Events with jets produced in association with a Z boson in proton-proton collisions can be used to study distributions sensitive to the vector boson fusion (VBF) process at CERN's Large Hadron Collider. This process is interesting to study because of its similarity to the VBF production of a Higgs boson as well as its sensitivity to new physics via the WWZ triple gauge coupling. Evidence for electroweak Zjj production beyond the 5 level is presented using data collected at a centre-of-mass energy of \sqrt{s} = 8 TeV by the ATLAS experiment in 2012. This constitutes the first observation of a VBF-like process. The detector-corrected cross sections measured in two fi ducial regions are in excellent agreement with the Standard Model expectations and have also been used to constrain anomalous triple gauge couplings. Furthermore, detector-corrected cross sections and diff erential distributions for inclusive Zjj production are presented in di fferent regions of phase space with varying sensitivity to the electroweak Zjj component. In addition, a performance study of the tracking algorithms used in the ATLAS high-level trigger system is presented.

In this thesis I have explored some of the ways in which the contexts of epistemology, ethics and designing architecture are each concerned with undecidable questions (that is, with those questions that have no right answers). Drawing on design research, second‐order cybernetics and radical constructivism, I have understood this undecidability to follow in each case from our being part of the situation in which we are acting. This idea is primarily epistemological (being part of the world we observe, we cannot verify the relationship between our understanding and the world beyond our experience as it is impossible to observe the latter) but can also be interpreted spatially and ethically. From this starting point I have developed connections between questions in architecture, epistemology and ethics in two parallel investigations. In the first, I have proposed a connection between design and ethics where design is understood as an activity in which ethical questioning is implicit. Rather than the usual application of ethical theory to practice, I have instead proposed that design can inform ethical thinking, both in the context of designing architecture and also more generally, through (1) the ways designers approach what Rittel (1972) called “wicked problems” (which, I argue, have the same structure as ethical dilemmas) and (2) the implicit consideration of others in design’s core methodology. In parallel to this I have explored the spatial sense of the idea that we are part of the world through a series of design investigations comprising projects set in everyday situations and other speculative drawings. Through these I have proposed reformulating the architectural theme of place, which is usually associated with phenomenology, in constructivist terms as the spatiality of observing our own observing and so as where the self‐reference of epistemology (that we cannot experience the world beyond our experience) becomes manifest.

This thesis describes the further improvement of an already developed by our group laser system capable of delivering high energy, frequency agile, flat-top pulses and its uses in non-resonant molecular scattering diagnostics in the form of coherent Rayleigh-Brillouin scattering, as well as for optical Stark deceleration of neutral H2 molecules. This laser system is capable of delivering two computer controlled flat-top pulses of variable duration (20~1000 ns) with energies up to 700 mJ per pulse and with linearly chirped frequencies up to 1.5 GHz. With the use of constant velocity lattices driven by this system we were able to accurately obtain coherent Brillouin scattering spectra of purified air in the hydrodynamic regime where, for the first time, we observed additional spectral peaks to the main Brillouin peak, as well as up to 40% reduction of the peak due to the interaction of the laser driven electrostrictive grating with the acoustic which was launched in the gas due to its thermalisation by the optical field. Furthermore, by utilising chirped frequency optical lattices, we were able to obtain accurate coherent Rayleigh-Brillouin spectra with signal-to-noise ratios in excess of 100, in a single laser shot ( 140ns) thus reducing the acquisition times needed for such spectra by ten orders of magnitude, rendering the technique ideal for combustion and transient flow diagnostics. Finally, we report on the use of this laser system as a tool for optical Stark deceleration of neutral H2 molecules, where through a Raman tagging scheme of the interacting molecules we are proposing an efficient way to monitor the interactions occurring within the decelerating optical lattice. We hope that this technique will pave the way for the production of narrow velocity spread molecular ensembles to be used in cold collisional studies as well as sympathetic cooling.

