3,676 research outputs found

    Community responses to seawater warming are conserved across diverse biological groupings and taxonomic resolutions

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    Temperature variability is a major driver of ecological pattern, with recent changes in average and extreme temperatures having significant impacts on populations, communities and ecosystems. In the marine realm, very few experiments have manipulated temperature in situ, and current understanding of temperature effects on community dynamics is limited. We developed new technology for precise seawater temperature control to examine warming effects on communities of bacteria, microbial eukaryotes (protists) and metazoans. Despite highly contrasting phylogenies, size spectra and diversity levels, the three community types responded similarly to seawater warming treatments of +3°C and +5°C, highlighting the critical and overarching importance of temperature in structuring communities. Temperature effects were detectable at coarse taxonomic resolutions and many taxa responded positively to warming, leading to increased abundances at the community-level. Novel field-based experimental approaches are essential to improve mechanistic understanding of how ocean warming will alter the structure and functioning of diverse marine communities

    The central image of a gravitationally lensed quasar

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    A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts there should be an odd number of images but, paradoxically, almost all observed lenses have 2 or 4 images. The missing image should be faint and appear near the galaxy's center. These ``central images'' have long been sought as probes of galactic cores too distant to resolve with ordinary observations. There are five candidates, but in one case the third image is not necessarily a central image, and in the others, the central component might be a foreground source rather than a lensed image. Here we report the most secure identification of a central image, based on radio observations of PMN J1632-0033, one of the latter candidates. Lens models incorporating the central image show that the mass of the lens galaxy's central black hole is less than 2 x 10^8 M_sun, and the galaxy's surface density at the location of the central image is more than 20,000 M_sun per square parsec, in agreement with expectations based on observations of galaxies hundreds of times closer to the Earth.Comment: Nature, in press [7 pp, 2 figs]. Standard media embargo applies before publicatio

    Schistosoma haematobium infection levels determine the effect of praziquantel treatment on anti-schistosome and anti-mite antibodies

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    Field studies show an association between schistosome infection and atopy, but the effects of anti-helminthic treatment on this association have not yet been investigated in human populations with different schistosome endemicity levels. This study aimed to compare the effects of anti-helminthic treatment on responses directed against the house dust mite Dermatophagoides pteronyssinus (Derp1) and Schistosoma haematobium in Zimbabwean populations living in high and low schistosome infection areas. Derp1- and schistosome-specific IgE and IgG4 antibodies were quantified by ELISA before and 6 weeks after anti-helminthic treatment. Following treatment, there were changes in the immune responses, which varied with place of residence. After allowing for the effects of sex, age and baseline infection intensity, there was no significant treatment effect on the change in anti-schistosome IgE and IgG4 in the high infection area. However, the anti-schistosome IgE/IgG4 ratio increased significantly, while anti-Derp1 IgE responses decreased as a result of treatment. In the low infection area, treatment resulted in a significant increase in anti-worm IgE levels, but there was no significant treatment effect on anti-schistosome or anti-Derp1 IgE/IgG4 ratios. Thus, the study shows that the level of schistosome endemicity affects the host responses to schistosome and mite antigens following anti-helminthic treatment

    Redox linked flavin sites in extracellular decaheme proteins involved in microbe-mineral electron transfer

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    Extracellular microbe-mineral electron transfer is a major driving force for the oxidation of organic carbon in many subsurface environments. Extracellular multi-heme cytochromes of the Shewenella genus play a major role in this process but the mechanism of electron exchange at the interface between cytochrome and acceptor is widely debated. The 1.8 Å x-ray crystal structure of the decaheme MtrC revealed a highly conserved CX8C disulfide that, when substituted for AX8A, severely compromised the ability of S. oneidensis to grow under aerobic conditions. Reductive cleavage of the disulfide in the presence of flavin mononucleotide (FMN) resulted in the reversible formation of a stable flavocytochrome. Similar results were also observed with other decaheme cytochromes, OmcA, MtrF and UndA. The data suggest that these decaheme cytochromes can transition between highly reactive flavocytochromes or less reactive cytochromes, and that this transition is controlled by a redox active disulfide that responds to the presence of oxygen

    Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.

