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Under voltammetric conditions, the neutral decamethylferrocene ([Me10Fc]) to cationic ([Me10Fc]+) FeII/IIIprocess is a well-known reversible outer-sphere reaction. A companion cationic [Me10Fc]+to dicationic [Me10Fc]2+FeIII/IVprocess has been reported under direct current (DC) cyclic voltammetric conditions at highly positive potentials in liquid SO2at low temperatures and in a 1.5:1.0 AlCl3/1-butylpyridinium chloride melt. This study demonstrates that in room-temperature ionic liquids containing the hard to oxidize and hydrophobic tris(pentafluoroethyl)trifluorophosphate anion, the [Me10Fc]+/2+process can be detected as a quasi-reversible reaction at glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Large amplitude Fourier-transformed alternating current (FT-AC) voltammetry minimizes background current contributions occurring at potentials similar to those of the FeIII/IVprocess in the second and higher-order harmonics. This enables a straightforward determination of the thermodynamics and kinetics for both the FeII/IIIand FeIII/IVprocesses. Unlike the ideal outer-sphere FeII/IIIprocess, the parameters of the FeIII/IVprocess may be impacted by ion-interaction effects. For the faster FeII/IIIprocess, heterogeneous rate constants are approximately 10 times smaller at BDD than those at GC electrodes. This electrode dependence is less pronounced for the slower FeIII/IVprocess. The slower BDD kinetics may be attributed in part to a density of states lower than that at GC.

As an oil displacement system for oil reservoir in-depth conformance control, the black nanosheet (BN) can fully play the role of reducing oil–water interfacial tension, emulsifying crude oil, and changing rock wettability. However, at present, the dispersion stability of BNs is poor, and aggregation is prone to occur, which leads to the aggregation and sedimentation of BNs before pumping, affecting their injection and oil displacement performance. This study used a fine organic synthesis method to prepare a modified BN. The stability performance of the BN in low salinity water was analyzed by using a multiple light stabilizer and zeta potential analyzer. A displacement device was employed to conduct oil displacement experiments on BNs before and after modification and to compare their oil displacement effects. Results showed that modified BNs with good stability can be prepared from BNs, cetyltrimethylammonium bromide, and urea. Transmission electron microscopy testing showed that the modified BN had a black powder flake structure of 70 × 400 nm, which indicated the potential for application in low-permeability oil reservoir oil recovery. The modified BN introduced cationic hydrophilic groups and alkyl long chains, increasing the absolute zeta potential from 11.10 to 13.50 mV. The thermal stability index value measured by multiple light scattering confirmed a significant improvement in its stability from a microscopic perspective. Compared with unmodified BNs, modified BNs can significantly increase the oil recovery degree, with an increase of 12.51 percentage points. The modified BNs developed in this work had good dispersion stability and a high oil displacement effect, which could provide a new chemical system for efficient development of low-permeability reservoirs.

Hydrogen embrittlement of pipelines depends on the hydrogen-induced cracking behavior of the pipeline steel microstructure. Based on molecular dynamics analysis, the ferrite–cementite (α-Fe/Fe3C) lamellar atomic structure with the Bagaryatskii orientation relationship was established, and stepwise relaxation of the conjugate gradient energy minimization and constant-temperature and constant-pressure relaxation were performed under NPT (the isothermal–isobaric) conditions. The mechanical property curves of the α-Fe/Fe3C models were obtained under different cementite terminal plane structures, and the evolution of the atomic structure was analyzed in detail. In addition, the influence of different hydrogen concentrations, different temperatures, different strain rates, changes in voids, and different micro-degrees of freedom on the deformation and failure mechanism of the model was investigated, aiming to provide a reliable way to explore the micro-mechanism of macro-cracking behavior of pipeline steel.

MgH2is considered as a promising hydrogen storage material for its high hydrogen storage capacity, low cost and abundant resource advantages. However, the low kinetics and high enthalpy formation of MgH2limit its wide application. From the perspective of adding catalysts to enhance the hydrogen storage properties of Mg-MgH2, this article elaborated the main catalysts based on Ti and Nb transition elements, including single oxide catalysts, binary oxides catalysts (combined with Ni, Na, Sr, V, etc.), multiple catalysts bound to carbon, and composite catalysts with Ti and Nb elements combined with MXene phase. Moreover, the main pathways of various catalysts to reduce the reaction activity and broaden the hydrogen desorption channel were also analyzed. The Ti-based catalysts can enhance the reactive sites of the matrix by forming multivalent states, while Nb-based catalysts broaden the hydrogen reaction channels by forming tiny Nb. By improving the size structure and enhancing the grain size stability, combined with carbon materials should be the future considerations.

