Reimagining identity: South African Chinese associations in post-apartheid Gauteng

This research focuses on Chinese associations in postapartheid South Africa and is primarily based on oral interviews done with numerous members and leaders of the different Chinese communities. Since democracy, longstanding Chinese associations, which draw their membership from the South African-Born Chinese (SABCs), have reimagined themselves and transformed from having largely political aims to focus predominantly on community and cultural pursuits. This is the result of political shifts and the increasing freedoms guaranteed to all races by democracy, although their membership is declining. However, partly owing to their ambiguous status and identity during apartheid, the Chinese have continued to face discrimination. Specifically, being initially excluded from affirmative action policies as well as being subjected to racism and prejudice in the democratic era. Thus, there is still space for these associations to act politically as these issues have been and are being addressed through democratic institutions. Lastly, the third wave of migration has further impacted the associational lives of the Chinese in South Africa. The significant differences between SABCs and recent Chinese migrants have not only created divisions between these two groups but have also called into question the “Chinese identity” of SABCs. However, there has also been significant, albeit situational, instances of collaboration and solidarity between these two groups and their relevant associations, thereby adding complexity to the interactions and identities of said communities

Study of the topological Hall effect on simple models

Recently, a chirality-driven contribution to the anomalous Hall effect has been found that is induced by the Berry phase and does not directly involve spin-orbit coupling. In this paper, we will investigate this effect numerically in a two-dimensional electron gas with a simple magnetic texture model. Both the adiabatic and non-adiabatic regimes are studied, including the effect of disorder. By studying the transition between both regimes the discussion about the correct adiabaticity criterium in the diffusive limit is clarified.Comment: 8 pages, 7 figures, revtex

Measuring carrier density in parallel conduction layers of quantum Hall systems

An experimental analysis for two parallel conducting layers determines the full resistivity tensor of the parallel layer, at magnetic fields where the other layer is in the quantum Hall regime. In heterostructures which exhibit parallel conduction in the modulation-doped layer, this analysis quantitatively determines the charge density in the doping layer and can be used to estimate the mobility. To illustrate one application, experimental data show magnetic freeze-out of parallel conduction in a modulation doped heterojunction. As another example, the carrier density of a minimally populated second subband in a two-subband quantum well is determined. A simple formula is derived that can estimate the carrier density in a highly resistive parallel layer from a single Hall measurement of the total system.Comment: 7 pages, 7 figure

Single-valley high-mobility (110) AlAs quantum wells with anisotropic mass

We studied a doping series of (110)-oriented AlAs quantum wells (QWs) and observed transport evidence of single anisotropic-mass valley occupancy for the electrons in a 150 \AA wide QW. Our calculations of strain and quantum confinement for these samples predict single anisotropic-mass valley occupancy for well widths $W$ greater than 53 \AA. Below this, double-valley occupation is predicted such that the longitudinal mass axes are collinear. We observed mobility anisotropy in the electronic transport along the crystallographic directions in the ratio of 2.8, attributed to the mass anisotropy as well as anisotropic scattering of the electrons in the X-valley of AlAs

Two essays on the universal and particular dimensions of culture

The first of the two essays was presented at the conference 'Ethnicity in an Age of Globalisation', held at Uganda Martyrs University, Kampala, Uganda, from 3-6 September 2001.Thesis (MA)--University of Stellenbosch, 2002.Babel or Piraeus? : globalisation, culture and tradition -- Between freedom and culture : Alain Finkielkraut's critique of multiculturalism.ENGLISH ABSTRACT: The conception of globalisation as a "programme" or "project" driven by a group of people or companies with a set agenda underlies much of the antagonistic discussion of globalisation. Protagonists of globalisation, in turn, often describe the process as inevitable progress. This paper analyses the process of globalisation and argues that it should not be understood as such a singular process. Rather, the concept "complex connectivity" - where the local and the global come' into closer contact and influence, or interpenetrate, one another more directly - facilitates a more nuanced analysis of globalisation -.This understanding of globalisation will be tested against the phenomenon of culture by posing two questions: Does globalisation lead to the destruction of local culture( s) by an encroaching singular global culture (i.e. is globalisation cultural imperialism)? Or alternatively: Does globalisation represent an opening .up and exchange between previously isolated cultures and societies? This paper argues in favour of the second position by employing John Tomlinson's existential definition of culture and his understanding of the dialectic that exists between the local and the global in complex connectivity. Instead of global culture, we can more properly speak of . "globalized" culture, which looks different in every local situation. This is a more optimistic answer to the cultural' effects of globalisation, and although some concerns remain, it seems clear that to understand globalisation as complex connectivity rules out many of the charges of cultural imperialism lodged against globalisation.AFRIKAANSE OPSOMMING: Baie van die hedendaagse antagonistiese diskussie oor globalisasie gaan uit van die veronderstelling dat globalisasie 'n 'program' of 'n 'projek' is wat deur 'n groep individue of maatskappye gedryf word. Voorstanders van globalisasie, daarenteen, beskou die proses dikwels as 'onafwendbare vooruitgang.' Hierdie opstel analiseer die proses van globalisasie en argumenteer dat globalisasie nie as so 'n eenduidige process verstaan moet word nie. Die konsep "complex connectivity" word ingespan om 'n meer genuanseerde analise van globalisasie te bied aangesien dit dui op die komplekse interaksie, of selfs interpenetrasie, tussen plaaslike en globale prosesse. Hierdie opvatting oor globalisasie word getoets aan die hand van kultuur deur twee teenstellende vrae te stel: Is globalisasie 'n enkelvoudige globale kultuur wat dreig om plaaslike kulture oor te neem en uiteindelik te vernietig (ook genoem kultuurimperialisme)? Of eerder: Is globalisasie 'n geleentheid tot groter openheid en interaksie tussen kulture en gemeenskappe wat voorheen van mekaar geïsoleer was? Die opstel argumenteer ten gunste van die tweede posisie deur gebruik te maak van John Tomlinson se eksistensiële definisie van kultuur en sy opvatting oor die interaksie tussen die plaaslike en die globale. Instede van globale kultuur kan ons eerder praat van 'geglobaliseerde' kultuur, wat telkens anders lyk in elke plaaslike opset. Hierdie posisie bied 'n versigtige, maar meer optimistiese antwoord op die kulturele impak van globalisasie deurdat veel van die aanklagte van kultuurimperialsime teen globalisasie afgewys word

