Submitted by Katiane Souza (katyane.souza@gmail.com) on 2016-04-22T01:10:08Z No. of bitstreams: 1 arquivototal.pdf: 1064839 bytes, checksum: 2614f98e6dd33a21d91ae37ffb55dc6e (MD5) / Made available in DSpace on 2016-04-22T01:10:08Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1064839 bytes, checksum: 2614f98e6dd33a21d91ae37ffb55dc6e (MD5) Previous issue date: 2006-02-20 / The preservation of seeds of economical value in liquid nitrogen or cryoconservation has the potential of extending the storage period almost indefinitely. However, during the freezing and thawing processes, the reached temperature can cause stress that could be lethal for many biological material species, including seeds. The capacity of seeds to resist to freezing in liquid nitrogen is configured as critical factor for the long term conservation. In this work and attempt was made to investigate the cryoconservation of herbaceous color cotton seeds from the cultivates BRS 200 Brown and BRS Green, material developed by Embrapa Algodão. In this case, the study was divided in four parts in the attempt to include all the stages for the establishment of a long term storage protocol in cryogenic temperatures. It was studied the determination of the high moisture freezing limit for the cryoconservation, the kinetics of cryogenic freezing in different temperatures, the storage in subzero temperatures for 12 months (cryoconservation), and, finally, the possible degradation of essential chemical substances to the germination process, considering the exposition of seeds to such extreme storage conditions. The high moisture freezing limit of cotton seeds from the two cultivates range from between 6-8%, while for the long term storage there was a drop in germination and vigor in the two cultivates in any of the temperatures and thawing methods used. It was verified that the freezing curves of these seeds mainly in the temperatures of -25, -45 and -170oC, in spite of the largest similarity with the cooling curves, they present, although in discrete way, the three characteristic phases of the curve of freezing of the pure water. With regard to the thermal diffusivity, it was concluded that it increases with the increase in humidity content, and it does not present a symmetrical behavior with temperature oscillation. The found results also allow to conclude that the seeds of the two cultivates have similar chemical composition and that, in general, there was a decrease in the reserve of chemical components during storage, except for the minerals. / A preservação de sementes de valor econômico em nitrogênio líquido, ou crioconservação tem o potencial de estender o período de armazenagem quase que indefinidamente. Contudo, durante o processo de congelamento e o descongelamento, a temperatura alcançada pode ocasionar estress podendo ser letal para muitas espécies de materiais biológicos inclusive sementes. A capacidade das sementes de resistir ao congelamento em nitrogênio líquido se configura como o fator crítico para a crioconservação. Dessa maneira, buscou-se no presente trabalho, pesquisar a crioconservação de sementes de algodão herbáceo colorido, das cultivares BRS 200 Marrom e BRS Verde, material desenvolvido pela Embrapa Algodão. Para tanto, o estudo foi dividido em quatro partes, buscando-se abranger todas as etapas para o estabelecimento de um protocolo de armazenamento a longo prazo em temperaturas criogênicas. Assim estudou-se a determinação do teor de água crítico para a crioconservação, a cinética de congelamento criogênico em diferentes temperaturas, a crioconservação, ou seja, o armazenamento em temperaturas subzero por 12 meses, e, finalmente, buscou-se avaliar a possível degradação de substâncias químicas essenciais ao processo de germinação, em decorrência da exposição das sementes a condições de armazenagem tão extremas. O teor de água limite para crioconservação das sementes de algodão das duas cultivares situa-se entre 6-8%, enquanto que para o armazenamento a longo prazo, observaram-se quedas no poder germinativo e no vigor das duas cultivares. Verificou-se que as curvas de congelamento destas sementes principalmente nas temperaturas de -25, -45 e -170oC, apesar da maior similaridade com as curvas de resfriamento, apresentam, ainda que de forma discreta, as três fases características da curva de congelamento da água pura. Com relação à difusividade térmica, concluiu-se que esta aumenta com o aumento do teor de umidade, e não apresenta um comportamento simétrico com a oscilação da temperatura. Os resultados obtidos permitem também concluir, que as sementes das duas cultivares tem composição química similares e que de maneira geral houve uma diminuição das concentrações dos componentes químicos de reserva no decorrer do armazenamento, com exceção dos minerais.

