ZCS redux

Learning classifier systems traditionally use genetic algorithms to facilitate rule discovery, where rule fitness is payoff based. Current research has shifted to the use of accuracy-based fitness. This paper re-examines the use of a particular payoff-based learning classifier system - ZCS. By using simple difference equation models of ZCS, we show that this system is capable of optimal performance subject to appropriate parameter settings. This is demonstrated for both single- and multistep tasks. Optimal performance of ZCS in well-known, multistep maze tasks is then presented to support the findings from the models

Valuable Ecologies: A Geography of Angling

Animals have occupied a prominent position in geographical research for some time (Philo and Wilbert 2000, Wolch and Emel, 1998) and the importance of animals in personal narratives of identity, place and space is widely accepted (see for example Matless et al., 2005). However, such research is predominantly focussed on understandings of mammals. This thesis contests this dominance by critically investigating the significance of fish in shaping understandings of animals. The work also connects with the burgeoning geographical interest with water (see for example, Gandy, 2002; Swyngedouw, 2004; Gandy, 2004, Kaika, 2005; and Braun 2005) but through an approach which steps away from understandings of water as just a resource to recognise that it is a resource that connects different issues, scales and approaches and has a materiality that shapes, and influences understandings of people and places. It also contributes to debates surrounding nature/society as it examines the interactions between humans and non-mammalian animals to interrogate issues relating to escape, wildness, nostalgia and connects large scale ‘landscape’ approaches to close-up encounters with the more-than-human world. These connections flow from the connectivity generated through water as it connects ‘diffuse’ issues into particular organisms. This connectivity has been exploited as fish are used as indicator species for public policy. Alongside this use as indicator species, fisheries management is usually science driven. Therefore running through the thesis is a critique of the role of the natural sciences and economics in shaping understandings fish as the political ecology of which fish, in which locations, are made to count. All this was achieved through a methodology that encouraged anglers to address the complexities, inconsistencies and tensions within their angling experience.European Social Fund and linked to the RELU project titled 'Sustainable and Holistic Food Chains

Statistical recovery of 21cm visibilities and their power spectra with Gaussian constrained realisations and Gibbs sampling

Radio interferometers designed to probe the 21cm signal from Cosmic Dawn and the Epoch of Reionisation must contend with systematic effects that make it difficult to achieve sufficient dynamic range to separate the 21cm signal from foreground emission and other effects. For instance, the instrument's chromatic response modulates the otherwise spectrally smooth foregrounds, making them difficult to model, while a significant fraction of the data must be excised due to the presence of radio frequency interference (RFI), leaving gaps in the data. Errors in modelling the (modulated and gappy) foregrounds can easily generate spurious contamination of what should otherwise be 21cm signal-dominated modes. Various approaches have been developed to mitigate these issues by (e.g.) using non-parametric reconstruction of the foregrounds, in-painting the gaps, and weighting the data to reduce the level of contamination. We present a Bayesian statistical method that combines these approaches, using the coupled techniques of Gaussian constrained realisations (GCR) and Gibbs sampling. This provides a way of drawing samples from the joint posterior distribution of the 21cm signal modes and their power spectrum in the presence of gappy data and an uncertain foreground model in a computationally scalable manner. The data are weighted by an inverse covariance matrix that is estimated as part of the inference, along with a foreground model that can then be marginalised over. We demonstrate the application of this technique on a simulated HERA-like delay spectrum analysis, comparing three different approaches for accounting for the foreground components.Comment: Updated to match accepted version. Note minor changes to power spectrum plots due to a small bugfi

Accidental exposure to electromagnetic fields from the radar of a naval ship: a descriptive study

Part of a crew on a Norwegian naval ship was exposed to the radar waves for approximately 7 min from an American destroyer during an incident at sea in August 2012. Information about the exposure was not given by the navy. This is a description of what happened with the crew on board after this event. 14 persons had been on the ship bridge or outside on the deck during the exposure and the rest of the crew had been inside the ship. 27 persons were examined at a hospital 6–8 months after the event, as they had developeda large number of symptoms from different organ systems. They were very worried about all types of possible adverse health effects due to the incident. All were examined by an occupational physician and anophthalmologist, by an interview, clinical examinations and blood tests at the hospital. The interview of the personnel revealed that they had not experienced any major heating during the episode. Their symptoms developed days or weeks after the radar exposure. They had no objective signs of adverse health effects at the examination related to the incident. Long-term health effect from the exposure is highly unlikely. The development of different symptoms after the incident was probably due to the fear of possible health consequences. Better routines for such incidents at sea should be developed to avoid this type of anxiety

