Showing papers by "Newcastle University published in 1986"

Chaotic streamlines in the ABC flows

Abstract: The particle paths of the Arnold-Beltrami-Childress (ABC) flows \[ u = (A \sin z+ C \cos y, B \sin x + A \cos z, C \sin y + B \cos x). \] are investigated both analytically and numerically. This three-parameter family of spatially periodic flows provides a simple steady-state solution of Euler's equations. Nevertheless, the streamlines have a complicated Lagrangian structure which is studied here with dynamical systems tools. In general, there is a set of closed (on the torus, T3) helical streamlines, each of which is surrounded by a finite region of KAM invariant surfaces. For certain values of the parameters strong resonances occur which disrupt the surfaces. The remaining space is occupied by chaotic particle paths: here stagnation points may occur and, when they do, they are connected by a web of heteroclinic streamlines.When one of the parameters A, B or C vanishes the flow is integrable. In the neighbourhood, perturbation techniques can be used to predict strong resonances. A systematic search for integrable cases is done using Painleve tests, i.e. studying complex-time singularities of fluid-particle trajectories. When ABC ≠ 0 recursive clustering of complex time singularities occurs that seems characteristic of non-integrable behaviour.

Haematogenous metastastic patterns in colonic carcinoma: An analysis of 1541 necropsies

Abstract: The sequence of events in haematogenous metastasis from colonic carcinoma was analysed, using 1541 necropsy reports from 16 centres. The findings are consistent with the cascade hypothesis that metastases develop in discrete steps, first in the liver, next in the lungs and finally, in other sites. Deviations of necropsy findings from the cascade model are largely explained on the basis of false negative reports. In only 216 of 1194 cases was there suggestive evidence that metastatic patterns (excluding lymph nodes) were causally related to lymphatic or non-haematogenous pathways. The incidence of metastatic involvement in 'other' (quaternary) sites correlated with target organ blood-flow (ml min-) per g, only when bone marrow and thyroid were excluded. In the thyroid the incidence was lower than expected on the basis of blood flow per g tissue; this may indicate that the thyroid is an unfavourable site for metastatic growth of colonic carcinoma. In the bone marrow it is higher; the latter may be due to delivery of cancer cells via both arterial blood and the vertebral venous plexus. Recognition of this pattern of metastases in the bone marrow could be important with respect of diagnosis and therapy, in patients with colonic carcinoma.

An empirical analysis of self‐employment in the U.K.

Abstract: The paper formulates a self-employment/paid-employment choice problem that draws upon Knight's notion that the individual responds to the risk-adjusted relative earnings opportunities in each sector. Based on a development of such choice-theoretic considerations, an econometric model is developed with the purpose of empirically examining the determinants of self-employment. The model features simultaneous determination of employment status and earnings, which allows for self-selectivity. The model is estimated using a sample of 4762 individuals from the General Household Survey for 1978. The estimation of the earnings equation enables a calculation of the self-employment/paid-employment earnings differential and the estimated probit equation for self-employment/paid-employment status facilitates the prediction of the probability of self-employment. The paper finds that there is positive selection bias in the observed earnings of employees, that the probability of self-employment depends positively on the earnings difference between the two sectors and that education and age are significant determinants of self-employment.

Regulation of gene expression by pH of the growth medium in Aspergillus nidulans.

Abstract: In the fungus Aspergillus nidulans the levels of a number of enzymes whose location is at least in part extracellular (e.g. acid phosphatase, alkaline phosphatase, phosphodiesterase) and of certain permeases (e.g. that for gamma-amino-n-butyrate) are controlled by the pH of the growth medium. For example, at acidic pH, levels of acid phosphatase are high and those of alkaline phosphatase are low whereas at alkaline pH the reverse is true. Mutations in five genes, palA, B, C, E and F, mimic the effects of growth at acid pH whereas mutations in pacC mimic the effects of growth at alkaline pH. palA, B, C, E and F mutations result in an intracellular pH (pHin) which is more alkaline than that of the wild type whereas pacC mutations result in a pHin more acidic than that of the wild type. This indicates that these mutations exert their primary effects on the regulation of gene expression by pH rather than on the pH homeostatic mechanism but that the expression of at least some component(s) of the pH homeostatic mechanism is subject to the pH regulatory system. It is suggested that pacC might be a wide domain regulatory gene whose product acts positively in some cases (e.g. acid phosphatase) and negatively in others (e.g. alkaline phosphatase). The products of palA, B, C, E and F are proposed to be involved in a metabolic pathway leading to synthesis of an effector molecule able to prevent the (positive and negative) action of the pacC product.(ABSTRACT TRUNCATED AT 250 WORDS)

