Likelihood-Based Estimation of a Proportional-Hazard, Competing- Risk Model with Grouped Duration Data

This short paper demonstrates two important results related to the estimation of competing-risk models under the proportional-hazards assumption with grouped duration data. First I show that the model with non-parametric baseline hazards is unidentifiable with only grouped duration data. Therefore one has to make functional form assumption for any meaningful inference. Secondly I demonstrate that under some parametric assumption such as piecewise constant baseline hazards, the sample likelihood function has explicit analytical form. Therefore there is no need for approximation. The approximation formula adopted by Deng et al (2000) and religiously followed by others is only a quasi likelihood function.competing risk models, duration models, default risk

Strong CMB Constraint On P-Wave Annihilating Dark Matter

We consider a dark sector consisting of dark matter that is a Dirac fermion and a scalar mediator. This model has been extensively studied in the past. If the scalar couples to the dark matter in a parity conserving manner then dark matter annihilation to two mediators is dominated by the P-wave channel and hence is suppressed at very low momentum. The indirect detection constraint from the anisotropy of the Cosmic Microwave Background is usually thought to be absent in the model because of this suppression. In this letter we show that dark matter annihilation to bound states occurs through the S-wave and hence there is a constraint on the parameter space of the model from the Cosmic Microwave Background.Comment: 5 pages, 3 figure

Is Trading Imbalance a Better Explanatory Factor in the Volatility Process? Intraday and Daily Evidence from E-mini S&P 500 Index Futures and Information-Based Hypotheses

This paper examines trading imbalance as well as traditional trading variables in the volume-volatility relation in futures market. Unlike the majority of studies which utilize daily data, our empirical investigation compares an array of intraday frequencies (from five minutes to one hour) with daily interval. The primary analysis is conducted through a series of GARCH tests and the findings are then confirmed by a set of two-stage least square regressions. Since this paper adopts an information-based framework to explain the volume-volatility relation, unexpected trading variables are used to proxy for new market information. Results indicate that different trading imbalance metrics are useful and more significant than traditional trading variables in explaining the volatility relation for all daily and intraday intervals. Empirical findings support the existence of asymmetric information hypothesis at all intervals. On the other hand, mixture of distributions and difference in opinion hypotheses are validated in only some intraday intervals. Moreover, not only are the conclusions from daily observations not the same as the ones from intraday counterparts but also there are differences in the results between longer and shorter intraday intervals.Futures markets, price volatility, trading imbalance, number and volume of trades, asymmetric information, difference in opinion, mixture of distributions, GARCH and persistence effect.

Prolonged environmental persistence requires efficient disinfection procedures to control Devriesea agamarum associated disease in lizards

Aims: Devriesea agamarum infection causes chronic proliferative dermatitis, especially in desert dwelling lizards. The present study was concerned with evaluating persistency of D. agamarum in the environment and the evaluation of the efficacy of various disinfection procedures. Methods and Results: First, the survival of D. agamarum was assessed both in dermal crusts obtained from clinically and naturally infected lizards, and during periods of prolonged nutrient starvation on dry surface, in moist sand and in distilled water. Secondly, a modified European Suspension Test was performed to determine the efficacy of eight procedures for the disinfection of equipment, environmental surfaces and the topical treatment of D. agamarum-associated dermal lesions. The bacterium proved to persist and remain viable for up to 57 days in dermal crusts and for more than 5 months in moist sand and distilled water. In contrast, survival on dry surfaces was limited. The results of the described dilution-neutralization method demonstrated that most of the tested disinfection procedures were sufficient in achieving a 5-decimal logarithmic reduction in the number of D. agamarum colony-forming units. The use of relatively low concentrations of hydrogen peroxide and a boric and peracetic acid solution on the other hand resulted in insufficient reduction in viable counts. Conclusions: Devriesea agamarum can persist for long periods of time in the environment, especially under moist conditions, making the use of suitable disinfection procedures necessary. Significance and Impact of the Study: This study demonstrates the need for a dry environment for most desert lizards and the use of effective disinfection procedures next to antimicrobial treatment to eliminate D. agamarum-associated disease from captive saurian collections

The complementary relationship between the Internet and traditional mass media: The case of online news and information

Background. The question whether old media are driven out of existence by new media has been a long concern in academic and industrial research but has received no definitive answer. Aim. This paper goes beyond most previous studies of Internet impact on traditional media, which have placed their relationship within a competition-based framework, to specifically investigate the complementary effect of online news and information usage on traditional sources. Method. Secondary data analysis of a national survey of 4270 Australians conducted in late 2003, employing hypothesis testing for the mean, partial correlations, and a linear regression analysis. Results. Online news and information usage at different usage levels is positively as so dated with the use of traditional news and information sources, especially those that are more information-intensive. Those who relied on the Internet the most for news and information still used traditional sources substantially. Conclusion. The findings suggest that even if a displacement effect takes place, there will be no replacement (absolute displacement): traditional media will still exist to complement the Internet in serving human beings' news and information needs