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BackgroundIn recent years, obesity has become a serious public health crisis in the United States. Although the problem of obesity is being addressed through a variety of strategies, the use of mobile apps is a relatively new development that could prove useful in helping people to develop healthy dietary habits. Though such apps might lead to health behavior change, especially when relevant behavior change theory constructs are integrated into them, the mechanisms by which these apps facilitate behavior change are largely unknown.ObjectiveThe purpose of this study was to identify which behavior change mechanisms are associated with the use of diet- and nutrition-related health apps and whether the use of diet- and nutrition-related apps is associated with health behavior change.MethodsA cross-sectional survey was administered to a total of 217 participants. Participants responded to questions on demographics, use of diet and nutrition apps in the past 6 months, engagement and likability of apps, and changes in the participant’s dietary behaviors. Regression analysis was used to identify factors associated with reported changes in theory and separately for reported changes in actual behavior, after controlling for potential confounding variables.ResultsThe majority of study participants agreed or strongly agreed with statements regarding app use increasing their motivation to eat a healthy diet, improving their self-efficacy, and increasing their desire to set and achieve health diet goals. Additionally, majority of participants strongly agreed that using diet/nutrition apps led to changes in their behavior, namely increases in actual goal setting to eat a healthy diet (58.5%, 127/217), increases in their frequency of eating healthy foods (57.6%, 125/217), and increases in their consistency of eating healthy foods (54.4%, 118/217). Participants also responded favorably to questions related to engagement and likability of diet/nutrition apps. A number of predictors were also positively associated with diet-related behavior change. Theory (P<.001), app engagement (P<.001), app use (P<.003), and education (P<.010) were all positively associated with behavior change.ConclusionsStudy findings indicate that the use of diet/nutrition apps is associated with diet-related behavior change. Hence, diet- and nutrition-related apps that focus on improving motivation, desire, self-efficacy, attitudes, knowledge, and goal setting may be particularly useful. As the number of diet- and nutrition-related apps continues to grow, developers should consider integrating appropriate theoretical constructs for health behavior change into the newly developed mobile apps.

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We have designed and constructed dye sensitized solar cells based on new, 3-D configurations of TiO(2) nanotubes. The overall efficiency of our best cells is 5.0% under standard air mass 1.5 global (AM 1.5 G) solar conditions, and the incident photon-to-current efficiency exceeds 60% over a broad part of the visible spectrum. Unlike prior nanotube-based cells where tubes are grown vertically in a 2-D array, the anodes of the present cells consist of tubes that extend radially in a 3-D array from a grid of fine titanium wires. The nanotubes are tens of micrometers in length, and the radial nature of the anode allows the photon absorption path length to exceed the electron transport distance (nanotube length). The cells are front-illuminated and do not require a transparent conductive oxide substrate at either the anode or cathode. The use of 3-D configured nanotubes and low-resistance titanium metal substrates are expected to enhance the performance and simplify the construction of large area dye-sensitized solar cells.

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