Showing papers by "University of Leeds published in 1980"
TL;DR: A critical evaluation of the kinetics and photochemistry of gas phase chemical reactions of neutral species involved in middle atmosphere chemistry (10-55 km altitude) was carried out by the authors under the auspices of the CODATA Task Group on Chemical Kinetics.
Abstract: This paper contains a critical evaluation of the kinetics and photochemistry of gas phase chemical reactions of neutral species involved in middle atmosphere chemistry (10–55 km altitude). The work has been carried out by the authors under the auspices of the CODATA Task Group on Chemical Kinetics. Data sheets have been prepared for 148 thermal and photochemical reactions, containing summaries of the available experimental data with notes giving details of the experimental procedures. For each reaction a preferred value of the rate coefficient at 298 K is given together with a temperature dependency where possible. The selection of the preferred value is discussed, and estimates of the accuracies of the rate coefficients and temperature coefficients have been made for each reaction. The data sheets are intended to provide the basic physical chemical data needed as input for calculations which model atmospheric chemistry. A table summarizing the preferred rate data is provided, together with an Appendix listing the available data on enthalpies of formation of the reactant and product species.
1,661 citations
01 Jul 1980
TL;DR: In this article, the theory and potential of a family of doubly salient electronically-switched reluctance motors is explored. But the most recent prototype has achieved a continuous rating which is 1.4 times that of the equivalent induction motor.
Abstract: The paper explores the theory and potential of a family of doubly salient electronically-switched reluctance motors. It is demonstrated that the machine provides the basis for fully-controllable variable-speed systems, which are shown to be superior to conventional systems in many respects. The motor retains all the advantages normally associated with induction motors and brings significant economy in the drive electronics. The basic modes of operation, analysis, design considerations and experimental results from a range of prototype motors up to 15 kW at 750 rev/min are described. The most recent prototype has achieved a continuous rating which is 1.4 times that of the equivalent induction motor.
791 citations
TL;DR: Two models, based on information minimisation and entropy maximisation principles, have been developed by the authors to estimate an O-D matrix from traffic counts based on knowledge of the paths followed by the vehicles over the network.
Abstract: For a large number of applications conventional methods for estimating an origin destination matrix become too expensive to use. Two models, based on information minimisation and entropy maximisation principles, have been developed by the authors to estimate an O-D matrix from traffic counts. The models assume knowledge of the paths followed by the vehicles over the network. The models then use the traffic counts to estimate the most likely O-D matrix consistent with the link volumes available and any prior information about the trip matrix. Both models can be used to update and improve a previous O-D matrix. An algorithm to find a solution to the model is then described. The models have been tested with artificial data and performed reasonably well. Further research is being carried out to validate the models with real data.
651 citations
TL;DR: Women who had previously given birth to one or more infants with a neural-tube defect were recruited into a trial of periconceptional multivitamin supplementation and found no difference in the number of infants/fetuses with an NTD.
560 citations
TL;DR: A cursory review of the literature reveals that the techniques used to assess psychomotor functions are diverse, often complex, frequently insensitive to drug induced changes and sometimes inconvenient to enact or replicate.
Abstract: A cursory review of the literature reveals that the techniques used to assess psychomotor functions are diverse, often complex, frequently insensitive to drug induced changes and sometimes inconvenient to enact or replicate. Adams (1974) used proof reading ability; Croucher & Hindmarch (1974), the duration of the spiral after effect ; Betts, Clayton & Mackay (1972), low speed car handling tasks; Malpas, Rowan, Joyce & Scott (1970), card sorting ability; Fargus & Hindmarch (1974), a cardriving simulator; Ashton, Hall, Savage, Telford & Thompson (1972), a pursuit rotor; File & Bond (1979), symbol copying; Van Houten & Zenhausern (1967), the absolute auditory threshold; Davis, Hollister, Overall, Johnson & Train (1976), short and long term memory; Ghoneim & Mewaldt (1977), verbal learning; Gendreau, Sherlock, Parsons, McLean, Scott & Suboske (1972), discrimination conditioning of the eyelid response; Gupta (1974), the kinaesthetic figural after effect.
