Shaping electron wave functions in a carbon nanotube with a parallel magnetic field

A magnetic field, through its vector potential, usually causes measurable changes in the electron wave function only in the direction transverse to the field. Here we demonstrate experimentally and theoretically that in carbon nanotube quantum dots, combining cylindrical topology and bipartite hexagonal lattice, a magnetic field along the nanotube axis impacts also the longitudinal profile of the electronic states. With the high (up to 17T) magnetic fields in our experiment the wave functions can be tuned all the way from "half-wave resonator" shape, with nodes at both ends, to "quarter-wave resonator" shape, with an antinode at one end. This in turn causes a distinct dependence of the conductance on the magnetic field. Our results demonstrate a new strategy for the control of wave functions using magnetic fields in quantum systems with nontrivial lattice and topology.Comment: 5 figure

International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) : Contributions to Understanding the Global Obesity Epidemic

The purpose of this review is to summarize the scientific contributions of the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) in extending our understanding about obesity in children from around the world. ISCOLE was a multi-national study of 9 to 11 year-old children from sites in 12 countries from all inhabited continents. The primary purpose was to investigate relationships between lifestyle behaviors and obesity, and the influence of higher-order characteristics such as behavioral settings, and physical, social and policy environments. ISCOLE has made several advances in scientific methodology related to the assessment of physical activity, dietary behavior, sleep and the neighborhood and school environments. Furthermore, ISCOLE has provided important evidence on (1) epidemiological transitions in obesity and related behaviors, (2) correlates of obesity and lifestyle behaviors at the individual, neighborhood and school levels, and (3) 24-h movement behaviors in relation to novel analytical techniques. A key feature of ISCOLE was the development of a platform for international training, data entry, and data quality for multi-country studies. Finally, ISCOLE represents a transparent model for future public-private research partnerships across low, middle and high-income countries.Peer reviewe

Emotional Eating, Health Behaviours, and Obesity in Children: A 12-Country Cross-Sectional Study

Eating in response to negative emotions (emotional eating, EE) may predispose an individual to obesity. Yet, it is not well known how EE in children is associated with body mass index (BMI) and health behaviours (i.e., diet, physical activity, sleep, and TV-viewing). In the present study, we examined these associations in a cross-sectional sample of 5426 (54% girls) 9–11-year-old children from 12 countries and five continents. EE, food consumption, and TV-viewing were measured using self-administered questionnaires, and physical activity and nocturnal sleep duration were measured with accelerometers. BMI was calculated using measured weights and heights. EE factor scores were computed using confirmatory factor analysis, and dietary patterns were identified using principal components analysis. The associations of EE with health behaviours and BMI z-scores were analyzed using multilevel models including age, gender, and household income as covariates. EE was positively and consistently (across 12 study sites) associated with an unhealthy dietary pattern (β = 0.29, SE = 0.02, p < 0.0001), suggesting that the association is not restricted to Western countries. Positive associations between EE and physical activity and TV viewing were not consistent across sites. Results tended to be similar in boys and girls. EE was unrelated to BMI in this sample, but prospective studies are needed to determine whether higher EE in children predicts the development of undesirable dietary patterns and obesity over time

Emotional Eating, Health Behaviours, and Obesity in Children: A 12-Country Cross-Sectional Study

Eating in response to negative emotions (emotional eating, EE) may predispose an individual to obesity. Yet, it is not well known how EE in children is associated with body mass index (BMI) and health behaviours (i.e., diet, physical activity, sleep, and TV-viewing). In the present study, we examined these associations in a cross-sectional sample of 5426 (54% girls) 9–11-year-old children from 12 countries and five continents. EE, food consumption, and TV-viewing were measured using self-administered questionnaires, and physical activity and nocturnal sleep duration were measured with accelerometers. BMI was calculated using measured weights and heights. EE factor scores were computed using confirmatory factor analysis, and dietary patterns were identified using principal components analysis. The associations of EE with health behaviours and BMI z-scores were analyzed using multilevel models including age, gender, and household income as covariates. EE was positively and consistently (across 12 study sites) associated with an unhealthy dietary pattern (β = 0.29, SE = 0.02, p < 0.0001), suggesting that the association is not restricted to Western countries. Positive associations between EE and physical activity and TV viewing were not consistent across sites. Results tended to be similar in boys and girls. EE was unrelated to BMI in this sample, but prospective studies are needed to determine whether higher EE in children predicts the development of undesirable dietary patterns and obesity over time

Sleep characteristics and health-related quality of life in 9- to 11-year-old children from 12 countries

