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Developing a management information system for coordinated predation management in South Africa
No full textPredation on livestock and wildlife is the most prominent facet of human-wildlife conflict worldwide. Yet, it is the least understood, in part due to the disparity in methods used to collect data and report results relating to predation and predation management. Predation management is a highly controversial issue, and the lack of scientific information is a major concern and impediment for initiatives to devise effective and acceptable management strategies. The purpose of this study was twofold: (a) to conduct a detailed farm-level investigation into predation vs predation management in areas where high levels of predation had previously been reported, and (b) to develop a tool to provide livestock farmers and wildlife ranchers with a means of reporting predation and practices employed to curb the impact of predation. Building on the groundwork laid by previous studies in South Africa, this study aimed to provide a basis for improving our understanding of the dynamics of human-predator conflict on farm level as well as on a larger scale in an attempt to address some of the current research gaps. This study explored a succession of methods to collect information on predation and predation management on farm-level and develop a tool to collect such data. Initially, questionnaires were used to collect data, concurrent with the process of developing a digital data collection tool. The data collected by means of the questionnaires were used to test this tool (two mobile device applications). The challenges presented during the study and those associated with other methods of data collection played a central role in the data collection methodology developed in the study. At the onset of the study, questionnaires were used to collect information on predation experienced, predator control methods practised, as well as other factors known to influence predation, such as demographic information, physical and managerial characteristics of a farm, and husbandry practices. Though showing potential to provide invaluable information, the questionnaire methodology used in the early phases of this study highlighted fundamental issues regarding the use of conventional data collection methods and the lack of coordinated predation management systems that thwarted the objectives initially set for this study. Consequently, the focus also shifted toward developing a Management Information System (MIS) through which predation management data may be used to develop sound mitigation strategies and, ultimately, inform Best Management Practices. This thesis discusses the development and value of digital data collection methods, specifically mobile device applications, for use in predation management. It also highlights the importance of coordinated action and institutional memory to ensure a structured and focused approach to inform improved predation management strategies in South Africa. To achieve this goal, a system of coordinated predation management must have an MIS at its core. Practical methodologies were developed to manage predation, focusing on more effective technology and procedures to collate relevant information for incorporation into a national database as part of an MIS. Data collected with such methodology presents the opportunity to assist authorities, landowners and other role players with a notable range of coordinated predation management options. The effective and sustainable management of mesopredators poses a range of complicated and varying challenges for responsible authorities and landowners, in South Africa but also worldwide. The outcome of this study is an important and valuable contribution to the knowledge base and insights available to manage damage-causing predators more sustainably. It laid a firm foundation for a comprehensive MIS to inform predation management in South Africa
Nutrition knowledge and nutritional advice practices of netball coaches in the Free State
No full textThis study described the demographic background and facilities available, as well as the nutrition knowledge and advice practices of coaches that train under 16 and under 18 netball players in the first or second netball league in the Free State. A descriptive study was conducted using an online questionnaire.
Ethical approval was obtained from the Health Sciences Research Ethics Committee (HSREC 185_2016) of the Faculty of Health Sciences, University of the Free State and Netball South Africa. The contact information of coaches was obtained from the Free State Netball Federation. Coaches were informed about the study and invited to participate via email. Participation was encouraged by sending out a follow-up invitation to all coaches, one month later, while an incentive in the form of a coaching course and netball equipment was offered to a randomly selected coach who participated in the study.
Forty four coaches are involved in coaching u/16 and u/18 netball in the Free State, all of whom were invited to participate. Only 34 completed the questionnaire. Coaches were asked to complete and online questionnaire that was used to determine facilities available to coaches, nutrition knowledge and advice practices of coaches. The median knowledge score of the coaches was 64.7%, indicating that the coaches in this study did not display adequate nutrition knowledge. Only four out of thirty four coaches achieved an adequate nutrition score of above 75%. Despite not using similar questionnaires, the knowledge scores obtained were comparable to other related studies. Demographic background data investigated did not so show significant differences in nutrition knowledge of coaches and the team coached, age, ethnicity, gender, netball league, coaching level, number of years coaching, previous nutrition education or training received, healthcare support and facilities available to coaches. Only a small percentage (29.4%) of coaches received formal education or training in nutrition. Just over half (58.8%) of the coaches had healthcare support available, with 41.2% of coaches having no support available. The most common healthcare support available included strength and conditioning trainers (32.4%) and a physiotherapist (23.5%). Coaches best understood questions related to “pre- training/competition and during training/competition food” and “weight loss”; scoring 80.0% and 75.0% for these sections, respectively. Questions on “recovery” and “supplement and ergogenic aids” had the lowest overall median correct score, of 50.0% each.
