Showing papers by "Keele University published in 1972"

Source locations of pattern-specific components of human visual evoked potentials. II. Component of extrastriate cortical origin.

Abstract: A study was made of the transverse distributions of human scalprecorded potentials evoked by the brief presentation of a pattern into different regions of a continuously illuminated diffuse field. The first two components of these visual evoked potentials (VEPs), designated C.I. (latency 65–80 msec) and C. II (latency 90–110 msec), were both greatly influenced by the retinal location of the stimulus pattern. In an initial study of the VEP waveforms with 12 subjects, followed by a more detailed investigation of the distribution of the individual components in 4 subjects, the following results were found. 1. Corresponding peaks (C. I and C. II) of the VEPs to stimulation of the upper and lower half-fields were inverted in polarity. 2. For the left and right half-field VEPs, the transverse distribution of C. I, but not of C. II, showed a polarity reversal across the midline. 3. Consistent differences were observed between the distributions of C. I for adjacent upper and lower quadrants, as well as between those for adjacent horizontal and vertical octants of the upper field. 4. Subjects differed in the degree of left-right asymmetry shown. There was also a much greater degree of interindividual consistency of quadrant and upper and lower half-field VEPs than for full-field or left and right half-field responses. 5. For C. I, an additive relationship was demonstrated between the half-field and the constituent quadrant VEP distributions.

An interpretation and analysis of recumbent‐folded deformed cross‐bedding

Abstract: Three main kinds of syndepositional deformation are found in cross-bedded sand-grade sediments. The first type is characterized by simple recumbent folds of broadly parabolic form. The second is marked by series of folds, with or without overturning. The third type is much more complex, presenting a combination of faulting, folding, and the local destruction of bedding. The type marked by recumbent folds is interpreted as due to the deformation of a liquefied (or perhaps fluidized) sand by current drag following an event in the majority of cases suspected to be an earthquake shock. By reference to empirical and theoretical studies of sedimenting systems, and the behaviour under small shear stresses of liquids of high viscosity, this physical model is developed analytically to yield equations describing the geometry of the deformations in terms of the thickness of the deformed bed, the settling velocity and concentration of particles in the liquefied sand, the viscosity of the liquefied sand, and the magnitude of the deforming force. The equations describe a fold surface that is a portion of a flat-lying parabola, and show that the proposed circumstances of deformation are plausible in terms of what is known of the real situation. They further reveal that, under the assumptions made in the analysis, the vertical height of the fold hinge above the base of the bed is a function only of the initial shape of the deformed cross-stratum, the shear rate in the liquefied materials, and the falling velocity and concentration of particles in the liquefied bed. The shapes of deformations calculated from the equations agree well with patterns observed from the geological record.

Moult-inducing Hormones of the Prothoracic Gland of Insects

Abstract: THE prothoracic gland of insects produces a hormone necessary for moulting to take place1–3, and a steroid hormone called ecdysone has been isolated from whole extracts of silk moth pupae (Bombyx mori) that brings about moulting in Calliphora larvae deprived of ring glands (containing the prothoracic gland). Similar compounds with moult-inducing properties have been found in whole extracts of a few insects and in numerous plants5, but the presence of this hormone in the prothoracic gland has not been demonstrated.

Color Centers in Simple Oxides

Abstract: “Simple oxides” is a vague term, and the reader of this chapter may well be excused for remarking at the end of his labors that nothing in these oxides appears simple. Furthermore, even if the oxides are simple, the color centers surely are not. What we really mean by this expression in our title is that we intend to confine our attention to those oxygen-containing materials in which point defect phenomena are sufficiently well understood that we can present a substantial discussion. This means that nearly all of what we have to say will concern the alkaline earth oxides, simply because these materials have received most attention and are now in a position where the seeds of much hard work throughout the last twenty years are producing fruit in the form of well-categorized color centers.

