Dry–rewetting（DW） disturbance frequently occurs in soils due to rainfall and irrigation, and the frequency of DW cycles might exert significant influences on soil microbial communities and their mediated functions....Dry–rewetting（DW） disturbance frequently occurs in soils due to rainfall and irrigation, and the frequency of DW cycles might exert significant influences on soil microbial communities and their mediated functions. However, how microorganisms respond to DW alternations in soils with a history of heavy metal pollution remains largely unknown.Here, soil laboratory microcosms were constructed to explore the impacts of ten DW cycles on the soil microbial communities in two contrasting soils（fluvo-aquic soil and red soil）under three copper concentrations（zero, medium and high）. Results showed that the fluctuations of substrate induced respiration（SIR） decreased with repeated cycles of DW alternation. Furthermore, the resistance values of substrate induced respiration（RS-SIR）were highest in non-copper-stressed（zero） soils. Structural equation model（SEM） analysis ascertained that the shifts of bacterial communities determined the changes of RS-SIR in both soils. The rate of bacterial community variance was significantly lower in noncopper-stressed soil compared to the other two copper-stressed（medium and high） soils,which might lead to the higher RS-SIR in the fluvo-aquic soil. As for the red soil, the substantial increase of the dominant group WPS-2 after DW disturbance might result in the low RS-SIR in the high copper-stressed soil. Moreover, in both soils, the bacterial diversity was highest in non-copper-stressed soils. Our results revealed that initial copper stress could decrease the resistance of soil microbial community structure and function to subsequent DW disturbance.展开更多
Climate change alters the intensity and frequency of drought and rewetting(D/W)events;however,the influence patterns of D/W on soil N_(2)O efflux in the water-limited area were not fully understood.Therefore,the impac...Climate change alters the intensity and frequency of drought and rewetting(D/W)events;however,the influence patterns of D/W on soil N_(2)O efflux in the water-limited area were not fully understood.Therefore,the impacts of D/W cycles varying in different extent of rewetting and frequency to N_(2)O efflux in two kinds of soil on the Loess Plateau were investigated.The incubation conditions consisted of 1)D/W treatments with four 7-day cycles from 10%water holding capacity(WHC)to 60%WHC or 90%WHC,2)constant moisture of 60%WHC and 90%WHC.The pulse of N_(2)O efflux rate under 10-60%WHC treatment was higher than that under 10-90%WHC treatment in calcic cambisols,while opposite trend was observed in earth-cumuli-orthic anthrosols.Meanwhile,the pulse of N_(2)O efflux rate decreased as cycle number increased for different wetting intensities and soil types.The direct N_(2)O efflux under 10-60%WHC and 10-90%WHC treatments were 5.49 and 1.89μg N_(2)O-N g^(-1)soil in calcic cambisols,with those being 1.92 and 10.85μg N_(2)O-N g^(-1)soil in earth-cumuli-orthic anthrosols,respectively.The N loss in earth-cumuli-orthic anthrosols was approximately 5.74 times greater than that in calcic cambisols under 10-90%WHC treatment,whereas the N loss under 10-60%WHC treatment was about 2.86 times greater in calcic cambisols than that in earth-cumuli-orthic anthrosols.This study suggested that extreme rainfall events can enhance the N_(2)O efflux and N loss in agricultural soils on the Loess Plateau in terms of soil type and wetting intensity,which should not be ignored in the N fertilizer management.展开更多
: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in...: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in the dark at night. After rewetting in the dark, photochemical activity and the structure of photosystem (PS) II were not recovered at all; the structure of PSI, energy transfer in phycobilisomes, and energy transfer from phycobilisomes to PSI were recovered within 5 min, as in the light. The recovery of energy transfer from phycobilisomes to PSII was light dependent and energy transfer from phycobilisomes to PSII was only partially recovered in the dark. These results suggest that the two-trigger control (water and light) of photo synthetic recovery may make N. flagelliforme avoid unnecessary energy consumption and, at the same time, the partial recovery of energy transfer from phycobilisomes to PSII in the dark could help N. flagelliforme accumulate more photosynthetic products during the transient period of rehydration-dehydration.展开更多
