Search Results (122)

This study investigated the role of synthetic mucus coatings in enhancing the physiological relevance of in vitro nasal spray deposition assessments using 3D-printed nasal cavity models. Synthetic mucus solutions, representing normal (0.25% w/v xanthan gum) and diseased (1% w/v xanthan gum) nasal conditions, were developed to mimic the viscoelastic properties of human nasal mucus. Their physical properties, including viscosity, surface tension, contact angle, and adhesivity on dry and synthetic mucus-coated stereolithography (SLA) surfaces, were systematically characterized. Comparative experiments evaluated the behavior of saline drops and liquid films on dry versus synthetic mucus-coated SLA surfaces at inclinations of 30°, 45°, and 60°. Observational deposition experiments using anatomically accurate nasal models were conducted under a 45° backward-tilted head position with gentle sniff airflow across uncoated, 0.25% w/v mucus-coated, and 1% w/v mucus-coated surfaces. Synthetic mucus coatings significantly influenced saline spray deposition patterns. On uncoated surfaces, deposition consisted of scattered droplets and limited film formation, mainly in the anterior and turbinate regions. In contrast, synthetic mucus coatings facilitated broader and more uniform liquid distribution due to diffusion and lubrication effects. These findings highlight the value of synthetic mucus coatings for better simulating nasal environments, offering insights to optimize nasal spray formulations and delivery devices. Full article

The well-known Poisson–Nernst–Planck model is a classical approach usedto describe ion transport in liquids. Extended versions of this model account for thegeneration–recombination of ions at equilibrium. In this paper, we investigate the influenceof the generation–recombination term on dielectric relaxation in an electrolytic cell shapedlike a slab, bounded by two parallel blocking electrodes. We show that in the adiabaticlimit—which holds when the reaction time is much longer than the dielectric relaxationtime—the electric current in the external circuit does not follow a simple relaxation mechanism.Instead, it is characterized by two distinct relaxation times: a short relaxationtime associated with dielectric relaxation and a longer relaxation time related to the iondissociation–association process. Conversely, this information could be used to assess thepresence and/or significance of the generation–recombination effect in an electrolytic cell. Full article

This work provides a comprehensive picture of the advances that the exponential expansion theory (EET) of autocorrelation functions relevant to liquids dynamics made possible in the last decade up to very recent times. The role of both longitudinal and transverse collective excitations in liquids is investigated by studying the main autocorrelation functions typically obtained either experimentally (when possible) or through molecular dynamics simulations. Examples for some classes of liquids are provided, especially intended for the understanding of dispersion curves, i.e., the collective mode frequencies as a function of the wavevector Q, which is inversely proportional to the length scale at which microscopic processes are probed. The main result of this work is the ubiquitous observation that the EET method works extremely well for all considered autocorrelation functions or spectra, either experimental or simulated. This paper provides also, in its final part, important hints for future research, based on an integration of the EET lineshape description within Bayesian inference analysis. Full article

Ionic liquids exhibit distinctive solvation and reactive properties, making them highly relevant for applications in energy storage, catalysis, and CO₂ capture. However, their complex molecular interactions, including proton transfer and physisorption/chemisorption, necessitate advanced computational efforts to model them at the atomic scale. This review examines key molecular dynamics approaches for simulating ionic liquid reactivity, including quantum-mechanical methods, conventional reactive force fields such as ReaxFF, and fractional force fields employed in PROTEX. The strengths and limitations of each method are assessed within the context of ionic liquid simulations. While quantum-mechanical simulations provide detailed electronic insights, their high computational cost restricts system size and simulation timescales. Reactive force fields enable bond breaking and formation in larger systems but require extensive parameterization. These approaches are well suited for investigating reaction pathways influenced by the local environment, which can also be partially addressed using multiscale simulations. Fractional force fields offer an efficient alternative for simulating significantly larger reactive systems over extended timescales. Instead of resolving individual reaction mechanisms in full detail, they incorporate reaction probabilities to model complex coupled reactions. This approach enables the study of macroscopic properties, such as conductivity and viscosity, as well as proton transport mechanisms like the Grotthuß process—phenomena that remain inaccessible to other computational methods. Full article

