Restoration of NAD + homeostasis protects C2C12 myoblasts and mouse levator ani muscle from mechanical stress-induced damage

Guotao Huang,Yong He,Li Hong,Min Zhou,Xiaohu Zuo,Zhihan Zhao 한국통합생물학회 2022 Animal cells and systems Vol.26 No.4

Excessive mechanical traction damages the levator ani muscle (LAM), increasing the incidence of pelvic floor dysfunction (PFD). In this study, we explored the effects of oxidized nicotinamide adenine dinucleotide (NAD+) on the damage to both muscle cells and LAM tissue induced by mechanical stress (MS) at the cellular and animal levels. The cell damage model was established using a four-point bending system. The LAM damage model was established using vaginal distention and traction. Exogenous addition of PJ34, an inhibitor of poly (ADP-ribose) polymerase-1 (PARP-1), and the nicotinamide mononucleotide (NMN) precursor of NAD+ increased NAD+ levels. ATP content and mitochondrial membrane potential were measured to assess mitochondrial function. NAD+ levels, cell viability, and PARP-1 activity were detected using commercial kits. DNA damage in cells was detected with immunofluorescence staining, and LAM damage was detected with tissue TUNEL staining. PARP-1 activity and DNA damage of LAM were detected by immunohistochemistry. A small amount of DNA damage and PARP-1 activation did not affect NAD+ levels, while excessive DNA damage and PARP-1 activation led to an imbalance of NAD+ homeostasis. Furthermore, increasing NAD+ levels in vivo and in vitro could rescue mitochondrial dysfunction and damage to both muscle cells and LAM tissue induced by MS. In conclusion, MS can induce damage to both C2C12 cells and LAM tissue. Restoring NAD+ homeostasis can rescue this damage by improving mitochondrial function.

Elastic stiffness of perfobond connections in composite structures

Xi Qin,Guotao Yang 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.2

Perfobond rib connectors are widely used in composite structures to achieve the composite action between the steel and the concrete, and empirical expressions for their strength and secant stiffness have been obtained by numerical simulations or push-out tests. Since perfobond connections are generally in an elastic state in the service process and the structural analysis are always based on the elastic properties of the members, the secant stiffness is not applicable for the normal structural analysis. However, the tangent stiffness of perfobond connections has not been introduced in previous studies. Moreover, the perfobond connections are bearing tension and shear force simultaneously when the composite beams subjected to torque or local loads, but the current studies fail to arrive at the elastic stiffness considering the combined effects. To resolve these discrepancies, this paper investigates the initial elastic stiffness of perfobond connections under combined forces. The calculation method for the elastic stiffness of perfobond connections is analyzed, and the contributions of the perfobond rib, the perforating rebar and the concrete dowel are investigated. A finite element method was verified with a high value of correlation for the test results. Afterwards, parametric studies are carried out using the reliable finite element analysis to explore the trends of several factors. Empirical equations for predicting the initial elastic stiffness of perfobond connections are proposed by the numerical regression of the data extracted by parametric studies. The equations agree well with finite element analysis and test results, which indicates that the proposed empirical equations reflect a high accuracy for predicting the initial elastic stiffness of perfobond connections.

Mixed boundary value problems for second order differential equations with different deviated arguments

Lihong Zhang,Guotao Wang,Guangxing Song 한국전산응용수학회 2011 Journal of applied mathematics & informatics Vol.29 No.1

This paper deals with second order differential equations with different deviated arguments α(t) and β(t, μ(t)). We investigate the existence of solutions of such problems with nonlinear mixed boundary conditions. To obtain corresponding results we apply the monotone iterative technique and the lower-upper solutions method. Two examples demonstrate the application of our results.

Load-slip curves of shear connection in composite structures: prediction based on ANNs

Kai Guo,Guotao Yang 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.5

The load-slip relationship of the shear connection is an important parameter in design and analysis of composite structures. In this paper, a load-slip curve prediction method of the shear connection based on the artificial neural networks (ANNs) is proposed. The factors which are significantly related to the structural and deformation performance of the connection are selected, and the shear stiffness of shear connections and the transverse coordinate slip value of the load-slip curve are taken as the input parameters of the network. Load values corresponding to the slip values are used as the output parameter. A two-layer hidden layer network with 15 nodes and 10 nodes is designed. The test data of two different forms of shear connections, the stud shear connection and the perforated shear connection with flange heads, are collected from the previous literatures, and the data of six specimens are selected as the two prediction data sets, while the data of other specimens are used to train the neural networks. Two trained networks are used to predict the load-slip curves of their corresponding prediction data sets, and the ratio method is used to study the proximity between the prediction loads and the test loads. Results show that the load-slip curves predicted by the networks agree well with the test curves.

