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Dissertations / Theses on the topic 'Gums and resins'

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Published: 4 June 2021
Last updated: 29 July 2024

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1

Sanares, Anna Marie E. "Tensile bond strength of simplified-step and all-in-one adhesives on light- and chemical- activated composite resins." Thesis, Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23300486.

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2

Nocanda, Xolani Wittleton. "A synthetic and spectrometric study of the initial phases in urea-formaldehyde resin formation." Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1005048.

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In a series ofpreIiminary studies of urea-formaldehyde reactions, the influence of the U:F molar ratio, the temperature and the catalyst were investigated. Subsequently, in a more rigorous evaluation of the influence of four variables on urea-formaldehyde resin formation, viz., U:F molar ratio, pH, temperature and reaction time, a set of twenty reactions were performed using a statistical approach. The results indicate that high resin viscosity is best achieved by using a high U:F molar ratio (1:2) and conducting the reaction at 90°C. Several basic components produced in urea-formaldehyde reactions have been synthesised, characterised by NMR spectroscopy, silylated using bis(trimethylsilyl)trifluoroacetamide and analysed by low resolution mass spectrometry. The use oftriazones as cross-linking agents has been investigated, and a series of 5-substituted triazones have been prepared and their mass fragmentation patterns explored using a combination of low and high resolution mass spectrometry. In order to facilitate interpretation of ¹³C NMR data obtained for U-F resins, internal rotation in various urea derivatives was investigated using variable temperature ¹H and ¹³C NMR spectroscopic study. Signal splittings observed below 247 K have been rationalised in terms of various rotameric structures.
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3

Rajesh, Raja Puthenkovilakom. "Interaction of Tackifier Resins with Water-based and Olefinic Polymers." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26483.

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The objective of this research was to investigate the interaction of tackifier resins in water-based and olefinic polymers for potential pressure sensitive adhesive applications. The first part of this research work was focused on evaluating the usefulness of olefinic block copolymer blends with two amorphous polyolefins (atactic propylene homopolymer and ethylene-propylene copolymer) as potential base polymers for hotmelt pressure-sensitive adhesives. Unsaturated and saturated hydrocarbon resins were studied as potential compatibilizing agents and rheology modifiers. Results show that the chemistry of hydrocarbon resins definitely influence the miscibility of the olefinic block polymer and amorphous polyolefin blends. Ethylene-propylene amorphous copolymer based blends seems to show better miscibility characteristics. Based on the learning from blend miscibility studies, we have successfully made pressure-sensitive adhesives for disposable diaper construction application with olefinic block copolymer/ethylene-propylene amorphous copolymer blends, containing unsaturated hydrocarbon resins and saturated hydrocarbon resins. These olefinic adhesives showed good sprayability characteristics, when applied using air assisted spiral spray equipment (Acumeter Spray Coater) and they showed good adhesive peel properties, which were comparable to the SBS based control. The second part of the study was focused on the evaluation of natural rubber latex-based pressure-sensitive adhesives (PSA) containing three different C5 aliphatic tackifier dispersions with different softening points. Natural rubber-based, water-borne PSA wet rheology (rheology in liquid state) was correlated to morphological analysis on a coating and converting stand point. Dry adhesive rheology was also studied and was then correlated to adhesive properties at different conditions. It has been learned that the type and amount of dispersing agents in tackifier dispersions has a major influence in wet rheology of the PSA formulations. Softening point of the dispersion seems to influence the dry adhesive rheology and adhesive properties such as peel, tack and shear.
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4

Wood, Jessica Lee. "Comparisons of silica polyamine composites and crosslinked polystyrenes resins." CONNECT TO THIS TITLE ONLINE, 2008. http://etd.lib.umt.edu/theses/available/etd-08272008-133833/.

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5

Tripplett, Kirsten Jill. "The ethnobotany of plant resins in the Maya cultural region of southern Mexico and Central America /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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6

Hardesty, Rudd Matthew. "Development of sensitometric techniques for the characterization of stereolitographic resins /." Online version of thesis, 1994. http://hdl.handle.net/1850/11735.

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7

Groff, Kimberly A. "Estimating adsorption equilibria of organic compounds on synthetic resins." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/20494.

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8

Schuck, Susan Marguerite 1957. "FLOWERING PHENOLOGY AND OUTCROSSING IN TETRAPLOID GRINDELIA CAMPORUM GREENE (GUMWEED, POLLINATION, ARIZONA)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276715.

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9

Karam, Hani Shukri. "Characterization of resins in alternative fuel mixtures." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74736.

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"Resins" is a class of compounds believed to play an important role in the conversion processes of coal and coal-related materials into oils. Methods currently used to isolate this fraction, generally lack reproducibility and yield impure and strongly overlapping fractions which do not reflect the actual group-type distribution in the liquid fuel. A separation method based on liquid column chromatography was developed, which divides liquid fuels into eight distinct and minimally overlapping chemical classes: five non-polar (saturated, mono-, di-, tri-, and polynuclear aromatics), one intermediate polar (resins) and two polar (asphaltenes and asphaltols) fractions. Chemical characterization of "resins fractions," derived from two alternative fuels (coal-derived liquid and sugarcane bagasse), was achieved by first subjecting them to acid-base-neutral separation, followed by analysis of each subfraction by GC/MS. Identification of the eluted components was carried out utilizing a library search system, by comparing retention times (indices) of 150 model compounds believed to exist in liquid fuels, on two fused silica capillary columns (Carbowax 20 M and SE-54), and by mass spectral interpretation. GC/MS results indicate that "resins" are mainly composed of weakly acidic (phenols, indanols, naphthols), mildly basic (benzoquinolines, chloroanilines, etc.), neutral-nitrogen (indoles and carbazoles), and oxygen (carbonyl) compounds, and are free of hydrocarbons.
Ph. D.
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10

Khattab, Ahmed. "Exploratory development of VARIM process for manufacturing high temperature polymer matrix composites." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4186.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Vita. Includes bibliographical references.
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11

Bhat, Prabhas M. "Simulation and validation of mold filling during Compression Resin Transfer Molding (CRTM) process." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 122 p, 2008. http://proquest.umi.com/pqdweb?did=1459914951&sid=8&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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12

McAninch, Ian M. "Evaluation of randomly oriented carbon nanotubes as reinforcement in plant oil resins." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 241 p, 2008. http://proquest.umi.com/pqdweb?did=1625774501&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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13

Butt, Arif. "Resin flow characterization during thermoplastic composite consolidation." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12010.

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14

Weideman, Mark H. "An infiltration/cure model for manufacture of fabric composites by the resin infusion process." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03032009-040744/.

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15

Roberts, Karen Narelle 1972. "An investigation of core-shell rubber modified vinyl ester resins." Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/8416.

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16

Makris, Stephen P. "Removal of resin and fatty acids from pulp mill wastewater streams." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-01062004-132204/unrestricted/makris%5Fstephen%5Fp%5F200405%5Fphd.pdf.

