Macroporous MnO2 electrodes obtained by template assisted electrodeposition for electrochemical capacitors

Macroporous MnO2 electrodes prepared by template-assisted electrodeposition using spherical polystyrene colloidal particles are studied. The wettability of such electrodes by a LiClO4 aqueous electrolyte is measured by the contact angle technique. Cyclic voltammetry experiments are performed in order to evaluate the use of these electrodes for electrochemical capacitor applications. The specific capacity obtained is about 60% higher than that obtained for flat MnO2 surfaces showing that, in spite of the wettability being lower, some penetration of the electrolyte into the pores must occur, increasing the electroactive area with respect to the flat electrode. Furthermore, the macroporous electrode showed excellent electrochemical stability, with neither a capacitance decrease nor a loss of morphology, after 1000 cycles

Lithium intercalation in nanostructured thin films of a mixed-valence layered vanadium oxide using an ionic liquid electrolyte

AbstractNanostructured thin films of a mixed-valence, layered vanadium oxide were prepared using layer-by-layer deposition. The thin films were characterized by electronic (UV–vis) spectroscopy, quartz crystal microbalance, profilometry and scanning electron microscopy techniques. The highest charge capacity was obtained for films that consisted of 25 bilayers. The electrochemical characterization of the films was performed in conventional organic solvent and ionic liquid (IL) based electrolytes. The results revealed better performance, in terms of stability during consecutive charge/discharge cycles, when ILs were employed. This can be attributed to several factors, including reduced mechanical stress caused by insertion of more than 1 mol of Li+ per mol of V5+ in the film structure, decrease of crystallinity in the electrode material during the first few charge/discharge cycles and/or formation of a more compatible SEI. Nanostructured thin films of layered vanadium oxide prepared using layer-by-layer deposition showed potential for applications in lithium microbatteries

Using Multilevel Regression and Poststratification to Estimate Physical Activity Levels from Health Surveys

Background: Large-scale health surveys often consider sociodemographic characteristics and several health indicators influencing physical activity that often vary across subpopulations. Data in a survey for some small subpopulations are often not representative of the larger population. Objective: We developed a multilevel regression and poststratification (MRP) model to estimate leisure-time physical activity across Brazilian state capitals and evaluated whether the MRP outperforms single-level regression estimates based on the Brazilian cross-sectional national survey VIGITEL (2018). Methods: We used various approaches to compare the MRP and single-level model (complete-pooling) estimates, including cross-validation with various subsample proportions tested. Results: MRP consistently had predictions closer to the estimation target than single-level regression estimations. The mean absolute errors were smaller for the MRP estimates than single-level regression estimates with smaller sample sizes. MRP presented substantially smaller uncertainty estimates compared to single-level regression estimates. Overall, the MRP was superior to single-level regression estimates, particularly with smaller sample sizes, yielding smaller errors and more accurate estimates. Conclusion: The MRP is a promising strategy to predict subpopulations’ physical activity indicators from large surveys. The observations present in this study highlight the need for further research, which could, potentially, incorporate more information in the models to better interpret interactions and types of activities across target populations

Histologie UV-Licht-bedingter maligner Hauttumore

Colloidal particles have been used to template the electrosynthesis of several materials, such as semiconductors, metals and alloys. The method allows good control over the thickness of the resulting material by choosing the appropriate charge applied to the system, and it is able to produce high density deposited materials without shrinkage. These materials are a true model of the template structure and, due to the high surface areas obtained, are very promising for use in electrochemical applications. In the present work, the assembly of monodisperse polystyrene templates was conduced over gold, platinum and glassy carbon substrates in order to show the electrodeposition of an oxide, a conducting polymer and a hybrid inorganic-organic material with applications in the supercapacitor and sensor fields. The performances of the resulting nanostructured films have been compared with the analogue bulk material and the results achieved are depicted in this paper.Partículas coloidais têm sido empregadas na síntese dirigida por molde de diversos materiais, tais como semicondutores, metais e ligas. Esse método permite um controle da espessura do material resultante através da escolha adequada da carga aplicada no sistema e é possível produzir materiais densamente depositados, sem rachaduras. Esses materiais são fidedignos à estrutura do molde e, devido às amplas áreas superficiais obtidas, são muito interessantes em aplicações eletroquímicas. Neste trabalho, a distribuição de um molde de poliestireno monodisperso foi realizada sobre substratos de ouro, platina e carbono vítreo com o intuito de exemplificar a eletrodeposição de um óxido, um polímero condutor e um material híbrido orgânico-inorgânico, com aplicações em supercapacitores e sensores. Os desempenhos dos eletrodos nanoestruturados foram comparados com os análogos massivos e os resultados obtidos são descritos