The thesis deals with molecular gastronomy as an expanding culinary direction and is focused on the use in chemistry teaching in primary and secondary education. There are described home experiments which were verified, documented and explained.

Desde meados do século XX, métodos analíticos, numéricos e experimentais foram utilizados para quantificar a eficiência térmica na soldagem a arco, isto é, a razão entre a energia do arco elétrico e a energia que é entregue ao material durante a soldagem. Conhecendo-se a eficiência térmica, as dimensões da chapa e as propriedades térmicas do metal de base, torna-se possível prever as taxas e tempos de resfriamento a partir de modelo analíticos. Consequentemente, permitindo a previsão das transformações de fase, garantindo que os valores das propriedades da junta soldada se enquadrem dentro de um intervalo desejado. Os modelos de previsão de taxa de resfriamento derivados a partir dos modelos analíticos de Rosenthal são validos apenas no regime quase estacionário. Todavia, estes modelos costumam ser utilizados com pouco critério, mesmo em situações em que este regime não é alcançado. Portanto, para o desenvolvimento de modelos mais precisos e acurados para previsões das taxas de resfriamento, torna-se necessário entender como os termos do balanço de energia se desenvolvem durante a soldagem, até atingir o regime quase estacionário. Este trabalho tem como objetivo desenvolver um entendimento mais abrangente dos fatores que impactam nos valores de taxas de resfriamento em juntas soldadas. Realizaram-se ensaios de calorimetria com nitrogênio líquido para diferentes tempos de soldagem, como também, foram coletados ciclos térmicos em diferentes posições ao longo do cordão, buscando entender como as variações no balanço de energia, ao longo da soldagem, impactam no material. A partir da Metodologia de Superfície de Resposta, foram obtidos os modelos empíricos da energia entregue ao material e da eficiência térmica do arco. Um novo entendimento acerca do balanço de energia na soldagem foi alcançado, servindo de base para o desenvolvimento e validação de um modelo preditivo de taxa de resfriamento, válido para diferentes condições de fluxo de energia no material. / Since the early 20th century, numerical and experimental methods have been used to quantify the thermal arc efficiency in welding, i.e., the ratio between the electric arc energy and the energy delivered to the material during welding. Knowing the thermal arc efficiency, the sample dimensions and the thermal properties of the base metal, it is possible to predict the cooling rates by analytical models. Consequently, allowing the prediction of phase transformations in the material, ensuring that values of welded joint properties are within a desired range. Cooling rate prediction models derived from Rosenthal\'s analytical models are valid only in quasi-stationary state. However, these models are used with little criterion, even in situations where this state is not achieved. Therefore, to development of more accurate and precise models for the prediction of cooling rate it become necessary to understand the evolution of the energy balance during the welding until the quasi-stationary state was reached. This work aims to develop a more comprehensive understanding of the factors that affect the cooling rate in welded joints. Calorimetry tests with liquid nitrogen were carried out for different welding times, and thermal cycles were collected at different positions along the weld bead, to understand how the variations in the energy balance during the welding affect the material. From the Response Surface Methodology, the empirical models of delivered energy and the thermal arc efficiency were obtained. A new understanding about the energy balance in the welding was found, that was used for the development and validation of a predictive model of cooling rate, valid for different condition of energy flow in the material.

