Behavior Of Solutions Research Articles

Dimolybdenum (II,II) paddlewheel complexes bearing non-steroidal anti-inflammatory drug ligands: Insights into the chemico-physical profile and first biological assessment

Multinuclear complexes are metal compounds featured by adjacent bound metal centers that can lead to unconventional reactivity. Some M2L4-type paddlewheel dinuclear complexes with monoanionic bridging ligands feature promising properties, including therapeutic ones. Molybdenum has been studied for the formation of multiple-bonded M2+ compounds due to their unique scaffold, redox, and spectroscopic properties as well as for applications in several fields including catalysis and biology. These latter are much less explored and only sporadic studies have been carried out. Here, a series of four dimolybdenum (II,II) carboxylate paddlewheel complexes were synthesized using different Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) as ligands. The reaction of (NH4)5[Mo2Cl9]·H2O with the selected NSAIDs in methanol produced the complexes Mo2(μ-O2CR)4 where RCO2 is ibuprofen (1), naproxen (2), aspirin (3) and indomethacin (4). The products were obtained in good yields and extensively characterized with integrated techniques. Stability and solution behaviour were studied using a mixed experimental and computational approach. Finally, the biological activity of 1 and 3 (i.e. the most reactive and the most stable compounds of the series, respectively) was preliminarily assessed confirming the disassembling of the molecules in the biological milieu. Overall, some very interesting results emerged for these unconventional compounds from a mechanistic point of view.

Dynamical behavior of analytical soliton solutions to the Kuralay equations via symbolic computation

Dynamical behavior of analytical soliton solutions to the Kuralay equations via symbolic computation

Surface activity, wettability and foam properties of quaternary ammonium surfactants with C-F/Si-H double hydrophobic backbone

This paper reported the synthesis of a novel quaternary surfactant (PFAS-Si) containing the C-F/Si-H double hydrophobic skeleton and the surface properties of its aqueous solution, which were investigated in comparison with those of the aqueous solutions of the fluorosurfactant (PFAS-IEt) and silicone surfactant (TMSAC) with similar hydrophobic chain structures. The critical micelle concentration (CMC) and the corresponding surface tension value (γCMC) of the PFAS-Si solution were 0.0612 mmol/L and 21.02 mN/m, respectively, which indicated that the PFAS-Si could substantially reduce the surface tension of water, and showed excellent surface activity. Meanwhile, the thermodynamic parameters of the micellization process, aggregation behavior, wettability, and foam properties of PFAS-Si solutions were systematically investigated. On the TEM negative staining photographs, it can be clearly seen that the aggregates of PFAS-Si in aqueous solution exhibit hollow spherical vesicles. In addition, the PFAS-Si solution exhibited superb wettability, and could achieve wetting of PTFE sheets at a very low concentration (0.168 mmol/L). Not only that, the PFAS-Si solution also had excellent foaming ability and foam stability. This work provided a new preparation idea for the development of high-performance specialty surfactants.

Osmotic dehydration with different agents induced pectin diversity: Physicochemical and structural properties of pectin from instant controlled pressure drop dried peach chips

Pectin as an important cell wall matrix that can be affected by osmotic dehydration (OD) pretreatment, determines the texture characteristics of dried fruit and vegetable products. This study investigated the effect of OD on the structural, thermal and rheological properties of pectin extracted from peach chips prepared by instant controlled pressure drop (DIC) drying. In detail, erythritol, glucose, and trehalose were selected as the osmotic agents (300 g/L). Pectin extracted from Ery-OD samples with a loose structure presented the highest molecular weight (432.9 kDa). The lowest content of arabinose (155.16 mg/g) and galactose (32.80 mg/g) were obtained in Glc-OD samples. With the infiltration of trehalose, the thermal stability of pectin was improved, which contributed to the uniform and complete network structure of pectin. 1H and 13C spectra analysis showed the significant alteration in pectin molecular structure induced by OD pretreatments, which affected the shear thinning behavior of pectin solution. Overall, the type of osmotic agents played a crucial role in the structural, thermal and rheological properties of pectin, which could reflect on the macro-texture characteristics of peach chips. This study would provide a theoretical basis for revealing the effect mechanism of OD on the texture of DIC fruit and vegetable chips at molecular level.

