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En este estudio se midió la microdureza Vickers del esmalte dental después de la exposición a tres bebidas industrializadas más consumidas en la ciudad de Lima y una bebida control, para evaluar el efecto erosivo de esta bebidas ácidas y su relación con la acidez titulable, el nivel de pH y el efecto buffer de las mismas. Se elaboraron 60 bloques de esmalte superficial de 2mm de espesor por 2-4mm de longitud; se colocaron en acrílico de curado rápido en moldes circunferenciales de 10mm de diámetro y 5mm de altura en diferentes colores (azul para la bebida carbonatada, anaranjado para la bebida refrescante, verde para la bebida isotónica y blanco para la bebida control; para poder diferenciarlos) los cuales se les dieron el paralelismo ente la superficie libre y la base del molde; luego se les dio un pulido tipo espejo para después ser llevados al microdurómetro Buehler donde se les midió la microdureza. Los datos obtenidos fueron analizados a través de la prueba estadística de TSTUDENT, ANALISIS DE VARIANZA ANOVA, TUKEY HSD, KRUSKAL WALLIS Y U DE MANN WHITNEY. Se concluyó que la microdureza superficial del esmalte disminuye significativamente luego de ser sometido a la acción de las bebidas ácidas estudiadas y que el efecto erosivo es inmediato y se incrementa con cada exposición. Se obtuvo como resultado que la bebida isotónica es más erosiva que las otras bebidas; y se concluyó que no hay una relación entre el efecto erosivo y los valores de pH, acidez titulable y efecto buffer las bebidas. / In this study we measured the Vickers microhardness of enamel after exposure to three industrialized beverages more consumed in the city of Lima, and a control beverage; we want to evaluate the erosive effect of the acidic beverages and their relation with the titratable acidity, the level of pH and buffer effect of this beverages. 60 blocks of surface enamel were made of 2mm thickness, and 2-4mm in length, were placed in fast curing acrylic circumferential mold of 10mm in diameter and 5mm in height, in different colors (blue for the carbonated drink, orange for the drink refreshing, green for the drink isotonic and white for the control beverage; to be differentiated); we gave them that the free surface being parallel with the base of the mold, then they were given a mirrorpolished for microhardness after that, they were being taken to Buehler where microhardness was measured. The data were analyzed by the statistical test T-STUDENT, ANALYSIS OF VARIANCE ANOVA, HSD TUKEY, YU WALLIS KRUSKAL WHITNEY MANN. It was concluded that the enamel surface microhardness decreases significantly after being subjected to the action of acidic drinks and the erosive effect is immediate and increases with each exposure. The result was that the isotonic beverage is more erosive than other drinks, and it was concluded that there is not a relationship between the erosive effect of pH values, titratable acidity and buffer effect of the beverages.

