Thesis (Ph.D.)--University of Ottawa, 2008. / Includes bibliographies.

Thesis (Ph.D.)--McMaster University, 2003. / Advisor: Daniel Yang. Includes bibliographical references (leaves 88-97). Also available via World Wide Web.

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on July 8, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Thesis (M.S.)--University of North Texas, May, 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 2006. / Includes bibliographical references and vita.

Proefschrift Rijksuniversiteit Groningen. / Met lit.opg.

Made available in DSpace on 2014-06-11T19:23:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-24Bitstream added on 2014-06-13T20:50:29Z : No. of bitstreams: 1 jorge_pcs_me_arafcf.pdf: 737046 bytes, checksum: dec84c3ab28e6bf448b4986f93072480 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os filmes e revestimentos biodegradáveis são usados para revestir os alimentos, agindo como barreira à umidade e a gases, reduzindo a respiração e as perdas de água por transpiração e desidratação, além do escurecimento enzimático, e mantendo as características do alimento, com aumento da vida de prateleira. Este trabalho teve como objetivos reunir informações sobre o uso da quitosana como revestimento de frutas e vegetais, visando dar suporte ao trabalho experimental; avaliar maçãs revestidas com quitosana comercial, durante o armazenamento à temperatura ambiente, simulando as condições de comercialização das frutas para o mercado interno; avaliar maçãs revestidas com quitosana comercial durante 6 meses de armazenamento sob atmosfera controlada e baixa temperatura, condições de estocagem das frutas para o mercado externo, seguido de armazenamento por 30 dias em atmosfera ambiente e baixa temperatura, visando simular o transporte das frutas para o mercado consumidor no exterior, e posteriormente estocadas à temperatura ambiente, simulando as condições de comercialização; e avaliar maçãs revestidas com quitosana modificada, quando submetidas à temperatura ambiente, visando prolongar a vida de prateleira durante a comercialização, após 6 meses de armazenamento sob atmosfera controlada e baixa temperatura, seguidos de armazenamento por 30 dias em atmosfera ambiente e baixa temperatura. Maçãs ‘Royal Gala’ foram produzidas na safra de 2009, e após a colheita foram separadas em 3 lotes, sendo as frutas do 1o lote revestidas com quitosana comercial; as do 2o lote imersas em solução de ácido acético, que foram usadas como branco e as maçãs do 3o lote não receberam tratamento e foram usadas como controle. Após 6 meses de armazenamento sob atmosfera controlada e baixa temperatura, seguido de mais 30 dias de armazenamento em atmosfera ambiente... / The films and biodegradable coatings are used to coat the food, acting as a barrier to moisture and gases, reducing the respiration and water loss by transpiration and dehydration in addition to the enzymatic browning, maintaining the characteristics of food, with increased of shelf life. This study aimed to gather information about the use of chitosan as a coating for fruits and vegetables, aiming to support the experimental work; evaluate apples coated with commercial chitosan coating during storage at ambient temperature, simulating the real conditions of sale of the fruit for the domestic market; evaluate apples coated with commercial chitosan during 6 months of storage under controlled atmosphere and low temperature, storage conditions of fruit for the export market, followed by 30 days storage under at ambient and low temperature, in order to simulate the transport of fruit to the consumer market abroad, and subsequently stored at ambient temperature, simulating the conditions of marketing; and evaluate apples coated with modified chitosan, at ambient temperature, in order to prolong the shelf life during marketing after six months storaged under controlled atmosphere and low temperature, followed by another 30 days storage under at ambient atmosphere and low temperature. ‘Royal Gala’ apples were produced in 2009 crop and after the harvest they were separated into 3 lots, the first batch of fruit coated with commercial chitosan, those from second lot were immersed in an acetic acid solution and used as blank and the third lot of apples used as controls received no treatment. After 6 storage months under controlled atmosphere and low temperature, followed by another 30 days storage under at ambient atmosphere and low temperature apples without any treatment were separated in 2 lots, being the first batch of fruit coated with modified chitosan, and the second batch used as controls... (Complete abstract click electronic access below)