X-ray photoemission characterization of La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} films

The Curie temperature and x-ray photoemission spectra of thin films of La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} (LCSMO) have been studied as a function of the Ca/Sr ratio. The films were grown by off-axis cosputtering from individual targets of La_{0.67}Ca_{0.33}MnO_{3} (LCMO) and La_{0.67}Sr_{0.33}MnO_{3} (LSMO) onto (100) oriented NdGaO_{3} substrates. The films grow with a (100) orientation, with no other orientations observed by x-ray diffraction. For the alloy mixtures, the Curie temperature, T_C, varies slowly as the Ca/Sr is decreased, remaining $\approx$ 300 K, while for the LCMO and LSMO films T_C is 260 and 330 K, respectively. The Mn-O valence structure is composed of two dominant peaks, whose positions undergo a change as the Ca fraction is decreased. The core lines behave as linear combinations of lines from pure LCMO and LSMO.Comment: 3 pages, 5 eps figures. To be published in Journal of Applied Physics (Proceedings of MMM'98

Different effects of Ni and Co substitution on the transport properties of BaFe2As2

We report resistivity and Hall effect results on Ba(Fe1-xNix)2As2 and compare them with those in Ba(Fe1-xCox)2As2. The Hall number RH is negative for all x values from 0.01 to 0.14, which indicates that electron carriers dominate the transport both in the magnetic and paramagnetic regime. We analyse the data in the framework of a two-band model. Without any assumption on the number of carriers, we show that the electron resistivity can be estimated with good accuracy in the low temperature paramagnetic range. Although the phase diagrams of the two families are very similar with respect to the extra electrons added in the system, we find that the transport properties differ in several aspects. First, we evidence that the contribution of holes to the transport is more important for Ni doping than for Co doping. Secondly, Ni behaves as a stronger scatterer for the electrons, as the increase of the residual electron resistivity rho/x is about four times larger for Ni than for Co in the most doped samples.Comment: 8 pages, 8 figure

Hole and Electron Contributions to the Transport Properties of Ba(Fe_(1-x)Ru_x)_2As_2 Single Crystals

We report a systematic study of structural and transport properties in single crystals of Ba(Fe_(1-x)Ru_x)_2As_2 for x ranging from 0 to 0.5. The isovalent substitution of Fe by Ru leads to an increase of the a parameter and a decrease of the c parameter, resulting in a strong increase of the AsFeAs angle and a decrease of the As height above the Fe planes. Upon Ru substitution, the magnetic order is progressively suppressed and superconductivity emerges for x > 0.15, with an optimal Tc ~ 20K at x = 0.35 and coexistence of magnetism and superconductivity between these two Ru contents. Moreover, the Hall coefficient RH which is always negative and decreases with temperature in BaFe2As2, is found to increase here with decreasing T and even change sign for x > 0.15. For x_Ru = 0.35, photo-emission studies have shown that the number of holes and electrons are similar with n_e = n_h ~ 0.11, that is twice larger than found in BaFe2As2 [1]. Using this estimate, we find that the transport properties of Ba(Fe_0.65Ru_0.35)_2As_2 can be accounted for by the conventional multiband description for a compensated semi-metal. In particular, our results show that the mobility of holes is strongly enhanced upon Ru addition and overcomes that of electrons at low temperature when x_Ru > 0.15.Comment: new version with minor correction