In order to obtain translucent tetragonal zirconia polycrystalline (TZP) ceramics, complete densification, and homogeneous microstructure free of agglomerates and residual pores are required. To achieve this goal, freeze granulation of the zirconia nanopowder was performed. A series of stable and homogeneous zirconia suspension without agglomerates was prepared, by varying the solids loading volume percentage, to study the influence of the suspension characteristics on the freeze granulation behaviors. The characteristics of the prepared powder granules in terms of their size, flowability, and packing behaviors were subsequently analyzed. Uni-axial dry-pressing of the optimal granulate was used to prepare ceramic green bodies, which demonstrated the level of high strength and rigidness suitable for green milling based on the principle of computer aided design (CAD) and computer aided machining (CAM). Green bodies were sintered in air under conventional pressure-less condition. The sample sintered at 1400oC demonstrated a high optical translucency.

Three 14 day trials were used to compare granulated paper(GP) to pine pellets(PP) and wood shavings(WS) as bedding for horses. During days 1 through 5 stalls were cleaned daily of feces only, and stalls were cleaned of both feces and saturated areas from days 6 to 14. For stall cleanliness, PP was cleaner than both GP and WS. Initial pH was greater for both GP and WS compared to PP. The water holding capacity for WS was greater than PP and GP. On day 5 there was ammonia detected for WS during trial 1. GP and WS emitted more ammonia than PP when air flow was restricted. Bacteria found in the nasal cavity were not different among bedding types. GP had more fungal growth. Minerals were found within the maximum tolerance of horses. Results indicate the use of GP as a bedding material for horses has potential.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The hamster model of experimental chronic bronchitis comprises a persistent increase in the proportion of bronchial granulated secretory cells after a single intratracheal instillation of elastase. This granulated secretory cell increase, which does not occur in the trachea, has been termed secretory cell metaplasia (SCM). Susceptibility of the bronchial epithelium may be due to a large population of elastase-responsive cells specific to this region. Three dimensional reconstruction of the major form of bronchial secretory cells revealed very little or no rough endoplasmic reticulum (RER), thus demonstrating significant regional heterogeneity since all epithelial secretory cells in the trachea have abundant RER. Animals with bronchial SCM were stimulated with pilocarpine to determine whether the cells subsequent to discharge would re-accumulate granules, thus indicating a permanent phenotypic change. However, bronchial secretory cells failed to discharge at doses equal to and greater than those claimed to be effective in rats. Elastase instilled intratracheally was immuno-localized in the hamster airways to assess the possibility of regional differences in cellular uptake of the enzyme. Elastase was not seen intracellularly in trachea or bronchus suggesting that initiation of bronchial SCM results from a cell surface effect, possibly because of elastase-specific sites on bronchial but not tracheal cells. Tracheal resistance was tested by challenging the epithelial cells in vivo and in vitro with very high doses of elastase. Light and electron microscopy revealed no evidence of a stimulation of the mucus synthetic apparatus, suggesting that tracheal epithelial cells are inherently resistant to proteolytic up-regulation. / 2999-01-01

Orientadora: Cecilia Laluce / Banca: Elaine Trovatti / Banca: Sandro Rogério de Sousa / Resumo: No Brasil a principal fonte de sacarose para produção de etanol provém da cana-de-açúcar, que gera uma alta quantidade de biomassa rica em celulose durante seu processo. A partir de tratamentos como hidrólise do bagaço ou palha da cana-de-açúcar é possível aumentar o rendimento da produção nacional de etanol. A hidrólise ácida gera uma maior quantidade de componentes tóxicos quando comparada a hidrólise enzimática, porém o custo dos reagentes é menor, pois as enzimas necessárias para hidrólise possuem alto valor e seu tempo do processo é maior. Um fator importante no processo de hidrólise é a forma em que se encontra a celulose na matéria prima, se em sua maior parte a celulose se encontra na forma amorfa, a hidrólise é mais fácil, pois