Geoelectrical prospection of disseminated sulfide mineral occurrences in Camaquã Sedimentary Basin, Rio Grande do Sul State, Brazil

The mineral exploration is a complex activity that should involve a combination of direct and indirect techniques of geological investigation. The growing demand for base metals in the national and international market provides the revaluation of mineral occurrences that can become deposits and mines. This paper presents the results of the electrical resistivity and induced polarization geophysical methods in azimuthal arrangement, applied in a mineral occurrence of disseminated copper sulfides, previously studied through trenches and core drilling, located in the Camaquã Sedimentary Basin, Rio Grande do Sul State, Brazil. The inversion models indicate the coincidence of high chargeability and low resistivity values. The integration of geophysical data permitted the elaboration of 3D attributes visualization models for the mineralization enclosed in volcanic tuffs. The integrated geophysical and geological analysis indicates the potential of a new mineralized area. © 2012 Sociedade Brasileira de Geofísica.

Carbon dioxide emissions under different soil tillage systems in mechanically harvested sugarcane

Soil tillage and other methods of soil management may influence CO 2 emissions because they accelerate the mineralization of organic carbon in the soil. This study aimed to quantify the CO2 emissions under conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT) during the renovation of sugarcane fields in southern Brazil. The experiment was performed on an Oxisol in the sugarcane-planting area with mechanical harvesting. An undisturbed or no-till (NT) plot was left as a control treatment. The CO2 emissions results indicated a significant interaction (p < 0.001) between tillage method and time after tillage. By quantifying the accumulated emissions over the 44 days after soil tillage, we observed that tillage-induced emissions were higher after the CT system than the RT and MT systems, reaching 350.09 g m-2 of CO2 in CT, and 51.7 and 5.5 g m-2 of CO2 in RT and MT respectively. The amount of C lost in the form of CO2 due to soil tillage practices was significant and comparable to the estimated value of potential annual C accumulation resulting from changes in the harvesting system in Brazil from burning of plant residues to the adoption of green cane harvesting. The CO 2 emissions in the CT system could respond to a loss of 80% of the potential soil C accumulated over one year as result of the adoption of mechanized sugarcane harvesting. Meanwhile, soil tillage during the renewal of the sugar plantation using RT and MT methods would result in low impact, with losses of 12% and 2% of the C that could potentially be accumulated during a one year period. © 2013 IOP Publishing Ltd.

Design of microstructure of zirconia foams from the emulsion template properties

In this work, we investigate the correlations between structural and rheological properties of emulsified aqueous sol and the porous microstructure of monolithic zirconia foams, manufactured by the integrative combination of the sol-gel and emulsification processes. Macroporous zirconia ceramics prepared using different amounts of decahydronaphthalene, as oil phase, are compared in terms of the emulsion microstructure and ceramic porosity. A combination of electrical conductivity, oil droplet diameter, and rheological measurements was used to highlight the key effect of the dynamic structural properties of the emulsion on the porosity of the ceramic zirconia foam. The minimization of drying shrinkage by appropriate sol-gel mineralization of the oil droplet wall enabled versatile and easy tuning of the ceramic foam microstructure, by fine adjustment of the emulsion characteristics. The foam with the highest porosity (90%) and the lowest bulk density (0.40 g cm-3) was prepared from emulsion with 80 wt% of decahydronaphthalene, which also showed a bicontinuous structure and elevated flow consistency. © The Royal Society of Chemistry 2013.

On the application of nanostructured electrodes prepared by Ti/TiO2/WO3 template : A case study of removing toxicity of indigo using visible irradiation

New assays with HepG2 cells indicate that Indigo Carmine (IC), a dye that is widely used as additive in many food and pharmaceutical industries exhibited cytotoxic effects. This work describes the development of a bicomponent nanostructured Ti/TiO2/WO3 electrode prepared by template method and investigates its efficiency in a photoelectrocatalytic method by using visible light irradiation and applied potential of 1V. After 2h of treatment there are reduction of 97% discoloration, 62% of mineralization and formation of three byproducts assigned as: 2-amine-5-sulfo-benzoic acid, 2,3-dioxo-14-indole-5-sulfonic acid, and 2-amino-α-oxo-5-sulfo-benzeneacetic acid were identified by HPLC-MS/MS. But, cytotoxicity was completely removed after 120min of treatment. © 2013 Elsevier Ltd.

