Residual Coefficient Of Variation Research Articles

The use of computed tomography for in vivo estimation of reticulo-rumen and omasum contents in Alpine goats

Precise in vivo measurement of reticulo-rumen content (volume and mass) is required for the study of digestive processes. Rumen-cannulated animals have been classically used for this purpose, and less invasive alternatives are currently investigated to meet the replacement, reduction, and refinement (3Rs) ethical considerations in animal science. The objective was to compare in vivo reticulo-rumen and omasum volumes assessed by computed tomography (CT) scan with postmortem measurement of their respective digesta masses in dairy goats. Twenty Alpine dairy goats were scanned by CT, and the volumes of the reticulo-rumen and omasum were measured by CT image postprocessing. Goats were slaughtered immediately after CT scan and the masses of reticulo-rumen and omasum digesta were measured. Simple linear regressions were performed between volumes measured in vivo by CT and the corresponding digesta wet masses measured postmortem. Reticulo-rumen and omasum volumes determined by CT were significantly and linearly regressed against the corresponding digesta masses measured postmortem (R2 = 0.72 and 0.87, residual standard deviation = 1.18 and 0.06 kg, and residual coefficient of variation = 11% and 12%, n = 20 and 19, respectively). The use of CT is a promising noninvasive method to measure volume and estimate digesta masses of reticulo-rumen and omasum in small ruminants.

Body Mass Index and Arterial Stiffness Are Associated With Greater Beat-to-Beat Blood Pressure Variability After Transient Ischemic Attack or Minor Stroke.

[Figure: see text].

Fitting Tails by the Empirical Residual Coefficient of Variation: The ercv Package

Fitting Tails by the Empirical Residual Coefficient of Variation: The ercv Package

Aging and death-associated changes in serum albumin variability over the course of chronic hemodialysis treatment.

BackgroundSeveral epidemiological studies have demonstrated associations between variability in a number of biological parameters and adverse outcomes. As the variability may reflect impaired homeostatic regulation, we assessed albumin variability over time in chronic hemodialysis (HD) patients.MethodsData from 1346 subjects who received chronic HD treatment from May 2001 to February 2015 were analyzed according to three phases of HD treatment: post-HD initiation, during maintenance HD treatment, and before death. The serum albumin values were grouped according to the time interval from HD initiation or death, and the yearly trends for both the albumin levels and the intra-individual albumin variability (quantified by the residual coefficient of variation: Alb-rCV) were examined. The HD initiation and death-associated changes were also analyzed using generalized additive mixed models. Furthermore, the long-term trend throughout the maintenance treatment period was evaluated separately using linear regression models.ResultsAlbumin levels and variability showed distinctive changes during each of the 3 periods. After HD initiation, albumin variability decreased and reached a nadir within a year. During the subsequent maintenance treatment period (interquartile range = 5.2–11.0 years), the log Alb-rCV showed a significant upward trend (mean slope: 0.011 ± 0.035 /year), and its overall mean was -1.49 ± 0.08 (equivalent to an Alb-rCV of 3.22%). During the 1–2 years before death, this upward trend clearly accelerated, and the mean log Alb-rCV in the last year of life was -1.36 ± 0.17. The albumin levels and variability were negatively correlated with each other and exhibited exactly opposite movements throughout the course of chronic HD treatment. Different from the albumin levels, albumin variability was not dependent on chronological age but was independently associated with an individual’s aging and death process.ConclusionThe observed upward trend in albumin variability seems to be consistent with a presumed aging-related decline in homeostatic capacity.

