Based on the effective-mass approximation and variational approach, excitonic optical properties are investigated theoretically in strained wurtzite （WZ） ZnO/MgxZn1-xO cylindrical quantum dots （QDs） for four diffe...Based on the effective-mass approximation and variational approach, excitonic optical properties are investigated theoretically in strained wurtzite （WZ） ZnO/MgxZn1-xO cylindrical quantum dots （QDs） for four different Mg compositions： x = 0.08, 0.14, 0.25, and 0.33, with considering a three-dimensional carrier confinement in QDs and a strong built-in electric field effect due to the piezoelectricity and spontaneous polarization. The ground-state exciton binding energy, the interband emission wavelength, and the radiative lifetime as functions of the QD structural parameters （height and radius） are calculated in detail The computations are performed in the case of finite band offset. Numerical results elucidate that Mg composition has of ZnO/MgxZn1-x 0 QDs. The ground-state exciton a significant influence on the exciton states and optical properties binding energy increases with increasing Mg composition and the increment tendency is more prominent for small height QDs. As Mg composition increases, the interband emission wavelength has a blue-shift if the dot height L 〈 3.5 nm, but the interband emission wavelength has a red-shift when L 〉 3.5 nm. Furthermore, the radiative lifetime increases rapidly with increasing Mg composition if the dot height L 〉 3 nm and the increment tendency is more prominent for large height QDs. The physical reason has been analyzed in depth.展开更多
Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous ...Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous species,Abies veitchii and Abies mariesii,dominate at low and high elevations,respectively,in the subalpine zone,central Japan.The aim of this study is to examine the effects of leaf age,elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species.Methods We here examined effects of leaf age,elevation and light conditions on photosynthesis,and leaf traits in A.veitchii and A.mariesii.Saplings of the two conifers were sampled in the understory and canopy gaps at their lower(1600 m)and upper(2300 m)distribution limits.Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits.The maximum photosynthetic rate of A.veitchii is correlated negatively with leaf mass per area(LMA)and non-structural carbohydrate(NSC)concentration.LMA increased at high elevations in the two species,whereas NSC concentrations increased only in A.veitchii.Therefore,the maximum photosynthetic rate of A.veitchii decreased at high elevations.Furthermore,maximum photosynthetic rates correlate positively with nitrogen concentration in both species.In the understory,leaf nitrogen concentrations decreased and increased in A.veitchii and A.mariesii,respectively.LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A.mariesii,suggesting it has a higher light-capture efficiency in dark conditions than does A.veitchii.This study concluded that A.mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A.veitchii,allowing A.mariesii to survive in the understory and to dominate at high elevations.展开更多
基金Supported by the Young Scientists Fund of the National Natural Science Foundation of China under Grant No. 11102100
文摘Based on the effective-mass approximation and variational approach, excitonic optical properties are investigated theoretically in strained wurtzite （WZ） ZnO/MgxZn1-xO cylindrical quantum dots （QDs） for four different Mg compositions： x = 0.08, 0.14, 0.25, and 0.33, with considering a three-dimensional carrier confinement in QDs and a strong built-in electric field effect due to the piezoelectricity and spontaneous polarization. The ground-state exciton binding energy, the interband emission wavelength, and the radiative lifetime as functions of the QD structural parameters （height and radius） are calculated in detail The computations are performed in the case of finite band offset. Numerical results elucidate that Mg composition has of ZnO/MgxZn1-x 0 QDs. The ground-state exciton a significant influence on the exciton states and optical properties binding energy increases with increasing Mg composition and the increment tendency is more prominent for small height QDs. As Mg composition increases, the interband emission wavelength has a blue-shift if the dot height L 〈 3.5 nm, but the interband emission wavelength has a red-shift when L 〉 3.5 nm. Furthermore, the radiative lifetime increases rapidly with increasing Mg composition if the dot height L 〉 3 nm and the increment tendency is more prominent for large height QDs. The physical reason has been analyzed in depth.
基金supported by grants(20292081)from the Ministry of Education,Culture,Sports,Science and Technology,Japan.
文摘Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous species,Abies veitchii and Abies mariesii,dominate at low and high elevations,respectively,in the subalpine zone,central Japan.The aim of this study is to examine the effects of leaf age,elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species.Methods We here examined effects of leaf age,elevation and light conditions on photosynthesis,and leaf traits in A.veitchii and A.mariesii.Saplings of the two conifers were sampled in the understory and canopy gaps at their lower(1600 m)and upper(2300 m)distribution limits.Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits.The maximum photosynthetic rate of A.veitchii is correlated negatively with leaf mass per area(LMA)and non-structural carbohydrate(NSC)concentration.LMA increased at high elevations in the two species,whereas NSC concentrations increased only in A.veitchii.Therefore,the maximum photosynthetic rate of A.veitchii decreased at high elevations.Furthermore,maximum photosynthetic rates correlate positively with nitrogen concentration in both species.In the understory,leaf nitrogen concentrations decreased and increased in A.veitchii and A.mariesii,respectively.LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A.mariesii,suggesting it has a higher light-capture efficiency in dark conditions than does A.veitchii.This study concluded that A.mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A.veitchii,allowing A.mariesii to survive in the understory and to dominate at high elevations.
