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Aerosols' influence on the interplay between condensation, evaporation and rain in warm cumulus cloud
O. Altaratz, I. Koren, T. Reisin, A. Kostinski, G. Feingold, Z. Levin,Y. Yin
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: A numerical cloud model is used to study the influence of aerosol on the microphysics and dynamics of moderate-sized, coastal, convective clouds that develop under the same meteorological conditions. The results show that polluted convective clouds start their precipitation later and precipitate less than clean clouds but produce larger rain drops. The evaporation process is more significant at the margins of the polluted clouds (compared to the clean cloud) due to a higher drop surface area to volume ratio and it is mostly from small drops. It was found that the formation of larger raindrops in the polluted cloud is due to a more efficient collection process.
Aerosols' influence on the interplay between condensation, evaporation and rain in warm cumulus cloud  [PDF]
O. Altaratz,I. Koren,T. Reisin,A. Kostinski
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: A numerical cloud model is used to study the influence of aerosol on the microphysics and dynamics of moderate-sized, coastal, convective clouds that develop under the same meteorological conditions. The results show that polluted convective clouds start their precipitation later and precipitate less than clean clouds but produce larger rain drops. The evaporation process is more significant at the margins of the polluted clouds (compared to the clean cloud) due to a higher drop surface area to volume ratio and it is mostly from small drops. It was found that the formation of larger raindrops in the polluted cloud is due to a more efficient collection process.
A modeling approach to evaluate the uncertainty in estimating the evaporation behaviour and volatility of organic aerosols  [PDF]
E. Fuentes,G. McFiggans
Atmospheric Measurement Techniques Discussions , 2011, DOI: 10.5194/amtd-4-6723-2011
Abstract: In this study a kinetic evaporation-condensation model was applied to assess the uncertainty in determining the volatility behaviour of organic particles from thermodenuder experiments, at conditions relevant to both ambient and laboratory measurements. A comprehensive theoretical parametric analysis showed that re-condensation in thermodenuder experiments is highly case-dependent, being strongly determined by the combined effects of aerosol mass loading, particle size and the kinetics of condensation. Because of this dependence it is possible to find cases with either negligible or significant levels of re-condensation at high organic mass loadings, thus accounting for the diverging degrees of re-condensation reported in previous experimental and modeling studies. From this analysis it was concluded that gas denudation should generally be applied in experiments with aerosol mass loading >30 μg m 3. However, thermograms may be lowered in the region below 45 °C as a result of the evaporation induced by denuders for compounds with saturation concentration C* > 1 μg m 3. A calibration curve relating C* (saturation concentration) and T50 (temperature at which 50% of aerosol mass evaporates) was theoretically derived and tested to infer volatility distributions from experimental thermograms. While this approach was found to hold at equilibrium, significant underestimation of the particle volatility was found under kinetically-controlled evaporation conditions. Because thermograms obtained at ambient aerosol loading levels are most likely to show departure from equilibrium, the application of a kinetic evaporation model is more suitable for inferring volatility properties of atmospheric samples than the calibration curve approach; however, this method implies significant uncertainty, due to the sensitivity of the kinetic model to the assumption of "effective" accommodation coefficient. Predictions of the evaporation-condensation behaviour of α-pinene SOA exhibited a large uncertainty in estimating the aerosol mass formation induced by cooling, depending on whether it was assumed that gas condensation was affected by the amorphous solid state of the particles. Evaluation of the dilution-induced evaporation of α-pinene SOA showed that the equilibrium partitioning theory underpredicts the aerosol mass concentration by a factor of between 5 and 10, with respect to kinetic calculations. Analysis in this study suggests that, the mass transfer kinetic coefficient, inclusive of diffusive kinetic limitations, is a critical unknown to both estimating the volatility pro
A modeling approach to evaluate the uncertainty in estimating the evaporation behaviour and volatility of organic aerosols
E. Fuentes ,G. McFiggans
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2012,
Abstract: The uncertainty in determining the volatility behaviour of organic particles from thermograms using calibration curves and a kinetic model has been evaluated. In the analysis, factors such as re-condensation, departure from equilibrium and analysis methodology were considered as potential sources of uncertainty in deriving volatility distribution from thermograms obtained with currently used thermodenuder designs. The previously found empirical relationship between C* (saturation concentration) and T50 (temperature at which 50% of aerosol mass evaporates) was theoretically interpreted and tested to infer volatility distributions from experimental thermograms. The presented theoretical analysis shows that this empirical equation is in fact an equilibrium formulation, whose applicability is lessened as measurements deviate from equilibrium. While using a calibration curve between C* and T50 to estimate volatility properties was found to hold at equilibrium, significant underestimation was obtained under kinetically-controlled evaporation conditions. Because thermograms obtained at ambient aerosol loading levels are most likely to show departure from equilibrium, the application of a kinetic evaporation model is more suitable for inferring volatility properties of atmospheric samples than the calibration curve approach; however, the kinetic model analysis implies significant uncertainty, due to its sensitivity to the assumption of "effective" net kinetic evaporation and condensation coefficients. The influence of re-condensation on thermograms from the thermodenuder designs under study was found to be highly dependent on the particular experimental condition, with a significant potential to affect volatility estimations for aerosol mass loadings >50 μg m 3 and with increasing effective kinetic coefficient for condensation and decreasing particle size. These results show that the geometry of current thermodenuder systems should be modified to prevent re-condensation.
