AC impedance study of degradation of porous nickel battery electrodes

AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low

Virtually impossible: limiting Australian children and adolescents daily screen based media use

Background: Paediatric recommendations to limit children’s and adolescents’ screen based media use (SBMU) to less than two hours per day appear to have gone unheeded. Given the associated adverse physical and mental health outcomes of SBMU it is understandable that concern is growing worldwide. However, because the majority of studies measuring SBMU have focused on TV viewing, computer use, video game playing, or a combination of these the true extent of total SBMU (including non-sedentary hand held devices) and time spent on specific screen activities remains relatively unknown. This study assesses the amount of time Australian children and adolescents spend on all types of screens and specific screen activities. Methods: We administered an online instrument specifically developed to gather data on all types of SBMU and SBMU activities to 2,620 (1373 males and 1247 females) 8 to 16 year olds from 25 Australian government and non-government primary and secondary schools. Results: We found that 45% of 8 year olds to 80% of 16 year olds exceeded the recommended < 2 hours per day for screen use. A series of hierarchical linear models demonstrated different relationships between the degree to which total SBMU and SBMU on specific activities (TV viewing, Gaming, Social Networking, and Web Use) exceeded the < 2 hours recommendation in relation to sex and age. Conclusions: Current paediatric recommendations pertaining to screen use exposure may no longer be tenable because screen based media are central in the everyday lives of children and adolescents. In any reappraisal of SBMU exposure times, researchers, educators and health professionals need to take cognizance of the extent to which screen use differs across specific screen activity, sex, and age

A latent growth curve model to estimate electronic screen use patterns amongst adolescents aged 10 to 17 years

Background: High quality, longitudinal data describing young people's screen use across a number of distinct forms of screen activity is missing from the literature. This study tracked multiple screen use activities (passive screen use, gaming, social networking, web searching) amongst 10- to 17-year-old adolescents across 24 months. Methods: This study tracked the screen use of 1948 Australian students in Grade 5 (n = 636), Grade 7 (n = 672), and Grade 9 (n = 640) for 24 months. At approximately six-month intervals, students reported their total screen time as well as time spent on social networking, passive screen use, gaming, and web use. Patterns of screen use were determined using latent growth curve modelling. Results: In the Grades 7 and 9 cohorts, girls generally reported more screen use than boys (by approximately one hour a day), though all cohorts of boys reported more gaming. The different forms of screen use were remarkably stable, though specific cohorts showed change for certain forms of screen activity. Conclusion: These results highlight the diverse nature of adolescent screen use and emphasise the need to consider both grade and sex in future research and policy

Cognitive Diversity and the Progress of Science

Science benefits from substantial cognitive diversity because cognitive diversity promotes scientific progress toward greater accuracy. Without diversity of goals, beliefs, and methods, science would neither generate novel discoveries nor certify representations with its present effectiveness. The revolution in geosciences is a principal case study.The role of cognitive diversity in discovery is explored with attention to computational results. Discovery and certification are inseparable. Moreover, diverse scientific groups agree convergently, and their agreements manifest an explanatory defense akin to the explanatory defense of realism. Scientists accept representations as a matter of their instrumental success in individual scientific research. Because scientists are diverse, this standard of acceptance means that widespread acceptance involves widespread instrumental success. This success is best explained through the accuracy of topics of agreement.The pessimistic induction is addressed; it fails to undermine the explanatory defense because past scientific successes don't resemble present ones in their degree of instrumental success; to make this point, instrumental success of representations of caloric and of oxygen are compared.Cognitive diversity challenges the methodological uniformity of scientific practice. Science lacks uniform methods and aims, and it ought to. It is argued that there is no sound basis for thinking that science aims. Moreover, the growth of science itself is not the growth of knowledge. Scientific communities rather than individual scientists are the main certifiers of scientific results. Hence, since knowledge requires a certifying belief formation process but the process relevant to science is not realized individually, science does not progress toward knowledge. The epistemology of science is socialized, but remains broadly realist because, even without a method of inquiry, science develops accurate representations of unobservable nature

On Point-Sets That Support Planar Graphs

A universal point-set supports a crossing-free drawing of any planar graph. For a planar graph with n vertices, if bends on edges of the drawing are permitted, universal point-sets of size n are known, but only if the bend-points are in arbitrary positions. If the locations of the bend-points must also be specified as part of the point-set, we prove that any planar graph with n vertices can be drawn on a universal set S of O(n2 / log n) points with at most one bend per edge and with the vertices and the bend points in S. If two bends per edge are allowed, we show that O(n log n) points are sufficient, and if three bends per edge are allowed, Θ(n) points are sufficient. When no bends on edges are permitted, no universal point-set of size o(n2 ) is known for the class of planar graphs.We show that a set of n points in balanced biconvex position supports the class of maximum degree 3 series-parallel lattices