According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a d...According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a displacement analytical expression is solved under a certain pressure. The results are in good agreement with experimental data, showing the validity of the formula. Combined with the damage caused by noise in clinic, it is found that the hardening of outer hair cells and outer stereocilia can lead to loss of hearing and generation of threshold shift. In addition, the results show that high frequency resonance occurs at the bottom of the basilar membrane （BM）, and low frequency resonance occurs at the top of the BM. This confirms the frequency selective characteristics of the BM. Further, using this formula can avoid interference of the envi- ronment and the technical level of the test personnel, and can evaluate performance of the OC objectively.展开更多
In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells...In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells （OHCs）, and reticular lamina （RL） is established by COMSOL. An initial pressure is applied to the fluid in the TC. The frequency response of the structure is analyzed, and the displacement of the BM is achieved. The results are in good agreement with the experimental data, confirming validity of the finite element model. Based on the model, the effect of fluid in the TC on the OC is studied. The results show that, when the pressure gradient is absent in the fluid, with the increase of the initial fluid pressure, the displacement of the BM increases. However, when the initial fluid pressure increases to a certain value, the increase rate of the displacement of the BM becomes very slow. The movement of the fluid amplifies the BM movement. Furthermore, the movement of the fluid can strengthen the movement of the OHCs and the shear movement of the stereocilia, especially in the vicinity of the characteristic frequency at which the amplification effect reaches a peak. Nevertheless, a pressure gradient in the fluid affects the BM movement.展开更多
Carbonaceous components contribute significant fraction of fine particulate matter (PM2.5). Study of organic carbon (OC) and elemental carbon (EC) in PM2.5 may lead to better understanding of secondary organic carbon ...Carbonaceous components contribute significant fraction of fine particulate matter (PM2.5). Study of organic carbon (OC) and elemental carbon (EC) in PM2.5 may lead to better understanding of secondary organic carbon (SOC) formation. This year-long (December 2008 to December 2009) field study was conducted in an animal agriculture intensive area in North Carolina of United States. Samples of PM2.5 were collected from five stations located in an egg production facility and its vicinities. Concentrations of OC/EC and thermograms were obtained using a thermal-optical carbon analyzer. Average levels of OC in the egg production house and at ambient stations were 42.7 μg/m3 and 3.26 - 3.47 μg/m3, respectively. Average levels of EC in the house and at ambient stations were 1.14 μg/m3 and 0.36 - 0.42 μg/m3, respectively. The OC to total carbon (TC) ratios at ambient stations exceeded 0.67, indicating a significant fraction of SOC presented in PM2.5. Principal factor analysis results suggested that possible major source of in-house PM2.5 was from poultry feed and possible major sources of ambient PM2.5 was from contributions of secondary inorganic and organic PM. Using the OC/EC primary ratio analysis method, ambient stations SOC fractions ranged from 68% to 87%. These findings suggested that SOC could appreciably contribute to total PM2.5 mass concentrations in this agriculture intensive area.展开更多
Aerosols represent an important source of terrestrial organic carbon(OC)from the East Asian continent to the China marginal seas,thus their provenance and transport play important roles in the global carbon cycle.Fift...Aerosols represent an important source of terrestrial organic carbon(OC)from the East Asian continent to the China marginal seas,thus their provenance and transport play important roles in the global carbon cycle.Fifty samples of total suspended particle were collected seasonally from the nearshore Huaniao Island(HNI)in East China Sea(ECS)from April 2018 to January 2019;and they were analyzed for total organic carbon(TOC)content and stable carbon isotope(δ^(13)C),as well as terrestrial bio-markers including n-alkanes(C_(20)-C_(33)),n-alkanols(C_(20)-C32)and n-fatty acids(n-FAs,C_(20)-C30),to distinguish the seasonal variabili-ties of terrestrial OC sources and reveal the influence of the long-range air mass transport on these sources.The TOC-δ^(13)C values(range from−27.3‰to−24.3‰)and molecular distributions of terrestrial biomarkers both suggested that terrestrial OC contribu-tions to aerosols had significant seasonal variations.The source indices of terrestrial biomarkers(e.g.,Fossil%=82.8%for n-alkanes)revealed that the fossil fuel OC contributions,including coal burning and