Showing papers by "University of Hull published in 1990"

Aerenchyma formation and associated oxygen movement in seminal and nodal roots of wheat.

Abstract: The present paper describes the effects of growth of roots of wheat (Triticum aestivum cv. Gamenya) in hypoxic nutrient solutions on acrenchyma formation and O2 movement from shoots to roots. Two types of roots were investigated: (1) seminal roots of 4–7-d-old seedlings, and (2) seminal and nodal roots of 10–28-d-old plants. Gas-filled porosity of seminal and nodal roots increased from 3 to 12% and from 5–7 to 11–15%, respectively, when the roots emerged in stagnant or N2-flushed solutions (0.003 mol m −3 O2) compared with growth in continuously acrated solutions (0.26 mol m −3 O2). However, neither root type increased in porosity when they were longer than 100–200 mm at the start of the exposure to these stagnant or N2-flushed treatments. A vernier microscope and cylindrical platinum-electrode were used to examine the relationship between root extension and transport of O2 from shoots to roots via the gas spaces. Measurements were made when the roots were in an anoxic medium and were dependent solely on O2 supplied from the shoots. For seminal roots of 5–7-d-old seedlings raised in stagnant solutions (90–100 mm), internal O2 transport was sufficient to support a rate of root elongation in the O2-free medium of between 0.03 and 0.17 mm h−1. When the O2 pressure around the shoots was increased from 20 to 100 kPa O2, the O2 concentrations at the walls of the expanding zone (2–7 mm from the tip) of these roots increased from 0.006 mol m−3 to between 0.04 and 0.26 mol m−3, and the rate of root extension increased five-fold. Oxygen transport to roots grown continuously in acrated solutions was considerably less than for roots raised in stagnant solutions; this difference was greater for seminal than for nodal roots. When the acrated seminal roots were longer than 100 mm and transferred to an O2-free root medium, O2 concentration became zero at the root tip causing elongation to cease. After 24 h of anoxia, none of these roots were able to resume elongation following a return to acrated solutions.

Use of intermittent stretch in the prevention of serial sarcomere loss in immobilised muscle.

Abstract: After immobilisation of muscle in a shortened position there is a reduction of muscle fibre length due to a loss of serial sarcomeres. Experiments have been carried out to determine whether short, daily periods of stretch prevent sarcomere loss and the resultant loss of range of joint motion. It was found that periods of stretch as short as 1/2 h daily were sufficient not only to prevent loss of sarcomeres but actually to cause an increase in the number of sarcomeres in series. Range of joint motion was normal. Such short periods of stretch were also found to prevent much of the muscle atrophy normally associated with immobilisation in the shortened position.

Liberating Systems Theory

Abstract: The aim of this chapter is to explore a number of possible interpretations of its title, ‘Liberating Systems Theory’ (‘LST’). Each of these selected meanings represents a theme, or a strand of study, that will be developed in one of the following chapters. Particular points of focus are: (a) Strand 1, the liberation of systems theory from a natural tendency toward self-imposed insularity (L’sT’); (b) Strand 2, the liberation of systems concepts from objectivist or subjectivist delusions (L’sT’); (c) Strand 3, the liberation of systems theory from internalized localized subjugations of discourse, (L’sT’); (d) Strand 4, systems theory for emancipation in response to domination and subjugation in work and social situations (‘LS’T); but in broader terms the book as a whole is concerned with (e) The liberation of systems theory in the sense of more cognitive illumination for the reader or prospective researcher or practitioner (‘LS’).

Dynamics of excimer laser ablation of superconductors in an oxygen environment

Abstract: The plume dynamics for excimer laser ablation of Y‐Ba‐Cu‐O in an O2 atmosphere have been studied using streak photography and spectroscopy. At pressures ≳1 mbar the expansion resembles a blast wave driven by the ablation products with mixing and reaction at the contact surface. A simple model for the plume range is developed which shows agreement with experiments.

