Exploring food shopping behaviours through a study of Ottawa social media.

This study explored the important attributes of the local food retail environments that residents from Ottawa, Ontario, Canada, used in recommending where to purchase fresh produce, including fruits and vegetables, in the Ottawa area. Drawing upon an approach originating in marketing and consumer research, qualitative thematic analysis was used to analyze 79 discussions from three social media platforms that occurred between 2015 and 2018. We identified three patterns of conversations about food shopping, characterized by participants describing important factors of their local retail food environments that shaped their recommendations for different retail food establishments: 1) Pleasant represented discussions where having a pleasurable food shopping experience was the main discussion point. 2) Thrifty discussions were marked primarily by economical management and discussed food shopping in pragmatic terms. 3) Compromise represented a group where discussions described needing to find a middle ground between affordability and quality. While not without limitations, our study was the first exploration of whether social media data could be useful for qualitatively evaluating local retail food environments. Our findings add to the conclusions of other researchers that social media data does not compromise on the breadth of views captured and can parallel findings from traditional methods. These findings have implications for nutrition researchers and practitioners who we encourage to consider social media discussion data in their work.

Opportunities for Qualitative Analysis of Social Media Platforms in Dietetic Research and Practice.

To date, most qualitative knowledge about individual eating patterns and the food environment has been derived from traditional data collection methods, such as interviews, focus groups, and observations. However, there currently exists a large source of nutrition-related data in social media discussions that have the potential to provide opportunities to improve dietetic research and practice. Qualitative social media discussion analysis offers a new tool for dietetic researchers and practitioners to gather insights into how the public discusses various nutrition-related topics. We first consider how social media discussion data come with significant advantages including low-cost access to timely ways to gather insights from the public, while also cautioning that social media data have limitations (e.g., difficulty verifying demographic information). We then outline 3 types of social media discussion platforms in particular: (i) online news article comment sections, (ii) food and nutrition blogs, and (iii) discussion forums. We discuss how each different type of social media offers unique insights and provide a specific example from our own research using each platform. We contend that social media discussions can contribute positively to dietetic research and practice.

Student Engagement with Community-Based Participatory Food Security Research: Exploring Reflections through Photovoice.

FoodARC is a research hub for community-based participatory research (CBPR) contributing to healthy, just, and sustainable food systems for all. University students, largely from dietetics programs, are engaged as co-learners and research partners. This study explores the contribution of CBPR to student learning on household food insecurity (HFI) and community food security (CFS) and ways to address these issues through practice. Photovoice, an arts-informed 3-phase participatory research process, was used to take pictures that reflected student experiences and insights regarding CBPR. Through a half-day guided discussion, 5 participants shared and discussed their photos and the meanings behind them with other participants and then collectively analyzed and interpreted common themes. Three overarching themes reflecting student learning and development associated with CBPR experiences were identified: students' expanded understandings of HFI and CFS as well as potential solutions to address these issues, their modeling of participatory ways of working, and applications to future professional practices. Student understandings about HFI and CFS through the integration of a community-engaged learning environment like CBPR results in important learning and personal and professional development. Learning is enriched and students are able to imagine their roles in addressing these issues through practice.

Salience and conflict of work and family roles among employed men and women.

The aim of this research was to determine the salience of work and family roles and to study the connection between role salience and the interference of different types of roles among working men and women. Self-assessment measurement scales were applied. The research involved 206 participants; 103 employed married couples from different regions of Croatia. The results show that roles closely connected to family are considered the most salient. However, men are mostly dedicated behaviourally to the role of a worker. Women dedicate more time and energy to the roles of a spouse, a parent, and a family member whereas men are more oriented towards the leisurite role. The highest level of conflict was perceived when it comes to work disturbing leisure. Gender differences appeared only for work-to-marriage conflict, with men reporting higher conflict than women. The research found proof of only some low correlations between the salience of different types of roles and work-family conflict.

Shared Opportunities on Institutional Lands: On-Site Food Production, Its Benefits, Barriers, and Opportunities.