vehicular emission,were higher in winter,mainly because of the long-range air mass transport from the north of the East Asian continent.The terrestrial plant OC contributions were higher in summer(e.g.,Wax%=32.4%for n-alkanes),likely due to local vegetation sources from HNI and East Asian continental air masses.Cluster analysis of air mass backward-trajectories clearly showed that transport pathway plays an important role in determining the organic constituents of aerosols in China marginal seas.A comparison of these terrestrial OC contributions from different air mass origins suggested that fossil fuel OC showed less variations among various air mass origins from northern China in winter,while terrestrial plant OC sources from northern and southern China in summer contributed more than that from the air masses transported through the ECS.These results provided a basis for future quantification of terrestrial OC from different origins in marine aerosols,by combining biomarker index and carbon isotopes.展开更多
The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Gl...The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Glacier retreat is occurring in this region due to climate change,leading to an increase in meltwater outflow with a high debris content.In August 2017,we collected a sediment Core Z3 from the central fjord near the Yellow River Station.Then,we used the widely used chronology method of 210Pb,^(137)Cs,and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord.The results showed that after the mid-late 1990s,the mass accumulation rate of this core increased from 0.10 g/(cm^(2)·a)to 0.34 g/(cm^(2)·a),while the flux of^(210)Pb_(ex)increased from 125 Bq/(m^(2)·a)to 316 Bq/(m^(2)·a).The higher sedimentary inventory of^(210)Pb_(ex)in Kongsfjord compared to global fallout might have been caused by sediment focusing,boundary scavenging,and riverine input.Similarities between the inventory of^(137)Cs and global fallout indicated that terrestrial particulate matter was the main source of^(137)Cs in fjord sediments.The sedimentation rate increased after 1997,possibly due to the increased influx of glacial meltwater containing debris.In addition,the^(137)Cs activity,percentage of organic carbon(OC),and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997,corresponding to a decrease in the mass balance of glaciers in the region.The results ofδ^(13)C,δ^(15)N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3.The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s.All these data indicate that global climate change has a significant impact on Arctic glaciers.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11272200 and11572186)
文摘According to the vibration characteristics of the organ of Corti （OC）, seven hypotheses are made to simplify the structure of the model, and a mechanical OC model is established. Using the variational principle, a displacement analytical expression is solved under a certain pressure. The results are in good agreement with experimental data, showing the validity of the formula. Combined with the damage caused by noise in clinic, it is found that the hardening of outer hair cells and outer stereocilia can lead to loss of hearing and generation of threshold shift. In addition, the results show that high frequency resonance occurs at the bottom of the basilar membrane （BM）, and low frequency resonance occurs at the top of the BM. This confirms the frequency selective characteristics of the BM. Further, using this formula can avoid interference of the envi- ronment and the technical level of the test personnel, and can evaluate performance of the OC objectively.
基金Project supported by the National Natural Science Foundation of China(Nos.11272200 and 11572186)
文摘In this paper, the effect of fluid in a tunnel of Corti （TC） on organ of Corti （OC） is studied. A three-dimensional OC model including basilar membrane （BM）, tectorial membrane （TM）, inner and outer hair cells （OHCs）, and reticular lamina （RL） is established by COMSOL. An initial pressure is applied to the fluid in the TC. The frequency response of the structure is analyzed, and the displacement of the BM is achieved. The results are in good agreement with the experimental data, confirming validity of the finite element model. Based on the model, the effect of fluid in the TC on the OC is studied. The results show that, when the pressure gradient is absent in the fluid, with the increase of the initial fluid pressure, the displacement of the BM increases. However, when the initial fluid pressure increases to a certain value, the increase rate of the displacement of the BM becomes very slow. The movement of the fluid amplifies the BM movement. Furthermore, the movement of the fluid can strengthen the movement of the OHCs and the shear movement of the stereocilia, especially in the vicinity of the characteristic frequency at which the amplification effect reaches a peak. Nevertheless, a pressure gradient in the fluid affects the BM movement.
