Gompertz and Weibull functions imply contrasting biological causes of demographic aging. The terms describing increasing mortality with age are multiplicative and additive, respectively, which could result from an increase in the vulnerability of individuals to extrinsic causes in the Gompertz model and the predominance of intrinsic causes at older ages in the Weibull model. Experiments that ma...

I describe a software reliability growth model that yields accurate parameter estimates even with a small amount of input data. The model is based on a proposed discrete analog of a Gompertz equation that has an exact solution. The difference equation tends to a differential equation on which the Gompertz curve model is defined, when the time interval tends to zero. The exact solution also tend...

the acute ecotoxicity of a set of mixture samples (washing powders, wastes, fuel extracts etc.) was assessed using four acute ecotoxicity assays with aquatic organisms (daphnia magna, poecilia reticulata, artemia salina and desmodesmus subspicatus). the experimental concentration-response curves were fitted by seven two-parameter sigmoid equations using non-linear regression. the regression pe...

Few investigations have been made of the species description trend of scale insects. The present study reports the discovery pattern and taxonomic efforts for this group based on global species and a literature dataset. In addition, three asymptotic models (Logistic, Gompertz, and Extreme Value) based on a discovery curve were used to predict the species number of scale insects. Our results sho...

Although the Gompertz formula accurately describes observed mortality distributions over most of their extent, their 'tail' is much longer than that of a Gompertz curve fitted to the whole data set. A simple candidate explanation is that the longest-lived subset of any population will necessarily be enriched in individuals that age more slowly than the average of that population. However, some ...

AIMS To investigate the relationship between decontamination procedures and seizure events caused by venlafaxine overdose and to estimate the time at which 90% of patients would have had their first seizure in the presence and absence of decontamination. METHODS Data were collected from 319 patients who took an overdose of venlafaxine on 436 occasions. Seizures occurred on 24 of 436 occasions...

Many analysis in epidemiological and prognostic studies and in studies of event history data require methods that allow for unobserved covariates or “frailties”. We consider the shared frailty model in the frame work of parametric proportional hazard model. There are certain assumptions about the distribution of frailty and baseline distribution. Mostly gamma distribution is considered for frai...

The purpose of this work was to study the effect of initial pH and yeast Saccharomyces Cerevisiae on biogas production from tofu wastewater (TW). The initial pH was varied in ranging of 5 – 9 in substrate without yeast (T5-T9) and with yeast (TY5-TY9). The results showed that optimum initial pH was 8. The maximum biogas was resulted in T8 (275 mL) and TY8 (421 mL). Yeast addition increased tota...