To identify fast-moving areas of current research, Science Watch turned to ISI's latest Research Front Database. These fronts, or "clusters," are active specialty areas consisting of a group of related journal articles that are frequently cited together by more current papers. The cited works are called the "core" of the specialty; they represent the intellectual foundations of the field. A specialty whose core includes many recently cited works is one undergoing rapid transformation: a hot field.

   Science Watch divided the specialty fields into two broad groupings. Biomedical fields, each having at least 15 core papers, appear in the table above. Fields in the physical sciences, with at least seven core papers each, are listed on page 2. In both tables, the fields are ranked according to their "newness"-that is, according to the average age of each field's core papers. All the fields listed exhibited an average age, among their core papers, of 1994 or younger. The fields are ranked from youngest to oldest; in other words, by immediacy.

   In addition, Science Watch selected five areas that, although having smaller cores (at least five papers), boast the most recent foundation literature. These "superhot" fields are listed on page 2.

   Sitting atop the biomedical ranking is one of the largest and fastest-moving fields in the entire survey-and a familiar topic in Science Watch: research covering various aspects of obesity in mice and humans, along with investigations of the obese gene product leptin. Thirty-five papers constitute the core of this front, including the most-cited of the lot: "Positional cloning of the mouse obese gene and its human homologue," by Y. Zhang and colleagues (see Nature, 372[6505]:425-32, 1 December 1994). This paper was a fixture in the Top Ten rankings in Biology during the autumn of 1996. Another core paper is a 1996 New England Journal of Medicine study of leptin concentrations in normal-weight and obese humans. This report is currently the most-cited paper in Medicine (see page 7 of this issue, paper #1).

   Another familiar topic-apoptosis, or programmed cell death-figures prominently in the biomedical ranking. One field concerns the so-called death domain, a region that is present in several proteins. Overexpression of these proteins usually leads to cell death. Another aspect of apoptosis centers on the interleukin-1b converting enzyme (ICE) family of proteases. The paper currently ranked fifth in the Biology Top Ten (see page 8 of this issue, paper #5), which Biology correspondent Jeremy Cherfas discussed at length in his previous column (see Science Watch 8[6]:8, November/December 1997) identifies a crucial link in the cell-death sequence involving the ICE family.    continued