Drying and rewetting(DRW)events cause the release of colloidal phosphorus(P_(coll),1-1000 nm)in leachate,and biochar is considered an effective inhibitor;however,the microbial mechanism remains elusive.In this study,t...Drying and rewetting(DRW)events cause the release of colloidal phosphorus(P_(coll),1-1000 nm)in leachate,and biochar is considered an effective inhibitor;however,the microbial mechanism remains elusive.In this study,three successive DRW cycles were performed on the soil columns to assess the effect of biochar addition on P_(coll) content and its possible associates,including phosphatase-producing microbial populations(phoD- and phoC-harboring microbial communities)and alkaline/acid phosphatase(ALP/ACP)activities.Results showed that the biochar addition significantly decreased the P_(coll) by 15.5-32.1%during three DRW cycles.The structural equation model(SEM)confirmed that biochar addition increased phoD- and phoC-harboring microbial communities and ALP/ACP activities,which reduces the release of P_(coll) into leachate.In addition,the manure biochar was more effective than the straw biochar in promoting competition and cooperation in the co-occurrence network(2-5%nodes increased on average),and the key taxa Proteobacteria and Cyanobacteria were identified as the dominant species of potential ALP/ACP activities and P_(coll) content.Our findings provide a novel understanding of biochar reducing P_(coll) loss from the phosphatase perspective by regulating the phoD-and phoC-harboring communities during DRW events.展开更多
The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved....The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved.These investigations describe the fundamental characteristics of liquid flow boiling and further the complicated rewetting phenomena,and have resulted in considerable insight intothe mechanism.展开更多
During multi-jet cooling,the complex hydrodynamic characteristics caused by the interaction between jets will affect the heat transfer of the plate.To further clarify the heat transfer characteristics in different flo...During multi-jet cooling,the complex hydrodynamic characteristics caused by the interaction between jets will affect the heat transfer of the plate.To further clarify the heat transfer characteristics in different flow regions,the double-jet cooling experiments were completed on a 50-mm-thick plate with the initial cooling temperature and jet angle in the range of 300–900°C and 0°–60°,respectively.The inverse heat conduction was used to calculate the surface temperature and heat flux.Furthermore,the rewetting phenomenon,maximum heat flux and maximum cooling speed were studied.The results show that increasing the angle between jet and wall normal would increase the wetting front’s width downstream of the jet point.When the jet angle was 60°,the maximum value increased by 37.29 mm compared with that when the angle was 0.The correlation between the width of the wetting front and the radial temperature gradient was further confirmed.In addition,it was found that the maximum heat flux would be affected by the duration of transition boiling,but not affected by complete wetting time.The results clarified the heat transfer mechanisms under various initial cooling temperature and inclination angle conditions on plate cooling in different flow regions,and provided valuable data for controlling heat transfer efficiency and improving cooling uniformity.展开更多
Improved wet pressing reduces the need for drying and consequently energy needed in papermaking. Accordingly, it is desirable to optimize wet pressing, but the process is very complex with many interacting variables. ...Improved wet pressing reduces the need for drying and consequently energy needed in papermaking. Accordingly, it is desirable to optimize wet pressing, but the process is very complex with many interacting variables. It is therefore desirable to employ a mathematical model that accounts for the major variables to estimate the effects of changes in equipment and operating variables. This paper descibes such a model called the Decreasing Permeability Model (DPM). Mill and pilot plant applications over a wide range of basis weights for paper and paper board are described.展开更多
