8,221 research outputs found

    Dr. Yang Zhong: an explorer on the road forever

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    On the morning of September 25th 2017, grievous news spread from the remote Ordos region of Inner Mongolia to Fudan University campus in Shanghai. Professor Yang Zhong, a famous botanist and the Dean of Fudan University’s graduate school, passed away in a tragic car accident while on a business trip

    Exploring metro vibrancy and its relationship with built environment: a cross-city comparison using multi-source urban data

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    Recent urban transformations have led to critical reflections on the blighted urban infrastructures and called for re-stimulating vital urban places. Especially, the metro has been recognized as the backbone infrastructure for urban mobility and the associated economy agglomeration. To date, limited research has been devoted to investigating the relationship between metro vitality and built environment in mega-cities empirically. This paper presents a multisource urban data-driven approach to quantify the metro vibrancy and its association with the underlying built environment. Massive smart card data is processed to extract metro ridership, which denotes the vibrancy around the metro station in physical space. Social media check-ins are crawled to measure the vitality of metros in virtual spaces. Both physical and virtual vibrancy are integrated into a holistic metro vibrancy metric using an entropy-based weighting method. Certain built environment characteristics, including land use, transportation and buildings are modeled as independent variables. The significant influences of built environmental factors on the metro vibrancy are unraveled using the ordinary least square regression and the spatial lag model. With experiments conducted in Shenzhen, Singapore and London, this study comes up with a conclusion that spatial distributions of metro vibrancy metrics in three cities are spatially autocorrelated. The regression analysis suggests that in all the three cities, more affluent urban areas tend to have higher metro virbrancy, while the road density, land use and buildings tend to impact metro vibrancy in only one or two cities. These results demonstrate the relationship between the metro vibrancy and built environment is affected by complex urban contexts. These findings help us to understand metro vibrancy thus make proper policy to re-stimulate the important metro infrastructure in the future

    Monolithically integrated ÎŒLEDs/HEMTs microdisplay on a single chip by a direct epitaxial approach

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    There is a significantly increasing demand on developing a microLED (ÎŒLED) based microdisplay which may be the only display system that can meet the requirements for augmented reality/virtual reality systems, helmet mounted displays, and head‐up displays. However, a number of fundamental challenges which cannot be met by any existing technologies need to be overcome before such a microdisplay with satisfied performance becomes possible. In this paper, a different type of integration concept using an epitaxial approach is proposed, aiming to monolithically integrate ÎŒLEDs and high electron mobility transistors (HEMTs) on a single chip. This concept can be potentially realized by using a selective epitaxial overgrowth method on a predefined HEMT template featuring microhole masks. Finally, the proposed epitaxial integration concept is translated into a prototype, demonstrating an 8 × 8 microLED microdisplay, where each ÎŒLED is electrically driven by an individual HEMT which surrounds its respective ÎŒLED via the gate bias of the HEMT

    Discovery of a high-altitude ecotype and ancient lineage of Arabidopsis thaliana from Tibet

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    Arabidopsis thaliana(A. thaliana) has long been a model species for dicotyledon study, and was the first flowering plant to get its genome completed sequenced [1]. Although most wild A. thaliana are collected in Europe, several studies have found a rapid A. thaliana west-east expansion from Central Asia [2]. The Qinghai-Tibet Plateau (QTP) is close to Central Asia and known for its high altitude, unique environments and biodiversity [3]. However, no wild-type A. thaliana had been either discovered or sequenced from QTP. Studies on the A. thaliana populations collected under 2000 m asl have shown that the adaptive variations associated with climate and altitudinal gradients [4]. Hence a high-altitude A. thaliana provides a precious natural material to investigate the evolution and adaptation process

