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We have developed a novel TfOH-catalyzed regioselective O-alkylation of 2-pyridones with diazo compounds in high regioselectivity. This protocol is characterized by mild reaction conditions, metal-free, and simplicity.

Frogeye leaf spot (FLS) causes severe yield loss in soybean and has been found in several countries worldwide. Therefore, it is necessary to select and utilize FLS-resistant varieties for the management of FLS. In the present study, 335 representative soybean materials were assessed for partial resistance to FLS race 7. Quantitative trait nucleotide (QTN) and FLS race 7 candidate genes were identified using genome-wide association analysis (GWAS) based on a site-specific amplified fragment sequencing (SLAF-seq) approach. A total of 23,156 single nucleotide polymorphisms (SNPs) were used to evaluate the level of linkage disequilibrium with a minor allele frequency ≥ 5 and deletion data < 3%. These SNPs covered about 947.01 MBP, nearly 86.09% of the entire soybean genome. In addition, a compressed mixed linear model was utilized to identify association signals for partial resistance to FLS race 7. A total of 15 QTNs associated with resistance were found to be novel for FLS race 7 resistance. A total of 217 candidate genes located in the 200 kb genomic region of these peak SNPs were identified. Based on gene association analysis, qRT-PCR, haplotype analysis and virus-induced gene silencing (VIGS) systems were used to further verify candidate genes Glyma.16G176800, Glyma.16G177300, Glyma.16G177400 and Glyma.16G182300. This indicates that these four candidate genes may participate in FLS race 7 resistance responses.

A novel highly selective N2-alkylation of indazoles with diazo compounds is described in good to excellent yields with high regioselectivity (N2/N1 up to 100/0) and excellent functional group tolerance.

The soybean cyst nematode (SCN, Heterodera glycine Ichinohe) is a major disease affecting soybean (Glycine max (L.) Merr.) production and yield. Breeding of new SCN-resistant cultivars and understanding their resistance mechanisms are valuable for improving SCN resistance of soybean. However, we still know little about resistance mechanisms to SCN. The purpose of our analysis was to understand the different resistance mechanisms of resistant and susceptible lines to SCN by dissecting their transcriptional changes during infection by SCN HG type 1.2.3.5.7. In this study, 119 recombinant inbred lines derived from a cross of cv. Dongnong L-204 (SCN resistant) and cv. Heinong 37 (SCN susceptible) were identified for resistance status to SCN HG type 1.2.3.5.7. Roots of the lines identified as extremely resistant or susceptible (L5, L89) were sequenced by transcriptome, and we obtained 66.61 Gb of data. Compared with the untreated control, there were 8394 and 6899 differentially expressed genes in SCN-infected roots of L5 and L89, respectively. Genes of metabolic pathways, biosynthesis of secondary metabolites, plant hormone signal transduction, and plant–pathogen interaction pathway were significantly expressed in both resistant and susceptible genotypes. The expression of genes of phenylpropanoid biosynthesis, flavonoid biosynthesis, thiamine metabolism, cutin, suberin and wax biosynthesis, and endocytosis pathway was significantly higher in the resistant line than the susceptible line. Transcription factor analysis showed that 88 transcription factors from 18 transcription factor families responded to SCN stress. Nine genes were identified by reverse transcriptase qPCR to be associated with SCN resistance. This study helps us to understand better the mechanism of soybean resistance to SCN.

Selective alkylation of 2-pyridone could solve a challenge in chemistry and streamline the synthesis of important molecules. Here we report the regioselective

The strong pressure wave in gas explosion accident could cause great casualties and property loss, which has become the main threat to safety of chemical process and further popularization of clean energy. In this research, unconfined explosion experiments under different methane concentrations at 27 m3 scale were performed with internal and external obstacles. The results showed that the flame buoyant effect was more obvious for the rich-fuel flame due to the excess methane accumulation. The reflection of the pressure wave could cause higher overpressure near the ground and the external obstacle enhanced the overpressure in the neighborhood. For 27 m3 scale explosion, the critical flame radius for the flame acceleration was larger than 1 m3 scale, because of the longer travelling distance for the reflection wave from the bottom. In addition, the acceleration exponent rose to 1.5 due to the full development of the hydrodynamic instability. The flame radius for peak overpressure, RM, was found to be at a certain distance from the outer obstacle bar center, which was 1.8 for Nb = 6, 1.35 for Nb = 4 and 0.9 for Nb = 2. The predicted results of peak overpressure agreed well with the experimental results, which extended the prediction model to the larger scale.

