In real world scheduling applications, machines might not be available during certain time periods due to deterministic or stochastic causes. In this article, the machine scheduling with availability constraints for both deterministic and stochastic cases with different environments, constraints and performance measures will be discussed. The existing body of research work in the literature will be completely reviewed and the NP-complete models will be identified.

In this study, single machine scheduling with exible maintenance is investigated with non-RESUMABLE jobs by minimizing the weighted number of tardy jobs. It is assumed that the machine stops for a constant interval time during the scheduling period to perform mainte-nance. In other words, the starting time of maintenance is the decision variable. By reviewing the literature, we noticed that this problem has not been studied yet. Ini-tially, it is proved that the problem is NP-hard. Then, a mathematical model is proposed and solved by the GAMS software. Because of the long time for solving the problem with an exact method, we develop a heuris-tic algorithm.

Background and Objective: With the development of nanotechnology and materials science, however, these materials also have been used increasingly with the potential toxic effects of many unknown substances and many nano-particles were built with new properties and new despite. Therefore, in this study the effects of feeding with different sources of iron and zinc in the tissue of common carp (Cyprinus carpio) were measured. Material and Methodology: For this purpose, 420 common carp (with an average initial weight 45±, 4. 7 g) was prepared, the fish sterilization and adapted to the laboratory conditions for 10 days. Then fish were randomly divided into seven groups, the first group was considered as control groups respectively and other fish received values of 10, 50 and 100 micrograms of iron and zinc nanoparticles per gram of food for 60 days. Findings: Microscopic studies of organs (liver, kidney) study showed that increasing the concentration of nano-materials could have more evenly histopathological lesions in the liver tissue and cells. In the medium and low concentrations of both nano-particle and in high doses of iron nanoparticles, by removing the inducer tissues could again resume their physiological activity, but in high doses, unlike the iron nano-particles, the repair tissue was not RESUMABLE. Discussion and Conclusion: From the above results it can be concluded that increasing the concentration of the nano-particles could increase tissue damage and can be considerable factors.