Objective: The aim of this pilot study is the evaluation and measurement of color stability from baseline until stabilization of color associated with bleaching and the dehydration and rehydration process of the teeth. Method: Six extracted intact human third molars were randomly selected, cleaned, and stored in artificial saliva at 370C. A custom positioning jig was fabricated for each tooth for reproducible color measurement. A baseline shade was recorded according to the Commission Internationale de l'Eclairage L*a*b* (CIE-L*a*b*) using a Minolta Chromameter CR-(200). Color measurement for all testing was taking at baseline, 15 min, 30 min, 2h, 12h and every 2 h thereafter until color stabilization occurred. Phase 1(dehydration-rehydration w/o bleaching): For dehydration, all teeth lightened and color stability occurred at 6 h. Rehydration of teeth to the baseline of color was achieved after 14 hours. Phase 2 (Effect of bleaching): An in-office bleach material (Zoom 25% HP) was applied to each tooth according to the Kwon technique (polyethylene wrap placed to cover the gel) for one hour. All comparisons were made to a Delta value of 2.6 (perceivable difference). Result: Phase 1: A mean äL*=-13.05(±15.62) was observed for tooth dehydration with no perceivable changes in chroma äa* and äb*. Phase 2: In-office bleaching produced dehydration and chroma changes when measured immediately after bleaching with a mean of äL*=-12.45(±2.4), äa*=0.31(±0.53), and äb*= 3.67(±1.76). After rehydration of bleached teeth, luminosity values (äL*) returned to normal and only chromaticity changes (äb#8727;) were observed with a mean of 4.77(%B11.91). Conclusion: Within the limits of this study, in-office bleaching produced dehydration and chroma changes, represented by äL* and äb*. Upon rehydration, the color changes were not as discernible. Further study will be conducted to determine the validity of these findings.

This thesis set out to investigate how heat stress may affect the oxidative balance and influence the activity patterns of animals. The use of wild animals has been scarce in testing the effects of heat stress on the oxidative balance of animals, especially under a simulated heat wave condition. Animals are expected to differ in their oxidative stress in response to heat stress, depending on their thermotolerance and the life history trait of activity is tested here as an indirect measure of thermotolerance. Therefore, two rodent species within the same family were used for experiments, one with a nocturnal activity rhythm and the other with a crepuscular/diurnal activity rhythm. Animals were tested firstly in a laboratory whole-body hyperthermia experiment, followed by a 3-day heat stress test with extreme temperatures. Following these experiments, animals were subjected to a simulated heat wave to determine how ecologically relevant temperatures may influence not just the oxidative balance of individuals, but also their activity patterns and water drinking in the absence of a microclimate. In order to determine the oxidative balance of individuals under control and heat treatment conditions, markers of oxidative damage and antioxidant defense were used. Markers for lipid and protein oxidation and a marker of enzymatic antioxidant activity and total non-enzymatic antioxidant activity were investigated in the liver, kidney, brain and heart. During the simulated heat wave, activity was measured with video recordings, with the videos analysed for water drinking behaviour as counts and time spent drinking water. During the whole-body hyperthermia experiment without the extreme temperatures, both species demonstrated no significant changes in liver oxidative markers except for high oxidative damage in the kidney for R. dilectus and high oxidative damage in the brain for M. namaquensis. During the 3-day acclimation experiment with extreme temperatures, both species were oxidatively stressed in the heart, with significant oxidative damage in the kidney for R. dilectus and significant oxidative damage in the liver for M. namaquensis. During the simulated heat wave, both species showed no significant changes in liver oxidative balance. The kidney was oxidatively stressed for M. namaquensis, with both species exhibiting signs of oxidative stress in the brain. Animals did not shift their activity during the heat wave, but rhythms demonstrated signs of disruption during the simulated heat wave. Activity increased during the day for both species during the heat wave. This was due to animals being uncomfortable and drinking more water. For the nocturnal species, the frequency of drinking water increased during the day and during the night during the simulated heat wave. The crepuscular species only increased in the amount of time spent drinking water during the day during the simulated heat wave. Overall, the nocturnal species was more susceptible to heat stress inducing either increased oxidative damage or reduced antioxidant defense compared to the crepuscular species, but this was tissue specific and also dependant on the experimental condition. It is recommended that future studies directly measure the reduced: oxidised state of individuals in addition to markers of defense and damage. / Thesis (PhD (Zoology))--University of Pretoria, 2019. / Zoology and Entomology / PhD (Zoology) / Unrestricted

