What mechanisms dominate the activity of Geminid Parent (3200) Phaethon?

A long-term sublimation model to explain how Phaethon could provide the Geminid stream is proposed. We find that it would take $\sim6$ Myr or more for Phaethon to lose all of its internal ice (if ever there was) in its present orbit. Thus, if the asteroid moved from the region of a 5:2 or 8:3 mean motion resonance with Jupiter to its present orbit less than $1$ Myr ago, it may have retained much of its primordial ice. The dust mantle on the sublimating body should have a thickness of at least $15$ m but the mantle could have been less than $1$ m thick $1000$ years ago. We find that the total gas production rate could have been as large as $10^{27}\rm~s^{-1}$ then, and the gas flow could have been capable of lifting dust particles of up to a few centimeters in size. Therefore, gas production during the past millennium could have been sufficient to blow away enough dust particles to explain the entire Geminid stream. For present-day Phaethon, the gas production is comparatively weak. But strong transient gas release with a rate of $\sim4.5\times10^{19}\rm~m^{-2}s^{-1}$ is expected for its south polar region when Phaethon moves from $0^\circ$ to $2^\circ$ mean anomaly near perihelion. Consequently, dust particles with radii of $<\sim260~\mu m$ can be blown away to form a dust tail. In addition, we find that the large surface temperature variation of $>600$ K near perihelion can generate sufficiently large thermal stress to cause fracture of rocks or boulders and provide an efficient mechanism to produce dust particles on the surface. The time scale for this process should be several times longer than the seasonal thermal cycle, thereby dominating the cycle of appearance of the dust tail.Comment: 10 pages, 5 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Measuring the Interdependence of Banks in Hong Kong

This paper assesses systemic linkages among banks in Hong Kong using the risk measure "CoVaR" derived from quantile regression. The CoVaR measure captures the co-movements of banks¡¯ default risk by taking into account their nonlinear relationship when the banks are in distress. Based on equity price information, our estimation results show that the default risks of the banks were interdependent during the recent crisis. Although local banks are generally smaller, their systemic importance is found to be similar to their international and Mainland counterparts, which may be due to a higher degree of commonality in the risk profile of local banks. Regarding the impact of external shocks on the banks, international banks are more likely to be affected by the equity price fall in the US market, while local banks are relatively more responsive to funding liquidity risk.Value-at-Risk, Systemic Risk, Risk Spillovers, Quantile Regression

Associations between child maltreatment and adolescents’ health-related quality of life and emotional and social problems in low-income families, and the moderating role of social support

This study aimed to examine the associations between different types of child maltreatment and health-related quality of life (HRQoL) and emotional and social problems in adolescents, and to examine the moderating effect of social support on those associations. A cross-sectional survey was conducted between January and June 2016 in Hong Kong. The sample comprised 351 parent and adolescent dyads from low-income families. The parents reported on child maltreatment (physical abuse, psychological aggression, and neglect), and the adolescents reported on their HRQoL, emotional problems, and social problems. The adolescents’ perceived social support was included as a potential moderator. Results of the study show that child physical abuse was strongly associated with emotional and social problems (B = 0.91-1.45, p &lt; .05). Lower overall HRQoL was associated with psychological aggression (B = −3.96, p &lt; .05) and neglect (B = −4.14, p &lt; .05). Physical functioning was affected by psychological aggression (B = −3.16, p &lt; .05), and emotional functioning was affected by neglect (B = −4.82, p &lt; .05). Social functioning was impacted by all three types of maltreatment (B = −9.16 to −5.26, p &lt; .05). This study extends previous literature by showing the varying effects of different types of child maltreatment on children’s health in the context of low-income families. The findings of this study also support that peer social support may buffer the effects of child physical abuse on adolescents’ emotional and social problems