Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effect...Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effective strategy to solve the puzzle.Herein,a single source hyperbranched polyborosi-lazane precursor containing hafnium(hb-PBSZ-Hf)is introduced and the SiBCNHf ceramic is obtained by further pyrolysis.The micro-sized tissues including HfC,SiC,HfB 2 nanocrystals and segregated carbons are in situ generated during annealing which not only increase EM wave absorption ability(minimum re-flection coefficient(RC_(min))is-56.71 dB with a thickness of 2.5 mm,effective absorption bandwidth(EAB)is 3.4 GHz),but also improve antioxidation property(less than 2 wt.%mass fluctuation at 1400℃in air).Theoretical simulation of complex permittivity suggests that SiBCNHf ceramic has an RC_(min)of less than-5 dB for the whole X-band even at 1100℃.Such SiBCNHf ceramic with superior high-temperature-resistance and antioxidation performance derived from single source precursors possesses great potential for EM wave absorbing coatings in high-temperature and harsh environments.展开更多
An effective method is proposed in this paper for the symplectic eigenvalue problem of a periodic structure with uniform stochastic properties. Since structural parameters are uncertain, the symplectic transfer matrix...An effective method is proposed in this paper for the symplectic eigenvalue problem of a periodic structure with uniform stochastic properties. Since structural parameters are uncertain, the symplectic transfer matrix of a typical substructure, which is described in the state space, also has sto chastic proper ties. An effec tive spec tral st ochastic finite elemen t method is adopted to ensure the symplectic orthogonality of the random symplectic matrix on the premise of certain precision. By means of the Rayleigh quotient method, the symplectic eigenvalue problem of random symplectic matrix is investigated. On the basis of this, the mean value and the standard deviation of the random eigenvalues are fully discussed. The comparison between the numerical results derived from the proposed method and the Monte-Carlo simulation indicates that the proposed method has high precision. This research provides a useful guidance for the dynamic analysis of periodic structures with stochastic properties.展开更多
This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this wo...This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this work,a set of morphable components are introduced as the basic building blocks for topology optimization,and the optimized structural layout can be found by optimizing the parameters characterizing the locations and geometries of the components explicitly.The degree of freedom(DOF)elimination technique is also employed to delete unnecessary DOFs at each iteration.Since the proposed approach solves the corresponding optimization problems in an explicit way,some challenging issues(e.g.,the large computational burden related to finite element analysis and sensitivity analysis,the localized eigenmodes in low material density regions,and the impact of excitation frequency on the optimization process)associated with the traditional approaches can be circumvented naturally.Numerical results show that the proposed approach is effective for solving topology optimization problems involving structural dynamic behaviors,especially when high-frequency responses are considered.展开更多
The development of modern science and technology has promoted the overlapping and mutual penetration among different disciplines, which led to the technological innovations in the field of mechanical engineering. The ...The development of modern science and technology has promoted the overlapping and mutual penetration among different disciplines, which led to the technological innovations in the field of mechanical engineering. The mechatronics technology conforms to the law of development of science and technology in today, and combines the mechanical technology and electronic technology together to integrate the logistics, energy flow and information flow. This paper briefly describes the concept of mechatronics and the elements of mechatronics technology, and elaborates on the application of mechatronics technology in three different areas of the Machinery Industry in the form of living examples, finally introduces the future developing direction of mechatronics technology.展开更多
Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant ar...Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes,respectively.Though the advantages of seed catalysts in facilitating the nucleation,achieving higher yield and better repeatability,as well as their effects on the morphologies of as-grown MoS2 have been studied,the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively,which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors.In this report,we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2.It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2.Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS),copper phthalocyanine (CuPc),and crystal violet (CV)),PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two.Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.展开更多
Poly(disulfide)s have been widely used in flexible wearable electronics,smart materials,and drug delivery.The synthesis of poly(disulfide)s usually utilizes external stimuli or toxic initiators to promote the polymeri...Poly(disulfide)s have been widely used in flexible wearable electronics,smart materials,and drug delivery.The synthesis of poly(disulfide)s usually utilizes external stimuli or toxic initiators to promote the polymerization.Here,we indicated that the long-range electronic effect can significantly alter the reactivity of the disulfide group.Accordingly,we established deprotonation-promoted ring-opening polymerization of thioctic acid(TA)as a highly effective and simple method to synthesize poly(disulfide)s due to the long-range electronic effect and nucleophilic carboxylate.Without external stimuli and initiators,simple mixing of TA and deprotonation reagent,choline bicarbonate,in different ratios at room temperature rapidly produced a series of high molecular weight(up to 772 kDa)ionic liquid crystal poly(disulfide)s elastomers with room temperature self-healing ability,adjustable conductivity(2.39×10^(−2)∼0.28×10^(−2)S m^(−1)),degradability,biocompatibility,antibacterial property,and tissue-like softness(Young’s moduli ranging from 18.2±6.0 to 111.1±36.7 kPa).The experiments and density functional theory calculations also revealed the principle of long-range electronic effect to establish a new synthetic strategy of poly(disulfide)s with superior properties favorable for bioelectronics.展开更多