Vented PMMA dust explosions were conducted in a 20-L spherical chamber with a venting diameter of 80 mm. The flame behaviors and overpressure characteristics at different dust concentrations and static activation pressure were studied. The development mechanism of external flame and the comparison results with two standards were analyzed. The results showed the reduction of dust concentration was necessary for mitigating the external flame, while blindly decreased the static activation pressure would bring greater risk. The characteristics of reduced explosion pressure inside the chamber were analyzed combined with external pressure. Then the rupture mechanism of the venting diaphragm was established based on the elastoplastic analysis. Two empirical modified equation for NFPA68 and EN14491 was established. For NFPA68, the volume correction coefficient of size effect was introduced and the inapplicability of NFPA68 at elevated static activation pressure was attributed to ignoring the compressibility and the choking phenomenon of high-speed fluid.

Aluminum dust explosion venting experiments with static activation pressure ranging from 70 kPa to 280 kPa were conducted in the 20 L spherical chamber with venting diameters from 20 mm to 125 mm. For the case of high activation pressure, the maximum flame length in experiments is 1.64 m, which is close to the prediction of standard, while the maximum width is significantly smaller than the prediction. New fitting formulas in a laboratory scale for flame length and width are obtained, which provide a reference for venting safety area design, and the effect of activation pressure, dust concentration and venting area are taken into account. By the comparison, the external pressure prediction of EN14491 shows a good performance and NFPA68 has an opposite trend with experiments. Based on the experimental results, it is found that the the external pressure attenuation is inversely proportional to the distance, which is different with the coefficient of the distance suggested by the standard EN 14491.

The suppression mechanism of inert gases for 5 μm aluminum dust explosion was investigated in a confined cuboid chamber. The characteristic parameters of flame propagation and explosion severity parameters that were affected by the inert gases were systematically studied. The results indicated that the minimum inerting volume fraction of carbon dioxide was lower than that of nitrogen, thereby indicating that the suppression effect of carbon dioxide on aluminum dust explosion was superior to that of nitrogen. To reveal the suppression mechanism on a micro level, a kinetic model that considered the surface kinetic mechanism was proposed. The results revealed that as the inerting volume fraction of the inert gas increased, the heterogeneous reactions that promoted the generation of intermediate species were mostly suppressed, while the heterogeneous reactions that consumed intermediate species were facilitated. Thus, carbon dioxide and nitrogen exerted certain suppression effects on surface reactions in their characteristic ways.

An electron transport layer (ETL) with excellent conductivity and suitable band alignment plays a key role in accelerating charge extraction and transfer for achieving highly efficient planar perovskite solar cells (PSCs). Herein, a novel diluted-cadmium sulfide quantum dot (CdS QD)-assisted SnO2 ETL has been developed with a low-temperature fabrication process. The slight addition of CdS QDs first enhances the crystallinity and flatness of SnO2 ETLs so that it provides a promising workstation to obtain high-quality perovskite absorption layers. It also amazingly increases the conductivity of the SnO2 ETL by an order of magnitude and regulates the energy level matching between the SnO2 ETL and perovskite. These outstanding properties greatly accelerate the charge extraction and transfer. Thus, the MAPbI3-based PSCs with such a diluted-CdSQD-assisted SnO2 ETL achieve a maximum power conversion efficiency of 20.78% and obtain a better stability of devices in air. These findings testify the importance and potential of semiconductor QD modification on ETLs, which may pave the way for developing such composite ETLs for further enhancing photovoltaic performance of planar PSCs.

This study examines the suppression effectiveness of fluorinated species CHF3 and C2HF5 on the premixed hydrogen-air explosions experimentally and numerically. The results demonstrate that as for stoichiometric and rich hydrogen-air mixtures, both CHF3 and C2HF5 can effectively reduce thermal expansion ratio and increase flame thickness, and then reduce the influence of hydrodynamic instability on the flame acceleration. Laminar burning velocity, the maximum of explosion pressure, the maximum rate of pressure rise and the absolute value of pressure impulse all decrease with increasing suppressant concentration at various equivalent ratios. The maximum of explosion pressures for stoichiometric flames is decreased by 11.54 % with 2 % CHF3 added, and decreased rapidly by 40.39 % with 2 % C2HF5 added. The hydrogen-rich mixtures cannot be ignited when C2HF5 content reaches 10 %. Numerical simulations have confirmed that both CHF3 and C2HF5 can effectively reduce the concentration of active radicals with the decrease order of H > OH > O. C2HF5 is more effective in suppressing explosions than CHF3 by converting more H atoms to HF formation through the elementary reactions CHF2 + H CHF + HF, CF2:O + H CF:O + HF, and CF2 + H = CF + HF.

