MODELING OF AGRICULTURAL SYSTEMS

The authors present an overview of agricultural systems models. Beginning with why systems are modeled and for what purposes, the paper examines types of agricultural systems and associated model types. The broad categories range from pictorial (iconic) models to descriptive analogue models to symbolic (usually mathematical) models. The uses of optimization versus non-optimizing mechanistic models are reviewed, as are the scale and aggregation challenges associated with scaling up from the plant cell to the landscape or from a farm enterprise to a world market supply-demand equilibrium Recent modeling developments include the integration of formerly stand-alone biophysical simulation models, increasingly with a unifying spatial database and often for the purpose of supporting management decisions. Current modeling innovations are estimating and incorporating environmental values and other system interactions. At the community and regional scale, sociological and economic models of rural community structure are being developed to evaluate long-term community viability. The information revolution is bringing new challenges in delivering agricultural systems models over the internet, as well as integrating decision support systems with the new precision agriculture technologies.Farm Management,

Models for application of radiation boundary condition for MHD waves in collapse calculations

The problem of reflection of magnetohydrodynamic (MHD) waves at the boundary of a numerical grid has to be resolved in order to obtain reliable results for the end state of the (isothermal) collapse of a rotating, magnetic protostellar cloud. Since the goal of investigating magnetic braking in collapse simulations is to see if the transport of angular momentum via alfven waves is large enough to solve the angular momentum problem an approximation that artificially suppresses large amplitudes in the MHD waves can be self-defeating. For this reason, four alternate methods of handling reflected waves where no assumptions are made regarding the amplitudes of the waves were investigated. In order to study this problem (of reflection) without interference from other effects these methods were tried on two simpler cases. The four methods are discussed

Patient-specific multi-dimensional CFD simulations based on 4D Flow-MRI for the haemodynamic assessment of aortic dissections and perfusion optimisation of vascular grafts

