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Elucidating the chemical structure of dissolved organic matter (DOM) is key to understanding this large yet enigmatic carbon pool. Over the last two decades much progress has been made in assigning exceptionally accurate molecular formulas of DOM owing to the application of ultrahigh resolution mass spectrometry, but little is known about the number of isomers in each molecular formula, a question essentially related to the total number of organic molecules in DOM. Such information is critical for a further understanding of the formation and long-term stability of refractory DOM in the ocean. In this work, we used ion mobility quadrupole time of flight liquid chromatography tandem mass spectrometry (IM Q-TOF LC/MS/MS) to analyze DOM samples collected in different aquatic environments including south Texas rivers, Gulf of Mexico, and South China Sea. Our data showed that generally less than 23% of all detected DOM formulas, which shared a small fraction of common molecules (ca. 12%) detected by direct-infusion Fourier transform ion cyclotron resonance MS, contained structurally distinct isomers (represented by “isomer clusters”). In addition, isomer diversity, in terms of how different the structures are, decreased with degradation in both natural and incubation samples. Specifically, the number of structurally distinct isomers was lower at river mouth and open ocean than coastal waters, where organic matter tends to be fresher due to high primary production; and with depth in water column, isomer diversity of DOM also decreased. Results from a set of incubation experiments also showed that the percentages of riverine DOM molecules that have multiple isomer clusters decreased with time, suggesting that biodegradation decreases the diversity of molecules from an isomer perspective. Overall, these results suggested that isomers, at least in a certain fraction of DOM, are highly constrained, and that degradation decreases its isomeric diversity.

We inoculated Tuber aestivum and Tuber sinoaestivum on Carya illinoinensis to explore the effects of inoculation on host plant growth, enzyme activities, the physicochemical properties of rhizosphere soil, the denitrifying bacterial community in the rhizosphere, and the distribution of mating type genes in the rhizosphere. We found that the Tuber spp. inoculation increased the height of the host plant and that the stem circumference of the host was greater two months after inoculation. Six months after inoculation, the peroxidase activity of the seedlings inoculated with T. sinoaestivum was higher than that of the control. At four and six months after inoculation, the superoxidase dismutase activities of the seedlings inoculated with T. aestivum were higher than those of the seedlings inoculated with T. sinoaestivum. Six months after inoculation, nitrate nitrogen content was lowest in the control and highest in the T. sinoaestivum treatment. Among the nirS-type denitrifying bacteria community, the relative abundances of Proteobacteria were high. T. aestivum and T. sinoaestivum inoculation did not affect the diversity of denitrifying bacteria. The mating type genes MAT1-1-1 and MAT1-2-1 were detected in the rhizosphere of C. illinoinensis inoculated with T. sinoaestivum and T. aestivum, and MAT1-1-1 dominated over MAT1-21. (c) 2021 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Melamine has been illegally adulterated in dairy food because of the rich nitrogen content and stable chemical properties in recent years. Therefore, the detection of melamine is of great significance for food safety supervision and human health protection. As melamine is a weak fluorescent substance, it is difficult to detect melamine directly by fluorescence spectroscopy. In this work, we found that melamine can significantly enhance the emission of the tetracycline–europium (EuTC) complex at 616 nm. Therefore, we took EuTC complex as a fluorescent probe to detect melamine. According to the characterizations of absorption spectra, molecular electrostatic potential distribution, and the time-resolved spectra, we speculated that tetracycline and melamine may form a complex through hydrogen bonding interaction in the melamine-EuTC reaction system, causing the melamine closer approach to Eu3+ and reducing the non-radiative energy loss of water molecules to Eu3+, which significantly enhanced the fluorescence intensity of EuTC. The fluorescence intensity of EuTC complex with melamine concentration in the range of 0.5–40.0 μM shows a good linear relationship, and the correlation coefficient is 0.9951 with the detection limit of 7.85 × 10−8 M. It shows a high sensitivity for the EuTC complex as a fluorescent probe to detect melamine, which provides a supplement and extension for the detection of melamine by fluorescence spectroscopy.

Available freshwater resources are becoming harder to obtain due to climate change, population growth, industrial development, and water pollution. The main technologies in the field of wastewater desalination include reverse osmosis, electrodialysis, thermal distillation, and adsorption etc. Capacitive deionization technology (CDI) belongs to a novel electrochemical desalination technology with low energy consumption and low environmental impact, simple equipment structure and convenient operation. With the importance of wastewater desalination highlighted, some great technological progress of CDI has been made in electrode materials, reactor structure and the hybrid process. In this paper, the development of CDI technology was expounded from three aspects to achieve the goal of strong adaptability, low cost and strong adsorption capacity by analysis of the latest research papers. Corresponding improved methods of CDI are summarized to solve the main technology bottlenecks such as the inefficient and vulnerable electrode materials, low selectivity and unreasonable unit structure, and limitations of single CDI unit for promoting the continuous development of CDI technology. HIGHLIGHTS The main technology bottlenecks of CDI were analyzed from three aspects.; Review the development of CDI based on electrode material, novel process and hybrid process.; New electrode materials are introduced and analyzed for the future development of CDI.; The energy consumption of novel FCDI-NF hybrid process is significantly reduced.

