Showing papers by "Newcastle University published in 1983"
TL;DR: In this article, the soliton solutions of the KdV and KP equations are written in wronskian form and shown by direct substitution to satisfy the equations and the associated Backlund transformation.
474 citations
TL;DR: In this paper, five procedures are presented for the determination of hydrogen peroxide and organic hydroperoxides (including organic peroxyacids) at concentrations of 1-10 μM in aqueous soltion.
286 citations
TL;DR: By means of a Backlund transformation for the Boussinesq equation in bilinear form, the wronskian form of the N-soliton solution of that equation is deduced as discussed by the authors.
228 citations
TL;DR: Although no differences were found in alpha-MSH content of skin from albino and pigmented rats or between involved and non-involved epidermis of patients with vitiligo, its predominance in humanEpidermis could suggest a relationship with the melanocyte or its melanin.
192 citations
TL;DR: In this paper, the effects of saturation of the main flux path can be incorporated in the generalized equations of alternating current machines in which the currents are deliberately chosen as the state variables.
Abstract: This paper shows how the effects of saturation of the main flux path can be incorporated in the generalized equations of alternating current machines in which the currents are deliberately chosen as the state variables. In the conventional equations linear magnetic conditions are assumed and the forms taken by these equations in various reference frames are well known. When saturation of the main flux path is taken into account, some parameters have to be modified and additional terms introduced; stator (and rotor) self inductances in orthogonal axes are no longer equal. These are the consequence of intersaturation - sometimes called cross-saturation; a phenomenon which has been mentioned in the literature but has not been subjected to general analysis. New forms of generalized equations are derived and their application to the analysis of induction motor starting transients described.
175 citations
TL;DR: It is suggested that partial cytochrome oxidase deficiency is the underlying defect in mitochondrial myopathy associated with the oculocraniosomatic syndromes.
174 citations
TL;DR: In this paper, carbon fibres, electrochemically treated using sulphuric acid and ammonium bicarbonate electrolytes, were analyzed by X-ray photoelectron spectroscopy.
163 citations
TL;DR: Electroencephalogram amplitude on the ectosylvian gyrus was reduced by middle cerebral artery occlusion in 25 of 26 experiments, and it was concluded that this gyrus is the principal site of ischae mic penumbra in the model.
Abstract: The gyral topography of the ischaemic penumbra associated with middle cerebral artery occlusion was studied in cats; local blood flow (hydrogen clearance, 2-min initial slope analysis), pial surface potassium activity (Kp), and electroencephalogram (EEG) amplitude were recorded on the ectosylvian, suprasylvian, and marginal gyri. Penumbral conditions were defined as a reduction of EEG amplitude in the absence of a major increase in Kp. Whole hemisphere cerebral blood flow prior to occlusion was 35.6 ± 11.4 (SD) ml 100 g−1 min−1 (n = 25), and fell significantly (p < 0.001) to 13.0 ± 4.7 (SD), 14.1 ± 6.6, and 23.8 ± 9.3 on ectosylvian, suprasylvian, and marginal gyri, respectively. Pre-occlusion Kp was 3.0 ± 0.59 mM (n = 53); sustained, steady-state increases in excess of 11.5 mM occurred in 5 of 7 (71%) experiments on ectosylvian gyrus, in 13 of 22 (59%) experiments on suprasylvian gyrus, and in 2 of 24 experiments on marginal gyrus. Transient increases in Kp occurred at ocdusion and resolved to baselines ...
159 citations
TL;DR: Each of the two lines shown to represent general susceptibility to perinatal problems, rather than the cumulative effect of diseases specific to low birthweight or to high birthweight, appears to have slopes of equal magnitude.
