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[Display omitted] • First report on h-BN doped β-MnO 2 nanobelts composite for supercapacitors. • The agglomeration behavior was improved by doping the gauze-like h-BN. • The h-BN/β-MnO 2 composite electrode possesses 578.4 F g−1 at 0.36 A g−1. • 97.1% capacitance retention even after 5000 cycles. The electrochemical performance of MnO 2 electrode material is limited by its poor electrical conductivity and cationic-protonic diffusion. In this work, we introduce the preparation of a novel h-BN/β-MnO 2 nanocomposite as superior electrode materials for extremely promising supercapacitors. The phase, surface morphologies and the internal atomic structures of the nanocomposite were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The electrochemical performance including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) was conducted under three-electrode system. The h-BN doped β-MnO 2 nanobelts composite electrode displayed a specific capacitance of 578.4F g−1 at a current density of 0.5 mA cm−2 (∼0.36 A g−1) and retained nearly 97.1 % capacitance even after 5000 cycles. [ABSTRACT FROM AUTHOR]

• The effect of size on molecular dynamics simulation results are considered. • Tensile and shear properties of amorphous silicon nitride with different densities calculated using molecular dynamics simulations. • The empirical equation between mechanical properties (Young's modulus, shear modulus, tensile strength, and shear strength) and density of amorphous silicon nitride is established. Silicon nitride fiber is among the most popular candidates for high-temperature wave-transparent ceramic matrix composites (CMC) in aerospace engineering, and the measurement of its mechanical properties has always been the focus of researchers. In this paper, a simple and effective molecular dynamics method is used to generate molecular dynamics models of amorphous silicon nitride (a -Si 3 N 4) materials with different densities, and it is verified that the developed models reflect the microstructure of the fiber. Based on analyzing the effects of size on the results, tensile and shear simulations are carried out to obtain the mechanical properties of the models with different densities. According to the research data obtained, the empirical equation between mechanical properties (Young's modulus, shear modulus, tensile strength, and shear strength) and density of fiber is established, and validated by the published experimental results. The empirical equation can not only predict the mechanical properties of fibers directly from the density but also provide a new way to measure the mechanical properties of fibers nondestructively. [Display omitted] [ABSTRACT FROM AUTHOR]

Oxygen plays a crucial role in the synthesis of boron nitride (BN) and the preparation of BN ceramics. The effects of oxygen content on the microstructure and properties of BN fibers treated at 1600 °C have not been studied yet. In this work, polymer-derived BN fibers are cured at 300 °C under oxygen and pyrolyzed at 600 °C, 700 °C and 800 °C under ammonia as the pre-heated BN fibers. Then, these pre-heated BN fibers are treated at 1600 °C under nitrogen as the final BN fibers. The compositions and microstructures of the pre-heated and final BN fibers are investigated. As the pre-heated temperature increases, the oxygen contents of the pre-heated BN fibers decrease to 24 wt%, 17 wt% and 5 wt%, respectively. The structures of the pre-heated BN fibers transform from amorphous BN to turbostratic BN. The oxygen in the pre-heated BN fiber volatilizes as boron oxide during treatment at 1600 °C, promoting the formation and growth of h-BN in the final BN fiber, with the maximum grain size reaching 74 × 20 nm (La × Lc). As the grain size of the final BN fiber increases, the Young's modulus, density and oxidation resistance level of the BN fiber improve, and the dielectric properties decrease. The final BN fiber that underwent pre-heating at 700 °C has the best comprehensive properties, with a tensile strength of 1.11 GPa and a Young's modulus of 265 GPa. This study researches the relationship between composition, structure and performance, and provides a scientific basis for the preparation process of BN fibers. • The initial BN fibers with gradient oxygen content are obtained by controlling the nitridation temperature after air curing. • The higher the oxygen content in the initial BN fibers, the better the crystallinity of the BN fibers treating at 1600 °C. • The tensile strength of BN fiber with a grain size of 34 × 11 nm (La × Lc) is 1.11 GPa, and the Young's modulus is 265 GPa. [ABSTRACT FROM AUTHOR]

This study assessed the effects of seven combinations of maize (Zea mays) genes phosphoenolpyruvate carboxylase (pepc), pyruvate phosphate dikinase (ppdk), and NADP-malic enzyme (nadp-me), on the photosynthesis of Arabidopsis. The photosynthetic rate, carboxylation efficiency, and shoot-dry-weight of Zmpepc (PC), Zmpepc + Zmppdk (PCK), Zmpepc + Zmnadp-me (PCM), and Zmpepc + Zmppdk + Zmnadp-me (PCKM) were significantly higher than those of the control wild-type (WT), with a trends to be PCKM > PCK > PC and PCM > WT. This indicated that Zmpepc was a prerequisite for improved photosynthetic performance; Zmppdk had a positive effect on Zmpepc , and the triple gene combination had the most significant synergistic effects. PCKM significantly enhanced activity of photosystem (PS)II (K, J phase) and PSI, light energy absorption (ABS/CSm) and conversion (TRo/ABS), and electron transfer (ETo/TRo). PCKM up-regulated 18 photosynthesis-related proteins, among which, 11 were involved in light reaction resulting in improved light-energy absorption and conversion efficiency, electron transfer, activity and stability of PSII and PSI, and the ATP and NADPH production. The remaining seven proteins were involved in dark reaction. The up-regulation of these proteins in PCKM improved the coordinated operation of light and dark reaction, increasing the photosynthesis and dry weight ultimately. These results also provide a promising strategy for the genetic improvement of the photosynthetic performance of C 3 crops by inserting major C 4 photosynthetic genes. • Arabidopsis was transformed with C 4 plant genes (Zmpepc , Zmppdk and Zmnadp-me). • Joint expression of the three C 4 plant genes significantly enhanced photosynthesis. • Eighteen proteins involved in photosynthetic process were up-regulated. • The light-energy absorption, conversion and CO 2 assimilation were all improved. • The overproduction of the metabolites of C 4 process may work as signals. [ABSTRACT FROM AUTHOR]

