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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Ethylene glycol rapid methods of detection

Blevins, Lori A. January 1900 (has links)
Master of Veterinary Bioscience / Department of Diagnostic Medicine/Pathobiology / Deon Van Der Merwe / Every year thousands of domestic animals are poisoned by ethylene glycol. Exposure is normally orally, but may be dermal, and poisonings are usually accidental and not malicious. Antifreeze, overwhelmingly the source of the ethylene glycol poisoning, is responsible for over 99% of reported cases. Storage, handling and proper disposal of ethylene glycol is extremely important in limiting access to this deadly product. Ethylene glycol exposures were involved in 1737 calls made to the American Society for the Prevention of Cruelty to Animals call center between 2006 and 2011. Dogs were involved in approximately 87% of exposures and cats in 13%. There were no seasonal or breed patterns. The most common clinical signs reported were neurological and gastrointestinal for both cats and dogs. Urinary calcium oxalate crystals were reported in 28.6% of exposed cats, and 21% of dogs. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to detect calcium oxalate crystals in wax-mounted kidneys from twenty total cases, ten of which were suspected ethylene glycol poisoning submitted to the Kansas State Veterinary Diagnostic Laboratory, and ten samples deemed negative by a pathologist using light microscopy. Pure calcium oxalate monohydrate was used as a reference, and a unique absorption peak was detected between wavenumbers 1290 cm[superscript]-1 and 1320 cm[superscript]-1. The drying of kidney tissues resulted in increased sensitivity for calcium oxalate. Crystal detection by the ATR-FTIR was compared to light microscopy. Bi-fringence of crystals allowed microscopic detection, but the ATR-FTIR specificity for the test was 100%, and sensitivity was 80% compared to traditional microscopy for ca-oxalate crystal identification. ATR-FTIR was also used to detect un-metabolized ethylene glycol in vomitus using wavenumbers 1084 cm[superscript]−1, 1039 cm[superscript]−1, and 882 cm[superscript]−1, but ethylene glycol was not detectable. Ethylene glycol concentrations in samples were much too low to be detected as ethylene glycol on the ATR-FTIR, as the limit of detection was not distinguishable until 5000 ppm using a serial dilution. These methods presented simple, reliable, quick, sensitive, stable, and highly adaptable tests for detection, diagnosis and treatment of ethylene glycol poisoning.
32

A non-syn-gas catalytic route to methanol production

Wu, Cheng-Tar January 2013 (has links)
At present, more than 80% of the world’s energy consumption and production of chemicals is originated from the use of fossil resources. There is a tremendous growing interest in utilising biomass molecules for energy provision due to their carbon neutrality. Lower alcohols such as methanol and ethanol if produced from biomass as transportation fuels as well as platform chemicals, can become strategically important for many energy/chemically starved countries. Currently, they are synthesised by indirect and inefficient processes. We show for the first time in this thesis study that ethylene glycol, the simplest representative of biomass-derived polyols, can be directly converted to these two lower alcohols by selective hydrogenolysis over modified Raney Ni and Cu catalysts in hydrogen atmosphere. This work provides essential information that may lead to the development of new catalysts for carbohydrate activation to methanol, a novel but important reaction concerning the important biomass conversion to transportable form of energy. Modification of electronic structure and the adsorption properties of Raney catalysts have therefore been achieved by blending with second metal(s). It is found that the activity and selectivity of this reaction can be significantly affected by this approach. In contrast, there is no subtle effect on methanol selectivity despite a great variation in the d-band centre positions of metal catalysts which show a distinctive effect on other products. Our result suggests that methanol is produced on specific surface sites independent from the other sites at an intrinsic rate and will not be converted to other products by the d-band alteration. On the other hand, it is reported in this thesis that a dramatic improvement in the combined selectivity to methanol/ethanol reaching 80% can be obtained over a Pd/Fe<sub>3</sub>O<sub>4</sub> catalyst under relatively milder conditions (20 bar and 195 oC). This direct production of the non-enzymatic bio-alcohols is established over a carefully prepared co-precipitated Pd/Fe<sub>3</sub>O<sub>4</sub> catalyst which gives a metallic phase of unexpectedly high dispersion ranging from small clusters to individual metal adatoms on defective iron oxide to give the required metal-support interaction for the novel synthesis. It is demonstrated that the small PdFe clusters on iron oxide surface provide the active species responsible for methanol production. In addition, a related Rh/Fe<sub>3</sub>O<sub>4</sub> catalyst synthesised by co-precipitation is also shown to be selective for CO<sub>2</sub> and H<sub>2</sub> production from a direct methane-oxygen oxidation reaction. As a result, 2.7% conversion of methane with selectivity ratio of CO<sub>2</sub>/H<sub>2</sub> = 4 in a mixed gas feed stream of CH<sub>2</sub>/O<sub>2</sub> = 30 at 300 <sup>o</sup>C is obtained. The reaction is operated in a kinetically controlled regime at 300<sup>o</sup>C, where the CO formation from reverse water gas shift reaction is greatly suppressed. It is evident that the Rh/Fe<sub>3</sub>O<sub>4</sub> acts as an interesting bifunctional catalyst for this reaction. This catalyst firstly gives a high dispersion of Rh which is expected to deliver a higher surface energy with enhanced activity. The Rh metal surface provides catalytically active sites for dissociation of methane to adsorbed hydrogen and carbon atoms effectively, and active oxygen on metal surface readily catalyses the carbon atoms to CO. Following these elementary reactions, the surface oxygen from Fe<sub>3</sub>O<sub>4</sub> subsequently converts it to CO<sub>2</sub> selectively at the metal-support interface. As a result, the novel study of catalytic biomass conversion and the discoveries of new catalysts are reported in this thesis.
33