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Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2004.
Lucian A. Lucia, Committee Member; Spyros G. Pavlostathis, Committee Member; Sujit Banerjee, Committee Chair; Yulin Deng, Committee Member; Howard L. Empie, Committee Member. Includes bibliographical references (leaves 146-155).
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17

Fernandes, Frederico Silva de Freitas. "Efeito do uso diário de um limpador químico enzimático sobre o biofilme de Candida albicans formado sobre materiais para base de próteses removíveis." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288090.

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Orientador: Altair Antoninha Del Bel Cury
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-17T11:17:25Z (GMT). No. of bitstreams: 1 Fernandes_FredericoSilvadeFreitas_D.pdf: 739091 bytes, checksum: 727731c2061dd20f60d28b6f01753ccf (MD5) Previous issue date: 2011
Resumo: Os limpadores químicos de prótese têm sido bastante indicados para o controle do biofilme formado sobre próteses removíveis de pacientes com comprometimento motor. Apesar de estudos prévios terem mostrado que uma única imersão nesses agentes é capaz de reduzir os níveis de Candida albicans do biofilme formado sobre próteses removíveis, pouco se sabe sobre o efeito do uso diário desses limpadores sobre o biofilme residual de Candida. Assim, o objetivo desse estudo foi avaliar a eficácia do uso diário de um limpador químico enzimático sobre o biofilme de C. albicans formado sobre a superfície de materiais para confecção de próteses removíveis; bem como a atividade enzimática das células de Candida desse biofilme após exposições diárias a esse limpador de prótese. Foram confeccionados espécimes de resina de polimetilmetacrilato (PMMA) e resina de poliamida, nos quais foi realizada, inicialmente, a padronização da rugosidade de superfície (0,34 ± 0,02 ?m). Após a formação da película adquirida, os espécimes foram divididos aleatoriamente em 12 grupos (n=9) para formação do biofilme de C. albicans por 72 horas. Após esse período, os espécimes foram tratados por 1, 4 ou 7 dias, sendo realizado um tratamento por dia, com um limpador químico enzimático (Polident 3 Minutes) ou com água destilada (controle negativo). Após os respectivos períodos de tratamento, os microrganismos remanescentes foram removidos da superfície dos espécimes por meio de ondas ultra-sônicas (7W por 30s). Em seguida, as unidades formadoras de colônia (UFC) foram calculadas e a atividade enzimática das células remanescentes foi avaliada. Os dados foram submetidos à ANOVA um fator ou dois fatores, seguido do teste de Tukey-Kramer. O biofilme de Candida albicans formado sobre a resina de poliamida apresentou maiores níveis de Candida e uma maior atividade fosfolipásica que o biofilme formado sobre a resina de PMMA (p<0,001). O limpador químico enzimático reduziu significantemente os níveis de Candida albicans em todos os períodos avaliados (p<0,001), entretanto os níveis desse microrganismo aumentaram com o tempo, sendo observada diferença estatisticamente significante entre os períodos avaliados (p<0,001). As exposições diárias a esse limpador químico aumentaram a virulência das células de Candida, no que diz respeito à atividade fosfolipásica. Nas condições desse estudo, conclui-se que o uso diário do limpador químico enzimático não foi capaz de impedir a proliferação de Candida albicans no biofilme residual, apesar de ter interferido no crescimento desse biofilme.
Abstract: Chemical cleansing with immersion in denture cleansers has been indicated for denture biofilm control in patients with limited motor capacity. Although previous studies have shown that a single immersion in those agents is able to substantially reduce Candida albicans biofilm levels, the effect of the routine use of denture cleansers on the Candida residual biofilm is poorly understood. This study evaluated the efficacy of daily use of an enzymatic denture cleanser on C. albicans biofilm formed on denture base materials; and the enzymatic activities of Candida biofilm cells after daily exposure to this cleanser agent. Polymethyl methacrylate (PMMA) and polyamide resins specimens were prepared (n=54), and their surface roughness was standardized (0.34 ±0.02 ?m). Saliva-coated specimens were randomly divided by lottery into 12 groups (n=9) for biofilm assay. C. albicans biofilm was formed for 72 hours, and then specimens were treated for 1, 4 or 7 days, once a day, with an enzymatic cleanser (Polident 3 Minutes), or distilled water (negative control). Remaining adherent microorganisms were removed from the treated specimens by ultrasonic waves at 7 watts for 30 seconds, and then colony-forming units (CFU) were calculated and remaining cells enzymatic activities were determined. Data were analyzed by 1-way or 2-way ANOVA followed by the Tukey-Kramer test. C. albicans biofilm formed on polyamide resin showed significantly higher Candida levels and phospholipase activity (p<0.001) than biofilm formed on PMMA resin. The enzymatic cleanser significantly reduced C. albicans levels in all evaluated periods (p<0.001); however, the number of this microorganism increased with time, showing statistical difference among the treatment periods (p<0.001). The daily exposure to the denture cleanser increased Candida cells virulence, with regard to phospholipase activity. Our study has shown that the enzymatic cleanser daily use did not prevent C. albicans proliferation in residual biofilm; however, this agent reduced this fungus rate of growth.
Doutorado
Protese Dental
Doutor em Clínica Odontológica
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18

Howes, Jeremy C. "Interfacial strength development in thermoplastic resins and fiber-reinforced thermoplastic composites." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/77899.

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The objective of this study was to develop tests that could be used to characterize autohesive strength development in amorphous thermoplastic resins and fiber-reinforced thermoplastic prepregs. All tests were performed using polysulfone P1700 thermoplastic resin and AS4/P1700 graphite-polysulfone prepreg. Two test methods were examined to measure autohesion in neat resin samples. These included an interfacial tension test based on the ASTM tensile adhesion test (ASTM D897) and a fracture toughness test using a compact tension (CT) specimen (based on the ASTM toughness test for metals ASTM E399-83). The interfacial tensile test proved to be very difficult to perform and with an unacceptable amount of data scatter. The data obtained using the compact tension test were repeatable and could be correlated with temperature and contact time. Autohesive strength development in fiber-reinforced prepreg samples was measured using a double cantilever beam (DCB) interlaminar fracture toughness test. The fracture mechanisms were determined to be different in the healed DCB specimen than the virgin specimen due to resin flow at the crack plane during the healing tests. The CT test was found suitable for use in determining the autohesive properties and self-diffusion coefficient of neat resin. The DCB test, although not suitable for autohesive testing, indicated that repair of thermoplastic matrix composites is possible; however, the repair will not be as tough as the virgin material.
Master of Science
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19

Kambly, Kiran. "Characterization of curing kinetics and polymerization shrinkage in ceramic-loaded photocurable resins for large area maskless photopolymerization (LAMP)." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31740.

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Das, Suman; Committee Member: Halloran, John; Committee Member: Henderson, Clifford; Committee Member: Kalaitzidou, Kyriaki. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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20

Siu, Wing Kwan May 1979. "Applications and microwave assisted synthesis of poly(ethylene glycol) modified Merrifield resins." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82427.

