The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the...The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.展开更多
An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substi...An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substituted alkyl sulfones.Notably,this process does not require a metal catalyst or metal powder reductant,highlighting its environmentally friendly features.The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups.Furthermore,the biologically active molecules and commercially available drugs with a late-stage modification are also highly compatible with this transformation.Mechanistic studies revealed that the reaction proceeds through a single-step process involving intramolecular radical cyclization,"SO_(2)"insertion,and external alkyl incorporation.展开更多
Gastric carcinoma(GC)is a malignancy with multifactorial involvement,multicellular regulation,and multistage evolution.The classic Correa's cascade of intestinal GC specifies a trilogy of malignant transformation ...Gastric carcinoma(GC)is a malignancy with multifactorial involvement,multicellular regulation,and multistage evolution.The classic Correa's cascade of intestinal GC specifies a trilogy of malignant transformation of the gastric mucosa,in which normal gastric mucosa gradually progresses from inactive or chronic active gastritis(Phase I)to gastric precancerous lesions(Phase II)and finally to GC(Phase III).Correa's cascade highlights the evolutionary pattern of GC and the importance of early intervention to prevent malignant transformation of the gastric mucosa.Intervening in early gastric mucosal lesions,i.e.,Phases I and II,will be the key strategy to prevent and treat GC.Natural products(NPs)have been an important source for drug development due to abundant sources,tremendous safety,and multiple pharmacodynamic mechanisms.This review is the first to investigate and summarize the multi-step effects and regulatory mechanisms of NPs on the Correa's cascade in gastric carcinogenesis.In Phase I,NPs modulate Helicobacter pylori urease activity,motility,adhesion,virulence factors,and drug resistance,thereby inhibiting H.pylori-induced gastric mucosal inflammation and oxidative stress,and facilitating ulcer healing.In Phase II,NPs modulate multiple pathways and mediators regulating gastric mucosal cell cycle,apoptosis,autophagy,and angiogenesis to reverse gastric precancerous lesions.In Phase III,NPs suppress cell proliferation,migration,invasion,angiogenesis,and cancer stem cells,induce apoptosis and autophagy,and enhance chemotherapeutic drug sensitivity for the treatment of GC.In contrast to existing work,we hope to uncover NPs with sequential therapeutic effects on multiple phases of GC development,providing new ideas for gastric cancer prevention,treatment,and drug development.展开更多
Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order mo...Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order modes.A structure of mini-array is adopted to improve the heat dissipation capacity and beam quality of BA QCLs.The active region is etched to form a multi-emitter and the channels are filled with In P:Fe,which acts as a lateral heat dissipation channel to improve the lateral heat dissipation efficiency.A device withλ~4.8μm,a peak output power of 122 W at 1.2%duty cycle with a pulse of 1.5μs is obtained in room temperature,with far-field single-lobed distribution.This result allows BA QCLs to obtain high peak power at wider pump pulse widths and higher duty cycle conditions,promotes the application of the mid-infrared laser operating in pulsed mode in th e field of standoff photoacoustic chemical detection,space optical communication,and so on.展开更多
Difluoromethyl compounds are widely found in natural products,bioactive molecule and pharmaceuticals.A visible-light induced difluoromethylation/cyclization of 2-aryl indoles is described to construct indolo[2,1-a]iso...Difluoromethyl compounds are widely found in natural products,bioactive molecule and pharmaceuticals.A visible-light induced difluoromethylation/cyclization of 2-aryl indoles is described to construct indolo[2,1-a]isoquinolin-6(5H)-one derivatives using the inexpensive and easy-to-handle HCF_(2)SO_(2)Na as an HCF2 sources.Diverse difluoromethylated indolo[2,1-a]isoquinolines were readily obtained in moderate to good yields.Mechanistic studies demonstrate that the reaction may involve a radical process.展开更多
In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particul...In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.展开更多
[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore ...[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.展开更多