Water transport study in crosslinked poly(ethylene oxide) hydrogels as fouling-resistant membrane coating materials

Ju, Hao 15 September 2010 (has links)
The major objective of this research is a systematic experimental exploration of hydrophilic materials that can be applied as coating materials for conventional ultrafiltration (UF) membranes to improve their fouling resistance against organic components. This objective is achieved by developing new, fouling-reducing membrane coatings and applying these coatings to conventional UF membranes, which can provide unprecedented reduction in membrane fouling and marked improvements in membrane lifetime. Novel polymeric materials are synthesized via free-radical photopolymerization of mixtures containing poly(ethylene glycol) diacrylate (PEGDA), photoinitiator, and water. PEGDA chain length (n=10-45, where n is the average number of ethylene oxide units in the PEGDA molecule) and water content in the prepolymerization mixture (0-80 wt.%) were varied. Crosslinked PEGDA (XLPEGDA) exhibited high water permeability and good fouling resistance to oil/water mixtures. Water permeability increased strongly with increasing the water content in the prepolymerization mixture. Specifically, for XLPEGDA prepared with PEGDA (n=13), water permeability increased from 0.6 to 150 L um/(m2 h bar) as prepolymerization water content increased from 0 to 80 wt.%. Water permeability also increased with increasing PEGDA chain length. Moreover, water permeability exhibits a strong correlation with equilibrium water uptake. However, solute rejection, probed using poly(ethylene glycol)s of well defined molar mass, decreased with increasing prepolymerization water content and increasing PEGDA chain length. That is, there is a tradeoff between water permeability and separation properties: Materials with high water permeability typically exhibit low solute rejections, and vice versa. The fouling resistance of XLPEGDA materials was characterized via contact angle measurements and static protein adhesion experiments. From these results, XLPEGDA surfaces are more hydrophilic in samples prepared at higher prepolymerization water content or with longer PEGDA chains, and the more hydrophilic surfaces generally exhibit less BSA accumulation. These materials were applied to polysulfone (PSF) UF membranes to form coatings on the surface of the PSF membranes. Oil/water crossflow filtration experiments showed that the coated PSF membranes had water flux values 400% higher than that of an uncoated PSF membrane after 24 h of operation, and the coated membranes had higher organic rejection than the uncoated membranes. / text
34

The Development of Photosensitive Surfaces to Control Cell Adhesion and Form Cell Patterns

