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Sample records for lariat crown ethers

  1. Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

    PubMed Central

    Cho, Dae Won

    2014-01-01

    Summary In this review, we describe direct and indirect photochemical approaches that have been developed for the preparation of phthalimide- and naphthalimide-based, lariat-type crown ethers. The direct route utilizes a strategy in which nitrogen-linked side chains containing polyethoxy-tethered phthalimides and naphthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which SET-promoted macrocyclization reactions of α-trialkylsilyl-terminated, polyethoxy-tethered phthalimides and naphthalimides are followed by a side chain introduction through substitution reactions at the amidol centers in the macrocyclic ethers. The combined observations made in these investigations demonstrate the unique features of SET-promoted photocyclization reactions that make them well-suited for the use in the synthesis of functionalized crown ethers. In addition, while some limitations exist for the general use of SET-photochemical reactions in large-scale organic synthesis, important characteristics of the photoinduced macrocyclization reactions make them applicable to unique situations in which high temporal and spatial control is required. PMID:24605169

  2. A highly K(+)-selective phenylaza-[18]crown-6-lariat-ether-based fluoroionophore and its application in the sensing of K+ ions with an optical sensor film and in cells.

    PubMed

    Ast, Sandra; Schwarze, Thomas; Müller, Holger; Sukhanov, Aleksey; Michaelis, Stefanie; Wegener, Joachim; Wolfbeis, Otto S; Körzdörfer, Thomas; Dürkop, Axel; Holdt, Hans-Jürgen

    2013-10-25

    Herein, we report the synthesis of two phenylaza-[18]crown-6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K(+) ions under simulated physiological conditions. The presence of a 2-methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat-free phenylaza-[18]crown-6 ether analogues. Probe 1 shows a high K(+)/Na(+) selectivity and a 2.5-fold fluorescence enhancement was observed in the presence of 100 mM K(+) ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8% per 1 mM K(+) within the range 1-10 mM K(+). The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K(+) ions on both the extracellular and intracellular levels. PMID:24105686

  3. Alkylated lariat ethers as solvent extraction reagents: Surveying the extraction of alkali metals by bis-t-octylbenzo-14-crown-4-acetic acid by use of potentiometric two-phase titration

    SciTech Connect

    Sachleben, R.A.; Moyer, B.A.; Case, F.I.; Garmon, S.A.

    1993-01-01

    Two-phase potentiometric titrimetry was used to survey the extraction of alkali metal cations from aqueous chloride solution by the lipophilic, ionizable lariat ether bis-(t-octylbenzo)-14-crown-4-acetic acid (BOB14C4AA) in o-xylene. Analysis of the data indicates that ion-exchange extraction by the crown-carboxylic acid at low loading (i.e., low conversion of BOB14C4AA to its salt form) is stronger for lithium ion than for the other alkali metals. Little or no selectivity occurs at high loadings. In comparison with the long-chain carboxylic acid 2-methyl-2-heptylnonanoic acid (HMHN), BOB14C4AA extracts lithium and sodium at significantly lower pH; in the loading range of 0.1 to 0.7, the pH shift is 1.4-1.8 pH units for sodium ion and 1.7-2.3 pH units for lithium ion. The titration data are interpreted in terms of aggregated organic-phase species. In the case of lithium extraction, clear evidence was found for a species in which neutral BOB14C4AA participates in the organic-phase complexation of the metal cation.

  4. Crown ethers in graphene

    SciTech Connect

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.

  5. Crown ethers in graphene

    DOE PAGESBeta

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-13

    Crown ethers, introduced by Pedersen1, are at their most basic level neutral rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted special attention for their ability to selectively incorporate various atoms2 or molecules within the cavity formed by the ring3-6. This property has led to the use of crown ethers and their compounds in a wide range of chemical and biological applications7,8. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity9,10. In this Letter, we report atomic-resolution images of the same basicmore » structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar and thus uniquely suited for the many applications that crown ethers are known for. First-principles calculations show that the close similarity of the structures seen in graphene with those of crown ether molecules also extends to their selectivity towards specific metal cations depending on the ring size. Atoms (or molecules) incorporated within the crown ethers in graphene offer a simple environment that can be easily and systematically probed and modeled. Thus, we expect that this discovery will introduce a new wave of investigations and applications of chemically functionalized graphene.« less

  6. Crown ethers in graphene

    NASA Astrophysics Data System (ADS)

    Guo, Junjie; Lee, Jaekwang; Contescu, Cristian I.; Gallego, Nidia C.; Pantelides, Sokrates T.; Pennycook, Stephen J.; Moyer, Bruce A.; Chisholm, Matthew F.

    2014-11-01

    Crown ethers are at their most basic level rings constructed of oxygen atoms linked by two- or three-carbon chains. They have attracted attention for their ability to selectively incorporate various atoms or molecules within the cavity formed by the ring. However, crown ethers are typically highly flexible, frustrating efforts to rigidify them for many uses that demand higher binding affinity and selectivity. Here we present atomic-resolution images of the same basic structures of the original crown ethers embedded in graphene. This arrangement constrains the crown ethers to be rigid and planar. First-principles calculations show that the close similarity of the structures should also extend to their selectivity towards specific metal cations. Crown ethers in graphene offer a simple environment that can be systematically tested and modelled. Thus, we expect that our finding will introduce a new wave of investigations and applications of chemically functionalized graphene.

  7. Metal ion complexation by ionizable crown ethers. Progress report, January 1, 1991--December 31, 1993

    SciTech Connect

    Bartsch, R.A.

    1993-07-01

    Cyclic and acyclic polyether compounds with pendent carboxylic acid, phosphonic acid monoethyl ester, sulfonic acid, phosphinic acid and hydroxamic acid groups have been synthesized. The proton-ionizable polyethers can come with and without lipophilic groups. Two types of lipophilic di-ionizable lariat ethers have been prepared. Conformations of proton-ionizable lariat ethers have been probed. Competitive alkali metal cation transport by syn-(decyl)dibenzo-16-crown-5-oxyacetic acid and lipophilic proton-ionizable dibenzo lariat ethers in polymer-supported liquid membranes was studied. Complexation of alkali metal cations with ionized lariat ethers was studied. Condensation polymerization of cyclic and acyclic dibenzo polyethers containing pendent mono-ionizable groups with formaldehyde produces novel ion exchange resins with both ion exchange sites for metal ion complexation and polyether binding sites for metal ion recognition. Resins prepared from lariat ether dibenzo phosphonic acid monoethyl esters show strong sorption of divalent heavy metal cations with selectivity for Pb{sup 2+}.

  8. A schiff-base bibracchial lariat ether forming a cryptand-like cavity for lanthanide ions.

    PubMed

    González-Lorenzo, Marina; Platas-Iglesias, Carlos; Avecilla, Fernando; Geraldes, Carlos F G C; Imbert, Daniel; Bünzli, Jean-Claude G; de Blas, Andrés; Rodríguez-Blas, Teresa

    2003-10-20

    We report here a structural and photophysical study of lanthanide(III) complexes with the di-deprotonated form of the bibracchial lariat ether N,N'-bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5. The X-ray crystal structures of [Ce(L(2)-2H)](ClO(4)).0.5H(2)O (2) and [Sm(L(2)-2H)](ClO(4)).C(3)H(8)O (5b) show the metal ion being nine-coordinated and deeply buried in the cavity of the dianionic receptor. Thanks to the formation of a pseudomacrocycle through pi-pi interaction between one of the phenol rings and one of the benzyl rings, the complexes present a cryptand-like structure in the solid state. (1)H and (13)C NMR studies on the La(III) complex point that the solid state structure is essentially maintained in acetonitrile solution. High-resolution laser-excited emission spectra of the crystalline Eu(III) complex demonstrate the presence of several coordination sites arising from different conformations of the crown moiety. The ligand-to-Eu(III) energy transfer is relatively efficient at low temperature, but back transfer is implied in the deactivation process, especially at room temperature, because the ligand triplet state lies at very low energy. However, the low energy of the (3)pipi state provides an efficient conversion of the visible light absorbed into near-infrared light emitted by the Nd(III) ion. PMID:14552647

  9. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Oing; McBreen, James

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

  10. Aza crown ether compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.O.; McBreen, J.

    1998-08-04

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.

  11. "Crown Ether" Synthesis: An Organic Laboratory Experiment.

    ERIC Educational Resources Information Center

    Field, Kurt W.; And Others

    1979-01-01

    This experiment is designed to acquaint the student with a macromolecular synthesis of a crown ether type compound. The starting materials are readily available and the product, a cyclic polyether, belongs to a class of compounds that has aroused the interest of chemist and biologist alike. (Author/BB)

  12. Crown Ethers in Nonaqueous Electrolytes for Lithium/Air Batteries

    SciTech Connect

    Xu, Wu; Xiao, Jie; Wang, Deyu; Zhang, Jian; Zhang, Jiguang

    2010-02-04

    The effects of three crown ethers, 12-crown-4, 15-crown-5, and 18-crown-6, as additives and co-solvents in non-aqueous electrolytes on the cell performance of primary Li/air batteries operated in a dry air environment were investigated. Crown ethers have large effects on the discharge performance of non-aqueous electrolytes in Li/air batteries. A small amount (normally less than 10% by weight or volume in electrolytes) of 12-Crown-4 and 15-crown-5 reduces the battery performance and a minimum discharge capacity appears at the crown ether content of ca. 5% in the electrolytes. However, when the content increases to about 15%, both crown ethers improve the capacity of Li/air cells by about 28% and 16%, respectively. 15-Crown-5 based electrolytes even show a maximum discharge capacity in the crown ether content range from 10% to 15%. On the other hand, the increase of 18-crown-6 amount in the electrolytes continuously lowers of the cell performance. The different battery performances of these three crown ethers in electrolytes are explained by the combined effects from the electrolytes’ contact angle, oxygen solubility, viscosity, ionic conductivity, and the stability of complexes formed between crown ether molecules and lithium ions.

  13. Phosphorus-nitrogen compounds. Part 20: Fully substituted spiro-cyclotriphosphazenic lariat (PNP-pivot) ether derivatives

    NASA Astrophysics Data System (ADS)

    Okumuş, Aytuğ; Bilge, Selen; Kılıç, Zeynel; Öztürk, Aslı; Hökelek, Tuncer; Yılmaz, Filiz

    2010-08-01

    The condensation reactions of partly substituted spiro-cyclotriphosphazenic lariat (PNP-pivot) ethers, N 3P 3[( o-NHPhO) 2R]Cl 4 [where R = -CH 2CH 2- ( 1) and -CH 2CH 2OCH 2CH 2- ( 2)] with morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) produce fully substituted morpholino ( 3 and 4) and 1,4-dioxa-8-azaspiro[4,5]deca ( 5 and 6) phosphazenes. These are the new examples of the spiro-cyclophosphazenic lariat ether derivatives with N 2O x ( x = 2 and 3) donor type containing 11- and 14-membered macrocycles. The solid state structures of 3, 5 and 6 have been determined by X-ray diffraction techniques. Compound 3 has intermolecular N-H…O hydrogen bond, compound 5 has intra- and intermolecular N-H…O hydrogen bonds, while compound 6 has intramolecular N-H…O and O-H…N and intermolecular N-H…O and O-H…O hydrogen bonds. The correlations of the endocyclic ( α) and exocyclic ( α') NPN bond angles with δP spiro values are investigated. The structural investigations of 3- 6 have been verified by elemental analyses, MS, FTIR, 1H, 13C and 31P NMR, DEPT and HETCOR techniques.

  14. Supramolecular polymers constructed by crown ether-based molecular recognition.

    PubMed

    Zheng, Bo; Wang, Feng; Dong, Shengyi; Huang, Feihe

    2012-03-01

    Supramolecular polymers, polymeric systems beyond the molecule, have attracted more and more attention from scientists due to their applications in various fields, including stimuli-responsive materials, healable materials, and drug delivery. Due to their good selectivity and convenient enviro-responsiveness, crown ether-based molecular recognition motifs have been actively employed to fabricate supramolecular polymers with interesting properties and novel applications in recent years. In this tutorial review, we classify supramolecular polymers based on their differences in topology and cover recent advances in the marriage between crown ether-based molecular recognition and polymer science. PMID:22012256

  15. Extraction of actinides and nitric acid by crown ethers

    SciTech Connect

    Rozen, A.M.; Nikolotova, Z.I.; Kartasheva, N.A.; Luk'yanenko, N.G.; Bogatskii, A.V.

    1982-10-01

    This work studied the extraction of thorium nitrate, and an extraction isotherm of uranyl nitrate was obtained; the distribution of HNO/sub 3/ was studied over a wide range of acidity (up to 18M), which uses different concepts on the mechanism of the process. The extraction of Pu(VI) and Np(IV) was studied up to a 12 M acidity; two crown ethers had not previously been used for the extraction of the actinides. A quantitative description of the equilibria studied is given, and the influence of the structure of the ethers on the complex formation is discussed.

  16. Increasing the thermopower of crown-ether-bridged anthraquinones.

    PubMed

    Ismael, Ali K; Grace, Iain; Lambert, Colin J

    2015-11-01

    We investigate strategies for increasing the thermopower of crown-ether-bridged anthraquinones. The novel design feature of these molecules is the presence of either () crown-ether or () diaza-crown-ether bridges attached to the side of the current-carrying anthraquinone wire. The crown-ether side groups selectively bind alkali-metal cations and when combined with TCNE or TTF dopants, provide a large phase-space for optimising thermoelectric properties. We find that the optimum combination of cations and dopants depends on the temperature range of interest. The thermopowers of both and are negative and at room temperature are optimised by binding with TTF alone, achieving thermpowers of -600 μV K(-1) and -285 μV K(-1) respectively. At much lower temperatures, which are relevant to cascade coolers, we find that for , a combination of TTF and Na(+) yields a maximum thermopower of -710 μV K(-1) at 70 K, whereas a combination of TTF and Li(+) yields a maximum thermopower of -600 μV K(-1) at 90 K. For , we find that TTF doping yields a maximum thermopower of -800 μV K(-1) at 90 K, whereas at 50 K, the largest thermopower (of -600 μV K(-1)) is obtain by a combination TTF and K(+) doping. At room temperature, we obtain power factors of 73 μW m(-1) K(-2) for (in combination with TTF and Na(+)) and 90 μW m(-1) K(-2) for (with TTF). These are higher or comparable with reported power factors of other organic materials. PMID:26426840

  17. Secondary Li battery incorporating 12-Crown-4 ether

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan (Inventor); Distefano, Salvador (Inventor)

    1992-01-01

    A rechargeable lithium battery which utilizes a polyethylene oxide (PEO) solid polymeric electrolyte complexed with a lithium salt is disclosed. The conductivity is increased an order of magnitude and interfacial charge transfer resistance is substantially decreased by incorporating a minor amount of 12-Crown-4 ether in the PEO-lithium salt solid electrolyte film. Batteries containing the improved electrolyte permit operation at a lower temperature with improved efficiency.

  18. Novel Ordered Crown Ether-Containing Polyimides for Ion Conduction

    NASA Technical Reports Server (NTRS)

    Irvin, Jennifer A.; Stasko, Daniel; Fallis, Stephen; Guenthner, Andrew J.; Webber, Cynthia; Blackwell, John; Chvalun, Sergei N.

    2003-01-01

    We report the synthesis and characterization of thermally-stable polyimides for use as battery and fuel cell electrolyte membranes. Dianhydrides used were 1,4,5,8- naphthalenetetracarboxylic dianhydride and/or 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. Diamines used were anti-4,4-diaminodibenzo-l8-crown-6, 4,4'- diaminodibenzo-24-crown-8, 2,2-bis(4-aminophenyl)hexafluoropropane, and/or 2,5- diaminobenzenesulfonic acid. The polymers were characterized using electrochemical impedance spectroscopy (EIS), thermal analysis and X-ray diffraction. Polymers containing the hexafluoroisopropylidene (HFIP) group were soluble in common organic solvents, while polymers without the HFIP group were very poorly soluble. Sulfonation yields polymers that are sparingly soluble in aqueous base and/or methanol. Degree of sulfonation, determined by titration, was between one and three sulfonate groups per repeat unit. Proton conductivity was determined as a function of water content, with a maximum conductivity of l x 10(exp -2) per centimeter when fully hydrated. Crown ether-containing polymers exhibit a high degree of order that may be indicative of crown ether channel formation, which may facilitate Li(+) transport for use in battery membranes.

  19. On the radiation stability of crown ethers in ionic liquids.

    SciTech Connect

    Shkrob, I.; Marin, T.; Dietz, M.

    2011-04-14

    Crown ethers (CEs) are macrocyclic ionophores used for the separation of strontium-90 from acidic nuclear waste streams. Room temperature ionic liquids (ILs) are presently being considered as replacements for traditional molecular solvents employed in such separations. It is desirable that the extraction efficacy obtained with such solvents should not deteriorate in the strong radiation fields generated by decaying radionuclides. This deterioration will depend on the extent of radiation damage to both the IL solvent and the CE solute. While radiation damage to ILs has been extensively studied, the issue of the radiation stability of crown ethers, particularly in an IL matrix, has not been adequately addressed. With this in mind, we have employed electron paramagnetic resonance (EPR) spectroscopy to study the formation of CE-related radicals in the radiolysis of selected CEs in ILs incorporating aromatic (imidazolium and pyridinium) cations. The crown ethers have been found to yield primarily hydrogen loss radicals, H atoms, and the formyl radical. In the low-dose regime, the relative yield of these radicals increases linearly with the mole fraction of the solute, suggesting negligible transfer of the excitation energy from the solvent to the solute; that is, the solvent has a 'radioprotective' effect. The damage to the CE in the loading region of practical interest is relatively low. Under such conditions, the main chemical pathway leading to decreased extraction performance is protonation of the macrocycle. At high radiation doses, sufficient to increase the acidity of the IL solvent significantly, such proton complexes compete with the solvent cations as electron traps. In this regime, the CEs will rapidly degrade as the result of H abstraction from the CE ring by the released H atoms. Thus, the radiation dose to which a CE/IL system is exposed must be maintained at a level sufficiently low to avoid this regime.

  20. Crown ether derivative assisted growth of oriented polyaniline nanotubes

    NASA Astrophysics Data System (ADS)

    Xia, Haibing; Cheng, Daming; Lam, Peisuan; Chan, Hardy Sze On

    2006-08-01

    We report a chemical route to synthesize oriented arrays of conducting polyaniline (PANI) nanotubes (60-150 nm in diameter and a few micrometres in length) by hydrogen-bonding directionality in the presence of a crown ether derivative (CE-SO3K) and ammonium persulfate (APS) in HCl solution. The morphology of the oriented PANI nanotubes was confirmed by SEM and TEM images. The effects of reaction conditions on the morphology of the resultant PANI nanostructures were studied. The chemical and electronic structures of the PANI nanotubes were also studied by FTIR and UV-vis spectrometry, respectively.

  1. Synthesis and fluorescence properties of divalent europium-poly(methacrylate containing crown ether structure) complexes

    SciTech Connect

    Higashiyama, N.; Nakamura, H.; Mishima, T.; Shiokawa, J.; Adachi, G. )

    1991-02-01

    This paper reports on divalent europium complexes with poly(methacrylate containing crown ether structure)s, poly(crown ether)s, prepared and their fluorescence properties studied. The polymers used were poly(15-crown-5-methyl methacrylate) (PMA15C5), copoly(15- crown-5-methyl methacrylate-X) (copoly(MA15C5-X)); (X = MMA, EMA, BMA, 2-methoxyethyl methacrylate (MAGI) 3,6,9,12,15- pentaoxahexadecyl methacrylate (MAG5)), poly(18-crown-6- methyl methacrylate) (PMA18C6), and copoly(18-crown-6-methyl methacrylate-MMA) (copoly(MA18C6-MMA)), which were obtained by bulk polymerization. The fluorescence properties of Eu{sup 2+} polymers activated by complexing Eu{sup 2+} ions with crown ether groups were measured in powder form. The Eu{sup 2+}-poly (crown ether)s irradiated by UV light generally gave blue bright emission in the region of 420-465 nm. It was Eu{sup 2+}-copoly(Ma15C5-X); (X = MMA, EMA, and MAG1) that showed the largest emission intensity among the Eu{sup 2+} polymers, and its emission intensity was ca. 20% of that for CaWO{sub 4}:Pb (NBS1026) whose quantum efficiency is about 76%. The intensities of emission for the Eu{sup 2+} polymers containing 15-crown-5 were much larger than that for the ones containing 18-crown-6.

  2. SOLUTION EFFECTS ON CESIUM COMPLEXATION WITH CALIXARENE CROWN ETHERS FROM LIQUID TO SUPERCRITICAL FLUIDS

    EPA Science Inventory

    Calixarene-crown ethers with rigid skeletons are superior to flexible crown ethers for separation of 137Cs from high level waste (HLW). However, this extraction methodology often requires undesirable solvents and the extraction efficiency is strongly dependent on the solvent pol...

  3. Construction of supramolecular organogels and hydrogels from crown ether based unsymmetric bolaamphiphiles.

    PubMed

    Gao, Lingyan; Xu, Donghua; Zheng, Bo

    2014-10-18

    A bolaamphiphilic low-molecular-weight gelator based on crown ether, which could self-assemble into organogels and hydrogels, was prepared. The contribution of each part of the structure to the gelation property was investigated by designing a series of analogues. A simple framework (crown ether-hydrophobic linkage-ammonium salt) was proposed. PMID:25174940

  4. Sorbents based on crown ethers: preparation and application for the sorption of strontium

    NASA Astrophysics Data System (ADS)

    Bezhin, N. A.; Dovhyi, I. I.

    2015-12-01

    The key approaches to the synthesis of crown ether-based sorbents, including immobilization both with and without covalent bonding, are reviewed. Examples of sorbent preparation using anodic oxidation, chemical modification of polymers, polycondensation reactions, chemical modification of inorganic supports and radiochemical synthesis for covalent bonding of crown ether moieties are considered. Immobilization methods without covalent bonding including support synthesis in the presence of crown ethers, impregnation of supports with a crown ether solution and the use of powdered crown ether as a sorbent are presented. The applications of sorbents for selective removal of strontium from solutions of radioactive waste and spent nuclear fuel, for radiochemical analysis (determination of strontium in water, soil and biological materials) and for separation of strontium and yttrium isotopes are discussed. The bibliography includes 114 references.

  5. Radium separation through complexation by aqueous crown ethers and ion exchange or solvent extraction

    SciTech Connect

    Chiarizia, R.; Dietz, M.L.; Horwitz, E.P.; Burnett, W.C.

    1997-11-01

    The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-crown-7 (21C7)) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium-calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes is discussed and a possible flowchart for the determination of {sup 226}Ra/{sup 228}Ra in natural waters is presented.

  6. Iptycene-derived crown ether hosts for molecular recognition and self-assembly.

    PubMed

    Han, Ying; Meng, Zheng; Ma, Ying-Xian; Chen, Chuan-Feng

    2014-07-15

    CONSPECTUS: Synthetic macrocyclic hosts have played key roles in the development of host-guest chemistry. Crown ethers are a class of macrocyclic molecules with unique flexible structures. They have served as the first generation of synthetic hosts, and researchers have extensively studied them in molecular recognition. However, the flexible structures of simple crown ethers and their relatively limited modes of complexation with guests have limited the further applications of these molecules. In recent years, researchers have moved toward fabricating interlocking molecules, supramolecular polymers, and other assemblies with specific structures and properties. Therefore, researchers have developed more complex crown ether-based macrocyclic hosts with multicavity structures and multicomplexation modes that provide more diverse and sophisticated host-guest systems. In this Account, we summarize our research on the synthesis and characterization of iptycene-derived crown ether hosts, their use as host molecules, and their applications in self-assembled complexes. Iptycenes including triptycenes and pentiptycenes are a class of aromatic compounds with unique rigid three-dimensional structures. As a result, they are promising building blocks for the synthesis of novel macrocyclic hosts and the construction of novel self-assembled complexes with specific structures and properties. During the last several years, we have designed and synthesized a new class of iptycene-derived crown ether hosts including macrotricyclic polyethers, molecular tweezer-like hosts, and tritopic tris(crown ether) hosts, which are all composed of rigid iptycene building blocks linked by flexible crown ether chains. We have examined the complexation behavior of these hosts with different types of organic guest molecules. Unlike with conventional crown ethers, the combination of iptycene moieties and crown ether chains provides the iptycene-derived crown ether hosts with complexation properties

  7. Design and synthesis of redox-switched lariat ethers and their application for transport of alkali and alkaline-Earth metal cations across supported liquid membrane.

    PubMed

    Awasthy, Anubhuti; Bhatnagar, Mamta; Tomar, Jyoti; Sharma, Uma

    2006-01-01

    A new class of redox-switched anthraquinone derived lariat ethers 1-(1-anthraquinonyloxy) 3, 6, 9 trioxaundecane 11-ol (M(1)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-ol (M(2)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-ol (M(3)), 1-(1-anthraquinonyloxy) 3 oxapentane 5-butane (M(4)), 1-(1-anthraquinonyloxy) 3, 6 dioxaoctane 9-methane (M(5)) and 1-(1-anthraquinonyloxy) 3 oxapentane 5-methane (M(6)) have been synthesized and characterized by spectral analysis. These ionophores were used in liquid membrane carrier facilitated transport of main group metal cations across supported liquid membrane (SLM). Cellulose nitrate membrane was used as membrane support. Effect of various parameters such as variation in concentration of metal as well as ionophore, effect of chain length and end group of ionophore have been studied. The sequence of metal ions transported by ionophore M(1) is Na(+) > Li(+) > K(+) > Ca(2+) > Mg(2+) and the order of metal ions transported by ionophores (M(2)-M(6)) is Li(+) > Na(+) > K(+) > Ca(2+) > Mg(2+). Ionophore M(1) is selective for Na(+), Li(+), and K(+) and ionophores (M(2)-M(6)) are selective for Li(+) and Na(+). PMID:17497021

  8. Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

    PubMed

    Masci, B; Saccheo, S; Fonsi, M; Varrone, M; Finelli, M; Nierlich, M; Thuéry, P

    2001-08-01

    Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain. PMID:11498633

  9. Development of the aza-crown ether metal complexes as artificial hydrolase.

    PubMed

    Yu, Lan; Li, Fang-zhen; Wu, Jiao-yi; Xie, Jia-qing; Li, Shuo

    2016-01-01

    Hydrolases play a crucial role in the biochemical process, which can catalyze the hydrolysis of various compounds like carboxylic esters, phosphoesters, amides, nucleic acids, peptides, and so on. The design of artificial hydrolases has attracted extensive attention due to their scientific significance and potential applications in the field of gene medicine and molecular biology. Numerous macrocyclic metal complexes have been used as artificial hydrolase in the catalytic hydrolysis of the organic substrate. Aza-crown ether for this comment is a special class of the macrocyclic ligand containing both the nitrogen atoms and oxygen atoms in the ring. The studies showed that the aza-crown complexes exhibited high activity of hydrolytic enzyme. However, the aza-crown ether metal complex as artificial hydrolase is still very limited because of its difficulty in synthesis. This review summarizes the development of the aza-crown ether metal complexes as the artificial hydrolase, including the synthesis and catalysis of the transition metal complexes and lanthanide metal complexes of aza-crown ethers. The purpose of this review is to highlight: (1) the relationship between the structure and hydrolytic activity of synthetic hydrolase; (2) the synergistic effect of metal sites and ligands in the course of organic compound hydrolysis; and (3) the design strategies of the aza-crown ethers as hydrolase. PMID:26460062

  10. Reaction of a bituminous coal with the potassium-crown ether reagent

    SciTech Connect

    Huang, S.; Wood, K.; Narayan, R.

    1986-09-01

    In this paper, the authors report on the reaction of a bituminous coal with a powerful yet selective site-specific reagent, namely, potassium-crown ether operating at room temperature and atmospheric pressure. The potassium-crown ether reagent can generate a stable solution of electrons at room temperature and atmospheric pressure. The small size of the electron and its high reactivity permits it to diffuse into the macromolecular coal network and transfer onto the aromatic substrates in the coal. This results in the formation of aromatic radical anions or dianions which undergo cleavage reactions at ether and diaryl alkane linkages.

  11. Metal-organic frameworks constructed from crown ether-based 1,4-benzenedicarboxylic acid derivatives.

    PubMed

    Chen, Teng-Hao; Schneemann, Andreas; Fischer, Roland A; Cohen, Seth M

    2016-02-21

    A series of unprecedented crown ether- and thiacrown ether-derivatized benzene dicarboxylic acid (H2bdc) ligands has been synthesized and incorporated into the prototypical isoreticular metal-organic framework (IRMOF) and UiO-66 materials. In the case of UiO-66, only MOFs comprised from a mixed-ligand composition, requiring both unsubstituted bdc and crown ether containing ligands, could be prepared. These are among the few ligand derivatives, and resulting MOFs, that incorporate a macrocyclic group directly on the bdc ligand, providing a new, modular platform for exploring new supramolecular and coordination chemistry within MOFs. PMID:26765588

  12. Differential Self-Assembly of Novel Redox Crown Ethers

    NASA Astrophysics Data System (ADS)

    Merithew, Andrew William

    Retinal prosthesis relies on the stimulation of living nerve tissue behind the rods and cones of the eye. The current state of the art relies on electrodes controlled by cameras which directly stimulate the nerve tissue to elicit a response to an image. These types of retinal implants have allowed for short-term crude vision in patients but have had limited long term success due to external battery packs and electroplating of the implanted electrodes. Ionic stimulation is one of the principle mechanisms that sensory neurons utilize in the generation of an action potential. In a complex transduction pathway, ionic gradients are constantly altered inside the neuron by voltage sensors or mechanically controlled gates embedded in the neuronal cell membrane; responsible for the open and close state of these ion channels. It has been demonstrated that local concentration increases of K + by direct injection proximal to the nerve can elicit nerve firing at a concentration of 15-20 mM (3-4X normal concentration) increase in K + concentration. As part of a larger concept of integrating biotechnology with nanofabrication, the materials for the development of potassium selective sequestration/storage and delivery were developed in the form of a redox-gated K+ selective crown ether. The structure of the anthraquinone-based crown was deduced by computational simulation and stoichiometry of the complex confirmed by mass spec. along with 2D diffusion NMR techniques. In this instance, the stoichiometry could be controlled by the addition of different salts to give a 1:1 complex with large, aromatic anions and a 2:1 complex with smaller anions such as triflate. The synthesis of the molecule was optimized by computational modeling and simulations of transport through an artificial membrane. The selectivity of the architecture developed was specific for K+ over Na+, the other major ionic species present in the blood. The mechanism influencing the self-assembly of this class of

  13. Release of Lariat Peanut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lariat is a high-oleic runner-type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) that has enhanced Sclerotinia blight and pod rot tolerance when compared to the cultivar Red River Runner. Lariat (experimental designation ARSOK-R35) is the result of a cross between cultivar Red River Ru...

  14. Metal ion complexation by ionizable crown ethers. Final report, January 1, 1988--June 30, 1994

    SciTech Connect

    Bartsch, R.A.

    1994-12-31

    During the report period a variety of new lipophilic ionizable crown ethers with pendent proton-ionizable groups has been synthesized. The ligands possess one or more ionizable group (carboxylic acid, phosphonic acid monoethyl ester, para-nitrophenol, phosphonic acid) attached to crown ether, monoazacrown ether or diazacrown ether frameworks. These novel chelating agents have either pendent or inward-facing proton-ionizable groups. Such lipophilic proton-ionizable crown ethers are designed for use in multiphase metal ion separations (solvent extraction, liquid membrane transport). In addition a series of proton-ionizable crown ethers without lipophilic groups was prepared to study how structural variations within the ligand influence metal ion complexation in homogeneous media as assessed by NMR spectroscopy or titration calorimetry. A third class of new metal ion-complexing agents is a series of lipophilic acyclic polyether dicarboxylic acids. Competitive solvent extractions of alkali metal and alkaline earth cations and of the mixed species have been conducted to reveal the influence of ring size, nature and attachment site of the lipophilic group, sidearm length, and proton-ionizable group identity and location upon the selectivity and efficiency of metal ion complexation. In addition to such studies of structural variation within the lipophilic proton-ionizable crown ether, the effect of changing the organic solvent and variation of the stripping conditions have been assessed. The influence of structural variations within lipophilic acyclic polyether dicarboxylic acids upon competitive solvent extraction of alkaline earth cations has been probed. Also a new chromogenic, di-ionizable crown ether with extremely high selectivity for Hg{sup 2+} has been discovered.

  15. Phase transition metal-crown ether coordination compounds tuned by metal ions.

    PubMed

    Ye, Qiong; Wang, Hui-Ting; Zhou, Lin; Kong, Li-Hui; Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi

    2016-01-21

    Two isostructural metal crown ether coordination compounds, (15-crown-5)(BiCl3) 1 and (15-crown-5)(SbCl3) 2, are discovered to show phase transitions above room temperature, where the phase transition temperature relates to the metal center. Compound 1 crystallizes in the chiral orthorhombic space group P212121 in the low temperature phase and undergoes a reversible phase transition around 365 K to crystallize in the polar orthorhombic space group Pna21 in the high temperature phase, accompanied by thermal and dielectric anomalies. The variable-temperature structure analyses of compound 1 show that the phase transition is rooted in the conformational change of the crown ether and the displacement of the Bi cation and Cl anion. PMID:26648559

  16. Stable Alkali-Metal Complexes of Hybrid Disila-Crown Ethers.

    PubMed

    Reuter, Kirsten; Buchner, Magnus R; Thiele, Günther; von Hänisch, Carsten

    2016-05-01

    The complexation ability of hybrid disilane and ethylene containing crown ether ring systems was analyzed using 1,2-disila[12]crown-4 (1), 1,2-disila[15]crown-5 (2), 1,2-disila[18]crown-6 (3), and 1,2,7,8-tetrasila[12]crown-4 (7). Alkali-metal complexes (Li(+), Na(+), K(+)) were obtained and analyzed via X-ray diffraction. The complex stability of [Li(1,2-disila[12]crown-4)](+) and [Li(1,2,7,8-tetrasila[12]crown-4)](+) was determined, in relation to the lithium complex of [12]crown-4, by density functional theory (DFT) calculations employing the BP86/def2-TZVP level of theory. In solution, the exchange of lithium cations between pure [12]crown-4 and hybrid [12]crown-4 is on even terms, as has been shown from the relative binding affinity of compounds 1 and 7 by means of dynamic proton nuclear magnetic resonance (NMR) spectroscopy. PMID:27082743

  17. Evaluation of polymer inclusion membranes containing crown ethers for selective cesium separation from nuclear waste solution.

    PubMed

    Mohapatra, P K; Lakshmi, D S; Bhattacharyya, A; Manchanda, V K

    2009-09-30

    Transport behaviour of (137)Cs from nitric acid feed was investigated using cellulose triacetate plasticized polymer inclusion membrane (PIM) containing several crown ether carriers viz. di-benzo-18-crown-6 (DB18C6), di-benzo-21-crown-7 (DB21C7) and di-tert-butylbenzo-18-crown-6 (DTBB18C6). The PIM was prepared from cellulose triacetate (CTA) with various crown ethers and plasticizers. DTBB18C6 and tri-n-butyl phosphate (TBP) were found to give higher transport rate for (137)Cs as compared to other carriers and plasticizers. Effect of crown ether concentration, nitric acid concentration, plasticizer and CTA concentration on the transport rate of Cs was also studied. The Cs selectivity with respect to various fission products obtained from an irradiated natural uranium target was found to be heavily dependent on the nature of the plasticizer. The present work shows that by choosing a proper plasticizer, one can get either good transport efficiency or selectivity. Though TBP plasticized membranes showed good transport efficiency, it displayed poor selectivities. On the other hand, an entirely opposite separation behaviour was observed with 2-nitrophenyloctylether (NPOE) plasticized membranes suggesting the possible application of the later membranes for the removal of bulk (137)Cs from the nuclear waste. The stability of the membrane was tested by carrying out transport runs for nearly 25 days. PMID:19398153

  18. Vertical ionisation potentials of a number of crown ethers from charge transfer bands of their EDA complexes

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sumanta; Sharma, Anubha; Nayak, Sandip K.; Mukherjee, Asok K.

    2002-11-01

    Vertical ionisation potentials ( IDv) of a number of crown ethers, viz. dibenzo-30-crown-10 (Crown 1), benzo-15-crown-5 (Crown 2), dibenzo-24-crown-8 (Crown 3), dicyclohexano-24-crown-8 (Crown 4) and 4'-nitrobenzo-15-crown-5 (Crown 5) are being reported for the first time from a study of EDA interaction of these crown ethers with a number of electron acceptors like C 60, C 70, o-chloranil, p-chloranil, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and pyromellitic diimide (PMD). The study has been carried out in CCl 4 medium by electronic absorption spectroscopy. Charge transfer (CT) absorption bands in the 360-900 nm range have been found in each case (excepting the 60 fullerene-Crown 4 system). The vertical ionisation potentials ( IDv) of all the crown ethers thus determined show a good correlation with those calculated by the semiempirical AM1 method. Of the six acceptors under study the vertical electron affinity of PMD was not found in the literature. This has also been determined from an analysis of the present hνCT data.

  19. Insights into the effects of 2:1 "sandwich-type" crown-ether/metal-ion complexes in responsive host-guest systems.

    PubMed

    Yu, Hai-Rong; Hu, Jia-Qi; Lu, Xiao-Hua; Ju, Xiao-Jie; Liu, Zhuang; Xie, Rui; Wang, Wei; Chu, Liang-Yin

    2015-01-29

    In-depth investigations of the specific ion-responsive characteristics based on 2:1 "sandwich" structures and effects of crown ether cavity sizes on the metal-ion/crown-ether complexation are systematically performed with a series of PNIPAM-based responsive copolymers containing similar contents of crown ether units with different cavity dimensions (12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lower critical solution temperature (LCST) values of copolymers in deionized water shift to lower temperatures gradually when the crown ether contents increase or the ring sizes decrease from 18C6 to 12C4. With increasing the concentrations of alkali metal ions (Na(+), K(+), Cs(+)) or the contents of pendent crown ether groups, the copolymers with different crown ether cavity sizes exhibit higher selectivity and sensitivity to corresponding cations. Importantly, the ion sensitivities of the copolymers in response to corresponding alkali metal ions increase dramatically with an increase in the crown ether cavity size. Interestingly, a linear relationship between the crown ether cavity size and the diameter of corresponding cation for the formation of stable 2:1 "sandwich" complexes is found for the first time, from which the size of metal ions or other guests that able to form 2:1 "sandwich" complexes with crown ethers can be deduced. The results in this work are valuable and useful for further developments and practical applications of various crown-ether-based smart materials. PMID:25562507

  20. Synthesis of ribo-hexopyranoside- and altrose-based azacrown ethers and their application in an asymmetric Michael addition.

    PubMed

    Rapi, Zsolt; Bakó, Péter; Keglevich, György; Szöllősy, Áron; Drahos, László; Hegedűs, László

    2013-01-10

    The synthesis of four new ribo-hexopyranoside-based chiral lariat ethers of monoaza-15-crown-5 type and two altropyranoside-based crown ethers were elaborated. Our syntheses utilized the regioselective ring opening of the oxiran moiety of the 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. The reaction of methyl-2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside with ethanolamine is especially of interest to afford a 3-substituted altropyranoside. One of the ribo-hexopyranoside-based lariat ethers with a 4-methoxyphenyl substituent induced an enantioselectivity of 80% when used as catalyst in the Michael addition of diethyl acetamidomalonate to trans-β-nitrostyrene under phase transfer catalytic conditions. PMID:23220061

  1. Extractant composition including crown ether and calixarene extractants

    DOEpatents

    Meikrantz, David H.; Todd, Terry A.; Riddle, Catherine L.; Law, Jack D.; Peterman, Dean R.; Mincher, Bruce J.; McGrath, Christopher A.; Baker, John D.

    2009-04-28

    An extractant composition comprising a mixed extractant solvent consisting of calix[4] arene-bis-(tert-octylbenzo)-crown-6 ("BOBCalixC6"), 4',4',(5')-di-(t-butyldicyclo-hexano)-18-crown-6 ("DtBu18C6"), and at least one modifier dissolved in a diluent. The DtBu18C6 may be present at from approximately 0.01M to approximately 0.4M, such as at from approximately 0.086 M to approximately 0.108 M. The modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol ("Cs-7SB") and may be present at from approximately 0.01M to approximately 0.8M. In one embodiment, the mixed extractant solvent includes approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic hydrocarbon diluent. The extractant composition further comprises an aqueous phase. The mixed extractant solvent may be used to remove cesium and strontium from the aqueous phase.

  2. Effects of Added Salts on Surface Tension and Aggregation of Crown Ether Surfactants.

    PubMed

    Suzuki, Maki; Fujio, Katsuhiko

    2016-01-01

    Two crown ether surfactants, dodecanoyloxymethyl- (C11Φ6) and octanoyloxymethyl-18-crown-6 (C7Φ6), were synthesized and the surface tension dependence on surfactant concentration of their aqueous solutions was measured both in the absence and presence of alkali chlorides to confirm the critical micelle concentration (CMC) is highest for the added cation that have an ionic diameter comparable to the hole size of the crown ether ring and that several break points on the surface tension vs. concentration curves occur for these crown ether surfactants. For C11Φ6 and C7Φ6, in the absence of salt, the surface tension vs. concentration curves had two break points. Using the solubilization of a water-insoluble dye as an indicator, we found that the break point at the higher concentration (m0) for C7Φ6 was due to micelle formation. Two break points were also observed for the aqueous solution of C11Φ6 in the presence of NaCl, KCl, RbCl, and CsCl salts at concentrations of 0.22 mol kg(-1) and for C7Φ6 with 0.22 mol kg(-1) KCl added. The CMC (m0) was found to be the highest for solutions containing K(+) salts because K(+) has an ionic diameter comparable to the hole size of 18-crown-6 ring. Furthermore, the CMC decreased as the ionic diameters of the added cations deviated from the hole size. The molecular areas at two break points, estimated by the Gibbs adsorption isotherm, except for that at the break point at mI of C7Φ6, were very small for an adsorbed monolayer. Further investigation is required to elucidate the reason for the break point at mI. PMID:26666275

  3. Reactivity of hydroxy- and aquo(hydroxy)-λ3-iodane-crown ether complexes.

    PubMed

    Miyamoto, Kazunori; Yokota, Yukie; Suefuji, Takashi; Yamaguchi, Kentaro; Ozawa, Tomoyuki; Ochiai, Masahito

    2014-04-25

    We have designed a series of hydroxy(aryl)-λ(3)-iodane-[18]crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ(3)-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ(3)-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases. PMID:24644216

  4. Improvement of Thiolate/Disulfide Mediated Dye-Sensitized Solar Cells through Supramolecular Lithium Cation Assembling of Crown Ether

    PubMed Central

    Liu, Linfeng; Li, Xiong; Chen, Jiangzhao; Rong, Yaoguang; Ku, Zhiliang; Han, Hongwei

    2013-01-01

    A supramolecular lithium cation assemblies of crown ether, [Li⊂12-crown-4]+, has been used to replace conventional tetraalkylammonium counterion in thiolate/disulfide (ET−/BET) mediated dye-sensitized solar cells (DSCs), which exhibit high stability and efficiency of 6.61% under 100 mW·cm−2 simulated sunlight illumination. PMID:23933601

  5. Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

    PubMed Central

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz; Riahi, Siavash

    2008-01-01

    Ionophore incorporated PVC membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. Potentiometric sensors have some outstanding advantages including simple design and operation, wide linear dynamic range, relatively fast response and rational selectivity. The vital component of such plasticized PVC members is the ionophore involved, defining the selectivity of the electrodes' complex formation. Molecular recognition causes the formation of many different supramolecules. Different types of supramolecules, like calixarenes, cyclodextrins and podands, have been used as a sensing material in the construction of ion selective sensors. Schiff's bases and crown ethers, which feature prominently in supramolecular chemistry, can be used as sensing materials in the construction of potentiometric ion selective electrodes. Up to now, more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anion complexes will be described. Liquid membrane sensors based on Schiff's bases and crown ethers will then be discussed.

  6. Intrinsic affinities of alkali cations for 15-crown-5 and 18-crown-6: Bond dissociation energies of gas-phase M{sup +}-crown ether complexes

    SciTech Connect

    More, M.B.; Ray, D.; Armentrout, P.B.

    1999-01-20

    Bond dissociation energies (BDEs) of M{sup +}[c-(C{sub 2}H{sub 4}O){sub 5}] and M{sup +}[c-(C{sub 2}H{sub 4}O){sub 6}] for M = Na, K, Rb, and Cs are reported. The BDEs are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation-crown ether complexes by xenon measured by using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissociation channel observed experimentally in endothermic loss of the ligand molecule. The cross section thresholds are interpreted to yield 0 and 298 K BDEs after accounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. For both 18-crown-6 and 15-crown-5, the BDEs decrease monotonically with increasing cation size. These results indicate that the intrinsic affinity of c-(C{sub 2}H{sub 4}O){sub 5} and c-(C{sub 2}H{sub 4}O){sub 6} for M{sup +} is determined principally by the charge density of the cation not by the ratio of the ionic radius to the cavity size. The BDEs reported here are in fair agreement with recent ab initio calculations at the MP2 level with 6-31+G* basis sets. The experimental values are systematically smaller than the computed values by 8 {+-} 2 kJ/mol per metal-oxygen interaction. The existence of less strongly bound isomers in the experimental apparatus for Rb{sup +}(15-crown-5) and Cs{sup +}(15-crown-5) appears likely, but their absence for Na{sup +} and K{sup +} complexes indicates interesting metal-dependent dynamics to the formation of such isomers.

  7. Conformation-Specific Electronic and Vibrational Spectroscopy of DIBENZO-15-CROWN-5 Ether in a Supersonic Jet.

    NASA Astrophysics Data System (ADS)

    Buchanan, Evan G.; Rodrigo, Chirantha P.; James, William H. James, III; Newby, Josh J.; Zwier, Timothy S.

    2009-06-01

    Crown ethers are oxygen containing cyclic structures noted for their ability to preferentially bind substrates such as ions and water. Despite the high symmetry inherent to the chemical structure, crown ethers are remarkably flexible, adapting their conformation to the substrate to which they are bound. As such, it is valuable to study the conformational preferences of the isolated crown ethers in the absence of any substrate. Here, we present the electronic and infrared spectroscopy of jet-cooled, isolated dibenzo-15-crown-5 ether (DB15C). By incorporating two phenyl rings into the crown, we are afforded the opportunity to explore the ultraviolet spectroscopy of both groups and the coupling between them. One-color resonant two-photon ionization, laser induced fluorescence, UV-UV holeburning, and resonant ion-dip infrared spectroscopies are used to provide conformation-specific electronic and infrared spectra of the three conformers. Additionally, single vibronic level dispersed fluorescence spectra provide evidence for the existence of close lying S_2 states in the two major conformers, located about 527 cm^{-1} above their S_1 counterparts. Based on a comparison with benzo-15-crown-5 ether, we surmise that the local conformation of the ethoxy groups about the two phenyl rings are different. Electronic energy transfer appears to be slow between these phenyl rings on the timescale of the excited state fluorescence. Finally, DFT and MP2 calculations will be presented as a basis for tentative structural assignments and provide insight into the excitonic coupling of the two chromophores.

  8. Solvent-Free Covalent Functionalization of Fullerene C60 and Pristine Multi-Walled Carbon Nanotubes with Crown Ethers.

    PubMed

    Henao-Holguín, Laura V; Meza-Laguna, Victor; Gromovoy, Taras Yu; Basiuk, Elena V; Rivera, Margarita; Basiuk, Vladimir A

    2016-06-01

    The goal of the present work was to test the feasibility of simple, one-step and solvent-free covalent functionalization of pristine multi-walled carbon nanotubes (MWNTs) and fullerene C60 (as a model system) with amino-substituted crown ethers, namely, 4'-aminobenzo-15-crown-5 and 4'-aminobenzo-1 8-crown-6. The attachment technique proposed is based on thermal instead of chemical activation, and can be considered as ecologically friendly. The suggested covalent binding mechanism is the nucleophilic addition of amino functionalities of crown ethers to the 6,6 bonds of pyracylene units in the case of C60, and to pentagonal (and probably other) defects of similar nature in the case of pristine MWNTs. The hybrids of crown ethers with MWNTs were characterized by means of scanning and transmission electron microscopy, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. The functionalized C60 samples were additionally studied by means of 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and laser desorption/ionization time-of-flight mass spectrometry. The approach proposed allows for a facile preparation of crown ether-functionalized pristine MWNTs without contamination with other chemical reagents, detergents and solvents, which is especially important for a vast variety of nanotube applications ranging from nanoelectronics to nanomedicine. PMID:27427687

  9. Highly selective methyl transfer from methylsilanes to phenylthallium(III) crown ether complexes

    SciTech Connect

    Kakiuchi, Fumitoshi; Furuta, Kiyonori; Murai, Shinji ); Kawasaki, Yoshikane )

    1993-01-01

    Reactions of (18-crown-6)phenylthallium(III) diperchlorate monohydrate (1a) with Me[sub 3]SiR (R = PhCH[sub 2], Et, Ph, CH[double bond]CH[sub 2], SiMe[sub 3], OSiMe[sub 3]) proceeded at 60[degrees]C to provide (18-crown-6)phenylmethylthallium(III) perchlorate (3) in good to excellent yields. Cleavage of the Me-Si bond in tetramethylsilane using 1a also occurred at 25[degrees]C, albeit for a long reaction time. The silicon-containing products of the reaction of 1a with benzyltrimethylsilane were siloxanes. Intramolecular trapping of the silyl fragments by a hydroxy group using (1,7-DTC)phenylthallium(III) bis(trifluoromethanesulfonate) (1b) was employed with trans-2-((trimethylsilyl)methyl)-1-cyclohexanol, affording a bicyclic silyl ether in 92% yield. 18 refs., 1 tab.

  10. A Ratiometric Luminescent Switch Based on Platinum Complexes Tethered to a Crown-Ether Scaffold.

    PubMed

    Sinn, Stephan; Biedermann, Frank; Vishe, Mahesh; Aliprandi, Alessandro; Besnard, Céline; Lacour, Jérôme; De Cola, Luisa

    2016-06-17

    A ratiometric chemosensor for potassium is reported, based on phosphorescent dinuclear cyclometalated Pt(II) complexes featuring a cis-crown ether as the cation-recognition unit. The metal complexes are blue luminescent in a non-aggregated state but become strongly orange emissive when in a close physical proximity, as is the case when the macrocycle is in the folded state. Upon binding of the cation, unfolding occurs, resulting in a pronounced change in the emission properties (e.g. emission wavelength), which can be used for ratiometric sensing applications. The reversibility of the binding was confirmed by competitive titration experiments with unsubstituted 18-crown-6; the system shows supramolecular switching behavior. PMID:26918952

  11. Studies of ion transport through a liquid membrane by using crown ethers

    SciTech Connect

    Gaikwad, A.G. , Trivandrum ); Noguchi, H.; Yoshio, Masaki )

    1991-01-01

    Studies on ion transport through a liquid membrane system composed of two extraction processes have been carried out. Kinetic models based on extraction processes with consideration of the controlled parameters were developed for mediated ion transport through liquid membranes, especially those using crown ethers as the ion carrier. A study of the concentration change in the receiving or source phase envisages the determination of the equilibrium constant by a kinetic method corresponding to the chemical reaction at the interface as well as the maximum initial flux through the membrane. The equilibrium constant values determined by the kinetic process were checked by the solvent extraction method.

  12. Complex formation of alkaline-earth cations with crown ethers and cryptands in methanol solutions

    SciTech Connect

    Buschman, H.J.

    1986-06-01

    The complexation of alkaline-earth cations by different crown ethers, azacrown ethers, and cryptands has been studied in methanol solutions by means of calorimetric and potentiometric titrations. The smallest monocyclic ligands examined from 2:1 complexes (ratio of ligand to cation) with cations which are too large to fit into the ligand cavity. With the smallest cryptand, only Sr/sup 2 +/ and Ba/sup 2 +/ ions are able to form exclusive complexes. In the case of the reaction of cryptand (211) with Ca/sup 2 +/, a separate estimation of stability constants for the formation of exclusive and inclusive complexes was possible for the first time. Higher values for stability constants are found for the reaction of alkaline-earth cations with cryptands compared to the reaction with alkali ions. This increase is only caused by favorable entropic contributions.

  13. Enantioseparations of primary amino compounds by high-performance liquid chromatography using chiral crown ether-based chiral stationary phase.

    PubMed

    Hyun, Myung Ho

    2013-01-01

    Liquid chromatographic resolution of racemic compounds containing a primary amino group has been known to be most successful when chiral crown ether-based chiral stationary phases (CSPs) are used. Among various crown ether-based CSPs, the stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel has been successfully applied in the resolution of various racemic compounds containing primary amino groups. In this chapter, the preparation of the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel and examples for the application to the enantioseparation of racemic compounds including α-amino acids, cyclic amines, amino alcohols, and chiral drugs are described. PMID:23283776

  14. Comparison of chiral separations of aminophosphonic acids and their aminocarboxylic acid analogs using a crown ether column.