Composed of a three-dimensional structure with a central core and multiple radiating linear “arms”, star polymers represent a significant type of branched macromolecular architectures. Due to the spatially defined core–shell-periphery architecture, star polymers have demonstrated their superiority in a variety of biomedical applications such as drug/gene delivery, molecular imaging, antibacterial agents, and so on. In this paper, we report the successful synthesis of a new type of star-shape poly(β-amino esters) with low molecular weight PEI as core and linear PAE (LPAE) as arms. This new star-PAE exhibits low cytotoxicity and high gene transfection efficacy. Star-PAE achieved between 264-fold and 14781-fold higher gene transfection efficiency of primary rat adipose derived mesenchymal stem cells in comparison with studies performed with the individual PEI and LPAE, respectively. The results suggest that star-PAE is a promising nonviral gene delivery vector.

The stability properties of dark solitons in quasi-one-dimensional Bose–Einstein condensate (BEC) loaded in a Jacobian elliptic sine potential with three-body interactions are investigated theoretically. The solitons are obtained by the Newton-Conjugate Gradient method. A stationary cubic-quintic nonlinear Schrödinger equation is derived to describe the profiles of solitons via the multi-scale technique. It is found that the three-body interaction has distinct effect on the stability properties of solitons. Especially, such a nonlinear system supports the so-called dark solitons (kink or bubble), which can be excited not only in the gap, but also in the band. The bubbles are always linearly and dynamically unstable, and they cannot be excited if the three-body interaction is absent. Both stable and unstable kinks, depending on the physical parameters, can be excited in the BEC system.

Aqueous zinc batteries dominate the primary battery market with alkaline chemistries and recently have been rejuvenated as rechargeable devices to compete for grid-scale energy storage applications. Tremendous effort has been made in the past few years and improved cyclability has been demonstrated in both alkaline, neutral, and mild acidic systems. In this review/perspective, we will elucidate the merits of rechargeable aqueous zinc batteries through side-by-side comparison to Li-ion batteries, examine the challenges and progress made in the pursuit of highly rechargeable alkaline and mild acidic batteries, and finally provide a holistic forward look at the technology. The focus is placed on static closed cell designs, while flow batteries and open systems like zinc-air batteries will not be included due to space constraint.

In this paper, an effective linearized element-free Galerkin (EFG) method is developed for the numerical solution of the complex Ginzburg–Landau (GL) equation. To deal with the time derivative and the nonlinear term of the GL equation, an explicit linearized procedure is presented. The unconditional stability and the error estimate of the procedure are analyzed. Then, a stabilized EFG method is proposed to establish linear algebraic systems. In the method, the penalty technique is used to facilitate the satisfaction of boundary conditions, and the stabilized moving least squares approximation is used to enhance the stability and performance. The linearized EFG method is a meshless method and possesses high precision and convergence rate in both space and time. Theoretical error and convergence of the linearized EFG method are analyzed. Finally, some numerical results are provided to demonstrate the efficiency of the method and confirm the theoretical results.

We propose a mathematical model based on probability theory to optimize COVID‐19 testing by a multistep batch testing approach with variable batch sizes. This model and simulation tool dramatically increase the efficiency and efficacy of the tests in a large population at a low cost, particularly when the infection rate is low. The proposed method combines statistical modeling with numerical methods to solve nonlinear equations and obtain optimal batch sizes at each step of tests, with the flexibility to incorporate geographic and demographic information. In theory, this method substantially improves the false positive rate and positive predictive value as well. We also conducted a Monte Carlo simulation to verify this theory. Our simulation results show that our method significantly reduces the false negative rate. More accurate assessment can be made if the dilution effect or other practical factors are taken into consideration. The proposed method will be particularly useful for the early detection of infectious diseases and prevention of future pandemics. The proposed work will have broader impacts on medical testing for contagious diseases in general.

Manganese-rich layered oxide materials hold great potential as low-cost and high-capacity cathodes for Na-ion batteries. However, they usually form a P2 phase and suffer from fast capacity fade. In this work, an O3 phase sodium cathode has been developed out of a Li and Mn-rich layered material by leveraging the creation of transition metal (TM) and oxygen vacancies and the electrochemical exchange of Na and Li. The Mn-rich layered cathode material remains primarily O3 phase during sodiation/desodiation and can have a full sodiation capacity of ca. 220 mAh g-1 . It delivers ca. 160 mAh g-1 specific capacity between 2-3.8 V with >86 % retention over 250 cycles. The TM and oxygen vacancies pre-formed in the sodiated material enables a reversible migration of TMs from the TM layer to the tetrahedral sites in the Na layer upon de-sodiation and sodiation. The migration creates metastable states, leading to increased kinetic barrier that prohibits a complete O3-P3 phase transition.

