92 research outputs found

    Solving geoinformatics parametric polynomial systems using the improved Dixon resultant

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    Improvements in computational and observational technologies in geoinformatics, e.g., the use of laser scanners that produce huge point cloud data sets, or the proliferation of global navigation satellite systems (GNSS) and unmanned aircraft vehicles (UAVs), have brought with them the challenges of handling and processing this “big data”. These call for improvement or development of better processing algorithms. One way to do that is integration of symbolically presolved sub-algorithms to speed up computations. Using examples of interest from real geoinformatic problems, we will discuss the Dixon-EDF resultant as an improved resultant method for the symbolic solution of parametric polynomial systems. We will briefly describe the method itself, then discuss geoinformatics problems arising in minimum distance mapping (MDM), parameter transformations, and pose estimation essential for resection. Dixon-EDF is then compared to older notions of “Dixon resultant”, and to several respected implementations of Gröbner bases algorithms on several systems. The improved algorithm, Dixon-EDF, is found to be greatly superior, usually by orders of magnitude, in both CPU usage and RAM usage. It can solve geoinformatics problems on which the other methods fail, making symbolic solution of parametric systems feasible for many problems

    Performance of [(18)F]flutemetamol amyloid imaging against the neuritic plaque component of CERAD and the current (2012) NIA-AA recommendations for the neuropathologic diagnosis of Alzheimer's disease

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    INTRODUCTION: Performance of the amyloid tracer [(18)F]flutemetamol was evaluated against three pathology standard of truth (SoT) measures including neuritic plaques (CERAD "original" and "modified" and the amyloid component of the 2012 NIA-AA guidelines). METHODS: After [(18)F]flutemetamol imaging, 106 end-of-life patients who died underwent postmortem brain examination for amyloid plaque load. Blinded positron emission tomography scan interpretations by five independent electronically trained readers were compared with pathology measures. RESULTS: By SoT, sensitivity and specificity of majority image interpretations were, respectively, 91.9% and 87.5% with "original CERAD," 90.8% and 90.0% with "modified CERAD," and 85.7% and 100% with the 2012 NIA-AA criteria. DISCUSSION: The high accuracy of either CERAD criteria suggests that [(18)F]flutemetamol predominantly reflects neuritic amyloid plaque density. However, the use of CERAD criteria as the SoT can result in some false-positive results because of the presence of diffuse plaques, which are accounted for when the positron emission tomography read is compared with the 2012 NIA-AA criteria

    Validity of a novel computerized cognitive battery for mild cognitive impairment

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    BACKGROUND: The NeuroTrax Mindstreams computerized cognitive assessment system was designed for widespread clinical and research use in detecting mild cognitive impairment (MCI). However, the capability of Mindstreams tests to discriminate elderly with MCI from those who are cognitively healthy has yet to be evaluated. Moreover, the comparability between these tests and traditional neuropsychological tests in detecting MCI has not been examined. METHODS: A 2-center study was designed to assess discriminant validity of tests in the Mindstreams Mild Impairment Battery. Participants were 30 individuals diagnosed with MCI, 29 with mild Alzheimer's disease (AD), and 39 healthy elderly. Testing was with the Mindstreams battery and traditional neuropsychological tests. Receiver operating characteristic (ROC) analysis was used to examine the ability of Mindstreams and traditional measures to discriminate those with MCI from cognitively healthy elderly. Between-group comparisons were made (Mann-Whitney U test) between MCI and healthy elderly and between MCI and mild AD groups. RESULTS: Mindstreams outcome parameters across multiple cognitive domains significantly discriminated among MCI and healthy elderly with considerable effect sizes (p < 0.05). Measures of memory, executive function, visual spatial skills, and verbal fluency discriminated best, and discriminability was at least comparable to that of traditional neuropsychological tests in these domains. CONCLUSIONS: Mindstreams tests are effective in detecting MCI, providing a comprehensive profile of cognitive function. Further, the enhanced precision and ease of use of these computerized tests make the NeuroTrax system a valuable clinical tool in the identification of elderly at high risk for dementia

    Progress toward standardized diagnosis of vascular cognitive impairment: Guidelines from the Vascular Impairment of Cognition Classification Consensus Study

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    INTRODUCTION: Progress in understanding and management of vascular cognitive impairment (VCI) has been hampered by lack of consensus on diagnosis, reflecting the use of multiple different assessment protocols. A large multinational group of clinicians and researchers participated in a two-phase Vascular Impairment of Cognition Classification Consensus Study (VICCCS) to agree on principles (VICCCS-1) and protocols (VICCCS-2) for diagnosis of VCI. We present VICCCS-2. METHODS: We used VICCCS-1 principles and published diagnostic guidelines as points of reference for an online Delphi survey aimed at achieving consensus on clinical diagnosis of VCI. RESULTS: Six survey rounds comprising 65-79 participants agreed guidelines for diagnosis of VICCCS-revised mild and major forms of VCI and endorsed the National Institute of Neurological Disorders-Canadian Stroke Network neuropsychological assessment protocols and recommendations for imaging. DISCUSSION: The VICCCS-2 suggests standardized use of the National Institute of Neurological Disorders-Canadian Stroke Network recommendations on neuropsychological and imaging assessment for diagnosis of VCI so as to promote research collaboration

    A history of post-communist remembrance: from memory politics to the emergence of a field of anticommunism

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    This article invites the view that the Europeanization of an antitotalitarian “collective memory” of communism reveals the emergence of a field of anticommunism. This transnational field is inextricably tied to the proliferation of state-sponsored and anticommunist memory institutes across Central and Eastern Europe (CEE), but cannot be treated as epiphenomenal to their propagation. The diffusion of bodies tasked with establishing the “true” history of communism reflects, first and foremost, a shift in the region’s approach to its past, one driven by the right’s frustration over an allegedly pervasive influence of former communist cliques. Memory institutes spread as the CEE right progressively perceives their emphasis on research and public education as a safer alternative to botched lustration processes. However, the field of anticommunism extends beyond diffusion by seeking to leverage the European Union institutional apparatus to generate previously unavailable forms of symbolic capital for anticommunist narratives. This results in an entirely different challenge, which requires reconciling of disparate ideological and national interests. In this article, I illustrate some of these nationally diverse, but internationally converging, trajectories of communist extrication from the vantage point of its main exponents: the anticommunist memory entrepreneurs, who are invariably found at the helm of memory institutes. Inhabiting the space around the political, historiographic, and Eurocratic fields, anticommunist entrepreneurs weave a complex web of alliances that ultimately help produce an autonomous field of anticommunism

    Civil society and global governance : the possibilities for global citizenship

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    In this article we reassert the role of governance as well as of civil society in the analysis of citizenship. We argue that to analyse global civil society and global citizenship it is necessary to focus on global governance. Just as states may facilitate or obstruct the emergence and development of national civil society, so too global governance institutions may facilitate or obstruct an emerging global civil society. Our key contention is that civil society at the global level thrives through its interaction with strong facilitating institutions of global governance. We start with a discussion of civil society and citizenship within the nation-state, and from there develop a model of global civil society and citizenship. Through analysing the impacts of various modes of global governance, we identify strategically appropriate forms of political and social engagement that best advance the prospects for global citizenship. <br /
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