Double bonds of internal olefins can be efficiently migrated to the terminal carbons and regioselectively hydroesterified with formates in the presence of Pd(OAc)_(2) and 1,2-DTBPMB under mild reaction conditions,prov...Double bonds of internal olefins can be efficiently migrated to the terminal carbons and regioselectively hydroesterified with formates in the presence of Pd(OAc)_(2) and 1,2-DTBPMB under mild reaction conditions,providing a wide variety of corresponding linear carboxylic esters bearing various functional groups in good yields and>20:1 linear/branch ratios.The reaction is optionally simple and does not need to use CO gas and acid co-catalysts.展开更多
An environmentally benign and practical preparation method for the Vilsmeier-Haack reagent (VH) has been developed by using phthaloyl dichloride with DMF in toluene or 2-chlorotoluene. Phthalic anhydride as the byprod...An environmentally benign and practical preparation method for the Vilsmeier-Haack reagent (VH) has been developed by using phthaloyl dichloride with DMF in toluene or 2-chlorotoluene. Phthalic anhydride as the byproduct was recovered in high yield by simple filtration. Some aromatic acids have been transformed into the corresponding acid chlorides in good yields by employing the isolated VH. Treatment of primary or secondary alcohols with VH gave alkyl formates or alkyl chlorides by depending on the reaction conditions.展开更多
Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity amo...Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relativ...This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relative motion dynamics model,a prescribed time output feedback control strategy is proposed.A prescribed-time extended state observer is designed to estimate the relative velocity and external disturbances.The disturbance estimates are then used as the feedforward component of the controller.Building on this framework,a novel prescribed-time active disturbance rejection control strategy for position tracking is developed via a backstepping control design.The convergence of the extended state observer and the stability of the closed-loop system are rigorously analyzed using Lyapunov stability theory.Numerical simulations are performed to validate the effectiveness of the proposed controller.展开更多
The multi-satellite electromagnetic formation flight system is nonlinear and strongly coupled,which makes modeling and optimization challenging.To simplify electromagnetic force evaluation and dynamics modeling,we int...The multi-satellite electromagnetic formation flight system is nonlinear and strongly coupled,which makes modeling and optimization challenging.To simplify electromagnetic force evaluation and dynamics modeling,we introduce a reference frame consistent with each satellite body frame,in which the electromagnetic dipoles and electromagnetic forces are represented as two-dimensional vectors.Then,the maneuver time is divided into time intervals,and different satellite sets are activated in each interval,converting the multi-satellite formation reconfiguration problem into an optimal trajectory problem of each two-satellite subsystem.To this end,a token-based dynamic programming method with a switching penalty of active satellite sets is proposed to determine the sequence of satellite sets participating in each time interval,thereby enabling all satellites to reach their desired states.For the two-satellite subsystem with the objectives of minimizing maneuver time and energy consumption,the Gauss pseudo-spectral method is employed to generate the optimal reconfiguration trajectory.Numerical simulations verify the effectiveness of the proposed optimization method.展开更多
Comprehensive Summary A Pd-catalyzed regioselective hydroesterification of alkyl terminal olefins with aryl formates is described.A wide variety of linear carboxylic esters bearing various functional groups can be obt...Comprehensive Summary A Pd-catalyzed regioselective hydroesterification of alkyl terminal olefins with aryl formates is described.A wide variety of linear carboxylic esters bearing various functional groups can be obtained in good yields with high regioselectivities under mild reaction conditions by using 1,2-DTBPMB or(p-F-Ph)3P as ligand.The reaction process is operationally simple and requires no handling of toxic CO or strong acid.The resulting aryl esters can be readily converted to other carboxylic acid derivatives.展开更多
An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl...An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl sources without the use of external carbon monoxide. The present catalytic system shows broad functional group tolerance and affords aryl benzoate derivatives in good to excellent yields.展开更多
