AbstractThis paper develops a new damage-plasticity model considering the compression-softening effect of RC. The model is based on the framework of a two-scalar damage-plasticity model, and adopts ...the elastoplastic damage energy release rates as the driven force of damage. To account for the compression-softening effect caused by transverse cracks of RC under shear, a softening coefficient is introduced in the model. With the modification, the new damage model can be used to simulate the typical shear behavior of cracked RC structures, which may not be captured by those models developed for plain concrete. Some computational aspects are also discussed. Finally, the model is validated through material tests and a series of RC member tests, and the results indicate that the proposed model has good performance in nonlinear analysis of RC structures.
Surface wave exploration has been increasingly used in near-surface geophysical investigations. However, the accuracy and efficiency of picking dispersion curves are key to surface wave inversion. ...Traditional dispersion curve extraction requires manual picking, and the extraction accuracy and efficiency depend on the experience and knowledge of the interpreters. Therefore, developing a fast, high-precision and intelligent dispersion curve extraction method is urgent. This paper improves the structure and output of the U-Net neural network and regards the picking process of dispersion curves as an image classification problem, which quickly and accurately extracts dispersion curves from dispersion energy images. After combining the dispersion energy images of synthetic seismic data with the manually extracted dispersion curve and the theoretical dispersion curve obtained by the Schwab-Knopoff algorithm, the ICM (energy image and dispersion curve extracted manually) training set and the ICS (energy image and dispersion curve calculated by Schwab-Knopoff algorithm) training set are created. The synthetic data tests verify the feasibility of the improved U-Net neural network for automatically picking multimode dispersion curves. The dispersion curve picking results corresponding to two different training sets reveal that the U-Net network model obtained from the ICS training sets exhibits better extraction accuracy. Additionally, we analyze the influence of the sample number of the training set on the dispersion curve picking effect of the improved U-Net and conclude that the improved U-Net network has the advantages of a low training set size requirement and a high dispersion curve extraction accuracy. Finally, the trained network extracts the dispersion curves of two groups of measured surface wave data and obtains plausible extraction results, further proving the proposed method's effectiveness.
Purpose
This paper aims to present a multi-scale stochastic damage model (SDM) for concrete and apply it to the stochastic response analysis of reinforced concrete shear wall structures.
...Design/methodology/approach
The proposed SDM is constructed at two scales, i.e. the macro-scale and the micro-scale. The general framework of the SDM is established on the basis of the continuum damage mechanics (CDM) at the macro-scale, whereas the detailed damage evolution is determined through a parallel fiber buddle model at the micro-scale. The parallel buddle model is made up of micro-elements with stochastic fracture strains, and a one-dimensional random field is assumed for the fracture strain distribution. To represent the random field, a random functional method is adopted to quantify the stochastic damage evolution process with only two variables; thus, the numerical efficiency is greatly enhanced. Meanwhile, the probability density evolution method (PDEM) is introduced for the structural stochastic response analysis.
Findings
By combing the SDM and PDEM, the probabilistic analysis of a shear wall structure is performed. The mean value, standard deviation and the probability density function of the shear wall responses, e.g., shear capacity, accumulated energy consumption and damage evolution, are obtained.
Originality/value
It is noted that the proposed method can reflect the influences of randomness from material level to structural level, and is efficient for stochastic response determination of shear wall structures.
•A multi-dimensional softened damage-plasticity model is developed for concrete.•The multi-layer shell element is used for numerical simulation of RC shear walls.•Quasi-Newton method with plasticity ...offset is adopted for the nonlinear solution.