Majority of coaches (82.3%) read about nutrition related issues. The internet (55.6%) was the most popular source of nutrition information. It was expected that those who read about nutrition related issues would display a better nutrition knowledge, however, no significant difference was found between the median knowledge correct score of coaches who read about nutrition compared to those who did not.
All coaches believed that good nutrition practices can improve sports performance, yet, only a small percentage (29.4%) were trained in nutrition and/or had adequate nutrition knowledge. Over half (55.9%) of the coaches reported that they provide advice to their netball players. No significant difference in knowledge scores between coaches who gave advice and those who did not give advice was found.
Most of the coaches (78.1%) have never made use of a professional to give nutrition advice to their players. Of the small percentage (21.9%) that did utilise a professional, most used doctors (57.1%). Dietitians (42.9%), sports nutritionists (28.6%), strength and conditioning trainers (28.6%) and physiotherapists (14.3%) were also used by coaches. Among the coaches providing advice on nutrition, 23.5% made use of outside professionals. Of the few (21.9%) coaches that made use of professionals, mostly professionals that may not be knowledgeable to deliver nutrition advice or where nutrition did not form part of their scope of practice, were used.
A large body of evidence on sports nutrition and its importance in exercise performance as well as overall health exists. The provision of good nutrition advice and information to netball players as well as other athletes is an area that clearly needs attention. Optimal strategies to increase coaches’ knowledge should be researched and/or created to provide assistance. Continued education programmes should be implemented, as part of the requirements as set forth by Netball South Africa, on a regular basis to ensure that athletes and coaches have sufficient nutrition knowledge and have access to reliable nutrition information
Detection of human papillomavirus types in head and neck squamous cell carcinoma
No full textHuman papillomaviruses (HPVs) are the aetiologic agents for diverse clinical conditions ranging from benign lesions to cervical cancer. HPVs have also been associated with head and neck squamous cell carcinomas (HNSCC), in both men and women. HNSCC refers to carcinomas that occur in different sub-sites of the head and neck including the larynx, oral cavity, oropharynx and sinonasal cavity. Studies have shown that the prevalence of HPV infection varies in different population groups from geographically distinct regions, with much higher burden documented in developed countries compared to less developed countries. For instance, HPV-associated HNSCC age‐standardized incidence rates (ASR) of over 1.25 per 100,000 were reported in countries in Europe and Northern America. However, the prevalence in less developed countries could be an underestimation due to limited studies. South Africa has a high incidence of oral squamous cell carcinoma, however not much is known about the prevalence of HNSCC cases due to HPV, or the HPV types associated with HNSCC. HPV associated HNSCCs have a better prognosis compared with HNSCCs caused by other agents such as smoking and alcohol. Currently there are limited tests and biomarkers for early diagnosis and prognosis of the cancer. Therefore, a better understanding of the molecular pathways of carcinogenesis is essential in order to select accurate predictive biomarkers and for the development of effective treatment. Technological advancements in molecular science have improved the discovery of potential biomarkers in cancer, including non-coding RNAs (ncRNAs) which are divided into small non-coding (200 bp). Most studies on biomarkers for application in diagnosis of cancers have focused on small non-coding RNAs using tissue samples. While little is known about the association of long non-coding RNAs such as antisense noncoding RNA in the INK4 locus (ANRIL), HOXA transcript at the distal tip (HOTTIP) and HOX transcript antisense intergenic RNA (HOTAIR) with use of less invasive samples such as blood. Therefore, the aims of the present study were firstly to determine the prevalence of HPV in head and neck cancer using archived specimens from patients with histologically confirmed HNSCCs submitted to the Department of Anatomical Pathology, Universitas Academic Laboratory in Bloemfontein, South Africa, between January 2004 and December 2014. HPV DNA was detected using conventional nested multiplex PCR targeting the L1 region and confirmed using in house type specific E6 primer pairs and a heminested PCR. A total of 780/994 samples tested were found to have intact DNA based on amplification of a partial reference gene. The 780 samples were further tested for the presence of HPV DNA. In total 57/780 (7.3%) were positive for the HPV DNA. High risk (HR) HPV types were more frequently detected than low risk (LR) HPV types. HPV16 was the most frequently detected HR type, and was detected in 26/57 (45.6%) HPV DNA positive biospies. Secondly, the study determined the phylogenetic relatedness and single nucleotide polymorphisms (SNPs) among the high risk HPV isolates using a Maximum Likelihood method for construction of phylogenetic trees. To determine the usefulness of partial L sequence data for identifying HPV lineages, a comparison was made using sequence data retrieved from GenBank for complete HPV genomes, complete L1 genes and partial L1 genes. Based on the outcome the ability to differentiate HPV lineages/sub-lineages was determined. HPV31 and 52 were classified with the L1 partial sequence data. With regards to HPV18 isolates, the partial L1 region was not diverse enough to identify