Showing papers by "University of Bath published in 1991"
TL;DR: This paper found that primary teachers hold particular images of teaching, mostly derived from their experiences in schools as pupils, which were sometimes highly influential in their interpretation of the course and of classroom practice.
890 citations
TL;DR: In this article, the iron storage protein ferritin is used to generate nanometre-sized iron sulphide particles by in situ reaction of the iron oxide core of the native ferritins.
Abstract: THEREis currently great interest in the synthesis of inorganic materials of nanometre dimensions. The small size of these particles endows them with unusual structural and optical properties that may find application in catalysis and electro-optical devices. Such materials may also prove valuable as precursor phases to strong ceramics. Many approaches to the synthesis of these materials have focused on constraining the reaction environment through the use of surface-bound organic groups1, polymers2,3, porous glasses4,5, zeolites6, phospholipid vesicles7,8 and reverse micelles9. Nanometre-sized particles may also be produced in vivo by microorganisms10. Here we describe a novel synthetic route based on the use of a supramolecular protein structure as a reaction cage in which to form inorganic phases. We show that the iron-storage protein ferritin can be used to generate nanometre-sized iron sulphide particles by in situ reaction of the iron oxide core of the native ferritin. Discrete nanoscale particles of manganese and uranium oxo-species can also be formed in the protein cavity. Our results highlight the potential of adapting natural bio-mineralization processes to problems in materials science, and suggest that the use of biological molecules and their synthetic analogues in mediating solid-state reactions constitutes a promising approach to nanophase engineering.
440 citations
TL;DR: In this paper, the surface of sisal fibres has been modified by mercerization and silane treatment to improve adhesion characteristics and moisture resistance, which is most effective in reducing moisture uptake of fibres in humid environments.
405 citations
TL;DR: The mycelium of higher fungi is portrayed as a developmentally versatile collective in which an initially dendritic pattern of branching is converted, by hyphal anastomosis, into a communication network as mentioned in this paper.
Abstract: The mycelium of higher fungi is portrayed as a developmentally versatile collective in which an initially dendritic pattern of branching is converted, by hyphal anastomosis, into a communication network. Spatial and functional patterns in the mycelium depend on the establishment of gradients allowing flow of protoplasmic resources and organelles via radial or tangential routes between source and sink regions. (...)
252 citations
TL;DR: The authors summarise some of the key features of teachers' knowledge that emerge from recent research and consider their possible implications for the training of teachers, and argue for a more prominent role for research in the evaluation and development of teachers professional education and in its defense at times of powerful external policy constraints.
238 citations
Book•
01 Jun 1991TL;DR: In this article, the authors compare domestic and foreign entry in the UK: 1983-84: P.A. Geroski and R. Masson, and international comparison of entry and exit: J. Cable and J. Schwalbach, J. Baldwin and P. Goreski.
Abstract: 1. Entry, Exit and the Competitive Process: D. Mueller 2. Entry and Market Contestability: The Evidence from the US: I. Kessides 3. Sunk Costs and Entry by Small and Large Plants: J. Mata 4. Domestic and Foreign Entry in the UK: 1983-84: P.A. Geroski 5. Domestic Entry in Norweigian Manufacturing Industries: N-H. Morch van der Fehr 6. Entry and Exit in Belgian Manufacturing: L. Sleuwaegen and W. Dehandschutter 7. Entry, Exit, Concentration and Market Contestability: J. Schwalbach 8. Entry During Explosive Growth: Korea During Take-off: K-Y. Jeong and R. Masson 9. The Effects of Business Conditions on Net Entry: Evidence from Japan: H. Yamawaki 10. Variation in Producer Turnover Across US Manufacturing Industries: T. Dunne and M. Roberts 11. Patterns of Entry, Exit and Merger in Yugoslavia: S. Estrin and T. Petrin 12. Innovation as a Means of Entry: An Overview: D. Audretswch and Z. Acs 13. Entry, Exit and Productivity Growth: J. Baldwin and P. Goreski 14. International Comparisons of Entry and Exit: J. Cable and J. Schwalbach 15. Some Data-driven Reflections on the Entry Process: P. Geroski.
