Bay-site carboxyl functionalized perylene diimide derivative 1,7-COOH-PDI-C_(12)(PDI-COOH)was synthesized and distinct enhanced fluorescence was observed through combining with calcium ion(Ca^(2+))in THF/H_(2)O soluti...Bay-site carboxyl functionalized perylene diimide derivative 1,7-COOH-PDI-C_(12)(PDI-COOH)was synthesized and distinct enhanced fluorescence was observed through combining with calcium ion(Ca^(2+))in THF/H_(2)O solution.The assembly and fluorescence behavior of PDI-COOH/Ca^(2+)were studied in detail by changing hydration state with different concentrations.Based on the differences in assembly morphology and stoichiometric ratios of PDICOOH/Ca^(2+),we proposed the fluorescence emission mechanism of PDI-COOH/Ca^(2+)in THF/H_(2)O and THF,respectively.This work reveals a novel strategy of aggregated state fluorescence enhancement and reminds us of the important role of water in molecular fluorescence emission and assembly.展开更多
Photoluminescence(PL)is one of the most important properties of metal nanoclusters(NCs).Achieving effi⁃cient white light emission in metal NCs with a precise structures is important for practical applications but rema...Photoluminescence(PL)is one of the most important properties of metal nanoclusters(NCs).Achieving effi⁃cient white light emission in metal NCs with a precise structures is important for practical applications but remains a great challenge.Here,we report the efficient white emission from Au_(10) NCs by elaborately deploying the surface chemistry engi⁃neering strategy.Specifically,the bis-aldehyde ligands of 4-hydroxyisophthalaldehyde(HOA)are decorated on the surface of Au_(10)(SG)_(10) NCs(glutathione denoted as SG)through the cross-linking reaction of imine bonds(-CH==N-).The combination of 477 nm blue emission from HOA ligands and 620 nm orange-yellow emission from Au_(10)(SG)_(10) NCs generates white-light emission in HOA-Au_(10)(SG)_(10) NCs in the solvent mixture of ethanol and water.More importantly,dynamic color tuning from blue light to yellow light is achieved by controlling the volume fraction of ethanol in the solvent mixture.In addi⁃tion,the as-formed imine bonds significantly improve the structural rigidity of HOA-Au_(10)(SG)_(10) NCs,resulting in the 51.2%absolute photoluminescence quantum yield(PLQY)of white emission.The present study exemplifies the paradigm to control the emission color and improve the PLQY of metal NCs through rational surface chemistry engineering.展开更多
Objective To characterize transmembrane protein 68(TMEM68)in an alternative triacylglycerol(TAG)biosynthesis pathway,and determine the interplay between TMEM68 and the canonical TAG synthesis enzyme acyl-CoA:diacylgly...Objective To characterize transmembrane protein 68(TMEM68)in an alternative triacylglycerol(TAG)biosynthesis pathway,and determine the interplay between TMEM68 and the canonical TAG synthesis enzyme acyl-CoA:diacylglycerol acyltransferase(DGAT).Methods Effects of exogenous fatty acid and monoacylglycerol on TAG synthesis and lipid droplet(LD)formation in TMEM68 overexpression and knockout cells treated with DGAT inhibitor or not were investigated by comparing LD morphology,Oil Red O staining,and measurement of TAG levels.LDs were stained with fluorescence dye and observed by confocal fluorescence microscopy.TAG levels were determined with an enzyme-based triglyceride assay kit.Colocalization of TMEM68 and DGAT1 was detected by co-expression and confocal fluorescence microscopy and their interaction was determined by co-immunoprecipitation.RT-qPCR and immunoblotting assay were used to detect the expression of DGAT1.Results The synthesis of TAG catalyzed by TMEM68 was independent of DGAT activity.Surplus exogenous fatty acids and monoacylglycerol promoted TAG synthesis mainly through DGAT in human neuroblastoma cells.The LDs formed by TMEM68 were different in morphology from those by DGAT.In addition,TMEM68 and DGAT1 colocalized in the same endoplasmic reticulum(ER)compartment but did not interact physically.TMEM68 overexpression reduced the expression of DGAT1,the major DGAT enzyme involved in TAG synthesis,while TMEM68 knockout had little impact.Conclusion The TMEM68-mediated TAG synthesis pathway has distinct features from the canonical DGAT pathway,however,TMEM68 and DGAT may coregulate intracellular TAG levels.展开更多
Large-area two-dimensional(2D)materials,such as graphene,MoS_(2),WS_(2),h-BN,black phosphorus,and MXenes,are a class of advanced materials with many possible applications.Different applications need different substrat...Large-area two-dimensional(2D)materials,such as graphene,MoS_(2),WS_(2),h-BN,black phosphorus,and MXenes,are a class of advanced materials with many possible applications.Different applications need different substrates,and each substrate may need a different way of transferring the 2D material onto it.Problems such as local stress concentrations,an uneven surface tension,inconsistent adhesion,mechanical damage and contamination during the transfer can adversely affect the quality and properties of the transferred material.Therefore,how to improve the integrity,flatness and cleanness of large area 2D materials is a challenge.In order to achieve high-quality transfer,the main concern is to control the interface adhesion between the substrate,the 2D material and the transfer medium.This review focuses on this topic,and finally,in order to promote the industrial use of large area 2D materials,provides a recipe for this transfer process based on the requirements of the application,and points out the current problems and directions for future development.展开更多