AIM: This article outlines preliminary findings of a 3-year project that explored on-site food production on institutional properties, primarily healthcare facilities. BACKGROUND: There are growing pressures on healthcare facilities to improve their food offerings and incorporate food gardens into their health programs. While several healthcare facilities produce food on-site, there are few studies that explore opportunities, capacities, and institutional barriers related to on-site food production. METHODS: The study employed mixed methods including historical review, case studies, surveys, interviews, pilot garden projects, and Geographic Information System mapping. The number of participating institutions varied by method. RESULTS: Benefits associated with on-site food production can be health, economic, environmental, and social. There are also institutional barriers including administrative roadblocks, perceived obstacles, and the difficulty in quantitatively, measuring the qualitatively documented benefits. CONCLUSIONS: The benefits of food gardens far outweigh the challenges. On-site food production has tremendous potential to improve nutrition for staff and patients, offer healing spaces, better connect institutions with the communities in which they are located, and provide the long-professed benefits of gardening for all involved-from therapeutic benefits and outdoor physical activities to developing skills and social relationships in ways that few other activities do.

Ballistic to diffusive crossover of heat flow in graphene ribbons.

Heat flow in nanomaterials is an important area of study, with both fundamental and technological implications. However, little is known about heat flow in two-dimensional devices or interconnects with dimensions comparable to the phonon mean free path. Here we find that short, quarter-micron graphene samples reach ~35% of the ballistic thermal conductance limit up to room temperature, enabled by the relatively large phonon mean free path (~100 nm) in substrate-supported graphene. In contrast, patterning similar samples into nanoribbons leads to a diffusive heat-flow regime that is controlled by ribbon width and edge disorder. In the edge-controlled regime, the graphene nanoribbon thermal conductivity scales with width approximately as ~W(1.8)(0.3), being about 100 W m(-1) K(-1) in 65-nm-wide graphene nanoribbons, at room temperature. These results show how manipulation of two-dimensional device dimensions and edges can be used to achieve full control of their heat-carrying properties, approaching fundamentally limited upper or lower bounds.

Probing the electronic structure at semiconductor surfaces using charge transport in nanomembranes.

The electrical properties of nanostructures are extremely sensitive to their surface condition. In very thin two-dimensional crystalline-semiconductor sheets, termed nanomembranes, the influence of the bulk is diminished, and the electrical conductance becomes exquisitely responsive to the structure of the surface and the type and density of defects there. Its understanding therefore requires a precise knowledge of the surface condition. Here we report measurements, using nanomembranes, that demonstrate direct charge transport through the π* band of the clean reconstructed Si(001) surface. We determine the charge carrier mobility in this band. These measurements, performed in ultra-high vacuum to create a truly clean surface, lay the foundation for a quantitative understanding of the role of extended or localized surface states, created by surface structure, defects or adsorbed atoms/molecules, in modifying charge transport through semiconductor nanostructures.

Quantum confinement, surface roughness, and the conduction band structure of ultrathin silicon membranes.

We report direct measurements of changes in the conduction-band structure of ultrathin silicon nanomembranes with quantum confinement. Confinement lifts the 6-fold-degeneracy of the bulk-silicon conduction-band minimum (CBM), Delta, and two inequivalent sub-band ladders, Delta(2) and Delta(4), form. We show that even very small surface roughness smears the nominally steplike features in the density of states (DOS) due to these sub-bands. We obtain the energy splitting between Delta(2) and Delta(4) and their shift with respect to the bulk value directly from the 2p(3/2)-->Delta transition in X-ray absorption. The measured dependence of the sub-band splitting and the shift of their weighted average on degree of confinement is in excellent agreement with theory, for both Si(001) and Si(110).

Influence of surface chemical modification on charge transport properties in ultrathin silicon membranes.

Ultrathin silicon-on-insulator, composed of a crystalline sheet of silicon bounded by native oxide and a buried oxide layer, is extremely resistive because of charge trapping at the interfaces between the sheet of silicon and the oxide. After chemical modification of the top surface with hydrofluoric acid (HF), the sheet resistance drops to values below what is expected based on bulk doping alone. We explain this behavior in terms of surface-induced band structure changes combined with the effective isolation from bulk properties created by crystal thinness.

Mechano-electronic superlattices in silicon nanoribbons.

