An evaluation of cardiovascular risk in early bereavement

Although bereavement is associated with adverse health, the mechanism is not well understood, in part because early psychological, behavioural and physiological changes remain incompletely characterised. In this thesis, the results of a prospective evaluation of cardiac risk factors in early bereavement are reported. Psychological, behavioural and physical changes associated with cardiac risk are documented with the main focus on physiological changes in the early acute bereavement period. The relationships between physiological risk factor changes observed and psychological state and social support in the early acute bereavement period are also explored. Bereaved (n=62) spouses and parents were evaluated within two weeks and at six months following loss using the Centre for Epidemiologic Studies-Depression (CES-D), Spielberger State Anxiety and Anger, Social Support Questionnaire (SSQ-6) and a behavioural questionnaire documenting changes in sleep behaviours, appetite, cigarette and alcohol consumption. Evaluation of cortisol, lipids, inflammatory and prothrombotic changes, 24-hour heart rate and blood pressure were also conducted. Bereaved participants were compared to a sample of non-bereaved individuals (n=50). Compared to non-bereaved, acutely bereaved participants had elevated symptoms of depression (mean 26.7 ±1.7 vs 5.9 ±0.7, p<0.001), anxiety (mean 47.4 ±2.0 vs 28.2 ±1.4, p<0.001) and anger (median 16.0 vs 15.0, p<0.001). Acutely, bereaved participants slept less than non-bereaved (mean 5.9 ±0.2 vs 7.2 ±0.2 hours, p<0.001) and were more likely to report reduced appetite (p<0.001) and changes to alcohol consumption (p<0.001). Compared to the non-bereaved, acutely bereaved participants had higher cortisol levels (median 306 vs 266, p=0.003), lower total cholesterol (median 4.9 vs 5.4, p=0.006), lower LDL (median 2.4 vs 2.9, p<0.001), higher neutrophils (median 4.0 vs 3.3, p=0.002), a trend towards higher vWF-ag (127 vs 114, p=0.055), higher 24-hour heart rate (mean 75.5 ± 1.9 vs 70.6 ± 1.2, p=0.008), lower SDNN (median 116 vs 129, p=0.04), and higher daytime blood pressure load (systolic mean load: 39.7 ± 0.03 vs 25.8 ± 0.02, p=0.005 and diastolic mean load 20.1 ± 0.02 vs 13.5 ± 0.02, p=0.008). At six months, in the bereaved participants, depression, anxiety and anger had reduced significantly (all p<0.001). Appetite had returned to normal and sleep time had increased (p<0.001). Heart rate (p=0.03), diastolic blood pressure load (p=0.03), VWFag (p=0.008) and neutrophil (p=0.001) levels were all lower compared to the initial acute assessment. Total cholesterol (p=0.01) and LDL (P=0.003) increased while HDL levels decreased (p=0.04) from the acute assessment to six months. Cortisol, SDNN and systolic blood pressure remained unchanged. At the acute initial assessment, no significant associations between symptoms of depression and physiological changes acutely were observed. Increased symptoms of anxiety were associated with higher heart rate (r=0.27, p=0.04), total cholesterol (r=0.29, p=0.02) and LDL (r=0.29, p=0.03) levels. Increased anger symptoms were associated with higher heart rate (r=0.27, p=0.04), daytime systolic blood pressure (r=0.28, p=0.04) and LDL levels (r=0.35, p=0.008). To determine if levels of social support were associated with lower cardiovascular risk, the relationships between levels of social support and physiological changes observed were described. No significant relationships between social support (availability or satisfaction) and physiological changes acutely were observed. In conclusion, the results offer insight into the psychological, behavioural and physiological changes that may contribute to health risk in the surviving spouse or parent in early bereavement. The recognition that bereavement is associated with increased cardiac risk should provide an impetus for individuals to act on cardiac symptoms by seeking medical advice and for health care providers to monitor such individuals more closely

Water security in South Africa: perceptions on public expectations and municipal obligations, governance and water re-use

South Africa is a water-scarce country with increasing pressure on its water resources. Urgent interventions are needed to protect water security within this rapidly developing country. This paper reports on an interdisciplinary Water Security Colloquium, convened by the South African Young Academy of Science in 2014. A selected group of water professionals from academia, civil society and local government was brought together to discuss water security under three focus themes: ‘public expectations and municipal obligations’, ‘water security and governance: challenges and advances’, and ‘water re-use: health and infrastructural considerations’. Participant perceptions were generated using a focus group methodology, combined with participatory data collection methods. Under each theme, inputs were categorised as ‘challenges’, ‘gaps in knowledge’, and ‘solutions/recommendations’ and these inputs were thereafter ranked in order of importance via a ‘voting’ process. Major challenges perceived included a lack of both skills and political will in government, a need to restore citizen trust in government intention and capability to deliver water-related services, and a failure to up-scale existing water re-use technology. Participants identified understanding of the process and implications of the Green and Blue Drop Programmes, knowledge transfer to the public, and the role of educators as major knowledge gaps. The top suggestions proposed included creating public awareness around and buy-in to initiatives to improve water security, accessible and user-friendly conversion of research results to implementation, and ensuring an active role for educators in creating awareness around water security. In view of the concerns identified, participants suggested as potential solutions: improving government and public understanding around water issues, incentivising water re-use and conservation, introducing rising block tariffs and improving human capacity development in the water sector. Developing the ecological infrastructure that protects both quantity and quality of water and building strong partnerships among all stakeholders were also recognised as key.Keywords: capacity development, education, governance, water security, water re-use, water conservation, local governmen

