We report the design and fabrication of chirped nano-indented gratings for enhanced surface plasmon polariton (SPP) coupling on gold thin films. The structures were produced by nanoindentation controlled by atomic force microscopy (AFM), enabling spatial modulation of the grating period with subwavelength precision, while preserving the integrity of the metallic film. The chirped geometry was engineered to provide an extended distribution of reciprocal lattice vectors, promoting improved momentum matching and increased tolerance to excitation conditions compared to uniform periodic gratings. The plasmonic response of the structures was investigated using scattering-type scanning near-field optical microscopy (s-SNOM). Analysis of the near-field images provides evidence of SPP excitation and propagation along the gold surface. The results demonstrate that AFM-based nanoindentation provides a versatile and flexible platform for tailoring plasmonic coupling mechanisms, offering a scalable approach for the realization of structurally engineered plasmonic interfaces with enhanced excitation performance.

​​University instruction is often framed as an entirely cognitive activity. But emotions are integral to learning, as well as to how people respond to questions of justice, care, and fairness. This affects ourselves, other people, and entities other than humans. Roland Tormey looks at how scholarship of the last thirty years has shifted from ‘conventional’ to more ‘critical’ views of emotion in learning. He examines how emotions like compassion, guilt, shame, ecoanxiety, outrage, embarrassment, and frustration have been found to arise when teaching sustainability topics in higher education. Since emotion is already integral to learning, and ignoring it won’t make it go away, a number of teaching strategies are useful to integrate emotion into sustainability education. These include: strategies to develop students’ emotional awareness and language; the explicit inclusion of emotions such as compassion in case studies and classroom examples; explicit foregrounding of problem-solving and group work methods when addressing sustainability topics; and strategies for reducing ecoanxiety in sustainability learning. These teaching approaches are simple enough to be tried by all teachers, even those who feel they do not have much expertise in emotion.

We develop a numerical method suited for simulating immiscible multi-material compressible fluid flows. To model these flows, we derive an original fully conservative six-equation system, closed by a stiffened-gas equation of state and a pressure equilibrium equation. Additionally, we introduce a second-order numerical scheme, in both space and time, specifically designed for capturing fluid interfaces in multi-dimensional configurations. To achieve second-order accuracy, we devise a multidimensional slope reconstruction method based on the stability criterion of local extrema diminishing. The second-order scheme associated with the fully conservative model results in the emergence of pressure profile oscillations. To mitigate these spurious oscillations, we demonstrate a set of essential properties. Firstly, we establish numerical stability conditions related to the slope reconstructions. Then, we show the compatibility between the energy equation and the transport of volume fractions. Next, we propose a two-step energy-compatible pressure reconstruction to ensure the positivity of thermodynamic quantities such as internal energy. Finally, the proposed approach is assessed through classical benchmark test cases, which confirm its accuracy, robustness, and ability to capture complex multi-material interface dynamics with sharp interfaces.

We introduce a notion of efficient stability for finite presentations of groups. Informally, a finite presentation using generators S and relations R is stable if any map from S to unitaries that approximately satisfies the relations (in the tracial norm) is close to the restriction of a representation of G to the subset S. This notion and variants thereof have been extensively studied in recent years, in part motivated by connections to property testing in computer science. The novelty in our work is the focus on efficiency, which, informally, places an onus on small presentations — in the sense of encoding length. The goal in this setup is to achieve non-trivial tradeoffs between the presentation length and its modulus of stability. With this goal in mind we analyze various natural examples of presentations. We provide a general method for constructing presentations of Zk2 from linear error-correcting codes. We observe that the resulting presentation has a weak form of stability exactly when the code is testable. This raises the question of whether testable codes give rise to genuinely stable presentations using this method. While we cannot show that this is the case in general, we leverage recent results in the study of non-local games in quantum information theory (Ji et al., Discrete Analysis 2021) to show that a specific instantiation of our construction, based on the Reed-Muller family of codes, leads to a stable presentation of Zk2 of size poly log(k) only. As an application, we combine this result with recent work of de la Salle (arXiv:2204.07084) to re-derive the quantum low-degree test of Natarajan and Vidick (IEEE FOCS’18), which is a key building block in the recent refutation of Connes’ Embedding Problem via complexity theory (Ji et al., arXiv:2001.04383).