o ataque ácido é mais efetivo, já na fase cristalina é necessária uma abordagem mais severa. O presente trabalho tem como objetivo analisar o efeito no rendimento dos processos de pré-tratamento e hidrólise relacionando o tamanho de partícula inicial. As análises realizadas apresentaram um aumento no rendimento em ambos procedimentos (pré-tratamento e hidrólise), porém o aumento não se apresentou significativo quando se pensa em escala industrial. / Abstract: In Brazil, the main source of saccharose for ethanol production is the sugarcane, which generates a high amount of biomass rich in cellulo se during its process. From treatments such as hydrolysis of bagasse or sugarcane straw it is possible to increase the efficiency of the national production of ethanol. Acid hydrolysis generates a larger amount of toxic components as compared to enzymatic hydrolysis, however the cost of reagents is lower because the enzymes that are needed for hydrolysis are costly and its process is slower. An important factor in the hydrolysis process is the form in which the cellulose is, in the raw material mostly of th e cellulose is in the amorphous form. Hydrolysis is easier, because the acid process is more effective, since the crystalline phase requires a more severe approach. This study aims to analyze the effect on the yield of pretreatment and hydrolysis processes relating to the initial particle size. The analyzes showed an increase in both procedures (pretreatment and hydrolysis), but the increase may not be significant when considering industrial scale. / Mestre

Resumo: O objetivo deste trabalho foi procurar conhecer os efeitos de três substâncias químicas, sulfluramida, fipronil e clorpirifós, sobre a espécie de formiga não-alvo Ectatomma brunneum (Hymenoptera: Formicidae: Ectatomminae), respondendo às seguintes questões: as marcas comerciais de iscas formicidas granuladas utilizadas neste trabalho são atrativas a esta espécie de formiga não-alvo ou simplesmente repelentes? Sendo atrativas, qual o comportamento exercido pelas operárias? Elas ingerem as iscas no local ou carregam para o interior do ninho? Há devolução? Em condições de múltipla escolha alimentar, esta atratividade permanece ou ocorre somente na ausência do alimento convencional? No que acarreta o contato direto e indireto das formigas com as iscas? Ocorre mortalidade significativa? Qual dos ingredientes ativos é mais prejudicial? Os produtos são seletivos? Os resultados obtidos através dos testes em laboratório revelaram que, em condições normais de exposição, as operárias de E. brunneum não foram repelidas pelas iscas formicidas. No entanto, não houve atratividade suficiente para induzir o carregamento ou ingestão. Quando esse material foi umedecido, a atratividade aumentou significativamente, permitindo que porções das iscas fossem ingeridas na própria arena de forrageamento ou carregadas para o interior do ninho e distribuídas aos outros indivíduos, não sendo registrada, em nenhum dos tratamentos, a devolução total ou parcial das porções carregadas. Após 48 horas de exposição, os três ingredientes ativos foram tóxicos, de modo que a população foi reduzida em 35,56% no tratamento com clorpirifós, 31,11% com sulfluramida e 30% com fipronil ao final de 20 dias de observação. As iscas à base de fipronil foram mais atrativas que as de sulfluramida e clorpirifós...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work aimed at contributing to a better knowledge on the effects of three chemical substances, sulfluramid, fipronil and chlorpyrifos, on the non-target species of ant Ectatomma brunneum (Hymenoptera: Formicidae: Ectatomminae), answering the following questions: are the brands of granulated insecticide baits employed in this work attractive to this species of non-target ant or are they just repellent? If attractive, what is the behavior exhibited by the workers? Do they ingest the baits in the spot or take them into the nest? Is there any devolution? Under conditions of multiple food choice, does this attractiveness remain or does it happen only in the lack of the conventional food? What is the outcome of direct or indirect contact between the ants and the baits? Is there significant mortality? Which of the active ingredients is the most harmful? Are the products selective? The results obtained from the tests in laboratory showed that, under conditions of normal exposure, the workers of E. brunneum were not repelled by the insecticide baits. Nevertheless, there was not enough attractiveness