THE RIO MATA CAVALO GROUP: THE GOLD MINERALIZATION AND ITS ORIGIN

As sequências metavulcano-sedimentares na serra do Espinhaço Meridional apresentam dificuldades para separação, principalmente do Supergrupo Rio das Velhas, até o presente. Apesar da grande similaridade, é possível distingui-lo do Grupo Rio Mata Cavalo. Esta é constituída por uma unidade metamáfica-ultramáfica derivada de basaltos toleíticos, e uma sequência de cobertura clasto-química, além de apresentar mineralizações de ouro e Minerais/Elementos do Grupo da Platina associados, principalmente a Formações Ferríferas Bandadas. Origem hidrotermal é atribuída à concentração destes metais nobres. Campanhas de prospecção e pesquisa mineral, na área estudada, foram realizadas para ouro. Os resultados até o presente permitem sugerir o emprego de uma Unidade Superior composta pelos sedimentos clasto-químicos e uma Unidade Inferior, que compreende as rochas vulcânicas, ambas compondo o Grupo Mata Cavalo. Desta forma, este Grupo apresenta em sua Unidade Superior rica em níveis de BIF compostas principalmente por magnetita com concentrações de ouro associadas a enriquecimento supérgeno. Palavras-chave: sequência metavulcano-sedimentar, mineralização de ouro, hidrotermalismo, Grupo Rio Mata Cavalo, Serra do Espinhaço. Meridional.

Aging of plasma-activated copper and gold surfaces and its hydrophilic recovery after water immersion

A significant increase of surface hydrophilicity of copper and gold surfaces was obtained after atmospheric pressure plasma treatment using the surface dielectric barrier discharge with specific electrode geometry, the so-called diffuse coplanar surface barrier discharge. Surface wettability was estimated using the sessile drop method with further calculation of the surface free energy. After the plasma treatments, it was observed that the treated surfaces exhibited hydrophobic recovery (or aging effect). The aging effect was studied in different storage environments, such as air, low and high vacuum. The role of plasma and the reasons of the following aging effect are discussed with respect to the observed hydrophilic recovery after immersing the aged surfaces into deionized water. The changes in the surface morphology, composition and bond structure are presented and discussed as well. (C) 2013 Elsevier B. V. All rights reserved.

Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines

A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir-Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by pi-A isotherms, BAM, UV-vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir-Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10(-7) mol L-1 were attained. (C) 2014 Elsevier B.V. All rights reserved.

Co-deposition of gold nanoparticles and metalloporphyrin using the langmuir-blodgett (LB) technique for Surface-Enhanced Raman Scattering (SERS)

The synergistic effect produced by metallic nanoparticles when incorporated into different systems empowers a research field that is growing rapidly. In addition, organometallic materials are at the center of intensive research with diverse applications such as light-emitting devices, transistors, solar cells, and sensors. The Langmuir-Blodgett (LB) technique has proven to be suitable to address challenges inherent to organic devices, since the film properties can be tuned at the molecular level. Here we report a strategy to incorporate gold nanoparticles (AuNPs) into the LB film by co-deposition in order to achieve surface-enhanced Raman scattering (SERS) of the zinc(II)-protoporphyrin (IX) dimethyl ester (ZnPPIX-DME). Prior to the LB co-deposition, the properties of the Langmuir monolayer of ZnPPIX-DME at the air-water interface, containing AuNPs in the subphase, are studied through the surface-pressure versus mean molecular area (π-A) isotherms. The ZnPPIX-DME+AuNPs π-A isotherm presented a significant shift to higher molecular area, suggesting an interaction between both ZnPPIX-DME molecules and AuNPs. Those interactions are a key factor allowing the co-deposition of both AuNPs and ZnPPIX-DME molecules onto a solid substrate, thus forming the LB film. SERS of ZnPPIX-DME was successfully attained, ensuring the spatial distribution of the AuNPs. Higher enhancement factors were found at AuNP aggregates, as a result of the intense local electromagnetic field found in the metal nanoparticle aggregates. The main vibrational bands observed in the SERS spectra suggest a physical adsorption of the ZnPPIX-DME onto the surface of AuNPs. The latter is not only in agreement with the interactions pointed out by the π-A isotherms but also suggests that this interaction is kept upon LB film co-deposition.