In this paper,we consider the price of catastrophe options with credit risk in a regime-switching model.We assume that the macroeconomic states are described by a continuous-time Markov chain with a finite state space...In this paper,we consider the price of catastrophe options with credit risk in a regime-switching model.We assume that the macroeconomic states are described by a continuous-time Markov chain with a finite state space.By using the measure change technique,we derive the price expressions of catastrophe put options.Moreover,we conduct some numerical analysis to demonstrate how the parameters of the model affect the price of the catastrophe put option.展开更多
While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LED...While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LEDs).Rather,quasi-two-dimensional(Q-2D)perovskites offer high photoluminescence quantum yield along with the advantages of bulk perovskites,making them ideal for high-performance LEDs.In Q-2D perovskites,the structure(which includes factors like crystal orientation,phase distribution,and layer thickness)directly influences how excitons and charge carriers behave within the material.Growth control techniques,such as varying the synthesis conditions or employing methods,allow for fine-tuning the structural characteristics of these materials,which in turn affect exciton dynamics and charge transport.This review starts with a description of the basic properties of Q-2D perovskites,examines crystal growth in solution,explains how structure affects energy transfer behavior,and concludes with future directions for Q-2D perovskite LEDs.By understanding and optimizing the structure-dependent behavior,researchers can better control exciton dynamics and charge transport,which are crucial for enhancing the performance of optoelectronic devices like solar cells and LEDs.展开更多
Objective To observe the value of isotropic volumetric MRI for displaying perineural spread(PNS)of cranial nerve(CN)in nasopharyngeal carcinoma.Methods Eighty-seven patients with pathologically proven nasopharyngeal c...Objective To observe the value of isotropic volumetric MRI for displaying perineural spread(PNS)of cranial nerve(CN)in nasopharyngeal carcinoma.Methods Eighty-seven patients with pathologically proven nasopharyngeal carcinoma were prospectively enrolled.MR scanning,including three-dimensional liver acquisition with volume acceleration-flexible(3D LAVA_Flex)image,T2WI with fat suppression(T2WI-FS),T1WI,contrast enhancement(CE)T1WI-FS of nasopharynx and neck region were performed.The displaying rates of CN PNS were evaluated and compared between 3D LAVA_Flex and T2WI-FS,T1WI,CE-T1WI-FS at patient level,CN group level and neural level,respectively.Results The displaying rate of CN PNS in all 87 nasopharyngeal carcinoma patients by 3D LAVA_Flex sequence was 49.43%(43/87),higher than that of conventional MRI(30/87,34.48%,P=0.001).Among 59 patients with advanced nasopharyngeal carcinoma diagnosed with conventional sequences,the displaying rate of CN PNS was 71.19%(42/59)by 3D LAVA-Flex sequence,higher than that of conventional MRI(30/59,50.85%,P=0.001).At both patient level and posterior CN level,significant differences of the displaying rate of CN PNS were found between 3D LAVA-Flex sequence and T2WI-FS,T1WI,CE-T1WI-FS,while at CN level,the displaying rates of mandibular nerve PNS,CNⅨ—ⅪPNS in jugular foramen(P<0.05)and CNⅨ—ⅫPNS in carotid space of 3D LAVA_Flex sequence were all significantly higher than that of T2WI-FS,T1WI and CE-T1WI-FS(all P<0.05),of PNS of CNⅢ—Ⅴin cavernous sinus were higher than that of T2WI-FS(P<0.05),while of PNS of hypoglossal nerve were significantly higher than that of T2WI-FS and T1WI(both P<0.05).Conclusion 3D LAVA_Flex sequence could be used to effectively display CN PNS of nasopharyngeal carcinoma.展开更多
Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attacke...Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attackers to obtain detailed knowledge of the target model in actual scenarios,so using gradient optimization to generate adversarial samples in the local surrogate model has become an effective black‐box attack strategy.However,these methods suffer from gradients falling into local minima,limiting the transferability of the adversarial samples.This reduces the attack's effectiveness and often ignores the imperceptibility of the generated adversarial samples.To address these challenges,we propose a novel attack algorithm called PGMRS‐KL that combines pre‐gradient‐guided momentum gradient optimization strategy and fake user generation constrained by Kullback‐Leibler divergence.Specifically,the algorithm combines the accumulated gradient direction with the previous step's gradient direction to iteratively update the adversarial samples.It uses KL loss to minimize the distribution distance between fake and real user data,achieving high transferability and imperceptibility of the adversarial samples.Experimental results demonstrate the superiority of our approach over state‐of‐the‐art gradient‐based attack algorithms in terms of attack transferability and the generation of imperceptible fake user data.