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Stuart JH Biddle CK John Wang Nikos LD Chatzisarantis 《Journal of sports sciences》2013,31(12):973-989
Three studies are reported of children and youth aged 11–19 years (n?=?3478) examining the nature of beliefs about athletic ability. Drawing on related research in academic, moral and stereotyping domains, development of a psychometric instrument assessing athletic ability beliefs is detailed. Support was found for a multidimensional hierarchical structure that is invariant across age and gender. Confirmatory factor analysis revealed a structure comprising two higher-order factors of entity and incremental beliefs underpinned by beliefs that athletic ability is stable and a gift (entity), and is open to improvement and can be developed through learning (incremental). Incremental beliefs, indirectly through a task goal orientation, and entity beliefs directly, predicted self-reported amotivation towards physical education and sport. On the other hand, enjoyment of physical activity in youth was predicted directly by task orientation and incremental beliefs. Predictions concerning the moderating role of perceived competence were not supported. Our findings highlight the importance of ability beliefs and goals in understanding the determinants of physical activity in children and youth. 相似文献
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AN Pisarchik R Jaimes-Reátegui C Rodríguez-Flores JH García-López G Huerta-Cuellar FJ Martín-Pasquín 《Journal of The Franklin Institute》2021,358(4):2561-2575
Extreme multistability is the coexistence of a large number of attractors which can be reached by varying initial conditions. In this paper we show how this fascinating phenomenon can be used for secure communication. The main advantage of the communication system based on extreme multistability over a conventional chaos-based communication system is its exceptionally high security. The proposed system consists of two identical six-order oscillators; one in the transmitter and another one in the receiver, each exhibiting the coexistence of a large number of chaotic attractors. The oscillators are synchronized using a private channel through one of the system variables, while the information is transmitted via a public channel through another variable. The information is encrypted by varying the initial condition of one of the state variables in the transmitter using a chaotic map, adhering message packages in a staggered form to the coexisting attractors within the same time series of another state variable, which leads to switching among the coexisting chaotic attractors. To ensure communication security, the duration of the packages is shorter than synchronization time, so that synchronization attacks are ineffective. 相似文献
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Jack Lyle Ken Coleman Joseph Fletcher Littell Joseph Julian Dick Cavett Christopher Porterfield 《Communication Booknotes Quarterly》2013,44(10):113-114
Jack Lyle's The People Look at Public Television: 1974 (Washington: Corporation for Public Broadcasting, 1975—$1.00, paper) Ken Coleman's So You Want to be a Sportscaster (New York: Hawthron Books, 1973—$5.95) Joseph Fletcher Littell (ed.) Coping with Television (Evanston, Ill.: McDougal, Littell, 1973— cost not given, paper) Joseph Julian's This Was Radio: A Personal Memoir (New York: Viking, 1975—$8.85) Dick Cavett and Christopher Porterfield's Cavett (New York: Harcourt, Brace Jevanovich, 1974—$8.95) 相似文献
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医学院校课程整合的经验教训:学生、课程负责人与改革领导者的观点 总被引：1，自引：0，他引：1
美国医学院校的课程整合改革方兴未艾.加州大学旧金山分校医学院从2001级新生开始对课程体系进行大幅调整,本研究调查了该校参与改革的不同群体,包括教育改革的领导者、受到直接影响的学生、新建课程的负责人等对课程改革的态度,了解其对课程整合实施一年内的成绩和挑战的看法.结果表明,他们对跨学科教学、跨学科系室协作、课程关联的建立、课程内容的排序及框架构建等四个主题有相同的看法,也有不小的分歧. 相似文献
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OBJECTIVE: To assess the predictive validity of continuous measures of problem recognition (PR), intentions to change (ITC), and overall readiness for change (RFC) among primary caregivers who received in-home services following substantiated reports of child abuse or neglect. METHOD: A modified version of the University of Rhode Island Change Assessment scale was included in interviews with a sample of 353 primary caregivers at 4 weeks, 16 weeks, and 1 year after referral for in-home services. Additional data were obtained from administrative records and caseworker surveys. Hierarchical linear and nonlinear models were used to assess relationships between PR, ITC, RFC and changes over time in measures of individual and family functioning (e.g., parenting behaviors, children's behaviors, housing and economic problems, social support, and life events). Bivariate probit regression analysis was used to examine relationships between PR, ITC, RFC and the likelihood of subsequent reports of child maltreatment and out-of-home placements within 1 year after referral. RESULTS: Initial problem recognition and intentions to change predict a few improvements in individual and family functioning, along with significant reductions in the likelihood of additional reports of child maltreatment within 1 year. Initial intentions to change also predict reductions in the substantiation of subsequent reports of maltreatment. An overall measure of readiness for change predicts reductions in the likelihood of out-of-home placement. CONCLUSIONS: Problem recognition and intentions to change predict somewhat different outcomes; hence, there are few advantages of a combined measure of readiness for change. Further inquiry is needed to determine whether and how these associations are mediated by intervention processes or other factors in child welfare services populations. 相似文献
