4,136 research outputs found
Dietary variation within and between populations of northeast Atlantic killer whales Orcinus orca inferred from δ13C and δ15N analyses
No full textEpidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, comparisons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this location. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same population by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring (Clupea harengus). There was no significant difference within Icelandic samples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel (Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were analyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet-tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Andrew D. White Professors-At-Large lectures.
No full textRecorded in Ithaca, NY by Cornell University., Sponsored by: Andrew D. White Professors-At-Large Program., Speaker(s): Well-known author., Reading, March 27, 1985.43 minutesWelty reads her short story, The Wide Net.1_1b7n8g9v1_hknzm40
The Life of the Author: D. H. Lawrence
No full textThe Life of the Author: D. H. Lawrence is a focused exploration of the whole of the author’s life and writing career. Combining biographical detail and close readings of works in different genres, the book illuminates the complexities of Lawrence’s writing through a careful, questioning approach to biographical sources and recent scholarship. Andrew Harrison provides original insights into Lawrence’s relationship to working-class experience, his anti-suffragist feminist views, his reaction to the Great War, his responses to racial and cultural difference, his attitudes towards sex, sexuality, and sexual identity, and much more
Mitogenome alignment of 159 unique haplotypes representing 455 individual killer whales
No full text<p><span>Genome sequences can reveal the extent of inbreeding in small populations. Here we present the first genomic characterization of type D killer whales, a distinctive eco/morphotype with a circumpolar, subantarctic distribution. Effective population size is the lowest estimated from any killer whale genome and indicates a severe population bottleneck. Consequently, type D genomes show among the highest level of inbreeding reported for any mammalian species (F<sub>ROH</sub> </span><span></span><span> 0.65). Detected recombination events of different haplotypes are up to an order of magnitude rarer than in other killer whale genomes studied to date. Comparison of genomic data from a museum specimen of a type D killer whale that stranded in New Zealand in 1955, with three modern genomes from the Cape Horn area, reveals high covariance and identity-by-state of alleles, suggesting these genomic characteristics and demographic history are shared among different social groups within this morphotype. Limitations to the insights gained in this study stem from the </span><span>non-independence of the three closely related modern genomes, the short coalescence time of most variation within the genomes, and the nonequilibrium population history which violates the assumptions of many model-based methods. Long-range linkage disequilibrium and extensive runs of homozygosity found in type D genomes provide the potential basis for coupling of genetic barriers to gene flow with other killer whale populations, and the distinctive morphology. </span></p><p>Funding provided by: European Research Council<br>Crossref Funder Registry ID: https://ror.org/0472cxd90<br>Award Number: ERC-COG-101045346</p><p>Funding provided by: NOAA National Marine Fisheries Service Office of Science and Technology<br>Crossref Funder Registry ID: https://ror.org/04950b532<br>Award Number: </p><p>Funding provided by: European Union<br>Crossref Funder Registry ID: https://ror.org/019w4f821<br>Award Number: 663830</p><p>This alignment is primarily comprised of the 158 unique mitochondrial genome haplotypes from Morin et al. 2015 <a href="https://doi.org/10.1111/mec.13284">https://doi.org/10.1111/mec.13284</a>, with the addition of three identical sequences derived from DNA extracted from three type D killer whales as described in the Foote et al. manuscript associated with this submission. The metadata associated with the Morin et al. (2015) dataset are available here: <a href="../dataset/doi:10.5061/dryad.fm4mk">https://datadryad.org/stash/dataset/doi:10.5061/dryad.fm4mk</a>.</p>
<p>Type D mitogenome sequences were generated as follows. Reads were mapped using BWA-MEM to the previously generated mitogenome sequence of the New Zealand type D specimen (accession KF164610; Foote et al. 2013). In a previous study of 139 killer whale mitogenome sequences (Morin et al. 2010), the inclusion of intra- and inter-lab PCR, library build, and sequencing replicates identified inconsistencies in the assembly of polynucleotide repeat regions: one of between nine and 14 Cs in a row (positions 1130–1144 in the original alignment), and another region of seven to eight As in a row (positions 5210–5217). Morin et al. (2010) therefore shortened these to a fixed set of nine Cs and seven As, respectively, to avoid introducing potentially erroneous variation into phylogenetic analysis in that and subsequent follow-up studies (e.g. Foote et al. 2013; Morin et al. 2015). We follow this same conservative approach in our mapping of mitogenomes and identification of sequence variation in this study. </p>
<p>Foote, A. D., P. A. Morin, R. L. Pitman, M. C. Avila-Arcos, J. W. Durban, A. van Helden, M.-S. Sinding, and T. P. Gilbert. 2013. Mitogenomic insights into a recently described and rarely observed killer whale morphotype. Polar Biology 36:1519–1523.</p>
<p>Morin, P. A., Archer, F. I., Foote, A. D., Vilstrup, J., Allen, E. E., Wade, P., ... & Harkins, T. (2010). Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome research, 20(7), 908-916.</p>
Mechanics of elastic networks
No full textWe consider a periodic lattice structure in d=2 or 3 dimensions with unit cell comprising Z thin elastic members emanating from a similarly situated central node. A general theoretical approach provides an algebraic formula for the effective elasticity of such frameworks. The method yields the effective cubic elastic constants for three-dimensional space-filling lattices with Z=4, 6, 8, 12 and 14, the last being the ‘stiffest’ lattice proposed by Gurtner & Durand (Gurtner & Durand 2014 Proc. R. Soc. A 470, 20130611. (doi:10.1098/rspa.2013.0611)). The analytical expressions provide explicit formulae for the effective properties of pentamode materials, both isotropic and anisotropic, obtained from the general formulation in the stretch-dominated limit for Z=d+1.Peer reviewe
Geophysical estimation of free-phase gas content and distribution in peatlands
