A GIS-based Bayesian approach for analyzing spatial-temporal patterns of traffic crashes

This thesis develops a GIS-based Bayesian approach for area-wide traffic crash analysis. Five years of crash data from Houston, Texas, are analyzed using a geographic information system (GIS), and spatial-temporal patterns of relative crash risk are identified based on a hierarchical Bayesian approach. This Bayesian approach is used to filter the uncertainty in the data and identify and rank roadway segments with potentially high relative risks for crashes. The results provide a sound basis to take preventive actions to reduce the risks in these segments. To capture the real safety indications better, this thesis differentiates the risks in different directions of the roadways, disaggregates different road types, and utilizes GIS to analyze and visualize the spatial relative crash risks in 3-D views according to different temporal scales. Results demonstrate that the approach is effective in spatially smoothing the relative crash risks, eliminating the instability of estimates while maintaining real safety trends. The posterior risk maps show high-risk roadway segments in 3-D views, which is more reader friendly than the conventional 2-D views. The results are also useful for travelers to choose relatively safer routes

MiR-452 negatively regulates osteoblast differentiation in periodontal ligament stem cells by targeting the polycomb-group protein, BMI1

Purpose: To determine whether miR-452 regulates osteoblast differentiation (OD) in human periodontal ligament stem cells (hPDLSCs) by targeting polycomb-group protein BMI1. Methods: hPDLSCs were stimulated to differentiate upon treatment with mineralization liquid. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to measure mRNA and protein expressions, respectively. Alkaline phosphatase (ALP) activity and Alizarin red staining were used to determine the osteogenic differentiation (OD) of hPDLSCs. The bioinformatics software, Targetscan, was used to predict the potential target of miR-452, while luciferase assay, qRT- PCR, and western blot were employed to verify the target gene of miR-452, BMI1. Results: MiR-452 was downregulated during the OD of hPDLSCs, but miR-452 overexpression inhibited the OD of hPDLSCs. BMI1 was identified as a direct target gene of miR-452 during the OD of hPDLSCs, while miR-452 overexpression correlated inversely with BMI1 expression during OD of hPDLSCs. Conclusion: Overexpression of miR-452 suppresses the OD of hPDLSCs by targeting BMI1.This study may provide potential diagnostic and therapeutic basis for OD in hPDLSCs

Quasi-periodic Variations of Coronal Mass Ejections with Different Angular Widths

Coronal mass ejections (CMEs) are energetic expulsions of organized magnetic features from the Sun. The study of CME quasi-periodicity helps establish a possible relationship between CMEs, solar flares, and geomagnetic disturbances. We used the angular width of CMEs as a criterion for classifying the CMEs in the study. Based on 25 years of observational data, we systematically analyzed the quasi-periodic variations corresponding to the CME occurrence rate of different angular widths in the northern and southern hemispheres, using frequency and time-frequency analysis methods. There are various periods for CMEs of different angular widths: 9 months, 1.7 years, and 3.3-4.3 years. Compared with previous studies based on the occurrence rate of CMEs, we obtained the same periods of 1.2(+-0.01) months, 3.1(+-0.04) months, ~6.1(+-0.4) months, 1.2(+-0.1) years, and 2.4(+-0.4) years. We also found additional periods of all CMEs that appear only in one hemisphere or during a specific solar cycle. For example, 7.1(+-0.2) months and 4.1(+-0.2) years in the northern hemisphere, 1(+-0.004) months, 5.9(+-0.2) months, 1(+-0.1) years, 1.4(+-0.1) years, and 2.4(+-0.4) years in the southern hemisphere, 6.1(+-0.4) months in solar cycle 23 (SC23) and 6.1(+-0.4) months, 1.2(+-0.1) years, and 3.7(+-0.2) years in solar cycle 24 (SC24). The analysis shows that quasi-periodic variations of the CMEs are a link among oscillations in coronal magnetic activity, solar flare eruptions, and interplanetary space.Comment: 18 pages, 8 figures, 4 tables, Accepted by AP

