Since the mid-1990s resin composite has been used for Class II restorations in stress-bearing areas as an alternative to amalgam. Reasons for this were the patients’ fear of mercury in dental amalgam and a growing demand for aesthetic restorations. During the last decades, the use of new resin composites with more optimized filler loading have resulted in reduced clinical wear. Improved and simplified amphiphilic bonding systems have been introduced. However, one of the main problems with resin composites, its polymerization shrinkage, has not been solved yet. During the polymerization of the resin composites, they shrink as a result of the conversion of the monomers into rigid polymers by a radical addition reaction. The resulting shrinkage stresses in the bonded resin composite restorations may cause adhesive failures at the resin composite/tooth structure interface and/or cohesive failures within the tooth or the resin composite. The interfacial failures may result in post-operative sensitivity, recurrent caries or pulpal injury. This thesis evaluates different restorative and light-curing techniques that are proposed to reduce the polymerization shrinkage and also the effect of new lightcuring units, light-emitting diodes (LED) and high-power quartz tungsten halogen (QTH) light on curing depth and degree of conversion of resin composites. Two restorative techniques using a polyacid-modified resin composite or a flowable resin composite in combination with conventional resin composite in sandwich restorations were evaluated in an intraindividual comparison with a conventional resin composite restoration. The durability of the polyacid-modified resin composite sandwich technique was investigated in a three year clinical follow-up study. A scanning electron microscope replica method was used for evaluation of the interfacial adaptation in vivo of both sandwich combinations. The depth of cure of the flowable resin composite was evaluated with the use of Wallace hardness testing. Degree of conversion for resin composite cured with the new LED units was evaluated with Fourier Transform Raman spectroscopy. Major results and conclusions from the studies are: • Neither the sandwich restoration with polyacid-modified resin composite nor the flowable resin composite improved the interfacial adaptation of the restorations. • No difference in durability was found between the sandwich restorations with polyacidmodified resin composite or the resin composite restorations. A low failure rate was observed for both types of restorations after a clinical observation time of three years. • The depth of cure of the flowable resin composite was higher than the depth of cure of the resin composite. It was found that the curing time of the resin composite studied could be reduced or the increment layer thickness increased compared to earlier recommendations. • LED curing units of the latest generation were able to cure resin composites to a higher degree of conversion than the control QTH unit • The use of soft-start curing did not improve the interfacial adaptation of neither of resin composite restorations tested.

Conventional fiber reinforced polymers (FRPs) require polymers such as epoxies that are not biodegradable, which have a significant impact on the environment. The first phase of the thesis aims at replacing conventional polymers with sustainable bio-polymers. The tensile mechanical properties of glass-FRP (GFRP) laminates using two types of organic furfuryl alcohol bio-resins extracted from renewable resources, such as corncobs, were investigated. Results are compared to control specimens fabricated using conventional epoxy resin. It was shown that by careful selection of viscosity of bio-resin, and type and dosage of catalyst, similar mechanical properties to epoxy-GFRP can be achieved. The second and third phases consisted of durability testing of the bio-resin GFRP. A total of 160 tension coupons and 81 unconfined and confined concrete cylinders wrapped with bio-resin-GFRP were studied. Conditioning was achieved by immersion of the specimens in saline solutions with 3% salt concentration, at 23, 40 and 55 degrees Celcius, for up to 300 days. Specimens were compared to epoxy-GFRP specimens aged in the same environment. Deterioration was quantified by tensile testing of the coupons and compression testing of the cylinders at various stages of exposure. The bio-resin-GFRP showed 33% less tensile strength retention than the epoxy-GFRP. The epoxy-GFRP and bio-resin-GFRP wrapped cylinders had the same un-aged confined axial compressive strength (fcc’), essentially a strengthening ratio (fcc’/fc’) of 2.24. After 300 days, the (fcc’/fc’) ratio retentions for the bio-resin-GFRP was 73% at all temperatures. Using the Arrhenius model, it was predicted that 61% retention in tensile strength of the bio-resin-GFRP and 65% retention of the compressive strength of wrapped cylinders would occur after 100 years in an environment with a mean annual temperatures of 10 degrees Celcius. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-08-24 00:02:25.683

The increasing demand for polymer matrix composites (PMCs) from the airframe industry raises the issues of productivity, cost and reproducibility of manufactured PMC components. Performance reproducibility is closely related to the manufacturing technique. Resin transfer moulding (RTM) offers the advantage of flexible manufacturing of net-shape PMC components with superior repeatability starting from ready-to-impregnate dry reinforcements. An RTM apparatus was developed for manufacturing PMC plates and demonstrator components representative of actual, PMC components and PMC moulds made and used in the airframe industry. The RTM process developed in this work involved making net-shape dry carbon fibre preforms and impregnating them an epoxy resin, targeting mould applications. Thermal repeatability of different net-shape PMC components manufactured using the RTM apparatus developed in-house was investigated. Effects of bonding an outer copper plate onto the PMC material, targeting mould applications known as integrally heated copper tooling (IHCT), were explored. Heat conduction through the PMC components was studied using simulation models validated by experimental data obtained primarily by thermography. Manufactured PMC components showed good repeatability, particularly in terms of thermal behaviour. The IHCT technique was found to be well suited for mould applications. Expected advantages of thermography were materialised. Finally, the simulation models developed were in good agreement with experimental data.