DNA damage response(DDR)is a highly conserved genome surveillance mechanism that preserves cell viability in the presence of chemotherapeutic drugs.Hence,small molecules that inhibit DDR are expected to enhance the an...DNA damage response(DDR)is a highly conserved genome surveillance mechanism that preserves cell viability in the presence of chemotherapeutic drugs.Hence,small molecules that inhibit DDR are expected to enhance the anti-cancer effect of chemotherapy.Through a recent chemical library screen,we identified shikonin as an inhibitor that strongly suppressed DDR activated by various chemotherapeutic drugs in cancer cell lines derived from different origins.Mechanistically,shikonin inhibited the activation of ataxia telangiectasia mutated(ATM),and to a lesser degree ATM and RAD3-related(ATR),two master upstream regulators of the DDR signal,through inducing degradation of ATM and ATR-interacting protein(ATRIP),an obligate associating protein of ATR,respectively.As a result of DDR inhibition,shikonin enhanced the anti-cancer effect of chemotherapeutic drugs in both cell cultures and in mouse models.While degradation of ATRIP is proteasome dependent,that of ATM depends on caspase-and lysosome-,but not proteasome.Overexpression of ATM significantly mitigated DDR inhibition and cell death induced by shikonin and chemotherapeutic drugs.These novel findings reveal shikonin as a pan DDR inhibitor and identify ATM as a primary factor in determining the chemo sensitizing effect of shikonin.Our data may facilitate the development of shikonin and its derivatives as potential chemotherapy sensitizers through inducing ATM degradation.展开更多
Eukaryotic chromosomes occupy specific territories in the nucleus,which is key for genome stability and function.Based on the spatiotemporal organization and compaction pattern,eukaryotic chromatins can be recognized ...Eukaryotic chromosomes occupy specific territories in the nucleus,which is key for genome stability and function.Based on the spatiotemporal organization and compaction pattern,eukaryotic chromatins can be recognized as transcriptionally active and loosely packed euchromatin in the nuclear interior and transcriptionally repressive and highly compacted heterochromatin at the nuclear periphery or around nucleoli(Fig.1).展开更多
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025034)National Science and Technology Major Project of China(No.J2019-VI-0017-0132).
文摘Electromagnetic(EM)wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions.Precursor derived ceramics(PDC)route is being evolved as an effective strategy to solve the puzzle.Herein,a single source hyperbranched polyborosi-lazane precursor containing hafnium(hb-PBSZ-Hf)is introduced and the SiBCNHf ceramic is obtained by further pyrolysis.The micro-sized tissues including HfC,SiC,HfB 2 nanocrystals and segregated carbons are in situ generated during annealing which not only increase EM wave absorption ability(minimum re-flection coefficient(RC_(min))is-56.71 dB with a thickness of 2.5 mm,effective absorption bandwidth(EAB)is 3.4 GHz),but also improve antioxidation property(less than 2 wt.%mass fluctuation at 1400℃in air).Theoretical simulation of complex permittivity suggests that SiBCNHf ceramic has an RC_(min)of less than-5 dB for the whole X-band even at 1100℃.Such SiBCNHf ceramic with superior high-temperature-resistance and antioxidation performance derived from single source precursors possesses great potential for EM wave absorbing coatings in high-temperature and harsh environments.
基金the National Natural Science Foundation of China (11402043, 11772084).
文摘An effective method is proposed in this paper for the symplectic eigenvalue problem of a periodic structure with uniform stochastic properties. Since structural parameters are uncertain, the symplectic transfer matrix of a typical substructure, which is described in the state space, also has sto chastic proper ties. An effec tive spec tral st ochastic finite elemen t method is adopted to ensure the symplectic orthogonality of the random symplectic matrix on the premise of certain precision. By means of the Rayleigh quotient method, the symplectic eigenvalue problem of random symplectic matrix is investigated. On the basis of this, the mean value and the standard deviation of the random eigenvalues are fully discussed. The comparison between the numerical results derived from the proposed method and the Monte-Carlo simulation indicates that the proposed method has high precision. This research provides a useful guidance for the dynamic analysis of periodic structures with stochastic properties.
基金Financial support from the National Natural Science Foundation of China (11821202,11872141,11922204,12002073)the National Key Research and Development Plan (2020YFB1709401)+1 种基金the Fundamental Research Funds for the Central Universities[DUT20RC (3)020]the 111 Project (B14013)is gratefully acknowledged.
文摘This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this work,a set of morphable components are introduced as the basic building blocks for topology optimization,and the optimized structural layout can be found by optimizing the parameters characterizing the locations and geometries of the components explicitly.The degree of freedom(DOF)elimination technique is also employed to delete unnecessary DOFs at each iteration.Since the proposed approach solves the corresponding optimization problems in an explicit way,some challenging issues(e.g.,the large computational burden related to finite element analysis and sensitivity analysis,the localized eigenmodes in low material density regions,and the impact of excitation frequency on the optimization process)associated with the traditional approaches can be circumvented naturally.Numerical results show that the proposed approach is effective for solving topology optimization problems involving structural dynamic behaviors,especially when high-frequency responses are considered.