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A microwave assisted methodology was developed to modify Merrifield resins (1-2% cross-linked containing 1.0-3.5 mmol Cl-/g) with different nominal molecular weights PEG (200-1000). The synthesis was also carried out by conventional heating to assess the differences between the two procedures. The most efficient synthesis was achieved by using microwave and by using PEG with molecular weight 200 and MR 2% crosslinked containing 1.25 mmol Cl -/g. The structural elucidation was carried out using Fourier transform infrared (FTIR) spectroscopy and elemental analyses. Upon pyrolsis-GC/MS analysis of the PEGylated MR, the PEG showed the tendency to undergo thermal degradation by the loss of a smaller PEG fragments. This observed degradation of PEG was less prominent during microwave assisted synthesis compared to conventional heating, in addition to faster reaction rates and higher yields. As expected, the PEGylated MR showed improved swelling properties in polar solvents. The chemical reactivity of the PEGylated Merrifield resin was confirmed by the esterification with pyruvic acid and by the substitution of hydroxyl group using thionyl chloride. In addition, the PEGylated MR was converted into (1) polymer-supported acid/base or redox indicator by the attachment of a blue organic dye - 2,6-dichloroindophenol (DCIP) through a nucleophilic substitution reaction and (2) beta-cyclodextrin trap, a water insoluble inclusion-complex, by immobilization of beta-cyclodextrin through cross-linking with 1,6-hexamethylene diisocyanate reagent.
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21

Lawrence, Jeffrey M. "Methodologies for resin flow prediction and manipulation in liquid composite molding processes." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 19.79Mb, 374 p, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3181855.

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22

Chohra, Mourad. "Modeling of filtration process during manufacturing of functionally graded composites with particulate suspensions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 1.57 Mb., 142 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430752.

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23

Do, Pete Binh. "Effect of textile preform structure on the mechanical properties and failure modes of composites from resin transfer molding process." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/8512.

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24

Hanneman, Andrew J. S. "Modification of wood extractives and hemicelluloses during thermomechanical pulping : implications for newsprint sizing /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/5540.

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25

Howdeshell, Kembra L. "Effects of exposure to environmentally-relevant levels of bisphenol A on mouse reproductive physiology and maternal behavior /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060107.

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26

Govignon, Quentin Paul Nicéphore Marc Marie. "Monitoring and simulation of the filling and post-filling stages of the resin infusion process /." e-Thesis University of Auckland, 2009. http://hdl.handle.net/2292/5630.

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Thesis (PhD--Mechanical Engineering)--University of Auckland, 2009.
" A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering." "Centre for Advanced Composite Materials." Includes bibliographical references.
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27

Shields, Karen M. "Resin transfer molding with powder-coated preforms." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/17988.

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28

MacRae, John Douglas. "Development and verification of a resin film infusion/resin transfer molding simulation model for fabrication of advanced textile composites." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-05092009-040737/.

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29

Cao, Xia. "Integrated Analysis of Low Profile Unsaturated Polyester and Vinylester Resins Cured at Low Temperatures." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039038413.

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30

Kenerson, Jonathan E. "Quality Assurance and Quality Control Methods for Resin Infusion." Fogler Library, University of Maine, 2010. http://www.library.umaine.edu/theses/pdf/KenersonJE2010.pdf.

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31

Scharf, Melissa. "The rheological effect of hydrocolloids on selected attributes of a lemon flavored beverage containing artificial sweeteners." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-01102009-063855/.

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32

Dunkleberger, Alisha J. "Bondo : not just for cars." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1345337.

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This creative project was a study of combining large-scale ceramics and polymer resin (Brandname: Bondo) vessels. This project came out of an earlier experiment combining metals and resin, and therefore the interest in combining clay and resin was a natural transition for me, since ceramics was my major focus. I had a definite interest in the challenge of marrying two very different materials; clay and resin, and by using this combination I would make vessels that were visually successful and engaged the viewer.The technical basis for all of the ceramic elements of the vessels is wheel throwing. The molds made for the resin parts of the piece were wheel thrown as well. This project was very unique and there was little documented technical information for me to rely on other than personal experimentation and ceramic knowledge.The visual elements of clay with its opaqueness, and resin with its translucent qualities offered great visual contrast. The use of color contrast between warm and cool colors became an important element of the pieces.From an expressive standpoint, I feel the form of the vessels is viewed as solid and confrontational, yet very compelling. The smooth surfaces and the lush vibrant colors compel the viewer to examine the forms. The pieces are commanding in size and strength, so the viewer is somewhat hesitant to view for too long. There is a visual push/pull, a contrast between these simple yet over-scaled layered forms that evokes an emotional push/pull as well.
Department of Art
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33

Wells, Ricardo Angelo. "Comparison of distribution coefficients of 14 elements on three cation exchangers." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2641.

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Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017.
Certain resins used in ion-exchange separation techniques have become very expensive. Although ion-exchange is an economical method to soften water it is important to keep the cost low during the process. Any exorbitant costs will make a process unattractive and eventually obsolete. Bio-Rad AG MP-50 macroporous resin (supplied by Bio-Rad Laboratories, Ltd.) at present costs approximately R20000 (twenty thousand rand) for 500 g compared to Amberlyst 15 R840.00 for 500 mL and Dowex Marathon MSC R312.34 macroporous resin for 500 mL (both supplied by Dow, Rohm and Haas Co). This motivated the research to determine by a comparative study if there is any difference in the efficiency and effectiveness in the quantitative analysis of trace elements when these resins are used. The following elements will be used to determine distribution coefficients for the elements on these resins: Mn, Fe(III), Co, Ni, Cu, Zn, Al, Ag, Cd, In, Ga, Tl, Pb and Bi in 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 4.0 M nitric acid solutions. Another question is whether there is a difference or a preference when selecting either a microporous or a macroporous resin for the ion-exchange separation. Determination of distribution coefficients for 46 elements had been done by Strelow (Strelow F. W., 1984) in nitric acid on Bio-Rad AG 50W-X8. The results obtained in this study will be compared with the distribution coefficients obtained by Strelow. The Bio-Rad, Amberlyst and Dowex resins were stirred for approximately 30 minutes in deionised water and then packed in a column. Impurities in the resin column were eluted with 5 M HCl and the resin was then rinsed with deionised water to remove the acid. Thereafter the resins was rinsed out of the column with deionised water, filtered off and then dried under vacuum in an oven at 60 0C for approximately 24 hours. Stock solutions of the elements were prepared as 0.1 M solutions and then diluted with deionised water to obtain solutions having the respective concentrations of 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 M. Quadruplicate reference standards of each element were prepared. Distribution coefficients of the elements on each resin were determined as described by Strelow (Strelow F. W., Distribution coefficients and ion exchange behaviour of some chloride complex forming elements with Bio Rad AG50W - X8 cation exchange resin in mixed Nitric-Hydrochloric acid solutions, 1989). From the distribution coefficients, obtained from the ICP-OES data, a selectivity series for the 14 elements, mentioned above, was arranged in the decreasing order for each resin’s affinity for the elements. The distribution coefficients also give an indication whether the elements can be quantitatively separated by the cation exchangers in nitric acid media. Elution curves for some elements were done to establish the experimental conditions for quantitative separations of the elements by column cation exchange chromatography.
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34

Brown, Janis Michelle. "Production of controlled networks and morphologies in toughened thermosetting resins using real-time, in-situ cure monitoring." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40306.

