Thèse de doctorat : Biologie cellulaire et moléculaire : Orléans : 2009. / Titre provenant de l'écran-titre.

Thèse doctorat : Chimie et Electrochimie Analytiques : Nancy 1 : 2005. / Titre provenant de l'écran-titre.

Thèse (Ph. D.)--Université Laval, 2007. / Bibliogr. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Thèse 3 cycle--Sc. des matériaux--Paris VI, 1974. / Bibliogr. p. 63-64. Résumés en français et en anglais.

Thèse (M.Sc.)--Université Laval, 2009. / Bibliogr.: f. 80-89. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Les silices nanostructurées sont des matériaux ultra-poreux (plus de 80% de porosité) utilisés pour la confection de Panneaux Isolants sous Vides (PIV). Elles possèdent des propriétés thermiques exceptionnelles, mais de piètres propriétés mécaniques.L’enjeu de cette thèse est d’étudier ces matériaux aux échelles de la particule (quelques nm), de l’agrégat de particules (quelques dizaines de nm) et de l’agglomérat d’agrégats (quelques centaines de nm), afin de mieux comprendre les comportements mécanique et thermique à l’aide de simulations, et de proposer des pistes pour améliorer le compromis thermique / mécanique. La nature particulaire du matériau et son caractère multi-échelle justifient l’utilisation de méthodes de simulations discrètes (DEM : Discrete Element Method). Un modèle original permettant de générer des agrégats à morphologiecontrôlée (dimension fractale, rayon de giration, porosité) est proposé. Le comportement à la compaction des agrégats est ensuite étudié par simulations DEM. Une approche par cyclage à faible densité a été développée pour obtenir des arrangements initiaux réalistes d’agrégats. La prépondérance des phénomènes adhésifs dans le système rend en effet celui-ci très sensible à l’arrangement initial. La réponse en traction des structures générées par compaction est également évaluée.L’influence de la morphologie des agrégats, de l’adhésion et du frottement ont été étudiées. L’accent est mis sur la comparaison de deux types de silices (pyrogénées et précipitées) présentant des morphologies différentes et pour lesquelles des données expérimentales permettent une confrontation avec les simulations. Les simulations présentées permettent d’apporter des réponses sur l’origine des différences de comportement mécanique observées expérimentalement pour ces deux types de silice.Une modélisation de la conductivité thermique du matériau, avec une focalisation sur la conductivité solide, est également proposée. / Nanostructured silicas are ultra-porous materials (more than 80 % porosity) used to make Vacuum Insulation Panels (VIP).They have exceptional thermal properties, but poor mechanical properties. The goal of this thesis is to study these materials at the scale of the particle (a few nm), the aggregate of particles (a few tens of nm) and the agglomerate of aggregates (a few hundred nm), in order to better understand mechanical and thermal behaviour using simulations, and to propose ways to improve the thermal / mechanical compromise. The particulate nature of the material and its multi-scale naturejustify the use of Discrete Element Methods (DEM). An original model allowing to generate aggregates with controlledmorphology (fractal dimension, radius of gyration, porosity) is proposed. The compaction behaviour of the aggregates is then studied by DEM. A low-density cycling approach has been developed to obtain realistic initial aggregate arrangements.The preponderance of adhesive phenomena in the system makes it very sensitive to the initial arrangement. The tensile response of structures generated by compaction is also evaluated. The influence of aggregate morphology, adhesion and friction were studied. Emphasis is placed on the comparison of two types of silica (pyrogenic and precipitated) with different morphologies and for which experimental data allow a comparison with simulations. The simulations presented allow us to provide answers on the origin of the differences in mechanical behaviour observed experimentally for these two types of silica.A modeling of the thermal conductivity of the material, with a focus on solid conductivity, is also proposed.