as to lead to transporting or ingesting. When the material was moistened, the attractiveness increased significantly, allowing portions of bait to be ingested at the very foraging arena or to be taken into the nest and distributed to the other individuals. Total or partial devolution of the portions carried was not observed in any of the treatments. After a 48 hour exposure the three active ingredients proved to be toxic, for the population was reduced in 35.56% in the treatment with chlorpyrifos, 31.11% with sulfluramid and 30% with fipronil at the end of 20 days of observation. The fipronil based baits were more attractive than the ones based on sulfluramid and chlorpyrifos...(Complete abstract click electronic access below) / Orientador: Edilberto Giannotti / Coorientador: Marcos Aparecido Pizano / Banca: Evoneo Berti Filho / Banca: Nivar Gobbi / Mestre

L'industrie nucléaire est une industrie génératrice de déchets, dont certains sont radioactifs. Ces déchets radioactifs ont des formes et des origines diverses, allant de la paire de gant de manutention faiblement contaminés, à la suspension aqueuse de produits de fissions hautement radioactifs. Dans ce travail, un type de déchet bien particulier a été étudié ; des boues issues de la décontamination d'effluents liquides radioactifs, possédant entre autres les trois particularités suivantes ; * Etre moyennement radioactif, selon les critères de l'ANDRA. * Etre composé d'une forte teneur en eau de constitution (ne pouvant être retirée par simple évaporation) ; * Etre composé d'un sorbant (PPFeNi) dont la stabilité chimique n'est pas assurée pour un pH supérieur à 11. Ces particularités font qu'un enrobage dans une matrice minérale forte consommatrice d'eau, et bas-pH (pH < 11) est envisageable. Le choix c'est alors porté sur le développement d'une matrice ettringitique réalisée à partir d'un mélange de Ciment d'Aluminate de Calcium (CAC) et de sulfate de calcium. Dans un premier temps, la stabilité du sorbant du césium utilisé dans cette étude a été testée dans différents environnements de pH (2 à 14) et de température. Pour cela des analyses chimiques de solution ainsi que des caractérisations du composé par diffraction de rayons X, FTIR et microscopie électronique à balayage-EDS ont permis de fixer les bornes de stabilité que la formulation ettringitique doit avoir. Puis une étude microstructurale (nature et morphologie des produits) de mélanges ettringitiques binaires CAC/sulfate de calcium type hémihydrate et/ou anhydrite a été effectuée afin de caractériser la stabilité de l'ettringite, hydrate fort consommateur d'eau. Les propriétés bas-pH ont été vérifiées notamment par analyse chimique de solutions porales. Certaines limites de ces systèmes concernant le dégagement de chaleur et la possible formation de systèmes expansifs ont été mises en évidence. L'effet de l'augmentation du rapport eau/liant, responsable d'un effet de dilution et permettant de réduire les deux effets précédents, a été également regardé pour ces systèmes binaires. Afin de réduire la chaleur dégagée à court terme tout en permettant le développement de l'hydratation à long terme de systèmes ettringitiques, ces systèmes binaires ont été substitués par des additions minérales à hydraulicité latente type laitier de haut fourneau. Une étude microstructurale de la réactivité du laitier et de la modification de l'assemblage ettringitique a montré une réactivité modérée de ce dernier à jeune âge conformément aux attentes. Pour favoriser sa réactivité à long terme par activation alcaline/sulfatique différentes proportions de sulfate de calcium à dissolution plus lente ont été testés. Les caractéristiques microstructurales de ces systèmes ternaires en présence de différentes teneurs en eau intrinsèquement liée à la nature de type boue du déchet a été étudiée. Enfin, les différentes informations sur l'effet des paramètres de formulation obtenues ont débouché sur la mise en place de tests sur des formulations contenant un déchet simulé inerte et enrichi en chlorures. Des essais systématiques de fluidité, de résistances mécaniques et pour certains d'entre eux d'expansion et de dégagement de chaleur doivent permettre d'identifier une série de mélanges adaptés au test à l'échelle de prototype industriel pour la cimentation de boues. / Nuclear industry generated waste including radioactive wastes, which have different forms and origins. The wastes produced by reprocessing of nuclear fuel are characterized by important water content, by