scholarly journals Application of the Classical Nucleation Theory for Quasi-real Systems Differ in Dipole Moment Value – the Role of Diffusion

2021 ◽  
Author(s):  
Kajetan Koperwas ◽  
Filip Kaśkosz ◽  
Frederic Affouard ◽  
Andrzej Grzybowski ◽  
Marian Paluch
Keyword(s):  
Dipole Moment ◽  
Model Systems ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Stability Behavior ◽  
Kinetic Aspect ◽  
Proposed Model ◽  
Structural Differences ◽  
Crystallization Tendency

Abstract In this paper, we examine the crystallization tendency for two quasi-real systems, which differ exclusively in the dipole moment's value. The main advantage of the studied system is the fact that despite that their structures are entirely identical, they exhibit different physical properties. Hence, the results obtained for one of the proposed model systems cannot be scaled to reproduce the results for another corresponding system, as it can be done for simple model systems, where structural differences are modeled by the different parameters of the intermolecular interactions. Our results show that both examined systems exhibit similar stability behavior below the melting temperature. This finding is contrary to the classical nucleation theory predictions, which differ significantly for them. On the basis of the performed studies, we suggest that a kinetic aspect of the classical nucleation theory seems to be a reason for reported discrepancies.

Nucleation and Glass Formation

1985 ◽  
Vol 57 ◽  
Author(s):  
D. R. Uhlmann ◽  
M. C. Weinberg
Keyword(s):  
Glass Formation ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Oxide Glass ◽  
Classical Nucleation Theory ◽  
Nucleation Kinetics ◽  
Formation Behavior ◽  
Homogeneous Crystal ◽  
Exponential Factors

AbstractThe role of nucleation kinetics in affecting glass formation behavior is discussed. Also considered are measurements of homogeneous crystal nucleation in a variety of liquids. For a number of oxide glass-forming liquids, available data indicate pre-exponential factors which are larger than those predicted from classical nucleation theory by factors of 1017 to 1049. Possible sources of this discrepancy are discussed.

scholarly journals Nonclassical Nucleation—Role of Metastable Intermediate Phase in Crystal Nucleation: An Editorial Prefix

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 174
Author(s):  
Fajun Zhang ◽  
José A. Gavira ◽  
Geun Woo Lee ◽  
Dirk Zahn
Keyword(s):  
Intermediate Phase ◽  
Solid Phase ◽  
Early Stage ◽  
Order Parameters ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Supersaturated Solution ◽  
Liquid Phases

Classical nucleation theory (CNT), which was established about 90 years ago, represents the most commonly used theory in describing nucleation processes. For a fluid-to-solid phase transition, CNT states that the solutes in a supersaturated solution reversibly form small clusters. Once a cluster reaches its critical size, it becomes thermodynamically stable and is favored for further growth. One of the most important assumptions of CNT is that the nucleation process is described by one reaction coordinate and all order parameters proceed simultaneously. Recent studies in experiments, computer simulations, and theory have revealed nonclassical features in the early stage of nucleation. In particular, the decoupling of order parameters involved during a fluid-to-solid transition leads to the so-called two-step nucleation mechanism, in which a metastable intermediate phase (MIP) exists in parallel to the initial supersaturated solution and the final crystals. These MIPs can be high-density liquid phases, mesoscopic clusters, or preordered states. In this Special Issue, we focus on the role of the various MIPs in the early stage of crystal nucleation of organic materials, metals and alloys, aqueous solutions, minerals, colloids, and proteins, and thus on various scenarios of nonclassical pathways of crystallization.

scholarly journals Modelling of the Polymorph Nucleation based on Classical Nucleation Theory

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 69 ◽  
Author(s):  
Lie-Ding Shiau
Keyword(s):  
Dissociation Rate ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Measured Weight ◽  
Polymorphic Crystals ◽  
Proposed Model ◽  
Competitive Mechanism ◽  
Period Data ◽  
Dissociation Rate Constants ◽  
Thermodynamic Instability

To elucidate the relative nucleation rates of different polymorphs, a competitive kinetic model is developed based on classical nucleation theory to describe the time evolution of two different polymorphic cluster size distributions controlled by the association and dissociation of the solute molecules during polymorph nucleation. Although there is only one type of the solute molecules, the agglomerated solute clusters are divided into two types–A form and B form, which resemble the structures and morphologies of the different mature polymorphs and eventually lead to the formation of two polymorphic crystals. A dissociation kernel is incorporated into the proposed model to account for gradual dissolution of the solute clusters smaller than a critical nucleus size due to the thermodynamic instability. By fitting the experimental induction period data and the final measured weight fractions of eflucimibe polymorphs with the proposed model, the association and dissociation rate constants for two polymorphs are determined. The developed model is satisfactory to explain the competitive mechanism of polymorph nucleation for eflucimibe that B form dominates at higher supersaturation while A form dominates at lower supersaturation. The results also indicate that A form is more stable than B form with a transition energy of 3.1kJ/mole at 35°C.

