Immobilization of 1,2-naphthoquinone-4-sulfonic acid on gold electrode: application for cysteamine detection using Michael addition

Fabrication and electrochemical characterization of adsorbed 1,2-naphthoquinone-4-sulfonic acid sodium (Nq)-modified gold electrode is described in a wide pH range (3.00–9.00) in 0.1 M phosphate buffer solution using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and double-step potential chronoamperometry methods. The resulting Nq thin film-modified gold electrode (Nq/Au) was tested successfully to recognize cysteamine in an aqueous solution. It is found that cysteamine participates in Michael addition reaction with adsorbed Nq on gold electrode to form the corresponding thioquinone derivative. The reoxidation of the adduct at a potential of about 650 mV less positive than cysteamine at the surface of the bare Au electrode leads to an increase in the oxidative current, which is proportional to the concentration of cysteamine. The calibration plot for cysteamine was found to be linear in the ranges of 6.0 × 10⁻⁵–4.5 × 10⁻³ M and 8.0 × 10⁻⁶–5.5 × 10⁻⁴ by CV and DPV, respectively.     

Characterization of the invariant reaction involving the L, η, γ and σ phases in the Ti–Al–Nb system

Ti–Al–Nb alloys have shown promising properties for high-temperature applications. Although the phase diagram has been well researched, several controversies exist over the high-temperature phase equilibria. Among them, the invariant reaction involving the L, γ, σ, η phases, which has been classified as either class 1 (eutectic reaction) or class 2 (transition reaction), has not been well developed. To address this invariant reaction, two alloys that cross through the invariant plane during solidification were investigated. Differential thermal analysis in conjunction with detailed microstructural analysis of the as-cast as well as heat-treated samples determined the invariant reaction to be a ternary eutectic reaction. The results of this study indicate that a large energy barrier is associated with nucleation of the σ phase from the liquid. Additionally, extension of the γ phase field is shown to extend further into the Nb-rich corner of the ternary system at elevated temperatures.     

Effect of hydride nucleation rate on the hydrogen capacity of Mg

The hydrogen capacity of magnesium is usually below its theoretical value of 7.6 wt.% hydrogen. Based on the model that hydrogen capacity is reached when the hydride colonies/grains nucleated on the surface of Mg powders impinge on each other, we designed two hydrogenation methods in order to shed light on the effect of hydride nucleation rate on the hydrogen capacity of a commercial pure magnesium powder. We have demonstrated that increasing the nucleation rate significantly reduces the hydrogen capacity. It is elucidated that at a high nucleation rate, the complete coverage of the powder surface is reached at a smaller volume fraction of magnesium hydride. The results of the analysis of the hydrogenation curves using the Johnson–Mehl–Avrami (JMA) equation revealed three stages of hydrogenation. The modification of the nucleation rate was found to affect stages 1 and 2, where the nucleation and growth of the hydride take place, most significantly.     

The effect of annealing on deformation and fracture of a nanocrystalline fcc metal

The tensile deformation and fracture behavior of electrodeposited nanocrystalline Ni–15% Fe alloy samples after annealing for 90 min at 250, 400 and 500 °C temperatures were investigated. The structure of the samples was studied using TEM and XRD techniques and the fracture surfaces were investigated employing SEM. The results of this study indicated that annealing at 250 °C modified grain size distribution slightly but resulted in a significant increase in the initial strain hardening rate. While the average grain size in the 400 °C sample was increased to 59 nm, its yield strength was comparable to the as-deposited alloy with a 9 nm grain size. The plastic tensile elongation of all annealed samples was lowered significantly to less than 1% from approximately 6% in the as-deposited state. These results are discussed in terms of the inhomogeneity of plastic deformation and the evolution of internal stresses in nanocrystalline materials.     

Nickel catalyst supported on magnesium oxide with high surface area and plate-like shape: A highly stable and active catalyst in methane reforming with carbon dioxide

Nanocrystalline magnesium oxide with a high surface area and a highly defective surface structure with plate-like shape was synthesized by a facile method using polyvinyl alcohol as a surfactant. The prepared MgO was employed as support for nickel catalysts with various nickel loadings in methane reforming with carbon dioxide. The results showed high catalytic activity and stability for the prepared catalysts due to the formation of NiO–MgO solid solution and high basicity of support. The 5% Ni/MgO catalyst was very effective in this process and exhibited stable catalytic performance for 50 h of reaction as well as a high resistance against carbon formation.     

