Development of novel nanoemulsions as delivery systems : A thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, New Zealand

Listed in 2016 Dean's List of Exceptional ThesesIn the past decades, emulsions have been widely used as delivery systems for incorporating bioactive compounds into foods. With the advancing of nanotechnology, smaller particles in the nanometric range (i.e. nanoemulsions) can be created with better properties that are more advantageous than conventional emulsions in terms of their stability to gravitational separation, optical clarity and better absorption of nutrients in drug delivery (with increased bioavailability). In particular, emulsification and solvent evaporation method has been used to produce nanoemulsions with optimum results. However, like conventional emulsions, protein-stabilised nanoemulsions become unstable when exposed to certain environmental stresses such as high temperatures, salt addition and extreme pH changes. Additionally, liquid emulsions are difficult to transport and use in some food systems while being susceptible to microbial spoilage. To remedy, a dry, stable emulsion system has to be obtained for their prospective future in food applications. The objective of this research was to develop nanoemulsions with useful attributes. The thesis consists of three main parts in which the first part studied the formation and properties of nanoemulsions using emulsification and solvent evaporation method; the second part delved into the making of dried nanoemulsion powders and the third part focused on the structural modifications of nanoemulsions and encapsulation of a bioactive compound lutein. To begin, an experimental study to optimise the conditions for producing nanoemulsions using emulsification and solvent evaporation methodology was performed under different processing conditions (microfluidisation pressures and number of passes), organic phase ratios and materials (oil types and emulsifiers). It was found that smaller oil droplets (around 80 nm in diameter) were achieved when increasing the microfluidisation pressure up to 12000 psi (80 MPa) for 4 passes at an organic phase ratio of 10:90. There was a progressive decrease in particle size with increasing emulsifier concentration up to a 1% (w/w) level for whey protein isolate (WPI) and lactoferrin but it did not decrease further at higher concentration. On the other hand, much larger oil droplets were formed in Tween 20 emulsions (120 – 450 nm). The environmental study showed that lactoferrin and Tween 20 emulsions have a better stability to pH changes (pH 2 – 12) and salt addition (0 – 500 mM NaCl or 0 – 90 mM CaCl2) than WPI stabilised nanoemulsions. After successful preparation of nanoemulsions, liquid nanoemulsions were converted to dried powders by spray drying or freeze drying. The nanoemulsions were mixed with different wall materials consisting of maltodextrin alone, trehalose alone or a 1:1 ratio of maltodextrin and trehalose at 10, 20 or 30% (w/w) solid concentration. Results showed that the powders containing 20% trehalose have better powder properties with lower moisture content and water activity, higher bulk density and good reconstitution in water. The freeze-dried powders showed excellent wettability and dispersibility in water but lower encapsulation efficiency than spray dried powders. In another part of study, nanoemulsions with modified interfacial structure were used to improve their stability to environmental stresses. The interactions between WPI and lactoferrin in aqueous solutions were first studied to explore the feasibility of using these two proteins to form complex interfacial structures at the droplet surface in the emulsions. Based on ζ-potential and turbidity measurements, both proteins were shown to interact with each other via electrostatic interactions at pH values between 6 and 8. The adsorption of protein layers on a gold surface that mimics the hydrophobic oil surface was also confirmed by a quartz crystal microbalance with dissipation (QCM-D) study. Next, a series of bi-layer nanoemulsions at different pH values and lactoferrin concentrations were prepared so as to determine the best conditions on the overall emulsion stability. It was shown that the stability of emulsions was dependent on both pH and lactoferrin concentration. At pH values close to pI of WPI (around pH 5), the nanoemulsions remained unstable regardless of the lactoferrin concentration used (0.25 – 5% w/w). The nanoemulsions at pH 6 were also unstable at low concentrations (0.5 – 1% w/w) presumably due to “bridging flocculation” and exhibited phase separation. Consequently, a lactoferrin concentration of 3% (w/w) was used to produce bi-layer nanoemulsions at pH 6. At pH 7 – 10, the bi-layer nanoemulsions were stable at all lactoferrin concentrations and formed a bi-layer structure at the interface of droplet. The formulated nanoemulsions (single layer and bi-layer emulsions) were subjected to a variety of environmental stresses and in vitro digestion under simulated gastrointestinal conditions. The emulsion stability to pH changes and salt addition was improved in the bi-layer emulsions containing WPI and lactoferrin when compared to the single layer nanoemulsions stabilised by WPI alone. However, the bi-layer emulsions were more susceptible to destabilisation on heating at temperatures above 60oC. The in vitro digestion of bi-layer nanoemulsions was similar to single layer nanoemulsions in which the protein hydrolysis of the interfacial layers results in extensive droplet flocculation. In subsequent formulations, lutein was incorporated in the emulsions as a model of bioactive compound for the application of nanoemulsions as a novel delivery system. The nanoemulsions well encapsulated lutein in their matrices with an encapsulation efficiency of 80% and contained small oil droplets (70 – 80 nm). All the emulsions were physically stable under the tested conditions up to 28 days at different storage temperatures (5, 20 and 40oC). However, there was a significant decrease in lutein content during storage especially at higher temperatures due to oxidative degradation. Nevertheless, the bi-layer nanoemulsions showed a better stability to lutein degradation. Based on in vitro cell toxicity studies on Caco-2 cells using MTT assay, both nanoemulsions did not show toxicity as the cell viability was more than 80% at 10 times or more dilution after 24 hours of incubation. The cellular uptake of lutein was higher in bi-layer nanoemulsions when compared to single layer emulsions. The present work demonstrated that nanoemulsions can be formed using emulsification and a solvent evaporation method. Dried microcapsules of nanoemulsions were formed with similar properties as their original nanoemulsions after reconstitution in water. The nanoemulsions with bi-layer interfacial structure have better stability to environmental changes than single layer emulsions. Nanoemulsions did not show more toxicity than their corresponding conventional emulsions with large oil droplets produced without the use of organic solvent. These have important implications in the use of nanoemulsions for encapsulation lutein or other bioactive compounds for applications in foods and beverages