Based on data from broadband dielectric spectroscopy (BDS) and a molecular model based on the Landau–de Gennes concept, the effect of confinement on the structural, dielectric, and dynamic properties of 4-n-pentyl-4′-cyanobiphenyl (5CB) in the nematic phase is studied. The dielectric permittivity and relaxation times were previously obtained by the BDS technique in a wide frequency range ($1\mathrm{MHz}\le \mathrm{f}\le 1\mathrm{GHz}$) in the nematic phase composed of 5CB molecules confined to Anopore membranes with pore sizes of 0.2 $\mathsf{\mu }$m. The distance-dependent values of the order parameter $P_2\left(r\right)$, the relaxation time $\tau \left(r\right)\equiv {\tau }_{00}^1\left(r\right)$, the rotational diffusion coefficient $D_{\perp }\left(r\right)$, and both rotational viscosity coefficients ${\gamma }_i\left(r\right)$ ($i=1,2$) as functions of the distance r away from the bounding surface are calculated by a combination of existing statistical-mechanical approaches and data obtained by the BDS technique. Reasonable agreement between the calculated and experimental values of ${\gamma }_i(i=1,2)$ for bulk 5CB is obtained. Full article

Dimer and trimer acids are interesting viscous liquids produced from fatty acids derived from renewable sources. The chemical structures of dimer and trimer acids are known and quite complex and are presented here, discussed and further elucidated through electronic absorption spectroscopy, FT-IR and Raman spectroscopy. Dimer and trimer acids have a number of applications in their original form or in the form of derivatives. In the present study, a series of esters of dimer and trimer acids with alcohols from renewable sources were synthesized for use as plasticizers for rubber and plastics. The polarity of the dimer and trimer acids as well as their esters with alcohols from renewable sources (dimerates and trimerates) were systematically studied using a Nile red solvatochromic probe. The resulting E(NR) values were compared with the E(NR) values of the most common types of rubber and plastics. Compatibility and other physical properties expected from the E(NR) scale were studied and successfully confirmed in tire tread rubber compound formulations and in nitrile rubber and PVC matrices, confirming once again the sensitivity and the validity of the Nile red solvatochromic polarity scale for the development of new plasticizers. The validity of the liquids polarity measured with the Nile Red dye is supported by the correlation found between the E(NR) scale and the dielectric constants (ε) of carboxylic acids (including dimer and trimer acids, hydrogenated dimer acids and isostearic acid) and alcohols. A correlation was even found linking the E(NR) values the with the ε values of thin solid films of rubbers and plastics. In the case of the esters the correlation of their E(NR) values was found with the length of the aliphatic chains of the alcohols used in the esterification. Full article

Utilizing the shake-flask technique under atmospheric pressure (101 kPa) within the temperature range of 293.2 to 313.2 K, the experimental solubility and density values of deferiprone were determined in binary mixtures of polyethylene glycol 400 and 1-propanol. The mole fraction solubility of deferiprone exhibited an augmentation with elevated temperature and increased polyethylene glycol 400 mass ratio in polyethylene glycol 400 + 1-propanol compositions. A subsequent regression analysis of the solubility data was conducted employing the van’t Hoff, λh, Yalkowsky, modified Wilson, Jouyban–Acree and Jouyban–Acree–van’t Hoff models upon the comprehensive evaluation of the entire dataset; the van’t Hoff equation demonstrated the most favorable regression. Furthermore, the findings of this study hold significance for advancing the understanding of the basic thermodynamic data pertinent to the crystallization and industrial separation processes of deferiprone. Full article

