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Sample records for crystalline substituted polyacetylenes

  1. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, I.; Morisato, Atsushi

    1998-01-13

    A separation membrane is described which is useful for gas separation, particularly separation of C{sub 2+} hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula shown in the accompanying diagram, wherein R{sub 1} is chosen from the group consisting of C{sub 1}-C{sub 4} alkyl and phenyl, and wherein R{sub 2} is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) [PMP]. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations. 4 figs.

  2. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, Ingo; Morisato, Atsushi

    1998-01-13

    A separation membrane useful for gas separation, particularly separation of C.sub.2+ hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula: ##STR1## wherein R.sub.1 is chosen from the group consisting of C.sub.1 -C.sub.4 alkyl and phenyl, and wherein R.sub.2 is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) ›PMP!. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations.

  3. Electro-Optically Active Monomers: Synthesis and Characterization of Thin Films of Liquid Crystalline Substituted Polyacetylenes

    NASA Technical Reports Server (NTRS)

    Duran, R. S.

    1995-01-01

    The overall objective of this study was the description of the behavior of mesogen substituted acetylene monomers and polymers in monolayer films at the air/water interface and as multilayer films including the formation of such films. Fundamental knowledge to be gained would include the effect of balancing hydrophilic and hydrophobic tendencies in a molecule more complex than the classical fatty acids or lipids. The effect of molecular shape on the packing and thus the ultimate stability of monolayers formed from these new molecules was explored. The work takes on the challenge of preorienting monomers in well-ordered arrays prior to attempting polymerization with the hope that order would be preserved in any resulting polymer. New knowledge gained with regard to the acetylenic monomers includes processing of the acetylene monomer into multi-layer films, followed by the design and synthesis of a second generation of improved monomer structure for superior LBK film transfer properties. A third generation of acetylenic monomer was synthesized which approaches more closely the goal of solid state polymerization of these materials. A parallel study took a different approach. The materials are pre-formed poly(phenylene-acetylene) polymers so questions about reactivity are mute. The materials are a variation on the well-known hairy-rod polymers with regard to their Langmuir film-forming properties. Overall, the goal was to demonstrate that these polymers could be processed into NLO materials with novel polar order.

  4. The effect of heteroatomic substitutions on the band gap of polyacetylene and polyparaphenylene derivatives

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Sok; Kertesz, Milkos

    1988-02-01

    The electronic structures of polyparaphenylene (PPP), polyacetylene (PA), and their derivatives with small energy gaps have been studied by the Hückel and MNDO crystal orbital methods. The effect of nuclear relaxation and heteroatomic substitution on the energy gaps (Eg) have been taken into account by compelete geometry optimization using periodic boundary conditions as opposed to earlier cluster based calculations. Calculations were done on the following polyacetylene derivatives: polypyrrole (PPy), polythiophene (PT), polyisothianaphthene (PITN), poly (5,5'-bithiophene methenyl) (PBTM, 11, X=S, R=H, m1=m2=1), and poly (5,5'-bipyrrole methenyl) (PBPM, 11, X=NH, R=H, m1=m2=1). Energetics and band gaps for the two isomeric forms, the quinoid and aromatic structures of PPy and PT, are discussed and critically compared with previous calculations. Perturbational molecular orbital theory is invoked to explain the narrower Eg for PITN, PBTM, and PBPM, relative to that of PA. Calculations for PPP derivatives {m-polybenzo[b]thiophene (PBT,5b), polybenzo[b,f]thieno[3,4-c]thiophene (PBTT, 5a, X=S), and polybenzo[b,f]pyrrolo[3,4-c]pyrrole (PBPP, 5a, X=NH)} show that the Eg of some of these polymers is substantially smaller than that of PPP. Comments on ways to stabilize structures with desired small energy gaps are made. A correlation of the Eg with heteroatom perturbation and geometrical relaxation is given. It is found that Eg is controlled not by aromatic vs quinoid contributions, but by the geometrical and heteroatomic effects on the frontier orbitals of the polymer.

  5. Optically active substituted polyacetylene@carbon nanotube hybrids: Preparation, characterization and infrared emissivity property study

    SciTech Connect

    Bu, Xiaohai; Zhou, Yuming Zhang, Tao; Wang, Yongjuan; Zhang, Zewu; He, Man

    2014-08-15

    Optically active substituted polyacetylene@multiwalled carbon nanotubes (SPA@MWCNTs) nanohybrids were fabricated by wrapping helical SPA copolymers onto the surface of modified nanotubes through ester bonding linkage. SPA copolymer based on chiral phenylalanine and serine was pre-polymerized by a rhodium zwitterion catalyst in THF, and evidently proved to possess strong optical activity and adopt a predominately one-handed helical conformation. Various characterizations including Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) demonstrated that the SPA had been covalently grafted onto the nanotubes without destroying their original graphite structure. The wrapped SPA was found to exhibit an enhancement in thermal stability and still maintained considerable optical activity after grafting. The infrared emissivity property of the nanohybrids at 8–14 μm was investigated in addition. The results indicated that the SPA@MWCNTs hybrid matrix could possess a much lower infrared emissivity value (ε=0.707) than raw MWCNTs, which might be due to synergistic effect of the unique helical conformation of optically active SPA and strengthened interfacial interaction between the organic polymers and inorganic nanoparticles. - Graphical abstract: Optically active SPA@MWCNTs nanohybrids with low infrared emissivity. - Highlights: • Synthesis of optically active SPA copolymer derived from serine and phenylalanine. • Preparation and characterization of optically active SPA@MWCNTs nanohybrids. • Application study of the SPA@MWCNTs nanohybrids (ε=0.707) in lowering the infrared emissivity.