<p>  </p> <p>Dried fruits have traditionally received little food safety attention despite multiple <em>Salmonella</em> and <em>E. coli</em> outbreaks associated with low-moisture foods. Given the popularity of dried apples, many consumers produce dried apples at home. However, little is known about this niche population, their apple drying practices and their sources of food safety information. Therefore, this thesis aimed to use apple drying as a case study to i) identify the fruit drying practices in a domestic setting, ii) determine the factors influencing the associated behaviors and iii) evaluate the food safety information in fruit drying recipes.</p> <p><br></p> <p>The first two studies used quantitative methods with survey data on home apple dryers in the United States. In the first, apple drying practices were identified and evaluated for level of food safety using a safe practice index. Then, regression analyses showed the influence of demographic factors, attitudes, perceived behavioral control (PBC), subjective norms, risk perception and exposure to food safety information on selected apple drying practices. The third study was a content analysis using a qualitative approach to analyze recipe information on blogs, YouTube videos, cookbooks and university extension publications.</p> <p><br></p> <p>Findings revealed that the level of safe food handling in home apple drying was low. Home apple dryers had inadequate frequency of handwashing during apple preparation, potential points of cross-contamination from kitchen tools, a lack of hurdle technology without an apple pre-treatment step, failure to incorporate a thermal kill step during drying, and a lack of objective measurements to ensure that target parameters are attained. The investigated demographic factors, risk perception and food safety information or training had significant influence on current safe apple handling behaviors. Attitudes, PBC and subjective norms were strong predictors of behavior intention. An evaluation of apple drying recipes showed that food safety emphasis was missing. There were omission of food safety controls and a lack of standardization in the recommended procedures.</p> <p><br></p> <p>The results provided handling practice data to support the development of more accurate food safety risk assessment models, and to guide the development of food safety education for home apple dryers. It urged the need for food safety improvement not only in home apple dryers’ practices, but also the information disseminated to them.</p>

Energy demand is projected to increase by 56% before 2040 and this will lead to the fast depletion of fossil fuels. Currently, biomass is the only sustainable source of organic carbon and liquid fuels. One major method of converting biomass involves the utilization of heterogeneous catalysts. However, there is still a lack of understanding in the reaction mechanisms and surface interactions between biomass-derived oxygenates and catalysts. Specifically, three important reactions are investigated: i) dehydration of glycerol, ii) hydrolysis of cellulose and cellobiose, and iii) hydrodeoxygenation of bio-oil. Some important concepts are gathered and provide insight into the most attractive conversion strategies. These concepts include the role of Lewis and Brønsted acid sites, synergistic effect between defect sites and functional groups, the advantage of weak acid sites, steric effect imposed by aromatic substituents, and the evolution of surface species in catalyst deactivation. These studies show that a deep understanding of surface chemistry can help to elucidate elementary reaction steps, and there is great potential in using heterogeneous catalysts for the conversion of biomass into targeted fuels and chemicals.

1. The free radical gas nitric oxide (NO) is now recognised as a ubiquitous and versatile signalling molecule and the investigation of its biological roles has involved a wide range of scientific disciplines in many different species. Yet despite this, its potential roles in the development of rhythmic motor activities in vertebrates have been largely ignored. 2. Physiological experiments recording extracellular ventral root output suggest that NO is playing an inhibitory role in the swimming system of Xenopus laevis larvae, shortening the duration of swim episodes and slowing swim frequency. Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry labelled three populations of neurons in the brainstem, which putatively co-localise NO with the aminergic neuromodulators serotonin (5-HT) and noradranaline (NA), and the fast descending inhibitory neurotransmitter, y-aminobutyric acid (GABA). This suggests that the inhibitory role is supraspinal in origin. 3. Intracellular recordings from neurons presumed to be spinal motor neurons provide further evidence for the inhibitory influence of NO. My experiments suggest that NO potentiates both glycinergic and y-aminobutyric acid (GABA)-ergic inhibition onto spinal motor neurons. The facilitation of the release of these inhibitory transmitters is consistent with the observed effects on swim frequency and swim episode duration, respectively. Additionally, NO appears to affect membrane properties, causing a pronounced membrane potential depolarisation and a decrease in membrane conductance. This suggests that NO shuts off a resting membrane conductance. 4. NADPH-diaphorase histochemistry was subsequently applied to determine the four dimensional expression of putative nitrergic neurons in the central nervous system and related structures. The developmental sequence of staining identifies groups and subgroups of interconnected intemeurons, and provides further clues to their identity. NADPH-diaphorase labelling was also located in the eyes, skin and blood vessels, further confirming the validity of this staining technique for identirying nitric oxide synthase. 5. In the related anuran species, Rana temporaria nitric oxide donor drugs appear to have no affect on swimming, but instead reliably initiates a non-rhythmic "lashing" motor pattern similar to that elicited by dimming of the illumination. Interestingly the NADPH-diaphorase technique labelled three clusters of apparently homologous interneurons in the brainstem and additionally the inner layer of the skin was intensely stained, implicating a species-specific role for NO released from brainstem neurons.

