Asexual species accumulate deleterious mutations through an irreversible process known as Muller's ratchet. Attempts to quantify the rate of the ratchet have ignored the role of temporal environmental heterogeneity even though it is common in nature and has the potential to affect overall ratchet rate. Here we examine Muller's ratchet in the context of conditional neutrality (i.e., mutations th...

Leli and Filskov (1979) reported cross-validated classification accuracy that equalled 83% for a discriminant function derived on two measures of intellectual deterioration. This investigation made a preliminary assessment of the clinical utility of this function through a clinical-actuarial classification paradigm. Wechsler-Bellevue Intelligence Scale Form I protocols from 12 nonpsychotic noni...

HEALTH ISSUE: Total fertility rates (TFRs) have decreased worldwide. The Canadian fertility rate has gone from 3.90 per woman in 1960 to 1.49 in 2000. However, not many studies have examined the impact on women's health of reduced fertility rates, delayed fertility and more births to unmarried women. This paper presents information on the relation between family size and specific determinants o...

Ageing in many organisms, including humans, is accompanied by marked alterations in both general and specific protein synthesis. Protein synthesis is normally under tight control by a broad array of regulatory factors, which facilitate appropriate rates of mRNA translation. Are the wide changes in protein synthesis simply a corollary of the ageing process or do they have a causative role in sen...

Bridges are critical assets for the safe, reliable and functional operation of transportation networks. Infrastructure asset managers responsible ensuring that these bridges adhere to rigorous safety standards using finite resources available agencies. To facilitate strategy development present decisions stakeholders, a life cycle analysis is commonly performed. Many bridge owners use stochasti...

this paper presents an inventory model for deteriorating items in which shortages are allowed. it is assumed that the production rate is proportional to the demand rate and greater than demand rate. the inventory model is developed by considering four different circumstances. the optimal of the problem is obtained with the help of mathematica 7 software. numerical examples are given to illustra...

This paper introduces a Weibull hazard model formulated by the aggregated Markov method to forecast the expected life length of highway facilities and equipments and the inspection/replacement processes of tunnel lighting systems. First, the paper focuses on presenting a methodology to overcome the estimation bias issues caused by the incompleteness of the data set due to the lack of full life ...

The parallel machine replacement problem consists of finding a minimum cost replacement policy for a finite population of economically interdependent machines. In this paper, we formulate a stochastic version of the problem and analyze the structure of optimal policies under general classes of replacement cost functions. We prove that for problems with arbitrary cost functions, there can be opt...

This paper presents the reliability and mean time to failure estimation of a deteriorating system that deteriorates with time. The system is two unit active parallel system where the units operates simultaneously. In this study maintenance is not allowed to the system. Laplace transforms is being utilize to solve the mathematical model developed. Expressions for reliability and Mean time to fai...

While the development and application of inventory control models of deterioration products is one of the main concerns of researchers and practitioners, most studies done in this field have focused on inventory models under fixed supply lead time assumption. In this paper, at first we study researches done in inventory control of deteriorating items and classify them based on modeling approach...