ORCID Profile
0000-0002-9518-7087
Current Organisations
Centers for Disease Control and Prevention
,
Australian National University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Atomic, Molecular, Nuclear, Particle and Plasma Physics | Dynamical Systems | Power and Energy Systems Engineering (excl. Renewable Power) | Plasma Physics; Fusion Plasmas; Electrical Discharges | Plasmas And Electrical Discharges | Pure Mathematics | Numerical Solution of Differential and Integral Equations | Theoretical Physics | Fluid Physics | Numerical and Computational Mathematics | Simulation And Modelling | Mathematical Physics | Classical Physics | Numerical Analysis | Turbulent Flows | Harmonic And Fourier Analysis | Space and Solar Physics | Thermodynamics And Statistical Physics | Other Plasma Physics
ANZSRC Socio-Economic Objective (SEO)
Physical sciences | Mathematical sciences | Nuclear Energy | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in the Mathematical Sciences | Biological sciences | Earth sciences | Energy transformation not elsewhere classified | Behavioural and cognitive sciences | Renewable energy not elsewhere classified (e.g. geothermal) |
Related Links
Publications
Action-gradient-minimizing pseudo-orbits and almost-invariant tori
Publisher: Elsevier BV
Date: 05-2012
Corrigendum: ‘Stepped pressure profile equilibria in cylindrical plasmas via partial Taylor relaxation [J. Plasma Physics (2006), vol. 72, part 6, pp. 1167–1171].’
Publisher: Cambridge University Press (CUP)
Date: 04-2021
Metamorphosis of plasma turbulence–shear-flow dynamics through a transcritical bifurcation
Publisher: American Physical Society (APS)
Date: 16-12-2002
Comment on “Radial Structure of High-Mode-Number Toroidal Modes in General Equilibrium Profiles”
Publisher: American Physical Society (APS)
Date: 29-05-1995
On the relationship between the multi-region relaxed variational principle and resistive inner-layer theory
Publisher: IOP Publishing
Date: 23-05-2023
Abstract: We show that the variational energy principle of the multi-region relaxed magnetohydrodynamic (MRxMHD) model can be used to predict finite-pressure linear tearing instabilities. In this model, the plasma volume is sliced into sub-volumes separated by ‘ideal interfaces’, and in each volume the magnetic field relaxes to a Taylor state, where the pressure gradient ∇ p = 0 . The MRxMHD model is implemented in the Stepped-Pressure Equilibrium Code (SPEC) so that the equilibrium solution in each region is computed while preserving the force balance across the interfaces. As SPEC computes the Hessian matrix (a discretized stability matrix), the stability of an MRxMHD equilibrium can also be computed with SPEC. In this article, using SPEC, we investigate the effect of local pressure gradients and the ∇ p = 0 in the vicinity of the resonant surface of a tearing mode. For low-beta plasma, we have been able to illustrate a relationship between the resistive singular-layer theory (Coppi et al 1966 Nucl. Fusion 6 101 Glasser et al 1975 Phys. Fluids 18 875–88) and the MRxMHD model. Within the singular layer, the volume-averaged magnetic helicity and the flux-averaged toroidal flux are shown to be the invariants for the linear tearing modes in SPEC simulations. Our technique to compute MRxMHD stability is first tested numerically in a cylindrical tokamak and its application in toroidal geometry is demonstrated. We demonstrate an agreement between the stability boundary obtained with SPEC simulation and the resistive inner-layer theories.
Induced scattering of light by light in a vacuum
Publisher: American Physical Society (APS)
Date: 12-1974
Are ghost surfaces quadratic-flux-minimizing?
Publisher: Elsevier BV
Date: 12-2009
Subdynamics of nonresonant wave-particle interactions
Publisher: American Physical Society (APS)
Date: 05-1986
Coordinate parameterisation and spectral method optimisation for Beltrami field solver in stellarator geometry
Publisher: IOP Publishing
Date: 03-11-2020
Abstract: The numerical solution of the stepped pressure equilibrium (Hudson et al 2012 Phys. Plasmas 19 112502) requires a fast and robust solver to obtain the Beltrami field in three-dimensional geometry such as stellarators. The spectral method implemented in the stepped pressure equilibrium code (SPEC) is efficient when the domain is a hollow torus, but ill-conditioning of the discretised linear equations occurs in the (solid) toroid due to the artificially singular coordinate parameterisation near the axis. In this work, we propose an improved choice for the reference axis to prevent coordinates surfaces from overlapping. Then, we examine the parity and asymptotics of the magnetic vector potential near the axis and suggest the use of recombined and rescaled Zernike radial basis functions. The maximum relative error in the magnetic field of the Wendelstein 7-X geometry is shown to reach 10 −9 at high resolution in a series of convergence tests and benchmarks against the boundary integral equation solver for Taylor states. The new method is also reported to significantly improve the accuracy of multi-volume SPEC calculations. A comparison between free-boundary SPEC and the analytical Dommaschk potential is presented with higher-than-usual Fourier resolution. It is illustrated that we are able to resolve low litude current sheets when an interface is placed where there is no flux surface in the analytic solution. This was previously concealed because of insufficient numerical resolution.
Energy loss due to binary collisions in a relativistic plasma
Publisher: American Physical Society (APS)
Date: 11-1979
Computation of multi-region relaxed magnetohydrodynamic equilibria
Publisher: AIP Publishing
Date: 07-2012
DOI: 10.1063/1.4890847
Abstract: We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes pressure anisotropy and general plasma flows. This anisotropic extension to our previous isotropic model is motivated by Sun and Finn's model of relaxed anisotropic magnetohydrodynamic equilibria. We prove that as the number of plasma regions becomes infinite, our anisotropic extension of MRxMHD reduces to anisotropic ideal MHD with flow. The continuously nested flux surface limit of our MRxMHD model is the first variational principle for anisotropic plasma equilibria with general flow fields.
