This chapter describes the three main macro-geographical areas of cruise tourism (North and Central America, Europe, and 'the rest of the world') and their seasonal complementarities. The chapter shows how complex the world cruise market is in its geographical dimensions.
Background-Reports on the impact of a loss in the central field of vision on optokinetic nystagmus (OKN) are varied. A study was therefore undertaken to reassess the role of the central retina in the generation of OKN in a large group of patients with age related macular degeneration. Methods-Four groups of 20 patients were examined: a control group without scotoma and three groups with absolute central scotomas measuring 1°-10°, 11°-20°, and 21°-30°. OKN was elicited with black and white stripes moving nasally to temporally or temporally to nasally on a screen subtending 54°× 41°at four velocities (15, 30, 45, and 60°/s). OKN gain was measured using infrared oculography. Results-There was no significant diVerence in OKN gain between the control group and those with scotomas of 1°-10°a nd 11°-20°. A significant diVerence in OKN gain was found between the group with scotomas of 21°-30°and all other groups at stimulus velocities of 30, 45, and 60°/s (p<0.05). OKN gain significantly diminished with increasing stimulus velocity (p<0.05). No statistically significant diVerence was found in OKN gain between stimuli moving temporally to nasally and nasally to temporally. Conclusion-Abnormalities of OKN gain were noted only in patients with large scotomas. An intact macula is therefore not necessary for the generation of OKN. (Br J Ophthalmol 2001;85:169-172) The optokinetic nystagmus (OKN) combines with the vestibulo-ocular reflex and the smooth pursuit system in the task of retinal image stabilisation.
The Benelux seaport qstem is among the most diversified in the world. It includes a series of specialized, niche ports, and two mainports in the full meaning of the word, Rotterdam and Antwerp. In their shadow, a second-order hub port, Zeebrugge, is gaining increasing recognition in port and shipowners' circles. The future of the ports is partly in their own hands, and partly beyond their control, as their prosperity is also conditioned by their hinterland relationships. The most original part of the article deals with a coherent structuring of their West-East and North-South intermodal links in a Benelux and European perspective, rather than taking into account sub-optimal national interests. The case for a new, highcapacity Rotterdam-Antwerp-Lile railway line, with a Zeebrugge-Ghent branch is explored.
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