No full textEmissions of methane and carbon dioxide gases from organic soils contribute to the global carbon cycle and may influence climate change. Revealing where these gases accumulate in the subsurface of saturated peat soils is a critical step towards understanding carbon cycling through peatlands. This dissertation presents field and laboratory geophysical investigations of free-phase gas contained within peatlands. Ground-penetrating radar (GPR) was used to estimate the vertical distribution of free- phase gas (FPG) in sites within the Glacial Lake Agassiz Peatland, MN. Bog-crest landforms were characterized by vertical variability in FPG and accumulations up to 24% FPG within the intervals 2-4 m deep. Lawn sites show lower volumes up to 12% FPG and a more even vertical gas distribution. These results demonstrate that spatial distribution of FPG varies vertically in the peat of Glacial Lake Agassiz peatlands depending on landform type. A second study was designed to elucidate spatial variability in FPG two-dimensionally along a transect crossing a bog crest, mid-slope lawn, and fen peat landforms. Variability in gas content and distribution was observed using GPR as a function of peat landform type. Estimated gas content up to 25% was observed in landforms dominated by woody surface vegetation. In the lawn, estimated gas content was > 15%, while estimated gas contents between 0% - 7% were found in the fen. Changes in gas content of up to 20% were observed over a transition between a stand of 10 m tall trees and a fen. These results support conceptual models based on accumulation and storage of FPG. Models relating geophysical measurements to pore water content limit the accuracy of FPG estimates. To improve these models, the dielectric properties of peat samples were measured in response to changes in water content. Dielectric permittivity was measured using GPR at water contents between 0.87 and 0.95 m3 m-3 on four samples with varying levels of humification. The resulting relationships indicate that there are differences in the permittivity-water content relationships between peat samples. Behavior of parameters in the dielectric mixing model indicates that variability in dielectric relationships may be attributed to peat structure.Ph.D.Includes bibliographical referencesIncludes vitaby Andrew D Parsekia
Morphologic and functional correlates of synaptic pathology in the cathepsin D knockout mouse model of congenital neuronal ceroid lipofuscinosis
No full textMutations in the cathepsin D (CTSD) gene cause an aggressive neurodegenerative disease (congenital neuronal ceroid lipofuscinosis) that leads to early death. Recent evidence suggests that presynaptic abnormalities play a major role in the pathogenesis of CTSD deficiencies. To identify the early events that lead to synaptic alterations, we investigated synaptic ultrastructure and function in presymptomatic CTSD knockout (Ctsd) mice. Electron microscopy revealed that there were significantly greater numbers of readily releasable synaptic vesicles present in Ctsd mice than in wild-type control mice as early as postnatal day 16. The size of this synaptic vesicle pool continued to increase with disease progression in the hippocampus and thalamus of the Ctsd mice. Electrophysiology revealed a markedly decreased frequency of miniature excitatory postsynaptic currents (mEPSCs) with no effect on paired-pulse modulation of the evoked excitatory post synaptic potentials in the hippocampus of Ctsd mice. The reduced mEPSCs frequency was observed before the appearance of epilepsy or any morphologic sign of synaptic degeneration. Taken together, these data indicate that CTSD is required for normal synaptic function and that a failure in synaptic trafficking or recycling may bean early and important pathologic mechanism in Ctsd mice; these presynaptic abnormalities may initiate synaptic degeneration in advance of subsequent neuronal loss
Diagnostic and prognostic of intermittent faults (by use of machine learning).
No full textThis thesis investigates novel intermittent fault detection and prediction techniques
for complex nonlinear systems.
Aerospace and defence systems are becoming progressively more complex, with
greater component numbers and increasingly complicated components and subcomponents.
At the same time, faults and failures are becoming more challenging to detect
and isolate, and the time that operators and maintenance technicians spend on faults is
rising.
Moreover, a serious problem has recently attracted a lot of attention in health diagnostics
of these complex systems. Detecting intermittent faults that persist for very
short durations and manifest themselves intermittently have become troublesome and
sometimes impossible (also known as “no fault found”).
In response to the above challenges, this thesis focuses on the development of a novel
methodology to detect intermittent faults of these complex systems. It further investigates
various probabilistic approaches to develop efficient fault diagnostic and prognostic
methods.
In the first stage of this thesis, a novel model (observer)-based intermittent fault detection
filter is presented that relies on the creation of a mathematical model of a laboratory scale
aircraft fuel system test rig to predict the output of the system at any given time.
Comparison between this prediction of output and actual output reveals the presence
of a fault. Later, the simulation results demonstrate that the performance of the model
(observer)-based fault detection techniques decrease significantly as system complexity
increases.
In the second stage of this research, a probabilistic data-driven method known as
a Bayesian network is presented. This is particularly useful for diverse problems of
varying size and complexity, where uncertainties are inherent in the system. Bayesian
networks that model sequences of variables are called dynamic Bayesian networks. To
introduce the time variable in the framework of probabilistic models while dealing with
both discrete and continuous variables in the fuel rig system, a hybrid dynamic Bayesian
network is proposed.
The presented results of data-driven fault detection show that the hybrid dynamic
Bayesian network is more effective than the static Bayesian network or model (observer)-
based methods for detecting intermittent faults.
Furthermore, the second stage of the research uses all the information captured from
the fault diagnostic techniques for intermittent fault prediction by using a probabilistic
non-parametric Bayesian method called Gaussian process regression, which is an aid for
decision-making using uncertain information.Engineering and Physical Sciences (EPSRC)PhD in Manufacturin
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