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Compared to conventional grinding, ultrasonic face grinding of SiC ceramic with vibration amplitude more than 3 μm has been proved to improve the machining efficiency but usually face the problem of reducing the workpiece surface quality. The material removal mechanism and ground surface quality by ultrasonic face grinding using minor vibration amplitude (less than 1 μm) still remains uncertain and needs to be further investigated. In the present work, experiments of ultrasonic face grinding of SiC ceramic are carried out to study the influence of processing parameters (e.g. depth of cut, wheel speed and ultrasonic vibration amplitude) on the surface finish. The results show that both the grinding forces and ground surface roughness increase significantly with the increase of depth of cut and the decrease of wheel speed. However, with the increase of ultrasonic vibration amplitude, the grinding forces decrease rapidly first and then keep steady, and the ground surface roughness shows three variation stages: dropping, climbing and stabilizing, which achieves the smallest value of 0.04 μm at the amplitude of 0.216 μm. From the analysis of acquired workpiece surface morphology and image processing result, the proportion of chunks and pits on the workpiece surface is reduced due to ductile removal in case of ultrasonic vibration amplitude less than 0.2 μm, but increases when the amplitude is more than 0.2 μm because the material is removed in brittle domain. Finally, a sample machined at relatively high wheel speed and minor vibration amplitude is provided to support the findings. The proposed investigation provides a new approach to achieve mirror surface of SiC ceramic using ultrasonic face grinding.

In this paper, using the variational principle, the existence and multiplicity of solutions for p x , q x -Kirchhoff type problem with Navier boundary conditions are proved. At the same time, the sufficient conditions for the multiplicity of solutions are obtained.

The B6Ca2 and B8Ca2 clusters adopt interesting inverse sandwich architectures, featuring a prolate B6 (or perfect B8) ring jammed with two capping Ca atoms. Both clusters show the high thermodynamic stability due to the double (σ and π) electronic delocalization. In present paper, we computationally studied the hydrogen storage of them. The results suggest that each Ca site in B6Ca2 and B8Ca2 clusters could store up six H2, yielding a gravimetric density of 14.2 wt% for B6Ca2 and 12.6 wt% for B8Ca2. The average adsorption energy for H2-adsorbed B6Ca2 and B8Ca2 complexes is within the scope of 0.12–0.15 eV per H2 at wB97XD level, hinting that two clusters could reversibly store and release hydrogen, which is positively confirmed by the Born-Oppenheimer molecular dynamics simulations. Both B6Ca2 and B8Ca2 nanoclusters are feasible hydrogen storage media under the ambient condition.

Climate- and weather-related disasters have become increasingly frequent and costly, resulting in substantial government spending on disaster assistance. Yet less is known about the effectiveness of disaster aid in enhancing community resilience to future disaster risks. This study examines multiple post-disaster aid programs implemented by the US federal government to support state and local governments as well as households and private businesses. Specifically, we estimate the risk-mitigating effects of these disaster-related programs by linking program spending with reported economic losses from flooding. Our empirical analysis utilizing panel data at the county level finds that low-interest disaster loans lead to the largest reduction in subsequent flooding damage, and grants targeting public infrastructure restoration and flood control measures also reduce future flooding losses. Results suggest a limited loss-mitigating effect of disaster cash aid given to private individuals. These findings provide important implications for federal disaster policy design and suggest that more efficiency gains could be realized by redistributing funds and streamlining processes across programs and agencies.

The oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephretidae), is a serious pest of fruits and vegetables and has developed high levels of insecticide resistance. ATP-binding cassette transporter genes (ABC transporters) are involved in mediating the energy-driven transport of many substances across membranes and are closely associated with development and insecticide detoxification. In this study, three ABC transporters in the H subfamily were identified, and the possible roles of these genes in B. dorsalis are discussed. Bioinformatics analysis revealed that those genes are conserved, typical of half-transporters. The expression profiles of BdABCH genes (BdABCHs) in the developmental stages, tissues, and following insecticide exposure, extreme temperature, warm- and cold-acclimated strain, starvation, and desiccation stress were determined by quantitative real-time PCR. Expression of BdABCHs can be detected in various tissues and in different developmental stages. They were most highly expressed in the hindgut and in newly emerged adults. The mRNA levels of BdABCHs in males (including most tissues and body segments) were higher than in females. The expression of BdABCH1 was significantly upregulated 3.8-fold in the cold-acclimated strain, and was significantly upregulated by 1.9-, 3.8- and 4.1-fold in the 0°C, starvation, and desiccation treatments, respectively. Treatment with malathion and avermectin at LD20 and LD30 concentrations produced no obvious changes in the levels of BdABCHs. BdABCHs may be involved in the transport of related hormones during eclosion, as well as water and inorganic salts. BdABCH1 also demonstrated that it is related to the ability to cope with adverse environments.

Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surface quality in terms of surface topography, subsurface microstructure, microhardness and residual stress obtained under different grinding conditions were evaluated comparatively. Experimental results indicated that the grinding force was influenced significantly by the competing predominance between the grinding parameters and the cross-sectional root workpiece profile. In addition, the root workpiece surface, including the root peak and valley regions, was produced with the large difference in surface quality due to the nonuniform grinding loads along the root workpiece profile in normal section. Detailed results showed that the surface roughness, subsurface plastic deformation and work hardening level of the root valley region were higher by up to 25%, 20% and 7% in average than those obtained in the root peak region, respectively, in the current investigation. Finally, the superior parameters were recommended in the creep feed profile grinding of the fir-tree blade root forms. This study is helpful to provide industry guidance to optimize the machining process for the high-valued parts with complicated profiles.

Zhengzhou is one of the most heavily polluted cities in China. This study collected samples of PM2.5 (atmospheric fine particulate matter with aerodynamic diameter ≤ 2.5 μm) at five sites in different functional areas of Zhengzhou in 2016 to investigate the chemical properties and sources of PM2.5 at three pollution levels, i.e., PM2.5 ≤ 75 μg/m3 (non-pollution, NP), 75 μg/m3 150 μg/m3 (heavy pollution, HP). Chemical analysis was conducted, and source categories and potential source region were identified for PM2.5 at different pollution levels. The health risks of toxic elements were evaluated. Results showed that the average PM2.5 concentration in Zhengzhou was 119 μg/m3, and the sum of the concentrations of SO42−, NO3−, and NH4+ increased with the aggravation of pollution level (23, 42, and 114 μg/m3 at NP, MP, and HP days, respectively). Positive Matrix Factorization analysis indicated that secondary aerosols, coal combustion, vehicle traffic, industrial processes, biomass burning, and dust were the main sources of PM2.5 at three pollution levels, and accounted for 38.4%, 21.6%, 16.7%, 7.4%, 7.7%, and 8.1% on HP days, respectively. Trajectory clustering analysis showed that close-range transport was one of the dominant factors on HP days in Zhengzhou. The potential source areas were mainly located in Xinxiang, Kaifeng, Xuchang, and Pingdingshan. Significant risks existed in the non-carcinogenic risk of As (1.4–2.3) for children at three pollution levels and the non-carcinogenic risk of Pb (1.0–1.4) for children with NP and MP days.

