Coronary haemodynamics and wave intensity analysis in aortic stenosis

Introduction: Coronary Wave Intensity Analysis (WIA) provides an invasive measure of energy transfer within the coronary circulation. I set out to derive a non-invasive measure of the backward expansion wave (BEW) responsible for coronary flow and assess it during exercise and in aortic stenosis (AS). Methods: 17 patients (mean age 60, 11 male) with normal cardiac function underwent invasive LAD WIA calculation using a pressure- and flow-tipped wire. Non-invasive WIA was calculated immediately after angiography from simultaneous PW Doppler of the LAD and a suprasystolic-cuff derived measure of central pressure. Non-invasive WIA was then assessed in 9 healthy volunteers whilst exercising on an exercise bike, 25 patients with varying degrees of AS (AVmax range: 2.41-5.43m/s) and 29 patients before, after and at 6 and 12 months following aortic valve intervention for severe AS. Results: Mean peak BEW was -14.7± 8.7x104 Wm-2s-2 invasively and -14.4± 8.2 Wm-2s-2 non-invasively and increased with exercise (at peak: -20.5±6.8Wm-2s-2, p=0.02) along with a rise in coronary flow (28.8cm/s to 42.1cm/s, p 0.06). A significant correlation was noted with the BEW and AS severity, strongest when valvulo-arterial impedence was assessed (r=-0.66, p<0.001). In severe AS, a reduction in coronary flow (0.41 to 0.33m/s, p<0.01) and the BEW (-22.1 vs 10.9x104Wm-2s-2, p<0.01) was seen after intervention. With LVH regression BEW increased (-21.6±12.6x104 Wm-2s-2 at 6 months) without a significant change in coronary flow. Conclusion: It is possible to construct a non-invasive measure of coronary WIA thus markedly increasing its applicability. Using this technique, the BEW is seen to increase during progressive levels of exercise accounting for the increase in coronary flow. The BEW progressively climbs with increasing AS, falls to sub-normal levels after aortic valve intervention but then increases to normal levels with LVH regression.Open Acces

Electrophysiological correlates of interference control in the Eriksen task

This thesis examined conflict monitoring in the Eriksen task in which participants must respond to a centrally positioned target arrow and ignore simultaneously presented distractors that flank the target. Distractors were either associated with a response congruent to the target, in conflict with the target, or, in a neutral condition, not associated with a response, instead producing only perceptual interference. This thesis extended on previous Eriksen research by systematically investigating the effect of varying the level of response conflict and task difficulty on stimulus processing in six studies and clarifying the functional role of ERP components elicited in the Eriksen task. Specifically, this was achieved by (a) varying the number of flanking distractors and, (b) the level of response conflict by using different permutations of incongruent distractors, (c) reducing target stimulus perceptibility through degradation, (d) utilising both valid and invalid information to increase response preparation and make conflict monitoring more difficult, and (e) providing feedback in a speeded version of the task. In all six studies, two N2 components were clearly delineated – the first of which was increased to stimuli requiring enhanced feature detection processes (N2a), while the second N2 component (N2b) was consistently observed to increase following the detection of response conflict. The P3 component, rarely considered in the Eriksen paradigm, was reduced at parietal sites and increased in latency as the discriminability of the target amongst the distractors became more difficult. The results suggest that the P3 component may reflect stimulus evaluation processes and equivocation related to the ease of target identification and concurrent response selection processes imperative for accurate task performance. This thesis also utilised digital filtering to clarify time-domain ERP results in terms of the relative contributions of activity in the alpha, theta and delta frequency ranges. Event-related theta oscillations contributed significantly to the morphology of the two N2 components reflecting allocation of focused attentional resources following the detection of perceptual (theta N2a) or response conflict (theta N2b). Activity in both theta and delta frequency ranges was robustly observed to contribute to the P3 component. An increased theta response at frontal sites was observed along with increases in task difficulty likely indexing the activation of anterior attentional resources. The results also suggest that the parietal delta P3 component reflects a refined form of equivocation, sensitive to the perceptibility of the target, and concomitant with the relative ease of accurate response selection. This thesis has clarified successful conflict monitoring and task performance in the Eriksen task, and the relationship with stimulus-locked ERP components in the time and frequency domains. The results suggest that the second frontally maximal N2 component reflects successful conflict monitoring, while the P3 component most probably reflects equivocation arising from difficult target identification and accurate response selection, rather than response conflict per se

Welcome to the post-digital city

The newly formed UCL Institute for Digital Innovation in the Built Environment operates at the interface of digital engineering, computer science and human experience

How Are Individual Differences in Schizotypy Related to Type 1 (Automatic/Heuristic) and Type 2 (Reflective/Effortful) Thinking Processes?