The multiferroic semiconductor (Ge,Mn)Te exhibits ferroelectricity, strong Rashba spin‐orbit coupling, and carrier‐mediated magnetic order, making it a unique platform for exploring the interplay between electronic, structural, and magnetic degrees of freedom. In this study, we investigate the ultrafast magnetization dynamics of Ge 0.85 Mn 0.15 Te using time‐resolved magneto‐optical spectroscopy. By separating magnetic and nonmagnetic contributions in the transient response, we identify two distinct laser‐induced magnetic phenomena, both arising from a photoinduced effective spin‐orbit torque. Coherent magnetization precession is driven by a laser‐induced increase in hole concentration, which modifies the occupation of Rashba‐split, spin‐locked valence band states, and shifts the position of the magnetic easy axis. The transient change in magnetic properties, observed as variations in the amplitude and coercive field of the pump‐induced change in ellipticity hysteresis loops, is attributed to laser‐induced modifications of the ferroelectric sublattice displacement, which affect the ferroelectric polarization and the associated Rashba spin‐orbit interaction. While the first type of optical spin‐orbit torque has already been observed in the diluted magnetic semiconductor (Ga,Mn)As, the second effect is unique to the multiferroic Rashba semiconductor (Ge,Mn)Te, opening new opportunities for all‐optical manipulation of magnetic order and spin‐orbit torque generation in spin‐orbitronic devices.

In this thesis, we present the advances in self-organised nano-pillar lattice fabrication, including improvements in graphene (Gr) transfer onto targets in ultra-high vacuum (UHV), demonstrated increase of Gr capped self-organised cluster thermal stability, and creation of a high-density nano-pillar heterostructure achieved by second layer self-organised cluster growth on a transferred 2D material patterned by the clusters below it. We first present an ion intercalation-based graphene delamination method for the creation of a PTFE-supported graphene bilayer from which one monolayer is transferred onto the target sample using wafer bonding in UHV. With this method we demonstrate mm-scale graphene coverage onto Ir(111) and Irclust/Gr/Ir(111) targets in UHV. The novel method was tested alongside the acid etching-based bilayer preparation method and compared using Raman spectroscopy. The ion intercalation delamination method was found to result in higher quality and homogeneity bilayer graphene stamps, compatibility with graphene growth on reusable Pt substrates with larger grains further increasing graphene quality, as well as lower doping due to avoiding exposure to etchants. After transfer on Ir(111), scanning tunnelling microscopy (STM) imaging revealed significantly larger domain sizes of the monolayer Gr transferred. Additionally, Auger electron spectroscopy (AES) measurements were used to quantify graphene transfer coverage on a large scale, showing around 50% coverage over mm scale for both Ir(111) and Irclust/Gr/Ir(111) targets. Then we investigate the effects on thermal stability of Gr-capped Irclust/Gr/Ir(111) in UHV. STM imaging of samples prepared at varied temperatures revealed increased resistance against Ostwald ripening and peripheral diffusion, with filling factor values 20% - 30% higher in Gr-capped areas areas for a temperature range from 750 K to 1250 K, demonstrating the usefulness of the system for magnetic nano-pillars with high blocking temperature. Finally, the fabrication of a high-density self-organised nano-pillar heterostructure was demonstrated by subsequent cluster growth, Gr transfer, and growth of a second layer of Ir on Gr/Ir(111). The resulting Irclust/Grtransfer/Irclust/Gr/Ir(111) heterostructure has been investigated using STM, with second layer clusters shown to self-organise on top of Gr-capped clusters, and apparent height measurements demonstrating two Ir-layer high clusters grown on top of transferred graphene. An alternative system that could potentially be extended to 3D growth of self-organised Co clusters on Au(11,12,12) surface has been capped with Gr on the mm-scale as observed using AES, with capped areas showing a preserved self-organised pattern as investigated with STM. The demonstrated achievements offer the foundations for further development of nano-pillar heterostructure with the potential for high-density magnetic nano-pillars.

Optical frequency combs link optical frequencies to electronically countable microwave sig- nals. Kerr microresonators miniaturize these sources, but extending their bandwidth remains challenging. The central aim of this thesis is to explore routes to broader optical frequency combs through the joint engineering of dispersion, resonator geometry, and excitation in three integrated architectures. The first part combines pulsed pumping and dispersion engineering in a silicon nitride (Si3N4) Euler racetrack. Synchronous electro-optic pulses supply high peak power at moderate average power. Adiabatic bends suppress parasitic spatial-mode conversion, while dispersion engineering and broadband extraction support an octave-spanning soliton microcomb at an electronically detectable repetition rate. Radio-frequency and heterodyne measurements distinguish the soliton from modulation instability and verify coherence at widely separated wavelengths. The second part combines gallium phosphide with photonic-crystal Fabryâ Pérot cavities whose chirped reflectors supply anomalous round-trip dispersion. Picosecond subharmonic pumping overcomes the thermo-refractive access barrier, enabling the first room-temperature dissipative Kerr solitons in GaP. Heterodyne noise measurements reveal the transfer of timing noise from the electro-optic drive. A modified Lugiatoâ Lefever model separates the nonlinear detuning shift caused by counter-propagating fields from the period-four dynamics and interleaved subcombs imposed by the drive. Finally, the Vernier effect in coupled rings reshapes the resonance spectrum into recurring hybridized dispersion valleys. A transfer-matrix model guides two device generations and relates measured hybridization to broadband comb generation. The analysis identifies a novel four-wave-mixing mechanism involving intra- and interband photon transfer between these valleys, offering a new route to spectral expansion in coupled-resonator systems. Together, these studies show that useful broadband microcombs require joint control of dispersion, loss, coupling, thermal dynamics, and the drive. Future work will focus on demon- strating f â 2f self-referencing, integrating pump-pulse generation and compression on chip, and achieving phase-locked comb generation across multiple Vernier valleys.

