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

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

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

A Gaussian process framework for modelling stellar activity signals in radial velocity data

To date, the radial velocity (RV) method has been one of the most productive techniques for detecting and confirming extrasolar planetary candidates. Unfortunately, stellar activity can induce RV variations which can drown out or even mimic planetary signals - and it is notoriously difficult to model and thus mitigate the effects of these activity-induced nuisance signals. This is expected to be a major obstacle to using next-generation spectrographs to detect lower mass planets, planets with longer periods, and planets around more active stars. Enter Gaussian processes (GPs) which, we note, have a number of attractive features that make them very well suited to disentangling stellar activity signals from planetary signals. We present here a GP framework we developed to model RV time series jointly with ancillary activity indicators (e.g. bisector velocity spans, line widths, chromospheric activity indices), allowing the activity component of RV time series to be constrained and disentangled from e.g. planetary components. We discuss the mathematical details of our GP framework, and present results illustrating its encouraging performance on both synthetic and real RV datasets, including the publicly-available Alpha Centauri B dataset.Comment: 24 pages, 14 figures. Accepted for publication in MNRA

How Brazil's sustainable cattle schemes could beef up to conserve forests and sustainable rural livelihoods

Cattle ranching is the largest driver of Brazilian deforestation, a relevant emitter of greenhouse gases, and an important source of local livelihoods. In response, many initiatives attempt to render Brazil’s beef production more environmentally and socially sustainable. Drawing on key informant interviews, this paper assesses the effectiveness of Brazil’s sustainable cattle schemes, with a particular focus on avoided deforestation in the Amazon biome; climate change mitigation; and improving the livelihoods of smallholder ranchers. We found that the sustainable cattle schemes have yet to reach scale and have yet to effectively halt forest loss, reduce greenhouse gas emissions, or sustain rural livelihoods. Thus far, cattle moratoria have achieved the greatest scale in addressing deforestation, but only by targeting the largest and thus most resourced ranches. In order to achieve both socially and environmentally sustainable cattle production, Brazil’s sustainable cattle schemes must scale up, and all governance groups interviewed recommended bottom-up, technical assistance to ranchers to achieve this. Mixed governance schemes, involving both state and non-state actors, were also widely advocated. Impacts were difficult to compare due to a lack of uniform monitoring and thus comparability across the schemes; tools for common measurement are recommended to better compare schemes’ effectiveness. The greatest perceived barriers were market-based: namely the lack of a sustainable beef brand and the associated lack of consumer demand. Respondents also noted the need for improved agronomic and technical assistance for ranchers. Social considerations in the schemes were found to be vague, and in some schemes, neglected

Evolutionary algorithm-based analysis of gravitational microlensing lightcurves

A new algorithm developed to perform autonomous fitting of gravitational microlensing lightcurves is presented. The new algorithm is conceptually simple, versatile and robust, and parallelises trivially; it combines features of extant evolutionary algorithms with some novel ones, and fares well on the problem of fitting binary-lens microlensing lightcurves, as well as on a number of other difficult optimisation problems. Success rates in excess of 90% are achieved when fitting synthetic though noisy binary-lens lightcurves, allowing no more than 20 minutes per fit on a desktop computer; this success rate is shown to compare very favourably with that of both a conventional (iterated simplex) algorithm, and a more state-of-the-art, artificial neural network-based approach. As such, this work provides proof of concept for the use of an evolutionary algorithm as the basis for real-time, autonomous modelling of microlensing events. Further work is required to investigate how the algorithm will fare when faced with more complex and realistic microlensing modelling problems; it is, however, argued here that the use of parallel computing platforms, such as inexpensive graphics processing units, should allow fitting times to be constrained to under an hour, even when dealing with complicated microlensing models. In any event, it is hoped that this work might stimulate some interest in evolutionary algorithms, and that the algorithm described here might prove useful for solving microlensing and/or more general model-fitting problems.Comment: 14 pages, 3 figures; accepted for publication in MNRA

A multi-wavelength view of the central kiloparsec region in the Luminous Infrared Galaxy NGC1614

The Luminous Infrared Galaxy NGC1614 hosts a prominent circumnuclear ring of star formation. However, the nature of the dominant emitting mechanism in its central ~100 pc is still under debate. We present sub-arcsecond angular resolution radio, mid-infrared, Pa-alpha, optical, and X-ray observations of NGC1614, aimed at studying in detail both the circumnuclear ring and the nuclear region. The 8.4 GHz continuum emission traced by the Very Large Array (VLA) and the Gemini/T-ReCS 8.7 micron emission, as well as the Pa-alpha line emission, show remarkable morphological similarities within the star-forming ring, suggesting that the underlying emission mechanisms are tightly related. We used an HST/NICMOS Pa-alpha map of similar resolution to our radio maps to disentangle the thermal free-free and non-thermal synchrotron radio emission, from which we obtained the intrinsic synchrotron power-law for each individual region within the central kpc of NGC1614. The radio ring surrounds a relatively faint, steep-spectrum source at the very center of the galaxy, suggesting that the central source is not powered by an AGN, but rather by a compact (r < 90 pc) starburst. Chandra X-ray data also show that the central kpc region is dominated by starburst activity, without requiring the existence of an AGN. We also used publicly available infrared data to model-fit the spectral energy distribution of both the starburst ring and a putative AGN in NGC1614. In summary, we conclude that there is no need to invoke an AGN to explain the observed bolometric properties of the galaxy.Comment: 13 pages, 7 figures, 5 tables. Accepted for publication in Ap

Effect of Growth Regulators and Micronutrients on Fruit Quality in Pomegranate

A field experiment was conducted at Fruit Research Farm of Haryana Agricultural University, Hisar to evaluate the effect of micronutrients and plant growth regulators on fruit quality in pomegranate cv. Jodhpur Red. The treatments comprising of two micronutrients (H3BO3 & ZnSO4 at 0.20, 0.40, 0.60 %), two growth regulators (2,4-D & NAA at 10, 20, 40 ppm) and water were applied fifteen and thirty days after fruit set. Application of 2,4-D at 40 ppm resulted in more total soluble solids. H3BO3 resulted in more ascorbic acid content when applied at fifteen days after fruit set. 2,4-D when applied at fifteen days after fruit set, significantly increased reducing sugar content. Application of micronutrients and growth regulators applied fifteen days after fruit set was more effective in improving fruit quality as compared to thirty days after fruit set