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  • 1
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    An Error in Ice-Temperature Measurement (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-01-01
    Description: An analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aUwhereais the bore-holt radius andUis the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 2
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    An Error in Ice-Temperature Measurement (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-01-01
    Description: An analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aU where a is the bore-holt radius and U is the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 3
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    Viscous flow in collapsible tubes of slowly varying elliptical cross-section (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-06-24
    Description: This paper is concerned with steady flow in collapsible tubes, such as veins, at fairly low Reynolds number. Lubrication theory is used to calculate the velocity and pressure distribution in an elliptical tube whose cross-sectional area and eccentricity vary slowly and in a given way with longitudinal distance x. The transverse velocity field and the effect of inertia on the primary velocity and pressure distributions are calculated to first order in the relevant small parameter. The results of these calculations are combined with a relationship between transmural pressure and the cross-sectional area at any x which is close to that measured in (large) veins, and are used to predict the pressure and flow in a collapsible tube when a given distribution of external pressure is applied. Different relationships between the tube perimeter and cross-sectional area are examined. The theory is applied to an experiment in which a segment of collapsible tube is supported between two rigid segments, and squeezed; predictions of the relationship between the pressure drop and flow rate are made for various experimental conditions. In particular, when the resistance of the downstream rigid segment is held constant, a range of flow rates is found in which the pressure drop falls as the flow rate is raised; this agrees with experiment. © 1977, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 4
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    Relationships between energy intake, nutritional state and lamb birth weight in Greyface ewes (1977)
    Cambridge University Press
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    Publication Date: 1977-12-01
    Description: SummaryIndividual feed intakes of housed mature Greyface (Border Leicester × Scottish Blackface) ewes were adjusted weekly to maintain plasma 3-hydroxybutyrate concentrations during the final 6 weeks of pregnancy at the following values: treatment 1 (adequately nourished; 17 ewes) less than 0·7 mmol/1; treatment 2 (moderately undernourished; 15 ewes) at about 1·1 mmol/1; treatment 3 (severely undernourished; 15 ewes) at about 1·6 mmol/1.The mean energy intakes (MJ metabolizable energy (ME)/day) required to maintain the prescribed nutritional states in single- and twin-bearing ewes were: treatment 1, 14·3 and 16·3; treatment 2, 10·6 and 11·6; treatment 3, 8·1 and 10·0 respectively.The moderate degree of undernourishment had no significant effect on the birth weight of single lambs, but reduced the birth weight of twins by 8·2%, while the more severe undernourishment reduced the birth weights of singles and twins by 21·5 and 25·8% respectively.Foetal energy requirements, estimated by regression analysis, appeared to decrease from more than 2 MJ ME/kg/24 h at 35 days prepartum to 1·54 MJ ME/kg/24 h in the week before parturition.The amounts of energy required to sustain the nutritional states of treatments 1–3 in non-pregnant ewes were calculated to be 348, 271 and 231 kJ ME/kg0.75/24 h, compared with a maintenance requirement, determined in this experiment, of 344 kJ ME/kg0.75/24h.It is concluded that in individually fed ewes a nutritional state characterized by plasma 3-hydroxybutyrate concentrations of 1·1 mmol/1 would constitute an acceptable compromise between an uneconomically high energy input and an excessive reduction in lamb birth weight.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 5
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    Effect of dietary corn oil on the linoleic acid content of adipose tissue lipids in barley-fed lambs (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-10-01
    Description: Ruminants have extremely low concentrations of polyunsaturated acids in their adipose tissue as a result of hydrogenation of dietary lipids by microbes in the rumen. The possible association between intake of ruminant products high in ‘saturated’ lipids and the incidence of atherosclerosis in man has stimulated research on procedures for altering the fatty acid composition of ruminant tissue lipids. Vegetable oils, emulsified with a protein, spray-dried, and treated with formaldehyde, have been found to be protected from hydrolysis and hydrogenation in the rumen (Cook et al. 1970; Scott, Cook & Mills, 1971). Their subsequent digestion in the small intestine, and absorption of the fatty acids by the animal, results in tissue lipids high in linoleic acid (Faichney et al. 1972; Faichney, Scott & Cook, 1973; Cook et al. 1972; Garrett et al. 1976).
