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Estudo das caracter?sticas f?sico-qu?micas e biol?gicas pela ades?o de osteoblastos em superf?cies de tit?nio modificadas pela nitreta??o em plasmaSilva, Jos? Sandro Pereira da January 2008 (has links)
SILVA, J. S. P. Estudo das caracter?sticas f?sico-qu?micas e biol?gicas pela
ades?o de osteoblastos em superf?cies de tit?nio modificadas pela nitreta??o
em plasma. 2008. 119 f. Tese (Doutorado) - Faculdade de Medicina, Universidade de S?o
Paulo. S?o Paulo, 2008. / Submitted by CECILIA SANTOS (cecilia@bczm.ufrn.br) on 2010-09-29T13:32:45Z
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license_rdf: 20464 bytes, checksum: d540d98f4c56c073d1d99228e27d53ca (MD5) / PURPOSE: The aim of this study was to evaluated the physico-chemical
properties of different titanium surfaces modified by means of low
temperature plasma nitridind on rat osteoblast cell adhesion and proliferation.
METHODS: Pure Titanium discs grade II was submitted to three different
surface preparations (polishing, glowglow discharge plasma nitriding in planar and
cathodic cage configurations). Surface parameters as roughness, wettability
and chemichal composition was determined to compare influency of gas
mixture on the modified surface material properties. Cellular morphology was
observed by scanning electron microscopy.To evaluate the effect of the
surface on cellular response, osteoblast cells (MC3T3) adhesion and
proliferation was quantified and data analised by Kruskal-Wallis and
Friedman statistical tests. RESULTS: plasma nitriding discs shows rougher
surfaces( p<0,02) in cathodic cage configuration andlower contact angle
values. MC3T3 cells attached on rough surfaces produced by cathodic cage
configuration was statistically significant p<0,05 compared to polished discs.
CONCLUSIONS: Glow discharge plasma nitriding improve titanium surface
roughness and wettability. MC3T3 cell adhesion behavior is related to substrate chemical composition and topography. Resumo: INTRODU??O: Superf?cies de tit?nio modificadas por diferentes m?todos
foram estudadas com base nos par?metros f?sicos e qu?micos de
caracteriza??o superficial e sua influ?ncia no comportamento de c?lulas pr?osteobl?sticas
(MC3T3) in vitro. M?TODOS: Discos de tit?nio
comercialmente puro grau II foram submetidos a tr?s m?todos de
modifica??o de superf?cie (polimento, nitretados em plasma em configura??o
planar e gaiola cat?dica). As diferentes superf?cies foram caracterizadas
para observar o efeito do processamento na estrutura da camada superficial,
na rugosidade e molhabilidade. Ensaios de ades?o e prolifera??o celular
usando linhagens de c?lulas pr?-osteobl?sticas MC3T3 foram realizados
para avaliar o efeito das novas superf?cies no comportamento celular in vitro.
RESULTADOS: Os resultados demonstraram que a nitreta??o em plasma
na configura??o de gaiola cat?dica produz superf?cies mais rugosas (p<0,02)
e com menores ?ngulos de contato com a ?gua. CONCLUS?ES: A ades?o
celular ? maior nas superf?cies mais rugosas do que nas superf?cies polidas
(p<0,05) e reagem de modo diferente a composi??o qu?mica do substrato e ? topografia da superf?cie
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O papel do centro hist?rico na cidade: um estudo comparativo entre Jo?o Pessoa e ToursSilva, Alzilene Ferreira da 14 May 2014 (has links)
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Previous issue date: 2014-05-14 / Trata-se de um estudo comparativo sobre os Centros Hist?ricos das cidades de Jo?o Pessoa, no Brasil, e Tours, na Fran?a. O intuito prec?puo reside em analisar o papel e as representa??es que s?o proeminentemente associadas aos Centros Hist?ricos das respectivas cidades - diferen?as e semelhan?as. Desse modo, faz-se necess?rio realizar um panorama dos hist?ricos dos Centros das cidades de Jo?o pessoa e Tours, verificando assim as principais fun??es, usos e pr?ticas sociais que contribu?ram/contribuem para a consolida??o de certas representa??es sobre os referidos n?cleos origin?rios. / In the contemporary scene, it is conspicuous that the patrimony and the culture have
assumed privileged positions in urban policies, presenting themselves as instruments
for transforming and shaping the aspect of cities. In the plot line of such glowing trend,
the competitiveness among cities has drawn more attention, for at present such urban
centers garner an image that makes them suitable for economic purposes, thus more
likely to attract investments and tourists. In the spotlight of such stage, the cities
become notable actors, directed by policies of urban rehabilitation. In such plot line,