IntroductionPrevious studies have linked short sleep duration, poor sleep quality, and late sleep timing with lower health-related quality of life (HRQoL) in children. However, almost all studies relied solely on self-reported sleep information, and most studies were conducted in high-income countries. To address these gaps, we studied both device-measured and self-reported sleep characteristics in relation to HRQoL in a sample of children from 12 countries that vary widely in terms of economic and human development.MethodsThe study sample included 6,626 children aged 9-11 years from Australia, Brazil, Canada, China, Colombia, Finland, India, Kenya, Portugal, South Africa, the United Kingdom, and the United States. Waist-worn actigraphy was used to measure total sleep time, bedtime, wake-up time, and sleep efficiency on both weekdays and weekends. Children also reported ratings of sleep quantity and quality. HRQoL was measured by the KIDSCREEN-10 survey. Multilevel regression models were used to determine the relationships between sleep characteristics and HRQoL.ResultsResults showed considerable variation in sleep characteristics, particularly duration and timing, across study sites. Overall, we found no association between device-measured total sleep time, sleep timing or sleep efficiency, and HRQoL. In contrast, self-reported ratings of poor sleep quantity and quality were associated with HRQoL.ConclusionsSelf-reported, rather than device-based, measures of sleep are related to HRQoL in children. The discrepancy related to sleep assessment methods highlights the importance of considering both device-measured and self-reported measures of sleep in understanding its health effects

Outdoor time and dietary patterns in children around the world

Abstract Background Whether outdoor time is linked to dietary patterns of children has yet to be empirically tested. The objective of this study was to examine the association between outdoor time and dietary patterns of children from 12 countries around the world. Methods This multinational, cross-sectional study included 6229 children 9–11 years of age. Children self-reported the time that they spent outside before school, after school and on weekends. A composite score was calculated to reflect overall daily outdoor time. Dietary patterns were assessed using a food frequency questionnaire, and two components were used for analysis: healthy and unhealthy dietary pattern scores. Results On average, children spent 2.5 h outside per day. After adjusting for age, sex, parental education, moderate-to-vigorous physical activity, screen time and body mass index z-score, greater time spent outdoors was associated with healthier dietary pattern scores. No association was found between outdoor time and unhealthy dietary pattern scores. Similar associations between outdoor time and dietary patterns were observed for boys and girls and across study sites. Conclusions Greater time spent outside was associated with a healthier dietary pattern in this international sample of children. Future research should aim to elucidate the mechanisms behind this association. </jats:sec

Correlates of compliance with recommended levels of physical activity in children

The purpose of this study was to describe children's daily compliance with moderate-to-vigorous physical activity (MVPA) recommendations across a week in different parts of the world, and to identify individual-and school-level correlates that may explain differences in daily MVPA compliance. The sample included 6553 children aged 9-11 years from 12 countries, and multilevel statistical analyses were used, including both child-and school-level variables. Most children did not comply with the MVPA guidelines on a daily basis: Chinese children complied the least, whereas Finnish, Australian, Colombian, UK, and Kenyan children complied the most. Boys (rate ratio [RR] = 1.47) and children with higher unhealthy diet scores (RR = 1.08) complied more, but overweight/obese children (RR = 0.81), earlier maturing children (RR = 0.93), and those who spent more time in screen activities (RR = 0.98) and sleeping (RR = 0.96) had the lowest compliance. At the school level, children with access to playground or sport equipment (RR = 0.88, for both) tended to comply less, whereas those with access to a gymnasium outside the school hours complied more with the MVPA guidelines (RR = 1.14). Significant between-country differences in children's daily MVPA compliance were observed, reflecting not only site characteristics, but also the importance of individual traits and local school contexts.Peer reviewe

Adsorption of choline benzoate ionic liquid on graphene, silicene, germanene and boron-nitride nanosheets: a DFT perspective

The adsorption of choline benzoate ([CH][BE]) ionic liquid (IL) on the surface of different hexagonal nanosheets has been studied using Density Functional Theory (DFT) methods. For this, the interaction mechanism, binding energies and electronic structure of [CH][BE] ionic liquid on four types of nanosheets, i.e., graphene, silicene, germanene and boron-nitride, were estimated and compared. The adsorption of [CH][BE] ionic liquid on different nanosheets is mainly featured by van der Waals forces, leading to strong benzoate ion–surface π-stacking. Likewise, there is also an important charge transfer from the anion to the sheet. The electronic structure analysis shows that Si- and Ge-based sheets lead to the largest changes in the HOMO and LUMO levels of choline benzoate. This paper provides new insights into the capability of DFT methods to provide useful information about the adsorption of ionic liquids on nanosheets and how ionic liquid features could be tuned through the adsorption on the suitable nanosheet.Ministerio de Economı´a y Competitividad (Spain, project CTQ2013-40476-R) and Junta de Castilla y León (Spain, project BU324U14)