This study investigated the heterogeneous responses of organic matter(OM)in highly-to over-mature source rocks during thermal maturation.An integrated analysis was conducted on the Raman spectroscopic and geochemical ...This study investigated the heterogeneous responses of organic matter(OM)in highly-to over-mature source rocks during thermal maturation.An integrated analysis was conducted on the Raman spectroscopic and geochemical signatures of shales from the Lower Silurian Longmaxi Formation and the Lower Cambrian Qiongzhusi Formation,as well as anthracites from the Lower Permian Shanxi–Formation and the Upper Carboniferous Taiyuan Formation(collectively referred to as the Shanxi Taiyuan Formations).Additionally,burial and thermal evolution modeling was employed to support the analysis.A systematic assessment of Raman spectral parameters(e.g.,the positions and intensity ratio of the D and G bands)revealed robust correlations between the thermal history patterns of source rocks and molecular structural evolution parameters.The subsequent mechanistic quantification demonstrated that the maturation state of the source rocks was subjected to the hierarchical control of three principal factors:Peak heating temperature,the duration of sustained thermal intensity,and effective maturation duration.In addition,comparative analyses demonstrated that the anthracites attained higher structural ordering under sustained thermal conditions.This contrasts with the disordered carbon matrices observed in the intermittently heated shales.Raman spectroscopy further revealed broader variations in the D and G band intensities of the Longmaxi Formation compared to the Qiongzhusi Formation.This difference is associated with their different thermal histories.The thermal burial histories confirm that shales in the Longmaxi Formation underwent thermal exposure at lower peak temperatures over a shorter duration compared to those in the Qiongzhusi Formation.Finally,this study established a maturity calibration model for over-mature source rocks through a systematic correlation between Raman peak height ratios(R_(D/G))and vitrinite reflectance(R_(o)).展开更多
Formate bioconversion plays a crucial role in achieving renewable resource utilization and green and sustainable development,as it helps convert formate to biofuels and biochemicals.However,to tap the full potential o...Formate bioconversion plays a crucial role in achieving renewable resource utilization and green and sustainable development,as it helps convert formate to biofuels and biochemicals.However,to tap the full potential of formate bioconversion,it is important to identify the most appropriate microbial hosts,design the most promising formate assimilation pathways,and develop the most efficient formate assimilation cell factories.Here,we summarize the formatotrophic microorganisms capable of assimilating formate into building blocks of cell growth and analyze the characteristics of formate assimilation pathways for transmitting formate into central carbon metabolism.Furthermore,we discuss microbial engineering strategies to improve the efficiency of formate utilization for producing high-value bioproducts.Finally,we highlight the key challenges of formate bioconversion and their possible solutions to advance the formate bioeconomy and biomanufacturing.展开更多
Foodborne bacteria produce biofilms and their viable but non-culturable(VBNC)formation,can affect food quality and safety.Studies have shown that these characteristics are regulated by the bacterial quorum sensing(QS)...Foodborne bacteria produce biofilms and their viable but non-culturable(VBNC)formation,can affect food quality and safety.Studies have shown that these characteristics are regulated by the bacterial quorum sensing(QS)system.Quenching the QS system of foodborne bacteria and blocking the expression of the corresponding genes may be an effective way to improve food quality and safety.Therefore,this article reviews the QS systems for foodborne bacteria,the regulatory mechanisms of QS systems in biofilm and VBNC formation and resuscitation,the research progress on quorum sensing inhibitors(QSIs)for Gram-negative and Gram-positive bacteria,and introduces QSIs from various sources.In addition,we have also summarized the current research issues on QS regulation of biofilms and VBNC formation.The systematic study of the QS phenomenon of foodborne bacteria in practical situations,the mechanism of bacterial QS cooperation-cheating,the screening of novel and highly active QSIs,the combination of QSIs and other technologies to improve their bioavailability,and the regulatory network between biofilm and VBNC formation and resuscitation are research directions that need to be paid attention to in the future.展开更多
The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have bee...The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.展开更多
Announcements for this section should be submitted in the correct format at least 3 months before the required date of publication.This list is provided as a service to readers;inclusion does not imply endorsement by ...Announcements for this section should be submitted in the correct format at least 3 months before the required date of publication.This list is provided as a service to readers;inclusion does not imply endorsement by the Hepatobiliary&Pancreatic Diseases International.展开更多
Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previo...Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previous research,providing a long-term perspective on carbonyl compound variations and their environmental implica-tions.Atmospheric observations were conducted at Beijing(BJ)and Xianghe(XH)during the summer and winter months of 2018,2019,and 2023 to study the sources and impacts of carbonyl compounds in typical urban areas and peri‑urban areas.Notably,concentrations in the summer of 2023 increased compared to 2018 and 2019.The predominant carbonyl compounds—formaldehyde,acetaldehyde,and acetone—accounted for over 60%of the total.The mean values of OFP in BJ ranged from 18.55 to 58.61μg/m3,lower than those in XH(29.82 to 65.48μg/m3),with formaldehyde and acetaldehyde contributing over 80%of the total.SOAP exhibited a similar pattern,with values in XH(69.21 to 508.55μg/m3)significantly exceeding those in BJ(34.47 to 159.78μg/m3).The PMF model highlighted vehicle exhaust,secondary pollution,and biomass combustion as major sources of carbonyl compounds,emphasizing differences in source contributions between the two regions.This study’s com-parative analysis over different years and locations provides new insights into the dynamic changes in carbonyl compounds and their environmental importance.These results not only reinforce the importance of carbonyl compounds regulation but also offer a valuable reference for evaluating and refining emission control strategies during this period.展开更多
Quantonenpollenites,a pollen taxon which was assumed to be angiosperm,is of great significance in confirming the geological age of its bearing strata.Aims to clarify the taxonomic affiliation of Quantonenpollenites,we...Quantonenpollenites,a pollen taxon which was assumed to be angiosperm,is of great significance in confirming the geological age of its bearing strata.Aims to clarify the taxonomic affiliation of Quantonenpollenites,we investigated the external morphology and internal structure using Light Microscopy(LM),Scanning Electron Microscopy(SEM),and Transmission Electron Microscopy(TEM).According to TEM observations,the exine of Quantonenpollenites pollen is unstratified with the absence of a columellar layer,and the exine is tightly connected with the intine.Based on comprehensive morphological evidence,especially the lack of columellar layer which is typical characteristics existing in almost all angiosperm pollen,the botanical affinity of Quantonenpollenites should be attributed to gymnosperms rather than angiosperms as previously thought.Through comparative analysis,it may have a close affinity with Ephedra,but further analytical data are still needed for verification.As a characteristic palynological type of the Quantou Formation in the Songliao Basin,the occurrence of Quantonenpollenites has indicative significance for determining the age of the hosting strata.By systematically clarifying the phylogenetic affiliation of Quantonenpollenites,together with the other associated palynomorphs,this study provides crucial reference materials for defining the stratigraphic age range of the Quantou Formation(Cenomanian to early Turonian),improves the resolution of stratigraphic age calibration of the Quantou Formation,and provides key paleontological evidence for the refined division of the terrestrial Cretaceous chronostratigraphic framework in the Songliao Basin.展开更多
Five new small theropod teeth and one manual ungual have recently been recovered from the Upper Cretaceous Nenjiang Formation in the Songliao Basin.The specimens were examined for their morphological characteristics,l...Five new small theropod teeth and one manual ungual have recently been recovered from the Upper Cretaceous Nenjiang Formation in the Songliao Basin.The specimens were examined for their morphological characteristics,leading to the identification of four distinct taxa.The first taxon consists of three foliodont teeth characterized by a pronounced basal constriction and large hook-like distal denticles,which can be attributed to Troodontidae.The second taxon is represented by an elongated tooth featuring prominent longitudinal ridges,allowing for its assignment to Paronychodon.The third taxon is a bladelike tooth with notably small distal denticles,corresponding to Richardoestesia.The fourth taxon comprises a manual ungual characterized by a transversely wide and nearly symmetrical proximal articular surface,fully enclosed ventral foramina,a flattened ventral surface,and the absence of a flexor tubercle,resembling Alvarezsauridae.These specimens significantly enhance the known dinosaur diversity of the Nenjiang Formation and provide crucial insights for understanding the terrestrial ecosystem in Northeast Asia during the Late Cretaceous.展开更多
Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the in...Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the intrinsic activity of Ni and Co catalytic centers.However,the dynamic evolution and atomic-scale synergy between these centers remain elusive.Herein,we fabricated NiCo_(2)O_(4)nanosheets supported on nickel foam,where Ni preferentially occupies tetrahedral sites to regulate the electronic configuration of octahedral Co.Experimental and theoretical results demonstrate that the incorporation of tetrahedral Ni induces low-to-intermediate spin transition in octahedral Co,thereby optimizing eg orbital occupancy and stabilizing active sites.This spin-state engineering establishes Ni-Co synergistic catalytic centers for the selective oxidation of glucose to formate(FA).At higher potential(≥1.4 V vs.RHE),octahedral Co undergoes reconstruction into excessive active CoOOH and CoO_(2)species,resulting in glucose overoxidation to CO_(2)and intensified competitive oxygen evolution.In contrast,at lower potentials(<1.4 V vs.RHE),tetrahedral Ni facilitates electron delocalization across the Ni–O–Co lattice,thereby stabilizing octahedral Co for glucose adsorption and oxidation.Subsequently,a coupled electrocatalytic system was constructed,achieving 80.7%FA yield with 91.3%Faradaic efficiency(FE)at NiCo_(2)O_(4)anode and H2 evolution rate of 696μmol h^(−1)with 99.9%FE at Pt cathode for 2 h under 1.35 V vs.RHE.This work provides a deep insight into spin-state regulation of the catalytic center,offering valuable guidance for rational catalyst design.展开更多
Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass,compromised bone microstructure,and an increased risk of fractures,primarily due to excessive osteoclast-mediated bone resorption relativ...Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass,compromised bone microstructure,and an increased risk of fractures,primarily due to excessive osteoclast-mediated bone resorption relative to osteoblast-mediated bone formation.While current anti-osteoporosis drugs,such as bisphosphonates and denosumab,predominantly focus on reducing bone resorption,osteoanabolic approaches are essential for restoring bone microarchitecture and ultimately reducing fracture risk.Traditional Chinese medicines(TCMs)and their active ingredients have long been used in China for osteoporosis prevention and treatment.This review provides a comprehensive evaluation of the effects and molecular mechanisms of 65 natural products across 24 categories on osteoblast-mediated bone formation.These compounds promote bone formation by regulating key transcription factors(RUNX2 and Osterix)and signaling pathways,including WNT/β-catenin,bone morphogenic protein(BMP),mitogen-activated protein kinase(MAPK),phosphoinositide 3-kinase/protein kinase B(PI3K/AKT),oxidative stress,autophagy,and epigenetic regulation.Notably,certain natural products[e.g.,icariin(ICA)]exert their effects through multiple targets and pathways.Many of these natural products have demonstrated significant therapeutic efficacy in animal models,such as ovariectomized(OVX)mice.Our findings suggest that natural products with kidney-tonifying,anti-inflammatory,and antioxidant properties,as well as those inhibiting adipocyte differentiation,may hold promise for osteoporosis treatment.Additionally,we highlight current research gaps and propose future directions,including high-throughput screening and validation in diverse animal models,development of novel bone-targeting delivery systems,and identification of natural compounds targeting osteocytes.展开更多
By means the in situ halogenation of the vinyl C-H bond in o-hydroxyphenyl enaminones,the step efficient synthesis of 3-diphenylphosphinyl chromones has been realized through the challenging construction of C-P(Ⅲ) bo...By means the in situ halogenation of the vinyl C-H bond in o-hydroxyphenyl enaminones,the step efficient synthesis of 3-diphenylphosphinyl chromones has been realized through the challenging construction of C-P(Ⅲ) bond by using diphenyl phosphine as reaction partner.In addition,the tunable synthesis of 2-phosphoryl chromanones has been achieved via hydrophosphorylation by simply modifying reaction conditions without using metal reagent.展开更多
UV-B application enhances the aroma quality of oolong tea;however,the underlying regulatory mechanism remains unclear.This study investigates the regulatory role of UV-B in the biosynthesis of a-farnesene,an important...UV-B application enhances the aroma quality of oolong tea;however,the underlying regulatory mechanism remains unclear.This study investigates the regulatory role of UV-B in the biosynthesis of a-farnesene,an important floral and fruity characteristic aroma.UV-B treatment significantly improved the aroma quality of‘Foshou’and‘Yuquan’oolong teas,increasing a-farnesene levels by 1.8-and 1.4-fold,respectively.The a-farnesene synthase(CsAFS),ELONGATED HYPOCOTYL 5(CsHY5),and myelocytomatosis protein 2(CsMYC2)exhibited a highly correlated expression pattern closely associated with a-farnesene accumulation.Single-factor treatment revealed that CsAFS expression was induced by both UV-B and mechanical wounding,with CsHY5 predominantly responding to UV-B radiation,while CsMYC2 primarily responded to tumbling-induced mechanical wounding signal.Transient suppression of CsHY5 in tea leaves reduced the expression of both CsAFS and CsMYC2 whereas CsMYC2 suppression decreased CsAFS expression.G-box motifs were identified in promoters of CsMYC2 and CsAFS,and the dual-luciferase reporter assay(LUC)and electrophoretic mobility shift assays(EMSA)demonstrated direct binding functions of CsHY5 to CsAFS and CsMYC2 promoters,as well as CsMYC2 to the CsAFS promoter.Based on sensory evaluation,odourant quantification,gene expression,and molecular functional analysis,we propose that UV-B radiation and tumbling-induced wounding signals synergistically regulate a-farnesene biosynthesis through a coordinated interaction of CsHY5 and CsMYC2 during oolong tea processing.These findings improve our understanding of flavour formation during oolong tea production and also provide novel insights into artificial light application in tea manufacturing.展开更多
基金financial support from the National Natural Science Foundation of China(Nos.22271024,21632005)Changzhou University.