Workers of Apis cerana cerana undergo an in-hive nursing to outdoor foraging transition, but the genes underlying this age-related transition remain largely unknown. Here, we sequenced the head transcriptomes of its 7-day-old normal nurses, 18- and 22-day-old normal foragers, 7-day-old precocious foragers and 22-day-old over-aged nurses to unravel the genes associated with this transition. Mapping of the sequence reads to Apis mellifera genome showed that the three types of foragers had a greater percentage of reads from annotated exons and intergenic regions, whereas the two types of nurses had a greater percentage of reads from introns. Pair- and group-wise comparisons of the five transcriptomes revealed 59 uniquely expressed genes (18 in nurses and 41 in foragers) and 14 nurse- and 15 forager-upregulated genes. The uniquely expressed genes are usually low-abundance long noncoding RNAs, transcription factors, transcription coactivators, RNA-binding proteins, kinases or phosphatases that are involved in signaling and/or regulation, whereas the nurse- or forager-upregulated genes are often high-abundance downstream genes that directly perform the tasks of nurses or foragers. Taken together, these results suggest that the nurse-forager transition is coordinated by a social signal-triggered epigenetic shift from introns to exons/intergenic regions and the resulting transcriptional shift between the nurse- and forager-associated genes.

The substitutional solute atom induced local lattice distortion (LLD) in dilute metal solid solution was believed to be uniform that may even be modeled by using soap bubble raft. Contrary to this conventional picture, we report in this manuscript that the Mo induced LLD in dilute Ti-Mo solid solution is highly non-uniform as evidenced by our first principles calculations. The non-uniform LLD is ascribed to the Jahn-Teller splitting of the degenerated d states of Mo atom. We propose that the substitutional solid solutions with non-uniform LLD should satisfy two conditions. With which, the solid-solutions suffering from non-uniform LLD are predicted. The non-uniform LLD is expected to result in non-spherical stress field around the solute atom, and, therefore, challenges the application of classical solid solution hardening model to this kind of solid solutions., Comment: 8 pages and 4 figures

In recent years, the ecological environment along highways in Tibetan Plateau has been severely affected due to the rapid construction of highways. In order to solve the problems of multiple indicators and inconsistent criteria in the ecological impact assessment of highways, and to scientifically screen assessment indicators, the paper proposes a multi-round indicator screening method, which combines literature analysis, expert rating, and statistical analysis. Based on this screening method, normalized difference vegetation index, land surface temperature, elevation, and normalized difference soil index are screened out. Combined with multiple linear regression, an ecological impact assessment model is established and applied to ecological impact assessment of Gonghe-Yushu Expressway. The results show that the expressway construction is the first driving force for the deterioration of the ecological environment along the roadside, and its interference range on the desert grassland ecosystem is greater than that on the agroforestry system. The ecological environment within 150 m on both sides of the expressway should be protected.

The B6Be2 and B8Be2 clusters, adopting fascinating inverse sandwich-like geometries, were recently predicted with quantum chemical calculations. Both systems exhibit the high stability and double aromaticity with 4σ/6π or 6σ/6π delocalized electrons. The hydrogen storage of two systems is studied in the present paper. Our calculations show that B6Be2 and B8Be2 clusters have the ultra-high capacity hydrogen storage, each Be site can bound up with seven H2 molecules, corresponding to a gravimetric density of 25.3 wt percentage (wt%) for B6Be2 and 21.1 wt% for B8Be2, respectively, which far exceeds the target (5.5 wt%) proposed by the US department of energy (DOE) in 2017. The average absorption energies of 0.10–0.45 eV/H2 for B6Be2 and 0.11–0.50 eV/H2 for B8Be2 at the wB97XD level suggest that both systems are ideal for reversible hydrogen storage and release. The reversibility of H2 molecules on B6Be2 and B8Be2 complexes are faithfully demonstrated with the Born-Oppenheimer molecular dynamics (BOMD) simulations. The Be-doped boron nanostructure is a promising candidate for ultra-high hydrogen storage materials.

Computational evidence is reported on a boron-based ternary Rb6Be2B6 cluster as the “Big Mac” sandwich on a subnanoscale with thickness of 0.58 nm. The core hexagonal B6 ring, occurring in the naked form due to double 6π/6σ aromaticity, is capped by two tetrahedral BeRb3 ligands. Such a B6 motif is scarce in boron clusters. The sandwich cluster has four-fold 2σ/6π/6σ/2σ aromaticity and its tetrahedral BeRb3 ligand is the simplest case of three-dimensional aromaticity (or spherical aromaticity). The sandwich can be formulated as a charge-transfer complex, [Rb3Be]3+[B6]6−[BeRb3]3+, whose components are held together by robust electrostatics, facilitating dual-mode dynamic fluxionality.

The typical electron-deficiency of the boron element renders fascinating architectures and chemical bonding to boron-based nanoclusters. We theoretically predict two di-Ca-doped boron clusters, B6Ca2 (D2h, 1Ag) and B8Ca2 (D8h, 1A1g), and both adopt interesting inverse sandwich geometries, showing an elongated D2h B6 or perfectly planar D8h B8 ring being sandwiched by two Ca atoms only, respectively. Natural atomic charge analyses indicate that the Ca atoms donate nearly all the 4s electrons to the B6 (or B8) ring, forming [Ca]2+[B6]4−[Ca]2+ and [Ca]2+[B8]4−[Ca]2+ charge transfer complexes. The interaction between the two Ca atoms and the boron rings is governed by robust electrostatics albeit by weaker B–Ca covalent interaction. Chemical bonding analyses show that B6Ca2 has 4σ and 6π delocalized electrons on the elongated B6 ring, leading to a conflicting aromatic system. B8Ca2, possessing 6σ and 6π delocalized electrons on the B8 ring, is doubly aromatic. Additionally, the B6Ca2 and B8Ca2 clusters show noticeable structural and electronic transmutation relative to their equivalent electronic B6Be2 and B8Mg2 clusters, respectively. The intrinsic reasons behind the transmutations are elucidated via in-depth bonding analyses.