Experimental and Theoretical Studies of Nano-Silica Solutions in Narrow Flow Paths Applied to Sealing Cement Cracks

Summary A cement crack is a typical cause of oil and gas well failure. Cracks weaken cement, reducing zonal isolation and fluid leakage. Nanoparticle (NP) gels are being tested for fracture treatment. When crushed into cracks, the flow behavior of NP problem solutions should be predicted. The potential efficacy of utilizing NP gels as a remedial measure for fractures is currently under investigation. It would be advantageous to determine if the flow behavior of solutions for NP problems can be anticipated when they are compressed into crevices. This study aimed to analyze the behavior of nano-silica solutions as they flow through ducts with rectangular cross-sections and varying crack dimensions. The introduction of NP solutions into the core leads to a decrease in pressure, which suggests that the nano-silica has been effectively transported through the crack. As the size of the fracture decreases, there is a corresponding increase in pressure drops, while the flow rate experiences a concurrent increase. This study presents responses of a pressure gradient to fluid concentration for a range of fracture widths, heights, and flow rates. The prediction of laminar flow in ducts is based on the linear correlation between the flow rate and the pressure gradient. Furthermore, the reduced pressure gradient indicates enhanced fluid flow within the fracture because of the amplified slot width. The fluid flow model proposed by Guo et al. (2022) was utilized to conduct a comparative analysis with the experimental data. Compared with test data, the model differs by roughly 90%. The technical cause of the flow model-observed data discrepancies is unknown. The flow model did not account for friction between NPs-NPs and NPs-walls in rough ducts. An empirical correlation has been found that quantifies the ratio as a function of nonsilica solution flow rate, cross-sectional geometry parameters, and nano-silica concentration. The correlation was calculated using nonlinear regression. The empirical relation and actual ratio have a significant correlation, as shown by R2 = 0.8965. In practice, Guo et al.’s (2022) hydraulic model’s pressure drops should be multiplied by the empirical correlation’s ratio to reduce errors.

Evaluation of the Nonlinear Response of KCl Solution to High-Amplitude Stimulation Using a Four-Point Cylindrical Gold Electrode.

A four-electrode system and high-voltage amplitude stimulation (with a voltage of more than 1 V) are always used for nonlinear spectroscopy of biological solutions like yeast suspension. Multiple studies indicate that yeast membrane activities are the primary source of the harmonics detected from yeast suspensions. However, other investigations have demonstrated that at least part of the harmonics are mainly due to the nonlinear impedance of the electrode-electrolyte interface. Here, we want to find a mathematical model to analyze the odd harmonics generated by the interface. The KCl solution is the basis of the essential medium used in yeast culture. No study models the nonlinear behavior of the KCl solution using four-electrode. We used a sinusoidal voltage with a low frequency and a high amplitude to test an ionic solution with 1, 30, and 130 mM of potassium chloride. The voltage had no direct current component. Here, we show that the relationship between the amplitude of the excitation voltage and the third harmonic of the current can be accurately represented using the Butler-Volmer equation. Additionally, we analyze the impact of potassium chloride (KCl) concentration on the behavior of the third harmonic. This paper presents a method and model that can be used for nonlinear spectroscopy studies of biological solutions using a four-electrode system with the aim of deriving information from cells without considering the interface effect.

Two Methods Based on Integral Equation Approaches in Analyzing Polyelectrolyte Solutions: Macrophase Separation.

To understand the phase behaviors of polyelectrolyte solutions, we provide two analytical methods to formulate a molecular equation of state for a system of fully charged polyanions (PAs) and polycations (PCs) in a monomeric neutral component, based on integral equation theories. The mixture is treated in a primitive and restricted manner. The first method utilizes Blum's approach to charged hard spheres, incorporating the chain connectivity contribution by charged spheres via Stell's cavity function method. The second method employs Wertheim's multi-density Ornstein-Zernike treatment of charged hard spheres with Baxter's adhesive potential. The pressures derived from these methods are compared to available molecular dynamics simulations data for a solution of PAs and monomeric counterions as a limiting case. Two-phase equilibrium for the system is calculated using both methods to evaluate the relative strength of phase segregation that leads to complex coacervation. Additionally, the scaling exponents for a selected solution near its critical point are examined.

Multiscale Computational Study of Cellulose Acetate-Water Miscibility: Insights from Molecularly Informed Field-Theoretic Modeling.

