864 research outputs found

    Expansion for the solutions of the Bogomolny equations on the torus

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    We show that the solutions of the Bogomolny equations for the Abelian Higgs model on a two-dimensional torus, can be expanded in powers of a quantity epsilon measuring the departure of the area from the critical area. This allows a precise determination of the shape of the solutions for all magnetic fluxes and arbitrary position of the Higgs field zeroes. The expansion is carried out to 51 orders for a couple of representative cases, including the unit flux case. We analyse the behaviour of the expansion in the limit of large areas, in which case the solutions approach those on the plane. Our results suggest convergence all the way up to infinite area.Comment: 26 pages, 8 figures, slightly revised version as published in JHE

    Whose perspective counts? A critical look at definitions of terms used for natural and near-natural forests

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    The way forests are defined, using terms such as ancient, old-growth, primary, sacred, or intact forest landscapes, has far-reaching impacts on how, why, and where forests are conserved and managed. Definitions of terms such as “old-growth forests” have been discussed individually but not collectively assessed. Here, we review the definitions and uses of terms associated with natural and near-natural forests using systematic mapping methods and critical analysis. Our findings reveal a variety of definitions for different terms, although a few frequently cited ones prevail. Our results also highlight the dominance of Western institutions and scientific knowledge in shaping global discourses on forest conservation, often at the expense of Indigenous and local perspectives. Despite the increasing recognition of the value-based benefits that forests provide, definitions that explicitly incorporate values are scarce. This omission of the voices of forest-proximate communities and a lack of consideration for their local values and needs result in recognition, contextual, and procedural inequities when employing mainstream terms to define natural and near-natural forests

    DAWN: a resource for yielding insights into the diversity among wheat genomes

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    Background: Democratising the growing body of whole genome sequencing data available for Triticum aestivum (bread wheat) has been impeded by the lack of a genome reference and the large computational requirements for analysing these data sets. Results: DAWN (Diversity Among Wheat geNomes) integrates data from the T. aestivum Chinese Spring (CS) IWGSC RefSeq v1.0 genome with public WGS and exome data from 17 and 62 accessions respectively, enabling researchers and breeders alike to investigate genotypic differences between wheat accessions at the level of whole chromosomes down to individual genes. Conclusions: Using DAWN we show that it is possible to visualise small and large chromosomal deletions, identify haplotypes at a glance and spot the consequences of selective breeding. DAWN allows us to detect the break points of alien introgression segments brought into an accession when transferring desired genes. Furthermore, we can find possible explanations for reduced recombination in parts of a chromosome, we can predict regions with linkage drag, and also look at diversity in centromeric regions.Nathan S. Watson-Haigh, Radosław Suchecki, Elena Kalashyan, Melissa Garcia and Ute Bauman

    The role of Epstein-Barr virus in adults with bronchiectasis : A prospective cohort study

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    Epstein-Barr virus (EBV) is implicated in the progression of chronic obstructive pulmonary disease. We aimed to determine whether EBV correlates with bronchiectasis severity, exacerbations, and progression. We collected induced sputum in healthy controls and spontaneous sputum at 3-6-month intervals and onset of exacerbations in bronchiectasis patients between March 2017 and October 2018. EBV DNA was detected with quantitative polymerase chain reaction. We collected 442 sputum samples from 108 bronchiectasis patients and 50 induced sputum samples from 50 healthy controls. When stable, bronchiectasis patients yielded higher detection rates of EBV DNA (48.1% vs 20.0%; P =.001), but not viral loads (mean log load, 4.45 vs 4.76; P =.266), compared with controls; 64.9% of patients yielded consistent detection status between 2 consecutive stable visits. Neither detection rate (40.8% vs 48.1%; P =.393) nor load (mean log load, 4.34 vs 4.45; P =.580) differed between the onset of exacerbations and stable visits, nor between exacerbations and convalescence. Neither detection status nor viral loads correlated with bronchiectasis severity. EBV loads correlated negatively with sputum interleukin-1β (P =.002), CXC motif chemokine-8 (P =.008), and tumor necrosis factor-α levels (P =.005). Patients initially detected with, or repeatedly detected with, EBV DNA had significantly faster lung function decline and shorter time to next exacerbations (both P .05). The EBV strains detected in bronchiectasis patients were phylogenetically homologous. Patients with detection of EBV DNA have a shorter time to bronchiectasis exacerbations. EBV may contribute to bronchiectasis progression

