Dissolution Of Crystals Research Articles

Simulation of the rate of dissolution of sucrose crystals

The article presents a nonlinear probabilistic mathematical model of the dissolution rate of sucrose crystals in multicomponent solutions. The developed model is based on the experimental data of A. Brighel-Müller, it is additive and consists of four terms. The first component describes the diffusion of sucrose molecules, the next two parts of the model interpret the reactions of sucrose with water and non-sugars with the formation of its hydrated molecules and sugar-non-sugar compounds. The fourth component characterizes the detachment of active sucrose molecules from the surface of the crystals under the influence of a solvent. In the simulation, a genetic algorithm was used with subsequent refinement of the model coefficients by the Hooke-Jeeves configuration method. The error in modeling the rate of dissolution of crystalline sugar relative to the experimental data of A. Brighel-Müller is ±7.8% at an iteration step of 1⋅10 −5 . The model can be used to assess the loss of sugar in the crystallization section, to control the melting of sugar crystals in syrup, outflow, rinse, purified juice, water. • A probabilistic model of the dissolution rate of sucrose crystals has been developed. • The specific rate of the dissolution process is additive, based on experiments. • The driving force is the difference in activity in saturated and diluted solutions. • The relation between mass and the linear size of the sucrose crystal is approximated. • A probabilistic model is used to optimize the dissolution of sucrose crystals.

Regeneration Growth as One of the Principal Stages of Diamond Crystallogenesis

Revealing the internal structure of diamonds is key to understanding the general regularities of crystal growth and dissolution. This paper presents and summarizes data on the internal structure of diamonds of different morphological types, colors and defect-impurity composition. In order to provide a comprehensive explanation of the stages of diamond growth, crystals and plates were observed, and panchromatic cathodoluminescence and photoluminescence techniques were applied. This article considers the mechanism of tangential growth from existing surfaces (regeneration growth) as an intermediate stage between normal and tangential crystal growth. The regeneration growth is very fast due to the absence of the limiting stage-nucleation of a new atomic layer. Cuboid diamonds were refaceted to stepped octahedrons by the regeneration growth mechanism. A schematic model of crystal habit transformation due to regeneration growth explains the internal structure of crystals in connection with their morphology and thermal history. The main variants of regeneration stage and its morphological manifestations were demonstrated. Most diamonds pass through the regeneration stage, and in many cases, it was a stage of growth termination.

EVALUATION OF IN VITRO ANTIUROLITHIATIC ACTIVITY OF ETHANOLIC EXTRACT OF PAVONIA ZEYLANICA (L) CAV

Objective: To evaluate in vitro antiurolithiatic activities of Pavonia zeylanica (L) Cav. Material and Methods: Whole plant of Ethanolic extract of Pavonia zeylanica was prepared and arranged in the three different concentrations (10mg/ml, 20mg/ml, and 30mg/ml). In vitro antiurolithiatic activity of Ethanolic extract of Pavonia zeylanica through turbidometric and titrimetric method was tested in terms of inhibition of calcium oxalate by nucleation and aggregation and dissolution of calcium oxalate, using the standard drug. Results: Standard drug has high percentage inhibition and dissolution ability and thus Ethanolic extract of Pavonia zeylanica also have a good percentage inhibition and dissolution ability was comparable to standard drug. Conclusion: The study concludes that the Ethanolic extract of Pavonia zeylanica have inhibitory effect on calcium oxalate for nucleation and aggregation assay. It also showed good dissolution of calcium oxalate crystals, so this extract has the good protection against Urolithiasis activity

Dissolution of Portlandite in Pure Water: Part 1 Molecular Dynamics (MD) Approach.

