Determination of Total Sulfur in Agricultural Samples by High-Resolution Continuum Source Flame Molecular Absorption Spectrometry

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

Expression, purification and spectroscopic analysis of an HdrC: An iron-sulfur cluster-containing protein from Acidithiobacillus ferrooxidans

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Doses and sources of nitrogen fertilizer and their effects on soil chemical properties and forage yield of Brachiaria brizantha cv. Xaraes

Forage plants, particularly the Brachiaria genus, are the main source of nutrients for cattle and are at times the only feed offered. The concentration of elements in the plant is related to the soil, fertilization, climate, season, variety, and cultural practices. An experiment on dystrophic Red-Yellow Latosol soil in Aracatuba, São Paulo was performed to evaluate the effects of the doses and sources of nitrogen fertilizers on the chemical properties of the soil and the dry matter yield of the grass Brachiaria brizantha cv. Xaraes. A randomized block design was employed involving three replicates in a 3 x 3 factorial, with three doses (100, 200 and 400 kg ha(-1) year(-1)) and three sources (Ajifer (R) L40, ammonium sulfate and urea) of nitrogen and a control treatment without nitrogen (zero). The greatest effects on the chemical properties of the soil as a function of nitrogen fertilization in the Xaraes grass were observed in the topsoil. The use of Ajifer (R) L40 and ammonium sulfate as sources of nitrogen had similar effects, with an increase in the sulfur content and a reduction in the soil pH at the superficial layer. The use of the fertilizers Ajifer (R) L40, ammonium sulfate and urea did not affect the micronutrient contents, except for Fe and Mn, and did not alter the sodium concentration or electrical conductivity of the soil. The dry matter yield of Xaraes grass was similar for all three nitrogen sources.

Electron time-of-flight measurements in sulfur interpreted via an extra surface mobility channel

Time-of-flight measurements were carried out in orthorhombic sulfur for various fields, ranging from -2 to -20 kV/cm. No dependence of the mobility with the electric field was found but the current, normalized by the initial current, showed an electric field dependence at small times, decaying faster for larger electric field. After the failure of the usual models in explaining the resultsincluding the assumption of depth-dependent density of trapsa model assuming an extra mobility channel near the surface provided a reasonable set of parameters independent of the electric field. The measurements were carried out at 8.5, 29, 53, 68, and 79°C. © 1988 The American Physical Society.

Sulfur and carbon isotopes in scapolite-bearing granulites of the São José do Rio Pardo area, Brazil

Sulfur and carbon isotope compositions of ten scapolites from granulite-facies rocks of the São José do Rio Pardo area, Guaxupé Complex, Brazil, were measured. Scapolite is the primary and major rock-forming mineral in these rocks (up to 40 volume %). The isotopic composition of the sulfate and carbonate group in the scapolite structure has δ34S values of +1.0‰ to +6.7‰, and δ13C values of -14.3‰ to -6.3‰, respectively. The sulfur isotope data may be related to an upper mantle (external) or lower crustal (internal) source for the sulfur, whereas the carbon appears to have been derived from an internal source. Thus, the carbon and sulfur isotope data can be explained without invoking an external (mantle) source. © 1993.

Fluorinated polymer films from r.f. plasmas containing benzene and sulfur hexafluorine

Mixtures of C6H6 and SF6 were polymerized in an r.f. discharge. Actinometry (quantitative optical emission spectroscopy) was used to determine trends in the plasma concentrations of the species F, H and CH as a function of the proportion of SF6 in the feed. Infrared spectroscopy and electron spectroscopy for chemical analysis were employed to characterize the deposited material. Increasing proportions of SF6 in the feed produced increased fragmentation of the benzene molecules and greater fluorination of the deposited material. The deposition rate, as determined by optical interferometry, was found to be enhanced about 4 times by the presence of 10-20% SF6 in the feed. At 50% SF6 in the feed, deposition rates were greater than in pure C6H6 plasmas despite the (probably large) etching effect of atomic fluorine from the discharge. Relationships between the plasma composition, electron density and temperature, film composition and growth rate are discussed. © 1992.

The effect of serum on in vitro maturation, in vitro fertilization and steroidogenesis of bovine oocytes co-cultured with granulosa cells.

The influence of fetal calf serum alone (FCS) or associated with proestrous (FCS+PCS), estrous (FCS+ECS) or metaestrous (FCS+MCS) cow serum added to the culture medium and of the steroids produced by co-cultured granulosa cells were evaluated in terms of the in vitro maturation (IVM) and fertilization (IVF) of bovine oocytes. Supplementation of the medium with FCS+ECS and FCS+MCS resulted in higher proportions of oocytes that reached metaphase II (96.0% and 93.3%, respectively) and in higher proportions of embryos that reached the four- and eight-cell/morula stages (51.9% and 65.6%, respectively), whereas the supplementation with FCS and FCS+PCS resulted in only 79.2% and 67.5%, respectively, of matured oocytes and 26.7% and 34.3%, respectively, of cleaved embryos. These findings show that the best IVM and IVF were obtained at lower concentrations of estradiol produced by co-cultured granulosa cells (supplementation with FCS+ECS: 10.3 ng/ml and FCS+MCS: 2.1 ng/ml), whereas the worst results in IVM and IVF occurred at higher concentrations of estradiol that were obtained with FCS (33.1 ng/ml) and FCS+PCS (19.9 ng/ml) supplementation. These data suggest an inhibitory effect of estradiol on resumption of oocyte meiosis in vitro.

