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Topics in Model Evaluation and Comparison
No full textStatistical modelling of data in real-world scenarios often require models that can
accommodate variability and dependence in a plethora of different ways. Within
the generalized linear modelling framework, various extended models are available
to address these commonly found problems. In this context, goodness-of-fit
assessment is pivotal for ensuring reliable inferential results. This includes, but
is not limited to, graphical tools, which can be helpful when deciding whether a
data sample can be a plausible realisation of a fitted model. In this thesis, we focussed
on the development of diagnostic measures and the comparison of different
modelling approaches, when applied to diverse types of data.
Initially, we present an overview of diagnostic analyses stemming from generalized
linear models, whilst illustrating different tools using two case studies from experiments
in ecology and agriculture. Then, we extend the graphical model selection
method known as half-normal plots with a simulated envelope. The simulated
envelope is such that, under a well-fitted model, the majority of points should
fall within its bounds. Nonetheless, closely related models tend to produce very
similar graphs. We propose a new distance-based framework that acts as an added
quantitative summary to the half-normal plot with a simulated envelope. This new
measure can effectively determine the most appropriate model when closely related
models are included. An extensive simulation study was carried out taking into
account many different scenarios. The results showed that the distance framework
exhibits robust performance in finding the true model and is comparable to BIC;
in some instances, it even displays superior efficacy.
Finally, we present a comparative analysis of different modelling frameworks applied
to interval-censored longitudinal data, which is bounded in the interval (0, 1).
We considered three approaches, where the first and second involved mixed and
marginal models using a transformation of the interval-censored response, and
the third incorporated the interval-censored nature in the likelihood. We found
that the accounting for the interval-censored nature of the data improved model
goodness-of-fit. However, the conclusions drawn from all three approaches were
qualitatively similar
The self-assembly of Glucagon
No full textGlucagon is a peptide that is known to undergo self-assembly at acidic pH resulting in fibrillar structures. While much is known about the morphology and kinetics in relation to the formation of these fibrillar structures, there is relatively little known about the self-assembly pathways that lead to these end state structures. Small changes in solution conditions are known to have dramatic effects on self-assembly of peptides and this is the case for Glucagon.
Glucagon has been shown to assemble via two competing pathways at acidic pH but the complexity of this assembly does not rest solely on the competition between the two assembly pathways. Oligomeric intermediates play a pivotal role in Glucagon’s fibrillogenesis at acidic pH. To date, there has been no detailed description of the changes in the oligomeric species that are present during the lag-phase for fibrillating Glucagon at acidic pH. This thesis aims to address this shortcoming by providing a detailed description of Glucagon’s lag-phase at pH 2.5.
Here an analysis of the lag-phase for Glucagon at pH 2.5 is presented using ThT assays, SE-HPLC, SDS-Page, Taylor Dispersion Analysis (TDA), Static Light Scattering (SLS) and Dynamic Light Scattering (DLS). Kinetic measurements from ThT assays demonstrated a reasonably well-defined lag-time for an assembly process that is fundamentally stochastic. Results using multiple techniques (SE-HPLC, SDS-Page, TDA and Light Scattering) showed that the starting point for the assembly process was mostly monomeric but had a small proportion of oligomeric content.
The effectiveness of various analytical techniques was examined by monitoring assembly during Glucagon’s lag-phase at the level of oligomer. It was found that while TDA was somewhat effective at monitoring changes in oligomerization, techniques such as SE-HPLC were shown to be ineffective in describing Glucagon’s lag-phase at the level of oligomer. This thesis also demonstrates that SLS and DLS are the best techniques to examine Glucagon’s lag-phase at the level of oligomer compared to the other techniques used.