In this paper, a rational analysis procedure is presented to model the typical cyclic behavior of reinforced concrete (RC) shear wall structures. A recently developed multi-dimensional softened damage-plasticity damage model, where the compression-softening effect of reinforced concrete is considered, is adopted to describe the concrete material behaviors. The steel material behaviors follow a modified Menegotto-Pinto model that including strain hardening, Bauschinger effect and tension stiffening. The multi-layer shell element, which is capable of simulating the coupled in-plane/out-of-plane bending as well as in-plane direct shear and the coupled bending-shear behavior of RC shear walls, is used for the finite element modeling of the structures. To overcome the convergence issues in the analysis procedure, the quasi-Newton method is adopted to solve the nonlinear finite equations and the iterative secant stiffness with plasticity offset for cyclic loading is introduced. Finally, several numerical simulations of RC shear walls with different failure modes are given, illustrating that the developed numerical model can accurately predict the cyclic behavior of RC shear wall structures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Introduction: The sofosbuvir-velpatasvir single-tablet regimen (Epclusa) is a newly FDA-approved inhibitor of hepatitis C virus (HCV). This meta-analysis aimed to investigate the safety and efficacy ...of velpatasvir-sofosbuvir in the treatment of chronic HCV infection. Methods: A comprehensive literature search of PubMed, Cochrane CENTRAL, EMBASE and Web of Science was conducted. Data from eligible studies were pooled in a fixed-effect meta-analysis model, using Open-Meta and RevMan software’s. Results: Pooled data showed that velpatasvir-sofosbuvir achieved sustained virological response (SVR12) rates of 94.2% (95% CI 90.7–97.7%, P < .001) in 1277 patients. The addition of ribavirin did not significantly increase the SVR12 (RR = 1.03, 95%CI 0.95, 1.11) in HCV genotype-1 patients and the SVR12 (RR = 1.09, 95%CI 0.86, 1.38) in HCV genotype-2 patients. However, adding ribavirin significantly increased SVR12 (RR = 1.13, 95% CI 1.04, 1.23) in genotype-3 patients. Conclusion: In conclusion, the 12-week regimen of sofosbuvir-velpatasvir was highly effective in HCV patients. Except for genotype-3, adding ribavirin was not associated with significant improvements in SVR12 rates.
To investigate effects of berberine (BBR) on cholesterol synthesis in HepG2 cells with free fatty acid (FFA)-induced steatosis and to explore the underlying mechanisms.
A steatosis cell model was ...induced in HepG2 cell line fed with FFA (0.5 mmol/L, oleic acid:palmitic acid = 2:1), and then treated with three concentrations of BBR; cell viability was assessed with cell counting kit-8 assays. Lipid accumulation in cells was observed through oil red O staining and total cholesterol (TC) content was detected by TC assay. The effects of BBR on cholesterol synthesis mediators were assessed by Western blotting and quantitative polymerase chain reaction. In addition, both silent information regulator 1 (SIRT1) and forkhead box transcription factor O1 (FoxO1) inhibitors were employed for validation.
FFA-induced steatosis was successfully established in HepG2 cells. Lipid accumulation and TC content in BBR groups were significantly lower (P < 0.05, P < 0.01), associated with significantly higher mRNA and protein levels of SIRT1(P < 0.05, P < 0.01), significantly lower sterol regulatory element-binding protein 2 (SREBP2) and 3-hydroxy 3-methylglutaryl-CoA reductase levels (P < 0.05, P < 0.01), as well as higher Acetyl-FoxO1 protein level (P < 0.05, P < 0.01) compared to the FFA only group. Both SIRT1 inhibitor SIRT1-IN-1 and FoxO1 inhibitor AS1842856 blocked the BBR-mediated therapeutic effects. Immunofluorescence showed that the increased SIRT1 expression increased FoxO1 deacetylation, and promoted its nuclear translocation.
BBR can mitigate FFA-induced steatosis in HepG2 cells by activating SIRT1-FoxO1-SREBP2 signal pathway. BBR may emerge as a potential drug candidate for treating nonalcoholic hepatic steatosis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The phytochemical investigation, including fractionation and purification of 70% acetone extracts of Juglans sigillata seed husks, an agricultural residue, led to the isolation of five low-molecular ...weight galloyltannins. The structures of the extractives were elucidated as 1,2,6-tri-O-galloyl-β-D-glucose (1), 3,4,6-tri-O-galloyl-β-D-glucose (2), 2,3,4,6-tetra-O-galloyl-β-D-glucose (3), 1,2,3,4,6-penta-O-galloyl-β-D-glucose (4), and tannic acid (5), primarily based on their spectral (NMR and MS) and chemical evidence. Galloyltannins 1-5 showed strong inhibitory activity against mushroom tyrosinase, with IC50 values ranging from 35.27 to 76.37 μM; kojic acid, which was used as a positive control, had an IC50 value of 342.14 μM. It was further found that 1-5 inhibited melanin production and exhibited intracellular tyrosinase activity, as well as down-regulated mRNA and protein expression levels of tyrosinase, in B16F10 mouse melanoma cells. Therefore, the isolated extractives from seed husks of J. sigillata may serve as potential candidates for hyperpigmentation remediation and as skin-whitening agents in the cosmetics industry.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Tree barks, as a type of forestry residues, are a rich and renewable bioresource that can produce high value-added products. Paulownia tomentosa var. tomentosa (PTT) has been extensively used in ...traditional Chinese medicine to cure various diseases. However, the antioxidative activity of the chemical constituents of the tree has not yet been investigated. In this study, the bark of PTT were extracted and fractioned. Then the resulting ethyl acetate (EtOAc) soluble fraction, which exhibited the strongest antioxidative effect, was subjected to repeated open column chromatography for purification. The screening process was carried out under the guidance antioxidative activity via diphenylpicrylhydrazyl (DPPH) radical scavenging assay. Eight phenolic compounds, glucodistylin (I), luteolin (II), ellagic acid (III), cistanoside F (IV), campneoside II (V), isocampneoside II (VI), verbascoside (VII), and isoverbascoside (VIII), were isolated and their structures were elucidated by various spectroscopic analyses. Among the phenolics, II~VIII showed significant antioxidative activity.
