List of Titles

Improvement of the pharmacological activity of menthol via enzymatic β-anomer-selective glycosylation

- Choi, Ha-Young, Kim, Bo-Min, Morgan, Abubaker M A, Kim, Joong Su, Kim, Won-Gon

Authors: Choi, Ha-Young , Kim, Bo-Min , Morgan, Abubaker M A , Kim, Joong Su , Kim, Won-Gon
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/67515 , vital:29106 , http://dx.doi.org/10.1186/s13568-017-0468-0
Description: Publisher version , Menthol has a considerable cooling effect, but the use range of menthol is limited because of its extremely low solubility in water and inherent flavor. (−)-Menthol β-glucoside was determined to be more soluble in water (>27 times) than (−)-menthol α-glucoside; hence, β-anomer-selective glucosylation of menthol is necessary. The in vitro glycosylation of (−)-menthol by uridine diphosphate glycosyltransferase (BLC) from Bacillus licheniformis generated (−)-menthol β-glucoside and new (−)-menthol β-galactoside and (−)-menthol N-acetylglucosamine. The maximum conversion rate of menthol to (−)-menthol β-D-glucoside by BLC was found to be 58.9%. Importantly, (−)-menthol β-D-glucoside had a higher cooling effect and no flavor compared with menthol. In addition, (−)-menthol β-D-glucoside was determined to be a non-sensitizer in a skin allergy test in the human cell line activation test, whereas menthol was a sensitizer.
Full Text:
Date Issued: 2017

Improving fold resistance prediction of HIV-1 against protease and reverse transcriptase inhibitors using artificial neural networks:

- Amamuddy, Olivier S, Bishop, Nigel T, Tastan Bishop, Özlem

Authors: Amamuddy, Olivier S , Bishop, Nigel T , Tastan Bishop, Özlem
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/148261 , vital:38724 , https://0-doi.org.wam.seals.ac.za/10.1186/s12859-017-1782-x
Description: Drug resistance in HIV treatment is still a worldwide problem. Predicting resistance to antiretrovirals (ARVs) before starting any treatment is important. Prediction accuracy is essential, as low-accuracy predictions increase the risk of prescribing sub-optimal drug regimens leading to patients developing resistance sooner. Artificial Neural Networks (ANNs) are a powerful tool that would be able to assist in drug resistance prediction. In this study, we constrained the dataset to subtype B, sacrificing generalizability for a higher predictive performance, and demonstrated that the predictive quality of the ANN regression models have definite improvement for most ARVs.
Full Text:
Date Issued: 2017

Quick View

Improving singlet oxygen generating abilities of phthalocyanines

- Nwahara, Nnamdi, Britton, Jonathan, Nyokong, Tebello

Authors: Nwahara, Nnamdi , Britton, Jonathan , Nyokong, Tebello
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188943 , vital:44800 , xlink:href="https://doi.org/10.1080/00958972.2017.1313975"
Description: Glutathione-capped graphene quantum dots (GQDs@GSH) were covalently linked to folic acid (FA). Aluminum tetrasulfonated phthalocyanine (ClAlTSPc) was then adsorbed on the GQDs@GSH-FA conjugate to form GQDs@GSH-FA/ClAlTSPc or on GQDs@GSH and pristine GQDs alone to form GQDs@GSH/ClAlTSPc and GQDs/ClAlTSPc, respectively. We report for the first time on the photophysicochemical behavior of the resulting nanoconjugates. The fluorescence quantum yields of pristine GQDs, GQDS@GSH, or GQDs@GSH-FA conjugate were quenched upon non-covalent interaction (π–π) with ClAlTSPc. There was an increase in triplet quantum yields from 0.38 for ClAlTSPc alone to 0.60, 0.75, and 0.73 when ClAlTSPc was linked to pristine GQDs, GQDs@GSH, and GQDs@GSH-FA, respectively. The singlet oxygen quantum yields also increased from 0.37 for ClAlTSPc alone to 0.42 (for ClALTSPc with pristine GQDs), 0.52 (for ClAlTSPc with GQDs@GSH), and 0.54 (for ClAlTSPc with GQDs@GSH-FA). Thus, the present work may lead to a new generation of carbon-based nanomaterial photodynamic therapy agents with overall performance superior to conventional agents in terms of singlet oxygen generation, water dispersibility, and biocompatibility.
Full Text:
Date Issued: 2017