The present paper analyses the erosive processes that have been developed in São Francisco de Assis county, between the peripheric depression and the Rio Grandense plateau. The studied area is located between the 55° 18'46"w and 55°16'00"w, 29°34'50"s and 29°32'55"s elose to, the new road RST 377. The study considers the drainage headcuts of a small hydrological basin connected to Ibicuí River, related to others in the neighborhood. The area is 357,72ha and the perimeter is 7929m. The purpose of this paper is to describe the gully and others erosive processes in different degrees of development, the factors that interfere in the origin and de evolution of the erosive processes in the region; to offer alternatives to stop the degradation of the erosive processes and the possible rehabilitation of the degraded areas, observing a restricted area. The identificated were elassified and maps were made. The erosive landforms have been studied by geomorphology alteration of the earth surface. l1's important to establish systems to observe the evolution of the erosive processes in arder to plan actions to preserve the productive areas and to stop the degradation of the environment in those areas and the around areas because processes like those are increasing in the whole region. / O presente estudo analisa feições erosivas que se desenvolvem em uma cabeceira de drenagem, no Município de São Francisco de Assis, entre a depressão periférica e o planalto Rio-Grandense. A área de estudo, localiza-se entre as coordenadas 55°18.46.w e 55°16.00.w e 29O34.50.s e 29O32.55.s, próxima a estrada nova (RST 377). O estudo avalia os processos erosivos em uma cabeceira de drenagem de uma bacia hidrográfica de pequena extensão associada ao Rio Ibicuí, comparada a outras bacias hidrográficas nas proximidades com área de 357,72ha e perímetro de 7929m. O objetivo do trabalho é descrever as voçorocas e outras feições em diferentes estágios de desenvolvimento, os fatores que intervém na gênese e a evolução dos processos erosivos na região; propor alternativas para contenção dos processos erosivos e possível reabilitação das áreas degradadas, observando uma área .modelo.. Foram identificadas, mapeadas e classificadas as voçorocas em vários estágios de desenvolvimento como também os areais e afloramentos rochosos. As feições erosivas são estudadas pela geomorfologia como as principais responsáveis pela modificação da superfície terrestre e como conseqüências do mau uso do solo. É importante implementar sistemas de informação que possam observar a evolução dos processos erosivos de modo a planejar ações para a preservação das áreas produtivas e conter a degradação ambiental na área e arredores, uma vez que processos semelhantes a esse se desenvolvem em toda a região.

A method for developing an erosive burning model for use in solid propellant design-and-analysis interior ballistics codes is described and evaluated. Using Direct Numerical Simulation, the primary mechanisms controlling erosive burning (turbulent heat transfer, and finite rate reactions) have been studied independently through the development of models using finite rate chemistry, and infinite rate chemistry. Both approaches are calibrated to strand burn rate data by modeling the propellant burning in an environment with no cross-flow, and adjusting thermophysical properties until the predicted regression rate matches test data. Subsequent runs are conducted where the cross-flow is increased from M=0.0 up to M=0.8. The resulting relationship of burn rate increase versus Mach Number is used in an interior ballistics analysis to compute the chamber pressure of an existing solid rocket motor. The resulting predictions are compared to static test data. Both the infinite rate model and the finite rate model show good agreement when compared to test data. The propellant considered is an AP/HTPB with an average AP particle size of 37 microns. The finite rate model shows that as the cross-flow increases, near wall vorticity increases due to the lifting of the boundary caused by the side injection of gases from the burning propellant surface. The point of maximum vorticity corresponds to the outer edge of the APd-binder flame. As the cross-flow increases, the APd-binder flame thickness becomes thinner; however, the point of highest reaction rate moves only slightly closer to the propellant surface. As such, the net increase of heat transfer to the propellant surface due to finite rate chemistry affects is small. This leads to the conclusion that augmentation of thermal transport properties and the resulting heat transfer increase due to turbulence dominates over combustion chemistry in the erosive burning problem. This conclusion is advantageous in the development of future models that can be calibrated to heat transfer conditions without the necessity for finite rate chemistry. These results are considered applicable for propellants with small, evenly distributed AP particles where the assumption of premixed APd-binder gases is reasonable.