Adaptive user interfaces

Abstract: Systems, methods, and computer-readable storage media for creating and displaying adaptive user interfaces are disclosed. An example method includes receiving a user interface by an application development environment, the application development environment providing the ability to allow authoring of a user interface that adapts to a screen size with any first abstracted size class value and any second abstracted size class value. The method then includes creating an application including the user interface wherein the application is configured to: determine a screen size of a device, the screen size including a first abstracted size class value and a second abstracted size class value; adapt the user interface according to the screen size including the first abstracted size class value and the second abstracted size class value; and display the adapted user interface on the device.

Beyond a System of Systems Methodologies

Abstract: This paper describes a research programme which used the idea that there is a ‘system of systems methodologies’ to analyse the relationship between OR and other systems-based, problem-solving approaches, and to relate different systems methodologies to appropriate problem-contexts. The results are promising for those who wish to broaden the theoretical basis of OR in order to extend its domain of effective application. Further progress, however, depends upon reconstituting the research programme on surer theoretical foundations. Unless this is done, both the potential of the original work and its initial intent risk being lost. It is now necessary to go beyond ‘a system of systems methodologies’ and to embed that work in an explicit proposal for a critical management science.

The carbon- and oxygen-isotope record of the Precambrian–Cambrian boundary interval in China and Iran and their correlation

Abstract: The fossiliferous section at Meishucun of Yunnan, China, is a candidate stratotype section for the Precambrian–Cambrian boundary. Early diagenetic dolomites and phosphorites have been sampled across the boundary interval here, and in the correlated section at Maidiping in Sichuanand Valiabad in Iran, for comparison of their carbon and oxygen isotopes. This is the first such study that is calibrated by biostratigraphy in the interval from the earliest (pre-Tommotian) skeletal fossils to trilobites. Although negative oxygen isotopes indicate a diagenetic signal in the Zhongyicun Member and basal Badaowan Member phosphorites, two carbon-isotope cycles are clearly present and can be correlated in dolomitic rocks between the two sections. The first appearance datum (FAD) of the earliest skeletal assemblage (zone I, Marker A), FAD of diverse micromolluscs (zone II, Marker B) and FAD of Chinese trilobites (zones IV, V) and Marker C appear at similar points on the carbon-isotope curve in the two Chinese sections. Integrated carbon-isotope and early skeletal fossil biostratigraphy is shown to have the potential to correlate further afield, with sections in Iran, as well as with India, Siberia, Morocco and Australia. We suggest that a distinctive positive excursion provides a global marker for the interval between Marker B and C in China and just below the Tommotian Stage of Siberia.

Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by Pseudomonas sp. Strain NCIMB 40135.

Abstract: A number of Pseudomonas species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these, Pseudomonas sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C2 to C6); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer synthesis occurred in batch culture after cessation of growth due to exhaustion of nitrogen. In continuous culture under nitrogen limitation up to 16.9% (wt/wt) polyhydroxyalkanoate was synthesized from glucose as the carbon source. The monomer units are mainly of the R-(−) configuration. Nuclear magnetic resonance studies confirmed the composition of the polymer. Differential scanning calorimetry suggested that the solvent-extracted polymer contained a significant proportion of crystalline material. The weight-average molecular weight of the polymer from glucose-grown cells was 143,000.

An assessment of metal contamination of sediments in the humber estuary, U.K.

Abstract: It is difficult to make an overall assessment of the degree of metal contamination in estuarine and marine sediments. This is a consequence of variations in analytical procedures between studies and the presence of an unknown natural background in the sediment. Measurement of total (rather than extractable) metal and normalization of concentrations as ratios to an element associated with clays provides a solution to the first difficulty. Expressing these values as enrichment factors relative to pre-industrial sediments from the same environment solves the second. Levels of anthropogenic enrichment of intertidal sediments in the Humber Estuary have been assessed relative to a baseline provided by sediments deposited in the Humber approximately 5000 years B.P. A sample of consolidated Holocene mud estimated to be at least 100 years old confirmed the appropriateness of this baseline. Normalization relative to Rb, which is not anthropogenically enriched, was the most suitable way to adjust for grain size. Levels of Ti, Fe, P, V, Cr, Mn, Ni, Cu, Zn, As, Y, Nb and Pb are elevated above this baseline. The most marked enrichments (between 3·5- and 6-fold) are of P, As, Pb, Cu and Zn. Normalized concentrations were spatially rather uniform with two exceptions. A single sample from the north bank showed elevated levels of Pb, Cu, Zn and Cr. An area receiving effluents from an industrialized zone on the south bank, including two titanium dioxide processing factories, showed high levels of a number of elements, particularly Nb. It is suggested that Nb may be a valuable tracer for effluents from the sulphate process of TiO 2 extraction.

