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Search Results: 1 - 10 of 227400 matches for " Gavin C. Young "
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A Gigantic Sarcopterygian (Tetrapodomorph Lobe-Finned Fish) from the Upper Devonian of Gondwana (Eden, New South Wales, Australia)
Ben Young, Robert L. Dunstone, Timothy J. Senden, Gavin C. Young
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053871
Abstract: Edenopteron keithcrooki gen. et sp. nov. is described from the Famennian Worange Point Formation; the holotype is amongst the largest tristichopterids and sarcopterygians documented by semi-articulated remains from the Devonian Period. The new taxon has dentary fangs and premaxillary tusks, features assumed to be derived for large Northern Hemisphere tristichopterids (Eusthenodon, Hyneria, Langlieria). It resembles Eusthenodon in ornament, but is distinguished by longer proportions of the parietal compared to the post-parietal shield, and numerous differences in shape and proportions of other bones. Several characters (accessory vomers in the palate, submandibulars overlapping ventral jaw margin, scales ornamented with widely-spaced deep grooves) are recorded only in tristichopterids from East Gondwana (Australia-Antarctica). On this evidence Edenopteron gen. nov. is placed in an endemic Gondwanan subfamily Mandageriinae within the Tristichopteridae; it differs from the nominal genotype Mandageria in its larger size, less pointed skull, shape of the orbits and other skull characters. The hypothesis that tristichopterids evolved in Laurussia and later dispersed into Gondwana, and a derived subgroup of large Late Devonian genera dispersed from Gondwana, is inconsistent with the evidence of the new taxon. Using oldest fossil and most primitive clade criteria the most recent phylogeny resolves South China and Gondwana as areas of origin for all tetrapodomorphs. The immediate outgroup to tristichopterids remains unresolved – either Spodichthys from Greenland as recently proposed, or Marsdenichthys from Gondwana, earlier suggested to be the sister group to all tristichopterids. Both taxa combine two characters that do not co-occur in other tetrapodomorphs (extratemporal bone in the skull; non-cosmoid round scales with an internal boss). Recently both ‘primitive’ and ‘derived’ tristichopterids have been discovered in the late Middle Devonian of both hemispheres, implying extensive ghost lineages within the group. Resolving their phylogeny and biogeography will depend on a comprehensive new phylogenetic analysis.
Impacts of Removing Badgers on Localised Counts of Hedgehogs
Iain D. Trewby, Richard Young, Robbie A. McDonald, Gavin J. Wilson, John Davison, Neil Walker, Andrew Robertson, C. Patrick Doncaster, Richard J. Delahay
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095477
Abstract: Experimental evidence of the interactions among mammalian predators that eat or compete with one another is rare, due to the ethical and logistical challenges of managing wild populations in a controlled and replicated way. Here, we report on the opportunistic use of a replicated and controlled culling experiment (the Randomised Badger Culling Trial) to investigate the relationship between two sympatric predators: European badgers Meles meles and western European hedgehogs Erinaceus europaeus. In areas of preferred habitat (amenity grassland), counts of hedgehogs more than doubled over a 5-year period from the start of badger culling (from 0.9 ha?1 pre-cull to 2.4 ha?1 post-cull), whereas hedgehog counts did not change where there was no badger culling (0.3–0.3 hedgehogs ha?1). This trial provides experimental evidence for mesopredator release as an outcome of management of a top predator.
