Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The...Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The results showed that the weather had obviously baroclinic characteristic.A strong cold tongue extended straight to Central Asia from the high latitude area,and the cold air was strong and deep.The driving effect of cold trough could accelerate it to move southward.The Aral Sea low vortex obstructed the warm air in the north in high latitude area,and the southwest air flow in the front of the vortex conducted to the transportation of water vapor to Central Asia.Compared with the climate average field of 1981-2010,the northwest flow at 500 hPa in May of 2019 was aggressive,which had frequently influenced Xinjiang by cold air from the north high latitude regions.The east flow of the bottom layer not only input cold air to Karamay,but also formed the windward slope effect with the terrain.Moreover,it increased the vertical wind shear and induced the upward movement.The center of high potential vorticity with high latitude fell southward,and the center of low potential vorticity in Central Asia moved eastward rapidly.They combined and then moved toward Xinjiang,which made the strong cold air erupt rapidly.When the right side of the moved axis of the high potential vorticity center and the strong west flow superposed over the Karamay area,the center of the strong rainfall area appeared 6 h later.展开更多
Foodborne pathogenic bacteria have been considered as a major risk factor for food safety. It is of great significance to carry out in-field screening of pathogenic bacteria to prevent the outbreaks of foodborne disea...Foodborne pathogenic bacteria have been considered as a major risk factor for food safety. It is of great significance to carry out in-field screening of pathogenic bacteria to prevent the outbreaks of foodborne diseases. In this study, a portable lab-on-a-disc platform with a microfluidic disc was developed for rapid and automatic detection of Salmonella typhimurium using a nickel nanowire(Ni NW) net for effective separation of target bacteria, horseradish peroxidase nanoflowers(HRP NFs) for efficient amplification of biological signals, and a self-developed smartphone APP for accurate analysis of colorimetric images. First,the microfluidic disc was preloaded with reagents and samples and centrifuged to form one bacterial sample column, one immune Ni NW column, one HRP NF column, two washing buffer columns and one tetramethylbenzidine(TMB) column, which were separated by air gaps. Then, a rotatable magnetic field was specifically developed to assemble the Ni NWs into a net, which was automatically controlled by a stepped motor to successively pass through the sample column for specific capture of target bacteria, the HRP NF column for specific label of target bacteria, the washing columns for effective removal of sample background and non-specific binding NFs, and the TMB column for colorimetric determination of target bacteria. The color change of TMB from colorless to blue was finally analyzed using the smartphone APP to quantitatively determine the target bacteria. This lab-on-a-disc platform could detect Salmonella typhimurium from 5.6 × 10^(1) CFU/20 μL to 5.6 × 10^(5) CFU/20 μL in 1 h with a lower detection limit of 56 CFU/20 μL. The recovery of target bacteria in spiked chicken samples ranged from 97.5% to 101.8%. This portable platform integrating separation, labeling, washing, catalysis and detection onto a single disc is featured with automatic operation, fast reaction, and small size and has shown its potential for in-field detection of foodborne pathogens.展开更多
文摘Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The results showed that the weather had obviously baroclinic characteristic.A strong cold tongue extended straight to Central Asia from the high latitude area,and the cold air was strong and deep.The driving effect of cold trough could accelerate it to move southward.The Aral Sea low vortex obstructed the warm air in the north in high latitude area,and the southwest air flow in the front of the vortex conducted to the transportation of water vapor to Central Asia.Compared with the climate average field of 1981-2010,the northwest flow at 500 hPa in May of 2019 was aggressive,which had frequently influenced Xinjiang by cold air from the north high latitude regions.The east flow of the bottom layer not only input cold air to Karamay,but also formed the windward slope effect with the terrain.Moreover,it increased the vertical wind shear and induced the upward movement.The center of high potential vorticity with high latitude fell southward,and the center of low potential vorticity in Central Asia moved eastward rapidly.They combined and then moved toward Xinjiang,which made the strong cold air erupt rapidly.When the right side of the moved axis of the high potential vorticity center and the strong west flow superposed over the Karamay area,the center of the strong rainfall area appeared 6 h later.
基金supported by National Natural Science Foundation of China (No. 32071899)Walmart Foundation (No.61626817)Walmart Food Safety Collaboration Center for its great support。
文摘Foodborne pathogenic bacteria have been considered as a major risk factor for food safety. It is of great significance to carry out in-field screening of pathogenic bacteria to prevent the outbreaks of foodborne diseases. In this study, a portable lab-on-a-disc platform with a microfluidic disc was developed for rapid and automatic detection of Salmonella typhimurium using a nickel nanowire(Ni NW) net for effective separation of target bacteria, horseradish peroxidase nanoflowers(HRP NFs) for efficient amplification of biological signals, and a self-developed smartphone APP for accurate analysis of colorimetric images. First,the microfluidic disc was preloaded with reagents and samples and centrifuged to form one bacterial sample column, one immune Ni NW column, one HRP NF column, two washing buffer columns and one tetramethylbenzidine(TMB) column, which were separated by air gaps. Then, a rotatable magnetic field was specifically developed to assemble the Ni NWs into a net, which was automatically controlled by a stepped motor to successively pass through the sample column for specific capture of target bacteria, the HRP NF column for specific label of target bacteria, the washing columns for effective removal of sample background and non-specific binding NFs, and the TMB column for colorimetric determination of target bacteria. The color change of TMB from colorless to blue was finally analyzed using the smartphone APP to quantitatively determine the target bacteria. This lab-on-a-disc platform could detect Salmonella typhimurium from 5.6 × 10^(1) CFU/20 μL to 5.6 × 10^(5) CFU/20 μL in 1 h with a lower detection limit of 56 CFU/20 μL. The recovery of target bacteria in spiked chicken samples ranged from 97.5% to 101.8%. This portable platform integrating separation, labeling, washing, catalysis and detection onto a single disc is featured with automatic operation, fast reaction, and small size and has shown its potential for in-field detection of foodborne pathogens.
