Quantitative electrical homogeneity assessment of nanowire transparent electrodes.

The homogeneous distribution of electric current (electrical homogeneity) is not guaranteed in nanowire electrodes but is crucial for the stability of the electrode and actually desirable in most applications. Despite the relevance of this feature, it is common practice to perform qualitative assessments at the electrode scale, thus masking local effects. To address this issue, we have developed a computational strategy to aid in the design of nanowire electrodes with improved electrical homogeneity. Nanowire electrodes are modeled as two-dimensional networks of stick and junction resistors (with resistance Rw and Rj, respectively) to simulate the electric conduction process. Electrodes are discretized into regular grids of squares and the electrical power of the network contained in each square is computed. The mismatch between the areal power density of the entire electrode and that of the squares provides a quantitative electrical homogeneity evaluation. Repeating the analysis with squares of different size yields an evaluation that spans across length scales. A scalar indicator, coined the homogeneity index, summarizes the results of the multiscale evaluation. The proposed strategy is employed to assess the electrical homogeneity of silver nanowire electrodes through the analysis of scanning electron microscopy images. Our results agree with the outcomes of the experimental assessment performed on the same electrodes. Parametric studies are performed by varying nanowire content and nanowire-to-junction resistance ratio Rw/Rj. We observe that a significant reduction of contact resistance is not necessary to ensure a high degree of homogeneity. The ideal condition of negligible junction resistance (Rw ≫ Rj) leads to the best-case scenario, a situation which is closely approached if Rw ≈ Rj (15% difference at the most in terms of homogeneity index).

An efficient computational approach for three-dimensional modeling and simulation of fibrous battery electrodes.

Fibrous electrodes are a promising alternative to conventional particle-based lithium-ion battery electrodes. In this contribution, we propose an efficient computational approach for the modeling and simulation of electrochemical phenomena taking place in fibrous electrodes during battery charge/discharge processes. Since each fiber is explicitly modeled by means of a dimensionally reduced embedded fiber model, the framework enables simulations in a three-dimensional setting with relatively modest discretization and computational requirements compared to simulations with fully resolved fiber discretizations. The approach is applied to electrodes with high volume fractions of high aspect ratio fibers. Various local and global quantities are analyzed and results are compared to those obtained with the standard finite element method and the pseudo-2D model.

Closing the Gap: Results of the Multicenter Canadian Randomized Controlled Trial of Structured Transition in Young Adults With Type 1 Diabetes.

OBJECTIVE: To determine if a structured transition program for young adults with type 1 diabetes improves clinic attendance, glycemic control, diabetes-related distress, quality of life, and satisfaction with care. RESEARCH DESIGN AND METHODS: In this multicenter randomized controlled trial, young adults (17-20 years) with type 1 diabetes were randomly assigned to a transition program with a transition coordinator or to standard care. The intervention lasted 18 months (6 in pediatric and 12 in adult care). The primary outcome was the proportion of participants who failed to attend at least one adult diabetes clinic visit during the 12-month follow-up after completion of the intervention. RESULTS: We randomized 205 participants, 104 to the transition program and 101 to standard care. Clinic attendance was improved in the transition program (mean [SD] number of visits 4.1 [1.1] vs. 3.6 [1.2], P = 0.002), and there was greater satisfaction with care (mean [SD] score 29.0 [2.7] vs. 27.9 [3.4], P = 0.032) and less diabetes-related distress (mean [SD] score 1.9 [0.8] vs. 2.1 [0.8], P = 0.049) reported than in standard care. There was a trend toward improvement in mean HbA1c (8.33% [68 mmol/mol] vs. 8.80% [73 mmol/mol], P = 0.057). During the 12-month follow-up, there was no difference in those failing to attend at least one clinic visit (P = 0.846), and the mean change in HbA1c did not differ between the groups (P = 0.073). At completion of follow-up, the groups did not differ with respect to satisfaction with care or diabetes-related distress and quality of life. CONCLUSIONS: Transition support during this 18-month intervention was associated with increased clinic attendance, improved satisfaction with care, and decreased diabetes-related distress, but these benefits were not sustained 12 months after completion of the intervention.

Salt concentration dependence of the mechanical properties of LiPF6/poly(propylene glycol) acrylate electrolyte at a graphitic carbon interface: A reactive molecular dynamics study.

This reactive molecular dynamics study explores the salt concentration dependence of the viscoelastic and mechanical failure properties of a poly(propylene glycol)/LiPF6-based solid polymer electrolyte (SPE) at a graphitic carbon electrode interface. To account for the finite-size effect of interface-confined SPE films, the properties of two distinct film thicknesses are compared with the respective bulk properties. Additionally, the effect of uniaxial compression in the interface-normal direction on free energy profiles of Li-ion SPE-desolvation is studied. © 2018 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 718-730.

