65 research outputs found

    Spin-transfer switching and thermal stability in an FePt/Au/FePt nanopillar prepared by alternate monatomic layer deposition

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    We fabricated a current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) nanopillar with a 1-nm-thick FePt free layer having perpendicular anisotropy using the alternate monatomic layer deposition method. Nanopillars consisting of [Fe (1 monolayer (ML))/Pt (1 ML)]n (n: the number of the alternation period) ferromagnetic layers and an Au spacer layer showed spin-transfer induced switching at room temperature.Comment: 11 page

    Integration and Diffusion in Sustainable Development Goals: Learning from the Past, Looking into the Future

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    One of the next major challenges for research and policy on sustainability is setting the post-2015 Development Agenda. This challenge arises as a direct result of the formal ending of the Millennium Development Goals (MDGs) in 2015 and as an outcome of the 2012 United Nations Conference on Sustainable Development (Rio+20). The post-2015 Development Agenda is expected to include two agendas: one on human well-being to advance the MDG targets and the other on planetary well-being, which requires a safe "operating space" within the Earth\u27s life-support system. In contrast to the MDGs, the Sustainable Development Goals (SDGs) are meant to apply to both developing and developed countries and create a space for development within the stable functioning of the Earth\u27s systems. However, what might this all look like? For answers, this paper reviews the achievements and reflections of the MDGs to date and identifies new challenges entailed in the shift of development goals from "millennium" to "sustainable". While most of the existing studies look at these two sets of issues separately, combining the two reveals two important features of the SDGs. First, SDGs need to integrate both human and planetary well-being in a goal, and second, goals, or sub-goals, need to be formulated at multiple levels, from global to local levels. While the MDGs represented no integrated goals, some of the existing proposals on SDGs include integrated goals. However, our analysis has shown that they do not present the vertical diffusion of goals. Considering both integration and diffusion in the architecture of SDGs is a remaining task

    Importance of individual events in temporal networks

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    Records of time-stamped social interactions between pairs of individuals (e.g., face-to-face conversations, e-mail exchanges, and phone calls) constitute a so-called temporal network. A remarkable difference between temporal networks and conventional static networks is that time-stamped events rather than links are the unit elements generating the collective behavior of nodes. We propose an importance measure for single interaction events. By generalizing the concept of the advance of event proposed by [Kossinets G, Kleinberg J, and Watts D J (2008) Proceeding of the 14th ACM SIGKDD International conference on knowledge discovery and data mining, p 435], we propose that an event is central when it carries new information about others to the two nodes involved in the event. We find that the proposed measure properly quantifies the importance of events in connecting nodes along time-ordered paths. Because of strong heterogeneity in the importance of events present in real data, a small fraction of highly important events is necessary and sufficient to sustain the connectivity of temporal networks. Nevertheless, in contrast to the behavior of scale-free networks against link removal, this property mainly results from bursty activity patterns and not heterogeneous degree distributions.Comment: 36 pages, 13 figures, 2 table

    Revisiting symmetries of lattice fermions via spin-flavor representation

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    Employing the spin-flavor representation, we investigate the structures of the doubler-mixing symmetries and the mechanisms of their spontaneous breakdown in four types of lattice fermion formulation. We first revisit the U(4)\timesU(4)A symmetries of the naive fermion with the vanishing bare mass m, and re-express them in terms of the spin-flavor representation. We apply the same method to the Wilson fermion, which possesses only the U(1) vector symmetry for general values of m. For a special value of m, however, there emerges an additional U(1) symmetry to be broken by pion condensation. We also explore two types of minimally doubled fermion, and discover a similar kind of symmetry enhancement and its spontaneous breakdown.Comment: 25 pages, no figure;v2 typos corrected;v3 Sec.2 is shortened. To appear in JHE

    Stretching Actin Filaments within Cells Enhances their Affinity for the Myosin II Motor Domain

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    To test the hypothesis that the myosin II motor domain (S1) preferentially binds to specific subsets of actin filaments in vivo, we expressed GFP-fused S1 with mutations that enhanced its affinity for actin in Dictyostelium cells. Consistent with the hypothesis, the GFP-S1 mutants were localized along specific portions of the cell cortex. Comparison with rhodamine-phalloidin staining in fixed cells demonstrated that the GFP-S1 probes preferentially bound to actin filaments in the rear cortex and cleavage furrows, where actin filaments are stretched by interaction with endogenous myosin II filaments. The GFP-S1 probes were similarly enriched in the cortex stretched passively by traction forces in the absence of myosin II or by external forces using a microcapillary. The preferential binding of GFP-S1 mutants to stretched actin filaments did not depend on cortexillin I or PTEN, two proteins previously implicated in the recruitment of myosin II filaments to stretched cortex. These results suggested that it is the stretching of the actin filaments itself that increases their affinity for the myosin II motor domain. In contrast, the GFP-fused myosin I motor domain did not localize to stretched actin filaments, which suggests different preferences of the motor domains for different structures of actin filaments play a role in distinct intracellular localizations of myosin I and II. We propose a scheme in which the stretching of actin filaments, the preferential binding of myosin II filaments to stretched actin filaments, and myosin II-dependent contraction form a positive feedback loop that contributes to the stabilization of cell polarity and to the responsiveness of the cells to external mechanical stimuli
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