Date of Issue : 16 June 2011
USPS will issue a set of four stamps on 16 June 2011, honouring four famous American scientists, chemist Melvin Calvin, botanist Asa Gray, physicist Maria Goeppert Mayer, and biochemist Severo Ochoa. The signature of all four scientists and their specific field of work is shown in the background of each stamp.The stamps are very nice for those collecting on Science and personalities.
Melvin Calvin was the first scientist to trace in detail the process of photosynthesis and conducted pioneering research on using plants as an alternative energy source. He won the Nobel Prize in chemistry in 1961.
Asa Gray, one of the first professional botanists in the United States, advanced the specialized field of plant geography and became the principal American advocate of evolutionary theory in the mid-nineteenth century.
Maria Goeppert Mayer developed a theoretical model that helped explain the structure of the atomic nucleus; for this work she became the only woman other than Marie Curie to win a Nobel Prize in physics.
Severo Ochoa, a biochemist, was the first scientist to synthesize ribonucleic acid (RNA) and competed in the race to decipher the genetic code. Ochoa won the Nobel Prize in physiology or medicine in 1959.
Special Covers
Rajasthan
4 special Cover released during 2nd Rajasthan Philatelic Exhibition RAJPEX 75
