This paper deals with the question of uniqueness of limit cycles in predator-prey systems of Gause type. By utilizing several transformations, these systems are reduced to a generalized Lienard system as discussed by Cherkas and Zhilevich and by Zhang. As a consequence, criteria for the uniqueness of limit cycles are derived, which include results of Cheng and is related to results in Liou and ...

Competition for shared resources has long been viewed as an important structuring agent in natural communities (Gause 1934; Strong 1980). Generally defined as the simultaneous use of limited resources by two or more organisms, competition can negatively impact population growth rates and influence community-level processes such as predation and/or how species respond to disturbances (Roughgarde...

We decompose the factor content of trade into Heckscher–Ohlin–Vanek trade and Ricardian trade. We measure factor content using only the United States' technology and also as Leontief advocated, using the local technology. In either case, differences in endowments are quite important in explaining the factor content of trade. If one uses raw estimated coefficients as a means of comparison, diffe...

Ratio-dependent predator-prey models are increasingly favored by field ecologists as an alternative or more suitable ones for predator-prey interactions where predation involves searching process. However, such models are not well studied mathematically in the past. In our recently work, we have shown that such models exhibit much richer dynamics than the traditional ones. This is especially tr...

Previous empirical tests have found that,contrary to the conclusions of the HeckscherOhlin model, the factor composition of traded goods fails to reveal relative factor abundance rankings. Using a nonparametric approach, this paper discusses the refutability of two of the assumptions of the HO model: that countries have identical homothetic preferences and identical constant returns to scale pr...