Plant stomatal phenotype traits play an important role in improving crop water use efficiency, stress resistance and yield. However, at present, the acquisition of phenotype traits mainly relies on manual measurement, which is time-consuming and laborious. In order to obtain high-throughput stomatal phenotype traits, we proposed a real-time recognition network SLPA-Net for stomata localization and phenotypic analysis. After locating and identifying stomatal density data, ellipse fitting is used to automatically obtain phenotype data such as apertures. Aiming at the problems of small stomata and high similarity to background, we introduced ECANet to improve the accuracy of stoma and aperture location. In order to effectively alleviate the unbalance problem in bounding box regression, we replaced the Loss function with a more effective Focal EIoU Loss. The experimental results show that SLPA-Net has excellent performance in the migration generalization and robustness of stomata and apertures detection and identification, as well as the correlation between stomata phenotype data obtained and artificial data.

Black nanosheets (BNs) and low-salinity water (LSW) flooding are two effective methods for improving oil recovery in low-permeability or ultra-low-permeability petroleum reservoirs. The former focuses on emulsification and interfacial tension reduction, while the latter focuses on wettability alteration. Combining BN with LSW is expected to achieve dual effects in oil recovery. However, there has been no research on the combination effect of BN and LSW on conglomerate reservoirs. Therefore, this study aims to investigate the oil imbibition mechanism of the BN–LSW composite system in the tight reservoir of Mahu Oilfield. The interfacial properties of the BN–LSW composite system were evaluated in terms of the oil–water interfacial tension, crude oil emulsification capability, and three-phase contact angle between oil, water, and rock. Through the imbibition experiment of the natural cores in Mahu Oilfield, the imbibition differences between single systems and the BN–LSW composite system were compared. The results showed that the BN–LSW composite system had minimal impact on the interfacial tension between oil and water compared to formation brine, LSW, and BN solution. However, the composite system demonstrated a significant emulsification effect with Mahu crude oil and alterated the wettability of the core. Compared to the single systems, the imbibition rate of the BN–LSW composite system was higher, resulting in an improved imbibition effect. The NMR T2signal explained the synergistic core imbibition effect of the BN–LSW composite system at the microscopic scale. The research outcomes of this study can provide a new approach for developing low-permeability and ultra-low-permeability reservoirs, holding practical value and reference significance.

To improve the current tracking performance, this article proposes a new fault-tolerant current control for the six-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) system with multifrequency quasi-proportional-resonant (QPR) control and back electromotive force (EMF) feedforward compensation, which can track the time-varying sinusoidal and nonsinusoidal reference currents in the stationary reference frame (SRF) under normal and fault conditions. First, the multifrequency QPR current controller with shunt topology is proposed to track the time-varying reference current in SRF, which can guarantee the current control performance regardless of the motor speed variation and the load torque change. Second, the optimized feedforward compensation method for the back EMF is proposed to further reduce the steady-state current tracking error, which takes the time delay of the digital implementation into consideration. Finally, the effectiveness of the proposed approach is verified on a 3 kW six-phase FTPMSM platform. The resulting six-phase FTPMSM system with the proposed current control has great current tracking performance, strong robustness to various external/internal disturbance, as well as low computational burden, which can guarantee the multiphase FTPMSM system performance in normal and fault conditions.

Plant stomata phenotypic traits can provide a basis for enhancing crop tolerance in adversity. Manually counting the number of stomata and measuring the height and width of stomata obviously cannot satisfy the high-throughput data. How to detect and recognize plant stomata quickly and accurately is the prerequisite and key for studying the physiological characteristics of stomata. In this research, we consider stomata recognition as a multi-object detection problem, and propose an end-to-end framework for intelligent detection and recognition of plant stomata based on feature weights transfer learning and YOLOv4 network. It is easy to operate and greatly facilitates the analysis of stomata phenotypic traits in high-throughput plant epidermal cell images. For different cultivars, multi-scales, rich background features, high density, and small stomata object images, the proposed method can precisely locate multiple stomata in microscope images and automatically give phenotypic traits of stomata. Users can also adjust the corresponding parameters to maximize the accuracy and scalability of automatic stomata detection and recognition. Experimental results on actual data provided by the National Maize Improvement Center show that the proposed method is superior to the existing methods in high stomata automatic detection and recognition accuracy, low training cost, strong generalization ability.