  6. Chiral monolithic absorbent constructed by optically active helical-substituted polyacetylene and graphene oxide: preparation and chiral absorption capacity.

    PubMed

    Li, Weifei; Wang, Bo; Yang, Wantai; Deng, Jianping

    2015-02-01

    Chiral monolithic absorbent is successfully constructed for the first time by using optically active helical-substituted polyacetylene and graphene oxide (GO). The preparative strategy is facile and straightforward, in which chiral-substituted acetylene monomer (Ma), cross-linker (Mb), and alkynylated GO (Mc) undergo copolymerization to form the desired monolithic absorbent in quantitative yield. The resulting monoliths are characterized by circular dichroism, UV-vis absorption, scanning electron microscopy (SEM), FT-IR, Raman, energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), XPS, and thermogravimetric analysis (TGA) techniques. The polymer chains derived from Ma form chiral helical structures and thus provide optical activity to the monoliths, while GO sheets contribute to the formation of porous structures. The porous structure enables the monolithic absorbents to demonstrate a large swelling ratio in organic solvents, and more remarkably, the helical polymer chains provide optical activity and further enantio-differentiating absorption ability. The present study establishes an efficient and versatile methodology for preparing novel functional materials, in particular monolithic chiral materials based on substituted polyacetylene and GO.

  7. Conjugated Substituted Ionic Polyacetylenes

    DTIC Science & Technology

    1993-05-05

    bis-2-pyridiniumethyne, for example, was found to be most reactive in Diels Alder reactions, followed by the corresponding 4-pyridinium derivative. The...Subramanyam, M.S. Chetan and Alexandre Blumstein 13.a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year, MonMf. ay) 15. PAGE COUNT Technical Report... Alder reaction involving ethynylpyridinium salts was first reported by Yamashita and coworkers 12 ,13 , who observed that 1,2-bis-2-pyridyl and 4

  8. Spin Exchange Interaction in Substituted Copper Phthalocyanine Crystalline Thin Films

    PubMed Central

    Rawat, Naveen; Pan, Zhenwen; Lamarche, Cody J.; Wetherby, Anthony; Waterman, Rory; Tokumoto, Takahisa; Cherian, Judy G.; Headrick, Randall L.; McGill, Stephen A.; Furis, Madalina I.

    2015-01-01

    The origins of spin exchange in crystalline thin films of Copper Octabutoxy Phthalocyanine (Cu-OBPc) are investigated using Magnetic Circular Dichroism (MCD) spectroscopy. These studies are made possible by a solution deposition technique which produces highly ordered films with macroscopic grain sizes suitable for optical studies. For temperatures lower than 2 K, the contribution of a specific state in the valence band manifold originating from the hybridized lone pair in nitrogen orbitals of the Phthalocyanine ring, bears the Brillouin-like signature of an exchange interaction with the localized d-shell Cu spins. A comprehensive MCD spectral analysis coupled with a molecular field model of a σπ − d exchange analogous to sp-d interactions in Diluted Magnetic Semiconductors (DMS) renders an enhanced Zeeman splitting and a modified g-factor of −4 for the electrons that mediate the interaction. These studies define an experimental tool for identifying electronic states involved in spin-dependent exchange interactions in organic materials. PMID:26559337

  9. Spin Exchange Interaction in Substituted Copper Phthalocyanine Crystalline Thin Films

    NASA Astrophysics Data System (ADS)

    Rawat, Naveen; Pan, Zhenwen; Lamarche, Cody J.; Wetherby, Anthony; Waterman, Rory; Tokumoto, Takahisa; Cherian, Judy G.; Headrick, Randall L.; McGill, Stephen A.; Furis, Madalina I.

    2015-11-01

    The origins of spin exchange in crystalline thin films of Copper Octabutoxy Phthalocyanine (Cu-OBPc) are investigated using Magnetic Circular Dichroism (MCD) spectroscopy. These studies are made possible by a solution deposition technique which produces highly ordered films with macroscopic grain sizes suitable for optical studies. For temperatures lower than 2 K, the contribution of a specific state in the valence band manifold originating from the hybridized lone pair in nitrogen orbitals of the Phthalocyanine ring, bears the Brillouin-like signature of an exchange interaction with the localized d-shell Cu spins. A comprehensive MCD spectral analysis coupled with a molecular field model of a σπ - d exchange analogous to sp-d interactions in Diluted Magnetic Semiconductors (DMS) renders an enhanced Zeeman splitting and a modified g-factor of -4 for the electrons that mediate the interaction. These studies define an experimental tool for identifying electronic states involved in spin-dependent exchange interactions in organic materials.