Enhanced photoelectric properties of n-ZnO NWs/p-Si heterojunction LEDs by inserting an insulating MgO layer using sol-gel method

Juan Yao,Guotao Lin,Zhenxi Du,Jun Liang,Huan He,Xiaoming Shen,Yuechun Fu 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.4

ZnO nanowires (ZnO NWs) were synthesized by hydrothermal method on Si (100) substrates, in which an insulating MgOlayer deposited using sol–gel method was inserted between the seed layer and Si substrate. The eff ects of MgO layer on themicrostructure, luminescence and electrical properties of ZnO NWs as well as n-ZnO NWs/p-Si heterojunction LEDs wereinvestigated. With the insertion of MgO layer, well-aligned ZnO NWs with good crystalline quality are obtained, which canbe attributed to the smooth seed layer with homogeneous globular particles. The electroluminescence spectra of n-ZnO NWs/MgO/p-Si heterojunction LEDs exhibit a broad emission band from near ultraviolet to yellow-green region. n-ZnO NWs/MgO/p-Si heterojunction also shows an enhanced ultraviolet photoluminescence effi ciency, and its defect-related visibleemission is greatly suppressed compared with that of n-ZnO NWs/p-Si heterojunction. The current–voltage curves of bothheterojunction LEDs present a typical rectifying behavior, but the rectifi cation ratio increases almost 5 times by insertingMgO layer, which is ascribed to a reduction in the leakage current under reverse bias voltage.

Elastic stiffness of stud connection in composite structures

Xi Qin,Guotao Yang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.4

In composite structures, shear connectors are crucial components to resist the relative slip between the steel and concrete, and thereby to achieve the composite actions. In the service stage, composite structures are usually in elastic state, so the elastic stiffness of the shear connection is a quite important parameter in the structural analysis of composite structures. Nevertheless, the existing studies mainly focus on the load-slip relationship rather than the tangent stiffness at the initial elastic stage. Furthermore, when composite beams subjected to torque or local load, shear connections are affected by both tensile force and shear force. However, the stiffness of shear connections under combined effects appears not to have been discussed hitherto. This paper investigates the initial elastic stiffness of stud connections under combined effects of biaxial forces. The initial expression and the relevant parameters are obtained by establishing a simplified analytical model of the stud connection. Afterwards, parametric finite element analysis is performed to investigate the effects of the relevant factors, including the stud length, stud diameter, elastic modulus of concrete, elastic modulus of steel and volume ratio of reinforcement. The feasibility of the proposed modelling has been proved by comparing with sufficient experimental tests. Based on the analytical analysis and the extensive numerical simulations, design equations for predicting the initial elastic stiffness of stud connections are proposed. The comparison between the equations and the data of finite element models demonstrates that the equations are accurate enough to serve for engineering communities.

Study on Formation of Microstructure in Rheo-Diecastings of Semi-Solid A380 Aluminum Alloy Slurry

Zhiyong Liu,Guotao Cui,Tan Wan,Weimin Mao 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

The formation of the microstructure in the rheo-diecastings were studied by the experiment of rheo-diecasting with semi-solidA380 Aluminum alloy slurry. The results show that the grain diameter and shape factor of primary α-Al grains decreased andincreased along the rheo-diecasting direction, respectively, making the primary α-Al grains gradually distributing uniformly. The combination of injection pressure and narrow gate of the runner and ingate was the main reason for the evolution of theprimary α-Al grains, moreover, the collision and friction among primary α-Al grains during the flling were helpful for therefnement and spheroidization of the primary α-Al grains. The residual liquid solidifed into the secondary solidifcationmicrostructure accompanied by the evolution of the primary α-Al grains. The accumulation of the fragments of the primaryα-Al grains, the secondary α2-Al nuclei or grains which formed in previous positions, the efective nucleation rate of theresidual liquid, and the collision and fraction among the secondary α2-Al grains and between the secondary α2-Al grainand the primary α-Al grains made the secondary solidifcation microstructure of the residual liquid present multiplex andcomplicate characteristics.

