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Crystal structure of quenched and in-field electroluminescent phosphors
- G. R. Fern, T. Ireland, P. Harris, J. Silver, R. Withnall, A. Salimian, P. K. Santra, M. Leoni, A. Erko, A. Lennie, C. C. Tang
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- Journal:
- Diamond Light Source Proceedings / Volume 1 / Issue SRMS-7 / October 2010
- Published online by Cambridge University Press:
- 30 September 2010, e106
- Print publication:
- October 2010
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Electroluminescent zinc sulfide doped with copper and chloride (ZnS:Cu, Cl) powder was heated to 400°C and rapidly quenched to room temperature. Comparison between the quenched and non-quenched phosphors using synchrotron radiation X-ray powder diffraction (XRPD) (λ = 0.828692 Å) and X-ray absorption spectroscopy (XAS) was made. XRPD shows that the expected highly faulted structure is observed with excellent resolution out to 150° 2θ (or to (12 2 2) of the sphalerite phase). The quenched sample compared to the unheated sample shows a large change in peak ratios between 46.7° and 46.9°, which is thought to correspond to the wurtzite (0 0 6), (0 3 2) and sphalerite (3 3 3)/(5 1 1) peaks. Hence, a large proportion of this sphalerite diffraction is lost from the material upon rapid quenching, but not when the material is allowed to cool slowly. The Zn K-edge XAS data indicate that the crystalline structures are indistinguishable using this technique, but do give an indication that the electronic structure has altered due to changing intensity of the white line. It is noted that the blue electroluminescence (EL) emission bands are lost upon quenching: however, a large amount of total EL emission intensity is also removed, which is consistent with our findings. We report the XRPD of a working alternating-current electroluminescence device in the synchrotron X-ray beam, which exhibits a new diffraction pattern when the device is powered in an AC field even though the phosphor is fixed in the binder. Significantly, only a few crystals are required to yield the diffraction data because of the high flux X-ray source. These in panel data show multiple sharp diffraction lines spread out under the region, where capillary data show broad diffraction intensity indicating that the phosphor powder is comprised of unique crystals, each having different structures.
Inflammatory Disease Processes and Interactions with Nutrition
- P. C. Calder, R. Albers, J.-M. Antoine, S. Blum, R. Bourdet-Sicard, G. A. Ferns, G. Folkerts, P. S. Friedmann, G. S. Frost, F. Guarner, M. Løvik, S. Macfarlane, P. D. Meyer, L. M'Rabet, M. Serafini, W. van Eden, J. van Loo, W. Vas Dias, S. Vidry, B. M. Winklhofer-Roob, J. Zhao
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- Journal:
- British Journal of Nutrition / Volume 101 / Issue S1 / May 2009
- Published online by Cambridge University Press:
- 01 May 2009, pp. 1-45
- Print publication:
- May 2009
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Inflammation is a stereotypical physiological response to infections and tissue injury; it initiates pathogen killing as well as tissue repair processes and helps to restore homeostasis at infected or damaged sites. Acute inflammatory reactions are usually self-limiting and resolve rapidly, due to the involvement of negative feedback mechanisms. Thus, regulated inflammatory responses are essential to remain healthy and maintain homeostasis. However, inflammatory responses that fail to regulate themselves can become chronic and contribute to the perpetuation and progression of disease. Characteristics typical of chronic inflammatory responses underlying the pathophysiology of several disorders include loss of barrier function, responsiveness to a normally benign stimulus, infiltration of inflammatory cells into compartments where they are not normally found in such high numbers, and overproduction of oxidants, cytokines, chemokines, eicosanoids and matrix metalloproteinases. The levels of these mediators amplify the inflammatory response, are destructive and contribute to the clinical symptoms. Various dietary components including long chain ω-3 fatty acids, antioxidant vitamins, plant flavonoids, prebiotics and probiotics have the potential to modulate predisposition to chronic inflammatory conditions and may have a role in their therapy. These components act through a variety of mechanisms including decreasing inflammatory mediator production through effects on cell signaling and gene expression (ω-3 fatty acids, vitamin E, plant flavonoids), reducing the production of damaging oxidants (vitamin E and other antioxidants), and promoting gut barrier function and anti-inflammatory responses (prebiotics and probiotics). However, in general really strong evidence of benefit to human health through anti-inflammatory actions is lacking for most of these dietary components. Thus, further studies addressing efficacy in humans linked to studies providing greater understanding of the mechanisms of action involved are required.