Today the environmental issues are a lot on the agenda and the environmental awareness are more and more common. New laws and restrictions on engines emissions are enforced and the demand on the engines gets higher and tougher. This leads to the engine testing playing a more crucial part than ever. Engine tests are done using an engine dynamometer. The dynamometer loads the engine by, in many different ways, absorbing the power and torque generated by engine. The most important functions of a dyno are to convey the power from the engine to the dyno, to load the engine, to measure the power and torque generated by the engine and to remove the excess heat that is generated.  Husqvarna is a Swedish company that produces garden and forest cutting tools, their most famous products are their chainsaws. Husqvarna does an extensive amount of engine testing, long time testing, functional testing and field testing. Some functional tests, such as start-ability after use is done in a climate chamber where the humidity and temperature can be set. Today, loading a chainsaw in -25 °C is a problem due to the fact that the most used dynamometer at Husqvarna is a water brake that freezes in minus degrees. This master thesis will answer the question on how to, for small engine, simulate the load that occurs during normal use of the engine and how to develop a dynamometer suitable for Husqvarna’s needs? The focus when developing the dynamometer will lie on solving the problem with minus degrees and having a good detachable coupling between the dyno and the chainsaw. The result is a hydraulic oil dynamometer. A hydraulic pump is attached to the guide bar and chainsaw using a detachable key way coupling and bearings. By controlling restriction of the flow in the hydraulic system the load can be controlled and also ultimately the RPM of the chainsaw. The hydraulic oil works fine in the minus degree as long as the right oil with the right viscosity range is used although a problem with the small chainsaws are that they are not reaching the full RPM in -25 °C. Mainly because of the backpressure created by the components in the system. This can be solved by minimizing the hydraulic systems total flow restriction.   However this problem doesn’t affect the testing methods as long as the chainsaw easily can be disconnected and freed from the dynamometer and then be run to full RPM which the coupling between the pump and chainsaw enables.

Na atualidade, o estudo da transformação martensítica é de grande importância na área acadêmica e tecnológica, devido à aplicação de aços e ferros fundidos com estruturas martensíticas. O estudo dos fenômenos da transformação martensítica envolve vários pesquisadores no mundo e é objeto de eventos como o ICOMAT e ESOMAT. O presente trabalho acompanhou a transformação martensítica por meio de técnicas experimentais a temperaturas sub-zero em um aço AISI D2 e uma liga Fe-Ni-C previamente austenitizadas. A literatura indica que o tratamento a temperaturas sub-zero pode melhorar propriedades dos aços temperados e revenidos. Foi explorado o uso dos métodos de ruído magnético de Barkhausen (MBN), para detectar a transformação de fase da austenita para a martensita durante o resfriamento sub-zero das amostras, usando três diferentes configurações: a emissão de ruído Barkhausen convencional estimulada por um campo magnético alternado; o método de Okamura que é a emissão de ruído magnético medido embaixo de um campo fixo (DC); e uma nova técnica experimental, que mede a emissão magnética espontânea durante a transformação na ausência de qualquer campo externo. Os fenômenos associados com a transformação de fase também foram medidos por resistividade elétrica e as amostras resultantes foram caracterizadas por microscopia óptica e eletrônica de varredura. Medições MBN no aço ferramenta AISI D2, austenitizadas a 1473K (1200C) e resfriadas a temperatura de nitrogênio líquido apresentaram uma mudança próximo de 225K (-48C) durante o resfriamento, que corresponde à temperatura Ms, como foi confirmado por medidas de resistividade. As medições da emissão de ruído magnético espontâneo, realizadas in situ durante o resfriamento da amostra imersa em nitrogênio líquido, mostraram que poderia ser detectado um fenômeno de estouro individual (burst), de forma similar às medições de emissão acústica (AE), o qual foi confirmado com a liga Fe-Ni-C. Este método de caracterização Spontaneous Magnetic Emission (SME) pode ser considerado uma nova ferramenta experimental para o estudo de transformações martensiticas em ligas ferrosas. Foi acompanhado o inicio da transformação martensítica por SME, em função do tamanho de grão, já que é conhecido pela literatura que o inicio da transformação martensítica (Ms), muda com a variação do tamanho de grão. / Martensitic transformations are of special interest both as an academic topic and as a technological issue, due to importance of steels and cast irons with martensitic structures. Studies of martensite transformation phenomena involve researchers all over the world and specific conferences and meetings, as ICOMAT and ESOMAT. The present work followed the martensitic transformation using different experimental techniques, during cooling at cryogenic temperatures samples of a AISI D2 cold work tool steel and also a Fe-Ni-C, previously austenitized. There are plenty of references in the literature suggesting that sub-zero cooling treatments could ameliorate the properties of quenched and tempered steels. The Magnetic Barkhausen Noise (MBN) method was applied during cooling to subzero temperatures of austenitic samples of a AISI D2 cold work tool steels (previously quenched from 1200ºC) and to a Invar-type Fe-Ni-C alloy. MBN is a non-destructive technique based on