Chemical models of hot molecular cores

2008 ◽  
pp. 368-371
Author(s):  
T. J. Millar ◽  
P. D. Brown
Keyword(s):  
Chemical Models

Chemometric Analysis of Substituent Effects. VIII. Alternative Interpretation of Substituent Effects (AISE)

1995 ◽  
Vol 60 (9) ◽  
pp. 1502-1528 ◽  
Author(s):  
Oldřich Pytela
Keyword(s):  
Multiple Bond ◽  
Substituent Effects ◽  
Alternative Interpretation ◽  
Class I ◽  
Reaction Centre ◽  
Correlation Equations ◽  
Class Iii ◽  
Substituent Constant ◽  
Chemical Models ◽  
The Individual

Alternative interpretation of substituent effects (AISE) starts from the presumption that a substituent only possesses a single property described by a single substituent constant. This property is transmitted to the reaction centre by three different ways depending on the interaction type in the triad reaction centre - basic skeleton - substituent. For interpretation it is substantial whether or not the substituent has p electrons at the atom adjacent to the basic skeleton. If it has none, the substituent belongs to class I and operates only by its basic effect described by the mentioned single substituent constant. Substituents of class II possess a free electron pair at the atom adjacent to the basic skeleton, and those of class III have a multiple bond between the first and the second atoms which is polarized in the direction from the basic skeleton. Substituent effects in class I are described by a substituent constant identical with σI constant. Substituents in classes II and III show additional effects proportional to the same constant. Hence, a separate treatment of substituent effects in the individual classes provides three straight lines intersecting in a common point. Mathematically, the description of substituent effects in this approach is expressed by a family of lines with a single explaining variable. The point of intersection, which is referred to as the iso-effect point, is not identical with the classic standard substituent - hydrogen - but is near to CN substituent. The approach given has the advantage of adopting a single substituent constant whose scale can be adjusted relatively precisely. Its drawback (like in the case of the correlation equations derived from the principle of separation of substituent effects) lies in a more extensive set of substituents needed for a correlation. The AISE principle has been applied to 318 series of experimental data describing effects of 32 substituents in a large variety of chemical models (aliphatic, alicyclic, aromatic, heteroaromatic, with or without direct conjugation between reaction centre and substituent) in both chemical reactions and equilibria. A comparison with two other correlation relations with two and three substituent constants for interpretation of substituent effects based on the principle of separation of the individual substituent effects showed that the closeness of AISE based correlations is comparable with that of the correlation equations currently used. It was somewhat less successful in the models with direct conjugation between reaction centre and substituent but the AISE principle can be used even in these cases.

scholarly journals Carbon-chain molecules in molecular outflows and Lupus I region – new producing region and new forming mechanism

2019 ◽  
Vol 488 (1) ◽  
pp. 495-511
Author(s):  
Yuefang Wu ◽  
Xunchuan Liu ◽  
Xi Chen ◽  
Lianghao Lin ◽  
Jinghua Yuan ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Molecular Cloud ◽  
Carbon Chain ◽  
Species Range ◽  
Chain Molecules ◽  
Forming Mechanism ◽  
Molecular Outflows ◽  
Chemical Models ◽  
Cloud Complex

Abstract Using the new equipment of the Shanghai Tian Ma Radio Telescope, we have searched for carbon-chain molecules (CCMs) towards five outflow sources and six Lupus I starless dust cores, including one region known to be characterized by warm carbon-chain chemistry (WCCC), Lupus I-1 (IRAS 15398-3359), and one TMC-1 like cloud, Lupus I-6 (Lupus-1A). Lines of HC3N J = 2 − 1, HC5N J = 6 − 5, HC7N J = 14 − 13, 15 − 14, 16 − 15, and C3S J = 3 − 2 were detected in all the targets except in the outflow source L1660 and the starless dust core Lupus I-3/4. The column densities of nitrogen-bearing species range from 1012 to 1014 cm−2 and those of C3S are about 1012 cm−2. Two outflow sources, I20582+7724 and L1221, could be identified as new carbon-chain-producing regions. Four of the Lupus I dust cores are newly identified as early quiescent and dark carbon-chain-producing regions similar to Lup I-6, which together with the WCCC source, Lup I-1, indicate that carbon-chain-producing regions are popular in Lupus I which can be regard as a Taurus-like molecular cloud complex in our Galaxy. The column densities of C3S are larger than those of HC7N in the three outflow sources I20582, L1221, and L1251A. Shocked carbon-chain chemistry is proposed to explain the abnormal high abundances of C3S compared with those of nitrogen-bearing CCMs. Gas-grain chemical models support the idea that shocks can fuel the environment of those sources with enough S+ thus driving the generation of S-bearing CCMs.

scholarly journals Chemical Models of Solute Acquisition in Glacial Melt Waters

1984 ◽  
Vol 30 (104) ◽  
pp. 49-57 ◽  
Author(s):  
R. Raiswell
Keyword(s):  
Closed System ◽  
Mineral Weathering ◽  
Hydrogen Ion ◽  
Mixing Ratio ◽  
System Models ◽  
Chemical Models ◽  
Rock Mineral ◽  
Carbonate Equilibria ◽  
Solute Acquisition ◽  
Final Composition

AbstractChemical models for the evolution of bulk melt waters can be constructed by assuming that rock mineral weathering and solute acquisition are controlled by carbonate equilibria. Different open- and closed- system models are defined by variations in the rates of weathering relative to the rate of hydrogen-ion supply by the dissolution and dissociation of CO2, and can be recognized by characteristic pH and ∑+relationships. The observed and inferred compositions of englacial and subglacial melt suggest that mixing is unlikely to be conservative and that closed-system conditions result where post-mixing weathering reactions occur. The final composition of bulk melt waters is determined by the mixing ratio between englacial and subglacial melt, the extent of post-mixing evolution, and opportunity for mixing with ground waters or re-equilibration with the atmosphere.

An efficient algorithm for corona simulation with complex chemical models

2017 ◽  
Vol 337 ◽  
pp. 233-251 ◽  
Author(s):  
Andrea Villa ◽  
Luca Barbieri ◽  
Marco Gondola ◽  
Andres R. Leon-Garzon ◽  
Roberto Malgesini
Keyword(s):  
Efficient Algorithm ◽  
Complex Chemical ◽  
Chemical Models

scholarly journals Toward Experimental Evolution with Giant Vesicles

Life ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 53 ◽  
Author(s):  
Hironori Sugiyama ◽  
Taro Toyota
Keyword(s):  
Chemical Evolution ◽  
Self Assembly ◽  
Experimental Evolution ◽  
Microfluidic Devices ◽  
Future Perspective ◽  
Cell Models ◽  
Giant Vesicles ◽  
Chemical Models ◽  
Recent Developments ◽  
Oil Emulsions

Experimental evolution in chemical models of cells could reveal the fundamental mechanisms of cells today. Various chemical cell models, water-in-oil emulsions, oil-on-water droplets, and vesicles have been constructed in order to conduct research on experimental evolution. In this review, firstly, recent studies with these candidate models are introduced and discussed with regards to the two hierarchical directions of experimental evolution (chemical evolution and evolution of a molecular self-assembly). Secondly, we suggest giant vesicles (GVs), which have diameters larger than 1 µm, as promising chemical cell models for studying experimental evolution. Thirdly, since technical difficulties still exist in conventional GV experiments, recent developments of microfluidic devices to deal with GVs are reviewed with regards to the realization of open-ended evolution in GVs. Finally, as a future perspective, we link the concept of messy chemistry to the promising, unexplored direction of experimental evolution in GVs.

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