Aortic dissection is a vascular pathology which affects 5-30 per million people. Due to regions of high shear stress and weakness in the vessel wall, the intimal layer of the aorta tears, separating it from the media and creating a channel known as a false lumen. AD is a progressive condition due to the cyclical relationship between structural changes and haemodynamic instability. Often, it is fatal in the absence of surgical intervention, with mortality rates up to 90% depending on the dissection type and severity. The preferred treatment for Type A and Type B aortic dissections is open and endovascular surgical intervention, respectively. With both treatment options, there are associated complications including graft migration, branch vessel hypoperfusion, endoleaks, stent strut fracture, thrombosis, and graft limb occlusion. Generally, these failure mechanisms are related to the internal flow regime and post-surgical haemodynamics. At present, it is difficult to predict the internal haemodynamics within these grafts before they are deployed. Therefore, this thesis seeks to understand whether we can use 4D Flow MRI in combination with CFD modelling to build pre-surgical models of aortic dissections to assist in surgical planning. Leveraging CFD in combination with 4D Flow-MRI mitigates the intrinsic limitations of each approach. With 4D Flow-MRI, it is possible to extract in vivo flow rates and wall motion, and elucidate qualitative and quantitative information on the evolution of blood flow throughout the cardiac cycle. However, the spatiotemporal resolution is limited and it is not possible to extract pressure or near-wall haemodynamics. CFD, in contrast, offers a significantly enhanced level of detail, permitting the calculation of clinically relevant parameters such as pressure, TAWSS, and OSI with high spatiotemporal resolution. To generate high-fidelity CFD models would require a methodology to process the quantitative blood flow data to extract anatomical information and calibrate boundary conditions. Commonly, this requires multiple imaging scans and boundary conditions rely on invasive measurements or several assumptions from multiple sources. In this thesis, we seek to extract all relevant information from a single 4D Flow-MRI scan to generate patient specific CFD models. To the best of our knowledge, this has not yet been performed before. We therefore present a methodology to generate high-contrast anatomical images from retrospective 4D flow-MRI data. This permitted successful segmentation and reconstruction of a healthy aorta, along with the true lumen and branch vessels of the dissected aorta. However, it was not possible to generate sufficient contrast within the false lumen due to low flow rates. To do so would require multi-VENC 4D Flow-MRI imaging which was not available during this study. Though it is possible to directly prescribe pressure (from an invasive catheter) and flow (from 4D Flow-MRI) waveforms as BCs to the CFD model, this is inappropriate for several reasons. Primarily, this is because branch flow and pressure waveforms are part of the desired solution for surgical planning. Secondly, the direct prescription of flow waveforms fails to yield correct pressure measurements since the downstream resistance and compliance is not accounted for, unlike in 3EWM BCs. Thirdly, the prescription of pressure waveforms requires invasive catheter measurements and increased patient burden. Therefore, we describe a methodology for the rapid estimation and calibration of patient specific Windkessel boundary conditions based on 4D Flow-MRI data. This yielded a perfusion distribution very similar to in vivo data without the need for requiring invasive pressure or flow measurements. Finally, we evaluated the haemodynamic environment in the aortae of healthy volunteers and Type B aortic dissection cases via coupled 0D-3D numerical modelling. Such simulations may assist in determining regions of vessel wall instability to identify patients who are at the highest risk of false lumen rupture. The present thesis shows that all the essential components required for a patient-specific CFD analysis could be derived from a single 4D Flow-MRI scan, with a view to replace CT imaging and non-specific boundary conditions. The methodologies presented could further be improved in the future, by utilising multi-VENC imaging and prescribing 4D Flow-MRI derived wall motion. This may reduce the burden on patients since it is a non-invasive, non-ionising approach which does not require intravenous contrast agents.Aortic dissection is a vascular pathology which affects 5-30 per million people. Due to regions of high shear stress and weakness in the vessel wall, the intimal layer of the aorta tears, separating it from the media and creating a channel known as a false lumen. AD is a progressive condition due to the cyclical relationship between structural changes and haemodynamic instability. Often, it is fatal in the absence of surgical intervention, with mortality rates up to 90% depending on the dissection type and severity. The preferred treatment for Type A and Type B aortic dissections is open and endovascular surgical intervention, respectively. With both treatment options, there are associated complications including graft migration, branch vessel hypoperfusion, endoleaks, stent strut fracture, thrombosis, and graft limb occlusion. Generally, these failure mechanisms are related to the internal flow regime and post-surgical haemodynamics. At present, it is difficult to predict the internal haemodynamics within these grafts before they are deployed. Therefore, this thesis seeks to understand whether we can use 4D Flow MRI in combination with CFD modelling to build pre-surgical models of aortic dissections to assist in surgical planning. Leveraging CFD in combination with 4D Flow-MRI mitigates the intrinsic limitations of each approach. With 4D Flow-MRI, it is possible to extract in vivo flow rates and wall motion, and elucidate qualitative and quantitative information on the evolution of blood flow throughout the cardiac cycle. However, the spatiotemporal resolution is limited and it is not possible to extract pressure or near-wall haemodynamics. CFD, in contrast, offers a significantly enhanced level of detail, permitting the calculation of clinically relevant parameters such as pressure, TAWSS, and OSI with high spatiotemporal resolution. To generate high-fidelity CFD models would require a methodology to process the quantitative blood flow data to extract anatomical information and calibrate boundary conditions. Commonly, this requires multiple imaging scans and boundary conditions rely on invasive measurements or several assumptions from multiple sources. In this thesis, we seek to extract all relevant information from a single 4D Flow-MRI scan to generate patient specific CFD models. To the best of our knowledge, this has not yet been performed before. We therefore present a methodology to generate high-contrast anatomical images from retrospective 4D flow-MRI data. This permitted successful segmentation and reconstruction of a healthy aorta, along with the true lumen and branch vessels of the dissected aorta. However, it was not possible to generate sufficient contrast within the false lumen due to low flow rates. To do so would require multi-VENC 4D Flow-MRI imaging which was not available during this study. Though it is possible to directly prescribe pressure (from an invasive catheter) and flow (from 4D Flow-MRI) waveforms as BCs to the CFD model, this is inappropriate for several reasons. Primarily, this is because branch flow and pressure waveforms are part of the desired solution for surgical planning. Secondly, the direct prescription of flow waveforms fails to yield correct pressure measurements since the downstream resistance and compliance is not accounted for, unlike in 3EWM BCs. Thirdly, the prescription of pressure waveforms requires invasive catheter measurements and increased patient burden. Therefore, we describe a methodology for the rapid estimation and calibration of patient specific Windkessel boundary conditions based on 4D Flow-MRI data. This yielded a perfusion distribution very similar to in vivo data without the need for requiring invasive pressure or flow measurements. Finally, we evaluated the haemodynamic environment in the aortae of healthy volunteers and Type B aortic dissection cases via coupled 0D-3D numerical modelling. Such simulations may assist in determining regions of vessel wall instability to identify patients who are at the highest risk of false lumen rupture. The present thesis shows that all the essential components required for a patient-specific CFD analysis could be derived from a single 4D Flow-MRI scan, with a view to replace CT imaging and non-specific boundary conditions. The methodologies presented could further be improved in the future, by utilising multi-VENC imaging and prescribing 4D Flow-MRI derived wall motion. This may reduce the burden on patients since it is a non-invasive, non-ionising approach which does not require intravenous contrast agents

Blended e-learning skeleton of conversation: improving formative assessment in undergraduate dissertation supervision

