Dissolution Model Research Articles

Experimental and mechanism study on wax deposit dissolution characteristics by light crude oil

During the sequential transportation of waxy crude oil and light oil, the previous formed wax deposits on the pipe wall will dissolve by light oil, which brings risks to the flow safety of the pipeline. This paper adopted a Couette wax deposit dissolution experimental device to systematically study the effects of dissolution duration, oil temperature, rotation speed and wax deposit properties on the dissolution characteristics of wax deposits. It is found that the dissolution of wax deposits is a process that starts quickly and then slows down. Moreover, the wax content of wax deposit also decreased during the dissolution process. The wax deposit dissolution process is mainly divided into five stages such as diffusion of wax molecules from wax deposit to the light oil and from bottom layer deposit to the wax deposit-oil interface, dissolution of wax crystal particles, weakening of wax deposit structural strength, and shear stripping of wax deposits. Finally, an empirical model of wax deposit dissolution was established and the undetermined parameters were fitted based on experimental data. The prediction results have good prediction accuracy with the experimental values.

Simulation and experimental studies on surface quality of vibration-assisted ECM

ABSTRACT Electrochemical machining (ECM) offers a superior technology for manufacturing hard-cutting metals such as modified Inconel 718 (IN718). However, in many cases, poor surface quality arises because of the specific dissolution characteristics of the material, hindering further application of the process. Vibration-assisted ECM (VA-ECM) has been proposed in the hope of solving the problem by oscillating the cathode. A multiphysics model was developed for pulsed ECM (PECM) and VA-ECM. Systematic experiments were performed to clarify the mechanism of cathode oscillation on surface quality and verify the computational results. With 20 Hz vibration frequency and 25% duty cycle, the surface roughness reaches 0.39 µm, show that higher oscillation frequency and lower duty cycle are effective in improving surface quality. Finally, dissolution models of modified IN718 under PECM and VA-ECM are proposed. By oscillating the cathode, electrolyte fluctuation is enhanced, electrolytic products are removed effectively, the surface quality is improved significantly.

Reaction order of near equilibrium calcite dissolution: Uncertainties and ambiguities of isotopic tracer methods

Dissolution of calcite in water is fundamental to geochemistry. Laboratory methods generally give consistent dissolution rates under conditions far from equilibrium, but close to equilibrium the measurement of dissolution using isotopes is complicated by poorly understood calcite-fluid isotopic exchange processes. This near-equilibrium isotopic exchange occurs in laboratory experiments at rates of order 10-9 to 10-13 mol/m2/s and decreases with experiment duration approximately as 1/time where time is measured from the start of the experiment. Such rates are fast enough to compete with dissolution in days-long experiments and consequently, net dissolution rates may not be measurable with isotopic tracer methods except in experiments carried out for long enough to allow the background exchange to dissipate sufficiently. To better define what should be expected for isotopic signals during dissolution, we develop a quasi-1D model for calcite dissolution that includes the mechanistically unconstrained isotopic exchange as well as solid state diffusion. We use the model, the observations reported in the literature, and the calcite dissolution rates in seawater reported by Naviaux et al., (2019a) to illustrate ambiguities in measurement of near-equilibrium calcite dissolution rates. The results suggest that the reaction order of calcite dissolution close to equilibrium could be 2 at both room temperature and the lower temperatures of the seafloor. The reaction order of near-equilibrium calcite dissolution is important for understanding calcite mineral surface processes, long-term behavior of dissolution on the seafloor, and alkalinity fluxes from modern seafloor sediments. Distinguishing between net dissolution, which affects fluid saturation state, and “exchange,” which doesn’t, is important but typically cannot be done with isotopic tracers alone.

Self Nanoelmusifying Drug Delivery System of Rosuvastatin: Bioavailability Evaluation and In vitro - In vivo Correlation.

