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Carbon Ring (carbon + ring)
Selected AbstractsApplication of CAMD in separating hydrocarbons by extractive distillationAICHE JOURNAL, Issue 12 2005Biaohua Chen Abstract The solvent is the core of extractive distillation, and a suitable solvent plays an important role in the economical design of extractive distillation. Computer-aided molecular design (CAMD) has been applied to rapidly screen the solvents for separating hydrocarbons by extractive distillation. The systems of propane/propylene, n-butane/1-butene, and n-heptane/benzene, respectively, as the representatives of C3, C4, and C6 hydrocarbons were investigated, and the potential solvents were selected by means of CAMD. The designed results were further proven by experiments and process simulation. The mechanism for separating hydrocarbons by extractive distillation is based on the different fluidities of the electron cloud of CC (no double bond), CC (one double bond), and ACH (aromatic carbon ring) bonds and thus different interactions between solvent and hydrocarbon molecules. To improve the separation ability of the main solvent, one strategy is to add some additive that can form hydrogen bonding with the main solvent to make into a mixture. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] EXAFS study of local atomic order about iodine in thyroxine, rat, human and sheep thyroidsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2008B. R. Orton Radioactive 125I emits short-range Auger electrons and represents a human health risk when incorporated in thyroglobulin of the thyroid. Quantitative evaluation of this risk can only be realised if local atomic order about iodine in the thyroid is known. Here, extended X-ray absorption fine structure (EXAFS) has been used to probe the local structure about iodine in pure thyroid hormone, thyroxine. These data are consistent with a model where iodine is bound to a single iodinated carbon ring linked to an oxygen atom, similar to a previously published model for monoiodotyrosine, a major iodinated residue in thyroglobulin. Several structural models for the local environment of iodine from rat, human and sheep have been tested and these data are found to be compatible with a slightly modified environment with respect to that found for thyroxine. The best-fit models include the following three components: (i) iodine covalently bonded to a tyrosine ring, as found for thyroxine; (ii) iodine bonded quasi-covalently to a carbonyl ligand in partially filled (50%) sites; (iii) partially filled sites (50,40%) of carbonyl ligands, with oxygen at van der Waals distances from iodine. Advantages of using Fourier-filtered EXAFS for complex crystal structures are discussed. [source] Quantum monte carlo methods for electronic structure of nanosystemsISRAEL JOURNAL OF CHEMISTRY, Issue 2-3 2002Lubos Mitas We provide a brief review of recent applications of quantum Monte Carlo (QMC) methods to the electronic structure of nanosystems. We report on calculations of carbon rings with second-order Jahn-Teller effect, energy ordering of silicon clusters, dissociation enthalpies of protonated hydrogen clusters, and other interesting challenges. We point out the QMC accuracy and outline a few ideas that characterize the current position of QMC among the electronic structure methods and its future development. [source] Pterocaryquinone, a Novel Naphthoquinone Derivative from Pterocarya tonkinesisCHINESE JOURNAL OF CHEMISTRY, Issue 12 2006Hong-Bing Liu Abstract Pterocaryquinone, a novel 1,4-naphthoquinone derivative, was isolated from Pterocarya tonkinesis and its structure was elucidated by spectroscopic methods. Pterocaryquinone is a new dimeric 1,4-naphthoquinone derivative having a pentacyclic skeleton with two five-membered carbon rings, which provided a novel structural skeleton for 1,4-naphthoquinone derivatives and showed apoptosis-inducing activity toward mouse cancer tsFT210 cells. [source] | ||||||||||