VictorJuiz/thesis huggingface dataset:
Terahertz nonlinear optics & III-V semiconductor nanowires

Most commercially available terahertz spectrometers make use of resonant and non-resonant methods to generate and detect THz radiation. This allows only the low frequency spectrum to be accessed, usually from 0.1 THz to 8 THz, severely limiting the range over which dynamics can be observed. In this thesis, the physics of non-linear optics is exploited and a state-of-the-art terahertz air-plasma generation and detection setup is showcased. THz radiation is generated through non-linear interaction of a two-colour laser field under a dry nitrogen atmosphere producing a plasma, while the detection is accomplished with an Air Biased Coherent Detection (ABCD) technique. The issue of phonon resonances, damage threshold, etalon effects and dispersion of crystals in the THz region are effectively bypassed. The system was specifically designed and built to ensure a robust experimental setup is obtained with several components being made by our physics workshop. Furthermore, significant improvements have been put in place to increase data acquisition speed and maximising signal-to-noise ratio for better results.
III-V semiconductor nanowires are playing an increasingly important role in the field of condensed matter physics. From nanoscale components to highly efficient photovoltaic devices, there is a strong urge to have a solid fundamental understanding of their optoelectronic properties. The air plasma system was used to demonstrate two novel ultrafast THz modulators based on GaAs semiconductor nanowires operating at very high THz bandwidth (up to 40 THz). A significant improvement in modulation depth was achieved, up to 45%, together with picosecond modulation speed. Additionally, to further widen the study of III-V nanowires, this thesis presents a study showing a direct relation between the nanowire length and the frequency of surface plasmon resonance in the terahertz regime. Theoretical calculations have been done to further strengthen this study with the simulations revealing higher electron mobilities than the previously reported values.
Finally, two smaller chapters were dedicated to the the study of the temperature-dependence of the refractive index of c-cut sapphire in the terahertz regime and the optoelectronic properties of hexagonal boron nitride (hBN) at equilibrium state. These provide fundamental insights into the potential usage of sapphire substrates as a replacement to quartz substrates as they are more robust and can support higher temperatures during growth and with the hBN laying the foundation for further avenues of research.

Advisor: Johnston, MB
Herz, LM
Il Cammin di Nostra Lingua: Ruggero Bonghi and the questione della lingua

In Italian history, the Risorgimento represents not only the push for political unification but a process of social change that manifested itself in the efforts to establish a national identity, develop a centralized system of government, and implement a comprehensive system of education. With the promulgation of a standardized language as the most fundamental component of achieving any degree of political, social, or educational cohesion, the nineteenth-century questione della lingua demonstrates – more than in any other period in Italian history – the interconnected nature of linguistic, literary, social, political, and economic cultures. It is precisely in this capacity that an analysis of a historical figure such as Ruggero Bonghi – who operated as a journalist, academic, and politician in equal capacities – provides incomparable insight into the extent to which the questione della lingua shaped every facet of Italian society. As someone who began engaging with the issue from the early 1850s – prior to Italy’s political unification – and continued working on initiatives pertaining to education until the 1890s – over three decades following the nation’s first piece of national educational legislation – Bonghi’s ideas and methods of addressing Italy’s linguistic, literary, and socio-political formation developed alongside the evolution of the language debate itself. This comprehensive study on Ruggero Bonghi and his involvement with the questione della lingua serves to not only elucidate the historical significance of a figure who has been largely overlooked in contemporary scholarship but also demonstrate – through the life and career of one particular individual who operated in both a literary and political perspective – the extent to which the language debate in Italy shaped more than simply the nation’s means of linguistic or artistic expression.

Advisor: Tandello, E
Investigating the role of lineage in the cortical integration of thalamic inputs

Primary sensory cortex receives and integrates inputs from first-order and higher-order thalamic nuclei. First-order inputs convey sensory information from the periphery and exhibit simple response properties, whereas higher-order inputs exhibit more complex response properties, provide contextual feedback, and can modulate first-order inputs. The data presented within this thesis show that the way in which cortical neurons integrate these thalamic inputs, reflects the progenitor cell from which the cortical neurons derive. Within layer 4 of mouse primary somatosensory cortex, excitatory neurons that derive from apical intermediate progenitors exhibit multi-whisker response properties and receive higher-order thalamic input, in a manner consistent with their dendritic morphology. These properties depend upon the expression levels of the transcription factor Lhx2, which when increased, abolishes the higher-order properties of apical intermediate progenitor-derived neurons, and disrupts the induction of sensory-evoked plasticity. These data reveal a lineage- dependent mechanism that establishes the integration and functional contribution of higher-order thalamic inputs within cortex.

