Frequency sweep rate dependence on the dielectrophoretic response of polystyrene beads and red blood cells     

T. N. G. Adams  K. M. Leonard  A. R. Minerick 《Biomicrofluidics》2013,7(6)

Alternating current (AC) dielectrophoresis (DEP) experiments for biological particles in microdevices are typically done at a fixed frequency. Reconstructing the DEP response curve from static frequency experiments is laborious, but essential to ascertain differences in dielectric properties of biological particles. Our lab explored the concept of sweeping the frequency as a function of time to rapidly determine the DEP response curve from fewer experiments. For the purpose of determining an ideal sweep rate, homogeneous 6.08 μm polystyrene (PS) beads were used as a model system. Translatability of the sweep rate approach to ∼7 μm red blood cells (RBC) was then verified. An Au/Ti quadrapole electrode microfluidic device was used to separately subject particles and cells to 10Vpp AC electric fields at frequencies ranging from 0.010 to 2.0 MHz over sweep rates from 0.00080 to 0.17 MHz/s. PS beads exhibited negative DEP assembly over the frequencies explored due to Maxwell-Wagner interfacial polarizations. Results demonstrate that frequency sweep rates must be slower than particle polarization timescales to achieve reliable incremental polarizations; sweep rates near 0.00080 MHz/s yielded DEP behaviors very consistent with static frequency DEP responses for both PS beads and RBCs.  相似文献   

Personal and Situational Factors Affecting Exercise Involvement: The Importance of Enjoyment     

Leonard M. Wankel 《Research quarterly for exercise and sport》2013,84(3):275-282

Abstract

Interviews were conducted with continuing participants (n=51) and dropouts (n=60) from a male employee fitness program in order to investigate programmatic, personal, and social factors affecting involvement. It was found that a combination of items pertaining to reactions to the program, goals for initially joining the program, and social support for involvement in the program could effectively discriminate between the participant and dropout groups. Continuing participants scored higher than dropouts on the goals to develop recreational skills, to go out with friends, to satisfy curiosity, to release competitive drive and to develop social relationships. They also reported a greater increase in positive reactions to the program over their period of involvement in it than did the dropouts. Continuing participants rated the level of friendship within the exercise class higher and reported receiving more encouragement for involvement from their friends and work supervisor than did dropouts. Participants reported greater liking for the program activities than did the dropouts, while dropouts reported a greater dislike for the inconvenient program schedule. Implications of the results for program organization and conduct are discussed.  相似文献   

Laboratory Assessment of Choice between Exercise or Sedentary Behaviors     

Linda S. Vara  Leonard H. Epstein 《Research quarterly for exercise and sport》2013,84(3):356-360

The purpose of this study was to compare cardiovascular fitness between obese and nonobese children. Based on body mass index, 118 were classified as obese (boys [OB] = 62, girls [OG] = 56), while 421 were nonobese (boys [NOB] = 196, girls [NOG] = 225). Cardiovascular fitness was determined by a 1-mile [1.6 km] run/walk (MRW) and estimated peak oxygen uptake (VO₂peak) and analyzed using two-way analyses of variance (Gender x Obese/Nonobese). MRW times were significantly faster (p < .05) for the NOB (10 min 34 s) compared to the OB (13 min 8 s) and the NOG (13 min 15 s.) compared to the OG (14 min 44 s.). Predicted VO₂peak values (mL·kg^-1·min^-1) were significantly higher (p < .05) for the NOB (48.29) compared to the OB (41.56) and the NOG (45.99) compared to the OG (42.13). MRW was compared between obese and nonobese participants on the President's Challenge (2005), the National Children and Youth Fitness Study, and FITNESSGRAM® HFZ standards. The nonobese boys and girls scored higher on all three, exhibiting better cardiovascular fitness as compared to obese counterparts.  相似文献   

Copyright and you     

Leonard D. DuBoff 《TechTrends》2005,49(5):12-14

Trademark, copyright and patent protections are necessary concerns in education and training, not only from an economic perspective, but for many other reasons. For example, Georgia Crown Distributing Co. was hired by the University of Georgia Alumni Association to distribute bottles of wine bearing the university’s logo  相似文献   

Scholarship vs. Repatriationism     

James W. Springer 《Academic Questions》2005,19(1):6-36

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Does the presentation style of questions inserted into text influence understanding and retention of science concepts?   总被引：1，自引：0，他引：1  

