Showing papers by "University of Oxford published in 1980"

Mapping of metabolites in whole animals by 31P NMR using surface coils.

Abstract: The metabolic state of skeletal muscle and brain within intact rats is monitored using high resolution phosphorus nuclear magnetic resonance. Regional disturbances in metabolism (for example, localised ischaemia) are easily observed, indicating the diagnostic possibilities of the method. Measurements are made using 'surface' radiofrequency coils, which we discuss in detail.

The basic uniformity in structure of the neocortex

Abstract: The number of neuronal cell bodies has been counted in a narrow strip (30 micrometers) through the depth of the neocortex in several different functional areas (motor, somatic sensory, area 17, frontal, parietal and temporal and in many species (mouse, rat, cat, monkey and man). With the exception of area 17 of the visual cortex in a number of primates the same absolute number (congruent to 110) of neurons has been found in all areas and in all species. In the binocular part of area 17 of the primates there are approximately 2.5 times more neurons. Thus in mammalian evolution the area of the neocortex increases in larger brains but the number of neurons through the depth remains constant, except in area 17 of primates. From these and other findings it is suggested that the intrinsic structure of the neocortex is basically more uniform than has been thought and that differences in cytoarchitecture and function reflect differences in connections.

Optimal interpolation and isarithmic mapping of soil properties. II. Block kriging.

Abstract: Summary Soil properties mapped in two intensive surveys had large nugget variances, leading to large estimation variances and erratic isarithms when mapped by punctual kriging. It is likely that both surveyors and survey clients are interested in average values of soil properties over areas rather than point values, and such values can be obtained by block kriging. Estimation variances are very much smaller, and maps of sodium and stone content at Plas Gogerddan, Central Wales, kriged over blocks 920m2, and thickness of cover loam at Hole Farm, Norfolk, kriged over blocks of 400m2, are much smoother than the punctually kriged maps. The map of Hole Farm has a distinct and meaningful regional pattern.

Optimal interpolation and isarithmic mapping of soil properties. I. The semi-variogram and punctual kriging

Abstract: Kriging is a means of spatial prediction that can be used for soil properties. It is a form of weighted local averaging. It is optimal in the sense that it provides estimates of values at unrecorded places without bias and with minimum and known variance. Isarithmic maps made by kriging are alternatives to conventional soil maps where properties can be measured at close spacings. Kriging depends on first computing an accurate semi‐variogram, which measures the nature of spatial dependence for the property. Estimates of semi‐variance are then used to determine the weights applied to the data when computing the averages, and are presented in the kriging equations. The method is applied to three sets of data from detailed soil surveys in Central Wales and Norfolk. Sodium content at Plas Gogerddan was shown to vary isotropically with a linear semi‐variogram. Ordinary punctual kriging produced a map with intricate isarithms and fairly large estimation variance, attributed to a large nugget effect. Stoniness on the same land varied anisotropically with a linear semi‐variogram, and again the estimation error of punctual kriging was fairly large. At Hole Farm, Norfolk, the thickness of cover loam varied isotropically, but with a spherical semi‐variogram. Its parameters were estimated and used to krige point values and produce a map showing substantial short‐range variation.

Two subsets of rat T lymphocytes defined with monoclonal antibodies.

Abstract: A new monoclonal mouse antibody that recognizes a subset of rat peripheral T cells has been prepared by immunizing mice with rat thymocyte glycoprotein. This antibody, designated MRC OX 8, labels all peripheral T cells that are unlabeled by the previously described W3/25 monoclonal antibody. No peripheral T cells were found that bound both antibodies, but, in contrast, 90% of thymocytes were doubly labeled. Thoracic duct lymphocytes of congenitally athymic nude rats were not labeled by either antibody, but the spleens of such animals contained both W3/25+ cells and MRC OX 8+ cells. These splenocyte subpopulations did not overlap. Using the fluorescence-activated cell sorter to isolate cells binding MRC OX 8 antibody, the phenotype of T cells mediating various T cell functions was established. Combining the present results with those published previously, it is shown that the cells providing help for antibody responses and those mediating graft-vs.-host reactions are phenotypically W3/25+ MRC OX 8-. On the other hand, parental T cells that suppress antibody formation in F1 hosts were identified as W3/25- MRC OX 8+. The relationship between the rat T cell subsets defined by these antibodies and those in the mouse identified by the Ly series of alloantibodies is discussed and a comparison made between teh rat W3/25+ subset and a recently identified human T cell subset.

