Influence of specimens' design and manufacturing process on microtensile bond strength to enamel: laboratory and FEA comparison

This study evaluated the effect of specimens' design and manufacturing process on microtensile bond strength, internal stress distributions (Finite Element Analysis - FEA) and specimens' integrity by means of Scanning Electron Microscopy (SEM) and Laser Scanning Confocal Microscopy (LCM). Excite was applied to flat enamel surface and a resin composite build-ups were made incrementally with 1-mm increments of Tetric Ceram. Teeth were cut using a diamond disc or a diamond wire, obtaining 0.8 mm² stick-shaped specimens, or were shaped with a Micro Specimen Former, obtaining dumbbell-shaped specimens (n = 10). Samples were randomly selected for SEM and LCM analysis. Remaining samples underwent microtensile test, and results were analyzed with ANOVA and Tukey test. FEA dumbbell-shaped model resulted in a more homogeneous stress distribution. Nonetheless, they failed under lower bond strengths (21.83 ± 5.44 MPa)c than stick-shaped specimens (sectioned with wire: 42.93 ± 4.77 MPaª; sectioned with disc: 36.62 ± 3.63 MPa b), due to geometric irregularities related to manufacturing process, as noted in microscopic analyzes. It could be concluded that stick-shaped, nontrimmed specimens, sectioned with diamond wire, are preferred for enamel specimens as they can be prepared in a less destructive, easier, and more precise way.

Effect of nitric oxide inhibitor and donor substances on the infammatory process caused by endodontic irrigants

Nitric oxide (NO) has been considered a key molecule in infammation. OBJECTIVE: The aim of this study was to evaluate the effect of treatment with L-NAME and sodium nitroprussiate, substances that inhibit and release NO, respectively, on tissue tolerance to endodontic irrigants. MATERIAL AND METHODS: The vital dye exudation method was used in a rat subcutaneous tissue model. Injections of 2% Evans blue were administered intravenously into the dorsal penial vein of 14 male rats (200-300 g). The NO inhibitor and donor substances were injected into the subcutaneous tissue in the dorsal region, forming two groups of animals: G1 was inoculated with L-NAME and G2 with sodium nitroprussiate. Both groups received injections of the test endodontic irrigants: acetic acid, 15% citric acid, 17% EDTA-T and saline (control). After 30 min, analysis of the extravasated dye was performed by light absorption spectrophotometry (620 nm). RESULTS: There was statistically signifcant difference (p<0.05) between groups 1 and 2 for all irrigants. L-NAME produced a less intense infammatory reaction and nitroprussiate intensifed this process. CONCLUSIONS: Independently of the administration of NO inhibitors and donors, EDTA-T produced the highest irritating potential in vital tissue among the tested irrigating solutions.

Biological activity of metal-edds (ethylenediaminedisuccinate) complexes in K562 and PBMC cells

The effect of S,S-ethylenediaminedisuccinic acid (edds) on the quenching of metal-catalyzed (metal = Mn, Fe, Co, Ni, Cu, Zn) oxidation of ascorbic acid was tested in vitro via oxidation of the fluorescent probe 1,2,3-dihydrorhodamine dihydrochloride. The pro-oxidant activity of iron was not fully suppressed, even at a four-fold molar excess of the ligand. The effect of serum on the toxicity to peripheral blood mononuclear cells (PBMC) and K562 cells was investigated. The cytotoxic effect of Fe-edds was abrogated in the presence of Trolox or serum proteins. The probable pathways of cell toxicity were investigated through blocking of the monocarboxylate transporters (MCT) in association with cell cycle studies by flow cytometry. Cells treated with metal complexes and alpha-cyano-4-hydroxycinnamic acid, a known MCT inhibitor, showed recovery of viability, suggesting that MCT proteins may be involved in the internalization of metal-edds complexes. The free acid induced cell cycle arrest in G0/G1 (PBMC) and S (K562) phases, suggesting direct DNA damage or interference in DNA replication.

Dependence of the crossover exponent with the diffusion rate in the generalized contact process model

We study how the crossover exponent, phi, between the directed percolation (DP) and compact directed percolation (CDP) behaves as a function of the diffusion rate in a model that generalizes the contact process. Our conclusions are based in results pointed by perturbative series expansions and numerical simulations, and are consistent with a value phi = 2 for finite diffusion rates and phi = 1 in the limit of infinite diffusion rate.

