The meshless element-free Galerkin method is developed for numerical analysis of hyperbolic initial-boundary value problems. In this method, only scattered nodes are required in the domain. Computational formulae of the method are analyzed in detail. Error estimates and convergence are also derived theoretically and verified numerically. Numerical examples validate the performance and efficiency of the method. 相似文献
Numerical integration poses greater challenges in Galerkin meshless methods than finite element methods owing to the non-polynomial feature of meshless shape functions. The reproducing kernel gradient smoothing integration (RKGSI) is one of the optimal numerical integration techniques in Galerkin meshless methods with minimum integration points. In this paper, properties, quadrature rules and the effect of the RKGSI on meshless methods are analyzed. The existence, uniqueness and error estimates of the solution of Galerkin meshless methods under numerical integration with the RKGSI are established. A procedure on how to choose quadrature rules to recover the optimal convergence rate is presented. 相似文献
Stem cells from apical papilla (SCAPs) are desirable sources of dentin regeneration. Epigallocatechin-3-gallate (EGCG), a natural component of green tea, shows potential in promoting the osteogenic differentiation of bone mesenchymal stem cells. However, whether EGCG regulates the odontogenic differentiation of SCAPs and how this occurs remain unknown. SCAPs from immature human third molars (16–20 years, n = 5) were treated with a medium containing different concentrations of EGCG or bone morphogenic protein 2 (BMP2), with or without LDN193189 (an inhibitor of the canonical BMP pathway). Cell proliferation and migration were analyzed using a CCK-8 assay and wound-healing assay, respectively. Osteo-/odontogenic differentiation was evaluated via alkaline phosphatase staining, alizarin red S staining, and the expression of osteo-/odontogenic markers using qPCR and Western blotting. We found that EGCG (1 or 10 μM) promoted the proliferation of SCAPs, increased alkaline phosphatase activity and mineral deposition, and upregulated the expression of osteo-/odontogenic markers including dentin sialophosphoprotein (Dspp), dentin matrix protein-1 (Dmp-1), bone sialoprotein (Bsp), and Type I collagen (Col1), along with the elevated expression of BMP2 and phosphorylation level of Smad1/5/9 (p < 0.01). EGCG at concentrations below 10 μM had no significant influence on cell migration. Moreover, EGCG-induced osteo-/odontogenic differentiation was significantly attenuated via LDN193189 treatment (p < 0.01). Furthermore, EGCG showed the ability to promote mineralization comparable with that of recombinant BMP2. Our study demonstrated that EGCG promotes the osteo-/odontogenic differentiation of SCAPs through the BMP–Smad signaling pathway. 相似文献
In this study,a non-enzymatic hydrogen peroxide sensor was successfully fabricated on the basis of copper sulfide nanoparticles/reduced graphene oxide(CuS/RGO) electrocatalyst.Using thiourea as reducing agent and sulfur donor,CuS/RGO hybrid was synthesized through a facile one-pot hydrothermal method,where the reduction of GO and deposition of CuS nanoparticles on RGO occur simultaneously.The results confirmed that the CuS/RGO hybrid helps to prevent the aggregation of CuS nanoparticles.Electrochemical investigation showed that the as-prepared hydrogen peroxide sensor exhibited a low detection limit of 0.18μmol/L(S/N = 3),a good reproducibility(relative standard deviation(RSD) of4.21%),a wide linear range(from 3 to 1215 μmol/L) with a sensitivity of 216.9 μA L/mmol/cm~2 under the optimal conditions.Moreover,the as-prepared sensor also showed excellent selectivity and stability for hydrogen peroxide detection.The excellent performance of CuS/RGO hybrid,especially the lower detection limit than certain enzymes and noble metal nanomaterials ever reported,makes it a promising candidate for non-enzymatic H_2O_2 sensors. 相似文献
The suitability of micellar electrokinetic capillary chromatography (MEKC) with laser-induced fluorescence (LIF) detection for simultaneous determination of two arginine analogues (homocysteine and homoarginine) and five closely related metabolites (asymmetric dimethyl-l-arginine, dimethyl-l-arginine, monomethyl-l-arginine, citrullin, and ornithine) in fluids from type 2 diabetics with peptic ulcer bleeding (PUB) has been investigated. 5-Carboxyfluorescein succinimidyl ester (CFSE) was chosen as the fluorescent labeling reagent and non-endogenous phenylpropanolamine (PPA) as the internal standard. Conditions affecting derivatization and separation were optimized. Under the optimum conditions, maximum derivatization could be achieved in 20 min at room temperature. Complete baseline separation was achieved in 10 min, and the relative standard deviations (RSD) of migration times and corrected peak areas were <3 % for intra-day assay and <5 % for inter-day assay. Limits of detection (LODs) were 0.12–1.70 nM for the eight analytes, which are well below the concentrations expected in real fluids. Compared with previously reported methods, 5 to 600-fold improvements in sensitivity were achieved by use of LIF detection. Sample preparation and analysis time were short and the derivatives of the analytes were highly stable. The method was fully validated with real plasma and urine and recoveries of spiked compounds were 95–102 % with the RSD <4 %.
Tetra-β-nitro-substituted nickel phthalocyanine (TN-NiPc) and hollow phthalocyanine (TN-H2Pc) were synthesized and investigated as novel organic electrode materials for rechargeable lithium batteries. After the two H atoms in the center of TN-H2Pc were replaced with Ni atoms, the interactive force between the phthalocyanine rings was reduced, which resulted in a fluffy morphology for the TN-NiPc that was beneficial to the transition of Li+. As a result, better electrochemical properties and reversibility were observed in the TN-NiPc electrodes compared to the TN-H2Pc electrode. The capacity of TN-NiPc electrode was stable at about 280 mAh g?1 at 0.2 C after 250 cycles at several different current rates of 0.1, 0.2, 0.5, and 1 C. The TN-NiPc based cathode materials may provide new opportunities for organic, flexible, and stable secondary lithium batteries.
Graphical Abstract The TN-NiPc electrode shows better electrochemical properties than that of TN-H2Pc electrode, which is due to the strong hydrogen bond interaction and π-π interaction of TN-H2Pc molecules, resulting in more dense stacking degree of the phthalocyanine ring and restricting the transport of Li+ .
Powdered crystal AMP was synthesized by precipitation method and different Cs-loading AMP samples were prepared in this work. They were studied by modern methods of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) to gain a better understanding of the ion exchange mechanism of ammonium molybdophosphate (AMP). The XRD patterns combined with the FT-IR analysis indicate that the Keggin structure is retained after Cs adsorption, while the changes of certain characteristic diffraction peaks show crystal lattice distortion caused by the mismatching sizes of Cs+ and [NH4]+. The TGA showed that the weight percent of H2O and [NH4]+ decreases as the amount of Cs adsorbed onto AMP increases, which corresponds with the theory of isomorphous exchange. 相似文献