This work aims to compare different nonlinear functions for describing the growth curves of Nelore females. The growth curve parameters, their (co)variance components, and environmental and genetic effects were estimated jointly through a Bayesian hierarchical model. In the first stage of the hierarchy, 4 nonlinear functions were compared: Brody, Von Bertalanffy, Gompertz, and logistic. The ana...

In this paper, we introduce a new four-parameter generalized version of the Gompertz model which is called Beta-Gompertz (BG) distribution. It includes some well-known lifetime distributions such as beta-exponential and generalized Gompertz distributions as special sub-models. This new distribution is quite flexible and can be used effectively in modeling survival data and reliability problems....

This work faces the problem of the origin of the logarithmic character of the Gompertzian growth. We show that the macroscopic, deterministic Gompertz equation describes the evolution from the initial state to the final stationary value of the median of a log-normally distributed, stochastic process. Moreover, by exploiting a stochastic variational principle, we account for self-regulating feat...

Mathematical models of population growth have been constructed to provide an abstract of some significant aspect of true ecological situation. In this paper, we put some models where the parameters of the biological growth model systematically change over time. Verhust (1838) first proposed three-parameter model for the growth of single-species populations [1,5,9] that shows a logistic sigmoid ...

Maximum lifespan has been one of the most common aging measures in comparative studies, while the Gompertz model has recently attracted both proponents and critics of its capacity to adequately describe the acceleration of mortality in the oldest age classes. The Gompertz demographic model describes age-dependent mortality rate acceleration and age-independent mortality using the parameters alp...

We develop a new generalized family of the Gompertz-G distribution, namely, Marshall-Olkin-Gompertz-G distribution. Statistical properties proposed model are presented. Some special cases distributions Maximum likelihood estimates parameters also determined. A simulation study was conducted to assess performance maximum estimates. Applications demonstrate usefulness Marshall-Olkin-Gompertz-Weib...

Estimation of growth curves of poultry species is of particular importance in animal science. This study aims at fitting hierarchical Gompertz growth curve to Japanese quails body weight data obtained from hatching to 56 days of age weekly. The model involved a random animal effect as well as sex and line effects in asymptotic weight parameters. Model parameters were estimated via Bayesian meth...

This paper proposes a non-phenomenological model of population growth that is based on the interactions between the individuals that compose the system. It is assumed that the individuals interact cooperatively and competitively. As a consequence of this interaction, it is shown that some well-known phenomenological population growth models (such as the Malthus, Verhulst, Gompertz, Richards, Vo...