670 research outputs found

    The annual course of precipitation over much of the United States: observed versus GCM simulation

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    General Circulation Models (GCMs) may be useful in estimating the ecological impacts of global climatic change. We analyzed seasonal weather patterns over the conterminous United States and determined that regional patterns of rainfall seasonality appear to control the distributions of the Nation's major biomes. These regional patterns were compared to the output from three GCMs for validation. The models appear to simulate the appropriate seasonal climates in the northern tier of states. However, the spatial extent of these regions is distorted. None of the models accurately portrayed rainfall seasonalities in the southern tier of states, where biomes are primarily influenced by the Bermuda High

    Bio-Hydrogen Production from Wastewater: A Comparative Study of Low Energy Intensive Production Processes

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    Billions of litres of wastewater are produced daily from domestic and industrial areas, and whilst wastewater is often perceived as a problem, it has the potential to be viewed as a rich source for resources and energy. Wastewater contains between four and five times more energy than is required to treat it, and is a potential source of bio-hydrogen—a clean energy vector, a feedstock chemical and a fuel, widely recognised to have a role in the decarbonisation of the future energy system. This paper investigates sustainable, low-energy intensive routes for hydrogen production from wastewater, critically analysing five technologies, namely photo-fermentation, dark fermentation, photocatalysis, microbial photo electrochemical processes and microbial electrolysis cells (MECs). The paper compares key parameters influencing H2 production yield, such as pH, temperature and reactor design, summarises the state of the art in each area, and highlights the scale-up technical challenges. In addition to H2 production, these processes can be used for partial wastewater remediation, providing at least 45% reduction in chemical oxygen demand (COD), and are suitable for integration into existing wastewater treatment plants. Key advancements in lab-based research are included, highlighting the potential for each technology to contribute to the development of clean energy. Whilst there have been efforts to scale dark fermentation, electro and photo chemical technologies are still at the early stages of development (Technology Readiness Levels below 4); therefore, pilot plants and demonstrators sited at wastewater treatment facilities are needed to assess commercial viability. As such, a multidisciplinary approach is needed to overcome the current barriers to implementation, integrating expertise in engineering, chemistry and microbiology with the commercial experience of both water and energy sectors. The review concludes by highlighting MECs as a promising technology, due to excellent system modularity, good hydrogen yield (3.6–7.9 L/L/d from synthetic wastewater) and the potential to remove up to 80% COD from influent streams

    A REVIEW OF 3D GIS FOR USE IN CREATING VIRTUAL HISTORIC DUBLIN

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    This paper illustrates how BIM integration with GIS is approached as part of the workflow in creating Virtual Historic Dublin. A design for a WEB based interactive 3D model of historic buildings and centres in Dublin City (Virtual Historic Dublin City) paralleling smart city initiates is now under construction and led by the National Monuments at the Office of Public Works in Ireland. The aim is to facilitate the conservation and maintenance of historic infrastructure and fabric and the dissemination of knowledge for education and cultural tourism using an extensive Historic Building Information Model. Remote sensing data is now processed with greater ease to create 3D intelligent models in Historic BIM. While the use of remote sensing, HBIM and game engine platforms are the main applications used at present, 3D GIS has potential to form part of the workflow for developing the Virtual Historic City. 2D GIS is now being replaced by 3D spatial data allowing more complex analysis to be carried out, 3D GIS can define and depict buildings, urban rural centres in relation to their geometry topological, semantic and visualisation properties. The addition of semantic attributes allows complex analysis and 3D spatial queries for modelling city and urban elements. This analysis includes fabric and structural elements of buildings, relief, vegetation, transportation, water bodies, city furniture and land use

    Current-Induced Entanglement of Nuclear Spins in Quantum Dots

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    We propose an entanglement mechanism of nuclear spins in quantum dots driven by the electric current accompanied by the spin flip. This situation is relevant to a leakage current in spin-blocked regions where electrons cannot be transported unless their spins are flipped. The current gradually increases the components of larger total spin of nuclei. This correlation among the nuclear spins markedly enhances the spin-flip rate of electrons and hence the leakage current. The enhancement of the current is observable when the residence time of electrons in the quantum dots is shorter than the dephasing time T*_2 of nuclear spins.Comment: 4 pages, 4 figure