the historical centers gain more visibility and are converted into venues for staging the
spectacle of everyday life. Overlapped in this process of producing images, the
phenomenon of gentrification recrudesces. Thus, the discussion threaded about the
patrimony gains strength in urban studies, keeping a close relationship with the ways
of perceiving the cities nowadays. This work is based on the principle that the historical
centers are engendered and fond by urban policies, working as transforming
instruments of city perceptions and living. In that sense, the way how the historic center
and the valuation assessed to old buildings are comprehended by the inhabitants is
largely guided by urban policies that outline a sellable image of the city. In the light of
such elaborations, an ethnographic research was made with focus on two different
contexts, namely: the historic centers of Jo?o Pessoa (Brazil) and Tours (France). It
was done in a comparative perspective, for it allows us to trace the main specificities
of each situation in order to highlight the similarities and distinctions about the two
regions mentioned above. The research aimed at apprehending how the pair
redevelopment-abandonment engendered by the urban policies influence on the
process of revaluation of historical centers by dwellers and to what extent there are
convergences regarding such kinds of interventions, as an object of policies of urban
and touristic development in Brazil and France. In order to make this work ? besides
the abundant bibliographic review carried out in libraries of several universities and
institutions in Brazil and France ? dwellers, merchants, teachers, representative people
of public agencies and former residents of the historic centers of both cities were
interviewed. In Tours, immigrants/Portuguese descendants were interviewed, point
that greatly contributed to the understanding of the historic center before Vieux Tours
renewal and restoration. Moreover a rich research on Archives and Public Agencies
was done, as well as investigations on newspaper and articles on the Internet. Thus,
in the context of the ethnography in historic centers, it was possible to notice that both
realities reveal similarities in a comparative analytical framework
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O drama do g?nio na metaf?sica do Belo de Schopenhauer: sua mais alta express?o no Torquato Tasso de Goethe / The drama of genius in the metaphysics of the Beautiful of Schopenhauer: its highest expression in the Torquato Tasso de GoetheSilva, Iasmim Cristina Martins da 02 March 2016 (has links)
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Previous issue date: 2016-03-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / To Schopenhauer, a genius is characterized by the surplus of the faculty of knowing, which allows these individuals to have immediate access to the Idea through the intuitive contemplation, while a pure being of the knowledge. However, this potentiality amplifies the genius? will, when the status of individual is retaken. According to the philosopher, the surplus of the faculty of knowing may take two guidances, which exclude themselves: the objective guidance, when one is freed from the bondage of the will, or the indirect guidance, occasion when the surplus is available to the individual guidance. As a consequence of the surplus, the genius either neglects suffering or suffers radically. This work intends to present the following hypothesis: the genius goes through existential drama that greatly surpasses the natural suffering inherent to other people. Thereunto Torquato Tasso, Goethe?s work, was utilized, since it has been mentioned by Schopenhauer / Para Schopenhauer, o que caracteriza o g?nio ? o excedente da faculdade de conhecer (genialidade) que lhe possibilita acesso imediato ? Ideia por meio da contempla??o intuitiva, enquanto puro sujeito do conhecimento. Todavia, esta mesma potencialidade amplifica a vontade do g?nio, quando este retoma a condi??o de indiv?duo. Segundo o fil?sofo, o excedente da faculdade de conhecer pode tomar duas orienta??es, excludentes entre si: a orienta??o objetiva, quando ele se torna livre da servid?o da vontade, ou a orienta??o subjetiva, ocasi?o em que o excedente se coloca a servi?o da vontade individual. Por conta dessas duas orienta??es do excedente, o g?nio ora se abst?m do sofrimento, ora sofre de maneira extremada. O presente trabalho pretende apresentar a hip?tese de que o g?nio vivencia um drama existencial, que ultrapassa sobremodo o sofrimento natural inerente aos outros homens. Para tanto, objetiva-se recorrer ? obra Torquato Tasso do Goethe, citada pelo pr?prio Schopenhauer.