Cellulose acetate (CA), a prominent water-soluble derivative of cellulose, is a promising biodegradable ingredient that has applications in films, membranes, fibers, drug delivery, and more. In this work, we present a molecularly informed field-theoretic model for CA to explore its phase behavior in aqueous solutions. By integrating atomistic details into large-scale field-theoretic simulations via the relative entropy coarse-graining framework, our approach enables efficient calculations of CA's miscibility window as a function of the degree of substitution (DS) of cellulose hydroxyl groups with acetate side chains. This allows us to capture the intricate phase behavior of CA, particularly its unique miscibility at intermediate substitution, without relying on experimental input. Additionally, the model directly probes CA solution behavior specific to the relative DS at C2, C3, and C6 alcohol sites, providing insights for the rational design of water-soluble CA for diverse applications. This work demonstrates a promising integration of molecularly informed field theories, complementing wet-lab experimentation, for engineering the next-generation polymeric materials with precisely tailored properties.

A Reduced-Symmetry Pd2L4 Cage from a Heterotopic Dipyridyl Ligand.

Two dipyridyl ligands, L3,3 and L3,4, have been used in combination with palladium(II) in the construction of metallosupramolecular species that show anion-dependent behavior in solution. A rare example of a low-symmetry (C2h) lantern-type cage is formed in one instance, [Pd2(L3,3)4]4+, while the isomeric ligand yields a larger double-walled square complex, [Pd4(L3,4)8]8+. [Pd2(L3,3)4](NO3)4 was isolated in crystalline form revealing two anions within the interior of the C2h-symmetry cage. The cage itself is held together by hydrogen bonding between "head-to-tail" pairs of ligands that reinforces the symmetry generated by the ditopic ligands. In solution, the cage with NO3- has sharp 1H nuclear magnetic resonance (NMR) signals at room temperature, while the BF4- analogue has broad signals that sharpen at higher temperatures or upon addition of (Bu4N)(NO3), highlighting the importance of the anion in templating or otherwise influencing self-assembly in solution. Altering the substitution position of one of the pyridyl rings yields a more "open" complex, with [Pd4(L3,4)8](NO3)8 being isolated as a crystalline solid. The double-walled square complex has a greater Pd···Pd separation due to the increased angle that the pyridyl groups subtend at the core of the ligand. NMR spectroscopy and mass spectrometry studies suggest a single species in the presence of nitrate but multiple species with tetrafluoroborate.

Stability of equilibrium states for a stochastic difference equation of exponential form

It is well know that many process and problems in different fields of sciences and engineering can be modelled by linear and nonlinear difference equations. Particularly, in case of systems biology, ecology, biochemistry, genetics and physiology dynamics, many population models are governed by exponential difference equations, and lot of papers were published in this matter. The goal of this work is to study a nonlinear second order difference equation of exponential form: Xn+1 = bXn + cXne−σXn−1, n ≥ 0 where the parameters b, c have arbitrary values, σ > 0 and the initial values, X0, X−1 are arbitrary positive numbers. Our equation has an equilibrium points and is exposed to additive stochastic perturbations that are assumed a sequence of independent random variables with zero mean, unit variance and these perturbations are proportional to the deviation of the system state Xn from equilibrium points, and the result is stochastic difference equation. We cannot find the solutions of nonlinear stochastic difference equations of exponential form in all cases. So, one can study the behavior of solutions by asymptotic stability of equilibrium points. Additionally, with the general method of Lyapunov functional constructions for stochastic difference equations with discrete time, we provide the necessary and sufficient conditions for the asymptotic mean square stability of the two equilibrium points (zero and positive) within the linear approximation of the stochastic difference equation. These conditions also serve as sufficient conditions for the stability in probability of the equilibrium points of the initial nonlinear equation. Finally, to demonstrate the validity of the obtained results, some numerical examples and simulations of equations solutions are made and numerous graphical illustrations of stability trajectories of solutions are plotted.

