Showing papers by "University College Dublin published in 1989"

Concentration and other determinants of bank profitability in Europe, North America and Australia

Abstract: This study reviews the performance of banks in twelve countries or territories in Europe, North America and Australia and examines the internal and external determination of profitability. To circumvent some of the difficulties in making comparisons between banks in different countries, the concept of ‘value added’ is introduced. Results parallel those in domestic U.S. studies and provide some support for the Edwards-Heggestad-Mingo hypothesis of risk avoidance by banks with a high degree of market power.

The selection of suitable indices for the measurement and analysis of fish condition

Abstract: A survey of the studies published in two leading fisheries journals revealed that the analysis and measurement of condition, based on length-weight data, has been performed using a wide variety of indices and statistical procedures. Eight forms of index were identified which can be categorized into those which measure the condition of individual fish, i.e. condition factors‘, and those which measure the condition of subpopulations as a whole, i.e. regressions of log, 10 weight on log, 10 length and the parameters of such regressions. Analysis of a test data set indicated that both the form of index and properties of the data set size can dictate the patterns of condition observed. The various indices were reviewed in terms of appropriateness, simplicity and statistical correctness. It was concluded that an index should be selected only after a detailed examination of both the underlying assumptions of the index and the properties of the data set.

Pollen tube tip growth.

Abstract: This review considers pollen tube growth with regard to current information on pollen tube cytoplasm, wall structure and calcium ion interactions with pollen tubes. Pollen tubes have a marked cytoplasmic Polarity with a number of distinct zones along the tube, each with a characteristic complement of cytoplasmic and nuclear structures. The cytoplasmic structures are characteristic of secretory cells with extensive endoplasmic reticulum cisternae and numerous dictyosomes. The dictyosomes produce secretory vesicles that are mainly directed to the extending tip of the tube, where they provide new plasma membrane and wall components. The rates of secretory vesicle production and delivery have been estimated, allowing quantitative assessments of the rate of delivery of materials to the tip. Pollen tubes contain cytoskeletal components, with microtubules and microfilament strands lying axially in the main tube and diffuse microfilament strands at the tip. The tube wall consists of an outer fibrous layer containing pectins and an inner, more homogeneous layer containing callose and cellulose-like microfibrils, possessing both β-1,4 and β-1,3 linkages. Protein is also present in the wall. The tube tip lacks the inner callosic wall. This type of structure is considered to be different from that of elongating sporophyte tissue cells which are enclosed by a wall containing layers of cellulose microfibrils. Calcium ions are required for pollen tube growth and, in at least some species, act as a chemotropic agent. High concentrations of calcium ions in the external medium inhibit growth. Pollen tubes contain some calcium ions bound to the cell wall and larger amounts located intracellularly, which enter the tube at the tip. This intracellular calcium is present as ions that exist freely within the cytoplasmic Matrix and as ions bound to membrane systems. The highest concentrations in both of these pools are found at the tip and in both they decline towards the base. The structure of the tip and the activity involved in providing components for plasma membrane and Wall assembly provide a basis for considering possible mechanisms of tip growth. Two hypotheses to account for the regulation of tip extension are considered, cell wall control and cytoskeletal control. In the cell wall hypothesis, control depends on an interaction between internal turgor pressure and a plastic cell wall. The mechanical properties of the wall are assumed to be partly dependent on the availability of external calcium ions to crosslink acidic pectin chains. According to this hypothesis, high external calcium ion concentrations cause cessation of tip growth due to increased mechanical resistance of the tip wall. Various observations on plant cell-wall interactions with calcium ions and on experimentally-treated pollen tubes provide evidence that does not support this hypothesis. The cytoskeletal control hypothesis of tip growth depends on the internal tip cytoskeleton to contain the tube tip cytoplasm against the internal turgor pressure during cell wall assembly. The activities and mechanical properties of the cytoskeleton are assumed to depend on the availability of external calcium ions. High external concentrations are believed to cause a state of rigor in the cytoskeleton and hence a cessation of tip growth. Some experimental evidence is presented which suggests that the effects of excess calcium ions are on intracellular processes, and not extracellular ones. The mitochondrial zone behind the tip is believed to maintain the tip calcium ion concentration at an optimal level for growth. Some comparisons are made between tip growth in pollen tubes and that in other tip growing cells. CONTENTS Summary 323 I. Introduction 324 II. Cytoplasm 326 III. Wall structure 332 IV. Calcium 335 V. Tip growth 339 VI. Conclusions 350 References 351.