In this work, the physical optics (PO) method based on multilayered medium theory is used to analyze high-frequency scattering characteristics of plasma sheath covering an aircraft. The ray intersection method is taken for occlusion judgment, but some errors occur on the edge between illuminated and shadowed regions of a target. Therefore, the iterative edge patch segmentation based on the adaptive mesh technique is proposed to reduce this error, which is significant to enhance the computational accuracy of the PO method. Furthermore, to simplify the computational process and validate the effectiveness of the adaptive mesh technique, the plasma sheath covering a RAM-C II aircraft is modeled with a five-layered isotropic medium. Compared with uniform fine segmentation, the proposed adaptive mesh technique markedly reduces the computational cost by an order of magnitude while maintaining the accuracy of the PO method. Moreover, high-frequency scattering characteristics of plasma sheath covering a RAM-C II aircraft under different flight conditions are presented via the bistatic radar cross Section (RCS) with observable attenuation effects. Hence, the PO method for multilayered media combined with the proposed lit region judgment method is suitable to analyze the scattering features of the electrically large coated target.

Introduction: The correlation between total and free polymyxin B (PMB including PMB1 and PMB2) exposure in vivo and acute kidney injury (AKI) remains obscure. This study explores the relationships between plasma exposure of PMB1 and PMB2 and nephrotoxicity, and investigates the risk factors for PMB-induced acute kidney injury (AKI) in critically ill patients. Methods: Critically ill patients who used PMB and met the criteria were enrolled. The total plasma concentration and plasma binding of PMB1 and PMB2 were analysed by liquid chromatography–tandem mass spectrometry and equilibrium dialysis. Results: A total of 89 patients were finally included, and AKI developed in 28.1% of them. The peak concentration of PMB1 (Cmax(B1)) (adjusted odds ratio (AOR) = 1.68, 95% CI 1.08–2.62, p= 0.023), baseline BUN level (AOR = 1.08, 95% CI 1.01–1.16, p= 0.039) and hypertension (AOR = 3.73, 95% CI 1.21–11.54, p= 0.022) were independent risk factors for PMB-induced AKI. The area under the ROC curve of the model was 0.799. When Cmax(B1) was 5.23 μg/ml or more, the probability of AKI was higher than 50%. The ratio of PMB1/PMB2 decreased after PMB preparation entered into the body. The protein binding rate in critically ill patients indicated significant individual differences. Free Cmax(B) and free Cmax(B1) levels in the AKI group were significantly (p< 0.05) higher than those in the non-AKI group. Total and free concentrations of PMB in patients showed a positive correlation. Conclusions: Both the ROC curve and logistic regression model showed that Cmax(B1) was a good predictor for the probability of PMB-induced AKI. Early therapeutic drug monitoring (TDM) of PMB should be considered in critically ill patients. Compared with Cmin(B), Cmax(B) and Cmax(B1) may be helpful for the early prediction of PMB-induced AKI in critically ill patients.

A spiro ent-clerodane homodimer with a rare 6/6/6/6/6-fused pentacyclic scaffold, spiroarborin (1), together with four new monomeric analogues (2–5), were isolated from Callicarpa arborea. Their structures were elucidated by comprehensive spectroscopic data analysis, quantum-chemical calculations, and X-ray diffraction. A plausible biosynthetic pathway of 1was proposed, and a biomimetic synthesis of its derivative was accomplished. Compound 1showed a potent inhibitory effect by directly binding to the YEATS domain of the 11-19 leukemia (ENL) protein with an IC50value of 7.3 μM. This gave a KDvalue of 5.0 μM, as recorded by a surface plasmon resonance binding assay.

Electrochemical reduction of the greenhouse gas CO2offers prospects for the sustainable generation of fuels and industrially useful chemicals when powered by renewable electricity. However, this electrochemical process requires the use of highly stable, selective, and active catalysts. The development of such catalysts should be based on a detailed kinetic and mechanistic understanding of the electrochemical CO2reduction reaction (eCO2RR), ideally through the resolution of active catalytic sites in both time (i.e., temporally) and space (i.e., spatially). In this Account, we highlight two advanced spatiotemporal voltammetric techniques for electrocatalytic studies and describe the considerable insights they provide on the eCO2RR. First, Fourier transformed large-amplitude alternating current voltammetry (FT ac voltammetry), as applied by the Monash Electrochemistry Group, enables the resolution of rapid underlying electron-transfer processes in complex reactions, free from competing processes, such as the background double-layer charging current, slow catalytic reactions, and solvent/electrolyte electrolysis, which often mask conventional voltammetric measurements of the eCO2RR. Crucially, FT ac voltammetry allows details of the catalytically active sites or the rate-determining step to be revealed under catalytic turnover conditions. This is well illustrated in investigations of the eCO2RR catalyzed by Bi where formate is the main product. Second, developments in scanning electrochemical cell microscopy (SECCM) by the Warwick Electrochemistry and Interfaces Group provide powerful methods for obtaining high-resolution activity maps and potentiodynamic movies of the heterogeneous surface of a catalyst. For example, by coupling SECCM data with colocated microscopy from electron backscatter diffraction (EBSD) or atomic force microscopy, it is possible to develop compelling correlations of (precatalyst) structure–activity at the nanoscale level. This correlative electrochemical multimicroscopy strategy allows the catalytically more active region of a catalyst, such as the edge plane of two-dimensional materials and the grain boundaries between facets in a polycrystalline metal, to be highlighted. The attributes of SECCM-EBSD are well-illustrated by detailed studies of the eCO2RR on polycrystalline gold, where carbon monoxide is the main product. Comparing SECCM maps and movies with EBSD images of the same region reveals unambiguously that the eCO2RR is enhanced at surface-terminating dislocations, which accumulate at grain boundaries and slip bands. Both FT ac voltammetry and SECCM techniques greatly enhance our understanding of the eCO2RR, significantly boosting the electrochemical toolbox and the information available for the development and testing of theoretical models and rational catalyst design. In the future, it may be possible to further enhance insights provided by both techniques through their integration with in situand in operandospectroscopy and microscopy methods.

