Cortical oscillatory activity associated with the perception of illusory and real visual contours

We used magnetoencephalography (MEG) to examine the nature of oscillatory brain rhythms when passively viewing both illusory and real visual contours. Three stimuli were employed: a Kanizsa triangle; a Kanizsa triangle with a real triangular contour superimposed; and a control figure in which the corner elements used to form the Kanizsa triangle were rotated to negate the formation of illusory contours. The MEG data were analysed using synthetic aperture magnetometry (SAM) to enable the spatial localisation of task-related oscillatory power changes within specific frequency bands, and the time-course of activity within given locations-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. In contrast to earlier studies, we did not find increases in gamma activity (> 30 Hz) to illusory shapes, but instead a decrease in 10–30 Hz activity approximately 200 ms after stimulus presentation. The reduction in oscillatory activity was primarily evident within extrastriate areas, including the lateral occipital complex (LOC). Importantly, this same pattern of results was evident for each stimulus type. Our results further highlight the importance of the LOC and a network of posterior brain regions in processing visual contours, be they illusory or real in nature. The similarity of the results for both real and illusory contours, however, leads us to conclude that the broadband (< 30 Hz) decrease in power we observed is more likely to reflect general changes in visual attention than neural computations specific to processing visual contours.

Ecological studies on:(a) the use of colonisation samplers in relation to biological surveillance of river water quality (b) the requirements of freshwater gastropoda

Some of the factors affecting colonisation of a colonisation sampler, the Standard Aufwuchs Unit (S. Auf. U.) were investigated, namely immersion period, whether anchored on the bottom or suspended, and the influence of riffles. It was concluded that a four-week immersion period was best. S. Auf. U. anchored on the bottom collected both more taxa and individuals than suspended ones. Fewer taxa but more individuals colonised S. Auf. U. in the potamon zone compared to the rhithron zone with a consequent reduction in the values of pollution indexes and diversity. It was concluded that a completely different scoring system was necessary for lowland rivers. Macroinvertebrates colonising S. Auf. U. in simulated streams, lowland rivers and the R. Churnet reflected water quality. A variety of pollution and diversity indexes were applied to results from lowland river sites. Instead of these, it was recommended that an abbreviated species - relative abundance list be used to summarise biological data for use in lowland river surveillance. An intensive study of gastropod populations was made in simulated streams. Lynnaea peregra increased in abundance whereas Potamopyrgas jenkinsi decreased with increasing sewage effluent concentration. No clear-cut differences in reproduction were observed. The presence/absence of eight gastropod taxa was compared with concentrations of various pollutants in lowland rivers. On the basis of all field work it appeared that ammonia, nitrite, copper and zinc were the toxicants most likely to be detrimental to gastropods and that P. jenkinsi and Theodoxus fluviatilis were the least tolerant taxa. 96h acute toxicity tests of P. jenkinsi using ammonia and copper were carried out in a flow-through system after a variety of static range finding tests. P. jenkinsi was intolerant to both toxicants compared to reports on other taxa and the results suggested that these toxicants would affect distribution of this species in the field.

Designing a safety management support system using open architecture databases: the requirements of information representation in the support of managers' risk-related decision-making

This research was conducted at the Space Research and Technology Centre o the European Space Agency at Noordvijk in the Netherlands. ESA is an international organisation that brings together a range of scientists, engineers and managers from 14 European member states. The motivation for the work was to enable decision-makers, in a culturally and technologically diverse organisation, to share information for the purpose of making decisions that are well informed about the risk-related aspects of the situations they seek to address. The research examined the use of decision support system DSS) technology to facilitate decision-making of this type. This involved identifying the technology available and its application to risk management. Decision-making is a complex activity that does not lend itself to exact measurement or precise understanding at a detailed level. In view of this, a prototype DSS was developed through which to understand the practical issues to be accommodated and to evaluate alternative approaches to supporting decision-making of this type. The problem of measuring the effect upon the quality of decisions has been approached through expert evaluation of the software developed. The practical orientation of this work was informed by a review of the relevant literature in decision-making, risk management, decision support and information technology. Communication and information technology unite the major the,es of this work. This allows correlation of the interests of the research with European public policy. The principles of communication were also considered in the topic of information visualisation - this emerging technology exploits flexible modes of human computer interaction (HCI) to improve the cognition of complex data. Risk management is itself an area characterised by complexity and risk visualisation is advocated for application in this field of endeavour. The thesis provides recommendations for future work in the fields of decision=making, DSS technology and risk management.