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-lumines...Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-luminescence(PL)quantum yield of monolayer(1L)TMDs is still quite low at room temperature,which severely lim-its their practical applications.Here we report a PL enhancement effect of 1L WS_(2) at room temperature when con-structing it into 1L-WS_(2)/hBN/1L-MoS_(2) vertical HSs.The PL enhancement factors(EFs)can be up to 4.2.By using transient absorption(TA)spectroscopy,we demonstrate that the PL enhancement effect is due to energy transfer from 1L MoS_(2) to 1L WS_(2).The energy transfer process occurs on a picosecond timescale and lasts more than one hundred picoseconds which indicates a prominent contribution from exciton-exciton annihilation.Furthermore,the PL en-hancement effect of 1L WS_(2) can be observed in 2L-MoS_(2)/hBN/1L-WS_(2) and 3L-MoS_(2)/hBN/1L-WS_(2) HSs.Our study provides a comprehensive understanding of the energy transfer process in the PL enhancement of 2D TMDs and a fea-sible way to optimize the performance of TMD-based optoelectronic devices.展开更多
Single-entity collisional electrochemistry(SECE)is a branch of single-entity electrochemistry.It can directly characterize entities/particles with single particle resolution through random collisions between particles...Single-entity collisional electrochemistry(SECE)is a branch of single-entity electrochemistry.It can directly characterize entities/particles with single particle resolution through random collisions between particles and electrodes in a solution,and obtain rich physicochemical information,thus becoming one of the frontiers of electroanalytical chemistry in the past two decades.Interestingly,the(micro/nanoscale)sensing electrodes have evolved from a polarizable liquid/liquid(mercury/liquid)interface to a solid/liquid interface and then to a liquid/liquid interface(i.e.,an interface between twoimmiscible electrolyte solutions,ITIES),as if they have completed a cycle(but in fact they have not).ITIES has become the latest sensing electrode in the booming SECE due to its polarizability(up to 1.1 V at the water/a,a,a-trifluorotoluene interface)and high reproducibility.The four measurement modes(direct electrolysis,mediated electrolysis,current blockade,and charge displacement)developed in the realm of SECE at solid/liquid interfaces have also been fully realized at the miniature ITIES.This article will discuss these four modes at the ITIES from the perspectives of basic concepts,operating mechanisms,and latest developments(e.g.,discovery of ionosomes,blockade effect of Faradaic ion transfer,etc.),and look forward to the future development and direction of this emerging field.展开更多
To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mat...To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.展开更多
In the early fault period of high-speed train systems, the interested characteristic signals are relatively weak and easily submerged in heavy noise. In order to solve this problem, a state-transition-algorithm (STA)-...In the early fault period of high-speed train systems, the interested characteristic signals are relatively weak and easily submerged in heavy noise. In order to solve this problem, a state-transition-algorithm (STA)-based adaptive stochastic resonance (SR) method is proposed, which provides an alternative solution to the problem that the traditional SR has fixed parameters or optimizes only a single parameter and ignores the interaction between parameters. To be specific, the frequency-shifted and re-scaling are firstly used to pre-process an actual large signal to meet the requirement of the adiabatic approximate small parameter. And then, the signal-to-noise ratio is used as the optimization target, and the STA-based adaptive SR is used to synchronously optimize the system parameters. Finally, the optimal extraction and frequency recovery of a weak characteristic signal from a broken rotor bar fault are realized. The proposed method is compared with the existing methods by the early broken rotor bar experiments of traction motor. Experiment results show that the proposed method is better than the other methods in extracting weak signals, and the validity of this method is verified.展开更多
Bauxite residue(BR),a by-product of the industrial production of alumina,has raised environmental concerns in the last decades,due to the presence of high amounts of alkali and various heavy metal ions.Limited studies...Bauxite residue(BR),a by-product of the industrial production of alumina,has raised environmental concerns in the last decades,due to the presence of high amounts of alkali and various heavy metal ions.Limited studies on the application of abandoned BR with massive consumption have been reported.In this study,the possibility of the revegetation using ryegrass growing on BR was discussed mainly through the growth indications and transfer of heavy metal ions in BR and plants.In the pot trails,ryegrass was seeded on BR,de-alkali BR,with(DBRO)or without(DBR)organic fertilizer,respectively.The results indicated that the remediation of bauxite residue can be achieved through de-alkali with acid neutralization.Elemental analysis indicated that the elements,except for Fe,Mn and Pb,were stable in plant roots,and ryegrass could hardly absorb Cd.But,some heavy metals such as Cu enriched in plants,which should be noted in revegetation on bauxite residue.展开更多
