3,597 research outputs found

    Transport enhancement from incoherent coupling between one-dimensional quantum conductors

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    We study the non-equilibrium transport properties of a highly anisotropic two-dimensional lattice of spin-1/2 particles governed by a Heisenberg XXZ Hamiltonian. The anisotropy of the lattice allows us to approximate the system at finite temperature as an array of incoherently coupled one-dimensional chains. We show that in the regime of strong intrachain interactions, the weak interchain coupling considerably boosts spin transport in the driven system. Interestingly, we show that this enhancement increases with the length of the chains, which is related to superdiffusive spin transport. We describe the mechanism behind this effect, compare it to a similar phenomenon in single chains induced by dephasing, and explain why the former is much stronger

    Direct evidence that twisted flux tube emergence creates solar active regions

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    The magnetic nature of the formation of solar active regions lies at the heart of understanding solar activity and, in particular, solar eruptions. A widespread model, used in many theoretical studies, simulations and the interpretation of observations, is that the basic structure of an active region is created by the emergence of a large tube of pre-twisted magnetic field. Despite plausible reasons and the availability of various proxies suggesting the accuracy of this model, there has not yet been a methodology that can clearly and directly identify the emergence of large pre-twisted magnetic flux tubes. Here, we present a clear signature of the emergence of pre-twisted magnetic flux tubes by investigating a robust topological quantity, called magnetic winding, in solar observations. This quantity detects the emerging magnetic topology despite the significant deformation experienced by the emerging magnetic field. Magnetic winding complements existing measures, such as magnetic helicity, by providing distinct information about field line topology, thus allowing for the direct identification of emerging twisted magnetic flux tubes

    The role of variation in genetic susceptibility to soybean rust on the photosynthetic competence of infected leaves.

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    Three soybean rust infection types have been reported: 1) tan lesions indicate a compatible and susceptible reaction, 2) red- brown (RB) lesion type has been associated with few non-sporulating uredinia representing a resistant reaction, and 3) immune reaction with no visible evidence of infection. Differences among cultivars would imply genotypic differences in tolerance, which can be define as the ability of the host to endure the presence of the pathogen with reduced disease symptoms and/or damages. Soybean rust-induced yield loss has been associated with reduction in light interception due to premature leaf loss and the lesions on the remaining green leaves. Incorporation of the effect of the pathogen on photosynthetic efficiency of disease leaves from different soybean cultivars in model to predict production might increase the accuracy and precision of the estimates supply by this model. Bastiaans (1991) proposed the concept of a "virtual lesion" and developed a simple model Y= (1-x)? to fit empirical data and describe the relationship between the reduction in relative photosynthesis in a diseased leaf (Y), and the disease severity (x). The value of â indicates whether the effect of disease on photosynthesis is higher (? > 1), lower (? < l) or equal (? = 1) to that accounted for by the observed diseased area. Reliable estimate of disease effects on growth and yield depends on the ability to accurate quantify the parameter ?. The objective of the current study was to determine the role of host-plant variation in disease susceptibility on soybean leaf gas exchange in field and control environment studies. The specific objectives are to quantify the ? value for SBR-infected leaves as influenced by plant growing conditions and genetic variation in disease susceptibility.Edição do Proceedings of the National Soybean Rust Symposium, New Orleans, 2009

    Quantum dynamics in photonic crystals

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    Employing a recently developed method that is numerically accurate within a model space simulating the real-time dynamics of few-body systems interacting with macroscopic environmental quantum fields, we analyze the full dynamics of an atomic system coupled to a continuum light-field with a gapped spectral density. This is a situation encountered, for example, in the radiation field in a photonic crystal, whose analysis has been so far been confined to limiting cases due to the lack of suitable numerical techniques. We show that both atomic population and coherence dynamics can drastically deviate from the results predicted when using the rotating wave approximation, particularly in the strong coupling regime. Experimental conditions required to observe these corrections are also discussed.Comment: 5 pages, 2 figures Updated with published versio

    Mapping urban infrastructure interdependencies and fuzzy risks

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    This is the final version of the article. Available from Elsevier via the DOI in this record.In this study, we considered the relationships between different types of CI and services to simulate possible cascading effects during extreme hazard conditions brought on by climate change and how to analyse impacts with limited data resources. An area in central Bristol, UK, was used as the case study to investigate the interdependencies among select assets and services. A wide range of plausible scenarios caused by pipe bursts in the area were simulated using the CADDIES 2D modelling framework, to identify the hotspots with high risk. The impact on CI, including water supply, electricity, wastewater, solid waste, transportation, telecommunication, and emergency services were assessed by the HAZUR tool. The analysis demonstrated that with limited data resources the dynamics of the interdependencies between CI networks can be highlighted and a basis of risk quantification can be established. The same procedure can be repeated to evaluate the impact of other types of hazards, or the compound hazard scenarios to provide a holistic assessment. Therefore, urban planners and managers can further explore options of interventions for setting up strategies to strengthen city resilience.This study is supported by the RESCCUE (RESilience to cope with Climate Change in Urban arEas) project, funded by the European Union Horizon 2020 research and innovation programme (Grant Agreement No. 700174)

    ‘It’s better than daytime television’: questioning the socio-spatial impacts of massage parlours on residential communities

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    It has been shown that street sex work is problematic for some communities, but there is less evidence of the effects of brothels. Emerging research also suggests that impact discourses outlined by residential communities and in regulatory policies should be critiqued, because they are often based on minority community voices, and limited tangible evidence is used to masquerade wider moral viewpoints about the place of sex work. Using a study of residents living in close proximity to brothels in Blackpool, this paper argues that impact is socially and spatially fluid. Impact needs to be evaluated in a more nuanced manner, which is considerate of the heterogeneity of (even one type of) sex work, and the community in question. Brothels in Blackpool had a variety of roles in the everyday socio-spatial fabric; thus also questioning the common assumption that sex work only impacts negatively on residential communities
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