Regulation of microRNAs in Inflammation-Associated Colorectal Cancer: A Mechanistic Approach

2020 ◽  
Vol 20 ◽  
Author(s):  
Sridhar Muthusami ◽  
Ilangovan Ramachandran ◽  
Sneha Krishnamoorthy ◽  
Yuvaraj Sambandam ◽  
Satish Ramalingam ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Molecular Mechanisms ◽  
Colorectal Carcinogenesis ◽  
Model Systems ◽  
Necrosis Factor Alpha ◽  
Multi Stage ◽  
Mechanistic Approach ◽  
Tnf Α ◽  
Factor Alpha

: The development of colorectal cancer (CRC) is a multi-stage process. The inflammation of the colon as in inflammatory bowel disease (IBD) such as ulcerative colitis (UC) or Crohn’s disease (CD) is often regarded as the initial trigger for the development of CRC. Many cytokines such as tumor necrosis factor alpha (TNF-α) and several interleukins (ILs) are known to exert proinflammatory actions, and inflammation initiates or promotes tumorigenesis of various cancers, including CRC through differential regulation of microRNAs (miRNAs/miRs). miRNAs can be oncogenic miRNAs (oncomiRs) or anti-oncomiRs/tumor suppressor miRNAs, and they play key roles during colorectal carcinogenesis. However, the functions and molecular mechanisms of regulation of miRNAs involved in inflammation-associated CRC are still anecdotal and largely unknown. Consolidating the published results and offering perspective solutions to circumvent CRC, the current review is focused on the role of miRNAs and their regulation in the development of CRC. We have also discussed the model systems adapted by researchers to delineate the role of miRNAs in inflammation-associated CRC.

Role of inflammation in the development of colorectal cancer

2020 ◽  
Vol 20 ◽  
Author(s):  
Sridhar Muthusami ◽  
R. Ileng Kumaran ◽  
Kokelavani Nampalli Babu ◽  
Sneha Krishnamoorthy ◽  
Akash Guruswamy ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Chronic Inflammation ◽  
Interleukin 1 ◽  
Cell Types ◽  
Model Systems ◽  
Cytokine Gene Expression ◽  
Necrosis Factor Alpha ◽  
Tnf Α ◽  
Proinflammatory Molecules

: Chronic inflammation can lead to the development of many diseases including cancer. Inflammatory bowel disease (IBD) that includes both ulcerative colitis (UC) and Crohn's disease (CD) are risk factors for the development of colorectal cancer (CRC). Many cytokines produced primarily by the gut immune cells either during or in response to localized inflammation in the colon and rectum are known to stimulate the complex interactions between the different cell types in the gut environment resulting in acute inflammation. Subsequently, chronic inflammation together with genetic and epigenetic changes has been shown to lead to the development and progression of CRC. Various cell types present in the colon such as enterocytes, Paneth cells, goblet cells and macrophages express receptors for inflammatory cytokines and respond to tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6 and other cytokines. Among the several cytokines produced, TNF-α and IL-1β are the key proinflammatory molecules that play critical roles in the development of CRC. The current review is intended to consolidate the published findings to focus on the role of proinflammatory cytokines, namely TNF-α and IL-1β, on inflammation (and the altered immune response) in the gut, to better understand the development of CRC in IBD, using various experimental model systems, preclinical and clinical studies. Moreover, this review also highlights the current therapeutic strategies available (monotherapy and combination therapy), to alleviate the symptoms or treat inflammationassociated CRC by using monoclonal antibodies or aptamers to block proinflammatory molecules, inhibitors of tyrosine kinases in inflammatory signaling cascade, competitive inhibitors of proinflammatory molecules, and the nucleic acid drugs like small activating RNAs (saRNAs) or microRNA (miRNA) mimics to activate tumor suppressor or repress oncogene/proinflammatory cytokine gene expression.

Social Networking Sites Continuance: An Application of Extended Theory of Planned Behaviour

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Himanshu Rajput
Keyword(s):  
Social Networking ◽  
Social Networking Sites ◽  
Theory Of Planned Behaviour ◽  
Standard Theory ◽  
Planned Behaviour ◽  
Privacy Concerns ◽  
Proposed Model ◽  
Continued Use ◽  
Moderating Role

Social networking sites (SNSs) have become popular in India with the proliferation of Internet. SNSs have gained the interests of academicians and researchers. The current study is an endeavor to understand the continuance of social networking sites in India. The study applies an extended version of theory of planned behavior. Additional factors privacy concerns and habits were incorporated into the standard theory of planned behaviour. A survey was conducted in a Central University in India. Overall, data was collected from 150 respondents. PLS-SEM was used to test the proposed model. All the hypotheses except the moderating role of habits between intentions and continued use of social networking sites, were supported by the results. Habits were found to affect continued use of social networking sites indirectly through continued intentions.

On the Structure of Lead(II) Complexes in Aqueous Solutions. I. Trinuclear Clusters

1995 ◽  
Vol 60 (4) ◽  
pp. 527-536 ◽  
Author(s):  
Martin Breza ◽  
Alena Manová
Keyword(s):  
Quantum Chemistry ◽  
Aqueous Solutions ◽  
Electronic Structures ◽  
Mndo Method ◽  
Model Systems ◽  
Trinuclear Clusters ◽  
The Stability ◽  
Semiempirical Mndo

Using semiempirical MNDO method of quantum chemistry the optimal geometries and corresponding electronic structures of [Pb3(OH)n]6-n model systems as well as of their hydrated [Pb3(OH)n(H2O)8-n]6-n analogues (n = 4, 5) are investigated. The most stable trinuclear lead(II) complexes present in aqueous solutions correspond to cyclo-(μ3-OH)(μ2-OH)3Pb32+, Pb(μ-OH)2Pb(μ-OH)2Pb2+, cyclo-(μ3-OH)2(μ2-OH)3Pb3+, Pb(OH)(μ-OH)2Pb(μ-OH)Pb(OH)+ and Pb(OH)(μ-OH)2Pb(μ-OH)2Pb+ systems. The key role of OH bridges (by vanishing direct Pb-Pb bonds) on the stability of individual isomers is discussed.

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