The current contribution proposes a multi-scale bridging modeling approach for the dissolution of crystals to connect the atomistic scale to the (sub-) micro-scale. This is demonstrated in the example of dissolution of portlandite, as a relatively simple benchmarking example for cementitious materials. Moreover, dissolution kinetics is also important for other industrial processes, e.g., acid gas absorption and pH control. In this work, the biased molecular dynamics (metadynamics) coupled with reactive force field is employed to calculate the reaction path as a free energy surface of calcium dissolution at 298 K in water from the different crystal facets of portlandite. It is also explained why the reactivity of the (010), (100), and (10) crystal facet is higher compared to the (001) facet. In addition, the influence of neighboring Ca crystal sites arrangements on the atomistic dissolution rates is explained as necessary scenarios for the upscaling. The calculated rate constants of all atomistic reaction scenarios provided an input catalog ready to be used in an upscaling kinetic Monte Carlo (KMC) approach.

The shrinking toe sign in gout

ObjectiveTo describe the frequency, clinical presentation and understand the pathophysiology of toe shortenings during urate-lowering treatment (ULT) of gout, a feature we called the shrinking toe sign. MethodsSequential foot photographs and radiographs of 1141 consecutive gouty patients followed-up for at least 6 months under ULT were retrospectively scrutinized. Features from patients with toe shortenings were extracted from anonymized files. Tophi adjacent to the shortening sites were semi quantified on foot photographs and toe shortenings were measured on radiographs with the Corel draw software (Corel corporation, Canada). Measurement concordance was assessed by concordance correlation coefficients (CCC) and correlation between tophus scores and toe shortenings was analyzed by using linear model with a patient random effect. 97 patients who did not develop toe shortening during ULT were analyzed as controls. ResultsShrinking toes were observed in 10 patients (0.9%) with tophaceous gout at joints with baseline destructive arthropathy. The first and second toes and metatarsophalangeal joints were predominantly involved. The sign was observed after serum urate had been lowered below the 300 and 360 µmol/l targets, in 8 and 2 patients, respectively. Measured shortenings (CCC: 0.99) correlated (p < 10−4) with decreases in tophus score (CCC: 0.91). Sequential radiograph analysis revealed that toe shortening was mainly due to lytic bone collapse during articular tophus dissolution. Comparison with controls showed that the sign developed in severe gout and in joints with more severe erosion score at baseline. ConclusionThe shrinking toe appears as rare feature of severe tophaceous gout, triggered by dissolution of bone-replacing tophi. Our findings reinforce the need to treat gout early, before destruction of bone scaffold by extensive tophi, as MSU crystal dissolution by ULT may further weaken these areas and induce their collapse.

Hyperpolarized Solution-State NMR Spectroscopy with Optically Polarized Crystals.

Nuclear spin hyperpolarization provides a promising route to overcome the challenges imposed by the limited sensitivity of nuclear magnetic resonance. Here we demonstrate that dissolution of spin-polarized pentacene-doped naphthalene crystals enables transfer of polarization to target molecules via intermolecular cross-relaxation at room temperature and moderate magnetic fields (1.45 T). This makes it possible to exploit the high spin polarization of optically polarized crystals, while mitigating the challenges of its transfer to external nuclei. With this method, we inject the highly polarized mixture into a benchtop NMR spectrometer and observe the polarization dynamics for target 1H nuclei. Although the spectra are radiation damped due to the high naphthalene magnetization, we describe a procedure to process the data to obtain more conventional NMR spectra and extract the target nuclei polarization. With the entire process occurring on a time scale of 1 min, we observe NMR signals enhanced by factors between -200 and -1730 at 1.45 T for a range of small molecules.