During the production of paper in paper mills, detrimental wood resin is released into the water circuit of the mill during the pulping process of the wood into fibres. This wood resin, termed pitch, can detrimentally deposit on the paper and on the paper machine equipment. The deposits mark the paper or can lead to a tear of the paper web involving a loss of output and a reduction in paper quality. Furthermore, the wood resinous compounds in paper mill effluents need to be reduced in order to minimise their toxic effects on water organisms. Talc has been the benchmark for many years as a mineral additive in pitch control. Since the papermaking process has changed over the years, the concept of mineral addition needs to be redefined and adopted towards the new circumstances. By understanding the fundamentals behind the adsorption of wood resin compounds from aqueous systems on to talc new mineral additives can be developed. A model for the determination of the aspect ratio of platy and rod-like particles has been developed, based on commonly available characterisations such as particle size, specific surface area and shape. It was found that the adsorption capacity of a mineral is directly proportional to its specific surface area, but only within its mineral family. Including the effect of surface hydrophilicity and hydrophobicity allowed fine tuning of the adsorption capacity of newly developed calcium carbonate grades. Furthermore, size exclusion effects, in porous, high surface area modified calcium carbonate, were seen to hinder complete coverage of the surface area by wood resin. With increasing pH, the adsorption efficiency of talc for colloidal wood resin was found to decrease. Under these alkaline conditions, which are common in modern paper making processes, talc preferentially adsorbed dissolved species. The use of the newly developed surface treated and modified calcium carbonates allowed more efficient adsorption of the colloidal fraction and, therefore, represent an efficient alternative to talc in pitch control. An increase in temperature led to an increased adsorption capacity of talc. This observation indicates the type of interaction tat controls the adsorption of hydrophobic pitch particles onto talc, i.e. the entropically favoured release of water from the hydrophobic talc surface as well as the hydrophobic methylene backbone of the hemicellulose.

Minimum blue intensity is a reflected light imaging technique that provides an inexpensive, robust and reliable surrogate for maximum latewood density. In this application it was found that temperature reconstructions from resin-extracted samples of Pinus sylvestris (L.) from Fennoscandia provide results equivalent to conventional x-ray densitometry. This paper describes the implementation of the blue intensity method using commercially available software and a flat-bed scanner. A calibration procedure is presented that permits results obtained by different laboratories, or using different scanners, to be compared. In addition, the use of carefully prepared and chemically treated 10-mm-diameter cores are explored; suggesting that it may not be necessary to produce thin laths with the rings aligned exactly perpendicular to the measurement surface.

Purpose: To compare the in-vitro shear bond strengths of a new paste-paste formulation of resin-modified glass-ionomer cement (Rm-GIC) to an exising powder-liquid formulation. The study will test the hypothesis that the new paste-paste formulation of Rm-GIC (Fuji-Cem ™, GC Corp, Tokyo, Japan) has the same bond strength as an existing popular powder-liquid formulation of Rm-GIC (Rely-X ™ Luting Cement, 3M, St. Paul, MN)Materials and Methods: A total of 33 human molars were sectioned parallel to the occlusal surface to expose mid-coronal dentin and mounted parallel to the bond shearing device on the universal testing machine (Instron). For Group I samples (Rely-X, n=15), the powder and liquid were measured and adjusted to achieve a ratio of 1.6 and mixed for 30 seconds as recommended by the manufacturer. For Group II (Fuji-Cem, n=18), the paste-paste was expressed from the paste-dispenser provided by the manufacturer and mixed for 10 seconds as recommended. After testing, the teeth from group II were bonded on a different site with the same material but mixed for 20 seconds (n=18). To ensure a uniform flow and bond surface area, the mixed cement was syringed into a cylindrical mould (diameter 2.38mm, height 2mm) and allowed to set under constant force. All samples were subjected to fracture by shear loading on a universal testing machine (Instron) at a uniform crosshead speed of .02" per minute and expressed as MPa. Values were analyzed at the pResults: Wilcoxon rank sums test showed significantly higher shear bond strength values for Rely-X compared to Fuji-Cem mixed both at 10 seconds and 20 seconds. Mixing for 20 seconds resulted in stronger bonds for Fuji-Cem compared to 10 seconds, but was still significantly lower than Rely-X.Conclusions: Within the limitations of the study, the Rely-X powder-liquid formula shows a significantly stronger dentin shear bond strength when compared to the new paste-paste formula of resin-modified glass ionomer cement, Fuji-Cem.

