Denudação química e implicações na composição das águas superficiais da Bacia do Rio Jaú (SP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tipo de cimentação em materiais duros do perfil de alteração da mina de fosfato da Anglo American, Catalão-GO

One of the main challenges in the mining sector at present, related to the optimization of mineral assets, consists in to find the best proportion of each geological material to be mined and homogenized to ensure high productivity and stability in ore processing plants. The stability of a mineral processing plant is factor for achieving operational excellence, as a stable performance of the plants ensures economy and adherence to financial planning businesses. Is already well Know that the feed rate of the processing plants is dependent on the hardness and quality of the ore. Therefore, the ore behavior predictability is the solution to ensure the stability of mineral processing plants. This work was developed in Anglo American Phosphate Brazil Ltda., at the Fazenda Chapadão Phosphate Mine, located in the southeastern portion of the state of Goiás, in the municipalities of Catalão and Ouvidor. The phosphate ore is the result of supergene apatite concentration in the weathering profile of the alkaline ultramafic phlogopitized rocks, intruded by foscoritic and carbonatitic rocks series. The weathering profile has about 100 meters thick and is divided into three basic types, from top to bottom, coinciding with decreasing intensity of weathering: oxidized ore, micaceous ore and weathered rock. In each portion of this weathering profile, mainly near the contacts between these three divisions, are hard materials, cemented by minerals such as apatite, quartz, goethite, monazite and barite. The different features presented by these materials makes to be vital the correct identification, quantification and location of different hard materials in the mine area, to maximize its use. The main objective of this study was to define the type of cementation of hard materials which predominates in each portion of the weathering profile in the mine, as well as their relationship with the protolith. The work involved geological mapping, channel sampling...

Petrografia e geoquímica das rochas metacarbonatíticas do Complexo Angico dos Dias, divisa Bahia/Piauí, Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Biogenic calcium phosphate transformation in soils over millennial time scales

Changes in bioavailability of phosphorus (P) during pedogenesis and ecosystem development have been shown for geogenic calcium phosphate (Ca-P). However, very little is known about long-term changes of biogenic Ca-P in soil. Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from centennial to millennial time scales. Phosphorus fractionation of Anthrosols resulted in overall consistency with the Walker and Syers model of geogenic Ca-P transformation during pedogenesis. The biogenic Ca-P (e.g., animal and fish bones) disappeared to 3% of total P within the first ca. 2,000 years of soil development. This change concurred with increases in P adsorbed on metal-oxides surfaces, organic P, and occluded P at different pedogenic time. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the crystalline and therefore thermodynamically most stable biogenic Ca-P was transformed into more soluble forms of Ca-P over time. While crystalline hydroxyapatite (34% of total P) dominated Ca-P species after about 600-1,000 years, beta-tricalcium phosphate increased to 16% of total P after 900-1,100 years, after which both Ca-P species disappeared. Iron-associated P was observable concurrently with Ca-P disappearance. Soluble P and organic P determined by XANES maintained relatively constant (58-65%) across the time scale studied. Disappearance of crystalline biogenic Ca-P on a time scale of a few thousand years appears to be ten times faster than that of geogenic Ca-P.

PHOSPHITE AS PHOSPHORUS SOURCE TO GRAIN YIELD OF COMMON BEAN PLANTS GROWN IN SOILS UNDER LOW OR ADEQUATE PHOSPHATE AVAILABILITY

The effects of foliar and soil applied phosphite on grain yield in common bean (Phaseolus vulgaris L.) grown in a weathered soil under low and adequate phosphate availability were evaluated. In the first experiment, treatments were composed of a 2 x 7 + 2 factorial scheme, with 2 soil P levels supplied as phosphate (40 e 200 mg P dm(-3) soil), 7 soil P levels supplied as phosphite (0-100 mg P dm(-3) soil), and 2 additional treatments (without P supply in soil, and all P supplied as phosphite). In the second experiment, treatments were composed of a 2 x 3 x 2 factorial scheme, with 2 soil phosphate levels (40 e 200 mg P dm(-3) soil), combined with 3 nutrient sources applied via foliar sprays (potassium phosphite, potassium phosphate, and potassium chloride as a control), and 2 foliar application numbers (single and two application). Additional treatments showed that phosphite is not P source for common bean nutrition. Phosphite supply in soil increased the P content in shoot (at full physiological maturity stage) and grains, but at the same time considerably decreased grain yield, regardless of the soil phosphate availability. Foliar sprays of phosphite decreased grain yield in plants grown under low soil phosphate availability, but no effect was observed in plants grown under adequate soil phosphate availability. In general, foliar sprays of phosphate did not satisfactorily improve grain yield of the common bean plants grown under low soil phosphate availability.

