Calculation Of Interaction Parameters Research Articles

Synthesis and optical properties of novel Bi2O3–Li2O–Al2O3–TeO2 glasses

Quaternary glasses of xBi2O3–20Li2O–5Al2O3–(75-x)TeO2 with varying compositions were produced by melt quenching. The purpose was to investigate their physical and optical characteristics. FTIR analysis was employed to examine the structural features of the glass system, followed by UV–Vis spectroscopy for verification of its optical properties. Density measurements performed with a densitometer revealed a rise from 4.68 g/cm³ to 5.06 g/cm³ as the Bi2O3 concentration increased. The refractive index value elevated from 2.6731 to 2.6975 alongside a notable rise in the Urbach energy range from 0.46 to 0.96 eV. As the amount of Bi2O3 varies from 0 to 5 mol%, there was a corresponding rise in the presence of BiO6 units associated with non-bridging oxygen atoms. This observation coincided with a weakening of the bismuth single bond strength, dropping from 283.54 kJ/mol to 158.71 kJ/mol. The optical transmittance decreases to 0.6518, while the reflection loss increases to 0.2108, with an increase in bismuth concentration from 0 to 5 mol%. As the bismuth content increases, both the polarizability of oxide ions and their optical basicity rise consistently, with polarizability values increasing from 2.9163 to 3.0910 Å3 and optical basicity values climbing from 1.0974 to 1.1297. The calculation of interaction parameters indicated that the inclusion of Bi2O3 in glass samples resulted in a shift from high covalency to ionicity, attributed to Bi2O3 acting as a glass modifier.

A polyethylene glycol-grafted pullulan polysaccharide adhesive improves drug loading capacity and release efficiency

In this study, polyethylene glycol was grafted onto pullulan polysaccharides, resulting in the development of a novel adhesive termed PLUPE, offering superior drug loading capacity and rapid release efficiency. The efficacy of PLUPE was rigorously evaluated through various tests, including the tack test, shear strength test, 180° peel strength test, and human skin adhesion test. The results demonstrated that PLUPE exhibited a static shear strength that was 4.6 to 9.3 times higher than conventional PSAs, ensuring secure adhesion for over 3 days on human skin. A comprehensive analysis, encompassing electrical potential evaluation, calculation of interaction parameters, and FT-IR spectra, elucidated why improved the miscibility between the drug and PSAs, that the significant enhancement of intermolecular hydrogen bonding in the PLUPE structure. ATR-FTIR, rheological, and thermodynamic analyses further revealed that the hydrogen bonding network in PLUPE primarily interacted with polar groups in the skin. This interaction augmented the fluidity and free volume of PSA molecules, thereby promoting efficient drug release. The results confirmed the safety profile of PLUPE through skin irritation tests and MTT assays, bolstering its viability for application in TDDS patches. In conclusion, PLUPE represented a groundbreaking adhesive solution for TDDS patches, successfully overcoming longstanding challenges associated with PSAs.

How does temperature modulate the structural properties of aggregated melamine in aqueous solution-An answer from classical molecular dynamics simulation.

In this study, classical molecular dynamics simulation of eight melamine molecules is carried out in water over a temperature range of 300 K to 380 K at an ambient pressure to examine the molecular details of melamine aggregation along with the impact of temperature on the aggregated state of melamine in water. It is found that the hydrogen bonds formed between sp3 N-sp2 N of melamine, which is mainly responsible for the aggregation over the sp3 N-sp3 N, are disturbed mainly by the rise in temperature. These outcomes are complemented by the consideration of an average number of hydrogen bonds per melamine and preferential interaction parameter calculations. The impact of temperature is negligible on the orientational probability between the two triazine cores. The π-π stacking interaction between the two triazine rings plays a less significant role on melamine aggregation. Dynamical calculations, by considering cluster structure analyses and dimer existence autocorrelation function, strengthen the fact of destabilization of aggregated melamine in water with the rise in temperature. With free energy of solvation, association constant along with the binding free energy between a melamine pair gives the thermodynamic point of view of the impact of elevated temperature on melamine aggregation. Interestingly, the potential of mean force calculation using an umbrella sampling technique explains the reasons, in depth, of how do sp3 N-sp2 N interactions confirm the decrease in the initial probability of growth of higher order clusters with the increase in temperature.