Evolutionary Processes in Competitive Markets: Beyond the Product Life Cycle:

Abstract: The traditional product life cycle framework has little to say about the competitive processes that accompany the evolution of a market. The first part of the article identifies the major shortcomi...

Respiration and microalgal growth: a review of the quantitative relationship between dark respiration and growth

Abstract: SUMMARY Biomass-specific, dark respiration rates of microalgae vary by almost two orders of magnitude from 0.01 to 0.6 d−1. In general, dark respiration rates increase with growth rates in both intraspecitic and interspecific comparisons, but the precise relationship between respiration and growth rate varies. Under optimal conditions, respiration rates are about 20-30% of growth rates, but the ratio of respiration to growth increases under suboptimal conditions. The intercept of plots of respiration rate vs. growth rate varied from < 0.01 to 0.4 d1, and the slopes of these relationships varied from < 0.1 to 1.0. Minimum maintenance metabolic rates of about 0.01 d 1 have been estimated for some microalgae by extrapolation of the initial slope of the light curve for growth to a hypothetical negative growth rate in darkness. The dimensionless total energy cost of synthesis and maintenance for heterotrophie growth of microalgae using either endogenously or exogenously supplied carbohydrates is typically 0.4-1.2 for growth with ammonia or urea as a nitrogen source and 0.7-1.4 for growth with nitrate as the nitrogen source.

Staphylococcus aureus bacteriophages mediating the simultaneous lysogenic conversion of beta-lysin, staphylokinase and enterotoxin A: molecular mechanism of triple conversion.

Abstract: A new group of serotype F bacteriophages of Staphylococcus aureus has been found which mediates the simultaneous triple-lysogenic conversion of enterotoxin A, staphylokinase and β-lysin. The phages were recovered from methicillin-resistant strains of S. aureus isolated in Irish hospitals between 1971 and 1988 and from strain PS42-D, which has been used as the propagating strain for the S. aureus typing phage 42D since before 1965. The molecular mechanism of triple conversion mediated by three of these phages was determined by molecular cloning, restriction endonuclease site mapping and hybridization analysis, and compared with the mechanism of β-lysin and staphylokinase conversion mediated by the serotype F, double-converting phage β 13. The genetic determinants mediating expression of enterotoxin A (entA) and staphylokinase (sak) were cloned from the DNA of the triple-converting phage and expression of the cloned determinants detected in Escherchia coli and S. aureus. The entA and sak determinants were closely linked in the phage DNA adjacent to the phage attachment site (attP) in each case and furthermore, the sak determinant of phage o 13 was also located near its attP. The restriction maps of the entA-, sak- and attP-containing DNA regions of the three triple-converting phages were very similar to each other and to the corresponding sak- and attP-containing DNA region of phage o 13. Hybridization analysis using a cloned β-lysin determinant (hlb) and cloned attP-containing DNA fragments as probes demonstrated that β-lysin conversion mediated by the triple-converting phages and phage o13 was caused by insertional inactivation of the chromosomally encoded hlb determinant by orientation-specific integration of phage DNA following lysogenization.

The great Irish famine

Abstract: The Irish Famine of 1846–50 was one of the great disasters of the nineteenth century, whose notoriety spreads as far as the mass emigration which followed it. Cormac O'Grada's concise survey suggests that a proper understanding of the disaster requires an analysis of the Irish economy before the invasion of the potato-killing fungus, Phytophthora infestans, highlighting Irish poverty and the importance of the potato, but also finding signs of economic progress before the Famine. Despite the massive decline in availability of food, the huge death toll of one million (from a population of 8.5 million) was hardly inevitable; there are grounds for supporting the view that a less doctrinaire attitude to famine relief would have saved many lives. This book provides an up-to-date introduction by a leading expert to an event of major importance in the history of nineteenth-century Ireland and Britain.