INTRODUCTION: Foods enter the oral cavity and mix with saliva. Some foods are not well tolerated, for instance, gluten proteins in individuals suffering from celiac disease (CD). Celiac disease is a chronic immune-mediated inflammation of the duodenum, triggered by gliadin component of gluten contained in wheat, barley and rye. In previous studies we showed that oral Rothia bacteria can degrade gliadin in vitro. The objective of this study was to gain more insights into the role of Rothia bacteria and subtilisin-A enzyme on gliadin digestion in vivo, with the ultimate goal to find new therapeutic options for CD. MATERIALS AND METHODS: Part I: Rothia bacterial proteins were analyzed for enzyme activity and subjected to LC-ESI-MS/MS. For in vivo, mice chow was prepared with and without R. aeria. Gliadin epitope abolishment was assessed in the mice stomach contents (n=9/group) by ELISA. Part II: Subtilisin-A was dissolved in various solutions, temperatures and incubation time to assess enzyme activity by using enzyme substrate (Suc-AAPF-pNA). Part III: PEGylation of subtilisin-A (Sub-A) was performed by mixing Sub-A with methoxy-polyethylene glycol (mPEG) and further encapsulated by polylactic-glycolic acid (PLGA). The activity of the modified enzyme to detoxify the immunogenic gliadin epitopes was evaluated at pH3.0. RESULTS: Part I: R. aeria gliadin-degrading enzyme was found to be a member of the subtilisin family. In vivo, gliadins immunogenic epitopes were reduced by 32.6%. Part II: Sub-A dissolved at pH1.5 showed a band of 27kDa, while it only showed bands below 10kDa when dissolved at pH7.0, suggesting auto-proteolysis. The enzyme activity was completely lost at temperatures exceeding 60°C and also reduced 4-fold after 6hr incubation at 37°C. Part III: PEGylation protected Sub-A from autolysis. The microencapsulated Sub-A-mPEG-PLGA showed significantly increased protection against acid exposure in vitro. In vivo, gliadin immunogenic epitopes were decreased by 60% in the stomach of the mice fed with chow containing Sub-A-mPEG-PLGA. CONCLUSION: The results provide proof for the contribution of oral Rothia bacteria to gliadin digestion and pharmaceutical modification can protect Sub-A from auto-digestion as well as from acidic insults, thus rendering the usefulness of coated subtilisins as a digestive aid for gluten degradation. / 2019-01-13T00:00:00Z

Shrinking down into nanoscale, materials exhibit huge property advantages over their bulk form. New forms of carbon at nanoscale have occupied the prominent position in modern materials research. With a very long history accompanying our human civilisation, carbon as a wonder material has once again contributed to our technological advances, as evidenced by the discoveries and research attractions in the last a few decades. Research into fullerenes (C60, C70, etc.), carbon nanotubes (CNTs) and graphene has been continued raising, because of the numerous novel properties associated with these new carbon forms1-3. On top of their excellent electronical, physical and chemical properties, CNTs and graphene also exhibit excellent mechanical properties including ultra-high tensile strength, Young’s Modulus, as well as high thermal conductivities. Research into carbon has also promoted the flourish of many new non-carbon nanomaterials, and typical examples include the inorganic fullerene-like tungsten disulphide (IF-WS2) nanoparticles (NPs), numerous oxide NPs and nanowires that also exhibit various remarkable properties, such as high hardness and anti-oxidation stability. To combine the outstanding performances of both carbon and non-carbon nanomaterials by marrying nanoscale carbon with various metal oxide particles, which forms the backbone of my thesis by carrying out the intensive investigations. In my project it have further validated the advantages of the resulting new carbon-coated NPs in different polymeric matrix composites. The main findings are as follows: 1. A home-made rotary chemical vapour deposit (RCVD) system has been modified and this versatile facility has been applied successfully to produce different types of graphitic carbon-coated nanocomposite particles, from micro- down to nano-scale, including IF-WS2, TiO2, ZnO, Y2O3, Cr2O3, CeO2 and ZrO2 etc. The production can be up to 30 g/per batch, which is 10s times more than using a traditional static furnace, by avoiding severe agglomeration. 2. The resulting coating consists of a few layered graphitic carbon with lattice space 0.34 nm. The thickness of the coating is simply controllable between 1-5 nm, depending on the deposition time (10~60 min), precursor injection flow rate (1.2~2.4 ml/L) and heating temperature (700~900 oC). Furthermore, the oxide core of ZnO@C was removed by heating under the H2/Ar atmosphere, and have successfully generated nano- to micro-scale, hollow, closed, and all-carbon structures. 3. The commercial Nylon 12 is applied to fabricate the metal oxide polymer composite. Using ZnO@C-Nylon 12 composite as an example, at 2 wt% content, the composites have achieved with the ultimate tensile strength increased by 27% (from 47.9 to 59.6 MPa), In particular, at 4 wt% content, the ZnO@C showed an impressive improvement in thermal conductivity of nearly 50% (From 0.21 t0 0.31 W∙m-1∙K-1), comparing 16% improvement for ZnO-Nylon 12 composite. 4. Apart from investigations of nylon composite, intensive studies of the Poly ether ether ketone (PEEK), an important high performance engineering thermoplastics polymer, and its nanocomposites reinforced by IF-WS2 and IF-WS2@C have been carried out in this thesis. The IF-WS2/PEEK composites exhibited not only an improvements of 24% (From 77.6 to 96.7 MPa) in the tensile strength (2 wt%), but also showed an extraordinary increase in thermal conductivity by 190%, from 0.248 to 0.719 W∙m-1∙K-1 at 8 wt%, higher onset decomposing temperatures (54 oC) against the plain PEEK. 5. Moreover, owing to the better dispersal capacity of IF-WS2@C NPs, the ternary IF-WS2@C-PEEK nanocomposites produced in this thesis displayed impressive mechanical properties, increased by 51% (From 77.6 to 120.9 MPa, at 2 wt%), and extremely greater thermal conductivity, with 235% (From 0.248 to 0.831 W∙m-1∙K-1 at 8 wt%), and better stability than the comparison IF-WS2-PEEK composites. The parameters influencing the coating quality and thickness have also been investigated. Further, their interface studies based on the FTIR and XPS techniques have verified the formation of chemical bonding (C=S bonding and carbon π-π bonding), rather than physically bonded together. The successful application of the generic RCVD process can be further extended to the processing of many new particles for an ultrathin carbon coating. Considering the vast amount of literature focusing on carbon, the project further processing of carbon-coated materials in composites could easily be tailored to achieve desired surface contacts with different matrices and leading to the better desired performance, as verified in this thesis for the advanced binary and ternary composites. Finally, this research is expecting to expand the application potentials of PEEK-based nanocomposites in critical areas where thermal conductivity and thermal stability are important.