Background The Zoige Plateau hosts the largest alpine peatland in the world,playing a crucial role in carbon sequestration and biodiversity conservation.However,this valuable ecosystem has been significantly impacted ...Background The Zoige Plateau hosts the largest alpine peatland in the world,playing a crucial role in carbon sequestration and biodiversity conservation.However,this valuable ecosystem has been significantly impacted by anthropogenic drainage for various purposes,prompting increased interests in ecological restoration efforts.This study evaluates changes in plant diversity,community composition,and biomass allocation across natural,drained,and rewetted peatlands,with a particular focus on variations in microtopography,including hollows and hummocks.Results Restoration showed significantly higher soil water content,which was 11.6%higher in hollows(to 88.5±0.09%)and 14.4%higher in hummocks(to 81.1±1.6%)of rewetted peatlands compared to natural peatlands(p<0.001).However,the water table depth did not differ significantly from that of natural peatlands(p=0.61).While peatland management did not significantly affect plant diversity,microtopography had a considerable impact on plant species richness,dominance,the Shannon-Wiener index,and evenness.Conversely,plant community com-position exhibited significant differences among natural,drained,and rewetted peatlands at both hollow and hum-mock microsites.Aboveground biomass was significantly higher in drained and rewetted peatlands compared to natural peatlands at both microsites,whereas belowground biomass was significantly lower in drained and rewet-ted peatlands,particularly in hummocks.Conclusions Rewetting raises water table depth but does not fully restore the original plant community compo-sition or biomass.Microtopography plays a vital role in influencing plant diversity and community composition,with hummocks showing greater resilience to drainage impacts.Our findings emphasize ecological consequences of peatland management practices and highlight the need for targeted restoration strategies to strengthen the resil-ience of these vital ecosystems.展开更多
An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potat...An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potato and radish were used as the testing materials. The results show that the sliced materials can be fluidised well in the centrifugal fluidized bed. The fiuidized curve has a maximum value and the critical fiuidised velocities Vary with the type of the test material, its shape and dimension as well as operating parameters. The sliced food materials can be dried very well and fast in the ceotrifugal fiuidised bed with a large productivity. The factors that influence the drying process were examined and discussed. The final shape and inner structure of the dried products were observed.The water recovery characteristics of the dried products were also investigated.展开更多
基金financially supported by the National Science Foundation of China (Nos. 51221892 and 41025004)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB15020200)
文摘Dry–rewetting（DW） disturbance frequently occurs in soils due to rainfall and irrigation, and the frequency of DW cycles might exert significant influences on soil microbial communities and their mediated functions. However, how microorganisms respond to DW alternations in soils with a history of heavy metal pollution remains largely unknown.Here, soil laboratory microcosms were constructed to explore the impacts of ten DW cycles on the soil microbial communities in two contrasting soils（fluvo-aquic soil and red soil）under three copper concentrations（zero, medium and high）. Results showed that the fluctuations of substrate induced respiration（SIR） decreased with repeated cycles of DW alternation. Furthermore, the resistance values of substrate induced respiration（RS-SIR）were highest in non-copper-stressed（zero） soils. Structural equation model（SEM） analysis ascertained that the shifts of bacterial communities determined the changes of RS-SIR in both soils. The rate of bacterial community variance was significantly lower in noncopper-stressed soil compared to the other two copper-stressed（medium and high） soils,which might lead to the higher RS-SIR in the fluvo-aquic soil. As for the red soil, the substantial increase of the dominant group WPS-2 after DW disturbance might result in the low RS-SIR in the high copper-stressed soil. Moreover, in both soils, the bacterial diversity was highest in non-copper-stressed soils. Our results revealed that initial copper stress could decrease the resistance of soil microbial community structure and function to subsequent DW disturbance.
基金This work was financially supported by the‘Hundred-talent Project’of the Chinese Academy of Sciences(A315021407).