A series of 6-substituted carbazole-based retinoic acid-related orphan receptor gamma-t (RORγt) modulators were discovered through 6-position modification guided by insights from the crystallographic profiles of the “short” inverse agonist 6. With the increase in the size of the 6-position substituents, the “short” inverse agonist 6first reversed its function to agonists and then to “long” inverse agonists. The cocrystal structures of RORγt complexed with the representative “short” inverse agonist 6(PDB: 6LOB), the agonist 7d(PDB: 6LOA) and the “long” inverse agonist 7h(PDB: 6LO9) were revealed by X-ray analysis. However, minor differences were found in the binding modes of “short” inverse agonist 6and “long” inverse agonist 7h. To further reveal the molecular mechanisms of different RORγt inverse agonists, we performed molecular dynamics simulations and found that “short” or “long” inverse agonists led to different behaviors of helixes H11, H11’, and H12 of RORγt. The “short” inverse agonist 6destabilizes H11’ and dislocates H12, while the “long” inverse agonist 7hseparates H11 and unwinds H12. The results indicate that the two types of inverse agonists may behave differently in downstream signaling, which may help identify novel inverse agonists with different regulatory mechanisms.

The search for novel forms of computing to the dominant von Neumann model-based approach is important as it will enable different classes of problems to be solved. Molecular computers are a promising alternative to semiconductor-based computers given their potential biocompatibility and cost advantages. The vast space of chemical reactions makes molecules a tunable, scalable, and energy-efficient computational vehicle. In molecular computers, memory and processing units can be combined into a single, inherently parallelized device. Here, we present a microdroplet array molecular computer to solve combinatorial optimization problems by employing an Ising Hamiltonian to map problems heuristically to droplet-droplet interactions. The droplets represent binary digits and problems are encoded in intra- and inter-droplet reactions. We propose two implementations: first, a hybrid classical-molecular computer that enforces inter-droplet constraints in a classical computer and, second, a purely molecular computer where the problem is entirely pre-programmed in the nearest-neighbor droplet reactions.

Ultralow-permeability oil reservoirs are characterized by small pore throats, ultralow permeability, and high fluid flow resistance, which often lead to challenging injection during water flooding processes. Black nanosheet, as an emerging sheet-like nano oil displacement material, can alter the wettability of reservoir rocks, effectively improving water injection performance. However, its dispersion stability in an aqueous solution is insufficient, leading to probable aggregation during water flooding and affecting the oil recovery efficiency. In this study, anionic-modified black nanosheet was developed using a chemical method. The dispersion stability of the anionic-modified black nanosheet was evaluated by using a multiple light stability analyzer and a ζ-potential analyzer. Additionally, the interfacial properties were assessed with a contact angle measurement instrument and emulsification experiments. Finally, the imbibition performance in ultralow-permeability oil reservoirs was evaluated through imbibition experiments combined with nuclear magnetic resonance technology. Results showed that sulfonate groups can be grafted onto black nanosheets by chemical methods. Anionic-modified black nanosheet exhibited a black sheet-like structure, showing potential applicability in ultralow-permeability oil reservoirs. The transmittance stability index (TSI) value of the anionic-modified black nanosheet decreased from 14.26 to 3.33, and the absolute value of ζ-potential increased from 10.4 to 27.5 mV, indicating significantly improved dispersion stability. The effect of anionic-modified black nanosheet on altering the surface wettability of oil-saturated rocks was more pronounced, and the crude oil emulsification effect was also enhanced. In addition, solutions of modified black nanosheets showed a better imbibition oil recovery performance. The nuclear magnetic resonance (NMR) T2spectrum revealed at the microscopic scale that the modified black nanosheet could facilitate the better imbibition from the small pores of ultralow-permeability reservoir core samples, thereby enhancing the efficiency of microscopic flooding.