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Chemical and physical changes occur during the processing of toughened thermosetting resins. A number of properties are related to the type and sequence of these changes. There is a need for the development of in-situ real-time sensors to follow these changes. Once these sensors are developed, they can be used to preferentially select networks and/or morphologies by feedback-controlled "intelligent" processing. A practical, durable, inexpensive Fourier Transform NearInfrared (FTNIR) fiber optic sensor was developed and the cure of a model toughened cyanate as well as a commercial paste adhesive was followed with this sensor In the near-infrared. The design was suitable for many applications. A mold was designed to incorporate the fiber sensor for composite applications. The growth of the normalized triazine (crosslink) peak appeared to follow second order kinetics. The normalized peak reflected chemical as well as physical changes. Analysis of the individual peaks showed significant physical effects. Conversion based on triazine concentration did not follow second order kinetics.
Ph. D.
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35

Saunders, Heath G. "Wax distribution quantification using digital image analysis techniques." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020230/.

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36

Schwarzlaff, Sabine Susanne. "Guar and locust bean gums as partial replacers of all-purpose flour in bread : an objective and sensory evaluation /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020247/.

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37

Cecere, James A. "Structure-property relationships of functionalized modifiers for thermosetting resin systems." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53927.

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Conventional methods of imparting toughness to ordinarily brittle thermosetting resins involve the incorporation of a second, discreet phase. Traditionally, this phase has been either a functionalized butadiene-acrylonitrile based elastomer or an unreactive thermoplastic. This dissertation describes the preparation, characterization, and evaluation of new functionalized polysiloxane elastomer and thermoplastic modifiers and their morphological implications to the toughening and physical behavior of, principally, epoxy thermosetting systems. Secondary amine-terminated poly(dimethyl-co-diphenyl siloxane) oligomers were found to be comparable tougheners to acrylonitrile-butadiene rubbers for a bisphenol-A based epoxy resin. The system that imparted the highest toughness was comprised of statistically placed 40% diphenyl and 60% dimethylsiloxane units with Mn̅ of 5000 g/mole loaded at 15% w/w. This composition resulted in a discreet second phase consisting of l μm spherical particles which were evenly dispersed throughout the cured epoxy matrix. Amine-terminated poly(arylene ether ketone) and poly(arylene ether sulfone) thermoplastics were reacted into an EPON 828/4,4'·DDS system. However, the polyketones proved to be ineffective toughening agents due to an incompatibility resulting in macroscopic phase separation. In contrast, the functionalized polysulfones were shown to be effective toughening agents, with the resultant morphology primarily a function of percent incorporation. At ~15% w/w, the polysulfone separated as l-2μm discreet particles while a 30% loading level resulted in a bicontinuous “honeycomb” morphology. The amine endgroups were shown to be necessary in controlling morphology and maximizing toughness. The polysulfone oligomers were also incorporated into a graphite fiber reinforced epoxy composite. Although improved mechanical properties were achieved, the toughness values were not as high as predicted by the neat resin evaluation. The morphology was less definable due to the complex nature and dimensions of the carbon fiber/matrix interactions. Finally, melt processing experiments indicated that amine-terminated polysulfones may act as effective processing aids for brittle bismaleimide systems, by reacting with the BMI, possibly via a Michael addition. This results in a chain extension and higher molecular weight without premature gelation occurring.
Ph. D.
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38

Faria, Tatiane Dias Marques. "Adesivo de borracha termoplastica reforçado com nanoargila." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267172.

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Orientador: Julio Roberto Bartoli
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Adesivos preparados com borracha termoplástica são de grande importância na indústria de adesivos sensíveis à pressão devido à sua grande versatilidade de processamento. Porém, geralmente estes adesivos apresentam desvantagens em ensaios em que temperaturas na faixa de 90º C são requeridas. Neste trabalho, foram preparados adesivos de borracha termoplástica com nanoargilas do tipo montmorilonita com duas organofilicidades diferentes, a fim de se estudar o desempenho das propriedades adesivas de peel, tack, shear e SAFT (Shear Adhesion Failure Temperature), além das propriedades de flamabilidade. Primeiramente, foram preparados masterbatches de resina hidrocarbônica e nanoargilas Cloisite® 20A e 25A (sendo a 20A mais organofílica) pelo processo de intercalação do fundido, através de extrusora dupla-rosca. Análises de difração de raios X e microscopia eletrônica de transmissão sugerem uma esfoliação da Cloisite® 20A na resina e uma intercalação da Closite® 25A. Depois, os masterbatches foram utilizados na preparação de compostos adesivos nas concentrações de 5 e 10 phr de nanoargilas, também em extrusora dupla-rosca. Ensaios de difração de raios X sugereriram a esfoliação das nanoargilas em todos os compostos adesivos, porém, pelas análises de microscopia eletrônica de transmissão, a amostra preparada com a Cloisite® 20A, na concentração de 10 phr, apresentou uma esfoliação relativamente maior. Ensaios dinâmico-mecânicos apresentaram significativo deslocamento da temperatura de transição vítrea (pico de tan d) para os adesivos preparados com a Cloisite® 20A, sugerindo a formação de nanocompósitos. Os módulos de armazenamento, na faixa de 70 a 93º C, obtidos com estes compostos adesivos, apresentaram também valores inferiores aos demais adesivos, sendo que a uma concentração de 10 phr o módulo foi o menor obtido e a uma concentração de 5 phr o módulo apresentou um valor intermediário. Os ensaios nas fitas adesivas demonstraram um maior equilíbrio de propriedades adesivas para o adesivo preparado com a Closite® 20A numa concentração de 5phr, apresentando este, módulo ótimo na faixa de temperatura de 70 a 93º C. Este adesivo manteve as propriedades de peel e tack próximas às do adesivo referência, melhorando significativamente as propriedades de shear a 70 e 93º C e SAFT. O ensaio de flamabilidade não foi conclusivo pois as amostras foram consideradas inflamáveis e houve muita variabilidade nos resultados obtidos para os tempos de queima.
Abstract: Adhesives prepared with thermoplastic rubber are very important for the pressure sensitive adhesives industry due to its easy processability. However, these adhesives are usually not indicated for applications in which temperature resistance around 90o C is required. In this study, thermoplastic rubber adhesives with nanoclays were prepared, in order to evaluate its adhesion performance: peel, tack, shear and SAFT. Moreover, the flammability properties are also going to be studied. Firstly, masterbatches of nanoclays Cloisite® 20A and 25A (being 20A more organophilic) and hydrocarbon resin were prepared through melt intercalation process, using a twin-screw extruder. Analysis through X ray difraction and transmission electronic microscopy suggests the exfoliation of Cloisite® 20A in the resin and the intercalation of Cloisite® 25A. After that, the masterbatches were used in the hot melt adhesives preparation, giving the nanoclays concentration of 5 and 10 phr. This process was also made in the twin-screw extruder. Analysis through X ray difraction showed again the exfoliation of the nanoclays in the adhesive, however, transmission electronic microscopy suggests that the sample prepared with Cloisite® 20A and concentration of 10phr presented the higher level of exfoliation. Dynamic-mechanical analysis showed a glass transition temperature shift (tan d peak) for the adhesives prepared with Cloisite® 20A, suggesting the formation of nanocomposites. The storage modulus of these adhesives, in the range from 70 to 93oC, showed values lower than the reference and other adhesives, being the adhesive with 20A and 10 phr the lowest modulus and the adhesive with 20A and 5 phr the intermediate value for the modulus. The testing done with the adhesive tapes, showed more balanced properties for the adhesive prepared with Cloisite® 20A and 5 phr, suggesting an optimal value for the modulus. This adhesive kept peel and tack properties close to the reference and showed improvements in properties like: 70 and 93oC shear and SAFT. Flammability testing was not conclusive because all samples were considered flammable and lots of variability was oberved in the burning times obtained.
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química
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39

