Bright 22 μ\mum Excess Candidates from WISE All-Sky Catalog and Hipparcos Main Catalog

In this paper we present a catalog which includes 141 bright candidates ($\leq10.27$ mag, V band) showing the infrared (IR) excess at 22 $\mu$m. Of which, 38 stars are known IR excess stars or disk, 23 stars are double or multiple stars and 4 are Be stars. While the remaining more than 70 stars are identified as the 22 $\mu$m excess candidates in our work. The criterion of selecting candidates is $K_s-[22]_{\mu m}$. All these candidates are selected from \emph{WISE} All-sky data cross-correlated with \emph{Hipparcos} Main Catalog and the likelihood-ratio technique is employed. Considering the effect of background, we introduce the \emph{IRAS} 100 $\mu$m level to exclude the high background. We also estimated the coincidence probability of these sources. In addition, we presented the optical to mid-infrared SEDs and optical images of all the candidates, and gave the observed optical spectra of 6 stars with NAOC's 2.16-m telescope. To measure for the dust amount around each star, the fractional luminosity is also provided. We also test whether our method of selecting IR excess stars can be used to search for extra-solar planets, we cross-matched our catalog with known IR-excess stars having planets but none is matched. Finally, we give the fraction of stars showing IR-excess for different spectral type of main-sequence stars.Comment: 45 pages, 16 figures, 4 tables. Accepted for publication in ApJ

Stretching self-interacting, partially directed, flexible and semi-flexible polymers by an external force

We study the model of a partially directed flexible or semi-flexible homopolymer on a square lattice, subject to an externally applied force, in a direction either parallel to, or perpendicular to the preferred direction. The polymer is self-interacting and can therefore undergo a collapse transition. We show that this model can be solved and we obtain the force-temperature phase diagrams which, for the case of flexible polymers, agree with that of Brak et al obtained using a different method. At sufficiently low temperatures, the polymer conformation changes from compact to coil state as the force is increased beyond a critical value. This transition is second or first order for the completely flexible or semi-flexible polymer, respectively.Comment: 17 pages, 8 figure

A Study of Learning Pressure, Learning Attitudes, and Achievement among Macau Undergraduates

The purpose of this study was to examine the relationships among learning pressure, learning attitudes, and academic achievement of university students; specifically, Chinese undergraduates from three universities in Macau. Convenience sampling was used in the current study, and a total of 135 questionnaires were retrieved. We found a significant, moderate, and positive correlation between learning pressure and learning attitudes. We also found a negative correlation between learning pressure and academic achievement. The last correlation we found, between learning attitude and academic achievement, was positive and significant. When we regressed learning pressure and learning attitudes on academic achievement, the results showed that both variables were effective predictors of achievement

Association between treatment with apixaban, dabigatran, rivaroxaban, or warfarin and the risk of osteoporotic fractures among patients with atrial fibrillation: A population-based cohort study

Background: It is unclear whether anticoagulant type is associated with the risk for osteoporotic fracture, a deleterious complication of anticoagulants among patients with atrial fibrillation (AF). Objective: To compare the risk for osteoporotic fracture between anticoagulants. Design: Population-based cohort study. Setting: Territory-wide electronic health record database of the Hong Kong Hospital Authority. Participants: Patients newly diagnosed with AF between 2010 and 2017 who received a new prescription for warfarin or a direct oral anticoagulant (DOAC) (apixaban, dabigatran, or rivaroxaban). Follow-up ended on 31 December 2018. Measurements: Osteoporotic hip and vertebral fractures in anticoagulant users were compared using propensity score–weighted cumulative incidence differences (CIDs). Results: There were 23 515 patients identified (3241 apixaban users, 6867 dabigatran users, 3866 rivaroxaban users, and 9541 warfarin users). Overall mean age was 74.4 years (SD, 10.8), ranging from 73.1 years (warfarin) to 77.9 years (apixaban). Over a median follow-up of 423 days, 401 fractures were identified (crude event number [weighted rate per 100 patient-years]: apixaban, 53 [0.82]; dabigatran, 95 [0.76]; rivaroxaban, 57 [0.67]; and warfarin, 196 [1.11]). After 24-month follow-up, DOAC use was associated with a lower risk for fracture than warfarin use (apixaban CID, −0.88% [95% CI, −1.66% to −0.21%]; dabigatran CID, −0.81% [CI, −1.34% to −0.23%]; and rivaroxaban CID, −1.13% [CI, −1.67% to −0.53%]). No differences were seen in all head-to-head comparisons between DOACs at 24 months (apixaban vs. dabigatran CID, −0.06% [CI, −0.69% to 0.49%]; rivaroxaban vs. dabigatran CID, −0.32% [CI, −0.84% to 0.18%]; and rivaroxaban vs. apixaban CID, −0.25% [CI, −0.86% to 0.40%]). Limitation: Residual confounding is possible. Conclusion: Among patients with AF, DOAC use may result in a lower risk for osteoporotic fracture compared with warfarin use. Fracture risk does not seem to be altered by the choice of DOAC. These findings may help inform the benefit–risk assessment when choosing between anticoagulants. Primary Funding Source: The University of Hong Kong and University College London Strategic Partnership Fund