Academisch proefschrift--Nijmegen. / Summary in English. Includes bibliographical references (p. [136]-139).

High resolution spectroscopic techniques are used to investigate the magnetic topology of the young, rapidly rotating star, AB Dor. Doppler images of AB Dor are produced using the Li I 6708 Å line and compared to images produced using Ca I and Fe i lines. A Li abundance of 2.9±0.3 dex is measured using LTE profile synthesis. By evaluating the effects of enhanced spot Li abundances we find that starspots are unlikely to lead to an overestimation of the photospheric Li abundance. While the Li I 6708 Å line is strengthened in the presence of starspots, the extent to which the Li I line equivalent width displays rotational modulation is diluted. A Zeeman Doppler imaging code, which maps the surface magnetic flux distributions on rapid rotators, has been developed and tested in this thesis. Reliability tests indicate that this technique is robust with respect to small errors in line and stellar parameters. Spectropolarimetric observations of AB Dor from three years are presented here. The technique of least squares deconvolution, combines the signal from over 1500 lines, enhancing the S/N of the observed dataset. Brightness and magnetic maps of AB Dor are reconstructed using the deconvolved profiles and show excellent agreement with maps produced using independently developed codes by J.-F. Donati. This points to the consistency of Doppler imaging techniques. Magnetic field maps show the presence of strong radial and azimuthal fields at almost all latitudes. This non-solar like distribution of magnetic flux may indicate the presence of a distributed dynamo component operating in the convection zones of rapid rotators. By tracing the positions of absorption transients in Ha, we find prominence complexes at almost all longitudes. Footpoint locations remain difficult to ascertain. Prominences are ejected over much shorter timescales than the timescale over which differential rotation should act further observations with closer time sampling are necessary to investigate the coronal topology further.

The Inkatha movement has received, large publicity over the few years since its revival and especially recently with the formation of an alliance between Inkatha, the ("Coloured") labour Party and the ("Indian") Reform Party, Thi3 paper was done to suggest a possible approach, for discussion, to the analysis of current political, ideological and economic developments in the reserve areas of the South African social formation. More specifically the paper hopes to provide information that could be relevant to an analysis of developments in the kwaZulu region. An elaboration of the hints at an approach, integration of factors relating to the stage of capitalism in the South African social formation and class struggle would have made this a more satisfactory paper for discussion. The approach adopted has to be extremely tentative at this stage, both because of the immediate and obvious problems associated with contemporary research and analysis (It is even less possible to approach the subject with "objectivity", to "distance oneself from it", than is the case with topics that can more properly be called "history") but also because of the dearth of material available on the reserve "homeland" areas and the difficult y of doing research in these areas. (Wages Commission research into conditions on wattle plantations, Cosmas Desmond and others and their work on resettlement etc., and subsequent responses to these investigations, give some idea of the sensitivity of thin work), In the first section I will introduce certain concepts relating to an analysis of the "homelands" through some recent writing on these areas. References will be to the kwaZulu region. The second section deal.3 specifically with the Inkatha movement. Information relating to this movement is provided and one issue is presented in greater detail, hut no rigorous attempt is mado to apply the mode of analysis of the first section to the issues around the position of 'Inkatha. Indicators exist but with so many dynamics operative they can be no more than that. However, I do not believe that it is possible to understand the political, economic and ideological developments in the "homelands" without keeping the questions raised in the first section in mind - and definitely impossible to come to an adequate understanding if these areas are looked at in isolation, ie if apparently "internal" events and processes are not situated within a context broadly defined by the specific stage of the development of capitalism in South Africa (monopoly dominance), and without keeping in mind the history of class struggle within the social formation. / Class formation in the South African reserve areas: Inkatha - a study