Membrane-based gas separation offers an energy-efficient alternative to conventional separation processes, but practical membranes must combine high permeance, selectivity, stability, mechanical robustness, and scalable fabrication. Carbon materials are promising candidates for gas separation membranes because of their structural versatility and chemical and physical stability. When fabricated as ultrathin selective layers with well-controlled molecular-sieving pores or channels, carbon membranes can combine short transport pathways with strong size selectivity. This thesis focuses on the design, synthesis, and characterization of ultrathin carbon-based membranes for gas separation, aiming to control molecular-sieving pores and channels at the angstrom scale to discriminate gas molecules with small differences in kinetic diameter. Two representative transport geometries are investigated: through-plane nanopores in porous graphene and confined channels between carbon layers or domains. The first part studies bottom-up synthesis of porous nanocrystalline graphene as an ultrathin molecular-sieving membrane. Nanopores are incorporated during graphene growth rather than by post-synthetic etching. By controlling the cooling rate during precipitation-based growth on nickel, graphene grain intergrowth and effective pore size can be tuned. Rapid cooling reduces the effective pore size and improves H2/CH4 selectivity from 6.2 to 53.3, demonstrating a synthesis-based strategy for angstrom-scale pore tuning. The second part develops 10-nm-thick carbon membranes derived from poly(4-vinylpyridine) by pyrolysis under controlled oxygen exposure. Trace O2 modifies the decomposition pathway of the polymer precursor during pyrolysis and transforms the resulting carbon membrane from a relatively uniform network into a disrupted ultramicroporous structure. The resulting multimodal ultramicroporous channels provide rapid transport pathways while retaining molecular-sieving capability. These 10-nm-thick carbon membranes achieved H2 permeance above 10,000 GPU (gas permeation units, 1 GPU = 3.35 × 10 -10 mol m-2 s-1 Pa-1) and H2/N2 mixture selectivity above 200 at 150 °C, showing that oxygen-modulated pyrolysis can overcome the thickness limitation of conventional carbon molecular sieve membranes. The third part addresses the challenge of structural characterization in fragile porous graphene membranes. Reliable pore analysis requires clean, suspended, and mechanically stable specimens, but conventional polymer-assisted transfer can leave residues that obscure nanopores, while direct transfer can damage porous films. Therefore, a polymer-free carbon nanotube mesh scaffold, termed CMesh, is developed to mechanically reinforce porous graphene during transfer and imaging. This scaffold enables robust atomic-resolution TEM/STEM characterization of pre-existing porous graphene and in situ heating studies up to 900 °C, providing a practical platform for linking nanopore structure with membrane transport. Overall, this thesis demonstrates an integrated strategy for engineering ultrathin carbon-based membranes by connecting synthesis, angstrom-scale pore/channel control, gas separation performance, and atomic-resolution characterization. The developed approaches provide new routes to tune through-plane nanopores and confined ultramicroporous channels, contributing to the development of high-performance molecular-sieving membranes for energy-efficient gas separation.

Coral reefs are among the most biodiverse and most threatened ecosystems on Earth, declining under ocean warming and recurrent mass bleaching. Whether they persist depends on how fast corals can adapt. In this context, this thesis assesses the adaptive potential of the reef-building coral Acropora millepora in the Coral Sea from a holobiont perspective, reading the environmental seascape, the host genome, the algal symbionts and the colony phenotype together across fourteen reef sites in two contrasting regions: the Capricorn Bunker Group, at the southern tip of the Australian Great Barrier Reef, and the remote Chesterfield-Bellona plateau of New Caledonia.