文摘The development of modern science and technology has promoted the overlapping and mutual penetration among different disciplines, which led to the technological innovations in the field of mechanical engineering. The mechatronics technology conforms to the law of development of science and technology in today, and combines the mechanical technology and electronic technology together to integrate the logistics, energy flow and information flow. This paper briefly describes the concept of mechatronics and the elements of mechatronics technology, and elaborates on the application of mechatronics technology in three different areas of the Machinery Industry in the form of living examples, finally introduces the future developing direction of mechatronics technology.
基金National Natural Science Foundation of China (Nos. 61774040, 61774042, and 51772317)National Young 1000 Talent Plan of China+1 种基金Shanghai Municipal Natural Science Foundation (Nos. 16ZR1402500, 16ZR1442700, and 17ZR1446500)Opening project of State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences, the National Key R&D program (No. 2017YFF0206106).
文摘Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes,respectively.Though the advantages of seed catalysts in facilitating the nucleation,achieving higher yield and better repeatability,as well as their effects on the morphologies of as-grown MoS2 have been studied,the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively,which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors.In this report,we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2.It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2.Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS),copper phthalocyanine (CuPc),and crystal violet (CV)),PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two.Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.
基金supported by the National Key Research and Development Program of China(grant nos.2021YFC2101800 and 2021YFC2400802)the National Natural Science Foundation of China(grantnos.52173117 and 21991123)+5 种基金Belt&Road Young Scientist Exchanges Project of Science and Technology Commission Foundation of Shanghai(grant no.20520741000)Ningbo 2025 Science and Technology Major Project(grant no.2019B10068)the Natural Science Foundation of Shanghai(grant no.20ZR1402500)Science and Technology Commission of Shanghai Municipality(grant nos.20DZ2254900and 20DZ2270800)the Fundamental Research Funds for the Central Universities,DHU Distinguished Young Professor Program(grant no.LZA2019001)the Biomedical Engineering fund of Shanghai Jiao Tong University(grant no.YG2021GD04).
文摘Poly(disulfide)s have been widely used in flexible wearable electronics,smart materials,and drug delivery.The synthesis of poly(disulfide)s usually utilizes external stimuli or toxic initiators to promote the polymerization.Here,we indicated that the long-range electronic effect can significantly alter the reactivity of the disulfide group.Accordingly,we established deprotonation-promoted ring-opening polymerization of thioctic acid(TA)as a highly effective and simple method to synthesize poly(disulfide)s due to the long-range electronic effect and nucleophilic carboxylate.Without external stimuli and initiators,simple mixing of TA and deprotonation reagent,choline bicarbonate,in different ratios at room temperature rapidly produced a series of high molecular weight(up to 772 kDa)ionic liquid crystal poly(disulfide)s elastomers with room temperature self-healing ability,adjustable conductivity(2.39×10^(−2)∼0.28×10^(−2)S m^(−1)),degradability,biocompatibility,antibacterial property,and tissue-like softness(Young’s moduli ranging from 18.2±6.0 to 111.1±36.7 kPa).The experiments and density functional theory calculations also revealed the principle of long-range electronic effect to establish a new synthetic strategy of poly(disulfide)s with superior properties favorable for bioelectronics.
基金supported by Guangdong Basic and Applied Basic Research Foundation(2021A1515011244,China)to Jinshan Tangthe National 111 Project of China(No.B13038,China)to Xinsheng Yao。
文摘DNA damage response(DDR)is a highly conserved genome surveillance mechanism that preserves cell viability in the presence of chemotherapeutic drugs.Hence,small molecules that inhibit DDR are expected to enhance the anti-cancer effect of chemotherapy.Through a recent chemical library screen,we identified shikonin as an inhibitor that strongly suppressed DDR activated by various chemotherapeutic drugs in cancer cell lines derived from different origins.Mechanistically,shikonin inhibited the activation of ataxia telangiectasia mutated(ATM),and to a lesser degree ATM and RAD3-related(ATR),two master upstream regulators of the DDR signal,through inducing degradation of ATM and ATR-interacting protein(ATRIP),an obligate associating protein of ATR,respectively.As a result of DDR inhibition,shikonin enhanced the anti-cancer effect of chemotherapeutic drugs in both cell cultures and in mouse models.While degradation of ATRIP is proteasome dependent,that of ATM depends on caspase-and lysosome-,but not proteasome.Overexpression of ATM significantly mitigated DDR inhibition and cell death induced by shikonin and chemotherapeutic drugs.These novel findings reveal shikonin as a pan DDR inhibitor and identify ATM as a primary factor in determining the chemo sensitizing effect of shikonin.Our data may facilitate the development of shikonin and its derivatives as potential chemotherapy sensitizers through inducing ATM degradation.
文摘Eukaryotic chromosomes occupy specific territories in the nucleus,which is key for genome stability and function.Based on the spatiotemporal organization and compaction pattern,eukaryotic chromatins can be recognized as transcriptionally active and loosely packed euchromatin in the nuclear interior and transcriptionally repressive and highly compacted heterochromatin at the nuclear periphery or around nucleoli(Fig.1).