Precipitates, including silicides and Ti3Al (α2) phase, and alloying elements distribution in a near α titanium alloy Ti65 (Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.3Nb- 1.0Ta-0.4Si-0.8W-0.05C) after solution treatment and aging process were characterized by using transmission electron microscopy (TEM) and atom probe tomography (APT). Quantitative composition analysis and TEM observation indicate that the silicides fit to (Ti, Zr)6(Si, Sn)3. Zr exhibits a β-stabilizing effect in near α titanium alloys but is weaker than other β stabilizing elements. The enriching tendency of the alloying elements in the retained β phase is in the order of Zr

We fabricated a van der Waals heterostructure of WS2–ReSe2 and studied its charge-transfer properties. Monolayers of WS2 and ReSe2 were obtained by mechanical exfoliation and chemical vapor deposition, respectively. The heterostructure sample was fabricated by transferring the WS2 monolayer on top of ReSe2 by a dry transfer process. Photoluminescence quenching was observed in the heterostructure, indicating efficient interlayer charge transfer. Transient absorption measurements show that holes can efficiently transfer from WS2 to ReSe2 on an ultrafast timescale. Meanwhile, electron transfer from ReSe2 to WS2 was also observed. The charge-transfer properties show that monolayers of ReSe2 and WS2 form a type-II band alignment, instead of type-I as predicted by theory. The type-II alignment is further confirmed by the observation of extended photocarrier lifetimes in the heterostructure. These results provide useful information for developing van der Waals heterostructure involving ReSe2 for novel electronic and optoelectronic applications and introduce ReSe2 to the family of two-dimensional materials to construct van der Waals heterostructures.

Because of their uncertain and destructive nature, natural disasters can pose severe shocks to societies and jurisdictions across all levels of government. Disaster-related financial risk is a critical problem in developing countries where people are highly vulnerable to the losses of natural hazards and climate change. This study empirically examines the fiscal impact of natural disasters at the provincial government level in China. Using a panel vector autoregression model, we find that natural disasters increase a province’s total governmental spending and intergovernmental revenues received from the central government while having little effect on its tax revenues. In particular, earthquakes and tropical storms cause larger impacts on spending and intergovernmental transfers. We also show that governments in higher-income Chinese provinces experience larger increases in spending and intergovernmental transfer following natural disasters than lower-income provincial governments. Our results provide important implications for the financial management of disaster risks in the developing context.

CdSiP2 (CSP) with outstanding mid-infrared nonlinear optical properties in the 3–5 μm and 8–12 μm windows has always been expected for application requirement, whereas the inadequate of absorption losses cannot be ignored as practical usage. The defect formation energies, electronic structure characteristics, structure distortion and related optical properties of CSP with some traditional and basic dopants M= (Mg, Al, Cu, Fe, and Mn) substituting Cd or Si sites are investigated by employing density functional theory (DFT). The calculations show that the energetically and thermally stable states in CSP crystals are Mg0, Al1+, Cu4+, Fe4+, Mn4+ at Cd sites and FeSi1+ at SiP2 reference states. Fe and Mn dopants at Cd sites bring abundant valences, including 0, +1, +2 and +4 charged states, and result in a mean absorption spectrum increase. New peaks appear in the density of states as the CuCd4+, FeCd4+, and MnCd4+ take shape, and thus affect the absorption spectrum. According to the calculation results, highly localized d orbitals of dopants should be mainly responsible for the absorption aberrance, because they not only lead to a mean absorption spectrum increase, but also bring new absorption peaks affecting the conversion efficiency along X/Y or Z directions.

Self-propulsion of droplets is of great significance in many fields. The spontaneous horizontal motion and self-jumping of droplets have been well realized in various ways. However, there is still a lack of an effective method to enable a droplet to rotate spontaneously and steadily. In this paper, by employing an acid droplet and a liquid metal, the spontaneous and steady rotation of droplets is achieved. For an acid droplet, it may spontaneously move when it is deposited on the surface of the liquid metal. By adjusting experimental parameters to the proper range, the self-rotation of droplet happens. This phenomenon originates from the fluctuation of the droplet boundary and the collective movement of bubbles that are generated by the chemical reactions between the acid droplet and liquid metal. This rotation has a simpler implementation method and more steady rotation state. Its angular velocity is much higher than that driven by other mechanisms. Moreover, the movements of acid droplets on the liquid metal are classified according to experimental conditions. The internal flow fields, the movements and distribution of bubbles, and the fluctuation of the droplet boundary are also explored and discussed. The theoretical model describing the rotational droplet is given. Our work may deepen the understanding of the physical system transition affected by chemical reactions and provide a new way for the design of potential applications, e.g., micro- and nanodevices.

Atomic-scale simulations are performed to investigate the interaction between prismatic interstitial loops and moving dislocations in nickel. Depending on their relative position, a loop either drags a dislocation elastically or decorates a dislocation with jogs, resulting in a systematic change of the critical stress for subsequent dislocation glide. Loop-decoration significantly reduces the mobility of a dislocation, and the critical shear stress can increase up to ten times larger than the conventional Peierls stress. This work presents the atomic-scale details of loop-dislocation interaction, thus providing reliable information for parameterizing debris-dislocation interaction in meso- or macro-scale simulations.

Microalloying is an effective approach to improve the mechanical properties of γ-TiAl intermetallic compound. Knowledge about the site occupancy of the ternary alloying element in the crystal lattice of γ-TiAl is highly demanded in order to understand the physics underlying the alloying effect. Previous first-principle methods-based thermodynamic models for the determination of the site occupancy were based on the point defect gas approximation with the interaction between the point defects neglected. In the present work, we include the point defect interaction energy in the thermodynamic model, which allows us to predict the site occupancy of the ternary alloying element in γ-TiAl beyond the point defect gas approximation. The model is applied to the γ-TiAl–Nb alloy. We show that, at low temperature, the site occupancy of Nb atoms depends on the composition of the alloy: Nb atoms occupy the Al sublattice for the Ti-rich alloy but occupy Ti sublattice for the Al-rich alloy. The fraction of Nb atoms occupying Al sublattice in the Ti-rich alloy decreases drastically, whereas the fraction of Nb atoms on the Ti sublattice in the Al-rich alloy decreases slightly with increasing temperature. At high temperature, Nb atoms occupy dominantly the Ti sublattice for both the Ti-rich and Al-rich alloys. The interaction between the point defects makes the Ti sublattice more favorable for the Nb atoms to occupy.

