The Cochrane Database of Systematic Reviews (CDSR) evolved in response to Archie Cochrane's challenge to the medical profession to assemble "a critical summary, adapted periodically, of all . . . relevant randomized controlled trials". CDSR has been an electronic publication from its inception and this has meant that Cochrane reviews (i) need not be constrained by lack of space; (ii) can be updated as new information becomes available and when mistakes or other ways of improving them are identified; and (iii) can be cross-linked to other, related sources of relevant information. Although CDSR has become widely cited, it must continue to evolve in the light of technological and methodological developments, and in response to the needs of people making decisions about health care.Keywords: Cochrane Collaboration, The Cochrane Database of Systematic Reviews, Health care, Randomized controlled trialsThe development of the Cochrane Collaboration has been described elsewhere (1;2;6;11-13;17;22;27). In this article, we describe the origins and evolution over the past 20 years of the Collaboration's principal product, that is, The Cochrane Database of Systematic Reviews (CDSR), and some of the features that set it apart from more traditional publications.In 1972, Archie Cochrane's book Effectiveness and Efficiency drew attention to the need to obtain better evidence to inform the development of health services, and emphasized the important role of evidence derived from randomized controlled trials (23). One consequence of this was that, encouraged by Cochrane himself, one of his readers (I. C.) began to assemble a collection of reports of randomized trials done to assess the effects of care during pregnancy, childbirth, and early infancy (the perinatal period).In a publication a few years later, Cochrane rated obstetrics and gynecology the medical specialty most guilty of ignoring the need to base clinical practice on reliable research evidence and issued a call to all specialties to assemble "a critical summary, adapted periodically, of all . . . relevant randomized controlled trials" (24). In response to Cochrane's challenges, staff at the recently established National Perinatal Epidemiology Unit in Oxford (10) (i) developed a computerized register of controlled trials from the collection of reports of trials in perinatal care mentioned above (8;34;43;44), (ii) demonstrated how data from similar studies could be combined to create overall estimates of effects (7;50), and (iii) Cochrane Database of Systematic Reviews (CDSR) began to establish the foundations for an international collaboration to prepare "critical summaries" of the studies included in the register (29).By the mid-1980 s, following the publication of other documents reinforcing Cochrane's messages, such as the U. S. Office of Technology Assessment's report on technology assessment in health care (45), the stage was set for the National Perinatal Epidemiology Unit in Oxford to coordinate the creation of a body of systematic reviews of interventions in ...

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In February 1994, The Terminal Island Treatment Plant experienced severe Nocardia foaming problems. Attempts to control foaming, such as lowering the MCRT and foam removal and wasting, met with limited success. In April 1994, a final clarifier cationic polymer injection system was used to combat poor settling activated sludge. After 3 days of polymer addition, foaming was eliminated. The effectiveness of the polymer as a Nocardia foam control agent was verified in subsequent foaming incidents by conducting the full-scale plant tests presented in this paper. Mechanisms are suggested for the action of the polymer in eliminating Nocardia foam. These include interaction with the foam-stabilizing surfactants present in the wastewater, and polymer flocculation of dispersed Nocardia filaments into the activated sludge floc. Water Enviroll. Res., 69,25 (1997).

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