Organics in environmental ices: sources, chemistry, and impacts
V. F. McNeill, A. M. Grannas, J. P. D. Abbatt, M. Ammann, P. Ariya, T. Bartels-Rausch, F. Domine, D. J. Donaldson, M. I. Guzman, D. Heger, T. F. Kahan, P. Klán, S. Masclin, C. Toubin,D. Voisin
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: The physical, chemical, and biological processes involving organics in ice in the environment impact a number of atmospheric and biogeochemical cycles. Organic material in snow or ice may be biological in origin, deposited from aerosols or atmospheric gases, or formed chemically in situ. In this manuscript, we review the current state of knowledge regarding the sources, properties, and chemistry of organic materials in environmental ices. Several outstanding questions remain to be resolved and fundamental data gathered before an accurate model of transformations and transport of organic species in the cryosphere will be possible. For example, more information is needed regarding the quantitative impacts of chemical and biological processes, ice morphology, and snow formation on the fate of organic material in cold regions. Interdisciplinary work at the interfaces of chemistry, physics and biology is needed in order to fully characterize the nature and evolution of organics in the cryosphere and predict the effects of climate change on the Earth's carbon cycle.
Role of Oxidants and Anti Oxidants in Patients with Cardiovascular Diseases  [cached]
Ujjwala Jayant kulkarni,Seema L. Jaw alekar; Vasant T. Surve and Y.A. Deshmukh
Asian Journal of Medical Sciences , 2010,
Abstract: Over the last two decades, it has become increasingly clear that reactive oxygen species (ROS), including free radicals are involved in cardiovascular diseases. In recent years, there has been a growing interest in the clinical implications of these oxidants. The ROS are common by-products of many oxidative biochemical and physiological processes. Therefore the present study was carried out to evaluate the total antioxidant capacity, lipid peroxidation and status of superoxide dismutase in patients with cardiovascular diseases. Total 185 patients of both sexes were included in the study and further classified into 3 groups as hypertensive, Ischemic heart disease and cerebrovascular disease/stroke. The 60 healthy subjects who were not on any kind of prescribed medication or dietary restrictions were included in the control group. MDA is estimated as a marker of lipid peroxidation, levels were significantly increased in all groups than controls (p<0.001). Superoxide dismutase and glutathione reductase activities was significantly low er in all groups than control (p<0.001), GPX levels were decreased in all groups except hypertension (p<0.001), NO level were decreased in all the groups except cerebrovascular disease / stroke when compared to the control. Significantly lower level of total antioxidant capacity and prominent scavenger of superoxide anion radicals suggests that failure of antioxidant defense mechanism against oxidative stress may be an important factor in the pathogenesis of cardiovascular diseases.
Effects of aerosol organics on cloud condensation nucleus (CCN) concentration and first indirect aerosol effect
J. Wang, Y.-N. Lee, P. H. Daum, J. Jayne,M. L. Alexander
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Aerosol microphysics, chemical composition, and CCN properties were measured on the Department of Energy Gulfstream-1 aircraft during the Marine Stratus/Stratocumulus Experiment (MASE) conducted over the coastal waters between Point Reyes National Seashore and Monterey Bay, California, in July 2005. Aerosols measured during MASE included free tropospheric aerosols, marine boundary layer aerosols, and aerosols with high organic concentration within a thin layer above the cloud. Closure analysis was carried out for all three types of aerosols by comparing the measured CCN concentrations at ~0.2% supersaturation to those predicted based on size distribution and chemical composition using K hler theory. The effect of aerosol organic species on predicted CCN concentration was examined using a single hygroscopicity parameterization. For aerosols with organics volume fraction up to 70%, such as the marine boundary layer and free troposphere aerosols, CCN concentration and the corresponding first indirect aerosol effect are insensitive to the properties of organics, and can be accurately predicted with a constant hygroscopicity for all organic species. This simplification can facilitate the prediction of indirect aerosol effects using physically-based parameterizations in large scale models. However, for the aerosols within the thin layers above clouds, organics contributed up to 90% of the total aerosol volume, and an accurate knowledge of the overall organic hygroscopicity is required to accurately predict CCN concentrations. Derivations of organic properties in future closure studies, when aerosols are dominated by organic species, would help constrain the descriptions of organics and aerosol-cloud parameterizations in large scale models.