The epidemiology of cancer.

Abstract: The epidemiology of cancer has a long history. It led to the discovery of several causes of cancer before techniques for the production of the disease in laboratory animals became available. In recent years, epidemiological studies have contributed to knowledge of cancer in five ways: by demonstrating geographical and temporal variations in incidence, by correlating incidence in different communities with the prevalence of social habits and environmental agents, by comparing the experience of individuals with and without cancer, by intervening to remove suspected agents and observing the results, and by making quantitative observations that test the applicability to man of models of the mechanism by which the disease is produced. Joint investigation of dietetic factors by epidemiologists and laboratory workers offers the brightest prospect of discovering new ways of preventing cancer in the near future. Advances in knowledge will eventually prevent the need for learning about cancer by seeing its production in man, but epidemiological enquiry will be needed for many years to monitor preventive programs and to provide quantitative measures of risk from hazards that cannot be avoided completely.

A Model for Flood Basalt Vulcanism

Abstract: The question of whether basaltic rocks in continental flood basalt provinces are primary magmas or whether they are descended in general from picritic parent magmas is reviewed. It is suggested that the latter is more likely to be correct on the evidence of phase relations and the relative rareness of mantle materials with appropriate Fe/Mg ratios. Major element variations in the residual liquids of fractional and equilibrium crystallization of basaltic magmas are modelled for a variety of crystallizing assemblages. It is concluded that crystallization of olivine, clinopyroxene, and plagioclase has a marked effect on buffering chemical change in many important elements. It is this effect which accounts for the apparent uniformity of large volumes of flood basalts, not, as has sometimes been supposed, a series of implausible coincidences in the amount of material fractionated from each magma batch. It is further argued that much of the variation seen in basalts may be imposed by polybaric fractionation operating throughout crustal depths, that is at pressures up to at least 12 kb. Parental picritic magmas rising from the mantle reach the surface in exceptional areas of crustal thinning. More usually, however, it is suggested that they intrude the base of the crust as a series of sills which differentiate into upper gabbroic and lower ultramafic portions. Much of the 'low pressure' fractionation of basaltic magmas may take place in this deep crustal sill complex and evolved liquids are transmitted to the surface as their density becomes sufficiently low. This implies that in areas of flood vulcanism a potentially large new contribution to the crust is made by underplating, the volumes of concealed cumulates being at least as large as the amount of erupted surface lava.

The Sensory Basis of Fish Schools: Relative Roles of Lateral Line and Vision*

Abstract: Quantitative analyses of the effects of temporary blindfolding (BL) or lateralis section (LS) on the schooling performance of saithe (Pollachius virens) are reported. Comparison of effects of the sensory deprivations on school structure and dynamics allow determination of the relative roles of the lateral lines and vision in normal schooling. Extended 3-dimensional records were made of the positions of sensorily deprived individuals in normal schools as well as whole schools with sensory treatments. 1. Blinding had little effect on the position experimental fish took up with respect to their neighbors within the school (Fig. 2). In contrast, lateralis section resulted in a great increase in the frequency of neighbors at 90° bearing (directly alongside) (Fig. 2). 2. Both BL and LS fish exhibited different characteristic nearest neighbor distances (NNDs) than controls, with blinding increasing NND and lateralis section decreasing NND (Fig. 4). 3. Importance of the lateral line in transmission of a fright response and sudden velocity changes within a school is demonstrated by experiments in which schools were intentionally startled. In schools of LS fish there exist significant relationships between latency to startle and the distance and angle between a fish and the startling object. Such relationships are not seen in normal schools: with intact lateral lines, fish respond with similar latencies to objects in all directions (Fig. 5). 4. Fish which are blindfolded are able nonetheless to match short-term changes in velocity of their neighbors and actually show higher correlations than do controls (Fig. 8 b). Lateralis section does not reduce correlations between fish and neighbors (Fig. 8 d) probably because LS fish take up positions at which they can best determine neighbors' velocities by vision alone.

