Increasing temperatures increase the risk of reproductive failure in a near threatened alpine groundnesting bird, the Cape Rockjumper Chaetops frenatus:
- Authors: Oswald, Krista N , Diener, Elizabeth F , Diener, John P , Cunningham, Susan J , Smit, Ben , Lee, Alan T K
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149324 , vital:38825 , https://0-doi.org.wam.seals.ac.za/10.1111/ibi.12846
- Description: A major cause of reproductive failure in birds is nest predation. Predation risk depends on predator type, as predators vary in their ecology and sensory modalities (e.g. visual vs. olfactory). Snakes (generally olfactory predators) are a major nest predator for small birds, with predation strongly associated with higher temperatures. We investigated nest survival in a ground‐nesting alpine species, the Cape Rockjumper Chaetops frenatus , endemic to alpine fynbos in southwestern South Africa. We collected 3 years of nest data, testing whether nest survival was related to (1) habitat stage (early post‐fire vs. late post‐fire habitat, ≤ 3 and > 3 years since fire respectively), (2) nest concealment and (3) temperature. We found that nests had better survival at lower temperatures, with snake predation (our main source of predation) increasing in higher temperatures.
- Full Text:
- Date Issued: 2020
Influence of intra-and interspecific variation in predator–prey body size ratios on trophic interaction strengths:
- Authors: Cuthbert, Ross N , Wasserman, Ryan J , Dalu, Tatenda , Kaiser, Horst , Weyl, Olaf L F , Dick, Jaimie T A , Sentis, Arnaud , McCoy, Michael W , Alexander, Mhairi E
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149358 , vital:38839 , https://0-doi.org.wam.seals.ac.za/10.1002/ece3.6332
- Description: Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking. We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.
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- Date Issued: 2020
Insect herbivores associated with Lycium ferocissimum (Solanaceae) in South Africa and their potential as biological control agents in Australia
- Authors: Chari, Lenin D , Mauda, EV , Martin, Grant D , Raghu, S
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407035 , vital:70331 , xlink:href="https://hdl.handle.net/10520/EJC-203b8dbc7b"
- Description: Lycium ferocissimum Miers (Solanaceae) is an indigenous shrub in South Africa but has become invasive in several countries including Australia, where chemical and mechanical control methods have proved costly and unsustainable. In Australia, biological control is being considered as a management option, but the herbivorous insects associated with the plant in its native range are not well known. The aim of this study was to survey the phytophagous insects associated with L. ferocissimum in South Africa and prioritise promising biological control agents. In South Africa, the plant occurs in two geographically distinct areas, the Eastern and Western Cape provinces. Surveys for phytophagous insects on L. ferocissimum were carried out repeatedly over a two-year period in these two regions. The number of insect species found in the Eastern Cape Province (55) was higher than that in the WesternCapeProvince (41), but insect diversity based on Shannon indices was highest in the Western Cape Province. Indicator species analysis revealed eight insect herbivore species driving the differences in the herbivore communities between the two provinces. Based on insect distribution, abundance, feeding preference and available literature, three species were prioritised as potential biological control agents. These include the leaf-chewing beetles Cassida distinguenda Spaeth (Chrysomelidae) and Cleta eckloni Mulsant (Coccinellidae) and the leaf-mining weevil Neoplatygaster serietuberculata Gyllenhal (Curculionidae).