Asymptotology—a cautionary tale
Publisher: Cambridge University Press (CUP)
Date: 07-2002
DOI: 10.1017/S1446181100007884
Abstract: The art of asymptotology is a powerful tool in applied mathematics and theoretical physics, but can lead to erroneous conclusions if misapplied. A seemingly paradoxical case is presented in which a local analysis of an exactly solvable problem appears to find solutions to an eigenvalue problem over a continuous range of the eigenvalue, whereas the spectrum is known to be discrete. The resolution of the paradox involves the Stokes phenomenon. The ex le illustrates two of Kruskal's Principles of Asymptotology.
Dual-active-ingredient, insecticidal nets for preventing malaria: a systematic review protocol [version 1; peer review: 1 approved with reservations, 1 not approved]
Publisher: F1000 Research Ltd
Date: 09-09-2022
DOI: 10.12688/F1000RESEARCH.123983.1
Abstract: Background: Malaria is caused by the Plasmodium parasite and is a highly transmissible disease representing a significant global public health burden. The provision of insecticide-treated mosquito nets (ITNs) has contributed to the reduction of malaria across endemic countries. However, the detection of insecticide resistance in many mosquito vector species potentially threatens the long-term effectiveness of ITNs. A novel method to reduce the impact of insecticide resistance is to treat mosquito nets with multiple active ingredients. Methods and analysis: This review will comprehensively search the literature (both published and unpublished) for any studies investigating the effectiveness of mosquito nets treated with multiple active ingredients, known henceforth as dual-active-ingredient (DAI) ITNs. The DAI ITNs of interest include those treated with a pyrethroid and non-pyrethroid insecticide (review question 1) or with a pyrethroid and an insect growth regulator (review question 2). Studies will be screened to meet the inclusion criteria by a minimum of two authors, followed by assessment of risk of bias (using appropriate risk of bias tools for randomised and non-randomised studies) and extraction of relevant information using structured forms by two independent authors. Meta-analyses will be carried out where possible for epidemiological outcomes and subgrouping will be considered. Certainty in the evidence will be established with GRADE assessments. Ethics and dissemination: A full review report will be submitted to the Vector Control and Insecticide Resistance Unit, Global Malaria Program, WHO. A version of this report will be submitted for publication in an open access peer-reviewed journal. The report will inform the development of WHO recommendations regarding the use of DAI ITNs for the prevention of malaria. This systematic review does not require ethics approval as it is a review of primary studies. Registration : PROSPERO ID: CRD42022333044
Spectrum of global ideal-magnetohydrodynamic three-dimensional ballooning modes
Publisher: Springer Science and Business Media LLC
Date: 2003
Particle orbits and drift surfaces in a heliac
Publisher: IOP Publishing
Date: 07-1998
Modulational Instabilities Due to Trapped Electrons
Publisher: American Physical Society (APS)
Date: 24-01-1972
Relaxed Plasma Equilibria and Entropy-Related Plasma Self-Organization Principles
Publisher: MDPI AG
Date: 14-11-2008
DOI: 10.3390/E10040621
Testing models and measurement invariance of the learning gains scale
Publisher: MDPI AG
Date: 31-10-2018
Abstract: This study tested the construct validity, factorial validity, and measurement invariance of the learning gains scale based on survey responses of a large s le (n = 536) of undergraduate students in two colleges at a university in Ethiopia. The analyses were performed through structural equation modeling technique using the stata 13 data analysis and statistical software package. The results demonstrate a 3-factor model representing the underlying construct satisfying the different model goodness-of-fit statistics and practical indexes. The observed factor loadings of variables within each factor and the correlations between the factors provide supporting evidence of construct validity. Measurement invariance tests were also confirmed acceptable levels of measurement equivalence between groups. Implications of the 3-factor model in higher education research are discussed.
Strong “Quantum” Chaos in the Global Ballooning Mode Spectrum of Three-Dimensional Plasmas
Publisher: American Physical Society (APS)
Date: 12-03-2001
Variational formulation of relaxed and multi-region relaxed magnetohydrodynamics
Publisher: Cambridge University Press (CUP)
Date: 27-11-2015
DOI: 10.1017/S0022377815001336
Abstract: Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor relaxation model for formation of macroscopically self-organized plasma equilibrium states, all these constraints are relaxed save for the global magnetic fluxes and helicity. A Lagrangian variational principle is presented that leads to a new, fully dynamical, relaxed magnetohydrodynamics (RxMHD), such that all static solutions are Taylor states but also allows state with flow. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-region relaxed magnetohydrodynamics (MRxMHD) is developed.
Spectrum of the ballooning Schrödinger equation
Publisher: IOP Publishing
Date: 03-1997
Eigenvalue problems for Beltrami fields arising in a three-dimensional toroidal magnetohydrodynamic equilibrium problem
Publisher: AIP Publishing
Date: 05-2007
DOI: 10.1063/1.2722721
Abstract: A generalized energy principle for finite-pressure, toroidal magnetohydrodynamic (MHD) equilibria in general three-dimensional configurations is proposed. The full set of ideal-MHD constraints is applied only on a discrete set of toroidal magnetic surfaces (invariant tori), which act as barriers against leakage of magnetic flux, helicity, and pressure through chaotic field-line transport. It is argued that a necessary condition for such invariant tori to exist is that they have fixed, irrational rotational transforms. In the toroidal domains bounded by these surfaces, full Taylor relaxation is assumed, thus leading to Beltrami fields ∇×B=λB, where λ is constant within each domain. Two distinct eigenvalue problems for λ arise in this formulation, depending on whether fluxes and helicity are fixed, or boundary rotational transforms. These are studied in cylindrical geometry and in a three-dimensional toroidal region of annular cross section. In the latter case, an application of a residue criterion is used to determine the threshold for connected chaos.