    PubMed

    Barnhart, Wesley W; Xia, Xiaoyang; Jensen, Randy; Gahm, Kyung H

    2013-07-01

    Crown ethers are capable of complexing with primary amines and have been utilized in chromatography to separate amino acid racemates. This application has been extended to resolve (1-amino-1-phenylmethyl)phosphonic acid and (1-aminoethyl)phosphonic acid racemates, along with their aminocarboxylic acid analogs (2-phenylglycine and alanine, respectively), via a ChiroSil RCA crown ether based chiral stationary phase. Effects of the organic modifier, temperature, and acid type and concentration on retention and selectivity were also investigated. Trends in retention and selectivity varied between aminophosponic acids and their aminocarboxylic analogs. Computer modeling and (1)H NMR analyses were performed to potentially gain a better understanding of interactions of the aforementioned molecules with the ChiroSil RCA chiral stationary phase. Theoretical predictions of the most stable conformations for (R)- and (S)-enantiomers were compared to elution order; it was found that the elution order agreed with molecular modeling such that the longest retention correlated with the predicted most stable complex between the enantiomer and crown ether. (1)H NMR demonstrated interactions of aminophosphonic and aminocarboxylic racemates with (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid in solution and was utilized to determine enantiomeric excess of (1-amino-1-phenylmethyl)phosphonic acid after its enantioenrichment via crystallization through diastereomeric salt formation with the crown ether followed by filtration. PMID:23703726

  15. Alkali-Ion-Crown Ether in Art and Conservation: The Applied Bioinorganic Chemistry Approach

    PubMed Central

    Hilfrich, Uwe; Taylor, Harold; Weser, Ulrich

    2004-01-01

    Dried varnish is rich in many ester moieties, which may be broken down into small, soluble compounds by esterase activity or alkaline hydrolysis. Two methods for varnish removal have been developed, including the treatment of either lipase or RbOH / PEG-400 crown ether which allow aged oil varnishes or paint coverings to be removed or thinned. These techniques are designed to proceed in a controlled manner without damaging lower paint or base layers. Unfortunately, lipase did not react with the aged ester groups of dried linseed oil varnish. Surprisingly, the varnish came off in the presence of Tris buffer alone which, in addition, formed reactive metal complexes. A better choice was the use of high Mr alkali ion polyethylene glycol–400 (PEG-400) crown ether type chelates. PEG-400 complexes alkali ions including rubidium and other alkaliions impeding the diffusion of their basic counter ions into lower varnish or paint layers. Possible migration of alkali metal ions into the paint layer during alkaline varnish removal was determined by labelling the cleansing solutions with 86Rb. Fortunately, varnish is degraded on the surface only. Lower paint or varnish layers are not attacked even if chemically similar to the varnish or over painting to be removed as virtually no 86Rb was detected on the paint surface. PMID:18365066

  16. Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether

    SciTech Connect

    Kadhane, Umesh; Andersen, Jens Ulrik; Ehlerding, Anneli; Hvelplund, Preben; Kirketerp, Maj-Britt S.; Lykkegaard, Morten Koecks; Nielsen, Steen Broendsted; Panja, Subhasis; Wyer, Jean Ann; Zettergren, Henning

    2008-11-14

    The behavior of protonated tryptophan (TrpH{sup +}) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the {pi}{sigma}*(NH{sub 3}) state inaccessible and hence prevents the N-H bond breakage which is an important fragmentation channel of TrpH{sup +}. As a result, on a long time scale (>10 {mu}s), photoexcited TrpH{sup +}(CE) decays exponentially whereas TrpH{sup +} displays a power-law decay. The only ions remaining in the latter case are Trp{sup +{center_dot}} radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290 nm were found for both TrpH{sup +} and TrpH{sup +}(CE)

  17. Liquid chromatographic resolution of mexiletine and its analogs on crown ether-based chiral stationary phases.

    PubMed

    Jin, Kab Bong; Kim, Hee Eun; Hyun, Myung Ho

    2014-05-01

    Mexiletine, an effective class IB antiarrhythmic agent, and its analogs were resolved on three different crown ether-based chiral stationary phases (CSPs), one (CSP 1) of which is based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid and the other two (CSP 2 and CSP 3) are based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. Mexiletine was resolved with a resolution (R(S)) of greater than 1.00 on CSP 1 and CSP 3 containing residual silanol group-protecting n-octyl groups on the silica surface, but with a resolution (R(S)) of less than 1.00 on CSP 2. The chromatographic behaviors for the resolution of mexiletine analogs containing a substituted phenyl group at the chiral center on the three CSPs were quite dependent on the phenoxy group of analytes. Namely, mexiletine analogs containing 2,6-dimethylphenoxy, 3,4-dimethylphenoxy, 3-methylphenoxy, 4-methylphenoxy, and a simple phenoxy group were resolved very well on the three CSPs even though the chiral recognition efficiencies vary with the CSPs. However, mexiletine analogs containing 2-methylphenoxy group were not resolved at all or only slightly resolved. Among the three CSPs, CSP 3 was found to show the highest chiral recognition efficiencies for the resolution of mexiletine and its analogs, especially in terms of resolution (R(S)). PMID:24677299

  18. pH-responsive supramolecular polymerization in aqueous media driven by electrostatic attraction-enhanced crown ether-based molecular recognition.

    PubMed

    Ji, Xiaofan; Zhu, Kelong; Yan, Xuzhou; Ma, Yingjie; Li, Jinying; Hu, Bingjie; Yu, Yihua; Huang, Feihe

    2012-07-26

    All the previously reported supramolecular polymers based on crown ether-based molecular recognition have been prepared in anhydrous organic solvents. This is mainly due to the weakness of crown ether-based molecular recognition in the presence of water. Here we report a linear supramolecular polymer constructed from a heteroditopic monomer in an aqueous medium driven by crown ether-based molecular recognition through the introduction of electrostatic attraction. In addition, the reversible transition between the linear supramolecular polymer and oligomers is achieved by adding acid and base. This study realizes the breakthrough of the solvent for supramolecular polymerization driven by crown ether-based molecular recognition from anhydrous organic solvents to aqueous media. It is helpful for achieving supramolecular polymerization driven by crown ether-based molecular recognition in a completely aqueous medium. PMID:22495805

  19. Rotamerism-driven large magnitude host-guest binding change in a crown ether derivatized pyridinium-phenolate series.

    PubMed

    Ay, Emel; Hobeika, Nelly; Chaumeil, Hélène; Tschamber, Théophile; Jin, Ming; Versace, Davy-Louis; Malval, Jean-Pierre

    2016-03-17

    Two TICTOID-based pyridinium-phenolates bearing a crown ether macrocycle have been designed for the complexation of a potassium cation. The nucleophilicity of the intraannular phenolate -O(-) function can be strongly modulated by biaryl twisting. Such a structure/electronic transduction effect gives rise to a host-guest binding change by more than two orders of magnitude. PMID:26948128

  20. Selective recognition and extraction of KBr via cooperative interactions with a urea functionalized crown ether dual-host.

    PubMed

    Akhuli, Bidyut; Ghosh, Pradyut

    2015-11-28

    Selective solid-liquid extraction of KBr is demonstrated for the first time with a crown ether based pentafluorophenyl urea functionalized dual-host receptor. (1)H-NMR and ITC studies have been carried out to illustrate the effect of cooperativity towards the recognition of alkali metal salts. PMID:26417887

  1. Coordination effect-regulated CO2 capture with an alkali metal onium salts/crown ether system

    SciTech Connect

    Yang, Zhen-Zhen; Jiang, Deen; Zhu, Xiang; Tian, Chengcheng; Brown, Suree; Do-Thanh, Chi-Linh; He, Liang-Nian; Dai, Sheng

    2014-01-01

    A coordination effect was employed to realize equimolar CO2 absorption, adopting easily synthesized amino group containing absorbents (alkali metal onium salts). The essence of our strategy was to increase the steric hindrance of cations so as to enhance a carbamic acid pathway for CO2 capture. Our easily synthesized alkali metal amino acid salts or phenolates were coordinated with crown ethers, in which highly sterically hindered cations were obtained through a strong coordination effect of crown ethers with alkali metal cations. For example, a CO2 capacity of 0.99 was attained by potassium prolinate/18-crown-6, being characterized by NMR, FT-IR, and quantum chemistry calculations to go through a carbamic acid formation pathway. The captured CO2 can be stripped under very mild conditions (50 degrees C, N-2). Thus, this protocol offers an alternative for the development of technological innovation towards efficient and low energy processes for carbon capture and sequestration.

  2. Aza-crown ether complex cation ionic liquids: preparation and applications in organic reactions.

    PubMed

    Song, Yingying; Cheng, Chen; Jing, Huanwang

    2014-09-26

    Aza-crown ether complex cation ionic liquids (aCECILs) were devised, fabricated, and characterized by using NMR spectroscopy, MS, thermogravimetric differential thermal analysis (TG-DTA), elemental analysis and physical properties. These new and room-temperature ILs were utilized as catalysts in various organic reactions, such as the cycloaddition reaction of CO2 to epoxides, esterification of acetic acid and alcohols, the condensation reaction of aniline and propylene carbonate, and Friedel-Crafts alkylation of indole with aldehydes were investigated carefully. In these reactions, the ionic liquid exhibited cooperative catalytic activity between the anion and cation. In addition, the aza-[18-C-6HK][HSO4]2 was the best acidic catalyst in the reactions of esterification and Friedel-Crafts alkylation under mild reaction conditions. PMID:25154312

  3. Recognition of silver cations by a cucurbit[8]uril-induced supramolecular crown ether.

    PubMed

    Geng, Qing-Xia; Wang, Fang; Cong, Hang; Tao, Zhu; Wei, Gang

    2016-02-28

    The host-guest interaction of cucurbit[8]uril (Q[8]) with a synthesized guest molecule, consisting of naphthalene and viologen moieties bridged by a carbon oxygen chain, was investigated by (1)H NMR and UV-Vis spectroscopy. The results indicated the formation of an inclusion complex in a ratio of 1 : 1 with a moderate association constant of Ka = (1.1 ± 0.2) × 10(6) L mol(-1). The formation of this special complex is driven by the markedly enhanced charge-transfer interaction between the electron-rich and electron-deficient guest molecule inside the hydrophobic cavity of Q[8], while the carbon oxygen chain stays outside of Q[8] to form a supramolecular crown ether. Screening of the metal cation substrate suggested that the inclusion complex recognizes Ag(+) ions with high selectivity, as shown by UV-Vis spectroscopy. PMID:26879150

  4. Probing Ternary Complex Equilibria of Crown Ether Ligands by Time-Resolved Fluorescence Spectroscopy

    PubMed Central

    2015-01-01

    Ternary complex formation with solvent molecules and other adventitious ligands may compromise the performance of metal-ion-selective fluorescent probes. As Ca(II) can accommodate more than 6 donors in the first coordination sphere, commonly used crown ether ligands are prone to ternary complex formation with this cation. The steric strain imposed by auxiliary ligands, however, may result in an ensemble of rapidly equilibrating coordination species with varying degrees of interaction between the cation and the specific donor atoms mediating the fluorescence response, thus diminishing the change in fluorescence properties upon Ca(II) binding. To explore the influence of ligand architecture on these equilibria, we tethered two structurally distinct aza-15-crown-5 ligands to pyrazoline fluorophores as reporters. Due to ultrafast photoinduced electron-transfer (PET) quenching of the fluorophore by the ligand moiety, the fluorescence decay profile directly reflects the species composition in the ground state. By adjusting the PET driving force through electronic tuning of the pyrazoline fluorophores, we were able to differentiate between species with only subtle variations in PET donor abilities. Concluding from a global analysis of the corresponding fluorescence decay profiles, the coordination species composition was indeed strongly dependent on the ligand architecture. Altogether, the combination of time-resolved fluorescence spectroscopy with selective tuning of the PET driving force represents an effective analytical tool to study dynamic coordination equilibria and thus to optimize ligand architectures for the design of high-contrast cation-responsive fluorescence switches. PMID:25313708

  5. Laser Spectroscopic Study of Cold Gas-Phase Host-Guest Complexes of Crown Ethers.

    PubMed

    Ebata, Takayuki; Inokuchi, Yoshiya

    2016-06-01

    The structure, molecular recognition, and inclusion effect on the photophysics of guest species are investigated for neutral and ionic cold host-guest complexes of crown ethers (CEs) in the gas phase. Here, the cold neutral host-guest complexes are produced by a supersonic expansion technique and the cold ionic complexes are generated by the combination of electrospray ionization (ESI) and a cryogenically cooled ion trap. The host species are 3n-crown-n (3nCn; n = 4, 5, 6, 8) and (di)benzo-3n-crown-n ((D)B3nCn; n = 4, 5, 6, 8). For neutral guests, we have chosen water and aromatic molecules, such as phenol and benzenediols, and as ionic species we have chosen alkali-metal ions (M(+) ). The electronic spectra and isomer-specific vibrational spectra for the complexes are observed with various laser spectroscopic methods: laser-induced fluorescence (LIF); ultraviolet-ultraviolet hole-burning (UV-UV HB); and IR-UV double resonance (IR-UV DR) spectroscopy. The obtained spectra are analyzed with the aid of quantum chemical calculations. We will discuss how the host and guest species change their flexible structures for forming best-fit stable complexes (induced fitting) and what kinds of interactions are operating for the stabilization of the complexes. For the alkali metal ion•CE complexes, we investigate the solvation effect by attaching water molecules. In addition to the ground-state stabilization problem, we will show that the complexation leads to a drastic effect on the excited-state electronic structure and dynamics of the guest species, which we call a "cage-like effect". PMID:27006080

  6. Reaction of premium Wyodak subbituminous coal with potassium-crown ether reagent

    SciTech Connect

    Huang, S.L.; Narayan, R.

    1987-01-01

    Coal conversions typically involve reacting coal under severe conditions of temperature and pressure. As a result, bond cleavage is nonselective and often accompanied by retrogressive (bond forming) reactions. This has resulted in less than satisfactory results in deducing coal structure, coal behavior, and reactivity. Incorrect model of the basic structural units of the coal, and the nature of the linkages joining these units have been postulated. In our laboratory, we are studying the solubilization of coal at ambient temperatures and pressures using a site-specific reagent potassium-crown ether (K-CE), and the characterization of the soluble coal oligomer fragments. The small size and high reactivity of the solvated electrons generated by the K-CE reagent, promotes cleavage reactions at ether, ester, and diarylethane linkages, resulting in depolymerization and solubilization of coal. Reduction of aromatic rings to dihydro and tetrahydro analogs also occur. In this paper we report on the solubilization of a Wyodak premium subbituminous coal using K-CE reagent. The characterization of the solubilized coal fragments by IR, NMR, GPC, and microanalysis, is described.

  7. Calixarene crown ether solvent composition and use thereof for extraction of cesium from alkaline waste solutions

    DOEpatents

    Moyer, Bruce A.; Sachleben, Richard A.; Bonnesen, Peter V.; Presley, Derek J.

    2001-01-01

    A solvent composition and corresponding method for extracting cesium (Cs) from aqueous neutral and alkaline solutions containing Cs and perhaps other competing metal ions is described. The method entails contacting an aqueous Cs-containing solution with a solvent consisting of a specific class of lipophilic calix[4]arene-crown ether extractants dissolved in a hydrocarbon-based diluent containing a specific class of alkyl-aromatic ether alcohols as modifiers. The cesium values are subsequently recovered from the extractant, and the solvent subsequently recycled, by contacting the Cs-containing organic solution with an aqueous stripping solution. This combined extraction and stripping method is especially useful as a process for removal of the radionuclide cesium-137 from highly alkaline waste solutions which are also very concentrated in sodium and potassium. No pre-treatment of the waste solution is necessary, and the cesium can be recovered using a safe and inexpensive stripping process using water, dilute (millimolar) acid solutions, or dilute (millimolar) salt solutions. An important application for this invention would be treatment of alkaline nuclear tank wastes. Alternatively, the invention could be applied to decontamination of acidic reprocessing wastes containing cesium-137.

  8. Theoretical study of the asymmetric phase-transfer mediated epoxidation of chalcone catalyzed by chiral crown ethers derived from monosaccharides

    NASA Astrophysics Data System (ADS)

    Makó, Attila; Menyhárd, Dóra K.; Bakó, Péter; Keglevich, György; Tőke, László

    2008-12-01

    The synthesis of a novel, optically active crown ether derived from α- D-altropyranoside is described. A significantly different asymmetric induction was generated by the α- D-glucopyranoside-, α- D-mannopyranoside- and α- D-altropyranoside-based chiral crown catalysts in the epoxidation of trans-chalcone with tert-butyl hydroperoxide under phase-transfer catalytic conditions. It was shown that absolute configuration of the crown-ring fused carbon atoms of the monosaccharides has a great impact on the enantioselectivity. The asymmetric induction could be well explained by considering the possible mechanistic pathway. Molecular modeling (MCMM) and subsequent DFT calculations - in accordance with the experimental results - indicate that the use of glucopyranoside-based catalyst 1 and that of mannopyranoside-based crown ether 2 results in the preferred formation of the opposite antipodes (2 R,3 S and 2 S,3 R, respectively) of the corresponding epoxyketone. At the same time, practically no asymmetric induction was proved if altropyranoside-based crown 3 is applied as the catalyst. The computational results are in qualitative agreement with the experimental data.

  9. SYNTHESIS OF NOVEL CROWN ETHERS BEARING THE exo-cis-2,3-NORBORNYL GROUP AS POTENTIAL Na+ AND K+ EXTRACTANTS

    SciTech Connect

    Robeson, R.M.; Bonnesen, P.

    2007-01-01

    The synthesis of a series of novel dinorbornyl-16-crown-5 and dinorbornyl-18-crown-6 ethers that incorporate the exo-cis-2,3-norbornyl moiety within the macrocycle framework is described. The key starting material for the crown ethers, exo-cis-2,3-norbornanediol, was successfully prepared on a large (>30g) scale in 88% yield from norbornylene by osmium tetroxide-catalyzed hydroxylation. The syn and anti isomers of the dinorbornyl-16-crown-5 ether family were prepared using diethylene glycol with ring closure achieved using a methallyl linkage. The isomers cis-syn-cis and cis-anti-cis di-norbornano-15-methyleno-16-crown-5 (6A and 6B) could be separated using column chromatography, and a single crystal of the syn isomer 6A suitable for X-ray crystal structure analysis was obtained, thereby confi rming the syn orientation. The syn and anti isomers of the dinorbornyl-18-crown-6 ether family were successfully prepared employing a different synthetic strategy, involving the potassium–templated cyclization of two bis-hydroxyethoxy-substituted exo-cis-2,3-norbornyl groups under high dilution conditions. Attempts to fully separate cis-syn-cis di-norbornano-18-crown-6 (10A) and cis-anti-cis di-norbornano-18-crown-6 (10B) from one another using column chromatography were unsuccessful. All intermediates and products were checked for purity using either thin layer chromatography or gas chromatography, and characterized by proton and carbon NMR. Crown ethers 6AB and 10AB are to our knowledge the fi rst crown ethers to incorporate the exo-cis-2,3-norbornyl moiety into the crown ring to be successfully synthesized and characterized.

  10. Enhanced performance in gas adsorption and Li ion batteries by docking Li(+) in a crown ether-based metal-organic framework.

    PubMed

    Bai, Linyi; Tu, Binbin; Qi, Yi; Gao, Qiang; Liu, Dong; Liu, Zhizhou; Zhao, Lingzhi; Li, Qiaowei; Zhao, Yanli

    2016-02-18

    Incorporating supramolecular interaction units, crown ether rings, into metal-organic frameworks enables the docking of metal ions through complexation for enhanced performance in H2 and CO2 adsorption and lithium ion batteries. PMID:26785426

  11. A responsive supramolecular metallogel constructed by coordination-driven self-assembly of a crown ether-based [3]pseudorotaxane and a diplatinum(II) acceptor.

    PubMed

    Xing, Hao; Wang, Hu; Yan, Xuzhou; Ji, Xiaofan

    2015-07-01

    Herein, a stimuli-responsive supramolecular metallogel was prepared by orthogonal coordination-driven self-assembly of a crown ether-based [3]pseudorotaxane and a 180° organic di-Pt(II) acceptor. PMID:26030667

  12. Alkaline-side extraction of technetium from tank waste using crown ethers and other extractants

    SciTech Connect

    Bonnesen, P.V.; Moyer, B.A.; Presley, D.J.; Armstrong, V.S.; Haverlock, T.J.; Counce, R.M.; Sachleben, R.A.

    1996-06-01

    The chemical development of a new crown-ether-based solvent-extraction process for the separation of (Tc) from alkaline tank-waste supernate is ready for counter-current testing. The process addresses a priority need in the proposed cleanup of Hanford and other tank wastes. This need has arisen from concerns due to the volatility of Tc during vitrification, as well as {sup 99}Tc`s long half-life and environmental mobility. The new process offers several key advantages that direct treatability--no adjustment of the waste composition is needed; economical stripping with water; high efficiency--few stages needed; non-RCRA chemicals--no generation of hazardous or mixed wastes; co-extraction of {sup 90}Sr; and optional concentration on a resin. A key concept advanced in this work entails the use of tandem techniques: solvent extraction offers high selectivity, while a subsequent column sorption process on the aqueous stripping solution serves to greatly concentrate the Tc. Optionally, the stripping solution can be evaporated to a small volume. Batch tests of the solvent-extraction and stripping components of the process have been conducted on actual melton Valley Storage Tank (MVST) waste as well as simulants of MVST and Hanford waste. The tandem process was demonstrated on MVST waste simulants using the three solvents that were selected the final candidates for the process. The solvents are 0.04 M bis-4,4{prime}(5{prime})[(tert-butyl)cyclohexano]-18-crown-6 (abbreviated di-t-BuCH18C6) in a 1:1 vol/vol blend of tributyl phosphate and Isopar{reg_sign} M (an isoparaffinic kerosene); 0.02 M di-t-BuCH18C6 in 2:1 vol/vol TBP/Isopar M and pure TBP. The process is now ready for counter-current testing on actual Hanford tank supernates.

  13. Separation of Long-Lived Fission Products Tc-99 and I-129 from Synthetic Effluents by Crown Ethers

    SciTech Connect

    Paviet-Hartmann, P.; Hartmann, T.

    2006-07-01

    To minimize significantly the radio-toxic inventory of nuclear geological repositories to come as well as to reduce the potential of radionuclides migration and to minimize long-term exposure, the concept of partitioning and transmutation (P/T) of nuclear waste is currently discussed. Transmutation offers the possibility to convert radio-toxic radionuclides with long half-lives into radionuclides of shorter half-lives, less toxic isotopes, or even into stable isotopes. Besides the most prominent isotopes of neptunium, plutonium, americium, and curium, the long-lived fission products Tc-99 and I-129 (half-lives of 2.13 x 10{sup 5} years, and 1.57 x 10{sup 7} years, respectively) are promising candidates for transmutation in order to prevent their migration from a nuclear repository. Partitioning and transmutation of the most radio-toxic radionuclides will not only minimize the nuclear waste load but most importantly will significantly reduce the long-term radio-toxic hazard of nuclear waste repositories to come. Prior to the deployment of partitioning and transmutation, selective extraction techniques are required to separate the radionuclides of concern. Since the discovery of crown ethers by C. Pedersen, various applications of crown ethers have drawn much attention. Although liquid-liquid extraction of alkali and alkali earth metals by crown ethers has been extensively studied, little data is available on the extraction of Tc-99 and I-129 by crown ethers. The methods developed herein for the specific extraction of Tc-99 and I-129 provide recommendations in support of their selectively extraction from liquid radioactive waste streams, mainly ILW. We report data on the solvent extraction of Tc-99 and I-129 from synthetic effluents by six crown ethers of varying cavity dimensions and derivatization. To satisfy the needs of new extractant systems we are demonstrating that crown ether (CE) based systems have the potential to serve as selective extractants for the

  14. Synthesis and Enantiomeric Recognition Studies of Optically Active Pyridino-Crown Ethers Containing an Anthracene Fluorophore Unit.

    PubMed

    Szemenyei, Balázs; Móczár, Ildikó; Pál, Dávid; Kocsis, Ivett; Baranyai, Péter; Huszthy, Péter

    2016-07-01

    Novel enantiopure pyridino-18-crown-6 ether-based sensor molecules containing an anthracene fluorophore unit were synthesized. Their enantiomeric recognition abilities toward the enantiomers of 1-phenylethylamine hydrogen perchlorate (PhEt), 1-(1-naphthyl)ethylamine hydrogen perchlorate (NapEt), phenylglycine methyl ester hydrogen perchlorate (PhgOMe), and phenylalanine methyl ester hydrogen perchlorate (PheOMe) were examined in acetonitrile using fluorescence spectroscopy. The sensor molecules showed appreciable enantiomeric recognition toward the enantiomers of NapEt, PhEt, and PhgOMe. The highest enantioselectivity was found in the case of crown ether containing isobutyl groups in the macroring and the enantiomers of NapEt. Chirality 28:562-568, 2016. © 2016 Wiley Periodicals, Inc. PMID:27349957

  15. Enantiomeric recognition of organic ammonium salts by chiral crown ethers based on the pyridino-18-crown-6 structure

    SciTech Connect

    Davidson, R.B.; Bradshaw, J.S.; Jones, B.A.; Dalley, N.K.; Christensen, J.J.; Izatt, R.M.

    1984-01-27

    Enantiomeric recognition by several chiral dimethyl-substituted macrocycles of the pyridino-18-crown-6 type for chiral organic ammonium salts has been studied by titration calorimetry in CH/sub 3/OH, temperature-dependent /sup 1/H NMR spectroscopy in CD/sub 2/CL/sub 2/, and selective crystallization. Results from the three procedures are consistent in demonstrating either host-guest recognition or nonrecognition in the systems investigated. Futhermore, enaniomeric recognition by one chiral host for a pair of chiral guests is correlated with X-ray crystallographic data for the same system. The chiral dimethyl-substituted ligands used in the study include three dimethyl diester pyridino-18-crown-6 ligands, dimethyl thiono diester pyridino-18-crown-6, and dimethyl-pyridino-18-crown-6 ligands. All of these ligands exhibited chiral recognition. Dimethylpyridino-18-crown-6 in complexation with (R)- and (S)-(..cap alpha..-(1-naphthyl)ethyl)ammonium perchlorate exhibited the largest ratio of ..delta..G/sub c/+ yet observed by the /sup 1/H NMR technique. A diphenyl-substituted diester pyridino-18-crown-6 where the phenyl substituents are in less rigid portion of the macrocycle failed to show chiral recognition.

  16. Hydrogen-bonding interactions and protic equilibria in room-temperature ionic liquids containing crown ethers.

    SciTech Connect

    Marin, T.; Shkrob, I.; Dietz, M.

    2011-04-14

    Nuclear magnetic resonance (NMR) spectroscopy has been used to study hydrogen-bonding interactions between water, associated and dissociated acids (i.e., nitric and methanesulfonic acids), and the constituent ions of several water-immiscible room-temperature ionic liquids (ILs). In chloroform solutions also containing a crown ether (CE), water molecules strongly associate with the IL ions, and there is rapid proton exchange between these bound water molecules and hydronium associated with the CE. In neat ILs, the acids form clusters differing in their degree of association and ionization, and their interactions with the CEs are weak. The CE can either promote proton exchange between different clusters in IL solution when their association is weak or inhibit such exchange when the association is strong. Even strongly hydrophobic ILs are shown to readily extract nitric acid from aqueous solution, typically via the formation of a 1:1:1 {l_brace}H{sub 3}O{sup +} {center_dot} CE{r_brace}NO{sub 3}{sup -} complex. In contrast, the extraction of methanesulfonic acid is less extensive and proceeds mainly by IL cation-hydronium ion exchange. The relationship of these protic equilibria to the practical application of hydrophobic ILs (e.g., in spent nuclear fuel reprocessing) is discussed.

  17. Halogen impact into new oxonium benzo-crown ether complexes with tetrachloro- and tetrabromoaurates(III).

    PubMed

    Pluzhnik-Gladyr, Sergei M; Kravtsov, Victor Ch; Fonari, Marina S; Kamalov, Gerbert L

    2014-05-21

    Five oxonium tetrahalogenaurate(III) (Hal = Cl, Br) benzo-crown ether (BCE) complexes are prepared and reported. The new compounds are [(H3O)(B18C6)(0.58)(4'-Cl-B18C6)0.42][AuCl4] 1, [(H3O)(B18C6)][AuCl4] 2, [(H3O)(4'-Br-B18C6)][AuCl4] 3, [(H3O)(4'-Br-B18C6)][AuBr4] 4, and [(H3O)(B18C6)][AuBr4] 5. The reaction medium, distinctive from the previously used aqua regia, allowed avoiding the unwanted nitration of initial macrocycles. The compositions and structures for 1, 3, 4, and 5 were proved by single crystal X-ray crystallography. The complete conversion of tetrachloroaurate(III) to the tetrabromoaurate(III) salts resulted in complex 4 isomorphous and isostructural to 3. All compounds form the laminated structures with alternation of cationic and anionic layers. The robustness of the anionic sheets is sustained by the halogen-halogen interactions and makes crucial impact on extraction of stoichiometric products in the case of tetrabromoaurate(III) salts. PMID:24671258

  18. Separation of calcium-48 isotope by crown ether chromatography using ethanol/hydrochloric acid mixed solvent.

    PubMed

    Okumura, Shin; Umehara, Saori; Fujii, Yasuhiko; Nomura, Masao; Kaneshiki, Toshitaka; Ozawa, Masaki; Kishimoto, Tadafumi

    2015-10-01

    Benzo-18-crown-6 ether resin embedded in porous silica beads was synthesized and used as the packing material for chromatographic separation of (48)Ca isotope. The aim of the present work is to develop efficient isotope enrichment process for double β decay nuclide (48)Ca. To this end, ethanol/HCl mixed solvent was selected as the medium for the chromatographic separation. Adsorption of calcium on the resin was studied at different HCl concentrations and different ethanol mixing ratios in batch-wise experiments. A very interesting phenomenon was observed; Ca adsorption is controlled not by the overall HCl concentration of the mixed solvent, but by the initial concentration of added HCl solution. Calcium break-through chromatography experiments were conducted by using 75v/v% ethanol/25v/v% 8M HCl mixed solvent at different flow rates. The isotope separation coefficient between (48)Ca and (40)Ca was determined as 3.8×10(-3), which is larger than that of pure HCl solution system. Discussion is extended to the chromatographic HETP, height equivalent to a theoretical plate. PMID:26358563

  19. Sodium ion-selective electrodes based on dibenzo-16-crown-5 compounds with pendent amide groups

    SciTech Connect

    Ohki, Akira; Maeda, Shigeru ); Lu, J.P.; Bartsch, R.A. )

    1994-05-15

    Potentiometric selectivities for alkali-metal cations of dibenzo-16-crown-5 compounds with amide-containing side arms attached to the central carbon atom of the three-carbon bridge have been determined in solvent polymeric membrane electrodes. The lariat ethers include N-alkyl- and N,N-dialkyl-sym-(R)-dibenzo-16-crown-5-oxyacetamides with R = hydrogen or an alkyl group. The presence of an alkyl group on the ring carbon which bears the amide-containing side arm markedly increases the Na[sup +]/K[sup +] selectivity of poly(vinyl chloride) matrix membrane electrodes with o-nitrophenyl octyl ether as the membrane solvent. Lariat ethers with a N,N-dipentyloxyacetamide group as the side arm and a geminal alkyl group of two or more carbon atoms exhibit high Na[sup +]K[sup +] selectivities (log K[sub Na,K][sup Pot] = [minus]2.1) with good selectivities for Na[sup +] over the other alkali-metal cations, H[sup +], NH[sub 4][sup +], and alkaline-earth-metal cations. 25 refs., 6 figs., 1 tab.

  20. Preparation and characterization of novel crown ether functionalized ionic liquid-based solid-phase microextraction coatings by sol-gel technology.

    PubMed

    Zhou, Xin; Xie, Peng-fei; Wang, Jiang; Zhang, Bei-bei; Liu, Ming-ming; Liu, Han-lan; Feng, Xiong-han

    2011-06-10

    A novel crown ether functionalized ionic liquid (IL), 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium hexafluorophosphate was synthesized and used as selective stationary phase to prepare task-specific IL-based solid phase microextraction (SPME) fibers by sol-gel method and free radical cross-linking technology. The underlying mechanism of the sol-gel reaction was proposed and the successful chemical bonding of the crown ether functionalized IL to the formed hybrid organic-inorganic copolymer coating was confirmed by FT-IR spectroscopy. The performance of this in situ created crown ether functionalized IL-based SPME fibers, was investigated in detail. The coating has porous surface structure, stable performance in high temperature (to 340 °C) and in different solutions (water, organic solvent, acid and alkali), and good coating preparation reproducibility. In contrast to the sol-gel derived 1-allyl-3-methyl imidazolium hexafluorophosphate-based coating prepared in our previous work with the identical procedure, the extraction performance of this newly developed sol-gel crown ether functionalized IL-based coating was superior for alcohols, phthalate esters, phenolic environmental estrogens, fatty acids and aromatic amines due to the introduction of benzo-15-crown-5 functional group in IL structure. Moreover, it was shown to provide higher or comparable extraction efficiencies for most analytes studied than did the commercial PDMS, PDMS/DVB and PA fibers. PMID:21531419

  1. Enantiomer-selective ultraviolet photolysis of temperature-controlled protonated tryptophan on a chiral crown ether in the gas phase

    NASA Astrophysics Data System (ADS)

    Fujihara, Akimasa; Sato, Takashi; Hayakawa, Shigeo

    2014-08-01

    Enantiomer-selective ultraviolet photolysis of temperature-controlled protonated tryptophan (TrpH+) on the chiral crown ether, (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6TA), was examined using a tandem mass spectrometer containing a temperature-variable 22-pole ion trap. The spectra of D-TrpH+-(+)-18C6TA at 9-320 K showed that the loss of NH2CH2COOH due to Cαsbnd Cβ bond cleavage decreased gradually with increasing temperature. The spectrum at room temperature was similar to that of L-TrpH+-(+)-18C6TA, which showed no temperature dependence on photolysis. The chiral-specific photolysis of cold D-TrpH+-(+)-18C6TA was attributed to the structures involving the chiral-dependent interactions of the Cαsbnd H group of TrpH+ with the oxygen atoms of (+)-18C6TA.

  2. Solvent extraction of lanthanoid picrates with crown ethers: preferential sandwich complexation and unique cation selectivities

    SciTech Connect

    Nakagawa, K.; Okada, S.; Inoue, Y.; Tai, A.; Hakushi, T.

    1988-11-15

    Quantitative solvent extractions of aqueous lanthanoid picrates with 15-crown-5 and 18-crown-6 were conducted at low ionic strength in the absence of background salts. An overwhelming preference for the sandwich complexation and unique cation selectivities were observed. The peak extraction constants were found for samarium with 15-crown-5 (1:2 stoichiometry) and for cerium and praseodymium with 18-crown-6 (1:1 and 1:2 stoichiometries, respectively). The facile sandwich complexation and unique cation selectivities are interpreted in terms of the heavy hydration of lanthanoid ions of high charge density.

  3. 12-crown-4 ether-assisted enhancement of ionic conductivity and interfacial kinetics in polyethylene oxide electrolytes

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    The electrical and electrochemical properties of thin films of polyethylene oxide electrolytes with and without 12-crown-4 ether (12Cr4) are studied as a function of temperature and in the frequency regime from 100 kHz to 0.1 Hz. These measurements were made on electrolytes containing LiCF3SO3, LiBF4, or LiClO4 salts. At a given temperature, the bulk conductivity for a particular salt depends on the 12Cr4 concentration, reaching a maximum for a ratio of 12Cr4 to Li of 0.003.

  4. Water Ionic Liquid-Crown Ether System Controlling Morphologies and Sizes of Soluble Polypyrrole Nanostructures and Their Self-Assembly Behaviors in the System

    NASA Astrophysics Data System (ADS)

    Yavari, Issa; Kowsari, Elaheh

    The present study reports a novel chemical route to synthesize different sizes of conducting polypyrrol (ppy) nanoparticles by hydrogen-bonding directionality in the presence of a crown ether, ionic liquid ([octmim]Br, octhyl-methyl imidazulim bromide) and ammonium persulfate in HCl solution. The morphology of the nanoparticle of PPy was confirmed by SEM images. The effects of reaction conditions on the morphology of the resultant ppy nanostructures were studied. The conductivity of the product varied with the mass ratio of aniline monomer to crown ether and IL. The chemical and electronic structures of the ppy nanoparticle were also studied by FT-IR and UV-Vis spectrometry, respectively.

  5. A taco complex derived from a bis-crown ether capable of executing molecular logic operation through reversible complexation.

    PubMed

    Mandal, Amal Kumar; Das, Priyadip; Mahato, Prasenjit; Acharya, Suhash; Das, Amitava

    2012-08-17

    As learned from natural systems, self-assembly and self-sorting help in interconnecting different molecular logic gates and thus achieve high-level logic functions. In this context, demonstration of important logic operations using changes in optical responses due to the formation of molecular assemblies is even more desirable for the construction of a molecular computer. Synthesis of an appropriate divalent as well as a luminescent crown ether based host 1 and paraquat derivatives, 2(PF(6))(2) and 3(PF(6))(2), as guests helped in demonstrating a reversible [3](taco complex) (1·{2(PF(6))(2)}(2) or 1·{3(PF(6))(2)}(2)) formation in nonpolar solvent. Detailed (1)H NMR studies revealed that two paraquat units were bound cooperatively by the two crown units in 1. Because of preorganization, the flexible host molecule 1 adopts a folded conformation, where each of two paraquat units remain sandwiched between the two aromatic units of each folded crown ether moiety in 1. Disassembly of the "taco" complex in the presence of KPF(6) and reassembly on subsequent addition of DB18C6 was initially demonstrated by (1)H NMR spectral studies, which were subsequently corroborated through luminescence spectral studies. Further, luminescence spectral responses as output signals with appropriate and two independent molecular inputs could be correlated to demonstrate basic logic operation like OR and YES gates, while the results of the three molecular inputs could be utilized to demonstrate important logic operation like an INHIBIT gate. PMID:22834483

  6. Extraction of protactinium-233 and separation from thermal neutron-irradiated thorium-232 using crown ethers

    SciTech Connect

    Jalhoom, Moayyed G.; Mohammed, Dawood A.; Khalaf, Jumah S.

    2008-07-01

    A new method was developed for the extraction and separation of {sup 233}Pa from thermal neutron-irradiated {sup 232}Th. Solutions of Pa{sup 233} were prepared in LiCI-HCl solutions from which appreciable extraction was obtained using dibenzo-18-crown-6 in 1,2-dichloroethane. The effects of cavity size, substitutions on the crown ring, type of the organic solvent, and temperature on extraction are discussed. Very high separation factors were obtained for the pairs {sup 233}Pa/{sup 232}Th (>105), {sup 233}Pa/{sup 233}U (> 1000), and {sup 232}U/{sup 232}Th (>60). (authors)

  7. Crown-Ether Derived Graphene Hybrid Composite for Membrane-Free Potentiometric Sensing of Alkali Metal Ions.

    PubMed

    Olsen, Gunnar; Ulstrup, Jens; Chi, Qijin

    2016-01-13

    We report the design and synthesis of newly functionalized graphene hybrid material that can be used for selective membrane-free potentiometric detection of alkali metal ions, represented by potassium ions. Reduced graphene oxide (RGO) functionalized covalently by 18-crown[6] ether with a dense surface coverage is achieved by the introduction of a flexible linking molecule. The resulting hybrid composite is highly stable and is capable of detecting potassium ions down to micromolar ranges with a selectivity over other cations (including Ca(2+), Li(+), Na(+), NH4(+)) at concentrations up to 25 mM. This material can be combined further with disposable chips, demonstrating its promise as an effective ion-selective sensing component for practical applications. PMID:26703780

  8. Structure of hydrated clusters of dibenzo-18-crown-6-ether in a supersonic jet--encapsulation of water molecules in the crown cavity.

    PubMed

    Kusaka, Ryoji; Inokuchi, Yoshiya; Ebata, Takayuki

    2008-11-01

    The structure of dibenzo-18-crown-6-ether (DB18C6) and its hydrated clusters has been investigated in a supersonic jet. Two conformers of bare DB18C6 and six hydrated clusters (DB18C6-(H(2)O)(n)) were identified by laser-induced fluorescence, fluorescence-detected UV-UV hole-burning and IR-UV double-resonance spectroscopy. The IR-UV double resonance spectra were compared with the IR spectra obtained by quantum chemical calculations at the B3LYP/6-31+G* level. The two conformers of bare DB18C6 are assigned to "boat" and "chair I" forms, respectively, among which the boat form is dominant. All the six DB18C6-(H(2)O)(n) clusters with n = 1-4 have a boat conformation in the DB18C6 part. The water molecules form a variety of hydration networks in the boat-DB18C6 cavity. In DB18C6-(H(2)O)(1), a water molecule forms the bidentate hydrogen bond with the O atoms adjacent to the benzene rings. In this cluster, the water molecule is preferentially hydrogen bonded from the bottom of boat-DB18C6. In the larger clusters, the hydration networks are developed on the basis of the DB18C6-(H(2)O)(1) cluster. PMID:18936847

  9. Investigation of bis-crown ethers for ion-selective electrodes by FT-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Egyed, O.; Izvekov, V. P.; Toth, K.; Holly, S.; Pungor, E.

    1990-03-01

    The structure of bis-benzo-15-crown-5 derivatives containing nitro groups and urethane linkages has been studied by FT-IR spectroscopy, regarding especially the secondary bonds (H-bridges) of the chain connecting the two crow rings of the molecule. It was concluded that the formation of an ion trap stabilized by intramolecular cross H-bonds between urethane NH groups and O atoms is presumable.

  10. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data. PMID:22653895

  11. Metallosupramolecular poly[2]pseudorotaxane constructed by metal coordination and crown-ether-based molecular recognition.

    PubMed

    Wei, Peifa; Li, Jinying; Yan, Xuzhou; Zhou, Qizhong

    2014-01-01

    A novel bis(m-phenylene)-32-crown-10 derivative bearing two π-extended pyridyl groups was synthesized, and its host-guest complexation with a paraquat derivative to form a threaded [2]pseudorotaxane was studied. Subsequently, a poly[2]pseudorotaxane was constructed with a metallosupramolecular polymer backbone via metal coordination, which was comprehensively confirmed by the combination of (1)H NMR, (31)P{(1)H} NMR, DOSY NMR, DLS, and EDX techniques. PMID:24328434

  12. The interaction between ketamine and some crown ethers in common organic solvents studied by NMR: The effect of donating atoms and ligand structure

    NASA Astrophysics Data System (ADS)

    Chekin, Fereshteh; Bordbar, Maryam; Fathollahi, Yaghoub; Alizadeh, Naader

    2006-02-01

    1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 °C. In order to evaluate the formation constants of the ketamine cation complexes, the CH 3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed.

  13. Regioselective carbon-oxygen bond cleavage reactions of aromatic ethers and esters with potassium metal/18-crown-6/THF as the electron-transfer reagent

    SciTech Connect

    Fish, R.H.; Dupon, J.W.

    1988-10-28

    The facile carbon-oxygen bond cleavage reactions of a variety of aromatic ethers and esters were studied with an electron-transfer reagent that consisted of potassium metal and 18-crown-6 in tetrahydrofuran (THF). The relative rates of carbon-oxygen bond cleavage, with these aromatic ethers and esters under electron-transfer conditions, was studied in competition with the standard, diphenyl ether. The order of relative reactivities was as follows: phenyl 2-hydroxybenzoate (10) (>2.0); phenyl 2-methoxybenzoate (11) (>2.0); phenyl 4-methoxybenzoate (12) (>2.0); 2-methoxyphenyl benzoate (13) (>2.0); 4-methoxyphenyl benzoate (14) (>2.0); 4-hydroxyphenyl benzoate (15) (1.6); benzyl benzoate (9) (1.3); 4-methoxyphenyl phenyl ether (5) (1.15); phenyl benzoate (8) (1.04); diphenyl ether (1) (1.0); dibenzyl ether (2) (0.98); 2-methoxyphenyl phenyl ether (6) (0.97); benzyl phenyl ether (3) (0.96); phenethyl phenyl ether (7) (0.77); and 4-hydroxyphenyl phenyl ether (4) (<0.1). From these relative rates, it is clear that electron-donating groups increase the relative rates of C-O bond cleavage in aromatic esters. Conversely, a methoxyl group has no apparent effect on the relative rates of aromatic ether C-O bond cleavage, while a hydroxyl group dramatically decreases the rate. Proton donors, tert-butyl alcohol and hydroquinone, decreased the rate of diphenyl ether cleavage. The regioselectivity for C-O bond cleavage of esters 8-15, i.e., carbonyl-oxygen versus carboxyl-carbon cleavage, showed selective carbonyl-oxygen bond cleavage.

  14. Selective solid-phase extraction of catecholamines from plasma using nanofibers doped with crown ether and their quantitation by HPLC with electrochemical detection.

    PubMed

    Chen, LiQin; Zhu, XingHua; Shen, Jun; Zhang, WanQi

    2016-07-01

    A simple and convenient preparation method has been developed for polymeric crown ethers containing the dibenzo-18-crown-6 subunit and electrospun composite nanofibers composed of polymeric crown ethers with polystyrene (PCE-PS). Furthermore, this composite nanofiber was used as a sorbent for selective extraction of plasma catecholamines, viz. dopamine (DA), norepinephrine (NE), and epinephrine (E). After the protein deposition of the plasma sample, the supernatant was adjusted to neutral pH with buffer solution. Then, the mixture was loaded and pushed through a column packed with composite nanofiber sorbent, and the analytes were eluted with 50 μL of acetic acid. The effectiveness of the plasma sample cleanup method was verified by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The PCE-PS packed column may prove clinically useful, as it provides a convenient and selective method for evaluation of human plasma catecholamines. Graphical Abstract Scheme showing the selective packed fiber SPE of catecholamines from spiked plasma using nanofibers doped with ploymeric crown ether. PMID:27173391

  15. Cesium and strontium extraction using a mixed extractant solvent including crown ether and calixarene extractants

    DOEpatents

    Meikrantz, David H.; Todd, Terry A.; Riddle, Catherine L.; Law, Jack D.; Peterman, Dean R.; Mincher, Bruce J.; McGrath, Christopher A.; Baker, John D.

    2007-11-06

    A mixed extractant solvent including calix[4]arene-bis-(tert-octylbenzo)-crown-6 ("BOBCalixC6"), 4',4',(5')-di-(t-butyldicyclo-hexano)-18-crown-6 ("DtBu18C6"), and at least one modifier dissolved in a diluent. The mixed extractant solvent may be used to remove cesium and strontium from an acidic solution. The DtBu18C6 may be present from approximately 0.01 M to approximately 0.4M, such as from approximately 0.086 M to approximately 0.108 M. The modifier may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol ("Cs-7SB") and may be present from approximately 0.01M to approximately 0.8M. In one embodiment, the mixed extractant solvent includes approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic hydrocarbon diluent. The mixed extractant solvent may form an organic phase in an extraction system that also includes an aqueous phase. Methods of extracting cesium and strontium as well as strontium alone are also disclosed.

  16. Absolute configuration and predominant conformations of a chiral crown ether-based colorimetric sensor: a vibrational circular dichroism spectroscopy and DFT study of chiral recognition.

    PubMed

    Merten, Christian; Hyun, Myung Ho; Xu, Yunjie

    2013-05-01

    In the present work, we report a comprehensive vibrational circular dichroism (VCD) spectroscopic study of a chiral crown ether which features an axial chiral 3.3'-diphenyl-1,1'-binaphthyl group as chiral moiety. By comparing the experimental and calculated VCD spectra, we show that the presumably very flexible crown ether preferably adopts only one ring conformation. Conformational flexibility is observed in the 2,4-dinitrophenyl-diazophenol group, which was previously introduced for colorimetric detection of primary amines and amino alcohols (Cho et al., Chirality 2011;23:349-353). The VCD spectra of the host-guest complexes with phenyl glycinol (PG) and phenyl alaninol have been studied as well. Based on the spectra calculated, it is shown that the diastereomeric complexes in general can be differentiated using VCD spectroscopy. Furthermore, the experimental VCD spectra of the complexes of the host molecule with PG support the above finding. PMID:23620265

  17. The LArIAT Experiment at Fermilab

    NASA Astrophysics Data System (ADS)

    Nutini, Irene; LArIAT Collaboration

    2016-02-01

    The LArIAT experiment at Fermilab is part of the International Neutrino program recently approved in the US. LArIAT aims to measure the main features of charged particles interactions in argon in the energy range (0.2 - 2.0 GeV) corresponding to the energy spectrum of the same particles when produced in a neutrino-argon interaction (neutrino energies of few GeV) typical of the short- and long-baseline neutrino beams of the Neutrino Program. Data collected from the 1 st Run are being analyzed for both Physics studies and a technical characterization of the scintillation light collection system. Two analysis topics are reported: the method developed for charged pion cross section measurement, based on the specific features of the LArTPC, and the development and test of the LArIAT custom-designed cold front-end electronics for SiPM devices to collect LAr scintillation light.

  18. Two highly stable and selective solid phase microextraction fibers coated with crown ether functionalized ionic liquids by different sol-gel reaction approaches.

    PubMed

    Shu, Jianjun; Xie, Pengfei; Lin, Danni; Chen, Rongfeng; Wang, Jiang; Zhang, Beibei; Liu, Mingming; Liu, Hanlan; Liu, Fan

    2014-01-01

    In this work, two novel crown ether functionalized ionic liquid (FIL)-based solid phase microextraction (SPME) fibers were prepared by sol-gel technology using the synthesized 1-(trimethoxysily)propyl 3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([TMSP(Benzo15C5)HIM][N(SO2CF3)2]) and 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium bis(trifluoromethanesulphonyl)imide ([A(Benzo15C5)HIM][N(SO2CF3)2]) as selective stationary phases. Owing to the introduction of trimethoxysilypropyl to the imidazole cation, the [TMSP(Benzo15C5)HIM][N(SO2CF3)2] could be chemically bonded to the formed sol-gel silica substrate through the hydrolysis and polycondensation reaction. Similarly, the [A(Benzo15C5)HIM][N(SO2CF3)2] was able to participate in the formation of the organic-inorganic copolymer coatings through the free radical crosslinking reaction. These two fibers were determined to have "bubble-like" surface characteristics analogous to a previously prepared [A(Benzo15C5)HIM][PF6]-based fiber. Their thermal stabilities were much higher than that of the [A(Benzo15C5)HIM][PF6]-based coating. They were capable of withstanding temperatures as high as 400°C without evident loss of the crown ether FILs. They also had strong solvent, acid and alkali resistance, good coating preparation reproducibility and high selectivity for medium polar to polar compounds. The high selectivity of these two fibers could be attributed to the strong ion-dipole, hydrogen bonding and π-π interactions provided by the synergetic effect of ILs and benzo-15-crown-5 functionalities. Moreover, the selectivity of these two fibers was rather different although the structures of these two crown ether FILs were very similar. This is maybe because the relative contents of the crown ether FILs chemically bonded to the organic-inorganic copolymer coatings were quite different when prepared by different sol-gel reaction approaches. PMID:24331051

  19. High extraction efficiency fiber coated with calix[4] open-chain crown ether for solid-phase microextraction of polar aromatic and aliphatic compounds.

    PubMed

    Liu, Mingming; Zeng, Zhaorui; Lei, Yun; Li, Haibing

    2005-11-01

    The calix[4] open-chain crown ether, 5,11,17,23-tetra-tert-butyl-25,27-di(2-allyloxyethoxyl)-26,28-dihydroxycalix[4]arene was synthesized and used for preparation of solid-phase microextraction (SPME) fibers of enhanced extraction efficiency. The new SPME coating made from calix[4] open-chain crown ether and hydroxyl-terminated silicone oil was developed with the aid of vinyltriethoxylsilane as bridge using sol-gel method and cross-linking technology. The efficiency of the novel fiber in the extraction of polar aromatic and aliphatic compounds, such as phenols, alcohols, and volatile fatty acids, was also investigated. Due to the introduction of the polar open-chain crown ether in calix[4]arene molecules, the calix[4] open-chain crown ether fiber showed much better selectivity and sensitivity to these polar compounds in comparison with calix[4]arene fiber. It also had superior extraction efficiency when compared to commercial poly(dimethylsiloxane)-divinylbenzene and polyacrylate fibers. Parts per billion to parts per trillion level detection limits were achieved for most of the analytes through SPME in conjunction with GC and flame ionization detector. The linear ranges were two to four orders of magnitude, and the RSD values were below 7% for all analytes. The novel fiber was applied to determine volatile alcohols and fatty acids in wine samples. The volatile-free wine prepared in this work was used to assure similar chemical environment for analytes in both calibration solutions and in real wine samples, thus compensating for possible matrix interferences. The established internal standard method using 4-methyl-2-pentanol as internal standard showed satisfactory accuracy and precision. PMID:16342796

  20. Ammonium-crown ether supramolecular cation-templated assembly of an unprecedented heterobicluster-metal coordination polymer with enhanced NLO properties.

    PubMed

    Zhang, Jinfang; Jia, Ding; Humphrey, Mark G; Meng, Suci; Zaworotko, Michael J; Cifuentes, Marie P; Zhang, Chi

    2016-03-01

    An ammonium-crown ether host-guest supramolecular cation-templated synthetic methodology has been developed to construct a structurally unprecedented heterobicluster-metal coordination polymer (HCM-CP 1) based on tetranuclear clusters [WS4Cu3](+) with different connection environments, pentanuclear clusters [WS4Cu4](2+), and Cu(+) building metal ions. HCM-CP 1 exhibits enhanced NLO properties, which may be ascribed to the incorporation of diverse building cluster components. PMID:26864604

  1. A novel pentiptycene bis(crown ether)-based [2](2)rotaxane whose two DB24C8 rings act as flapping wings of a butterfly.

    PubMed

    Ma, Ying-Xian; Meng, Zheng; Chen, Chuan-Feng

    2014-04-01

    A novel [2](2)rotaxane based on pentiptycene-derived bis(crown ether) can be efficiently synthesized via a "click chemistry" method and the subsequent N-methylation. Due to the different affinities of DB24C8 with the ammonium and triazolium stations, the wing-flapping movement of the DB24C8 "wings" in the [2](2)rotaxane can be easily achieved by acid/base stimulus. PMID:24635015

  2. Discussion on the complexing ability of the uranyl ion with several crown ethers and cryptands in water and in propylene carbonate

    SciTech Connect

    Brighli, M.; Fux, P.; Lagrange, J.; Lagrange, P.

    1985-01-02

    Interactions of the uranyl ion (UO/sub 2//sup 2 +/) with some common crown ethers (12C4, 15C5, 18C6, DB-18C6) and cryptands (22,222) are investigated in aqueous and propylene carbonate (PC) solutions, I = 0.1 M ((TEA)ClO/sub 4/). Stability constants of the complexes formed are determined by potentiometric and spectrophotometric measurements. Discussions on the stability constants of the complexes allow us to postulate whether or not direct uranyl-macrocycle bonds are obtained. In PC solution, uranyl inner-sphere complexes with 18C6, DB-18C6, 22, and 222 are formed with the uranyl ion probably inside or partially enclosed in the ligand cavity. In aqueous media, complexation occurs only with crown ethers by formation of hydrogen bonds between hydrogen of water molecules of the hydrate shell of the uranyl ion and oxygen atoms of the crown ether (UO/sub 2//sup 2 +/ outer-sphere complexes). 31 references, 5 figures, 3 tables.