Background: Human reasoning is often conceptualised within ‘dual process’ frameworks, comprising Type 1 (automatic/heuristic) and Type 2 (reflective/effortful) processes, as well as ‘thinking styles’. These processes have not yet been comprehensively investigated in relation to schizotypy; a continuum of normal variability of psychosis-like characteristics and experiences. This could provide insights into thinking processes associated with psychosis-related phenomena, bypassing the limitations of psychiatric diagnosis and the confounding factors associated with clinical populations. Aims: This study sought to investigate whether individual differences in schizotypy (‘unusual experiences’ and ‘introvertive anhedonia’) were related to thinking processes and thinking styles. Another aim was to examine how schizotypy, thinking processes and thinking styles were related to cognitive reflection, informed by dual process theories. Method: The study employed a cross-sectional design and data was collected through an online survey. A large sample (n = 1,512) completed several measures pertaining to personality and reasoning. Correlations examined the association between schizotypy and reasoning processes. Regression analysis was used to further examine predictors of cognitive reflection, and multiple mediation models tested whether thinking styles and processes mediated the association between schizotypy and cognitive reflection. Results: Schizotypy was associated with greater reliance on intuitive thinking, less reliance on deliberative thinking, as well as a hastier, less reflective reasoning style. Unusual experiences, thinking processes and thinking style were independent predictors of cognitive reflection, and schizotypy contributed to significant additional variance in reflection over other predictor variables. Thinking processes and thinking style had a small mediating effect on the relationship between schizotypy and cognitive reflection. Conclusion: These findings add novel and meaningful contributions to the literature on schizotypy and decision making, and potentially allude to similar reasoning processes to those reported in psychosis. Clinical implications include potential useful targets for therapy, and several promising avenues for future research are suggested

Conceptual framework of a Project Bank Account (PBA) blockchain payment application for the construction industry

The UK government published a guidance document in 2012 stipulating the use of project bank accounts (PBA) to promote fair and prompt payment practices in the construction industry. PBA utilises a project-specific escrow bank account to provide greater cash flow auditability and mitigate cascading payments down the supply chain. However, PBA is bureaucratic to manage and costly to set up. This paper will investigate whether blockchain can be used as an alternative system for executing PBA payments

Archival Study of Blockchain Applications in the Construction Industry From Literature Published in 2019 and 2020

Purpose: This paper aims to investigate proposed blockchain applications in the construction industry from contemporary literature. Methodology: Archival studies will be used to obtain academic content from secondary sources. An explorative strategy will be adopted with no preconception or biases on the preferred route of execution. Blockchain is a fast-evolving technology with a high rate of yearly progression; therefore, this paper refines the search to recently published material in 2019 and 2020. Data is collected in two stages, firstly, categories of research are extrapolated from secondary literature and recorded into a table, and afterwards, the corresponding proposed application of blockchain is documented and reviewed. Findings: An adequate breadth and variety of categories are substantiated from archival literature, which effectively contributes to the extraction of proposed blockchain applications for construction. The data collection extracts 19 categories from the explorative study, in which 19 proposed solutions (one per category) is presented. All of the advisory content for the proposed solutions were obtained from a deliberated selection of 21 academic study papers. Limitations: The study is limited to one proposed application per category, totalling 19 proposed solutions; however, assessing various approaches per category could not be researched comparatively due to voluminous information. Thus, recommendations incorporate a holistic case study of one subject category which incorporates a multitude of various proposed applications. Originality: This paper contributes to new knowledge through extrapolating proposed blockchain applications from academic literature in 2019 and 2020

Development of a New Business Model to Measure Organizational and Project-Level SDG Impact—Case Study of a Water Utility Company

Achievement of the United Nations’ 2030 Global Goals for Sustainability is of paramount importance. However, for engineers and project managers to take meaningful action, they need the practical tools, processes and leadership to turn grand rhetoric into viable engineering solutions. Linking infrastructure project sustainability performance to sustainable development goals (SDG) targets is problematic. This article builds on the previous development of an innovative infrastructure business model, called the “Infrastructure SDG Impact-Value Chain” (IVC) to link local-level project delivery with global-level SDG impacts. It uses a case study of a water utility company to demonstrate how the IVC business model can integrate the “triple bottom line” to ensure the balanced definition of success across economic, environmental and social thematic areas. The results led to a proposed methodology for business leaders to align stakeholders on a common definition of project success during the design phase. The study includes the selection of longer-term outcomes and strategic SDG impacts, which, it is suggested, are improved definitions of project success. Although the findings that are from a single case study cannot automatically be extended to the entire water industry, the study’s methodology has potential to be used to evaluate multiple projects across different sectors. The practical application is significant since it offers the flexibility to be used at both project and portfolio levels, thereby linking tactical delivery to organisational SDG impacts and leading to improved investment decisions with increased likelihood of success in achieving the SDG 2030 targets

Towards fully-automated code compliance checking of building regulations: challenges for rule interpretation and representation

Before the building design is finalised, it needs to be checked against regulations. Traditionally, manual compliance checking is error-prone and time-consuming. As a solution, automatic compliance checking (ACC) was proposed. Many studies have focused on the crucial ACC rule interpretation process, yet no research has synthesised the themes and identified future research opportunities. This paper thus aims to fill this gap by conducting a systematic literature review and identifying challenges facing this field. Findings revealed that the representation development process lacks a methodological backdrop. Understandings of rules, representations, and relationships between them are insufficient. Potential solutions were proposed to address these challenges