VictorJuiz/thesis huggingface dataset:
Novel electrocatalysts for ammonia synthesis and hydrogen evolution
Keywords: hydrogen evolution reaction

This thesis explores the activity of single atom metal catalysts on graphene-like support (SACs) and metal nitrides for the nitrogen reduction reaction (NRR). Furthermore, extensive analysis of HER activity and in-situ characterisation are carried out to derive a structure-activity relationship of SACs in the hydrogen evolution reaction (HER).
To that end, a library of single atom transition metals on nitrogen-doped graphene (M-NGs) with comparable compositions is synthesised by a carbon backbone method. Their HER activity is assessed showing Ru-NG and Co-NG to be highly active. The data is correlated with the φ factor, a computationally suggested descriptor for electron density on the metal site constituting the first experimental substantiation of this design principle. Additionally it is found that HER activity on cobalt-containing SACs can be further tuned by changing the coordination environment of the metal via the inclusion of oxygen into the first coordination shell. In in-situ XANES and IR spectroelectrochemical thiocyanate poisoning experiments three distinct active sites are observed and it is suggested that distortion from the square planar Co-N4 environment caused by axial oxygen ligands leads to decreased HER activity.
In the second part of this thesis Co3Mo3N was identified as a potential electrocatalyst for the direct reduction of N2 to N3- in molten chloride eutectics. Based on experimental evidence and previous literature reports, a Mars van Krevelen-type mechanism is suggested for the reaction in which Li+ ions facilitate the activation of dinitrogen, as well as enable participation of the lattice nitrogen of Co3Mo3N.
Practical Bayesian optimisation for hyperparameter tuning
Keywords: Gaussian process
machine learning
global optimisation
hyperparameter optimisation
Bayesian optimisation
artificial intelligence

Advances in machine learning have had, and continue to have, a profound effect on scientific research and industrial activities. We are able to uncover insights contained within large troves of data and develop models to solve problems that seemed infeasible until recently. Before we can train a model, we have to define high-level properties, also known as the model’s hyperparameters. Examples include the architecture of a neural network, the class and parameters of a stochastic optimisation algorithm, the number of trees in a random forest or the kernel in a Gaussian process. One of the key challenges in developing good machine learning models is choosing good values for these hyperparameters.
Evaluating the quality of a set of hyperparameters is usually computationally costly, as it requires us to first train a model specified by the hyperparameters before we can evaluate a score. The computational costs of scoring a configuration means that we want to perform this hyperparameter search with as few trials as possible. Bayesian optimisation (BO) is a general-purpose efficient global optimisation technique that has proven to be remarkably effective for many expensive optimisation tasks, including hyperparameter tuning. This thesis brings together multiple contributions aimed at making BO more practically applicable, focussing on uncertain-input measurements as well as model hyperparameter tuning.
The case of data with input noise is relevant when we are modelling (or finding extremal values of) a quantity defined on a spatial grid. We undertake a comparative study evaluating existing uncertain-input GP methods, and develop a novel approach based on the unscented transform that outperforms existing uncertain-input methods.
We then address the question of parallelising BO to make optimal use of available computing resources. We develop a novel class of methods for asynchronous parallel BO, and demonstrate empirically the benefits of our approach, as well as more generally showing the advantages of asynchronous over synchronous BO.
Finally, we propose a new framework for dealing with a mixture of categorical and continuous hyperparameters. With few exceptions, model hyperparameters consist of both categorical and continuous variables, but BO approaches have mainly focussed on continuous search spaces. We present a novel framework that combines multi-armed bandits with continuous BO methods and leverages each of their strengths to achieve state-of-the-art performance on real-world optimisation tasks.
A generic subject: The interplay of morphosyntax and the human conceptual system
Keywords: acquisition
psycholinguistics
kind reference
genericity
morphosyntax

How can we account for our extensive knowledge about the world, given that we individually experience very little of it? This thesis considers the mechanisms involved in the acquisition of generic statements. One approach to explain this feat, in light of our limited direct experience of instances of kinds, suggests that language gives us the tools to go beyond our environment. This thesis argues that variation in the morphosyntactic make-up of a generic subject can affect our understanding of how properties are linked to a kind. One significant challenge for the acquisition of generic subjects is the lack of an overt marker, which means that no generic subject unambiguously encodes genericity. Still, generic subjects can easily be interpreted generically in novel concept acquisition tasks instead of being assigned episodic reference. Experimental research has addressed this puzzle from developmental perspectives Gelman et al. (2010); Prasada (2000); Cimpian et al. (2011) and quantificational ones (e.g. the covert generic operator gen, Carlson, 1989; Krifka et al., 1995). The findings are novel as this thesis pays special attention to previously less investigated singular generic subjects. It considers number and definiteness and their links to the human conceptual system as the main variables of the make-up of generic subjects. Comparing the morphosyntactic differences of bare plural, indefinite singular, and definite singular subjects experimentally shows that they each raise expectations of tight category-property links, modulated by other available cues. To better understand the developmental trajectory of generic subjects, this thesis compares adult and child participants’ responses to learning about novel kinds. This includes indefinite and definite singular subjects, for which children receive comparatively little input and which are normally deemed highly ambiguous between generic and episodic interpretations. This thesis concludes that our conceptualisation of novel kinds is dependent on morphosyntactic cues, but crucially, this is further modulated by additional information, such as pre-existing world knowledge, phonological or visual cues.
Voices in the dark: energy and the politics of living in refugee camps
Keywords: politics of living
forced migration
ethnography
renewable energy
refugee camps

