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El modelo de dínamo magnetohidrodinámico (MHD) es el más aceptado para describir el origen de los campos magnéticos celestes. Cualitativamente, el mismo propone que en una región convectiva de un objeto celeste puede convertirse energía cinética en magnética, provisto que exista un tenue campo magnético de fondo. Como resultado, se produce una amplificación local del campo magnético inicial, dando lugar a uno asociado al propio objeto celeste. A pesar de la simplicidad de esta descripción cualitativa y de haber sido formulado hace más de 100 años, el modelo de dínamo MHD presenta aún múltiples problemas abiertos. A modo de ejemplo, en el caso del campo magnético celeste más próximo, el terrestre, aún resulta esquiva la formulación de un modelo reducido que permita reproducir la topología y variabilidad temporal del campo geomagnético. Otro problema que atañe al geodínamo y a numerosos dínamos experimentales, es la influencia de las condiciones de contorno, particularmente las electromagnéticas, en la posibilidad de tener un dínamo autosostenible. Tal vez la principal dificultad en el tratamiento de estos problemas es que el fenómeno de dínamo MHD es inherentemente no lineal, requiriendo capturar la dinámica turbulenta del flujo. Por este motivo, es frecuente en esta área el estudio mediante simulaciones numéricas, preferentemente de alto orden. En esta tesis se presenta un estudio numérico del problema del geodínamo, incluyendo el desarrollo e implementación de técnicas numéricas de alto orden previamente inexplorados en contextos MHD. Se estudian primeramente las características que posee un modelo simple de geodínamo que consiste en una esfera rotante, con bordes conductores y sin convección. Se reportan las soluciones obtenidas para distintas combinaciones de los números de Ekman (asociado a la rotación) y Reynolds magnético (asociado a la advección magnética). Asimismo se compara la topología y la variabilidad temporal de algunas de las soluciones contra datos geomagnéticos, encontrando numerosos puntos de acuerdo. Posteriormente, se introduce una técnica de alto orden para resolver las ecuaciones de dínamo convectivo empleando un método de continuación de Fourier. Esta novedosa conjugación permite resolver problemas de flujos confinados, empleando diferentes condiciones de contorno manteniendo convergencia de alto orden. La técnica resultante se implementa en un nuevo código paralelo para una geometría cartesiana tridimensional (3D) llamado SPECTER, aunque puede ser fácilmente extendida a otro tipo de dominios. Empleando SPECTER, se estudian a continuación tres problemas paradigmáticos: los flujos de Poiseuille y Hartmann, junto con la convección de Rayleigh-Bénard. Este estudio permite evaluar el correcto desempeño de la técnica y del propio código, reproduciendo resultados previos para dicho conjunto de problemas. Finalmente, se emplea SPECTER para estudiar la influencia de las condiciones de contorno electromagnéticas en el número de Reynolds magnético crítico a partir del cuál un dínamo convectivo puede mantener un campo magnético en el tiempo. Las conclusiones obtenidas al respecto resultan de gran utilidad para proyectos de dínamos experimentales actualmente en marcha, como así también para la comunidad de geodínamo en general. The magnetohydrodynamic (MHD) dynamo model is the most accepted one for describing the origin of celestial magnetic fields. Qualitatively, it proposes that in a fluid convective layer inside the celestial object kinetic to magnetic energy conversion can take place, given a faint background magnetic field. As a result, a local amplification of the starting magnetic field is attained, leading to one associated with the celestial object itself. Despite the simplicity of this qualitative description, and of having been formulated over 100 years ago, the MHD dynamo problem still