  3. A Highly K(+) -Selective Fluorescent Probe - Tuning the K(+) -Complex Stability and the K(+) /Na(+) Selectivity by Varying the Lariat-Alkoxy Unit of a Phenylaza[18]crown-6 Ionophore.

    PubMed

    Schwarze, Thomas; Schneider, Radu; Riemer, Janine; Holdt, Hans-Jürgen

    2016-01-01

    A desirable goal is to synthesize easily accessible and highly K(+) /Na(+) -selective fluoroionophores to monitor physiological K(+) levels in vitro and in vivo. Therefore, highly K(+) /Na(+) -selective ionophores have to be developed. Herein, we obtained in a sequence of only four synthetic steps a set of K(+) -responsive fluorescent probes 4, 5 and 6. In a systematic study, we investigated the influence of the alkoxy substitution in ortho position of the aniline moiety in π-conjugated aniline-1,2,3-triazole-coumarin-fluoroionophores 4, 5 and 6 [R=MeO (4), EtO (5) and iPrO (6)] towards the K(+) -complex stability and K(+) /Na(+) selectivity. The highest K(+) -complex stability showed fluoroionophore 4 with a dissociation constant Kd of 19 mm, but the Kd value increases to 31 mm in combined K(+) /Na(+) solutions, indicating a poor K(+) /Na(+) selectivity. By contrast, 6 showed even in the presence of competitive Na(+) ions equal Kd values (Kd (K+) =45 mm and Kd (K+/Na+) =45 mm) and equal K(+) -induced fluorescence enhancement factors (FEFs=2.3). Thus, the fluorescent probe 6 showed an outstanding K(+) /Na(+) selectivity and is a suitable fluorescent tool to measure physiological K(+) levels in the range of 10-80 mm in vitro. Further, the isopropoxy-substituted N-phenylaza[18]crown-6 ionophore in 6 is a highly K(+) -selective building block with a feasible synthetic route. PMID:26473334

  4. Spectroscopy, NMR and DFT studies on molecular recognition of crown ether bridged chiral heterotrinuclear salen Zn(II) complex

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Ruan, Wen-Juan; Chen, Jia-Mei; Zhang, Ying-Hui; Zhu, Zhi-Ang

    2005-12-01

    A barium-containing crown ether bridged chiral heterotrinuclear salen Zn(II) complex BaZn 2L(ClO 4) 2, where L is a folded dinuclear chiral ( R, R)-salen ligand, has been synthesized and characterized by elemental analysis, 1H NMR, UV-vis, IR, circular dichroism (CD) spectra, and mass spectra. As a folded dinuclear chiral host, its recognition with achiral guests (imidazole derivatives), rigid bidentate guest (1,4-diazobicyclo[2,2,2]octane, DABCO) and chiral guests (amino acid methyl esters) was investigated by means of UV-vis spectrophotometric titration, CD spectra. The association constants of D-amino acid methyl esters are found to be higher than those of their L-enantiomer. The sandwich-type binding of BaZn 2L(ClO 4) 2-DABCO supramolecular assembly was specially studied via 1H NMR titration and 1H ROESY. To understand the recognition on molecular level, density functional theory (DFT) calculations on B3LYP/LanL2DZ were performed on the minimal energy conformations of host, guests, and host-guest complexes. The minimal energy conformations were obtained by molecular mechanics (MM) optimization and molecular dynamics (MD) simulation. The results of single point energy, HOMO energy, and charges transfer were analyzed. The results of theoretical calculations are in good agreement with the experimental data.

  5. Effects of 12-Crown-4 ether on the ionic conductivity and electrode kinetics of electrolytes in polyethylene oxide

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.

    1990-01-01

    Results are described of investigations of the electrical and electrochemical properties of thin films of polyethylene oxide (PEO) electrolytes with and without 12-Crown-4 ether (12Cr4) as a function of temperature and in the frequency regime 100 kHz-0.1 Hz. These measurements were made for LiCF3SO3, LiBF4, and LiClO4 salts. At a given temperature, the bulk conductivity, sigma, (S/cm), for a particular salt, depends on the 12Cr4 concentration with sigma reaching a maximum at about 3 mM 12Cr4. Of the three salts studied, the sigma is the highest for PEO/LiBF4 with 3 mM 12Cr4. The ac and dc measurements yield a lower charge transfer resistance for 12Cr4-incorporated samples than for samples without. Plating/stripping of Li occurs at a potential closer to Li(+)/Li for 12Cr4 samples than those without. The conductivities of a thin (about 100 microns) and a thick (400 microns) films are similar.

  6. UV and IR Spectroscopy of Cold H2O(+)-Benzo-Crown Ether Complexes.

    PubMed

    Inokuchi, Yoshiya; Ebata, Takayuki; Rizzo, Thomas R

    2015-11-12

    The H2O(+) radical ion, produced in an electrospray ion source via charge transfer from Eu(3+), is encapsulated in benzo-15-crown-5 (B15C5) or benzo-18-crown-6 (B18C6). We measure UV photodissociation (UVPD) spectra of the (H2O·B15C5)(+) and (H2O·B18C6)(+) complexes in a cold, 22-pole ion trap. These complexes show sharp vibronic bands in the 35 700-37 600 cm(-1) region, similar to the case of neutral B15C5 or B18C6. These results indicate that the positive charge in the complexes is localized on H2O, giving the forms H2O(+)·B15C5 and H2O(+)·B18C6, in spite of the fact that the ionization energy of B15C5 and B18C6 is lower than that of H2O. The formation of the H2O(+) complexes and the suppression of the H3O(+) production through the reaction of H2O(+) and H2O can be attributed to the encapsulation of hydrated Eu(3+) clusters by B15C5 and B18C6. On the contrary, the main fragment ions subsequent to the UV excitation of these complexes are B15C5(+) and B18C6(+) radical ions; the charge transfer occurs from H2O(+) to B15C5 and B18C6 after the UV excitation. The position of the band origin for the H2O(+)·B18C6 complex (36323 cm(-1)) is almost the same as that for Rb(+)·B18C6 (36315 cm(-1)); the strength of the intermolecular interaction of H2O(+) with B18C6 is similar to that of Rb(+). The spectral features of the H2O(+)·B15C5 complex also resemble those of the Rb(+)·B15C5 ion. We measure IR-UV spectra of these complexes in the CH and OH stretching region. Four conformers are found for the H2O(+)·B15C5 complex, but there is one dominant form for the H2O(+)·B18C6 ion. This study demonstrates the production of radical ions by charge transfer from multivalent metal ions, their encapsulation by host molecules, and separate detection of their conformers by cold UV spectroscopy in the gas phase. PMID:26491792

  7. Design, synthesis, characterization, and OFET properties of amphiphilic heteroleptic tris(phthalocyaninato) europium(III) complexes. The effect of crown ether hydrophilic substituents.

    PubMed

    Gao, Yingning; Ma, Pan; Chen, Yanli; Zhang, Ying; Bian, Yongzhong; Li, Xiyou; Jiang, Jianzhuang; Ma, Changqin

    2009-01-01

    Two amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with hydrophilic crown ether heads and hydrophobic octyloxy tails [Pc(mCn)(4)]Eu[Pc(mCn)(4)]Eu[Pc(OC(8)H(17))(8)] [m = 12, n = 4, H(2)Pc(12C4)(4) = 2,3,9,10,16,17,23,24-tetrakis(12-crown-4)phthalocyanine; m = 18, n = 6, H(2)Pc(18C6)(4) = 2,3,9,10,16,17,23,24-tetrakis(18-crown-6)phthalocyanine; H(2)Pc(OC(8)H(17))(8) = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] (1, 2) were designed and prepared from the reaction between homoleptic bis(phthalocyaninato) europium compound [Pc(mCn)(4)]Eu[Pc(mCn)(4)] (m = 12, n = 4; m = 18, n = 6) and metal-free H(2)Pc(OC(8)H(17))(8) in the presence of Eu(acac)(3).H(2)O (Hacac = acetylacetone) in boiling 1,2,4-trichlorobenzene. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods and electrochemically studied. With the help of the Langmuir-Blodgett technique, these typical amphiphilic triple-decker complexes were fabricated into organic field effect transistors (OFET) with top contact configuration on bare SiO(2)/Si substrate, hexamethyldisilazane-treated SiO(2)/Si substrate, and octadecyltrichlorosilane (OTS)-treated SiO(2)/Si substrate, respectively. The device performance is revealed to be dependent on the species of crown ether substituents and substrate surface treatment. OFETs fabricated from the triple decker with 12-crown-4 hydrophilic substituents, 1, allow the hole transfer in the direction parallel to the aromatic phthalocyanine rings. In contrast, the devices of a triple-decker compound containing 18-crown-6 as hydrophilic heads, 2, transfer holes in a direction along the long axis of the assembly composed of face-to-face aggregated triple-decker molecules, revealing the effect of molecular structure, specifically the crown ether substituents on the film structure and OFET functional properties. The carrier mobility for hole as high as 0.33 cm(2) V(-1) s(-1) and current modulation of 7.91 x 10

  8. Design and synthesis of the next generation of crown ethers for waste separations: An interlaboratory comprehensive proposal. 1997 annual progress report

    SciTech Connect

    Moyer, B.A.; Dietz, M.L.; Alexandratos, S.D.; Hay, B.P.

    1997-09-01

    'The purpose of this task is to undertake the design, synthesis, and characterization of the next generation of crown ethers for metal-ion separations applicable to the US Department of Energy''s (DOE''s) environmental needs. The general target problem is the removal of alkali and alkaline-earth metal contaminants from certain environmental and waste streams. Although not a radioactivity hazard, Li{sup +} ions leaching from burial sites containing more than 12 metric tons of lithium compounds contaminate the groundwater at the Oak Ridge Y-12 Plant and have raised noncompliance concerns because of the resultant toxicity to aquatic biota. A more highly visible problem has been treatment of high-level wastes stored in underground tanks at Oak Ridge National Laboratory (ORNL), Idaho National Engineering and Environmental Laboratory, and especially the Hanford Site. The fission products {sup 90}Sr and {sup 137}Cs have been explicitly targeted for removal by the following DOE programs: the Office of Environmental Management, the Office of Science and Technology, the Tank Waste Remediation System, the Tanks Focus Area, and the Efficient Separations and Processing Cross-Cutting Program. These seemingly ubiquitous fission products also appear in soil and groundwater at numerous DOE sites. In addition, radium has recently been named as a target contaminant at the Niagara Falls Storage Site. Unfortunately, the separations technologies needed to address these problems either do not exist or exhibit substantial deficiencies. Established techniques such as solvent extraction and ion exchange certainly have a strong role to play, especially as enhanced with the use of the new highly selective metal-ion hosts such as crown ethers and calixarenes. Recently applied results in the United States, France, Russia, and elsewhere have demonstrated the effective performance of crown ethers under realistic or actual process conditions for the removal of alkali and alkaline-earth metal ions

  9. Retention behavior of common mono- and divalent cations on calcinated silica gel columns in ion chromatography with conductimetric detection and the use of nitric acid, containing crown ethers, as eluents.

    PubMed

    Ohta, Kazutoku; Kusumoto, Keiji; Takao, Yasumasa; Towata, Atsuya; Kawakami, Shoji; Murase, Yoshio; Ohashi, Masayoshi

    2002-05-17

    Ion chromatographic behavior of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) on columns packed with silica gels (Super Micro Bead Silica Gel B-5, SMBSG B-5) calcinated at 200, 400, 600, 800 and 1000 degrees C for 5 h was investigated using nitric acid containing crown ethers [18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane) and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane)] as eluent. When using 0.5 mM HNO3 as the eluent, the calcination had almost no effect on the improvement of peak resolution between these mono- and divalent cations. In contrast, when using 0.5 mM HNO3 containing crown ethers as the eluent, with increasing the calcinating temperature, the amount of crown ethers adsorbed on the corresponding calcinated SMBSG B-5 silica gels columns increased and, as a consequence, peak resolution between these mono- and divalent cations was quite improved. Excellent simultaneous separation of these mono- and divalent cations was achieved on column (150x4.6 mm I.D.) packed with the SMBSG B-5 silica gel calcinated at 1000 degrees C by elution with 0.5 mM HNO3 containing either 1.0 mM 18-crown-6 or 5.0 mM 15-crown-5. PMID:12108647

  10. Ludwig-Soret effect of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol: Temperature, molecular weight, and hydrogen bond effect

    NASA Astrophysics Data System (ADS)

    Maeda, Kousaku; Shinyashiki, Naoki; Yagihara, Shin; Wiegand, Simone; Kita, Rio

    2015-09-01

    The thermal diffusion, also called the Ludwig-Soret effect, of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol is investigated as a function of temperature by thermal diffusion forced Rayleigh scattering. The Soret coefficient, ST, and the thermal diffusion coefficient, DT, show a linear temperature dependence for all studied compounds in the investigated temperature range. The magnitudes and the slopes of ST and DT vary with the chemical structure of the solute molecules. All studied molecules contain ether and/or hydroxyl groups, which can act as acceptor or donor to form hydrogen bonds, respectively. By introducing the number of donor and acceptor sites of each solute molecule, we can express their hydrogen bond capability. ST and DT can be described by an empirical equation depending on the difference of donor minus acceptor sites and the molecular weight of the solute molecule.

  11. Ludwig-Soret effect of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol: Temperature, molecular weight, and hydrogen bond effect.

    PubMed

    Maeda, Kousaku; Shinyashiki, Naoki; Yagihara, Shin; Wiegand, Simone; Kita, Rio

    2015-09-28

    The thermal diffusion, also called the Ludwig-Soret effect, of aqueous solutions of ethylene glycol oligomers, crown ethers, and glycerol is investigated as a function of temperature by thermal diffusion forced Rayleigh scattering. The Soret coefficient, ST, and the thermal diffusion coefficient, DT, show a linear temperature dependence for all studied compounds in the investigated temperature range. The magnitudes and the slopes of ST and DT vary with the chemical structure of the solute molecules. All studied molecules contain ether and/or hydroxyl groups, which can act as acceptor or donor to form hydrogen bonds, respectively. By introducing the number of donor and acceptor sites of each solute molecule, we can express their hydrogen bond capability. ST and DT can be described by an empirical equation depending on the difference of donor minus acceptor sites and the molecular weight of the solute molecule. PMID:26429021

  12. Influence of temperature and crown ether complex formation on the charge partitioning between z and c fragments formed after electron capture by small peptide dications

    NASA Astrophysics Data System (ADS)

    Ehlerding, Anneli; Jensen, Camilla S.; Wyer, Jean A.; Holm, Anne I. S.; Jørgensen, Palle; Kadhane, Umesh; Larsen, Mikkel K.; Panja, Subhasis; Poully, Jean Christophe; Worm, Esben S.; Zettergren, Henning; Hvelplund, Preben; Brøndsted Nielsen, Steen

    2009-04-01

    Electron capture by peptide dications results in N-C[alpha] bond cleavage to give c+ and z or c and z+ fragments. In this work we have investigated how crown ether (18-crown-6 = CE) complex formation and a change in the internal energy affect the charge division between the z and c fragments. Both complex formation and a high temperature have the effect of breaking internal ionic hydrogen bonds. The crown ether complex also lowers the probability of internal proton transfer between the two fragments, and reduces the recombination energy of the charged group it targets. The systems under study were doubly protonated di- and tripeptides, [AK+2H]2+, [AR+2H]2+, [KK+2H]2+ and [GHK+2H]2+ (A = alanine, K = lysine, R = arginine, G = glycine and H = histidine). For crown ether complexes the formation of z+ ions was always preferred over c+ ions. In the case of [GHK+2H]2+, the bare ion dissociated into z2+ + c1 and z1 + c2+ from cleavage of the first and second N-C[alpha] bond, respectively, whereas z1+ fragment ions had higher yield than c2+ for [GHK+2H]2+(CE). The internal energy of the ions was changed by storing them in a 22-pole ion trap in which they were equilibrated to a temperature between -60 and 90 °C in collisions with helium gas. The average internal energy increased by about 0.4 eV from the lowest to the highest temperature for the dipeptides and 0.6 eV for the tripeptide. More fragmentation occurred at the higher temperature, as observed by an increase in the formation of b+ and y+ ions after breakage of the peptide bond of vibrationally hot even-electron cations and from secondary reactions of z+ radical cations within the time window of the experiment. However, the z+ to c+ partitioning was not found to depend significantly on temperature in the measured range. In addition the decay of [GHK+H]+/[GHK+2H]+ and [AK+H]+ formed after electron capture by [GHK+2H]2+ and [AK+2H]2+ was found to occur on a microsecond to millisecond timescale. The data are well

  13. Liquid chromatographic resolution of 3-amino-1,4-benzodiazepin-2-ones on crown ether-based chiral stationary phases.

    PubMed

    Park, Je Young; Jin, Kab Bong; Hyun, Myung Ho

    2012-05-01

    3-Amino-5-phenyl (or 5-methyl)-1,4-benzodiazepin-2-ones, which are chiral precursors of anti-respiratory syncytial virus active agents, were resolved on three different chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid or (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. Among the three CSPs, the CSP that is based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 and containing residual silanol group-protecting n-octyl groups on the silica surface was found to be most effective with the use of 80% ethanol in water containing perchloric acid (10 mM) and ammonium acetate (1.0 mM) as a mobile phase. The separation factors (α) and resolutions (R(S) ) were in the range of 1.90-3.21 and 2.79-5.96, respectively. From the relationship between the analyte structure and the chromatographic resolution behavior, the chiral recognition mechanism on the CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was proposed to be different from that on the CSP based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6. In addition, the chromatographic resolution behavior of the most effective CSP was investigated as a function of the composition of aqueous mobile phase containing organic and acidic modifier and ammonium acetate. PMID:22508444

  14. Direct stereochemical resolution of aspartame stereoisomers and their degradation products by high-performance liquid chromatography on a chiral crown ether based stationary phase.

    PubMed

    Motellier, S; Wainer, I W

    1990-09-21

    The direct stereochemical resolution of the four stereoisomers of aspartame (N-DL-alpha-aspartyl-DL-phenylalanine methyl ester) and their degradation products was achieved on a high-performance liquid chromatography chiral stationary phase based upon a chiral crown ether. The chromatographic conditions included a mobile phase composed of aqueous perchloric acid adjusted to a pH of 2.8 and modified with 1.5% of 2-propanol and a temperature gradient. The active L,L-isomer (sold under the brand name NutraSweet) was measured in a diet cola and coffee sweetened with NutraSweet. Degradation products of NutraSweet were also detected but no racemization of stereochemical contamination was observed. PMID:2150410

  15. The influence of water-ethanol mixture on the thermodynamics of complex formation between 18-crown-6 ether and L-phenylalanine

    NASA Astrophysics Data System (ADS)

    Usacheva, T. R.; Sharnin, V. A.; Chernov, I. V.; Matteoli, E.; Terekhova, I. V.; Kumeev, R. S.

    2012-08-01

    The influence of water-ethanol mixture composition on the complex formation between 18-crown-6 ether and L-phenylalanine was studied by titration calorimetry at Т = 298.15 K. The standard thermodynamic parameters (ΔrGо, ΔrHо, ТΔrSо) of formation of [Phe18C6] molecular complex were calculated from data obtained by means of the microcalorimetric system TAM III (TA Instruments, USA) at X(EtOH) = 0.0/0.6 mol fraction. The stability of [Phe18C6] and the mechanism of complexation in water were investigated using the 1Н and 13С NMR spectroscopy. The increase of EtOH concentration results in an increase of the complex stability and of the exothermicity of complexation.

  16. A Focus on Triazolium as a Multipurpose Molecular Station for pH-Sensitive Interlocked Crown-Ether-Based Molecular Machines

    PubMed Central

    Coutrot, Frédéric

    2015-01-01

    The control of motion of one element with respect to others in an interlocked architecture allows for different co-conformational states of a molecule. This can result in variations of physical or chemical properties. The increase of knowledge in the field of molecular interactions led to the design, the synthesis, and the study of various systems of molecular machinery in a wide range of interlocked architectures. In this field, the discovery of new molecular stations for macrocycles is an attractive way to conceive original molecular machines. In the very recent past, the triazolium moiety proved to interact with crown ethers in interlocked molecules, so that it could be used as an ideal molecular station. It also served as a molecular barrier in order to lock interlaced structures or to compartmentalize interlocked molecular machines. This review describes the recently reported examples of pH-sensitive triazolium-containing molecular machines and their peculiar features. PMID:26491633

  17. A Focus on Triazolium as a Multipurpose Molecular Station for pH-Sensitive Interlocked Crown-Ether-Based Molecular Machines.

    PubMed

    Coutrot, Frédéric

    2015-10-01

    The control of motion of one element with respect to others in an interlocked architecture allows for different co-conformational states of a molecule. This can result in variations of physical or chemical properties. The increase of knowledge in the field of molecular interactions led to the design, the synthesis, and the study of various systems of molecular machinery in a wide range of interlocked architectures. In this field, the discovery of new molecular stations for macrocycles is an attractive way to conceive original molecular machines. In the very recent past, the triazolium moiety proved to interact with crown ethers in interlocked molecules, so that it could be used as an ideal molecular station. It also served as a molecular barrier in order to lock interlaced structures or to compartmentalize interlocked molecular machines. This review describes the recently reported examples of pH-sensitive triazolium-containing molecular machines and their peculiar features. PMID:26491633

  18. Selective transport of Pb2+ and Cd2+ across a phospholipid bilayer by a cyclohexanemonocarboxylic acid-capped 15-crown-5 ether.

    PubMed

    Hamidinia, Shawn A; Steinbaugh, Gregory E; Erdahl, Warren L; Taylor, Richard W; Pfeiffer, Douglas R

    2006-03-01

    A cyclohexanemonocarboxylic acid-capped 15-crown-5 ether was synthesized and found to be effective as an ionophore for Pb2+ and Cd2+, transporting them across a phospholipid bilayer membrane. Transport studies were carried out using 1-palmitoyl-2-oleoyl-sn-glycerophosphatidylcholine (POPC) vesicles containing the chelating indicator 2-([2-bis(carboxymethyl)amino-5-methylphenoxy]methyl)-6-methoxy-8-bis(carboxymethyl)aminoquinoline (Quin-2). Data obtained at pH 7.0 using this system, show that the synthetic ionophore transports divalent cations with the selectivity sequence Pb2+ > Cd2+ > Zn2+ > Mn2+ > Co2+ > Ni2+ > Ca2+ > Sr2+. Selectivity factors, based on the ratio of individual initial cation transport rates, are 280 (Pb2+/Ca2+), 62 (Pb2+/Zn2+), 68 (Cd2+/Ca2+), and 16 (Cd2+/Zn2+). Plots of log initial rate versus logM(n+) or log ionophore concentration suggest that Pb2+ and Cd2+ are transported primarily as a 1:1 cation-ionophore complex, but that complexes with other stoichiometries may also be present. The ionophore transports Pb2+ and Cd2+ by a predominantly electrogenic mechanism, based upon an enhanced rate of transport that is produced by agents which dissipate transmembrane potentials. The rate of Pb2+ transport shows a biphasic pH dependence with the maximum occurring at pH approximately 6.5. The high selectivity for Pb2+ and Cd2+ displayed by the cyclohexanecarboxylic acid-capped 15-crown-5 ether suggests potential applications of this ionophore for the treatment of Pb and Cd intoxication, and removal of these heavy metals from wastewater. PMID:16488017

  19. Structures of potassium calix[4]arene crown ether inclusion complexes and application in polymerization of rac-lactide.

    PubMed

    Li, Yingguo; Zhao, Hongwei; Mao, Xiaoyang; Pan, Xiaobo; Wu, Jincai

    2016-06-21

    Reaction of 1,3-dipropoxy-p-tert-butyl-calix[4]arene (L(1)H2) with KN(SiMe3)2 afforded a one-dimensional (1D) chain complex [K2L(1)]n (1). Upon reaction with 1 equivalent 18-crown-6, complex 1 can convert to complex [K2(18-crown-6)L(1)] (2) which possesses a sandwich structure. Treatment of two calix[4]arene-crown ligands of 1,3-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(2)H2) and 1,2-dihydroxy-p-tert-butyl-calix[4]arene-crown-5 (L(3)H2) with KN(SiMe3)2 gave the dinuclear complex [K2L(2)] (3) and the mononuclear complex [K(THF)L(3)H] (4), respectively. Complexes 1-4 were all characterized by single-crystal X-ray diffraction techniques. The variable temperature (1)H NMR spectrum indicates there is a quick rotation equilibrium of the two phenoxy groups in complex 3. In addition, complexes 1-4 have been tested for the ring-opening polymerization (ROP) of rac-lactide and the results showed that complexes 2 and 3 are highly active for the ROP of rac-lactide. The obtained polymers displayed low dispersity values (Đ) and the molecular weights are close to the calculated ones. Furthermore, complexes 2 and 3 show moderate isoselectivities of Pm = 0.67 and Pm = 0.73, respectively. PMID:27222057

  20. Chiral stationary phase covalently bound with a chiral pseudo-18-crown-6 ether for enantiomer separation of amino compounds using a normal mobile phase.

    PubMed

    Hirose, Keiji; Yongzhu, Jin; Nakamura, Takashi; Nishioka, Ryota; Ueshige, Tetsuro; Tobe, Yoshito

    2005-03-01

    In order to apply the excellent chiral recognition ability of chiral pseudo-18-crown-6 ethers that we developed to chiral separation, we prepared a chiral stationary phase (CSP) by immobilizing a chiral pseudo-18-crown-6-type host on 3-aminopropyl silica gel. A chiral column was prepared by the slurry-packing method in a stainless steel HPLC column. A liquid chromatography system using this CSP combined with the detection by mass spectrometry was used for enantiomer separation of amino compounds. A normal mobile phase can be used on this CSP as opposed to conventional dynamic coating-type CSPs. Enantiomers of 18 common natural amino acids were efficiently separated. The chiral separation observed for amino acid methyl esters, amino alcohols, and lipophilic amines was fair using this HPLC system. In view of the correlation between the enantiomer selectivity observed in chromatography and the complexion in solution, the chiral recognition in host-guest interactions might contribute to this enantiomer separation. PMID:15704196

  1. DFT-B3LYP study of interactions between host biphenyl-1-aza-18-crown-6 ether derivatives and guest Cd(2+): NBO, NEDA, and QTAIM analyses.

    PubMed

    Behjatmanesh-Ardakani, R; Pourroustaei-Ardakani, F; Taghdiri, M; Kotena, Zahrabatoul Mosapour

    2016-07-01

    This report present the results of natural energy decomposition analysis (NEDA), natural bond orbital (NBO), and quantum theory of atoms in molecules (QTAIM) calculations of three derivatives of biphenyl-1-aza-18-crown-6 ether and their 1:1 complexes with Cd(2+). All calculations used the B3LYP density functional theory in combination with the 6-311G and WTBS basis sets for ligands and Cd(2+) ion, respectively. Ligands 1 and 3 have a single 1-aza-18-crown-6, substituent; ligand 2 has two such substituents. The results show that, in the optimized geometries of the complexes, the distance between N and Cd(2+) is greater than the distance between O and Cd(2+). NBO and QTAIM data confirm these results. There was no stabilization energy or bond critical point for N · · · Cd(2+) in NBO or QTAIM, respectively. Data show that the O · · · Cd(2+) interaction is a kind of closed shell interaction. The trend of the calculated stabilization energy was similar to the experimental data. Different contributions of interaction energies for complex formation were analyzed by NEDA, and the results show that the main component of the interactions is accounted for by polarization. PMID:27271162

  2. Extraction of Cesium by a Calix[4]arene-Crown-6 Ether Bearing a Pendant amine Group

    SciTech Connect

    Harmon, Ben; Ensor, Dale; Delmau, Laetitia Helene; Moyer, Bruce A

    2007-01-01

    The goal of this work was to evaluate the role of the amino group of 5-aminomethylcalix[4]arene-[bis-4-(2-ethylhexyl)benzo-crown-6] (AMBEHB) in the extraction of cesium from acidic and basic mixtures of sodium nitrate and other concentrated salts. The extraction of cesium from nitrate media was measured as a function of extractant concentration, nitrate concentration, cesium concentration, and pH over the range 1-13. The initial studies showed a moderate decrease in the extraction of cesium in acidic media, which indicated the binding of cesium by the calixarene-crown was weakened by the protonation of the amine group. The results also indicated that a 1:1:1 Cs-ligand-nitrate complex is formed in the organic phase. To further evaluate AMBEHB, the empirical data were mathematically modeled to determine the formation constants of the complexes formed in the organic phase. The resulting formation constants showed that the attachment of the amine group to the calixarene-crown molecule reduced the binding stability for the cesium ion upon contact with an acidic solution. This supports the hypothesis of charge repulsion as the basis for more efficient stripping of cesium via pH-switching.

  3. Supramolecular Alternating Polymer from Crown Ether and Pillar[5]arene-Based Double Molecular Recognition for Preparation of Hierarchical Materials.

    PubMed

    Li, Hui; Fan, Xiaodong; Qi, Miao; Yang, Zhen; Zhang, Haitao; Tian, Wei

    2016-01-01

    A novel supramolecular alternating polymer is constructed based on double molecular recognition events of benzo-21-crown-7 with a secondary ammonium salt and of pillar[5]arene with a neutral guest. The resulting polymer is utilized to prepare hierarchical materials with different dimensionalities for the first time. These materials included zero-dimensional spherical aggregates, one-dimensional nanofibers, two-dimensional microstructured films, and three-dimensional ordered glue. This development will be helpful for designing and preparing supramolecular hierarchical materials with different dimensionalities. PMID:26555439

  4. Ab initio and density functional theoretical design and screening of model crown ether based ligand (host) for extraction of lithium metal ion (guest): effect of donor and electronic induction.

    PubMed

    Boda, Anil; Ali, Sk Musharaf; Rao, Hanmanth; Ghosh, Sandip K

    2012-08-01

    The structures, energetic and thermodynamic parameters of model crown ethers with different donor, cavity and electron donating/ withdrawing functional group have been determined with ab initio MP2 and density functional theory in gas and solvent phase. The calculated values of binding energy/ enthalpy for lithium ion complexation are marginally higher for hard donor based aza and oxa crown compared to soft donor based thia and phospha crown. The calculated values of binding enthalpy for lithium metal ion with 12C4 at MP2 level of theory is in good agreement with the available experimental result. The binding energy is altered due to the inductive effect imparted by the electron donating/ withdrawing group in crown ether, which is well correlated with the values of electron transfer. The role of entropy for extraction of hydrated lithium metal ion by different donor and functional group based ligand has been demonstrated. The HOMO-LUMO gap is decreased and dipole moment of the ligand is increased from gas phase to organic phase because of the dielectric constant of the solvent. The gas phase binding energy is reduced in solvent phase as the solvent molecules weaken the metal-ligand binding. The theoretical values of extraction energy for LiCl salt from aqueous solution in different organic solvent is validated by the experimental trend. The study presented here should contribute to the design of model host ligand and screening of solvent for metal ion recognition and thus can contribute in planning the experiments. PMID:22318713

  5. A novel fluorescent probe for Cr3 + based on rhodamine-crown ether conjugate and its application to drinking water examination and bioimaging

    NASA Astrophysics Data System (ADS)

    Diao, Quanping; Ma, Pinyi; Lv, Linlin; Li, Tiechun; Wang, Xinghua; Song, Daqian

    2016-03-01

    A trivalent chromium (Cr3 +) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine-crown ether conjugate. This probe displayed a favorable selectivity for Cr3 + over a range of other common metal ions in DMF/H2O (3:7, v/v; PBS buffer 50 mmol L- 1; pH = 6.8) solution, leading to prominent fluorescence "OFF-ON" switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L- 1 (S/N = 3). The binding ratio of RhC-Cr3 + complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr3 + in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L- 1, and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr3 + in living cells with a fluorescence enhancement signal.

  6. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodong; Lei, Ming; Zhou, Yi; Song, Bo; Li, Yongfang

    2015-08-01

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH3NH3PbI3-XClX. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (Jsc). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  7. ACE applied to the quantitative characterization of benzo-18-crown-6-ether binding with alkali metal ions in a methanol-water solvent system.

    PubMed

    Ehala, Sille; Makrlík, Emanuel; Toman, Petr; Kasicka, Václav

    2010-01-01

    ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo-18-crown-6-ether (B18C6) and several alkali metal ions, Li(+), Na(+), K(+), Rb(+) and Cs(+), in a mixed binary solvent system, methanol-water (50/50 v/v). The apparent binding (stability) constants (K(b)) of B18C6-alkali metal ion complexes in the hydro-organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25 degrees C, and the constant ionic strength, 10 mM. In the 50% v/v methanol-water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K(b)=2.89+/-0.17), the weakest complex with cesium ion (log K(b)=2.04+/-0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol-water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water. PMID:20108263

  8. A novel fluorescent probe for Cr(3+) based on rhodamine-crown ether conjugate and its application to drinking water examination and bioimaging.

    PubMed

    Diao, Quanping; Ma, Pinyi; Lv, Linlin; Li, Tiechun; Wang, Xinghua; Song, Daqian

    2016-03-01

    A trivalent chromium (Cr(3+)) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine-crown ether conjugate. This probe displayed a favorable selectivity for Cr(3+) over a range of other common metal ions in DMF/H2O (3:7, v/v; PBS buffer 50 mmol L(-1); pH=6.8) solution, leading to prominent fluorescence "OFF-ON" switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L(-1) (S/N=3). The binding ratio of RhC-Cr(3+) complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr(3+) in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L(-1), and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr(3+) in living cells with a fluorescence enhancement signal. PMID:26641281

  9. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    SciTech Connect

    Liu, Xiaodong; Zhou, Yi E-mail: songbo@suda.edu.cn Song, Bo E-mail: songbo@suda.edu.cn; Lei, Ming; Li, Yongfang E-mail: songbo@suda.edu.cn

    2015-08-10

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH{sub 3}NH{sub 3}PbI{sub 3−X}Cl{sub X}. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (J{sub sc}). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  10. Comparison of polarimetry and crown ether-based HPLC chiral stationary phase method to determine (L)-amino acid optical purity.

    PubMed

    Lee, Mee Sung; Khan, F Nawaz; Shin, Sung Chul; Jeong, Euh Duck; Kim, Hae Gyeong; Kim, Mi Jin; Cho, Yoon Jae; Cha, Jae-Young; Hyun, Myung Ho; Jin, Jong Sung

    2012-11-15

    Although various pharmacopoeias provide titration methods to assay (L)-amino acid content, none of these methods distinguish between (L)- and (D)-amino acids and do not consider the presence of enantiomeric impurities. Consequently, these methods are limited in scope to describe the relationship between content and specific rotation, [α]. In this study, the US Pharmacopoeia method was compared with the crown ether-based high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) method to determine (L)-amino acid content and specific rotation. The (L)-amino acid content specified by the US Pharmacopoeia method was not consistent with the specific rotation in the presence of enantiomeric impurities, whereas the HPLC-CSP method was very effective for determining the (L)-amino acid content and the optical purity. The other advantage is that the HPLC-CSP method requires amino acid samples of quite low concentration (as low as 1 μg/mL), whereas the pharmacopoeia method requires higher concentrations (20-110 mg/mL). PMID:22868097

  11. Muon Charge Sign Determination in LArIAT

    NASA Astrophysics Data System (ADS)

    Soubasis, Brandon; LArIAT Collaboration

    2016-03-01

    LArTPC In A Test beam experiment (LArIAT) at the Fermilab aims to calibrate and characterize liquid argon time projection chambers with a beam of charges particles. Liquid Argon Time Projection Chamber (LArTPC) are ideal neutrino detectors which has full 3D-imaging and particle Identification (PID) capability. Processes for which the μ undergoes capture vs. decay in LArIAT TPC for sign-determination (without magnetic field) is one area of studies we are currently interested in. Systematic study of the processes following μ- capture in argon have never been performed and LArTPC sign-determination capability has never been explored. Statistical analysis on topological criteria can be used to determine the sign of a particle's charge (without magnetic field). LArIAT test beam with selectable polarity will provide data for direct measurement of the sign separation efficiency (and purity) for muons.

  12. Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation.

    PubMed

    Tabacchi, Gloria; Silvi, Serena; Venturi, Margherita; Credi, Alberto; Fois, Ettore

    2016-06-17

    Pseudorotaxanes formed by a dibenzo[24]crown-8 ring (R) and a dialkylammonium axle bearing either two E- or two Z-azobenzene units (EE-A or ZZ-A) revealed useful for the construction of light-powered molecular machines and motors, as they provide the opportunity of photocontrolling self-assembly/disassembly processes. The potential energies profiles for the dethreading of these complexes have been investigated by adopting a combination of first-principles molecular dynamics, metadynamics and quantum-chemical geometry optimization approaches. While the dethreading of the EE-A axle is associated with a monotonic energy increase, for that of the ZZ-A axle a transition state and an intermediate structure, in which the components are still threaded together, are found. The rate determining step for the dethreading of the ZZ axle has a higher energy barrier than that of the EE axle, in agreement with the experimental kinetic data. Moreover, the results suggest that the elliptic shape of the ring cavity is important for discriminating between the E and Z terminal azobenzene during dethreading. PMID:26918775

  13. Liquid chromatographic resolution of amino acid esters of acyclovir including racemic valacyclovir on crown ether-based chiral stationary phases.

    PubMed

    Ahn, Seong Ae; Hyun, Myung Ho

    2015-03-01

    Valacyclovir, a potential prodrug for the treatment of patients with herpes simplex and herpes zoster, and its analogs were resolved on two chiral stationary phases (CSPs) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel. In order to find out an appropriate mobile phase condition, various mobile phases consisting of various organic modifiers in water containing various acidic modifiers were applied to the resolution of valacyclovir and its analogs. When 30% acetonitrile in water containing any of 0.05 M, 0.10 M, or 0.15 M perchloric acid was used as a mobile phase, valacyclovir and its analogs were resolved quite well on the two CSPs with the separation factors (α) in the range of 2.49 ~ 6.35 and resolutions (RS ) in the range of 2.95 ~ 12.21. Between the two CSPs, the CSP containing residual silanol protecting n-octyl groups on the silica surface was found to be better than the CSP containing residual silanol groups. PMID:25626672

  14. Alkaline-Side Extraction of Cesium from Savannah River Tank Waste Using a Calixarene-Crown Ether Extractant

    SciTech Connect

    Bonnesen, P.V.; Delmau, L.H.; Haverlock, T.J.; Moyer, B.A.

    1998-12-01

    Results are presented supporting the viability of the alkaline-side CSEX process as a potential replacement for the In-Tank Precipitation process for removal of cesium from aqueous high-level waste (HLW) at the Savannah River Site (SRS). Under funding from the USDOE Efficient Separations and Crosscutting program, a flowsheet was suggested in early June of 1998, and in the following four months, this flowsheet underwent extensive testing, both in batch tests at ORNL and ANL and in two centrifugal-contactor tests at ANL. To carry out these tests, the initial ESP funding was augmented by direct funds from Westinghouse Savannah River Corporation. The flowsheet employed a solvent containing a calixarene-crown hybrid compound called BoBCalixC6 that was invented at ORNL and can now be obtained commercially for government use from IBC Advanced Technologies. This special extractant is so powerful and selective that it can be used at only 0.01 M, compensating for its expense, but a modifier is required for use in an aliphatic diluent, primarily to increase the cesium distribution ratio D{sub Cs} in extraction. The modifier selected is a relatively economical fluorinated alcohol called Cs3, invented at ORNL and so far available. only from ORNL. For the flowsheet, the modifier is used at 0.2 M in the branched aliphatic kerosene Isopar{reg_sign} L. Testing at ORNL and ANL involved simulants of the SRS HLW. After extraction of the Cs from the waste simulant, the solvent is scrubbed with 0.05 M HNO{sub 3} and stripped with a solution comprised of 0.0005 M HNO{sub 3} and 0.0001 M CsNO{sub 3}. The selection of these conditions is justified in this report, both on the basis of experimental data and underlying theory.

  15. Synergistic adsorption of heavy metal ions and organic pollutants by supramolecular polysaccharide composite materials from cellulose, chitosan and crown ether

    PubMed Central

    Mututuvari, Tamutsiwa M.; Tran, Chieu D.

    2013-01-01

    We have developed a simple one-step method to synthesize novel supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS) and benzo-15-crown 5 (B15C5). Butylmethylimidazolium chloride [BMIm+Cl−], an ionic liquid (IL), was used as a sole solvent for dissolution and preparation of the composites. Since majority of [BMIm+Cl−] used was recovered for reuse, the method is recyclable. The [CEL/CS + B15C5] composites obtained retain properties of their components, namely superior mechanical strength (from CEL), excellent adsorption capability for heavy metal ions and organic pollutants (from B15C5 and CS). More importantly, the [CEL/CS + B15C5] composites exhibit truly supramolecular properties. By itself CS, CEL and B15C5 can effectively adsorb Cd2+, Zn2+ and 2,4,5-trichlorophenol. However, adsorption capability of the composite was substantially and synergistically enhanced by adding B15C5 to either CEL and/or CS. That is, the adsorption capacity (qe values) for Cd2+ and Zn2+ by [CS + B15C5], [CEL + B15C5] and [CEL + CS + B15C5] composites are much higher than combined qe values of individual CS, CEL and B15C5 composites. It seems that B15C5 synergistically interact with CS (or CEL) to form more stable complexes with Cd2+ (or Zn2+), and as a consequence, the [CS + B15C5] (or the [CEL + B15C5]) composite can adsorb relatively larger amount Cd2+ (or Zn2+). Moreover, the pollutants adsorbed on the composites can be quantitatively desorbed to enable the [CS + CEL + B15C5] composites to be reused with similar adsorption efficiency. PMID:24333678

  16. Supramolecular Dimerization and [2 + 2] Photocycloaddition Reactions of Crown Ether Styryl Dyes Containing a Tethered Ammonium Group: Structure-Property Relationships.

    PubMed

    Ushakov, Evgeny N; Vedernikov, Artem I; Lobova, Natalia A; Dmitrieva, Svetlana N; Kuz'mina, Lyudmila G; Moiseeva, Anna A; Howard, Judith A K; Alfimov, Michael V; Gromov, Sergey P

    2015-12-31

    Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from ≤10(-4) to 0.38. The latter value is unusually high for olefins in solution. PMID:26650887

  17. New NO donor ligands and complexes containing furfuryl or crown ether moiety: Syntheses, crystal structures and tautomerism in ortho-hydroxy substituted compounds as studied by UV-vis spectrophotometry

    NASA Astrophysics Data System (ADS)

    Şahin, Duygu; Koçoğlu, Serhat; Şener, Öznur; Şenol, Cemal; Dal, Hakan; Hökelek, Tuncer; Hayvalı, Zeliha

    2015-12-01

    NO donor ligands were prepared by the condensation of methoxy substituted salicylaldehyde with 5-methylfurfurylamine (1 and 2) and 4‧-aminobenzo-15-crown 5 (3-5). New crown ether ligands of Schiff base type (3-5) containing recognition sites for alkali metal and transition guest cations. Ni(II) complexes (1a-5a) have been synthesized with bidentate NO donor Schiff base ligands (1-5) with Ni(CH3COO)2.·4H2O. Monotopic crystalline 1:1 (Na+:ligand) sodium complexes (3b-5b) of the crown ether ligands were also prepared. Schiff bases (1-5) and complexes (1a-5a, 3b-5b) were characterized by elemental analyses, FT-IR, 1H-, 13C-NMR and mass spectroscopies. The crystal structures of 1, 1a and 2 were verified by X-ray diffraction analysis. The tautomeric equilibria (phenol-imine, O-H⋯N and keto-amine, O⋯H-N forms) have been systematically studied by using UV-vis spectrophotometry for the o-hydroxy substituted compounds (1-5). The UV-visible spectra of these ligands (1-5) were recorded and commented in polar, non-polar, acidic and basic media.

  18. Optical and electrochemical properties of heteroditopic ion receptors derived from crown ether-based calix[4]arene with amido-anthraquinone pendants.

    PubMed

    Chailap, Benjamat; Tuntulani, Thawatchai

    2012-05-14

    Two heteroditopic receptors based on a calix[4]arene crown ether containing amidoanthraquinone pendants in cone and 1,3-alternate conformations (1 and 2, respectively) were synthesized. Photophysical properties of 1 and 2 were studied by UV-vis and fluorescence spectrophotometry in dried CH(3)CN. Both 1 and 2 showed the highest sensitivity towards F(-) through the appearance of a new charge transfer band at 500 nm and the enhancement of the emission spectra at λ(em) = 542 nm and 528 nm respectively. Interestingly, in the presence of K(+), the fluorescence intensity of 1 at 542 nm increased around 2 fold compared to that in the absence of K(+) upon addition of F(-), while this phenomenon was not observed in the case of receptor 2. Cyclic voltammograms of receptors 1 and 2 showed two consecutive one-electron reversible waves in 40% v/v CH(3)CN in CH(2)Cl(2), corresponding to two single-electron reductions to give mono- and dianions species at E(1/2)I = -1.21 V and E(1/2)II = -1.66 V as well as E(1/2)I = -1.25 V and E(1/2)II = -1.71 V, respectively. H(2)PO(4)(-) gave remarkable potential shifts (ca. 200 mV) of the second reduction waves (E(1/2)II) of both free 1 and 2. In the presence of K(+), only receptor 1 gave remarkable potential shifts in its redox wave II upon adding F(-) and AcO(-). Therefore, receptors 1 and 2 exhibited dual sensing modes by fluorescence spectrophotometry and cyclic voltammetry. The topology of ligands also played an important role in cooperative binding properties of heteroditopic receptor 1 possessing a closer distance between a cation and an anion binding. On the other hand, the two ion binding sites of receptor 2 were separated by a longer distance and did not support the cooperative binding. This resulted in the abstraction of K(+) from receptor 2 upon addition of anions. PMID:22469902

  19. Cowboy Fluid Mechanics: Lariat Modes of a Viscous Rope

    NASA Astrophysics Data System (ADS)

    Ribe, Neil; Badr, Sarah; Morris, Stephen

    2009-11-01

    A thin filament of viscous fluid falling onto a surface winds itself into a helical coil whose angular frequency of rotation φ depends on the fall height H, the flow rate, and the fluid properties. We have studied a novel variant of this phenomenon in which the nozzle ejecting the fluid rotates about a vertical axis at a constant rate φ. In laboratory experiments using viscous corn syrup, we observe that the filament coils in the normal way when φφ. However, when φ φ and H is sufficiently large, a new ``lariat'' mode appears in which the filament is thrown outward in the form of a spiral of large diameter (up to tens of cm) rotating at a rate 0.9φ. The transition between the coiling and lariat modes is hysteretic with respect to variations in φ. In addition to the laboratory experiments, we will also present preliminary results of numerical calculations of the lariat mode based on a ``slender body'' model for a viscous filament with inertia.

  20. Scintillation light detection system in LArIAT

    NASA Astrophysics Data System (ADS)

    Kryczynski, P.

    2016-02-01

    The LArIAT experiment is currently taking data at Fermilab using a Liquid Argon TPC, with the aim of studying particle interactions and characterizing detector response for neutrino detectors using argon. In parallel, it serves as a test-bench to develop and evaluate the performance of the simulation, reconstruction, and analysis software used in LAr neutrino experiments. LArIAT also takes advantage of the scintillating capabilities of liquid argon and will evaluate the feasibility of using the light signal to determine calorimetric information and particle identification. To test this possibility, a scintillation light detection system consisting of high Quantum Efficiency (QE) PMT and Silicon Photomultiplier (SiPM) devices is installed in the cryostat, viewing the interior of the TPC. Light collection efficiency is maximized by means of lining the walls with reflector foils covered by a wavelength shifter layer. Collecting the light reflected at the boundaries of the active volume greatly improves also the uniformity of the light yield. Presented here are initial results of the LArIAT light detection system calibration together with the preliminary results of the dedicated simulation and its application in future LAr TPC experiments

  1. Crown ether-modified electrodes for the simultaneous stripping voltammetric determination of Cd(II), Pb(II) and Cu(II).

    PubMed

    Serrano, Núria; González-Calabuig, Andreu; del Valle, Manel

    2015-06-01

    This work describes the immobilization of 4-carboxybenzo-18-crown-6 (CB-18-crown-6) and 4-carboxybenzo-15-crown-5 (CB-15-crown-5) assisted by lysine on aryl diazonium salt monolayers anchored to the surface of graphite-epoxy composite electrodes (GEC), and their use for the simultaneous determination of Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry (DPASV). These modified electrodes display a good repeatability and reproducibility with detection and quantification limits at levels of µg L(-1) (ppb), confirming their suitability for the determination of Cd(II), Pb(II) and Cu(II) ions in environmental samples. The overlapped nature of the multimetal stripping measurements was resolved by employing the two-sensor array CB-15-crown-5-GEC and CB-18-crown-6-GEC, since the metal complex selectivity exhibited by the considered ligands could add some discrimination power. For the processing of the voltammograms, Discrete Wavelet Transform and Causal Index were selected as preprocessing tools for data compression coupled with an artificial neural network for the modeling of the obtained responses, allowing the resolution of mixtures of these metals with good prediction of their concentrations (correlation with expected values for an external test subset better than 0.942). PMID:25863381

  2. Studies of a pyridino-crown ether-based chiral stationary phase on the enantioseparation of biogenic chiral aralkylamines and α-amino acid esters by high-performance liquid chromatography.

    PubMed

    Lévai, Sándor; Németh, Tamás; Fődi, Tamás; Kupai, József; Tóth, Tünde; Huszthy, Péter; Balogh, György Tibor

    2015-11-10

    This paper reports the enantioseparation ability of a pyridino-18-crown-6 ether-based chiral stationary phase [(S,S)-CSP-1]. The enantiomeric discrimination of chiral stationary phase (S,S)-CSP-1 was evaluated by HPLC using the mixtures of enantiomers of various protonated primary aralkylamines [1-phenylethylamine hydrogen perchlorate (PEA), 2,3-dihydro-1H-inden-1-amine (1-aminoindan), 2,2'-(1,2-diaminoethane-1,2-diyl) diphenol (HPEN)] and perchlorate salts of α-amino acid esters [alanine benzyl ester (Ala-OBn), phenylalanine benzyl ester (Phe-OBn), phenylalanine methyl ester (Phe-OMe), phenylglycine methyl ester (PhGly-OMe), glutamic acid dibenzyl ester (Glu-diOBn), and valine benzyl ester (Val-OBn)]. The best enantioseparation was achieved in the case of PEA. The high enantioselectivity was rationalized by the strong π-π interaction of the extended π system of the aryl-substituted pyridine unit. PMID:26218505

  3. Widespread alternative and aberrant splicing revealed by lariat sequencing

    PubMed Central

    Stepankiw, Nicholas; Raghavan, Madhura; Fogarty, Elizabeth A.; Grimson, Andrew; Pleiss, Jeffrey A.

    2015-01-01

    Alternative splicing is an important and ancient feature of eukaryotic gene structure, the existence of which has likely facilitated eukaryotic proteome expansions. Here, we have used intron lariat sequencing to generate a comprehensive profile of splicing events in Schizosaccharomyces pombe, amongst the simplest organisms that possess mammalian-like splice site degeneracy. We reveal an unprecedented level of alternative splicing, including alternative splice site selection for over half of all annotated introns, hundreds of novel exon-skipping events, and thousands of novel introns. Moreover, the frequency of these events is far higher than previous estimates, with alternative splice sites on average activated at ∼3% the rate of canonical sites. Although a subset of alternative sites are conserved in related species, implying functional potential, the majority are not detectably conserved. Interestingly, the rate of aberrant splicing is inversely related to expression level, with lowly expressed genes more prone to erroneous splicing. Although we validate many events with RNAseq, the proportion of alternative splicing discovered with lariat sequencing is far greater, a difference we attribute to preferential decay of aberrantly spliced transcripts. Together, these data suggest the spliceosome possesses far lower fidelity than previously appreciated, highlighting the potential contributions of alternative splicing in generating novel gene structures. PMID:26261211

  4. Absorption and biotransformation of polybrominated diphenyl ethers DE-71 and DE-79 in chicken (Gallus gallus), mallard (Anas platyrhynchos), American kestrel (Falco sparverius) and black-crowned night-heron (Nycticorax nycticorax) eggs

    USGS Publications Warehouse

    McKernan, Moira A.; Rattner, Barnett A.; Hatfield, Jeff S.; Hale, Robert C.; Ottinger, Mary Ann

    2010-01-01

    We recently reported that air cell administration of penta-brominated diphenyl ether (penta-BDE; DE-71) evokes biochemical and immunologic effects in chicken (Gallus gallus) embryos at very low doses, and impairs pipping (i.e., stage immediately prior to hatching) and hatching success at 1.8 ug g-1 egg (actual dose absorbed) in American kestrels (Falco sparverius). I n the present study, absorption of polybrominated diphenyl ether (PBDE) congeners was measured following air cell administration of a penta-BDE mixture (11.1 ug DE-71 g-1 egg) or an octa-brominated diphenyl ether mixture (octa-BDE; DE-79; 15.4 ug DE-79 g-1 egg). Uptake of PBDE congeners was measured at 24 h post-injection, midway through incubation, and at pipping in chicken, mallard (Anas platyrhynchos), and American kestrel egg contents, and at the end of incubation in black-crowned night-heron (Nycticorax nycticorax) egg contents. Absorption of penta-BDE and octa-BDE from the air cell into egg contents occurred throughout incubation; at pipping, up to 29.6% of penta-BDE was absorbed, but only 1.40-6.48% of octa-BDE was absorbed. Higher brominated congeners appeared to be absorbed more slowly than lower brominated congeners, and uptake rate was inversely proportional to the log Kow of predominant BDE congeners. Six congeners or co-eluting pairs of congeners were detected in penta-BDE-treated eggs that were not found in the dosing solution suggesting debromination in the developing embryo, extraembryonic membranes, and possibly even in the air cell membrane. This study demonstrates the importance of determining the fraction of xenobiotic absorbed into the egg following air cell administration for estimation of the lowest-observed-effect level.

  5. Supramolecular side-chain poly[2]pseudorotaxanes formed by orthogonal coordination-driven self-assembly and crown-ether-based host-guest interactions.

