Potential roles for differential body size and microhabitat complexity in mediating biotic interactions within invasive freshwater amphipod assemblages

Cannibalism and intraguild predation (IGP) are common amongst freshwater amphipod crustacean aswsemblages, particularly between individuals of different body size, with IGP of smaller by larger species. The decline of Gammarus tigrinus Populations in mainland Europe has been accompanied by the arrival of the Ponto-Caspian invader Dikerogammarus villosus and previous studies have implicated IGP of G. tigrinus by the larger D. villosus as the principal driving force in this replacement. We examined how factors such as microhabitat and body size may mediate both cannibalism within G. tigrinus populations and IGP by D. villosus and thus contribute to field patterns of coexistence and exclusion. A field Survey of an invaded Dutch fake indicated that G. tigrinus and D. villosus differed in distribution. with D. villosus being the numerically dominant amphipod (80-96 %) on the rocky boulder Substrate of the shoreline and G. tigrinus being the dominant amphipod (100 %) in the crushed shell/sand matrix immediately adjacent to this. Laboratory microcosm experiments indicated that G. tigrinus cannibalism, particularly of smaller by larger size classes, may be common. In addition, although D. villosus predation of all G. tigrinus size classes was extreme, the smallest size classes Suffered the highest predation. Indeed, when exposed to D. villosus, predation of larger G. tigrinus was lowest when smaller G. tigrinus were also present. Increasing microhabitat complexity from a simple bare substrate littered with Dreissena polymorpha zebra mussels to a Crushed shell/sand matrix significantly reduced both cannibalism and IGP. Our Study emphasizes the need to consider both life history stages and habitat template, when considering the impacts of biotic interactions and it also emphasizes that complex, interacting factors may be mediating the range expansion of D. villosus.

Statistic Complexity: Combining Kolmogorov Complexity with an Ensemble Approach

Background: The evaluation of the complexity of an observed object is an old but outstanding problem. In this paper we are tying on this problem introducing a measure called statistic complexity.

Antecedents and Consequences of Social Identity Complexity: Intergroup Contact, Distinctiveness Threat, and Outgroup Attitudes

Social identity complexity defines people's more or less complex cognitive representations of the interrelationships among their multiple ingroup identities. Being high in complexity is contingent on situational, cognitive, or motivational factors, and has positive consequences for intergroup relations. Two survey studies conducted in Northern Ireland examined the extent to which intergroup contact and distinctiveness threat act as antecedents, and outgroup attitudes as consequences, of social identity complexity. In both studies, contact was positively, and distinctiveness threat negatively, associated with complex multiple ingroup perceptions, whereas respondents with more complex identity structures also reported more favorable outgroup attitudes. Social identity complexity also mediated the effects of contact and distinctiveness threat on attitudes. This research highlights that the extent to which individuals perceive their multiple ingroups in more or less complex and differentiated ways is of central importance to understanding intergroup phenomena.

Situating relational ontology and transformative activist stance within the ‘everyday’ practice of coteaching and cogenerative dialogue.

This paper attempts to advance the thinking in Stetsenko’s paper by situating the concepts of relational ontology and transformative activist stance in the context of coteaching and cogenerative dialogue. In so doing, we hope to make Stetsenko’s ideas more operational in terms of access and application by researchers, teachers, policy makers and other stakeholders in education. Stetsenko argues that moving from relational ontology to a transformative activist stance can be considered as moving from participation to contribution. When this model was applied to coteaching and cogenerative dialogue, it was apparent that the coteaching and cogenerative dialogue moved further, from contribution to shared contribution, adding even greater potential for transformation. The paper also discusses the use of cultural historical activity theory in articulating the relationships, dynamics and interpretations of coteaching and cogenerative dialogue in relation to the wider context of their application.

A Low Complexity Video Watermarking in H.264 Compressed Domain

In this paper, a new blind and readable H.264 compressed domain watermarking scheme is proposed in which the embedding/extracting is performed using the syntactic elements of the compressed bit stream. As a result, it is not necessary to fully decode a compressed video stream both in the embedding and extracting processes. The method also presents an inexpensive spatiotemporal analysis that selects the appropriate submacroblocks for embedding, increasing watermark robustness while reducing its impact on visual quality. Meanwhile, the proposed method prevents bit-rate increase and restricts it within an acceptable limit by selecting appropriate quantized residuals for watermark insertion. Regarding watermarking demands such as imperceptibility, bit-rate control, and appropriate level of security, a priority matrix is defined which can be adjusted based on the application requirements. The resulted flexibility expands the usability of the proposed method.

Strategic Complexity and Success - Small Firms Strategies in a Mature Market

his paper develops a typology of strategic options for small firms in the furniture industry and examines the extent to which firms are re-engineering their strategies in response to profit performance. Empirical analysis is based on data from 39 firms with between 10 and 100 employees in the Irish furniture industry. Three main results emerge from the analysis. First, firms in the Irish furniture industry predominantly adopt “simple” business development strategies. Secondly, in terms of profit performance, we find no evidence that simple strategies unambiguously outperform more complex approaches. Instead, the success of both simple and complex business strategies is directly related to the strength of firms’ resource base. Finally, systematic differences were found in firms’ ability or willingness to re-engineer their strategies in the light of their profit performance.

A similarity measure for graphs with low computational complexity

We present and analyze an algorithm to measure the structural similarity of generalized trees, a new graph class which includes rooted trees. For this, we represent structural properties of graphs as strings and define the similarity of two Graphs as optimal alignments of the corresponding property stings. We prove that the obtained graph similarity measures are so called Backward similarity measures. From this we find that the time complexity of our algorithm is polynomial and, hence, significantly better than the time complexity of classical graph similarity methods based on isomorphic relations. (c) 2006 Elsevier Inc. All rights reserved.

Information theoretic measures of UHG graphs with low computational complexity

We introduce a novel graph class we call universal hierarchical graphs (UHG) whose topology can be found numerously in problems representing, e.g., temporal, spacial or general process structures of systems. For this graph class we show, that we can naturally assign two probability distributions, for nodes and for edges, which lead us directly to the definition of the entropy and joint entropy and, hence, mutual information establishing an information theory for this graph class. Furthermore, we provide some results under which conditions these constraint probability distributions maximize the corresponding entropy. Also, we demonstrate that these entropic measures can be computed efficiently which is a prerequisite for every large scale practical application and show some numerical examples. (c) 2007 Elsevier Inc. All rights reserved.