This work is aimed at evaluating hydrogen cloud explosion with built-in obstacles experimentally and theoretically. The flame front evolution is captured using infrared filtering technology and the explosion overpressure at four monitoring points is measured using free-field sound pressure sensor. The laminar flame model and turbulent flame model are established to theoretically predict maximum explosion overpressure in advance. The results demonstrated that the flame acceleration of hydrogen cloud explosion with built-in obstacles is attributed to mutual promotion of flame instabilities and obstacle-induced turbulence. The effects of built-in obstacles on maximum flame front velocity is relatively limited and maximum value of flame wrinkling factor is ΞΔ,max = 3.64. As the distance between pressure sensor and ignition source increases, the maximum explosion overpressure, positive overpressure impulse and absolute value of negative overpressure impulse are decreased monotonously. The positive overpressure and negative overpressure are mainly affected by steel pipe number in vertical and horizontal direction, rather than length of steel pipe cross-section. The velocity of explosion overpressure propagating in the air is c = 350.88 m/s. The maximum explosion overpressure should be significantly underestimated by laminar flame model, the turbulent flame model could be used to satisfactorily predict maximum explosion overpressure at four monitoring points.

The suppression effect of expandable graphites (EGs) on 5 μm aluminum dust explosions was systematically studied in an open-space dust apparatus. Flame propagation behaviors showed that flame structures became more discrete and more irregular after the addition of EGs. The flame propagation velocities declined variously owing to the suppression effect of EGs. Meanwhile, the optimum suppression concentration for each EG was determined. It was proved that the suppression effect was improved remarkably by increasing the expandable ratios of EGs. Moreover, expandable ratios of EGs had a preferable influence on the suppression effect in comparison with size distributions. Scanning electron microscopy demonstrated that the volumes of EGs increased by several hundred times when encountered with high temperature and the surface got fluffy and multihole. Based on above results, the suppression mechanism of EG for aluminum dust explosions was summarized in this paper in detail.

To effectively mitigate accidental biomass dust explosion, the suppression capacities of NaHCO3 and NH4H2PO4 for biomass dust explosion were determined. Suppression mechanism of biomass flame was further revealed. Poplar sawdust and peanut shell dust with two particle size distributions were employed. A high-speed camera was used for to capture flame propagation behavior and microstructure. Flame temperature was measured by a fine thermocouple. Results showed that the consequences of poplar sawdust explosion are greater than peanut shell dust. By increasing the concentration of NaHCO3 and NH4H2PO4, the average flame velocity and flame temperature of pulverized biomass dust were significantly decreased. The minimum suppression concentration of NaHCO3 was about 30% lower than that of NH4H2PO4. The suppressants could consume key radicals of biomass flame, resulting in lower flame speed and lower flame temperature. The heat absorbed by NH4H2PO4 decomposition was about 6.5 times that of NaHCO3 decomposition. However, the extra heat released from the exothermic reactions of NH4H2PO4 could enhance biomass combustion. Hence, NaHCO3 has a better suppression performance than NH4H2PO4 for biomass dust explosion.

Selective alkylation of indazoles is still a highly challenging topic in chemistry and the synthesis of important molecules. Herein, a novel highly selective

Background To investigate the effect of circular RNA circ ACAP2 on apoptotic phenotype of rat cardiomyocytes and its molecular mechanism. Methods Left anterior descending ligation was used to establish a rat myocardial infarction (MI) model, and real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of circ ACAP2 in apoptotic rat cardiomyocytes. The stability of circ ACAP2 was tested by actinomycin D and RNase R. H9C2 cells were infected by recombinant circ ACAP2 adenovirus (rAd-circ ACAP2), and the expression of apoptotic related genes Bax and BCL-2 in H9C2 was detected. Double luciferase reporter gene experiment, RNA antisense purification experiment and RNA Pull-Down experiments verified the binding effect of circ ACAP2 and miR-29. Results RT-qPCR results showed that the expression of circ ACAP2 was increased in cardiomyocytes of MI rats. Actinomycin D and RNase R experiment confirmed that circ ACAP2 had better stability and resistance to RNase R degradation than its host gene ACAP2 mRNA. Overexpression of circ ACAP2 promotes apoptosis. The double luciferase reporter gene assay, RNA antisense purification assay and RNA Pulldown assay consistently confirmed the specific binding effect between circ ACAP2 and miR-29, and circ ACAP2 promoted the apoptotic phenotype in rats. Conclusions The expression of circ ACAP2 increased in cardiomyocytes after MI and promoted apoptosis by binding to miR-29.

