Brightest Cluster Galaxy Alignments in Merging Clusters

The orientations of brightest cluster galaxies (BCGs) and their host clusters tend to be aligned, but the mechanism driving this is not clear. To probe the role of cluster mergers in this process, we quantify alignments of 38 BCGs in 22 clusters undergoing major mergers (up to $\sim 1$ Gyr after first pericenter). We find alignments entirely consistent with those of clusters in general. This suggests that alignments are robust against major cluster mergers. If, conversely, major cluster mergers actually help orient the BCG, such a process is acting quickly because the orientation is in place within $\sim 1$ Gyr after first pericenter.Comment: accepted to Ap

Online Naturalization: Evolving Roles in Online Knowledge Production Communities

Web-based peer production communities, like Wikipedia and open source software, have created digital artifacts of growing cultural, financial, and technological importance. Understanding how and why people choose to join these communities, and why they eventually leave them, is therefore an important topic. We take all of the edit data from six years of activity on the online genealogy wiki WeRelate, and create monthly snapshots of behavior and interaction networks for all 9,570 users who edited the site. We use machine learning to cluster these behavioral snapshots into four behavioral roles . We identify one of these roles as being indicative of a community of practice, and we investigate how users move from role to role. As in many other online, peer production projects, the vast majority of users are only active for a short time, and contribute very little while a small number of users contribute a great deal. Figuring out how to recruit and encourage these users is very important to the success of peer production projects. We use visualizations, regression analysis, and stochastic actor-oriented modeling of four different types of interaction networks to study whether these very active users represent a community of practice that new users can learn from and join. We also study how people leave the community, and whether there are signals that someone is starting to disengage. We do not find much evidence that these users go through a period of legitimate peripheral participation or acculturation. Rather, those who will become core members show behavior that is similar to long-term core members from their first few months on the site. We find that these core members show a clear trend of disengaging from the community over a few months before leaving completely, indicating a period where intervention may be effective. We also find a potentially effective intervention, as those who are actively interacting with others who are core members are less likely to disengage. Our findings provide implications for understanding how online communities function, how interaction networks influence user activity, and how those who are members of these communities might make them more effective. The study also provides a new methodological framework for studying the influence of communicative interactions in online communities

Anarchists, Punks and Vegans - oh my! Ethnography of an anti-capitalist Community of Dissent

Although ethnographies dealing with anti-capitalist activism, veganism or the punk scene are far from uncommon, until recently the temptation has been to view these groups as separate and distinct, rather than diffuse and overlapping. Using data gathered during interviews and participant observation in some parts of urban New Zealand, this study offers a sketch of the boundaries of the Community embodied by that overlap. Participants' own definitions for key terms such as anarchism, punk and capitalism/consumerism are presented and scrutinised in order to provide a starting point for this analysis. A lineage of thought is juxtaposed with each of these terms, with the intention of contesting some of the popular stereotypes surrounding them. The Community's own sense of difference is then explored through the responses of participants, which are analysed and some commonalities suggested. The most critical of these is the perception amongst participants of a greater engagement with their choices than they generally considered to be the case within the mainstream. Finally, some internal divisions within the Community are noted and a model for the radicalisation and mediation of dissent is suggested to explain this

Correlates of variability in killer whale stereotyped call repertoires.

Killer whales vocalisations include repertoires of stereotyped call types (Ford 1984). There is strong evidence that these vocalisations are learnt (Hoelzel and Osborne 1986; Bain 1989; Deecke et al. 2000; Yurk et al. 2002). Call types can be group specific or shared amongst a number of groups, depending upon the social structure of the population or the call type (Ford 1991; Deecke 2003). It is thought that these call types function in the group cohesion and coordination (Hoelzel and Osborne 1986; Ford 1989 1991; Miller 2000, 2002). Some call types contain two overlapping, independently modulated, components each having different transmission properties (Miller 2002), these call types have a higher estimated active space than single- component call types (Miller 2006).This thesis investigates the evolution of these call type repertoires, focusing on call type usage and structure of the Southern Resident population over a period of 27 years, but including comparisons with other populations. I present evidence of hetero-specific mimicry and further evidence for vocal production and usage learning in killer whales. I compared the relative frequency of use of call types between two time periods (1977-81 & 2001-2003) and between contexts, such as direction changes with directional travel and multi-pod aggregations with single pods. I found a strong correlation of relative call type usage for each pod between the two time periods and each pod was easily acoustically distinguishable from the other two pods in both periods. The implications of these results for a role of call type repertoires in kin recognition are discussed. The least cohesive pod produced a significantly higher proportion of two-component call types than the other two more cohesive pods. Lone whales separated from their pod also used a rare subset of two-component call types rather than their pod's main call types. In recordings of multi-pod aggregations I recorded a high proportion of the same subset of two-component call types not commonly produced by any of the three pods individually, these call types were used in significantly higher proportions when all three pods were converging or socialising rather than travelling. These contextual correlates suggest that call types are selectively used and shared between groups based on their transmission properties. Each of the Southern Resident pods, J к and L, were found to increase the duration of their primary call type 10-15% in the presence of vessel noise in recordings made between 2001 & 2003. This response was not detected in recording from two earlier time periods, (1977 or 1989-1992). This change in behaviour correlated with an increase over the past decade in vessel presence around this population and may be an anti-masking strategy. I also compared the range and mean minimum and maximum fundamental frequency of the call types within the repertoires of six North Pacific killer whale populations. There was a degree of homogeneity in the range of call type fundamental frequencies within the repertoires of populations of the same ecotype, but differences between ecotypes. Offshore call types generally had a higher pitch fundamental frequency than transient or resident call types. All three resident populations had call types in their repertoires that had a maximum fundamental frequency 3 kHz higher than found in any transient call type

