Ligation is a form of chemical self-assembly that involves dynamic formation of strong covalent bonds in the presence of weak associative forces. We study an extremely simple form of ligation by means of a dissipative particle dynamics (DPD) model extended to include the dynamic making and breaking of strong bonds, which we term dynamically bonding dissipative particle dynamics (DDPD). Then we use a chemical genetic algorithm (CGA) to optimize the model’s parameters to achieve a limited form of ligation of trimers—a (...) proof of principle for the evolutionary design of self-assembling chemical systems. (shrink)

The experience of time and temporally extended events is a fundamental property of mind, and of time-based media arts. In dealing with properties of time, does the operational logic of contemporary media production tools cohere with philosophical views on the experience of time? This article considers a range of views on the phenomenal experience of time as they relate to the production of time-based media. Embedded within our production technologies, the artist is faced with a new philosophical instrument: the production (...) timeline. The timeline utility in most time-based media software (and non-digital precursors) adopts the cinematic model as its operating metaphor; a series of frames, assembled one after the other in sequence. But the timeline brings new temporal complications such as reversibility, hierarchy and modifiability. The timeline also contorts time into a spatialized dimension, represented as a linear vector within the software interface. Automatic adoption of the linear timeline and the frame as the base unit of temporal thinking is problematic. J. M. E. McTaggart’s argument for the unreality of time based on contradictions within a range of possible temporal modal logics is compared with approaches to animation and editing software, and also interactive media software and their unique approach to time as potential events is considered. (shrink)

We study the effects of environmental catastrophes on the evolution of a population of sensory-motor agents with individually evolving mutation rates, and compare these effects in a variety of control systems. A catastrophe makes the balance shift toward the need for evolutionary novelty, and we observe the mutation rate evolve upwards. As the population adapts the sensory-motor strategies to the new environment and the balance shifts toward a need for evolutionary memory, the mutation rate falls. These observations support the hypothesis (...) that second-order evolution of the mutation flexibly balances the need for evolutionary “novelty” and “memory,” both of which are controlled by the mutation rate. (shrink)