Intercropping and residue retention contribute to high yield and quality of crops. However, their coupled effects on rhizospheric microbial communities under a continuous vegetable cropping system have not been adequa...Intercropping and residue retention contribute to high yield and quality of crops. However, their coupled effects on rhizospheric microbial communities under a continuous vegetable cropping system have not been adequately addressed. The objective of the present study was to assess the effects on soil microbial community and yields of waxy maize（Zea mays L.） intercropped with or without residue retention in a continuous broccoli（Brassica oleracea L.） cropping system, i.e., relay intercropping of broccoli and waxy maize（B/M-B）, relay intercropping of broccoli and waxy maize with residue retention（B/MR-B）, and broccoli monoculture（B-B）. The biomass yields of spring and autumn vegetables in B/MR-B were 16.3%–32.5% and 30.1%–46.1% higher than those of B-B,respectively. Autumn vegetable economic yields of B/MR-B were 28.2%–40.3% higher than B-B. The average well color development followed the order： B/MR-B ＆gt; B/M-B ＆gt; B-B. The Shannon index, Simpson index, and Mc Intosh index were higher in B/MR-B than under monoculture. A principal component analysis showed that microbial communities of B/MR-B soils differed from those of B/M-B and B-B soils. Carbon（C） sources utilized by the rhizosphere microorganisms were mainly carbohydrates, carboxylic acids, amino acids, and polymers; however, the C sources for the soil microbial community differed between intercropping and monoculture. The communities from B/MR-B preferred amino acids and polymers. Available nitrogen（N）, potassium（K）, and phosphorus（P） had an obvious impact on soil microbial community. Additionally, the C source utilization by microorganisms was significantly affected by p H and available K and P. Cropping system diversification through relay intercropping and residue retention effectively improved the functional diversity of the soil microbial communities and increased the yields of vegetables.展开更多
A new configuration of the confinement structure is utilized to improve optoelectronic performance, including threshold current, ac current gain, optical bandwidth, and optical output power of a single quantum well tr...A new configuration of the confinement structure is utilized to improve optoelectronic performance, including threshold current, ac current gain, optical bandwidth, and optical output power of a single quantum well transistor laser. Considering the drift component in addition to the diffusion term in electron current density, a new continuity equation is developed to analyze the proposed structures. Physical parameters, including electron mobility, recombination lifetime, optical confinement factor, electron capture time, and photon lifetime, are calculated for new structures. Based on solving the continuity equation in separate confinement heterostructures, the threshold current reduces 67%, the optical output power increases 37%, and the-3 d B optical bandwidth increases to 21 GHz（compared to 19.5 GHz in the original structure） when the graded index layers of AlξGa1-ξAs（ξ：0.05 → 0 in the left side of quantum well, ξ：0 → 0.02 in the right side of quantum well） are used instead of uniform Ga As in the base region.展开更多
基金financially supported by the Special Research Funding for Public Benefit Industries (Agriculture) of China (No. 201503121)the Key Projects in the National Science and Technology Pillar Program during the Twelfth Five-year Plan Period, China (No. 2012BAD14B07)
文摘Intercropping and residue retention contribute to high yield and quality of crops. However, their coupled effects on rhizospheric microbial communities under a continuous vegetable cropping system have not been adequately addressed. The objective of the present study was to assess the effects on soil microbial community and yields of waxy maize（Zea mays L.） intercropped with or without residue retention in a continuous broccoli（Brassica oleracea L.） cropping system, i.e., relay intercropping of broccoli and waxy maize（B/M-B）, relay intercropping of broccoli and waxy maize with residue retention（B/MR-B）, and broccoli monoculture（B-B）. The biomass yields of spring and autumn vegetables in B/MR-B were 16.3%–32.5% and 30.1%–46.1% higher than those of B-B,respectively. Autumn vegetable economic yields of B/MR-B were 28.2%–40.3% higher than B-B. The average well color development followed the order： B/MR-B ＆gt; B/M-B ＆gt; B-B. The Shannon index, Simpson index, and Mc Intosh index were higher in B/MR-B than under monoculture. A principal component analysis showed that microbial communities of B/MR-B soils differed from those of B/M-B and B-B soils. Carbon（C） sources utilized by the rhizosphere microorganisms were mainly carbohydrates, carboxylic acids, amino acids, and polymers; however, the C sources for the soil microbial community differed between intercropping and monoculture. The communities from B/MR-B preferred amino acids and polymers. Available nitrogen（N）, potassium（K）, and phosphorus（P） had an obvious impact on soil microbial community. Additionally, the C source utilization by microorganisms was significantly affected by p H and available K and P. Cropping system diversification through relay intercropping and residue retention effectively improved the functional diversity of the soil microbial communities and increased the yields of vegetables.
文摘A new configuration of the confinement structure is utilized to improve optoelectronic performance, including threshold current, ac current gain, optical bandwidth, and optical output power of a single quantum well transistor laser. Considering the drift component in addition to the diffusion term in electron current density, a new continuity equation is developed to analyze the proposed structures. Physical parameters, including electron mobility, recombination lifetime, optical confinement factor, electron capture time, and photon lifetime, are calculated for new structures. Based on solving the continuity equation in separate confinement heterostructures, the threshold current reduces 67%, the optical output power increases 37%, and the-3 d B optical bandwidth increases to 21 GHz（compared to 19.5 GHz in the original structure） when the graded index layers of AlξGa1-ξAs（ξ：0.05 → 0 in the left side of quantum well, ξ：0 → 0.02 in the right side of quantum well） are used instead of uniform Ga As in the base region.
