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In the development process of large-scale railway transportation system, there are various line structures, resulting in drastic fluctuations of traction power supply system, which brings great difficulties to ensure the power supply capacity of traction power supply system. Traditional power flow calculation methods, such as N-R method and PQ decomposition method, can only calculate highly linearized direct power supply system, and are no longer applicable to new power supply systems. Therefore, it is necessary to study a suitable method to analyze the power supply capacity of AT traction power supply system effectively and accurately. In this paper, firstly, the AT traction power supply system model is built, including substation, substation and AT substation. Then, according to the basic parameters and operation characteristics of electric locomotive, the equivalent circuit model of electric locomotive is built to realize the complete restoration of traction power supply system. Then, the power flow of traction power supply system under different working conditions is calculated, and the power supply capacity under single-vehicle light load, single-vehicle heavy load, multi-vehicle light load and multi-vehicle heavy load is explored. Finally, the model is used to verify it again, and a substantial conclusion is obtained.

Social security systems were successively established in most developing countries in the 1980s and 1990s. To ensure the long-term sustainability of these newly established systems it is essential to carefully monitor the economic impact. Based on the panel data of 21 developing countries from 2000 to 2016, this paper is the first to apply the panel threshold model to empirically analyze the relationship between national health expenditures and economic growth under different levels of human capital. The results show that health expenditure and economic growth have significant interval effects because of the different levels of human capital. Specifically, when human capital levels are low, health expenditure is significantly negatively correlated with economic growth. When human capital is at a medium level, health expenditure has a positive but not significant impact on economic growth. When the level of human capital is high, the positive economic impact of the health expenditure is significantly enhanced. In addition, subgroup analyses indicate that population aging and low fertility aggravate the negative impact of health expenditures on economic growth. This study provides reliable analysis and can be used by developing countries to maintain a long-term sustainable social security system.

Development of new direct methanol fuel cell catalyst is a hot topic of current research. In this article, we adopted a simple method of synthesizing a PtNi alloy catalyst in one step at room temperature. In order to study the optimum proportion of platinum salt and nickel salt in the experiment by changing the molar ratio of platinum and nickel in the solution, five different proportions of PtNi alloy catalysts were obtained. The successful synthesis of PtNi alloy catalyst was proved by XRD and other characterization methods. The electrochemical properties of the above electrocatalysts were investigated using CV, LSV and other testing methods. The results show that PtNi-4 alloy catalyst exhibits excellent catalytic activity in both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) tests, and their initial potential and current density are similar to commercial Pt/C catalysts in ORR. In summary, the prepared PtNi-4 alloy catalyst can be used as an anode or cathode catalyst in direct methanol fuel cells.

Corrosion protection of epoxy coatings containing phytic acid doped polyaniline nanofibers(PANI–PA–NFs) loaded with benzotriazole (PANI-PA-NFs/BTA) for Q235 carbon steel was studied in this work. Synthesized PANI–PA–NFs and the coating performances were characterized in detail. The specific area and inhibitor load rate of the prepared PANI-PA-NFs are 69.4 m2 g−1 and 10.3%, respectively. Epoxy coating containing 2 wt. % PANI-PA-NFs/BTA shows the best protection ability and self-healing function. The self-healing function of epoxy coating containing PANI-PA-NFs/BTA is attributed to the synergistic effect between PANI-PA and BTA.

A facile and efficient strategy is described in this communication for preparing a molecular catalyst/semiconductor hybrid photoanode by immobilizing a cobalt cubane water oxidation catalyst onto a porous BiVO4 electrode via electrochemical polymerization. With the introduction of Vpa as the anchoring linkage, the poly-1/Vpa/Al2O3/BiVO4 photoanode exhibits high performance as well as stability for photoelectrochemical water oxidation.

Carbon supported and nitrogen coordinated single Mn site (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (

In order to effectively solve the issue of that the workshop production abnormal is difficult to effectively control in discrete manufacturing enterprise, this paper explored the associative entity that is related to influence factors of production abnormal. And the influence indicators are identified from the three aspects of the space-time characteristics, the static characteristics and dynamic characteristics, then the comprehensive and reasonable influence indicator system is established; secondly, this paper gives the data source and the quantitative methods of the influence index from the technical point of view; thirdly, a prediction model based on hybrid neural networks (HNN) over time series is given.