Rodrigues, Karen da Silva. "Reciclagem de PETpc na incorporação da formulação de uma tinta em pó." reponame:Repositório Institucional da UCS, 2016. https://repositorio.ucs.br/handle/11338/1394.

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A crescente utilização de embalagens de PET tem como conseqüência elevada geração de resíduos sólidos. A reciclagem é uma alternativa para a reutilização deste material polimérico. Este trabalho tem como objetivo avaliar a influência da incorporação de 2,5, 5 e 7,5% (m/m) de pó de PETpc em substituição à carga mineral sulfato de bário (BaSO4) em uma tinta em pó base resina poliéster de formulação comercial. Foram utilizados dois processos de obtenção da tinta: no processo 1, a tinta foi processada na extrusora dupla rosca (processo convencional) e no processo 2, primeiramente a resina e o PETpc foram extrusados na extrusora mono rosca e após todos os componentes da tinta foram homogeneizados na extrusora dupla rosca. As tintas foram aplicadas em corpos de prova de aço carbono AISI 1005 de dimensões 70 mm x 120 mm x 0,75 mm submetidos ao pré-tratamento de fosfatização de zinco. O pó de PETpc, o PET flake e as tintas em pó obtidas foram caracterizadas a partir de análise granulométrica, espectroscopia de infravermelho por transformada de Fourier (FTIR), análise termogravimétrica (TGA) e calorimetria exploratória diferencial (DSC). O efeito da incorporação do pó de PETpc nas propriedades mecânicas e de desempenho à corrosão das tintas foi avaliado com ensaios de medida de brilho, aderência, flexibilidade, resistência ao impacto, ângulo de contato, exposição à névoa salina (NS), espectroscopia impedância eletroquímica (EIE) e análises de microscopia eletrônica de varredura por emissão de campo (MEV/FEG). Os resultados evidenciaram que a incorporação do pó de PETpc na tinta em pó não interferiu no comportamento térmico das tintas obtidas com o processo 1, porém reduziu o brilho e visualizou-se trincas na concentração de 2,5% de pó de PETpc. Nas tintas obtidas a partir do processo 2, observou-se alteração no comportamento térmico das tintas verificado nos ensaios de TGA e DSC, bem como alterações no filme de tinta com aumento do brilho e também no ensaio de flexibilidade que com 5% de pó de PETpc apresentou melhor resultado. Nos ensaios de impacto, névoa salina, ângulo de contato e aderência, não houve alteração nos resultados obtidos com os dois processos utilizados. No ensaio de EIE as tintas com adição superior a 2,5% de pó de PETpc não apresentaram corrosão. Desta forma, os resultados indicam que a incorporação de pó de PETpc em uma tinta em pó base resina poliéster pode ter uma utilização promissora, pois melhora as propriedades da tinta e ainda pode ser uma alternativa para a utilização dos resíduos de PETpc.
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The Growing use of PET packaging results in high generation of solid waste. Recycling is an alternative For a polymeric material this reuse. This study aims to evaluate the influence of incorporation of 2.5, 5 and 7.5% (m/m) of PETpc powder to replace the mineral filler barium sulfate (BaSO4) in a coating base polyester resin. Two coatings obtain procedures were used: method 1 coating was processed in twin screw extruder (conventional method) and the method 2, first resin and PETpc were extruded in the single extruder thread and after all coatings components were homogenised in twin screw extruder. The coatings were applied on carbon steel AISI 1005 samples of 70 mm x 120 mm x 0.75 mm dimensions with prephosphating treatment were used. The PETpc powder, the PET flake and powder coatings obtained were characterized from thermal analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of incorporating of PETpc powder on mechanical properties and corrosion resistance of the coatings were evaluated by gloss measurement tests, adhesion, flexibility, impact resistance, exposure to salt spray (NS) electrochemical impedance spectroscopy (EIS) and analysis of scanning electron field emission (SEM/FEG). The results showed that the incorporation of PETpc powder in the powder coatings did not affect the thermal behavior of the coatings obtained by the process 1, but reduced gloss and in the flexibility test visualized cracks in the concentration of 2.5% PETpc powder. In the coatings obtained from the process 2 was observed change in the thermal behavior of the coatings seen in the TGA and DSC testing, as well as changes in the coatings film with increase in the gloss and also in the flexibility test as with 5% PETpc powder showed the better results. Impact tests, salt spray, contact angle and grip there was no change in the results obtained with the two processes used. In test EIS powder coatings adding more than 2.5% PETpc powder showed no corrosion. Thus, the results indicate that the incorporation of PETpc powder on powder coating based polyester resin may be a promising use for improving the properties of the coating and may also be an alternative to the use of waste PETpc.
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40

Conrad, Matthew. "Experimental investigations and theoretical modeling of large area maskless photopolymerization with grayscale exposure." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45965.

