Scattering of a Long Cosmic String by a Rotating Black Hole

The scattering of a straight, infinitely long string by a rotating black hole is considered. We assume that a string is moving with velocity v and that initially the string is parallel to the axis of rotation of the black hole. We demonstrate that as a result of scattering, the string is displaced in the direction perpendicular to the velocity by an amount kappa(v,b), where b is the impact parameter. The late-time solution is represented by a kink and anti-kink, propagating in opposite directions at the speed of light, and leaving behind them the string in a new ``phase''. We present the results of the numerical study of the string scattering and their comparison with the weak-field approximation, valid where the impact parameter is large, b/M >> 1, and also with the scattering by a non-rotating black hole which was studied in earlier works.Comment: 27 pages, 14 figures, to be published in Classical and Quantum Gravit

THE LAODAMIA SIMILE IN CATULLUS 68: REFLECTIONS ON LOVE AND LOSS

In Catullus’ poem 68 he compares his beloved, generally identified as Lesbia, to the mythological figure of Laodamia in a long simile covering 57 lines. Laodamia epitomises the ideal wife, both passionate and loyal and so much in love with her new husband Protesilaus, that she cannot bear to live without him. Therefore she appears to be the perfect comparison for a beloved woman as seen through the eyes of her infatuated lover. But at a closer reading of the poem the interpretation of the simile turns out to be much more complex than that. Lesbia is not loyal and she is not Catullus’ wife. He admits both these facts near the end of the poem. Furthermore, Laodamia turns out to have two referents: Lesbia and the poet himself. In this paper I will be looking at various interpretations of the Laodamia simile as well as adding my own thoughts on this complex and beautiful poem

Numerical simulations of self-gravitating magnetized disks

We present the first global simulations of self-gravitating magnetized tori. The simulations are performed with Zeus-2D and GLOBAL. We find the magnetorotational instability (MRI) to behave similarly in a self-gravitating environment as in previous simulations of non self-gravitating systems: enhancement of turbulent angular momentum transport follows the linear phase. The torus quickly develops a two component structure composed of an inner thick disk in Keplerian rotation and an outer massive disk. We compare this result with zero mass global simulations in 2D, and also present preliminary results of 3D simulations.Comment: 6 pages, 6 figures, kluwer.cls, To appear in the proceedings of "Magnetic fields and star formation: Theory versus observations", Madrid,April 21-25 200

Opening the doors of learning: Increasing access to music degrees

This article is contextualized for Music and is a response to the CHE (2013) Report that proposes a flexible curriculum structure for undergraduate degrees in South Africa, to address student under preparedness. Research states that music graduates need well developed identities in music, as well as generic, transferable skills to ensure lifelong employment and that a bachelor of music degree is best suited for this. However, in the South African context, the bachelor of music degree qualification is not accessible to the majority of prospective students as they are under prepared to study music at tertiary level. Only a minority of learners receive quality music education at school, while the majority of learners, including those from low socio-economic communities, do not receive formal music education. Under preparedness to study music, has traditionally been addressed through certificates and diploma qualifications in music. A discussion, and interpretation of the literature, has led to the researcher to develop an alternate framework to both improve student access to music degrees and manage under preparedness. The proposed approach advocates that music departments at universities adopt the framework of the national certificate vocation as an alternative to certificates and diplomas. The alternative curriculum structure for music, would be a more cost effective way to address under preparedness, improve academic success and lead to high skill levels. The study is situated in a constructivist, interpretive worldview, with a qualitative research design. Purposive sampling in the form of the choice of literature for the theoretical framework was adopted. While this theoretical study is contextualized for music, it is applicable to other fields

Structural characterisation of ferrihaem in solution : insights into the mechanism of formation of malaria pigment and its inhibition by aryl methanol antimalarial drugs

Includes abstract.Includes bibliographical references (leaves 207-221)

Evolution of massive and magnetized protoplanetary disks

We present global 2D and 3D simulations of self-gravitating magnetized tori. We used the 2D calculations to demonstrate that the properties of the MRI are not affected by the presence of self-gravity: MHD turbulence and enhanced angular momentum transport follow the linear growth of the instability. In 3D, we have studied the interaction between an $m=2$ gravitational instability and MHD turbulence. We found its strength to be significantly decreased by the presence of the latter, showing that both instabilities strongly interact in their non-linear phases. We discuss the consequences of these results.Comment: 8 pages, 7 figures, to appear in the proceedings of the XIXth IAP colloquium "Extrasolar Planets: Today and Tomorrow" held in Paris, France, 2003, June 30 - July 4, ASP Conf. Serie

Evolution of self-gravitating magnetized disks. I- Axisymmetric simulations

In this paper and a companion work, we report on the first global numerical simulations of self-gravitating magnetized tori, subject in particular to the influence of the magnetorotational instability (MRI). In this work, paper I, we restrict our calculations to the study of the axisymmetric evolution of such tori. Our goals are twofold: (1) to investigate how self-gravity influences the global structure and evolution of the disks; and (2) to determine whether turbulent density inhomogeneities can be enhanced by self-gravity in this regime. As in non self-gravitating models, the linear growth of the MRI is followed by a turbulent phase during which angular momentum is transported outward. As a result, self-gravitating tori quickly develop a dual structure composed of an inner thin Keplerian disk fed by a thicker self-gravitating disk, whose rotation profile is close to a Mestel disk. Our results show that the effects of self-gravity enhance density fluctuations much less than they smooth the disk, and giving it more coherence. We discuss the expected changes that will occur in 3D simulations, the results of which are presented in a companion paper.Comment: 20 pages, 7 figures, accepted for publication in Ap

The palynology of tertiary sediments from a palaeochannel in Namaqualand, South Africa.

Main articleA site in amaqualand, Western Cape Province, has yielded a diverse and well-preserved pa lynoflora. The site consists of a quarry, exposing a palaeochannel containing fluviatile sands, silts and clays with accompanying peat horizons. This paper presents a qualitative account of the pollen and pore assemblages extracted from the peats. Ang iosperms were dominant both in terms of the number of individuals and the recognised types. Identification were made where possible with reference to published illustrations and descriptions. There was a total of 69 palynomorph types, including spores, gymnosperm and angiosperm pollen.Non

Evolution of self-gravitating magnetized disks. II- Interaction between MHD turbulence and gravitational instabilities

We present 3D magnetohydrodynamic (MHD) numerical simulations of the evolution of self--gravitating and weakly magnetized disks with an adiabatic equation of state. Such disks are subject to the development of both the magnetorotational and gravitational instabilities, which transport angular momentum outward. As in previous studies, our hydrodynamical simulations show the growth of strong m=2 spiral structure. This spiral disturbance drives matter toward the central object and disappears when the Toomre parameter Q has increased well above unity. When a weak magnetic field is present as well, the magnetorotational instability grows and leads to turbulence. In that case, the strength of the gravitational stress tensor is lowered by a factor of about~2 compared to the hydrodynamical run and oscillates periodically, reaching very small values at its minimum. We attribute this behavior to the presence of a second spiral mode with higher pattern speed than the one which dominates in the hydrodynamical simulations. It is apparently excited by the high frequency motions associated with MHD turbulence. The nonlinear coupling between these two spiral modes gives rise to a stress tensor that oscillates with a frequency which is a combination of the frequencies of each of the modes. This interaction between MHD turbulence and gravitational instabilities therefore results in a smaller mass accretion rate onto the central object.Comment: 31 pages, 19 figures, accepted for publication in ApJ, animation avalaible at http://www2.iap.fr/users/fromang/simu3d/simu3d.htm