The following thesis titled SPHERE OF INFLUENCE is about development. I discuss my efforts to develop as an artist addressing observation and awareness of the self and our surroundings. I will discuss how this relates to my approach with materials and process and will explain not only what the sculpture titled SPHERE OF INFLUENCE has come to represent for me, but also the reactions of viewers during the temporary installation of the SPHERE OF INFLUENCE at the Anderson Gallery at Virginia Commonwealth University from May 5th 2006 through May 14th, 2006. I will explain the SPHERE OF INFLENCE'S function as both an object meant to evoke an awareness of what and who surrounds its space and as a metaphor of my efforts to surpass personal and artistic boundaries.

In my photographic work, I contrast natural and man-made objects abstracted by manipulation of scale. Details of the objects are blown up to proportions larger than life. By distorting the scale, I aim to allow the audience to view the image out of context, enabling the viewer to see it for its aesthetic value rather than the object's functional purpose.

Les éléments de terres rares (REEs) sont de plus en plus utilisés dans une multitude d’applications, notamment la fabrication d’aimants, de batteries rechargeables et les écrans de téléviseurs. Ils sont pour la plupart des métaux trivalents peu solubles dans les eaux naturelles. Comme pour les métaux divalents, le risque écologique des REEs est très probablement étroitement lié à leurs spéciations chimiques. Cependant, le comportement du samarium (Sm) dans les matrices environnementales est très peu connu et il n'existe actuellement aucune technique pour évaluer sa spéciation chimique. Dans cette optique, la technique d'échange d'ions (IET) sur la résine Dowex a été optimisée pour mesurer le samarium libre en solution. Les temps d'équilibre ont d'abord été déterminés pour des solutions tamponnées de samarium (Sm 6,7x10-8 M ; MES 1,0 mM M ; pH 6,0) en présence du nitrate de sodium (de 0,01M à 0,5 M). Pour ces diverses forces ioniques, l’équilibre thermodynamique n’est atteint que pour NaNO3 0,5M. Un autre mode d’utilisation de la résine (mode dynamique) a donc été développé pour tenir compte des conditions environnementales et évaluer efficacement le samarium libre. Les impacts des ligands organiques tels le NTA, l’EDTA, le citrate, l’acide malique et l’acide fulvique Suwannee River Standard I (SRFA) ont été étudiés par l’IET en mode dynamique. Une grande corrélation a été trouvée plus entre les taux d’accumulation de samarium sur la résine d’échange pour différents rapports NTA : Sm, EDTA : Sm, SRFA : Sm et le samarium libre. Par contre, aucune corrélation significative n’a été observée pour les ligands citrate et acide malique compte tenu des complexes qu’ils forment avec le samarium et qui s’adsorbent aussi sur la résine Dowex. Les concentrations Sm3+ mesurées par la technique IET ont été fortement corrélées avec celles prédites par le modèle WHAM 7.0 en utilisant la constante de stabilité obtenue par titration de SRFA par extinction de la fluorescence. Par ailleurs, la formation de colloïdes de samarium en fonction du pH influe grandement sur la détermination du samarium libre et doit être prise en compte dans la spéciation du samarium. L'IET assisté par des techniques auxiliaires comme le dosage par extinction de la fluorescence et le SP-ICPMS pourrait être une technique utile pour évaluer les concentrations de Sm biodisponible dans les eaux naturelles. / Samarium is present in several high technology products such as magnets, lasers, etc., however little is known about to what extent it can pollute environmental matrices. For divalent metals such as Cd, Cu and Ni, toxicity has often been closely correlated with the free ion concentration. Unfortunately, there are currently no techniques available for evaluating the speciation of samarium in environmental matrices. In this study, an economical and easy to use ion exchange technique (IET) using a resin has been studied for use in measuring free samarium. In order to optimize the IET for free samarium determinations, equilibrium times were first determined for pH buffered solutions of samarium (6.7x10 8 M Sm, 1.0 mM MES, pH 6.0) in the presence of different concentrations of sodium nitrate (NaNO3: 0.01 M to 0.5 M). Equilibrium was only attained for the highest concentration of NaNO3. Therefore, another technique using dynamic measurements on the Dowex resin was developed. Thus, the impacts of different organic ligands such as EDTA, citrate, malic acid and Suwannee River fulvic acid Standard I (SRFA) have been investigated using IET in dynamic mode. The calibration of the technique using different concentrations of NTA, EDTA, citrate, malic acid and fulvic acid (SRFA) allowed the determination of accumulation rates. Strong correlations were found between accumulation rates and the free samarium when using EDTA and NTA to control free samarium. The correlation was very low in case of citrate and malic acid suggesting that their complexes with samarium were adsorbed on the resin. Finally, fluorescence quenching titrations (FQT) and SP-ICPMS were used to determine samarium speciation. The free samarium determined by IET is strongly correlated to that calculated by WHAM 7.0 using the stability constant from FQT and that from Sonke (2006). However, the free Sm resulted from IEC-SP-ICPMS technique has been overestimated once compared to that found using VMinteQ or WHAM 7.0 models. The Sm particulates determined by SP-ICPMS have demonstrated that pH has a great influence on Sm exchange on resin and has to be considered while measuring free samarium. Thus, the IET should be associated to other techniques such as fluorescence quenching titration and SP-ICPMS for evaluating the bioavailable Sm concentrations in natural waters.

