Food Sovereignty in the City: Challenging Historical Barriers to Food Justice

Local food initiatives are steadily becoming a part of contemporary cities around the world and can take on many forms. While some of these initiatives are concerned with providing consumers with farm-fresh produce, a growing portion are concerned with increasing the food sovereignty of marginalized urban communities. This chapter provides an analysis of urban contexts with the aim of identifying conceptual barriers that may act as roadblocks to achieving food sovereignty in cities. Specifically, this paper argues that taken for granted commitments created during the birth of the modern city could act as conceptual barriers for the implementation of food sovereignty programs and that urban food activists and programs that challenge these barriers are helping to achieve the goal of restoring food sovereignty to local communities, no matter their reasons for doing so. At the very least, understanding the complexities of these barriers and how they operate helps to strengthen ties between urban food projects, provides these initiatives with ways to undermine common arguments used to support restrictive ordinances and policies, and illustrates the transformative potential of food sovereignty movements

Acceleration of sub-relativistic electrons with an evanescent optical wave at a planar interface

We report on a theoretical and experimental study of the energy transfer between an optical evanescent wave, propagating in vacuum along the planar boundary of a dielectric material, and a beam of sub-relativistic electrons. The evanescent wave is excited via total internal reflection in the dielectric by an infrared (lambda = 2 mu m) femtosecond laser pulse. By matching the electron propagation velocity to the phase velocity of the evanescent wave, energy modulation of the electron beam is achieved. A maximum energy gain of 800 eV is observed, corresponding to the absorption of more than 1000 photons by one electron. The maximum observed acceleration gradient is 19 +/- 2 MeV/m. The striking advantage of this scheme is that a structuring of the acceleration element's surface is not required, enabling the use of materials with high laser damage thresholds that are difficult to nano-structure, such as SiC, Al2O3 or CaF2. (C) 2017 Optical Society of Americ