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Large Area Maskless Photopolymerization (LAMP) is a technology being developed to fabricate integrally-cored ceramic molds for the investment casting of turbine airfoils. In LAMP, ultraviolet (UV) light in the form of bitmap images is projected from a spatial light modulator (SLM) onto a photocurable ceramic material system (PCMS). Exposed and unexposed regions are determined through black and white portions of the bitmaps, respectively. UV light induces photopolymerization and the formation of an insoluble solidified network. Three-dimensional structures are built layer-by-layer through sequential application and curing of PCMS layers of 100 micron thickness. To date, ceramic molds fabricated using LAMP have been successfully implemented in investment casting of single-crystal turbine airfoils without internal cooling schemes. Two particularly important challenges for the fabrication of airfoil molds with internal cooling passages are: (a) fabrication of unsupported structures in the mold geometry and; (b) mitigation of internal stresses that arise during layer-by-layer build-up due to volumetric shrinkage during photopolymerization. Unsupported geometries arise in nearly every cored airfoil mold and often in a location where support structures cannot be easily removed after fabrication. Internal stresses generated by volumetric shrinkage can lead to cracking during binder burnout (BBO), sintering and casting. This thesis aims to simultaneously address these challenges through the investigation of grayscale exposure to control the degree of monomer conversion during photopolymerization of single and multiple layers. The effective intensity of the UV light incident on the monomer system can be reduced by selectively turning off pixels within the nominally "white" or "on" regions of the projected bitmaps, effectively producing an exposure with a lower light intensity. In an effort to reduce internal stresses in the mold, the grayscale exposure can be tuned to create regions of uncured or partially cured monomer within the mold geometry to reduce the connectivity between cured regions and thus reduce the net effect of volumetric shrinkage. Grayscale exposure can also be used to generate support structures with a low degree of polymerization to create a gel state beneath and surrounding the unsupported segments of the mold, which can be washed away after completion of mold fabrication. In order to successfully utilize grayscale techniques in LAMP, the cure depth must be predicted. This is accomplished through cure depth measurements at different exposure times to develop a "working curve." In addition, the degree of monomer conversion and its relation to cure depths resulting from grayscale exposure must be understood. Measurements of the degree of conversion are obtained through Fourier Transform Infrared spectroscopy (FTIR). Empirical models are developed and compared to theoretical predictions. Also, the scattering length pixelation model is introduced as a technique to predict the light intensity distribution within the PCMS for exposure patterns at multiple length scales. Results from these grayscale investigations are then applied to LAMP and the effectiveness of grayscale to fabricate unsupported geometries and internal stresses from volumetric shrinkage is discussed.
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41

Schwarzlaff, Sabine S. "Guar and locust bean gums as partial replacers of all-purpose flour in bread: an objective and sensory evaluation." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/45620.

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The purpose of this research was to determine whether all-purpose flour could be partially replaced with locust bean gum (LBG) and guar gum, and produce an acceptable bread product. A pilot study determined that up to 4% gum replacement for flour was feasible. All bread treatments were evaluated objectively by standing height, texture, color, and cell size. Moisture determinations were obtained for each bread variation. Sensory quality was examined by consumer testing. The amount of heat required to break the hydrogen bonds in amylopectin, indicative of bread staling, was measured by differential scanning calorimetry (DSC) for all bread treatments. Two percent LBG replacement significantly increased standing height. Firmness of bread increased with an increase in gum; the 4% guar bread was significantly firmer. Crumb color was not significantly different for any of the five bread treatments. Crust color, however, was significantly lighter for the control in comparison to the 2 and 4% guar, and 4% LBG breads. Two percent guar produced a more even cell size distribution throughout the bread crumb. For all 5 bread formulations moistures were not significantly different. Sensory evaluation determined a significant difference between the control and 4% LBG. The 4% LBG bread was preferred, although not significantly. Both gums were found to retard bread staling and 2% LBG was the most effective in lengthening the shelf life of the bread product. Objective and sensory evaluation indicated both gums produced acceptable bread products for consumer consumption and possible use in further research.
Master of Science
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42

Golestanian, Hossein. "Modeling of process induced residual stresses and resin flow behavior in resin transfer molded composites with woven fiber mats /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841293.

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43

Sharifi, Mohammad S. "Fractionations and analysis of trunk exudates from pistacia genus in relation to antimicrobial activity." Thesis, View thesis, 2006. http://handle.uws.edu.au:8081/1959.7/35517.

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H. pylori is one of the most significant discoveries in gastroenterology in the past century. It is associated with a wide range of gastroduodenal pathologies and gastric cancer. Antibiotic resistance in H. pylori has emerged as a significant clinical problem. The body of work contained within this dissertation was carried out to investigate an alternative therapy based on observations of the traditional therapy for gastric disease in the Middle East. One of these traditional therapies centres on plants belonging to the Pistacia genus. This study represents the first reported investigation into the composition and biological activity of the trunk bark exudates of Pistacia atlantica Kurdic (P. a. Kurdica), Pistacia atlantica Mutica (P. a. Mutica) and Pistacia atlantica Cabolica (P. a. Cabolica), resinous gums that have been termed here ‘Kurdica Gum’, ‘Mutica Gum ’ and ‘Cabolica Gum ’ respectively. The antimicrobial screening of the trunk exudates of the genus Pistacia led to the characterization of the most active fraction of the Kurdica gum. This fraction was subsequently subjected to sub-fractionation leading to the discovery of fundamentally new information that went beyond H. pylori, expanding the original parameters of the project. The extent of these findings suggests that new classes of antibiotics might have been discovered. Primary studies on their structure and potential mechanism of action has been undertaken. Thirteen novel antimicrobial agents were identified. Based on the characteristics of these isolated fractions, 50 new compounds were modelled; of which 30 hypothetically have an MIC consistent with contemporary antibiotics and could represent viable lead compounds for commercial development.
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44

Fernandes, Frederico Silva de Freitas. "Efeito de limpadores quimicos sobre biofilmes de Candida formados sobre a superficie de materiais para base de proteses removiveis." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288368.