No description available.

Doctor of Philosophy / Department of Chemical Engineering / Keith L. Hohn / In this study, Cu/ZSM-5 catalysts were used to catalyze the hydrodeoxygenation of 2,3-butanediol to butenes in a single reactor in the presence of hydrogen. The carbon selectivity of butenes increased with increasing SiO₂/Al₂O₃ ratio (lowering acidity of zeolite) and H₂/2,3-butanediol ratio. Cu/ZSM-5 with a SiO₂/Al₂O₃ ratio of 280 showed the best activity toward the production of butenes. On zeolite ZSM-5(280), the carbon selectivity of butenes increased with increasing copper loading and 19.2wt% of CuO showed the highest selectivity of butenes (maximum 71%). The optimal reaction temperature is around 250 °C. Experiments demonstrated that methyl ethyl ketone (MEK) and 2-methylpropanal are the intermediates in the conversion of 2,3-butanediol to butenes. The optimal performance toward the production of butene is the result of a balance between copper and acid catalytic functions. Due to the functionalized nature of 2,3-butanediol, a variety of reactions can occur during the conversion of 2,3-butanediol, especially when multiple catalyst functionalities are present. To investigate the role of the metal (Cu) and acid sites in the process of reaction, the reaction kinetics for all major intermediate products (acetoin, MEK, 2-methylpropanal, 2-butanol and 2-methyl-1-propanol) were measured over Cu/ZSM-5(280), HZSM-5(280), and Cu/SiO₂ at 250 °C. The results showed that Cu is the active site for hydrogenation reactions, while the acidic sites on the zeolite are active for dehydration reactions. In addition, dehydration of alcohols over the zeolite is much faster than hydrogenation of ketone (MEK) and aldehyde (2-methylpropanal). A kinetic model employing Langmuir-Hinshelwood kinetics was constructed in order to predict 2,3-butanediol chemistry over Cu/ZSM-5(280). The goal of this model was to predict the trends for all species involved in the reactions. Reactions were assumed to occur on two sites (acid and metal sites) with competitive adsorption between all species on those sites. Two different types of mesoporous materials (Al-MCM-48, Al-SBA-15) and hierarchical zeolite (meso-ZSM-5) were loaded with ~20wt% CuO and investigated in the conversion of 2,3-butanediol to butenes. The results showed that the existence of mesopores on the catalysts (Al-MCM-48 and Al-SBA-15 types) could decrease the selectivities of products from cracking reactions, especially C₃= and C₅=−C₇= by comparison with the catalyst with ~20wt% CuO loaded on the regular HZSM-5(280); meanwhile, the selectivity of C₈= from oligomerization of butenes was found to increase with increasing pore size of the catalysts. With respect to Cu/meso-ZSM-5(280) catalyst, it can be seen that the catalyst performs in a similar way to both Cu/ZSM-5(280) catalyst and mesoporous copper catalysts (Cu/Al-MCM-48 and Cu/Al-SBA-15) since both micropores (diameter of ~0.55 nm) and mesopores (pore size of ~23 nm) exist on meso-ZSM-5(280). The results from Cu catalysts were compared with four other metal catalysts (Ni, Pd, Rh and Pt). It was found that Cu is not very active for hydrogenation of butenes, but is active for hydrogenation of carbonyl groups (C=O) to form hydroxyl groups (−OH). Pd, on the other hand, is active in further hydrogenating butenes and other unsaturated hydrocarbons. Both Ni and Rh catalysts are good for hydrogenation of olefins and cracking of heavy hydrocarbons; however, Rh is not as good as Ni for the hydrogenation of the carbonyl group (C=O) of MEK. In addition, Pt favors the formation of heavy aromatics such as 5-ethyl-1,2,3,4-tetrahydro-naphthalene, while Pd is active for the production of xylene.

