Chromoplasts are colored plastids that synthesize and store massive amounts of carotenoids.Chromoplast number and size define the sink strength for carotenoid accumulation in plants.However,nothing is known about the ...Chromoplasts are colored plastids that synthesize and store massive amounts of carotenoids.Chromoplast number and size define the sink strength for carotenoid accumulation in plants.However,nothing is known about the mechanisms controlling chromoplast number.Previously,a natural allele of Orange(OR),OR^His,was found to promote carotenoid accumulation by activating chromoplast differentiation and increasing carotenoid biosynthesis,but cells in orange tissues in melon fruit and cauliflower OR mutant have only one or two enlarged chromoplasts.In this study,we investigated an OR^His variant of Arabidopsis OR,genetically mimicking the melon OR^His allele,and found that it also constrains chromoplast number in Arabidopsis calli.Both in vitro and in vivo experiments demonstrate that OR^His specifically interacts with the Membrane Occupation and Recognition Nexus domain of ACCUMULATION AND REPLICATION OF CHLOROPLASTS 3(ARC3),a crucial regulator of chloroplast division.We further showed that OR^His interferes with the interaction between ARC3 and PARALOG OF ARC6(PARC6),another key regulator of chloroplast division,suggesting a role of OR^His in competing with PARC6 for binding to ARC3 to restrict chromoplast number.Overexpression or knockout of ARC3 in Arabidopsis OR^His plants significantly alters total carotenoid levels.Moreover,overexpression of the plastid division factor PLASTID DIVISION 1 greatly enhances carotenoid accumulation.These division factors likely alter carotenoid levels via their influence on chromoplast number and/or size.Taken together,our findings provide novel mechanistic insights into the machinery controlling chromoplast number and highlight a potential new strategy for enhancing carotenoid accumulation and nutritional value in food crops.展开更多
Arc spraying with the cored wires was applied to deposit FeMnCr/Cr3C2 coatings on low carbon steel substrates, namely FM1, FM2 and FM3. Thermal shock resistances of the coatings were investigated to assess the influen...Arc spraying with the cored wires was applied to deposit FeMnCr/Cr3C2 coatings on low carbon steel substrates, namely FM1, FM2 and FM3. Thermal shock resistances of the coatings were investigated to assess the influence of Cr3C2 content on thermal shock resistance. Characteristics of the coatings under thermal cycling test were studied by optical microscopy, field emission scanning electron microscope （FE-SEM） and energy dispersion spectrum （EDS）, X-ray diffraction （XRD）. The experimental results show that hardness of the coatings increases, bonding strength decreases slightly with increase of the Cr3C2 content of the coatings. As a result, FM2 coating possesses the best thermal shock resistance, attributing to its better thermal expansion matches and wettability than those of FM3 coating, less oxide rate than that of FM1 coating restraining from cracks formation and propagation in coatings.展开更多
A 3D Magnetohydrodynamics （MHD） arc model in conjunction with an arc move- ment model is applied to simulate the arc rotation as well as to solve its effect on the pressure in an auto-expansion circuit breaker. The ...A 3D Magnetohydrodynamics （MHD） arc model in conjunction with an arc move- ment model is applied to simulate the arc rotation as well as to solve its effect on the pressure in an auto-expansion circuit breaker. The rotation of the arc driven by an external electromagnetic force is simulated in the case with 200 kA of the short circuit current and 16 ms of arc duration. The arc rotating process and the speed of arc rotation have been obtained in the simulation. A comparison of the pressure in the expansion volume with and without an external magnetic field has been carried out based on the calculation results of two cases. The results of the simulation reveal that the arc rotation, which causes more energy exchange between the arc and its sur- rounding gas, can evidently bring about the pressurization in the expansion volume, which would contribute to more effective arc quenching at current zero and further reducing operation power.展开更多
A 3-phase a.c. arc plasma reactor with large volume plasma has been developed for the synthesis of new carbon nano-structures. One of the main characteristics of the plasma system is related to the absence of a fixed ...A 3-phase a.c. arc plasma reactor with large volume plasma has been developed for the synthesis of new carbon nano-structures. One of the main characteristics of the plasma system is related to the absence of a fixed neutral point. This gives rise to a rich and complex phenomenology related to instabilities and arc motion since the arcs are ＂burning＂ freely in the gas flow between the three electrodes. This paper is dedicated to the analysis of the behavior of such a system under typical conditions using argon and nitrogen as plasma gases. A classification of are configuration, arc commutating, arc interaction, arc motion and arc instabilities are discussed based on ultra high-speed cine camera analysis. A simple model describing the time evolution of the system is also presented and compared with the experimental measurements. The results show that an adequate control could allow the improvement of the overall system.展开更多
Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, ...Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.展开更多
The arc corrosion evolution of Cu-20 vol.% Ti_3 AlC_2 cathodes is presented here. After eroded by 3, 4, 5, 6, 7, 8, 9, 10 kV DC voltage, respectively, the surface morphologies were characterized by field emission scan...The arc corrosion evolution of Cu-20 vol.% Ti_3 AlC_2 cathodes is presented here. After eroded by 3, 4, 5, 6, 7, 8, 9, 10 kV DC voltage, respectively, the surface morphologies were characterized by field emission scanning electron microscope with craters and protrusions. Compared to small craters and dense protrusions of the morphology by high voltage, the eroded surface was covered with bigger craters and sparse protrusions at low voltage. No crack was discovered on the surface even at 10 kV. By means of energy dispersive spectroscopy and Raman spectroscopy, the decomposition of Cu-20 vol.% Ti_3 AlC_2 cathode to CuO,Al__2 O_3 and TiO_2 were proved. Meanwhile, W anode is oxidized to WO_2. The peak current increases with the increasing breakdown voltage, which is recorded by a digital memory oscilloscope.展开更多
基金This work was supported by Agriculture and Food Research Initiative competitive awards grant nos.2016-67013-24612 and 2019-67013-29162 from the United States Department of Agriculture National Institute of Food and Agriculture.C.Cwas supported by the United States Department of Energy,Office of Science,Basic Energy Sciences award number DE-FG02-06ER15808 to K.W.O.