Rosuvastatin, most commonly used in the form of calcium salt, belongs to the statin groups of synthetic antihyperlipidemic agents. Rosuvastatin possesses high permeability, however, its aqueous solubility is poor, causing a slow dissolution rate in water. Consequently, this dissolution rate has a decisive role in the release and absorption of rosuvastatin in the gastrointestinal tube. The aims of this study were to evaluate the absorption of the drug from the self-nano emulsifying drug delivery system of rosuvastatin (Ros SNEDDS) compared to rosuvastatin substance and to develop a level-A in vitro-in vivo correlation (IVIVC) for Ros SNEDDS. An in-house developed LC-MS/MS method was used to determine the concentrations of rosuvastatin in dog plasma. Six beagle dogs received an intravenous dose, Ros SNEDDS, rosuvastatin substance. In vitro dissolution of the Ros SNEDDS was carried out with different conditions. Correlation models were developed from the dissolution and absorption results of Ros SNEDDS. The results showed a 1.7-fold enhanced oral bioavailability and 2.1-time increase of rosuvastatin Cmax in Ros SNEDDS form, compared to the rosuvastatin substance. A 900 ml dissolution medium of pH of 6.6 has demonstrated its suitability, the in vitro dissolution model was studied and supported by the Weibull equation with a weighting factor of 1/y2 as it presented the lowest values of AIC. Ros SNEDDS demonstrated higher bioavailability of rosuvastatin in comparison to rosuvastatin substance and established a level A IVIVC used in future bioequivalence trials.

A Numerical Time Integration Procedure for Secondary Dendrite Arm Spacing in Hyper-Peritectic Steel Alloys

AbstractA numerical time integration procedure for the calculation of the secondary dendrite arm spacing (SDAS) in FeC hyper-peritectic alloys is presented, a preferred group of low-carbon casting steel. The procedure incorporates a three-stage thin arm dissolution model, which is solved at each time step using Newton–Raphson iteration. This is coupled to a coarsening model based on the integral forms of the dissolution model, which are solved using Gaussian quadrature, as well as a growth model for solid fraction evolution. The procedure can easily be embedded into numerical models for solidification, in which the space–time evolution of the SDAS is required for determining the dynamic permeability in the mushy zone. Higher order approximations for both growth and solute concentration evolution can easily be incorporated. Temperature dependence of thermophysical parameters is taken into account using inter-dendritic solidification empirical models, and an alloy-specific peritectic reaction constant is used to determine the isothermal peritectic holding time. The procedure is validated against experimental data presented in literature. Various cases of SDAS as a function of local solidification time, cooling rate and carbon composition are investigated. The method is compared to experimental results of SDAS obtained from test castings of a hyper-peritectic steel alloy and can be used to iteratively determine the alloy-specific peritectic reaction constant by comparing the solid fraction evolution during the peritectic reaction with that found from the experimental cooling curve.

CFD-DEM modeling of particle dissolution behavior in stirred tanks

A CFD-DEM particle dissolution model was established to study the particle dissolution process in a stirred tank. Firstly, the model's accuracy in simulating particle size and solute concentration was validated against experimental results, the errors were 6.13% and 12.5%, respectively. Secondly, the study delved into the mechanism of mass transfer dissolution from three dimensions: solute concentration distribution, particles spatial distribution, and energy dissipation rate of particles. It was found that the larger the concentration gradient, the better the dissolution of particles. As the dissolution progresses, the coupling force between the fluid and the particles weakens, and smaller particles are more easily suspended. Lastly, the dissolution behavior of particles at different rotation speeds was investigated. Stirring speed can significantly improve the dissolution rate of particles in the particle suspension and dispersion stage, but the difference of different rotational speeds on the dissolution rate becomes smaller in the particle circulation flow stage.

Do more egalitarian men experience less union dissolution? A couple‐level analysis

AbstractObjectiveWe consider whether heterosexual unions in which male partners are more gender egalitarian experience less union dissolution.BackgroundGender revolution theory argues that as men become more egalitarian in their attitudes and behaviors, female partners experience reduced work–family conflict, and couples enjoy more stable partnerships. In contrast, the “flip side” perspective argues that consequences of men's increased egalitarian behavior for their own experience of role incompatibility may counterbalance effects on union stability.MethodAnalyzing a sample of roughly 46,600 women‐years from the British Household Panel Survey and Understanding Society (1993–2019), we estimate random‐intercept and fixed‐effects models of union dissolution. Explanatory variables include, for each partner, measures of egalitarianism in gender role attitudes and weekly housework hours.ResultsOdds of union dissolution are not associated with men's absolute level of egalitarian attitudes, but they are higher when men's attitudes are less egalitarian than their partner's. Neither the absolute number of men's housework hours, nor their share of total housework, is associated with the odds of dissolution.ConclusionsOur findings are not generally supportive of gender revolution theory. Counterbalancing effects may provide an explanation for the findings, as per the flip side approach.ImplicationsTaking a couple‐level perspective advances understanding of the associations between gender egalitarianism and union dissolution.