Employability management needs analysis and the ICT sector in Europe:the case of small and medium-sized enterprises

The purpose of this paper is to deal with the outcomes of a so-called “employability management needs analysis” that is meant to provide more insight into current employability management activities and its possible benefits for Information and Communication Technology (ICT) professionals working in Small- and Medium-sized enterprises (SMEs) throughout Europe. A considerable series of interviews (N=107) were conducted with managers in SMEs in seven European countries, including Germany, Greece, Italy, the Netherlands, Norway, Poland, and the UK. A semi-structured interview protocol was used during the interviews to cover three issues: employability (13 items), ageing (8 items), and future developments and requirements (13 items). Analysis of all final interview transcriptions was at a national level using an elaborate common coding scheme. Although an interest in employability emerged, actual policy and action lagged behind. The recession in the ICT sector at the time of the investigation and the developmental stage of the sector in each participating country appeared connected. Ageing was not seen as a major issue in the ICT sector because managers considered ICT to be a relatively young sector. There appeared to be a serious lack of investment in the development of expertise of ICT professionals. Generalization of the results to large organizations in the ICT sector should be made with caution. The interview protocol developed is of value for further research and complements survey research undertaken within the employability field of study. It can be concluded that proactive HRM (Human Resource Management) policies and strategies are essential, even in times of economic downturn. Employability management activities are especially important in the light of current career issues. The study advances knowledge regarding HRM practices adopted by SMEs in the ICT sector, especially as there is a gap in knowledge about career development issues in that particular sector.

The performance of stabilized and unstabilized minestone in an aqueous environment with emphasis on its erosion resistance

Britain's sea and flood defences are becoming increasingly aged and as a consequence, more fragile and vulnerable. As the government's philosophy on resources shifts against the use of prime quarried and dredged geo-materials, the need to find alternative bulk materials to bolster Britain's prone defences becomes more pressing. One conceivable source for such a material is colliery waste or minestone. Although a plethora of erosion-abrasion studies have been carried out on soils and soil-cements, very little research has been undertaken to determine the resistance of minestone and its cement stabilized form to the effects of water erosion. The thesis reviews the current extent to which soil-cements, minestone and cement stabilized minestone (CSM) have been employed for hydraulic construction projects. A synopsis is also given on the effects of immersion on shales, mudstones and minestone, especially with regard to the phenomena of slaking. A laboratory study was undertaken featuring a selection of minestones from several British coalfields. The stability of minestone and CSM in sea water and distilled water was assessed using slaking tests and immersion monitoring and the bearing on the use of these materials for hydraulic construction is discussed. Following a review of current erosion apparatus, the erosion/abrasion test and rotating cylinder device were chosen and employed to assess the erosion resistance of minestone and CSM. Comparison was made with a sand mix designed to represent a dredged sand, the more traditional, bulk hydraulic construction material. The results of the erosion study suggest that both minestone and CSM were more resistant to erosion and abrasion than equivalently treated sand mixes. The greater resistance of minestone to the agents of erosion and abrasion is attributed to several factors including the size of the particles, a greater degree of cement bonding and the ability of the minestone aggregate to absorb, rather than transmit shock waves produced by impacting abrasive particles. Although minestone is shown to be highly unstable when subjected to cyclic changes in its moisture content, the study suggests that even in an intertidal regime where cyclic immersion does takes place, minestone will retain sufficient moisture within its fabric to prevent slaking from taking place. The slaking study reveals a close relationship between slaking susceptibility and total pore surface area as revealed by porosimetry. The immersion study shows that although the fabric of CSM is rapidly attacked in sea water, a high degree of the disruption is associated with the edges and corners of samples (ie. free surface) while the integrity of the internal fabric remains relatively intact. CSM samples were shown to be resilient when subjected to immersion in distilled water. An overall assessment of minestone and CSM would suggest that with the implementation of judicious selection and appropriate quality control they could be used as alternative materials for flood and sea defences. It is believed, that even in the harsh regime of a marine environment, CSM could be employed for temporary and sacrificial schemes.