With the rapid development of mobile Internet, public access to information channels have undergone disruptive changes. This article novel coronavirus pneumonia epidemic situation and other public emergencies, analyzed the current public access to information channel characteristics, discussed the new situation of traditional media information dissemination challenges, and put forward some measures to enhance the transmission power, aimed at improving the effectiveness of journalism.

We demonstrate photonic generative adversarial networks (GANs) based on a phase-change metasurface mode converter (PMMC) array and perform the handwritten-like number generation task.

Transformer has emerged as a popular deep neural network (DNN) model for Neural Language Processing (NLP) applications and demonstrated excellent performance in neural machine translation, entity recognition, etc. However, its scaled dot-product attention mechanism in auto-regressive decoder brings a performance bottleneck during inference. Transformer is also computationally and memory intensive and demands for a hardware acceleration solution. Although researchers have successfully applied ReRAM-based Processing-in-Memory (PIM) to accelerate convolutional neural networks (CNNs) and recurrent neural networks (RNNs), the unique computation process of the scaled dot-product attention in Transformer makes it difficult to directly apply these designs. Besides, how to handle intermediate results in Matrix-matrix Multiplication (MatMul) and how to design a pipeline at a finer granularity of Transformer remain unsolved. In this work, we propose ReTransformer - a ReRAM-based PIM architecture for Transformer acceleration. ReTransformer can not only accelerate the scaled dot-product attention of Transformer using ReRAM-based PIM but also eliminate some data dependency by avoiding writing the intermediate results using the proposed matrix decomposition technique. Moreover, we propose a new sub-matrix pipeline design for multi-head self-attention. Experimental results show that compared to GPU and Pipelayer, ReTransformer improves computing efficiency by 23.21× and 3.25×, respectively. The corresponding overall power is reduced by 1086× and 2.82×, respectively.

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Increasing catalytic activity and durability of atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable Co-N-C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm-2 in a practical H2 /air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

Wheel polygonisation is a wavy wear on wheel’s circumference, which aggravates the wheel-rail interaction and prematurely invalidates or damages the components of vehicle-track system. This paper presents an investigation into the formation mechanism of high-order polygonal wear of metro train wheels through field experiments and numerical simulations. Some necessary field experiments are conducted to obtain the characteristics of the irregular wear of the wheels and the dynamics responses of the vehicle components. The numerical modal analysis of vehicle’s key components is performed. Furthermore, a long-term wheel wear model is built including a vehicle-track dynamics model coupled with a local wear model. The metro vehicle-track coupled dynamics model considers the flexibilities of the wheelset and track, where the wheelset and track are modelled using finite element method. The effects of elastic deformation of the wheelsets and rails on creepages, creep forces and wheel wear can be considered in the model. The investigation results indicate that the dominating order of wheel polygonal wear is 11–16, corresponding to wavelengths of 165–240 mm. The formation mechanism of high-order wheel polygonal wear is the P2 resonance of some types of track structure, and the first bending resonance of the wheelset can accelerate the development of wheel polygonal wear.

Background The CRISPR/Cas9 system, composed of a single-guide RNA for target recognition and a Cas9 protein for DNA cleavage, has the potential to revolutionize agriculture as well as medicine. Even though extensive work has been done to improve the gene editing activity of CRISPR/Cas9, little is known about the regulation of this bacterial system in eukaryotic host cells, especially at the post-transcriptional level. Results Here, we evaluate the expression levels of the two CRISPR/Cas9 components and the gene editing efficiency in a set of Arabidopsis mutants involved in RNA silencing. We find that mutants defective in the post-transcriptional gene-silencing pathway display significantly higher Cas9 and sgRNA transcript levels, resulting in higher mutagenesis frequencies than wild-type controls. Accordingly, silencing of AGO1 by introduction of an AGO1-RNAi cassette into the CRISPR/Cas9 vector provides an increase in gene editing efficiency. Co-expression of the viral suppressor p19 from the tomato bushy stunt virus to suppress the plant RNA-silencing pathway shows a strong correlation between the severity of the phenotypic effects caused by p19 and the gene editing efficiency of the CRISPR/Cas9 system for two different target genes, AP1 and TT4. Conclusions This system has useful practical applications in facilitating the detection of CRISPR/Cas9-induced mutations in T1 plants as well as the identification of transgene-free T2 plants by simple visual observation of the symptom severity caused by p19. Our study shows that CRISPR/Cas9 gene editing efficiency can be improved by reducing RNA silencing in plants. Electronic supplementary material The online version of this article (10.1186/s13059-018-1529-7) contains supplementary material, which is available to authorized users.

