This thesis describes a study of resource brokering in a computational Grid for high energy physics. Such systems are being devised in order to manage the unprecedented workload of the next generation particle physics experiments such as those at the Large Hadron Collider. A simulation of the European Data Grid has been constructed, and calibrated using logging data from a real Grid testbed. This model is then used to explore the Grid's middleware configuration, and suggest improvements to its scheduling policy. The expansion of the simulation to include data analysis of the type conducted by particle physicists is then described. A variety of job and data management policies are explored, in order to determine how well they meet the needs of physicists, as well as how efficiently they make use of CPU and network resources. Appropriate performance indicators are introduced in order to measure how well jobs and resources are managed from different perspectives. The effects of inefficiencies in Grid middleware are explored, as are methods of compensating for them. It is demonstrated that a scheduling algorithm should alter its weighting on load balancing and data distribution, depending on whether data transfer or CPU requirements dominate, and also on the level of job loading. It is also shown that an economic model for data management and replication can improve the efficiency of network use and job processing.

Two assumptions pervade contemporary metaphysics: that there is a fundamental level to reality, and that physics will one day describe it. In the first part of this thesis, I consider whether physics may have a greater role for fundamentality metaphysics than that which it is typically accorded. In particular, I consider whether physics might contribute not just to questions of the content of an assumed fundamental level, but to the existence of such a level itself. I argue that if we are to use physics to do such a thing, it must be through what I call the 'internal' approach, in which fundamentality questions are addressed through the lens of extant physical theory. Through two case studies drawn from particle physics, I show that it is indeed possible to deny fundamentality through this means - or at least, that one may do so as legitimately as one may make other propositions of physicalistic metaphysics. While this is a non-trivial achievement, the internal approach nevertheless imposes a profound limitation on the sort of fundamentality that we can use physics to deny, in that it precludes the denial of fundamental physical principles. This raises the question of whether such principles ought to be regarded as somehow more fundamental even than particles. I argue that this question is naturally construed as the question of whether we ought to regard the category of dynamical structures as more ontologically fundamental than the category of objects. The claim that structure is ontologically prior to objects is the signature claim of ontic structuralism, and in the second part of this thesis I consider whether it can be defended. I ultimately argue that structuralism can indeed be supported, but that it is only its moderate version that is vindicated.

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The cross section for charm and beauty jets ts is measured in neutral current deep inelastic scattering in e-p collisions at HERA 11. The data set used is based on an integrated luminosity of 189 pb-1 and was recorded using the HI detector in 2006 and 2007. A method, based on the distance of closest approach of the track to the primary vertex, is used to identify the fractions of events associated with heavy-flavoured mesons.

Magnet Power Supplies (MPSs) for high current magnet loads are extensively used in high energy physics applications such as partical-beam excitation and control for particle accelerator systems. The requirements for MPSs include very low output waveform ripple and demanding transient performance. In addition, low volume and high efficiency are also a benefit in many applications. The purpose of this project was to investigate the suitable converter topology for a DC magnet load using the example power converter specification used to power the Diamond Light Source Storage Ring Quadrupole Magnets. The proposed converter was based on soft-switching resonant converter technology. The input stage consisted of a three phase diode rectifier with a DC link capacitor connected on the grid. The output stage was composed of a synchronous current doubler rectifier (SCDR) linked to the input stage using a series resonant parallel loaded (SRPL) inverter with a high frequency step down transformer. The dynamic model of the converter suitable for control design was based on a DQ approach. The power losses analysis was also presented to predict the converter efficiency. The converter was simulated using a MATLAB simulink in conjunction with PLECS. The design and construction of the converter including the magnet load emulator were presented in detail. Simulation and experimental results verify the feasibility of the proposed converter topology and the modelling method. Finally, the experimental converter power losses compared to the simulated losses estimation confirm the reliability of the power losses principle.