PEN Joins "ABR"

International PEN is a worldwide organisation of writers, consisting of 130 centres in ninety-one countries. PEN was founded in 1921 to promote friendship and cooperation among writers everywhere, regardless of their political positions. It fights for freedom of expression and opposes political censorship. Above all, it vigorously defends those writers who suffer under oppressive regimes.Australia Council, La Trobe University, National Library of Australia, Holding Redlich, Arts Victori

Energy-Efficient ID-based Group Key Agreement Protocols for Wireless Networks

One useful application of wireless networks is for secure group communication, which can be achieved by running a Group Key Agreement (GKA) protocol. One well-known method of providing authentication in GKA protocols is through the use of digital signatures. Traditional certificate-based signature schemes require users to receive and verify digital certificates before verifying the signatures but this process is not required in ID-based signature schemes. In this paper, we present an energy-efficient ID-based authenticated GKA protocol and four energy-efficient ID-based authenticated dynamic protocols, namely Join, Leave, Merge and Partition protocol, to handle dynamic group membership events, which are frequent in wireless networks. We provide complexity and energy cost analysis of our protocols and show that our protocols are more energyefficient and suitable for wireless networks.

Shadow removal utilizing multiplicative fusion of texture and colour features for surveillance image

Automated surveillance systems often identify shadows as parts of a moving object which jeopardized subsequent image processing tasks such as object identification and tracking. In this thesis, an improved shadow elimination method for an indoor surveillance system is presented. This developed method is a fusion of several image processing methods. Firstly, the image is segmented using the Statistical Region Merging algorithm to obtain the segmented potential shadow regions. Next, multiple shadow identification features which include Normalized Cross-Correlation, Local Color Constancy and Hue-Saturation-Value shadow cues are applied on the images to generate feature maps. These feature maps are used for identifying and removing cast shadows according to the segmented regions. The video dataset used is the Autonomous Agents for On-Scene Networked Incident Management which covers both indoor and outdoor video scenes. The benchmarking result indicates that the developed method is on-par with several normally used shadow detection methods. The developed method yields a mean score of 85.17% for the video sequence in which the strongest shadow is present and a mean score of 89.93% for the video having the most complex textured background. This research contributes to the development and improvement of a functioning shadow eliminator method that is able to cope with image noise and various illumination changes

Road Tales of the Sultan of Pahang

Creative Work

Prevalence and effects of gastro-oesophageal reflux during spirometry in subjects undergoing reflux assessment

