The diving and ranging behaviour of southern elephant seal, Mirounga leonina, bulls

Geolocation-Time-depth Recorders (GLTDRs) were used to record the diving and ranging behaviour of eleven southern elephant seal, Mirounga leonina, adult males from sub-Antarctic Marion ( n = 7) and Macquarie ( n = 4) Islands during their pelagic annual cycle. A total of 39 897 dives during 894 days were recorded and were categorised into twelve dive types which were hypothesized to serve in travelling, searching for prey, exploration, resting, benthic foraging, pelagic foraging and combinations of two or more functions, and seals dived virtually continuously (86%-92% of the time underwater) most often to depths ranging from 390 m to 920 m and dive durations from 18.6 min to 36.6 min (maximum duration= 80 min) spending only 2.4 min to 3.6 min on the surface between dives. Although the maximum measured dive depths for two males from Marion Island (1 446 m and I 452 m) are the deepest dives measured yet for male southern elephant seals, these seals often exceeded the depth limit of the GLTDRs. The Macquarie males travelled to Antarctica mostly foraging benthically over the Antarctic continental shelf whilst the males from Marion Island stayed relatively close to the island, diving deeper and longer pursuing pelagic prey species. The results in this study suggest that different physical environmental conditions resulted in the different diving behaviours displayed by M leonina males. 11Dissertation (MSc (Zoology))--University of Pretoria, 1998.Zoology and EntomologyMSc (Zoology)Unrestricte

Evaluating the relationship between Modis and AVHRR vegetation indices

Student Number : 0216831W - MSc research report - School of Environmental Sciences - Faculty of ScienceThis report deals with the relationship between the NDVI obtained from the NOAA AVHRR sensor and that obtained from the MODIS sensor. The relationship is quantitatively assessed for distinct polygons over various land-cover types in the northeastern Kwa-Zulu Natal Province of South Africa. Spatial and temporal variations in the relationships are addressed and discussed with reference to spectral response, sunsensor- target geometries and atmospheric factors. Specifically, various methods are investigated to estimate a MODIS-equivalent NDVI from the AVHRR NDVI and in so doing create the potential to develop a self-consistent NDVI between the historically available AVHRR NDVI dataset and the relatively new MODIS NDVI dataset. NOAA-16 AVHRR NDVI data and AQUA MODIS NDVI data for the two-year period from January 2002 to December 2003 are used to develop the method. A linear relationship exists between the AVHRR and MODIS NDVI. However, spatial variations in the relationship in terms of land-cover and mean NDVI are pointed out. The potential of atmospheric corrections applied to AVHRR data through a radiative transfer atmospheric correction model to improve the relationship between the two NDVI datasets is also investigated. The importance of geo-location accuracy of the AVHRR NDVI dataset is assessed in the light of the accuracy obtainable with the proposed method to estimate a MODIS-equivalent NDVI from the AVHRR NDVI. A method to estimate the MODIS NDVI from the AVHRR NDVI that takes the mean AVHRR NDVI value into account, as opposed to a constant linear relationship over all the points, is proposed. Atmospheric correction is shown not to improve the accuracy of the method in a statistically significant way. The root-mean-square error of the proposed method is in the order of 0.05 NDVI units and varies between 0.5 and 2 standard deviations of the MODIS NDVI over an entire season