Abstract: The study of perinatal mortality requires a sound understanding of the influence of birthweight on perinatal mortality. This paper discusses one aspect of this problem--the pattern of weight-specific mortality. Mortality is very high at the lowest birthweights, falls to a minimum within the range of the most frequent birthweights, but rises again for the heaviest birthweights. Such a curve is best displayed and modelled by plotting the ratio of deaths to survivors on a logarithmic scale. Transformed in this way, perinatal risk may be regarded as the sum of three components--one independent of birthweight, one which decreases linearly with birthweight and one which increases linearly with birthweight. These two lines appear to have slopes of equal magnitude. Each is shown to represent general susceptibility to perinatal problems, rather than the cumulative effect of diseases specific to low birthweight or to high birthweight.
148 citations
TL;DR: The rhynchosaur Hyperodapedon gordoni from the late Triassic of Elgin, northeast Scotland, was a squat 1.3 m long reptile with a specialized skull that had a good sense of smell and diurnal vision and a precision-shear bite.
Abstract: The rhynchosaur Hyperodapedon gordoni from the late Triassic of Elgin, northeast Scotland, was a squat 1.3 m long reptile with a specialized skull. The partial remains of about 35 individuals were studied largely from casts. There is a broad size range (? age), and two morphs may be distinguished on the basis of proportions (? sexual dimorphism). Hyperodapedon had a large nasal capsule and a large eye with sclerotic plates. These indicate a good sense of smell and diurnal vision. There was no tympanum, but Hyperodapedon could probably detect sound via skin behind the quadrate, and via its throat and large hyoids. Evidence from the jaw articulation and tooth wear shows that Hyperodapedon had a precision-shear bite. Food was probably scraped up with the premaxillary beak and manipulated by a powerful tongue. The batteries of teeth on maxilla and dentary retained open roots throughout their functional life with no normal reptilian replacement. The hindlimb was adapted for scratch-digging, from a comparison of its claws with those of modern mammals. The diet probably consisted of tough, but not hard, plant material. The forelimb may have been held in a semi-sprawling pose with humerus rotation im portant in locomotion. The hindlimb was adapted for a semi-erect gait and the femur moved back and forwards with little rotation. Hyperodapedon is found in aeolian sands, and its skeletons show little physical disturbance, although there is evidence of scavenging. The late Triassic rhynchosaurs from Elgin, India, Brazil and Argentina form a close taxonomic group quite distinct from those of the middle Triassic, on the basis of univariate and multivariate analyses. The Indian form is returned to the genus Hyperodapedon as H. huxleyi since it is so similar to the Elgin form. Hyperodapedon differs from the South American Scaphonyx in the presence of lingual teeth on the dentary. The early Triassic Mesosuchus probably belongs to a separate family rather distinct from the true Rhynchosauridae. Rhynchosaurs have no special relationship with the sphenodontids, and they form a distinct, and important, lineage within the PermoTriassic diapsid radiation.
124 citations
TL;DR: The frequency distribution of birthweight can be summarized by three parameters and it is shown that the three parameters together help to explain the apparent paradox that male infants suffer a higher perinatal mortality than females despite there being fewer light male births.
Abstract: The influence of birth weight on perinatal mortality is examined with a focus on the frequency distribution of birth weight. It is suggested that the distribution is essentially Gaussian and that the predominant distribution is composed largely of term births while the residual distribution is composed almost entirely of pre-term births. Attention is also given to the apparent paradox that male infants suffer higher perinatal mortality than females despite there being fewer light male births. (ANNOTATION)
TL;DR: Even after adjustments for age, etc., apparent Vm and Km vary unpredictably among individuals with a coefficient of variation between 10 to 20%, and approximately 50% respectively.