224 citations
TL;DR: In this article, an adaptive stabilizer is described for a class of single-input nonlinear systems modelled as a controlled differential inclusion on R n, which has a discontinous feedback structure and incorporates a gain of Nussbaum type.
220 citations
TL;DR: In this article, the authors argue that the existing debate emphasizes the more uninteresting aspects of the peer review system and that the operation of old boyism, as currently understood would have little effect on the overall direction of science.
Abstract: Peer review of grant applications, it has been suggested, might be distorted by what is popularly termed old boyism, cronyism, or particularism. We argue that the existing debate emphasizes the more uninteresting aspects of the peer review system and that the operation of old boyism, as currently understood would have little effect on the overall direction of science. We identify a phenomenon of cognitive particularism, which we consider to be more important than the institutional cronyism analyzed in previous studies. We illustrate with material drawn from observation of grant-awarding commit tees of the (British) Science and Engineering Research CounciL In the concluding discussion, we explore some of the possible implications for the peer review system.
215 citations
TL;DR: It is demonstrated that the two methods for bounding the overall properties of nonlinear composites generate precisely the same information, and hence that differences noted by Ponte Castaneda arise from comparing optimal bounds obtained from the new procedure with sub-optimal bounds obtaining from the original one.
Abstract: A new method for bounding the overall properties of nonlinear composites, proposed byPonte Castaneda (J. Mech. Phys. Solids 39, 45, 1991), is compared with an older prescription based on a generalization to nonlinear behaviour of the Hashin-Shtrikman procedure. It is demonstrated that the two methods generate precisely the same information, and hence that differences noted by Ponte Castaneda arise from comparing optimal bounds obtained from the new procedure with sub-optimal bounds obtained from the original one. The relative advantages of either procedure are discussed.
185 citations
01 Jan 1991
TL;DR: Insects are members of the Arthropoda, and among the characteristics of this phyllum is the presence of an external skeleton or cuticle, which serves a variety of functions in addition to the skeletal roles of support and muscle anchorage.
Abstract: Insects are members of the Arthropoda Among the characteristics of this phyllum is the presence of an external skeleton or cuticle Because of its location, the cuticle serves a variety of functions in addition to the skeletal roles of support and muscle anchorage The defensive capability of the cuticle is clear since only one group of entomopathogens, the fungi, have acquired the ability to invade insects actively via this route The other major groups of disease-causing microorganisms, the viruses and bacteria, are restricted primarily to the alimentary canal, where the midgut provides an exposed mucosal surface
TL;DR: The hypothesis that IL-6 is produced locally in human bone by osteoblasts under the direction of other cytokines is supported, which could have implications in bone remodeling, haemopoiesis, and systemic responses to local injury.
Abstract: Interleukin 6 (IL-6) probably plays a central role in the acute phase response and in haemopoiesis and may be involved in the control of bone turnover. We have studied the release of IL-6 from human trabecular bone cells treated with a variety of stimuli using a specific bioassay. In serum free medium, unstimulated human osteoblast-like cells produced IL-6 in the range of 1000-2050 pg/ml/24 h. Recombinant human interleukin 1 (IL-1 alpha) (10(-13)-10(-11) M), tumor necrosis factor alpha (TNF alpha) (10(-9)-10(-7) M) and lipopolysaccharide (5-500 ng/ml) all stimulated release of IL-6 from human bone cells. Maximal levels of 17,000 pg/ml were observed using the highest concentration of IL-1. 1,25(OH)2D3 and PTH did not stimulate IL-6 release. Using a specific sheep antihuman IL-6 antibody, all IL-6 activity could be neutralized. In parallel studies, ROS 17/2.8 rat osteosarcoma cells released around 50 pg/ml of IL-6 under basal conditions which were increased to a maximum of 900 pg/ml by treatment with PTH (10(-9) M). The cytokines were less effective and 1,25(OH)2D3 again had no effect. Modulation of expression of IL-6 mRNA in human osteoblast cells was examined using a human complementary deoxyribonucleic acid probe. The mRNA was constitutively expressed, and IL-1 (10(-11) M) and TNF (10(-7) M) induced further mRNA expression within 2 h, which was sustained over 24 h. 1,25(OH)2D3 (10(-7) M), IL-6 (2000 pg/ml), and PTH (10(-9) M) exerted no effects at any time point. Dexamethasone (10(-6) M) suppressed both basal and IL-1- and TNF-induced IL-6 mRNA expression. IL-6 receptor mRNA was constitutively expressed but was not regulated by any of the above agents. It is clear that rodent and human osteoblasts differ in their production of IL-6 and its modulation. These data support the hypothesis that IL-6 is produced locally in human bone by osteoblasts under the direction of other cytokines. This could have implications in bone remodeling, haemopoiesis, and systemic responses to local injury.
