Estrutura e desempenho das agropecuárias em dois países emergentes: um estudo comparativo entre Brasil e China

The paper compares the evolution of the brasilian and chinese agriculture emphasizing the post II World War period. It tries to show the structural changes in the agriculture in both countries and characterizing the dynamics of them. For both countries, the effort of industrialization after 1945 meant to sacrify the agriculture to a second plan. In the 1970’ Brazil and China begin to modernize their agriculture and adjust it to new challangers put by the necessity of guarantee the food security. The paper concludes that, in spite of some present problems, both countries face adequately the defiance on their agriculture.

A comparative evaluation of open loop and closed loop drug administration strategies in the treatment of AIDS.

In recent years, many researchers in the field of biomedical sciences have made successful use of mathematical models to study, in a quantitative way, a multitude of phenomena such as those found in disease dynamics, control of physiological systems, optimization of drug therapy, economics of the preventive medicine and many other applications. The availability of good dynamic models have been providing means for simulation and design of novel control strategies in the context of biological events. This work concerns a particular model related to HIV infection dynamics which is used to allow a comparative evaluation of schemes for treatment of AIDS patients. The mathematical model adopted in this work was proposed by Nowak & Bangham, 1996 and describes the dynamics of viral concentration in terms of interaction with CD4 cells and the cytotoxic T lymphocytes, which are responsible for the defense of the organism. Two conceptually distinct techniques for drug therapy are analyzed: Open Loop Treatment, where a priori fixed dosage is prescribed and Closed Loop Treatment, where the doses are adjusted according to results obtained by laboratory analysis. Simulation results show that the Closed Loop Scheme can achieve improved quality of the treatment in terms of reduction in the viral load and quantity of administered drugs, but with the inconvenience related to the necessity of frequent and periodic laboratory analysis.