The Identified $\Lambda\Lambda$-Hypernuclei and the Predicted H-Particle

Abstract: The existence of the H particle, the dihyperon predicted by Jaffe, would bring into question the existence of double hypernuclei. We review the two double hypernucleus events published in the literature. We include an independent report, hitherto unpublished, which was made on the $\Lambda\Lambda^{10}$Be event in 1963 and clarifies the salient features of the event; this report reaffirms its published interpretation. We have made a simple calculation of the energy spectrum for $\Xi^-$ hyperons produced with K$^-$ beams in past emulsion experiments, with a result which accounts adequately for the paucity of reported double hypernucleus events. We outline a hybrid emulsion experiment that would locate $\Xi^-$ hyperon interactions efficiently and could thereby greatly improve our knowledge of double hypernuclei.

Immunohistological features in the synovium obtained from clinically uninvolved knee joints of patients with rheumatoid arthritis

Abstract: The spectrum of immunohistological change in the affected joints of patients with rheumatoid arthritis has been well described. In this study, the immunohistological features in synovial membrane obtained from apparently uninvolved knee joints of 16 patients with active untreated rheumatoid arthritis were examined and compared to tissue from control subjects. Synovial tissue was obtained by needle biopsy. Hyperplasia of the synovial lining layer, present in 69%, was the most frequently observed abnormality in synovium obtained from uninvolved joints. Perivascular mononuclear cell infiltration was present in 31% and consisted predominantly of helper T-cells. Increased vascularity and fibrin deposition were not notable features. Clinically overt synovitis emerged in only two patients during a follow-up period of up to 36 months. In conclusion, a considerable degree of histological change was observed in the apparently uninvolved knee joints of patients with active rheumatoid arthritis. The presence of subclinical synovitis challenges current concepts of disease activity and clinical remission. Further study is required to determine whether the features described may be associated with progressive joint erosion.

Short Paper: Ophiolitic detritus in the Ordovician sediments of South Mayo, Ireland

Abstract: Sandstones from Ordovician sediments of the South Mayo Trough, western Irish Caledonides, show marked stratigraphic variation in their major and trace element geochemistry. High Cr, Ni, and Mg concentrations of ultramafic derivation succeed high Ti and Fe concentrations of mafic provenance This sequence is interpreted as the result of the progressive unroofing of an ophiolite. A possible sedimentary linkage with ophiolite lithologies in the Clew Bay Domain to the north would indicate minimal post-Arenig transcurrent displacement. The South Mayo flysch with its ophiolitic detritus is typical of Caledonian flysch sequences which pre-date the mid-Ordovician Taconic deformation, but differs in character from those of late Ordovician age.

Optimal arrangement of components via pairwise rearrangements

Abstract: : The authors introduce the notion of comparison of the criticality of two nodes in a coherent system, and develop a monotonicity property of the reliability function under component pairwise rearrangement. They use this property to find the optimal component arrangement. Worked examples illustrate the methods proposed. Keywords: Optimization; Permutations; Nodes.

Progress in metric-affine gauge theories of gravity with local scale invariance

Abstract: Einstein's general relativity theory describes very well the gravitational phenomena in themacroscopic world. In themicroscopic domain of elementary particles, however, it does not exhibit gauge invariance or approximate Bjorken type scaling, properties which are believed to be indispensible for arenormalizable field theory. We argue that thelocal extension of space-time symmetries, such as of Lorentz and scale invariance, provides the clue for improvement. Eventually, this leads to aGL(4, R)-gauge approach to gravity in which the metric and the affine connection acquire the status ofindependent fields. The Yang-Mills type field equations, the Noether identities, and conformal models of gravity are discussed within this framework. After symmetry breaking, Einstein's GR surfaces as an effective “low-energy” theory.

