A study of the main oxidation products of natural pyrite by voltammetric and photoelectrochemical responses

(Photo)electrochemical experiments on pyrite electrodes in acetic acid-acetate buffer (pH = 4.5) are conducted to clarify the main oxidation reactions and the nature of the products. Electrochemical reactions in the -0.40 to 1.25 V (SHE) potential range are studied, and the production of iron (III) polysulfide from anodically formed iron oxides and polysulfides is discussed. Charges experimentally obtained are considered for the estimation of the most likely stoichiometry of the metallic polysulfide. The photoselectivity of the pyrite corrosion process indicates that the oxidation reactions of Fe2+ and S-2(2-) an not consecutive. The changes in stoichiometry and/or annihilation of crystalline structure defects are responsible for the observed photosensitivity of pyrite. A description of light effects on the interfacial behaviour and stability of pyrite is presented in terms of conduction and valence band energies, and thermodynamic potentials. (C) 2001 Elsevier Science B.V. All rights reserved.

Identification and characterization of excretory/secretory products of Giardia duodenalis trophozoites

One of the major questions concerning Giardia is the understanding of pathophysiological processes associated with small intestine abnormalities. There are evidences that Giardia trophozoites contain and/or release proteolytic enzymes that may be implicated in the host intestinal epithelium. The present investigation was undertaken to examine the protease activity in excretory/secretory (E/S) products of Giardia duodenalis trophozoites of an axenic Brazilian strain (BTU-11) and the reference strain Portland 1 (P1). E/S products from trophozoites of each strain in conditioned medium were tested with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) for the protein profiles, and the protease activity was analyzed using substrate-impregnated SDS-PAGE (gelatin and collagen) and hemoglobin assay. The proteases characterization was based on inhibition assays including synthetic inhibitors. Electrophoresis analysis of E/S products revealed a banding pattern composed by few bands (4 to 6 bands) in the migration region of 123 to 28 kDa. Proteolytic products were detected in the conditioned medium by trophozoites of both assayed strains. In the gels containing copolymerized gelatin and collagen, E/S products promoted substrate degradation and the most evident proteolysis zones were distributed in the migration regions of 77 to 18 kDa and 145 to 18 kDa, respectively, in the patterns of gelatinolytic and collagenolytic activities. Degradation of hemoglobin was also observed, and the pattern of hydrolysis was similar in both E/S products assayed. Inhibitor assays showed that the main proteolytic activity in both E/S products is due to cysteine proteases, although the presence of serine proteases was also indicated. Degradation of substrates including collagen and hemoglobin could lead us to speculate different functions of Giardia excreted/secreted proteases in vivo, but to confirm this possibility and to elucidate its implication on host-parasite interactions, further experiments applying protocols for the purification of proteases are necessary. Even so, our observations are relevant and hold the perspective for the understanding about protease activity in Giardia trophozoites of axenic strain isolated in an endemic area.

Characterization of the excretory/secretory products of Dermatobia hominis larvae, the human bot fly

Proteolytic activity in excretory/secretory products (ESP) of first- (L1), second- (L2) and third-instar (L3) larvae of Dermatobia hominis was analyzed through gelatin-gel and colorimetric enzyme assays with the chromogenic substrates azocasein and BApNA. The functional characterization of proteases was based on inhibition assays including synthetic inhibitors. ESP were obtained from new-hatched larvae reared in the laboratory and from second- and third-instar larvae removed from naturally infested cattle. Gelatin-gel analysis evidenced few bands of proteolysis, predominantly of high apparent molecular masses, in ESP of L1, whereas in the gel of L2 and U ESP there was a wide range of proteolytic activity most of them not resolved in a single species. Azocasein assays revealed a progressive increase of protease activity from first- to third-instar larvae. Protease inhibitor assays revealed a predominance of metalloproteases in L1 ESP that could be related to a skin penetration process and to a diversion of host immune response. The predominance of serine proteases in L2 and L3 and the great tryptic activity presented by L3 ESP were attributed to an increasing trophic activity by the growing larvae, since the viability of adult flies strictly depends on larval abilities to assimilate nutrients from the host. Taking together, these results suggest that Dematobia larvae secrete/excrete different proteases that may be related to diverse functions during host penetration and infestation, which reinforces the relevance of the study of such proteolytic enzymes. (C) 2009 Elsevier B.V. All rights reserved.

On the calculation of inner products of Schur functions

Two methods for calculating inner products of Schur functions in terms of outer products and plethysms are given and they are easy to implement on a machine. One of these is derived from a recent analysis of the SO(8) proton-neutron pairing model of atomic nuclei. The two methods allow for generation of inner products for the Schur functions of degree up to 20 and even beyond.