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Un modèle génératif pour le développement de serveurs Internet / A generative model for Internet servers developmentLoyauté, Gautier 05 September 2008 (has links)
Les serveurs Internet sont des logiciels particuliers. Ils doivent répondre aux demandes d'un grand nombre de clients distants, supporter leur évolution et être robustes car ils ne s'arrêtent jamais. Les modèles de concurrence permettent d'entrelacer les traitements d'un grand nombre de clients. Aucun consensus ne se dégage sur un meilleur modèle. Pour s'abstraire du modèle de concurrence, je propose un modèle de développement de serveurs Internet. Les outils de vérification formelle permettent d'accroître la sûreté des logiciels mais il est nécessaire de leur fournir un modèle simple du logiciel. Le modèle de développement que je propose est utilisé pour générer le serveur et son modèle formel. Le décodage d'une requête cliente dépend du modèle de concurrence. Je propose d'utiliser un générateur d'analyseur syntaxique qui s'abstrait de ce problème et automatise le développement du décodage / Internet servers are software with specific features. Indeed, they answer request of wide and distant clients, support the customer evolution and be robust because they never stop. The concurrency models allow to interleave the statements of wide customers. No general agreement frees on a better model. To abstract himself from the concurrency model, I propose a development model of Internet servers. Model checkers allow to increase the software safety. But, it is necessary to provide a simple model of software to check it. I propose to use my development model of servers in order to genrate ther server automatically and its formal model. Finally as the request parsing depends on the concurrency model, I propose to use Tatoo, a parser generator. Tatoo abstracts himself from this dependency and automates the development of parsing
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Produ??o e caracteriza??o de implantes nanotexturizados de tit?nio associado a libera??o gradual de f?rmacosVeleda, Paula Pr? 30 August 2012 (has links)
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Previous issue date: 2012-08-30 / The aim of this study was to assess, in vivo, the effect of two different surface treatments of titanium implants - plasma-spray (PSA) and nano-textured plasma-spray (PSA-nano) - at the bone-to-implant interface (osseointegration), associated or not to the recombinant human growth hormone (rhGH). Twenty-four prototypes of pure titanium implants, 6-mm long and 2-mm wide, were especially fabricated in a cylindrical shape and placed in 12 New Zealand rabbit s tibiae. The implants were divided into four groups: 1) PSA implants without rhGH, 2) PSA implants with rhGH, 3) PSA-nano implants without rhGH and, lastly, 4) PSA-nano implants with rhGH. The animals were sacrificed 14 and 42 after the surgeries. Samples were collected and analysed by optical microscopy (OM), scanning electronic microscopy (SEM) and infrared microscopy (μ-FTIR), besides the pull-out mechanical test. The results showed that in the early stage of osseointegration, the recombinant human growth hormone has favored new bone formation, regardless the surface treatment. Howev-er, in the later stage, the nano-textured surface, even without the hormone, has made a positive influence on the new bone formation, when compared to its use with hormone. In this stage, only the plasma-spray surface (PSA) has been favored by the growth hormone / O objetivo deste trabalho foi avaliar, in vivo, o efeito de dois diferentes trata-mentos de superf?cie de implantes de tit?nio - plasma-spray (PSA) e plasma-spray nanotexturizado (PSA-nano) - na interface osso-implante (osseointegra??o), associ-ados ou n?o ao horm?nio do crescimento humano recombinante (rhGH). Vinte e quatro prot?tipos de implantes de tit?nio puro, medindo 6 mm de comprimento por 2 mm de di?metro, foram especialmente confeccionados em uma forma cil?ndrica e colocados na t?bia de 12 coelhos da ra?a New Zealand. Os implantes foram dividi-dos em quatro grupos: 1) implantes PSA sem rhGH, 2) implantes PSA com rhGH, 3) implantes PSA-nano sem rhGH e, por ?ltimo, 4) implantes PSA-nano com rhGH. Os animais foram sacrificados 14 e 42 dias ap?s as cirurgias. As amostras foram cole-tadas e analisadas por microscopia ?ptica (MO), microscopia eletr?nica de varredura (MEV) e microscopia de infravermelho (μ-FTIR), al?m do teste mec?nico de pull-out. Os resultados mostraram que no est?gio inicial da cicatriza??o, o horm?nio do cres-cimento recombinante humano favoreceu a neoforma??o ?ssea, independente do tipo de superf?cie. Por?m, no est?gio tardio, a nanotexturiza??o, sem a presen?a do horm?nio, exerceu uma influ?ncia positiva na neoforma??o ?ssea, quando compa-rada ao seu emprego com o horm?nio. Neste est?gio, apenas a superf?cie de plas-ma-spray (PSA) foi favorecida pelo horm?nio do crescimento