sub-lineages. For HPV45, data for the partial L1 gene was able to discriminate sub-lineages within lineage B but not clearly within the A lineage. Similarly, for HPV16 and 33 clear discrimination of sublineages was not possible. However overall, although the partial L1 sequence data was too conserved for sub-lineage discrimination, it was possible to resolve lineages for some of the HPV types, particularly HPV31 and 52. The identification of biomarkers for early detection of cancers, including HNSCC, would have benefit for any patient. Hence a previously described potential biomarker, HOTAIR was investigated. The expression levels of HOTAIR in laryngeal squamous cell carcinoma (LSCC) patients and healthy volunteers were determined using real time quantitative PCR (RT-qPCR) assay. Patient biopsies were also screened for HPV DNA. Total RNA was extracted from whole blood of patients presenting to Universitas Academic Hospital with histologically confirmed LSCC and healthy volunteers, while DNA was extracted from the LSCC biopsies. Most of the patients, 80% (4/5) had an advanced tumour (T3 and T4), with advanced stage cancer (stages III and IV). The majority of the patients 80% (4/5) did not show lymph node invasion nor metastasis. Histopathology revealed moderately differentiated squamous cell carcinoma in one patient while well differentiated histopathology was seen in the rest of the patients. The mean expression level of the biomarker was found to be significantly higher (p=0.03) in blood collected from patients with laryngeal cancer compared to controls (6.39± 2.13 versus 10.19± 2.24, respectively), with a 13.9-fold overexpression in laryngeal cancer patients’ blood as compared to expression in blood from healthy participants. HPV DNA was detected in 1/5 biopsy samples. The results suggest that further investigation of expression levels of HOTAIR as a potential biomarker is warranted.National Research Foundation (NRF)Poliomyelitis Research Foundation (PRF
Ecotoxicological effects of treated and untreated wastewater on the life cycle of Helix pomatia (Pulmonata) exposed in artificial soil
No full textWater treatment plants, which are established to convert wastewater into reusable water of suitable quality are under gross neglect in South Africa. As such, most of these treatment plants do not function optimally. The present study was conducted to determine the ecotoxicological effects of treated and untreated wastewater from the Maluti-A-Phofung wastewater treatment plant in Phuthaditjhaba. To do so, Wastewater samples were collected from the treatment plant, while a total of 300 Individuals of Helix pomatia were purchased from a breeder in Phuthaditjhaba. Each treatment was comprised of 10 snails placed in 2000g of OECD soil spiked with different concentrations (0, 25, 50, 75 and 100%) of wastewater. The ecotoxicological effects of the wastewater were determined by assessing the biomass, survival reproduction (cocoon production and juvenile emergence), and biomarker responses (Catalase activity Acetylcholinesterase) of H. pomatia. The results showed that there was a significant decrease (P<0.05) in the survival of H. pomatia from the control for both treatments groups. Reproduction results showed that there was a significant reduction (P<0.05) in cocoon production between H. pomatia exposed in controls and all the treatments groups for untreated and treated effluent. Similar results were observed for juvenile emergence. The results also indicated that H. pomatia exposed to untreated and treated wastewater showed significant reductions in biomass compared to the control. The differences were between the control groups and 100% groups for both exposure substrates (P < 0.05). An EC10 of 0,425% and EC50 of 6.233% were calculated for juvenile emergence and EC10 of 5,751% and EC50 of 5.751% were calculated for egg production in untreated wastewater. After 60 days of exposure, biomarkers were conducted and the results showed there was no statistical difference in AChE activities for H. pomatia exposed in control soils and soils spiked with treated and untreated wastewater, despite the fact that the activity seemed higher in H. pomatia exposed to soils spiked with treated wastewater. Similar results were found in catalase activity for H. pomatia exposed in soils spiked with treated and untreated wastewater, despite the fact that higher CAT activity seems to occur in the untreated wastewater Results from this study highlight the toxic effects of wastewater pollution in the Maluti A Phofung wastewater treatment plant If the wastewater treatment plant continues to improperly manage their wastewater with similar contents or more continues to improperly manage their wastewater with similar contents or more this this could could lead to lead to a decline in biodiversity, and also contribute to decline in biodiversity, and also contribute to the alteration of alteration of ecosystem balance.Afromontane Research Uni
Re-defining place: integrating two typologies of public dwelling [the institution and commercial/trade] by using principles of collective [urban] dwelling: addressing conflict spaces in architecture by proposing a collaborative dialogue between the market [ranging from non-permanent stalls to permanent commercial shops]: and the formal institution [a library and media centre], as frames for the urban in-between spaces
No full textThis dissertation sets out to investigate two typologies of public architecture in collaboration, to pose as the frames (edges) for in-between spaces. The project
investigates the possibility to integrate the public institution and market typologies in architecture and present a form of hybrid concept to transcend the frames
(edges) in order to regenerate the central urban dwelling place and create a new identity in a small town.
