Showing papers by "University of Exeter published in 1978"

The shear strength of trabecular bone from the femur, and some factors affecting the shear strength of the cement-bone interface.

Abstract: The shear strength of trabecular bone from the femur has been studied. In general, the strongest trabecular bone is found close to the cortico-cancellous junction, though its shear strength depends also on the relationship of the trabeculae to the plane of shear. Some factors affecting the shear strength of the cement-bone interface have been investigated. In vitro, maximal cement-bone interface shear strength is obtained by exposing and thoroughly cleaning strong trabecular bone, and then forcing onto it under pressure low viscosity cement.

The effects of context and content on immediate processing in reading

Abstract: Four experiments were conducted to examine the processes by which fluent readers comprehend prose. In each study the material was presented a few words at a time on an on-line visual display and th...

The decline of the otter Lutra lutra L. in Britain: an analysis of hunting records and discussion of causes

Abstract: The records of one pack of Otter Hounds hunting in southwest England are examined for the period 1907 to 1971 as well as the records of all packs active in Britain between 1950 and 1976. The hunting success per unit effort varies from year to year depending on changes in hunting conditions but longer term changes can also be identified. The hunting success of the Culmstock Otter Hounds (hunting in parts of south-west England) increased steadily from 1907 to 1956 but in most of England and south Wales the success rate of the hunts declined rapidly after 1957. There was also a decline in success in northern England and southern Scotland but to a lesser extent, while in north Wales and Eire, there is no evidence for a decline. These changes are considered to reflect changes in otter populations but the extent of the decline in hunting success (to between 37% and 55% of previous levels in the southern hunts) is probably less than the actual decline in otter numbers. There are no signs of a recovery in the population but indications of a continuing decline up to 1976. The reason for the increasing population in the first half of the century in south-west England is probably the decrease in persecution since the nineteenth century. A variety of causes for the crash in the late 1950s are considered and the factor most likely to be responsible is the introduction of the dieldrin group of insecticides in 1956. Use of these compounds has been increasingly restricted since 1963 and the possible reasons for the failufe of the otter population to recover are listed but no firm conclusions can be drawn as yet.

Some clinically relevant variables affecting the mechanical behaviour of bone cement.

Abstract: The effects of 12 clinically relevant variables upon the basic mechanical properties of acrylic cement are reported. Attention is drawn to the facts that these variables may at times coexist to lead to serious reductions in the strength of the cement, and that the operating surgeon may exercise a substantial influence on the effective mechanical properties of the cement he is using.

Hypersexuality: implications for a theory of dependence.

Abstract: Summary It is argued that a theory of dependence must take into account forms of excessive appetitive behaviour which do not have psychoactive drugs as their object. Excessive heterosexuality is an important but neglected example. Some of the clinical and autobiographical literature on the topic. is reviewed, particularly the extended autobiography My Secret Life. Hypersexuality as an entity has been criticized on a number of grounds: the distribution of sexual behaviour in the population is continuous not discontinuous; the concept is ill defined and rests upon loosely used constructs such as loss of control; it ignores personal and social relativity in the definition of sexual normality, and in particular it betrays the operation of a double standard for judging behaviour of the two sexes. These problems of concept and definition are paralleled in discussions of other excessive behaviours such as excessive drinking and excessive gambling.

Timing in the motor programming of typing

Abstract: In developing a theory of motor programming of skilled performance it has been suggested that an abstract, structural representation in the program specifies both a sequence of responses and expressive features of the sequence, such as timing, stress and intonation, which are mapped separately into the response output. In the case of typing, which does not require expressive features, it has previously been assumed that response timing is governed more simply by a timekeeper providing a stochastically regular beat. Two sets of specially constructed texts were given to a fast typist and the results support the idea that skilled typing is paced by a regular beat. They also show that there were systematic rhythmic departures from the beat, which arose from contingencies of keyboard movement but were not the simple consequences of these; rather they may be regarded as structured anticipations of the contingencies, and as such are analogous to the expressive features of speech and playing music.

