1,288 research outputs found
Emergence of novel magnetic order at finite temperature in overdoped pnictides
We examine the temperature dependence of the magnetic ordering in the
frustrated Heisenberg model in presence of two different kind of
dopants: vacancies or magnetic impurities. We demonstrate that, irrespective to
their magnetic ratio, the introduction of impurities quenches the order by
disorder selection mechanism associated with an Ising-like phase transition at
low temperatures and gives way to a (anticollinear) order . The
presence of dopants triggers a non trivial competition between entropically
selected states (collinear) and energetically favoured ones (anticollinear) in
dependence of both dilution and temperature. While in case of magnetic
impurity, the interesting magnetic phases are observed for full range of
temperature and doping, in case of nonmagnetic impurities every magnetic order
is destroyed at all temperatures above dilution. At fixed low
temperature and tuning the doping we show a first order phase transition
leading to the re-entrance of the Ising-like order with percolation of islands
of order. At fixed doping and varying the temperature we observe a
transition from the anticollinear to the collinear phase assisted by a new
emerging magnetic phase in the presence of magnetic impurities, whilst in case
of vacancies this transition is characterised by a coexistent region of both.
Furthermore, tuning the magnetic moment of the impurities, a complete collapse
of the Ising-like order is attained. This is in agreement with observations of
Ir dopant atoms in superconducting Ba(FeIr)As with
Dynamic polarization vision in mantis shrimps
Gaze stabilization is an almost ubiquitous animal behaviour, one that is required to see the world clearly and without blur. Stomatopods, however, only fix their eyes on scenes or objects of interest occasionally. Almost uniquely among animals they explore their visual environment with a series pitch, yaw and torsional (roll) rotations of their eyes, where each eye may also move largely independently of the other. In this work, we demonstrate that the torsional rotations are used to actively enhance their ability to see the polarization of light. Both Gonodactylus smithii and Odontodactylus scyllarus rotate their eyes to align particular photoreceptors relative to the angle of polarization of a linearly polarized visual stimulus, thereby maximizing the polarization contrast between an object of interest and its background. This is the first documented example of any animal displaying dynamic polarization vision, in which the polarization information is actively maximized through rotational eye movements
Looking to the past to ensure the future of the world's oldest living vertebrate: Isotopic evidence for multi-decadal shifts in trophic ecology of the Australian lungfish
Meeting the conservation challenges of long‐lived animal species necessitate long‐
term assessments of trophic ecology. The use of dietary proxies, such as ratios of
naturally occurring stable isotopes in animal tissues demonstrating progressive
growth, has shown considerable promise to reconstruct trophic histories of long‐
lived organisms experiencing environmental change. Here, we combine innovative
radiocarbon scale‐ageing techniques with stable isotope analysis of carbon and nitrogen from cross sections of scale to reconstruct the trophic ecology of Australian lungfish (Neoceratodus forsteri) across its remaining global distribution. Over a 65‐year
period, we found pronounced temporal shifts in the δ13C and δ15N isotopic ratios
of lungfish that coincided with a period of hydrological modification by dams and
land‐use intensification associated with agriculture and livestock grazing. In the
Brisbane and Burnett Rivers, whose hydrology is substantially regulated by large
dams, lungfish showed consistent trends of δ13C depletion and δ15N enrichment over
time. This may indicate anthropogenic changes in background isotopic levels of basal
energy sources and/or that additional seston exported downstream from impoundments represent a carbon source that was previously unavailable, thus shifting
lungfish diet from benthic‐dominated primary production typical of unmodified river
systems, to pelagic carbon sources. By contrast, δ13C ratios of lungfish in the unregulated Mary River were more stable through time, whereas δ15N ratios increased
during a period of dairy industry expansion and increased application of nitrogen
fertilization and then subsequently decreased at the same time that rates of pasture
development declined and nutrient inputs presumably decreased. In conclusion, we
provide evidence for human‐caused alterations in background isotopic levels and
potential changes in availability of benthic versus pelagic energy resources supporting
Australian lungfish and demonstrate how detectable trophic signals in long‐lived fish
scales can reveal long‐term anthropogenic changes in riverine ecosystems.American Philosophical Society; Australian
Research Council, Grant/Award Number:
LP130100118; Mohamed bin Zayed Species
Conservation Fund; National Geographic
Society
Testing biodiversity theory using species richness of reef-building corals across a depth gradient
Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution
Complete Genome Sequence and Comparative Metabolic Profiling of the Prototypical Enteroaggregative Escherichia coli Strain 042
Background \ud
Escherichia coli can experience a multifaceted life, in some cases acting as a commensal while in other cases causing intestinal and/or extraintestinal disease. Several studies suggest enteroaggregative E. coli are the predominant cause of E. coli-mediated diarrhea in the developed world and are second only to Campylobacter sp. as a cause of bacterial-mediated diarrhea. Furthermore, enteroaggregative E. coli are a predominant cause of persistent diarrhea in the developing world where infection has been associated with malnourishment and growth retardation. \ud
