The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical func...The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical functions during human locomotion, e.g. body support and propulsion, stability maintenance and impact absorption. These need the human foot to be rigid and damped to transmit ground reaction forces to the upper body and maintain body stability, and also to be compliant and resilient to moderate risky impacts and save energy. How does the human foot achieve these apparent conflicting functions？ In this study, we propose a phase-dependent hypothesis for the overall locomotor functions of the human foot complex based on in-vivo measurements of human natural gait and simulation results of a mathematical foot model. We propse that foot functions are highly dependent on gait phase, which is a major characteristics of human locomotion. In early stance just after heel strike, the foot mainly works as a shock absorber by moderating high impacts using the viscouselastic heel pad in both vertical and horizontal directions. In mid-stance phase （-80% of stance phase）, the foot complex can be considered as a springy rocker, reserving external mechanical work using the foot arch whilst moving ground contact point forward along a curved path to maintain body stability. In late stance after heel off, the foot complex mainly serves as a force modulator like a gear box, modulating effective mechanical advantages of ankle plantiflexor muscles using metatarsal-phalangeal joints. A sound under- standing of how diverse functions are implemented in a simple foot segment during human locomotion might be useful to gain insight into the overall foot locomotor functions and hence to facilitate clinical diagnosis, rehabilitation product design and humanoid robot development.展开更多
Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coh...Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coherenceterms—the vacuum-induced coherence (VIC) terms.In this paper,we find that,if the interference is optimized,thetwo-photon absorption properties of this atom system can be significantly modified and electromagnetically-inducedtransparency (EIT) is dependent on this interference.Furthermore,we find that in all the cases the coherence can suppressor enhance the partial two-photon transparency,while the complete transparency window is still strictly preserved,whichmeans that it cannot be affected by the VIC.Another important result is the finding of the crucial role played by therelative phase between the probe and coupling fields:the relative height of absorption peaks can be modulated by therelative phase.The physical interpretation of the phenomena has been given.展开更多
Phased-Mission Systems(PMS)are widely applied in aerospace,telecommunication and intelligent systems for multiple,consecutive and non-overlapping phases of missions.The phasedependent stresses and system structure cau...Phased-Mission Systems(PMS)are widely applied in aerospace,telecommunication and intelligent systems for multiple,consecutive and non-overlapping phases of missions.The phasedependent stresses and system structure cause some difficulties to the reliability analysis of PMSs.In this paper,we analyze the physical isolation effects on the degradation speeds and across-phase damage accumulations of failure mechanisms.And,some corresponding reliability and unreliability formulas are derived.Besides,a hierarchical Binary Decision Diagram(BDD)-based modeling method is proposed for incorporating functional and physical isolation effects into BDD models,and the analytical method with phase algebras is introduced for studying the failure behavior of PMS with functional dependence.In the case study,we evaluate the collision avoidance system of a fixed-wing unmanned aerial vehicle as an example to demonstrate the proposed modeling and analysis method.Results show that the physical isolation effects have significant influences on the degradations of components,which deserves detailed analysis for a more practical and realistic PMS’s failure behavior.展开更多
The properties of two-dimensional(2D)materials are highly dependent on their phase and thickness.Various phases exist in tin disulfide(SnS_(2)),resulting in promising electronic and optical properties.Hence,accurately...The properties of two-dimensional(2D)materials are highly dependent on their phase and thickness.Various phases exist in tin disulfide(SnS_(2)),resulting in promising electronic and optical properties.Hence,accurately identifying the phase and thickness of SnS_(2)nanosheets is prior to their optoelectronic applications.Herein,layered 2H-SnS_(2)and 4H-SnS_(2)crystals were grown by chemical vapor transportation and the crystalline phase of SnS_(2)was characterized by X-ray diffraction,ultralow frequency(ULF)Raman spectroscopy and high-resolution transmission