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Biomedical subjects

B F Manly

Publications and source records attributed to B F Manly.

12 recordsLinked to original sources
PubMed2001

An introduction to contingent (closed-loop) brain electrical stimulation for seizure blockage, to ultra-short-term clinical trials, and to multidimensional statistical analysis of therapeutic efficacy.

Automated seizure blockage is a top research priority of the American Epilepsy Society. This delivery modality (referred to herein as contingent or closed loop) requires for implementation a seizure detection algorithm for control of delivery of therapy via a suitable device. The authors address the many potential advantages of this modality over conventional alternatives (periodic or continuous), and the challenges it poses in the design and analysis of trials to assess efficacy and safety-in the particular context of direct delivery of electrical stimulation to brain tissue. The experimental designs of closed-loop therapies are currently limited by ethical, technical, medical, and practical considerations. One type of design that has been used successfully in an in-hospital "closed-loop" trial using subjects undergoing epilepsy surgery evaluation as their own controls is discussed in detail. This design performs a two-way comparison of seizure intensity, duration, and extent of spread between the control (surgery evaluation) versus the experimental phase, and, within the experimental phase, between treated versus untreated seizures. The proposed statistical analysis is based on a linear model that accounts for possible circadian effects, changes in treatment protocols, and other important factors such as change in seizure probability. The analysis is illustrated using seizure intensity as one of several possible end points from one of the subjects who participated in this trial. In-hospital ultra-short-term trials to assess safety and efficacy of closed-loop delivery of electrical stimulation for seizure blockage are both feasible and valuable.

Anticonvulsants↗
PubMed1998

Interpreting comparative experiments on parasite burdens in animals using randomization and canonical variates.

Comparative experiments on parasite burdens present difficulties for modelling and interpretation: data tend to have highly skewed distributions, some standard methods of testing for effects have low power, and there is a need to make allowance for dependencies among the various measurements. Randomization testing and canonical variates analysis are advocated as a means of minimising these problems.

Abomasum↗
PubMed1983

Analysis of polymorphic variation in different types of habitat.

A correlation between the distribution of an organism and features of its environment can be taken as indirect evidence of natural selection. Biologists may therefore collect samples from polymorphic populations at a number of locations, classify the locations into habitat types, and consider whether the distribution of morphs varies with the habitat. Statistical aspects of this type of study are discussed in this paper. A randomization test for habitat effects is proposed and a negative binomial model is suggested for the distribution of morphs from random locations within one type of habitat. Data on the distribution of Cepaea hortensis and C. nemoralis snails in southern England provide an example. For both species there is clear evidence of differences between habitats, although the morph distributions are rather variable within habitats. The negative binomial model suggests that, for the snail data, variation in morph proportions is mainly due to location differences. The binomial sampling error is relatively unimportant unless the sample size at a location is very small. Therefore it is reasonable to analyse morph proportions by standard methods without giving different weights to data from different locations. The snail data are analysed in this way. Discriminant function analyses are used to test for habitat effects. The relationships between C. hortensis and C. nemoralis morph frequencies within one habitat are examined by a canonical correlation analysis.

Animals↗
PubMed1977

A new index for the intensity of natural selection.

A new index for the intensity of natural selection is proposed, based upon the double exponential model for fitness functions. This index is defined as a variance and is such that a value of zero indicates no selection while a value of one indicates quite strong selection. The use of the index is demonstrated using published data on the survival of human infants with different birth weights and gestation times.

Biological Evolution↗
PubMed1976

Some examples of double exponential fitness functions.

The advantages of using a double exponential fitness function are pointed out for the analysis of differential survival data. The uses of this type of function are illustrated on Bumpus' (1898) data on the survival of English sparrows after a severe storm and also on Cook and O'Donald's (1971) data on the over-winter survival of a large sample of snails.

Animals↗
PubMed1975

A second look at some data on a cline.

The release-recapture data given in table 1 of Kettlewell et al.'s (1969) paper on a cline in the frequencies of the typica and edda morphs of the moth. Amathes glareosa have been re-analysed. Estimates of daily survival probabilities have been calculated and these have been "explained" in terms of differences between localities of release and the morph involved. The conclusions of Kettlewell et al. (1969) with regard to the survival of the moths have not been confirmed.

Animals↗