This thesis deals with the variability of hop oils in the hop cones. Hops is the most important raw material for the production of beer and hop oils are the most important group of compounds responsible for the aroma of hops and thus the beer. Essential oils are applied in commercial quality assessment of cone hops for beer production. Essential oils have also hop buffer and antibacterial effects and pharmacology are used for suppressing agitation, restlessness and insomnia. Essential oils are complex mixtures of hundreds of natural compounds of different chemical composition. They represent a mixture of carbon compounds, oxygen compounds and sulfur compounds. The content of hop oils in the hop cones depends on the genetic characteristics of the variety, growing area, the average temperature, rainfall, and other conditions cultivation. This work was performed by steam distillation determination of hop oils. The determination was carried out on samples from 2012 and 2013, the essential oil content was profitable in 2012. Highest value of the hop oils was measured in a variety of Premiant from Tršice growing region (837 micro liters.100g-1). The lowest value then the variety Saaz classical form of the Saaz hop-growing area (220 mocro liters.100g-1).

Botanical pesticides that include essential oils are considered to be one of the possible alternatives to synthetic chemical pesticides in plant protection, therefore it is important to develop our knowledge about these natural substances. This Master thesis comprises the residual analysis of selected compounds contained in Cymbopogon citratus Stapf, Pelargonium graveolens L'Hér and Thymus vulgaris L. essential oils after their application on plant material. The chemical composition of each essential oil was initially analyzed by gas chromatography - mass spectrometry (GC - MS). This analysis helped to select three representative compounds for each essential oil and the residues were determined for each of them. Citral, Geranyl-acetate and Limonene were selected for C. citratus, b-Citronellol, Geraniol and Linalool for P. graveolens and Thymol, p-Cymene and g-Terpinene for T. vulgaris. Two new methods to determine botanical pesticide residues were developed. The new methods should provide faster and easier analysis. One of them uses Solid Phase Microextraction method (SPME). The other one, that was applied in the residual analysis, uses hexane for extraction. The results show that essential oils' persistence is very low on the surface of plant material, which would imply they are environmentally friendly and safe for human health assuming correct manipulation with these substances.

The aim of this thesis was to find biologically active substances that would be suitable as natural conservatives for herbal sirups, in our case elderflower sirup. Because esential oils are among biologically active substances well known for their antimicrobial aktivity we chose thyme, lemongrass and clove bud essencial oils to be tested on the eldeerflower sirup. Potencial use in a private small scale production was one of the reasons for this particular topic and therefore its technological inovation. The emulgated essential oil was mixed with the sirup and observed for 14 days for the colonies forming units (CFU) which was determined by the drop plate technique. Cultivation was done at a room temperature 22° C as its expected by the consumer that sirups may be stored this way. After the cultivation the numbers of colony forming units were counted and turned into a logaritmic value. Clove essential oil proved a significant difference between control specimen and the essential oil preserved specimen. Statistically remarkable corelation was found also between different concentrations. As well as clove, lemongrass essencial oils proved certain antimicrobiologial activity also with statistical significance. Thyme essential oil proved antimicrobiological activity as well only with no significant difference between concentrations. Essential oils are suitable as natural conservatives for not only their proven antimicrobiological activity but also low price and easy application.

The aim of this thesis was gathering current literature data on factors (internal - the type, stage of development) and (external - soil and climatic conditions for cultivation) that most affect the oil content in the genus Mentha L. On the basis of the results obtained during laboratory analysis of quantitative content of essential oils in plants of the genus Mentha L. taxa planted on an experimental plot of garden-technical faculty in the refrigerator was a hypothesis based harvesting time, the impact of species and cultivars on the essential oil content is confirmed. Further, the predicted calculation that based on the current state of the essential nutri-ents in the soil experimental plot could be the addition of nitrogen fertilizer to increase the amount of green mass, and while maintaining the integrity of the plants, especially leaf area increase the total yield of oil from the cultivated taxa genus Mentha L. The direct impact of climatic conditions on essential oil content was not established due to the very dry summer with little rainfall and dependence on irrigation.