The influence of upper-body pre-cooling on repeated sprint performance in moderate ambient temperatures     

Stephen S Cheung  Alicia M Robinson 《Journal of sports sciences》2013,31(7):605-612

In this study, we examined the effects of upper-body pre-cooling before intermittent sprinting exercise in a moderate environment. Seven male and three female trained cyclists (age 26.8±5.5 years, body mass 68.5±9.5?kg, height 1.76±0.13?m, [Vdot]O_2peak 59.0±11.4?mL?·?kg^?1?·?min^?1; mean±s) performed 30?min of cycling at 50% [Vdot]O_2peak interspersed with a 10-s Wingate cycling sprint test at 5?min intervals. The exercise was performed in a room controlled at 22^oC and 40% relative humidity. In the control session, the participants rested for 30?min before exercise. In the pre-cooling session, the participants wore the upper segment of a liquid conditioning garment circulating 5^oC coolant until rectal temperature decreased by 0.5^oC. Rectal temperature at the start of exercise was significantly lower in the pre-cooling (36.5±0.3^oC) than in the control condition (37.0±0.5^oC), but this difference was reduced to a non-significant 0.4^oC throughout exercise. Mean skin temperature was significantly lower in the pre-cooling (30.7±2.3^oC) than in the control condition (32.5±1.6^oC) throughout exercise. Heart rate during submaximal exercise was similar between the two conditions, although peak heart rate after the Wingate sprints was significantly lower in the pre-cooling condition. With pre-cooling, mean peak power (909±161?W) and mean overall power output (797±154?W) were similar to those in the control condition (peak 921±163?W, mean 806±156?W), with no differences in the subjective ratings of perceived exertion. These results suggest that upper-body pre-cooling does not provide any benefit to intermittent sprinting exercise in a moderate environment.  相似文献   

HKUST’s Experience with CONSER: A Two Decade Partnership     

Shuk Man Ada Cheung 《Cataloging & classification quarterly》2020,58(3-4):342-350

Abstract

The Library of the Hong Kong University of Science and Technology (HKUST), as the only CONSER full member outside North America, has entered into its twentieth year of CONSER membership. This article provides a historical overview of the Library’s participation in the program, its considerations and concerns when it first joined CONSER, and challenges and benefits it experienced over the years. The PCC-related activities that the Library has participated in have increased its growth in the field. The article concludes with future challenges the Library and its community will face.  相似文献   

Microfluidic fabrication of water-in-water (w/w) jets and emulsions     

Cheung Shum H  Varnell J  Weitz DA 《Biomicrofluidics》2012,6(1):12808-128089

We demonstrate the generation of water-in-water (w/w) jets and emulsions by combining droplet microfluidics and aqueous two-phase systems (ATPS). The application of ATPS in microfluidics has been hampered by the low interfacial tension between typical aqueous phases. The low tension makes it difficult to form w/w droplets with conventional droplet microfluidic approaches. We show that by mechanically perturbing a stable w/w jet, w/w emulsions can be prepared in a controlled and reproducible fashion. We also characterize the encapsulation ability of w/w emulsions and demonstrate that their encapsulation efficiency can be significantly enhanced by inducing formation of precipitates and gels at the w/w interfaces. Our work suggests a biologically and environmentally friendly platform for droplet microfluidics and establishes the potential of w/w droplet microfluidics for encapsulation-related applications.  相似文献   

In situ pressure measurement within deformable rectangular polydimethylsiloxane microfluidic devices     

Cheung P  Toda-Peters K  Shen AQ 《Biomicrofluidics》2012,6(2):26501-2650112

In this paper, we present a simple procedure to incorporate commercially available external pressure transducers into existing microfluidic devices, to monitor pressure-drop in real-time, with minimal design modifications to pre-existing channel designs. We focus on the detailed fabrication steps and assembly to make the process straightforward and robust. The work presented here will benefit those interested in adding pressure drop measurements in polydimethylsiloxane (PDMS) based microchannels without having to modify existing channel designs or requiring additional fabrication steps. By using three different devices with varying aspect ratio channels (wh0, width/depth), we demonstrate that our approach can easily be adapted into existing channel designs inexpensively. Furthermore, our approach can achieve steady state measurements within a matter of minutes (depending on the fluid) and can easily be used to investigate dynamic pressure drops. In order to validate the accuracy of the measured pressure drops within the three different aspect ratio devices, we compared measured pressure drops of de-ionized water and a 50 wt. % glycerol aqueous solution to four different theoretical expressions. Due to the deformability of PDMS, measured pressure drops were smaller than those predicted by the rigid channel theories (plate and rectangular). Modification of the rigid channel theories with a deformability parameter α provided better fits to the measured data. The elastic rectangular expression developed in this paper does not have a geometric restriction and is better suited for microchannels with a wider range of aspect ratios.  相似文献   

Firey linear combinations of convex bodies     

熊革  肖启名 《上海大学学报(英文版)》2009,13(2):102-104

For convex bodies, the Firey linear combinations were introduced and studied in several papers. In this paper the mean width of the Firey linear combinations of convex bodies is studied, and the lower bound of the mean width of the Firey linear combinations of convex body and its polar body is given.  相似文献   

The key factors affecting students’ individual interest in school science lessons     

