We consider a nonlinear structured population model with a distributed recruitment term. The question of the existence of non-trivial steady states can be treated (at least!) in three different ways. One approach is to study spectral properties of a parametrized family of unbounded operators. The alternative approach, on which we focus here, is based on the reformulation of the problem as an in...

The main interest in epidemic models stems from their use in uncovering certain qualitative features of epidemic processes. A deterministic model of a general epidemic in a population with an arbitrary number of separate population centers is presented. The mixing within each center is assumed to be homogeneous, and the usual threshold theorem holds for each population. The mixing between cente...

"The purpose of this [one-page] note is to empirically investigate the impact of geographic after-tax real income differentials on geographic population growth rate differentials. The focus is on population growth rates in Florida's 67 counties over the period 1980-88." The authors conclude that "even after allowing for a variety of other location-influencing factors, including coastal access...

Population geneticists have shown that the effects of local extinction and recolonization on selectively neutral genetic diversity are sensitive to the number of individuals that migrate between groups. Here, we employ a spatially explicit metapopulation model to investigate the extent to which the effects of local extinction on selectively neutral cultural diversity and change are sensitive to...

Kazakhstan has very rich walnut genetic resources; however there is no ongoing walnut breeding program. Kazakhstan government has several projects in cooperation with Russia, USA, Bulgaria, Czech Republic and Poland for plant breeding purposes. In the present research walnut genetic resources originated from Jabağıl, Tulkıbas, Sayram, Lenger, and Botanical Garden of International Hodja Ahmet Ye...