Estimation of Genetic Parameters in Coffea canephora Var. Robusta

The objective of this work was to assess the genetic parameters in Coffea robusta clones using mixed model. The experiments were carried out during four years, in complete block design, and one plant per plot, at Oratorio of Minas Gerais state, Brazil. The clones were evaluated for vigor, reaction to rust, reaction to Cercospora, number of ortotropicos branches, number of plegiotropics branches, plant height, diameter of stem, fruit maturity, diameter of canopy, fruit size and production of fruits. The data were analyzed using the mixed model methodology (REML/ BLUP) of Selegen software for estimation of genetic parameters in C. canephora breeding. The results showed a low genetic variability among the clones of Robusta for all the evaluated traits. On the other hand, relatively high residual coefficient of variation for most of the traits was recorded implying that these traits seem to be highly influenced by the environmental variation. However, in this study the estimates of individual heritability in the broad sense (h2g) was of low magnitude, but were significant for all traits except yield (sac/ha). The estimated repeatability for most of the traits was low indicating the irregularity of the superiority of the individuals among the measurements showing that genotype selection based on these traits is not reliable strategy. Generally, there was low interaction with year, as observed by the genotypic correlation across measurement (rgmed) for most of the characters evaluated demonstrating that selection can be performed at any of the development stages used for measurement.

Variance residual life function based on double truncation

Since, most of the real observations in industrial and reliability studies, are left, right or doubly truncated data, studying the reliability concepts of the components of a system or a device based on conditional random variables, are important and usual. One of the important and applicable reliability concepts, that recently has gathered the attention of the researchers, is the variance residual life. In this paper, we try to study some of the reliability properties of the variance residual life based on doubly truncated data. Its monotonicity properties and relations with doubly truncated mean residual life and doubly truncated residual coefficient of variation are discussed. Furthermore, the lower (upper) bound for it under some conditions is obtained. We also discuss and find the similar results for discrete random ageing which its differences with the continuous case, are noticeable. Finally, some examples due to this subject are mentioned.

Reliability of Cycling Gross Efficiency Using the Douglas Bag Method

The aim of this study was to establish the reliability of gross efficiency (GE) measurement (the ratio of mechanical power input to metabolic power output, expressed as a percentage) using the Douglas bag method. The experiment was conducted in two parts. Part 1 examined the potential for errors in the Douglas bag method arising from gas concentration analysis, bag residual volume, and bag leakage or gas diffusion rates. Part 2 of this study examined the within-subject day-to-day variability of GE in 10 trained male cyclists using the Douglas bag method. Participants completed three measurements of GE on separate days at work rates of 150, 180, 210, 240, 270, and 300 W. The results demonstrate that the reliability of gas sampling is high with a coefficient of variation (CV) <0.5% for both O2 and CO2. The bag residual volume CV was ∼15%, which amounts to +0.4 L. This could cause the largest error, but this can be minimized by collecting large gas sample volumes. For part 2, a mean CV of 1.5% with limits of agreement of +0.6% in GE units, around a mean GE of 20.0%, was found. The Douglas bag method of measuring expired gases and GE was found to have very high reliability and could be considered the gold-standard approach for evaluating changes in GE. Collecting larger expired gas samples minimizes potential sources of error.

Variance residual life function in discrete random ageing

The random variable Xt= X − t¦X ≥ t, which is called the residual life random variable, has gathered the attention of most researchers in reliability. The mean and the variance of this variable in continuous distribution have been studied by several authors. But, in discrete case, only in recent years, some studies have been done for the mean of this variable. In this paper, we define and study the properties of variance of Tk= T − k¦T ≥ k where T is a discrete random variable. Besides similar results for discrete and continuous lifetime distributions, relationships with its mean, monotonicity and the associated ageing classes of distributions are obtained for discrete cases. Furthermore, some characterization results about the class of increasing (decreasing) variance residual life distributions based on mean residual life and residual coefficient of variation, are presented and the lower and upper bound for them are achieved.

Validation of a method for simultaneous determination of tocopherols and tocotrienols in cereals using Normal Phase HPLC