Abstract: Previously reported routine Phenytoin clinical pharmacokinetic data from Japan, England, and Germany were analysed to estimate population pharmacokinetic parameters. There were 780 steady-state phenytoin concentrations and associated dosage rates (mg/day) from 322 patients. The patient group spanned paediatric and adult ages, mean age being 18.4 ± 17.3 (SD) years; 53% were males. The data were analysed using NONMEM, a computer programme designed for population pharmacokinetic analysis. Estimates of the influence of age, gender, data source, height and weight on the maximum elimination rate (Vm) and Michaelis-Menten constant (Km) were obtained. The Vm and Km of a 70kg adult male European were estimated to be 415 mg/day and 5.7 mg/L, respectively. Vm is not influenced by gender, age or data source. The parameters of a power function of height and weight were estimated to adjust Vm for body size. The best function adjusts Vm in proportion to weight to the 0.6 power; height contains no useful information. Km is not influenced by gender. The Km for patients less than 15 years old is 43% less than that of older patients. The Km of Japanese patients appears to be 23% less than that for European patients. Even after adjustments for age, etc., apparent Vm and Km vary unpredictably among individuals with a coefficient of variation between 10 to 20%, and approximately 50% respectively.
TL;DR: Impairment of in vivo synaptosomal uptake is a marker of simultaneous widespread damage to neurones, rather than of a change restricted to the synaptic compartment, although the present findings cannot exclude reversible, substrate-limited impairment of uptake in vivo.
Abstract: The nature of the ischaemic penumbra, as defined by suppression of electroencephalogram amplitude in the absence of increase in steady state pial surface potassium activity in excess of 13 mM, was examined in the marginal gyrus of cats subjected to middle cerebral artery occlusion. In vitro synaptosomal neurotransmitter uptake, water content (specific gravity), and histopathology at the light and electron microscopic level were studied and the results compared with those obtained at deeper, critical levels of ischaemia (less than 15 ml 100 g−1 min−1). [3H]4-Aminobutyric acid uptake was 104% of control in the marginal gyrus (NS), and 61 and 48% (p < 0.05) in critical ischaemia. It is concluded that impairment of in vivo synaptosomal uptake is a marker of simultaneous widespread damage to neurones, rather than of a change restricted to the synaptic compartment, although the present findings cannot exclude reversible, substrate-limited impairment of uptake in vivo. Reductions in specific gravity were seen on...
TL;DR: It is of more value to measure blood urea and ammonia concentrations routinely shortly after starting valproate therapy than to do conventional liver function tests, because it could significantly impair liver function when there is an additional insult.
TL;DR: In this paper, the authors examined the corrosion fatigue of the aluminium-zinc-magnesium alloy 7017-T651 in seawater at frequencies from 0.1 to 70 Hz and found that the changes in fracture mode observed at certain critical crack velocities, and their dependence upon the square root of the reciprocal of the frequency of loading, are consistent with an environment-enhanced crack growth rate involving diffusion of hydrogen ahead of the crack tip during each fatigue cycle.
TL;DR: The results of experiments are consistent with the hypothesis that males are larger as a result of a mechanical constraint and not intrasexual competition for mates.
Abstract: In natural streams, males are bigger than females in precopula pairs of the freshwater amphipod Gammarus pulex. A set of experiments is described, the results of which are consistent with the hypothesis that males are larger as a result of a mechanical constraint and not intrasexual competition for mates. Where the male in a pair is relatively larger than the female the swimming performance is superior to those pairs in which the male and female are of similar sizes. This minimises the risk of being washed downstream by the current.
TL;DR: The well known soliton solutions of the Kadomtsev-Petviashvili equations are written in terms of determinants of Wronskian form as mentioned in this paper.
Abstract: The well known soliton solutions of the Kadomtsev-Petviashvili equations are written in terms of determinants of Wronskian form. By using this compact representation together with the Hirota bilinear form of the equations, it is demonstrated by elementary algebraic methods that the N -soliton solution satisfies the evolution equation and the N and N + 1-soliton solutions satisfy the associated Backlund transformation. The relation of these results to the eigensolutions of the inverse scattering method and to the more usual representation of the N -soliton solution is also given.
TL;DR: It is concluded that there may be relatively few opportunities for the use of predators in ‘classical’ biological control, other than in glasshouses, and there is a need for the encouragement of naturally occurring, often polyphagous, predators in many outdoor crops.
TL;DR: Preliminary studies after ‘high dose’ metoclopramide demonstrate accumulation to high plasma concentrations with linear kinetics, suggesting that current high dose regimens are unnecessarily cumbersome.
