Medium earth orbits

MEO/HEO Satellites (Medium Earth Orbit or High E. orbit).317... 

Geostationary Earth Orbit), 5 IGSO (Inclined Geosynchronous Orbit) and 4 MEO (Medium Earth Orbit) - BeiDou system (BDS) has formally begun to provide services to China and the surrounding areas since December 2012 (Report...2013,... 

Meteorites from the asteroid belt are a potential source of some of the purine bases present in RNA. As asteroids travel in their orbits between Mars and Jupiter they collide with each other and pieces are broken off that vary in size from large bodies (potential meteorites) to dust particles. If the energy of the collision is great enough, this material is propelled out of its orbit into the interplanetary medium and some of the material eventually reaches the Earth. Approximately 10 kg of asteroidal material reached the primitive Earth s surface (6). This corresponds to a layer of material weighing 2x10 kg/m if spread uniformly over the surface of the Earth. The carbon content of the soluble organics present (1%) is equivalent to a layer of carbon compounds 25 m thick on the primitive Earth. Since meteorites contain about 1 ppm of purines and pyrimidines, then about lO kg of these compounds were on the primitive Earth. 

In glass, rare-earth luminescence has in general higher quantum efficiencies than the luminescence of the 3d and 4d ions. This is due to the fact that the 4f orbitals are rather isolated from the surrounding medium. The luminescence quantum efficiency is defined as the number of photons emitted divided by the number of photons absorbed, and in most cases is equal to the ratio of the measured lifetime to the radiative lifetime of a given level. 

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