The unremunerated reserve requirement and net capital flows: Chile in the 1990s

Includes bibliography

CO2-C losses and carbon quality of selected Maritime Antarctic soils

Polar Regions are the most important soil carbon reservoirs on Earth. Monitoring soil carbon storage in a changing global climate context may indicate possible effects of climate change on terrestrial environments. In this regard, we need to understand the dynamics of soil organic matter in relation to its chemical characteristics. We evaluated the influence of chemical characteristics of humic substances on the process of soil organic matter mineralization in selected Maritime Antarctic soils. A laboratory assay was carried out with soils from five locations from King George Island. We determined the contents of total organic carbon, oxidizable carbon fractions of soil organic matter, and humic substances. Two in situ field experiments were carried out during two summers, in order to evaluate the CO2-C emissions in relation to soil temperature variations. The overall low amounts of soil organic matter in Maritime Antarctic soils have a low humification degree and reduced microbial activity. CO2-C emissions showed significant exponential relationship with temperature, suggesting a sharp increase in CO2-C emissions with a warming scenario, and Q10 values (the percentage increase in emission for a 10°C increase in soil temperature) were higher than values reported from elsewhere. The sensitivity of the CO2-C emission in relation to temperature was significantly correlated with the humification degree of soil organic matter and microbial activity for Antarctic soils. © 2012 Antarctic Science Ltd.

Non-labile plant C contributes to long-lasting macroaggregation of an Oxisol

Decomposition of plant material influences soil aggregation dynamics in ways that are still poorly understood, especially for Oxisols, in which oxides are believed to play a dominant role. In an incubation experiment, we investigated (i) the effect of plant material addition from selected monocot and dicot species on soil organic C (SOC), carbohydrate composition, fungal and total microbial biomass, and aggregation of an Oxisol; and (ii) the relationship among these properties and C mineralization patterns. The experiment was carried out at 25 °C for 180 d after addition of 11 plant materials (4 g C kg-1 soil) and a control (no plant material added). Mineralization of C during the incubation was described considering two pools of C (labile and non-labile) using a first-order plus linear fitting. Compared to the control, corn materials showed larger pentose input, greater mineralization rates for the non-labile C pool (k), greater soil pentose content (xylose + arabinose) and larger mean weight diameter of soil water-stable aggregates at 180 d of incubation. These effects were independent of changes in SOC content, suggesting that total C accrual and macroaggregation may be decoupled processes in this Oxisol. Our results support the hypothesis that the non-labile plant C pool contributes to the long-lasting stability of macroaggregates of this Oxisol and that this effect is mediated by plant and soil pentoses. We propose that plant pentose content and the decomposition rate of the slow pool (k) are useful parameters for the prediction of plant effects on aggregation dynamics of Oxisols and the selection of soil conservation practices. © 2012.

Biocompatibility and biomineralization assessment of a new root canal sealer and root-end filling material

Objective: This study investigated the short-term subcutaneous tissue reaction and biomineralization ability of two epoxy-based root canal sealers containing calcium hydroxide (MBP and MBPc) and ProRoot MTA. Materials and methods: Polyethylene tubes containing the materials were implanted into the dorsal connective tissue of Wistar rats (n = 52) for 7 or 30 days; empty implanted tubes served as controls. Specimens were stained with hematoxylin-eosin and von Kossa stain or left unstained for observation under polarized light. Qualitative and quantitative evaluations of all tissue reactions were performed. One-way anova and the Kruskal-Wallis test were used for statistical analysis (P < 0.05). Results: No significant differences were observed among the groups. All three materials induced mild-to-moderate tissue reactions at 7 days, which decreased over time. Dystrophic mineralization and birefringent structures were observed only in the ProRoot MTA ® group. Conclusion: Both MBP and MBPc appear to be biocompatible but do not stimulate biomineralization. © 2012 John Wiley & Sons A/S.

Does excess weight interfere with bone mass accumulation during adolescence?

