Perturbation Theory for the Breakdown of Mean-Field Kinetics in Oscillatory Reaction-Diffusion Systems

Spatially-distributed, nonequilibrium chemical systems described by a Markov chain model are considered. The evolution of such systems arises from a combination of local birth-death reactive events and random walks executed by the particles on a lattice. The parameter \gamma, the ratio of characteristic time scales of reaction and diffusion, is used to gauge the relative contributions of these two processes to the overall dynamics. For the case of relatively fast diffusion, i.e. \gamma << 1, an approximate solution to the Markov chain in the form of a perturbation expansion in powers of \gamma is derived. Kinetic equations for the average concentrations differ from the mass-action law and contain memory terms. For a reaction- diffusion system with Willamowski-Rossler reaction mechanism, we further derive the following two results: a) in the limit of \gamma --> 0 these memory terms vanish and the mass-action law is recovered; b) the memory kernel is found to assume a simple exponential form. A comparison with numerical results from lattice gas automaton simulations is also carried out.Comment: 18 pages, 5 figures. To appear in J. Chem. Phy

Creating the Technopolis: High-Technology Development in Austin, Texas

New institutional alliances, driven by the rapid increase in and diversity of new technologies, are altering the strategy and tactics of economic development. As a result, communities across the world are seeking to create modern technopoleis or city-states that interactively link technology commercialization with public and private sectors to spur economic growth and diversification through high-technology company development. This paper develops the conceptual framework of a technopolis wheel from studying the dynamics of high-technology development and economic growth in Austin, Texas. It describes seven segments within the technopolis: the university, large technology companies, small technology companies, federal government, state government, local government and support groups. (Author's preprint.)IC2 Institut

Magnetic Properties of Pd_(0.996)Mn_(0.004) Films for High Resolution Thermometry

We have previously reported on the temperature and magnetic field dependence of the magnetic susceptibility of thin Pd_(1−x)Mn_x alloy films. Extensive new measurements on sputtered films show that a commercial quality sputtering process produces a film with the same dependence of Curie temperature on x as previously reported for bulk samples of the same material. These measurements and parameters from the Renormalization Group theory for a Heisenberg ferromagnet, yield an estimate for T_c of 1.16 ± 0.01 K when x − 0.004, consistent with previously reported bulk result

Effects of suspended sediments on the development of eggs and larvae of striped bass and white perch

The possible ecological effects of suspended sediments are manifold. Briefly, suspended sediments may cause an increased surface for microorganism growth, fewer temperature fluctuations, chemical adsorption or absorption, blanketing, mechanical-abrasive actions, and light penetration reduction (Cairns, 1968). Sherk and Cronin (1970) have pointed out that the above effects have been little studied in the estuarine environment. The ecological effects of suspended sediments on fish eggs and larvae may be of prime importance t o the C and D Canal area, an important spawning and primary nursery area for a variety of estuary: e species (Johnson,1972). This section discusses the effects of suspended sediment on the eggs and larvae of striped bass and white perch