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Over the course of history, different means of object and person identification as well as verification have evolved for user authentication. In recent years, a new concern has emerged regarding the accuracy of verifiable authentication and protection of personal identifying information (PII), because previous misuses have resulted in significant financial loss. Such losses have escalated more noticeably because of human identity-theft incidents due to breaches of PII within multiple public-access environments. Although the use of various biometric and radio frequency identification (RFID) technologies is expanding, resistance to using these technologies for user authentication remains an issue. This study addressed the effect of individuals’ perceptions on their resistance to using multi-method authentication systems (RMS) in public-access environments and uncovered key constructs that may significantly contribute to such resistance. This study was a predictive study to assess the contributions of individuals’ perceptions of the importance of organizational protection of their PII, noted as Perceived Value of Organizational Protection of PII (PVOP), authentication complexity (AC), and invasion of privacy (IOP) on their resistance to using multi-method authentication systems (RMS) in public-access environments. Moreover, this study also investigated if there were any significant differences on the aforementioned constructs based on age, gender, prior experience with identity theft, and acquaintance experience with identity theft. As part of this study, a rollout project was implemented of multi-factor biometric and RFID technologies for system authentication prior to electronic-commerce (e-commerce) use in public-access environments. The experimental group experienced the multi-factor authentication and also was trained on its use. Computer users (faculty & students) from a small, private university participated in the study to determine their level of PVOP, IOP, and AC on their resistance to using the technology in public-access environments. Multiple Linear Regression (MLR) was used to formulate a model and test predictive power along with the significance of the contribution of the aforementioned constructs on RMS. The results show that all construct measures demonstrated very high reliability. The results also indicate that the experimental group of the multi-factor authentication had lower resistance than the control group that didn’t use the technology. The mean increases indicate an overall statistically significant difference between the experimental and control groups overall. The results also demonstrate that students and participants’ increased levels of education indicate an overall statistically significant decrease in resistance. The findings demonstrate that overall computer authentication training do provide added value in the context of measuring resistance to using newer multi-method authentication technology.

Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes. In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry. A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation. The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.

Thesis (MBA)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The Centre of Excellence for Invasion Biology (C+B) is a research centre that provides bursaries for post-graduate students to study in the field of "Invasion Biology". One of the goals of the centre is to ensure that 50% of the funded students are from previously disadvantaged groups. However, since its inception in 2004 it has consistently been unable to meet this goal. The researcher, who has insight in the centre's marketing activities and has knowledge of marketing, is of the opinion that the reason for this failure is due to the lack of knowledge of the target market and the lack of a targeted marketing strategy. As background this report investigates the theory related to marketing and whether this is applicable to a centre such as the C-I-B. The conclusion that the marketing theory is relevant to the C-I-B, lead to a market research project that informed the development of a marketing strategy suggestion which the researcher believes will address the stated problem. The report concludes with recommendations to other stakeholders who should address the deeper lying problems which surface at secondary school level. / AFRIKAANSE OPSOMMING: Die Sentrum van Uitnemendheid vir Indringer Biologie (S-I-S) is 'n sentrum wat beurse voorsien vir nagraadse studente wat studeer in die veld van "Indringer Biologie". Een van die sentrum se doelwitte is om te verseker dat 50% van sy studente deur voorheen benadeelde groepe verteenwoordig word. Sedert sy ontstaan in 2004 kon die sentrum nog nooit hierdie doel bereik nie. Die navorser, wat insae het in die bemarkingsaktiwiteite van die sentrum en kennis dra van bemarkingsbeginsels, is van mening dat hierdie probleem die gevolg is van gebrekkige kennis van die teikenmark en 'n gebrek aan 'n gefokusde bemarkingsstrategie. As agtergrond ondersoek hierdie verslag die teorie ten opsigte van bemarking en of hierdie teorie relevant is vir 'n sentrum soos die S-I-B. Die gevolgtrekking was dat die teorie wel relevant is vir die S-I-B en het gelei tot 'n marknavorsingsprojek wat bygedra het tot die ontwikkeling van 'n bemarkingsstrategie voorstel, wat die navorser glo die probleem sal aanspreek. Die verslag sluit af met voorstelle aan die ander belanghebbendes wat verantwoordelikheid behoort te neem vir die dieperliggende probleme wat op sekondere vlak geidentifiseer is.