Competition-based model of pheromone component ratio detection in the moth

For some moth species, especially those closely interrelated and sympatric, recognizing a specific pheromone component concentration ratio is essential for males to successfully locate conspecific females. We propose and determine the properties of a minimalist competition-based feed-forward neuronal model capable of detecting a certain ratio of pheromone components independently of overall concentration. This model represents an elementary recognition unit for the ratio of binary mixtures which we propose is entirely contained in the macroglomerular complex (MGC) of the male moth. A set of such units, along with projection neurons (PNs), can provide the input to higher brain centres. We found that (1) accuracy is mainly achieved by maintaining a certain ratio of connection strengths between olfactory receptor neurons (ORN) and local neurons (LN), much less by properties of the interconnections between the competing LNs proper. An exception to this rule is that it is beneficial if connections between generalist LNs (i.e. excited by either pheromone component) and specialist LNs (i.e. excited by one component only) have the same strength as the reciprocal specialist to generalist connections. (2) successful ratio recognition is achieved using latency-to-first-spike in the LN populations which, in contrast to expectations with a population rate code, leads to a broadening of responses for higher overall concentrations consistent with experimental observations. (3) when longer durations of the competition between LNs were observed it did not lead to higher recognition accuracy

Setback distances as a conservation tool in wildlife-human interactions : testing their efficacy for birds affected by vehicles on open-coast sandy beaches

In some wilderness areas, wildlife encounter vehicles disrupt their behaviour and habitat use. Changing driver behaviour has been proposed where bans on vehicle use are politically unpalatable, but the efficacy of vehicle setbacks and reduced speeds remains largely untested. We characterised bird-vehicle encounters in terms of driver behaviour and the disturbance caused to birds, and tested whether spatial buffers or lower speeds reduced bird escape responses on open beaches. Focal observations showed that: i) most drivers did not create sizeable buffers between their vehicles and birds; ii) bird disturbance was frequent; and iii) predictors of probability of flushing (escape) were setback distance and vehicle type (buses flushed birds at higher rates than cars). Experiments demonstrated that substantial reductions in bird escape responses required buffers to be wide (&gt; 25 m) and vehicle speeds to be slow (&lt; 30 km h-1). Setback distances can reduce impacts on wildlife, provided that they are carefully designed and derived from empirical evidence. No speed or distance combination we tested, however, eliminated bird responses. Thus, while buffers reduce response rates, they are likely to be much less effective than vehicle-free zones (i.e. beach closures), and rely on changes to current driver behaviou

Setback distances as a conservation tool in wildlife-human interactions : testing their efficacy for birds affected by vehicles on open-coast sandy beaches

In some wilderness areas, wildlife encounter vehicles disrupt their behaviour and habitat use. Changing driver behaviour has been proposed where bans on vehicle use are politically unpalatable, but the efficacy of vehicle setbacks and reduced speeds remains largely untested. We characterised bird-vehicle encounters in terms of driver behaviour and the disturbance caused to birds, and tested whether spatial buffers or lower speeds reduced bird escape responses on open beaches. Focal observations showed that: i) most drivers did not create sizeable buffers between their vehicles and birds; ii) bird disturbance was frequent; and iii) predictors of probability of flushing (escape) were setback distance and vehicle type (buses flushed birds at higher rates than cars). Experiments demonstrated that substantial reductions in bird escape responses required buffers to be wide (&gt; 25 m) and vehicle speeds to be slow (&lt; 30 km h-1). Setback distances can reduce impacts on wildlife, provided that they are carefully designed and derived from empirical evidence. No speed or distance combination we tested, however, eliminated bird responses. Thus, while buffers reduce response rates, they are likely to be much less effective than vehicle-free zones (i.e. beach closures), and rely on changes to current driver behaviou

Gain control network conditions in early sensory coding

Gain control is essential for the proper function of any sensory system. However, the precise mechanisms for achieving effective gain control in the brain are unknown. Based on our understanding of the existence and strength of connections in the insect olfactory system, we analyze the conditions that lead to controlled gain in a randomly connected network of excitatory and inhibitory neurons. We consider two scenarios for the variation of input into the system. In the first case, the intensity of the sensory input controls the input currents to a fixed proportion of neurons of the excitatory and inhibitory populations. In the second case, increasing intensity of the sensory stimulus will both, recruit an increasing number of neurons that receive input and change the input current that they receive. Using a mean field approximation for the network activity we derive relationships between the parameters of the network that ensure that the overall level of activity of the excitatory population remains unchanged for increasing intensity of the external stimulation. We find that, first, the main parameters that regulate network gain are the probabilities of connections from the inhibitory population to the excitatory population and of the connections within the inhibitory population. Second, we show that strict gain control is not achievable in a random network in the second case, when the input recruits an increasing number of neurons. Finally, we confirm that the gain control conditions derived from the mean field approximation are valid in simulations of firing rate models and Hodgkin-Huxley conductance based models

Asymmetric WIMP dark matter

In existing dark matter models with global symmetries the relic abundance of dark matter is either equal to that of anti-dark matter (thermal WIMP), or vastly larger, with essentially no remaining anti-dark matter (asymmetric dark matter). By exploring the consequences of a primordial asymmetry on the coupled dark matter and anti-dark matter Boltzmann equations we find large regions of parameter space that interpolate between these two extremes. Interestingly, this new asymmetric WIMP framework can accommodate a wide range of dark matter masses and annihilation cross sections. The present-day dark matter population is typically asymmetric, but only weakly so, such that indirect signals of dark matter annihilation are not completely suppressed. We apply our results to existing models, noting that upcoming direct detection experiments will constrain a large region of the relevant parameter space.Comment: 32 pages, 6 figures, updated references, updated XENON100 bounds, typo in figure caption correcte