A novel synthesis of C2-spiroindoline derivatives based on the cascade reaction of 2-aryl-3H-indoles with cyclo- propanols is presented. The formation of product involves Rh(III)-catalyzed aryl C(sp2)—H bond alkylati...A novel synthesis of C2-spiroindoline derivatives based on the cascade reaction of 2-aryl-3H-indoles with cyclo- propanols is presented. The formation of product involves Rh(III)-catalyzed aryl C(sp2)—H bond alkylation of 2-aryl- 3H-indole, which is followed by intramolecular spiroannulation. In this tandem process, cyclopropanol acts as not only an alkylating agent but also a masked nucleophile to take part in the construction of the spirocyclic scaffold. Meanwhile, air acts as an economical and sustainable oxidant to promote the regeneration of the active catalyst. By using this method, hybrid compounds containing the central scaffolds of some clinical drugs were prepared effectively. In general, this newly developed method has advantages such as easily obtainable substrates, concise synthetic procedure, excellent atom-economy, good compatibility with diverse functional groups and ready scalability.展开更多
Indole[2,1-α]isoquinolines are an important class of bioactive molecules and show good antibacterial activity.In the present study,an efficient copper(I)-catalyzed acylation/cyclization has been developed for the con...Indole[2,1-α]isoquinolines are an important class of bioactive molecules and show good antibacterial activity.In the present study,an efficient copper(I)-catalyzed acylation/cyclization has been developed for the construction of indolo[2,1-α]isoquinoline derivatives by utilizing 2-aryl-N-acryloyl indole and benzohydrazide as reactants in the presence of CuI as catalyst and tert-butyl hydroperoxide as oxidant.The present protocol exhibits good functional group tolerance,and a series of acylated indole[2,1-α]isoquinolines were synthesized in moderate to good yields.Radical trapping experiments indicated that the reaction may involve a radical process.展开更多
Aberration-corrected focus scanning is crucial for high-precision optics,but the conventional optical systems rely on bulky and complicated dynamic correctors.Recently,Shiyi Xiao's group proposed a method using tw...Aberration-corrected focus scanning is crucial for high-precision optics,but the conventional optical systems rely on bulky and complicated dynamic correctors.Recently,Shiyi Xiao's group proposed a method using two rotating cascaded transmissive metasurfaces for adaptive aberration correction in focus scanning.The optimized phase profiles enable precise control of the focal position for scanning custom-curved surfaces.This concept was experimentally validated by two allsilicon meta-devices in the terahertz regime,paving the way for high-precision and compact optical devices in various applications.展开更多
Using molecular dynamics methods,simulations of collision cascades in polycrystalline tungsten(W)have been conducted in this study,including different primary-knock-on atom(PKA)directions,grain sizes,and PKA energies ...Using molecular dynamics methods,simulations of collision cascades in polycrystalline tungsten(W)have been conducted in this study,including different primary-knock-on atom(PKA)directions,grain sizes,and PKA energies between 1 keV and 150 keV.The results indicate that a smaller grain size leads to more defects forming in grain boundary regions during cascade processes.The impact of high-energy PKA may cause a certain degree of distortion of the grain boundaries,which has a higher probability in systems with smaller grain sizes and becomes more pronounced as the PKA energy increases.The direction of PKA can affect the formation and diffusion pathways of defects.When the PKA direction is perpendicular to the grain boundary,defects preferentially form near the grain boundary regions;by contrast,defects are more inclined to form in the interior of the grains.These results are of great significance for comprehending the changes in the performance of polycrystalline W under the high-energy fusion environments and can provide theoretical guidance for further optimization and application of W-based plasma materials.展开更多