Nutrition and inflammatory processes
- P. C. Calder, R. Albers, J.-M. Antoine, S. Blum, R. Bourdet-Sicard, G. A. Ferns, G. Folkerts, P. S. Friedmann, G. S. Frost, F. Guarner, M. Løvik, S. Macfarlane, P. D. Meyer, L. M'Rabet, M. Serafini, W. van Eden, J. van Loo, W. vas Dias, S. Vidry, B. M. Winklhofer-Roob, J. Zhao
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- Journal:
- Proceedings of the Nutrition Society / Volume 67 / Issue OCE1 / May 2008
- Published online by Cambridge University Press:
- 12 May 2008, E9
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Intake rates and the functional response in shorebirds (Charadriiformes) eating macro-invertebrates
- John D. Goss-Custard, Andrew D. West, Michael G. Yates, Richard W. G. Caldow, Richard A. Stillman, Louise Bardsley, Juan Castilla, Macarena Castro, Volker Dierschke, Sarah. E. A. Le. V. dit Durell, Goetz Eichhorn, Bruno J. Ens, Klaus-Michael Exo, P. U. Udayangani-Fernando, Peter N. Ferns, Philip A. R. Hockey, Jennifer A. Gill, Ian Johnstone, Bozena Kalejta-Summers, Jose A. Masero, Francisco Moreira, Rajarathina Velu Nagarajan, Ian P. F. Owens, Cristian Pacheco, Alejandro Perez-Hurtado, Danny Rogers, Gregor Scheiffarth, Humphrey Sitters, William J. Sutherland, Patrick Triplet, Dave H. Worrall1, Yuri Zharikov, Leo Zwarts, Richard A. Pettifor
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- Journal:
- Biological Reviews / Volume 81 / Issue 4 / November 2006
- Published online by Cambridge University Press:
- 24 July 2006, pp. 501-529
- Print publication:
- November 2006
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As field determinations take much effort, it would be useful to be able to predict easily the coefficients describing the functional response of free-living predators, the function relating food intake rate to the abundance of food organisms in the environment. As a means easily to parameterise an individual-based model of shorebird Charadriiformes populations, we attempted this for shorebirds eating macro-invertebrates. Intake rate is measured as the ash-free dry mass (AFDM) per second of active foraging; i.e. excluding time spent on digestive pauses and other activities, such as preening. The present and previous studies show that the general shape of the functional response in shorebirds eating approximately the same size of prey across the full range of prey density is a decelerating rise to a plateau, thus approximating the Holling type II (‘disc equation’) formulation. But field studies confirmed that the asymptote was not set by handling time, as assumed by the disc equation, because only about half the foraging time was spent in successfully or unsuccessfully attacking and handling prey, the rest being devoted to searching.
A review of 30 functional responses showed that intake rate in free-living shorebirds varied independently of prey density over a wide range, with the asymptote being reached at very low prey densities (<150/m−2). Accordingly, most of the many studies of shorebird intake rate have probably been conducted at or near the asymptote of the functional response, suggesting that equations that predict intake rate should also predict the asymptote.
A multivariate analysis of 468 ‘spot’ estimates of intake rates from 26 shorebirds identified ten variables, representing prey and shorebird characteristics, that accounted for 81% of the variance in logarithm-transformed intake rate. But four-variables accounted for almost as much (77.3%), these being bird size, prey size, whether the bird was an oystercatcher Haematopus ostralegus eating mussels Mytilus edulis, or breeding. The four variable equation under-predicted, on average, the observed 30 estimates of the asymptote by 11.6%, but this discrepancy was reduced to 0.2% when two suspect estimates from one early study in the 1960s were removed. The equation therefore predicted the observed asymptote very successfully in 93% of cases.
We conclude that the asymptote can be reliably predicted from just four easily measured variables. Indeed, if the birds are not breeding and are not oystercatchers eating mussels, reliable predictions can be obtained using just two variables, bird and prey sizes. A multivariate analysis of 23 estimates of the half-asymptote constant suggested they were smaller when prey were small but greater when the birds were large, especially in oystercatchers. The resulting equation could be used to predict the half-asymptote constant, but its predictive power has yet to be tested.
As well as predicting the asymptote of the functional response, the equations will enable research workers engaged in many areas of shorebird ecology and behaviour to estimate intake rate without the need for conventional time-consuming field studies, including species for which it has not yet proved possible to measure intake rate in the field.