Modeling and validation of autoinducer-mediated bacterial gene expression in microfluidic environments

Biosensors exploiting communication within genetically engineered bacteria are becoming increasingly important for monitoring environmental changes. Currently, there are a variety of mathematical models for understanding and predicting how genetically engineered bacteria respond to molecular stimuli in these environments, but as sensors have miniaturized towards microfluidics and are subjected to complex time-varying inputs, the shortcomings of these models have become apparent. The effects of microfluidic environments such as low oxygen concentration, increased biofilm encapsulation, diffusion limited molecular distribution, and higher population densities strongly affect rate constants for gene expression not accounted for in previous models. We report a mathematical model that accurately predicts the biological response of the autoinducer N-acyl homoserine lactone-mediated green fluorescent protein expression in reporter bacteria in microfluidic environments by accommodating these rate constants. This generalized mass action model considers a chain of biomolecular events from input autoinducer chemical to fluorescent protein expression through a series of six chemical species. We have validated this model against experimental data from our own apparatus as well as prior published experimental results. Results indicate accurate prediction of dynamics (e.g., 14% peak time error from a pulse input) and with reduced mean-squared error with pulse or step inputs for a range of concentrations (10 μM–30 μM). This model can help advance the design of genetically engineered bacteria sensors and molecular communication devices.     

Safety in unpredictable complex systems – a framework for the analysis of safety derived from the nuclear power industry

The increasing complexity and power of our technologies compels us to find new ways in which to conceptualise, understand and maintain their safety in the long term. Some complex technological industries have performed better than others in terms of applying sustained and systematic approaches to the maintenance of safety. The United States nuclear power industry can be seen as an ideal test-bed for the development of safety initiatives, being responsible for the control of potentially unpredictable technology that involves extraordinary forces and costs. This paper describes and formalises a framework for better understanding the safety of complex socio-technological systems, based on key events in the development of safety in the United States nuclear power industry. The framework comprises two components: (1) a state-space approach for better conceptualising system failures, the benefits of incident reporting and remedial safety initiatives; and (2) a set of milestones that can be used to assess the development of safety in socio-technological industries. Healthcare and the United States nuclear power industry both represent complex socio-technological systems with similar technical characteristics. However, safety strategies in healthcare have not kept pace with the increasing complexity of clinical practice, and there have been international calls for improvements in patient safety. The framework is applied to the analysis of safety in healthcare, demonstrating its utility as an alternative safety analogy in healthcare. Use of the framework indicates substantial scope for improvements in healthcare safety through major evidence-based system redesign. By lowering the threshold for the reporting of incident data to include accident precursors, it is possible to identify problem areas before patient harm occurs.     

Cognitive Style and Problem Behaviour in Boys Referred to Residential Special Schools

The paper considers aberrant behaviour in the context of cognitive style with reference to both diagnosis and treatment.

Aims.

The aims of the study were to investigate whether the style of pupils with behaviour problems was different from that of children with no reported problems, and also to consider how pupils of different style manifested their problem behaviours.

Sample.

The sample comprised 83 male pupils aged 10‐18 years from two residential special schools.

Method.

The sample were given the Cognitive Styles Analysis to assess their positions on the Wholist‐Analytic and Verbal‐Imagery style dimensions. The pupil records of the special school pupils who were at the extreme of the style dimensions were also examined.

Results.

When their style characteristics were contrasted with a Comparison Sample of 413 12‐16‐year‐old males attending 10 secondary schools, the special school pupils had a significantly higher proportion of both Wholists and Verbalisers, than the Comparison Group. Further, the inspection of the records indicated that the types of social behaviour and behaviour problems exhibited varied with style, and particularly on the Wholist‐Analytic dimension.

Conclusion.

The results were considered to have implications for the origins and treatment of problem behaviour.     

Distributed Departments: A New Approach to Protecting the Vitality of Small Programs

The Texas Electronic Coalition for Physics was established in 2000 as a means of demonstrating that by linking together, small programs can maintain their vitality in higher education. Using Interactive Television, the Internet, telephones, faxes, and other electronic media, five physics programs scattered across the state of Texas formed a distributed physics department. In addition to jointly offering lecture courses, the group (i) established procedures for operating as a unified entity, (ii) encouraged research regardless of location, (iii) provided a locus for professional camaraderie, (iv) created a distance-based advanced physics laboratory course, and (v) developed assessment tools for measuring success in a distance environment. Through these, the coalition demonstrated that a distributed department can carry out all of the functions associated with a traditional department.     

Letter from the Editors

Journal of Science Teacher Education -