Classical nucleation theory has been a useful tool for predicting the phenomena of nucleation for the past seventy years. However the model has several limitations, which in some examples give rise to predicted rates that are several orders of magnitude in error. One such example is that of sulphuric acid and water nucleation which has long been framed as an important source of cloud condensation nuclei and therefore has implications for the climate, both locally and globally. In addition stratospheric aerosol injection of molecules containing sulphur, including sulphuric acid, are of interest as a potential geoengineering technique. The focus for this study is to improve upon our understanding of water and sulphuric acid nucleation. The initial phase of the project concerned performing quantum chemistry calculations which go beyond the macroscopic description employed by classical nucleation theory. Kohn-Sham density functional theory has been successfully employed in the fields of condensed matter, material physics and chemistry. However one of the assumptions of the theory is the classical treatment of the nuclei. The path integral molecular dynamics technique is used here to test this assumption on small clusters of sulphuric acid and water. We find that the introduction of zero point motion has a small effect on the equilibrium properties of certain configurations in line with expected behaviour. An interesting structure is found which serves to emphasise the importance of liquid like behaviour in this cluster at room temperature. The first study demonstrated the computational expense of treating systems at the microscopic scale using quantum chemistry approaches. The second phase of the research focused upon finding a suitable classical potential to employ within a molecular dynamics scheme, which would drastically reduce the computational expensive of performing simulations. This potential would be required to retain the ability for protons to transfer between selected species. The empirical valence bond method was chosen for its straightforward implementation and its similarity to traditional classical schemes. However some modifications were required to implement the scheme. Two algorithms were designed to identify species within the system and treat them in a fashion suitable for use in the empirical valence bond method. In addition the empirical valence bond method also needed to be parametrised for the sulphuric acid and water system. This was achieved by using the particle swarm optimisation technique, which performed force matching parametrisation using the Kohn-Sham density functional theory work from the previous phase of the project. The model was fully programmed in FORTRAN 90/95 and was incorporated into DL-POLY version 4.03. It is tested against the density functional theory data to which it is parametrised to check that the main features of the quantum chemistry are retained within the empirical valence bond technique. A puzzling issue appeared in preliminary molecular dynamics simulations performed with DL-POLY 4.03. The issue arises from a constraint imposed to fix the centre of mass. The solution to the modified Langevin equation introduced by this constraint is derived. The results are then compared to the puzzling DL-POLY simulations and found to be consistent. The constraint is then removed for all further simulations. The developed empirical valence bond potential was used to perform simulations of small clusters of sulphuric acid and water. We test the level of hydration required to ionise the system and find it to be in line with literature values. A thermodynamic integration scheme that was suitable for this system was derived. Preliminary simulations were performed using the model to compute free energies for use with classical nucleation theory in order to calculate nucleation rates.

This thesis describes three experiments with cold rubidium atoms. The first experiment implements a rocking ratchet with cold atoms in driven dissipative optical lattices, and explores a fundamental feature of ratchets: current reversals. It precisely investigates current reversals as observed by varying the driving frequency. It is found that this kind of current reversal in the frequency domain is determined by dissipation-induced symmetry breaking. The second experiment explores vibrational mechanics for a system of cold atoms in an optical lattice. A high frequency strong driving field was applied in order to renormalise the optical potential. It was observed that the amplitude of the potential is indeed renormalised and can be controlled by the high frequency driving field. This is detected by two methods: via the study of the diffusion properties and via the observation of the directed transport. The final experiment is the realisation and characterisation of a Bose-Einstein condensate of rubidium atoms.

Molecular nitrogen, N₂, is the most abundant molecule in the terrestrial atmosphere. Its cation N₂⁺ is therefore prevalent in the earth's ionosphere as well as in nitrogen plasmas produced for reasons varying from lightning strikes to combustion. Any model which seeks to describe plasmas in air must contain a description of nitrogen ion chemistry. Despite this, there is a distinct paucity of data describing electron-N₂⁺ interactions and the resultant bound and quasi-bound electronic structure of N₂. The characterisation of these states is essential for describing dissociative recombination which is the main destroyer of molecular ions in a plasma. This thesis aims to alleviate this problem by performing extensive ab initio R-matrix calculations to create a comprehensive map of the highly-excited electronic structure of N₂ which can the be used to perform a dissociative recombination cross-section calculation. Potential energy curves were found by performing resonant and bound state calculations for all singlet and triplet molecular symmetries of N₂ up to l ≤ 4. The use of a dense grid meant that highly-excited electronic states could be found with an unprecedented level of detail. Many of the states were previously unknown. A new fitting method was developed for the characterisation of resonant states using the time-delay method. It was shown that whilst the R-matrix method is not competitive with conventional quantum chemistry techniques for low lying valence states, it is particularly appropriate for highly-excited states, such as Rydberg states. The data gained from these calculations was then used as an input for a multichannel quantum defect theory calculation of a dissociative recombination cross-section. A description is given of how to prepare the data from the R-matrix calculation for input into a multichannel quantum defect theory dissociative recombination cross-section calculation. Cross-sections were found for v=0-3 including three ionic cores. Whilst previous studies of dissociative recombination using R-matrix data required some empirical intervention, the cross-section found in this thesis is completely ab initio and is in good agreement with experiment.

This thesis addresses the emergent electrostatics of two-dimensional, toroidal magnetic models that possess XY symmetry, providing a platform for novel investigations into the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. The BKT transition drives the thermal dissociation of bound pairs of topological defects in many two-dimensional systems, including the two-dimensional XY model of magnetism. The XY model is closely analogous to the two-dimensional Coulomb gas, but can be simulated without computing the long-range interactions of the Coulombic system. This thesis elucidates this paradox by showing that Villain's approximation to the XY model is strictly equivalent to the Maggs-Rossetto (MR) electrostatic model when applied to the two-dimensional Coulomb gas. The mapping is used to probe the BKT transition through the application of the MR algorithm to the two-dimensional Coulomb gas. By simulating the Coulombic system, fluctuations in the winding of charges around the torus are shown to turn on at the BKT transition temperature. These topological-sector fluctuations in the electric field therefore signal the high-temperature phase of the transition. It is then shown that the effective critical exponent of Bramwell-Holdsworth (BH) theory can be measured in superfluid ⁴He films, which correspond to effective Coulomb gases in the limit of large but finite system size. With the Coulombic system taken as the base BKT system, it is inferred that BH theory is a general property of BKT systems.

