Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications.Here,we propose a wideband low-scattering metasurface that can realize an in-band reconfigurabl...Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications.Here,we propose a wideband low-scattering metasurface that can realize an in-band reconfigurable transparent window by altering the operation states of the PIN diodes loaded on the structures.The metasurface is composed of a band-pass frequency selective surface(FSS)sandwiched between two polarization conversion metasurfaces(PCMs).PIN diodes are integrated into the FSS to switch the transparent window,while a checkerboard configuration is applied in PCMs for the diffusive-reflective function.A sample with 20×20 elements is designed,fabricated,and experimentally verified.Both simulated and measured results show that the in-band functions can be dynamically switched between beam-splitting scattering and high transmission by controlling the biasing states of the diodes,while low backscattering can be attained outside the passband.Furthermore,the resonant structures of FSS also play the role of feeding lines,thus significantly eliminating extra interference compared with conventional feeding networks.We envision that the proposed metasurface may provide new possibilities for the development of an intelligent stealth platform and its antenna applications.展开更多
The conserved microRNA396(miR396)is involved in plant growth,development,and abiotic stress response in multiple plant species through regulating its targets,Growth Regulating Factor(GRF)transcription factor genes.How...The conserved microRNA396(miR396)is involved in plant growth,development,and abiotic stress response in multiple plant species through regulating its targets,Growth Regulating Factor(GRF)transcription factor genes.However,the role of miR396 has not yet been characterized in perennial monocot species.In addition,the molecular mechanism of miR396-mediated abiotic stress response remains unclear.To elucidate the role of miR396 in perennial monocot species,we generated transgenic creeping bentgrass(Agrostis stolonifera)overexpressing Osa-miR396c,a rice miRNA396 gene.Transgenic plants exhibited altered development,including less shoot and root biomass,shorter internodes,smaller leaf area,fewer leaf veins,and epidermis cells per unit area than those of WT controls.In addition,transgenics showed enhanced salt tolerance associated with improved water retention,increased chlorophyll content,cell membrane integrity,and Na^(+)exclusion during high salinity exposure.Four potential targets of miR396 were identified in creeping bentgrass and up-regulated in response to salt stress.RNA-seq analysis indicates that miR396-mediated salt stress tolerance requires the coordination of stress-related functional proteins(antioxidant enzymes and Na+/H+antiporter)and regulatory proteins(transcription factors and protein kinases).This study establishes a miR396-associated molecular pathway to connect the upstream regulatory and downstream functional elements,and provides insight into the miRNA-mediated regulatory networks.展开更多
MicroRNA396(miR396)has been demonstrated to regulate flower development by targeting growth-regulating factors(GRFs)in annual species.However,its role in perennial grasses and its potential involvement in flowering ti...MicroRNA396(miR396)has been demonstrated to regulate flower development by targeting growth-regulating factors(GRFs)in annual species.However,its role in perennial grasses and its potential involvement in flowering time control remain unexplored.Here we report that overexpression of miR396 in a perennial species,creeping bentgrass(Agrostis stolonifera L.),alters flower development.Most significantly,transgenic(TG)plants bypass the vernalization requirement for flowering.Gene expression analysis reveals that miR396 is induced by long-day(LD)photoperiod and vernalization.Further study identifies VRN1,VRN2,and VRN3 homologs whose expression patterns in wild-type(WT)plants are similar to those observed in wheat and barley during transition from short-day(SD)to LD,and SD to cold conditions.However,compared to WT controls,TG plants overexpressing miR396 exhibit significantly enhanced VRN1 and VRN3 expression,but repressed VRN2 expression under SD to LD conditions without vernalization,which might be associated with modified expression of methyltransferase genes.Collectively,our results unveil a potentially novel mechanism by which miR396 suppresses the vernalization requirement for flowering which might be related to the epigenetic regulation of VRN genes and provide important new insight into critical roles of a miRNA in regulating vernalization-mediated transition from vegetative to reproductive growth in monocots.展开更多
Reconfigurable intelligent surface(RIS)is emerged as a promising technique to solve the challenges faced by future wireless communication networks.Although the most commonly used electrically-controlled RISs can achie...Reconfigurable intelligent surface(RIS)is emerged as a promising technique to solve the challenges faced by future wireless communication networks.Although the most commonly used electrically-controlled RISs can achieve millisecond-scale speed of dynamic switch,they have a large number of microwave circuit elements(such as PIN diodes or varactors)which will bring non-negligible insertion loss,and the complicity of the bias network to electrically addressing each element will increase with the expansion of the RIS aperture.Aiming at further reducing the fabrication cost and power consumption,herein an electromechanical RIS used for sub-6G wireless communication is proposed.The electromechanical RIS is designed with a passive metasurface and step-motor driver modules,providing simultaneous high-efficiency reflection(over 80%)and continuous reflection phase coverage of 360.Through electromechanical control,the RIS system can realize different reflective wavefront shaping,and has been employed in the indoor sub-6G wireless environment demonstrating a maximum signal improvement of 8.3 dB.The proposed electromechanical RIS is particularly useful for wireless signal enhancement in static blind area,and has the obvious advantage of not requiring continuous power supply after the RIS being regulated.Therefore,it greatly reduces the overall cost and power consumption which may have potentials in indoor application scenarios for improving wireless communication performance.展开更多
