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What's Hot This Summer?

Want to know what's hot in fashion? Watch what the beautiful people wear. Curious what's hot in science? Check out the papers that scientists cite the most. In 1999, the biggest buzz surrounded a highly specialized field called color superconductivity in quark matter. Other fashionable areas included the duality between string and gauge theory in physics, the Toll receptor in the fruit fly, which plays an important role in immunology, and the risks of transgenic crops.

The hit parade is compiled yearly by the Institute for Scientific Information (ISI), a database publishing company in Philadelphia whose information scientists comb through citations in papers from more than 7000 peer-reviewed journals. ISI researchers use a computer algorithm to find papers less than 15 years old that were frequently cited in the previous year; the program then looks for pairs or groups of these articles frequently cited together. If the program finds a sufficiently large group of popular papers, it declares the group the core of a "hot" area and searches the key words to determine the topic. The newer the group of oft-cited papers, the hotter the field.

A myriad of citations doesn't guarantee that a paper presents importance, cautions Bruce Lewenstein, a professor of science communication at Cornell University in Ithaca, New York. Papers may be cited frequently, he says, because they beg repudiation, or describe a widely employed technique. Researchers may even have simply fallen into the habit of citing them. However, Lewenstein says, the ISI ratings mean more than a simple count of citations because they identify areas of interest: "The advantage is that they are defining disciplines as the researchers are defining them."

The search yielded three rankings: one for biomedicine, with at least 11 core papers; one for physics, with at least eight; and a list of "superhot" fields whose core papers are less numerous (six to eight) but very recent.

Rank Field No. of core papers
1. Toll receptor in the immune system signaling 11
2. Caspase activation and other aspects of apoptosis 25
3. Protein sequence databases 13
4. Chemokine receptors and dendritic cells 14
5. Orexin peptide and regulation feeding 11
6. Regulation of embryonic left-right asymmetry 21
7. Gene expression analysis using microarrays 28
8. Issues in human transplantation of porcine cells 11
9. The ARF-p53 tumor suppression pathway 13
10. b-catenin mutation in human cancers 33
11. Combination therapy in management of HIV 12
12. Complete microbial genome sequences 16

Rank Field No. of core papers
1. Duality between string theory and gauge theory 8
2. Anti-de Sitter space/conformal field theory correspondence 16
3. Characteristics of the spin-Peierls compound NaV2O5 15
4. Investigations of Bose-Einstein condensates 16
5. Fabrication and characterization of AlGaN/GaN structures 13
6. Photonic properties of macroporous materials 17
7. b-peptides and oligomers of b-amino acids 19
8. Properties and applications of zinc-oxide materials 17
9. Growth and properties of GaN surfaces 18
10. Quantum cloning and quantum copying 10

Rank Field No. of core papers
1. Color superconductivity in quark matter 7
2. Characterization of DNA polymorphisms in disease genes 6
3. Issues in treatment of Helicobacter pylori infection 8
4. Complications in genetically engineered crops 6
5. The hospitalist model of inpatient care 6
6. Antidepressant medication and sexual dysfunction 6