Quasisymmetric magnetic fields in asymmetric toroidal domains
Publisher: AIP Publishing
Date: 11-2021
DOI: 10.1063/5.0065633
Abstract: We explore the existence of quasisymmetric magnetic fields in asymmetric toroidal domains. These vector fields can be identified with a class of magnetohydrodynamic equilibria in the presence of pressure anisotropy. First, using Clebsch potentials, we derive a system of two coupled nonlinear first order partial differential equations expressing a family of quasisymmetric magnetic fields in bounded domains. In regions where flux surfaces and surfaces of constant field strength are not tangential, this system can be further reduced to a single degenerate nonlinear second order partial differential equation with externally assigned initial data. Subclasses of solutions are then constructed by specifying as input the form the flux function, which enforces boundary shape and nested flux surfaces. In particular, we exhibit smooth quasisymmetric vector fields, which correspond to local solutions of anisotropic magnetohydrodynamics in asymmetric toroidal domains such that tangential boundary conditions are fulfilled on a portion of the bounding surface. These solutions are local because they lack periodicity in the toroidal angle. The problems of boundary shape and locality are also discussed. We find that magnetic fields with Euclidean isometries can be fitted into asymmetric domains and that the mathematical difficulty encountered in the derivation of global quasisymmetric magnetic fields lies in the topological obstruction toward global extension affecting local solutions of the governing nonlinear first order partial differential equations.
Magnetohydrodynamic stability of plasmas with ideal and relaxed regions
Publisher: Cambridge University Press (CUP)
Date: 10-2009
DOI: 10.1017/S0022377809008095
Abstract: A unified energy principle approach is presented for analysing the magnetohydrodynamic (MHD) stability of plasmas consisting of multiple ideal and relaxed regions. The gauge a = ξ × B for the vector potential, a , of linearized perturbations is used, with the equilibrium magnetic field B obeying a Beltrami equation, ∇ × B = α B , in relaxed regions. In a region with such a force-free equilibrium Beltrami field we show that ξ obeys the same Euler–Lagrange equation whether ideal or relaxed MHD is used for perturbations, except in the neighbourhood of the magnetic surfaces where B · ∇ is singular. The difference at singular surfaces is analysed in cylindrical geometry: in ideal MHD only Newcomb's small solutions are allowed, whereas in relaxed MHD only the odd-parity large solution and even-parity small solution are allowed. A procedure for constructing global multi-region solutions in cylindrical geometry is presented. Focusing on the limit where the two interfaces approach each other arbitrarily closely, it is shown that the singular-limit problem encountered previously by Hole et al. in multi-region relaxed MHD is stabilized if the relaxed-MHD region between the coalescing interfaces is replaced by an ideal-MHD region. We then present a stable ( k , pressure) phase-space plot, which allows us to determine the form a stable pressure and field profile must take in the region between the interfaces. From this knowledge, we conclude that there exists a class of single-interface plasmas that were found to be stable by Kaiser and Uecker, but are shown to be unstable when the interface is resolved.
Quantum chaos analysis of the ideal interchange spectrum in a stellarator
Publisher: Cambridge University Press (CUP)
Date: 12-2006
Equilibria and stability in partially relaxed plasma-vacuum systems
Publisher: IOP Publishing
Date: 17-07-2007
Bifurcation in electrostatic resistive drift wave turbulence
Publisher: AIP Publishing
Date: 10-2007
DOI: 10.1063/1.2796106
Abstract: The Hasegawa-Wakatani equations, coupling plasma density, and electrostatic potential through an approximation to the physics of parallel electron motions, are a simple model that describes resistive drift wave turbulence. Numerical analyses of bifurcation phenomena in the model are presented, that provide new insights into the interactions between turbulence and zonal flows in the tokamak plasma edge region. The simulation results show a regime where, after an initial transient, drift wave turbulence is suppressed through zonal flow generation. As a parameter controlling the strength of the turbulence is tuned, this zonal-flow-dominated state is rapidly destroyed and a turbulence-dominated state re-emerges. The transition is explained in terms of the Kelvin-Helmholtz stability of zonal flows. This is the first observation of an upshift of turbulence onset in the resistive drift wave system, which is analogous to the well-known Dimits shift in turbulence driven by ion temperature gradients.
Multi-region relaxed magnetohydrodynamics with flow
Publisher: AIP Publishing
Date: 04-2014
DOI: 10.1063/1.4870008
Abstract: We present an extension of the multi-region relaxed magnetohydrodynamics (MRxMHD) equilibrium model that includes plasma flow. This new model is a generalization of Woltjer's model of relaxed magnetohydrodynamics equilibria with flow. We prove that as the number of plasma regions becomes infinite, our extension of MRxMHD reduces to ideal MHD with flow. We also prove that some solutions to MRxMHD with flow are not time-independent in the laboratory frame, and instead have 3D structure which rotates in the toroidal direction with fixed angular velocity. This capability gives MRxMHD potential application to describing rotating 3D MHD structures such as "snakes" and long-lived modes.