Little is known about the impact application of fertilizer and manure nutrients on the nutrient stoichiometry of crop–soil–microbe systems. We ask the question to what extent the nutrient availability in the microbe–soil–plant system may be affected by the application of fertilizers or manures. The influence of application of inorganic fertilizers or composted manure on the concentrations of carbon (C), nitrogen (N), and phosphorus (P) and their stoichiometric ratios in soil, microbial biomass, enzymes, and plant tissues within the rhizosphere of maize was investigated in a maize–wheat rotation established for 10 years in China. The higher rate of composted manure was most effective in increasing soil C, N, and P contents and the microbial biomass. Microbes changed biomass stoichiometry instead of regulating related enzyme secretion under different nutrient supplies. Although plants and microbes showed tight but different relationships with the two nutrient sources, competition for N consistently occurred. Pearson’s inter-correlation demonstrates stable Redfield-like C:N:P fractions existed in soil properties and related enzyme activity, but was not always found in crop and microbial biomass after fertilizer and manure application. The results indicate that soil microbial functioning and coupled feedback with the plants are important in maintaining the stability of fertilized/manured agricultural ecosystems.

Pt-Ni alloy nanoclusters are essential for high-performance catalysis, and the full description for the finite temperature properties is highly desired. Here we developed an efficient machine learning method to evaluate the accurate structure-stability correspondence in a Pt(85-x)-Nix nanocluster over the structural space with a dimension of 3.84 × 1025. On the basis of the physical model and big-data analysis, for the first time, we demonstrated that the segregation-extent bond order parameter (BOP) and the shell-resolved undercoordination ratio play the key roles in the structural stability. This a priori knowledge extremely reduced the computational costs and enhanced the accuracies. With the 500-sample train data set generated by density functional theory (DFT)-level geometry optimizations, we fit the machine-learning excess energy potential and verified the mean-square-error is

Sodium-ion batteries are promising candidates for energy storage application, but the absence of high-capacity and low-cost anode materials significantly limits their practical specific energy and ...

A silicon (Si) anode is a high-capacity alternative for carbonaceous anodes in lithium ion batteries. However, a large volume change during cycling and continuous side reactions with the electrolyt...

It is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe–N–C catalysts using zeolite imidazole framework (ZIF-8) and iron (III) thiocyanate (Fe(SCN)3) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)3 is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)3 molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe–N4 complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 ​m2 ​g−1 and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 ​M HClO4 electrolyte and 0.1 ​M KOH electrolyte, in which the half-wave potential reaches 0.81 ​V and 0.92 ​V (vs. RHE), respectively. Remarkable stability is also attained, which loses 2 ​mV only after 10000 potential cycles in O2-saturated 0.1 ​M HClO4 and remains almost constant in O2-saturated 0.1 ​M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.

Conventional wound healing materials suffer from low efficiency, poor mechanical strength, and nontunable properties. Responsive hydrogels are appealing candidates for tissue engineering. Herein, we developed a double-cross-linked hydrogel system composed of hyperbranched PEG-based polymer, comprising pre-cross-linked acetal structure and numerous terminal acrylate groups, which can form hydrogels in situ and can be further strengthened by UV irradiation. The hyperbranched glycidyl methacrylate-co-poly(ethylene glycol) diacrylate polymers (HB-GMA-PEGs) were first synthesized via in situ deactivation enhanced atom transfer radical polymerization (DE-ATRP). A series of pre-cross-linked materials were achieved after postfunctionalization. The material can absorb a high amount of water to form hydrogels, and the gel stiffness was evaluated in detail before and after UV irradiation. The in vitro cytotoxicity experiments were conducted with the resulting materials and have demonstrated their good biocompatibili...

The Burton-Miller boundary integral formulation is solved by a complex variable boundary element-free method (CVBEFM) for the boundary-only meshless analysis of acoustic problems with arbitrary wavenumbers. To regularize both strongly singular and hypersingular integrals and to avoid the computation of the solid angle and its normal derivative, a weakly singular Burton-Miller formulation is derived by considering the normal derivative of the solid angle and adopting the singularity subtraction procedures. To facilitate the implementation of the CVBEFM and the approximation of gradients of the boundary variables, a stabilized complex variable moving least-square approximation is selected in the meshless discretization procedure. The results show the accuracy and efficiency of the present CVBEFM and reveal that the method can produce satisfactory results for all wavenumbers, even for extremely large wavenumbers such as κ = 10 000.

The augmented moving least squares (AMLS) approximation is a meshless scheme to construct continuous functions by using fundamental solutions as basis functions. By incorporating the AMLS approximation into the method of fundamental solutions (MFS), the localized MFS can significantly reduce the computational load and accelerate the solution progress of the MFS. In this paper, error estimates of the AMLS approximation and the localized MFS are established for anisotropic heat conduction problems. Numerical examples are also presented to verify the convergence and accuracy of the methods.

The cycling performance of batteries is largely determined by the electrode-electrolyte interphase associated with the chemical and electrochemical properties of electrolyte salts and solvents. In ...