Based on the micro individual data from China Health and Nutrition Survey (CHNS) database and the development of China’s medical and health system reform since the reform and opening-up in 1978, this paper applies a two-tier stochastic frontier model to measure the degree of asymmetric information between physicians and patients in China’s medical service market and estimate the impact of bargaining on the final price of health care both holistically and annually. The empirical results show that: 1) The information mastered by physicians and patients have significant but opposing effects on the final medical service price. Physicians hold more information relative to patients and thus have stronger bargaining power. 2) Almost all patients will be forced to accept a medical price higher than the benchmark price by 16.52% on average by receiving excessive and expensive medical services, despite the differences in bargaining power between physicians and patients are highly heterogeneous. 3) The series of medical reforms in China had different impacts on medical care pricing efficiency. Especially, the early medical reforms could impose a positive impact on the efficiency of the medical market in the initial stage. I further propose that the path choice of China’s new round of medical reform should be as follows: It is necessary to insist on government-led efforts to protect the public welfare of medical services, and to introduce market mechanisms to mobilize social resources and improve the efficiency of the medical market. In addition, I point out that the establishment and improvement of the general practitioner system may reduce the degree of information asymmetry between physicians and patients, thus alleviating China's deteriorating physician-patient relationship.

Alkylated mercury species (monomethylmercury, MeHg, and dimethylmercury, DMeHg) exhibit significant bioaccumulation, and pose significant risks to ecosystems and human health. Although decades of research have been devoted to understanding MeHg formation and degradation, little is known about the DMeHg formation in aquatic systems. Here, we combine complementary experimental and computational approaches to examine MeHg speciation and DMeHg formation in sulfidic aqueous solutions, with an emphasis on the formation and decomposition of the binuclear bis(methylmercuric(ii)) sulfide complex (CH3Hg)2S. Experimental data indicate that the reaction 2CH3Hg+ + HS- ⇄ (CH3Hg)2S + H+ has a log K = 26.0 ± 0.2. Thus, the binuclear (CH3Hg)2S complex is likely to be the dominant MeHg species under high MeHg concentrations typically used in experimental investigations of MeHg degradation by sulfate-reducing bacteria (SRB). Our finding of a significant abiotic removal mechanism for MeHg in sulfidic solutions through the formation of relatively insoluble (CH3Hg)2S suggests careful reexamination of reported "oxidative demethylation" of MeHg by SRB and perhaps other obligate anaerobes. We provide evidence for slow decomposition of (CH3Hg)2S to DMeHg and HgS, with a first-order rate constant k = 1.5 ± 0.4 × 10-6 h-1. Quantum chemical calculations suggest that the reaction proceeds by a novel mechanism involving rearrangement of the (CH3Hg)2S complex facilitated by strong Hg-Hg interactions that activate a methyl group for intramolecular transfer. Predictions of DMeHg formation rates under a variety of field and laboratory conditions indicate that this pathway for DMeHg formation will be significant in laboratory experiments utilizing high MeHg concentrations, favoring (CH3Hg)2S formation. In natural systems with relatively high MeHg/[H2S]T ratios (the oxic/anoxic interface, for example), DMeHg production may be observed, and warrants further investigation.

Simple yet efficient design of an outstanding multifunctional electrocatalyst is crucial for advanced energy conversion and storage devices. Herein, we report the synthesis of an N-enriched hierarchically porous carbon electrocatalyst, which demonstrated excellent overall oxygen electrode activity (ΔE = EOER,10 − EORR,1/2 of 0.770 V) and impressive durability in 0.1 M KOH. The activity of our material integrates a high BET surface area (1547.13 m2 g−1), accessible N dopant and suitable porous architectures. The material is formed by mixing cicada sloughs with ZnCl2, as the inorganic pore-fabricating agent, with ball milling followed by annealing treatment. Unexpectedly, the nitrogen reduction reaction (NRR) with excellent production yield (NH3: 15.7 μg h−1 mg−1 cat., faradaic efficiency: 1.45%) and selectivity is achieved at −0.2 V vs. RHE under ambient conditions. The present trifunctional catalytic activities are markedly better than leading results reported in recent literature. These results highlight the significance of deliberate structural engineering in the preparation of multifunctional electrocatalysts for versatile electrochemical reactions.

