Using Class Based Document Frequency to Select Features in Text Classification

Document Frequency(DF)is reported to be a simple yet quite effective measure for feature selection in text classification,which is a key step in processing big textual data collections.The calculation is based on how many documents in a collection contain a feature,which can be a word,a phrase,a n-gram,or a specially derived attribute.It is an unsupervised and class independent metric.Features of the same DF value may have quite different distribution over different categories,and thus have different discriminative power over categories.For example,in a binary classification problem,if feature A only appears in one category,but feature B,which has the same DF value as feature A,is evenly distributed in both categories.Then,feature A is obviously more effective than feature B for classification.To overcome this weakness of the original document frequency feature selection metric,we,therefore,propose a class based document frequency strategy to further refine the original DF to some extent.Extensive experiments on three text classification datasets demonstrate the effectiveness of the proposed measures.Using Class Based Document Frequency to Select

Rb Protein is Essential to the Senescence-Associated Heterochromatic Foci Formation Induced by HMGA2 in Primary WI38 Cells

Cellular senescence is an irreversible form of cell cycle arrest that provides a barrier to neoplastic transformation. The integrity of the Rb （Retinoblastoma） pathway is necessary for the formation of the senescence-associated heterochromatin foci （SAHF） that offers a molecular basis for the stability of the senescent state. Surprisingly, although high mobility group A2 protein （HMGA2） can promote tumorigenesis and inhibit Rb function in tumor cells, high-level expression of HMGA2 is sufficient to induce SAHF formation in primary cells. It therefore becomes significant to determine whether Rb protein is necessary in HMGA2-induced SAHF formation. In this study, we established the cellular senescence and SAHF assembly W138 cell model by ectopic expression of HMGA2, in which typical senescent markers were seen, including notable upregulation of p53, p21 and p16, and elevated SA-[3-galactosidase staining together with downregulation of E2F target genes. We then showed that the Rb pathway inhibitor E7 protein was able to partly abolish the ability of SAHF formation alter HMGA2 expression in W138 cells, indicating that Rb is a crucial factor for HMGA2-induced SAHF formation. However. Rb depletion did not completely rescue the cell growth arrest induced by HMGA2, suggesting that Rb is not an exclusive pathway for HMGA2-induced senescence in W138 cells.

Photocatalytic degradation of mixed pollutants in aqueous wastewater using mesoporous 2D/2D TiO_(2)(B)-BiOBr heterojunction

There are multiple contaminants in practical wastewater;and the photodegradation of mixed pollutants is a challenge in the field of photocatalysis.Herein,we design a mesoporous 2D/2D TiO_(2)(B)-BiOBr heterojunction photocatalyst for the photodegradation of mixed pollutants.Such a coupling structure results in an enhancement in the disconnection of photoexcited carriers,and the increase of absorption and reaction sites.The 2D/2D TiO_(2)(B)-BiOBr demonstrates outstanding photocatalytic activity for photodegrading rhodamine B(RhB),methyl orange(MO),tetracycline hydrochloride(TCH),and bisphenol A(BPA)simultaneously under visible light,which is 4.7,1.4,23 and 16.4 times as high as that of original BiOBr,respectively.Our work represents a possible solution to devise promising and efficient photocatalysts for the treatment of practical wastewater in the near future.