An urban design project is proposed with a 1) library + media centre institution and 2) an open shopping centre + market, for the Historical Market Square in
the town of Standerton, with the aim to redefine an important place in the degenerated town centre.
At present, the site contains a shopping complex that will be demolished. However, the current shops on site will be included in the new design.
The clients for the project are Lekwa Municipality of Standerton (urban design and market), Fortress REIT Limited for the commercial buildings (owners of the
shopping complex currently on the site), and the Gert Sibande College for the library complex. One of the clients, Fortress REIT Limited, requested a more
interactive shopping and entertainment complex, because the current shops are experiencing diminishing interest. A new mall being built on the periphery of
the town exacerbates the diminishing interest in the current complex. The Lekwa municipality and the Gert Sibande College were invited to participate in the
design of the new development. The Municipality will represent the interest of the people of Standerton, focusing on the urban design and historical
monuments on the site. The Gert Sibande College is one of the fastest growing district colleges in the country and the largest in Mpumalanga. It will not only be
representative of the college, but also the inhabitants of Standerton, within the educational sphere.
The site for the proposed new design is located in the centre of town, on the west side of Beyers Naude Road, the main road of Standerton. The site consists of
an entire city block and was originally the market or main public square of Standerton.
The back of the current reticent complex spans about 70% of the city block’s edge, completely cutting off access and ignoring the presence of some of
Standerton’s most significant and historic buildings. The most prominent space on the site, around the monuments, have been allocated to parking.
Letting the edges of the new development be partially dissolved and/or transcended, allows for integration, habitation, and connection with the people, the
memory, and the history of Standerton.
Introducing public space at the foot of a new institution provides the people of Standerton with a platform to express, engage, and dwell. Memory and meaning
can be restored as the proposed buildings, which serve as frames for the liminal dwelling spaces, combines the new with the existing fabric. The history of the
town and site can be celebrated as the project layers the three past typologies on the site together, namely a market (1891), a garden and public square (1960).
and a commercial complex (1980), to function in collaboration with one another. Urban space becomes the mediator between typologies and the addition of the
library and media centre promotes the cultural identity of the past, present, and future Standerton.
Architecture and urban design become the agents through which history can be remembered. The town can be regenerated by restoring an important place,
and encouraging interaction and expression from the public. Place making by transcending boundaries becomes one of the objectives, transforming the
stagnant existing into a fluctuating and vibrant new town centre for people to dwell in
Bethulie 1896-1907, met spesifieke verwysing na die Anglo-Boereoorlog
No full textThis study, entitled Bethulie 1896-1907, with specific reference to the Anglo-Boer War, aims to investigate, reconstruct, and evaluate the impact and consequences of the Anglo-Boer War on a Free State town and district, in this case Bethulie. Due to the fact that the study focuses on a particular geographical area and community, the study contains a very strong genealogical and social history foundation. Research on Bethulie during the Anglo-Boer War is often dominated by information about the Bethulie concentration camp, specifically because of the inhumane conditions that prevailed in the camp and the resulting high death rate. For the purposes of this study, however, the focus is more on Bethulie as a strategic town and the impact that the AngloBoer War had on the inhabitants, their families and their living conditions, as well as on the Bethulie district. Bethulie was considered a strategic town in the sense that the main railway line from East London to Bloemfontein crossed the railway bridge over the Orange River near the town. In order to understand the impact of the war on the community, the date of departure was decided on as 1896 (the Jameson Raid). The first chapter provides an overview of the Bethulie district, which includes topography, geology, climate, infrastructure, residents and economic prosperity. The study further focuses on the process of the war, with specific reference to the role of the Bethulie commando, as well as the British invasion of the Southern Free State, the scorched-earth policy and the