Rubidium phosphate can be more conveniently obtained by extracting trace Rb+ from the salt lake brine. Rb_3PO_4 was found to be an excellent heterogeneous catalyst for transfer hydrogenation. Rb_3PO_4 lost 70% of its ...Rubidium phosphate can be more conveniently obtained by extracting trace Rb+ from the salt lake brine. Rb_3PO_4 was found to be an excellent heterogeneous catalyst for transfer hydrogenation. Rb_3PO_4 lost 70% of its active sites after adsorbing water, but the remaining was not affected. The reductions of aldehydes and ketones, when promoted by Rb_3PO_4, were allowed at room temperature. The activities of substrates at room temperature followed a descending order of 2,6-dichlorobenzaldehyde> 4-bromobenzaldehyde>benzaldehyde>acetophenone>anisaldehyde>butanone. A new catalytic cycle postulating a six-membered cyclic transition state for the reductions of aldehydes and ketones was proposed. These results exploited the catalytic usage of Rb_3PO_4 and worth in industrial application.展开更多
A novel periodic mount was presented. A theoretical model was developed to describe the dynamics of wave propagation in the novel periodic mount. The model was derived using Hamilton's energy conservation principl...A novel periodic mount was presented. A theoretical model was developed to describe the dynamics of wave propagation in the novel periodic mount. The model was derived using Hamilton's energy conservation principle. The characteristics of wave propagation in unit cell were analyzed by transfer matrix formulation. Numerical examples were given to illustrate the effectiveness of the periodic mount. The experiments were carried out to identify the predications of the theoretical model. The obtained results show that the experimental results coincide with the prediction of theoretical model. No pass bands appear in the overall frequency range measured when waves propagate in the longitude direction of the periodic mount. These dramatic results demonstrate its potential as an excellent mount in attenuating and isolating vibration transmission.展开更多
To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding ...To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding stress development of bars adhered to grout concrete was analyzed. The local bonding stress—slip curve was obtained. Based on the test results,a new bonding stress— slip constitutive model between bars and grout concrete was proposed. The results show that the maximum bonding stress is not influenced by the bar bond length,but it is strengthened when the splitting strength of grout concrete is increased. The model matches the experimental results well,and the regressing coefficient equals 1.7.展开更多
Diallyl disulfide was synthesized by phase transfer catalyst （PTC） during microwave irradiation. The effects of different factors, such as the power of microwave irradiation, the time of microwave irradiation, PTC r...Diallyl disulfide was synthesized by phase transfer catalyst （PTC） during microwave irradiation. The effects of different factors, such as the power of microwave irradiation, the time of microwave irradiation, PTC reagents amount and the mole ratio of reactants, on the yield of product were investigated. The structure of diallyl disulfide was characterized by infrared spectra, mass spectra and ^1 H nuclear magnetic resonance. The bioactivity of diallyl disulfide was evaluated by cell viability assay on HepG2 hepatoma cells. The results show that the optimal reaction conditions are as follows： tetrabutylammonium bromide（TBAB） selected as a PTC, the mass ratio of TBAB to sodium disulfide of 0.021 ： 1, the power of irradiation of 195 W, the reaction time of 12 rain, and the mole ratio of sodium disulfide to allyl chloride of 0.65 ： 1. The yield of diallyl disulfide is 82.2%. The synthetical diallyl disulfide appears to be cytotoxic to HepG2 heoatoma cells in a dose-dependent manner.展开更多
文摘Bay-site carboxyl functionalized perylene diimide derivative 1,7-COOH-PDI-C_(12)(PDI-COOH)was synthesized and distinct enhanced fluorescence was observed through combining with calcium ion(Ca^(2+))in THF/H_(2)O solution.The assembly and fluorescence behavior of PDI-COOH/Ca^(2+)were studied in detail by changing hydration state with different concentrations.Based on the differences in assembly morphology and stoichiometric ratios of PDICOOH/Ca^(2+),we proposed the fluorescence emission mechanism of PDI-COOH/Ca^(2+)in THF/H_(2)O and THF,respectively.This work reveals a novel strategy of aggregated state fluorescence enhancement and reminds us of the important role of water in molecular fluorescence emission and assembly.