TL;DR: It is concluded that inquiline species strictly following Emery's rule could have evolved by the intraspecific route, and such species provide evidence for West-Eberhard's “alternative adaptation” hypothesis that between-species diversity frequently stems from diversity within species.
Abstract: Inquiline ant species are workerless social parasites whose queens reproduce in colonies of other species alongside the host queens. Inquilines arise either when one non-parasitic species evolves into an inquiline parasite of another non-parasitic species (the interspecific hypothesis), or by the speciation of intraspecific inquilines from their host stock (the intraspecific hypothesis): it is unlikely that inquilines evolve from other forms of social parasite. This paper reviews the evidence for and against the inter-and intraspecific hypotheses. All inquilines are close phylogenetic relatives of their host species (loose ‘Emery's rule’), and some are their host's closest relative (strict ‘Emery's rule’). A problem for the interspecific hypothesis is how to explain the strict Emery's rule, because phylogenetic constraints on host choice are probably quite weak. By contrast, the intraspecific hypothesis has difficulty accounting for the parasites' sympatric reproductive isolation.
Facultative polygyny, in which queens may found colonies alone or by adoption into an existing multi-queen colony, should promote the evolution of small intraspecific inquilines. This is because small colony-founding queens should preferentially seek adoption, which provides the opportunity to produce a sexual-only brood. We suggest that microgynes, i.e. miniature queens found in some polygynous ants, represent such parasites. We review the evidence that inquiline species have evolved intraspecifically from microgynes in Myrmica ants. The coexistence within a species of a monogynous (singly-queened) and a polygynous form is probably a phenomenon usually unconnected with inquiline evolution.
The reproductive isolation of intraspecific inquilines plausibly arises from divergent breeding behaviour associated with the parasites' small size. Such divergence could involve either a temporal separation in mating episodes, with small parasites maturing early, or a spatial separation, with small males being sexually-selected to mate near the nest with small queens seeking adoption, instead of in mating aggregations.
We conclude that inquiline species strictly following Emery's rule could have evolved by the intraspecific route. If so, such species provide evidence for West-Eberhard's “alternative adaptation” hypothesis that between-species diversity frequently stems from diversity within species. They also represent likely cases of sympatric speciation. We suggest work on the parasites' phytogeny, genetics, behaviour and mating biology to test these conclusions further.
TL;DR: The general requirement of an appropriate spatial charge density across the cavity surface rather than specific amino acid residues could explain how, in spite of an almost complete lack of identity between the amino acid sequences of bacterioferritin and mammalian ferritins, ferrihydrite is deposited within the cavity of both proteins under similar reconstitution conditions.
TL;DR: Field experiments and analyses are presented that test both the assumptions and the predictions of a model that showed how the swarm raids of the army ant Eciton burchellimight be self-organizing, i.e., based on hundreds of thousands of interactions among the foraging workers rather than a central administration or hierarchical control.
