in the latter two cases, silicon poses a slight hazard as an irritant. it is hazardous if inhaled. the occupational safety and health administration osha has set the legal limit for silicon exposure in the workplace as 15 mg/m 3 total exposure and 5 mg/m 3 respiratory exposure over an 8-hour workday.
typical background concentrations of chromium in environmental media are: atmosphere <10 ng m −3; soil <500 mg kg −1; vegetation <0.5 mg kg −1; freshwater <10 μg l −1; seawater <1 μg l −1; sediment <80 mg kg −1. chromium is mined as chromite fecr 2 o 4 ore.
a number of significant scientific events occurred in 2014, including the first robotic landing on a comet and the first complete stem-cell-assisted recovery from paraplegia.the year also saw a significant expansion in the worldwide use and sophistication of technologies such as unmanned aerial vehicles and wearable electronics.. the united nations declared 2014 the international year of .
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a number of significant scientific events occurred in 2014, including the first robotic landing on a comet and the first complete stem-cell-assisted recovery from paraplegia. the year also saw a significant expansion in the worldwide use and sophistication of technologies such as unmanned aerial vehicles and wearable electronics .
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the reduction of contaminants in pig iron that negatively affect material properties, such as sulfur and phosphorus, yields cast iron containing 2–4% carbon, 1–6% silicon, and small amounts of manganese. pig iron has a melting point in the range of 1420–1470 k, which is lower than either of its two main components, and makes it the first .
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