An analysis of seashell calcium carbonate dissolution caused by ocean acidification based on chemistry equilibrium

Ocean acidification is a serious marine ecosystem problem caused by the abundant human emission of CO2. It is now a prevalent cognition that the dissolution of CO2 tends to raise the concentration of H+ in the ocean and therefore make it more acidic. Anthropogenic CO2 emission exacerbates the situation. This will then lead to another obvious problem---the dissolution of calcium carbonate shells of certain ocean organisms. This article will present a brief dissolution model, which can provide an analysis of the acidification effects from two perspectives---both the forming and the dissolution of seashells. The model shows an exponential relationship between the dissolved Ca2+ concentration and the pH of seawater. It also presents the anticipation regarding a dissolution turning point in (approximately) 2090 under the RCP8.5 scenario. This turning point indicates an abrupt acceleration of calcium carbonate shells dissolution. The result depicts the drastic but possible change in the seawater solution system and gives a warning signal of a probable deadline for us to control the CO2 emission. Hopefully, it will attract more scholars to pay attention to this topic and figure out methodologies to avoid the possible tragedy.

Predicting gastric emptying of drug substances taken under postprandial conditions by combination of biorelevant dissolution and mechanistic in silico modeling

Physiologically based pharmacokinetic (PBPK) models can help to understand the effects of gastric emptying on pharmacokinetics and in particular also provide a platform for understanding mechanisms of food effects, as well as extrapolation between different postprandial conditions, whether standardized clinical or patient-oriented, non-clinical conditions. By integrating biorelevant dissolution data from the GastroDuo dissolution model into a previously described mechanistic model of fed-state gastric emptying, we simulated the effects of a high-calorie high-fat meal on the pharmacokinetics of sildenafil, febuxostat, acetylsalicylic acid, theobromine and caffeine. The model was able to simulate the variability in Cmax and tmax caused by the presence of the stomach road. The main influences investigated to affect the gastric emptying process were drug solubility (theobromine and caffeine), tablet dissolution rate (acetylsalicylic acid) and sensitivity to gastric motility (sildenafil and febuxostat). Finally, we showed how PBPK models can be used to extrapolate pharmacokinetics between different prandial states using theobromine as an example with results from a clinical study being presented.

Adaptive mesh based efficient approximations for Darcy scale precipitation–dissolution models in porous media

AbstractIn this work, we consider the Darcy scale precipitation–dissolution reactive transport 1D and 2D models in a porous medium and provide the adaptive mesh based numerical approximations for solving them efficiently. These models consist of a convection‐diffusion‐reaction PDE with reactions being described by an ODE having a nonlinear, discontinuous, possibly multi‐valued right hand side describing precipitate concentration. The bulk concentration in the aqueous phase develops fronts and the precipitate concentration is described by a free and time‐dependent moving boundary. The time adaptive moving mesh strategy, based on equidistribution principle in space and governed by a moving mesh PDE, is utilized and modified in the context of present problem for finite difference set up in 1D and finite element set up in 2D. Moreover, we use a predictor corrector based algorithm to solve the nonlinear precipitation–dissolution models. For equidistribution approach, we choose an adaptive monitor function and smooth it based on a diffusive mechanism. Numerical tests are performed to demonstrate the accuracy and efficiency of the proposed method by examples through finite difference approach for 1D and finite element approach in 2D. The moving mesh refinement accurately resolves the front location of Darcy scale precipitation–dissolution reactive transport model and reduces the computational cost in comparison to numerical simulations using a fixed mesh.

