68 resultados para Ammonium molybdate


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This work concerns the influence of industrialized agriculture in the tropics on precipitation chemistry. A total of 264 rain events were sampled using a wet-only collector in central Sao Paulo State, Brazil, between January 2003 and July 2007. Electroneutrality balance calculations (considering H(+), K(+), Na(+), NH(4)(+), Ca(2)(+), Mg(2)(+), Cl(-), NO(3)(-), SO(4)(2-), F(-), PO(4)(3-), H(3)CCOO(-), HCOO(-), C(2)O(4)(2-) and HCO(3)(-)) showed that there was an excess of cations (similar to 15%), which was attributed to the presence of unmeasured organic anion species originating from biomass burning and biogenic emissions. On average, the three ions NH(4)(+), NO(3)(-) and H(+) were responsible for >55% of the total ion concentrations in the rainwater samples. Concentrations (except of H(+)) were significantly higher (t-test; P = 0.05), by between two to six-fold depending on species, during the winter sugar cane harvest period, due to the practice of pre-harvest burning of the crop. Principal component analysis showed that three components could explain 88% of the variance for measurements made throughout the year: PC1 (52%, biomass burning and soil dust resuspension); PC2 (26%, secondary aerosols); PC3 (10%, road transport emissions). Differences between harvest and non-harvest periods appeared to be mainly due to an increased relative importance of road transport/industrial emissions during the summer (non-harvest) period. The volume-weighted mean (VWM) concentrations of ammonium (23.4 mu mol L(-1)) and nitrate (17.5 mu mol L(-1)) in rainwater samples collected during the harvest period were similar to those found in rainwater from Sao Paulo city, which emphasizes the importance of including rural agro-industrial emissions in regional-scale atmospheric chemistry and transport models. Since there was evidence of a biomass burning source throughout the year, it appears that rainwater composition will continue to be affected by vegetation fires, even after sugar cane burning is phased out as envisaged by recent Sao Paulo State legislation. (C) 2011 Elsevier Ltd. All rights reserved.

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We evaluate hemolymph osmotic and ionic regulatory abilities and characterize a posterior gill microsomal (Na(+), K(+))-ATPase from the marine swimming crab, Callinectes ornatus, acclimated to 21 parts per thousand or 33 parts per thousand salinity. C ornatus is isosmotic after acclimation to 21 parts per thousand but is hyposmotic at 33 parts per thousand salinity; hemolymph ions do not recover initial levels on acclimation to 21 parts per thousand salinity but are anisoionic compared to ambient concentrations, revealing modest regulatory ability. NH(4)(+) modulates enzyme affinity for K(+), which increases 187-fold in crabs acclimated to 33%. salinity. The (Na(+), K(+))-ATPase redistributes into membrane fractions of different densities, suggesting that altered membrane composition results from salinity acclimation. ATP was hydrolyzed at maximum rates of 182.6 +/- 7.1 nmol Pi min(-1) mg(-1) (21 parts per thousand) and 76.2 +/- 3.5 nmol Pi min(-1) mg(-1) (33 parts per thousand), with little change in K(M) values (approximate to 50 mu mol L(-1)). K(+) together with NH(4)(+) synergistically stimulated activity to maximum rates of approximate to 240 nmol Pi min(-1) mg(-1). K, values for ouabain inhibition (approximate to 110 mu mol L(-1)) decreased to 44.9 +/- 1.0 mu mol L(-1) (21 parts per thousand) and 28.8 +/- 1.3 mu mol L(-1) (33 parts per thousand) in the presence of both K(+) and NH(4)(+). Assays employing various inhibitors suggest the presence of mitochondrial F(0)F(1)- and K(+)- and V-ATPase activities in the gill microsomes. (C) 2009 Elsevier Inc. All rights reserved.