Dosage du polyisoprène et des résines de la biomasse de guayule (Parthenium argentatum) par spectroscopie proche infrarouge (SPIR) Méthodes d'extraction par solvant de référence Un protocole basé sur l'extraction accélérée (ASE) avec l'acétone (EA) (résine) puis l'hexane (EH) (polyisoprène, PI) a été sélectionné et optimisé (rendement maximal; adapté à l'analyse de séries) ; quantification d'abord basée sur le poids de l'extrait (gravimétrie). L'EH est maximal à 120°C après étapes avec l'acétone à 40°C (plan d'expérience). La contamination croisée a été confirmée par SEC et FTIR (5 à 29%), conduisant à une deuxième méthode basée sur résine et PI et non plus sur EA et EH, incluant le PI de faible masse molaire (Mw) de l'EA. Ces 2 méthodes de référence ont servi à calibrer la SPIR (chimiométrie/PLS, coeff. beta) afin de relier signature spectrale, PI, résine. ASE-SPIR, couplés ici pour la première fois, ont été plus performants (R² 0.96; 0.98; RPD 4.8; 4.6; EA et EH resp.) que les méthodes de la littérature, grâce aux 215 échantillons représentatifs (génotypes, saison, âge du guayule, climat). La méthode tenant compte de la contamination est moins performante (erreur exp. due aux analyses SEC et FTIR; variation de composition des résines). Ayant montré la dégradation du PI au cours de l'extraction, un autre protocole a été étudié (biomasse humide, un solvant, une seule étape, 20°C) afin d'accéder au Mw «natif », donnant 2.106 g au lieu de 6.105 avec la biomasse séchée; il faut donc être prudent face aux Mw de guayule de la littérature. Ce travail montre la nécessité de tenir compte de la complexité de la biomasse de guayule (échelle cellulaire/PI vacuolaire, résine des canaux; moléculaire/instabilité chimique) lors de l'extraction du PI pour l'analyse structurale. Ces méthodes analytiques ont contribué à produire des prototypes (gant non allergisant, pneu) à haut Mw et à l'acclimatation en Europe dans le cadre du projet EU-Pearls. / Measurement of resin and polyisoprene in Parthenium argentatum (guayule) biomass using near infrared spectroscopy (NIRS) -Associated solvent-based reference methods .A protocol based on sequential extraction with acetone (resin) and hexane (polyisoprene, PI) with accelerated solvent extraction (ASE) was optimized and selected (maximized yield; adapted to large series) instead of Soxhlet and homogenizer. Quantification was first based on extract weight (gravimetry). Hexane extract was maximized at 120°C, after acetone steps at 40°C, through an experimental design. Cross contamination was confirmed and quantified (5 to 29%; SEC and FTIR). This gave a second method based on resin and PI, instead of crude extracts, accounting for low average molar mass PI (Mw) extracted by acetone instead of hexane. Both reference methods were used for calibrating NIRS applied to powdered biomass, with chemometric tools (PLS loadings, beta coefficients) to interpret spectral bands vs PI-resin relationship. ASE, not used before as reference, is highly reliable, and calibration with gravimetry (R² 0.96; 0.98; RPD 4.8; 4.6; for acetone and hexane extract) better than published data, thanks to the 215 samples covering genotypes, harvest date, plant age, climate. The method using cross contamination was less efficient because of higher experimental error induced by additional SEC and FTIR, and change in resin composition. Having set NIRS methods, a new protocol (single solvent THF, minimized processing, 20°C, fresh biomass) was designed to avoid degradation, yielding PI extracts with Mw above 2.106g/mole, closer to in vivo structure (6.105 when using dried guayule); caution to sample preparation in literature dealing with guayule PI structure. This calls for considering the complex structure of guayule biomass (PI in cells; resin in ducts; chemical instability) when extracting PI. These methods allowed producing high PI Mw glove and tire prototypes and domesticating this new crop in Europe within the EU-Pearls project.