Purely competitive evolutionary dynamics for games

We introduce and analyze a purely competitive dynamics for the evolution of an infinite population subject to a 3-strategy game. We argue that this dynamics represents a characterization of how certain systems, both natural and artificial, are governed. In each period, the population is randomly sorted into pairs, which engage in a once-off play of the game; the probability that a member propagates its type to its offspring is proportional only to its payoff within the pair. We show that if a type is dominant (obtains higher payoffs in games with both other types), its 'pure' population state, comprising only members of that type, is globally attracting. If there is no dominant type, there is an unstable 'mixed' fixed point; the population state eventually oscillates between the three near-pure states. We then allow for mutations, where offspring have a non-zero probability of randomly changing their type. In this case, the existence of a dominant type renders a point near its pure state globally attracting. If no dominant type exists, a supercritical Hopf bifurcation occurs at the unique mixed fixed point, and above a critical (typically low) mutation rate, this fixed point becomes globally attracting: the implication is that even very low mutation rates can stabilize a system that would, in the absence of mutations, be unstable.Comment: 13 pages, 6 figure

The introductory astronomy course at the University of Cape Town: probing student perspectives

We report on research carried out to improve teaching and student engagement in the introductory astronomy course at the University of Cape Town. This course is taken by a diverse range of students, including many from educationally disadvantaged backgrounds. We describe the development of an instrument, the Introductory Astronomy Questionnaire (IAQ), which we administered as pre- and post-tests to students enrolled in the course. The instrument comprised a small number of questions which probed three areas of interest: student motivation and expectations, astronomy content, and worldview. Amongst our findings were that learning gains were made in several conceptual areas, and that students appeared to develop a more nuanced view of the nature of astronomy. There was some evidence that the course had a positive impact on students' worldviews, particularly their attitudes towards science. We also identified a promising predictor of course success that could in future be used to identify students requiring special teaching intervention.Comment: 19 pages, 2 figures. Accepted for publication in Physical Review Special Topics - Physics Educatio

Ground water quality assessment for irrigation in Palwal block of Palwal district, Haryana, India

The present study examined the quality of groundwater for agriculture purpose in a 49785 ha region comprising Palwal block of Palwal district of Haryana state by focusing on spatial variability of electrical conductivity (EC), cationic and anionic composition of CO32-, HCO3-, Cl-, SO42-, Ca2+, Mg2+, Na+ and K+ of the ground water. It was found 75% of the samples showed EC values up to 4 dS/m and the maximum value of EC was found as 10.55 dS/m. Out of one hundred thirty three ground water samples 34.8 % were of good quality, 49.2 % saline and 16.0 % alkali in nature. Out of the saline water, 24.2, 1.5 and 23.5 % were marginally saline, saline and high SAR saline, respectively. In alkali group, 2.3, 2.3 and 11.4 % were marginally alkali, alkali and high alkali, respectively. Residual sodium carbonate (RSC) and sodium adsorption ratio (SAR) varied from nil to 5.50 me L-1 and 2.50 to 23.41 (m mol L-1)½, respectively. Counter map maps of EC, SAR, RSC and water quality of groundwater used for irrigation in the block were prepared through GIS to study spatial variability

Pinning down the mass of Kepler-10c: the importance of sampling and model comparison

Initial RV characterisation of the enigmatic planet Kepler-10c suggested a mass of $\sim17$ M$_\oplus$, which was remarkably high for a planet with radius $2.32$ R$_\oplus$; further observations and subsequent analysis hinted at a (possibly much) lower mass, but masses derived using RVs from two different spectrographs (HARPS-N and HIRES) were incompatible at a $3\sigma$-level. We demonstrate here how such mass discrepancies may readily arise from sub-optimal sampling and/or neglecting to model even a single coherent signal (stellar, planetary, or otherwise) that may be present in RVs. We then present a plausible resolution of the mass discrepancy, and ultimately characterise Kepler-10c as having mass $7.37_{-1.19}^{+1.32}$ M$_\oplus$, and mean density $3.14^{+0.63}_{-0.55}$ g cm$^{-3}$.Comment: 7 pages, 4 figures. Accepted for publication in MNRAS Letter

Coffee certification in Brazil: compliance with social standards and its implications for social equity

© 2018, The Author(s). This paper addresses the relationship between compliance with social performance criteria (the social outcomes that must be achieved for certification) and procedural (management) criteria and this relationship’s significance for social equity at both farm and wider landscape levels. We consider social performance compliance to be pertinent to farm-level equity, and the relative compliance of small versus large farms to be pertinent to landscape-level equity. Certification’s management requirements are often deemed disproportionately burdensome for small, resource-poor producers, and hence a barrier to landscape-level equity. There is a lack of research examining how management criteria impact the ability of different sized farms to meet certification’s social performance requirements. We analysed 435 certification audits, covering all Brazilian coffee farms that sought Rainforest Alliance certification from 2006 to 2014 inclusive: 80 individual farms and 23 groups of farms. In principle, undergoing group certification permits smallholders to benefit from economies of scale. Our analysis revealed a statistically significant, positive correlation between compliance with procedural (managing sustainability plans) and social performance criteria. This correlation was stronger for groups than individual farms. Group farms’ compliance was statistically equivalent to that of individual farms, suggesting that group certification is achieving its intended purpose of socio-economic levelling of certified farmers. Over time, certified farms’ average compliances improved. Our findings suggest that management requirements play an important role in improving smallholders’ overall social sustainability performance and that group certification may help resource-poor smallholders achieve those requirements. Further work is required to understand causal mechanisms underlying the relationships we present

A strategic plan for operating in a commercialised environment.

