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Articles 1 - 8 of 8

Full-Text Articles in Physics

New Particle Growth And Shrinkage Observed In Subtropical Environments, L. H. Young, Shan-Hu Lee, V. P. Kanawade, T-C. Hsiao, Y. L. Lee, B-F. Hwang, Y-J. Liou, H-T. Hsu, P-J. Tsai Jan 2013

New Particle Growth And Shrinkage Observed In Subtropical Environments, L. H. Young, Shan-Hu Lee, V. P. Kanawade, T-C. Hsiao, Y. L. Lee, B-F. Hwang, Y-J. Liou, H-T. Hsu, P-J. Tsai

Biostatistics, Environmental Health, and Epidemiology Publications

We present the first systematic analysis for new particle formation (NPF), growth and shrinkage of new particles at four different sites in subtropical central Taiwan. A total of 14 NPF events were identified from 137 days of ambient measurements during a cold and warm season. The measured formation rates of 10 nm particles (J10) and growth rates were in the range of 4.4–30 cm−3s−1 and 7.4–24 nm h−1, respectively. The onset of NPF events coincided with decreases of condensation sink (CS) and increases of SO2 under enhanced atmospheric mixing and ...


The Effect Of Trimethylamine On Atmospheric Nucleation Involving H2so4, M. E. Erupe, A. A. Viggiano, Shan-Hu Lee May 2011

The Effect Of Trimethylamine On Atmospheric Nucleation Involving H2so4, M. E. Erupe, A. A. Viggiano, Shan-Hu Lee

Biostatistics, Environmental Health, and Epidemiology Publications

Field observations and quantum chemical calculations have shown that organic amine compounds may be important for new particle formation involving H2SO4. Here, we report laboratory observations that investigate the effect of trimethylamine (TMA) on H2SO4-H2O nucleation made under aerosol precursor concentrations typically found in the lower troposphere ([H2SO4] of 106−107 cm−3; [TMA] of 180–1350 pptv). The threshold [H2SO4] needed to produce the unity J was from 106−107 cm−3 and the slopes of Log J vs. Log ...


Ternary Homogeneous Nucleation Of H2so4, Nh3, And H2o Under Conditions Relevant To The Lower Troposphere, D. R. Benson, J. H. Yu, A. Markovich, Shan-Hu Lee May 2011

Ternary Homogeneous Nucleation Of H2so4, Nh3, And H2o Under Conditions Relevant To The Lower Troposphere, D. R. Benson, J. H. Yu, A. Markovich, Shan-Hu Lee

Biostatistics, Environmental Health, and Epidemiology Publications

Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements of THN have failed to reproduce atmospheric observations. Here, we report first laboratory observations of THN made under conditions relevant to the lower troposphere ([H2SO4] of 106–107 cm−3, [NH3] of 0.08–20 ppbv, and a temperature of 288 K). Our observations show that NH3 can enhance atmospheric H2SO4aerosol nucleation and the enhancement factor (EF) in nucleation ...


Isoprene Suppression Of New Particle Formation In A Mixed Deciduous Forest, V. P. Kanawade, B. T. Jobson, A. B. Guenther, M. E. Erupe, S. N. Pressley, S. N. Tripathi, Shan-Hu Lee Jan 2011

Isoprene Suppression Of New Particle Formation In A Mixed Deciduous Forest, V. P. Kanawade, B. T. Jobson, A. B. Guenther, M. E. Erupe, S. N. Pressley, S. N. Tripathi, Shan-Hu Lee

Biostatistics, Environmental Health, and Epidemiology Publications

Production of new particles over forests is an important source of cloud condensation nuclei that can affect climate. While such particle formation events have been widely observed, their formation mechanisms over forests are poorly understood. Our observations made in a mixed deciduous forest with large isoprene emissions during the summer displayed a surprisingly rare occurrence of new particle formation (NPF). Typically, NPF events occur around noon but no NPF events were observed during the 5 weeks of measurements. The exceptions were two evening ultrafine particle events. During the day, sulfuric acid concentrations were in the 106 cm−3 range ...