In vitro and in vivo evaluation of the biocompatibility of a calcium phosphate/poly(lactic-co-glycolic acid) composite

This study assess the effects of bioceramic and poly(lactic-co-glycolic acid) composite (BCP/PLGA) on the viability of cultured macrophages and human dental pulp fibroblasts, and we sought to elucidate the temporal profile of the reaction of pulp capping with a composite of bioceramic of calcium phosphate and biodegradable polymer in the progression of delayed dentine bridge after (30 and 60 days) in vivo. Histological evaluation of inflammatory infiltrate and dentin bridge formation were performed after 30 and 60 days. There was similar progressive fibroblast growth in all groups and the macrophages showed viability. The in vivo study showed that of the three experimental groups: BCP/PLGA composite, BCP and calcium hydroxide (Ca(OH)(2)) dentin bridging was the most prevalent (90 %) in the BCP/PLGA composite after 30 days, mild to moderate inflammatory response was present throughout the pulp after 30 days. After 60 days was observed dentine bridging in 60 % and necrosis in 40 %, in both groups. The results indicate that understanding BCP/PLGA composite is biocompatible and by the best tissue response as compared to calcium hydroxide in direct pulp capping may be important in the mechanism of delayed dentine bridge after 30 and 60 days.

Efficacy of Cosmetic Formulations Containing Dispersion of Liposome with Magnesium Ascorbyl Phosphate, Alpha-Lipoic Acid and Kinetin

The present study aimed to evaluate the photoprotective effects of cosmetic formulations containing a dispersion of liposome with magnesium ascorbyl phosphate (MAP), alpha-lipoic acid (ALA) and kinetin, as well as their effects on the hydration and viscoelastic skin properties. The photoprotection was determined in vitro (antioxidant activity) and in vivo on UV-irradiated hairless mouse skin. The hydration effects were performed with the application of the formulations under study on the forearm of human volunteers and skin conditions were analyzed before and after a single application and daily applications during 4 weeks in terms of transepidermal water loss (TEWL), skin moisture and viscoelastic properties. The raw material under study possessed free-radical scavenging activity and the formulation with it protected hairless mouse skin barrier function against UV damage. After 4 weeks of application on human skin, the formulation under study enhanced stratum corneum skin moisture and also showed hydration effects in deeper layers of the skin. Thus, it can be concluded that the cosmetic formulation containing a dispersion of liposome with MAP, ALA and kinetin under study showed photoprotective effects in skin barrier function as well as pronounced hydration effects on human skin, which suggests that this dispersion has potential antiaging effects.

Adsorption of phosphate from aqueous solution by hydrous zirconium oxide

Synthetic ZrO2 center dot nH(2)O was used for phosphate removal from aqueous solution. The optimum adsorbent dose obtained for phosphate adsorption on to hydrous zirconium oxide was 0.1 g. The kinetic process was described very well by a pseudo-second-order rate model. The phosphate adsorption tended to increase with the decrease in pH. The adsorption capacity increased from 61 to 66 mg g(-1) when the temperature was increased from 298 to 338 K. A phosphate desorption of approximately 74% was obtained using water at pH 12.

Surfactant-assisted intercalation of high molecular weight poly(ethylene oxide) into vanadyl phosphate di-hydrate

A high molecular weight poly(ethylene oxide)/layered vanadyl phosphate di-hydrate intercalation compound was synthesized via the surfactant-assisted approach. Results confirmed that surfactant molecules were replaced with the polymer, while the lamellar structure of the matrix was retained, and that the material presents high specific surface area. In addition, intercalation produced a more thermally stable polymer as evidenced by thermal analysis. (C) 2011 Elsevier Ltd. All rights reserved.

GENETIC VARIABILITY OF SUGARCANE-ASSOCIATED DIAZOTROPHIC BACTERIA CAPABLE OF INORGANIC PHOSPHATE SOLUBILIZING

The sugarcane is a culture of great importance for the Brazilian agriculture. Every year this culture consumes great amounts of nitrogen and phosphate fertilizers. However, the use of plant growth-promoting bacteria can reduce the use of the chemical fertilizers, contributing to the economy and the environment conservation. So, the goal of this study was to select sugarcane-associated diazotrophic bacteria able to solubilize inorganic phosphate and to evaluate the genetic diversity of these bacteria. A total of 68 diazotrophic bacteria, leaf and root endophytic and rizoplane, of three sugarcane varieties. The selection of inorganic phosphate solubilizing diazotrophic bacteria was assayed by the solubilization index (SI) in solid medium containing insoluble phosphate. The genetic variability was analyzed by the BOX-PCR technique. The results showed that 74% of the diazotrophic strains were able to solubilize inorganic phosphate, presenting classes of different SI. The results showed that the vegetal tissue and the genotype plant influenced in the interaction between phosphate solubilizing diazotrophic bacteria and sugarcane plants. BOX-PCR revealed high genetic variability among the strains analyzed. So, sugarcane-associated diazotrophic bacteria express the capacity to solubilize inorganic phosphate and they present high genetic diversity.

