Millimeter wave satellite communication studies. Results of the 1981 propagation modeling effort

Theoretical modeling associated with rain effects on millimeter wave propagation is detailed. Three areas of work are discussed. A simple model for prediction of rain attenuation is developed and evaluated. A method for computing scattering from single rain drops is presented. A complete multiple scattering model is described which permits accurate calculation of the effects on dual polarized signals passing through rain

Associations among Physical Activity, Health Indicators, and Employment in 12th Grade Girls

Objectives: This study compared physical activity, sedentary behaviors, and other health indicators between 1381 employed and nonemployed 12th grade girls. Methods: The girls were from 22 high schools in South Carolina (2002-2003); 56% of the girls were African American, and the mean age was 17.7 (0.6) years. Physical activity and sedentary behaviors were measured using the 3-Day Physical Activity Recall (3DPAR). Fitness, depressive symptoms, and smoking behavior were assessed. Results: Fifty percent of the girls were employed, and on average, employed girls worked 9.6 30-minute blocks per day. Girls who worked reported significantly (p≤0.001) higher average total metabolic equivalents (METs) (mean [M] 66.4, SE 0.5) than girls who did not work (M 59.5, SE 0.5). Also, a higher percent of girls who worked reported 2+ blocks of moderate to vigorous physical activity (MVPA) (89.3%), and fewer (20.2%) reported 4+ blocks of electronic media (EM) compared with girls who did not work (MVPA 62.7%, EM 41.7%). After on-the-job activity was subtracted, total METs for girls who worked was reduced to 48.0 (SE 0.4), and only 48.5% reported 2 or more blocks on average of MVPA. No significant differences (p\u3e0.05) were found between girls who reported working (W) and those who did not (NW) for body mass index (BMI) (W: M 25.2, SE 0.2; NW: M 24.6, SE 0.2), depression scores (W: M 14.4, SE 0.5); NW: M 14.4, SE 0.5), fitness (W: M 11.3 kg ● m/min/kg, SE 0.2; NW: M 11.7 kg ● m/min/kg, SE 0.2), or smoking during the past 30 days (W: 18.5%; NW: 17.4%). Conclusions: Nearly one third of employed high school girls\u27 total physical activity occurred while they were at work. Employed girls also spent less time using electronic media. Employment was not associated with fitness, smoking, or depressive symptoms in 12th grade girls

Longitudinal Invariance of the Center for Epidemiologic Studies-Depression Scale among Girls and Boys in Middle School

This study tested the longitudinal factorial invariance of a theoretically consistent, higher-order model for Center for Epidemiologic Studies-Depression (CES-D) scores among adolescent girls and boys in middle school. Data were collected from 2,416 adolescents who completed a survey containing the CES-D in the fall of 1998, spring of 1999, and spring of 2000. The invariance analyses were conducted using LISREL 8.50 with maximum likelihood estimation and the Satorra-Bentler scaled chi-square statistic and standard errors. The higher-order model demonstrated longitudinal, as well as gender, invariance of the overall factor structure and first- and second-order structure coefficients, first-order factor variances, second-order factor variances, and covariances, and item uniquenesses. The results demonstrate that meaningful comparisons of composite CES-D scores can be made across time among girls and boys in middle school

Naturally-Occurring Changes in Social-Cognitive Factors Modify Change in Physical Activity During Early Adolescence

Purpose To determine whether naturally-occurring changes in children’s motives and beliefs are associated with the steep decline in physical activity observed from childhood to early adolescence. Methods Latent growth modeling was applied in longitudinal tests of social-cognitive influences, and their interactions, on physical activity in a large cohort of boys and girls evaluated annually between 5th and 7th grades. Results Measurement equivalence of motives and beliefs was confirmed between boys and girls. After adjustment for gender and maturity differences, physical activity declined less in children who reported the least decreases in self-efficacy for overcoming barriers to activity and perceived parental support. Physical activity also declined less in students who persistently felt they had more parental and friend support for activity compared to those who reported the largest decrease in support from friends. After further adjustment for race, the decline in physical activity was less in those who had the largest decrease in perceived barriers and maintained a favorable perception of their neighborhood environment. Changes in enjoyment and social motives were unrelated to change in physical activity. Conclusion Using an objective measure of physical activity, we confirm that naturally-occurring changes in children’s beliefs about barriers to physical activity and their ability to overcome them, as well as perceptions of their neighborhood environment and social support, are concurrent with age-related declines in children’s physical activity. The longitudinal findings confirm these putative social-cognitive mediators as plausible, interacting targets of interventions designed to mitigate the marked decline in physical activity that occurs during the transition between elementary and middle schools

Failure of Post-Action Stages of the Transtheoretical Model to Predict Change in Regular Physical Activity: A Multiethnic Cohort Study

Background: Predicting variation in meeting recommended levels of physical activity is important for public health evaluation. Purpose: The purpose of this study is to determine the predictive value of stages of the Transtheoretical Model (TTM) for classifying people who meet the US Healthy People 2010 guideline for regular physical activity. Methods: A cohort (N = 497) from a random, multiethnic sample of 700 adults living in Hawaii was assessed at 6-month intervals three or more times for 2 years. Latent transition analysis was used to classify people according to TTM stages and separately according to whether they met the guideline. The predictive value of pre- vs. post-action stages was then tested. Results: Stages were more likely to falsely classify people as meeting the guideline than to falsely classify them as not meeting it. Probabilities of predicting 6-month transitions were about 50% for the stable class of meeting the guideline each time and just 25% for transitions between meeting and not meeting the guideline. Conclusion: The TTM post-action stages had limited usefulness in this cohort. Further longitudinal study is needed to determine whether TTM stages can accurately classify transitions from physical inactivity to physical activity below recommended levels

