64 research outputs found
Variação no teor de alumínio trocável do solo, influenciada pela aplicação de carbonato de cálcio
This paper describes the data obtained when calcium carbonate was added to eleven acid soils from Brazil. One hundred grams of each soil were incubated in Erlenmeyer flask for 60 days with 100 mg and 300 mg of calcium carbonate. After 10, 30 and 60 days, soil samples were taken from each one of the Erlenmeyer flasks and the following determinations were performed: exchangeable aluminum and exchangeable soidity extracted wirh 1 N KCl solution; pH of aqueous soil suspension; pH of the 1 N KCl soil extract. The following conclusions seem justified from the data obtained. a. The addition of calcium carbonate increases both the pH of aqueous suspension and the pH of KCl 1 N extract, depending also upon the amount of CaCO3 applied and upon the soil itself. b. The addition of calcium carbonate decreases both the exchangeable aluminium and the exchangeable acidity content, depending on the applied amount of CaCO3 and on the soil itself. c. The exchangeable aluminium is one of the different components but does not constitute the only source of the soil acidity.O presente trabalho descreve o estudo da variação do alumínio trocável, da acidez titulável, do pH da suspensão aquosa e do pH do extrato de KCl 1 N, em função da quantidade de carbonato de cálcio, aplicada a onze amostras de solos procedentes de diversas regiões do Brasil. A adição de 100 mg e de 300 mg de carbonato de cálcio, passado em peneira nº 325, com 43 microns de abertura de malha, a 100 g das amostras dos onze solos estudados, seguida de um período de repouso de 10 a 60 dias, evidenciou que: a. ocorreu uma diminuiu mais ou menos pronunciada no teor de alumínio trocável e no de acidez titulável extraídos com solução 1 N de KCl, dependendo da dose aplicada de carbonato de cálcio e do solo; b. ocorreu uma elevação mais ou menos acentuada no pH da suspensão aquosa e no do extrato de KCl IN, dependendo também da quantidade aplicada de carbonato de cálcio e do solo; c. a magnitude da variação nas citadas características permitem esclarecer que o alumínio trocável, apesar de ser um componente, não constitui, porém, a única fonte de acidez do solo
Searching for Radio Pulsars in 3EG Sources at Urumqi Observatory
Since mid-2005, a pulsar searching system has been operating at 18 cm on the
25-m radio telescope of Urumqi Observatory. Test observations on known pulsars
show that the system can perform the intended task. The prospect of using this
system to observe 3EG sources and other target searching tasks is discussed.Comment: a training project about MSc thesi
Effect of short period feed supplementation during early lactation on performance of cows and calves raised in extensive system
Suplementação com gordura protegida para vacas de corte desmamadas precocemente mantidas em pastagem natural
Tolerância de cultivares de trigo (Triticum aestivum L.) ao alumínio e ao manganês: VI. influência do alumínio e do manganês e do grau de tolerância a cada elemento na absorção do fósforo
Tolerância de cultivares de trigo (Triticum aestivum L.) ao alumínio e ao manganês: IV. influência do manganês e do grau de tolerância ao manganês sobre as concentrações de P, Ca, Mg, Fe, Mn, Zn e Cu das partes aéreas e Ca, Fe e Mn das raízes
Aluminum and maganese tolerance of wheat (Triticum aestivum L.) cultivars: II. screening for manganese tolerance
Thyrty wheat cultivars were evaluated by means of culture in nutritive solutions containing 0.0, 8.0, 16.0, 24.0 e 32.0 ppm of Mn, under greenhouse conditions. After 17 days in the nutritive solutions, the dry matter weight of roots and aerial parts were measured. When the analysis of variance was signficant, the study of the regression equations for each parameter and cultivars showed CNTl and Frontana as sucetible, Sonora 63 and Maringá slightly suscetible, being the others (26) tolerant.O objetivo do presente estudo foi identificar em 30 cultivares de trigo o grau de tolerância ao manganês. Para isso, foi realizado um experimento em casa de vegetação onde as plantas foram desenvolvidas em soluções nutritivas 0,0, 8,0, 16,0, 24,0 e 32,0 ppm de manganês, durante um período de 17 dias. Nos dados de peso de matéria seca das raízes e peso da matéria seca das partes aéreas, procedeu se uma análise de variância e nos cultivares onde houve efeitos significativos de um ou outro parâmetro, realiizou-se uma análise de regressão ate o 3º grau, considerando-se a equação significativa de maior grau como representativa. Em função das analises de variância e das equações de regressão obtidas, constatou-se que os cultivares CNTl e Frontana foram suscetíveis ao manganês, Sonora 63 e Maringá medianamente tolerante e as demais (26) tolerantes
Aluminum and manganese tolerance of wheat (Triticum aestivum L.) cultivars: I. screening for aluminum tolerance
Tendo-se como objetivo a identificação do grau de tolerância ao alumínio de 30 cultivares de trigo, foi realizado um experimento em casa de vegetação, onde as plantas foram desenvolvidas em soluções nutritivas contendo 0,0, 2,5, 5,0, 7,5 e 10,0 ppm de alumínio, por um período de 12 dias. Procedeu-se à análise da variância para os dados de comprimento das raízes e peso da matéria seca das raízes e das partes aéreas, Para cada um dos parâmetros em que o alumínio exerceu efeito significativo, realizou-se uma análise de regressão até o 3º grau, considerando-se a equação significativa de maior grau como representativa. A partir das equações de regressão foram calculadas as concentrações de alumínio necessárias para produzir em cada cultivar 80% do peso da matéria seca das partes aéreas e das raízes e 80% do comprimento das raízes, considerando-se como 100% os valores correspondentes ao tratamento sem alumínio. Os resultados obtidos com o uso dos critérios referidos permitiram classificar os cultivares em 4 grupos de tolerância.Thirty wheat cultivars were evaluated by means of cultures in nutritive solutions containing 0.0. (check), 2.5, 5.0, 7.5 and 10.0 ppm of Al, under greenhouse conditions. After 12 days in the nutritive solutions, the length and dry matter weight of roots, as well as dry matter weight, of aerial parts were measured. Considering as 100% the data estimated from the check treatments, the Al concentrations needed to produce 80% of dry matter (roots and aerial parts) and root length were calculated through regression equations. According to the results, 4 groups of tolerance were established