Effect of hydraulic retention time and temperature on submerged membrane bioreactor (SMBR) performance

Water shortages and strict environmental provisions necessitate wastewater renovation using various wastewater treatment methods, among which applications of submerged membrane bioreactors (SMBRs) are rapidly increasing due to their advantages such as high loading capacity and quality of effluent. In this work, the effect of hydraulic retention time (HRT 8, 10 and 12 h) and temperature (25, 30 and 35°C) on membrane fouling and sludge production was investigated in a 5-Liter SMBR equipped with immersed PVDF hollow fiber membrane module. Phenolic synthetic wastewater and acclimatized activated sludge with phenol during a 2-month period were used as toxic and microbial sources, respectively. Results showed that by increasing HRT membrane fouling decreases, while excellent treatment performance of over 99.5% phenol and 95% COD removals was achieved at all HRTs. Therefore, HRT=8 h corresponding to the highest effluent flow rate of 12 L/m²·h was used to investigate the effect of temperature, resulting in phenol and COD removals of higher than 99 and 96%, respectively, at all temperatures. Membrane fouling occurred at 12, 5 and 3 days for 25, 30 and 35 °C, respectively. Additionally, the effect of HRT and temperature on mixed liquor volatile suspended solid (MLVSS) as a measure of biomass was examined. MLVSS concentration showed decreases with increasing HRT and temperature. Overall, it was shown that SMBR can be used to efficiently treat phenolic wastewater at a range of flow rates and temperatures, among which HRT=8 h and T=25 °C are the preferred operating conditions, resulting in high flow rate and low membrane fouling.     

Micromorphology analysis and bond strength of two adhesives to Er,Cr:YSGG laser‐prepared vs. Bur‐prepared fluorosed enamel

Preservation of enamel during composite veneer restorations of fluorosed teeth could be achieved by conservative preparation with Erbium lasers. This study evaluated the effect of fluorosed enamel preparation with Er,Cr:YSGG vs. conventional diamond bur on the micromorphology and bond strength of a self‐etch and an etch‐and‐rinse adhesives. Er,Cr:YSGG laser or diamond bur preparation was performed on the flattened midbuccal surfaces of 70 extracted human premolars with moderate fluorosis (according to Thylstrup and Fejerskov index, TFI = 4–6). Adper Single Bond (SB) with acid etching for 20 or 40 s and Clearfil SE Bond (SEB) alone or with additional etching was applied in four laser groups. The same adhesive procedures were used in three bur groups except for 40 s of etching along with SB. After restoration, microshear bond strength was measured (MPa). Data were analyzed using ANOVA and Tamhane tests (α = 0.05). Six additional specimens were differently prepared and conditioned for scanning electron microscopy evaluation. The highest and lowest bond strengths were obtained for bur‐prepared/SB (39.5) and laser‐prepared/SEB (16.9), respectively, with a significant difference (P = 0.001). The different adhesive procedures used associated to two adhesives exhibited insignificantly lower bonding in laser‐prepared groups compared to bur‐prepared ones (P > 0.05), with the exception of additional etching/SEB, which bonded significantly higher to bur‐prepared (36.4) than to laser‐prepared enamel (18.7, P = 0.04). Morphological analyses revealed a delicate etch pattern with exposed enamel prisms on laser‐prepared fluorosed enamel after acid etching and less microretentive pattern after self‐etching primer. The etch‐and‐rinse adhesive was preferred in the laser‐prepared fluorosed enamel in terms of bonding performance. Microsc. Res. Tech. 77:779–784, 2014. © 2014 Wiley Periodicals, Inc.     

An Omniphobic Spray Coating Created from Hierarchical Structures Prevents the Contamination of High-Touch Surfaces with Pathogens

Engineered surfaces that repel pathogens are of great interest due to their role in mitigating the spread of infectious diseases. A robust, universal, and scalable omniphobic spray coating with excellent repellency against water, oil, and pathogens is presented. The coating is substrate-independent and relies on hierarchically structured polydimethylsiloxane (PDMS) microparticles, decorated with gold nanoparticles (AuNPs). Wettability studies reveal the relationship between surface texturing of micro- and/or nano-hierarchical structures and the omniphobicity of the coating. Studies of pathogen transfer with bacteria and viruses reveal that an uncoated contaminated glove transfers pathogens to >50 subsequent surfaces, while a coated glove picks up 10⁴ (over 99.99%) less pathogens upon first contact and transfers zero pathogens after the second touch. The developed coating also provides excellent stability under harsh conditions. The remarkable anti-pathogen properties of this surface combined with its ease of implementation, substantiate its use for the prevention of surface-mediated transmission of pathogens.     

Coordination of bioenergy supply chains under government incentive policies: a game-theoretic analysis

Clean Technologies and Environmental Policy - Biomass as an abundant renewable energy source can play a vital role in controlling the greenhouse gas emissions. The distributed nature of biomass and...