GaN ultraviolet(UV)p-i-n photodetectors(PDs)with a 40 nm thin p-GaN contact layer are fabricated on sapphire substrates,which exhibit enhanced quantum efficiency especially in a deep-UV wavelength range.The PDs show g...GaN ultraviolet(UV)p-i-n photodetectors(PDs)with a 40 nm thin p-GaN contact layer are fabricated on sapphire substrates,which exhibit enhanced quantum efficiency especially in a deep-UV wavelength range.The PDs show good rectification behavior and low dark current in pA level for reverse bias up to-10 V.Under zero bias,the maximum quantum efficiency of the PD at 360 nm is close to 59.4%with a UV/visible rejection ratio more than 4 orders of magnitude.Even at a short wavelength of 280 nm,the quantum efficiency of the PD is still around 47.5%,which is considerably higher than that of a control device with a thicker p-GaN contact layer.The room temperature thermal noise limited detectivity of the PD is calculated to be~4.96×10^(14) cm·Hz^(1/2)W^(-1).展开更多
A hydroponic study was conducted to determine the effects of selenium（Se： 0, 3, 6 μmol L^-1） on senescence-related oxidative stress in garlic plants grown under two sulfur（S） levels. We evaluated the yields of p...A hydroponic study was conducted to determine the effects of selenium（Se： 0, 3, 6 μmol L^-1） on senescence-related oxidative stress in garlic plants grown under two sulfur（S） levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose（0.3 μmol L^-1） at low S level showed higher yields（12.0% increase in fresh weight yield, 13.7% increase in dry weight yield） than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glut athione peroxidase and catalase, but lower superoxide dismutase activities. Changes in Fv/Fm values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.展开更多
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB327504,2011CB922100 and 2011CB301900the National Natural Science Foundation of China under Grant Nos 60825401,60936004,11104130 and 60990311.
文摘GaN ultraviolet(UV)p-i-n photodetectors(PDs)with a 40 nm thin p-GaN contact layer are fabricated on sapphire substrates,which exhibit enhanced quantum efficiency especially in a deep-UV wavelength range.The PDs show good rectification behavior and low dark current in pA level for reverse bias up to-10 V.Under zero bias,the maximum quantum efficiency of the PD at 360 nm is close to 59.4%with a UV/visible rejection ratio more than 4 orders of magnitude.Even at a short wavelength of 280 nm,the quantum efficiency of the PD is still around 47.5%,which is considerably higher than that of a control device with a thicker p-GaN contact layer.The room temperature thermal noise limited detectivity of the PD is calculated to be~4.96×10^(14) cm·Hz^(1/2)W^(-1).
基金funded by the Agricultural Research Special Funds for Public Welfare Projects from the Ministry of Agriculture of the People’s Republic of China (200903018)
文摘A hydroponic study was conducted to determine the effects of selenium（Se： 0, 3, 6 μmol L^-1） on senescence-related oxidative stress in garlic plants grown under two sulfur（S） levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose（0.3 μmol L^-1） at low S level showed higher yields（12.0% increase in fresh weight yield, 13.7% increase in dry weight yield） than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glut athione peroxidase and catalase, but lower superoxide dismutase activities. Changes in Fv/Fm values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.