Quick View

Improving the cold tolerance of false codling moth, thaumatotibia leucotreta, for better performance in a sterile insect release programme

- Daniel, Claire Ashleigh

Authors: Daniel, Claire Ashleigh
Date: 2017
Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction -- Effect of temperature on , Cryptophlebia leucotreta -- Biological control -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Insecticides , Citrus fruit industry -- South Africa
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/5271 , vital:20803
Description: The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a major pest of citrus and other important crops in Sub-Saharan Africa. The introduction of a sterile insect technique (SIT) programme for FCM in South Africa has proven to be very effective in the control of FCM. The objective was to flood citrus orchards with large numbers of sterile males resulting in a ratio of at least 10 sterile to 1 wild moth, increasing the probability of a female moth mating with a sterile male. This target is often achieved and the programme is generally successful, however there are some challenges regarding this programme. The mass rearing environment, artificial diet, handling methods and irradiation have an impact on sterile insect quality as environmental differences between the rearing facility and field, influences the insect phenotype and competitiveness. This is evident as wild male moths can theoretically actively fly at a temperature of 12°C and laboratory-reared sterilized moths, due to the radiation treatment, appear unable to fly below 20°C. As a consequence, sterile males are out-competed by wild males during the cooler months of the year. This is detrimental to the SIT programme as FCM do not undergo diapause, meaning they are active during winter and will still reproduce. Therefore, to maximize the effect of the SIT programme, it is vital to increase the flight ability of mass reared sterile males at lower temperatures. Various studies have shown that by adding cryoprotectants to the basic laboratory diets increases the cold tolerance of certain insects and thus may allow them to be mobile at lower temperatures, however it imperative that any chemical used to augment the commercial diet of the insect has no negative effects on the insect physiology and development. To investigate this detail for FCM, five generations of FCM were reared on diets augmented with various known insect cryoprotectants. These augmented FCM were subsequently used in experiments designed to determine firstly, if the cryoprotectants had a positive result on the cold tolerance of the FCM, and secondly, if they had any adverse effects on other physiological aspects such as duration of development. Laboratory trials indicated that the flight ability of male FCM was improved when larvae were reared on diets augmented with trehalose and cholesterol (with an average of 40 % of cholesterol and trehalose augmented males that flew at 15 °C where 0 % of the control flew). Results obtained during the field trials support the laboratory results as there was a significant increase in the number of trehalose augmented moths caught in the field during March and July (winter). Results also showed potential for cholesterol to be used as an additive. Other important findings show that both cholesterol and trehalose have no negative impacts on developmental rate, pupal size, and egg production and viability. Trehalose was found to increase the pupal mass of male and female FCM, as well as the number of eggs laid per female. Cholesterol was found to increase developmental rate and the number of eggs laid. The main findings of this study were that diet additives could improve the massrearing of FCM for SIT and the competitiveness of the males, especially at lower temperatures. However, the additives were expensive and cost could well be a constraint to the wide scale implementation of the new technology.
Full Text:
Date Issued: 2017

Quick View

In conversation with Andrew Tshabangu and Thembinkosi Goniwe "Footprints" exhibition:

- Lila, Philiswa

Authors: Lila, Philiswa
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/146489 , vital:38530 , https://www.ru.ac.za/artsofafrica/exhibitionsperformances/inzwi/
Description: Inzwi! was an art event during the 2017 National Arts Festival in Grahamstown that celebrated the 5th anniversary of the Lucid Lunchbox, a student-led series of talks linked to the Arts of Africa and Global Souths research programme at Rhodes University. During the festival, five sets composed of three videos interjected the talks presented by Dineo Seshee Bopape and Beth Diane Armstrong, as well as a conversation between Andrew Tshabangu, Thembinkosi Goniwe and Philiswa Lila. The event intended to trigger reflection and dialogue, through a ‘wake-up call’ to grapple with our collective heritage and struggles, our fears and points of departure in order to envision futures. The selection of videos drew from the work of Rhodes Fine Art students, Alumni and Artists in Residence. Works on display addressed matters of identity (social, political and/or fictional); social engagement and activism; religious and spiritual practices in African contexts; race and white supremacy; and, finally, patronising relations in the art world. Borrowing from the words of Weléla Mar Kindred, the choreography of this event, like others that have been propelling black body politics in recent movements, is one of "communal healing, strength and solidarity".
Full Text:
Date Issued: 2017

Quick View

In vitro antimicrobial activity of the methanol extract and compounds from the wood of Ficus elastica Roxb. ex Hornem. aerial roots

- Meyer, Franck, Fannang, Simone Véronique, Noundou, Xavier Siwe, Krause, Rui W M, Teinkela, Jean Emmanuel Mbosso, Vardamides, Juliette Cathérine, Mpondo, Albert Emmanuel Mpondo, Azebaze, Anatole Guy Blaise, Nguedia, Jules Clément Assob

Authors: Meyer, Franck , Fannang, Simone Véronique , Noundou, Xavier Siwe , Krause, Rui W M , Teinkela, Jean Emmanuel Mbosso , Vardamides, Juliette Cathérine , Mpondo, Albert Emmanuel Mpondo , Azebaze, Anatole Guy Blaise , Nguedia, Jules Clément Assob
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/126154 , vital:35854 , https://doi.org/10.1016/j.sajb.2017.03.026
Description: Ficus elastica Roxb. ex Hornem., an edible plant belonging to the family of Moraceae, is traditionally used against skin infections and allergies besides having diuretic properties. This study aimed at investigating the antimicrobial activity of the wood of F. elastica aerial roots against a set of bacteria (Staphylococcus aureus; Escherichia coli, Proteus vulgaris, Providencia stuartii and Pseudomonas aeruginosa) and a yeast (Candida albicans). A mixture of linear aliphatic alkanes with n-hexacosane as major compound, β-sitosterol, biochanin A, sitosteryl 3-O-β-D-glucopyranoside (1), elasticamide (2), elastiquinone (3) and ficusoside B (4) were purified and characterized. Antimicrobial activities, expressed as minimum inhibitory concentration (MIC), indicated that the methanol extract showed MIC of 39.1 μg/mL; the lowest values were obtained for 3 and 4, with MIC as low as 4.9 μg/mL, smaller than the values of reference antibiotics (25 μg/mL). Furthermore, as most of the studied samples exhibited Minimum Microbicidal Concentration/Minimum Inhibitory Concentration (MMC/MIC) ratios lower than 4, a microbicidal effect was clearly exhibited. The overall results provided evidence that the wood of F. elastica aerial roots, as well as some of its isolated components might be potential sources of new antimicrobial drugs.
Full Text:
Date Issued: 2017

Quick View

Incidence of unnatural deaths in Transkei subregion of South Africa (1996 –2015)

