Analytical variation in metabolic profile testing
Summary Results are presented demonstrating quality control of the analytical procedures used during the application of metabolic profile tests to dairy herds over a period of 3 years. The significance of analytical variance is discussed in relation to the average population variance in dairy herds. It is concluded that analytical variance can be restricted to reasonable proportions providing that careful quality control is continuously employed.
Week-to-week variation in blood composition of dairy cows and its effect on interpretations of metabolic profile tests.
Abstract Blood samples were collected weekly from 16 cows in a dairy herd between November and April in two years (10 cows in year 1; six cows in year 2) and analysed for several blood metabolites. Week-to-week variations were very small for blood haemoglobin and serum magnesium but large for serum potassium, sodium and calcium. Except for these three constituents, and possibly serum albumin, variations were within acceptable limits and did not constitute an important source of error in interpretation of results of metabolic profile tests. For blood glucose there appeared to be both clinical and statistical justifications for reducing the reference range from ±2 to ±1·8 standard deviations.
Modelling of Mooney viscosity relaxation in natural rubber
Abstract Better assessment of natural rubber (NR) quality and processability, through the identification of new attributes, is still a major challenge. With this scope, 12 model samples of natural polyisoprene and two of synthetic polyisoprene were characterized in terms of Mooney torque relaxation, using the standardized ISO289 method (ML(1+4)100, explained later in the Section 1 ). The main purpose of this study was to identify a model that gave a better fit for the experimental decay of Mooney torque over time (ML(t)=f(t)) than the usual power law model used before (Y=at−b, [G.M. Bristow, A.G. Sears, The use of novel parameters in the assessment of natural rubber processability, NR Technol. 18 (1987); H.G. Burhin, W. Spreutels, J.M. Campbell, MV2000 Mooney viscometer: Mooney relaxation measurements on raw polymers and compounded rubber stocks, Kautsch. Gummi Kunstst. 43 (1990) 431]). The results showed that a generalized Maxwell model, and the Wu–Abbott empirical model ( Y = 1 − a Ln ( t ) − ( b t / ( c + t ) ) ) [T. Wu, J.A. Abbott, Firmness and force relaxation characteristics of tomatoes stored intact or as slices, Postharvest Biol. Technol. 24 (2002) 59–68], recently used for describing stress relaxation of tomato flesh, allowed a better description of the relaxation curve for the samples studied than the power law or stretched exponential traditionally used. Moreover, the total relaxation time (τm) given by the generalized Maxwell model showed good correlation with the total gel content of the samples studied.