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Efeito da aplica??o de molibd?nio em caupi (Vigna unguiculata (L.) Walp.) em condi??es de campo / Effect of Mo application in cowpea (Vigna unguiculata (L.) Walp.) growth at field conditions.Alves, Jos? Milton 27 January 2005 (has links)
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Previous issue date: 2005-01-27 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Two experiments were carried out at field conditions in the Department de Fitotecnia
UFRRJ with the aims of the study the effect of molybdenum in cowpea (Vigna unguiculata
(L.) Walp.). The seeds from the cultivar CNCx 409-11F-P2 were used with a plant population
of 200.000 plants.ha-1. The first experiment was arranged in a factorial block design with 4
replications, 5 levels of Mo (100, 200, 400, 800 g.ha-1) applied in the leaves and the control, 3
times of application (32 days after germination, flowering period and seed pod filling). During
the plant development, 3 harvests were made: 48 and 79 DAG and at the end of plant grown.
The parameters analyzed were: number and weight of nodules, shoot and root dry weight and
productivity. At the second experiment, the treatments were applied: two levels of pH (5.5
and 6.5); six levels of Mo (20, 40, 80, 160, 1280 g. ha-1) applied in the leaves and the control;
2 ways of Mo application (in the soil and foliar application); with 4 replications. The
harvests were made at 62, 73 and 87 DAG and at the end of plant growth. The parameters
analyzed were: number and weight of nodules, shoot and root dry weight, productivity and
Mo concentration in the seeds. The foliar applications of Mo increase the number of nodules.
Occurred a significant variation of weight of nodules shoot and root dry weight in function of
the form of Mo application, soil or leaves. The range of Mo concentration in the seeds was
between 0,45 and 26,93 g.Mo.semente-1. / Este trabalho foi desenvolvido na ?rea experimental do Departamento de Fitotecnia da
UFRRJ com o objetivo de estudar a aplica??o de molibd?nio em plantas de caupi (Vigna
unguiculata (L.) Walp). Foram conduzidos dois experimentos utilizando sementes da
linhagem CNCx 409-11F-P2 obtendo-se uma popula??o final de 200 mil plantas.ha-1. O
primeiro experimento foi conduzido em um esquema fatorial em delineamento em blocos ao
acaso com 4 repeti??es, 5 n?veis de Mo aplicados via foliar (100, 200, 400, 800 g.ha-1) e
testemunha, 3 ?pocas de aplica??o (32 Dias Ap?s a Germina??o, Flora??o Plena e
Enchimento dos Gr?os), num total de 60 parcelas. Durante o per?odo de desenvolvimento da
cultura foram realizadas coletas das plantas com 48 e 79 DAG e no final do ciclo da cultura,
para determina??o do n?mero de n?dulos, do peso de n?dulos secos, do peso da parte a?rea e
da raiz secas e produtividade. No segundo experimento foram utilizados 2 n?veis de pH (5,5 e
6,5), 6 n?veis de Mo via foliar (20, 40, 80, 160, 1280 g.ha-1) e testemunha, 2 formas de
aplica??o do molibd?nio (sulco e foliar) que ocorreu com 56 DAG e 4 repeti??es, num total
de 96 parcelas. Foram realizadas coletas das plantas com: 62, 73 e 87 DAG e no final do
desenvolvimento da cultura, onde foram determinados o n?mero de n?dulos, peso de n?dulos
secos, do peso da parte a?rea e da raiz secas, produtividade e concentra??o de molibd?nio nas
sementes. A aplica??o foliar de Mo aumentou o n?mero de n?dulos das plantas de caupi.
Ocorreu uma grande varia??o das caracter?sticas avaliadas, peso de n?dulo, raiz e parte a?rea
secas em fun??o da forma de aplica??o de Mo e do pH do solo. O aumento da concentra??o
de molibd?nio nas sementes foi linear, independente da forma de aplica??o e do pH. As
concentra??es de Mo encontradas nas sementes ficaram entre 0,45 a 26,93 g.Mo.semente-1.