Obesity and osteoporosis are important global health problems characterized by increasing prevalence with high impact on morbidity and mortality. The objective of this review was to determine whether excess weight during adolescence interferes with bone mass accumulation. If bone mineral gain can be optimized during puberty, adults are less likely to suffer from the devastating complications of osteoporosis. The increased fracture risk in obese children has also been attributed to a lower bone mass for weight compared to non-obese children. Thus, adiposity present in this age group may not result in the protection of bone mass, in contrast to what has been observed in adults. However, studies involving adolescents have reported both protective and detrimental effects of obesity on bone. The results and mechanisms of these interactions are controversial and have not been fully elucidated, a fact highlighting the extreme relevance of this topic and the need to monitor intervening and interactive variables. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Degradation of dipyrone via advanced oxidation processes using a cerium nanostructured electrocatalyst material

This work studied the degradation of dipyrone, via electrochemical processes and via electro-Fenton reaction using a 4% CeO2/C gas diffusion electrode (GDE) prepared via modified polymeric precursor method. This material was used to electrochemically generate H2O2 through oxygen reduction. The mean crystallite sizes estimated by the Scherrer equation for 4% CeO2/C were 4 nm for CeO2-x (0 4 4) and 5 nm for CeO2 (1 1 1) while using transmission electron microscopy (TEM) the mean nanoparticle size was 5.4 nm. X-ray photoelectron spectroscopy (XPS) measurements revealed nearly equal concentrations of Ce(III) and Ce(IV) species on carbon, which contained high oxygenated acid species like CO and OCO. Electrochemical degradation using Vulcan XC 72R carbon showed that the dipyrone was not removed during the two hour electrolysis in all applied potentials by electro-degradation. Besides, when the Fenton process was employed the degradation was much similar when using cerium catalysts but the mineralization reaches just to 50% at -1.1 V. However, using the CeO2/C GDE, in 20 min all of the dipyrone was degraded with 26% mineralization at -1.3 V and when the Fenton process was employed, all of the dipyrone was removed after 5 min with 57% mineralization at -1.1 V. Relative to Vulcan XC72R, ceria acts as an oxygen buffer leading to an increase in the local oxygen concentration, facilitating H2O2 formation and consequently improving the dipyrone degradation © 2013 Elsevier B.V. All rights reserved.

GFAAS determination of mercury in muscle samples of fish from Amazon, Brazil

In the present study, a simple, rapid and sensitive method was developed for the determination of mercury concentrations in the muscle tissue of fish from the Brazilian Amazon using graphite furnace atomic absorption spectrometry (GFAAS) following acid mineralization of the samples in an ultrasonic cold water bath. Using copper nitrate as a chemical modifier in solution and sodium tungstate as permanent modifier, we were able to attain thermal stabilization of the mercury up to the atomisation temperature of 1600 °C in the GFAAS assay. The calculated limits of detection (LOD) and quantification (LOQ) were 0.014 and 0.047 mg kg-1, respectively. © 2013 Elsevier Ltd. All rights reserved.

Photoelectrocatalysis based on Ti/TiO2 nanotubes removes toxic properties of the azo dyes Disperse Red 1, Disperse Red 13 and Disperse Orange 1 from aqueous chloride samples

This work describes the efficiency of photoelectrocatalysis based on Ti/TiO2 nanotubes in the degradation of the azo dyes Disperse Red 1, Disperse Red 13 and Disperse Orange 1 and to remove their toxic properties, as an alternative method for the treatment of effluents and water. For this purpose, the discoloration rate, total organic carbon (TOC) removal, and genotoxic, cytotoxic and mutagenic responses were determined, using the comet, micronucleus and cytotoxicity assays in HepG2 cells and the Salmonella mutagenicity assay. In a previous study it was found that the surfactant Emulsogen could contribute to the low mineralization of the dyes (60% after 4h of treatment), which, in turn, seems to account for the mutagenicity of the products generated. Thus this surfactant was not added to the chloride medium in order to avoid this interference. The photoelectrocatalytic method presented rapid discoloration and the TOC reduction was ≥87% after 240min of treatment, showing that photoelectrocatalysis is able to mineralize the dyes tested. The method was also efficient in removing the mutagenic activity and cytotoxic effects of these three dyes. Thus it was concluded that photoelectrocatalysis was a promising method for the treatment of aqueous samples. © 2013 Elsevier Ltd.