- Full Text:
- Date Issued: 2020
Integrated computational approaches and tools for allosteric drug discovery:
- Authors: Amamuddy, Olivier S , Veldman, Wade , Manyumwa, Colleen , Khairallah, Afrah , Agajanian, Steve , Oluyemi, Odeyemi , Verkhivker, Gennady M , Tastan Bishop, Özlem
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163012 , vital:41004 , https://doi.org/10.3390/ijms21030847
- Description: Understanding molecular mechanisms underlying the complexity of allosteric regulation in proteins has attracted considerable attention in drug discovery due to the benefits and versatility of allosteric modulators in providing desirable selectivity against protein targets while minimizing toxicity and other side effects. The proliferation of novel computational approaches for predicting ligand–protein interactions and binding using dynamic and network-centric perspectives has led to new insights into allosteric mechanisms and facilitated computer-based discovery of allosteric drugs. Although no absolute method of experimental and in silico allosteric drug/site discovery exists, current methods are still being improved. As such, the critical analysis and integration of established approaches into robust, reproducible, and customizable computational pipelines with experimental feedback could make allosteric drug discovery more efficient and reliable. In this article, we review computational approaches for allosteric drug discovery and discuss how these tools can be utilized to develop consensus workflows for in silico identification of allosteric sites and modulators with some applications to pathogen resistance and precision medicine. The emerging realization that allosteric modulators can exploit distinct regulatory mechanisms and can provide access to targeted modulation of protein activities could open opportunities for probing biological processes and in silico design of drug combinations with improved therapeutic indices and a broad range of activities.
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- Date Issued: 2020
Integrated landscape change analysis of protected areas and their surrounding landscapes: application in the Brazilian Cerrado
- Authors: Bellón, Beatriz , Blanco, Julien , de Vos, Alta , de Oliviera Roque, Fabio , Pays, Olivier , Renaud, Pierre-Cyril
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148681 , vital:38763 , https://doi.org/10.3390/rs12091413
- Description: Remote sensing tools have been long used to monitor landscape dynamics inside and around protected areas. Hereto, scientists have largely relied on land use and land cover (LULC) data to derive indicators for monitoring these dynamics, but these metrics do not capture changes in the state of vegetation surfaces that may compromise the ecological integrity of conservation areas’ landscapes. Here, we introduce a methodology that combines LULC change estimates with three Normalized Difference Vegetation Index-based proxy indicators of vegetation productivity, phenology, and structural change. We illustrate the utility of this methodology through a regional and local analysis of the landscape dynamics in the Cerrado Biome in Brazil in 2001 and 2016. Despite relatively little natural vegetation loss inside core protected areas and their legal buffer zones, the different indicators revealed significant LULC conversions from natural vegetation to farming land, general productivity loss, homogenization of natural forests, significant agricultural expansion, and a general increase in productivity. These results suggest an overall degradation of habitats and intensification of land use in the studied conservation area network, highlighting serious conservation inefficiencies in this region and stressing the importance of integrated landscape change analyses to provide complementary indicators of ecologically-relevant dynamics in these key conservation areas.
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- Date Issued: 2020
Integrating Ecosystem Services and Disservices in Valuing Smallholder Livestock and Poultry Production in Three Villages in South Africa
- Authors: Herd-Hoare, Shannon C , Shackleton, Charlie M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/176089 , vital:42659 , https://doi.org/10.1016/j.ufug.2020.126740 , https://doi.org/10.21504/RUR.c.5388515.v1
- Description: This study presents an integrated examination of both the ecosystem services (ES) and ecosystem disservices (EDS) associated with smallholder animal husbandry in rural livelihoods in three villages in southeast South Africa. It recognises the contribution of ES supporting and resulting from smallholder livestock and poultry production, but also details the limiting factors or EDS, such as tick-borne disease, birds of prey or unpalatable rangeland, produced by the same system. Using a mixed-methods approach, including focus group discussions with various Participatory Learning and Action (PLA) activities, key informant interviews, household surveys and land-use change mapping on GIS, we consider the relative value and benefits from ES after the effects of EDS, as well as the management and strategies that households adopt to minimise EDS.