Heavy metal concentrations in soils from a remote oceanic island, Fernando de Noronha, Brazil

This paper examines the role of parent rock, pedogenetic processes and airborne pollution in heavy metal accumulation in soils from a remote oceanic island, Fernando de Noronha, Brazil. We studied five soil profiles developed from different volcanic rocks. Mineralogical composition and total concentrations of major and trace elements were determined in 43 samples. The obtained concentrations range for heavy metals were: Co: 26-261 ppm; Cu: 35-97 ppm; Cr: 350-1446 ppm; Ni: 114-691 ppm; Zn: 101-374 ppm; Hg: 2-150 ppb. The composition of soils is strongly affected by the geochemical character of the parent rock. Pedogenesis appears to be responsible for the accumulation of Zn, Co, and, to a lesser extent, of Ni and Cu, in the upper, Mn- and organic carbon-enriched horizons of the soil profiles. Pedogenic influence may also explain the relationship observed between Cr and the Fe. Hg is likely to have been added to the soil profile by long-range atmospheric transport. Its accumulation in the topsoil was further favoured by the formation of stable complexes with organic matter. Clay minerals do not appear to play an important role in the fixation of heavy metals.

Remoção de Pb2+ e Cr3+ em solução por zeólitas naturais associadas a rochas eruptivas da formação serra geral, bacia sedimentar do Paraná

The capacity of natural zeolites and its host rock (dacite) to remove Pb2+ and Cr3+ from aqueous solutions has been investigated. Results showed that both samples prefer to remove Pb2+ instead of Cr3+. Almost 100% of Pb2+ was removed from solutions with concentration until 50 mg L-1 and 100 mg L-1 of this metal, respectively by dacite and zeolite. The equilibrium of metals adsorption process was reached during the first 30 min by both materials. Na+ can be used to recover Pb2+, but not to remove Cr3+ from the treated samples. The Sips model showed a good fit for experimental data of this study.

Screening process for activity determination of conductive oxide electrodes for organic oxidation

A modified method for the calculation of the normalized faradaic charge (q fN) is proposed. The method involves the simulation of an oxidation process, by cyclic voltammetry, by employing potentials in the oxygen evolution reaction region. The method is applicable to organic species whose oxidation is not manifested by a defined oxidation peak at conductive oxide electrodes. The variation of q fN for electrodes of nominal composition Ti/RuX Sn1-X O2 (x = 0.3, 0.2 and 0.1), Ti/Ir0.3Ti0.7O2 and Ti/Ru0.3Ti0.7O2 in the presence of various concentrations of formaldehyde was analyzed. It was observed that electrodes containing SnO2 are the most active for formaldehyde oxidation. Subsequently, in order to test the validity of the proposed model, galvanostatic electrolyses (40 mA cm-2) of two different formaldehyde concentrations (0.10 and 0.01 mol dm-3) were performed. The results are in agreement with the proposed model and indicate that this new method can be used to determine the relative activity of conductive oxide electrodes. In agreement with previous studies, it can be concluded that not only the nature of the electrode material, but also the organic species in solution and its concentration are important factors to be considered in the oxidation of organic compounds.

Reaproveitamento de óxidos de manganês de pilhas descartadas para eletrocatálise da reação de redução de oxigênio em meio básico

The oxygen reduction reaction was studied in alkaline media using manganese oxides obtained from spent batteries as electrocatalysts. Three processes were used to recover manganese oxides from spent batteries. The particles obtained were in the range from 8 to 11 nm. The electrochemical experiments indicated a good electrocatalytic activity toward oxygen reduction using the different samples and showing approximately a direct transference of 4 electrons during the process. Even though all the processes were efficient, the best result was observed for the prepared sample using reactants of low cost.

Metallochlorophylls of magnesium, copper and zinc: evaluation of the influence of the first coordination sphere on their solvatochromism and aggregation properties

In this study the role of different metal centers (magnesium, zinc and copper) on the enhancement of the hydrophilic character of metallochlorophylls, was evaluated. The solvatochromism as well as the aggregation process for these compounds in water/ethanol mixtures at different volume ratios were evaluated using Fluorescence, and Resonant Light Scattering (RLS) measurements, aiming to characterize the behavior of these compounds. Independently on the studied metallochlorophyll, the presence of at least 60% of water results in a considerable increase in the fluorescence emission, probably a direct consequence of a lower aggregation of these compounds, which is confirmed by the results from RLS measurements. Additionally, the results suggest that magnesium and zinc chlorophyll should be promising phototherapeutic agents for Photodynamic Therapy.

