On the origin of the Korteweg-de Vries equation

The Korteweg-de Vries equation has a central place in a model for waves on shallow water and it is an example of the propagation of weakly dispersive and weakly nonlinear waves. Its history spans a period of about sixty years, starting with experiments of Scott Russell in 1834, followed by theoretical investigations of, among others, Lord Rayleigh and Boussinesq in 1871 and, finally, Korteweg and De Vries in 1895. In this essay we compare the work of Boussinesq and Korteweg-de Vries, stressing essential differences and some interesting connections. Although there exist a number of articles, reviewing the origin and birth of the Korteweg-de Vries equations, connections and differences, not generally known, are reported.Comment: minor corrections; 25 pages, 3 figure

The views of commerce students regarding "free" higher education in South Arica

At the end of 2015, student protests (demanding ‘free’ higher education) took place at most South African universities. An official answer from the South African government regarding ‘free higher education’ is still being awaited. In the meantime, a zero present increase in university fees for 2016 and an increase of not more than 8% for 2017 was announced. South Africa is known for expensive higher education as tuition fees increase every year. Many students struggle to fund their studies, while government subsidies to higher education institution decrease. The question that remains is: Will it be feasible for South Africa to implement ‘free higher education’?This study aimed to investigate the perceptions of commerce students at one South African university regarding the feasibility of ‘free’ higher education. A questionnaire was used as research instrument which consisted of Likert-scale statements regarding general ideas about ‘free higher education’ as well as open-ended questions asking students about the definition of ‘free higher education’ and the effects on the South African economy.The results proposed that even though most students were aware of the students protests regarding ‘free higher education’ that took place, not all of them agreed with it. The respondents realised that it is not feasible for South Africa to implement ‘free higher education’ at this moment in time.Despite the views of these commerce students, if ‘free higher education’ were considered as a viable option in South Africa, implementation considerations should be examined. These issues will be discussed in a follow-up study.

Does "free" higher education in South Africa make economic sense? Views of commerce students

AbstractStudent protests demanding ‘free’ higher education at South Africa universities in 2015 is a reminder that there are still a lot of unresolved issues regarding the inequalities due to the apartheid era in the higher education system. Some of these issues include insufficient state funding of higher education, the increase of tuition fee and unpaid student debt. Even though ‘free’ higher education sounds appealing, the question is whether implementing ‘free’ higher education would make economic sense in South Africa. The study aimed to investigate the perceptions of commerce students at one South African university regarding the economic feasibility of ‘free’ higher education and how it might affect the South African economy. The research aimed to give a descriptive analysis of the perceptions of commerce students and were empirically investigated by means of a questionnaire, containing both open and closed questions. Gaining understanding into student perceptions can be invaluable, as they are considered the livelihood of higher education institutions.The results show that the respondents do not think that ‘free’ higher education make economic sense in South Africa as the economy is too weak and there is too much corruption and wasteful spending in government. The respondents also indicated that the economy will mostly be negatively affected by ‘free’ higher education in that there will be an increase of the financial burden on the South African economy and tax payer. They also regard other government services to be of greater importance than implementing ‘free’ higher education.The results of this study are not necessarily generalisable beyond the scope of the particular institution, but the findings do create a platform for the continued debate on the importance, economic feasibility and implementation of ‘free’ higher education in South Africa.

Determination of the Night Sky Background around the Crab pulsar using its optical pulsation

The poor angular resolution of imaging gamma-ray telescopes is offset by the large reflector areas of next generation telescopes such as MAGIC (17~m diameter), which makes the study of optical emission associated with some gamma-ray sources feasible. Furthermore, the extremely fast time response of photomultipliers (PMs) makes them ideal detectors for fast (subsecond) optical transients and periodic sources like pulsars. The optical pulse of the Crab pulsar was detected with the HEGRA CT1 central pixel using a modified PM, similar to the future MAGIC camera PMs. The purpose of these periodic observations was to determine the light of the night sky (LONS) for the galactic anticenter Crab region.Our results are between 2.5 and 3 times larger than the previously measured LONS (outside the galactic plane), as expected since the Crab pulsar is in the galactic plane, which implies a slightly higher energy threshold for Crab observations, if the higher value of CT1 measured LONS rate for galactic sources is used.Comment: 19 pages, 6 figures, accepted by Astroparticle Physic

