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In this study, two green procedures for Silver-Graphene Oxide (Ag-GO) nanocomposite synthesis were investigated. As a common method, AgNO 3 was first loaded on the GO surface and then was reduced and stabilized by walnut green husk extract, producing Ag-GO-І. As an innovative approach, GO was first exposed to the extract and then the AgNO 3 was added as the second step, producing Ag-GO-П. Physicochemical properties, antibacterial and cytotoxicity activity of both nanocomposites were subsequently studied comparing with free silver nanoparticles (AgNPs) and pure GO. Based on the results, exposure of GO to the extract, as a reducing agent, at the first/last step of the synthesis process resulted in the fundamental differences in the final products. So that, high amounts of agglomerated silver nanoparticles were formed between the GO sheets, when using the common method, whereas in Ag-GO-П, small AgNPs were formed on the GO sheets without aggregation, entirely covering the sheets. Antibacterial and cytotoxic behavior of these nanomaterials could be compared as AgNPs > Ag-GO-П > Ag-GO-І. It is assumed that these differences are due to control of unwanted nucleation in the synthesis process that Ag nanoparticles are smaller with less agglomeration when the GO surfaces are pre-treated with reducing agent.

The dynamic shear modulus of soils is needed to predict soil behavior in response to cyclic loading. Even though the effective stress has been shown to have a significant impact on the dynamic modulus of water-saturated and dry soils, its effect on the dynamic shear modulus of unsaturated soils has not been evaluated. Specifically, studies on the dynamic response of unsaturated soils have characterized variations in small-strain shear modulus (G max) as a function of the degree of saturation or matric suction alone. In contrast, this study evaluates the use of the suction stress characteristic curve to characterize the impact of mean effective stress (' m) on the dynamic shear modulus of unsaturated sand. A fixed-free resonant column test device was adapted with a hanging column setup so that the small-strain dynamic shear modulus could be measured for sand specimens under different confining pressures and matric suction values. Trends between the small strain shear modulus and effective stress for unsaturated sand were found to be different from those reported in the literature, where G max varied linearly with the square root of ' m .

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This paper presents a study on the simulation of cone penetration tests (CPTs) using the discrete element model (DEM) method. This study’s main objective is to investigate the effect of different modeling parameters and simulation configurations on the ability of three-dimensional DEM simulations to replicate realistic CPT tip resistance (qc) and friction sleeve shear stress (fs) measurements. The CPT tests were simulated in virtual calibration chambers (VCCs) containing particles calibrated to model the behavior of sand. The parameters investigated included the granular assembly properties, interparticle contact parameters, particle–probe interface characteristics, and simulation configuration. Results indicate that the interparticle contact parameters, boundary conditions, and void ratio have an important role in the tip resistance and friction sleeve measurements obtained from the simulations. Particle-level interactions such as particle displacements and rotations and interparticle contact forces were analyzed throughout to provide insight into the differences in measured CPT response. Interpretation of the qc and fs measurements using soil behavior type (SBT) charts for soil classification indicates that the simulated CPT response is representative of the response of coarse-grained soils measured during field soundings. Analysis of results within the SBT framework can provide insight into the influence of soil particle properties on CPT-based soil classification.

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BackgroundContrast-induced nephropathy (CIN) is one of the most important complications of angiography in patients with chronic kidney disease (CKD) or diabetes mellitus. The prevention of CIN can decrease therapeutic costs and hospital stays. There is controversy in the literature over the preventive effect of statins on CIN.ObjectivesThis study was designed to evaluate the preventive effect of atorvastatin on CIN after angiography in CKD and diabetic patients.Patients and MethodsIn this placebo-controlled, double-blind clinical trial, patients with diabetes mellitus or CKD (15 < GFR < 60 mL/min, Cr > 1.5 mg/dL) and an age range of 55 - 75 years candidated for angiography were included. The patients were randomized to 2 groups: one group receiving atorvastatin (80 mg/d from 48 h before angiography) and the other one receiving a placebo. All the patients received intravenous isotonic saline and N-acetylcysteine. CIN was defined as an increase in serum creatinine more than 0.5 mg/dL or more than 25% from the baseline values.ResultsTotally, 220 patients at a mean age of 63.85 ± 8.89 years and a mean body mass index of 31.41 ± 5.99 kg/m2 were evaluated. In comparison of before-after values, there was a significant increase in serum creatinine in the placebo group (P = 0.000). The incidence of CIN was significantly higher in the control group 24 hours after angiography (P = 0.010); however, at a 48-hour interval, there was no significant difference in CIN between the 2 groups.ConclusionsStandard hydration and N-acetylcysteine and atorvastatin (80 mg) reduced the incidence of CIN, and this regimen was more effective than was the regimen of hydration and N-acetylcysteine (without atorvastatin) in decreasing CIN. Accordingly, it is reasonable to prescribe atorvastatin before angiography in high-risk patients.