872 research outputs found

    Smart hydrogels based on responsive star-block copolymers

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    Electrostatic attraction of nanoobjects - a versatile strategy towards mesostructured transition metal compounds

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    This highlight summarizes current challenges of mesostructuring and focuses on the scope and the potential of the ELAN – (electrostatic attraction of nanoobjects) strategy in mesostructuring of transition metal compounds. It discusses the limitations of this concept and highlights prominent examples. ELAN exploits the Coulomb attraction between inorganic precursors and polymeric templates in order to prevent macrophase separation. Essential requirements for ELAN are tailor-made, mesoscopic polyelectrolytic templates and charged molecular oligo-ions or stable colloids carrying a surface charge. The ELAN-strategy is highly reliable and opens the way to crystalline, mesoporous transition metal compounds with predefined polymorphism. It also provides the possibility to adjust wall chemistry and reactivity as well as the flexibility to synthesise different mesostructures (spheres, non-woven arrays or hexagonally ordered phases)

    Morphology of the first zoeal stage of the commensal southwestern Atlantic crab Austinixa aidae (Righi 1967) (Brachyura: Pinnotheridae), hatched in the laboratory

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    6 páginas, 2 figuras, 1 tabla.The first zoeal stage of the endemic southern Atlantic pinnotherid crab Austinixa aidae is described and illustrated based on laboratory-hatched material from ovigerous females collected from the upper burrows of the thalassinidean shrimp Callichirus major at Ubatuba, São Paulo, Brazil. The zoeae of Austinixa species can be distinguished from other pinnotherids and especially from zoeae of the closely related species of Pinnixa by the telson structure.FLM is grateful to CNPq for a research fellowship (Proc. 301359/2007-210 5).Peer reviewe

    New approach to the visualization of international scientific collaboration

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    Chinchilla-Rodríguez, Z., Vargas-Quesada, B., Hassan-Montero, Y., González-Molina, A., Moya-Anegón, F. New approach to the visualization of international scientific collaboration. Information Visualization, 9 (4): 277-287, Winter 2010. DOI: 10.1057/ivs.2009.31In this study, visual representations are created in order to analyze different aspects of scientific collaboration at the international level. The main objective is to identify the international facet of research by following the flow of knowledge as expressed by the number of scientific publications, and then establishes the main geographical axes of output, showing the interrelationships of the domain, the intensity of these relations, and how the different types of collaboration are reflected in terms of visibility. Thus, the methodology has a twofold application, allowing us to detect significant differences that help characterize patterns of behaviour of a geographical system of output, along with the generation of representations that serve as interfaces for domain analysis and information retrieval.Peer reviewe

    Field theoretic approach to the counting problem of Hamiltonian cycles of graphs

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    A Hamiltonian cycle of a graph is a closed path that visits each site once and only once. I study a field theoretic representation for the number of Hamiltonian cycles for arbitrary graphs. By integrating out quadratic fluctuations around the saddle point, one obtains an estimate for the number which reflects characteristics of graphs well. The accuracy of the estimate is verified by applying it to 2d square lattices with various boundary conditions. This is the first example of extracting meaningful information from the quadratic approximation to the field theory representation.Comment: 5 pages, 3 figures, uses epsf.sty. Estimates for the site entropy and the gamma exponent indicated explicitl
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