Dissolution of gas in a stationary liquid layer: A diffusion-kinetic model and experimental studies

An analytic model of gas dissolution in a stationary liquid layer is presented. This model considers for the first time the intrinsic kinetics of the process of gas dissolution in a liquid characterized by the rate of gas absorption/desorption reaction at the gas–liquid interface. Within the framework of the presented model, it is shown that the process of gas dissolution in a stationary liquid layer occurs either in the diffusion-kinetic regime or in the diffusion regime. In the diffusion-kinetic regime, the rate of gas dissolution in a stationary liquid layer is affected by both the intensity of gas diffusion through the liquid layer and the intrinsic kinetics of the gas dissolution process in the liquid; in the diffusion regime, the rate of gas dissolution in a stationary liquid layer is limited only by the intensity of gas diffusion through the liquid layer. Experiments were carried out to study the kinetics of methane dissolution in a stationary layer of water at different temperatures. From the comparison of calculated and experimental data, the values of the diffusion coefficient of methane in water were determined, and it was also established that the process of methane dissolution in a stationary layer of water occurs in the diffusion regime. A new empirical correlation for calculating the diffusion coefficient of methane in water in the temperature range from 273 to 323.15 K was obtained based on our and available data points: D[m2/s]=exp(−12.64−2250.5/T[K]).

Model validation and interpretation of the interaction between glass and cement in an integrated glass dissolution experiment

This article presents the modeling results from the interaction between simulated nuclear waste glasses and ordinary Portland cement (OPC). In general, the modeling results are in good agreement with the experimental results. A diffusion-based glass dissolution model well describes the release of B and Li from the glass, and a reactive transport model well describes the profiles of dissolved glass elements in the cement. It is found that the effective diffusion coefficient of Li in the cement is much larger than that of B. Sorption of both Li and B onto the cement is required to better fit their measured diffusion profiles. For B profiles in the cement, one spatially uniform distribution coefficient is needed, while for Li, sorption needs to be linked to the gel-like secondary phase at the surface of the cement. The effective diffusion coefficients for both Li and B are relatively low and can be linked to the pore-filling effects of the gel-like secondary phase. Even though it is generally believed that nuclear waste glass will dissolve faster in cementitious environments, the results show that the gel-like secondary phase can both seal the cement and act as a strong sorbent for dissolved glass species, thus inhibiting the migration of dissolved glass species.

AI-driven design of customized 3D-printed multi-layer capsules with controlled drug release profiles for personalized medicine

Personalized medicine aims to effectively and efficiently provide customized drugs that cater to diverse populations, which is a significant yet challenging task. Recently, the integration of artificial intelligence (AI) and three-dimensional (3D) printing technology has transformed the medical field, and was expected to facilitate the efficient design and development of customized drugs through the synergy of their respective advantages. In this study, we present an innovative method that combines AI and 3D printing technology to design and fabricate customized capsules. Initially, we discretized and encoded the geometry of the capsule, simulated the dissolution process of the capsule with classical drug dissolution model, and verified it by experiments. Subsequently, we employed a genetic algorithm to explore the capsule geometric structure space and generate a complex multi-layer structure that satisfies the target drug release profiles, including stepwise release and zero-order release. Finally, Two model drugs, isoniazid and acetaminophen, were selected and fused deposition modeling (FDM) 3D printing technology was utilized to precisely print the AI-designed capsule. The reliability of the method was verified by comparing the in vitro release curve of the printed capsules with the target curve, and the f2 value was more than 50. Notably, accurate and autonomous design of the drug release curve was achieved mainly by changing the geometry of the capsule. This approach is expected to be applied to different drug needs and facilitate the development of customized oral dosage forms.

A Refined Thin-Film Model for Drug Dissolution Considering Radial Diffusion - Simulating Powder Dissolution.