Renormalised canonical perturbation theory for stochastic propagators
Publisher: IOP Publishing
Date: 12-1976
Anomalous transport barriers due to sheared radial electric fields in tokamaks
Publisher: IOP Publishing
Date: 11-1995
Global Variability in Administrative Approval Prescription Criteria for Biologic Therapy in Severe Asthma
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JAIP.2021.12.027
Abstract: Regulatory bodies have approved five biologics for severe asthma. However, regional differences in accessibility may limit the global potential for personalized medicine. To compare global differences in ease of access to biologics. In April 2021, national prescription criteria for omalizumab, mepolizumab, reslizumab, benralizumab, and dupilumab were reviewed by severe asthma experts collaborating in the International Severe Asthma Registry. Outcomes (per country, per biologic) were (1) country-specific prescription criteria and (2) development of the Biologic Accessibility Score (BACS). The BACS composite score incorporates 10 prescription criteria, each with a maximum score of 10 points. Referenced to European Medicines Agency marketing authorization specifications, a higher score reflects easier access. Biologic prescription criteria differed substantially across 28 countries from five continents. Blood eosinophil count thresholds (usually ≥300 cells/μL) and exacerbations were key requirements for anti-IgE/anti-IL-5/5R prescriptions in around 80% of licensed countries. Most countries (40% for dupilumab to 54% for mepolizumab) require two or more moderate or severe exacerbations, whereas numbers ranged from none to four. Moreover, 0% (for reslizumab) to 21% (for omalizumab) of countries required long-term oral corticosteroid use. The BACS highlighted marked between-country differences in ease of access. For omalizumab, mepolizumab, benralizumab, and dupilumab, only two, one, four, and seven countries, respectively, scored equal or higher than the European Medicines Agency reference BACS. For reslizumab, all countries scored lower. Although some differences were expected in country-specific biologic prescription criteria and ease of access, the substantial differences found in the current study present a challenge to implementing precision medicine across the world.
Energy Principle with Global Invariants for Toroidal Plasmas
Publisher: American Physical Society (APS)
Date: 04-08-1980
Relaxed magnetohydrodynamics with ideal Ohm's law constraint
Publisher: Cambridge University Press (CUP)
Date: 02-2022
DOI: 10.1017/S0022377821001355
Abstract: The gap between a recently developed dynamical version of relaxed magnetohydrodynamics (RxMHD) and ideal MHD (IMHD) is bridged by approximating the zero-resistivity ‘ideal’ Ohm's law (IOL) constraint using an augmented Lagrangian method borrowed from optimization theory. The augmentation combines a pointwise vector Lagrange multiplier method and global penalty function method and can be used either for iterative enforcement of the IOL to arbitrary accuracy, or for constructing a continuous sequence of magnetofluid dynamics models running between RxMHD (no IOL) and weak IMHD (IOL almost everywhere). This is illustrated by deriving dispersion relations for linear waves on an MHD equilibrium.
Residual insecticide surface treatment for preventing malaria: a systematic review protocol
Publisher: Cold Spring Harbor Laboratory
Date: 14-12-2021
DOI: 10.1101/2021.12.13.21267747
Abstract: Malaria presents a significant global public health burden, although substantial progress has been made, with vector control initiatives such as indoor residual surface spraying with insecticides and insecticide treated nets. There now exists many different approaches to apply residual insecticide to indoor and outdoor surfaces in malaria endemic settings. This review aims to synthesise the best available evidence regarding full or partial indoor or outdoor residual insecticide surface treatment for preventing malaria. This review will comprehensively search the literature (both published and unpublished) for any studies investigating the effectiveness of residual insecticide surface treatment for malaria. Studies will be screened to meet the inclusion criteria by a minimum of two authors, followed by assessment of risk of bias (using appropriate risk of bias tools for randomised and non-randomised studies) and extraction of relevant information using structured forms by two independent authors. Meta-analysis will be carried out where possible for epidemiological outcomes such as malaria, anaemia, malaria related mortality, all-cause mortality and adverse effects. Certainty in the evidence will be established with GRADE assessments. A full review report will be submitted to the Vector Control & Insecticide Resistance Unit, Global Malaria Program, WHO. A version of this report will be submitted for publication in an open access peer-reviewed journal. The report will inform the development of WHO recommendations regarding residual insecticide treatment for malaria. This systematic review does not require ethics approval as it is a review of primary studies. PROSPERO, ID 293194 (in progress as of 24 th November, 2021)
Energy Principle with Globial Invariants for Toroidal Plasmas
Publisher: American Physical Society (APS)
Date: 06-10-1980
Helical bifurcation and tearing mode in a plasma-a description based on Casimir foliation
Publisher: IOP Publishing
Date: 22-08-2012
Relaxed MHD states of a multiple region plasma
Publisher: IOP Publishing
Date: 19-05-2009
DOI: 10.1088/0029-5515/49/6/065019
Abstract: We calculate the stability of a multiple relaxation region MHD (MRXMHD) plasma, or stepped-Beltrami plasma, using both variational and tearing mode treatments. The configuration studied is a periodic cylinder. In the variational treatment, the problem reduces to an eigenvalue problem for the interface displacements. For the tearing mode treatment, analytic expressions for the tearing mode stability parameter Δ′, being the jump in the logarithmic derivative in the helical flux across the resonant surface, are found. The stability of these treatments is compared for m = 1 displacements of an illustrative reverse field pinch-like configuration, comprising two distinct plasma regions. For pressureless configurations, we find the marginal stability conclusions of each treatment to be identical, confirming the analytical results in the literature. The tearing mode treatment also resolves ideal MHD unstable solutions for which Δ′ → ∞: these correspond to displacement of a resonant interface. Wall stabilization scans resolve the internal and external ideal kink. Scans with increasing pressure are also performed: these indicate that both variational and tearing mode treatments have the same stability trends with β, and show destabilization in configurations with increasing core pressure. Combined, our results suggest that variational stability of MRXMHD configurations is sufficient for both ideal and tearing (Δ′ 0) stability. Such configurations, and their stability properties, are of emerging importance in the quest to find mathematically rigorous solutions of ideal MHD force balance in 3D geometry.
