Showing papers by "University of Bath published in 1973"

Probability and statistics in engineering and management science

Abstract: Introduction and Data Description An Introduction to Probability One-Dimension Random Variables Functions of One Random Variable and Expectation Joint Probability Distributions Some Important Discrete Distributions Some Important Continuous Distributions The Normal Distribution Random Samples and Sampling Distributions Parameter Estimation Tests of Hypotheses Design and Analysis of Single-Factor Experiments: The Analysis of Variance Design of Experiments with Several Factors Simple Linear Regression and Correlation Multiple Regression Nonparametric Statistics Statistical Quality Control and Reliability Engineering Stochastic Processes and Queueing Statistical Decision Theory References Appendix Answers to Selected Exercises Index.

A Consumer Purchasing Model with Erlang Inter-Purchase Times

Abstract: The gamma-Poisson form of the negative binomial distribution (NBD) model generally gives a good fit to many aspects of repeat-buying behavior for a wide range of frequently bought branded consumer goods. Nonetheless, empirical evidence suggests that purchasing a particular brand-size in successive equal time-periods tends to be more regular than Poisson. An alternative model is therefore examined in which inter-purchase times for a given consumer are described by an Erlang distribution rather than by the negative exponential distribution implicit in the Poisson assumption of the NBD model. But it is found that the NBD model is robust to this kind of departure. Because of its greater simplicity, the NBD model therefore seems preferable for practical use.

The cuticle: A barrier to liquid and particle penetration of the shell of the hen's egg

Abstract: Synopsis The cuticle of the egg shell prevents water‐soluble dyes and carbon black from entering the majority of pores. A small percentage of eggs obtained from a commercial flock had no cuticle and their shells were easily invaded by carbon black. Chemical or physical removal of cuticle resulted in the pores being flooded with water which carried in carbon black. Such eggs did not, however, absorb water at a rate equal to that of eggs from which a piece of shell had been removed. This indicated that the pores without a cap and plug of cuticular material resisted the movement of water. The role of the cuticle and shell in repelling water is discussed and a function akin to that of the plastron of insect eggs proposed.

Trade Wind and Temperature Correlations down a Deep-sea Core off the Saharan Coast

Abstract: IN discussions relating to any possible climatic change that may occur even within our own lifetime, it is apparent1 that studies of Pleistocene climatic changes are becoming increasingly valuable. Obviously it is desirable to have as complete a picture as possible of the Pleistocene period, and towards this end we now report a method that seemingly gives an estimate of wind strength throughout the last 700,000 yr.

Self-Similar Problems in Elastodynamics

Abstract: This paper presents a formulation of self-similar mixed boundary-value problems of elastodynamics that is a natural extension of one already developed by the writer for elastostatic problems. By thus exposing the analytical structure that is common to both the dynamic and static problems, the existence of properties common to certain static and dynamic problems is explained, and further such properties are derived. Common features of both two-dimensional and three-dimensional problems are brought out by reducing them to Hilbert problems, directly in two dimensions and by introducing the Radon transform in three dimensions. Several applications of the theory are presented, typical problems involving the indentation of a half-space by a conical or wedge-shaped indentor, and cracks expanding under the influence of a non-uniform applied stress. More difficult problems, that have not before been formulated, include dynamic indentation problems with adhesion, and problems of cracks expanding on interfaces between dissimilar materials. A method of solution of such problems is presented and an example of each type is worked out in detail. The method of analysis hinges upon representations of the solutions of 9 unmixed ’ self-similar problems for half-spaces, which are obtained by use of an alternative to Cagniard’s technique whose application is routine, even for an anisotropic half-space. The representations provide more general solutions of the unmixed problems than were available previously. The main singularities, or 9 arrivals ’, of the stress fields are extracted from the representations; these expressions are new and should be useful for certain problems in seismology. It is predicted, for instance, that a crack expanding on an interface can generate a ‘conical wave’, that is, a region in which the singularity has a logarithmic component as well as a step function, even in its P -wave arrival, which could not occur for a crack in a homogeneous medium. The properties of the equations of elastodynamics that are employed are that they are linear, homogeneous and self-adjoint and the methods that are developed are equally applicable to any other system with these properties.