Error recovery in asynchronous systems

Abstract: A framework for the provision of fault tolerance in asynchronous systems is introduced. The proposal generalizes the form of simple recovery facilities supported by nested atomic actions in which the exception mechanisms only permit backward error recovery. It allows the construction of systems using both forward and backward error recovery and thus allows the exploitation of the complementary benefits of the two schemes. Backward recovery, forward recovery, and normal processing activities can occur concurrently within the organization proposed. Exception handling is generalized to provide a uniform basis for fault tolerance schemes with the atomic action structure. The generalization includes a resolution scheme for concurrently raised exceptions based on an exception tree and an abortion scheme that permits the termination of the internal atomic actions. An automatic resolution mechanism is outlined for exceptions in atomic actions which allows users to separate their recovery schemes from the details of the underlying algorithms.

Gut hormones and 'minimal enteral feeding'

Abstract: . Previously we have identified multiple surges in plasma concentrations of gut hormones post-natally in enterally fed term and preterm infants. In this study on 104 preterm infants we have shown that such surges are induced after ingestion of very small quantities of human milk. Whereas 6-day-old exclusively parenterally fed infants showed no postnatal elevation in enteroglucagon, gastrin, GIP, motilin and neurotensin, infants recovering from hyaline membrane disease who had received restricted enteral nutrition had similar hormone surges to those seen in well infants on full enteral feeds. Significant elevations in enteroglucagon, gastrin and GIP occurred after a cumulative mean enteral feed volume since birth of only 24 ml (12 ml/kg body weight) had been consumed and after a mean total intake of 96 ml (50 ml/kg) the response was maximal. Greater feed volumes were required to produce a neurotensin or motilin surge, but even these volumes were substantially lower than those required for full enteral feeding. In view of the proposed roles of gut hormones in the adaptation to extrauterine nutrition these data have implications for mammalian biology and raise the possibility that ‘minimal enteral feeding’ might have a clinical therapeutic role in infants undergoing prolonged parenteral nutrition.

An Efficient Algorithm to Generate Official Statistical Reporting Areas: The Case of the 1984 Travel-to-Work Areas Revision in Britain

Abstract: Travel-to-work areas (T.T.W.A.s) are used by the Department of Employment for the reporting of monthly local unemployment statistics. T.T.W.A.s are also used to demarcate those parts of Britain to benefit from the public expenditure on industry under regional policy. The 1984 revision of T.T.W.A. boundaries provided academics with a rare opportunity to help rationalize official statistical areas. This involved the specification of zone-design criteria and the implementation of these in a regionalization methodology. It was found that methods based on the model of local labour market areas yielded the most reasonable set of boundaries. The final methodology is detailed here, together with the actual parameter values used in the analysis that produced the new T.T.W.A.s. The paper ends by considering the implementation of the results, and evaluates the new areas against the old T.T.W.A.s.

Early intellectual dysfunction following coronary bypass surgery.