Pointwise estimates on the fundamental solution to nonlocal diffusion equation

In this article we study the pointwise behavior of the fundamental solution S ( t , x ) to the nonlocal diffusion model u t = D ( J ∗ u − u ) on R , S ( t , x ) can be written as e − Dt δ ( x ) + S 0 ( t , x ) , where S 0 ( t , x ) is called the regularizing part. Under some conditions on J and its Fourier transform J ^ , we obtain some new pointwise estimates on S 0 ( t , x ) . Then we apply our results to study the spatial dynamics of the nonlocal diffusion population model in a shifting environment considered in Li et al. [Spatial dynamics of a nonlocal dispersal population model in a shifting environment. J Nonlinear Sci. 2018;28:1189–1219]. In our study the convolution kernel J can be assumed to be more general, i.e. not necessarily of compact support, also the proof is greatly simplified. It is our believe that these pointwise estimates possess their own interest in further studying nonlocal diffusion models.

Rheological behavior and solution pH response properties of nanoparticle-regulated low surface tension systems.

Regarding the rheological properties of fluids, certain nanoparticles can markedly modify the rheological behavior of low surface tension solutions by interacting with surfactant molecules. In this work, a low surface tension fluid with cetyltrimethylammonium chloride was prepared, and the silica nanoparticles were uniformly dispersed into it by ultrasonic dispersion. By adjusting the size, shape, and concentration of nanoparticles, the fluid behavior can be changed from Newtonian to non-Newtonian with finely tuned viscosity and characterized by a shear-thinning rheological behavior. In addition, this work explored how variations in environmental temperature and solution pH affect the rheological responses of the low surface tension suspension system. The experimental findings revealed that increasing the temperature substantially decreases the system's viscosity and induces a shear-thickening behavior. It is particularly significant that, under extreme pH conditions (either strongly acidic or alkaline), the viscosity of the nanoparticle suspensions was markedly enhanced at a particle concentration of 10 000 ppm. This interesting result coincided with a notable reduction in the zeta potential and an increase in the average particle size, suggesting an intensified aggregation of particles within the suspension system. A mechanism detailing the interaction between silica nanoparticles and surfactant micelles was proposed. This work indicates that the incorporation of nanoparticles into surfactant solutions offers a powerful approach to modulating fluid rheology across various conditions.

Soliton, breather, lump, interaction solutions and chaotic behavior for the (2+1)-dimensional KPSKR equation

Nonlinear evolution equations are widely applied in various fields, and understanding their solutions is crucial for predicting and controlling the behavior of complex systems. In this paper, the (2+1)-dimensional Kadomtsev–Petviashvili–Sawada–Kotera–Ramani (KPSKR) equation is investigated, which has rich physical significance in nonlinear waves. Making use of Hirota’s bilinear form, soliton, breather and lump solutions of the (2+1)-dimensional KPSKR equation are derived. The interactions between lump solutions and exponential function, as well as between lump solutions and hyperbolic cosine function, are explored. Furthermore, the chaotic behavior of 1-soliton, 2-soliton, lump and interaction solutions are studied via applying the Duffing chaotic system. The physical structure and characteristics of begotten results are illustrated through 3D plots and corresponding two-dimensional profiles. These results indicate that the strategies utilized are more direct and effective, enriching the study of dynamics in high-dimensional nonlinear differential equations.

Existence and asymptotic behavior of solutions for nonhomogeneous Schrödinger–Poisson system with exponential and logarithmic nonlinearities

Existence and asymptotic behavior of solutions for nonhomogeneous Schrödinger–Poisson system with exponential and logarithmic nonlinearities

Dynamical behaviors of vector localized wave solutions for the coupled modified Korteweg-de Vries equations

Dynamical behaviors of vector localized wave solutions for the coupled modified Korteweg-de Vries equations

Hydrogel coating containing heparin and cyclodextrin/paclitaxel inclusion complex for retrievable vena cava filter towards high biocompatibility and easy removal

Aiming to improve the retrieval rate of retrievable vena cava filters (RVCF) and extend its dwelling time in vivo, a novel hydrogel coating loaded with 10 mg/mL heparin and 30 mg/mL cyclodextrin/paclitaxel (PTX) inclusion complex (IC) was prepared. The drug-release behavior in the phosphate buffer solution demonstrated both heparin and PTX could be sustainably released over approximately two weeks. Furthermore, it was shown that the hydrogel-coated RVCF (HRVCF) with 10 mg/mL heparin and 30 mg/mL PTX IC effectively extended the blood clotting time to above the detection limit and inhibited EA.hy926 and CCC-SMC-1 cells' proliferation in vitro compared to the commercially available bare RVCF. Both the HRVCF and the bare RVCF were implanted into the vena cava of sheep and retrieved at at 2nd and 4th week after implantation, revealing that the HRVCF had a significantly higher retrieval rate of 67 % than the bare RVCF (0 %) at 4th week. Comprehensive analyses, including histological, immunohistological, and immunofluorescent assessments of the explanted veins demonstrated the HRVCF exhibited anti-hyperplasia and anticoagulation properties in vivo, attributable to the hydrogel coating, thereby improving the retrieval rate in sheep. Consequently, the as-prepared HRVCF shows promising potential for clinical application to enhance the retrieval rates of RVCFs.

