101,923 research outputs found
Edward L. Ullmann, 1913-1976
No full textCaralp Raymonde. Edward L. Ullmann, 1913-1976. In: Annales de Géographie, t. 85, n°472, 1976. p. 725
Edward L. Ullmann, 1913-1976
No full textCaralp Raymonde. Edward L. Ullmann, 1913-1976. In: Annales de Géographie, t. 85, n°472, 1976. p. 725
Validation of cluster analysis results on validation data: A systematic framework
No full textCluster analysis refers to a wide range of data analytic techniques for class discovery and is popular in many application fields. To assess the quality of a clustering result, different cluster validation procedures have been proposed in the literature. While there is extensive work on classical validation techniques, such as internal and external validation, less attention has been given to validating and replicating a clustering result using a validation dataset. Such a dataset may be part of the original dataset, which is separated before analysis begins, or it could be an independently collected dataset. We present a systematic, structured review of the existing literature about this topic. For this purpose, we outline a formal framework that covers most existing approaches for validating clustering results on validation data. In particular, we review classical validation techniques such as internal and external validation, stability analysis, and visual validation, and show how they can be interpreted in terms of our framework. We define and formalize different types of validation of clustering results on a validation dataset, and give examples of how clustering studies from the applied literature that used a validation dataset can be seen as instances of our framework. This article is categorized under: Technologies > Structure Discovery and Clustering Algorithmic Development > Statistics Technologies > Machine Learning
Establishment of the invasive perennial herb Bunias orientalis L.: An experimental approach
No full textDietz H, Ullmann I, Steinlein T. Establishment of the invasive perennial herb Bunias orientalis L.: An experimental approach. Acta Oecologia. 1999;20(6):621-632
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Heidelberg, Universitätsbibliothek Heidelberg, Heid. Hs. 2800 III A - 114: Nachlass Karl Ullmann: Brief von Johann T. Hemsen an Carl Ullmann
No full textSonochemically enhanced Ullmann reactions
No full textDuring the Ullmann coupling reaction of 2-iodonitrobenzene in the presence of a four-fold excess of copper in DMF, the reaction rate increases 50-fold when ultrasound is introduced via a tapered microtip (diameter 1 16in). If a stud (diameter 1 2in) is used the rate increases 64-fold. Electron microscopy and particle size analysis show that sonication reduces the average particle size of copper by a factor of four. However, this alone is insufficient to explain the increase in reaction rate. Replacement of DMF by decalin or toluene was found to lead to substantial reductions in rate.</p
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Reflective writing analytics - Validating machine learning approaches
No full textReflective writing is an important educational practice to train reflective thinking. Currently, researchers must manually analyze these writings, limiting practice and research because the analysis is time and resource consuming. This presentation based on Ullmann (2019) shows results from an empirical study evaluating whether machine learning can be used to automate the manual analysis of reflection in writings. The study investigated eight categories that are often used in models to assess reflective writing, and the evaluation is based on 76 student essays (5,080 sentences) that are largely from third-and second-year health, business, and engineering students. To test the automated analysis of reflection in writings, machine learning models were built based on a random sample of 80% of the sentences. These models were thentested on the remaining 20% of the sentences. Overall, the standardized evaluation shows that five out of eight categories can be detected automatically with substantial or almost perfect reliability, while the other three categories can be detected with moderate reliability (Cohen's κ ranges between .53 and .85). The accuracies of the automated analysis were on average 10% lower than the accuracies of the manual analysis. These findings enable reflection analytics that is immediate and scalable.
Ullmann, T. D. (2019). Automated Analysis of Reflection in Writing: Validating Machine Learning Approaches. International Journal of Artificial Intelligence in Education, 29(2), 217–257. https://doi.org/10.1007/s40593-019-00174-
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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