VictorJuiz/thesis huggingface dataset:
Shock and release of tantalum studied via molecular dynamics and femtosecond x-ray diffraction
Keywords: shock physics
molecular dynamics
x-ray diffraction
tantalum
plasticity

The response of solid matter to shock compression is complexified considerably by its strength, or its ability to withstand shear stress. Strength is challenging to measure experimentally under shock conditions and even harder to model, due to its being an extremely complicated function of the loading conditions. Our understanding of material strength and the way it manifests under dynamic loading thus remains, to a great extent, incomplete. This work presents studies of two phenomena arising from strength under the conditions of shock compression and release by means of multimillion-atom molecular dynamics simulations and femtosecond x-ray diffraction. The role of shock-induced grain interactions is first explored via simulations of elementary polycrystals. Such interactions are found to control the plasticity mechanisms activated under shock compression and the limiting shear stress state to which the polycrystal settles in the wake of the shock. A combined experimental-computational study of plastic-work heating under the conditions of shock release is then presented. An algorithm for extracting the temperature of released samples from their diffraction image is derived and verified on synthetic data. When applied to experimental data, the algorithm shows that the temperatures of shock-released tantalum foils vastly exceed those expected from a conventional isentropic release. The underlying microphysical processes responsible for the heating are then interrogated via large-scale simulations of crystals under shock and release. A heat equation is used to identify plastic-work heating owed to the sample’s exceptional strength during its rapid release as the culprit, thus challenging the conventional assumption that shock release is a universally isentropic process.
Next generation dark-field microscopy: from high-speed single particle tracking to label-free imaging
Keywords: label-free imaging
high-speed single particle tracking
dark-field microscopy
tethered particle motion

This thesis details the improvement and implementation of a total internal reflection dark-field scattering microscope, in terms of pushing the boundaries of its sensitivity and spatiotemporal resolution, to study the bending flexibility of DNA on biologically important length scales. Furthermore, by observing the scattering intensity response to the reconfiguration of the electric double layer on a substrate, dark-field microscopy has been brought into the field of label-free imaging, establishing a novel contrast mechanism. Specifically, Chapter 2 describes the basics of light scattering and tethered particle motion and elaborates various designs to apply total internal reflection-based dark-field microscopy. After characterisation and quantitative comparison regarding their signal-to-noise ratio and background noise suppression performance, high- speed tracking of 20 nm diameter gold nanoparticles with few nanometre localisation precision and few microsecond exposure time is demonstrated with the optimised set-up. Chapter 3 combines this imaging capability with tethered particle motion to directly address the mechanical properties of double-stranded DNA shorter than 160 base pairs without significant volume exclusion effect. Chapter 4 takes the advantage of the short DNA tether functionalised with a charged gold nanoparticle which behaves like a nanospring in the presence of an alternating electric field, to measure the electrophoretic force and charge with femtonewton sensitivity. In the last chapter, total internal reflection-based dark-field microscopy is applied to optically image the electric double layer around nanostructures on an ITO substrate based on the potentiodynamic optical contrast mechanism and thus proves its potential, at least in principle, for label-free imaging at the single molecule level.
Between expectations of frictionless mobility and complex realities. Decisions and experiences of German professionals living and working in Britain.
Keywords: Germany
family migration
migration
UK
mobility
professionals
highly-skilled
developed country
EU

The aim of the DPhil thesis is to explore the particular case of the migration decision-making and experiences of German professionals in Britain. Not only is the mobility of professionals an integral factor for the economies, but it is also promoted and facilitated on the national and EU levels. Mobile professionals may be regarded as the ideal type of mover: invisible, young, highly-talented, competent in the local language, well-integrated. Indeed, due to these characteristics, they are assumed to integrate easily and enjoy the mobile lifestyle. However, some empirical studies highlight the complexities of this mobility suggesting that even those highly-desired mobile professionals are not immune to challenges, which may lead to instability, insecurity, and stress, suggesting that such migration is not as frictionless and easy as may be suggested.
In this thesis, I aim to address these aspects. Based on the qualitative analysis of 64 interviews with professionals and some of their partners, I draw our attention to the complexities in the lives of these privileged mobile professionals. On the one hand, German professionals moving to Britain may exemplify the notion of frictionless mobility, as they enjoy the right to move freely, they are educated, young, competent in the English language, employed according to their qualifications, and well-integrated. On the other hand, their mobility is more constrained than it first appears and their migratory experiences are not immune to challenges or unanticipated obstacles, such as Brexit. Furthermore, having partners or children may present additional challenges for the households, and not only impact the relocation strategies of the household but also impact the migratory experience of each partner. Discussing these aspects contributes to our understating of the particularities of the experiences of mobile professionals relocating between affluent countries, as well as highlights the realities and complexities of mobility and the lives of these highly-desired professionals.
On some computations of refined Donaldson-Thomas invariants
Keywords: Donaldson-Thomas invariants
Moduli spaces of sheaves and pairs
Calabi-Yau algebras
Quivers

