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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.
21

Identificação de canal natural de escoamento superficial por análise morfométrica na unidade hidrográfica do Pipiripau – DF

Correia, Tatiane Eugênia Rezende 06 June 2016 (has links)
Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Geografia, 2016. / Submitted by Fernanda Percia França (fernandafranca@bce.unb.br) on 2016-07-04T13:14:11Z No. of bitstreams: 1 2016_TatianeEugêniaRezendeCorreia.pdf: 14419182 bytes, checksum: d73ee97472ae5e782136fd79053e7587 (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2016-08-03T22:23:41Z (GMT) No. of bitstreams: 1 2016_TatianeEugêniaRezendeCorreia.pdf: 14419182 bytes, checksum: d73ee97472ae5e782136fd79053e7587 (MD5) / Made available in DSpace on 2016-08-03T22:23:41Z (GMT). No. of bitstreams: 1 2016_TatianeEugêniaRezendeCorreia.pdf: 14419182 bytes, checksum: d73ee97472ae5e782136fd79053e7587 (MD5) / A identificação de porções da paisagem com propensão à saturação e ao escoamento superficial é fundamental, pois são ambientes que propiciam o transporte de poluentes e detritos, bem como podem ser áreas de risco à erosão. A avaliação geoambiental e de parâmetros morfométricos em modelos digitais de terreno permitem definir com precisão ambientes sensíveis na paisagem, assim como, constitui uma estratégia que pode ser automatizada exigindo poucos insumos, recursos e tempo para sua aplicação. O objetivo do presente trabalho foi diferenciar canais efêmeros, intermitentes e perenes por análise morfométrica. Foram utilizados a análise geoambiental, o Índice Topográfico (IT) e o modelo limiar de escoamento superficial para distinguir os canais quanto a sua perenidade. Foram realizadas vistorias in loco na Unidade Hidrográfica (UH) do Pipiripau-DF para a diferenciação dos canais constituindo a verdade de campo, bem como foram avaliadas as características geomorfológicas, de uso, ocupação e cobertura vegetal da área na atualidade e em 1967. Pelas análises, foi possível identificar os geoambientes mais propensos a ocorrência de canal natural de escoamento superficial (efêmero), e que a relação área de contribuição e declividade permite a diferenciação de canais quanto a sua perenidade. A aplicação de modelos como o IT e limiar de escoamento, comparados a realidade de campo, indicaram um limiar de 11 no caso do IT e 225 para o modelo de limiar de escoamento para a diferenciação de canais perenes e intermitentes de canais efêmeros. Considerando a similaridade das características dos geoambientes no grupo geológico do Paranoá, entende-se ser possível aplicar os limiares encontrados para a diferenciação de canais em 65% do DF e contribuir na definição de áreas protegidas, assim como, possibilita a identificação de áreas hidrologicamente sensíveis na paisagem que necessitam de proteção para a gestão dos recursos hídricos no território. O estudo da paisagem como visto aqui, além de fornecer subsídio à análise de vertentes, pode auxiliar em trabalhos futuros, na identificação de campos de murundus e veredas, bem como na discussão a respeito do tamanho adequado das áreas de preservação permanente. Serve ainda de subsídio para a definição de áreas propícias à Reserva Legal, com o intuito de proteger áreas de contribuição e hidrologicamente sensíveis em bacias hidrográficas. ________________________________________________________________________________________________ ABSTRACT / The identification of landscape portions prone to saturation and surface runoff is critical since those provide the transport of pollutants and debris and may be erosion risk areas. The geoenvironmental and morphometric parameters evaluation in digital terrain models allows the precise definition of sensitive environments in the landscape. In addition, this strategy requiring few inputs, resources, and time for automated application. The main goal of this study was to distinguish ephemeral, intermittent and perennial waterways using morphometric analysis. In order to achieve this goal, some methods were used such as the geo-environmental analysis, the Topographic Index (IT) and the threshold model flow to distinguish the waterways for its continuity. Inspections were carried out in situ in the Hydrographic Unit (UH) of Pipiripau in Brazilian Federal District (DF) for the differentiation of waterways stablishing this work´s ground truth. Data collected in 1967 and by the time of this project were evaluated for its geomorphological characteristics of use and occupation and the area vegetation. The analysis of this study enabled to identify Geoenvironments where is most likely to occur gullies and also concluded that the relation between the contribution area and slope allowed to classify the waterways by its continuity. The use of the models showed a threshold of 11 by using IT and 225 by using the threshold model flow to distinguish the waterways for its continuity. Considering the similarities of the Geoenvironments characteristics in geological Paranoá Group one can conclude the applicability the thresholds results to distinguish 65% of waterways in DF and also to identity areas that should be protected. The results also enabled the identification in the landscape of hydrologically sensitive areas in need for protection, contributing for the territory water resources management. This landscape study can provide assistance for further studies in identifying termite mounds fields and for the discussion on the appropriate size of permanent preservation areas. In addition, it is an instrument on the definition of areas prone to legal reserve, in order to protect areas of contribution and hydrologically sensitive in watersheds.
22