Binary Mixed Micelles of Polyoxyethylene (10) Stearyl Ether with Polysorbate 20 and Polysorbate 60: Thermodynamic Description

AbstractComprehension of the nature of the micellisation process is of great importance for the characterisation of micelles and the assessment of their applications. In this research, the influences of temperature and the length of the hydrophobic chain on the micellisation process of polyoxyethylene (10) stearyl ether (PE10) with polysorbate 20 and polysorbate 60 were studied. Values of critical micelle concentrations (CMC) of the individual surfactants and of their binary mixtures were acquired by spectrofluorimetric measurements, in the temperature range 273.15–313.15 K, using pyrene as a probe molecule. Obtained CMC values served for the calculation of interaction parameters and excess Gibbs energies of the mixed micelles. It was found that in PE10—polysorbate 20 mixed micelles (due to a shorter hydrophobic segment of polysorbate 20 molecule) PE10 alkyl chains were more likely to assume globular conformations in the interior of micelles, in comparison to PE10—polysorbate 60 mixed micelles (in which hydrophobic segments had the same lengths). For each analysed binary system, interaction parameter decreased with the rise of temperature. It could be assumed that on higher temperatures the hydrophobic chains of studied surfactants were more likely to take globular conformations, having higher values of conformational freedom. This observation implied that the process of micellisation was followed by an increase in entropy. Accordingly, the excess Gibbs energy of micellisation was determined not only by entropic contributions, but also by enthalpic input.

Liquid–liquid equilibria in the ternary and multicomponent systems involving hydrocarbons, thiophene or pyridine and ionic liquid (1-benzyl-3-metylimidazolium bis(trifluorometylsulfonyl)imide)

Liquid-liquid equilibrium for eight ternary systems involving one hydrocarbon (from a series involving aliphatics n-hexane, n-heptane, i-octane or aromatics toluene) one solute (thiophene or pyridine) and an ionic liquid (IL, 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) was experimentally measured at atmospheric pressure and 25 °C. Equilibrium data are presented qualitatively, with solubility curves and quantitatively, with tie lines. The appropriateness of IL for extractive desulfurization, denitrification and dearomatization was evaluated with respect to solute distribution ratio, selectivity and efficiency of IL. Extraction experiments with seven-component systems model solutions and real refinery FCC gasoline have been performed. The equilibrium data were used for the calculation of interaction parameters of NRTL and UNIQUAC activity coefficient models.

An investigation into the influence of drug–polymer interactions on the miscibility, processability and structure of polyvinylpyrrolidone-based hot melt extrusion formulations

While hot melt extrusion is now established within the pharmaceutical industry, the prediction of miscibility, processability and structural stability remains a pertinent issue, including the issue of whether molecular interaction is necessary for suitable performance. Here we integrate the use of theoretical and experimental drug–polymer interaction assessment with determination of processability and structure of dispersions in two polyvinylpyrrolidone-based polymers (PVP and PVP vinyl acetate, PVPVA). Caffeine and paracetamol were chosen as model drugs on the basis of their differing hydrogen bonding potential with PVP. Solubility parameter and interaction parameter calculations predicted a greater miscibility for paracetamol, while ATR-FTIR confirmed the hydrogen bonding propensity of the paracetamol with both polymers, with little interaction detected for caffeine. PVP was found to exhibit greater interaction and miscibility with paracetamol than did PVPVA. It was noted that lower processing temperatures (circa 40°C below the Tg of the polymer alone and Tm of the crystalline drug) and higher drug loadings with associated molecular dispersion up to 50% w/w were possible for the paracetamol dispersions, although molecular dispersion with the non-interactive caffeine was noted at loadings up to 20% w./w. A lower processing temperature was also noted for caffeine-loaded systems despite the absence of detectable interactions. The study has therefore indicated that theoretical and experimental detection of miscibility and drug–polymer interactions may lead to insights into product processing and extrudate structure, with direct molecular interaction representing a helpful but not essential aspect of drug–polymer combination prediction.