文摘Photoluminescence(PL)is one of the most important properties of metal nanoclusters(NCs).Achieving effi⁃cient white light emission in metal NCs with a precise structures is important for practical applications but remains a great challenge.Here,we report the efficient white emission from Au_(10) NCs by elaborately deploying the surface chemistry engi⁃neering strategy.Specifically,the bis-aldehyde ligands of 4-hydroxyisophthalaldehyde(HOA)are decorated on the surface of Au_(10)(SG)_(10) NCs(glutathione denoted as SG)through the cross-linking reaction of imine bonds(-CH==N-).The combination of 477 nm blue emission from HOA ligands and 620 nm orange-yellow emission from Au_(10)(SG)_(10) NCs generates white-light emission in HOA-Au_(10)(SG)_(10) NCs in the solvent mixture of ethanol and water.More importantly,dynamic color tuning from blue light to yellow light is achieved by controlling the volume fraction of ethanol in the solvent mixture.In addi⁃tion,the as-formed imine bonds significantly improve the structural rigidity of HOA-Au_(10)(SG)_(10) NCs,resulting in the 51.2%absolute photoluminescence quantum yield(PLQY)of white emission.The present study exemplifies the paradigm to control the emission color and improve the PLQY of metal NCs through rational surface chemistry engineering.
文摘Objective To characterize transmembrane protein 68(TMEM68)in an alternative triacylglycerol(TAG)biosynthesis pathway,and determine the interplay between TMEM68 and the canonical TAG synthesis enzyme acyl-CoA:diacylglycerol acyltransferase(DGAT).Methods Effects of exogenous fatty acid and monoacylglycerol on TAG synthesis and lipid droplet(LD)formation in TMEM68 overexpression and knockout cells treated with DGAT inhibitor or not were investigated by comparing LD morphology,Oil Red O staining,and measurement of TAG levels.LDs were stained with fluorescence dye and observed by confocal fluorescence microscopy.TAG levels were determined with an enzyme-based triglyceride assay kit.Colocalization of TMEM68 and DGAT1 was detected by co-expression and confocal fluorescence microscopy and their interaction was determined by co-immunoprecipitation.RT-qPCR and immunoblotting assay were used to detect the expression of DGAT1.Results The synthesis of TAG catalyzed by TMEM68 was independent of DGAT activity.Surplus exogenous fatty acids and monoacylglycerol promoted TAG synthesis mainly through DGAT in human neuroblastoma cells.The LDs formed by TMEM68 were different in morphology from those by DGAT.In addition,TMEM68 and DGAT1 colocalized in the same endoplasmic reticulum(ER)compartment but did not interact physically.TMEM68 overexpression reduced the expression of DGAT1,the major DGAT enzyme involved in TAG synthesis,while TMEM68 knockout had little impact.Conclusion The TMEM68-mediated TAG synthesis pathway has distinct features from the canonical DGAT pathway,however,TMEM68 and DGAT may coregulate intracellular TAG levels.
基金the National Key R&D Program of China(2022YFA1505200)the National Natural Science Foundation of China(22472140,22021001)the Fundamental Research Funds for the Central Universities(20720210017 and 20720210009)。
文摘Large-area two-dimensional(2D)materials,such as graphene,MoS_(2),WS_(2),h-BN,black phosphorus,and MXenes,are a class of advanced materials with many possible applications.Different applications need different substrates,and each substrate may need a different way of transferring the 2D material onto it.Problems such as local stress concentrations,an uneven surface tension,inconsistent adhesion,mechanical damage and contamination during the transfer can adversely affect the quality and properties of the transferred material.Therefore,how to improve the integrity,flatness and cleanness of large area 2D materials is a challenge.In order to achieve high-quality transfer,the main concern is to control the interface adhesion between the substrate,the 2D material and the transfer medium.This review focuses on this topic,and finally,in order to promote the industrial use of large area 2D materials,provides a recipe for this transfer process based on the requirements of the application,and points out the current problems and directions for future development.
