The thermal evolution of nuclear matter at zero temperature and definite baryon number density in chiral perturbation theory

The thermal properties of cold dense nuclear matter are investigated with chiral perturbation theory. The evolution curves for the baryon number density, baryon number susceptibility, pressure and the equation of state are obtained. The chiral condensate is calculated and our result shows that when the baryon chemical potential goes beyond $1150 \mathrm{MeV}$, the absolute value of the quark condensate decreases rapidly, which indicates a tendency of chiral restoration.Comment: 17 pages, 9 figures, revtex

Characteristics of profiles of gamma-ray burst pulses associated with the Doppler effect of fireballs

In this paper, we derive in a much detail the formula of count rates, in terms of the integral of time, of gamma-ray bursts in the framework of fireballs, where the Doppler effect of the expanding fireball surface is the key factor to be concerned. Effects arising from the limit of the time delay due to the limited regions of the emitting areas in the fireball surface and other factors are investigated. Our analysis shows that the formula of the count rate of fireballs can be expressed as a function of $\tau$ which is the observation time scale relative to the dynamical time scale of the fireball. The profile of light curves of fireballs depends only on the relative time scale, entirely independent of the real time scale and the real size of the objects. It displays in detail how a cutoff tail, or a turn over, feature (called a cutoff tail problem) in the decay phase of a light curve can be formed. This feature is a consequence of a hot spot in the fireball surface, moving towards the observer, and was observed in a few cases previously. By performing fits to the count rate light curves of six sample sources, we show how to obtain some physical parameters from the observed profile of the count rate of GRBs. In addition, the analysis reveals that the Doppler effect of fireballs could lead to a power law relationship between the $FWHM$ of pulses and energy, which were observed previously by many authors.Comment: 38 pages, 10 figures; accepted for publication in ApJ (10 December 2004, v617

UNDERSTANDING ONLINE GROUP PURCHASE DECISION MAKING: A MEANS-END CHAIN APPROACH

Given the enormous growth and significant impacts of group buying on Internet business marketplaces, this study aims to understand consumer decision making process in an online group buying context from a Means-end Chain (MEC) theory perspective. The laddering interview technique was used to interview 58 online group buying users and to capture their reasons behind the online shopping behaviour, with grounded theory used to determine categories. The study found 35 factors in relation to consumer decision making process, which were classified into attributes, consequences, and values. The hierarchical relationships among 35 factors were developed, in which consumer decision making paths were identified. This study has the potential to make significant contributions to both IS research and e-business regarding consumer online group buying decision making process by identifying not only the major consequences/ benefits consumers emphasising, but also the concrete attributes which directly correspond with these benefits as well as the goals/values consumers aim to achieve

Port Investments on Coastal and Marine Disasters Prevention: An Economic and Policy Investigation

Located along shorelines, seaports are highly vulnerable to coastal and marine natural disasters. Damage caused by disasters can be prevented or alleviated if sufficient investments are made in a timely manner. However, despite a wide range of investment options and well-developed engineering expertise, port investment on disaster prevention remains a challenging task involving great complexities. This paper develops an integrated economic model for the analysis of disaster-prevention investments at a “landlord” port. It simultaneously considers the uncertainty of disaster occurrence and associated return of prevention investments, the information accumulation and related investment timing, and the spillovers (externalities) of investment among stakeholders. Our analysis shows that the timing of port investments depends on the probability of disasters. Immediate investment is optimal for disasters with very high probability, while investment should be postponed if such a probability is very low. Optimal timing for cases of intermediate probability cannot be determined analytically, as it is influenced by other factors such as discount rate, information accumulation and efficiency of investments. Positive externalities between a port and its tenants lead to under-investment, which can be corrected by coordination between stakeholders. However, since there are risks of “over-investment” due to uncertainty, government intervention is only optimal with a good understanding of disaster probability distribution

ACUTE EFFECTS OF HIGH-DEFINITION TRANSCRANIAL DIRECT CURRENT STIMULATION ON DYNAMIC POSTURAL STABILITY IN A Y-BALANCE TASK

Purpose: The present study aimed to investigate whether anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) could affect dynamic postural stability in healthy young adults. Methods: A randomized, crossover, double-blind experimental design was used in this study. Effects of tDCS on dynamic postural stability were assessed baseline and immediately after tDCS. Results: a-tDCS of M1 significantly decreased the COP of medial-lateral displacement on the posteromedial and posterolateral direction, and path length on the posteromedial direction in the Y-balance, while no significant changes in the sham tDCS (s-tDCS) condition. Conclusion: This study provided evidence that a-tDCS enhanced dynamic postural stability in healthy young adult