety and delays construction progress. This paper presents an air cabin ventilation system of the tunnel during construction. Theoretical calculations show that the energy consumption of this ventilation system is reduced by 20.7% compared with blowing ventilation, especially since the resistance loss along the air duct is reduced by 47.04%. A 3D numerical model validated with field test data was employed to discuss the air cabin structural parameters on the ventilation efficiency of the axial fan. The results show that the relative pressure on the fan’s end face increases when the air cabin’s length–width ratio is R = 1:2. The fan spacing S = 2–4 m can ensure the larger relative pressure of multiple fans. The significant difference in air demand between the left and right sides causes the disordered airflow. Set a middle diaphragm length of 1.5 D in the air cabin, which can effectively reduce the phenomenon. The middle diaphragm with a radian of 30°effectively reduced the local loss by 59.40%. The proposed ventilation system shortens the ventilation distance and has the advantages of low energy consumption and resistance loss. It improves the construction environment and is a valuable means of ventilation design for tunnel construction.

Background Trimethylamine-N-Oxide (TMAO) is a proatherogenic and prothrombotic metabolite. Our study examined the association of plasma TMAO level with cardiovascular and all-cause mortality in hemodialysis (HD) patients. Methods Patients who were at least 18 years-old and received HD for at least 6 months were enrolled within 6 months. Patients with coronary heart disease, congestive heart failure, arrhythmia, or stroke within 3 months before study onset were excluded. The primary endpoints were cardiovascular and all-cause death, and the secondary endpoint was cerebrovascular death. Results We recruited 252 patients and divided them into a high-TMAO group (>4.73 μg/mL) and a low-TMAO group (≤4.73 μg/mL). The median follow-up time was 73.4 months (interquartile range: 42.9, 108). A total of 123 patients died, 39 from cardiovascular disease, 19 from cerebrovascular disease, and 65 from other causes. Kaplan-Meier analysis indicated that the high-TMAO group had a greater incidence of cardiovascular death (Log-Rank: p = 0.006) and all-cause death (Log-Rank: p

Numerous mountain highway tunnels in China do not satisfy the current traffic design standards and therefore need to be rebuilt or expanded. The drilling-blasting method is the primary method employed in China for expanding mountain highway tunnels, and it is crucial to monitor the vibrations caused by blasting. This study conducted a field investigation of the vibrations caused by blasting during the expansion of Yujiaya tunnel, which was built in 1999. The blasting-induced vibrations in the new and old concrete linings were monitored and analyzed during the expansion. The measured values of the peak particle velocity (PPV) varied within the range of 0.097–8.246 cm/s. The attenuation law of the PPV was determined via a regression analysis using Sadovsky’s empirical formula. The relationship between the main vibration frequency and the distance from the blasting source was expressed as a power function. Finally, the safety distances of the concrete linings subject to blasting vibrations were analyzed and discussed.

A multilevel secure access control strategy for distributed system was proposed,which could guarantee the data confidentiality and security,through adding platform and middleware modules.The security policy was described in the XACML language,and the security and flexibility of the policy were analyzed.

During the jet grouting process, large volumes of high pressurized fluids injected into the soils will cause significant ground displacements, which may bring harmful impacts on surrounding environment. Therefore, it is essential to provide an accurate estimation of the ground displacement in the design stage. Based on multiple nonlinear regression (MNLR) and support vector regression (SVR), the prediction approaches are established, respectively. The column radius (Rc), Young’s modulus (E), and distance from column center to target point (LOA) are selected as the input parameters, while the displacement of target point A at the radial direction (δA) is taken as the output parameter. Comparisons results on the prediction performance of ground displacements indicate that the MNLR-based approach has a better prediction effect. The design charts of the MNLR-based approach for predicting the ground displacement are created, which will be helpful for the practicing engineers to get a quick estimation.

The core content of the convergence constraint method is to determine the reasonable support time and support stiffness. The stiffness of shotcrete in supporting structure is dynamic. The support stiffness of shotcrete is roughly calculated in engineering, which results in a waste of materials and increases the risk of construction. Therefore, in this study, considering the time-varying characteristics of shotcrete, combined with the elastic-plastic theory and the space effect of excavation surface, the calculation equation describing the support reaction curve is given. An example is given to show that the stiffness of shotcrete considering time-varying effect is lower than that of shotcrete without time-varying effect, and the difference is the most obvious in the age of 0–3 days. However, in the later stage, the stiffness growth rate of shotcrete considering time-varying effect is higher than that of shotcrete without time-varying effect. This study can predict the whole process of the support reaction curve, which can make the application of the convergence constraint method in tunnel support design more accurate, and provide a theoretical basis for the design of supporting structure in the process of tunnel construction.

