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Numerical research is done on grain boundary diffusion of Cu-Ni bilayer thin films. Together, the composition-dependent interdiffusion coefficient and the position of the grain boundary are considered. Fick’s second law provides a quantitative assessment of the effects of grain size, volume, grain boundary diffusion coefficient, diffusion temperature, and time on the depth profile. Regarding the situation where the plateau values of the Ni concentration in the Cu layer and the Cu concentration in the Ni layer are almost the same for the case where the Ni intrinsic diffusion coefficient is significantly bigger than that for Cu, a detailed explanation is provided. We may produce a profile that is like the direct volume diffusion profile with a relative inaccuracy of 7.53% by using a method that is provided to eliminate the impacts of grain boundaries and grain size on the grain boundary diffusion profile. For most of the circumstances covered in this study, the technique is effective. The transformation of the grain boundary diffusion profile yields a composition-dependent interdiffusion coefficient, and the calculation’s outcome is consistent with the theoretical conclusion drawn from the Darken equation. Thin films of Cu (150 nm)/Ni (150 nm)/SiOx/Si (100 nm) were produced as examples, and Auger electron spectroscopy was used to determine the respective depth profiles. The calculated diffusion parameters, namely, the pre-exponential factor and the activation energy, are well within the bounds of the available data.

The energy surplus caused by the alternating current (AC) system’s failure results in a severe overvoltage problem in Bai hetan-Jiangsu ±800 kV hybrid cascade direct current (DC) project. However, the insulated gate bipolar transistor’s (IGBT) off-state voltage is the crucial reason for the insufficient voltage capacity of modular multilevel converter (MMC). Therefore, analysis and suppression of the off-state overvoltage are of vital significance. The off-state model of IGBT in an MMC converter is established, and the process of IGBT’s turning off is analyzed. Then, based on the characteristics of IGBT’s off-state and traditional resistance switching strategy, the gate modulation drive strategy is proposed, and the equivalent topology of the MMC submodule with the strategy is established. Finally, MMC submodule models with gate modulation drive and resistance switching strategy, respectively, are built in simulation software, and two groups of data are compared under multiple groups of the control cycle and reference current slope given. The simulation results show that the gate modulation drive supresses the off-state overvoltage on IGBT better than the resistance switching strategy. Moreover, the shorter the control cycle and the less reference current slope, the better the overvoltage suppression.

Based on the network model and the regular solution model, the equilibrium surface and interface segregations are investigated for the Ni(111)2 at%(Au) nano-films under diffusion-induced stress and intrinsic stress. The size effect with respect to the film thickness, the interlayer interactions and the heteroepitaxial strain in the film are taken into account. The equilibrium layer concentration in the film with the lowest Gibbs free energy of the system is obtained according to the coordinate descent method. The influences of diffusion-induced stress and intrinsic compressive/tensile stress, temperature and bulk concentration on the equilibrium layer concentration of segregation in the film are quantitatively evaluated.

In this work, nanoporous gold (NPG) fabricated using a modified solid-phase reaction method was developed as an electrocatalyst for the nonenzymatic detection of hydrogen peroxide (H2O2). The NPG morphology and structure were characterized by scanning electron microscopy and high-resolution transmission electron microscopy. The fabricated NPG exhibited a nanoporous framework with numerous structural defects. The NPG-based amperometric H2O2 sensor had a good selectivity, reproducibility, and low detection limit (0.3 μM) under near physiological conditions (pH = 7.4). The sensitivities of this sensor over concentration ranges of 0.002–5 mM and 5–37.5 mM were 159 and 64 μA mM−1 cm−2, respectively. These results indicate that the developed NPG is a promising material for the electrochemical sensing of H2O2.

