#4544a American Scientists, Strip of Four
[2309]

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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.