The yellow hypergiants HR 8752 and rho Cassiopeiae near the evolutionary border of instability

High-resolution near-ultraviolet spectra of the yellow hypergiants HR 8752 and rho Cassiopeiae indicate high effective temperatures placing both stars near the T_eff border of the ``yellow evolutionary void''. At present, the temperature of HR 8752 is higher than ever. For this star we found Teff=7900+-200 K, whereas rho Cassiopeiae has Teff=7300+-200 K. Both, HR 8752 and rho Cassiopeiae have developed strong stellar winds with Vinf ~ 120 km/s and Vinf ~ 100 km/s, respectively. For HR 8752 we estimate an upper limit for the spherically symmetric mass-loss of 6.7X10^{-6}M_solar/yr. Over the past decades two yellow hypergiants appear to have approached an evolutionary phase, which has never been observed before. We present the first spectroscopic evidence of the blueward motion of a cool super/hypergiant on the HR diagram.Comment: 13 pages including 3 figures. Accepted for publication in ApJ Letter

Inclusive Quasi-Elastic Charged-Current Neutrino-Nucleus Reactions

The Quasi-Elastic (QE) contribution of the nuclear inclusive electron scattering model developed in Nucl. Phys. A627 (1997) 543 is extended to the study of electroweak Charged Current (CC) induced nuclear reactions, at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for, among other nuclear effects, long range nuclear (RPA) correlations, Final State Interaction (FSI) and Coulomb corrections. Predictions for the inclusive muon capture in $^{12}$C and the reaction $^{12}$C $(\nu_\mu,\mu^-)X$ near threshold are also given. RPA correlations are shown to play a crucial role and their inclusion leads to one of the best existing simultaneous description of both processes, with accuracies of the order of 10-15% per cent for the muon capture rate and even better for the LSND measurement.Comment: 31 pages and 14 figures, accepted for publication as a regular article in Physical Review

Inclusive Muon Capture in Light Nuclei

We study total muon capture rates in light nuclei, taking into account renormalizations of the nuclear vector and axial vector strengths. We estimate the influence in the results of uncertainties of the spin-isospin interaction parameter and nuclear densities. A few of these reactions are theoretical benchmarks for physics involving searches for neutrino oscillations. New experiments in muon capture in several targets are suggested, in the light of some discrepancies with theory, crudeness of some experimental results and relevance to neutrino physics.Comment: 11 pages, Latex, no figures. Submitted to Phys.Lett.

Ecological agriculture in South-India : an agro-economic comparison and study of transition

This report describes two research programmes carried out on ecological agriculture in South-India. Experiences of twelve farmers in transition towards ecological agriculture are described and analysed. The comparative performance of seven farmer pairs, consisting of one ecological and one conventional reference farm, is analysed in relation to agronomic and economic performanc

Nutrient partitioning and response to insulin challenge at different planes of nutrition during lactation in goats of high vs. low milk production potential

The aim of this experiment was to determine the effect of genetic selection for milk production on nutrient partitioning at a high vs. a low plane of nutrition. Twelve Indigenous goat does and eight Saanen x Indigenous crossbred does were allocated to either a basal diet formulated to provide energy for maintenance or the basal diet supplemented with maize so as to maintain a plasma glucose concentration of 3.5 mmol/l throughout lactation. Milk yield was not reduced by the low plane of nutrition in either genotype. The sustained rate of milk production at the low level of nutrition was achieved by increased mobilisation of endogenous nutrients from body reserves, evidenced as a greater loss of body mass at the low plane of nutrition in both breeds. The Saanen crossbred genotype, which produced twice as much milk as the Indigenous genotype, lost 19% of initial mass by week 10 of lactation, whereas mass losses in the indigenous goat never exceeded 7%, with the result that repletion of initial (week one) mass was achieved by week six of lactation. Plasma glucose concentrations were depressed to a smaller extent by insulin in the Saanen crossbred than in the Indigenous goat at weeks 3, 7 and 11 of lactation. Although there was evidence for a genotype x nutrition interaction during early lactation, this did not persist throughout lactation. The majority of data derived from this study indicates that the two genotypes reacted in a similar manner to plane of nutrition, with the main differences between milk yield potential being occasioned by differences in the extent of mobilisation of endogenous body reserves mediated by differences in insulin sensitivity. (South African Journal of Animal Science, 2000, 30(3): 178-185