The use of desiccant materials is crucial in many applications, such as dehumidification rotors, in OLED screen and as desiccant materials in dish washers, for example. Upsalite® is a novel, anhydrous, micro-mesoporous, and large surface area structure consisting of amorphous magnesium carbonate which has been shown to exhibit a good water sorption capacity. Depending on the heat treatment of Upsalite® after synthesis, the material exhibits different sorption capacity and hydrolytic stability. Calcined Upsalite® has a higher sorption capacity compared to as-synthesized, but crystallizes into nesquehonite when stored in a relative humidity of 100 % for several days. The need to stabilize the material arises and the use of two different aminosilanes as surface stabilizers has been evaluated. Two different deposition techniques from gas phase have been used, atomic layer deposition and vapor phase grafting, which are evaluated and compared.   The results of the functionalization show an increase in decomposition temperature by ~25 °C of the functionalized materials compared to non-functionalized. The initial water sorption capacity of the functionalized material increases by up to 80 %, when stored in a relative humidity of 100 % for 24 h and shows a stabilizing effect after five cycles of repeated exposure to high humidity. The long term stability seems to have decreased due to pore collapse, when the functionalized material is cycled 5 times for one week in a repeated relative humidity of 100 %. The stability of the material when exposed to two liquids of different pH was also evaluated and the functionalized material exhibits a slower increase of the pH in the buffer solution, implying a retardation of Upsalite® dissolution. The conclusion is that a functionalization of the material with aminosilane increases the initial sorption capacity and has a stabilizing effect.

This diploma thesis studies short fiber reinforced composites for dental applications. Barium particulate filler, nanosilica and short glass and polyvinylalcohol fibers were added to the matrix consisting of four dimethacrylate types of monomers. The effect on material properties was observed. For characterization of different types of composite materials following methods were used: thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), three point bending test for notched and un-notched samples and scanning electron microscopy (SEM). Viscoelastic properties, modulus of elasticity and strength, critical values of stress intensity factor and strain energy release rate and polymerization shrinkage of composite materials were determined. It is possible to improve these properties of composite materials by adding short fibres to particulate reinforced composite. To make this modification more efficient, it is necessary to change surface treatment of fibres and preparation method of short fiber reinforced composites. Viscosity of material has raised after adding short fibers and processing of these types of dental material in dental laboratory is considered difficult to provide.

Betalaínas são pigmentos vegetais encontrados em algumas espécies de flores fluorescentes. Betalaínas derivadas de aminocumarinas primárias (cBeets) e carboestiril 124 (csBeet124) foram desenvolvidas em nosso grupo de pesquisa para serem usadas como sondas fluorescentes em aplicações de biologia celular. Esta dissertação de mestrado mostra o efeito da metilação das porções imínicas das cBeets e da csBeet124 sobre as suas cinéticas de hidrólise e propriedades fotofísicas. Os quatro derivados N-metilados foram semissintetizados a partir do acomplamento entre o ácido betalâmico e as aminas secundárias em rendimentos entre 15 − 60%. A N-metilação na porção imínica das betalaínas resultou em um aumento da estabilidade hidrolítica de cerca de 20 vezes, sem afetar drasticamente os perfis de absorção e fluorescência ou os rendimentos quânticos de fluorescência. Os resultados obtidos são importantes na ampliação do conhecimento acerca das relações entre a estrutura e as propriedades de betalaínas em solução aquosa. / Betalains are plant pigments found in some species of fluorescent flowers. Betalains derived from primary aminocoumarins (cBeets) and carbostyril 124 (csBeets124) were developed in our research group to be used as fluorescent cell probes. This dissertation shows the effect of the methylation at the imine portion from cBeets and csBeet124 on their hydrolitic kinetics and photophysical properties. The four N-methylated derivatives were semisynthesized from the coupling between betalamic acid and the secondary amines within 15 − 60% yields. N-methylation at the iminic portion of betalains resulted in a hydrolytic stability increase of about 20-fold without affecting drastically their absorption and fluorescence profiles or fluorescence quantum yield. The results obtained are important to increase the knowledgement about the relationships between structure and properties of betalains in aqueous solution