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 6
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    Nutrition and growth of gnotobiotic lambs (1977)
    Cambridge University Press
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    Publication Date: 1977-06-01
    Description: SUMMARYSeventeen gnotobiotic lambs were reared up to 21 weeks of age on cows’ milk followed by sterile solid diets similar to diets fed to conventional lambs. Seven were given limited defined populations of rumen bacteria, seven were left uninoculated and three were dosed with rumen contents from conventional sheep (‘conventionalized’). The lambs were reared in four groups corresponding to four lambing seasons.Gnotobiotic lambs fed cows’ milk ad libitumgrew at similar rates and converted feed into live-weight gain with similar efficiency to conventional lambs. The gnotobiotic lambs irrespective of inoculation and the two conventionalized lambs in the first three groups failed to maintain growth on solid diets when milk feeding had been stopped. However, three gnotobiotic lambs in the fourth group, two of which were inoculated, continued to grow satisfactorily for at least 6 weeks on a solid diet alone, and the inoculation of defined populations of bacteria appeared to confer an advantage. The conventionalized lamb in the fourth group suffered a severe temporary setback, following which it grew well.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 7
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    Fatty acid composition of depot fats from gnotobiotic lambs (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-02-01
    Description: SUMMARYThe fatty acid composition of the depot fats of lambs reared for 4–5 months under gnotobiotio conditions have been determined and an estimate made of the endogenous synthesis of stearic acid.In an uninoculated gnotobiotic lamb no hydrogenation of dietary lipids occurred in the rumen and this was reflected in the virtual absence of trans acids in depot lipids. In this animal the stearic acid content of perirenal depot fat accounted for 16% of the total fatty acids which was similar to the value found in newborn lambs (17%). Inoculation of the rumen of two gnotobiotic lambs with seven species of bacteria resulted in the establishment of partial hydrogenation processes in the rumen. Various trans isomers of octadecenoic acids were produced in these lambs from the dietary fatty acids but no stearic acid was formed.These findings are compared with the fatty acid composition of depot fats of other herbivorous and omnivorous animals.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 8
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    Clifford Embleton and Cuchlaine A. M. King. Periglacial geomorphology. [Glacial and periglacial geomorphology. Second edition. Vol. 2.] London, Edward Arnold, 1975. [xj, 203 p. £8.95 (cloth), £4.50 (paper). (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-01-01
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 9
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    Aerodynamic sound in a relaxing medium (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-12-21
    Description: In this paper we formulate the aerodynamic sound problem for a relaxing medium in a rather general way, independent of the details of the relaxation process. The medium is characterized by an appropriate relaxation time τ0 and by a frozen (af0) and an equilibrium (ae0) sound speed. The equation describing aerodynamic sound in such a medium is the familiar one describing acoustic waves in a non-equilibrium medium but subjected to aerodynamic sound sources expressed in terms of a frozen and an equilibrium form of the Lighthill stress tensor. The far-field result for both compact and non-compact sources in the frequency range ω 〉 τ0 −1 can be expressed as the ratio of far-field densities for the relaxing and non-relaxing propagation medium: [Formula Ommited] where x is the observation distance and the subscript L stands for “Lighthill”. The result for the main radiated aerodynamic sound, which comes from sources in the range ω 〈 τ0 −1, essentially propagates in a manner described by the lower-order equilibrium waves, the diffusive effects from the higher-order waves being small, and the result for compact sources is a restatement of Lighthill's result in terms of the equilibrium propagation speed with the source region identically in equilibrium. For non-compact sources the propagation is still given by ae0 but the source region is now understood to encompass relaxation effects, the details of which are left unspecified. © 1977, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 10
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    The generation of sound by vorticity waves in swirling duct flows (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-06-24
    Description: Swirling flow in an axisymmetric duct can support vorticity waves propagating parallel to the axis of the duct. When the cross-sectional area of the duct changes a portion of the wave energy is scattered into secondary vorticity and sound waves. Thus the swirling flow in the jet pipe of an aeroengine provides a mechanism whereby disturbances produced by unsteady combustion or turbine blading can be propagated along the pipe and subsequently scattered into aerodynamic sound. In this paper a linearized model of this process is examined for low Mach number swirling flow in a duct of infinite extent. It is shown that the amplitude of the scattered acoustic pressure waves is proportional to the product of the characteristic swirl velocity and the perturbation velocity of the vorticity wave. The sound produced in this way may therefore be of more significance than that generated by vorticity fluctuations in the absence of swirl, for which the acoustic pressure is proportional to the square of the perturbation velocity. The results of the analysis are discussed in relation to the problem of excess jet noise. © 1977, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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