Tree population and community dynamics in a Brazilian tropical semideciduous forest

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of Airborne-Particle Abrasion and Mechanico-Thermal Cycling on the Flexural Strength of Glass Ceramic Fused to Gold or Cobalt-Chromium Alloy

Purpose: To evaluate the effect of airborne-particle abrasion and mechanico-thermal cycling on the flexural strength of a ceramic fused to cobalt-chromium alloy or gold alloy.Materials and Methods: Metallic bars (n = 120) were made (25 mm x 3 mm x 0.5 mm): 60 with gold alloy and 60 with Co-Cr. At the central area of the bars (8 mm x 3 mm), a layer of opaque ceramic and then two layers of glass ceramic (Vita VM13, Vita Zahnfabrick) were fired onto it (thickness: 1 mm). Ten specimens from each alloy group were randomly allocated to a surface treatment [(tungsten bur or air-particle abrasion (APA) with Al(2)O(3) at 10 mm or 20 mm away)] and mechanico-thermal cycling (no cycling or mechanically loaded 20,000 cycles; 10 N distilled water at 37 degrees C and then thermocycled 3000 cycles; 5 degrees C to 55 degrees C, dwell time 30 seconds) combination. Those specimens that did not undergo mechanico-thermal cyclingwere stored inwater (37 degrees C) for 24 hours. Bond strength was measured using a three-point bend test, according to ISO 9693. After the flexural strength test, failure types were noted. The data were analyzed using three factor-ANOVA and Tukey's test (alpha = 0.05).Results: There were no significant differences between the flexural bond strength of gold and Co-Cr groups (42.64 +/- 8.25 and 43.39 +/- 10.89 MPa, respectively). APA 10 and 20 mm away surface treatment (45.86 +/- 9.31 and 46.38 +/- 8.89 MPa, respectively) had similar mean flexural strength values, and both had significantly higher bond strength than tungsten bur treatment (36.81 +/- 7.60 MPa). Mechanico-thermal cycling decreased the mean flexural strength values significantly for all six alloy-surface treatment combinations tested when compared to the control groups. The failure type was adhesive in the metal/ceramic interface for specimens surface treated only with the tungsten bur, and mixed for specimens surface treated with APA 10 and 20 mm.Conclusions: Considering the levels adopted in this study, the alloy did not affect the bond strength; APA with Al(2)O(3) at 10 and 20 mm improved the flexural bond strength between ceramics and alloys used, and the mechanico-thermal cycling of metal-ceramic specimens resulted in a decrease of bond strength.

BODE Index and GOLD Staging as Predictors of 1-Year Exacerbation Risk in Chronic Obstructive Pulmonary Disease

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

Transforming open mining pits into fish farms: Moving towards sustainability

The legacy of mining activities has typically been land 'returned to wildlife', or, at some sites, degraded to such an extent that it is unsuitable for any alternate use. Progress towards sustainability is made when value is added in terms of the ecological, social and economic well-being of the community. In keeping with the principles of sustainable development, the innovative use of flooded open pits and tailings impoundments as commercial, recreational or ornamental fish farms should be considered in some locations, as it could make a significant contribution to the social equity, economic vitality and environmental integrity of mining communities. This article highlights the growing significance of aquaculture and explores the benefits and barriers to transforming flooded pits and impoundments into aquaculture operations. Among other benefits, aquaculture may provide a much-needed source of revenue, employment and, in some cases, food to communities impacted by mine closure. Further, aquaculture in a controlled closed environment may be more acceptable to critics of fish farming who are concerned about fish escapes and viral transmissions to wild populations. Despite the potential benefits, aquaculture in flooded pits and impoundments is not without its complications - it requires a site-specific design approach that must consider issues ranging from metals uptake by fish, to the long-term viability of the aquatic system as fish habitat, to the overall contribution of aquaculture to sustainability. © 2004 United Nations. Published by Blackwell Publishing.

Influence of thermal and mechanical cycling on the flexural strength of ceramics with titanium or gold alloy frameworks

