Systematic front distortion and presence of consecutive fronts in a precipitation system

A new simple reaction-diffusion system is presented focusing on pattern formation phenomena as consecutive precipitation fronts and distortion of the precipitation front.The chemical system investigated here is based on the amphoteric property of aluminum hydroxide and exhibits two unique phenomena. Both the existence of consecutive precipitation fronts and distortion are reported for the first time. The precipitation patterns could be controlled by the pH field, and the distortion of the precipitation front can be practical for microtechnological applications of reaction-diffusion systems

Micro and macro level stochastic simulation of reaction-diffusion systems

We provide numerical simulations for nonlinear reaction-diusion systems, which arise from a micro and macro level model of pattern formation (Liesegang phenomenon). In both cases we apply a stochastic approach: a discrete stochastic model and concentration perturbation in a deterministic model

Fatty acid droplet self-division driven by a chemical reaction

Division of a millimeter-sized and compartmentalized fatty acid droplet is triggered by a chemical pH clock reaction operating on the ten-second time scale. The autonomous pH change inside the compartment translates into the deprotonation of the fatty acid molecules, leading to a negative interfacial tension at the water-oil interface inside the droplet. This phenomenon induces the expansion of the droplet, which is followed by its division into daughter droplets governed by the Plateau-Rayleigh instability. © 2014 the Owner Societies

Transition of liesegang precipitation systems: simulations with an adaptive grid pde method

The dynamics of the Liesegang type pattern formation is investigated in a centrally symmetric two-dimensional setup. According to the observations in real experiments, the qualitative change of the dynamics is exhibited for slightly different initial conditions. Two kinds of chemical mechanisms are studied; in both cases the pattern formation is described using a phase separation model including the Cahn-Hilliard equations. For the numerical simulations we make use of a recent adaptive grid PDE method, which successfully deals with the computationally critical cases such as steep gradients in the concentration distribution and investigation of long time behavior. The numerical simulations show a good agreement with the real experiments

Dispersion of aerosol particles in the free atmosphere using ensemble forecasts

The dispersion of aerosol particle pollutants is studied using 50 members of an ensemble forecast in the example of a hypothetical free atmospheric emission above Fukushima over a period of 2.5 days. Considerable differences are found among the dispersion predictions of the different ensemble members, as well as between the ensemble mean and the deterministic result at the end of the observation period. The variance is found to decrease with the particle size. The geographical area where a threshold concentration is exceeded in at least one ensemble member expands to a 5-10 times larger region than the area from the deterministic forecast, both for air column "concentration" and in the "deposition" field. We demonstrate that the root-mean-square distance of any particle from its own clones in the ensemble members can reach values on the order of one thousand kilometers. Even the centers of mass of the particle cloud of the ensemble members deviate considerably from that obtained by the deterministic forecast. All these indicate that an investigation of the dispersion of aerosol particles in the spirit of ensemble forecast contains useful hints for the improvement of risk assessment

Effects of the climate change on regional ozone dry deposition

This impact study investigates connections between the regional climate change and the tropospheric ozone deposition over different vegetations in Hungary due to the possible changes of atmospheric and environmental properties. The spatial and temporal variability of the dry deposition velocity of ozone was estimated for different time periods (1961–1990 for reference period and two future scenarios: 2021–2050 and 2071–2100). Simulations were performed with a sophisticated deposition model using the RegCM regional climate model results as an input. We found a significant reduction of the ozone deposition velocities during summer months, which predicts less ozone damage to the vegetation in the future. However elevated ozone concentration and changed plant physiology can compensate the effect of this reduction

Spatial and temporal variability of ozone deposition

Soil moisture and ozone deposition velocity under continental climate conditions were estimated using a newly developed algorithm. The relationship between soil moisture and deposition velocity was investigated and analysed. These results emphasize the importance of a sophisticated parameterization of soil moisture in surface-atmosphere interaction processes