    Propagator of a Charged Particle with a Spin in Uniform Magnetic and Perpendicular Electric Fields

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    We construct an explicit solution of the Cauchy initial value problem for the time-dependent Schroedinger equation for a charged particle with a spin moving in a uniform magnetic field and a perpendicular electric field varying with time. The corresponding Green function (propagator) is given in terms of elementary functions and certain integrals of the fields with a characteristic function, which should be found as an analytic or numerical solution of the equation of motion for the classical oscillator with a time-dependent frequency. We discuss a particular solution of a related nonlinear Schroedinger equation and some special and limiting cases are outlined.Comment: 17 pages, no figure

    The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang

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    We propose a cosmological scenario in which the hot big bang universe is produced by the collision of a brane in the bulk space with a bounding orbifold plane, beginning from an otherwise cold, vacuous, static universe. The model addresses the cosmological horizon, flatness and monopole problems and generates a nearly scale-invariant spectrum of density perturbations without invoking superluminal expansion (inflation). The scenario relies, instead, on physical phenomena that arise naturally in theories based on extra dimensions and branes. As an example, we present our scenario predominantly within the context of heterotic M-theory. A prediction that distinguishes this scenario from standard inflationary cosmology is a strongly blue gravitational wave spectrum, which has consequences for microwave background polarization experiments and gravitational wave detectors.Comment: 67 pages, 4 figures. v2,v3: minor corrections, references adde

    Neoatherosclerosis development following bioresorbable vascular scaffold implantation in diabetic and non-diabetic swine

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    Background: DM remains a risk factor for poor outcome after stent-implantation, but little is known if and how DM affects the vascular response to BVS. Aim: The aim of our study was to examine coronary responses to bioresorbable vascular scaffolds (BVS) in swine with and without diabetes mellitus fed a ‘fast-food’ diet (FF-DM and FF-NDM, respectively) by sequential optical coherence tomography (OCT)-imaging and histology. Methods: Fifteen male swine were evaluated. Eight received streptozotocin-injection to induce DM. After 9 months (M), 32 single BVS were implanted in epicardial arteries with a stent to artery (S/A)-ratio of 1.1:1 under quantitative coronary angiography (QCA) and OCT guidance. Lumen, scaffold, neointimal coverage and composition were assessed by QCA, OCT and near-infrared spectroscopy (NIRS) pre- and/or post-procedure, at 3M and 6M. Additionally, polarization-sensitive (PS)-OCT was performed in 7 swine at 6M. After sacrifice at 3M and 6M, histology and polymer degradation analysis were performed. Results: Late lumen loss was high (~60%) within the first 3M after BVS-implantation (P0.20). Neointimal coverage was highly heterogeneous in all swine (DM vs. NDM P>0.05), with focal lipid accumulation, irregular collagen distribution and neointimal calcification. Likewise, polymer mass loss was low (~2% at 3M, ~5% at 6M;P>0.20) and not associated with DM or inflammation. Conclusion: Scaffold coverage showed signs of neo-atherosclerosis in all FF-DM and FF-NDM swine, scaffold polymer was preserved and the vascular response to BVS was not influenced by diabetes

    Balanced harvest: concept, policies, evidence, and management implications

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    Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries

    The Release of Cytochrome c from Mitochondria during Apoptosis of NGF-deprived Sympathetic Neurons Is a Reversible Event

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    During apoptosis induced by various stimuli, cytochrome c is released from mitochondria into the cytosol where it participates in caspase activation. This process has been proposed to be an irreversible consequence of mitochondrial permeability transition pore opening, which leads to mitochondrial swelling and rupture of the outer mitochondrial membrane. Here we present data demonstrating that NGF-deprived sympathetic neurons protected from apoptosis by caspase inhibitors possess mitochondria which, though depleted of cytochrome c and reduced in size, remained structurally intact as viewed by electron microscopy. After re-exposure of neurons to NGF, mitochondria recovered their normal size and their cytochrome c content, by a process requiring de novo protein synthesis. Altogether, these data suggest that depletion of cytochrome c from mitochondria is a controlled process compatible with function recovery. The ability of sympathetic neurons to recover fully from trophic factor deprivation provided irreversible caspase inhibitors have been present during the insult period, has therapeutical implications for a number of acute neuropathologies
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