David Atkinson

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Analysis of arbuscular mycorrhizal (AM) fungal diversity through morphological characters of spores and intraradicular hyphae has suggested previously that preferential associations occur between plants and AM fungi. A field experiment was established to investigate whether AM fungal diversity is affected by different host plants in upland grasslands.(More)
In biological tissue, all eigenvalues of the diffusion tensor are assumed to be positive. Calculations in diffusion tensor MRI generally do not take into account this positive definiteness property of the tensor. Here, the space of positive definite tensors is used to construct a framework for diffusion tensor analysis. The method defines a distance(More)
Metabolic energy fuels all biological processes, and therefore theories that explain the scaling of metabolic rate with body mass potentially have great predictive power in ecology. A new model, that could improve this predictive power, postulates that the metabolic scaling exponent (b) varies between 2/3 and 1, and is inversely related to the elevation of(More)
An inverse relationship between organism size and rearing temperature is widely observed in ectotherms ('the temperature-size rule', TSR). This has rarely been quantified for related taxa, and its applicability to protists also required testing. Here, we quantify the relationship between temperature and mean cell volume within the protists by a(More)
The fiber tracts generated using diffusion MRI are usually simply displayed and assessed visually for a specific clinical or medical research purpose. This paper proposes computational techniques that can be used to study the shape of the tracts and make interindividual comparisons. These methods make use of fundamental geometric invariants, such as(More)
An inverse relationship between temperature during ontogeny and final body size is widespread in ectotherms, but poorly understood. Evidence suggests that within organs, this "temperature-size rule" (TSR) may also apply to cell size with no change in numbers. So how closely do reductions in size and number of cells and other repeated structures correlate(More)
The Eppley curve describes an exponential function that defines the maximum attainable daily growth rate of marine phytoplankton as a function of temperature. The curve was originally fitted by eye as the upper envelope of a data set, and despite its wide use, the reliability of this function has not been statistically tested. Our analysis of the data using(More)
Attenuation correction is an essential requirement for quantification of positron emission tomography (PET) data. In PET/CT acquisition systems, attenuation maps are derived from computed tomography (CT) images. However, in hybrid PET/MR scanners, magnetic resonance imaging (MRI) images do not directly provide a patient-specific attenuation map. The aim of(More)
Electrical Impedance Tomography (EIT) is an imaging method which enables a volume conductivity map of a subject to be produced from multiple impedance measurements. It has the potential to become a portable non-invasive imaging technique of particular use in imaging brain function. Accurate numerical forward models may be used to improve image(More)
Motion of an object degrades MR images, as the acquisition is time-dependent, and thus k-space is inconsistently sampled. This causes ghosts. Current motion correction methods make restrictive assumptions on the type of motions, for example, that it is a translation or rotation, and use special properties of k-space for these transformations. Such methods,(More)