Objectives: The aim of this study was to evaluate the effect of thermal and mechanical cycling alone or in combination, on the flexural strength of ceramic and metallic frameworks cast in gold alloy or titanium. Methods: Metallic frameworks (25 mm × 3 mm × 0.5 mm) (N = 96) cast in gold alloy or commercial pure titanium (Ti cp) were obtained using acrylic templates. They were airborne particle-abraded with 150 μm aluminum oxide at the central area of the frameworks (8 mm × 3 mm). Bonding agent and opaque were applied on the particle-abraded surfaces and the corresponding ceramic for each metal was fired onto them. The thickness of the ceramic layer was standardized by positioning the frameworks in a metallic template (height: 1 mm). The specimens from each ceramic-metal combination (N = 96, n = 12 per group) were randomly assigned into four experimental fatigue conditions, namely water storage at 37 °C for 24 h (control group), thermal cycling (3000 cycles, between 4 and 55 °C, dwell time: 10 s), mechanical cycling (20,000 cycles under 10 N load, immersion in distilled water at 37 °C) and, thermal and mechanical cycling. A flexural strength test was performed in a universal testing machine (crosshead speed: 1.5 mm/min). Data were statistically analyzed using two-way ANOVA and Tukey's test (α = 0.05). Results: The mean flexural strength values for the ceramic-gold alloy combination (55 ± 7.2 MPa) were significantly higher than those of the ceramic-Ti cp combination (32 ± 6.7 MPa) regardless of the fatigue conditions performed (p < 0.05). Mechanical and thermo-mechanical fatigue decreased the flexural strength results significantly for both ceramic-gold alloy (52 ± 6.6 and 53 ± 5.6 MPa, respectively) and ceramic-Ti cp combinations (29 ± 6.8 and 29 ± 6.8 MPa, respectively) compared to the control group (58 ± 7.8 and 39 ± 5.1 MPa, for gold and Ti cp, respectively) (p < 0.05) (Tukey's test). While ceramic-Ti cp combinations failed adhesively at the metal-opaque interface, gold alloy frameworks exhibited a residue of ceramic material on the surface in all experimental groups. Significance: Mechanical and thermo-mechanical fatigue conditions decreased the flexural strength values for both ceramic-gold alloy and ceramic-Ti cp combinations with the results being significantly lower for the latter in all experimental conditions. © 2007 Academy of Dental Materials.

Minas do Cuiabá, ilha dos sertões: considerações sobre o papel da metrópole na expansão dos domínios portugueses na América (1721-1728)

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

Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids

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

Microbiological or Chemical Models of Enamel Secondary Caries Compared by Polarized-Light Microscopy and Energy Dispersive X-ray Spectroscopy

Different secondary caries models may present different results. The purpose of this study was to compare different in vitro secondary caries models, evaluating the obtained results by polarized-light microscopy (PLM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Standardized human enamel specimens (n = 12) restored with different materials (Z250 conventional composite resin-CRZ, Freedom polyacid-modified composite resin-CRF, Vitremer resin-modified glass-ionomer-GIV, and Fuji IX conventional glass-ionomer cement-GIF) were submitted to microbiological (MM) or chemical caries models (CM). The control group was not submitted to any caries model. For MM, specimens were immersed firstly in sucrose broth inoculated with Streptococcus mutans ATCC 35688, incubated at 37 degrees C/5% CO(2) for 14 days and then in remineralizing solution for 14 days. For CM, specimens were submitted to chemical pH-cycling. Specimens were ground, submitted to PLM and then were dehydrated, gold-sputtered and submitted to SEM and EDS. Results were statistically analyzed by Kruskall-Wallis and Student-Newman-Keuls tests (alpha = 0.05). No differences between in vitro caries models were found. Morphological differences in enamel demineralization were found between composite resin and polyacid-modified composite resin (CRZ and CRF) and between the resin-modified glass-ionomer and the glass-ionomer cement (GIF and GIV). GIF showed higher calcium concentration and less demineralization, differing from the other materials. In conclusion, the glass-ionomer cement showed less caries formation under both in vitro caries models evaluated. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 90B: 635-640, 2009

Ability of different restorative materials to prevent in situ secondary caries: analysis by polarized light-microscopy and energy-dispersive X-ray

Secondary caries is the main cause of direct restoration replacement. The purpose of this study was to analyze enamel adjacent to different restorative materials after in situ cariogenic challenge using polarized-light microscopy (PLM), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDS). Twelve volunteers, with a low level of dental plaque, a low level of mutans streptococci, and normal salivary flow, wore removable palatal acrylic appliances containing enamel specimens restored with Z250 composite, Freedom composite, Fuji IX glass-ionomer cement, or Vitremer resin-modified glass-ionomer for 14 days. Volunteers dripped one drop of 20% sucrose solution (n = 10) or distilled water (control group) onto each specimen 8 times per day. Specimens were removed from the appliances and submitted to PLM for examination of the lesion area (in mm(2)), followed by dehydration, gold-sputtering, and submission to SEM and EDS. The calcium (Ca) and phosphorus (P) contents were evaluated in weight per cent (%wt). Differences were found between Z250 and Vitremer, and between Z250 and FujiIX, when analyzed using PLM. Energy-dispersive X-ray analysis results showed differences between the studied materials regarding Ca %wt. In conclusion, enamel adjacent to glass-ionomer cement presented a higher Ca %wt, but this material did not completely prevent enamel secondary caries under in situ cariogenic challenge.