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / This thesis examines the role of agricultural activity in the process of invasion of west coast renosterveld fragments by annual alien grass species. This highly endangered vegetation type has less than 5% remaining, it is vital to understand the mechanisms allowing invasion of annual alien grasses in order to effectively prevent the loss of the many rare and endemic species found in west coast renosterveld. This study was divided into three major components. Firstly the distribution of indigenous and alien plant species in relation to fence lines, separating active agricultural fields from untransformed vegetation, was described. Regression analysis was used to test for relationships between distances from agricultural fields and soil physical and chemical characteristics in natural vegetation. Cover by annual alien invasive grasses in untransformed vegetation decreased significantly with distance away from agricultural land. Secondly alien and indigenous grass seed banks were sampled along the transects, at the same sites, in order to establish whether the seed banks correlated with above ground cover. Results varied among sites and seed banks were correlated with the vegetation cover at only one site. It appears that there are a multitude of factors determining the distribution of annual alien grass cover. Thirdly a greenhouse experiment established the role that nitrogen plays in the success of the alien grass Avena fatua. This species was grown in competition with three indigenous species, an annual forb (Dimorphotheca pluvialis), a geophyte (Oxalis purpurea) and an indigenous perennial grass (Tribolium uniolae) at three levels of soil nitrogen. The geophyte was largely unaffected, while growth of the annual and indigenous perennial grasses was negatively affected by competition with A. fatua. Nitrogen did not seem to affect competitive interactions. Management of these renosterveld patches, in order to conserve them effectively, will require a multi-faceted approach, including prevention of further invasion and removal of invasive grasses already present.

The invasion of individuals into new habitats can pose a major threat to native species and to biodiversity itself. However, the consequences of invasions for native populations that are not fully reproductively isolated from their invaders are not yet well explored. Here I chose the Trinidadian guppy, Poecilia reticulata, to investigate how different population traits shaped the outcome of Haskins's introduction, a well-documented invasion of Guanapo river guppies into the Turure river. I especially concentrated on the importance of behaviour for invasive success. I investigated if the spread of Guanapo guppies is due to superiority in behaviour, life-history and/or genetics, or if the outcome of this translocation is due to chance. Despite the fact that by today the invasive front has passed the Turure's confluence with the River Quare many kilometres downstream of the introduction site, and the original genotype only survives in small percentages, as was revealed by genetic analysis in this and other studies, no obvious differences between invasive and native populations could be detected in any of the tested behavioural, life-history and genetic traits. When tested for mate choice, neither Guanapo nor Oropuche (Turure) males seemed to be able to distinguish between the population origin of females, but courted and mated at random. At the same time, females did not prefer to school with individuals of the same population over schooling with more distantly related females. The formation of mixed schools after an invasive event is therefore likely. Because female guppies showed a very low willingness to mate, even after having been separated from males for up to six months, sperm transfer through forced copulations will become more important. Taken together, these behaviours could increase the speed of population mixing after an invasion without the need for behavioural superiority of the invasive population. When tested for their schooling abilities, offspring of mixed parentage, in contrast to pure breds, displayed a large amount of variety in the time they spent schooling, a circumstance that can potentially influence survival rates and therefore the direction of gene pool mixing. Guanapo fish did not show reproductive superiority in a mesocosm experiment, where both populations were mixed in different proportions. On the contrary, in two out of three mixed treatments, the amount of Oropuche (Turure) alleles was significantly higher than expected from the proportion of initially stocked fish. The almost complete absence of distinguishable traits other than genetic variation between the examined populations that belong to different drainage systems, opposes the recent split of the guppy into two different species following drainage system borders, as is argued in this thesis. However, the successful invasion of the Turure by Guanapo guppies and the nearly entire disappearance of the original population can be explained in absence of differing population traits. Here I demonstrate how behavioural and genetic interactions between subspecies influence the outcome of biological invasions and second, how factors other than population traits, such as the geographic situation, can produce an advantageous situation for the invader even in the absence of population differences.

