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The temperatures of black and white stripes on two zebras and a zebra hide were measured, throughout separate sunny days in Kenya. There is a 12–15oC difference between living zebras’ stripe temperatures throughout the middle seven daytime hours. The hide temperatures reach 16oC higher than the living zebras. Like all equids, zebras sweat to keep cool. Movement of sweat away from the skin is accelerated by the recently discovered surfactant equid protein latherin, a vital component of cooling in racehorses. Latherin decreases the surface tension of the sweat, facilitating evaporative cooling at the hair tips. We suggest that the abrupt temperature difference between the stripes causes chaotic air movement above the hair surface, thus enhancing evaporative heat dissipation. This cooling mechanism explains the lower temperatures of living zebra stripes than those of the inanimate hide. We observed that the black stripes can be separately erected, while the white remain flat. This may further refine the mechanism. There is an ongoing debate about the function of zebra stripes, recently focussed on the fact that stripes deter biting flies. The data and observations in this paper suggest that the primary function of the stripes may be thermoregulation and a secondary benefit, fly-deterrence. 相似文献
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Alison A. Carr-Chellman 《Systemic Practice and Action Research》2000,13(4):587-612
This reflective action research study examines faculty experience with distance education. Distance education has become increasingly of interest in higher education and is seen by many as the opportunity for systemic change in higher education. This study is a reflective action research project which examined the author's experiences teaching a distance version of a basic instructional design course at the same time as teaching a residential version of that same course. The examination finds significant faculty issues that emerged during the experience and specifically found concerns with the distance education learner. In the end, the study finds that as a tool for systemic change of higher education, distance delivery will have to engage faculty with their concerns in more substantive ways than they have to date. In essence, this study asserts that the current demands on distance educators are not motivating for traditional faculty members because of increased time demands, lack of traditional rhythm, lack of personal contact with students, and less evident interest among distant students in the areas that faculty value. 相似文献
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This paper examines the intersection of work focused on user-design between Drs. Banathy and Carr-Chellman. Definitions of user-design and evolution of the field are offered along with directions for future research and theory. 相似文献
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Yokoyama S Woods SL Boyle GM Aoude LG MacGregor S Zismann V Gartside M Cust AE Haq R Harland M Taylor JC Duffy DL Holohan K Dutton-Regester K Palmer JM Bonazzi V Stark MS Symmons J Law MH Schmidt C Lanagan C O'Connor L Holland EA Schmid H Maskiell JA Jetann J Ferguson M Jenkins MA Kefford RF Giles GG Armstrong BK Aitken JF Hopper JL Whiteman DC Pharoah PD Easton DF Dunning AM Newton-Bishop JA Montgomery GW Martin NG Mann GJ Bishop DT Tsao H Trent JM Fisher DE Hayward NK Brown KM 《Nature》2011,480(7375):99-103