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LR Keytel JH Goedecke TD Noakes H Hiiloskorpi R Laukkanen L van der Merwe 《Journal of sports sciences》2013,31(3):289-290
The aims of this study were to quantify the effects of factors such as mode of exercise, body composition and training on the relationship between heart rate and physical activity energy expenditure (measured in kJ?·?min?1) and to develop prediction equations for energy expenditure from heart rate. Regularly exercising individuals (n = 115; age 18?–?45 years, body mass 47?–?120?kg) underwent a test for maximal oxygen uptake ([Vdot]O2max test), using incremental protocols on either a cycle ergometer or treadmill; [Vdot]O2max ranged from 27 to 81?ml?·?kg?1?·?min?1. The participants then completed three steady-state exercise stages on either the treadmill (10?min) or the cycle ergometer (15?min) at 35%, 62% and 80% of [Vdot]O2max, corresponding to 57%, 77% and 90% of maximal heart rate. Heart rate and respiratory exchange ratio data were collected during each stage. A mixed-model analysis identified gender, heart rate, weight, [Vdot]2max and age as factors that best predicted the relationship between heart rate and energy expenditure. The model (with the highest likelihood ratio) was used to estimate energy expenditure. The correlation coefficient (r) between the measured and estimated energy expenditure was 0.913. The model therefore accounted for 83.3% (R 2) of the variance in energy expenditure in this sample. Because a measure of fitness, such as [Vdot]O2max, is not always available, a model without [Vdot]O2max included was also fitted. The correlation coefficient between the measured energy expenditure and estimates from the mixed model without [Vdot]O2max was 0.857. It follows that the model without a fitness measure accounted for 73.4% of the variance in energy expenditure in this sample. Based on these results, we conclude that it is possible to estimate physical activity energy expenditure from heart rate in a group of individuals with a great deal of accuracy, after adjusting for age, gender, body mass and fitness. 相似文献
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We provide a wide-ranging review of health-related physical activity in children and adolescents using a behavioural epidemiology framework. In contrast to many other reviews, we highlight issues associated with true sedentary behaviours alongside physically active behaviours. Specifically, we review the evidence concerning the links between physical activity and cardiovascular disease, overweight and obesity, psychosocial measures, type II diabetes, and skeletal health. Although the evidence is unconvincing at times, several factors lead to the conclusion that promoting physical activity in youth is desirable. A review of the prevalence of physical activity and sedentary behaviours shows that many young people are active, but this declines with age. A substantial number are not adequately active for health benefits and current trends in juvenile obesity are a cause for concern. Prevalence data on sedentary behaviours are less extensive but suggest that total media use by young people has not changed greatly in recent years. Most children and adolescents do not exceed recommended daily hours of TV viewing. Physical activity is unrelated to TV viewing. We also identified the key determinants of physical activity in this age group, highlighting demographic, biological, psychological, behavioural, social and environmental determinants. Interventions were considered for school, family and community environments. Finally, policy recommendations are offered for the education, governmental, sport and recreation, health, and mass media sectors. 相似文献
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OBJECTIVE: To identify individual, family, and caseworker characteristics associated with problem recognition (PR) and intentions to change (ITC) in a sample of caregivers who received in-home child welfare services following substantiated reports of child abuse or neglect. METHODS: Caregivers were interviewed at 4 weeks, 16 weeks, and 1 year after referral for in-home services. In these interviews, the University of Rhode Island Change Assessment scale assessed PR and ITC in relation to caregiving practices. Additional data were obtained from administrative records and surveys of in-home services caseworkers. We used growth models to identify caregiver, family, and caseworker characteristics associated with initial levels of PR and ITC, and with changes in PR and ITC over time. RESULTS: Contrary to expectations, there were no overall increases in PR and ITC during the first 4 months of in-home services. PR and ITC scores fluctuated over time, in relation to some external events, case characteristics, and caseworker characteristics; however, we were able to account for small portions of the variance in PR and ITC. Controlling for social desirability bias and other variables in the analysis, negative life events, lack of network support, and the severity of caregiver depression were associated with greater PR; housing problems were associated with lower PR. Caregiver depression and age were associated with ITC. Caregivers whose children had been removed from their homes showed significant increases in ITC in the first few months of in-home services. The duration of caseworkers' child welfare experience predicted increases in their clients' PR in the first 4 months and more frequent contacts with an experienced caseworker predicted small, but significant increases in ITC over time. CONCLUSIONS: PR and ITC are associated with somewhat different case characteristics and may be affected by caseworkers' experience. 相似文献
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