Cytokines as mediators of chemotherapy-associated cognitive changes: Current evidence, limitations and directions for future research

10.1371/journal.pone.0081234PLoS ONE812-POLN

Large amplitude electrochemical impedance spectroscopy for characterizing the performance of electrochemical capacitors

Electrochemical impedance spectroscopy (EIS) has been applied to the study of electrodeposited thin films of manganese dioxide as used in electrochemical capacitors. Conventionally EIS employs a relatively small AC excitation signal to provide valuable characterization on electrode features such as the series resistance, charge transfer and double layer charge storage processes, as well as mass transport. The small excitation signal is used so as to focus on the processes occurring within that potential domain allowing for considerable resolution across the full potential window. In this work we have compared the output from this conventional analysis with data from the application of a large amplitude AC excitation signal; i.e., an AC signal that spans the full potential window of the manganese dioxide electrode. Not only does this allow access to electrochemical data representative of the full range of domains within the manganese dioxide structure, it also facilitates performance analysis (determination of specific power and energy data) of the electrode in a much more efficient manner than conventional means, as well as enables separation of the total specific capacitance into its non-faradaic and faradaic components

Electrochemically active surface area effects on the performance of manganese dioxide for electrochemical capacitor applications

The specific surface area, morphology and electrochemical performance of thin films of electrodeposited manganese dioxide have been examined. Electrodeposition of these films was carried out using chronoamperometry, using times ranging from 10 to 120 s in order to obtain deposits with different masses. Using a novel approach to analysing the chronoamperometric i–t data, the specific surface area of the electrodeposited material was found to range from 13 to 67 m2/g across the range of deposition times, with short deposition times leading to higher specific surface areas. This has implications on the electrodeposition mechanism of manganese dioxide, which favours crystallite nucleation initially, leading to a high surface area material, followed by growth of these crystallites leading to a denser, lower surface area electrode material. This is the first time that the electrochemically active surface area of porous electrode materials has been determined. This decrease in surface area with deposition time was also reflected in the specific capacitance values of the material, which decreased slightly with increased deposition time, and hence lower surface area

Mass transport properties of manganese dioxide phases for use in electrochemical capacitors: structural effects on solid state diffusion

The solid state mass transport characteristics of various manganese dioxide phases has been examined with a focus on their use in electrochemical capacitors. The phases examined included gamma-MnO2 (electrolytic manganese dioxide), beta-MnO2 (Pyrolusite), Ramsdellite, delta-MnO2 (Birnessite), alpha-MnO2 (Cryptomelane) and lambda-MnO2. Diffusion within each phase was examined using electrochemical impedance spectroscopy (EIS) and step potential electrochemical spectroscopy (SPECS). A root D (where A is surface area and D is the diffusion coefficient) decreases with depth of discharge, and is also affected by the phase of manganese dioxide studied, with gamma-MnO2 exhibiting the highest A root D value. Overall, values of A root D varied between 3 x 10(-8) - 2 x 10(-10) m(3)/s(1/2)/g, which is comparable with literature data. These results also provide information on the kinetics of lattice expansion and contraction which occurring during cycling. High surface area phases such as gamma-MnO2, Ramsdellite and Cryptomelane, showed significant hysteresis in lattice contraction which is attributed to the diffusion of protons through surface domains. Low surface area phases (Pyrolusite and lambda-MnO2) did not display this hysteresis, suggesting that proton diffusion occurs predominantly in the bulk of the material. No direct correlation between mass transport and specific capacitance is observed, suggesting that other material properties contribute to specific capacitance

