Quinone‐Rich Poly(dopamine) Magnetic Nanoparticles for Biosensor Applications

Novel core‐shell quinone‐rich poly(dopamine)–magnetic nanoparticles (MNPs) were prepared by using an in situ polymerization method. Catechol groups were oxidized to quinone by using a thermal treatment. MNPs were characterized by using X‐ray diffraction, X‐ray photoelectron spectroscopy, atomic force microscopy, magnetic force microscopy, UV/Vis, Fourier‐transform infrared spectroscopy, and electrochemical techniques. The hybrid nanomaterial showed an average core diameter of 17 nm and a polymer‐film thickness of 2 nm. The core‐shell nanoparticles showed high reactivity and were used as solid supports for the covalent immobilization of glucose oxidase (Gox) through Schiff base formation and Michael addition. The amount of Gox immobilized onto the nanoparticle surface was almost twice that of the nonoxidized film. The resulting biofunctionalized MNPs were used to construct an amperometric biosensor for glucose. The enzyme biosensor has a sensitivity of 8.7 mA M ^?1 cm^?2, a low limit of detection (0.02 mM ), and high stability for 45 days. Finally, the biosensor was used to determine glucose in blood samples and was checked against a commercial glucometer.     

Reactions of Phosphate Radicals with Monosubstituted Benzenes. A Mechanistic Investigation

The kinetics and reaction mechanism of phosphate radicals with substituted benzenes, PhX (X=OH, Me, H, Cl, MeO, and CHO), were studied by flash photolysis and continuous irradiation of aqueous solutions containing potassium peroxodiphosphate (K₄[(PO₃)₂O₂]). The rate constants for the reactions of phosphate radicals with the aromatic contaminants PhX were measured and the reaction intermediates and products detected. A correlation between the logarithm of the rate constant for every substrate with H₂PO₄^., HPO₄^.?, and PO₄^.2? and the logarithm of the dissociation constant K_a for H₃PO₄, , and was found. A general mechanism is proposed (Scheme 1), which accounts for the experimental results.     

Comparative study of the electronic structure of alkaline-earth borides (MeB2; Me=Mg, Al, Zr, Nb, and Ta) and their normal-state conductivity

By means of density functional theory the electronic structure of the MgB₂ superconductor was characterized and compared with that of the related iso-structural systems: AlB₂, ZrB₂, NbB₂, and TaB₂. Using the full potential-linearized augmented plane wave (FP-LAPW) method and the generalized gradient approximation, the electronic density distribution, density of states, and band structures were obtained for these compounds. The electrical conductivity, which cannot be easily measured in the c-direction, was calculated, in the relaxation time approximation using band structure results. It was found that the two-dimensional (2D) crystal structure character of these metallic diborides is also reflected in the electronic charge distribution. This 2D pattern is not reproduced in the electrical conductivity as it is, for instance, in the superconductor high T_c cuprates. The calculations indicate a bulk, yet anisotropic, conductivity for all these compounds.     

Reversible 1,4 migration of a silyl group from oxygen to carbon: an unexpected route to α-trialkylsilyl ketoximes

Anions generated from trialkylsilyl ethers of methyl ketoximes (1) undergo anionic rearrangement with 1,4 migration of the silyl group. After protonation, the resulting α-trialkylsilyl ketoximes (2), suffer thermal rearrangement with 1,4 migration of the silyl group from carbon to oxygen.     

Theoretical study of Aun clusters (n = 1–5) deposited on a rutile TiO2 (110) slab,concerning structure and stability

The initial nucleation of gold clusters Au_n (n = 1–5) on TiO₂ rutile (110) reduced surface is studied using density functional theory and a full-potential augmented-plane-wave method implemented in the WIEN2k code. The first two gold atoms remained tied to the surface with a bond length similar to those belonging to other well-known related materials, while the other gold atoms do not spread over the surface; they preferred to form a new layer. The occurrence of relativistic effects produced a preferential triangle geometry for Au₃ and a combination of triangular units for Au₄ and Au₅. The Au–Au average distance increased from n = 2 to n = 5, indicating an expansion with a tendency to the bond distance found in the bulk. We are reporting an early 2D→3D transition of small folding, from Au₃→Au₄, followed by an Au₄→Au₅ transition of evident 3D character.     

Plasma ions dynamics in the wake of a short laser pulse

A new physical effect of a plasma channel formation by the ponderomotive force of a wakefield generated by a laser pulse with a length of the order of the electron plasma wavelength is discussed. For a narrow pulse, wherein the width is less than c/omega(pe) ( omega(pe) and c are the plasma frequency and light velocity, respectively), the channel has an annular form with on-axis density maximum. The depth of the channel increases with the distance from the pulse until the phase mixing arises and the wake starts to break. The linear fluid theory is used to obtain the scaling for wave-breaking conditions. The results of numerical simulations for high intensity laser pulses are in good agreement with theoretical predictions.     

Advances in the generation of a new emulsified fuel

The development of a new emulsified fuel is described, from the conceptual idea to the semi-industrial tests of the final product. The starting point was the necessity to lower the particulate matter (PM) emissions produced by the combustion of more than 200 MBD of heavy fuel oil (HFO) used for electric power conversion. The major component of HFO is a vacuum residue of the oil refining process mixed with light cycle oils to make it pumpable. An alternative to handle and burn the high viscosity residue (solid at room temperature) is by converting it in an oil-in-water emulsion. The best emulsions resulted of 70% residue in 30% water, Sauter Mean Diameter of 10–20 μm and a stability of more than 90 days. Spray burning tests of the emulsion against HFO in a semi-industrial 500 kW furnace showed a reduction in PM emissions of 24–36%.     

An augmented velocity–vorticity–pressure formulation for the Brinkman equations

This paper deals with the analysis of a new augmented mixed finite element method in terms of vorticity, velocity, and pressure, for the Brinkman problem with nonstandard boundary conditions. The approach is based on the introduction of Galerkin least‐squares terms arising from the constitutive equation relating the aforementioned unknowns and from the incompressibility condition. We show that the resulting augmented bilinear form is continuous and elliptic, which, thanks to the Lax–Milgram theorem, and besides proving the well‐posedness of the continuous formulation, ensures the solvability and stability of the Galerkin scheme with any finite element subspace of the continuous space. In particular, Raviart–Thomas elements of any order for the velocity field, and piecewise continuous polynomials of degree k + 1 for both the vorticity and the pressure, can be utilized. A priori error estimates and the corresponding rates of convergence are also given here. Next, we derive two reliable and efficient residual‐based a posteriori error estimators for this problem. The ellipticity of the bilinear form together with the local approximation properties of the Clément interpolation operator are the main tools for showing the reliability. In turn, inverse inequalities and the localization technique based on triangle‐bubble and edge‐bubble functions are utilized to show the efficiency. Finally, several numerical results illustrating the good performance of the method, confirming the properties of the estimators and showing the behavior of the associated adaptive algorithms, are reported. Copyright © 2015 John Wiley & Sons, Ltd.