基金supported by the Jiangsu University Philosophy and Social Science Research Project(Grant No.2019SJA1326).
文摘In this paper,we consider the price of catastrophe options with credit risk in a regime-switching model.We assume that the macroeconomic states are described by a continuous-time Markov chain with a finite state space.By using the measure change technique,we derive the price expressions of catastrophe put options.Moreover,we conduct some numerical analysis to demonstrate how the parameters of the model affect the price of the catastrophe put option.
文摘While three-dimensional perovskites have high defect tolerance and an adjustable bandgap,their charges tend to be free rather than forming excitons,making them unsuitable for use in efficient light-emitting diodes(LEDs).Rather,quasi-two-dimensional(Q-2D)perovskites offer high photoluminescence quantum yield along with the advantages of bulk perovskites,making them ideal for high-performance LEDs.In Q-2D perovskites,the structure(which includes factors like crystal orientation,phase distribution,and layer thickness)directly influences how excitons and charge carriers behave within the material.Growth control techniques,such as varying the synthesis conditions or employing methods,allow for fine-tuning the structural characteristics of these materials,which in turn affect exciton dynamics and charge transport.This review starts with a description of the basic properties of Q-2D perovskites,examines crystal growth in solution,explains how structure affects energy transfer behavior,and concludes with future directions for Q-2D perovskite LEDs.By understanding and optimizing the structure-dependent behavior,researchers can better control exciton dynamics and charge transport,which are crucial for enhancing the performance of optoelectronic devices like solar cells and LEDs.
文摘Objective To observe the value of isotropic volumetric MRI for displaying perineural spread(PNS)of cranial nerve(CN)in nasopharyngeal carcinoma.Methods Eighty-seven patients with pathologically proven nasopharyngeal carcinoma were prospectively enrolled.MR scanning,including three-dimensional liver acquisition with volume acceleration-flexible(3D LAVA_Flex)image,T2WI with fat suppression(T2WI-FS),T1WI,contrast enhancement(CE)T1WI-FS of nasopharynx and neck region were performed.The displaying rates of CN PNS were evaluated and compared between 3D LAVA_Flex and T2WI-FS,T1WI,CE-T1WI-FS at patient level,CN group level and neural level,respectively.Results The displaying rate of CN PNS in all 87 nasopharyngeal carcinoma patients by 3D LAVA_Flex sequence was 49.43%(43/87),higher than that of conventional MRI(30/87,34.48%,P=0.001).Among 59 patients with advanced nasopharyngeal carcinoma diagnosed with conventional sequences,the displaying rate of CN PNS was 71.19%(42/59)by 3D LAVA-Flex sequence,higher than that of conventional MRI(30/59,50.85%,P=0.001).At both patient level and posterior CN level,significant differences of the displaying rate of CN PNS were found between 3D LAVA-Flex sequence and T2WI-FS,T1WI,CE-T1WI-FS,while at CN level,the displaying rates of mandibular nerve PNS,CNⅨ—ⅪPNS in jugular foramen(P<0.05)and CNⅨ—ⅫPNS in carotid space of 3D LAVA_Flex sequence were all significantly higher than that of T2WI-FS,T1WI and CE-T1WI-FS(all P<0.05),of PNS of CNⅢ—Ⅴin cavernous sinus were higher than that of T2WI-FS(P<0.05),while of PNS of hypoglossal nerve were significantly higher than that of T2WI-FS and T1WI(both P<0.05).Conclusion 3D LAVA_Flex sequence could be used to effectively display CN PNS of nasopharyngeal carcinoma.
基金The National Natural Science Foundation of China (61876001)Opening Foundation of State Key Laboratory of Cognitive Intelligence,Opening Foundation of State Key Laboratory of Cognitive Intelligence(iED2022-006)Scientific Research Planning Project of Anhui Province (2022AH050072)
文摘Attackers inject the designed adversarial sample into the target recommendation system to achieve illegal goals,seriously affecting the security and reliability of the recommendation system.It is difficult for attackers to obtain detailed knowledge of the target model in actual scenarios,so using gradient optimization to generate adversarial samples in the local surrogate model has become an effective black‐box attack strategy.However,these methods suffer from gradients falling into local minima,limiting the transferability of the adversarial samples.This reduces the attack's effectiveness and often ignores the imperceptibility of the generated adversarial samples.To address these challenges,we propose a novel attack algorithm called PGMRS‐KL that combines pre‐gradient‐guided momentum gradient optimization strategy and fake user generation constrained by Kullback‐Leibler divergence.Specifically,the algorithm combines the accumulated gradient direction with the previous step's gradient direction to iteratively update the adversarial samples.It uses KL loss to minimize the distribution distance between fake and real user data,achieving high transferability and imperceptibility of the adversarial samples.Experimental results demonstrate the superiority of our approach over state‐of‐the‐art gradient‐based attack algorithms in terms of attack transferability and the generation of imperceptible fake user data.
