A novel and unusual palladium‐catalyzed 4+2 annulation of cyclopropenes with benzosilacyclobutanes is reported. This reaction occurred through chemoselective Si−C(sp2) bond activation in synergy with ...ring expansion/insertion of cyclopropenes to form new C(sp2)−C(sp3) and Si−C(sp3) bonds. An array of previously elusive bicyclic skeleton with high strain, silabicyclo4.1.0heptanes, were formed in good yields with excellent diastereoselectivity under mild conditions. An asymmetric version of the reaction with a chiral phosphoramidite ligand furnished a variety of chiral bicyclic silaheterocycle derivatives with good enantioselectivity (up to 95.5:4.5 er). Owing to the mild reaction conditions, the good stereoselectivity profile, and the ready availability of the functionalized precursors, this process constitutes a useful and straightforward strategy for the synthesis of densely functionalized silacycles.
When Si−C meets C=C bond activation: Cyclopropenes were functionalized stereoselectively with benzosilacyclobutanes by palladium‐catalyzed Si−C(sp2) bond activation and a ring‐expansion/4+2 annulation sequence to form new C(sp2)−C(sp3) and Si−C(sp3) bonds of silabicyclo4.1.0heptanes. The transformation provided an array of these previously elusive highly strained bicyclic skeletons in good yields with high selectivity (see scheme).
In the early February, 2020, we called up an experts’ committee with more than 30 Chinese experts from 11 national medical academic organizations to formulate the first edition of consensus statement ...on diagnosis, treatment and prevention of coronavirus disease 2019 (COVID-19) in children, which has been published in this journal. With accumulated experiences in the diagnosis and treatment of COVID-19 in children, we have updated the consensus statement and released the second edition recently. The current version in English is a condensed version of the second edition of consensus statement on diagnosis, treatment and prevention of COVID-19 in children. In the current version, diagnosis and treatement criteria have been optimized, and early identification of severe and critical cases is highlighted. The early warning indicators for severe pediatric cases have been summarized which is utmost important for clinical practice. This version of experts consensus will be valuable for better prevention, diagnosis and treatment of COVID-19 in children worldwide.
Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here we provide an up-to-date review ...on the spatial distributions of ticks and tick-borne pathogens in China. We map at the county level 124 tick species, 103 tick-borne agents, and human cases infected with 29 species (subspecies) of tick-borne pathogens that were reported in China during 1950-2018. Haemaphysalis longicornis is found to harbor the highest variety of tick-borne agents, followed by Ixodes persulcatus, Dermacentor nutalli and Rhipicephalus microplus. Using a machine learning algorithm, we assess ecoclimatic and socioenvironmental drivers for the distributions of 19 predominant vector ticks and two tick-borne pathogens associated with the highest disease burden. The model-predicted suitable habitats for the 19 tick species are 14‒476% larger in size than the geographic areas where these species were detected, indicating severe under-detection. Tick species harboring pathogens of imminent threats to public health should be prioritized for more active field surveillance.
AtDjB1 belongs to the J-protein family in Arabidopsis thaliana. Its biological functions in plants are largely unknown.
In this study, we examined the roles of AtDjB1 in resisting heat and oxidative ...stresses in A. thaliana using reverse genetic analysis.
AtDjB1 knockout plants (atj1-1) were more sensitive to heat stress than wildtype plants, and displayed decreased concentrations of ascorbate (ASC), and increased concentrations of hydrogen peroxide (H2O2) and oxidative products after heat shock. Application of H2O2 accelerated cell death and decreased seedling viability in atj1-1. Exogenous ASC conferred much greater thermotolerance in atj1-1 than in wildtype plants, suggesting that a lower concentration of ASC in atj1-1 could be responsible for the increased concentration of H2O2 and decreased thermotolerance. Furthermore, AtDjB1 was found to localize to mitochondria, directly interact with a mitochondrial heat-shock protein 70 (mtHSC70-1), and stimulate ATPase activity of mtHSC70-1. AtDjB1 knockout led to the accumulation of cellular ATP and decreased seedling respiration, indicating that AtDjB1 modulated the ASC concentration probably through affecting the function of mitochondria.
Taken together, these results suggest that AtDjB1 plays a crucial role in maintaining redox homeostasis, and facilitates thermotolerance by protecting cells against heat-induced oxidative damage.
•A new color image encryption algorithm is proposed.•A novel Staged composite chaotic mapping model has been proposed and it has almost no window period and it is very early to enter the chaotic ...state.•The encryption uses the Hopfield chaotic neural network, which has a good effect on the diffusion process.•The information entropy and anti-cutting and noise attacks of the proposed method is better than existing algorithm.
In this paper, a new chaotic color image encryption algorithm is proposed. This algorithm uses a composite chaotic map combined with a staged Logistic map and Tent map for initial key processing and then obtains the parameters required for Arnold mapping through a function transformation needed to scramble the image. The diffusion phase uses Hopfield chaotic neural network to generate the self-diffusion chaotic matrix, and the key is generated by a function transformation; finally, the scrambled image is XORed with the key to obtain the final ciphertext image. Experimental results show that the proposed algorithm improves encryption efficiency, has good security performance, and can resist common attack methods.
•A new color image encryption scheme is proposed based on the spatiotemporal chaos of the two dimensional nonlinear coupled map lattices (2DNLCML) and genetic operations.•Due to the spatial nonlinear ...coupling, this 2DNLCML system can generate superior pseudo-random sequences for image encryption.•The scheme employs genetic operations followed by mutation and crossover operation using binary encoding, which consumes a low amount of computational cost.•Simulation results indicate that the proposed scheme has a good encryption effect and can resist various typical attacks.