Nutrient accumulation in 'Fantasy' net melon cultivated on substrate

Knowledge of the most essential nutrients for plant growth facilitates the efficient handling of its nutrition, especially when they are grown on a substrate supported by fertigation. The objective of this study was to determine the accumulation of nutrients in net melon grown on a substrate and understand the relationship between mineral nutrition and plant growth. The Fantasy hybrid was cultivated in pots containing a substrate consisting of a mixture of sand and peanut shells (ratio, 1:1). Determination of nutrient accumulation was performed in 6 seasons. The substrate was chemically characterized before and after cultivation. Harvesting occurred 78 days after transplantation, resulting in an average yield of 70,120 kg·ha-1. Substrate analysis showed a small increase in nutrient levels by the end of cultivation. The order of nutrient accumulation was as follows: N>Ca>K>P>Mg>S>B> Fe>Mn>Zn>Cu.

Partitioning of net primary production in Eucalyptus and Acacia stands and in mixed-species plantations: Two case-studies in contrasting tropical environments

The introduction of nitrogen fixing species (NFS) in fast-growing tree plantations is an alternative option to reduce fertilizer inputs. However, the success of mixed-species plantations depends on the balance between positive interactions among species (resulting from facilitation and/or complementarity) and the negative effects of interspecific competition.Using a carbon budget approach and coupling measurements of standing biomass, aboveground litterfall and soil CO2 efflux, we assessed the influence of replacing half of eucalypt trees by Acacia mangium on total belowground carbon flux (TBCF), net primary production (NPP) and its partitioning between above- and belowground growth at two tropical sites in Brazil (Itatinga) and in Congo (Kissoko) exhibiting contrasting climates, edaphic conditions and wood productions.Annual soil CO2 efflux (FS) was significantly lower in the acacia monocultures than in eucalypt monocultures and mixed-species stands at both sites. Annual FS was significantly lower at Itatinga compared to Kissoko for all stands while TBCF was significantly lower in the eucalypt stands only. In the eucalypt monocultures we found a significantly lower aboveground NPP (ANPP) and wood production (wood NPP) at Kissoko compared to Itatinga that was almost fully balanced by a significantly higher belowground NPP (BNPP), leading to similar NPP. Similarly, acacia monocultures exhibited significantly higher ANPP and wood NPP at Itatinga than at Kissoko. The mixed-species stands exhibited a significantly lower wood NPP and ANPP than the eucalypt monocultures at the Brazilian site while NPP of the mixture was not significantly different than the average NPP of the two monocultures. At the Congolese site, NPP of the mixture was significantly higher than the average NPP of the two monocultures. NPP was similar in the mixed-species stand and the eucalypt monoculture with a significantly lower partitioning of NPP to belowground production, leading to a one third higher wood biomass at harvest in the mixed-species stand.A positive effect of growing eucalypts with the nitrogen fixing acacia trees on stand wood production occurred at Kissoko but not at Itatinga. Mixed-species plantations with NFS can be advocated at sites where the productive gains resulting from nitrogen fixation are not compromised by other resource limitations. © 2012 Elsevier B.V.

Selenium fractionation from plasma, muscle and liver of Nile tilapia (Oreochromis niloticus)

This paper presents the results obtained from selenium fractionation in plasma, muscle and liver samples of Nile tilapia's (Oreochromis niloticus) after protein separation. The plasma, muscle and liver proteome was obtained by 2D-PAGE, and selenium in protein spots was qualitatively and quantitatively determined by synchrotron radiation X-ray fluorescence and graphite furnace atomic absorption spectrometry (GFAAS). The fluorescence spectra indicated the presence of selenium in three protein spots of plasma, two of muscle and one of liver. Selenium was found to be distributed mainly in proteins with a molar mass smaller than 57.0 kDa and with pI in the range of 5.9-9.6, with one exception in the plasma sample, which presented protein with a molar mass of 60.0 kDa. After acid mineralization of the protein spots, a GFAAS determination of the concentration of selenium bound to these proteins indicated a range of 1.35-6.82 mg per g of protein. © 2013 Springer Science+Business Media New York.