Abstract: Metoclopramide is rapidly and well absorbed from the gastrointestinal tract, and in man undergoes variable first-pass metabolism (oral bioavailability 32 to 100%). In man, N-4 sulphate conjugation is an important pathway of metabolism and after oral administration the ratio of free to conjugated metoclopramide in urine correlates with the plasma AUC. The elimination half-life of metoclopramide is dose-dependent after both intravenous and oral administration of single doses between 5 and 20mg. Metabolic profiles in animal species studied are very different from man. The clearance of metoclopramide is reduced in patients with renal failure to approximately 50% of normals and the terminal half-life is prolonged; this is despite the fact that renal clearance of free drug accounts for only 20% of the administered dose in normals. Preliminary studies after 'high dose' metoclopramide demonstrate accumulation to high plasma concentrations with linear kinetics, suggesting that current high dose regimens are unnecessarily cumbersome.
TL;DR: The results show that post-operative dental pain is variable in its nature and intensity, but reaches its maximum intensity in the first 12 hours post-operatively.
TL;DR: In this paper, the authors used K-Ar and40Ar/39Ar studies of Mesozoic ocean floor basalts and Tertiary plutonic and volcanic rocks from Maio, Cape Verde Islands, have been determined to elucidate the magmatic evolution of this ocean island.
TL;DR: A model is constructed of a database that can be accessed and modified concurrently by a number of users, and an approximate solution is presented that is based on the dynamic acquisition of entities and locking.
Abstract: A model is constructed of a database that can be accessed and modified concurrently by a number of users, and an approximate solution is presented. The resource allocation policies considered involve dynamic acquisition of entities and locking; deadlock is avoided by limiting the number of consecutive attempts to acquire a particular entity. The accuracy of the approximation is evaluated by simulations. Several generalizations aimed at improving the practicality of the model are described.
TL;DR: In this paper, the authors used the saturation remanence normalization method to estimate the paleointensity of more than 50 samples of the Apollo 11 low and high potassium basalts and found that the oldest samples are among the most weakly magnetized.
Abstract: A lunar surface field comparable in intensity to the earth's magnetic field, existing from 3.6 to 3.8 AE, is suggested by paleointensity estimation measurements of more than 50 lunar samples by means of the saturation remanence normalization method. The present data differ from previous descriptions of the lunar field's variation with time, in that the oldest samples are among the most weakly magnetized, and the time of extrusion of the Apollo 11 low and high potassium basalts is suggested to have dropped in paleointensity by an order of magnitude. The coincidence of the high field era with the termination of basin forming impacts at the beginning of mare basalt extrusion suggests a common cause, such as the close approach of the moon to the earth at 3.8 AE.
TL;DR: A concept of whole-body protein metabolism in the metabolic response to trauma is advocated whereby protein breakdown is largely obligatory to the response, whereas synthesis responds to substrate availability.
Abstract: Whole-body protein metabolism was determined by a primed constant-rate infusion of L-[ 1-14C ]leucine in patients before and after elective surgery, the nutritional intake being carefully controlled and the surgical stress in individuals being assessed. Pre-operatively, whole-body protein flux (P less than 0.05) and synthesis (P less than 0.05), along with amino acid oxidation (P less than 0.01), increased with nutritional intake whereas protein breakdown remained unaltered. Whole-body protein balance also correlated with intake (P = 0.001). Postoperatively, whole-body protein metabolism was determined with patients either fasted (group 1) or fed (group 2) and the change in metabolism in each individual from a pre-operative study, carried out in the fed state, was calculated. Whole-body protein breakdown increased in both groups (group 1, + 0.91 +/- 0.74 g day-1 kg-1; mean +/- SD, n = 7: group 2, + 0.47, + 0.63 and + 1.01 g day-1 kg-1, n = 3), the change being significant in those fasted after surgery (P less than 0.05). However, the pattern of change in whole-body protein synthesis was entirely different in each group, rising in those fed throughout (+ 0.32, + 0.41 and + 0.66 g day-1 kg-1, n = 3) but falling in those fasted after surgery (-0.38, -0.80 and -1.33 g day-1 kg-1, n = 3). The changes in metabolism appeared more marked in those undergoing greatest surgical stress. Some of the factors involved in the calculations are discussed and their effects on the overall conclusions are considered. A concept of whole-body protein metabolism in the metabolic response to trauma is advocated whereby protein breakdown is largely obligatory to the response, whereas synthesis responds to substrate availability.