Identifying the Intellectual Virtues in a Demon World  [PDF]
M. C. Young
Open Journal of Philosophy (OJPP) , 2012, DOI: 10.4236/ojpp.2012.24036
Abstract: Within contemporary epistemology, notions of intellectual virtue have come to fulfill a prominent role in attempts to provide an account of knowledge. Notions of such virtue can vary, and one particular aspect of this variance concerns how to construe the relationship between the intellectual virtues and particular epistemic ends. The goal of this article is to defend an instrumental connection between the intellectual virtues and the epistemic end of true belief. One type of skeptical argument that attempts to sever this connection, a Cartesian Demon argument, is considered. This Cartesian Demon argument will be summarized, as well as three responses to it. The claim that truth-conduciveness is a tenable criterion for identifying the intellectual virtues is then defended. It is acknowledged that the possibility of a Cartesian Demon does initiate scepticism, but that this scepticism is directed toward identifying specific intellectual virtues and not toward the instrumental connection between intellectual virtue and true belief.
Developing a school-based drug prevention program to overcome barriers to effective program implementation: The CLIMATE schools: Alcohol module  [PDF]
Laura E. Vogl, Maree Teesson, Nicola C. Newton, Gavin Andrews
Open Journal of Preventive Medicine (OJPM) , 2012, DOI: 10.4236/ojpm.2012.23059
Abstract: Although effective school-based alcohol prevention programs do exist, the overall efficacy of these programs has been compromised by implementation failure. The CLIMATE Schools: Alcohol Module was developed to overcome some of the obstacles to high fidelity program implementation. This paper details this development of the CLIMATE Schools: Alcohol Module. The development involved two stages, both of which were considered essential. The first stage, involved reviewing the literature to ensure the program was based on the most effecttive pedagogy and health promotion practice and the second stage involved collaborating with teachers, students and specialists in the area of alcohol and other drugs, to ensure these goals were realised. The final CLIMATE Schools: Alcohol Module consists of computer-driven harm minimisation program which is based on a social influence approach. The program consists of six lessons, each with two components. The first component involves students completing an interactive computer-based program, with the second consisting of a variety of individual, small group and class-based activities. This program was developed to provide an innovative new platform for the delivery of drug education and has proven to be both feasible and effective in the school environment. The success of this program is considered to be testament to this collaborative development approach.
Polyploidy and the Evolution of Complex Traits
Lukasz Huminiecki,Gavin C. Conant
International Journal of Evolutionary Biology , 2012, DOI: 10.1155/2012/292068
Abstract: We explore how whole-genome duplications (WGDs) may have given rise to complex innovations in cellular networks, innovations that could not have evolved through sequential single-gene duplications. We focus on two classical WGD events, one in bakers’ yeast and the other at the base of vertebrates (i.e., two rounds of whole-genome duplication: 2R-WGD). Two complex adaptations are discussed in detail: aerobic ethanol fermentation in yeast and the rewiring of the vertebrate developmental regulatory network through the 2R-WGD. These two examples, derived from diverged branches on the eukaryotic tree, boldly underline the evolutionary potential of WGD in facilitating major evolutionary transitions. We close by arguing that the evolutionary importance of WGD may require updating certain aspects of modern evolutionary theory, perhaps helping to synthesize a new evolutionary systems biology. 1. Introduction Characteristic changes in karyotype number have allowed researchers to infer polyploidy events for many decades [1]. It was thus with a reasonably long history of research that Susumo Ohno was able to suggest that polyploidy was a vital route to evolutionary innovation [2]. Ohno was of course a forceful proponent of a general role for duplication in evolution: writing that “[if evolution occurred only through changes allele frequencies] … from a bacterium only numerous forms of bacteria would have emerged […B]ig leaps in evolution required the creation of new gene loci with previously nonexistent functions” [2]. What is less obvious on first reading is his distinction between the role played by WGD and that played by other, smaller scale, duplications (or SSDs). While the differences in the scales of these events are self-evident, there are at least two other features of WGD that are critical in giving rise to these differing roles. The first is that, as many authors have reported, particular functional classes of genes (e.g., transcription factors, kinases, ribosomal proteins, and cyclins) are duplicated by WGD more frequently than by SSD [3–8]. Ohno had in fact explored the most likely reason for this difference: “hub” genes with many interactions with other loci, be those interactions regulatory, protein interaction or metabolic, will tend to respond poorly to a change in copy number. As a result, they will tend to survive in duplicate after WGD but will not survive after smaller scale events [2, 5, 9–11]. This idea has now been termed the dosage balance hypothesis [12–14]. The second difference between single-gene and genome duplication is the kind of