Donaldson and Thomas defined Donaldson-Thomas (DT) invariants for moduli spaces of sheaves on proper Calabi-Yau threefolds in [DT,T]. The definition has been extended to more general moduli spaces of objects in 3-Calabi-Yau categories, and in the last few years there has been an increasing interest in studying refinements of DT invariants. This thesis is devoted to the computation of the generating series of refined DT invariants in some geometric examples.
In Chapter 2 we compute the generating series of refined DT invariants for the moduli space 𝑀n,r of higher rank framed sheaves on ℙ3, generalizing the result of [BBS] for the Hilbert scheme of n points on ℂ3. We describe 𝑀n,r as a global critical locus by means of the Beilinson spectral sequence, and compute the generating series using motivic wallcrossing. We interpret the result as a count of r-tuples of weighted 3D partitions in analogy with the refined topological vertex [IKV].
In Chapter 3 we study the refined DT invariants for the moduli space Prn,d of higher rank (framed) stable pairs on the resolved conifold. Applying twice the Beilinson spectral sequence, we identify Prn,d with the moduli space of PT-stable representations of the r-framed conifold quiver with superpotential, generalizing a result of [NN11]. We compute a product expansion for the generating series of refined DT invariants of Prn,d, and we compare our results with the partition function counting U(1)-instantons on the minimal resolution of an Ar-1 surface singularity.
In Chapter 4 we study the universal generating series of motivic DT invariants for deformations of graded 3-Calabi-Yau algebras. We consider Jacobi algebras which are derived equivalent to the resolved conifold and the resolution of a line of An-singularities, and investigate their marginal deformations. The universal series of motivic DT invariants are affected by the deformations, and their variation is interpreted in terms of virtual classes of some special representation varieties associated to the quiver.
Solidarity as a transformative practice
Keywords: solidarity
domination
intersectionality
justice
social movements
mutuality
knowledge
prefiguration
standpoint theory
power asymmetries
transformation
feminism
deference
transformative experience

In this thesis, I investigate the meaning, importance, and potential of political solidarity. By studying existing theories and reflecting on real-world cases, I present a normative account of solidarity suited to confront the globalized, overlapping injustices we face in our world today. I argue in Chapter 1 that we should conceptualize solidarity as a political bond, realized through action, that unites members of social groups on the basis of a shared understanding of reality and a shared commitment to justice; and as a socially, interpersonally, and personally transformative practice. In Chapter 2, I consider a question familiar from feminist debates: whether and how a cohesive political unity can make sense of the divergent experiences, interests, and needs of the social groups it brings together. I argue that acknowledging and mitigating the relations of asymmetric power that exist between solidary agents is a precondition for unity. I then consider the numerous challenges solidary individuals face when attempting to relate to each other prefiguratively, as equals, within entrenched structures of domination in Chapter 3. I propose a series of diachronic norms to guide solidary agents in navigating power and knowledge asymmetries. In Chapter 4, I turn to the process of personal transformation undergone by solidary agents. I examine what sort of knowledge individuals gain through solidarity, how new knowledge translates into changed motivations, and the nature of these transformed motivations. I conclude by suggesting that solidarity discloses possibilities for freedom.
Three essays on measuring political behaviour
Keywords: reponsiveness
campaign finance
representation
measurement
quantitative
experiments
variance