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- Date Issued: 2020
Integrating livelihoods and forest conservation through beekeeping in northern KwaZulu-Natal:
- Authors: Ricketts, K , Shackleton, Charlie M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/176358 , vital:42687 , https://doi.org/10.1080/0376835X.2019.1698408
- Description: South Africa has potential to export honey products through promoting beekeeping as an income generating opportunity amongst rural communities. Formalised beekeeping may also reduce wild fires initiated by hunters of wild bee hives. This study examined the contribution of the African Honey Bee (AHB) initiative to rural livelihoods and the incidence of forest fires using a mixed methods approach. The initiative increased incomes of newly trained and active beekeepers, although success rates and honey yields were variable. Core challenges included not catching bees, theft and vandalism of hives, insufficient bee forage, drought and pests. Most respondents also perceived an increase in crop size since AHB began, although few attributed this to pollination from the bees. The number of wild fires attributed to honey hunters more than halved after AHB began. Future steps need to reduce the challenges and integrate beekeeping into broader agriculture and forest conservation programmes.
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- Date Issued: 2020
Integrative taxonomy reveals hidden diversity in the southern African darters genus Nannocharax Günther 1867 (Characiformes: Distichodontidae):
- Authors: Bragança, Pedro H N , Smith, Timothy G , Vreven, Emmanuel J W M N , Chakona, Albert
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163510 , vital:41044 , https://0-doi.org.wam.seals.ac.za/10.1111/jfb.14535
- Description: The present study explored the diversity of Nannocharax within southern Africa by implementing three species delimitation methods for a data set consisting of 37 mitochondrial cytochrome oxidase subunit I sequences. Two unilocus coalescent methods, the General Mixed Yule Coalescent (GMYC) and the Bayesian implementation of the Poisson Tree Processes (bPTP), and a genetic distance method, the Automatic Barcode Gap Discovery (ABGD), were applied. Both GMYC and bPTP delimited the same operational taxonomic units (OTUs), revealing a higher diversity for the genus in the region than previously recognised, whereas the ABGD failed to delimit the same candidate species.
- Full Text:
- Date Issued: 2020
Integrative taxonomy reveals hidden diversity in the southern African darters genus Nannocharax Günther 1867 (Characiformes: Distichodontidae):
- Authors: Bragança, Pedro H N , Smith, Timothy G , Vreven, Emmanuel J W M N , Chakona, Albert
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163543 , vital:41047 , https://0-doi.org.wam.seals.ac.za/10.1111/jfb.14535
- Description: The present study explored the diversity of Nannocharax within southern Africa by implementing three species delimitation methods for a data set consisting of 37 mitochondrial cytochrome oxidase subunit I sequences. Two unilocus coalescent methods, the General Mixed Yule Coalescent (GMYC) and the Bayesian implementation of the Poisson Tree Processes (bPTP), and a genetic distance method, the Automatic Barcode Gap Discovery (ABGD), were applied. Both GMYC and bPTP delimited the same operational taxonomic units (OTUs), revealing a higher diversity for the genus in the region than previously recognised, whereas the ABGD failed to delimit the same candidate species.
- Full Text:
- Date Issued: 2020
Intermediate disturbance promotes diversity and the conservation of dung beetles (Scarabaeoidea: Scarabaeidae and Aphodiidae) in the Eastern Cape, South Africa
- Authors: Tocco, Claudia , Midgley, John M , Villet, Martin H
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442195 , vital:73966 , https://doi.org/10.1016/j.baae.2020.10.005
- Description: Environmental fluctuations, such as changes in climate, agricultural management and anthropogenic land-use patterns can affect the diversity of organisms inhabiting an area. Losses of biodiversity alter ecosystems processes, eroding their capacity to deliver ecosystem services. Dung beetles are critical ecosystem service providers, making them an ideal ecological indicator to explore the effects of land-use change on biodiversity. Dung beetles were sampled across three land-use types, in the summers of 2015 and 2016 in the Eastern Cape province, South Africa. Game ranching is regarded as a relatively low-intensity land use type. It was compared with cattle ranching (medium intensity) and dairy farming (high intensity) to examine their effect on dung beetle assemblage metrics (abundance, species richness and true Shannon diversity index), guild diversity (as nesting guilds) and spatial turnover. The intermediate grazing intensity of cattle ranching supported a higher abundance and diversity of both whole dung beetle assemblage and the nesting guilds, followed by the game ranches and then dairy farms. Differences between the sampling years were dependent on the beetle nesting guild, and largely correlated with rainfall and temperature. Cattle and game ranches shared a higher number of species than either shared with dairy farms. Whittaker's Beta-diversity index showed the highest species turnover between game ranches and dairy farms. A mix of game and cattle ranching, minimising dairy farming or restricting it to already ecological degraded sites, appears the best alternative for maintenance of dung beetle diversity and their ecosystem services. The year-to-year trends of the data were in general consistent, confirming that dung beetles are reliable ecological indicators; but also suggest that climate change that affects rainfall will result in the reduction of the abundance and diversity of this key ecological group.
