42,672 research outputs found

    Fungal community survey of Fraxinus excelior in New Zealand

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    The European Ash tree (Fraxinus excelsior) is widely grown throughout Europe. As a large deciduous tree species, it grows a tall, domed crown and has an attractive tree shape, so it is considered as a popular amenity tree species. European Ash is planted as an important forestry species in some European countries, and also often used for furniture making, due to its excellent wood quality. Ash species were introduced into New Zealand upon colonization in the 1800s. Recently, ash trees throughout Europe have been observed to become damaged or die due to a severe disease known as ash dieback, caused by the fungus Chalara fraxinea. We are concerned about what will happen to the introduced ash tree in New Zealand. To our knowledge, there have been no studies on the fungi that inhabit ash trees in New Zealand. It is unknown which fungal species were present in ash at the time of the introduction to New Zealand, or which New Zealand fungi colonized ash tree after the introduction. Currently, ash dieback is not believed to be present in New Zealand. The aim of this project was to determine the possible fungal communities on ash trees in New Zealand. We collected bark, bud and wood from three healthy ash trees, and used DNA-based methods to identify the fungi that inhabited these trees. We compared our study with a similar Swedish study to find differences and similarities in the fungi present on New Zealand and European ash trees. In total, we found 90 different fungal species. Of these species found, seven fungi could be species that came to New Zealand with the introduced ash tree. We also found one fungus that could possibly be said to have come from New Zealand. The pathogen causing ash dieback, Chalara fraxinea, was not detected

    Ion-mediated RNA structural collapse: effect of spatial confinement

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    RNAs are negatively charged molecules residing in macromolecular crowding cellular environments. Macromolecular confinement can influence the ion effects in RNA folding. In this work, using the recently developed tightly bound ion model for ion fluctuation and correlation, we investigate the confinement effect on the ion-mediated RNA structural collapse for a simple model system. We found that, for both Na+^+ and Mg2+^{2+}, ion efficiencies in mediating structural collapse/folding are significantly enhanced by the structural confinement. Such an enhancement in the ion efficiency is attributed to the decreased electrostatic free energy difference between the compact conformation ensemble and the (restricted) extended conformation ensemble due to the spatial restriction.Comment: 22 pages, 5 figure

    Socially Trusted Collaborative Edge Computing in Ultra Dense Networks

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    Small cell base stations (SBSs) endowed with cloud-like computing capabilities are considered as a key enabler of edge computing (EC), which provides ultra-low latency and location-awareness for a variety of emerging mobile applications and the Internet of Things. However, due to the limited computation resources of an individual SBS, providing computation services of high quality to its users faces significant challenges when it is overloaded with an excessive amount of computation workload. In this paper, we propose collaborative edge computing among SBSs by forming SBS coalitions to share computation resources with each other, thereby accommodating more computation workload in the edge system and reducing reliance on the remote cloud. A novel SBS coalition formation algorithm is developed based on the coalitional game theory to cope with various new challenges in small-cell-based edge systems, including the co-provisioning of radio access and computing services, cooperation incentives, and potential security risks. To address these challenges, the proposed method (1) allows collaboration at both the user-SBS association stage and the SBS peer offloading stage by exploiting the ultra dense deployment of SBSs, (2) develops a payment-based incentive mechanism that implements proportionally fair utility division to form stable SBS coalitions, and (3) builds a social trust network for managing security risks among SBSs due to collaboration. Systematic simulations in practical scenarios are carried out to evaluate the efficacy and performance of the proposed method, which shows that tremendous edge computing performance improvement can be achieved.Comment: arXiv admin note: text overlap with arXiv:1010.4501 by other author