Fisheries Production: Management Institutions, Spatial Choice, and the Quest for Policy Invariance

The fishery-dependent data used to estimate fishing production technologies are shaped by the incentive structures that influence fishermen’s purposeful choices across their multiple margins of production. Using a combination of analytical and simulation methods, we demonstrate how market prices and regulatory institutions influence a dominant short-run margin of production—the deployment of fishing time over space. We show that institutionally driven spatial selection leads to only a partial exploration of the full production set, yielding poorly identified estimates of production possibilities outside of the institutionally dependent status quo. The implication is that many estimated fisheries production functions suffer from a lack of policy invariance and may yield misleading predictions for even the most short-run of policy evaluation tasks. Our findings suggest that accurate assessment of the impacts of a policy intervention requires a description of the fishing production process that is sufficiently structural so as to be invariant to institutional changes.Ye

Linking in domain-swapped protein dimers

The presence of knots has been observed in a small fraction of single-domain proteins and related to their thermodynamic and kinetic properties. The exchanging of identical structural elements, typical of domain-swapped proteins, make such dimers suitable candidates to validate the possibility that mutual entanglement between chains may play a similar role for protein complexes. We suggest that such entanglement is captured by the linking number. This represents, for two closed curves, the number of times that each curve winds around the other. We show that closing the curves is not necessary, as a novel parameter $G'$, termed Gaussian entanglement, is strongly correlated with the linking number. Based on $110$ non redundant domain-swapped dimers, our analysis evidences a high fraction of chains with a significant intertwining, that is with $|G'| > 1$. We report that Nature promotes configurations with negative mutual entanglement and surprisingly, it seems to suppress intertwining in long protein dimers. Supported by numerical simulations of dimer dissociation, our results provide a novel topology-based classification of protein-swapped dimers together with some preliminary evidence of its impact on their physical and biological properties.Comment: v2: some new paragraphs and new abstrac