Methanol oxidation is a very important reaction in diret methanol fuel cells. Developing stable and efficient Pt-based catalysts with a convenient method has been on the stage recently. Herein, we employed a convenient one-pot method to synthesize Pt nanoparticles encapsulated by polyoxometalates (POMs) spreading on a few layers of graphene oxide with a nickel foam as a conductive substrate. Four kinds of samples with different Pt loadings were finally obtained by adjusting the H2PtCl6 concentration, named as PPGN-n (n = 1, 2, 3, 4). The microscopic structure of the sample was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It was proved that small-sized Pt nanoparticles with a diameter of ca. 2.47 nm spreaded on graphene oxide (GO) with the nickle foam support were successfully synthesized. The synthesized electrocatalysts exhibited higher electrocatalytic activities than commercial Pt/C for methanol oxidation in electrocatalytic tests. The mass activity of PPGN-1 of 250.6 mA mg−1 can be achieved. During the synthesis, POM was used as a bifunctional reagent; as a reductant for reducing chloroplatinic acid and a stabilizer for the regulation of the Pt nanoparticle size simultaneously. POM cooperated rapid synthesis of Pt nanoparticles can offer a new route for designing and synthesising electrocatalysts.

Although significant efforts have been devoted to designing efficient electrocatalysts for the oxygen evolution reaction, further progress is still needed regarding modulating the microstructures of electrocatalysts to further improve catalytic activity. Herein, utilizing ionic compound NaF and heteroatom-N-rich urea as morphology directing reagents, ultralong needle-like N-doped Co(OH)F supported on carbon fiber paper has been synthesized through a one-step hydrothermal method. Specifically, the hydrothermal kettle provides a stable environment for the formation of ultra-long needle-like structures. Meanwhile, with the addition of halogen anion F− and heteroatom N, a wealth of oxygen vacancies are obtained, and the OER activity is enhanced. The as-prepared N-doped Co(OH)F-CFP (N:Co(OH)F-CFP) has excellent hydrophilicity, which facilitates its contact with the electrolyte and then accelerates the passing of electrons back and forth between the surface of the material and the electrolyte. Under alkaline conditions, N:Co(OH)F-CFP's OER activity is superior to that of IrO2. Its potential can reach 1.540 V (vs. RHE) at 10 mA cm−2 with a Tafel slope of 69.75 mV dec−1 in 1 M KOH solution.

Electrocatalytic nitrogen reduction (NRR) to produce ammonia (NH3 ) at ambient conditions is a promising alternative for the Haber-Bosch process. However, developing highly active and stable NRR catalysts to replace precious metals remains challenging. Herein, we report an unusual NRR electrocatalyst with a single Zn(I) site supported on hollow porous N-doped carbon nanofibers (Zn1 N-C). The Zn1 N-C nanofibers exhibit an outstanding NRR activity with a high NH3 yield rate of ∼16.1 μg NH3 h-1 mgcat -1 at -0.3 V and Faradaic efficiency (FE) of 11.8% in alkaline media, surpassing other previously reported carbon-based NRR electrocatalysts in which the transition metal is dispersed atomically and anchored at nitrogen (TM-Nx ) sites. 15 N2 isotope labeling experiments confirm that the feeding gas is the only nitrogen source in the production of NH3 . Structural characterizations reveal that atomically dispersed Zn(I) sites with Zn-N4 moieties serve as real active sites, and nearby graphitic N site synergistically facilitates the NRR activity. In situ attenuated total reflectance-Fourier transform infrared measurement and theoretical calculation demonstrate that the formation of initial *NNH intermediate is the rate-limiting step toward NH3 generation. It also indicates the graphitic N atom adjacent to the tetracoordinate Zn-N4 center significantly lowers the energy barrier for this process to accelerate hydrogenation kinetics. This article is protected by copyright. All rights reserved.