Solidary labour: its nature and marginalisation

Abstract: This paper represents an attempt to analyse the labour involved in producing and reproducing caring relationships as a form of work. The term ‘solidary’or ‘love labour’is coined to differentiate this kind of work from other forms of human service work, domestic work and/or economic labour. We suggest that solidary labour cannot be understood as a structural necessity emanating from the political and economic requirements of the wider system. Yet, the latter approach has been the modal one in both structural functionalist and Marxist analyses of caring. Caring and being cared for involve the construction of symbolic bonds regardless of the economic context in which they are embedded. The sociological understanding of these, demands that we take account of the situated meaning of solidary relations and not merely reduce them to by products of structural forces. In the latter part of the paper we use time-budget studies and other surveys to show how solidary labour is being marginalised in our society. In particular, we argue that both domestic labour and productive material labour are in open competition with solidary labour for the use of time. Research to date would suggest that solidary labour is the loser in this competition.

Antiproliferative action of benzodiazepines in cultured brain cells is not mediated through the peripheral-type benzodiazepine acceptor.

Abstract: The benzodiazepines, Ro 5-4864, diazepam, clonazepam, and also PK-11195, inhibited, at micromolar concentrations, the proliferation of rat C6 glioma and mouse neuro-2A neuroblastoma cells in culture. The cells possessed high levels of "peripheral-type" high-affinity benzodiazepine binding sites as judged by binding assays and displacement potencies. However, the different potencies and specificities of compounds for the antiproliferative actions and binding affinities for the binding site suggest that the antiproliferative actions were not mediated through the peripheral-type binding site. In support of this, these compounds have also been shown to inhibit proliferation of some nonneuronal cultured cell lines, e.g., mouse SP2/O-Ag 14 hybridoma and rat NCTC epithelial cells, which have no detectable high-affinity peripheral-type benzodiazepine binding sites.

Extension and partial optimization of a modified Smith predictor and controller for unstable processes with time delay

Abstract: Extension and partial parameter optimization are applied to a modified Smith predictor and controller, designed by de Paor( 1985) for a class of unstable processes having transfer functions of the form k1A exp(—sT)/B, where A is a monic, Hurwitz polynomial of degree (n — l) and the nth degree monic polynomial B has a single right half-plane root at s=λ It is found that for l = 1,2,3 asymptotic stability can be achieved for λ T> 1, which more than doubles the best result obtained earlier. For a specific process, responses are compared with those obtained using the optimum stability PI controller of de Paor and O'Malley (1989). The advantages of the optimized, modified predictor in terms of tightness of control and faster settling time are highlighted

Observation of TeV Gamma-rays from the Crab Nebula

Abstract: The Whipple Observatory 10 m Reflector operating as a 37-pixel camera has been used to observe the Crab Nebula in TeV gamma rays. Using gamma-ray image selection a detection is reported at the 9.0 sigma level; this corresponds to a flux of 1.8 x 10-11 photons-cm-2-s-1 above 0.7 TeV.

Reciprocal Ammonium Transport Into and Out of Plant Roots: Modifications by Plant Nitrogen Status and Elevated Root Ammonium Concentration

Abstract: Wheat and oat were grown for 20 d on a nitrate-containing solution (nitrogen-replete plants) or for the last 6 d of this period on a nitrate-free solution (nitrogen-depleted plants). Exposure of the nitrogen-depleted plants on day 20 to nitrate-free solutions containing 500 mmol m 1 ammonium (96 A% 15N) resulted in a cumulative net influx of 15N-ammonium over an 8 h period that was appreciably greater than that of the nitrogen-replete plants. Both the initial rate and the more restricted rate after the first hour were enhanced by nitrogen deprivation. In the nitrogen-replete plants, cumulative net efflux of endogenous 14N ammonium was approximately equivalent to net ammonium uptake during the first hour, and was essentially complete after 1-2 h. Pretreating nitrogen-depleted plants for 5 h in 500 mmol m "3 15N-ammonium (99 A% 15N) resulted in root ammonium concentrations of 12-7 ±1-1 and 16 0 + 0-4 /?mol gpw for wheat and oat, respectively. Subsequent net efflux of 15N-ammonium to 500 mmol m~3 exogenous 14N-ammonium exceeded these initial amounts within 2 h. Increasing ambient 14N-ammonium to 5000 mmol m 3 increased net l5N-ammonium efflux such that net loss of the maximal original amount in the root tissue was exceeded within 0-75 h. The data for both species indicate substantial reciprocal transfers of ammonium into and out of roots of ammonium-treated plants and a significant degradation of recently synthesized products of ammonium assimilation concurrent with ammonium assimilation.