Exploring the Mid-Late Holocene interactions between ecological and climate variations in semi-arid areas such as Songnen grasslands (northeastern China) provide insights into how future vegetation changes and hydrological variations may have an impact on semi-arid ecosystems, in general. In this study, we present a high-resolution palaeoecological dataset covering the past 7300 years. For this purpose, a peat section has been sampled from the shore of Dabusu lake situated in the southwestern part of the Songnen grasslands. We use pollen analyses to reconstruct the regional and local vegetation dynamics, and measure TOC (total organic carbon) and the degree of peat humification to study changes in regional and local biomass. Diatom analysis, grain size analysis, and CaCO3 contents are used to assess the water-table fluctuations of the Dabusu peatlands. The results show that from 7300 to 6000 cal BP, Dabusu peatlands were characterized by grasslands, dominated by Poaceae plants and high-water level. From 6000 to 910 cal BP, forest-steppes and dry-steppes dominated in the region alternatively. The water level of Dabusu peatlands experienced relatively low levels following an earlier rapid decline around 6000–5100 cal BP. Then after a slight increase between 5100 and 4000 cal BP, it remained at a relatively low level until 910 cal BP. After 910 cal BP, steppe vegetation dominated in the region and the water level of Dabusu peatlands slightly rose. By comparing these features with regional climate change, we show that EASM circulations might be the main driving forces controlling the regional paleovegetation dynamics and hydrological variations. This outcome is critical for the understanding of the long-term interactions between vegetation, hydrology, and climate of mid-latitude semi-arid grasslands.

Although phytolith analysis is a promising tool for reconstructing the palaeovegetation in grassland ecosystems, no phytolith study has yet attempted to quantitatively reconstruct the corresponding plant community characteristics. Questions remain regarding whether or not soil phytoliths can quantitatively reflect various aspects of grassland physiognomy, and how well modern phytoliths represent the quantitative characteristics of grassland ecosystems. These are important scientific issues in the field of phytolith analysis, which require further research on the modern phytoliths of grassland ecosystems. In order to explore the potential of phytolith analysis in the temperate grassland region, we have for the first time established a modern soil phytolith reference dataset by exploring the relationships between soil phytoliths and plant species inventory data from 77 sites in the Songnen grassland in Northeast China. The results show that phytolith assemblages can clearly distinguish Leymus chinensis grassland, Stipa grassland and mesophytic herb grassland. In addition, we found that the Ic phytolith index could discriminate samples of L. chinensis grassland from the other samples, while the Iph phytolith index proved to be less reliable in the region. In addition, in terms of quantitative plant community characteristics, the soil phytoliths showed a good correspondence with plant community cover and species richness, but not with biomass and diversity index. The transfer functions established in this study can provide reliable estimates of community cover and species richness in the Songnen grassland. In addition, phytoliths are shown to have the potential to reconstruct the taxonomic abundance of the aboveground plant community. This study is a major advance in the application of phytolith analysis to the quantitative estimation of plant community characteristics, and it provides a modern phytolith reference for the quantitative reconstruction of the paleovegetation of grassland ecosystems.

Graphene of thickness a few atomic layers has been grown in Ni/a-C bilayers at temperatures as low as 300 °C by Ni-induced crystallization of the amorphous carbon (a-C) in high vacuum. The mechanism of such very low-temperature growth of graphene has been investigated by a combinatorial experimental approach including x-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, x-ray photoelectron spectroscopy and transmission electron microscopy. The growth of this few atomic layer thickness graphene has been found to be mediated by a coupled grain-boundary (GB) diffusion/surface diffusion mechanism. GBs in the top Ni sublayer provide fast diffusion paths for C atoms through the Ni layer, as a result of which graphene layers form above the Ni. The revealed low-temperature growth mechanism of graphene induced by contact with a metal can be applicable in advancing research fields as metal-matrix graphene composites and advanced energy storage devices.