Measurement and modelling of oxygen release from roots of phragmites australis

Abstract: Radial oxygen flux from adventitious and lateral roots of Phragmites australis in stagnant and streaming oxygen-free waters were measured polarographically. The potential for oxygen release to anaerobic sediments was predicted by extrapolating from this data and by mathematical modelling, and the oxidation of sediments demonstrated by indicator dye and redox potential measurements. Oxygen losses from roots were much greater during the day than at night and reflected the substantial day-time throughflow convection of gases from culm to rhizome which occurs in this species. Lateral roots, borne at frequencies of ≤120/cm of adventitious root were identified as potentially the major source of oxygen release. Predictions of sediment oxygenation based on oxygen release from single adventitious roots plus laterals in a streaming oxygen-free water-flow system, yielded values of 5-12 g O2 m-2 d-1, based on 150 shoots m-2, the conservative estimate of 10 roots per shoot, and a mean rhizome oxygen concentration of 17%. Mathematical modelling predictions amounted to 4.6-9.6 g of O2 m-2 d-1 based on the same shoot and root numbers, with 600 laterals/root, soil oxygen demand of 50-500 ng cm-3 s-1, and soil oxygen diffusivities from 0.3(clay)-0.85(sand) x 10-5 cm2 s-1. It was estimated that the respective amounts of oxygen likely to diffuse into the sediment from the soil surface would be be 1.0-7.3 g m-2 d-1. It is emphasised that sediment oxygenation by roots may be enhanced proportionally only by greater root numbers, not greater sediment oxygen demand.

Movement variability and bradykinesia in parkinson's disease

Abstract: When making discrete aiming movements, patients with Parkinson's disease show greater inherent variability in the endpoints of their movements than do normal subjects. Endpoint variability can be reduced, by moving more slowly, by utilizing visual guidance, and by making small amplitude movements. The greater variability of patients is not a universal finding, but depends on the conditions of movement. For small movements the performance of patients equates to that of controls. For larger movements the results indicate that if sufficient time is available, patients can use visual guidance (if available) to reduce the variability of their movements to the level of normals. Patients can generate fast and/or large amplitude arm movements if required, but they are erratic if made in the dark or over a short duration. Their difficulty lies not so much in the magnitude of muscle force available to them, but rather in an inability to produce it consistently for any given movement attempted. Bradykinesia may in part result from this inherent variability in that parkinsonian patients, in order to maintain accuracy within acceptable limits, are forced to increase the duration of their movements to a level where they can make use of visual guidance. In any event, theoretical explanations for the movement disorder in Parkinson's disease advanced in the literature need to take some account of this increased variability of movement.

Motor set in Parkinson's disease.

Abstract: Three experiments employing a five-choice button-pressing task tested the ability of Parkinsonian patients to learn and generate sequences of movement, and to switch between alternative sequences at will. It was found that patients could learn and generate individual patterns of movement normally, even complex ones involving an incompatible stimulus-response relationship. They had difficulty, however, in maintaining a sequence if two different ones had been learnt and subjects were required to switch spontaneously from one to the other within a trial. Providing external cues at the start of each sequence to guide the ordering of movements improved the stability of patients' performance. Most errors in sequencing consisted of reverting to the alternative pattern of movement. Parkinsonian subjects thus show an impairment in motor set similar to that found previously in cognitive activity.

Liberating Systems Theory: Toward Critical Systems Thinking:

Abstract: This article contains an exploration of a number of the many interpretations of its title Liberating Systems Theory. It is in fact a point of reflection on the way to realizing Critical Systems Thinking. Particular points of focus are critical theory integrated to practice in systems "problem solving," and the history and progress of systems thinking, considering critically the relationship of the past with progressively emerging future ends, i.e., emerging Critical Systems Thinking.