Abstract: As part of a major prospective study of neurological and psychological complications of coronary artery bypass graft surgery, involving 312 patients, detailed psychometric testing was carried out before and after operation on 298 patients using a battery of 10 standard tests of intellectual function. This report is concerned with the early neuropsychological dysfunction detectable one week after operation. Two hundred and thirty-five patients (79 per cent of the cohort) showed impairment in some aspect of cognitive function at the seventh day after operation. Only 63 patients (21 per cent) showed no deterioration from levels before operation in any of the 10 test scores. One hundred and twenty-three of the patients whose scores deteriorated had no symptoms while in hospital. Eighty-nine patients complained of cognitive impairment, and 23 patients were considered to be overtly disabled by their intellectual dysfunction, during the period soon after operation. There is therefore a high incidence of early cerebral dysfunction detectable by psychometric testing following coronary artery bypass graft surgery. Often this was not of sufficient severity to cause serious concern to the patients or to interfere with their everyday activities in the hospital environment.

Bend loss measurements on high numerical aperture single-mode fibers as a function of wavelength and bend radius

Abstract: The results of an investigation into the bend loss as a function of wavelength for single-radius bends in monomode fibers are given. The fibers considered have a high numerical aperture and a protective coating which has a refractive index greater than that of the cladding. For these fibers the pure bend loss is shown to be the dominant loss mechanism over the wavelength range 633-1152 nm. In addition, oscillations in the loss are observed as the bend radius is varied at the longer wavelengths. These oscillations are shown to result from the coupling of light under weak coupling conditions from a whispering gallery mode in the cladding formed by the pure bend loss, to the fundamental mode in the core. An expression is derived which relates the bend radius at which the minima in the oscillations occur to the fiber parameters and a qualitative explanation is given for the reduction in the oscillation amplitude as the bend radius and wavelength are decreased. A criterion is identified for assessing the strength of the coupling between the whispering gallery mode and fundamental mode. Using this criterion the attenuation coefficient of the pure bend loss at which a transition from weak to strong coupling occurs is determined and is found to agree with observations. The effect of the coupling strength between the whispering gallery mode and the fundamental mode on the characteristics of the pure bend loss is discussed. Finally, possible applications arising from the results of this work are identified.

The role of mucus in the protection of the gastroduodenal mucosa.

Abstract: There is good evidence that the adherent mucus plays an important role in the protection of gastroduodenal mucosa from the endogenous aggressors acid and pepsin. Adherent mucus provides a stable unstirred layer which supports surface neutralization of acid by mucosal bicarbonate output and acts as a permeability barrier to luminal pepsin. The adherent mucus layer is continuous. True thickness of the mucus layer and its continuity can only be observed on unfixed sections of mucosa, since histological fixatives and preparation for electron microscopy can cause dehydration and shrinkage of the mucus gel. The structure of adherent gastric mucus is deficient in patients with peptic ulcer disease because of decreased polymerization of the component glycoproteins. This impairment of the mucus barrier is associated with raised amounts of pepsin 1, which digests the mucus layer more aggressively than the major pepsin, pepsin 3, under conditions that pertain both in the stomach (pH 2) and duodenum (pH 4-5). Adherent mucus does not appear to offer much protection against exogenous damaging agents, e.g. alcohol and aspirin. These agents permeate the mucus barrier, damaging the underlying epithelium. The subsequent epithelial repair process is protected by a gelatinous coat over ten times thicker and distinct from the normal adherent mucus layer. Our recent studies show this gelatinous coat to be primarily a fibrin-based gel with mucus and necrotic cells.

Tests for comparing two estimated spectral densities

Abstract: . This paper was motivated by a problem in the gas industry and describes a number of periodogram-based tests of the hypothesis that two independent time-series are realizations of the same stationary process. Non-parametric tests analogous to the maximum periodogram ordinate and cumulative periodogram tests for white noise are compared with a likelihood ratio test based on a postulated quadratic model for the log spectral ratio. The latter is found to be generally more powerful against alternatives in which the two series are realizations of different low order AR processes. The operation of the likelihood ratio test is illustrated by two sets of data, the classic Beveridge wheat price series and a set of data supplied by British Gas.

Abdominal pain in six-year-olds: an epidemiological study in a new town*

Abstract: — This study investigated recurrent abdominal pain in all 494 second-year infant children in a new town using a postal questionnaire followed by sampling and detailed interview. A prevalence of between 24.5 and 26.9% was found and there were associations with psychiatric deviance both at home and at school. There were also associations with social support of the mother, difficulties in settling into school and status of house ownership. Details of parental management of their children's symptoms are described.

