Citation Histories Attest To 1990 Nobelists' Wide Influence

What does it take to win a Nobel Prize in science? An in-depth look at the citation records of this year's Nobel winners affirms that it takes more than good science. Not only must a laureate's work cross the frontiers of research--it must also be disseminated throughout the international scientific community. The citation records of the six North Americans who clinched the 1990 awards in medicine, chemistry, and physics (The Scientist, Nov. 12, 1990, page 8) indicate the broad and decisive impact these eminent individuals have had in their fields. Medicine or Physiology Two medical doctors on opposite coasts of the continental United States shared this year's Nobel Prize in medicine or physiology. E. Donnall Thomas and Joseph E. Murray were honored for their breakthrough research in transplant medicine. Thomas, 70, director emeritus of the Seattle-based Fred Hutchinson Cancer Research Center's Division of Clinical Research, was cited for his work on bone marrow transplantation. In 1956, Thomas successfully transplanted donor marrow into a human patient. During the next decade, Thomas and his group at the University of Washington developed ways to improve tissue typing to better match donors with hosts. They also worked on the problem of graft-versus-host disease, an autoimmune dys- function. In addition to the Nobel Prize, Thomas shared the 1990 Gairdner Foundation International Award with six other scientists in recognition of their contributions to medical science (The Scientist, Nov. 12, 1990, page 25). Throughout his career, Thomas has received numerous other honors, including the Kettering Prize of the General Motors Cancer Research Foundation (1981) and the Robert Roesler de Villiers Award from the Leukemia Society of America (1983). Had Thomas received the Gairdner award last year, he would have definitely made The Scientist's list of "nominees" for this year's Nobel in medicine or physiology (The Scientist, Oct. 1, 1990, page 17). That list was based on the combination of prizes won and citation histories. In terms of citations earned, Thomas is certainly a superstar: According to the Institute for Scientific Information's (ISI) Science Citation Index (SCI), he was the 180th most cited scientist for the period 1965 to 1978 (The Scientist, May 7, 1990, page 24); 22nd for the period 1973 to 1984 (The Scientist, Feb. 19, 1990, page 22); and 21st for the period 1981 to 1988 (The Scientist, Oct. 1, 1990, page 18). Thomas is the author or coauthor of more than 90 papers that have been cited in excess of 50 times each. His most cited article is the first installment of a two-part series that reviews research on bone marrow transplantation in rodents, dogs, primates, and human patients (E.D. Thomas, et al., "Bone-marrow transplantation," New England Journal of Medicine, 292:832-902, 1975). As of June 1990, this state-of-the-art review article has received close to 1,280 citations. The accompanying chart shows a year-by-year breakdown of the citations to Thomas's article. Within a year of publication, the number of references to this paper skyrocketed. In general, the number of citations to this paper had steadily increased, beginning to decline only in the last couple of years. Wrote Thomas of this article: "In retrospect, the manuscript was a potpourri of topics including a brief history of the field, a review of the more significant advances based on work in animals, particularly the canine model, and a review of the developments that set the stage for marrow transplantation in man. Unlike most reviews, the article contained a great deal of clinical data and interpretation that had not been published previously." This article, he continued, "provided a convenient reference for those who have subsequently written on the subject of marrow transplantation" (Current Contents, No. 21, page 20, 24 May 1982). Murray, 71, professor of surgery, emeritus, at Harvard Medical School and Brigham and Women's Hospital in Boston, shared the Nobel Prize in medicine or physiology with Thomas for his pioneering work in transplant medicine. Murray performed the first successful kidney transplant between identical twins in 1954. He later used organs from unrelated and deceased donors. Although Murray does not classify as a "Citation Superstar" in the sense that Thomas does, his work nonetheless has been highly influential. Murray's research also exemplifies the type of work Alfred Nobel wished to recognize--that which benefits humanity. Says Thomas E. Starzl, professor of surgery and head of transplantation at the University of Pittsburgh Medical Center, the selection of Murray as a recipient of the Nobel Prize "was a recognition of the importance of the field of transplantation." Adds Starzl, himself a noted researcher in transplant medicine (The Scientist, Hot Team, page 24, Feb. 5, 1990), "No one deserved it more. Joe [Murray] was already there when the rest of us arrived." Murray's most cited article (G.J. Dammin, N.P. Couch, J.E. Murray, "Prolonged survival of skin homografts in uremic patients," Annals of the New York Academy of Sciences, 64:967-76, 1957) has received more than 250 citations to date. Based on a known antigenic relationship between the skin and the kidney, Murray and his colleagues studied skin homografts in patients with diseased kidneys to better understand the absence of organ rejection among some of these patients. In essence, the researchers concluded that if an immune response within the patient causes rejection, then an impaired immune response would cause prolonged survival of the grafted tissue. The citation history of this article and Thomas's review paper are shown on the same graph. Unlike Thomas's paper, Murray's article never really reached a peak. Instead, it has oscillated between four and 20 citations per year, remaining fairly level since its publication. The drastic difference between the citation histories of the two Nobel laureates' most cited papers could very well be tied to the nature of the two papers themselves. Whereas Thomas's paper is a review article (review articles tend to be frequently cited), Murray's article is based on clinical findings. Also, this paper's conclusion, that grafted tissue survives because of an impaired immune response, may have become part of transplant medicine's "accepted" body