Study of the inhibiting effect of a quaternary ammonium surfactants mixture synthesized from petroleum fraction (reformate) against the carbon steel corrosion in HCl 1 M

Quaternary ammonium cationic surfactants were synthesized from reformate, a liquid mixture of hydrocarbons (aromatics, naphthenes and paraffins), via chloromethylation/quaternization sequences. The petroleum surfactants thus obtained were evaluated as corrosion inhibitors for carbon steel in 1 M HCl, by gravimetry, potentiodynamic polarization and electrochemical impedance spectroscopy. The corrosion inhibiting efficiency was assessed as functions of surfactant concentration. The results showed that the inhibiting efficiency increased with surfactant concentration; its optimal value of 70 % was for a surfactant concentration of 320 mg/L at 25 °C. Potentiodynamic polarization measurements showed that the mixture acts as a mixed type inhibitor. The corrosion inhibiting mechanism is thought to proceed via an adsorption of the surfactant molecules on the steel surface, generating a film and hindering the active sites. Our experimental adsorption data were found to obey the Langmuir adsorption isotherm. SEM images of the treated specimens, revealing the likely formation of a protective film, demonstrated the inhibiting capacity of the petroleum quaternary ammonium surfactants against the carbon steel corrosion.     

Copper(II) trimethylacetate complexes with 3,5-dimethylpyrazole

Specific features of the chemical behavior and structure of copper(II) trimethylacetate complexes with 3,5-dimethylpyrazole have been considered based on X-ray crystallographic data.     

A Label-Free Biosensor for Protein Detection Based on Ring Slots in a Photonic Crystal

Journal of Russian Laser Research - We design a miniaturized and highly-sensitive biosensor based on a photonic-crystal aslant cavity (AC) to detect protein concentrations. The AC has seven ring...     

Strong isochronism of polynomial reversible dynamical systems on the plane with homogeneous nonlinearities of degree 4

We find the maximum order and initial polar angle of strongly isochronous two-dimensional polynomial reversible systems with homogeneous nonlinearities of the fourth degree.     

Construction of a linear Pfaff system of Fuchsian type with algebraic manifold of singularities

We present a constructive proof of the existence of a two-dimensional completely integrable Fuchsian Pfaff system on CP ⁿ with four singular surfaces forming a pencil, with 2-step solvable monodromy group, and with fundamental solution matrix realizing a given homomorphism.     

Cyphostemmins A-B, two new antifungal oligostilbenes from Cyphostemma crotalarioides (Vitaceae)

Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and ¹H and ¹³C NMR spectroscopic data.     

Nanomaterials in mass spectrometry ionization and prospects for biological application

The rapid development of nanotechnology has revolutionized scientific developments in recent decades. Mass spectrometry (MS) measurements are no exception and have benefited greatly from integration of nanomaterials in every step of analysis. This brief review summarizes recent developments in the field with the focus on the use of nanomaterials as alternative media to facilitate analyte ionization in laser-desorption ionization–mass spectrometry (LDI–MS) and secondary ion mass spectrometry (SIMS). The biological applications of both techniques are also detailed. The use of nanomaterials in other aspects of MS analysis, for example in sample clean-up and indirect analyte quantification, is briefly discussed.     

On the Lévy–Khintchine representation of q-Bessel negative definite functions

We study q-Bessel negative definite functions and use their properties to give a proof of Lévy–Khintchine representation of q-infinitely divisible probability measures.     

General Decay Rate for Nonlinear Thermoviscoelastic System with a Weak Damping and Nonlinear Source Term

Mediterranean Journal of Mathematics - In this paper, we consider a nonlinear system of thermoviscoelastic with a nonlinear boundary damping and nonlinear source, in a bounded domain Ω, under...     

Adhesion of protective coatings with modified filler

The effect of physical (ultrasonic) and chemical (exposure in 3% solution of acetic acid) activation of filler on the adhesion strength of the protective coatings based on styrene–acrylic dispersions to different substrates is studied. It is shown that modification of kaolins allows one to increase the adhesion strength by 40–50% in the case of the physical activation and by 1.1–1.2 times in the case of chemical activation. The best results are achieved with the use of E-21 dispersion as the polymer matrix.