Sosnovskio barščio ir uosialapio klevo plitimo tyrimai buvo atliekami Pasvalio ir Kauno rajonuose. Tyrimo metu buvo nustatoma šių augalų plitimo ypatumai, efektyviausios kontrolės priemonės, invazijos agresyvumo lygmenys. Gauti tyrimai parodė, kad vanduo daro didesnę įtaką uosialapio klevo išplitimo atstumams nei vėjas, nes jų buvo aptinkama visame 10 km tirtos upės pakrantės ruože, o toliausiai vėjo pagalba atsiradę savaiminukai buvo aptikti iki 100 metrų nuo motininio medžio. Šie augalai dera gausiai, vidutiniškai vienas uosialapio klevo medis subrandina 70 tūkst. Sėklų. Sosnovskio barščio 1 m2 aptikta apie 7,5 tūkst. sėklų. Veiksmingiausia kontrolės priemonė uosialapiui klevui yra mažų savaiminukų naikinimas, nes kertant paaugusius medžius jie sėkmingai atželia iš kelmo ataugų. Sosnovskio barščio kontrolei, jų kasimas yra veiksmingiau nei purškimas, nes kasant atželia 45 % naikinamų augalų, o tik purškiant – 85 %. Apskaičiuotas invazyvumo lygmuo parodo, jog Sosnovskio barštis yra invazyvesnis nei uosialapis klevas. Uosialapio klevo invazyvumo lygmuo yra 0,42, o Sosnovskio barščio - 0,56. / The research on the spread of heracleum sosnowskyi and acer negundo was carried out in the regions of Pasvalys and Kaunas. The research focuses on the spread features of these plants, most effective control measures and the level of invasion. The results showed that water had larger influence on the spread of acer negundo than wind as some spontaneous trees were found in all 10 kilometers onshore area. The longest distance from the parent tree revealed to be approximately 100 meters. These plants fruit abundantly, approximately one mature tree of acer negundo produces 70 thousands of seeds. Heracleum sosnowskyi matures about 7.5 thousands of seeds / 1 m2. The most effective control measure of acer negundo is destroying spontaneous seedlings because cutting of the grown trees isn’t effective, they regrow from the stumps. For a control of heracleum sosnowskyi digging is more effective than spraying, because 45 % of the spontaneous seedlings regrow after digging while 85 % of them regrow after spraying. Calculated level of invasion shows that heracleum sosnowskyi is more invasive than acer negundo. A level of invasion of acer negundo is 0.42, heracleum sosnowskyi – 0.56.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Non-native species are recognized as a major component of global environmental change. Their ecological impacts are numerous and include the alteration of whole ecosystem processes as well as the loss of native biodiversity. As such, understanding the processes that drive the invasion of non-native species is essential for the control and management thereof. Numerous research approaches have been used to provide insight on the history and ecology of non-native species invasions. However, recent approaches employing molecular techniques have greatly helped in solving taxonomic issues associated with some of these species; identifying sources of invasions; and shedding light on colonization dynamics. Lantana camara, a globally invasive and highly variable species complex, is one of the most notorious plant invaders in South Africa. The species has been associated with negative impacts in agricultural areas, decreased invertebrate diversity, livestock mortality, and where it occurs along riparian areas- decreased water quality and obstruction to accessing water sources. This project aimed to review L. camara invasions in South Africa and to unravel patterns of spread in L. camara along the Sabie-Sand catchment in South Africa’s flagship protected area, the Kruger National Park, using a molecular approach. The findings of the first part of the study highlight that L. camara has successfully spread across South Africa with only four known introduction events, and this can be attributed to the species’ broad ecological tolerance, its use in the horticultural industry, and a variety of dispersal vectors (birds, humans and rivers). Furthermore, although sale of the species is prohibited in the country, it will continue to spread naturally and also has the potential to expand its distribution under changing climate scenarios. The second part of the study highlights that spread along the Sabie-Sand catchment is primarily river-driven and that the Sand tributary is the invasion source in the system. Because the Sand tributary originates outside the Kruger National Park, and only a small portion is under park management, the implications for spread are important. / AFRIKAANSE OPSOMMING: Nie-inheemse spesies word erken as 'n belangrike komponent van die globale omgewing verandering. Hulle ekologiese impak is talle en sluit in die verandering van ekosisteem prosesse asook die verlies van inheemse biodiversiteit. As sodanig, die begrip van die prosesse wat lei tot die inval van 'n nie-inheemse spesies is noodsaaklik vir die beheer en bestuur daarvan. Talle navorsingsbenaderings is gebruik om insig te gee oor die geskiedenis en ekologie van nie-inheemse spesies invalle. Onlangse benaderings soos die gebruik van molekulêre tegnieke, help in die oplossing van taksonomiese kwessies wat verband hou met 'n paar van hierdie spesies,in