Fundamental issues of political representation persist in modern democratic states. Policies favoured by large majorities of the population are not acted upon by elected representatives. Direct forms of democratic policymaking are increasingly used to settle policy disputes. And the amount of money in politics continues to grow. At the same time, new sources of data allow us to test the political behaviour of democratic actors in novel ways. Across three papers, this thesis explores how representation and policymaking operate in modern democratic systems and how researchers should measure political behaviour in these contexts.
In Chapter 2, I ask why popular legislation is passed by direct democratic means instead of by the legislature? I use a combination of district-level voting data, ideological estimates of financial donors, and a survey of state legislators to test competing theories of ballot initiative success in the United States. I argue that direct democratic policymaking is necessary when issues lie outside mainstream policy networks. Legislators appear averse to policies that are novel, untested, or go against the preferences of their financial supporters. In Chapter 3, I show how experimentalists can make valid statistical inferences when their data contains group-level structures. I illustrate this guidance using both Monte Carlo simulations and a review of experimental publications over the past three years. In Chapter 4, I examine how campaign finance disclosure affects vote choice in both representative and direct democratic contexts. Applying the lessons of the previous chapter, I use conjoint experiments to show that while voters can use disclosure information to inform vote choice, these effects are crowded out once partisan, ideological and issue cues are made explicit. Across all three chapters, I develop inferential techniques designed to account for limitations of observed data and, in particular, incomplete data.
Motion capture and musculoskeletal simulation tools to measure prosthetic arm functionality
Keywords: Sensitivity analysis
Affordable prosthetics
Motion analysis
Kinematics
Musculoskeletal modelling
Model validation
In Vivo analysis
Device personalisation
Compensatory movements
Kinetics
Upper limb prosthesis

The incidences of major upper limb (UL) loss or absence are increasing, while the prosthetic outcomes have remained poor. The human UL relies on the coordination of each of its joints (and the trunk in some instances) to achieve function; and this function, along with the sensory capabilities provided by the hand, is impaired due to amputations or absence of the UL (or a part thereof). Typical prosthetic devices that are used to supplement this missing function (and structure) lack controllable distal joint(s) necessitating compensatory movements during functional task execution. There is evidence in the literature that suggests that such compensatory movements are linked to poor prosthetic outcomes as well as secondary complications (such as repetitive strain injuries) in the contralateral arm owing to overuse. Most studies objectively characterising these movements have focussed on various types of kinematic and kinetic analyses. However, no studies have aimed at understanding these compensatory movements through a detailed musculoskeletal (MSK) model-based approach. Gaining better insights into compensatory movements is likely to be an essential step in measuring the functionality of a prosthetic arm.
The overall aim of this research is to use motion capture and state-of-the-art MSK simulation tools to measure prosthetic arm functionality. It is hypothesised that by comparing the functional performance of prosthesis limb users (simulated or actual) during select task execution with that of non-disabled individuals, we can identify and better understand prominent ‘functional disparities’ and help propose solutions to remedy these issues. In this study, select functional or goal-oriented tasks were performed in a standardised manner by non-disabled individuals and prosthetic limb users (both simulated and actual) in a three-dimensional optical motion capture laboratory setting. The measured motion data was then used to drive a detailed biomechanical (or MSK) model to calculate outputs such as joint angles, joint loading, and muscle loading.
This study adds to the kinematic (i.e. joint angles) and kinetic (i.e. joint and muscle loading) database of UL movements necessary to understand how a simulated (constraint-induced) or an actual transradial prosthesis user with a lack of a controllable distal joint(s) compensates relative to non-disabled individuals. The results provide valuable information such as increased disparities in joint angles, joint forces and moments during prosthesis usage (both actual and simulated) for characterising compensatory movements. By gaining in vivo information about the movement patterns adopted by prosthetic limb users, prosthetic devices and rehabilitation protocols could be personalised to enhance aspects such as function to improve prosthetic outcomes in the long-term.
Bioinspired MWCNT-reinforced alumina composite materials
Keywords: Nanomaterials
Biomimetic
Composites
Carbon nanotubes
Ceramics

Nacre, a ceramic composite found in seashells, has baffled scientists due to its extraordinary mechanical properties. Consequently, nacre has been a main source of inspiration to create strong and tough ceramic composites that mimic nacre’s microstructure. The precise microstructural features responsible for its unique combination of high strength and toughness are however debated, and efforts to mimic and improve upon nature’s design have not led to commercial applications of ceramic nacre-like composites.
This dissertation details the replication of nacre’s microstructural architecture with technical ceramics and nanomaterials. Instead of nacre’s calcium carbonate building blocks, alumina was used, and instead of its organic phase, multi-walled carbon nanotubes (MWCNTs) were incorporated. To design a nacreous microstructure, freeze casting of alumina nanoparticles was used to template a microstructure of aligned lamellae over macroscopic length scales. Although successful, the fabricated lamellar microstructures’ macroscopic orientation was hard to consistently reproduce using this technique and the resulting composites, unlike nacre, fail in a completely brittle fashion. Therefore, alumina platelets that closely resemble the platelets in nacre were investigated. A recipe to homogeneously coat these platelets in situ with MWCNT was developed, and MWCNT growth and catalyst modification was studied in-depth. The resulting combined building blocks were sintered into a composite that displays a graceful failure mechanism like nacre does, with several toughening mechanisms observed to be active. In addition, nacre-like alumina/MWCNT composite materials have been synthesised using a variety of MWCNT dispersion techniques. All studied nacre-like composites showed characteristic macroscopic interlocking behaviour and remain interlocked after crack initiation which prevented complete failure and gave these composites a residual strength. Pure nacre-like alumina specimens have also been tested in high strain rate and impact tests, where these materials showed a significant improvement over nontextured alumina.
Truthmaker Ontology
Keywords: Ontology
Grounding
Metaontology
Fundamentality
Ontological Commitment
Truthmaking
Ontological Method

