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The coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution. It is of great value in rational evaluation of prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. A kind of characteristic finite difference schemes is put forward, from which optimal order estimates in l 2 norm are derived for the error in the approximate solutions. The research is important both theoretically and practically for the model analysis in the field, the model numerical method and software development. [ABSTRACT FROM AUTHOR]

Pseudomembranous colitis is mainly caused by antibiotics and Clostridium difficile infection. But conditions such as gastrointestinal surgery, antacid medication, anti-neoplastic agent or immunosuppressive agent which influences the normal flora of colon can induce colitis without the administration of any antibiotics. We experienced a 13 year-old male who was taking low-dose methotrexate for juvenile rheumatoid arthritis complained diarrhea and abdominal pain for 3 weeks. Sigmoidoscopic findings revealed diffuse patch yellowish pseudomembranes on the rectum. Histologic finding was compatible to pseudomembranous colitis. His symptom was improved after stop taking methotrexate and the administration of metronidazole. If a patient treated with immunosuppressive agents or antineoplastic agents complains diarrhea, fever or abdominal pain and has not improved with conservative care, pseudomembranous colitis should be taken into account as a differential diagnosis and prompt treatment is required for better prognosis.