Biomedical subjects

Igor Mezic

Publications and source records attributed to Igor Mezic.

5 recordsLinked to original sources

PubMed2006

Agent-based modeling of drinking behavior: a preliminary model and potential applications to theory and practice.

OBJECTIVES: We developed a preliminary agent-based simulation model designed to examine agent-environment interactions that support the development and maintenance of drinking behavior at the population level. METHODS: The model was defined on a 1-dimensional lattice along which agents might move left or right in single steps at each iteration. Agents could exchange information about their drinking with each other. In the second generation of the model, a "bar" was added to the lattice to attract drinkers. RESULTS: The model showed that changes in drinking status propagated through the agent population as a function of probabilities of conversion, rates of contact, and contact time. There was a critical speed of population mixing beyond which the conversion rate of susceptible nondrinkers was saturated, and the bar both enhanced and buffered the rate of propagation, changing the model dynamics. CONCLUSIONS: The models demonstrate that the basic dynamics underlying social influences on drinking behavior are shaped by contacts between drinkers and focused by characteristics of drinking environments.

Alcohol Drinking↗

PubMed2004

Implications of systems dynamic models and control theory for environmental approaches to the prevention of alcohol- and other drug use-related problems.

The approach described in this article is premised on the idea that drug and alcohol use-related problems are heterogeneously distributed with respect to population and geography, and therefore, are essentially local problems. More specifically, it is argued that viewing a local community as an interacting set of systems that support or buffer the occurrence of specific substance misuse outcomes, opens up to research two important prospects. The first of these involves creating adequate systems models that can capture the primary community structures and relationships that support public health problems such as alcohol and drug misuse and related outcomes. The second entails rationally testing control strategies that have the potential to moderate or reduce these problems. Understanding and controlling complex dynamic systems models nowadays pervades all scientific disciplines, and it is to research in areas such as biology, ecology, engineering, computer sciences, and mathematics that researchers in the field of addictions must turn to in order to better study the complexity that confronts them as they try to understand and prevent problems resulting from alcohol and drug use and misuse. Here we set out what such a systems-based understanding of alcohol- and drug use-related problems will require and discuss its implications for public policy and prevention programming.

Humans↗

PubMed2002

Chaotic mixer for microchannels.

It is difficult to mix solutions in microchannels. Under typical operating conditions, flows in these channels are laminar-the spontaneous fluctuations of velocity that tend to homogenize fluids in turbulent flows are absent, and molecular diffusion across the channels is slow. We present a passive method for mixing streams of steady pressure-driven flows in microchannels at low Reynolds number. Using this method, the length of the channel required for mixing grows only logarithmically with the Péclet number, and hydrodynamic dispersion along the channel is reduced relative to that in a simple, smooth channel. This method uses bas-relief structures on the floor of the channel that are easily fabricated with commonly used methods of planar lithography.

Chemical Phenomena↗

PubMed1999

Residence-time distributions for chaotic flows in pipes.

In this paper we derive two rigorous properties of residence-time distributions for flows in pipes and mixers motivated by computational results of Khakhar et al. [Chem. Eng. Sci. 42, 2909 (1987)], using some concepts from ergodic theory. First, a curious similarity between the isoresidence-time plots and Poincare maps of the flow observed in Khakhar et al. is resolved. It is shown that in long pipes and mixers, Poincare maps can serve as a useful guide in the analysis of isoresidence-time plots, but the two are not equivalent. In particular, for long devices isoresidence-time sets are composed of orbits of the Poincare map, but each isoresidence-time set can be comprised of many orbits. Second, we explain the origin of multimodal residence-time distributions for nondiffusive motion of particles in pipes and mixers. It is shown that chaotic regions in the Poincare map contribute peaks to the appropriately defined and rescaled axial distribution functions. (c) 1999 American Institute of Physics.

Journal Article↗

PubMed1999

A method for visualization of invariant sets of dynamical systems based on the ergodic partition.

We provide an algorithm for visualization of invariant sets of dynamical systems with a smooth invariant measure. The algorithm is based on a constructive proof of the ergodic partition theorem for automorphisms of compact metric spaces. The ergodic partition of a compact metric space A, under the dynamics of a continuous automorphism T, is shown to be the product of measurable partitions of the space induced by the time averages of a set of functions on A. The numerical algorithm consists of computing the time averages of a chosen set of functions and partitioning the phase space into their level sets. The method is applied to the three-dimensional ABC map for which the dynamics was visualized by other methods in Feingold et al. [J. Stat. Phys. 50, 529 (1988)]. (c) 1999 American Institute of Physics.

Journal Article↗