Variability during spirometry can persist despite control of technical and personal factors. We postulate spirometry induces gastro-oesophageal reflux (GOR), which may cause variability and affect results of spirometry. Fifty-eight (58) subjects undergoing GOR investigation with oesophageal manometry and 24hr pH monitoring were recruited. Oesophageal dysmotility and GOR were assessed as part of clinical care. Subjects performed 2 sets of spirometry separated by a 10-minute rest period. The assessment of GOR during spirometry procedure (defined by a lower oesophageal pH<4) started from the first set of spirometry and concluded when the second set of spirometry was completed. We calculated variability (%) of FEV1, FVC and PEFR within each set as well as changes over 10-minutes. Twenty-six subjects (45%) recorded GOR during assessment. Of these, 23 subjects recorded GOR during the 10-minute rest period. Four subjects had GOR recorded only during spirometry tests. We did not find variability of spirometry parameters between the groups with and without GOR during spirometry procedure. However, in subjects with GOR, we found small but significant reductions of PEFR (0.5L/s, 8%, p<0.001) and FEV1 (84 mL, 3%, p = 0.048) in the second set of spirometry compared to the first spirometry set. This pilot study demonstrates that GOR can occur during and following spirometry. Presence of GOR during spirometry in this patient population caused small decreases in PEFR and FEV1 when it is repeated 10-minutes later however not increase variability in a single series of measurements

Using continuous spatial configuration for bezel issues in a multi-mobile system

With the rapid moving technology and innovation, the current digital technology such as smartphones and tabletop system have become vital necessities to accommodate people’s daily activities. As a more robust alternative to tabletop system, the multi-mobile system is also benefiting humans’ interaction by combining multiple mobile devices to become a shared and larger touch surface display. This paper demonstrates the study on effects of bezels on a multi-mobile system which allows users to perform collaborative drawing task with mobile devices in an ad-hoc manner. Unfortunately, gaps and physical design of the mobile devices between the mobile displays cause inherent design problems to the multi-display structure. Before conducting the experiments, two prototypes have been designed; high-fidelity prototype (without solution) and iterative prototype (with the continuous spatial configuration). Two user studies have been conducted with the prototypes by observing groups of students performing an interactive drawing task and the findings were compared. Results from the first user study show gaps and disjointed objects were observed in the drawing outcomes, while in the second user study, where the Continuous Spatial Configuration was implemented as a solution to this bezel issue, the gaps and spaces between the screens were eliminated by 94.8%. From this study, it is believed that implementing the Continuous Spatial Configuration in the prototype designs can improve the user experience in the context of collaboration beyond the use of expensive tabletops systems

新加坡闽南话借词 balu 的特征及来源初步调查 = The Nature and Origin of Singapore Southern Min Loanword Balu: A Preliminary Investigation

Master'sMASTER OF ART

Putra BINGO : from pen and paper to digital

Gamification is one of the trends in education that is best suited to the current learning environment. Putra BINGO is a transformative assessment tool that uses gamification techniques. This research starts by elaborating the concept of Putra BINGO and its implementation using traditional method with pen and paper. The feedbacks gathered from the implementation are analyzed and applied to develop a multiplayer educational online game using Unity Game Engine. This paper describes details of the development for its two components; the database and the digital online game. Putra Bingo is available on PC and Android devices. It required additional plugins such as Photon Networking to handle game communication between multiple players. This is crucial to accommodate its test case application as an alternative assessment for teamwork skills using Rubrics and questionnaires. Further research will be conducted to enhance its functionality and user experience after the initial development of the digital online version is completed

A Two-Layer Gene Circuit for Decoupling Cell Growth from Metabolite Production

SummaryWe present a synthetic gene circuit for decoupling cell growth from metabolite production through autonomous regulation of enzymatic pathways by integrated modules that sense nutrient and substrate. The two-layer circuit allows Escherichia coli to selectively utilize target substrates in a mixed pool; channel metabolic resources to growth by delaying enzymatic conversion until nutrient depletion; and activate, terminate, and re-activate conversion upon substrate availability. We developed two versions of controller, both of which have glucose nutrient sensors but differ in their substrate-sensing modules. One controller is specific for hydroxycinnamic acid and the other for oleic acid. Our hydroxycinnamic acid controller lowered metabolic stress 2-fold and increased the growth rate 2-fold and productivity 5-fold, whereas our oleic acid controller lowered metabolic stress 2-fold and increased the growth rate 1.3-fold and productivity 2.4-fold. These results demonstrate the potential for engineering strategies that decouple growth and production to make bio-based production more economical and sustainable