928 resultados para 640305 Production of unrefined precious metal ingots and concentrates


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Background: Exposure to ultraviolet (UV) radiation causes various forms of acute and chronic skin damage, including immunosuppression, inflammation, premature aging and photodamage. Furthermore, it induces the generation of reactive oxygen species, produces proinflammatory cytokines and melanocyte-stimulating hormone (MSH) and increases tyrosinase activity. The aim of this study was to evaluate the potential photoprotective effects of Rheum rhaponticum L. rhizome extract on human UV-stimulated melanocytes.Methods: The effects of Rheum rhaponticum rhizome extract on tyrosine kinase activity, and on interleukin-1α (IL-1α), tumour necrosis factor α (TNF-α), and α-MSH production in human epidermal melanocytes were evaluated under UV-stimulated and non-stimulated conditions. Antioxidant activity was evaluated by lipid peroxidation and 1,1-dyphenyl-2-picryl-hydrazyl (DPPH) assays, while anti-tyrosinase activity was evaluated by the mushroom tyrosinase method.Results: Rheum rhaponticum L. rhizome extract showed in vitro antioxidant properties against lipid peroxidation, free radical scavenging and anti-tyrosinase activities, and inhibited the production of IL-1α, TNF-α, α-MSH, and tyrosine kinase activity in melanocytes subjected to UV radiation.Conclusions: These results support the inclusion of Rheum rhaponticum L. rhizome extract into cosmetic, sunscreen and skin care products for the prevention or reduction of photodamage. © 2013 Silveira et al; licensee BioMed Central Ltd.

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The first measurement of vector-boson production associated with a top quark-antiquark pair in proton-proton collisions at √s=7 TeV is presented. The results are based on a data set corresponding to an integrated luminosity of 5.0 fb-1, recorded by the CMS detector at the LHC in 2011. The measurement is performed in two independent channels through a trilepton analysis of tt̄Z events and a same-sign dilepton analysis of tt̄V (V=W or Z) events. In the trilepton channel a direct measurement of the tt̄Z cross section σtt̄Z=0.28-0.11+0.14 (stat)-0.03+0.06 (syst) pb is obtained. In the dilepton channel a measurement of the tt̄V cross section yields σtt̄V=0.43-0.15+0.17 (stat)-0.07+0.09 (syst) pb. These measurements have a significance, respectively, of 3.3 and 3.0 standard deviations from the background hypotheses and are compatible, within uncertainties, with the corresponding next-to-leading order predictions of 0.137-0.016+0.012 and 0.306-0.053+0.031 pb. © 2013 CERN. Published by the American Physical Society.

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Synthesis, characterization and thermal decomposition of bivalent transition metal α-hydroxyisobutyrates, M(C4H7O 3)2·nH2O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as the thermal behaviour of α-hydroxyisobutyric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), infrared spectroscopy (FTIR), TG-DSC coupled to FTIR, elemental analysis and complexometry. All the compounds were obtained as dihydrated, except the copper one which was obtained in the anhydrous state. The thermal decomposition of the anhydrous compounds occurs in a single or two steps and the final residue up to 235 C (Mn), 300 C (Fe), 305 C (Co), 490 C (Ni), 260 C (Cu) and 430 C (Zn) is Mn2O3, Fe2O3, Co3O 4, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity and identification of the gaseous products evolved during the thermal decomposition of these compounds. Copyright © 2013 Published by Elsevier B.V. All rights reserved.

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The purpose of this work was to determine the levels of protein and the amino acid distribution in the cell mass of yeast strains (Saccharomyces sensu stricto) originated from Brazilian bioethanol industries. The protein was analyzed with the Kjeldahl method and the amino acids, by using high-performance liquid chromatography (HPLC). The percentages of the protein found ranged from 39 to 49%. The results show that in spite of some variation in numbers between the different yeast strains, all of them presented an amino acid profile similar to the one in the literature for S. cerevisae. The amino acids that have occurred in the largest amounts were: aspartic, glutamic acids and lysine, and those in the lowest amounts were: cysteine and methionine. Although the characteristics of the feedstock used and the process conditions are determinant of the protein values obtained in dry mass, this work elucidates that the intrinsic properties of the yeast strain influence these values.

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Scope. To elucidate the morphological and biochemical in vitro effects exerted by caffeine, taurine, and guarana, alone or in combination, since they are major components in energy drinks (EDs). Methods and Results. On human neuronal SH-SY5Y cells, caffeine (0.125-2 mg/mL), taurine (1-16 mg/mL), and guarana (3.125-50 mg/mL) showed concentration-dependent nonenzymatic antioxidant potential, decreased the basal levels of free radical generation, and reduced both superoxide dismutase (SOD) and catalase (CAT) activities, especially when combined together. However, guarana-treated cells developed signs of neurite degeneration in the form of swellings at various segments in a beaded or pearl chain-like appearance and fragmentation of such neurites at concentrations ranging from 12.5 to 50 mg/mL. Swellings, but not neuritic fragmentation, were detected when cells were treated with 0.5 mg/mL (or higher doses) of caffeine, concentrations that are present in EDs. Cells treated with guarana also showed qualitative signs of apoptosis, including membrane blebbing, cell shrinkage, and cleaved caspase-3 positivity. Flow cytometric analysis confirmed that cells treated with 12.5-50 mg/mL of guarana and its combinations with caffeine and/or taurine underwent apoptosis. Conclusion. Excessive removal of intracellular reactive oxygen species, to nonphysiological levels (or antioxidative stress), could be a cause of in vitro toxicity induced by these drugs. © 2013 Fares Zeidán-Chuliá et al.