Marker-assisted selection (MAS) and genomic selection (GS) breeding have greatly improved the efficiency of rice breeding. Due to the influence of epistasis and gene pleiotropy, how to ensure the actual breeding effect of MAS and GS is still a difficult problem to overcome. In this study, 113 indicarice varieties (V) and their 565 testcross hybrids (TC) were used as materials to investigate the genetic basis of 12 quality traits and 9 agronomic traits. The original traits and general combining ability of parents, as well as the original traits and mid-parent heterosis of testcross hybrids were subjected to genome-wide association analysis. In total, 381 primary significantly associated loci (SAL) and 1759 secondary SALs that had epistatic interaction with these primary SALs were detected. 322 candidate genes located within or nearby the SALs were screened, of which 204 were cloned genes. A total of 39 MAS molecular modules that are beneficial for trait improvement was identified by pyramiding the superior haplotype of candidate genes and desirable epistatic allele of secondary SALs. All the SALs were used to construct genetic networks, in which 91 pleiotropic loci were investigated. Additionally, we estimated the accuracy of genomic prediction in parent varieties and testcross hybrids by incorporating no SALs, primary SALs, secondary SALs or epistatic effect SALs as covariates. Although the prediction accuracy of the four models was mostly not significantly different in the TC dataset, the incorporation of primary SALs, secondary SALs, and epistatic effect SALs significantly improved the prediction accuracy of 5(26%), 3(16%), and 11(58%) traits in the V dataset, respectively. These results suggested that SALs and epistatic effect SALs identified based on additive genotype can provide considerable predictive power for parental lines. These results provide insights into the genetic basis of complex traits and valuable information for molecular breeding in rice.

Carbon-encapsulated metal–organic framework (MOF) composite is one kind of emerging new catalyst with high efficiency and has gained much attention. However, for this kind of composite catalyst, the key to improving its catalytic activity and durability is to realize the effective dispersion of MOF nanoparticles (NPs) and enhance the interaction between MOF NPs and the carbon matrix, which remain a significant challenge. Herein, ultrafine MOF NPs within multichamber carbon spheres (MOF@MCCS), for the first time, have been rationally synthesized by a two-step double-solvent strategy for high-performance catalysts. The precise loading of guest MOFs can be achieved by adjusting the multichamber structure and calcination extent of the multichamber polymer (MCP), and the particle size of MOFs can be as low as 13.2 nm. Due to the formation of abundant carbon defects in the pyrolysis process of MCPs, the special structure and synergistic effect make the material exhibit higher catalytic activity and durability. More importantly, this method is universal and can be extended to different MOF systems. The two-step double-solvent strategy not only prepares a unique structure of MOF@MCCS-type host–guest-encapsulated catalysts but also provides a new idea for the design of high-efficiency catalysts with better performance and higher durability.

Hollow carbon-based nanospheres (HCNs) have been demonstrated to show promising potential in a large variety of research fields, particularly electrochemical devices for energy conversion/storage. The current synthetic protocols for HCNs largely rely on template-based routes (TBRs), which are conceptually straightforward in creating hollow structures but challenged by the time-consuming operations with a low yield in product as well as serious environmental concerns caused by hazardous etching agents. Meanwhile, they showed inadequate ability to build complex carbon-related architectures. Innovative strategies for HCNs free from extra templates thus are highly desirable and are expected to not only ensure precise control of the key structural parameters of hollow architectures with designated functionalities, but also be environmentally benign and scalable approaches suited for their practical applications.

Circular RNAs (circRNAs) produced from back-spliced exons are widely expressed, but individual circRNA functions remain poorly understood owing to the lack of adequate methods for distinguishing circRNAs from cognate messenger RNAs with overlapping exons. Here, we report that CRISPR–RfxCas13d can effectively discriminate circRNAs from mRNAs by using guide RNAs targeting sequences spanning back-splicing junction (BSJ) sites featured in RNA circles. Using a lentiviral library that targets sequences across BSJ sites of highly expressed human circRNAs, we show that a group of circRNAs are important for cell growth mostly in a cell-type-specific manner and that a common oncogenic circRNA, circFAM120A, promotes cell proliferation by preventing the mRNA for family with sequence similarity 120A (FAM120A) from binding the translation inhibitor IGF2BP2. Further application of RfxCas13d–BSJ-gRNA screening has uncovered circMan1a2, which has regulatory potential in mouse embryo preimplantation development. Together, these results establish CRISPR–RfxCas13d as a useful tool for the discovery and functional study of circRNAs at both individual and large-scale levels.