This thesis showed how SLS data can be deconvoluted into a 5-component distribution of the species that are present in the self-assembling system and how this
allows for mechanistic insights into Glucagon’s assembly process during the lag-phase. Changes in the distributions of the oligomeric content were shown during the assembly process for Glucagon at pH 2.5. Analysing changes to these distributions a plausible description of the oligomeric distribution of the critical nucleus that precedes fibril formation was deduced. This thesis shows how a shift in the proportion of oligomers between two low order populations coincides with the nucleation step with the emerging population providing a size distribution for the critical nucleus. The kinetics for the self-assembling system was analysed and the most transient species occurring during the aggregation reaction were identified. The kinetic description allowed for the identification of the most likely rate limiting step for the aggregation reaction.
Glucagon’s self-assembly at pH 3.6 was studied using acetate buffers. Kinetic experiments from ThT assays demonstrated that variation of both ionic strength and the buffering cation profoundly affected Glucagon’s self-assembly. TEM data showed that stable amorphous aggregates can form under low ionic strength conditions that are not precursors to any fibril formation. The ThT fluorescent probe was shown to accelerate the assembly of these amorphous aggregates. At higher ionic strengths Glucagon was shown to fibrillate at pH 3.6 Specific interactions with fibrillating Glucagon at pH 3.6 were observed for acetate buffers using sodium, potassium, and magnesium cations, leading to varying degrees of peptide stabilization
Navigating the Regulatory Landscape of Voluntary Sustainability Standards in International Food Trade: A Multilateral Interplay
No full textVoluntary sustainability standards (VSSs) are non-mandatory criteria designed to foster sustainable practices throughout the global supply chain. These standards are particularly prevalent in the agri-food sector, where they aim to support wider public policy objectives such as sustainable food production, animal welfare, healthy lifestyle, and labour conditions. Significant challenges arises from the fact that VSSs, despite their voluntary nature, they often impose mandatory effect in the global supply chain. They also often lack easily-identifiable features of the product themselves. These creates systematic problems for the global food trade system, where conventional regulation address governmental measures on goods with specific inherent characteristics that can be clearly identified in the final product. This article explored the interrelationship among private VSSs, national regulations and international treaties within the agri-food industry. It highlights ambiguity surrounding the regulatory framework for VSSs under the WTO law, noting the absence of a consensus on how relevant provisions should be interpreted. Despite the diversity among various VSSs, VSSs, this article argues for the potential for harmonization and equivalence among VSSs. By aligning various VSSs and with technical regulations, it is possible to strike a balance between trade liberalization and promotion of sustainable practices
On the Effective Implementation of Control Structures to Multi-DoF wave Energy Converters
No full textMaximising energy output through advanced control strategies is pivotal for the economic viability of wave
energy converters (WECs). However, most existing literature
primarily focuses on theoretical case studies, where WECs are
constrained to operate in a single degree of freedom (DoF).
This simplification is made due to the added complexity of
optimizing across multiple DoFs. In this study, we assess the
necessity of incorporating multiple DoFs within the control
framework, evaluating its effectiveness in a numerical simulation environment that replicates WEC performance across
multiple DoFs. To provide a basis for comparison, we contrast
the conventional PI controller with the innovative LiteCon
controller. Our study reveals two key findings: (i) Single DoF
control may suffice when the primary DoF of the power takeoff system is accurately identified, and (ii) the straightforward
LiteCon controller outperforms the traditional PI controller by
a significant margin
Advancing an Embodied Understanding of Accessibility for Persons with Disabilities
No full textThe UN Convention on the Rights of Persons with Disabilities (CRPD) includes accessibility among its general principles and articulates it in Article 9. Further, accessibility obligations are included in several other provisions of the Convention. In that regard, the CRPD recognizes the significance of accessibility as an enabling factor, and as a precondition for persons with disabilities to participate fully in society. Embracing an interdisciplinary approach, and on foot of arts-based research in the form of inclusive dance, this article aims to re-construe the inherent dimensions of accessibility as a normative concept. It puts forward an ‘embodied understanding’ of accessibility with a view of advancing existing legal analysis and adding to traditional cognitive ways of knowing. On the whole, this article identifies three inherent and intertwined facets of such embodied understanding of accessibility—namely, respect for difference, collaboration and care, and layered complexity. It argues that this embodied understanding may help achieving the overall paradigm shift of the CRPD
