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Polymer-fullerene blend films are of increasing interest in the field of organic solar cells. This thesis describes the use of transient absorption spectroscopy (TAS) as a means to study charge generation and recombination in these blend films. In blend films of P3HT and PCBM, the absorption spectrum associated with the positive and negative charges have been identified and the transient decay kinetics analysed to reveal the mechanisms leading to charge recombination losses in the films. The effects of annealing treatment, along with the effects of decreasing polymer regioregularity or different polymer chain terminating end-groups on the blend film properties and morphology are also discussed. For films with a low concentration of PCBM in polystyrene, absorption and emission from the individual PCBM molecules are observed. As the PCBM concentration is increased, aggregation related changes causes the absorption in the visible region to increase disproportionately, an additional emission peak at higher energies to appear and a decrease in the lifetime of the PCBM triplet excited state. These changes are linked to electronic interactions between fullerenes in a molecular crystal form of PCBM. Blends of F8BT polymer with PCBM show poor photovoltaic device performance. This is explained by the quick deactivation of the F8BT excited state by Förster energy transfer to the PCBM. As the PCBM excited state is stable compared to the charge separated state, the PCBM triplet is formed via inter-system crossing from the singlet to be the final product of photoexcitation. The high energy of the charge separated state is interpreted as a result of the high F8BT HOMO energy.

Thesis (D.Sc.)--University of the Witwatersrand, Faculty of Health Sciences, 2012.

Reperfusion of the isolated rat heart following 10 min of coronary artery ligation under constant flow conditions results in the development of arrhythmias - premature ventricular contractions (PVCs), ventricular tachycardia (VT) and ventricular fibrillation (VF). Increasing concentrations of magnesium (0 - 4.8 mM) and/or potassium (2.5 - 10.0 mM) attenuate, while calcium (0.6 - 2.4 mM) exacerbates these arrhythmias. The protective effects of magnesium and potassium were additive. Magnesium reduced heart rate, perfusion pressure and developed tension. Potassium reduced perfusion pressure and increased developed tension. These haemodynamic effects contributed to the antiarrhythmic action of magnesium but did not completely account for its antiarrhythmic action. Calcium increased developed tension and heart rate and reduced perfusion pressure. Post-ligation administration of magnesium and potassium also protected against reperfusion arrhythmias. These results demonstrate that reperfusion arrhythmias are significantly affected by the ionic environments of the heart. Superoxide dismutase (5 - 20 Um1-1 ), glutathione (10 -5 - 10-3M), ascorbic acid (10-4 -5 x 10-4 M) and histidine (5 x 10-3 M) when given before coronary artery ligation attenuated the development of reperfusion arrhythmias. Mannitol (2 x 10-2 M) and catalase (100 - 300 Uml-1) did not have any significant effect on reperfusion arrhythmias when given alone but they did potentiate the effect of superoxide dismutase. Glutathione and a combination of superoxide dismutase, catalase and mannitol also reduced the incidence of reperfusion induced ventricular fibrillation when given just before reperfusion. Ferrous ion exacerbated the severity of reperfusion arrhythmias. Mannitol (2 x 10-2 M), catalase (100 uml-1) and histidine (5 x 10-3 M) when given before coronary ligation or just before reperfusion prevented the effect of ferrous ion while superoxide dismutase did not, indicating that the presence of ferrous ion is important for the production of hydroxyl radicals. Pretreatment with 6- OHDA attenuated the incidence of reperfusion arrhythmias but pre-ligation administration of allopurinol had no effect on reperfusion arrhythmias. By perfusing hearts with ferricytochrome C it was possible to show an increased reduction of ferricytochrome C during the first minute of reperfusion which could be prevented by the addition of superoxide dismutase and 6-OHDA treatment. These results provide evidence that oxygen free radicals are produced and may be important in the genesis of reperfusion induced arrhythmias in the isolated rat heart. Adenosine (10-6 M), verapamil (10 -8 - 10-7 M), ZK 36374 (10-10 - 10 -9 M) and sodium nitroprusside (10-6 -10-9 M) attenuate the incidence of reperfusion arrhythmias which may be via a coronary steal effect. Agents which affect arachidonic acid metabolism yielded conflicting results which may reflect nonspecific mechanisms other than inhibition of arachidonic acid metabolism. Glutathione and a mixture of superoxide dismutase, catalase and mannitol when given before coronary ligation and just before reperfusion reduced the increase in 86 rubidium efflux rate constant shown on reperfusion. The effect of glutathione on 86 rubidium efflux may be at least in part due to its vasodilator effect. Superoxide generation by xanthine/xanthine oxidase system increased the rate of efflux of 86 rubidium. A mixture of superoxide dismutase, catalase and mannitol also reduced the transient increase in the rate of release of 3H-noradrenaline shown to be produced on reperfusion after 10 min of ischaemia in the isolated rat heart.

