A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion （SPDC） effect of nonlinear crystal. An absolute calibration system of detector qu...A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion （SPDC） effect of nonlinear crystal. An absolute calibration system of detector quantum efficiency is performed. And its principle and experimental setup are introduced. A continuouswave （CW） ultraviolet （351 nm）, diode-pumped, frequency-doubled, and solid-state laser is used to pump BBO crystal. The quantum efficiencies of the photomultiplier at 633, 702, and 789 nm are measured respectively. The coincidence peaks are observed using coincidence circuit. Some measurement factors including the filter bandwidth of trigger channel, the detector position alignment and polarization of the pump light are analyzed. The uncertainties of this calibration method are also analyzed, and the relative uncertainties of total calibration are less than 5.8%. The accuracy of this method could be improved in the future.展开更多
Aroma(volatile)compounds play important ecological functions in plants,and also contribute to the quality of plant-derived foods.Moreover,chiral aroma compounds affect their functions in plants and lead to different f...Aroma(volatile)compounds play important ecological functions in plants,and also contribute to the quality of plant-derived foods.Moreover,chiral aroma compounds affect their functions in plants and lead to different flavor quality properties.Formations of chiral aroma compounds are due to the presence of enzymes producing these compounds in plants,which are generally involved in the final biosynthetic step of the aroma compounds.Here,we review recent progress in research on the plant-derived enzymes producing chiral aroma compounds,and their changes in response to environmental factors.The chiral aroma enzymes that have been reported produce(R)-linalool,(S)-linalool,(R)-limonene,and(S)-limonene,etc.,and these enzymes are found in various plant species.We also discuss the origins of enantioselectivity in the plant-derived enzymes producing chiral aroma compounds and summarize the potential use of plants containing enzymes producing chiral aroma compounds for producing chiral flavors/fragrances.展开更多
基金the National Natural Science Foundation of China under Grant No.60378027.
文摘A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion （SPDC） effect of nonlinear crystal. An absolute calibration system of detector quantum efficiency is performed. And its principle and experimental setup are introduced. A continuouswave （CW） ultraviolet （351 nm）, diode-pumped, frequency-doubled, and solid-state laser is used to pump BBO crystal. The quantum efficiencies of the photomultiplier at 633, 702, and 789 nm are measured respectively. The coincidence peaks are observed using coincidence circuit. Some measurement factors including the filter bandwidth of trigger channel, the detector position alignment and polarization of the pump light are analyzed. The uncertainties of this calibration method are also analyzed, and the relative uncertainties of total calibration are less than 5.8%. The accuracy of this method could be improved in the future.
基金supported by the financial supports from the Guangdong Basic and Applied Basic Research Foundation(2020A1515010539)the Medical Science and Technology Research Foundation of Guangdong Province,China(A2019046)+1 种基金Guangdong Province Higher Vocational Colleges&Schools Pearl River Scholar(50117G25002)the Key Project of Universities in Guangdong Province(2021ZDZX4066).
文摘Aroma(volatile)compounds play important ecological functions in plants,and also contribute to the quality of plant-derived foods.Moreover,chiral aroma compounds affect their functions in plants and lead to different flavor quality properties.Formations of chiral aroma compounds are due to the presence of enzymes producing these compounds in plants,which are generally involved in the final biosynthetic step of the aroma compounds.Here,we review recent progress in research on the plant-derived enzymes producing chiral aroma compounds,and their changes in response to environmental factors.The chiral aroma enzymes that have been reported produce(R)-linalool,(S)-linalool,(R)-limonene,and(S)-limonene,etc.,and these enzymes are found in various plant species.We also discuss the origins of enantioselectivity in the plant-derived enzymes producing chiral aroma compounds and summarize the potential use of plants containing enzymes producing chiral aroma compounds for producing chiral flavors/fragrances.