Severe high-order polygonal wear has been found on metro train wheels of one metro line in China, which causes considerable vibration of vehicle components and disturbing interior noise. Field tests and numerical simulations were conducted to investigate the formation mechanism and key influencing factors of wheel high-order polygonisation. Wheel out-of-roundness (OOR), vibration behavior of vehicle components, and rail surface irregularities were tested. On-site measurement results indicate that the wheels exhibit 13th- to 16th-order polygonal wear. The dominant wavelengths are about 165–203 mm. The experimental results show that the wheel polygonisation is related to the first-order bending vibration of the wheelset and the P2 resonance generated on ladder sleeper tracks and steel spring floating slab tracks. A long-term wear model was developed to further study the cause of wheel polygonisation, which included a vehicle–track coupled dynamic model, considering the flexibility of the wheelset and track, as well as a wear model. The effects of operating speeds, P2 resonance frequencies for different tracks, and wheelset flexibility on the development of wheel polygonisation were investigated. Based on the experimental and simulation results, it is further believed that the P2 resonance is the main cause of the higher-order polygonal wear of wheels, and the first-order bending vibration of the wheelset can exacerbate the wheel polygonisation.

Electrochemical nitrogen reduction reaction (NRR) under ambient conditions is an attractive approach to synthesizing NH3, but remains a significant challenge due to insufficient NH3 yields and low Faraday efficiency (FE). Among studied NRR catalyst formulations, molecular catalysts with well-defined FeN4 configuration structures allow the establishment of a precise structural model for elucidating the complex multiple proton and electron transfer NRR processes competing with the undesirable hydrogen evolution reaction (HER). Inspired by biological nitrogenase, Fe sites can activate the N2 due to their strong interactions with N2. The unoccupied d orbital of Fe endows it the ideal electron acceptor and donor, which offers an attractive chemical property to facilitate NRR activity. Herein, we explore a molecular iron catalyst, i.e., tetraphenylporphyrin iron chloride (FeTPPCl) for the NRR. It exhibits promising NRR activity with the highest NH3 yield (18.28 ± 1.6 μg h−1 mg−1cat.) and FE (16.76 ± 0.9 %) at −0.3 V vs. RHE in neutral electrolytes. Importantly, 15N isotope labeling experiments confirm that the synthesized NH3 originates from the direct reduction of N2 in which 1H NMR spectroscopy and colorimetric methods were performed to quantify NH3 production. Also, operando electrochemical Raman spectroscopy studies confirm that the Fe–Cl bond breakage in the FeTPPCl catalyst is a prerequisite for initiating the NRR. Density functional theory (DFT) calculations further reveal that the active species is Fe porphyrin complex [Fe(TPP)]2− and the rate-determining step is the first hydrogenation of N2 via the alternating mechanism on the [Fe0]2− sites. This work provides a new concept to use structurally defined molecular single iron catalysts to elucidate NRR mechanisms and design optimal active sites with enhanced reaction activity and selectivity for NH3 production under ambient conditions.

The development of stable, highly active and cheap electrocatalysts towards the oxygen evolution reaction (OER) has been an ongoing challenge due to practical problems such as slow kinetics and high overpotential. Herein, we utilized a one-pot hydrothermal method to prepare cobalt/nickel molybdate hierarchical microflowers on conductive carbon cloth (MMoO4-CC, M = Co, Ni) as three-dimensional self-supported electrodes for the oxygen evolution reaction. CoMoO4-CC showed better catalytic activity than NiMoO4-CC. Benefiting from the synergistic effect of a large active area, fast charge and mass transport as well as a three-dimensional conducting path, the CoMoO4-CC nanosheet electrode showed a large current density and a relatively low starting potential, delivering 10 mA cm−2 current densities at an overpotential of 290 mV and a Tafel slope of 94 mV dec−1. Furthermore, the CoMoO4-CC nanomaterial shows better electrocatalytic stability than IrO2-CCa, which could be a promising electrocatalyst for large-scale water oxidation.

A simple and effective method to prepare photocatalytically active electrodes for water oxidation is described in this paper. The precious-metal-free catalyst, Co4O4(O2CMe)4(4-vinylpy)4 (py = pyridine) was electrochemically polymerised on a RuP-sensitised TiO2 (RuP = [Ru(bpy)2(4,4′-(PO3H2)2bpy2)]Cl2) and on a TiO2 surface codecorated with vinyl phosphate (Vpa) and RuP for applications in molecular photoelectrochemical (PEC) devices. With a Vpa chain as the anchoring group, the photoanode poly-Co4O4+Vpa/RuP/TiO2 demonstrated a significantly higher PEC performance compared to poly-Co4O4/RuP/TiO2. The introduction of a Vpa chain allows better immobilisation of catalyst and enhances the electron transport between the photosensitiser and the catalyst. A photocurrent density of ∼100 μA cm−2 was achieved in a Na2SO4 solution at pH 7.0 under a 0.4 V external bias, with a faradaic efficiency of 76% for oxygen production.