    PubMed

    Xing, Hao; Wei, Peifa; Yan, Xuzhou

    2014-06-01

    The themes of coordination-driven self-assembly, host-guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes. Specifically, a bis(p-phenylene)-34-crown-10 derivative 1 bearing two pyridyl groups polymerizes into a side-chain poly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4 in the presence of paraquat. Interestingly, by adding a competitive guest 3, the poly[2]pseudorotaxane can realize a conversion in one pot. PMID:24819441

  6. The effect of ring size variation on the structure and stability of lanthanide(III) complexes with crown ethers containing picolinate pendants.

    PubMed

    Roca-Sabio, Adrián; Mato-Iglesias, Marta; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos

    2011-01-14

    The coordination properties of the macrocyclic receptor N,N'-bis[(6-carboxy-2-pyridyl)methylene]-1,10-diaza-15-crown-5 (H(2)bp15c5) towards the lanthanide ions are reported. Thermodynamic stability constants were determined by pH-potentiometric titration at 25 °C in 0.1 M KCl. A smooth decrease in complex stability is observed upon decreasing the ionic radius of the Ln(III) ion from La [log K(LaL) = 12.52(2)] to Lu [log K(LuL) = 10.03(6)]. Luminescence lifetime measurements recorded on solutions of the Eu(III) and Tb(III) complexes confirm the absence of inner-sphere water molecules in these complexes. (1)H and (13)C NMR spectra of the complexes formed with the diamagnetic La(III) metal ion were obtained in D(2)O solution and assigned with the aid of HSQC and HMBC 2D heteronuclear experiments, as well as standard 2D homonuclear COSY and NOESY spectra. The (1)H NMR spectra of the paramagnetic Ce(III), Eu(III) and Yb(III) complex suggest nonadentate binding of the ligand to the metal ion. The syn conformation of the ligand in [Ln(bp15c5)](+) complexes implies the occurrence of two helicities, one associated with the layout of the picolinate pendant arms (absolute configuration Δ or Λ), and the other to the five five-membered chelate rings formed by the binding of the crown moiety (absolute configuration δ or λ). A detailed conformational analysis performed with the aid of DFT calculations (B3LYP model) indicates that the complexes adopt a Λ(λδ)(δδλ) [or Δ(δλ)(λλδ)] conformation in aqueous solution. Our calculations show that the interaction between the Ln(III) ion and several donor atoms of the crown moiety is weakened as the ionic radius of the metal ion decreases, in line with the decrease of complex stability observed on proceeding to the right across the lanthanide series. PMID:21116555

  7. Crown Gall

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown gall disease occurs on diverse dicotyledonous and gymnospermous plant species worldwide. Reports of crown gall on hop date back to at least 1929, and the disease has been reported from most countries where hop is or has been grown commercially. The epidemiology of the causal bacterium, Agrob...

  8. Crown gall

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown gall is uncommon in alfalfa. The disease has been reported from alfalfa stands in the Imperial Valley of California, but rare infected plants can be found occasionally in other parts of the U.S. Symptoms: The galls or tumor-like overgrowths form on the crown branches at or slightly below t...

  9. A homolog of lariat-debranching enzyme modulates turnover of branched RNA

    PubMed Central

    Garrey, Stephen M.; Katolik, Adam; Prekeris, Mantas; Li, Xueni; York, Kerri; Bernards, Sarah; Fields, Stanley; Zhao, Rui; Damha, Masad J.; Hesselberth, Jay R.

    2014-01-01

    Turnover of the branched RNA intermediates and products of pre-mRNA splicing is mediated by the lariat-debranching enzyme Dbr1. We characterized a homolog of Dbr1 from Saccharomyces cerevisiae, Drn1/Ygr093w, that has a pseudo-metallophosphodiesterase domain with primary sequence homology to Dbr1 but lacks essential active site residues found in Dbr1. Whereas loss of Dbr1 results in lariat-introns failing broadly to turnover, loss of Drn1 causes low levels of lariat-intron accumulation. Conserved residues in the Drn1 C-terminal CwfJ domains, which are not present in Dbr1, are required for efficient intron turnover. Drn1 interacts with Dbr1, components of the Nineteen Complex, U2 snRNA, branched intermediates, and products of splicing. Drn1 enhances debranching catalyzed by Dbr1 in vitro, but does so without significantly improving the affinity of Dbr1 for branched RNA. Splicing carried out in in vitro extracts in the absence of Drn1 results in an accumulation of branched splicing intermediates and products released from the spliceosome, likely due to less active debranching, as well as the promiscuous release of cleaved 5′-exon. Drn1 enhances Dbr1-mediated turnover of lariat-intermediates and lariat-intron products, indicating that branched RNA turnover is regulated at multiple steps during splicing. PMID:24919400

  10. Crown wart

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown wart has been found widely distributed in Australia, New Zealand, and European countries. It has been recorded sporadically in India (Punjab), South Africa, South America (Ecuador, Chile, Peru), Panama, Mexico, and Canada (British Columbia). In the United States, it has been found more frequ...

  11. Dental crowns

    MedlinePlus

    ... cover a tooth Replace a misshapen tooth or dental implant Correct a misaligned tooth Talk to your dentist ... the tooth pulled and replaced with a tooth implant. Your crown could chip or crack: If you grind your teeth or clench your jaw, you may need to ...

  12. Alkali-metal ion coordination in uranyl(VI) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li(+)-, Na(+)- and K(+)-uranyl(VI)-peroxide-carbonate systems.

    PubMed

    Zanonato, Pier Luigi; Szabó, Zoltán; Vallet, Valerie; Di Bernardo, Plinio; Grenthe, Ingmar

    2015-10-01

    The constitution and equilibrium constants of ternary uranyl(vi) peroxide carbonate complexes [(UO2)p(O2)q(CO3)r](2(p-q-r)) have been determined at 0 °C in 0.50 M MNO3, M = Li, K, and TMA (tetramethyl ammonium), ionic media using potentiometric and spectrophotometric data; (17)O NMR data were used to determine the number of complexes present. The formation of cyclic oligomers, "[(UO2)(O2)(CO3)]n", n = 4, 5, 6, with different stoichiometries depending on the ionic medium used, suggests that Li(+), Na(+), K(+) and TMA ions act as templates for the formation of uranyl peroxide rings where the uranyl-units are linked by μ-η(2)-η(2) bridged peroxide-ions. The templating effect is due to the coordination of the M(+)-ions to the uranyl oxygen atoms, where the coordination of Li(+) results in the formation of Li[(UO2)(O2)(CO3)]4(7-), Na(+) and K(+) in the formation of Na/K[(UO2)(O2)(CO3)]5(9-) complexes, while the large tetramethyl ammonium ion promotes the formation of two oligomers, TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-). The NMR spectra demonstrate that the coordination of Na(+) in the five- and six-membered oligomers is significantly stronger than that of TMA(+); these observations suggest that the templating effect is similar to the one observed in the synthesis of crown-ethers. The NMR experiments also demonstrate that the exchange between TMA[(UO2)(O2)(CO3)]5(9-) and TMA[(UO2)(O2)(CO3)]6(11-) is slow on the (17)O chemical shift time-scale, while the exchange between TMA[(UO2)(O2)(CO3)]6(11-) and Na[(UO2)(O2)(CO3)]6(11-) is fast. There was no indication of the presence of large clusters of the type identified by Burns and Nyman (M. Nyman and P. C. Burns, Chem. Soc. Rev., 2012, 41, 7314-7367) and possible reasons for this and the implications for the synthesis of large clusters are briefly discussed. PMID:26331776

  13. Speciation of a group I intron into a lariat capping ribozyme

    PubMed Central

    Meyer, Mélanie; Nielsen, Henrik; Oliéric, Vincent; Roblin, Pierre; Johansen, Steinar D.; Westhof, Eric; Masquida, Benoît

    2014-01-01

    The lariat-capping (LC) ribozyme is a natural ribozyme isolated from eukaryotic microorganisms. Despite apparent structural similarity to group I introns, the LC ribozyme catalyzes cleavage by a 2′,5′ branching reaction, leaving the 3′ product with a 3-nt lariat cap that functionally substitutes for a conventional mRNA cap in the downstream pre-mRNA encoding a homing endonuclease. We describe the crystal structures of the precleavage and postcleavage LC ribozymes, which suggest that structural features inherited from group I ribozymes have undergone speciation due to profound changes in molecular selection pressure, ultimately giving rise to an original branching ribozyme family. The structures elucidate the role of key elements that regulate the activity of the LC ribozyme by conformational switching and suggest a mechanism by which the signal for branching is transmitted to the catalytic core. The structures also show how conserved interactions twist residues, forming the lariat to join chemical groups involved in branching. PMID:24821772

  14. Application of lariat lock catch knot suture in the achilles tendon rupture

    PubMed Central

    Wang, Baocang; Feng, Xiaona; Yan, Ming; Wang, Hui; Li, Yong

    2015-01-01

    The aim of this study was to summarize the clinical experience of repairing the Achilles tendon rupture by lariat lock catch knot suture. Between January 2011 and February, 2014, 32 cases of the Achilles tendon rupture were treated by lariat lock catch knot suture. There were 26 males and 6 females, with the average age of 39 years (range 17-53 years), including 13 left knees and 19 right knees. 29 wounds healed by first intention, and 3 cases who were performed local flap transfer due to necrosis of skin were healed by second intention. Thirty-two cases were followed up 10-25 months (13 months on average). No re-rupture of Achilles tendon or deep infection occurred during follow-up period. According to Arner-Lindholm assessment standard, the results were excellent in 19 cases and good in 13 cases, the excellent and good rate was 100%. Lariat lock catch knot suture is a safe and effective method for repairing Achilles tendon. PMID:26770612

  15. Crystal structure of the inverse crown ether tetra­kis­[μ2-bis­(tri­methyl­sil­yl)amido]-μ4-oxido-dicobalt(II)disodium, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O)

    PubMed Central

    Hansen, Christopher B.; Filatov, Alexander S.; Hillhouse, Gregory L.

    2016-01-01

    The title compound, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O), (I), represents a new entry in the class of inverse crown ethers. In the mol­ecule, each Co atom is formally in the oxidation state +II. The structure contains one half of a unique mol­ecule per asymmetric unit with the central μ4-oxido ligand residing on an inversion center, leading to a planar coordination to the Na and Co atoms. In the crystal, bulky tri­methyl­silyl substituents prevent additional inter­actions with cobalt. However, weak inter­molecular Na⋯H3C—Si inter­actions form an infinite chain along [010]. The structure is isotypic with its Mg, Mn and Zn analogues. PMID:27308041

  16. Crystal structure of the inverse crown ether tetra-kis-[μ2-bis-(tri-methyl-sil-yl)amido]-μ4-oxido-dicobalt(II)disodium, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O).

    PubMed

    Hansen, Christopher B; Filatov, Alexander S; Hillhouse, Gregory L

    2016-06-01

    The title compound, [Co2Na2{μ2-N(SiMe3)2}4](μ4-O), (I), represents a new entry in the class of inverse crown ethers. In the mol-ecule, each Co atom is formally in the oxidation state +II. The structure contains one half of a unique mol-ecule per asymmetric unit with the central μ4-oxido ligand residing on an inversion center, leading to a planar coordination to the Na and Co atoms. In the crystal, bulky tri-methyl-silyl substituents prevent additional inter-actions with cobalt. However, weak inter-molecular Na⋯H3C-Si inter-actions form an infinite chain along [010]. The structure is isotypic with its Mg, Mn and Zn analogues. PMID:27308041

  17. An Improved Method for the Separation of Lead-210 from Ra-DEF for Radioactive Equilibrium Experiments: Microscale Liquid-Liquid Extraction Using a Polymer-Supported Crown Ether

    NASA Astrophysics Data System (ADS)

    Dietz, Mark L.; Horwitz, E. Philip

    1996-02-01

    A novel extraction chromatographic material, comprised of a solution of a lead-selective macrocyclic polyether (di-t-butylcyclohexano-18-crown-6) in isodecanol sorbed on an inert polymeric support, is shown to provide a rapid and simple means for the separation of lead-210 from its daughter products for subsequent radiochemical experimentation.

  18. Two-state model based on electron-transfer reactivity changes to quantify the noncovalent interaction between Co(NH3)5Cl2+ and 18-crown-6 ether: the effect of second-sphere coordination on electron-transfer processes.

    PubMed

    Borreguero, M; Prado-Gotor, R

    2008-04-01

    The electron-transfer reaction between [Fe(CN)6]4- and [CoCl(NH3)5]2+ was studied in the presence of 18-crown-6 ether (18C6) in different reaction media constituted by water and acetonitrile as organic cosolvent at 298.2 K. The results corresponding to this reaction show a clear influence of 18C6 on the kinetics: a positive catalytic effect. Trends in the observed reactivity are explained by a change in the degree of association of one of the reactants (the cobalt complex) with the 18C6. This association is governed by an equilibrium constant that depends on the dielectric constant of the medium. The results show an increase of the rate constants for the electron-transfer process as the 18-crown-ether concentration increases and an increase of the binding free energy of the cobalt complex to the 18C6 when the electrostatic field of the medium becomes weaker. An analysis of the experimental data allows not only the reactivity changes associated with adducts formation processes for an electron-transfer reaction but also information on the binding free energy of the cobalt complex to the 18C6 to be obtained, which can be quantified by using a two-state model. We have found a good correlation between the energy of binding and the Kosower's Z-value. The influence of the 18C6 in the intramolecular electron transfer in the binuclear complex [Fe(CN)5pzCo(NH3)5] has been also investigated. PMID:18311956

  19. Molecular characterization of a new member of the lariat capping twin-ribozyme introns

    PubMed Central

    2014-01-01

    Background Twin-ribozyme introns represent a complex class of mobile group I introns that harbour a lariat capping (LC) ribozyme and a homing endonuclease gene embedded in a conventional self-splicing group I ribozyme (GIR2). Twin-ribozyme introns have so far been confined to nucleolar DNA in Naegleria amoeboflagellates and the myxomycete Didymium iridis. Results We characterize structural organization, catalytic properties and molecular evolution of a new twin-ribozyme intron in Allovahlkampfia (Heterolobosea). The intron contains two ribozyme domains with different functions in ribosomal RNA splicing and homing endonuclease mRNA maturation. We found Allovahlkampfia GIR2 to be a typical group IC1 splicing ribozyme responsible for addition of the exogenous guanosine cofactor (exoG), exon ligation and circularization of intron RNA. The Allovahlkampfia LC ribozyme, by contrast, represents an efficient self-cleaving ribozyme that generates a small 2′,5′ lariat cap at the 5′ end of the homing endonuclease mRNA, and thus contributes to intron mobility. Conclusions The discovery of a twin-ribozyme intron in a member of Heterolobosea expands the distribution pattern of LC ribozymes. We identify a putative regulatory RNA element (AP2.1) in the Allovahlkampfia LC ribozyme that involves homing endonuclease mRNA coding sequences as an important structural component. PMID:25342998

  20. Structural basis of lariat RNA recognition by the intron debranching enzyme Dbr1.

    PubMed

    Montemayor, Eric J; Katolik, Adam; Clark, Nathaniel E; Taylor, Alexander B; Schuermann, Jonathan P; Combs, D Joshua; Johnsson, Richard; Holloway, Stephen P; Stevens, Scott W; Damha, Masad J; Hart, P John

    2014-01-01

    The enzymatic processing of cellular RNA molecules requires selective recognition of unique chemical and topological features. The unusual 2',5'-phosphodiester linkages in RNA lariats produced by the spliceosome must be hydrolyzed by the intron debranching enzyme (Dbr1) before they can be metabolized or processed into essential cellular factors, such as snoRNA and miRNA. Dbr1 is also involved in the propagation of retrotransposons and retroviruses, although the precise role played by the enzyme in these processes is poorly understood. Here, we report the first structures of Dbr1 alone and in complex with several synthetic RNA compounds that mimic the branchpoint in lariat RNA. The structures, together with functional data on Dbr1 variants, reveal the molecular basis for 2',5'-phosphodiester recognition and explain why the enzyme lacks activity toward 3',5'-phosphodiester linkages. The findings illuminate structure/function relationships in a unique enzyme that is central to eukaryotic RNA metabolism and set the stage for the rational design of inhibitors that may represent novel therapeutic agents to treat retroviral infections and neurodegenerative disease. PMID:25123664

  1. A group III twintron encoding a maturase-like gene excises through lariat intermediates.

    PubMed Central

    Copertino, D W; Hall, E T; Van Hook, F W; Jenkins, K P; Hallick, R B

    1994-01-01

    The 1605 bp intron 4 of the Euglena gracilis chloroplast psbC gene was characterized as a group III twintron composed of an internal 1503 nt group III intron with an open reading frame of 1374 nt (ycf13, 458 amino acids), and an external group III intron of 102 nt. Twintron excision proceeds by a sequential splicing pathway. The splicing of the internal and external group III introns occurs via lariat intermediates. Branch sites were mapped by primer extension RNA sequencing. The unpaired adenosines in domains VI of the internal and external introns are covalently linked to the 5' nucleotide of the intron via 2'-5' phosphodiester bonds. This bond is susceptible to hydrolysis by the debranching activity of the HeLa nuclear S100 fraction. The internal intron and presumptive ycf13 mRNA accumulates primarily as a linear RNA, although a lariat precursor can also be detected. The ycf13 gene encodes a maturase-like protein that may be involved in group III intron metabolism. Images PMID:7512259

  2. Using 15-crown-5, 18-crown-6 and dicyclohexano-18-crown-6 for Am, Ce, Eu and Cm extraction from acid solutions

    SciTech Connect

    Romanovski, V.V.; Proyaev, V.V.; Wester, D.W.

    1994-08-01

    The extraction from nitric acid of Am, Eu, Ce, Cm(III) tracers by 15-crown-5 (15C5), 18-crown-6 (18C6), dicyclohexano-18-crown-6 (DCH18C6) as well as mixtures of crown ethers and chlorinated cobalt dicarbollide (ChCoD) in nitrobenzene solutions has been investigated. It was revealed that 18C6 is selective for Ce, Am and Cm compared with Eu. The addition of 18C6 to a solution of ChCoD allows Am and Cm to be separated from lanthanides by using this extractant more efficiently. The separation factors of Ce, Am, Cm and Eu are increased as a function of the ionic strength of the aqueous phase for extraction by mixtures of 18C6 and ChCoD and of DCH18C6 and ChCoD.

  3. Light-based triggering and reconstruction of Michel electrons in LArIAT

    NASA Astrophysics Data System (ADS)

    Foreman, W.

    2016-01-01

    The LArIAT Experiment aims to calibrate the liquid argon time projection chamber (LArTPC) using a beam of charged particles at the Fermilab Test Beam Facility. It is equipped with a novel scintillation light readout system using PMTs and custom SiPM preamplifier boards to detect light from reflector foils coated with wavelength-shifting TPB. A trigger on delayed secondary flashes of light captures events containing stopping cosmic muons together with the Michel electrons coming from their subsequent decay. This dedicated Michel trigger supplies an abundant sample of low-energy electrons throughout the detector's active volume, providing opportunities to study the combined calorimetric capabilities of the light system and the TPC. Preliminary results using scintillation light to study properties of the Michel electron sample are presented.

  4. Non-coding RNA generated following lariat-debranching mediates targeting of AID to DNA

    PubMed Central

    Zheng, Simin; Vuong, Bao Q.; Vaidyanathan, Bharat; Lin, Jia-Yu; Huang, Feng-Ting; Chaudhuri, Jayanta

    2015-01-01

    SUMMARY Transcription through immunoglobulin switch (S) regions is essential for class switch recombination (CSR) but no molecular function of the transcripts has been described. Likewise, recruitment of activation-induced cytidine deaminase (AID) to S regions is critical for CSR; however, the underlying mechanism has not been fully elucidated. Here, we demonstrate that intronic switch RNA acts in trans to target AID to S region DNA. AID binds directly to switch RNA through G-quadruplexes formed by the RNA molecules. Disruption of this interaction by mutation of a key residue in the putative RNA-binding domain of AID impairs recruitment of AID to S region DNA, thereby abolishing CSR. Additionally, inhibition of RNA lariat processing leads to loss of AID localization to S regions and compromises CSR; both defects can be rescued by exogenous expression of switch transcripts in a sequence-specific manner. These studies uncover an RNA-mediated mechanism of targeting AID to DNA. PMID:25957684

  5. MnBr₂/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield.

    PubMed

    Hausmann, David; Kuzmanoski, Ana; Feldmann, Claus

    2016-04-21

    The reaction of manganese(ii) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80-130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn(2+) cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn(2+) coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)](+) cation - with Mn(2+) coordinated by six oxygen atoms and Br - and a [MnBr(18-crown-6)MnBr4](-) anion. In this anion, Mn(2+) is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn(2+) cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination. PMID:26956783

  6. The Influence of Crown Ether and Alcohol on Unsaturation and Molar Mass of Poly(propylene oxide)s Prepared by Use of Potassium t-Butoxide: Reinvestigation of Chain Transfer Reactions

    PubMed Central

    Jurek-Suliga, Justyna; Skrzeczyna, Kinga; Gabor, Jadwiga; Łężniak, Marta

    2016-01-01

    Potassium t-butoxide dissolved in tetrahydrofuran effectively initiates homogeneous polymerization of propylene oxide at room temperature. Unsaturation and molar mass (Mn) of the polymers prepared depend on the presence of additives, such as macrocyclic ligand 18-crown-6 (L) and t-butanol. Application of the ligand alone results in distinct increase of unsaturation and decrease of Mn, whereas use of t-BuOH leads to simultaneous decrease of unsaturation and Mn. Activation of t-BuOK/t-BuOH system with the ligand causes further decrease of unsaturation, that is, from 12.0 to 3.5 mol % for OK/OH (1/3) and OK/OH/L (1/3/2) systems, respectively. Unexpectedly, Mn of the polymers obtained does not practically change (~4800). This result differs from that reported earlier for neat PO polymerization initiated potassium 1-methoxy-2-propoxide/1-methoxy-2-propanol, in which in the presence of the same ligand Mn increases to ~12 400 for the same ratio of reagents. The mechanism of studied processes was discussed. PMID:27528874

  7. Pentabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Pentabromodiphenyl ether ; CASRN 32534 - 81 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  8. Hexabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Hexabromodiphenyl ether ; CASRN 36483 - 60 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  9. Ethyl ether

    Integrated Risk Information System (IRIS)

    Ethyl ether ; CASRN 60 - 29 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  10. Tetrabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tetrabromodiphenyl ether ; CASRN 40088 - 47 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  11. Nonabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Nonabromodiphenyl ether ; CASRN 63936 - 56 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  12. Tribromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Tribromodiphenyl ether ; CASRN 49690 - 94 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  13. Octabromodiphenyl ether

    Integrated Risk Information System (IRIS)

    Octabromodiphenyl ether ; CASRN 32536 - 52 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarc

  14. The acrylic jacket crown.

    PubMed

    Bell, A M

    1975-04-01

    An attempt has been made to cover briefly the many applications of the acrylic jacket crown. It is readily understandable that this type of restoration has many shortcomings but at the same time it has many useful and important applications in dentistry when properly employed. It is hoped that the specialist and generalist alike will have found some new and useful applications of the acrylic jacket crown. PMID:1090464

  15. A lariat-functionalized copper(II) diimine-dioxime complex.

    PubMed

    Kiani, Salma; Staples, Richard J; Packard, Alan B

    2002-12-01

    The dimeric title copper(II) complex, diaqua-1kappaO,2kappaO-bis[3,9-dimethyl-6-(2-pyridylmethyl)-4,8-diazaundeca-3,8-diene-2,10-dione dioximato(1-)]-1k(4)N(2),N(4),N(8),N(10);1:2kappa(5)O(2):N(2),N(4),N(8),N(10)-dicopper(II) diperchlorate, [Cu(2)(C(17)H(24)N(5)O(2))(2)](ClO(4))(2), crystallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) A] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to Cu(II). PMID:12466608

  16. Circular RNA biogenesis can proceed through an exon-containing lariat precursor

    PubMed Central

    Barrett, Steven P; Wang, Peter L; Salzman, Julia

    2015-01-01

    Pervasive expression of circular RNA is a recently discovered feature of eukaryotic gene expression programs, yet its function remains largely unknown. The presumed biogenesis of these RNAs involves a non-canonical ‘backsplicing’ event. Recent studies in mammalian cell culture posit that backsplicing is facilitated by inverted repeats flanking the circularized exon(s). Although such sequence elements are common in mammals, they are rare in lower eukaryotes, making current models insufficient to describe circularization. Through systematic splice site mutagenesis and the identification of splicing intermediates, we show that circular RNA in Schizosaccharomyces pombe is generated through an exon-containing lariat precursor. Furthermore, we have performed high-throughput and comprehensive mutagenesis of a circle-forming exon, which enabled us to discover a systematic effect of exon length on RNA circularization. Our results uncover a mechanism for circular RNA biogenesis that may account for circularization in genes that lack noticeable flanking intronic secondary structure. DOI: http://dx.doi.org/10.7554/eLife.07540.001 PMID:26057830

  17. A lariat-functionalized copper(II) diimine—dioxime complex

    PubMed Central

    Kiani, Salma; Staples, Richard J.; Packard, Alan B.

    2013-01-01

    The dimeric title copper(II) complex, diaqua-1κO,2κO-bis[3,9-dimethyl-6-(2-pyridylmethyl)-4,8-diazaundeca-3,8-diene-2,10-dione dioximato(1–)]-1k4N2,N4,N8,N10;1:2κ5O2:N2,-N4,N8,N10-dicopper(II) diperchlorate, [Cu2(C17H24N5O2)2]-(ClO4)2, crystallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) Å] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to CuII. PMID:12466608

  18. A Rolling Circle Replication Mechanism Produces Multimeric Lariats of Mitochondrial DNA in Caenorhabditis elegans

    PubMed Central

    Lewis, Samantha C.; Joers, Priit; Willcox, Smaranda; Griffith, Jack D.; Jacobs, Howard T.; Hyman, Bradley C.

    2015-01-01

    Mitochondrial DNA (mtDNA) encodes respiratory complex subunits essential to almost all eukaryotes; hence respiratory competence requires faithful duplication of this molecule. However, the mechanism(s) of its synthesis remain hotly debated. Here we have developed Caenorhabditis elegans as a convenient animal model for the study of metazoan mtDNA synthesis. We demonstrate that C. elegans mtDNA replicates exclusively by a phage-like mechanism, in which multimeric molecules are synthesized from a circular template. In contrast to previous mammalian studies, we found that mtDNA synthesis in the C. elegans gonad produces branched-circular lariat structures with multimeric DNA tails; we were able to detect multimers up to four mtDNA genome unit lengths. Further, we did not detect elongation from a displacement-loop or analogue of 7S DNA, suggesting a clear difference from human mtDNA in regard to the site(s) of replication initiation. We also identified cruciform mtDNA species that are sensitive to cleavage by the resolvase RusA; we suggest these four-way junctions may have a role in concatemer-to-monomer resolution. Overall these results indicate that mtDNA synthesis in C. elegans does not conform to any previously documented metazoan mtDNA replication mechanism, but instead are strongly suggestive of rolling circle replication, as employed by bacteriophages. As several components of the metazoan mitochondrial DNA replisome are likely phage-derived, these findings raise the possibility that the rolling circle mtDNA replication mechanism may be ancestral among metazoans. PMID:25693201

  19. Stability constants and thermodynamic data for complexes of 12-crown-4 with alkali metal and alkaline-earth cations in methanol solutions

    SciTech Connect

    Buschmann, H.

    1987-03-01

    The formation of 1:1- and 2:1-complexes of the crown ether 12C4 with mono- and bivalent cations was studied in methanol solutions by calorimetric, potentiometric and conductometric titrations. It is shown that not all donor atoms of the ligand 12C4 take part in complex formation. The accuracy of the three experimental methods are checked by comparing the results for the complexation of alkali ions with crown ether 18C6.

  20. A ferric-cyanide-bridged one-dimensional dirhodium complex with (18-crown-6)potassium cations.

    PubMed

    Kim, Y; Kim, S J; Nam, W

    2001-03-01

    The crystal structure of the title compound, catena-poly[bis[aqua(18-crown-6)potassium] diaqua(18-crown-6)potassium [[tetra-mu-benzoato-2:3 kappa(8)O:O'-mu-cyano-1:2 kappa(2)C:N-tetracyano-1 kappa C-irondirhodium(Rh-Rh)]-mu-cyano-1 kappa C:3' kappa N] octahydrate], [K(18-crown-6)(H(2)O)](2)[K(18-crown-6)(H(2)O)(2)][FeRh(2)(C(7)H(5)O(2))(4)(CN)(6)] x 8H(2)O, where (18-crown-6) is 1,4,7,10,13,16-hexaoxacyclooctadecane (C(12)H(24)O(6)), has been determined. Ferric cyanides connect the dirhodium units to form a one-dimensional chain compound. [K(18-crown-6-ether)(H(2)O)(2)] cations (with inversion symmetry) and [K(18-crown-6-ether)(H(2)O)] cations (in general positions) are located between the chains. PMID:11250572

  1. Bisthioxanthylidene biscrown ethers as potential stereodivergent chiral ligands.

    PubMed

    Geertsema, Edzard M; Schoevaars, Anne Marie; Meetsma, Auke; Feringa, Ben L

    2006-11-21

    The concept of bisthioxanthylidene biscrown ethers as potential stereodivergent chiral ligands in asymmetric synthesis is introduced. Substituted bisthioxanthylidenes may be chiral and can exist as stable enantiomers due to their folded structure. As a result, both a right-handed helix (P) and left-handed helix (M) are present in this type of molecule. This offers the unique possibility to construct two crown ether moieties, attached to the same molecule, of which one exhibits (P)-helicity and the other (M)-helicity. When the crown ether moieties differ in size they can be complexed selectively with a base containing a cation of appropriate diameter. In this manner the (P)-helix and the (M)-helix can be activated selectively to serve as a chiral environment for base catalyzed asymmetric synthesis. Thus, we envisioned the new concept of a single chiral ligand to separately synthesize two enantiomers of a chiral product just by varying the added base. For this purpose, four new bisthioxanthylidene monocrown ethers and two new bisthioxanthylidene biscrown ethers were synthesized. Two biscrowns and two monocrowns were separated into their respective enantiomers (HPLC) and optical data (UV and CD) were collected to ensure stability of enantiomers at ambient temperatures. Ion complexation of one mono- and two biscrown ethers with potassium and sodium cations was investigated. PMID:17312964

  2. All-ceramic crowns.

    PubMed

    Lehner, C R; Schärer, P

    1992-06-01

    Despite the good appearance and biocompatibility of dental porcelains, failures are still of considerable concern because of some limited properties common to all-ceramic crown systems. As in the years before, pertinent scientific articles published between November 1990 and December 1991 focused on strengthening mechanisms and compared fracture toughness for different ceramic systems by using various test methods. Some evaluated the clinical implications thereon for seating and loading crowns and measured wear against different ceramic surface conditions. Recently introduced with pleasing aesthetic qualities, IPS-Empress (Ivoclar, Schaan, Liechtenstein), a new European leucite-reinforced glass-ceramic, has finally drawn attention in some journals and has been reviewed with promising in vitro test results. Using a simple press-molding technique, well-fitting crowns, inlays, and veneers can be fabricated without an additional ceramming procedure. Again, only long-term clinical trials will validate achievements compared with other all-ceramic systems and with well-established metal ceramics. PMID:1325848

  3. Poly(arylene ether)s containing pendent ethynyl groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Jensen, Brian J. (Inventor)

    1996-01-01

    Poly(arylene ether)s containing pendent ethynyl and substituted ethynyl groups and poly(arylene ether) copolymers containing pendent ethynyl and substituted ethynyl groups are readily prepared from bisphenols containing ethynyl and substituted ethynyl groups. The resulting polymers are cured up to 350.degree. C. to provide crosslinked poly(arylene ether)s with good solvent resistance, high strength and modulus.

  4. An electrochemical investigation of the effect of macrocycle ring size on the binding of di- and trivalent lanthanide cations by 12-crown-4,4-tert-butylbenzo-15-crown-5, and dibenzo-30-crown-10 in propylene carbonate

    SciTech Connect

    Massaux, J.; Desreux, J.F.

    1982-06-02

    The complexation in anhydrous proplene carbonate of the lanthanide ions by various macrocylic polyethers featuring from four to ten oxygen atoms has been investigated by a competitive potentiometric technique with lead(II) or thallium(I) as auxilliary ions. The stability of the complexes appears to depend primarily on the relative sizes of the metal ions and of the internal cavity of each macrocycle. It depends also on the rigidity of the ligands and is influenced by solvation effects. The small ligands 12-crown-4 (1) and 15-crown-5 (2) exhibit a similar behavior: they form 1:2 lanthanide complexes, the stability of which decreases with decreasing ionic radius despite the higher charge density of the metal ions. The presence of an electron-withdrawing phenyl group, as in 4-tert-butylbenzo-15-crown-5 (3), leads to a strong reduction of the stability constants. A maximum stability of 1:1 complexes of 3 is found at Nd(III) while a marked minimum is observed at Gd(III) in the complexation curve of dibenzo-30-crown-10 (5). Divalent samarium and ytterbium are more strongly coordinated than the corresponding trivalent ions by the crown ethers 1-5. The larger divalent ions fit better into the internal cavity of 5 and they form stable 1:2 sandwich complexes with 1 and 3. The properties of the complexes described in the present work are completely different from those reported so far in the case of noncylic ligands.

  5. Raman spectra and conformations of dibenzo- and dicyclohexano-18-crown-6

    NASA Astrophysics Data System (ADS)

    Takeuchi, Hideo; Arai, Takaki; Harada, Issei

    1990-06-01

    Conformations of dibenzo-18-crown-6 (DBC), dicyclohexano-18-crown-6 (DCC) and their alkali cation complexes in the solid state and in solution have been investigated by Raman spectroscopy. The Raman spectra were analysed by using the relationships between Raman frequencies and conformations previously found for unsubstituted crown ethers. DBC takes a conformation, ( tCttGttG't) 2, with gauche ( G) or gauche' ( G') 2CH 2 bonds, trans ( t) CO bonds and cis ( C) OCCO linkages at the benzene rings, when it complexes with a cation in the solid state and in solution. Uncomplexed DBC adopts another conformation in the solid state, which contains both the trans and gauche conformations about the CH 2CH 2 and CO bonds. In solution, uncomplexed DBC exists as a mixture of conformers including the two conformers described above. Vibrational couplings between the oxyethylene and cyclohexane rings are strong in DCC and its strength depends on the crown conformation. The cation-bound crown rings of DCC isomers A and B in solution predominantly take the same conformation, ( tG'ttGt) 3, found for the crystalline isomer B-NaBr complex. A metastable conformer containing trans CH 2CH 2 bonding is found for the Na + complexes of both isomers in solution. Uncomplexed DCC adopts different crown ring conformations in isomers A and B in the solid state and diverse conformational states in solution.

  6. Synthesis and Cytotoxicity of Silicon and Germanium Containing Pyridine Oxime O-Ethers

    PubMed Central

    Abele, Edgars; Abele, Ramona; Arsenyan, Pavel; Shestakova, Irina; Kanepe, Iveta; Antonenko, Inga; Popelis, Juris; Lukevics, Edmunds

    2003-01-01

    Silicon and germanium containing pyridine aldoxime, ketoxime and amidoxime O-ethers have been prepared using phase transfer catalytic systems oxime alkyl halide solid KOH 18-crown-6 benzene and oxime alkyl halide solid K2CO3 or Cs2CO3 18-crown-6 toluene. Cytotoxic activity of silicon and germanium containing pyridine oxime O-ethers was tested in vitro on two monolayer tumor cell lines: MG- 22A (mouse hepatoma) and HT-1080 (human fibrosarcoma). O-[3-Yriethylsilylpropyl]- and O-[3-(1-methyl- 1-silacyclopentyl)propyl] oximes of pyridine aldehydes and ketones exhibit high cytotoxicity. Presence of methyl group in the pyridine ring considerably decreased activity of amidoxime O-ethers. Oxime ethers containing two elements are essentially inactive. For 2-acetylpyridine oxime ethers the activity increases in order of alkyl substituents: Et3GeCH2CH2SiMe2CH2 < Et3SiCH2CH2CH2 < (CH2)4SiCH2CH2CH2. Cytotoxicity of ketoxime O-ethers is considerably lower in comparison with aldoxime O-ethers. PMID:18365061

  7. Halogen derivatives of benzo- and dibenzocrown ethers: synthesis, structure, properties and application

    NASA Astrophysics Data System (ADS)

    Pluzhnik-Gladyr, S. M.

    2016-02-01

    Methods of synthesis of halogenated benzo- and dibenzocrown ether derivatives are surveyed: halogenation of benzo- and dibenzocrown ethers with molecular halogens, N-halosuccinimides in the solid phase and different media (water, ethanol, halohydrocarbons) and hypohalites in water, as well as the 'assembly' method. Reactions of these compounds are considered: synthesis of phosphorus-containing crown ethers, organometallic synthesis, the Heck and Sonogashira reactions, synthesis of acetylene derivatives and other reactions. Special attention is focused on the complexing properties of halogenated benzocrown ethers with respect to ionic guests and neutral organic molecules. The possibility of synthesis of complexes of such compounds in the solid phase is demonstrated. The extraction and sorption properties of halogenated benzo- and dibenzocrown ethers are considered. Examples of practical use of these compounds are presented. The bibliography includes 203 references.

  8. Removal of failed crown and bridge

    PubMed Central

    Rahul, G R.; Poduval, Soorya T.; Shetty, Karunakar

    2012-01-01

    Crown and bridge have life span of many years but they fail for a number of reasons. Over the years, many devices have been designed to remove crowns and bridges from abutment teeth. While the removal of temporary crowns and bridges is usually very straightforward, the removal of a definitive cast crown with unknown cement is more challenging. Removal is often by destructive means. There are a number of circumstances, however, in which conservative disassembly would aid the practitioner in completing restorative/endodontic procedures. There are different mechanisms available to remove a failed crown or bridge. But there is no information published about the classification of available systems for crown and bridge removal. So it is logical to classify these systems into different groups which can help a clinician in choosing a particular type of system depending upon the clinical situation. The aim of this article is to provide a classification for various crown and bridge removal systems; describe how a number of systems work; and when and why they might be used. A PubMed search of English literature was conducted up to January 2010 using the terms: Crown and bridge removal, Crown and bridge disassembly, Crown and bridge failure. Additionally, the bibliographies of 3 previous reviews, their cross references as well as articles published in various journals like International Endodontic Journal, Journal of Endodontics and were manually searched. Key words:Crown and bridge removal, Crown and bridge disassembly, Crown and bridge failure. PMID:24558549

  9. Coibamide A, a natural lariat depsipeptide, inhibits VEGFA/VEGFR2 expression and suppresses tumor growth in glioblastoma xenografts.

    PubMed

    Serrill, Jeffrey D; Wan, Xuemei; Hau, Andrew M; Jang, Hyo Sang; Coleman, Daniel J; Indra, Arup K; Alani, Adam W G; McPhail, Kerry L; Ishmael, Jane E

    2016-02-01

    Coibamide A is a cytotoxic lariat depsipeptide isolated from a rare cyanobacterium found within the marine reserve of Coiba National Park, Panama. Earlier testing of coibamide A in the National Cancer Institute in vitro 60 human tumor cell line panel (NCI-60) revealed potent anti-proliferative activity and a unique selectivity profile, potentially reflecting a new target or mechanism of action. In the present study we evaluated the antitumor activity of coibamide A in several functional cell-based assays and in vivo. U87-MG and SF-295 glioblastoma cells showed reduced migratory and invasive capacity and underwent G1 cell cycle arrest as, likely indirect, consequences of treatment. Coibamide A inhibited extracellular VEGFA secreted from U87-MG glioblastoma and MDA-MB-231 breast cancer cells with low nM potency, attenuated proliferation and migration of normal human umbilical vein endothelial cells (HUVECs) and selectively decreased expression of vascular endothelial growth factor receptor 2 (VEGFR2). We report that coibamide A retains potent antitumor properties in a nude mouse xenograft model of glioblastoma; established subcutaneous U87-MG tumors failed to grow for up to 28 days in response to 0.3 mg/Kg doses of coibamide A. However, the natural product was also associated with varied patterns of weight loss and thus targeted delivery and/or medicinal chemistry approaches will almost certainly be required to improve the toxicity profile of this unusual macrocycle. Finally, similarities between coibamide A- and apratoxin A-induced changes in cell morphology, decreases in VEGFR2 expression and macroautophagy signaling in HUVECs raise the possibility that both cyanobacterial natural products share a common mechanism of action. PMID:26563191

  10. Development of HPLC Chiral Stationary Phases Based on (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid and Their Applications.

    PubMed

    Hyun, Myung Ho

    2015-09-01

    Crown ether-based chiral stationary phases (CSPs) have been known to be useful for the resolution of racemic primary amino compounds. In particular, CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid have been reported to be useful for the resolution of secondary amino compounds as well as primary amino compounds. In this article, the process of developing various CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to improve the chiral recognition efficiency and/or the stability of the CSPs and their applications to the resolution of various primary and nonprimary amino compounds are reviewed. PMID:26237013

  11. INTRAVENOUS ETHER ANESTHESIA

    PubMed Central

    Eger, Edmond I.; Johnson, Edward A.

    1963-01-01

    From a study of intravenous ether anesthesia, it was concluded that ether diluted to a 5 per cent solution in 5 per cent dextrose and water may be used to induce and maintain a smooth and easily controlled anesthetic state similar to that obtained with inhalation ether but without the dependence of the latter technique on ventilation. Cough and laryngospasm were absent. Adequate spontaneous respiration can be maintained with this technique. The technique is particularly useful in endoscopy during which the airway is often not available for anesthetic administration. PMID:14051486

  12. Vinyl ether silicones

    SciTech Connect

    Herzig, C.; Dauth, J.; Deubzer, B.; Weis, J.

    1995-12-01

    Siloxanes with vinyl ether groups are prepared by hydrosilylation reaction of dihydrosiloxanes with divinyl ethers in excess. Different stoichiometry, produces linear copolymers of different viscosities and double bond concentrations always with an active vinyl ether group at each chain end. Polymerisations triggered by UV light were done with mixtures of these compounds and a series of onium salts. Very fast cure is observed even with low doses at 290 nm. V.E. silicones are found to cure essentially quantitative. The comparison with other highly reactive cationic monomers revealed that compounds are among the fastest curing prepolymers in cationic chemistry.

  13. Genotoxicity of glycol ethers.

    PubMed Central

    McGregor, D B

    1984-01-01

    The genetic toxicology of glycol ethers is reviewed. Ethylene glycol monomethyl ether (EGME) and diglyme have been more extensively studied than other members of this series. Most results indicate a lack of genotoxic potential, but certain tests have yielded positive responses with certain compounds. Ethylene glycol monoethyl ether (EGEE) induced sister chromatid exchanges and chromosomal aberrations in cultured cells. Both EGME and diglyme induced mouse sperm head morphological changes, male rat weak dominant lethal mutations and marked, but reversible, loss of male rat fertility. PMID:6541999

  14. Catalytic oxidation of dimethyl ether

    DOEpatents

    Zelenay, Piotr; Wu, Gang; Johnston, Christina M.; Li, Qing

    2016-05-10

    A composition for oxidizing dimethyl ether includes an alloy supported on carbon, the alloy being of platinum, ruthenium, and palladium. A process for oxidizing dimethyl ether involves exposing dimethyl ether to a carbon-supported alloy of platinum, ruthenium, and palladium under conditions sufficient to electrochemically oxidize the dimethyl ether.

  15. A surprising host-guest relationship between 1,2-dichloroethane and the cesium complex of tetrabenzo-24-crown-8

    SciTech Connect

    Levitskaia, T.G.; Bryan, J.C.; Sachleben, R.A.; Lamb, J.D.; Moyer, B.A.

    2000-02-02

    The structure of the complex [Cs(tetrabenzo-24-crown-8)(1,2-dichloroethane){sub 2}](NO{sub 3}){sm{underscore}bullet}H{sub 2}O was shown by X-ray crystallography to involve an unprecedented bidentate coordination of two 1,2-dichloroethane solvent molecules to the Cs{sup +} cation via the four chlorine atoms. The coordination of the solvent molecules occurs within two clefts between facing benzo groups, one pair of benzo groups related to the other pair by an improper noncrystallographic 90{degree} rotation. Resembling the seam on a tennis ball, the crown ether envelops the metal cation within a cagelike arrangement of eight crown ether oxygen atoms. Good geometric and electronic complimentarily characterizes the apparent host-guest relationship between the cleft environment and the solvent molecules. The complete encapsulation of the cation by the crown ether and two solvent molecules explains well the speciation behavior observed in liquid-liquid extraction of CsNO{sub 3} or CsClO{sub 4} from aqueous solution to 1,2-dichloroethane solutions of the alkylated analogues 4,4{double{underscore}prime}- or 4,5{double{underscore}prime}-bis(tert-octylbenzo)dibenzo-24-crown-8. In the extraction process studied at 25 C, simple 1:1 metal/crown complexes form in the solvent phase, as modeled by the program SXLSQI. The complex cation and counteranion are present both as ion-pairs, postulated to be ligand-separated ion-pairs as suggested by the crystal structure, and as dissociated ions. In agreement with a theoretical treatment of ion-pairing, the ion-pairs possess unusually low stability and exhibit no discrimination between the anions, largely ascribed to the large effective radius of the complex metal cation. Values of log K{sub f} corresponding to the formation of the complex cations Cs[bis(tert-octylbenzo)-dibenzo-24-crown-8]{sup +} in 1,2-dichloroethane at 25 C average 10.5 {+-} 0.2 for both positional isomers of the crown ether and for their 3:2 mixture. Overall, these

  16. Conformation-Specific Infrared and Ultraviolet Spectroscopy of DIBENZO-15-CROWN-5-(H2O)1-CLUSTER: Reshaping a Binding Pocket

    NASA Astrophysics Data System (ADS)

    Buchanan, Evan G.; Rodrigo, Chirantha P.; Gutberlet, Anna K.; Zwier, Timothy S.

    2010-06-01

    Crown ethers are oxygen containing macrocycles noted for their ability to preferentially bind substrates such as ions and water. Despite the high symmetry inherent to the chemical structure, crown ethers are remarkably flexible, adapting their conformation to the substrate to which they are bound. Here, we present the conformational preferences of the singly hydrated dibenzo-15-crown-5 ether (DB15C) complex formed and cooled in a supersonic jet. The resonance enhanced two-photon ionization, UV-UV Hole-burning, and resonant ion-dip infrared spectra lead to the identification of a single DB15C-(H2O)1 conformer with the water doubly hydrogen bonded to the crown. Single vibronic level dispersed fluorescence identified both electronic origins and the coupling between the two chromophores. Finally, infrared population transfer spectroscopy is used to study the monomer conformer populations formed by infrared photodissocation of the complex via the water OH stretch transitions, providing unique insight to the energy flow between water and crown.

  17. Pd-catalyzed amination in the synthesis of a new family of macropolycyclic compounds comprising diazacrown ether moieties.

    PubMed

    Yakushev, Alexei A; Chernichenko, Nataliya M; Anokhin, Maxim V; Averin, Alexei D; Buryak, Alexei K; Denat, Franck; Beletskaya, Irina P

    2014-01-01

    N,N'-bis(bromobenzyl) and N,N'-bis(halopyridinyl) derivatives of diaza-12-crown-4, diaza-15-crown-5 and diaza-18-crown-6 ethers were synthesized in high yields. The Pd-catalyzed macrocyclization reactions of these compounds were carried out using a variety of polyamines and oxadiamines were carried out to give novel macrobicyclic and macrotricyclic compounds of the cryptand type. The dependence of the yields of macropolycycles on the nature of the starting diazacrown derivatives and polyamines was established. Generally N,N'-bis(3-bromobenzyl)-substituted diazacrown ethers and oxadiamines provided better yields of the target products. The highest yield of the macrobicyclic products reached 57%. PMID:24434669

  18. Synthesis and characterization of a chiral, aza-15-crown-5-functionalized ferrocenyldiphosphine ligand for asymmetric catalysis

    SciTech Connect

    Landis, C.R.; Sawyer, R.A.; Somsook, E.

    2000-03-20

    A chiral ferrocenyldiphosphine ligand that is functionalized with an aza crown ether, (S)-1-[(R)-1{prime},2-bis(diphenylphosphino)ferroceny]ethyl-1-aza-2,3-benzo-15-crown-5(1), has been synthesized. Both the resolved and racemic ligands react rapidly with Pt(II) precursors to form stable metal-ligand adducts; the complexes PtMeI(rac-1) and PtMe{sub 2}(rac-1) have been characterized crystallographically. Reaction of rac-1 with [Rh(NBD){sub 2}]OTf yields [Rh(NBD)(rac-1)]OTf. The three-dimensional solution structure of [Rh(NBD)(rac-1)]OTf has been determined by NOESY experiments and analysis using the two-dimensional conformer population analysis algorithm (2DCPA). The NOESY data reveal rapid, pairwise chemical exchange between vinyl protons. The complex [Rh(NBD)(rac-1)]OTf is a catalyst precursor for hydrogenation reactions. However, the authors demonstrate that the liability of the aza crown ether may limit the ability of these catalysts to control selectivity via secondary interactions.

  19. Marginal accuracy of temporary composite crowns.

    PubMed

    Tjan, A H; Tjan, A H; Grant, B E

    1987-10-01

    An in vitro study was conducted to quantitatively compare the marginal adaptation of temporary crowns made from Protemp material with those made from Scutan, Provisional, and Trim materials. A direct technique was used to make temporary restorations on prepared teeth with an impression as a matrix. Protem, Trim, and Provisional materials produced temporary crowns of comparable accuracy. Crowns made from Scutan material had open margins. PMID:2959770

  20. Triethylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monoethyl ether ; CASRN 112 - 50 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  1. Triethylene glycol monobutyl ether

    Integrated Risk Information System (IRIS)

    Triethylene glycol monobutyl ether ; CASRN 143 - 22 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  2. Propylene glycol monoethyl ether

    Integrated Risk Information System (IRIS)

    Propylene glycol monoethyl ether ; CASRN 52125 - 53 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  3. p-Bromodiphenyl ether

    Integrated Risk Information System (IRIS)

    p - Bromodiphenyl ether ; CASRN 101 - 55 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  4. Chloromethyl methyl ether (CMME)

    Integrated Risk Information System (IRIS)

    Chloromethyl methyl ether ( CMME ) ; CASRN 107 - 30 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  5. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, J.V.

    1996-10-22

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of the above formula together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  6. Propenyl ether monomers for photopolymerization

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  7. Glycol Ethers As Groundwater Contaminants

    NASA Astrophysics Data System (ADS)

    Ross, Benjamin; Johannson, Gunnar; Foster, Gregory D.; Eckel, William P.

    1992-01-01

    Ether derivatives of dihydroxy alcohols, which are formed from ethylene or propylene, comprise an important group of groundwater contaminants known as glycol ethers. Compounds in this group are used as solvents, cleaning agents, and emulsifiers in many chemical products and manufacturing operations. Glycol ethers have been associated with a variety of toxic effects, and some compounds in the group are relatively potent teratogens. The limited information available suggests that glycol ethers are contaminants in groundwater, especially in anaerobic plumes emanating from disposal of mixed industrial and household waste. Most methods used to analyze groundwater samples cannot adequately detect μg/? (ppb) concentrations of glycol ethers, and the existing methods perform worst for the most widely used and toxic species. A new method capable of analyzing μg/? concentrations of glycol ethers was recently developed, and its use is recommended for groundwater samples where glycol ethers are likely to be present.

  8. Pipe weld crown removal device

    SciTech Connect

    Sword, C.K.; Sette, P.J.

    1992-11-24

    A device is provided for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels. 2 figs.

  9. Pipe weld crown removal device

    SciTech Connect

    Sword, C.K.; Sette, P.J.

    1991-12-31

    This invention is comprised of a device that provides for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels.

  10. Pipe weld crown removal device

    DOEpatents

    Sword, Charles K.; Sette, Primo J.

    1992-01-01

    A device is provided for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of the weld, a plurality of grinding wheels, supported by the cage assembly for grinding down the crown of the weld, and a plurality of support shafts, each extending longitudinally along the joined pipe sections, parallel thereto, for individually mounting respective grinding wheels. Each end of the support shafts is mounted for rotation in a bearing assembly housed within a radially directed opening in a corresponding one of the cage rings so as to provide radial movement of the associated shaft, and thus of the associated grinding wheel, towards and away from the weld. A first drive sprocket provides rotation of the cage assembly around the pipe sections while a second drive unit, driven by a common motor, provides rotation of the grinding wheels.

  11. Sclerotinia stem and crown rot of chickpea

    Technology Transfer Automated Retrieval System (TEKTRAN)

    White mold of chickpea is caused by three soil borne fungi Sclerotinia sclerotiorum, S. minor and S. trifoliorum, causing either stem rot and crown rot. Stem infection, usually above ground and initiated by ascospores through carpogenic germination of scleroia produces stem rot, whereas crown infe...

