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1.
T. L. Clemens L. J. Fraher J. L. H. O'Riordan C. J. Little A. Dale 《Chromatographia》1980,13(3):141-144
Summary A simple, reproducible method for the biological synthesis of tritiated 24,25-dihydroxycholecalciferol, 25,26-dihydroxycholecalciferol and 1,25-dihydroxycholecalciferol is described. Kidney homogenates from both vitamin D deficient and replete chicks were usedin vitro to generate these dihydroxylated metabolites using 25 (23,24-3H) hydroxycholecalciferol as the substrate. Tritiated products were purified by Sephadex LH 20 chromatography followed by high-performance liquid chromatography; the identity of each metabolite was established by chromatography with authentic crystalline preparations.Presented at the Symposium organised by the Chromatography Discussion Group, held at Hatfield Lodge on 29 November 1979. 相似文献
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We consider first the initial-boundary value problem for the parabolic equation
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The development of glucose diagnostic devices with low detection limits is of key importance in diabetes-related research. New highly sensitive sensors are required for non-invasive detection of glucose in bodily fluids, other than blood, and an electrochemical sensor based on a single gold nanowire for rapid, reliable and quantitative detection of low glucose concentrations (10 μM-1 mM), is presented in this paper. Single gold nanowire devices are fabricated at silicon chip substrates using a hybrid electron beam-photolithography approach. Critical dimensions of the nanowires are characterised using a combination of scanning electron and atomic force microscopies. Fabricated nanowire devices are characterised by direct electrical probing and cyclic voltammetry to explore functionality. The voltammetric detection of glucose was performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the range of 10 μM-100 mM, with an extremely high sensitivity of 7.2 mA mM(-1) cm(-2) and a low detection limit of 3 μM (S/N = 3). The sensor demonstrated high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol). 相似文献
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Summary We examine the problem:u+a(x)u–b(x)u=f(x) for 0<x<1,a(x)>0,b(x)>,
2
= 4>0,a, b andf inC
2 [0, 1], in (0, 1],u(0) andu(1) given. Using finite elements and a discretized Green's function, we show that the El-Mistikawy and Werle difference scheme on an equidistant mesh of widthh is uniformly second order accurate for this problem (i.e., the nodal errors are bounded byCh
2, whereC is independent ofh and ). With a natural choice of trial functions, uniform first order accuracy is obtained in theL
(0, 1) norm. On choosing piecewise linear trial functions (hat functions), uniform first order accuracy is obtained in theL
1 (0, 1) norm. 相似文献
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L
1 andL
∞ Uniform convergence of a difference scheme for a semilinear singular perturbation problem
Summary A nonlinear difference scheme is given for solving a semilinear singularly perturbed two-point boundary value problem. Without any restriction on turning points, the solution of the scheme is shown to be first order accurate in the discreteL
1 norm, uniformly in the perturbation parameter. When turning points are excluded, the scheme is first order accurate in the discreteL
norm, uniformly in the perturbation parameter.Partly supported by the Arts Faculty Research Fund of University College, Cork 相似文献
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Numerical approximations to the solution of a singularly perturbed elliptic convection–diffusion problem in two space dimensions are generated using a monotone finite difference operator on a tensor product of piecewise‐uniform Shishkin meshes. The bilinear interpolants of these numerical approximations are parameter‐uniformly convergent to the solution of the continuous problem, in the pointwise maximum norm. In this article, discrete approximations to the first derivatives of the solution are shown to be globally first‐order (up to logarithmic factors) uniformly convergent, when the errors are scaled within the analytical layers of the continuous problem. Numerical results are presented to illustrate the theoretical error bounds established in an appropriated weighted C1–norm. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 225–252, 2015 相似文献
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Paul A. Farrell John J. H. Miller Eugene O'Riordan Grigorii I. Shishkin. 《Mathematics of Computation》1998,67(222):603-617
In this paper fitted finite difference methods on a uniform mesh with internodal spacing , are considered for a singularly perturbed semilinear two-point boundary value problem. It is proved that a scheme of this type with a frozen fitting factor cannot converge -uniformly in the maximum norm to the solution of the differential equation as the mesh spacing goes to zero. Numerical experiments are presented which show that the same result is true for a number of schemes with variable fitting factors.
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O'Riordan DL Stanton WR Eyeson-Annan M Gies P Roy C 《Photochemistry and photobiology》2000,71(1):60-64
Cumulative and intermittent sun exposure are risk factors for skin cancer, highlighting the need to monitor exposure during childhood. There is currently very little available information concerning the accuracy of self-reported levels of sun exposure, particularly for very young children. In this study, UV radiation (UVR) exposure measured by polysulfone dosimeters worn on the wrist was compared with a measure of estimated exposure using a diary based on recall at the end of the 4 day study period and ambient dosimetric measures. Results of the study indicate that the relative UVR exposures expressed as a fraction of daily total ambient received during the 4 day period by young children and mothers are similar. A high level of association was obtained for the estimated levels of exposure between young children and their mothers. Moderate correlations were evident for dosimeter readings of mother and child on weekends with no significant association on weekdays. The association between estimated exposure and dosimeter readings was poor and needs improvement. This may be achieved by greater consideration of structural and environmental factors that influence the levels of UVR exposure received by individuals and by increasing the level of specificity in the measurement instruments. Methodological issues such as recall of exposure after several days, quantity of sun exposure and more precise measurement of grades of exposure when outside may have more impact than previously expected, and further information is being sought with a larger sample for exposure during the summer months. 相似文献
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