Numerical and experimental multi-linear modelling of wave energy devices
No full textThe escalating demand in global energy requirements and the soaring price of traditional
fossil fuels, in combination with global awareness to follow a pathway toward
decarbonisation, are fuelling research and development into novel technologies to
harness renewable energy sources. Ocean wave energy, a significant and untapped
source of renewable energy, if economically viable, can make a promising avenue for
sustainable energy generation. In the drive for the development and more efficient
operation of wave energy converters (WECs), effective control systems, which can
maximise converted energy for a given capital cost, are crucial. Model-based control
systems contribute to the majority of energy-maximising control systems of WECs,
with a need for a suitable mathematical model. Physics-based models, numerical
simulations, full-scale tests, or laboratory-scale tests can be used to develop WEC
models, each presenting distinct methodologies and challenges, yielding models
with a diverse range of accuracy. The effectiveness of model-based control relies on
the precision of the WEC model upon which the controller is based, given that WEC
controllers have shown considerable sensitivity to inaccuracies in their underlying
models. Among the distinct WEC modelling techniques, the determination of
models from data (using either physical or numerical experiments) is an effective
route to derive representative (linear and nonlinear) WEC models. In this thesis,
both numerical wave tank (NWT) and physical wave tank (PWT) experiments are
considered to estimate a range of adequate linear WEC models capable of meeting
the requirements of a control system by the employment of the proper test signals
(specific to each test setup) to cover the full operational space of the system. Many
uncertainty parameters in the data-driven models with sources differing significantly
in NWT and PWT experiments, may hinder accurate WEC model determination
for efficient (model-based) control strategies. Within this scope, the current study
considers the range of tests that can be performed, the uncertainty sources, and
the range of post-processing techniques that can be applied in NWT and PWT tests
for a point-absorber type system, with an aim to get the most realistic hydrodynamic
WEC models. Moreover, in NWT testing, a comprehensive representation of input
signal synthesis and characterisation is carried out, to provide sufficient fidelity
in Computational Fluid Dynamics (CFD)- based NWT tests and, in PWT testing,
specific focus is directed towards the quantification of uncertainty and external
disturbance, specifically tailored to the PWT under study, with the corresponding
effects are mitigated by applying effective data-processing steps.
Multi-linear hydrodynamic WEC models (obtained either from NWT or PWT
testing), serve as a starting point for model-based linear WEC controller synthesis.
Finally, with a view to robust WEC control, a (single) nominal model and uncertainty
bound are quantified from multi-linear models obtained from NWT tests, and robust
control results are provided to demonstrate the efficacy of the modelling and
control philosophy
Recognizing professional development of mathematics and statistics learning support staff
No full textTutors play an important role in effective Mathematics Learning Support, and ensuring good initial training and development is key. Typically, in the UK and Ireland, tutors do not gain any formal recognition for the training they receive. This paper details a four competences model of training for tutors and presents the analysis of feedback from 11 tutors and two staff involved in piloting the model at two institutions. The model, which is informed by professional development guidelines, consultation across the mathematical sciences community, and enabled by a national Mathematics Learning Support Network, provides immediate recognition of the professional development undertaken and is amenable to formal accreditation. A structure of four digital badges is used to assign immediate value to the training and development of tutors. To add further value for tutors, a capstone tutor badge has been established for those completing all four competences. Thematic analysis of feedback from the piloting of the model identifies three overarching themes: the importance of community, developing as a professional, and motivating and enabling professional development. Although primarily of interest to those involved in Mathematics Learning Support, the innovative structure of the model and the insights gained from its piloting are such that it offers potential for genuine transferability across other subject disciplines
