Pollution has become a very serious threat to our environment. Monitoring pollution is the rst step toward planning to save the environment. The use of dierential equations, monitoring pollution has become possible. In this paper, a Ritz-collocation method is introduced to solve non-linear oscillatory systems such as modelling the pollution of a system of lakes. The method is based upon Bernoul...

Since achieving W3C recommendation status in 2004, the Web Ontology Language (OWL) has been successfully applied to many problems in computer science. Practical experience with OWL has been quite positive in general; however, it has also revealed room for improvement in several areas. We systematically analyze the identified shortcomings of OWL, such as expressivity issues, problems with its sy...

To the Editor: We agree with the Perspective article by Lehman and Guercio (March 7 issue)1 that national clinical exams are expensive. We also agree with First et al.2 that such exams positively shape the educational and assessment programs of medical schools, promote standardization of accreditation criteria, and provide an essential service to the public by filtering out candidates in need o...

Among different staining methods used to demonstrate the nuclear abnormalities, Feulgen is one of the most reliable method. Feulgen staining is specific, sensitive method for evaluating the DNA damages.It has been shown that using non-DNA specific stains for monitoring the nuclear anomalies lead to false-positive or false-negative results. From self-experience, immersing the stained slides in h...