Estudo da sensibilidade da estimativa de vento no modelo WAsP relativa à rugosidade superficial

SILVA, Relbert Vieira 31 January 2013 (has links)
Submitted by Victor Hugo Albuquerque Rizzo (victor.rizzo@ufpe.br) on 2015-04-15T13:34:04Z No. of bitstreams: 2 DISSERTAÇÃO Rolbert Vieira Silva.pdf: 6692602 bytes, checksum: c60776703a82719ba0a8db46a67207c7 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-04-15T13:34:04Z (GMT). No. of bitstreams: 2 DISSERTAÇÃO Rolbert Vieira Silva.pdf: 6692602 bytes, checksum: c60776703a82719ba0a8db46a67207c7 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013 / Para o estudo de viabilidade de uma central geradora eólica é necessário calcular a produção anual de energia esperada. O modelo computacional WAsP® (Wind Atlas Analysis Application Program) é usado para gerar dados para a elaboração de atlas eólicos, estimar o potencial de uma região e calcular a produção de energia. Um dos parâmetros de entrada do modelo é a rugosidade superficial ou comprimento de rugosidade z0, que é usado para caracterizar a cobertura superficial do solo. A literatura indica que o parâmetro comprimento de rugosidade pode ser um valor subjetivo, uma vez que é estimado com base em vários critérios subjetivos. Neste trabalho, vários conceitos físicos importantes para o entendimento do processo de modelagem foram abordados e discutidos. A metodologia WAsP® e o modelo de mudança de rugosidade são apresentados de forma simplificada. A sensibilidade do modelo WAsP® ao parâmetro rugosidade superficial foi avaliada ao simular vários cenários. O grau de precisão necessário para a definição da rugosidade, os erros nas estimativas de vento na extrapolação vertical e horizontal e o impacto na intensidade de turbulência de uma área foram as principais análises realizadas. Os resultados mostram que a adoção de premissas inadequadas na definição do comprimento de rugosidade superficial pode levar a avaliação do recurso eólico a resultados significativamente discrepantes que poderiam ser cruciais para o sucesso de um empreendimento eólico em termos de rentabilidade desejada.
23

Produção, purificação e caracterização de biosurfactantes produzidos por linhagens de Bacillus subtilis

Santos, Cristine Fior Clemente dos 28 July 2018 (has links)
Orientador : Glaucia Maria Pastore / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-07-28T00:46:26Z (GMT). No. of bitstreams: 1 Santos_CristineFiorClementeDos_D.pdf: 43427689 bytes, checksum: 6cdb1d14cef42b14acdca1f05afc3e01 (MD5) Previous issue date: 2001 / Resumo: O resumo poderá ser visualizado no texto completo da tese digital / Abstract: The abstract is available with the full electronic document / Doutorado / Doutor em Ciência de Alimentos
24

Management of Superficial Venous Thrombosis: A Systematic Review of Literature and Survey of Canadian Physicians