Diffusion of fission products and radiation damage in SiC

A major problem with most of the present nuclear reactors is their safety in terms of the release of radioactivity into the environment during accidents. In some of the future nuclear reactor designs, i.e. Generation IV reactors, the fuel is in the form of coated spherical particles, i.e. TRISO (acronym for Triple Coated Isotropic) particles. The main function of these coating layers is to act as diffusion barriers for radioactive fission products, thereby keeping these fission products within the fuel particles, even under accident conditions. The most important coating layer is composed of polycrystalline 3C-SiC. This paper reviews the diffusion of the important fission products (silver, caesium, iodine and strontium) in SiC. Because radiation damage can induce and enhance diffusion, the paper also briefly reviews damage created by energetic neutrons and ions at elevated temperatures, i.e. the temperatures at which the modern reactors will operate, and the annealing of the damage. The interaction between SiC and some fission products (such as Pd and I) is also briefly discussed. As shown, one of the key advantages of SiC is its radiation hardness at elevated temperatures, i.e. SiC is not amorphized by neutron or bombardment at substrate temperatures above 350°C. Based on the diffusion coefficients of the fission products considered, the review shows that at the normal operating temperatures of these new reactors (i.e. less than 950°C) the SiC coating layer is a good diffusion barrier for these fission products. However, at higher temperatures the design of the coated particles needs to be adapted, possibly by adding a thin layer of ZrC.http://iopscience.iop.org/hb201

Research contract relationship between a large industry partner and South African universities.

We propose and evaluate a contractual structuring instrument (in the form of a Framework Research Agreement) in support of research collaboration partnerships between universities and large industry, specifically for the case of large industry in the South African context. This study includes one large South African originated industry (as the pioneer of concluding Framework Research Agreements with several universities) and multiple South African universities, and stretches over several decades. This study was done within the broader context of the challenges and benefits experienced by both industry and university in the academic engagement sphere of industry–university collaboration. By providing insight from both industry and university perspectives, factors impacting on academic engagement (with specific emphasis on the legislative framework, contractual aspects, institutional research contract practices and institutional risks), are considered and discussed. Recommendations are made for improved industry–university collaboration by sharing experiences from the industry and universities on challenges faced, managing the expectations and proposing mechanisms to support constructive research collaboration through a mutually beneficial contractual framework instrument.Significance:• A novel Framework Research Agreement as a contractual instrument was developed and pioneered by the industry partner with several South African universities, to create a transparent framework based on fair contracting and determinable remuneration principles.• This study specifically highlights the need for a contractual instrument, in which the intention is to build a long-term contractual relationship to support industry–university collaboration and academic engagement within the existing South African legislative framework.• It further draws attention to research contract management practices and contractual aspects, which until now have been largely ignored in industry–university collaboration and academic engagement frameworks of this kind

Deconvolution models for determining the real surface composition of InP (1 0 0) after bombardment with 5 keV Ar ions at different angles

Low energy ion bombardment can induce compositional changes in the surfaces of compound materials. A fundamental problem is to determine which of the two main mechanisms caused the compositional change, viz. preferential sputtering or bombardment-induced segregation. This paper describes a method, using Auger electron spectroscopy (AES) taken at different angles, to determine the real (top) surface concentrations for an InP (1 0 0) surface after 5 keV Ar+ bombardment at varying impact angles. This bombardment results in an altered near-surface layer. This altered surface layer is amorphised and has a non-stoichiometric surface composition. AES intensity measures the average concentration over the information depth. In this paper, two deconvolution models were used to determine concentration vs depth distributions from the AES intensities. These two models were then used to calculate a surface concentration for each case. Using a deconvolution model in which chemical effects and segregation dominate, the calculated surface concentration was larger than 1, indicating an unphysical surface concentration. Applying a ballistic deconvolution model in the quantification equation, the surface concentration values determined, agree within 5% to the values obtained from TRIDYN simulations. From this follows that argon ion bombardment-induced compositional changes in InP are mainly due to preferential sputtering and ion beam mixing and (to a lesser extent) bombardment-induced diffusion.http://www.elsevier.com/locate/nimb2020-12-01hj2019Physic

Aspekte van die ekologiese toestand van die Mvotirivier in die Stanger-omgewing, KwaZulu-Natal