Association of Small Hydrophobic Solute in Presence of the Osmolytes Urea and Trimethylamine-N-oxide

Influences of two naturally occurring osmolytes, urea and trimethylamine-N-oxide (TMAO), on hydrophobic interactions of methane are investigated by performing molecular dynamics (MD) simulations. In this study, we have used two different models of methane: one is of single united site (UA), and the other contains 5-sites (AA). We observe that two methane models behave similarly in pure water and in aqueous osmolyte solutions except for the fact that AA model of methane behaves slight differently in aqueous binary urea solution. Our potentials of mean force (PMF) calculations followed by association constant estimation and cluster structure analyses suggest urea-induced enhancement of methane association for the methane AA model. For both models, we observe the dehydration of methane molecules in presence of osmolytes. We also find the collapse of the second shell of water by urea and water structure enhancement by TMAO molecules. Our preferential interaction parameter calculations show that in binary aqueous urea solution methane molecules are expelled by urea molecules and this effect is more pronounced for the AA model. On the other hand, in binary aqueous TMAO solution, methane prefers to interact more with TMAO than water. Our water orientational structure calculations show that the orientation of water molecules near to hydrophobic moiety is anisotropic and osmolytes have a negligible effect on it. We also observe the osmolyte-induced water-water hydrogen bond lifetime increase in the hydration shell of methane as well as in the subsequent layers.

Comparison between surface excitation parameter obtained from QUEELS and SESINIPAC

Surface excitations significantly influence the measured peak intensities in elastic peak electron spectroscopy. They are characterised by the surface excitation parameter (SEP) defined as the change in excitation probability of an electron caused by the presence of the surface in comparison with an electron moving in an infinite medium. It is thus important to have a large database of SEP values or to have the possibility to determine it with a user‐friendly software. Recently, Novák developed the programme Software for Electron Solid Inelastic Interaction Parameter Calculations (SESINIPAC) within the model of Tung, Chen, Kwei and Chou, which allows to determine inelastic mean free path, differential inelastic mean free path, SEP and differential SEP for various energy loss function models and dispersion relations with as only input the energy loss function of the material. Using SESINIPAC, we calculate SEP for 27 different types of materials (metals, semiconductors and insulators) and for various angles and energies. We compare these results with those obtained previously with the software Quantitative Analysis of Electron Energy Losses at Surfaces (QUEELS), which uses the Yubero‐Tougaard model. We show that the dependence on angle of emission and energy is quite similar for the two models. However, the absolute values calculated with SESINIPAC are generally larger than those calculated with QUEELS, and the mean relative difference is 20% for metals and semiconductors but exceeds 50% for insulators. Copyright © 2012 John Wiley & Sons, Ltd.

Polarized microwave forward model simulations for tropical storm Fanoos

In the present study, forward radiative transfer simulations are carried out for the tropical cyclone Fanoos that hit the coast off south India in December 2005. The in-house radiative transfer package used for this study employs the doubling and adding method to calculate radiances leaving the top of the one dimensional precipitating atmosphere. The particle drop size distribution is assumed to follow a modified gamma distribution in respect of the cloud liquid water and cloud ice water content. For precipitation, the Marshall-Palmer particle size distribution is used. All the hydrometeor particles are assumed to be spherical and Lorentz Mie theory is used to evaluate the interaction parameters like absorption, scattering coefficients and polarized scattering matrix. In order to validate the drop size distributions and interaction parameter calculations, the simulated brightness temperatures are compared with the TMI measured brightness temperatures for all the channels. For carrying out this exercise, vertical hydrometeors retrieved by TMI are used as input. The differences between simulated and measured brightness temperatures are found to be within ±10%. The maximum difference in the brightness temperatures between the present work and the Eddington model which the TRMM algorithm employs is about 4.5K. This may become significant when retrieval of precipitation is attempted by combining the forward model with a suitable retrieval strategy, under tropical conditions.

