1,721,115 research outputs found
Evaluation of release of antioxidant from high density polyethylene by planar chromatography
No full textIrganox 1330 (1,3,5‐trimethyl‐2,4,5‐tris(3’,5'‐ditert‐butyl)‐4'‐hydroxybenzyl)‐benzene) (I), an alkylphenol compound used as antixodiant in the production of high density polyethylene (HDPE), was the subject of this study. The quantity of I given up by polyethylene samples of different thickness to aqueous and lipophilic media simulating food was studied by planar chromatography (PC). The manner of antioxidant release was also investigated. The chromatographic method developed was found satisfactory for the quantification of I in the migration studies undertaken, and had quantification limits (12 ng/deposit) suitable for quality control of HDPE. © 1998 Taylor and Francis Group LLC
Disease Mapping via Negative Binomial Regression M- quantiles
No full textWe introduce a semi-parametric approach to ecological regression for disease mapping, based on modelling the regression M-quantiles of a Negative Binomial variable. The proposed method is robust to outliers in the model covariates, including those due to measurement error, and can account for both spatial heterogeneity and spatial clustering. A simulation experiment based on the well-known Scottish lip cancer data set is used to compare the M-quantile modelling approach with a disease mapping approach based on a random effects model. This suggests that the M-quantile approach leads to predicted relative risks with smaller root mean square error. The paper concludes with an illustrative application of the M-quantile approach, mapping low birth weight incidence data for English Local Authority Districts for the years 2005-2010
Near Infrared reflectance analysis: features and applications in pharmaceutical and biomedical analysis
No full textGrowing interest has recently been expressed for the qualitative and quantitative analytical capabilities of Near Infrared Reflectance Spectroscopy (NIRS) in the measurement of physical and chemical parameters. The authors described the details of the method and its applications in the pharmaceutical and biomedical sectors
A Hierarchical Bayesian Model for the Analysis of Spatio-Temporal Variation in Disease Risk
No full textAnalysis of guazatine mixture by Lc and LC-MS and antimycotic activity determination of principal components
No full textiminodi(octamethylene)diamine, octamethylenebis(imino-octamethylene) diamine and carbamonitrile. In this work, the analysis of guazatine mixture by LC and LC–MS has been treated for the first time. In the guazatine mixture diamine derivatives account for 40% of the constituents of guazatine, triamines for 46%, tetramines for 11% and other amine derivatives for 3%. The most abundant individual components are the fully
guanidated triamine (GGG, 30.6%) and the fully guanidated diamine (GG, 29.5%) followed by the monoguanidated diamine (GN, 9.8%) and a
diguanidated triamine (GGN, 8.1%). The identification and separation of main components of commercial guazatine was performed through a new LC–MS method. The separation was performed on an Alltima C18 column using linear gradient elution (formic acid in water and acetonitrile) with UV-detection at 200 nm and the identification was performed by ESI+-mass spectrometry analysis. The main components (GN, GG, GNG, GGN, GGG and GGGG) were then purified and separated from the mixture. Antimycotic activity of guazatine derivatives was determined on different species and strains belonging to genus Candida. The results obtained suggest that GNG and GGGG components can further be developed in new antifungal compounds with high potential for the treatment of Candida infections
Compatibility results for conditional distributions
No full textIn various frameworks, to assess the joint distribution of a -dimensional random vector , one selects some putative conditional distributions . Each is regarded as a possible (or putative) conditional distribution for given . The are compatible if there is a joint distribution for with conditionals . Three types of compatibility results are given in this paper. First, the are assumed to take values in compact subsets of . Second, the are supposed to have densities with respect to reference measures. Third, a stronger form of compatibility is investigated. The law with conditionals is requested to belong to some given class of distributions. Two choices for are considered, that is, exchangeable laws and laws with identical univariate marginals
Polarographic determination of pyrethroid residues in stored cereals
No full textA new method for determination of the total cyanopyrethroid residue concentration in stored cereals by differential-pulse polarography is proposed. Cyanopyrethroids were previously extracted with a non-polar solvent and purified by solid-phase extraction. The total pyrethroid residue concentrations are determined by differential-pulse polarography of 3-phenoxybenzaldehyde formed quantitatively by rapid and reproducible alkaline alcoholysis of the sample. The method is linear, quantitative and reproducible for maize and wheat analysis in the range 0.1-3.0 mg kg-1. A thin-layer chromatographic method for identification of six widely used cyanopyrethroids in the sample is described. The electronic reduction process of 3-phenoxybenzaldehyde is examined and the reduction products isolated and identified
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