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Abstract Arctic single‐layer mixed‐phase clouds were studied using a one‐dimensional model that incorporated the adaptive habit growth model for ice microphysics. The base case was from the Indirect and Semidirect Aerosol Campaign, and it was perturbed over a range of cloud‐average temperatures, maximum (per model run) ice nuclei (IN) concentrations, and large‐scale subsidence velocities. For each parameter combination, the model was iterated out to 48 hr, and the time, called the glaciation time, to complete disappearance of liquid recorded if this occurred within the 48 hr. Dependence of glaciation times on cloud‐average temperatures from −30°C to −5°C, maximum IN concentrations from 0.10 to 30 L−1, and strong–no subsidence, with both isometric and habit‐dependent ice crystal growth, were investigated. For isometric crystal growth, the relationship between the critical maximum IN concentration (INcrit), the maximum (per model run) IN concentration above which a mixed‐phase cloud glaciated within a fixed model runtime, and cloud‐average temperature was monotonic. INcritdecreased with decreasing cloud‐average temperature. Strengthening of subsidence led to a further decrease in INcritfor every cloud‐average temperature. For habit‐dependent ice crystal growth, the relationship between INcritand cloud‐average temperature was nonmonotonic. Ice crystals develop dendritic and columnar habits near −15°C and −7°C, respectively, and at these two temperatures, ice crystals grew and depleted supercooled liquid water faster than the case when ice crystals grew isometrically. This led to deep local minima in INcritaround these two temperatures in the model runs. Habit‐dependent ice crystal growth, coupled with changes in cloud‐average temperature, INcrit, and subsidence strength, led to significant changes in Arctic single‐layer mixed‐phase cloud lifetimes.
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Impurity retention and pharmaceutical solid solutions: visualizing the effect of impurities on dissolution and growth using dyed crystals
Pharmaceutical solid solutions are gaining increased interest as alternatives to salts and co-crystals for the enhancement of drug solubility and dissolution kinetics. Industrially, they are also responsible for the entrapment of potentially toxic impurities in drug substances. The accidental incorporation of process impurities into the lattice of a growing crystal, or the intentional incorporation of an additive, can vastly alter the product's properties. Reported effects include solubility enhancements, changes in melting point, shifting polymorph stabilities, growth inhibition, and change in crystal habit, among others. This work combines the fields of impurity rejection, solid solutions, and dyeing crystals, to provide visual evidence of those effects, and to further demonstrate how impure regions in a single crystal can present vastly different behaviors to the purified regions of the same crystal. The work revolves around four model host–guest pairs, two of them previously unreported. These include mixed crystals of acetaminophen with curcumin, sulforhodamine B, and acid fuchsin, as well as potassium sulfate dyed with acid fuchsin. Results challenge common assumptions in the study of multicomponent crystals, demonstrating how neglecting composition anisotropy may lead to misdiagnosing solid solutions as surface adsorbed impurities in impurity retention diagnostics, and how neglecting the habit-modifying effects of dissolved impurities may lead to the use of erroneous models for growth inhibition. At the same time, we present opportunities for the development of novel impurity rejection and crystal engineering strategies, aiding the growth of anisotropic crystals with properties that can be fine-tuned in continuum.
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- PAR ID:
- 10567651
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- CrystEngComm
- Volume:
- 26
- Issue:
- 38
- ISSN:
- 1466-8033
- Page Range / eLocation ID:
- 5337 to 5350
- Subject(s) / Keyword(s):
- crystallization solid solutions impurities pharmaceutical solubility
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d4ce00742e
