Modelling of a microfluid ultrasonic particle separator

Particles within an ultrasonic standing wave experience an acoustic force causing the particles tomove to certain positions within the acoustic field. This phenomenon can be used to manipulate particles and so provides a means to separate, concentrate or trap particles, cells or spores. The work described is applied to a micro-engineered flow-through device for processing small samples and incorporates a fluid filled chamber of depth typically between 100 and 200µm, and therefore approaches microfluidic dimensions. The successful design and subsequent performance of such devices rely on the predictability of particle trajectories which are influenced predominantly by acoustic and fluid flow fields. Therefore, the majority of this research seeks an understanding of the nature of these fields and, in turn, reliable simulation of particle trajectories.Computational fluid dynamics (CFD) modelling is used to develop a robust 2-dimensional model of the device’s microchannels and is used to predict the presence of eddy regions, associated with the etch fabrication techniques, which are likely to disrupt the separation process. Based on a geometric study, simulations and subsequent test results on a fabricated device have revealedgeometric modifications which minimise these eddy flows and promote the existence of laminar flow within the main channel of the device. Finite element analysis (FEA) provides a method to investigate the 2-dimensional characteristics of the acoustic field and reveals variations in acoustic pressure across the width of the device, giving rise to lateral radiation forces frequently reported in similar ultrasonic devices. This work investigates acoustic enclosure modes in 2 or 3-dimensions as a possible cause of these lateralvariations, with modelled results matching well with experiment. A particle force model has also been developed which predicts the motion of particles through the device, and by which concentration and separation performance may be calculated. This tool isused to investigate acoustic design, operating conditions and separation performance for both the micro-engineered device and a device based on a quarter-wavelength, providing valuable insight into various trends observed.The novelty in this work is the application of macro-scale numerical techniques to microengineered ultrasonic particle manipulators and the execution of an extensive analysis of the design and operation of such devices. These analyses have demonstrated, and therefore have explained, various phenomena associated with the fluid and acoustic fields, and how they influence particle separation performance. The development of similar devices can be aided by the use of the numerical simulation methods featured throughout this thesis

Narration in the novels of selected nineteenth-century women writers : Jane Austen, The Bronte Sisters, and Elizabeth Gaskell

In this studyi apply a feminist-narratological grid to the works under discussion. I show how narration is used as strategy to highlight issues of concern to women, hereby attempting to make a contribution in the relatively new field of feminist narratology. Chapter One provides an analysis of Pride and Prejudice as an example of a feminist statement by Jane Austen. The use of omniscient narration and its ironic possibilities are offset against the central characters' perceptions, presented by means of free indirect style. Chapter Two examines The Tenant of Wildfell Hall as a critique of Wuthering Heights, both in its use of narrative frames and in its at times moralistic comment. The third and fourth chapters focus on Charlotte Bronte. Her ambivalences about the situation of women, be they writers, narrators or characters, are explored. These are seen to be revealed in her narrative strategies, particularly in her attainment of closure, or its lack. Chapter Five explores the increasing sophistication of the narrative techniques of Elizabeth Gaskell, whose early work Mary Barton is shown to have narrative inconsistencies as opposed to her more complex last novel Wives and Daughters. Finally, I conclude that while the authors under discussion use divergent methods, certain commonalities prevail. Among these are the presentation of alternatives women have within their constraining circumstances and the recognition of their moral accountability for the choices they make.English StudiesD. Litt. et Phil. (English

Dream and the preternatural in the poetry of Walter de la Mare

From Chapter 1: In this chapter I hope to illustrate in general terms how de la Mare's interest in dream and the preternatural pervades his work. His views on reality and in what it truly consists will be considered and definitions provided of various terms used throughout this study. These will approximate as closely as possible the meanings they acquire through de la Mare's own use of them. Some detailed reference to his work, especially to his prose introduction to the anthology Behold, This Dreamer! and to his poem "Dreams", will provide support for the statements made. Finally, an attempt will be made to place de la Mare, briefly and in broad outline, within his literary context, again with particular reference to his interest in dream and the preternatural and where it corresponds to or deviates from what one could expect from a poet of this period

Dream and the preternatural in the poetry of Walter de la Mare

From Chapter 1: In this chapter I hope to illustrate in general terms how de la Mare's interest in dream and the preternatural pervades his work. His views on reality and in what it truly consists will be considered and definitions provided of various terms used throughout this study. These will approximate as closely as possible the meanings they acquire through de la Mare's own use of them. Some detailed reference to his work, especially to his prose introduction to the anthology Behold, This Dreamer! and to his poem "Dreams", will provide support for the statements made. Finally, an attempt will be made to place de la Mare, briefly and in broad outline, within his literary context, again with particular reference to his interest in dream and the preternatural and where it corresponds to or deviates from what one could expect from a poet of this period

Intertidal habitat mapping for ecosystem goods and services: Tairua harbour

In January 2013, Waikato Regional Council (WRC) contracted the National Institute of Water and Atmospheric Research (NIWA), to develop rapid assessment techniques for mapping of intertidal habitats associated with the provision of ecosystem goods and services. Ecosystem goods and services are defined as ‘the direct and indirect benefits that humankind receives or values from natural or semi-natural habitats’ and include the provision of food and raw materials, waste treatment, processing and storage, disturbance prevention, sediment retention, water filtration and regulation, nutrient regulation, gas and climate regulation, habitat structure and cultural services such as spiritual heritage and leisure and recreation (Townsend et al. 2010). Assessment techniques were to be trialled and implemented for the intertidal area of the Tairua estuary with the view of providing: • Descriptions of habitat types that may be linked to levels of ecosystem goods and services. • Descriptions of the techniques involved in differentiating and mapping habitats, and an analysis of the precision and accuracy/validity of the methods. This report documents the evolution of the methodology and a proof of concept using Tairua estuary as a test case to build a habitat map. The goal is to generate precursor maps that will facilitate the mapping of ecosystem goods and services in the near future