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Methods \ud
In this study we determined the complete genomic sequence of E. coli 042, the prototypical member of the enteroaggregative E. coli, which has been shown to cause disease in volunteer studies. We performed genomic and phylogenetic comparisons with other E. coli strains revealing previously uncharacterised virulence factors including a variety of secreted proteins and a capsular polysaccharide biosynthetic locus. In addition, by using Biolog™ Phenotype Microarrays we have provided a full metabolic profiling of E. coli 042 and the non-pathogenic lab strain E. coli K-12. We have highlighted the genetic basis for many of the metabolic differences between E. coli 042 and E. coli K-12. \ud
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Conclusion \ud
This study provides a genetic context for the vast amount of experimental and epidemiological data published thus far and provides a template for future diagnostic and intervention strategies
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The Met Office Unified Model Global Atmosphere 6.0/6.1 and JULES Global Land 6.0/6.1 configurations
We describe Global Atmosphere 6.0 and Global Land 6.0: the latest science configurations of the Met Office Unified Model and JULES land surface model developed for use across all timescales. Global Atmosphere 6.0 includes the ENDGame dynamical core, which significantly increases mid-latitude variability improving a known model bias. Alongside developments of the model’s physical parametrisations, ENDGame also increases variability in the tropics, which leads to an improved representation of tropical cyclones and other tropical phenomena. Further developments of the atmospheric and land surface parametrisations improve other aspects of model performance, including the forecasting of surface weather phenomena. We also describe Global Atmosphere 6.1 and Global Land 6.1, which include a small number of long-standing differences from our main trunk configurations that we continue to require for operational global weather prediction. Since July 2014, GA6.1/GL6.1 has been used by the Met Office for operational global NWP, whilst GA6.0/GL6.0 was implemented in its remaining global prediction systems over the following year
Citrobacter rodentium is an unstable pathogen showing evidence of significant genomic flux.
Citrobacter rodentium is a natural mouse pathogen that causes attaching and effacing (A/E) lesions. It shares a common virulence strategy with the clinically significant human A/E pathogens enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC) and is widely used to model this route of pathogenesis. We previously reported the complete genome sequence of C. rodentium ICC168, where we found that the genome displayed many characteristics of a newly evolved pathogen. In this study, through PFGE, sequencing of isolates showing variation, whole genome transcriptome analysis and examination of the mobile genetic elements, we found that, consistent with our previous hypothesis, the genome of C. rodentium is unstable as a result of repeat-mediated, large-scale genome recombination and because of active transposition of mobile genetic elements such as the prophages. We sequenced an additional C. rodentium strain, EX-33, to reveal that the reference strain ICC168 is representative of the species and that most of the inactivating mutations were common to both isolates and likely to have occurred early on in the evolution of this pathogen. We draw parallels with the evolution of other bacterial pathogens and conclude that C. rodentium is a recently evolved pathogen that may have emerged alongside the development of inbred mice as a model for human disease
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UK consensus guidelines for the delivery of unexpected news in obstetric ultrasound: The ASCKS framework
Background: Studies indicate there is a need to improve the delivery of unexpected news via obstetric ultrasound, but there have been few advances in this area. One factor preventing improvement has been a lack of consensus regarding the appropriate phrases and behaviours which sonographers and ultrasound practitioners should use in these situations. Aims: To develop consensus guidelines for unexpected news delivery in Early Pregnancy Unit and Fetal Anomaly Screening Programme NHS settings. Methods: A workshop was conducted to identify priorities and reach consensus on areas of contention. Contributors included interdisciplinary healthcare professionals, policy experts, representatives from third-sector organisations, lay experts and academic researchers (n = 28). Written and verbal feedback was used to draft initial guidance which was then circulated amongst the wider writing group (n = 39). Revisions were undertaken until consensus was reached. Results: Consensus guidelines were developed outlining the behaviours and phrases which should be used during scans where unexpected findings are identified. Specific recommendations included that: honest and clear communication should be prioritised, even with uncertain findings; technical terms should be used, but these should be written down together with their lay interpretations; unless expectant parents use other terminology (e.g. ‘foetus’), the term ‘baby’ should be used as a default, even in early pregnancy; at the initial news disclosure, communication should focus on information provision. Expectant parents should not be asked to make decisions during the scan. Conclusions: These recommendations can be used to develop and improve news delivery interventions in obstetric ultrasound settings. The full guidelines can be accessed online as supplemental material and at https://doi.org/10.5518/100/24
Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context
Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts
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