Simple Stellar Population Models as probed by the Large Magellanic Cloud Star Cluster ESO 121-SC03

The presence of blue straggler stars (BSs) in star clusters has proven a challenge to conventional simple stellar population (SSP) models. Conventional SSP models are based on the evolution theory of single stars. Meanwhile, the typical locations of BSs in the colour-magnitude diagram of a cluster are brighter and bluer than the main sequence turn-off point. Such loci cannot be predicted by single-star evolution theory. However, stars with such properties contribute significantly to the integrated light of the cluster. In this paper, we reconstruct the integrated properties of the Large Magellanic Cloud cluster ESO 121-SC03, based on a detailed exploration of the individual cluster stars, and with particular emphasis on the cluster's BSs. We find that the integrated light properties of ESO 121-SC03 are dramatically modified by its BS component. The integrated spectral energy distribution (ISED) flux level is significantly enhanced toward shorter wavelengths, and all broad-band colours become bluer. When fitting the fully integrated ISED of this cluster based on conventional SSP models, the best-fitting values of age and metallicity are significantly underestimated compared to the true cluster parameters. The age underestimate is $\sim40$ per cent if we only include the BSs within the cluster's half-light radius and $\sim60$ per cent if all BSs are included. The corresponding underestimates of the cluster's metallicity are $\sim30$ and $\sim60$ per cent, respectively. The populous star clusters in the Magellanic Clouds are ideal objects to explore the potential importance of BSs for the integrated light properties of more distant unresolved star clusters in a statistically robust manner, since they cover a large range in age and metallicity.Comment: 11 pages, 7 figures, 2 tables, accepted for publication in MNRA

The Evolution of Globular Clusters in the Galaxy

We investigate the evolution of globular clusters using N-body calculations and anisotropic Fokker-Planck (FP) calculations. The models include a mass spectrum, mass loss due to stellar evolution, and the tidal field of the parent galaxy. Recent N-body calculations have revealed a serious discrepancy between the results of N-body calculations and isotropic FP calculations. The main reason for the discrepancy is an oversimplified treatment of the tidal field employed in the isotropic FP models. In this paper we perform a series of calculations with anisotropic FP models with a better treatment of the tidal boundary and compare these with N-body calculations. The new tidal boundary condition in our FP model includes one free parameter. We find that a single value of this parameter gives satisfactory agreement between the N-body and FP models over a wide range of initial conditions. Using the improved FP model, we carry out an extensive survey of the evolution of globular clusters over a wide range of initial conditions varying the slope of the mass function, the central concentration, and the relaxation time. The evolution of clusters is followed up to the moment of core collapse or the disruption of the clusters in the tidal field of the parent galaxy. In general, our model clusters, calculated with the anisotropic FP model with the improved treatment for the tidal boundary, live longer than isotropic models. The difference in the lifetime between the isotropic and anisotropic models is particularly large when the effect of mass loss via stellar evolution is rather significant. On the other hand the difference is small for relaxation- dominated clusters which initially have steep mass functions and high central concentrations.Comment: 36 pages, 11 figures, LaTeX; added figures and tables; accepted by Ap

A Recommitment Strategy for Long Term Private Equity Fund Investors

This paper develops a reinvestment strategy for private equity which aims to keep its portfolio weight equal to a desired strategic allocation, while taking into account the illiquid nature of private equity. Historical simulations (1980-2005) show that our dynamic strategy is capable of maintaining a stable investment level that is close to the target. This does not only hold for unrestricted portfolios, but also for investments limited to buyout or venture capital, a specific region, or management experience. This finding is of great importance for investors, because private equity funds have a finite lifetime and uncertain cash flows

WI-FI in the ivory tower: reducing isolation of the law PhD student through social media networks

This paper was presented at the 2013 National Wellness for Law Forum, 21 – 22 February 2013.Research students no longer need to spend long hours on campus under the gaze of their supervisors. Ubiquitous access to online databases and communication tools means that many PhD students operate in splendid isolation, away from the bustle and distractions of campus life. But this freedom may also bring with it strong feelings of isolation from academic community and peer support. The authors of this study have commenced an inquiry into whether the connectivity and interactivity of social media can provide a vital social lifeline for research students (particularly law students who work largely independently and are not frequently part of large research teams) in order to address these feelings of isolation. The role of social media in shaping academic identity and voice is also addressed. It considers a number of significant UK studies of higher degree by research students and their relevance for Australia and outlines the results of a small pilot survey conducted in an Australian law school.Melissa de Zwart, Bernadette Richard

THE INFLUENCE OF POTENTILLA REPTANS EXTRACTS ON THE PHYSIOLOGY OF AGROPYRON REPENS L. PLANTS

During the experiments, the influence of the aqueous extracts obtained from the leaves of Potentilla reptans on the physiology of Agropyron repens was studied.Agropyron repens is a plant of spontaneous flora of Romania, growing on cultivated and uncultivated soils and is one of the most harmful plants in agriculture.In areas where Potentilla reptans grows, couch grass growth is inhibited; this demonstrates that this plant can have an allelopatic action on the couch grass. During these experiments, aqueous extracts from the leaves of Potentilla reptans were used in concentrations of 5 g / l, 10 g / l, 15 g / l and 20 g / l. These extracts were used in order to water the Agropyron repens plants .The experiments focused on the intensity of leaf photosynthesis, leaf respiration intensity, transpiration intensity, leaf water content and chlorophyll content.In the variant with a concentration of 5 g / l, photosynthesis had much lower values, and at 20 g / l the process was reduced by about 50%.Regarding the respiration process, there was an increase, but only at high concentrations of the extracts (15 and 20 g / l). At low concentrations, the differences from the control were undetectable.In the control variant, the intensity of leaf transpiration had the lowest value. In the other variants, it has been found to intensify the transpiration process in proportion to the increase in the concentration of the extracts