COVID-19 and the agri-food system in the United States and Canada.

Agri-food supply chains in North America have become remarkably efficient, supplying an unprecedented variety of items at the lowest possible cost. However, the initial stages of the COVID-19 pandemic and the near-total temporary loss of the foodservice distribution channel, exposed a vulnerability that many found surprising. Instead of continued shortages, however, the agri-food sector has since moved back to near normal conditions with prices and production levels similar to those typically observed in years prior to the pandemic. Ironically, the specialization in most food supply chains designed for "just-in-time" delivery to specific customers with no reserve capacity, which led to the initial disruptions, may have also been responsible for its rapid rebound. A common theme in assessing the impacts across the six commodities examined is the growing importance of understanding the whole supply chain. Over the longer term, a continuation of the pandemic could push the supply chain toward greater consolidation of firms and diversification of products given the increasing option value of maintaining flexibility. Other structural changes will be felt through input markets, most notably labour, as the trend toward greater automation will continue to accelerate as a response to meeting concerns about a consistent supply of healthy and productive workers. The economic fall out from the pandemic may lead to greater concentration in the sector as some firms are not able to survive the downturn and changes in consumer food buying behaviour, including movement toward online shopping and enhanced demand for attributes associated with resiliency, such as local. On the other hand, online shopping may provide opportunities for small producers and processors to shorten supply chains and reach customers directly. In the long term, COVID-19 impacts on global commerce and developing country production are more uncertain and could influence poverty reduction. While COVID-19's impacts on North American agriculture should have minimal effect on the Sustainable Development Goals (SDGs) through food prices, the ongoing global trends in trade and agribusiness accelerated by the pandemic are relevant for achievement of the SDGs.

Optimisation of high average power optical parametric generation using a photonic crystal fiber.

In this paper the length of a photonic crystal fiber is optimised to perform high average output power parametric generation with maximum efficiency. It is shown that the fiber length has to be increased up to 150 m, well beyond the walk-off distance between the pump and signal/idler, to optimize the generation efficiency. In this regime, the Raman process can take over from four-wave mixing and lead to supercontinuum generation. It is shown that the parametric wavelength conversion is directional; probably due to small variations in the core dimensions along the fiber length. The fiber exhibits up to 40% conversion efficiency, with the idler (0.9 microm) and the signal (1.3 microm) having a combined output power of over 1.5 W.