文摘Double bonds of internal olefins can be efficiently migrated to the terminal carbons and regioselectively hydroesterified with formates in the presence of Pd(OAc)_(2) and 1,2-DTBPMB under mild reaction conditions,providing a wide variety of corresponding linear carboxylic esters bearing various functional groups in good yields and>20:1 linear/branch ratios.The reaction is optionally simple and does not need to use CO gas and acid co-catalysts.
文摘An environmentally benign and practical preparation method for the Vilsmeier-Haack reagent (VH) has been developed by using phthaloyl dichloride with DMF in toluene or 2-chlorotoluene. Phthalic anhydride as the byproduct was recovered in high yield by simple filtration. Some aromatic acids have been transformed into the corresponding acid chlorides in good yields by employing the isolated VH. Treatment of primary or secondary alcohols with VH gave alkyl formates or alkyl chlorides by depending on the reaction conditions.
文摘Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
文摘This study investigates prescribed-time position tracking control for electromagnetic satellite formations subject to model uncertainties and external disturbances.Using the Clohessy-Wiltshire equations as the relative motion dynamics model,a prescribed time output feedback control strategy is proposed.A prescribed-time extended state observer is designed to estimate the relative velocity and external disturbances.The disturbance estimates are then used as the feedforward component of the controller.Building on this framework,a novel prescribed-time active disturbance rejection control strategy for position tracking is developed via a backstepping control design.The convergence of the extended state observer and the stability of the closed-loop system are rigorously analyzed using Lyapunov stability theory.Numerical simulations are performed to validate the effectiveness of the proposed controller.
文摘The multi-satellite electromagnetic formation flight system is nonlinear and strongly coupled,which makes modeling and optimization challenging.To simplify electromagnetic force evaluation and dynamics modeling,we introduce a reference frame consistent with each satellite body frame,in which the electromagnetic dipoles and electromagnetic forces are represented as two-dimensional vectors.Then,the maneuver time is divided into time intervals,and different satellite sets are activated in each interval,converting the multi-satellite formation reconfiguration problem into an optimal trajectory problem of each two-satellite subsystem.To this end,a token-based dynamic programming method with a switching penalty of active satellite sets is proposed to determine the sequence of satellite sets participating in each time interval,thereby enabling all satellites to reach their desired states.For the two-satellite subsystem with the objectives of minimizing maneuver time and energy consumption,the Gauss pseudo-spectral method is employed to generate the optimal reconfiguration trajectory.Numerical simulations verify the effectiveness of the proposed optimization method.
基金support from the National Natural Science Foundation of China(22271024,21632005)and Changzhou University.
文摘Comprehensive Summary A Pd-catalyzed regioselective hydroesterification of alkyl terminal olefins with aryl formates is described.A wide variety of linear carboxylic esters bearing various functional groups can be obtained in good yields with high regioselectivities under mild reaction conditions by using 1,2-DTBPMB or(p-F-Ph)3P as ligand.The reaction process is operationally simple and requires no handling of toxic CO or strong acid.The resulting aryl esters can be readily converted to other carboxylic acid derivatives.
基金We are grateful to the National Natural Science Foundation of China，the Education Department of Henan Province science and technology research projects (No.13A150681) for financial support of this research
文摘An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl sources without the use of external carbon monoxide. The present catalytic system shows broad functional group tolerance and affords aryl benzoate derivatives in good to excellent yields.
基金supported by the National Natural Science Foundation of China(42362022)the Open Fund of the Shaanxi Key Laboratory of Petroleum Accumulation Geology(PAG-202406)the Open Fund of the Mine Geology and Environment Academician and Expert Workstation(2024OITYSZJGZZ-005)。
文摘This study investigated the heterogeneous responses of organic matter(OM)in highly-to over-mature source rocks during thermal maturation.An integrated analysis was conducted on the Raman spectroscopic and geochemical signatures of shales from the Lower Silurian Longmaxi Formation and the Lower Cambrian Qiongzhusi Formation,as well as anthracites from the Lower Permian Shanxi–Formation and the Upper Carboniferous Taiyuan Formation(collectively referred to as the Shanxi Taiyuan Formations).Additionally,burial and thermal evolution modeling was employed to support the analysis.A systematic assessment of Raman spectral parameters(e.g.,the positions and intensity ratio of the D and G bands)revealed robust correlations between the thermal history patterns of source rocks and molecular structural evolution parameters.The subsequent mechanistic quantification demonstrated that the maturation state of the source rocks was subjected to the hierarchical control of three principal factors:Peak heating temperature,the duration of sustained thermal intensity,and effective maturation duration.In addition,comparative analyses demonstrated that the anthracites attained higher structural ordering under sustained thermal conditions.This contrasts with the disordered carbon matrices observed in the intermittently heated shales.Raman spectroscopy further revealed broader variations in the D and G band intensities of the Longmaxi Formation compared to the Qiongzhusi Formation.This difference is associated with their different thermal histories.The thermal burial histories confirm that shales in the Longmaxi Formation underwent thermal exposure at lower peak temperatures over a shorter duration compared to those in the Qiongzhusi Formation.Finally,this study established a maturity calibration model for over-mature source rocks through a systematic correlation between Raman peak height ratios(R_(D/G))and vitrinite reflectance(R_(o)).