The interface and its role in carrier transfer/recombination dynamics for the planar perovskite solar cells prepared under fully open air conditions

Fei Wang,Yiqing Chen,Guotao Han,Qianlong Zhang,Qilin Ma 한국물리학회 2016 Current Applied Physics Vol.16 No.10

The planar heterojunction perovskite solar cells, where the perovskite film is deposited directly onto a flat hole blocking layer, have recently attracted a great deal of attention owing to their high performance and ease of processing. However, the interface and its underlying role in carrier transport/recombination kinetics for such perovskite devices prepared under ambient air is still obscure. Herein, we addressed this issue by a dynamic intensity modulated photovoltage spectroscopy (IMVS) model using a continuity equation. The interface and its role in charge-carrier transport/recombination kinetics have been explored and discussed as an approach to understand the origin of the photovoltaic properties for the devices prepared under ambient air. The experimental IMVS responses were measured and satisfactorily fitted to the analytical results. Compared to the typical IMVS model based on dye-sensitized solar cells (DSSCs), the better IMVS fitting results presented in this study indicated that there was a discrepancy between the planar perovskite devices and those of DSSCs in electron transport/recombination properties, because carrier transfer across the TiO2/liquid electrolyte interface in DSSCs has been modified. That is, the Schottky interface in DSSCs needs to be replaced by the semiconductor heterojunction interface in perovskite solar cells (PSCs). Besides, the interface exhibits a more significant role in determining the carrier transport/recombination process by influencing the boundary conditions in a continuity equation. Furthermore, the intensity modulated photocurrent/photovoltage spectroscopy responses demonstrated that the carrier recombination characteristic is ultimately related with the surface and defect density in the interface. Interfacial modification, such as air-annealing, resulting in crystallographic changes, oxygen passivation, and variation in grain domain size, could suppress carrier recombination and prolong charge lifetime, which can yield more photo-generated electrons to be collected by anode, subsequently resulting in strikingly improving photovoltaic performance of the devices. In short, the dynamic IMVS model would help in elucidating the role of interface and the importance of interfacial modification or even interface design in order to obtain a highly efficient solar cell. The study can not only pave the way to construct the currentvoltage curve using a continuity equation model, but also provide new insights into the performance-improving steps for the PSCs prepared under fully open air conditions, which is of great importance for their future commercialization.

Axially-loaded multiplanar tubular KTX-joints: numerical analysis

Chenhui Zhang,Bo Zou,Guotao Yang 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.2

With the development of spatial structures, the joints are becoming more and more complex to connect tubular members of spatial structures. In this study, an approach is proposed to establish high-efficiency finite element model of multiplanar KTX-joint with the weld geometries accurately simulated. Ultimate bearing capacity the KTX-joint is determined by the criterion of deformation limit and failure mechanism of chord wall buckling is studied. Size effect of fillet weld on the joint ultimate bearing capacity is preliminarily investigated. Based on the validated finite element model, a parametric study is performed to investigate the effects of geometric and loading parameters of KT-plane brace members on ultimate bearing capacity of the KTX-joint. The effect mechanism is revealed and several design suggestions are proposed. Several simple reinforcement methods are adopted to constrain the chord wall buckling. It is concluded that the finite element model established by proposed approach is capable of simulating static behaviors of multiplanar KTX-joint; chord wall buckling with large indentation is the typical failure mode of multiplanar KTX-joint, which also increases chord wall displacements in the axis directions of brace members in orthogonal plane; ultimate bearing capacity of the KTX-joint increases approximately linearly with the increase of fillet weld size within the allowed range; the effect mechanism of geometric and loading parameters are revealed by the assumption of restraint region and interaction between adjacent KT-plane brace members; relatively large diameter ratio, small overlapping ratio and small included angle are suggested for the KTX-joint to achieve larger ultimate bearing capacity; the adopted simple reinforcement methods can effectively constrain the chord wall buckling with the design of KTX-joint converted into design of uniplanar KT-joint.

Permeability Anisotropy of Columnar Jointed Rock Masses

Lifang Zou,Weiya Xu,Guotao Meng,Yu Ning,Huanling Wang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

This paper investigated the anisotropic permeability of columnar jointed rock masses at Baihetan hydropower station in Southwest China. Discrete element analysis is conducted to evaluate the hydraulic Representative Elemental Volume (REV) size of jointed rock masses. It is found to be 5m×5m and it is seven times of the column length. Research shows that permeability tensor of the jointed rocks exists. The maximum principle permeability is 3.47 × 10−14 m2 and the minimum principle permeability is 1.39 × 10−14 m2. The direction of maximum principle permeability is 72 degrees anticlockwise from the positive x- axis direction, which is along the same direction of the column length. A continuum hydro-mechanical coupling analysis is carried out on water infill of a tailrace tunnel in columnar basalt. An equivalent anisotropic mechanical model is applied in the numerical simulation. Anisotropic deformation and anisotropic permeability characteristics are investigated under the condition that the angle between maximum principle stress axis and maximum principle permeability axis is 72 degrees. Results show that anisotropic seepage field has an effort on anisotropic deformation field.