This thesis examines two central issues: firstly, how energy is valued and perceived by refugees and humanitarian practitioners, and, secondly, how energy is accessed and governed in refugee camps. It draws on empirical evidence collected from households, enterprises and humanitarian operations in Kenyan and Rwandan camps to argue that energy is of critical importance for refugee life. The thesis shows how energy is valued for social and practical reasons, with refugees often finding and securing their own access to energy. Small and informal enterprises within camps are the main providers of energy access for refugee homes and businesses, especially when institutional actors fail to meet needs. Within community facilities and humanitarian operations, provision of energy is intermittent and often absent. While refugee users and enterprises are aware of the value of energy, humanitarians undervalue its importance. Using a theoretical framing centred around the politics of living, the research critically questions the role of humanitarian agencies and argues that energy in camps is always political. In other words, humanitarians make choices about the distribution of resources and access to energy in a way that restricts energy activities and this has notably political effects.
The reality of Eternal Recurrence
Keywords: Eternal Recurrence
Reality
Metaphysical
Interpretation
Origin of science
Nietzsche
Exegesis

This thesis presents a novel account of Nietzsche’s idea of Eternal Recurrence of the Same (ER). I argue that ER should be understood neither as theoretical cosmology, nor hypothetical thought-experiment, but as metaphysical interpretation of reality.
The thesis is composed of four chapters. In chapter 1 I argue that certain motivations underlying the consensus views on how to interpret ER are unfounded assumptions that need not be made. I discuss these motivations and their discursive consequences with a view to opening the way for metaphysical, non-theoretical understandings of ER. Thus, I dispel possibilities that ER is not literal by removing the assumptions I believe ground them.
In chapter 2 I examine Nietzsche’s attitude to science in order to show that his criticism for all theoretical science as an adherent of the ascetic ideal leads to the conclusion that ER could not be a theoretical account of the universe. Following from this, I argue that the unpublished “proofs” for ER and zeitatomenlehre note are not supporting a physical theory but are alternative experimental interpretations of reality set within a scientific paradigm.
In chapter 3 I move to an outline of Nietzsche’s metaphysical and interpretative way of understanding reality, specifically in relation to his appropriation of Heraclitan ideology to describe the world metaphysically, and use of Dionysos through a particular interpretative lens. I show that the Heraclitan and Dionysian are linked and are linked in relation to ER, pointing towards the sense in which I argue one ought to understand ER: as a metaphysical interpretation of reality, graspable only through the Dionysian perspective.
In chapter 4 I turn to a close exegesis of the key passages on ER to show that they evidence a metaphysical ER, set within Dionysian interpretation of reality. I argue that close analysis is required to draw out the way Nietzsche expresses the Dionysian interpretative nature of ER in vividly depicting the experience of coming to realise it.
Intensity-dependent effects in the Accelerator Test Facility 2 and extrapolation to future electron-positron linear colliders
Keywords: wakefields
CLIC
short-range
PLACET
CERN
ATF2
GdfidL
ILC
Intensity-dependent effects
long-range

The high energy physics community considers electron-positron linear colliders in order to complement the results obtained at the Large Hadron Collider. In order to achieve the design luminosity above 1034 cm-2s-1, these linear colliders require a nanometer beam size at the Interaction Point (IP). The electron and positron beams are transported inside the Beam Delivery Systems (BDS) from the linear accelerators (LINACS) to the IP. The beam is focused by two strong quadrupoles in the Final Focus System (FFS) where chromatic effects and aberrations are corrected thanks to a local chromaticity correction scheme. Two projects are being studied now, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). Their FFS and the local chromaticity correction are being tested at the Accelerator Test Facility 2 (ATF2) at KEK in Japan. This test facility has been studying this matter for more than 20 years, achieving two of its main goals: obtaining a stable beam size around 37 nm at the IP and an orbit stabilisation with a nanometer precision at the IP. However, these goals were achieved at 10% of the nominal beam intensity. Indeed, when increasing the beam intensity, the beam becomes more unstable and its size grows. This is mainly due to wakefields in the ATF2 extraction line. Ultra-relativistic electrons going through the beam pipe interact with the surrounding structure and create an electromagnetic field, the wakefield. This field interacts with electrons inside the same bunch (short-range wakefield) but also with electrons in the following bunches (long-range wakefield). In ATF2, one considers that bellows, flanges and cavity BPMs are the main sources of wakefield. This effect results in increasing significantly the beam size at the IP. This thesis will show the impact of these intensity-dependent effects inside ATF2 and how to mitigate them. It will also show the impact of the same intensity-dependent effects in future electron-positron linear colliders, the ILC and CLIC.
The role of YAP and cell of origin during the progression of pancreatic neoplastic lesions to invasive ductal adenocarcinoma
Keywords: KRAS
pancreatic cancer
YAP
Pancreatic ductal adenocarcinoma
oncogene
Genetically engineered mouse model

