1 A prospective randomised trial was conducted to compare aminoglycoside dose prediction based on individually measured pharmacokinetic data, with dosage based on physician intuition. 2 After 2 days of therapy more patients in the pharmacokinetic group had achieved both peak (6-10 mg l-l) and trough (1-2 mg l-1) target plasma concentrations (P = 0.007), peaks alone (P = 0.01) and troughs alone (P = 0.01). Their mean (s.e. mean) peak concentration was 6.49 ± 0.39 mg 1-1 compared with 4.27 ± 0.52 mg 1-1 in the control group (P = 0.001), with trough concentrations of 1.44 ± 0.22 mg F-1 and 0.94 ± 0.21 mg F' respectively (P = 0.054). 3 After 5 days of therapy, peak and trough concentrations were still significantly higher in the pharmacokinetic group despite empirical dose adjustment (P = 0.01 and P = 0.013 respectively). 4 The mean (s.e. mean) daily dose of aminoglycoside was higher in the computer group (312 ± 17 mg vs 203 ± 13 mg, P = 0.001). 5 These findings suggest that dose estimation based on measured pharmacokinetic parameters is superior at achieving target plasma drug concentrations.

A model describing the population trends for any number of races of rust in the urediospore stage during a single growing season is presented. The general case for the field is subsequently modified to describe trends in a population of rust races under constant conditions. A term which gives an estimate of the relative survival ability of each race in the population is finally obtained. This term allows the trends in the composition of the mixture to be predicted. The theoretical proportion of strain 21 Anz-2,3,7 in amixture of strains 21 Anz-2,7 and 21 Anz-2,3,7 of P. graminis trifici over a number of generations was compared with the proportion of strain 21 Anz-2,3,7 in an experimental population of the same two strains over the same period. The model was found to be a good first approximation to the results obtained with the experimental population.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. A deterministic mathematical model is constructed to describe the population growth in colonies of the grain beetle, Tribolium confusuin, under laboratory conditions. It is shown how (1) changes in the egg laying rate and adult mortality, (2) the destruction of some eggs by larvae as well as by adults, and (3) the destruction of some small larvae by larvae and adults, lead to a theoretical population growth which agrees closely with the laboratory experiments.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract. A deterministic mathematical model is constructed to describe the population growth in colonies of the grain beetle, Tribolium confusum, under laboratory conditions. It isshown how the eating of eggs by adults can account for the main features of the observed population growth, in particular the occurrence of a maximum in the adult numbers and the tendency then to reach a steady state.

If the various parameters describing the behavior of species in competition are known, and the populations at any time are given, then the corresponding populations a short time later can be calculated. In this way a deterministic mathematical model can be set up to imitate the progress of the populations. This model gave a satisfactory result when applied to a particular laboratory experiment.