  10. Spin Exchange Interaction in Substituted Copper Phthalocyanine Crystalline Thin Films.

    PubMed

    Rawat, Naveen; Pan, Zhenwen; Lamarche, Cody J; Wetherby, Anthony; Waterman, Rory; Tokumoto, Takahisa; Cherian, Judy G; Headrick, Randall L; McGill, Stephen A; Furis, Madalina I

    2015-11-12

    The origins of spin exchange in crystalline thin films of Copper Octabutoxy Phthalocyanine (Cu-OBPc) are investigated using Magnetic Circular Dichroism (MCD) spectroscopy. These studies are made possible by a solution deposition technique which produces highly ordered films with macroscopic grain sizes suitable for optical studies. For temperatures lower than 2 K, the contribution of a specific state in the valence band manifold originating from the hybridized lone pair in nitrogen orbitals of the Phthalocyanine ring, bears the Brillouin-like signature of an exchange interaction with the localized d-shell Cu spins. A comprehensive MCD spectral analysis coupled with a molecular field model of a σπ - d exchange analogous to sp-d interactions in Diluted Magnetic Semiconductors (DMS) renders an enhanced Zeeman splitting and a modified g-factor of -4 for the electrons that mediate the interaction. These studies define an experimental tool for identifying electronic states involved in spin-dependent exchange interactions in organic materials.

  11. Functional disubstituted polyacetylenes: Synthesis, liquid crystallinity, light emission, and fluorescent photopatterning of biphenyl-containing poly(1-phenyl-octyne)s with different functional bridges.

    PubMed

    Lam, Jacky W Y; Qin, Anjun; Dong, Yuping; Lai, Lo Ming; Häussler, Matthias; Dong, Yongqiang; Tang, Ben Zhong

    2006-11-02

    Biphenyl (Biph)-containing 1-phenyl-1-octynes and their polymers are synthesized, and the effects of functional bridge groups on the mesomorphic and optical properties of the polymers are studied. The nonmesomorphic disubstituted acetylene monomers (C6H13)C[triple bond]C(C6H4)O(CH2)12O-Biph-OC7H15 (1), (C6H13)C[triple bond]C(C6H4)O(CH2)11OOC-Biph-OC7H15 (2), and (C6H13)C[triple bond]C(C6H4)CO2(CH2)12OOC-Biph-OC7H15 (3) are prepared by multistep reaction routes and converted into their corresponding polymers P1-P3 by a WCl6-Ph4Sn catalyst. The structures and properties of the polymers are characterized and evaluated by NMR, TGA, DSC, POM, XRD, UV, and PL analyses. The mesogenic pendants have endowed the polymers with high thermal stability (> or =400 degrees C). While P1 exhibits no liquid crystallinity, P2 and P3 form enantiotropic S(A) phase with a monolayer structure. Upon photoexcitation, the polymers emit blue and blue-green lights of 460 and 480 nm, respectively, in THF with quantum efficiencies larger than 30%. UV irradiation of a thin film of P2 through a mask oxidizes and quenches the light emission of the exposed regions, generating a two-dimensional luminescent photoimage.

  12. High pressure chemistry of substituted acetylenes

    SciTech Connect

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-01-25

    High pressure in situ synchrotron x-ray diffraction experiments were performed on substituted polyacetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C{triple_bond}CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-Si{triple_bond}CH] to investigate pressure-induced chemical reactions. The starting samples were the low temperature crystalline phases which persisted metastably at room temperature and polymerized beyond 11 GPa and 26 GPa for TBA and ETMS respectively. These reaction onset pressures are considerably higher than what we observed in the shockwave studies (6.1 GPa for TBA and 6.6 GPa for ETMS). Interestingly, in the case of ETMS, it was observed with fluid ETMS as starting sample, reacts to form a semi-crystalline polymer (crystalline domains corresponding to the low-T phase) at pressures less than {approx}2 GPa. Further characterization using vibrational spectroscopy is in progress.

  13. Qualitative and quantitative determination of polyacetylenes in different Bupleurum species by high performance liquid chromatography with diode array detector and mass spectrometry.

    PubMed

    Huang, Hai-Qiang; Su, Juan; Zhang, Xi; Shan, Lei; Zhang, Wei-Dong

    2011-02-25

    Polyacetylenes are main toxic ingredients in Bupleurum longiradiatum, a poisonous plant that has ever been misused as substitutes for Chaihu (Bupleuri Radix). For the first time, a high-performance liquid chromatography method coupled with diode array detector and mass spectrometry (HPLC-DAD-MS) was developed for qualitative and quantitative analysis of nine polyacetylenes in Bupleurum species. All references, including two new polyacetylenes, were isolated from B. longiradiatum and purified using a semi-preparation HPLC chromatography. The analysis was performed on a TSKgel ODS-100V C18 column (3 μm, 150 mm x 4.6 mm i.d.) using a gradient system of acetonitrile and water, with diode array detection (254 nm). The method was validated for linearity, precision, accuracy, limit of detection and quantification. A total of 27 Bupleurum samples were examined with this method, which showed a great variety in the distribution and contents of the polyacetylenes. It was found that polyacetylenes (1-8) were the main ingredients in B. longiradiatum, while a few kinds of polyacetylenes (5-8) were also identified in B. smithii, B. smithii var. parvifolium, B. bicaule and B. angustissimum. However, no polyacetylenes (1-9) were detected in the authentic Chaihu samples and the other Bupleurum species. The results indicated that the toxic B. longiradiatum could readily be distinguished from other medicinal Bupleurum species based on the polyacetylene profiles, and the guidelines and quality control of polyacetylenes for Chaihu are useful. The acute toxicity of the ethanol extract of B. longiradiatum and its fractions was also investigated.