Pancreatic ductal adenocarcinoma (PDAC) is considered one of the most fatal cancer types with a very low survival rate. The development of dysplasia in normal ductal epithelium is the initiating step of the disease, which then undergoes multiple grades of pancreatic intraepithelial neoplasia (PanIN) lesions before developing into invasive adenocarcinoma. KRAS mutations occur during early stages of malignant transformation and act as a critical event in both initiating and maintaining PDAC development. Alongside, an oncogene, YAP, is emerging to play a role in the facilitation of neoplastic precursor lesions to invasive cancer in KRAS mutated pancreas. Canonically, YAP’s activation is negatively regulated by the tumour suppressive Hippo pathway by inhibiting the protein’s nuclear localisation. In order to elucidate the mechanism by which YAP promotes early progression of PanIN lesions, I explored the association of YAP with the components of KRAS-mediated MAPK signalling pathway. Firstly, I show an association between YAP and phosphorylated ERK1/2 both in pancreatic cancer cells and low-grade PanIN lesions of Kras-mutated mice. In these PanIN lesions, I demonstrate the nuclear expression of YAP to be heterogeneous and associate this with PanIN lesions’ origin from different cell types. I show ductal-derived precursor lesions in Kras mutated mice and PDAC in human samples to positively correlate with high nuclear expression of YAP. To further understand this role of YAP in ductal-derived PDAC, I establish YAP depleted 3D pancreatic organoid system isolated from ductal cells of Kras mutated mouse pancreas. From this study, I present the potential role of YAP as a useful marker to identify ductal-derived PanIN lesions and PDAC.
miRNA biogenesis and developmental phase transition in the liverwort M. polymorpha
Keywords: HASTY
M. polymorpha
rhizoid development
DICER-LIKE1
reproductive phase transition
miRNA biogenesis
gametangiophores

microRNAs (miRNAs) are important regulators of gene expression and plant development. Some miRNAs, together with their target genes, have conserved functions among the major land plant lineages. An important miRNA-regulated developmental pathway is the ageing pathway that controls the juvenile to adult transition and the vegetative to reproductive transition in flowering plants. This thesis presents evidence that the function of HASTY (HST), a regulator of the ageing pathway through miRNA processing in the flowering plant Arabidopsis thaliana, is conserved in the bryophyte Marchantia polymorpha. MpHST negatively regulates the timing of the reproductive transition in male M. polymorpha, which is consistent with AtHST inhibiting phase transitions in A. thaliana. In contrary, MpHST positively regulates the reproductive transition in female M. polymorpha plants. This suggests a sex-specific function of MpHST in the dioecious liverwort and presents a new aspect of phase change regulation. This thesis also reports that another core regulator of miRNA biogenesis, DICER-LIKE 1 (DCL1), controls growth, morphogenesis and organ differentiation through miRNA processing in M. polymorpha, as it does in angiosperms. Moreover, a novel role was discovered for MpDCL1 – MpDCL1 represses the reproductive phase transition in the absence of the normally required far-red light inductive signal. This occurs in a sex-dependent manner – similar to the requirement of MpHST to delay phase transition in male plants, MpDCL1 represses phase change under non-inductive conditions in male plants. I propose that miRNAs, including sex-specific miRNAs, are involved in controlling phase change in the early divergent embryophyte M. polymorpha. This suggests that HST-regulated phase change operated in the common ancestor of liverworts and angiosperms, one of the first land plants.
Degradation-aware optimal control of grid-connected lithium-ion batteries
Keywords: Degradation
Techno-economic assessment
Optimisation
Lifetime prediction
Lithium ion batteries

