675 research outputs found
The role of the labour bureaux in South Africa: A critique of the Riekert Commission Report
African Studies Seminar series. Paper presented 1980
Asymmetric Ejecta of Cool Supergiants and Hypergiants in the Massive Cluster Westerlund 1
We report new 5.5 GHz radio observations of the massive star cluster Westerlund 1, taken by the Australia Telescope Compact Array, detecting nine of the ten yellow hypergiants (YHGs) and red supergiants (RSGs) within the cluster. Eight of nine sources are spatially resolved. The nebulae associated with the YHGs Wd1-4a, -12a and -265 demonstrate a cometary morphology - the first time this phenomenon has been observed for such stars. This structure is also echoed in the ejecta of the RSGs Wd1-20 and -26; in each case the cometary tails are directed away from the cluster core. The nebular emission around the RSG Wd1-237 is less collimated than these systems but once again appears more prominent in the hemisphere facing the cluster. Considered as a whole, the nebular morphologies provide compelling evidence for sculpting via a physical agent associated with Westerlund 1, such as a cluster wind
South Africa's regional political economy: A critical analysis of reform strategy in the 1980s.
African Studies Seminar series. Paper presented October, 1985Since the late 1970s the apartheid state has faced a sustained
and deepening crisis of legitimation.(1) This crisis has been
exacerbated by the attempt, and failure, to implement the post-
Soweto 'Total Strategy' reforms - reforms which, in the case of
the black people of South Africa, left the territorial and
political basis of grand apartheid intact. Since the end of the
short-lived boom of 1979-82, the crisis of political legitimacy
has been amplified by the slide into economic depression, and the
scope for concessionary economic reforms has been drastically
curtailed.
For some time, the state has been caught up with the
immediate threat of escalating opposition in the townships, the
symptoms of the deepening economic crisis and spreading
international hostility to apartheid. But while this has been
happening, elements within the ruling groups, both inside and
outside the state, have for some time been attempting to map out
a longer-term strategic offensive aimed at defusing political
conflict and re-structuring the economy. Faced with a shrinking
material basis for concessionary economic reform and growing
mobilisation behind the demand for the extension of political
rights, the country's ruling groups have begun the search for
political solutions to the crisis.
The schemes now being formulated take as their starting point
the ultimate inevitability of political incorporation of black
people into a single national state in South Africa. They aim to
meet this in ways that ensure that real power remains in the
hands of the ruling classes.
The move towards political reforms for black people has gone
beyond the stage of discussion and planning in certain areas of
policy. Already an important pillar of the emerging strategy has
gained expression in local government measures passed in 1985.
(2) However much of what is planned has so far only appeared in
general policy statements. It is also evident that important
facets of the strategy are still in the stage of formulation or
are deliberately being held back for the moment. The fluidity of
political conditions in South Africa is such that state strategy
is the subject matter of open debate and contestation, and is
unusually susceptible to official reconsideration and
reformulation. Nevertheless we believe it is possible to identify
the major contours of an emerging strategy which has been pursued
with increasing determination by reformers within the commanding
heights of the state since late in 1984.
This offensive is significant in that it goes well beyond the
policy package associated with the Wiehahn and Riekert Commission
reports, the Koornhof Bills, the new constitution, and the
confederation of ethnic states - it goes beyond the 'Total
Strategy' formulated by PW Botha in the late 1970s. (3) In
contrast to these policies, it is based on an abandonment of the
political and territorial premises of apartheid, though not
necessarily of race or ethnicity, and envisages the eventual reincorporation
of the bantustans into a single national South
African state.
The manner in which this will occur is by no means clear or
decided. However, this process of political re-integration of the
bantustans is intended ultimately to result in the reorganisation
of the territorial basis of South Africa's economic
and political system. Central to the reform strategy is the
conception that the present provinces and bantustans will be
superceded by metropolitan and regionally-based administrative
structures through a process of merging, absorption and crosscutting
of present geographical boundaries. It is this geographic
outcome of the intended reform strategy that has led us to
describe the complex of evolving measures as the state's regional
strategy.