Polyoxometalates (POMs) have been proposed as electromaterials for lithium-based batteries because they provide access to multiple electron transfer reactions coupled to fast lithium ion transport processes and high stability over many redox cycles. Consequently, knowledge of reversible potentials and Li+cation–POM anion interactions provides a strategic basis for their further development. In this study, detailed cyclic voltammetric studies of a series of [XVVM11O40]n−(XVM11n–) POMs (where X (heteroatom) = P (n= 4), As (n= 4), and S (n= 3) and M (addenda atom) = Mo, W) have been undertaken in CH3CN in the presence of LiClO4, with n-Bu4NPF6also present when required to keep the ionic strength close to constant value of 0.1 M. An analysis of the data has allowed the impact of the POM charge, and addenda and hetero atoms on the reversible potentials and the interaction between Li+and the oxidized XVVM11n–and reduced XVIVM11(n+1)–forms of the VV/IVredox couple to be determined. The SVV/IVM113–/4–process is independent of the Li+concentration, implying the absence of the association of this cation with either SVVM113–or SVIVM114–redox levels. However, lithium-ion association constants for both VVand VIVredox levels were obtained from a comparison of simulated and experimental cyclic voltammograms for the reduction of the more negatively charged XVVM114–(X = P, As; M = Mo, W), since the Li+interaction with these more negatively charged POMs is much stronger. The interaction between Li+and the oxidized, XVVM11n–, and reduced, XVIVM11(n+1)–, forms was also investigated by 51V NMR and EPR spectroscopy, respectively, and it was confirmed that, due to their lower charge density, SVVM113–and SVIVM114–interact significantly less strongly with the lithium ion than XVVM114–and XVIVM115–(X = P, As). The lithium–POM association constants are substantially smaller than the corresponding proton association constants reported previously, which is attributed to a smaller surface charge density. The much stronger impact of Li+on the WVI/V- and MoVI/V-based reductions that occur at more negative potentials than the VV/IVprocess also has been qualitatively evaluated.

The hydrogenation of CO2 to CH4 can realize the utilization of CO2, which has an important implications to both the energy and environment. As a result of the low catalytic activity of the supported Ni/SiO2 catalyst, the ZrO2 is added to improve its catalytic performance by the impregnation method. The experimental results show that ZrO2 is an effective promoter to enhance the low-temperature catalytic activity of Ni/SiO2 catalyst.

Addition of low concentrations of water to an aprotic solvent can lead to large changes in the thermodynamics of some electrode processes. In contrast, the impact of water addition on the electrode kinetics of such systems has yet to be established. Herein, direct current and Fourier transformed alternating current voltammetric studies were undertaken at a glassy carbon electrode to investigate changes in the thermodynamics, kinetics, and diffusivity of the [Ru(CN)6]4–/3–process in propylene carbonate (PC, 0.10 M n-Bu4NPF6) that occur on addition of up to 1.87 M water and in fully aqueous 0.10 M KCl electrolyte media. The formal reversible potential (Ef0) for the [Ru(CN)6]4–/3–couple is −0.66 V versus Fc0/+(Fc = ferrocene) in PC and shifts substantially in the positive direction by ∼0.35 V in the presence of 1.87 M water, and it is established to be 1.0 V more positive in fully aqueous media. In comparison, Ef0for the Fc0/+process only changes by ∼20 mV versus a Pt quasi reference electrode in the presence of 1.87 M water, emphasizing the impact of charge and structure on the thermodynamics. Modeling the water-induced shift in Ef0in terms of solvent interaction implies that transfer of approximately four water molecules in the secondary coordination sphere accompanies the oxidation of [Ru(CN)6]4–to [Ru(CN)6]3–. Despite the implied large level of solvent rearrangement, the heterogeneous electron transfer rate constant only increases from 1.81 × 10–2cm s–1in “dry” PC to 3.38 × 10–2cm s–1on addition of 1.87 M water to PC. An increase in diffusivity of [Ru(CN)6]4–was observed but is not evident in the Fc0/+process under the same conditions; hence, it is probably not simply due to the small decrease in viscosity that occurs on addition of low concentrations of water. Some, but not all, aspects of the kinetics are in qualitative agreement with Marcus theory predictions.