Manufacturing high-quality zinc oxide (ZnO) devices demands control of the orientation of ZnO materials due to the spontaneous and piezoelectric polarity perpendicular to the c-plane. However, flexible electronic and optoelectronic devices are mostly built on polymers or glass substrates which lack suitable epitaxy seeds for the orientation control. Applying cubic-structure seeds, it was possible to fabricate polar c-plane and nonpolar m-plane aluminium-doped zinc oxide (AZO) films epitaxially on flexible Hastelloy substrates through minimizing the lattice mismatch. The growth is predicted of c-plane and m-plane AZO on cubic buffers with lattice parameters of 3.94–4.63 Å and 5.20–5.60 Å, respectively. The ∼80 nm-thick m-plane AZO film has a resistivity of ∼11.43 ± 0.01 × 10−4 Ω cm, while the c-plane AZO film shows a resistivity of ∼2.68 ± 0.02 × 10−4 Ω cm comparable to commercial indium tin oxide films. An abnormally higher carrier concentration in the c-plane than in the m-plane AZO film results from the electrical polarity along the c-axis. The resistivity of the c-plane AZO film drops to the order of 10−5 Ω cm at 500 K owing to the semiconducting behaviour. Epitaxial AZO films with low resistivities and controllable orientations on flexible substrates offer optimal transparent electrodes and epitaxy seeds for high-performance flexible ZnO devices.

Young and mature leaves of three Acer truncatum varieties with different leaf colors were examined. Transcriptome sequencing and flavonoid metabolism were used to analyze the differential gene expression associated with different leaf colors and growth stages and the relationships between gene expression and flavonoid and anthocyanin contents to improve ornamental value and develop flavonoid-rich A. truncatum. Kyoto Encyclopedia of Genes and Genomes database annotation of differentially expressed genes indicated that the following genes were related to flavonoid synthesis: phenylpropanoid biosynthesis genes (PAL, C4H, 4CL and CHS), flavonoid biosynthesis genes (E2.1.1.104, CHI, FLS, F3'5'H and ANR), anthocyanin biosynthesis genes (ANS, DFR, HCT, BZ1, GT1, and UGT79B1), isoflavonoid biosynthesis genes (HIDH and CYP81E17), and their transcriptional regulator (MYB). A total of 234 types of flavonoids were detected. The types and contents of anthocyanins in the red-leaf varieties 'Hong Jingling' and 'Caidie Fanfei' were significantly higher than those in the green leaf cultivar 'Lv Baoshi', especially morning glory 3-O-glucoside, delphinidin 3-O-glucoside, and pelargonium-3-O-glucoside, which were not detected in 'Lv Baoshi'. Combined omics analysis showed that downregulated expression of C4H, CHS and F3'5'H and upregulated expression of FLS reduced the supply of raw materials for anthocyanin synthesis, and downstream ANR upregulation converted anthocyanins to procyanidins, increasing the total flavonoid content. F3'5'H expression was downregulated in the leaves of each variety with development, resulting in the accumulation of catechins and the gradual greening of the leaves. F3'5'H was significantly depleted in the young leaves of 'Hong Jingling' and 'Caidie Fanfei' compared with the young leaves of 'Lv Baoshi', while ANS and BZ1 were enriched significantly. It is concluded that F3'5'H, BZ1, and ANS are the key genes needed for breeding red A. truncatum and that ANR is the key gene needed for breeding varieties with a high flavonoids contens. These results may facilitate genetic modification or selection for further improvement of the ornamental qualities and flavonoid content of A. truncatum.

