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Institution

University of Johannesburg

EducationJohannesburg, South Africa
About: University of Johannesburg is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Tourism. The organization has 8070 authors who have published 22749 publications receiving 329408 citations. The organization is also known as: UJ.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors focus on the Karoo basins sensu stricto of south-central Africa, synthesizing their sedimentological and stratigraphic features in relation to the tectonic and climatic controls on accommodation and sedimentation.

550 citations

Journal ArticleDOI
TL;DR: Existing metrics in phylogenetic diversity metrics are organized by expanding on a unifying framework for phylogenetic information to improve the choice, application, and interpretation of phylo‐diversity metrics.
Abstract: The use of phylogenies in ecology is increasingly common and has broadened our understanding of biological diversity. Ecological sub-disciplines, particularly conservation, community ecology and macroecology, all recognize the value of evolutionary relationships but the resulting development of phylogenetic approaches has led to a proliferation of phylogenetic diversity metrics. The use of many metrics across the sub-disciplines hampers potential meta-analyses, syntheses, and generalizations of existing results. Further, there is no guide for selecting the appropriate metric for a given question, and different metrics are frequently used to address similar questions. To improve the choice, application, and interpretation of phylo-diversity metrics, we organize existing metrics by expanding on a unifying framework for phylogenetic information. Generally, questions about phylogenetic relationships within or between assemblages tend to ask three types of question: how much; how different; or how regular? We show that these questions reflect three dimensions of a phylogenetic tree: richness, divergence, and regularity. We classify 70 existing phylo-diversity metrics based on their mathematical form within these three dimensions and identify ‘anchor’ representatives: for α-diversity metrics these are PD (Faith's phylogenetic diversity), MPD (mean pairwise distance), and VPD (variation of pairwise distances). By analysing mathematical formulae and using simulations, we use this framework to identify metrics that mix dimensions, and we provide a guide to choosing and using the most appropriate metrics. We show that metric choice requires connecting the research question with the correct dimension of the framework and that there are logical approaches to selecting and interpreting metrics. The guide outlined herein will help researchers navigate the current jungle of indices.

548 citations

Journal ArticleDOI
26 Sep 2013-Nature
TL;DR: The findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300–400 million years earlier than previous indications for Earth surface oxygenation.
Abstract: The distribution of chromium isotopes and redox-sensitive metals in the Nsuze palaeosol and in the Ijzermyn iron formation from the Pongola Supergroup, in South Africa, suggests that there were appreciable levels of atmospheric oxygen about three billion years ago, some 300–400 million years earlier than previous indications for Earth surface oxygenation. The first long-term oxygenation of the Earth's atmosphere — the Great Oxidation Event — is thought to have occurred around 2.3 billion years ago, although there is some geochemical evidence for transient atmospheric oxygenation as early as 2.7 billion years ago. Sean Crowe et al. examine the distribution of chromium isotopes and other metals that act as indicators for oxidative weathering in ancient soil and rock samples from South Africa. Their measurements suggest that oxygen-driven weathering was taking place 3 billion years ago, implying the presence of appreciable levels of atmospheric oxygen. This oxygen was probably produced by photosynthesis, indicating that cyanobacteria may have evolved by this time. This suggests an early evolution of oxygenic photosynthesis, 600 million years before the Great Oxidation Event. It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10−5 times present levels) for about the first 2 billion years of Earth’s history1. The first long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event2,3. Geochemical indications of transient atmospheric oxygenation, however, date back to 2.6–2.7 billion years ago4,5,6. Here we examine the distribution of chromium isotopes and redox-sensitive metals in the approximately 3-billion-year-old Nsuze palaeosol and in the near-contemporaneous Ijzermyn iron formation from the Pongola Supergroup, South Africa. We find extensive mobilization of redox-sensitive elements through oxidative weathering. Furthermore, using our data we compute a best minimum estimate for atmospheric oxygen concentrations at that time of 3 × 10−4 times present levels. Overall, our findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300–400 million years earlier than previous indications for Earth surface oxygenation.

543 citations

Journal ArticleDOI
TL;DR: This review focuses on the utilization of cellulose as an adsorbent in natural/modified form or as a precursor for activated carbon (AC) for adsorbing substances from water and reports a few controversies and unresolved questions concerning the preparation/properties of ACs from cellulose.

529 citations

Journal ArticleDOI
TL;DR: It is shown that high-impact-factor developmental journals are heavily skewed toward publishing articles with data from WEIRD populations, and there is a habitual dependence on convenience sampling and little evidence that the discipline is making any meaningful movement toward drawing from diverse samples.

523 citations


Authors

Showing all 8414 results

NameH-indexPapersCitations
Vinod Kumar Gupta16571383484
Arnold B. Bakker135506103778
Trevor Vickey12887376664
Ketevi Assamagan12893477061
Diego Casadei12373369665
Michael R. Hamblin11789959533
E. Castaneda-Miranda11754556349
Xiaoming Li113193272445
Katharine Leney10845952547
M. Aurousseau10340344230
Mika Sillanpää96101944260
Sahal Yacoob8940825338
Evangelia Demerouti8523649228
Lehana Thabane8599436620
Sahal Yacoob8439935059
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023196
2022526
20213,152
20202,933
20192,706
20182,150