Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 +/- 0.13 g cm(-3) and 1.62 +/- 0.38 g cm(-3) for PM1.8 and 1.73 +/- 0.14 g cm(-3) and 1.67 +/- 0.37 g cm(-3) for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 mu m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 mu m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.
Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 +/- 0.13 g cm(-3) and 1.62 +/- 0.38 g cm(-3) for PM1.8 and 1.73 +/- 0.14 g cm(-3) and 1.67 +/- 0.37 g cm(-3) for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 mu m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 mu m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.
Liu J, Liu C, Cole M, Belkin NJ, Zhang X. Exploring and predicting search task difficulty, in Proceedings of the 21st ACM international conference on Information and knowledge management.; 2012:1313–1322.
We performed measurements of nitrous acid (HONO) during the PRIDE-PRD2006 campaign in the Pearl River Delta region 60 km north of Guangzhou, China, for 4 weeks in June 2006. HONO was measured by a LOPAP in-situ instrument which was setup in one of the campaign supersites along with a variety of instruments measuring hydroxyl radicals, trace gases, aerosols, and meteorological parameters. Maximum diurnal HONO mixing ratios of 1–5 ppb were observed during the nights. We found that the nighttime build-up of HONO can be attributed to the heterogeneous NO2 to HONO conversion on ground surfaces and the OH + NO reaction. In addition to elevated nighttime mixing ratios, measured noontime values of ≈200 ppt indicate the existence of a daytime source higher than the OH + NO→HONO reaction. Using the simultaneously recorded OH, NO, and HONO photolysis frequency, a daytime additional source strength of HONO (PM) was calculated to be 0.77 ppb h−1 on average. This value compares well to previous measurements in other environments. Our analysis of PM provides evidence that the photolysis of HNO3 adsorbed on ground surfaces contributes to the HONO formation.
We performed measurements of nitrous acid (HONO) during the PRIDE-PRD2006 campaign in the Pearl River Delta region 60 km north of Guangzhou, China, for 4 weeks in June 2006. HONO was measured by a LOPAP in-situ instrument which was setup in one of the campaign supersites along with a variety of instruments measuring hydroxyl radicals, trace gases, aerosols, and meteorological parameters. Maximum diurnal HONO mixing ratios of 1-5 ppb were observed during the nights. We found that the nighttime build-up of HONO can be attributed to the heterogeneous NO2 to HONO conversion on ground surfaces and the OH + NO reaction. In addition to elevated nighttime mixing ratios, measured noontime values of approximate to 200 ppt indicate the existence of a daytime source higher than the OH + NO -> HONO reaction. Using the simultaneously recorded OH, NO, and HONO photolysis frequency, a daytime additional source strength of HONO (P-M) was calculated to be 0.77 ppb h(-1) on average. This value compares well to previous measurements in other environments. Our analysis of P-M provides evidence that the photolysis of HNO3 adsorbed on ground surfaces contributes to the HONO formation.
In this paper, we examine the impact of family size on maternal health outcomes by exploiting the tremendous change in family size under the One-Child policy in China. Using data from the China Health and Nutrition Survey 1993-2006, we find that mothers with fewer children have a higher calorie intake and a lower probability of being underweight and having low blood pressure; meanwhile, they have a higher probability of being overweight. This would occur if a smaller family size increases the food consumption of mothers, leading underweight women to attain a normal weight and normal weight women becoming overweight. Robust tests are performed to provide evidence on the hypothesis that the tradeoff between children's quantity and mother's "quality" is through a budget constraint mechanism, that is, having more children decreases the resource allocated to mothers and affects their health outcomes.