Duffett, Lisa January 2018 (has links)
Superficial venous thrombosis (SVT) is a common inflammatory and thrombotic pathology occurring within a superficial vein. SVT can result in distressing symptoms of redness and pain in the affected area and exposes patients to a risk of developing deep vein thrombosis (DVT) and pulmonary embolism (PE). Various therapeutic options are available to patients including anti-inflammatories, anti-coagulation and surgical procedures, however which of these therapies is the best first line treatment remains unknown. Several randomized controlled trials have been conducted addressing this question, yet methodological and design flaws have limited the translation of their results into a change of clinical practice. The following thesis consists of a multi-step process of reviewing the evidence to date followed by a process of engaging with clinician stakeholders with the goal of designing a randomized control trial that would provide a meaningful answer to patients and their clinicians. In the first step of this process, a systematic review of the literature was performed, including a meta-analysis to estimate pooled risk of developing symptomatic venous thromboembolic (VTE) complications in patients with isolated SVT following various treatments. These results were then presented to expert Canadian clinicians in a series of surveys using a Delphi process to determine the clinical trial design that would have the greatest impact on changing clinical practice. An additional survey of expert clinicians was conducted to determine current practice variation in the diagnosis, management, and follow up of patients with SVT, in order to design a clinical trial that best reflected current standard Canadian clinical practice. Our systematic review identified 15 articles and including 5775 patients. Quality and assessment of risk of bias was moderate for most included studies. The findings of our meta-analysis identified that Fondaparinux, at prophylactic dose, to had the lowest event rate of 2.0 events per 100 patient years of follow-up (95% CI 0.4 to 4.7, I2=33%) for the primary outcome of deep vein thrombosis (DVT) or pulmonary embolism (PE) during follow-up. Pooled event rates ranged from 8.6-16.6 events per 100 patient-years across other treatment categories, including placebo/observation only, with an event rate of 10.5 events per 100-patient years (95% CI 3.0 to 22.0). Heterogeneity was moderate to high for most pooled estimates, limiting the interpretation of these findings. Our survey of practice variation among expert Canadian clinicians revealed wide practice variation in in diagnosis and therapeutic management including sub-groups (e.g. cancer). There was agreement that clinical equipoise exists for the optimal treatment of SVT (77% of respondents), supporting the need for further research. Two rounds of surveys were performed using Delphi process methods, resulting in consensus for the design of a future randomized control trial (RCT). The agreed on design was for a randomized control trial comparing a direct oral anticoagulant (DOAC) such as Rivaroxaban, to Non-Steroidal Anti-Inflammatories (NSAIDs), using a non-inferiority RCT design with a non-inferiority margin of 3%. Future direction of this research will be to continue stakeholder engagement by engaging patients in the clinical trial design, followed by development of a pilot RCT protocol and application for peer-reviewed funding.
25

Bilateral Upper Extremity Thrombophlebitis Related to Intravenous Amiodarone: A Case Report

Aljitawi, Omar, Shabaneh, Baha, Whitaker, Jack 01 August 2005 (has links)
A 47-year-old male had bilateral upper extremity thrombophlebitis after use of intravenous amiodarone for sustained ventricular tachycardia complicating myocardial infarction. Intravenous amiodarone has been widely used since it was introduced 20 years ago for severe intractable arrhythmias. Superficial thrombophlebitis was frequently noted in the early case reports when high-dose intravenous amiodarone was used. Superficial thrombophlebitis could extend hospitalization and become a significant source of distress to our patients. Some authors recommend insertion of a central line to administer intravenous amiodarone especially with expected extended use of therapy. The treating physician should be vigilant and switch from intravenous therapy to oral therapy as soon as the patient's condition stabilizes and oral therapy can be started.
26

