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Argon–argon (or 40 Ar/ 39 Ar) dating is a radiometric dating method invented to supersede potassium–argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes.
Ar contamination. Most of the argon in Earth's atmosphere was produced by electron capture of long-lived 40 K (40 K + e − → 40 Ar + ν) present in natural potassium within Earth. The 39 Ar activity in the atmosphere is maintained by cosmogenic production through the knockout reaction 40 Ar (n,2n) 39 Ar and similar reactions. The half-life of 39
The Ar–Ar dating method was developed to measure the presence of extraneous argon. Great care is needed to avoid contamination of samples by absorption of non-radiogenic 40 Ar from the atmosphere. The equation may be corrected by subtracting from the 40 Ar measured value of the amount present in the air where 40 Ar is 295.5 times more ...
Argon is far more narcotic (about 2.3 times more) than the cheaper and more readily available nitrogen at depth, so it loses out to nitrogen in all roles as a primary breathing gas. If the maximum operating depth for air owing to narcosis is taken to be 40 metres (130 ft), then for 20% argox (20% O 2, 80% Ar) it would be 14.5 metres (48 ft). [a]
Animation of main (green truss structure) and jib boom (purple truss structure) articulation. This specific example uses a level luffing mechanism to maintain the load at approximately the same vertical height as the jib moves through its range of travel.
A gin pole in use loading logs A gin pole used to install a weather vane atop the 200-foot steeple of a church Roof trusses being assembled with gin poles. A gin pole is a mast supported by one or more guy-wires that uses a pulley or block and tackle mounted on its upper end to lift loads. The lower end is braced or set in a shallow hole and ...
C-25 (75% argon/25% CO 2) is commonly used by hobbyists and in small-scale production. Limited to short circuit and globular transfer welding. Common for short-circuit gas metal arc welding of low carbon steel. C-20 (80% argon/20% CO 2) is used for short-circuiting and spray transfer of carbon steel.
The FGM-148 Javelin, or Advanced Anti-Tank Weapon System-Medium (AAWS-M), is an American-made man-portable anti-tank system in service since 1996 and continuously upgraded. It replaced the M47 Dragon anti-tank missile in US service. [ 11 ]