Coprecipitation mechanisms of Zn by birnessite formation and its mineralogy under neutral pH conditions

Birnessite (δ-Mn(IV)O2) is a great manganese (Mn) adsorbent for dissolved divalent metals. In this study, we investigated the coprecipitation mechanism of δ-MnO2 in the presence of Zn(II) and an oxidizing agent (sodium hypochlorite) under two neutral pH values (6.0 and 7.5). The mineralogical characteristics and Zn–Mn mixed products were compared with simple surface complexation by adsorption modeling and structural analysis. Batch coprecipitation experiments at different Zn/Mn molar ratios showed a Langmuir-type isotherm at pH 6.0, which was similar to the result of adsorption experiments at pH 6.0 and 7.5. X-ray diffraction and X-ray absorption fine structure analysis revealed triple-corner-sharing inner-sphere complexation on the vacant sites was the dominant Zn sorption mechanism on δ-MnO2 under these experimental conditions. A coprecipitation experiment at pH 6.0 produced some hetaerolite (ZnMn(III)2O4) and manganite (γ-Mn(III)OOH), but only at low Zn/Mn molar ratios (< 1). These secondary precipitates disappeared because of crystal dissolution at higher Zn/Mn molar ratios because they were thermodynamically unstable. Woodruffite (ZnMn(IV)3O7•2H2O) was produced in the coprecipitation experiment at pH 7.5 with a high Zn/Mn molar ratio of 5. This resulted in a Brunauer–Emmett–Teller (BET)-type sorption isotherm, in which formation was explained by transformation of the crystalline structure of δ-MnO2 to a tunnel structure. Our experiments demonstrate that abiotic coprecipitation reactions can induce Zn–Mn compound formation on the δ-MnO2 surface, and that the pH is an important controlling factor for the crystalline structures and thermodynamic stabilities.

Calculation of Crystal-Solution Dissociation Constants.

The calculation of dissociation constants is an important problem in molecular biophysics. For such a calculation, it is important to correctly calculate both terms of the binding free energy; that is, the enthalpy and entropy of binding. Both these terms can be computed using molecular dynamics simulations, but this approach is very computationally expensive, and entropy calculations are especially slow. We develop an alternative very fast method of calculating the binding entropy and dissociation constants. The main part of our approach is based on the evaluation of movement ranges of molecules in the bound state. Then, the range of molecular movements in the bound state (here, in molecular crystals) is used for the calculation of the binding entropies and, then (using, in addition, the experimentally measured sublimation enthalpies), the crystal-to-vapor dissociation constants. Previously, we considered the process of the reversible sublimation of small organic molecules from crystals to vapor. In this work, we extend our approach by considering the dissolution of molecules, in addition to their sublimation. Similar to the sublimation case, our method shows a good correlation with experimentally measured dissociation constants at the dissolution of crystals.

Multicomponent Crystal of Trimethoprim and Citric Acid: Solid State Characterization and Dissolution Rate Studies

BACKGROUND: Trimethoprim is a broad spectrum antimicrobial agent with low solubility in water which causes low bioavailability in systemic circulation.&#x0D; AIM: The purpose of this study was to prepare multicomponent crystals of trimethoprim and citric acid to increase the solubility and dissolution rate of trimethoprim.&#x0D; MATERIALS AND METHODS: Multicomponent crystals were prepared by solvent evaporation method. Characterizations of multicomponent crystalline solid phase properties were carried out by powder X-ray diffraction (PXRD) analysis, differential scanning calorimetry (DSC), FT-IR spectroscopy, scanning electron microscopy (SEM). Solubility and dissolution rate tests were carried out in aqueous medium.&#x0D; RESULTS: The PXRD characterization results showed a new X-ray diffraction pattern in the multicomponent crystal phase. DSC analysis showed the formation of a new endothermic peak. This indicates the formation of a multicomponent crystal phase between trimethoprim and citric acid. The results of the SEM analysis indicate the formation of a new crystal habit. Solubility of multi-component crystal phase of trimethoprim increased 7 times compared to intact trimethoprim. The dissolution of trimethoprim and multicomponent crystals in 0.1 N HCl medium at 60 minutes was 56.36% and 95.57% and CO2-free distilled water medium was 43.03% and 88.26%, respectively.&#x0D; CONCLUSIONS: From the results of the study, it can be concluded that the multicomponent phase of trimethoprim crystals with citric acid successfully increase the solubility and dissolution rate of trimethoprim significantly.

A glance into the future of gout.