the detection of the signal generated when ferromagnetic materials are subjected to an oscillating external magnetic field. In order to study the austenite to martensite transformation, three different configurations were tested: conventional Barkhausen using an oscillating magnetic field, a method proposed by Okamura, which uses a fixed magnetic field and a new method that detects spontaneous magnetic emissions (SME) on the absence of any applied magnetic field. Other phenomena associated with the transformation were followed using electrical resistivity measurements, optical microscopy and X-ray diffraction. MBN measurements on a cold work tool steel AISI D2, austenitized at 1473K (1200ºC) and quenched to room temperature, made during further cooling to liquid nitrogen temperature, presented a clear change of signal intensity near 225K (-48ºC), corresponding to Ms temperature, as confirmed by resistivity measurements. The SME in situ measurements during cooling of samples in liquid nitrogen were able to detect single burst (landslide nucleation and growth) phenomena, in a manner similar to the Acoustic Emission (AE) measurements; these results have been confirmed also with measurements on a Fe-Ni-C alloy. The new Spontaneous Magnetic Emission (SME) characterization method can be considered a new experimental tool for the study of martensitic transformations in ferrous alloys. The beginning temperature for the martensitic transformation detected using SME, electric resistivity and MBN were compared with estimates using the Andrews empirical equation (linear, 1965) for the Ms temperature. The effect of the austenite grain size on the beginning of the martensitic transformation was studied using SME, as it is known that the Ms temperature depends on the austenite grain size.

The goal of this research was to quantify the degradation experienced by a polymer electrolyte fuel cell after storage at subzero temperatures ranging from 0 to -40°C. The performance loss was determined by comparing the polarization and other applicable power curves before and after the subzero storage cycle. The causes of this performance degradation were investigated by the use of Scanning Electron Microscope, Energy Dispersive x-ray Spectroscopy, and porosity scanning technologies. It was found that there are two distinct types of degradation experienced by the membrane. The first type was identified as a variance of the actual voltage - current relationship of the cell. The membrane experienced a 2 - 15% power reduction depending on the load applied to the cell. This mode of degradation only pertained to the initial freeze/thaw cycle and was not observed after any number of subsequent cycles. The cause of this type of degradation has been hypothesized to be related to the delamination of the proton exchange, gas diffusion, and micro porous layers. The second type of degradation was only observed during the subsequent cycles, and mainly affected the high power regions of the operating range. A 5% reduction in current density and power output was observed as a result of further freeze/thaw cycles. Mass transport limitations may have been caused by the destruction of the meso-porous gas diffusion and micro-porous layers. The pore size, volume, and membrane surface area were quantified using a B.E.T. porosity scanner. The results showed that the pore diameter of the catalyst and proton exchange layer did not increase significantly. The porosity scanner did indicate that a pore volume increased by a factor of ten and was confirmed by the surface area measurements of the membrane. The S.E.M. investigations allowed visual inspection of the membrane's structural integrity. Physical separation of the catalyst and gas diffusion layers was observed in the experimental sample, while a more homogeneous assembly was seen in the control sample.

The possible existence of extraterrestrial life forms has been of interest to humans for many millennia. In the past few decades space travel has provided an opportunity to search life outside of Earth. Chiral molecules are critical molecules in Earth-based life and are among the first chemical molecules sought after as proof of potential extraterrestrial life; however, identification of these chiral molecules is difficult due the lack of sensitive instruments. The objective of this work is to develop a benchmark reaction to be used as a guide in the development of instrumentation, such as a polarimeter, to be used in the search for extraterrestrial life. To achieve this objective, to investigate the enzyme mandelate racemase (MR), which catalyzes the racemization between the enantiomers of mandelate. MR is a member of the enolase superfamily, which contains a (alpha/beta)7-b barrel domain, the fold most frequently found among all known protein structures. Activity of the enzyme was measured at low temperatures and in non-aqueous media, as these are the conditions that represent extraterrestrial terrain. We find that mandelate racemase (MR) is active in concentrated ammonium salt solutions and water-in-oil microemulsions in a temperature range between 30C to 70C; however, the enzyme is not active in several organic cryosolvents. The stability of the structure of MR was also explored. Using differential scanning calorimetry (DSC) we observe the unfolding of the enzyme was irreversible and therefore kinetically controlled. We also found proof for divergent evolution of the enolase superfamily, providing evidence for divergent evolution across the MR and muconate lactonizing enzyme (MLE) subfamilies has been demonstrated. However, we also conclude that reactions yielding a polarimetric signal, such as racemizations employed in this work, are suitable as a tool to find signs of life.