Keywords: Cortical development
Sensory processing
Advisor: Akerman, C
Probing dark matter with resonant dynamics of the Galactic bar

This thesis provides a novel dynamical evidence for dark matter by measuring for the first time the deceleration of the Galactic bar. This spin-down of the bar requires the transfer of energy and angular momentum to dark matter by dynamical friction, which not only is in conflict with modified gravity theories, but also imposes constraints on the kinematics and nature of dark matter.
The deceleration of the Galactic bar is quantified using the astrometric and photometric data of the Solar neighbourhood stars recently obtained by the Gaia space telescope. When the bar spins down, the resonant phase-space drifts radially outward through the stellar disk while growing in volume, thereby capturing new stars along its path. Since these trapped stars conserve the action of libration, which quantifies the amplitude of motion around the resonance, the resonant phase-space grows just like tree-rings, adding new layers of trapped stars at its surface. Together with the negative metallicity gradient in the disk, this implies a prominent increase in stellar metallicity towards the resonance centre. We detected this tell-tale signal in the bar's corotation resonance, thus quantitatively proving the bar's slowdown. During the course of this research, we also resolved the long-standing issue on the origin of the Hercules stellar stream and provided a precise estimate on the bar's current pattern speed.
Furthermore, in order to constrain the phase-space distribution of dark matter from the measured slowing rate of the bar, we developed a theory of dynamical friction in the non-linear regime in the slow limit of bar evolution. Using the resonant angle-action coordinates, we successfully modelled the long-term oscillation and saturation of dynamical friction as a result of the non-linear phase mixing in the trapped phase-space.

Keywords: Local stellar kinematics
Dynamical friction
Dark matter
Galactic bar
Resonant dynamics
Advisor: Schönrich, R
Ubiquitous sensing for security in smart homes

In recent years, smart home systems have become increasingly popular. With this increased popularity has come a newfound prevalence of IoT devices with varied sensor functionality in peoples' homes. These types of IoT devices are widely considered to be insecure and many problem-specific solutions have been proposed. However, we argue that the widespread presence of diverse sensors in and of itself can—and should—be used to strengthen the security of smart home environments.
In this thesis, we show that the ubiquity of sensors in modern smart homes can improve the overall security of smart home systems, and that it can enable new security functions. To this end, we introduce two security systems based on ubiquitous sensors already available in modern smart homes. The first is a drone detection system that relies only on radio signal strength information that can be provided by most wireless consumer devices. The second is an event verification system for event-driven smart homes that uses physical event signatures from a multitude of sensors to verify the occurrence of physical events in smart home environments. We then analyze how such systems are affected by two advanced types of attackers: an opportunistic attacker who can wait for and predict attack opportunities, and an attacker who can compromise sensor data to create these opportunities themselves. Finally, we demonstrate that contextual information widely available in smart homes can be employed for context-aware sensor selection due to improved situational awareness.
Extrapolating from the insights gained within this thesis, we argue that ubiquitous sensing has significant potential to provide stronger security properties in smart home systems, as it allows for the combination of fine-grained sensor data with high-level event information. Crucially, this added security can be achieved with existing smart home devices—without impacting their original functions.

Advisor: Martinovic, I
Sámi youth: Identity complexity of an indigenous Scandinavian people

The Sámi people of Scandinavia are a group of indigenous people who for the most part reside within an area known as Sápmi where they engage with their traditional, social and cultural realities while also being full participants in the modern day Nordic existence. When it comes to the Sámi youth, they are faced with a perplexing, extraordinary and distinctive negotiation of figuring out who they are within the overall coexistence of their traditional and modern selves. This thesis seeks to understand, describe, analyse and conceptualise the complex identities of young Sámi indigenous people through a long-term, cooperative, cross-section exploration into the contextual reality of a group of young Sámi existing within a certain time and space in the heart of Sápmi. In this study more than two years worth of ethnographic data collected in the field with young Sámi participants is processed in order to conceptualise the findings into a comprehensive understanding of the Sámi youth complex, multifaceted and dynamic identities. This gave rise to the novel idea and theory of the identity prism and its functionalities as a way forward for discussing and comprehending human identity. The identity prism as a superordinate unit of understanding the self offers an in-depth exposition of the anthropological meaning of the individual identity as created by both the private thought of the self and the social meaning of the shared environments in a dynamic system of interactions, exchanges, reflections, refractions and self-continuity. As part of the overall power hierarchy, the prismatic understanding of identity in terms of the self and the other proposes a way of perception of the modern, multicultural, globalised reality by considering the complex, multifaceted and dynamic nature of human identity.

