BACKGROUND Many analyses of the determinants of fertility make a distinction between proximate and background determinants. The former include behavioral factors such as the use of contraception or abortion through which the background determinants (e.g., social and economic variables) affect fertility. These relationships were first recognized by Davis and Blake (1956), who defined a large set...

Fibrotic disorders account for an increasing burden of disease-associated morbidity and mortality worldwide. Although numerous risk factors have been recognized, the etiologies of many of these clinical syndromes have not been identified, and they are often termed idiopathic or cryptogenic. Here, we provide an evolutionary perspective on fibrosis aimed at elucidating its etiopathogenesis. By as...

Scientists, in their endeavors, deal with different levels of causation, which can be conceptualized on a continuum of proximate to ultimate. Proximate causes refer to more immediate variables, ultimate to those more remote. For example, if you were asked why you were reading this chapter, a proximate explanation might be that it was recommended for a course you were teaching or taking; an ulti...

The distinctions inherent in the proximate-ultimate dichotomy have a long history. I examined several issues related to this distinction. It is important that distinctions among different problem areas be made so that the type of answer presented in research in animal behavior is appropriate for the type of questions being asked. This may require more than the two-way distinction between the pr...

pearl millet has tolerance to harsh growing conditions such as drought. it is at least equivalent to maize and generally superior to sorghum in protein content and metabolizable energy levels. thus it is of importance for poultry feeding. amino acid (aa) determination is expensive and time consuming. therefore nutritionists have prompted a search for alternatives to estimate aa levels. traditio...

Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical suppor...

Development and projections of wireless PDAs enable to envisage the design of new application classes that exploit short range and direct communications (e.g. one-hop communications). In a close future we may imagine mobile users dynamically and spontaneously exchanging information as soon as they are close enough. In such a context, a connection between two nodes may be broken at any time beca...