Thesis (MBA)-University of Natal, Durban, 2002.This report evaluates the business plan at Eskom's Matla power station by comparing it to grounded theory to establish whether the strategies selected prepare the station to be competitive in a commercialised environment. It is assumed that the key success factors in a commercialised environment would be low cost operation and service delivery to meet customer demands. It is shown that the business plan is deficient in many regards, but the strategies selected are adequate in preparing the station for operation in a commercial environment. A questionnaire is used to determine management buy-in to the strategies selected to gauge support for the strategies. Reasons for strategies not meeting all objectives are also looked at and recommendations are made to improve· the business plan and the implementation of the strategies selected. The question of whether the strategies support corporate strategy is answered by comparing the vision, mission and strategies selected by the station to the vision and mission of Eskom Holdings and Eskom Generation. The findings here were that, although long and awkward, the mission statement supports corporate mission, while the vision contradicts corporate vision. Matla's vision supports growth through diversification while Eskom Holdings and Eskom Generation focus on core business

Antecedents and Consequences of Nepotism: A Social Psychological Exploration

Nepotism is a phenomenon that has engulfed the nature of work in private-and public-sector organisations for centuries. Nepotism is not limited to third world countries; it occurs both in individualistic and collectivistic cultures. So, it is a worldwide issue which needs addressing in today's society. In spite of the relevance and vast reach of nepotism, psychological studies into the concept are scant. It remains largely unknown why some people endorse nepotistic practices, whereas others do not. Similarly, the consequences of nepotism for individuals and organisations remain poorly understood. The aim of this thesis is to contribute towards addressing these gaps. This thesis starts by examining psychological constructs that predict variations in the perception and endorsement of nepotism between individuals (Study 1) and countries (Study 2). Studies 3 and 4 investigate the actual and perceived consequences of nepotism on employees. The aim of the studies is to advance the research body around nepotism by adopting a psychological perspective examining the genesis of nepotism at an individual and country level to aid our understanding of antecedents and consequences of nepotism. Findings from Study 1 highlight that Social Dominance Orientation (SDO) - a psychological trait that reflects a preference for inequality and social stratification - is instrumental in predicting attitudes towards nepotism; the higher the levels of SDO possessed by an individual the more they are inclined to endorse nepotistic practices. Findings from Study 2, a cross-cultural study, further underscore the importance of social dominance and power distance in promoting individual- and country-level differences in the endorsement of nepotism. India a high-power distance country with a collectivist culture had the highest prevalence and endorsement of nepotism when compared to the USA, with Trinidad and Greece falling in between the former two countries. Variations in SDO and family orientation contributed to explain individual-level variations in the endorsement of nepotism as well as differences between countries. Studies 3 and 4 examine the role of qualifications as a factor that may moderate the consequences of nepotism for individuals and organisations. Study 3 indicates that individuals recruited through nepotistic means and suitably qualified thrive in their jobs; they have higher levels of performance, enhanced well-being and experience greater levels of autonomy and control. In contrast, individuals hired through nepotistic means without suitable levels of qualification showed evidence of poor psychological well-being, lower levels of autonomy and control, and underperformance. All in all, the study highlights potential benefits and drawbacks of nepotistic hirings and the crucial role of qualifications in determining whether nepotism produces positive or negative outcomes. Probing the perceived consequences of nepotism with and without qualifications, Study 4 showed that people appear to have a limited understanding of the importance of qualifications for determining employees' well-being and levels of autonomy and control. The thesis concludes with a discussion of contributions, limitations, and areas for future research

Inferring probabilistic stellar rotation periods using Gaussian processes

Variability in the light curves of spotted, rotating stars is often non-sinusoidal and quasi-periodic --- spots move on the stellar surface and have finite lifetimes, causing stellar flux variations to slowly shift in phase. A strictly periodic sinusoid therefore cannot accurately model a rotationally modulated stellar light curve. Physical models of stellar surfaces have many drawbacks preventing effective inference, such as highly degenerate or high-dimensional parameter spaces. In this work, we test an appropriate effective model: a Gaussian Process with a quasi-periodic covariance kernel function. This highly flexible model allows sampling of the posterior probability density function of the periodic parameter, marginalising over the other kernel hyperparameters using a Markov Chain Monte Carlo approach. To test the effectiveness of this method, we infer rotation periods from 333 simulated stellar light curves, demonstrating that the Gaussian process method produces periods that are more accurate than both a sine-fitting periodogram and an autocorrelation function method. We also demonstrate that it works well on real data, by inferring rotation periods for 275 Kepler stars with previously measured periods. We provide a table of rotation periods for these 1132 Kepler objects of interest and their posterior probability density function samples. Because this method delivers posterior probability density functions, it will enable hierarchical studies involving stellar rotation, particularly those involving population modelling, such as inferring stellar ages, obliquities in exoplanet systems, or characterising star-planet interactions. The code used to implement this method is available online.Comment: Submitted to MNRAS. Replaced 27/06/2017: corrections made to koi_periods.cs