L’alimentation des pays industrialisés, souvent trop riche en glucides et en lipides, a engendré une augmentation marquée de l’obésité et favorisé le risque de diabète. Face à ce constat, l’industrie agroalimentaire s’est efforcée de développer des produits allégés. Au sucre, ont ainsi été substitués les édulcorants acaloriques, molécules au goût sucré non métabolisées par le corps humain. Ces édulcorants sont souvent obtenus par voie de synthèse chimique comme l’aspartame, l’acésulfame K ou encore le sucralose. S’ils sont autorisés dans la confection de produits alimentaires, la toxicité de ces édulcorants et leur impact sur la santé humaine nourrissent cependant les débats au sein de la communauté scientifique, ainsi des solutions alternatives sont envisagées. Stevia rebaudiana Bertoni est une plante originaire du Paraguay. Son intérêt principal réside dans le fait qu’elle contient des molécules acaloriques au goût sucré, les glycosides de stéviol, dont les plus connus sont le rébaudioside A et le stévioside. Les études effectuées sur ces diterpènes glycosilés tendent à souligner leur innocuité. Ils présenteraient même des vertus thérapeutiques, comme des propriétés anti-hypertensive ou antidiabétique, et semblent ainsi être une alternative prometteuse au sucre et aux édulcorants artificiels. Notre étude s’est orientée sur l’extraction aqueuse des glycosides de stéviol des feuilles de Stévia. A l’échelle laboratoire, nous avons pu mettre en évidence que la cinétique d’extraction des molécules cibles est principalement limitée par la diffusion des solutés dans la matrice solide végétale. Il n’y aurait pas de réaction chimique, de gonflement de la matière ou de modification de la porosité pendant le processus d’extraction. Nous avons également pu souligner que la préparation de la matière (séchage et broyage) et les conditions opératoires (température, ratio liquide-solide et agitation) sont des facteurs prépondérants sur l’efficacité d’extraction des édulcorants. A l’échelle pilote, les résultats obtenus en systèmes discontinu et continu ont pu mettre en exergue des influences similaires de la préparation de la matière et des conditions opératoires ; nous avons de plus pu démontrer que la qualité du mélange des phases solide et liquide était un facteur clé à l’efficacité de l’extraction. Fort de ces résultats nous avons pu développer un procédé d’extraction en système continu, adapté à l’extraction des glycosides de stéviol des feuilles de Stévia, et combiné à une étape de séparation solide-liquide. Au travers de nos différentes expériences, nous avons pu décrire précisément son fonctionnement et optimiser l’extraction afin de pouvoir envisager une transposition à l’échelle industrielle. / Industrialized countries food, often too rich in carbohydrates and fat, has resulted in an important increase in obesity and risk of diabetes. Given this fact, the food industry tries to develop diet products. Sugar was substituted by calorie-free sweeteners, sweet-tasting molecules non-metabolized by the human body. These sweeteners are often obtained by chemical synthesis such as aspartame, acesulfame K or sucralose. Even if they are allowed in the manufacture of food products, the toxicity of these sweeteners and their impact on human health raise debate within the scientific community, so alternatives are being considered. Stevia rebaudiana Bertoni is a plant native from Paraguay. Its main interest lies in the fact that it contains calorie-free sweet tasting molecules, steviol glycosides, of which the most common are rebaudioside A and stevioside. Studies of these glycosylated diterpenes tend to highlight its safety. They even present therapeutic characteristics, such as anti-hypertensive or anti-diabetic properties, and thus seem to be a promising alternative to sugar and artificial sweeteners. Our study focused on the aqueous extraction of steviol glycosides from Stevia leaves. At thelaboratory scale, we were able to demonstrate that extraction kinetics of target molecules are mainly limited by diffusion of solutes in the plant solid matrix. There would be no chemical reaction, swelling of the plant material, or modification of the porosity during the extraction process. We have also shown that the preparation of the plant material (drying and milling) and the operating conditions (temperature, liquid-solid ratio and agitation) are overriding factors on the sweeteners’ extraction efficiency. At the pilot scale, the results obtained in batch and continuous systems could highlight similar influences with the preparation of the plant material and the operating conditions. We have also shown that the quality of the mixing of solid and liquid phase was a key factor in extraction efficiency. With these results we have developed a continuous extraction process, suitable for the extraction of steviol glycosides from Stevia leaves, which has combined with a step of solid-liquid separation. Through our experimentation we have accurately described its operation and optimized the extraction in order to consider a transposition to the industrial scale.