文摘Carbonaceous components contribute significant fraction of fine particulate matter (PM2.5). Study of organic carbon (OC) and elemental carbon (EC) in PM2.5 may lead to better understanding of secondary organic carbon (SOC) formation. This year-long (December 2008 to December 2009) field study was conducted in an animal agriculture intensive area in North Carolina of United States. Samples of PM2.5 were collected from five stations located in an egg production facility and its vicinities. Concentrations of OC/EC and thermograms were obtained using a thermal-optical carbon analyzer. Average levels of OC in the egg production house and at ambient stations were 42.7 μg/m3 and 3.26 - 3.47 μg/m3, respectively. Average levels of EC in the house and at ambient stations were 1.14 μg/m3 and 0.36 - 0.42 μg/m3, respectively. The OC to total carbon (TC) ratios at ambient stations exceeded 0.67, indicating a significant fraction of SOC presented in PM2.5. Principal factor analysis results suggested that possible major source of in-house PM2.5 was from poultry feed and possible major sources of ambient PM2.5 was from contributions of secondary inorganic and organic PM. Using the OC/EC primary ratio analysis method, ambient stations SOC fractions ranged from 68% to 87%. These findings suggested that SOC could appreciably contribute to total PM2.5 mass concentrations in this agriculture intensive area.
基金This study was supported by the National Natural Science Foundation of China(No.U1706219).This is MCTL(Key Laboratory of Marine Chemistry Theory and Technology)contribution#237.
文摘Aerosols represent an important source of terrestrial organic carbon(OC)from the East Asian continent to the China marginal seas,thus their provenance and transport play important roles in the global carbon cycle.Fifty samples of total suspended particle were collected seasonally from the nearshore Huaniao Island(HNI)in East China Sea(ECS)from April 2018 to January 2019;and they were analyzed for total organic carbon(TOC)content and stable carbon isotope(δ^(13)C),as well as terrestrial bio-markers including n-alkanes(C_(20)-C_(33)),n-alkanols(C_(20)-C32)and n-fatty acids(n-FAs,C_(20)-C30),to distinguish the seasonal variabili-ties of terrestrial OC sources and reveal the influence of the long-range air mass transport on these sources.The TOC-δ^(13)C values(range from−27.3‰to−24.3‰)and molecular distributions of terrestrial biomarkers both suggested that terrestrial OC contribu-tions to aerosols had significant seasonal variations.The source indices of terrestrial biomarkers(e.g.,Fossil%=82.8%for n-alkanes)revealed that the fossil fuel OC contributions,including coal burning and vehicular emission,were higher in winter,mainly because of the long-range air mass transport from the north of the East Asian continent.The terrestrial plant OC contributions were higher in summer(e.g.,Wax%=32.4%for n-alkanes),likely due to local vegetation sources from HNI and East Asian continental air masses.Cluster analysis of air mass backward-trajectories clearly showed that transport pathway plays an important role in determining the organic constituents of aerosols in China marginal seas.A comparison of these terrestrial OC contributions from different air mass origins suggested that fossil fuel OC showed less variations among various air mass origins from northern China in winter,while terrestrial plant OC sources from northern and southern China in summer contributed more than that from the air masses transported through the ECS.These results provided a basis for future quantification of terrestrial OC from different origins in marine aerosols,by combining biomarker index and carbon isotopes.
基金The National Natural Science Foundation of China under contract Nos 42107251 and 41706089the Natural Science Foundation of Fujian Province under contract No.2020J05232.
文摘The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Glacier retreat is occurring in this region due to climate change,leading to an increase in meltwater outflow with a high debris content.In August 2017,we collected a sediment Core Z3 from the central fjord near the Yellow River Station.Then,we used the widely used chronology method of 210Pb,^(137)Cs,and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord.The results showed that after the mid-late 1990s,the mass accumulation rate of this core increased from 0.10 g/(cm^(2)·a)to 0.34 g/(cm^(2)·a),while the flux of^(210)Pb_(ex)increased from 125 Bq/(m^(2)·a)to 316 Bq/(m^(2)·a).The higher sedimentary inventory of^(210)Pb_(ex)in Kongsfjord compared to global fallout might have been caused by sediment focusing,boundary scavenging,and riverine input.Similarities between the inventory of^(137)Cs and global fallout indicated that terrestrial particulate matter was the main source of^(137)Cs in fjord sediments.The sedimentation rate increased after 1997,possibly due to the increased influx of glacial meltwater containing debris.In addition,the^(137)Cs activity,percentage of organic carbon(OC),and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997,corresponding to a decrease in the mass balance of glaciers in the region.The results ofδ^(13)C,δ^(15)N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3.The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s.All these data indicate that global climate change has a significant impact on Arctic glaciers.
