Feeding activity of scallops and mussels measured simultaneously in the field: Repeated measures sampling and implications for modelling

Many studies on the biology of bivalves have focused on identifying the importance of various environmental factors in regulating feeding behaviour in order to predict ingestion and growth responses in a variety of habitats. When taking into consideration the diversity of studies undertaken and the variety of methodologies employed, it is perhaps not surprising that there have been inconsistencies in both interspecific and intraspecific comparisons. In order to compare and contrast the way in which feeding activities of a mussel species (Mytilus edulis) and a scallop species (Placopecten magellanicus) respond to environmental factors and seston characteristics, we exposed both species simultaneously to a fluctuating assemblage of natural particles found in their local environment. Similar sizes of mussels (40-73 mm) and scallops (40-88 mm) were held in flow through chambers at two different sites in Atlantic Canada on four separate occasions, during which environmental conditions, including seston characteristics, were monitored and individual clearance rates were measured. Because the same individuals were measured over time, repeated-measures statistical procedures were used to analyze the data. Results indicate that weight standardized clearance rates of mussels were significantly higher than those of scallops only at the highest concentration tested (12.8 mg l^− 1), which translates into almost 3 times more material being filtered. Scallops appeared to respond to fluctuations in environment parameters and suspended food particles more consistently than mussels. These data suggest that the feeding behaviour of these two species is mediated differently by the same environmental parameters. Our study also demonstrates the importance of selecting appropriate statistical tests (e.g., repeated measures) for the analyses of data obtained from repeated sampling of the same individuals over time, and the need to consider species-specific feeding responses when developing models that predict the influence of bivalve feeding on ecosystem function.     

Response-adaptive regression for longitudinal data

We propose a response-adaptive model for functional linear regression, which is adapted to sparsely sampled longitudinal responses. Our method aims at predicting response trajectories and models the regression relationship by directly conditioning the sparse and irregular observations of the response on the predictor, which can be of scalar, vector, or functional type. This obliterates the need to model the response trajectories, a task that is challenging for sparse longitudinal data and was previously required for functional regression implementations for longitudinal data. The proposed approach turns out to be superior compared to previous functional regression approaches in terms of prediction error. It encompasses a variety of regression settings that are relevant for the functional modeling of longitudinal data in the life sciences. The improved prediction of response trajectories with the proposed response-adaptive approach is illustrated for a longitudinal study of Kiwi weight growth and by an analysis of the dynamic relationship between viral load and CD4 cell counts observed in AIDS clinical trials.     

Optimal weight in estimating and comparing areas under the receiver operating characteristic curve using longitudinal data

In the setting of longitudinal study, subjects are followed for the occurrence of some dichotomous outcome. In many of these studies, some markers are also obtained repeatedly during the study period. Emir et al. introduced a non-parametric approach to the estimation of the area under the ROC curve of a repeated marker. Their non-parametric estimate involves assigning a weight to each subject. There are two weighting schemes suggested in their paper: one for the case when within-patient correlation is low, and the other for the case when within-subject correlation is high. However, it is not clear how to assign weights to marker measurements when within-patient correlation is modest. In this paper, we consider the optimal weights that minimize the variance of the estimate of the area under the ROC curve (AUC) of a repeated marker, as well as the optimal weights that minimize the variance of the AUC difference between two repeated markers. Our results in this paper show that the optimal weights depend not only on the within-patient control--case correlation in the longitudinal data, but also on the proportion of subjects that become cases. More importantly, we show that the loss of efficiency by using the two weighting schemes suggested by Emir et al. instead of our optimal weights can be severe when there is a large within-subject control--case correlation and the proportion of subjects that become cases is small, which is often the case in longitudinal study settings.     

超声重复辐照孕鼠对子代海马NMDA神经损伤的影响

摘要 目的：探讨超声重复辐照孕鼠对子代海马N-甲基-D天冬氨酸(N-methyl-D aspartic acid,NMDA)神经损伤的影响。方法：孕12~14 d昆明种小鼠27只随机平分为三组-对照组、短时间辐照组、长时间辐照组。用超声探头在各组孕鼠进行辐照0 min、10 min与20 min,让母鼠自然分娩哺育幼仔,将各组仔鼠随机挑选12只,检测仔鼠海马组织NMDA表达与神经损伤情况。结果：辐照过程中无孕鼠死亡,短时间辐照组、长时间辐照组仔鼠第30 d与60 d的总路程、中央路程、中央时间都少于对照组(P<0.05),长时间辐照组低于短时间辐照组(P<0.05)。短时间辐照组、长时间辐照组仔鼠第60 d的神经元细胞凋亡指数、海马组织乙酰胆碱酯酶含量都高于对照组(P<0.05),NMDA蛋白相对表达水平低于对照组(P<0.05),长时间辐照组与短时间辐照组对比差异也都有统计学意义(P<0.05)。结论：超声重复辐照孕鼠能抑制仔鼠海马组织NMDA蛋白表达,促进神经元细胞凋亡与提高乙酰胆碱酯酶含量,从而降低仔鼠的自主记忆活动能力。     