文摘Climate change alters the intensity and frequency of drought and rewetting(D/W)events;however,the influence patterns of D/W on soil N_(2)O efflux in the water-limited area were not fully understood.Therefore,the impacts of D/W cycles varying in different extent of rewetting and frequency to N_(2)O efflux in two kinds of soil on the Loess Plateau were investigated.The incubation conditions consisted of 1)D/W treatments with four 7-day cycles from 10%water holding capacity(WHC)to 60%WHC or 90%WHC,2)constant moisture of 60%WHC and 90%WHC.The pulse of N_(2)O efflux rate under 10-60%WHC treatment was higher than that under 10-90%WHC treatment in calcic cambisols,while opposite trend was observed in earth-cumuli-orthic anthrosols.Meanwhile,the pulse of N_(2)O efflux rate decreased as cycle number increased for different wetting intensities and soil types.The direct N_(2)O efflux under 10-60%WHC and 10-90%WHC treatments were 5.49 and 1.89μg N_(2)O-N g^(-1)soil in calcic cambisols,with those being 1.92 and 10.85μg N_(2)O-N g^(-1)soil in earth-cumuli-orthic anthrosols,respectively.The N loss in earth-cumuli-orthic anthrosols was approximately 5.74 times greater than that in calcic cambisols under 10-90%WHC treatment,whereas the N loss under 10-60%WHC treatment was about 2.86 times greater in calcic cambisols than that in earth-cumuli-orthic anthrosols.This study suggested that extreme rainfall events can enhance the N_(2)O efflux and N loss in agricultural soils on the Loess Plateau in terms of soil type and wetting intensity,which should not be ignored in the N fertilizer management.
文摘: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in the dark at night. After rewetting in the dark, photochemical activity and the structure of photosystem (PS) II were not recovered at all; the structure of PSI, energy transfer in phycobilisomes, and energy transfer from phycobilisomes to PSI were recovered within 5 min, as in the light. The recovery of energy transfer from phycobilisomes to PSII was light dependent and energy transfer from phycobilisomes to PSII was only partially recovered in the dark. These results suggest that the two-trigger control (water and light) of photo synthetic recovery may make N. flagelliforme avoid unnecessary energy consumption and, at the same time, the partial recovery of energy transfer from phycobilisomes to PSII in the dark could help N. flagelliforme accumulate more photosynthetic products during the transient period of rehydration-dehydration.
基金National Natural Science Foundation of China(42277005,22076163)Key Research and Development Project of Science and Technology Department of Zhejiang Province(2023C02016,2023C02019)Bingtuan Science and Technology Program(2021DB019).
文摘Drying and rewetting(DRW)events cause the release of colloidal phosphorus(P_(coll),1-1000 nm)in leachate,and biochar is considered an effective inhibitor;however,the microbial mechanism remains elusive.In this study,three successive DRW cycles were performed on the soil columns to assess the effect of biochar addition on P_(coll) content and its possible associates,including phosphatase-producing microbial populations(phoD- and phoC-harboring microbial communities)and alkaline/acid phosphatase(ALP/ACP)activities.Results showed that the biochar addition significantly decreased the P_(coll) by 15.5-32.1%during three DRW cycles.The structural equation model(SEM)confirmed that biochar addition increased phoD- and phoC-harboring microbial communities and ALP/ACP activities,which reduces the release of P_(coll) into leachate.In addition,the manure biochar was more effective than the straw biochar in promoting competition and cooperation in the co-occurrence network(2-5%nodes increased on average),and the key taxa Proteobacteria and Cyanobacteria were identified as the dominant species of potential ALP/ACP activities and P_(coll) content.Our findings provide a novel understanding of biochar reducing P_(coll) loss from the phosphatase perspective by regulating the phoD-and phoC-harboring communities during DRW events.
基金Project supported by the National Natural Science Foundation of Chinaalso by NSFNASA of U.S.
文摘The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved.These investigations describe the fundamental characteristics of liquid flow boiling and further the complicated rewetting phenomena,and have resulted in considerable insight intothe mechanism.
基金the National Key Research and Development Programs of China(Grant No.2017YFB0305102).