In this master thesis, the thermoregulation model proposed by Heath (1970) was updated, integrating the effects of the hydration level on the thermoregulation behavior and the thermal tolerance limits of the Bull Frog, Lithobates catesbeianus (Chapter I). For the thermoregulation behavior the preferred body temperatures (PBT) of hydrated and dehydrated individuals were measured, and as thermal tolerance, the Voluntary Thermal Maximum (VTMax) and the Critical Thermal Maximum (CTMax) were measured in groups of individuals with different hydration levels. Chapter II uses the information collected in chapter I to evaluate the effects of the hydration level on the time to loss the locomotor function of L.catesbeianus individuals exposed to their VTMax. Both chapters indicates that dehydration negatively affects not only the thermoregulation behavior and thermal tolerance of this species, but also the time it takes for individuals to lose their locomotor function when exposed to their VTMax. Our data suggest that dehydration is an important variable that must be included to evaluate the effects of high temperatures and dry conditions on wet skin ectotherms. The temperature-dehydration integration and its effects on these organisms can be included in mechanistic distribution models to update their climate vulnerability under current and future scenarios of climate change / Nesta tese de mestrado foi atualizado o modelo de termorregulação proposto por Heath (1970), integrando os efeitos do nível de hidratação sobre o comportamento de termorregulação e a tolerância térmica da Rã touro, Lithobates catesbeianus (Capitulo I). Para o comportamento de termorregulação foram medidas as temperaturas corpóreas preferenciais (pelas suas siglas em inglês, PBT) de indivíduos hidratados e desidratados, e como tolerância térmica, foram medidas a temperatura voluntária máxima e a temperatura crítica máxima (pelas suas siglas em inglês, VTMax e CTMax, respetivamente) em grupos de indivíduos com diferentes níveis de hidratação. O capítulo II utiliza as informações levantadas no capitulo I para avaliar os efeitos do nível de hidratação sobre o tempo de perda da função locomotora de indivíduos de L.catesbeianus expostos a sua VTMax. O conjunto de dados dos capítulos I e II apontam que a desidratação afeta negativamente não só o comportamento de termorregulação e tolerância térmica desta espécie, mas também o tempo necessário para os indivíduos perderem sua função locomotora ao serem expostos a sua VTMax. Nossos dados sugerem que a desidratação é uma variável importante que deve ser incluída para avaliar os efeitos das altas temperaturas e secas nos ectotermos de pele úmida. A integração temperatura-desidratação e seus efeitos nestes organismos podem ser incluídos em modelos de distribuição mecanicistas para atualizar a vulnerabilidade climática deles nos cenários atuais e futuros das mudanças climáticas

Orientador: Sandra Helena Unêda Trevisoli / Coorientador: Edina Regina Moresco / Banca: Viviane Formice Vianna / Banca: Everlon Cid Rigobelo / Banca: Ivana Marino Bárbaro Torneli / Banca: Eduardo /custodio Gasparino / Resumo: O melhoramento genético de trigo para a região do Cerrado brasileiro visa o desenvolvimento de genótipos adaptados à condições de calor e seca, além de produtivos. Neste sentido, o objetivo do presente estudo foi avaliar a tolerância de cultivares de trigo submetidas aos estresses térmico e hídrico, por meio da avaliação de caracteres relevantes para o melhoramento da cultura, bem como estudar a relação entre eles. Para tanto, 30 cultivares de trigo foram submetidas à quatro condições em casa de vegetação: Controle, Seca, Seca+Calor, e Calor, aplicando os estresses do período do emborrachamento até o final da antese, por meio da suspensão da irrigação e da exposição à temperaturas elevadas. Foram avaliados os caracteres: dias para o emborrachamento, dias para o espigamento, dias para a antese, ciclo, altura da planta, nº de espigas por planta, peso médio de espigas, peso de grãos por espiga, tamanho médio de espigas, nº de espiguetas por espiga, nº de grãos por espiga e porcentagem de espiguetas férteis. Foram realizadas análises de variância individuais e conjunta, análise de correlações genéticas e fenotípicas, análise de componentes principais e análise de agrupamento pelos métodos de Ward e "K-means". Os resultados da análise de variância conjunta entre os ambientes Controle, Seca e Calor indicaram a existência de interação genótipo x ambiente para as características ciclo, nº de espigas por planta, peso médio de espigas, peso de grãos por espiga, tamanho médio de espigas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Wheat breeding for brazilian Cerrado region aims the development of productive genotypes adapted to heat and drought. In this sense, the objective of the present study was to evaluate the tolerance of wheat cultivars subjected to heat and drought stresses, as well as to study the relationships between traits that are relevant to wheat breeding. Therefore, 30 cultivars were conducted in four different greenhouse environments, namely: Control, Drought, Drought + Heat, and Heat, applying the stresses in the period of booting until final anthesis, by suspending the irrigation and exposing to high temperatures. Were evaluated the number of days to booting, number of days to heading, number of days to anthesis, cycle, plant height, number of spikes per plant, mean spike weight, mean grain weight, mean spike size, number of spikelets per spike, number of grains per spike and percentage of fertile spikelets. Was performed individual and joint analysis of variance, genotypic and phenotypic correlations analysis, principal component analysis and cluster analysis by Ward's and "K-means" methods. The results of the joint variance analysis between the Control, Drought, and Heat environments indicated the existence of genotype x environment interactions for the variables cycle, number of spikes per plant, mean spike weight, mean grain weight, mean spike size, number of spikelets per spike, number of grains per spike and percentage of fertile spikelets. The correlations between the producti... (Complete abstract click electronic access below) / Doutor

