The problem with Kappa

It is becoming clear that traditional evaluation measures used in Computational Linguistics (including Error Rates, Accuracy, Recall, Precision and F-measure) are of limited value for unbiased evaluation of systems, and are not meaningful for comparison of algorithms unless both the dataset and algorithm parameters are strictly controlled for skew (Prevalence and Bias). The use of techniques originally designed for other purposes, in particular Receiver Operating Characteristics Area Under Curve, plus variants of Kappa, have been proposed to fill the void. This paper aims to clear up some of the confusion relating to evaluation, by demonstrating that the usefulness of each evaluation method is highly dependent on the assumptions made about the distributions of the dataset and the underlying populations. The behaviour of a number of evaluation measures is compared under common assumptions. Deploying a system in a context which has the opposite skew from its validation set can be expected to approximately negate Fleiss Kappa and halve Cohen Kappa but leave Powers Kappa unchanged. For most performance evaluation purposes, the latter is thus most appropriate, whilst for comparison of behaviour, Matthews Correlation is recommended

Earth's multi-scale topographic response to global mantle flow

Earth's surface topography is a direct physical expression of our planet's dynamics. Most is isostatic, controlled by variations in thickness and density within the crust and lithosphere, but a significant proportion arises due to forces exerted by underlying mantle convection. This dynamic topography directly connects the evolution of surface environments to Earth's deep interior, but it remains poorly understood: predictions from mantle flow simulations are often inconsistent with inferences from the geological record, with little consensus about its spatial pattern, wavelength and amplitude. Here, we demonstrate that previous comparisons between predictive models and observational constraints have been biased by subjective choices. Using measurements of residual topography beneath the world's oceans, and an innovative statistical approach to performing spherical harmonic analyses, we generate a robust estimate of Earth's oceanic residual topography power spectrum. Our analyses imply power of 0.5 +- 0.35 km^2 and peak amplitudes of 0.8 +- 0.1 km at long-wavelength (~10^4 km), decreasing by roughly one order of magnitude at shorter wavelengths (~10^3 km). We show that geodynamical simulations can only be reconciled with these observational constraints if they incorporate lithospheric structure and its impact on global mantle flow, illustrating that both deep (long-) and shallow (shorter-wavelength) processes are crucial to generating the observed surface response. Our results imply that dynamic topography is intimately connected to the structure and evolution of Earth's lithosphere, presenting a challenge to the reconstruction of its temporal evolution and impact at Earth's surface

Development of an activated carbon-based system for combined plasmapheresis and adsorption in the treatment of sepsis

This paper looks at the development of an activated carbon-based system for combined plasmapheresis and adsorption in the treatment of sepsi

A novel system for combined plasmapheresis and adsorption in the treatment of sepsis, based on activated carbon

This paper looks at a novel system for combined plasmapheresis and adsorption in the treatment of sepsis, based on activated carbo

Assessing the in vitro biocompatibility of a novel carbon device for the treatment of sepsis

The aim of the present study was to conduct a preliminary investigation into the blood biocompatibility of a novel, uncoated carbon for use in a filtration/adsorption device for the treatment of sepsis. Carbon well prototypes were manufactured from phenol-formaldehyde-aniline-based pyrolysed carbons using monolithic polymer technology. Inflammatory blood cell and plasma protein mediation of the inflammatory response were evaluated using the novel carbon prototypes and compared with dialyser membrane and tissue culture plate controls. Assays determining monocyte and granulocyte adhesion, platelet adhesion and activation, granulocyte activation and complement activation were performed. Preliminary findings suggest an adsorptive but passivating carbon surface. Moderate levels of monocyte and granulocytes adhesion were seen in conjunction with adsorption of plasma proteins to the carbon surface. Activation of granulocyte and adherent platelets was not detected and the complement cascade was not activated by the carbons, indicating a surface compatible with blood contact. The results support the further development of the proposed carbon-based device for the treatment of sepsis

The in vitro adsorption of cytokines by polymer-pyrolysed carbon

This study investigated a range of phenolformaldehydeaniline based pyrolysed carbon matrices and their component materials, for their ability to adsorb a range of inflammatory cytokines crucial to the progression of sepsis. The efficiency of adsorption of the target molecules from human plasma was assessed and compared to that of Adsorba® 300C, a commercially available cellulose-coated activated charcoal. Results indicate that a number of the primary carbon/resin materials demonstrate efficient adsorption of the cytokines studied here (TNF, IL-6 and IL-8), comparable to other adsorbents under clinical investigation. Our findings also illustrate that these adsorbent capabilities are retained when the primary particles are combined to form a pyrolysed carbon matrix. This capability will enable the engineering of the carbon matrix porosity allowing a blend of carbonised particle combinations to be tailored for maximum adsorption of inflammatory cytokines. The present findings support further investigation of this carbon material as a combined carbon-based filtration/adsorbent device for direct blood purification