Linear Free‐Energy Relationships Applied to the 13C NMR Chemical Shifts in 4‐Substituted N‐[1‐(Pyridine‐3‐ and ‐4‐yl)ethylidene]anilines

Two series of 4‐substituted N‐[1‐(pyridine‐3‐ and ‐4‐yl)ethylidene]anilines have been synthesized using different methods of conventional and microwave‐assisted synthesis, and linear free‐energy relationships have been applied to the ¹³C NMR chemical shifts of the carbon atoms of interest. The substituent‐induced chemical shifts have been analyzed using single substituent parameter and dual substituent parameter methods. The presented correlations describe satisfactorily the field and resonance substituent effects having similar contributions for C1 and the azomethine carbon, with exception of the carbon atom in para position to the substituent X. In both series, negative ρ values have been found for C1′ atom (reverse substituent effect). Quantum chemical calculations of the optimized geometries at MP2/6‐31G++(d,p) level, together with ¹³C NMR chemical shifts, give a better insight into the influence of the molecular conformation on the transmission of electronic substituent effects. The comparison of correlation results for different series of imines with phenyl, 4‐nitrophenyl, 2‐pyridyl, 3‐pyridyl, 4‐pyridyl group attached at the azomethine carbon with the results for 4‐substituted N‐[1‐(pyridine‐3‐ and ‐4‐yl)ethylidene]anilines for the same substituent set (X) indicates that a combination of the influences of electronic effects of the substituent X and the π₁‐unit can be described as a sensitive balance of different resonance structures.     

Deposition of Gold Nanoparticles on Polypropylene Nonwoven Pretreated by Dielectric Barrier Discharge and Diffuse Coplanar Surface Barrier Discharge

The aim of this study was to examine and compare the potentials of two different ambient air plasma treatments: volume dielectric barrier discharge and diffuse coplanar surface barrier discharge, for the activation of polypropylene (PP) nonwovens surface. This was done in order to enhance the deposition of gold nanoparticles (AuNPs) onto PP surface. AuNPs were attached onto PP surface from colloidal solution prepared without stabilizers. Scanning electron microscopy, atomic force microscopy, attenuated total reflection-Fourier transform infrared spectroscopy, water absorption, and AuNPs uptake were used to assess the surface changes due to the plasma treatment, and to evaluate the durability of the achieved treatment effects. Finally, as a very important aspiration of the research, antibacterial activity of AuNPs loaded PP nonwovens against pathogens Staphylococcus aureus and Escherichia coli was evaluated in vitro. The plasma modified PP nonwovens have highly improved wetting and sorption properties. The PP nonwovens loaded with 17–62 mg/kg AuNPs exhibit antibacterial activity against tested pathogens. Surprisingly, this activity was enhanced by the first sample rinsing.     

Dynamic model of methane–water diffusion

This paper presents a mathematical model to describe the time evolution of the diffusion process of methane exchange between liquid and gaseous phases. In order to reach the equilibrium, the distribution of gas in the liquid phase decreases to a constant value over time. Generalized model is analyzed under the assumption that both, reversible and irreversible form of absorption and desorption, occur at the same time. For the application in case of the real system of methane–water, model is developed under the assumption that the processes of absorption and desorption are irreversible. From the experimental data are determined the coefficients of model and their dependence on initial conditions, with constant end conditions. This paper tests the introduced theoretical model on the existing experimental data.     

More on a hyperbolic‐cotangent class of difference equations

We present a natural method for solving the difference equation where , parameter a, and initial values x_?j, , , are real or complex numbers. As a concrete example, the case k = 1, l = 2 is studied in detail, and several interesting formulas for solutions and objects used in the analysis of the equation are given. A useful remark on solvability of difference equations on complex domains is presented and used here.     

Supersymmetric non-linear σ model onE 8/SO(10)×SU(3)×U(1)

We calculate the Kähler potential of theE ₈/SO(10)×SU(3)×U(1) homogeneous space. Some quasi Nambu-Goldstone fermions living in the corresponding supersymmetric non-linear σ model are identified with the usual three families of quarks and leptons, and one mirror family. We also show that the dynamical breakdown of supersymmetry does not occur in this model.     

Excitonic diffusion in thin molecular films

The analyses of exciton diffusion in thin molecular films have shown that the diagonal elements of the diffusion tensor, usually called diffusion coefficients, depend on the layer index labeling layers in the direction of disturbed symmetry. The particular analysis was done for a thin film having four layers. In this structure only two layers are occupied by optical excitations. It means that in the four layer film two films occur in which optical excitations can travel. The subfilm contains a boundary layer that noticeably differs from the subfilm with internal layers. If the subfilm contains the boundary layer, the diffusion coefficient of this layer differs from the diffusion coefficient of any internal layer. If the subfilm contains two internal layers, the diffusion coefficient of these layers are equal, expectably from the viewpoint of physics. The exciton diffusion is very low due to the high exciton energies. This work was supported by the Serbian Ministry of Science and Technology: Grant No 1895.     

Electrons in thin films

The method of evaluation of broken-symmetry Green’s function is presented. This method was applied to electron subsystem of a thin film. It was found that electron concentrations are spatially dependent and their spatial distribution proves the existence of skin effect. The skin effect is most expressed in the films of minimal thickness. The internal energy of electrons lying in the film Fermi volume, decreases with the increase of temperature. It is the consequence of the Pauli principle, which does not allow change of electron velocities. Introduced heat increases electron effective masses and this leads to the decrease of internal energy.     

Study of interaction between nitrogen DBD plasma-treated viscose fibers and divalent ions Ca2+ and Cu2+

Viscose fibers were treated with atmospheric pressure dielectric barrier discharge (DBD) plasma obtained in nitrogen in order to activate the fiber surface prior to sorption of the divalent ions Ca²⁺ and Cu²⁺. Methylene blue sorption was used for estimation of carboxyl group formation on the surface after DBD plasma treatment, through the degree of fabric staining (K/S). Sorption of divalent ions was performed from solutions of each individual ion and from solutions of calcium and copper in succession onto untreated and plasma-treated viscose samples. The quantity of sorbed metal was determined from the neutralization and iodometric titration method. Scanning electron microscopy coupled with energy dispersive X-ray analysis was used for fiber morphology and surface characterization before and after plasma treatment, and after metal ions sorption. Experiments revealed copper microparticles formation on the fiber surface when sorption of copper was performed on samples with bonded calcium. Further analysis confirmed that for growth of copper particles, both calcium ions and nitrogen DBD plasma pretreatments are necessary.     

Kinetics of Spontaneous Hydrolysis of O-(2,2-Dimethylcyclopentyl)-methylfluorophosphonate and of Hydrolysis During Constant pH Value of the Reaction Medium

Hydrolysis of O-(2,2-dimethylcyclopentyl)-methylfluorophosphonate in dilute aqueous solution was investigated. Rates of hydrolysis of O-(2,2-dimethylcyclopentyl)-methylfluorophosphonate were measured as a function of pH (in the range from 3 to 9 and without keeping the pH-value constant--in a spontaneous hydrolysis) and temperature (in the range from 25°;C to 40°;C). Objective of these investigations was to simulate real processes of degradation of highly toxic compounds in nature, getting information about rates of degradation, in order to obtain most efficient systems for their removal.