The aim of this article is to describe, anticipate and
critically analyse the outlines of the emerging regional
strategy. Its three major components are new controls on labour
movement and settlement, regional development policies (notably
industrial decentralisation), and local and second tier
government reforms and corresponding constitutional changes. We
examine each of these three components and their
interconnections. A central issue taken up in the paper is the debate over the
possible construction of a federal system in South Africa. We
examine major alternative conceptions of the basis of federalism
- geographic and ethnic - and show how they correspond to or
contradict other plans to divide South Africa into metropolitan
and wider planning and administrative regions.
The paper ends with an assessment and critical analysis of
the regional strategy
A radio census of the massive stellar cluster Westerlund 1
CONTEXT: Massive stars and their stellar winds are important for a number of feedback processes. The mass lost in the stellar wind can help determine the end-point of the star as a neutron star (NS) or a black hole (BH). However, the impact of mass loss on the post-main sequence evolutionary stage of massive stars is not well understood. Westerlund 1 is an ideal astrophysical laboratory in which to study massive stars and their winds in great detail over a large range of different evolutionary phases. AIMS: We aim to study the radio emission from Westerlund 1, in order to measure radio fluxes from the population of massive stars, and determine mass-loss rates and spectral indices where possible. METHODS: Observations were carried out in 2015 and 2016 with the Australia Telescope Compact Array (ATCA) at 5.5 and 9 GHz using multiple configurations, with maximum baselines ranging from 750 m to 6 km. RESULTS: Thirty stars are detected in the radio from the fully concatenated dataset, ten of which are Wolf-Rayet stars (WRs) (predominantly late type WN stars), five yellow hypergiants (YHGs), four red supergiants (RSGs), one luminous blue variable (LBV), the sgB[e] star W9, and several OB supergiants. New source detections in the radio are found for five WR stars, and five OB supergiants. These detections lead to evidence for three new OB supergiant binary candidates, which is inferred from derived spectral index limits. CONCLUSIONS: Spectral indices and index limits were determined for massive stars in Westerlund 1. For cluster members found to have partially optically thick emission, mass-loss rates were calculated. Under the approximation of a thermally emitting stellar wind and a steady mass-loss rate, clumping ratios were then estimated for eight WRs. Diffuse radio emission was detected throughout the cluster. Detections of knots of radio emission with no known stellar counterparts indicate the highly clumped structure of this intra-cluster medium, likely shaped by a dense cluster wind
Piloted simulation study of two tilt-wing flap control concepts, phase 2
A two phase piloted simulation study has been conducted in the Ames Vertical Motion Simulator to investigate alternative wing and flap controls for tilt-wing aircraft. This report documents the flying qualities results and findings of the second phase of the piloted simulation study and describes the simulated tilt-wing aircraft, the flap control concepts, the experiment design and the evaluation tasks. The initial phase of the study compared the flying qualities of both a conventional programmed flap and an innovative geared flap. The second phase of the study introduced an alternate method of pilot control for the geared flap and further studied the flying qualities of the programmed flap and two geared flap configurations. In general, the pilot ratings showed little variation between the programmed flap and the geared flap control concepts. Some differences between the two control concepts were noticed and are discussed in this report. The geared flap configurations had very similar results. Although the geared flap concept has the potential to reduce or eliminate the pitch control power requirements from a tail rotor or a tail thruster at low speeds and in hover, the results did not show reduced tail thruster pitch control power usage with the geared flap configurations compared to the programmed flap configuration. The addition of pitch attitude stabilization in the second phase of simulation study greatly enhanced the aircraft flying qualities compared to the first phase
Harnessing triaryloxonium ions for aryne generation
Arynes are highly reactive and versatile intermediates for the functionalization of aromatic rings that are often generated using strong bases or fluoride sources, which, in some cases, can limit functional group tolerance. Here we demonstrate that triaryloxonium ions can be transformed into arynes through treatment with solid potassium phosphate at room temperature. A substantial range of functional group-bearing arynes, including 4,5-pyrimidynes, may be generated and trapped using cycloaddition reactions with high yields. Other arynophiles including nitrones, alkenes and azides are compatible with these conditions. Quantum computation in conjunction with an intramolecular kinetic isotope study is consistent with an elimination, unimolecular, conjugate base-like mechanism of elimination to form the aryne. These investigations demonstrate that the oxonium ion is a powerful electron-withdrawing group and a particularly effective leaving group. We anticipate that this study will stimulate further investigations into the synthetic utility of aryl oxonium ions
