A state-of-the-art gas phase chemical mechanism for modeling atmospheric chemistry on a regional scale is presented. The second generation Regional Acid Deposition Model (RADM2) gas phase chemical mechanism, like its predecessor RADM1, is highly nonlinear, since predicted ozone, surfate, nitric acid and hydrogen peroxide concentrations are complicated functions of NOx and nonmethane hydrocarbon concentrations. The RADM2 chemical mechanism is an upgrade of RADM1 in that (1) three classes of higher alkanes are used instead of one, (2) a more detailed treatment of aromatic chemistry is used, (3) the two higher alkene classes now represent intemal and terminal alkenes, (4) ketones and dicarbonyl species are treated as classes distinct from aldehydes, (5) isoprene is now included as an explicit species, and (6) there is a more detailed treatment of peroxy radical-peroxy radical reactions. As a result of these improvements the RADM2 mechanism simulates the concentrations of peroxyacetyl nitrate, HNO3, and H202 under a wide variety of environmental conditions. Comparisons of RADM2 mechanism with the RADM1 mechanism predictions and selected environmental chamber experimental results indicate that for typical atmospheric conditions, both mechanisms reliably predict 03, surfate and nitric acid concentrations. The RADM2 mechanism gives lower and presumably more realistic predictions of H202 because of its more detailed treatment of peroxy radical-peroxy radical reactions. INTRODUCYIONOne of the most important components of any regional air quality model is its gas phase chemical mechanism. Gas phase chemical transformation rates, as well as emissions, transport and deposition, determine the distribution of gas phase species. The relationship between emissions of reactive organic species, sulfur and nitrogen oxides and regional air pollution effects associated with ozone and acid deposition is highly dependent on the gas phase chemistry of the polluted continental troposphere. Transformation rates also affect transport and deposition rates of trace species, which are highly dependent on the chemical form of the species.Aqueous phase reactions in clouds are major contributors to atmospheric acidification, thus it is very important for the gas phase mechanism to predict correct concentrations of species that are needed for aqueous-phase chemistry. Midday summertime gas phase sulfur dioxide and nitrogen dioxide oxidation rates are only about 5 and 40% per hour, respectively [Calvert and Stockwell, 1983; Stockwell, 1986; Calvert et al., 1985]. However, gas phase chemistry supplies reactants such as ozone and hydrogen peroxide to cloud water, where the conversion rates of sulfur dioxide to sulfate can be several hundred percent per hour or more [Calvert et al., 1985]. These rapid aqueous phase oxidation rates depend on the gas phase concentrations, solubility, and rate of mass transfer of oxidizing agents such as hydrogen peroxide, ozone, methyl hydrogen peroxide, peroxy acetic acid, and HO and HO 2 radicals [Calvert et al., 1985...

By means of a special variable separation approach, a common formula with some arbitrary functions has been obtained for some suitable physical quantities of various (2+1)-dimensional models such as the Davey-Stewartson (DS) model, the Nizhnik-Novikov-Veselov (NNV) system, asymmetric NNV equation, asymmetric DS equation, dispersive long wave equation, Broer-Kaup-Kupershmidt system, long wave-short wave interaction model, Maccari system, and a general (N+M)-component Ablowitz-Kaup-Newell-Segur (AKNS) system. Selecting the arbitrary functions appropriately, one may obtain abundant stable localized interesting excitations such as the multidromions, lumps, ring soliton solutions, breathers, instantons, etc. It is shown that some types of lower dimensional chaotic patterns such as the chaotic-chaotic patterns, periodic-chaotic patterns, chaotic line soliton patterns, chaotic dromion patterns, fractal lump patterns, and fractal dromion patterns may be found in higher dimensional soliton systems. The interactions between the traveling ring type soliton solutions are completely elastic. The traveling ring solitons pass through each other and preserve their shapes, velocities, and phases. Some types of localized weak solutions, peakons, are also discussed. Especially, the interactions between two peakons are not completely elastic. After the interactions, the traveling peakons also pass through each other and preserve their velocities and phases, however, they completely exchange their shapes.

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Over the last 50 years, the use of nitrogen (N) and phosphorus (P) fertilizers has increased at a faster rate than global food production, resulting in substantial decreases of N and P efficiency in agriculture (Fig. 1). Thus, considerable amounts of N and P fertilizers have been wasted in agroecosystems, and the alteration of N and P biogeochemical cycles is among the most visible impacts of human activities on ecosystem services, far exceeding the hypothesized "planetary boundaries" for N and approaching those for P (Rockström et al., 2009). Projections for the future suggest that a substantial further increase in N and P fertilizer use will occur to cope with increasing food demand (Tilman et al., 2001;Vance et al., 2003). Tilman et al. (2001) predicted that global consumption of fertilizer P will increase from 34.

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Purpose: Vigorous physical activity is often considered a risk factor for knee and hip osteoarthritis (OA), but its effect on spinal OA is poorly

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