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...

Correspondence: J.G. Widdicombe, Sherrington School of Physiology, St Thomas' Hospital Campus (UMDS), Lambeth Palace Road, London SE1 7EH, UK. The paper by HOHLFELD et al. [1] in this issue shows that, in rats, bronchoconstriction due to inhaled acetylcholine is inhibited by inhaled aerosols of surfactant. Bronchoconstriction was assessed from changes in total lung resistance; other parameters ...

We present a closed form solution to the perpetual American double barrier call option problem in a model driven by a Brownian motion and a compound Poisson process with exponential jumps. The method of proof is based on reducing the initial irregular optimal stopping problem to an integro-differential free-boundary problem and solving the latter by using continuous and smooth fit. The obtained...

The extracellular space (ECS) consists of the narrow channels between brain cells together with their geometrical configuration and contents. Despite being only 20-60 nm in width, the ECS typically occupies 20% of the brain volume. Numerous experiments over the last 50 years have established that molecules moving through the ECS obey the laws of diffusion but with an effective diffusion coeffic...

This paper assesses the welfare impact of trade and technology diffusion as well as the change in the cross-country distribution of GDP due to removal of trade costs and diffusion barriers. The model extends the multi-country Ricardian trade model of Alvarez and Lucas (2007) to include technology diffusion with diffusion barriers. A key feature of the model is that some countries export goods p...

Crystal violet (CV) was removed from aqueous solutions using walnut shell (WS) as an adsorbent. The effect of initial ph, contact time, adsorbent level and temperature on CV adsorption, were studied in batch mode. The results indicated that both the Langmuir and the Freundlich equations effectively described the adsorption equilibrium. A pseudo second-order kinetics provided a perfect fit for t...

Enhanced atomic migration was an early observation from experimental studies into nanocrystalline solids. This contribution presents an overview of the available diffusion data for simple metals and ionic materials in nanocrystalline form. It will be shown that enhanced diffusion can be interpreted in terms of atomic transport along the interfaces, which are comparable to grain boundaries in co...

In this paper we present a generalization of a simple solid-on-solid epitaxial model of thin films growth, when surface morphology anisotropy is provoked by anisotropy in model control parameters: binding energy and/or diffusion barrier. The anisotropy is discussed in terms of the height-height correlation function. It was experimentally confirmed that the difference in diffusion barriers yield...