A novel and efficient annulation of pentane-2,4-dione with 2-(2-bromophenyl)quinazolin-4(3H)-one was disclosed in DMF catalyzed by CuI/l-proline in the presence of Cs2CO3. This procedure experienced the consecutive α-arylation of carbonyl, deacylation but no dehydration reaction for the synthesis of 6-hydroxy-6-methyl-5,6-dihydro-8H-isoquinolino[1,2-b]quinazolin-8-ones in good yields.

The volume modeling of the sigma phase is an indispensable complement to the integrated computational material design of technologically important materials, such as high-alloy steels and Ni-based superalloys. The molar volume of the sigma phase is influenced by both the atomic mixing (the volume variation affected by this factor is caused by composition alteration rather than site occupation change) and atomic order (i.e. atomic constituent distribution or site occupancy preference on inequivalent sites of a crystal). In the present work, we developed a new integrated thermodynamic and molar volume model to consider physically both mixing and order factors. The integrated model was built within the compound energy formalism (CEF), enabling the thermodynamic calculations to determine equilibrium site occupancies for the subsequent volume calculations. The model parameters of the CEF were assigned by using the first-principles calculated energies and molar volumes of the complete sets of ordered configurations of the sigma phase, as well as the extrapolated molar volumes of the pure elements in the hypothetic sigma phase structure. Such extrapolation for pure elements is based on the experimental data from the literature and the first-principles calculations. We applied the integrated model to study the binary compounds, e.g. Cr-Co, Cr-Fe, Cr-Mn, Mo-Fe, Mo-Mn, Mo-Re, Re-Cr, Re-Fe, Re-Mn, Nb-Al, Ta-Al, V-Fe, V-Ni, and ternary compounds Cr-Fe-X (X = Co and Ni). The integrated thermodynamic and molar volume databases can predict successfully the molar volume of the binary and ternary sigma compounds. As most experimental volume data were measured at room temperature and atmospheric pressure, and the first-principles calculations were performed at 0 K, the present model parameters are valid at about room temperature and atmospheric pressure.

Employing atomic-scale simulations, the response of a high-angle grain boundary (GB), the soft/hard GB, against external loading was systematically investigated. Under tensile loading close to the hard orientation, strain-induced dynamic recrystallization was observed to initiate through direct soft-to-hard grain reorientation, which was triggered by stress mismatch, inhibited by surface tension from the soft-hard GB, and proceeded by interface ledges. Such grain reorientation corresponds with expansion and contraction of the hard grain along and perpendicular to the loading direction, respectively, accompanied by local atomic shuffling, providing relatively large normal strain of 8.3% with activation energy of 0.04 eV per atom. Tensile strain and residual dislocations on the hard/soft GB facilitate the initiation of dynamic recrystallization by lowering the energy barrier and the critical stress for grain reorientation, respectively.

The ductile-to-brittle transition is commonly observed in metastable β-titanium (Ti) alloys containing ω-precipitates, while the fundamental understanding on ω-embrittlement hitherto remains elusive. In this work, the prototypical Ti-20 wt% Mo metastable β-Ti alloy has been systematically investigated by coupling experiments and first-principles calculation to eliminate this puzzle. It is shown that the structural evolution of ω-phase controls the deformation mechanism transition of twinning-to-slip in Ti Mo alloy, being the origin of ductile-to-brittle transition of this alloy. The initial trigonal ω-structure continuously collapses to hexagonal ω-structure (structural collapse) whilst Mo-atoms are rejected out concurrently (stoichiometric varieties), both leading to hardening of ω-precipitates. This self-hardening of ω-precipitates was further rationalized in terms of the enhanced propensity for a covalent character of the atomic bond demonstrated by the electronic density of states (DOS) from first-principles calculation. Specifically, the self-hardening behavior of ω-precipitates promotes dislocation slip on isolated planes in lieu of correlative slip on successive planes inside ω1-variant, while dislocations are completely blocked ahead ω2/ω3/ω4-variants. This in turn renders the transition from deformation twinning that contributes to great macro-plasticity to ordinary dislocation slip that contributes to localized deformation bands in the present Ti Mo alloy.

The synthesis, structures and properties of three new Zn2+-trimesate (BTC3−) coordination polymers (CPs), {[Zn(BTC) (NH3)2]·2H2O}n (1), {[Zn3(BTC)2(NH3)2(H2O)6]·2H2O}n (2) and {[Zn3(BTC)2(NH3)6]·5H2O}n (3), have been reported. They were isolated under the ammoniacal circumstance by dissolving 1,3,5-benzenetricarboxylic acid (H3BTC) and zinc acetate in different mixed-solvents. The three CPs were comprehensively characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis and Fourier Transform Infrared analysis. Their photoluminescence properties were also studied. The results reveal that solvents play important roles on the structures and topologies of the obtained CPs. The crystallographic studies manifest that the CPs 1–3 are 1D chain, 1D ladder and 2D layer structures, respectively.

ω phase precipitating in a β -Ti alloy is generally detrimental to the ductility and plasticity of the alloy.To understand the influence of ω phase on the mechanical properties of β -Ti alloys, the property of the β/ω interface is demanded.In this regard, we calculate the interface energies ( γ int ), cleavage energies ( γ cl ), and generalized stacking fault energies ( γ ) of the β/ω interfaces with different orientations using a first-principles method.Our calculations predict interface energies of 0.32 J m−2 and 0.03 J m−2 for the ( 1 1 1 ¯ ) β / ( 0 0 0 1 ) ω and ( 1 1 2 ) β / ( 1 0 1 ¯ 0 ) ω interfaces, respectively.The strong anisotropy of the interface energy contributes to the ellipsoid-like morphology of ω phase with its major axis parallel to the 〈 1 1 1 〉 β direction.The influence of the interface on the ductility of the alloy is discussed with the calculated cleavage energies and the unstable stacking fault energies ( γ us ) extracted from the generalized stacking fault energy (GSFE). The γ cl / γ us ratio of the ( 1 1 2 ) β / ( 1 0 1 ¯ 0 ) ω interface is lower than those of the main slip planes of the bulk phases, indicating that this interface is prone to crack initiation and propagation as compared to the bulk and contributes to theω-embrittlement of β -Ti alloys.

The maximize energy captured from the wind of a grid-connected variable speed Wind Energy Conversion System (WECS) based on a Permanent Magnet Synchronous Generator (PMSG) is investigated in this paper. An adaptive back-stepping control scheme is applied to achieve maximum power point tracking in the coefficient of maximum power. The features of the proposed control scheme are that it deals with the random nature of wind speed, the uncertainties and external perturbations the acting on WECS effectively, where the bounds of the perturbations are not known in advance. At the same time, a proof of the convergence of the closed-loop system under the proposed controller is derived using the Lyapunov stability theory. Finally, simulations are conducted to illustrate the effectiveness of the proposed approach.

