Kinetic instabilities that limit {\beta} in the edge of a tokamak plasma: a picture of an H-mode pedestal

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak (MAST) have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM steep gradients in pressure, P, and density, ne, form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes (KBMs) in the pedestal and microtearing modes (MTMs) in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal.Comment: Final version as it appeared in PRL (March 2012). Minor improvements include: shortened abstract, and better colour table for figures. 4 pages, 6 figure

Comment on "Drip Paintings and Fractal Analysis", arXiv:0710.4917v2, by K. Jones-Smith, H. Mathur and L.M. Krauss

In a recent manuscript (arXiv:0710.4917v2), Jones-Smith et al. attempt to use the well-established box-counting technique for fractal analysis to "demonstrate conclusively that fractal criteria are not useful for authentication". Here, in response to what we view to be an extremely simplistic misrepresentation of our earlier work by Jones-Smith et al., we reiterate our position regarding the potential of fractal analysis for artwork authentication. We also point out some of the flaws in the analysis presented in by Jones-Smith et al.Comment: Comment on arXiv:0710.4917v2 [cond-mat.stat-mech

Electric Light: Automating the Carceral State During the Quantification of Everything

This dissertation traces the rise of digitally-driven policing technologies in order to make sense of how prevailing logics of governance are transformed by ubiquitous computing technology. Beginning in the early 1990s, police departments and theorists began to rely on increasingly detailed sets of metrics to evaluate performance. The adoption of digital technology to streamline quantitative evaluation coincided with a steep decline in measured crime that served as a proof-of-concept for the effectivity of digital police surveillance and analytics systems. During the turbulent first two decades of the 21st century, such digital technologies were increasingly associated with reform projects designed to improve the transparency and accountability of police departments. This dissertation challenges that assertion, and argues that digitization functions to make “numerical” and “mathematical” racial and sexual violence that is internal to policing neoliberal political economy. Rather than transparency and accountability, this dissertation posits that the effect of digitally-driven police technology is the accelerative disentangling of the “human” from “life” and “life” from government. The consequence has been the ossification of a racialized carceral under the aegis of putatively anti-racist technocratic governance

Microstability analysis of pellet fuelled discharges in MAST

Reactor grade plasmas are likely to be fuelled by pellet injection. This technique transiently perturbs the profiles, driving the density profile hollow and flattening the edge temperature profile. After the pellet perturbation, the density and temperature profiles relax towards their quasi-steady-state shape. Microinstabilities influence plasma confinement and will play a role in determining the evolution of the profiles in pellet fuelled plasmas. In this paper we present the microstability analysis of pellet fuelled H-mode MAST plasmas. Taking advantage of the unique capabilities of the MAST Thomson scattering system and the possibility of synchronizing the eight lasers with the pellet injection, we were able to measure the evolution of the post-pellet electron density and temperature profiles with high temporal and spatial resolution. These profiles, together with ion temperature profiles measured using a charge exchange diagnostic, were used to produce equilibria suitable for microstability analysis of the equilibrium changes induced by pellet injection. This analysis, carried out using the local gyrokinetic code GS2, reveals that the microstability properties are extremely sensitive to the rapid and large transient excursions of the density and temperature profiles, which also change collisionality and beta e significantly in the region most strongly affected by the pellet ablation.Comment: 21 pages, 10 figures. This is an author-created, un-copyedited version of an article submitted for publication in Plasma Physics and Controlled Fusion. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Regarding the editorial by Sau and Ng. 'Hypertrophic cardiomyopathy risk stratification based on clinical or dynamic electrophysiological features: two sides of the same coin'

This Letter to the Editor refers to article ‘Hypertrophic cardiomyopathy risk stratification based on clinical or dynamic electrophysiological features: two sides of the same coin’ by Sau A, Ng, FS https://doi.org/10.1093/europace/euad072. ‘Response to the letter to the editor EUPC-D-23-00362 of Richard Saumarez’, by Arunashis Sau and Fu Siong Ng, https://doi.org/10.1093/europace/euad174