Utilization of energy-providing substrates in the isolated working rat heart.

Abstract: 1. An improved perfusion system for the isolated rat heart is described. It is based on the isolated working heart of Neely, Liebermeister, Battersby & Morgan (1967) (Am. J. Physiol. 212, 804-814) and allows the measurement of metabolic rates and cardiac performance at a near-physiological workload. The main improvements concern better oxygenation of the perfusion medium and greater versatility of the apparatus. Near-physiological performance (cardiac output and aortic pressure) was maintained for nearly 2 h as compared with 30 min or less in the preparations of earlier work. 2. The rates of energy release (O2 uptake and substrate utilization) were 40-100% higher than those obtained by previous investigators, who used hearts at subphysiological workloads. 3. Values are given for the rates of utilization of glucose, lactate, oleate, acetate and ketone bodies, for O2 consumption and for the relative contributions of various fuels to the energy supply of the heart. Glucose can be replaced to a large extent by lactate, oleate or acetate, but not by ketone bodies. 4. Apart from quantitative differences there were also major qualitative differences between the present and previous preparations. Thus insulin was not required for maximal rates of glucose consumption at near-physiological, in contrast with subphysiological, workloads when glucose was the sole added substrate. When glucose oxidation was suppressed by the addition of other oxidizable substrates (lactate, acetate or acetoacetate), insulin increased the contribution of glucose as fuel for cardiac energy production at high workload. 5. In view of the major effects of workload on cardiac metabolism, experimentation on hearts performing subphysiologically or unphysiologically is of limited value to the situation in vivo.

Attribution of Responsibility: From Man the Scientist to Man As Lawyer

Abstract: Publisher Summary In this chapter, attribution of responsibility: From Man, to Scientist to Man as the Lawyer, is discussed. The expression “attribution of responsibility” has two major connotations. First, it suggests a clearly demarcated area of research concerned with the study of how responsibility is assigned. Second, the use of the term “attribution” in the expression implies that the assignment of responsibility is described as a process that is directly comparable to the perception of causality as studied in attribution research. Both these inferences are challenged in this chapter, for the recent popularity of attribution theory that has not been matched by an equally discriminating terminology. The chapter considers the attribution of responsibility from three different points of view, taken explicitly into account in social psychology. Recent theoretical developments in attribution are discussed in the chapter. Despite the voluminous and increasing literature purporting to deal with attribution of responsibility, empirical research on this topic appears deficient in several respects. Factors as language and social context are very likely to influence attributions of responsibility.