electron microscope.As-grown crystals were mechanically exfoliated to single-and few-layer nanosheets,which were investigated by optical microscopy,atomic force microscopy and ULF Raman spectroscopy.Although the 2H-SnS_(2)and 4H-SnS_(2)nanosheets have similar optical contrast on SiO_(2)/Si substrates,their ULF Raman spectra obviously show different shear and breathing modes,which are highly dependent on their phases and thicknesses.Interestingly,the SnS_(2)nanosheets have shown phase-dependent electrical properties.The 4H-SnS_(2)nanosheet shows a current on/off ratio of 2.58×10^(5) and excellent photosensitivity,which are much higher than those of the 2H-SnS_(2)nanosheet.Our work not only offers an accurate method for identifying single-and few-layer SnS_(2)nanosheets with different phases,but also paves the way for the application of SnS_(2)nanosheets in highperformance optoelectronic devices.展开更多
Diluted magnetic oxides have evolved into a popular branch of materials science during the last decade. In the first few years, people attributed the ferromagnetism to the magnetic dopants. However, the observat...Diluted magnetic oxides have evolved into a popular branch of materials science during the last decade. In the first few years, people attributed the ferromagnetism to the magnetic dopants. However, the observation of ferromagnetism in undoped HfO2 thin films made it more controversial and promoted extensive research on the ferromagnetism in various undoped oxides. Both of the experimental w-orks and theoretical studies have shown that intrinsic defects in oxide nanomaterials play a crucial role in the origin of such an unexpected ferromagnetism, in spite of some contradicting views which kind of defects is predominant. In the past several years, we have conducted systematic and thorough research on the room temperature ferromagnetism in undoped ZrO2 thin films, and clarif some physics behind it. We firstly prepared undoped ZrO2 thin films by different w-ays, such as Pulsed electron bean deposition, magnetron sputtering, and electron beam evaporation, and successfully obtained ZiO2 thin films wdth different crystalline structure, in particular a pure high-temperature stabilized one, by adjusting some preparation parameters during the deposition process or post-annealing treatment. A phase-dependent ferromagnetism w-as then confinmed to exist in such ZiO2 thin films. Further, w-e conducted exhaustive defect analysis and characterization by X-ray photoelectron spectroscopy, photoluminescence spectra, and electron paramagnetic resonance, respectively, and found the oxygen vacancy, specifically the single ionized oxygen vacancy （Vo＋） , has a remarkable influence on the enhancement of ferromagnetism. Herein, we will review the work in detail on the phase-dependent and oxygen vacancy-enhanced room temperature ferromagnetism in undoped ZrO2 thin films.Keywords Zi thin film ferromagnetism phase-dependent oxygen vacancy展开更多
Precisely controlling gene expression is beneficial for optimizing biosynthetic pathways for improving the production.However,promoters in nonconventional yeasts such as Ogataea polymorpha are always limited,which res...Precisely controlling gene expression is beneficial for optimizing biosynthetic pathways for improving the production.However,promoters in nonconventional yeasts such as Ogataea polymorpha are always limited,which results in incompatible gene modulation.Here,we expanded the promoter library in O.polymorpha based on transcriptional data,among which 13 constitutive promoters had the strengths ranging from 0–55%of PGAP,the commonly used strong constitutive promoter,and 2 were growth phase-dependent promoters.Subsequently,2 hybrid growth phase-dependent promoters were constructed and characterized,which had 2-fold higher activities.Finally,promoter engineering was applied to precisely regulate cellular metabolism for efficient production ofβ-elemene.The glyceraldehyde-3-phosphate dehydrogenase gene GAP was downregulated to drive more flux into pentose phosphate pathway(PPP)and then to enhance the supply of acetyl-CoA by using phosphoketolase-phosphotransacetylase(PK-PTA)pathway.Coupled with the phase-dependent expression of synthase module(ERG20∼LsLTC2 fusion),the highest titer of 5.24 g/L with a yield of 0.037 g/(g glucose)was achieved in strain YY150U under fed-batch fermentation in shake flasks.This work characterized and engineered a series of promoters,that can be used to fine-tune genes for constructing efficient yeast cell factories.展开更多
