Age at menarche (AAM), time of first menstrual period, is an important developmental milestone in females. Follow-up data from 1,302 adolescent twins and their sisters were used to partition the normal variation in AAM. The proportion of censoring was 14.1%. Both a standard and a survival analysis method were used. The best fitting model from the survival analysis method was an ACE model, where...

In many engineering applications, we have to combine probabilistic, interval, and fuzzy uncertainty. For example, in environmental analysis, we observe a pollution level x(t) in a lake at different moments of time t, and we would like to estimate standard statistical characteristics such as mean, variance, autocorrelation, correlation with other measurements. In environmental measurements, we o...

Depression in adults is heritable with about 40 % of the phenotypic variance due to additive genetic effects and the remaining phenotypic variance due to unique (unshared) environmental effects. Common environmental effects shared by family members are rarely found in adults. One possible explanation for this finding is that there is an interaction between genes and the environment which may ma...

Although single-species deterministic difference equations have long been used in modeling the dynamics of animal populations, little attention has been paid to how stochasticity should be incorporated into these models. By deriving stochastic analogues to difference equations from first principles, we show that the form of these models depends on whether noise in the population process is demo...

When facing the challenges of environmental change, such as habitat fragmentation, organisms have to adjust their phenotype to adapt to various environmental stresses. Recent studies show that epigenetic modifications could mediate environmentally induced phenotypic variation, and this epigenetic variance could be inherited by future generations, indicating that epigenetic processes have potent...

We examined the possible role of religious upbringing as a mediator of the shared environmental influences and as a moderator of the genetic influences on the risk of alcohol use initiation in a large population-based sample of Dutch adolescent and young adult twins (1967 twin pairs). There was not a significant association between religious participation and alcohol use initiation among Dutch ...

The objective was to determine appropriate analytical models considering cytoplasmic inheritance for birth weight (BWT, n = 35,604), weaning weight (WWT, n = 34,114), fleece weight (FWT, n = 38,113) and number born (NB, n = 39,029) for Rambouillet sheep. For BWT, models that included dam by year, dam by number born, and sire by dam effects, in addition to direct and maternal effects, were signi...

We examined mean effects and variance moderating effects of measures of physical activity and fitness on six measures of adiposity and their reciprocal effects in a subsample of the population-representative Danish Twin Registry. Consistent with prior studies, higher levels of physical activity suppressed variance in adiposity, but this study provided further insight. Variance suppression appea...

In this paper, we demonstrate how simulation studies can be used to answer questions about identifiability and consequences of omitting effects from a model. The methodology is presented through a case study where identifiability of genetic and/or individual (environmental) maternal effects is explored. Our study system is a wild house sparrow (Passer domesticus) population with known pedigree....

The magnitude of inbreeding depression, a central parameter in the evolution of plant mating systems, can vary depending on environmental conditions. However, the underlying genetic mechanisms causing environmental fluctuations in inbreeding depression, and the consequences of this variation for the evolution of self-fertilization, have been little studied. Here, we consider temporal fluctuatio...