12,746 research outputs found

    Measuring the world city network: new results and developments

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    Analytical Solution of the Voter Model on Disordered Networks

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    We present a mathematical description of the voter model dynamics on heterogeneous networks. When the average degree of the graph is μ2\mu \leq 2 the system reaches complete order exponentially fast. For μ>2\mu >2, a finite system falls, before it fully orders, in a quasistationary state in which the average density of active links (links between opposite-state nodes) in surviving runs is constant and equal to (μ2)3(μ1)\frac{(\mu-2)}{3(\mu-1)}, while an infinite large system stays ad infinitum in a partially ordered stationary active state. The mean life time of the quasistationary state is proportional to the mean time to reach the fully ordered state TT, which scales as T(μ1)μ2N(μ2)μ2T \sim \frac{(\mu-1) \mu^2 N}{(\mu-2) \mu_2}, where NN is the number of nodes of the network, and μ2\mu_2 is the second moment of the degree distribution. We find good agreement between these analytical results and numerical simulations on random networks with various degree distributions.Comment: 20 pages, 8 figure

    Charging Ultrasmall Tunnel Junctions in Electromagnetic Environment

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    We have investigated the quantum admittance of an ultrasmall tunnel junction with arbitrary tunneling strength under an electromagnetic environment. Using the functional integral approach a close analytical expression of the quantum admittance is derived for a general electromagnetic environment. We then consider a specific controllable environment where a resistance is connected in series with the tunneling junction, for which we derived the dc quantum conductance from the zero frequency limit of the imaginary part of the quantum admittance. For such electromagnetic environment the dc conductance has been investigated in recent experiments, and our numerical results agree quantitatively very well with the measurements. Our complete numerical results for the entire range of junction conductance and electromagnetic environmental conductance confirmed the few existing theoretical conclusions.Comment: 7 pages, 3 ps-figure

    Quantum Conductance of the Single Electron Transistor

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    The quantum conductance of the single-electron tunneling (SET) transistor is investigated in this paper by the functional integral approach. The formalism is valid for arbitrary tunnel resistance of the junctions forming the SET transistor at any temperature. The path integrals are evaluated by the semiclassical method to yield an explicit non-perturbation form of the quantum conductance of the SET transistor. An anomaly of the quantum conductance is found if the tunnel resistances are much smaller than the quantum resistance. The dependence of the conductance on the gate voltage is also discussed.Comment: 4 pages including some mathe details of cond-mat/990806

    KSTAR: An algorithm to predict patient-specific kinase activities from phosphoproteomic data

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    Kinase inhibitors as targeted therapies have played an important role in improving cancer outcomes. However, there are still considerable challenges, such as resistance, non-response, patient stratification, polypharmacology, and identifying combination therapy where understanding a tumor kinase activity profile could be transformative. Here, we develop a graph- and statistics-based algorithm, called KSTAR, to convert phosphoproteomic measurements of cells and tissues into a kinase activity score that is generalizable and useful for clinical pipelines, requiring no quantification of the phosphorylation sites. In this work, we demonstrate that KSTAR reliably captures expected kinase activity differences across different tissues and stimulation contexts, allows for the direct comparison of samples from independent experiments, and is robust across a wide range of dataset sizes. Finally, we apply KSTAR to clinical breast cancer phosphoproteomic data and find that there is potential for kinase activity inference from KSTAR to complement the current clinical diagnosis of HER2 status in breast cancer patients

    A Comparison of U. S. and European University-Industry Relations in the Life Sciences

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    We draw on diverse data sets to compare the institutional organization of upstream life science research across the United States and Europe. Understanding cross-national differences in the organization of innovative labor in the life sciences requires attention to the structure and evolution of biomedical networks involving public research organizations (universities, government laboratories, nonprofit research institutes, and research hospitals), science-based biotechnology firms, and multinational pharmaceutical corporations. We use network visualization methods and correspondence analyses to demonstrate that innovative research in biomedicine has its origins in regional clusters in the United States and in European nations. But the scientific and organizational composition of these regions varies in consequential ways. In the United States, public research organizations and small firms conduct R&D across multiple therapeutic areas and stages of the development process. Ties within and across these regions link small firms and diverse public institutions, contributing to the development of a robust national network. In contrast, the European story is one of regional specialization with a less diverse group of public research organizations working in a smaller number of therapeutic areas. European institutes develop local connections to small firms working on similar scientific problems, while cross-national linkages of European regional clusters typically involve large pharmaceutical corporations. We show that the roles of large and small firms differ in the United States and Europe, arguing that the greater heterogeneity of the U. S. system is based on much closer integration of basic science and clinical development
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