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•Natural compound isocampneoside II (ICD) was isolated from genus Paulownia.•ICD exhibited good antioxidant ability on superoxide radical scavenging activity, reducing power, and ...metal chelating.•ICD showed protective effect against oxidative protein damage induced by hydroxyl radicals.•ICD could ameliorate H2O2-induced oxidative stress and apoptosis in PC12 cells.•ICD inhibited cell apoptosis and Bax/Bcl-2 ratio induced by H2O2.
Oxidative stress has been considered as a major cause of cell damage in various neurodegenerative disorders. One of the reasonable strategies for delaying the disease’s progression is to prevent reactive oxygen species (ROS) mediated cellular injury by dietary or pharmaceutical augmentation of free radical scavengers. Isocampneoside II (ICD) is an active phenylethanoid glycoside isolated from the medicinal hardwood genus Paulownia. This study was designed to explore free radical scavenging potential of ICD in different in vitro systems and its protective role in hydrogen peroxide (H2O2)-induced oxidative stress and apoptotic death in cultured rat pheochromocytoma (PC12) cells. The results showed ICD eliminated approximately 80.75% superoxide radical at the concentration of 0.1mg/ml and inhibited metal chelating by 22.07% at 8mg/ml. Additionally, ICD showed a strong ability on reducing power and provided protection against oxidative protein damage induced by hydroxyl radicals. Pretreatment of PC12 cells with ICD prior to H2O2 exposure elevated cell viability, enhanced activity of superoxide dismutase and catalase, and decreased levels of malondialdehyde and intracellular ROS. Furthermore, ICD inhibited cell apoptosis and Bax/Bcl-2 ratio induced by H2O2. These findings suggested ICD may be considered as a potential antioxidant agent and should encourage for further research in neurodegenerative diseases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•The 1:4-scale SNL PCCV model is numerically investigated in details.•Interactions between steel materials and concrete are implicitly accounted for.•Fracture energy based evolution laws for the ...stress and damage are employed.•Appropriate modifications of the material constitutive relations are presented.•Limit capacity and ultimate failure mode of the PCCV model can be captured.
This work addresses the numerical modeling and simulation of prestressed concrete containment vessels (PCCVs) using the damaged-plasticity model for concrete and accounting for its interactions with the steel materials (i.e., the steel rebars, liner plate and prestressed tendons). Specifically, the 1:4-scale PCCV model tested by the Sandia National Lab (SNL) is considered. For concrete a novel fracture energy based method is employed to produce the data for the softening curve and damage evolution law such that mesh size independent numerical results can be guaranteed. To facilitate the finite element modeling, the interactions between steel and concrete are indirectly modeled by modifying appropriately the stress-strain relations of the steel materials as in Hsu and Mo (2010). The SNL PCCV model is then numerically modeling and symmetrically investigated. The effects of various strategies in modifying the steel stress-strain relations are discussed. It is found that, in addition to the prestressed tendons, the interactions between the liner plate/steel bars and concrete play non-negligible roles in correctly predicting the limit capacity and ultimate failure mode of the PCCV model. The numerical results obtained from the presented method, i.e., the limit capacity, failure mode, deformations and strains around crucial locations, etc., agree well with the experimental data, illustrating its capability in modeling the mechanical behavior of the PCCV like structures.
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GEOZS, IJS, KILJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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