The question as to how the ratio of horizontal to vertical transmission depends on the coefficient of horizontal transmission is investigated in host-parasite models with one or two parasite strains. In an apparent paradox, this ratio decreases as the coefficient is increased provided that the ratio is taken at the equilibrium at which both host and parasite persist. Moreover, a completely vert...

the gravity method is one of the first geophysical techniques used in oil and gas exploration. an algorithm is developed for a fast quantitative interpretation of gravity data generated by geometrically simple but also the estimated depths and other model parameters of a buried structure. following abdelrahman et al (1989). the general gravity anomaly expression produced by a sphere, an infinit...

New Caledonian (NC) crows are the most sophisticated tool manufacturers other than humans. The diversification and geographical distribution of their three Pandanus tool designs that differ in complexity, as well as the lack of ecological correlates, suggest that cumulative technological change has taken place. To investigate the possibility that high-fidelity social transmission mediated this ...

Cultural evolution is a complex process that can happen at several levels. At the level of individuals in a population, each human bears a set of cultural traits that he or she can transmit to its offspring (vertical transmission) or to other members of his or her society (horizontal transmission). The relative frequency of a cultural trait in a population or society can thus increase or decrea...

The evolution of virulence was studied in a virus subjected to alternating episodes of vertical and horizontal transmission. Bacteriophage f1 was used as the parasite because it establishes a debilitating but non-fatal infection that can be transmitted vertically (from a host to its progeny) as well as horizontally (infection of new hosts). Horizontal transmission was required of all phage at s...

We measured the eye movements of three sisters with Niemann-Pick type C disease who had a selective defect of vertical saccades, which were slow and hypometric. Horizontal saccades, and horizontal and vertical pursuit and vestibular eye movements were similar to control subjects. The initial movement of oblique saccades was mainly horizontal and most of the vertical component occurred after the...

We compared horizontal and vertical smooth pursuit eye movements in five healthy human subjects. When maintenance of pursuit was tested using predictable waveforms (sinusoidal or triangular target motion), the gain of horizontal pursuit was greater, in all subjects, than that of vertical pursuit; this was also the case for the horizontal and vertical components of diagonal and circular tracking...

Vertical phoria (vertical vergence in the absence of binocular feedback) can be trained to vary with non-visual cues such as vertical conjugate eye position, horizontal conjugate eye position and horizontal vergence. These prior studies demonstrated a low-level association or coupling between vertical vergence and several oculomotor cues. As a test of the potential independence of multiple eye-...

multinational corporations (mncs) are major actors in contemporary world. their negative and positive impacts on human life make clear the need for expanding their responsibilities. the aim of this article is to show how responsibilities of mncs evolve during recent 50-60 years. through two sections, the article examines vertical and horizontal expansion of mncs’ responsibilities and then recen...