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Multiple sclerosis is at a checkpoint: advancing the program

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Neural Regeneration Research 2025年第3期20卷 811-812页

作者： Brandon C.Smith Jessica L.Williams department of Neurosciences Lerner Research InstituteCleveland ClinicClevelandOHUSA department of Biological Geologicaland Environmental SciencesCleveland State UniversityClevelandOHUSA

Multiple sclerosis(MS) is a chronic inflammatory and demyelinating disease of the central nervous system(CNS). Patients with MS experience sensory and motor function loss due to myelin and/or axon damage perpetuated b... 详细信息

关键词： Hauser sclerosis damage

Heat Flux Apportionment to Heterogeneous Surfaces Using Flux Footprint Analysis

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Advances in atmospheric sciences 2008年第1期25卷 107-116页

作者：彭谷亮蔡旭晖张宏升李爱国胡非 Monique Y.LECLERC department of environmental sciences Peking University department of atmospheric sciences Peking University State Key Laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Science Laboratory for environmental Physics University of Georgia

Heat flux data collected from the Baiyangdian Heterogeneous Field Experiment were analyzed using the footprint method. High resolution （25 m） Landsat-5 satellite imaging was used to determine the land cover as one of four surface types： farmland, lake, wetland, or village. Data from two observation sites in September 2005 were used. One site （Wangjiazhai） was characterized by highly heterogeneous surfaces in the central area of the Baiyangdian： lake/wetland. The other site （Xiongxian） was on land with more uniform surface cover. An improved Eulerian analytical flux footprint model was used to determine “source areas” of the heat fluxes measured at towers located at each site from surrounding landscapes of mixed surface types. In relative terms results show that wetland and lake areas generally contributed most to the observed heat flux at Wangjiazhai, while farmland contributed most at Xiongxian. Given the areal distribution of surface type contributions, calculations were made to obtain the magnitudes of the heat flux from lake, wetland and farmland to the total observed flux and apportioned contributions of each surface type to the sensible and latent heat fluxes. Results show that on average the sensible heat flux from wetland and farmland were comparable over the diurnal cycle, while the latent heat flux from farmland was somewhat larger by about 30-50 W m-2 during daytime. The latent and sensible fluxes from the lake source in daytime were about 50 W m-2 and 100 W m-2 less, respectively, than from wetland and farmland. The results are judged reasonable and serve to demonstrate the potential for flux apportionment over heterogeneous surfaces.

关键词： Eulerian analytical model flux footprint heat flux heterogeneous surface

Origin of high particle number concentrations reaching the St. Louis, Midwest Supersite

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Journal of environmental sciences 2015年第8期27卷 219-231页

作者： Benjamin de Foy James J.Schauer department of Earth and atmospheric sciences Saint Louis University Civil and environmental Engineering University of Wisconsin

Ultrafine particles are associated with adverse health effects. Total Particle Number Concentration（TNC） of fine particles were measured during 2002 at the St. Louis — Midwest supersite. The time series showed overall low level with frequent large peaks. The time series was analyzed alongside criteria pollutant measurements and meteorological observations. Multiple regression analysis was used to identify further contributing factors and to determine the association of different pollutants with TNC levels. This showed the strong contribution of sulfur dioxide（SO2） and nitrogen oxides（NO x） to high TNC levels. The analysis also suggested that increased dispersion resulting from faster winds and higher mixing heights led to higher TNC levels. Overall, the results show that there were intense particle nucleation events in a SO2 rich plume reaching the site which contributed around 29% of TNC. A further 40% was associated with primary emissions from mobile sources. By separating the remaining TNC by time of day and clear sky conditions,we suggest that most likely 8% of TNC are due to regional nucleation events and 23% are associated with the general urban background.

关键词： atmospheric aerosols Particle number concentrations Fine particles Sulfur dioxide plumes Mobile source emissions

Wall losses of oxygenated volatile organic compounds from oxidation of toluene:Effects of chamber volume and relative humidity

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Journal of environmental sciences 2022年第4期34卷 475-484页

作者： Shanshan Yu Long Jia Yongfu Xu Hailiang Zhang Qun Zhang Yuepeng Pan State Key Laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China department of atmospheric Chemistry and environmental sciences College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China

Vapor wall losses can affect the yields of secondary organic *** effects of surfaceto-volume(S/V)ratio and relative humidity(RH)on the vapor-wall interactions were investigated in this *** oxygenated volatile organic compounds(OVOCs)were generated from toluene-H_(2)O_(2)*** average gas to wall loss rate constant(k_(gw))of OVOCs in a 400 L reactor(S/V=7.5 m^(-1))is 2.47(2.41 under humid conditions)times higher than that in a 5000 L reactor(S/V=3.6 m-1)under dry *** contrast,the average desorption rate constant(k_(wg))of OVOCs in 400 L reactor is only 1.37(1.20 under humid conditions)times higher than that in 5000 L reactor under dry *** shows that increasing the S/V ratio can promote the wall losses of *** contrast,the RH effect on k_(gw)is not *** average k_(gw)value under humid conditions is almost the same as under dry conditions in the 400 L(5000 L)***,increasing RH can decrease the desorption *** average k_(wg)value under dry conditions is 1.45(1.27)times higher than that under humid conditions in the 400 L(5000 L)*** high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.

