Link Prediction via Matrix Completion

Inspired by practical importance of social networks, economic networks, biological networks and so on, studies on large and complex networks have attracted a surge of attentions in the recent years. Link prediction is a fundamental issue to understand the mechanisms by which new links are added to the networks. We introduce the method of robust principal component analysis (robust PCA) into link prediction, and estimate the missing entries of the adjacency matrix. On one hand, our algorithm is based on the sparsity and low rank property of the matrix, on the other hand, it also performs very well when the network is dense. This is because a relatively dense real network is also sparse in comparison to the complete graph. According to extensive experiments on real networks from disparate fields, when the target network is connected and sufficiently dense, whatever it is weighted or unweighted, our method is demonstrated to be very effective and with prediction accuracy being considerably improved comparing with many state-of-the-art algorithms

PROLONGING HEALTHY WORKING LIVES: THE ASSOCIATION OF JOB CHARACTERISTICS AND WORKFORCE EXIT WITH MENTAL AND COGNITIVE HEALTH IN MID- AND LATE LIFE

Objectives: Because work and health interacts with each other over the life course, job characteristics and health factors associated with labor force participation deserve great research attention to reduce disease burden and protect human capital. This dissertation aimed to examine the association between psychosocial job characteristics and cognitive decline (Chapter 2 and 3) and the association between insomnia symptoms and job exit (Chapter 4) among middle-aged and older adults. Methods: In Chapter 2, the association between cumulative work activities and cognitive changes was examined by multiple linear regression, using data from the Baltimore Epidemiologic Catchment Area (ECA) follow-up study and the Occupational Information Network. The interaction between workplace social interaction and physical demands was tested. In Chapter 3, the association between job strain at midlife and changes in cognitive function later in life was examined in a sample from the Baltimore ECA study using multiple linear regression models. In Chapter 4, the association between insomnia symptoms and subsequent job exit was examined in a nationally representative sample from the Health and Retirement Study using multinomial logistic regression models. Results: In Chapter 2, higher cumulative mental demands or social interaction were significantly associated with less decrease in cognitive function as assessed by the Mini-Mental State Examination (MMSE) and the Immediate and Delayed Word Recall tasks. Higher cumulative physical demands were associated with greater decline in the MMSE, and the association was moderated by social interaction. In Chapter 3, participants with high strain jobs had significantly greater cognitive decline as assessed by the MMSE and Immediate Word Recall task, compared to those with low strain jobs. Analyses of Chapter 4 found that having more insomnia symptoms was associated with increased odds of health-related job exit. There was no association between insomnia and job exit due to non-health reasons. Conclusions: The studies demonstrated potential intervention points in the workplace for promoting cognitive health later in life, and indicated the potential economic burden of insomnia that was attributable to reducing people’s working lives. Future research should investigate the role of workplace social support in improving the psychosocial work environment and prolonging workforce participation

Discovery of An Active Intermediate-Mass Black Hole Candidate in the Barred Bulgeless Galaxy NGC 3319

We report the discovery of an active intermediate-mass black hole (IMBH) candidate in the center of nearby barred bulgeless galaxy $\rm NGC~3319$. The point X-ray source revealed by archival Chandra and XMM-Newton observations is spatially coincident with the optical and UV galactic nuclei from Hubble Space Telescope observations. The spectral energy distribution derived from the unresolved X-ray and UV-optical flux is comparable with active galactic nuclei (AGNs) rather than ultra-luminous X-ray sources, although its bolometric luminosity is only $3.6\times10^{40}~\rm erg~s^{-1}$. Assuming an Eddington ratio range between 0.001 and 1, the black hole mass (M_\rm{BH}) will be located at $3\times10^2-3\times10^5~M_{\odot}$, placing it in the so-called IMBH regime and could be the one of the lowest reported so far. Estimates from other approaches (e.g., fundamental plane, X-ray variability) also suggest M_\rm{BH}\lesssim10^5~M_{\odot}.Similar to other BHs in bulgeless galaxies, the discovered IMBH resides in a nuclear star cluster with mass of $\sim6\times10^6~M_{\odot}$. The detection of such a low-mass BH offers us an ideal chance to study the formation and early growth of SMBH seeds, which may result from the bar-driven inflow in late-type galaxies with a prominent bar such as $\rm NGC~3319$.Comment: ApJ accepted, 2 tables, 6 figure

Oceanic accretionary belt in the West Qinling Orogen: Links between the Qinling and Qilian orogens, China

We present an integrated study of ophiolite complexes and island arc rocks from the Tianshui-Wushan Accretionary Belt, West Qinling Orogen. The West Qinling Orogen is important because it links the Qinling orogen to the east and the Qilian and Kunlun orogens to the west. The link between these orogens is commonly assumed, but has little study in detail. Zircon U-Pb analyses from ophiolitic rocks indicate the oceanic lithosphere formed in the Cambrian (530–500 Ma). Pillow lavas in the ophiolite complex show geochemical signatures of enriched MORB, suggesting they represent remnants of an oceanic plateau or seamounts. The island arc rocks include a volcanic complex with basalt-andesite and boninite of Late Ordovician age (460–440 Ma), and a serpentinized peridotite massif. The serpentinized peridotite most likely represent a highly refractory mantle residue with subsequent melt-rock interaction at ~450 Ma, suggesting that it formed in a forearc setting. The co-occurrence of ophiolite complexes and island arc rocks indicates that Tianshui-Wushan Accretionary Belt is an oceanic suture zone caused by oceanic subduction in the Early Paleozoic. The island arc rocks most likely represent the early product of an Izu-Bonin-Mariana (IBM)-type intra-oceanic arc, developed in response to a collision between an oceanic plateau and a continental margin. Our study permits a tectonic correlation between the Tianshui-Wushan Accretionary Belt in the West Qinling Orogen and the South Qilian Accretionary Belt in the Qilian Orogen, thereby establishing the continuity between the Early Paleozoic orogenic belts along the southern margin of the North China Craton

Expression and Localization of Stanniocalcin-1 in Bovine Osteoblasts

As a novel glycoprotein hormone, Stanniocalcin-1 (STC-1) was first identified in teleost species, and it is involved in the regulation of mineral homeostasis in bony fish and mammals. STC-1 can not only affect the mammals bone development, but also protect neurons from the damage of ischemia, and stimulate the angiogenic response. Although it is widely expressed in rodent skeletons, whether this hormone is expressed in the skeleton of ruminant animals, like bovines, is still unknown. Here, we investigated the expression of STC-1 in bovine osteoblasts by using immunocytochemical staining and RT-PCR. Our results show that the mRNA and protein of STC-1 are expressed in the bovine osteoblasts during later differentiation periods 10th day in vitro. The present data support the notion that STC-1 may play a role in the process of bovine bone development