A theory of the rate of sublimation

Miyamoto, Susumu

doi:10.1039/tf9332900794

Cited by 23 publications

(6 citation statements)

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“…The opposite process of Ga-atom reincorporation from the surface back to the lattice is assumed to be less temperature dependent, particularly proportional to the T 1/ factor. 14 Additionally, both reincorporation and desorption are assumed to happen only to the "free" Ga-atoms (adatoms) already on the surface (i.e., not directly from the lattice in the case of desorption), while leaving the lattice is possible only for Ga-atoms at lattice sites that are not covered by the "free" Ga-atoms preaccumulated on the surface. This means that during annealing, double-and multiple layers of "free" Ga-atoms on the surface are not considered to occur significantly in the proposed model.…”

Section: Methodsmentioning

confidence: 99%

“…The rates of Ga-atom leaving the GaN lattice (to become Ga adatoms on the surface) and their irreversible desorption from it were both assumed to be proportional to the Arrhenius factors e – E a / k B T where E a is the activation energy of the particular process and k B T (the product of the Boltzmann constant and absolute temperature) is the average thermal energy of Ga-atoms. The opposite process of Ga-atom reincorporation from the surface back to the lattice is assumed to be less temperature dependent, particularly proportional to the factor . Additionally, both reincorporation and desorption are assumed to happen only to the “free” Ga-atoms (adatoms) already on the surface (i.e., not directly from the lattice in the case of desorption), while leaving the lattice is possible only for Ga-atoms at lattice sites that are not covered by the “free” Ga-atoms preaccumulated on the surface.…”

Section: Methodsmentioning

confidence: 99%

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Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Zubialevich

Pampili

Parbrook

2020

Crystal Growth & Design

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Thermal annealing of top−down fabricated GaN nanocolumns (NCs) was investigated over a wide range of temperatures for ammonia-rich atmospheres of both nitrogen and hydrogen. It was found that in contrast to the annealing of planar GaN layers, where surface morphology change is governed purely by material decomposition, reshaping of GaN NCs is strongly affected by competition between different crystallographic facets, which in turn depends on ambient atmosphere and temperature. A qualitative mechanism explaining the observed behavior has been proposed. On the basis of the analysis of these annealing results, growth conditions suitable for either predominantly lateral expansion of the NCs turning their sidewalls into six well-defined vertical m-plane facets, or, vice versa, their infilling from the base regions between the NCs were determined. GaN NC arrays of increased filling factors as compared to the as top−down fabricated ones have been demonstrated using these optimized growth conditions.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Zubialevich

Pampili

Parbrook

2020

Crystal Growth & Design

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“…The glycine and the water sublimation rate (molec cm −2 s −1 ) from the surface can be calculated through the Hertz-Knudsen relation (Miyamoto 1933…”

Section: Glycine Density Profilementioning

confidence: 99%

Distributed glycine in comet 67P/Churyumov-Gerasimenko

Hadraoui

Cottin

Ivanovski

et al. 2019

A&A

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Most of the gaseous molecules that are detected in cometary atmospheres are produced through sublimation of nucleus ices. Distributed sources may also occur, that is, production within the coma, from the solid component of dust particles that are ejected from the nucleus. Glycine, the simplest amino acid, was observed episodically in the atmosphere of comet 67P/Churyumov-Gerasimenko (67P) by the ROSINA mass spectrometer on board the Rosetta probe. A series of measurements on 28 March 2015 revealed a distributed density profile at between 14 and 26 km away from the nucleus. We here present and discuss three study cases: (i) glycine emitted directly and only from the nucleus, (ii) glycine emitted from the sublimation of solid-state glycine on the dust particles that are ejected from the nucleus, and (iii) glycine molecules embedded in water ice that are emitted from the sublimation of this ice from the dust particles that are ejected from the nucleus. A numerical model was developed to calculate the abundance of glycine in the atmosphere of comet 67P as a function of the distance from the nucleus, and to derive its initial abundance in the lifted dust particles. We show that a good fit to the observations corresponds to a distributed source of glycine that is embedded in sublimating water ice from dust particles that are ejected from the nucleus (iii). The few hundred ppb of glycine embedded in water ice on dust particles (nominally 170 ppb by mass) agree well with the observed distribution.

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“…The classical Noyes–Whitney relationship was explained using Boltzman’s thermodynamic principles as early as in 1933 44. However, a well founded mathematical model for reaction‐limited dissolution has not been proposed until recently.…”

Section: The Evolution Of Gi Drug Absorption Analysismentioning

confidence: 99%

Computational‐Regulatory Developments in the Prediction of Oral Drug Absorption

Valsami

Macheras

2011

Molecular Informatics

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Early prediction of human intestinal absorption is important in selection of potential orally administered drugs. Various computational models for prediction of the fraction of dose absorbed, Fa, have been developed. In 1989, a sigmoidal relationship between Fa and drug absorption potential was shown. Since then various physicochemical descriptors of molecules (lipophilicity, polar surface area, hydrogen bond descriptors) have been found to correlate with human intestinal absorption and various attempts in estimating Fa have been reported. Most studies rely on the presupposition that Fa is mainly dependent on drug's solubility, which drives the dissolution rate in the gastrointestinal (GI) fluids, and the rate of passive drug transport across the intestinal membrane. In the same vein, the biopharmaceutics classification system (BCS) and the relevant FDA guideline classify drugs in four categories according to their aqueous solubility and permeability. However, the biopharmaceutics drug disposition classification system (BDDCS) revealed the poor predictability of permeability estimates for Fa and the major role of transporters for GI uptake of drugs. The role of solubility in the reaction limited model of dissolution and the ubiquitous presence of supersaturated solubility-dissolution phenomena in the GI lumen, call for a more physiologically relevant consideration of GI absorption.

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A theory of the rate of sublimation

Cited by 23 publications

References 0 publications

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Thermal Stability of Crystallographic Planes of GaN Nanocolumns and Their Overgrowth by Metal Organic Vapor Phase Epitaxy

Distributed glycine in comet 67P/Churyumov-Gerasimenko

Computational‐Regulatory Developments in the Prediction of Oral Drug Absorption

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