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This investigation provides an extensive characterization of the modulation by ATP, Mg(2+), Na(+), K(+) and NH(4)(+) of a gill microsomal (Na(+),K(+))-ATPase from Callinectes danae acclimated to 15 parts per thousand salinity. Novel findings are the lack of high-affinity ATP-binding sites and a 10-fold increase in enzyme affinity for K(+) modulated by NH4+, discussed regarding NH4+ excretion in benthic marine crabs. The (Na(+),K(+))-ATPase hydrolyzed ATP at a maximum rate of 298.7 +/- 16.7 nmol Pi min(-1) mg(-1) and K(0.5) = 174.2 +/- 9.8 mmol L(-1) obeying cooperative kinetics (n(H) = 1.2). Stimulation by sodium (V = 308.9 +/- 15.7 nmol Pi min(-1) mg(-1), K(0.5) = 7.8 +/- 0.4 mmol L(-1)), magnesium (299.2 +/- 14.1 nmol Pi min(-1) mg(-1), K(0.5) = 767.3 +/- 36.1 mmol L(-1)), potassium (300.6 +/- 153 nmol Pi min(-1) mg(-1), K(0.5) = 1.6 +/- 0.08 mmol L(-1)) and ammonium (V = 345.1 +/- 19.0 nmol Pi min(-1) mg(-1), K(0.5) = 6.0 +/- 0.3 mmol L(-1)) ions showed site-site interactions. Ouabain inhibited (Na(+),K(+))-ATPase activity with K(1) = 45.1 +/- 2.5 mu mol L(-1), although affinity for the inhibitor increased (K(1) = 22.7 +/- 1.1 mu mol L(-1)) in 50 mmol L(-1) NH(4)(+). Inhibition assays using ouabain plus oligomycin or ethacrynic acid suggest mitochondrial F(0)F(1)- and K(+)-ATPase activities, respectively. Ammonium and potassium ions synergistically stimulated specific activity up to 72%, inferring that these ions bind to different sites on the enzyme molecule, each modulating stimulation by the other. (C) 2009 Elsevier Inc. All rights reserved.

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Four Saccharomyces cerevisiae Brazilian industrial ethanol production strains were grown, under shaken and static conditions, in media containing 22% (w/v) sucrose supplemented with nitrogen sources varying from a single ammonium salt (ammonium sulfate) to free amino acids (casamino acids) and peptides (peptone). Sucrose fermentations by Brazilian industrial ethanol production yeasts strains were strongly affected by both the structural complexity of the nitrogen source and the availability of oxygen. Data suggest that yeast strains vary in their response to the nitrogen source`s complex structure and to oxygen availability. In addition, the amount of trehalose produced could be correlated with the fermentation performance of the different yeasts, suggesting that efficient fuel ethanol production depends on finding conditions which are appropriate for a particular strain, considering demand and dependence on available nitrogen sources in the fermentation medium.

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Glucose and fructose fermentations by industrial yeasts strains are strongly affected by both the structural complexity of the nitrogen Source and the availability of oxygen. In this Study two Saccharomyces cerevisiae industrial wine strains were grown, under shaken and static conditions, in a media containing either a) 20% (w/v) glucose, or b) 10% (w/v) fructose and 10% (w/v) glucose or c) 20% (w/v) fructose, all supplemented with nitrogen Sources varying from a single ammonium salt (ammonium Sulfate) to free amino acids (casamino acids) and peptides (peptone). Data Suggest that 1 complex Structured nitrogen source is not submitted to the same control mechanisms as those involved in the utilization of simpler structured nitrogen Sources, and mutual interaction between carbon and nitrogen Sources, including the mechanisms involved ill the regulation of aerobic/anaerobic metabolism, may play in important role in defining yeast fermentation performance and the differing response to the structural complexity of the nitrogen Source, with a strong impact oil fermentation performance.

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The objective of this study was to verify the protein turnover rates of healthy older persons under a usual protein-rich diet and to compare values to those described in the literature. This cross-sectional study was conducted at Metabolism Unit, Univ. Hospital of the School of Medicine of Ribeirao Preto, Univ. of Sao Paulo, Brazil. In this study, 7 healthy older persons aged 65.4 +/- 2.8 y, with BMI 22.7 +/- 2.4 kg/m(2) and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9-h whole-body (15)N-glycine single-dose study was performed after an overnight fast. During the study, each subject received 6 isoenergetic, isonitrogenous meals at 2-h intervals based on their average intake. Ammonium, urea, and total nitrogen were quantified and analyzed by mass spectrometry, with the determination of total protein turnover rates by the (15)N-glycine method. The results show that total nitrogen output was 3.2 +/- 0.96 g/N and intake 7.7 +/- 1 g/N, (15)N nitrogen flux was 30.6 +/- 6.3 g/9 h. Endogenous nitrogen balance was positive (4.5g +/- g/N in 9 h). In conclusion, the protein turnover of healthy older persons under a usual protein-rich diet is positive during the fed state and has synthesis and degradation rates similar to those previously described in studies involving diet adaptation periods.