A method for the simultaneous determination of tocols (α-, β-,γ-, δ-tocopherols and α-, β-,γ-, δ-tocotrienols) in cereals using Normal Phase-HPLC (Merck; column LiChroCART 250-4, Lichrospher Si 60, 5 μm) with fl uorescent detection (Ex290 nm/Em350 nm) was validated. A mixture of hexane, ethyl acetate and acetic acid (97.3:1.8:0.9, v/v/v) was used as the eluent (1.6 ml/min). The analyses were performed after spectrophotometric standardization of standard ethanol solutions. The residual coeffi cients of variation for the regression equation y= ax 2 + bx + c were 0.001-3.8%, with r 2 >0.999. The limit of quantitation was 0.05 mg/kg, the upper limit of determination range from 40 to 60 mg/kg, repeatability 6.2-11.8%, and reproducibility 8.7-18.4%. Uncertainty of the method (P≤0.05), estimated for the analyses performed in replicate, ranged from 28.9 to 85.9% for the tocol concentration of 0.05-0.80 μg/ml and from 14.7 to 27.3% for the concentrations above 0.80 μg/ml. Recovery was 93.3-103.1%. The analytical method described is precise, fast and inexpensive.

AVALIAÇÃO DA INTERAÇÃO GENÓTIPO X AMBIENTE EM CANA-DE-AÇÚCAR VIA MODELOS MISTOS

The objective of this study was to evaluate yield, adaptability, and stability of sugarcane genotypes using the harmonic mean of relative performance of genotypic values method (MHPRVG), and to compare it with the method of differences of the segmented straight line weighted by the residual coefficient of variation (DRRB-CV), based on the Pi statistic from Linn & Binns. Employing the augmented block design, with five blocks, seventy clones and two checks were evaluated. Two experiments were carried out in each of seven environments in Minas Gerais State. Evaluations were performed in plant and ratoon. Considering the selection for sugar yield, adaptability, and stability, three clones performed better: RB947520, RB957712, and P86-42. The MHPRVG method was highly correlated with the parameters of the DRRB-CV method, and with the genotypic values that took into account the genotype x environment mean interaction. All the correlations between these statistical measurements were greater than 0.90. However, the MHPRVG method has the advantage that the results appear on the same scale of the characters evaluated, which could be directly interpreted as genetic values. Another advantage for clone selection is that this method takes into consideration simultaneously the criteria yield, adaptability, and stability. KEY-WORDS: Mixed models, REML/BLUP, stability, MHPRVG method.

Gamma regression improves Haseman-Elston and variance components linkage analysis for sib-pairs.

Existing standard methods of linkage analysis for quantitative phenotypes rest on the assumptions of either ordinary least squares (Haseman and Elston [1972] Behav. Genet. 2:3-19; Sham and Purcell [2001] Am. J. Hum. Genet. 68:1527-1532) or phenotypic normality (Almasy and Blangero [1998] Am. J. Hum. Genet. 68:1198-1199; Kruglyak and Lander [1995] Am. J. Hum. Genet. 57:439-454). The limitations of both these methods lie in the specification of the error distribution in the respective regression analyses. In ordinary least squares regression, the residual distribution is misspecified as being independent of the mean level. Using variance components and assuming phenotypic normality, the dependency on the mean level is correctly specified, but the remaining residual coefficient of variation is constrained a priori. Here it is shown that these limitations can be addressed (for a sample of unselected sib-pairs) using a generalized linear model based on the gamma distribution, which can be readily implemented in any standard statistical software package. The generalized linear model approach can emulate variance components when phenotypic multivariate normality is assumed (Almasy and Blangero [1998] Am. J. Hum Genet. 68: 1198-1211) and is therefore more powerful than ordinary least squares, but has the added advantage of being robust to deviations from multivariate normality and provides (often overlooked) model-fit diagnostics for linkage analysis.

A Criterion for Burn-in that Balances Mean Residual Life and Residual Variance

Optimum burn-in times have been determined for a variety of criteria such as mean residual life and conditional survival. In this paper we consider a residual coefficient of variation that balances mean residual life with residual variance. To study this quantity, we develop a general result concerning the preservation ofbathtub distributions. Using this result, we give a condition so that the residual coefficient of variation is bathtub-shaped. Furthermore, we show that it attains its optimum value at a time that occurs after the mean residual life function attains its optimum value, but not necessarily before the change point of the failure rate function.