Steady-State Aerosol Distributions In The Extra-Tropical, Lower Stratosphere And The Processes That Maintain Them, J. C. Wilson, Shan-Hu Lee, J. M. Reeves, C. A. Brock, H. H. Jonsson, B. G. Lafleur, M. Loewenstein, J. Podolske, E. Atlas, K. Boering, G. Toon, D. Fahey, T. P. Bui, G. Diskin, F. Moore Nov 2008

Steady-State Aerosol Distributions In The Extra-Tropical, Lower Stratosphere And The Processes That Maintain Them, J. C. Wilson, Shan-Hu Lee, J. M. Reeves, C. A. Brock, H. H. Jonsson, B. G. Lafleur, M. Loewenstein, J. Podolske, E. Atlas, K. Boering, G. Toon, D. Fahey, T. P. Bui, G. Diskin, F. Moore

Biostatistics, Environmental Health, and Epidemiology Publications

Measurements of aerosol, N2O and OCS made in the Northern Hemisphere below 21 km altitude following the eruption of Pinatubo are presented and analyzed. After September 1999, the oxidation of OCS and sedimentation of particles in the extra-tropical overworld north of 45 N are found to maintain the aerosol in a steady state. This analysis empirically links precursor gas to aerosol abundance throughout this region. These processes are tracked with age-of-air which offers advantages over tracking as a function of latitude and altitude. In the extra-tropical, lowermost stratosphere, normalized volume distributions appear constant in time after the fall ...


The Effects Of Airmass History On New Particle Formation In The Free Troposphere: Case Studies, D. R. Benson, Li-Hao Young, Shan-Hu Lee, T. L. Campos, D. C. Rogers, J. Jensen Jan 2008

The Effects Of Airmass History On New Particle Formation In The Free Troposphere: Case Studies, D. R. Benson, Li-Hao Young, Shan-Hu Lee, T. L. Campos, D. C. Rogers, J. Jensen

Biostatistics, Environmental Health, and Epidemiology Publications

Recent aircraft studies showed that new particle formation (NPF) is very active in the free troposphere. And, these observations lead to a new question: when does NPF not occur? Here, we provide case studies to show how different meteorological parameters affect NPF in the upper troposphere, using the aerosol size distributions measured at latitudes from 18° N–52° N and altitudes up to 14 km during the NSF/NCAR GV Progressive Science Missions. About 95% of the total samples showed the NPF feature with median number concentrations of particles with diameters from 4 to 9 nm (N4–9), 288 ...


Laboratory Studies Of H2so4/H2o Binary Homogeneous Nucleation From The So2+Oh Reaction: Evaluation Of The Experimental Setup And Preliminary Results, L. H. Young, D. R. Benson, F. R. Kameel, J. R. Pierce, H. Junninen, M. Kulmala, Shan-Hu Lee Jan 2008

Laboratory Studies Of H2so4/H2o Binary Homogeneous Nucleation From The So2+Oh Reaction: Evaluation Of The Experimental Setup And Preliminary Results, L. H. Young, D. R. Benson, F. R. Kameel, J. R. Pierce, H. Junninen, M. Kulmala, Shan-Hu Lee

Biostatistics, Environmental Health, and Epidemiology Publications

Binary homogeneous nucleation (BHN) of sulphuric acid and water (H2SO4/H2O) is one of the most important atmospheric nucleation processes, but laboratory observations of this nucleation process are very limited and there are also large discrepancies between different laboratory studies. The difficulties associated with these experiments include wall loss of H2SO4 and uncertainties in estimation of H2SO4 concentration ([H2SO4]) involved in nucleation. We have developed a new laboratory nucleation setup to study H2SO4/H2O BHN kinetics and provide relatively constrained [H ...


The Elusive Thermotropic Biaxial Nematic Phase In Rigid Bent-Core Molecules, Bharat R. Acharya, Andrew Primak, Theo J. Dingemans, Edward T. Samulski, Satyendra Kumar Aug 2003

The Elusive Thermotropic Biaxial Nematic Phase In Rigid Bent-Core Molecules, Bharat R. Acharya, Andrew Primak, Theo J. Dingemans, Edward T. Samulski, Satyendra Kumar

Physics Publications

The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(p-hydroxyphenyl)-l,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D2h, in which the overall long axes of the molecules are oriented parallel to each other to define the major axis of ...