In order to study the deformation stability of rock slope during the excavation of cutting slope and ensure the safety of rock slope during construction and operation period, this article analyzed the deformation law of a typical slope excavation by monitoring the surface deformation and the internal displacement of the rock mass. The surface deformation of the slope is monitored by setting monitoring points, and the internal deformation of the slope is monitored by installing multipoint displacement meters and inclinometers. Therefore, the relationship between slope excavation and deformation is obtained. The analysis of monitoring results shows that the slope is stable before excavation, and the displacement of the slope is gradually increased with the slope excavation. After the excavation, the displacement of each slope tends to converge. The maximum displacement in surface monitoring points is 12.30 mm, and the displacement parallels to the direction of the expressway. The maximum vertical displacement in surface monitoring points is 10.60 mm which occurred in the third step; the maximum internal displacement is 11.02 mm which mainly occurs in the weak structural plane of the rock boundary. During the excavation of the weak rock slope, the slope rock mass is prone to large displacement deformation. After the excavation, the slope surface displacement and internal displacement tend to converge in a short time.

Abstract Tissue engineering produces constructs with defined functions for the targeted treatment of damaged tissue. A complete spinal cord injury (SCI) model is generated in canines to test whether in vitro constructed neural network (NN) tissues can relay the excitatory signal across the lesion gap to the caudal spinal cord. Established protocols are used to construct neural stem cell (NSC)‐derived NN tissue characterized by a predominantly neuronal population with robust trans‐synaptic activities and myelination. The NN tissue is implanted into the gap immediately following complete transection SCI of canines at the T10 spinal cord segment. The data show significant motor recovery of paralyzed pelvic limbs, as evaluated by Olby scoring and cortical motor evoked potential (CMEP) detection. The NN tissue survives in the lesion area with neuronal phenotype maintenance, improves descending and ascending nerve fiber regeneration, and synaptic integration with host neural circuits that allow it to serve as a neuronal relay to transmit excitatory electrical signal across the injured area to the caudal spinal cord. These results suggest that tissue‐engineered NN grafts can relay the excitatory signal in the completely transected canine spinal cord, providing a promising strategy for SCI treatment in large animals, including humans.

Landslide of loose rock mass at mountain tunnel exit occurs easily, and prediction of landslide position is one of the engineering problems to be solved urgently. Currently, existing and used prediction methods, such as field monitoring measurement, numerical analysis, nonlinear theories, and the geometric method, play a very important role and have their limitations. For example, there is a bigger difference between calculation mode by Wang et al.’s method and actual engineering situation; besides, there exists a relatively big discrepancy between the predicted and true position. Aiming to solve this problem, this article combined theoretical analysis and actual engineering situation to establish an optimal calculation mode. At the same time, this article re-deduced instability criteria based on the stress-transferring theory and examined the factors that influence solutions. The improved method can predict landslide position more accurately because the parameters (β, s, H, α, γ, c, φ, and T) related to the occurrence of landslide are taken into consideration. It is pointed out that landslide possibly occurs in the case of Δ ≥ 0 and Y ≤ 0. In addition, the equations s1

Grouting has been deemed as one of the most effective measures for mitigation of ground movements during tunnel construction in soft soil. Notwithstanding that, a reliable measure to quantitatively evaluate the grouting-induced ground movements during shield tunnelling in soft soil has not yet been developed. This paper presents a simple method capable of quantitatively estimating the ground movements associated with grouting for tunnel-boring operations where the grouting parameters and soil properties are taken into consideration. The grouting process is simplified as the expansion of a cylindrical cavity with a uniform radial stress applied at soil-grout interface in a half plane, and the analytical solution proposed by Verruijt is introduced for determining the ground movements by the expansion of the cylindrical cavity. The proposed method is verified with a case history undertaken in London Clay. The results obtained suggest that this procedure would be helpful in managing the grouting parameters adopted in upcoming soft ground tunnelling project and mitigating the environmental impacts on nearby properties.