TL;DR: In this paper, Nitrogen mineralization and immobilization were investigated in two soils incubated with ammonium sulphate or pig slurry over a range of temperatures and moisture contents, and it was found that the rate of immobilization increased with increasing moisture content, though the period of nett immobilization was shorter.
Abstract: Nitrogen mineralization and immobilization were investigated in two soils incubated with ammonium sulphate or pig slurry over a range of temperatures and moisture contents. A reduction in the mineralization of soil organic N was observed in soils incubated with 100 μg NH 4 + -Ng −1 soil as ammonium sulphate at 30°C but not at lower temperatures. Addition of 100 μg NH 4 + -N g −1 soil as pig slurry resulted in a period of nett immobilization lasting up to 30 days at 5°C. Although the length of the immobilization phase was shorter at higher temperatures the total N immobilized was similar. The subsequent rate of mineralization in slurry-treated soils was not significantly greater ( P = 0.05) than in untreated soils. There was no evidence of any subsequent increased mineralization arising from the immobilized N or slurry organic N for up to 175 days. The rate of immobilization was found to increase with increasing moisture content, though the period of nett immobilization was shorter, so that the amount of N immobilized was similar over a range of moisture contents from 10 to 40%. Approximately 40% of the NH 4 + -N in the slurry was immobilized under the incubation conditions used.
TL;DR: Osteomalacia has different manifestations, and probably different causes, before and after the start of haemodialysis, and these two stages of renal failure should be clearly distinguished in reports of renal bone disease.
Abstract: The case records of 327 patients who underwent bone biopsy in late or terminal renal failure, before any form of dialysis or transplantation, were examined for clues to the aetiology of renal osteomalacia and its manifestations. Fifty four per cent of the biopsies showed pure osteitis fibrosa, 34 per cent osteomalacia with osteitis fibrosa and 12 per cent showed neither abnormality. Osteomalacia was strongly associated with chronic pyelonephritis and obstructive uropathy as primary renal disease. In two matched groups of 100 each, and within the major primary diseases, it was associated with acidosis, hypocalcaemia and normophosphataemia (as opposed to hyperphosphataemia). There was no association with known length or uraemia and only a weak and inconsistent relationship with severity of uraemia. In the few patients studied, there was no relationship between osteomalacia and serum 25-hydroxycholecalciferol level. In contrast to the state of patients treated by haemodialysis, osteomalacia in this undialysed group was manifested by a higher level of serum alkaline phosphatase than pure osteitis fibrosa, serum iPTH did not differ between the groups, there was no predominance of symptoms in one group, other than proximal myopathy which had a weak association with osteomalacia, and Looser zones were more common than complete fractures. Our study shows that osteomalacia has different manifestations, and probably different causes, before and after the start of haemodialysis. These two stages of renal failure should be clearly distinguished in reports of renal bone disease.
TL;DR: Data is presented on the improvement of histological renal osteodystrophy in CAPD patients and relate this to serum concentrations of calcium, phosphate, 25 hydroxycholecalciferol [25-(0H)CC] and immunoreactive parathormone (PTH) and sequential serum aluminum concentrations are reported.
TL;DR: It is suggested that the enzyme defective in the patients was the mitochondrial acetoacetyl CoA thiolase involved in ketone body utilization in extrahepatic tissues.
TL;DR: In this article, it is shown that the set of activity vectors which satisfy the constraint will, in general, be nonconvex, which militates against the determination of an efficient solution.