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    The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures

    Entangled-State Cycles of Atomic Collective-Spin States

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    We study quantum trajectories of collective atomic spin states of NN effective two-level atoms driven with laser and cavity fields. We show that interesting ``entangled-state cycles'' arise probabilistically when the (Raman) transition rates between the two atomic levels are set equal. For odd (even) NN, there are (N+1)/2(N+1)/2 (N/2N/2) possible cycles. During each cycle the NN-qubit state switches, with each cavity photon emission, between the states (N/2,m>±N/2,m>)/2(|N/2,m>\pm |N/2,-m>)/\sqrt{2}, where N/2,m>|N/2,m> is a Dicke state in a rotated collective basis. The quantum number mm (>0>0), which distinguishes the particular cycle, is determined by the photon counting record and varies randomly from one trajectory to the next. For even NN it is also possible, under the same conditions, to prepare probabilistically (but in steady state) the Dicke state N/2,0>|N/2,0>, i.e., an NN-qubit state with N/2N/2 excitations, which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure

    Spatio-temporal Models of Lymphangiogenesis in Wound Healing

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    Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total

    Shortfalls and Solutions for Meeting National and Global Conservation Area Targets

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    Governments have committed to conserving 17% of terrestrial and 10% of marine environments globally, especially “areas of particular importance for biodiversity” through “ecologically representative” Protected Area (PA) systems or other “area-based conservation measures”, while individual countries have committed to conserve 3–50% of their land area. We estimate that PAs currently cover 14.6% of terrestrial and 2.8% of marine extent, but 59–68% of ecoregions, 77–78% of important sites for biodiversity, and 57% of 25,380 species have inadequate coverage. The existing 19.7 million km2 terrestrial PA network needs only 3.3 million km2 to be added to achieve 17% terrestrial coverage. However, it would require nearly doubling to achieve, costefficiently, coverage targets for all countries, ecoregions, important sites, and species. Poorer countries have the largest relative shortfalls. Such extensive and rapid expansion of formal PAs is unlikely to be achievable. Greater focus is therefore needed on alternative approaches, including community- and privately managed sites and other effective area-based conservation measures.We are grateful to the many individuals and organizations who contribute to the IUCN Red List of Threatened Species,WDPA, or to identification of IBAs or AZEs. We thank A. Bennett for help with data collation and N. Dulvy, W. Laurance, and D. Faith for helpful comments on an earlier draft. This work was supported by the Cambridge Conservation Initiative Collaborative Fund and Arcadia.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/conl.1215

    Understanding the theoretical underpinning of the exercise component in a fall prevention programme for older adults with mild dementia: a realist review protocol

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    Background Older adults with mild dementia are at an increased risk of falls. Preventing those at risk from falling requires complex interventions involving patient-tailored strength- and balance-challenging exercises, home hazard assessment, visual impairment correction, medical assessment and multifactorial combinations. Evidence for these interventions in older adults with mild cognitive problems is sparse and not as conclusive as the evidence for the general community-dwelling older population. The objectives of this realist review are (i) to identify the underlying programme theory of strength and balance exercise interventions targeted at those individuals that have been identified as falling and who have a mild dementia and (ii) to explore how and why that intervention reduces falls in that population, particularly in the context of a community setting. This protocol will explain the rationale for using a realist review approach and outline the method. Methods A realist review is a methodology that extends the scope of a traditional narrative or systematic evidence review. Increasingly used in the evaluation of complex interventions, a realist enquiry can look at the wider context of the intervention, seeking more to explain than judge if the intervention is effective by investigating why, what the underlying mechanism is and the necessary conditions for success. In this review, key rough programme theories were articulated and defined through discussion with a stakeholder group. The six rough programme theories outlined within this protocol will be tested against the literature found using the described comprehensive search strategy. The process of data extraction, appraisal and synthesis is outlined and will lead to the production of an explanatory programme theory. Discussion As far as the authors are aware, this is the first realist literature review within fall prevention research and adds to the growing use of this methodology within healthcare. This synthesis of evidence will provide a valuable addition to the evidence base surrounding the exercise component of a fall intervention programme for older adults with mild dementia and will ultimately provide clinically relevant recommendations for improving the care of people with dementia
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