Abstract: We present field experiments and analyses that test both the assumptions and the predictions of a model that showed how the swarm raids of the army ant Eciton burchelli might be self-organizing, i.e., based on hundreds of thousands of interactions among the foraging workers rather than a central administration or hierarchical control. We use circular mill experiments to show that the running velocity of the ants is a sigm.oidal function of the strength of their trail pheromones and provide evidence that the swarm raid is structured by the interaction between outbound and inbound forager traffic mediated by the pheromones produced by both of these sets of ants. Inbound traffic is also affected by the distribution of prey, and hence, sites of prey capture alter the geometry of the raid. By manipulating the prey distributions for E. burchelli swarms, we have made them raid in a form more typical of other army ant species. Such self-organization of raids based on an interaction between the ants and their environment has profound consequences for interpretations of the evolution of army ant species.
TL;DR: This chapter reviews the potential roles of Melanin-Concentrating Hormone (MCH) in mammals and suggests that the organization found in bony fish may differ slightly from that in other vertebrates.
Abstract: Publisher Summary This chapter reviews the potential roles of Melanin-Concentrating Hormone (MCH) in mammals. The MCH has a striking effect in teleost fish, causing them to become pale in color. The endocrine repertoire to comparative studies on lower vertebrates shows that identical or highly homologous hormones occur in all vertebrate classes, their physiological roles may differ. A hormone is involved with several diverse functions even within one animal, but the emphasis on a particular function can shift during the course of evolution, so that homologous hormones in fishes and mammals may serve different roles in the two classes. A hormone or neuropeptide exerting an obscure effect in mammals might elicit a response in lower vertebrates, which is the cause of its discovery. There are many examples of physiological events that are regulated by two opposing hormones, an arrangement that gives rapid and finer control than changing titers of a single hormone. The distribution of MCH perikarya and fibers is examined in few species and suggests that the organization found in bony fish may differ slightly from that in other vertebrates.
TL;DR: The findings strongly suggest that sedation can arise from H1‐receptor antagonism alone, and provide further support for the belief that the histaminergic system is concerned with the regulation of alertness in man.
Abstract: 1. The effects of 10 mg (+)- and (-)-chlorpheniramine and 5 mg (+)- and (-)-dimethindene on daytime sleep latencies, digit symbol substitution and subjective assessments of mood and well-being were studied in 6 healthy young adult humans. Each subject also took 5 mg triprolidine hydrochloride as an active control and two placebos. 2. Daytime sleep latencies were reduced with triprolidine, (+)-chlorpheniramine and (-)-dimethindene, and subjects also reported that they felt more sleepy after (+)-chlorpheniramine and (-)-dimethindene. Performance on digit symbol substitution was impaired with (+)-chlorpheniramine. 3. Changes in measures with (-)-chlorpheniramine and (+)-dimethindene were not different from changes with placebo. 4. In the present study, changes in measures of drowsiness and performance were limited to the enantiomers with high affinity for the histamine H1-receptor. These findings strongly suggest that sedation can arise from H1-receptor antagonism alone, and provide further support for the belief that the histaminergic system is concerned with the regulation of alertness in man.
TL;DR: In this paper, the defect imaging capability of a pulsed video thermography system is assessed by detailed quantitative analysis of its performance in imaging a set of well characterized artificial defects in a steel test-piece.
Abstract: The defect imaging capability of a pulsed video thermography system is assessed by detailed quantitative analysis of its performance in imaging a set of well characterized artificial defects in a steel test-piece. An analytical model is presented which provides an understanding of the imaging process. A method is proposed for the determination of defect depth by exploiting the temporal dependences of images.
TL;DR: In this article, the results of ultrasonic irradiation of polystyrene solutions in toluene, benzene and carbon tetrachloride were described and the effect of a range of conditions such as ultrasonic intensity, solution concentration and varying solvents were investigated.
Abstract: The results of ultrasonic irradiation of polystyrene solutions in toluene, benzene and carbon tetrachloride are described. The effect of a range of conditions such as ultrasonic intensity, solution concentration and varying solvents were investigated. The non-random nature of the degradation process was clearly demonstrated and the effect of different solvents was interpreted in terms of their thermodynamic properties.
TL;DR: The sites and modes of action of these polyamine amide toxins are reviewed with particular reference to their structure-activity relationships and Electrophysiological studies, including those employing Xenopus oocytes, are reviewed and future prospects for the use of polyamines amides in therapy are discussed.