This study presents the design of an erbium-doped fiber laser(EDFL) featuring switchable wavelength intervals achieved through the implementation of cascaded and parallel Lyot filters. The proposed laser system utiliz...This study presents the design of an erbium-doped fiber laser(EDFL) featuring switchable wavelength intervals achieved through the implementation of cascaded and parallel Lyot filters. The proposed laser system utilizes a cascaded and parallel configuration of three Lyot filters, facilitated by a polarization beam splitter(PBS) for branch switching. The transmission properties of the filter are analyzed through theoretical modeling and experimental validation using the transmission matrix method. The experimental results are found to be consistent with the theoretical predictions, demonstrating the effectiveness of the proposed design. By adjusting the polarization controllers(PCs), the proposed laser can switch between wavelength spacings of 0.46 nm, 0.27 nm, and 0.76 nm, with a maximum optical signal-to-noise ratio(OSNR) of 38 d B. However, the stability of the laser with a 0.27 nm spacing is not high due to wavelength competition. Power fluctuation for 0.46 nm and 0.76 nm intervals is less than 0.93 d B and 0.78 d B in 1 h, with wavelength fluctuation less than 0.068 nm and 0.19 nm, respectively. This EDFL has the advantages of simple structure, great flexibility, and switchability, which can be applied to fiber optic sensing, wavelength division multiplexing(WDM) networks, and other fields that require a very flexible light source.展开更多
This paper focuses on the problem of leaderfollowing consensus for nonlinear cascaded multi-agent systems.The control strategies for these systems are transformed into successive control problem schemes for lower-orde...This paper focuses on the problem of leaderfollowing consensus for nonlinear cascaded multi-agent systems.The control strategies for these systems are transformed into successive control problem schemes for lower-order error subsystems.A distributed consensus analysis for the corresponding error systems is conducted by employing recursive methods and virtual controllers,accompanied by a series of Lyapunov functions devised throughout the iterative process,which solves the leaderfollowing consensus problem of a class of nonlinear cascaded multi-agent systems.Specific simulation examples illustrate the effectiveness of the proposed control algorithm.展开更多
Chiral cyclic amino alcohols with contiguous stereocenters are key building blocks in the synthesis of bioactive molecules and pharmaceuticals.Artificial cascade biocatalysis represents an attractive method for the sy...Chiral cyclic amino alcohols with contiguous stereocenters are key building blocks in the synthesis of bioactive molecules and pharmaceuticals.Artificial cascade biocatalysis represents an attractive method for the synthesis of chiral molecules bearing multiple stereocenters from readily available materials.Here we reported an artificial cascade biocatalysis comprising an epoxide hydrolase,an alcohol dehydrogenase,and a reductive aminase or an amine dehydrogenase.It can be utilized to access all four stereoisomers of 2-aminocyclohexanol with two contiguous stereocenters in high yields(up to 95%)and excellent stereoselectivity(up to 98%de)starting from readily available cyclohexene oxide without isolation of the intermediates.Additionally,the biocatalytic cascade has been successfully extended to the production of structurally diverse 2-(alkylamino)cyclohexanols by replacing ammonia with different organic amines.展开更多
Asperfilasin A(1),featuring a unique 5/5 cyclopenta[c]pyrrol-one bicyclic core,represents a newly discovered skeletal cytochalasan isolated from Aspergillus flavipes.The enantioselective total synthesis was efficientl...Asperfilasin A(1),featuring a unique 5/5 cyclopenta[c]pyrrol-one bicyclic core,represents a newly discovered skeletal cytochalasan isolated from Aspergillus flavipes.The enantioselective total synthesis was efficiently accomplished from the key intermediate(S)-6 with three contiguous stereocenters in 5 steps and the synthetic 1 induced G2/M-phase cell cycle arrest of HT29 cells and apoptosis of HL60 and NB4 cells by activation of caspase-3 and degradation of PARP.(S)-6,bearing three contiguous chiral centers,was efficiently constructed by a novel Nazarov cyclization reaction containing basic nitrogen,which was less developed,primarily due to the incompatibility of basic nitrogen under acidic reaction conditions.This reaction allows a wide range of pentadienone substrates containing basic nitrogen to undergo Nazarov cyclization in a single regioselective and diastereoselective manner and is capable of generating three stereocenters simultaneously.Furthermore,the mechanism of the Nazarov cyclization and the origin of the regio-and diastereoselectivity were elucidated by DFT calculations and deuteration experiments,providing valuable insights into the reaction and serving as a guide for future applications involving substrates containing basic nitrogen.展开更多
Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial...Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial characteristics and final outburst scale remains a fundamental challenge in geomechanics.This study conceptualizes outbursts as deterministic cascade systems through integrated physical simulations combining high-sensitivity infrasound monitoring with energy analysis under controlled gas pressure(0.5–1.0 MPa)and confining stress(5–10 MPa)conditions.Our complementary analytical algorithms—the absolute amplitude integral and predominant period function—revealed characteristic step-wise patterns in outburst development.Quantitative analysis established a robust correlation(R2=0.91)between initial acoustic response and final outburst intensity.Energy analysis demonstrated that gas expansion dominates the outburst process(91.81%–99.09%of total energy),with desorption gas contributing 59.1%–77.7%.Time-frequency analysis showed systematic frequency migration from high(12–15 Hz)to low(4–8 Hz)bands during outburst progression,reflecting hierarchical spatial scale expansion.The concentrated energy release(>20%of total)within initial 0.2 s provides a mechanistic basis for the deterministic nature of outburst evolution.These mechanistic insights establish a quantitative framework for developing physics-based monitoring protocols and risk assessment methodologies applicable to underground coal mining operations.展开更多
基金financial support from the National Natural Science Foundation of China(Nos.22125108,22101238,22331004 and 22121001)Yunnan Fundamental Research Project(No.202401CF070024)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20211059)the Project of Science and Technology of Xuzhou Government(No.KC22080)NFFTBS(No.J1310024)。
文摘The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.
基金the Scientific Research Fund of Hunan Provincial Education Department(21B0262 and 22B1094)the Natural Science Foundation of Hunan Province(2022JJ40857)the Hunan Provincial Innovation Foundation For Postgraduate(CX20230757)forfinancial support.
文摘An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substituted alkyl sulfones.Notably,this process does not require a metal catalyst or metal powder reductant,highlighting its environmentally friendly features.The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups.Furthermore,the biologically active molecules and commercially available drugs with a late-stage modification are also highly compatible with this transformation.Mechanistic studies revealed that the reaction proceeds through a single-step process involving intramolecular radical cyclization,"SO_(2)"insertion,and external alkyl incorporation.
基金supported by the Chengdu University of Traditional Chinese Medicine"Xinglin Scholars"Program,China(Grant No.:MPRC2023014).
文摘Gastric carcinoma(GC)is a malignancy with multifactorial involvement,multicellular regulation,and multistage evolution.The classic Correa's cascade of intestinal GC specifies a trilogy of malignant transformation of the gastric mucosa,in which normal gastric mucosa gradually progresses from inactive or chronic active gastritis(Phase I)to gastric precancerous lesions(Phase II)and finally to GC(Phase III).Correa's cascade highlights the evolutionary pattern of GC and the importance of early intervention to prevent malignant transformation of the gastric mucosa.Intervening in early gastric mucosal lesions,i.e.,Phases I and II,will be the key strategy to prevent and treat GC.Natural products(NPs)have been an important source for drug development due to abundant sources,tremendous safety,and multiple pharmacodynamic mechanisms.This review is the first to investigate and summarize the multi-step effects and regulatory mechanisms of NPs on the Correa's cascade in gastric carcinogenesis.In Phase I,NPs modulate Helicobacter pylori urease activity,motility,adhesion,virulence factors,and drug resistance,thereby inhibiting H.pylori-induced gastric mucosal inflammation and oxidative stress,and facilitating ulcer healing.In Phase II,NPs modulate multiple pathways and mediators regulating gastric mucosal cell cycle,apoptosis,autophagy,and angiogenesis to reverse gastric precancerous lesions.In Phase III,NPs suppress cell proliferation,migration,invasion,angiogenesis,and cancer stem cells,induce apoptosis and autophagy,and enhance chemotherapeutic drug sensitivity for the treatment of GC.In contrast to existing work,we hope to uncover NPs with sequential therapeutic effects on multiple phases of GC development,providing new ideas for gastric cancer prevention,treatment,and drug development.
