Fadiga em dormentes de concreto reforçados com fibras de aço

A prestressed concrete monoblock railroad tie was designed to attend the characteristics of a Brazilian railroad track with 1,600 mm gauge and 320 kN axle load. Concrete ties specimens were manufactured without and with steel fibers in a volume fraction of 60 kg/m3 (0.76 % by volume), and three different initial prestress forces. Static and fatigue tests were carried out on the ties. Static tests showed that steel fibers increase the first crack and ultimate bending moments, increase significantly the slip force of the prestressing tendons, reduce crack width, add higher ductility to the ties and decrease the stress in the prestressing tendons. Under dynamic loading the steel fibers decreased the stress in the prestressing tendons by about 50%, which improved significantly the fatigue strength of the tie. A tie without fibers failed after only 150,000 cycles. However, a similar tie, with fibers, resisted 3,000,000 cycles without suffering fatigue failure.

Mensuração do comprimento das fibras para a determinação da madeira juvenil em Eucalyptus citriodora

The juvenile wood has peculiar characteristics from the anatomical structure and physical-mechanical properties, considering these aspects the knowledge of the wood is essential for wood adequate utilization. The aim of this work was to determinate the zone of juvenile wood of pith-bark direction in Eucalyptus citriodora. The juvenile and mature wood zones were determined across fiber length measurement in various height in the tree stem. Results showed that juvenile wood zone occurs approximately up to the 45 at 55 mm from the pith.

Efeito da calagem e sulfato de amônio no algodão. I - Transporte de cátions e ânions no solo

Applying lime on the soil surface in soils managed under no-tillage has caused an excess of basic cations in the most superficial layers of the soil profile. On the other hand, subsoil acidity is considered a constraint to the development of deep plant roots. The objective of this study was to evaluate Ca 2+, Mg 2+, NO 3- and SO 4 2- leaching in the soil profile as affected by liming and top dressing nitrogen fertilization in cotton, grown with straw cover on the soil surface. Cotton plants (Gossypium hirsutum) were grown for 60 days in PVC columns filled with a Distroferric Red Latosol (sand loam Rhodic Oxisol) with liming applied over the straw on the soil surface, incorporated liming 0-20 cm deep, or without liming. Nitrogen was applied at rates of 0, 50, 100 and 150 kg ha -1 as ammonium sulfate. The PVC columns were set up in layers of 0-5, 5-10, 10-20, 20-30 and 30-30 cm, totaling 15.71 dm 3. The ammonium sulfate application caused intense leaching of SO 4 2- in the soil, irrespective of the lime application method. Liming increased the concentration of NO 3 in the 0-20 cm soil layer, whereas the correction of the soil acidity did not affect the NO 3- concentration in the 30-50 cm soil layer. The influence of ammonium sulfate on Ca 2+ leaching below 20 cm was only observed in the soil with incorporated lime. Nitrogen application resulted in extensive Mg 2+ leaching from the soil, regardless of the lime application method. In the soil layer below 30 cm, SO 4 2- presented a higher correlation than NO 3- in the formation of ionic pairs with Ca 2+ and Mg 2+.

Morfologia e morfometria dos tipos de fibras do músculo reto abdominal de cadelas (canis familiaris) durante a gestação

The present paper deals with the evaluation of morphological and morphometric alterations of slow-twist (I) and fast-twitch (II) fibers of rectus abdominis muscle of adult female dog during pregestational phase, at 30 and 60 days of pregnancy and at 30 days after the parturition. At the every phases, using the open biopsy technique, muscle samples were collected. The samples were plunged. Histological sections were cut in a microtome. For general morphology, some sections were stained with HE. Subsequent sections were reacted for myofibrillar ATPase (m-ATPase), after alkaline (pH 10.4) and acid (pH 4.4) pre-incubations, in order to identificate type I and II fibers. In the pre-gestational phase, muscle tissue revealed to be composed by fibers with different diameters, presenting polygonal outlines and one or more periphery nuclei. At 30 days of pregnancy, muscle fiber characteristics were similar. At 60 days, in addition to the existence of normal fibers, polymorphic and small diameter fibers were frequent. At 30 days after the parturation, the morphology of muscle fiber were similar to that observed in the pre-gestational phase. In the four phases, type II fiber diameters were lager than type I. The diameters of both fiber types showed a significant reduction in the 30 days phase and a significative increasing at 60 days. The expansion of the abdominal wall during the pregnancy represents a chronic stimulus, induced changes in the morphology and in the fiber type diameters.