  14. Ab initio study of single-crystalline and polycrystalline elastic properties of Mg-substituted calcite crystals.

    PubMed

    Zhu, L-F; Friák, M; Lymperakis, L; Titrian, H; Aydin, U; Janus, A M; Fabritius, H-O; Ziegler, A; Nikolov, S; Hemzalová, P; Raabe, D; Neugebauer, J

    2013-04-01

    We employ ab initio calculations and investigate the single-crystalline elastic properties of (Ca,Mg)CO3 crystals covering the whole range of concentrations from pure calcite CaCO3 to pure magnesite MgCO3. Studying different distributions of Ca and Mg atoms within 30-atom supercells, our theoretical results show that the energetically most favorable configurations are characterized by elastic constants that nearly monotonously increase with the Mg content. Based on the first principles-derived single-crystalline elastic anisotropy, the integral elastic response of (Ca,Mg)CO3 polycrystals is determined employing a mean-field self-consistent homogenization method. As in case of single-crystalline elastic properties, the computed polycrystalline elastic parameters sensitively depend on the chemical composition and show a significant stiffening impact of Mg atoms on calcite crystals in agreement with the experimental findings. Our analysis also shows that it is not advantageous to use a higher-scale two-phase mix of stoichiometric calcite and magnesite instead of substituting Ca atoms by Mg ones on the atomic scale. Such two-phase composites are not significantly thermodynamically favorable and do not provide any strong additional stiffening effect.

  15. Antimycobacterial polyacetylenes from Levisticum officinale.

    PubMed

    Schinkovitz, Andreas; Stavri, Michael; Gibbons, Simon; Bucar, Franz

    2008-05-01

    No conflicts of interest concerning financial matters or personal relationships exist between the authors and those who might bias this work. The present work is in part included the PhD thesis of A. Schinkovitz (University of Graz) but has not been published elsewhere previously. The dichloromethane extract of the roots of Levisticum officinale L. (Apiaceae) exhibited significant antimycobacterial activity against Mycobacterium fortuitum and Mycobacterium aurum in a microtiter plate dilution assay and was further analysed following a bioassay-guided fractionation strategy. 3(R)-Falcarinol (3(R)-(-)-1,9-heptadecadien-4,6-diin-3-ol] and 3(R)-8(S)-falcarindiol [3(R)-8(S)-(+)-1,9-heptadecadien-4,6-diin-3,8-diol] could be identified as the active components in this extract. The minimal inhibitory concentration (MIC) of 3(R)-falcarinol against M. fortuitum and M. aurum was 16.4 microM while that of 3(R)-8(S)-falcarindiol was 30.7 microM against M. fortuitum and 61.4 microm against M. aurum, respectively. Previously, 3(R),8(R)-dehydrofalcarindiol was isolated from Artemisia monosperma and surprisingly this polyacetylene exhibited no antimycobacterial activity at 128 microg/mL. This indicates that the terminal methyl group is vital for retention of antimycobacterial activity. Reference antibiotics ethambutol and isoniazid exhibited an activity of 115.5 microM and 14.6 microM against M. fortuitum, and 3.4 microM and 29.2 microM against M. aurum, respectively.

  16. Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5Sn0.5Te

    NASA Astrophysics Data System (ADS)

    Zhong, R. D.; Schneeloch, J. A.; Liu, T. S.; Camino, F. E.; Tranquada, J. M.; Gu, G. D.

    2014-07-01

    Indium substitution turns the topological crystalline insulator (TCI) Pb0.5Sn0.5Te into a possible topological superconductor. To investigate the effect of the indium concentration on the crystal structure and superconducting properties of (Pb0.5Sn0.5)1-xInxTe, we have grown high-quality single crystals using a modified floating-zone method and have performed systematic studies for indium content in the range 0≤x≤0.35. We find that the single crystals retain the rocksalt structure up to the solubility limit of indium (x ˜0.30). Experimental dependencies of the superconducting transition temperature (Tc) and the upper critical magnetic field (Hc2) on the indium content x have been measured. The maximum Tc is determined to be 4.7 K at x =0.30, with μ0Hc2(T =0)≈5 T.

  17. Raman Scattering in Carbon Nanosystems: Solving Polyacetylene.

    PubMed

    Heller, Eric J; Yang, Yuan; Kocia, Lucas

    2015-03-25

    Polyacetylene has been a paradigm conjugated organic conductor since well before other conjugated carbon systems such as nanotubes and graphene became front and center. It is widely acknowledged that Raman spectroscopy of these systems is extremely important to characterize them and understand their internal quantum behavior. Here we show, for the first time, what information the Raman spectrum of polyacetylene contains, by solving the 35-year-old mystery of its spectrum. Our methods have immediate and clear implications for other conjugated carbon systems. By relaxing the nearly universal approximation of ignoring the nuclear coordinate dependence of the transition moment (Condon approximation), we find the reasons for its unusual spectroscopic features. When the Kramers-Heisenberg-Dirac Raman scattering theory is fully applied, incorporating this nuclear coordinate dependence, and also the energy and momentum dependence of the electronic and phonon band structure, then unusual line shapes, growth, and dispersion of the bands are explained and very well matched by theory.

