Performance Assessment of Feature Detection Algorithms: A Methodology and Case Study on Corner Detectors

In this paper we describe a generic methodology for evaluating the labeling performance of feature detectors. We describe a method for generating a test set and apply the methodology to the performance assessment of three well-known corner detectors: the Kitchen-Rosenfeld, Paler et al. and Harris-Stephens corner detectors. The labeling deficiencies of each of these detectors is related to their discrimination ability between corners and various of the features which comprise the class of noncorners

An improved rotation-invariant thinning algorithm

Ahmed & Ward have recently presented an elegant, rule-based rotation-invariant thinning algorithm to produce a single-pixel wide skeleton from a binary image. We show examples where this algorithm fails on two-pixel wide lines and propose a modified method which corrects this shortcoming based on graph connectivity

The contribution of AMPA receptors to neuropathic pain

Neuropathic pain is defined as pain arising as a result of damage to or dysfunction of the nervous system and is often resistant to opiate analgesics, making it difficult to treat using conventional therapies. Underlying the development of this chronic pathological pain state is a process of neuronal plasticity termed central sensitisation, involving changes from the spinal to the cortical levels of the central nervous system. Central sensitisation may result in thermal hyperalgesia and mechanical and cold allodynia which are commonly found in this condition. Neurons in the dorsal horn undergo plastic changes during central sensitisation, markedly altering their response profile to sensory stimulation. Glutamate is the major excitatory neurotransmitter at synapses between primary afferents and spinal dorsal horn neurons and plays a vital role in the generation of neuronal plasticity. Several key receptors are involved in altering the sensitivity of these neurons, including ionotropic and metabotropic glutamate receptors and peptidergic receptors.This study was designed to investigate the role of AMPA, NMDA, mGlu group I and VPAC₂ receptors (Rs) in the generation of neuropathic pain. Firstly, the behavioural reflex responses of naive rats to intrathecal administration of low doses of these receptor agonists, singly or in combinations were investigated. Combinations of two or more agonists caused increased behavioural responses to thermal and mechanical stimuli. The combination of AMPA with mGluR group I and VPAC₂ R agonists, showed a synergistic effect whereas other combinations were less than additiveExpression of AMPA R GluRl and GluR2 subunits in the superficial dorsal horn was studied using confocal immunofluorescence. In the chronic constriction injury (CCI) model of neuropathic pain both the number of GluRl-immunopositive cell bodies and the level of GluRl expression within cells decreased significantly in lamina II of the dorsal horn, ipsilateral to the injury. In contrast, there was no change in GluR2 expression or the degree of colocalisation of GluRl and GluR2 subtypes within individual cells following CCI.The subcellular distribution of GluRl subunits was also noted to change significantly as a result of CCI. GluRl subunits were found to redistribute distally into neuronal processes in lamina II cells ipsilateral to CCI and also in response to acute intrathecal AMPA treatment. This redistribution may reflect an increase in the number of GluRl-containing receptors associated with synaptic sites.The relationship between the presynaptic marker protein, Bassoon and GluRl - immunopositive cells was investigated, showing a significant increase in the number of Bassoon immunopositive puncta associated with each GluRl-immunopositive cell ipsilateral to nerve injury. The subcellular redistribution of GluRl subunits caused by CCI was reversed upon behavioural recovery and also by intrathecal administration of a combination of antagonists to NMDA R, mGluRl/5 and VPAC₂ R, whereas an AMPA R antagonist alone had no effect.These results suggest that AMPA Rs are important in the central sensitisation underlying neuropathic pain. However, it is clear that several receptors are involved in triggering maximal behavioural responses, and potential therapeutic interventions may be more effective if designed to target more than one receptor type. There is also evidence to suggest that AMPA Rs may have differing roles dependant upon their subtype composition, so subtype-specific antagonists may potentially be useful in treatment of neuropathic pain

Decomposition of high dimensional pattern spaces for hierarchical classification

summary:In this paper we present a novel approach to decomposing high dimensional spaces using a multiobjective genetic algorithm for identifying (near-)optimal subspaces for hierarchical classification. This strategy of pre-processing the data and explicitly optimising the partitions for subsequent mapping onto a hierarchical classifier is found to both reduce the learning complexity and the classification time with no degradation in overall classification error rate. Results of partitioning pattern spaces are presented and compared with various algorithms

Improved sampling of the pareto-front in multiobjective genetic optimizations by steady-state evolution: a Pareto converging genetic algorithm

Previous work on multiobjective genetic algorithms has been focused on preventing genetic drift and the issue of convergence has been given little attention. In this paper, we present a simple steady-state strategy, Pareto Converging Genetic Algorithm (PCGA), which naturally samples the solution space and ensures population advancement towards the Pareto-front. PCGA eliminates the need for sharing/niching and thus minimizes heuristically chosen parameters and procedures. A systematic approach based on histograms of rank is introduced for assessing convergence to the Pareto-front, which, by definition, is unknown in most real search problems. We argue that there is always a certain inheritance of genetic material belonging to a population, and there is unlikely to be any significant gain beyond some point; a stopping criterion where terminating the computation is suggested. For further encouraging diversity and competition, a nonmigrating island model may optionally be used; this approach is particularly suited to many difficult (real-world) problems, which have a tendency to get stuck at (unknown) local minima. Results on three benchmark problems are presented and compared with those of earlier approaches. PCGA is found to produce diverse sampling of the Pareto-front without niching and with significantly less computational effort