Based on the spatiotemporal chaos of the two Dimensional Nonlinear Coupled Map Lattices (2DNLCML) and genetic operations, a new optical color image encryption scheme is proposed. Because of the spatial nonlinear coupling which replaces traditional adjacent coupling, the 2DNLCML system contains good features such as ergodic pseudo-random sequence, less periodic windows in bifurcations and larger range of parameters in chaotic dynamics, which is more suitable for image encryption. The scheme also performs genetic operations including mutation and crossover for binary coding, thus reducing the computational complexity. Simulations have been carried out and the results demonstrate that the proposed algorithm has properties of large key space, high sensitivity to key, strong resisting attack. So, it is more secure and effective algorithm for encryption of digital images.
Pollution of residual plastic film in arable lands is a severe problem in China. In this study, the status of residual film and influential factors were investigated using the methods of farm survey ...in combination with questionnaires and quadrat sampling at a large number of field sites in Xinjiang Uygur Autonomous Region, China. The results showed that the amount of film utilization increased largely and reached to 1.8×10~5 t in 2013. Similarly, the mulching area also substantially increased in recent decades, and reached to 2.7×10~5 ha in the same year. According to the current survey, 60.7% of the sites presented a greater mulch residue than the national film residue standard（75 kg ha~（–1））, and the maximum residual amount reached 502.2 kg ha~（–1） in Turpan, Xinjiang. The film thickness, the mulching time and the crop type all influenced mulch residue. The thickness of the film had significantly negative correlation with the amount of residual film（P0.05）, while the mulching years had significantly positive correlation with it（P0.05）. The total amount of residual film in Xinjiang was 3.43×105 t in 2011, which accounted for 15.3% of the cumulative dosage of mulching. Among all the crops, the cotton fields had the largest residual amount of mulch film（158.4 kg ha~（–1））, and also the largest contribution（2.6×10~5 tons） to the total amount of residual film in Xinjiang.
Many healthcare workers were infected by coronavirus disease 2019 (COVID-19) early in the epidemic posing a big challenge for epidemic control. Hence, this study aims to explore perceived infection ...routes, influencing factors, psychosocial changes, and management procedures for COVID-19 infected healthcare workers.
This is a cross-sectional, single hospital-based study. We recruited all 105 confirmed COVID-19 healthcare workers in the Zhongnan Hospital of Wuhan University from February 15 to 29, 2020. All participants completed a validated questionnaire. Electronic consent was obtained from all participants. Perceived causes of infection, infection prevention, control knowledge and behaviour, psychological changes, symptoms and treatment were measured.
Finally, 103 professional staff with COVID-19 finished the questionnaire and was included (response rate: 98.1%). Of them, 87 cases (84.5%) thought they were infected in working environment in hospital, one (1.0%) thought their infection was due to the laboratory environment, and 5 (4.9%) thought they were infected in daily life or community environment. Swab of throat collection and physical examination were the procedures perceived as most likely causing their infection by nurses and doctors respectively. Forty-three (41.8%) thought their infection was related to protective equipment, utilization of common equipment (masks and gloves). The top three first symptoms displayed before diagnosis were fever (41.8%), lethargy (33.0%) and muscle aches (30.1%). After diagnosis, 88.3% staff experienced psychological stress or emotional changes during their isolation period, only 11.7% had almost no emotional changes. Arbidol (Umifenovir; an anti-influza drug; 69.2%) was the drug most commonly used to target infection in mild and moderate symptoms.
The main perceived mode of transmission was not maintaining protection when working at a close distance and having intimate contact with infected cases. Positive psychological intervention is necessary.
A palladium‐catalyzed enantioselective intramolecular σ‐bond cross‐exchange between C−I and C−C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all‐carbon ...quaternary stereocenter. Pd/TADDOL‐derived phosphoramidite is found to be an efficient catalytic system for both C−C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density‐functional theory (DFT) calculation studies support the ring‐opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving PdIV species.
In exchange: An enantioselective cross‐exchange between C−I and C−C bonds is realized by palladium‐catalyzed sequential oxidative addition and reductive elimination. Chiral indanones bearing an alkyl iodide group and an all‐carbon quaternary stereocenter are synthesized in good yields and enantioselectivities.
Summary
As the largest cultivated fiber crop in the world, cotton (Gossypium hirsutum) is often exposed to various biotic stresses during its growth periods. Verticillium wilt caused by Verticillium ...dahliae is a severe disease in cotton, and the molecular mechanism of cotton resistance for Verticillium wilt needs to be further investigated. Here, we revealed that the cotton genome contains nine types of GST genes. An evolutionary analysis showed that a newly identified cluster (including Gh_A09G1508, Gh_A09G1509 and Gh_A09G1510) located on chromosome 09 of the A‐subgenome was under positive selection pressure during the formation of an allotetraploid. Transcriptome analysis showed that this cluster participates in Verticillium wilt resistance. Because the Gh_A09G1509 gene showed the greatest differential expression in the resistant cultivar under V. dahliae stress, we overexpressed this gene in tobacco and found that its overexpression resulted in enhanced Verticillium wilt resistance. Suppression of the gene cluster via virus‐induced gene silencing made cotton plants of the resistant cultivar Nongda601 significantly susceptible. These results demonstrated that the GST cluster played an important role in Verticillium wilt resistance. Further investigation showed that the encoded enzymes of the cluster were essential for the delicate equilibrium between the production and scavenging of H2O2 during V. dahliae stress.
Significance statement
Evolution of the glutathione S‐transferases gene family was clarified in the Gossypium genus. A newly identified tau cluster in the A‐subgenome was shown to have undergone adaptive evolution, and provided Verticillium wilt resistance in cotton.
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