The effects of economic integration on trade

Abstract: This article provides a critical analysis of the models and methods which have been used to estimate the effects of economic integration on trade and suggests the most fruitful lines of further development. Both the problem of the examination of the effects of past events and problems in the prediction of future changes are tackled. In particular the drawbacks of the method of estimation of the effects of previous integration as a residual from models which explain what would have happened had the integration not taken place are shown. It is concluded that the most fruitful avenue of approach lies in the estimation of models which provide an economic explanation of trade flows and their changes, and can hence be used for both the explanation of the effects of previous integration and the prediction of future events.

Discrimination of polymorphous stimulus sets by pigeons

Abstract: Pigeons were trained to perform a visual discrimination between stimulus sets in which the presence of any two of three positive features made a stimulus positive, while any two of three negative features made it negative (there were thus three different positive and three different negative stimuli). After training, the birds were exposed to test stimuli that contained either all three positive or all three negative features. In Experiment I three pigeons were successfully trained by a successive method, and subsequently responded to the test stimuli as though they were positive or negative respectively. In Experiment II four pigeons were trained by a simultaneous method. Three learned the discrimination and generalized appropriately to the test stimuli, but they showed no preference between positive test and positive training stimuli, nor any consistent difference in speed of response to them; and similar results were found for negative stimuli. It is argued from this that the pigeons learned to respond...

Rare earth evidence for the origin of the Nûk gneisses Buksefjorden region, southern West Greenland

Abstract: Rare earth element (REE) concentrations have been determined (by the INAA method) for the c. 2,800 m.y. old Nuk gneisses from the Buksefjorden region, southern West Greenland. Samples include dioritic to granodioritic gneisses and synplutonic mafic dykes; a Malene metagabbro and Qorqut granite were analysed for comparisons. The early Nuk gneisses, diorites and tonalites, have mildly fractionated REE patterns which are interpreted as resulting from partial melting of garnetbearing amphibolite or granulite. Early Nuk trondhjemitic gneisses possess downward convex patterns with prominent positive Eu anomalies; they may be related to the diorites and tonalites by the separation of hornblende in a residue of partial melting or fractional crystallization. Most of the later Nuk grey gneisses have extremely fractionated linear patterns which were derived from a source very rich in garnet, possibly eclogite. REE patterns measured in the late Nuk Ilivertalik granite complex are mildly fractionated but with a high overall abundance consistent with an origin by partial melting of mafic lower crustal material. Two sets of synplutonic mafic dykes have strongly fractionated patterns similar to those found in alkali basalts. The geochemical variations suggest that the igneous precursors of the Nuk gneisses were not cogenetic, but were derived from widely differing sources.

Structure‐Activity Relationships for the Lipid‐Mobilising Action of Locust Adipokinetic Hormone

Abstract: A series of compounds structurally related to adipokinetic hormone, the decapeptide neurohormone < Glu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2, have been prepared by synthesis and by enzymic cleavages of synthetic hormone. Their relative agonist activities in mobilising lipids over a fixed time interval (1 h) in locusts were assessed. The similar time courses for lipid release shown by two of the peptide analogues and adipokinetic hormone suggest that the analogues and the hormone are transported to the receptors on the fat body cells, and are also degraded, at similar rates. Consequently, the analogue activities can be correlated with the structural requirements of the locust fat body hormone receptors. The requirements for activity demonstrated in this study are as follows. Residues 1–8 from the N-terminus are necessary to elicit some activity (20%). Residues 5 and 7 in the octapeptide can be changed without affecting activity but l-pyroglutamic acid as the N-terminal residue is necessary for maximum activity both in the octapeptide and the decapeptide. Full activity is achieved only by adding the dipeptide glycyl threonine amide to the active octapeptide ‘core’. In the decapeptide, residues cannot be interchanged to the same extent as in the octapeptide without reducing activity. The peptide probably has to be uncharged. Inactive analogues of seven residues or less do not interfere in the hormone-receptor interaction.

The Use and Character of Wood in Prehistoric Britain and Ireland.