Chemometrics for environmental monitoring: a review

Environmental monitoring is necessary to ensure the overall health and conservation of an ecosystem. However, ecosystems (e.g.\ua0air, water, soil), are complex, involving numerous processes (both native and external), inputs, contaminants, and living organisms. As such, monitoring an environmental system is not a trivial task. The data obtained from natural systems is often multifaceted and convoluted, as a multitude of inputs can be intertwined within the matrix of the information obtained as part of a study. This means that trends and important results can be easily overlooked by conventional and single dimensional data analysis protocols. Recently, chemometric methods have emerged as a powerful method for maximizing the details contained within a chemical data set. Specifically, chemometrics refers to the use of mathematical and statistical analysis methods to evaluate chemical data, beyond univariant analysis. This type of analysis can provide a quantitative description of environmental measurements, while also having the capacity to reveal previously overlooked trends in data sets. Applying chemometrics to environmental data allows us to identify and describe the inter-relationship of environmental drivers, sources of contamination, and their potential impact upon the environment. This review aims to provide a detailed understanding of chemometric techniques, how they are currently used in environmental monitoring, and how these techniques can be used to improve current practices. An enhanced ability to monitor environmental conditions and to predict trends would be greatly beneficial to government and research agencies in their ability to develop environmental policies and analytical procedures

A synchrotron X-ray powder diffraction and step potential electrochemical spectroscopy study on the change in manganese dioxide capacitive behaviour during cycling

In this work, the factors leading to the overall capacitance of manganese dioxide electrochemical capacitor materials, i.e. the double layer and pseudocapacitive behaviour, have been separated using Step Potential Electrochemical Spectroscopy (SPECS). In addition, variations in these parameters have been linked to regions of structural change in the material. In regions where ion diffusion into the bulk of a material is a facile process, the pseudocapacitive charge storage shows an increase. In addition, the double layer capacitance has been shown to increase with reduced protonation of the material surface. This has been attributed to variations in electronic resistance and also an increase in the number of sites that can accommodate electrostatic charge. Further, the origin of the residual current seen in previous experiments has been determined. In structures where ion diffusion into the bulk is a facile process, the residual currents are related to this process. Where there is no bulk ion diffusion, the residual currents have been assigned to the production of soluble Mn 2+

Mapping the Three‐Dimensional Nanostructure of the Ionic Liquid–Solid Interface Using Atomic Force Microscopy and Molecular Dynamics Simulations

Abstract Ionic liquids (ILs) are a widely investigated class of solvents for scientific and industrial applications due to their desirable and “tunable” properties. The IL–solid interface is a complex entity, and despite intensive investigation, its true nature remains elusive. The understanding of the IL–solid interface has evolved over the last decade from a simple 1D double layer, to a 2D ordered interface, and finally a liquid‐specific, complex 3D ordered liquid interface. However, most studies depend solely on one technique, which often only examine one aspect of the interfacial nanostructure. Here, a holistic study of the protic IL–solid interface is presented, which provides a more detailed picture of IL interfacial solvation. The 3D nanostructure of the ethylammonium nitrate (EAN)–mica interface is investigated using a combination of 1D, 2D, and 3D amplitude modulated‐atomic force microscopy and molecular dynamics simulations. Importantly, it is found that the EAN–mica interface is more complex than previously reported, possessing surface‐adsorbed, near‐surface, surface‐normal, and lateral heterogeneity, which propagates at relatively large distances from the solid substrate. The work presented in this study meaningfully enhances the understanding of the IL–solid interface

Analysis of Pathogenic Bacterial and Yeast Biofilms Using the Combination of Synchrotron ATR-FTIR Microspectroscopy and Chemometric Approaches

Biofilms are assemblages of microbial cells, extracellular polymeric substances (EPS), and other components extracted from the environment in which they develop. Within biofilms, the spatial distribution of these components can vary. Here we present a fundamental characterization study to show differences between biofilms formed by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Pseudomonas aeruginosa, and the yeast-type Candida albicans using synchrotron macro attenuated total reflectance-Fourier transform infrared (ATR-FTIR) microspectroscopy. We were able to characterise the pathogenic biofilms’ heterogeneous distribution, which is challenging to do using traditional techniques. Multivariate analyses revealed that the polysaccharides area (1200–950 cm−1) accounted for the most significant variance between biofilm samples, and other spectral regions corresponding to amides, lipids, and polysaccharides all contributed to sample variation. In general, this study will advance our understanding of microbial biofilms and serve as a model for future research on how to use synchrotron source ATR-FTIR microspectroscopy to analyse their variations and spatial arrangements