Evaluation of a concept-based physical education unit for energy balance education.

BACKGROUND: Physical education (PE) is a key channel that impacts children's decisions and behaviors for healthful living. This study evaluated the effects of a concept-based PE (CBPE) instructional unit, featured by energy balance (EB) education, on students' knowledge learning, situational interest, cognitive, and physical engagements as well as teachers' perceptions. METHODS: Fourth and 5th grade students (n = 468) in a mid-western state of the United States were recruited as the participants. Four elementary schools were randomized to the CBPE or control groups. Students' EB knowledge, situational interest, cognitive engagement, and physical engagement were measured by a knowledge test, the Situational Interest Scale-Elementary, written task sheets, and accelerometers, respectively, while teachers' perceptions of the CBPE unit were captured by individual interviews at the end of the experiment. RESULTS: The CBPE group showed a significant increase in EB knowledge, while the control did not. Both groups showed a similar increasing trend for situational interest over time, although the statistical results favored the control group. For physical engagement, the CBPE group demonstrated a statistically different but substantively similar level of in-class physical activity compared to the control group. The CBPE group also showed a moderate level of cognitive engagement throughout the unit. The PE teachers reported overall positive perceptions about teaching the CBPE unit. CONCLUSION: These results support the utility of the CBPE unit in enhancing EB education along with facilitating positive student interest and engagement as well as positive teaching experiences.

Planar n-Si/PEDOT:PSS hybrid heterojunction solar cells utilizing functionalized carbon nanoparticles synthesized via simple pyrolysis route.

Herein, we present a facile and simple strategy for in situ synthesis of functionalized carbon nanoparticles (CNPs) via direct pyrolysis of ethylenediaminetetraacetic acid (EDTA) on silicon surface. The CNPs were incorporated in hybrid planar n-Si and poly(3,4-etyhlenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells to improve device performance. We demonstrate that the CNPs-incorporated devices showed increased electrical conductivity (reduced series resistance) and minority carrier lifetime (better charge carrier collection) than those of the cells without CNPs due to the existence of electrically conductive sp 2-hybridized carbon at the heterojunction interfaces. With an optimal concentration of CNPs, the hybrid solar cells exhibited power conversion efficiency up to 11.95%, with an open-circuit voltage of 614 mV, short-circuit current density of 26.34 mA cm-2, and fill factor of 73.93%. These results indicate that our approach is promising for the development of highly efficient organic-inorganic hybrid solar cells.

Ultrathin Al2O3 interface achieving an 11.46% efficiency in planar n-Si/PEDOT:PSS hybrid solar cells.

Hybrid organic-inorganic photovoltaic devices consisting of poly(3,4-etyhlenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and n-type silicon have recently been investigated for their cost-efficiency and ease of fabrication. We demonstrate that the insertion of an ultrathin Al2O3 layer between n-Si and PEDOT:PSS significantly improves photovoltaic performance in comparison to the conventional interfacial oxide employing SiO2. A power-conversion efficiency of 11.46% was recorded at the optimal Al2O3 thickness of 2.3 nm. This result was achieved based upon increased built-in potential and improved charge collection via the electron blocking effect of Al2O3. In addition, the hydrophilicity enhanced by Al2O3 improved the coating uniformity of the PEDOT:PSS layer, resulting in a further reduction in surface recombination.

Highly active and durable carbon nitride fibers as metal-free bifunctional oxygen electrodes for flexible Zn-air batteries.

The design of flexible, highly energetic, and durable bifunctional oxygen electrocatalysts is indispensable for rechargeable metal-air batteries. Herein we present a simple approach for the development of carbon nitride fibers co-doped with phosphorus and sulfur, grown in situ on carbon cloth (PS-CNFs) as a flexible electrode material, and demonstrate its outstanding bifunctional catalytic activities toward ORR and OER compared to those of precious metal-based Pt/C and IrO2 on account of the dual action of P and S, numerous active sites, high surface area, and enhanced charge transfer. Furthermore, we demonstrate the flexibility, suitability, and durability of PS-CNFs as air electrodes for primary and rechargeable Zn-air batteries. Primary Zn-air batteries using this electrode showed high peak power density (231 mW cm-2), specific capacity (698 mA h g-1; analogous energy density of 785 W h kg-1), open circuit potential (1.49 V), and outstanding durability of more than 240 h of operation followed by mechanical recharging. Significantly, three-electrode rechargeable Zn-air batteries revealed a superior charge-discharge voltage polarization of ∼0.82 V at 20 mA cm-2, exceptional reversibility, and continuous charge-discharge cycling stability during 600 cycles. This work provides a pioneering strategy for designing flexible and stretchable metal-free bifunctional catalysts as gas diffusion layers for future portable and wearable renewable energy conversion and storage devices.