Abstract: Wood was one of early man's most valuable and important raw materials. It furnished him with shelter, heat and a range of tools and weapons necessary for his survival. It was perhaps the first material to be employed for tools, even before stone was actively worked, yet wood hardly figures in the minds of many archaeologists, and it plays no part in the traditional, outmoded but convenient Three Age system of European Prehistory: Stone-Bronze-Iron. Yet there is hardly a tool or weapon used by Stone Age, Bronze Age or Iron Age man or woman which did not have a wooden part, and it is the purpose of this paper to point out the wealth of information that is available, or could be obtained, from studies of wooden artifacts.The reason for neglect of such studies is obvious. Wood is perishable; it decays if left exposed, it is easily broken, it burns to nothing, it rots in the soil, it loses its surface in moving water. Its survival for long periods of time is exceptional, and requires certain conditions of deliberate or accidental burial. Yet wood as a fact and a feature of prehistoric economy cannot be disputed. Without the survival of wooden remains, our knowledge of the Neolithic and Bronze Age lake-side settlements in Switzerland would be quartered, and our information about the Iron Age villages at Glastonbury and Biskupin would be substantially reduced. Only in circumstances where conditions are exceptionally favourable has wood survived in an identifiable state, and in these situations it can tell us much about economic life. Grahame Clark expressed the view long ago that ‘less attention (should be) paid to amassing residual fossils from sites unfavourable to the survival of the organic materials which play so important a part in the economy of simple societies, and more to exploring sites where these materials are likely to survive’ (Clark 1940, 58).

The Measurement and Interpretation of Urethral Pressures Obtained by the Method of Brown and Wickham

Abstract: Summary— The most significant error in routine measurement of urethral pressure by the Brown-Wickham method is caused by the slow response of the system to increasing pressure Errors due to viscous pressure losses in the measuring catheter and to variable orientation of the catheter sideholes are not normally important The distensibility of the urethra may be estimated from the variation of the measured pressure with infusion flow rate in the range above 2 ml/min In highly distensible urethras the pressure actually measured is similar to the true pressure in the undistended urethra, but in less distensible urethras this is not so Substantial leakage, at a flow rate of 2 ml/min or more, begins to occur when the intravesical pressure is approximately equal to the maximum pressure in the undistended urethra Therefore, in highly distensible urethras the maximum measured pressure is a satisfactory guide to the intravesical pressure needed for substantial leakage In less distensible urethras, however, substantial leakage may occur when the intravesical pressure is perhaps 25 cm H2O below the maximum pressure measured in the urethra Leakage at very low flow rates may be possible through some urethras when the intravesical pressure is very low indeed The urethral closure pressure profile, as ordinarily measured, is not a reliable guide to the possibility of such leakage With care, the method of Brown and Wickham gives satisfactory measurements of the urethral closure pressure profile However, the maximum profile pressure exceeds, sometimes by a considerable amount, the bladder pressure needed to cause leakage

The effects of the 1976 drought and autumn rainfall on stream solute levels

Abstract: Operation of a previously existing sampling network during the 1976 drought has provided an opportunity to assess the effects of the drought and subsequent autumn rainfall on the water quality characteristics of a small catchment (9·3 km3) in East Devon. The availability of records for past years has enabled these data to be compared with longer-term response characteristics. Analysis indicates that the 1976 drought produced a unique solute response, with levels rising markedly during the autumn flush which resulted from the heavy rainfall following the drought period. Concentrations of several ions increased 3–4 times and NO3-N levels exhibited even greater increases of up to 50-fold. Some of the factors responsible for these increases and some implications are considered.

