Modeling the airborne particle complex as a source-oriented external mixture

A Lagrangian air quality model is developed which represents the airborne particle complex as a source-oriented external mixture. In a source-oriented external mixture, particles of the same size can evolve to display different chemical compositions that depend on the chemical and hygroscopic properties of the primary seed particles initially emitted from different sources. In contrast, previous models initialize the airborne particles as an internal mixture in which all particles of the same size are assumed to have the same chemical composition. Test cases show that representation of the aerosol as an internal mixture can distort the predicted particle composition and concentration in the HNO_3/NH_3/HCl/H_2SO_4/aerosol Cl^−/SO_4=/NO_3^−/NH_4^+/Na^+ system when Na^+ and SO_4^(=) exist in separate particles, as may occur when sea spray coexists with long-distance transport of anthropogenic sulfates. Tests also indicate that the external mixture model can predict the evolution of a nearly monodisperse aerosol into a bimodally distributed aerosol as relative humidity increases, qualitatively matching observations. The source-oriented external mixture model is applied to predict the size and composition distribution of airborne particles observed at Claremont, California, on August 28, 1987. Calculations produce an aerosol mass distribution that is distinctly bimodal in the size range from 0.1 μm to 1.0 μm particle diameter, matching field observations. External mixture calculations also predict specific differences in composition between particles of the same diameter. The external mixture model is expected to have applications including exploration of the cause of the particle-to-particle differences seen by time-of-flight mass spectrometers that measure single particle size and composition in the atmosphere

An empirical parameterization of subsurface entrainment temperature for improved SST anomaly simulations in an intermediate ocean model

An empirical model for the temperature of subsurface water entrained into the ocean mixed layer (Te) is presented and evaluated to improve sea surface temperature anomaly (SSTA) simulations in an intermediate ocean model (IOM) of the tropical Pacific. An inverse modeling approach is adopted to estimate Te from an SSTA equation using observed SST and simulated upper-ocean currents. A relationship between Te and sea surface height (SSH) anomalies is then obtained by utilizing a singular value decomposition (SVD) of their covariance. This empirical scheme is able to better parameterize Te anomalies than other local schemes and quite realistically depicts interannual variability of Te, including a nonlocal phase lag relation of Te variations relative to SSH anomalies over the central equatorial Pacific. An improved Te parameterization naturally leads to better depiction of the subsurface effect on SST variability by the mean upwelling of subsurface temperature anomalies. As a result, SSTA simulations are significantly improved in the equatorial Pacific; a comparison with other schemes indicates that systematic errors of the simulated SSTAs are significantly small apparently due to the optimized empirical Te parameterization. Cross validation and comparisons with other model simulations are made to illustrate the robustness and effectiveness of the scheme. In particular it is demonstrated that the empirical Te model constructed from one historical period can be successfully used to improve SSTA simulations in anothe

Beethoven\u27s Eroica Sketchbooks: From Scribbles to Symphony

This paper will help readers to gain new insights on Beethoven’s Symphony No. 3 in E-flat Op. 55, also known as Eroica, by exploring the sketches related to this symphony. The background of the piece is discussed, and the sketches have been compared to the completed symphony. Beethoven’s sketching process was dramatically different from other composers of his time, and his sketches included even more musical material than was eventually included in the symphony

Effects of fasting, feeding, and bisphosphonate administration on serum calcitriol levels in phosphate-deprived rats

Effects of fasting, feeding, and bisphosphonate administration on serum calcitriol levels in phosphate-deprived rats.BackgroundIn a recent study, we showed in phosphate-deprived rats that morning feeding decreased serum phosphate and increased serum calcium values as compared with similar rats fasted overnight, and high doses of bisphosphonates did not reduce the magnitude of hypercalcemia. In the present study, we evaluated in phosphate-deprived rats whether serum calcitriol values were: (1) affected by the differences in serum phosphate induced by morning feeding and overnight fasting, (2) correlated with changes in serum phosphate levels, and (3) influenced by bisphosphonate administration.MethodsFour groups of rats were studied: (1) low-phosphate diet (LPD; P < 0.05%), (2) LPD + the bisphosphonate pamidronate (APD), (3) normal diet (ND; P 0.6%), and (4) ND + APD. Both diets contained 0.6% calcium. In rats receiving APD, high doses (0.8 mg/kg) were given subcutaneously four times during the study. On day 11, rats were sacrificed after an overnight fast or two to four hours after morning feeding.ResultsIn the fed phosphate-deprived rats (LPD and LPD + APD), serum phosphate levels were less (P < 0.05) and serum calcium levels were greater (P < 0.05) than in similar rats fasted overnight. In rats on the ND (ND and ND + APD), no differences were observed between fed and fasted rats. In phosphate-deprived rats, serum calcitriol levels were greater (LPD, P < 0.05) or tended to be greater (LPD + APD, P = 0.10) in the fed than in the fasted groups. In APD-treated rats, serum calcitriol values were greater than in rats not given APD whether rats were (1) fed or fasted, or (2) on an LPD or ND. An inverse correlation was present between serum phosphate and serum calcitriol (r = -0.58, P = 0.001). In a stepwise regression model in which serum calcitriol was the dependent variable and independent variables were APD administration and serum calcium, phosphate, and PTH, serum phosphate (P = 0.003) had an inverse and APD (P < 0.001) administration a direct effect on serum calcitriol (r2 = 0.59).ConclusionCalcitriol synthesis is rapidly inducible in rats during chronic phosphate deprivation, and the increase in serum calcitriol values is best attributed to feeding-induced decreases in serum phosphate. APD administration independently increases serum calcitriol levels in rats on normal and phosphate-deprived diets. Finally, whether our results in the rat are applicable to the clinical setting should be evaluated because in previous human studies of dietary phosphate restriction, serum calcitriol measurements were performed the morning after an overnight fast

Effect of Emissions Control Strategies on the Size and Composition Distribution of Urban Particulate Air Pollution

The predicted behavior of the size- and chemical-composition distribution of airborne particles in the Los Angeles area is examined as it changes in response to specific emissions control strategies. Model calculations indicate that strategies currently envisioned to control the emissions of primary particles in the Los Angeles area effectively reduce the atmospheric concentrations of particles between 0.1−0.3 μm particle diameter and above 2.5 μm particle diameter but do little to reduce particulate concentrations between 0.6 and 0.8 μm particle diameter. Analysis reveals that in Los Angeles, most atmospheric particles with diameters between 0.6−0.8 μm begin as water-soluble nonsea salt background particles over the Pacific Ocean which then are transformed by significant accumulation of gas-to-particle conversion products as they are advected across the urban area. Control of primary particulate emissions alone does not reduce the amount of secondary aerosol which forms in the atmosphere and may even serve to redistribute this secondary material to particles with diameters that scatter light more efficiently. Strategies originally designed to reduce ambient ozone concentrations through the control of emissions of reactive organic gases (ROG) and oxides of nitrogen (NO_x) would reduce fine particle mass concentrations at Claremont CA on August 28, 1987 by 9.5% under the conditions studied here, primarily by reducing aerosol nitrate concentrations. Additional controls on ammonia emissions would suppress aerosol nitrate formation further. The simultaneous use of all gas-phase and particle-phase emissions control measures studied here would reduce atmospheric particle concentrations by 46% at Claremont, CA, relative to the base case 1987 summer conditions