Monte Carlo Simulations of Globular Cluster Evolution - II. Mass Spectra, Stellar Evolution and Lifetimes in the Galaxy

We study the dynamical evolution of globular clusters using our new 2-D Monte Carlo code, and we calculate the lifetimes of clusters in the Galactic environment. We include the effects of a mass spectrum, mass loss in the Galactic tidal field, and stellar evolution. We consider initial King models containing N = 10^5 - 3x10^5 stars, and follow the evolution up to core collapse, or disruption, whichever occurs first. We find that the lifetimes of our models are significantly longer than those obtained using 1-D Fokker-Planck (F-P) methods. We also find that our results are in very good agreement with recent 2-D F-P calculations, for a wide range of initial conditions. Our results show that the direct mass loss due to stellar evolution can significantly accelerate the mass loss through the tidal boundary, causing most clusters with a low initial central concentration (Wo <~ 3) to disrupt quickly in the Galactic tidal field. Only clusters born with high initial central concentrations (Wo >~ 7) or steep initial mass functions are likely to survive to the present and undergo core collapse. We also study the orbital characteristics of escaping stars, and find that the velocity distribution of escaping stars in collapsing clusters looks significantly different from the distribution in disrupting clusters. We calculate the lifetime of a cluster on an eccentric orbit in the Galaxy, such that it fills its Roche lobe only at perigalacticon. We find that such an orbit can extend the lifetime by at most a factor of a few compared to a circular orbit in which the cluster fills its Roche lobe at all times.Comment: 32 pages, including 10 figures, to appear in ApJ, minor corrections onl

Stand und Tendenzen der DV-Unterstützung der zentralen Universitätsverwaltung

<p>The red points illustrate the locations of the orthologs (including the orthologs with <i>e</i> = 0) on the horizontal axis, and the black lines represent the divergence scores (<i>e</i>) of these orthologs on the vertical axis. The area of elevated evolutionary distance on the beggining portion of Chromosome 1 corresponds to an area with significant differences in linkage disequilibrium between Indian-derived and Chinese rhesus macaques [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123624#pone.0123624.ref013" target="_blank">13</a>].</p

Preliminary Integrated Chronostratigraphy of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica

Chronostratigraphic data available for the preliminary age model for the upper 700 m for the AND-1B drill core include diatom biostratigraphy, magnetostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr ages on calcareous fossil material, and surfaces of erosion identifi ed from physical appearance and facies relationships recognised in the AND-1B drill core. The available age data allow a relatively well-constrained age model to be constructed for the upper 700 m of the drill core. Available diatom biostratigraphic constraints and 40Ar/39Ar ages allow a unique correlation of ~70% of the AND- 1B magnetic polarity stratigraphy with the Geomagnetic Polarity Time Scale (GPTS). Unique correlation is not possible in several coarse diamictite intervals with closely spaced glacial surfaces of erosion and sparse microfl ora. However, the age model indicates relatively rapid (up to 1 m/k.y.) and continuous accumulation of intervening fi ner grained diatomaceous intervals punctuated by several half- to millionyear hiatuses representing more than half of the last 7 m.y. in the AND-1B record. The mid- to late Pleistocene is represented by superimposed diamictite units separated from upper Pliocene alternating diamictites/diatomites by a ~1 m.y. hiatus co-incident with a regionally correlated seismic reflection surface. A c. 100 m-thick diatomite represents a signifi cant portion of the early Pliocene record in the AND-1B drill core. Strata below ~620 m are late Miocene in age; however, biostratigraphic constraints are absent below 586 m and correlation with the GPTS is relatively unconstrained. At the time of writing, the only chronostratigraphic data available below 700 mbsf include three 40Ar/39Ar ages on volcanic clasts from near 1280 mbsf affording a maximum depositional age of 13.57 Ma for the base of the AND-1B drill core

A comparison between Asian and Australasia backpackers using cultural consensus analysis