关键词： Vapor wall loss Surface-to-volume ratio Relative humidity Toluene Smog chamber Oxygenated volatile organic compounds

Effects of Street-Bottom and Building-Roof Heating on Flow in Three-Dimensional Street Canyons

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Advances in atmospheric sciences 2010年第3期27卷 513-527页

作者： Jae-Jin KIM Jong-Jin BAIK department of environmental atmospheric sciences Pukyong National University School of Earth and environmental sciences Seoul National University

Using a computational fluid dynamics （CFD） model, the effects of street-bottom and building-roof heating on flow in three-dimensional street canyons are investigated. The building and street-canyon aspect ratios are one. In the presence of street-bottom heating, as the street-bottom heating intensity increases, the mean kinetic energy increases in the spanwise street canyon formed by the upwind and downwind buildings but decreases in the lower region of the streamwise street canyon. The increase in momentum due to buoyancy force intensifies mechanically induced flow in the spanwise street canyon. The vorticity in the spanwise street canyon strengthens. The temperature increase is not large because relatively cold above-roof-level air comes into the spanwise street canyon. In the presence of both street-bottom and building-roof heating, the mean kinetic energy rather decreases in the spanwise street canyon. This is caused by the decrease in horizontal flow speed at the roof level, which results in the weakening of the mean flow circulation in the spanwise street canyon. It is found that the vorticity in the spanwise street canyon weakens. The temperature increase is relatively large compared with that in the street-bottom heating case, because relatively warm above-roof-level air comes into the spanwise street canyon.

关键词： street canyon flow CFD model street-bottom heating building-roof heating mean kineticenergy vorticity

Understanding unusually high levels of peroxyacetyl nitrate(PAN) in winter in Urban Jinan,China

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Journal of environmental sciences 2018年第9期30卷 249-260页

作者： Lu Liu Xinfeng Wang Jianmin Chen Likun Xue Wenxing Wang Liang Wen Dandan Li Tianshu Chen Environment Research Institute School of Environmental Science and EngineeringShandong University Shanghai Key Laboratory of atmospheric Particle Pollution and Prevention Department of Environmental Science and EngineeringInstitute of Atmospheric SciencesFudan University Institute for Climate and Global Change Research School of Atmospheric SciencesNanjing University

Peroxyacetyl nitrate （PAN）, as a major secondary pollutant, has gained increasing worldwide attentions, but relevant studies in China are still quite limited. During winter of 2015 to summer of 2016, the ambient levels of PAN were measured continuously by an automatic gas chromatograph equipped with an electron capture detector （GC-ECD） analyzer at an urban site in Jinan （China）, with related parameters including concentrations of 03, NO, NO2, PM2.5, HONO, the photolysis rate constant of NO2 and meteorological factors observed concurrently. The mean and maximum values of PAN concentration were （1.89 ± 1.42） and 9.61 ppbv respectively in winter, and （2.54 ± 1.44） and 13.47 ppbv respectively in summer. Unusually high levels of PAN were observed during severe haze episodes in winter, and the formation mechanisms of them were emphatically discussed, Study showed that high levels of PAN in winter were mainly caused by local accumulation and strong photochemical reactions during haze episodes, while mass transport played only a minor role. Accelerated photochemical reactions （compared to winter days without haze） during haze episodes were deduced by the higher concentrations but shorter lifetimes of pAN, which was further supported by the sufficient solar radiation in the photolysis band along with the high concentrations of precursors （NO2, VOCs） and HONO during haze episodes. In addition, significant PAN accumulation during calm weather of haze episodes was verified by meteorological data.