The widely used Streptococcus pyogenes Cas9 (SpCas9) requires NGG as a protospacer adjacent motif (PAM) for genome editing. Although SpCas9 is a powerful genome-editing tool, its use has been limited on the targetable genomic locus lacking NGG PAM. The SpCas9 variants xCas9 and Cas9-NG have been developed to recognize NG, GAA, and GAT PAMs in human cells. Here, we show that xCas9 cannot recognize NG PAMs in tomato, and Cas9-NG can recognize some of our tested NG PAMs in the tomato and Arabidopsis genomes. In addition, we engineered SpCas9 (XNG-Cas9) based on mutations from both xCas9 and Cas9-NG, and found that XNG-Cas9 can efficiently mutagenize endogenous target sites with NG, GAG, GAA, and GAT PAMs in the tomato or Arabidopsis genomes. The PAM compatibility of XNG-Cas9 is the broadest reported to date among Cas9s (SpCas9 and Cas9-NG) active in plant.

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Transgenic mouse studies suggest that γ-aminobutyric acid type A (GABAA) receptors containing β3 subunits mediate important effects of etomidate, propofol, and pentobarbital. Zebrafish, recently introduced for rapid discovery and characterization of sedative-hypnotics, could also accelerate pharmacogenetic studies if their transgenic phenotypes reflect those of mammals. The authors hypothesized that, relative to wild-type, GABAA-β3 functional knock-out (β3-/-) zebrafish would show anesthetic sensitivity changes similar to those of β3-/- mice. Methods Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 mutagenesis was used to create a β3-/- zebrafish line. Wild-type and β3-/- zebrafish were compared for fertility, growth, and craniofacial development. Sedative and hypnotic effects of etomidate, propofol, pentobarbital, alphaxalone, ketamine, tricaine, dexmedetomidine, butanol, and ethanol, along with overall activity and thigmotaxis were quantified in 7-day postfertilization larvae using video motion analysis of up to 96 animals simultaneously. Results Xenopus oocyte electrophysiology showed that the wild-type zebrafish β3 gene encodes ion channels activated by propofol and etomidate, while the β3-/- zebrafish transgene does not. Compared to wild-type, β3-/- zebrafish showed similar morphology and growth, but more rapid swimming. Hypnotic EC50s (mean [95% CI]) were significantly higher for β3-/-versus wild-type larvae with etomidate (1.3 [1.0 to 1.6] vs. 0.6 [0.5 to 0.7] µM; P < 0.0001), propofol (1.1 [1.0 to 1.4] vs. 0.7 [0.6 to 0.8] µM; P = 0.0005), and pentobarbital (220 [190 to 240] vs. 130 [94 to 179] μM; P = 0.0009), but lower with ethanol (150 [106 to 213] vs. 380 [340 to 420] mM; P < 0.0001) and equivalent with other tested drugs. Comparing β3-/-versus wild-type sedative EC50s revealed a pattern similar to hypnosis. Conclusions Global β3-/- zebrafish are selectively insensitive to the same few sedative-hypnotics previously reported in β3 transgenic mice, indicating phylogenetic conservation of β3-containing GABAA receptors as anesthetic targets. Transgenic zebrafish are potentially valuable models for sedative-hypnotic mechanisms research.

OER is the key step to increase the rate of water-splitting reaction. Design and construction of appropriate defects is an effective strategy to enhance catalytic activity. Mn has stronger e−–e− repulsion by the local influence of its 3d orbital electrons. When Mn(III) was successfully introduced into two dimensional F-doped Ni(OH)2, it can tune the surface electronic structure of the F-doped Ni(OH)2 to increase its oxygen deficiency content. In this work, the as-synthesized Mn and F co-doped Ni(OH)2–NF on Ni foam (Mn–F/Ni(OH)2–NF) shows remarkable oxygen evolution performance, exhibiting 233 mV overpotential at 20 mA cm−2, and the Tafel slope is 56.9 mV dec−1 in 1 M KOH. The performance is better than that of the same loading of IrO2 on Ni foam. Density functional theory (DFT) calculations further show that the introduction of oxygen defects can significantly improve the OER catalytic performance of Mn–F/Ni(OH)2–NF.