Cheng, Nan 13 September 2012 (has links)
Cell adhesion is the first step of cell response to materials and the extracellular matrix (ECM), and is essential to all cell behaviours such as cell proliferation, differentiation, migration and apoptosis for anchor-dependent cells. Therefore, studies of cell attachment have important implications to control and study cell behaviours. During many developed techniques for cell attachment, the manipulation of surface chemistry is a very important method to control initial cell attachment. To control cell adhesion on a two-dimensional surface is a simple model to study cell behaviours, and is a fundamental topic for cell biology, tissue engineering, and the development of biosensors. From the engineering point of view, the preparation of a material with controllable surface chemistry can help studies of cell behaviours and help scientists understand how surface features and chemistry influence cell behaviours. During the fabrication, the challenge is to create a surface with heterogeneous surface properties in the micro scale and subsequently to guide cell initial adhesion. In order to control cell adhesion in a spatial and temporal manner, a photochemical method to control surface chemistry was employed to control the surface property for cell adhesion in this project. Two photocleavable derivatives of the nitrobenzyl group were tried on two types of surfaces: a model self-assembled monolayer (SAM) with alkanethiol-gold surface and biodegradable chitosan. Reactive functional groups on two different surfaces can be inactivated by covalent binding with these photocleavable molecules, and light can be further introduced into the system as a stimulus to recover their reactivity. By simply applying a photomask with diffe
35

Solubility Ratios, Encapsulation Efficiency, and Size of Beta-sitosterol Loaded Poly(Lactide)-Block-Poly(Ethylene glycol) Polymeric Micelles

Alqarni, Ali 31 July 2019 (has links)
β-sitosterol/poly(ethylene glycol)-block-poly(lactic acid) (PLA-b-PEG) complexes were prepared by solution blending in purified water and ethanol. The mixture of water and ethanol is a suitable solvent system for the two components. The complex was studied by using Nuclear Magnetic Resonance (NMR) spectroscopy and Differential Scanning Calorimetry (DSC). β-sitosterol is a drug that may reduce the swelling of benign prostatic hyperplasia (BPH) and diminishing inflammation. However, it is hydrophobic and difficult to deliver in aqueous solution. Since PLA-b-PEG has amphiphilic properties, the complex described here may enhance delivery of this drug for treatment of BPH. Proton NMR (1HNMR) of the complexes shows that the methylene (CH2) protons of the PEG, the (-O-CH-) of PLA, and (CH3) of PLA are slightly shifted because of its non-covalent interaction with β-sitosterol. The complex formation was supported by 2-D NMR (NOESY) spectroscopy. NOESY spectra show cross peaks, indicating the interaction between the two components. DSC of the complexes shows thermal characteristics that are different from the individual components. In particular, the PEG in the complex shows a lower melting point and decreased crystallinity compared to the pure PEG. The melting point is lowered from 57°C to 55.3 °C for the PEG-b-PLA/β-sitosterol (5%) complex. Under the same condition, the melting point of PLA dropped from 170 °C to 130 °C. Atomic force microscopy shows changes in the surface morphology of the copolymer from crystalline to amorphous when incorporated with the drug. NMR, DSC, AFM, and MTT assay studies suggest the formation of a relatively stable β-sitosterol/poly(lactic acid)-block-poly(ethylene glycol) complex. The cell proliferation assay (MTT assay) suggests significant inhibition of the stimulation of growth of prostate cancer cells upon addition the complex.
36

Oxidação direta do etileno glicol sobre catalisadores eletroquímicos binários à base de Pt, Pd, e Sn suportados em carbono para aplicação em células alcalinas / Direct oxidation of ethylene glycol by binary electrochemical catalysts based on Pt, Pd and Sn supported on carbon substrate for application in alkaline fuel cells