Changes in the proximate body composition of the landlocked sea lamprey Petromyzon marinus (L.) during larval life and metamorphosis

Abstract: Estimates were made of the growth rates and proximate body composition of larval and metamorphosing P. marinus (L.) collected at various times of the year from Shelter Valley Creek, Lake Ontario. Analysis of length-frequency data indicates that the average duration of larval life was 6 years, with metamorphosis occurring predominantly in the length range above 13 cm. Increases in length were almost entirely restricted to the warmest months and did not take place during the final year of larval life. Three categories were thus recognized for the proximate analysis: ammocoetes 13 cm and metamorphosing individuals. In ammocoetes <13 cm, seasonal differences were observed in the regression coefficients in the logarithmic relationships between wet weight and length and between each of water, lipid and ash and the wet weight. No such difference was found for the regressions between protein and wet weight. For a fixed length (9 cm), the wet weight varied only slightly during the year, although a small peak was seen in May. When considered on the basis of fixed weight (1 g), the relative amount of lipid deposited was greatest in May/July, coincident with a high diatom density. The water content followed an inverse pattern to that of lipid, while the protein and ash contents showed little seasonal variation and exhibited values lower than those normally found in teleosts. Throughout the last year of larval life, the animal stored a greater proportion of lipid, presumably to facilitate the energy demands of metamorphosis during which this food store underwent a marked reduction.

Statistical Inference Regarding Markov Chain Models

Abstract: The paper reviews different techniques for examining sequential dependencies in a series of observations each of which can have c possible outcomes The relationship between the likelihood ratio test and information theory is described The paper also considers how the techniques need to be modified in situations where two successive outcomes are always different

A 24-hour rhythm in passive-avoidance behaviour in rats.

Abstract: The 24 h variation in the passive avoidance response of rats was measured. Different groups of 18 animals were tested at 4 hourly intervals throughout 24 h. In all cases, retention was measured 48 h after the first trial. All animals were housed under controlled conditions for 14 days before testing. A significant 24-h rhythm in passive avoidance response was found, the maximum and minimum effects being in the middle of the light and dark phases respectively.

Scientists and Social Scientists as Information Users: a comparison of results of science user studies with the investigation into information requirements of the social sciences:

Abstract: This paper seeks to draw generalized profiles of a scientist and a social scientist as an information user. The profilts are based rrpon the results of a selection of science user studies and the I...

Observations on the morphology, behaviour and salinity tolerance of downstream migrating River lampreys (Lampetra fluviatitis)

Abstract: Downstream migrating Lampetra fluviatitis were caught at night in elver trawls from the lower reaches of the River Severn during the high spring tides of 1970,1971 and 1972. The length and weight-frequency curves indicated that in 1970 and 1972, the populations consisted mainly of animals of single year class. On the basis of previous estimates of the duration of larval life, they were thus probably five years old, while a small group of larger animals may have been one year older. In 1971, there was a greater proportion of larger animals, several of which differed in their weight/length relationship from others in this sample and from those of 1971 and 1972, possibly reflecting differences in feeding conditions during larval life. Laboratory studies on the activity rhythms of downstream migrants showed that emergence from the substrate and swimming was primarily nocturnal, with an initial large peak in free-swimming activity at the onset of darkness and a smaller peak at the transition from the dark to the light phase. During the light period, these animals showed a significant preference for burrowing or lying in regions of gravel and pebbles. Downstream migrants examined in May/June 1972 were capable of being acclimated to full strength sea water (34–35°/00) and a large proportion (80%) survived for three weeks or more after direct transfer. Parallels are drawn between the biology of this stage in the lamprey life cycle with that of similar stages in salmonid fishes.

Ascospore Wall Development in Saccharomyces cerevisiae

Abstract: Ascospore delimitation in Saccharomyces cerevisiae is initiated by a pair of unit membranes between which the spore wall is subsequently laid down.

The interaction of 3-deoxy-3-fluoro-D-glucose with the hexose-transport system of the human erythrocyte.

