Štúdium vplyvu chloridov a bromidov na kritickú micelovú koncentráciu a parciálny mólový objem kvartérnej amóniovej soli

The critical micelle concentration (CMC) of the selected surfactant belonging to quaternary ammonium salts with chemical designation N,N-dimethyl-N-(3-((1R,5S)-1,8,8-trimethyl-2,4-dioxo-3-azabicyclo[3.2.1]octane-3yl)propyl)hexadecane-1-amine bromide was determined. Simultaneously, the effect of the addition of various concentrations of NaCl, KCl, NaBr, and KBr salts on the CMC value of the substance was observed and compared with those obtained in an aqueous solution at T = 296,15 K. Based on the results obtained, it was concluded that NaCl and KCl salts decreased the critical micelle concentration, while NaBr and KBr salts did not support micellization and CMC values therefore increased. In the case of solutions of a substance in the salt environment, when compared to the substance's solution in distilled water, a decrease in partial molar volume was observed. From the concentration density dependencies of the substance, an ionization degree of α was determined. Finally, the molar Gibbs energy ∆G° was also calculated and found negative for all salt solutions, while increase with their increasing concentration.

Вероятности оже-переходов и сечения эмиссии электронов при распаде вакансии на 2pπ-орбитали в квазимолекуле Ne-=SUP=-+-=/SUP=--Ne

The Auger transition probabilities are calculated while filling a vacancy on 2pπ orbital in a Ne+-Ne quasimolecule, a short-lived system which is formed when ion and atom approach each other and decays when they scatter. For the first time calculations were performed for various degrees of particles ionization in quasimolecule. It was found that with increase of collision energy and decrease of distance of the closest approach of particles the system ionization degree increases very significantly (from 2 to 6). Using of the quantum mechanical approach and taking into account the dynamics of collisions made it possible for the first time to describe quantitatively the experimental spectra of Auge electrons for a complex many-electron quasimolecule. From the whole variety of possible Auger decay channels the dominant contribution of the transition was established, from the initial 3dπ-3dπ state to the 2pπ orbital.

Sustainability of active bulk plasma with high electronegativity incapacitive high frequency plasma

In a high-frequency capacitively coupled plasma (HF-CCP), few studies have been carried out for the transport of charged particles in the active bulk plasma with high electronegativity. The electric field E(t), specifically, time-varying reduced field E(t)/Ng provides key knowledge about the characteristics of collisional bulk plasma. Numerical modeling is the only method for estimating E(t)/Ng, while a limited number of collision cross sections and related transport parameters are available. Under these circumstances, we discuss how to estimate the reduced field E(t)/Ng, i.e., E(t) in active bulk plasma with high electronegativity in HF-CCP through investigation of the correlation between the DC-critical reduced field (E/Ng)Crit: and the HF-effective reduced field (E(t)/Ng)eff . Our previous discussion on the correlation is validated by increasing the number of results of (E(t)/Ng)eff . The relation between the electronegativity and the ionization degree is derived from the sustainable condition in the bulk plasma.

The pH-dependent Swelling of Weak Polyelectrolyte Hydrogels Modeled at Different Levels of Resolution

The swelling of polyelectrolyte hydrogels has been often explained using simple models derived from the Flory-Rehner model. While these models qualitatively predict the experimentally observed trends, they also introduce strong approximations and neglect some important contributions. Consequently, they sometimes incorrectly ascribe the observed trends to contributions which are of minor importance under the given conditions. In this work, we investigate the swelling properties of weak (pH-responsive) polyelectrolyte gels at various pH and salt concentrations, using a hierarchy of models, gradually introducing various approximations. For the first time, we introduce a three-dimensional particle-based model which accounts for the topology of the hydrogel network, for electrostatic interactions between gel segments and small ions and for acid-base equilibrium coupled to the Donnan partitioning of small ions. This model is the most accurate one, therefore, we use it as a reference when assessing the effect of various approximations. As the first approximation, we introduce the affine deformation, which allows us to replace the network of many chains by a single chain, while retaining the particle-based representation. In the next step, we use the mean-field approximation to replace particles by density fields, combining the Poisson-Boltzmann equation with elastic stretching of the chain. Finally, we introduce an ideal gel model by neglecting the electrostatics while retaining all other features of the previous model. Comparing predictions from all four models allows us to understand which contributions dominate at high or low pH or salt concentrations. We observe that the field-based models overestimate the ionization degree of the gel because they underestimate the electrostatic interactions. Nevertheless, a cancellation of effects on the electrostatic interactions and Donnan partitioning causes that both particle-based and field-based models consistently predict the swelling of the gels as a function of pH and salt concentration. Thus, we can conclude that any of the employed models can rationalize the known experimental trends in gel swelling, however, only the particle-based models fully account for the true effects causing these trends. The full understanding of differences between various models is important when interpreting experimental results in the framework of existing theories and for ascribing the observed trends to particular contributions, such as the Donnan partitioning of ions, osmotic pressure or electrostatic interactions.