Macin is a family of antimicrobial peptides (AMPs) and is involved in the immune responses of marine mollusks. In the present study, a novel Mytimacin (denoted as Hd-mtmc 6) was identified from the small abalone Haliotis diversicolor by RNA-seq and RACE techniques. Hd-mtmc 6 contained a coding sequence of 243 bp and encoded 80 amino acids, with a putative peptide mytimacin 6 consisting of 61 amino acid residues. The mature peptide of Hd-mtmc 6 exhibited typical characteristics of AMPs, including net positive charge (+4), higher hydrophobic residue ratio (37%), and lower molecular mass. Eight cysteines in the mature peptide formed four disulfide bond bridges (C1-C6, C2-C5, C3-C7, and C4-C8). Moreover, the presence of the macin domain, a three-dimensional structure similar to that of hydramacin-1, and a phylogenetic relationship suggested that Hd-mtmc 6 could be a new member of the invertebrate macin family. In unchallenged abalone, the Hd-mtmc 6 transcript was expressed in all tested tissues and could be detected at different stages of embryonic development. Vibrio harveyi challenge caused a significant Hd-mtmc 6 transcripts upregulation within 2 - 6 h in the mantle and hepatopancreas. Our results suggested that Hd-mtmc 6 may be involved in innate immune responses of small abalone. Further investigations are required to confirm its antibacterial activity at the protein level.

A new method is proposed to determine the original in-depth distribution of composition directly by the deconvolution of measured depth profiling data using the MRI (Mixing-Roughness-Information) depth resolution function. To overcome the ill-conditioned problem that is often experienced in the deconvolution procedure, the regularization method and the TV-Tikhonov algorithm are employed. The method is applied for the case that the original depth-concentration distribution is either a smooth function or a square wave function and the corresponding arithmetic mean errors are determined accordingly. The noise effects from “measured” data on the deconvoluted profile are also quantitatively evaluated.

The thermal oxidation of ZrAl2 in the temperature range of 550–750 °C in pure oxygen has been investigated by a combinational experimental approach using X-ray diffraction, scanning electron microscopy/energy dispersive spectrometer, Auger electron spectroscopy and cross-sectional transmission electron microscopy. The thermal oxidation leads to the growth of anomalously thick (up to 4.5 μm) amorphous (Zr0.33Al0.67)O1.66 surficial layers at temperatures as high as 750 °C. The oxidation kinetics obeys a parabolic law with an activation energy of 143 kJ/mol. The underlying mechanism for the formation of such micrometer-thick amorphous oxide surficial layers has been discussed on the basis of interface thermodynamics and the occurrence of high interface stability associated with a synchronous oxidation of Al and Zr elements.

A comparison is performed between the experimentally determined variation of the layer thickness at 50 at% with the primary ion energy and the prediction of this variation and of the layer thickness at 50% amplitude by the Mixing-Roughness-Information depth (MRI) model for SIMS depth profiles of Ge/Si multilayers. Reasonable agreement was obtained by taking into account the influence of the primary ion energy on both preferential sputtering and atomic mixing length. In both cases, the determined layer thickness increases with ion energy for the component with higher sputtering rate (Ge) and decreases for the one with lower sputtering rate (Si).

Multilayer profiles are studied using the MRI model with extension to preferential sputtering. The results show a clear distinction with respect to the main contributions to the depth resolution, namely surface and interface roughness, and atomic mixing. For dominating roughness, the effect of preferential sputtering is more pronounced for the residual surface composition profile (detected by XPS and AES), but it is zero for the sputtered matter composition profile (detected by SIMS). Dominating mixing results in a strong effect of preferential sputtering on the shape of the profile. While in that case its effect on the XPS or AES depth profile is relatively moderate, its effect on the SIMS depth profile is surprisingly strong and appears to be in contradiction to textbook statements. Interface width, location and layer thickness are always affected by preferential sputtering in XPS and AES depth profiles, but SIMS depth profiles are only affected if the contribution of atomic mixing to depth resolution cannot be ignored. In conclusion, a new definition of multilayer resolution is proposed which is based on the normalized amplitude of the wave-like profiles. The successful application of MRI model extended for preferential sputtering is given for fitting an experimental AES depth profile of an Ag/Ni multilayer.