基金supported by the National Natural Science Foundation of China(22378166)the Basic Research Program of Jiangsu and Jiangsu Basic Research Center for Synthetic Biology(BK20233003)+1 种基金the Fundamental Research Funds for the Central Universities(JUSRP622001)the Open Funding Project of Key Laboratory of Industrial Biotechnology Ministry of Education(KLIB-KF202403).
文摘Formate bioconversion plays a crucial role in achieving renewable resource utilization and green and sustainable development,as it helps convert formate to biofuels and biochemicals.However,to tap the full potential of formate bioconversion,it is important to identify the most appropriate microbial hosts,design the most promising formate assimilation pathways,and develop the most efficient formate assimilation cell factories.Here,we summarize the formatotrophic microorganisms capable of assimilating formate into building blocks of cell growth and analyze the characteristics of formate assimilation pathways for transmitting formate into central carbon metabolism.Furthermore,we discuss microbial engineering strategies to improve the efficiency of formate utilization for producing high-value bioproducts.Finally,we highlight the key challenges of formate bioconversion and their possible solutions to advance the formate bioeconomy and biomanufacturing.
基金financially supported by the National Natural Science Foundation of China(32202191)and(32272279)the Key R&D Project of Shandong Province(2023CXPT007 and 2024CXPT014)the Key R&D Project of Qingdao Science and Technology Plan(24-2-3-4-zyyd-jch).
文摘Foodborne bacteria produce biofilms and their viable but non-culturable(VBNC)formation,can affect food quality and safety.Studies have shown that these characteristics are regulated by the bacterial quorum sensing(QS)system.Quenching the QS system of foodborne bacteria and blocking the expression of the corresponding genes may be an effective way to improve food quality and safety.Therefore,this article reviews the QS systems for foodborne bacteria,the regulatory mechanisms of QS systems in biofilm and VBNC formation and resuscitation,the research progress on quorum sensing inhibitors(QSIs)for Gram-negative and Gram-positive bacteria,and introduces QSIs from various sources.In addition,we have also summarized the current research issues on QS regulation of biofilms and VBNC formation.The systematic study of the QS phenomenon of foodborne bacteria in practical situations,the mechanism of bacterial QS cooperation-cheating,the screening of novel and highly active QSIs,the combination of QSIs and other technologies to improve their bioavailability,and the regulatory network between biofilm and VBNC formation and resuscitation are research directions that need to be paid attention to in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.12534013,12047561,and 12104507)the Science and Technology Innovation Program of Hunan Province(Grant Nos.2025ZYJ001 and 2021RC4026)the National University of Defense Technology Research Fund Project.
文摘The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.
文摘Announcements for this section should be submitted in the correct format at least 3 months before the required date of publication.This list is provided as a service to readers;inclusion does not imply endorsement by the Hepatobiliary&Pancreatic Diseases International.
基金supported by the National Natural Science Foundation of China(Nos.41905108 and 42130704).
文摘Carbonyl compounds play a pivotal role in the formation of secondary pollutants such as O_(3) and SOA,signifi-cantly impacting air quality and human health.This study extended the observation period compared to previous research,providing a long-term perspective on carbonyl compound variations and their environmental implica-tions.Atmospheric observations were conducted at Beijing(BJ)and Xianghe(XH)during the summer and winter months of 2018,2019,and 2023 to study the sources and impacts of carbonyl compounds in typical urban areas and peri‑urban areas.Notably,concentrations in the summer of 2023 increased compared to 2018 and 2019.The predominant carbonyl compounds—formaldehyde,acetaldehyde,and acetone—accounted for over 60%of the total.The mean values of OFP in BJ ranged from 18.55 to 58.61μg/m3,lower than those in XH(29.82 to 65.48μg/m3),with formaldehyde and acetaldehyde contributing over 80%of the total.SOAP exhibited a similar pattern,with values in XH(69.21 to 508.55μg/m3)significantly exceeding those in BJ(34.47 to 159.78μg/m3).The PMF model highlighted vehicle exhaust,secondary pollution,and biomass combustion as major sources of carbonyl compounds,emphasizing differences in source contributions between the two regions.This study’s com-parative analysis over different years and locations provides new insights into the dynamic changes in carbonyl compounds and their environmental importance.These results not only reinforce the importance of carbonyl compounds regulation but also offer a valuable reference for evaluating and refining emission control strategies during this period.