Keywords: youth
identity prism
Sámi
indigeneity
identity
Regiodivergent nucleophilic fluorination under hydrogen bonding phase transfer catalysis

Chapter 1 briefly introduces the different concepts that have been applied in regioselective catalysis. Non-catalyst controlled and catalyst-controlled methods for inducing regioselectivity are presented. Despite the abundance of fluorination methods, no catalytic regiodivergent nucleophilic fluorination has been recorded in literature to the best of our knowledge. The potential of hydrogen bonding phase transfer catalysis (HBPTC) is then discussed as a viable method to address this problem. Finally, the aim of this thesis is summarised.
Chapter 2 focuses on the efforts taken towards the development of a novel hydrogen bonding-mediated regioselective nucleophilic fluorination. The effect of hydrogen bond donor (HBD) urea organocatalysts on altering fluoride’s anion kinetic preference is demonstrated. It is also presented that HBD urea organocatalysts are capable of not only changing the kinetic regiochemical preference of fluoride, but also induce a thermodynamic product equilibration. First, this chapter focuses on the substrate of choice and then expands on the development and optimisation of a kinetically and thermodynamically controlled regiodivergent nucleophilic fluorination protocol.
Chapter 3 presents the scope of the urea-catalysed regioselective fluorination. Substrate synthesis and the efforts made to expand the synthetic applicability of the developed methodology are also presented.
Chapter 4 describes our attempts towards merging our developed catalytic regioselective fluorination with a kinetic resolution process and presents proof of concept for a novel regiodivergent parallel kinetic resolution.
Chapter 5 gives full experimental procedures and characterisation data for all novel compounds.

Keywords: Regiodivergent
Phase Transfer Catalysis
Nucleophilic Fluorination
organocatalysis
Hydrogen Bonding
parallel kinetic resolution
Advisor: Gouverneur, V
Sexual selection and reproductive trade-offs in caring parents

Successful reproduction depends on individuals both obtaining mates and other reproductive resources, and producing offspring that are capable of surviving to maturity. However, for each of these investments they must draw on a finite pool of resources leading to trade-offs that can influence selection on both competitive and parental investment. As such, species are often characterised by one sex which focuses investment on reproduction and parental care and one which invests predominantly in intrasexual competition. However, there are important cases where males or females are selected to invest heavily in both reproduction and competition. In teleost fish, male-only parental care is the predominant parental strategy, but males typically also compete more intensely for mates than females. In polygynous species, females usually provide the majority of the parental care and invest in reproduction through eggs or foetal nourishment. However, female-female competition for resources that will improve reproduction can also be an important selective force in females and drive the evolution of competitive traits. How do the constraints imposed by a trade-off between reproduction and competition influence selection in these two cases? In this thesis I use a combination of experimental, observational and meta-analytical methods to investigate male-only parental care and female-female competition in fish. By analysing the costs and benefits of paternal care across species I show that care may be sexually selected in males, as females prefer males already guarding eggs, and that this preference in females may improve offspring survival. Using laboratory experiments and field observations on the harem-breeding cichlid, Lamprologus ocellatus, I find support for a trade-off between competition and reproduction in females and show that competition for male contributions to care may influence the outcomes of this trade-off. This work demonstrates that in some cases, relaxation of the trade-off between parental investment and intrasexual competition may select for parents that are both competitive and caring, but in other cases, this trade-off may still impose constraints on the evolution or expression of competitive or parental traits.

Keywords: Female competition
Female choice
Parental care
Sexual selection
Advisor: Green, J
Griffin, A
Rhodium(I) catalysis for intermolecular alkyne hydroacylation and desymmetrisation

This thesis discloses the uses and development of rhodium(I) catalysis within intermolecular hydroacylation and asymmetric [2+2+2] cycloadditions.
Chapter 1 provides a general overview of the key methods and tethering strategies within the field rhodium(I) catalysed hydroacylation.
Chapter 2 describes the diverse synthesis of fully saturated O- and N-heterocycles through a hydroacylation/conjugate-addition sequence.
Chapter 3 uses azine N-oxides as novel directing groups for aldehyde C–H activation within intermolecular hydroacylation reactions.
Chapter 4 presents a short field overview of rhodium(I) catalysed [2+2+2] cycloaddition, before applying this reaction to sulfoximine desymmetrisation.