Mass mammography. The time for reappraisal.

Abstract: Of the four randomized controlled trials of mass mammography completed to date, the New York HIP trial used obsolete technology and was not designed to assess mammography in the absence of physical examination; the Swedish Two-County trial had serious methodological flaws; the U.K. trial was incompletely documented but showed no significant benefit; and the Malmo trial, which was perfect in design and execution, showed no benefit. Paradoxicially, with each successive trial and an increasing sophistication of mammography, the benefit of screening was becoming not greater but less. This may be summarized by comparing the number of women who would have to be offered mammography for one breast cancer death prevented or postponed in the respective trials: 5,000 in the HIP trial, 13,000 in the Two-County trial, 18,000 in the U.K. trial, and 68,000 in the Malma trial. The enthusiasts in favor of mass mammography have created an atmosphere of false optimism. They have not informed the public about the very small potential benefit nor about the risks associated with screening, especially the risks of false positive diagnoses and of unnecessary surgical operations. This is an unacceptable situation, and the ethical vacuum in which population screening takes place needs to be filled with guidelines to protect women who are “targeted” for screening.

Retinal morphogenesis in the rainbow trout, Salmo gairdneri.

Abstract: The post-embryonic development of the neural retina and the pigment epithelium of the rainbow trout was analysed by electron microscopy. Particular attention was paid to the period when these fish change from photonegative to photopositive behaviour. In photoreceptors, light-sensitive outer segments arise prior to synapses. Subsequent rapid synaptogenesis in the inner plexiform layer results in the establishment of the pathway between photoreceptors and ganglion cells. Interreceptor contacts and feedback synapses, associated with the integration of colour and spatial information, appear when the fish become photopositive, swim to the water surface and begin exogenous feeding. Retinal development parallels that of higher optic centres and visual acuity, as reported by other authors.

Uptake and apparent utilization of urea and ammonium nitrate in wheat seedlings

Abstract: Intact wheat (Triticum aestivum cv. Quern) seedlings that were grown in presence or absence of NH4NO3 were exposed to solutions containing CO(NH2)2, NH4NO3, CO(NH2)2 + NH4NO3, CO(NH2)2 + KNO3 and CO(NH2)2 + (NH4)2SO4 for consecutive periods of 3, 3, 6, 12 and 24h and N uptake determined by solution depletion measurements. Differences in ethanol-soluble N and ethanol-insoluble N content of roots and shoots of control (zero time) seedlings and seedlings exposed to CO(NH2)2, NH4NO3 and CO(NH2)2 + NH4NO3 for 48 h were used to characterize N utilization during/following uptake.

The high maltose-producing α-amylase of Penicillium expansum

Abstract: An α-amylase capable of producing exceptionally high levels of maltose (74%) from starch has been identified from a strain of Penicillium expansum. The enzyme is produced extracellularly and was purified to homogeneity by starch adsorption and Sephadex gel filtration chromatography. P. expansum α-amylase has a pH optimum of 4.5 and is stable in the pH range of 3.6–6.0. Other properties include a temperature optimum of 60° C, a molecular weight of 69 000 and an isoelectric point of 3.9. The most outstanding feature of the P. expansum enzyme is its ability to yield 14% more maltose and 17.1% less maltotriose than a currently used commercial enzyme. This may be partly explained by the greater affinity of this new enzyme for maltotriose (K m=0.76 mM) relative to the commerical enzyme, Fungamyl (K m=2.9 mM). The enzyme reported here is unique among fungal α-amylases in being able to produce such high levels of maltose and its physicochemical properties suggest that it has potential for commercial development.