Control of stereogenic oxygen in a helically chiral oxonium ion
The control of tetrahedral carbon stereocentres remains a focus of modern synthetic chemistry and is enabled by their configurational stability. By contrast, trisubstituted nitrogen1, phosphorus2 and sulfur compounds3 undergo pyramidal inversion, a fundamental and well-recognized stereochemical phenomenon that is widely exploited4. However, the stereochemistry of oxonium ions—compounds bearing three substituents on a positively charged oxygen atom—is poorly developed and there are few applications of oxonium ions in synthesis beyond their existence as reactive intermediates5,6. There are no examples of configurationally stable oxonium ions in which the oxygen atom is the sole stereogenic centre, probably owing to the low barrier to oxygen pyramidal inversion7 and the perception that all oxonium ions are highly reactive. Here we describe the design, synthesis and characterization of a helically chiral triaryloxonium ion in which inversion of the oxygen lone pair is prevented through geometric restriction to enable it to function as a determinant of configuration. A combined synthesis and quantum calculation approach delineates design principles that enable configurationally stable and room-temperature isolable salts to be generated. We show that the barrier to inversion is greater than 110 kJ mol−1 and outline processes for resolution. This constitutes, to our knowledge, the only example of a chiral non-racemic and configurationally stable molecule in which the oxygen atom is the sole stereogenic centre
Evaluation of a Droplet Digital Polymerase Chain Reaction Format for DNA Copy Number Quantification
ABSTRACT: Droplet digital polymerase chain reaction (ddPCR) is a new technology that was recently commercialized to enable the precise quantification of target nucleic acids in a sample. ddPCR measures absolute quantities by counting nucleic acid molecules encapsulated in discrete, volumetrically defined, water-in-oil droplet partitions. This novel ddPCR format offers a simple workflow capable of generating highly stable partitioning of DNA molecules. In this study, we assessed key performance parameters of the ddPCR system. A linear ddPCR response to DNA concentration was obtained from 0.16 % through to 99.6 % saturation in a 20,000 droplet assay corresponding to more than 4 orders of magnitude of target DNA copy number per ddPCR. Analysis of simplex and duplex assays targeting two distinct loci in the Lambda DNA genome using the ddPCR platform agreed, within their expanded uncertainties, with values obtained using a lower density microfluidic chamber based digital PCR (cdPCR). A relative expanded uncertainty under 5 % was achieved for copy number concentration using ddPCR. This level of uncertainty is much lower than values typically observed for quantification of specific DNA target sequences using currently commercially available real-time and digital cdPCR technologies
Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1
In this paper we discuss the radio continuum and X-ray properties of the
so-far poorly studied Galactic supernova remnant (SNR) G5.9+3.1. We present the
radio spectral energy distribution (SED) of the Galactic SNR G5.9+3.1 obtained
with the Murchison Widefield Array (MWA). Combining these new observations with
the surveys at other radio continuum frequencies, we discuss the integrated
radio continuum spectrum of this particular remnant. We have also analyzed an
archival XMM-Newton observation, which represents the first detection of X-ray
emission from this remnant. The SNR SED is very well explained by a simple
power-law relation. The synchrotron radio spectral index of G5.9+3.1, is
estimated to be 0.420.03 and the integrated flux density at 1GHz to be
around 2.7Jy. Furthermore, we propose that the identified point radio source,
located centrally inside the SNR shell, is most probably a compact remnant of
the supernova explosion. The shell-like X-ray morphology of G5.9+3.1 as
revealed by XMM-Newton broadly matches the spatial distribution of the radio
emission, where the radio-bright eastern and western rims are also readily
detected in the X-ray while the radio-weak northern and southern rims are weak
or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as
well as the north, east, and west rims of the SNR are fit successfully with an
optically thin thermal plasma model in collisional ionization equilibrium with
a column density N_H~0.80x cm and fitted temperatures spanning
the range kT~0.14-0.23keV for all of the regions. The derived electron number
densities n_e for the whole SNR and the rims are also roughly comparable
(ranging from ~ cm to ~ cm, where f
is the volume filling factor). We also estimate the swept-up mass of the X-ray
emitting plasma associated with G5.9+3.1 to be ~.Comment: Accepted for publication in A&
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