El objetivo del presente trabajo, es la proposición de una lectura propia de la poesía del autor chileno Claudio Bertoni Lemus. El eje central de la propuesta es la comprensión de algunos poemas de su obra a través del prisma que él mismo brinda: la ironía. El método utilizado fue el estudio de tres de sus poemarios, Ni yo , De vez en cuando y Jóvenes buenas mozas , concadenando su aprehensión a las lecturas de textos acerca de la figura retórica de la ironía y el carnaval, con el fin de comprobar que las lecturas más comunes de la obra bertoniana- que la tildan de humorística y cotidiana por sobre todo- no son correctas, pues su trabajo sería más bien irónico y enmascarado lo que implicaría una estructura poética superficial contraria a la subyacente, cómica y trágica respectivamente. Podemos decir que con el análisis realizado, hemos logrado develar la naturaleza sufriente de la obra bertoniana, la cual, apoyada por la máscara de la comicidad y la sencillez de un hablar coloquial y muchas veces prosaico, esconde el verdadero sentir del poeta, quien experimenta la soledad y sobretodo una lucidez demasiado aguda, que lo convierte en un hablante clown-doliente, en un Pierrot contemporáneo.

Claudio Bertoni Lemus, nacido en 1946, poeta, fotógrafo y artista visual, chileno, aún vivo y residente en Concón. Cursó sus estudios básicos en el Liceo Alemán de Santiago, para luego realizar estudios de Filosofía en la Universidad de Chile, los que dejó inconclusos, también hizo estudios de música en el Conservatorio Nacional. Fue percusionista del primer grupo jazz-rock chileno, llamado Fusión. En 1964 viaja a Estados Unidos, becado por la American Field Service, viaja específicamente a Denver, lugar donde se desarrolla parte de la mítica novela En el camino, del escritor beat Jack Kerouac. En 1972, siguiendo la línea de los viajes, parte a Londres y París, con la también poeta y artista visual, Cecilia Vicuña, con quien integró la agrupación artística “Tribu No”. En Inglaterra tomarán contacto con parte del grupo Fluxus y será allí donde publique su primer libro, en formato artesanal, El cansador intrabajable (Beau Geste Press, 1973), al igual que Cecilia Vicuña su Sabor a mí (Beau Geste Press, 1973), ambos reeditados por Ediciones Universidad Diego Portales. Regresa en 1976 a Concón, donde residen sus padres y donde debe enfrentar la enfermedad y muerte de su madre. También debe hacerse cargo, ya en Chile decididamente, de su inestabilidad siquiátrica y de las fuertes crisis que le sobrevienen. En 1993 recibe la beca Guggenheim. Ha traducido poemas del escritor Charles Bukowski.

Stevia or Stevia rebaudiana Bertoni are two of the numerous names of this subtropical plant with a sweetening power as much as 300 times higher than in case of sucrose. Stevia is a plant with a very interesting, but up to this date not very utilised potential. The fields of its application, processing, cultivation and wintering options have not been explored very extensively, and therefore I have decided to elaborate this topic related to the impact of the environmental conditions for growing of Stevia rebaudiana. The resources for the text of the diploma thesis were formed by available specialised publications and the Internet. The first part of the thesis represents a brief overview of the whole issue concerning the topic of Stevia rebaudiana. The objectives, hypotheses and methodology of the conducted research, including the findings based on the plant growing as well, and the evaluation of the experiment results have been included in the second part. The purpose of the thesis was to expand the knowledge regarding cultivation, reproduction methods and wintering options of the stevia plants. A field and a greenhouse experiments were staged with a focus on temperature indicators during the growing season and their impact on the total number of wintered plants. Simultaneously, an evaluation of the dry matter yield of the plants per an area unit and statistical processing and evaluation of the experiment results have been performed. Further, a determination of seed germination for Stevia rebaudiana in laboratory conditions has been conducted. The research results have shown that the plants obtained vegetatively are more suitable for cultivation due to a higher yield of the dry matter in both greenhouse as well as field conditions. The only pests invading stevia were the whiteflies appearing only in the greenhouse environment. Variable conditions were arranged for the wintering of the Stevia rebaudiana plants within the experiment; and in spite of the various materials and thermal insulation layers, the plants have not successfully wintered in an unheated environment. On the contrary, in the heated greenhouse space, most of the plants have successfully wintered. The stevia seed germination was low and proves the opinion of the majority of authors. The dry matter yields also matched the yields mentioned in the specialised literature.