When examined at the nanometer length scale, metallic liquids exhibit extensive ordering. Bonding enthalpies are balanced against entropic tendencies resulting in a rich complicated behavior that leads to clustering that depends on temperature but evolves on picosecond time scales. The structural organization of metallic liquids affects their thermophysical properties, such as viscosity and density, thus influencing the ability of a metallic liquid to form useful technological phases, such as metallic glasses. The time-dependent pair correlation function (the Van Hove function) was determined for metallic-glass forming Cu₄₉Zr₄₅Al₆ at 1060 °C from time-of-flight inelastic neutron scattering measurements made using the Neutron Electrostatic Levitation facility at the Spallation Neutron Source. The time for changes in local atomic connectivity, which is the timescale of atomic ordering, was determined by examining the decay of the nearest neighbor peak. The results of rigorous statistical analyses were used to distinguish between competing models of ordering, suggesting that a stretched exponential model of coordination number change is valid for this system. Full article

The behavior of the energy of the peaks of the first UV/Vis absorption band and the presence or absence of isosbestic points in this band with changing temperature for all-trans-DPH and all-trans-β-carotene, dissolved in 1-chlorobutane or hydrocarbon solvents, allows us to show conclusively whether these compounds transform their all-trans-molecular structures into a structure of their conformers. From these analyses, it is concluded that in these solvents, all-trans-DPH is not thermally transformed to its conformer s-cis-DPH in a temperature range from 133 K to 350 K. On the other hand, all-trans-β-carotene, as a model-compound, does show changes in its molecular structure in these solvents with changing temperature. We also show that a portion of all-trans-DPH dissolved in cis-Decalin, at room temperature, slowly transforms into its conformer s-cis-DPH. Full article

The relation between the pressure and molar concentration (in mol/L) of real gases in a low- to medium-pressure range is precisely described by a logarithmic two-parameter equation. Increasing the concentration caused an increase in pressure and also the weakening of the effect due to intermolecular interactions, forming the basis for an equation with an adjusted parameter. Exceeding a critical concentration by a further increase caused a switch to another set of parameters in the same equation. At high pressure, a second switch to an exponential term was observed. This equation of state, defined segment by segment, was attributed to three different structures of the medium. The validity of the equations found was verified with experimental data reported in the literature for helium, neon, argon, krypton, and xenon and is discussed in more detail for argon. The temperature dependence of the parameters of the equations is reported and the formation of a liquid phase is discussed. Full article

Raman scattering measurements were performed on 1 mol dm⁻³ aqueous calcium nitrate (Ca(NO₃)₂) and sodium nitrate (NaNO₃) solutions containing 4% (w/w) D₂O in a temperature range from 25 to 350 °C and pressure of 40 MPa. As the temperature increased, the N–O symmetric stretching vibrational band (ν₁) of NO₃⁻ at 1045–1047 cm⁻¹ shifted to a lower wavenumber by 5~6 cm⁻¹. The band analysis using one Lorentzian component showed that the full-width at half maximum (FWHM) did not change significantly below 175 °C but increased rapidly above 200 °C for both solutions. The peak area for an aqueous Ca(NO₃)₂ solution showed a breakpoint between 225 and 250 °C, suggesting a change in the coordination shell of NO₃⁻ at 175~250 °C. The OD symmetric stretching vibrational band of HDO water was deconvoluted into two Gaussian components at 2530 and 2645 cm⁻¹; the former component has high temperature dependence that is ascribed to the hydrogen bonds, whereas the latter one shows less temperature dependence due to the non-hydrogen bonds of water. X-ray scattering measurements were performed on a 1 mol dm⁻³ aqueous Ca(NO₃)₂ solution at 25 to 210 °C and 40 MPa. Empirical potential structure refinement (EPSR) modeling was used to analyze the X-ray scattering data. Ca²⁺ forms a rigid coordination shell consisting of about seven water molecules at 2.48 Å and one NO₃⁻ at 25~170 °C, with further water molecules substituted by NO₃⁻ at 210 °C. NO₃⁻ is surrounded by 13~14 water molecules at an N–Ow distance of 3.6~3.7 Å. The tetrahedral network structure of solvent water pertains from 25 to 170 °C but is transformed to a dense packing arrangement at 210 °C. Full article