文摘Broad area quantum cascade lasers(BA QCLs)have significant applications in many areas,but suffer from demanding pulse operating conditions and poor beam quality due to heat accumulation and generation of high order modes.A structure of mini-array is adopted to improve the heat dissipation capacity and beam quality of BA QCLs.The active region is etched to form a multi-emitter and the channels are filled with In P:Fe,which acts as a lateral heat dissipation channel to improve the lateral heat dissipation efficiency.A device withλ~4.8μm,a peak output power of 122 W at 1.2%duty cycle with a pulse of 1.5μs is obtained in room temperature,with far-field single-lobed distribution.This result allows BA QCLs to obtain high peak power at wider pump pulse widths and higher duty cycle conditions,promotes the application of the mid-infrared laser operating in pulsed mode in th e field of standoff photoacoustic chemical detection,space optical communication,and so on.
文摘Difluoromethyl compounds are widely found in natural products,bioactive molecule and pharmaceuticals.A visible-light induced difluoromethylation/cyclization of 2-aryl indoles is described to construct indolo[2,1-a]isoquinolin-6(5H)-one derivatives using the inexpensive and easy-to-handle HCF_(2)SO_(2)Na as an HCF2 sources.Diverse difluoromethylated indolo[2,1-a]isoquinolines were readily obtained in moderate to good yields.Mechanistic studies demonstrate that the reaction may involve a radical process.
基金Supported by the National Natural Science Foundation of China(62105039)。
文摘In the process of power scaling large-area Quantum Cascade Lasers(QCLs),challenges such as degradation of beam quality and emission of multilobed far-field modes are frequently encountered.These issues become particularly pronounced with an increase in ridge width,resulting in multimode problems.To tackle this,an innovative multi ridge waveguide structure based on the principle of supersymmetry(SUSY)was proposed.This structure comprises a wider main waveguide in the center and two narrower auxiliary waveguides on either side.The high-order modes of the main waveguide are coupled with the modes of the auxiliary waveguides through mode-matching design,and the optical loss of the auxiliary waveguides suppresses these modes,thereby achieving fundamental mode lasing of the wider main waveguide.This paper employs the finite difference eigenmode(FDE)method to perform detailed structural modeling and simulation optimization of the 4.6μm wavelength quantum cascade laser,successfully achieving a single transverse mode QCL with a ridge width of 10μm.In comparison to the traditional single-mode QCL(with a ridge width of about 5μm),the MRW structure has the potential to increase the gain area of the laser by 100%.This offers a novel design concept and methodology for enhancing the single-mode luminous power of mid-infrared quantum cascade lasers,which is of considerable significance.
文摘[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.
文摘A novel synthesis of C2-spiroindoline derivatives based on the cascade reaction of 2-aryl-3H-indoles with cyclo- propanols is presented. The formation of product involves Rh(III)-catalyzed aryl C(sp2)—H bond alkylation of 2-aryl- 3H-indole, which is followed by intramolecular spiroannulation. In this tandem process, cyclopropanol acts as not only an alkylating agent but also a masked nucleophile to take part in the construction of the spirocyclic scaffold. Meanwhile, air acts as an economical and sustainable oxidant to promote the regeneration of the active catalyst. By using this method, hybrid compounds containing the central scaffolds of some clinical drugs were prepared effectively. In general, this newly developed method has advantages such as easily obtainable substrates, concise synthetic procedure, excellent atom-economy, good compatibility with diverse functional groups and ready scalability.