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Atributos ed?ficos e aduba??o nitrogenada em cana de a??car em tabuleiros costeiros: respostas a sistemas de colheita com e sem queima da palhada / Edaphic attributes and nitrogen fertilizitation in sugarcane on coastal tableland region: response to harvesting system with and without previous burning of strawOLIVERA, Ana Paula Pessim de 27 February 2013 (has links)
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Previous issue date: 2013-02-27 / CAPES / To evaluate the impacts of trash management on soil quality and sugarcane production in the Brazilian region of coastal tableland three studies were conducted and are presented in distinct chapters. In the first chapter, a literature review, the results of research with sugarcane and changes in biological, chemical and physical soil properties, in response to trash management and their relationship with soil quality, are presented. In general, the data suggest that harvesting without burning affects positively the soil properties and improves soil quality. However, the studies are not sufficient to inform about the effect of mechanical harvesting without burning of trash in the tableland soils. In the second chapter they were evaluated the effect of N fertilization of green sugarcane on the stalk productivity, the trash accumulation, the relationship between the number and weight of stalks, the extraction and accumulation of nutrients in the fresh stalks and trash, and the sugarcane technological quality. This study was conducted in the LASA distillery, in Linhares municipality, Esp?rito Santo State, with ratoon cane, varieties RB86 7515 and RB91 8639, in a Xanthic Udult soil. The experiment was set in a randomized blocks design with the control (without N) and four treatments with N applied as ammonium sulphate (80, 100, 120, and 160 kg N ha-1) in four replicates. The N had a significant effect on stalks productivity. The relationship between the number and weight of stalks was significant for the dosages of 80 kg N ha-1 (both varieties) and 100 kg N ha-1 (only the RB91 8639 variety). There was significant effect of N rates on the cane technological quality only in the second cycle studied. The extractions of N, P and K were significant for the N levels. The third chapter is a simulation study conducted with the APSIM-Sugar cropping systems model, based on data from the log-term experiment (duration of 23 years) in the municipaliy of Linhares-ES. This study had as goal to investigate the impact of trash management after harvesting on sugarcane production and the long-term fate of N contained in trash. The objectives were: to investigate if the model was capable of reproducing the trends of the major N pools (cane yields and soil organic carbon) in the long term experiment; and using the parameterized model to evaluate how the relationship between N fertilizer and yield (and losses of N to the environment) varies with the trash management. The trash management systems conditions simulated were: retention of trash at harvest (100 %, GCTB); half retention of trash at harvest (50%); and burnt cane trash. The N fertilizer management system was simulated by varying N fertilizer application from 0 to 240 kg ha-1 (in 40 kg ha-1 increments) rates on the ratoon crops. The cane yield and soil organic C responded positively to the trash management systems (GCTB and half GCTB), but the magnitude of the response is dependent on N-fertilizer applied on crops. Half removal of trash might reduce the extent of yield increasing potential. When the trash deposition is a recent practice, additional N fertilizer is required by the crop, to avoid yield reduction caused by the N immobilization. The simulations also indicated that the average environmental losses of N were greater from trash retained systems for all rates on N fertilizer applied. / Para avaliar o impacto do manejo da palhada sobre a qualidade do solo e produ??o de cana-de-a??car na regi?o dos Tabuleiros Costeiros, tr?s estudos foram conduzidos e s?o apresentados em cap?tulos. No primeiro cap?tulo, em forma de revis?o de literatura s?o apresentados os resultados de pesquisas com cana-de-a??car e altera??es nas propriedades biol?gicas, qu?micas e f?sicas do solo em resposta ao manejo da palha, e sua rela??o com a qualidade do solo. Do conjunto de dados, se infere que a colheita sem queima com manuten??o da palha altera positivamente as propriedades ed?ficas e melhora a qualidade do solo. Por?m, os estudos s?o insuficientes para suprir informa??es sobre o efeito da colheita mec?nica e sem queima da palhada da cana sobre os solos de tabuleiro. No segundo cap?tulo foram avaliados, os efeitos da aduba??o nitrogenada, em cana crua, sobre a produtividade de colmos, ac?mulo de palhada, rela??o entre n?mero e peso colmo, extra??o e ac?mulo de nutrientes nos colmos frecos e na palhada, e sobre a qualidade tecnol?gica da cana de a??car. O estudo foi realizado na destilaria LASA no munic?pio de Linhares-ES, com cana soca, variedades RB 867515 e RB 918639, em ARGISSOLO AMARELO. Os tratamentos consistiram de cinco doses de N-Sulfato de am?nio (sem N, 80, 100, 120 e 160 kg de N ha-1), arranjados em desenho experimental de blocos casualizados com quatro