Chemical bonding and quadrupole splittings of 57Fe Mössbauer spectrum in active sites of oxyhemoglobin as calculated by X α -discrete variation method

Results of quantum-chemical X α -discrete variation method (X α -DVM) calculations of interaction parameters between iron (II) and oxygen molecule in active sites of α- and β-subunits of oxyhemoglobin are presented within three models: without extra electron and in spin-unrestricted mode (model I); without extra electron and in spin-restricted mode (model II); with extra electrons in spin-unrestricted mode (model III). The electronic structure and 57Fe quadrupole splitting ΔE Q for the active site of α- and β-subunits (within model I) and only of the α-subunit (within models II and III) of oxyhemoglobin are calculated. The differences in ΔE Q values for these three models are discussed.

A polarized microwave radiative transfer model for passive remote sensing

The objective of the present work is to develop a general purpose, polarized, microwave radiative transfer forward model, including calculation of interaction parameters for fast, simultaneous and accurate generation of radiances, for use in a wide variety of atmospheric retrieval applications. This complete polarized model includes the generation of atmospheric profiles, calculation of the interaction parameters and the solution of the vector radiative transfer equations. In the present work, the doubling and adding method is used to calculate radiances. Mie theory is used for spherical particles to evaluate the polarized scattering matrix. Two types of sea surface models applicable for specular and diffuse surfaces respectively are implemented. The model has been validated against standard benchmark cases and experimental data available in literature. While the model is itself generic, parametric studies are performed to study the influence of the vertical structure of the atmosphere, for two polarizations and a set of frequencies to be used on the microwave imager aboard the proposed Indo-French climate research satellite MEGHA-TROPIQUES.

Surface and transport properties of Au–In liquid alloys

Thermodynamic quantities on Au–In liquid alloys have been used as the input data for the interaction parameter calculations in the framework of the complex formation model (CFM). Once the interaction energies are computed the surface (surface tension and surface composition) and transport properties (chemical diffusion and viscosity) as well as the microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) have been calculated. The concentration and temperature dependent surface tension values have been compared with our new set of experimental data, obtained by the large drop method in the temperature range of T = 1273–1493 K. The anomalous change of surface tension for some alloy compositions may be attributed to a retention of order in the Au–In melts which is similar to the atomic arrangement in solid Au–In.

Surface and transport properties of Au–Sn liquid alloys

The present work is an experimentally based investigation of the applicability of the complex formation model (CFM) in the framework of statistical mechanical theory in conjunction with quasi-lattice theory (QLT) to describe the surface and transport properties of Au–Sn liquid alloys. Depending on melting temperatures, the surface tension of molten Au and Au–Sn alloys has been measured by the pinned-large drop method in the temperature range of T = 1275–1493 K. The calculations have been done with various objectives in view, i.e., to analyse existing thermodynamic data related to the peculiarities of the Au–Sn phase diagram, to use these data as the input for the interaction parameter calculations, to calculate the surface properties (surface tension and surface composition) and to compare the computed data with a new set of the surface tension experimental data as well as to predict the values of dynamic properties (chemical diffusion and viscosity). Some information on the structure of Au–Sn liquid alloys are given in terms of the microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter).