549 citations
TL;DR: In this article, a model of the evolution and isotopic composition of ambient argon retained within the metamorphic host rocks during cooling was presented, based on a step-heating argon analysis of both neutron irradiated and unirradiated samples.
313 citations
TL;DR: Dose-related improvements in the self-reported ratings of getting to sleep and perceived quality of sleep were generally associated with reductions in theSelf-reported levels of alertness and behavioural integrity the morning following the nocturnal administration of sedative hypnotic and anti-anxiety agents.
Abstract: The Leeds Sleep Evaluation Questionnaire comprises ten self-rating 100-mm-line analogue questions concerned with aspects of sleep and early morning behaviour. The questionnaire has been used to monitor subjectively perceived changes in sleep during psychopharmacological investigations involving a variety of psychoactive agents, including sedative-hypnotics, antidepressants, anxiolytics, CNS stimulants, and antihistamines. Dose-related improvements in the self-reported ratings of getting to sleep and perceived quality of sleep were generally associated with reductions in the self-reported levels of alertness and behavioural integrity the morning following the nocturnal administration of sedative hypnotic and anti-anxiety agents. Psychostimulants on the other hand, impaired subjective ratings of sleep and produced increases in early morning assessments of alertness. Certain antidepressant and antihistaminic agents produced effects similar to the sedative-hypnotics, while others did not affect self-reported aspects of sleep and early morning behaviour.
292 citations
TL;DR: In this article, the problem of determining the steady axially symmetrical motion induced by a sphere rotating with constant angular velocity about a diameter in an incompressible viscous fluid which is at rest at large distances from it is considered.
Abstract: The problem of determining the steady axially symmetrical motion induced by a sphere rotating with constant angular velocity about a diameter in an incompressible viscous fluid which is at rest at large distances from it is considered. The basic independent variables are the polar co-ordinates (r, θ) in a plane through the axis of rotation and with origin at the centre of the sphere. The equations of motion are reduced to three sets of nonlinear second-order ordinary differential equations in the radial variable by expanding the flow variables as series of orthogonal Gegenbauer functions with argument μ = cosθ. Numerical solutions of the finite set of equations obtained by truncating the series after a given number of terms are obtained. The calculations are carried out for Reynolds numbers in the range R = 1 to R = 100, and the results are compared with various other theoretical results and with experimental observations.The torque exerted by the fluid on the sphere is found to be in good agreement with theory at low Reynolds numbers and appears to tend towards the results of steady boundary-layer theory for increasing Reynolds number. There is excellent agreement with experimental results over the range considered. A region of inflow to the sphere near the poles is balanced by a region of outflow near the equator and as the Reynolds number increases the inflow region increases and the region of outflow becomes narrower. The radial velocity increases with Reynolds number at the equator, indicating the formation of a radial jet over the narrowing region of outflow. There is no evidence of any separation of the flow from the surface of the sphere near the equator over the range of Reynolds numbers considered.
267 citations
TL;DR: The data suggest that mammary tumour development is best inhibited in the constant presence of an antioestrogen i.e., biological half-life, as well as potency, is important for antitumour activity.
214 citations
TL;DR: The authors showed that volcanism in the Ethiopian region of the Afro-Arabian Rift System began earlier than previously suspected and that Quaternary volcanism was not restricted to the axial zone.
Abstract: It has been suggested that volcanism in the Ethiopian region of the Afro–Arabian Rift System has migrated with time, both laterally towards the present axial zone1–3 and longitudinally southwards from the Red Sea4,5. Field data and K–Ar isotopic ages from southwestern Ethiopia, summarised below, indicate that volcanism in this area began earlier than previously suspected, and that Quaternary volcanism was not restricted to the axial zone. That major rifting in this region did not happen until the late Miocene6,7 is corroborated.
TL;DR: In this paper, the authors considered the flow of a uniform stream past an impermeable vertical surface embedded in a saturated porous medium and which is supplying heat to the porous medium at a constant rate.
