Against ambiguity

This paper argues that the widespread belief that ambiguity is beneficial in design communication stems from conceptual confusion. Communicating imprecise, uncertain and provisional ideas is a vital part of design teamwork, but what is uncertain and provisional needs to be expressed as clearly as possible. This paper argues that viewing design communication as conveying permitted spaces for further designing is a useful rationalisation for understanding what designers need from their notations and computer tools, to achieve clear communication of uncertain ideas. The paper presents a typology of ways that designs can be uncertain. It discusses how sketches and other representations of designs can be both intrinsically ambiguous, and ambiguous or misleading by failing to convey information about uncertainty and provisionality, with reference to knitwear design, where communication using inadequate representations causes severe problems. It concludes that systematic use of meta-notations for conveying provisionality and uncertainty can reduce these problems.

Carbon dioxide from earthworks: A bottom-up approach

Concerns over climate change mean engineers need to understand the greenhouse gas emissions associated with infrastructure projects. Standard coefficients are increasingly used to calculate the embodied emissions of construction materials, but these are not generally appropriate to inherently variable earthworks. This paper describes a new tool that takes a bottom-up approach to calculating carbon dioxide emissions from earthworks operations. In the case of bulk earthworks this is predominantly from the fuel used by machinery moving materials already on site. Typical earthworks solutions are explored along with the impact of using manufactured materials such as lime.

An analysis of the cooperative mechano-sensitive feedback between intracellular signaling, focal adhesion development, and stress fiber contractility

Cells communicate with their external environment via focal adhesions and generate activation signals that in turn trigger the activity of the intracellular contractile machinery. These signals can be triggered by mechanical loading that gives rise to a cooperative feedback loop among signaling, focal adhesion formation, and cytoskeletal contractility, which in turn equilibrates with the applied mechanical loads. We devise a signaling model that couples stress fiber contractility and mechano-sensitive focal adhesion models to complete this above mentioned feedback loop. The signaling model is based on a biochemical pathway where IP3 molecules are generated when focal adhesions grow. These IP3 molecules diffuse through the cytosol leading to the opening of ion channels that disgorge Ca2+ from the endoplasmic reticulum leading to the activation of the actin/myosin contractile machinery. A simple numerical example is presented where a one-dimensional cell adhered to a rigid substrate is pulled at one end, and the evolution of the stress fiber activation signal, stress fiber concentrations, and focal adhesion distributions are investigated. We demonstrate that while it is sufficient to approximate the activation signal as spatially uniform due to the rapid diffusion of the IP3 through the cytosol, the level of the activation signal is sensitive to the rate of application of the mechanical loads. This suggests that ad hoc signaling models may not be able to capture the mechanical response of cells to a wide range of mechanical loading events. © 2011 American Society of Mechanical Engineers.