The rarity of gene shuffling in conserved genes
Gavin C Conant, Andreas Wagner
Genome Biology , 2005, DOI: 10.1186/gb-2005-6-6-r50
Abstract: We have studied shuffling in genes that are conserved between distantly related species. Specifically, we estimated the incidence of gene shuffling in ten organisms from the three domains of life: eukaryotes, eubacteria, and archaea, considering only genes showing significant sequence similarity in pairwise genome comparisons. We found that successful gene shuffling is very rare among such conserved genes. For example, we could detect only 48 successful gene-shuffling events in the genome of the fruit fly Drosophila melanogaster which have occurred since its common ancestor with the worm Caenorhabditis elegans more than half a billion years ago.The incidence of gene shuffling is roughly an order of magnitude smaller than the incidence of single-gene duplication in eukaryotes, but it can approach or even exceed the gene-duplication rate in prokaryotes. If true in general, this pattern suggests that gene shuffling may not be a major force in reshaping the core genomes of eukaryotes. Our results also cast doubt on the notion that introns facilitate gene shuffling, both because prokaryotes show an appreciable incidence of gene shuffling despite their lack of introns and because we find no statistical association between exon-intron boundaries and recombined domains in the two multicellular genomes we studied.How do genes with new functions originate? This remains one of the most intriguing open questions in evolutionary genetics. Three principal mechanisms can create genes of novel function: point mutations and small insertions or deletions in existing genes; duplication of entire genes or domains within genes, in combination with mutations that cause functional divergence of the duplicates [1-3]; and recombination between dissimilar genes to create new recombinant genes (see, for example [4,5]). We here choose to call only this kind of recombination gene shuffling, excluding, for example, duplication of domains within a gene. In such a gene shuffling event, the parenta
Perceptions of the value of traditional ecological knowledge to formal school curricula: opportunities and challenges from Malekula Island, Vanuatu
Joe McCarter, Michael C Gavin
Journal of Ethnobiology and Ethnomedicine , 2011, DOI: 10.1186/1746-4269-7-38
Abstract: Participants reported that TEK had eroded on Malekula, and identified the formal school system as a principal driver. Most interviewees believed that if an appropriate format could be developed, TEK could be included in the formal education system. Such an approach has potential to maintain customary knowledge and practice in the focus communities. Participants identified several specific domains of TEK for inclusion in school curricula, including ethnomedical knowledge, agricultural knowledge and practice, and the reinforcement of respect for traditional authority and values. However, interviewees also noted a number of practical and epistemological barriers to teaching TEK in school. These included the cultural diversity of Malekula, tensions between public and private forms of knowledge, and multiple values of TEK within the community.TEK has potential to add value to formal education systems in Vanuatu by contextualising the content and process of curricular delivery, and by facilitating character development and self-awareness in students. These benefits are congruent with UNESCO-mandated goals for curricular reform and provide a strong argument for the inclusion of TEK in formal school systems. Such approaches may also assist in the maintenance and revitalisation of at-risk systems of ethnobiological knowledge. However, we urge further research attention to the significant epistemological challenges inherent in including TEK in formal school, particularly as participants noted the potential for such approaches to have negative consequences.The spread of western modes of formal education (defined here as institutionalised, chronologically graded, and hierarchically structured systems of education [1]) has been recognised as a key driver of global social change [2]. There are serious concerns, however, that formal education systems in some areas of the world do not adequately account for local knowledge and cultural diversity [3,4]. This results in school system