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Orientadores: Altair Antoninha Del Bel Cury, Tatiana Pereira Cenci
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Biofilme de Candida spp formado na superfície de próteses removíveis é considerado o principal fator etiológico da candidose, a qual é a infecção oral fúngica mais prevalente em humanos. Em pacientes com comprometimento motor, o uso de limpadores químicos é indicado para o controle desse biofilme, entretanto, pouco se conhece sobre o efeito desses agentes sobre o biofilme de Candidas não-albicans. Adicionalmente, a literatura é escassa de estudos avaliando a formação de biofilme de Candida sobre novos materiais para base de próteses. Assim, o objetivo desse estudo foi avaliar o efeito de limpadores químicos sobre o biofilme mono e multi-espécie de Candida formado sobre a superfície de materiais para confecção de próteses removíveis. Foram confeccionados espécimes de resina de polimetilmetacrilato (PMMA) e resina poliamida, os quais, após a padronização da rugosidade de superfície (0,34 ± 0,02 µm), foram submetidos à avaliação da energia livre de superfície (ELS) ou à formação de biofilme. Biofilme de Candida albicans e/ou Candida glabrata foi formado por 72 h, sendo os espécimes, previamente, submetidos à formação da película adquirida. Após o período de formação do biofilme, os espécimes foram submetidos aos tratamentos, segundo o tempo recomendado por cada fabricante: limpador químico enzimático (3 min); limpador químico sem enzimas (5 min); e hipoclorito de sódio (NaOCl) a 0,5% (10 min). A água destilada e deionizada foi utilizada como controle. Após os tratamentos, os espécimes foram sonicados (7W por 30s) em solução salina, para remoção das células aderidas. Essa solução foi serialmente diluída em solução salina e semeada em CHROMagar® Candida. O número de células viáveis de Candida foi expresso em unidades formadoras de colônia (UFC)/mm2. Os dados da ELS e ângulo de contato foram submetidos a ANOVA um fator, enquanto que os dados de células viáveis de Candida foram submetidos a ANOVA três fatores, seguido do teste de Tukey-Kramer. Todos os biofilmes avaliados apresentaram maior crescimento na resina de poliamida (p<0,0001), entretanto, essa resina apresentou um menor valor de ELS quando comparada à resina de PMMA. Os limpadores químicos, contendo ou não enzimas, reduziram significantemente os níveis de Candida, sem haver diferença estatística entre eles (p=0,9999). Entretanto, o NaOCl a 0,5% foi mais eficaz, na medida em que resultou na ausência de células viáveis. Em todas as situações avaliadas, a C. glabrata apresentou maiores valores de células viáveis do que a C. albicans (p=0,0002). Nas condições desse estudo, conclui-se que a resina de poliamida possibilitou uma maior proliferação de Candida; e os limpadores químicos comerciais foram eficazes na redução dos níveis de Candida spp, mas apenas a solução de hipoclorito de sódio a 0,5% resultou na ausência de células viáveis na superfícies dos materiais testados
Resumo: Os limpadores químicos de prótese têm sido bastante indicados para o controle do biofilme formado sobre próteses removíveis de pacientes com comprometimento motor. Apesar de estudos prévios terem mostrado que uma única imersão nesses agentes é capaz de reduzir os níveis de Candida albicans do biofilme formado sobre próteses removíveis, pouco se sabe sobre o efeito do uso diário desses limpadores sobre o biofilme residual de Candida. Assim, o objetivo desse estudo foi avaliar a eficácia do uso diário de um limpador químico enzimático sobre o biofilme de C. albicans formado sobre a superfície de materiais para confecção de próteses removíveis; bem como a atividade enzimática das células de Candida desse biofilme após exposições diárias a esse limpador de prótese. Foram confeccionados espécimes de resina de polimetilmetacrilato (PMMA) e resina de poliamida, nos quais foi realizada, inicialmente, a padronização da rugosidade de superfície (0,34 ± 0,02 ?m). Após a formação da película adquirida, os espécimes foram divididos aleatoriamente em 12 grupos (n=9) para formação do biofilme de C. albicans por 72 horas. Após esse período, os espécimes foram tratados por 1, 4 ou 7 dias, sendo realizado um tratamento por dia, com um limpador químico enzimático (Polident 3 Minutes) ou com água destilada (controle negativo). Após os respectivos períodos de tratamento, os microrganismos remanescentes foram removidos da superfície dos espécimes por meio de ondas ultra-sônicas (7W por 30s). Em seguida, as unidades formadoras de colônia (UFC) foram calculadas e a atividade enzimática das células remanescentes foi avaliada. Os dados foram submetidos à ANOVA um fator ou dois fatores, seguido do teste de Tukey-Kramer. O biofilme de Candida albicans formado sobre a resina de poliamida apresentou maiores níveis de Candida e uma maior atividade fosfolipásica que o biofilme formado sobre a resina de PMMA (p<0,001). O limpador químico enzimático reduziu significantemente os níveis de Candida albicans em todos os períodos avaliados (p<0,001), entretanto os níveis desse microrganismo aumentaram com o tempo, sendo observada diferença estatisticamente significante entre os períodos avaliados (p<0,001). As exposições diárias a esse limpador químico aumentaram a virulência das células de Candida, no que diz respeito à atividade fosfolipásica. Nas condições desse estudo, conclui-se que o uso diário do limpador químico enzimático não foi capaz de impedir a proliferação de Candida albicans no biofilme residual, apesar de ter interferido no crescimento desse biofilme.
Abstract: Candida denture biofilm is considered the the primary aetiological agent for the development of oral candidosis, which is the most common fungal oral infection in humans. Although, for patients with limited motor capacity, chemical cleansing with immersion in denture cleansers has been shown to be effective in controlling Candida biofilm accumulation, limited data is available on the effect of those cleansing agents on other Candida species biofilms. Additionally, few studies have examined the development of Candida biofims on novel denture materials. This study evaluated the efficacy of denture cleansers on C. albicans and C. glabrata single and dual-species biofilms formed on novel denture base materials. Specimens of polymethylmetacrylate resin (PMMA) and polyamide resin were prepared and had their surface roughness standardized (0.34 ± 0.02 µm). Part of the specimens had their surface free energy measured and the other specimens were submitted to the biofilm assays. C. albicans and/or C. glabrata biofilm was formed for 72 hours on saliva-coated specimens. On the 3rd day, specimens were treated with an enzymatic cleanser, denture cleanser or 0.5% sodium hypochlorite (NaOCl) solution by soaking for, 3, 5 and 10 min, respectively. Water was used as negative control. After treatment, adhered cells were detached from the acrylic resin surface by ultrassonic waves at 7 watts for 30 seconds in phosphate buffered saline solution (PBS). This solution was serially diluted in PBS and plated on CHROMagar® Candida. Candida viable cell were expressed in colony forming units per surface area (CFU/mm2). Data of surface free energy and contact angle were analyzed by one-way ANOVA, and data of Candida species were analyzed by three way-ANOVA followed by Tukey-Kramer test. All tested biofilms displayed significantly higher growth on polyamide thermoplastic resin (p<0.0001), which presented the lowest SFE. Denture cleansers significantly decreased Candida spp levels, with no statistical difference between them (p=0.9999); however, 0.5% NaOCl solution was more effective, since, after treatment, no viable cell was observed. Candida glabrata revealed significantly higher CFU counts when compared to Candida albicans under all experimental conditions (p=0.0002). Our study has shown that polyamide resins may present a convenient substratum for microbial colonization. Although denture cleansers reduced Candida levels, sodium hypochlorite should be preferred as it was efficient to eliminate Candida cells from the tested materials
Abstract: Chemical cleansing with immersion in denture cleansers has been indicated for denture biofilm control in patients with limited motor capacity. Although previous studies have shown that a single immersion in those agents is able to substantially reduce Candida albicans biofilm levels, the effect of the routine use of denture cleansers on the Candida residual biofilm is poorly understood. This study evaluated the efficacy of daily use of an enzymatic denture cleanser on C. albicans biofilm formed on denture base materials; and the enzymatic activities of Candida biofilm cells after daily exposure to this cleanser agent. Polymethyl methacrylate (PMMA) and polyamide resins specimens were prepared (n=54), and their surface roughness was standardized (0.34 ±0.02 ?m). Saliva-coated specimens were randomly divided by lottery into 12 groups (n=9) for biofilm assay. C. albicans biofilm was formed for 72 hours, and then specimens were treated for 1, 4 or 7 days, once a day, with an enzymatic cleanser (Polident 3 Minutes), or distilled water (negative control). Remaining adherent microorganisms were removed from the treated specimens by ultrasonic waves at 7 watts for 30 seconds, and then colony-forming units (CFU) were calculated and remaining cells enzymatic activities were determined. Data were analyzed by 1-way or 2-way ANOVA followed by the Tukey-Kramer test. C. albicans biofilm formed on polyamide resin showed significantly higher Candida levels and phospholipase activity (p<0.001) than biofilm formed on PMMA resin. The enzymatic cleanser significantly reduced C. albicans levels in all evaluated periods (p<0.001); however, the number of this microorganism increased with time, showing statistical difference among the treatment periods (p<0.001). The daily exposure to the denture cleanser increased Candida cells virulence, with regard to phospholipase activity. Our study has shown that the enzymatic cleanser daily use did not prevent C. albicans proliferation in residual biofilm; however, this agent reduced this fungus rate of growth.
Mestrado
Protese Dental
Mestre em Clínica Odontológica
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45

Kuan, Yean-Der. "Process-induced damage evolution and management in resin transfer molding of composite panels /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9998490.