eventual origin of the Bethulie concentration camp. These aspects are presented in more detail as follows: The Bethulie commando: Emphasis is placed on the strength of this commando; preparations and call-up for military service; invasion of the Northeast Cape Colony; the various battles that this military unit took part in; with most of this commando being taken prisoner of war in the Brandwater Basin in July 1900; guerrilla actions in the district; and the peace agreement on 31 May 1902. British involvement: British involvement at Bethulie begins with an exploration by Major E.A. Altham of the Bethulie environment before the war, which was published in a later British intelligence report; Major-General William Gatacre and the battle at Stormberg in December 1899 with, inter alia, the Bethulie commando; the British advance to Bethulie and Bethulie 1896-1907, met spesifieke verwysing na die Anglo-Boereoorlog the battle in March 1900 at the Bethulie bridges; skirmishes in the Bethulie district; the erection of the Bethulie–Springfontein blockhouse line; the operations of the Bethulie Town Guard; and the British administration in the district. The Bethulie concentration camp: The origins; housing; rations; medical care; British officials; medical staff; illnesses; deaths; spiritual care of those who lived in the camp by the church; education; the camp orphanage; as well as hands-uppers and joiners, receive attention. The penultimate chapter focuses on the rebuilding of the town and its community after the devastating war and includes aspects such as resettlement of the inhabitants on their farms; post-war compensation; the Kransdraai labour colony; various other social challenges; as well as the prominent role of the church in building a post-war Bethulie community. The chapter concludes with the first election in 1907, after self-government was granted to the Orange River Colony in 1906. The final chapter is an overall evaluation.Afrikaans: Hierdie studie, getiteld Bethulie 1896-1907, met spesifieke verwysing na die AngloBoereoorlog, het ten doel om die impak en gevolge van die Anglo-Boereoorlog op ʼn
Vrystaatse dorp en distrik, in hierdie geval Bethulie, te ondersoek, te rekonstrueer en te
evalueer. Omrede die studie op ʼn bepaalde geografiese gebied en sy gemeenskap fokus, bevat
dit derhalwe ʼn baie sterk genealogiese en sosiale geskiedenis-onderbou.
Navorsing oor Bethulie tydens die Anglo-Boereoorlog word dikwels oorheers deur inligting
oor die Bethulie-konsentrasiekamp, juis vanweë die onmenslike omstandighede wat in die
kamp geheers het en die uitsonderlike groot aantal sterftes. Vir doeleindes van hierdie studie
word egter meer gefokus op Bethulie as strategiese dorp en die impak wat die AngloBoereoorlog op die inwoners, hul gesinne en lewensomstandighede asook op die Bethuliedistrik gehad het. Bethulie is as ʼn strategiese dorp beskou, in dié sin dat die hoofspoorlyn vanaf Oos-Londen na Bloemfontein oor ʼn spoorbrug oor die Oranjerivier digby die dorp geloop het.
Om die impak van die oorlog op die gemeenskap te verstaan, is op 1896 (die Jameson-inval)
as vertrekdatum besluit. In die eerste hoofstuk word ʼn oorsig van die Bethulie-distrik verskaf,
wat die topografie, geologie, klimaat, infrastruktuur, inwoners en ekonomiese welvaart
insluit. Die studie behels verder die krygsverloop, met spesifieke verwysing na die rol van die
Bethulie-kommando, asook die Britse inval in die Suid-Vrystaat, die verskroeideaardebeleid
en die uiteindelike ontstaan van die Bethulie-konsentrasiekamp. Genoemde aspekte word
soos volg in meer besonderhede weergegee:
Die Bethulie-kommando: Klem word gelê op die sterkte van hierdie kommando;
voorbereidings en oproep tot krygsdiens; die inval in die Noordoos-Kaapkolonie; die
onderskeie gevegte waaraan hierdie krygsmag deelgeneem het; die krygsgevangeneming van
die grootste gedeelte van hierdie kommando in die Brandwaterkom in Julie 1900; guerrillaoptrede in die distrik; en die vrede op 31 Mei 1902.
Britse betrokkenheid: Britse betrokkenheid by Bethulie begin met ʼn verkenning van die
Bethulie-omgewing voor die oorlog deur majoor E.A. Altham, wat in ʼn latere Britse
intelligensieverslag gepubliseer is; generaal-majoor William Gatacre en sy mag se geveg te
Stormberg in Desember 1899 met onder meer die Bethulie-kommando; die Britse opmars na
Bethulie 1896-1907, met spesifieke verwysing na die Anglo-Boereoorlog, Bethulie en die geveg in Maart 1900 by die Bethulie-brûe; skermutselings in die Bethuliedistrik; die oprig van die Bethulie–Springfontein blokhuislyn; die werksaamhede van die Bethulie Town Guard; en die Britse administrasie in die distrik.
Die Bethulie-konsentrasiekamp: Die ontstaan; behuising; rantsoene; mediese versorging;
Britse amptenare; mediese personeel; siektes; sterftes; die geestelike versorging van die
kampbewoners deur die kerk; onderwys; die kampweeshuis; asook hensoppers en joiners,
geniet aandag.