Wheat is one of the staple food crops worldwide and breeding for high yield wheat is critical to meet the need of increasing world population. To determine the factors that limit wheat yield potential in Henan province, China, 30 wheat cultivars that have been widely grown in Henan province since 1940s were evaluated for grain yield and related physiological traits. The results show that grain yield has been significantly increased since 1940s, with an annual genetic gain of 1.09%, and the increased yield after 1900s was attributed to the introduction of 1BL/1RS translocation. The significant yield increase mainly resulted from a significant increase in grain number per spike (GNPS), thousand kernel weight (TKW) and harvest index (HI), and a significant decrease in plant height due to utilization of semi-dwarfing genes. The genetic improvement of assimilate accumulation and translocation was mainly reflected by the improvement in post-anthesis assimilate accumulation (PoAAA) and post-anthesis transportion rate (PoATR) of pre-anthesis assimilates (PrAA), with genetic gains of 0.63% and 1.89%, respectively. The improvement of the PoAAA was closely related to an increase in net photosynthetic rates ( P n ) of flag leaves at anthesis and 20 days after anthesis, and leaf area index (LAI) at 20 days after anthesis; whereas the improvement of the PoATR of the PrAA was closely associated with the improvement of accumulation and redistribution of the assimilates accumulated in stems and sheaths. As yield increased, the source-sink ratio significantly decreased, reflecting that the source has been gradually becoming a limiting factor to grain yield increase. Therefore, diverse strategies should be adopted to improve biomass (source) in future wheat breeding to meet the need of continuous increasing in wheat yield. [ABSTRACT FROM AUTHOR]

• A simple and efficient method for generating and characterizing the microstructure of a -BN is proposed based on the classical molecular dynamics simulation. • Various densities and microstructures of a -BN could be successfully generated, which is mainly composed of the B 3 N 3 hexagonal ring. • High-density a -BN obtained from either high annealing temperature or high initial density, possesses high Young's modulus and fracture strength. • During the tensile process, the micro-voids in high-density of a -BN gradually undergoes expansion, elongation, mergence stages, and the fracture of a -BN. In this paper, a simple and effective strategy for generating the microstructure of a -BN is firstly proposed based on classical molecular dynamics methods, and then is validated by characterizing the microstructure. The characterization analysis show that: i) a -BN with different densities and microstructures could be successfully generated mainly composed of the B 3 N 3 hexagonal ring; ii) a- BN constructed by the combinations of the basic structural units with small size is more reasonable; iii) high-density a -BN, obtained at either high annealing temperature or high initial density, has discretely distributed micro-voids with larger scattering size distribution. The microstructure of the generated a- BN is subjected to tensile loading simulation, and the results showed the Young's modulus and fracture strength increase with increasing annealing temperature or initial density. During the tensile process, the micro-voids in high-density of a -BN gradually undergoes expansion, elongation, and mergence stages, and the ultimate fracture of a -BN. [ABSTRACT FROM AUTHOR]

• The influence of various factors on mechanical properties of h -BNNS are systematically investigated via classical MD simulations. • The effect of temperature and the ratio of circular-region radius to nanoindenter radius are greater than other factors. • Failure mechanism of mono-layer h -BNNS starts with discrete point defects, gradually expands and merges to form hole defects, and causes structural fracture. • Fracture mode of multi-layer h -BNNS will translate from the bottom-top failure to the top–bottom failure accompanying with increasing thickness. Hexagonal boron nitride nanosheets (h -BNNS) is one kind of promising 2D materials due to its outstanding mechanical properties especially at elevated temperature. However, the experimentally measured mechanical properties of h -BNNS have great dispersions due to the intricate experimental measurement conditions. In the present study, the classical molecular dynamics simulations are performed to study the effect of various experimental factors on the mechanical properties of h -BNNS based on nanoindentation, including: size, temperature, loading rate of nanoindenter, ratio of circular-region radius to nanoindenter radius, and thickness (the number of layers). Meanwhile, the evolution of microstructure of h -BNNS up to fracture are investigated to elucidate its fracture mechanism during nanoindentation process. The results indicate that the Young's modulus and fracture strength of h -BNNS gradually decreases with the increasing temperature, and the mechanical properties of h -BNNS remain relatively stable when the ratio of circular-region radius to nanoindenter radius and the circular-region radius is bigger than 10 and 18 nm, respectively. Based on the evolutionary process of the microstructure of h -BNNS, the results not only show the failure process of h -BNNS, but also reveal the conversion of the fracture mode in multi-layer h -BNNS, that is, it will be translated from the bottom-top to the top–bottom fracture with increasing thickness. [ABSTRACT FROM AUTHOR]