  12. Developmental toxicity of diphenyl ether herbicides in nestling American kestrels.

    PubMed

    Hoffman, D J; Spann, J W; LeCaptain, L J; Bunck, C M; Rattner, B A

    1991-11-01

    Beginning the day after hatching, American kestrel (Falco sparverius) nestlings were orally dosed for 10 consecutive days with 5 microliters/g of corn oil (controls) or one of the diphenyl ether herbicides (nitrofen, bifenox, or oxyfluorfen) at concentrations of 10, 50, 250, or 500 mg/kg in corn oil. At 500 mg/kg, nitrofen resulted in complete nestling mortality, bifenox in high (66%) mortality, and oxyfluorfen in no mortality. Nitrofen at 250 mg/kg reduced nestling growth as reflected by decreased body weight, crown-rump length, and bone lengths including humerus, radius-ulna, femur, and tibiotarsus. Bifenox at 250 mg/kg had less effect on growth than nitrofen, but crown-rump, humerus, radius-ulna, and femur were significantly shorter than controls. Liver weight as a percent of body weight increased with 50 and 250 mg/kg nitrofen. Other manifestations of impending hepatotoxicity following nitrofen ingestion included increased hepatic GSH peroxidase activity in all nitrofen-treated groups, and increased plasma enzyme activities for ALT, AST, and LDH-L in the 250-mg/kg group. Bifenox ingestion resulted in increased hepatic GSH peroxidase activity in the 50- and 250-mg/kg groups. Nitrofen exposure also resulted in an increase in total plasma thyroxine (T4) concentration. These findings suggest that altricial nestlings are more sensitive to diphenyl ether herbicides than young or adult birds of precocial species. PMID:1942122

  13. Colour measurements of all ceramic crown systems.

    PubMed

    Rosenstiel, S F; Porter, S S; Johnston, W M

    1989-09-01

    The objectives of this study were: (i) to determine variability among colour parameters of five different ceramic crown systems; and (ii) to measure the effect of using coloured luting agents on restoration colour. The crown systems studied were Cerestore, Dicor, Hi-Ceram, Renaissance, and Vitadur-N. Five crowns for each system were made according to manufacturer's instructions with the same nominal shade (Vita Lumin Vacuum A2) to fit an Ivorine central incisor tooth. Restoration thickness was adjusted to within +/- 0.1 mm (+/- 0.05 mm in the mid-facial area where colour measurements were to be made) with the aid of a dial calliper prior to glazing or, in the case of Dicor, surface staining. Where a core was part of the system this was fabricated to the minimum recommended thickness. The crowns were cemented using luting agents of five different colours in a randomly chosen sequence. The colour of each restoration/cement combination was measured three times using a small-area colorimeter (Minolta CR-121). The variance of each colour parameter (L*, a*, b*) was statistically compared for each crown system using an analysis of variance procedure, as was the effect of the cement. Observed differences were related to visual perception by using the colour difference formula. There were statistically significant differences among the variances of the crown systems and the cements, with significant interactions between crown systems and direction of colour and between cement and direction of colour. Restorations made with different ceramic crown systems had noticeably different colour despite having the same nominal shade. Changing the shade of the luting agent had a perceivable effect on Dicor crowns and, to a lesser extent, on Vitadur-N crowns but not on the other systems due, presumably, to the opacity of their core materials. PMID:2809851

  14. Conformational effect of dicyclo-hexano-18-crown-6 on isotopic fractionation of zinc: DFT approach

    SciTech Connect

    Boda, A.; Singha Deb, A. K.; Ali, Sk. M.; Shenoy, K. T.; Ghosh, S. K.

    2014-04-24

    Generalized gradient approximated BP86 density functional employing triple zeta valence plus polarization (TZVP) basis set has been used to compute the reduced partition function ratio and isotopic separation factor for zinc isotopes. The isotopic separation factor was found to be in good agreement with the experimental results. The isotopic separation factor was found to depend on the conformation of the crown ether ligand. The trans-trans conformation shows the highest fractionation compared to cis-cis conformer. The present theoretical results can thus be used to plan the isotope separation experiments.

  15. Synthesis and Characterization of Macrocyclic Polyether N,N'-Diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6.

    PubMed

    Toeri, Julius; Laborie, Marie-Pierre

    2016-01-01

    In this study an efficient and direct production procedure for a macrocyclic polyether N,N'-diallyl-7,16-diaza-1,4,10,13-tetraoxa-dibenzo-18-crown-6 from the reaction of catechol and N,N-bis(2-chloroethyl)prop-2-en-1-amine in n-butanol in the presence of a strong base is reported. The synthesis involves a two-step addition of sodium hydroxide to enhance the cyclization process, and at the end of the reaction, the reaction mixture is neutralized and the solvent replaced with water in-situ through distillation to afford a relatively pure precipitate that is easily recrystallized from acetone. The yield of the macrocycle was 36%-45% and could be scaled-up to one-mole quantities. The structure and purity of this compound was verified on the basis of elemental analysis, IR, UV-Vis, ¹H-, (13)C-NMR, 2D-NMR, mass spectroscopy, and thermal analysis. The white crystalline compound has a sharp melting point of 124 °C and a crystallization temperature of 81.4 °C determined by differential scanning calorimetry. Our motivation behind the synthesis of the bibracchial lariat azacrown polyether ligand was to examine its possible applications in ion-selective polymer-supported materials. PMID:26840284

  16. Bacterial degradation of glycol ethers.

    PubMed

    Kawai, F

    1995-12-01

    Assimilation of ethyleneglycol (EG) ethers by polyethyleneglycol-utilizing bacteria was examined. Ethyleneglycol ether-utilizing bacteria were also isolated from soil and activated sludge samples by enrichment-culture techniques. Three strains (4-5-3, EC 1-2-1 and MC 2-2-1) were selected and characterized as Pseudomonas sp. 4-5-3, Xanthobacter autotrophicus, and an unidentified gram-negative, non-spore-forming rod respectively. Their growth characteristics were examined: Pseudomonas sp. 4-5-3 assimilated EG (diethyleneglycol, DEG) monomethyl, monoethyl and monobutyl ethers, DEG, propanol and butanol. X. autotrophicus EC 1-2-1 grew well on EG monoethyl and monobutyl ethers, EG and primary alcohols (C1-C4), and slightly on EG monomethyl ether. The strain MC 2-2-1 grew on EG monomethyl ether, EG, primary alcohols (C1-C4), and 1,2-propyleneglycol (PG). The mixed culture of Pseudomonas sp. 4-5-3 and X. autotrophicus EC 1-2-1 showed better growth and improved degradation than respective single cultures towards EG monomethyl, monoethyl or monobutyl ethers. Intact cells of Pseudomonas sp. 4-5-3 degraded various kinds of monoalkyl ethers, which cannot be assimilated by the strain. Metabolic products were characterized from reaction supernatants of intact cells of Pseudomonas sp. 4-5-3 with EG or DEG monoethyl ethers: they were analyzed by thin-layer chromatography and GC-MS and found to be ethoxyacetic acid and ethoxyglycoxyacetic acid. Also, PG monoalkyl ethers (C1-C4), dipropyleneglycol monoethyl and monomethyl ethers and tripropyleneglycol monomethyl ether were assimilated by polypropyleneglycol-utilizing Corynebacterium sp. 7. PMID:8597556

  17. Developmental toxicity of diphenyl ether herbicides in birds

    USGS Publications Warehouse

    Hoffman, D.J.; Rattner, B.A.; Bunck, C.M.

    1991-01-01

    Diphenyl ether herblcldes, includlng nitrofen, have been identified as mammalian teratogens and cause perinatal mortality. American kestrel (Falco sparverius) nestlings were orally dosed for 10 days w1th 5 ul/g of corn oil (controls) or one of the diphenyl ether herbicides (nitrofen, bifenox, or oxyfluorofen). At 500 mg/kg, nitrofen resulted in complete mortality, bifenox in high (66%) mortality, and oxyfluorofen in no mortality. Nitrofen, at 250 mg/kg, reduced nestling growth, as reflected by decreased body weight and bone length. Bifenox at 250 mg/kg had less effect on growth than nitrofen but crown rump, humerus, radiusulna and femur lengths were significantly less than controls. Liver welght (percent of body welght) increased with 50 mg/kg nitrofen. Other manifestations of hepatotoxicity following nitrofen ingestion included increased hepatic GSH peroxidase activity with 0 mg/kg nitrofen, and increased plasma enzyme activities for ALT, AST. and LDHL with 250 mg/kg. Blfenox lngestion (50 mg/kg) resulted in increased hepatlc GSH peroxidase activity. Nitrofen exposure increased total plasma thyroxlne (T4) concentratlon. These findings suggest that altricial nestllng kestrels are more sensitive to diphenyl ether herbicides than precocial young or adult birds.

  18. Poly(arylene ether)s That Resist Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul; Smith, Joseph G., Jr.

    1994-01-01

    Novel poly(arylene ether)s containing phosphine oxide (PAEPO's) made via aromatic nucleophilic displacement reactions of activated aromatic dihalides (or, in some cases, activated aromatic dinitro compounds) with new bisphenol monomers containing phosphine oxide. Exhibited favorable combination of physical and mechanical properties and resistance to monatomic oxygen in oxygen plasma environment. Useful as adhesives, coatings, films, membranes, moldings, and composite matrices.

  19. Ether and Relativity

    NASA Astrophysics Data System (ADS)

    Farhoudi, Mehrdad; Yousefian, Maysam

    2016-05-01

    We consider one of the fundamental debates in performing the relativity theory, namely, the ether and the relativity points of view, in a way to aid the learning of the subjects. In addition, we present our views and prospects while describing the issues that being accessible to many physicists and allowing broader views. Also, we very briefly review the two almost recent observations of the Webb redshift and the ultra high energy cosmic rays, and the modified relativity models that have been presented to justify them, wherein we express that these justifications have not been performed via a single model with a single mechanism.

  20. Induction of Crown Gall on Carrot Slices.

    ERIC Educational Resources Information Center

    Babich, H.; Fox, K. D.

    1998-01-01

    Argues that the transfer of plasmid from a bacterium to a plant cell has received little attention. Presents an experiment for studying this type of genetic transformation using the causative agent of crown gall, a malignant plant tumor. (DDR)

  1. Analysis of geophysical logs from six boreholes at Lariat Gulch, former U.S. Air Force site PJKS, Jefferson County, Colorado

    USGS Publications Warehouse

    Paillet, Frederick L.; Hodges, Richard E.; Corland, Barbara S.

    2002-01-01

    This report presents and describes geophysical logs for six boreholes in Lariat Gulch, a topographic gulch at the former U.S. Air Force site PJKS in Jefferson County near Denver, Colorado. Geophysical logs include gamma, normal resistivity, fluid-column temperature and resistivity, caliper, televiewer, and heat-pulse flowmeter. These logs were run in two boreholes penetrating only the Fountain Formation of Pennsylvanian and Permian age (logged to depths of about 65 and 570 feet) and in four boreholes (logged to depths of about 342 to 742 feet) penetrating mostly the Fountain Formation and terminating in Precambrian crystalline rock, which underlies the Fountain Formation. Data from the logs were used to identify fractures and bedding planes and to locate the contact between the two formations. The logs indicated few fractures in the boreholes and gave no indication of higher transmissivity in the contact zone between the two formations. Transmissivities for all fractures in each borehole were estimated to be less than 2 feet squared per day.

  2. Allene ether Nazarov cyclization.

    PubMed

    Tius, Marcus A

    2014-05-01

    The ease of synthesis and the exceptional reactivity of alkoxyallenes has led to their use in a large number of highly diverse applications. This Report describes their use in various versions of the allene ether Nazarov cyclization. Following a brief introduction to the Nazarov cyclization (Section 1), the oxidative cyclization of vinyl alkoxyallenes is discussed first (Section 2). Nazarov cyclizations of α-alkoxyallenyl vinyl ketones and of α-alkoxyallenyl vinyl tertiary carbinols are covered (Section 3). The discovery and the subsequent rational design of acetals that serve as chiral auxiliaries on the allene in highly enantioselective Nazarov cyclizations is explained (Section 4). Interrupted Nazarov cyclizations of alkoxyallenes that are generated in situ from the isomerization of propargyl ethers on solid supports are discussed, including the evolution of a highly diastereoselective, chiral auxiliary controlled version of the reaction. Some applications of the methodology to natural products total synthesis have been included so as to provide the reader with benchmarks with which to judge the utility of the methodology. PMID:24196585

  3. Selective extraction of cesium from acidic nitrate solutions with didodecylnaphthalenesulfonic acid synergized with bis(tert-butylbenzo)-21-crown-7

    SciTech Connect

    McDowell, W.J.; Case, G.N. ); McDonough, J.A.; Bartsch, R.A. )

    1992-12-01

    The behavior of other crown ether-synergized sulfonic acid extraction systems suggested that the title system would be selective for cesium. Synthesis of the new lipophilic crown ether, bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7), allowed testing of this hypothesis. Under nonloading conditions, the distribution coefficient for cesium between a toluene solution 0.025 M in didodecylnaphthalenesulfonic acid (HDDNS) and D(tBB)21C7 and an aqueous phase 0.1 M in nitric acid is 100 with separation factors of 1.2 from rubidium, 5.6 from potassium, and 294 from sodium. Under loading and competitive extraction conditions, the distribution coefficients were lower (5 for cesium), but the separation factors remained in the same order and of useful magnitude, 1.5 from rubidium, 6.4 from potassium, and 192 from sodium. Increasing the concentrations of D(tBB)21C7 and HDDNS in the organic phase gives higher distribution coefficients for cesium as did lower aqueous acid concentrations. 23 refs., 8 figs., 1 tab.

  4. Crown cover chart for oak savannas. Forest Service technical brief

    SciTech Connect

    Law, J.R.; Johnson, P.S.; Houf, G.

    1994-07-01

    Although oak savannas have been defined in many ways, they are characterized by scattered trees, largely comprised of oaks, and a sparse ground layer rich in grasses and forbs. The crown cover chart can be used to estimate the crown cover of trees as a percent of total area. Potential applications of the chart include monitoring changes in savanna crown cover, determining needed reductions in crown cover, and defining the savanna state. in restoring savannas that have grown into closed canopy stands, one can use the chart to estimate initial crown cover before restoration work is begun and again after crown cover has been reduced.

  5. Functionalization of poly(aryl ether ether ketone)

    SciTech Connect

    Wang, Fei; Roovers, J.

    1993-12-31

    Bromomethyl and dibromomethyl substituted poly(aryl ether ether ketone) have been prepared from methyl poly(aryl ether ether ketone) by bromination with bromine. These brominated polymers are intermediates that can be further functionalized by: hydrolysis, oxidation, substitution etc. A series of new functionalized PEEK polymers has been prepared. The functional group includes -CH{sub 2}OH, -CH{sub 2}OCH{sub 3}, -CHO, -COOH, -COOCH{sub 3}, -CH{sub 2}CN, -CH{sub 2}COOH, -CH{sub 2}OCOCH{sub 3}, -CH{sub 2}N{sup +}H(CH{sub 2}CH{sub 3}){sub 2}Br{sup {minus}}, -CH{sub 2}N(CH{sub 2}CH{sub 3}){sub 2}, -CH{sub 2}N{sup +}H(CH{sub 2}CH{sub 3}){sub 3}Br{sup {minus}}.

  6. Polyarylene Ethers with Improved Properties

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor); Jensen, B. J. (Inventor); Havens, S. J. (Inventor)

    1986-01-01

    This invention relates to novel polyarylene ethers which possess the combination of high strength, toughness, and high use temperature with ease of extrusion and formation into complex objects. These polyarylene ethers are suitable for use in adhesives, coatings, films, membranes, and composite matrices. The polyarylene ethers of this invention are the polycondensation products from the reaction of either 1,3-bis (4-chloro or fluorobenzoyl) benzene with any one of the following bisphenolic compounds: bis (3-hydroxyphenyl) methane; bis (4-hydroxyphenyl) methane; 1,1-dimethyl-bis (4-hydroxyphenyl)methane, or 9,9-bis (4-hydroxyphenyl) fluorene. Random and block copolymers are also comprehended.

  7. Imide/Arylene Ether Copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Hergenrother, Paul M.; Bass, Robert G.

    1991-01-01

    New imide/arylene ether copolymers prepared by reacting anhydride-terminated poly(amic acids) with amine-terminated poly(arylene ethers) in polar aprotic solvents. Each resulting copolymer may have one glass-transition temperature or two, depending on chemical structure and/or compatibility of block units. Most of copolymers form tough, solvent-resistant films with high tensile properties. Films cast from solution tough and flexible, and exhibit useful thermal and mechanical properties. Potentially useful as moldings, adhesives, or composite matrices. Because of flexible arylene ether blocks, these copolymers easier to process than polyimides.

  8. Complexation of Donor-Acceptor Substituted Aza-Crowns with Alkali and Alkaline Earth Metal Cations. Charge Transfer and Recoordination in Excited State.

    PubMed

    Volchkov, Valery V; Gostev, Fedor E; Shelaev, Ivan V; Nadtochenko, Viktor A; Dmitrieva, Svetlana N; Gromov, Sergey P; Alfimov, Mikhail V; Melnikov, Mikhail Ya

    2016-03-01

    Complexation between two aza-15-crown-5 ethers bearing electron donor and acceptor fragments and alkali and alkaline earth perchlorates has been studied using absorption, steady-state fluorescence and femtosecond transient absorption spectroscopy. The spectral-luminescent parameters, the stability and dissociation constants of the complexes were calculated. The intramolecular charge transfer reaction takes place both in the excited state of the crowns and their complexes 1:1; the latter is subjected to photorecoordination resulting in a weakening or a complete disruption of coordination bond between nitrogen atom and metal cation, disposed within a cavity of the crown. The compounds investigated can be viewed as novel optical molecular sensors for alkali and alkaline-earth metal cations. The photoejection of a metal cation into the bulk was not observed. PMID:26670689

  9. Rearrangements of Cycloalkenyl Aryl Ethers.

    PubMed

    Törincsi, Mercedesz; Nagy, Melinda; Bihari, Tamás; Stirling, András; Kolonits, Pál; Novak, Lajos

    2016-01-01

    Rearrangement reactions of cycloalkenyl phenol and naphthyl ethers and the acid-catalyzed cyclization of the resulting product were investigated. Claisen rearrangement afforded 2-substituted phenol and naphthol derivatives. Combined Claisen and Cope rearrangement resulted in the formation of 4-substituted phenol and naphthol derivatives. In the case of cycloocthylphenyl ether the consecutive Claisen and Cope rearrangements were followed by an alkyl migration. The mechanism of this novel rearrangement reaction is also discussed. PMID:27104504

  10. Imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1992-01-01

    Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

  11. 9. VIEW OF CROWN POINT LOOKING NORTH. VISTA HOUSE, UPPER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. VIEW OF CROWN POINT LOOKING NORTH. VISTA HOUSE, UPPER RETAINING WALL, FLAG POLE AND PARKING LOT IN VIEW. - Historic Columbia River Highway, Crown Point, East of Corbett, Troutdale, Multnomah County, OR

  12. Castable glass ceramic crowns and their reaction to endodontic therapy.

    PubMed

    Cohen, B D; Wallace, J A

    1991-07-01

    The purpose of this investigation was to determine how castable glass (Dicor) crowns would react to both cold testing and endodontic access intervention. Full crown preparations were made on six extracted maxillary teeth. The teeth were then forwarded to Dentsply International, York, Pa. Six castable glass crowns were fabricated to fit these teeth and returned to us. Subsequently the teeth were dried and the crowns were cemented. Scanning electron micrographs of the cemented crowns were made, and endodontic access openings were drilled. The teeth were also cold tested with standard methods. The teeth were then again subjected to scanning electron microscopy to determine any changes the crowns might have undergone. One crown cracked around the gingival collar as scanning electron microscopy was performed. The other crowns did not exhibit any problems such as cracking or crazing from either the access openings or the cold testing. PMID:1891229

  13. 11. DETAIL VIEW LOOKING EAST OF MASONRY RAILING AT CROWN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. DETAIL VIEW LOOKING EAST OF MASONRY RAILING AT CROWN POINT. ASHLAR EXAMPLE ON LEFT. RANDOM RUBBLE ON RIGHT. BEACON ROCK IN DISTANCE. - Historic Columbia River Highway, Crown Point, East of Corbett, Troutdale, Multnomah County, OR

  14. Space, Time, Ether, and Kant

    NASA Astrophysics Data System (ADS)

    Wong, Wing-Chun Godwin

    This dissertation focused on Kant's conception of physical matter in the Opus postumum. In this work, Kant postulates the existence of an ether which fills the whole of space and time with its moving forces. Kant's arguments for the existence of an ether in the so-called Ubergang have been acutely criticized by commentators. Guyer, for instance, thinks that Kant pushes the technique of transcendental deduction too far in trying to deduce the empirical ether. In defense of Kant, I held that it is not the actual existence of the empirical ether, but the concept of the ether as a space-time filler that is subject to a transcendental deduction. I suggested that Kant is doing three things in the Ubergang: First, he deduces the pure concept of a space-time filler as a conceptual hybrid of the transcendental object and permanent substance to replace the category of substance in the Critique. Then he tries to prove the existence of such a space-time filler as a reworking of the First Analogy. Finally, he takes into consideration the empirical determinations of the ether by adding the concept of moving forces to the space -time filler. In reconstructing Kant's proofs, I pointed out that Kant is absolutely committed to the impossibility of action-at-a-distance. If we add this new principle of no-action-at-a-distance to the Third Analogy, the existence of a space-time filler follows. I argued with textual evidence that Kant's conception of ether satisfies the basic structure of a field: (1) the ether is a material continuum; (2) a physical quantity is definable on each point in the continuum; and (3) the ether provides a medium to support the continuous transmission of action. The thrust of Kant's conception of ether is to provide a holistic ontology for the transition to physics, which can best be understood from a field-theoretical point of view. This is the main thesis I attempted to establish in this dissertation.

  15. 28. Photocopy of Crown Roller Mill illustration; originally published in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. Photocopy of Crown Roller Mill illustration; originally published in The Crown Roller Mill, Northwestern Miller 9 (May 21, 1880): 321; SHOWING WEST SIDE, LOOKING EAST - Crown Roller Mill, 105 Fifth Avenue, South, West Side Milling District, Minneapolis, Hennepin County, MN

  16. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  17. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  18. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  19. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  20. 21 CFR 872.3770 - Temporary crown and bridge resin.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Temporary crown and bridge resin. 872.3770 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3770 Temporary crown and bridge resin. (a) Identification. A temporary crown and bridge resin is a device composed of a material, such...

  1. Ionizable calixarene-crown ethers with high selectivity for radium over light alkaline earth metal ions

    SciTech Connect

    Chen, X.; Ji, M.; Fisher, D.R.; Wai, C.M.

    1999-11-15

    {alpha} particle emitters are of increasing interest as the radionuclide attached to monoclonal antibodies of other targeting mechanisms for applications in cell-directed therapy of cancer. {alpha} particles are more effective than {beta}{sup {minus}} particles for cell-killing and promise a more effective treatment of cancer than other forms of radiation. This is because {alpha} particles have high initial energy (4--8 MeV), short path lengths (40--80 {micro}m, or several cell diameters), and consequently greater energy dissipation per unit length. Cell-directed immunotherapy can help improve irradiation of tumor cells while sparing normal tissues. The success of this approach will require effective chemistry for attaching the radionuclide to the antibody. Therefore, a concerted effort has been directed toward the design of chelating agents capable of holding the desired {alpha}-emitting radionuclide, both selectively and with high stability, to the antibody.

  2. Sulfonimide-containing poly(arylene ether)s and poly(arylene ether sulfone)s, methods for producing the same, and uses thereof

    DOEpatents

    Hofmann, Michael A.

    2006-11-14

    The present invention is directed to sulfonimide-containing polymers, specifically sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, and processes for making the sulfonimide-containing poly(arylene ether)s and sulfonimide-containing poly(arylene ether sulfone)s, for use conductive membranes and fuel cells.

  3. Cementing porcelain-fused-to-metal crowns.

    PubMed

    Vadachkoria, D

    2009-12-01

    The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/micro flora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper cement. Popular use of cements for PFM crowns has shifted from zinc phosphate and glass ionomer cements to resin-reinforced glass ionomer, or RRGI, cements. This change has been rapid and profound. Dental cements have always been less than ideal materials, but this is shift to the relatively new RRGI category justified. Resin-reinforced glass ionomer (RRGI) cements appear to be better than zinc phosphate and glass ionomer cements when placing porcelain-to-metal crowns. RRGI cements, such as RelyX Luting, Fuji Plus and Vitremer Luting Cement, satisfy more of the ideal characteristics of PFM cementation than any other previous cement. Expansion of all three cements has not caused any apparent problems with the cements when used with PFM or metal crowns, but these cements, however, should be avoided when cementing all-ceramic crowns. PMID:20090144

  4. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  5. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  6. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  7. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  8. 21 CFR 872.3330 - Preformed crown.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... greater gold and metals of the platinum group intended to be affixed temporarily to a tooth after removal of, or breakage of, the natural crown (that portion of the tooth that normally protrudes above the...) tooth until the adult tooth erupts. (b) Classification. Class I (general controls). The device is...

  9. Aspergillosis in a red-crowned crane

    USGS Publications Warehouse

    Stroud, R.K.; Duncan, R.M.

    1983-01-01

    An unusual form of pulmonary aspergillosis in a red-crowned crane (Grus japonensis) is described in this report. The major lesion is unique because it closely resembles a lesion referred to as an aspergilloma. An aspergilloma is a single large granulomatous lesion that resembles a tumor and is caused by fungi of the genus Aspergillus.

  10. Cerec anterior crowns: restorative options with monolithic ceramic materials.

    PubMed

    Reich, Sven; Fiedlar, Kurt

    2013-01-01

    The aim of this article is to discuss the different types of monolithic ceramic crowns that can be placed on anterior teeth with existing shoulder preparations. Anterior crowns were indicated for the teeth 12 to 22 in the present case. The patient, a 65-year-old male, had received all-ceramic crowns 20 years earlier, which had started to develop cracks and palatal fractures over the last few years. The patient's teeth were prepared and four sets of crowns were fabricated using different monolithic ceramic materials: IPS e.max CAD, Cerec Blocs C In, VITABLOCS Real Life, and ENAMIC. Both shade characterization and crystallization firing were performed on the monolithic lithium disilicate glass ceramic crowns. The silicate ceramic crowns received glaze firing alone. The crowns made of hybrid ceramic (ENAMIC) were treated with a polymer sealant. PMID:24555406

  11. Crown Features Extraction from Low Altitude AVIRIS Data

    NASA Astrophysics Data System (ADS)

    Ogunjemiyo, S. O.; Roberts, D.; Ustin, S.

    2005-12-01

    Automated tree recognition and crown delineations are computer-assisted procedures for identifying individual trees and segmenting their crown boundaries on digital imagery. The success of the procedures is dependent on the quality of the image data and the physiognomy of the stand as evidence by previous studies, which have all used data with spatial resolution less than 1 m and average crown diameter to pixel size ratio greater than 4. In this study we explored the prospect of identifying individual tree species and extracting crown features from low altitude AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) data with spatial resolution of 4 m. The test site is a Douglas-fir and Western hemlock dominated old-growth conifer forest in the Pacific Northwest with average crown diameter of 12 m, which translates to a crown diameter pixel ratio less than 4 m; the lowest value ever used in similar studies. The analysis was carried out using AVIRIS reflectance imagery in the NIR band centered at 885 nm wavelength. The analysis required spatial filtering of the reflectance imagery followed by application of a tree identification algorithm based on maximum filter technique. For every identified tree location a crown polygon was delineated by applying crown segmentation algorithm. Each polygon boundary was characterized by a loop connecting pixels that were geometrically determined to define the crown boundary. Crown features were extracted based on the area covered by the polygons, and they include crown diameters, average distance between crowns, species spectral, pixel brightness at the identified tree locations, average brightness of pixels enclosed by the crown boundary and within crown variation in pixel brightness. Comparison of the results with ground reference data showed a high correlation between the two datasets and highlights the potential of low altitude AVIRIS data to provide the means to improve forest management and practices and estimates of critical

  12. 40 CFR 721.3380 - Anilino ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Anilino ether. 721.3380 Section 721... Anilino ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as anilino ether (P-83-910) is subject to reporting under this section...

  13. 40 CFR 721.3364 - Aliphatic ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aliphatic ether. 721.3364 Section 721... Aliphatic ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an aliphatic ether (PMN P-93-1381) is subject to reporting under...

  14. 40 CFR 721.3364 - Aliphatic ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aliphatic ether. 721.3364 Section 721... Aliphatic ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an aliphatic ether (PMN P-93-1381) is subject to reporting under...

  15. 40 CFR 721.3374 - Alkylenediolalkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylenediolalkyl ether. 721.3374... Substances § 721.3374 Alkylenediolalkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as an alkylenediolalkyl ether (PMN P-93-362) is subject...

  16. 40 CFR 721.3437 - Dialkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dialkyl ether. 721.3437 Section 721... Dialkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as dialkyl ether (PMN P-93-1308) is subject to reporting under this...

  17. 40 CFR 721.3374 - Alkylenediolalkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkylenediolalkyl ether. 721.3374... Substances § 721.3374 Alkylenediolalkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as an alkylenediolalkyl ether (PMN P-93-362) is subject...

  18. 40 CFR 721.3437 - Dialkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dialkyl ether. 721.3437 Section 721... Dialkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as dialkyl ether (PMN P-93-1308) is subject to reporting under this...

  19. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  20. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  1. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  2. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  3. 21 CFR 868.5420 - Ether hook.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ether hook. 868.5420 Section 868.5420 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5420 Ether hook. (a) Identification. An ether hook is a...

  4. Stabilizing distressed glass furnace melter crowns

    SciTech Connect

    1997-08-01

    Before the advent of pump casting, hot patching a melter or regenerator crown was extremely time and labor intensive. During these installations, known to many as the bucket brigade, the slurry was mixed on floor level and hauled in 50--65 lb batches up to 100 ft to the top of the crown. Today, in a single shift, a crew of seven can accomplish what took two days and a crew of {approximately}25 in the past. The first application of pump-casting zircon patch occurred on the AZS crown of an insulation-wool-glass furnace. For this application, 23 in. of insulating firebrick had to be removed to gain access to the fused AZS surface. The zircon patch was applied by pumping the mix from floor level up {approximately}60 ft to the crown by means of a concrete pump. Postmortems were performed on samples from two of the gas-fired TV-panel-glass furnaces. These postmortems were performed to determine if alterations occurred on the hot face of exposed zircon patch and, if so, how much alteration did occur. There was no destructive alteration because of alkali penetration into the patch. In fact, only trace amounts of lead, barium and strontium were detected, no further than 1 in. from the hot face. There was slight loss of P{sub 2}O{sub 5} on the hot face because of migration of phosphate toward the cold face, but it did not decrease the integrity of the patch. The dissociation of zircon was <3% baddelyite detected, all within an in. of the hot face.

  5. Fracture strength of ceramic monolithic crown systems of different thickness.

    PubMed

    Nordahl, Niklas; Vult von Steyern, Per; Larsson, Christel

    2015-09-01

    The objective of this study was to evaluate fracture strength of high-translucent (HTZ) and low-translucent (LTZ) zirconia and glass-ceramic (LDS) crowns. HTZ and LTZ crowns were made with thicknesses of; 0.3 mm, 0.5 mm, 0.7 mm, 1.0 mm, and 1.5 mm; and LDS crowns of 1.0 mm and 1.5 mm thicknesses. Each group consisted of 10 crowns. All crowns underwent artificial aging before loading until fracture. Mean fracture strengths varied from 450 N to 3,248 N in the LTZ group, 438 N to 3,487 N in the HTZ group, and 1,030 N to 1,431 N in the LDS group. The load at fracture of HTZ and LTZ crowns was equal. The load at fracture of yttria-stabilized tetragonal zirconia polycrystals crowns was significantly greater than LDS crowns (P = 0.000). Two types of fractures were recorded; complete and partial crack-like fracture. The crack type fracture occurred most frequently in all groups except in the thicker LTZ groups (1.0 mm and 1.5 mm). According to this study, there is no difference in strength between crowns made of high-translucent or low-translucent zirconia. At equal thickness, the strength of zirconia crowns was significantly greater than that of lithium-disilicate glass-ceramic. PMID:26369491

  6. Lacinilene C 7-methyl ether

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lacinilene C 7-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells....

  7. Desoxyhemigossypol-6-methyl-ether

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desoxyhemigossypol-6-methyl ether is an antimicrobial compound produced by the cotton plant in response to attack by pathogens. For the first time, we now report the crystal structure of this compound. This may prove useful in studies on the interaction of the compound with pathogenic fungal cells...

  8. Bis(chloromethyl)ether (BCME)

    Integrated Risk Information System (IRIS)

    Bis ( chloromethyl ) ether ( BCME ) ; CASRN 542 - 88 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments f

  9. Propylene glycol monomethyl ether (PGME)

    Integrated Risk Information System (IRIS)

    Propylene glycol monomethyl ether ( PGME ) ; CASRN 107 - 98 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assess

  10. Bis(chloroethyl)ether (BCEE)

    Integrated Risk Information System (IRIS)

    Bis ( chloroethyl ) ether ( BCEE ) ; CASRN 111 - 44 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments fo

  11. p,p\\'-Dibromodiphenyl ether

    Integrated Risk Information System (IRIS)

    p , p ' - Dibromodiphenyl ether ; CASRN 2050 - 47 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for

  12. Remarkable reinforcement of a supramolecular gel constructed by heteroditopic [18]crown-6-based molecular recognition.

    PubMed

    Noh, Eunyoung; Park, Sunhong; Kang, Sunwoo; Lee, Jin Yong; Lee, Jin Young; Jung, Jong Hwa

    2013-02-18

    The heteroditopic crown ether-based ligand 1 containing the diazafluorenylimino group as a binding site for the Zn(2+) and Cs(+) was synthesized. The ligand 1 can be gelated in DMSO/water with and without Cs(+) in the presence of the Zn(2+) ion. Interestingly, the remarkable gelation reinforcement of gel 1 occurred with Cs(+) in the presence of Zn(2+), which is due to the formation of a sandwich complex. According to DFT calculations, one Zn(2+) is bound to two diazafluorenylimino moieties in a tetrahedral structure. In addition, one Cs(+) ion is bound to two crown-rings. The Zn(2+)-diazafluorenylimino ligand gel without Cs(+) shows a spherical structure with 250-800 nm diameter, whereas the Zn(2+)-diazafluorenylimino-based ligand gel with Cs(+) shows a fiber structure with 60-70 nm diameter and several micrometers of lengths. The rheological properties of the Zn(2+)-diazafluorenylimino-based ligand gel were strongly dependent on the presence of Cs(+). PMID:23325608

  13. An Investigation Into the Integrity of Fit of Provisional Crowns Using Current Proprietary Temporary Crown Materials.

    PubMed

    Taylor, Philip D; Georgakis, Georgios; Niggli, Jason

    2016-06-01

    Three methods of direct provisional crown construction were investigated for accuracy of marginal fit. A modified proprietary crown coping was compared to Bis GMA and isobutyl methacrylate resin provisional crowns with margins modified by using a flowable composite and 'bead on' isobutyl methacrylate respectively. Measurement was at 50x magnification at seven sites over the fit surface. Data was analyzed using SPSS version 13.0.1 and measurement compared using the Mann Whitney test set at a significance level of 0.05. Reliability was checked using the Bland Altman test. Statistical significant differences were found between the three groups. The order of best fit was Bis-GMA and flowable composite > isobutyl methacrylate with 'bead on' margins > Bis-GMA modified implant temporary coping. The clinical significance is that the Bis GMA and flowable composite combination can be used with equal confidence to traditional methods of temporarisation. PMID:27424335

  14. [Gdansk combined crown with occlusal rest. 1. Clinical and laboratory preparation of combined crown with occlusal rest on the basis of cast crown].

    PubMed

    Tejchman, H; Czerwińska, W

    1990-01-01

    The combined crown used since many years in the Prosthetic Laboratory, Institute of Stomatology, Medical Academy in Gdańsk contains an occlusal rest basis of a cast crown (the metal part is of a gold alloy or chromium-nickel steel, with veneer of acrylateor Colorstat) provides, owing to a special preparation of the abutment tooth and laboratory procedure, full stabilization of the crown, protection of parodontium and good maintenance of the veneer which plays a cosmetic role in this type of crown. The combined crowns with occlusal rest are particularly suitable for supporting bridgeworks. They may be applied onto devitalized or live teeth since they require less extensive grinding of teeth. PMID:2103019

  15. A novel pollution pattern: Highly chlorinated biphenyls retained in Black-crowned night heron (Nycticorax nycticorax) and Whiskered tern (Chlidonias hybrida) from the Yangtze River Delta.

    PubMed

    Zhou, Yihui; Yin, Ge; Asplund, Lillemor; Qiu, Yanling; Bignert, Anders; Zhu, Zhiliang; Zhao, Jianfu; Bergman, Åke

    2016-05-01

    Contamination of organochlorine pesticides (OCPs), polychlorinated diphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and their methylated counterparts (MeO-PBDEs) were determined in Black-crowned night heron (Nycticorax nycticorax) and Whiskered tern (Chlidonias hybrida) from two drinking water sources, e.g. Tianmu lake and East Tai lake in Yangtze River Delta, China. A novel PCBs contamination pattern was detected, including 11% and 6.9% highly chlorinated biphenyls (PCBs with eight to ten chlorines) in relation to total PCB concentrations in the Black-crowned night heron and Whiskered tern eggs, respectively. The predominating OCPs detected in the present study were 4,4'-DDE, with concentration range 280-650 ng g(-1) lw in Black-crowned night heron and 240-480 ng g(-1) lw in Whiskered tern, followed by β-HCH and Mirex. 6-MeO-BDE-90 and 6-MeO-BDE-99 are the two predominant congeners of MeO-PBDEs whereas 6-OH-BDE-47 contributes mostly to the OH-PBDEs in both species. Contamination level was considered as median or low level compared global data. PMID:26705146

  16. The low temperature radiolysis of cis-syn-cis-dicyclohexano-18-crown-6 complexes with alkaline earth metal nitrates: An evidence for energy transfer to the macrocyclic ligand

    NASA Astrophysics Data System (ADS)

    Zakurdaeva, O. A.; Nesterov, S. V.; Shmakova, N. A.; Sokolova, N. A.; Feldman, V. I.

    2015-10-01

    Formation of paramagnetic intermediates in macrocyclic complexes of cis-syn-cis-dicyclohexano-18-crown-6 (DCH18C6) with alkaline earth metal nitrates under X-rays irradiation was studied by EPR spectroscopy. NO32- dianions appear to be predominant intermediate species in the samples irradiated at 77 K at low doses (up to 40 kGy). This result was interpreted as an evidence for energy transfer within the complex from crown ether to nitrate anion. Increase in the absorbed dose from 40 kGy to 284 kGy results in built-up of a new EPR signal assigned to macrocyclic -CH2-ĊH-O- radicals produced from crown ether moieties. Thermal annealing of the irradiated macrocyclic complexes at 273 К led to fast decay of NO32- . This process was accompanied by a formation of -CH2-ĊH-O- radicals in secondary reactions. The nature of the metal cations coordinated in the macrocycle cavity had no appreciable effect on the composition of radical products and their post-radiation transformations.

  17. Zirconia crowns - the new standard for single-visit dentistry?

    PubMed

    Wiedhahn, Klaus; Fritzsche, Günter; Wiedhahn, Claudine; Schenk, Olaf

    2016-01-01

    Zirconia crowns combine the advantages of metal restorations, such as minimally invasive tooth preparation and ease of cementation, with those of full ceramic crowns, such as low thermal conductivity and tooth color. With the introduction of a high-speed sintering procedure, it is possible to produce and cement zirconia crowns and small monolithic bridges in a Cerec Single Visit procedure. This new procedure is compared to established chairside methods. PMID:27027100

  18. An Overview of Preformed Metal Crowns. Part 1: Conventional Technique.

    PubMed

    Rogers, Helen J; Batley, Haris A; Deery, Chris

    2015-12-01

    This article details the clinical techniques for conventional preformed metal crown placement. It aims to increase the readers' awareness of the clinical advantages of preformed metal crowns and the indications for their use. The second part will discuss the Hall Technique. CPD/Clinical Relevance: This two-part article aims to guide the reader through the conventional and alternative techniques available for placement of a preformed metal crown whilst providing an update of the evidence for each. PMID:26855999

  19. Quantitative characterization of clumping in Scots pine crowns

    PubMed Central

    Stenberg, Pauline; Mõttus, Matti; Rautiainen, Miina; Sievänen, Risto

    2014-01-01

    Background and Aims Proper characterization of the clumped structure of forests is needed for calculation of the absorbed radiation and photosynthetic production by a canopy. This study examined the dependency of crown-level clumping on tree size and growth conditions in Scots pine (Pinus sylvestris), and determined the ability of statistical canopy radiation models to quantify the degree of self-shading within crowns as a result of the clumping effect. Methods Twelve 3-D Scots pine trees were generated using an application of the LIGNUM model, and the crown-level clumping as quantified by the crown silhouette to total needle area ratio (STARcrown) was calculated. The results were compared with those produced by the stochastic approach of modelling tree crowns as geometric shapes filled with a random medium. Key Results Crown clumping was independent of tree height, needle area and growth conditions. The results supported the capability of the stochastic approach in characterizing clumping in crowns given that the outer shell of the tree crown is well represented. Conclusions Variation in the whole-stand clumping index is induced by differences in the spatial pattern of trees as a function of, for example, stand age rather than by changes in the degree of self-shading within individual crowns as they grow bigger. PMID:24431344

  20. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective

  1. Water's Role in Reshaping a Macrocycle's Binding Pocket: Conformation-Specific Infrared and Ultraviolet Spectroscopy of BENZO-15-CROWN-5-(H_{2}O)_{n}-CLUSTERS (n = 1, 2)

    NASA Astrophysics Data System (ADS)

    Shubert, V. Alvin; Müller, Christian W.; James, William H. James, III; Zwier, Timothy S.

    2009-06-01

    Crown ethers are well-studied examples of flexible macrocycles with a high binding selectivity for substrates, especially cations. We investigated the conformational preferences of the singly and doubly complexed water clusters of the crown ethers benzo-15-crown-5 (B15C) and its amino-derivative 4'-aminobenzo-15-crown-5 (ABC) cooled in a supersonic jet expansion. The fluorescence excitation, resonance enhanced two-photon ionization (R2PI), UV-UV holeburning (UVHB), fluorescence-dip infrared (FDIR), resonant ion-dip infrared (RIDIR) and novel IR-IR-UV holeburning^{1} spectra allowed for the identification of two B15C-(H_{2}O)_{1} conformers and one ABC-(H_{2}O)_{1} conformer. These conformers are characterized by an all-planar arrangement of the atoms directly bound to the benzene ring in which the crown ether macrocycle opens up to a symmetric structure and accomodates a doubly and triply H-bonded H_{2}O molecule in two distinct ways, respectively. Two B15C-(H_{2}O)_{2} conformers and one ABC-(H_{2}O)_{2} conformer were identified. One of the B15C-(H_{2}O)_{2} conformers contains a macrocycle configuration identical to that found in the monohydrated clusters with an H-bonding topology in which the H_{2}O molecules occupy both available sites simultaneously. The second B15C-(H_{2}O)_{2} conformer is assigned to an H-bond pattern in which the two H_{2}O molecules are concatenated to form an H-bonded bridge involving only three of the four available O-H-bonds (see figure). (1) V. A. Shubert and T. S. Zwier, J. Phys. Chem. A, 2007, 111, 13283.

  2. Liquid Densities of Fluorinated Ethers

    NASA Astrophysics Data System (ADS)

    Nakazawa, Noriaki; Sako, Takeshi; Nakane, Takashi; Sekiya, Akira; Kawamura, Mitsutaka; Sato, Masahito; Mochizuki, Yuji; Takada, Naoto; Yasumoto, Masahiko

    The liquid densities of thirteen fluorinated ethers which are expected as promising candidates of CFC alternatives were measured at temperatures from 278 K to 323 K and atmospheric pressure. The fluorinated ethers used in this study are 1-difluoromethoxy-1,1, 2- trifluoroethane, 1-methoxy-1, 1,2,2-tetrafluoroethane, 1-methoxy-2,2 ,3 ,3- tetrafluoropropane, 1-methoxy-1-trifluoromethy1-2,2 ,2- trifluoroethane, 1-methoxy-1,1,2,2, 3-hexafluoropropane,1-difluoromethoxy-2,2, 3, 3 -tetrafluoropropane, 1-methoxy-heptafluoropropane,1-difluoromethoxy-2, 2, 3, 3, 3-pentafluoropropane, 1- (2, 2, 2-trifruoroethoxy) -1, 1, 2,2-tetrafluoroethane, 1-pentafluoroethoxy-1, 1, 2, 2-tetrafluoroethane,2-trifluoromethoxy-1, 1, 1,2-tetrafluorobutane, 1-proxynonafluorobutane, and 1-ethoxy-undecafluoropentane. The liquid density has been measured by the vibrating tube densitometer (ANTON PARR, DMA 602) within an error of 0.07%. The liquid densities decrease monotonically with increase of temperature.

  3. Measuring exposures to glycol ethers.

    PubMed

    Clapp, D E; Zaebst, D D; Herrick, R F

    1984-08-01

    In 1981, NIOSH began investigating the potential reproductive health effects resulting from exposures to a class of organic solvents known generically as glycol ethers (GE). This research was begun as a result of the NIOSH criteria document development program which revealed little data available on the health effects of glycol ether exposure. Toxicologic research was begun by NIOSH and other researchers which suggested substantial reproductive effects in animals. These animal data motivated a study of human exposures in the occupational setting. In 1981 and 1982 NIOSH conducted several walk-through surveys which included preliminary measurements of exposures in a variety of industries including painting trades, coal mining, production blending and distribution facilities, aircraft fueling, and communications equipment repair facilities. The human exposure data from these surveys is summarized in this paper with most results well below 1 parts per million (ppm) and only a few values approaching 10 ppm. Blood samples were collected at one site resulting in GE concentrations below the limit of detection. Exposures to airborne glycol ethers, in the industries investigated during the collection of this data, revealed several problems in reliably sampling GE at low concentrations. It became apparent, from the data and observations of work practices, that air monitoring alone provided an inadequate index of GE exposure. Further field studies of exposure to GE are anticipated, pending location of additional groups of exposed workers and development of more reliable methods for characterizing exposure, especially biological monitoring. PMID:6499824

  4. Evaluation of wild Juglans species for crown gall resistance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Paradox, the most widely used rootstock in CA walnut production, is highly susceptible to the causal agent of crown gall (CG) Agrobacterium tumefaciens. The bacterial pathogen induces the formation of large tumors around the crown of the tree resulting in a reduction in both vigor and yield. If left...

  5. Management of Rhizoctonia root and crown rot of subarbeet

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rhizoctonia root and crown rot is caused by the fungus Rhizoctonia solani and is one of the most severe soil-borne diseases of sugarbeet in Minnesota and North Dakota. Rhizoctonia root and crown rot may reduce yield significantly, and diseased beets may cause problems in storage piles. Fields with...

  6. Estimating canine tooth crown height in early Australopithecus.

    PubMed

    Plavcan, J Michael; Ward, Carol V; Paulus, Faydre L

    2009-07-01

    Canine tooth size reduction and the associated reduction in canine dimorphism is a basal hominin character that also provides important evidence for models of behavioral evolution. Two specimens of Australopithecus anamensis (KNM-KP 29287 and KNM-KP 29283) that do not preserve the canine crown, but do preserve the root or alveolus, appear to suggest that canine size variation and canine dimorphism in this species may have been greater than in other hominins. We evaluate canine root and crown dimensions in a series of extant hominoids, and estimate canine crown height in Australopithecus afarensis and A. anamensis. Our results demonstrate that it is possible to generate estimates of canine crown height from basal canine crown and root dimensions with a moderate degree of accuracy. Estimates of maxillary canine crown size for A. anamensis are slightly larger than those of A. afarensis, and are approximately the same size as canines of modern female chimpanzees. Estimated mandibular canine crown height is very similar in the two species. Variation within the A. anamensis sample of estimated canine crown heights is similar to that of modern humans, suggesting a low degree of sexual dimorphism. Inclusion of estimates for KNM-KP 29287 and KNM-KP 29283 does not substantially increase either the estimate of overall canine size or variation for A. anamensis. PMID:19482334

  7. Crystalline Imide/Arylene Ether Copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Hergenrother, Paul M.; Bass, Robert G.

    1991-01-01

    Series of imide/arylene ether block copolymers prepared by using arylene ether blocks to impart low melt viscosity, and imide blocks to provide high strength and other desirable mechanical properties. Work represents extension of LAR-14159 on imide/arylene ether copolymers in form of films, moldings, adhesives, and composite matrices. Copolymers potentially useful in variety of high-temperature aerospace and microelectronic applications.

  8. LaRC-ITPI/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Working, Dennis C.

    1991-01-01

    As part of an effort to develop high performance structural resins for aerospace applications, work has continued on block copolymers containing imide and arylene ether segments. The arylene ether block used in this study contains a bulky fluorene group in the polymer backbone while the imide block contains an arylene ketone segment similar to that in the arylene ether block and has been named LaRC-ITPI. A series of imide/arylene ether block and segmented copolymers were prepared and characterized. Films were prepared from these copolymers and mechanical properties were measured.

  9. Flow-Induced Crystallization of Poly(ether ether ketone)

    NASA Astrophysics Data System (ADS)

    Nazari, Behzad; Rhoades, Alicyn; Colby, Ralph

    The effects of an interval of shear above the melting temperature Tm on subsequent isothermal crystallization below Tm is reported for the premier engineering thermoplastic, poly(ether ether ketone) (PEEK). The effect of shear on the crystallization rate of PEEK is investigated by means of rheological techniques and differential scanning calorimetry (DSC) under a protocol of imposing shear in a rotational cone and plate rheometer and monitoring crystallization after quenching. The rate of crystallization at 320 °C was not affected by shear for shear rates <7 s-1 at 350 °C, whereas intervals of adequate shear at higher shear rates prior to the quench to 320 °C accelerated crystallization significantly. As the duration of the interval of shear above 7 s-1 is increased, the crystallization time decreases but at each shear rate eventually saturates once the applied specific work exceeds ~120 MPa. The annealing of the flow-induced precursors was also investigated. The nuclei were fairly persistent at temperatures close to 350 °C, however very unstable at temperatures above 375 °C. This suggests that the nanostructures formed under shear might be akin to crystalline lamellae of greater thickness, compared to quiescently crystallized lamellae.

  10. Crowns and other extra-coronal restorations: try-in and cementation of crowns.

    PubMed

    Wassell, R W; Barker, D; Steele, J G

    2002-07-13

    Having successfully negotiated the planning, preparation, impression and prescription of your crown, the cementation stage represents the culmination of all your efforts. This stage is not difficult, but a successful outcome needs as much care as the preceding stages. Once a restoration is cemented there is no scope for modification or repeat You have to get it right first time. Decemented crowns often have thick layers of residual cement suggesting problems with either initial seating or cement handling. When the fate of restorations costing hundreds of pounds depends on correct proportioning of cements and the quality of the mix, the value of a well-trained and experienced dental nurse is easy to see. Both dentist and nurse need a working knowledge of the materials they are handling. PMID:12171196

  11. Earliest known crown-group salamanders.

    PubMed

    Gao, Ke-Qin; Shubin, Neil H

    2003-03-27

    Salamanders are a model system for studying the rates and patterns of the evolution of new anatomical structures. Recent discoveries of abundant Late Jurassic and Early Cretaceous salamanders are helping to address these issues. Here we report the discovery of well-preserved Middle Jurassic salamanders from China, which constitutes the earliest known record of crown-group urodeles (living salamanders and their closest relatives). The new specimens are from the volcanic deposits of the Jiulongshan Formation (Bathonian), Inner Mongolia, China, and represent basal members of the Cryptobranchidae, a family that includes the endangered Asian giant salamander (Andrias) and the North American hellbender (Cryptobranchus). These fossils document a Mesozoic record of the Cryptobranchidae, predating the previous record of the group by some 100 million years. This discovery provides evidence to support the hypothesis that the divergence of the Cryptobranchidae from the Hynobiidae had taken place in Asia before the Middle Jurassic period. PMID:12660782

  12. Clinical outcome of double crown-retained implant overdentures with zirconia primary crowns

    PubMed Central

    Buergers, Ralf; Ziebolz, Dirk; Roediger, Matthias

    2015-01-01

    PURPOSE This retrospective study aims at the evaluation of implant-supported overdentures (IODs) supported by ceramo-galvanic double crowns (CGDCs: zirconia primary crowns + galvano-formed secondary crown). MATERIALS AND METHODS In a private practice, 14 patients were restored with 18 IODs (mandible: 11, maxilla: 7) retained by CGDCs on 4 - 8 implants and annually evaluated for technical and/or biological failures/complications. RESULTS One of the 86 inserted implants failed during the healing period (cumulative survival rate (CSR) implants: 98.8%). During the prosthetic functional period (mean: 5.9 ± 2.2 years), 1 implant demonstrated an abutment fracture (CSR-abutments: 98.2%), and one case of peri-implantitis was detected. All IODs remained in function (CSR-denture: 100%). A total of 15 technical complications required interventions to maintain function (technical complication rate: 0.178 treatments/patients/year). CONCLUSION Considering the small sample size, the use of CGDCs for the attachment of IODs is possible without an increased risk of technical complications. However, for a final evaluation, results from a larger cohort are required. PMID:26330981

  13. Survival rates of porcelain molar crowns-an update.

    PubMed

    Kassem, Amr Shebl; Atta, Osama; El-Mowafy, Omar

    2010-01-01

    The aim of this study was to identify recent studies that dealt with the clinical performance of porcelain molar crowns and to explore the possibility of grouping the findings from similar studies together to draw overall conclusions. A MEDLINE literature search was conducted in early 2009 covering the preceding 12 years. Seventeen studies were indentified. However, only seven met the specific inclusion criteria and were analyzed. Among seven studies, five European countries were covered. Five studies reported on Procera AllCeram molar crowns while one reported on In-Ceram Alumina and Spinell crowns and another on CEREC crowns. For comparison, one additional study that reported on premolar crowns was included. In the five Procera AllCeram studies, 235 molar crowns were evaluated for 5 or more years, of which 24 failed. When the results of the five studies on the performance of Procera AllCeram molar crowns were considered collectively, an overall failure rate of 10.2% was found at 5 or more years. Int J Prosthodont 2010;23:60-62. PMID:20234895

  14. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  15. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT....108 Ethyl ether. (a) Odor. Characteristic odor. (b) Specific gravity at 15.56 °/15.56 °C. Not...

  16. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  17. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  18. 27 CFR 21.108 - Ethyl ether.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Ethyl ether. 21.108 Section 21.108 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.108 Ethyl ether. (a) Odor. Characteristic odor....

  19. Purification of aqueous cellulose ethers

    SciTech Connect

    Bartscherer, K.A.; de Pablo, J.J.; Bonnin, M.C.; Prausnitz, J.M.