Date: 2017
Subjects: South Africa Death 2078-6204 Journal article
Language: English
Type: text , article
Identifier: http://hdl.handle.net/11260/6172 , vital:45258 , xlink:href=": https://doi.org/10.1080/20786190.2017.1292697"
Description: Background: Unnatural deaths are a serious and preventable public health problem in South Africa. Such an event is more than the death of an individual who has died in an unnatural way. It has a negative and long-lasting impact on family members as well as on society as a whole. Objective: To study the pattern of unnatural deaths in the Transkei sub-region of South Africa. Method: A record review was undertaken from 1996 to 2015 of 24 693 medico-legal autopsies performed at Mthatha Forensic Pathology Laboratory. Results: At the Mthatha Forensic Pathology Laboratory, 24 693 autopsies were performed between 1996 and 2015 on people who had died unnatural deaths. The average rate of unnatural death is 205 per 100 000 per year in this region. The figure is 160 per 100 000 among males and 44 per 100 000 among females. The rate of unnatural death has increased from 153 per 100 000 in 1996 to 260 per 100 000 in 2015. In two-thirds (69%) of cases, the cause of death is related to trauma. Slightly less than half (45%) of the victims in this study were murdered. Conclusion: There is an increasing trend of unnatural deaths in the Mthatha region of South Africa. The male-to-female ratio is 3.8:1, and about half (48%) of the victims were between 11 and 30 years old. This situation needs the urgent attention of the law enforcement agencies. Keywords: unnatural deaths, traumatic deaths, violent death
Full Text:
Date Issued: 2017

Quick View

Integrating Afrocentric approaches for meaningful learning of science concepts

- Chikunda, Charles, Ngcoza, Kenneth M

Authors: Chikunda, Charles , Ngcoza, Kenneth M
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , book chapter
Identifier: http://hdl.handle.net/10962/436248 , vital:73252 , ISBN 978-3-319-45989-9 , https://doi.org/10.1007/978-3-319-45989-9_
Description: Economic and social development in any modern country re-lies heavily on a sound scientific and technological base. Es-sentially, science constitutes an area of any nation’s education system where many of the skills that are needed to stimulate development are learned, such as securing good health, fighting diseases, protecting the environment, farming and de-veloping agriculture and developing new industries and tech-nologies and even building resilience to climate change. There is a need therefore for a country to harness the intellectual and scientific capacity of its young people. Ironically, however, sci-ence (especially physical sciences) is one of the least popular areas within the educational system of most developing countries. Research shows that students’ and especially girls’ low interest in science and their relatively negative attitudes are at least partially attributed to the way science is taught at school.
Full Text:
Date Issued: 2017

Quick View

Integrating biodiversity considerations into urban golf courses: Managers’ perceptions and woody plant diversity in the Eastern Cape, South Africa

- Jarrett, Mitchell, Shackleton, Charlie M

Authors: Jarrett, Mitchell , Shackleton, Charlie M
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/180353 , vital:43356 , xlink:href="https://doi.org/10.1080/1747423X.2017.1325525"
Description: Rapid rates of urbanisation affect biodiversity through habitat fragmentation and loss. Because urban golf courses are large green spaces, they potentially harbour much biodiversity if managed for such. The area of untransformed land of golf courses in the Eastern Cape (South Africa) was determined using Geographic Information System (GIS), the woody plant composition of a subsample was determined by field sampling and the greenkeepers were interviewed. There was a significant relationship between climate and woody cover, species richness and percentage native plants but not species diversity. There was no relationship between management scores and species richness, diversity and percentage native. Significant relationships were evident between woody plant species richness and course income, number of grounds staff, number of club members and greenkeepers’ years of experience. These results suggest a complex suite of factors that play a role in the woody plant composition of urban golf courses and their contribution to urban biodiversity.
Full Text:
Date Issued: 2017

Quick View

Integrating Climate Change Adaptation (CCA) and Disaster Risk Reduction (DRR) for greater local level resilience: lessons from a multi-stakeholder think-tank