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A search for exclusive or quasi-exclusive W+W- production by photon-photon interactions, pp → p(*)W +W-p(*), at √s=7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 fb-1. Events are selected by requiring a μ ±e∓ vertex with no additional associated charged tracks and dilepton transverse momentum p T(μ ±e∓) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 ± 0.4 signal events with 0.84 ± 0.15 background. The tail of the dilepton p T distribution is studied for deviations from the standard model. No events are observed with p T > 100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters α0,C W/λ2 with a dipole form factor and an energy cutoff Λcutoff = 500 GeV are of the order of 10-4. © 2013 CERN for the benefit of the CMS collaboration.

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The objectives of the present study were to estimate genetic parameters of monthly test-day milk yield (TDMY) of the first lactation of Brazilian Holstein cows using random regression (RR), and to compare the genetic gains for milk production and persistency, derived from RR models, using eigenvector indices and selection indices that did not consider eigenvectors. The data set contained monthly TDMY of 3,543 first lactations of Brazilian Holstein cows calving between 1994 and 2011. The RR model included the fixed effect of the contemporary group (herd-month-year of test days), the covariate calving age (linear and quadratic effects), and a fourth-order regression on Legendre orthogonal polynomials of days in milk (DIM) to model the population-based mean curve. Additive genetic and nongenetic animal effects were fit as RR with 4 classes of residual variance random effect. Eigenvector indices based on the additive genetic RR covariance matrix were used to evaluate the genetic gains of milk yield and persistency compared with the traditional selection index (selection index based on breeding values of milk yield until 305 DIM). The heritability estimates for monthly TDMY ranged from 0.12 ± 0.04 to 0.31 ± 0.04. The estimates of additive genetic and nongenetic animal effects correlation were close to 1 at adjacent monthly TDMY, with a tendency to diminish as the time between DIM classes increased. The first eigenvector was related to the increase of the genetic response of the milk yield and the second eigenvector was related to the increase of the genetic gains of the persistency but it contributed to decrease the genetic gains for total milk yield. Therefore, using this eigenvector to improve persistency will not contribute to change the shape of genetic curve pattern. If the breeding goal is to improve milk production and persistency, complete sequential eigenvector indices (selection indices composite with all eigenvectors) could be used with higher economic values for persistency. However, if the breeding goal is to improve only milk yield, the traditional selection index is indicated. © 2013 American Dairy Science Association.

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

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Listeria monocytogenes, considered as one of the most important foodborne pathogens, is easily found on surfaces, particularly in the form of a biofilm. Biofilms are aggregates of cells that facilitate the persistence of these pathogens in food processing environments conferring resistance to the processes of cleaning and may cause contamination of food during processing, thus, representing a danger to public health. Little is known about the dynamics of the formation and regulation of biofilm production in L.monocytogenes, but several authors reported that the luxS gene may be a precursor in this process. In addition, the product of the inlA gene is responsible for facilitating the entry of the microorganism into epithelial cells that express the receptor E-cadherin, also participates in surface attachment. Thus, 32 strains of L.monocytogenes isolated from different foods (milk and vegetables) and from food processing environments were analyzed for the presence of these genes and their ability to form biofilms on three different surfaces often used in the food industry and retail (polystyrene, glass and stainless steel) at different temperatures (4, 20 and 30°C). All strains had the ilnA gene and 25 out of 32 strains (78.1%) were positive for the presence of the luxS gene, but all strains produced biofilm in at least one of the temperatures and materials tested. This suggests that genes in addition to luxS may participate in this process, but were not the decisive factors for biofilm formation. The bacteria adhered better to hydrophilic surfaces (stainless steel and glass) than to hydrophobic ones (polystyrene), since at 20°C for 24h, 30 (93.8%) and 26 (81.3%) produced biofilm in stainless steel and glass, respectively, and just 2 (6.2%) in polystyrene. The incubation time seemed to be an important factor in the process of biofilm formation, mainly at 35°C for 48h, because the results showed a decrease from 30 (93.8%) to 20 (62.5%) and from 27 (84.4%) to 12 (37.5%), on stainless steel and glass, respectively, although this was not significant (. p=0.3847). We conclude that L.monocytogenes is capable of forming biofilm on different surfaces independent of temperature, but the surface composition may be important factor for a faster development of biofilm. © 2013 Elsevier Ltd.

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The purpose of this study is to carry on a thermoeconomic analysis at a biodiesel production plant considering the irreversibilities in each step (part I: biodiesel plant under study and functional thermoeconomic diagram [1]), making it possible to calculate the thermoeconomic cost in US$/kWh and US$/l of the biodiesel production, and the main byproduct generated, glycerin, incorporating the credits for the CO2 that is not emitted into the atmosphere (carbon credits). Assuming a sale price for both the biodiesel and the byproduct (glycerin), the annual revenue of the total investment in a plant with a capacity of 8000 t/year of biodiesel operating at 8000 h/year was calculated. The variables that directly or indirectly influence the final thermoeconomic cost include total annual biodiesel production, hours of operation, manufacturing exergy cost, molar ratio in the transesterification reaction, reaction temperature and pressure in the process. Depending on the increase or decrease in sale prices for both biodiesel and glycerin, the payback is going to significantly increase or decrease. It is evident that, in exergy terms, the sale of glycerin is of vital importance in order to reduce the biodiesel price, getting a shorter payback period for the plant under study. © 2013 Elsevier Ltd. All rights reserved.

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Includes bibliography