762 research outputs found

    Semantic browsing of digital collections

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    Visiting museums is an increasingly popular pastime. Studies have shown that visitors can draw on their museum experience, long after their visit, to learn new things in practical situations. Rather than viewing a visit as a single learning event, we are interested in ways of extending the experience to allow visitors to access online resources tailored to their interests. Museums typically have extensive archives that can be made available online, the challenge is to match these resources to the visitor’s interests and present them in a manner that facilitates exploration and engages the visitor. We propose the use of knowledge level resource descriptions to identify relevant resources and create structured presentations. A system that embodies this approach, which is in use in a UK museum, is presented and the applicability of the approach to the broader semantic web is discussed

    Spontaneous Water Oxidation at Hematite (α-Fe_2O_3) Crystal Faces

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    Hematite (α-Fe_2O_3) persists as a promising candidate for photoelectrochemical water splitting, but a slow oxygen evolution reaction (OER) at its surfaces remains a limitation. Here we extend a series of studies that examine pH-dependent surface potentials and electron-transfer properties of effectively perfect low-index crystal faces of hematite in contact with simple electrolyte. Zero-resistance amperometry (ZRA) was performed in a two electrode configuration to quantify spontaneous dark current between hematite crystal face pairs (001)/(012), (001)/(113), and (012)/(113) at pH 3. Exponentially decaying currents initially of up to 200 nA were reported between faces over 4 min experiments. Fourth-order ZRA kinetics indicated rate limitation by the OER for current that flows between (001)/(012) and (001)/(113) face pairs, with the (012) and (113) faces serving as the anodes when paired with (001). The cathodic partner reaction is reductive dissolution of the (001) face, converting surface Fe^(3+) to solubilized aqueous Fe^(2+), at a rate maintained by the OER at the anode. In contrast, OER rate limitation does not manifest for the (012)/(113) pair. The uniqueness of the (001) face is established in terms of a faster intrinsic ability to accept the protons required for the reductive dissolution reaction. OER rate limitation inversely may thus arise from sluggish kinetics of hematite surfaces to dispense with the protons that accompany the four-electron OER. The results are explained in terms of semiquantitative energy band diagrams. The finding may be useful as a consideration for tailoring the design of polycrystalline hematite photoanodes that present multiple terminations to the interface with electrolyte

    Travel to school and housing markets: a case study of Sheffield, England

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    How children travel to school is at the centre of a complex set of interrelated issues with significant policy implications. This paper reviews the relation of patterns of travel to school to concerns about public health, school choice, urban form, and residential housing markets. The spatial relations between pupils’ homes and the schools that they attend provides the basis of an analytical framework that links local neighbourhood characteristics, school performance, and house prices to the distance and mode of travel to school and the level of ‘excess commuting’ in the urban system. A unique analysis of several integrated micro-datasets from Sheffield, UK, suggests that, while there are high levels of excess commuting, there remains a complex interrelationship between housing and neighbourhood characteristics, school performance, and commuting patterns. There are differences between the pictures for primary schools and secondary schools. Policies aimed at promoting transport efficiency and those promoting school choice are likely to remain in tension

    Collaborative writing with young people with disabilities: raising new questions of authorship and agency

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    The process of communication between author and reader is a critical issue in examining any text. When considering the communication of ideas from young people whose voices are seldom heard, the journey from author to audience has particular significance. The construction of children and young people as ‘authors’ is important, especially for those with learning difficulties or who struggle to comply with the current emphasis on spelling, punctuation and grammar. This article relates to a UK Research-Council-funded three-year collaborative research project involving the co-creation of fictional stories with young people with disabilities to represent aspects of their lives. Drawing on frameworks from narratology, I analyse the co-creation of one of the stories, and present an interpretation and elaboration of the discourse structure of narrative fiction to illustrate the complexities of the relationship between the multi-faceted ‘author’ and community ‘reader’ of these stories. The combination of qualitative research and fictional prose has particular characteristics and implications for the dissemination and communication of research findings; while extending feminist critique of Barthes’ claim for the death of the author provides new insights for engaging children in writing with their own voice

    Complementarity of information sent via different bases

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    We discuss quantitatively the complementarity of information transmitted by a quantum system prepared in a basis state in one out of several different mutually unbiased bases (MUBs). We obtain upper bounds on the information available to a receiver who has no knowledge of which MUB was chosen by the sender. These upper bounds imply a complementarity of information encoded via different MUBs and ultimately ensure the security in quantum key distribution protocols.Comment: 9 pages, references adde

    Polarization and Belief Dynamics in the Black and White Communities: An Agent-Based Network Model from the Data

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    Public health care interventions—regarding vaccination, obesity, and HIV, for example—standardly take the form of information dissemination across a community. But information networks can vary importantly between different ethnic communities, as can levels of trust in information from different sources. We use data from the Greater Pittsburgh Random Household Health Survey to construct models of information networks for White and Black communities--models which reflect the degree of information contact between individuals, with degrees of trust in information from various sources correlated with positions in that social network. With simple assumptions regarding belief change and social reinforcement, we use those modeled networks to build dynamic agent-based models of how information can be expected to flow and how beliefs can be expected to change across each community. With contrasting information from governmental and religious sources, the results show importantly different dynamic patterns of belief polarization within the two communities

    Methods for comparing the performance of energy-conversion systems for use in solar fuels and solar electricity generation

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    The energy-conversion efficiency is a key metric that facilitates comparison of the performance of various approaches to solar energy conversion. However, a suite of disparate methodologies has been proposed and used historically to evaluate the efficiency of systems that produce fuels, either directly or indirectly, with sunlight and/or electrical power as the system inputs. A general expression for the system efficiency is given as the ratio of the total output power (electrical plus chemical) divided by the total input power (electrical plus solar). The solar-to-hydrogen (STH) efficiency follows from this globally applicable system efficiency but only is applicable in the special case for systems in which the only input power is sunlight and the only output power is in the form of hydrogen fuel derived from solar-driven water splitting. Herein, system-level efficiencies, beyond the STH efficiency, as well as component-level figures of merit are defined and discussed to describe the relative energy-conversion performance of key photoactive components of complete systems. These figures of merit facilitate the comparison of electrode materials and interfaces without conflating their fundamental properties with the engineering of the cell setup. The resulting information about the components can then be used in conjunction with a graphical circuit analysis formalism to obtain “optimal” system efficiencies that can be compared between various approaches. The approach provides a consistent method for comparison of the performance at the system and component levels of various technologies that produce fuels and/or electricity from sunlight
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