Abstract: The flow of a uniform stream past an impermeable vertical surface embedded in a saturated porous medium and which is supplying heat to the porous medium at a constant rate is considered. The cases when the flow and the buoyancy forces are in the same direction and when they are in opposite direction are discussed. In the former case, the flow develops from mainly forced convection near the leading edge to mainly free convection far downstream. Series solutions are derived in both cases and a numerical solution of the equations is used to describe the flow in the intermediate region. In the latter case, the numerical solution indicates that the flow separates downstream of the leading edge and the nature of the solution near this separation point is discussed.
TL;DR: In this paper, vertical profiles of concentrations of iodate-and total-iodine have been measured at thirty stations in the Pacific, Atlantic and Antarctic Oceans, and the salinity-normalised iodine profiles are indicative of both iodine removal and iodate reduction in the euphotic zone.
TL;DR: A gradient of habitat complexities generated by different species of algae demonstrated how increased micro-spatial complexity-allows for significant linearly related increase in harpacticoid species number and diversity, and the importance of habitat structural complexity is stressed.
TL;DR: The muscle actions necessary to resist external forces have been calculated in greater detail than before and the effects of muscle actions concerned with hand function and wrist stabilisation have been allowed for at the elbow.
TL;DR: The excretory pattern of X, the isolation of the pure compound from pooled pregnancy urine and the chemical structure are reported, which suggest initially that this compound was steroidal in nature.
Abstract: The regular occurrence of a peak due to an unidentified substance (X) in the gas chromatographic traces obtained from phenolic extracts of urine from human pregnant and non-pregnant females has been reported1. The biphasic excretion of X with maxima in the luteal phase of the ovulatory cycle and relatively high levels in the first trimester of pregnancy were noteworthy and suggested that the substance may have a biological significance. Close similarities between the excretory pattern, the chemical and chromatographic properties of X and of those of the known phenolic steroids suggested initially that this compound was steroidal in nature. The same, or a similar, substance seems to be excreted in the vervet monkey (Cercopithecus aethiops pygerythrus)2. We now report the excretory pattern of X in more detail, the isolation of the pure compound from pooled pregnancy urine and the chemical structure. The structure determined by mass spectrometry, IR spectroscopy and NMR spectrometry is: trans-(±)-3,4-bis[(3-hydroxy phenyl)methyl]dihydro-2-(3H)-furanone (HPMF) and was confirmed by synthesis.
TL;DR: In this paper, a modified version of the Mardia-puri correlation coefficient p2 iS was proposed for bivariate angular distributions and bivariate distributions on general manifolds, and its properties were examined and compared with those of other bidirectional correlation coefficients.
Abstract: SUMMARY A correlation coefficient p2 iS proposed for bivariate angular distributions and for bivariate distributions on general manifolds. In the cylindrical case p2 iS the coefficient of Mardia (1976), and for the bivariate angular case it is a modified version of the correlation coefficient of Mardia & Puri (1978). Some properties of p2 are examined and compared with those of other bidirectional correlation coefficients. In particular, this coefficient is found to be closely connected with important exponential families of distributions. Further, the asymptotic distribution of the sample version of p2 under the hypothesis of independence does not depend on the marginal distributions. Thus it is asymptotically robust against concentration in the bivariate angular case. The regression models arising from complete dependence as measured by p2 are examined. A numerical example is given.
TL;DR: X-ray microanalysis has confirmed, and measured, the phosphorus content of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas, and fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyph phosphate granules by cytoplasmic streaming.
Abstract: Summary
X-ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm-3) of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high-voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra-matrical mycelium in soil measured in the light microscope were around 12·6 cm h-1. From these data a flux rate of about 2·7 × 10-8 mol P cm-2 s-1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.
TL;DR: A new theory is presented which describes quadrupedal as well as bipedal walking by evaluating separately the work done by each leg instead of deriving net work from mechanical energy fluctuations, showing that for any given speed there is an optimum which minimizes the energy cost of locomotion.