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)and their heterostructures(HSs)exhibit unique optical properties and show great promise for developing next-generation optoelectronics.However,the photo-luminescence(PL)quantum yield of monolayer(1L)TMDs is still quite low at room temperature,which severely lim-its their practical applications.Here we report a PL enhancement effect of 1L WS_(2) at room temperature when con-structing it into 1L-WS_(2)/hBN/1L-MoS_(2) vertical HSs.The PL enhancement factors(EFs)can be up to 4.2.By using transient absorption(TA)spectroscopy,we demonstrate that the PL enhancement effect is due to energy transfer from 1L MoS_(2) to 1L WS_(2).The energy transfer process occurs on a picosecond timescale and lasts more than one hundred picoseconds which indicates a prominent contribution from exciton-exciton annihilation.Furthermore,the PL en-hancement effect of 1L WS_(2) can be observed in 2L-MoS_(2)/hBN/1L-WS_(2) and 3L-MoS_(2)/hBN/1L-WS_(2) HSs.Our study provides a comprehensive understanding of the energy transfer process in the PL enhancement of 2D TMDs and a fea-sible way to optimize the performance of TMD-based optoelectronic devices.
基金supported by the National Natural Science Foundation of China(No.21904143).
文摘Single-entity collisional electrochemistry(SECE)is a branch of single-entity electrochemistry.It can directly characterize entities/particles with single particle resolution through random collisions between particles and electrodes in a solution,and obtain rich physicochemical information,thus becoming one of the frontiers of electroanalytical chemistry in the past two decades.Interestingly,the(micro/nanoscale)sensing electrodes have evolved from a polarizable liquid/liquid(mercury/liquid)interface to a solid/liquid interface and then to a liquid/liquid interface(i.e.,an interface between twoimmiscible electrolyte solutions,ITIES),as if they have completed a cycle(but in fact they have not).ITIES has become the latest sensing electrode in the booming SECE due to its polarizability(up to 1.1 V at the water/a,a,a-trifluorotoluene interface)and high reproducibility.The four measurement modes(direct electrolysis,mediated electrolysis,current blockade,and charge displacement)developed in the realm of SECE at solid/liquid interfaces have also been fully realized at the miniature ITIES.This article will discuss these four modes at the ITIES from the perspectives of basic concepts,operating mechanisms,and latest developments(e.g.,discovery of ionosomes,blockade effect of Faradaic ion transfer,etc.),and look forward to the future development and direction of this emerging field.
基金Project(2006AA03Z523) supported by the National High-Tech Research and Development Program of ChinaProject(08C26224302178) supported by the Innovation Foundation of Central South University,China
文摘To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.
基金Projects(61490702,61773407,61803390,61751312)supported by the National Natural Science Foundation of ChinaProject(61725306)supported by the National Science Foundation for Distinguished Young Scholars of China+5 种基金Project(61621062)supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of ChinaProject(2017TP1002)supported by Hunan Provincial Key Laboratory,ChinaProject(6141A0202210)supported by the Program of the Joint Pre-research Foundation of the Chinese Ministry of EducationProject(61400030501)supported by the General Program of the Equipment Pre-research Field Foundation of ChinaProject(2016TP1023)supported by the Science and Technology Project in Hunan Province Hunan Science and Technology Agency of ChinaProject(2018FJ34)supported by the Science and Technology Project in Shaoyang Science and Technology Agency of China
文摘In the early fault period of high-speed train systems, the interested characteristic signals are relatively weak and easily submerged in heavy noise. In order to solve this problem, a state-transition-algorithm (STA)-based adaptive stochastic resonance (SR) method is proposed, which provides an alternative solution to the problem that the traditional SR has fixed parameters or optimizes only a single parameter and ignores the interaction between parameters. To be specific, the frequency-shifted and re-scaling are firstly used to pre-process an actual large signal to meet the requirement of the adiabatic approximate small parameter. And then, the signal-to-noise ratio is used as the optimization target, and the STA-based adaptive SR is used to synchronously optimize the system parameters. Finally, the optimal extraction and frequency recovery of a weak characteristic signal from a broken rotor bar fault are realized. The proposed method is compared with the existing methods by the early broken rotor bar experiments of traction motor. Experiment results show that the proposed method is better than the other methods in extracting weak signals, and the validity of this method is verified.