The supervision of undergraduate student dissertations is an area in need of research. Although some studies have already addressed this, these are primarily based on academic staff responses. This study contributes to knowledge by gathering the responses of students and focusing on formative electronic assessment. Data was collected using a student focus group and student questionnaire. The findings suggest that good supervisor-student communication is crucial to the supervision process and a number of students felt unhappy with this aspect. It is suggested that to improve the undergraduate student dissertation experience, a combination of face-to-face and electronic formative assessment is used. In addition, the Blended E-learning Skeleton of Conversation model provides a sound theoretical framework that could guide supervisors and students in the supervision process. This model is advocated for use in dissertation module design and in supervisor development

Novel beings and assisted nonexistence

This article engages with the legal regulation of end-of-existence decision-making for novel beings, specifically assisted nonexistence for such entities. I explain the concept of a legal model for assisted death by reference to the substantive features of legal regimes in three jurisdictions in which assisted suicide or euthanasia is lawful. I consider how these models might fit novel beings who may require or prefer assistance to end their own existence by reference to the constituent features—abstract legal ingredients—that models for assisted death share. I argue that extant models may block some novel beings’ access to end-of-existence assistance or fail to track what matters to them. I then examine the merits of adopting a universal model for assisted nonexistence, that is, a legal framework whose substantive features capture the end-of-existence concerns of both human and novel beings. Consideration of a unified legal framework may illuminate the discussion of assisted nonexistence for humans and novel beings. However, I argue that while novel beings may have similar interests to humans, they may be relevantly different also. The prima facie case for adopting a one regime to rule us all approach to assisted nonexistence may be defeated by reasons for divergent regulation

Social inequalities in rural England: Impacts on young people post-2008

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper investigates the cumulative impacts of the 2008 economic crisis and its aftermath (including policy changes) on young people in a sparsely populated rural area of northern England. The paper locates the research in the context of youth studies, Bourdieu's theory of practice, concepts of welfare regimes and welfare mix, and studies of the impacts of the crisis and austerity policies on the distribution of social and societal risk. The empirical findings reveal the challenges which faced young people in rural England before the financial crisis still persist. Moreover, the overwhelming reliance of young people on family for support generates further inequalities through what might be termed ‘secondary impact austerity’: young people feel indirectly and unevenly the economic effects and policy changes which impact on parents' and communities' ability to offer them support. Thus, changes to the welfare system, loss of services and less secure forms of employment exacerbate the transfer of social risk and the deepening of poverty for vulnerable groups. This is worsened in this rural area by the moral imperatives which stigmatise access to state and charitable support. Thus, moral capital and local habitus intersect with social, economic and cultural capitals in structuring inequalities.Newcastle Universit

Applying the Verona Coding Definitions of Emotional Sequences (VR-CoDES) in the dental context involving patients with complex communication needs : an exploratory study

This study was conducted as part of a larger collaborative study funded by the EPSRC, between the University of St Andrews and the University of Dundee.Objective The VR-CoDES has been previously applied in the dental context. However, we know little about how dental patients with intellectual disabilities (ID) and complex communication needs express their emotional distress during dental visits. This is the first study explored the applicability of the VR-CoDES to a dental context involving patients with ID. Methods Fourteen dental consultations were video recorded and coded using the VR-CoDES, assisted with the additional guidelines for the VR-CoDES in a dental context. Both inter- and intra-coder reliabilities were checked on the seven consultations where cues were observed. Results Sixteen cues (eight non-verbal) were identified within seven of the 14 consultations. Twenty responses were observed (12 reducing space) with four multiple responses. Cohen's Kappa were 0.76 (inter-coder) and 0.88 (intra-coder). Conclusion With the additional guidelines, cues and responses were reliably identified. Cue expression was exhibited by non-verbal expression of emotion with people with ID in the literature. Further guidance is needed to improve the coding accuracy on multiple providers’ responses and to investigate potential impacts of conflicting responses on patients. Practice implications The findings provided a useful initial step towards an ongoing exploration of how healthcare providers identify and manage emotional distress of patients with ID.PostprintPeer reviewe

The statistics of multi-planet systems

We describe statistical methods for measuring the exoplanet multiplicity function - the fraction of host stars containing a given number of planets - from transit and radial-velocity surveys. The analysis is based on the approximation of separability - that the distribution of planetary parameters in an n-planet system is the product of identical 1-planet distributions. We review the evidence that separability is a valid approximation for exoplanets. We show how to relate the observable multiplicity function in surveys with similar host-star populations but different sensitivities. We also show how to correct for geometrical selection effects to derive the multiplicity function from transit surveys if the distribution of relative inclinations is known. Applying these tools to the Kepler transit survey and radial-velocity surveys, we find that (i) the Kepler data alone do not constrain the mean inclination of multi-planet systems; even spherical distributions are allowed by the data but only if a small fraction of host stars contain large planet populations (> 30); (ii) comparing the Kepler and radial-velocity surveys shows that the mean inclination of multi-planet systems lies in the range 0-5 degrees; (iii) the multiplicity function of the Kepler planets is not well-determined by the present data.Comment: 34 pages, 10 figure