Moderating Effect of the Neighborhood Physical Activity Environment on the Relation Between Psychosocial Factors and Physical Activity in Children: A Longitudinal Study

Background Few studies have examined the moderating role of neighbourhood environments on the relation between psychosocial factors and physical activity, and results of these studies are mixed. This study examined this relationship in 636 fifth to seventh graders from South Carolina, USA. Methods From 2010 to 2013, children and their parent/guardian completed annual self-reported surveys assessing psychosocial factors, and children wore accelerometers for 1 week each year. Neighbourhood environments were classified as supportive or non-supportive for physical activity (PA) based on in-person audits of facilities near children’s homes and windshield surveys of children’s streets. Growth curve analyses were completed to assess the moderating effect of the neighbourhood physical activity environment (NPAE) on the relation between psychosocial factors and total physical activity (TPA) over time. Results Significant interactions on TPA were found for (1) time, NPAE and parent-reported parent support for PA; (2) time, NPAE and child-reported equipment in the home; (3) child-reported parental support for PA and time; (4) child-reported parental support for PA and NPAE; (5) PA self-schema and time and (6) child-reported parental encouragement and time. Parental support and a supportive NPAE were important for TPA, especially as children transitioned to middle school, whereas home equipment and a supportive NPAE were important for fifth graders’ TPA. Conclusion Consistent with the socioecological model, PA behaviour was dependent on interacting effects across levels of influence. Generally, both a supportive NPAE and positive psychosocial factors were needed to support TPA. Factors influencing PA across multiple levels should be addressed in PA interventions

Effects of chronic exercise on feelings of energy and fatigue: A quantitative synthesis

The authors investigated the effect of chronic exercise on feelings of energy and fatigue using metaanalytic techniques. Chronic exercise increased feelings of energy and lessened feelings of fatigue compared with control conditions by a mean effect delta of 0.37. The effect varied according to the presence or absence of a placebo control or whether chronic exercise was completed alone or in combination with an additional therapy. Investigations that used a placebo control and examined chronic exercise alone found no effect of chronic exercise on feelings of energy and fatigue. Certain placebo controls may increase feelings of energy and lessen feelings of fatigue when used with older adults or people with psychological distress. The results highlight the need for research identifying the most useful control conditions for accurately interpreting mental health outcome data obtained in chronic exercise investigations

Scale Development for Perceived School Climate for Girls’ Physical Activity

Objectives: To test an original scale assessing perceived school climate for girls\u27 physical activity in middle school girls. Methods: Confirmatory factor analysis (CFA) and structural equation modeling (SEM). Results: CFA retained 5 of 14 original items. A model with 2 correlated factors, perceptions about teachers\u27 and boys\u27 behaviors, respectively, fit the data well in both sixth and eighth-graders. SEM detected a positive, significant direct association of the teacher factor, but not the boy factor, with girls\u27 self-reported physical activity. Conclusions:School climate for girls\u27 physical activity is a measurable construct, and preliminary evidence suggests a relationship with physical activity

Scale Development for Perceived School Climate for Girls’ Physical Activity

Objectives: To test an original scale assessing perceived school climate for girls\u27 physical activity in middle school girls. Methods: Confirmatory factor analysis (CFA) and structural equation modeling (SEM). Results: CFA retained 5 of 14 original items. A model with 2 correlated factors, perceptions about teachers\u27 and boys\u27 behaviors, respectively, fit the data well in both sixth and eighth-graders. SEM detected a positive, significant direct association of the teacher factor, but not the boy factor, with girls\u27 self-reported physical activity. Conclusions: School climate for girls\u27 physical activity is a measurable construct, and preliminary evidence suggests a relationship with physical activity

Relationship between psychological and biological factors and physical activity and exercise behaviour in Filipino students

The aim of the present study was threefold. Firstly, it investigated whether a general measure or specific measure of motivational orientation was better in describing the relationship between motivation and exercise behaviour. Secondly, it examined the relationship between the four most popular indirect methods of body composition assessment and physical activity and exercise patterns. Thirdly, the interaction between motivation and body composition on physical activity and exercise behaviour was explored in a sample of 275 Filipino male and female students. Males were found to have higher levels of exercise whereas females had higher levels of physical activity. Furthermore, general self-motivation together with body weight and percentage body fat were found to be the best predictor of exercise behaviour whereas the tension/pressure subscale of the ‘Intrinsic Motivation Inventory’ (IMI) was the best predictor of levels of physical activity. However, significant gender differences were observed. That is, for the males only self-motivation and for the females only body weight and BMI predicted exercise behaviour. Also, tension/pressure predicted physical activity levels for the females but not the males. No inverse relationship was found between the four body composition measures and exercise and physical activity behaviour. The results support the notion that the psychobiological approach might be particularly relevant for high intensity exercise situations but also highlights some important gender differences. Finally, the results of this study emphasise the need for more cross-cultural research