Abstract: 1. By using an optical method the kinetic parameters of hexose transport across the human erythrocyte membrane were determined for several sugars. The series of half-saturated constants is as follows: 3-deoxy-3-fluoro-d-glucose = 3-O-methyl-d-glucose

Digital-summation threshold-logic gates: a new circuit element

Abstract: Threshold-logic gates are memoryless, multiple-binary-input single-binary-output circuits that operate by an arithmetic summation process to determine the 0 or 1 gate output state The availability of such gates would be of great advantage to digitial system design A new approach to the circuit realisation of such gates is presented here, ie to use digital-summation techniques within the gate circuitry, as distinct from the analogue-summation techniques previously employed The adoption of digital summation removes the former circuit-tolerance problems, and allows gates with great potential usefulness to be readily designed

Protein synthesis patterns in barley embryos during germination

Abstract: The incorporation pattern of [14C] amino-acid into protein during the first 8 h of germination in isolated barley embryos (Hordeum vulgare) is described. Two maxima were recognised. The first, at 4 h, was entirely accounted for by scutellum activity and the second, at 8 h, coincided with active radicle elongation. An intervening minimum was situated at 5.5 h. The first peak was insensitive to actinomycin-D but the second showed a partial inhibition by this compound. Only slight changes in enzyme activity were associated with these periods of increased synthesis. Incorporation of [17-14C] kaurenoic acid into compounds co-chromatographing with gibberellins was followed over the same period in both embryos and scutella and high activity was found after only 2–4 h. It is concluded that, on the basis of protein synthetic activity, the scutellum is the most probable source of the initial gibberellin stimulus.

Circadian rhythms of activity, ventilatory frequency and heart rate in the adult River lamprey, Lampetra fluviatilis

Abstract: Activity and the electrocardiogram and respiratory potentials of 17 adult River lampreys, Lampetra fluviatilis, acclimated to 7°± 1°C and a light/dark cycle of 11/13 hours, were recorded throughout the spawning run (November to April). Activity was far greater in the dark in all but the sexually mature animals, reflecting behaviour in the field. A circadian rhythm was also observed in the heart rate during periods of inactivity, and this was correlated with an increase in ventilatory frequency or amplitude. A similar rhythm was not present in the sexually mature animals. Moreover, heart and ventilatory frequencies tended to increase during the spawning run. A whole number ratio between heart rate and ventilatory frequency was seen in only 11 of 425 recordings.

A two-sample procedure for selecting the population with the largest mean from several normal populations with unknown variances

Abstract: SUMMARY This paper gives a two-sample procedure for selecting the population with the largest mean from k normal populations with unknown variances. The method is based on a twosample procedure proposed by Stein (1945). Tables necessary for the application of the procedure are given for selected values of k. Comparisons of the minimum values of the expected sample sizes using the proposed procedure are made with the corresponding single-sample sizes for known variances (Bechhofer, 1954). Comparisons are also made of the expected total sample sizes for the single-sample procedure, the two-sample procedure given in this paper and the two-sample procedure proposed by Bechhofer, Dunnett & Sobel (1954) which assumes that the populations have known variance ratios. It is shown that the expected total sample sizes are not much increased by ignorance of the variance ratios.

Training science teachers in methodology.

Abstract: This article describes the philosophy behind and the problems involved in developing a curriculum appropriate to the training of science teachers in methodology.

The effects of hallucinogenic drugs on maze exploration in the rat over a 24 hour period

Abstract: 1. The variation with clock-hour in the behaviour of naive rats in a Y-maze has been recorded.2. The number of entries recorded was highest during the light period while the number of faecal boluses was highest during the dark period. Rearing showed a biphasic periodicity.3. The responses to LSD, mescaline and amphetamine also showed significant variation with clock-hour.4. In general, amphetamine, 1.25 mg/kg, increased the number of entries and the number of rears, the effect being greatest at the end of the light period. LSD, 100 mug/kg, and mescaline, 12.5 mg/kg, decreased the number of entries and the number of rears.5. All three drugs decreased the number of faecal boluses. The possible significance of these responses in terms of an effect on the emotional state of the animals is discussed.

Lamprey Growth and Biological Conditions in the Bristol Channel Region

Abstract: IN view of public disquiet over the possible deterioration of some of our rivers and coastal waters, including the Severn estuary, it is encouraging to find some evidence, although indirect, that as far as the populations of migratory lampreys are concerned, conditions in the area of the Bristol Channel appear to be at least as favourable for their survival and growth as was the case ten years ago.