Avalanches on a conical bead pile: scaling with tuning parameters

Uniform spherical beads were used to explore the behavior of a granular system near its critical angle of repose on a conical bead pile. We found two tuning parameters that could take the system to a critical point where a simple power-law described the avalanche size distribution as predicted by self-organized criticality, which proposed that complex dynamical systems self-organize to a critical point without need for tuning. Our distributions were well described by a simple power-law with the power {\tau} = 1.5 when dropping beads slowly onto the apex of a bead pile from a small height. However, we could also move the system from the critical point using either of two tuning parameters: the height from which the beads fell onto the top of the pile or the region over which the beads struck the pile. As the drop height increased, the system did not reach the critical point yet the resulting distributions were independent of the bead mass, coefficient of friction, or coefficient of restitution. All our apex-dropping distributions for any type of bead (glass, stainless steel, zirconium) showed universality by scaling onto a common curve with {\tau} = 1.5 and {\sigma} = 1.0, where 1/{\sigma} is the power of the tuning parameter. From independent calculations using the moments of the distribution, we find values for {\tau} = 1.6 \pm 0.1 and {\sigma} = 0.91 \pm 0.15. When beads were dropped across the surface of the pile instead of solely on the apex, then the system also moved from the critical point and again the avalanche size distributions fell on a common curve when scaled similarly using the same values of {\tau} and {\sigma}. We also observed that an hcp structure on the base of the pile caused an emergent structure in the pile that had six faces with some fcc or hcp structure.Comment: 8 pages, 6 figures; submitted to Granular Matter; Reformatted into LaTeX from Word; Fixed typo in uncertainty of tau; Rearranged two paragraphs to improve flo

Organometallic Pillarplexes That Bind DNA 4-Way Holliday Junctions and Forks

Holliday 4-way junctions are key to important biological DNA processes (insertion, recombination, and repair) and are dynamic structures that adopt either open or closed conformations, the open conformation being the biologically active form. Tetracationic metallo-supramolecular pillarplexes display aryl faces about a cylindrical core, an ideal structure to interact with open DNA junction cavities. Combining experimental studies and MD simulations, we show that an Au pillarplex can bind DNA 4-way (Holliday) junctions in their open form, a binding mode not accessed by synthetic agents before. Pillarplexes can bind 3-way junctions too, but their large size leads them to open up and expand that junction, disrupting the base pairing, which manifests in an increased hydrodynamic size and lower junction thermal stability. At high loading, they rearrange both 4-way and 3-way junctions into Y-shaped forks to increase the available junction-like binding sites. Isostructural Ag pillarplexes show similar DNA junction binding behavior but lower solution stability. This pillarplex binding contrasts with (but complements) that of metallo-supramolecular cylinders, which prefer 3-way junctions and can rearrange 4-way junctions into 3-way junction structures. The pillarplexes’ ability to bind open 4-way junctions creates exciting possibilities to modulate and switch such structures in biology, as well as in synthetic nucleic acid nanostructures. In human cells, the pillarplexes do reach the nucleus, with antiproliferative activity at levels similar to those of cisplatin. The findings provide a new roadmap for targeting higher-order junction structures using a metallo-supramolecular approach, as well as expanding the toolbox available to design bioactive junction binders into organometallic chemistry

Organometallic Pillarplexes that bind DNA 4-way Holliday Junctions and Forks.

Holliday 4-way junctions are key to important biological DNA processes (insertion, recombination and repair) and are dynamic structures which adopt either open or closed conformations, with the open conformation being the biologically active form. Tetracationic metallo-supramolecular pillarplexes display aryl faces about a cylindrical core giving them an ideal structure to interact with the central cavities of open DNA junctions. Combining experimental studies and MD simulations we show that an Au pillarplex can bind DNA 4-way junctions (Holliday junctions) in their open form, a binding mode not accessed by synthetic agents before. The Au pillarplexes can bind designed 3-way junctions too but their large size leads them to open up and expand that junction, disrupting the base pairing which manifests in an increase in hydrodynamic size and a lower junction thermal stability. At high loading they re-arrange both 4-way and 3-way junctions into Y-shaped DNA forks to increase the available junction-like binding sites. The structurally related Ag pillarplexes show similar DNA junction binding behaviour, but a lower solution stability. This pillarplex binding contrasts with (but complements) that of the metallo-supramolecular cylinders, which prefer 3-way junctions and we show can rearrange 4-way junctions into 3-way junction structures. The ability of pillarplexes to bind open 4-way junctions creates exciting possibilities to modulate and switch such structures in biology, as well as in synthetic nucleic acid nanostructures where they are key interconnecting components. Studies in human cells, confirm that the pillarplexes do reach the nucleus, with antiproliferative activity at levels similar to those of cisplatin. The findings provide a new roadmap for targeting higher order junction structures using a metallo-supramolecular approach, as well as expanding the toolbox available to design bioactive junction-binders into organometallic chemistry

Whistleblowing, communication and consequences: Lessons from the Norwegian national lottery

Whistleblowing, Communication and Consequences offers the first in-depth analysis of the most publicized, and morally complex, case of whistleblowing in recent European history: the Norwegian national lottery, Norsk Tipping. With contributions from the whistleblower himself, as well as from key voices in the field, this book offers unique perspectives and insights into not only this fascinating case, but into whistleblowing and wrongdoing in organizations more broadly. An international team of scholars use fourteen different theoretical lenses to show the complex and multi-faceted nature of whistleblowing. The book begins with an ethnographic account by the whistleblower story and proceeds into an analysis of the literature and conceptual topics related to that whistleblowing incident to present the lessons that can be learnt from this extreme example of institutional failure. This fascinating, complex, and multi-theoretical book will be of great interest to scholars, students and industry leaders in the areas of public relations, corporate communication, leadership, corporate social responsibility, whistleblowing and organizational resistanc

The rhetoric of organizational stability and creativity: an analysis of the term ‘platform’

This article analyses the term platform as it surfaced in interview data from Norway and the United States that was collected in a field research project on organizational technology use. Through an inductive analysis of the term’s use in six interviews, a conceptualization of the term reveals it to be rhetorical in nature, expressing the interplay between stability and creativity. In order to explain the rhetorical aspects we describe, the authors turn to the rhetorical critic Kenneth Burke’s work to aid in conceptualizing the term, specifically his understanding of scene and agency. The authors present the conceptualization to help researchers on two levels. On the micro-level, we offer an analysis of the term platform. On the macro-level, we illustrate how grounded theory can help locate other terms that have unacknowledged salience to researchers, consultants, and interviewees.&nbsp

Complex adaptive systems, attractors, and patching: a complex systems science analysis of organizational change

This study focuses the lens of complex systems science (CSS) on the widely varying experiences of interventionary change in organizations. Two very different types of organizations are studied. Instances of attempted Total Quality Management-type change at both the organizational and project levels in each firm are analyzed, with one attempt successful, the other not. The complex adaptive system model of CSS, and two of its lower level constructs: attractors and patching, are applied metaphorically to analyze the change experiences of the two organizations. The analysis emphasizes the essential role of communicative interaction in the natural dynamics of social change. The CSS focus offers new analytical insights into the unpredictable nature of organizational change processes, and suggests the potential aid such insights might offer. Implications for theory and practice in the application of complex systems science to organizational theory, with am emphasis on communication, are discussed, and areas for further research are suggested.Communication Studie