In solid basic catalysis field, how to achieve optimized activity and desired stability through elaborate control over basic site properties remains a challenge. In this work, taking advantage of the structure memory effect of layered double hydroxides (LDHs), rehydrated Ca4Al1-xGax-LDHs and Ca4Al1-xInx-LDHs catalysts were prepared and applied in aldol condensation reaction that isobutyraldehyde (IBD) reacts with formaldehyde (FA) to obtain hydroxypivalaldehyde (HPA). Notably, the resulting re-Ca4Al0.90Ga0.10-LDHs exhibits an extraordinarily-high catalytic activity (HPA yield: 72%), which is to our best knowledge the highest level in this reaction. The weak Bronsted basic site, 7-coordinated Ca-OH group, which serves as an active site, catalyzes the condensation process and promotes the product desorption. Studies on structure-property correlations demonstrate that Ga as a structural promoter induces a moderate expansion of the laminate lattice, which results in a significant increase in the concentration of weak basic sites in re-Ca4Al0.90Ga0.10-LDHs, accounting for its high catalytic activity. This work illuminates that geometric structure of basic active sites can be tuned via introducing catalyst additive, which leads to a largely improved performance of hydrotalcite solid basic catalysts towards aldol condensation reaction.

Oxygen vacancies (OVs) have emerged as an efficient strategy to modulate the electronic structures, conductivity, and electrochemical properties of WO3. However, the OVs are easily absorbed by wate...

In this paper, we use finite element analysis (FEA) to study the linear viscoelastic response of polyurea, a type of hard–soft block copolymer. A Niblack’s algorithm-based technique employed on atomic force microscopy images provides geometry inputs for the FEA model, while the viscoelastic master curves of the soft matrix are obtained via a combination of dynamic mechanical analysis data and molecular dynamic (MD) estimations. In this microstructural image-based FEA framework, we introduce an interphase area of altered properties between the hard and soft domains. Both spatial and property distributions of this interphase area affect the viscoelastic response of the copolymer system. To quantitatively investigate the impact of structural and property features of the interphase on the energy storage and dissipation of a system during linear perturbation, we develop a statistical descriptor representation of the interphase region related to physical parameters. Utilizing decision-tree and random forest concepts from machine learning, we apply a ranking algorithm to identify the most significant features for four different mechanical response descriptors. Results show that the total interphase volume fraction and shifting factor distributions in the interphase area dominate the magnitude of the tan δ peak, whereas the magnitudes of the shifting factors primarily affect the tan δ peak location in frequency space. This method allows us to readily identify the dominant features impacting individual properties and paves the way for material design of hard–soft block copolymer systems.

The localized method of fundamental solutions (LMFS) is an efficient meshless collocation method that combines the concept of localization and the method of fundamental solutions (MFS). The resultant system of linear algebraic equations in the LMFS is sparse and banded and thus, drastically reduces the storage and computational burden of the MFS. In the LMFS, the moving least square (MLS) approximation, based on fundamental solutions, is used to construct approximate solution at each node. In this paper, this fundamental solutions-based MLS approximation, named as an augmented MLS (AMLS) approximation, is generalized to any point in the computational domain. Computational formulas, theoretical properties and error estimates of the AMLS approximation are derived. Then, taking Laplace equation as an example, this paper sets up a framework for the theoretical error analysis of the LMFS. Finally, numerical results are presented to verify the efficiency and theoretical results of the AMLS approximation and the LMFS. Convergence and comparison researches are conducted to validate the accuracy, convergence and efficiency.

A Burton-Miller boundary element-free method is developed by using the Burton-Miller formulation for meshless and boundary-only analysis of Helmholtz problems. The method can produce a unique solution at all wavenumbers and is valid for Dirichlet, Neumann and mixed problems simultaneously. An efficient numerical integration procedure is presented to handle both strongly singular and hypersingular boundary integrals directly and uniformly. Numerical results reveal that this direct meshless method only involves boundary nodes and can deal with Helmholtz problems at extremely large wavenumbers.

A complex variable boundary point interpolation method (CVBPIM) is presented for numerical analysis of the nonlinear Signorini problem. To reduce the computational cost and to improve the stability of the point interpolation method, a complex variable point interpolation method (CVPIM) is developed to construct meshless shape functions with interpolation properties. By using a projection technique to deal with the nonlinear inequality boundary conditions, and combining boundary integral equations with the CVPIM to establish discrete linear algebraic systems, the CVBPIM is an easy-to-implement and boundary-only meshless method for nonlinear Signorini problems. Numerical results are presented to show the accuracy and efficiency of the method.

An augmented moving least squares (AMLS) approximation is presented in this paper for constructing approximate functions in meshless methods. The basis functions in the AMLS approximation, differ from monomial basis functions in the classical moving least squares (MLS) approximation, involve fundamental solutions of the underlying differential equations, and thus enhance the performance of the MLS approximation. As the MLS approximation, the AMLS approximation can also be used for curve and surface fitting. Numerical examples involving 2D and 3D Laplace, Helmholtz and modified Helmholtz equations in complicated domains reveal that the accuracy of the AMLS approximation is about 104 ~ 106 times higher than that of the MLS approximation.

