In the hydrodynamic regime, the evolution of a stochastic lattice gas with symmetric hopping rules is described by a diffusion equation with densitydependent diffusion coefficient encapsulating all microscopic details of the dynamics. This diffusion coefficient is, in principle, determined by a Green– Kubo formula. In practice, even when the equilibrium properties of a lattice gas are analytica...

It has been previously proposed that acetylene reduction data at subsaturating acetylene concentrations could be interpreted by use of the Michaelis-Menten equation, based on the acetylene concentration external to the nodules. One difficulty of this view is that the assumption that the system is not diffusion limited is violated when studying intact nodules. The presence of a gas diffusion bar...

For simulations of fluid dynamics in astrophysics, physical viscosity and diffusion are typically neglected. However, in this high Reynolds number regime, real fluids become highly turbulent and turbulent processes mediate substantial transport of momentum and heat that is diffusive in nature. In the absence of models for these processes, code-dependent numerical effects dominate how diffusion ...

Introduction During gas ventilation, gas transport within the alveolar sac is dominated by diffusion. In liquid ventilation, perfluorocarbon (PFC) introduced into the alveolar space acts as a diffusion barrier to gas transport since the diffusivities of oxygen and carbon dioxide in this medium are four orders of magnitude lower than in air. Therefore convection in the PFC layer resulting from t...

Transients have utmost importance in the lifetime and performance degradation of PEM fuel cells. Recent studies show that cyclic transients can induce hygro-thermal fatigue. In particular, the amount of water in the membrane varies significantly during transients, and determines the ionic conductivity and the structural properties of the membrane. In this work, we present three-dimensional time...

Chronic heart failure (CHF) disturbs the alveolar-capillary interface and increases the resistance to gas transfer. Alveolar-capillary membrane conductance (D(M)) and capillary blood volume (V(c)) are subcomponents of the lung diffusion capacity. Elevation of the capillary pressure causes alveolar-capillary membrane stress failure (i.e. increase in capillary permeability to water and ions, and ...

‎A computational technique for solution of mathematical model of gas solution in a fluid is presented‎. ‎This model describes the change of mass of the gas volume due to diffusion through the contact surface‎. ‎An appropriate representation of the solution based on the M"{u}ntz polynomials reduces its numerical treatment to the solution of a linear system of algebraic equations‎. ‎Numerical exa...

We develop and analyze 1ϩ1-and 2ϩ1-dimensional ͑d͒ models for multilayer homoepitaxial growth of metal films at low temperatures (T), where intralayer terrace diffusion is inoperative. This work is motivated by recent variable-temperature scanning tunneling microscopy studies of Ag/Ag͑100͒ homoepitaxy down to 50 K. Adsorption sites are bridge sites in our 1ϩ1d models, and fourfold hollow sites in o...

Despite massive success of shale gas production in the US in the last few decades there are still major concerns with the steep decline in wellbore production and the large uncertainty in a long-term projection of decline curves. A reliable projection must rely on a mechanistic understanding of methane release in shale matrix-a limiting step in shale gas extraction. Using molecular simulations,...