Indiana University-Purdue University Indianapolis (IUPUI) / Erosive tooth wear (ETW) is a growing dental condition often associated with aging. This in-vitro project comprised three studies aiming to investigate the impact of tooth age on ETW susceptibility and prevention. In the first study, un-identified extracted premolars were collected and had their ages estimated using validated dental forensic methods. The premolars were examined to investigate the relationship between age and presence and severity of ETW, as well as other main dental-hard tissues conditions. ETW, dental caries, fluorosis, extrinsic staining and tooth color were evaluated using established clinical indices. In the second study, the tooth age impact on ETW susceptibility and response to preventive treatments (Sn+F, NaF, and de-ionized water control) were evaluated using representative samples from the initial study. Enamel and dentin specimens were prepared and subjected to daily erosion-treatmentremineralization cycling procedure. Surface loss (SL) was determined during and after the cycling, by optical profilometry. Similar protocol was adopted in the third study with the addition of toothbrushing abrasion to the model, in order to explore the interplay between age and toothpaste abrasivity on erosion-abrasion development. SL was measured during and after the erosion-toothbrushing-remineralization cycling. The relationships between age and the investigated variables were assessed using linear regression models. In conclusion: 1. The presence and severity of ETW, dental caries, and extrinsic staining increased with age, while of enamel fluorosis decreased. Tooth also showed to be darker with age. 2. Susceptibility of enamel and dentin to demineralization increased with age. Sn+F showed the highest anti-erosive efficacy, and was not affected by age. NaF showed lower efficacy on dentin, which increased with age. 3. Enamel and dentin SL increased with toothpaste abrasivity level. Dentin SL also increased with age. Age effect on enamel SL was observed only with low abrasive toothpaste. Age-related changes on enamel and dentin affected ETW development. / 2020-05-17

Master of Science / Department of Biological & Agricultural Engineering / Aleksey Y. Sheshukov / Soil erosion is one of the main reasons for agricultural land degradation in the world. Losses of land because of high soil erosion rates and rapidly expanding population result in significant reduction of cultivated land area per capita, and shortage of food on the global scale. Soil erosion can be a major source of sediment in the aquatic systems leading to reduction of organism population and poor water quality. Many factors affect soil erodibility, such as, soil properties, rainfall, topographic features, land use, and management practices, among others. The impacts of soil moisture content, however, are not well understood and. therefore, the primary goal of this study was to quantify two soil erodibility parameters, the erodibility coefficient and critical shear stress, under different soil moisture conditions using the jet erosion test (JET). The JET test uses the apparatus (called mini-JET) that creates an impinging jet of water into the soil and records the resulting scour depth over time. The scour depth time series are then fitted into a non-linear soil erosion equation, yielding the sought values of erodibility parameters. For this study, more than 40 soil samples were collected from several sites in Kansas, processed, and prepared to conduct JET tests in the lab setting. The effects of tillage and soil moisture content were of interest to this study. The results showed varied effects of soil type and sample soil moisture condition on the scour depth development and parameters sensitivity. The critical shear stress decreased and the erodibility coefficient increased with the increase of initial moisture content for clay loam soil, while critical shear stress did not change for sandy loam soil. The study also revealed higher erosive properties of soil collected from the tilled field compared to the no-till field.

