Showing papers by "University of Leeds published in 1991"
TL;DR: In this paper, it was suggested that in many ferromagnetic materials there may occur particles distinct in magnetic character from the general matrix, and below the critical size, depending on shape, for which domain boundary formation is energetically possible.
Abstract: It is suggested that in many ferromagnetic materials there may occur particles distinct in magnetic character from the general matrix, and below the critical size, depending on shape, for which domain boundary formation is energetically possible. For such single-domain particles, change of magnetization can take place only by rotation of the magnetization vector. As the field changes continuously, the resolved magnetization may change discontinuously at critical values of the field. The character of the magnetization curves depends on the degree of magnetic anisotropy of the particle and on the orientation of easy axes with respect to the field. The magnetic anisotropy may arise from the shape of the particle, from magnetocrystalline effects, and from strain. A detailed quantitative treatment is given of the effect of shape anisotropy when the particles have the form of ellipsoids of revolution, along with a less detailed treatment for the general ellipsoidal form.
1,401 citations
TL;DR: The proof of correctness of the algorithm relies on recent theory of rapidly mixing Markov chains and isoperimetric inequalities to show that a certain random walk can be used to sample nearly uniformly from within K within Euclidean space.
Abstract: A randomized polynomial-time algorithm for approximating the volume of a convex body K in n-dimensional Euclidean space is presented. The proof of correctness of the algorithm relies on recent theory of rapidly mixing Markov chains and isoperimetric inequalities to show that a certain random walk can be used to sample nearly uniformly from within K.
702 citations
TL;DR: The method was highly sensitive and could detect a single melanoma cell from a cell line in 2 ml normal blood, and could prove useful in the diagnosis of primary or metastatic cancers, in assessing prognosis, and in detecting residual disease after treatment.
665 citations
TL;DR: An improved tomographic method, using a more realistic background Earth model and surface-reflected as well as direct seismic phases, shows that slabs beneath the Japan and Izu Bonin island arcs are deflected at the boundary between upper and lower mantle, whereas those beneath the northern Kuril and Mariana arcs sink into the lower mantle.
Abstract: The seismic tomography problem does not have a unique solution, and published tomographic images have been equivocal with regard to the deep structure of subducting slabs. An improved tomographic method, using a more realistic background Earth model and surface-reflected as well as direct seismic phases, shows that slabs beneath the Japan and Izu Bonin island arcs are deflected at the boundary between upper and lower mantle, whereas those beneath the northern Kuril and Mariana arcs sink into the lower mantle.
545 citations
TL;DR: eGL show morphological and antigenic heterogeneity and the study of granulated lymphocytes in pathological endometrium and decidua will require careful phenotypic and morphological analysis of accurately dated samples.
Abstract: Granulated lymphocytes with an unusual antigenic phenotype (CD56+ CD38+ CD2 +/- CD3- CD16-) form a substantial proportion of leukocytes in human endometrial stroma. The purpose of this study was to examine morphological and antigenic heterogeneity in endometrial granulated lymphocytes (eGL) in imprint preparations, paraffin-embedded sections and frozen sections. eGL in decidual imprints showed variations in cell size, nuclear size, shape and chromatin content and the number and size of cytoplasmic granules. eGL were detected in paraffin-embedded sections using phloxine tartrazine, alcian blue and toluidine blue stains. There was no difference in the number of eGL among the three stains but the granules appeared smaller and more regular when stained with toluidine blue. The proportion of stromal cells which were leukocytes increased from 8.2% in proliferative endometrium to 31.7% in early pregnancy decidua. The number of CD56+ and CD38+ cells increased in late secretory endometrium; CD56+ cells formed greater than 75% of the leukocytes in first trimester decidua. The increased number of CD2+ cells in decidua was not comparable with CD56+ and CD38+ cells suggesting that a lower proportion of CD56+ cells in first trimester decidua coexpress CD2, an observation which was supported by double labelling studies. eGL therefore show morphological and antigenic heterogeneity and the study of granulated lymphocytes in pathological endometrium and decidua will require careful phenotypic and morphological analysis of accurately dated samples.