- Pereira, Taryn, Shackleton, Sheona E, Donkor, Felix Kwabena

Authors: Pereira, Taryn , Shackleton, Sheona E , Donkor, Felix Kwabena
Date: 2017
Subjects: Climatic changes -- South Africa , Climatic changes -- South Africa -- Eastern Cape -- South Africa
Language: English
Type: text
Identifier: http://hdl.handle.net/10962/62027 , vital:28097
Description: The last few years have seen one of the most severe droughts in recent times in the southern African region, and news headlines are increasingly full of warnings about heavy storms, fires and floods. There is no doubt that extreme hydro-meteorological events, and their multiple and potentially disastrous impacts, are at the forefront of the public consciousness at the present time and are one of the key concerns regarding the impacts of climate change in the region. While the links between extreme climate events, disaster risk reduction (DRR - see Box 1) and climate change adaptation (CCA - see Box 2) are recognised in the South African Climate Change White Paper, this is not the case for the whole region. Furthermore, even if there is national recognition of the need to synergise these two spheres of endeavour, this does not always trickle down to effective policy, planning and implementation at the local level.
Full Text:
Date Issued: 2017

Quick View

Intellectualisation of isiXhosa literature: the case of Jeff Opland

- Kaschula, Russell H

Authors: Kaschula, Russell H
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/67030 , vital:29022 , https://doi.org/10.17159/2309-9070/tvl.v.54i2.413
Description: publisher version , The origins of the intellectualisation of written isiXhosa literature are often attributed to the missionaries John Ross and John Bennie. They set up a printing press in the Tyhume Valley which later became known as Lovedale Press. They introduced written isiXhosa in 1823 and for this they are acknowledged as the first to write and publish in isiXhosa. This article attempts to trace this intellectualisation process of isiXhosa literature, concentrating on a critique and assessment of the life-long work of Professor Jeff Opland, who has contributed enormously to the present understanding of both oral and written isiXhosa literature. It is argued in this article that his corpus of books and academic articles require some contextualisation within the broader debate of the continued intellectualisation of isiXhosa language and literature. Reference is also made to the Opland isiXhosa literature archive and its contribution to the further intellectualisation of isiXhosa literature. It is suggested in this article that Opland is one of the greatest contributors to academic debates concerning isiXhosa literature and history. Izibongo or oral poems written by, and about Jeff Opland are analysed to further enhance the context of his contribution.
Full Text:
Date Issued: 2017

Quick View

Interacting motif networks located in hotspots associated with RNA release are conserved in Enterovirus capsids

- Ross, Caroline J, Knox, Caroline M, Tastan Bishop, Özlem

Authors: Ross, Caroline J , Knox, Caroline M , Tastan Bishop, Özlem
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/124855 , vital:35704 , https://doi.10.1002/1873-3468.12663
Description: Enteroviruses are responsible for a multitude of human diseases. Expansion of the virus capsid is associated with a cascade of conformational changes that allow the subsequent release of RNA. For the first time, this study presents a comprehensive bioinformatic screen for the prediction of interacting motifs within intraprotomer interfaces and across respective interfaces surrounding the fivefold and twofold axes. The results identify a network of conserved motif residues involved in interactions in enteroviruses that may be critical to capsid stabilisation, providing guidelines towards developing antivirals that interfere with viral expansion during RNA release.
Full Text:
Date Issued: 2017

Quick View

Interactions between two biological control agents released on Pereskia aculeata Miller (Cactaceae), in South Africa