Enfoques de aprendizaje y de estudio de los estudiantes universitarios

Mahncke Torres, Margarita 28 April 2010 (has links)
Aquest treball de recerca té per objectiu determinar com aborden l'aprenentatge els estudiants universitaris i quins són els factors que expliquen la seva adopció d'un o altre enfocament.S'aborda el tema sota el paradigma dels diferents Enfocaments d'Aprenentatge que descriu la manera com els estudiants entenen el seu aprenentatge considerant la intenció particular del subjecte i la relació entre el subjecte i el context en què es troba.Per recollir les dades s'ha utilitzat l'adaptació al castellà del qüestionari dissenyat per John Biggs denominat Qüestionari sobre el Procés d'Estudi. Les dades obtingudes a través d'aquest qüestionari ens han permès conèixer si els estudiants adopten un enfocament a l'hora d'aprendre superficial, profund o d'èxit en les diferents assignatures que cursen.Els resultats indiquen que els enfocaments es relacionen estretament amb algunes metodologies d'ensenyament que els promouen o inhibeixen, Així com amb els sistemes d'avaluació de l'aprenentatge. / Este trabajo de investigación tiene por objetivo determinar cómo abordan su aprendizaje los estudiantes universitarios y qué influye en su adopción de tal o cual enfoque de estudio.Se aborda el tema bajo el paradigma Enfoques de Aprendizajes que describe la manera de cómo los estudiantes abordan un contenido de aprendizaje considerando la intención particular del sujeto y la relación entre el sujeto y el contexto en el que se encuentra. Para ello fue utilizado el cuestionario preparado por John Biggs denominado Cuestionario sobre el Proceso de Estudio. El resultado de este Cuestionario permitió conocer qué enfoques de aprendizaje, superficial, profundo o de logro, los estudiantes adoptan para abordar las exigencias de aprendizaje de las asignaturas que cursan. Además, encontramos que los enfoques se relacionan estrechamente con algunas metodologías de enseñanza que los promueven o inhiben, como por ejemplo las evaluaciones del aprendizaje. / This research work aims to determine how universities students address their learning and what influences their decision of what approach to study to about. It uses the Learning Approaches paradigm which describes the way students address a learning content, considering the particular intention of the students and the relationship between them and the context in where they learn. To this end, it used the questionnaire prepared by John Biggs called Study Process Questionnaire (SPQ). The result of this questionnaire allowed to know what approaches to learning, achievement, superficial or deep, students adopt to address the learning requirements in the classes they take. In addition, we find that these approaches are closely related to some of the methods of teaching promoting or inhibiting them, such as learning assessments.
27

Monte Carlo Investigation into Superficial Cancer Treatments of the Head and Neck

Currie, Bryn Edward January 2007 (has links)
This thesis presents the findings of the investigation into the Monte Carlo simulation of superficial cancer treatments of the head and neck region. The EGSnrc system of codes for the Monte Carlo simulation of the transport of electrons and photons through a phantom representative of either a water phantom or treatment site in a patient is utilised. Two clinical treatment units are simulated using the BEAMnrc system of codes: the Varian Medical Systems Clinac® 2100C accelerator for 6MeV electron fields and the Pantak Therapax SXT 150 X-ray unit for 80kV and 100kV photon fields. Depth dose, profile and isodose curves are compared against those measured from a PTW MP3 water phantom with good agreement being achieved. Quantitative dose distributions are determined for both MeV electron and kV photon fields with treatment sites containing high atomic number materials, rapidly sloping surfaces and different density interfaces. This highlights the relatively high level of dose deposition of dose in tissue-bone and tissue-cartilage interfaces in the kV photon fields. From these dose distributions DVH and dose comparators are used to assess the simulated treatment fields.
28

Tendons with dissimilar functions have different structural and material properties

