Modeling ion channel dynamics through reflected stochastic differential equations

Ion channels are membrane proteins that open and close at random and play a vital role in the electrical dynamics of excitable cells. The stochastic nature of the conformational changes these proteins undergo can be significant, however current stochastic modeling methodologies limit the ability to study such systems. Discrete-state Markov chain models are seen as the "gold standard," but are computationally intensive, restricting investigation of stochastic effects to the single-cell level. Continuous stochastic methods that use stochastic differential equations (SDEs) to model the system are more efficient but can lead to simulations that have no biological meaning. In this paper we show that modeling the behavior of ion channel dynamics by a reflected SDE ensures biologically realistic simulations, and we argue that this model follows from the continuous approximation of the discrete-state Markov chain model. Open channel and action potential statistics from simulations of ion channel dynamics using the reflected SDE are compared with those of a discrete-state Markov chain method. Results show that the reflected SDE simulations are in good agreement with the discrete-state approach. The reflected SDE model therefore provides a computationally efficient method to simulate ion channel dynamics while preserving the distributional properties of the discrete-state Markov chain model and also ensuring biologically realistic solutions. This framework could easily be extended to other biochemical reaction networks. © 2012 American Physical Society.

Group dynamics and software engineering

This paper reports on an experiment that was conducted to determine the extent to which group dynamics impacts on the effectiveness of software development teams. The experiment was conducted on software engineering project students at the Queensland University of Technology (QUT).

Stigmergy in Web 2.0 : a model for site dynamics

Building Web 2.0 sites does not necessarily ensure the success of the site. We aim to better understand what improves the success of a site by drawing insight from biologically inspired design patterns. Web 2.0 sites provide a mechanism for human interaction enabling powerful intercommunication between massive volumes of users. Early Web 2.0 site providers that were previously dominant are being succeeded by newer sites providing innovative social interaction mechanisms. Understanding what site traits contribute to this success drives research into Web sites mechanics using models to describe the associated social networking behaviour. Some of these models attempt to show how the volume of users provides a self-organising and self-contextualisation of content. One model describing coordinated environments is called stigmergy, a term originally describing coordinated insect behavior. This paper explores how exploiting stigmergy can provide a valuable mechanism for identifying and analysing online user behavior specifically when considering that user freedom of choice is restricted by the provided web site functionality. This will aid our building better collaborative Web sites improving the collaborative processes.

The Roots of Danger: Violent Crime in Global Perspective

Prentice Hall’s Masters Series in Criminology brings the work of true masters to life for a new audience of readers, presenting brief and accessible introductions to crime and criminology topics from some of the leading scholars in criminology today. All authors in the series are true academic pioneers, and each book in the series pulls from the authors’ decades of research and writing in their fields. The first and only series of its kind, Prentice Hall’s Masters Series in Criminology introduces readers to the scholars and issues that are at the core of modern criminology.

Creating Institutions: Linking the Local and the Global in the Travel of Crime Policies

Institutions represent the ‘technologies of the social.’ They are increasingly modelled and transported to other cultures and societies, and criminal justice institutions—traditional, parochial, and local as they are—are no exception to this. Problems of crime and insecurity have engendered the travelling of institutions from the centre to the periphery and vice versa. This paper will explore the problems which arise from travelling and modelling, and from the transport and creation of institutions in the area of criminal justice. An important feature in the travel of criminal justice institutions is the use of ‘local knowledge’ and its role in this process.

Tampere region under the microscope : a critical analysis from the knowledge perspective

Purpose – In the context of global knowledge economy, knowledge-based urban development (KBUD) is seen as an effective development strategy for city-regions to survive, flourish and become highly competitive urban agglomerations – i.e., a knowledge city-region. This paper aims to evaluate the KBUD dynamics, capacity and potentials of a rapidly emerging knowledge city-region of Finland – Tampere region. Design/methodology/approach – The paper undertakes a review of the literature on regional development in the knowledge economy era. It adopts a qualitative analysis technique to scrutinize the dynamics, capacity and potentials of Tampere region. The semi-structured interview process starts with the pre-determined key actors of the city-region with an aim of determining the other key players. Next, with the participation of all key players to the interviews, the research reveals the principal issues, assets and mechanisms that relate to KBUD, and portrays the strengths, weaknesses, opportunities and threats of the city-region. A critical analysis of the findings along with the previous studies is undertaken to provide a clear picture of the dynamics, capacity and potentials of the emerging knowledge city-region. Originality/value – This paper reports the findings of a pioneering study focusing on the investigation of the KBUD dynamics, capacity and potentials of Tampere region. The paper critically evaluates the city-region from the knowledge perspective with the lens of KBUD, and the lessons learned and the methodological approach of the paper shed light to other city-regions seeking such development. Practical implications – The paper discusses the findings of a study from Tampere region that critically scrutinizes the KBUD experience of the city-region. The research provides an invaluable opportunity to inform the regional decision-, policy- and plan-making mechanisms by determining key issues, actors, assets, processes and potential development directions for the KBUD of Tampere region.