Desde meados do século XX, métodos analíticos, numéricos e experimentais foram utilizados para quantificar a eficiência térmica na soldagem a arco, isto é, a razão entre a energia do arco elétrico e a energia que é entregue ao material durante a soldagem. Conhecendo-se a eficiência térmica, as dimensões da chapa e as propriedades térmicas do metal de base, torna-se possível prever as taxas e tempos de resfriamento a partir de modelo analíticos. Consequentemente, permitindo a previsão das transformações de fase, garantindo que os valores das propriedades da junta soldada se enquadrem dentro de um intervalo desejado. Os modelos de previsão de taxa de resfriamento derivados a partir dos modelos analíticos de Rosenthal são validos apenas no regime quase estacionário. Todavia, estes modelos costumam ser utilizados com pouco critério, mesmo em situações em que este regime não é alcançado. Portanto, para o desenvolvimento de modelos mais precisos e acurados para previsões das taxas de resfriamento, torna-se necessário entender como os termos do balanço de energia se desenvolvem durante a soldagem, até atingir o regime quase estacionário. Este trabalho tem como objetivo desenvolver um entendimento mais abrangente dos fatores que impactam nos valores de taxas de resfriamento em juntas soldadas. Realizaram-se ensaios de calorimetria com nitrogênio líquido para diferentes tempos de soldagem, como também, foram coletados ciclos térmicos em diferentes posições ao longo do cordão, buscando entender como as variações no balanço de energia, ao longo da soldagem, impactam no material. A partir da Metodologia de Superfície de Resposta, foram obtidos os modelos empíricos da energia entregue ao material e da eficiência térmica do arco. Um novo entendimento acerca do balanço de energia na soldagem foi alcançado, servindo de base para o desenvolvimento e validação de um modelo preditivo de taxa de resfriamento, válido para diferentes condições de fluxo de energia no material. / Since the early 20th century, numerical and experimental methods have been used to quantify the thermal arc efficiency in welding, i.e., the ratio between the electric arc energy and the energy delivered to the material during welding. Knowing the thermal arc efficiency, the sample dimensions and the thermal properties of the base metal, it is possible to predict the cooling rates by analytical models. Consequently, allowing the prediction of phase transformations in the material, ensuring that values of welded joint properties are within a desired range. Cooling rate prediction models derived from Rosenthal\'s analytical models are valid only in quasi-stationary state. However, these models are used with little criterion, even in situations where this state is not achieved. Therefore, to development of more accurate and precise models for the prediction of cooling rate it become necessary to understand the evolution of the energy balance during the welding until the quasi-stationary state was reached. This work aims to develop a more comprehensive understanding of the factors that affect the cooling rate in welded joints. Calorimetry tests with liquid nitrogen were carried out for different welding times, and thermal cycles were collected at different positions along the weld bead, to understand how the variations in the energy balance during the welding affect the material. From the Response Surface Methodology, the empirical models of delivered energy and the thermal arc efficiency were obtained. A new understanding about the energy balance in the welding was found, that was used for the development and validation of a predictive model of cooling rate, valid for different condition of energy flow in the material.

MSCAGR (Animal Science) / Department of Animal Science / The Boer goat (Capra hircus) is one of the most desirable goat breeds for meat production. The impact of cryopreservation on the viability of its semen depends on the extenders, freezing and thawing methods. This study evaluated the effects on sperm viability in Boer goat semen extended using Bioxcell, Biladyl and Ham’s F10, and frozen in semen straws placed on a rack at 4, 5, 6 or 7 cm above the surface of liquid nitrogen. After storage in liquid nitrogen for 7 days, the frozen semen was thawed at 37 oC for 30 seconds or 90 oC for 5 seconds. Samples of sperm were also frozen to -196 oC in a programmable freezer, as the control regime for the freezing treatments. Sperm morphology, motility and viability were evaluated using the computer aided sperm analysis (CASA) system in a randomised design in which the treatments were in a 3 (extender) X 5 (freezing regime) and X 2 (thawing regime) factorial arrangement. The extenders Bioxcell and Biladyl were affected in the total motility, progressive motility and static (P<0.01), the motility was overall maintained only in straws placed at 5 cm above the liquid nitrogen level, with significant difference for the interaction extender X freezing regime in the total motility (p<0.01), non-progressive motility (p<0.05) and progressive motility (p<0.01), the 37 oC for 30 sec thawing regime had significantly more (P<0.05) in cut-head spermatozoa. Ham’s F10 extender had significantly lower normal spermatozoa (P<0.05) compare to Biladyl and Bioxcell extenders. In conclusion, the extender type, freezing and thawing regime were important factors for consideration in goat semen / NRF