Abstract: A new theory is presented which describes quadrupedal as well as bipedal walking. It avoids errors which occurred in previous theories by evaluating separately the work done by each leg instead of deriving net work from mechanical energy fluctuations. It takes particular account of two parameters, the duty factor β (the fraction of the stride for which each foot is on the ground) and a parameter q which defines the time course of the force on each foot. It shows that for any given speed there is an optimum (β,q) which minimizes the energy cost of locomotion. These (β,q) are only a little different for bipeds and quadrupeds except near the critical speed at which the optimum moves abruptly from walking (high β) to running (low β). Walking men use (β, q) close to the theoretical optima, but with slightly higher q. Walking dogs and sheep use q which are lower than the optimum values except at very low speeds. Some of the energy which would otherwise be required for locomotion may be saved by storage of elastic strain energy in tendons etc. This mechanism is more effective in running than in fast walking, which may be why men change from walking to running at lower speeds than the inelastic theory suggests.
TL;DR: A simple method of Fourier analysis has been used to analyse the records and shows differences between walking and running, between slow and fast walking, between accelerated and decelerated walking and between different individuals walking at the same speed.
TL;DR: In this article, the major and trace element and isotope results are reported on volcanic rocks from the islands of Dominica and St. Kitts in the Lesser Antilles, showing that the majority of the andesites and dacites on Dominica, and by analogy in the rest of the arc, are produced by fractional crystallisation of basaltic magma.
TL;DR: It is concluded that the maximal ST/HR slope reliably predicted the presence and severity of coronary artery disease, as determined by coronary arteriography in each of the patients with anginal pain.
Abstract: A new exercise electrocardiography test has been examined in patients with angina pectoris; the rate of development of ST segment depression with respect to increases in heart rate during exercise on a bicycle ergometer was measured during exercise using 13 leads in 64 patients. The steepest slope of regression lines relating displacement of ST segment to increases in heart rate (maximal ST/HR slope) was used as an index of myocardial ischaemia and was compared with the results of coronary angiography which were determined by the radiologists and the cardiologist responsible for the management of these patients. The maximal ST/HR slope could be derived consistently from a linear ST/HR relationship (r greater than 0.95) only in 50 patients with significant coronary artery disease (greater than or equal to 75% liminal narrowing). The ranges of the maximal ST/HR slope in 17 patients with single-vessel disease, in 18 patients with double-vessel disease and in 15 patients with triple-vessel disease were different from each other and the differences between the means were statistically significant (P less than 0.0005). The maximal ST/HR slopes for the patients with single-vessel disease were also different from those in the 14 patients in whom significant coronary disease could not be demonstrated. In contrast, the criteria of heart rate at which ST segment depression began, maximum ST segment depression, rate-pressure product and heart rate attained at the end of the test showed an overlap between the groups of the patients studied; using the usual exercise test criteria in the same population, there were three false negative results, one false positive result and the results in eight of the patients were indeterminate. It is concluded that the maximal ST/HR slope, used as an index of myocardial ischaemia, reliably predicted the presence and severity of coronary artery disease, as determined by coronary arteriography in each of the patients with anginal pain.
TL;DR: In this paper, the authors presented new absolute measurements of the thermal conductivity of the five noble gases at a nominal temperature of 275°C and over a range of pressures, using a transient hot-wire apparatus whose design and operational equations have been published earlier.
Abstract: The paper presents new absolute measurements of the thermal conductivity of the five noble gases at a nominal temperature of 275°C and over a range of pressures Measurements were made in a transient hot-wire apparatus whose design and operational equations have been published earlier These values replace the earlier data generated in the same instrument, which has undergone a number of improvements introduced since The most essential difference is an improved design of the cell, the use of bare platinum wires of 7 μm in diameter, and provision for temperature calibration of electric resistance in situ The present data enjoy an enhanced level of confidence and their accuracy is estimated at ±03% It is remarkable that the present absolute values of thermal conductivity at zero density combined with earlier absolute values of viscosity, also extrapolated to zero density, satisfy the Eucken relation with an error not exceeding 025%
TL;DR: It was shown that amphetamine and fenfluramine gave rise to quite distinctive readjustments to the structure of feeding behaviour, which throw light on the way in which pharmacological agents may impede food consumption and upon the neurochemical systems believed to be involved in the expression offeeding behaviour.
