Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters

We present new (B,I) photometry for the globular cluster systems in eight Brightest Cluster Galaxies (BCGs), obtained with the ACS/WFC camera on the Hubble Space Telescope. In the very rich cluster systems that reside within these giant galaxies, we find that all have strongly bimodal color distributions All the BCGs show population gradients, with much higher relative numbers of red clusters within 5 kpc of their centers, consistent with their having formed at later times than the blue, metal-poor population. A striking new feature of the color distributions emerging from our data is that for the brightest clusters (M_I < -10.5) the color distribution becomes broad and less obviously bimodal. we suggest that it may be a characteristic of many BCGs. Furthermore, the blue (metal-poor) clusters become progressively redder with increasing luminosity, following a mass/metallicity scaling relation Z ~ M^0.55. We argue that these GCS characteristics are consistent with a hierarchical-merging formation picture in which the metal-poor clusters formed in protogalactic clouds or dense starburst complexes with gas masses in the range 10^7 - 10^10 M_Sun, but where the more massive clusters on average formed in bigger clouds with deeper potential wells where more pre-enrichment could occur.Comment: 48 pages, 24 Figures, PDF, Submitted to Astrophys.J. and refereed. For complete pdf file with better figures, see: http://physwww.mcmaster.ca/%7Eharris/Preprints.htm

Effects of Thermal Stress on Dual Task Performance and Attention Allocation

A visual-visual dual task was designed to test the effect of the thermal environment on dual task performance and attention allocation. The temperatures selected for testing were 20 and 35°C Wet Bulb Globe Temperature (WBGT) in experiment 1 and 25, 30 and 35°C Wet Bulb Globe Temperature (WBGT) in experiment 2. In experiment 1, 34 volunteers were randomly assigned to one of the two temperature conditions. A variable representing accuracy on both tasks was coded such that a correct response was assigned only if the participant answered correctly on both tasks. In experiment 2, 42 volunteers were randomly assigned to one of three temperature conditions and instructed vary the amount of attention allocated to each task. Individual differences in single task performance were controlled by equating the baselines of single task performance. Once individual differences in single task capacity were controlled, statistically significant differences in performance were demonstrated. Mean accuracy was computed over a one-hour testing period in each temperature condition. Participants’ mean accuracy in the 35°C condition (38.18%) was substantially less than in the 20°C condition (50.88%). Further, statistically significant differences in performance were detected: in the ability to equally divide attention, effectively allocate attention, and in the relative divided attention cost under thermal stress

Multiplying unitary random matrices - universality and spectral properties

In this paper we calculate, in the large N limit, the eigenvalue density of an infinite product of random unitary matrices, each of them generated by a random hermitian matrix. This is equivalent to solving unitary diffusion generated by a hamiltonian random in time. We find that the result is universal and depends only on the second moment of the generator of the stochastic evolution. We find indications of critical behavior (eigenvalue spacing scaling like $1/N^{3/4}$) close to $\theta=\pi$ for a specific critical evolution time $t_c$.Comment: 12 pages, 2 figure

Economic Impact of Prospective Risk Management Instruments Under Alternative Policy Scenarios

The main objective was to assess the risk of farmers in the European Union and to analyze the impact of agricultural policy changes on the main components of income namely price and production risks. In order to achieve this, qualitative considerations and quantitative analyses covering the period 2004 – 2018 have been made. Future policy scenarios have been defined, taking into account likely Common Agricultural Policy developments, including possible outcomes of the Doha round of the WTO negotiations. Subsequently, the economic impact of policy scenarios in conjunction with a set of prospective risk management instruments for the European Union are determined.Portfolio analysis, Policy scenarios, Risk Management Instruments,

Determining Customary International Law Relative to the Conduct of Hostilities in Non-international Armed Conflicts

In 1987, the 6th annual American Red Cross-Washington College of Law Conference on International Humanitarian Law convened to discuss the 1977 Protocols Additional to the 1949 Geneva Conventions. This article outlines the proceedings of the various workshops, serving as a richly detailed scholarly source for a significant historical event

Radial Velocity Studies of Close Binary Stars.IV

Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of ten close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), HT Vir. All systems are double-lined spectroscopic binaries with only two of them not being contact systems (SW Lyn and GSC 8-324) and with five (FI Boo, V2150 Cyg, V899 Her, EX Leo, V2377 Oph) being the recent photometric discoveries of the Hipparcos satellite project. Five of the binaries are triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, HT Vir). Three (or possibly four) companions in the triple-lined systems show radial-velocity changes during the span of our observations suggesting that these are in fact quadruple systems. Several of the studied systems are prime candidates for combined light and radial-velocity synthesis solutions.Comment: aastex5.0, 5 figures in PS; submitted to Astron.

Radial Velocity Studies of Close Binary Stars.VIII

Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the seventh set of ten close binary systems: V410 Aur, V523 Cas, QW Gem, V921 Her, V2357 Oph, V1130 Tau, HN UMa, HX UMa, HD 93917, NSV 223. All systems, but three (V523 Cas, HD 93917, NSV 223), were discovered photometrically by the Hipparcos mission. All systems are double-lined (SB2) binaries and all, but the detached, very close system V1130 Tau, are contact binaries. The broadening-function permitted improvement of the orbital elements for V523 Cas, which was the only system observed before for radial velocity variations. Spectroscopic/visual companions were detected for V410 Aur and HX UMa.Comment: AASTeX5, 4 figures, 3 tables, to appear AJ, June 200

Induced pluripotent stem cells (iPSCs) derived from a patient with frontotemporal dementia caused by a R406W mutation in microtubule-associated protein tau (MAPT)

AbstractSkin fibroblasts were obtained from a 59-year-old woman diagnosed with frontotemporal dementia. The disease is caused by a R406W mutation in microtubule-associated protein tau (MAPT). Induced pluripotent stem cells (iPSCs) were established by electroporation with episomal plasmids containing hOCT4, hSOX2, hKLF2, hL-MYC, hLIN-28 and shP53. iPSCs were free of genomically integrated reprogramming genes, contained the expected c.1216C>T substitution in exon 13 of the MAPT gene, expressed the expected pluripotency markers, displayed in vitro differentiation potential to the three germ layers and had normal karyotype. The iPSC line may be useful for studying hereditary frontotemporal dementia and TAU pathology in vitro