Chemiker sind Alchemisten, Köche Hexenmeister des Geschmacks. Beide Berufsgruppen haben sich in den vergangenen Jahren den Abenteuern des experimentellen Kochens bei sehr kalten Temperaturen verschrieben. Die Kombination von Chemie und Kochen bringt neue und spektakuläre kulinarische Kreationen hervor und schafft avantgardistische Gaumenverführungen mit verblüffenden Sinneserlebnissen und dies bei den sehr tiefen Temperaturen des flüssigen Stickstoffs (-196 °C) und des Trockeneises (-78.5 °C). Das Molekulare Kochen bei tiefen Temperaturen lebt von den spannungsgeladenen Gegensätzen von Wärme und Kälte und führt im Resultat zu neuartigen, bisher unbekannten Geschmackserlebnissen. Gleichzeitig wirkt die Molekulare Küche bei tiefen Temperaturen als Ideen- und Impulsgeber für innovative Speisen und Getränke und betritt dabei Neuland der Avantgarde-Küche, in der es dem sinnlichen Genuss eine neue, richtungsweisende Dimension verleiht. Dabei bedient sich das Molekulare Kochen mit flüssigem Stickstoff bzw. Trockeneis des Wissens um chemische und physikalische Prozesse. Dies macht die Molekularküche in der Kälte so spannend, denn sie bewegt sich damit auf dem Grenzgebiet der traditionellen Cuisine und den Wissensgebieten der Naturwissenschaften Chemie und Physik und führt zu einer gegenseitigen Wissensbereicherung in diesen Disziplinen. In diesem Buch wird der Autor, ein Chemiker, zum Grenzgänger seines Fachgebiets und verknüpft sein Wissen aus dem Chemielabor mit dem aus der Küche. Er schafft damit einen Ort für das Kochen mit Kälte und lässt Sie an außergewöhnlichen, unvergesslichen Geschmackserlebnissen sowie an chemischen und kulinarischen Augenfreuden teilhaben. Voraussetzung für ein erfolgreiches Kochen in der Kälte ist das Wissen um die Kältemittel wie dem flüssigen Stickstoff und dem Trockeneis. Deshalb befasst sich diese Schrift neben avantgardistischen Kochrezepten auch mit den beiden Kältemitteln, so dass beide Aspekte, nämlich die Chemie und die Küche, miteinander vereint werden. Basierend darauf, und gepaart mit diesen Erkenntnissen, werden innovative, „eiskalte“ Cocktails und Speisen vom Popcorn, über Bananasplit bis zu Espuma vorgestellt. Es handelt sich dabei um Speisen, die im Inneren flüssig bleiben, aber außen eine feste, krustige Hülle aufweisen, die beim Erwärmen im Mund zerplatzt, dabei kalte „Nebel“ bildet und sich so ein köstlicher Geschmack auf der Zunge ausbreitet. Ein unvergessliches Gaumen-Erlebnis! Des Weiteren werden einfache, aber spektakuläre und effektvolle chemische Experimente zu vereinzelten Kochrezepten rund um das Thema Molekulare Küche bei tiefen Temperaturen vorgestellt, die die Kochvorführungen bereichern und zeigen, dass die „Chemie“ zwischen Chemikern und Köchen stimmt. Die chemischen Vorgänge mit Reaktionsgleichungen zu den einzelnen Experimenten sind in Kapitel 4 dieser Schrift für Chemieinteressierte aufgeführt. In diesem Sinne wünscht der Autor beim Lesen, Experimentieren mit Flüssigstickstoff und Trockeneis, sowie beim Genießen der zubereiteten Köstlichkeiten viel Vergnügen und verspricht eine interessante Reise in die Molekulare Küche bei tiefen Temperaturen.

<p>In this study, universal databases and semi-empirical correlations are developed for cryogenic two-phase heat transfer and pressure drop in heated tubes undergoing flow boiling.</p>

Diplomová práce se zabývá studiem projektu tepelného spínače a dosažených výsledků. Zaměřuje se především na vývoj zařízení pro zkoušení tepelného spínače v podmínkách odpovídající prostředí planety Marsu. První část práce se zabývá především popisem vývoje zkušební komory určené pro simulaci extrémních podmínek, tj. nízkého tlaku a teplot, od předběžného návrhu až po konečnou podobu komory, která bude použita pro předepsané zkoušky. Práce popisuje také důvody úprav některých částí komory a uvádí návrhy řešení nepředvídaných událostí, které vznikly v průběhu testů. Cílem druhé části práce je návrh kampaně pro zkoušení tepelného spínače od úvodních zkoušek ověření základní funkčnosti komory, přes ověření vlastností a nastavení všech systémů měřícího zařízení, až po zkoušky na prvních vzorcích a závěrečném kvalifikačním modelu tepelného spínače. Dále se práce zaměřuje na postup vyhodnocení naměřených dat a jevů, které jej ovlivňují. Kalibrační zkoušky zařízení, systémů a postupu vyhodnocení naměřených dat, které byly provedeny na speciálně navržených náhradních vzorcích, jsou téměř u konce. Jakmile budou výsledky schváleny, zkušební komora i navržené postupy měření budou připraveny pro požadované zkoušení vzorků tepelného spínače.