基金supported by the National Key Research and Development Program of China (2023YFC2906701)National Natural Science Foundation of China (42372041, 42072027)China Geological Survey (DD20221646)
文摘Quantonenpollenites,a pollen taxon which was assumed to be angiosperm,is of great significance in confirming the geological age of its bearing strata.Aims to clarify the taxonomic affiliation of Quantonenpollenites,we investigated the external morphology and internal structure using Light Microscopy(LM),Scanning Electron Microscopy(SEM),and Transmission Electron Microscopy(TEM).According to TEM observations,the exine of Quantonenpollenites pollen is unstratified with the absence of a columellar layer,and the exine is tightly connected with the intine.Based on comprehensive morphological evidence,especially the lack of columellar layer which is typical characteristics existing in almost all angiosperm pollen,the botanical affinity of Quantonenpollenites should be attributed to gymnosperms rather than angiosperms as previously thought.Through comparative analysis,it may have a close affinity with Ephedra,but further analytical data are still needed for verification.As a characteristic palynological type of the Quantou Formation in the Songliao Basin,the occurrence of Quantonenpollenites has indicative significance for determining the age of the hosting strata.By systematically clarifying the phylogenetic affiliation of Quantonenpollenites,together with the other associated palynomorphs,this study provides crucial reference materials for defining the stratigraphic age range of the Quantou Formation(Cenomanian to early Turonian),improves the resolution of stratigraphic age calibration of the Quantou Formation,and provides key paleontological evidence for the refined division of the terrestrial Cretaceous chronostratigraphic framework in the Songliao Basin.
基金Supported by National Nature Science Foundation of China(No.41202012)Ministry of Science and Higher Education of the Russian Federation(No.123120600034-2)。
文摘Five new small theropod teeth and one manual ungual have recently been recovered from the Upper Cretaceous Nenjiang Formation in the Songliao Basin.The specimens were examined for their morphological characteristics,leading to the identification of four distinct taxa.The first taxon consists of three foliodont teeth characterized by a pronounced basal constriction and large hook-like distal denticles,which can be attributed to Troodontidae.The second taxon is represented by an elongated tooth featuring prominent longitudinal ridges,allowing for its assignment to Paronychodon.The third taxon is a bladelike tooth with notably small distal denticles,corresponding to Richardoestesia.The fourth taxon comprises a manual ungual characterized by a transversely wide and nearly symmetrical proximal articular surface,fully enclosed ventral foramina,a flattened ventral surface,and the absence of a flexor tubercle,resembling Alvarezsauridae.These specimens significantly enhance the known dinosaur diversity of the Nenjiang Formation and provide crucial insights for understanding the terrestrial ecosystem in Northeast Asia during the Late Cretaceous.
基金financially supported by the National Natural Science Foundation of China (22472199)Chinese Universities Scientific Fund (15055009)Central University Guided Funds for Building World-Class Universities (Disciplines) and Advancing Characteristic Development
文摘Electrocatalytic glucose oxidation to high-value chemicals provides a sustainable route for biomass valorization.NiCo-based catalysts have emerged as promising candidates for glucose oxidation reaction owing to the intrinsic activity of Ni and Co catalytic centers.However,the dynamic evolution and atomic-scale synergy between these centers remain elusive.Herein,we fabricated NiCo_(2)O_(4)nanosheets supported on nickel foam,where Ni preferentially occupies tetrahedral sites to regulate the electronic configuration of octahedral Co.Experimental and theoretical results demonstrate that the incorporation of tetrahedral Ni induces low-to-intermediate spin transition in octahedral Co,thereby optimizing eg orbital occupancy and stabilizing active sites.This spin-state engineering establishes Ni-Co synergistic catalytic centers for the selective oxidation of glucose to formate(FA).At higher potential(≥1.4 V vs.RHE),octahedral Co undergoes reconstruction into excessive active CoOOH and CoO_(2)species,resulting in glucose overoxidation to CO_(2)and intensified competitive oxygen evolution.In contrast,at lower potentials(<1.4 V vs.RHE),tetrahedral Ni facilitates electron delocalization across the Ni–O–Co lattice,thereby stabilizing octahedral Co for glucose adsorption and oxidation.Subsequently,a coupled electrocatalytic system was constructed,achieving 80.7%FA yield with 91.3%Faradaic efficiency(FE)at NiCo_(2)O_(4)anode and H2 evolution rate of 696μmol h^(−1)with 99.9%FE at Pt cathode for 2 h under 1.35 V vs.RHE.This work provides a deep insight into spin-state regulation of the catalytic center,offering valuable guidance for rational catalyst design.