In the context of the quantum-mechanical description of single-molecule surface-enhanced Raman scattering,intensity-field correlation measurements of photons emitted from a plasmonic cavity are explored,theoretically,...In the context of the quantum-mechanical description of single-molecule surface-enhanced Raman scattering,intensity-field correlation measurements of photons emitted from a plasmonic cavity are explored,theoretically,using the technique of conditional homodyne detection.The inelastic interplay between plasmons and vibrations of a diatomic molecule placed inside the cavity can be manifested in phase-dependent third-order fluctuations of the light recorded by the aforesaid technique,allowing us to reveal signatures of non-classicality(indicatives of squeezing)of the outgoing Raman photons.展开更多
文摘The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical functions during human locomotion, e.g. body support and propulsion, stability maintenance and impact absorption. These need the human foot to be rigid and damped to transmit ground reaction forces to the upper body and maintain body stability, and also to be compliant and resilient to moderate risky impacts and save energy. How does the human foot achieve these apparent conflicting functions？ In this study, we propose a phase-dependent hypothesis for the overall locomotor functions of the human foot complex based on in-vivo measurements of human natural gait and simulation results of a mathematical foot model. We propse that foot functions are highly dependent on gait phase, which is a major characteristics of human locomotion. In early stance just after heel strike, the foot mainly works as a shock absorber by moderating high impacts using the viscouselastic heel pad in both vertical and horizontal directions. In mid-stance phase （-80% of stance phase）, the foot complex can be considered as a springy rocker, reserving external mechanical work using the foot arch whilst moving ground contact point forward along a curved path to maintain body stability. In late stance after heel off, the foot complex mainly serves as a force modulator like a gear box, modulating effective mechanical advantages of ankle plantiflexor muscles using metatarsal-phalangeal joints. A sound under- standing of how diverse functions are implemented in a simple foot segment during human locomotion might be useful to gain insight into the overall foot locomotor functions and hence to facilitate clinical diagnosis, rehabilitation product design and humanoid robot development.
基金National Natural Science Foundation of China under Grant Nos.90503088 and 10775100the Fund of Theoretical Nuclear Center of HIRFL of China
文摘Due to interaction with the vacuum of the radiation field,a K-type atomic system with near-degenerateexcited and ground levels,which is driven by two strong coherent fields and two weak probe fields,has additional coherenceterms—the vacuum-induced coherence (VIC) terms.In this paper,we find that,if the interference is optimized,thetwo-photon absorption properties of this atom system can be significantly modified and electromagnetically-inducedtransparency (EIT) is dependent on this interference.Furthermore,we find that in all the cases the coherence can suppressor enhance the partial two-photon transparency,while the complete transparency window is still strictly preserved,whichmeans that it cannot be affected by the VIC.Another important result is the finding of the crucial role played by therelative phase between the probe and coupling fields:the relative height of absorption peaks can be modulated by therelative phase.The physical interpretation of the phenomena has been given.
基金National Natural Science Foundation of China(Nos.62073009 and 61573043)。
文摘Phased-Mission Systems(PMS)are widely applied in aerospace,telecommunication and intelligent systems for multiple,consecutive and non-overlapping phases of missions.The phasedependent stresses and system structure cause some difficulties to the reliability analysis of PMSs.In this paper,we analyze the physical isolation effects on the degradation speeds and across-phase damage accumulations of failure mechanisms.And,some corresponding reliability and unreliability formulas are derived.Besides,a hierarchical Binary Decision Diagram(BDD)-based modeling method is proposed for incorporating functional and physical isolation effects into BDD models,and the analytical method with phase algebras is introduced for studying the failure behavior of PMS with functional dependence.In the case study,we evaluate the collision avoidance system of a fixed-wing unmanned aerial vehicle as an example to demonstrate the proposed modeling and analysis method.Results show that the physical isolation effects have significant influences on the degradations of components,which deserves detailed analysis for a more practical and realistic PMS’s failure behavior.
基金supported by the National Natural Science Foun-dation of China(Nos.51832001,21571101 and 51322202)the Natural Science Foundation of Jiangsu Province in China(No.BK20161543)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.15KJB430016).