    1990-07-01

    Manufacture of cellulose ethers usually involves high amounts of salt by-products. For application of the product, salt must be removed. In this work, we have studied the injection of high-pressure CO{sub 2} into an aqueous polymer-salt solution; we find that upon addition of isopropanol in addition to CO{sub 2}, the solution separates into two phases. One phase is rich in polymer and water, and the other phase contains mostly isopropanol, water and CO{sub 2}. The salt distributes between the two phases, thereby offering interesting possibilities for development of a new purification process for water-soluble polymers. This work presents experimental phase-equilibrium data for hydroxyethyl cellulose and sodium carboxymethyl cellulose with sodium acetate and potassium sulfate, respectively, in the region 40{degree}C and 30 to 80 bar. Based on these data, we suggest a process for the manufacture and purification of water-soluble cellulose ethers. 15 refs., 14 figs., 9 tabs.

  20. Bacterial Utilization of Ether Glycols

    PubMed Central

    Fincher, Edward L.; Payne, W. J.

    1962-01-01

    A soil bacterium capable of using oligo- and polyethylene glycols and ether alcohols as sole sources of carbon for aerobic growth was isolated. The effects of substituent groups added to the ether bonds on the acceptability of the compounds as substrates were studied. Mechanisms for the incorporation of two-carbon compounds were demonstrated by the observation that acetate, glyoxylate, ethylene glycol, and a number of the tricarboxylic acid cycle intermediates served as growth substrates in minimal media. The rate of oxidation of the short-chained ethylene glycols by adapted resting cells varied directly with increasing numbers of two-carbon units in the chains from one to four. The amount of oxygen consumed per carbon atom of oligo- and polyethylene glycols was 100% of theoretical, but only 67% of theoretical for ethylene glycol. Resting cells oxidized oligo- and polyethylene glycols with 2 to 600 two-carbon units in the chains. Longer chained polyethylene glycols (up to 6,000) were oxidized at a very slow rate by these cells. Dehydrogenation of triethylene glycol by adapted cells was observed, coupling the reaction with methylene blue reduction. PMID:13945208

  1. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    PubMed

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified. PMID:27198539

  2. Turner syndrome isochromosome karyotype correlates with decreased dental crown width.

    PubMed

    Rizell, S; Barrenäs, M-L; Andlin-Sobocki, A; Stecksén-Blicks, C; Kjellberg, H

    2012-04-01

    The aim of this project was to study possible influences of Turner syndrome (TS) karyotype and the number of X chromosomes with intact short arm (p-arm) on dental crown width. Primary and permanent mesio-distal crown width was measured on plaster casts from 112 TS females. The influence on crown width of four karyotypes: 1. monosomy (45,X), 2. mosaic (45,X/46,XX), 3. isochromosome, and 4. other, and the number of intact X chromosomal p-arms were investigated. In comparisons between karyotypes, statistically significant differences were found for isochromosome karyotype maxillary second premolars, canines, laterals, mandibular first premolars, and canines, indicating that this karyotype was the most divergent as shown by the most reduced crown width. When each karyotype group were compared versus controls, all teeth in the isochromosome group were significantly smaller than controls (P < 0.01-0.001). The 45,X/46,XX karyotype expressed fewer and smaller differences from controls, while 45,X individuals seemed to display an intermediate tooth width compared with 45,X/46,XX and isochromosomes. No significant difference in crown width was found comparing the groups with one or two intact X chromosomal p-arms. Both primary and permanent teeth proved to have a significantly smaller crown width in the entire group of TS females compared to healthy females. We conclude that the isochromosome group deviates most from other karyotypes and controls, exhibiting the smallest dental crown width, while individuals with 45,X/46,XX mosaicism seemed to have a less affected crown width. An influence of the number of intact p-arms on crown width could not be demonstrated in this study. PMID:21303812

  3. Unique case of a geminated supernumerary tooth with trifid crown

    PubMed Central

    Ather, Hunaiza; Sheth, Sanket Milan; Muliya, Vidya Saraswathi

    2012-01-01

    Gemination, a relatively uncommon dental anomaly, is characterized by its peculiar representation as a tooth with a bifid crown and a common root and root canal. It usually occurs in primary dentition. To come across gemination in a supernumerary tooth is a rare phenomenon. The purpose of this paper is to present a unique case of hyperdontia wherein gemination in an impacted supernumerary tooth resulted in a trifid crown unlike the usual bifid crown. The role of conventional radiographs as well as computed tomography, to accurately determine the morphology and spatial location, and to arrive at a diagnosis, is also emphasized in this paper. PMID:23071971

  4. 6. BRIDGE LOOKING SOUTH FROM CROWN POINT STATE PARK SHOWING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. BRIDGE LOOKING SOUTH FROM CROWN POINT STATE PARK SHOWING SURROUNDING DEVELOPMENT FROM CONSTRUCTION OF DAM - Columbia River Bridge at Grand Coulee Dam, Spanning Columbia River at State Route 155, Coulee Dam, Okanogan County, WA

  5. Estimation of crown closure from AVIRIS data using regression analysis

    NASA Technical Reports Server (NTRS)

    Staenz, K.; Williams, D. J.; Truchon, M.; Fritz, R.

    1993-01-01

    Crown closure is one of the input parameters used for forest growth and yield modelling. Preliminary work by Staenz et al. indicates that imaging spectrometer data acquired with sensors such as the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) have some potential for estimating crown closure on a stand level. The objectives of this paper are: (1) to establish a relationship between AVIRIS data and the crown closure derived from aerial photography of a forested test site within the Interior Douglas Fir biogeoclimatic zone in British Columbia, Canada; (2) to investigate the impact of atmospheric effects and the forest background on the correlation between AVIRIS data and crown closure estimates; and (3) to improve this relationship using multiple regression analysis.

  6. Surgical crown lengthening: a periodontal and restorative interdisciplinary approach.

    PubMed

    Parwani, Simran R; Parwani, Rajkumar N

    2014-01-01

    Surgical crown lengthening helps to provide an adequate retention form for proper tooth preparation, thus enabling dentists to create esthetically pleasing and healthy restorations. Long-term stability requires accurate diagnosis and development of a comprehensive treatment plan in each case. This sequence of events stresses the importance of communication between the restorative dentist and the periodontist. This article presents 2 cases that involve surgical crown lengthening (including mucoperiosteal flap and ostectomy) for the restoration of teeth. PMID:25369395

  7. Failure Probability of Three Designs of Zirconia Crowns.

    PubMed

    Ramos, Gabriela Freitas; Monteiro, Evelyn Barbosa; Bottino, Marco Antonio; Zhang, Yu; Marques de Melo, Renata

    2015-01-01

    This study used a two-parameter Weibull analysis for evaluation of the lifespan of fully or partially porcelain-/glaze-veneered zirconia crowns after fatigue test. A sample of 60 first molars were selected and prepared for full-coverage crowns with three different designs (n = 20): traditional (crowns with zirconia framework covered with feldspathic porcelain), modified (crowns partially covered with veneering porcelain), and monolithic (full-contour zirconia crowns). All specimens were treated with a glaze layer. Specimens were subjected to mechanical cycling (100 N, 3 Hz) with a piston with a hemispherical tip (Ø = 6 mm) until the specimens failed or up to 2 × 10⁶ cycles. Every 500,000 cycles, the fatigue tests were interrupted and stereomicroscopy (10×) was used to inspect the specimens for damage. The authors performed Weibull analysis of interval data to calculate the number of failures in each interval. The types and numbers of failures according to the groups were: cracking (13 traditional, 6 modified) and chipping (4 traditional) of the feldspathic porcelain, followed by delamination (1 traditional) at the veneer/core interface and debonding (2 monolithic) at the cementation interface. Weibull parameters (β, scale; η, shape), with a two-sided confidence interval of 95%, were: traditional-1.25 and 0.9 × 10⁶ cycles; modified-0.58 and 11.7 × 10⁶ cycles; and monolithic-1.05 and 16.5 × 10⁶ cycles. Traditional crowns showed greater susceptibility to fatigue, the modified group presented higher propensity to early failures, and the monolithic group showed no susceptibility to fatigue. The modified and monolithic groups presented the highest number of crowns with no failures after the fatigue test. The three crown designs presented significantly different behaviors under fatigue. The modified and monolithic groups presented less probability of failure after 2 × 10⁶ cycles. PMID:26509988

  8. Failure probability of three designs of zirconia crowns

    PubMed Central

    Ramos, G. Freitas; Monteiro, E. Barbosa Carmona; Bottino, M.A.; Zhang, Y.; de Melo, R. Marques

    2015-01-01

    Objectives This study utilized a 2-parameter Weibull analysis for evaluation of lifetime of fully or partially porcelain-/glaze-veneered zirconia crowns after fatigue test. Methods Sixty first molars were selected and prepared for full-coverage crowns with three different designs(n = 20): Traditional –crowns with zirconia framework covered with feldspathic porcelain; Modified– crowns partially covered with veneering porcelain; and Monolithic–full-contour zirconia crowns. All specimens were treated with a glaze layer. Specimens were subjected to mechanical cycling (100N, 3Hz) with a piston with hemispherical tip (Ø=6 mm) until the specimens failed or up to 2×106 cycles. Every 500,000 cycles intervals, the fatigue tests were interrupted, and stereomicroscopy (10 X) was used to inspect the specimens for damage. We performed Weibull analysis of interval data to calculate the number of failures in each interval. Results The types and number of failures according to the groups were: cracking (Traditional-13, Modified-6) and chipping (Traditional-4) of the feldspathic porcelain, followed by delamination (Traditional-1) at the veneer/core interface and debonding (Monollithic-2) at the cementation interface. Weibull parameters (beta, scale; and eta, shape), with a two-sided confidence interval of 95%, were: Traditional – 1.25 and 0.9 × 106cycles; Modified– 0.58 and 11.7 × 106 cycles; and Monolithic – 1.05 and 16.5 × 106 cycles. Traditional crowns showed greater susceptibility to fatigue, the Modified group presented higher propensity to early failures, and the Monolithic group showed no susceptibility to fatigue. The Modified and Monolithic groups presented the highest number of crowns with no failures after the fatigue test. Conclusions The three crown designs presented significantly different behaviors under fatigue. The Modified and the Monolithic groups presented less probability to failure after 2×106cycles. PMID:26509988

  9. Composite fuselage crown panel manufacturing technology

    NASA Technical Reports Server (NTRS)

    Willden, Kurtis; Metschan, S.; Grant, C.; Brown, T.

    1992-01-01

    Commercial fuselage structures contain significant challenges in attempting to save manufacturing costs with advanced composite technology. Assembly issues, material costs, and fabrication of elements with complex geometry are each expected to drive the cost of composite fuselage structures. Boeing's efforts under the NASA ACT program have pursued key technologies for low-cost, large crown panel fabrication. An intricate bond panel design and manufacturing concepts were selected based on the efforts of the Design Build Team (DBT). The manufacturing processes selected for the intricate bond design include multiple large panel fabrication with the Advanced Tow Placement (ATP) process, innovative cure tooling concepts, resin transfer molding of long fuselage frames, and utilization of low-cost material forms. The process optimization for final design/manufacturing configuration included factory simulations and hardware demonstrations. These efforts and other optimization tasks were instrumental in reducing cost by 18 percent and weight by 45 percent relative to an aluminum baseline. The qualitative and quantitative results of the manufacturing demonstrations were used to assess manufacturing risks and technology readiness.

  10. Standardisation of crown-rump length measurement.

    PubMed

    Ioannou, C; Sarris, I; Hoch, L; Salomon, L J; Papageorghiou, A T

    2013-09-01

    Correct estimation of gestational age is essential for any study of ultrasound biometry and for everyday clinical practice. However, inconsistency in pregnancy dating may occur through differences in measurement methods or errors during measurement. In the INTERGROWTH-21(st) Project, pregnancies are dated by the last menstrual period, provided that it is certain and associated with a regular menstrual cycle, and the gestational age by dates concurs with a first-trimester ultrasound crown-rump length (CRL) estimation. Hence, there was a need to standardise CRL measurement methodology across the study sites in this international, multicentre project to avoid systematic differences in dating. To achieve uniformity we undertook the following steps: the ultrasound technique was standardised by disseminating an illustrated, operating manual describing CRL plane landmarks and calliper application, and posters describing the correct acquisition technique were disseminated for quick reference. To ensure that all ultrasonographers understood the methodology, they forwarded a log-book to the INTERGROWTH-21(st) Ultrasound Coordinating Unit, containing the answers to a written test on the manual material and five images of a correctly acquired CRL. Interpretation of CRL was also standardised by ensuring that the same CRL regression formula was used across all study sites. These methods should minimise potential systematic errors in dating associated with pooling data from different health institutions, and represent a model for standardising CRL measurement in future studies. PMID:23678951

  11. The energetic characterization of pineapple crown leaves.

    PubMed

    Braga, R M; Queiroga, T S; Calixto, G Q; Almeida, H N; Melo, D M A; Melo, M A F; Freitas, J C O; Curbelo, F D S

    2015-12-01

    Energetic characterization of biomass allows for assessing its energy potential for application in different conversion processes into energy. The objective of this study is to physicochemically characterize pineapple crown leaves (PC) for their application in energy conversion processes. PC was characterized according to ASTM E871-82, E1755-01, and E873-82 for determination of moisture, ash, and volatile matter, respectively; the fixed carbon was calculated by difference. Higher heating value was determined by ASTM E711-87 and ash chemical composition was determined by XRF. The thermogravimetric and FTIR analyses were performed to evaluate the thermal decomposition and identify the main functional groups of biomass. PC has potential for application in thermochemical processes, showing high volatile matter (89.5%), bulk density (420.8 kg/m(3)), and higher heating value (18.9 MJ/kg). The results show its energy potential justifying application of this agricultural waste into energy conversion processes, implementing sustainability in the production, and reducing the environmental liabilities caused by its disposal. PMID:26233737

  12. Cost studies for commercial fuselage crown designs

    NASA Technical Reports Server (NTRS)

    Walker, T. H.; Smith, P. J.; Truslove, G.; Willden, K. S.; Metschan, S. L.; Pfahl, C. L.

    1991-01-01

    Studies were conducted to evaluate the cost and weight potential of advanced composite design concepts in the crown region of a commercial transport. Two designs from each of three design families were developed using an integrated design-build team. A range of design concepts and manufacturing processes were included to allow isolation and comparison of cost centers. Detailed manufacturing/assembly plans were developed as the basis for cost estimates. Each of the six designs was found to have advantages over the 1995 aluminum benchmark in cost and weight trade studies. Large quadrant panels and cobonded frames were found to save significant assembly labor costs. Comparisons of high- and intermediate-performance fiber systems were made for skin and stringer applications. Advanced tow placement was found to be an efficient process for skin lay up. Further analysis revealed attractive processes for stringers and frames. Optimized designs were informally developed for each design family, combining the most attractive concepts and processes within that family. A single optimized design was selected as the most promising, and the potential for further optimization was estimated. Technical issues and barriers were identified.

  13. Electronic and infrared spectral and thermal studies on the molecular complex of dibenzo-18-crown-6 and iodine

    NASA Astrophysics Data System (ADS)

    Shahada, L. A.

    2005-06-01

    The interaction of the crown ether dibenzo-18-crown-6 (DBC) with iodine has been studied in CHCl 3 at room temperature. The charge-transfer absorptions, far infrared and thermal measurements of the formed charge-transfer complex were recorded and discussed. The results obtained show the formation of the pentaiodide complex with the general formula [(DBC)] + I 5-. The pentaiodide ion, I 5-, is described as I 3-(I 2) confirmed by the observation of the characteristic absorptions for I 3- ion around 365 and 290 nm. In addition, the far infrared spectrum of the solid complex shows the three vibrations of I 3- unit is at 141, 113 and 71 cm -1 assigned to νas(I-I) and νs(I-I) and δ(I 3-), respectively, while the band related to the vibration of I 2 unit is observed at 180 cm -1. Vibration analysis of the obtained data shows that the symmetry of I 3- unit could be non-linear with C 2 v symmetry. The structure of the formed pentaiodide complex was further supported by thermal gravimetric analysis measurements.

  14. Manganese sequestration and improved high-temperature cycling of Li-ion batteries by polymeric aza-15-crown-5

    NASA Astrophysics Data System (ADS)

    Li, Zicheng; Pauric, Allen D.; Goward, Gillian R.; Fuller, Timothy J.; Ziegelbauer, Joseph M.; Balogh, Michael P.; Halalay, Ion C.

    2014-12-01

    Mn cation trapping by polymeric aza-15-crown-5 ethers is an effective means for mitigating the consequences of Mn dissolution in Li-ion batteries. Mn cations trapping was investigated in lithium manganese oxide (LMO) spinel-graphite (GR) cells containing 1 M LiPF6 in ethylene carbonate (EC):diethyl carbonate (DEC) 1:2 v/v. A commercial polyolefin separator membrane coated with poly[divinylbenzene-(vinylbenzyl-aza-15-crown-5)-vinylbenzylchloride)] effected a 39% reduction in capacity loss rate during cycling at 50 °C with 100% depth of discharge (DOD) at C/5 rate. Simultaneously, a 50-60% reduction in the Mn deposited at the negative electrode, and a 6× to 10× increase in the Mn on the coated separator were observed for cells with coated separators, over baseline cells with plain separators. X-ray absorption near-edge spectroscopy (XANES) yielded average oxidation states near +3 for Mn cations in graphite electrodes and separators from cycled cells, suggesting that Mn metal or in oxidation state +2 can only be minor fractions of the Mn existing outside the positive electrode. We discuss the implications of these results for choosing an optimal chelating agent. We also show that the cation chelating polymer reported here is compatible with existing manufacturing processes for Li-ion battery separators.

  15. Interaction of Cesium Ions with Calix[4]arene-bis(t-octylbenzo-18-crown-6): NMR and Theoretical Study

    SciTech Connect

    Kriz, Jaroslav; Dybal, Jiri; Vanura, Petr; Moyer, Bruce A

    2011-01-01

    Using 1H, 13C, and 133Cs NMR spectra, it is shown that calix[4]arene-bis (t-octylbenzo-18-crown-6) (L) forms complexes with one (L 3 Cs ) and two (L 3 2Cs ) Cs ions offered by cesium bis(1,2-dicarbollide) cobaltate (CsDCC) in nitrobenzene-d5. The ions interact with all six oxygen atoms in the crown-ether ring and the electrons of the calixarene aromatic moieties. According to extraction technique, the stability constant of the first complex is log nb(L 3 Cs ) = 8.8 ( 0.1. According to 133Cs NMR spectra, the value of the equilibrium constant of the second complex is log Knb (2)(L 3 2Cs ) = 6.3(0.2, i.e., its stabilization constant is log nb(L 3 2Cs ) = 15.1 ( 0.3. Self-diffusion measurements by 1H pulsed-field gradient (PFG) NMRcombined with density functional theory (DFT) calculations suggest that one DCC ion is tightly associated with L 3 Cs , decreasing its positive charge and consequently stabilizing the second complex, L 3 2Cs . Using a saturation-transfer 133Cs NMR technique, the correlation times ex of chemical exchange between L 3 Cs and L 3 2Cs as well as between L 3 2Cs and free Cs ions were determined as 33.6 and 29.2 ms, respectively.

  16. Solvent-induced crystallization of poly(ether ether ketone)

    NASA Astrophysics Data System (ADS)

    McPeak, Jennifer Lynne

    The purpose of this study was learn how the diffusion, swelling, and crystallization processes are coupled during solvent-induced crystallization of poly(ether ether ketone) (PEEK). Unoriented amorphous PEEK films were immersed in aprotic organic liquids at ambient temperature and bulk properties or characteristics were monitored as a function of immersion time. The sorption behavior, T g and Tm° suppression, crystallinity, and dynamic mechanical response were correlated as a function of solvent chemistry and immersion time. The saturation time of methylene chloride, 1,3-dichloropropane, tetrahydrofuran, cyclopentanone, chlorobenzene, toluene, diethyl ketone, and ethylbenzene in amorphous PEEK films were found to range from hours to days depending on the level of polymer-solvent interactions. In-situ isochronal DMA spectra show that the Tg of PEEK was suppressed from 150°C to below ambient temperature such that crystallization was kinetically feasible during ambient immersion. In addition, an increase in viscoelastic dispersion was attributed to the presence of crystallinity. From dynamic mass uptake and wide-angle x-ray diffraction (WAXD) results, it was found that the bulk sorption rate was equal to the bulk crystallization rate for all solvent systems that promoted SINC and PEEK exhibited diffusion-limited crystallization, irrespective of the nature of the transport mechanism. In addition, the solvent-induced crystals exhibit preferred orientation as supported by photographic WAXD. A distinct sorption front, observed with scanning electron microscopy, further supports the scenario of diffusion-controlled crystallization and one-dimensional diffusion. Isothermal DMA spectra for THF, cyclopentanone, and chlorobenzene, indicate that, as the solvent diffuses into the films, the stiffness of the polymer decreases at short times, begins to increase, and then reaches a relatively time-independent value. It was determined that the initial decrease in the storage

  17. Crown depth as a result of evolutionary games: decreasing solar angle should lead to shallower, not deeper crowns.

    PubMed

    Vermeulen, Peter Johannes

    2014-06-01

    There is a general notion in the literature that, with increasing latitude, trees have deeper crowns as a result of a lower solar elevation angle. However, these predictions are based on models that did not include the effects of competition for light between individuals. Here, I argue that there should be selection for trees to increase the height of the crown base, as this decreases shading by neighbouring trees, leading to an evolutionarily stable strategy (ESS). Because the level of between-tree shading increases with decreasing solar angle, the predicted ESS will shift to higher crown base height. This argument is supported by a simulation model to check for the effects of crown shape and the change of light intensity that occurs with changing solar angle on model outcomes. So, the lower solar angle at higher latitudes would tend to select for shallower, and not deeper, crowns. This casts doubt on the common belief that a decreasing solar angle increases crown depth. More importantly, it shows that different assumptions about what should be optimized can lead to different predictions, not just for absolute trait values, but for the direction of selection itself. PMID:24548219

  18. Development of Conductometric Sensor Based on 25,27-Di-(5-thio-octyloxy)calix[4]arene-crown-6 for Determination of Ammonium.

    PubMed

    Saiapina, O Y; Kharchenko, S G; Vishnevskii, S G; Pyeshkova, V M; Kalchenko, V I; Dzyadevych, S V

    2016-12-01

    The conductometric sensor based on 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 was developed for the quantitative analysis of ammonium. The calixarene was immobilized on the surface of the planar interdigitated electrodes by attachment of its dialkyl sulfide groups to the surface of the gold electrodes. The intrinsic ability of the calixarene to capture ammonium was studied in the conductometric measuring mode and by the electrochemical impedance spectroscopy. The developed sensor showed high selectivity to ammonium in the presence of mono-, di-, and trivalent cations. Selective and highly sensitive detection of ammonium resulted from the complexation between the ammonium ions and a crown-ether fragment of the upper rim of the 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 macrocycle. The developed sensor had high signal repeatability. Its sensitivity was found to be satisfactory for the forthcoming sensor application in the water-sample analysis; the linear range was 0.01-1.5 mM and limit of detection 10 μM. PMID:26911569

  19. Alkali metal, alkaline earth metal, and ammonium ion selectivities of dibenzo-16-crown-5 compounds with functional side arms in ion-selective electrodes

    SciTech Connect

    Ohki, Akira; Lu, J.P.; Huang, X.; Bartsch, R.A. )

    1994-12-01

    Potentiometric selectivities of 11 dibenzo-16-crown-5 compounds for alkali metal, alkaline earth metal, and ammonium ions have been determined in solvent polymeric membrane electrodes. The ionophores bear one or two pendent groups on the central carbon of the three-carbon bridge in the polyether ring. Side-arm variation includes OCH[sub 3], OCH[sub 2]CH[sub 2]OCH[sub 3], OCH[sub 2]CO[sub 2]C[sub 2]H[sub 5], OCH[sub 2]C(O)N(C[sub 2]H[sub 5])[sub 2], and OCH[sub 2]C(O)N(C[sub 5]H[sub 11])[sub 2] units. Attachment of a propyl group to the ring carbon that bears an extended, oxygen-containing side arm increases the selectivity for Na[sup +] relative to larger alkali metal and alkaline earth metal cations. For a given side arm, a linear relationship is obtained when the enhancement in Na[sup +] selectivity produced by attachment of a geminal propyl group is plotted against the diameter of the interference ion. Potentiometric responses of the dibenzo-16-crown-5 compounds are rationalized in terms of the crown ether ring size and the oxygen basicity, conformational positioning, and rigidity of the side arm. 22 refs., 3 figs., 2 tabs.

  20. Development of Conductometric Sensor Based on 25,27-Di-(5-thio-octyloxy)calix[4]arene-crown-6 for Determination of Ammonium

    NASA Astrophysics Data System (ADS)

    Saiapina, O. Y.; Kharchenko, S. G.; Vishnevskii, S. G.; Pyeshkova, V. M.; Kalchenko, V. I.; Dzyadevych, S. V.

    2016-02-01

    The conductometric sensor based on 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 was developed for the quantitative analysis of ammonium. The calixarene was immobilized on the surface of the planar interdigitated electrodes by attachment of its dialkyl sulfide groups to the surface of the gold electrodes. The intrinsic ability of the calixarene to capture ammonium was studied in the conductometric measuring mode and by the electrochemical impedance spectroscopy. The developed sensor showed high selectivity to ammonium in the presence of mono-, di-, and trivalent cations. Selective and highly sensitive detection of ammonium resulted from the complexation between the ammonium ions and a crown-ether fragment of the upper rim of the 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 macrocycle. The developed sensor had high signal repeatability. Its sensitivity was found to be satisfactory for the forthcoming sensor application in the water-sample analysis; the linear range was 0.01-1.5 mM and limit of detection 10 μM.

  1. Phenylethynl-terminated poly(arylene ethers)

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Bryant, Robert G. (Inventor); Hergenrother, Paul M. (Inventor)

    1993-01-01

    Phenylethynyl-terminated poly(arylene ethers) are prepared in a wide range of molecular weights by adjusting monomer ratio and adding an appropriate amount of 4-fluoro- 4'-phenylethynyl benzophenone during polymer synthesis. The resulting phenylethynyl-terminated poly(arylene ethers) react and crosslink upon curing for one hour at 350 C to provide materials with improved solvent resistance, higher modulus, and better high temperature properties than the linear, uncrosslinked polymers.

  2. Imide/arylene ether copolymers. I

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    The preparation of a series of novel imide/arylene ether copolymers is described together with the results of viscosity and DSC Tg(Tm) measurements. The copolymers were synthesized from an arylene ether block and either an amorphous or semicrystalline imide block. One block copolymer was end-capped, and the molecular weight was controlled to improve compression moldability. The paper also presents results of mechanical properties tests on copolymer samples.

  3. Open-grown crown radius of eleven bottomland hardwood species: Prediction and use in assessing stocking

    SciTech Connect

    Goelz, J.C.G.

    1996-08-01

    Equations were prepared to predict crown radius for eleven species of open-grown bottomland hardwood trees. Crown radius was predicted as a function of diameter at breast height (dbh) and as a function of dbh, total height, and crown ratio. Equations were prepared for individual species and species groups. Pecan has the largest crowns over a broad range of dbh. Eastern cottonwood has the smallest crowns for most levels of dbh. Sweetgum has relatively small crowns for trees of small dbh, but crown radius is comparable to most species at the largest dbh. The crown radius predictions may be used to calculate crown competition factor. B-lines of stocking may be calculated that represent a stand of one species as well as a mixed-species stand of any particular species proportion.

  4. 3D statistical failure analysis of monolithic dental ceramic crowns.

    PubMed

    Nasrin, Sadia; Katsube, Noriko; Seghi, Robert R; Rokhlin, Stanislav I

    2016-07-01

    For adhesively retained ceramic crown of various types, it has been clinically observed that the most catastrophic failures initiate from the cement interface as a result of radial crack formation as opposed to Hertzian contact stresses originating on the occlusal surface. In this work, a 3D failure prognosis model is developed for interface initiated failures of monolithic ceramic crowns. The surface flaw distribution parameters determined by biaxial flexural tests on ceramic plates and point-to-point variations of multi-axial stress state at the intaglio surface are obtained by finite element stress analysis. They are combined on the basis of fracture mechanics based statistical failure probability model to predict failure probability of a monolithic crown subjected to single-cycle indentation load. The proposed method is verified by prior 2D axisymmetric model and experimental data. Under conditions where the crowns are completely bonded to the tooth substrate, both high flexural stress and high interfacial shear stress are shown to occur in the wall region where the crown thickness is relatively thin while high interfacial normal tensile stress distribution is observed at the margin region. Significant impact of reduced cement modulus on these stress states is shown. While the analyses are limited to single-cycle load-to-failure tests, high interfacial normal tensile stress or high interfacial shear stress may contribute to degradation of the cement bond between ceramic and dentin. In addition, the crown failure probability is shown to be controlled by high flexural stress concentrations over a small area, and the proposed method might be of some value to detect initial crown design errors. PMID:27215334

  5. Anaerobic biodegradation of ether compounds by ether bond-cleaving bacteria and methanogenic consortia

    SciTech Connect

    Dwyer, D.F.

    1989-01-01

    Ether compounds are manufactured for use in nonionic detergents, plastics, pesticides and other products and occur as toxic organic compounds, the most famous being tetrachlorodibenzo-p-dioxin. Ether compounds were considered recalcitrant to anaerobic biodegradation due to the lack of an appropriate oxidant for ether bond-cleavage in reducing environments. Many of these compounds reside in anaerobic environments or are exposed to anaerobic waste treatment processes. Thus, it is of interest to identify: (i) whether ether compounds are anaerobically biodegradable, (ii) the anaerobic microorganisms able to degrade these compounds, and (iii) the mechanism(s) of anaerobic ether bond-cleavage. The ether bonds of polyethylene glycol (PEG; HO-(CH{sub 2}CH{sub 2}-O-){sub n}H), phenyl ether ((C{sub 6}H{sub 5}){sub 2}O), and dibenzo-p-dioxin ((C{sub 6}H{sub 4}){sub 2}O{sub 2}) were shown to be degraded in methanogenic consortia enriched with these compounds and polyethoxylate (nonionic) surfactants as substrates. Two anaerobic microorganisms which used PEGs as sole substrates were isolated and characterized. Desulfovibrio desulfuricans strain DG2 degraded the monomer ethylene glycol and oligomers up to tetraethylene glycol (HO-(CH{sub 2}CH{sub 2}-O-){sub 4}H) in length. Bacteroides sp. strain PG1 degraded diethylene glycol and all other polymer lengths of PEG. PEGs were degraded by Bacteroides sp. strain PG1 via an external depolymerization which was either a hydrolytic or a reductive cleavage of the ether bond. The ether bond of diaryl ethers was apparently cleaved by a reductive mechanism which produced benzene and phenol as products from phenyl ether degradation and benzene and, by indirect analysis, catechol from dibenzo-dioxin.

  6. Gingival health in relation to clinical crown length: a case report

    PubMed Central

    2009-01-01

    Introduction Gingival margin position in relation to synthetic crowns and crown length could be etiological factors in gingival health. Case presentation A 27-year-old male presented with necrotizing ulcerative gingivitis with short clinical crowns suggestive of altered passive eruption. Three years after the initial diagnosis, he presented with crowns on the maxillary incisors. There were short clinical crowns and marked gingival inflammation. Conclusion Placement of the crown margin could be an etiological factor in gingival inflammation. Therefore, should the margin be subgingival, equigingival or supragingival? PMID:20062553

  7. Gingival health in relation to clinical crown length: a case report

    PubMed Central

    2009-01-01

    Introduction Gingival margin position in relation to synthetic crowns and crown length could be etiological factors in gingival health. Case presentation A 27-year-old male presented with necrotizing ulcerative gingivitis with short clinical crowns suggestive of altered passive eruption. Three years after the initial diagnosis, he presented with crowns on the maxillary incisors. There were short clinical crowns and marked gingival inflammation. Conclusion Placement of the crown margin could be an etiological factor in gingival inflammation. Therefore, should the margin be subgingival, equigingival or supragingival? PMID:20184687

  8. Biology and control of the raspberry crown borer (Lepidoptera: Sesiidae).

    PubMed

    McKern, Jacquelyn A; Johnson, Donn T; Lewis, Barbara A

    2007-04-01

    This study explored the biology of raspberry crown borer, Pennisetia marginata (Harris) (Lepidoptera: Sesiidae), in Arkansas and the optimum timing for insecticide and nematode applications. The duration of P. marginata's life cycle was observed to be 1 yr in Arkansas. Insecticide trials revealed that bifenthrin, chlorpyrifos, imidacloprid, metaflumizone, and metofluthrin efficacy were comparable with that of azinphosmethyl, the only labeled insecticide for P. marginata in brambles until 2005. Applications on 23 October 2003 for plots treated with bifenthrin, chlorpyrifos, and azinphosmethyl resulted in >88% reduction in larvae per crown. Applications on 3 November 2004 of metaflumizone, metofluthrin, and bifenthrin resulted in >89% reduction in larvae per crown. Applications on 7 April 2005 for metofluthrin, imidacloprid, bifenthrin, metaflumizone, and benzoylphenyl urea resulted in >64% reduction in the number of larvae per crown. Applications on 6 May 2004 did not reduce larval numbers. The optimum timing for treatments was found to be between October and early April, before the larvae tunneled into the crowns of plants. Applying bifenthrin with as little as 468 liters water/ha (50 gal/acre) was found to be as effective against larvae as higher volumes of spray. Nematode applications were less successful than insecticides. Nematode applications of Steinernemafeltiae, Steinernema carpocapsae, and Heterorhabditis bacteriophora reduced larvae counts per plant by 46, 53, and 33%, respectively. PMID:17461064

  9. Effect of cements on fracture resistance of monolithic zirconia crowns

    PubMed Central

    Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

    2016-01-01

    Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a standard (ISO 9917-1:2004). Second, load-to-failure test was performed to analyze the crown fracture resistance. CAD/CAM-produced monolithic zirconia crowns with a minimal thickness of 0.5 mm were prepared and cemented to dies with each cement. The crown–die samples were loaded until fracture. Results The compressive strength of SRC, RC-D and RC-C was significantly higher than those of ZPC and GIC (p < 0.05). However, there was no significant difference in the fracture load of the crown between the groups. Conclusion The values achieved in the load-to-failure test suggest that monolithic zirconia crowns with a minimal thickness of 0.5 mm may have good resistance against fracture regardless of types of cements. PMID:27335900

  10. Digital modeling technology for full dental crown tooth preparation.

    PubMed

    Dai, Ning; Zhong, Yicheng; Liu, Hao; Yuan, Fusong; Sun, Yuchun

    2016-04-01

    A dental defect is one of the most common oral diseases, and it often requires a full crown restoration. In this clinical operation, the dentist must manually prepare the affected tooth for the full crown so that it has a convergence angle between 4° and 10°, no undercuts, and uniform and even shoulder widths and depths using a high speed diamond bur in the patient׳s mouth within one hour, which is a difficult task that requires visual-manual operation. The quality of the tooth preparation has an important effect on the success rate of the subsequent prosthodontic treatment. This study involved research into digital modeling technology for full dental crown tooth preparation. First, the margin line of the tooth preparation was designed using a semi-automatic interactive process. Second, the inserting direction was automatically computed. Then, the characteristic parameters and the constraints on the tooth preparation were defined for the model. Next, the shoulder and axial surface of the tooth preparation were formed using parametric modeling. Finally, the implicit surface of a radial basis function was used to construct the tooth preparation׳s occlusal surface. The experimental results verified that the method of digital modeling for full crown preparation proposed in this study can quickly and accurately implement personalized designs of various parameters, such as the shoulder width and the convergence angle; it provides a digital design tool for full crown preparation. PMID:26945598

  11. Orthodontic band retention on primary molar stainless steel crowns.

    PubMed

    Beemer, R L; Ferracane, J L; Howard, H E

    1993-01-01

    The retention of orthodontic bands cemented on primary molar stainless steel crowns (SSC) was studied in vitro. Unitek maxillary and mandibular 1st and 2nd primary molar SSC were fitted with one of four commonly used orthodontic bands (Unitek regular, Unitek narrow, Rocky Mountain, or custom bands made from SSC) using glass ionomer cement. The cemented samples were tested for their resistance to dislodgment on the Instron Universal Testing Machine (Instron Engineering Corp., Canton, MA) in tensile mode. Alpha level for statistical significance was set at alpha = 0.05. Unitek regular bands cemented on the 2nd molar crowns and Unitek narrow bands cemented on the 1st molar crown samples had equivalent or superior resistance to dislodgment compared with the other bands in the study. When the inside of the band and the outside band-bearing surfaces of selected crowns were lightly scored with a diamond bur prior to cementation, samples exhibited significantly superior retention. Subgroup means increased from 107 to 330%, compared to the values obtained in their preroughened state. The mean values obtained using the roughened band/crown interface technique (range 52.9 +/- 7.6 to 73.6 +/- 8.4 lbs) compared favorably with retention values from the literature for orthodontic bands cemented on permanent molar and premolar teeth. PMID:8153003

  12. Experimental investigation of the abrasive crown dynamics in orbital atherectomy.

    PubMed

    Zheng, Yihao; Belmont, Barry; Shih, Albert J

    2016-07-01

    Orbital atherectomy is a catheter-based minimally invasive procedure to modify the plaque within atherosclerotic arteries using a diamond abrasive crown. This study was designed to investigate the crown motion and its corresponding contact force with the vessel. To this end, a transparent arterial tissue-mimicking phantom made of polyvinyl chloride was developed, a high-speed camera and image processing technique were utilized to visualize and quantitatively analyze the crown motion in the vessel phantom, and a piezoelectric dynamometer measured the forces on the phantom during the procedure. Observed under typical orbital atherectomy rotational speeds of 60,000, 90,000, and 120,000rpm in a 4.8mm caliber vessel phantom, the crown motion was a combination of high-frequency rotation at 1000, 1500, and 1660.4-1866.1Hz and low-frequency orbiting at 18, 38, and 40Hz, respectively. The measured forces were also composed of these high and low frequencies, matching well with the rotation of the eccentric crown and the associated orbital motion. The average peak force ranged from 0.1 to 0.4N at different rotational speeds. PMID:27160429

  13. A study of donor-acceptor in the charge transfer molecular complexes of some thiacrown ethers with dihalogen molecules by DFT method.

    PubMed

    Oftadeh, Mohsen; Moghadary, Mitra; Solimannejad, Mohammad; Semnani, Abolfazl

    2013-01-01

    The molecular complexes of 1,3,5-trithiane, (TT), tetrathia-8-crown-4, (TT8C4), and trithia-9-crown-3 , (TT9C3) with dihalogens in the ground state were investigated in the gas and dicholoromethane phases using B3LYP method and 6-31G** and 6-31+G** bases sets. In both TT and TT8C4 complexes, it is predicted that charge transfer takes place from the dihalogen to the thiacrown ether molecule; the magnitude trend of the total CT was ICl > IBr > I2, and Cl2 > Br2 > I2, respectively. There was not such a trend with TT9C3. The frequency analysis showed that all complexes in the excited state were unstable. The analysis of natural bond orbitals and comparison of the calculated thermodynamic quantities of the complexes between the gas phase and tetrachloromethane solution confirmed the results. PMID:23841337

  14. Conformations and Barriers to Methyl Group Internal Rotation in Two Asymmetric Ethers: Propyl Methyl Ether and Butyl Methyl Ether

    NASA Astrophysics Data System (ADS)

    Long, B. E.; Dechirico, F.; Cooke, S. A.

    2012-06-01

    The conformational preferences of the O-C-C-C unit are important in many biological systems with the unit generally preferring a gauche configuration compared to an anti configuration. Butyl methyl ether and propyl methyl ether provide very simple systems for this phenomenom to manifest. Pure rotational spectra of the title molecules have been recorded using chirped pulse Fourier transform microwave spectroscopy (CP-FTMW). In the case of butyl methyl ether, only one conformer has been observed. This conformer has torsional angles of COCC = 180°, OCCC = 62° and CCCC = 180° (anti-gauche-anti) and rotational constants of A = 10259.4591(33) MHz, B = 1445.6470(13) MHz, and C = 1356.2944(14) MHz. The rotational spectrum was doubled and has been analyzed to produce an effective barrier to methyl group internal rotation of 780(35) cm-1. A prior rotational spectroscopic study on propyl methyl ether had focused only on the high energy anti-anti conformer. We have analyzed spectra from the lowest energy anti-gauche conformer and the spectroscopic constants will be presented. A summary of the differences in conformational energies and methyl group internal rotation barriers for the class of aliphatic asymmetric ethers will be presented. K. N. Houk, J. E. Eksterowicz, Y.-D. Wu, C. D. Fuglesang, D. B. Mitchell. J. Am. Chem. Soc. 115 (4170), 1993. Hiroshi Kato, Jun Nakagawa, Michiro Hayashi. J. Mol. Spectrosc. 80 (272), 1980.

  15. Four 3-cyanodifurazanyl ethers: potential propellants.

    PubMed

    Averkiev, Boris B; Antipin, Mikhail Yu; Sheremetev, Aleksey B; Timofeeva, Tatiana V

    2003-07-01

    In earlier papers, we described the synthesis and structures of bis(3-nitrofurazan-4-yl) ether, C(4)N(6)O(7), (I), bis[3-(nitro-N,N,O-azoxy)furazan-4-yl] ether, C(4)N(10)O(9), (II), and bis[3-(5H-[1,2,3]triazolo[4,5-c]furazan-5-yl)furazan-4-yl] ether, C(8)N(14)O(5), (III). Here we compare the structures of (I)-(III) with those of four 3-cyanodifurazanyl ethers, namely bis(3-cyanofurazan-4-yl) ether, C(6)N(6)O(3), (IV), 3-cyanofurazanyl 3-nitrofurazanyl ether, C(5)N(6)O(5), (V), 3,4-bis(3-cyanofurazan-4-yloxy)furazan, C(8)N(8)O(5), (VI), and bis[3-(3-cyanofurazan-4-yloxy)furazan-4-yl]diazene, C(10)N(12)O(6), (VII). It was found that the geometric parameters of the difurazanyl ether fragments are similar in these structures and therefore not influenced by substituent effects; however, the conformation of this fragment is different, viz. structures (I), (III), (V) and (VI) have approximate C(2) symmetry, and structures (II), (IV) and (VII) have C(s) symmetry. Dense crystal packing (1.626-1.898 Mg m(-3)) is characteristic for all these hydrogen-free compounds. A linear correlation is also determined between crystal density and 'molecular density' (M/V), where M is the mass of a molecule and V is the molecular volume. PMID:12855864

  16. Stabilization of alkylated azacrown ether by fatty acid at the air-water interface.

    PubMed

    Zarbakhsh, Ali; Campana, Mario; Webster, John R P; Wojciechowski, Kamil

    2010-12-01

    The adsorbed amount of partially deuterated dihexadecyl-diaza-18-crown-6 ether (d-ACE16) in the presence of different chain length fatty acids as a function of surface pressure was determined by neutron reflectometry technique. The highest adsorbed amount of the azacrown ether was observed for the mixture of ACE16 with hexadecanoic (palmitic) acid, pointing to the importance of chain length matching between the two species for optimum stabilization of the mixed monolayer. The contrast variation technique was used to estimate the contribution to the total adsorbed amount from stearic acid and ACE16. It was found that the mixed Langmuir monolayer is stable against dissolution up to a surface pressure of 20 mN m(-1). Above this pressure, however, the spread and adsorbed amounts start to deviate, indicative of partial dissolution into the aqueous subphase. The consequences of this behavior for the transport of metal ions through the interfaces of permeation liquid membranes (PLMs) are discussed. PMID:21049946

  17. Chipping Resistance of Graded Zirconia Ceramics for Dental Crowns

    PubMed Central

    Zhang, Y.; Chai, H.; Lee, J.J.-W.; Lawn, B.R.

    2012-01-01

    A serious drawback of veneering porcelains is a pronounced susceptibility to chipping. Glass-infiltrated dense zirconia structures can now be produced with esthetic quality, making them an attractive alternative. In this study, we examined the hypothesis that such infiltrated structures are much more chip-resistant than conventional porcelains, and at least as chip-resistant as non-infiltrated zirconia. A sharp indenter was used to produce chips in flat and anatomically correct glass-infiltrated zirconia crown materials, and critical loads were measured as a function of distance from the specimen edge (flat) or side wall (crown). Control data were obtained on zirconia specimens without infiltration and on crowns veneered with porcelains. The results confirmed that the resistance to chipping in graded zirconia is more than 4 times higher than that of porcelain-veneered zirconia and is at least as high as that of non-veneered zirconia. PMID:22232142

  18. Materials design of ceramic-based layer structures for crowns.

    PubMed

    Lawn, B R; Deng, Y; Lloyd, I K; Janal, M N; Rekow, E D; Thompson, V P

    2002-06-01

    Radial cracking has been identified as the primary mode of failure in all-ceramic crowns. This study investigates the hypothesis that critical loads for radial cracking in crown-like layers vary explicitly as the square of ceramic layer thickness. Experimental data from tests with spherical indenters on model flat laminates of selected dental ceramics bonded to clear polycarbonate bases (simulating crown/dentin structures) are presented. Damage initiation events are video-recorded in situ during applied loading, and critical loads are measured. The results demonstrate an increase in the resistance to radial cracking for zirconia relative to alumina and for alumina relative to porcelain. The study provides simple a priori predictions of failure in prospective ceramic/substrate bilayers and ranks ceramic materials for best clinical performance. PMID:12097438

  19. [Study on the compatibility of slip casting aluminous ceramic crowns

    PubMed

    Wan, Q B; Xue, M; You, L; Du, C S; Chao, Y L

    1997-03-01

    One of the key factors for a good slip casting aluminous ceramic crown is good compatibility between its core material and the veneering porcelain.The chemical and thermal compatibility of two slip casting aluminous ceramic crown systems(In-Ceram and GI-I) were investigated by means of SEM and EDAX,thermal shock tests were also performed to evaluate the crazing resistance.The results showed: the crazing resistance of In-Ceram was 158 degrees centigrade,and that of GI-I was degrees centigrade;there existed tightly bonded interfaces between the slip casting aluminous ceramic cores and the veneering porcelains in both of the two systems,where ion transferences were found.The results also suggested good compatibility of the two slip casting aluminous ceramic crown systems. PMID:15159959

  20. Crown-formation time of a fossil hominid premolar tooth.

    PubMed

    Beynon, A D; Dean, M C

    1987-01-01

    Studies using surface or internal enamel growth indicators in hominids have suggested that crown-formation times were shorter than those in modern man. The crown-formation time in a robust australopithecine premolar tooth was calculated by counting enamel cross-striations, which correspond to daily increments of formation, on a replica of the fractured internal enamel surface of cuspal enamel using scanning electron microscopy. Cervical enamel completion time was estimated using other growth indicators including striae, and using measured and calculated cross-striation repeat intervals, giving a completion time of approx. 2.4 yr. This is much shorter than reported premolar crown formation times in modern man. These findings support the concept of an abbreviated period of dental development, with implications on the duration of the growth period in early hominids. PMID:3130039

  1. Uniform versus Asymmetric Shading Mediates Crown Recession in Conifers

    PubMed Central

    Schoonmaker, Amanda L.; Lieffers, Victor J.; Landhäusser, Simon M.

    2014-01-01

    In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta) and shade tolerant white spruce (Picea glauca). We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1), complete uniform shading of the entire tree, (2) light asymmetric shading where the lower 1/4–1/3 of the tree crown was shaded, (3) heavy asymmetric shading as in (2) except with greater light reduction and (4) control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality – mediated by an asymmetry in light exposure of the crown. PMID:25136823

  2. Museum security and the Thomas Crown Affair.

    SciTech Connect

    Michaud, E. C.

    2010-01-01

    Over the years, I've daydreamed about stealing a Vermeer, a Picasso, or Rembrandt. It tickles me, as much as watching the reboot of The Thomas Crown Affair. Why is it, do you suppose, so much fun to think about stealing a world renowned piece off the wall of a major metropolitan museum? Is it the romantic thoughts of getting away with it, walking past infrared detectors, and pressure sensors ala Indiana Jones with the sack of sand to remove the idol without triggering the security system? Is it the idea of snatching items with such fantastic prices, where the romance of possessing an item of such value is less intoxicating than selling it to a private collector for it to never be seen again? I suspect others share my daydreams as they watch theater or hear of a brazen daylight heist at museums around the world, or from private collections. Though when reality sets in, the mind of the security professional kicks in. How could one do it, why would one do it, what should you do once it's done? The main issue a thief confronts when acquiring unique goods is how to process or fence them. They become very difficult to sell because they are one-of-a-kind, easy to identify, and could lead to the people involved with the theft. The whole issue of museum security takes up an ironic twist when one considers the secretive British street artist 'Banksy'. Banksy has made a name for himself by brazenly putting up interesting pieces of art in broad daylight (though many critics don't consider his work to be art) on building walls, rooftops, or even museums. I bring him up for a interesting take on what may become a trend in museum security. In March of 2005, Banksy snuck a piece of his called 'Vandalized Oil Painting' into the Brooklyn Museum's Great Historical Painting Wing, plus 3 other pieces into major museums in New York. Within several days, 2 paintings had been torn down, but 2 stayed up much longer. In his home country of the UK, a unauthorized piece he created and placed

  3. Dental enamel growth, perikymata and hypoplasia in ancient tooth crowns.

    PubMed Central

    Hillson, S W

    1992-01-01

    This paper describes the hypoplastic defects commonly seen on the surface of ancient human tooth crowns, excavated from archaeological sites, and presents a new method for estimating the ages at which these defects were initiated during life. The method is based upon examination of microscopic incremental structures on the enamel surface and it is possible also to apply it to reconstruction of the sequence and timing of dental crown development. The method of examination is non-destructive and allows full use to be made of the large numbers of complete, unworn dentitions which are found amongst archaeological remains. Images Figure 1. Figure 4. PMID:1404194

  4. Marginal and Internal Fit of Conventional Metal-Ceramic and Lithium Disilicate CAD/CAM Crowns.

    PubMed

    Nam, Se-Jin; Yoon, Mi-Jung; Kim, Won-Hee; Ryu, Gil-Ju; Bang, Min-Ki; Huh, Jung-Bo

    2015-01-01

    This study aimed to evaluate and compare the marginal and internal gap widths of lithium disilicate computer-aided design / computer-assisted manufacture (LDC) crowns and conventionally produced porcelain-fused-to-metal (PFM) crowns. A convenience sample of 21 patients treated with a single restoration was selected. PFM and LDC crowns were fabricated for each selected abutment tooth, following traditional crown preparation. Silicone replicas were produced, and internal gaps and marginal gaps were measured. Internal gaps were significantly larger for the axial and occlusal surfaces of LDC crowns than for those of PFM crowns (P < .001). Marginal gaps were not significantly different (P > .05). Both LDC crowns and PFM crowns showed clinically acceptable marginal fit. PMID:26340013

  5. Evaluation of marginal fit of 2 CAD-CAM anatomic contour zirconia crown systems and lithium disilicate glass-ceramic crown

    PubMed Central

    Ji, Min-Kyung; Park, Ji-Hee; Park, Sang-Won; Yun, Kwi-Dug; Oh, Gye-Jeong

    2015-01-01

    PURPOSE This study was to evaluate the marginal fit of two CAD-CAM anatomic contour zirconia crown systems compared to lithium disilicate glass-ceramic crowns. MATERIALS AND METHODS Shoulder and deep chamfer margin were formed on each acrylic resin tooth model of a maxillary first premolar. Two CAD-CAM systems (Prettau®Zirconia and ZENOSTAR®ZR translucent) and lithium disilicate glass ceramic (IPS e.max®press) crowns were made (n=16). Each crown was bonded to stone dies with resin cement (Rely X Unicem). Marginal gap and absolute marginal discrepancy of crowns were measured using a light microscope equipped with a digital camera (Leica DFC295) magnified by a factor of 100. Two-way analysis of variance (ANOVA) and post-hoc Tukey's HSD test were conducted to analyze the significance of crown marginal fit regarding the finish line configuration and the fabrication system. RESULTS The mean marginal gap of lithium disilicate glass ceramic crowns (IPS e.max®press) was significantly lower than that of the CAD-CAM anatomic contour zirconia crown system (Prettau®Zirconia) (P<.05). Both fabrication systems and finish line configurations significantly influenced the absolute marginal discrepancy (P<.05). CONCLUSION The lithium disilicate glass ceramic crown (IPS e.max®press) had significantly smaller marginal gap than the CAD-CAM anatomic contour zirconia crown system (Prettau®Zirconia). In terms of absolute marginal discrepancy, the CAD-CAM anatomic contour zirconia crown system (ZENOSTAR®ZR translucent) had under-extended margin, whereas the CAD-CAM anatomic contour zirconia crown system (Prettau®Zirconia) and lithium disilicate glass ceramic crowns (IPS e.max®press) had overextended margins. PMID:26330973

  6. Macromolecular leakage benath full cast crowns. Part II: The diffusion of lipopolysaccharide and dextran.

    PubMed

    Coleman, A J

    1996-01-01

    Fifteen extracted molars were prepared for crowns. Crowns with access ports (one facial, one lingual) were cast in gold. Teeth and crowns luted with provisional cement with filters inserted into the ports were immersed in a solution of labeled macromolecules (FITC-dextran, TRITC-LPS) and evaluated for leakage. Filters were retrieved and analyzed by use of fluorescent microscopy. Leakage of LPS and dextran occurred as early as 2 weeks beneath crowns luted with a provisional cement (NoGenol). PMID:8850458

  7. Mutagenicity of aromatic glycidyl ethers with Salmonella.

    PubMed

    Rosman, L B; Chakraborty, P K; Messerly, E A; Sinsheimer, J E

    1988-09-01

    6 aromatic glycidyl ethers containing naphthyl, biphenyl or benzylphenyl substituents were synthesized. These epoxides together with the commercially available compounds 2-biphenylyl glycidyl ether were examined for dose-mutagenicity relationships using the plate incorporation Ames test with Salmonella typhimurium strains TA100 and TA1535. Structure-mutagenicity relationships were further examined for these compounds and 3 phenyl glycidyl ethers by concurrent testing at a single dose with strain TA100. Meaningful correlations could not be established for the mutagenicity of these epoxides to their molecular volumes, partition values, nor to their reactivities with the model nucleophile, 4-(4-nitrobenzyl) pyridine. However, it was noted that increased conjugated aromatic unsaturation with its resulting planarity led to increased mutagenicity and that this effect decreased when it was further removed from the epoxide moiety. PMID:3045534

  8. Inhalation anaesthesia: from diethyl ether to xenon.

    PubMed

    Bovill, J G

    2008-01-01

    Modern anaesthesia is said to have began with the successful demonstration of ether anaesthesia by William Morton in October 1846, even though anaesthesia with nitrous oxide had been used in dentistry 2 years before. Anaesthesia with ether, nitrous oxide and chloroform (introduced in 1847) rapidly became commonplace for surgery. Of these, only nitrous oxide remains in use today. All modern volatile anaesthetics, with the exception of halothane (a fluorinated alkane), are halogenated methyl ethyl ethers. Methyl ethyl ethers are more potent, stable and better anaesthetics than diethyl ethers. They all cause myocardial depression, most markedly halothane, while isoflurane and sevoflurane cause minimal cardiovascular depression. The halogenated ethers also depress the normal respiratory response to carbon dioxide and to hypoxia. Other adverse effects include hepatic and renal damage. Hepatitis occurs most frequently with halothane, although rare cases have been reported with the other agents. Liver damage is not caused by the anaesthetics themselves, but by reactive metabolites. Type I hepatitis occurs fairly commonly and takes the form of a minor disturbance of liver enzymes, which usually resolves without treatment. Type II, thought to be immune-mediated, is rare, unpredictable and results in a severe fulminant hepatitis with a high mortality. Renal damage is rare, and was most often associated with methoxyflurane because of excessive plasma fluoride concentrations resulting from its metabolism. Methoxyflurane was withdrawn from the market because of the high incidence of nephrotoxicity. Among the contemporary anaesthetics, the highest fluoride concentrations have been reported with sevoflurane, but there are no reports of renal dysfunction associated with its use. Recently there has been a renewed interest in xenon, one of the noble gases. Xenon has many of the properties of an ideal anaesthetic. The major factor limiting its more widespread is the high cost, about

  9. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns.

