Late Quaternary glaciation in Southern Africa: moraine ridges and glacial deposits at Mount Enterprise in the Drakensberg of the Eastern Cape Province,South Africa

Late Quaternary moraines and diamictons containing striated clasts are described from near Elliot in the Drakensberg of South Africa. An equilibrium line altitude (ELA) of 2109 m is suggested for the palaeoglacier associated with the innermost moraine. This glacier was fed by a very extensive snowblow area and the ELA may reflect the temperature–precipitation–wind ELA rather than the temperature–precipitation ELA and be considerably below the ‘regional’ ELA. Mean annual air temperatures when glaciation occurred were probably at least 10.0°C below those of the present. Copyright © 2001 John Wiley & Sons, Ltd.     

Constraining the 13C neutron source in AGB stars through isotopic analysis of trace elements in presolar SiC

Abstract— Analyses of the isotopic compositions of multiple elements (Mo, Zr, and Ba) in individual mainstream presolar SiC grains were done by resonant ionization mass spectrometry (RIMS). While most heavy element compositions were consistent with model predictions for the slow neutron capture process (s‐process) in low‐mass (1.5–3 M_⊙) asymptotic giant branch stars of solar metallicity when viewed on single‐element three‐isotope plots, grains with compositions deviating from model predictions were identified on multi‐element plots. These grains have compositions that cannot result from any neutron capture process but can be explained by contamination in some elements with solar system material. Previous work in which only one heavy element per grain was examined has been unable to identify contaminated grains. The multi‐element analyses of this study detected contaminated grains which were subsequently eliminated from consideration. The uncontaminated grains form a data set with a greatly reduced spread on the three‐isotope plots of each element measured, corresponding to a smaller range of ¹³C pocket efficiencies in parent AGB stars. Furthermore, due to this reduced spread, the nature of the stellar starting material, previously interpreted as having solar isotopic composition, is uncertain. The constraint on ¹³C pocket efficiencies in parent stars of these grains may help uncover the mechanism responsible for formation of ¹³C, the primary neutron source for s‐process nucleosynthesis in low‐mass stars.     

Advanced programming methods and data structures for computational modelling using edge‐based finite volume methods

The generation of a numerical model must consider the separate issues of the governing equations, the numerical representation of those equations, the data structure that describes the model, the choice of programming language and finally the implementation and code management issues. These issues are considered as a whole in this paper and as a consequence, 10 golden rules for numerical modelling are proposed. By way of application, a saturated–unsaturated flow problem is modelled using the Richards equation and an innovative edge‐based finite volume method. The implementation uses a novel data structure. This is shown to have over 91% code re‐use and hence code written in this way is highly flexible and applicable to many different problems. By way of example, a compacted core earth filled dam problem has been solved. Finally, we conclude that this advanced programming method can significantly reduce code development time. Copyright © 2004 John Wiley & Sons, Ltd.     

The 2dF Galaxy Redshift Survey: a targeted study of catalogued clusters of galaxies

We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at     that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of     clusters of     This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.     

Resolved nuclear CO(1–0) emission in APM 08279+5255: gravitational lensing by a naked cusp?

The ultraluminous broad absorption line quasar APM 08279+5255 is one of the most luminous systems known. Here, we present an analysis of its nuclear  CO(1–0)  emission. Its extended distribution suggests that the gravitational lens in this system is highly elliptical, probably a highly inclined disc. The quasar core, however, lies in the vicinity of a naked cusp, indicating that APM 08279+5255 is truly the only odd-image gravitational lens. This source is the second system for which the gravitational lens can be used to study structure on sub-kiloparsec scales in the molecular gas associated with the AGN host galaxy. The observations and lens model require CO distributed on a scale of ∼400 pc. Using this scale, we find that the molecular gas mass makes a significant, and perhaps dominant, contribution to the total mass within a couple of hundred parsecs of the nucleus of APM 08279+5255.