18,306 research outputs found

    Poisson transition rates from time-domain measurements with finite bandwidth

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    In time-domain measurements of a Poisson two-level system, the observed transition rates are always smaller than those of the actual system, a general consequence of finite measurement bandwidth in an experiment. This underestimation of the rates is significant even when the measurement and detection apparatus is ten times faster than the process under study. We derive here a quantitative form for this correction using a straightforward state-transition model that includes the detection apparatus, and provide a method for determining a system's actual transition rates from bandwidth-limited measurements. We support our results with computer simulations and experimental data from time-domain measurements of quasiparticle tunneling in a single-Cooper-pair transistor.Comment: 4 pages, 5 figure

    Trees and the urban environment - weighing risks and benefits

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    The presence of mature, broad-leafed trees in urban areas is increasingly evidenced as being beneficial for public health, mental well-being and the environment. Consequently, any loss of such trees should be regarded as increasing risk, potentially with significant consequences. Currently, austerity measures and fragmented policies are tending to miss out on the opportunities presented by a greener environment, and some policies connected with, for example, road safety and highway engineering have the potential to reduce tree presence if disproportionately applied, as does fear of litigation

    Design for play: a guide to creating successful play spaces.

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    de Branges-Rovnyak spaces: basics and theory

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    For SS a contractive analytic operator-valued function on the unit disk D{\mathbb D}, de Branges and Rovnyak associate a Hilbert space of analytic functions H(S){\mathcal H}(S) and related extension space D(S){\mathcal D(S)} consisting of pairs of analytic functions on the unit disk D{\mathbb D}. This survey describes three equivalent formulations (the original geometric de Branges-Rovnyak definition, the Toeplitz operator characterization, and the characterization as a reproducing kernel Hilbert space) of the de Branges-Rovnyak space H(S){\mathcal H}(S), as well as its role as the underlying Hilbert space for the modeling of completely non-isometric Hilbert-space contraction operators. Also examined is the extension of these ideas to handle the modeling of the more general class of completely nonunitary contraction operators, where the more general two-component de Branges-Rovnyak model space D(S){\mathcal D}(S) and associated overlapping spaces play key roles. Connections with other function theory problems and applications are also discussed. More recent applications to a variety of subsequent applications are given in a companion survey article

    Destruction and regrowth of lithospheric mantle beneath large igneous provinces

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    Large igneous provinces (LIPs) are formed by enormous (i.e., frequently >106 km3) but short-lived magmatic events that have profound effects upon global geodynamic, tectonic, and environmental processes. Lithospheric structure is known to modulate mantle melting, yet its evolution during and after such dramatic periods of magmatism is poorly constrained. Using geochemical and seismological observations, we find that magmatism is associated with thin (i.e., ≲80 km) lithosphere and we reveal a striking positive correlation between the thickness of modern-day lithosphere beneath LIPs and time since eruption. Oceanic lithosphere rethickens to 125 km, while continental regions reach >190 km. Our results point to systematic destruction and subsequent regrowth of lithospheric mantle during and after LIP emplacement and recratonization of the continents following eruption. These insights have implications for the stability, age, and composition of ancient, thick, and chemically distinct lithospheric roots, the distribution of economic resources, and emissions of chemical species that force catastrophic environmental change

    Immunization of networks with community structure

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    In this study, an efficient method to immunize modular networks (i.e., networks with community structure) is proposed. The immunization of networks aims at fragmenting networks into small parts with a small number of removed nodes. Its applications include prevention of epidemic spreading, intentional attacks on networks, and conservation of ecosystems. Although preferential immunization of hubs is efficient, good immunization strategies for modular networks have not been established. On the basis of an immunization strategy based on the eigenvector centrality, we develop an analytical framework for immunizing modular networks. To this end, we quantify the contribution of each node to the connectivity in a coarse-grained network among modules. We verify the effectiveness of the proposed method by applying it to model and real networks with modular structure.Comment: 3 figures, 1 tabl

    Single-strand selective monofunctional uracil-DNA glycosylase (SMUG1) deficiency is linked to aggressive breast cancer and predicts response to adjuvant therapy

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    Uracil in DNA is an important cause of mutagenesis. SMUG1 is a uracil DNA glycosylase that removes uracil through base excision repair. SMUG1 also processes radiation induced oxidative base damage as well as 5-fluorouracil incorporated into DNA during chemotherapy. We investigated SMUG1 mRNA expression in 249 primary breast cancers. SMUG1 protein expression was investigated in 1165 breast tumours randomised into two cohorts [training set (n=583) and test set (n=582)]. SMUG1 and chemotherapy response was also investigated in a series of 315 ER negative tumours (n=315). For mechanistic insights, SMUG1 was correlated to biomarkers of aggressive phenotype, DNA repair, cell cycle and apoptosis. Low SMUG1 mRNA expression was associated with adverse disease specific survival (p=0.008) and disease free survival (p=0.008). Low SMUG1 protein expression (25%) was associated with high histological grade (p<0.0001), high mitotic index (p<0.0001), pleomorphism (p<0.0001), glandular de-differentiation (p=0.0001), absence of hormonal receptors (ER-/PgR-/AR) (p<0.0001), presence of basal-like (p<0.0001) and triple negative phenotypes (p<0.0001). Low SMUG1 protein expression was associated with loss of BRCA1 (p<0.0001), ATM (p<0.0001) and XRCC1 (p<0.0001). Low p27 (p<0.0001), low p21 (p=0.023), mutant p53 (p=0.037), low MDM2 (p<0.0001), low MDM4 (p=0.004), low Bcl-2 (p=0.001), low Bax (p=0.003) and high MIB1 (p<0.0001) were likely in low SMUG1 tumours. Low SMUG1 protein expression was associated with poor prognosis in univariate (p<0.001) and multivariate analysis (p<0.01). In ER+ cohort that received adjuvant endocrine therapy, low SMUG1 protein expression remains associated with poor survival (p<0.01). In ER- cohort that received adjuvant chemotherapy, low SMUG1 protein expression is associated with improved survival (p=0.043). Our study suggests that low SMUG1 expression may correlate to adverse clinicopathological features and predict response to adjuvant therapy in breast cancer
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