Myocardial energy utilisation in relation to canine circulatory control, studied by multi-variate analysis and computer simulation

Imperial Users onl

Recursive Program Optimization Through Inductive Synthesis Proof Transformation

The research described in this paper involved developing transformation techniques which increase the efficiency of the noriginal program, the source, by transforming its synthesis proof into one, the target, which yields a computationally more efficient algorithm. We describe a working proof transformation system which, by exploiting the duality between mathematical induction and recursion, employs the novel strategy of optimizing recursive programs by transforming inductive proofs. We compare and contrast this approach with the more traditional approaches to program transformation, and highlight the benefits of proof transformation with regards to search, correctness, automatability and generality

Hard Frost: Structures of Feeling in New Zealand Literature, 1908–1945

John Newton’s Hard Frost opens by chiming the death knell for New Zealand literature. New Zealand writing, or at least the habit of thinking about it as such – a habit instilled so carefully and well by the arbiters of cultural nationalism – is over

Online Assessment System with Integrated Study (OASIS) to enhance the learning of Electrical Engineering students: an action research study

World-wide, there has been a large increase in tertiary student numbers, not entirely matched by funding increases. Consequently, instructors are faced with large, diverse classes, and find themselves struggling to provide adequate assessment and prompt feedback, two quantities critical in an effective learning environment. Personal computers and the Internet can help solve this problem. The aim of this study was to develop, implement and validate a Web-based software package that, through providing practice and assessment opportunities, improved student learning and reduced marking and related mundane aspects of instructor workload. At the start of the study, such a package already existed in prototype form: OASIS (Online Assessment System with Integrated Study). As the study progressed, this software package was first fully rewritten and then repeatedly modified. OASIS delivers individualised tasks, marks student responses, supplies prompt feedback, and logs student activity. Staff can deliver sets of practice questions and assessments to students: assessments may involve different questions for different students, not just numerically different versions of the same questions. Given my role as teacher, the traditional research ideal of observing without affecting the research environment was both impossible and unconscionable. In particular, since preliminary evidence suggested that OASIS did enhance student learning, I could not adopt a ‘two groups’ approach to the research, with one group using OASIS while the other did not. Instead, an action research methodology was seen as most appropriate for my double role of teacher and researcher.This methodology enabled me, in the light of my findings, to continuously modify the learning environment and enhance student learning. The action research proceeded through a spiral of one-semester cycles of planning, acting, observing and reflecting. To maximize rigour, the research ran through eight cycles over four years and involved considerable triangulation. OASIS itself collected much quantitative data. Further data were collected via interview, survey, email and informal discussion from three groups: current students, postgraduates and academics. My colleagues provided alternative perceptions and interpretations, as did Physics Department academics who were using OASIS, and an external academic who interviewed academics and investigated the implementation of OASIS. Perhaps surprisingly, academics had generally adopted OASIS to promote student learning rather than to decrease their own workloads. In some cases workloads were reduced; however, where OASIS assessments augmented rather than replaced existing traditional assessments, workloads actually went up slightly. All instructors who used OASIS reported enhanced student learning and wished to continue using it. Student surveys, interviews, focus-group discussions and informal feedback showed that students found the software easy to use and considered that it helped them improve their skills and understanding. OASIS questions were preferred over textbook questions. Students commonly requested OASIS to be available in more of their areas of study. In general students wanted hints or model answers though some argued against their provision.The majority of students were enthusiastic about the use of OASIS for practice, and activity logs revealed that they did use OASIS extensively. These logs also revealed the motivating power of assessments: typically half the online practice activity took place in the last 36 hours prior to assessments. Interviews provided further interesting insights into the ways different students approached their studies and assessments. However, students did voice concerns about the validity of OASIS assignments, noting their peers could rely on the efforts of others to score highly in these. A number of steps were carried out in an attempt to defuse these concerns, including: disabling OASIS practice during assignments, basing assignments on previously unseen questions, and providing different assignment questions to different students. While this study has achieved the goal of developing, implementing and validating OASIS, many future opportunities exist. OASIS may be used in schools as well as universities. Non-numerical questions, where answers may be somewhere between right and wrong, are possible. OASIS can also be used to deliver concept inventories to students to support research into concept acquisition and retention