Geochemistry, Origin and Tectonic Environment of the Basic and Acidic Rocks of Cornubia, England

Abstract: The Cornubian (south-west England) greenstones are predominantly spilitic in character and represent the outpouring of submarine pillow lavas, penecontemporaneous with Devonian-Carboniferous sedimentation, and subsequent intrusive dolerite, diabase and gabbroic bodies. Geochemically they are nearly all representative of continental alkaline basalts with relatively low K/Rb, Sr/Rb, Na/K; K/Ba ratios and high Ti, 7.r, and are distinct from all oceanic basalts. The Cornubian granite batholith as a whole exhibits higher than usual Li, Rb, Cs, F, Cl, B, Sn, U, Pb and possibly Th contents compared with other granites, and coupled with a low K/Rb ratio demonstrates the highly evolved character of the exposed plutons. Both the geochemistry and tectonic setting of the greenstones and granites of Cornubia are compared with rocks of similar age and type in western Europe and a speculative model developed for their genesis in terms of a plate tectonic-based orogenic model. It is considered that the greenstones are the moderately well differentiated basaltic products of `primary' alkaline basalt magma derived from a subduction zone deep in the upper mantle under Cornubia. On the basis of experimental granite systems, the presence of almandine-rich garnets and low initial Sr 87 /Sr 86 ratio, the granite batholith was developed in place by the anatexis of deep anhydrous crustal materials and subsequently underwent differentiation at higher crustal levels. It is also suggested that during the Devonian-Carboniferous periods an active subduction zone existed in the Tethyan region between an essentially static European plate (composed of continental crust) and a north-eastward moving African plate (its leading edge formed of oceanic crust) which culminated in the Armorican-Variscan orogeny. It is further postulated that the spasmodic occurrence of alkaline basaltic magma derivatives and mineralisation in Cornubia during the Mesozoic may also be associated with the continued presence of a subduction zone in the Tethyan region until the Alpine orogeny.

Limonitic concretions from the european jurassic, with particular reference to the “snuff-boxes” of southern england

Abstract: Large discoid (1–30 cm), carbonate-rich limonitic concretions or “snuff-boxes” are contained in stratigraphically condensed limestones from the Jurassic of southern England and parts of Europe. Their general association with conglomerates and algal stromatolites suggests formation in turbulent shallow water on submarine swells, or a shallow marginal shelf. The surprisingly uniform growth-form of the “snuff-boxes”, together with their gradation into obvious calcareous oncolites and stromatolites, is taken as evidence that they too may have been formed, at least partially, under algal influence. The geochemistry of the concretions, dominantly ferruginous, with subordinate phosphate, suggests deposition in an epicontinental environment, probably under the influence of considerable river drainage. They therefore contrast with the more trace-element rich ferromanganese nodules which occur in some condensed pelagic sequences.

The effect of relative formant amplitude on the perceived identity of synthetic vowels.

Abstract: The perceptual effect of varying the relative amplitude of the formants in two-formant synthetic vowels has been investigated. It was found that as the amplitude of the second formant was reduced t...

Retail turnover in the East Midlands: A regional application of a gravity model

Abstract: Gibson M and Pullen M (1972) Retail turnover in the East Midlands: A regional application of a gravity model, Reg Studies 6, 183–196 A gravity model of the type developed by Black is constructed on a regional scale covering the East Midlands Economic Planning Region The model is calibrated on the 1961 Census of Distribution, and is used to forecast shopping turnover in local authority areas for 1981 A strong pattern emerges of rapid growth in suburbs and often sluggish growth in large urban centres Allowance for the effects of increasing congestion and increasing car ownership generally reinforce these conclusions Some of the problems arising from the operation and the use for forecasting of the gravity model are discussed

Evoked Potentials to Changes in the Chromatic Contrast and Luminance Contrast of Checkerboard Stimulus Patterns