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- Date Issued: 2020
Intraspecific mitochondrial gene variation can be as low as that of nuclear rRNA:
- Authors: Matumba, Tshifhiwa G , Oliver, Jody , Barker, Nigel P , McQuaid, Christopher D , Teske, Peter R
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160401 , vital:40442 , https://doi.org/10.12688/f1000research.23635.2
- Description: Mitochondrial DNA (mtDNA) has long been used to date historical demographic events. The idea that it is useful for molecular dating rests on the premise that its evolution is neutral. Even though this idea has long been challenged, the evidence against clock-like evolution of mtDNA is often ignored. Here, we present a particularly clear and simple example to illustrate the implications of violations of the assumption of selective neutrality.
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- Date Issued: 2020
Introduction “New” theory,“post” North-South representations, praxis
- Authors: Rodrigues, Cae , Payne, Phillip G , Grange, Lesley L , Carvalho, Isabel C , Steil, Carlos A , Lotz-Sisitka, Heila , Linde-Loubser, Henriette
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182736 , vital:43858 , xlink:href="https://doi.org/10.1080/00958964.2020.1726265"
- Description: At a recent academic conference in the South, nine of us grappled for four days with these “old” questions and their presence within the “new” discourse of “post” environmental education research. We struggled for an additional six-month period of email exchange to see and feel these questions in our own research. That slow, rich, and deeper academic exchange between us culminated in a research agenda, partially (re)presented in a collectively constructed Mindmap (Figure 1), for critiquing the post/new whose framing is described in the remainder of this Introduction to the politics of knowledge production. That politic of slowly and judiciously engaging a collective form of criticism culminates in identifying the research problem, and questions, of this Special Issue (SI) about the role and place of allegedly new theory in the global discourse of allegedly post environmental education research. This specially assembled issue of The Journal of Environmental Education (JEE) is our best effort to (partially) represent a considerable amount of thought about the challenge presented by “post” and “new” Western thought. In translating our collective thought processes to a SI, we anticipate the reflexivity of the field will be critically advanced through engaging a number of emerging debates (Robottom and Hart, 1993) identified in the following pages of this Introduction, and in three “sample” articles specially written by Isabel Carvalho, Carlos Steil and Francisco Abraão Gonzaga, Louise Sund and Karen Pashby, and Phillip Payne, and an “in process” Conclusion written by Cae Rodrigues. There remains much work to do. This SI is only a start of reengaging overdue debates about the post (Hart, 2005).
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- Date Issued: 2020
Investigation of electrocatalytic behaviour of low symmetry cobalt phthalocyanines when clicked to azide grafted carbon electrodes
- Authors: Mpeta, Lakethe S , Sen, Pinar , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186304 , vital:44483 , xlink:href="https://doi.org/10.1016/j.jelechem.2020.113896"
- Description: This work describes the electrochemical properties of low symmetry cobalt phthalocyanines namely, tris-[(4-tert-butylphenoxy)-4-(pent-4-yn-1-yloxy) phthalocyaniato] cobalt (II) (3) and tris-[(4-tert-butylphenoxy)-4-(4-ethybylbenzyl-oxy) phthalocyaniato] cobalt (II) (5). The complexes were characterized by a number of techniques including UV–Vis, mass, and infrared spectra, as well as elemental analysis. The glassy carbon electrodes were first azide functionalized then clicked to low symmetry phthalocyanines. The click reaction was confirmed using X-ray photoelectron spectra. The constructed electrodes showed excellent electrocatalytic activity towards hydrazine oxidation. Oxidation peaks with low potentials of 0.21 V and 0.26 V, for complexes 3 and 5, respectively were obtained. Complex-5 gave a better detection limit of 0.94 μM and electrocatalytic rate constant of 5.6 × 106 M−1 s−1.