Currently adopted cross-linking methods in rubber industry are suffering from variable persistent issues, including the utilization of toxic curing packages, release of volatile organic compounds (VOCs) and difficulties in the recycling of end-of-life materials. It is of great importance to explore a green cross-linking strategy in the area. Herein, we report a new “green” strategy based on hydrolyzable ester cross-links for cross-linking diene-typed elastomers. As a proof of concept, a commercial carboxylated nitrile rubber (XNBR) is efficiently cross-linked by a bio-based agent, epoxidized soybean oil (ESO), without any toxic additives. ESO exhibits an excellent plasticization effect and excellent scorch safety for XNBR. The cross-linking density and mechanical properties of the ESO-cured XNBR can be manipulated in a wide range by changing simply varying the content of ESO. In addition, zinc oxide (ZnO) performs as a catalyst to accelerate the epoxide opening reaction and improve the cross-linking efficiency, serving as reinforcement points to enhance the overall mechanical properties of the ESO-cured XNBR. Furthermore, the end-of-life elastomer materials demonstrate a closed-loop recovery by selectively cleaving the ester bonds, resulting in very high recovery of the mechanical performance of the recycled composites. This strategy provides an unprecedented green avenue to cross-link diene elastomers and a cost-effective approach to further recycle the obtained cross-linked elastomers at high efficiency.

Soil bacteria are widely recognized for their roles in nutrient cycling, such as for nitrogen and phosphorus, and for promoting soil health. However, the relationship between soil bacteria and the availability of calcium, magnesium, iron, manganese, copper and zinc under different climatic conditions in orchard systems remains poorly understood. Here, we explored the relationship between soil bacteria and metal nutrient availability and uptake by apple trees based on 36 soil samples from three climate zones that span the major apple-producing areas in China. The results indicated that six phyla (e.g., Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Nitrospirae, and Proteobacteria) in the soil bacterial communities were positively related to the metal nutrients availability, especially to calcium (16 OTUs) and magnesium (19 OTUs). At the class level, Alphaproteobacteria improved the availability of calcium, magnesium, iron, manganese and copper, while Actinobacteria improved the availability of zinc and altered absorption by the roots and the contents in leaves. We found that the underground bacterial community diversity was determined by climatic conditions and soil properties, which altered the effect of bacteria on soil metal nutrients availability, and led to differences of nutritional content in the aboveground plant portions. Therefore, soil bacteria played a central role in this process for sustainable development in apple orchard systems.

O3-layered metal oxides are promising cathode materials for high-energy Na-ion batteries (SIBs); however, they suffer from fast capacity fade. Here, we develop a high-performance O3-NaNi0.68Mn0.22C...

In this paper, we focus on the task query-based video localization, i.e., localizing a query in a long and untrimmed video. The prevailing solutions for this problem can be grouped into two categories: i) Top-down approach: It pre-cuts the video into a set of moment candidates, then it does classification and regression for each candidate; ii) Bottom-up approach: It injects the whole query content into each video frame, then it predicts the probabilities of each frame as a ground truth segment boundary (i.e., start or end). Both two frameworks have respective shortcomings: the top-down models suffer from heavy computations and they are sensitive to the heuristic rules, while the performance of bottom-up models is behind the performance of top-down counterpart thus far. However, we argue that the performance of bottom-up framework is severely underestimated by current unreasonable designs, including both the backbone and head network. To this end, we design a novel bottom-up model: Graph-FPN with Dense Predictions (GDP). For the backbone, GDP firstly generates a frame feature pyramid to capture multi-level semantics, then it utilizes graph convolution to encode the plentiful scene relationships, which incidentally mitigates the semantic gaps in the multi-scale feature pyramid. For the head network, GDP regards all frames falling in the ground truth segment as the foreground, and each foreground frame regresses the unique distances from its location to bi-directional boundaries. Extensive experiments on two challenging query-based video localization tasks (natural language video localization and video relocalization), involving four challenging benchmarks (TACoS, Charades-STA, ActivityNet Captions, and Activity-VRL), have shown that GDP surpasses the state-of-the-art top-down models.

Nano-modified bitumen binders can be tailored to exhibit excellent properties for potential application in pavement engineering. However, a homogeneous dispersion of nano-materials in bitumen is still a challenge, which obscures the maximum property improvement of bitumen that can be achieved. In this study, a CNT sponge, which is a macroscopic assembly of nanotubes and represents one of the most promising lightweight carbon nanomaterials with homogeneous three-dimensional network and a high porosity, was used to reinforce bitumen. Bitumen can autonomously penetrate into the porous CNT sponge, and fill up all the pores, forming a bitumen/CNT nanocomposite with homogeneous CNT dispersion quality. We found that, the addition of CNTs significantly improves the performance of bitumen at elevated temperatures, as indicated by the much improved properties of stiffness, rutting resistance, creep and recovery behavior as well as high-temperature stability. Such effective modification of bitumen by CNT are ascribed to the highly uniform dispersion of CNTs, as well as the percolation structure formed throughout bitumen matrix. This study highlights the importance of CNT dispersion quality, and sheds light on the bitumen property improvement that could be achieved.

Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm−2) deliver ~750 mAh g−1 specific capacity, 92% capacity retention over 500 cycles. This work is a leap in silicon anode development and provides insights into the design of electrode materials for other batteries., The authors here construct hierarchical porous CNT@Si@C microspheres as anodes for Li-ion batteries, enabling both high electrochemical performance and excellent mechanical strength. The work highlights the importance of mechanical properties in developing battery materials for practical applications.