Empathy induced altruism is considered as the motivation of human cooperation, one of the most prominent pro-social behaviours in society. To explore the empathy-cooperation link, this thesis presents a series of empirical studies designed to uncover how reliable this association is. Specifically, the introductory chapters present an evidence-based systematic review and discussion of current theories, which take a critical view of the methodological approaches and provide the context and theoretical motivations for the empirical work of the thesis. The empirical chapters present four studies conducted in the laboratory to evaluate empathy-cooperation association, as well as other potential mediating factors via Public Goods Game (PGG) reflecting collective action in society (total approx. 540 participants). Study 1 was a replication of a highly cited finding that has been often used to support theoretical claims regarding the positive empathy-cooperation link, which in the present case was not found when examined using the PGG set up. Study 2 further explored the empathy-cooperation link alongside the impact of personal values as an information signal to support cooperative behaviour, to this end, shared social values predicted cooperative behaviour above and beyond empathy. Study 3 examined the extent to which empathy could be used to support cooperation in heterogeneous group settings by manipulating the distribution of endowments and the origin of endowments; again empathy had a limited effect on levels of cooperation. Study 4 was a replication of Study 3, but using a 2-player PGG, leading to differences between the patterns of results from the previous experiment. The concluding section considers the implications of the findings for current theories that build on the empathy-cooperation link. Overall the experimental findings do not support the statement that empathy induction is an effective way of promoting cooperation in PGG when financial incentives are involved. This enriches the understanding of empathy-cooperation.

The aim of this thesis was to discover the mechanism for non-photochemical laser-induced nucleation (NPLIN), which is a technique for inducing nucleation of crystals with laser light without absorption. The mechanism of the optical Kerr effect (OKE) was suggested by Garetz et al. [Physical Review Letters 77, 3475–3476 (1996)] to give an explanation for NPLIN. Since the feasibility of the OKE mechanism for NPLIN has been questioned, a series of experiments on NPLIN of aqueous supersaturated urea were carried out to quantify the relationship between crystal alignment and laser polarization. Digital imaging of crystal growth during laser irradiation showed that nascent needle-shaped crystals of urea were not aligned with the direction of the electric field of the laser. Additionally, work on glycine was aimed at verifying the possibility to control the polymorph of the obtained crystal via the laser polarization. However, our finding shows that the probability of γ-glycine is more likely to increase with increasing supersaturation; and the influence of laser polarization on the resulting morphologies is not strong as reported by Sun et al. [Crystal Growth & Design 6, 684–689 (2006)]. Furthermore, in another work on NPLIN of L-histidine, based on Sun et al. [Crystal Growth & Design 8, 1720–1722 (2008)], we were unable to reproduce the results as stated in Sun’s published paper. We find their results exhibit a large uncertainty when recalculated through the Wilson score interval for binomial distributions. On account of these revised uncertainties, it is unlikely that laser polarization gives polymorphism control. Comparison with the nucleation probability of unfiltered samples in the work of urea and glycine shows that the number of filtered samples nucleated as a result of NPLIN was largely decreased. Moreover, experiments on NPLIN of NaCl and KCl also exhibited that the number of filtered samples nucleated was significantly lower than that of unfiltered samples. This downward tendency in nucleation probability after filtration cannot be explained by Garetz’s OKE mechanism. On account of this, an alternative mechanism named particle-heating mechanism was proposed, and supported by experiments on NPLIN of sodium acetate. Sodium acetate experiments showed that the crystallization of sodium acetate can be induced by a single pulse of a nanosecond laser (1064 nm) with minimum power of 0.1 J cm−2. As discovered by Oliver et al. [D. Oliver, PhD Thesis, Edinburgh University, 2014], anhydrous or trihydrate sodium acetate can be formed under the effects of different organic and inorganic additives, such as poly- (methacrylic acid) and disodium hydrogen phosphate. We demonstrate that crystalline growth velocities and crystal morphology can be influenced by these additives. We find that high levels of additive cause only nucleation of bubbles. By counting the number of crystals, which is approximately consistent to the number of bubbles observed, video microscopy of laser-induced crystallization of sodium acetate has revealed that the general mechanism of NPLIN is most likely to be caused by a particle-heating mechanism. Chapter 8 of the thesis describes a number of solute molecules that were tested using NPLIN, but failed. In terms of improvements for future work or a perspective on NPLIN, detailed suggestions have been described in Chapter 9, which also gives a summary of all work presented.