Recently, two new polymorphs have been added to the nematic class: the polar-twisted nematic (N_PT) in 2016 and the ferroelectric nematic (N_F) in 2020. Comprised of achiral molecules, both exhibit local polar ordering and adopt modulated structures, right- and left-handed helical organizations—form chirality—albeit on vastly different dimensional scales; modulations have a ~10 nanometer pitch in the N_PT and ~500 nm in the N_F. Here, we focus on the structure and symmetries of the N_PT phase and the ensuing physical properties. Based on an array of order parameters that fully describe the molecular ordering and the nano-modulations thereof, we present a consistent formulation of the dielectric, optical, surface anchoring, and elasticity properties of the N_PT materials. We show that these properties are distinctly different from those associated with an elastically modulated, locally uniaxial, nematic. Full article

With the continuous growth of global energy demand, greenhouse gas emissions are also rising, leading to serious challenges posed by climate change. Carbon Capture, Utilization, and Storage (CCUS) technology is considered one of the key pathways to mitigate climate change. Among the CCUS technologies, CO₂ storage in offshore saline aquifers has gained significant attention in recent years. This paper conducts an in-depth analysis of the Sleipner and Snøhvit projects in Norway and the Tomakomai project in Japan, exploring key issues related to the application, geological characteristics, injection strategies, monitoring systems, and simulation methods of CO₂ storage in offshore saline aquifers. This study finds that CO₂ storage in offshore saline aquifers has high safety and storage potential but faces several challenges in practical applications, such as geological reservoir characteristics, technological innovation, operational costs, and social acceptance. Therefore, it is necessary to further strengthen technological innovation and policy support to promote the development and application of CO₂ storage in offshore saline aquifers. This study provides valuable experiences and insights for similar projects worldwide, contributing to the sustainable development of CO₂ storage in offshore saline aquifers and making a greater contribution to achieving global net-zero emission targets. Full article

This study investigates the dynamics of thermal plumes interacting with the liquid–air interface in straight-chain alcohols and their mixtures using a photothermal imaging technique based on thermal lensing. This method enables the indirect measurement of temperature gradients via changes in refractive index caused by localized laser heating. Employing a collimated laser beam, the results show the formation and evolution of cylindrical heated zones and their interactions with the liquid–air interface. The study reveals that, while some alcohols exhibit stable surface behaviors, others demonstrate complex dynamical behaviors, including strong stable steady-state oscillations. The findings contribute to understanding fluid dynamics in molecular liquids near their liquid–air interfaces. Full article

Understanding the interactions between solutes and solvents is vital in many areas of the chemical sciences. Solvation free energy (SFE) is an important thermodynamic property in characterising molecular solvation and so accurate prediction of this property is sought after. The One-Dimensional Reference Interaction Site Model (RISM) is a well-established method for modelling solvation, but it is known to yield large errors in the calculation of SFE. In this work, we show that a single machine learning free energy functional for RISM can accurately model solvation thermodynamics in multiple solvents. A convolutional neural network is trained on solvation free energy density functions calculated by RISM for small organic molecules in approximately 100 different solvent systems. We achieve an average RMSE of 1.41 kcal/mol and an ${\mathrm{R}}^2$ of 0.89 across all solvent systems. We also compare the performance for the most and least commonly represented solvents and show that higher accuracy is generally seen with higher volumes of data, with RMSE values of 0.69–1.29 kcal/mol and ${\mathrm{R}}^2$ values of 0.78–0.97 for solvents with more than 50 data points. We have shown that machine learning can greatly improve solvation free energy predictions in RISM, while demonstrating that the methodology is generalisable across solvent systems. This represents a significant step towards a universal machine learning SFE functional for RISM. Full article