Results 1 - 10 of 95155
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[en] A new chemiluminescence (CL) method is proposed for the determination of phentolamine, which is based on the reaction between studied drug and Cerium(IV) (Ce(IV)) in a nitric acid medium and measurement of the CL intensity produced by rhodamine 6G used as a sensitizer. In the optimum conditions, CL intensities are proportional to concentrations of the studied drug over the range 1x10-9-1x10-6 g/ml with a detection limit of 4x10-10 g/ml. The relative standard deviation (R.S.D.) is 3.4% for 1x10-7 g/ml phentolamine (n=11). The method has been applied to the determination of studied drug in injections and biological fluids with satisfactory results
[en] Mixture models are receiving considerable significance in the last years. Practical situations in reliability and survival analysis may be addressed by using mixture models. When making inferences on them, besides the estimates of the parameters, a sensitivity analysis is necessary. In this paper, a general technique to estimate local prior sensitivities in finite mixtures of distributions from natural exponential families having quadratic variance function (NEF-QVF) is proposed. Those families include some distributions of wide use in reliability theory. An advantage of this method is that it allows a direct implementation of the sensitivity measure estimates and their errors. In addition, the samples that are drawn to estimate the parameters in the mixture model are re-used to estimate the sensitivity measures and their errors. An illustrative application based on insulating fluid failure data is shown.
[en] Highlights: → The sensitivity and uncertainty analyses were performed to comprehend the reliability of the XT-ADS neutronic design. → The uncertainties deduced from the covariance data for the XT-ADS criticality were 0.94%, 1.9% and 1.1% by the SCALE 44-group, TENDL-2009 and JENDL-3.3 data, respectively. → When the target accuracy of 0.3%Δk for the criticality was considered, the uncertainties did not satisfy it. → To achieve this accuracy, the uncertainties should be improved by experiments under an adequate condition. - Abstract: The XT-ADS, an accelerator-driven system for an experimental demonstration, has been investigated in the framework of IP EUROTRANS FP6 project. In this study, the sensitivity and uncertainty analyses were performed to comprehend the reliability of the XT-ADS neutronic design. For the sensitivity analysis, it was found that the sensitivity coefficients were significantly different by changing the geometry models and calculation codes. For the uncertainty analysis, it was confirmed that the uncertainties deduced from the covariance data varied significantly by changing them. The uncertainties deduced from the covariance data for the XT-ADS criticality were 0.94%, 1.9% and 1.1% by the SCALE 44-group, TENDL-2009 and JENDL-3.3 data, respectively. When the target accuracy of 0.3%Δk for the criticality was considered, the uncertainties did not satisfy it. To achieve this accuracy, the uncertainties should be improved by experiments under an adequate condition.
[en] When reporting best estimates as measurement results, systematic influences near the natural limit are introduced that originate not only in the possible inconsistency of the analytical procedure but also in the conversion of the primary measurement results to best estimates. It has been shown that the probability density distribution resembling shifting of values observed in the unfeasible region to the limit of the feasible range (the natural limit) introduces a smaller systematic influence than the Bayesian posterior, resembling censoring with repetition of the measurements that result in observed values in the unfeasible region. The drawback that the uncertainty intervals calculated with the Bayesian posterior do not encompass the natural limit and may not encompass the observed value, although it lies within the feasible region, is avoided by using the probability density distribution resembling shifting. Therefore, such best estimates introduce a smaller systematic influence into the measurement results and are better suited as inputs for subsequent analyses. (author)
[en] The unique action of paclitaxel to stabilise microtubules and block cells at the radiosensitive G2/M phase of the cell cycle, suggests it may sensitise tumours to radiotherapy. Since the use of paclitaxel may be compromised in drug resistant tumours due to drug efflux by P-glycoprotein, the ability of paclitaxel to sensitise multidrug resistant cells to radiation was examined in HL60 cells and a multidrug resistant subline, H/E8, developed by intermittent treatment with epirubicin. Poster 201. (author)
[en] Equations are derived that connect the mass of a representative sample and such components of the total variance which characterize the dispersion of the results of neutron activation analysis (NAA), such as the variances of nonuniformity and replicate reproducibility. A method is proposed to estimate the minimum mass of a representative sample in the NAA of nonhomogeneous materials
[en] When conducting sensitivity and uncertainty analysis, most of the global sensitivity techniques assume parameter independence. However, it is common that the parameters are correlated with each other. For models with correlated inputs, we propose that the contribution of uncertainty to model output by an individual parameter be divided into two parts: the correlated contribution (by the correlated variations, i.e. variations of a parameter which are correlated with other parameters) and the uncorrelated contribution (by the uncorrelated variations, i.e. the unique variations of a parameter which cannot be explained by any other parameters). So far, only a few studies have been conducted to obtain the sensitivity index for a model with correlated input. But these studies do not distinguish between the correlated and uncorrelated contribution of a parameter. In this study, we propose a regression-based method to quantitatively decompose the total uncertainty in model output into partial variances contributed by the correlated variations and partial variances contributed by the uncorrelated variations. The proposed regression-based method is then applied in three test cases. Results show that the regression-based method can successfully measure the uncertainty contribution in the case where the relationship between response and parameters is approximately linear
[en] ROC (Receiver-Operator-Characteristics) analysis permits an evaluation of the diagnostic performance of imaging systems by incorporating the individual decision threshold of the diagnostician that determines the relation between sensitivity and specificity of a tested system. It therefore facilitates the comparison between different imaging systems and observers. A thorough knowledge and sophistication of this methodology is of special importance in the comparison of digital and conventional projection radiography because the images in question may have a very similar character. The method is explained and special points of interest (standard of 'truth', size of sample, lesion conspicuity and localisation, viewing time and determination of significance) are emphasized. (orig.)
[de]Die ROC-Analyse ermoeglicht eine Einschaetzung der diagnostischen Leistung bildgebender Verfahren unter Beruecksichtigung der individuellen Entscheidungsschwelle der Betrachter, die wesentlich das Verhaeltnis zwischen Sensitivitaet und Spezifitaet eines Verfahrens bestimmt. Daher eignet sich die ROC-Analyse (Receiver-Operator-Characteristics) zum Vergleich zwischen verschiedenen bildgebenden Techniken und verschiedenen Betrachtern. Eine gute Beherrschung dieser Methodik und ihre Verfeinerung ist besonders wichtig fuer den Vergleich der digitalen und der konventionellen Radiographie, da die zu vergleichenden Bilder haeufig einen sehr aehnlichen Charakter aufweisen. Anhand von eigenen Studien wird die Methodik erlaeutert, und Problempunkte wie Bestimmung der 'Wahrheit', benoetigte Kollektivgroesse, Auffaelligkeit der Laesion, Lokalisierung der Laesion, Rolle der Betrachtungszeit sowie der Signifikanzbestimmung werden behandelt. (orig.)