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The start of the second running period of the Large Hadron Collider in 2015, delivering proton-proton collisions at a centre-of-mass energy of 13 TeV, marks a new era in the study of particles containing charm quarks with samples of unprecedented size being recorded by the LHCb experiment. This thesis first presents cross-section measurements for D0, D+, Ds+, and D*+ at 13 TeV, supplemented by a measurement of the same cross-sections at 5 TeV, leading to very precise, double-differential cross-section ratios that are hugely beneficial for constraining theoretical uncertainties in quantum chromodynamics. This is followed by a study into the potential for extracting the parameters describing the oscillation of neutral D0 mesons in doubly-cabibbo suppressed decays into a kaon and three pions, exploiting the very large data samples recorded at 13 TeV. These studies show that this decay can be used to heavily constrain the mixing parameters, leading to a substantial improvement of the uncertainties on them when included in the world average. However, these large datasets create computational challenges due to the sheer amount of recorded data, which is especially true for the LHCb simulation effort. Therefore, this thesis also discusses work undertaken to increase the speed at which simulated samples can be created by one order of magnitude.

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The functionality of devices that utilise TiO2 is heavily influenced by the interactions which occur at the surface and interface. Developing a full mechanistic understanding of these interactions is essential, and the focus of the work presented in this thesis. The interactions of phenylphosphonic acid (PPA) and [C4C1Im][BF4] with the surface of anatase(101) have been investigated using X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy because of their potential applications in dye-sensitised solar cells. XPS data suggests that at 0.15 monolayer (ML) coverage PPA adsorbs in a bidentate geometry following the deprotonation of both P-OH groups. At 0.85 ML coverage there is a shift to a mixed bidentate/monodentate binding mode. NEXAFS spectroscopy data shows that the phenyl ring is oriented 65 ±4 away from the surface plane and twisted 57 ±11 away from the [101] azimuth. [C4C1Im][BF4] is found to order at the surface of anatase(101) via electrostatic attraction only at low coverages, with the imidazolium ring oriented 32 ± 4 from the surface. XPS data suggests that the anion undergoes a surface induced degradation to form BF3, resulting in incorporation of F into O vacancies. The behaviour of metallic clusters supported on metal oxide supports and the nature of the crystal structure modification of TiO2 following doping with impurity ions both have important implications in catalysis. XPS and scanning tunnelling microscopy (STM) data show that the interaction of Ag with the anatase(101) surface leads to a metal-surface charge transfer, as evidenced by the reduction of Ti4+ to Ti3+, and the formation of 3D size limiting clusters. Under exposure to 3 mbar CO/H2O, partial oxidation of the Ag clusters in conjunction with the formation of a transient Ag-carbonyl species is observed. Upon returning to ultra-high vacuum these species disappear. XPS and photoelectron diffraction (PhD) have been employed and show that nitrogen doping results in an additional Ti species due to TiO2-N. XPS suggests that nitrogen exists in substitutional sites, a conclusion which is reinforced by the PhD data where the N 1s and O 1s modulation functions exhibit similarities. Theoretical modulation functions are yet to be calculated and future work will aim to provide quantitative information regarding the substitutional nature of this system. The effect of adventitious carbon on Ti implants has been modelled by studying peptide adsorption on single crystal TiO2, both as-prepared and pyrocatechol capped. XPS shows that pyrocatechol successfully prevents the adsorption of adventitious carbon species from air and leads to a greater uptake of RGD, which bonds to Ti atoms via the deprotonated carboxylate groups. An increased uptake of RGD is also observed on the SLActive surface and we conclude that the chemistry of the hydrocarbon overlayer governs the uptake of RGD, and may affect osseointegration.

In the Summer of 2015, the Large Hadron Collider resumed operation after a two-year shutdown, providing proton-proton collisions at a record energy of 13 TeV. This thesis presents two measurements of data recorded by the ATLAS detector in proton-proton collisions at the LHC. The first is a measurement of the top-quark pair production cross-section. A dataset of 85 inverse picobarn recorded during an early operating period at the new centre-of-mass energy is used. The cross-section is measured in the single-lepton final state using a high-momentum electron or muon. Measured cross-section values from the two sub-channels and the combination are all consistent within their uncertainties with predictions from theoretical calculations. The second analysis using ATLAS data is a measurement of colour flow in top-quark pair events based on a dataset of 36.1 inverse femtobarn. This measurement also uses the single-lepton final state. Observables are constructed from the jet-pull vector, a momentum-weighted angular moment of a jet, which are sensitive to the colour flow in the signal event topology. Two scenarios are considered: the two jets originating from the hadronically decaying W boson and the two b-tagged jets from the top-quark decays. Observables derived from the former are sensitive to colour flow of a colour singlet while those derived from the latter probe the overall top-quark pair colour-flow. The measured observables are corrected for detector effects by unfolding them to particle level. Normalised unfolded distributions are compared to theoretical predictions taken from simulation and the agreement is quantified. Good agreement between the measured data and the predictions is observed for some combinations of observables and predictions. However, none of the predictions describes data well across all measured observables. A model with exotic colour flow is also constructed. The data favours the predictions from simulation according to the Standard Model over the model with exotic colour flow.

