59 resultados para non-additivity of Faradaic current

em Deakin Research Online - Australia


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A study was conducted to evaluate the unexpected non-additivity of Faradaic and capacitance currents encountered in the case of ionic liquids. The results highlight that the non-additivity of Faradaic and capacitance currents should be considered in IL electrochemistry when multiple solutes are present.

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Unexpected nonadditivity of currents encountered in the electrochemistry of mixtures of ferrocene (Fc) and cobaltocenium cation (Cc+) as the PF6 - salt has been investigated by direct current (dc) and Fourier-transformed alternating current (ac) cyclic voltammetry in two aprotic (1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate) and three protic (triethylammonium formate, bis(2-hydroxyethyl)ammonium acetate, and triethylammonium acetate) ionic liquids (ILs). The voltammetry of the individual Fc0/+ and Cc+/0 couples always exhibits near-Nernstian behavior at glassy carbon and gold electrodes. As expected for an ideal process, the reversible formal potentials and diffusion coefficients at 23 ( 1 °C in each IL determined from measurement on individual Fc and Cc+ solutions were found to be independent of electrode material, concentration, and technique used for the measurement. However, when Fc and Cc+ were simultaneously present, the dc and ac peak currents per unit concentration for the Fc0/+ and Cc+/0 processes were found to be significantly enhanced in both aprotic and protic ILs. Thus, the apparent diffusion coefficient values calculated for Fc and Cc+ were respectively found to be about 25 and 35% larger than those determined individually in the aprotic ILs. A similar change in the Fc0/+ mass transport characteristics was observed upon addition of tetrabutylammonium hexafluorophosphate (Bu4NPF6), and the double layer capacitance also varied in distinctly different ways when Fc and Cc+ were present individually or in mixtures. Importantly, the nonadditivity of Faradaic current is not associated with a change in viscosity or from electron exchange as found when some solutes are added to ILs. The observation that the 1H NMR T1 relaxation times for the proton resonance in Cc+ also are modified in mixed systems implies that specific interaction with aggregates of the constituent IL ionic species giving rise to subtle structural changes plays an important role in modifying the mass transport, double layer characteristics, and dynamics when solutes of interest in this study are added to ILs. Analogous voltammetric changes were not observed in studies in organic solvent media containing 0.1 M added supporting electrolyte. Implications of the nonadditivity of Faradaic and capacitance terms in ILs are considered.

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This thesis examined television current affairs interviewing to determine the influence of the cultural politics of Australian commercial and non-commercial networks. Marketplace pressures to rate highly was the major influence on commercial programs resulting in the use of shorter dramatic interviews, more celebrities, fewer politicians, hidden cameras and ambush interviews.

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The determination of urea is important in a wide range of fields, including clinical diagnostics, environmental monitoring and food science. Numerous analytical techniques have been developed for the determination of urea, with no single technique dominant in all areas because of the diversity of applications. An overview of the existing analytical methodologies for urea is presented, and some new approaches are discussed, particularly those based on chemiluminescence detection to improve the sensitivity and the selectivity for the determination of this important analyte.

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This paper studies the effect of the normal distribution assumption on the power and size of the sign test, Wilcoxon's signed rank test and the t-test when used in one-sample location problems. Power functions for these tests under various skewness and kurtosis conditions are produced for several sample sizes from simulated data using the g-and-k distribution of MacGillivray and Cannon.

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Individuals typically believe that they are less likely than the average person to experience negative events. Such “unrealistic optimism” (UO) has been assessed in two ways: directly (via a single question, requiring comparison of own risk to that of the average person) and indirectly (via separate questions about own risk and that of the average person). The study examined the equivalence of the direct and indirect measures of female students' UO for unwanted pregnancy. Participants (N = 120) answered questions about their own risk, that of the average female student, and their own risk relative to that of the average female student; responses and response times were recorded. There was only a moderate association between direct- and indirect-UO. Direct-UO was strongly associated with estimate of own risk, but only moderately associated with estimate of the average student's risk. Response times for the comparative risk and own risk questions did not differ, but participants took significantly longer to answer the question about average student's risk. The results suggest that the two measures of UO are not equivalent, but, rather, that individuals answering a comparative risk question focus mainly on their own risk, at the expense of that of the average person.

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Policy addressing the provision of primary care after hours (AH) is currently in flux because of concerns about equity of access and cost. In this study we examine the effects of socioeconomic disadvantage on access to AH care and episodes of not seeking AH care when needed among users and non-users of AH care. The effects of health on these relationships were also explored. The total sample consisted of 5538 users of AH care and 891 non-users of AH care who were randomly selected for telephone interviews. Factors determining AH care included accessibility that is structural barriers to use of care such as distance and transport, as well as affordability and availability. Logistic regression was used to determine the impact of financial disadvantage on episodes of not seeking AH care. Barriers to use of AH care and household health were subsequently added to the models to assess their impact. The results suggested that there were inequities in access to AH care but these were a function of barriers to AH care use rather than financial disadvantage per se. Accessibility and availability were significant barriers to use of AH clinics among both user and non-user samples. Affordability was only a significant barrier among users of AH care. The study suggests that policy aimed at reducing these barriers may effectively address inequities in AH care but that to be optimally effective policy change would also need to be accompanied by changes in consumer awareness.

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Education services is included as part of the General Agreement on Trade in Services (GATS). This inclusion, however, has not gone without its critics, and discussions about the liberalization of education remain distinctly polarized. This article seeks to bring a more balanced debate to the mix by presenting the case of New Zealand, one of the most liberalized World Trade Organization (WTO) Members in trade in education services. Through this case study, it is discussed how New Zealand has chosen to shape the growth of the education market and steer its developments by including controlled mechanisms as part of its regulatory framework.

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The study was descriptive and exploratory utilising survey methodology. The major outcome was a list of recommendations encompassing educational, professional, and management issues.