  18. Raman Scattering in Carbon Nanosystems: Solving Polyacetylene

    PubMed Central

    2015-01-01

    Polyacetylene has been a paradigm conjugated organic conductor since well before other conjugated carbon systems such as nanotubes and graphene became front and center. It is widely acknowledged that Raman spectroscopy of these systems is extremely important to characterize them and understand their internal quantum behavior. Here we show, for the first time, what information the Raman spectrum of polyacetylene contains, by solving the 35-year-old mystery of its spectrum. Our methods have immediate and clear implications for other conjugated carbon systems. By relaxing the nearly universal approximation of ignoring the nuclear coordinate dependence of the transition moment (Condon approximation), we find the reasons for its unusual spectroscopic features. When the Kramers–Heisenberg–Dirac Raman scattering theory is fully applied, incorporating this nuclear coordinate dependence, and also the energy and momentum dependence of the electronic and phonon band structure, then unusual line shapes, growth, and dispersion of the bands are explained and very well matched by theory. PMID:27162945

  19. Ion beam modification of polyacetylene films

    NASA Astrophysics Data System (ADS)

    Lin, Senhao; Sheng, Kanglong; Bao, Jinrong; Rong, Tingwen; Zhou, Zhiyi; Zhang, Lanping; Zhu, Dezhang; Shen, Zhiquan; Yan, Mujie

    1989-03-01

    Low energy ion implantation of polyacetylene films synthesized with rare earth compound catalysts have been studied for potassium, sodium and iodine at the energy region of 15 to 30 keV. Film samples prepared in different ways, thermally treated and/or chemically doped, were irradiated up to 1 × 10 17 ions/cm 2. The resulting surface property modifications of the (CH) x films were examined by various kinds of techniques. Compensation effects of the dopants and electrical conductivity changes in the implanted regions were observed. Some of the implanted film samples exhibited diode like characteristics. Discussions on the experimental results are presented.

  20. Solid-state photochemistry of crystalline pyrazolines: reliable generation and reactivity control of 1,3-biradicals and their potential for the green chemistry synthesis of substituted cyclopropanes.

    PubMed

    Shiraki, Saori; Vogelsberg, Cortnie S; Garcia-Garibay, Miguel A

    2012-12-01

    To expand on the limited number of examples that exist in the literature for the solid-state photodenitrogenation of azoalkanes, a series of crystalline 7-alkyl-2,3,7-triazabicyclo[3.3.0]oct-2-ene-6,8-diones with varying 4,4-substituents were prepared. Their photochemical behavior in solution and in the solid state was dependent on the 4,4-substitution of the 1-pyrazoline ring, with unsubstituted pyrazoline giving a mixture of products both in solution and in the solid state. Diphenyl substituted pyrazolines denitrogenate spontaneously in solution but require light exposure to react quantitatively in the solid state. t-Butyl-phenyl substituted pyrazolines were shown to denitrogenate both chemo- and diastereoselectively in solution and in the solid state to yield a single product in quantitative yield.

  1. Distinct molecular structures and hydrogen bond patterns of α,α-diethyl-substituted cyclic imide, lactam, and acetamide derivatives in the crystalline phase

    NASA Astrophysics Data System (ADS)

    Krivoshein, Arcadius V.; Ordonez, Carlos; Khrustalev, Victor N.; Timofeeva, Tatiana V.

    2016-10-01

    α,α-Dialkyl- and α-alkyl-α-aryl-substituted cyclic imides, lactams, and acetamides show promising anticonvulsant, anxiolytic, and anesthetic activities. While a number of crystal structures of various α-substituted cyclic imides, lactams, and acetamides were reported, no in-depth comparison of crystal structures and solid-state properties of structurally matched compounds have been carried out so far. In this paper, we report molecular structure and intermolecular interactions of three α,α-diethyl-substituted compounds - 3,3-diethylpyrrolidine-2,5-dione, 3,3-diethylpyrrolidin-2-one, and 2,2-diethylacetamide - in the crystalline phase, as studied using single-crystal X-ray diffraction and IR spectroscopy. We found considerable differences in the patterns of H-bonding and packing of the molecules in crystals. These differences correlate with the compounds' melting points and are of significance to physical pharmacy and formulation development of neuroactive drugs.

  2. Biosynthesis and Function of Polyacetylenes and Allied Natural Products

    PubMed Central

    Minto, Robert E.; Blacklock, Brenda J.

