Structural properties of polyaniline films

This thesis describes the experimental investigations of the structural properties of the conductive polymer, poly aniline. These studies have been performed on free-standing film samples, solution cast using the solvent N- methyl-2-pyrrolidinone (NMP). Such specimens have enabled a wealth of detailed information about polyaniline to be derived. The polymer itself was synthesised in the emeraldine base form using a chemical route optimised at Durham. The product was then assessed for its chemical structure and molecular weight using (^13)c NMR, elemental analysis and gel permeation chromatography. The process of fabricating the polymer into free-standing films is discussed and assessed. It has been shown that such films may be oriented by the application of uniaxial stress at elevated temperatures and this procedure has been described and analysed in detail. This stretching process aligns the polymer chains on a molecular level and hence produces changes in the physical properties of films. In particular, upon doping to the conducting emeraldine salt form by protonation in aqueous HCl, stretch oriented films display a remarkable increase in conductivity (parallel to the stretch direction) over their unstretched, doped counterparts. Various thermal analysis techniques, including dynamic mechanical thermal analysis, dielectric thermal analysis, thermomechanical analysis and infrared spectroscopy have been used to probe the physical properties of polyaniline films. Using these techniques a number of important thermal transitions have been observed and furthermore the stretch alignment process has been rationalised. Infrared orientational analysis has revealed detailed information about the molecular orientation produced during macroscopic stretching of a film. The type and degree of chain orientation has been analysed as well as the geometrical structure of a single chain. X-ray diffraction has probed the crystalline fraction of polyaniline films. Various aspects concerning the crystalline fraction of film samples has been derived along with an orientational analysis which has been contrasted with the infrared results. An even greater amount of structural information has been revealed by neutron diffraction and this technique has enabled a detailed examination of the structure of the crystalline phases of polyaniline to be made

Lattice-gas Monte Carlo study of adsorption in pores

A lattice gas model of adsorption inside cylindrical pores is evaluated with Monte Carlo simulations. The model incorporates two kinds of site: (a line of) ``axial'' sites and surrounding ``cylindrical shell'' sites, in ratio 1:7. The adsorption isotherms are calculated in either the grand canonical or canonical ensembles. At low temperature, there occur quasi-transitions that would be genuine thermodynamic transitions in mean-field theory. Comparison between the exact and mean-field theory results for the heat capacity and adsorption isotherms are provided

A study of the thermal runaway of lithium-ion batteries : a Gaussian process based global sensitivity analysis

A particular safety issue with Lithium-ion (Li-ion) cells is thermal runaway (TR), which is the exothermic decomposition of cell components creating an uncontrollable temperature rise leading to fires and explosions. The modelling of TR is difficult due to the broad range of cell properties and potential conditions. Understanding the effect that thermophysical and heat transfer characteristics have on the TR abuse model output is essential to develop more accurate and robust TR models. This study uses global sensitivity analysis (GSA) to investigate the effect of the cell parameters on the outcome of TR events. Using a Gaussian Process (GP) surrogate model to calculate the Sobol’ indices, it is shown that the emissivity value is the dominant thermo-characteristic throughout the overall abuse scenario. Further analysis, investigating three key TR features shows the conductivity coefficient to be the most important with respect to the maximum temperature reached during TR. Results demonstrate that researchers can confidently estimate some thermo-characteristics but require accurate characterisation of the emissivity and conductivity coefficient to ensure robust predictions. Given the importance of battery technology to aid in global de-carbonisation, these findings are key to increasing their safe design and operation

Neural correlates of the inverse base rate effect

The inverse base rate effect (IBRE) is a nonrational behavioral phenomenon in predictive learning. Canonically, participants learn that the AB stimulus compound leads to one outcome and that AC leads to another outcome, with AB being presented three times as often as AC. When subsequently presented with BC, the outcome associated with AC is preferentially selected, in opposition to the underlying base rates of the outcomes. The current leading explanation is based on error-driven learning. A key component of this account is prediction error, a concept previously linked to a number of brain areas including the anterior cingulate, the striatum, and the dorsolateral prefrontal cortex. The present work is the first fMRI study to directly examine the IBRE. Activations were noted in brain areas linked to prediction error, including the caudate body, the anterior cingulate, the ventromedial prefrontal cortex, and the right dorsolateral prefrontal cortex. Analyzing the difference in activations for singular key stimuli (B and C), as well as frequency matched controls, supports the predictions made by the error-driven learning account

Tall tales from de Sitter space II: Field theory dualities

We consider the evolution of massive scalar fields in (asymptotically) de Sitter spacetimes of arbitrary dimension. Through the proposed dS/CFT correspondence, our analysis points to the existence of new nonlocal dualities for the Euclidean conformal field theory. A massless conformally coupled scalar field provides an example where the analysis is easily explicitly extended to 'tall' background spacetimes.Comment: 31 pages, 2 figure

Human Sources:The Journalist and the Whistle-blower in the Digital Era

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Molecular biology of histidine decarboxylase and prostaglandin receptors

Histamine and prostaglandins (PGs) play a variety of physiological roles as autacoids, which function in the vicinity of their sources and maintain local homeostasis in the body. They stimulate target cells by acting on their specific receptors, which are coupled to trimeric G proteins. For the precise understanding of the physiological roles of histamine and PGs, it is necessary to clarify the molecular mechanisms involved in their synthesis as well as their receptor-mediated responses. We cloned the cDNAs for mouse l-histidine decarboxylase (HDC) and 6 mouse prostanoid receptors (4 PGE2 receptors, PGF receptor, and PGI receptor). We then characterized the expression patterns and functions of these genes. Furthermore, we established gene-targeted mouse strains for HDC and PG receptors to explore the novel pathophysiological roles of histamine and PGs. We have here summarized our research, which should contribute to progress in the molecular biology of HDC and PG receptors