基金supported by the National Natural Science Foundation of China(No.31800059)。
文摘Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass,compromised bone microstructure,and an increased risk of fractures,primarily due to excessive osteoclast-mediated bone resorption relative to osteoblast-mediated bone formation.While current anti-osteoporosis drugs,such as bisphosphonates and denosumab,predominantly focus on reducing bone resorption,osteoanabolic approaches are essential for restoring bone microarchitecture and ultimately reducing fracture risk.Traditional Chinese medicines(TCMs)and their active ingredients have long been used in China for osteoporosis prevention and treatment.This review provides a comprehensive evaluation of the effects and molecular mechanisms of 65 natural products across 24 categories on osteoblast-mediated bone formation.These compounds promote bone formation by regulating key transcription factors(RUNX2 and Osterix)and signaling pathways,including WNT/β-catenin,bone morphogenic protein(BMP),mitogen-activated protein kinase(MAPK),phosphoinositide 3-kinase/protein kinase B(PI3K/AKT),oxidative stress,autophagy,and epigenetic regulation.Notably,certain natural products[e.g.,icariin(ICA)]exert their effects through multiple targets and pathways.Many of these natural products have demonstrated significant therapeutic efficacy in animal models,such as ovariectomized(OVX)mice.Our findings suggest that natural products with kidney-tonifying,anti-inflammatory,and antioxidant properties,as well as those inhibiting adipocyte differentiation,may hold promise for osteoporosis treatment.Additionally,we highlight current research gaps and propose future directions,including high-throughput screening and validation in diverse animal models,development of novel bone-targeting delivery systems,and identification of natural compounds targeting osteocytes.
基金financially supported by the National Natural Science Foundation of China (No.22261026)。
文摘By means the in situ halogenation of the vinyl C-H bond in o-hydroxyphenyl enaminones,the step efficient synthesis of 3-diphenylphosphinyl chromones has been realized through the challenging construction of C-P(Ⅲ) bond by using diphenyl phosphine as reaction partner.In addition,the tunable synthesis of 2-phosphoryl chromanones has been achieved via hydrophosphorylation by simply modifying reaction conditions without using metal reagent.
基金supported by the National Natural Science Foundation of China(Grant No.32072623)the National Key Research and Development Program of China(Grant No.2021YFD1601103).
文摘UV-B application enhances the aroma quality of oolong tea;however,the underlying regulatory mechanism remains unclear.This study investigates the regulatory role of UV-B in the biosynthesis of a-farnesene,an important floral and fruity characteristic aroma.UV-B treatment significantly improved the aroma quality of‘Foshou’and‘Yuquan’oolong teas,increasing a-farnesene levels by 1.8-and 1.4-fold,respectively.The a-farnesene synthase(CsAFS),ELONGATED HYPOCOTYL 5(CsHY5),and myelocytomatosis protein 2(CsMYC2)exhibited a highly correlated expression pattern closely associated with a-farnesene accumulation.Single-factor treatment revealed that CsAFS expression was induced by both UV-B and mechanical wounding,with CsHY5 predominantly responding to UV-B radiation,while CsMYC2 primarily responded to tumbling-induced mechanical wounding signal.Transient suppression of CsHY5 in tea leaves reduced the expression of both CsAFS and CsMYC2 whereas CsMYC2 suppression decreased CsAFS expression.G-box motifs were identified in promoters of CsMYC2 and CsAFS,and the dual-luciferase reporter assay(LUC)and electrophoretic mobility shift assays(EMSA)demonstrated direct binding functions of CsHY5 to CsAFS and CsMYC2 promoters,as well as CsMYC2 to the CsAFS promoter.Based on sensory evaluation,odourant quantification,gene expression,and molecular functional analysis,we propose that UV-B radiation and tumbling-induced wounding signals synergistically regulate a-farnesene biosynthesis through a coordinated interaction of CsHY5 and CsMYC2 during oolong tea processing.These findings improve our understanding of flavour formation during oolong tea production and also provide novel insights into artificial light application in tea manufacturing.