    2008-01-01

    Polyacetylenic natural products are a substantial class of often unstable compounds containing a unique carbon-carbon triple bond functionality, that are intriguing for their wide variety of biochemical and ecological functions, economic potential, and surprising mode of biosynthesis. Isotopic tracer experiments between 1960 and 1990 demonstrated that the majority of these compounds are derived from fatty acid and polyketide precursors. During the past decade, research into the metabolism of polyacetylenes has swiftly advanced, driven by the cloning of the first genes responsible for polyacetylene biosynthesis in plants, moss, fungi, and actinomycetes, and the initial characterization of the gene products. The current state of knowledge of the biochemistry and molecular genetics of polyacetylenic secondary metabolic pathways will be presented together with an up-to-date survey of new terrestrial and marine natural products, their known biological activities, and a discussion of their likely metabolic origins. PMID:18387369

  3. Spatial tissue distribution of polyacetylenes in carrot root.

    PubMed

    Baranska, Malgorzata; Schulz, Hartwig

    2005-06-01

    The presented results show the usefulness of Raman spectroscopy in the investigation of polyacetylenes in carrot root. The components are measured directly in the plant tissue without any preliminary sample preparation. Compared with the strong polyacetylene signals the spectral impact of the surrounding biological matrix is weak, except for carotenoids, and therefore it does not contribute significantly to the obtained results. Three different Raman mapping techniques applied here have revealed essential information about the investigated compounds. Using point acquisition several spectra have been measured to demonstrate the complex composition of the polyacetylene fraction in carrot root. The molecular structures of falcarinol, falcarindiol and falcarindiol 3-acetate are similar but their Raman spectra exhibit differences demonstrated by the shift of their -C triple bond C- mode. Line mapping performed along the diameter of transversely cut carrot roots has been used to investigate the relative concentration of polyacetylenes and carotenoids. An area map provides detailed information regarding the distribution of both components. It has been found that high accumulation of polyacetylenes is located in the outer section of the root, namely the pericyclic parenchyma, and in the phloem part close to the secondary cambium. The highest concentration of carotenes is seen in the immediate vicinity to polyacetylene conglomerates.

  4. Polarons and bipolarons in cis-polyacetylene

    NASA Astrophysics Data System (ADS)

    Utz, Wolfram; Förner, Wolfgang

    1998-05-01

    We present a parametrization for the Pariser-Parr-Pople Hamiltonian for the description of cis-polyacetylene (cPA). In contrast to trans-polyacetylene, we have to include symmetry breaking between neighboring sites into the Su-Schrieffer-Heeger-type one-electron part of the Hamiltonian. Our parametrization is based on correlated ab initio calculations on cis-hexatriene and on the results of independent calculations found in the literature. For open-shell systems (singly charged polarons) we use the annihilated unrestricted Hartree-Fock method to avoid the artificial spin contaminations inherent in UHF (unrestricted HF) calculations, which lead to the inclusion of fractions of the correlation energy in UHF total energies which cannot be controlled and are different for different systems and even for different geometries of the same system. Thus UHF is useless for the calculation of potential hypersurfaces and thus in turn for dynamical simulations. We find that in cPA singly-charged polarons are formed, while in doubly-charged chains stable bipolarons are found, although of a quite large width. This is in contrast to recent results reported by Shimoi and Abe [Y. Shimoi and S. Abe, Synth. Met. 69, 687 (1995) and Phys. Rev. B 50, 14 781 (1994)] who found that two singly-charged polarons are more stable for realistic parameter values than a doubly-charged bipolaron. We further find that the charged polarons are mobile in the chain and thus we conclude that polarons and bipolarons can serve as charge carriers (the latter ones spinless) in doped cPA.

  5. First-principles calculations on anharmonic vibrational frequencies of polyethylene and polyacetylene in the Gamma approximation.

    PubMed

    Keçeli, Murat; Hirata, So; Yagi, Kiyoshi

    2010-07-21

    The frequencies of the infrared- and/or Raman-active (k=0) vibrations of polyethylene and polyacetylene are computed by taking account of the anharmonicity in the potential energy surfaces (PESs) and the resulting phonon-phonon couplings explicitly. The electronic part of the calculations is based on Gaussian-basis-set crystalline orbital theory at the Hartree-Fock and second-order Møller-Plesset (MP2) perturbation levels, providing one-, two-, and/or three-dimensional slices of the PES (namely, using the so-called n-mode coupling approximation with n=3), which are in turn expanded in the fourth-order Taylor series with respect to the normal coordinates. The vibrational part uses the vibrational self-consistent field, vibrational MP2, and vibrational truncated configuration-interaction (VCI) methods within the Gamma approximation, which amounts to including only k=0 phonons. It is shown that accounting for both electron correlation and anharmonicity is essential in achieving good agreement (the mean and maximum absolute deviations less than 50 and 90 cm(-1), respectively, for polyethylene and polyacetylene) between computed and observed frequencies. The corresponding values for the calculations including only one of such effects are in excess of 120 and 300 cm(-1), respectively. The VCI calculations also reproduce semiquantitatively the frequency separation and intensity ratio of the Fermi doublet involving the nu(2)(0) fundamental and nu(8)(pi) first overtone in polyethylene.