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Objectives: The aim of this study was to explore the therapeutic opportunities of each step of 3-step etch-and-rinse adhesives. Methods: Etch-and-rinse adhesive systems are the oldest of the multi-generation evolution of resin bonding systems. In the 3-step version, they involve acid-etching, priming and application of a separate adhesive. Each step can accomplish multiple goals. Acid-etching, using 32-37% phosphoric acid (pH 0.1-0.4) not only simultaneously etches enamel and dentin, but the low pH kills many residual bacteria. Results: Some etchants include anti-microbial compounds such as benzalkonium chloride that also inhibits matrix metalloproteinases (MMPs) in dentin. Primers are usually water and HEMA-rich solutions that ensure complete expansion of the collagen fibril meshwork and wet the collagen with hydrophilic monomers. However, water alone can re-expand dried dentin and can also serve as a vehicle for protease inhibitors or protein cross-linking agents that may increase the durability of resin-dentin bonds. In the future, ethanol or other water-free solvents may serve as dehydrating primers that may also contain antibacterial quaternary ammonium methacrylates to inhibit dentin MMPs and increase the durability of resin-dentin bonds. The complete evaporation of solvents is nearly impossible. Significance: Manufacturers may need to optimize solvent concentrations. Solvent-free adhesives can seal resin-dentin interfaces with hydrophobic resins that may also contain fluoride and antimicrobial compounds. Etch-and-rinse adhesives produce higher resin-dentin bonds that are more durable than most 1 and 2-step adhesives. Incorporation of protease inhibitors in etchants and/or cross-linking agents in primers may increase the durability of resin-dentin bonds. The therapeutic potential of etch-and-rinse adhesives has yet to be fully exploited. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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Purpose: This study evaluated the effect of the incorporation of the antimicrobial monomer methacryloyloxyundecylpyridinium bromide (MUPB) on the hardness, roughness, flexural strength, and color stability of a denture base material. Materials and Methods: Ninety-six disk-shaped (14-mm diameter x 4-mm thick) and 30 rectangular (65 x 10 x 3.3 mm(3)) heat-polymerized acrylic resin specimens were divided into three groups according to the concentration of MUPB (w/w): (A) 0%, (B) 0.3%, (C) 0.6%. Hardness was assessed by a hardness tester equipped with a Vickers diamond penetrator. Flexural strength and surface roughness were tested on a universal testing machine and a surface roughness tester, respectively. Color alterations (Delta E) were measured by a portable spectrophotometer after 12 and 36 days of immersion in water, coffee, or wine. Variables were analyzed by ANOVA/Tukey HSD test (alpha = 0.05). Results: The following mean results (+/-SD) were obtained for hardness (A: 15.6 +/- 0.6, B: 14.6 +/- 1.7, C: 14.8 +/- 0.8 VHN; ANOVA: p = 0.061), flexural strength (A: 111 +/- 17, B: 105 +/- 12, C: 88 +/- 12 MPa; ANOVA: p = 0.008), and roughness (A: 0.20 +/- 0.11, B: 0.20 +/- 0.11, C: 0.24 +/- 0.08 mu m; ANOVA: p = 0.829). Color changes of immersed specimens were significantly influenced by solutions and time (A: 9.1 +/- 3.1, B: 14.8 +/- 7.5, C: 13.3 +/- 6.1 Delta E; ANOVA: p < 0.05). Conclusions: The incorporation of MUPB affects the mechanical properties of a denture base acrylic resin; however, the only significant change was observed for flexural strength and may not be critical. Color changes were slightly higher when resin containing MUPB was immersed in wine for a prolonged time; however, the difference has debatable clinical relevance.