Overcoming challenges to effectiveness of mobile markets in US food deserts.

The purpose of this research is to investigate whether mobile food markets may be effective in facilitating healthy food choices in food deserts. We investigate who does and does not use mobile food markets and why, and whether mobile markets have the potential to alter attitudes and food choices, and if so, how? We use a focus group study at four sites in the US to ask groups of mobile market shoppers and non-shoppers about their shopping, cooking, and eating attitudes and behaviors. We find that mobile market shoppers eat significantly more servings of fruits and vegetables, however, both shoppers and non-shoppers perceive fruits and vegetables as luxury items, and both groups lack knowledge about what is a serving and what is the recommended number of servings per day. Both groups identified the following needs for mobile markets to be more successful: increased awareness and advertising; affordability; improved convenience by offering more stops and hours, as well as greater variety of items for one-stop shopping; emphasis on value and service; and building trust within communities.

Ballistic Evaporation and Solvation of Helium Atoms at the Surfaces of Protic and Hydrocarbon Liquids.

Atomic and molecular solutes evaporate and dissolve by traversing an atomically thin boundary separating liquid and gas. Most solutes spend only short times in this interfacial region, making them difficult to observe. Experiments that monitor the velocities of evaporating species, however, can capture their final interactions with surface solvent molecules. We find that polarizable gases such as N2 and Ar evaporate from protic and hydrocarbon liquids with Maxwell-Boltzmann speed distributions. Surprisingly, the weakly interacting helium atom emerges from these liquids at high kinetic energies, exceeding the expected energy of evaporation from salty water by 70%. This super-Maxwellian evaporation implies in reverse that He atoms preferentially dissolve when they strike the surface at high energies, as if ballistically penetrating into the solvent. The evaporation energies increase with solvent surface tension, suggesting that He atoms require extra kinetic energy to navigate increasingly tortuous paths between surface molecules.