Stellarator stability with respect to global kinetic ballooning modes
Publisher: IOP Publishing
Date: 16-03-2006
Resistive stability of cylindrical MHD equilibria with radially localized pressure gradients
Publisher: AIP Publishing
Date: 06-2019
DOI: 10.1063/1.5099354
Abstract: As a step toward understanding 3D magnetohydrodynamic (MHD) equilibria, for which smooth solutions may not exist, we develop a simple cylindrical model to investigate the resistive stability of MHD equilibria with alternating regions of constant and nonuniform pressure, producing states with continuous total pressure (i.e., no singular current sheets) but discontinuities in the parallel current density. We examine how the resistive stability characteristics of the model change as we increase the localization of pressure gradients at fixed radii, which approaches a discontinuous pressure profile in the zero-width limit. Equilibria with continuous pressure are found to be unstable to moderate/high-m modes and apparently tend toward ideal instability in some cases. We propose that additional geometric degrees of freedom or symmetry breaking via island formation may increase the parameter space on which equilibria of our model are physically realizable, while preserving the radial localization of pressure gradients. This is consistent with the possibility of realizing, in practice, 3D MHD equilibria which support both continuously nested flux surfaces (where ∇p ≠ 0) and chaotic field regions (where ∇p = 0).
Effectiveness of dual active ingredient insecticide-treated nets in preventing malaria: A systematic review and meta-analysis
Publisher: Public Library of Science (PLoS)
Date: 16-08-2023
DOI: 10.1371/JOURNAL.PONE.0289469
Abstract: Malaria vectors have demonstrated resistance to pyrethroid-based insecticides used in insecticide-treated nets, diminishing their effectiveness. This systematic review and meta-analysis investigated two forms of dual active-ingredient (DAI) insecticide-treated nets (ITN(s)) for malaria prevention. A comprehensive search was conducted on July 6 th 2022. The databases searched included PubMed, Embase, CINAHL, amongst others. Trials were eligible if they were conducted in a region with ongoing malaria transmission. The first DAI ITN investigated were those that combined a pyrethroid with a non-pyrethroid insecticides. The second DAI ITN investigated were that combined a pyrethroid with an insect growth regulator. These interventions were compared against either a pyrethroid-only ITN, or ITNs treated with pyrethroid and piperonyl-butoxide. Assessment of risk of bias was conducted in duplicate using the Cochrane risk of bias 2 tool for cluster-randomised trials. Summary data was extracted using a custom data-extraction instrument. This was conducted by authors THB, JCS and SH. Malaria case incidence was the primary outcome and has been meta-analysed, adverse events were narratively synthesised. The review protocol is registered on PROSPERO (CRD42022333044). From 9494 records, 48 reports were screened and 13 reports for three studies were included. These studies contained data from 186 clusters and all reported a low risk of bias. Compared to pyrethroid-only ITNs, clusters that received pyrethroid-non-pyrethroid DAI ITNs were associated with 305 fewer cases per 1000-person years (from 380 fewer cases to 216 fewer cases) (IRR = 0.55, 95%CI: 0.44–0.68). However, this trend was not observed in clusters that received pyrethroid-insect growth regulator ITNs compared to pyrethroid-only ITNs (from 280 fewer cases to 135 more) (IRR = 0.90, 95%CI: 0.73–1.13). Pyrethroid-non-pyrethroid DAI ITNs demonstrated consistent reductions in malaria case incidence and other outcomes across multiple comparisons. Pyrethroid-non-pyrethroid DAI ITNs may present a novel intervention for the control of malaria.
Non-axisymmetric, multi-region relaxed magnetohydrodynamic equilibrium solutions
Publisher: IOP Publishing
Date: 08-12-2012
On the non-existence of stepped-pressure equilibria far from symmetry
Publisher: IOP Publishing
Date: 25-10-2021
Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries—Resonant response of a plasma slab
Publisher: AIP Publishing
Date: 04-2017
DOI: 10.1063/1.4979350
Abstract: The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm–Kulsrud–Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad–Shafranov equation applies, even at finite ripple litude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple litude is calculated by invoking the conservation of magnetic helicity in the two regions separated by the current sheet. At low ripple litude, “half islands” appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical litude, these islands disappear and the rotational transform develops a discontinuity across the current sheet.