Souza, Leticia Lopes de 15 June 2016 (has links)
Os catalisadores eletroquímicos binários de PtSn/C, PdSn/C e PtPd/C foram sintetizados em diferentes proporções pelo método da redução via borohidreto, posteriormente estes foram caracterizados por microscopia eletrônica de transmissão, difração de raios X, espectroscopia no infravermelho por transformada de Fourier (PtSn/C e PdSn/C) e energia dispersiva de raios X. As atividades eletroquímicas dos diferentes materiais preparados foram avaliadas por intermédio de voltametria cíclica, cronoamperometria e curvas de polarização em célula a combustível alimentada diretamente por etileno glicol em eletrólito alcalino. As curvas de densidade de potência indicaram que os catalisadores eletroquímicos contendo Sn e Pd são mais ativos para a reação de oxidação do etileno glicol, especialmente a composição 70%:30% - relação molar entre os metais suportados em carbono - dos catalisadores PtSn/C, PdSn/C e PtPd/C todos superando as medidas de potência do Pt/C. Este resultado indica que a adição de Sn e Pd favorece a oxidação do etileno glicol em meio alcalino. O melhor desempenho observado para os catalisadores eletroquímicos PtSn/C, PdSn/C e PtPd/C (70%:30%) poderia estar associado à sua maior seletividade quanto a formação de oxalato, ou seja , a formação deste produto resulta em um maior número de elétrons, por consequência em maiores valores de corrente. / Binary electrochemical catalysts PtSn/C, PdSn/C and PtPd/C were synthesized in different proportions by the method of reduction via borohydride. These were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (PtSn/C and PdSn/C) and energy dispersive X-ray. The electrochemical activities of the different materials prepared were evaluated by cyclic voltammetry, chronoamperometry and polarization curves for fuel cell powered directly by ethylene glycol in an alkaline electrolyte. Power density curves indicated that the electrochemical catalysts Sn-containing or Pd-containing are more active for ethylene glycol oxidation reaction, particularly the (70%:30%) composition of PtSn/C, PdSn/C and PtPd/C, all of them exceeding power measurements of Pt/C. These results indicate that the addition of Sn and Pd promotes the oxidation of ethylene glycol in an alkaline medium and this improved performance may be associated with a higher selectivity for the formation of oxalate that results in a larger number of electrons, consequently enhancing the current values.
37

Efeito de cátions alcalinos e cinética complexa durante a eletro-oxidação de etileno glicol / Cations effect and complex kinetics during ethylene glycol electro-oxidation

