37 research outputs found

    Inference of population structure using multilocus genotype data: dominant markers and null alleles

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    Dominant markers such as amplified fragment length polymorphisms (AFLPs) provide an economical way of surveying variation at many loci. However, the uncertainty about the underlying genotypes presents a problem for statistical analysis. Similarly, the presence of null alleles and the limitations of genotype calling in polyploids mean that many conventional analysis methods are invalid for many organisms. Here we present a simple approach for accounting for genotypic ambiguity in studies of population structure and apply it to AFLP data from whitefish. The approach is implemented in the program structure version 2.2, which is available from http://pritch.bsd.uchicago.edu/structure.html

    Prion Switching in Response to Environmental Stress

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    Evolution depends on the manner in which genetic variation is translated into new phenotypes. There has been much debate about whether organisms might have specific mechanisms for “evolvability,” which would generate heritable phenotypic variation with adaptive value and could act to enhance the rate of evolution. Capacitor systems, which allow the accumulation of cryptic genetic variation and release it under stressful conditions, might provide such a mechanism. In yeast, the prion [PSI+] exposes a large array of previously hidden genetic variation, and the phenotypes it thereby produces are advantageous roughly 25% of the time. The notion that [PSI+] is a mechanism for evolvability would be strengthened if the frequency of its appearance increased with stress. That is, a system that mediates even the haphazard appearance of new phenotypes, which have a reasonable chance of adaptive value would be beneficial if it were deployed at times when the organism is not well adapted to its environment. In an unbiased, high-throughput, genome-wide screen for factors that modify the frequency of [PSI+] induction, signal transducers and stress response genes were particularly prominent. Furthermore, prion induction increased by as much as 60-fold when cells were exposed to various stressful conditions, such as oxidative stress (H2O2) or high salt concentrations. The severity of stress and the frequency of [PSI+] induction were highly correlated. These findings support the hypothesis that [PSI+] is a mechanism to increase survival in fluctuating environments and might function as a capacitor to promote evolvability

    A self-crosslinking monomer, ?-pinene methacrylate: understanding and exploiting hydrogen abstraction

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    Crosslinking is a valuable route to creating new polymeric materials and normally involves introduction of a cross linker or some form of secondary processing. Here we report the discovery and analysis of a self-crosslinking sustainable terpene derived monomer, ?-pinene methacrylate (?PMA). This monomer undergoes crosslinking during free radical homopolymerisation and with comonomers e.g. methyl methacrylate (MMA). ?PMA does not appear to contain any obvious functionality that would induce crosslinking such as vinyl bonds, but we postulate that it may undergo a fortuitous abstraction of a hydrogen atom from the pendant group. A combined computational (DFT) and experimental approach has been applied to investigate this. Further, we used DFT analysis to predict the behaviour of a related monomer, beta-pinene methacrylate (?PMA). To the best of our knowledge this is the first-time that self-crosslinking has been observed in free radical polymerisation of methacrylates via chain transfer through hydrogen abstraction from a pendant group. We have exploited this crosslinking to generate new, renewable poly high internal phase emulsions (polyHIPEs) that could rival those derived from fossil-based styrene- polyHIPEs and we have done this in a process which does not require any additional cross-linking agent

    Localization, outsourcing, and supplier networks in Taiwan\u27s machine tool industry

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    It has been argued that Taiwan\u27s small and medium sized companies represent the real engine behind the island\u27s remarkable economic growth. As an internationally successful industry comprised mostly of small and medium sized firms, Taiwan\u27s machine tool industry is an interesting example of how such growth has been achieved. This dissertation looks at a number of factors, including localization, outsourcing, and supplier networks, to better understand the industry\u27s development. To do so, this thesis has drawn on a number of different sources, including data from Taiwan\u27s Ministry of Economic Affairs and the island\u27s machine tool trade association, the results of a mail survey, company interviews, annual reports, and the work of scholars both in Taiwan and elsewhere. This dissertation finds Taiwan\u27s machine tool makers located in and around Taichung (a city in central Taiwan) constitute a multi-centered industrial district of locally owned, specialized companies. Moreover, that clustering, in concert with active and articulated supplier networks, seems to have helped improve firm performance and promote innovation. This dissertation has also assembled a substantial amount of information on the structure of supplier networks in Taiwan\u27s machine tool industry. In so doing, it has revealed that firms in the industry engage in a high level of outsourcing and that there exist a number of different network configurations, including star, ring, tiered, and multi-centered networks. Factors that appear to influence the structure of supplier networks include location, product attributes, scale economies, the competitive and developmental environment of the supply base, bargaining strength, and interfirm trust

    Three views of China’s economic future

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    Globalization and competitive advantage

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    Localization, outsourcing, and supplier networks in Taiwan\u27s machine tool industry

    No full text
    It has been argued that Taiwan\u27s small and medium sized companies represent the real engine behind the island\u27s remarkable economic growth. As an internationally successful industry comprised mostly of small and medium sized firms, Taiwan\u27s machine tool industry is an interesting example of how such growth has been achieved. This dissertation looks at a number of factors, including localization, outsourcing, and supplier networks, to better understand the industry\u27s development. To do so, this thesis has drawn on a number of different sources, including data from Taiwan\u27s Ministry of Economic Affairs and the island\u27s machine tool trade association, the results of a mail survey, company interviews, annual reports, and the work of scholars both in Taiwan and elsewhere. This dissertation finds Taiwan\u27s machine tool makers located in and around Taichung (a city in central Taiwan) constitute a multi-centered industrial district of locally owned, specialized companies. Moreover, that clustering, in concert with active and articulated supplier networks, seems to have helped improve firm performance and promote innovation. This dissertation has also assembled a substantial amount of information on the structure of supplier networks in Taiwan\u27s machine tool industry. In so doing, it has revealed that firms in the industry engage in a high level of outsourcing and that there exist a number of different network configurations, including star, ring, tiered, and multi-centered networks. Factors that appear to influence the structure of supplier networks include location, product attributes, scale economies, the competitive and developmental environment of the supply base, bargaining strength, and interfirm trust
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