The population biology of two species of eyefluke, Diplostomum spathaceum and Tylodelphys clavata, in roach and rudd

Abstract: Infections of roach (Rutilis rutilus), and rudd (Scardinius erythrophthalmus), by the eyeflukes Diplostomun spathaceum and Tylodelphys clavata were studied in a lake over a three year period. T. clavata first appeared at the beginning of the study. Roach were heavily infected by both parasites, whereas the rudd contained very few specimens of either species. A small number of roach-rudd hybrids were also examined, and appeared to have a susceptibility intermediate between the parental types. Levels of T. clavata in roach increased throughout the study. This parasite had a life span of a year or less in the fish, and was continuously lost from the population. This loss was balanced by a minor infection period in April/May and a major one extending from August until January. The fish continued to accumulate infections until they reached a size of about 130 mm, but thereafter intensity fluctuated about the level reached. D. spathaceum infections similarly increased throughout the period of study, and there was a suggestion of a wave of infection in the spring. This parasite has a much longer life span, and levels of infection increased with fish size, only falling in the largest, and therefore oldest, hosts. The major changes in the parasite populations in the roach were reflected, to a lesser extent, in the rudd. Both species were over-dispersed, but the data from roach was too heterogeneous to fit to any theoretical models, whereas that from the rudd was found to conform to a Negative Binomial distribution.

Genetic structure of a natural population of Coriolus versicolor (L. ex Fr.) Quél.

Abstract: Experiments were carried out to investigate genetic relationships within a population of Coriolus versicolor (a polyporaceous basidiomyceto causing white rot of wood) present in a birch stump. The population consisted of individual dikaryons occupying longitudinally continuous columns of decay separated from one another by narrow, dark, relatively undecayed interaction zones. These dikaryons were shown to be genetically homogeneous throughout their respective decay columns by dedikaryotization procedures. They were mutually antagonistic when paired in culture, but monokaryons derived from their fruit-bodies were interfertile. Experiments using synthesized dikaryons indicated that antagonism is inevitable between genetically distinct mycelia, but that the intensity of interaction diminishes with increased relatedness. Results of pairings between synthesized dikaryons and monokaryons varied according to the relatedness of the isolates. Antagonism invariably occurred when the monokaryon contained a nucleus differing from both nuclei in the dikaryon, but this did not necessarily prevent dikaryotization. Often in this situation dikaryotized sectors developed in the monokaryon visibly separated by zones of antagonism (‘tracks’). Where the monokaryon contained the same nucleus as one of the components of the dikaryon, antagonism usually occurred initially, but normally the colonies eventually fused.

Survival of aquatic hyphomycetes in terrestrial situations

Abstract: Oak leaf disks inoculated with some aquatic hyphomycetes were transferred to leaf litter in a wood to test their ability to survive under terrestrial water regimes. Of the ten species tested four could not be recovered after relatively short periods, three died out after 8 months, one after 11 months and the remaining two survived for 12 months or more. The species surviving the strongest were not those commonly reported from terrestrial sites. Naturally infected leaves from streams showed a similar response when placed on land. Metabolic activity — indicated by the invasion of adjacent leaves — was shown in only two species, and was slight in these cases. Survival was poor in leaves exposed by flood in trees beside a river and in inoculated leaf disks exposed similarly.

A Comment on ‘Theory and Practice in Social Work’

Abstract: Brian Sheldon's article makes a number of important points about the relationship between theory and practice in social work. It is true that there is a danger of greater separation rather than integration between the two, and I agree that a certain infuriating style of electicism, under which new ideas are accommodated rather than developed, criticised or tested, is characteristic of both teachers and practitioners. It is also true that social workers are notoriously unwilling to recognize the validity of research findings or to heed them in their practice. However, I believe that Sheldon's notion of a 'knowledge base' for social work is misleading in a number of ways. Without wishing to defend the present relationship between the academic and the practical, or much in the content of either, I would offer the following criticisms of his analysis and alternatives. 1. His analogy with the pharmacist, though amusing, is unhelpful. It is presumably intended to imply an unfavourable contrast between the 'knowledge base' of social work and that of medicine. But it does not take a great deal of imagination to produce a pharmaceutical nightmare based on the present state of the medical profession. The dispensary student might point out to his prospective customer that the vast majority of his 'remedies' are in fact palliatives or drugs designed to suppress symptoms rather than cure ills. Many of the rest have harmful side effects, or are psychologically addictive, or both. In the treatment of psychosomatic and psychiatric 'illness', he might discover theoretical contradictions as confusing as any in social work; in abortion, contraception and euthenasia equally conflicting moral imperatives. He might add that most major advances in the prevention of illness were made not through medicine but through the work of public health officials and hygienists, with the exception of the discovery of the few original 'wonder' drugs, such as penicillin. Finally, the dispenser might indicate that many are coming to believe that a combination of good