Electrocatalytic oxidation of methanol by the [Ru3O(OAc)6(py)2(CH3OH)]3+cluster: improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system

The [Ru3O(Ac)6(py)2(CH3OH)]+ cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/Ru 3III,III,III /Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two RuIV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states.

A concise enantioselective synthesis of (+)-endo-brevicomin accomplished by a tellurium/metal exchange reaction

A homoenolate generated by tellurium/lithium exchange reaction was employed in a straightforward enantioselective synthesis of (+)-endo-brevicomin in 70% yield and 84.4% e.e.

Spectroscopic characterization and investigation of the dynamic of charge compensation process of supramolecular films derived from tetra-2-pyridyl-1,4-pyrazine ligand

This work describes the infrared spectroscopy characterization and the charge compensation dynamics in supramolecular film FeTPPZFeCN derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) with hexacyanoferrate, as well as the hybrid film formed by FeTPPZFeCN and polypyrrole (PPy). For supramolecular film, it was found that anion flux is greater in a K+ containing solution than in Li+ solution, which seems to be due to the larger crystalline ionic radius of K+. The electroneutralization process is discussed in terms of electrostatic interactions between cations and metallic centers in the hosting matrix. The nature of the charge compensation process differs from others modified electrodes based on Prussian blue films, where only cations such as K+ participate in the electroneutralization process. In the case of FeTPPZFeCN/PPy hybrid film, the magnitude of the anions’s flux is also dependent on the identity of the anion of the supporting electrolyte.

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes

A metal-free protocol was developed to synthesize indanes by ring contraction of 1, 2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser's reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH3CN, 2 , 2, 2-trifluoroethanol (TFE), 1 , 1, 1, 3, 3, 3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH2Cl2) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1, 3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry

Nutritional characteristics and in vitro digestibility of silages from different corn cultivars harvested at two cutting heights

The objective of this study was to evaluate the nutritional traits and in vitro digestibility of silages from different corn cultivars harvested at two cutting heights. It was evaluated 11 cultivars (Dina 766, Dina 657, Dina 1000, P 3021, P 3041, C 805, C 333, AG 5011, FO 01, Dina co 9621 and BR 205) harvest 5 cm above ground (low) and 5 cm below the intersection of the first ear (high). It was used a random block design (three blocks), arranged in a 11 × 2 factorial scheme. Silages from plants harvested at high cutting height presented average content of dry matter significantly superior to silages from plants harvested at low height. Cultivars FO 01, AG 5011, Dina co 9621 and Dina 766 presented greater content of crude protein than cultivars C 805, P 3041 and P 3021, which presented the lowest contents of this nutrient. The raise in the cut height increased in vitro dry matter true digestibility coefficients and in vitro dry matter digestibility of silage evaluated. The increase in cut height improved nutritive value of silages by decreasing concentrations of fibrous fractions and increasing in vitro dry matter digestibility.

Evaluation of corn cultivars harvested at two cutting heights for ensilage

The objective of this study was to evaluate the agronomic characteristics, bromatological-chemical composition and digestibility of 11 corn cultivars (Zea mays) harvested at two cutting heights. Cultivars D 766, D 657, D 1000, P 3021, P 3041, C 805, C 333, AG 5011, FO 01, CO 9621 and BR 205 were evaluated when they were harvested 5 cm above ground (low) and 5 cm below the insertion of the first ear (high). The experiment was designed as random blocks, with three replicates, arranged in an 11 x 2 factorial scheme. Cultivars presented similar productions of forage dry matter and grains. Percentages of stalk, leaf, straw, cob and kernel fractions were different among cultivars, as well as dry matter content of the whole plant at harvest. Considering the whole plant, only the contents of gross energy, nitrogen in neutral detergent fiber, and in vitro neutral and acid detergent fiber digestibility did not differ among cultivars. Increase on the cutting height improved forage quality due to the reduction of stalk and leaf fractions and contents of cell wall constituents.