Testament to conversations on critical systems thinking between two systems practitioners

Abstract: This is a testament to conversations held in Berne and Fribourg, Switzerland, in late 1988. The main theme that we present concerns seeking to find an adequate epistemology for systems practice, to find a “truly” critical approach, by shifting our interests from “systems science” to “systems rationality” (i.e., by “reaching out” toward a systems epistemological ideal) and by dealing with sociological phenomena such as the “effects of material conditions” and false consciousness and inequalities associated with these. Social rationalities relating to positivism, interpretivism, and critique are considered. Limitations and legitimacies of these rationalities in social contexts are made explicit in these discussions.

The Douglas-Peucker algorithm for line simplification: re-evaluation through visualization

Abstract: The primary aim of this paper is to illustrate the value of visualization in cartography and to indicate that tools for the generation and manipulation of realistic images are of limited value within this application. This paper demonstrates the value of visualization within one problem in cartography, namely the generalisation of lines. It reports on the evaluation of the Douglas-Peucker algorithm for line simplification. Visualization of the simplification process and of the results suggest that the mathematical measures of performance proposed by some other researchers are inappropriate, misleading and questionable.

Determination of L-ascorbic acid in fruit and vegetable juices by flow injection with immobilised ascorbate oxidase.

Abstract: Ascorbate oxidase was immobilised on cyanogen bromide activated-Sepharose 4B and incorporated in a flow-injection system with amperometric detection at a glassy carbon electrode at +0.6 V. On passage through the immobilised ascorbate oxidase a fraction of the L-ascorbic acid was converted into dehydroascorbic acid and the decrease in signal was measured. This could be directly related to the amount of L-ascorbic acid present. The calibration graph was linear over the range 0-400 ng ml(-1) with a correlation coefficient of 0.9994. The detection limit (2 sigma) in phosphate buffer (0.08 M, pH 5.5) was 4.0 ng ml(-1). The relative standard deviation for a 200 ng ml(-1) standard was 1.0% (n = 10) and the sampling throughput was 30 samples h(-1). The method was used for the simple and rapid determination of L-ascorbic acid in fruit and vegetable juice.

Long-term survival of sclerotia of Sclerotium cepivorum and Stromatinia gladioli

Abstract: In an experiment with pure-culture sclerotia of Sclerotium cepivorum and Stromatinia gladioli a large proportion of the sclerotia survived burial for 20 years in the field in the absence of host plants. Some evidence for metabolic activity or leakage leading to the gradual erosion of the sclerotial contents was obtained with S. cepivorum. The results of other experiments suggested that, for unknown reasons, a variable proportion of sclerotia formed naturally on infected plants may decay shortly after their formation, but those which survive beyond this limited period are likely to remain viable for many years. The viability of sclerotia was also reduced by prolonged flooding, but the period for which land would have to be under water excludes this as a method of eliminating sclerotia from infested land in the UK. Treatment with the mycoparasite Teratosperma oligocladum did not affect the survival or infectivity of sclerotia of S. cepivorum or S. gladioli.

Corrosion performance of layered coatings produced by physical vapour deposition

Abstract: Potentiodynamic methods were used to investigate the relative corrosion protection provided on 304 stainless steel by various coating and pretreatment routes designed to isolate the substrate from the environment. These include combinations of plasma oxidizing, plasma nitriding and chromium, nickel and titanium nitride coatings produced by triode ion plating methods. It is shown that optimization of the layer structure and galvanic coupling are vital where a combination of wear and corrosion resistance is required. Nickel interlayers under TiN, for example, are shown to provide improved protection against corrosion. Attempts to increase corrosion resistance by producing a passive layer through a d.c. plasma processing stage on the substrate were not so successful, and the reasons for this are discussed.

Enhanced plasma nitriding at low pressures: A comparative study of d.c. and r.f. techniques

Abstract: Increasing industrial interest in the use of enhanced low pressure ion plating techniques for surface coating applications led the authors to examine the applicability of discharge enhancement to the plasma nitriding process. The performance of various d.c. diode, triode and r.f. systems is discussed in terms of surface layer growth rate, hardness profiles and coverage uniformity. It is shown that a correlation of visual and optical emission spectroscopy analyses of practical discharges with predictive equations for plasma phenomena can be useful in explaining observed discharge effects, thus assisting development and optimization of the plasma nitriding process.