‘A Joycean Smutmonger’: Echoes of Joyce in Máirtín Ó Cadhain’s Rural Modernism
No full textSince its publication, critics of Máirtín Ó Cadhain’s Irish-language masterpiece Cré na Cille (1949; Graveyard Clay) have consistently namechecked James Joyce’s Ulysses (1922), usually for the sole purpose of conveying its perceived difficulty and/or vulgarity. Indeed, Cré na Cille was first refused publication because, in Ó Cadhain’s words, it was too long and too ‘Joycean’. Ó Cadhain himself evidently saw his work as existing in dialogue with his renowned progenitor and during a late lecture revelled in retelling an overheard conversation in which he was described as nothing more than a ‘Joycean smutmonger’. This article goes beyond such surface-level comparisons to unpick how Ó Cadhain proffers a radical portrayal of rural Irish modernity to compare with Joyce’s predominantly urban equivalent. It argues that Ó Cadhain’s characters, like those found in Joyce’s oeuvre, are consistently forced to navigate the forces of tradition and modernity, which existed at the heart of rural Irish society in the mid-twentieth century. This essay will first compare how Ó Cadhain and Joyce treat the predicaments of a young woman preparing for emigration in their respective short stories ‘An Bhliain 1912’ and ‘Eveline’, before moving on to treat Ó Cadhain’s experiments in form and language in Cré na Cille. In particular, it will examine such experimentation in the context of his lasting obsession with Finnegans Wake (1939), as evidenced by his stated belief that he ‘could write a work like Finnegans Wake’. Informed by recent developments in ‘alternative modernities’, this essay attempts to offer a nascent definition of what might be signified by ‘rural modernism’ in an Irish context
New Cisalpine Celtic inscriptions from canton Ticino (CH)
No full textA presentation of two hitherto unpublished Cisalpine Celtic graffiti from Ticino, Switzerland
(LexLep TI·55 and TI·56).
During an autopsy trip to Ticino, Switzerland, for the research project Celtic Language and
Identity in Northern Italy and the Alpine Region in October 2023,1
I was shown two unpublished graffiti, written in the Lepontic alphabet, from find places in the canton – one in storage at
the Ufficio cantonale dei beni culturali in Bellinzona, one on exhibition in the Museo Castello
di Montebello.2 The present short paper presents the inscriptions, which have also been included
in the digital edition Lexicon Leponticum (LexLep) with the sigla TI·55 and TI·56
Hamstring Strain Injury Prevention: Current Beliefs and Practices of Practitioners Working in Major League Baseball
No full textHamstring strain injury (HSI) is the most frequently sustained injury in Major League Baseball (MLB). However, the beliefs and practices of practitioners working in MLB regarding HSI risk factors and prevention strategies in baseball athletes have not been documented.
Objective
To document the current beliefs and practices of practitioners working in MLB regarding HSI prevention.
Design
Cross-sectional study.
Setting
Major League Baseball via an online survey.
Patients or Other Participants
Athletic trainers, physical therapists, and strength and conditioning coaches working in MLB during the 2021 season.
Data Collection and Analysis
An online survey was conducted, with participants completing the survey once. Questions pertained to risk factor identification, the use and perceived effectiveness of prevention strategies, and barriers to implementation. Descriptive statistics were calculated for each question.
Results
A total of 91 responses were received featuring respondents from 28 of 30 MLB organizations. The perceived most important intrinsic risk factors were tolerance to high-speed running for first-time HSI and previous HSI for recurrent injury. The perceived most important extrinsic risk factor for both first-time and recurrent HSI was internal communication between staff. The perceived most effective prevention strategies were managing overall workload, regular exposure to high-speed running, and periodization. The most used prevention strategies were core or lumbopelvic strengthening, traditional resistance-training exercises, and managing overall workload. Approximately half (53%) of respondents reported barriers to effective implementation of HSI prevention strategies, including player and coach buy-in, compliance, workload management, and scheduling.
Conclusions
This was the first survey to investigate MLB practitioner beliefs and practices regarding HSI prevention. Responses from practitioners regarding their beliefs about risk factors and appropriate prevention strategies varied, and discrepancies existed between the perceived most effective strategies and those most frequently used