The difference in the microstructural and texture evolution of Al films grown on amorphous SiO2 (a-SiO2) and amorphous Ge (a-Ge) substrates have been investigated. Surprisingly, the a-Ge substrate was found to change the preferred orientation of Al grains from the conventional (1 1 1) to the unconventional (1 1 0). The effect of the high mobility of Ge atoms at the metal-semiconductor interface on the microstructural and texture evolution of the metal thin film was studied. The diffusion of the Al adatoms on the a-Ge substrate was suppressed owing to the segregation of Ge atoms at the film surface. The mobility of Al grain boundaries was also suppressed because of grain-boundary wetting by the Ge atoms. It is concluded that the a-Ge substrate could tailor the Al grain orientation from (1 1 1) to (1 1 0) owing to the change in the film-growth mode from three-dimensional to two-dimensional nucleation. The concept of interaction-induced island-growth model, which is based on the Volmer–Weber growth model, is also discussed here. This work thus demonstrates how the atomic mobility at the interface of the metal thin film and the semiconductor substrate controls the film microstructure and texture during deposition.

High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a high-energy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energy-dispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10 nm and 62 nm upon milling for 2 h–50 h, respectively. The finally formed Al-Si interfaces after ball milling for 50 h are well-cohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at 550 °C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites.

The preferential sputtering and the mass conservation upon AES and SIMS depth profiling have been evaluated quantitatively based on the Mixing-Roughness-Information (MRI) model. The simulation results demonstrated that (a) the preferential sputtering plays an important role in the reconstruction of the true concentration-depth profile; (b) the mass conservation is a nature consequence in SIMS depth profiling but it is not fulfilled in AES depth profiling; (c) the layer thickness can be determined by applying the mass conservation law in AES depth profiling if the atoms preferentially sputtered out from the mixing zone are taken into account.

Many prehistoric cultural sites with distinctive regional characteristics have been discovered on fixed aeolian dunes in Nenjiang River Basin, Northeast China. The rise and decline of these cultures was substantially influenced by the regional environmental evolution. To elucidate how human activity responded to environmental changes, we conducted analyses of phytoliths, grain-size and organic content of a natural sediment profile at Honghe Neolithic site. The phytolith analysis shows that the vegetation was dominated by C3 Pooideae, and the grain-size analysis shows that the site was strongly affected by the winter monsoon and that the sediment source was regionally-derived aeolian sand from Songnen Sandy Land. The environment of Nenjiang River Basin experienced several periods of sand dune mobilization and stabilization: During 7024-4233 cal yr BP, 3414-2433 cal yr BP and 1700-1000 cal yr BP the dunes of Songnen Sandy Land were stable and the environment was warm and wet. During 4233-3,414 cal yr BP, 2433-1,700 cal yr BP and 1000 cal yr BP-present the dunes were mobile and the climate was cold and dry. In addition, the global 4.2 ka cold climatic event is recorded in the section. Correspondingly, the human history can be divided into three periods: (I) Neolithic Age (7024-4,233 cal yr BP) when the winter monsoon was weak, the sand dunes were stable and the environment was warm and wet. Human activity was relatively intense during this period, manifested by the Angangxi Culture in the middle reaches of Nenjiang River, a representative of the ‘Fishing-Hunting Neolithic Culture’. However, only a small number of tombs post-dating 4200 cal yr BP have been found in the Angangxi district (II) Bronze Age (4233-2,433 cal yr BP). The Xiaolaha Cultural sites in the lower reaches of Nenjiang River, which inherited the characteristics of the Angangxi Culture, flourished during 3800-3260 cal yr BP, and after a transitional period it gradually evolved into the Baijinbao Culture (2800-2,500 cal yr BP). This pattern of evolution shows that human activity diminished in the middle reaches of Nenjiang River after 4233 cal yr BP, in response to the colder and drier environment. (III) Post-Warring States period (2433 cal yr BP - present). The Hanshu II culture prospered during 2380-2067 cal yr BP, and the Hongmashan Culture was the dominant culture during 2000-1700 cal yr BP. Historical documents and archaeological evidence revealed that frequent wars interrupted the continuity of human cultural development after 2000 cal yr BP in the Nenjiang River Basin.