A facile and efficient strategy is described in this communication for preparing a molecular catalyst/semiconductor hybrid photoanode by immobilizing a cobalt cubane water oxidation catalyst onto a porous BiVO4 electrode via electrochemical polymerization. With the introduction of Vpa as the anchoring linkage, the poly-1/Vpa/Al2O3/BiVO4 photoanode exhibits high performance as well as stability for photoelectrochemical water oxidation.

The electrochemical CO2 reduction reaction (CO2 RR) is a promising strategy to achieve electrical-to-chemical energy storage while closing the global carbon cycle. The carbon-supported single-atom catalysts (SACs) have great potential for electrochemical CO2 RR due to their high efficiency and low cost. The metal centers' performance is related to the local coordination environment and the long-range electronic intercalation from the carbon substrates. This review summarizes the recent progress on the synthesis of carbon-supported SACs and their application toward electrocatalytic CO2 reduction to CO and other C1 and C2 products. Several SACs are involved, including MNx catalysts, heterogeneous molecular catalysts, and the covalent organic framework (COF) based SACs. The controllable synthesis methods for anchoring single-atom sites on different carbon supports are introduced, focusing on the influence that precursors and synthetic conditions have on the final structure of SACs. For the CO2 RR performance, the intrinsic activity difference of various metal centers and the corresponding activity enhancement strategies via the modulation of the metal centers' electronic structure are systematically summarized, which may help promote the rational design of active and selective SACs for CO2 reduction to CO and beyond.

Before the COVID-19 vaccines from Pfizer and Moderna were authorized, governments around the world have adopted strict lockdown measures in response to the threat from the unprecedented COVID-19 pandemic. Because of the negative impact on freedom of movement, the economy, and society at large, the question of when and how to safely reopen an economy is urgent. Based on the data of daily confirmed COVID-19 cases from all 31 provincial capitals on the Chinese mainland, this paper is the first to apply the synthetic control method to empirically analyze the causal effect of reopening the economy in three provincial capitals on their increase in new cases. Data showed that the number of new infection cases in all three cities remained at zero for several consecutive days before reopening. Reopening the economy did not have a significant adverse effect on the increase in the number of new infections in these three cities for at least a week after reopening. This study contains lessons for other countries of the world by providing timely and reliable causal evidence on the timing and support safeguards for reopening an economy during COVID-19.

One “silver lining” of the COVID-19 pandemic has been the reduction in air pollution that followed lockdowns. Unfortunately, this unintended air pollution decline will likely be short-lived. As regions begin to recover their economies, travel and industrial activity will increase the ambient pollutants quickly offsetting the improvement in air quality. Therefore, it is urgent to clarify the causal impact of reopening an economy on air quality during COVID-19. Based on city-level daily air quality data in China, this paper is the first to empirically analyze the causal effect of reopening the economy in the provincial capital Lanzhou on concentrations of four air pollutants using the synthetic control method. The results show that the reopening caused a significant increase in the concentration of NO2 by as much as 30 μg/m3 (an increase of 75% from the lockdown level) and a significant increase in O3 concentrations by 60μg/m3 (a 60% increase) which peaked on the 6th day after the restart. The reopening also led to significant fluctuations in SO2 and CO concentrations. This study contains useful conclusions by providing timely and reliable causal evidence on the lasting impact of COVID-19 on air quality.

Atomically dispersed and nitrogen coordinated single iron site (i.e., FeN4) catalysts (Fe-N-C) are the most promising platinum group metal (PGM)-free cathode for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). However, current Fe-N-C catalysts are limited by the inferior exposure of active FeN4 sites due to the inevitable agglomeration of particles in cathodes. Herein, we report a self-assembled strategy to synthesize the atomically dispersed FeN4 site catalysts with a hierarchically porous matrix derived from dual-size Fe-doped ZIF-8 crystal precursors by using large particles to support small particles. The tailored structure is effective in mitigating the particle migration, agglomeration, and spatial overlap, thereby exposing increased accessible active sites and facilitating mass transport. The best performing catalyst composed of 100 nm “nucleated seed” assembled by 30 nm “satellite” demonstrates exceptional ORR activity in acidic electrolyte and membrane electrode assembly. This work provides new concepts for designing hierarchically porous catalysts with single metal atom dispersion via self-assembly of ZIF-8 crystal precursors with tunable particle sizes and nanostructures.

