982 resultados para leaching and dissolution experiment


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This work aims at studying the influence of the concentration of calcite, its grain size and sintering temperature to obtain porous coating formulations that meet the design specifications. The experiments involved the physical-chemical and mineralogical caracterization of the raw materials, and mechanical tests on specimens dried and sintered, performing a planning mixture and factorial experiment, using the response surface methodology. The ceramic bodies studied were prepared by dry process, characterized, placed in conformity by uniaxial pressing and sintered at temperatures of 940 º C, 1000ºC, 1060ºC, 1120°C and 1180°C using a fast-firing cycle. The crystalline phases formed during sintering at temperatures under study, revealed the presence of anorthite and wolastonite, and quartz-phase remaining. These phases were mainly responsible for the physical and mechanical properties of the sintered especimens. The results shown that as increases the participation of carbonate in the composition of ceramic bodies there is an increase of water absorption and a slight reduction in linear shrinkage for all sintering temperatures. As for the mechanical strength it was observed that it tended to decrease for sintering at temperatures between 940 ° C and 1060 ° C and to increase for sintering at temperatures above 1060 ° C occurring with greater intensity for compositions with higher content of calcite. The resistence decreased with increasing participation of quartz in all sintering temperatures. The decrease in grain size of calcite caused a slight increase in water absorption for formulation with the same concentration of carbonate, remaining virtually unchanged the results of linear shrinkage and mechanical strength. In conclusion, porous ceramic coating (BIII) can be obtained using high concentrations of calcite and keeping the properties required in technical standards and that the particle size of calcite can be used as tuning parameter for the properties of ceramic products.

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This work proposes a transdisciplinary approach that integrates transpersonal psychology exercises with astronomy teaching, seeking to allow one to reintegrate the sky in his/her daily life, expand his/her environmental awareness and eventually experiment the unity between human and cosmos. This proposal intends to collaborate with the supplying of education, which lacks initiatives of this kind, with the promotion of an integration of the scientific knowledge with the human experience that transcends the materialistic and fragmentary objectives of the current educational system. As a result of that lack, the teachers formation is also poor as for an integral and transdisciplinary approach. Besides, we also approached in this research the necessity to propose alternatives so that the educators may work in a more assertive way with the environmental and anthropological crisis in which we are living. Our working hypothesis is that the contents of astronomy, when they are dealt in a holisticanthropological focus and are related with transpersonal psychology practices, can come to be an efficient cultural-academic vehicle, capable of propitiating an expansion of consciousness and changes in the way one conceives the world. Such changes are necessary so that a more solidary, fair and ecologically balanced life may come to exist and prevail in the planet. Part of the collection of data was done through the ethnographic method, once an anthropological interpretation is inextricably associated with this kind of educational intervention, which will naturally include ethno-visions of the universe as well as specific cultural elements. In the beginning the scope of this research was a group of students attending the Astronomy assignment in an undergraduate Geography course (UFRN), in which we accomplished participant observation, half-open interviews and the first experimental practices mentioned. After the evaluation of the first data collected from that initial group, we elaborated an academic extension course, Laboratory in Cosmoeducation, and we offered it to teachers of the 1st and 2nd cycles of the fundamental level of the Alceu Amoroso Lima State School, located in the North Zone of Natal. We prized self-experimentation in that course, so that the teachers could enrich their repertoire of personal experiences, stimulating meditative reflections and eventual changes in the ways of conceiving the world and in their pedagogical practice. The transdisciplinary attitude permeated all our educational action, because this approach transcends the boundaries of disciplines, seeking essentially the integral development of the human being. The process has made us realize that the practice of looking at the sky , as a way of reintegrating it into daily life, provokes a process of expansion of the consciousness and of reintegration of the self in a wider level of environmental interrelation. According to the results, the occurrence of conceptual and existential changes of the world vision of the participant teachers was evident, reassuring ourselves of the idea that the interface between astronomy teaching and the practices of transpersonal psychology can contribute to the recovery of a holistic relationship between the human being and the cosmos and to inspire the arising of a more wide-ranging ethics, based on universal, impartial and sustainable values