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46

Barnett, Nina (Kuentzer). "Permeability characterization and microvoid prediction during impregnation of fiber tows in dual-scale fabrics." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.70 Mb., 144 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430754.

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47

Sharifi, Mohammad S. "Fractionations and analysis of trunk exudates from pistacia genus in relation to antimicrobial activity." View thesis, 2006. http://handle.uws.edu.au:8081/1959.7/35517.

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Thesis (Ph.D.) -- University of Western Sydney, 2006.
A thesis presented to the University of Western Sydney, College of Health and Science, School of Biomedical and Health Sciences, in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliography.
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48

Nalla, Ajit R. "Closed-loop flow control approaches for VARTM." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.86 Mb., 89 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430781.

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49

Tomotani, Ester Junko. "Imobilização da invertase em resina de troca iônica (tipo Dowex®): seu uso na modificação da sacarose." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/9/9134/tde-16082017-104536/.

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A invertase comercial (Bioinvert®) foi imobilizada por adsorção em resinas aniônicas do tipo Dowex® [1x8:50-400, 1x4:50-400 e 1x2:100-400, todos copolímeros estireno-divinilbenzênicos, porém de granulometria (50-400 mesh) e quantidades de ligações cruzadas diferentes (2-8%)] em meio aquoso. A melhor percentagem de adsorção da invertase nas resinas foi observada em pH 5,5 a 32°C, tendo o complexo Dowex®1x4-200/lnvertase apresentado índice de adsorção e coeficiente de imobilização iguais a 100%. Os parâmetros cinéticos e termodinâmicos foram determinados para a invertase solúvel e insolúvel de Bioinvert® e também para a invertase purificada (Fluka®). O complexo Dowex®1 x4-200/Bioinvert® apresentou-se estável durante as reações sem desprendimento da enzima do suporte. Os parâmetros termodinâmicos da forma solúvel e insolúvel da Fluka® foram idênticos aos do Bioinvert®, no entanto, após a imobilização apresentou uma redução de 28% na sua atividade. O estudo da atividade transferásica de ambas as formas de Bioinvert® em diferentes concentrações de sacarose foram analisadas através da cromatografia de camada delgada. A estabilidade operacional e de estocagem foi também determinada para o complexo Dowex®1x4-200/Bioinvert®.
The invertase (trademarked as Bioinvert®) solubilized in deionized water was immobilized by adsorption on anion exchange resins, collectively named Dowex®, [1x8:50-400, 1x4:50-400 and 1x2:100-400, styrene-divinylbenzene copolymers, with different granulometry (50-400mesh) and different degrees of cross-linking (2-8%)]. The best percentage of adsorption of invertase on resins was observed in pH 5.5 at 32°C and the complex Dowex®1x4-200/invertase has shown a coupling yield and an immobilization coefficient equal to 100%. The thermodynamic and kinetic parameters for sucrosehydrolysis for both soluble and insoluble enzyme were evaluated to Bioinvert® and purified invertase purchased from Fluka®. The complex Dowex®/Bioinvert® was stable without any desorption of enzyme from the support during the reaction and having the thermodynamic parameters equal to the soluble formo However, the loss of activity for immobilized Fluka® was found to be 28% when compared to the soluble one. The transfructosylating activity of Bioinvert® in both forms in different concentrations of sucrose was investigated through TLC. In regard to insoluble Bioinvert® its storage and operational stability were also determined.
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50

Hammond, Vincent H. "Verification of a two-dimensional infiltration model for the resin transfer molding process." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41537.

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A two-dimensional fmite element model for the infiltration of a dry textile preform by an injected resin has been verified. The model, which is based on the finite element/control volume technique, determines the total infiltration time and the pressure increase at the mold inlet associated with the RTM process. Important input data for the model are the compaction and permeability behavior of the preform along with the kinetic and rheological behavior of the resin.

The compaction behavior for several textile preforms was determined by experimental methods. A power law regression model was used to relate fiber volume fraction to the applied compaction pressure. Results showed a large increase in fiber volume fraction with the initial application of pressure. However, as the maximum fiber volume fraction was approached, the amount of compaction pressure required to decrease the porosity of the preform rapidly increased.

Similarly, a power law regression model was used to relate permeability to the fiber volume fraction of the preform. Two methods were used to measure the permeability of the textile preform. The first, known as the steady state method, measures the permeability of a saturated preform under constant flow rate conditions. The second, denoted the advancing front method, determines the permeability of a dry preform to an infiltrating fluid. Water, corn oil, and an epoxy resin, Epon 815, were used to determine the effect of fluid type and viscosity on the steady state permeability behavior of the preform. Permeability values measured with the different fluids showed that fluid viscosity had no influence on the permeability behavior of 162 E-glass and TTI IM7/8HS preforms.

Permeabilities measured from steady state and advancing front experiments for the warp direction of 162 E-glass fabric were similar. This behavior was noticed for tests conducted with corn oil and Epon 815. Comparable behavior was observed for the warp direction of the TTl 1M7/8HS preform and corn oil.

Fluid/fiber interaction was measured through the use of the single fiber pull-out test. The surface tension of both the corn oil and Epon 815 was determined. The contact angle between these two fluids and glass and carbon fibers was also measured. These tests indicated that the glass fiber had a lower contact angle than the carbon fiber and therefore is wet out better than the carbon fiber by both fluids. This result is attributed to the sizing commonly used on the carbon fibers.

Mold filling and flow visualization experiments were performed to verify the analytical computer model. Frequency dependent electromagnetic sensors were used to monitor the resin flow front as a function of time. For the flow visualization tests, a video camera and high resolution tape recorder were used to record the experimental flow fronts. Comparisons between experimental and model predicted flow fronts agreed well for all tests. For the mold filling tests conducted at constant flow rate injection, the model was able to accurately predict the pressure increase at the mold inlet during the infiltration process. A kinetics model developed to predict the degree of cure as a function of time for the injected resin accurately calculated the increase in the degree of cure during the subsequent cure cycle.
Master of Science

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