This study tests the differences in the shared understanding of the backpacker cultural domain between two groups: backpackers from Australasia and backpackers from Asian countries. A total of 256 backpackers responded to a questionnaire administered in Kuala Lumpur, Bangkok and Krabi Province (Thailand). Cultural consensus analysis (CCA) guided the data analysis, to identify the shared values and the differences in the backpacker culture of the two groups. The findings revealed that while the two groups share some of the backpacker cultural values, some other values are distinctively different from one another. The study provides the first empirical evidence of the differences in backpacking culture between the two groups using CCA. Based on the study findings, we propose some marketing and managerial implications

Black liquor and the hangover effect: fish assemblage recovery dynamics following a pulse disturbance

Anthropogenic perturbations impact aquatic systems causing wide-ranging responses, from assemblage restructuring to assemblage recovery. Previous studies indicate the duration and intensity of disturbances play a role in the dynamics of assemblage recovery. In August 2011, the Pearl River, United States, was subjected to a weak black liquor spill from a paper mill which resulted in substantial loss of fish in a large stretch of the main channel. We quantified resilience and recovery of fish assemblage structure in the impacted area following the event. We compared downstream (impacted) assemblages to upstream (unimpacted) assemblages to determine initial impacts on structure. Additionally, we incorporated historic fish collections (1988–2011) to examine impacts on assemblage structure across broad temporal scales. Based on NMDS, upstream and downstream sites generally showed similar assemblage structure across sample periods with the exception of the 2 months postdischarge, where upstream and downstream sites visually differed. Multivariate analysis of variance (PERMANOVA) indicated significant seasonal variation among samples, but found no significant interaction between impacted and unimpacted assemblages following the discharge event. However, multivariate dispersion (MVDISP) showed greater variance among assemblage structure following the discharge event. These results suggest that 2 months following the disturbance represent a time period of stochasticity in regard to assemblage structure dynamics, and this was followed by rapid recovery. We term this dynamic the “hangover effect” as it represents the time frame from the cessation of the perturbation to the assemblage's return to predisturbance conditions. The availability and proximity of tributaries and upstream refugia, which were not affected by the disturbance, as well as the rapid recovery of abiotic parameters likely played a substantial role in assemblage recovery. This study not only demonstrates rapid recovery in an aquatic system, but further demonstrates the value of continuous, long-term, data collections which enhance our understanding of assemblage dynamics.Ye

Kinship ties across the lifespan in human communities

A hypothesis for the evolution of long post-reproductive lifespans in the human lineage involves asymmetries in relatedness between young immigrant females and the older females in their new groups. In these circumstances, inter-generational reproductive conflicts between younger and older females are predicted to resolve in favour of the younger females, who realize fewer inclusive fitness benefits from ceding reproduction to others. This conceptual model anticipates that immigrants to a community initially have few kin ties to others in the group, gradually showing greater relatedness to group members as they have descendants who remain with them in the group. We examine this prediction in a cross-cultural sample of communities, which vary in their sex-biased dispersal patterns and other aspects of social organization. Drawing on genealogical and demographic data, the analysis provides general but not comprehensive support for the prediction that average relatedness of immigrants to other group members increases as they age. In rare cases, natal members of the community also exhibit age-related increases in relatedness. We also find large variation in the proportion of female group members who are immigrants, beyond simple traditional considerations of patrilocality or matrilocality, which raises questions about the circumstances under which this hypothesis of female competition are met. We consider possible explanations for these heterogenous results, and we address methodological considerations that merit increased attention for research on kinship and reproductive conflict in human societies. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'

Reproductive inequality in humans and other mammals

To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving offspring) among males and smaller sex differences in reproductive skew than most other mammals, while nevertheless falling within the mammalian range. Additionally, female reproductive skew is higher in polygynous human populations than in polygynous nonhumans mammals on average. This patterning of skew can be attributed in part to the prevalence of monogamy in humans compared to the predominance of polygyny in nonhuman mammals, to the limited degree of polygyny in the human societies that practice it, and to the importance of unequally held rival resources to women’s fitness. The muted reproductive inequality observed in humans appears to be linked to several unusual characteristics of our species—including high levels of cooperation among males, high dependence on unequally held rival resources, complementarities between maternal and paternal investment, as well as social and legal institutions that enforce monogamous norms