Constraining past episodes of climate change and glacial response is critical for understanding future impacts of climate change, especially in the high latitudes where warming is expected to be rapid and most of Earth's glaciers exist. Many studies of past glacier size utilize rare isotopes called cosmogenic nuclides to perform surface exposure dating. Since most areas of Earth's surface that were previously glaciated were covered by erosive ice, which stripped away pre-existing cosmogenic nuclides, surface exposure dating yields the timing of the most recent deglaciation. However, in some high latitude areas where glacial ice is cold-based and non-erosive (so-called 'ghost glaciers'), the assumptions of surface exposure dating are violated. Alternate approaches are required to constrain the complex histories of such landscapes. My doctoral dissertation focuses on both developing and employing alternative approaches to studying glacial history in the high latitudes, where glacial ice is non-erosive and dating rock surfaces with a single cosmogenic nuclide does not yield exposure ages. Here, I utilize optimized laboratory methods, paired analyses of two cosmogenic isotopes (10Be and 26Al), numerical models to assess possible exposure/burial histories, and Monte Carlo simulations to constrain uncertainties. To study the exposure and burial history of long-preserved landscapes in the Arctic, I investigate landscapes in two high-latitude locations: Thule, northwestern Greenland; and Cumberland Sound, southern Baffin Island, Canada. Bedrock surfaces, sampled on Baffin Island, exhibit evidence of long-lived subaerial weathering and have simple 10Be exposure ages up to 160,000 yr, despite being glaciated until ~10,000 yr. Simple exposure ages tend to increase with elevation, suggesting more effective erosion in the fjords and longer-term preservation of the uplands. Minimum limiting total histories calculated with 26Al/10Be range up to several million years, with periods of exposure representing ~20% of the total history, describing surfaces that have been alternately preserved beneath non-erosive glacial ice and weathered subaerially over many glacial/interglacial cycles. Boulders, sampled at both sites, have simple 10Be exposure ages up to 78,000 yr in Thule and 79,000 yr on Baffin Island, and yield multi-modal age distributions. Simple exposure ages of boulders tend to under-estimate bedrock ages in the cases of paired bedrock/boulder samples. Minimum limiting total histories calculated with 26Al/10Be range up to 700,000 yr in Thule and several million years on Baffin Island, with periods of exposure representing only a small portion of the total history. Forward numerical models suggest that boulders have been repeatedly reworked, likely experiencing partial or complete shielding during interglacial periods because of rotation and/or burial by till. The landscapes I assess here preserve histories of hundreds of thousands to millions of years, and represent a complex interplay of interglacial exposure, subglacial preservation beneath cold-based ice, periglacial processes, and subaerial weathering. Although such landscapes represent methodological challenges, they contain valuable information about long-term variations in glacial extent and climate.

In recent years, due to the high prevalence of dental erosion, therapies to prevent the occurrence or inhibit the progression of this condition have been searched. The purpose of this thesis was to present four articles that evaluated possible preventive measures for enamel erosion. Specifically, it was evaluated: article I - the effect of five types of vegetable oils against initial enamel erosion; article II - protective effect of palm oil alone or associated with a fluoride solution against erosive enamel wear (chemicalmechanical/ toothbrushing); article III - the protective potential against erosive tooth wear of an aspartame solution, used as mouthwash prior to acid exposure; article IV - the effectiveness of a dentifrice with calcium silicate, phosphate and fluoride on the prevention of erosive wear (chemical-mechanical/toothbrushing). In all articles, deionized water (DW) was used as negative control and a solution (SS) or dentifrice (SD) containing fluoride and stannous as positive control. The response variable adopted was loss of surface hardness for article I and enamel loss in height for articles II, III and IV. In article I, two volunteers used the intraoral appliance for 2 hours to form the acquired pellicle and then the enamel blocks of each study group were treated in vitro by 5 different vegetable oils at 2 different concentrations (5 or 100%). Then, the blocks were immersed in artificial saliva for 2 minutes and subjected to 0.5% citric acid for 2 minutes. Data were analyzed by one-way ANOVA and Tukey\'s test (p <0.05). Among the evaluated vegetable oils, palm oil was the only one that presented protective potential against initial enamel erosion, resulting in less hardness loss than DW and SS. In Article II, volunteers used intraoral appliances in situ for 5 days, in