Tongji University

About: Tongji University is a education organization based out in Shanghai, China. It is known for research contribution in the topics: Population & Adsorption. The organization has 76116 authors who have published 81176 publications receiving 1248911 citations. The organization is also known as: Tongji & Tóngjì Dàxué.

Data mining for the Internet of Things: literature review and challenges

Abstract: The massive data generated by the Internet of Things (IoT) are considered of high business value, and data mining algorithms can be applied to IoT to extract hidden information from data. In this paper, we give a systematic way to review data mining in knowledge view, technique view, and application view, including classification, clustering, association analysis, time series analysis and outlier analysis. And the latest application cases are also surveyed. As more and more devices connected to IoT, large volume of data should be analyzed, the latest algorithms should be modified to apply to big data. We reviewed these algorithms and discussed challenges and open research issues. At last a suggested big data mining system is proposed.

Composite acoustic medium with simultaneously negative density and modulus.

Abstract: We fabricated an acoustic composite structure consisting of a periodic array of interspaced membranes and side holes. Experimental data on the transmission, effective density, and phase velocity are presented. The system exhibits two critical frequencies, omega{SH} and omega{c}. Our metamaterial is double negative and transparent for frequencies lower than omega{SH}. For the frequencies omega{SH}

Distinct features of H3K4me3 and H3K27me3 chromatin domains in pre-implantation embryos

Abstract: Three papers in this issue of Nature use highly sensitive ChIP–seq assays to describe the dynamic patterns of histone modifications during early mouse embryogenesis, showing that oocytes have a distinctive epigenome and providing insights into how the maternal gene expression program transitions to the zygotic program. Genomic analysis of chromatin states in early embryos has been technically difficult, owing to the limited number of cells available for analysis. Three papers in this issue of Nature use highly sensitive ChIP–seq assays to describe the dynamic patterns of histone modifications during early mouse embryogenesis. Arne Klungland and colleagues find that the oocyte genome is associated with broad non-canonical domains of histone H3K4me3 which seem to function in preventing deposition of DNA methylation. Wei Xie and colleagues find that the oocyte genome is associated with broad non-canonical domains of histone H3K4me3 which overlap with domains of low DNA methylation and seem to contribute to gene silencing. Shaorong Gao and colleagues map histone H3K4me3 and H3K27me3 modifications in pre-implantation embryos and focus on the re-establishment of histone modifications during zygotic genome activation. They find that the breadth of H3K4me3 domains is highly dynamic and that H3K4me3 re-establishes rapidly on promoter regions whereas H3K27me3 is mostly absent from these regions. Taken together—and with previously published work—these studies show that the oocyte has a distinctive epigenome and provide insights into how the maternal gene expression program transitions to the zygotic program. Histone modifications have critical roles in regulating the expression of developmental genes during embryo development in mammals1,2. However, genome-wide analyses of histone modifications in pre-implantation embryos have been impeded by the scarcity of the required materials. Here, by using a small-scale chromatin immunoprecipitation followed by sequencing (ChIP–seq) method3, we map the genome-wide profiles of histone H3 lysine 4 trimethylation (H3K4me3) and histone H3 lysine 27 trimethylation (H3K27me3), which are associated with gene activation and repression4,5, respectively, in mouse pre-implantation embryos. We find that the re-establishment of H3K4me3, especially on promoter regions, occurs much more rapidly than that of H3K27me3 following fertilization, which is consistent with the major wave of zygotic genome activation at the two-cell stage. Furthermore, H3K4me3 and H3K27me3 possess distinct features of sequence preference and dynamics in pre-implantation embryos. Although H3K4me3 modifications occur consistently at transcription start sites, the breadth of the H3K4me3 domain is a highly dynamic feature. Notably, the broad H3K4me3 domain (wider than 5 kb) is associated with higher transcription activity and cell identity not only in pre-implantation development but also in the process of deriving embryonic stem cells from the inner cell mass and trophoblast stem cells from the trophectoderm. Compared to embryonic stem cells, we found that the bivalency (that is, co-occurrence of H3K4me3 and H3K27me3) in early embryos is relatively infrequent and unstable. Taken together, our results provide a genome-wide map of H3K4me3 and H3K27me3 modifications in pre-implantation embryos, facilitating further exploration of the mechanism for epigenetic regulation in early embryos.

Pressure-sensitive properties and microstructure of carbon nanotube reinforced cement composites

Abstract: Carbon nanotubes (CNTs) treated by using a mixed solution of H2SO4 and HNO3 were uniformly dispersed into cement paste by means of ultrasonic energy. Electrical resistivity and pressure-sensitive properties under cyclic compressive loading of this composite were analyzed and compared to that of untreated-CNT reinforced cement paste. Results show that the addition of treated or untreated CNTs to cement paste leads to a notable decrease in volume electrical resistivity and a distinct enhancement in compressive sensitivity. The microstructures of these cement composites were analyzed by using scanning electron microscope. The microscopic observation reveals that both treated and untreated CNTs were dispersed homogenously in the cement matrix. For untreated CNT-reinforced cement composites, the CNTs with glossy surface were zigzag and cling to cement matrix; the bridging of cracks and a well three-dimensional meshwork were also observed. For treated-CNT reinforced cement composites, the surface of CNTs was covered by C–S–H, which leads to a higher mechanical strength. The contact points of the treated-CNTs in composites were much fewer than that of the untreated-CNTs in cement matrix composites, which leads to a higher compressive sensitive properties and a lower electrical conductivity.