Karl Landsteiner Karl Landsteiner Karl Landsteiner, , (14 June 1868 – 26 June 1943) was an Austrian biologist, physician, and immunologist. He distinguished the main blood groups in 1900, having developed the modern system of classification of blood groups from his identification of the presence of agglutinins in the blood, and identified, with Alexander S. Wiener, the Rhesus factor, in 1937, thus enabling physicians to transfuse blood without endangering the patient's life. With Constantin Levaditi and Erwin Popper, he discovered the polio virus in 1909. He received the Aronson Prize in 1926. In 1930, he received the Nobel Prize in Physiology or
Nobel Prize controversies Chao was the first to experimentally identify positrons through electron–positron annihilation, but did not realize what they were. Anderson, Chao's classmate at Caltech, used the same radioactive source, , as Chao. (Historically, was known as "thorium C double prime" or "ThC", see decay chains.) Fifty years later, Anderson admitted that Chao had inspired his discovery: Chao's research formed the foundation from which much of Anderson's own work developed. Chao died in 1998, without sharing in a Nobel Prize acknowledgment. The 1923 prize went to Robert Millikan "for his work on the elementary charge of electricity and on the photoelectric effect".