Oxygen

…Earth through their use of hydrogen, oxygen, carbon, nitrogen and phosphorus. Drawing on his book Elemental, the conversation connects these biogeochemical changes across deep time with sustainability and choices that could reduce human environmental impacts.

…It distinguishes abundant nitrogen and oxygen from trace gases whose concentrations respond strongly to human emissions. Measurements are used to compare natural changes with human influences relevant to climate.

…and requires a constant supply of oxygen. Second and third order neurons are supplied by the retinal circulation, whose characteristics are similar to brain circulation. However, the photoreceptor region, which occupies half of the retinal thickness, is avascular, and relies on diffusion of oxygen from the choroidal circulation, whose properties are very different, as well as the retinal circulation. By fitting diffusion models to oxygen measurements made with oxygen microelectrodes, it is possible to understand the relative roles