which 4 ex vivo erosive cycling with 0.5% citric acid for 2 minutes was carried out. Prior to the first and third erosive challenge, DW, SS and palm oil associated or not to SS were applied on enamel blocks by administration of one drop of the respective solution, followed by acid immersion. Then, the abrasive challenge was performed (brushing for 15 seconds). Data were submitted to 2-way ANOVA and Tukey\'s test (p <0.05). For both, erosion and erosion + abrasion, palm oil alone or associated to SS resulted in less enamel loss than DW, but did not differ from SS. In article III, 4x/day volunteers performed in situ mouthwashes with DW, SS or 0.024% aspartame solution. Then half enamel blocks were immersed ex vivo in intrinsic (0.01M hydrochloric acid pH 2.3) and the other half in extrinsic (0.03 citric acid pH 2.4 for 2 minutes) acid challenge for 5 days. After statistical analysis (2-way ANOVA and Tukey\'s test, p <0.05), it was observed that aspartame was similar to DW and resulted in greater loss of enamel than SS. Hydrochloric acid promoted higher enamel loss than citric acid. In article IV, volunteers used intraoral appliances in situ for 5 days and 4 erosive cycling with 0.5% citric acid for 2 minutes was carried out. Right after the first and third cycling of the day the dentifrices, including the one with addition of calcium silicate, phosphate and fluoride, were applied for 1 minute and then, half of the enamel specimens were brushed for 15 seconds (abrasion). Statistical analysis was performed by 2-way ANOVA and Fischer\'s exact test (p <0.05). The dentifrice containing calcium silicate, sodium phosphate and fluoride protected the enamel against erosion similar to SD; but when subjected to abrasion by brushing, it showed similar enamel loss than DW, demonstrating no protective effect. Among the tested preventive measures, palm oil presented promising results in the prevention of erosive tooth wear, similarly to a stannous-solution. Aspartame, however, did not present a preventive effect against erosive tooth wear caused by intrinsic or extrinsic acid. The dentifrice containing calcium silicate, sodium phosphate and fluoride only presented a preventive effect against erosion but it did not show a protective effect against erosive tooth wear. / Devido à alta prevalência de erosão dentária encontrada nos últimos anos, tem se buscado terapias para prevenir a ocorrência ou inibir o avanço desta condição. O propósito deste estudo foi apresentar quatro artigos que avaliaram possíveis medidas preventivas para erosão dentária do esmalte. Especificamente, foram avaliados: artigo I - o efeito de cinco tipos de óleos vegetais contra a erosão inicial; artigo II - capacidade protetora do óleo de dendê sozinho ou associado uma solução fluoretada contra desgaste dentário erosivo (químido-mecânico/escovação); artigo III - o potencial protetor contra o desgaste dentário erosivo de uma solução com aspartame, utilizada como bochecho previamente a exposição ácida; artigo IV - a eficácia da aplicação do dentifrício com adição de silicato de cálcio, fosfato e flúor na prevenção do desgaste erosivo (químido-mecânico/escovação). Em todos os artigos adotou-se água deionizada (AD) como controle negativo e solução (SE) ou dentifrício (DE) contendo fluoreto e estanho como controle positivo. A variável de resposta adotada foi perda de dureza de superfície para o artigo I e perda de tecido dental duro em altura para os artigos II, III e IV. No artigo I, dois voluntários utilizaram o dispositivo intrabucal durante 2 horas para formação da película adquirida e em seguida, os blocos de esmalte de cada grupo em estudo foram tratados in vitro por 5 diferentes óleos vegetais em 2 concentrações distintas (5 ou 100%). A seguir, os blocos foram imersos em saliva artificial por 2 minutos e então, em ácido cítrico 0,5% por 2 minutos. Os dados foram analisados por ANOVA 1 critério e teste de Tukey (p<0,05). Dentre os óleos vegetais avaliados, o óleo de dendê foi o único que apresentou potencial protetor contra erosão inicial do esmalte pois resultou em menor perda de dureza quando comparado a AD e SE. No artigo II, voluntários utilizaram aparelhos palatinos in situ por 5 dias, sendo realizadas 4 ciclagens erosivas ex vivo em ácido cítrico 0,5% por 2 minutos, anteriormente a primeira e a terceira ciclagem a AD, o SE e o óleo de dendê associado ou não à SE foram aplicados nos blocos de esmalte por meio da administração de uma gota da respectiva solução, seguida da imersão ácida e então, o desafio abrasivo foi realizado (escovação por 15 segundos). Os dados foram submetidos