The contamination of 316L stainless steel surfaces within an electrospray ionisation source of a mass spectrometer is investigated. An accelerated method of contamination is used. Following initial test method development and investigation of the contamination resulting on the ion transfer components (sample cone, outer cone and extraction cone), flat samples are employed within the ionisation source. This enables characterisation of the contamination composition, morphology and build-up with time. Blood plasma is introduced into the mass spectrometer as it is a widely analysed substance that is known to result in contamination. The contamination from a mixture of human blood plasma, diluted in methanol, and a water/acetonitrile mobile phase is found to contain inorganic NaCl crystals embedded in a matrix of organic residues. The morphology shows self-organising features as the contamination builds. A model is proposed to explain the morphology, involving rapid evaporation of the droplets that impinge on the stainless steel surface. Two types of surface modification are considered for the stainless steel: electrochemically grown films and coatings deposited by vapour deposition. A method for electrochemical film growth is developed, enabling nanoporous films to be formed on the stainless steel in 5 M sulphuric acid at 60°C by square wave pulse polarisation between active or transpassive and passive potentials. The films are characterised using glow discharge optical emission spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, Rutherford backscattering spectroscopy and nuclear reaction analysis. The films are shown to be chromium- and molybdenum-rich relative to the substrate, and to consist mainly of sulphates, oxides and hydroxides. The morphology and composition of the films are discussed in relation to the polarisation conditions and mechanism of film formation. A range of vapour deposited coatings are considered: TiN, TiC, TiB2, Graphit-iC, and diamond-like carbon coatings with Si and N2 dopants and with varying sp2:sp3 ratios. In addition, a hydrophobic coating is deposited on the stainless steel by immersion, in order to provide a significant variation in surface energy. Surface analysis of the coatings is carried out, considering their sp2:sp3 ratios, their electrical conductivities, their water contact angle, and the various components of the surface energy. The contamination build-up on the surface of uncoated 316L stainless steel is compared with that on stainless steel with the various surface modifications. A method for quantification of the build-up of contamination on flat samples is developed using white light interferometry. The surface modifications which result in the slowest contamination build-up with time are then applied to the ion transfer components of the mass spectrometer. The robustness of the mass spectrometric response for the selected coated surfaces is compared with that of the uncoated stainless steel. The electrochemically grown films and two of the doped diamond-like carbon coatings are found to be successful in reducing the build-up of contamination.