Betalaínas são pigmentos vegetais encontrados em algumas espécies de flores fluorescentes. Betalaínas derivadas de aminocumarinas primárias (cBeets) e carboestiril 124 (csBeet124) foram desenvolvidas em nosso grupo de pesquisa para serem usadas como sondas fluorescentes em aplicações de biologia celular. Esta dissertação de mestrado mostra o efeito da metilação das porções imínicas das cBeets e da csBeet124 sobre as suas cinéticas de hidrólise e propriedades fotofísicas. Os quatro derivados N-metilados foram semissintetizados a partir do acomplamento entre o ácido betalâmico e as aminas secundárias em rendimentos entre 15 − 60%. A N-metilação na porção imínica das betalaínas resultou em um aumento da estabilidade hidrolítica de cerca de 20 vezes, sem afetar drasticamente os perfis de absorção e fluorescência ou os rendimentos quânticos de fluorescência. Os resultados obtidos são importantes na ampliação do conhecimento acerca das relações entre a estrutura e as propriedades de betalaínas em solução aquosa. / Betalains are plant pigments found in some species of fluorescent flowers. Betalains derived from primary aminocoumarins (cBeets) and carbostyril 124 (csBeets124) were developed in our research group to be used as fluorescent cell probes. This dissertation shows the effect of the methylation at the imine portion from cBeets and csBeet124 on their hydrolitic kinetics and photophysical properties. The four N-methylated derivatives were semisynthesized from the coupling between betalamic acid and the secondary amines within 15 − 60% yields. N-methylation at the iminic portion of betalains resulted in a hydrolytic stability increase of about 20-fold without affecting drastically their absorption and fluorescence profiles or fluorescence quantum yield. The results obtained are important to increase the knowledgement about the relationships between structure and properties of betalains in aqueous solution

No description available.

La produzione e l’uso del Metile di Bromuro, un fumigante estesamente usato in agricoltura, sono stati sottoposti a severe restrizioni dovute alla sua azione di depletore dello strato di ozono. Questa tesi è rivolta ad indagare il destino e le caratteristiche ambientali di due tra le più importanti alternative chimiche all’uso del Bromuro di Metile: l’ 1,3-Dicloropropene (1,3-D) e la Cloropicrina (CP). 1,3-D è un fumigante del suolo, con spiccata attività nematocida, consistente di due isomeri (Z), e (E)-1,3-D; nella sua formulazione sono presenti, inoltre, un esteso numero di impurezze clorurate potenzialmente correlate al processo produttivo. In laboratorio, è stato effettuato uno studio per valutare la stabilità idrolitica delle impurezze clorurate e per prevederne, quindi, il destino ambientale. Allo stesso tempo un piano di monitoraggio è stato svolto per valutare il leaching dell’1,3-D, dei suoi metaboliti, e delle impurezze clorurate. La CP è anch’essa un fumigante del suolo, caratterizzato da un importante profilo tossicologico. Questo lavoro ha valutato l’esposizione degli operatori e l’emissione in atmosfera durante e dopo l’applicazione nel suolo, secondo le pratiche agronomiche vigenti. Infine tramite l’applicazione di modelli matematici quali FOCUS PELMO e FOCUS PEARL si è valutato il destino ambientale della CP rispetto alle acque di falda. La simulazione è stata eseguita in 5 scenari europei realistici. / Production and use of methyl bromide, a soil fumigant, are being restricted because of this chemical’s deleterious effects on stratospheric ozone concentrations. This research examines the environmental fate and properties of methyl bromide replacement: 1,3-Dichloropropene (1,3-D), and Chloropicrin (CP). 1,3-D is a broad-spectrum soil fumigant used to control numerous species of soil-borne plant-parasitic nematodes. 1,3-D consists of two isomers, (Z)- and (E)-1,3-D, and has a number of low-level chlorinated compounds that could potentially be part of the manufacturing process. This study has investigated the hydrolytic stability, under biotic and abiotic conditions, of an extensive representative list of 1,3-D potentially related chlorinated compounds. Furthermore, a monitoring programme was carried out to investigate the leaching of all of this compounds. CP is a broad-spectrum fumigant chemical which is extensively used in agriculture and has an important toxicological profile. This study has assessed CP emission in the atmosphere and operator exposure during and after application in soil through injection of the test substances with routine agronomical application. Finally the environmental fate of CP and its metabolite dichloronitromethane in groundwater were investigated through the use of simulation model FOCUS PELMO and FOCUS PEARL using fully justified input parameters in five realistic scenarios.

