Small x divergences in a heavy quark-antiquark state

With the current state of similarity renormalisation group approach to light-front QCD, it is possible to address with a degree of generality the issue of light-cone zero modes. We find, contrary to earlier results in a less general framework, that infrared divergences associated with the zero modes do not cancel out in a color singlet heavy quark-antiquark states, except for the lowest order in the nonrelativistic expansion.Comment: 3 pgs. Talk, originally entitled "Die Hard with Vengence", presented at the Int. Light-Cone Workshop "Light-Cone Physics: Particles and Strings", Trento 200

The Accord and Strikes: An International Perspective

This paper examines the relationship between Australian and world strike activity between 1960 and 1998. Appropriate indices are constructed for which evidence of a long-run equilibrium relation is found between Australian and world strike activity. The evidence suggests Australian and world strike rate indices are cointegrated with a breakpoint in that relation occurring sometime in the very late 1960s or early 1970s. No breakpoints are in evidence before, during or after the period (1983-96) of the Accord. This result is consistent with the view that the decline in strike activity in Australia during the period of the Accord was not a singularly Australian experience.The Accord, strikes, strike activity, Australia

Quarkonia in Hamiltonian Light-Front QCD

A constituent parton picture of hadrons with logarithmic confinement naturally arises in weak coupling light-front QCD. Confinement provides a mass gap that allows the constituent picture to emerge. The effective renormalized Hamiltonian is computed to ${\cal O}(g^2)$, and used to study charmonium and bottomonium. Radial and angular excitations can be used to fix the coupling $\alpha$, the quark mass $M$, and the cutoff $\Lambda$. The resultant hyperfine structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much more reader-friendly); corrected error in self-energ

Light-front Hamiltonians for heavy quarks and gluons

A boost-invariant light-front Hamiltonian formulation of canonical quantum chromodynamics provides a heuristic picture of the binding mechanism for effective heavy quarks and gluons.Comment: 10 pages, 6 figures, Invited talk at the Workshop on Light-Cone QCD and Nonperturbative Hadron Physics (LC2005), Cairns, Australia, 7-15 Jul 200

From the bottom to the top: Assessing the potential subsurface migration of fracking-related fluids along natural geological pathways

Over the last century humans have increasingly gone from just extracting fluids from the subsurface to also injecting them, for example hydraulic fracturing (fracking) for shale gas. Concurrently, there has been increased environmental interest in how injected fluids might interact with natural groundwater systems. One potential environmental impact of fracking is the contamination of shallow groundwater from the upward migration of injected and formation fluids along natural geological pathways. High-permeability fault and fracture zones have generally been regarded as the highest-risk pathway. Therefore, the first aim of this thesis was to determine a horizontal respect distance between fluid injection locations and known faults. Using published microseismic data a horizontal respect distance of ~900 m was proposed. The second aim of this thesis was to consider complex geological structure in numerical models to investigate hydrogeological factors which might increase the vulnerability of shallow groundwater resources to the potential upward migration of fracking-related fluids. Using 2D and 3D numerical models four hydrogeological factors increased the vulnerability of a shallow aquifer to upward fluid migration from an underlying shale reservoir: increased stimulated fracture extent; greater amounts of overpressure; the presence of low-permeability faults; and the absence of deep high-permeability formations. Low-permeability faults acted to compartmentalise groundwater, thereby discouraging regional horizontal flow whilst encouraging upward flow through strata. The integration of groundwater quality and seismic reflection data provided a novel method for identifying compartmentalisation, but compartmentalisation could not be identified from surface water quality data in the studied basin. However, analysis of surface water quality data could demonstrate regional-scale groundwater-surface water interactions. Importantly, this thesis highlights the need to understand and model interactions between deep groundwater, shallow groundwater, and surface waters by integrating data from a variety of industry and environmental regulatory sources

Note on restoring manifest rotational symmetry in hyperfine and fine structure in light-front QED

We study the part of the renormalized, cutoff QED light-front Hamiltonian that does not change particle number. The Hamiltonian contains interactions that must be treated in second-order bound state perturbation theory to obtain hyperfine structure. We show that a simple unitary transformation leads directly to the familiar Breit-Fermi spin-spin and tensor interactions, which can be treated in degenerate first-order bound-state perturbation theory, thus simplifying analytic light-front QED calculations. To the order in momenta we need to consider, this transformation is equivalent to a Melosh rotation. We also study how the similarity transformation affects spin-orbit interactions.Comment: 17 pages, latex fil

Initial bound state studies in light-front QCD

We present the first numerical QCD bound state calculation based on a renormalization group-improved light-front Hamiltonian formalism. The QCD Hamiltonian is determined to second order in the coupling, and it includes two-body confining interactions. We make a momentum expansion, obtaining an equal-time-like Schrodinger equation. This is solved for quark-antiquark constituent states, and we obtain a set of self-consistent parameters by fitting B meson spectra.Comment: 38 pages, latex, 5 latex figures include

Recruiting and engaging new mothers in nutrition research studies: lessons from the Australian NOURISH randomised controlled trial

Background: Despite important implications for the budgets, statistical power and generalisability of research findings, detailed reports of recruitment and retention in randomised controlled trials (RCTs) are rare. The NOURISH RCT evaluated a community-based intervention for first-time mothers that promoted protective infant feeding practices as a primary prevention strategy for childhood obesity. The aim of this paper is to provide a detailed description and evaluation of the recruitment and retention strategies used. Methods: A two stage recruitment process designed to provide a consecutive sampling framework was used. First time mothers delivering healthy term infants were initially approached in postnatal wards of the major maternity services in two Australian cities for consent to later contact (Stage 1). When infants were about four months old mothers were re-contacted by mail for enrolment (Stage 2), baseline measurements (Time 1) and subsequent random allocation to the intervention or control condition. Outcomes were assessed at infant ages 14 months (Time 2) and 24 months (Time 3). Results: At Stage 1, 86% of eligible mothers were approached and of these women, 76% consented to later contact. At Stage 2, 3% had become ineligible and 76% could be recontacted. Of the latter, 44% consented to full enrolment and were allocated. This represented 21% of mothers screened as eligible at Stage 1. Retention at Time 3 was 78%. Mothers who did not consent or discontinued the study were younger and less likely to have a university education. Conclusions: The consent and retention rates of our sample of first time mothers are comparable with or better than other similar studies. The recruitment strategy used allowed for detailed information from non-consenters to be collected; thus selection bias could be estimated. Recommendations for future studies include being able to contact participants via mobile phone (particular text messaging), offering home visits to reduce participant burden and considering the use of financial incentives to support participant retention