Water Ice in 2060 Chiron and its Implications for Centaurs and Kuiper Belt Objects

We report the detection of water ice in the Centaur 2060 Chiron, based on near-infrared spectra (1.0 - 2.5 micron) taken with the 3.8-meter United Kingdom Infrared Telescope (UKIRT) and the 10-meter Keck Telescope. The appearance of this ice is correlated with the recent decline in Chiron's cometary activity: the decrease in the coma cross-section allows previously hidden solid-state surface features to be seen. We predict that water ice is ubiquitous among Centaurs and Kuiper Belt objects, but its surface coverage varies from object to object, and thus determines its detectability and the occurrence of cometary activity.Comment: 18 pages, 3 figures, accepted by ApJ Letter

Biometric identity-based cryptography for e-Government environment

Government information is a vital asset that must be kept in a trusted environment and efficiently managed by authorised parties. Even though e-Government provides a number of advantages, it also introduces a range of new security risks. Sharing confidential and top-secret information in a secure manner among government sectors tend to be the main element that government agencies look for. Thus, developing an effective methodology is essential and it is a key factor for e-Government success. The proposed e-Government scheme in this paper is a combination of identity-based encryption and biometric technology. This new scheme can effectively improve the security in authentication systems, which provides a reliable identity with a high degree of assurance. In addition, this paper demonstrates the feasibility of using Finite-state machines as a formal method to analyse the proposed protocols

Population of the Scattered Kuiper Belt

We present the discovery of three new Scattered Kuiper Belt Objects (SKBOs) from a wide-field survey of the ecliptic. This continuing survey has to date covered 20.2 square degrees to a limiting red magnitude of 23.6. We combine the data from this new survey with an existing survey conducted at the University of Hawaii 2.2m telescope to constrain the number and mass of the SKBOs. The SKBOs are characterized by large eccentricities, perihelia near 35 AU, and semi-major axes > 50 AU. Using a maximum-likelihood model, we estimate the total number of SKBOs larger than 100 km in diameter to be N = 3.1 (+1.9/-1.3) x 10^4 (1 sigma) and the total mass of SKBOs to be about 0.05 Earth masses, demonstrating that the SKBOs are similar in number and mass to the Kuiper Belt inside 50 AU.Comment: 15 pages, 3 figure

Trade and Linked Exchange; Price Discrimination Through Transaction Bundling

In this paper we try to explain how price discrimination can cause bilateral trade patterns of the type seen under countertrade agreements. We interpret countertrade as a form of transaction bundling which can discriminate between potential trading partners and we combine characteristics from both explanations as to the existence of countertrade. There is both price discrimination through transaction bundling, and informational asymmetry in the form of uncertainty in the quality of the goods produced by trading partners in less developed countries (LDCs) leading to a partner preference from the side of the Western (DC) firm. Our paper shows that although the ability of firms in LDCs to overcome their creditworthiness constraints by engaging in countertrade arrangements may be restricted by this quality uncertainty as it reduces the willingness of a firm in a DC to exchange, the trade volume prospects of a firm in a LDC can be considerably enhanced if a countertrade transaction does occur. Our paper goes beyond the case of linked exchange, which is only one of the three cases of transaction bundling examined. The other two cases are that of the Western firm being a monopoly selling a bundle of two goods used as a benchmark case, and the more interesting case of the Western firm being the buyer of two goods and setting both two separate buying prices and a bundling (i.e. package) purchase price. Many procurement decisions are not simply a matter of price, but also the identity and reputation of the supplier matters, especially when the supplier is located in an LDC. We show than when bundling its purchases, the Western firm buyer will be willing to offer a bundled price greater than the sum of the two separate prices, as the option of a bundled purchase would increase its pro…ts even if there are no complementarities between the goods bundled. In our model the argument is that just as it is profitable for a monopolist to offer mixed bundling at a bundled price which is lower than the sum of the individual prices (hence exploiting the average willingness to pay), it is also profitable for a monopsonist to offer a bundled purchase price which is higher that the sum of the individual prices on offer (hence exploiting the average willingness to sell). Equally interestingly, it is found that a LDC can substantially increase its sales of a good with a high degree of quality uncertainty by being offered to bundle it with the sale of a more basic good with a low degree of quality uncertainty

SN2002bu -- Another SN2008S-like Transient

We observed SN2002bu in the near-IR with the Hubble Space Telescope, the mid-IR with the Spitzer Space Telescope and in X-rays with Swift 10 years after the explosion. If the faint L_H\sim100 Lsun HST near-IR source at the transient position is the near-IR counterpart of SN2002bu, then the source has dramatically faded between 2004 and 2012, from L\sim10^6.0 Lsun to L\sim10^4.5 Lsun. It is still heavily obscured, tau_V\sim5 in graphitic dust models, with almost all the energy radiated in the mid-IR. The radius of the dust emission is increasing as R\simt^(0.7+/-0.4) and the optical depth is dropping as tau_V\simt^(-1.3+/-0.4). The evolution expected for an expanding shell of material, tau_V\sim1/t^2, is ruled out at approximately 2 sigma while the tau_V\simt^(-0.8) to t^(-1) optical depth scaling for a shock passing through a pre-existing wind is consistent with the data. If the near-IR source is a chance superposition, the present day source can be moderately more luminous, significantly more obscured and evolving more slowly. While we failed to detect X-ray emission, the X-ray flux limits are consistent with the present day emissions being powered by an expanding shock wave. SN2002bu is clearly a member of the SN2008S class of transients, but continued monitoring of the evolution of the spectral energy distribution is needed to conclusively determine the nature of the transient.Comment: Submitted to Ap

Fermi gas in harmonic oscillator potentials

Assuming the validity of grand canonical statistics, we study the properties of a spin-polarized Fermi gas in harmonic traps. Universal forms of Fermi temperature $T_F$, internal energy $U$ and the specific heat per particle of the trapped Fermi gas are calculated as a {\it function} of particle number, and the results compared with those of infinite number particles.Comment: 8 pages, 1 figure, LATE