Peripheral artery disease (PAD) and osteoporosis have recently been shown to be associated; with the parallel occurrence suggesting that PAD related ischemia may cause or enhance the onset of osteoporosis. In order to determine the mechanism linking osteoporosis and PAD this paper will examine the effects of ischemia and mechanical stimulation on bone remodeling. An immunohistochemistry protocol for vessel marking in bone was also developed. Ischemia was induced in a mouse model to determine vascular and mechanical property changes in bone in response to hypoxia, and mechanical loading-induced remodeling was analyzed for vascular changes. Both ischemia and mechanical loading increased bone vessel density, with ischemic bone increases seen at day 7 and 14. Bone stiffness increased after induced ischemia at day 28. These results point to resultant hypoxia from ischemia drives bone mechanical property changes, likely through stimulation of bone remodeling. We also conclude that an increase in vessel density is seen after induced mechanical loading of bone. Establishing the vascular contribution to the remodeling process may reveal treatment opportunities for remodeling-dependent pathologies such as osteoporosis.

When a moving dot, which is tracked by the eyes and enclosed in a moving framework, suddenly stops while the enclosing framework continues its motion, the dot is seen to describe a curved path. This illusion can be explained only by assuming that extra-retinal signals are taken into account in interpreting retinal information. The form of the illusion, and the fact that the phenomenal path cannot be explained on the basis of positional information alone, suggests that the perceived path is computed by integrating (instantaneous) velocity information over time. A vector addition model embodying a number of simplifying assumptions is found to qualitatively fit the experimental data. A number of follow-up studies are suggested.

Varenicline is used to treat tobacco dependence. While varenicline decreases craving during a quit attempt, no studies have investigated its effect on cue-induced craving. Varenicline has also been shown to decrease alcohol consumption in animal and humans. This double-blind, randomized, placebo-controlled trial investigated the effect of varenicline on tobacco and alcohol cue-induced craving and alcohol consumption in dependent smokers/light drinkers. Tobacco and alcohol craving were assessed at baseline and after 2-weeks of drug administration using the QSU and ACQ. Significant decreases in cigarette and alcohol craving were observed between the pre- and post-drug session in the varenicline group on QSU Factor 1(87.5811.66 vs.70.5820.79, p=0.008) and ACQ Total (3.371.16 vs. 2.661.15, p=0.004) scores. This effect remained significant after correction for craving during neutral cues in the alcohol but not tobacco condition. No significant decreases in alcohol consumption were seen. These results suggest varenicline decreases overall craving, but not cue-induced craving specifically.

Varenicline is used to treat tobacco dependence. While varenicline decreases craving during a quit attempt, no studies have investigated its effect on cue-induced craving. Varenicline has also been shown to decrease alcohol consumption in animal and humans. This double-blind, randomized, placebo-controlled trial investigated the effect of varenicline on tobacco and alcohol cue-induced craving and alcohol consumption in dependent smokers/light drinkers. Tobacco and alcohol craving were assessed at baseline and after 2-weeks of drug administration using the QSU and ACQ. Significant decreases in cigarette and alcohol craving were observed between the pre- and post-drug session in the varenicline group on QSU Factor 1(87.5811.66 vs.70.5820.79, p=0.008) and ACQ Total (3.371.16 vs. 2.661.15, p=0.004) scores. This effect remained significant after correction for craving during neutral cues in the alcohol but not tobacco condition. No significant decreases in alcohol consumption were seen. These results suggest varenicline decreases overall craving, but not cue-induced craving specifically.