Óxido e fosfato de nióbio, calcinados em diferentes temperaturas, foram usados como catalisadores na reação de desidratação de 1-butanol, onde o efeito da temperatura de reação, da massa de catalisador e da vazão de butanol sobre a conversão e seletividade a butenos foram avaliadas através de um plano experimental. Foram caracterizadas as propriedades cristalográficas dos catalisadores. A maioria dos catalisadores apresentaram uma estrutura amorfa, mas algumas amostras apresentaram uma estrutura cristalina quando calcinadas em maiores temperaturas, 500 e 850 °C para o NbO e NbP, respectivamente. Nos testes reacionais, observou-se que o aumento da temperatura de calcinação dos catalisadores reduziu a conversão de 1-butanol. O catalisador fosfato de nióbio apresentou maior atividade, já que foi obtida uma conversão similar à do óxido de nióbio com uma massa 5 vezes menor, indicando a presença de sítios ácidos mais ativos. Além disso, a variável reacional que teve maior efeito na conversão foi a vazão de alimentação de 1-butanol; e seu aumento causou um decréscimo nos valores de conversão. Este comportamento indicou que a ordem aparente da reação é menor que um, o que foi confirmado por um modelo cinético baseado em lei de potência, o qual ajustado aos dados experimentais resultou em uma ordem aparente em torno de zero Equações fenomenológicas de velocidade de reação baseadas no modelo LHHW foram desenvolvidos. O teste estatístico F de Fisher foi utilizado para comparar os modelos fenomenológicos obtidos: para o óxido de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta apenas a adsorção de butanol foi considerado o mais adequado; para o fosfato de nióbio calcinado em 400 °C o modelo heterogêneo que leva em conta a adsorção de butanol e de água foi o mais adequado. Para ambos os catalisadores, com exceção do NbO calcinado em 500 °C, foi observada uma significativa isomerização de 1-buteno a 2-buteno, principalmente nas condições que foi obtida uma maior conversão de butanol. Este fato comprova a elevada força ácida destes catalisadores. A seletividade a 2-buteno foi maior ou igual a 1-buteno em todas as temperaturas e condições de reação com fosfato de nióbio. Para o óxido de nióbio, a seletividade a 2-buteno foi maior em poucas condições reacionais. / Niobium oxide and phosphate, calcined at different temperatures, were used as catalysts in the 1-butanol dehydration reaction, where the effect of reaction temperature, catalyst mass and butanol flow rate on conversion and selectivity to butenes were evaluated through an experimental design. The catalysts crystallographic properties were characterized. Most catalysts presented an amorphous structure, but some samples presented a crystalline structure when calcined at higher temperatures, 500 and 850 °C for NbO and NbP, respectively. In the reaction testes, it was observed that the increase in the catalysts calcination temperature decreased the 1-butanol conversion. The niobium phosphate catalyst presented higher activity, since it was obtained a similar conversion to that of niobium oxide with a mass 5 times lower, indicating the presence of more active acidic sites. Furthermore, the reaction variable that had the highest effect on the conversion was in the 1-butanol feeding flow rate; and its growth caused a decrease in the conversion values. This behavior indicated that the apparent reaction order is lower than one, which was confirmed through a kinetic model based on power law, which adjusted to the experimental data resulted in an apparent order around zero Phenomenological equations of reaction rate based on the LHHW model were developed. The Fisher statistical test was used to compare the phenomenological models obtained: for the niobium oxide calcined at 400 °C the heterogeneous model that takes into account only the adsorption of butanol was considered the most adequate; for the niobium phosphate calcined at 400 °C the heterogeneous model that takes into account the adsorption of butanol and of water was the most adequate. For both catalysts, with the exception of NbO calcined at 500 °C, a significant isomerization of 1-butene to 2-butene was observed, mainly in the conditions that were obtained a higher conversion of butanol. This fact proves the elevated acid strength of these catalysts. The selectivity to 2-butene was higher or equal to 1-butene at all reaction temperature and conditions where niobium phosphate was employed. For the niobium oxide, the selectivity to 2-butene was higher in a few reaction conditions.