- Mnqeta, Zezethu

Authors: Mnqeta, Zezethu
Date: 2017
Subjects: Pereskia aculeata -- Biological control , Cactus -- Biological control -- South Africa , Alien plants -- Biological control -- South Africa , Flea beetles -- South Africa , Coreidae -- South Africa , Insects as biological pest control agents -- South Africa
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/7949 , vital:21327
Description: Pereskia aculeata Miller (Cactaceae) is an alien invasive plant introduced into South Africa from Brazil, which has negative impacts on native biodiversity in South Africa. Phenrica guerini Bechyne (Chrysomelidae) and Catorhintha schaffneri Brailovsky & Garcia (Coreidae) are two biological control agents released against P. aculeata in South Africa. Phenrica guerini was first released against P. aculeata, in 1991, followed by C. schaffneri in 2014. The overall aim of this study was to improve the biological control programme against P. aculeata in order to decrease its density to a level where it does not threaten the native biodiversity of South Africa. The first part of this study evaluated the efficacy of P. guerini on P. aculeata at Port Alfred (Eastern Cape) to better understand the role of P. guerini in the biological control of P. aculeata. An insecticide exclusion experiment was conducted over 100 days. Plots with P. guerini had a mean of 187 (SE ± 62) fewer leaves/m2 than plots without P. guerini. The agent reduced percentage cover in plots with P. guerini, with a mean of 19.42% (SE ± 3.15) lower cover than plots without P. guerini. Although P. guerini had an impact on P. aculeata at Port Alfred previous studies have indicated that a reduction to below 50% cover is required for native biodiversity to recover and the agent only reduced cover to 62% at Port Alfred. Phenrica guerini has therefore not reduced percentage cover sufficiently to completely control the weed. The data collected from Port Alfred was compared to the performance of the agent nationwide. Although P. guerini was found at far more sites than previously recorded, there were very few sites with comparable levels of damage to Port Alfred. This evidence suggests that P. guerini is not sufficiently damaging to reduce P. aculeata to acceptable levels and other biological control agents should be considered.Interactions between two biological control agents can have complex and unexpected impacts for a biological control programme. The second part of this study was to investigate interactions between C. schaffneri and P. guerini under laboratory conditions to test whether the two agents, individually or jointly, enhanced or reduced their impact on P. aculeata. Potted P. aculeata plants were exposed to one of four treatments: control (no agents), P. guerini only, C. schaffneri only and both species in combination. Four stocking densities, ranging from 2 to 12 insects per plant were used. Catorhintha schaffneri alone at high densities was more damaging than all other treatments with a significantly greater reduction in the mean number of leaves, 11.7 (SE ± 1.29), and shoot lengths, 2.17cm (SE ± O. 75). Even at lower density treatments, the combination of the two agents was not significantly more damaging than C. schaffneri alone and C. schaffneri was always more damaging than P. guerini alone. Mortality of P. guerini was significantly higher than C. schaffneri at the highest stocking density when in combination. Phenrica guerini contributes towards the biological control of P. aculeata at some sites in South Africa but not enough to completely control the weed. The antagonistic interaction between P. guerini and C. schaffneri suggests that these agents should not be released together because this would impact negatively on the overall biocontrol programme against P. aculeata. Catorhintha schaffneri should be released at sites were P. guerini is not present and evaluations of the success of this agent in the field should be conducted. Extrapolation of laboratory-based studies into the field is often challenging so mass-rearing of P. guerini should continue until there is convincing proof that C. schaffneri alone is more effective than P. guerini in the field.
Full Text:
Date Issued: 2017

Quick View

Interrogating citizen journalism practices: a case study of Rhodes University’s Lindaba Ziyafika Project

- Nyathi, Sihle, Garman, Anthea

Authors: Nyathi, Sihle , Garman, Anthea
Date: 2017
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/158915 , vital:40240 , https://doi.org/10.1080/23743670.2016.1259740
Description: Several scholars have noted that citizen journalism in the West is essentially an online phenomenon, driven by the affordability of Internet technologies. In Africa, projects such as Ushahidi in Kenya have been enabled by platforms such as cell phones and social networks. Voices of Africa, based in southern Africa, publishes on the web only. Publishing on the Internet presumes a citizenry which is relatively well educated; has familiarity with, and access to, new media as a form of social communication; and is confident in their right to participate in newly developed public spheres – particularly those online.
Full Text:
Date Issued: 2017

Quick View

Introduction: Researching sustainable development learning pathways towards progression in learning and work