Significant new mechanical and electronic phenomena can arise in single-crystal semiconductors when their thickness reaches nanometer dimensions, where the two surfaces of the crystal are physically close enough to each other that what happens at one surface influences what happens at the other. We show experimentally that, in silicon nanomembranes, through-membrane elastic interactions cause the double-sided ordering of epitaxially grown nanostressors that locally and periodically highly strains the membrane, leading to a strain lattice. Because strain influences band structure, we create a periodic band gap modulation, up to 20% of the band gap, effectively an electronic superlattice. Our calculations demonstrate that discrete minibands can form in the potential wells of an electronic superlattice generated by Ge nanostressors on a sufficiently thin Si(001) nanomembrane at the temperature of 77 K. We predict that it is possible to observe discrete minibands in Si nanoribbons at room temperature if nanostressors of a different material are grown.

Electronic transport in nanometre-scale silicon-on-insulator membranes.

The widely used 'silicon-on-insulator' (SOI) system consists of a layer of single-crystalline silicon supported on a silicon dioxide substrate. When this silicon layer (the template layer) is very thin, the assumption that an effectively infinite number of atoms contributes to its physical properties no longer applies, and new electronic, mechanical and thermodynamic phenomena arise, distinct from those of bulk silicon. The development of unusual electronic properties with decreasing layer thickness is particularly important for silicon microelectronic devices, in which (001)-oriented SOI is often used. Here we show--using scanning tunnelling microscopy, electronic transport measurements, and theory--that electronic conduction in thin SOI(001) is determined not by bulk dopants but by the interaction of surface or interface electronic energy levels with the 'bulk' band structure of the thin silicon template layer. This interaction enables high-mobility carrier conduction in nanometre-scale SOI; conduction in even the thinnest membranes or layers of Si(001) is therefore possible, independent of any considerations of bulk doping, provided that the proper surface or interface states are available to enable the thermal excitation of 'bulk' carriers in the silicon layer.

Memory effects and nonequilibrium transport in open many-particle quantum systems.

Full understanding of the relaxation mechanisms and far-from-equilibrium transport in modern mesoscopic structures requires that such systems be treated as open. We therefore generalize some of the core elements of the Kadanoff-Baym-Keldysh nonequilibrium Green's function formalism, inherently formulated for closed systems, to treatment of an open system, coupled with its environment. We define the two-time correlation functions and analyze the influence of the memory effects on the open-system transport. In the transient regime, the two-time correlation functions clearly show four distinct terms: a closed-system-like term, an entanglement term, and two memory terms that depend explicitly on the initial state of the environment. We show that it is not possible to completely eliminate the influence of the environment by a fortunate choice of the initial state, and approximating the system as closed is valid only in the limit of negligible system-environment coupling, which is never the case in the transient regime. We derive the transport equations for transients that properly account for the system-environment coupling. On the other hand, we address the important issue of transport in a far-from-equilibrium steady state. We show that, once a steady state is reached, the balance between the driving and relaxation forces implies that the two-time correlation functions regain a closed-system-like form, but with an effective, modified system Hamiltonian, and with the system statistical operator unrelated to that of the initial state. We emphasize that the difference between the transient and the far-from-equilibrium steady-state regimes, crucial for theoretical investigation of nonequilibrium quasiparticle transport, effectively lies within the different relative magnitude of the combined entanglement and memory terms with respect to the closed-system-like term in two-time correlation functions.

Partial-trace-free time-convolutionless equation of motion for the reduced density matrix.

Evolution of a system, coupled to its environment and influenced by external driving fields, is an old problem that remains of interest. In this paper, we derive an equation of motion for the reduced system density matrix, which is time convolutionless and free of the partial trace with respect to the environment states. This new approach uses an extension of the projection-operator technique, which incorporates an isomorphism between the system's Liouville space and the unit eigenspace of the projection operator induced by the uniform environment density matrix. Numerical application of the present approach is particularly useful in large externally driven systems, as the partial-trace-free equation is given in terms of submatrices significantly smaller than the matrices in the conventional time-convolutionless approaches, which alleviates the computational burden. We also show that all time-convolutionless approaches, conventional or partial-trace-free, are based upon a hidden underlying assumption of time reversibility of the system's evolution. This feature puts significant constraints on applicability of time-convolutionless approaches when employing approximations that yield time irreversibility. Also, we investigate the application of the approach in the description of far-from-equilibrium systems.