Toward a planar black silicon technology for 50 µm-thin crystalline silicon solar cells.

Auger and surface recombinations are major drawbacks that deteriorate a photon-to-electron conversion efficiencies in nanostructured (NS) Si solar cells. As an alternative to conventional frontside nanostructuring, we report how backside nanostructuring is beneficial for carrier collection during photovoltaic operation that utilizes a 50-µm-thin wafer. Ultrathin (4.3-nm-thin) zinc oxide was also effective for providing passivated tunneling contacts at the nanostructured backsides, which led to the enhancement of 24% in power conversion efficiency.

Comparison of Consumer and Research Monitors under Semistructured Settings.

PURPOSE: This study evaluated the relative validity of different consumer and research activity monitors during semistructured periods of sedentary activity, aerobic exercise, and resistance exercise. METHODS: Fifty-two (28 male and 24 female) participants age 18-65 yr performed 20 min of self-selected sedentary activity, 25 min of aerobic exercise, and 25 min of resistance exercise, with 5 min of rest between each activity. Each participant wore five wrist-worn consumer monitors [Fitbit Flex, Jawbone Up24, Misfit Shine (MS), Nike+ Fuelband SE (NFS), and Polar Loop] and two research monitors [ActiGraph GT3X+ on the waist and BodyMedia Core (BMC) on the arm] while being concurrently monitored with Oxycon Mobile (OM), a portable metabolic measuring system. Energy expenditure (EE) on different activity sessions was measured by OM and estimated by all monitors. RESULTS: Mean absolute percent error (MAPE) values for the full 80-min protocol ranged from 15.3% (BMC) to 30.4% (MS). EE estimates from ActiGraph GT3X+ were found to be equivalent to those from OM (± 10% equivalence zone, 285.1-348.5). Correlations between OM and the various monitors were generally high (ranged between 0.71 and 0.90). Three monitors had MAPE values lower than 20% for sedentary activity: BMC (15.7%), MS (18.2%), and NFS (20.0%). Two monitors had MAPE values lower than 20% for aerobic exercise: BMC (17.2%) and NFS (18.5%). None of the monitors had MAPE values lower than 25% for resistance exercise. CONCLUSION: Overall, the research monitors and Fitbit Flex, Jawbone Up24, and NFS provided reasonably accurate total EE estimates at the individual level. However, larger error was evident for individual activities, especially resistance exercise. Further research is needed to examine these monitors across various activities and intensities as well as under real-world conditions.

A formative evaluation of the SWITCH® obesity prevention program: print versus online programming.

BACKGROUND: SWITCH® is an evidence-based childhood obesity prevention program that works through schools to impact parenting practices. The present study was designed as a formative evaluation to test whether an online version of SWITCH® would work equivalently as the established print version. METHODS: Ten elementary schools were matched by socio-economic status and randomly assigned to receive either the print (n = 5) or online (n = 5) version. A total of 211 children from 22, 3(rd) grade classrooms were guided through the 4 month program by a team of program leaders working in cooperation with the classroom teachers. Children were tasked with completing weekly SWITCH® Trackers with their parents to monitor goal setting efforts in showing positive Do (≥60 minutes of moderate-to-vigorous physical activity), View (≤2 hours of screen time), and Chew (≥5 servings of fruits and vegetables) behaviors on each day. A total of 91 parents completed a brief survey to assess project-specific interactions with their child and the impact on their behaviors. RESULTS: The majority of parents (93.2%) reported satisfactory experiences with either the online or print SWITCH® program. The return rate for the SWITCH® Trackers was higher (42.5% ± 11%) from the print schools compared to the online schools (27.4% ± 10.9%). District program managers rated the level of teacher engagement in regards to program facilitation and the results showed a higher Trackers return rate in the highly engaged schools (38.5% ± 13.3%) than the lowly engaged schools (28.6 ± 11.9%). No significant differences were observed in parent/child interactions or reported behavior change (ps > .05) suggesting the equivalence in intervention effect for print and online versions of the SWITCH® program. CONCLUSIONS: The findings support the utility of the online SWITCH® platform but school-based modules are needed to facilitate broader school engagement by classroom teachers and PE teachers.

Mie resonance-mediated antireflection effects of Si nanocone arrays fabricated on 8-in. wafers using a nanoimprint technique.

We fabricated 8-in. Si nanocone (NC) arrays using a nanoimprint technique and investigated their optical characteristics. The NC arrays exhibited remarkable antireflection effects; the optical reflectance was less than 10% in the visible wavelength range. The photoluminescence intensity of the NC arrays was an order of magnitude larger than that of a planar wafer. Optical simulations and analyses suggested that the Mie resonance reduced effective refractive index, and multiple scattering in the NCs enabled the drastic decrease in reflection. PACS: 88.40.H-; 88.40.jp; 81.07.Gf.