The development of calibration and adaptive filtering procedures for neuromagnetic studies of human visual function

This thesis first considers the calibration and signal processing requirements of a neuromagnetometer for the measurement of human visual function. Gradiometer calibration using straight wire grids is examined and optimal grid configurations determined, given realistic constructional tolerances. Simulations show that for gradiometer balance of 1:104 and wire spacing error of 0.25mm the achievable calibration accuracy of gain is 0.3%, of position is 0.3mm and of orientation is 0.6°. Practical results with a 19-channel 2nd-order gradiometer based system exceed this performance. The real-time application of adaptive reference noise cancellation filtering to running-average evoked response data is examined. In the steady state, the filter can be assumed to be driven by a non-stationary step input arising at epoch boundaries. Based on empirical measures of this driving step an optimal progression for the filter time constant is proposed which improves upon fixed time constant filter performance. The incorporation of the time-derivatives of the reference channels was found to improve the performance of the adaptive filtering algorithm by 15-20% for unaveraged data, falling to 5% with averaging. The thesis concludes with a neuromagnetic investigation of evoked cortical responses to chromatic and luminance grating stimuli. The global magnetic field power of evoked responses to the onset of sinusoidal gratings was shown to have distinct chromatic and luminance sensitive components. Analysis of the results, using a single equivalent current dipole model, shows that these components arise from activity within two distinct cortical locations. Co-registration of the resulting current source localisations with MRI shows a chromatically responsive area lying along the midline within the calcarine fissure, possibly extending onto the lingual and cuneal gyri. It is postulated that this area is the human homologue of the primate cortical area V4.

A comparative study on the pyrolysis of metal- and ash-enriched wood and the combustion properties of the gained char

This study aims to investigate the pyrolysis behaviour of metal-contaminated wood and the combustion properties of char derived from wood pyrolysis. Seven metals (Na, Mg, Ca, Zn, Cd, Pb and Fe(III)) were introduced to willow in cation form by ion-exchange and the thermal behaviour of demineralised samples and samples with additional ash were also investigated. The results show that the char yield increased from 21% to 24-28% and levoglucosan yield in vapour phase decreased from 88% to 62-29% after the addition of inorganic compounds, even though the metal binding capacity of wood varied from one metal ion to another. While char yield seems to be effected mainly by the concentration of the metal ions, levoglucosan yield was more dependent on the ionic species especially when sodium ions were present. When combustion experiments were carried out with char made of the metal enriched wood, two consecutive steps were observed, both effected by the presence of inorganic compounds. The first step was identified as the release and combustion of volatiles, while the second peak of the burning profile is the actual combustion of the fixed carbon. The burnout temperatures, estimated ignition indices and the conversion indicate that the type and not the amount of metal ions were the determining factors during the second step of combustion. © 2012 Published by Elsevier B.V.

The effects of ownership and stock liquidity on the timing of repurchase transactions

We analyze detailed monthly data on U.S. open market stock repurchases (OMRs) that recently became available following stricter disclosure requirements. We find evidence that OMRs are timed to benefit non-selling shareholders. We present evidence that the profits to companies from timing repurchases are significantly related to ownership structure. Institutional ownership reduces companies' opportunities to repurchase stock at bargain prices. At low levels, insider ownership increases timing profits and at high levels it reduces them. Stock liquidity increases profits from timing OMRs.

The role of pinning and instability in a class of non-equilibrium growth models

We study the dynamics of a growing crystalline facet where the growth mechanism is controlled by the geometry of the local curvature. A continuum model, in (2+1) dimensions, is developed in analogy with the Kardar-Parisi-Zhang (KPZ) model is considered for the purpose. Following standard coarse graining procedures, it is shown that in the large time, long distance limit, the continuum model predicts a curvature independent KPZ phase, thereby suppressing all explicit effects of curvature and local pinning in the system, in the "perturbative" limit. A direct numerical integration of this growth equation, in 1+1 dimensions, supports this observation below a critical parametric range, above which generic instabilities, in the form of isolated pillared structures lead to deviations from standard scaling behaviour. Possibilities of controlling this instability by introducing statistically "irrelevant" (in the sense of renormalisation groups) higher ordered nonlinearities have also been discussed.

When the requirements for adaptation and high integrity meet

Two classes of software that are notoriously difficult to develop on their own are rapidly merging into one. This will affect every key service that we rely upon in modern society, yet a successful merge is unlikely to be achievable using software development techniques specific to either class. This paper explains the growing demand for software capable of both self-adaptation and high integrity, and advocates the use of a collection of "@runtime" techniques for its development, operation and management. We summarise early research into the development of such techniques, and discuss the remaining work required to overcome the great challenge of self-adaptive high-integrity software. © 2011 ACM.

The science of writing an article – or is it art?

Getting your work published is an important aim for anyone undertaking research. This paper described how to prepare your work for peer review. Some recommendations are detailed i.e ensure yourself that your work is of good quality, decide is which journal you want to submit it to, follow the required style and be structured. Finally, a few tips and the reviewer's checklist are reminded.