Comparative ecophysiology of CAM and C3 bromeliads. III. Environmental influences on CO2 assimilation and transpiration

Abstract: Field measurements of the gas exchange of epiphytic bromeliads were made during the dry season in Trinidad in order to compare carbon assimilation with water use in CAM and C3 photosynthesis. The expression of CAM was found to be directly influenced by habitat and microclimate. The timing of nocturnal CO2 uptake was restricted to the end of the dark period in plants found at drier habitats, and stomatal conductance in two CAM species was found to respond directly to humidity or temperature. Total night-time CO2 uptake, when compared with malic-acid formation (measured as the dawn-dusk difference in acidity, ΔH+), could only account for 10–40% of the total ΔH+ accumulated. The remaining malic acid must have been derived from the refixation of respired CO2 (recycling). Within the genus Aechmea (12 samples from four species), recycling was significantly correlated with night temperature at the six sample sites. Recycling was lowest in A. fendleri (54% of ΔH+ derived from respired CO2), a CAM bromeliad with little water-storage parenchyma that is restricted to wetter, cooler regions of Trinidad. Gas-exchange rates of C3 bromeliads were found to be similar to those of the CAM bromeliads, with CO2 uptake from 1 to 3 μmol m−2 s−1 and stomatal conductances generally up to 100 mmol m−2 s−1. The midday depression of photosynthesis occurred in exposed habitats, although photosynthetically active radiation (PAR) limited photosynthesis in shaded habitats. CO2 uptake of the C3 bromeliad Guzmania lingulata was saturated at around 500 μmol m−2 s−1 PAR, suggesting that epiphytic plants found in the shaded forest understorey are shade-tolerant rather than shade-demanding. Transpiration ratios (TR) during CO2 fixation in CAM (Phase I and IV) and C3 bromeliads were compared at different sites in order to assess the efficiency of water utilization. For the epiphytes displaying marked uptake of CO2, TR were found to be lower than many previously published values. In addition, the average TR values were very similar for dark CO2 uptake in CAM (42 ± 41, n= 12), Phase IV of CAM (69 ± 36, n= 3) and for C3 photosynthesis (99 ± 73, n= 4) in these plants. It appears that recycling of respired CO2 by CAM bromeliads and efficient use of water in all phases of CO2 uptake are physiological adaptations of bromeliads to arid microclimates in the humid tropics.

Is otitis media a major cause of specific developmental language disorders

Abstract: It is known that children with a persistent conductive hearing loss do poorly on tests of linguistic and educational attainment, but it is less clear whether significant impairments persist after hearing has returned to normal. If so, then an early history of recurrent otitis media could be an important cause of the types of developmental language disorders seen by speech therapists. In a study of 69 four-year-old children with specific developmental language disorders, history of ear infections was assessed by parental questionnaire. Compared to a control group, a significantly higher level of hospital attendance for middle ear disease was reported in language-disordered children, but the groups did not differ in the number of episodes of ear infections reported, suggesting that referral to an ENT department is determined by the child's language status as well as by history of otitis media. Comparisons of language-disordered children with and without a history of recurrent otitis media revealed no differ...

Diazoxide in the management of patients with insulinoma.

Abstract: The control of severe hypoglycemic symptoms in patients with insulin-secreting islet tumors (insulinoma) of the pancreas is an important aspect of management. A series of 24 patients with insulinomas whose ages ranged from 5 months to 73 years seen at one center over a period of 17 years is described. The presenting symptoms and the effect of these on their lifestyles are discussed. Diazoxide has been used to control hypoglycemic symptoms in 18 of the 24 patients. Fourteen patients have received diazoxide for varying periods of time prior to successful surgery and 4 have received long-term therapy. Three of these patients are highlighted to show various aspects of benefit and problems from the use of diazoxide. The mean dosage of diazoxide was 400 mg/day and the mean duration of therapy was 10 months. The control of symptoms was good in 8, fair in 6, and poor in 4. The main side effects observed were hirsutism (56%), ankle edema (50%), weight gain (38%), and nausea (11%). These side effects were well tolerated and the benefits of therapy were felt to outweigh disadvantages. Side effects only necessitated discontinuation of diazoxide in 1 patient who developed a severe hypersensitivity reaction. Our results show that diazoxide has a role to play in the management of patients with insulinoma during preoperative tumor localization and can also be used when surgery is contraindicated or when laparotomy is unsuccessful.

