The clinic applications of bioabsorbable magnesium (Mg) and its alloys have been significantly restricted owing to their poor corrosion resistance. Besides elemental alloying, surface modification ...and functionality is a major approach to increasing corrosion resistance for magnesium alloys. This article reviews the cutting-edge advances and progress of biodegradable surface coatings upon Mg alloys over the last decades, aims to build up a knowledge framework of surface modification on biodegradable Mg alloys. A considerable number of conversion, deposition, mechanical and functional coatings and their preparation methods are discussed. The emphasis has been placed on the composition of chemical conversion and deposited coatings to overcome the disadvantages of adhesion, corrosion resistance and biocompatibility of a single coating for biomedical materials. The issues have been addressed on the integration of the structural and functional factors of the composite coatings.
•A novel data model termed hybrid k-nearest-neighbor graph is proposed to represent the data sets.•A clustering method is developed based on the hybrid k-nearest-neighbor graph.•A novel internal ...validity index is proposed to evaluate the validity of nonlinear clustering results.
Most of the existing clustering methods have difficulty in processing complex nonlinear data sets. To remedy this deficiency, in this paper, a novel data model termed Hybrid K-Nearest-Neighbor (HKNN) graph, which combines the advantages of mutual k-nearest-neighbor graph and k-nearest-neighbor graph, is proposed to represent the nonlinear data sets. Moreover, a Clustering method based on the HKNN graph (CHKNN) is proposed. The CHKNN first generates several tight and small subclusters, then merges these subclusters by exploiting the connectivity among them. In order to select the optimal parameters for CHKNN, we further propose an internal validity index termed K-Nearest-Neighbor Index (KNNI), which can also be used to evaluate the validity of nonlinear clustering results by varying a control parameter. Experimental results on synthetic and real-world data sets, as well as that on the video clustering, have demonstrated the significant improvement on performance over existing nonlinear clustering methods and internal validity indices.
A monophase nickel phosphide/carbon (Ni5P4/C) composite with a thin carbon shell is controllably synthesized via the two‐step strategy of a wet‐chemistry reaction and a solid‐state reaction. In this ...fabrication, the further diffusion of phosphorus atoms in the carbon shell during the solid‐state reaction can be responsible for a chemical transformation from a binary phase of Ni5P4‐Ni2P to monophase Ni5P4. Galvanostatic charge‐discharge measurements indicate that the Ni5P4/C composite exhibits a superior, high rate capacibility and good cycling stability. About 76.6% of the second capacity (644.1 mA h g−1) can be retained after 50 cycles at a 0.1 C rate. At a high rate of 3 C, the specific capacity of Ni5P4/C is still as high as 357.1 mA h g−1. Importantly, the amorphous carbon shell can enhance the conductivity of the composite and suppress the aggregation of the active particles, leading to their structure stability and reversibility during cycling. As is confirmed from X‐ray‐diffraction analysis, no evident microstructural changes occur upon cycling. These results reveal that highly crystalline Ni5P4/C is one of the most promising anode materials for lithium‐ion batteries.
Monophase nickel phosphide/carbon (Ni5P4/C) composites are controllably synthesized via a two‐step reaction: a wet‐chemistry reaction and a solid‐state reaction. Highly crystalline Ni5P4/C spheres with uniform morphology are obtained. The composites exhibit a high specific capacity and rate performance, as well as good cyclic stability, making them one of the most promising anode materials for lithium‐ion batteries.
A Fe2O3@NiO core/shell nanorod array on carbon cloth was prepared with the aid of hydrothermal synthesis combined with subsequent chemical bath deposition. The resultant array structure is composed ...of Fe2O3 nanorods as the core and interconnected ultrathin NiO nanoflakes as the shell. As an anode material for lithium-ion batteries, the heterostructured array electrode delivers a high discharge capacity of 1047.2 mA h g(-1) after 50 cycles at 200 mA g(-1), and 783.3 mA h g(-1) at a high current density of 2000 mA g(-1). The excellent electrochemical performance is attributed to the unique 3D core/shell nanorod array architecture and a rational combination of two electrochemical active materials. Our growth approach offers a simple and effective technique for the design and synthesis of a transition metal oxide hierarchical array that is promising for high-performance electrochemical energy storage.
The methylotrophic yeast
Pichia
pastoris
is widely used in recombinant expression of eukaryotic proteins owing to the ability of post-translational modification, tightly regulated promoters, and high ...cell density fermentation. However, episomal plasmids for heterologous gene expression and the CRISPR/Cas9 system for genome editing have not been well developed in
P.
pastoris
. In the present study, a panel of episomal plasmids containing various autonomously replicating sequences (ARSs) were constructed and their performance in transformation efficiency, copy numbers, and propagation stability were systematically compared. Among the five ARSs with different origins, panARS isolated from
Kluyveromyces
lactis
was determined to have the best performance and used to develop an efficient CRISPR/Cas9 based genome editing system. Compared with a previously reported system using the endogenous and most commonly used ARS (PARS1), the CRISPR/Cas9 genome editing efficiency was increased for more than tenfold. Owing to the higher plasmid stability with panARS, efficient CRISPR/Cas9-mediated genome editing with a type III promoter (i.e.
SER
promoter) to drive the expression of the single guide RNA (sgRNA) was achieved for the first time. The constructed episomal plasmids and developed CRISPR/Cas9 system will be important synthetic biology tools for both fundamental studies and industrial applications of
P.
pastoris
.
A simple approach has been developed for anchoring three-dimensional network structured Ni–P nanowires on reduced graphene oxide (GO) via a one-pot solvothermal method. Both the reduction of GO and ...deposition of Ni–P nanowires are achieved by introducing NaH2PO2·H2O in the reaction medium. Without GO in the reaction system, Ni–P nanowires are ready to be assembled to urchin-like microspheres. The hybrid electrode of Ni–P nanowires/reduced GO composite exhibits enhanced electrocatalytic activity towards the oxidation of methanol in alkaline solution compared with the bare urchin-like Ni–P microspheres, which is attributed to the larger surface area and improved conductivity resulting from the introduction of graphene sheets.
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•Anchoring 3D network structured Ni–P nanowires on reduced graphene oxide.•One-pot solvothermal method for synthesis of Ni–P/graphene composite.•Ni–P nanowires are ready to be assembled to urchin-like microspheres.•Ni–P/graphene exhibits enhanced electrocatalytic activity towards methanol oxidation.
Two additives of ethylene diamine tetraacetic acid (EDTA) and ammonium chloride (NH4Cl) were separately used in the electrodeposition of Zn–Ni alloy films from a deep eutectic solvent. The effects of ...these two additives on electrodeposition behavior, composition, morphology, and corrosion performance of the Zn–Ni alloys were investigated. The electrodeposition behaviors of Zn–Ni alloy revealed by the cyclic voltammetry show that the addition of EDTA to the Zn–Ni electrolyte enhances the Zn incorporation into the alloy film while the addition of NH4Cl produces an opposite effect by suppressing Zn incorporation into the film. With an increase of EDTA concentration in the electrolyte, the Zn content of the Zn–Ni films increases, while the grain size of the deposits and the current efficiency of the plating process decrease. The increase of NH4Cl concentration in the electrolyte would significantly refine the grain size of the electrodeposited Zn–Ni films, reduce the Zn content and increase the cathodic current efficiency. The corrosion testing indicates that the barrier corrosion resistances of Zn–Ni films electrodeposited from NH4Cl containing electrolytes are superior to those electrodeposited from EDTA-containing electrolytes, which in turn are superior to those electrodeposited from additive-free electrolytes.
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