535 citations
TL;DR: It is suggested that muscles that are optimally adapted for their tasks in running should do positive work with constant efficiency, and that mammals exploit these energy-saving mechanisms.
Abstract: Energy can be saved in terrestrial locomotion in many different ways. The maximum shortening speeds (Vmax) of the muscles can be adjusted to their optimum values for the tasks required of them. The moments exerted by the muscles at different joints can be adjusted to keep the ground force in line with the leg so that muscles do not work against each other. The joints of the legs can be kept as straight as possible, minimizing muscle forces and work requirements. Walking gaits should be selected at low Froude numbers (a dimensionless speed parameter) and running gaits at high Froude numbers. Tendon and other springs can be used to store elastic strain energy and to return it by elastic recoil. This paper aims to show how these energy-saving mechanisms work and to what extent mammals exploit them. Arguments based on our rather limited knowledge of the relationship between the mechanical performance of muscle and its metabolic energy consumption are used throughout. They suggest that muscles that are optimally adapted for their tasks in running should do positive work with constant efficiency.
442 citations
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TL;DR: In this article, the authors show that the flow caused by a supersonic gas jet is self-similar under certain conditions and that the type of similarity solution depends on the density distribution of the gas through which the jet propagates.
Abstract: General arguments and numerical calculations are used to show that the flow caused by a supersonic gas jet is self-similar under certain conditions. If we assume that the jet has a high initial Mach number and is generated in a region small compared to its length, then the type of similarity solution depends on the density distribution of the gas through which the jet propagates. If this density decreases faster than 1/R 2 , where R is the distance from the source, then the length of the jet increases linearly with time and it may evolve into a classical double if it subsequently encounters a region of higher density.
397 citations
TL;DR: Food craving was found to be only weakly related to dietary restraint, but highly and significantly correlated with external eating, emotional eating and susceptibility to hunger, and dysphoric mood was prominent prior to the cravings themselves.
342 citations
309 citations
01 Jan 1991
TL;DR: In this article, a new technique is presented for determining burning velocities and stretch effects in laminar flames, and applied to hydrogen/air mixtures, and the validity of the simple model has been tested by using it to analyse the results of the detailed simulations.
Abstract: A new technique is presented for determining burning velocities and stretch effects in laminar flames, and applied to hydrogen/air mixtures. The speeds of expanding spherical flames, measured by high-speed schlieren cine-photography, are shown to vary with flame radius. A simple phenomenological model has been developed to analyse the data and obtain the 1-D flame speed by extrapolation to infinite radius. A computer program has also been developed for detailed simulation of expanding flames. The validity of the simple model has been tested by using it to analyse the results of the detailed simulations. The true 1-D flame speeds in this case are known from planar flame modelling using the same kinetic scheme. The simple model predicted flame speeds within 2% of the true values over most of the stoichiometric range. This demonstrates that our extrapolation procedure is sound and will produce reliable results when applied to experimental data. Since the flame speeds derived from experiments are 1-D values, multiplying them by the density ratio gives 1-D burning velocities (S u 0 ). Burning velocities are reported for mixtures containing 9 to 68% hydrogen. The maximum S u 0 is 2.85 ms −1 , considerably less than most burner-derived values. The discrepancies can be explained by flow divergence and stretch effects perturbing burner measurements. Planar flame modelling reproduces the experimental burning velocities to within 3% over most of the stoichiometric range. The rate at which the measured flame speed approaches its limiting value depends on flame thickness and flame stretch. By subtracting the flame thickness term, Markstein lengths can be derived. Again values are given across the whole stoichiometric range. They are negative in lean mixtures (i.e. stretch increases the burning rate) but positive in stoichiometric and rich (stretch reducing burning rate). This is in line with predictions based on Lewis number considerations.
289 citations
TL;DR: John Blundell advocates a systems approach to the study of appetite control, where drug-induced changes in feeding should be interpreted according to a system which involves behaviour, peripheral physiology and brain neural pathways.
TL;DR: The results of PCR amplification and partial 16S rRNA gene sequence analysis strongly support the contention that the gastric organisms previously recovered from a pig, a baboon, and rhesus monkeys are H. pylori.