The environmental seascape was characterised from satellite remote sensing, as eighty descriptors of thermal stress, water quality, salinity and currents computed over four time windows, and was used to guide sampling across the environmental range rather than across geography alone. Colony morphology, colour, health and microhabitat were scored from standardised in situ photographs of 268 colonies. The host genome of 236 colonies was resolved by low-coverage whole genome sequencing (lcWGS), and the algal symbionts of 237 colonies by ITS2 metabarcoding. Genome-environment associations were then scanned with LFMM2 and SAMbada, cross-checked against the environment-free PCAdapt selection scan, and integrated, alongside the symbionts and the phenotype, in redundancy analyses that projected a polygenic adaptive index across the reefs.

The two regions form two genetically distinct units, each effectively panmictic within itself, separated by low but consistent differentiation and with Chesterfield-Bellona carrying about three times the nucleotide diversity of the Capricorn Bunker Group. Within Chesterfield-Bellona, genetic differentiation increases with geographic distance, a stepping-stone pattern absent from the Capricorn. Phenotype, symbiont community and host genome separate the same two regions, the dominant Cladocopium type profile switching between them. Candidate loci associated with sea surface temperature anomalies and heat-stress metrics fall in molecular chaperones, an antioxidant transporter, and extracellular-matrix and cilia genes, a set that recurs in independent global coral studies. The adaptive index draws a warm, clear-water-adapted pole across the Chesterfield-Bellona plateau, strongest in its north, grading to a cooler, more turbid-adapted pole in the Capricorn Bunker Group. It is on the Chesterfield-Bellona plateau that the adaptive signal of the host, the symbiont community and colony health agree, a first step towards seascape genomics at the scale of the holobiont.

Because the two regions lie far apart, the regional contrast between them is confounded with the environment, the symbionts and the host structure, so adaptive signals within each region were harder to resolve. However, sampled in June and September 2023, months before the severe 2024 El Niño marine heatwave, the colonies offer a rare opportunity to test in the field whether the genotypes predicted to be heat-adapted actually survived. Conserving the adaptive potential of corals, in a climate that no longer holds still, means reading the host, the symbiont and the environment together.

AI control is a field of study intended to provide a second layer of defense should our efforts at AI alignment fail. Starting with the premise that an AI system is misaligned, AI control is concerned with designing mechanisms to either prevent misbehavior or catch the AI red-handed. In this thesis, we present an overview of AI control alongside several contributions to the field, split into the following chapters:

Overview of AI control. To motivate AI control, we begin with a survey of theoretical and empirical evidence of misalignment in modern AI systems. Then, we discuss the high-level principles that guide AI control mitigations, covering common deployment contexts, the specific threats that AI control aims to prevent, and how AI control evaluations are conducted. We also introduce a distinction between concentrated and diffuse threats from untrusted AI models and discuss why these two types of threats demand different mitigations. Concentrated threats are those that unfold over a short period of time. The science of concentrated threats, sometimes called concentrated AI control, is more developed; following prior work, we present a mathematical model that can be used to evaluate the safety of concentrated AI control protocols.

Control tax. In this chapter, we study a concentrated AI control protocol called trusted monitoring. Trusted monitoring proceeds by having a weaker trusted AI model assign suspiciousness scores to the actions of the untrusted model, with the most suspicious actions escalated for human auditing. To evaluate trusted monitoring, we have language models generate solutions to competitive programming problems that contain subtle bugs. We then test how well other models can distinguish these "backdoored" solutions from the correct ones. Using the mathematical model from the previous chapter, we show how to compute the safety of trusted monitoring analytically in the limit of a large number of deployed AI agents. Finally, we combine our applied and theoretical results under the framework of the control tax---the operational and financial cost of integrating trusted monitoring into AI pipelines.

Adaptive attacks on AI control protocols. In this chapter, we present simple attacks that subvert existing monitoring-based protocols in concentrated AI control. The most common kind of trusted monitor used in control protocols is a prompted language model, and language models are notoriously susceptible to prompt injections. We exploit this vulnerability to demonstrate that trusted monitors can be induced to label most of the code they see as not suspicious, rendering them essentially useless. Our language model-generated prompt injections generalize across several monitors. Using the mathematical model from the previous chapters, we show the disastrous downstream effects of these prompt injections on the safety of multiple control protocols.

Diffuse AI control on fuzzy tasks. In this chapter, we propose a red-teaming framework for evaluating training interventions against diffuse threats from a misaligned AI, such as deliberately underperforming on difficult-to-grade tasks. We show that a misaligned AI can subvert the process of generating ML experiment ideas even when optimized against scores assigned by a weaker model. We also show that there exist prompts for the weak scorer that significantly improve its robustness, though efficiently discovering such prompts with realistic affordances remains an open problem.