Molecular motions in a smectic A phase by incoherent quasielastic neutron scattering

Abstract: Results are presented of incoherent quasi-elastic neutron-scattering measurements in ethyl 4-(4′acetoxybenzylidene) aminocinnamate (EABAC) in crystal, S A and nematic phases. Discussion is concentrated on data for the S A phase of an aligned, tail deuteriated, sample for Q⊥n and Q‖n, where Q is the scattering vector and n the direction of the unique axis (the layer normal). The scattering law S(Q, ω) is found to be essentially identical for the two directions. Analysis of the results shows that the molecules undergo rapid reorientation about the long axes with D r∼3×1010 rad s-1, together with a random but bound motion predominantly normal to the layers with an r.m.s. amplitude 1/2∼1·2-1·8 A, depending on the model, and a correlation time ∼ 10-11 s.

Polymorphism in Coriolus versicolor and its relation to interfertility and intraspecific antagonism

Abstract: When dikaryotic isolates from morphologically distinct fruit-bodies of Coriolus versicolor were paired in culture, antagonism was always observed, both when they were obtained from widely separated localities, or even from the same substratum. Antagonism between mycelia in the same sub.stratum results in the formation of narrow, dark, relatively undecayed interaction zones which delimit the decay by each dikaryon to a particular column of wood. Fruit-bodies formed by a single decay column, or collected from substrata uniformly decayed by C. versicolor and having no interaction zones, were of the same morphological type, regardless of position. They had the same mating type factors, and hence were likely to be part of the same dikaryotic mycelium. Monokaryons from fruit-bodies formed by different columns in the same substratum, or from widely separated localities, even when differing markedly in morphology, were usually completely interfertile. The antagonism between the corresponding dikaryons was therefore a purely vegetative reaction resulting in the delimitation of individual mycelia in potentially interbreeding populations. These genetic differences between individuals were also shown by the polymorphism of their fruit-bodies.

Oxidation state of iron in the Littleham Mudstone Formation of the New Red Sandstone Series (Permian-Triassic) of southeast Devon, England

Abstract: The Littleham Mudstone Formation of southeast Devon consists predominantly of red lutites of Late Permian or Early Triassic age. Present within the lutites are spherical pale patches that have sharp boundaries against the red lutite and often contain dark, organic centers rich in uranium and vanadium. Chemical and Mossbauer analysis of the oxidation state of iron in this formation shows that the red lutite contains an average total iron content of about 5.5%, with an Fe2+/Fe3+ ratio of 0.16, while the pale material has a total iron content of 2.7%, with an Fe2+/Fe3+ ratio of 1.2. In the pale material, iron is present only within silicate (clay material) lattice sites, but the red lutite contains hematite as well. The hematite has an important superparamagnetic component and is considered to have a bimodal grain size distribution with two modes of occurrence: as interlayer crystals within clay minerals and as external coatings or grains. The Fe2+/Fe3+ ratios and total iron content show that the red lutite is not merely the pale material with hematite added, but that about 50% of the Fe2+ in the clay mineral lattice in the pale material is oxidized to Fe3+ in the red lutite. This change in oxidation state is not coincident with the pale-red boundary but begins within the pale patches. The mechanism by which this occurred is considered to be an in situ oxidation that produced the red lutite, accompanied by the precipitation of ferric hydroxide from solution. This process is inhibited in the pale patches where Fe2+ ions would be more soluble and readily removed. Geotechnical tests on the lutites show that the spherical patches must have formed after a thickness of 1,000 to 1,300 m of overlying strata had been deposited. This thickness encompasses the whole of the Triassic beds of southeast Devon and implies that the reddening occurred at the end of Triassic or in early Jurassic time. It is suggested that the reddening was aided by a change from arid to humid climate that occurred in the area at this time.