DNA-based Self-Assembly of Chiral Plasmonic Nanostructures with Tailored Optical Response

Surface plasmon resonances generated in metallic nanostructures can be utilized to tailor electromagnetic fields. The precise spatial arrangement of such structures can result in surprising optical properties that are not found in any naturally occurring material. Here, the designed activity emerges from collective effects of singular components equipped with limited individual functionality. Top-down fabrication of plasmonic materials with a predesigned optical response in the visible range by conventional lithographic methods has remained challenging due to their limited resolution, the complexity of scaling, and the difficulty to extend these techniques to three-dimensional architectures. Molecular self-assembly provides an alternative route to create such materials which is not bound by the above limitations. We demonstrate how the DNA origami method can be used to produce plasmonic materials with a tailored optical response at visible wavelengths. Harnessing the assembly power of 3D DNA origami, we arranged metal nanoparticles with a spatial accuracy of 2 nm into nanoscale helices. The helical structures assemble in solution in a massively parallel fashion and with near quantitative yields. As a designed optical response, we generated giant circular dichroism and optical rotary dispersion in the visible range that originates from the collective plasmon-plasmon interactions within the nanohelices. We also show that the optical response can be tuned through the visible spectrum by changing the composition of the metal nanoparticles. The observed effects are independent of the direction of the incident light and can be switched by design between left- and right-handed orientation. Our work demonstrates the production of complex bulk materials from precisely designed nanoscopic assemblies and highlights the potential of DNA self-assembly for the fabrication of plasmonic nanostructures.Comment: 5 pages, 4 figure

Local Convergence and Global Diversity: From Interpersonal to Social Influence

Axelrod (1997) showed how local convergence in cultural influence can preserve cultural diversity. We argue that central implications of Axelrod's model may change profoundly, if his model is integrated with the assumption of social influence as assumed by an earlier generation of modelers. Axelrod and all follow up studies employed instead the assumption that influence is interpersonal (dyadic). We show how the combination of social influence with homophily allows solving two important problems. Our integration of social influence yields monoculture in small societies and diversity increasing in population size, consistently with empirical evidence but contrary to earlier models. The second problem was identified by Klemm et al.(2003a,b), an extremely narrow window of noise levels in which diversity with local convergence can be obtained at all. Our model with social influence generates stable diversity with local convergence across a much broader interval of noise levels than models based on interpersonal influence.Comment: 20 pages, 3 figures, Paper presented at American Sociological Association 103rd Annual Meeting, August 1-4, 2008, Boston, MA. Session on Mathematical Sociolog

International Coercion, Emulation and Policy Diffusion: Market-Oriented Infrastructure Reforms, 1977-1999

Why do some countries adopt market-oriented reforms such as deregulation, privatization and liberalization of competition in their infrastructure industries while others do not? Why did the pace of adoption accelerate in the 1990s? Building on neo-institutional theory in sociology, we argue that the domestic adoption of market-oriented reforms is strongly influenced by international pressures of coercion and emulation. We find robust support for these arguments with an event-history analysis of the determinants of reform in the telecommunications and electricity sectors of as many as 205 countries and territories between 1977 and 1999. Our results also suggest that the coercive effect of multilateral lending from the IMF, the World Bank or Regional Development Banks is increasing over time, a finding that is consistent with anecdotal evidence that multilateral organizations have broadened the scope of the “conditionality” terms specifying market-oriented reforms imposed on borrowing countries. We discuss the possibility that, by pressuring countries into policy reform, cross-national coercion and emulation may not produce ideal outcomes.http://deepblue.lib.umich.edu/bitstream/2027.42/40099/3/wp713.pd

Deconstructing the outsider puzzle: The legitimation journey of novelty

The proposition that outsiders often are crucial carriers of novelty into an established institutional field has received wide empirical support. But an equally compelling proposition points to the following puzzle: the very same conditions that enhance outsiders' ability to make novel contributions also hinder their ability to carry them out. We seek to address this puzzle by examining the contextual circumstances that affect the legitimation of novelty originating from a noncertified outsider that challenged the status quo in an established institutional field. Our research case material is John Harrison's introduction of a new mechanical method for measuring longitude at sea-the marine chronometer- which challenged the dominant astronomical approach.We find that whether an outsider's new offer gains or is denied legitimacy is influenced by (1) the outsider's agency to further a new offer, (2) the existence of multiple audiences with different dispositions toward this offer, and (3) the occurrence of an exogenous jolt that helps create a more receptive social space. We organize these insights into a multilevel conceptual framework that builds on previouswork but attributes a more decisive role to the interplay between endogenous and exogenous variables in shaping a field's shifting receptiveness to novelty. The framework exposes the interdependencies between the micro-, meso-, and macro-level processes that jointly affect an outsider's efforts to introduce novelty into an existing field

Back to the past: the individual and its role in creativity in organisations

O objetivo deste texto é realçar o papel do indivíduo na criatividade nas organizações. Esse papel tem sido estranhamente remetido para um plano secundário, à medida que as modernas visões da criatividade a definem, sobretudo, com relação ao contexto em que ocorre. De fato, na perspectiva atual, a criatividade não pode ser entendida sem se considerarem os contextos funcional, relacional e organizacional nos quais está inserido o trabalhador. Tais são as considerações da maior parte dos autores que escreve sobre o tópico, como sejam Amabile (1996), Csikszentmihalyi (1996), ou, mais recentemente, Glăveanu (2010a, 2010b). Essa corrente dominante, com origem no interacionismo psico-social, tem ainda influenciado o desenvolvimento teórico de outros conceitos em psicologia, sociologia, e, na sequência, nas ciências sociais e humanas, e na gestão. Essa supremacia no que concerne a criatividade, tem conduzido os autores a olvidar o papel do indivíduo no processo e no resultado criativos, chegando a retirar-lhe a responsabilidade e o protagonismo pela geração e produção de ideias. Desse modo, no presente texto, recuperam-se os argumentos em favor da centralidade da pessoa na criatividade, defendendo-se que esta tem uma existência isolada de influências externas, e que, como tal, devem relembrar-se as bases individuais da criatividadeThe goal of the current text is to highlight the role of the individual in creativity in organisations. This role has been strangely disregarded in recent years, as modern accounts of creativity have been emphasising the idea that creativity is only defined in context. This main stream argues that creativity is a process that essentially occurs within a functional, relational, and organisational context in which workers are inserted. Key authors defending such a position include the likes of Amabile (1996), Csikszentmihalyi (1996), and, more recently, Glăveanu (2010a, 2010b). This is a vision rooted in the psychosocial interactionist perspective, which has also had a considerable impact in other areas in psychology, sociology, management and other social and human sciences. This supremacy, with regards to creativity, has led many to forget the role of the individual person in the creative process and output, removing their responsibility and protagonism for generating and producing ideas. Hence, the current text intends to bring back to discussion the individual bases of creativity, that people can have an existence isolated from external influences, further defending that the concept can and should be defined out of context, rather than in contextinfo:eu-repo/semantics/publishedVersio