Gout is characterized by monosodium urate (MSU) crystal deposits in and within joints. These deposits result from persistent hyperuricaemia and most typically lead to recurrent acute inflammatory episodes (gout flares). Even though some aspects of gout are well characterized, uncertainties remain; this upcoming decade should provide further insights into many of these uncertainties. Synovial fluid analysis allows for the identification of MSU crystals and unequivocal diagnosis. Non-invasive methods for diagnosis are being explored, such as Raman spectroscopy and imaging modalities. Both ultrasound and dual-energy computed tomography (DECT) allow the detection of MSU crystals; this not only provides a mean of diagnosis, but also has furthered gout knowledge defining the presence of a preclinical deposition in asymptomatic hyperuricaemia. Scientific consensus establishes the beginning of gout as the beginning of symptoms (usually the first flare), but the concept is currently under review. For effective long-term gout management, the main goal is to promote crystal dissolution treatment by reducing serum urate below 6 mg/dL (or 5 mg/dL if faster crystal dissolution is required). Current urate-lowering therapies’ (ULTs) options are limited, with allopurinol and febuxostat being widely available, and probenecid, benzbromarone, and pegloticase available in some regions. New xanthine oxidase inhibitors and, especially, uricosurics inhibiting urate transporter URAT1 are under development; it is probable that the new decade will see a welcomed increase in the gout therapeutic armamentarium. Cardiovascular and renal comorbidities are common in gout patients. Studies determining whether optimal treatment of gout will positively impact these comorbidities are currently lacking, but will hopefully be forthcoming. Overall, the single change that will most impact gout management is greater uptake of international rheumatology society recommendations. Innovative strategies, such as nurse-led interventions based on these recommendations have recently demonstrated treatment success for people with gout.

Polymorphism and distinct physicochemical properties of the phloretin–nicotinamide cocrystal

Two novel polymorphs of a cocrystal involving phloretin and nicotinamide were identified and found where the polymorphs show distinct crystal structures, photoluminescence, and dissolution rates.

EVALUATION OF IN-VITRO LITHOLYTIC ACTIVITY OF PLANT BOUGAINVILLEA SPECTABILIS

The aim of present investigation is to evaluate the in-vitro anti urolithiatic activity of the leaves of the plant Bougainvillea spectabilis (Willd.). Ethanolic and aqueous extracts of Bougainvillea spectabilis fresh leaves were prepared. Homogenous precipitation methods were used to prepare artificial stones of calcium oxalate. Semi-permeable membrane of eggs was used as dissolution bags. Different in-vitro anti urolithiatic studies were used such as method of mineralization and titrimetric method to evaluate the inhibition and dissolution of stone crystal using standard drug Cystone. In inhibition as well as dissolution models, the ethanolic extract of Bougainvillea spectabilis has shown better capability to dissolve calcium oxalate. Cystone exhibited strongly inhibitory action in both, the method of mineralization and titrimetric assay. Thus, it was concluded that the ethanolic extract of Bougainvillea spectabilis exhibited inhibitory action in both of the methods to a significant level and the bioactive natural products present in leaf extracts of Bougainvillea spectabilis can be used in the development of new pharmaceuticals that enhances therapeutic use in renal calculi.

Cocrystals of flavonoids with 4,4′-ethylenebispyridine: Crystal structures analysis, dissolution behavior, and anti-tumor activity

The concepts of crystal engineering was utilized to acquire cocrystals of EBP with flavonoids. Four cocrystals were synthesized and characterized, as well their single crystal structures were revealed. The powder dissolution profiles of the cocrystals were determined and the antitumor activities were analyzed and compared with the corresponding physical mixtures. The results showed that the cocrystals of Myr·EBP and Gen·EBP display better anti-tumor effect against HCT-8 and CaCO-2 cancer cells.