Botryoidal platinum, palladium and potarite from the Bom Sucesso stream, Minas Gerais, Brazil: Compositional zoning and origin

Platinum-Pd nuggets from the Born Sucesso stream alluvium Minas Gerais, Brazil. have been investigated by electron-probe microanalysis. The nuggets attain 1 mm in maximum dimension and have a botryoidal habit, with pronounced compositional core-to-margin zoning of internal structures, Although there is a wide variation in internal morphology and individual zones vary markedly in thickness (<1-100 mum), a typical composite arborescent nugget comprises a broad irregular core region of massive auriferous Pd-Hg alloy (potarite delta-PdHg) or cavity space + relict potarite enclosed by a narrow zone of platiniferous, palladium or alloy of near Pt50Pd50 composition, and is progressively oscillatory zoned by palladian platinum, with growth eventually enveloping the whole botryoidal colony, to a narrow rim of palladian platinum or pure platinum. Other nuggets comprise an arborescent to dendritic core of auriferous potarite, a broad internal zone of either pure platinum or palladian platinum, and a narrow rim of platinum, the mineral palladium contains up to about 65 at.% Pd; this is the first detailed modern confirmation of palladium in its type locality. Auriferous potarite ranges in composition from similar toPd(3)Hg(2) to near Pd(Hg,Au). The origin of these nuggets remains unclear, but their mineralogy is broadly equivalent to that of palladian gold. potarite and platinum in alluvial sediments and overburden from Devon, England, which are considered to be detrital, and their platinum-group-clement geochemistry is consistent with precipitation from hydrothermal fluids. We suggest that the Bom Sucesso nuggets resulted from high-level episodic hydrothermal alteration of mafic and ultramafic rocks within the drainage basin, with the remobilized Pt and Pd precipitated in open spaces in the enclosing metaquartzites.

Validation of hysteroscopic view in cases of endometrial hyperplasia and cancer in patients with abnormal uterine bleeding

STUDY OBJECTIVE: To validate hysteroscopic view with histology in cases of endometrial hyperplasia and cancer in patients with abnormal uterine bleeding (AUB)DESIGN: Retrospective study.(Canadian Task Force classification II-3).SETTING: University teaching hospitals in Rio de Janeiro and São Paulo, and private office in Rio de Janeiro.PATIENTS: Four thousand and fifty-four patients with AUB in whom hysteroscopic views were complete and the histologic result was conclusive.INTERVENTION: Four thousand and fifty-four office hysteroscopies with complete views and conclusive histologic results. The material for histologic examination was obtained through biopsy of the lesion in an outpatient unit or through the resection of the entire lesion in patients who underwent surgery. Histology was considered the gold standard and compared with the hysteroscopic view.MEASUREMENTS AND MAIN RESULTS: In the histology of the 4054 examinations, 613 (15.2%) were endometrial hyperplasia, and 105 (2.6%) were endometrial cancer. The most frequent hysteroscopic finding was endometrial polyps (31.2%). In endometrial hyperplasia, the sensitivity of the hysteroscopic view was 56.3% (95% CI 52.21-60.2%), specificity was 89.1% (95% CI 88.0%-90.1%), positive predictive value (PPV) was 48.0% (95% CI 44.3%-51.7%), negative predictive value (NPV) was 92.0% (95% Cl 90.1%-92.9%), and accuracy was 72.7% (95% CI 70.7%-74.7%). Accuracy was defined as the proportion of correct results among the hysteroscopic examinations. In endometrial cancer, the sensitivity of the hysteroscopic view was 80.0% (95% Cl 71.1%-87.2%), specificity was 99.5% (95% CI 99.2%-99.7%), PPV was 81.5% (95% Cl 72.7%-88.5%), NPV was 99.5% (95% CI 99.2%-99.7%), and accuracy was 89.8% (95% CI, 85.9%-93.6%). In the 814 patients (20.0%) in whom the hysteroscopic view was normal, there were no false negatives for endometrial cancer; however, there were 37 (4.5%) false negatives for endometrial hyperplasia. In the histologic cases of endometrial cancer, 101 (96.2%) hysteroscopic views were compatible with cancer or hyperplasia (80.0% and 16.2%, respectively). Ninety-seven out of 103 hysteroscopic views with cancer findings (94.2%) had histologic diagnosis of cancer or hyperplasia (81.5% and 12.6%, respectively).CONCLUSION: It seems that even in face of good validity of hysteroscopic view for endometrial hyperplasia and cancer, histologic study is mandatory in the presence of any lesion as the hysteroscopic view cannot completely replace the histologic study in patients with AUB. (C) 2006 AAGL. All rights reserved.