high pH and temperature sensitivity. The cementation in ettringite systems might be a promising solution to solidify radioactive wastes. Mixtures of Calcium Aluminate Cement (CAC) and calcium sulfate are planned to be used, instead of Ordinary Portland Cement (OPC), to form a significant amount of ettringite able to catch water molecules when forming. Moreover, due to the low pH of CAC-based matrices, the latter have a good compatibility with the compounds used to stabilize active elements. Initially, the stability of the sorbent of cesium used in this study was tested in different pH environments (2 to 14) and temperature. Chemical analysis and different microstructural characterizations like X-ray diffraction, FTIR and SEM-EDS have allowed to set stability limits of ettringite systems. Then microstructural study on binary systems composed by mixture of CAC/calcium sulfate (hemihydrate and/or anhydrite) was realized to characterize ettringite stability during the time of hydration. Low pH properties were checked by chemical pore solutions analysis. However, the heat generated by hydration and the possible formation of expansive systems require an increase of e/s ratio and additional components like Ground Granulated Furnace Slag (GGBS). These two parameters were studied subsequently. Microstructural study of GGBS reactivity and the modification of ettringite assemblage were showed that GGBS act as filler at early time of hydration. To promote the GGBS reactivity at long term of hydration by alkaline and sulfate activation, different nature of calcium sulfate was used. Then the microstructural characteristic of this ternary system in presence of different e/s ratio was studied. Finally, different information on the effect of formulation parameters obtained led to the development of tests on formulations containing an inert simulated waste and enriched in chlorides. Systematic tests of fluidity, mechanical strength and for some expansion and heat generation should identify a series of mixtures adapted to test prototype to industrial scale for cementing wastes.

In recent years, scientific studies are carried out to find new refractory material. Having good mechanical properties under very high temperatures, refractories are widely used in industries like iron, steel, glass, cement and pottery. Researches are focused on monolithic refractory making because of their superior properties comparing to conventional firebrick refractories. Providing a mono-block body, having no joints makes the monolithic refractories more durable at elevated temperatures. Easier production and installation are two main points that people are choosing monolithic refractories, thus an economy is made. In this study, for monolithic refractory production, high alumina cement was used as binding material. It is known that the increase in alumina (Al2O3) content increases the high temperature resistance, so that crushed firebrick, having 85% Al2O3 was used as aggregate. Pozzolanic materials, which are silica fume, fly ash, ground granulated firebrick and ground granulated blast furnace slag, were added to improve physical and mechanical properties of mortar. With the addition of steel fibres, change in compressive strength and flexural strength was observed.Superplasticizer was used to understand its behaviour under high temperatures. Portland cement containing mortars were also prepared to make comparison with high alumina cement containing specimens. Specimens were prepared in 5x5x5 cm and 4x4x16 cm prisms. They were cured for one day at curing room, then heated to 105&deg / C and then heated to 1100&deg / C. Weight, size and ultrasound velocity change, compressive strength and flexural strength tests were done to determine physical and mechanical properties of the monolithic refractories, before and after heating. Heated and non-heated specimens were pulverized for microstructural investigation with X-Ray diffraction (XRD) method. Using high alumina cement with 50 &ndash / 60 % granulated blast furnace slag or granulated firebrick, by the weight of cement, and crushed firebrick as aggregate, a satisfactory monolithic refractory material was made. It was observed that, mechanical properties were decreased at the Portland cement used mortars after several times of heating and cooling cycles. Also, it was determined that the microstructure of the high alumina cement containing mortars did not deteriorate much at 1100&deg / C, as long as there was no change observed from the results.