of knowledge and, thus, not frequently cited. Chemistry Elias J. Corey, 62, of Harvard University was the sole winner of the 1990 Nobel Prize in chemistry. The Nobel committee cited Corey, Sheldon Emery Professor of Organic Chemistry at Harvard, for his development of theory and methodology and for his groundbreaking research in the synthesis of organic molecules--a process pertinent to the manufacture of compounds such as drugs, paints, and pesticides. Corey advocated a method of organic synthesis known as retrosynthesis. Through this method, Corey showed that it would be easier to synthesize a natural compound by first breaking it down into its basic essential parts than by trying to build the desired compound through the "trial and error" process of adding components to a simpler, but similar, compound. He augmented this method by developing computer modeling programs that help researchers narrow their choices. Perhaps Corey's most noteworthy research has been his work on the synthesis of prostaglandins and other related human hormones. Like Thomas, Corey ranks among those researchers whom The Scientist calls "Citation Super- stars." Corey was the 21st most cited scientist for the period 1965 to 1978 (The Scientist, Feb. 19, 1990, page 22); 133rd during 1973 to 1984 (The Scientist, April 16, 1990, page 22); and 73rd for the period 1981 to 1988 (The Scientist, Oct. 1, 1990, page 18). Corey's research earned him numerous awards, including the American Chemical Society's Award in Pure Chemistry (1960), the Wolf Foundation Prize for Chemistry (1986), and the National Medal of Science (1988). Corey's citation record and list of honors qualified him for inclusion in The Scientist's list of "nominees" for this year's Nobel Prize in chemistry (The Scientist, Sept. 17, 1990, page 16). Corey's extensive citation history stems from the simple fact that his contributions to the field of organic synthesis chemistry have been embraced by almost every scientist working in that area. "Dr. Corey's work has influenced virtually everyone in the field of synthesis on two levels," says Dennis P. Curran, professor of chemistry at the University of Pittsburgh and regular contributor to The Scientist's "Articles Alert" column. "One level of influence is conceptual," says Curran. "The thought processes that he has introduced and popularized now pervade every aspect of synthesis planning. These processes are introduced to beginning students of synthesis and soon become almost second nature. The second level is practical: Dr. Corey has pioneered an incredible number of new reagents and transformations. Everyone in the field routinely uses synthetic methods that were either invented or significantly improved by Corey." Corey's most cited paper is a short article that describes one of these numerous contributions to synthesis research--a more efficient reagent for oxidizing a variety of alcohols to carbonyl compounds (E.J. Corey and J.W. Suggs, "Pyridinium chlorochromate: an efficient reagent for oxidation of primary and secondary alcohols to carbonyl compounds," Tetrahedron Letters, 31:2647-50, 1975). [Editor's note: In the Sept. 17, 1990, issue of The Scientist, Corey's most cited article was incorrectly identified.] Since its publication, this article has been cited almost 1,590 times by other scientists. The citation history of this paper, as charted in the accompanying graph, shows that by 1982 (seven years after publication), citations to this paper reached their peak. Although the number of yearly citations is declining, the paper is still highly cited, averaging a little more than 100 citations per year. Physics Three scientists shared the 1990 Nobel Prize in physics: Jerome I. Friedman, 60; Henry W. Kendall, 64; and Richard E. Taylor, 60, were honored for their work that provided experimental evidence for the existence of quarks. Friedman, William A. Coolidge Professor of Physics at MIT, has been a faculty member at the institute since 1960. Kendall, an MIT faculty member since 1961, is the director and founding member of the Union of Concerned Scientists. Taylor, a professor of physics at the Stanford Linear Accelerator Center (SLAC), has been with the center since it was founded in 1962. Friedman, Kendall, and Taylor led a team of researchers that conducted a series of experiments from 1967 to 1973 at SLAC to prove the quark model previously proposed by Murray Gell-Mann and George Zweig of the California Institute of Technology. During these experiments, the team fired high-energy electrons produced by the accelerator at neutrons and protons and observed the electron scattering. "The high probability of these violent scatterings," says Jacques Lefran!ois, a particle physicist at CERN in Geneva, "revealed the existence of point-like objects [quarks] inside protons and neutrons." It was a revelation, he adds, that the Nobel committee was long overdue in recognizing. These experiments, says Lefran-!ois, had profound consequences on the field of particle physics that were "perhaps not fully understood at the time." For example, he says, these experiments aided in the search for understanding the strong force (the force that binds subatomic particles) by shifting the focus from the interactions of protons and neutrons to that of quarks instead. Not surprisingly, Friedman, Kendall, and Taylor's most cited article is one based on experiments the trio carried out at SLAC: E.D. Bloom, et al., "High-energy inelastic e-p scattering at 6 and 10," Physical Review Letters, 23:930-4, 1969. The citation history of this particular article is plotted in the accompanying graph. As is shown, the number of citations to this paper rose dramatically within the first two years of its publication, reaching a peak in 1971. Its citation frequency then dropped off just as rapidly, reaching a low in 1977 and remaining at this level for the past 12 years. This citation history, says Lefran!ois, could reflect the inauguration of quarks into the canon of particle physics. When the experiments were first reported, the proven existence of quarks was a "hot" topic. For the last decade, however, the fact that quarks exist has been accepted, and particle physicists now focus their efforts on identifying different types of quarks.

Citation Histories Attest To 1990 Nobelists' Wide Influence

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