Octacalcium phosphate crystals including a higher density dislocation improve its materials osteogenecity

Herein, we show that the enhanced osteogenecity of octacalcium phosphate (OCP) biomaterial, recently identified as an important element in hybrid organic–inorganic nanocomposites involved in the initial hydroxyapatite crystal expansion in mammal bones, results from an enhanced chemical property, stemming from the presence of lattice strain and dislocations. Two types of OCPs were synthesized by wet-chemical processing in the presence (c-OCP) and absence (w-OCP) of gelatin, respectively, and subjected to structural, chemical, and biological analyses. High-resolution transmission electron microscopy (HRTEM) and fast Fourier transform (FFT) analyses revealed that c-OCP crystals contained approximately six times higher edge dislocations with Burgers vectors perpendicular to a-axis than that in the case of w-OCP. The dissolution of c-OCP crystal in tris-HCl buffer occurred toward the long axis of the crystal, most likely, toward the lattice strain along the c-axis direction, while w-OCP crystal dissolved toward the a-axis direction. The study suggested that the increment of internal energy by the higher dislocation density contributed promoting c-OCP dissolution and hydrolysis through decreasing the activation energy. c-OCP crystal displayed enhanced in vitro mesenchymal stem 2D cell and 3D spheroid differentiation, in vivo bone formation, and apatite crystallographic orientation in critical-sized rat calvarial defect model as compared to w-OCP crystal, at the same time, converting to apatite structure earlier than w-OCP. The present study demonstrates that dislocation-related dissolution along with enhanced conversion of OCP is a determinant in bone induction, which may be relevant to normal bone development utilizing OCP biomaterials.

Copper oxalate formation by lichens and fungi

The present work focuses on the revealing the patterns of copper oxalates formation under the influence of lichens and fungi by combination of the results of field studies and model experiments. These findings create the scientific basis for the potential microbial technology applications (ore enrichment, monuments conservation, environment bioremediation, etc.). Copper oxalate moolooite Cu(C2O4)·H2O was discovered in saxicolous lichen Lecidea inops on the weathered chalcopyrite ore of Voronov Bor deposit (Central Karelia, Russia). Bioinspired syntheses of moolooite and wheatleyite Na2Cu(C2O4)2 2H2O with the participation of the microscopic fungi Aspergillus niger (active producer of oxalic acid) were carried out on weathered Cu-ore from the Voronov Bor deposit. It was shown that morphology of moolooite crystals is controlled both by the underlying rock and by the species composition of microorganisms. Iron ions (sourced from the underlying rock) in the crystallization medium inhibits the moolooite formation. The observed intensive dissolution of moolooite crystals are well explained by washing effect of the intratalline solutions which depends on repeatedly dehydration / rehydration cycles in the lichens. Joint interpretation of original and published data shows that moolooite along with other cooper oxalates are biominerals.

Beyond Equilibrium: Kinetic Isotope Fractionation in High-Temperature Environments

Igneous and metamorphic rocks exhibit greater isotopic heterogeneity than expected from equilibrium. Large nonequilibrium isotope effects can arise from diffusion and chemical reactions, such as crystal growth and dissolution. The effects are time-dependent and can, therefore, be used to probe timescales of igneous and metamorphic processes that are inaccessible to direct observation. New discoveries of isotopic variability in nature, informed by diffusion and reaction modeling, can provide unique insights into the formation of rocks in the interiors of planetary bodies.

Ba attachment and detachment fluxes to and from barite surfaces in 137Ba-enriched solutions with variable [Ba2+]/[SO42−] ratios near solubility equilibrium