Approximate Solution of the Thomas–Fermi Equation for Free Positive Ions

The approximate solution of the nonlinear Thomas–Fermi (TF) equation for ions is found by the Fermi method. The solution is based on the new asymptotic representation of the TF ion size valid for any ionization degree. The two universal functions and their derivatives, introduced by Fermi, are calculated by recent effective algorithms for the Emden–Fowler type equations with the accuracy sufficient for majority of applications. The comparison of our results with those obtained previously shows high accuracy and validity for arbitrary values of ionization degree. This study could potentially be of interest for the statistical TF method applications in physics and chemistry.

Specific features of praseodymium extraction by intergel system based on polyacrylic acid and poly-4-vinylpyridine hydrogels

Some technological solutions contain valuable components and can become an additional source of rare-earth elements to satisfy the current production demands. This research provides the study on using a combination of polyacrylic acid hydrogel (hPAA) and hydrogel of poly-4-vinylpyridine (hP4VP) in different molar ratios for praseodymium ions sorption from its nitrate solution. The mutual activation of the hydrogels in an aqueous medium provides their transformation into a highly ionized state by the conformational and electrochemical changes in properties during their remote interaction. The electrochemical properties of solutions were studied by the methods of electrical conductivity, and pH measurements of the solutions. The research showed that the maximum activation of hydrogels was revealed within the molar ratio of hPAA:hP4VP equal to 1:5. Moreover, the total praseodymium ions sorption degree after 24 hours of sorption by individual hPAA and hP4VP was 54 % and 47 %, respectively, whereas the praseodymium ions sorption degree by the hPAA–hP4VP intergel system in the molar ratio 1:5 became 62 %. A slight increase in the sorption degree of praseodymium ions by the intergel system in comparison with individual hydrogels can be explained by the achievement of a higher ionization degree of hydrogels being activated in the hPAA–hP4VP interpolymer system by the remote interaction effect.

Effect of constant collision mean free time on the boundary layer of the active collisional warm plasma

The plasma boundary layer is analyzed for a plasma in contact with a conducting plain surface where the ion temperature is comparable with the electron temperature and the plasma pressure is sufficiently high. The variations of electrical potential from the plasma-presheath boundary to the wall is studied using the fluidal formalism of plasma in three approaches; plasma and sheath asymptotic solutions and full solution. In the full solution approach, fluidal equations lead to a singularity when the ion velocity reaches the ion thermal speed. It is shown that removing the singularity causes a well-defined eigenvalue problem and leads to smooth solutions for the model equations. Some of the applicable aspects such as the floating velocity and density of ions, the floating electrical potential and an estimation of the floating thickness of the boundary layer are obtained. The dependency of these quantities on the ionization degree, the ion temperature and ion-neutral collision is examined too.

Ion Exchange Dynamics in Cerium Nitrate Solution Regulated by Remotely Activated Industrial Ion Exchangers

Many technological solutions contain valuable components as waste and can become an additional source of rare-earth elements to meet the needs of modern production. The development of technologies based on commercially available and cheap sorbents reveals the possibility for rare earth recovery from various solutions. This paper provides research on using a combination of KU-2-8 and AV-17-8 ion exchangers in different molar ratios for cerium ions sorption from its nitrate solution. The mutual activation of the ion exchangers in an aqueous medium provides their transformation into a highly ionized state by the conformational and electrochemical changes in properties during their remote interaction. The ion exchange dynamics of solutions were studied by the methods of electrical conductivity, pH measurements, and atomic emission analysis of the solutions. The research showed that the maximum activation of polymers was revealed within the molar ratio of KU-2-8:AV-17-8 equal to 3:3. In more detail, in comparison to AV-17-8, this interpolymer system showed an increase in the sorption degree by more than 1.5 times after 6 h of interaction. Moreover, compared with KU-2-8, the same interpolymer system showed an increase in the degree of cerium ions sorption by seven times after 24 h of interaction. As a result, the total cerium ions sorption degree after 48 h of sorption by individual KU-2-8 and AV-17-8 was 38% and 44%, respectively, whereas the cerium ions sorption degree by the same interpolymer system in the molar ratio 3:3 became 51%. An increase in the sorption degree of cerium ions by the interpolymer system in comparison with individual ion exchangers can be explained by the achievement of a high ionization degree of ion exchangers being activated in the interpolymer system by the remote interaction effect.

Growth of Magnetorotational Instability in Circumstellar Disks around Class 0 Protostars

We investigate the possibility of the growth of magnetorotational instability (MRI) in disks around Class 0 protostars. We construct a disk model and calculate the chemical reactions of neutral and charged atoms, molecules and dust grains to derive the abundance of each species and the ionization degree of the disk. Then, we estimate the diffusion coefficients of non-ideal magnetohydrodynamics effects such as ohmic dissipation, ambipolar diffusion and the Hall effect. Finally, we evaluate the linear growth rate of MRI in each area of the disk. We investigate the effect of changes in the strength and direction of the magnetic field in our disk model and we adopt four different dust models to investigate the effect of dust size distribution on the diffusion coefficients. Our results indicate that an MRI active region possibly exists with a weak magnetic field in a region far from the protostar where the Hall effect plays a role in the growth of MRI. On the other hand, in all models the disk is stable against MRI in the region within <20 au from the protostar on the equatorial plane. Since the size of the disks in the early stage of star formation is limited to ≲ 10–20 au, it is difficult to develop MRI-driven turbulence in such disks.