The optical extinction characteristics of the three kinds of microalgae Nannochloropsis maritirna, Ellip- soidion sp. (277.03), and Dunaliella tertiolecta were determined using an improved transmission method, in th...The optical extinction characteristics of the three kinds of microalgae Nannochloropsis maritirna, Ellip- soidion sp. (277.03), and Dunaliella tertiolecta were determined using an improved transmission method, in the 300-1800 nm spectral range. These three microalgae are promising candidates for the production of biofuels such as bio-hydrogen and biodiesel. The improved transmission method determines the spec- tral extinction coefficient of the microalgae. This is based on the measured transmittance, and employs an optical model that takes into consideration multiple reflections and refractions at the air-glass and glass-liquid interfaces. Silicon dioxide microspheres of monodisperse size were used as a model to verify the proposed method. The optical constants of the culture medium, size distributions, and extinction cross-sections of the microalgae cells were measured and analyzed. The improved transmission method is demonstrated to yield more accurate results than the traditional method. The spectral extinction effi- ciencies of the three kinds of microalgae show significant differences in the near ultraviolet and visible spectral regions. The spectral extinction efficiencies also exhibit small differences in the longer wave- length range of 950-1800 rim, with values generally less than 1.0. The measured extinction characteristics data of the three microalgae and the presented measurement method will facilitate process modeling in ohotobioreactors for biofuel oroduction.展开更多
In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types: a majority filled wit...In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types: a majority filled with granite porphyry and a minority filled with quartz syenite porphyry. Many cone sheets show evidence of multiple magma intrusion events. Some granite porphyry sheets' multiple chilled margins display magmatic roll structures indicating that turbulent magma flowed up the fractures. In one upward-closing cone-sheet K-feldspar phenocrysts floated up through fluid granite porphyry magma and became concentrated at the top providing direct evidence of shallow-level crystal fractionation, confirmed by published rock analyses. Accreted lapilli with K-feldspar crystal cores occur only in the inner parts of a minority of cone-sheets and field relationships indicate that they must have formed beneath the ground surface. Similar lapilli occur in erupted ignimbrites preserved in the collapsed caldera. Voids between lapilli in cone-sheets indicate the presence of volumes of gas below the surface that could have flowed upwards as fast-moving hot gas streams. We propose a mechanism of formation that began with subterranean magmatic rolls with K-feldspar crystal cores that formed on dyke walls, and became detached. Then they were caught up in rising gas streams and erupted at the surface. Thus accreted lapilli formed underground, were erupted along with blobs of fluid glass in escaping gases, and transported over the surface in nuées ardentes, to settle and cool as ignimbrite flows.展开更多
基金Project supported by the Joint Fund of Ministry of Education for Equipment Pre-research (Grant No. 8091B032112)the National Natural Science Foundation of China (Grant Nos. 62271243 and 62071215)+2 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central UniversitiesJiangsu Provincial Key Laboratory of Advanced Manipulating Technique of Electromagnetic Wave
文摘Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications.Here,we propose a wideband low-scattering metasurface that can realize an in-band reconfigurable transparent window by altering the operation states of the PIN diodes loaded on the structures.The metasurface is composed of a band-pass frequency selective surface(FSS)sandwiched between two polarization conversion metasurfaces(PCMs).PIN diodes are integrated into the FSS to switch the transparent window,while a checkerboard configuration is applied in PCMs for the diffusive-reflective function.A sample with 20×20 elements is designed,fabricated,and experimentally verified.Both simulated and measured results show that the in-band functions can be dynamically switched between beam-splitting scattering and high transmission by controlling the biasing states of the diodes,while low backscattering can be attained outside the passband.Furthermore,the resonant structures of FSS also play the role of feeding lines,thus significantly eliminating extra interference compared with conventional feeding networks.We envision that the proposed metasurface may provide new possibilities for the development of an intelligent stealth platform and its antenna applications.