Sitta, Elton Fabiano 11 May 2012 (has links)
Exemplos de comportamento complexo podem ser encontrados em vários sistemas na natureza, como dinâmica de populações, formação de padrões em pelos de animais e a auto regulação do metabolismo. Em geral, sistemas químicos e eletroquímicos apresentam também esse tipo de comportamento complexo e são comumente escolhidos como sistemas-modelo para estudar esses aspectos, uma vez que as variáveis são facilmente controláveis e as medidas são precisas. Apesar dos esforços realizados nas últimas duas décadas, existem ainda lacunas a serem preenchidas entre o mecanismo de reação e a teoria que explica as oscilações. Visando contribuir para o assunto, o presente trabalho trata da eletro-oxidação de etileno glicol sobre platina em meio alcalino em regime potenciostático e galvanostático. Utilizando Espectroscopia de Infravermelho por Transformada de Fourier in situ acoplada com técnicas eletroquímicas, é observado um decréscimo na razão entre a produção de carbonato/oxalato quando o raio dos cátions alcalinos é diminuído na seguinte ordem: Li+ &lt; Na+ &lt; K+. A origem de tal tendência pode ser dada em termos das interações não-covalentes entre os cátions e as espécies oxigenadas adsorvidas na superfície. Os aspectos não-lineares da reação são estudados aumentando a resistência entre o eletrodo de trabalho e o potenciostato. Oscilações com frequências tão altas quanto 40 Hz são observadas, sendo que estas se tornam mais lentas e complexas com o aumento da resistência, mimetizando o comportamento em controle galvanostático. O pH mostrou-se fundamental para o aparecimento do comportamento oscilatório, observado somente nos valores de pH 0, 2 e 14. Baixas correntes de oxidação e baixas frequências de oscilação em meio ácido são contrastadas com altas correntes e frequências em meio alcalino. Além disso, o efeito da temperatura é testado tanto em regime voltamétrico quanto nas séries temporais oscilatórias em pH ácido e alcalino. Em meio ácido, a energia de ativação decresce à medida que o potencial torna-se próximo ao potencial de pico e esta heterogeneidade está, provavelmente, conectada à diferentes rotas reacionais. A energia de ativação calculada através da frequência remete a valores intermediários aos encontrados em regime voltamétrico. Apesar de valores comuns encontrados para os termos de ativação sob regime voltamétrico em meio alcalino, as frequências de oscilação se mostraram quase invariantes com a temperatura, indicando que o sistema apresenta a chamada compensação de temperatura. / Examples of complex behavior can be found in several systems in nature such as population dynamics, animal coat patterns formation and metabolism self-assembly. In general, chemical and electrochemical systems also display this complex behavior and are commonly chosen as workhorses to study these aspects, once the variables are easily controlled and the measurements are precise. Despite the efforts made in this area in the last two decades, there are still gaps between the reaction mechanism and the theory underlying the oscillations. To shed some light on the non-linear aspects of alcohol electro-oxidation, the present work deals with the study the ethylene glycol electro-oxidation reaction in platinum and alkaline media from both gavanostatic and potenciostático control. By means of in situ Fourier Infrared Spectroscopy coupled with electrochemical techniques, it is found a decrease in the ratio of carbonate/oxalate production when the alkaline cations size decreases in the following order: Li+ &lt; Na+ &lt; K+. The origin of this tendency can be rationalized in terms of non-covalent interaction between cations and adsorbed oxygenated species. These interactions are proportional to the cation size and it influences directly the number of available free sites for alcohol adsorption. The non-linear aspects of the reaction are also studied increasing the total resistance between the working electrode and