Truthmaker Ontology is the metaontological thesis that ontology should be framed as a search for truthmakers: the things in the world in virtue of which true representations are true. This dissertation develops Truthmaker Ontology in new ways, arguing that it offers an attractive mode of thinking about the subject matter and method of ontological inquiry. I begin by arguing that, if ontology is to live up to its aspirations to be a serious enterprise, we must abandon the orthodox view that ontology concerns what there is. The remaining chapters develop Truthmaker Ontology as an alternative. First, I clarify the two central notions on which my version of the approach rests: the truthmaking relation between truths and their truthmakers, and the grounding relation between truths and other truths. I then use these two notions to develop a heterodox view of the subject matter of ontology, whereby ontological status comes apart from what it’s true to say there is. Briefly, what has ontological status is just what makes a contribution as a fundamental truthmaker. Since not everything that can truly be said to exist is a fundamental truthmaker, the question of whether ‘There are Fs’ is true doesn’t settle the ontological question about Fs. Next I turn to questions of method, starting with the methodologically important notion of ontological commitment: the ontological commitments of a theory, I claim, are the entities its holders rationally ought to admit as truthmakers. I then discuss the implications of Truthmaker Ontology for the measure of ontological parsimony, which I compare favourably to the recent view that parsimony only measures a theory’s requirements on what is ontologically basic. I close by consolidating the case for Truthmaker Ontology, arguing that it avoids the pitfalls of orthodoxy and has attractive consequences for some perennial ontological debates.
A study of Mandarin homophony
Keywords: Chinese
Mandarin
Homophones
Phonetics

An investigation into the distribution of homophones was conducted using a large written corpus (Da, 2007). Both tone and homophony were found to be systematically uneven, with a tendency toward clustering. Syllables with the full complement of tones have, on average, higher homophone densities than those with fewer tonally-specified syllables, indicating a beneficial role of increasing homophone density in lexical processing. Three experiments were conducted to test this hypothesis. In Experiment 1, participants were shown tonally-unspecified pinyin and asked to produce a character. Participants gave the most frequent character matching the pinyin, except when two characters of differing homophone density but similar lexical frequency were in direct competition (e.g. the two highest frequency wan characters were associated with different tones). In this case, it was found that the slightly lower frequency, but higher homophone density character was selected, indicating a facilitative role of homophone density. In Experiment 2, participants were shown tonally-specified pinyin followed by characters, and asked to judge whether the two matched. Character frequency (not the cumulative frequency of all homophones) was found to be the primary determinant of response time, with higher frequency characters responded to faster than lower frequency characters regardless of homophone density. However, increasing homophone density was found to speed responses for all frequencies. High frequency characters were always faster than low frequency characters, but low frequency characters with high homophone density were faster than low frequency characters with low homophone density. In Experiment 3, participants read aloud characters embedded in context sentences. High frequency words were more reduced (i.e. shorter in duration) than low frequency homophone mates. High frequency characters with many homophones were shorter than high frequency characters with few homophones, while the opposite held for low frequency characters.
Antiphon the Sophist's critique of law
Keywords: Antiphon
The Sophists
anomia and friendlessness
Ancient Greek social contract theories
nomos-phusis distinction
Sophistic legal thought

Antiphon has often been singled out by scholars as the Sophist who gave expression to the most radical critique of law. He is often spoken of as an immoralist thinker, who recommended that people reject the established laws and pursue solely what is in their self-interest. In this thesis, the grounds for ascribing the label of immoralist to Antiphon will be assessed. I will argue that it is misguided to view Antiphon in this regard on two principal counts: his purpose in 'On Truth' is to underline the inconsistencies and failings of existing legislation, and in no way to advocate for people to disregard the laws in force; in both 'On Truth' and in 'On Concord,' he shows an attachment to the laws, and in the second of the two works, he even advances a reason for why they should be regarded as salutary and beneficial.