The distributed delay was firstly proposed by Volterra in the 1930s since it is more realistic than discrete delay and has been introduced in many dynamical systems. In this paper, we establish a diffusive viral infection model with general incidence function and distributed delays subject to the homogeneous Neumann boundary conditions. Firstly, we prove the existence, uniqueness, positivity and boundedness of solutions of the model. Then, by using the linearization method and constructing appropriate Lyapunov functionals, we show that the global dynamics of the model is determined by the reproductive numbers for viral infection $$\mathcal {R}_{0}$$ , which implies that the global stability of the model precludes the existence of complex dynamical behaviors such as Hopf bifurcation and patter formation. Furthermore, an example is presented and numerical simulations are also carried out to illustrate the main results.

It remains urgent to make continuous efforts on well-designed and highly active non-precious metal (NPM) electrocatalysts for the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), thus helping greatly reduce the fuel cell cost. Due to an unsatisfied stability caused by Fenton reaction for Fe-based materials, Co-based materials bear much more expectations as one type of NPM electrocatalysts to be applied in the ORR. Here we report a novel strategy to synthesize a series of mesoporous nitrogen-doped carbon-supported cobalt electrocatalysts (Co-DCD-CA), which takes full advantage of electrostatic interaction between carboxyl in citric acid (CA) and amidogen in dicyandiamide (DCD) as well as chelating interaction between citric acid and cobalt cation. When CA is employed as carbon source, the optimal derivative of the Co-DCD-2-CA-900 electrocatalyst exhibits a higher ORR activity with a half-wave potential at 0.75 V, which is 60 mV higher than that prepared using Ketjenblack EC 300 J (Co-DCD-2-EC-900) as the carbon support. Besides, the effects of pyrolysis temperature as well as DCD to CA ratio on the ORR activity are detailedly investigated.

Data-driven methods have attracted increasingly more attention in materials research since the advent of the material genome initiative. The combination of materials science with computer science, statistics, and data-driven methods aims to expediate materials research and applications and can utilize both new and archived research data. In this paper, we present a data driven and deep learning approach that builds a portion of the structure–property relationship for polymer nanocomposites. Analysis of archived experimental data motivates development of a computational model which allows demonstration of the approach and gives flexibility to sufficiently explore a wide range of structures. Taking advantage of microstructure reconstruction methods and finite element simulations, we first explore qualitative relationships between microstructure descriptors and mechanical properties, resulting in new findings regarding the interplay of interphase, volume fraction and dispersion. Then we present a novel deep learning approach that combines convolutional neural networks with multi-task learning for building quantitative correlations between microstructures and property values. The performance of the model is compared with other state-of-the-art strategies including two-point statistics and structure descriptor-based approaches. Lastly, the interpretation of the deep learning model is investigated to show that the model is able to capture physical understandings while learning.

In this paper, the variational multiscale interpolating element-free Galerkin (VMIEFG) method is developed to obtain the numerical solution of the nonlinear Darcy–Forchheimer model. We use the interpolating moving least squares method instead of the moving least squares approximation to construct meshless shape functions with delta function properties. Then the flux boundary condition of the Darcy–Forchheimer model can be handled easily. Hughes’ variational multiscale (HVM) method is applied to overcome the numerical oscillation caused by equal-order basis for the velocity and pressure. Moreover, the HVM ensures that the resultant formulation in the VMIEFG method is consistent and the stabilization parameter (or tensor) appears naturally. Consequently, the stabilization parameter is free of user-defined. The fixed point iteration method is used to deal with the nonlinear term. Some numerical examples are provided to illustrate the stability and performance of the proposed method for solving the nonlinear Darcy–Forchheimer model.

The calorific value of coal mainly depends on the content of combustible organic elements and ash, and is a comprehensive indicator of coal quality. It is of great significance to quickly obtain the calorific value of coal entering the boiler for the optimal control of coal blending and combustion in thermal power generation. However, the measurement repeatability of LIBS for the coal calorific value has not yet met the requirement of a standard deviation (SD) of less than 120 J g−1 in the Chinese national standard. This paper innovatively proposes an analytical method of XRF-assisted LIBS, which can not only analyze the combustible organic light elements by LIBS, but also can analyze the inorganic ash-forming elements by XRF with high stability, thus greatly improving the measurement repeatability of the coal calorific value. According to the stability of intensity, the elemental emission lines in the LIBS and XRF spectra are selected reasonably, and the prediction model is established through principal component analysis and multiple regression. The experimental results show that the SD of coal calorific values predicted is 72 J g−1, which is one order of magnitude lower than the 700 J g−1 of traditional LIBS, and fully meets the requirement of the national standard. It is found that the measurement instability of the calorific value mainly comes from the contribution of the C line, and the SD of the calorific value can be further reduced to 56 J g−1 by means of spectral screening. This XRF-assisted LIBS technology with ultra-repeatability is expected to be applied in power plants, coal chemical industries and other industrial fields that need to pay close attention to coal quality.

Tuning the compositions and structures of Pd-based nanomaterials and their supports has shown great potentials in facilitating the sluggish ethanol oxidation reaction (EOR) in alkaline direct ethan...

The shuttling effect of the polysulfide (PS) is the most detrimental factor that causes capacity fading of Li–S batteries. By substituting carbon atoms with heteroatoms, the host materials can prov...

