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Evolutionary theory predicts that most populations should consist of roughly as many males as females. Recently, a variety of populations have been described which show very different proportions of the two sexes, especially in invertebrate species that contain individuals whose offspring are almost all female. Some of these instances can now be explained by the diverse actions of various ‘selfish’ elements residing in the cytoplasm of the individuals, which are transmitted exclusively through the female line. These instances of curious sex ratios exemplify an important principle: the fitness of genes, rather than of individuals, is the primary currency of evolution. 相似文献
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Lee P. Rylands Simon J. Roberts Howard T. Hurst 《European Journal of Sport Science》2017,17(2):127-131
The aim of this study was to ascertain if gear ratio selection would have an effect on peak power and time to peak power production in elite Bicycle Motocross (BMX) cyclists. Eight male elite BMX riders volunteered for the study. Each rider performed three, 10-s maximal sprints on an Olympic standard indoor BMX track. The riders’ bicycles were fitted with a portable SRM power meter. Each rider performed the three sprints using gear ratios of 41/16, 43/16 and 45/16 tooth. The results from the 41/16 and 45/16 gear ratios were compared to the current standard 43/16 gear ratio. Statistically, significant differences were found between the gear ratios for peak power (F(2,14)?=?6.448; p?=?.010) and peak torque (F(2,14)?=?4.777; p?=?.026), but no significant difference was found for time to peak power (F(2,14)?=?0.200; p?=?.821). When comparing gear ratios, the results showed a 45/16 gear ratio elicited the highest peak power,1658?±?221?W, compared to 1436?±?129?W and 1380?±?56?W, for the 43/16 and 41/16 ratios, respectively. The time to peak power showed a 41/16 tooth gear ratio attained peak power in ?0.01?s and a 45/16 in 0.22?s compared to the 43/16. The findings of this study suggest that gear ratio choice has a significant effect on peak power production, though time to peak power output is not significantly affected. Therefore, selecting a higher gear ratio results in riders attaining higher power outputs without reducing their start time. 相似文献
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The purpose of this study was to assess the power output of field-based downhill mountain biking. Seventeen trained male downhill cyclists (age 27.1 +/- 5.1 years) competing nationally performed two timed runs of a measured downhill course. An SRM powermeter was used to simultaneously record power, cadence, and speed. Values were sampled at 1-s intervals. Heart rates were recorded at 5-s intervals using a Polar S710 heart rate monitor. Peak and mean power output were 834 +/- 129 W and 75 +/- 26 W respectively. Mean power accounted for only 9% of peak values. Paradoxically, mean heart rate was 168 +/- 9 beats x min(-1) (89% of age-predicted maximum heart rate). Mean cadence (27 +/- 5 rev x min(-1)) was significantly related to speed (r = 0.51; P < 0.01). Analysis revealed an average of 38 pedal actions per run, with average pedalling periods of 5 s. Power and cadence were not significantly related to run time or any other variable. Our results support the intermittent nature of downhill mountain biking. The poor relationships between power and run time and between cadence and run time suggest they are not essential pre-requisites to downhill mountain biking performance and indicate the importance of riding dynamics to overall performance. 相似文献
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Benjamin Gonzalez O’Brien Elizabeth Hurst Loren Collingwood 《Mass Communication and Society》2019,22(6):756-778
The refugee sanctuary movement in the United States has shifted to include undocumented immigrants fleeing violence and economic strife. Given the negative tenor of coverage of undocumented immigration, and ties between framing and policy views on immigration, how the media frames sanctuary cities is likely to impact public perceptions of these cities and their policies. To assess media coverage of sanctuary policies, we analyzed articles from five national newspapers from 1980 to 2017 with both human content analysis and dictionary-based computational analysis. We find that framing around religion/morality and conflict has decreased, while stories focusing on crime and partisanship have increased. We discuss implications for public opinion and the likelihood that the American public will take their cues from media framing and elite discourse when it comes to sanctuary policies. 相似文献
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Mizuki H. Wyant Elizabeth H. Hurst Justin Reedy 《Journal of Intercultural Communication Research》2020,49(4):372-393
ABSTRACT This study examined international students’ interests in public issues in the U.S. and motivational factors behind their discourse or avoidance of such issues. In-depth interviews with international students revealed that they discuss certain public issues in the U.S. to gain or exchange information and knowledge, because these issues are relevant to themselves and others, or due to the misconceptions that others have about their country. Moreover, international students tend to avoid certain public issues because of the level of their knowledge and lack of interest in such issues and in order to avoid dissonance caused by the public issues. 相似文献
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Susan Hurst Dominic Marsh Dean Brown Shona Forbes 《New Review of Academic Librarianship》2017,23(4):442-452
This case study describes the creation of a leisure reading collection in the Clifford Whitworth library at the University of Salford. It briefly surveys existing literature on leisure reading collections and looks at the growing interest among U.K. academic libraries in recreational reading. It considers the reasons for promoting reading as a leisure activity to students and describes the processes of selecting, purchasing, and marketing the collection at Salford. It also considers possible future developments for the collection and the evaluation of the library's attempts to encourage a culture of reading among Salford students. The positive response to the collection suggests the development of leisure reading is a worthwhile activity for academic libraries to focus on and the study contains useful information for others who are interested in creating a similar collection. 相似文献
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Managerialism and equalities: tensions within widening access policy and practice for disabled students in UK universities 总被引:1,自引:0,他引:1
Sheila Riddell Elisabet Weedon Mary Fuller Mick Healey Alan Hurst Katie Kelly Linda Piggott 《Higher Education》2007,54(4):615-628
This paper draws on a four-year longitudinal ESRC funded project examining learning experiences of disabled students in higher
education in four universities. The focus here is on institutional responses to the demands of audit culture and legislation
in relation to making reasonable adjustments for students with impairments. The data comes from institutional documents and
face-to-face interviews with key informants within the institutions. The findings indicate that quality assurance regimes
and legislation have had some positive effect on improving access for disabled students; however, local factors and type of
institution also have a major impact on the way that national policies are expressed in particular contexts. 相似文献