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1.
《中国化学快报》2020,31(12):3183-3189
Engineered nanomaterials have attracted significantly attention as one of the most promising antimicrobial agents for against multidrug resistant infections. The toxicological responses of nanomaterials are closely related to their physicochemical properties, and establishment of a structure-activity relationship for nanomaterials at the nano-bio interface is of great significance for deep understanding antibacterial toxicity mechanisms of nanomaterials and designing safer antibacterial nanomaterials. In this study, the antibacterial behaviors of well-defined crystallographic facets of a series of Au nanocrystals, including {100}-facet cubes, {110}-facet rhombic dodecahedra, {111}-facet octahedra, {221}-facet trisoctahedra and {720}-facet concave cubes, was investigated, using the model bacteria Staphylococcus aureus. We find that Au nanocrystals display substantial facet-dependent antibacterial activities. The low-index facets of cubes, octahedra, and rhombic dodecahedra show considerable antibacterial activity, whereas the high-index facets of trisoctahedra and concave cubes remained inert under biological conditions. This result is in stark contrast to the previous paradigm that the high-index facets were considered to have higher bioactivity as compared with low-index facets. The antibacterial mechanism studies have shown that the facet-dependent antibacterial behaviors of Au nanocrystals are mainly caused by differential bacterial membrane damage as well as inhibition of cellular enzymatic activity and energy metabolism. The faceted Au nanocrystals are unique in that they do not induce generation of reactive oxygen species, as validated for most antibiotics and antimicrobial nanostructures. Our findings may provide a deeper understanding of facet-dependent toxicological responses and suggest the complexities of the nanomaterial-cell interactions, shedding some light on the development of high performance Au nanomaterials-based antibacterial therapeutics.  相似文献   
2.
徐志庭  金楚华 《数学季刊》2006,21(2):271-277
By using the averaging technique, we obtain new oscillation criteria for second order delay differential equation with nonlinear neutral term. These results generalize and improve some known results about neutral delay differential equation of second order.  相似文献   
3.
Oneofthemostimportantaimsofphotochemistryisthedesignandconstructionofmoleculardevicesforener gyconversionandinformationprocessing .Thephotoactivemoleculardevicesarebasedonthephotoinducedelectrontransferbetweendonor acceptortypeorganiccompoundsandaccept…  相似文献   
4.
CompoundsformedfromCu ,AgandAuwithdithio lateligands ,suchasthedialkyldithiocarbamate (DTC) ,mercaptothiazoline (HMT)anddialkyldithiophosphates(DDP) ,haveplayedanimportantroleintechnology .1Cu(I) Sclustersalsohavebeenimplicatedinbiologyasan ti oxidants .2Thecuban…  相似文献   
5.
In this paper, bifurcation trees of periodic motions in a periodically forced, time-delayed, hardening Duffing oscillator are analytically predicted by a semi-analytical method. Such a semi-analytical method is based on the differential equation discretization of the time-delayed, nonlinear dynamical system. Bifurcation trees for the stable and unstable solutions of periodic motions to chaos in such a time-delayed, Duffing oscillator are achieved analytically. From the finite discrete Fourier series, harmonic frequency-amplitude curves for stable and unstable solutions of period-1 to period-4 motions are developed for a better understanding of quantity levels, singularity and catastrophes of harmonic amplitudes in the frequency domain. From the analytical prediction, numerical results of periodic motions in the time-delayed, hardening Duffing oscillator are completed. Through the numerical illustrations, the complexity and asymmetry of period-1 motions to chaos in nonlinear dynamical systems are strongly dependent on the distributions and quantity levels of harmonic amplitudes. With the quantity level increases of specific harmonic amplitudes, effects of the corresponding harmonics on the periodic motions become strong, and the certain complexity and asymmetry of periodic motion and chaos can be identified through harmonic amplitudes with higher quantity levels.  相似文献   
6.
7.
In the design of the cost function in the nonlinear finite control set model predictive control (FCS-MPC) system, the traditional method based on weighting factors demonstrates some limitations, such as the weighting factors adjusting and heavy predictive calculation due to the increased number of voltage vectors applied in controlling multilevel converters. This paper proposes a simplified FCS-MPC method based on common mode voltage satisfactory optimization, which could considerably reduce the predictive calculation by the optimized switch combination and simplify the cost function design. Moreover, satisfactory optimization is adopted to achieve the accuracy control of common-mode voltage amplitude without adjusting process of weighting factors. The simulation and experimental results verify the feasibility of this control strategy.  相似文献   
8.
In this paper, we develop a fast block Jacobi method for linear systems based on discrete wavelet transform (DWT). Traditional wavelet-based methods for linear systems do not fully utilize the sparsity and the multi-level block structure of the transformed matrix after DWT. For the sake of numerical efficiency, we truncate the transformed matrix to be a sparse matrix by letting the small values be zero. To combine the advantages of the direct method and the iterative method, we solve the sub-systems appropriately based on the multi-level block structure of the transformed matrix after DWT. Numerical examples show that the proposed method is very numerically effective.  相似文献   
9.
Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS2/MoO3 nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO3/MoS2 composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO3/MoS2 composites. According to Raman spectroscopy results, as-obtained defect-rich MoS2 is confirmed to be a metallic 1T-phase MoS2. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g−1 and up to 1720.6 mAh g−1 after 317 cycles under a current density of 0.2 A g−1). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g−1 at 2 A g−1 after 700 cycles and 584.8 mAh g−1 at 5 A g−1 after 800 cycles). Moreover, at a rate of 1 A g−1, the average specific capacity is maintained at 661 mAh g−1. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.  相似文献   
10.
This paper concerns with the problem of how to running an insurance company to maximize his total discounted expected dividends. In our model, the dividend rate is limited in [0,M] and the company is allowed to transfer any proportion of risk by reinsuring. So there are two strategies which we call dividend strategy and reinsurance strategy. The objective function and the corresponding optimal two strategies are the solution and the two free boundaries of the following Barenblatt parabolic equation
vt?max0a1?(12a2σ2vxx+aμvx)+cv?max0lM?[(1?vx)l]=0
under certain boundary conditions on an angular domain
QT={(x,t)|0<x<Mt,0<tT}.
The main effort is to analyze the properties of the solution and the free boundaries to show the optimal decision for the insurance company.  相似文献   
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