Exploring Reionization-Era Quasars IV: Discovery of Six New z≳6.5z \gtrsim 6.5 Quasars with DES, VHS and unWISE Photometry

This is the fourth paper in a series of publications aiming at discovering quasars at the epoch of reionization. In this paper, we expand our search for $z\sim 7$ quasars to the footprint of the Dark Energy Survey (DES) Data Release One (DR1), covering $\sim 5000$ deg$^2$ of new area. We select $z\sim 7$ quasar candidates using deep optical, near-infrared (near-IR) and mid-IR photometric data from the DES DR1, the VISTA Hemisphere Survey (VHS), the VISTA Kilo-degree Infrared Galaxy (VIKING) survey, the UKIRT InfraRed Deep Sky Surveys -- Large Area Survey (ULAS) and the unblurred coadds from the Wide-field Infrared Survey Explore ($WISE$) images (unWISE). The inclusion of DES and unWISE photometry allows the search to reach $\sim$ 1 magnitude fainter, comparing to our $z \gtrsim 6.5$ quasar survey in the northern sky (Wang et al. 2018). We report the initial discovery and spectroscopic confirmation of six new luminous quasars at $z>6.4$, including an object at $z=7.02$, the fourth quasar yet known at $z>7$, from a small fraction of candidates observed thus far. Based on the recent measurement of $z \sim 6.7$ quasar luminosity function using the quasar sample from our survey in the northern sky, we estimate that there will be $\gtrsim$ 55 quasars at $z > 6.5$ at $M_{1450} < -24.5$ in the full DES footprint.Comment: 8 pages, 3 figures, submitted to A

Dietary Diversity and Its Contribution to the Magnitude of Anaemia among Pregnant Women:Evidence from Rural Areas of Western China

Background: Prenatal anaemia causes serious consequences for both mother and foetus, and dietary factors are suggested to be associated with anaemia. However, research in pregnant women living in rural areas is limited. We aim to assess the contribution of dietary diversity to the magnitude of prenatal anaemia in rural China and identify the interactions between dietary diversity and several sociodemographic and maternal characteristics in relation to anaemia. 'Methods: A multi-stage random cluster sampling method was used to select pregnant women in rural western China. The Woman’s Dietary Diversity Score was created to measure dietary diversity, which was recoded into terciles. Multinomial logistic regression models were used to assess the associations between dietary diversity score terciles and the magnitude of prenatal anaemia. Multiplicative interactions were tested by adding the product term of dietary diversity and several sociodemographic and maternal characteristics into the regression models. Results: Out of 969 participants, 54.3% were measured as anaemic, with 28.6% mildly anaemic and 25.7% moderately to severely anaemic. There was an absence of agreement between self-reported and measured anaemia status (κ = 0.28, 95% CI [0.22–0.34]). Participants in the highest dietary diversity score tercile had lower odds of being moderately to severely anaemic after adjusting for potential confounders (RRR = 0.65, 95% CI [0.44, 0.98]). In participants with moderate to severe anaemia, significant interactions were found between dietary diversity score terciles, age, and parity (p for interaction &lt; 0.05).Conclusions: The prevalence of prenatal anaemia in rural China remains high, and pregnant women living in these areas are insufficiently aware of their anaemia status. Improving dietary diversity is needed to manage prenatal anaemia in rural areas.</p

Fast Fourier transport analysis of surface structures fabricated by laser interference lithography

This paper presents an FFT (fast Fourier transform) analytical method for the study of surface structures fabricated by laser interference lithography (LIL). In the work, the FFT analytical method combined with Gaussian fitting is used to determine the periods and pattern distributions of surface structures from frequency spectra. For LIL, the processing parameters of incident and azimuth angles can be obtained corresponding to the period and pattern distribution. This work facilitates the detection of micro- and nano-structures, the analysis of pattern distribution in engineering, and the processing error analysis of LIL