http://hdl.handle.net/2173/31632 Wed, 19 Jun 2013 17:38:26 GMT 2013-06-19T17:38:26Z http://hdl.handle.net/2173/87462 Title: Antioxidant capacity of novel amine derivatives of buckminsterfullerene: determination of inhibition rate constants in a model oxidation system Authors: Allen, Norman S.; Zeynalov, Eldar B.; Taylor, Kimberley; Birkett, Paul R. Abstract: The radical scavenging efficiency of fullerenes can be significantly activated by means of a connection with hydrogen donating groups of antioxidants such as phenolic, amine and sulfhydryl. The developed system of conjugated σ–π bonds arranged in the fullerene molecule in a closed shape can promote a strong resonance effect on the grafted units and increase the hydrogen atom abstraction efficiency. In this case the known ability of fullerene to trap alkyl radicals might be combined with the strong chain breaking functionality to afford a new class of antioxidants with bimodal action. Explorations in the field of fullerene derivatives on their antioxidant performance provide novel information on the potential stabilization properties of this type of molecular structure. A series of amine derivatives of buckminsterfullerene (C60) with tethered aliphatic chain, cycloaliphatic and aromatic fragments were synthesized and their antioxidant activity was determined. The antioxidant activity of the investigated derivatives was studied by measuring the inhibition rate constants for their reaction with alkyl and peroxy radicals in a model cumene initiated (2,2′-azobisisobutyronitrile, AIBN) oxidation experiments and compared to that recorded under identical experiments for buckminsterfullerene itself and commercial primary aromatic amine stabilizers. The results indicate that linking the amine moieties groups directly to the fullerene core gives rise to a new chain breaking antioxidant mode for the buckminsterfullerene while cyclic fragments containing the same but distant amine group do not reveal this ability. The inhibition rate constants for trapping of peroxy radicals by the amine derivatives were found to be higher than that of known aromatic amine antioxidants Neozone-D and Naugard 445. In addition the C60 part of these molecules acts synergistically by trapping alkyl radicals with inhibition rate constants which exceed that of underivatised fullerene. The amine derivative containing sterically hindered piperidine and pyrrolidine fragments also heighten the inherent rate constant of buckminsterfullerene for scavenging alkyl radicals due to the additional antioxidant contribution promoted by the radical-quenching ability of the formed nitroxyl intermediates. These novel C60–amine conjugates may be considered as promising molecules for broad-spectrum radical scavenging antioxidants. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Polymer Degradation and Stability, published by and copyright Elsevier. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2173/87462 2009-01-01T00:00:00Z http://hdl.handle.net/2173/85059 Title: Parametric modelling of magnetic fine particle systems: the role of single domain particle size distributions and magnetic anisotropy Authors: Hoon, Steve R.; Lambrick, David B. Abstract: We demonstrate the effects and role of anisotropy and particle size distributions upon the values of constitutive parameters determined from experimental M(H) loops of single domain nanoparticle systems. We employ experimental and magnetic material parameters as inputs to a numerical programme run from a graphical user interface (GUI) to permit modelling and interpretation of experimental data and assessment of the stability of the constitutive parameters so derived and characterisation of the departures observed from pure Langevin behaviour. Description: Full-text of this article is available at http://www.iop.org/EJ/article/-search=66921671.5/1742-6596/17/1/001/jpconf5_17_001.pdf?request-id=5f83bda9-3b09-40ce-93d2-14a9ee0cadbe Sat, 01 Jan 2005 00:00:00 GMT http://hdl.handle.net/2173/85059 2005-01-01T00:00:00Z http://hdl.handle.net/2173/85058 Title: Geochemical and mineral magnetic characterisation of urban sediment particulates, Manchester, UK Authors: Robertson, D. J.; Taylor, Kevin G.; Hoon, Steve R. Abstract: Urban sediments are part of a complex system in which particulates accumulate potentially toxic pollutants, ultimately posing a threat to urban water-bodies and public health. It is therefore important to recognise sources, signatures and pathways of urban particulates. Urban sediment samples were analysed from both inner and outer city road surfaces of Manchester, UK. High metal concentrations, coupled with the largely ferrimagnetic multi-domain (MD) mineral magnetic composition of the particulates, indicate inputs of anthropogenic origin, primarily particulates derived from automobiles, as being the dominant source to the urban sediment system. Iron and Pb concentrations show a clear spatial trend, whereby concentrations are enhanced in the inner city samples. Lead concentrations for inner and outer city samples average 354 and 185 μg g−1, respectively. Iron concentrations for inner and outer city samples average 11302 and 6486 μg g−1, respectively. Sequential extraction analysis shows the metals Mn, Fe, Zn and Pb are largely associated with the reducible fraction, whereas Cu is largely associated with the oxidisable fraction. Zinc is the only metal showing significant association with the exchangeable fraction (up to 33%), suggesting that it may be the most susceptible metal to mobilisation during runoff. Metal fractions identified as showing larger associations with the reducible and oxidisable fractions will continue to be vulnerable to mobilisation as a result of changes in ambient pH and/or redox conditions. Mineral magnetic concentration parameters, such as the saturation isothermal remanent magnetisation (SIRM), together with hysteresis parameters such as the coercive force and interparametric ratios (such as (Bo)cr/Hc and IRM-100mT/SIRM) show that ferrimagnetic MD minerals dominate the Manchester urban sediments. Average results for frequency-dependent susceptibility as a percentage (2%) suggest that the composition of these Manchester sediments is not dominated by soil-derived material, and therefore magnetically coarser, anthropogenically-derived material is dominant. Unlike Pb and Fe concentrations, mineral magnetic characteristics of the Manchester urban sediment samples exhibit no significant spatial variation. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Applied Geochemistry, published by and copyright Pergamon. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/2173/85058 2003-01-01T00:00:00Z http://hdl.handle.net/2173/85077 Title: On magnetic properties of DyNi5−xAlx (x=0, 1, 1.5, 2, 2.5, 3) intermetallics Authors: Lambrick, David B.; Blažina, Z.; Hoon, Steve R. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Journal of Materials Science Letters, published by and copyright Kluwer. Tue, 01 Jan 2002 00:00:00 GMT http://hdl.handle.net/2173/85077 2002-01-01T00:00:00Z