文摘During multi-jet cooling,the complex hydrodynamic characteristics caused by the interaction between jets will affect the heat transfer of the plate.To further clarify the heat transfer characteristics in different flow regions,the double-jet cooling experiments were completed on a 50-mm-thick plate with the initial cooling temperature and jet angle in the range of 300–900°C and 0°–60°,respectively.The inverse heat conduction was used to calculate the surface temperature and heat flux.Furthermore,the rewetting phenomenon,maximum heat flux and maximum cooling speed were studied.The results show that increasing the angle between jet and wall normal would increase the wetting front’s width downstream of the jet point.When the jet angle was 60°,the maximum value increased by 37.29 mm compared with that when the angle was 0.The correlation between the width of the wetting front and the radial temperature gradient was further confirmed.In addition,it was found that the maximum heat flux would be affected by the duration of transition boiling,but not affected by complete wetting time.The results clarified the heat transfer mechanisms under various initial cooling temperature and inclination angle conditions on plate cooling in different flow regions,and provided valuable data for controlling heat transfer efficiency and improving cooling uniformity.
文摘Improved wet pressing reduces the need for drying and consequently energy needed in papermaking. Accordingly, it is desirable to optimize wet pressing, but the process is very complex with many interacting variables. It is therefore desirable to employ a mathematical model that accounts for the major variables to estimate the effects of changes in equipment and operating variables. This paper descibes such a model called the Decreasing Permeability Model (DPM). Mill and pilot plant applications over a wide range of basis weights for paper and paper board are described.
基金The National Natural Science Foundation of China(32241035,32471767)the“Kezhen-Bingwei”Young Talents(2022RC004)
文摘Background The Zoige Plateau hosts the largest alpine peatland in the world,playing a crucial role in carbon sequestration and biodiversity conservation.However,this valuable ecosystem has been significantly impacted by anthropogenic drainage for various purposes,prompting increased interests in ecological restoration efforts.This study evaluates changes in plant diversity,community composition,and biomass allocation across natural,drained,and rewetted peatlands,with a particular focus on variations in microtopography,including hollows and hummocks.Results Restoration showed significantly higher soil water content,which was 11.6%higher in hollows(to 88.5±0.09%)and 14.4%higher in hummocks(to 81.1±1.6%)of rewetted peatlands compared to natural peatlands(p<0.001).However,the water table depth did not differ significantly from that of natural peatlands(p=0.61).While peatland management did not significantly affect plant diversity,microtopography had a considerable impact on plant species richness,dominance,the Shannon-Wiener index,and evenness.Conversely,plant community com-position exhibited significant differences among natural,drained,and rewetted peatlands at both hollow and hum-mock microsites.Aboveground biomass was significantly higher in drained and rewetted peatlands compared to natural peatlands at both microsites,whereas belowground biomass was significantly lower in drained and rewet-ted peatlands,particularly in hummocks.Conclusions Rewetting raises water table depth but does not fully restore the original plant community compo-sition or biomass.Microtopography plays a vital role in influencing plant diversity and community composition,with hummocks showing greater resilience to drainage impacts.Our findings emphasize ecological consequences of peatland management practices and highlight the need for targeted restoration strategies to strengthen the resil-ience of these vital ecosystems.
文摘An experimental investigation on the fluidization and drying characteristics of sliced food products in a centrifugal fluidized bed dryer was carried out. The rotating speed ranges from 300 rpm to 500 rpm.Sliced potato and radish were used as the testing materials. The results show that the sliced materials can be fluidised well in the centrifugal fluidized bed. The fiuidized curve has a maximum value and the critical fiuidised velocities Vary with the type of the test material, its shape and dimension as well as operating parameters. The sliced food materials can be dried very well and fast in the ceotrifugal fiuidised bed with a large productivity. The factors that influence the drying process were examined and discussed. The final shape and inner structure of the dried products were observed.The water recovery characteristics of the dried products were also investigated.
