Nucleon spin structure describes the partonic structure of nucleon (proton and neutron) intrinsic angular momentum (spin).
 The key question is how the nucleon's spin, whose magnitude is 1/2ħ, is carried by its constituent partons (quarks and gluons).
 It was originally expected before the 1980s that quarks carry all of the nucleon spin, but later experiments contradict this expectation.
 In the late 1980s, the European Muon Collaboration (EMC) conducted experiments that suggested the spin carried by quarks is not sufficient to account for the total spin of the nucleons.
 This finding astonished particle physicists at that time, and the problem of where the missing spin lies is sometimes referred to as the proton spin crisis.
Georg Robert Döpel (3 December 1895 in Neustadt – 2 December 1982 in Ilmenau) was a German experimental nuclear physicist.
 He was a participant in a group known as the "first "Uranverein"", which was spawned by a meeting conducted by the "Reichserziehungsministerium", in April 1939, to discuss the potential of a sustained nuclear reaction.
 He worked under Werner Heisenberg at the University of Leipzig, and he conducted experiments on spherical layers of uranium oxide surrounded by heavy water.
 He was a contributor to the German nuclear energy project (Uranprojekt).
 In 1945, he was sent to Russia to work on the Soviet atomic bomb project.
 He returned to Germany in 1957, and he became professor of applied physics and director of the "Institut für Angewandte Physik" at the "Hochschule für Elektrotechnik", now Technische Universität, in Ilmenau (Thuringia).
As early as 1929, two Melbourne commercial radio stations, 3UZ and 3DB were conducting experimental mechanical television broadcasts - these were conducted in the early hours of the morning, after the stations had officially closed down.
 In 1934 Dr Val McDowall at amateur station 4CM Brisbane conducted experiments in electronic television.
Michael Vasilyevich Matyushin (Russian: Михаил Васильевич Матюшин ; 1861 in Nizhny Novgorod – 14 October 1934 in Leningrad) was a Russian painter and composer, leading member of the Russian avant-garde.
 In 1910–1913 Matyushin and his wife Elena Guro (1877–1913) were key members of the Union of the Youth, an association of Russian Futurists.
 Matyushin, a professional musician and amateur painter, studied physiology of human senses and developed his own concept of the fourth dimension connecting visual and musical arts, a theory that he put to practice in the classrooms of Leningrad Workshop of Vkhutein and INHUK (1918–1934) and summarized in his 1932 "Reference of Colour" (Cправочник по цвету).
Matyushin conducted experiments at his Visiology Center (Zorved) to demonstrate that expanding visual sensitivity from retinian optical centers would enable the discovery of "new organic substance and rhythm in the apprehension of space."
 He tried to teach himself and his students to see with both eyes, each independently, and to widen the field of their vision.
 He describes some of his work and ideas in a long essay titled "An Artist's Experience of the New Space."
Bruno Nikolaus Maria Weber (21 May 1915 in Trier – 23 September 1956 in Homburg) was a German physician, bacteriologist and Hauptsturmführer (1944), at Auschwitz, in the branch of the Hygiene Institute of the Waffen SS.
 He was chief of the Hygienic Institute.
 He organized experiments involving the interaction of different human blood types in unwilling prisoner-patients.
 He also conducted experiments using barbiturates and morphine derivatives for mind-control purposes.
Josef Mengele (] ; 16 March 19117 February 1979) was a German "Schutzstaffel" (SS) officer and physician in Auschwitz concentration camp during World War II.
 Mengele was a member of the team of doctors responsible for the selection of victims to be killed in the gas chambers and for performing deadly human experiments on prisoners.
 Arrivals deemed able to work were admitted into the camp, and those deemed unfit for labor were immediately killed in the gas chambers.
 Mengele left Auschwitz on 17 January 1945, shortly before the arrival of the liberating Red Army troops.
 After the war, he fled to South America, where he evaded capture for the rest of his life.
Marie Louis Victor Galippe (29 May 1848 - February 1922, Autouîl) was a French microbiologist and an eminent physician.
 He conducted experiments on microbiology in human life and also published notes on a variety of subjects including dental hygiene.
Frederick Gordon Spear (often F. Gordon Spear or F.G. Spear; 1895–1980) was a British physician and researcher.
 Originally trained in tropical medicine, he spent time working in what was then the Belgian Congo.
 After his return to England in 1923, he became interested in radiology and radiobiology.
 As a member of the Medical Research Council, he was involved in the decision to continue work at Strangeways Research Laboratory following the 1926 death of founder Thomas Strangeways.
 He served as Deputy Director under the laboratory's longtime director Honor Fell from 1931 to 1958.
 While at Strangeways he conducted experiments on the effects of radiation on cells and tissues, particularly tissue cultures derived from cancers.
 He was known for forceful rhetoric in support of the then-controversial field of tissue culture and its potential in informing clinical practice.
Bion 4 or Cosmos 936 ("Бион 4", "Космос 936") was a Bion satellite.
 The mission involved nine countries, including the United States, in a series of biomedical research experiments.
 The experiments were primarily follow-ups to the Bion 3 (Cosmos 782) flight.
 Scientists from the Bulgaria, Czechoslovakia, East Germany, France, Hungary, Poland, Romania, Soviet Union and the United States conducted experiments in physics and biology on the mission.
 The mission ended after 19.5 days.
Jona Laks (born 1930) is a Polish Jewish Holocaust survivor who was subject to human experimentation by Josef Mengele at the Auschwitz concentration camp.
 After the war she founded and served as chairwoman of the Organization of the Mengele Twins.
 In January 2015 she addressed the United Nations General Assembly at its International Day of Commemoration in Memory of the Victims of the Holocaust Memorial Ceremony.
 She has been featured in several documentary films.

Question: What is the nationality of the physician who conducted experiments on Jona Laks ?
Answer: German