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- PublicationMathematical modelling of domestic water flowA model was developed to simulate water flow with reliable parameters allowing the analysis of water consumption in selected areas. The model was applied to investigate the daily water consumption by domestic users in County Sligo, Ireland. The water flow data was obtained in 15 minute intervals from bulk meters in selected areas. The water consumption data was averaged in different time interval formats and fitted to the model. In all cases, the parameters were consistent (α=0.05) and the correlation coefficients (r2) were high, thus demonstrating the reliability of this approach.
- PublicationDevelopment of a bivariate mathematical model to characterize simultaneously the dose-time-responses of pro-oxidant agentsThe available data about the interference of oxidation compounds in the oxidation kinetics of process such as lipid oxidation chain reactions, the resistance of pharmaceutical drugs, the effects of free radical agents in cell tissue, the damage caused in DNA, etc, are examples of the many applications for in vivo and in vitro assays. However, often in these bio-assays, only semi-quantitative conclusions can be obtained, due to the use of quantification procedures disregarding kinetic considerations. A pseudo-mechanistic model is proposed which is based on the accumulative Weibull's function, and represents a formal transfer from the field of the dose-response relationships. It allows researchers to obtain the simultaneous solution of a series of oxidation activities as a function of concentration and time. It describes satisfactorily simulations in which reaction compounds interact through a second order kinetic scheme. Its application is simple: it provides parametric estimates, which characterize the oxidative process; facilitates rigorous comparisons between the effects of distinct compounds in different systems; reduces the sensitivity to the experimental error; and its mathematical form constitutes a useful orientation to prepare more economic and efficient trial designs. The model was assayed, firstly, using the kinetic simulation of the oxidative process, and finally, it was applied to a variety of experimental data from other authors in different systems and conditions, obtaining highly satisfactory results in all cases. In all experimental data tested, the calculated parameters were always statistically significant (Student’s t-test, α = 0.05), the equations were consistent (Fisher’s F-test) and the goodness of fit (adj R2, adjusted coefficient of multiple determination) were up to 0.98.
- PublicationA new microplate procedure for simultaneous assessment of lipophilic and hydrophilic antioxidants and pro-oxidants, using crocin and β-carotene bleaching methods in a single combined assay: Tea extracts as a case studyβ-Carotene and crocin bleaching reactions are the basis of two methods extensively used to quantify antioxidant and pro-oxidant activities. They are appropriate for lipophilic and hydrophilic matrices, respectively, and can provide useful complementary information in the study of complex natural extracts containing components with variable degrees of polarity. In this regard, a microplate procedure (Carotene Combined Bleaching) is proposed that enables the combination of both methods in a single, informative and less expensive method which is also faster to carry out. As an illustrative model, the method was applied to test a set of commercial lipophilic and hydrophilic antioxidants and some predictable pro-oxidant agents. Afterwards, as a food compound case study, the antioxidant activity of five types of tea extracts (Green, Blue, White, Black and Red) were characterized and their equivalent potential activity was calculated using commercial antioxidants on the basis of the new procedure developed in this research. The activity of the tea extracts decreased in the following order: (a) In a predominantly lipophilic environment: White > Black > Red > Blue > Green tea extracts; and (b) In a predominantly hydrophilic environment: Green > Red > White > Black > Blue tea extracts
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