Effects of rooting media, indolbutyric acid and fertilization on the rooting of rose (Rosa sp. 'Dalas') leafy cuttings

The objectives of this study were to evaluate the effects of rooting media (vermiculite, carbonized rice bark, fenolic spume and sand), presence of IBA (indole-3-butyric acid) and presence of fertilization during the rooting of rose (Rosa sp.) leafy cuttings, Dalas cultivar. This investigation was carried out in Jaboticabal (Sao Paulo State - Brazil) during the period of March to April 1997. The experimental design was a randomized block in a factorial arrangement. It consisted of 16 treatments (the 4 rooting media combined with IBA concentrated solutions - 0 and 1.000 ppm and fertilizer - 0 and commercial product with macro and micronutrients, applied weekly) with 3 replicates. The evaluations were 30 days after cuttings showed that the best rooting percentage occurs in sand (98%), followed by vermiculite (90%) and fenolic spume (87%) and cuttings treated with IBA (95%), while the fertilization showed no promoting effects. The number of cuttings roots wasn't affected with rooting media or DBA treatment, while the fertilization showed effective.

Influence of organic and chemical fertilization on the yield of flowers, contents and composition of essential oil of (Chamomilla recutita (L.) Rauschert)

A field experiment was conducted with chamomile (Chamomilla recutita [L.] Rauschert), in an area of the Olericulture and Medicinal Plants of the Horticulture Department at UNESP - Jaboticabal Campus, with the aim to evaluate the influence of organic and chemical fertilization on the yield of flowers, and content and composition of the essential oil of chamomile. The experimental design for the yield of flowers consisted of randomized blocks with 7 treatments and 4 replications, for the analysis of the contents and composition of the oil, the completely randomized block was used and for analysis of the correlation between harvesting and treatment, the split-plot design into randomized blocks was used. The treatments tested were: no fertilization, green manure (Mucuna aterrima + Crotalaria spectabilis), green manure (plant cocktail), organic fertilizer (farmyard manure), N as urea, N as ammonium sulphate, NPK with N supplement as ammonium sulphate. There was no influence of the treatments on the yield of flowers nor on the essential oil content; on the other hand both characteristics did show significant differences in harvesting times (Tukey 5%). The main yield was 885.90 kg/ha dry flowers and the mean oil content was 0,86%. The green manure treatment (M. aterrima + C. spectabilis) showed a higher percentage of chamazulene content, with a highly significant difference in harvesting times (Tukey 1%). The a-bisabolol percentages did not evidence significant differences between treatments. However, among harvesting times, there was a variation. A negative correlation was verified between the chamazulene and abisabolol percentages; the first increasing - from 21.02 to 36.17% - and the latter decreasing - from 14.12 to 8.72 % - from the first to the sixth harvest. The observed mean content of chamazulene was 14.64 % and a-bisabolol was 16.72 %.

Sulfur-containing palladacycles as catalyst precursors for the heck reaction

(formula presented) The air, water, and highly thermally stable sulfur-containing palladacycles, mainly derived from the ortho-palladation of benzylic thioethers, are exceptional catalyst precursors for the Heck reaction. The reaction can be performed with aryl iodides, bromides, and chlorides, with acrylic esters and styrene, leading to turnover numbers up to 1 850 000.

Sulfur-containing palladacycles: Efficient phosphine-free catalyst precursors for the Suzuki cross-coupling reaction at room temperature

Cyclopalladated compounds derived from the ortho-metalation of benzylic tert-butyl thioethers are excellent catalyst precursors for the Suzuki cross-coupling reaction of aryl bromides and chlorides with phenylboronic acid under mild reaction conditions. A broad range of substrates and functional groups are tolerated in this protocol, and highly catalytic activity is attained.

Nitrogen and potassium fertilization of 'Nanicao' banana (Musa AAA Cavendish subgroup) under irrigated and non-irrigated conditions

A field experiment was carried out in São Paulo State, Brazil, with the objective of investigating the response of 'Nanicao' banana (Musa AAA Cavendish subgroup) to nitrogen and potassium fertilization under irrigated and non-irrigated conditions during two crop seasons. The effects of cropping on some soil chemical properties were also investigated. A split-plot design was used with irrigation (micro-sprinkler) and no irrigation applied to main plots, and a combination of four rates of N (0, 200, 400 and 800 kg N ha-1) and K (0, 300, 600 and 900 kg K2O ha-1) as the sub-plot treatments. Irrigation caused a significant increase in fruit yield and determined the response to N and K fertilizers. In spite of a high level of exchangeable K, a positive response to K application was observed on the plant crop in non-irrigated plants. Fruit yield was impaired by N application in the plant crop (1st cycle). A positive response to N application was observed in the 2nd cycle. Soil pH decreased with increasing N rates. Exchangeable K was significantly reduced due to crop exhaustion.