The n-alkane concentrations in buds and leaves of browsed broadleaf trees

The concentration of n-alkanes in the cuticular wax of plants can be used to estimate the composition of the diet selected by free-ranging animals. The aims of this study were to characterize the n-alkane profiles of developing leaves and evaluate the degree of chemical discrimination between six browsed broadleaf tree species: European ash (Fraxinus excelsior L.), flowering ash (Fraxinus ornus L.), hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), mountain ash (Sorbus aucuparia L.) and beech (Fagus sylvatica L). The effect of the stage of development was examined by considering five different vegetative stages: dormant bud (DB), late bud (LB), young leaf (YL), mature leaf (ML) and senescing leaf (SL). Five samples per each vegetative stage and species, gathered in a mixed woodland of the Italian Eastern Alps between February and October, were analysed for their n-alkane concentrations (C23–C36).The residual coefficient of variation was 15·5% on average for the individual n-alkanes considered. There were noticeable differences in individual and total n-alkanes content between species. In particular, C27 was the predominant n-alkane in beech and C33 was found in high proportions in the two species of Fraxinus; hazel and flowering ash had a higher total n-alkanes content than the overall mean, while the lowest values were found in hornbeam and beech. The n-alkane profile also underwent important changes during the vegetative development, with different extent and direction according to the species. In the three successive leaf stages, a tendency for a progressive increase in the longest chain homologues was observed. In any case, the young leaf stage differed most from the contiguous stages.Canonical discriminant analysis indicated that the n-alkane profile of buds and leaves were mathematically distinguishable and the chemical differences between species were persistent over the plant vegetative development.

Rapid evolution of larval development time during mass‐rearing in the melon fly, Bactrocera cucurbitae

AbstractA quantitative genetic analysis of rapid evolution of a life history trait has been conducted on the first 24 generations of mass‐rearing in the melon fly Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae). The phenotypic variance of larval development time in each generation was divided into genetic and residual components. Mean and phenotypic coefficients of variation of larval development time decreased gradually as generations proceeded as a result of artificial selection for shorter larval period in the mass‐rearing procedure. There was a trend that additive genetic coefficients of variation in larval development time decreased with generations. These changes are entirely attributed to genetic responses to laboratory selection under the mass‐rearing environment because the population was maintained at a very large size so as to exclude random genetic drift and inbreeding depression, which would be other factors responsible for the observed genetic changes. The residual coefficients of variation in larval development time did not change with generations. Realized heritability of larval development time was low. The heritabilities for larval development time estimated from parent–offspring regression at generations 60 and 70, when the evolutionary plateau was asymptotically reached, were not significantly larger than 0.

Comparison of three methods for the in vivo estimation of body composition in dairy ewes

Three methods for estimating in vivo body fat in sheep, by the assessment of body water using the deuterium oxide (Ddilution technique, adipose cell size (ACS) measurement and body condition scoring (BCS), were studied in mature ewes and compared to results obtained after slaughter and chemical analyses. Twenty Lacaune dairy ewes were slaughtered at three stages of lactation (30 days (n = 8), 60 days (n = 8) and 110 days (n = 4)), with a mean body weight (BW) of 72.7 ± 7.6 kg, 16.0 t 4.7 kg of body lipids (LIP) and 42.7 ± 3.8 kg of total body water. Body fatness ranged from 10.3 to 28.8 % of empty body weight. Although the ewes were relatively fat, the mean adipose cell volume of subcutaneous pericaudal or sternal adipose tissue (209 or 287 pl, respec- tively) was in the lower range of previously reported values, while cells from omental adipose tissue had a larger mean volume (804 pl) than has been previously reported. Due to differences in the frame of ewes, prediction of body lipids through D,O, ACS and BCS was improved by including body weight in the model. The best equations using ACS were obtained with subcutaneous fat tissues (sternal tissue: residual coefficient of variation (rCV) = 13.9 % and pericaudal: rCV = 17.8 %), fol- lowed by internal tissue (omental: rCV = 19.5 %). The rCVs of the prediction of body lipids with these in vivo methods were in general agreement with published works on cattle or sheep i.e. D 8.8 %, pericaudal ACS: 13.9 % and BCS: 16.7 %. The interest and limitations of the methods studied are dis- cussed in terms of different experimental objectives and constraints. (© Elsevier / Inra)