Comparison of copper and tungsten carbide calibration spheres

Author Posting. © Acoustical Society of America, 1984. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 75 (1984): 612-616, doi:10.1121/1.390489.The properties of calibration spheres made from electrical‐grade copper, denoted Cu, and tungsten carbide with 6% cobalt binder, denoted WC, are examined theoretically. Effects of variations in material, medium, and equipment parameters are determined for spheres intended to calibrate 38‐kHz echo sounders when a target strength of order −41.5 dB is required. The derived 30.4‐mm‐diam Cu sphere and selected 38.1‐mm‐diam WC ball bearing show different dependences on the varied parameters. Changes in the material and equipment parameters within wide ranges will not upset a precision calibration with expected ±0.1‐dB accuracy. Adjustment of the calibration value of  backscattering cross section with changing temperature is generally necessary for elastic spheres. This is the case for the present WC sphere, but not for the Cu sphere by virtue of its optimization with respect to temperature. Greater hardness is found to be insufficient for choosing between the two; the particular application must be considered. Pragmatic criteria for sphere selection are discussed

Comparing Kirchhoff-approximation and boundary-element models for computing gadoid target strengths

To establish the validity of the boundary-element method (BEM) for modeling scattering by swimbladder-bearing fish, the BEM is exercised in several ways. In a computation of backscattering by a 50-mm-diam spherical void in sea water at the four frequencies 38.1, 49.6, 68.4, and 120.4 kHz, agreement with the analytical solution is excellent. In computations of target strength as a function of tilt angle for each of 15 surface-adapted gadoids for which the swimbladders were earlier mapped, BEM results are in close agreement with Kirchhoff-approximation-model results at each of the same four frequencies. When averaged with respect to various tilt angle distributions and combined by regression analysis, the two models yield similar results. Comparisons with corresponding values derived from measured target strength functions of the same 15 gadoid specimens are fair, especially for the tilt angle distribution with the greatest standard deviation, namely 16°

Toward a transformed system to address child abuse and family violence in New Zealand

Executive Summary Introduction The Glenn Inquiry (TGI) has contracted Institute of Environmental Science and Research Limited (ESR) to bring together the relevant experience and expertise to collaboratively model a transformed system to address child abuse and neglect (CAN) and family violence (FV) in New Zealand. Our approach We have treated the task of reducing FV and CAN as a ‘wicked problem’1; that is, reducing FV and CAN is a problem that cannot be solved once and for all, and is not a matter of simply applying expert knowledge. The methods used in this project have been chosen because they are appropriate for working with wicked problems: stakeholder engagement, systems thinking and inter-disciplinary analysis. In this report, we refer to both CAN and FV. We recognise that, for some purposes, dealing with CAN requires particular strategies and treatment; however, the purpose of this report is to develop a transformed system that will reduce both CAN and other forms of FV. While the underlying causes of CAN and other FV may be considered independently, and some responses to each form of abuse will need to be particular, this report proposes a wider system of responses that will enable targeted interventions for each form of abuse. We use the term ‘family violence’ in this report in the sense it has come to be understood in Aotearoa, and is used in Te Rito: New Zealand Family Violence Prevention Strategy. In this use, FV includes intimate partner violence, child abuse and neglect, elder abuse, inter-sibling abuse and parental abuse. The project consisted of four work-streams: A review of the international and national literature on what would constitute a high performing system to address CAN and FV, including a review of New Zealand’s current approach with a focus on government legalisation, policies and initiatives; Qualitative modelling of the system dynamics associated with the existing way in which New Zealand has responded to CAN and FV; A secondary (sociological) analysis of suggestions for system improvement from the People’s Report; and, Developing a systemic model of a transformed system through collaborative workshops with sector experts

Ecological structure of diversity-dependent diversification in Phanerozoic marine bivalves

Rigorous analysis of diversity-dependence—the hypothesis that the rate of proliferation of new species is inversely related to standing diversity—requires consideration of the ecology of the organisms in question. Differences between infaunal marine bivalves (living entirely within the sediment) and epifaunal forms (living partially or completely above the sediment–water interface) predict that these major ecological groups should have different diversity dynamics: epifaunal species may compete more intensely for space and be more susceptible to predation and physical disturbance. By comparing detrended standing diversity with rates of diversification, origination, and extinction in this exceptional fossil record, we find that epifaunal bivalves experienced significant, negative diversity-dependence in origination and net diversification, whereas infaunal forms show little appreciable relationship between diversity and evolutionary rates. This macroevolutionary contrast is robust to the time span over which dynamics are analysed, whether mass-extinction rebounds are included in the analysis, the treatment of stratigraphic ranges that are not maximally resolved, and the details of detrending. We also find that diversity-dependence persists over hundreds of millions of years, even though diversity itself rises nearly exponentially, belying the notion that diversity-dependence must imply equilibrial diversity dynamics