A significant focus of toxicological research is the identification of electrophiles that covalently modify DNA to form addition products (adducts). These products can be generated when aryl radical species react at the C8-site of 2'-deoxyguanosine (dG) to form C8-aryl-dG adducts, which are mutagenic lesions. While this form of DNA modification is detrimental, C8-aryl-dG adducts also possess intriguing properties that can be exploited for beneficial purposes. This thesis is an investigation of one mechanism believed to contribute to the mutagenicity of C8-aryl-dG adducts, as well as a study of the photophysical properties of adducts that allow for their application as fluorescent probes. A common property of C8-aryl-dG adduction is accompaniment of abasic site formation. To determine how the C8-aryl moiety contributes to sugar loss, UV-Vis spectroscopy has been employed to determine hydrolysis kinetics, with C8-aryl-dG adducts found to be more prone than dG to acid-catalyzed hydrolysis. Despite adduct reactivity in acidic media, all adducts are relatively stable at pH 7, suggesting they are unlikely intermediates of abasic site formation at physiological pH. These results have allowed for development of a new rationale for depurination observed upon C8-aryl-dG adduction within duplex DNA. The determination of photophysical parameters of C8-heteroaryl-dG adducts reveals that these nucleosides behave as fluorophores with high fluorescence quantum yields (φfl). These adducts also exhibit emission sensitivity to their solvent environment and H-bonding interactions. C8-Heteroaryl-dG adducts were incorporated in the oligonucleotide 5'-CTCG1G2CG3CCATC, at the G1 and G3 sites, that contains the recognition sequence of the NarI Type II restriction enzyme. Hybridization of the modified NarI oligonucleotides to the complementary strand containing either the C or G nucleobase opposite the adduct allowed for characterization of duplex structures by circular dichroism (CD), UV melting temperature analysis and fluorescence spectroscopy. Results suggest that the C8-heteroaryl-dG adduct favours an anti conformation with base-paired with C, while a syn conformation is favoured when base-paired to G. Adduct conformation of bulky C8-dG adducts is believed to be correlated with their known mutagenic activity. C8-Heteroaryl-dG modified nucleosides could therefore be used as fluorescent models of these adducts to aid in elucidation of adduct-induced mutagenesis in biological systems. / NSERC