- Full Text:
- Date Issued: 2020
Lions do not change rivers: complex African savannas preclude top-down forcing by large carnivores
- Authors: Comley, Jessica , Joubert, Christoffel J , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149215 , vital:38816 , https://doi.org/10.1016/j.jnc.2020.125844
- Description: Trophic cascade theories such as the ‘behaviourally-mediated trophic cascade hypothesis’ (BMTCH), have mainstreamed as ecological tools for conserving biodiversity and restoring ecosystems. The BMTCH relies on indirect negative effects of large carnivores through suppression of mesocarnivore activity and habitat use. Importantly, effects of top carnivores on mesocarnivores varies over time and space, is dependent on the species involved, and local context. In South Africa, there are very few free-ranging carnivores, as populations are often restricted to enclosed reserves. While predator-proof fences reduce human-wildlife conflict, they also influence space use within communities. We used an enclosed reserve with a relatively full complement of carnivores to test the generality of the BMTCH in the African context. Using single-species, multi-season occupancy models we investigated the spatial dynamics of multiple carnivores. We also investigated spatial partitioning by vegetation type and temporal partitioning.
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- Date Issued: 2020
Living phosphatic stromatolites in a low-phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleosystems
- Authors: Buttner, Steffen H , Isemonger, Eric W , Isaacs, Michelle , van Niekerk, Deon , Sipler, Rachel E , Dorrington, Rosemary A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429450 , vital:72611 , xlink:href="https://doi.org/10.1111/gbi.12415"
- Description: In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin. The microbial communities appear to be also similar to those proposed to have formed fossil phosphatic stromatolites. Phosphatic domains in the material from Cape Recife are spatially and texturally associated with carbonate precipitates, but form distinct entities separated by sharp boundaries. Electron Probe Micro-Analysis shows that Ca/P ratios and the overall chemical compositions of phosphatic precipitates are in the range of octacalcium phosphate, amorphous tricalcium phosphate and apatite. The coincidence in time of the emergence of phosphatic stromatolites in the fossil record with a major episode of atmospheric oxidation led to the assumption that at times of increased oxygen release the underlying increased biological production may have been linked to elevated phosphorus availability. The stromatolites at Cape Recife, however, form in an environment where ambient phosphorus concentrations do not exceed 0.28μM, one to two orders of magnitude below the previously predicted minimum thresh-old of >5 μM for biogenic phosphate precipitation in paleo-systems. Accordingly, we contest the previously proposed suitability of phosphatic stromatolites as a proxy for high ambient phosphate concentrations in supratidal to shallow ocean settings in earth history.
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- Date Issued: 2020
Low-frequency observations of the giant radio galaxy NGC 6251:
- Authors: Cantwell, T M , Bray, J D , Croston, J H , Scaife, A M M , Mulcahy, D D , Best, P N , Brüggen, M , Brunetti, G , Callingham, J R , Clarke, A O , Hardcastle, M J , Harwood, J J , Heald, G , Heesen, V , Iacobelli, M , Jamrozy, M , Morganti, R , Orru, E , O’Sullivan, S P , Riseley, C J , Röttgering, H J A , Shulevski, A , Sridhar, S S , Tasse, C , Van Eck, C L
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149931 , vital:38913 , https://0-doi.org.wam.seals.ac.za/10.1093/mnras/staa1160
- Description: We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies.
