2,869 research outputs found
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 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 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 m but the mantle could have been less
than m thick years ago. We find that the total gas production rate
could have been as large as 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 is
expected for its south polar region when Phaethon moves from to
mean anomaly near perihelion. Consequently, dust particles with radii
of can be blown away to form a dust tail. In addition, we find
that the large surface temperature variation of 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
An Ultra-Sensitive Electrochemical Enzyme Immunoassay for Thyroid Stimulating Hormone in Human Serum
A sensitive heterogeneous electrochemical enzyme immunoassay has been developed for thyroid stimulating hormone (TSH) by modifying a commercially available two-site immunoenzymometric assay. p-Aminophenyl phosphate (PAPP) was used as the substrate of alkaline phosphatase, and hydrolysed to p-aminophenol (PAP). The amount of PAP produced from the assay was proportional to the amount of TSH in the sample. Detection of PAP was done by oxidative amperometry in a flow injection system. The working electrode was a glassy carbon electrode whose potential was held at +325 mV (vs Ag/AgCl). The amperometric detection of PAP required only 1 μl of sample (the range of linearity: 50.0 fmol-100 pmol PAP, the limit of detection: 10.9 fmol PAP). Intra-assay precision over the assay range of linearity (0.02–60 mIU l−1 or 0.02–60 pIU TSH) showed a maximum RSD of 8.0%, and a low detection limit of 0.01 mIU l−1 or 0.01 pIU TSH. The study also indicates that this two-site electrochemical enzyme immunoassay correlates well with the Bio-Rad\u27s immunoradiometric assay currently used in our medical center (r = 0.992, slope = 1.53, n = 43) and a highly sensitive immunochemiluminometric assay in the Nichols Institute (r = 0.986, slope = 0.499, n = 23)
Comparing Sales Strategies Using the Markov Chain Relationship Model
In this paper, the author applied the concept of the Markov chain and divided sales procedures into several indexes and states; use the state index for connecting success in sales and customer relations into Pfeifer’s method, establish a mathematical model, and demonstrate its result. In order to increase profits and decrease the cost of sales for the company, we further classify customers and propose different sale strategies. Case study and analysis are provided to elaborate the approach and its contribution to sales and CRM (customer relationship management) strategy
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