Development of a single dilution ELISA to detect antibody to Dermatophilus congolensis in goat and cattle sera

A solid phase immunosorbent assay to detect antibodies to Dermatophilus congolensis in ruminant sera was developed to be used as a single dilution ELISA in large epidemiological surveys. Optimal conditions for the test are described. The use of blocking proteins to reduce non specific binding was necessary. Non fat dry cow milk and fetal calf serum were the only two efficient blocking agents out of six tested. Comparison of 4 antigenic fractions obtained after sonication differential centrifugations of D. congolensis cultures showed that cell-wall (CW) or membrane (M) enriched preparations were more specific than a crude extract (CR) or a soluble (S) antigen. Whole spores and filaments performed poorly as antigens. The best sensitivity and specificity of the ELISA were obtained when the cut-off point of positivity was fixed at mean absorbance of negative sera + 2.58 sd. The specificity was then 97.6% either with M or CR antigen. The sensitivity was improved from 93.4% with CR to 98.2% with M antigen. Threshold values for a positive test varied between the 3 geographical areas tested. CW and M were also the most efficient antigens for discerning between serotypes of D. congolensis. The precision of the test was evaluated with CR antigen and expressed in residual coefficient of variation (CV). The precision was CV = 5.1% when each serum was titrated in duplicate and the antibody levels were expressed in absorbances. The expression of antibody levels in arbitrary standard units estimated from calibration curves reduced the precision (CV = 13.8%). Several methods were tested to decrease between plate variability but these did not greatly improve the reproducibility Since it was shown that the main source of variation was within the plate.

Pharmacokinetics of quinidine in male patients. A population analysis.

Quinidine pharmacokinetic behaviour was evaluated in 139 adult hospitalised men receiving oral quinidine therapy. A total of 391 serum quinidine concentrations were measured by enzyme immunoassay for routine clinical purposes. The NONMEM programme was used to examine the relationship between quinidine pharmacokinetics and several potential covariates. A 1-compartment open model with first-order absorption and elimination was assumed. The mean apparent volume of distribution (Vd) was about 230L. When measured, alpha 1-acid glycoprotein (AAG) levels were not included in the analysis. Oral quinidine clearance (CL) decreased with age, severe congestive heart failure and renal disease, and increased in patients with a history of alcohol abuse. The interpatient variability in CL and the intrapatient residual variability expressed as coefficients of variation (CV) were 28 and 31%, respectively. When AAG values were incorporated into the analysis, the only important covariates of CL were the AAG measurements and the presence of renal dysfunction as indicated by a calculated creatinine clearance of less than 50 ml/min (3 L/h). The interpatient variability in CL and the residual intrapatient CVs decreased to approximately 24 and 26%, respectively. Improvement of the CL model by inclusion of measured AAG strongly suggests that quinidine elimination is dependent on the free concentration of drug in plasma and supports the use of free serum quinidine concentrations when evaluating and monitoring quinidine therapy.

Pharmacokinetics of the digoxin-quinidine interaction via mixed-effect modelling.

It was the purpose of this study to evaluate the effect of quinidine administration on the population estimates of the volume of distribution (Vdpop) and clearance (CLpop) of digoxin. The data collected on 94 patients included 230 measured serum digoxin concentrations, height, age, sex, weight (wt), serum creatinine, history of digoxin and quinidine administration and the presence or absence of congestive heart failure (CHF). Using the NONMEM software program, estimates were obtained for CLpop and Vdpop. Variables tested for inclusion in the CLpop model were creatinine clearance (CLCR), CHF, wt, ideal bodyweight, quinidine (QUIN) [both as a discrete variable and in a dose-dependent manner], and body surface area. Variables tested for inclusion in the Vdpop model were CLCR, wt, ideal bodyweight, body surface area and quinidine. During model building a p-value of 0.05 was chosen for variable inclusion. The final model was as follows: CLpop (L/h) = (3.1 + 0.0516 x CLCR) x QUIN Vdpop (L) = (4.03 + 0.0832 x CLCR) x wt F = 0.82 where F is bioavailability. In the above, QUIN is 0.567 if quinidine is being concurrently administered and 1.0 if it is not. The coefficient of variation (CV) of CLpop was 44% while that of Vdpop was 48%. The residual intrasubject CV was 26%. These results compare favourably with previously derived methods of estimating digoxin CLpop and Vdpop but may improve on those methods due to the inclusion of quinidine in the model. These better estimates should result in improved initial dosage of digoxin.