the potenciostat. It is observed oscillation frequencies as high as 40 Hz. Those non-linearities turned slower and more complex as the resistance increases, mimicking the behavior observed under galvanostatic control. The pH is a decisive parameter to the oscillatory behavior, observed only at pH 2, 4 and 14. Low oxidation currents under potential control followed by low frequency oscillations observed in acid media are in contrast to the high current and frequency in alkaline. Moreover the temperature effect is tested in both cyclic voltammetry profile and oscillatory time series in acid and alkaline media. In acid media, the activation energy decrease as the potential turns closer to the peak potential region, this heterogeneity is probably caused by different reactions. The activation energy calculated by oscillation frequency remits to intermediates values in relation to that found under voltammetry control. Although ordinary values for the activation factors are found under linear voltammetry control mode at pH 14, the oscillations frequencies are almost independent of the temperature, indicating that the system shows the, so called, temperature compensation.
38

Oxidação direta do etileno glicol sobre catalisadores eletroquímicos binários à base de Pt, Pd, e Sn suportados em carbono para aplicação em células alcalinas / Direct oxidation of ethylene glycol by binary electrochemical catalysts based on Pt, Pd and Sn supported on carbon substrate for application in alkaline fuel cells

Leticia Lopes de Souza 15 June 2016 (has links)
Os catalisadores eletroquímicos binários de PtSn/C, PdSn/C e PtPd/C foram sintetizados em diferentes proporções pelo método da redução via borohidreto, posteriormente estes foram caracterizados por microscopia eletrônica de transmissão, difração de raios X, espectroscopia no infravermelho por transformada de Fourier (PtSn/C e PdSn/C) e energia dispersiva de raios X. As atividades eletroquímicas dos diferentes materiais preparados foram avaliadas por intermédio de voltametria cíclica, cronoamperometria e curvas de polarização em célula a combustível alimentada diretamente por etileno glicol em eletrólito alcalino. As curvas de densidade de potência indicaram que os catalisadores eletroquímicos contendo Sn e Pd são mais ativos para a reação de oxidação do etileno glicol, especialmente a composição 70%:30% - relação molar entre os metais suportados em carbono - dos catalisadores PtSn/C, PdSn/C e PtPd/C todos superando as medidas de potência do Pt/C. Este resultado indica que a adição de Sn e Pd favorece a oxidação do etileno glicol em meio alcalino. O melhor desempenho observado para os catalisadores eletroquímicos PtSn/C, PdSn/C e PtPd/C (70%:30%) poderia estar associado à sua maior seletividade quanto a formação de oxalato, ou seja , a formação deste produto resulta em um maior número de elétrons, por consequência em maiores valores de corrente. / Binary electrochemical catalysts PtSn/C, PdSn/C and PtPd/C were synthesized in different proportions by the method of reduction via borohydride. These were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (PtSn/C and PdSn/C) and energy dispersive X-ray. The electrochemical activities of the different materials prepared were evaluated by cyclic voltammetry, chronoamperometry and polarization curves for fuel cell powered directly by ethylene glycol in an alkaline electrolyte. Power density curves indicated that the electrochemical catalysts Sn-containing or Pd-containing are more active for ethylene glycol oxidation reaction, particularly the (70%:30%) composition of PtSn/C, PdSn/C and PtPd/C, all of them exceeding power measurements of Pt/C. These results indicate that the addition of Sn and Pd promotes the oxidation of ethylene glycol in an alkaline medium and this improved performance may be associated with a higher selectivity for the formation of oxalate that results in a larger number of electrons, consequently enhancing the current values.
39