Multiple Comparisons in Nonlinear Repeated Measurements

It is interest to compare functions of parameters in nonlinear models for repeated measurements. In a pharmacokinetic model, the maximum value of the model would be a nonlinear function of some unknown parameters. In this paper, simultaneous confidence intervals of functions of parameters in a nonlinear model for repeated mesurement data are considered to compare the populations.     

Experiments with Three-Treatment Three-Period Crossover Design: Analysis Through the General Linear Model

In this paper we consider balanced three-treatment three-period crossover designs. Using a strategy similar to that applied in the analysis of split-plot experiments we describe both the within and the between sample units models, as well as the corresponding Analysis of Variance. We illustrate these procedures with a numerical example and discuss their implementation through computer programs designed for the analysis of the general linear model.     

Efectividad de la vacuna antigripal en la prevención de la gripe en personas mayores de 65 años

IntroductionInfluenza is one of the diseases with the greatest epidemiological impact and of maximum relevance in the management of health services. The flu vaccine can have great variability each season, so our objective was to find out the effectiveness of the flu vaccine for the 2017/2018 season for the prevention of severe cases of flu in people over 65 years of age in a 385-bed acute general hospital.Material and methodStudy of cases and controls. All hospitalized patients with laboratory-confirmed influenza older than 65 years during the 2017/2018 season were included. Those who met the criteria for a severe case of influenza were considered cases. Those who did not meet the severity criteria were considered controls. Factors associated with the development of severe influenza were calculated.ResultsThe median age was 68 years (SD 91.87). The attack rate was 0.23 per hundred inhabitants and the vaccine effectiveness was 38%. The vaccinated and unvaccinated groups were different in terms of age (p < 0.0481). Vaccination status against severe influenza was found to be an independent protective factor (OR = 0.840; 0.746-0.913).ConclusionsThe effectiveness of influenza vaccination provided greater protection against infection and reduced the severity of influenza in older hospitalized patients. These findings should be taken into account to improve vaccination strategies and achieve better vaccination coverage in the population at risk.     

Weighted rank regression for clustered data analysis

Summary .   We consider ranked-based regression models for clustered data analysis. A weighted Wilcoxon rank method is proposed to take account of within-cluster correlations and varying cluster sizes. The asymptotic normality of the resulting estimators is established. A method to estimate covariance of the estimators is also given, which can bypass estimation of the density function. Simulation studies are carried out to compare different estimators for a number of scenarios on the correlation structure, presence/absence of outliers and different correlation values. The proposed methods appear to perform well, in particular, the one incorporating the correlation in the weighting achieves the highest efficiency and robustness against misspecification of correlation structure and outliers. A real example is provided for illustration.     

Extensive Reorganization of the Plastid Genome of <Emphasis Type="Italic">Trifolium subterraneum</Emphasis> (Fabaceae) Is Associated with Numerous Repeated Sequences and Novel DNA Insertions

The plastid genome of Trifolium subterraneum is 144,763 bp, about 20 kb longer than those of closely related legumes, which also lost one copy of the large inverted repeat (IR). The genome has undergone extensive genomic reconfiguration, including the loss of six genes (accD, infA, rpl22, rps16, rps18, and ycf1) and two introns (clpP and rps12) and numerous gene order changes, attributable to 14–18 inversions. All endpoints of rearranged gene clusters are flanked by repeated sequences, tRNAs, or pseudogenes. One unusual feature of the Trifolium subterraneum genome is the large number of dispersed repeats, which comprise 19.5% (ca. 28 kb) of the genome (versus about 4% for other angiosperms) and account for part of the increase in genome size. Nine genes (psbT, rbcL, clpP, rps3, rpl23, atpB, psbN, trnI-cau, and ycf3) have also been duplicated either partially or completely. rpl23 is the most highly duplicated gene, with portions of this gene duplicated six times. Comparisons of the Trifolium plastid genome with the Plant Repeat Database and searches for flanking inverted repeats suggest that the high incidence of dispersed repeats and rearrangements is not likely the result of transposition. Trifolium has 19.5 kb of unique DNA distributed among 160 fragments ranging in size from 30 to 494 bp, greatly surpassing the other five sequenced legume plastid genomes in novel DNA content. At least some of this unique DNA may represent horizontal transfer from bacterial genomes. These unusual features provide direction for the development of more complex models of plastid genome evolution. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.