Journal of Basrah Researches (Sciences)

In this work , I introduce a relations among four kinds of continuous functions ( i.e. continuous , -continuous , weakly - -continuous , weakly - -continuous ) and relations among four open functions ( i.e. open , -open , -open , -open ) in Topological , Bitopological and Tritopological spaces

Waiting for service is part of our daily life. The study of queues determines the measures of performance of a queuing situation. This information is used to decide on an appropriate level of service for the facility may be offered. We consider in this study the simulation of a heavy traffic single runway airport. We are interested to study the situation for two different cases: first, the service offered to the airplane that reaches first (either landing or taking-off), the second, the priority is given to the landing airplanes rather to takeoff airplanes. The later case is crucial, because it is a matter of risk in waiting for a long time for landing. However, the taking-off airplanes will not get permission to takeoff unless there is no airplane predisposition to landing. Our objective is to provide decision makers with comparative information that may be of help to take an appropriate action to determine a suitable service level for the airport. The airport aims to reduce the waiting time for the landing airplanes beside keeping the takeoff airplanes waiting for a reasonable time.

A total of 158 specimen of seastar collected during the period from Feb. 1999 to Apr. 2000 from Khor Al- Umia (North-West Arabian Gulf). The stomachs of all collected seastar were dissected and the food composition were analyzed. Mollusca occurred in 87% of all stomachs containing food and contributed 94% of food volume. The most important food items were Monodonata vermiculata, Mitrella blanda, Solen vagina, Paphia texilla. There was no distinct seasonal difference in the composition of the diet, but tendency to minimize feeding activity in February-April, probably related to the spawning period.

The effect of Co++ and Cd++ on the growth rate and photosynthesis efficiency of bluegreen alga Oscillatoria amoena was studied under controlled laboratory conditions. These metals were treated with alga at different concentrations media (1, 2 and 5 ppm) of both elements. The growth rate of alga was inhibited by different concentrations of metals. Cd++ was more toxic than Co++. The results concerning the effects of different concentrations of heavy metals on photosynthesis (O2 evolution) has shown reduction of the amount of O2 evolution by alga in response to the increase of Cd++ and Co++ concentrations, photosynthesis was more sensitive to Cd++ concentration than to that of Co++.