Abstract: We designed a polymerase chain reaction (PCR) for amplifying the Helicobacter pylori gene encoding 16S rRNA. Primers for the specific detection of H. pylori were designed for areas of the 16S rRNA gene in which there is the least sequence homology between H. pylori and its closest relatives. The specificity of detection was confirmed by ensuring that the primers did not amplify DNA extracts from the campylobacters H. cinaedi, H. mustelae, and Wolinella succinogenes, which are the closest relatives of H. pylori, as determined by 16S rRNA sequencing. Serial dilution experiments revealed the detection of as little as 0.1 pg of DNA by PCR and 0.01 pg by nested PCR. H. pylori DNA was detected successfully in clinical paraffin-embedded and fresh gastric biopsy specimens from patients positive for the bacterium and also in fecal suspensions seeded with the organism. The DNA from the nonculturable coccoid form of H. pylori was also identified by the primers. Universal primers designed for highly conserved areas on the 16S rRNA gene enabled large amplification products to be produced for direct sequencing analysis. Gastric bacteria resembling H. pylori have been isolated from animals. DNA of these animal gastric bacteria amplified with H. pylori-specific primers yielded PCR products identical to those from human isolates of H. pylori, as confirmed by the use of a 20-base radiolabelled probe complementary to an internal sequence flanked by the H. pylori-specific primers. The results of PCR amplification and partial 16S rRNA gene sequence analysis strongly support the contention that the gastric organisms previously recovered from a pig, a baboon, and rhesus monkeys are H. pylori.
TL;DR: The results indicate the important role of free sulphydryl groups in the development of the high surface viscoelasticity of adsorbed globular proteins at the oil-water interface.
TL;DR: The results indicate that this region of the genome contains a cluster of genes, mutation in any of which results in failure of the enzymes and extracellular polysaccharide to be synthesized.
Abstract: The cosmid clone. pIJ3020 containing DNA from the plant pathogenic bacterium Xanthomonas campestris pathovar campestris has previously been shown to complement a non-pathogenic mutant defective in synthesis of extracellular enzymes. The DNA cloned in pIJ3020 was analysed by mutagenesis with Tn5 and Tn5lac and by nucleotide sequencing. The results indicate that this region of the genome contains a cluster of genes, mutation in any of which results in failure of the enzymes and extracellular polysaccharide to be synthesized. The designation rpf (regulation of pathogenicity factors) is proposed for these genes. The nucleotide sequence of one gene (rpfC) predicts a protein product with homology to conserved domains of both sensor and regulator proteins of prokaryotic two-component regulatory systems, which are usually involved in regulating gene expression in response to environmental stimuli.
TL;DR: The stable transformation of Physcomitrella patens to either G418 or hygromycin B resistance following polyethylene glycol-mediated direct DNA uptake by protoplasts is reported.
Abstract: We report the stable transformation of Physcomitrella patens to either G418 or hygromycin B resistance following polyethylene glycol-mediated direct DNA uptake by protoplasts. The method described in this paper was used successfully in independent experiments carried out in our two laboratories. Transformation was assessed by the following criteria: selection of antibiotic-resistant plants, mitotic and meiotic stability of phenotypes after removal of selective pressure and stable transmission of the character to the offspring; Southern hybridisation analysis of genomic DNA to show integration of the plasmid DNA; segregation of the resistance gene following crosses with antibiotic-sensitive strains; and finally Southern hybridisation analysis of both resistant and sensitive progeny. In addition to stable transformants, a heterogeneous class of unstable transformants was obtained.
TL;DR: The histopathological evidence which supports a link between H. pylori-associated chronic inflammation in the stomach and duodenum and peptic ulceration at these sites is explored.
Abstract: While the presence of acid is necessary for the development of peptic ulceration, reduced mucosal resistance is increasingly acknowledged as the major factor in ulcerogenesis. The principal cause of diminished mucosal resistance to acid 'attack' is chronic inflammation. In this paper I shall explore the histopathological evidence which supports a link between H. pylori-associated chronic inflammation in the stomach and duodenum and peptic ulceration at these sites.
TL;DR: Among the Asians, high EAT and BSQ scores were associated with a more traditional cultural orientation and not with greater Westernisation, and it is probable that these findings reflect the cultural and familial difficulties faced by these Asian girls growing up in Britain.