Faint blue stars situated out of the galactic plane have been studied using a variety of techniques. Stromgren photometry has been obtained for a number of these stars and classifications derived from the photometry. An interference filter centred at 3775 A near the Balmer discontinuity has been used in conjunction with the Stromgren filters. Observation of Stromgren standard stars, bright B stars and faint blue stars have been used to study the behaviour of the colours (u-38) and (38-b). Reddening-free parameters [u-38] and [38-b] have been evaluated and [38-b] is found to be linearly related to the Crawford Hβ index for B-type dwarfs, giants and supergiants. This relationship has been used to derive absolute magnitudes and distances for faint apparently normal B stars. [38-b] allows this work to be done at fainter magnitudes than possible with Hβ photometry. A filter pair centred on the HeII λ4686 line has been used to study 0-type stars including 0 subdwarfs. The resulting index is strongly correlated with the equivalent width of the Hell line and has a range of 0ᵐ.13. It is possible to separate sd0, 0 and 0f stars using this index. Although the index is correlated with absolute magnitude for 0 and 0f stars, the detailed behaviour precludes the accurate determination of absolute magnitude for dwarfs and giants. Theoretical indices have been computed from the models of Kudritzki and agree well with the results for stars with high helium abundance. These computations suggest that it is possible to separate sdO and DO stars with this system. The results have also been compared with the work of Auer and Mihalas. 30 A/mm image tube spectra have been used for Ealmer line width measurement and radial velocity determination. The line widths were used to estimate surface gravities for faint blue stars in conjunction with temperatures determined from the Stromgren [u-b] index. The results indicate that 30 A/mm image tube spectra can be used successfully for surface gravity determination. 75 A/mm image tube spectra have been used for spectral classification as a check on the classification provided by Stromgren photometry. The kinematics of certain subdwarfs and main sequence stars at high galactic latitude have been considered. Proper motions have been employed as a check for subluminosity using appropriate absolute magnitudes. Galactic orbits have been computed using the Schmidt model of the galactic force field. Several B-type dwarfs and subdwarfs were found to have been ejected from the galactic plane at high velocity. Thirty percent of the stars previously classified as normal dwarfs were found to be subluminous. The evolutionary implications of these results are discussed.

We present new, accurate astrophysical parameters for both components of the six short-period Algol-type binary stars RZ Cas, AT Peg, TX UMa, AF Gem, RU UMi and HU Tau. The accuracy of the astrophysical parameters is ensured by the determination of a mass ratio for each of the systems from the spectroscopic orbits of both components via the cross correlation technique. For RZ Cas and AT Peg we have developed a simple technique to correct the observed photometry for the presence of the secondary component. Spectral classification of the primary component of AT Peg was aided by the use of an improved Doppler tomography technique. The systems RZ Cas, AT Peg, TX UMa, AF Gem and HU Tau are found to be apparently normal semi-detached Algol-type systems and accurate masses and radii have been determined with a typical precision of a few percent. For RU UMi we have been able to confirm the suspected semi-detached configuration. We have compiled a list of nine Algol-type binary stars, five from this study, for which the observed astrophysical parameters have been determined accurately using a combination of both spectroscopic and photometric data in a self-consistent solution. The general model of non-conservative case B evolution adequately explains the properties of these systems as a group. Angular momentum loss via a magnetic stellar wind is shown to be an important factor in the evolution of these systems. However, there appear to be no published evolutionary models which can be used to estimate the properties of the progenitors of these systems. For the more massive systems the best available models predict periods that are too large by ~50-250% and luminosities for the faint components that are too high by factors of 10-20.

edited by Michael Athans ... [et al.]. / "December 1982." / Includes bibliographies and index. / Office of Naval Research Contract no. ONR/N00014-77-C-0532 NR041-519

edited by Michael Athans and Alexander H. Levis. / "December 1985." / Includes bibliographies and index. / Office of Naval Research Contract no. ONR/N00014-77-C-0532 NR-041-519

No description available.

Proceedings, 2nd ARETS Symposium, University of Arizona / Westward Look Resort, Tucson, Arizona, Nov. 2, 3, 4 1971.

Edited by David A. Berkowitz and Arthur M. Squires. / Includes bibliographical references.