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- Date Issued: 2020
Maintenance of public and private urban green infrastructure provides significant employment in Eastern Cape towns, South Africa:
- Authors: King, A , Shackleton, Charlie M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/176074 , vital:42657 , https://doi.org/10.1016/j.ufug.2020.126740
- Description: Urban green infrastructure (UGI) provides numerous environmental, social and economic benefits through direct and indirect use of ecosystem services. The maintenance of UGI also provides work opportunities for skilled and unskilled workers in the public and private sectors, so-called green collar jobs. However, the extent and benefit of such employment has rarely been examined, especially in a developing country context where unemployment is often high. We quantified the number of green collar jobs and wage levels across all green collar categories in 12 towns of the Eastern Cape via means of questionnaires and interviews. Overall, we enumerated 17 429 jobs, receiving approximately ZAR503 million (US$37 million) per year. The number of jobs was strongly linked to town size, but the number of jobs per unit area was inversely related to the level of underdevelopment or deprivation per town.
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- Date Issued: 2020
Making visible the affective dimensions of scholarship in postgraduate writing development work
- Authors: Clarence, Sherran
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/439495 , vital:73601 , https://doi.org/10.47989/kpdc63
- Description: Many university writing and student academic development centres serve both under-and postgraduate student-writers. However, it is not always clear that the training and development of those who work with writers accounts fully for the affective dimensions of postgraduate writing, specifically. Especially at the doctoral level, where an original contribution to knowledge is required, writers need to take on a confident authorial voice in their work, both written and in conversation with others. Research, however, shows that many doctoral students struggle with this. This paper argues that, to be truly successful and fit for purpose, peer writing development work needs to understand the nature of postgraduate learning and writing from more than just the technical perspective of writing a successful thesis. Writer-focused work at this level needs to account for the affective dimensions of writing and research as well, to engage students in more holistic, critical, and forward-looking conversations about their writing, and their own developing scholarly identity. The paper offers insights into the different affective dimensions of postgraduate writing, especially those under-considered in much practical work with postgraduate writers, and offers suggestions for a whole-student tutoring approach at this level.
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- Date Issued: 2020
Mapping subtidal estuarine habitats with a remotely operated underwater vehicle (ROV):
- Authors: Wasserman, J , Claassens, Louw , Adams, J B
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150163 , vital:38945 , DOI: 10.2989/1814232X.2020.1731598
- Description: Subtidal habitats have not yet been accounted for in habitat maps of South African estuaries. In this study, a novel method for mapping subtidal estuarine habitats, using a remotely operated underwater vehicle (ROV) piloted from a boat, was developed and tested in the Knysna Estuary. Video footage was recorded along 48 transects across the width of the estuary, and then reviewed to identify, classify and map habitats. Using the method developed in this study, 21 hours of footage was recorded over 15 days of sampling, and about 30 hours of post-processing was carried out to map an area exceeding 850 ha. This study has produced the first baseline dataset of subtidal habitats for a South African estuary. Additionally, the study revealed the previously unknown distribution of the invasive red seaweed Asparagopsis taxiformis, and the underestimation in previous studies of the estuary of area cover of eelgrass Zostera capensis by 130 ha.
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- Date Issued: 2020
Maximal-entropy initial state of the Universe as a microscopic description of inflation:
- Authors: Brustein, Ram , Medved, A J M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149682 , vital:38874 , https://0-doi.org.wam.seals.ac.za/10.1103/PhysRevD.101.123502
- Description: We propose that the initial state of the Universe was an isotropic state of maximal entropy. Such a state can be described in terms of a state of closed, interacting, fundamental strings in their high-temperature Hagedorn phase, which constitutes a novel microscopic model for the state of the Universe when it is at the highest sustainable temperature. This state resolves the big-bang singularity by replacing the past of the hot big-bang Universe and sets inflationary initial conditions for the subsequent evolution of the thermal radiation and the semiclassical cosmological geometry. The entropy density in this state is equal to the square root of the energy density in Planck units, while the pressure is positive and equal to the energy density.
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- Date Issued: 2020