基金supported by Biotechnology Risk Assessment Grant Program competitive grant no.2010-33522-21656from the USDA National Institute of Food and Agriculture,as well as the USDA grant CSREES SC-1700450.
文摘The conserved microRNA396(miR396)is involved in plant growth,development,and abiotic stress response in multiple plant species through regulating its targets,Growth Regulating Factor(GRF)transcription factor genes.However,the role of miR396 has not yet been characterized in perennial monocot species.In addition,the molecular mechanism of miR396-mediated abiotic stress response remains unclear.To elucidate the role of miR396 in perennial monocot species,we generated transgenic creeping bentgrass(Agrostis stolonifera)overexpressing Osa-miR396c,a rice miRNA396 gene.Transgenic plants exhibited altered development,including less shoot and root biomass,shorter internodes,smaller leaf area,fewer leaf veins,and epidermis cells per unit area than those of WT controls.In addition,transgenics showed enhanced salt tolerance associated with improved water retention,increased chlorophyll content,cell membrane integrity,and Na^(+)exclusion during high salinity exposure.Four potential targets of miR396 were identified in creeping bentgrass and up-regulated in response to salt stress.RNA-seq analysis indicates that miR396-mediated salt stress tolerance requires the coordination of stress-related functional proteins(antioxidant enzymes and Na+/H+antiporter)and regulatory proteins(transcription factors and protein kinases).This study establishes a miR396-associated molecular pathway to connect the upstream regulatory and downstream functional elements,and provides insight into the miRNA-mediated regulatory networks.
基金supported in part by Biotechnology Risk Assessment Grant Program competitive grant no.2019-33522-30102 from the USDA and National Institute of Food and Agriculture and the United States Golf Association,Inc.grant no.2016-25-575 as well as the Sichuan Science and Technology Program grant no.2019YFH0064.
文摘MicroRNA396(miR396)has been demonstrated to regulate flower development by targeting growth-regulating factors(GRFs)in annual species.However,its role in perennial grasses and its potential involvement in flowering time control remain unexplored.Here we report that overexpression of miR396 in a perennial species,creeping bentgrass(Agrostis stolonifera L.),alters flower development.Most significantly,transgenic(TG)plants bypass the vernalization requirement for flowering.Gene expression analysis reveals that miR396 is induced by long-day(LD)photoperiod and vernalization.Further study identifies VRN1,VRN2,and VRN3 homologs whose expression patterns in wild-type(WT)plants are similar to those observed in wheat and barley during transition from short-day(SD)to LD,and SD to cold conditions.However,compared to WT controls,TG plants overexpressing miR396 exhibit significantly enhanced VRN1 and VRN3 expression,but repressed VRN2 expression under SD to LD conditions without vernalization,which might be associated with modified expression of methyltransferase genes.Collectively,our results unveil a potentially novel mechanism by which miR396 suppresses the vernalization requirement for flowering which might be related to the epigenetic regulation of VRN genes and provide important new insight into critical roles of a miRNA in regulating vernalization-mediated transition from vegetative to reproductive growth in monocots.