Com o crescimento empenho da medicina humana e veterinária na busca de biomateriais osteointegráveis, o estudo histológico se faz presente na interpretação e apresentação por resultados histomorfológicos das interações dos materiais implantados com o tecido ósseo, possibilitando o conhecimento da velocidade de neoformação óssea. A proposta deste trabalho foi avaliar por estudo histológico a bioatividade do composto ósseo de Ricinus granulado e hidroxiapatita sintética, implantados no osso ilíaco de coelhos, possibilitando uma melhor compreensão das interações das interfaces osso/implante, frente aos resultados histomorfológicos, sendo interpretados e apresentados por análise descritiva qualitativa. Foram selecionados 30 coelhos, fêmeas, Oryctolagus cuniculus, grupo geneticamente modificado - Botucatu, idade adulta de 90 dias, peso entre 2,55 e 3,1 Kg divididos em 3 grupos de 10 animais (G1, G2 e G3) sendo que o tempo de pós-operatório foi de G1 com 45 dias, G2 com 70 dias e G3 com 120 dias. Cada animal recebeu 3 defeitos ósseos no osso ilíaco, sendo que dois foram preenchidos pelos biomateriais: hidroxiapatita sintética e composto ósseo de Ricinus granulado e o terceiro para controle. Após a eutanásia, o osso ilíaco foi removido, identificado e submetido ao procedimento histológico. Concluiu-se através da avaliação histológica a crescente modificação da estrutura inicial para a deposição de nova formação óssea, sobressaindo células gigantes de corpo estranho (em alguns casos), fibroblastos e abundante presença de tecido conjuntivo sem diferenciação óssea. E os materiais foram considerados como biocompatíveis e biologicamente ativos. / With the growing commitment of human and veterinary medicine in the search for biomaterials osseointegration, the histological study is present in the interpretation and presentation of results of histomorphologic interactions of materials implanted with bone tissue, providing a speed of bone formation. The proposal was evaluated by histological study the bioactivity of the compound of granulated Ricinus and synthetic hydroxyapatite implanted in rabbit iliac bone, allowing a better understanding of the interactions of bone-implant interface, as compared with histopathologic results, and interpreted and presented by qualitative descriptive analysis. We used 30 female rabbits, Oryctolagus cuniculus, group - Botucatu, adulthood in 90 days, weighing between 2.55 and 3.1 kilograms divided into 3 groups of 10 animals (G1, G2 and G3) and that the length after surgery was 45 days with G1, G2 in 70 days and G3 with 120 days. Each animal received 3 bone defects in the pelvic bone, two of which were completed by biomaterials: synthetic hydroxyapatite and compound of granulated Ricinus and the third for control. After euthanasia, the iliac bone was removed, identified and subjected to histological procedures. It was concluded by the increasing histological modification of the initial structure for the deposition of new bone formation, towering giant cells of foreign body (in some cases), fibroblasts and abundant presence of connective tissue without bone differentiation. And the materials were considered as biocompatible and biologically active.

No estudo da osteointegração, os resultados adquiridos através dos softwares analisadores de imagens contribuirão para que se tenha uma melhor visualização da interface tecido biológico/material implantado. O objetivo deste trabalho foi avaliar, por meio de estudos histológico, morfométrico e densitométrico, as interfaces tecido ósseo/materiais implantados em comparação com o grupo controle (coágulo), descrevendo qualitativa e quantitativamente os resultados dessas análises. Foram selecionados 16 coelhos, Oryctolagus cuniculus, com idade de 90 dias, sendo estes divididos em quatro grupos de quatro animais (G1, G2, G3 e G4), com períodos pós-operatórios de sete, 15, 21 e 35 dias. Em cada animal, foram feitos dois defeitos ósseos nas tíbias direitas, preenchidos com o biomaterial Composto Ósseo de Ricinus (C.O.R.) granulado e o Grupo Controle (coágulo); na tíbia esquerda, preencheu-se com o biomaterial Hidroxiapatita (HAP-91). Após a eutanásia, as peças cirúrgicas foram removidas, identificadas e submetidas às análises. A análise histológica evidenciou, para os dois biomateriais, um grande aporte de células osteoprogenitoras e, com o avanço dos períodos experimentais, a deposição de um tecido ósseo