Aspects of the ecological state of the Mvoti River in the Stanger area, KwaZulu-Natal Water is a scarce resource and if its quantity and quality are insufficient, it cannot provide the necessary goods and services to the various water consumers. Biomonitoring is used to determine the ecological state of water resources through the use of various biotic indices. The initiation of the River Health Programme (RHP) in South Africa has given sufficient momentum to biomonitoring of rivers in South Africa. The RHP has developed and refined various biomonitoring indices to assess the ecological state of ecosystem components. The Mvoti River, in the vicinity of Stanger, is subjected to extensive water abstraction, which is then utilised for irrigation, industrial use, urban water requirements and various domestic uses by informal settlements. Previous studies on the river indicated that it is in a severely degraded state, especially below the confluences of the Nchaweni and Mbozambo rivers. Thus, this assessment of the current ecological status of the Mvoti River was undertaken to possibly identify the main causes of the degraded state. The study was undertaken during the high (February) and low flow (August) periods in 2005. Selected monitoring sites included sites used in previous studies on the Mvoti River as well as sites on the Nchaweni and Mbozambo tributaries. The RHP methods were implemented in this study to determine the ecological state of the macroinvertebrate and fish communities. Habitat indices and water samples were also used to assess the state of the abiotic components. The habitat indices implemented in this study were the Habitat Quality Index (HQI) and Integrated Habitat Assessment System (IHAS). Physicochemical water analyses were done during each sampling period to assess the water quality. The biotic indices used included the South African Scoring System 5 (SASS5) index to assess the macro-invertebrate community and the Fish Assemblage Integrity Index (FAII) to assess the fish community. The lower Mvoti River contains very little habitat of good quality to support the biotic communities. The habitat is generally degraded due to the destruction of the riparian zone and the dominance of alien vegetation in the form of reeds. This, together with land-use and water abstraction activities, has caused high sediment loads in the lower Mvoti River which are continually moving. The results have shown that site MR1 is in an almost natural state with few modifications. The relative reference site, MR2, was, except for the fish community that showed various modifications, in good condition. The condition of the sites downstream decreased as the various activities around Stanger started to impact on the river. Site MR4 located directly below all activities surrounding Stanger was in a poor ecological state. The results of the Nchaweni and Mbozambo tributaries also indicated that the macroinvertebrate and fish communities are in a degraded condition due to the poor water quality in these systems. The main impact on the Mvoti River and its tributaries is the low habitat diversity together with the altered water quality associated with the multitude of activities in the Stanger area. Overall, the Mvoti River is in a seriously degraded state with even the reference site being subjected to impacts that could potentially be harmful to the ecosystem. The ecological state of the river decreases as it moves past Stanger and is subjected to the impacts from the Nchaweni and Mbozambo rivers in the form of nutrients and salinity concentrations. The impacts on the Mvoti River have a multitude of different sources and if the aquatic ecosystem is to improve, only a collective effort will be of any value

Transmission line filters with harmonic parallel foster sections

Conventional wideband bandstop filters use Cauer prototypes, but become nonrealizable with Kuroda–Levy transforms for bandwidths of 150% or more. Transmission line filters with harmonic stubs have been shown to be realizable at these bandwidths, but have limited performance ranges due to the fixed positions of the transmission zeros. In this article, two structures that use shunt Foster resonators that enable the shift of the transmission zeros are described. Simulated and measured properties show that greatly improved performance can be realized while not adding to the complexity of the structurehttp://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1098-2760hb201

Temperature and relative humidity trends in the northernmost region of South Africa, 1950–2016