Glycerol (GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals (mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite (denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid (GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations (XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptδ+ species at metal-support interface, which accelerates bond cleavage of α-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.

Fe3O4@PANI@rGO/EP coating with a tunable surface roughness was prepared by a facile spraying method under the assistance of magnetic field for enhancing microwave absorption properties. The structure and microwave absorption properties of nanocomposite coating were characterized and compared as a function of magnetic field. It was found that the surface roughness of nanocomposite coating increased with increasing in magnetic field, which further improved the microwave absorption performance. Fe3O4@PANI@rGO/EP with a surface roughness of 1.93 μm showed a minimum RL value of − 28.2 dB at 10.5 GHz with a thickness of only 1.0 mm and a bandwidth of 5.5 GHz from 8.1 to 13.6 GHz (

The long-term performance of current heat-resistant ferritic steels used in steam generators is primarily limited by microstructure degradation as a result of coarsening or transformation of precipitates. To improve the microstructural stability, a heat-resistant ferritic steel was designed via computational thermodynamics to exclusively contain metal carbonitride (MX) precipitates as the primary means for strengthening at elevated temperatures. The volume fraction of precipitates is 0.35 vol pct, about one-seventh of P91. These MX precipitates are either V-rich or Nb-rich with plate-like or spheroidal morphology, respectively. The precipitate size remains almost constant at 973 K for up to 3000 hours aging. Electron diffraction analysis revealed a Baker-Nutting orientation relationship between the precipitate and the matrix. Consistent with the thermodynamics-based design, M23C6-, Laves-, and Z phase were not detected. The creep threshold stress, derived from high-temperature compressive creep tests, are evaluated to be 63 ± 1 and 43 ± 2 MPa at 923 K and 973 K, respectively, on par with or slightly better than P91. This study reveals that MX precipitates in ferritic steels coarsen slowly at temperatures up to 973 K and that a relatively small volume fraction of MX precipitates can provide effective long-term creep performance at elevated temperatures.

SF6 has good insulation performance and is widely used in power equipment. But as climate change intensifies, the need for substitute gases is growing. While a lot of research focusing on the insulation performance of substitute gases has been done, little has been focused on their effects on temperature rise, though temperature rise is important for the safe operation of the power equipment. In this article, a 40.5-kV medium-voltage cubic gas-insulator switchgear (C-GIS) is modeled and simulated by the electromagnetic-fluid-temperature multiphysical coupled method. By implementing CFX Expression Language (CEL), the influence of temperature on thermal conductivity, density, viscosity, and specific heat capacity of gas is able to be coupled into the simulations, thus improving the accuracy of the simulations. The airflow and temperature distribution of the C-GIS with SF6 are obtained, and the temperature rise distribution is verified by experimental results. On this basis, simulation studies are conducted to analyze the influence of different filling gases on the temperature rise of the C-GIS. First, the influence of single filling gases including N2, CO2, and pressurized air is analyzed by the simulations. Second, the temperature rise distributions of the C-GIS when filled with a mixture of SF6 and N2 with different proportions of mole fraction are also obtained. By analyzing the changes in temperature rise distribution under different situations, it can be found that the temperature rise with N2, CO2, or pressurized air is relatively high. When the gas mixture is used, the maximum temperature tends to decrease with the increase of SF6 usage. According to the results of this article, it can provide a reference for selecting suitable substitute gas of SF6.

In the past few years, great progress has been made in nonprecious metal catalysts, which hold the potential as alternative materials to replace platinum in proton exchange membrane fuel cells. One type of nonprecious metal catalyst, Fe-N-C, has displayed similar catalytic activity as platinum in rotating disk electrode tests; however, rapid degradation of Fe-N-C catalyst-based fuel cells is always observed, which limits its practical application. Although considerable research has been devoted to study the degradation of the catalyst itself, rather less attention has been paid to the membrane electrode assembly that makes the mechanism of fuel cell degradation remain unclear. In this work, a high-performance Fe-N-C catalyst-based membrane electrolyte assembly is prepared and used to study its degradation mechanism. The fuel cell performs with an initial peak power density as high as 1.1 W cm-2 but suffers a current loss of 52% at 0.4 V over 20 h only. The experimental and DFT calculation results indicate that Fe at active sites of catalysts is attacked by hydroxyl free radicals decomposed from H2O2, which is further leached out, causing an increase in activity loss. The ionomer of the catalyst layer and the membrane is further contaminated by the leached Fe ions, which results in an enlarged membrane resistance and cathode catalyst layer proton conduction resistance, greatly influencing the cell performance. In addition, it has been assumed in previous studies that the quick performance loss of Fe-N-C-based fuel cells is caused by water flooding within the catalyst layer, which is proved to be incorrect in our study through a dry-out experiment.