This master thesis is oriented on study antimicrobial effects extracts and macerates from cure Stevia rebaudiana Bertoni. Teoretical part describes basic information about plant Stevia, summary of health significant matters contained in Stevia and posobilities preparing extracts from Stevia. Antimicrobial effects extracts and macerates from cure Stevia were testing on food-borne bacteria (Bacillus cereus and Micrococcus luteus) and yeasts (Geotrichum candidum and Hansenula anomala). Microorganism, extracts and macerates were chosen on basis previous study (Study of antimicrobial effects Stevia Rebaudiana extracts, Eva Rakovská). For screening antimicrobial activity were determined the growth curves by using turbidimetrie for bacteria and direct treetment metod of cells number for yeasts. Antimicrobial effects were confirmed aplication with diffusion pit method on the agar ranges. From the results flow the testing extracts and macerates from stevia analysed antimicrobial effects. The best effect was demostrated on macerates and the most sensitive was bacteria Micrococcus luteus with the best inhibitoring effects.

The steviolglycosides are the natural, sweet substances from Stevia rebaudiana Bertoni. It affect human health positively and its sweetness is 300x stronger than the sweetness of sucrose. That's why it's used to sweetening the commercial products. Because of its potential properties it's good to have an appropriate method to isolate it. High performance liquid chromatography ( HPLC) is based on the separation of analyte between two immiscible phases with high pressure pump and appropriately chosen stationary phase in the column. Than the analytes come out from the column in different retention times. This master´s thesis follows up selection of the best HPLC system for isolation of the main steviolglycosides and its analysis in commercial products. In the theoretical part of the thesis is described the origin, basic characteristics, botanical description, cultivation and affect to the human health of Stevia rebaudiana Bertoni and its use in food industry. There are also concisely characterized the sweet substances contained in the plant, so called steviolglycosides. Than there are given the theoretical basics of high performance liquid chromatography, HPLC instrumentation and its specific applications at sleviolglycosides with the basic chromatographic parameters. The object of the first experimental part was to research the optimum conditions for time and separation effective chromatographic analysis and select the best chromatographic system for isolation of steviolglycosides. In the second experimental part, I have compared and defined the main steviolglycosides (stevioside, rebaudioside A) in nine selected products, commercially available in Czech republic, with the best chromatographic method. In these products was the contain of the stevioside or rebaudioside A confirmed or refused.

Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.

<p>Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.</p>

Flavonoids were identified and quantified in samples of dry leaves of plant Stevia rebaudiana Bertoni. Content of flavonols (kaempherol, quercetin, myricetin, rutin) and flavons (apigenin, luteolin) were compared in three samples (standard leaves of Stevia rebaudiana Bertoni, Stevia rebaudiana Bertoni origin from Ukraine and from Czech republic), that were extracted by three extraction methods (PSE, ultrasonic extraction, Soxhlet extraction) with two polar solvents, methanol and ethanol, in combination with non-polar hexane. Extracts were analyzed by HPLC with detection UV-VIS. Antioxidant activity and total content of flavonoids in extracts were measured by spectrometry. Stable free radical DPPH. was used for determination of scavenging effect in extracts. PSE was the most effective extraction method with this conditions – 120 °C, dynamic mode and with methanol like solvent.