Dressed test particles, oscillation centres and pseudo-orbits
Publisher: IOP Publishing
Date: 19-05-2012
Anderson localization of ballooning modes, quantum chaos and the stability of compact quasiaxially symmetric stellarators
Publisher: AIP Publishing
Date: 23-04-2002
DOI: 10.1063/1.1448344
Abstract: The radially local magnetohydrodynamic (MHD) ballooning stability of a compact, quasiaxially symmetric stellarator (QAS), is examined just above the ballooning beta limit with a method that can lead to estimates of global stability. Here MHD stability is analyzed through the calculation and examination of the ballooning mode eigenvalue isosurfaces in the 3-space (s,α,θk) s is the edge normalized toroidal flux, α is the field line variable, and θk is the perpendicular wave vector or ballooning parameter. Broken symmetry, i.e., deviations from axisymmetry, in the stellarator magnetic field geometry causes localization of the ballooning mode eigenfunction, and gives rise to new types of nonsymmetric eigenvalue isosurfaces in both the stable and unstable spectrum. For eigenvalues far above the marginal point, isosurfaces are topologically spherical, indicative of strong “quantum chaos.” The complexity of QAS marginal isosurfaces suggests that finite Larmor radius stabilization estimates will be difficult and that fully three-dimensional, high-n MHD computations are required to predict the beta limit.
Diamagnetic drift stabilized ballooning modes in a 3D heliotron
Publisher: IOP Publishing
Date: 08-12-2012
Exact oscillation-centre transformations
Publisher: IOP Publishing
Date: 1978
Turbulent edge structure formation in complex configurations
Publisher: AIP Publishing
Date: 21-08-2003
DOI: 10.1063/1.1602074
Abstract: Formation of nonlinear structures in drift-Alfvén turbulence is investigated in the often complex edge geometries of stellarator and tokamak configurations, by analysis of drift wave turbulence simulations using a model in which three-dimensional magnetic geometries are approximated. The structures of parallel mode extension, radially sheared zonal flows and perpendicular mode spectra are highlighted in particular for three-dimensional stellarator magnetic fields and shaped tokamaks. Specific characteristics of advanced stellarators in comparison to (lower aspect ratio) circular tokamaks are a less pronounced ballooning structure of the modes, a strong influence of local magnetic shear on litude structure and average, and stronger level of zonal flows due to lower geodesic curvature.
Hamilton–Jacobi theory for continuation of magnetic field across a toroidal surface supporting a plasma pressure discontinuity
Publisher: Elsevier BV
Date: 07-2010
Time-dependent relaxed magnetohydrodynamics: Inclusion of cross helicity constraint using phase-space action
Publisher: AIP Publishing
Date: 06-2020
DOI: 10.1063/5.0005740
Abstract: A phase-space version of the ideal magnetohydrodynamic (MHD) Lagrangian is derived from first principles and shown to give a relabeling transformation when a cross-helicity constraint is added in Hamilton's Action Principle. A new formulation of time-dependent “relaxed” magnetohydrodynamics is derived using microscopic conservation of mass and macroscopic constraints on total magnetic helicity, cross helicity, and entropy under variations of density, pressure, fluid velocity, and magnetic vector potential. This gives Euler–Lagrange equations consistent with previous work on both ideal and relaxed MHD equilibria with flow, but generalizes the relaxation concept from statics to dynamics. The application of the new dynamical formalism is illustrated for short-wavelength linear waves, and the interface connection conditions for Multiregion Relaxed MHD (MRxMHD) are derived. The issue of whether E+u×B=0 should be a constraint is discussed.
Predicting nonresonant pressure-driven MHD modes in equilibria with low magnetic shear
Publisher: AIP Publishing
Date: 2021
DOI: 10.1063/5.0032489
Abstract: Nonresonant internal modes can be difficult to anticipate as there is no resonant surface in the plasma. However, equilibria that are unstable to multiple nonresonant magnetohydrodynamic (MHD) modes may be more prone to global loss of confinement since these instabilities generate spatially extended linear displacements, potentially enhancing magnetic field line chaos via nonlinear interactions. Here, we successfully predict the unstable nonresonant pressure-driven modes for equilibria with zero shear in the plasma core, irrational q on axis, and a central pressure gradient, which is consistent with pre-crash profiles in sawtoothing tokamak plasmas in the large-aspect-ratio limit. A criterion for identifying nonresonant modes most likely to be unstable is developed from the convergents of the continued fraction representation of q0. A higher-order analysis of the standard Energy Principle reveals the conditions under which these modes are expected to dominate. Linear growth rate spectra, as a function of toroidal mode number (up to n = 30), calculated using the initial-value extended-MHD code, M3D-C1, recover the characteristic dependence observed for ideal infernal modes. Nonresonant modes have also been invoked in some ideal sawtooth crash models. This work provides a mechanism to predict the mode numbers of infernal modes and, potentially, the width of some post-sawtooth-crash profiles.
Minimally Constrained Model of Self-Organized Helical States in Reversed-Field Pinches
Publisher: American Physical Society (APS)
Date: 30-07-2013
Computation of multi-region relaxed magnetohydrodynamic equilibria
Publisher: AIP Publishing
Date: 11-2012
DOI: 10.1063/1.4765691
Abstract: We describe the construction of stepped-pressure equilibria as extrema of a multi-region, relaxed magnetohydrodynamic (MHD) energy functional that combines elements of ideal MHD and Taylor relaxation, and which we call MRXMHD. The model is compatible with Hamiltonian chaos theory and allows the three-dimensional MHD equilibrium problem to be formulated in a well-posed manner suitable for computation. The energy-functional is discretized using a mixed finite-element, Fourier representation for the magnetic vector potential and the equilibrium geometry and numerical solutions are constructed using the stepped-pressure equilibrium code, SPEC. Convergence studies with respect to radial and Fourier resolution are presented.