Insights into Phosphate Cooperativity and Influence of Substrate Modifications on Binding and Catalysis of Hexameric Purine Nucleoside Phosphorylases

The hexameric purine nucleoside phosphorylase from Bacillus subtilis (BsPNP233) displays great potential to produce nucleoside analogues in industry and can be exploited in the development of new anti-tumor gene therapies. In order to provide structural basis for enzyme and substrates rational optimization, aiming at those applications, the present work shows a thorough and detailed structural description of the binding mode of substrates and nucleoside analogues to the active site of the hexameric BsPNP233. Here we report the crystal structure of BsPNP233 in the apo form and in complex with 11 ligands, including clinically relevant compounds. The crystal structure of six ligands (adenine, 2'deoxyguanosine, aciclovir, ganciclovir, 8-bromoguanosine, 6-chloroguanosine) in complex with a hexameric PNP are presented for the first time. Our data showed that free bases adopt alternative conformations in the BsPNP233 active site and indicated that binding of the co-substrate (2'deoxy) ribose 1-phosphate might contribute for stabilizing the bases in a favorable orientation for catalysis. The BsPNP233-adenosine complex revealed that a hydrogen bond between the 5' hydroxyl group of adenosine and Arg(43*) side chain contributes for the ribosyl radical to adopt an unusual C3'-endo conformation. The structures with 6-chloroguanosine and 8-bromoguanosine pointed out that the Cl-6 and Br-8 substrate modifications seem to be detrimental for catalysis and can be explored in the design of inhibitors for hexameric PNPs from pathogens. Our data also corroborated the competitive inhibition mechanism of hexameric PNPs by tubercidin and suggested that the acyclic nucleoside ganciclovir is a better inhibitor for hexameric PNPs than aciclovir. Furthermore, comparative structural analyses indicated that the replacement of Ser(90) by a threonine in the B. cereus hexameric adenosine phosphorylase (Thr(91)) is responsible for the lack of negative cooperativity of phosphate binding in this enzyme.

C-Phycocyanin protects SH-SY5Y cells from oxidative injury, rat retina from transient ischemia and rat brain mitochondria from Ca2+/phosphate-induced impairment

Oxidative stress and mitochondrial impairment are essential in the ischemic stroke cascade and eventually lead to tissue injury. C-Phycocyanin (C-PC) has previously been shown to have strong antioxidant and neuroprotective actions. In the present study, we assessed the effects of C-PC on oxidative injury induced by tert-butylhydroperoxide (t-BOOH) in SH-SY5Y neuronal cells, on transient ischemia in rat retinas, and in the calcium/phosphate-induced impairment of isolated rat brain mitochondria (RBM). In SH-SY5Y cells, t-BOOH induced a significant reduction of cell viability as assessed by an MTT assay, and the reduction was effectively prevented by treatment with C-PC in the low micromolar concentration range. Transient ischemia in rat retinas was induced by increasing the intraocular pressure to 120 mmHg for 45 min, which was followed by 15 min of reperfusion. This event resulted in a cell density reduction to lower than 50% in the inner nuclear layer (INL), which was significantly prevented by the intraocular pre-treatment with C-PC for 15 min. In the RBM exposed to 3 mM phosphate and/or 100 mu M Ca2+, C-PC prevented in the low micromolar concentration range, the mitochondrial permeability transition as assessed by mitochondrial swelling, the membrane potential dissipation, the increase of reactive oxygen species levels and the release of the pro-apoptotic cytochrome c. In addition, C-PC displayed a strong inhibitory effect against an electrochemically-generated Fenton reaction. Therefore, C-PC is a potential neuroprotective agent against ischemic stroke, resulting in reduced neuronal oxidative injury and the protection of mitochondria from impairment. (C) 2012 Elsevier Inc. All rights reserved.