This thesis uses Cluster & Double Star multi-spacecraft missions with support from ground magnetometer and solar wind data to investigate several aspects of the terrestrial mag- netosphere relating to the magnetotail and substorms. The rst study investigated connections between bursty bulk ows (BBFs) detected by the Cluster spacecraft and dipo- larisation detected by the Double Star spacecraft, in the Cluster tail seasons of 2004 & 2005. Simulataneous detections of which were linked heavily to the expansion and recovery phase of substorms. It was found that less than a third of the events can be in any way linked directly. Also, the times when BBFs were detected were distinctly di erent to the times for dipolarisations. The conclusion is that multiple X-lines could be responsible, or simply that these phenomena arise from di erent causes. The second study investigated the statistical ow pro les of BBFs using the Cluster spacecraft. Due to the varied sep- aration distance of the Cluster satellites in 2004 & 2005, the ow channels were probed at two di erent ranges. The typical shape of the ow pro le of BBFs was recovered. The typical width of BBFs was estimated as 2.5 { 3.5 RE. The ow pro le shape was probed for periods of high & low auroral electrojet activity. It was found that the ow width is broader during high activity. This is possibly due to a more well developed reconnection site. The last study investigated the manifestation of azimuthal pressure gradients in the tail plasma sheet in relation to substorms. Use was made of Cluster 1 & Cluster 3 during three case intervals in 2006. Total pressure was evaluated using ion and magne- tometer measurements. It was found that there were no pre-onset pressure gradient build ups, as reported by previous published work. However, pressure gradients were detected for times corresponding to substorm expansion phase and for times without signi cant auroral electrojet activity. The latter may be attributed to pseudo-break up events.

Iron oxide nanoparticles are a popular choice for many current technologies, especially those with applications in biology and medicine. Novel syntheses that aim to improve their physicochemical properties, or adapt them to distinct practical applications, are constantly being reported. However, the reproducibility of these methods is not commonly studied, leading to promising products that have little chance of being commercially manufactured. Adherence to good manufacturing practice standards is a decisive factor in determining whether a material may be granted regulatory approval for industrial or clinical use. As such, tight control on the synthetic conditions is crucial to obtain consistent products. In this work initial experimentation was focused on the use of sodium carbonate―an environmentally friendly base―for the synthesis of iron oxide nanoparticles. Mild reaction conditions and slow kinetics allowed for the study of the reaction mechanism and led to controllable and reproducible results. However, functionalised suspensions could not be obtained due to the adsorption of carbonate onto the nanoparticle surface. A microwave reactor was then introduced to take advantage of the surface selective heating effect, aiding ligand exchange and enabling the production of nanoparticles with a range of surface functionalities. Their potential for magnetic hyperthermia, a promising therapeutic tool for the treatment of cancer, was investigated. Citric acid-iron oxide nanoparticles exhibited the highest heating performance, with an intrinsic loss power of 4.1 nHm2kg-1, which is 30% better than the best commercially available equivalent. Finally, their potential to treat near-surface or accessible tumours was tested in vitro on a human melanoma DX3 cell model. The results showed a controllable cell death via selective apoptosis or necrosis depending on the field and frequency applied. Time-lapse fluorescent microscopy experiments allowed the first direct observation of magnetic hyperthermia in adherent cells, where total-population cell death by apoptosis was observed.

We use high-resolution numerical simulations of disc galaxies to study spiral arms and their dynamical influence on nearby stars. We find that in the numerical simulations the spiral arms are winding, transient features whose pattern speeds decrease with radius in such a way that the pattern speed is almost equal to the rotation curve of the galaxy. We validate this for normal and barred-spirals, and demonstrate that there is no significant offset of different star-forming tracers across the spiral arm. We show from the dynamics of nearby star particles that star particles are drawn towards and join the spiral arm from behind (in front of) the arm and migrate towards the outer (inner) regions of the disc until the arm disappears. The resulting gain (loss) of angular momentum of star particles behind (in front of) the spiral arm is termed radial migration, and occurs over the entire radial range analyzed. A direct consequence of ubiquitous co-rotation radii is that the guiding centre radii of particles are changed while their degree of random motion is unchanged. We show that there are several types of migrator particles, as well as particles that do not migrate, that each have a different orbital evolution. We show that the orbital type depends on position in configuration and phase space, and show how the orbits can make up moving group features in velocity space. We investigate the correlation between the galactic shear rate and the pitch angle of both individual density waves and the apparent co-rotating spiral arms. We find that, in both cases, higher galactic shear rates produce more tightly wound spiral arms, in agreement with observation. We find also that winding spiral arms can naturally explain the scatter in the pitch angle-shear rate relation seen from observations.