文摘Indole[2,1-α]isoquinolines are an important class of bioactive molecules and show good antibacterial activity.In the present study,an efficient copper(I)-catalyzed acylation/cyclization has been developed for the construction of indolo[2,1-α]isoquinoline derivatives by utilizing 2-aryl-N-acryloyl indole and benzohydrazide as reactants in the presence of CuI as catalyst and tert-butyl hydroperoxide as oxidant.The present protocol exhibits good functional group tolerance,and a series of acylated indole[2,1-α]isoquinolines were synthesized in moderate to good yields.Radical trapping experiments indicated that the reaction may involve a radical process.
文摘Aberration-corrected focus scanning is crucial for high-precision optics,but the conventional optical systems rely on bulky and complicated dynamic correctors.Recently,Shiyi Xiao's group proposed a method using two rotating cascaded transmissive metasurfaces for adaptive aberration correction in focus scanning.The optimized phase profiles enable precise control of the focal position for scanning custom-curved surfaces.This concept was experimentally validated by two allsilicon meta-devices in the terahertz regime,paving the way for high-precision and compact optical devices in various applications.
基金Project supported by the National MCF Energy Research and Development Program of China(Grant No.2018YFE0308101)the National Key Research and Development Program of China(Grant No.2018YFB0704000)+1 种基金the Suqian Science and Technology Program(Grant No.K202337)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.23KJD490001).
文摘Using molecular dynamics methods,simulations of collision cascades in polycrystalline tungsten(W)have been conducted in this study,including different primary-knock-on atom(PKA)directions,grain sizes,and PKA energies between 1 keV and 150 keV.The results indicate that a smaller grain size leads to more defects forming in grain boundary regions during cascade processes.The impact of high-energy PKA may cause a certain degree of distortion of the grain boundaries,which has a higher probability in systems with smaller grain sizes and becomes more pronounced as the PKA energy increases.The direction of PKA can affect the formation and diffusion pathways of defects.When the PKA direction is perpendicular to the grain boundary,defects preferentially form near the grain boundary regions;by contrast,defects are more inclined to form in the interior of the grains.These results are of great significance for comprehending the changes in the performance of polycrystalline W under the high-energy fusion environments and can provide theoretical guidance for further optimization and application of W-based plasma materials.
基金supported by the Primary Research and Development Plan of Zhejiang Province (No.2023C03014)the Key Research and Development Program of Zhejiang Province (No.2022C03037)。
文摘This study presents the design of an erbium-doped fiber laser(EDFL) featuring switchable wavelength intervals achieved through the implementation of cascaded and parallel Lyot filters. The proposed laser system utilizes a cascaded and parallel configuration of three Lyot filters, facilitated by a polarization beam splitter(PBS) for branch switching. The transmission properties of the filter are analyzed through theoretical modeling and experimental validation using the transmission matrix method. The experimental results are found to be consistent with the theoretical predictions, demonstrating the effectiveness of the proposed design. By adjusting the polarization controllers(PCs), the proposed laser can switch between wavelength spacings of 0.46 nm, 0.27 nm, and 0.76 nm, with a maximum optical signal-to-noise ratio(OSNR) of 38 d B. However, the stability of the laser with a 0.27 nm spacing is not high due to wavelength competition. Power fluctuation for 0.46 nm and 0.76 nm intervals is less than 0.93 d B and 0.78 d B in 1 h, with wavelength fluctuation less than 0.068 nm and 0.19 nm, respectively. This EDFL has the advantages of simple structure, great flexibility, and switchability, which can be applied to fiber optic sensing, wavelength division multiplexing(WDM) networks, and other fields that require a very flexible light source.
基金National Natural Science Foundation of China(No.12071370)。
文摘This paper focuses on the problem of leaderfollowing consensus for nonlinear cascaded multi-agent systems.The control strategies for these systems are transformed into successive control problem schemes for lower-order error subsystems.A distributed consensus analysis for the corresponding error systems is conducted by employing recursive methods and virtual controllers,accompanied by a series of Lyapunov functions devised throughout the iterative process,which solves the leaderfollowing consensus problem of a class of nonlinear cascaded multi-agent systems.Specific simulation examples illustrate the effectiveness of the proposed control algorithm.