Quantum chemical calculations at both density functional theory (DFT) and single-point CCSD(T) levels suggest that Be2B6 (D6h, 3A1g) and Be2B7+ (D7h, 3A2′) clusters adopt interesting inverse sandwich structures with spin-triplet ground states, featuring a perfect planar B6 (or B7) monocyclic boron ring being sandwiched by two lone Be atoms. There is pronounced charge transfer from the Be atoms to the monocyclic boron rings, leading to [Be]2+[B6]4−[Be]2+ and [Be]2+[B7]3−[Be]2+ charge transfer complexes. Chemical bonding analysis showed that Be2B6 and Be2B7+ clusters have σ/π double aromaticity with 4σ and 6π delocalized electrons on the boron rings. The Be2B6 inverse sandwich possesses the smallest monocyclic boron ring motif in Be-doped boron clusters to date.

Variant selection during solid–solid phase transformation in titanium alloys affects greatly the microstructure and mechanical properties of the alloys. Theoretical investigations of the variant selection were generally performed by using phase field simulation that considers solely the elastic coherency strain energy. In the present work, we develop a model to determine the variant selection directly from first-principles calculations. The source of the variant selection is considered to be the varying free energy gains (including both bulk and interface contributions) induced by the transformation from the parent phase to different variants of the product phase. This model is applied to investigate the effects of shear stress and alloy composition on ω variant selection during athermal β → ω transformation in binary Ti-xMo ( x ≤ 25 at.%) alloys. The random distribution of the atoms in the alloy is described by using virtual crystal approximation (VCA). We show that the tendency of variant selection becomes stronger with increasing shear stress. With increasing Mo concentration, the favorable ω variant transfers from one to another, except for the ω phase with very small particle size (e.g., radius R ≤ 1 nm) where one variant is always selected. The critical Mo concentration for the transfer of the favorable ω variant approaches to 5 at.% with increasing size of the ω phase particles and remains almost unchanged against the shear stress. At the critical Mo concentration, the considered variants have equal free energy gains and there is no variant selection. This finding opens the possibility of controlling the variant selection and the associated microstructure by changing the composition of the alloys.

There has been a growing interest in understanding whether and how people adapt to extreme weather events in a changing climate. This article presents one of the first empirical analyses of adaptation to flooding on a global scale. Using a sample of 97 countries between 1985 and 2010, we investigate the extent and pattern of flood adaptation by estimating the effects of a country's climatological risk, recent flood experiences, and socioeconomic characteristics on its flood-related fatalities. Our results provide mixed evidence on adaptation: countries facing greater long-term climatological flooding risks do not necessarily adapt better and suffer fewer fatalities; however, after controlling for the cross-country heterogeneity, we find that more recent flooding shocks have a significant and negative effect on fatalities from subsequent floods. These findings may suggest the short-term learning dynamics of adaptation and potential inefficacy of earlier flood control measures, particularly those that promote increased exposure in floodplains. Our findings provide important implications for climate adaptation policy making and climate modeling.

Dissolutive wetting, i.e. droplet wets and simultaneously dissolves its solid substrates, is of great significance in both academic research and practical applications. The diffusion interface at the moving contact line is one of the answers to the Huh-Scriven paradox. Besides, dissolutive wetting is the bottleneck problem in many practical fields, such as metal alloy processes, shale gas exploitation, drug release, etc. Furthermore, dissolutive wetting involves complex physical processes, i.e. wetting, diffusion and convection. The coupling transport of mass and momentum as well as the internal convection in the droplet increases the difficulty in studying dissolutive wetting. Even though previous works have been done on metal/metal, metal/ceramic systems, there has been no experimental observation on the flow details in droplets and changes of the solid-liquid interface due to the opacity of the materials in dissolutive wetting. Thus, the physical mechanism of dissolutive wetting is still far from being well understood. Based on the problems mentioned above, in this paper, dynamics of dissolutive wetting of droplets on solid surfaces is investigated by physical mechanics. From a new perspective, we carry out the molecular dynamic simulations of glucose and water dissolution pairs. we match the parameters that dominate the dissolutive wetting in our simulations with real experimental parameters. By this method, the simulation systems are simplified and the glucose molecules can be regarded as Lennard Jones particles. Experiments are also designed to show the in situ real time measurement of the dissolutive wetting. In order to obtain the flow details in the droplet, we select three pairs of high transparent materials. Beyond that, we built a dimensionless number space that divides the dissolutive wetting into two types. For small Pelect number, the convection effect is ignored. But when Pelect number is greater than one, the convection effect that leads to the uniform of the solute distribution must be considered. Morever, we obtain that the droplet follows different scaling laws in different dissolutive wetting stages. In the early stage, the surface tension dominates and the scaling law satisfies the Tanner law. Whereas scaling law in dissolutive wetting changes while diffusion and convection effect are more obvious with the dissolution of solutes. Compared with the non-convective process, the internal convection increases the energy dissipation within the dissolution pairs in our experiments and inhibits the spreading of the droplets to a certain extent. We also find that the coupling effect of dissolution and wetting process will have important influences on the molecular structure of the droplet. Overall, we establish multiscale dissolutive wetting model and reveal the scaling laws of droplet spreading in dissolutive wetting by physical mechanics. Our findings may help to further understand the mechanisms of dissolutive wetting and provide theoretical guidance of practical applications that involve dissolutive wetting.

Monotone recurrence relations give rise to a class of dynamical systems on the high-dimensional cylinder which generalizes the class of monotone twist maps. A solution of a monotone recurrence relation corresponds to an equilibrium of the generalized Frenkel–Kontorova (FK) model. The Aubry–Mather theory for monotone recurrence relations says that for each ω ∈ R there is a Birkhoff minimizer with rotation number ω. Whether all Birkhoff minimizers of rotation number ω form a foliation is a question like whether there is an invariant circle with rotation number ω for a monotone twist map. In this paper we give a criterion for the existence of minimal foliations and study its continuity. The depinning force F d ( ω ) , depending on rotation numbers, is a critical value of the driving force for the FK model, under which there are Birkhoff equilibria and hence the system is pinned, and above which there are no Birkhoff equilibria of rotation number ω and the system is sliding. We show that all Birkhoff minimizers with irrational rotation number ω form a foliation if and only if F d ( ω ) = 0 . If ω = p / q is rational, then F d ( p / q ) = 0 if and only if all ( p , q ) -periodic Birkhoff minimizers constitute a foliation. Moreover, we show that F d ( ω ) is continuous at irrational ω and Holder continuous at Diophantine points, and it also depends continuously on system parameters.