  6. Chemical and pharmacological progress on polyacetylenes isolated from the family apiaceae.

    PubMed

    Chen, Yuemei; Peng, Shiyi; Luo, Qiongzhi; Zhang, Juan; Guo, Qiang; Zhang, Yuan; Chai, Xingyun

    2015-04-01

    This review presents an up-to-date survey of natural polyacetylenes isolated from the family Apiaceae, and their biosynthesis and biological activities up to May 2013, with 107 references. A total of 103 polyacetylenes from 72 species of 41 genera of Apiaceae have been isolated so far, among which falcarinol-type polyacetylenes are most widely distributed.

  7. On the formation of polyacetylenes and cyanopolyacetylenes in Titan's atmosphere and their role in astrobiology.

    PubMed

    Kaiser, Ralf I; Mebel, Alexander M

    2012-08-21

    This tutorial review compiles recent experimental and theoretical studies on the formation of polyacetylenes (H(C≡C)(n)H) and cyanopolyacetylenes (H(C≡C)(n)CN) together with their methyl-substituted counterparts (CH(3)(C≡C)(n)H, CH(3)(C≡C)(n)CN) as probed under single collision conditions in crossed beam studies via the elementary reactions of ethynyl (CCH) and cyano radicals (CN) with unsaturated hydrocarbons. The role of these key reaction classes in the chemical evolution of Titan's orange-brownish haze layers is also discussed. We further comment on astrobiological implications of our findings with respect to proto-Earth and present a brief outlook on future research directions.

  8. Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx)1−yInyTe: Topological and Superconducting Properties

    DOE PAGES

    Zhong, Ruidan; Schneeloch, John; Li, Qiang; ...

    2017-02-16

    Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1-xSnx)1-yInyTe. For samples with a tin concentration x≤50% , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to `2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with `6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, with a transitionmore » temperature, Tc , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.« less

  9. Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1$-$xSnx)1$-$yInyTe: Topological and Superconducting Properties

    DOE PAGES

    Zhong, Ruidan; Schneeloch, John; Li, Qiang; ...

    2017-02-16

    Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1-xSnx)1-yInyTe. For samples with a tin concentration x ≤ 50% , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ~2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with `6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, withmore » a transition temperature, Tc , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.« less

  10. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    NASA Astrophysics Data System (ADS)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  11. Effects of the Hubbard Interaction and Electrostatic Pinning in Polyacetylene

    DTIC Science & Technology

    1988-03-01

    has been used with end of the chain. In this work we consider the pinning the framework of the continuum modelO to study the resulting from a point...for polyacetylene. This model Hamiltonian includes the mental observation, where very careful measurements of lattice kinetic energy and couples the ir

  12. Effects of harvesting date and storage on the amounts of polyacetylenes in carrots, Daucus carota.

    PubMed

    Kjellenberg, Lars; Johansson, Eva; Gustavsson, Karl-Erik; Olsson, Marie E

    2010-11-24

    The amounts of three main polyacetylenes in carrots; falcarinol, falcarindiol, and falcarindiol-3-acetate, were determined by HPLC, during three seasons, in carrots harvested several times per season and at different locations in Sweden. The amounts of falcarindiol first decreased from a relatively high level and then increased later in the harvest season. The amounts of falcarindiol-3-acetate showed similar variations, whereas the amounts of falcarinol did not exhibit any significant variation during the harvest season. During storage the amount of polyacetylenes leveled off, increasing in samples initially low and decreasing in samples initially high in polyacetylenes. The amounts of all polyacetylenes varied significantly due to external factors and between stored and fresh samples. This variation opens up possibilities to achieve a chemical composition of polyacetylenes at harvest that minimizes the risk of bitter off-taste and maximizes the positive health effects reported in connection with polyacetylenes in carrots.

  13. Cooperative Magnetism in Crystalline N-Aryl-substituted Verdazyl Radicals: First-Principles Predictions and Experimental Results.

    PubMed

    Eusterwiemann, Steffen; Dresselhaus, Thomas; Doerenkamp, Carsten; Janka, Oliver; Niehaus, Oliver; Massolle, Anja; Daniliuc, Constantin; Eckert, Hellmut; Pöttgen, Rainer; Neugebauer, Johannes; Studer, Armido

    2017-03-20

    We report on a series of eight diaryl-6-oxo-verdazyl radicals containing a tert-butyl group at the C(3) position regarding their crystal structure and magnetic properties by means of magnetic susceptibility measurements in combination with quantum chemical calculations using the first-principles bottom-up approach. The latter method allows for a qualitative prediction and detailed analysis of the correlation between solid state architecture and magnetic properties. Although the perturbation in the molecular structure by varying the substituent of the N-aryl-ring may appear small, the effects upon the structural parameters controlling intermolecular magnetic coupling interactions are strong, resulting in a wide spectrum of cooperative magnetic behavior. The non-substituted 1,5-diphenyl-3-t.butyl-6-oxo-verdazyl radical features a ferromagnetic one-dimensional spin ladder type magnetic network, an extremely rarely observed phenomenon for verdazyl radicals. By varying substituents at the phenyl group, different non-isostructural compounds were obtained with widely different magnetic motifs ranging from linear and zig-zag one-dimensional chains to potentially two-dimensional networks, from which we predict magnetic susceptibility data that are in qualitative agreement with experiments and reveal a large sensitivity to molecular packing effects. The present study advances the fundamental understanding between solid state structure and magnetism in organically based radical systems.