Correction for ‘Regioselective O-alkylation of 2-pyridones by TfOH-catalyzed carbenoid insertion’ by Zhewei Yan et al., Chem. Commun., 2023, 59, 106–109, https://doi.org/10.1039/d2cc05676c.

Flame suppression mechanism of KHCO3 for 100 nm PMMA dust explosions was investigated experimentally and computationally. The effect of KHCO3 particle size on the suppression efficiency was examined. The study revealed that the larger the proportion of added KHCO3, the more significant the suppression effect on flame, for KHCO3 particles with a fixed particle size distribution. The suppression effects were significantly increased with the decreasing of KHCO3 particle size distributions. For endothermic mechanism, when the KHCO3 particles with three particle sizes were mixed with 100 nm PMMA, the heat absorption peaks exhibited at the initial stage, in which the heat absorption values were 28 J/g, 26 J/g and 21 J/g, respectively. A kinetics model was established to reveal the chemical suppression mechanism. It was presented that the mole fractions of key flame radicals (H and OH) were obviously reduced during the chain reaction processes with the addition of KHCO3. For KHCO3 particles, the formation of catalytic cycle K ⇔ KOH converted H and OH radicals into a stable combustion product H2O, resulting in a lower flame speed and flame temperature.

The effect of monoammonium phosphate (NH4H2PO4) particles on 5 μm aluminum dust flames is investigated experimentally and computationally. NH4H2PO4 in three particle size is employed to determine the inhibition efficiency on aluminum flame propagation. Flame inhibition mechanism considering both gas and surface chemistry of aluminum particles is developed. Results show that the inhibition effectiveness monotonously increases as NH4H2PO4 particle size is reduced to 25 μm. Flame morphology and flame microstructure change with the addition of different particle size NH4H2PO4. Small NH4H2PO4 particles within the range studied have a greater reduction in average flame propagation compared to the coarser one. Meanwhile, the fine NH4H2PO4 particles almost decompose completely during the penetration of aluminum flame and then undergo a sufficient chemical interaction with the flame. The simulations indicate that the decomposition products of NH4H2PO4 particles obstruct the oxidation of aluminum particles through flame radical consumption. Additionally, the addition of NH4H2PO4 can reduce the vaporization rate and surface reaction rate of aluminum particles.

The suppression effect of melamine cyanurate (MCA) and melamine polyphosphate (MPP) on the flame propagation of aluminum dust were studied experimentally. The results indicated that the concentration of MPP required to supress the aluminum dust explosion was lower than MCA. As the concentration of suppressant increased, the acceleration and the maximum flame speed extremely decreased, and the flame morphology became isolated spot flames. The MPP addition exerted a stronger suppression effect on the temperature of aluminum flame compared to MCA addition. Meanwhile, the mechanism of flame suppression was further investigated. Decomposition of MCA and MPP particles could absorb the heat released from the flame front. Scanning electron microscopy demonstrated that the gas phase reaction of aluminum particles was suppressed by MCA and MPP, resulting in a larger particle size of the explosion products. XRD results indicated that MCA and MPP did not react with aluminum. Gaseous products of suppressant decomposition altered flame chemistry by radically recombining O atom and reducing AlO, which resulted in less amount of heat release, lower flame speed and lower flame temperature.

Low molecular weight heparins (LMWHs) are heterogeneous mixtures of glycosaminoglycan chains composed of mixture of different lengths and substitution patterns. Structural characterization and quality control of LMWHs have always been challenging. The Chinese drug regulatory authorities have been committed to improve the supervision standards of LMWHs to better regulate the quality and safety of LMWHs in current Chinese market. In the present paper, 80 batches of three types LMWHs (dalteparin, enoxaparin and naldroparin) marketed in China from different manufacturers were studied by

An electron transport layer (ETL) with excellent conductivity and suitable band alignment plays a key role in accelerating charge extraction and transfer for achieving highly efficient planar perovskite solar cells (PSCs). Herein, a novel diluted-cadmium sulfide quantum dot (CdS QD)-assisted SnO