文摘Chiral cyclic amino alcohols with contiguous stereocenters are key building blocks in the synthesis of bioactive molecules and pharmaceuticals.Artificial cascade biocatalysis represents an attractive method for the synthesis of chiral molecules bearing multiple stereocenters from readily available materials.Here we reported an artificial cascade biocatalysis comprising an epoxide hydrolase,an alcohol dehydrogenase,and a reductive aminase or an amine dehydrogenase.It can be utilized to access all four stereoisomers of 2-aminocyclohexanol with two contiguous stereocenters in high yields(up to 95%)and excellent stereoselectivity(up to 98%de)starting from readily available cyclohexene oxide without isolation of the intermediates.Additionally,the biocatalytic cascade has been successfully extended to the production of structurally diverse 2-(alkylamino)cyclohexanols by replacing ammonia with different organic amines.
基金supported by the National Natural Science Foundation of China(Nos.81725021,81903461)the National Key R&D Program of China(No.2022YFA1503200)the Natural Science Foundation of Hubei Province(No.ZRMS2023000340)。
文摘Asperfilasin A(1),featuring a unique 5/5 cyclopenta[c]pyrrol-one bicyclic core,represents a newly discovered skeletal cytochalasan isolated from Aspergillus flavipes.The enantioselective total synthesis was efficiently accomplished from the key intermediate(S)-6 with three contiguous stereocenters in 5 steps and the synthetic 1 induced G2/M-phase cell cycle arrest of HT29 cells and apoptosis of HL60 and NB4 cells by activation of caspase-3 and degradation of PARP.(S)-6,bearing three contiguous chiral centers,was efficiently constructed by a novel Nazarov cyclization reaction containing basic nitrogen,which was less developed,primarily due to the incompatibility of basic nitrogen under acidic reaction conditions.This reaction allows a wide range of pentadienone substrates containing basic nitrogen to undergo Nazarov cyclization in a single regioselective and diastereoselective manner and is capable of generating three stereocenters simultaneously.Furthermore,the mechanism of the Nazarov cyclization and the origin of the regio-and diastereoselectivity were elucidated by DFT calculations and deuteration experiments,providing valuable insights into the reaction and serving as a guide for future applications involving substrates containing basic nitrogen.
基金funded by the National Natural Science Foundation of China(No.52464016)the Guizhou Provincial Foundation Research Project(No.QKHJC-[2024]Youth 141)+1 种基金the Guizhou Provincial Basic Research Program(No.MS[2025]632)the Young Researcher Growth Project of Guizhou Provincial Department of Education(No.QJJ-[2024]25).
文摘Coal and gas outbursts constitute a critical hazard in underground mining operations,characterized by rapid transitions from localized instability to catastrophic failure.Understanding the relationship between initial characteristics and final outburst scale remains a fundamental challenge in geomechanics.This study conceptualizes outbursts as deterministic cascade systems through integrated physical simulations combining high-sensitivity infrasound monitoring with energy analysis under controlled gas pressure(0.5–1.0 MPa)and confining stress(5–10 MPa)conditions.Our complementary analytical algorithms—the absolute amplitude integral and predominant period function—revealed characteristic step-wise patterns in outburst development.Quantitative analysis established a robust correlation(R2=0.91)between initial acoustic response and final outburst intensity.Energy analysis demonstrated that gas expansion dominates the outburst process(91.81%–99.09%of total energy),with desorption gas contributing 59.1%–77.7%.Time-frequency analysis showed systematic frequency migration from high(12–15 Hz)to low(4–8 Hz)bands during outburst progression,reflecting hierarchical spatial scale expansion.The concentrated energy release(>20%of total)within initial 0.2 s provides a mechanistic basis for the deterministic nature of outburst evolution.These mechanistic insights establish a quantitative framework for developing physics-based monitoring protocols and risk assessment methodologies applicable to underground coal mining operations.