Improving froth characteristics and flotation recovery of phosphate ores with nonionic surfactants

The beneficial effect of a series of nonylphenol polyethylene glycol ether surfactants were tested in the flotation of phosphate ores in which the mixtures of sodium oleate and dodecane were used as collectors. In order to elucidate the flotation results, equilibrium surface tension of single and binary surfactant solutions prepared with sodium oleate and nonionic surfactants were investigated. Synergism between surfactants was determined by observing the change in surface tension of solutions and by the calculation of interaction parameter from surface tension data. The lowering of surface tension of sodium oleate solutions was observed in the presence of nonionic surfactants. The interaction parameter between sodium oleate and a nonionic surfactant (i.e., NP-4) was calculated to be −0.21, showing attraction between the two surfactant molecules. The nonionic surfactant NP-4 was then tested in batch flotation of phosphate ores. The beneficial effect of nonionic surfactant was obtained at different collector dosages and surfactant combinations.

Superspreading of Trisiloxane Surfactant Mixtures on Hydrophobic Surfaces 2. Interaction and Spreading of Aqueous Trisiloxane Surfactant−N-Alkyl-Pyrrolidinone Mixtures in Contact with Polyethylene

On the basis of the results of interfacial adsorptions of an ethoxylated trsiloxane(L77) and its mixtures with various N-alkyl-pyrrolidinones, the changes in interfacial pressure at the air/aqueous solution, polyethylene/aqueous solution, and air/polyethylene interfaces caused by the surfactant mixture solutions have been evaluated by use of the Gibbs equation. At the air/aqueous solution interface, the change in the surface tension, (ΔγLA), is always positive, indicating that there is no effect that could enhance spreading at this interface upon the addition of N-alkyl-pyrrolidinones to the trisiloxane surfactant solution. At the polyethylene/aqueous solution interface, the change in interfacial pressure, (ΔπSL), can be positive when N-alkyl-pyrrolidinones are mixed at a certain ratio, indicating that the mixtures can show a spreading enhancement effect at this interface. Compared with the changes at the air/aqueous solution interface and the polyethylene/aqueous solution interface, the change in interfacial pressure at the solid/air interface, (ΔπSA), is insignificant. The change in the value of the spreading coefficient (SMixL/S − S L77L/S) on polyethylene film of an aqueous solution of the ethoxylated trisiloxane L77 upon the addition to it of an N-alkyl-pyrrolidinone has been evaluated from these changes in the interfacial pressures. It was found that the change in the spreading coefficient is in about the same order as the enhancement of its spreading factor (SF) on the polyethylene. In addition, the interaction (β) parameters of L77 with the different pyrrolidinones at the various interfaces have been calculated. βσLA for all mixtures was between 0 and −1, indicating that the interaction at the air/aqueous solution interfaces is very weak. However, the values of βσSL were between −2.7 and −6.7 for the mixtures with those N-alkyl-pyrrolidinones that produce enhancement of the superspreading of aqueous solution of L77 on polyethylene, indicating a significant attractive interaction with L77 at the polyethylene/aqueous solution interface. A comparison of values of the mole fraction of L77 at the polyethylene/aqueous solution interface, either calculated or measured from adsorption data, shows that the nonideal solution treatment of the data for calculation of interaction parameters is valid.

Use of ab initio interaction energies for the prediction of phase equilibria in the system nitrogen–ethane

Ab initio molecular orbital methods have been used for calculations of interaction parameters of the UNIQUAC and NRTL activity coefficient model to predict phase equilibria in the system nitrogen–ethane. The UNIQUAC and NRTL model with ab initio parameters, calculated on the MP4 and QCISD(T) theory level, have been used in different gE-mixing rules to predict high-pressure vapor–liquid- (VLE) and vapor–liquid–liquid-equilibria (VLLE) by the Peng–Robinson and the Soave–Redlich–Kwong equation of state. The results have been compared to predictions based on UNIFAC with the PSRK-mixing rule. The results using ab initio-UNIQUAC are poor. However, ab initio-NRTL gives good VLE-predictions with all gE-mixing rules and with both equations of state. Only in the temperature range below 133 K, where the VLLE occur, is ab initio-NRTL inferior to the predictions by UNIFAC.