Die voorlaaste hoofstuk fokus op die heropbou van die dorp en sy gemeenskap ná die
verwoestende oorlog en bevat aspekte soos die hervestiging van die inwoners op hul plase;
naoorlogse kompensasie; die Kransdraai-arbeidskolonie; verskeie ander maatskaplike
uitdagings; asook die prominente rol van die kerk in die opbou van ʼn naoorlogse Bethuliegemeenskap. Die hoofstuk sluit af met die eerste verkiesing in 1907, ná die toekenning van
selfbestuur aan die Orange River Colony in 1906. Die slothoofstuk is ʼn oorhoofse evaluering
An audit of central nervous system tumours as diagnosed at Universitas Academic Hospital in Bloemfontein, Free State from 2007 - 2017
No full textTumours of the central nervous system are a common and challenging entity seen by Neurosurgery Departments worldwide. It is the cause of significant morbidity and mortality worldwide. Since the advent of Neurosurgery there has been an immense interest in classifying these tumours to enable prognostication and optimize the management of these tumours. Various classification systems have been used with the latest being the 2016 WHO classification of tumours of the central nervous system. The discovery of the molecular and genetic basis of these tumours and the development of these characteristics to aid in the diagnosis and management of these tumours, have had a great impact on the classification of these tumours. In developed countries, tumour registries exist to optimize the diagnosis and management of these tumours and to identify fields of possible further research and development. There is a lack of such registries in most developing countries and the need exist to establish such registries. The aim of this study is to implement a central nervous system tumour registry at the Universitas Academic Hospital in Bloemfontein to assist with the diagnosis, management and further resource implementation to optimize our management of these tumours and to enable us to compare our data with the international and national data bases
Photography Arts Centre: an architectural exploration of place and identity in Bloemfontein
No full textThis dissertation explores the transformation of a nonplace into a place by developing an identity in an architectural intervention with the aid of its context. It proposes a photography training centre in the central part of Bloemfontein rich in urban diversity. The aim of this photographic facility is to design a meaningful place of learning and activity by including and expanding upon the context’s urban fabric and making it a part of the site’s new identity. The client is an emerging small business by the name of DYD and Sons Pty Limited. This company believes that it could leverage on a collaborative effort between it and the Central University of Technology’s (CUT) Department of Design and Studio Art, Bloemfontein Camera Club and the College of Digital Photography to develop a non-linear model of learning the art of photography in the urban fabric of the centre of Bloemfontein. The dissertation is split into four main parts. The study first recognises the problems and aims associated with the project in terms of typology, topology, morphology and building tectonics. The second part communicates the theoretical, conceptual and precedent framework that informs the design’s development. The third part is the exploration of the design process leading up to the proposed design resolution. Part four concludes the dissertation with a reflection on the design’s successes and comments on the design process
Investigating the optical properties of gold decorated CdS nanoparticles via physical techniques
No full textQuantum dots are very important in modern technology, which is driven by decreasing machinery size, while enhancing performance. Quantum dots form an integral part of nanoparticles (NPs) with a particle size that varies between 2-10 nm. The preparation of these materials is very important, with structural, optical and morphological studies showing dependence on synthesis conditions. In this work, cadmium sulphide (CdS) NPs were prepared using the chemical precipitation method. To control the particle size, thioglycerol (TG) was used as a capping agent with particle size dependent on the TG concentration. Scanning electron microscope and transmission electron microscope investigations showed that agglomerated particles were formed due to the high surface energies that are associated with very small particles. In order to study the role of the reaction conditions on the stabilizing of the particle surface, the particles were prepared using two different solvents: water and ethanol. X-ray diffraction (XRD) data showed that the use of water solvent resulted in particles consisting of a mixed phases of wurtzite and cubic structures. The quantum confinement effect was first observed in the colour change of the prepared samples. In the absence of TG, the sample had an orange colour, however, by introducing 0.1 mL of TG, the colour of the particles turned yellow while at 0.8 mL of TG the particles had a whitish-lemon colour. This effect was confirmed by the blue shift to lower wavelengths of the absorbance spectra obtained with the ultraviolet-visible (UV-Vis) technique. The blue shift is associated with a decreasing particle size. The increased sulphur content with an increasing TG concentration also increased the photoluminescence (PL) recombination rate. Thus preparation of CdS NPs with the water solvent