repeti??es. Houve efeito significativo de doses de N sobre produtividade de colmos. A associa??o entre n?mero e peso de colmos foi significativa para 80 kg N ha-1 (ambas as variedades) e 100 kg ha-1 (para a variedade RB91 8639). Houve efeito significativo das doses de N sobre a qualidade tecnol?gica da cana apenas no segundo ciclo de cultivo estudado. As extra??es dos nutrientes N, P e K mostraram signific?ncia para as doses de N. O terceiro cap?tulo, relata um estudo de simula??o conduzido com o APSM-Sugar cropping systems model, com dados de um experimento de campo de longa dura??o (cerca de 23 anos) em Linhares-ES. Este estudo se prop?s a investigar o impacto do manejo da palhada ap?s a colheita sobre a produtividade da cana e o destino em longo prazo do N contido na palha. Os objetivos foram: investigar se o modelo foi capaz de reproduzir as tend?ncias de maiores ?pools? de N (rendimento de cana e C org?nico no solo) no experimento de longa dura??o; e usar o modelo parametrizado para investigar como a rela??o entre o N-fertilizante e rendimento (e perdas de N para o ambiente) varia com o manejo da palhada. As condi??es de manejo da palha simuladas foram: 100% e 50% da palhada retida ap?s a colheita; e palhada queimada. O manejo da aduba??o foi simulado para variar com as doses de N de 0 a 240 kg ha-1 (com incrementos de 40 kg ha-1) em cana soca. O rendimento de cana e o C org?nico do solo foram bem representados pelo modelo. O rendimento de cana respondeu positivamente aos sistemas de manejo da palhada (100% e 50% de reten??o), mas a magnitude da resposta depende da aduba??o nitrogenada. A remo??o de 50% da palha pode reduzir o efeito de rendimento potencial. Quando a deposi??o da palhada ? pr?tica recente, N adicional ? requerido pela cultura para evitar redu??o do rendimento causada pela imobiliza??o do N. As simula??es tamb?m indicam que as perdas ambientais de N foram maiores nos sistemas com cana crua para todas as doses de N.
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Nanocaractérisation d'oxydes à changement de résistance pour les mémoires résistives / Nanocharacterization of resistance switching oxides for resistive memoriesCalka, Pauline 17 October 2012 (has links)
En raison de leur faible consommation d'énergie, les mémoires non volatiles (MNV) sont En raison de leur faible consommation d'énergie, les mémoires non-volatiles sont particulièrement intéressantes pour l'électronique portative (clé USB, téléphone, ordinateur portable …). Les mémoires Flash, qui dominent le marché, atteignent leurs limites physiques et doivent être remplacées. L'introduction de nouveaux matériaux et architectures mémoire est proposée. Les mémoires OxRRAM (Oxide Resistive Random Access Memory) sont des candidats potentiels. Il s'agit de structures M-O-M (Métal-Oxyde-Métal). Le stockage de l'information est basé sur la modulation de la résistance de l'oxyde à l'application d'un champ électrique ou d'un courant. Une meilleure compréhension du mécanisme de changement de résistance de ces dispositifs est nécessaire pour contrôler leurs performances. Nous nous intéressons au claquage diélectrique de l'oxyde, qui initie le mécanisme de changement de résistance. Les mesures physico-chimiques à l'échelle nanométrique sont indispensables à sa compréhension et font défaut dans la littérature. Dans cette thèse, nous proposons des mesures physico-chimiques, des mesures électriques et des méthodes de préparation d'échantillon adaptées. Les oxydes de nickel et d'hafnium sont investigués. En plus de la dégradation électrique (chute de résistance), les modifications de ces deux oxydes sont investiguées à trois niveaux : la composition chimique, la morphologie et la structure électronique. Mots-clés : mémoire résistive, mécanisme de changement de résistance, claquage diélectrique, NiO, HfO2, spectroscopie de photoélectrons, microscopie électronique en transmission, microscopie à forme atomique, lacunes d'oxygène. / With low energy consumption, non-volatile memories are interesting for portative applications (USB, mobile phone, laptop …). The Flash memory technology is reaching its physical boundaries and needs to be replaced. New materials and architectures are currently investigated. Oxide Resistive Random Access Memory (OxRRAM) is considered as a good candidate. It is based on a M-O-M (Metal-Oxide-Metal) stack. The information is stored using an electric field or a current that modulates the resistance of the oxide. A better understanding of the resistance switching mechanism is required in order to control the performances of the devices. We investigate the dielectric breakdown that activates the resistance switching properties. Physico-chemical characterization at the nanoscale is required. In this work, we propose proper physico-chemical and electrical measurements. Sample preparation is also considered. Nickel and hafnium oxide are investigated. Besides the evolution of the electrical properties, we analyze the oxide modification at three levels : the chemical composition, the morphology and the electronic structure. Keywords : resistive memory, resistance switching mechanism, dielectric breakdown, NiO, HfO2, photoelectron spectroscopy, electronic transmission microscopy, atomic force microscopy, oxygen vacancies.
