Structure determination of new algal toxins using NMR methods

Shellfish are considered a delicacy by many consumers. In NZ, as in many overseas countries, there is a now thriv¬ing shellfish industry servicing both domestic and inter-national markets. Periodically shellfish accumulate harm¬ful levels of a variety of algal toxins, including domoic acid, yessotoxins, pectenotoxins and brevetoxins. When this occurs, regulatory authorities may impose harvesting closures which have a consequential economic impact on both farmers and staff employed to harvest and market shellfish products

A statistical model for isolated convective precipitation events

To study the diurnal evolution of the convective cloud field, we develop a precipitation cell tracking algorithm which records the merging and fragmentation of convective cells during their life cycles, and apply it on large eddy simulation (LES) data. Conditioning on the area covered by each cell, our algorithm is capable of analyzing an arbitrary number of auxiliary fields, such as the anomalies of temperature and moisture, convective available potential energy (CAPE) and convective inhibition (CIN). For tracks that do not merge or split (termed "solitary"), many of these quantities show generic, often nearly linear relations that hardly depend on the forcing conditions of the simulations, such as surface temperature. This finding allows us to propose a highly idealized model of rain events, where the surface precipitation area is circular and a cell's precipitation intensity falls off linearly with the distance from the respective cell center. The drop-off gradient is nearly independent of track duration and cell size, which allows for a generic description of such solitary tracks, with the only remaining parameter the peak intensity. In contrast to the simple and robust behavior of solitary tracks, tracks that result from merging of two or more cells show a much more complicated behavior. The most intense, long lasting and largest tracks indeed stem from multi-mergers - tracks involved in repeated merging. Another interesting finding is that the precipitation intensity of tracks does not strongly depend on the absolute amount of local initial CAPE, which is only partially consumed by most rain events. Rather, our results speak to boundary layer cooling, induced by rain re-evaporation, as the cause for CAPE reduction, CIN increase and shutdown of precipitation cells.Comment: Manuscript under review in Journal of Advances in Modeling Earth System

Genetic Algorithms in Time-Dependent Environments

The influence of time-dependent fitnesses on the infinite population dynamics of simple genetic algorithms (without crossover) is analyzed. Based on general arguments, a schematic phase diagram is constructed that allows one to characterize the asymptotic states in dependence on the mutation rate and the time scale of changes. Furthermore, the notion of regular changes is raised for which the population can be shown to converge towards a generalized quasispecies. Based on this, error thresholds and an optimal mutation rate are approximately calculated for a generational genetic algorithm with a moving needle-in-the-haystack landscape. The so found phase diagram is fully consistent with our general considerations.Comment: 24 pages, 14 figures, submitted to the 2nd EvoNet Summerschoo

Coming out as a human capitalist: community development at the nexus of people and place

Community development

SHRIMP PROCESSING IN THE SOUTHEAST: SUPPLY PROBLEMS AND STRUCTURAL CHANGE

Agribusiness,