文摘Chromoplasts are colored plastids that synthesize and store massive amounts of carotenoids.Chromoplast number and size define the sink strength for carotenoid accumulation in plants.However,nothing is known about the mechanisms controlling chromoplast number.Previously,a natural allele of Orange(OR),OR^His,was found to promote carotenoid accumulation by activating chromoplast differentiation and increasing carotenoid biosynthesis,but cells in orange tissues in melon fruit and cauliflower OR mutant have only one or two enlarged chromoplasts.In this study,we investigated an OR^His variant of Arabidopsis OR,genetically mimicking the melon OR^His allele,and found that it also constrains chromoplast number in Arabidopsis calli.Both in vitro and in vivo experiments demonstrate that OR^His specifically interacts with the Membrane Occupation and Recognition Nexus domain of ACCUMULATION AND REPLICATION OF CHLOROPLASTS 3(ARC3),a crucial regulator of chloroplast division.We further showed that OR^His interferes with the interaction between ARC3 and PARALOG OF ARC6(PARC6),another key regulator of chloroplast division,suggesting a role of OR^His in competing with PARC6 for binding to ARC3 to restrict chromoplast number.Overexpression or knockout of ARC3 in Arabidopsis OR^His plants significantly alters total carotenoid levels.Moreover,overexpression of the plastid division factor PLASTID DIVISION 1 greatly enhances carotenoid accumulation.These division factors likely alter carotenoid levels via their influence on chromoplast number and/or size.Taken together,our findings provide novel mechanistic insights into the machinery controlling chromoplast number and highlight a potential new strategy for enhancing carotenoid accumulation and nutritional value in food crops.
文摘Arc spraying with the cored wires was applied to deposit FeMnCr/Cr3C2 coatings on low carbon steel substrates, namely FM1, FM2 and FM3. Thermal shock resistances of the coatings were investigated to assess the influence of Cr3C2 content on thermal shock resistance. Characteristics of the coatings under thermal cycling test were studied by optical microscopy, field emission scanning electron microscope （FE-SEM） and energy dispersion spectrum （EDS）, X-ray diffraction （XRD）. The experimental results show that hardness of the coatings increases, bonding strength decreases slightly with increase of the Cr3C2 content of the coatings. As a result, FM2 coating possesses the best thermal shock resistance, attributing to its better thermal expansion matches and wettability than those of FM3 coating, less oxide rate than that of FM1 coating restraining from cracks formation and propagation in coatings.
基金supported by National Natural Science Foundation of China (Nos.51177005 and 51477004)
文摘A 3D Magnetohydrodynamics （MHD） arc model in conjunction with an arc move- ment model is applied to simulate the arc rotation as well as to solve its effect on the pressure in an auto-expansion circuit breaker. The rotation of the arc driven by an external electromagnetic force is simulated in the case with 200 kA of the short circuit current and 16 ms of arc duration. The arc rotating process and the speed of arc rotation have been obtained in the simulation. A comparison of the pressure in the expansion volume with and without an external magnetic field has been carried out based on the calculation results of two cases. The results of the simulation reveal that the arc rotation, which causes more energy exchange between the arc and its sur- rounding gas, can evidently bring about the pressurization in the expansion volume, which would contribute to more effective arc quenching at current zero and further reducing operation power.
基金supported by National Natural Science Foundation of China (No. 10375065)Anhui Natural Science Foundation (03045102)+1 种基金Europeam Commission projects NanoComp HPRN-CR-2000-0037PlasmaCarb G5RD-CT-1999-00173
文摘A 3-phase a.c. arc plasma reactor with large volume plasma has been developed for the synthesis of new carbon nano-structures. One of the main characteristics of the plasma system is related to the absence of a fixed neutral point. This gives rise to a rich and complex phenomenology related to instabilities and arc motion since the arcs are ＂burning＂ freely in the gas flow between the three electrodes. This paper is dedicated to the analysis of the behavior of such a system under typical conditions using argon and nitrogen as plasma gases. A classification of are configuration, arc commutating, arc interaction, arc motion and arc instabilities are discussed based on ultra high-speed cine camera analysis. A simple model describing the time evolution of the system is also presented and compared with the experimental measurements. The results show that an adequate control could allow the improvement of the overall system.
文摘Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.
基金supported by the National Natural Science Foundation of China(Grant No.51571078)
文摘The arc corrosion evolution of Cu-20 vol.% Ti_3 AlC_2 cathodes is presented here. After eroded by 3, 4, 5, 6, 7, 8, 9, 10 kV DC voltage, respectively, the surface morphologies were characterized by field emission scanning electron microscope with craters and protrusions. Compared to small craters and dense protrusions of the morphology by high voltage, the eroded surface was covered with bigger craters and sparse protrusions at low voltage. No crack was discovered on the surface even at 10 kV. By means of energy dispersive spectroscopy and Raman spectroscopy, the decomposition of Cu-20 vol.% Ti_3 AlC_2 cathode to CuO,Al__2 O_3 and TiO_2 were proved. Meanwhile, W anode is oxidized to WO_2. The peak current increases with the increasing breakdown voltage, which is recorded by a digital memory oscilloscope.