mais desenvolvido. Estes resultados qualitativos corroboraram com a análise morfométrica, evidenciando a osteointegração pela aproximação das corticais ósseas. Com o estudo densitométrico, pôde-se acompanhar, por imagens tridimensionais e coloridas, o desempenho de cada biomaterial implantado e o grupo controle com o tecido ósseo. Concluiu-se que os dois biomateriais implantados se comportam de uma maneira muito desejável para que se constituam como uma escolha de materiais substitutos da reposição óssea. / In the study of osseointegration, the results acquired through the images analysis softwares, contribute in order to have a better view of the biological tissue/ material implanted interface. The aim of this study was to evaluate through studies: histological, morphometric and densitometric, the interactions of bone tissue / implanted materials in comparison with the control group (clot), and describing qualitatively and quantitatively the results of these analyzes. Were selected 16 rabbits, Oryctolagus cuniculus, with 90 days of age and divided into four groups of four animals (G1, G2, G3 and G4), and postoperative periods of seven, 15, 21 and 35 days. In each animal, two bone defects were made on the right tibia, and were filled with the (C.O.R.) Compound Bone of granulated Ricinus biomaterial and control group (clot); and in the left tibia, filled it with (HAP-91) Hydroxyapatite biomaterial. After euthanasia, the tibial bone was removed, identified and submitted for analyzes. The histological analysis showed for both biomaterials, a large amount of osteoprogenitor cells and, with the advancement of the experimental periods, the deposition of more developed bone tissue. These qualitative results corroborated with the morphometric analysis, showing the osseointegration by approximation of the cortical bones. With the densitometric study, could be accompanied, by three-dimensional images and colorful, the performance of each implanted biomaterial and the control group with the bone tissue. It was concluded that both implanted biomaterials behave in a manner very desirable to be constituted as a choice of substitute materials for the bone replacement.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-10-10T17:18:18Z No. of bitstreams: 1 2011 - Talita de Santana Matos.pdf: 652723 bytes, checksum: 16c30eb83b6db70231ab44534e188e6c (MD5) / Made available in DSpace on 2016-10-10T17:18:18Z (GMT). No. of bitstreams: 1 2011 - Talita de Santana Matos.pdf: 652723 bytes, checksum: 16c30eb83b6db70231ab44534e188e6c (MD5) Previous issue date: 2011-10-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / A study was conducted to evaluate the agronomic efficiency of nitrogen fertilizer with slow-release urea, measuring their losses by volatilization of NH3-N, N2O emission and recovery of fertilizer nitrogen applied as top dressing compared with commercioal urea to corn crop. All experiments were conducted at Embrapa Agrobiology. Firstly, the experiments were performed under controlled conditions in a greenhouse using soil layer of 0-10 cm of a haplic planosol. In the first experiment, the plastic trays were used as experimental units for evaluation of losses due to volatilization chambers with the aid of semi-open static free (SALE). Commercial urea was applied (UC), urea + KCl (UK), humic acid + urea (UH), urea + zeolitic sandstone (UZ) and urea + gypsum (UG) in two conditions of pH (5.4 and 6,5). Secondly, the other experiment was conducted using plastic pots containing the same soil samples as experimental units where they were planted three plants of Brachiaria decumbens. In this case, fertilizers were enriched with 15N, in two pH conditions too (pH 5,4 and 6,5). Treatments UZ and UK were more efficient in retaining N in the soil than the UC, with smaller losses through volatilization of NH3-N, and 20,2 and 15,8% on condition of lime and 22 and 17,2% when Liming did not occur, respectively. The UK fertilizer and UG showed overall increase of about 149 and 146% on dry biomass production at the end of the cycle on condition of pH 5,4. At pH 6,5 UG fertilizer showed yield increases of 149,3%. The accumulation of N in the plant and was 279,2 and 270,3 mg N.vaso-1 when no lime was applied to the UK and UG treatments, respectively, and the limed, 207.4 and 200,6 mg N. vaso-1 for the treatments UG and UH, respectively. Treatments UZ and UK had the highest recovery of