die identifisering van bronne van invalle, en om lig te werp op die kolonisasie dinamika. Lantana camara, 'n wêreldwye indringende en spesie kompleks, is een van die mees berugte plantindringer in Suid-Afrika. Die spesie is geassosieer met negatiewe gevolge in landbou gebiede, afgeneem ongewerwelde diversiteit, vee mortaliteit, en waar dit voorkom saam oewer gebiede - afgeneem kwaliteit van die water en obstruksie tot waterbronne. Hierdie projek is daarop gemik om om L. camara invalle in Suid-Afrika te hersien en patrone van verspreiding te ontrafel in L. camara langs die Sabie-Sand-opvanggebied in Suid-Afrika se vlagskip beskermde gebied, die Kruger Nasionale Park, met behulp van 'n molekulêre benadering. Die bevindinge van die eerste deel van die studie wys dat L. camara het suksesvol versprei oor die hele Suid-Afrika met slegs vier bekende inleiding gebeure, en dit kan toegeskryf word aan die spesie se breë ekologiese verdraagsaamheid, die gebruik daarvan in die hortologie bedryf, en 'n verskeidenheid van die verspreiding vektore (voëls, mens en riviere). Verder, hoewel die verkoop van die spesie in die land verbied word, sal dit natuurlik voortgaan om te versprei en het ook die potensiaal om uit te brui onder veranderende klimaat scenario's. Die tweede deel van die studie wys dat versprei langs die Sabie-Sandopvanggebied hoofsaaklik rivier-gedrewe is en dat die Sand sytak die inval bron is. Omdat die Sand sytak buite die Kruger Nasionale Park ontstaan, en slegs 'n klein gedeelte onder park bestuur is, is die implikasies vir verspreiding belangrik. / Financial support from the DST-NRF Centre of Excellence for Invasion Biology and the Working for Water (WfW) Programme through their collaborative project on “Research for Integrated Management of Invasive Alien Species” and Stellenbosch University’s Subcommittee B Young Researcher's Fund

Activator Protein-1(AP-1) family plays a central role in the transcriptional regulation of many genes that are associated with cell proliferation, migration, metastasis, and survival. Transforming growth factor beta (TGF-β) is a multi-functional regulatory cytokine that regulates many aspects of cellular function, including cellular proliferation, migration, and survival. This study investigated the role of FOS proteins in TGF-β signaling in prostate cancer cell proliferation, migration, and invasion. DU145 and PC3 prostate cancer cells were exposed to TGF-β1 at varying time and dosage, RT-PCR, western blot and immunofluorescence analyses were used to determine TGF-β1 effect on FOS mRNA and protein expression levels as well as FosB sub-cellular localization. Transient silencing of FOS protein was used to determine their role in cell proliferation, migration and invasion. Our data showed that FOS mRNA and proteins were differentially expressed in human prostate epithelial (RWPE-1) and prostate cancer cell lines (LNCaP, DU145, and PC3). TGF-β1 induced the expression of FosB at both the mRNA and protein levels in DU145 and PC3 cells, whereas cFos and Fra1 were unaffected and Fra2 protein expression increased in PC3 cell only. Immunofluorescence analysis showed an increase in the accumulation of FosB protein in the nucleus of PC3 cells after treatment with exogenous TGF-β1. Selective knockdown of endogenous FosB by specific siRNA did not have any effect on cell proliferation in PC3 and DU145 cells. However, basal and TGF-β1-and EGF- induced cell migration was significantly reduced in DU145 and PC3 cells lacking endogenous FosB. TGF-β1- and EGF-induced cell invasion were also significantly decreased after FosB knockdown in PC3 cells. Transient silencing of Fra2 resulted in decrease in cell proliferation in PC3 cells whereas transient silencing of cFos resulted in an increase in cell number in PC3 cells. And lastly, TGF-β1 reduced FosB: cJun dimerization; cJun knockdown increased cell migration in PC3 cells and its over expression decreased cell migration in DU145 cells. Our data suggest that FosB is required for migration and invasion in prostate cancer cells. We also conclude that TGF-β1 effect on prostate cancer cell migration and invasion may be mediated through the induction of FosB.

Knowledge of sex allocation trade-offs with tree growth in insect-pollinated woody plants is limited, particularly in invasive plants. This study examined patterns of growth and reproductive investment in a North American invasive plant species, Triadica sebifera, I hypothesized that the energy limitations of smaller trees may result in the production of more male reproductive structures that are energetically less costly. Diameter at breast height was a significant predictor of seed and catkin mass and regression can describe these relationships across sites. Seed and catkin mass were positively correlated across sites. The relationship between the seed mass:catkin mass ratio and DBH was not significant, nor was seed mass:catkin mass and total investment. Results showed a significant positive relationship between total reproductive investment and tree size across sites. Seed mass:catkin mass ratio and reproduction investment showed substantial variation among individual trees of similar size within sites.