A eletrooxidação de etileno glicol: estudo dos caminhos reacionais em superfícies de PtRu em meio alcalino / The electrooxidation of ethylene glycol: study of the reaction paths in PtRu surfaces in alkaline medium

Nascimento, Diego Rogério Pinto do 27 July 2016 (has links)
Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-02T19:15:27Z No. of bitstreams: 1 DiegoNascimento.pdf: 1137977 bytes, checksum: 18e235c8d743ce1d2f6c7baa61ad30c3 (MD5) / Made available in DSpace on 2017-06-02T19:15:27Z (GMT). No. of bitstreams: 1 DiegoNascimento.pdf: 1137977 bytes, checksum: 18e235c8d743ce1d2f6c7baa61ad30c3 (MD5) Previous issue date: 2016-07-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / Short chain alcohols have been studied for possible use in fuel cells. The ethylene glycol oxidation electrode Pt and PtRu, in alkaline medium, showed great efficiency and increasing the current density was evidenced by a gradual rise in temperature, which confirms that the temperature is a significant factor for the electrooxidation glycol favoring the formation of oxygenated species and facilitating the oxidation adsorbates. The ethylene glycol oxidation products on the surfaces of Pt and PtRu were identified by high-performance liquid chromatography and the presence of glycolaldehyde was confirmed as alcohol oxidation product of Pt and glycolaldehyde and glicoato on surfaces of PtRu. Bimetallic PtRu electrodes were prepared by electrodeposition in five different proportions: 94:06; 90:10; 88:12; 83:17 and 77:23. The percentage of both metals was determined by EDX technique. significant currents were obtained from these electrodes, since they were used as working electrodes. The best results are related to glycol oxidation on PtRu electrode (77:23), because it made possible the oxidation of alcohol to study less anodic potential, which was verified by glycol oxidation beginning around 0.25 V, as well have caused a significant decrease in the region characteristic of hydrogen. Thus, the PtRu alloy catalyst is considered to be good catalyst for CO oxidation and ethylene glycol in the alkaline medium. The number of moles to glycol oxidation products were determined at temperatures of 25 to 55 ° C for both a flat eterodo Pt as to eletrodeposito PtRu (77:23) and its activation energy was determined for each electrode the current data from the apalicação equaçãi Arrhenius, meeting 24.29 and 32.02 kJ.mol-1 to the flat electrode of Pt and PtRu eletrodepositdos respectively. / Álcoois de cadeias pequenas têm sido estudados para possível uso em células de combustível. A oxidação de etileno glicol em eletrodos de Pt e PtRu, em meio alcalino, mostrou grande eficiência e o aumento da densidade de corrente foi evidenciado por uma elevação gradual da temperatura, o que confirma que a temperatura é um fator significativo para a eletrooxidação do glicol, favorecendo a formação de espécies oxigenadas e facilitando a oxidação de adsorbatos. Os produtos de oxidação de etileno glicol em superfícies de Pt e PtRu foram identificados por cromatografia líquida de alta eficiência e a presença de glicolaldeido foi confirmada como produto de oxidação do álcool sobre Pt e glicolaldeido e glicoato sobre superfícies de PtRu. Os eletrodos bimetálicos de PtRu, foram preparados por eletrodeposição em cinco proporções diferentes: 94:06; 90:10; 88:12; 83:17 e 77:23. A porcentagem de ambos os metais foi determinado pela técnica de EDX. Foram obtidas correntes significativas a partir destes eletrodos, uma vez que os mesmos foram utilizados como eletrodos de trabalho. Os melhores resultados estão relacionados à oxidação do glicol em eletrodo PtRu (77:23), pois possibilitou a oxidação do álcool em estudo a potenciais menos anódicos, o que foi verificado pelo inicio de oxidação do glicol por volta de 0,25 V, além de ter ocasionado uma significativa diminuição na região característica do hidrogênio. Assim, o catalisador de liga de PtRu é considerado como bom catalisador para oxidação de CO e de etileno glicol no meio alcalino. O número de mol para os produtos de oxidação do glicol foram determinados às temperaturas de 25 e 55°C tanto para um eterodo liso de Pt quanto para o eletrodeposito de PtRu (77:23) e as respectivas energias de ativação para cada eletrodo foi determinada pelos dados de corrente obtidos a partir da apalicação da equaçãi de Arrhenius, encontrando-se 24,29 e 32,02 KJ.mol-1 para o eletrodo liso de Pt e PtRu letrodepositdos, respectivamente.
40