A fast algorithm for determining the best combination of local alignments to a query sequence
Gavin C Conant, Andreas Wagner
BMC Bioinformatics , 2004, DOI: 10.1186/1471-2105-5-62
Abstract: We propose a graph-based algorithm for combining multiple local alignments to a query sequence into the single combination of alignments that either covers the maximal portion of the query or results in the single highest alignment score to the query. This algorithm can help study the process of genome rearrangement, improve functional gene annotation, and reconstruct the evolutionary history of recombined proteins. The algorithm takes O(n2) time, where n is the number of local alignments considered.We discuss two example applications of the algorithm. The algorithm is able to provide useful reconstructions of the metazoan mitochondrial genome. It is also able to increase the percentage of a query sequence's amino acid residues for which similar stretches of amino acids can be found in sequence databases.The introduction of the Smith-Waterman local alignment algorithm [1] and the subsequent development of the FASTA [2] and BLAST [3,4] database search tools has revolutionized comparative sequence studies. In the age of completely sequenced genomes, these algorithms are often used to compare a DNA or protein sequence of unknown function – a query sequence – with one or more reference sequences. Such reference sequences are often contained in databases of many thousand DNA or protein sequences. If the query sequence is similar to one or more reference sequences with known function, an informed guess about the function of the query sequence is possible. Sequence alignment algorithms, by their nature, assume that similarities between pairs of sequences are linearly ordered (homologous residues occur in the same order in both sequences). Thus, these algorithms are not well-suited to compare sequences that have undergone rearrangements through recombination. However, during evolution, rearrangements of genomic DNA occur frequently and on all scales, from individual genes to entire genomes. To give but a few examples: the mouse chromosome 16 shows substantial regions of syn
Evaluating the reliability of point estimates of wetland reference evaporation
H. Gavin,C. T. Agnew
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2003,
Abstract: The Penman-Monteith formulation of evaporation has been criticised for its reliance upon point estimates so that areal estimates of wetland evaporation based upon single weather stations may be misleading. Typically, wetlands comprise a complex mosaic of land cover types from each of which evaporative rates may differ. The need to account for wetland patches when monitoring hydrological fluxes has been noted. This paper presents work carried out over a wet grassland in Southern England. The significance of fetch on actual evaporation was examined using the approach adopted by Gash (1986) based upon surface roughness to estimate the fraction of evaporation sensed from a specified distance upwind of the monitoring station. This theoretical analysis (assuming near-neutral conditions) reveals that the fraction of evaporation contributed by the surrounding area increases steadily to a value of 77% at a distance of 224 m and thereafter declines rapidly. Thus, point climate observations may not reflect surface conditions at greater distances. This result was tested through the deployment of four weather stations on the wetland. The resultant data suggested that homogeneous conditions prevailed so that the central weather station provided reliable areal estimates of reference evaporation during the observation period March–April 1999. This may be a result of not accounting for high wind speeds and roughness found in wetlands that lead to widespread atmospheric mixing. It should be noted this analysis was based upon data collected during the period March-April when wind direction was constant (westerly) and the land surface was moist. There could be more variation at other times of the year that would lead to greater heterogeneity in actual evaporation. Keywords: evaporation, Penman-Monteith, automatic weather station, fetch, wetland
The Renormalized Stress Tensor in Kerr Space-Time: Numerical Results for the Hartle-Hawking Vacuum
Gavin Duffy,Adrian C. Ottewill
Physics , 2005, DOI: 10.1103/PhysRevD.77.024007
Abstract: We show that the pathology which afflicts the Hartle-Hawking vacuum on the Kerr black hole space-time can be regarded as due to rigid rotation of the state with the horizon in the sense that when the region outside the speed-of-light surface is removed by introducing a mirror, there is a state with the defining features of the Hartle-Hawking vacuum. In addition, we show that when the field is in this state, the expectation value of the energy-momentum stress tensor measured by an observer close to the horizon and rigidly rotating with it corresponds to that of a thermal distribution at the Hawking temperature rigidly rotating with the horizon.
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