Keywords: C-H activation
[2+2+2] cycloaddition
Desymmetrisation
Rhodium
Hydroacylation
Advisor: Willis, M
Cognitive foreclosure

Digital markets now fundamentally intertwine with our social and economic lives. International enforcement actions, the US and EU Google cases in particular, demonstrate how from a behavioural economic perspective digital platforms may be beginning to implicate antitrust’s two most fundamental doctrinal components—conduct and market power—in nuanced ways. In short, the regulatory and policy landscape showcases that we may be moving closer towards an antitrust world whereby firms can manipulate consumers’ psychological shortcomings to foreclose competition – a new form of nefarious conduct that might appropriately be termed “cognitive foreclosure”. And because consumers’ cognitive anomalies are the drivers behind this new form of potentially anti-competitive conduct, consumers simultaneously are the potential solution. The behavioural deviation from perfect competition, then, would need to be “substantial” and “sustainable” such that consumers cannot short-circuit these emerging market failures themselves. This Thesis proffers digital platform markets as one context in which such a deviation may be expected to occur and hence warrant antitrust intervention.

Keywords: Economics
Competition law
Antitrust
Behavioural economics
Technology
Advisor: Ezrachi, A
Encountering death in the visual and verbal culture of classical Athens

This thesis builds a picture of culturally-mediated encounters with death in classical Athens. Starting from the premise that death is a mystery, that no one knows what death is and what it is like, I ask two core questions. First, how does visual and verbal culture drawn from the classical period (broadly conceived, to encompass late archaic/early classical and early fourth-century material) generate encounters with death? Second, how does it prompt reflections on the imaginative processes involved in responding to death from the perspective of the living? My approach is by way of case studies, and each chapter covers a distinct medium: literary philosophy, painted pots, tragic drama, temple sculpture, and historiography. My claim is that existential reflection in classical Athens was not confined to a group of elite thinkers and to the texts that they produced, texts that were self- consciously philosophical or that made death the explicit focus of enquiry. Reflections on death were also generated by diffuse and idiosyncratic interactions between individuals and visual or verbal media in a variety of contexts across Athens, and by dialogues between those encounters. Texts and material culture generated and shaped encounters with death, and also generated and shaped epistemological reflections on the imaginative nature of those encounters—upon the immediate and wider cultural frameworks within which such imaginative processes took place. In my conclusion, I expand this claim by considering the wider implications of my thesis when set against a background of intense intellectual and cultural activity in classical Athens.

Keywords: Pots
Cultural History
Temple of Athena Nike
Verbal
Images
Epistemology
Sophocles' Oedipus at Colonus
Texts
Existential reflection
Imagination
Death
Plato's Phaedo
Classical Athens
Thucydides' Plague
Culturally-mediated reflection
Visual
Advisor: Elsner, J
Budelmann, F
Transmission ecology of the gut microbiota in wild mice

Gut microbiota forms an influential part of its host animal’s phenotype, but how variation in gut microbiota arises is poorly understood. Attempts to explain microbiota variation with traits of the host individual, such as physiology or genetics, have had limited success, and an emerging view is that microbiota is greatly shaped by processes operating between individuals, such as transmission of microbes among hosts. Parallel lines of research have shown that both transmission through social contacts and contacts with the natural environment can shape microbiota, but the relative importance of these transmission processes remains unclear. In this thesis, I use novel RFID-tracking technology and molecular microbiota profiling to study microbiota transmission in populations of wild wood mice. Combining methods from network theory and metacommunity theory I study how gut microbiota is transmitted through social contact networks among mice as well as through exposure to broader living environment and other sympatric species therein. I show that social contact networks strongly predict the microbiota composition independent of kinship and shared exposure to the same space and that transmission of microbes from the environment likewise shapes microbiota independently of social relationships, but far less so than social transmission. Further, these two transmission routes seem to transmit different sets of gut microbes, with environmental transmission being influential for aerotolerant bacteria while social networks functioning as a transmission pathway specifically for anaerobic microbes. Finally, I show that social contacts and space-sharing between individuals of different sympatric species can spread gut microbes across species boundaries within a mixed-species rodent community. The key findings are verified with alternative statistical frameworks and replicated in two separate study populations. These findings provide striking evidence for transmission processes in shaping the gut microbiota of wild mammals and emphasize the importance of considering contexts beyond individuals in explaining microbiota variation.

Keywords: social networks
metacommunity ecology
Apodemus
microbiome
network theory
transmission
microbiota
Advisor: Knowles, S
Coulson, T
Firth, J