Abstract: An observational procedure for examining the micro-structure of eating has been employed to establish the characteristic behaviour patterns displayed after various pharmacological manipulations. Using a double dissociation design it was shown that amphetamine and fenfluramine gave rise to quite distinctive readjustment to the structure of feeding behaviour. Amphetamine anorexia was characterized by a long initial delay, following which feeding was typified by infrequent short bursts of rapid eating. These effects were antagonised by the dopamine receptor blocking agent, pimozide. Fenfluramine exerted a more restricted pattern of action characterised by a marked slowing of the rate of eating. This effect was countered by the serotonin receptor blocking agent methergoline. These data throw light on the way in which pharmacological agents may impede food consumption and upon the neurochemical systems believed to be involved in the expression of feeding behaviour.
TL;DR: In this paper, the three principal refractive indices of poly(ethylene terephthalate) were found to be 1.645, 1.573, and 1.541.
TL;DR: Castrated male sheep were prepared with cannulae in the hepatic portal vein and jugular vein through which infusions lasting for 3 hr were made so that feeding behaviour could be studied.
Abstract: 1. Castrated male sheep were prepared with cannulae in the hepatic portal vein and jugular vein through which infusions lasting for 3 hr were made. Animals had free access to a pelleted feed the weight of which was continuously recorded so that feeding behaviour could be studied.
2. Infusion into the portal vein of a mixture of salts of short-chain fatty acids (acetate, propionate, butyrate: 55, 30, 15) caused a dose-dependent depression in food intake, feeding stopping completely with 4·0 m-mole/min of the mixture. Jugular infusion depressed intake slightly, compared with controls.
3. Separate infusions of salts of the three acids showed that the effect of the mixture was due almost entirely to its propionate content; 1·2 m-mole/min of propionate into the portal vein almost completely prevented feeding (39 g eaten per 3 hr) compared with jugular infusion at the same rate (210 g) or no infusion (205 g).
4. Surgical sectioning of the hepatic nerve plexus around the wall of the hepatic artery was attempted. Of seven animals which recovered normal food intake, three continued to eat during portal vein infusions of propionate at 1·2 m-mole/min; these sheep were subsequently shown to have been at least 95% denervated. One animal was 50% denervated and ate normally during some infusions but not others. In the remaining three, feeding was suppressed by portal vein infusion of propionate, and these were less than 75% denervated.
5. It was concluded that there are receptors in the liver which are sensitive to propionate and which have afferent fibres in the hepatic plexus.
TL;DR: In this paper, electron microprobe analyses and 40Ar/39Ar geochronology of certain ophioliterelated metamorphic rocks from beneath the Pindos, Vourinos, Othris and Euboea Ophiolites of Greece show that they were formed mainly from ocean-type basalts, in part under P-T conditions of the upper mantle and that they have ages between 170-180 m.y.
Abstract: Whole rock, electron microprobe analyses and 40Ar/39Ar geochronology of certain ophioliterelated metamorphic rocks from beneath the Pindos, Vourinos, Othris and Euboea ophiolites of Greece show that they were formed mainly from ocean-type basalts, in part under P-T conditions of the upper mantle and that they have ages between 170–180 m.y. The evidence presented is inconsistent with the view that these sub-ophiolite metamorphic rocks were produced by the obduction of ocean-type crust onto a continental margin, or that they are remnant slices of Palaeozoic ‘basement’, but is consistent with their formation by thrusting and related metamorphism occurring within ocean lithosphere during the Lower to Middle Jurassic. It is proposed that this intraoceanic metamorphism was caused by the inception of a fault zone which subsequently became the transport surface for the main phase of ophiolite emplacement that occurred in the Hellenides from the Late Jurassic to Early Cretaceous.
TL;DR: A review of 34, 201 multigravid deliveries found 47 patients who had severe pre-eclampsia after previous normotensive, non-albuminuric pregnancies, and evidence supports the idea of a paternal immunogenetic factor in pre- eClampsia.
TL;DR: Marker enzymes for other subcellular components showed that this treatment completely removed contamination by mitochondria and endoplasmic reticulum and contamination by lysosomes was decreased three-fold.