Vitrificação de embriões Mus domesticus domesticus contidos em volumes diferentes de 9,0 m de etileno glicol. / Vitrification of mus domesticus domesticus embryos exposed to differents volumes of 9.0 m ethylene glycol solution

Assaf, Sabrina Silveira January 2003 (has links)
Os experimentos tiveram como objetivo determinar a taxa de eclosão dos embriões vitrificados em volumes diferentes de 9,0 M de etileno glicol. Simultaneamente, testou-se dois procedimentos de estocagem dos fios de teflon, denominados caixa de aço inoxidável e globete/raque. No experimento I, os 881 embriões coletados foram distribuídos em 4 tratamentos: tratamento 1 (T1= controle): 307 embriões foram cultivados in vitro em meio PBSm, acrescido de 0,4% de BSA; tratamento 2 (T2): 292 embriões foram expostos à solução de glicerol 10% acrescida de 0,4% de BSA, envasados em palhetas de 0,25 mL e submetidos ao congelamento pelo método rápido em Biocool; tratamento 3 (T3): 138 embriões foram expostos durante 2 minutos à solução de desidratação (10% de EG + 6% BSA em PBSm) e então transferidos para a solução de vitrificação (50% de EG + 6% de BSA em PBSm), onde permaneceram por 30 segundos e foram colocados em volume de 1 μL no interior de um fio de teflon, medindo 0,4 mm de diâmetro, 2,0 cm de comprimento e 0,05 mm de espessura. Os fios foram acondicionados em uma caixa de aço inoxidável para serem armazenados em nitrogênio líquido; tratamento 4 (T4): 144 embriões foram expostos à solução de desidratação (10% de EG + 6% BSA em PBSm) e após 2 minutos, foram transferidos para a solução de vitrificação (50% de EG + 6% BSA em PBSm), onde permaneceram por 30 segundos, sendo após transferidos para um volume de 1 μL no interior do fio de teflon. Os fios de teflon foram estocados em globetes unidos às raques e mantidos em nitrogênio líquido. Após o aquecimento, os embriões foram cultivados em PBSm suplementado com 0,4% de BSA. As taxas de eclosão embrionária observadas foram: T1=76,29% (245/307); T2=41,05% (117/292); T3=37,98% (54/138) e T4=26,78% (37/144). No segundo experimento, 747 embriões foram distribuídos em 3 tratamentos: tratamento 1 (T1= controle): 80 embriões foram cultivados in vitro em meio KSOM acrescido de 0,4% de BSA; tratamento 2 (T2): 334 embriões expostos em solução de glicerol 10% acrescida de 0,4% de BSA, foram envasados em palhetas de 0,25 mL e submetidos ao congelamento pelo método rápido em Biocool; tratamento 3 (T3): 333 blastocistos foram expostos durante 2 minutos à solução de desidratação (10% de EG + 0,4% BSA em PBSm) e então transferidos para tubos eppendorf de 2,0 mL em contato com a solução de vitrificação (50% de EG + 0,4% BSA em PBSm). Após o cultivo in vitro, as taxas de eclosão embrionária observadas nos 3 tratamentos foram respectivamente: 88,75% (71/80), 40,44% (141/334) e 19,70% (66/333). Baseado nesses resultados conclui-se que embriões Mus domesticus domesticus submetidos à técnica de vitrificação após exposição à solução de 9,0 M de etileno glicol e envase em fios de teflon assegurou índices satisfatórios de sobrevivência embrionária. As taxas de sobrevivência dos embriões Mus domesticus domesticus foi independente do procedimento de estocagem em botijão de nitrogênio líquido. A vitrificação em solução de 9,0 M de etileno glicol com envase em tubos eppendorf não foi eficiente para promover altas taxas de sobrevivência embrionária, mas proporcionou segurança biológica aos embriões, durante o armazenamento. / This work was performed with Mus domesticus domesticus embryos to verify the in vitro viability of vitrified embryos using differents volumes of ethylene glycol–based solution. The experiment I consisted of four treatments. The 881 collected embryos were arranged as follows: treatment 1(control): 307 fresh embryos were cultured in vitro in PBSm + 0.4% BSA without being exposed to either dehydration or cryoprotectants agents; treatment 2: 292 embryos were loaded into 0.25 mL french straws containing 10% glycerol + 0.4% BSA in PBSm and after 10 minutes the straws were submitted to the rapid-freezing procedure (Biocool®, controlled freezer); treatment 3:138 embryos were exposed during 2 minutes to a dehydration solution (10% ethylene glycol + 6% BSA in PBSm) and then transferred to the vitrification solution (50% ethylene glycol + 6% BSA in PBSm) in teflon wire with 0.4 mm diameter, 2 cm length and 0.05 mm thickness containing the drop of 1μL volume, and placed into stainless steel box for the storage in LN2; treatment 4:144 embryos were exposed to a dehydration solution (10% ethylene glycol + 6% BSA in PBSm) and after 2 minutes were transferred to the teflon wire, that was previousily loaded with 1μL of the vitrification solution (50% ethylene glycol + 6% BSA in PBSm). Finally, the teflon wires were placed into plastic globets attached to aluminum canes and maintained in LN2. After thawing, the embryos were serially washed in PBSm, and then cultured in PBSm supplemented with 0.4% BSA. The hatched blastocyst rates observed in the treatments were: T1=76.29% (245/307); T2=41.05% (117/292); T3=37.98% (54/138) and T4=26.78% (37/144). In the second experiment, 747 embryos were arranged as follows: treatment 1(control): consisted of 80 fresh embryos cultured in vitro in KSOM medium + 0.4% BSA without being exposed to either dehydration or cryoprotectants agents; treatment 2: 334 embryos were loaded into 0.25 mL french straws containing 10% glycerol + 0.4% BSA in PBSm and after 10 minutes the straws were submitted to the rapid-freezing procedure (Biocool®, controlled freezer); treatment 3: 333 embryos were exposed during 2 minutes to a dehydration solution (10% ethylene glycol + 0.4% BSA in PBSm) and then transferred to the eppendorf tubes loaded with the vitrification solution (50% ethylene glycol + 0.4% BSA in PBSm). After in vitro culture, the hatched blastocysts rates observed were: T1=88.75% (71/80); T2=40.44% (141/334) and T3=19.70% (66/333). Based on these results it is concluded that the embryos of Mus domesticus domesticus submitted to vitrification procedure after being exposed to 9.0 M of ethylene glycol – based solution and loaded in teflon wires were efficient to promote satisfactory embryo survival rates. The survival rate of Mus domesticus domesticus embryos was independent of the LN2 storage procedure. The vitrification procedure after being exposed to 9.0 M of ethylene glycol – based solution and loaded in eppendorf tubes were not efficient to promote high embryo survival rate, but to warrant the embryo’s biologically security during storage in liquid nitrogen.

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