In this report we build on existing theories of Edge Localised Modes (ELMs) that incorporate the theory of Magnetic Relaxation, firstly by introducing the effects of the bootstrap current and secondly by applying the relaxation model to the field of ELM mitigation. The bootstrap current is a toroidal plasma current that arises spontaneously as a result of the confinement of the plasma. It is shown that the effect of introducing this current is to split the ELM widths associated with this model into two classes; one group with large ELM widths, the other with small ELM widths. An analytical study is then carried out which provides a theoretical basis for this bifurcation of results. Finally the idea of ELM mitigation using Resonant Magnetic Perturbations will be introduced before the Relaxation Theory of ELMs is used to give new insight into ELM mitigation results.

At present, high energy particle colliders, like the Large Hadron Collider (LHC), are used to investigate the nature and interactions of the elementary particles that make up matter. The precise determination of an interaction cross section at the LHC relies heavily on a robust determination of the delivered luminosity over a given time period. Two analyses are documented in this thesis. The first analysis comprised an investigation of the LHC beam density functions during van der Meer (vdM) scans. vdM scans are used by the ATLAS experiment to calibrate the visible interaction rates measured by a number of luminosity monitoring detectors to the absolute luminosity scale. The vdM scan methodology assumes that the beam density functions factorise in the horizontal and vertical directions. An investigation was carried out to test this assumption by using experimentally determined luminous region parameters, together with data from luminosity monitors in ATLAS, to constrain beam models defined as the sum of two or three Gaussian functions. The impact of the vertex-position resolution on this analysis was also investigated. The vdM scans analysed were performed during the 2012 proton-proton and 2013 proton-lead and lead-proton data-taking runs of the LHC. The second analysis reported is a feasibility study centred on the extraction of the cross section of the electroweak production of a leptonically decaying high mass off-shell Z boson in association with two hadronic jets (Zjj). The study used a dataset corresponding to $32.9 \,\mathrm{fb^{-1}}$ collected by ATLAS during the proton-proton data-taking run in 2016. The analysis was carried out in two channels, comprising Z boson decays to either a pair of muons or to a pair of electrons. The analysis first measured the on-shell electroweak Zjj cross section in the muon and electron channels using Zjj events in which the dilepton invariant mass was close to the rest mass of the Z boson. The analysis techniques were then extended to Zjj events in which the invariant mass of the dilepton pair was higher than the Z boson rest mass. The signal significance of high mass electroweak Zjj production was found to be around five sigma in the combined muon and electron channels for the dataset analysed. The study therefore demonstrated how, and to what degree of precision, the high mass electroweak Zjj production cross section could be measured using the dataset analysed and future LHC datasets.

Spectral line observations are of vital importance in astrophysics. Hydrogen recombination lines are a uniquely powerful tracer of ionised gas in the Galaxy, and of star formation and gas kinematics in other galaxies. Improvements in receiver performance at ~GHz frequencies has generated renewed interest in recombination lines from other galaxies. The 76m Lovell Telescope should be sensitive enough to detect recombination lines from new galaxies in 10-100 hrs. Jodrell Bank Observatory has been without a dedicated spectral line backend for more than 15 years. The advancement of digital technology means a step-change in bandwidth and resolution capability is now possible. A ROACH2 board was configured as a spectrometer with up to ≈15kHz resolution in two polarisations across 512MHz bandwidth and up to ≈62.5kHz resolution across 2GHz bandwidth in one polarisation. Signal transport systems were developed to allow observation of signals from the MkII and Lovell telescopes by the spectrometer. The 2GHz primary system was found to be dominated by correlated noise, introduced by the e-MERLIN frequency conversion system. Initial observations of the H96-103α recombination line were found to be dominated by the band shape, which will limit calibration accuracy. The MkII telescope was commissioned for use in spectral line observations. The C-band receiver showed good performance. f_knee≈17mHz across 250kHz was found, scaling with bandwidth as expected. The telescope pointing accuracy was found to be a limiting factor, with offsets up to ~50% of the half-power beam width observed. Nevertheless hourly corrections demonstrated that sources could be tracked with ≲10% incremental offsets required. A 1hr observation of the calibrator NGC 7027 indicated ≈6% increase in the effective system noise, indicating long observations are well-represented by the radiometer equation. The RFI environment at Jodrell Bank was examined. C-band was found to be largely available for observation. The range of H96-103αRRLs were reliably observable. L-band is densely populated with ~10⁹ Jy signals. The protected band was observed over a four-week period using the Lovell Telescope. A strong correlation is found between human activity and the presence of RFI in the protected band, indicating that even where parts of L-band appear free from coherent RFI, sensitive total-power observations must take place at night. The future of RRL studies from Jodrell Bank is in C-band Galactic plane surveys using the MkII; extragalactic RRL work is unfeasible. The Galactic anti-centre is sparsely observed. The MkII is capable of a fully-sampled survey of 10-20 square degrees with T_rms ~1mK sensitivity in ~ 100 days observing time.

Two experimental campaigns were performed at the Collinear Resonance Ionization Spectroscopy (CRIS) experiment, located at the ISOLDE radioactive-beam facility. The spectroscopic quadrupole moment of 203Fr was measured. Its magnitude with respect to the other even-N francium isotopes below N = 126 suggests an onset of static deformation. However, calculations of the static and total deformation parameters reveal that it cannot be considered as purely statically deformed. The neutron-rich radium isotopes were investigated. The spectroscopic quadrupole moment of 231Ra was measured and the continuation of increasing quadrupole deformation with neutron number in neutron-rich radium isotopes was further established. Measurements of the changes in mean-square charge radii of 231-233Ra allowed the odd-even staggering parameter to be calculated for 230-232Ra. A normal odd-even staggering which increases in magnitude with neutron number was observed in these isotopes.

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