Abstract: A survey of 204 south-Asian and 355 Caucasian schoolgirls was conducted in Bradford using the EAT-26 and the BSQ. At interview, seven Asian girls and two Caucasian girls met DSM-III-R criteria for bulimia nervosa, yielding a prevalence of 3.4% and 0.6% respectively. One Asian girl met DSM-III-R criteria for anorexia nervosa. Factor analyses of the EAT and BSQ supported their cross-cultural conceptual equivalence in this south-Asian population. Among the Asians, high EAT and BSQ scores were associated with a more traditional cultural orientation and not with greater Westernisation. It is probable that these findings reflect the cultural and familial difficulties faced by these Asian girls growing up in Britain.
TL;DR: In this article, the influence of protein-polysaccharide interactions on the surface and emulsifying properties of β-lactoglobulin at pH 7 has been investigated for systems containing the non-ionic polysaccharides dextran, and the anionic polysccharide dextrans sulphate and propylene glycol alginate (PGA).
TL;DR: It is concluded that at least one of the synaptic targets of cholinergic terminals in the substantia nigra are the dendrites and perikarya of dopaminergic neurons and that in the ferret at least, thedendrites of dopaminationergic neurons that descend into the pars reticulata receive multiple synaptic inputs from individual cholinergic axons.
TL;DR: In this paper, a Mesozoic tectonic model for the West African rift system is proposed, which shows a series of strike-slip fault zones diverging into Africa from the Gulf of Guinea and dissipating their shear movement into the development of extensional basins orientated perpendicular to these faults zones.
TL;DR: An investigation into the application of the genetic algorithm in the optimization of structural design and the basic operations of selection, crossover, mutation and parameter scaling are presented.
TL;DR: In this paper, the authors describe recent developments in the field with particular reference to flocculation of negatively charged particles by high-molecular-weight cationic polyelectrolytes by polymer bridging or charge neutralization.
TL;DR: Evidence is presented for the generation of a Cu(I)-semiquinone state by substrate reduction of several amine oxidases under anaerobic conditions, and it is suggested that the Cu( I)-semquinone may be the catalytic intermediate that reacts directly with oxygen.
Abstract: The role of copper in copper-containing amine oxidases has long been a source of debate and uncertainty. Numerous electron paramagnetic resonance (EPR) experiments, including rapid freeze-quench studies, have failed to detect changes in the copper oxidation state in the presence of substrate amines. One suggestion that copper reduction might occur, has never been confirmed. Copper amine oxidases contain another cofactor, recently identified as 6-hydroxydopa quinone (topa quinone), which is reduced by substrates. Copper has been implicated in the reoxidation of the substrate-reduced enzyme, but the failure to detect any copper redox change has led to proposals that Cu(II) acts as a Lewis acid, that it has an indirect role in catalysis, or that it serves a structural role. We present evidence for the generation of a Cu(I)-semiquinone state by substrate reduction of several amine oxidases under anaerobic conditions, and suggest that the Cu(I)-semiquinone may be the catalytic intermediate that reacts directly with oxygen.
TL;DR: A framework for sensitivity analysis in multi-objective decision-making within a Bayesian context, allowing for simultaneous variation in all the data, benefiting from the recent advances in optimisation theory and the advent of cheap computer power is introduced.
TL;DR: P53 protein was detected by immunohistochemistry in 42% of 52 colorectal adenocarcinomas and positive tumours were significantly more frequent in the distal colon, and demonstrated a higher rate of cell proliferation.
Abstract: p53 protein was detected by immunohistochemistry in 42% of 52 colorectal adenocarcinomas. Positive tumours were significantly more frequent in the distal colon, and demonstrated a higher rate of cell proliferation. No correlation was found with tumour grade, Dukes' stage, presence of DNA aneuploidy or patient survival. The role of p53 in colorectal carcinogenesis is discussed with particular reference to differences between proximal and distal large bowel cancers.
TL;DR: In this paper, the mixing layer that forms at their confluence is distorted by interacting with a separation zone which forms in the lee of the mouth of the shallower channel, which imparts a complex three-dimensional flow to the junction, promoting vertical fluid upwelling and significantly enhancing rapid mixing within the flow of the shallow tributary, while retarding the rate of mixing across the deeper channel.