基金Projects(51704329,51705540)supported by the National Natural Science Foundation of ChinaProject(2018JJ3671)supported by the Hunan Provincial Natural Science Foundation,China+1 种基金Project(2015CX005)supported by the Innovation Driven Plan of Central South University,ChinaProject(B14034)supported by the National 111 Project,China
文摘Bauxite residue(BR),a by-product of the industrial production of alumina,has raised environmental concerns in the last decades,due to the presence of high amounts of alkali and various heavy metal ions.Limited studies on the application of abandoned BR with massive consumption have been reported.In this study,the possibility of the revegetation using ryegrass growing on BR was discussed mainly through the growth indications and transfer of heavy metal ions in BR and plants.In the pot trails,ryegrass was seeded on BR,de-alkali BR,with(DBRO)or without(DBR)organic fertilizer,respectively.The results indicated that the remediation of bauxite residue can be achieved through de-alkali with acid neutralization.Elemental analysis indicated that the elements,except for Fe,Mn and Pb,were stable in plant roots,and ryegrass could hardly absorb Cd.But,some heavy metals such as Cu enriched in plants,which should be noted in revegetation on bauxite residue.
基金Project(21576074)supported by the National Natural Science Foundation of China
文摘Rubidium phosphate can be more conveniently obtained by extracting trace Rb+ from the salt lake brine. Rb_3PO_4 was found to be an excellent heterogeneous catalyst for transfer hydrogenation. Rb_3PO_4 lost 70% of its active sites after adsorbing water, but the remaining was not affected. The reductions of aldehydes and ketones, when promoted by Rb_3PO_4, were allowed at room temperature. The activities of substrates at room temperature followed a descending order of 2,6-dichlorobenzaldehyde> 4-bromobenzaldehyde>benzaldehyde>acetophenone>anisaldehyde>butanone. A new catalytic cycle postulating a six-membered cyclic transition state for the reductions of aldehydes and ketones was proposed. These results exploited the catalytic usage of Rb_3PO_4 and worth in industrial application.
基金Project(50775225) supported by the National Natural Science Foundation of China
文摘A novel periodic mount was presented. A theoretical model was developed to describe the dynamics of wave propagation in the novel periodic mount. The model was derived using Hamilton's energy conservation principle. The characteristics of wave propagation in unit cell were analyzed by transfer matrix formulation. Numerical examples were given to illustrate the effectiveness of the periodic mount. The experiments were carried out to identify the predications of the theoretical model. The obtained results show that the experimental results coincide with the prediction of theoretical model. No pass bands appear in the overall frequency range measured when waves propagate in the longitude direction of the periodic mount. These dramatic results demonstrate its potential as an excellent mount in attenuating and isolating vibration transmission.
基金Project(2006BAJ03A01-05) supported by National Science and Technology Pillar Program during the 11th Five-Year Plan Period of ChinaProject (JG200705) supported by Key Laboratory of Structural Engineering of Shenyang Jianzhu University, China
文摘To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding stress development of bars adhered to grout concrete was analyzed. The local bonding stress—slip curve was obtained. Based on the test results,a new bonding stress— slip constitutive model between bars and grout concrete was proposed. The results show that the maximum bonding stress is not influenced by the bar bond length,but it is strengthened when the splitting strength of grout concrete is increased. The model matches the experimental results well,and the regressing coefficient equals 1.7.
基金Project (C03050205) supported by the National Natural Science Foundation of China
文摘Diallyl disulfide was synthesized by phase transfer catalyst （PTC） during microwave irradiation. The effects of different factors, such as the power of microwave irradiation, the time of microwave irradiation, PTC reagents amount and the mole ratio of reactants, on the yield of product were investigated. The structure of diallyl disulfide was characterized by infrared spectra, mass spectra and ^1 H nuclear magnetic resonance. The bioactivity of diallyl disulfide was evaluated by cell viability assay on HepG2 hepatoma cells. The results show that the optimal reaction conditions are as follows： tetrabutylammonium bromide（TBAB） selected as a PTC, the mass ratio of TBAB to sodium disulfide of 0.021 ： 1, the power of irradiation of 195 W, the reaction time of 12 rain, and the mole ratio of sodium disulfide to allyl chloride of 0.65 ： 1. The yield of diallyl disulfide is 82.2%. The synthetical diallyl disulfide appears to be cytotoxic to HepG2 heoatoma cells in a dose-dependent manner.