Poverty is behaviour: an evaluation of life history theory in Cape Town

This study used data from 2090 young adults and their households collected in a longitudinal survey in Cape Town from 2002 to 2009. The study examined factors influencing the educational achievement of the participants including environment, schools, parents and individual’s own behaviour. Multivariate regression was used to analyse the data. Results showed that the education system had the largest influence followed by adolescent behaviour and then parental behaviour. The environment had no significant effect. Both gender and wealth declined in importance when the behavioural variables were added to the model supporting the hypothesis that behaviour is associated with educational achievement and hence poverty. The findings of this research suggest that the Education Department appears to have non-educational objectives and family processes influences educational achievement. These circumstances need to be transformed if educational achievement and thereby poverty or inequality is to be addressed. Future surveys examining young adults should include more details of the environment, early childhood experiences, family processes and the parent/child relationship

Patterns of Design

In a straightforward meta-level shift of focus, we use design patterns as a medium and process for capturing insight about the process of design. We survey mainstream design genres, and draw conclusions about how they can help inform the design of intelligent systems

Role of Fiber Orientation in Atrial Arrythmogenesis

Electrical wave-front propagation in the atria is determined largely by local fiber orientation. Recent study suggests that atrial fibrillation (AF) progresses with enhanced anisotropy. In this work, a 3D rabbit atrial anatomical model at 20 × 20 × 20 μm3 resolution with realistic fiber orientation was constructed based on the novel contrast-enhanced micro-CT imaging. The Fenton-Karma cellular activation model was adapted to reproduce rabbit atrial action potential period of 80 ms. Diffusivities were estimated for longitudinal and transverse directions of the fiber orientation respectively. Pacing was conducted in the 3D anisotropic atrial model with a reducing S2 interval to facilitate initiation of atrial arrhythmia. Multiple simulations were conducted with varying values of diffusion anisotropy and stimulus locations to evaluate the role of anisotropy in initiating AF. Under physiological anisotropy conditions, a rapid right atrial activation was followed by the left atrial activation. Excitation waves reached the atrio-ventricular border where they terminated. Upon reduction of conduction heterogeneity, re-entry was initiated by the rapid pacing and the activation of both atrial chambers was almost simultaneous. Myofiber orientation is an effective mechanism for regulating atrial activation. Modification of myoarchitecture is proarrhythmic

Backbone Fragility and the Local Search Cost Peak

The local search algorithm WSat is one of the most successful algorithms for solving the satisfiability (SAT) problem. It is notably effective at solving hard Random 3-SAT instances near the so-called `satisfiability threshold', but still shows a peak in search cost near the threshold and large variations in cost over different instances. We make a number of significant contributions to the analysis of WSat on high-cost random instances, using the recently-introduced concept of the backbone of a SAT instance. The backbone is the set of literals which are entailed by an instance. We find that the number of solutions predicts the cost well for small-backbone instances but is much less relevant for the large-backbone instances which appear near the threshold and dominate in the overconstrained region. We show a very strong correlation between search cost and the Hamming distance to the nearest solution early in WSat's search. This pattern leads us to introduce a measure of the backbone fragility of an instance, which indicates how persistent the backbone is as clauses are removed. We propose that high-cost random instances for local search are those with very large backbones which are also backbone-fragile. We suggest that the decay in cost beyond the satisfiability threshold is due to increasing backbone robustness (the opposite of backbone fragility). Our hypothesis makes three correct predictions. First, that the backbone robustness of an instance is negatively correlated with the local search cost when other factors are controlled for. Second, that backbone-minimal instances (which are 3-SAT instances altered so as to be more backbone-fragile) are unusually hard for WSat. Third, that the clauses most often unsatisfied during search are those whose deletion has the most effect on the backbone. In understanding the pathologies of local search methods, we hope to contribute to the development of new and better techniques