With the accelerating deployment of intermittent renewable energy sources, the need for balancing on the power system is ever increasing. Even though lithium-ion (Li-ion) batteries are not yet cost-competitive with other solutions for most applications, the number of grid-connected Li-ion batteries is expected to increase sharply in the coming years.
Due to the sunk costs of the upfront investment, understanding the lifetime of a battery is crucial for the business case. Nevertheless, predicting the lifetime of a battery is not straightforward. Many degradation mechanisms reduce the total energy which can be stored in a battery, thus decreasing its lifetime. This thesis begins with an extensive literature review into the causes of this battery degradation, both qualitatively and quantitatively. Various physics-based degradation models are combined into one flexible battery degradation model which is used to study which mechanisms cause degradation under which operating conditions.
The model is then carefully formulated for optimisation in a power system application. While a battery makes revenue from trading power on the day-ahead market, it degrades. The physics-based model is used to optimise the usage profile of the battery, determining when to buy power (charging the battery) and when to sell (discharging the battery), in order to maximise revenue while minimising degradation. These optimal profiles are compared to profiles which are obtained using state-of-the-art economic optimisation models.
Finally, Li-ion batteries were cycled with different usage profiles in an experimental validation. The battery degradation was measured monthly, while the revenue each battery could make was also tracked. It is shown that the usage profiles determined by the physics-based model outperform the profiles from conventional optimisation models. The revenue can be increased by 17% while at the same time decreasing the degradation by 31%. This implies that such physics-based models can increase the revenue and the lifetime of grid-connected batteries, increasing the net profit by over 300%.
Building synaptic plasticity rules that learn generalisation-apt neuronal architectures
Keywords: pattern separation
synaptic plasticity
memory
generalisation

One of the hallmarks of intelligent behaviour is the ability to generalise, i.e. to make use of information from specific experiences to solve unencountered scenarios. Here I focus on the generalisation task of transitive inference, which tests the ability to infer that stimulus A is preferable to C, based solely on previous training that A is preferred over B and B is preferred over C. Such inference tasks are thought to be performed by hippocampal-entorhinal circuits and rely heavily on recurrent and conjunctive connectivity to bind associated stimuli. Notably, a 3-layer recurrent neural network model called REMERGE (Kumaran & McClelland, 2012) can solve the transitive inference task through recall dynamics in a circuit that also relies on recurrent and conjunctive connectivity. However, it is not clear how the architecture could be constructed by a learning rule. Here, I develop a biologically plausible non-linear Hebbian plasticity rule to build REMERGE’s connectivity starting from an all-to-all architecture. I separate the problem of learning the complete architecture into two parts: 1 - how to learn input connections and 2 - how to learn output connections. For the first part, I design a learning rule that forms connections from coincidentally stimulated inputs to separated conjunctive units in the hidden layer. Learning the second set of weights requires a more complex rule that takes into account a reward signal if the choice was correct, allowing only connections that lead to reward to be strengthened. Ultimately, the results predict a reorganisation of recurrent activity flow across training by potentiating feedforward and feedback connections in hippocampal-entorhinal stimulus pathways, and the need of reward-dependent plasticity to form connections to response neurons. My model bridges the gap between conceptual models of generalisation and how to learn them through biologically plausible plasticity rules.
Gilded wreaths of the late Classical and Hellenistic periods
Keywords: origin
oak
wreaths
wire
analysis
Gilding
ancient Greek world
technology
pigments
gold leaf
kaolin
significance
textiles
Scanning Electron Microscope
ivy
XRF
Hellenistic
myrtle
copper
Raman

This thesis is the first major piece of research in the last 30 years to focus specifically on gilded wreaths. It is the result of close study of some 170 wreaths in Greece and Southern Italy, dating to the Late Classical and Hellenistic periods. This allowed the wreaths to be classified into seven main types, the earliest of which were found in Macedonia in Northern Greece. Wreaths of a different design, making more use of clay and less of copper, are also presented, which are mainly from central and southern Greece. The wreaths from Southern Italy make a useful contrast, similar in many ways to the material in Greece, but with some resemblance to earlier items from Italy such as wreath-diadems. The materials used to make the wreaths have been analysed with hand-held XRF and, in some instances, a Scanning Electron Microscope; the results are presented here for the first time. Very little analytical work has been done before on gilded wreaths, which made use of a range of materials including copper, gold and clay. Most of the wreaths are in fragments and not on view in the museums, and so are described in some detail, with illustrations, in the catalogue. The wreaths raise intriguing questions as to why they were buried in graves but appear not to have been used in sanctuaries. They are found with males and females, young and old - did they have some sort of apotropaic function, or did they mark the status of the individual? Could they have marked various stages in life (rites de passage), such as adolescence, marriage, giving birth and death? Gilded wreaths are found often in multiples in Macedonia, sometimes with solid gold wreaths, raising further questions as to why the deceased and their families felt it necessary for them to be buried with more than one wreath. Did the wreaths have a religious significance, or were the relatives simply seeking to show their wealth in consigning this valuable material to the grave? Is it possible to tell whether their use was solely funerary, or could they have been worn also by the living? Some answers to these many questions are put forward.