Unfinished Turns in French: How Context Matters

On occasions, speakers do not complete their turns in conversation. Such syntactically-incomplete turns are not treated with repair or misunderstanding. The responses that they receive display a clear understanding of the actions that the unfinished turns embodied. In this article, using conversation analysis (CA), I describe the systematic occurrence of unfinished turns in French conversation. I show that context is necessary to the understanding of this type of turn and I describe the nature of that context. Data analysis reveals that unfinished turns are understandable primarily by reference to their sequential position. I conclude that unfinished turns are a locally- managed resource fitted to the particulars of the talk in progress and built upon the context that the sequences that house them have so far provided.

Towards a predictive model of Ca²⁺ puffs

We investigate key characteristics of Ca²⁺ puffs in deterministic and stochastic frameworks that all incorporate the cellular morphology of IP[subscript]3 receptor channel clusters. In a first step, we numerically study Ca²⁺ liberation in a three dimensional representation of a cluster environment with reaction-diffusion dynamics in both the cytosol and the lumen. These simulations reveal that Ca²⁺ concentrations at a releasing cluster range from 80 µM to 170 µM and equilibrate almost instantaneously on the time scale of the release duration. These highly elevated Ca²⁺ concentrations eliminate Ca²⁺ oscillations in a deterministic model of an IP[subscript]3R channel cluster at physiological parameter values as revealed by a linear stability analysis. The reason lies in the saturation of all feedback processes in the IP[subscript]3R gating dynamics, so that only fluctuations can restore experimentally observed Ca²⁺ oscillations. In this spirit, we derive master equations that allow us to analytically quantify the onset of Ca²⁺ puffs and hence the stochastic time scale of intracellular Ca²⁺ dynamics. Moving up the spatial scale, we suggest to formulate cellular dynamics in terms of waiting time distribution functions. This approach prevents the state space explosion that is typical for the description of cellular dynamics based on channel states and still contains information on molecular fluctuations. We illustrate this method by studying global Ca²⁺ oscillations.