Cattail pollen (CP) and pine pollen (PP) are traditional Chinese medicine, which are used for bleeding blood and immunity enhancement activity respectively. Due to the economic benefits, they are occasionally adulterated with bee pollen. In this study, CP, PP and 6 kinds of bee pollen (dandelion pollen, sunflower pollen, lotus pollen, rhus pollen, buckwheat pollen, corn pollen) were collected and observed by the scanning electron microscope. And then, Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy were used to identify and analyze these 8 kinds of pollens. It is found that PP and CP could be identified from bee pollen through the position, intensity and shape of saccharide and protein characteristic peaks in the FT-IR spectra. The FT-IR spectra of PP, CP and bee pollen are almost similar. 2D-IR spectra exhibited significant differences in automatic peak positions, especially in the range of 760–1400 cm−1. CP and PP have three consistently strong automatic peaks around 1150, 1204, and 1233 cm−1. The sequences of the absorption intensities of them all are 1204 cm−1 > 1233 cm−1 > 1150 cm−1. While CP has no obvious strong automatic peaks compared with PP in the range of 830–1140 cm−1. In conclusion, FT-IR and 2D-IR technology are the effective method for distinguish CP and PP from these 6 kinds of bee pollen.

Escherichia coli (E. coli) is the most common pathogen in both hospital and community settings, and is capable of causing infections that can lead to serious consequences. Quinolones, one of the most common antibiotics in clinical use, are effective weapons to treat E. coli infections. However, the resistance of E. coli to quinolones develops rapidly and spreads widely. Thus, it has become increasingly urgent to enhance the potency of quinolones against both drug-susceptible and drug-resistant E. coli. This review aims to summarize the recent developments of quinolone derivatives with potential activity against E. coli, and to discuss the structure-activity relationship for further rationale design of this kind of derivatives.

The development of synthetic methods to obtain high value-added mesoporous Al-MCM-41 from a low-cost silicon-aluminum source with low toxicity is an active research topic in solid waste resource utilization. In particular, the controlled synthesis of MCM-41 with a two-level pore distribution is a challenging task. In this work, the synthesis of unimodal and bimodal mesoporous Al-MCM-41s was achieved using acids with different degrees of ionization from coal gasification fine residue (CGFR) as bulk solid waste generated by the coal gasification process. We determined that the degree of acid ionization affected the self-assembly of inorganic/organic species as well as condensation processes, resulting in some changes of the hexagonal mesoscopic structure. The unimodal mesoporous Al-MCM-41 with acetic acid HAc and bimodal mesoporous Al-MCM-41s with an inorganic acid environment (HCl, HNO3 or H2SO4) could be effectively prepared in a controllable manner by the silicon and aluminum source obtained at alkali dissolution time 6 h and crystallization conditions at pH 10.5 and 383 K in 72 h. Moreover, the synthesis of Al-MCM-41-HAc with different SiO2/Al2O3 molar ratios (18–89) could also be realized by different alkali dissolution times. And alkali dissolution time (2–24 h) and the crystallization conditions (pH 4.5–11.5, temperatures 373–393 K, and time 48–96 h) also affected the formation of unimodal and bimodal mesoporous Al-MCM-41-HAc. In addition, the maximum adsorption amount onto bimodal mesoporous Al-MCM-41-H2SO4 (476.19 mg g−1 at 308 K) was larger than that onto unimodal mesoporous Al-MCM-41-HAc (243.90 mg g−1 at 303 K). The mesoporous Al-MCM-41s showed good stability.

For the high-dimensional Frenkel–Kontorova model on lattices, we have concluded that there are heteroclinic connections between neighboring Birkhoff minimizers which are more periodic. This conclusion is based on the existence of neighboring elements, i.e., the existence of gaps. By adding a large enough oscillation to the local potential, I prove that all minimal foliations can be destroyed into minimal laminations, and hence there always exist gaps.

The application of double electron‐electron resonance (DEER) with site‐directed spin labeling (SDSL) to measure distances in proteins and protein complexes in living cells puts rigorous restraints on the spin‐label. The linkage and paramagnetic centers need to resist the reducing conditions of the cell. Rigid attachment of the probe to the protein improves precision of the measured distances. Here, three two‐armed GdIII complexes, GdIII‐CLaNP13a/b/c were synthesized. Rather than the disulfide linkage of most other CLaNP molecules, a thioether linkage was used to avoid reductive dissociation of the linker. The doubly GdIII labeled N55C/V57C/K147C/T151C variants of T4Lysozyme were measured by 95 GHz DEER. The constructs were measured in vitro, in cell lysate and in Dictyostelium discoideum cells. Measured distances were 4.5 nm, consistent with results from paramagnetic NMR. A narrow distance distribution and typical modulation depth, also in cell, indicate complete and durable labeling and probe rigidity due to the dual attachment sites., Two armed and ready! A two armed, thus rigid, GdIII‐CLaNP13 probe for double electron–electron resonance (DEER) measurements on proteins can be used to measure nanometer distances in cells with high precision.

Drought is one of the most important environmental factors limiting plant growth and productivity. The molecular mechanisms underlying plant drought resistance are complex and not yet fully understood. Here, we show that the Arabidopsis MADS-box transcription factor AGL16 acts as a negative regulator in drought resistance by regulating stomatal density and movement. Loss-of-AGL16 mutants were more resistant to drought stress and had higher relative water content, which was attributed to lower leaf stomatal density and more sensitive stomatal closure due to higher leaf ABA levels compared with the wild type. AGL16-overexpressing lines displayed the opposite phenotypes. AGL16 is preferentially expressed in guard cells and down-regulated in response to drought stress. The expression of CYP707A3 and AAO3 in ABA metabolism and SDD1 in stomatal development was altered in agl16 and overexpression lines, making them potential targets of AGL16. Using chromatin immunoprecipitation, transient transactivation, yeast one-hybrid, and electrophoretic mobility shift assays, we demonstrated that AGL16 was able to bind the CArG motifs in the promoters of the CYP707A3, AAO3, and SDD1 and regulate their transcription, leading to altered leaf stomatal density and ABA levels. Taking our findings together, AGL16 acts as a negative regulator of drought resistance by modulating leaf stomatal density and ABA accumulation.