Revealing the microstructural stability of a three-phase soft solid (ice cream) by 4D synchrotron X-ray tomography

Understanding the microstructural stability of soft solids is key to optimizing formulations and processing parameters to improve the materials' properties. In this study, in situ synchrotron X-ray tomography is used to determine the temperature dependence of ice-cream's microstructural evolution, together with the underlying physical mechanisms that control microstructural stability. A new tomographic data processing method was developed, enabling the features to be segmented and quantified. The time-resolved results revealed that the melting-recrystallization mechanism is responsible for the evolution of ice crystal size and morphology during thermal cycling between −15 and −5 °C, while coalescence of air cells is the dominant coarsening mechanism controlling air bubble size and interconnectivity. This work also revealed other interesting phenomena, including the role of the unfrozen matrix in maintaining the ice cream's microstructural stability and the complex interactions between ice crystals and air structures, e.g. the melting and recrystallization of ice crystals significantly affect the air cell's morphology and the behavior of the unfrozen matrix. The results provide crucial information enhancing the understanding of microstructural evolution in multi-phase multi-state complex foodstuffs and other soft solids

Pruning of genetic programming trees using permutation tests

We present a novel approach based on statistical permutation tests for pruning redundant subtrees from genetic programming (GP) trees that allows us to explore the extent of effective redundancy . We observe that over a range of regression problems, median tree sizes are reduced by around 20% largely independent of test function, and that while some large subtrees are removed, the median pruned subtree comprises just three nodes; most take the form of an exact algebraic simplification. Our statistically-based pruning technique has allowed us to explore the hypothesis that a given subtree can be replaced with a constant if this substitution results in no statistical change to the behavior of the parent tree – what we term approximate simplification. In the eventuality, we infer that more than 95% of the accepted pruning proposals are the result of algebraic simplifications, which provides some practical insight into the scope of removing redundancies in GP trees

Drug-resistant genotypes and multi-clonality in Plasmodium falciparum analysed by direct genome sequencing from peripheral blood of malaria patients.

Naturally acquired blood-stage infections of the malaria parasite Plasmodium falciparum typically harbour multiple haploid clones. The apparent number of clones observed in any single infection depends on the diversity of the polymorphic markers used for the analysis, and the relative abundance of rare clones, which frequently fail to be detected among PCR products derived from numerically dominant clones. However, minority clones are of clinical interest as they may harbour genes conferring drug resistance, leading to enhanced survival after treatment and the possibility of subsequent therapeutic failure. We deployed new generation sequencing to derive genome data for five non-propagated parasite isolates taken directly from 4 different patients treated for clinical malaria in a UK hospital. Analysis of depth of coverage and length of sequence intervals between paired reads identified both previously described and novel gene deletions and amplifications. Full-length sequence data was extracted for 6 loci considered to be under selection by antimalarial drugs, and both known and previously unknown amino acid substitutions were identified. Full mitochondrial genomes were extracted from the sequencing data for each isolate, and these are compared against a panel of polymorphic sites derived from published or unpublished but publicly available data. Finally, genome-wide analysis of clone multiplicity was performed, and the number of infecting parasite clones estimated for each isolate. Each patient harboured at least 3 clones of P. falciparum by this analysis, consistent with results obtained with conventional PCR analysis of polymorphic merozoite antigen loci. We conclude that genome sequencing of peripheral blood P. falciparum taken directly from malaria patients provides high quality data useful for drug resistance studies, genomic structural analyses and population genetics, and also robustly represents clonal multiplicity

GPML: an XML-based standard for the interchange of genetic programming trees

We propose a Genetic Programming Markup Language (GPML), an XML based standard for the interchange of genetic programming trees, and outline the benefits such a format would bring in allowing the deployment of trained genetic programming (GP) models in applications as well as the subsidiary benefit of allowing GP researchers to directly share trained trees. We present a formal definition of this standard and describe details of an implementation. In addition, we present a case study where GPML is used to implement a model predictive controller for the control of a building heating plant

The case for open science: rare diseases.

The premise of Open Science is that research and medical management will progress faster if data and knowledge are openly shared. The value of Open Science is nowhere more important and appreciated than in the rare disease (RD) community. Research into RDs has been limited by insufficient patient data and resources, a paucity of trained disease experts, and lack of therapeutics, leading to long delays in diagnosis and treatment. These issues can be ameliorated by following the principles and practices of sharing that are intrinsic to Open Science. Here, we describe how the RD community has adopted the core pillars of Open Science, adding new initiatives to promote care and research for RD patients and, ultimately, for all of medicine. We also present recommendations that can advance Open Science more globally