La surface d’un implant ou d’un système à libération contrôlée de médicament est la première zone en contact avec les systèmes physiologiques. Les propriétés de surface vont alors définir le devenir à court et long termes de ces biomatériaux dans l’organisme. Pour améliorer la biointégration mais aussi l’efficacité des matériaux en contact avec les fluides et tissus biologiques, un fin contrôle des phénomènes se produisant à l’interface biologique est nécessaire. Cette thèse s’intéresse à l’étude de trois types de surfaces pouvant modéliser celles de biomatériaux couramment employés. Dans un premier temps, la stabilité hydrolytique de surface amino-fonctionnalisée a été investiguée. L’amino-fonctionnalisation de surface via l’emploi de monocouche auto-assemblée rencontre un intérêt certain pour l’ancrage de diverses molécules, macromolécules, systèmes colloïdaux et cellules. Cependant, le manque de stabilité en milieu aqueux limite grandement leurs perspectives d’utilisation pour la fonctionnalisation de surface de biomatériaux. Dans ce manuscrit, une monocouche amino-fonctionnalisée à base d’aminoalkylsilane a été greffée sur des substrats de silicate (silice et mica). L’extrême stabilité hydrolytique rapportée pour cette monocouche permet une immersion prolongée en milieu aqueux et sur une large gamme de pH. Les paramètres ayant été identifiés comme impactant cette stabilité sont l’organisation de la monocouche, la densité de greffage et la longueur de la chaîne carbonée de l’aminoalkylsilane. Dans un second temps, les propriétés lubrifiantes en milieu aqueux de surfaces structurées sont rapportées. Le besoin en surface autolubrifiante couvre une large variété de biomatériaux tels que les substituts cartilagineux, les dispositifs oculaires ou bien les cathéters. Des structures dômes ont été produites sur des surfaces via l’immobilisation de particules. Des particules polymériques à base de polyélectrolytes sensibles aux variations de pH ont permis l’obtention de structures molles et déformables alors que l’immobilisation de particules de silice a permis la formation de structures dures. Deux mécanismes majeurs contrôlant les propriétés de frottement ont été mis en évidence. Les surfaces structurées à partir de polyélectrolytes présentent des propriétés de frottement directement corrélées au gonflement et donc à la teneur en eau de ces structures. Ce ii gonflement peut être contrôlé par le pH du milieu aqueux. Plus les structures sont gonflées, plus le coefficient de frottement est faible. En revanche, avec des structures dures obtenues par l’immobilisation de particules de silice, le roulement de ces particules permet d’obtenir sous certaines conditions des coefficients de frottement extrêmement faibles. Dans ce cas, la nature du lien entre la particule et le substrat importe peu et un dégreffage systématique de certaines particules est observé pour permettre le mouvement des surfaces tout en limitant les forces de frottement. Dans un troisième temps, la complexation de simples brins de siARN via différentes natures d’interactions a été étudiée à l’aide de surfaces modèles de chimie variable. Cette étude a permis de démontrer la possibilité d'adsorber des simples brins de siARN via des interactions non-électrostatiques sur des surfaces planes. Des interactions hydrophobes et les liaisons hydrogène ont par la suite pu être employées pour complexer cet acide nucléique avec des formulations micellaires et liposomales non-cationiques. Cette étude permet d'envisager la conception de nanovecteurs non-cationiques et donc moins toxiques pour la délivrance de simples brins de siARN. Les travaux présentés dans ce manuscrit contribuent à l’élargissement des connaissances en matière de propriétés physico-chimiques de surface aux interfaces biologiques. / The surface of an implant or a drug delivery system is the first area of contact with biological environment. The surface properties of these biomaterials will define the short and long term behavior in the organism. To improve biointegration and efficiency, a fine control of the biological interface is required. This thesis investigates three different kind of surfaces modelling commonly used biomaterials. First, the hydrolytic stability of amino-functionalized surfaces was investigated. The amino-functionalization using self-assembled monolayers is required for the anchorage of molecules, macromolecules, colloidal systems and cells onto biomaterials. However, the lack of stability in aqueous media limits their use. In this manuscript, an amino-functionalized self-assembled monolayer made of aminoalkylsilane was grafted onto silicate substrates (silica and mica). The extreme robustness that we reported for this monolayer allows immersion into aqueous media for a wide range of pH and over long periods of time. The most important parameters that were identified that significantly impact the hydrolytic stability are the order of the monolayers, the grafting density and the length of the alkyl chain of the aminoalkylsilane. Second, the lubricant properties in aqueous media of structured surfaces are reported. The need in self-lubricant surfaces is required in a wide variety of biomaterials such as the cartilage substitute, ocular medical device or catheters. Domed structures were produced on surfaces through immobilization of particles. Polymeric nanoparticles composed of pH-sensitive polyelectrolytes were used to prepared soft and deformable structures while the immobilization of silica particles allows hard structures to be created. Two main mechanisms controlling friction properties were identified. Friction properties of structured surfaces made of polyelectrolytes were controlled by the swelling and the water content of the particles. This swelling can be tuned by changing the pH of the aqueous media. An increase in particle swelling leads to a decrease in the friction coefficient. However, with the hard structures, the rolling of the particles in some cases can also lead to extremely low friction coefficient. In that case, the nature of the attachment of iv the particle to the surface does not matter and systematic degrafting of some particles was observed which allows surfaces to slide with small friction forces. Third, the complexation of a single-stranded siRNA through different interactions was investigated with model surfaces of various chemistry. The results show that ss-siRNA can adsorb onto hydrophilic (positively and negatively charged) as well as on hydrophobic substrates suggesting that the complexation can occur through hydrophobic interactions and hydrogen bonding in addition to electrostatic interactions. This study suggests that non-electrostatic interactions could be exploited to complement electrostatic interactions in the design of less toxic nanocarriers and that non-cationics nanovectors can be employed as a potential single-stranded siRNA delivery systems. The results presented in this thesis contribute to increase the knowledge in the field of physico-chemistry surface properties of biological interfaces.