A Laccase/Chitosan‐Lambda‐Carrageenan Based Voltammetric Biosensor for Phenolic Compound Detection

In this contribution, a new concept of voltammetric catechol biosensor, based on the encapsulation of laccase (LAC) in a chitosan+lambda‐carrageenan (CHIT+CAR) polyelectrolyte complex (PEC) employing a simple coacervation process is presented. Chitosan (CHIT) was prepared from α‐chitin extracted from shrimp shells and lambda‐carrageenan (CAR) was extracted from red algae, both polysaccharides and PEC being characterized using FTIR spectrometry and electrochemistry. Cyclic voltammetry was utilized to determine the analytical features of the laccase (LAC) biosensor for catechol detection. The linear range was from 10^?20 M to 10^?14 M with a sensitivity of 1.55 mA/p[catechol] and a limit of detection of 3×10^?21 M.The laccase biosensor exhibits good repeatability (RSD 2.38 %) and stability (four weeks). The developed biosensor was tested by applying it to the evaluation of the total polyphenolic content in natural oil samples.     

Prestressed FRP and interface slip effect on interfacial stresses analysis: the new FRP sheets rigidity model

This paper presents an improved bi-material beam theory with adhesive interface and the new prestressed-fiber reinforced polymer (FRP) – model, which has been applied to the study the problem of interfacial stresses. This work explicitly considers the interfacial slip effect on the structural performance by including both the effect of adherend shear deformations and the fiber volume fraction of the prestressed laminates. This new method needs only one differential equation to determine both shear and normal interfacial stress, which is one aspect that has not been taken into account by the previous studies in the literature. A parametrical study is carried out to show the effects of some design variables, e.g., stiffness and thickness of adhesive layer and FRP plate.     

Palladium-catalysed direct arylation of heteroaromatics with functionalised bromopyridines

The regioselective 5-arylation of a variety of heteroaromatics with functionalised pyridyl bromides using palladium catalyst gives a simple access to functionalised heteroarylated pyridines. The target products were obtained in moderate to good yields using only 1 mol % PdCl(C₃H₅)(dppb) as the catalyst. Substituents, such as fluoro, acetyl, nitrile, nitro, methoxy or amino on the pyridyl bromide are tolerated. However, the nature of the substituents has an important influence on the yields. Electron-withdrawing substituent favours the reaction; whereas electron-donating are unfavourable.     

Global existence and stability of a nonlinear wave equation with variable-exponent nonlinearities

ABSTRACT

In this paper, we consider a nonlinear wave equation with damping and source terms of variable-exponent types. First, we use the stable-set method to prove a global result. Then, by applying an integral inequality due to Komornik, we obtain the stability result.     

Anti-Ferromagnetic Structure and Magnetic Properties of FeO with GGA+U+SOC Study

Physics of the Solid State - The magnetic stability and electronic properties of the FeO compound are investigated using the framework of an all-electron full-potential linearized augmented-plane...     

Temperature, pressure, and isotope effects on the structure and properties of liquid water: a lattice approach

We present a lattice model to describe the effect of isotopic replacement, temperature, and pressure changes on the formation of hydrogen bonds in liquid water. The approach builds upon a previously established generalized lattice theory for hydrogen bonded liquids [B. A. Veytsman, J. Phys. Chem. 94, 8499 (1990)], accounts for the binding order of 1/2 in water-water association complexes, and introduces the pressure dependence of the degree of hydrogen bonding (that arises due to differences between the molar volumes of bonded and free water) by considering the number of effective binding sites to be a function of pressure. The predictions are validated using experimental data on the temperature and pressure dependence of the static dielectric constant of liquid water. The model is found to correctly reproduce the experimentally observed decrease of the dielectric constant with increasing temperature without any adjustable parameters and by assuming values for the enthalpy and entropy of hydrogen bond formation as they are determined from the respective experiments. The pressure dependence of the dielectric constant of water is quantitatively predicted up to pressures of 2 kbars and exhibits qualitative agreement at higher pressures. Furthermore, the model suggests a--temperature dependent--decrease of hydrogen bond formation at high pressures. The sensitive dependence of the structure of water on temperature and pressure that is described by the model rationalizes the different solubilization characteristics that have been observed in aqueous systems upon change of temperature and pressure conditions. The simplicity of the presented lattice model might render the approach attractive for designing optimized processing conditions in water-based solutions or the simulation of more complex multicomponent systems.     

Speciation of Fe(II) and Fe(III) effect on CaCO3 crystallization

The present work was carried out to investigate separately the effect of Fe²⁺ and Fe³⁺ on the precipitation kinetics and the microstructure of CaCO₃. For this an experimental procedure was proposed. Precipitation tests were made by using the dissolved‐CO₂ degassing method. Both air and nitrogen were employed to strip the CO₂ from a Ca(HCO₃)₂ solution initially rich in this gas. At anoxic medium, it was shown that iron (II) prolongs the nucleation step and decelerates the crystalline growth rate. X‐ray diffraction analysis shows that its presence inhibits calcite and promotes aragonite variety. By using air, the reaction medium is rich in oxygen and iron (II) is rapidly oxidized. Seeing the higher solution pH (> 6.5), iron hydroxide forms before the onset of CaCO₃ precipitation and plays a role of seed permitting to initiate CaCO₃ nucleation. So, contrary to the observed effect of iron (II), the presence of iron (III) accelerates the precipitation rate of CaCO₃. As for iron (II), iron (III) inhibits calcite formation but favored the vaterite variety instead of the aragonite one.     

Crystal structure of a new pentadentate symmetrical: di[4-(phenylimino)pentan-2-one] ether. Structural and electrochemical studies of its Co<Superscript>II</Superscript>, Ni<Superscript>II</Superscript>, Cu<Superscript>II</Superscript> and Cd<Superscript>II</Superscript> complexes

The crystal structure of a new symmetrical pentadentate N₂O₃ Schiff base: di[4-(phenylimino)pentan-2-one] ether (H₂L) is described. In the solid state, the ligand appears as a keto-imine tautomer, while in DMSO solution, the eneamine form is observed. This ligand coordinates cobalt(II), nickel(II), copper(II) and cadmium(II). The structures of these new complexes are described using infrared and electronic spectroscopy, ¹H-n.m.r. and d.s.c. The cyclic voltammograms of the ligand and the complexes in DMF are discussed.     

Lithium Doping Effect for Enhancing Thermoelectric and Optoelectronic Performance of Co2NbAl

JETP Letters - Cobalt-rich Heusler compounds represent a very interesting family of Heusler alloys owing to their performance in spintronics and magnetic devices. The quaternary Heusler, created by...