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However, the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the death zone, where it is generally believed that no human body can acclimatize.
Country codes are defined by the International Telecommunication Union (ITU) in ITU-T standards E.123 and E.164. The prefixes enable international direct dialing (IDD). Country codes constitute the international telephone numbering plan. They are used only when dialing a telephone number in a country or world region other than the caller's.
For international access the NANP is assigned the country code 1, which is dialed as a prefix in the international E.164 telephone numbering plan. The trunk prefix for dialing long-distance calls, across numbering plan area (NPA) boundaries within Canada or to other NANP countries, is also 1.
High-altitude adaptation in humans is an instance of evolutionary modification in certain human populations, including those of Tibet in Asia, the Andes of the Americas, and Ethiopia in Africa, who have acquired the ability to survive at altitudes above 2,500 meters (8,200 ft). [1]
The four area codes form an overlay numbering plan for the same geographic region, where area code 905 was established in October 1993 in an area code split from area code 416. When 289 was overlaid on June 9, 2001, all local calls required ten-digit dialing .
The human body has optimal endurance below 150 m (490 ft) elevation. [6] The concentration of oxygen (O 2) in air is 20.9% so the partial pressure of O 2 (PO 2) at sea level is about 21.2 kPa (6.3 inHg; 3.07 psi). In healthy individuals, this saturates hemoglobin, the oxygen-binding red pigment in red blood cells. [7]
Height is the vertical distance above a reference point, commonly the terrain elevation. In UK aviation radiotelephony usage, the vertical distance of a level, a point or an object considered as a point, measured from a specified datum; this is referred to over the radio as height, where the specified datum is the airfield elevation (see QFE) [2]
This is a list of international dialing prefixes used in various countries for direct dialing of international telephone calls.These prefixes are typically required only when dialling from a landline, while in GSM-compliant mobile phone (cell phone) systems, the symbol + before the country code may be used irrespective of where the telephone is used at that moment; the network operator ...