We measured barium attachment and detachment fluxes from and to barite crystal surfaces in solutions with [Ba]/[SO4] ratios from 0.06 to 52. The doping of 137Ba in the initial experimental solutions enabled us to measure unidirectional fluxes near solubility equilibrium (Q/K ≈ 1.0) in batch reactors. Both attachment and detachment fluxes increase with [Ba]/[SO4] ratios. As expected, since the solutions were near solubility equilibrium (SI≈0.0n), the attachment and detachment fluxes were nearly equal.The experimental data can be fit accurately using the Zhang and Nancollas (1998) (ZN98) process-based AB crystal growth model, which describes crystal growth and dissolution through nucleation and propagation of kink sites. Simultaneous fitting step velocity data of Kowacz et al. (2007) significantly reduced the number of non-uniqueness solutions. The remarkable fit implies that barite recrystallization at room temperature near equilibrium and moderate supersaturation occurs via ion-by-ion addition and removal, rather than the formation of amorphous precursors or aggregation of particles. The model is best fit using different detachment frequencies for Ba and SO4, suggesting the ZN98 assumption that detachment frequencies should be the same for the constituent ions does not apply to barite. Based on experimental data and model fitting, Ba attachment and detachment fluxes at a fixed saturation state increase with [Ba]/[SO4] ratios monotonically. This has potentially significant implications for interpreting isotope and trace element cycling in natural environments.

A three dimensional kinetic Monte Carlo defect-free crystal dissolution model for biological systems, with application to uncertainty analysis and robust optimization

The objective of this study was to construct a novel kinetic Monte Carlo (kMC) model to predict the complete dissolution of nanoscale crystals. The developed framework was designed to predict the dissolution of a wide variety of crystalline minerals, regardless of their composition and crystal structure. The proposed framework was used to explore ways of enhancing crystal dissolution processes by assessing the variability from environmental uncertainties and by performing robust optimization to improve the dissolution performance. The approach was used to simulate calcium carbonate dissolution within the human gastrointestinal system. Polynomial chaos expansions (PCEs) were used to propagate the parametric uncertainty through the kMC model. Robust optimization was subsequently performed to determine the crystal design parameters that achieve target dissolution specifications using low-order PCE coefficient models. The results showcased the applicability of the kMC crystal dissolution model and the need to account for dissolution uncertainty within key biological applications.

Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

Current reactive transport model (RTM) uses transport control as the sole arbiter of differences in reactivity. For the simulation of crystal dissolution, a constant reaction rate is assumed for the entire crystal surface as a function of chemical parameters. However, multiple dissolution experiments confirmed the existence of an intrinsic variability of reaction rates, spanning two to three orders of magnitude. Modeling this variance in the dissolution process is vital for predicting the dissolution of minerals in multiple systems. Novel approaches to solve this problem are currently under discussion. Critical applications include reactions in reservoir rocks, corrosion of materials, or contaminated soils. The goal of this study is to provide an algorithm for multi-rate dissolution of single crystals, to discuss its software implementation, and to present case studies illustrating the difference between the single rate and multi-rate dissolution models. This improved model approach is applied to a set of test cases in order to illustrate the difference between the new model and the standard approach. First, a Kossel crystal is utilized to illustrate the existence of critical rate modes of crystal faces, edges, and corners. A second system exemplifies the effect of multiple rate modes in a reservoir rock system during calcite cement dissolution in a sandstone. The results suggest that reported variations in average dissolution rates can be explained by the multi-rate model, depending on the geometric configurations of the crystal surfaces.

Ligand-Free Processable Perovskite Semiconductor Ink.

Traditional covalent semiconductors require complex processing methods for device fabrication due to their high cohesive energies. Here, we develop a stable, ligand-free perovskite semiconductor ink that can be used to make patterned semiconductor-based optoelectronics in one step. The perovskite ink is formed via the dissolution of crystals of vacancy-ordered double perovskite Cs2TeX6 (X = Cl-, Br-, I-) in polar aprotic solvents, leading to the stabilization of isolated [TeX6]2- octahedral anions and free Cs+ cations without the presence of ligands. The stabilization of the fundamental perovskite ionic octahedral building blocks in solution creates multifunctional inks with the ability to reversibly transform between the liquid ink and the solid-state perovskite crystalline system in air within minutes. These easily processable inks can be patterned onto various materials via dropcasting, spraying or painting, and stamping, highlighting the crucial role of solvated octahedral complexes toward the rapid formation of phase-pure perovskite structures in ambient conditions.