Purpose: Absolute measurement of radiant power in the X-ray region is essential for many applications in astrophysics, spectroscopy, and X-ray diagnostics. This paper presents a dependable method of absolute measurement of radiant power for synchrotron radiation monochromatized X-rays. Methods: A free-air ionization chamber was examined closely and employed as the detector in the present work. Its measuring principle was discussed, and the correction factors were determined. Absolute measurement of radiant power for synchrotron radiation monochromatized X-rays in the region of 6–20 keV was performed using the free-air ionization chamber at Beijing Synchrotron Radiation Facility. As a verification and an important application, photodiodes were calibrated against the free-air ionization chamber. Results: Relative standard uncertainties of absolute measurement using free-air ionization chamber are about 1%. Calibration of photodiodes within the photon energy range from 6 to 20 keV has relative standard uncertainties below 1.5%. Conclusion: The free-air ionization chamber is qualified to be used in many disciplines to support the measurement of optical radiation.

The rational design of binuclear Au(I)–Au(I), Au(II)–Au(II), and Au(I)–Au(III) complexes requires an understanding of how the redox states interconvert. Herein, the electrochemical interconversion of the three oxidation states I, II, and III is reported on the voltammetric (cyclic and rotating disk electrode) time scales for binuclear gold complexes containing C6F4PPh2as a ligand, to demonstrate for the first time formation of a binuclear Au(II)–Au(II) from a Au(I)–Au(III) complex. Results are supported by bulk electrolysis and coulometry with reaction products being identified by 31P NMR and UV–vis spectroscopy. All electrochemical processes involve an overall two-electron charge-transfer process with no one-electron intermediate being detected. Importantly, the kinetically rather than thermodynamically favored isomer [Au2IIX2(μ-2-C6F4PPh2)2] is formed on redox cycling of [XAuI(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuIIIX] (X = Cl, ONO2). Finally, a mechanism is proposed to explain the simultaneous change of coordination of the chelating carbanionic ligand to bridging mode and interconversion of oxidation states in binuclear gold complexes.

The electrochemical properties of boron-doped diamond (BDD) electrodes are strongly influenced by the boron doping level and the presence of sp2carbon impurities. In this study, the impact of highly localized sp2carbon concentrated at the edge of a BDD electrode, arising from laser cutting during fabrication and exposed during electrode polishing, on the resulting overall electrode kinetics is identified. Fourier transformed large-amplitude alternating current (FTAC) voltammetric data for the usually ideal Fc0/+(Fc = ferrocene) process in the highly viscous ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate show relatively poor agreement with simulations based on a uniformly active electrode surface using the Butler–Volmer formalism for the electrode kinetics. In this ionic liquid medium, the impact of heterogeneity on the macroscopic electrode activity is enhanced under the conditions of slow mass transport, where sites of disparate activities are spatially decoupled on the voltammetric time scale. Physically blocking this edge region leads to a response that is much more consistent with a uniform electrode and substantially improves the agreement between the FTAC voltammetric experiment and simulation (standard heterogeneous electron-transfer rate constant, k0= 0.0015 cm s–1). To complement the macroscopic measurements, local voltammetric measurements with an electrochemical droplet cell show directly that the sp2carbon found in the edge region is able to support much faster electron-transfer kinetics for the Fc0/+process than the sp3BDD surface. Overall, this study demonstrates that caution should be taken in reporting electrode kinetic data obtained at BDD or any other heterogeneous electrode materials. Macroscopic electrode kinetic characterization in traditional electrochemical media such as acetonitrile is blind to such heterogeneities in the activity. However, tuning the diffusional time scale through the use of FTAC voltammetry in viscous ionic liquids provides a powerful approach for detecting the spatially nonuniform electrode activity.

We report the observation of electron-induced unidirectional planar molecular rotation of para-chlorostyrene on Si(100), studied by scanning tunneling microscopy (STM) at room temperature and by ab initio theory. This bifunctional molecule is shown to be favorable to the electron-induced rotation since the phenyl group acts as a pivot and the vinyl as a lever arm. In the initial configuration, both phenyl and vinyl are attached to silicon dimers along the same row of the substrate. The first electron from the STM tip is observed to induce a lateral shift of the vinyl to “state 1” in which the vinyl is bound asymmetrically to one side of a silicon dimer. The second electron is found to give rise to a ∼60° rotation to “state 2”, a configuration in which the vinyl has swung around the phenyl to an adjacent dimer row. The impulsive two-state (I2S) model was employed to explain the conversion of the initial state to state 1 and the conversion of state 1 to state 2. These two successive impulses were computed by the I2S model to be the result of excitation to different configurations in an anionic excited state. Following addition of the second electron, the repulsion between the asymmetric vinyl and the surface was shown to give rise to a torque with the magnitude and direction required to explain the observed rotation.

