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Search Results: 1 - 10 of 147844 matches for " Craig B. Dalton "
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Use of a geographic information system to track smelter-related lead exposures in children: North Lake Macquarie, Australia, 1991–2002
Alan Willmore, Tim Sladden, Lucy Bates, Craig B Dalton
International Journal of Health Geographics , 2006, DOI: 10.1186/1476-072x-5-30
Abstract: An analysis of serial blood lead levels (BLL) of children less than 13 years of age in North Lake Macquarie participating in voluntary blood lead screening. Distance to the smelter and soil lead concentration of the child's place of residence was calculated. Categorical analysis of BLL by residential distance from smelter, residential soil lead concentration, age and year of sample was calculated. Linear regression models were fit for blood lead levels against residential distance from smelter, the log of residential soil lead concentration, age and year of BLL sample.Geometric mean BLLs were statistically significantly higher for distances less than 1.5 kilometres from the smelter and for residential soil lead concentrations greater than 300 ppm. Yearly BLLs since 1995 were statistically significantly lower than for preceding years, with an average decrease of 0.575 μg/dL per year since 1991. BLLs are statistically significantly higher for children whose age is 1 to 3 years old. Linear regression modelling of BLL predicted a statistically significant decrease in BLL of 3.0831 μg/dL per kilometre from the smelter and a statistically significant increase in BLL of 0.25 μg/dL per log of lead in residential soil. The model explained 28.2% of the variation in BLL.Residential distance to the smelter, log of residential soil lead concentration, child's age and year of BLL sample are statistically significant factors for predicting elevated BLLs in children living near a North Lake Macquarie lead smelter.Newcastle is a city on the Australian eastern seaboard with a history of heavy industry including coal mining; metal smelting, production and fabrication; and mineral export via a deep water port facility. Over time, heavy industry in the area has been scaled back, including the recent closure of the Cockle Creek lead-zinc smelter in September 2003. The smelter is situated approximately 20 kilometres southwest of Newcastle city on Cockle Creek, which drains into the northe
A structured framework for improving outbreak investigation audits
Craig B Dalton, Tony D Merritt, David N Durrheim, Sally A Munnoch, Martyn D Kirk
BMC Public Health , 2009, DOI: 10.1186/1471-2458-9-472
Abstract: A framework for prioritising which outbreak investigations to audit, an approach for conducting a successful audit, and a template for audit trigger questions was developed and trialled in four foodborne outbreaks and a respiratory disease outbreak in Australia.The following issues were identified across several structured audits: the need for clear definitions of roles and responsibilities both within and between agencies, improved communication between agencies and with external stakeholders involved in outbreaks, and the need for development of performance standards in outbreak investigations - particularly in relation to timeliness of response. Participants considered the audit process and methodology to be clear, useful, and non-threatening. Most audits can be conducted within two to three hours, however, some participants felt this limited the scope of the audit.The framework was acceptable to participants, provided an opportunity for clarifying perceptions and enhancing partnership approaches, and provided useful recommendations for approaching future outbreaks. Future challenges include incorporating feedback from broader stakeholder groups, for example those of affected cases, institutions and businesses; assessing the quality of a specific audit; developing training for both participants and facilitators; and building a central capacity to support jurisdictions embarking on an audit. The incorporation of measurable performance criteria or sharing of benchmark performance criteria will assist in the standardisation of outbreak investigation audit and further quality improvement.Outbreak investigation is a core function of public health agencies. Suboptimal outbreak investigation endangers both public health and agency reputations. Surprisingly, there is little guidance on enhancing the quality of outbreak investigation and control provided to public health agencies. Audits of clinical medical and nursing practice are conducted as part of continuous quality
Estimating the Disease Burden of Pandemic (H1N1) 2009 Virus Infection in Hunter New England, Northern New South Wales, Australia, 2009
Fatimah S. Dawood,Kirsty G. Hope,David N. Durrheim,Rodney Givney,Alicia M. Fry,Craig B. Dalton
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009880
Abstract: On May 26, 2009, the first confirmed case of Pandemic (H1N1) 2009 virus (pH1N1) infection in Hunter New England (HNE), New South Wales (NSW), Australia (population 866,000) was identified. We used local surveillance data to estimate pH1N1-associated disease burden during the first wave of pH1N1 circulation in HNE.
THE APM CLUSTER SURVEY: CLUSTER DETECTION AND LARGE-SCALE STRUCTURE
G. B. Dalton
Physics , 1995,
Abstract: The APM Cluster Survey was based on a modification of Abell's original classification scheme for galaxy clusters. Here we discuss the results of an investigation of the stability of the statistical properties of the cluster catalogue to changes in the selection parameters. For a poor choice of selection parameters we find clear indications of line-of-sight clusters, but there is a wide range of input parameters for which the statistical properties of the catalogue are stable. We conclude that clusters selected in this way are indeed useful as tracers of large-scale structure.
Theory of decoherence in Bose-Einstein condensate interferometry
B J Dalton
Physics , 2007, DOI: 10.1088/1742-6596/67/1/012059
Abstract: A full treatment of decoherence and dephasing effects in BEC interferometry has been developed based on using quantum correlation functions for treating interferometric effects. The BEC is described via a phase space distribution functional of the Wigner type for the condensate modes and the positive P type for the non-condensate modes. Ito equations for stochastic condensate and non-condensate field functions replace the functional Fokker-Planck equation for the distribution functional and stochastic averages of field function products determine the quantum correlation functions.