Steam reforming (SR) of pure butanol and a specific mixture (butanol/acetone/ethanol = 6/3/1, mass ratio) assumed as a model of bio-butanol raw mixture have been researched over mesoporous MgO supported Ni catalysts with various particle size (3.6–8.8 nm). The catalysts were characterized by N 2 adsorption, H 2 -TPR, XRD, XPS and TEM. The volcano-like curves were observed when the H 2 yield and H 2 selectivity were plotted as a function of the nickel particle size in butanol steam reforming (BSR) and acetone–butanol–ethanol steam reforming (ABESR) reactions. Prepared mesoporous Ni 0.12 /MgO catalysts exhibited the highest catalytic performance in two model reaction systems. Surprisingly, the Ni particle size effects in BSR developed difference with counterpart in ABESR. Specifically, the catalytic performance of mesoporous Ni 0.20 /MgO even outperform that of mesoporous Ni 0.08 /MgO catalyst with respect to lower by-products selectivity and higher hydrogen yield in ABESR compared to BSR results.

Steam reforming (SR) of single model molecules (acetone, butanol, and ethanol) and a specific mixture (butanol/acetone/ethanol = 6/3/1, mass ratio) assumed as a model of biobutanol raw mixture has been researched over mesoporous Nix/MgO catalysts (x represented nickel mole percent in Ni–Mg) at 673–873 K. The result showed reactant conversion at lower temperatures allowed ranking the three single-molecule compounds as the function of SR activity as follows: ethanol > acetone > butanol. The catalytic performance of mesoporous Ni0.12/MgO catalyst with lower Ni component containing enough active sites outperformed that of mesoporous Ni0.16/MgO catalyst which was more inclined to sinter in all SR tests of single-component compounds except at 673 K. On the contrary, the catalytic behavior of Ni0.16/MgO (richer in nickel) was superior to that of Ni0.12/MgO catalyst in SR of multicomponent compounds. Moreover, in acetone–butanol–ethanol steam reforming (ABESR), SR of ethanol suffered competition from acetone and ...

A series of Ni-based catalysts supported on different MgO supports were investigated for hydrogen production via steam reforming (SR) of acetic acid (HAc). Three types of NiO and MgO solid solutions were prepared by co-precipitation of Ni(NO3)2 and Mg(NO3)2, impregnation of Ni(NO3)2 on MgO, and impregnation of Ni(NO3)2 on mesoporous MgO (denoted as MgO-m), respectively. The Ni-based catalysts were prepared by reducing these solid solutions at 650 °C in 10% H2/Ar. N2 adsorption results showed that the Brunauer–Emmett–Teller (BET) surface area of NiO/MgO-m solid solution was 3.0 and 2.3 times that of NiO–MgO and NiO/MgO solid solutions, respectively. The Ni/MgO-m catalyst showed the best catalytic performance, and the H2 yield can be enhanced by ∼160% by using the Ni/MgO-m catalyst. Ni/MgO-m kept its high activity up to 20 h of reaction. Thermogravimetry (TG) results indicated that no significant change was observed for the amount of carbon deposits on used Ni/MgO-m after 3 h on stream. Two kind of carbon s...

Tissue engineering approaches combine a bioscaffold with stem cells to provide biological substitutes that can repair bone defects and eventually improve tissue functions. The prospective bioscaffold should have good osteoinductivity. Surface chemical and roughness modifications are regarded as valuable strategies for developing bioscaffolds because of their positive effects on enhancing osteogenic differentiation. However, the synergistic combination of the two strategies is currently poorly studied. In this work, a nanoengineered scaffold with surface chemistry (oxygen-containing groups) and roughness (Rq = 74.1 nm) modifications was fabricated by doping nanohydroxyapatite (nHA), chemically crosslinked graphene oxide (GO) and carboxymethyl chitosan (CMC). The biocompatibility and osteoinductivity of the nanoengineered CMC/nHA/GO scaffold was evaluated in vitro and in vivo, and the osteogenic differentiation mechanism of the nanoengineered scaffold was preliminarily investigated. Our data demonstrated that the enhanced osteoinductivity of CMC/nHA/GO may profit from the surface chemistry and roughness, which benefit the β1 integrin interactions with the extracellular matrix and activate the FAK–ERK signaling pathway to upregulate the expression of osteogenic special proteins. This study indicates that the nanocomposite scaffold with surface chemistry and roughness modifications could serve as a novel and promising bone substitute for tissue engineering.