Batson, Emma Louise January 2002 (has links)
No description available.
29

Estudios de reactividad química en micelas reversas de monoesteres de sacarosa

Ortega Moreno, Anakenna Dennis January 2012 (has links)
Memoria para optar al título profesional de Químico / En los últimos años, la industria de los surfactantes ha comenzado a remplazar las materias primas derivadas de la industria petroquímica por compuestos más amigables con el medio ambiente. Con esta premisa, se han desarrollado familias de surfactantes no iónicos derivados de diferentes azúcares, entre ellos los ésteres de sacarosa, cuya cabeza polar corresponde a una sacarosa y la cola hidrofóbica, a un ácido graso. Estos compuestos presentan baja toxicidad, son no alergénicos y fácilmente biodegradables. El uso de estos surfactantes como agentes dispersantes para solubilizar agua y/o compuestos solubles en ella, en solventes orgánicos (microemulsiones), son de gran interés en procesos de extracción líquido-líquido de proteínas o minerales y en síntesis de nanopartículas. Una aplicación interesante de estos sistemas es como reactores a escala molecular, cuya funcionalidad depende del contenido de agua al interior del ““pool”” acuoso de la micela ([H2O]/[surfactante], R). Este parámetro se utiliza para estudiar la capacidad del sistema como microrreactor, demostrándose que las propiedades del ““pool”” pueden influir positiva o negativamente en reacciones, equilibrios o síntesis que se desarrollen en él. Desde el punto de vista tecnológico y medio ambiental, el empleo de las micelas reversas derivadas de la sacarosa como microrreactores presenta un gran número de ventajas. Sin embargo, su complicada purificación hace que el estudio de estos surfactantes sea limitado a utilizar mezclas de derivados (mono y poliésteres). A partir de estos antecedentes, se realizó una modificación a la metodología propuesta por Vlahov y Col. para la síntesis de estos surfactantes, obteniendo una alta selectividad para el derivado monosustituido en la posición 6-O de la sacarosa, para cinco largos de cadena distintos derivados de ácidos grasos (cáprico (C10), láurico (C12), mirístico (C14), palmítico (C16) y esteárico (C18).) Con los monoésteres sintetizados, se estudio la reactividad en el “pool” acuoso micelar y la influencia de la interfase en el comportamiento de distintos sistemas. Se correlacionó la estructuración de las moléculas de agua por la presencia de los grupos hidroxilos de la sacarosa con las propiedades fluorescentes de la molécula piranina, observándose un cambio cuando R es mayor a 10, siendo este rango más amplio que el observado en micelas reversas de AOT (R=5), que es el surfactante al que más se hace referencia en la literatura. Se estudió si este cambio en la estructuración del agua y por consiguiente en la viscosidad del entorno, tienen un efecto importante en el equilibrio monómero/dímero del Azul de Metileno (MB), en la reactividad del oxígeno molecular singulete, O2(1Δg), y en cinéticas de reacciones al interior de la micela. En presencia de micelas reversas de monoésteres de sacarosa, aumenta la velocidad experimental consumo/generación de O2(1Δg) con 1,3-difenilisobenzofurano (DPBF) como desactivante, comparada con la observada en cloroformo. Además, la constante de desactivación total de O2(1Δg) por astaxantina aumenta en medio microheterogéneo, posiblemente debido a su localización en la interfase, consecuencia de su estructura química. Cuando se estudió la cinética de reacción entre ioduro y hexacianoferrato III, se observó un máximo en el valor de la constante cuando la estructuración del agua se comienza a parecer a la del agua pura (R=10). El tiempo de vida del estado triplete excitado de la Rosa de Bengala se ve afectado por el cambio de viscosidad del “pool” acuso, ya que disminuye, en comparación con el obtenido en agua pura, a medida que la razón [H2O]/[surfactante] aumenta. El equilibrio monómero/dímero del MB dentro del “pool” acuoso de micelas reversas de ésteres de sacarosa está desfavorecido, lo que es coincidente con lo observado por otros autores en alcoholes. Cuando se determinó la constante de desactivación total de O2(1Δg) utilizando DPBF, se observó un efecto negativo en micelas reversas, determinándose para la constante de velocidad es menor que el determinado en cloroformo. La reacción Diels-Alder entre cicliopentadieno y N-etilmaleimida, es levemente mayor en el sistema microheterogéneo que en cloroformo, lo cual indica que la interfase altamente estructurada estaría impidiendo la libre difusión del dienófilo. En definitiva las micelas reversas de ésteres de sacarosa son sistemas adecuados para ser empleados como microrreactores, y la presencia de azúcar en la interfase da origen a un comportamiento físicoquímico diferente al de otros sistemas micelares. / During the last years, surfactant industry has been replacing petrochemical raw material with environmental friendly materials. Several sugar derived families of surfactants are being tested, among them sucrose esters. The structure of this surfactant involves a polar head, sucrose moiety, highly substituted with hydroxyl groups and a hydrophobic chain derived from a fatty acid. These compounds have low toxicity, are hypoallergenic and they are easily biodegradable. These surfactants are widely employed to disperse water or water-soluble molecules in organic solvents (microemulsion stabilization). They are also applied in catalysis enzymatic and nanoparticle synthesis. One of the most attractive uses for these compounds is as microreactors, with properties directly dependent on the amount and structure of water inside the micellar “pool”. From the technological and environmental point of view, the use of surfactants derived from sucrose have a lot of advantages, but, consequence of their complex purification they are usually employed as mixtures of mono and polyesters. We proposed a modification to the stoichiometry of the synthetic methodology proposed by Vlahov et Al., affording the derivate monosubstituted in the position 6-O with a high selectivity. The five compounds with different alkyl chain length (capric (C10), lauric (C12), myristic (C14), palmitic (C16) and stearic (C18)) were obtained with yields around 20%. Reactivity studies were performed to analyze the effect of the water structuration influenced by hydroxyl groups of sucrose in the micellar water “pool”. Photophysic behaviour of pyranine, allows us to observe changes in water structuration when the ratio [H2O]/[surfactant], R, is above 10. This range is narrow for reverse micelle of AOT (the change is observed at R=5). The presence of sucrose moiety promotes a highly structured interface. We studied how the structuration and the viscosity of micellar water “pool” affect: the methylene blue equilibrium monomer/dimer; the formation and reactivity of molecular singlet oxygen, O2(1Δg); and finally the reactivity of organic and inorganic compounds. The presence of reversed micelles increases the O2(1Δg) consumption/generation rate with 1,3-diphenylisobenzofurane (DPBF) used as quencher, when compared with pure chloroform. Furthermore, the total deactivation rate constant of O2(1Δg) by astaxanthin (ASTA) increases in the presence of reverse micelles, because this water-soluble carotenoid is located in the interface. The kinetic study for the reaction between iodide and hexacyanoferrate III, shows a highest rate constant when water structuration resembles to pure water (R near 10). Additionally, Rose Bengal triplet state lifetime is affected by viscosity changes in the water “pool”, and oxygen solubility. Lifetime decreases when the ratio [H2O]/[surfactant] increases, reaching lower values than the one observed in pure water. Methylene blue monomer/dimer equilibrium is hindered in the presence of sucrose ester reverse micelle, behaviour previously reported for this dye in alcoholic solution. The DPBF total quenching rate constant of O2(1Δg) is reduced in the presence of micelles. Diels-Alder reaction involving cyclopentadiene and N-ethylmaleimide, is disfavored referred to chloroform, because the highly structured interface inhibits reactants diffusion. In summary, sucrose ester reverse micelles are promising systems to be employed as micro-reactors, the presence of sucrose moieties yields a highly structured interface, with particular physical chemical properties. / Fondecyt
30