Statistical Mechanics of Ideal Fermions in a Thin Film
Publisher: American Physical Society (APS)
Date: 05-01-1968
Nature of ideal MHD instabilities as described by multi-region relaxed MHD
Publisher: IOP Publishing
Date: 28-04-2022
Abstract: In this work, the stepped pressure equilibrium code (SPEC) (Hudson et al 2012 Phys. Plasmas 19 112502), which computes the equilibria of the multi-region relaxed magnetohydrodynamic energy principle (MRxMHD), has been upgraded to determine the MRxMHD stability in toroidal geometry. A theoretical formalism for SPEC is obtained by relating the second variation of the MRxMHD energy functional to the Hessian matrix, enabling the prediction of magnetohydrodynamic (MHD) linear instabilities. Negative eigenvalues of this matrix imply instability. Further, we demonstrate our method on simplified test scenarios in both tokamak and stellarator magnetic topologies, with a systematic comparison study between the marginal stability prediction of the SPEC with the ideal MHD stability code packages CAS3D and MISHKA-1.
Theoretical description of chirping waves using phase-space waterbags
Publisher: IOP Publishing
Date: 27-04-2021
Abstract: The guiding centre dynamics of fast particles can alter the behaviour of energetic particle (EP) driven modes with chirping frequencies. In this paper, the applicability of an earlier trapped assing locus model (Hezaveh et al 2017 Nucl. Fusion 57 126010) has been extended to regimes where the wave trapping region can expand and trap ambient particles. This extension allows the study of waves with up-ward and down-ward frequency chirping across the full range of EP orbits. Under the adiabatic approximation, the phase-space of EPs is analysed by a Lagrangian contour approach where the islands are discretised using phase-space waterbags. In order to resolve the dynamics during the fast formation of phase-space islands and find an appropriate initialisation for the system, full-scale modelling is implemented using the bump-on-tail code. In addition to investigating the evolution of chirping waves with deepening potentials in a single resonance, we choose specific pitch-angle ranges in which higher resonances can have a relatively considerable contribution to the wave-particle interaction. Hence, the model is also solved in a double-resonance scenario where we report on the significant modifications to the behaviour of the chirping waves due to the 2nd resonance. The model presented in this paper gives a comprehensive 1D paradigm of long range frequency chirping signals observed in experiments with both up-ward and down-ward chirping and multiple resonances.
A comparison of incompressible limits for resistive plasmas
Publisher: IOP Publishing
Date: 25-05-2004
The infinite interface limit of multiple-region relaxed magnetohydrodynamics
Publisher: AIP Publishing
Date: 03-2013
DOI: 10.1063/1.4795739
Abstract: We show the stepped-pressure equilibria that are obtained from a generalization of Taylor relaxation known as multi-region, relaxed magnetohydrodynamics (MRXMHD) are also generalizations of ideal magnetohydrodynamics (ideal MHD). We show this by proving that as the number of plasma regions becomes infinite, MRXMHD reduces to ideal MHD. Numerical convergence studies illustrating this limit are presented.
Genome-wide association studies of cognitive and motor progression in Parkinson's disease
Publisher: Cold Spring Harbor Laboratory
Date: 08-05-2020
DOI: 10.1101/2020.05.07.20084343
Abstract: Background: There are currently no treatments that stop or slow the progression of Parkinson's disease (PD). Case-control genome-wide association studies (GWASs) have identified variants associated with disease risk, but not progression. Objective: To identify genetic variants associated with PD progression in GWASs. Methods: We analysed three large, longitudinal cohorts: Tracking Parkinson's, Oxford Discovery, and the Parkinson's Progression Markers Initiative. We included clinical data for 3,364 patients with 12,144 observations (mean follow-up 4.2 years). We used a new method in PD, following a similar approach in Huntington's disease, where we combined multiple assessments using a principal components analysis to derive scores for composite, motor, and cognitive progression. These scores were analysed in linear regressions in GWASs. We also performed a targeted analysis of the 90 PD risk loci from the latest case-control meta-analysis. Results: There was no overlap between variants associated with PD risk, from case-control studies, and PD age at onset versus PD progression. The APOE ϵ4 tagging variant, rs429358, was significantly associated with the rate of composite and cognitive progression in PD. No single variants were associated with motor progression. However in gene-based analysis, variation across ATP8B2, a phospholipid transporter related to vesicle formation, was nominally associated with motor progression (p=5.3 x 10^-6). Conclusions: This new method in PD improves measurement of symptom progression. We provide strong evidence that the APOE ϵ4 allele drives progressive cognitive impairment in PD. We have also reported loci of interest which need to be tested in further studies.
Generalized action-angle coordinates defined on island chains
Publisher: IOP Publishing
Date: 17-12-2013
Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity
Publisher: Springer Science and Business Media LLC
Date: 18-01-2020
DOI: 10.1007/S00401-019-02107-8
Abstract: The IPDGC (The International Parkinson Disease Genomics Consortium) and EADB (Alzheimer Disease European DNA biobank) are listed correctly as an author to the article, however, they were incorrectly listed more than once.
A reduced global Alfvén eigenmodes model for Mirnov array data on the H-1NF heliac
Publisher: IOP Publishing
Date: 23-06-2011
Plasmoid solutions of the Hahm-Kulsrud-Taylor equilibrium model
Publisher: AIP Publishing
Date: 08-2013
DOI: 10.1063/1.4817276
Abstract: The Hahm–Kulsrud (HK) [T. S. Hahm and R. M. Kulsrud, Phys. Fluids 28, 2412 (1985)] solutions for a magnetically sheared plasma slab driven by a resonant periodic boundary perturbation illustrate fully shielded (current sheet) and fully reconnected (magnetic island) responses. On the global scale, reconnection involves solving a magnetohydrodynamic (MHD) equilibrium problem. In systems with a continuous symmetry, such MHD equilibria are typically found by solving the Grad–Shafranov equation, and in slab geometry the elliptic operator in this equation is the 2-D Laplacian. Thus, assuming appropriate pressure and poloidal current profiles, a conformal mapping method can be used to transform one solution into another with different boundary conditions, giving a continuous sequence of solutions in the form of partially reconnected magnetic islands (plasmoids) separated by Syrovatsky current sheets. The two HK solutions appear as special cases.
