University of Exeter

About: University of Exeter is a education organization based out in Exeter, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 15820 authors who have published 50650 publications receiving 1793046 citations. The organization is also known as: Exeter University & University of the South West of England.

An Examination of the Long Run Performance of UK Acquiring Firms

Abstract: This study examines a comprehensive data set of large domestic takeovers by UK listed companies between 1984 and 1992. The contribution of this paper is to show, by using a series of models of abnormal returns, together with the Ibbotson (1975) ‘Returns Across Time Series’ model and a simple cross-sectional model of returns across all listed UK companies, that the average abnormal return for up to two years post-acquisition is unambiguously and significantly negative. In particular, acquirers financing a takeover through equity, and single (as opposed to regular) acquirers exhibit significant negative performance. There is also some evidence to suggest that diversifying acquirers perform worse than non-diversifying acquirers and that recommended bids are associated with poorer subsequent under-performance by acquirers than are hostile bids.

Unmanned Aerial Vehicles (UAVs) and Artificial Intelligence Revolutionizing Wildlife Monitoring and Conservation.

Abstract: Surveying threatened and invasive species to obtain accurate population estimates is an important but challenging task that requires a considerable investment in time and resources. Estimates using existing ground-based monitoring techniques, such as camera traps and surveys performed on foot, are known to be resource intensive, potentially inaccurate and imprecise, and difficult to validate. Recent developments in unmanned aerial vehicles (UAV), artificial intelligence and miniaturized thermal imaging systems represent a new opportunity for wildlife experts to inexpensively survey relatively large areas. The system presented in this paper includes thermal image acquisition as well as a video processing pipeline to perform object detection, classification and tracking of wildlife in forest or open areas. The system is tested on thermal video data from ground based and test flight footage, and is found to be able to detect all the target wildlife located in the surveyed area. The system is flexible in that the user can readily define the types of objects to classify and the object characteristics that should be considered during classification.

The genetics of metal tolerance in vascular plants.

Abstract: SUMMARY In many parts of the world soils are detrimental to plant growth owing to elevated levels of metal ions, caused either by natural processes or by the result of man's activities. Many plants have evolved ecotypes or varieties that are able to grow more-or-less normally on these soils. This paper reviews our knowledge of the genetics of this phenomenon. The nature of tolerance and the problems of its measurement are discussed. Tolerance is frequently measured by an index produced by comparing growth in a contaminated environment with growth in a control environment. It is argued that this measurement is inappropriate for many genetical studies, and that it is frequently more useful to use growth at a single critical level of metal as a measure of tolerance. Polygenic inheritance provides a null hypothesis that has to be tested in a genetical analysis. Examples of major genes for tolerance to aluminium, arsenic, boron, cadmium, copper and manganese are discussed. Even where major genes have been demonstrated, it is probable that other minor genes, ‘modifiers’, are present as well. Because of the nature of tolerance as a character, dominance and epistasis are likely to vary with the level of metal at which an analysis is performed. Tolerance is generally found to be dominant at some levels of the metal. Studies which have mapped tolerance genes, particularly to aluminium and salt, are discussed. The specificity of tolerance is a matter of some confusion. Some studies indicate that tolerances evolve independently to different metals, but others have suggested that tolerance to one metal may often confer a degree of tolerance to some other metals. Very little is known about the molecular genetics of tolerance, and the mechanisms of tolerance to most metals. The possible role of phytochelatins and metallothionein-like proteins in metal tolerance is discussed. The distribution of tolerance in natural populations suggests that tolerance is a disadvantage in uncontaminated environments, but how this ‘cost’ arises is not known. There is some evidence that the disadvantage to tolerance may be associated more with the modifiers of tolerance than with the primary tolerance gene. The study of the genetics of tolerance is of importance in planning breeding programmes to produce tolerant crops for use in areas where metal contamination is a limiting factor in productivity. It can also assist in understanding the mechanisms of tolerance, as exemplified by the study of the mechanism of arsenic tolerance in Holcus lanatus. Important areas for further research are discussed.

Independent signaling pathways regulate cellular turgor during hyperosmotic stress and appressorium-mediated plant infection by Magnaporthe grisea.

Abstract: The phytopathogenic fungus Magnaporthe grisea elaborates a specialized infection cell called an appressorium with which it mechanically ruptures the plant cuticle. To generate mechanical force, appressoria produce enormous hydrostatic turgor by accumulating molar concentrations of glycerol. To investigate the genetic control of cellular turgor, we analyzed the response of M. grisea to hyperosmotic stress. During acute and chronic hyperosmotic stress adaptation, M. grisea accumulates arabitol as its major compatible solute in addition to smaller quantities of glycerol. A mitogen-activated protein kinase–encoding gene OSM1 was isolated from M. grisea and shown to encode a functional homolog of HIGH-OSMOLARITY GLYCEROL1 ( HOG1 ), which encodes a mitogen-activated protein kinase that regulates cellular turgor in yeast. A null mutation of OSM1 was generated in M. grisea by targeted gene replacement, and the resulting mutants were sensitive to osmotic stress and showed morphological defects when grown under hyperosmotic conditions. M. grisea Δ osm1 mutants showed a dramatically reduced ability to accumulate arabitol in the mycelium. Surprisingly, glycerol accumulation and turgor generation in appressoria were unaltered by the Δ osm1 null mutation, and the mutants were fully pathogenic. This result indicates that independent signal transduction pathways regulate cellular turgor during hyperosmotic stress and appressorium-mediated plant infection. Consistent with this, exposure of M. grisea appressoria to external hyperosmotic stress induced OSM1 -dependent production of arabitol.

Genomic islands of divergence in hybridizing Heliconius butterflies identified by large-scale targeted sequencing.

Abstract: Heliconius butterflies represent a recent radiation of species, in which wing pattern divergence has been implicated in speciation. Several loci that control wing pattern phenotypes have been mapped and two were identified through sequencing. These same gene regions play a role in adaptation across the whole Heliconius radiation. Previous studies of population genetic patterns at these regions have sequenced small amplicons. Here, we use targeted next-generation sequence capture to survey patterns of divergence across these entire regions in divergent geographical races and species of Heliconius. This technique was successful both within and between species for obtaining high coverage of almost all coding regions and sufficient coverage of non-coding regions to perform population genetic analyses. We find major peaks of elevated population differentiation between races across hybrid zones, which indicate regions under strong divergent selection. These ‘islands’ of divergence appear to be more extensive between closely related species, but there is less clear evidence for such islands between more distantly related species at two further points along the ‘speciation continuum’. We also sequence fosmid clones across these regions in different Heliconius melpomene races. We find no major structural rearrangements but many relatively large (greater than 1 kb) insertion/deletion events (including gain/loss of transposable elements) that are variable between races.