    PubMed

    Lameira, Deborah Pacheco; Buarque e Silva, Wilkens Aurélio; Andrade e Silva, Frederico; De Souza, Grace M

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37 °C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength. PMID:26576423

  10. Automated individual tree crown delineation from LIDAR data using morphological techniques

    NASA Astrophysics Data System (ADS)

    Jing, L.; Hu, B.; Li, H.; Li, J.; Noland, T.

    2014-03-01

    In current tree crown delineation from LiDAR data, treetops and 3D geometric shapes of tree crowns are frequently extracted from LiDAR-derived Crown Height Model (CHM) and used as references to localize and delineate crowns. However, it is difficult to detect deciduous treetops and delineate deciduous tree crowns. The 3D shape of a crown, which can be derived from CHM, may be taken as a half ellipsoid, and any horizontal slice of the ellipsoid contains the treetop and indicates not only the location but also the spatial extent of the crown. Based on such slices, a novel multi-scale method for individual tree crown delineation from CHM was proposed in this study. This method consists mainly of two steps: (1) morphologically open the CHM over the scale range of target tree crowns; and (2) take local maxima within each resulting opened CHM as the horizontal slices of target crowns at the corresponding scale level and integrate all the slices within the scale range together to represent the spatial distribution of target crowns. In an experiment on CHMs over two natural closed canopy forests in Ontario, Canada, the proposed method accurately delineated the majority of the tree crowns from closed canopy forests.

  11. Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

    PubMed Central

    Kwon, Taek-Ka; Pak, Hyun-Soon; Han, Jung-Suk; Lee, Jai-Bong; Kim, Sung-Hun

    2013-01-01

    PURPOSE All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS The mean fracture strengths were as follows: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain. PMID:23755332

  12. 41. LOOKING WEST AT BUILDING NO. 519, ETHER AND ALCOHOL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. LOOKING WEST AT BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, (LEFT) AND BUILDING NO. 521, ETHER VAULT, (RIGHT) IN FOREGROUND - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  13. 37. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, NORTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    37. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, NORTHWEST CORNER OF BUILDING. BUILDING NO. 521 (ETHER VAULT) IN BACKGROUND LEFT. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  14. Crystalline imide/arylene ether copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

    1995-01-01

    Crystalline imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly)arylene ethers) in polar aprotic solvents and chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The block copolymers of the invention have one glass transition temperature or two, depending on the particular structure and/or the compatibility of the block units. Most of these crystalline block copolymers for tough, solvent resistant films with high tensile properties. While all of the copolymers produced by the present invention are crystalline, testing reveals that copolymers with longer imide blocks or higher imide content have increased crystallinity.

  15. Vinyl ethers containing an epoxy group. XVI. Reaction of glycidol vinyloxyethyl ether with acetals

    SciTech Connect

    Nedolya, N.A.; Khil'ko, M.Ya.; Trofimov, B.A.; Sigalov, M.V.

    1988-10-10

    In order to obtain branched acetals with epoxide groups (prospective monomers and intermediates) the authors investigated the reaction of acetaldehyde diethyl and di(1,1,3-trihydrotetrafluoropropyl) acetals with glycidol vinyloxyethyl ether. The addition of acetals to vinyl epoxy ethers was realized, and the first representative of compounds of this type, i.e., 9-glycidyloxy-6-ethoxy-4-methyl-3,7-dioxanonane, was obtained. It was also impossible to add a fluoroacetal to butyl vinyl ether (0.08-1.00 wt. % of catalyst CF/sub 3/COOH, BF/sub 3//times/ OEt/sub 2/, 20-80/degree/C, 0.5-3 h).

  16. Randomized, Controlled Clinical Trial of Bilayer Ceramic and Metal-Ceramic Crown Performance

    PubMed Central

    Esquivel-Upshaw, Josephine; Rose, William; Oliveira, Erica; Yang, Mark; Clark, Arthur E.; Anusavice, Kenneth

    2013-01-01

    Purpose Analyzing the clinical performance of restorative materials is important, as there is an expectation that these materials and procedures will restore teeth and do no harm. The objective of this research study was to characterize the clinical performance of metal-ceramic crowns, core ceramic crowns, and core ceramic/veneer ceramic crowns based on 11 clinical criteria. Materials and Methods An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study. The following three types of full crowns were fabricated: (1) metal-ceramic crown (MC) made from a Pd-Au-Ag-Sn-In alloy (Argedent 62) and a glass-ceramic veneer (IPS d.SIGN veneer); (2) non-veneered (glazed) lithium disilicate glass-ceramic crown (LDC) (IPS e.max Press core and e.max Ceram Glaze); and (3) veneered lithia disilicate glass-ceramic crown (LDC/V) with glass-ceramic veneer (IPS Empress 2 core and IPS Eris). Single-unit crowns were randomly assigned. Patients were recalled for each of 3 years and were evaluated by two calibrated clinicians. Thirty-six crowns were placed in 31 patients. A total of 12 crowns of each of the three crown types were studied. Eleven criteria were evaluated: tissue health, marginal integrity, secondary caries, proximal contact, anatomic contour, occlusion, surface texture, cracks/chips (fractures), color match, tooth sensitivity, and wear (of crowns and opposing enamel). Numerical rankings ranged from 1 to 4, with 4 being excellent, and 1 indicating a need for immediate replacement. Statistical analysis of the numerical rankings was performed using a Fisher’s exact test. Results There was no statistically significant difference between performance of the core ceramic crowns and the two veneered crowns at year 1 and year 2 (p > 0.05). All crowns were rated either as excellent or good for each of the clinical criteria; however, between years 2 and 3, gradual roughening of the occlusal surface occurred in some of the ceramic-ceramic crowns

  17. High octane ethers from synthesis gas-derived alcohols

    SciTech Connect

    Klier, K.; Herman, R.G.; Johansson, M.; Feeley, O.C.

    1992-01-01

    The objective of the proposed research is to synthesize high octane ethers, primarily methyl isobutyl ether (MIBE) and methyl tertiary butyl ether (MTBE), directly from H{sub 2}/CO/CO{sub 2} coal-derived synthesis gas via alcohol mixtures that are rich in methanol and 2-methyl-1-propanol (isobutanol). The overall scheme involves gasification of coal, purification and shifting of the synthesis gas, higher alcohol synthesis, and direct synthesis of ethers.

  18. 2006 U.S. oat crown rust race survey

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown rust severities and resulting yield losses were much lower in 2006 throughout much of the U.S. compared to 2005. Widespread drought conditions throughout the central plains limited disease development. A total of 102 and 27 isolates were collected from the spring and winter oat growing regions...

  19. Spatiotemporal characterization of Sclerotinia crown rot epidemics in pyrethrum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sclerotinia crown rot, caused by Sclerotinia minor and S. sclerotiorum is a disease of pyrethrum in Australia that may cause substantial decline in plant density. The spatiotemporal characteristics of the disease were quantified in 14 fields spread across three growing seasons. Fitting the binary ...

  20. Suppressors of oat crown rust resistance in interspecific oat crosses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Attempts to transfer disease resistance genes between related species may be hindered by suppression, or lack of expression, of the trait in the interspecific combination. In crosses of diploid oat Avena strigosa (Schreb.) accession CI6954SP with resistance to oat crown rust Puccinia coronata f. sp....

  1. Towards an optimized method of olive tree crown volume measurement.

    PubMed

    Miranda-Fuentes, Antonio; Llorens, Jordi; Gamarra-Diezma, Juan L; Gil-Ribes, Jesús A; Gil, Emilio

    2015-01-01

    Accurate crown characterization of large isolated olive trees is vital for adjusting spray doses in three-dimensional crop agriculture. Among the many methodologies available, laser sensors have proved to be the most reliable and accurate. However, their operation is time consuming and requires specialist knowledge and so a simpler crown characterization method is required. To this end, three methods were evaluated and compared with LiDAR measurements to determine their accuracy: Vertical Crown Projected Area method (VCPA), Ellipsoid Volume method (VE) and Tree Silhouette Volume method (VTS). Trials were performed in three different kinds of olive tree plantations: intensive, adapted one-trunked traditional and traditional. In total, 55 trees were characterized. Results show that all three methods are appropriate to estimate the crown volume, reaching high coefficients of determination: R2 = 0.783, 0.843 and 0.824 for VCPA, VE and VTS, respectively. However, discrepancies arise when evaluating tree plantations separately, especially for traditional trees. Here, correlations between LiDAR volume and other parameters showed that the Mean Vector calculated for VCPA method showed the highest correlation for traditional trees, thus its use in traditional plantations is highly recommended. PMID:25658396

  2. Delineation of individual tree crowns for mobile laser scanning data

    NASA Astrophysics Data System (ADS)

    Wu, Rosen; Chen, Yiping; Wen, Chenglu; Wang, Cheng; Li, Jonathan

    2016-03-01

    The information of individual trees plays an important role in urban surveying and mapping. With the development of Light Detection and Ranging (LiDAR) technology, 3-Dimenisonal (3D) structure of trees can be generated in point clouds with high spatial resolution and accuracy. Individual tree segmentations are used to derive tree structural attributes such as tree height, crown diameter, stem position etc. In this study, a framework is proposed to take advantage of the detailed structures of tree crowns which are represented in the mobile laser scanning (MLS) data. This framework consists of five steps: (1) Automatically detect and remove ground points using RANSAC; (2) Compress all the above ground points to image grid with 3D knowledge reserved; (3) Simplify and remove unqualified grids; (4) Find tree peaks using a heuristic searching method; (5) Delineate the individual tree crowns by applying a modified watershed method. In an experiment on the point clouds on Xiamen Island, China, individual tree crowns from MLS point cloud data are successfully extracted.

  3. 14. Photograph of sheet 2 (general plan; section @ crown, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Photograph of sheet 2 (general plan; section @ crown, plan, and elevation) of the Indiana State Highway Commission repair plans of 1969 for the Cicott Street Bridge. Photograph of a 24' by 36' print made from microfilm in the archives of the Indiana Department of Transportation in Indianapolis. - Cicott Street Bridge, Spanning Wabash River at State Road 25, Logansport, Cass County, IN

  4. Identification of new sources of partial resistance to oat crown

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Control of oat crown rust (Puccinia coronata f.sp. avenae) has traditionally been achieved with the use of cultivars with race-specific seedling genes (Pc genes), but this resistance typically is only effective for 3-5 years once a cultivar becomes widely grown. Over 90 Pc genes have been described ...

  5. Towards an Optimized Method of Olive Tree Crown Volume Measurement

    PubMed Central

    Miranda-Fuentes, Antonio; Llorens, Jordi; Gamarra-Diezma, Juan L.; Gil-Ribes, Jesús A.; Gil, Emilio

    2015-01-01

    Accurate crown characterization of large isolated olive trees is vital for adjusting spray doses in three-dimensional crop agriculture. Among the many methodologies available, laser sensors have proved to be the most reliable and accurate. However, their operation is time consuming and requires specialist knowledge and so a simpler crown characterization method is required. To this end, three methods were evaluated and compared with LiDAR measurements to determine their accuracy: Vertical Crown Projected Area method (VCPA), Ellipsoid Volume method (VE) and Tree Silhouette Volume method (VTS). Trials were performed in three different kinds of olive tree plantations: intensive, adapted one-trunked traditional and traditional. In total, 55 trees were characterized. Results show that all three methods are appropriate to estimate the crown volume, reaching high coefficients of determination: R2 = 0.783, 0.843 and 0.824 for VCPA, VE and VTS, respectively. However, discrepancies arise when evaluating tree plantations separately, especially for traditional trees. Here, correlations between LiDAR volume and other parameters showed that the Mean Vector calculated for VCPA method showed the highest correlation for traditional trees, thus its use in traditional plantations is highly recommended. PMID:25658396

  6. EVALUATION OF WILD JUGLANS SPECIES FOR CROWN GALL RESISTANCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crown Gall disease of walnut is caused by the ubiquitous soil-borne bacterium, Agrobacterium tumefaciens which is able to transfer a specific piece of its own DNA into the genome of the plant host cell. The result of this genetic transformation is the autonomous undifferentiated massive growth of i...

  7. Restoration of decayed primary incisors using strip crowns.

    PubMed

    Pollard, M A; Curzon, J A; Fenlon, W L

    1991-05-01

    Caries of the primary incisors is a common problem that can be arrested if recognized early enough. However, the arrested decay is unsightly. Celluloid 'strip' crown forms, used with composite resin, now allow the restoration of even the most badly decayed primary incisors. The authors describe this quick and efficient technique. PMID:1884866

  8. Primate molar crown formation times and life history evolution revisited.

    PubMed

    Macho, G A

    2001-12-01

    Comparative studies have convincingly demonstrated that the pattern and timing of tooth emergence are highly correlated with life-history variables and brain size. Conversely, a firm relationship between molar formation time and life-history variables has not yet been established. It seems counterintuitive that one aspect of dental development should be correlated with life-history variables, whereas the other should not. In order to shed light on this apparent discrepancy this study analyzed all data on primate molar crown formations available in the published literature in relation to life-history variables, brain size, and female body mass. Crown formation times were found to be particularly highly correlated with both female body mass and brain size. Species that depart from the overall brain/body allometry by being relatively large-bodied, e.g., Gorilla gorilla and later Theropithecus oswaldi, also have shorter molar crown formation times than expected. The reverse is not found for species that depart from the overall brain/body allometry due to their larger brains, i.e., Homo sapiens. This finding is interpreted within an evolutionary and ecological framework. Specifically, by focusing on ecological commonalities, a scenario is proposed which may allow predictions to be made about the evolutionary history of other extinct primates also. If confirmed in future studies, crown formation time may again become a powerful tool in evolutionary enquiry. PMID:11748692

  9. Laser pediatric crowns performed without anesthesia: a contemporary technique.

    PubMed

    Jacboson, B; Berger, J; Kravitz, R; Patel, P

    2003-01-01

    Extensive caries resulting in the need for a stainless steel crown in primary teeth may now be prepared with the use of the WaterlaseTM YSGG Laser, (Biolase) hard and soft-tissue laser. The use of the laser eliminates the need for local anesthesia, thereby providing optimal patient comfort and compliance. PMID:14604135

  10. Evolution of the mandibular third premolar crown in early Australopithecus.

    PubMed

    Delezene, Lucas K; Kimbel, William H

    2011-06-01

    The Pliocene hominins Australopithecus anamensis and Australopithecus afarensis likely represent ancestor-descendent taxa--possibly an anagenetic lineage--and capture significant change in the morphology of the canine and mandibular third premolar (P(3)) crowns, dental elements that form the canine honing complex in nonhuman catarrhines. This study focuses on the P(3) crown, highlighting plesiomorphic features in A. anamensis. The A. afarensis P(3) crown, in contrast, is variable in its expression of apomorphic features that are characteristic of geologically younger hominins. Temporal variation characterizes each taxon as well. The A. anamensis P(3) from Allia Bay, Kenya expresses apomorphic character states, shared with A. afarensis, which are not seen in the older sample of A. anamensis P(3)s from Kanapoi, Kenya, while spatiotemporal differences in shape exist within the A. afarensis hypodigm. The accumulation of derived features in A. afarensis results in an increased level of P(3) molarisation. P(3) molarisation did not evolve concurrent with postcanine megadontia and neither did the appearance of derived aspects of P(3) occlusal form coincide with the loss of canine honing in hominins, which is apparent prior to the origin of the genus Australopithecus. A. afarensis P(3) variation reveals the independence of shape, size, and occlusal form. The evolution of the P(3) crown in early Australopithecus bridges the wide morphological gap that exists between geologically younger hominins on the one hand and extant apes and Ardipithecus on the other. PMID:21481921

  11. 39. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    39. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, LOOKING AT SOUTHWEST CORNER WITH BUILDING NO. 521, ETHER VAULT, AND BUILDING NO. 519-A, ETHER & ALOCOHL STORAGE TANKS, IN BACKGROUND RIGHT. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  12. 40 CFR 721.10551 - Bisphenol S mono ether (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Bisphenol S mono ether (generic). 721... Substances § 721.10551 Bisphenol S mono ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as bisphenol S mono ether (PMN...

  13. 40 CFR 721.10551 - Bisphenol S mono ether (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Bisphenol S mono ether (generic). 721... Substances § 721.10551 Bisphenol S mono ether (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as bisphenol S mono ether (PMN...

  14. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Haloalkyl substituted cyclic ethers... Substances § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  15. 40 CFR 721.3520 - Aliphatic polyglycidyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aliphatic polyglycidyl ether. 721.3520... Substances § 721.3520 Aliphatic polyglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance aliphatic polyglycidyl ether (PMN P-89-1036) is subject...

  16. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Haloalkyl substituted cyclic ethers... Substances § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  17. 40 CFR 721.3438 - Chlorohydroxyalkyl butyl ether (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Chlorohydroxyalkyl butyl ether... Specific Chemical Substances § 721.3438 Chlorohydroxyalkyl butyl ether (generic). (a) Chemical substance... chlorohydroxyalkyl butyl ether (PMN P-99-1295) is subject to reporting under this section for the significant new...

  18. 40 CFR 721.3438 - Chlorohydroxyalkyl butyl ether (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Chlorohydroxyalkyl butyl ether... Specific Chemical Substances § 721.3438 Chlorohydroxyalkyl butyl ether (generic). (a) Chemical substance... chlorohydroxyalkyl butyl ether (PMN P-99-1295) is subject to reporting under this section for the significant new...

  19. 40 CFR 721.3480 - Halogenated biphenyl glycidyl ethers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated biphenyl glycidyl ethers... Substances § 721.3480 Halogenated biphenyl glycidyl ethers. (a) Chemical substance and significant new uses... ethers (PMNs P-90-1844, P-90-1845, and P-90-1846) are subject to reporting under this section for...

  20. 40 CFR 721.3480 - Halogenated biphenyl glycidyl ethers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated biphenyl glycidyl ethers... Substances § 721.3480 Halogenated biphenyl glycidyl ethers. (a) Chemical substance and significant new uses... ethers (PMNs P-90-1844, P-90-1845, and P-90-1846) are subject to reporting under this section for...

  1. 40 CFR 721.3486 - Polyglycerin mono(4-nonylphenyl) ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyglycerin mono(4-nonylphenyl) ether... Substances § 721.3486 Polyglycerin mono(4-nonylphenyl) ether. (a) Chemical substance and significant new uses...-nonylphenyl) ether (PMN P-94-2230) is subject to reporting under this section for the significant new...

  2. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  3. 40 CFR 721.3465 - Stilbene diglycidyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Stilbene diglycidyl ether. 721.3465... Substances § 721.3465 Stilbene diglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as stilbene diglycidyl ether (PMN P-96-1427) is subject...

  4. 40 CFR 721.3550 - Dipropylene glycol dimethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Dipropylene glycol dimethyl ether. 721... Substances § 721.3550 Dipropylene glycol dimethyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as dipropylene glycol dimethyl ether (PMN...

  5. 40 CFR 721.3486 - Polyglycerin mono(4-nonylphenyl) ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polyglycerin mono(4-nonylphenyl) ether... Substances § 721.3486 Polyglycerin mono(4-nonylphenyl) ether. (a) Chemical substance and significant new uses...-nonylphenyl) ether (PMN P-94-2230) is subject to reporting under this section for the significant new...

  6. 40 CFR 721.3430 - 4-Bromophenyl phenyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 4-Bromophenyl phenyl ether. 721.3430... Substances § 721.3430 4-Bromophenyl phenyl ether. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance 4-bromophenyl phenyl ether (CAS No. 101-55-3) is subject to...

  7. 40 CFR 721.3500 - Perhalo alkoxy ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Perhalo alkoxy ether. 721.3500 Section... Substances § 721.3500 Perhalo alkoxy ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as perhalo alkoxy ether (PMN P-83-1227)...

  8. 40 CFR 721.3550 - Dipropylene glycol dimethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Dipropylene glycol dimethyl ether. 721... Substances § 721.3550 Dipropylene glycol dimethyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as dipropylene glycol dimethyl ether (PMN...

  9. 40 CFR 721.3420 - Brominated arylalkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Brominated arylalkyl ether. 721.3420... Substances § 721.3420 Brominated arylalkyl ether. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as brominated arylalkyl ether (P-83-906)...

  10. 40 CFR 721.3500 - Perhalo alkoxy ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Perhalo alkoxy ether. 721.3500 Section... Substances § 721.3500 Perhalo alkoxy ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as perhalo alkoxy ether (PMN P-83-1227)...

  11. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  12. 40 CFR 721.3430 - 4-Bromophenyl phenyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 4-Bromophenyl phenyl ether. 721.3430... Substances § 721.3430 4-Bromophenyl phenyl ether. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance 4-bromophenyl phenyl ether (CAS No. 101-55-3) is subject to...

  13. 40 CFR 721.3520 - Aliphatic polyglycidyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Aliphatic polyglycidyl ether. 721.3520... Substances § 721.3520 Aliphatic polyglycidyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance aliphatic polyglycidyl ether (PMN P-89-1036) is subject...

  14. Alkyl Aryl Ether Bond Formation with PhenoFluor**

    PubMed Central

    Shen, Xiao; Neumann, Constanze N.; Kleinlein, Claudia; Claudia, Nathaniel W.; Ritter, Tobias

    2015-01-01

    An alkyl aryl ether bond formation reaction between phenols and primary and secondary alcohols with PhenoFluor has been developed. The reaction features a broad substrate scope and tolerates many functional groups, and substrates that are challenging for more conventional ether bond forming processes may be coupled. A preliminary mechanistic study indicates reactivity distinct from conventional ether bond formation. PMID:25800679

  15. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  16. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  17. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  18. 21 CFR 520.1846 - Polyoxyethylene (23) lauryl ether blocks.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Polyoxyethylene (23) lauryl ether blocks. (a) Specifications. Each molasses-based block contains 2.2 percent polyoxyethylene (23) lauryl ether. (b) Sponsor. See No. 067949 in § 510.600(c) of this chapter. (c) Conditions of... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Polyoxyethylene (23) lauryl ether blocks....

  19. Brief communication: Molar development and crown areas in early Australopithecus.

    PubMed

    Lacruz, Rodrigo S; Ramirez Rozzi, Fernando V; Wood, Bernard A; Bromage, Timothy G

    2012-08-01

    Recent studies suggest that the hypodigms representing the two earliest Australopithecus (Au. anamensis and Au. afarensis) form an ancestor-descendant lineage. Understanding the details of this possible transition is important comparative evidence for assessing the likelihood of other examples of ancestor-descendant lineages within the hominin clade. To this end we have analyzed crown and cusp base areas of high resolution replicas of the mandibular molars of Au. anamensis (Allia Bay and Kanapoi sites) and those of Au. afarensis (Hadar, Laetoli, and Maka). We found no statistically significant differences in crown areas between these hypodigms although the mean of M(1) crowns was smaller in Au. anamensis, being the smallest of any Australopithecus species sampled to date. Intraspecies comparison of the areas of mesial cusps for each molar type using Wilcoxon signed rank test showed no differences for Au. anamensis. Significant differences were found between the protoconid and metaconid of Au. afarensis M(2)s and M(3)s. Furthermore, the area formed by the posterior cusps as a whole relative to the anterior cusps showed significant differences in Au. afarensis M(1)s and in Au. anamensis M(2)s but no differences were noted for M(3)s of either taxon. Developmental information derived from microstructural details in enamel shows that M(1) crown formation in Au. anamensis is similar to Pan and shorter than in H. sapiens. Taken together, these data suggests that the overall trend in the Au. anamensis-Au. afarensis transition may have involved a moderate increase in M(1) crown areas with relative expansion of distal cusps. PMID:22623291

  20. Synthesis and characterizations of electrospun sulfonated poly (ether ether ketone) SPEEK nanofiber membrane

    NASA Astrophysics Data System (ADS)

    Hasbullah, N.; Sekak, K. A.; Ibrahim, I.

    2016-07-01

    A novel electrospun polymer electrolyte membrane (PEM) based on Sulfonated Poly (ether ether ketone) were prepared and characterized. The poly (ether ether ketone) PEEK was sulfonated using concentrated sulfuric acid at room temperature for 60 hours reaction time. The degree sulfonation (DS) of the SPEEK are 58% was determined by H1 NMR using area under the peak of the hydrogen shielding at aromatic ring of the SPEEK. Then, the functional group of the SPEEK was determined using Fourier transfer infrared (FTIR) showed O-H vibration at 3433 cm-1 of the sulfonated group (SO2-OH). The effect of the solvent and polymer concentration toward the electrospinning process was investigated which, the DMAc has electrospun ability compared to the DMSO. While, at 20 wt.% of the polymer concentration able to form a fine and uniform nanofiber, this was confirmed by FESEM that shown electrospun fiber mat SPEEK surface at nano scale diameter.

  1. Review of glycol ether and glycol ether ester solvents used in the coating industry.

    PubMed Central

    Smith, R L

    1984-01-01

    Ethylene oxide-based glycol ether and glycol ether ester solvents have been used in the coatings industry for the past fifty years. Because of their excellent performance properties (evaporation rate, blush resistance, flow-out and leveling properties, solubility for coating resins, solvent activity, mild odor, good coupling ability, good solvent release) a complete line of ethylene oxide-based solvents of various molecular weights has been developed. These glycol ether and glycol ether ester solvents have better solvent activity for coating resin than ester or ketone solvents in their evaporation rate range. The gloss, flow and leveling, and general performance properties of many coating systems are dependent on the use of these products in the coating formula. Because of the concern about the toxicity of certain ethylene oxide-based solvents, other products are being evaluated as replacements in coating formulas. PMID:6499793

  2. Method and apparatus for controlling an earthworking implement to preserve a crown on a road surface

    NASA Technical Reports Server (NTRS)

    Staub, Michael D. (Inventor); Alster, Louis G. (Inventor); Lundquist, Steve D. (Inventor)

    1999-01-01

    A method and apparatus for controlling an earthworking implement on an earthworking machine to preserve a crown on the surface of a road, including determining the position of the crown on the road surface, choosing a sloped grade on one side of the crown, positioning the earthworking implement on the sloped grade so that a first end of the earthworking implement is on the road surface. The processor determines a desired position of a second end of the earthworking implement so that the second end overlaps the crown and the earthworking implement does not cut the crown.

  3. Distribution of ether in two postmortem cases.

    PubMed

    Cox, Dawn; DeRienz, Rebecca; Jufer Phipps, Rebecca A; Levine, Barry; Jacobs, Aaron; Fowler, David

    2006-10-01

    Diethyl ether (ether) is a volatile liquid that was used in the 1800s as an anesthetic agent; however, it is no longer used for this purpose, partly because of its odor and flammability. Two postmortem cases in which ether was detected are presented. The first case was an 18-year-old male found hanging from a basement ceiling brace in a semi-sitting position with a gas mask covering his face. A container of Prestone starting fluid and a bong were found on the floor close to the body. The second case was a 20-year-old male found unresponsive in his dormitory room with two black plastic trash bags secured over his head. Two saturated rags and a resealable bag containing a clear liquid were contained within these trash bags. An almost empty can of Tradco starting fluid was also found at the scene. Ether concentrations were determined by headspace gas chromatography-mass spectrometry in the selective ion monitoring mode. In case #1, the medical examiner ruled that the cause of death was asphyxia due to hanging; the manner of death was undetermined. In case #2, the medical examiner ruled that the cause of death was asphyxia and the manner of death was suicide. PMID:17132265

  4. POLYBROMINATED DIPHENYL ETHERS IN SOUTHERN MISSISSIPPI CATFISH

    EPA Science Inventory

    Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in a wide variety of consumer products. Concerns surrounding these compounds are primarily due do their ubiquitous presence in the environment as well as in human tissue, such as milk, coupled with evidence indi...

  5. Elastic electron scattering by ethyl vinyl ether

    SciTech Connect

    Khakoo, M. A.; Hong, L.; Kim, B.; Winstead, C.; McKoy, V.

    2010-02-15

    We report measured and calculated results for elastic scattering of low-energy electrons by ethyl vinyl ether (ethoxyethene), a prototype system for studying indirect dissociative attachment processes that may play a role in DNA damage. The integral cross section displays the expected {pi}{sup *} shape resonance. The agreement between the calculated and measured cross sections is generally good.

  6. The introduction of ether in Paris revisited.

    PubMed

    Defalque, Ray J; Wright, A J

    2008-04-01

    Modern accounts of the introduction of ether anesthesia in France are mainly based on a letter written in February 1947 to the editor of the Boston Medical and Surgical Journal by Francis Willis Fisher, a young Boston surgeon at that time a student in Paris. Fisher's letter hints that his efforts were the main impetus to the acceptance of ether by the French academic surgeons. The authors have reviewed the contemporary medical literature, especially the numerous French journals, relative to that event. Their review suggests that Fisher was largely ignored by the French surgeons and by his young competitors then studying in Paris. He seems to have exaggerated his role in the acceptance of ether anesthesia in France. The reviewed literature also provides some additional details and some corrections to Fisher's account. Modern accounts of the introduction of ether in France have relied heavily on a letter sent in February 1847 to the editor of the Boston Medical & Surgical Journal by Francis W. Fisher, a young Boston physician then studying in Paris. Fisher's report is often vague, occasionally incorrect, and probably exaggerates his role in the acceptance of anesthesia in Paris. This review attempts to complement and correct Fisher's account. PMID:20506770

  7. Bis(2-chloro-1-methylethyl) ether

    Integrated Risk Information System (IRIS)

    Bis ( 2 - chloro - 1 - methylethyl ) ether ; CASRN 108 - 60 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assess

  8. Methyl tert-butyl ether (MTBE)

    Integrated Risk Information System (IRIS)

    Methyl tert - butyl ether ( MTBE ) ; CASRN 1634 - 04 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments f

  9. Ethylene glycol monobutyl ether (EGBE) (2-Butoxyethanol)

    Integrated Risk Information System (IRIS)

    Ethylene glycol monobutyl ether ( EGBE ) ( 2 - Butoxyethanol ) ; CASRN 111 - 76 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I (

  10. Biomonitoring Polybrominated Diphenyl Ethers in Lactating Women

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Breast milk is a valuable biological specimen for biomonitoring lipid-soluble polybrominated diphenyl ethers (PBDEs). The goal of this project was to determine the levels of PBDEs in breast milk of lactating women from the Seacoast region of New Hampshire and to examine potential relationships betw...

  11. Dimensionally Stable Ether-Containing Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Fay, Catharine C. (Inventor); St.Clair, Anne K. (Inventor)

    1999-01-01

    Novel polyimide copolymers containing ether linkages were prepared by the reaction of an equimolar amount of dianhydride and a combination of diamines. The polyimide copolymers described herein possess the unique features of low moisture uptake, dimensional stability, good mechanical properties, and moderate glass transition temperatures. These materials have potential application as encapsulants and interlayer dielectrics.

  12. Imide/arylene ether block copolymers

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Hergenrother, P. M.; Bass, R. G.

    1991-01-01

    Two series of imide/arylene either block copolymers were prepared using an arylene ether block and either an amorphous or semi-crystalline imide block. The resulting copolymers were characterized and selected physical and mechanical properties were determined. These results, as well as comparisons to the homopolymer properties, are discussed.

  13. Polyimides Containing Carbonyl and Ether Connecting Groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.; Havens, Stephen J.

    1987-01-01

    Semicrystallinity gives rise to tough, solvent-resistant polymers. New polyimides prepared from reaction of aromatic dianhydrides with new diamines containing carbonyl and ether connecting groups between aromatic rings. Damines prepared from reaction of 4-aminophenol with activated aromatic difluoro compounds in presence of potassium carbonate. These types of polymers have potential applications in molded products, films, adhesives, and composites.

  14. OsCAND1 is required for crown root emergence in rice.

    PubMed

    Wang, Xiao-Fei; He, Fen-Fang; Ma, Xiao-Xia; Mao, Chuan-Zao; Hodgman, Charlie; Lu, Chun-Gui; Wu, Ping

    2011-03-01

    Crown roots are main components of the fibrous root system and important for crops to anchor and absorb water and nutrition. To understand the molecular mechanisms of crown root formation, we isolated a rice mutant defective in crown root emergence designated as Oscand1 (named after the Arabidopsis homologous gene AtCAND1). The defect of visible crown root in the Oscand1 mutant is the result of cessation of the G2/M cell cycle transition in the crown root meristem. Map-based cloning revealed that OsCAND1 is a homolog of Arabidopsis CAND1. During crown root primordium development, the expression of OsCAND1 is confined to the root cap after the establishment of fundamental organization. The transgenic plants harboring DR5::GUS showed that auxin signaling in crown root tip is abnormal in the mutant. Exogenous auxin application can partially rescue the defect of crown root development in Oscand1. Taken together, these data show that OsCAND1 is involved in auxin signaling to maintain the G2/M cell cycle transition in crown root meristem and, consequently, the emergence of crown root. Our findings provide new information about the molecular regulation of the emergence of crown root in rice. PMID:20978084

  15. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, James V.

    1996-01-01

    Propenyl ether monomers of formula V A(OCH.dbd.CHCH.sub.3).sub.n wherein n is an integer from one to six and A is selected from cyclic ethers, polyether and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  16. Process for making propenyl ethers and photopolymerizable compositions containing them

    DOEpatents

    Crivello, J.V.

    1996-01-23

    Propenyl ether monomers of formula A(OCH{double_bond}CHCH{sub 3}){sub n} (V) wherein n is an integer from one to six and A is selected from cyclic ethers, polyether, and alkanes are disclosed. The monomers are readily polymerized in the presence of cationic photoinitiators, when exposed to actinic radiation, to form poly(propenyl ethers) that are useful for coatings, sealants, varnishes and adhesives. Compositions for preparing polymeric coatings comprising the compounds of formula V together with particular cationic photoinitiators are also disclosed, as are processes for making the monomers from allyl halides and readily available alcohols. The process involves rearranging the resulting allyl ethers to propenyl ethers.

  17. Fracture resistance of computer-aided design/computer-aided manufacturing-generated composite resin-based molar crowns.

    PubMed

    Harada, Akio; Nakamura, Keisuke; Kanno, Taro; Inagaki, Ryoichi; Örtengren, Ulf; Niwano, Yoshimi; Sasaki, Keiichi; Egusa, Hiroshi

    2015-04-01

    The aim of this study was to investigate whether different fabrication processes, such as the computer-aided design/computer-aided manufacturing (CAD/CAM) system or the manual build-up technique, affect the fracture resistance of composite resin-based crowns. Lava Ultimate (LU), Estenia C&B (EC&B), and lithium disilicate glass-ceramic IPS e.max press (EMP) were used. Four types of molar crowns were fabricated: CAD/CAM-generated composite resin-based crowns (LU crowns); manually built-up monolayer composite resin-based crowns (EC&B-monolayer crowns); manually built-up layered composite resin-based crowns (EC&B-layered crowns); and EMP crowns. Each type of crown was cemented to dies and the fracture resistance was tested. EC&B-layered crowns showed significantly lower fracture resistance compared with LU and EMP crowns, although there was no significant difference in flexural strength or fracture toughness between LU and EC&B materials. Micro-computed tomography and fractographic analysis showed that decreased strength probably resulted from internal voids in the EC&B-layered crowns introduced by the layering process. There was no significant difference in fracture resistance among LU, EC&B-monolayer, and EMP crowns. Both types of composite resin-based crowns showed fracture loads of >2000 N, which is higher than the molar bite force. Therefore, CAD/CAM-generated crowns, without internal defects, may be applied to molar regions with sufficient fracture resistance. PMID:25683749

  18. Wear of double crown systems - electroplated vs. casted female part

    PubMed Central

    BAYER, Stefan; KRAUS, Dominik; KEILIG, Ludger; GÖLZ, Lina; STARK, Helmut; ENKLING, Norbert

    2012-01-01

    Objectives The wear of telescopic crowns is a common problem often reducing the patient's satisfaction with the denture and resulting in a renewal of the denture. The study aims to compare the wear behavior of conical crowns using electroplated copings (group E) with standard telescopic crowns with cast female parts (group C). Material and Methods 10 conical crowns were milled for each group of a cast gold alloy. The specimen of group E had a conicity of 2º. The cast secondary crowns of group C had a 0º design. The electroplated coping was established by direct electroforming. An apparatus accomplishing 10,000 wear cycles performed the wear test. The retentive forces and the correlating distance during insertion and separation were measured. The wear test was separated in a start phase, an initial wear phase and the long term wear period. The retention force value and the force-distance integral of the first 0.33 mm of each cycle were calculated. Results The retentive forces were significantly higher for group E and the integrals were significantly lower for this group except the integral at cycle 10,000. The changes of retention force and integral did not differ significantly between both groups in all phases. The change of the integrals as well as the integral at the particular cycles showed higher interquartile distances for group C. Conclusions Within the limitations of this study the tested conical crowns showed clinically acceptable retentive properties. The values reached a range comparable to retentive elements tested in recent literature. The values of group C showed higher ranges. The force measured for group E was significantly higher than for group C but the integrals showed an opposite tendency. The results indicate that an exclusive analysis of the force is not sufficient as the integral is not equivalent to the force although it describes the retentive property of the system in a better way than the force over a distance is described. Both systems

  19. Certain glycol ethers eliminated from toxic chemical release reporting requirements

    SciTech Connect

    1994-09-01

    Effective June 28, 1994, the U.S. Environmental Protection Agency (EPA) eliminated high molecular weight glycol ethers from the reporting requirements of section 313 of the Emergency Planning and Community Right-To-Know Act of 1986 (EPCRA). EPCRA (42 U.S.C. 11023) is also referred to as Title III of the Superfund Amendments and Reauthorization Act (SARA) of 1986. EPA redefined the glycol ethers category list of chemicals subject to reporting based on an EPA review of available human health data on short-chain glycol ethers. EPA is removing only the surfactant glycol ethers, which are high molecular weight glycol ethers, i.e., those with pendant alkyl groups and that typically have eight or more carbon atoms. The redefinition retains certain glycol ethers (i.e., ethylene glycol ethers where there are 1,2, or 3 repeating ethylene oxide groups) in the category. These are reasonably anticipated to cause adverse human health effects.

  20. Comparison of Primary Molar Crown Dimensions with Stainless Steel Crowns in a Sample of Iranian Children

    PubMed Central

    Afshar, Hossein; Kamali Sabeti, Arghavan; Shahrabi, Mahdi

    2015-01-01

    Background and aims. Due to anatomic variation in tooth anatomy between populations, this study compared the buccolingual (BL) and mesiodistal (MD) dimensions of primary molars with those of stainless steel crowns (SSCs) in anIranian population. Materials and methods. Impressions were taken from both dental arches of children, and casts were poured. Teeth with caries, restoration, hypoplasia or other dental anomalies were excluded. 216 primary molars were selected and divided into 4 groups of 54 each (maxillary and mandibular first and second primary molars). MD/BL dimensions were measured using a digital caliper with 0.01 mm precision on casts and SCCs (3M brand). Data were assessed using paired t-test, post hoc test and ANOVA. P < 0.05 was considered statistically significant. Results. The MD dimension of the lower first molar SSC and the BL dimension of the lower second molar SSC had the least difference with the corresponding values of the respective teeth. The MD dimension of the upper second molar SSC and the BL dimension of the upper first molar SSC had the greatest difference with the corresponding values in the respective teeth. Comparison of the two different brands of SSCs for the upper first molar revealed that both types had significant differences with the teeth in terms of both MD (P = 0.0) and BL (P = 0.0) dimensions. Conclusion. In the studied population, best adaptation was seen in second lower molars and the least adaptationswere seen in first and second upper molars. PMID:26236433

  1. Chemistry of enol ethers. LXXXVIII. Condensation of the tetraethylacetal of malonaldehyde with /beta/-substituted enol alkyl ethers

    SciTech Connect

    Makin, S.M.; Kruglikova, R.I.; Kharitonova, O.V.; Arshava, B.M.

    1988-03-10

    The action of /beta/-substituted enol ethers on the tetraethylacetal of malonaldehyde gave the acetals of 1,5- and 1,7-dialdehydes. The nature of the substituent in the enol ether was found to affect the regioselectivity of the reaction: condensation with ethers containing an electron-withdrawing substituent leads to 1,5-dialdehyde acetals, while condensation with ethers containing a strong electron-donor substituent leads to 1,7-dialdehyde acetals. The condensation of malonaldehyde tetraethylacetal with /beta/-substituted enol alkyl ethers was carried out at room temperature in the presence of zinc chloride as catalyst.

  2. Modeling tree crown dynamics with 3D partial differential equations.

    PubMed

    Beyer, Robert; Letort, Véronique; Cournède, Paul-Henry

    2014-01-01

    We characterize a tree's spatial foliage distribution by the local leaf area density. Considering this spatially continuous variable allows to describe the spatiotemporal evolution of the tree crown by means of 3D partial differential equations. These offer a framework to rigorously take locally and adaptively acting effects into account, notably the growth toward light. Biomass production through photosynthesis and the allocation to foliage and wood are readily included in this model framework. The system of equations stands out due to its inherent dynamic property of self-organization and spontaneous adaptation, generating complex behavior from even only a few parameters. The density-based approach yields spatially structured tree crowns without relying on detailed geometry. We present the methodological fundamentals of such a modeling approach and discuss further prospects and applications. PMID:25101095

  3. [Application of low noble alloys in telescoped crowns].

    PubMed

    Susulić, T

    1989-01-01

    It is known that low noble alloys (Hera SG, Aurea-Heraus, Stabilor-Degussa, Midgold-Bego etc.) are used woredwide for the preparation of prosthetic constructions. For this reason attempts to produce low noble alloys with the properties equal to those of more expensive high noble alloys, are justified, as they are cheap and available to a great number of patients. The Yugoslav producer of dental materials "Zlatarna Celje" has produced a low noble alloy named Midor S. The comparative investigations of resistance to the mouth, performed at the University School of Dentistry in Ljubljana and in the Laboratory of Metallurgy of "Zlatarna Celje", have shown that this alloy was more resistant to corrosion than 22 karat, high noble alloy. In our Department Mikdor S was experimentally tested on telescoped crowns. The obtained results showed the satisfactory hardness and resistance to attrition between the internal and external crowns within the limits of tolerance which made it suitable for use. PMID:2489991

  4. Effect of sandblasting on fracture load of titanium ceramic crowns

    PubMed Central

    Moldi, Arvind I.; Bhandari, Kishor Singh; Nagral, Sharanbassapa; Deshpandey, Sumit; Kulkarni, Pawan

    2015-01-01

    Purpose of the Study: It is difficult to achieve a reliable bond between the titanium and veneering porcelain. The aim of this study was to evaluate the bond strength between titanium ceramic crowns. Materials and Methods: The surfaces of titanium copings were divided in two groups. Group A sandblasted with 250 um (n = 10) and Group B without sandblasting (n = 10). Low-fusing porcelain was bonded over copings. A universal testing machine was used to determine the fracture load (N) of the crowns. All data were compared using Student's t-test. Results: There was a significant difference in fracture toughness between two groups (P = 0.05). The mean value of fracture strength for Group A was 721.66 N and for Group B was 396.39 N. Conclusions: Sandblasting improves the bond strength between titanium, and ceramic, mechanical bonding plays a crucial role in the bonding between titanium and ceramic. PMID:26929517

  5. Fabrication of all-ceramic crowns by a new method.

    PubMed

    Masuda, Takayuki; Kakimoto, Kazutoshi; Takahashi, Kazuya; Komasa, Yutaka

    2016-01-01

    A new method of all-ceramic production using alumina coping has been developed. The present study investigates the influence of secondary firing (glass infiltration firing) conditions. Samples of porcelain build-up without secondary firing were also assessed. The suitability of coping that included secondary firing was found to be affected by the rate of temperature increase during the secondary firing. However, cracking developed in the fired porcelain if porcelain was built up onto secondarily-fired coping. In contrast, cracking did not occur with coping that was not secondarily fired. The bending strength after porcelain build-up was 70 MPa or higher, suggesting the possibility of clinical applications as an anterior crown. These findings establish that this is method of producing all-ceramic crowns that allows for low-cost manufacture in a short period of about 1 h. PMID:27041020

  6. Crown Gall Disease and Hairy Root Disease 1

    PubMed Central

    Gelvin, Stanton B.

    1990-01-01

    The neoplastic diseases crown gall and hairy root are incited by the phytopathogenic bacteria Agrobacterium tumefaciens and Agrobacterium rhizogenes, respectively. Although the molecular mechanism of T-DNA transfer to the plant most likely is the same for both species, the physiological basis of tumorigenesis is fundamentally different. Crown gall tumors result from the over-production of the phytohormones auxin and cytokinin specified by A. tumefaciens T-DNA genes. Although the T-DNA of some Riplasmids of A. rhizogenes contains auxin biosynthetic genes, these loci are not always necessary for hairy root formation. Recent experiments suggest that hairy root tumors result from the increased sensitivity of transformed cells to endogenous auxin levels. An understanding of hairy root tumorigenesis will likely result in an increased knowledge of plant developmental processes. Images Figure 1 PMID:16667272

  7. Electric field gradient and electronic properties of crown thioether compounds

    NASA Astrophysics Data System (ADS)

    Lima, Filipe Camargo Dalmatti Alves; Nascimento, Rafael Rodrigues Do; Gonçalves, Marcos Brown; Cottenier, Stefaan; Caldas, Marília Junqueira; Petrilli, Helena Maria

    2010-04-01

    We compare published TDPAC experiments on 111Cd in the crown thioether C6H12S3AgCl with ab-initio electronic structure calculations performed within the framework of the Density Functional Theory using the Projector Augmented Wave method. We conclude from this comparison that the Cd atom at the very moment of the TDPAC experiment is positively charged, and we point out to a methodological difference between reproducing experimental electric-field gradients in molecules versus solid metals.

  8. Taphonomic aspects of crowned hawk-eagle predation on monkeys.

    PubMed

    Sanders, William J; Trapani, Josh; Mitani, John C

    2003-01-01

    This study provides a taphonomic analysis of prey accumulations of crowned hawk-eagles (Stephanoaetus coronatus) from Ngogo, Kibale National Park, Uganda, collected over 37 months from below nests of two eagle pairs. Crowned hawk-eagles are powerful predators capable of killing animals much larger than themselves, and are significant predators of cercopithecoid monkeys in forest habitats throughout sub-Saharan Africa. At Ngogo, 81% of the individuals in the kill sample are monkeys. Redtail monkeys (Cercopithecus ascanius) are particularly well represented in the sample, making up 66% of monkeys identified to species. Despite an impressive killing apparatus, crowned hawk-eagles are fastidious eaters that inflict far less damage to bone than mammalian predators. Examination of skeletal material from the Ngogo kill sample reveals that crania, hindlimb elements, and scapulae survive predation better than do other bones. Crania of adults are typically complete and accompanied by mandibles, while crania of young individuals are usually dissociated from mandibles and lack basicrania and faces. Long bones are often whole or show minimal damage. Thin bones, such as crania and innominates, are marked by numerous nicks, punctures, and "can-opener" perforations. Scapular blades are heavily raked and shattered. Along with the strong preference for cercopithecoids, these distinct patterns of bone survival and damage indicate the feasibility of recognizing specific taphonomic signatures of large raptors in fossil assemblages. Berger and Clarke (1995) hypothesized that crowned hawk-eagles or similar large raptors were principally responsible for the accumulation of the late Pliocene fossil fauna from Taung, South Africa, including the type infant skull of Australopithecus africanus. The results of our study suggest that the faunal composition and type of damage to the hominid skull and other bone from Taung are consistent with the predatory activities of large raptors. More

  9. In-cylinder flows of a motored four-stroke engine with flat-crown and slightly concave-crown pistons

    SciTech Connect

    Huang, R.F.; Yang, H.S.; Yeh, C.-N.

    2008-04-15

    The temporal and spatial evolution processes of the in-cylinder flow structures and turbulence intensities in the symmetry and offset planes of a motored four-valve, four-stroke engine during the intake and compression strokes are diagnosed by using a particle image velocimeter. Two pistons of different crown shapes (flat-crown and slightly concave-crown pistons) are studied. The inception, establishment, and evolution of the tumbling vortical flow structures during the intake and compression strokes are clearly depicted. Quantitative strengths of the rotating vortical flow motions are presented by a dimensionless parameter, the tumble ratio, which can represent the mean angular velocity of the vortices in the target plane. The turbulence intensity of the in-cylinder flow is also calculated by using the measured time-varying velocity data. The results show that the flat-crown piston induces higher bulk-averaged tumble ratio and turbulence intensity than the slightly concave-crown piston does because the tumble ratio and turbulence generated by the flat-crown piston in the offset planes during the compression stroke are particularly large. The engine with the flat-crown piston also presents larger torque and power outputs and lower hydrocarbon emission than that with the slightly concave-crown piston. This might be caused by the enhanced combustion in the engine cylinder due to the stronger tumble ratio and turbulence intensity. (author)

  10. Reliability of metalloceramic and zirconia-based ceramic crowns.

    PubMed

    Silva, N R F A; Bonfante, E A; Zavanelli, R A; Thompson, V P; Ferencz, J L; Coelho, P G

    2010-10-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing. PMID:20660796

  11. Plant responses to Agrobacterium tumefaciens and crown gall development

    PubMed Central

    Gohlke, Jochen; Deeken, Rosalia

    2014-01-01

    Agrobacterium tumefaciens causes crown gall disease on various plant species by introducing its T-DNA into the genome. Therefore, Agrobacterium has been extensively studied both as a pathogen and an important biotechnological tool. The infection process involves the transfer of T-DNA and virulence proteins into the plant cell. At that time the gene expression patterns of host plants differ depending on the Agrobacterium strain, plant species and cell-type used. Later on, integration of the T-DNA into the plant host genome, expression of the encoded oncogenes, and increase in phytohormone levels induce a fundamental reprogramming of the transformed cells. This results in their proliferation and finally formation of plant tumors. The process of reprogramming is accompanied by altered gene expression, morphology and metabolism. In addition to changes in the transcriptome and metabolome, further genome-wide (“omic”) approaches have recently deepened our understanding of the genetic and epigenetic basis of crown gall tumor formation. This review summarizes the current knowledge about plant responses in the course of tumor development. Special emphasis is placed on the connection between epigenetic, transcriptomic, metabolomic, and morphological changes in the developing tumor. These changes not only result in abnormally proliferating host cells with a heterotrophic and transport-dependent metabolism, but also cause differentiation and serve as mechanisms to balance pathogen defense and adapt to abiotic stress conditions, thereby allowing the coexistence of the crown gall and host plant. PMID:24795740

  12. In vitro study of fracture strength of provisional crown materials

    PubMed Central

    Sayin, Gulsum; Kara, Ozlem

    2015-01-01

    PURPOSE The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns. MATERIALS AND METHODS A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37℃ for 24 hours, and then they were thermocycled (TC, 5000×, 5-55℃) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (α=.05). RESULTS Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01). CONCLUSION Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique. PMID:25722834

  13. Study of an NC system of machining crown gears

    NASA Astrophysics Data System (ADS)

    Xu, Xiaogang; Wang, Huaqing; Yan, Jian; Gao, Shenyou

    2005-12-01

    Crown gear couplings are usually used in metallurgy and steel rolling equipments, which is manufactured by duplicating processing in common. The method makes the manipulator work hard, and the efficiency is low. The machining precision is limited to the shape of the mold and it is difficult to control the movement of machines table. This work stated an NC system to use hobbing machine. It consists of an industrial control computer, grating sensor, servo- motor and its driver source, servo driver card and other I/O equipments of inputting and outputting. The grating sensor was installed in the axial direction to trace the instantaneous position of gob rest. The radial movement of the machine table was controlled by a servomotor. When the computer captures the axial signal, this system controls the machine table by moving ahead or backwards according to the calculated value of interpolation theory. Thus, two dimensions (axial and radial) associated movement was realized while the crown gear was processed. The feature of the system is that a grating sensor used in the axial direction replaces the servomotor. By making a little change in the mechanism of the machine, NC can be implement and its redesign cost is very low. The design software has an interpolation function for a circular arc and line. The system has been used on a Y1380 gear hobbing machine, and the correlative software of machining crown gear has been designed as well. Satisfactory results have been obtained, showing facility and reliability in practical operation.

