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YANG, CHEN NING

(Yang Zhenning in pinyin, 1922- ), a prominentChinese American physicistand one of the most in­fluential theoretical physicists in the world in thesecond halfof the twentieth century. He alsoplayedan active role in U.S.- China scientificrelations.

Born in Hefei, China, Yang grew up on thecampus ofTsinghua (Qjnghua) University in Bei­jing where his father, Yang Wuzhi, was a professorof mathematics. He was an excellent student buthis sheltered environment collapsed with the Jap ­anese invasion in 1937. He fled with his family tosouthern Chin a and studied physics in the eliteSouthwestern Associated University in Kunming.After receiving his BS in 1942 and MS in 1944,he taught in a middle school for one year, wherehe met his future wife, Du Zhili.

In 1945, Yang won a Boxer fellowship andcame to the University of Chicago to study withthe great physicist Enrico Fermi and gave himselfthe nickname "Frank" in honor of Ben Franklin.

Although deeply influenced by Fermi's way ofdoing physics, Yang ended up taking his PhDin theoretical physics in 1947 with the physicistEdward Teller because Yang,as a foreigner, couldnot enter Argonne National Laboratory wh ereFermi conducted his experiments.

Yang taught at Chicago for one year beforemoving to the Institute for Advanced Stu dy atPrinceton, New Jersey, initially as a visitor butlater as a permanent member at the invitation of itsdirector). Robert Oppenheimer. In the summerof 1954, when visiting the Brookhaven NationalLaboratory on Long Island, he devised, with thegraduate student Robert Mills , the so-calledYang- Mills gauge field theory to describe patternsof interactions between elementary particles. Ithas since become one of the most fundamentaltheories in physicswith far-reaching impact.

Yang's best-known contribution to physicscame as a result of collaboration with T.D. Lee ofColumbia University, a fellow Chinese Americanphysicist whom he had met in Chicago when bothstudied under Fermi. Trying to solve the puzzles

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in the behaviors of subatomic particles, they pro­posed in 1956 the possibility that in the so-called"weak interactions" the commonly presumed lawofleft-right parity was violated. Initially receivedwith much skepticism, they were soon, however,proven right in an experiment conducted by a thirdChineseAmerican physicist, Chien-Shiung Wu ofColumbia, in collaboration with colleagues at theNational Bureau of Standards. The news electri­fied the world of physics and Yang and Lee re­ceived the Nobel Prize in Physics in 1957.

Yang and Lee continued their collaborationuntil 1962 when personal friction developed be­tween the two, in part over credit for their famousdiscovery. In 1966 Yang moved to the new StonyBrook campus of the State University of NewYork, where he stayed until retirement in 1999and contributed much to the school's develop­ment. In this period he collaborated with RodneyJ. Baxter and came up with the Yang-Baxter equa­tion, another major breakthrough in physics withwidespread applications and growing importancein physics and mathematics.

Yangspent much ofhis energy in his later yearspromoting U.S.-China scientific relations, withhis first visit back to China in 1971. He becamepresident of the National Association of ChineseAmericans in 1977 and pushed for the successfulrenormalization of U.S.-China relations. Throughpublic speeches and frequent visits, he has playedan active role in promoting science and educationin mainland China, Taiwan, Hong Kong, and therest of East Asia. In 2003, Yang moved to Chinafollowing the death ofDu Zhili and then marriedWeng Fan, a graduate student in English in Guang­zhou, and during the second decade ofthe twenty­first century, he split his time between Tsinghuaand the Chinese University ofHong Kong.

[See also Fermi, Enrico; Lee, Tsung-Dao;Nobel Prize in Biomedical Research; Oppen­heimer, J. Robert; Physics; Teller, Edward;andWu, Chten-Shiung.]

BIBLIOGRAPHY

Bernstein, Jeremy. A Comprehensible World. NewYork: Random House, 1967. Contains a profile

ofTsung-Dao Lee and Chen Ning Yang, ''AQues­tion of Parity," first published in TheNew Yorker,12 May 1962, pp. 49-103.

Jiang, Caijian. Guijan yu duicheng zh! mei: YangZhenning zhuan (The Beauty of Gauge and Sym­metry: A Biography of Chen Ning Yang) . Taipei:Tianxia Press, 2002 .

Yang, Chen Ning. Selected Papers 1945-80 with Com­mentary. San Francisco: W. H. Freeman, 1983.

ZuoyueWang

YELLOW FEVER

Yellow fever was a major epidemic disease in theAtlantic world from the time ofits importation viathe West African slave trade in the seventeenthcentury to its effective control by the mid-twenti­eth. The disease is caused by a virus that is spreadby mosquitoes of the Aedes genus, and it featuresdramatic symptoms ofhigh fever, headache, jaun­dice, and a diffuse bleeding tendency. This last fea­ture caused bleeding in the stomach, which, whenforcibly ejected, generated the grisly symptom ofblack vomit that so distinguished the terrible in­fection. Case mortality rates could appear as highas 50 percent because the milder caseswent unrec­ognized. Imported from West Africa, the first out ­breaks struck the Caribbean in the mid-seventeenthcentury and reached the cities of Boston, NewYork, and Philadelphiain the 1690s.Throughout itshistory in North America, yellow fever remainedlargelyan urban disease, travelingon the trade routesconnecting American cities to tropical locales.

The disease flared dramatically in Philadelphiain 1793, when it disrupted the new federal govern ­ment and caused the first major controversy overthe causes of epidemic disease. One side arguedthat the disease arose spontaneously from the filthcoating the streets and docks; others claimed thatit was an imported pestilence. Arguments abou tpublic-health policy flowed from these theories,with one side promoting sanitation and the othe rquarantine. All segments of the population wereaffected, although the affluent found some protec­tion in flight, and African Americans appeared tosuffer less than others.

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