The geography of technological change in the information economy

Abstract: Hepworth M. (1986) The geography of technological change in the information economy, Reg. Studies 20, 407–424. Innovations in information technology are transforming urban and regional systems through their impacts on production and distribution processes. Case studies of Canadian multi-locational firms are used to examine this spatio-economic transformation in the context of the new information-based service economy. By focusing on computer networks as spatial systems of information technology, it is shown that these innovations can lead to centralized and decentralized patterns of direct production and office activity. New insights are also developed into the telecommunications-transportation trade-off and the key role of telecommunications in regional development.

Cross-Saturation in Smooth-Air-Gap Electrical Machines

Abstract: A detailed analysis of the phenomenon of cross-saturation is presented and it is shown that in a smooth-air-gap quadrature-phase machine this phenomenon is similar to the phenomenon of the demagnetizing effect of cross-magnetizing armature reaction in a d.c. machine. In a quadrature-phase smooth-air-gap machine the resultant air-gap flux density distribution is decreased over one half of the pole-pitch and is increased under the other half of the pole-pitch and due to saturation the decrease is greater than the increase. Thus under saturated conditions, if the resultant m.m.f. distribution is displaced from the magnetic axes of the windings, a change in the quadrature-axis magnetizing current will cause a change of flux linkage in the direct-axis winding and vice versa, a change in the direct-axis magnetizing current will cause a change of flux linkage in the quadrature-axis winding. It is an important result that cross-saturation can also exist if the m.m.f. distributions are assumed to be sinusoidal. A physical derivation of the cross-saturation coupling factor is presented and a test is described which shows the existence of cross-saturation. A theoretical analysis of the experiment gives results which are in good agreement with the experimental results.

The Politics Carnes Lord: Aristotle , The Politics, translated with an Introduction, Notes and Glossary. Pp. 284; 2 maps. Chicago and London: University of Chicago Press, 1984. £29.75.

Abstract: which is not the aim of the Bude series. L. provides useful first aid for the puzzled reader, but does not do much to put him on the track of recent scholarly work on Aristotle's physical theory generally. The same may be said of the introduction, in so far as it deals with the content of the Meteorologica and its place in Aristotle's work. The Meteorologica is, for instance, an interesting test-case for theories about Aristotelian scientific method and the role of dialectic in that method. L. displays little concern for such questions. In his De Caelo, Moraux showed what a Bude editor can contribute to the understanding even of a much-studied work: L.'s Meteorologica is, on the contrary, a sadly missed opportunity.

The effect of altering area of application and dose per unit area on sensitization by DNCB.

Abstract: We have investigated the contributions of dose per unit area and area of application to the degree of sensitivity induced by dinitrochlorobenzene (DNCB). Subjects sensitized with 35.4 micrograms/cm2 showed equal sensitization whether the total dose was 250 micrograms applied to 7.1 cm2 or 62.5 micrograms applied to 1.8 cm2. Three groups of subjects were sensitized with 16.4 micrograms/cm2 applied as 56 micrograms on 3.5 cm2, 116 micrograms on 7.1 cm2 or 232 micrograms on 14.2 cm2. Although the total dose changed by a factor of four, the proportions of subjects sensitized were comparable (66, 50 and 55% respectively), and their degrees of reactivity were similar. This contrasts with previous findings that when the area of sensitization was fixed and the concentration was increased over a similar range, highly significant increases in the proportion of sensitized subjects and degree of reactivity occurred.