presents many unsolved questions. For instance, in the case of the closest celestial magnetic field, i.e. the geomagnetic field, a reduced model which gives accurate predictions of the field’s topology and time variability is still being actively pursued. Another problem, involving both the geodynamo and laboratory experiments, is the influence of boundary conditions, particularly electromagnetic ones, in the feasibility of attaining a self sustaining dynamo. Perhaps the biggest hurdle in the treatment of these problems is the fact that the MHD dynamo is inherently non-linear, requiring the turbulent dynamic of the flow to be accurately captured. For this reason, it is customary in dynamo research to employ numerical simulations, preferentially with high order convergence. In this thesis a numerical study of the geodynamo problem is presented, including the development and implementation of high order numerical techniques previously unexplored in MHD contexts. First studied are the features of a simplified geodynamo model, one consisting of a rotating spherical cavity with conducting boundaries and without convection. The obtained solutions are reported as a function of the Ekman number (associated to the rotation rate) and the magnetic Reynolds number (associated with magnetic field advection). Additionally the topology and time variability of a subset of the solutions are compared against geomagnetic data, finding considerable agreement. Afterwards, a novel high order technique is introduced for numerically evolving the convective dynamo equations by means of a Fourier Continuation method. This novel approach allows solving for confined flows employing different boundary conditions while at the same time keeping high order convergence.The resulting algorithms are implemented for a three-dimensional (3D) cartesian geometry in a new parallel code name SPECTER, although it can be easily extended to domains with different geometries. Employing SPECTER, three para- digmatic fluid dynamic problems are studied, namely: Poiseuille and Hartmann flows together with Rayleigh-Bénard convection. This study evaluates the correct performance of the proposed technique and the code itself, reproducing several previous results for the aforementioned set of problems. Finally, SPECTER is employed to study the influence of the electromagnetic boundary conditions in the critical magnetic Reynolds number for which a convective dynamo becomes self-sustaining. The obtained results are of great interest for ongoing experimental dynamo projects as well as to the much broader geodynamo community. Fil: Fontana, Mauro. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Antibiotic residues in milk are a serious health and technological problem in dairy processes. This study aims to verify the absence of administered antimicrobials after therapeutic treatments, taking into consideration the withdrawal period, and to evaluate the reliability of screening tests under field conditions after confirmatory HPLC-HRMS (High Performance Liquid Chromatography-High-Resolution Mass Spectrometry) Orbitrap analysis. Moreover, the presence of expected or non-targeted metabolites was investigated using the new Compound Discoverer approach. The presence of antimicrobial drugs was shown in 29% of the samples, and also sometimes their metabolites (for enrofloxacin and lincomycin), despite the fact that samples were collected at the seventh milking. Moreover, in 9% of the samples, undeclared treatments were revealed due to the presence of both parent drugs and metabolites. Lastly, the putative identification of two new enrofloxacin metabolites, ENRO-N-methylacetamide and ENRO-ornithine, was proposed. In the light of this evidence, it must be borne in mind that metabolites, some of which are pharmacologically active, may also pose a risk to consumers and for the entire processing of milk in the cheese industries.