A Mobile App for the Self-Management of Type 1 Diabetes Among Adolescents: A Randomized Controlled Trial.

BACKGROUND: While optimal blood glucose control is known to reduce the long-term complications associated with type 1 diabetes mellitus, adolescents often struggle to achieve their blood glucose targets. However, their strong propensity toward technology presents a unique opportunity for the delivery of novel self-management interventions. To support type 1 diabetes self-management in this population, we developed the diabetes self-management app bant, which included wireless blood glucose reading transfer, out-of-range blood glucose trend alerts, coaching around out-of-range trend causes and fixes, and a point-based incentive system. OBJECTIVE: The primary objective was to evaluate bant 's effect on hemoglobin A1c (HbA1c) through a randomized controlled trial (RCT). Secondary measures (eg, self-monitoring of blood glucose [SMBG]) were also collected to assess bant 's impact on the self-management behaviors of adolescents with type 1 diabetes. METHODS: We enrolled 92 adolescents into a 12-month RCT, with 46 receiving usual care and 46 receiving usual care plus bant. Clinical outcome data were collected at quarterly research visits via validated tools, electronic chart review, glucometer downloads, and semistructured interviews. App satisfaction was assessed at 6 and 12 months, and at trial end, users ranked bant components based on perceived usefulness. Mobile analytics captured frequency of blood glucose uploads, which were used to categorize participants into high, moderate, low, or very low engagement levels. RESULTS: Linear mixed models showed no changes in primary and secondary clinical outcomes. However, exploratory regression analysis demonstrated a statistically significant association between increased SMBG and improved HbA1c in the intervention group. For a subgroup of bant users taking SMBG ≥5 daily, there was a significant improvement in HbA1c of 0.58% (P=.02), while the parallel subgroup in the control arm experienced no significant change in HbA1c (decrease of 0.06%, P=.84). Although app usage did diminish over the trial, on average, 35% (16/46 participants) were classified as moderately or highly engaged (uploaded SMBG ≥3 days a week) over the 12 months. CONCLUSION: Although primary analysis of clinical outcomes did not demonstrate differences between the bant and control groups, exploratory analysis suggested that bant may positively impact the use of SMBG data and glycemic control among youth. The next generation of bant will aim to remove barriers to use, such as deploying the app directly to personal devices instead of secondary research phones, and to explore the utility of integrating bant into routine clinical care to facilitate more frequent feedback. Future evaluations of mHealth apps should consider more robust research tools (eg, ResearchKit) and alternative RCT study designs to enable more rapid and iterative evaluations, better suited to the nature of rapidly evolving consumer technology. TRIAL REGISTRATION: ClinicalTrials.gov NCT01899274; https://clinicaltrials.gov/ct2/show/NCT01899274 (Archived by WebCite at http://www.webcitation.org/6qWrqF1yw).

Cell flexibility affects the alignment of model myxobacteria.

Myxobacteria are social bacteria that exhibit a complex life cycle culminating in the development of multicellular fruiting bodies. The alignment of rod-shaped myxobacteria cells within populations is crucial for development to proceed. It has been suggested that myxobacteria align due to mechanical interactions between gliding cells and that cell flexibility facilitates reorientation of cells upon mechanical contact. However, these suggestions have not been based on experimental or theoretical evidence. Here we created a computational mass-spring model of a flexible rod-shaped cell that glides on a substratum periodically reversing direction. The model was formulated in terms of experimentally measurable mechanical parameters, such as engine force, bending stiffness, and drag coefficient. We investigated how cell flexibility and motility engine type affected the pattern of cell gliding and the alignment of a population of 500 mechanically interacting cells. It was found that a flexible cell powered by engine force at the rear of the cell, as suggested by the slime extrusion hypothesis for myxobacteria motility engine, would not be able to glide in the direction of its long axis. A population of rigid reversing cells could indeed align due to mechanical interactions between cells, but cell flexibility impaired the alignment.

Computational study of the drag and oscillatory movement of biofilm streamers in fast flows.

Hydrodynamic conditions have a significant impact on the biofilm lifecycle. Not well understood is the fact that biofilms, in return, also affect the flow pattern. A decade ago, it was already shown experimentally that under fast flows, biofilm streamers form and oscillate with large amplitudes. This work is a first attempt to answer the questions on the mechanisms behind the oscillatory movement of the streamers, and whether this movement together with the special streamlined form of the streamers, have both a physical and biological benefit for biofilms. In this study, a state of the art two-dimensional fluid-structure interaction model of biofilm streamers is developed, which implements a transient coupling between the fluid and biofilm mechanics. Hereby, it is clearly shown that formation of a Kármán vortex street behind the streamer body is the main source of the periodic oscillation of the streamers. Additionally it is shown that the formation of streamers reduces the fluid forces which biofilm surface experiences.