While carrying out a liquid-liquid extraction using dichloromethane and a sample of lake water, Jennifer Apell, a graduate student at MIT, observed the formation of an emulsion in the sample, likely due to the presence of certain chemicals in the water. When she let the dichloromethane and water separate, air bubbles became trapped by the emulsion layer at the dichloromethane/water interface, creating the effect seen in this picture. Apell is studying the bioavailable concentration of polychlorinated biphenyls (PCBs) in contaminated water bodies to assess their risk to living organisms.
Front view, 1 KW NIC radio transmitter manufactured by Cardwell for Intercity Radio Telegraph Co, 1922. This represents a very small but efficient radio transmitter designed for severe service with minimum maintenance; used by the US Bureau of Lighthouses
Hypatia of Alexandria (350? - 415) as depicted by Masolino da Panicale, 1428. Hypatia was the daughter of Theon, the last curator of the Alexandria library. She taught mathematics and astronomy and also made improvements on a hydrometer, a device used for the measurement of specific gravity of a liquid.