Fraxinellone (1) is a naturally occurring degraded limonoid isolated from Meliaceae and Rutaceae plants. As a potential natural-product-based insecticidal agent, fraxinellone has been structurally modified to improve its activity. Furan ring of fraxinellone is critical in exhibiting its insecticidal activity, but with few modifications. Herein, C-ring-modified cyclopropyl analogues were semi-synthesized by Rh(II)-catalyzed cyclopropanation. The structures of the target compounds were well characterized by NMR and HRMS. The precise three-dimensional structural information of 3a was established by X-ray crystallography. Their insecticidal activity was evaluated against Mythimna separata Walker by a leaf-dipping method. Compound 3c exhibited stronger insecticidal activity than 1 and toosendanin against M. separata with teratogenic symptoms during the different periods, implying that cyclopropanation of the furan ring could strengthen the insecticidal activity of fraxinellone.

As sessile organisms, plants must be highly adaptable to the changing environment by modifying their growth and development. Plants rely on their underground part, the root system, to absorb water and nutrients and to anchor to the ground. The root is a highly dynamic organ of indeterminate growth with new tissues produced by root stem cells. Plants have evolved unique molecular mechanisms to fine-tune root developmental processes, during which phytohormones play vital roles. These hormones often relay environmental signals to auxin signaling that ultimately directs root development programs. Therefore, the crosstalk among hormones is critical in the root development. In this review, we will focus on the recent progresses that jasmonic acid (JA) and ethylene signaling are integrated into auxin in regulating root development of Arabidopsis thaliana and discuss the key roles of transcription factors (TFs) ethylene response factors (ERFs) and homeobox proteins in the crosstalk.

International audience; We report a comprehensive study on the structure and elastic constants of epitaxial cubic δ-TaxN (x ≈ 1) layers deposited by reactive magnetron sputtering at 570 °C on MgO(001), MgO(110) and MgO(111) substrates. X-ray diffraction shows that all layers are single-phase and have a single-crystal rocksalt-structure, growing with an epitaxial cube-on-cube relationship with respect to their MgO substrates. For (001)-orientation, Brillouin light scattering provides the measurement of c44 (137 ± 3 GPa) and c12 (130 ± 5 GPa) single-crystal elastic constants, while picosecond laser ultrasonics (PLU) provides the third independent one, c11 (530 ± 10 GPa). For (110)- and (111)-orientations, PLU provides selectively the following combinations, (c11+c12+2c44)/2 and (c11+2c12+4c44)/3, respectively. Electrical resistivity measurements show evidence of point defects in the films despite a composition close to 1:1 stoichiometry. Point defects (metal and nitrogen vacancies) are considered in our first-principles calculations to find closer agreement between experimental and theoretical lattice parameter, mass density, sound velocities and elastic constants. Sound velocities and elastic constants are found to be particularly sensitive to the presence of vacancies, resulting into a more compliant and less anisotropic material. While only ∼ − 1% mismatch is found between predicted defect-free and experimental lattice parameters, huge differences of −27% and +180% are observed for c11 and c44, respectively. These discrepancies can be rationalized by considering the presence of point defects (metal vacancy and/or Schottky defect) in concentration ∼11% in the as-deposited TaN films, a compositional value that corresponds to the lowest formation energy of δ-TaNx structure.

Esterases (ESTs) play important roles in metabolizing various physiologically endogenous and exogenous compounds, and various environmental xenobiotics in insects. The psocid, Liposcelis bostrychophila is a major pest of stored products worldwide and rapidly develops resistance to commonly insecticides. However, the involvement of ESTs in insecticide metabolization and the application of RNAi approach in psocids have not been well elucidated. In this study, we characterized four LbEST genes and investigated the transcriptional levels of these genes at different developmental stages and under different insecticides exposures to assess their potential roles in response to insecticides. The four LbESTs contain a catalytic triad (Ser-His-Glu) linked to an oxyanion hole and acyl pocket involved in substrate stabilization during its hydrolysis. Synergism observed with the esterase-inhibitor DEF suggests the involvement of esterases in malathion detoxification. LbESTs were expressed during the whole of developmental stages, but predominant abundance in the first nymphal instar and adult stage. The mRNA level of three LbEST genes (except for LbEST4) was induced (1.29- to 5.60 fold) in response to malathion or deltamethrin exposures, indicating that these esterases are involved in the detoxification process. Silencing of LbEST1, LbEST2 or LbEST3 through dsRNA feeding led to a higher mortality of psocids upon the malathion treatment compared to controls (1.83 to 2.69-fold), demonstrating that these esterase genes play roles in malathion detoxification in L. bostrychophila. Our study provides new evidence for understanding of the function and regulation mechanism of esterases in L. bostrychophila in insecticide detoxification. The current study also suggests that the present RNAi method could be applied for gene functional studies in psocids.

The increase in extreme weather events due to climate change poses serious challenges to public transit systems. These events disrupt transit operations, impair service quality, increase threats to public safety, and damage infrastructure. Despite the growing risk of extreme weather and climate change, little is known about how public managers recognize, experience and address these risks. Using data from a national study of public transit agencies we investigate the types of extreme weather events transit agencies are experiencing, the associated risks, and how agencies are preparing for them. We find that while extreme events are commonly experienced by transit agencies across states and transit managers perceive increased risks from these events, most agencies rely on the traditional emergency management approach to address extreme weather ex post rather than taking a proactive approach to mitigating the adverse weather impact on transit assets and infrastructure ex ante. Managers report that a lack of access to financial resources is the greatest challenge for undertaking adaptation and preparation. We conclude with a discussion of what these findings mean for understanding organizational adaptation behavior as well as climate adaptation policy making.

We investigated surface properties of metals by performing first-principles calculations. A systematic database was established for the surface relaxation, surface energy (γ), and surface stress (τ) for metallic elements in the periodic table. The surfaces were modeled by multi-layered slab structures along the direction of low-index surfaces. The surface energy γ of simple metals decreases as the atomic number increases in a given group, while the surface stress τ has its minimum in the middle. The transition metal series show parabolic trends for both γ and τ with a dip in the middle. The dip occurs at half-band filling due to a long-range Friedel oscillation of the surface charge density, which induces a strong stability to the Peierls-like transition. In addition, due to magnetic effects, the dips in the 3d metal series are shallower and deeper for γ and τ, respectively, than those of the 4d and 5d metals. The surface stress of the transition metals is typically positive, only Cr and Mn have a negative τ for the (100) surface facet, indicating that they are under compression. The light actinides have an increasing γ trend according to the atomic number. The present work provides a useful and consistent database for the theoretical modelling of surface phenomena.