Assessment of by-products of chlorination and photoelectrocatalytic chlorination of an azo dye

The present work describes a more efficient methodology for the chlorination of water containing disperse dyes, where the chlorinated byproducts identified by mass spectra are compared. this investigation, we tested the degradation of Cl Disperse Blue 291 dye, 2-[(2-Bromo-4,6-dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide) a commercial azo dye with mutagenic properties. The present work evaluates the photoelectrocatalytic efficiency of removing the Cl Disperse Blue 291 dye from a wastewater of the textile industry. We employed NaCl as a supporting electrolyte. It should be noted that photoelectrocatalytic techniques are non-conventional method of generating chlorine radicals. The by-products formed in this process were analyzed using spectrophotometry, liquid chromatography, dissolved organic carbon, mass spectral analysis and mutagenicity assays. The process efficiency was compared with the conventional chlorination process adopted during sewage and effluents treatment processes. This conventional chlorination process is less efficient in removing color, total organic carbon than the photoelectrochemistry technique. Furthermore, we shall demonstrate that the mutagenicity of the generated by-products obtained using photoelectrocatalysis is completely different from that obtained by the conventional oxidation of chloride ions in the drinking wafer treatment process. (C) 2012 Published by Elsevier B.V.

Finite group actions on products of spheres

In this work we make some contributions to the theory of actions of finite groups on products of spheres. Suppose that the group Z(q)(tau) acts freely on the product of k copies of spheres. Question: Is r less than or equal to k? We solve this question for several values of r and k.

On the hardy space H¹ on products of half-spaces

We show that the Hardy space H¹ anal (R2+ x R2+) can be identified with the class of functions f such that f and all its double and partial Hubert transforms Hk f belong to L¹ (R2). A basic tool used in the proof is the bisubharmonicity of |F|q, where F is a vector field that satisfies a generalized conjugate system of Cauchy-Riemann type.

Predicting beef carcass retail products of Mediterranean buffaloes by real-time ultrasound measures

Twenty eight Mediterranean buffaloes bulls were scanned with real-time ultrasound (RTU), slaughtered, and fabricated into retail cuts to determine the potential for ultrasound measures to predict carcass retail yield. Ultrasound measures of fat thickness, ribeye area and rump fat thickness were recorded three to five days prior to slaughter. Carcass measurements were taken, and one side of each carcass was fabricated into retail cuts. Stepwise regression analysis was used to compare possible models for prediction of either kilograms or percent retail product from carcass mesaurements and ultrasound measures. Results indicate that possible prediction models for percent or kilograms of retail products using RTU measures were similar in their predictive power and accuracy when compared to models derived from carcass measurements. Both fat thickness and ribeye area were over-predicted when measured ultrasonically compared to measurements taken on the carcass in the cooler. The mean absolute differences for both traits are larger than the mean differences, indicating that some images were interpreted to be larger and some smaller than actual carcass measurements. Ultrasound measurements of REA and FT had positive correlations with carcass measures of the same traits (r=.96 for REA and r=.99 for FT). Standard errors of prediction currently are being used as the standard to certify ultrasound technicians for accuracy. Regression equations using live weight (LW), rib eye area (REAU) and subcutaneous fat thickness (FTU) between 12(th) and 13 (th) ribs and also over the biceps femoris muscle (FTP8) by ultrasound explained 95% of the variation in the hot carcass weight when measure immediately before slaughter.

Characterization of the colloidal products of pentacarbonyliron oxidation

Pentacarbonyliron was oxidized with H2O2, in organic solvents, to give colloidal sols. The aqueous-ethanolic sol is highly stable and undergoes thermally-reversible coagulation. Its solid phase was found to be a non-crystalline Fe (III) hydroxoacetate which is transformed to α-Fe2O3 when heated to 300°C. Iron-bound acetate groups are assumed to have a major role in the sol stability, by preserving the amorphous solid phase. Dry hydroxoacetate particles were heated under vacuum; scanning electron microscopy revealed that these particles coalesce and grow, as in a sintering process but at low temperatures (100-250°). © 1987.

Efeito da escória de siderurgia na nutrição e desenvolvimento inicial de eucalipto

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Assessment of the breakdown products of solar/UV induced photolytic degradation of food dye tartrazine

The food dye tartrazine (CI 19140) was exposed to UV irradiation from an artificial source, a mercury vapor lamp, and a natural one, sunlight. It was observed that conditions such as energy dose, irradiation time, pH and initial dye concentration affected its discoloration. There was 100% of color removal, after 30 min of irradiation, when a dye solution 1 x 10(-5) mol L-1 was submitted to an energy dose of 37.8 J cm(-2). Liquid Chromatography coupled to Diode Array Detection and Mass Spectrometry confirmed the cleavage of the chromophore group and the formation of five by-products at low concentration. Although by-products were formed, the Salmonella/microsome mutagenicity assay performed for both, the dye solution at a dose of 5.34 mg/plate and the solutions obtained after exposure to UV irradiation, did not present mutagenic activity for TA98 and TA100 with and without S9. (C) 2014 Elsevier Ltd. All rights reserved.

Immunomodulatory Effects of Palladium(II) Complexes of 1,2,4-Triazole on Murine Peritoneal Macrophages

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