applied N by plants, with values of 65,5 and 61,9% without lime, 60,2 and 45,7% with lime, respectively. Thirdly, other experiment was conducted at the experimental field at Embrapa Agrobiology in order to quantify the PNV, N2O emissions and efficiency of nitrogen fertilizer use (NFUE) slow-release by a corn crop on N balance Treatments consisted of field application of nitrogen fertilizers in coverage along the rows and a control treatment. Emissions of N2O were evaluated using static chambers closed. Was used fertilizers enriched with 15N in little plots for the assessment of NFUE. The treatments UZ and UK reduced the losses of N-NH3 by volatilization in approximately 18 and 14%, respectively. These losses corresponded to 32,3 and 35,7% of total N applied to soil. For N2O emissions the UK treatment showed the largest emission of N2O losses reaching values of 2.02 kgN.ha-1. The highest yield of grain were obtained by treatments that UG and UZ had a better response of grain production reaching values of 9666 and 9940 kg ha-1 respectively. To NFUE treatment UZ showed the highest values of N recovered reaching 67% of the total N applied system soil plant. / O trabalho objetivou avaliar a efici?ncia agron?mica de fertilizantes nitrogenados de libera??o lenta baseados no uso da ureia, quantificando suas perdas por volatiliza??o de NNH3 (PNV), emiss?o de N2O e a recupera??o do N-fertilizante aplicado em cobertura em compara??o com a ureia comercial na cultura de milho. Todos os esperimentos foram conduzidos na Embrapa Agrobiologia. Os primeiros experimentos foram realizados em condi??es controladas em casa de vegeta??o, utilizando solo da camada de 0-10 cm de um Planossolo H?plico. No primeiro experimento foram usadas bandejas pl?sticas como unidades experimentais para avalia??o das perdas por volatiliza??o com aux?lio de c?maras semi-aberta livre est?tica (SALE). Aplicou-se ureia comercial (UC), ureia + KCl (UK), ureia + ?cido h?mico (UH), ureia +arenito zeol?tico (UZ) e ureia +gesso agr?cola (UG) em duas condi??es de pH (5,4 e 6,5). O outro experimento utilizou vasos pl?sticos contendo amostras do mesmo solo como unidades experimentais onde foram plantados 3 plantas de Brachiaria decumbens. Neste caso os fertilizantes foram enriquecidos com 15N, tamb?m em duas condi??es de pH (pH 5,4 e 6,5). Os tratamentos UZ e UK foram mais eficientes na reten??o do N no solo do que a UC, apresentando menores perdas por volatiliza??o de N-NH3 de 20,2 e 15,8% sob condi??o de calagem e 22 e 17,2% quando sem calagem, respectivamente. Os fertilizantes UK e UG apresentaram aumento total de aproximadamente 149 e 146% na produ??o de biomassa seca ao final do ciclo da cultura em condi??o de pH 5,4. Em pH 6,5 o fertilizante UG apresentou aumento de rendimento de 149,3%. O ac?mulo de N na planta foi de 279,2 e 270,3 mg N.vaso-1 quando n?o foi aplicado calagem para os tratamentos UK e UG, respectivamente e quando com calagem, 207,4 e 200,6 mg N.vaso-1 para os tratamentos UG e UH, respectivamente. Os tratamentos UZ e UK apresentaram maior recupera??o pelas plantas do N aplicado, com valores de 65,5 e 61,9% sem calagem e 60,2 e 45,7% com calagem, respectivamente. O outro experimento foi realizado no campo na ?rea experimental da Embrapa Agrobiologia com objetivo de quantificar as perdas por volatilza??o de am?nio, as emiss?es de N2O e a efici?ncia do uso de fertilizantes nitrogenados (EUFN) de libera??o lenta pela cultura de milho, no balan?o de N. Os tratamentos consistiram da aplica??o no campo em cobertura dos fertilizantes nitrogenados ao lado da linha de plantio e um tratamento controle. As emiss?es de N2O foram avaliadas utilizando-se c?maras est?ticas fechadas. Foi utilizado fertilizantes enriquecidos com 15N em microparcelas para a avalia??o da EUFN. Os tratamentos UZ e UK reduziram as perdas de N-NH3 por volatiliza??o em aproximadamente 18 e 14%, respectivamente. Estas perdas corresponderam a 32,3 e 35,7% do total de N aplicado no solo. Para as emiss?es de N2O o tratamento UK foi o que apresentou maiores perdas por emiss?o de N2O atingindo valores de 2,02 kg N.ha-1. As maiores produtividades de gr?o foram obtidas pelos tratamentos UG e UZ que apresentaram melhor resposta de produ??o de gr?os atingindo valores de 9.666 e 9.940 kg.ha-1, respectivamente. Para EUFN o tratamento UZ apresentou o maior valor de N recuperado chegando a 67% do total do N aplicado no sistema solo-planta.