Abstract: CHANNEL confluences have received considerable recent attention in the fields of geomorphology1–3, sedimentology4–9 and hydraulic engineering10–13. Where channels join, rapid changes in fluid velocity, turbulence intensity, channel hydraulic geometry and bed geometry may occur14–17. Previous models of junction dynamics have tended to assume that the confluent channels are of equal depth10,18, a condition that may be found only rarely in natural junctions; more often, the depths of confluent channels are different19. This discordance is commonly the result of the forma-tion, at the mouth of each confluent channel, of bars that possess steep avalanche faces which dip into a central junction scour1,2,5,20. Here we suggest that when channels of different depth join, the mixing layer that forms at their confluence is distorted by interacting with a separation zone which forms in the lee of the mouth of the shallower channel. This mixing-layer distortion imparts a complex three-dimensional flow to the junction, promoting vertical fluid upwelling and significantly enhancing rapid mixing within the flow of the shallow tributary, while retarding the rate of mixing across the flow of the deeper channel. Suspended sediments or contaminants within the deeper channel may be transferred rapidly across the flow of the shallower tributary, upwelling downstream of the junction.
TL;DR: In this article, the authors present a survey of the use and limitations of financial distress prediction models in a management context, focusing on the use of unaided human decision-makers and statistical models.
Abstract: SUMMARY
Throughout the 1980s there has been continued interest in developing financial distress prediction models for both large and small firms. There has, however, been no survey of this literature directed towards assessing the uses and limitations of these models in a management context. The purpose of the paper is, therefore, to indicate the managerial uses and limitations associated with adopting financial distress prediction models. The paper achieves this end by considering in section two the current financial distress prediction techniques and their limitations. Section three examines the relevance of the predicted event (usually actual failure), the usefulness of multi-outcome models and the appropriateness of various sample selection methods. A review of the range and adequacy of the financial and non-financial information used to construct predictive models forms the basis of the fourth section and is followed in section five by a review of the validity of the claims made on behalf of their predictive accuracy. The following section examines the efficacy of other methods of predicting distress, and reviews the ‘man versus model’ literature concerning the relative abilities of unaided human decision-makers and statistical models. The final section offers conclusions and suggests where future work might be directed.
TL;DR: In this article, some techniques for carrying out ultrasonic measurements are described, the theories needed to convert measurements into the relevant physical properties of emulsions and suspensions are presented and a number of typical applications of the technique are illustrated.
TL;DR: In this paper, the effect of incorporating aromatic groups into self-assembled alkanethiol monolayers was studied using a variety of techniques including ellipsometry, wetting, reflection-absorption FTIR, surface (contact) potential, and surface enhanced Raman spectroscopy (SERS).
Abstract: The effect of incorporating aromatic groups into self-assembled alkanethiol monolayers was studied using a variety of techniques including ellipsometry, wetting, reflection-absorption FTIR, surface (contact) potential, and surface enhanced Raman spectroscopy (SERS). The quality of the monolayers produced was found to be dependent on both the size of the dipole introduced into the film and the length of the aliphatic chain above the aromatic group
TL;DR: In this article, an expanding puddle model is developed from the Early Jurassic of England, where rapid sea-level rise leads to marine-sediment starvation due to sediment entrapment in flooded river valleys.
Abstract: Many black shales in thick epicontinental basinal successions formed beneath an oxygen-restricted puddle of deep water. Other black shales formed during rapid transgression when basinal deposition expanded to cover basin-margin areas normally characterized by shallow-water deposition. An expanding-puddle model is developed from the Early Jurassic of England wherein rapid sea-level rise leads to marine-sediment starvation due to sediment entrapment in flooded river valleys. Subsidence, sea-level rise, and decreased sediment supply during early transgression are suggested to lead to rapid deepening and therefore the expansion of the are of the puddle such that, in previously shallow-water areas, black shales rest on condensed basal transgressive lags or unconformities that in turn rest on shallow-water facies. Reestablishment of sediment influx and aggradation in excess of any continued sea-level rise cause shallowing throughout the basin and the cessation of black-shale formation.