Abstract: Many of the classical psychophysical studies of colour vision (and especially the experiments which established a foundation for the measurement of colour) were matching experiments (Maxwell, 1860; Abney, 1903; Konig, 1903). In these early studies the subject looked at a patch of light which was sharply divided down the middle (Wright, 1928, 1946; Guild, 1931). In some experiments his task was to adjust the brightnesses of the two halves of the stimulus until they appeared equal; in other experiments he adjusted the wavelengths of the two halves of the stimulus until he could just distinguish a difference between the hues of the left and right side of the stimulus. It has been well known to experimenters for at least 40 years that an over-enthusiastic subject could generate almost as many problems as a subject whose mind was not engaged with psychophysical considerations. McCree, working in W.D. Wright’s laboratory, carried out a study of this curious phenomenon (McCree, 1960). By voluntarily attempting to suppress eye movements by fixating as steadily as possible, many subjects were able to grossly degrade their power to distinguish between lights of different wavelengths. Both McCree and the present author turned out to be particularly susceptible to this effect of steady voluntary fixation. These two subjects were able to degrade very markedly their ability to distinguish between the hues of stimuli located as far apart as red and blue.

The development of ESN children's understanding of conservation in a range of attribute situations.

Abstract: Summary. 115 children from an ESN school were pre-tested on Piaget-type conservation tasks involving seven different attributes: number, substance, length, distance, area, weight and volume. 51 of these children, who failed to conserve in relation to two or more attributes, were studied further. Aged 10 to 16 years, IQ 50–77, they were divided into three groups matched for age, IQ and level of initial understanding of conservation. One group was instructed on conservation of a variety of attributes, a second group on conservation of area only; and the third group was given practice in reading. Post-tested after one week and then two months, 30 of the 34 instructed children consistently recognised, generalised, and gave reasons for conservation on both post-tests. No control child improved in understanding of conservation by the time of the second post-test.

Precambrian Rocks South of Erquy and around St Cast, Côtes-du-Nord

Abstract: THIS communication is prompted by two recent articles concerned with geological and radiometric evidence bearing on the nature and age relationships of two groups of Precambrian rocks along the north Brittany coast between St Brieuc and St Malo. The first, by Vidal et al.1 is concerned with the age of a group of spilitic rocks which outcrop south of Erquy, whereas the second, by Hameurt and Jeannette2, deals with the nature and age of a group of metamorphic rocks which outcrop around St Cast.

In vitro culture of carnation rust, Uromyces dianthi

Abstract: Axenic cultures of Uromyces dianthi (Pers.) Niessl. were grown from uredio-spores, by using techniques and media similar to those of Williams, Scott & Kuhl (1966) and Williams, Scott, Kuhl & Maclean (1967). Extended periods of incubation were necessary for the development of colonies. Media containing yeast extract, peptone and casein hydrolysate, singly or in combination, initiated and supported cultures of U. dianthi . The hyphal segments were typically binucleate. Growth was optimal at 18–20 °C, on media of pH 5·8–6·2. Spore-like cells were found in the mycelium of older colonies. These spore-like cells were capable of germination and of initiating new saprophytic growths.

Reduction in the work function of stainless steel by electric fields

Abstract: The work function of stainless steel surfaces in a clean vacuum system at 10-9 Torr was reduced by as much as 1.6 eV by transverse electrostatic fields of the order of 1 V cm-1. Preliminary results are presented.

Cortical Evoked Potentials

Abstract: Buttressed by some undeniably sloppy evoked potential research there are some who would dismiss out of hand the recording of electrical signals from the human scalp as being comparable to “holding an oscilloscope probe six feet in diameter up to a computer and pronouncing from the resultant waveform on the underlying structure and function”. Such extreme views are often associated with an implication that the method of recording electrical activities of individual nerve cells is the only electrophysiological technique which merits serious scientific consideration. This view has more than a grain of truth in it. Although a fair case can be made for the clinical possibilities of scalp recording, it is certainly true that the contribution made by the scalp recording method to our present day understanding of brain function are very much less than the contributions made by single-cell recording. It could be argued that although a deal of taxpayers’ money has been absorbed by evoked potential research, the scientific returns have been many articles, much equivocal data, but little additional understanding of brain function.

A real-time speech synthesis system

Abstract: A system for synthesizing speech is described. It consists of an electronic synthesizer controlled by a small digital computer. The computer uses stored rules to convert a phonetic input into the analogue voltages required for driving the synthesizer. It has been found possible to make the system operate in real time so that the acoustic output is generated at normal speaking rates.