Beyond buoyancy and vision: the potential for the Root effect to deliver oxygen to tissues other than the swim bladder and eye
Teleost fish possess a unique, pH-sensitive hemoglobin (Hb) that, in the presence of an acidosis, substantially reduces the affinity and carrying capacity for O₂ (Root effect). To date, this efficient O₂ delivery mechanism is only known for filling a swim bladder (SB) against huge pressure gradients (> 50 atm) associated with depth and for oxygenating the metabolically active, yet avascular retinal tissue of the eye. In spite of the clear benefits to O₂ delivery for buoyancy and vision, no study has been conducted to determine whether the Root effect may be important in optimizing O₂ delivery to other tissues such as muscle, which is the focus of this research.During environmental or exercise-induced stress, blood pH may fall; however, some fish regulate red blood cell (RBC) intracellular pH (pHi) by releasing catecholamines that activate the sodium/proton (Na⁺/H⁺) exchanger (βNHE) on the RBC membrane. The βNHE removes H⁺s from the RBC resulting in an intracellular alkalosis, an increase in Hb–O₂ affinity, and O₂ uptake at the respiratory surfaces is safeguarded, which is the ultimate goal of this mechanism. In our proposed model, when adrenergically stimulated blood encounters plasma-accessible carbonic anhydrase (CA), an enzyme found in the RBC but also membrane-bound and potentially plasma-accessible in select locations, it will catalyze H⁺s removed from the RBC to form CO₂. This CO₂ will back-diffuse into the RBC creating an intracellular acidosis (extracellular alkalosis), reducing Hb–O₂ affinity, and ultimately elevating PO₂ via the Root effect. We created an in vitro closed system using rainbow trout (Oncorhynchus mykiss) blood where we can (1) simulate an acid-induced Root effect, (2) adrenergically stimulate the RBCs, and finally (3) short-circuit the βNHE via CA (CA-mediated Root effect), all of which can be monitored in real-time ( Fig. 1). Data generated currently support our Hypothesis: adrenergic RBC pH regulation can be short-circuited in the presence of plasma-accessible CA, therefore generating a Root effect increase in PO₂. In fact, if this scenario also occurs in the tissues of O. mykiss, CA-mediated short-circuiting of adrenergic pH regulation can facilitate an increase in PO₂ over 30 times that which would be generated in vertebrates possessing only a Bohr shift! We are ready to test our model in vivo by implanting fiber-optic O₂ sensors in O. mykiss muscle while simulating environmental and exercise stress with and without CA blockers. Furthermore, even though CA is not found in general circulation, there are membrane-bound and potentially plasma-accessible isoforms in muscle endothelia, and research is underway to localize this enzyme to understand the relationship between location and function of the short-circuiting.\ud
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Teleost fish, which are more numerous than all other vertebrates combined (terrestrial and aquatic), have evolved an extraordinary O₂ delivery mechanism, the Root effect, that allows O₂ delivery to the eye and to the SB, thus allowing efficient buoyancy regulation, which may be one of the most important factors responsible for the extensive adaptive radiation in teleost fishes. Therefore, it is particularly interesting that the Root effect has not yet been investigated for general O₂ delivery. If the Root effect can also facilitate general O₂ delivery in vivo, which our data currently support, this would help shed insight into how the Root effect was selected for prior to the evolution of the βNHE, choroid gland and retia of the eye, and the gas gland and rete mirabile associated with the SB
Tolerância de cultivares de trigo (Triticum aestivum L.) ao alumínio e ao manganês: III. influência do alumínio e do grau de tolerância ao alumínio sobre as concentrações de P, Ca e Mg das partes aéreas
This study was made to detect possible inter-relations among Al concentrations or tolerance, and P, Ca and Mg concentrations in the aerial parts of 10 wheat cultivar, showing differential tolerance to Al, and growing in nutritive solutions containing 0.0, 2.5, 5.0, 7.5 and 10.0 ppmof Al, under greenhouse conditions. The results showed no relationship among P, Ca and Mg concentrations and Al concentrations in the nutritive solutions and no Al tolerance degree from the cultivars.Este estudo foi feito visando verificar a influência do Al sobre as concentrações de P, Ca e Mg das partes aéreas e detectar possíveis relações entre as concentrações desses mesmos elementos com o grau de tolerância ao Al de cultivares de trigo. Nas partes aéreas de plantas de 10 cultivares de trigo apresentando tolerância diferencial ao alumínio e desenvolvidas em soluções nutritivas contendo 0,0, 2,5, 5,0, 7,5 e 10,0 ppm de Al foram determinados o P, Ca e Mg. Os resultados mostraram que o grau de tolerância ao Al dos cultivares de trigo não está relacionado com as concentrações de P, Ca e Mg das partes aéreas e que as concentrações desses mesmos elementos se comportam diferentemente em função das concentrações de Al na solução
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