Determination of the human tissue interaction parameters for Monte Carlo dose calculations in radiotherapy

Monte Carlo dose calculation techniques for clinical photon and electron beams potentially predict the dose with an accuracy of better than +/- 2%. However, to achieve this precision, knowledge of the interaction properties in each volume element is essential. In the present paper a method for mass density to total cross section conversion is described. This method is based on a detailed analysis of the interaction data for body tissues (ICRU Report 46) and allows the conversion without knowing the atomic composition. The analysis resulted in various fit functions allowing the calculation of interaction parameters for arbitrary materials using the corresponding cross sections in water. Together with standard procedures to calculate mass densities from a given CT number distribution, the method represents an effective and accurate algorithm to determine photon interaction coefficients, electron stopping powers as well as electron scatter parameters.

A self-consistent model for predicting interaction parameters in multicomponent alloys

Several models have been proposed to predict interaction parameters in multicomponent alloys from the physical characteristics of constituent elements. But all these models are not self-consistent, i.e., they do not meet the basic requirement of the reciprocal relation, eij=eji, automatically. In this article, a new and self-consistent model is proposed by coupling Chou’s geometric solution model with Miedema’s model on the enthalpy of mixing for binary alloys. The new model is applied to the calculation of interaction parameters in a large number of iron-based alloys, and the agreement between calculation and experimental data is found to be reasonable.

O+‐O collision frequency in high‐speed flows

Throughout much of the terrestrial thermosphere and ionosphere, the motions of the neutral and ionized constituents are closely coupled and relative velocities are small, of the order of 100 m s−1 or less. This is particularly true at midlatitudes to low latitudes where typical velocities in the neutral gas due to tidal forcing are only 20‐50 m s−1. However, the solar wind‐magnetosphere interaction drives a large‐scale convection pattern in the polar ionosphere. When the rapid adjustment of the plasma to changes in the solar wind is combined with the slower response of the more massive neutral gas, large relative velocities on the order of 1 km s−1 can exist for substantial lengths of time. This will be more common during periods of high geomagnetic activity, as a result of the greater number of magnetic substorms and other particle precipitation events. When a significant relative velocity is present, the calculation of interaction parameters of the two gases passing through each other, such as collision frequency, must include that velocity. These effects are usually neglected when interpreting wind and ion drift observations. We show how the collision frequency is affected by a directed relative velocity between any two gases interacting with a power law or exponential potential energy curves. The directed velocity increases the collision frequency at all temperatures for most ion‐neutral interactions. For certain power law potentials, such as the charge quadrupole, the collision frequency is decreased. We present an analytic solution for the high‐speed collision integral using the resonance charge exchange cross section.

Calculation of interaction parameters for binary solid-SCF equilibria using several EOS and mixing rules

Binary interaction parameters (BIPs) have been computed for the description of solid-supercritical-fluid equilibrium using solubility data. Several combinations of cubic equations-of-state and mixing rules have been studied, computing parameters and average errors for over 30 systems for which experimental data were available in the literature. The computation was done by defining an objective function, and minimizing it by a suited algorithm — Fibonacci (golden section) algorithm to find one binary interaction parameter and the Nelder and Mead (Simplex) method to find two interaction parameters. Equations-of-state (EOS's) chosen for this study were Redlich-Kwong (RK), Soave (SRK), and Peng-Robinson (PR), whereas the mixing rules used were quadratic (van der Waals) and cubic. Good agreement was found between computed values and the few values found in the literature. Results using one interaction parameter for the three EOS indicate that, globally, there is no significant difference in the prediction ability of these EOS. Differences among the EOS were found when the errors for individual systems were compared. These differences were explained in terms of the ability of the EOS to predict specific molecular interactions that occur in these systems. For the PR-EOS, two mixing rules were compared. The corresponding results show no substantial difference for these mixing rules. Finally, the results for the PREOS using one BIP were compared to those for which two BIPs were used. A marked reduction in the errors was observed when the second BIP was included in the analysis.