3,847 research outputs found

    “The historical triumph in Sicily” The Artistic Legacy of William Ogilivie

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    Efficient electrocatalytic water oxidation at neutral and high pH by adventitious nickel at nanomolar concentrations

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    Electrolytic water oxidation using earth-abundant elements is a key challenge in the quest to develop cheap, large surface area arrays for solar-to-hydrogen conversion. There have been numerous studies in this area in recent years, but there remains an imperative to demonstrate that the current densities reported are indeed due to the species under consideration and not due to the presence of adventitious (yet possibly highly active) contaminants at low levels. Herein, we show that adventitious nickel at concentrations as low as 17 nM can act as a water oxidation catalyst in mildly basic aqueous solutions, achieving stable (tens of hours) current densities of 1 mA cm–2 at overpotentials as low as 540 mV at pH 9.2 and 400 mV at pH 13. This nickel was not added to the electrolysis baths deliberately, but it was found to be present in the electrolytes as an impurity by ICP-MS. The presence of nickel on anodes from extended-time bulk electrolysis experiments was confirmed by XPS. In showing that such low levels of nickel can perform water oxidation at overpotentials comparable to many recently reported water oxidation catalysts, this work serves to raise the burden of proof required of new materials in this field: contamination by adventitious metal ions at trace loadings must be excluded as a possible cause of any observed water oxidation activity

    Kinematic artifacts in prestack depth migration.

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    Strong refraction of waves in the migration velocity model introduces kinematic artifacts¿coherent events not corresponding to actual reflectors¿into the image volumes produced by prestack depth migration applied to individual data bins. Because individual bins are migrated independently, the migration has no access to the bin component of slowness. This loss of slowness information permits events to migrate along multiple incident-reflected ray pairs, thus introducing spurious coherent events into the image volume. This pathology occurs for all common binning strategies, including common-source, common-offset, and common-scattering angle. Since the artifacts move out with bin parameter, their effect on the final stacked image is minimal, provided that the migration velocity model is kinematically correct. However, common-image gathers may exhibit energetic primary events with substantial residual moveout, even with the kinematically accurate migration velocity model

    First row transition metal catalysts for solar-driven water oxidation produced by electrodeposition

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    As our reliance on renewable energy resources increases, so will our need to store this energy in the form of chemical fuels to iron-out peaks and troughs in supply. Sunlight, the most plentiful source of renewable energy, is especially problematic in this regard as it is so diffuse. One way to convert solar irradiation to fuels effectively would be to develop large surface area photo-electrochemical devices that could use sunlight directly to split water into H2 and O2. However, in order to be feasible, such an approach requires that these devices (and their components) are extremely cheap. In this review, we will discuss catalysts for the water oxidation half-reaction of electrochemical water splitting that can be produced by electrodeposition (a technique well suited to large-scale, low-cost applications), and that are based on the comparatively plentiful and inexpensive first row transition metals. Special attention will be paid to the electrodeposition conditions used in the various examples given, and structure-function relationships for electrochemical water oxidation for the materials produced by these techniques will be elucidated

    CAMMUAZA, or the ceremony used at the Induction of a Birman into the Order of Priesthood, called Phonghi, or Rhahaan (1795) by Michael Symes, edited by Michael W. Charney

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    This account of the induction ceremony for Buddhist monks was included as Appendix V in Michael Symes, An Acount of an Embassy to the Kingdom of Ava, Sent by the Governor-General of India in the Year 1795 (London: W. Bulmer & Co., 496-500). Symes, then a major in the 76th Regiment, made numerous valuable observations on Burmese culture, society, government, and history. While it is clear that he did consult the accounts of other visitors to Burma, most of his material was derived from first-hand observation or from material provided by Burmese acquaintances, and the following account was likely derived from the latter

    Probing the effects of steric bulk on the solution-phase behaviour and redox chemistry of cobalt-diimine complexes

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    Cobalt-diimine complexes are important structural and redox-active elements in supramolecular assemblies. However, functionalisation of the diimine ligand adjacent to the N-donor atoms can affect dramatically the types of Co-diimine complexes that can form and their redox activity. Herein, we compare the solution phase and redox chemistry of Co(II) complexes with 1,10-phenanthroline, 5,5′-dimethyl-2,2′-bipyridine and 2,9-dimethyl-1,10-phenanthroline (neocuproine). In acetonitrile solutions containing Co(NO3)2 and neocuproine, the dominant species is the mono-diimine complex [Co(neocuproine)(NO3)(CH3CN)2]+. This complex cannot be oxidised, either electrochemically nor with iodine. We rationalise this behaviour by considering the steric constraints placed upon the metal centre by the bulky methyl substituents on the neocuproine ligand. Furthermore, from solutions of [Co(neocuproine)(NO3)(CH3CN)2]+, crystals of formula [Co(neocuproine)2(NO3)]+·[Co(neocuproine)(NO3)3]− can be obtained. We believe that this work will guide the development of Co-diimine supramolecular assemblies by highlighting the extent to which substituents close to the N-donor atoms affect which species form in solution, and their likely redox activity

    An economic assessment of a proposed dry land Leucaena development within the Brigalow Belt of Central Queensland: An operational case study perspective

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    This following case study focuses on beef production using dry land leucaena to increase production on a property of alluvial scrub flats south of Biloela, Queensland. The investment proposal is for development of the property through the growing of the fodder legume tree crop leucaena. The benefit of finishing cattle on leucaena is estimated using partial budgeting techniques. The case study reports on aspects of agronomic, managerial, production and economic considerations for 174 hectares of dry land leucaena development, staged over four years. A discounted cash flow approach was applied in order to model expected returns over time. Net cash flows between the existing grass based operation and the proposed leucaena supplemented operation are estimated. Comparison between grass only and leucaena supplemented gross margins provide the marginal benefit from developing leucaena. These future cash flows were discounted to assign their present values. Productive capacity estimates were used in the analysis. Expected yields and weight gain from grass fed operations were available from detailed management records. However, given the lack of scientifically verified data on expected leucaena production across land types, production estimates were based on localised production results and sourced from technical extension experts. The use of adult equivalents and accounting for the opportunity cost of maintaining particular herd structures allows for direct comparison of gross margins across different land types and herd structures. By choosing to plant leucaena, the owner is $144,939 better off, achieves a 22% internal rate of return, a benefit-cost ratio of 3.2:1, and breaks even on the investment in seven years.Production Economics,

    Russell Square: a lifelong resource for teaching and learning

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    A quarter of a century ago, in 1978, Birkbeck College’s Faculty of Continuing Education (FCE, then the Department for Extra-Mural Studies of the federal University) moved to the offices that it now occupies in numbers 26 and 25 Russell Square. Then, as now, FCE was the one of the largest and most active extra-mural departments of any British university, with an enormous range of courses covering virtually every subject taught in ‘internal’ university departments and many more besides 1. Some of these courses have, from time to time, used Russell Square as a learning resource. Many more staff and students alike have (along with thousands of local workers, tourists and residents) used the square’s gardens for relaxation and recovery, without reflecting on its origins or present significance. This Occasional Paper examines the past and present fabric of Russell Square (‘the Square’) as a resource for teaching and learning. It is a composite narrative assembled by FCE staff whose disciplines range from nature conservation through garden history and architectural history to social policy. It deconstructs the Square as an entity and attempts to decipher some of its ‘meanings’ that provide links between subjects taught within FCE. We hope that it will stimulate discussion about the way this single ‘place’ – our Square - can be ‘seen’ or interpreted in different ways for diverse purposes, and about the way that it can be used as a resource for teaching and learning across disciplines
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