Development of bio-based xylan composites for food packaging applications
- Authors: Naidu, Darrel Sarvesh
- Date: 2020
- Subjects: Xylanases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48544 , vital:40886
- Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
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- Date Issued: 2020
Guidelines for and evaluation of the design of technology-supported lessons to teach basic programming principles to deaf and hard of hearing learners: a case study of a school for the deaf
- Authors: Wassermann, Ulza
- Date: 2018
- Subjects: Deaf -- Education , Hearing impaired children -- Education Computers and people with disabilities Communication devices for people with disabilities Information technology -- Education
- Language: English
- Type: Thesis , Masters , MIT
- Identifier: http://hdl.handle.net/10948/36347 , vital:33925
- Description: Deaf and Hard of Hearing (DHH) learners are part of a diverse population with unique learning challenges, strengths and needs. Learning material should be developed specifically for them to provide for their needs and capitalise on their strengths. These materials should include visual material and strategies as well as sign language. Furthermore, DHH learners have the same capacity for learning as hearing learners. However, in South Africa, DHH learners do not have adequate access to training in computer-related subjects, and therefore no material exists that has been developed specifically for DHH learners who want to learn a programming language. This research provides guidelines on the way technology-supported lessons can be designed to teach basic programming principles using the programming language Scratch, to DHH learners. Provision was made for the South African context where limited technology is available at most schools for DHH learners, but where most educators have access to Microsoft Office applications – specifically MS PowerPoint. Two goals were pursued. The primary goal of this research project was to determine the user experience (UX) of the participants (both learners and educators) during and after using and attending the technology-supported lessons. This was achieved through a case study. Four UX evaluation elements were evaluated in this project. They were: usability, accessibility, emotional user reaction, and hedonic aspects. Questionnaires, semi-structured interviews as well as participant-observation were used to determine the UX of participants. The UX evaluation provided sufficient evidence to claim that UX of participants was satisfactory, and therefore the guidelines that were developed to create technology-supported lessons to teach basic programming principles to DHH learners were appropriate. The secondary goal was to develop guidelines for the design of technology-supported lessons to teach programming to DHH learners, and to apply these guidelines to develop a high-fidelity, fully functional prototype – a set of technology-supported lessons. This was achieved through a prototype construction research strategy. The lessons consisted of two vocabulary lessons and one programming lesson. The words that were taught in the vocabulary lesson were either terms appearing in the interface of Scratch, or words needed in the explanation of programming principles and Scratch context. The programming lesson (a PowerPoint slide show) was a guide for the educator to present the content in a logical way, and not to leave out important information. It used multimedia techniques (colour, pictures, animation) to explain programming concepts, and to display the tasks to be completed to the learners, so that they could remember the sequence of the steps. Practical strategies have been included in the guidelines to address the learning challenges DHH experience in the following areas: Comprehension skills, application of knowledge and knowledge organisation, relational and individual-item orientations, metacognition, memory, distractibility. The guidelines referred to techniques and principles that can be followed to design the interface and navigation tools of a technology-supported lesson; enhance communication with DHH learners, and provide support for them to work independently; specify the educator’s role and attitude when facilitating or presenting programming lessons and to structure a programming lesson.
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- Date Issued: 2018
The development of novel cancer targeting agents
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
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- Date Issued: 2011