  14. Mapping of the oat crown rust resistance gene Pc91.

    PubMed

    McCartney, C A; Stonehouse, R G; Rossnagel, B G; Eckstein, P E; Scoles, G J; Zatorski, T; Beattie, A D; Chong, J

    2011-02-01

    Crown rust is an important disease of oat caused by Puccinia coronata Corda f. sp. avenae Eriks. Crown rust is efficiently and effectively managed through the development of resistant oat varieties. Pc91 is a seedling crown rust resistance gene that is highly effective against the current P. coronata population in North America. The primary objective of this study was to develop DNA markers linked to Pc91 for purposes of marker-assisted selection in oat breeding programs. The Pc91 locus was mapped using a population of F7-derived recombinant inbred lines developed from the cross 'CDC Sol-Fi'/'HiFi' made at the Crop Development Centre, University of Saskatchewan. The population was evaluated for reaction to P. coronata in field nurseries in 2008 and 2009. Pc91 mapped to a linkage group consisting of 44 Diversity Array Technology (DArT) markers. DArTs were successfully converted to sequence characterized amplified region (SCAR) markers. Five robust SCARs were developed from three non-redundant DArTs that co-segregated with Pc91. SCAR markers were developed for different assay systems, such that SCARs are available for agarose gel electrophoresis, capillary electrophoresis, and Taqman single nucleotide polymorphism detection. The SCAR markers accurately postulated the Pc91 status of 23 North American oat breeding lines. PMID:20862449

  15. Immediate maxillary lateral incisor implants with nonocclusal loading provisional crowns.

    PubMed

    Peñarrocha, Miguel; Lamas, Joana; Peñarrocha, Maria; Garcia, Berta

    2008-01-01

    This clinical report series describes a treatment modality involving immediately placed dental implants in maxillary lateral incisor sites using noncemented immediate provisional crowns retained with calcinable copings (prosthetic complement used in preparing the metal for the definitive prosthesis). Ten implants were placed in eight patients for the replacement of maxillary lateral incisors: two immediate and eight corresponding to cases of agenesis. All were subjected to immediate rehabilitation with provisional acrylic resin crowns in nonocclusal loading. One implant failed 3 weeks after placement due to acute local trauma. The other nine remained functional within the mouth, with normal clinical and radiological characteristics after a minimum of 12-month follow-up. Immediate placement of implant fixed provisional restorations retained by friction in maxillary lateral incisors offers an esthetic solution, eliminates the need for a removable provisional restoration, and avoids implant failures associated with excess cement or screw loosening. Moreover, in the case of extractions, immediate placement and provisionalization of implants in maxillary lateral incisors can effectively optimize the peri-implant esthetic results by maintaining the existing hard and soft tissue architecture of the replaced tooth. As no cement or screws are required, and the provisional crowns are placed in nonocclusal loading, the risk of complications is minimized. PMID:17927733

  16. Reliability of Metalloceramic and Zirconia-based Ceramic Crowns

    PubMed Central

    Silva, N.R.F.A.; Bonfante, E.A.; Zavanelli, R.A.; Thompson, V.P.; Ferencz, J.L.; Coelho, P.G.

    2010-01-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing. PMID:20660796

  17. Simulation of clinical fractures for three different all-ceramic crowns.

    PubMed

    Oilo, Marit; Kvam, Ketil; Gjerdet, Nils R

    2014-06-01

    Comparison of fracture strength and fracture modes of different all-ceramic crown systems is not straightforward. Established methods for reliable testing of all-ceramic crowns are not currently available. Published in-vitro tests rarely simulate clinical failure modes and are therefore unsuited to distinguish between the materials. The in-vivo trials usually lack assessment of failure modes. Fractographic analyses show that clinical crowns usually fail from cracks initiating in the cervical margins, whereas in-vitro specimens fail from contact damage at the occlusal loading point. The aim of this study was to compare three all-ceramic systems using a clinically relevant test method that is able to simulate clinical failure modes. Ten incisor crowns of three types of all-ceramic systems were exposed to soft loading until fracture. The initiation and propagation of cracks in these crowns were compared with those of a reference group of crowns that failed during clinical use. All crowns fractured in a manner similar to fracture of the clinical reference crowns. The zirconia crowns fractured at statistically significantly higher loads than alumina and glass-ceramic crowns. Fracture initiation was in the core material, cervically in the approximal areas. PMID:24698209

  18. Incisor crown bending strength correlates with diet and incisor curvature in anthropoid primates.

    PubMed

    Deane, Andrew S

    2015-02-01

    Anthropoid incisors are large relative to the postcanine dentition and function in the preprocessing of food items. Previous analyses of anthropoid incisor allometry and shape demonstrate that incisor morphology is correlated with preferred foods and that more frugivorous anthropoids have larger and more curved incisors. Although the relationship between incisal crown curvature and preferred foods has been well documented in extant and fossil anthropoids, the functional significance of curvature variation has yet to be conclusively established. Given that an increase in crown curvature will increase maximum linear crown dimensions, and bending resistance is a function of linear crown dimensions, it is hypothesized that incisor crown curvature functons to increase incisor crown resistance to bending forces. This study uses beam theory to calculate the mesiodistal and labiolingual bending strengths of the maxillary and mandibular incisors of hominoid and platyrrhine taxa with differing diets and variable degrees of incisal curvature. Results indicate that bending strength correlates with incisal curvature and that frugivores have elevated incisor bending resistance relative to folivores. Maxillary central incisor bending strengths further discriminate platyrrhine and hominoid hard- and soft-object frugivores suggesting this crown is subjected to elevated occlusal loading relative to other incisors. These results are consistent with the hypothesis that incisor crown curvature functions to increase incisor crown resistance to bending forces but does not preclude the possibility that incisor bending strength is a composite function of multiple dentognathic variables including, but not limited to, incisor crown curvature. PMID:25156755

  19. Simulation of clinical fractures for three different all-ceramic crowns

    PubMed Central

    Øilo, Marit; Kvam, Ketil; Gjerdet, Nils R

    2014-01-01

    Comparison of fracture strength and fracture modes of different all-ceramic crown systems is not straightforward. Established methods for reliable testing of all-ceramic crowns are not currently available. Published in-vitro tests rarely simulate clinical failure modes and are therefore unsuited to distinguish between the materials. The in-vivo trials usually lack assessment of failure modes. Fractographic analyses show that clinical crowns usually fail from cracks initiating in the cervical margins, whereas in-vitro specimens fail from contact damage at the occlusal loading point. The aim of this study was to compare three all-ceramic systems using a clinically relevant test method that is able to simulate clinical failure modes. Ten incisor crowns of three types of all-ceramic systems were exposed to soft loading until fracture. The initiation and propagation of cracks in these crowns were compared with those of a reference group of crowns that failed during clinical use. All crowns fractured in a manner similar to fracture of the clinical reference crowns. The zirconia crowns fractured at statistically significantly higher loads than alumina and glass-ceramic crowns. Fracture initiation was in the core material, cervically in the approximal areas. PMID:24698209

  20. Ether bridge formation in loline alkaloid biosynthesis

    PubMed Central

    Pan, Juan; Bhardwaj, Minakshi; Faulkner, Jerome R.; Nagabhyru, Padmaja; Charlton, Nikki D.; Higashi, Richard M.; Miller, Anne-Frances; Young, Carolyn A.; Grossman, Robert B.; Schardl, Christopher L.

    2014-01-01

    Lolines are potent insecticidal agents produced by endophytic fungi of cool-season grasses. These alkaloids are composed of a pyrrolizidine ring system and an uncommon ether bridge linking carbons 2 and 7. Previous results indicated that 1-aminopyrrolizidine was a pathway intermediate. We used RNA interference to knock down expression of lolO, resulting in the accumulation of a novel alkaloid identified as exo-1-acetamidopyrrolizidine based on high-resolution MS and NMR. Genomes of endophytes differing in alkaloid profiles were sequenced, revealing that those with mutated lolO accumulated exo-1-acetamidopyrrolizidine but no lolines. Heterologous expression of wild-type lolO complemented a lolO mutant, resulting in the production of N-acetylnorloline. These results indicated that the non-heme iron oxygenase, LolO, is required for ether bridge formation, probably through oxidation of exo-1-acetamidopyrrolizidine. PMID:24374065

  1. Cyclic ethers adsorbed on Ru(001)

    NASA Astrophysics Data System (ADS)

    Walczak, M. M.; Thiel, P. A.

    1990-11-01

    The three cyclic ethers 1,3-dioxane. 1,4-dioxane and 1,3,5-trioxane all exhibit multiple desorption states from Ru(001) between 200 and 310 K, in addition to the multilayer and metastable states at lower temperature. Most distinctive are the two low-temperature α-states. which are similar in shape, position, and relative population for all three compounds. This suggests that these states are associated with configurations which are accessible to all three molecules. The data also indicate that there is some molecular decomposition to gaseous CO and H 2. 1,4-Dioxane yields the largest amounts of these decomposition products, suggesting that this molecule is most susceptible to surface-catalyzed decomposition. The desorption data for the three cyclic ethers are grossly similar to each other, and also to the straight-chain diethers which we have previously studied.

  2. Synthesis of new liquid crystalline diglycidyl ethers.

    PubMed

    Mohammed, Issam Ahmed; Hamidi, Rashidah Mohamed

    2012-01-01

    The phenolic Schiff bases I-VI were synthesized by condensation reactions between various diamines, namely o-dianisidine, o-tolidine and ethylenediamine with vanillin or p-hydroxybenzaldehyde and subsequent reactions between these phenolic Schiff bases and epichlorohydrin to produce new diglycidyl ethers Ia-VIa. The structures of these compounds were confirmed by CHN, FT-IR, (1)H-NMR, and (13)C-NMR spectroscopy. Their thermotropic liquid crystalline behavior was studied using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All the diglycidyl ethers prepared exhibit nematic mesophases, except for Va and VIa, which did not show any transition mesophases, but simply flow to liquids. PMID:22233565

  3. Poly(Arylene Ether Imidazole) Surface Films

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Towell, Timothy W.; Tompkins, Stephen S.

    1993-01-01

    Films adhere well to some substrates, provide smooth surfaces, and facilitate release from molds. Thin films of thermoplastic poly(arylene ether imidazole)s (PAEI's) particularly suitable for use as surface modifiers for graphite/epoxy or graphite/bismaleimide composite panels. Molecule of PAEI includes imidazole groups along its backbone that co-cure with epoxies or bismaleimides during processing. Films thermally stable and resistant to bombardment by energetic electrons.

  4. Nikola Tesla, the Ether and his Telautomaton

    NASA Astrophysics Data System (ADS)

    Milar, Kendall

    2014-03-01

    In the nineteenth century physicists' understanding of the ether changed dramatically. New developments in thermodynamics, energy physics, and electricity and magnetism dictated new properties of the ether. These have traditionally been examined from the perspective of the scientists re-conceptualizing the ether. However Nikola Tesla, a prolific inventor and writer, presents a different picture of nineteenth century physics. Alongside the displays that showcased his inventions he presented alternative interpretations of physical, physiological and even psychical research. This is particularly evident in his telautomaton, a radio remote controlled boat. This invention and Tesla's descriptions of it showcase some of his novel interpretations of physical theories. He offered a perspective on nineteenth century physics that focused on practical application instead of experiment. Sometimes the understanding of physical theories that Tesla reached was counterproductive to his own inventive work; other times he offered new insights. Tesla's utilitarian interpretation of physical theories suggests a more scientifically curious and invested inventor than previously described and a connection between the scientific and inventive communities.

  5. Biodegradation of glycol ethers in soil

    SciTech Connect

    Gonsior, S.J.; West, R.J.

    1995-08-01

    Because of the widespread use of glycol ethers in applications ranging from consumer products to use as chemical intermediates, there is a need to better understand the fate of these compounds in the environment. Soil biodegradation studies were conducted for three propylene glycol ethers: 1-methoxy-2-propanol, 1-phenoxy-2-propanol, and 1-methoxy-2-propanol acetate. The test compounds were labeled with carbon-14 at either the methoxy or phenoxy substituents. Biodegradation of the three compounds was observed in two sandy loam soils. The time required for disappearance of 50% of the test compounds ranged from < 1 d at 0.2 ppm (w/w) to <7 d at 107 ppm. Degradation rates were slower in a sandy soil, reflecting the lower concentration of microorganisms present. No significant accumulation of intermediate products was observed, and ultimate yields of {sup 14}CO{sub 2} were in the range of 40 to 65% of the initial concentration. Results indicated that the glycol ethers were degraded in a variety of soils under aerobic conditions.

  6. Chemistry and adhesive properties of poly(arylene ether)s containing heterocyclic units

    NASA Technical Reports Server (NTRS)

    Connell, John W.

    1991-01-01

    Novel poly(arylene ether)s containing heterocyclic units were prepared, characterized, and evaluated as adhesives and composite matrices. The polymers were prepared by reacting a heterocyclic bisphenol with an activated aromatic dihalide in a polar aprotic solvent, using potassium carbonate. The polymerizations were generally carried out in N,N-dimethylacetamide at 155 C. In some cases, where the polymers were semicrystalline, higher temperatures and thus higher boiling solvents were necessary to keep the polymers in solution. Heterocyclic rings incorporated into the poly(arylene ether) backbone include phenylquinoxaline, phenylimidazole, benzimidazole, benzoxazole, 1,3,4-oxadiazole, and 1,2,4-triazole. The polymers were characterized by differential scanning calorimetry, solution viscosity, X-ray diffraction, thin film, and adhesive and (in some cases) composite properties. The glass transition temperatures, crystalline melt temperature, solubility, and mechanical properties varied depending upon the heterocyclic ring. The chemistry and properties of these materials are discussed.

  7. Holographic evaluation of the marginal fit of complete crowns loaded at central fossa

    NASA Astrophysics Data System (ADS)

    Chen, Terry Y.; Chang, Guan L.; Wu, Shih H.

    1993-07-01

    In dentistry, the defect of cementation on the margins of crowns accumulates bacterial plaque easily. This can result in recurrent caries and periodontal disease. In this paper holographic interferometry is applied to study the effect of masticatory force on various complete crowns. Four complete molar crowns made from different casting materials (Au, Pd-Ag, Ni-Cr, and PFM) were tested. The horizontal displacements of two points near the margin, measured by the method of multiple observations, could be as large as 15 micrometers under normal load (25 kgw). However, the marginal discrepancy of all four crowns estimated were quite small (< 0.2 micrometers ). This also indicates that the cementation between the crown and the tooth is quite good. Nevertheless, when the load was increased to 45 kgw, a defect of cementation was found on the Pd-Ag crown.

  8. Forest Crown Cover Estimation in Northern Boreal and Temperate European Forest

    NASA Astrophysics Data System (ADS)

    Sirro, Laura; Hame, Tuomas; Ahola, Heikki; Lonnqvist, Anne

    2012-04-01

    A method for forest crown cover estimation using high resolution optical earth observation data was developed and tested at four study sites in Europe. Crown cover was estimated using the probability estimation method of VTT and Image2006 data. The accuracy of the crown cover predictions was assessed using reference data that were collected by visual interpretation of very high resolution aerial and space borne imagery. The average crown cover values in the reference data varied from 17 % to 86 % and in the predictions from 18 % to 80 %. The absolute root mean square error of the crown cover predictions varied between 14 % and 33 %. The results of the study showed that it is possible to map forest crown cover with twenty to thirty meter spatial resolution optical earth observation data using the single pixel values. However, understanding the variable results at different sites requires further investigation.

  9. Fracture Resistance of Non-Metallic Molar Crowns Manufactured with CEREC 3D

    NASA Astrophysics Data System (ADS)

    Madani, Dalia A.

    Objectives. To compare fracture strength and fatigue resistance of ceramic (ProCAD, Ivoclar-Vivadent) (C) and resin composite (Paradigm MZ100, 3M/ ESPE) (R) crowns made with CEREC-3D. Methods. A prepared ivorine molar tooth was duplicated to produce 40 identical prepared specimens made of epoxy resin (Viade). Twenty (C) crowns and 20 (R) were cemented to their dies using resin cement. Ten of each group were subjected to compressive loading to fracture. The remaining 10 of each group were subjected to mechanical cyclic loading for 500,000 cycles. The survivors were subjected to compressive loading to fracture. Results. No significant difference in mean fracture load was found between the two materials. However, only 30% of the (C) crowns vs. 100% of the (R) crowns survived the cyclic loading test. Conclusions. (R) crowns demonstrated higher fatigue Resistance than (C) crowns in-vitro and might better resist cracking in-vivo.

  10. Room temperature rechargeable magnesium batteries with sulfur-containing composite cathodes prepared from elemental sulfur and bis(alkenyl) compound having a cyclic or linear ether unit

    NASA Astrophysics Data System (ADS)

    Itaoka, Kanae; Kim, In-Tae; Yamabuki, Kazuhiro; Yoshimoto, Nobuko; Tsutsumi, Hiromori

    2015-11-01

    Room temperature rechargeable magnesium (Mg) batteries are constructed from Mg as a negative material, sulfur (S)-containing composite prepared from elemental sulfur and the bis(alkenyl) compound having a crown ether unit (BUMB18C6) or linear ether unit (UOEE) as a positive material and the simple electrolyte (0.7 mol dm-3 Mg[N(SO2CF3)2]2-triglyme (G3) solution). The reaction between molten S and the bis(alkenyl) compound (BUMB18C6 or UOEE) provides the sulfur-containing composite, S-BUMB18C6 or S-UOEE. Both of the sulfur-containing composites are electrochemically active in the Mg salt-based electrolyte, acetonitrile- or G3- Mg[N(SO2CF3)2]2 electrolyte. The first discharge capacity of the test cells with the sulfur-containing composite is 460 Ah kg-1 (per the weight of sulfur in the composite) with the S-BUMB18C6 electrode and 495 Ah kg-1 with the S-UOEE electrode. According to the continuous charge-discharge cycle tests (at 10th cycle), the discharge capacity of the test cell with the S-BUMB18C6 electrode (68.1 Ah kg-1) is higher than that with the S-UOEE electrode (0.18 Ah kg-1). The crown ether units in the S-BUMB18C6 composite may create ion-conducting paths in the cathode, prevent rise in the internal resistance of the cathode, and provide better cycle performance of the test cells with the S-BUMB18C6 composite electrode than that with the S-UOEE electrode.

  11. Azidated Ether-Butadiene-Ether Block Copolymers as Binders for Solid Propellants

    NASA Astrophysics Data System (ADS)

    Cappello, Miriam; Lamia, Pietro; Mura, Claudio; Polacco, Giovanni; Filippi, Sara

    2016-07-01

    Polymeric binders for solid propellants are usually based on hydroxyl-terminated polybutadiene (HTPB), which does not contribute to the overall energy output. Azidic polyethers represent an interesting alternative but may have poorer mechanical properties. Polybutadiene-polyether copolymers may combine the advantages of both. Four different ether-butadiene-ether triblock copolymers were prepared and azidated starting from halogenated and/or tosylated monomers using HTPB as initiator. The presence of the butadiene block complicates the azidation step and reduces the storage stability of the azidic polymer. Nevertheless, the procedure allows modifying the binder properties by varying the type and lengths of the energetic blocks.

  12. Development of quantitative structure property relationships for poly(arylene ether)s.

    PubMed

    Hamerton, I; Howlin, B J; Larwood, V

    1995-02-01

    The technique of quantitative structure-activity relationships (QSAR) is well accepted by the drug design community. The analogous technique of quantitative structure-property relationships (QSPR) has applications in the field of polymer chemistry. A variety of molecular modeling and molecular orbital techniques was used to find molecular descriptors that could be used to derive an empirical equation to describe the glass transition temperature of two related classes of poly(arylene ether)s. The derived equation was then used to predict the thermal characteristics of another polymer of the same type. PMID:7794828

  13. Electroless nickel-phosphorus coating on poly (ether ether ketone)/carbon nanotubes composite

    NASA Astrophysics Data System (ADS)

    Zhai, Tong; Di, Lizhi; Yang, De'an

    2014-05-01

    In order to improve electromagnetic shielding property of poly (ether ether ketone)/carbon nanotubes composite, a nickel-phosphorus coating was covered on the composite by electroless plating. The morphologies of the substrates and the coatings were characterized by SEM. XPS was performed to analyze the surface composition and chemical states before and after chemical etching. The results showed that lots of microscopic holes appeared and evenly distributed on the surface, and the concentration of hydrophilic groups on the surface increased after the composite was etched. Thermal shock test showed that the adhesive strength between the coating and the composite was good.

  14. Screw-retained crown restorations of single implants: A step-by-step clinical guide

    PubMed Central

    Assaf, Mohammad; Gharbyeh, Alaa’ Z. Abu

    2014-01-01

    This paper shows the clinical steps for preparing a screw-retained crown for the restoration of a single implant. Impression-taking using open-tray technique and delivery of the crown is presented in a step-by-step manner elucidated by detailed photographs. Furthermore, the advantages and disadvantages of screw-retained crowns are discussed in comparison with the cemented restorations. PMID:25512742

  15. Fracture Strength of Aged Monolithic and Bilayer Zirconia-Based Crowns

    PubMed Central

    Lameira, Deborah Pacheco; Silva, Wilkens Aurélio Buarque e; Silva, Frederico Andrade e; De Souza, Grace M.

    2015-01-01

    The purpose of this study was to evaluate the effect of design and surface finishing on fracture strength of yttria-tetragonal zirconia polycrystal (Y-TZP) crowns in monolithic (1.5 mm thickness) and bilayer (0.8 mm zirconia coping and 0.7 mm porcelain veneer) configuration after artificial aging. Bovine incisors received crown preparation and Y-TZP crowns were manufactured using CAD/CAM technique, according to the following groups (n = 10): Polished monolithic zirconia crowns (PM); Glazed monolithic zirconia crowns (GM); Bi-layer crowns (BL). Crowns were cemented with resin cement, submitted to artificial aging in a chewing simulator (2.5 million cycles/80 N/artificial saliva/37°C), and tested for fracture strength. Two remaining crowns referring to PM and GM groups were submitted to a chemical composition analysis to measure the level of yttrium after aging. One-way ANOVA and Tukey's test (P = .05) indicated that monolithic zirconia crowns presented similar fracture strength (PM = 3476.2 N ± 791.7; GM = 3561.5 N ± 991.6), which was higher than bilayer crowns (2060.4 N ± 810.6). There was no difference in the yttrium content among the three surfaces evaluated in the monolithic crowns. Thus, monolithic zirconia crowns present higher fracture strength than bilayer veneered zirconia after artificial aging and surface finishing does not affect their fracture strength. PMID:26576423

  16. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  17. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  18. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  19. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  20. 40 CFR 721.10067 - Ether amine phosphonate salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Ether amine phosphonate salt (generic... Specific Chemical Substances § 721.10067 Ether amine phosphonate salt (generic). (a) Chemical substances... ether amine phosphonate salt (PMNs P-05-57, P-05-58, P-05-59, P-05-61, P-05-62, P-05-63, P-05-64, and...

  1. Antioxidative and anticancer activities of various ethanolic extract fractions from crown-of-thorns starfish (Acanthaster planci).

    PubMed

    Lee, Chi-Chiu; Hsieh, Hernyi Justin; Hsieh, Cheng-Hong; Hwang, Deng-Fwu

    2014-11-01

    Many studies currently researching marine invertebrates to determine the therapeutic potential of their bioactive materials have been showing very promising results. The crown-of-thorns starfish Acanthaster planci, an Echinodermata of the class Asteroidea, is infamous as the unique venomous starfish and as a destroyer of coral reefs. Starfish possesses many useful pharmacological and biological characteristics. In this study, A. planci was extracted with 70% ethanol and lyophilized to obtain an ethanol fraction. The ethanol fraction was dissolved with water and defatted with petroleum ether to obtain a non-polar fraction. The residual solution was successively partitioned with ethylacetate and butanol to obtain an ethylacetate fraction and butanol fraction, respectively. Four fractions were used to examine the antioxidant and anticancer properties. The ethanol fraction of A. planci contained the highest antioxidant effects such as ABTS, DPPH, Fe(2+) chelating activity and reducing power when compared with four fractions. Among the four fractions, the butanol fraction was especially shown to inhibit human malignant melanoma A375.S2 cells' proliferation, which is involved in the apoptotic progression. This fraction could induce apoptosis and even necrosis in A375.S2 cells as evidenced by double staining with an Annexin V-FITC and PI assay and DNA fragmentation analysis. These results indicated that the starfish A. planci is a good resource for obtaining the biologically active substances for antioxidant and anticancer effects. PMID:25305737

  2. A tree canopy height delineation method based on Morphological Reconstruction—Open Crown Decomposition

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Jing, L.; Li, Y.; Tang, Y.; Li, H.; Lin, Q.

    2016-04-01

    For the purpose of forest management, high resolution LIDAR and optical remote sensing imageries are used for treetop detection, tree crown delineation, and classification. The purpose of this study is to develop a self-adjusted dominant scales calculation method and a new crown horizontal cutting method of tree canopy height model (CHM) to detect and delineate tree crowns from LIDAR, under the hypothesis that a treetop is radiometric or altitudinal maximum and tree crowns consist of multi-scale branches. The major concept of the method is to develop an automatic selecting strategy of feature scale on CHM, and a multi-scale morphological reconstruction–open crown decomposition (MRCD) to get morphological multi-scale features of CHM by: cutting CHM from treetop to the ground; analysing and refining the dominant multiple scales with differential horizontal profiles to get treetops; segmenting LiDAR CHM using watershed a segmentation approach marked with MRCD treetops. This method has solved the problems of false detection of CHM side-surface extracted by the traditional morphological opening canopy segment (MOCS) method. The novel MRCD delineates more accurate and quantitative multi-scale features of CHM, and enables more accurate detection and segmentation of treetops and crown. Besides, the MRCD method can also be extended to high optical remote sensing tree crown extraction. In an experiment on aerial LiDAR CHM of a forest of multi-scale tree crowns, the proposed method yielded high-quality tree crown maps.

  3. Extracting oil palm crown from WorldView-2 satellite image

    NASA Astrophysics Data System (ADS)

    Korom, A.; Phua, M.-H.; Hirata, Y.; Matsuura, T.

    2014-02-01

    Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for biomass estimation from high resolution satellite (HRS) image. This study examined extraction of individual OP crown from a WorldView-2 image using twofold algorithms, i.e., masking of Non-OP pixels and detection of individual OP crown based on the watershed segmentation of greyscale images. The study site was located in Beluran district, central Sabah, where matured OPs with the age ranging from 15 to 25 years old have been planted. We examined two compound vegetation indices of (NDVI+1)*DVI and NDII for masking non-OP crown areas. Using kappa statistics, an optimal threshold value was set with the highest accuracy at 90.6% for differentiating OP crown areas from Non-OP areas. After the watershed segmentation of OP crown areas with additional post-procedures, about 77% of individual OP crowns were successfully detected in comparison to the manual based delineation. Shape and location of each crown segment was then assessed based on a modified version of the goodness measures of Möller et al which was 0.3, indicating an acceptable CSGM (combined segmentation goodness measures) agreements between the automated and manually delineated crowns (perfect case is '1').

  4. Extracting Oil Palm Crown from WorldView-2 Satellite Image

    NASA Astrophysics Data System (ADS)

    Korom, A.; Phua, M.-H.; Hirata, Y.; Matsuura, T.

    2014-02-01

    Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for biomass estimation from high resolution satellite (HRS) image. This study examined extraction of individual OP crown from a WorldView-2 image using twofold algorithms, i.e., masking of Non-OP pixels and detection of individual OP crown based on the watershed segmentation of greyscale images. The study site was located in Beluran district, central Sabah, where matured OPs with the age ranging from 15 to 25 years old have been planted. We examined two compound vegetation indices of (NDVI+1)*DVI and NDII for masking non-OP crown areas. Using kappa statistics, an optimal threshold value was set with the highest accuracy at 90.6% for differentiating OP crown areas from Non-OP areas. After the watershed segmentation of OP crown areas with additional post-procedures, about 77% of individual OP crowns were successfully detected in comparison to the manual based delineation. Shape and location of each crown segment was then assessed based on a modified version of the goodness measures of [14] which was 0.3, indicating an acceptable CSGM (combined segmentation goodness measures) agreements between the automated and manually delineated crowns (perfect case is '1').

  5. Divinyl ether synthase gene and protein, and uses thereof

    DOEpatents

    Howe, Gregg A.; Itoh, Aya

    2011-09-13

    The present invention relates to divinyl ether synthase genes, proteins, and methods of their use. The present invention encompasses both native and recombinant wild-type forms of the synthase, as well as mutants and variant forms, some of which possess altered characteristics relative to the wild-type synthase. The present invention also relates to methods of using divinyl ether synthase genes and proteins, including in their expression in transgenic organisms and in the production of divinyl ether fatty acids, and to methods of suing divinyl ether fatty acids, including in the protection of plants from pathogens.

  6. Divinyl ether synthase gene, and protein and uses thereof

    DOEpatents

    Howe, Gregg A.; Itoh, Aya

    2006-12-26

    The present invention relates to divinyl ether synthase genes, proteins, and methods of their use. The present invention encompasses both native and recombinant wild-type forms of the synthase, as well as mutants and variant forms, some of which possess altered characteristics relative to the wild-type synthase. The present invention also relates to methods of using divinyl ether synthase genes and proteins, including in their expression in transgenic organisms and in the production of divinyl ether fatty acids, and to methods of suing divinyl ether fatty acids, including in the protection of plants from pathogens.

  7. Functionalized poly(arylene ethers) as toughness modifiers for bismaleimides

    NASA Technical Reports Server (NTRS)

    Stenzenberger, H. D.; Roemer, W.; Hergenrother, P. M.; Jensen, B.; Breitigam, W.

    1990-01-01

    A family of novel, low molecular weight functionalized poly(arylene ether) resins has been investigated to ascertain its members' toughness-imparting contribution to neat bismaleimide (BMI) resin and BMI-matrix laminate composite properties. Attention is given to the contribution of the reactive poly(arylene ether)'s backbone chemistry to fracture toughness, as well as to the comparative influence of high and low molecular weight reactive poly(arylene ether) types on the modified BMI resin systems. The modified BMIs possess a polyphase morphology, with good adhesion between the thermoplastic nodules and the host thermoset systems.

  8. Antioxidant activity of alkyl hydroxytyrosyl ethers in unsaturated lipids.

    PubMed

    Cert, Rosa; Madrona, Andrés; Espartero, José Luis; Pérez-Camino, M Carmen

    2015-06-01

    The antioxidant activity of ethyl and octyl hydroxytyrosyl ethers toward lipids was determined using the Rancimat and open cup methods at high temperatures and 50 °C, respectively. The effect of the unsaturation of the matrix was evaluated using sunflower, soya, and fish refined oils. The antioxidant activities of alkyl hydroxytyrosyl ethers (HTy ethers), hydroxytyrosyl esters, and free hydroxytyrosol are similar, and are much higher than that of α-tocopherol at the same millimolar concentration. The relationship between the induction period and the concentration of the HTy ethers is a sigmoidal curve; an accurate concentration of HTy ethers is necessary to achieve maximum activity, as it increases with the level of matrix unsaturation. The presence of tocopherols in commercial oils affects the antioxidant effect of HTy ethers. Thus, the addition of a low concentration of HTy ethers results in a positive effect, whereas the effect of the addition of high amounts of ethers is slightly less than that of the phenol alone. The addition of HTy ethers to commercial refined oils increases the stability of the oils and preserves tocopherols and polyunsaturated fatty acids from oxidation, enabling the oils to maintain their nutritional properties for longer periods of time. PMID:26018773

  9. Ether Cleavage Re-Investigated: Elucidating the Mechanism of BBr3-Facilitated Demethylation of Aryl Methyl Ethers

    PubMed Central

    Kosak, Talon M; Conrad, Heidi A; Korich, Andrew L; Lord, Richard L

    2015-01-01

    One of the most well-known, highly utilized reagents for ether cleavage is boron tribromide (BBr3), and this reagent is frequently employed in a 1:1 stoichiometric ratio with ethers. Density functional theory calculations predict a new mechanistic pathway involving charged intermediates for ether cleavage in aryl methyl ethers. Moreover, these calculations predict that one equivalent of BBr3 can cleave up to three equivalents of anisole, producing triphenoxyborane [B(OPh)3] prior to hydrolysis. These predictions were validated by gas chromatography analysis of reactions where the BBr3:anisole ratio was varied. Not only do we confirm that sub-stoichiometric equivalents may be used for ether demethylation, but the findings also support our newly proposed three cycle mechanism for cleavage of aryl methyl ethers. PMID:26693209

  10. Basal ganglia—thalamus and the “crowning enigma”

    PubMed Central

    Garcia-Munoz, Marianela; Arbuthnott, Gordon W.

    2015-01-01

    When Hubel (1982) referred to layer 1 of primary visual cortex as “… a ‘crowning mystery’ to keep area-17 physiologists busy for years to come …” he could have been talking about any cortical area. In the 80’s and 90’s there were no methods to examine this neuropile on the surface of the cortex: a tangled web of axons and dendrites from a variety of different places with unknown specificities and doubtful connections to the cortical output neurons some hundreds of microns below. Recently, three changes have made the crowning enigma less of an impossible mission: the clear presence of neurons in layer 1 (L1), the active conduction of voltage along apical dendrites and optogenetic methods that might allow us to look at one source of input at a time. For all of those reasons alone, it seems it is time to take seriously the function of L1. The functional properties of this layer will need to wait for more experiments but already L1 cells are GAD67 positive, i.e., inhibitory! They could reverse the sign of the thalamic glutamate (GLU) input for the entire cortex. It is at least possible that in the near future normal activity of individual sources of L1 could be detected using genetic tools. We are at the outset of important times in the exploration of thalamic functions and perhaps the solution to the crowning enigma is within sight. Our review looks forward to that solution from the solid basis of the anatomy of the basal ganglia output to motor thalamus. We will focus on L1, its afferents, intrinsic neurons and its influence on responses of pyramidal neurons in layers 2/3 and 5. Since L1 is present in the whole cortex we will provide a general overview considering evidence mainly from the somatosensory (S1) cortex before focusing on motor cortex. PMID:26582979

  11. Unicuspid and bicuspid tooth crown formation in squamates.

    PubMed

    Handrigan, Gregory R; Richman, Joy M

    2011-12-15

    The molecular and developmental factors that regulate tooth morphogenesis in nonmammalian species, such as snakes and lizards, have received relatively little attention compared to mammals. Here we describe the development of unicuspid and bicuspid teeth in squamate species. The simple, cone-shaped tooth crown of the bearded dragon and ball python is established at cap stage and fixed in shape by the differentiation of cells and the secretion of dental matrices. Enamel production, as demonstrated by amelogenin expression, occurs relatively earlier in squamate teeth than in mouse molars. We suggest that the early differentiation in squamate unicuspid teeth at cap stage correlates with a more rudimentary tooth crown shape. The leopard gecko can form a bicuspid tooth crown despite the early onset of differentiation. Cusp formation in the gecko does not occur by the folding of the inner enamel epithelium, as in the mouse molar, but by the differential secretion of enamel. Ameloblasts forming the enamel epithelial bulge, a central swelling of cells in the inner enamel epithelium, secrete amelogenin at cap stage, but cease to do so by bell stage. Meanwhile, other ameloblasts in the inner enamel epithelium continue to secrete enamel, forming cusp tips on either side of the bulge. Bulge cells specifically express the gene Bmp2, which we suggest serves as a pro-differentiation signal for cells of the gecko enamel organ. In this regard, the enamel epithelial bulge of the gecko may be more functionally analogous to the secondary enamel knot of mammals than the primary enamel knot. PMID:21932327

  12. Novel high T{sub g} high-strength poly(aryl ether)s

    SciTech Connect

    Banerjee, S.; Maier, G.

    1999-08-01

    A novel 2-perfluoroalkyl-activated bisfluoro monomer has been synthesized successfully using a Pd(0)-catalyzed cross-coupling reaction of 4-fluoro-3-trifluoromethyl phenyl boronic acid with 4,4{prime}-dibromodiphenylbenzene. This monomer was converted to novel poly(aryl ether)s by nucleophilic displacement of the fluorine atoms on the benzene ring with several bisphenols. The products obtained by displacement of the fluorine atoms exhibit weight average molar masses up to 1.06 {times} 10{sup 5} g/mol in GPC. These poly(aryl ether)s showed outstanding thermooxidative stability up to 534 C for 5% weight loss in TGA under synthetic air and high glass transition temperatures (T{sub g}) even up to 300 C in DSC and DMTA. These polymers are soluble in a wide range of organic solvents, e.g., CHCl{sub 3}, THF, NMP, DMF, toluene, etc., and are insoluble in DMSO and acetone. Transparent thin films of these polymers cast from DMF exhibited tensile strengths up to 115 MPa, moduli up to 2.59 GPa, and elongations up to 120% depending on their exact repeating unit structures. These values are comparable to those of high performance thermoplastic materials such as PEEK or Ultem PEI.

  13. Novel high T[sub g] high-strength poly(aryl ether)s

    SciTech Connect

    Banerjee, S.; Maier, G. . Lehrstuhl fuer Makromolekulare Stoffe)

    1999-08-01

    A novel 2-perfluoroalkyl-activated bisfluoro monomer has been synthesized successfully using a Pd(0)-catalyzed cross-coupling reaction of 4-fluoro-3-trifluoromethyl phenyl boronic acid with 4,4[prime]-dibromodiphenylbenzene. This monomer was converted to novel poly(aryl ether)s by nucleophilic displacement of the fluorine atoms on the benzene ring with several bisphenols. The products obtained by displacement of the fluorine atoms exhibit weight average molar masses up to 1.06 [times] 10[sup 5] g/mol in GPC. These poly(aryl ether)s showed outstanding thermooxidative stability up to 534 C for 5% weight loss in TGA under synthetic air and high glass transition temperatures (T[sub g]) even up to 300 C in DSC and DMTA. These polymers are soluble in a wide range of organic solvents, e.g., CHCl[sub 3], THF, NMP, DMF, toluene, etc., and are insoluble in DMSO and acetone. Transparent thin films of these polymers cast from DMF exhibited tensile strengths up to 115 MPa, moduli up to 2.59 GPa, and elongations up to 120% depending on their exact repeating unit structures. These values are comparable to those of high performance thermoplastic materials such as PEEK or Ultem PEI.

  14. Unprecedented reactions: from epichlorohydrin to epoxyglycidyl substituted divinyl ether and its conversion into epoxyglycidyl propargyl ether

    PubMed Central

    Yao, Yiwu; Li, Zheng; Qiu, Yatao; Bai, Jinhong; Su, Jinyue; Zhang, Dayong; Jiang, Sheng

    2015-01-01

    The reaction of epichlorohydrin with concentrated sodium hydroxide in hexane under phase transfer conditions has surprisingly led to the formation of the symmetrical di(3-epoxyglycidyl-1-propenyl) ether 1 which contains both nucleophilic and electrophilic moieties. When it was reacted with n-butyllithium, intermediate 1 once again surprisingly generated epoxyglycidyl propargyl ether, which was further reacted in situ with a variety of benzaldehydes to furnish the corresponding substituted propargylic alcohols in good yields. While the reaction is operationally simple, it provides a powerful method for the synthesis of the important products from commodity materials such as epichlorohydrin. Moreover, these reactions may have revealed that some fundamental properties of the hydroxide anion in those once thought straightforward reactions are not well understood. A careful analysis of the experimental data suggests that an unprecedented concerted elimination of the epoxyglycidyl ether with sodium hydroxide may be operative and an alpha deprotonation followed by alpha elimination of the di(3-epoxyglycidyl-1-propenyl) ether with alkyllithium may have been involved. PMID:26383123

  15. Brominated-chlorinated diphenyl ethers formed by thermolysis of polybrominated diphenyl ethers at low temperatures.

    PubMed

    Rupp, Silke; Metzger, Jörg W

    2005-09-01

    Polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants (BFRs) used mainly as additives in different kinds of plastic material. Various PBDEs are found in all environmental compartments as well as in tissue and blood serum of animals and humans due to their persistence and tendency to bioaccumulate. Emission of PBDEs into the environment can occur during recycling of PBDE-containing plastic material or during their uncontrolled or insufficient combustion as e.g. in accidental fires or landfill fires. Under these circumstances, PBDEs can also function as precursor molecules for the formation of polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). In this study, we qualitatively investigated the reaction of two PBDE congeners, 2,2',4,4'-tetrabromo diphenyl ether (BDE 47) and 2,2',4,4',5,5'-hexabromo diphenyl ether (BDE 153), as well as hexabromobenzene (HBB), a flame retardant used in the past, when exposed to temperatures between 250 degrees C and 500 degrees C. The formed reaction products were analysed by high resolution gas chromatography-low resolution mass spectrometry (HRGC-LRMS). Among others brominated-chlorinated diphenyl ethers were formed by chlorodebromination of the PBDEs. In addition, thermolysis of BDE 47 and BDE 153 in the presence of tetrachloromethane as model substance for an organic chlorine source was studied. Thermal treatment of HBB resulted in the formation of brominated-chlorinated benzenes. PMID:16083771

  16. Unprecedented reactions: from epichlorohydrin to epoxyglycidyl substituted divinyl ether and its conversion into epoxyglycidyl propargyl ether

    NASA Astrophysics Data System (ADS)

    Yao, Yiwu; Li, Zheng; Qiu, Yatao; Bai, Jinhong; Su, Jinyue; Zhang, Dayong; Jiang, Sheng

    2015-09-01

    The reaction of epichlorohydrin with concentrated sodium hydroxide in hexane under phase transfer conditions has surprisingly led to the formation of the symmetrical di(3-epoxyglycidyl-1-propenyl) ether 1 which contains both nucleophilic and electrophilic moieties. When it was reacted with n-butyllithium, intermediate 1 once again surprisingly generated epoxyglycidyl propargyl ether, which was further reacted in situ with a variety of benzaldehydes to furnish the corresponding substituted propargylic alcohols in good yields. While the reaction is operationally simple, it provides a powerful method for the synthesis of the important products from commodity materials such as epichlorohydrin. Moreover, these reactions may have revealed that some fundamental properties of the hydroxide anion in those once thought straightforward reactions are not well understood. A careful analysis of the experimental data suggests that an unprecedented concerted elimination of the epoxyglycidyl ether with sodium hydroxide may be operative and an alpha deprotonation followed by alpha elimination of the di(3-epoxyglycidyl-1-propenyl) ether with alkyllithium may have been involved.

  17. Provisional Crown Dislodgement during Scuba Diving: A Case of Barotrauma

    PubMed Central

    Gulve, Meenal Nitin; Gulve, Nitin Dilip

    2013-01-01

    Changes in ambient pressure, for example, during flying, diving, or hyperbaric oxygen therapy, can lead to barotrauma. Although it may seem that this issue was neglected in dental education and research in recent decades, familiarity with and understanding of these facts may be of importance for dental practitioners. We report the case of a patient who experienced barotrauma involving dislodgement of a provisional crown during scuba diving. Patients who are exposed to pressure changes as a part of their jobs or hobbies and their dentists should know the causes of barotrauma. In addition, the clinician must be aware of the possible influence of pressure changes on the retention of dental components. PMID:23984113

  18. Infrared Imagery of Crown-Fire Dynamics during FROSTFIRE.

    NASA Astrophysics Data System (ADS)

    Coen, Janice; Mahalingam, Shankar; Daily, John

    2004-09-01

    A thorough understanding of crown-fire dynamics requires a clear picture of the three-dimensional winds in and near the fire, including the flaming combustion zone and the convective updrafts produced by the fire. These observations and analyses present a unique high-spatial-resolution and high-temporal-resolution perspective of the motions within crown fires propagating up a forested 20° slope under light winds of 3 m s-1 during the FROSTFIRE experiment in interior Alaska. The purpose of this work is to calculate combustion-zone winds and examine mechanisms for the rapid propagation of crown fires. An infrared imager was used to detect high-temperature regions produced by incandescent soot particles in and near the fire and to produce a sequence of high-frequency (60 Hz), high-resolution (0.375 m × 0.8 m) two-dimensional images of temperature. An image-flow-analysis technique was applied to these data to derive wind fields in the image plane. Maximum updrafts of 32 60 m s-1 accompany maximum downdrafts of 18 30 m s-1. Horizontal wind speeds of 12 28 m s-1 show strong inflow into the base of the convective updrafts and imply recirculation of air and incomplete combustion products from the fire. Motions were more complex than a single large convective plume or many buoyant tree-scale plumes rising separately. Instead, repeated examples of narrow flaming fingers, representing a scale larger than individual trees, initially burst upslope along the ground for tens of meters at speeds up to 28 48 m s-1 before turning upward. These bursts exceeded ambient environmental winds, those considered to be driving the fire, by a factor of 10 and were low enough to propagate the crown fire actively by both igniting and preheating/ drying canopy fuel ahead of the fire. Average spread rates were 0.75 1.11 m s-1, with a peak 10-s spread rate of 1.26 m s-1. This powerful, dynamic mechanism of fire spread could explain firefighter reports of being overtaken by

  19. Rapid Self-Assembly of Uranyl Polyhedra into Crown Clusters

    SciTech Connect

    Sigmon, Ginger E.; Burns, Peter C.

    2011-06-22

    Clusters built from 32 uranyl peroxide polyhedra self-assemble and crystallize within 15 min after combining uranyl nitrate, ammonium hydroxide, and hydrogen peroxide in aqueous solution under ambient conditions. These novel crown-shaped clusters are remarkable in that they form so quickly, have extraordinarily low aqueous solubility, form with at least two distinct peroxide to hydroxyl ratios, and form in very high yield. The clusters, which have outer diameters of 23 Å, topologically consist of eight pentagons and four hexagons. Their rapid formation and low solubility in aqueous systems may be useful properties at various stages in an advanced nuclear energy system.

  20. Provisional Crown Dislodgement during Scuba Diving: A Case of Barotrauma.

    PubMed

    Gulve, Meenal Nitin; Gulve, Nitin Dilip

    2013-01-01

    Changes in ambient pressure, for example, during flying, diving, or hyperbaric oxygen therapy, can lead to barotrauma. Although it may seem that this issue was neglected in dental education and research in recent decades, familiarity with and understanding of these facts may be of importance for dental practitioners. We report the case of a patient who experienced barotrauma involving dislodgement of a provisional crown during scuba diving. Patients who are exposed to pressure changes as a part of their jobs or hobbies and their dentists should know the causes of barotrauma. In addition, the clinician must be aware of the possible influence of pressure changes on the retention of dental components. PMID:23984113

  1. Generation of a crowned pinion tooth surface by a plane

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Zhang, J.; Handschuh, R. F.

    1988-01-01

    The topology of a crowned spur pinion tooth surface that reduces the level of transmission errors due to misalignment is described. The geometry of the modified pinion tooth surface and of the regular involute gear tooth surface is discussed. The tooth contact analysis between the meshing surfaces is also described. Generating a modified pinion tooth surface by a plane whose motion is controlled by a 5-degree-of-freedom system is investigated. The numerical results included indicate that the transmission error remains low as the gears are misaligned.

  2. Production of durene from alcohols and ethers

    SciTech Connect

    Fowles, P. E.; Yan, T. Y.

    1985-06-18

    Durene is recovered from a mixture rich in durene and containing hydrocarbons boiling in the gasoline range by cooling the mixture to a point where crystallization occurs and separating the crystallized durene. The durene subsequently is washed with a wash fluid. The wash fluid which can be methanol, is returned to a process wherein it is converted to gasoline and durene. The separated mother liquor is added to the gasoline fraction. The original mixture of durene and gasoline is obtained by the catalytic conversion of alcohols and ethers.

  3. Obstetric and Other Uses of Ether Before Ether Day, According to the Boston Medical and Surgical Journal of 1828-1846.

    PubMed

    Stoller, Sundrayah N; Minehart, Rebecca D; Alston, Theodore A

    2016-04-01

    From the inception of the Boston Medical and Surgical Journal in 1828 until the prominent public demonstration of surgical anesthesia on Ether Day of 1846, ether was often mentioned in the journal. Many of the examples were related to obstetrics. Because molecular structures were not available in the early 1800s, diverse volatile liquids were termed ethers. In addition to sulphuric ether, so-called ethers included cyanide-releasing propionitrile and ethanolic solutions of chloroform and of the potent vasodilator ethyl nitrite. Familiarity with anesthetically unsuitable ethers may have long deterred consideration of inhaled sulphuric ether for analgesia and anesthesia. PMID:27080505

  4. [Retention of crowns as affected by film thickness of zinc phosphate cement and taper angle of crowns (author's transl)].

    PubMed

    Otani, H; Goto, T

    1979-10-01

    Dependence of the retention of crowns at their axial wall on the film thickness of zinc phosphate cement and the taper angle was investigated. Stainless steel dies, composed of a preparation and an occlusally perforated crown the taper angle of which was 2.9, 5.7, 8.5 and 11.3 degrees respectively (Fig. 1, (a) and (b)), were cemented within three min. after the start of mix with a Shofu Micro Cement having a powder-liquid ratio of 1.5 g/0.5 cc. The thickness of the cement layer at the axial wall was regulated to a given value between 9 and 55 mu through the use of a discrepancy measurer. A Shimazu Autograph tensile test machine was employed to measure 48-hr retention (kg/cm2). The retention of the crowns was strongly dependent on the cement film thickness and the taper angle when the film thickness was below a critical value (15 mu in this experiment), but not when the film thickness was above this value (Fig. 3). This may be explained by the term of mechanical interlocking of either of the unreacted powder grains and the matrix phase in the luting cement, as schematically drawn in Fig. 6. The same findings were more evidently appeared on the semilogarythmic diagram in Fig. 4. In this diagram, the critical value was shown as intersection of two straight lines which could be drawn through all the measurements for four taper angles, using the least squares. PMID:295065

  5. IRIS Toxicological Review of Decabromodiphenyl Ether (2008 Final)

    EPA Science Inventory

    EPA is announcing the release of the final report, Toxicological Review of Decabromodiphenyl Ether: in support of the Integrated Risk Information System (IRIS). The updated Summary for Decabromodiphenyl Ether and accompanying Quickview have also been added to the IRIS Data...

  6. HPLC and TLC characterisation of ecdysteroid alkyl ethers.

    PubMed

    Lapenna, Silvia; Dinan, Laurence

    2009-10-01

    Semi-synthetic ecdysteroid alkyl ethers have increased potential over natural ecdysteroids as actuators of ligand-inducible gene-expression systems based on the ecdysteroid receptor for in vivo applications. However, a scalable synthesis of these compounds has yet to be developed. We report a set of reversed-phase (RP; C(18) and C(6)) and normal-phase (NP; diol) HPLC systems which can be used to analyse and separate ecdysteroid ethers with single or multiple O-methyl substitutions at the 2alpha-, 3beta-, 14alpha-, 22- and 25-positions. The elution order of methyl ether analogues of the prototypical ecdysteroid 20-hydroxyecdysone (20E) was 3-methyl<2-methyl<14-methyl<25-methyl<22-methyl with both C(18)- and C(6)-RP-HPLC, when eluted with methanol/water mixtures. Further, the elution order of 20E 22-O-alkyl ethers was methylethers can also be adequately resolved by NP-HPLC and silica HPTLC. On the latter, detection of ecdysteroid O-alkyl ethers with the p-anisaldehyde/sulphuric acid reagent distinguishes 22-O-alkyl ethers from non-22-O-alkyl ether analogues by the colour of the resulting spot. PMID:19648067

  7. 48. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    48. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, 5TH LEVEL, LOOKING NORTH AT ETHER AND ALCOHOL CONDENSERS AT TOP OF TOWER. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  8. Process for producing dimethyl ether from synthesis gas

    DOEpatents

    Pierantozzi, R.

    1985-06-04

    This invention pertains to a Fischer Tropsch process for converting synthesis gas to an oxygenated hydrocarbon with particular emphasis on dimethyl ether. Synthesis gas comprising carbon monoxide and hydrogen are converted to dimethyl ether by carrying out the reaction in the presence of an alkali metal-manganese-iron carbonyl cluster incorporated onto a zirconia-alumina support.

  9. 29 CFR 1926.1108 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false bis-Chloromethyl ether. 1926.1108 Section 1926.1108 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...-Chloromethyl ether. Note: The requirements applicable to construction work under this section are identical...

  10. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  11. 29 CFR 1915.1008 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false bis-Chloromethyl ether. 1915.1008 Section 1915.1008 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... § 1915.1008 bis-Chloromethyl ether. Note: The requirements applicable to shipyard employment under...

  12. 40 CFR 721.3485 - Hydrofluorocarbon alkyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluorocarbon alkyl ether. 721... Substances § 721.3485 Hydrofluorocarbon alkyl ether. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a hydrofluorocarbon alkyl...

  13. 29 CFR 1926.1106 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Methyl chloromethyl ether. 1926.1106 Section 1926.1106 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... § 1926.1106 Methyl chloromethyl ether. Note: The requirements applicable to construction work under...

  14. 29 CFR 1915.1006 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false Methyl chloromethyl ether. 1915.1006 Section 1915.1006 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Hazardous Substances § 1915.1006 Methyl chloromethyl ether. Note: The requirements applicable to...

  15. 29 CFR 1926.1108 - bis-Chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false bis-Chloromethyl ether. 1926.1108 Section 1926.1108 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...-Chloromethyl ether. Note: The requirements applicable to construction work under this section are identical...

  16. 40 CFR 721.825 - Certain aromatic ether diamines.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Certain aromatic ether diamines. 721.825 Section 721.825 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC... Substances § 721.825 Certain aromatic ether diamines. (a) Chemical substances and significant new...

  17. 29 CFR 1926.1106 - Methyl chloromethyl ether.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Methyl chloromethyl ether. 1926.1106 Section 1926.1106 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... § 1926.1106 Methyl chloromethyl ether. Note: The requirements applicable to construction work under...

  18. 46. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    46. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, CONTROL PANEL LEVEL (2ND DECK) OF ETHER AND ALCOHOL STILL BUILDING, LOOKING NORTH, SHOWING TWO ALCOHOL DISTILLATION TOWERS BEHIND 'MIXED SOLVENT UNIT' CONTROL PANEL. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  19. 47. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    47. BUILDING NO. 519, ETHER AND ALCOHOL RECOVERY HOUSE, INTERIOR, 4TH LEVEL, LOOKING NORTH AT TOPS OF ALCOHOL AND ETHER DISTILLATION TOWERS. - Picatinny Arsenal, 500 Area, Powder Factory & Power House, State Route 15 near I-80, Dover, Morris County, NJ

  20. Preparation of highly fluorinated diols containing ether linkages.

    NASA Technical Reports Server (NTRS)

    Rochow, S. E.; Stump, E. C., Jr.

    1970-01-01

    Hydroxy-terminated perfluoroethers and polyurethane resins derived from ethers have outstanding chemical resistance and good thermal properties. They can be used as potting compounds, coatings, and seals. The hydroxy-terminated ethers serve as intermediates in the synthesis of highly fluorinated elastomers and adhesives.