UCDs as Probes of the Major and Minor Merger Histories of Galaxies

Two competing theories posit that Ultra Compact Dwarfs (UCDs) form either as the stripped nuclei of dwarf galaxies or as giant globular clusters (GGCs) associated with the largest globular cluster (GC) systems. By focussing on the field and group environments where young UCDs may be most common, we have discovered the first UCD that is clearly the result of recent (<4 Gyr ago) stripping of a companion galaxy. However, we have also found a definitive case of a multiple-UCD system created via GC formation processes, which are likely associated with major galaxy mergers. We demonstrate that it is possible to reliably distinguish the two types of UCD, thereby probing both the major and minor merger histories of individual galaxies.Comment: 2 pages, 1 figure, to appear in the proceedings of the conference "A Universe of Dwarf Galaxies" (Lyon, June 14-18, 2010

The Pinch Technique to All Orders

The generalization of the pinch technique to all orders in perturbation theory is presented. The effective Green's functions constructed with this procedure are singled out in a unique way through the full exploitation of the underlying Becchi-Rouet-Stora-Tyutin symmetry. A simple all-order correspondence between the pinch technique and the background field method in the Feynman gauge is established.Comment: 10 pages, 4 figures; one reference added, typos corrected; final version to match the pubblished on

On the survivability and detectability of terrestrial meteorites on the moon

Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (≤45°) impacts, or both. We outline possible mechanisms for locating such materials on the Moon and conclude that searching for them would be a scientifically valuable activity for future lunar exploration

Role of carbon dioxide and ion transport in the formation of sub-embryonic fluid by the blastoderm of the Japanese quail

1. The explanted blastoderm of the Japanese quail was used to explore the role of ions and carbon dioxide in determining the rate of sub-embryonic fluid (SEF) production between 54 and 72 h of incubation. 2. Amiloride, an inhibitor of Na+/H+ exchange, at concentrations of 10-3 to 10-6 M substantially decreased the rate of SEF production when added to the albumen culture medium. N-ethylmaleimide, an inhibitor of V type H+ ATPase, also decreased this rate but only to a small extent at the highest dose applied, 10-3 M. Both inhibitors had no effect on SEF production when added to the SEF. 3. The inhibitors of cellular bicarbonate and chloride exchange, 4-acetamido-4-'isothiocyano-2, 2-'disulphonic acid (SITS) and 4,4'diisothiocyanostilbene-2,2-'disulphonic acid (DIDS), had no effect upon SEF production. 4. Ouabain, an inhibitor of Na+/K+ ATPase, decreased SEF production substantially at all concentrations added to the SEF (10-3 to 10-6 M). Three sulphonamide inhibitors of carbonic anhydrase, acetazolamide, ethoxzolamide and benzolamide, decreased SEF production when added to the SEF at concentrations of 10-3 to 10-6 M. Benzolamide was by far the most potent. Neither ouabain nor the sulphonamides altered SEF production when added to the albumen culture medium. 5. Using a cobalt precipitation method, carbonic anhydrase activity was localised to the endodermal cells of the area vasculosa. The carbonic anhydrase activity was primarily associated with the lateral plasma membranes, which together with the potent inhibitory effect of benzolamide, suggests the carbonic anhydrase of these cells is the membrane-associated form, CA IV. 6. The changes in SEF composition produced by inhibitors were consistent with the production of SEF by local osmotic gradients. 7. It is concluded that a Na+/K+ ATPase is located on the basolateral membranes of the endodermal cells of the area vasculosa , and that a sodium ion/hydrogen ion exchanger is located on their apical surfaces. Protons for this exchanger would be provided by the hydration of CO2 catalysed by the membrane-associated carbonic anhydrase. Furthermore, it is proposed that the prime function of the endodermal cells of the area vasculosa is the production of SEF

Two Stage Auctions II: Common-Value Strategies and the Winner's Curse

game theory ; supply ; economic models ; economic equilibrium

An Envy-Free Cake Division Algorithm

mathematics

Two Stage Auctions I: Private-Value Strategies

game theory ; economic equilibrium ; information

Fair Division by Point Allocation

economic theory

Fair Division Pareto-Optimality Versus Strategic Robustness

economic theory

Flexible modeling of dependence in volatility processes

This paper proposes a novel stochastic volatility model that draws from the exist- ing literature on autoregressive stochastic volatility models, aggregation of autoregres- sive processes, and Bayesian nonparametric modelling to create a stochastic volatility model that can capture long range dependence. The volatility process is assumed to be the aggregate of autoregressive processes where the distribution of the autoregressive coefficients is modelled using a flexible Bayesian approach. The model provides insight into the dynamic properties of the volatility. An efficient algorithm is defined which uses recently proposed adaptive Monte Carlo methods. The proposed model is applied to the daily returns of stocks