基金supported by National Natural Science Foundation of China(62071215,62271243,91963128)National Key Research and Development Program of China(2017YFA0700201)the Joint Fund of Ministry of Education for Equipment Pre-research(8091B032112),Priority Academic Program Development of Jiangsu Higher Education Institutions,Fundamental Research Funds for the Central Universities and Jiangsu Provincial Key Laboratory of Advanced Manipulating Technique of Electromagnetic Wave.
文摘Reconfigurable intelligent surface(RIS)is emerged as a promising technique to solve the challenges faced by future wireless communication networks.Although the most commonly used electrically-controlled RISs can achieve millisecond-scale speed of dynamic switch,they have a large number of microwave circuit elements(such as PIN diodes or varactors)which will bring non-negligible insertion loss,and the complicity of the bias network to electrically addressing each element will increase with the expansion of the RIS aperture.Aiming at further reducing the fabrication cost and power consumption,herein an electromechanical RIS used for sub-6G wireless communication is proposed.The electromechanical RIS is designed with a passive metasurface and step-motor driver modules,providing simultaneous high-efficiency reflection(over 80%)and continuous reflection phase coverage of 360.Through electromechanical control,the RIS system can realize different reflective wavefront shaping,and has been employed in the indoor sub-6G wireless environment demonstrating a maximum signal improvement of 8.3 dB.The proposed electromechanical RIS is particularly useful for wireless signal enhancement in static blind area,and has the obvious advantage of not requiring continuous power supply after the RIS being regulated.Therefore,it greatly reduces the overall cost and power consumption which may have potentials in indoor application scenarios for improving wireless communication performance.
文摘The optical extinction characteristics of the three kinds of microalgae Nannochloropsis maritirna, Ellip- soidion sp. (277.03), and Dunaliella tertiolecta were determined using an improved transmission method, in the 300-1800 nm spectral range. These three microalgae are promising candidates for the production of biofuels such as bio-hydrogen and biodiesel. The improved transmission method determines the spec- tral extinction coefficient of the microalgae. This is based on the measured transmittance, and employs an optical model that takes into consideration multiple reflections and refractions at the air-glass and glass-liquid interfaces. Silicon dioxide microspheres of monodisperse size were used as a model to verify the proposed method. The optical constants of the culture medium, size distributions, and extinction cross-sections of the microalgae cells were measured and analyzed. The improved transmission method is demonstrated to yield more accurate results than the traditional method. The spectral extinction effi- ciencies of the three kinds of microalgae show significant differences in the near ultraviolet and visible spectral regions. The spectral extinction efficiencies also exhibit small differences in the longer wave- length range of 950-1800 rim, with values generally less than 1.0. The measured extinction characteristics data of the three microalgae and the presented measurement method will facilitate process modeling in ohotobioreactors for biofuel oroduction.
基金financially supported by the National Nature Science Foundation of China (No. 41272079)
文摘In addition to syenite ring dykes and multiple alkaline granite stocks, the sub-volcanic Houshihushan alkaline ring complex near Shanhaiguan, Qinhuangdao City, contains cone-sheets of two types: a majority filled with granite porphyry and a minority filled with quartz syenite porphyry. Many cone sheets show evidence of multiple magma intrusion events. Some granite porphyry sheets' multiple chilled margins display magmatic roll structures indicating that turbulent magma flowed up the fractures. In one upward-closing cone-sheet K-feldspar phenocrysts floated up through fluid granite porphyry magma and became concentrated at the top providing direct evidence of shallow-level crystal fractionation, confirmed by published rock analyses. Accreted lapilli with K-feldspar crystal cores occur only in the inner parts of a minority of cone-sheets and field relationships indicate that they must have formed beneath the ground surface. Similar lapilli occur in erupted ignimbrites preserved in the collapsed caldera. Voids between lapilli in cone-sheets indicate the presence of volumes of gas below the surface that could have flowed upwards as fast-moving hot gas streams. We propose a mechanism of formation that began with subterranean magmatic rolls with K-feldspar crystal cores that formed on dyke walls, and became detached. Then they were caught up in rising gas streams and erupted at the surface. Thus accreted lapilli formed underground, were erupted along with blobs of fluid glass in escaping gases, and transported over the surface in nuées ardentes, to settle and cool as ignimbrite flows.