TL;DR: Using an application of linear programming known as Data Envelopment Analysis (DEA), a method is described in this paper to compare products which vary in excellence along a number of dimensions, and for each of which there might be associated costs.
Abstract: Using an application of linear programming known as Data Envelopment Analysis (DEA), a method is described to compare products which vary in excellence along a number of dimensions, and for each of which there might be a number of associated “costs”. The method is illustrated by comparing published benchmarks of 37 computer printers. Potential uses of a DEA analysis of products might be: to assist corporate buyers who may need to reconcile a diversity of present and future uses in one standardised purchase; in competitor analysis; in determining unexplored market niches; and as a normative model of product excellence against which product purchasing behaviour could be compared.
TL;DR: The down-regulation of GLUT4 due to the chronic-insulin treatment is associated with a marked resistance of the cells to restimulate glucose transport and particularly to recruit furtherGLUT4 to the cell-surface following an additional insulin treatment, suggesting that starvation, acute-ins insulin, and chronic- Insulin treatments regulate glucose transporter availability through independent mechanisms.
TL;DR: In this paper, the synthesis of potent antioxidants utilizing indenoindole or indoenindoline pharmacophores is described, and the antioxidant behavior and the oxidation potentials of these compounds are correlated.
TL;DR: In this article, the mechanism of action of chitinolytic enzymes is discussed, and the chitinase fractions eluted from a sephadex column had activity against chitosan and chitotriose.
TL;DR: Salmonella enteritidis was found to be resistant to the antimicrobial properties of the albumen and influenced by the size of inoculum, the site of contamination relative to yolk movement, and the presence of iron in the inoculum.
Abstract: The effect of some factors on the growth of Salmonella enteritidis phage type 4 in artificially contaminated shell eggs was investigated. Salmonella enteritidis was found to be resistant to the antimicrobial properties of the albumen. Growth occurred on storage at 25 degrees C but not at 4 or 10 degrees C. The rate and extent of infection was influenced by the size of inoculum, the site of contamination relative to yolk movement, and the presence of iron in the inoculum.
TL;DR: Family health services authorities are appropriate systems for studying output of general practice but their performance indicators need to be refined and to be linked to other relevant factors, notably the performance of hospital, community, and social services.
Abstract: OBJECTIVE--To examine whether variations in the activities of general practice among family health service authorities can be explained by the populations characteristics and the organisation and resourcing of general practice. DESIGN--The family health services authorities were treated as discrete primary health care systems. Nineteen performance indicators reflecting the size, distribution, and characteristics of the population served; the organisation of general practice (inputs); and the activities generated by general practitioners and their staff (output) were analysed by stepwise regression. SETTING--90 family health services authorities in England. MAIN OUTCOME MEASURES--Rates of cervical smear testing, immunisation, prescribing, and night visiting. RESULTS--53% of the variation in uptake of cervical cytology was accounted for by Jarman score (t = -3.3), list inflation (-0.41), the proportion of practitioners over 65 (-0.64), the number of ancillary staff per practitioner (2.5), and 70% of the variation in immunisation rates by standardised mortality ratios (-6.6), the proportion of practitioners aged over 65 (-4.8), and the number of practice nurses per practitioner (3.5). Standardised mortality ratios (8.4), the number of practitioners (2.3), and the proportion over 65 (2.2), and the number of ancillary staff per practitioner (-3.1) accounted for 69% of variation in prescribing rates. 54% of the variation in night visiting was explained by standardised mortality ratios (7.1), the proportion of practitioners with lists sizes below 1000 (-2.2), the proportion aged over 65 (-0.4), and the number of practice nurses per practitioner (-2.5). CONCLUSIONS--Family health services authorities are appropriate systems for studying output of general practice. Their performance indicators need to be refined and to be linked to other relevant factors, notably the performance of hospital, community, and social services.
TL;DR: Within this framework, intercountry (European) comparisons of life expectancy and age-specific mortality for both sexes are used to illustrate a shift over time in the social aetiology of disease from economic to behaviourally based causality.