The northernmost Limpopo Province is located in one of the warmest regions of South Africa, where the agricultural sector is prone to heat stress. The aim of this study was to explore air temperature and relative humidity trends for the region, which have implications for agricultural adaptation and management (amongst other sectors). In particular, we investigated seasonal, annual and decadal scale air temperature and relative humidity changes for the period 1950–2016. Positive temperature trends were recorded for this period, averaging +0.02 °C/year, with the strongest changes observed in mean maximum summer temperatures (+0.03 °C/year). Interannual temperature variability also increased over time, especially for the period 2010–2016, which presents probability densities of <50% for minimum temperatures. Positive relative humidity trends (+0.06%/year) were also recorded for the period 1980– 2016, but proved to be the least predictable weather parameter, with probability densities of <0.5% across seasons for the study period. Considering the substantial interannual variability in temperature and relative humidity, there is clear increased risk for the agricultural sector, particularly for small-scale farmers who generally have limited capacity to adapt. Climate science focusing on the southern African region should continue to establish the impact of climate change and variability on specific small-scale farming systems and enterprises, with recommendations for strategic adaptation based on up-to-date evidence. SIGNIFICANCE : • Heat indices have increased, and variability in temperature and relative humidity has substantially increased over recent decades. • Changes in air temperature and relative humidity have direct and/or indirect negative effects on sectors such as agriculture, leading to reduced productivity. • The small-scale farming sector, which contributes significantly to national food security in developing countries, is the production system most exposed and vulnerable to observed changes/extremes in temperature and relative humidity. • There is an urgent need to build capacity of small-scale farmers for appropriate adaptation to observed changes in climate based on up-to-date evidence.Open Society Foundationhttp://www.sajs.co.zahj2021Geography, Geoinformatics and Meteorolog

Are high elevation crag lizards sensitive to climate change?

Crag lizards are restricted to montane areas where biota are strongly exposed to the effects of climate change. We investigated the factors shaping the distribution of Drakensberg crag lizards (Pseudocordylus melanotus melanotus; Cordylidae) by quantifying their elevational ranges, availability of shelter and prey as well as the thermal environment at three elevations. We recorded expected body temperatures using copper models of the lizards at each elevation in the field and in the laboratory, estimating the duration for which lizards must shelter from high temperatures. This correlated strongly with field observations of lizard activity during winter, spring and summer. Our models predicted that at lower elevations, lizards would shelter for longer periods each day, resulting in a marked reduction in time available for essential activities such as feeding and breeding, possibly explaining why these animals do not occur at lower elevations. The distribution and survival of these animals therefore appear to be impacted by the degree to which daytime temperatures limit their activity. Modelling future climate change scenarios at the high elevation site indicates that crag lizards would be resilient against small to moderate warming reflected by RCP4.5 climate change predictions, but populations are unlikely to persist under conditions predicted in the RCP8.5 scenario. This study is important as, unlike broader-scope studies that cannot quantify climate change impacts on individual species, we combine detailed field data with laboratory measurements and modelling of a single species to assess the ecological constraints to which crag lizards are exposed.The University of Pretoria and the National Research Foundation.https://onlinelibrary.wiley.com/journal/14429993hj2022Geography, Geoinformatics and MeteorologyPhysicsZoology and Entomolog

Kinetics of solid-state reactions between zirconium thin film and silicon carbide at elevated temperatures

Solid state reactions between a thin film (133 nm) of Zr and bulk single crystalline 6H-SiC substrates have been studied at temperatures between 600 °C and 850 °C for durations of 30, 60 and 120 min under high vacuum conditions. The deposited film and reaction zones were investigated by Rutherford backscattering spectrometry (RBS) and X-ray diffraction. The RBS spectra were simulated in order to obtain the deposited layer thickness, reaction zone compositions and reaction zone thickness. The as-deposited spectra fit well with those annealed at 600 °C, thus showing there were no reactions taking place. At temperatures of 700 °C and above, Zr reacted with the SiC substrate and formed a mixed layer of Zr carbide (ZrCx) and Zr silicides (ZrSi, Zr2Si and Zr5Si3). Annealing at 850 °C for 240 min revealed that all the deposited Zr had completely reacted. The interface reaction follows the parabolic growth law thereby indicating diffusion controlled reaction kinetics. The activation energy for the diffusion process obtained was 1.6 eV in the relatively narrow temperature range 700–850 °C.http://www.elsevier.com/locate/nimbhb201