The dynamics of Trifolium repens in a permanent pasture. II. Internode length and the movement of shoot axes

White clover moves through pastures as a result of its clonal growth. The rate at which each shoot axis moves is determined by the rate at which new modules are produced at the apex, the rate at which old modules die at the base, and the length of internode separating adjacent modules. Internode length was much more variable than the birth rate of modules, and was affected by more factors. A multiple regression on ten variables accounted for only 78% of the variation in internode length, with a residual coefficient of variation of 36%. For any given level of the explanatory variables, 5% of internodes were longer than 2.5-times or shorter than 0.4-times the length predicted from the fitted regression model. Internode length is therefore more sensitive than birth rate to environment, and is affected by environmental factors not measured in this study. The variables that affected internode length were, in order of the magnitude of their effects: number, length and proximity of roots supporting an internode as it elongates; maturity of the shoot axis; mean soil temperature during the period of elongation; differences between plants; flowering; duration of bright sunshine during the period of elongation; number of mature leaves supporting an internode as it elongates; maturity of the module; mean stocking rate before birth and during the period of elongation; partial burial of the shoot axis. Axes moved an average of 13.3 cm a -1 . During summer, the average extension rate of mature apices was 0.7 mm per day, ranging up to 2.5 mm per day. Extension rate varied with temperature through a response of both birth rate of modules and length of internodes. In all other respects, within-plant variation in extension rate resulted almost entirely from variation in internode length.

Estimation of carcass and growth composition in the growing pig.

In the 1st of 2 experiments to evaluate different methods of estimating body composition in the growing pig, 80 castrated Dutch Large White X Dutch Landrace [male] piglets, from 16 litters and aged 10-11 wk, were assigned to 14 treatment groups involving various combinations of housing system (in metabolic cages, in groups in a calorimeter, or individually in a pen), feeding (ad lib. or 85 or 74% of ad lib.) and weight at slaughter (25, 65 or 105 kg). In the 2nd experiment, 16 [male] and 16 [female] Dutch Landraces from 4 litters born under specific-pathogen-free (SPF) conditions were used. Half the piglets were reared under SPF conditions, and the remainder were suckled by a host sow and reared under normal farm conditions until 6-8 wk of age, when they were placed in groups in calorimeters and were fed an irradiated diet at approx. 80% of the mean intake capacity estimated in experiment 1. Eight pigs were slaughtered at the onset of the experiment, and the remaining 24 at 105 kg body weight. Nitrogen balance was measured frequently during growth, and backfat thickness was measured ultrasonically before slaughter. After slaughter, the carcasses were dissected anatomically and into commercial cuts, and the tissues were analysed chemically. Detailed results are tabulated. In the live animal, ultrasonic measurement of backfat thickness gave the best estimate of body composition (Rsuperscript 2 = 0.6), the residual standard deviation for muscle percentage being 1.9. With increasing percentage of muscle in the carcass, the proportion of protein in the carcass and in the total body increased, and the proportion of chemical fat decreased. The variation in protein percentage was less than that in fat percentage. Regression analysis indicated that the muscle percentage in the carcass can be estimated accurately from a linear combination of percentage of ham + loin and carcass weight, the residual standard deviation being 0.9 and the residual coefficient of variation 1.5-2.0%. Estimates of muscle percentage based on backfat thickness, protein percentage in the carcass and fat percentage were less accurate than the above regression, the coefficients of variation being approx. twice as large. Values of measurements of nitrogen deposition by nitrogen balance and by comparative slaughter differed, the latter technique yielding the more accurate results. (Abstract retrieved from CAB Abstracts by CABI’s permission)