文摘The properties of two-dimensional(2D)materials are highly dependent on their phase and thickness.Various phases exist in tin disulfide(SnS_(2)),resulting in promising electronic and optical properties.Hence,accurately identifying the phase and thickness of SnS_(2)nanosheets is prior to their optoelectronic applications.Herein,layered 2H-SnS_(2)and 4H-SnS_(2)crystals were grown by chemical vapor transportation and the crystalline phase of SnS_(2)was characterized by X-ray diffraction,ultralow frequency(ULF)Raman spectroscopy and high-resolution transmission electron microscope.As-grown crystals were mechanically exfoliated to single-and few-layer nanosheets,which were investigated by optical microscopy,atomic force microscopy and ULF Raman spectroscopy.Although the 2H-SnS_(2)and 4H-SnS_(2)nanosheets have similar optical contrast on SiO_(2)/Si substrates,their ULF Raman spectra obviously show different shear and breathing modes,which are highly dependent on their phases and thicknesses.Interestingly,the SnS_(2)nanosheets have shown phase-dependent electrical properties.The 4H-SnS_(2)nanosheet shows a current on/off ratio of 2.58×10^(5) and excellent photosensitivity,which are much higher than those of the 2H-SnS_(2)nanosheet.Our work not only offers an accurate method for identifying single-and few-layer SnS_(2)nanosheets with different phases,but also paves the way for the application of SnS_(2)nanosheets in highperformance optoelectronic devices.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50931002,51072094 and 51372135)the Ministry of Education of the People’s Republic of China(Grant No.113007A)the Tsinghua University Initiative Scientific Research Program
文摘Diluted magnetic oxides have evolved into a popular branch of materials science during the last decade. In the first few years, people attributed the ferromagnetism to the magnetic dopants. However, the observation of ferromagnetism in undoped HfO2 thin films made it more controversial and promoted extensive research on the ferromagnetism in various undoped oxides. Both of the experimental w-orks and theoretical studies have shown that intrinsic defects in oxide nanomaterials play a crucial role in the origin of such an unexpected ferromagnetism, in spite of some contradicting views which kind of defects is predominant. In the past several years, we have conducted systematic and thorough research on the room temperature ferromagnetism in undoped ZrO2 thin films, and clarif some physics behind it. We firstly prepared undoped ZrO2 thin films by different w-ays, such as Pulsed electron bean deposition, magnetron sputtering, and electron beam evaporation, and successfully obtained ZiO2 thin films wdth different crystalline structure, in particular a pure high-temperature stabilized one, by adjusting some preparation parameters during the deposition process or post-annealing treatment. A phase-dependent ferromagnetism w-as then confinmed to exist in such ZiO2 thin films. Further, w-e conducted exhaustive defect analysis and characterization by X-ray photoelectron spectroscopy, photoluminescence spectra, and electron paramagnetic resonance, respectively, and found the oxygen vacancy, specifically the single ionized oxygen vacancy （Vo＋） , has a remarkable influence on the enhancement of ferromagnetism. Herein, we will review the work in detail on the phase-dependent and oxygen vacancy-enhanced room temperature ferromagnetism in undoped ZrO2 thin films.Keywords Zi thin film ferromagnetism phase-dependent oxygen vacancy
基金This research was supported by the National Key Research and Development Project(2023YFC3503900)Liaoning Distinguished Scholar Program(2023JH6/100500001)。
文摘Precisely controlling gene expression is beneficial for optimizing biosynthetic pathways for improving the production.However,promoters in nonconventional yeasts such as Ogataea polymorpha are always limited,which results in incompatible gene modulation.Here,we expanded the promoter library in O.polymorpha based on transcriptional data,among which 13 constitutive promoters had the strengths ranging from 0–55%of PGAP,the commonly used strong constitutive promoter,and 2 were growth phase-dependent promoters.Subsequently,2 hybrid growth phase-dependent promoters were constructed and characterized,which had 2-fold higher activities.Finally,promoter engineering was applied to precisely regulate cellular metabolism for efficient production ofβ-elemene.The glyceraldehyde-3-phosphate dehydrogenase gene GAP was downregulated to drive more flux into pentose phosphate pathway(PPP)and then to enhance the supply of acetyl-CoA by using phosphoketolase-phosphotransacetylase(PK-PTA)pathway.Coupled with the phase-dependent expression of synthase module(ERG20∼LsLTC2 fusion),the highest titer of 5.24 g/L with a yield of 0.037 g/(g glucose)was achieved in strain YY150U under fed-batch fermentation in shake flasks.This work characterized and engineered a series of promoters,that can be used to fine-tune genes for constructing efficient yeast cell factories.
文摘In the context of the quantum-mechanical description of single-molecule surface-enhanced Raman scattering,intensity-field correlation measurements of photons emitted from a plasmonic cavity are explored,theoretically,using the technique of conditional homodyne detection.The inelastic interplay between plasmons and vibrations of a diatomic molecule placed inside the cavity can be manifested in phase-dependent third-order fluctuations of the light recorded by the aforesaid technique,allowing us to reveal signatures of non-classicality(indicatives of squeezing)of the outgoing Raman photons.