Stepped pressure profile equilibria in cylindrical plasmas via partial Taylor relaxation
Publisher: Cambridge University Press (CUP)
Date: 12-2006
Statistical characterization of the interchange-instability spectrum of a separable ideal-magnetohydrodynamic model system
Publisher: American Physical Society (APS)
Date: 27-12-2004
The effects of informal cooperative learning pedagogy on teaching effectiveness, task orientation, and learning satisfaction in undergraduate classrooms in Ethiopia
Publisher: Informa UK Limited
Date: 22-05-2020
Neuronal intranuclear inclusion disease is genetically heterogeneous
Publisher: Wiley
Date: 10-08-2020
DOI: 10.1002/ACN3.51151
Spectrum of multi-region-relaxed magnetohydrodynamic modes in topologically toroidal geometry
Publisher: IOP Publishing
Date: 02-2017
Assessing the dimensionality and educational impacts of integrated ICT literacy in the higher education context
Publisher: Australasian Society for Computers in Learning in Tertiary Education
Date: 28-03-2018
DOI: 10.14742/AJET.2957
Abstract: The purpose of this paper is threefold: first, to introduce a conceptual model for assessing undergraduate students’ integrated information and communication technology (ICT) literacy capacity that involves 12 items generated from the modified version of the Australasian Survey of Student Engagement (AUSSE) questionnaire (Coates, 2010) second, to illustrate the construct validity and internal consistency of the model as implemented in a s le of undergraduate students (n = 536) enrolled in two colleges within a large Ethiopian university and third, to further demonstrate the criterion validity of the model by examining predictive validity of the identified ICT literacy factors on student learning outcomes. A multi-method approach is used, which comprises correlation analysis, multiple regression analysis and structural equation modelling (SEM) techniques. The main finding is the support found for the 4-factor model consisting of ICT use, cognitive process, reading task and writing task. Results of the multi-method approach provide specific guidelines to higher education (HE) institutions using this approach to evaluate ICT literacy capacity and the resultant learning outcomes among their undergraduate students. The paper provides a conceptual model and supporting tools that can be used by other HE institutions to assist in the evaluation of students’ ICT literacy capacities.
Computation of linear MHD instabilities with the multi-region relaxed MHD energy principle
Publisher: IOP Publishing
Date: 11-02-2021
Abstract: Over the last decade, a variational principle based on a generalisation of Taylor’s relaxation, referred to as multi-region relaxed magnetohydrodynamics (MRxMHDs) has been developed. The numerical solutions of the MRxMHD equilibria have been constructed using the Stepped Pressure Equilibrium Code (SPEC) (Hudson et al 2012 Phys. Plasmas 19 112502). In principle, SPEC could also be established to describe the MRxMHD stability of an equilibrium. In this work, a theoretical framework is developed to relate the second variation of the energy functional to the so-called Hessian matrix, enabling the prediction of MHD linear instabilities of cylindrical plasmas, and is implemented in SPEC. The negative and positive eigenvalues of the Hessian matrix predict the stability of an equilibrium. Verification studies of SPEC stability results with the M3D- C 1 code and the tearing mode Δ ′ criterion have been conducted for ideal and resistive MHD instabilities, respectively, in a pressureless cylindrical tokamak, and have shown good agreement. Our stability analysis is a critical step towards understanding the MHD stability of three-dimensional MHDs where nested flux surfaces, magnetic islands and stochastic regions co-exist.
Related Organisations
Training And Research Unit Of Excellence, College Of Medicine
Location: Malawi
Academic Medical Center - University Of Amsterdam
Location: Netherlands
Related Funding Activities
(Emergence And Control Of Self-organisation In Fusion Plasmas: Through The International Thermonuclear Experimental Reactor (ITER) And Beyond)
Start Date: 2011
End Date: 2013
Funder: Australian Research Council
View Funded ActivityProject DP140100790
Start Date: 2014
End Date: 2016
Funder: Australian Research Council
View Funded ActivityHidden Symmetries And Fusion Energy
Start Date: 2018
End Date: 2022
Funder: Simons Foundation
View Funded ActivityMulti-Region Relaxation Dynamics In Fusion And Stellar Plasmas
Start Date: 2017
End Date: 2019
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0452728
Start Date: 2004
End Date: 12-2007
Amount: $255,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP1093797
Start Date: 2010
End Date: 12-2013
Amount: $285,000.00
Funder: Australian Research Council
View Funded ActivityLinkage - International - Grant ID: LX0347292
Start Date: 07-2003
End Date: 07-2005
Amount: $9,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP110102881
Start Date: 2011
End Date: 12-2014
Amount: $255,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0343765
Start Date: 2003
End Date: 12-2008
Amount: $605,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP140100790
Start Date: 2014
End Date: 05-2018
Amount: $270,000.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354716
Start Date: 12-2003
End Date: 12-2004
Amount: $10,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP170102606
Start Date: 2017
End Date: 12-2021
Amount: $353,500.00
Funder: Australian Research Council
View Funded ActivityResearch Networks - Grant ID: RN0460006
Start Date: 07-2004
End Date: 06-2009
Amount: $1,500,000.00
Funder: Australian Research Council
View Funded Activity