Machine Learning to Classify Cardiotocography for Fetal Hypoxia Detection

Fetal hypoxia can cause damaging consequences on babies' such as stillbirth and cerebral palsy. Cardiotocography (CTG) has been used to detect intrapartum fetal hypoxia during labor. It is a non-invasive machine that measures the fetal heart rate and uterine contractions. Visual CTG suffers inconsistencies in interpretations among clinicians that can delay interventions. Machine learning (ML) showed potential in classifying abnormal CTG, allowing automatic interpretation. In the absence of a gold standard, researchers used various surrogate biomarkers to classify CTG, where some were clinically irrelevant. We proposed using Apgar scores as the surrogate benchmark of babies' ability to recover from birth. Apgar scores measure newborns' ability to recover from active uterine contraction, which measures appearance, pulse, grimace, activity and respiration. The higher the Apgar score, the healthier the baby is.We employ signal processing methods to pre-process and extract validated features of 552 raw CTG. We also included CTG-specific characteristics as outlined in the NICE guidelines. We employed ML techniques using 22 features and measured performances between ML classifiers. While we found that ML can distinguish CTG with low Apgar scores, results for the lowest Apgar scores, which are rare in the dataset we used, would benefit from more CTG data for better performance. We need an external dataset to validate our model for generalizability to ensure that it does not overfit a specific population.Clinical Relevance- This study demonstrated the potential of using a clinically relevant benchmark for classifying CTG to allow automatic early detection of hypoxia to reduce decision-making time in maternity units.</p

Machine learning on cardiotocography data to classify fetal outcomes: A scoping review

Introduction: Uterine contractions during labour constrict maternal blood flow and oxygen delivery to the developing baby, causing transient hypoxia. While most babies are physiologically adapted to withstand such intrapartum hypoxia, those exposed to severe hypoxia or with poor physiological reserves may experience neurological injury or death during labour. Cardiotocography (CTG) monitoring was developed to identify babies at risk of hypoxia by detecting changes in fetal heart rate (FHR) patterns. CTG monitoring is in widespread use in intrapartum care for the detection of fetal hypoxia, but the clinical utility is limited by a relatively poor positive predictive value (PPV) of an abnormal CTG and significant inter and intra observer variability in CTG interpretation. Clinical risk and human factors may impact the quality of CTG interpretation. Misclassification of CTG traces may lead to both under-treatment (with the risk of fetal injury or death) or over-treatment (which may include unnecessary operative interventions that put both mother and baby at risk of complications). Machine learning (ML) has been applied to this problem since early 2000 and has shown potential to predict fetal hypoxia more accurately than visual interpretation of CTG alone. To consider how these tools might be translated for clinical practice, we conducted a review of ML techniques already applied to CTG classification and identified research gaps requiring investigation in order to progress towards clinical implementation. Materials and method: We used identified keywords to search databases for relevant publications on PubMed, EMBASE and IEEE Xplore. We used Preferred Reporting Items for Systematic Review and Meta-Analysis for Scoping Reviews (PRISMA-ScR). Title, abstract and full text were screened according to the inclusion criteria. Results: We included 36 studies that used signal processing and ML techniques to classify CTG. Most studies used an open-access CTG database and predominantly used fetal metabolic acidosis as the benchmark for hypoxia with varying pH levels. Various methods were used to process and extract CTG signals and several ML algorithms were used to classify CTG. We identified significant concerns over the practicality of using varying pH levels as the CTG classification benchmark. Furthermore, studies needed to be more generalised as most used the same database with a low number of subjects for an ML study. Conclusion: ML studies demonstrate potential in predicting fetal hypoxia from CTG. However, more diverse datasets, standardisation of hypoxia benchmarks and enhancement of algorithms and features are needed for future clinical implementation.</p

Evolution of Stage 1 Twin-to-Twin Transfusion Syndrome (TTTS): Systematic Review and Meta-Analysis.

OBJECTIVES: The natural history of stage 1 Twin-to-twin transfusion syndrome (TTTS) remains unclear and its optimal management is yet to be established. The main aims of this meta-analysis were to quantify the incidence of progression in stage 1 TTTS and to ascertain survival in these pregnancies. METHODS: MEDLINE, EMBASE, and The Cochrane Library were searched. Reference lists within each article were hand-searched for additional reports. The outcomes included incidence of progression and survival in stage 1 TTTS. Randomized controlled trials, cohort and case-control studies were included. Case reports, studies including three or fewer cases of stage 1 TTTS, and editorials were excluded. Proportion meta-analysis was used for analysis (Registration number: CRD42016036190). RESULTS: The search yielded 3,085 citations; 18 studies were included in the review (172 pregnancies to assess progression and 433 pregnancies to assess the survival). The pooled incidence of progression in stage 1 TTTS was 27% [95% CI 16-39%]. The pooled overall survival, double survival and at least one survival in the pregnancies managed expectantly were 79% [95% CI 62-92%], 70% [95% CI 54-84%] and 87% [95% CI 69-98%], respectively. In those undergoing amnioreduction, the corresponding figures were 77% [95% CI 68-85%], 67% [95% CI 57-76%] and 86% [95% CI 76-94%], respectively. The survival rates were 68% [95% CI 54-81%], 54% [95% CI 36-72%], and 81% [95% CI 69-90%], when laser surgery was performed. CONCLUSIONS: The optimal initial management of stage 1 TTTS remains in equipoise. The ongoing randomized trial comparing immediate laser surgery versus conservative management should provide a definitive answer