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Avalia??o do estresse oxidativo induzido por superf?cies de tit?nioQueiroz, Jana Dara Freires de 29 November 2011 (has links)
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Previous issue date: 2011-11-29 / Commercially pure Titanium (cp Ti) is a material largely used in orthopedic and
dental implants due to its biocompatibility properties. Changes in the surface of
cp Ti can determine the functional response of the cells such as facilitating
implant fixation and stabilization, and increased roughness of the surface has
been shown to improve adhesion and cellular proliferation. Various surface
modification methods have been developed to increase roughness, such as
mechanical, chemical, electrochemical and plasma treatment. An argon plasma
treatment generates a surface that has good mechanical proprieties without
chemical composition modification. Besides the topography, biological
responses to the implant contribute significantly to its success. Oxidative stress
induced by the biomaterials is considered one of the major causes of implant
failure. For this reason the oxidative potential of titanium surfaces subjected to
plasma treatment was evaluated on this work. CHO-k1 cells were cultivated on
smooth or roughed Ti disks, and after three days, the redox balance was
investigated measuring reactive oxygen species (ROS) generation, total
antioxidant capacity and biomarkers of ROS attack. The results showed cells
grown on titanium surfaces are subjected to intracellular oxidative stress due to
hydrogen peroxide generation. Titanium discs subjected to the plasma
treatment induced less oxidative stress than the untreated ones, which resulted
in improved cellular ability. Our data suggest that plasma treated titanium may
be a more biocompatible biomaterial. / O Tit?nio comercialmente puro (cpTi) ? amplamente utilizado em implantes
ortop?dicos e dentais gra?as ?s suas propriedades f?sico-qu?micas. Mudan?as
na superf?cie do cpTi podem determinar respostas funcionais nas c?lulas
influenciando a fixa??o e estabiliza??o do implante. Muitos m?todos de
modifica??o na superf?cie podem ser aplicados para aumentar a rugosidade
como, por exemplo, tratamentos mec?nicos, qu?micos, eletroqu?micos e a
plasma. Este ?ltimo, quando realizado em atmosfera de arg?nio gera uma
superf?cie rugosa com boas propriedades mec?nicas sem alterar a composi??o
qu?mica do material. Superf?cies rugosas geralmente s?o mais biocompat?veis
que as lisas, pois esse tipo de topografia facilita os processos de ades?o e
prolifera??o celular. Al?m da topografia, as rea??es biol?gicas desencadeadas
em resposta ao implante contribuem de forma significativa para o sucesso do
mesmo. Dentre estas rea??es, o estresse oxidativo tem sido apontado como
um dos principais respons?veis por falhas na implanta??o. Diante do exposto, o
potencial oxidativo das superf?cies de tit?nio tratadas e n?o tratadas a plasma
em atmosfera de arg?nio foi avaliado neste trabalho. Para tanto, c?lulas CHOk1
foram cultivadas sobre as superf?cies de tit?nio (tratadas e n?o tratadas).