We aim to present a refined thin-film model describing the drug particle dissolution considering radial diffusion in spherical boundary layer, and to demonstrate the ability of the model to describe the dissolution behavior of bulk drug powders. The dissolution model introduced in this study was refined from a radial diffusion-based model previously published by our laboratory (So et al. in Pharm Res. 39:907-17, 2022). The refined model was created to simulate the dissolution of bulk powders, and to account for the evolution of particle size and diffusion layer thickness during dissolution. In vitro dissolution testing, using fractionated hydrochlorothiazide powders, was employed to assess the performance of the model. Overall, there was a good agreement between the experimental dissolution data and the predicted dissolution profiles using the proposed model across all size fractions of hydrochlorothiazide. The model over-predicted the dissolution rate when the particles became smaller. Notably, the classic Nernst-Brunner formalism led to an under-estimation of the dissolution rate. Additionally, calculation based on the equivalent particle size derived from the specific surface area substantially over-predicted the dissolution rate. The study demonstrated the potential of the radial diffusion-based model to describe dissolution of drug powders. In contrast, the classic Nernst-Brunner equation could under-estimate drug dissolution rate, largely due to the underlying assumption of translational diffusion. Moreover, the study indicated that not all surfaces on a drug particle contribute to dissolution. Therefore, relying on the experimentally-determined specific surface area for predicting drug dissolution is not advisable.

Flexible modelling of the dissolution performance of directly compressed tablets

In this study, a compartmental disintegration and dissolution model is proposed for the prediction and evaluation of the dissolution performance of directly compressed tablets. This dissolution model uses three compartments (Bound, Disintegrated, and Dissolved) to describe the state of each particle of active pharmaceutical ingredient. The disintegration of the tablet is captured by three fitting parameters. Two disintegration parameters, β0 and βt,0, describe the initial disintegration rate and the change in disintegration rate, respectively. A third parameter, α, describes the effect of the volume of dissolved drug on the disintegration process. As the tablet disintegrates, particles become available for dissolution. The dissolution rate is determined by the Nernst-Brunner equation, whilst taking into account the hydrodynamic effects within the vessel of a USP II (paddle) apparatus. This model uses the raw material properties of the active pharmaceutical ingredient (solubility, particle size distribution, true density), lending it towards early development activities during which time the amount of drug substance available may be limited. Additionally, the strong correlations between the fitting parameters and the tablet porosity indicate the potential to isolate the manufacturing effects and thus implement the model as part of a real-time release testing strategy for a continuous direct compression line.

Oxide dissolution and oxygen diffusion scenarios in niobium and implications on the Bean–Livingston barrier in superconducting cavities

We generalize a native Nb2O5 dissolution model [G. Ciovati, Appl. Phys. Lett. 89, 022507 (2006)] to sequential overlayer dissolutions, multilayer dissolution, and realistic temperature profiles, which may be applicable to other materials. The model is applied to secondary ion mass spectrometry depth profile measurements for varying temperature profiles and two-step oxide dissolution in Nb and found to agree well. In the context of the Meissner screening response due to impurity profiles on the length scale of the London penetration depth, the shallow diffusion of O impurities results in a substantial decrease in the peak supercurrent density near the surface. In this framework, oxide dissolution and oxygen diffusion can account for a rise in peak supportable magnetic field in SRF cavities with baking time and a suppression after the optimal baking time is reached, in good agreement with peak-field baking temperatures and times as well as recent quench field measurements.

A quantitative study on the terrestrial input to the tropical Northeast Atlantic

Eolian dust and riverine discharge are identified as two key components of terrestrial input to the oceans. They supply micronutrients to the oceans and modify marine carbon biogeochemistry and global climate through dust-land-ocean interactions. However, it is challenging to accurately constrain regional terrestrial inputs in the past, with currently available models and geochemical proxies. The present study utilizes sedimentary wtCaCO3% records to estimate lithogenic fluxes. The depth-dependance of CaCO3 preservation in the Holocene and Last Glacial Maximum (LGM) sediments in two major basins of the tropical Northeast Atlantic Ocean is described using a carbonate dissolution model. Results show that during the LGM, reduced dust deposition and slight drops of fluvial input are found in the Canary Basin and Cape Verde margins, respectively. To supplement, carbonate deposition during the LGM indicates that the deep subtropical Northeast Atlantic is seized by more sluggish deep waters relative to today.