Derek Cheung 《International Journal of Science Education》2018,40(1):1-23

Individual interest in school science lessons can be defined as a relatively stable and enduring personal emotion comprising affective and behavioural reactions to events in the regular science lessons at school. Little research has compared the importance of different factors affecting students’ individual interest in school science lessons. The present study aimed to address this gap, using a mixed methods design. Qualitative interview data were collected from 60 Hong Kong junior secondary school students, who were asked to describe the nature of their interest in science lessons and the factors to which they attribute this. Teacher interviews, parent interviews, and classroom observations were conducted to triangulate student interview data. Five factors affecting students’ individual interest in school science lessons were identified: situational influences in science lessons, individual interest in science, science self-concept, grade level, and gender. Quantitative data were then collected from 591 students using a questionnaire. Structural equation modelling was applied to test a hypothesised model, which provided an acceptable fit to the student data. The strongest factor affecting students’ individual interest in school science lessons was science self-concept, followed by individual interest in science and situational influences in science lessons. Grade level and gender were found to be nonsignificant factors. These findings suggest that teachers should pay special attention to the association between academic self-concept and interest if they want to motivate students to learn science at school.  相似文献   

The influence of upper-body pre-cooling on repeated sprint performance in moderate ambient temperatures     

Cheung S  Robinson A 《Journal of sports sciences》2004,22(7):605-612

In this study, we examined the effects of upper-body pre-cooling before intermittent sprinting exercise in a moderate environment. Seven male and three female trained cyclists (age 26.8+/-5.5 years, body mass 68.5+/-9.5 kg, height 1.76+/-0.13 m, V O2peak 59.0+/-11.4 mL. kg(-1). min(-1); mean+/-s) performed 30 min of cycling at 50% V O2peak interspersed with a 10-s Wingate cycling sprint test at 5 min intervals. The exercise was performed in a room controlled at 22 degrees C and 40% relative humidity. In the control session, the participants rested for 30 min before exercise. In the pre-cooling session, the participants wore the upper segment of a liquid conditioning garment circulating 5 degrees C coolant until rectal temperature decreased by 0.5 degrees C. Rectal temperature at the start of exercise was significantly lower in the pre-cooling (36.5+/-0.3 degrees C) than in the control condition (37.0+/-0.5 degrees C), but this difference was reduced to a non-significant 0.4 degrees C throughout exercise. Mean skin temperature was significantly lower in the pre-cooling (30.7+/-2.3 degrees C) than in the control condition (32.5+/-1.6 degrees C) throughout exercise. Heart rate during submaximal exercise was similar between the two conditions, although peak heart rate after the Wingate sprints was significantly lower in the pre-cooling condition. With pre-cooling, mean peak power (909+/-161 W) and mean overall power output (797+/-154 W) were similar to those in the control condition (peak 921+/-163 W, mean 806+/-156 W), with no differences in the subjective ratings of perceived exertion. These results suggest that upper-body pre-cooling does not provide any benefit to intermittent sprinting exercise in a moderate environment.  相似文献   

Experimenter language choice and ethnic affirmation by Chinese trilinguals in Hong Kong     

Michael H. Bond  Man-King Cheung 《Int J Intercult Relat》1984,8(4):347-356

When communicating with a member of his or her ethnic in-group, a multilingual typically uses his common first language. If, however, the multilingual uses a common second or third language, we believe this choice will indicate his or her endorsement of attitudes believed to be held by that language out-group. An audience will respond to this implicit statement by a shift in its ethnically relevant altitudes either towards or away from the position of the speaker. Convergence is assumed to occur if relations between the language communities are harmonious, ethnic affirmation if relations are hostile. To explore this reasoning, experimenters addressed Chinese trilinguals in their first language of Cantonese, their second language of English, or their third language of Mandarin. When instructed in Mandarin, subjects assumed their experimenter held more traditional Chinese beliefs and they themselves completed a measure of traditional Chinese beliefs in a more Western direction. Although most Hong Kong students at university are ambivalent about their colonial status under Great Britain, they oppose Hong Kong's reversion to China in 1997 and are threatened by this prospect. Consequently, we believe that they responded to an experimenter speaking the Mandarin language of China by affirming a more Western identity.  相似文献   

Examining students’ affective commitment toward country: a case study of a Singapore primary school     

Khe Foon Hew  Wing Sum Cheung 《Asia Pacific Journal of Education》2011,31(1):19-31

The purpose of this study was to examine students’ affective commitment toward Singapore. Affective commitment refers to the sense of attachment to the nation state. The sample was taken from 286 students in a primary school. In the first section of the paper, we described the design of a Likert-type Affective Commitment to Country questionnaire. Factor analyses (principal component analysis and confirmatory factor analysis) showed evidence of construct validity for the 10-item scale, and an overall Cronbach alpha reliability coefficient of 0.91. In the second section, we reported the statistics related to the students’ affective commitment scores. Overall, a positive affective commitment toward the country was found. Results of our t-test analyses revealed that no statistically significant difference was found between boys and girls for each of the questionnaire items. However, students who had higher academic achievement reported significantly higher scores than their lower ability counterparts with regard to six items of the questionnaire. Suggestions for future research are discussed.  相似文献   

Application of text mining to the development and validation of a geographic search filter to facilitate evidence retrieval in Ovid MEDLINE: An example from the United States     

Antoinette Cheung MPH  Evan Popoff MSc  Shelagh M. Szabo MSc 《Health information and libraries journal》2023,40(2):169-180

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