The expansion of urban underpass has become the mainstream of development to cope with urban congestion, and the effect on adjacent existing structures during enlarging construction is also an important issue in the construction process. In order to better understand the influence of tunneling on adjacent structures, the pedestrian underpass expanding project above-crossing Xi’an Metro Line 1 was investigated. The aim was to analyze the deformation curves characteristics of adjacent structures by field observation of ground settlement, heave of existing tunnels, and settlement of piles. The results show that the ground settlement curve in the vertical direction of the underpass is similar to the shape of V, and the maximum settlement appearing in the center line of underpass is 18.7 mm. Due to the effect of existing tunnels on the ground deformation, the settlement curve in the parallel direction of the underpass is similar to the shape of M. Above-crossing tunneling would cause the existing tunnels to heave, and the heave mainly occurs in the range of −6 m to 12 m between the pedestrian tunnel face and the center line of each tunnel. The heave curve is similar to the shape of inverted U. The settlement of piles is linear with its axial stress and significantly affected by its location. The settlement curve of piles is similar to the shape of S in two dimensions. On the basis of deformation curves, this paper presents some equations to describe the shape of V, M, inverted U, and S, respectively, by the inverted Gaussian distribution curve, superimposed Gaussian distribution curve, Gaussian distribution curve, and arctangent function.

The interfacial compatibility between compact TiO2 and perovskite layers is critical for the performance of planar heterojunction perovskite solar cells (PSCs). A compact TiO2 film employed as an electron-transport layer (ETL) was modified using 3-aminopropyl trimethoxy silane (APMS) hydrolysate. The power conversion efficiency (PCE) of PSCs composed of an APMS-hydrolysate-modified TiO2 layer increased from 13.45 to 15.79%, which was associated with a significant enhancement in the fill factor (FF) from 62.23 to 68.04%. The results indicate that APMS hydrolysate can enhance the wettability of γ-butyrolactone (GBL) on the TiO2 surface, form a perfect CH3NH3PbI3 film, and increase the recombination resistance at the interface. This work demonstrates a simple but efficient method to improve the TiO2/perovskite interface that can be greatly beneficial for developing high-performance PSCs.

The title compound, [Zn(C7H4NO4)2(C12H8N2)(H2O)], has been synthesized. X-Ray analysis reveals that it is a neutral zinc(II) mononuclear carboxylate complex based on mixed N- and O-donor ligands. The Zn atom is five-coordinate in a distorted trigonal-bipyramidal coordination environment involving two O atoms of two monodentate 2-nitrobenzoate molecules, two N atoms of a 1,10-phenanthroline molecule and one O atom of a water molecule. The axial positions are occupied by a carboxylate O atom from the 2-nitrobenzoate ligand and an N atom from the 1,10-phenanthroline ligand [N—Zn—O = 167.66 (9)°]. [ABSTRACT FROM AUTHOR]

The solubility of -sitosteryl maleate and stigmasteryl maleate in acetone and ethyl acetate was determined by a dynamic method. The results show that the solubility of -sitosteryl maleate or stigmasteryl maleate in ethyl acetate or acetone increases when temperatures increase, and the solubility of -sitosteryl maleate is higher than that of stigmasteryl maleate in two solvents in the range of experimental temperatures. The relation between the experimental solubility as mole fractions and temperatures could be correlated by means of expressions of the form log(1/x) A/TBfor the researched systems. [ABSTRACT FROM AUTHOR]

Abstract Background To date, it has repeatedly been demonstrated that infusing bone marrow-derived stem cells (BMSCs) into acellular nerve scaffolds can promote and support axon regeneration through a peripheral nerve defect. However, harvesting BMSCs is an invasive and painful process fraught with a low cellular yield. Methods In pursuit of alternative stem cell sources, we isolated stem cells from the inguinal subcutaneous adipose tissue of adult Sprague–Dawley rats (adipose-derived stem cells, ADSCs). We used a co-culture system that allows isolated adult mesenchymal stem cells (MSCs) and Schwann cells (SCs) to grow in the same culture medium but without direct cellular contact. We verified SC phenotype in vitro by cell marker analysis and used red fluorescent protein-tagged ADSCs to detect their fate after being injected into a chemically extracted acellular nerve allograft (CEANA). To compare the regenerative effects of CEANA containing either BMSCs or ADSCs with an autograft and CEANA only on the sciatic nerve defect in vivo, we performed histological and functional assessments up to 16 weeks after grafting. Results In vitro, we observed reciprocal beneficial effects of ADSCs and SCs in the ADSC–SC co-culture system. Moreover, ADSCs were able to survive in CEANA for 5 days after in vitro implantation. Sixteen weeks after grafting, all results consistently showed that CEANA infused with BMSCs or ADSCs enhanced injured sciatic nerve repair compared to the acellular CEANA-only treatment. Furthermore, their beneficial effects on sciatic injury regeneration were comparable as histological and functional parameters evaluated showed no statistically significant differences. However, the autograft group was roundly superior to both the BMSC- or ADSC-loaded CEANA groups. Conclusion The results of the present study show that ADSCs are a viable alternative stem cell source for treating sciatic nerve injury in lieu of BMSCs.