Background: Adenosine deaminase (ADA) is an important enzyme in purine metabolism and is known as a potential therapeutic target for the treatment of lymphoproliferative disorders and cancer. Traditional Chinese Herbal Medicine (TCHM) is widely used alone or in combination with chemotherapy to treat cancer, due to its ability to deliver a broad variety of bioactive secondary metabolites as promising sources of novel organic natural agents. Objective: In the present study, 29 varieties of medicinal plants were screened for the presence of ADA inhibitors. Results: Extracts from Reynoutria japonica, Glycyrrhiza uralensis, Lithospermum erythrorhizon, Magnolia officinalis, Gardenia jasminoides, Stephania tetrandra, Commiphora myrrha, Raphanus sativus and Corydalis yanhusuo demonstrated strong ADA inhibition with rates greater than 50%. However, Reynoutria japonica possessed the highest ADA inhibitory activity at 95.26% and so was used in our study for isolating the ADA inhibitor to be further studied. Eight compounds were obtained and their structures were identified. The compound H1 had strong ADA inhibitory activity and was deduced to be emodin by 1H and 13C-NMR spectroscopic analysis with an IC50 of 0.629 mM. The molecular docking data showed that emodin could bind tightly to the active site of ADA. Our results demonstrated that emodin displayed a new biological activity which is ADA inhibitory activity with high cytotoxic activity against K562 leukemia cells. The bioactivity of cordycepin was significantly increased when used in combination with emodin. Conclusion: Emodin may represent a good candidate anti-cancer therapy and adenosine protective agent.

A model is presented for the chemomechanical coupling of kinesin motors, which proposes that the rate constants of the chemical reaction are independent of the external force. On the basis of the model, we study theoretically the movement dynamics of the motors under varying external force and ATP concentration, such as the forward to backward stepping ratio, velocity, dwell time between two mechanical steps, stall force, and so on. The theoretical results reproduce quantitatively the diverse and even contradictory available single-molecule experimental data for different species of the motors. Furthermore, we study the dependence of the chemomechanical coupling ratio on ATP concentration and external force, with both ATP concentration and external force having large effects on the chemomechanical coupling.

Recent years have witnessed a tremendous upsurge in constructing multifunctional heterostructured photocatalysts by capitalizing on the semiconductor building blocks of varying dimensionalities in terms of their synergistic superior charge separation/transfer efficiency. Nevertheless, tunable modulation of charge transfer viastructure engineering still constitutes a challenge. Herein, zero-dimensional single-layered graphitic-carbon nitride (C3N4) quantum dots (g-C3N4QDs) and two-dimensional (2D) nanoporous CdS nanosheets (NSs) were utilized as assembly units for strategically constructing well-defined g-C3N4QDs/CdS NS heterostructures viaa facile and green electrostatic self-assembly approach, by which g-C3N4QDs were uniformly and intimately tethered on the CdS NSs framework. Intriguingly, such g-C3N4QDs/CdS NS heterostructures demonstrate an unconventional charge transfer pathway owing to the unique energy level structure of g-C3N4QDs and CdS NSs dictated by structure engineering. It was significant to unveil that the g-C3N4QDs/CdS NS heterostructure exhibits versatile and remarkably boosted photoredox performances toward anaerobic reduction of aromatic nitro compounds and mineralization of organic pollutants along with prominent photo-corrosion resistance under visible light irradiation in comparison with single and various bulk counterparts. The underlying reasons accounting for the considerably improved photoredox performances of g-C3N4QDs/CdS NS heterostructures were uncovered including boosted charge separation/transfer afforded by peculiar structural merits of C3N4QDs and 2D CdS NSs, intimate interfacial contact and a unique spatial interfacial integration mode. Furthermore, predominant active species in the photoredox reactions were systematically explored and unambiguously determined, based on which, a photocatalytic mechanism was presented. It is hoped that our work could spur further interest in rationally designing diverse heterostructured photocatalysts and simultaneously provide new insights into the spatial charge transfer in multifarious photoredox catalysis for substantial solar energy conversion.

With the advancement in X-ray astronomical detection technology, various celestial polarization detection projects have been initiated. To meet the calibration requirements of polarimeters on the ground, a polarized X-ray radiation facility was designed for this study. The design was based on the principle that X-rays incident at 45° on a crystal produce polarized X-rays, and a second crystal was used to measure the polarization of the X-rays produced by the facility after rotation. The effects of different diaphragm sizes on the degree of polarization were compared, and the facility produced X-rays with polarization degrees of up to 99.55 ± 0.96% using LiF200 and LiF220 crystals. This result revealed that the polarization of incident X-rays is one of the factors affecting the diffraction efficiency of crystals. The replacement of different crystals can satisfy the calibration requirements of polarized X-ray detectors with more energy points in the energy range (4–10) keV. In the future, the facility should be placed in a vacuum environment to meet the calibration requirements at lower energies.