A Method for Efficiently Predicting the Radial Distribution Function and Osmotic Coefficients of Aqueous Electrolyte Solutions.

The prediction of the structural and thermodynamic properties of electrolyte solutions is critical for a huge range of practical situations where these solutions play a vital role. Theoretical models, such as the continuum solvent model, attempt to explain the behavior of solutions using a coarse-grained description of the interactions of species in the solution, whereas molecular simulations aim to directly compute the behavior of the solution, including the interactions between all ions and molecules in the system. Both methods have limitations: theoretical models are generally less accurate because they rely on assumptions, while molecular simulations require significant computational resources, particularly if higher accuracy is desired. To address these issues, we propose an affordable and effective method that combines the advantages of the modified Poisson-Boltzmann equation (MPBE) with classical molecular dynamics (MD) simulations to predict the radial distribution functions and thermodynamic properties of electrolyte solutions. We demonstrate a method of using the MPBE to compute the short-range potential of mean force (PMF) from the radial distribution functions (RDFs) and vice versa. Furthermore, we provide insights into the relationship between the RDFs and the short-range PMF based on the MPBE. Our analysis reveals that the effective short-range PMFs can be approximately calculated using low concentration simulations but the short-range PMFs are slightly concentration-dependent in simulations at higher concentrations. Additionally, we demonstrate that for concentrated solutions, osmotic coefficients can be calculated in agreement with experiment using a virial approach. This is based on the effective short-range PMFs and RDFs obtained from the MPBE method. Our proposed MPBE can therefore accelerate the calculation of the structural and thermodynamic properties of electrolyte solutions.

Corrosion Performance of Cu Doped AlCrFeNiMn HEA Synthesized via Arc-Melting

The development of novel corrosion resistant components is essential since malfunction of materials like super alloys during industrial applications might cause financial loss. Arc-melting and casting were used to create AlCrFeCuNi high entropy alloys (HEAs), which were then doped with various atomic percentages of copper (Cu). Investigations were conducted into the effects of Cu on the evolution of microstructural features, corrosion behavior in various solutions, nano hardness, and thermal stability. The alloy samples had a dendritic microstructure with three different phase zones, as seen by scanning electron micrographs, and EDS validated the elements that were included into the alloys. The behavior of the HEAs’ nano hardness and corrosion resistance significantly improved with the addition of Cu. In NaOH and Na2SO4 solutions, 3 at.% Cu samples demonstrated superior resistance to corrosion. With NaCl and H2SO4 solutions, 5 at.% Cu samples displayed greater corrosion resistance. The sample with 1 at.% Cu showed superior corrosion resistance in HCl solution.

Asymptotic Behavior of Solutions of the Nonstationary Schrödinger Equation on the Semi-Axis with a Potential Which Slowly Depends on Time

Asymptotic Behavior of Solutions of the Nonstationary Schrödinger Equation on the Semi-Axis with a Potential Which Slowly Depends on Time

Numerical simulation for an initial-boundary value problem of time-fractional Klein-Gordon equations

This paper mainly presents numerical solutions to an initial-boundary value problem of the time-fractional Klein-Gordon equations. We developed a numerical scheme with the help of the finite difference methods and the predictor-corrector methods to find numerical solutions of the considered problems. The proposed scheme is based on discretizing the considered problems with respect to spatial and temporal domains. Numerical results are derived for some illustrative problems, and the outputs are compared with the exact solution in the integer order case. The solution behavior and 3D graphics of the discussed problems are demonstrated using the proposed scheme. Finally, the proposed scheme, which does not require solving large systems of linear equations, can be extended and modified to handle other classes of time-fractional PDEs.