    AN INITIAL DESIGN FRAMEWORK FOR VIRTUAL HISTORIC DUBLIN

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    As a single coherent model, the proposed Virtual Historic Dublin City will improve the current approaches for planning, conserving, presenting and interpreting cultural heritage buildings and their environments. The combination of digital recording, modelling and data management systems enable the interaction with complex, interlinked three-dimensional structures containing rich and diverse underlying data. End users can encompass architectural and engineering conservation, education and research, in addition to public engagement and cultural tourism. In this paper a digital design framework is presented, based on state of the art current approaches for recording, modelling and presenting Virtual Historic Dublin. The modelling sites and structures is based on remotely sensed survey data which is processed and modelled in Historic BIM or GIS allowing the addition of semantic attributes. Archiving and storage of both models and knowledge and information attributes requires open systems and server data base capable of handling vector and point cloud information in addition to other digital data. The dissemination and interaction with the models and attached knowledge attributions is based on combining game engine platforms, Historic BIM, Historic GIS and access to compatible storage and data base

    Responding to the crisis: are policies aimed at a strong indigenous industrial base a necessary condition for sustainable economic growth?

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    peer-reviewedWe examine whether a strong indigenous manufacturing base is a necessary condition for sustainable economic growth in the case of two small, open economies, Ireland and Sweden. Sweden has been impacted by the economic crisis to a lesser degree than Ireland; we explore (through a manufacturing activity lens) the reasons for the asymmetric impacts and ask if the nature of the shock is related to 'Economic Sovereignty' and to the type of industrial policy. We argue Sweden was less affected given that its indigenous firms control the highly export-focused and technology-based engineering sector whereas in Ireland high-technology sectors are controlled by foreign firms. In terms of policy implications, we suggest that industrial policy should aim for sustainable economic activity and growth such that industrial activity within the economy should be able to minimise the impact of asymmetric shocks such as the current global economic recession.ACCEPTEDpeer-reviewe

    Culturable Root Endophyte Communities are Shaped by Both Warming and Plant Host Identity in the Rocky Mountains, USA

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    Understanding the biogeographic patterns of root-associated fungi and their sensitivity to temperature may improve predictions of future changes in terrestrial biodiversity and associated ecosystem processes, but data are currently limited. Anticipating change will require combining observational data, which predict how climatic factors limit current species distributions, with direct manipulations of climate, which can isolate responses to specific climate variables. Root endophytes are common symbionts of plants, particularly in arctic and alpine environments, yet their responses to climate warming are not resolved. Here, we directly cultured endophytic fungi from roots collected along altitudinal gradients in replicated mountain watersheds and from a 27 y field warming experiment in the Rocky Mountains, USA, to improve understanding of climate impacts on fungal root endophytes. Fungal taxa that were common at high elevations declined most under climate warming, whereas low elevation dominants responded neutrally or increased with experimental warming. Altitudinal gradients in fungal communities were strongly specific to the plant host species. Specifically, Poa species had 25–60% greater fungal isolate abundance and 25–38% greater fungal diversity at high elevations than at low elevation sites. In contrast, Festuca thurberi had 64% lower fungal diversity on roots at high elevation than at low elevation. Our results help to improve understanding of the potential for climate change to alter plant-fungal interactions in mountain ecosystems

    Single quantum dot states measured by optical modulation spectroscopy

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    Using optical modulation spectroscopy, we report the direct observation of absorption lines from excitons localized in GaAs single quantum dot potentials. The data provide a measurement of the linewidth, resonance energy, and oscillator strength of the transitions, and show that states which decay primarily by nonradiative processes can be directly probed using this technique. The experiments establish this technique for the characterization of single quantum dot transitions, thereby complementing luminescence studies. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70527/2/APPLAB-75-19-2933-1.pd

    Demonstration of Universal Parametric Entangling Gates on a Multi-Qubit Lattice

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    We show that parametric coupling techniques can be used to generate selective entangling interactions for multi-qubit processors. By inducing coherent population exchange between adjacent qubits under frequency modulation, we implement a universal gateset for a linear array of four superconducting qubits. An average process fidelity of F=93%\mathcal{F}=93\% is estimated for three two-qubit gates via quantum process tomography. We establish the suitability of these techniques for computation by preparing a four-qubit maximally entangled state and comparing the estimated state fidelity against the expected performance of the individual entangling gates. In addition, we prepare an eight-qubit register in all possible bitstring permutations and monitor the fidelity of a two-qubit gate across one pair of these qubits. Across all such permutations, an average fidelity of F=91.6±2.6%\mathcal{F}=91.6\pm2.6\% is observed. These results thus offer a path to a scalable architecture with high selectivity and low crosstalk
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