Fabrication of Gold Nano‐Structures with Azopolymer Templates

Fabrication of gold nano‐patterns has been demonstrated employing surface relief structures created on films of an azobenzene‐functionalized polymer as templates. The surface relief templates were photoinscribed on the azopolymer films in one‐step with two laser beams. Thin layers of gold were over‐coated on the polymer templates by thermal evaporation. Gold lines of a few hundred nanometer width were successfully fabricated by pyrolyzing the azobenzene polymer. Sub‐micron gold dots were also created. The resulting gold structures exhibited the same periodicity as the polymer templates.     

Spectroelectrochemical identity of Prussian blue films in various electrolytes: comparison of time-derivative voltabsorptometric responses with conventional cyclic voltammetry

Using Prussian blue (PB) electrodeposited on gold-covered foil as a model system, we have demonstrated the usefulness of the time-derivative measurements of absorbance versus potential (linear potential-scan voltabsorptometry) for spectroelectrochemical characterization of thin electrochromic films. The time-derivative signals were monitored for PB at 680 and 420 nm in potassium, sodium and lithium electrolytes. Information obtained from cyclic voltabsorptometry is equivalent or complementary to that from conventional cyclic voltammetry. In the case of PB films investigated in lithium electrolyte, the voltabsorptometric time-derivative peaks are better defined than the respective voltammetric peaks. The combination of voltabsorptometry with voltammetry enables molar absorptivity and/or film loading to be determined. Also, concentration changes of differently colored mixed-valence redox centers can be monitored as a function of applied potential. Received: 16 January 1997 / Accepted: 11 March 1997     

A lower bound estimate of the critical load for compressible elastic solids

We determine lower bound estimates for the critical load for hyperelastic solids under monotonic dead load processes. By considering the Hadamard criterion of infinitesimal stability, we first determine a lower bound for the Hadamard stability functional; then, we develop a procedure for optimal lower bound estimates for the critical load. As examples, we apply our procedure to generalized Blatz-Ko solids under simple extension, simple compression and rectilinear shear, and compare our results with other proposals contained in the literature.     

Photoactivatable V-Shaped Bifunctional Quinone Methide Precursors as a New Class of Selective G-quadruplex Alkylating Agents

Combining the selectivity of G-quadruplex (G4) ligands with the spatial and temporal control of photochemistry is an emerging strategy to elucidate the biological relevance of these structures. In this work, we developed six novel V-shaped G4 ligands that can, upon irradiation, form stable covalent adducts with G4 structures via the reactive intermediate, quinone methide (QM). We thoroughly investigated the photochemical properties of the ligands and their ability to generate QMs. Subsequently, we analyzed their specificity for various topologies of G4 and discovered a preferential binding towards the human telomeric sequence. Finally, we tested the ligand ability to act as photochemical alkylating agents, identifying the covalent adducts with G4 structures. This work introduces a novel molecular tool in the chemical biology toolkit for G4s.     

Influence of Initial pH Value on the Adsorption of Reactive Black 5 Dye on Powdered Activated Carbon: Kinetics,Mechanisms, and Thermodynamics

The aim of this work was to investigate the influence of initial pH value (pH₀) on the isothermal adsorption of Reactive Black 5 (RB5) dye on commercial powdered activated carbon. Four initial pH values were chosen for this experiment: pH₀ = 2.00, 4.00, 8.00, and 10.00. In order to investigate the mechanism of adsorption kinetic, studies have been performed using pseudo-first-order and pseudo-second-order kinetic models as well as an intraparticle diffusion model. In addition, thermodynamic parameters of adsorption were determined for pH₀ = 4.00. Results of this research showed that the initial pH value significantly influences the adsorption of RB5 dye onto activated carbon. The highest adsorption capacities (q_e) and efficiencies of decolouration were observed for initial pH values of pH₀ = 2.00 (q_e = 246.0 mg g⁻¹) and 10.00 (q_e = 239.1 mg g⁻¹) due to strong electrostatic interactions and attractive π···π interactions, respectively. It was also shown that the adsorption of RB5 dye on activated carbon at all initial pH values is kinetically controlled, assuming a pseudo-second-order model, and that intraparticle diffusion is not the only process that influences on the adsorption rate.     

The Wound-Healing Effect of Mango Peel Extract on Incision Wounds in a Murine Model

Mangifera indica can generate up to 60% of polluting by-products, including peels. However, it has been shown that flavonoids and mangiferin are mainly responsible for the antioxidant, anti-inflammatory, and antibacterial activities closely related to the wound-healing process. The chemical composition of MEMI (methanolic extract of M. indica) was analyzed by HPLC-DAD, as well as concentrations of total phenol (TPC) and flavonoids (TFC) and antioxidant activity (SA₅₀). Wound-healing efficacy was determined by measurements of wound contraction, histological analysis, and tensiometric method; moreover, anti-inflammatory, antibacterial, and acute dermal toxicity (OECD 402) were also evaluated. Phenol, resorcinol, conjugated resorcinol, and mangiferin were detected. TPC, TFC, and SA₅₀ were 136 mg GAE/g, 101.66 mg QE/g, and 36.33 µg/mL, respectively. Tensile strength and wound contraction closure did not show significant differences between MEMI and dexpanthenol groups. Histological analysis (after 14 days) shows a similar architecture between MEMI treatment and normal skin. MEMI exhibits a reduction in edema. Staphylococcus epidermidis had an MIC of 2 mg/mL, while Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli reached 4 mg/mL. The MEMI showed no signs of toxicity. Therefore, this study demonstrates multiple targets that flavonoids and mangiferin of MEMI may present during the healing process.     

Kinetic study of nickel(II) complexation by pteroylglutamic acid

The kinetics of the complexation of NiII by pteroylglutamic acid have been studied in the 545 ∘C range, the ionic strength (0.6 M) being regulated with KNO3, in the 5.5–7.0pH range, using the stopped-flow method. Under the experimental conditions two processes were observed. The faster process was detected in the millisecond range and is associated with the reaction between NiII and the ligand. The slower is observed within a few seconds. Complementary equilibrium studies were made at 25 ∘C. The results are consistent with the formation of a 1:1 complex between the reactants, and a mechanism is proposed to account for the observed behaviour. Equilibrium constants for the NiII plus pteroylglutamic acid system, as well as activation parameters, are reported. This revised version was published online in June 2006 with corrections to the Cover Date.