"Estudo in vitro do efeito de três diferentes agentes clareadores sobre a dureza e rugosidade do esmalte dentário bovino"

Riehl, Heraldo 15 April 2002 (has links)
Foi avaliada a influência de três tipos distintos de agentes clareadores sobre a rugosidade e a dureza Vickers do esmalte bovino. Quarenta incisivos centrais inferiores foram divididos em quatro grupos: 1o.) água deionizada (controle); 2o.) peróxido de hidrogênio a 35%; 3o.) palescence X-tra e 4o.) Opalescence Regular a 10%. Os ensaios foram executados antes e depois dos tratamentos. As médias iniciais e finais obtidas de rugosidade (expressos em micrometros) foram, respectivamente, de 58,4 e 58,9 para os dentes do grupo 1, de 62,9 e 399,6 para os do 2, de 60,5 e 282,1 para os do 3 e de 56,4 e 58,5 para os do 4; quanto à dureza (expressos em números puros) foram, respectivamente, de 259,2 e 258,9 para os do grupo 1, de 256,7 e 172,8 para os do 2, de 259,7 e 213,1 para os do 3 e de 260,3 e 259,4 para os do 4. Foi estatisticamente constatado que os espécimes dos grupos 2 e 3 mostraram alterações nas propriedades estudadas; consequentemente, receberam um tratamento adicional, denominado ameloplastia com ácido (através de uma aplicação do produto Opalustre), o qual permitiu a recuperação dos valores originais, para ambas as propriedades referidas. / The influence of 3 whitenning agents upon rugosity and Vickers hardness of bovine dental enamel was evaluated. It were used 40 lower central incisives, divided into 4 groups: 1st) deionized water, 2nd) 35% hidrogen peroxide, 3rd) Opalescence X-tra and 4th) Opalescence Regular 10%. Essays were performed before and after treatments. The inicial and final average values to rugosity (im micrometers) were respectively 58,4 and 58,9 to the teeth from the first group, 62,9 and 399,6 to these of the second, 60,5 and 282,1 to these of the third and 56,4 and 58,5 to these of the fourth; to the hardness (as pure numbers) they were respectively 259,2 and 258,9 to the teeth of the first group, 256,7 and 172,8 to these of the second, 259,7 and 213,1 to these of the third and 260,3 and 259,4 to these of the fourth. It was statiscally detected changes in the specimens of groups 2 and 3; due to this, an adittional treatment, named ameloplasty with acid, promoted a recuperation of original values, to both the studied characteristics.

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