Accidental exposure to electromagnetic fields from the radar of a naval ship; a descriptive study

Part of a crew on a Norwegian naval ship was exposed to the radar waves for approximately 7 min from an American destroyer during an incident at sea in August 2012. Information about the exposure was not given by the navy. This is a description of what happened with the crew on board after this event. 14 persons had been on the ship bridge or outside on the deck during the exposure and the rest of the crew had been inside the ship. 27 persons were examined at a hospital 6–8 months after the event, as they had developeda large number of symptoms from different organ systems. They were very worried about all types of possible adverse health effects due to the incident. All were examined by an occupational physician and anophthalmologist, by an interview, clinical examinations and blood tests at the hospital. The interview of the personnel revealed that they had not experienced any major heating during the episode. Their symptoms developed days or weeks after the radar exposure. They had no objective signs of adverse health effects at the examination related to the incident. Long-term health effect from the exposure is highly unlikely. The development of different symptoms after the incident was probably due to the fear of possible health consequences. Better routines for such incidents at sea should be developed to avoid this type of anxiety.publishedVersio

Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean

Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models

Pockmarks in the Witch Ground Basin, central north sea

Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. Quantitative estimates for methane release from marine sediments are scarce, and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios. Here, we use 2‐D and 3‐D seismic reflection, multibeam bathymetric, geochemical, and sedimentological data to (I) map and describe pockmarks in the Witch Ground Basin (central North Sea), (II) characterize associated sedimentological and fluid migration structures, and (III) analyze the related methane release. More than 1,500 pockmarks of two distinct morphological classes spread over an area of 225 km2. The two classes form independently from another and are corresponding to at least two different sources of fluids. Class 1 pockmarks are large in size (>6 m deep, >250 m long, and >75 m wide), show active venting, and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources. Class 2 pockmarks, which comprise 99.5% of all pockmarks, are smaller (0.9–3.1 m deep, 26–140 m long, and 14–57 m wide) and are limited to the soft, fine‐grained sediments of the Witch Ground Formation and possibly sourced by compaction‐related dewatering. Buried pockmarks within the Witch Ground Formation document distinct phases of pockmark formation, likely triggered by external forces related to environmental changes after deglaciation. Thus, greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present‐day fluxes but require an analysis of the pockmark forming processes through geological time

Automation of route identification and optimisation based on data-mining and chemical intuition.

Data-mining of Reaxys and network analysis of the combined literature and in-house reactions set were used to generate multiple possible reaction routes to convert a bio-waste feedstock, limonene, into a pharmaceutical API, paracetamol. The network analysis of data provides a rich knowledge-base for generation of the initial reaction screening and development programme. Based on the literature and the in-house data, an overall flowsheet for the conversion of limonene to paracetamol was proposed. Each individual reaction-separation step in the sequence was simulated as a combination of the continuous flow and batch steps. The linear model generation methodology allowed us to identify the reaction steps requiring further chemical optimisation. The generated model can be used for global optimisation and generation of environmental and other performance indicators, such as cost indicators. However, the identified further challenge is to automate model generation to evolve optimal multi-step chemical routes and optimal process configurations.This work was funded in part by the EPSRC project “Terpenebased Manufacturing for Sustainable Chemical Feedstocks” EP/K014889. The PhD scholarship of WC is funded by the EPSRC Doctoral Training Centre in Sustainable Chemical Technologies (EP/G03768X/1). We gratefully acknowledge collaboration with RELX Intellectual Properties SA and their technical support, which enabled us to mine REAXYS. PMJ is grateful to Peterhouse and the Cambridge Trust for PhD scholarships

Wireless Neurosensor for Full-Spectrum Electrophysiology Recordings during Free Behavior

SummaryBrain recordings in large animal models and humans typically rely on a tethered connection, which has restricted the spectrum of accessible experimental and clinical applications. To overcome this limitation, we have engineered a compact, lightweight, high data rate wireless neurosensor capable of recording the full spectrum of electrophysiological signals from the cortex of mobile subjects. The wireless communication system exploits a spatially distributed network of synchronized receivers that is scalable to hundreds of channels and vast environments. To demonstrate the versatility of our wireless neurosensor, we monitored cortical neuron populations in freely behaving nonhuman primates during natural locomotion and sleep-wake transitions in ecologically equivalent settings. The interface is electrically safe and compatible with the majority of existing neural probes, which may support previously inaccessible experimental and clinical research