resulted in luminescence from green, yellow, and red emission. The annealing of the 0.3 mL sample resulted in sintering of the small particles making up bulk particles with a hexagonal structure upon a phase transformation temperature. This change in phase introduced infrared emission in the PL spectra. This emission was obtained in the as-prepared samples in the ethanol solvent. Its source was unreacted cadmium chloride (CdCl2) species. Ethanol solvent could not completely dissolve the starting material in the reaction. This resulted in the appearance of strong Cd(OH)2 peaks in the XRD pattern. Also, the XRD pattern showed a cubic zinc blende structure to be dominant in the formed particles with a size of 6.3 nm, 3.0 nm, 3.0 nm, 2.9 nm, and 2.6 nm for S0 (no TG), S1 (0.1 mL TG), S2 (0.2 mL TG), S3 (0.3 mL TG), and S5 (0.8 mL TG), respectively. These were all in the domain of quantum dots and the introduction of TG in this batch took the NP size to sizes below the exciton Bohr radius of CdS. Thereafter the deposition of gold (Au) co-catalyst on the CdS surface was done using physical methods in the top-down approach. It was observed that Au nanoclusters deposited with pulsed laser deposition (PLD) and sputter coating (SPC) enhanced the absorbance of CdS in the UVVis spectra. Nanocomposites prepared with the SPC technique showed the highest absorbance enhancement due to the larger cluster formation which was observed with time-of-flight secondary ion mass spectroscopy as agglomerated clusters. PL spectra showed a decreased luminescence, which showed a decrease in the electron-hole recombination. This is of high importance in the field of photocatalysis for water splitting. This occurred due to the transfer of electrons from the highest occupied states in the CdS semiconductor to the lowest unoccupied states in the Au metal.Department of Science and Technology (DST
Luminescence properties of ZnO and ZnO: Eu³⁺ nanostructures and thin films
No full textEu3+ doped ZnO thin films and ZnO nanorods were successfully prepared by using different techniques. Successful incorporation of Eu3+ ions in the ZnO matrix and preferred orientation along the c-axis for the films and the nanorods were achieved. The structure, morphology, luminescence and stability of the samples under electron beam irradiation were investigated. Firstly: Low Eu3+ concentration (0.4, 0.6, 0.8, and 1 mol%) doped ZnO thin films were successfully prepared using the spin coating technique. The preferred orientation of the films was reduced with increasing Eu3+ content. The average particle sizes and the optical band gap of the films decreased with increasing Eu3+ concentration. The films were excited at 325 nm and 464 nm using a xenon lamp. Upon excitation at 325 nm, the films exhibited band to band emission at ~378 nm and a broad deep level emission due to defects, with a small peak associated with characteristic Eu3+ emission at 614 nm that protruded from the broad band deep level emission. Upon excitation at 464 nm the characteristic Eu3+ emission features were observed and their intensity increased with increasing Eu3+ content until 0.6 mol% of Eu3+ and was then quenched. Multipole-multipole interaction, defects created due to the differences in ionic radii and charge states of Eu3+ and Zn2+ were found to contribute to luminescence quenching. Judd-Ofelt intensity parameters and asymmetry ratio analysis revealed the dependence of the Eu3+ emission intensity on the local environment around the Eu3+ ions in the host. Secondly: ZnO thin films doped with higher Eu3+ concentration up to 4 mol% were also successfully prepared using a sol-gel spin coating technique. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Zn atoms in their doubly ionized state (Zn2+), while Eu atoms were found to be present in their divalent (Eu2+) and trivalent (Eu3+) states. Excitation spectra showed a broad band near 288 nm which was attributed to the charge transfer between O to Eu3+. For the excitation at 464 nm, the doped samples exhibited only the characteristic emissions of Eu3+ which were attributed to the 5D0-7FJ (J = 0, 1, 2, 3, 4) transitions, respectively. The Eu3+ emission intensity increased with increasing Eu3+ concentration up to 3 mol% and was then quenched. Cathodoluminescence (CL) spectra showed only the Eu3+ characteristic emission similar to PL excited at 464 nm. Judd-Ofelt intensity indicated strong covalence of Eu-O bond and higher asymmetry in the vicinity of the Eu3+ ions. The optimum sample (3 mol%) was degraded in vacuum under electron beam irradiation for 160 C/cm2 (about 22 h). The CL intensity showed a slight decrease at the initial electron dose at ~ 30 C/cm2 and then stabilized at further electron dosages. XPS analysis confirmed the formation of defects as a result of electron beam irradiation. Slight changes of the surface morphology and roughness were observed from the degraded area. Thirdly: Eu3+ (3 mol%) doped ZnO thin films were deposited by pulsed laser deposition (PLD) at different oxygen partial pressures (vacuum, 5.9 x 10-2 Torr, 8 x 10-2 Torr and 10 x 10-2 Torr). The 002 X-ray diffraction (XRD) peak of the thin film initially increased with an increase in the oxygen partial pressure, but then slightly decreased. The film thickness, roughness and emission intensity also followed the same trend. The films' morphology improved as a function of increasing oxygen pressure. When excited by a He-Cd laser at 325 nm, the film