William H. Leonard 《科学教学研究杂志》1987,24(1):27-37

The purpose of this research was to determine the relative effects of the presentation style of questions inserted into text materials for students in university introductory biology. The sample was randomly assigned to seven treatment groups of approximately equal size and read a 2,354-word passage on bacterial adaptations taken from a popular university general biology textbook. Experimental treatment groups read the same passage with (1) questions placed at the beginning of selected paragraphs and with the questions presented with (2) underlining, (3) in uppercase, (4) set above the paragraph, (5) underlined and set above, and (6) set above in uppercase respectively. The criterion variable was a 20-item multiple-choice exam with five possible answers per question given once to all students immediately after they read the passage and again exactly four weeks later. Presentation strategy groups were contrasted against the reading without questions groups. Four of the six groups reading with questions at the beginning of the paragraph scored significantly higher on the test given immediately after the reading than the group reading without questions. There were no significant differences between any of the group scores for the test given four weeks after reading. Other differences in results between these strategies and implications for text writers are discussed.  相似文献   

Neurobehavioral factors associated with referral for learning problems in a community sample: evidence for an adaptational model for learning disorders     

Waber DP  Weiler MD  Forbes PW  Bernstein JH  Bellinger DC  Rappaport L 《Journal of learning disabilities》2003,36(5):467-483

We evaluated community general education (CGE; n = 178), community special education (CSE; n = 30) and hospital-referred (HR, n = 145) children (ages 7-6 to 11-11) prospectively over a 2-year period. During this period, 17 CGE children were referred for evaluation (community referred; CR). Prior to referral, CR children performed more poorly than community-nonreferred (CNR) children on cognitive ability, academic achievement, attention problems, and information processing. CR group performance was equivalent to that of CSE and HR groups, but HR children showed poorer academic achievement. Referred children performed more poorly on all measures than nonreferred, whether they met formal diagnostic criteria for a learning disorder or not. Learning disorders may be better conceptualized as a context-dependent problem of functional adaptation than as a disability analogous to physical disabilities, raising questions about the validity of using psychometric test scores as the criterion for identification.  相似文献   

Parental coping with children's negative emotions: relations with children's emotional and social responding   总被引：2，自引：0，他引：2  

Fabes RA  Leonard SA  Kupanoff K  Martin CL 《Child development》2001,72(3):907-920

This study examined the relation between parents' reactions to children's negative emotions and social competence. Additionally, the role of parental emotional distress in children's emotional socialization was examined. The emotional reactions of 57 preschoolers (33 girls, 24 boys; M age = 59.2 months) were observed during their free-play interactions. Parents (mostly mothers) completed questionnaires about their reactions to children's negative emotions. An index of children's social competence was obtained from teachers. Results indicated that the relation between harsh parental coping strategies and children's emotional responding was moderated by parental distress. In addition, the relation of the interaction of parental coping and distress to children's social competence was mediated by children's level of emotional intensity. It was concluded that distressed parents who use harsh coping strategies in response to children's negative emotions have children who express emotion in relatively intense ways. In turn, these children find it relatively difficult to behave in a socially competent manner.  相似文献   

The Potential to Develop a Career in Science: Young Women's Issues and Their Implications for Careers Guidance Initiatives     

Helen M. Madill  Anna-Lisa Ciccocioppo  Leonard L. Stewin  Margaret-Ann Armour  T. Craig Montgomerie 《International journal for the advancement of counseling》2004,26(1):1-19

An exploratory study of career decision-making was conducted with young women in science, engineering, and technology programs in colleges, universities, and technical institutes. The participants described issues impacting on their continuation in their programs such as educational policies, levels of financial support, and the degree of gender equity expected and encountered. Difficulties with financial resources, institutional policies, and combining studying and working roles were recurrent themes. Family members and other role models and educational and work experiences were important influences in career decision-making. Recommendations for counselling to enhance the undergraduate experience and directions for future research are outlined.  相似文献   

Differences in Student Outcomes by Types of Living–Learning Programs: The Development of an Empirical Typology     

Karen Kurotsuchi Inkelas  Matthew Soldner  Susan D. Longerbeam  Jeannie Brown Leonard 《Research in higher education》2008,49(6):495-512

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