International audience; The formation of the sigma phase in technologically important materials influences greatly their mechanical properties. Fundamental knowledge on the sigma phase is demanded to understand the phase stability and reasonably control its precipitation. The present work clarifies the atomic bonding characteristics of the binary sigma phase including A-Al (A = Nb, Ta) and transition metal systems (TM-TM) based on the electronic density of states (DOS) and electron localization function (ELF) calculated by using first-principles methods. We show that the atomic bonds of the binary sigma phase exhibit both metallic and covalent characters. The completely ordered A66.7Al33.3 (A = Nb, Ta) sigma compounds bear higher stability than their counterparts with atomic disordering. Besides, for a TM-TM sigma compound, the constituent atom with more electron shells or less valence electrons presents stronger electronic stability. When increasing its atomic occupancy on a specific site, the atomic bonding on the site becomes stronger.

International audience; The present work systematically clarifies the influence of the atomic mixing and the atomic order (i.e. atomic constituent distribution or site occupancy preference on inequivalent sites of a crystal) on the molar volume of the binary sigma phase. We calculated the molar volumes of 21 binary sigma compounds with different atomic order by using EMTO-CPA (Exact Muffin-Tin Orbitals - Coherent Potential Approximation) method. The calculation results follow a similar trend as the experimental data. Moreover, the calculated molar volumes with respect to the composition of the sigma phase in disordered states show that the sigma compounds do not comply with the linear volume-composition relationship. This is due to the influence of the atomic mixing and the deviation can be either negative or positive depending on the tendency of electron loss or gain of the two constituent elements. Additionally, we compared the molar volume difference (ΔVm = Vdisorder-Vorder) between the hypothetically disordered and ordered states of the binary sigma compounds. The results indicate that the effect of the atomic order on the molar volume of the sigma phase depends on the size difference and the electron configurations of the two constituent elements

An intricate understanding of the fundamental β→α phase transformation upon the presence of metastable ω phase is vital for tailoring the multiphase microstructures of titanium and titanium alloys for various specific applications. To approach this, the structures and energetics of heterophase interfaces among α, β, and ω in titanium were thoroughly investigated, using the combination of high-resolution transmission electron microscopy and first-principles density functional theory calculations. The results strongly suggest that metastable ω does not necessarily act as the precursor of α but can reduce the energy barrier for α nucleation in β. The ω/β interfaces acts as favorable nucleation sites for α which, once forms, tends to grow favorably into the β matrix. These findings validate the ω-assisted α nucleation mechanism, and adequately rationalize many TEM observations on titanium alloys.

As an important cephalopods species, Sepiella maindroni fishery has suffered a severe decline due to over-fishing since the 1980s. Stock enhancement has been applied to the resource recovery of this species, but a sexual precocity appeared in breeding process. In order to understand the regulatory mechanism of this phenomenon, we generated the whole transcriptome of S. maindroni based on the total RNA of tissue samples (eyestalk, peduncle, tentacle, gill, muscle and ovary) using Illumina RNA-seq technology. De novo assembly was performed using Trinity software and a total of 31,979,244 high-quality clean reads were randomly assembled to produce 74,245 contigs. All contigs were further assembled and clustered into 58,224 unigenes. Among the predictable unigenes, a total of 14,346 unigenes were annotated based on protein databases. We assessment the annotation completeness using BUSCO software package and the result showed that 91.5% protein-coding genes were found in our assembled transcripts. At last, we predicted the structure of all unigenes using TransDecoder software and MIcroSAtellite identification tool, respectively. Result showed that a total of 26,037 nucleotide sequences of coding regions (direction of the sequences is 5′ → 3′) were confirmed to the protein database and a total of 13,471 simple sequence repeats were identified. Our goal was to provide an important foundation for future genomic research on the cephalopod and further evaluate the effectiveness of stock enhancement.

Four silver(I) coordination polymers (CPs), namely {Ag3(cpyz)(btc)}n (1), {Ag2(cpyz)(pta)}n (2), {Ag3(mpyz)2(btc)·2(H2O)}n (3), {Ag2(mpyz)(pta)·2(H2O)}n (4), [cpyz = 2-chloropyrazine, H3btc = 1,3,5-benzene tricarboxylic, mpyz = 2,6-dimethylpyrazine, H2pta = phthalic acid] have been synthesized and characterized. X-ray diffraction indicates that, 1 shows a 3D supramolecular structure with a 1D silver chain containing an infinite Ag3 units; 2 features a 3D supramolecular framework with Ag-O and Ag-Ag interaction and cpyz ligand adopts monodentate mode making no contribution to the dimensionality; in 3, the silver atom links mpyz ligand and btc anion into a 2D layer connected by Ag-Ag interaction between neighboring layers into the 3D network, with Zigzag Ag4 units; in 4, Ag(I) coordinates pta benzene dicarboxylates to generate a one-dimensional infinite chain, connecting by nitrogen ligand to exhibit a 2D 44-sql network. The results suggest that benzene dicarboxylates and the kinds of pyrazine derivatives play significant roles in the formation of such coordination architectures. The photoluminescence and thermogravimetric analysis (TGA) of the complexes were measured.

Solute atoms such as Fe, Co, and Ni diffuse abnormally fast in α-Ti, which influences significantly the mechanical properties of the titanium alloys. Various mechanisms (e.g., the interstitial diffusion mechanism and solute-vacancy complex mechanism) have been proposed to account for the fast diffusion of these solutes in α-Ti. To elucidate such diffusion mechanism, a first-principles method is employed to calculate the formation energies, migration energy barriers, and solute-vacancy binding energies of the substitutional and interstitial solute atoms including Al, Si, Sn, V, Mn, Fe, Co, Ni, and Cu in α-Ti. Based on the calculated parameters, the diffusion mechanisms are discussed. Comparing the formation energies of the substitutional and interstitial solutes, we find that all the solute atoms prefer the substitutional configuration to the interstitial one. The interstitial migration energy barriers are quite low for all the solutes. Al and Sn diffuse mainly through normal vacancy mediated mechanism due to the high substitutional to interstitial preferential energy that leads to very low fraction of interstitial solutes (about 10 − 15 ∼ 10 − 16 at 1000 K) at thermal equilibrium state and high interstitial diffusion activation energy. The 3d metal solute atoms, especially Mn, Fe, and Co, are fast diffusers and the diffusion coefficients are dominated by the interstitial mechanism because of their sizable thermal equilibrium interstitial fractions (several percent at 1000 K). The solute-vacancy complex mechanism is not likely to account for the fast diffusions in α-Ti. We show that the direct chemical interaction between the solute and matrix atoms determines the site-occupancy of the solute atoms in α-Ti besides the atomic size effect that was commonly believed to be responsible for the fast diffusions.