    A Unified Approach to the Classical Statistical Analysis of Small Signals

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    We give a classical confidence belt construction which unifies the treatment of upper confidence limits for null results and two-sided confidence intervals for non-null results. The unified treatment solves a problem (apparently not previously recognized) that the choice of upper limit or two-sided intervals leads to intervals which are not confidence intervals if the choice is based on the data. We apply the construction to two related problems which have recently been a battle-ground between classical and Bayesian statistics: Poisson processes with background, and Gaussian errors with a bounded physical region. In contrast with the usual classical construction for upper limits, our construction avoids unphysical confidence intervals. In contrast with some popular Bayesian intervals, our intervals eliminate conservatism (frequentist coverage greater than the stated confidence) in the Gaussian case and reduce it to a level dictated by discreteness in the Poisson case. We generalize the method in order to apply it to analysis of experiments searching for neutrino oscillations. We show that this technique both gives correct coverage and is powerful, while other classical techniques that have been used by neutrino oscillation search experiments fail one or both of these criteria.Comment: 40 pages, 15 figures. Changes 15-Dec-99 to agree more closely with published version. A few small changes, plus the two substantive changes we made in proof back in 1998: 1) The definition of "sensitivity" in Sec. V(C). It was inconsistent with our actual definition in Sec. VI. 2) "Note added in proof" at end of the Conclusio

    Physics at BES-III

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    This physics book provides detailed discussions on important topics in τ\tau-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.Comment: Edited by Kuang-Ta Chao and Yi-Fang Wan

    Partial wave analysis of J/psi to p pbar pi0

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    Using a sample of 58 million J/ψJ/\psi events collected with the BESII detector at the BEPC, more than 100,000 J/ψ→ppˉπ0J/\psi \to p\bar p \pi^0 events are selected, and a detailed partial wave analysis is performed. The branching fraction is determined to be Br(J/ψ→ppˉπ0)=(1.33±0.02±0.11)×10−3Br(J/\psi \to p \bar p \pi^0)=(1.33 \pm 0.02 \pm 0.11) \times 10^{-3}. A long-sought `missing' N∗N^*, first observed in J/ψ→pnˉπ−J/\psi \to p \bar n \pi^-, is observed in this decay too, with mass and width of 2040−4+3±252040_{-4}^{+3}\pm 25 MeV/c2^2 and 230−8+8±52230_{-8}^{+8}\pm 52 MeV/c2^2, respectively. Its spin-parity favors 3/2+{3/2}^+. The masses, widths, and spin-parities of other N∗N^* states are obtained as well.Comment: Add one author nam

    Observation of Y(2175) in J/ψ→ηϕf0(980)J/\psi\to \eta\phi f_0(980)

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    The decays of J/ψ→ηϕf0(980)(η→γγ,ϕ→K+K−,f0(980)→π+π−)J/\psi\to \eta\phi f_0(980) (\eta\to \gamma\gamma, \phi \to K^+K^-, f_0(980)\to\pi^+\pi^-) are analyzed using a sample of 5.8×1075.8 \times 10^{7} J/ψJ/\psi events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around 2.182.18 GeV/c2c^2 with about 5σ5\sigma significance is observed in the ϕf0(980)\phi f_0(980) invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of m=2.186±0.010(stat)±0.006(syst)m=2.186\pm 0.010 (stat)\pm 0.006 (syst) GeV/c2c^2 and Γ=0.065±0.023(stat)±0.017(syst)\Gamma=0.065\pm 0.023 (stat)\pm 0.017 (syst) GeV/c2c^2, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process e+e−→γISRϕf0(980)e^+e^-\to\gamma_{ISR}\phi f_0(980). The production branching ratio is determined to be Br(J/ψ→ηY(2175))⋅Br(Y(2175)→ϕf0(980))⋅Br(f0(980)→π+π−)=(3.23±0.75(stat)±0.73(syst))×10−4Br(J/\psi\to\eta Y(2175))\cdot Br(Y(2175)\to\phi f_0(980))\cdot Br(f_0(980)\to\pi^+\pi^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}, assuming that the Y(2175) is a 1−−1^{--} state.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let
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