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The nitrogen in wheat is essential for obtaining high yields, not only the dose but also the time and the way of application are critical, reducing potential leaching and the cost of production. The objective is evaluating leaf and sidedressing nitrogen application on wheat crop in years of 2006 and 2007. A randomized blocks design in a factorial scheme 5x3x2 was used. The treatments consisted of five doses of nitrogen in the solution (0; 2.5; 5.0; 7.5 and 10%), three application times (at tillering: 30 days after plant emergency (DAE), at full flowering (50 DAE) + in the beginning of grain formation (70 DAE) and at tillering + in the beginning of grain formation), with and without sidedressing nitrogen applied at 40 DAE, using urea as source. They were evaluated: chlorophyll and nitrogen content in leaf, number of spikelets per ear, number of grains per ear, mass of grains per ear, number of grains per spikelet, mass hectolitric, mass of 100 grains and productivity of grains. The application of nitrogen topdressing in both years, influenced the yield characteristics of wheat. The times of leaf nitrogen only affected the leaf N content. The leaf nitrogen concentrations increased linearly the number of grains per spikelets, grains per spike, chlorophyll content, grain weight per ear and grain yield, and reduced mean weight per hectoliter, only in 2007.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The present work aims at defining the panicle and spikelet maturity of Avena strigosa Schreb. Four experiments were carried out under field conditions during 1989 (E1 and E2) and 1990 (E3 and E4) in Botucatu county, São Paulo State, Brazil. The sowings were made in 04.19.89 (E1) and 06.18.89 (E2). Maturity of panicle was evaluated by weekly (E1) or biweekly harvests (E2) beginning at total emergence of the panicle. In E3 and E4, sowing was made in 06.04.90 and each experiment had a single harvest date (E3 = 11.01.90 and E4 = 11.07.90). After harvest, the spikelets with similar stage of development were grouped and evaluated. Based on dry matter accumulation and germination percentage of the seeds, it was observed that the maturity of the seeds in the panicle was reached at 28 and 35 days after total emergence of the panicle in the April sowing, and between 24.5 and 28 days in the June sowing. During this period a few percentage of panicles not yet yellow became all yellow, the cariopsis at semi-hard stage became hard and moisture of the seeds dropped from 32% to 12%. The maturity of the seeds in the spikelet was reached when the glumes changed their color from yellowish to yellow, the lemma and palea changed from yellow with black strips to black, the cariopsis changed from farinaceous stage to semi-hard and the moisture content of the seeds changed from 40% to 25%.

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This work describes the primary and tectonic-metamorphic structures of the Eleuterio Formation, cropping 1 km NW of the village of Eleuterio, State of Sao Paulo. The structural feature have been studied chiefly in low grade metamorphic siltites, arkoses and conglomerates. The textural evolution is marked by fragmentation, clay minerals reaction, pression solution with silica recrystallization, mechanical rotation in minerals, fluid circulation and dissolution, mica beards, the possibily crystallization of biotite and epidote, and so on. The tectonic metamorphic foliation now described is supposed to be formed by simple shear with a possible pure shear component. -English summary

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The aim of this work was to evaluate the influence of compression force and humidity in the dissolution profile of tablets formulation. As hidroclorotyiazide presents real problems of bioavailability, it was incorporate as standard drug in a formulation of tablets to study the mechanical resistance, time of disintegration and dissolution profile in function of humidity and compression force. The time of disintegration was not affected by the compression force, but it was influenced by humidity. The dissolution profile was altered by the compression force and for the humidity as well. Both factors can alter the bioavailability of drugs dispensed in the form of tablets.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Although the management of the coffee crop is well established in Brazil, there is still room for its improvement in relation natural resources available in each region, aiming the increase in productivity. Here are presented results regarding the fate of the fertilizer nitrogen (N) applied to a coffee plantation related to the prevailing soil water conditions. Soil water balances are discussed, which allowed evaluation of the root distribution, determinations of the crop coefficient and of the soil water conditions during the development of the crop. Approximately, 60% of the root system was distributed in the 0-0.3 m soil layer and the average crop coefficient was 1.1 for 3 to 5 year old plants. Using an N label, the 15N, it was possible to study the distribution of N in the plant and in the soil and establishes general N balances, which also include losses like leaching and volatilization. After two years of ammonium sulfate application, at rates of 280 (1st year) and 350 (2nd year) kg.ha-1 of N, in four equal application performed during the period of positive growth rate, the recuperation of fertilizer N were 19.1% by the aerial plant part and 9.4% by the roots, 12.6% remained in the soil and 11.2% in the litter; 0.9% was lost by volatilization and 2.3% by leaching; 26.3% was exported through harvesting and 18.2% remained in non evaluated compartments. From the applied 630 kg.ha -1 of N during the two years, 180 kg.ha -1 of N were found in the plant (shoot and root), which corresponds to 28.6%; 150 kg.ha -1 of N remained available for the next years(soil and litter), and only 20 kg.ha -1 of N were effectively lost (volatilization and leaching).

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