Propriedades químicas de um latossolo vermelho de cerrado cultivado com algodão sob diferentes preparos e adubações

The high rate of mineralization of organic matter on savannah soils, which is reached fi ve times faster than in temperate regions, leads us to the challenge of electing the best system of management that maintains and/or increase it in soil, guaranteeing its quality and sustainability. In this sense the present research aimed to study the effects of green, organic and mineral manure on the chemical properties on the chemical properties of an Oxisol, on Savannah area, cultivated with cotton (Gossypium hirsutum) under conventional tillage and no-tillage in the pasture fi eld (Brachiaria decumbens) for 20 years. The experimental design was a randomized block design with split plots. The main plots consisted of two treatments: conventional tillage and no-tillage, and the subplots of six treatments: control (no fertilizer), mineral fertilizer recommended for the crop, according to the soil chemical analysis, organic fertilizer (cattle manure - 20 t ha-1), organic fertilizer (cattle manure - 20 t ha-1) + 1/2mineral fertilization recommended according to the analysis of soil, green manure-1 (Crotalaria juncea) and green manure-2 (Pennisetum americanum). There were studied the following soil chemical properties: P, OM, pH, K, Ca, Mg, Al, Al + H, S, exchange capacity cations and base saturation. The soil samples for the analysis were performed on layers of 0,00-0,05 m, 0,05-0,10 and 0,10-0,20 m. Then it came the following conclusions: the fertilization interfere in soil chemical properties and the preparation did not interfere, the cattle manure and its association with the mineral fertilizer caused increasing level elements in the soil, Crotalaria juncea and Pennisetum americanum did not infl uence on soil chemical properties.

Valor nutricional do farelo de algodão para alor a tilśpia do nilo (Oreochromis niloticus)

Cottonseed meals (CSM) with different protein levels (35, 39 and 40%) were evaluated to determine their chemical composition and measure apparent digestibility coefficients (ADC) of dry matter, protein, amino acids, energy, lipid and minerals for Nile tilapia. Apparent digestibility coefficients were determined using a reference purified diet containing 0.1% of chromic oxide indicator, and test diets contained 60% of reference diet and 40% of test ingredients. Results showed that apparent digestibility coefficients of cottonseed meals were different (p < 0.05). The apparent digestibility coefficients were: dry matter, 53.45-54.32%; crude protein, 71.56-74.81%; energy, 53.80-58.60%; lipid, 85.37-89.11%; phosphorus, 33.75-34.50%; calcium, 41.21-43.75%; iron, 62.02-79.85%; zinc, 0-67.41%; copper, 13.37-14.27%; essential amino acids, 71.39-79.17%; and non-essential amino acids, 77.08-82.58%. The ADC of protein did not reflect the majority of amino acids ADC showing variation in individual digestibility of amino acids and among cottonseed meals. Cottonseed meal can be used as protein succedaneum in Nile tilapia diets.

Farelo de algodão em rações para suínos nas fases de crescimento e terminação

Forty-eight pigs with 63 day olds and average weight of 23.40±1.3 kg, were allotted in a randomized block design with three treatments(0%, 10% and 20% of cottonseed meal (FA) in diets) and eight replicates with two pigs (one barrow and one gilt). The blocks were used to control changes in initial body weight. Experimental period was the growth phase (63 to 106 days old) and growing-finishing (63 to 147 days old). In each phase the diets were isonutritives, varying however the levels of crude fiber. The levels of cottonseed meal (FA) did not affect (p>0.05) the performance of animals during the growth phase or during the total period of evaluation (growingfinishing). The qualitative parameters of manure indicated that the FA determined decrease in the nitrogen and phosphorus content, but only in the growth phase. In the finishing phase the increase in the FA inclusion promoted an increase in dry matter content. Although FA can be used in up to 20% in diets for pigs in the growing and finishing phase, it is necessary to include L-lysine and soybean oil which causes an increase in cost per kg produced pig.

Crecimiento vegetativo, producción y calidad de las fibras en plantas de algodonero sometidas a estrés mineral

Potassium, like nitrogen, it constitutes an essential element for growth, development and production of cotton crops. Moreover, these elements are directly related to fiber formation and when provided in suitable doses, influences its quality. The aim of the experiments was to evaluate the influence of potassium on biometric parameters, yield and quality of cotton fibers. For this purpose, plants of the cultivar Delta opal were grown in a greenhouse with altered potassium fertilization, simulating K deficiency and two overdoses. During the different phenological stages, biometric variables were analyzed including the production of fibers and their qualitative parameters. The sub-dose and the overdoses treatments of K, changed all the evaluated parameters, demonstrating the importance of potassium fertilizer on them.

Velocidade de absorção do glufosinate e seus efeitos em plantas daninhas e algodão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Persistência de cloreto de Mepiquat em plantas de algodão em função da precipitação

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desafios internacionais à política agrícola norte-americana: o contencioso do algodão entre Brasil e Estados Unidos e o CAFTA-DR

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)