62 research outputs found

    NASS

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    Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 49-50).The selection of targeted survey questions and the design of survey questionnaires are instrumental in the social networks research. With the accelerating growth of theory and experimental knowledge in the area of social network analysis, there is a need for a centralized questionnaire database system for the collection and appropriate utilization of these questions and feedbacks used for social networks research. Our project aims to provide a content-driven back-end database system and an online user interface to assist researchers to make intelligent selection of survey questions and design of questionnaires based on current area-specific knowledge within social network analysis.by Aaron Du.M.Eng

    An Hα\alpha Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40%\% ALFALFA \ion{H}{1} Survey

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    We present the observed Hα\alpha flux and derived star formation rates (SFRs) for a fall sample of low-surface-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40%\% ALFALFA {\ion{H}{1}} survey - SDSS DR7 photometric data, and all the HαH\alpha images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and HαH\alpha flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}-rich, their SFRs derived from the extinction and filter-transmission-corrected HαH\alpha flux, are less than 1M_{\sun}yr1yr^{-1}. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star-forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories

    An Hα\alpha Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40%\% ALFALFA \ion{H}{1} Survey

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    We present the observed Hα\alpha flux and derived star formation rates (SFRs) for a fall sample of low-surface-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40%\% ALFALFA {\ion{H}{1}} survey - SDSS DR7 photometric data, and all the HαH\alpha images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and HαH\alpha flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}-rich, their SFRs derived from the extinction and filter-transmission-corrected HαH\alpha flux, are less than 1M_{\sun}yr1yr^{-1}. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star-forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories

    A Trilayer Structure with Surface Binary Microsphere Array for Radiative Cooling and Heating Regulation

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    Passive daytime radiative cooling is of tremendous interest but would overcool during cold nights or winter days, exacerbating the heating cost, especially in high-latitude areas. Integrating the heating and cooling in one photothermal system can avoid cooling penalties and potential barriers for wide practical scenarios. Herein, we demonstrate a trilayer structure with visible and infrared spectral engineering for all-season radiative cooling and heating. The cooling mode with a solar reflectivity of 0.95 and a mid-infrared emissivity of 0.98 endows a comparable daytime subambient cooling of 9.8 °C with a theoretically net cooling power of 76.6 W/m2. Meanwhile, the heating mode with a solar absorptivity of 0.88 and a mid-infrared emissivity of 0.28 yields a daytime above-ambient heating of 16.3 °C with a theoretical net heating power of 667.8 W/m2. Promisingly, the surface binary microsphere array further enhances the mid-infrared emissivity, superhydrophobicity, and environmental durability, making the trilayer structure a viable pathway for thermal management with great potential in electricity savings and CO2 emission reduction. This work offers new possibilities for designing next-generation radiative cooling materials, greatly widening the scope of use

    An ethylene biosynthesis enzyme controls quantitative variation in maize ear length and kernel yield.

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    Maize ear size and kernel number differ among lines, however, little is known about the molecular basis of ear length and its impact on kernel number. Here, we characterize a quantitative trait locus, qEL7, to identify a maize gene controlling ear length, flower number and fertility. qEL7 encodes 1-aminocyclopropane-1- carboxylate oxidase2 (ACO2), a gene that functions in the final step of ethylene biosynthesis and is expressed in specific domains in developing inflorescences. Confirmation of qEL7 by gene editing of ZmACO2 leads to a reduction in ethylene production in developing ears, and promotes meristem and flower development, resulting in a ~13.4% increase in grain yield per ear in hybrids lines. Our findings suggest that ethylene serves as a key signal in inflorescence development, affecting spikelet number, floral fertility, ear length and kernel number, and also provide a tool to improve grain productivity by optimizing ethylene levels in maize or in other cereals

    Natural Coevolution of Tumor and Immunoenvironment in Glioblastoma.

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    Isocitrate dehydrogenase (IDH) wild-type glioblastoma (GBM) has a dismal prognosis. A better understanding of tumor evolution holds the key to developing more effective treatment. Here we study GBM\u27s natural evolutionary trajectory by using rare multifocal samples. We sequenced 61,062 single cells from eight multifocal IDH wild-type primary GBMs and defined a natural evolution signature (NES) of the tumor. We show that the NES significantly associates with the activation of transcription factors that regulate brain development, including MYBL2 and FOSL2. Hypoxia is involved in inducing NES transition potentially via activation of the HIF1A-FOSL2 axis. High-NES tumor cells could recruit and polarize bone marrow-derived macrophages through activation of the FOSL2-ANXA1-FPR1/3 axis. These polarized macrophages can efficiently suppress T-cell activity and accelerate NES transition in tumor cells. Moreover, the polarized macrophages could upregulate CCL2 to induce tumor cell migration. SIGNIFICANCE: GBM progression could be induced by hypoxia via the HIF1A-FOSL2 axis. Tumor-derived ANXA1 is associated with recruitment and polarization of bone marrow-derived macrophages to suppress the immunoenvironment. The polarized macrophages promote tumor cell NES transition and migration. This article is highlighted in the In This Issue feature, p. 2711

    Separase Phosphosite Mutation Leads to Genome Instability and Primordial Germ Cell Depletion during Oogenesis

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    To ensure equal chromosome segregation and the stability of the genome during cell division, Separase is strictly regulated primarily by Securin binding and inhibitory phosphorylation. By generating a mouse model that contained a mutation to the inhibitory phosphosite of Separase, we demonstrated that mice of both sexes are infertile. We showed that Separase deregulation leads to chromosome mis-segregation, genome instability, and eventually apoptosis of primordial germ cells (PGCs) during embryonic oogenesis. Although the PGCs of mutant male mice were completely depleted, a population of PGCs from mutant females survived Separase deregulation. The surviving PGCs completed oogenesis but produced deficient initial follicles. These results indicate a sexual dimorphism effect on PGCs from Separase deregulation, which may be correlated with a gender-specific discrepancy of Securin. Our results reveal that Separase phospho-regulation is critical for genome stability in oogenesis. Furthermore, we provided the first evidence of a pre-zygotic mitotic chromosome segregation error resulting from Separase deregulation, whose sex-specific differences may be a reason for the sexual dimorphism of aneuploidy in gametogenesis

    The role of miRNAs in colorectal cancer progression and chemoradiotherapy

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    Colorectal cancer (CRC) is known as the third most common cancer as well as the fourth most deadly cancer worldwide. CRC accounts for approximately 10 % of all new cancer cases globally, remaining the second most frequent cause of cancer-related deaths. MicroRNAs (miRNAs) are a class of small noncoding RNAs that can affect a variety of cellular and molecular targets. Depending on the cell environment in which the information is expressed, miRNAs can serve as a CRC suppressor or promoter and play essential roles in several biological processes. In this review, we summarized the relationship between miRNAs and proliferation, metastasis, angiogenesis, autophagy, apoptosis, and the chemoradiotherapy of CRC, revealing that relevant miRNAs could serve as potential targets for CRC therapy
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