Effects of aerosol organics on cloud condensation nucleus (CCN) concentration and first indirect aerosol effect  [PDF]
J. Wang,Y.-N. Lee,P. H. Daum,J. Jayne
Atmospheric Chemistry and Physics Discussions , 2008,
Abstract: Aerosol microphysics, chemical composition, and CCN properties were measured on the Department of Energy Gulfstream-1 aircraft during the Marine Stratus/Stratocumulus Experiment (MASE) conducted over the coastal waters between Point Reyes National Seashore and Monterey Bay, California, in July 2005. Aerosols measured during MASE included free tropospheric aerosols, marine boundary layer aerosols, and aerosols with high organic concentration within a thin layer above the cloud. Closure analysis was carried out for all three types of aerosols by comparing the measured CCN concentrations at 0.22% supersaturation to those predicted based on size distribution and chemical composition using K hler theory. The effect of aerosol organic species on predicted CCN concentration was examined using a single hygroscopicity parameterization. For aerosols with organics volume fraction up to 70%, such as the marine boundary layer and free troposphere aerosols, CCN concentration and the corresponding first indirect aerosol effect are insensitive to the properties of organics, and can be accurately predicted with a constant hygroscopicity for all organic species. This simplification can facilitate the prediction of indirect aerosol effects using physically-based parameterizations in large scale models. However, for the aerosols within the thin layers above clouds, organics contributed up to 90% of the total aerosol volume, and a detailed knowledge of organic hygroscopicity is required to accurately predict CCN concentrations. Derivations of organic properties in future closure studies, when aerosols are dominated by organic species, would help constrain the descriptions of organics and aerosol-cloud parameterizations in large scale models.
Oxidants and Anti-Oxidants in Turbot Seminal Plasma and Their Effects on Sperm Quality Oxidants and Anti-Oxidants in Turbot Seminal Plasma and Their Effects on Sperm Quality  [PDF]
HAN Mingming,DING Fuhong,MENG Zhen,LEI Jilin
- , 2015,
Abstract: In this research, the concentration and activity of oxidants and anti-oxidants in turbot semen, and their effects on sperm quality were studied. The results showed that superoxide dismutase(SOD), catalase, glutathione reductase(GR), uric acid, vitamin E(VE) and vitamin C(VC) were more abundant in seminal plasma than in spermatozoa. The variation for each of them was specific. In seminal plasma, the activity of SOD and GR increased from November 15, November 30 to December 15, and then decreased on December 30. The concentrations of both VC and uric acid decreased during the first 3 sampling times and increased on December 30. The oxidants in seminal plasma accumulated to the highest on December 30. Lactic acid(LA) and ATP levels decreased to the lowest on December 30. The correlation analysis showed that GR had the significant positive relevance to sperm motility and VSL/VCL, while ·OH had negative relevance to them
Organics in the Northeastern Pacific and their impacts on aerosol hygroscopicity in the subsaturated and supersaturated regimes
K. C. Kaku, D. A. Hegg, D. S. Covert, J. L. Santarpia, H. Jonsson, G. Buzorius,D. R. Collins
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2006,
Abstract: Aerosol samples were collected by aircraft during the summer of 2004 in the Northeastern Pacific and compared to measurements of aerosol hygroscopicity. Chemical speciation analyses of the samples revealed that a significant portion of the marine aerosols was organic, and on average 8% of the total aerosol mass was insoluble organic material, tentatively attributed to natural marine emissions. Two chemical models were explored in an attempt to achieve closure between the marine aerosol chemical and physical properties through reproduction of the observed aerosol growth, both in the subsaturated and supersaturated regimes. Results suggest that at subsaturated relative humidities, the nonideal behavior of water activity with respect to aerosol chemistry has an important effect on aerosol growth. At supersaturations, the underprediction of critical supersaturations by all models suggests the hypothesis that formation of a complete monolayer by the insoluble organics may inhibit the activation of aerosols to form cloud droplets.
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