Word: oxygenation
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RECOVERING. CHUN DOO HWAN, 64, former South Korean President; from a 26-day hunger strike; in Seoul. Chun was arrested in December for his role in the 1979 coup that brought him to power. He was given oxygen and an intravenous drip, and should be well enough to be tried in about a month...
...hospitals could simply refuse to treat Medicaid patients. Managed care, meanwhile, is still touted as a cost-saving panacea. And it does hold promise, as many state experiments attest. But there may be only so much efficiency to be extracted from the treatment of, say, disabled seniors tethered to oxygen machines...
...Without oxygen to aerate tissues and make vital structural components like collagen, notes Knoll, animals simply cannot grow large. But for most of earth's history, the production of oxygen through photosynthesis - the metabolic alchemy that allowed primordial algae to turn carbon dioxide, water and sunlight into energy - was almost perfectly balanced by oxygen-depleting processes, especially organic decay. Indeed, the vast populations of algae that smothered the Precambrian oceans generated tons of vegetative debris, and as bacteria decomposed this slimy detritus, they performed photosynthesis in reverse, consuming oxygen and releasing carbon dioxide, the greenhouse gas that traps heat...
...oxygen to rise, then, the planet's burden of decaying organic matter had to decline. And around 600 million years ago, that appears to be what happened. The change is reflected in the chemical composition of rocks like limestone, which incorporate two isotopes of carbon in proportion to their abundance in seawater - carbon 12, which is preferentially taken up by algae during photosynthesis, and carbon 13, its slightly heavier cousin. By sampling ancient limestones, Knoll and his colleagues have determined that the ratio of carbon 12 to carbon 13 remained stable for most of the Proterozoic Eon, a boggling expanse...
...conduits that take food in at one end and expel wastes at the other, may be the key to the Cambrian explosion. Their reasoning goes something like this: animals grazed on the algae, packaging the leftover organic material into fecal pellets. These pellets dropped to the ocean depths, depriving oxygen-depleting bacteria of their principal food source. The evidence? Organic lipids in ancient rocks, notes Hayes, underwent a striking change in carbon-isotope ratios around 550 million years ago. Again, the change suggests that food sources rich in carbon 12, like algae, were being "express mailed" to the ocean floor...