23,011 research outputs found

    A case report of intracranial vertebral-basilar artery hypoplasia presenting with episodic dizziness

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    Basilar artery hypoplasia (BAH) is usually accompa-nied with unilateral vertebral artery hypoplasia (VAH); however, BAH with bilateral VAHs composing verte-bral-basilar artery hypoplasia (VBAH) is indeed a rare curiosity. A 61-year-old woman presented with epi-sodic dizziness for ten years. It accompanied with headache, bilateral tinnitus and blurred vision. Time-of-flight magnetic resonance angiogram with T2 true fast imaging in steady state precession confirmed the VBAH, rather than a stenosis. Symptoms subsided after daily oral aspirin and life-style change has been recommended for three months. The following one year was uneventful, and hearing improved. Finally, we conclude that the episodic dizziness with sensori-neural hearing impairment might attribute to the VBAH. It appears that life-style change was the main therapy and the antiplatelet was simply a supplementary on

    Light Hadron Spectroscopy and Decay at BESIII

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    Light hadron spectroscopy plays an important role in understanding the decay dynamics of unconventional hadronic states, such as strangeonium and glueballs. BESIII provides an ideal avenue to search for these exotic states thanks to a huge amount of data recorded at various energy points in the tau-charm mass region including J/psi resonance. This report summarizes recent results of the BESIII experiment related to the glueballs and strangeonium-like states.Comment: 6 pages, 5 figures, Conference proceeding of FPCP-201

    Intensified Arctic warming under greenhouse warming by vegetation–atmosphere–sea ice interaction

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    Observations and modeling studies indicate that enhanced vegetation activities over high latitudes under an elevated CO2 concentration accelerate surface warming by reducing the surface albedo. In this study, we suggest that vegetation-atmosphere-sea ice interactions over high latitudes can induce an additional amplification of Arctic warming. Our hypothesis is tested by a series of coupled vegetation-climate model simulations under 2xCO(2) environments. The increased vegetation activities over high latitudes under a 2xCO(2) condition induce additional surface warming and turbulent heat fluxes to the atmosphere, which are transported to the Arctic through the atmosphere. This causes additional sea-ice melting and upper-ocean warming during the warm season. As a consequence, the Arctic and high-latitude warming is greatly amplified in the following winter and spring, which further promotes vegetation activities the following year. We conclude that the vegetation-atmosphere-sea ice interaction gives rise to additional positive feedback of the Arctic amplification.open1188sciescopu

    Absorbate-Induced Piezochromism in a Porous Molecular Crystal

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    Atmospherically stable porous frameworks and materials are interesting for heterogeneous solid–gas applications. One motivation is the direct and selective uptake of pollutant/hazardous gases, where the material produces a measurable response in the presence of the analyte. In this report, we present a combined experimental and theoretical rationalization for the piezochromic response of a robust and porous molecular crystal built from an extensively fluorinated trispyrazole. The electronic response of the material is directly determined by analyte uptake, which provokes a subtle lattice contraction and an observable bathochromic shift in the optical absorption onset. Selectivity for fluorinated absorbates is demonstrated, and toluene is also found to crystallize within the pore. Furthermore, we demonstrate the application of electronic structure calculations to predict a physicochemical response, providing the foundations for the design of electronically tunable porous solids with the chemical properties required for development of novel gas-uptake media

    Investigating the Capability of Precision in Robotic Grinding

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    Most robotic grinding focus on the surface finish rather than accuracy and precision. However ever increased demand on complex component manufacture requires to advance robot grinding capability so that more practical and competitive accurate systems can be developed. The current study focuses on improving the level of accuracy of robotic grinding, which is a significant challenge in robot application because the kinematic accuracy of robot movement is much more complex than normal CNC machine tools. Aiming to improve accuracy and efficiency the work considers all quality of measures including surface roughness and the accuracy of size and form. For that to be done, a repeatability test is firstly preformed to observe the distributions of the joint positions and how well the robot responds to its programmed position using a dial gauge method and a circuit trigger method. After that, a datum setting method is performed to assess the datum alignment with the robot. Hence, a mathematical model based on regression analyses applies towards the collected data to observe closely any error correlation when setting up a datum to perform the grinding procedure

    Necessary and sufficient conditions of solution uniqueness in 1\ell_1 minimization

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    This paper shows that the solutions to various convex 1\ell_1 minimization problems are \emph{unique} if and only if a common set of conditions are satisfied. This result applies broadly to the basis pursuit model, basis pursuit denoising model, Lasso model, as well as other 1\ell_1 models that either minimize f(Axb)f(Ax-b) or impose the constraint f(Axb)σf(Ax-b)\leq\sigma, where ff is a strictly convex function. For these models, this paper proves that, given a solution xx^* and defining I=\supp(x^*) and s=\sign(x^*_I), xx^* is the unique solution if and only if AIA_I has full column rank and there exists yy such that AITy=sA_I^Ty=s and aiTy<1|a_i^Ty|_\infty<1 for i∉Ii\not\in I. This condition is previously known to be sufficient for the basis pursuit model to have a unique solution supported on II. Indeed, it is also necessary, and applies to a variety of other 1\ell_1 models. The paper also discusses ways to recognize unique solutions and verify the uniqueness conditions numerically.Comment: 6 pages; revised version; submitte

    Computer games: A double-edged sword?

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    Excessive computer game playing (ECGP) has already become a serious social problem. However, limited data from experimental lab studies are available about the negative consequences of ECGP on players' cognitive characteristics. In the present study, we compared three groups of participants (current ECGP participants, previous ECGP participants, and control participants) on a Multiple Object Tracking (MOT) task. The previous ECGP participants performed significantly better than the control participants, which suggested a facilitation effect of computer games on visuospatial abilities. Moreover, the current ECGP participants performed significantly worse than the previous ECGP participants. This more important finding indicates that ECGP may be related to cognitive deficits. Implications of this study are discussed. © 2008 Mary Ann Liebert, Inc.published_or_final_versio

    A procedure for the change point problem in parametric models based on phi-divergence test-statistics

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    This paper studies the change point problem for a general parametric, univariate or multivariate family of distributions. An information theoretic procedure is developed which is based on general divergence measures for testing the hypothesis of the existence of a change. For comparing the accuracy of the new test-statistic a simulation study is performed for the special case of a univariate discrete model. Finally, the procedure proposed in this paper is illustrated through a classical change-point example
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