deposited in vacuum exhibited an intense UV emission at ~ 379 nm, broad-weak deep level emission in the region from 450 nm to 700 nm, as well as a small peak associated with the characteristic emission of the 4f – 4f transitions of Eu3+ at 616 nm standing out from the deep levels emission for the films deposited in oxygen partial pressure. When the Eu3+ ions were selectively excited at 464 nm, only the characteristic emission of the 4f – 4f transitions of Eu3+ were observed at 536 nm, 578 nm, 595 nm, 616 nm, 656 nm and 707 nm corresponding to the 5D1 – 7F0, 5D0 – 7FJ (J = 0, 1, 2, 3 and 4) transitions. When excited at 288 nm, the film deposited in vacuum only exhibited a broad peak centred at 585 nm which was due to the ZnO deep defect levels. The O to Eu3+ charge transfer band near 288 nm was observed for the films deposited in oxygen, and its intensity increased with increasing oxygen pressure. The samples prepared in oxygen exhibited characteristic emission of Eu3+ with an increase in intensity for increasing oxygen partial pressure. No CL was observed for the sample prepared in vacuum, whereas only the characteristic emission of Eu3+ was detected for the films obtained in oxygen partial pressure. Current-voltage measurements of the p-type Si/ZnO:Eu3+ junctions showed a diodelike behaviour with turn on voltage of about 10 V. Fourthly: For Eu3+ doped ZnO (ZnO:Eu3+) thin films deposited by PLD, the oxygen working atmosphere, deposition time and target-substrate distance were optimized to achieve the best luminescence and morphology properties. The surface and luminescence stability of the film under electron beam irradiation was also studied. The CL intensity of the Eu3+ dominant peak at 616 nm increased slightly during the initial stage of electron irradiation, after which it stabilized. XPS high resolution spectra of the O 1s peak confirmed the creation of new defects during electron beam irradiation. Atomic force microscopy images revealed that the particle sizes increased slightly during irradiation (degradation). Colour rendering and purity of the CL spectra were slightly changed during degradation. Fifthly: Preferentially c-axis oriented ZnO nanorods were grown on a ZnO seed layer spin coated on a crystalline silicon substrate. A low temperature aqueous chemical growth method using the chemical bath deposition (CBD) technique was used to grow the ZnO nanorods. The samples were annealed at 700 °C in a reducing atmosphere (H2/Ar) with a relative ratio of 5%:95% for different times (20, 30 and 50 min). XRD analysis revealed that the crystallite sizes increased with increasing annealing time up to 30 min and then decreased for longer annealing time. Scanning electron microscope images showed a successful growth of the vertically-aligned ZnO nanorods which were approximately 500 nm in length and 50 nm in diameter. The diameter of the nanorods increased with increasing annealing time up to 30 min and then decreased when the annealing time was increased further. PL measurements confirmed that the un-annealed sample exhibited two distinct emissions, namely the band to band emission around 378 nm and a broad orange emission centred at 600 nm which was due to the oxygen related defects. The annealed samples exhibited only a broad green emission centred at 500 nm and their intensities increased with annealing time. The highest intensity was recorded for the sample annealed for 30 min and the intensity decreased for further annealing time. The deconvoluted PL peak of the green emission indicated that three different kinds of defects were responsible for the emission at 500 nm. The decay measurements indicated that the green emission (500 nm) had an average lifetime of 11.58 µs. The quantum yield of the sample annealed for 30 min was measured using an integrating sphere at a wavelength of 325 nm and it was found to be 43%. The surface state, chemical and luminescence stability of the sample with higher luminescence intensity were investigated under electron beam irradiation. Auger electron spectroscopy, XPS and secondary electron microscopy (SEM) were used. The CL intensity was monitored concurrently with the Auger peak-to-peak heights using the same electron beam. The degradation experiment was performed in vacuum and in an oxygen ambient. According to the AES spectra, all the principal elements (zinc and oxygen) were detected as well as carbon, which was removed at the initial stage of electron beam irradiation. No chemical change was observed during electron beam irradiation. In vacuum, the CL intensity decreased to almost half of its initial intensity after 100 C/cm2 electron dose and then stabilized. In the oxygen atmosphere, the CL intensity also decreased initially up to a dose of ~10 C/cm2 and thereafter recovered to about 90% of its original intensity and stabilized after a dose of ~100 C/cm2. No difference in the chemical state of Zn was observed with XPS for the original and degradaded samples. Only a small change in the defect contribution part of the O peak was observed. SEM images for the original and degraded samples showed that the electron beam irradiation induced surface changes in the morphology of the ZnO nanorods. These results suggest that the ZnO nanorods and ZnO:Eu3+ thin films are promising green and red materials for optoelectronic devices such as light emitting diodes (LEDs) and flat panel displays (FPDs) among others.African Laser Centre (ALC)National Laser Centre (NLC