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A new bootstrap-aggregating (bagging) ensemble learning algorithm is proposed based on classification certainty and semantic correlation to improve the classification accuracy of ensemble learning. First, two predetermined thresholds are introduced to construct the long and short-text sample subsets, and different deep learning methods are compared to construct the optimal base classifier groups for each sample subsets. Then, the random sampling method employed in traditional bagging classification algorithms is improved, and a threshold group based random sampling method is proposed to obtain long and short training sample subsets of each iteration. Finally, the sample classification certainty of the base classifiers for different categories is defined, and the semantic correlation information is integrated with the traditional weighted voting classifier ensemble method to avoid the loss of important information during the sampling process. The experimental results on multiple datasets demonstrate that the algorithm significantly improves text classification accuracy and outperforms typical deep learning algorithms. The proposed algorithm achieves the improvements of approximately 0.082, 0.061 and 0.019 on CNews dataset when the F1 measurement is used over the traditional ensemble learning algorithms such as random forest, M_ADA_A_SMV and CNN_SVM_LR. Moreover, it achieves the best F1 values of 0.995, 0.985, and 0.989 on the datasets of Spam, CNews, and SogouCS datasets, respectively, when compared with the ensemble learning algorithms using different base classifiers. [ABSTRACT FROM AUTHOR]

Feature selection, which can reduce the dimensionality of vector space without sacrificing the performance of the classifier, is commonly used in spam filtering. As many classifiers cannot deal with the features with large dimensions, the noisy, irrelevant and redundant data should be removed from the feature spaces. In this paper, a two-step based hybrid feature selection method, called TFSM, is proposed. Firstly, we select the most discriminative features by an existing document frequency based feature selection method (called ODFFS). Secondly, we select the remaining features by combining the ODFFS and a newly proposed term frequency based feature selection method (called NTFFS). Moreover, we propose a new optimizing meta-heuristic method, called GOPSO, to improve the convergence rate of standard particle swarm optimization. In the experiments, Support Vector Machine (SVM) and Naïve Bayesian (NB) classifiers are used on four corpuses: PU2, PU3, Enron-spam and Trec2007. The experimental results show that, TFSM is significantly superior to information gain, comprehensively measure feature selection, t-test based feature selection, term frequency based information gain and improved term frequency inverse document frequency method on four corpuses when SVM and NB are applied respectively. [ABSTRACT FROM AUTHOR]

To extend the current understanding of the mercury-mediated cytotoxic effect, five neural cell lines established from different animal species were comparatively analyzed using three different endpoint bioassays: thiazolyl blue tetrazolium bromide, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay (MTT), neutral red uptake assay (NRU), and Coomassie blue assay (CB). Following a 24-hr exposure to selected concentrations of mercury chloride (HgCl2) and methylmercury (II) chloride (MeHgCl), the cytotoxic effect on test cells was characterized by comparing their 50% inhibition concentration (IC50) values. Experimental results indicated that both these forms of mercury were toxic to all the neural cells, but at very different degrees. The IC50 values of MeHgCl among these cell lines ranged from 1.15±0.22 to 10.31±0.70μmol/L while the IC50 values for HgCl2 were much higher, ranging from 6.44±0.36 to 160.97±19.63μmol/L, indicating the more toxic nature of MeHgCl. The IC50 ratio between HgCl2 and MeHgCl ranged from 1.75 to 96.0, which confirms that organic mercury is much more toxic to these neural cells than inorganic mercury. Among these cell lines, HGST-BR and TriG44 derived from marine sea turtles showed a significantly high tolerance to HgCl2 as compared to the three mammalian neural cells. Among these neural cells, SK-N-SH represented the most sensitive cells to both chemical forms of mercury., (Copyright © 2015. Published by Elsevier B.V.)