Phase space theory of Bose-Einstein condensates and time-dependent modes
B. J. Dalton
Physics , 2011, DOI: 10.1016/j.aop.2012.06.005
Abstract: A phase space theory approach for treating dynamical behaviour of Bose-Einstein condensates applicable to situations such as interferometry with BEC in time-dependent double well potentials is presented. Time-dependent mode functions are used, chosen so that one, two,.. highly occupied modes describe well the physics of interacting condensate bosons in time dependent potentials at well below the transition temperature. Time dependent mode annihilation, creation operators are represented by time dependent phase variables, but time independent total field annihilation, creation operators are represented by time independent field functions. Two situations are treated, one (mode theory) is where specific mode annihilation, creation operators and their related phase variables and distribution functions are dealt with, the other (field theory) is where only field creation, annihilation operators and their related field functions and distribution functionals are involved. The paper focuses on the hybrid approach, where the modes are divided up between condensate (highly occupied) modes and non-condensate (sparsely occupied) modes. It is found that there are extra terms in the Ito stochastic equations both for the stochastic phases and stochastic fields, involving coupling coefficients defined via overlap integrals between mode functions and their time derivatives. For the hybrid approach both the Fokker-Planck and functional Fokker-Planck equations differ from those derived via the correspondence rules, the drift vectors are unchanged but the diffusion matrices contain additional terms involving the coupling coefficients. Results are also presented for the combined approach where all the modes are treated as one set.
Relative Phase States in Quantum-Atom Optics
B J Dalton
Physics , 2011,
Abstract: Relative phase is treated as a physical quantity for two mode systems in quantum atom optics, adapting the Pegg-Barnett treatment of quantum optical phase to define a linear Hermitian relative phase operator via first introducing a complete orthonormal set of relative phase eigenstates. These states are contrasted with other so-called phase states. Other approaches to treating phase and previous attempts to find a Hermitian phase operator are discussed. The relative phase eigenstate has maximal two mode entanglement, it is a fragmented state with its Bloch vector lying inside the Bloch sphere and is highly spin squeezed. The relative phase states are applied to describing interferometry experiments with Bose-Einstein condensates (BEC), particularly in the context of a proposed Heisenberg limited interferometry experiment. For a relative phase eigenstate the fractional fluctuation in one spin operator component perpendicular to the Bloch vector is essentially only of order 1/N, so if such a highly spin squeezed state could be prepared it may be useful for Heisenberg limited interferometry. An approach for preparing a BEC in a state close to a relative phase state is suggested, based on adiabatically changing parameters in the Josephson Hamiltonian starting from a suitable energy eigenstate in the Rabi regime.
Scaling of Decoherence Effects in Quantum Computers
B. J. Dalton
Physics , 2002, DOI: 10.1080/09500340308234544
Abstract: The scaling of decoherence rates with the number of q-bits is studied for a simple quantum computer model. Two state q-bits are localised around well-separated positions via trapping potentials, but vibrational motion of q-bits centre of mass motion occurs. Coherent one and two q-bit gating processes are controlled by external classical fields and facilitated by a high Q cavity mode. Decoherence due to q-bit and cavity mode coupling to a bath of spontaneous emission modes, cavity decay modes and to the vibrational modes is treated. A non-Markovian treatment of the short time behaviour of the fidelity is presented, enabling time scales for decoherence to be determined, together with their dependence on q-bit number for the case where the q-bit/cavity mode system is in a pure state and the baths are in thermal states.
Decoherence effects in Bose-Einstein condensate interferometry. I General Theory
B. J. Dalton
Physics , 2010, DOI: 10.1016/j.aop.2010.10.006
Abstract: The present paper outlines a basic theoretical treatment of decoherence and dephasing effects in interferometry based on single component BEC in double potential wells, where two condensate modes may be involved. Results for both two mode condensates and the simpler single mode condensate case are presented. A hybrid phase space distribution functional method is used where the condensate modes are described via a truncated Wigner representation, and the basically unoccupied non-condensate modes are described via a positive P representation. The Hamiltonian for the system is described in terms of quantum field operators for the condensate and non-condensate modes. The functional Fokker-Planck equation for the double phase space distribution functional is derived. Equivalent Ito stochastic equations for the condensate and non-condensate fields that replace the field operators are obtained, and stochastic averages of products of these fields give the quantum correlation functions used to interpret interferometry experiments. The stochastic field equations are the sum of a deterministic term obtained from the drift vector in the functional Fokker-Planck equation, and a noise field whose stochastic properties are determined from the diffusion matrix in the functional Fokker-Planck equation. The noise field stochastic properties are similar to those for Gaussian-Markov processes in that the stochastic averages of odd numbers of noise fields are zero and those for even numbers of noise field terms are sums of products of stochastic averages associated with pairs of noise fields. However each pair is represented by an element of the diffusion matrix rather than products of the noise fields themselves. The treatment starts from a generalised mean field theory for two condensate mode. The generalized mean field theory solutions are needed for calculations using the Ito stochastic field equations.
Two-Mode Theory of BEC Interferometry
B J Dalton
Physics , 2006, DOI: 10.1080/09500340600677682
Abstract: A theory of BEC interferometry in an unsymmetrical double-well trap has been developed for small boson numbers, based on the two-mode approximation. The bosons are initially in the lowest mode of a single well trap, which is split into a double well and then recombined. Possible fragmentations into separate BEC states in each well during the splitting/recombination process are allowed for. The BEC is treated as a giant spin system, the fragmented states are eigenstates of S^2 and Sz. Self-consistent sets of equations for the amplitudes of the fragmented states and for the two single boson mode functions are obtained. The latter are coupled Gross-Pitaevskii equations. Interferometric effects may be measured via boson numbers in the first excited mode
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