Ap?s tr?s dias de cultivo o potencial oxidativo foi investigado por meio da
quantifica??o de esp?cies reativas, an?lise da capacidade antioxidante e
an?lise de biomarcadores de dano oxidativo (lipoperoxida??o, carbonila??o
prot?ica e oxida??o das bases do DNA). Os resultados obtidos indicam que
ambas as superf?cies de tit?nio induzem estresse oxidativo, sendo o per?xido
de hidrog?nio a principal esp?cie envolvida. O tratamento a plasma reduziu os
danos oxidativos e promoveu melhora na habilidade celular em responder ao
estresse oxidativo. Deste modo, a modifica??o da superf?cie de tit?nio atrav?s
do tratamento a plasma pode ser uma alternativa para a obten??o de um
material com melhor biocompatibilidade. / 2020-01-01
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Modifica??o do eletrodo AWS E7018 com adi??o de filmes finos externos de PVC e Al, para soldagem de a?o C-MnRamos, Moacir Bispo 07 December 2015 (has links)
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Previous issue date: 2015-12-07 / O presente trabalho prop?e a modifica??o do revestimento de eletrodos de baixo hidrog?nio, propiciando uma alternativa para execu??o de soldagem com o AWS E-7018 sem precisar resseca-los, reduzindo por conseguinte os custos financeiros e o tempo de fabrica??o de soldas estruturais de alta resist?ncia. As soldas deste estudo foram produzidas a partir de eletrodos com revestimento b?sico (higrosc?picos) - processo manual - pintados com tinta spray de alum?nio para altas temperaturas ou revestidos com filmes finos de PVC e de papel alum?nio (99,9%), comumente utilizados para prote??o de alimentos. A premissa b?sica ?, que estabelecendo uma barreira entre a atmosfera e o revestimento do eletrodo, poder-se-? diminuir os efeitos da alta higroscopicidade apresentada pelo revestimento, minimizando assim, a principal fonte de fornecimento de hidrog?nio ? po?a de fus?o durante a soldagem, tamb?m ? esperado, que a adi??o de novos materiais no revestimento ? po?a de fus?o, provoque altera??es metal?rgicas no metal depositado e consequentemente altera??es nas propriedades mec?nicas. Mensurar o hidrog?nio dissolvido no metal depositado ap?s soldado com os eletrodos modificados, avaliar a influencia dessas modifica??es nas microestruturas produzidas, nas propriedades mec?nicas da solda resultante e comparar esses resultados obtidos com procedimentos de soldagem padr?o normatizados e com os novos eletrodos imperme?veis recentemente desenvolvidos, balizou o estudo. Os resultados obtidos, na maioria das amostras soldadas com eletrodos modificados, apresentaram aumento significativo da resist?ncia mec?nica e de tenacidade, justificados pelo aumento percentual de ferrita acicular no metal depositado, sem, contudo, eleva??o significativa da dureza, quando comparados com a soldagem com eletrodo AWS E-7018 da forma tradicional. O hidrog?nio difus?vel nos eletrodos modificados manteve-se dentro do estabelecido pelos c?digos internacionais. / This paper suggests modifications in coating of electrodes providing an alternative for execution of welding with low hydrogen electrode AWS E7018 without having to dry it, reducing thus the cost and time of manufacturing of high resistance welds. The welds in this research were developed with basic coated electrodes (hygroscopic) ? SMAW process ? externally painted with aluminum spray paint for high temperatures or wrapped with thin plastic films (PVC) and aluminum foil films used commonly for food protection. The basic premise is that establishing a barrier between the atmosphere and the electrode coating could reduce the effects of high hygroscopicity presented by coatings of low hydrogen, minimizing this way the main source of supply of hydrogen to the fusion pool during welding. It is also expected that the addition of new materials from the electrode coating to the fusion pool would induce metallurgical changes in the deposited metal and, as a consequence, modifications in its mechanical properties. This research dealt with measuring the dissolved hydrogen in the deposited metal after welding with modified electrodes, evaluating the influence of these changes in the produced microstructures and in the mechanical properties of the resulting weld, and comparing the obtained results with the standard welding procedures and with the recently developed waterproof electrodes. The results obtained in most samples welded with modified electrodes showed increased mechanical resistance and increased tenacity due to the increased percentage of acicular ferrite in metal deposited without significant elevation of hardness, when compared with the traditional welding with AWS E7018 electrode and with ELBR?S BRH4R waterproof electrode. The diffusing hydrogen measured in the modified electrodes was kept inside the parameters defined by international codes.
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