Mathematical modeling of dispersed CO2 dissolution in ionic liquids: Application to carbon capture

We develope a 2D computational fluid dynamic (CFD) model in COMSOL Multiphysics® to investigate CO2 absorption in an ionic liquid ([Bmim][TCM]). Factors such as pressure (1–20 bar), temperature (278–330 K), inlet gas velocity (0.0001–1 ▪), sparger radius to column diameter ratio (0.1–0.5), and column height to diameter ratio (1–3) are investigated. A quadratic model for absorption behavior (p-value < 0.0001 and R2 > 0.98) is developed. Four sparger geometries are considered, and the optimal values for column height to diameter and sparger radius to column diameter are estimated. The maximum CO2 concentration is obtained at a pressure of 18.26 bar, temperature of 309.5 K, velocity of 0.825 ▪, the sparger radius to column diameter of 0.414, and column height to diameter of 2.5.

Efficiency of single pharmaceutical surfactants to mimic intestinal biorelevant media solubilization and dissolution of etravirine: Comparison of intrinsic and film dissolution models

We understand that quality control dissolution media may best anticipate in vivo product performance by mimicking in vivo media, but preferably involve at most a single pharmaceutical surfactant for routine laboratory use. The objective here was to estimate the concentrations of six pharmaceutical surfactants to mimic etravirine solubility and intrinsic dissolution rate, as well as dissolution rate from a film model, in each Fed State Simulated Intestinal Fluid Version 2 (FeSSIF-V2) and Fasted State Simulated Intestinal Fluid Version 2 (FaSSIF-V2). Solubility studies and colloid sizing measurements were conducted. Results indicate that all six surfactants were more efficient than FeSSIF-V2 or FaSSIF-V2 at solubilizing drug, and also exhibited higher micelle diffusivities than FeSSIF-V2 and FaSSIF-V2 mixed-micelles. The rank-order potency (on mM basis) of the six pharmaceutical surfactants to mimic etravirine solubility in each FeSSIF-V2 and FaSSIF-V2 was: polysorbate 80 (PS80) > polysorbate 20 (PS20) > polyoxyethylene(23) lauryl ether (POE23) > POE10 > hexadecyltrimethylammonium bromide (HEX) > sodium lauryl sulfate (SLS). This rank-order potency was almost the same to mimic drug dissolution rate into each FeSSIF-V2 and FaSSIF-V2, except POE10 > POE23. For the most potent surfactant, PS80, 0.461 mM and 0.140 mM PS80 was estimated to mimic etravirine's solubility and dissolution rate into FeSSIF-V2, respectively, using the intrinsic dissolution model. The low PS80 concentration to mimic dissolution rate reflects the relatively high diffusivity of PS80 micelles, compared to FeSSIF-V2 mixed-micelle diffusivity, which was the case for all six pharmaceutical surfactants. Results are also presented in terms of a film dissolution model for surfactant-mediated dissolution, where dissolution enhancement was less than that in the intrinsic dissolution model, and the film model required lower surfactant concentration than in intrinsic dissolution model to mimic FeSSIF-V2-enhanced dissolution. Findings have promised to identify single pharmaceutical surfactant concentrations that mimic key performance attributes of biorelevant media.

Towards atomistic modelling of solid Pb-O formation and dissolution in liquid lead coolant: Interatomic potential development

Microscopic description of solid Pb-O formation and dissolution in liquid lead coolant is important for the modelling of fast neutron reactors. For this purpose, in this work we develop interatomic potential models for lead melt with dissolved oxygen. Potentials fitting is based on ab initio density functional theory (DFT) calculations and quantum molecular dynamics. Two different potential models are trained on the DFT data using the force-matching method: a computationally cheap embedded atom method (EAM) potential and a computationally expensive machine-learned moment tensor potential (MTP) that allows reproducing DFT data very accurately. The potentials are further validated to reproduce the properties of lead melt and the coordination of oxygen atoms in molten lead. The diffusion coefficient for oxygen in molten lead is calculated and compared with the available experimental data. We analyse how these interatomic potential models describe the crystal structure of the solid lead oxide to consider PbO nucleation and dissolution in molten lead. We extensively discuss the arising problems with the description of long-range electrostatic interactions. The possibility of matching the experimental data on the oxygen solubility limit by tuning the EAM potential is shown.