- Lotz-Sisitka, Heila, Ramsarup, Preesha, Bolton, Heidi

Authors: Lotz-Sisitka, Heila , Ramsarup, Preesha , Bolton, Heidi
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , bulletin
Identifier: http://hdl.handle.net/10962/436401 , vital:73269 , ISBN bulletin , https://www.saqa.org.za/wp-content/uploads/2023/02/SAQA-Bulletin-2017-1.pdf#page=37
Description: Environment and sustainable development issues are increasingly seen as complex, multi-faceted and integral to social and economic development, as can be seen from the recently proclaimed sustainable development goals (www.globalgoals.org1 ). As societies grapple with the rapid and catastrophic effects of environmental degradation, anthropogenic earth system change and a long history of unsustainable development, educa-tional systems have had to attempt to comprehend meaningfully, the im-plications. Within post-apartheid South Africa, these challenges are mark-edly more complex. In a country facing fundamental national transfor-mation on every front, the environment and sustainable development discourses are raising significant new challenges for work and learning systems.
Full Text:
Date Issued: 2017

Quick View

Investigating herbivory and plant origin on tall-statured grasses in South Africa

- Canavan, Kim

Authors: Canavan, Kim
Date: 2017
Subjects: Insects as biological pest control agents -- South Africa , Arundo donax , Giant reed -- South Africa , Giant reed -- Biological control -- South Africa , Phragmites australis , Phragmites mauritianus , Phragmites , Tetramesa romana , Biological invasions -- South Africa , Wasps -- Host plants , Wasps -- South Africa
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/6147 , vital:21051
Description: South African riparian zones have been heavily degraded through anthropogenic activities such as dam construction and extraction of water for irrigation, which has resulted in a loss of ecosystem services and functioning. A consequence of such disturbances to riparian areas is in their susceptibility to invasive alien species (IAS). One such IAS is the giant reed, Arundo donax L. (Poaceae), introduced to South Africa in the 1700s largely for erosion control. Arundo donax has since greatly expanded in the country and is now one of the most abundant IAS. Arundo donax has been found to displace native vegetation and in South Africa this will most likely lead to the displacement of the native tall-statured grasses, Phragmites australis (Cav.) Trin. ex Steud. and Phragmites mauritianus Kunth. This study aimed to enhance our understanding of the tall-statured grasses A. donax, P. australis and P. mauritianus to better manage them in riparian areas. For A. donax, biological control is seen as the most viable option to control stands in the long-term. However, before such a programme is put in place, it is important to first collect baseline data that can be used to guide the direction of the biological control project in South Africa. For the Phragmites spp., despite being a dominant vegetative type in riparian areas, very little is known about their status in South Africa. Furthermore, there have been increasing reports of both Phragmites species having an expansion of their range and abundance. In North America, there has been a similar trend of reed expansion and through molecular work it was determined that a cryptic invasion has occurred with the introduction of an invasive non-native haplotype from Europe. It is therefore unknown if Phragmites spp. populations are expanding due to anthropogenic activities or due to a cryptic invasion. To address these shortfalls in knowledge the study investigated the tall-statured grasses in two parts; firstly, molecular techniques are used to explore the plant origin and genetic diversity of A. donax, P. australis and P. mauritianus and secondly using the Enemy Release Hypothesis as a framework, herbivore assemblages for each reed was determined across their distribution in South Africa. Molecular-techniques determined that both P. australis and P. mauritianus had only one haplotype - known as haplotype K and haplotype V respectively, across their distribution. For P. australis, haplotype K shares a close connection with populations from a Mediterranean lineage and this was further confirmed with a shared grass-waxy band. The direction and timing of genetic exchange between the two regions could not be ascertained and thus still remains unknown. Microsatellite analysis determined that both Phragmites spp. had a high genetic diversity compared to worldwide lineages. With no evidence of any cryptic invasions of haplotypes from other regions, both Phragmites spp. populations are likely to be native to South Africa. For A. donax all populations across South Africa were determined to be haplotype M1; a cosmopolitan haplotype that has an ancient native range in Afghanistan and Pakistan (Indus Valley). Populations were found to have no genetic diversity and thus can be considered one clone. A pre-introductory survey determined a list of herbivores associated with each tall- statured grass. For A. donax, a total of seven herbivores were found. Of these, one herbivore, a galling wasp, Tetramesa romana Walker (Hymenoptera: Eurytomidae) was found to be highly abundant and widely distributed in South Africa. Tetramesa romana is already a biological control agent in North America and thus is likely exerting some pressure on A. donax populations in South Africa. For both Phragmites spp. a total of ten herbivores were found, although having higher species richness compared to A. donax, when compared to other regions, these native species have a relatively low species richness. Providing baseline data on plant origin, genetic diversity and herbivory on A. donax, P. australis and P. mauritianus has provided important information on managing these species in riparian ecosystems in South Africa. For the Phragmites spp. with no evidence of any cryptic invasions, it is recommended that reed stands continue to be managed as native species. Phragmites spp. are important dominant vegetative species and thus should be protected; however, if reed stands become expansive, control methods can be put in place to focus on managing spread and abundance. For A. donax, this study was able to provide pivotal information in guiding the biological control programme. By determining the ancient lineage of South African populations, research can be focused in this area to find potential biological control agents. Lastly, the pre-introductory survey determined that a biological control agent, T. romana was already established with an unknown introduction and also highlighted potential plant parts that should be targeted. In particular, no rhizome feeding herbivores were found in South Africa and therefore this highlights an important niche that should be explored in biological control agents.
Full Text:
Date Issued: 2017