关键词： Peroxyacetyl nitrate Winter Haze episodes North China Plain

Discrepancy and Applicability of Various Similarity Functions in Flux Calculations Under Stable Conditions

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Advances in atmospheric sciences 2007年第4期24卷 644-654页

作者：郭晓峰张宏升蔡旭晖康凌李万彪杜金林 department of atmospheric sciences School of PhysicsPeking UniversityBeijing 100871 department of environmental sciences Peking UniversityBeijing 100871

Based on data obtained during the Hualhe River Basin Experiment （HUBEX） in 1999, this study intends to detect the quantitative discrepancies in the momentum （τ0）, sensible heat （H0） and latent heat （E0） fluxes among six sets of similarity functions with the aerodynamic method. It also aims to clarify the applicability of the functions under stable conditions. The relative discrepancy was studied with the normalized transfer coefficients for τ0, H0 and E0, namely CD, CH and CQ, respectively. Except for one set of functions that adopted a rather small von Kármán＇s constant （0.365）, the relative discrepancy in τ0 among the other functions was less than 10%, while that in H0（E0） sometimes reached 25% when the bulk Richardson number （R/B） was less than 0.07. The absolute discrepancy in the fluxes was studied with statistical computations. Among the six sets of functions, the discrepancy in τ0, H0 and E0 sometimes reached 0.03 kg m^-1 s^-2, 4 W m^-2 and 10 W m^-2, respectively, and the discrepancy in the energy balance ratio sometimes exceeded 0.1. Furthermore, when RiB exceeded the critical value （Ric） for a specific set of functions, no fluxes could be derived with the functions. It is therefore suggested that RiB be compared with Ric before computing the fluxes if RiB is less than Ric. Finally, two sets of nonlinear similarity functions are recommended, due to their unlimited applicability in terms of RiB.

关键词： aerodynamic method turbulent flux surface layer similarity function energy balance

Impact of UV-A Radiation on Erythemal UV and UV-index Estimation over Korea

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Advances in atmospheric sciences 2015年第12期32卷 1639-1646页

作者： Sang Seo PARK Yun Gon LEE Jung Hyun KIM department of atmospheric sciences Yonsei University department of atmospheric sciences Chungnam National University

Because total UV （TUV） in the UV-A region is 100 times higher than in the UV-B region, UV-A is a considerable compo- nent when calculating erythemal UV （EUV） and UV-index. The ratio of EUV to TUV in the UV-A value [EUV（A）/TUV（A）] is investigated to convert the EUV（A） from TUV（A） for broadband observation. The representative value of EUV（A）/TUV（A）, from the simulation study, is 6.9 × 10^- 4 changing from 6.1 ×10^-4 to 7.0 × 10^ -4 as aerosol optical depth, total ozone and solar zenith angle change. By adopting the observational data of EUV（B） and TUV（A） from UV-biometer measurements at Yonsei University [（37.57°N, 126.95°E）, 84 m above sea level], the EUV irradiance increases to 15% of EUV（B） due to the consideration of EUV（A） from the data of TUV（A） observation. Compared to the total EUV observed from the Brewer spec- trophotometer at the same site, the EUV（B） from the UV-biometer observes only 95% of total EUV, and its underestimation is caused by neglecting the effect of UV-A. However, the sum of EUV（B） and EUV（A） [EUV（A＋B）] from two UV-biometers is 10% larger than the EUV from the Brewer spectrophotometer because of the spectral overlap effect in the range 320-340 nm. The correction factor for the overlap effect adjusts 8% of total EUV.

关键词： erythemal UV total UV UV-B UV-biometer

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

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Advances in atmospheric sciences 2021年第7期38卷 1238-1251页

作者： Hailiang ZHANG Yongfu XU Long JIA Min XU State Key Laboratory of atmospheric Boundary Layer Physics and atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China department of atmospheric Chemistry and environmental sciences College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China

Acetaldehyde is one of the important VOC species of O_(3)precursors in the atmospheric *** influences of relative humidity(RH)and initial VOC/NOx ratio(R_(CN))on the formation of O_(3)are studied in smog chamber experiments,and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental *** low-RH conditions(RH=11.6%±1.1%),the O_(3)concentration at 6 h increases first and then decreases with the increase of R_(CN),and the R_(CN)at the inflection point of O_(3)concentrations is *** high-RH experiments(RH=78.8%±1.0%),variation of the O_(3)concentration at 6 h with R_(CN)is similar to that in low-RH experiments,but the R_(CN)at the inflection point is *** has no significant effect on the O_(3)concentrations under low R_(CN)(3).Compared with the experimental results,original MCM v3.3.1 greatly underestimates the O_(3)*** of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO_(3)on the reactor surface into the original MCM can reduce the difference between the simulated O_(3)concentrations and the experimental results at 6 h from 24%−35%and 17%−49%to 6%−26%and 10%−42%under low-and high-RH conditions,*** maximum incremental reactivity(MIR)of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb−1 without considering the effect of other VOCs.

关键词： ozone acetaldehyde photochemical reaction MCM