There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

For economical and ecological reasons, synthetic chemists are confronted with the increasing obligation of optimizing their synthetic methods. Maximizing efficiency and minimizing costs in the production of molecules and macromolecules constitutes, therefore, one of the most exciting challenges of synthetic chemistry.1-3 The ideal synthesis should produce the desired product in 100% yield and selectivity, in a safe and environmentally acceptable process.4 It is now well recognized that organometallic homogeneous catalysis offers one of the most promising approaches for solving this basic problem.2 Indeed, many of these homogeneous processes occur in high yields and selectivities and under mild reaction conditions. Most importantly, the steric and electronic properties of these catalysts can be tuned by varying the metal center and/or the ligands, thus rendering tailor-made molecular and macromolecular structures accessible.5,6 Despite the fact that various efficient methods, based on organometallic homogeneous catalysis, have been developed over the last 30 years on the laboratory scale, the industrial use of homogeneous catalytic processes is relatively limited.7 The separation of the products from the reaction mixture, the recovery of the catalysts, and the need for organic solvents are the major disadvantages in the homogeneous catalytic process. For these reasons, many homogeneous processes are not used on an industrial scale despite their benefits. Among the various approaches to address these problems, liquidliquid biphasic catalysis (“biphasic catalysis”) has emerged as one of the most important alternatives.6-11 The concept of this system implies that the molecular catalyst is soluble in only one phase whereas the substrates/products remain in the other phase. The reaction can take place in one (or both) of the phases or at the interface. In most cases, the catalyst phase can be reused and the products/substrates are simply removed from the reaction mixture by decantation. Moreover, in these biphasic systems it is possible to extract the primary products during the reaction and thus modulate the product selectivity.12 For a detailed discussion about this and other concepts of homogeneous catalyst immobilization, the reader is referred elsewhere.6,7 These biphasic systems might combine the advantages of both homogeneous (greater catalyst efficiency and mild reaction conditions) and heterogeneous (ease of catalyst recycling and separation of the products) catalysis. The advent of water-soluble organometallic complexes, especially those based on sulfonated phosphorus-containing ligands, has enabled various biphasic catalytic reactions to be conducted on an industrial scale.13-15 However, the use of water as a * Corresponding author. Fax: ++ 55 51 3316 73 04. E-mail: dupont@iq.ufrgs.br. 3667 Chem. Rev. 2002, 102, 3667−3692

https://www.chem.ccu.edu.tw/~joyce/referance/gump/IL/Chem.%20Rev.%202002,%20102,%203667.pdf

Ionic liquid (molten salt) phase organometallic catalysis.

Within the framework of green chemistry, solvents occupy a strategic place. To be qualified as a green medium, these solvents have to meet different criteria such as availability, non-toxicity, biodegradability, recyclability, flammability, and low price among others. Up to now, the number of available green solvents are rather limited. Here we wish to discuss a new family of ionic fluids, so-called Deep Eutectic Solvents (DES), that are now rapidly emerging in the current literature. A DES is a fluid generally composed of two or three cheap and safe components that are capable of self-association, often through hydrogen bond interactions, to form a eutectic mixture with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C. These DESs exhibit similar physico-chemical properties to the traditionally used ionic liquids, while being much cheaper and environmentally friendlier. Owing to these remarkable advantages, DESs are now of growing interest in many fields of research. In this review, we report the major contributions of DESs in catalysis, organic synthesis, dissolution and extraction processes, electrochemistry and material chemistry. All works discussed in this review aim at demonstrating that DESs not only allow the design of eco-efficient processes but also open a straightforward access to new chemicals and materials.

Deep eutectic solvents: syntheses, properties and applications

We calculate the mobilities ui of the metal cations Li+, Na+, K+, Rb+, Cs+, and Ca2+ and the halides F-, Cl-, Br-, and I- at infinite dilution by molecular dynamics simulation using the SPC/E model for water at 25 °C and a reaction field for the long-range interactions. The ion mobilities show the same trends as the experimental results with distinct maxima for cations and anions. The mobilities (defined by ui = Di/kT) of the corresponding uncharged species are also determined by simulation and are in qualitative agreement with Stokes' law. The mobilities of Li+, Na+, K+, Rb+ and F- increase on discharge, whereas Cl, Br, and I have smaller mobilities than the corresponding anions. The mobility of the fictitious I+ ion, which differs from I- only in its charge, lies between that of I- and I in the order uI < uI+ < uI−. The residence time of water in the first solvation shell of small cations (Li+ and Na+) and Ca2+ decreases when the ions are discharged, while the opposite is observed on neutralizing I-, su...

http://omh.umeche.maine.edu/pdfs/JPCB_102_4193_98.pdf

Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C

Intermolecular potentials suitable for molecular dynamics or Monte Carlo simulations have been developed for dimethyl imidazolium and methyl ethyl imidazolium ions. The predicted crystal structures were compared with experimental crystal structures for chloride and PF− 6 salts and found to be satisfactory when the dominant electrostatic interactions were modelled by either an accurate distributed multipole description or a simplified atomic point charge model. A further simplification of using united atoms in place of methyl or methylene groups on the side chains gave a much less satisfactory reproduction of the crystal structures. Liquid dimethyl imidazolium chloride and dimethyl imidazolium PF− 6 were simulated using the explicit atom and united atom potentials. The local structure showed a strong preference for the chloride ions to be located in certain regions around the cation, and a similar, but less strong localization of the larger PF− 6. Significant differences in density and diffusion rates were...

Intermolecular potentials for simulations of liquid imidazolium salts

Molecular dynamics simulations of mixtures of 1,3-dialkyl imidazolium ionic liquids and water have been performed in order to investigate the microscopic physical properties as a function of composition. The behavior of two ionic liquids has been compared, namely 1,3-dimethylimidazolium chloride and 1,3-dimethylimidazolium hexafluorophosphate. The hexafluorophosphate ionic liquids are known to be more hydrophobic as solvents than the corresponding chloride liquids. This is manifested in our simulations by differences in the signs of both the excess volumes and the enthalpies of mixing. However, there is surprisingly little difference in the microscopic properties. In both liquids, water molecules tend to be isolated from each other in mixtures with more ions than water molecules. When the molar proportion of water molecules reaches 75%, a percolating network of waters is found as well as some isolated molecules and small clusters. In all cases, molecular motion becomes faster as the proportion of water in...

A Simulation Study of Water−Dialkylimidazolium Ionic Liquid Mixtures

Ghostly streams from the formation of the Galaxy’s halo

We have been using atomistic simulation for the last 10 years to study properties of imidazolium-based ionic liquids. Studies of dissolved molecules show the importance of electrostatic interactions in both aromatic and hydrogen-bonding solutes. However, the local structure strongly depends upon ion–ion and solute–solvent interactions. We find interesting local alignments of cations at the gas–liquid and solid–liquid interfaces, which give a potential drop through the surface. If the solid interface is charged, this charge is strongly screened over distances of a few nanometres and this screening decays on a fast time scale. We have studied the sensitivity of the liquid structure to force-field parameters and show that results from ab initio simulations can be used in the development of force fields.

Ruth M. Lynden-Bell

Papers

Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C

Intermolecular potentials for simulations of liquid imidazolium salts

A Simulation Study of Water−Dialkylimidazolium Ionic Liquid Mixtures

Ghostly streams from the formation of the Galaxy’s halo

Simulations of ionic liquids, solutions, and surfaces.