Interpersonal Comparability and Social Choice Theory

Abstract: At a general level, the information that may be required to enable a planner to judge which of two states is socially preferable may be of a diverse character. It is convenient to partition this information into the welfare and non-welfare characteristics of social states. Welfare characteristics consist of the individual welfares achieved in different states; minimally, individual welfares will be ordinal and interpersonally non-comparable, but it is possible to consider situations where information about the cardinality and/or interpersonal comparability of welfares is also relevant. Non-welfare characteristics are more difficult to describe; as well as a physical description of a particular state, they may also be a description of the evolution of a state. Thus, for example, non-welfare characteristics may include information about whether claims bestowed in the past are settled in the state under consideration. In the language of social choice theory, if welfare characteristics are not always deemed relevant then the SWF (the rule for moving from characteristics to an ordering of social states) is said to be imposed, and if non-welfare characteristics are not deemed relevant then the SWF is said to be neutral. Social choice theory is conventionally concerned with nonimposed SWFs; although rarely mentioned, much of it also deals with non-neutral SWFs. For instance, in the problem studied by Arrow (1963), neutrality is not invoked and it does not follow from the axioms that he lays down. Arrow showed that there exists a dictator but, when this dictator is indifferent between two states, it is possible that non-welfare characteristics of the states will determine the social ordering. On the other hand, Arrow took welfares to be ordinal and non-comparable so that a considerable amount of information about welfares was deemed irrelevant, given that such information might be available. In a series of recent papers, the implications of allowing information concerned with the cardinal and comparable nature of welfares to influence the social ordering have been considered. Most of these studies have dealt with the characterization of either utilitarianism (d'Aspremont and Gevers (1977), Deschamps and Gevers (1978), Maskin (1978)) or the lexicographic extension to the Rawlsian maximin criterion (leximin) (Hammond (1976a), Sen (1976) and (1977), Strasnick (1976), d'Aspremont and Gevers (1977), Deschamps and Gevers (1978), Gevers (1979)). As these rules are neutral, conditions must be invoked which ensure the neutrality of the derived social ordering. This paper considers the derivation of non-imposed and non-neutral social orderings when individual welfares satisfy various measurability/comparability assumptions. The axioms used by Arrow are modified so as to admit the influence of different types of information. Section 2 deals with the formulation of the problem and there is a discussion of the various assumptions that can be made about the measurability/comparability of welfares. Section 3 considers the influence that non-welfare characteristics can have upon the social ordering. Further, a procedure is developed which allows permissible rules to be

Modifying Lax equations and the second Hamiltonian structure

Abstract: where P+ is a differential operator whose coefficients are differential polynomials in u, that is, polynomials in u and its x-derivatives u (s~. (The subscript + may be ignored at this point: we introduce it so as not to conflict with the notation in the main body of the paper.) Since L, is an operator of order zero, for (1.2) to make sense P, must be chosen so that the commutator on the right has order zero too; (1.2) is then equivalent to an evolution equation for u, that is, an equation of the form

Late Quaternary history of the Nile

Abstract: During the intertropical cold dry phase from ∼20,000 to 12,500 yr BP, the aggrading Nile was a braided, highly seasonal river. With a headwaters change to warmer, wetter conditions, it became an incised, sinuous, suspended load river. Overflow from Lake Victoria and severe floods in Egypt heralded the change in Nile regime.

Elementary particle theory

Abstract: An Introduction to Quarks and Partons. By F.E. Close. Pp.481. (Academic: London, New York and San Francisco, 1979.) £26.40; $54.50.

K, L, and M shell generalized oscillator strengths and ionization cross sections for fast electron collisions

Abstract: Generalized oscillator strengths and ionization cross sections by fast electron impact are calculated for K, L, and M shells. A nonrelativistic Hartree–Slater program is used to generate the initial states as well as the continuum wave functions. Core edge shapes and their dependence on momentum transfer are computed within this atomic model up to some tens or hundreds of eV above threshold. Some comparisons are made with experimental measurements and though details near threshold are not predicted, the gross shape of the spectrum is in quite good agreement with these data. While we confirm that the hydrogenic model is a reasonable approximation for K edges, we expect our computations to be useful in obtaining more accurate total cross sections for L and M shell excitation.

On flow through furrowed channels. Part 1. Calculated flow patterns

Abstract: Bellhouse et al. (1973) have developed a high-efficiency membrane oxygenator which utilizes pulsatile flow through furrowed channels to achieve high mass transfer rates. We present numerical solutions of the time-dependent two-dimensional Navier–Stokes equations in order to show the structure of the flow. Experimental observations which support this work are presented in a companion paper (Stephanoff, Sobey & Bellhouse 1980). Steady flow through a furrowed channel will separate provided the Reynolds number is sufficiently large. The effect of varying the Reynolds number and the geometric parameters is given and comparisons with solutions calculated using the modern boundary-layer theory of Smith (1976) show excellent agreement. Unsteady flow solutions are given as the physical and geometric parameters are varied. The structure of the flow patterns leads to an explanation of the high efficiency of the devices of Bellhouse.