Partitioning and extraction of collagenase from Penicillium aurantiogriseum in poly(ethylene glycol)/phosphate aqueous two-phase system

Purification of collagenase produced by Penicillium aurantiogriseum URM4622 was carried using a PEG/phosphate aqueous two-phase system (ATPS). A 2(3)-full experimental design was used to investigate the influence of PEG molar mass, PEG concentration and phosphate concentration on the selected responses, namely partition coefficient, activity yield and purification factor. The ATPS was composed of PEG (molar mass of 550, 1500 and 4000 g/mol) at concentrations of 15.0, 17.5 and 20.0% (w/w) and phosphate at concentrations of 12.5, 15.0 and 17.5% (w/w). The best results of one-step extraction of collagenase from the fermentation broth (partition coefficient of 1.01, activity yield of 242% and purification factor of 23.5) were obtained at pH 6.0 using 20.0% (w/w) PEG 550 and 17.5% (w/w) phosphate. The results of this preliminary study demonstrate that the selected ATPS is satisfactorily selective for the extraction of such a collagenase. (C) 2012 Elsevier B.V. All rights reserved.

Cytocompatibility of Porous Biphasic Calcium Phosphate Granules With Human Mesenchymal Cells by a Multiparametric Assay

This work aims to evaluate the cytocompatibility of injectable and moldable restorative biomaterials based on granules of dense or porous biphasic calcium phosphates (BCPs) with human primary mesenchymal cells, in order to validate them as tools for stem cell-induced bone regeneration. Porous hydroxyapatite (HA) and HA/beta-tricalcium phosphate (beta-TCP) (60: 40) granules were obtained by the addition of wax spheres and pressing at 20 MPa, while dense materials were compacted by pressing at 100 MPa, followed by thermal treatment (1100 degrees C), grinding, and sieving. Extracts were prepared by 24-h incubation of granules on culture media, with subsequent exposition of human primary mesenchymal cells. Three different cell viability parameters were evaluated on the same samples. Scanning electron microscopy analysis of the granules revealed distinct dense and porous surfaces. After cell exposition to extracts, no significant differences on mitochondrial activity (2,3-bis(2-methoxy-4-nitro-5-sulfophenly)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide) or cell density (Crystal Violet Dye Elution) were observed among groups. However, Neutral Red assay revealed that dense materials extracts induced lower levels of total viable cells to porous HA/beta-TCP (P < 0.01). Calcium ion content was also significantly lower on the extracts of dense samples. Porogenic treatments on BCP composites do not affect cytocompatibility, as measured by three different parameters, indicating that these ceramics are well suited for further studies on future bioengineering applications.

IMPROVEMENT TO THE MARGINAL COPING FIT OF COMMERCIALLY PURE TITANIUM CAST IN PHOSPHATE-BONDED INVESTMENT BY USING A SIMPLE PATTERN COATING TECHNIQUE

Statement of problem. Coatings of zirconite, Y2O3 or ZrO2 on wax patterns before investing in phosphate-bonded investments have been recommended to reduce the reaction layer in titanium castings, but they are not easily obtainable. Spinel-based investments are relatively stable with molten titanium and could be used as coatings to improve the quality of castings made with those investments. Purpose. The purpose of this study was to evaluate the effect of pattern coating with a commercial spinel-based investment before investing in 1 of 3 phosphate-bonded investments on the marginal coping fit and surface roughness of commercially pure titanium castings. Material and methods. Ten square acrylic resin patterns (12 x 12 x 2 mm) per group were invested in the phosphate-bonded investments Rematitan Plus (RP), Rema Exakt (RE), and Castorit Super C (CA) with or without a coating of the spinel-based investment, Rematitan Ultra (RU). After casting, the specimens were cleaned and the surface roughness was measured with a profilometer. Copings for dental implants with conical abutment were invested, eliminated, and cast as previously described. The copings were cleaned and misfit was measured with a profile projector (n=10). For both tests, the difference between the mean value of RU only and each value of the phosphate-bonded investment was calculated, and the data were analyzed by 2-way ANOVA and Tukey's HSD test (alpha=.05). In addition, the investment roughness was measured in bar specimens (30 x 10 x 10 mm), and the data (n=10) were analyzed by 1-way ANOVA and Tukey's HSD post hoc test (alpha=.05). Results. Two-way ANOVA for casting surface roughness was significant because of the investment, the coating technique, and the interaction between variables. One-way ANOVA was performed to prove the interaction term, and Tukey's post hoc test showed that RP with coating had the lowest mean, while RP had the highest. CA with coating was not different from RP with coating or CA without coating. RE with coating was similar to CA, while RE was different from all groups. For coping marginal fit, the 2-way ANOVA was significant for the investment, the coating technique, and the interaction between variables. The interaction was analyzed by1-way ANOVA and Tukey's HSD test that showed no significant difference among the coated groups, which had better marginal fit than the groups without coating. Among the groups without coating, CA had significant lower marginal misfit than RP, while RE was not different from CA and RP. For the investment surface roughness, the 1-way ANOVA was significant. CA and RU were smoother than RE and RP (P<.001). Conclusions. The coating technique improved the quality of castings fabricated with phosphate-bonded investments. (J Prosthet Dent 2012;108:51-57)