Two isomeric benzodithiophene-fused perylene diimides, BPDI-1 and BPDI-2, are designed and synthesized via photo-induced ring-closure reaction between perylene diimide (PDI) acceptor and both isomeric benzodithiophene donor cores, including benzo[2,1-b:3,4-b']dithiophene (BDP) and benzo[1,2-b:4,3-b']dithiophene (BdT). The effect of structural isomerism on the molecular geometry, absorption, energy level, film morphology as well as photovoltaic performance is comparatively studied. It is found that the variation of the S atom substituted position in the donor cores results in distinct molecular geometries for the newly-developed BPDI-1 and BPDI-2 acceptors. Compared with BDP-containing BPDI-1, the incorporation of BdT core endows BPDI-2 with a remarkably enhanced backbone distortion. When blended with the commercially available polymer donor (PTB7-Th), such twisted structure feature for the BPDI-2 acceptor plays a key role in reducing molecule aggregation, which is helpful for the enhancements of short-circuit current density and photovoltaic efficiency effectively. As a result, non-fullerene solar cells fabricated from BPDI-2 acceptor achieve higher photovoltaic efficiency (4.44%) than that of BPDI-1 (2.98%), mainly benefited from superior short-circuit current density. This work provides us comparative understanding of isomeric geometry and device performance.

During the legume-rhizobium symbiotic interaction, rhizobial invasion of legumes is primarily mediated by a plant-made tubular invagination called an infection thread (IT). Here, we identify a gene in Lotus japonicus encoding a leucine-rich repeat receptor-like kinase (LRR-RLK), RINRK1 (Rhizobial Infection Receptor-like Kinase1), that is induced by Nod factors (NFs) and is involved in IT formation but not nodule organogenesis. A paralog, RINRK2, plays a relatively minor role in infection. RINRK1 is required for full induction of early infection genes, including Nodule Inception (NIN), encoding an essential nodulation transcription factor. RINRK1 displayed an infection-specific expression pattern, and NIN bound to the RINRK1 promoter, inducing its expression. RINRK1 was found to be an atypical kinase localized to the plasma membrane and did not require kinase activity for rhizobial infection. We propose RINRK1 is an infection-specific RLK, which may specifically coordinate output from NF signaling or perceive an unknown signal required for rhizobial infection.

Fusarium wilt is a devastating fungal disease in strawberries caused by Fusarium spp. We aimed to determine the role of earthworms and arbuscular mycorrhizal (AM) fungi in preventing Fusarium oxysporum (Fof) infection in strawberry plants. AM fungi, Fof and the copy number of Actinomyces genes were determined by a quantitative real-time polymerase chain reaction. The Shannon–Wiener index for microbial communities was determined by their terminal restriction fragment length polymorphism profiles. Structural equation modelling was used to establish the relationships between the disease index and abiotic/biotic variables. Earthworms and AM fungi could individually or interactively prevent the infection of strawberry plants by Fof. Earthworms significantly decreased the copy number of Fof in the soil. The AM fungi increased the copy number of Actinomycetes and bacterial diversity and decreased the disease index of Fusarium wilt. Correlation analysis indicated that the root Ca and shoot Mg contents and the number of AM gene copies in plant roots had a significant negative correlation with the disease index of Fusarium wilt and the number of gene copies of Fof in plant roots. The addition of earthworms and AM fungi to soil is a promising biological control method for the prevention of Fusarium wilt in strawberries and acts via an increase in the soil organic matter content, regulation of the soil environment, and improved root (P, Ca, Mg and Fe) and shoot (N, P, K, Ca and Mg) nutrient contents.

Despite tremendous progress has been achieved in the past two decades, the lack of high-performance catalysts suitable for long-term operation remains a great challenge in realizing the commercial application of direct methanol fuel cell technology. Here, we reported a simple approach for one-pot synthesis of PtCu alloy nanoframes along with their exciting electro-catalytic performance for methanol oxidation. PtCu alloys with highly-open nanoframe structures have been achieved in presence of a structure-directing agent like polyvinyl pyrrolidone (PVP) and reducing solvent like sodium borohydride. Such PtCu alloy nanoframes show tremendous improvement in the methanol electrooxidation with a highest mass activity of 1.64 A mg Pt −1 (much lower onset potential compared to Pt alone), which is believed to be much higher compared to that of the commercial Pt/C catalyst and most of the literature reports, indicating a better alloy formation and highly active sites created by highly open nanoframes structures.

In addition to conventional linear, branched, crosslinked and dendritic polymers, single chain cyclized/knotted polymers (SCKPs) have emerged as a new class of polymer structure showing unique properties. Here, we report the development of bacterial resistant SCKPs and investigate how the single chain cyclized/knotted structure affects the performance of polymer materials in bacterial resistance. Four SCKPs were synthesized by reversible addition fragmentation chain transfer (RAFT) homopolymerization of multivinyl monomers (MVMs) and then crosslinked by ultraviolet (UV) light to form SCKP films. Regardless of MVM types, the four SCKP films always showed much higher bacterial resistance ability, and up to 75% of bacterial attachment and biofilm formation were reduced in comparison with the corresponding non‐SCKP films which are directly made from the polymerization of MVMs. These results highlight the critical role of the single chain cyclized/knotted structure in enhancing the bacterial resistance of polymeric materials. Further mechanistic studies revealed that the surface morphology and altered hydrophobicity induced by the single chain cyclized/knotted structure could account for the enhanced bacterial resistant performance of the SCKP films.