We study the statistical mechanics of small DNA loops emphasizing the competition between elasticity, supercoiling, and denaturation. Motivated by recent experiments and atomistic molecular dynamics simulation, we propose a new coarse-grained phenomenological model of DNA. We extend the classical elastic rod models to include the possibility of denaturation and nonlinear twist elasticity. Using this coarse-grained model, we obtain a phase diagram in terms of fractional overtwist and loop size that can be used to rationalize a number of experimental results which have also been confirmed by atomistic simulations.

This paper seeks to review the business strategy and product data management literature in an attempt to establish the nature of the relationship between them. One obvious linking theme is that of information systems strategies and their alignment with business processes, and therefore attention has also been given to this body of literature. The conclusions are that there is little well-researched understanding about the nature of the relationship and little concrete evidence of the relative importance of product data management in achieving overall business objectives. Therefore, if manufacturing organizations are to be able to invest wisely in product data management, substantial research is required to address the fundamental business and technical issues that have emerged as a result of this review.

The business requirements for better document management in engineering environments are forever increasing and the underlying technologies for implementing system solutions are changing rapidly. In these contexts, it is vital that the strategic aspects of the document management decision-making processes and the user and functional requirements of document management are fully understood prior to consideration of shorter term implementation decisions. This paper goes some way to providing guidelines on addressing these issues through the development of a structured approach to engineering document management, coupled with the specification of generic process and data models which can form the basis for developing company-specific strategies, plans, models and requirements before committing to investments in technology to implement solutions. The paper is therefore specifically aimed at those engineering, production, project and quality managers within manufacturing companies who have the responsibility for implementing data and document management systems. Relationships with relevant standards and technology, and future issues are briefly discussed.