Submitted by Aline Batista (alinehb.ufpel@gmail.com) on 2019-11-14T12:43:42Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_Mauro_Fontana.pdf: 2061587 bytes, checksum: 13d8f797a91e515b231fd71d9e5cf857 (MD5) Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2019-11-14T14:07:49Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_Mauro_Fontana.pdf: 2061587 bytes, checksum: 13d8f797a91e515b231fd71d9e5cf857 (MD5) Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2019-11-14T14:07:55Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_Mauro_Fontana.pdf: 2061587 bytes, checksum: 13d8f797a91e515b231fd71d9e5cf857 (MD5) Made available in DSpace on 2019-11-14T14:08:00Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_Mauro_Fontana.pdf: 2061587 bytes, checksum: 13d8f797a91e515b231fd71d9e5cf857 (MD5) Previous issue date: 2018-08-30 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES A produção de vinho e derivados transforma cerca de 20 % do peso original das uvas em resíduo, sendo o bagaço o principal co-produto. Esse bagaço formado basicamente de cascas e sementes de uva, apresenta compostos de alto valor nutricional, e possui grande quantidade de compostos fenólicos com ação antioxidante o qual pode ser aproveitado na indústria alimentícia. Assim, objetivou-se com o presente estudo desenvolver e caracterizar farinhas de bagaço de uva, de diferentes cultivares Vitis vinifera, elaboradas por meio e desidratação e de liofilização, além de analisar as propriedades tecnológicas, nutricionais e sensoriais de biscoitos tipo cookie desenvolvidos com substituição parcial de farinha de trigo por farinha de bagaço de uva desidratado. Na análise de composição centesimal as farinhas apresentaram comportamentos distintos, tanto entre os tratamentos, quanto entre os tipos estudados, com destaque para os altos teores de fibra (acima de 14g.100g-1), conteúdo de minerais e Índice de Solubilidade em Água (ISA). Os três biscoitos tipo cookies elaborados, apresentaram elevados teores de proteína e fibras sendo classificados como fontes de ambas. Os testes microbiológicos apontaram total segurança para consumo alimentar dos biscoitos. Os cookies foram analisados por análise sensorial com escala hedônica e intenção de compra onde os resultados foram satisfatórios. The production of wines and other products transforms about 20% of the original weight of the grapes into waste and the residue is the main co-product. This marc basically consists of skin and seeds of grapes that present compounds of high nutritional value, and has a large amount of phenolic compounds with antioxidant action, and can be used in the food industry. Thus, the objective of this study was to develop and characterize bagasse grape flours of different cultivars Vitis vinifera, elaborated by means of dehydration and freeze-drying, as well as to analyze the technological, nutritional and sensory properties of cookies developed with partial substitution of wheat flour for dehydrated grape marc flour. In the analysis of the centesimal composition the flours presented different behaviors, both among the treatments and among the studied types, with emphasis on high fiber contents (above 14g.100g-1), mineral content and Water Solubility Index (WSI). The three cookies elaborated, presented high levels of protein and fibers being classified as sources of both. Microbiological tests indicated total safety for food consumption of biscuits. Cookies were analyzed by sensorial analysis with hedonic scale and purchase intention where the results were satisfactory.

Hace más de un siglo que Bernard Brunhes propuso la existencia de reversiones del campo magnético terrestre en escalas de tiempo geológicas. Esta teoría, hacia mediados del siglo XX, logró la aceptación de la comunidad científica. No obstante, aún no ha sido posible establecer mecanismos precisos que permitan explicar las reversiones geomagnéticas. El presente trabajo muestra que, aún en una geometría sencilla, las ecuaciones de la magnetohidrodinámica difusiva y rotante contienen todos los ingredientes para reproducir satisfactoriamente numerosos rasgos del campo magnético terrestre, entre ellos los cambios en la polaridad del momento dipolar magnético. Asimismo se verifica la existencia de un extenso rango de frecuencias donde el momento dipolar magnético presenta invariancia de escala, fenómeno conocido como ruido 1 / f . Se conjetura que esta última característica, asociada a la presencia de memoria de largo plazo en el sistema, posee relación directa con la aparición de reversiones., More than one century ago, Bernard Brunhes proposed the existence of reversals in Earth’s magnetic field at geological time scales. Halfway through the XX century, this theory got acceptance within the scientific community. Nonetheless, efforts to establish precise mechanisms to account for these reversals have been, so far, unsuccessful. In this work we show that, even for simple geometries, diffusive and rotating magnetohydrodynamic’s equations present the key ingredients to reproduce several features of the geomagnetic field, including polarity reversals of the magnetic dipole moment. Moreover we demonstrate the existence of a wide range of frequencies where dipole moment’s power spectrum presents scale invariance, a characteristic known as 1/f noise. We argue that this feature, associated to long-term memory phenomena, has a direct connection with the spontaneous flipping of the geomagnetic field., Facultad de Ciencias Astronómicas y Geofísicas