Quick View

Investigating the effects various compilers have on the electromagnetic signature of a cryptographic executable

- Frieslaar, Ibraheem, Irwin, Barry V W

Authors: Frieslaar, Ibraheem , Irwin, Barry V W
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/430207 , vital:72673 , https://doi.org/10.1145/3129416.3129436
Description: This research investigates changes in the electromagnetic (EM) signatures of a cryptographic binary executable based on compile-time parameters to the GNU and clang compilers. The source code was compiled and executed on a Raspberry Pi 2, which utilizes the ARMv7 CPU. Various optimization flags are enabled at compile-time and the output of the binary executable's EM signatures are captured at run-time. It is demonstrated that GNU and clang compilers produced different EM signature on program execution. The results indicated while utilizing the O3 optimization flag, the EM signature of the program changes. Additionally, the g++ compiler demonstrated fewer instructions were required to run the executable; this related to fewer EM emissions leaked. The EM data from the various compilers under different optimization levels was used as input data for a correlation power analysis attack. The results indicated that partial AES-128 encryption keys was possible. In addition, the fewest subkeys recovered was when the clang compiler was used with level O2 optimization. Finally, the research was able to recover 15 of 16 AES-128 cryptographic algorithm's subkeys, from the the Pi.
Full Text:
Date Issued: 2017

Quick View

Investigating the electromagnetic side channel leakage from a raspberry pi

- Frieslaar, Ibraheem, Irwin, Barry V W

Authors: Frieslaar, Ibraheem , Irwin, Barry V W
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/429548 , vital:72621 , https://ieeexplore.ieee.org/abstract/document/8251771
Description: This research investigates the Electromagnetic (EM) side channel leakage of a Raspberry Pi 2 B+. An evaluation is performed on the EM leakage as the device executes the AES-128 cryptographic algorithm contained in the Crypto++ library in a threaded environment. Four multi-threaded implementations are evaluated. These implementations are Portable Operating System Interface Threads, C++11 threads, Threading Building Blocks, and OpenMP threads. It is demonstrated that the various thread techniques have distinct variations in frequency and shape as EM emanations is leaked from the Raspberry Pi. Additionally, noise is introduced while the cryptographic algorithm executes. The results indicates that tt is still possible to visibly see the execution of the cryptographic algorithm. However, out of 50 occasions the cryptographic execution was not detected 32 times. It was further identified when calculating prime numbers, the cryptographic algorithm becomes hidden. Furthermore, the analysis pointed in the direction that when high prime numbers are calculated there is a window where the cryptographic algorithm can not be seen visibly in the EM spectrum.
Full Text:
Date Issued: 2017

Showing items 221 - 240 of 489