University of Leeds

Leeds, W.Yorkshire, United Kingdom

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Leeds Institute of Health Sciences (LIHS)
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School of Earth and Environment
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Institute of Psychological Sciences
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    ABSTRACT: Hibiscus sabdariffa extracts have attracted attention because of potentially useful bioactivity. However, there have been no systematic studies of extraction efficiencies of H. sabdariffa. The nature of extracts used in different studies has varied considerably, making comparisons difficult. Therefore, a systematic study of extracts of H. sabdariffa made with different solvents was carried out using water, methanol, ethyl acetate and hexane in the presence/absence of formic acid, using different extraction times and temperatures. The extracts were analysed for total polyphenol content, antioxidant capacity using DPPH, FRAP and TEAC assays, and specific anthocyanins were determined using HPLC and LC–MS. The results showed the highest antioxidant capacities were obtained by extracting using water, with or without formic acid, for 10 min at 100 °C. These extracts provided the highest concentrations of cyanidin 3-sambubioside and delphinidin 3-sambubioside. It will be important to use extraction conditions giving optimal extraction efficiencies for subsequent bioactivity experiments.
    Food Chemistry 12/2014; 164:23–29.
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    ABSTRACT: The thermal conductivity of the components of the membrane electrode assembly (MEA) and GDL must be accurately estimated in order to better understand the heat transfer processes in the proton exchange membrane (PEM) fuel cells. In this study, an experimental investigation has been performed to measure the through-plane thermal conductivity and the contact resistance for a number of gas diffusion layer (GDL) materials. The sensitivity of these quantities to the temperature, PTFE content and micro porous layer (MPL) coating has been undertaken. In addition, the through-plane thermal conductivity of the membrane has been measured and reported as a function of temperature and water content. Further, the through-plane thermal conductivity of the catalyst layer has been determined as a function of temperature and platinum loading. It has been found that the through-plane thermal conductivity of the components of the MEA decreases when the temperature increases, and the through-plane thermal conductivity of the GDL is significantly lower than its in-plane thermal conductivity.
    Journal of Power Sources 12/2014; 270:59–67.
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    ABSTRACT: Higher conscientiousness (C) predicts better health outcomes. Recent research suggests that stress may play an important role in explaining this relationship. The current study aimed to establish whether C moderates the relationship between daily hassle appraisals, daily affect, and physical symptoms. A daily diary design was used, where participants (N = 103) completed a baseline measure of C followed by a 14-day daily diary, providing daily details of hassles (primary and secondary appraisals) experienced as well as positive and negative affect and physical symptoms. Hierarchical linear modelling revealed that Total C (as well as two facets of C: Order and Industriousness) moderated the relationship between stress appraisals and positive affect. Specifically, the negative association between the daily appraisal of hassles as stressful (i.e., where perceived demands outweighed perceived resources) and positive affect was stronger for lower and average levels of C, Order, and Industriousness. No significant moderated effects were found for negative affect or physical symptoms. The Order facet was also found to be an important factor predicting attrition. The current study provided evidence that C and two of its facets can moderate the relationship between hassle appraisal and positive affect. C may exert part of its influence on health by modifying the effects of daily stressors. What is already known on this subject? Conscientiousness has a significant positive effect on longevity and health status. While the performance of health behaviours may partially account for this relationship, evidence suggests that it does not fully mediate the effect. Research has begun to look at stress as a possible additional explanatory variable, and there is evidence that Conscientiousness moderates the relationship between stress and health behaviours. What does this study add? Shows that Conscientiousness and two of its facets (Order and Industriousness) moderate the relationship between hassle appraisal and positive affect. Highlights the importance of studying lower order facets of personality in health research. Suggests that Conscientiousness may exert part of its influence on health by modifying the effects of daily stressors.
    British Journal of Health Psychology 11/2014; 19:311-328.


  • Address
    Woodhouse Lane, LS2 9JT, Leeds, W.Yorkshire, United Kingdom
  • Head of Institution
    Sir Alan Langland
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    +44 (0) 113 244 3923
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British Journal of Social Psychology 12/2010; 40(4):471 - 499.

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