a ANOVA 2 critérios e teste de Tukey (p<0,05). Tanto para erosão como para erosão+abrasão, o óleo de dendê sozinho ou associado à SE resultou em menor perda de esmalte do que AD, porém não diferiu da SE. No artigo III, os voluntários realizaram bochechos in situ 4x/dia com 0,024% de aspartame e então, metade dos blocos de esmalte foram submetidos ex vivo ao desafio com ácido intrínseco (ácido clorídrico a 0.01M pH 2.3) e a outra metade ao extrínseco (ácido cítrico 0.03M pH 2.4) durante 5 dias. Após análise estatística (ANOVA 2 critérios e teste de Tukey, p<0,05), constatou-se que o aspartame foi similar à AD e resultou em maior perda de esmalte do que SE; sendo que o ácido clorídrico promoveu maior perda de esmalte do que o ácido cítrico. No artigo IV, voluntários utilizaram aparelhos palatinos in situ por 5 dias e foram realizadas 4 ciclagens erosivas em ácido cítrico 0,5% por 2 minutos, sendo que logo após a primeira e terceira ciclagem do dia, os dentifrícios, incluindo o com adição de silicato de cálcio, fosfato e flúor foram aplicados por 1 minuto e metade dos espécimes foram escovados por 15 segundos (abrasão). A análise estatística foi realizada por ANOVA 2 critérios e teste exato de Fischer (p<0.05). O dentifrício contendo silicato de cálcio, fosfato de sódio e flúor protegeu o esmalte contra a erosão semelhantemente ao DE. Porém quando a abrasão por escovação foi associada, o mesmo resultou em perda de esmalte semelhante a AD e portanto, não houve efeito protetor. Dentre as medidas preventivas testadas o óleo de dendê apresentou resultados promissores na prevenção do desgaste dentário erosivo, se assemelhando ao estanho. Já o aspartame, não apresentou efeito preventivo contra o desgaste dentário erosivo causado por ácido intrínseco ou extrínseco. O dentifrício contendo silicato de cálcio, fosfato de sódio e flúor, só apresentou efeito preventivo contra a erosão, mas não foi capaz de proteger o esmalte contra o desgaste dentário erosivo.

As formas naturais do relevo costeiro são resultantes da atuação e interação de processos continentais, oceânicos e atmosféricos. Dentre as diversas feições costeiras destacam-se as falésias e, nesta tese, serão discutidas estas feições esculpidas na Formação Barreiras, sendo esta uma vasta área sedimentar que se estende desde o estado do Rio de Janeiro até o estado do Amapá. Há um grande conjunto de elementos em interação atuando na morfogênese e evolução das falésias e estes são considerados dentro de uma perspectiva de análise sistêmica, sendo estes agrupados e caracterizados como elementos de um Sistema Natural, considerando-se o sistema como um conjunto formado por materiais, processos e formas, tratados, nesta tese, como um sistema geomórfico dinâmico com entrada (inputs) e saída (outputs) de energia e materiais identificáveis, dirigidos e controlados pelas condições ambientais, no qual inúmeros tipos de processos ocorrem simultaneamente. Estudos teóricos e de campo foram realizados em Beberibe-CE, Mucuri-BA e Tibau do Sul-RN e possibilitaram a observação e identificação de características e indícios da morfogênese e evolução das falésias, permitindo a proposição de uma classificação, dentro de um quadro regional da Formação Barreiras, destas feições em: 1) falésia precedida por praia; 2) falésia não precedida por praia. / Natural forms of coastal relief are the result of the action and interaction of continental, oceanic and atmospheric processes. Among various coastal features, cliffs stand out and in this thesis, we discuss these features carved into Formação Barreiras, which is a vast sedimentary area stretching from Rio de Janeiro to Amapá State. There is a large set of elements in interaction taking part in the morphogenesis and in the evolution of cliffs which are considered here within the perspective of a systemic analysis. These elements are classified and characterized as elements of a \"Natural System\", considered system as a whole formed by materials, processes and forms, treated, in this thesis, as a dynamic geomorphic system with inputs and outputs of strenght and materials identifiable, directed and controlled by environmental conditions, in which numberless types of material processes occur simultaneously. Theoretical and field studies performed in Beberibe-CE, Mucuri-BA and Tibau do Sul-RN, allowed us to observe and identify characteristics and evidences of cliffs morphogenesis and evolution, making possible we propose a classification of these features, within a regional framework of Formação Barreiras: 1) cliffs preceded by a beach; 2) cliffs not preceded by a beach.