Na atualidade, o estudo da transformação martensítica é de grande importância na área acadêmica e tecnológica, devido à aplicação de aços e ferros fundidos com estruturas martensíticas. O estudo dos fenômenos da transformação martensítica envolve vários pesquisadores no mundo e é objeto de eventos como o ICOMAT e ESOMAT. O presente trabalho acompanhou a transformação martensítica por meio de técnicas experimentais a temperaturas sub-zero em um aço AISI D2 e uma liga Fe-Ni-C previamente austenitizadas. A literatura indica que o tratamento a temperaturas sub-zero pode melhorar propriedades dos aços temperados e revenidos. Foi explorado o uso dos métodos de ruído magnético de Barkhausen (MBN), para detectar a transformação de fase da austenita para a martensita durante o resfriamento sub-zero das amostras, usando três diferentes configurações: a emissão de ruído Barkhausen convencional estimulada por um campo magnético alternado; o método de Okamura que é a emissão de ruído magnético medido embaixo de um campo fixo (DC); e uma nova técnica experimental, que mede a emissão magnética espontânea durante a transformação na ausência de qualquer campo externo. Os fenômenos associados com a transformação de fase também foram medidos por resistividade elétrica e as amostras resultantes foram caracterizadas por microscopia óptica e eletrônica de varredura. Medições MBN no aço ferramenta AISI D2, austenitizadas a 1473K (1200C) e resfriadas a temperatura de nitrogênio líquido apresentaram uma mudança próximo de 225K (-48C) durante o resfriamento, que corresponde à temperatura Ms, como foi confirmado por medidas de resistividade. As medições da emissão de ruído magnético espontâneo, realizadas in situ durante o resfriamento da amostra imersa em nitrogênio líquido, mostraram que poderia ser detectado um fenômeno de estouro individual (burst), de forma similar às medições de emissão acústica (AE), o qual foi confirmado com a liga Fe-Ni-C. Este método de caracterização Spontaneous Magnetic Emission (SME) pode ser considerado uma nova ferramenta experimental para o estudo de transformações martensiticas em ligas ferrosas. Foi acompanhado o inicio da transformação martensítica por SME, em função do tamanho de grão, já que é conhecido pela literatura que o inicio da transformação martensítica (Ms), muda com a variação do tamanho de grão. / Martensitic transformations are of special interest both as an academic topic and as a technological issue, due to importance of steels and cast irons with martensitic structures. Studies of martensite transformation phenomena involve researchers all over the world and specific conferences and meetings, as ICOMAT and ESOMAT. The present work followed the martensitic transformation using different experimental techniques, during cooling at cryogenic temperatures samples of a AISI D2 cold work tool steel and also a Fe-Ni-C, previously austenitized. There are plenty of references in the literature suggesting that sub-zero cooling treatments could ameliorate the properties of quenched and tempered steels. The Magnetic Barkhausen Noise (MBN) method was applied during cooling to subzero temperatures of austenitic samples of a AISI D2 cold work tool steels (previously quenched from 1200ºC) and to a Invar-type Fe-Ni-C alloy. MBN is a non-destructive technique based on the detection of the signal generated when ferromagnetic materials are subjected to an oscillating external magnetic field. In order to study the austenite to martensite transformation, three different configurations were tested: conventional Barkhausen using an oscillating magnetic field, a method proposed by Okamura, which uses a fixed magnetic field and a new method that detects spontaneous magnetic emissions (SME) on the absence of any applied magnetic field. Other phenomena associated with the transformation were followed using electrical resistivity measurements, optical microscopy and X-ray diffraction. MBN measurements on a cold work tool steel AISI D2, austenitized at 1473K (1200ºC) and quenched to room temperature, made during further cooling to liquid nitrogen temperature, presented a clear change of signal intensity near 225K (-48ºC), corresponding to Ms temperature, as confirmed by resistivity measurements. The SME in situ measurements during cooling of samples in liquid nitrogen were able to detect single burst (landslide nucleation and growth) phenomena, in a manner similar to the Acoustic Emission (AE) measurements; these results have been confirmed also with measurements on a Fe-Ni-C alloy. The new Spontaneous Magnetic Emission (SME) characterization method can be considered a new experimental tool for the study of martensitic transformations in ferrous alloys. The beginning temperature for the martensitic transformation detected using SME, electric resistivity and MBN were compared with estimates using the Andrews empirical equation (linear, 1965) for the Ms temperature. The effect of the austenite grain size on the beginning of the martensitic transformation was studied using SME, as it is known that the Ms temperature depends on the austenite grain size.