  14. Polyacetylenic compounds, ACAT inhibitors from the roots of Panax ginseng.

    PubMed

    Rho, Mun-Chual; Lee, Hyun Sun; Lee, Seung Woong; Chang, Jong Sun; Kwon, Oh Eok; Chung, Mi Yeon; Kim, Young Kook

    2005-02-23

    Acyl-CoA: cholesterol acyltransferase (ACAT), which plays a role in the absorption, storage, and production of cholesterol, has been explored as a potential target for pharmacological intervention of hyperlipidemia and atherosclerotic disease. In our search for ACAT inhibitors from natural sources, the petroleum ether extract of Panax ginseng showed moderate inhibition of ACAT enzyme from rat liver microsomes. Bioactivity-guided fractionations led to the isolation of one new polyacetylenic compound, (9R,10S)-epoxy-16-heptadecene-4, 6-diyne-3-one (1), in addition to the previously reported polyacetylenic compounds 2 and 3. Their chemical structures were elucidated on the basis of spectroscopic evidence (UV, IR, NMR, and MS). The compounds 1, 2, and 3 showed significant ACAT inhibition with IC(50) values of 35, 47, and 21 microM, respectively.

  15. Anticomplement activity of polyacetylenes from leaves of Dendropanax morbifera Leveille.

    PubMed

    Chung, Ill-Min; Song, Hong-Keun; Kim, Sun-Jin; Moon, Hyung-In

    2011-05-01

    The present study evaluated the anticomplement effect of polyacetylenes from Dendropanax morbifera (Araliaceae) in the classical pathway complement system. The leaves of D. morbifera were evaluated with regard to its anticomplement activity, and its active principles identified following activity-guided isolation. An aqueous CCl(4) fraction of the leaves of D. morbifera exhibited significant anticomplement activity on the classical pathway complement system, which was expressed as total hemolytic activity. Three polyacetylenes isolated from the leaves of D. morbifera, namely (3S)-falcarinol (1), (3S,8S)-falcarindiol (2) and (3S)-diynene (3). Compounds 1, 2 and 3 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 87.3 µM, 15.2 µM and 39.8 µM. Among the compounds tested, 2 showed the most potent anticomplement activity (IC(50), 15.2 µM).

  16. First-principles study of polyacetylene derivatives bearing nitroxide radicals

    NASA Astrophysics Data System (ADS)

    Bilgiç, Beyza; Kılıç, Çetin; Esat, Burak

    2011-09-01

    Electrodes made of organic polymers bearing redox-active radical pendant groups have attractive features for use in rechargeable batteries. Electronic structure and electrochemical properties of cathode- and anode-active organic polymers are investigated here by means of first-principles calculations performed in the framework of the density functional theory. We consider organic radical polymers (ORPs) that consist of trans-polyacetylene derivatives bearing a variety of nitroxide radicals. A number of neutral and charged supercells are utilized to compute the ionization potentials and electron affinities as well as the one-electron states of these ORPs. By revealing the polyacetylene-derived highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) as well as the radical-derived singly occupied molecular orbital (SOMO), the variation of the SOMO energy within the HOMO-LUMO gap is determined in the course of the oxidization or reduction of ORPs. Our results indicate that the ionization potential I and electron affinity A of polyacetylene would act as a lower or upper bound in the variation of the electrochemical potential of cathode- or anode-active ORPs in the course of battery discharge or charge owing to pinning of the radical-derived SOMO to the polyacetylene-derived HOMO or LUMO. Accordingly, it is anticipated that the electrochemical “window” [-I,-A] of the polymeric backbone of ORPs will impose certain limitations in accomplishing a high charge/discharge voltage range in a totally organic rechargeable battery with positive and negative electrodes made of cathode- and anode-active ORPs, respectively. On the other hand, our findings suggest that one could, in principle, take advantage of using two different (conducting) polymeric backbones in the anode and cathode with adjusted HOMO and LUMO offsets once the electron transfer is accomplished to take place through the conducting backbones.

  17. Lattice dynamics and conjugation length in Trans-polyacetylene

    NASA Astrophysics Data System (ADS)

    Piseri, L.; Tubino, R.; Paltrinieri, L.; Dellepiane, G.

    1983-04-01

    A force field for the infinite trans-polyene chain which includes the contribution of delocalized forces is proposed. Phonon energies throughout the Brillouin zone are evaluated and compared with the i.r. and Raman data of trans-polyacetylene and with the C=C streching frequencies of a number of short polyenes. The experimental resonant Raman bandshapes for (CH) χ and (CD) χ are well accounted for by the calculated dispersion of the phonon frequencies. Some conclusions on the conjugation length of the polymer are reached.

  18. Lignans, phenylpropanoids and polyacetylenes from Chaerophyllum aureum L. (Apiaceae).

    PubMed

    Rollinger, Judith M; Zidorn, Christian; Dobner, Michael J; Ellmerer, Ernst P; Stuppner, Hermann

    2003-01-01

    Sub-aerial parts of Chaerophyllum aureum L. yielded two polyacetylenes, falcarinol (1), falcarindiol (2), three lignans, namely nemerosin (3), deoxypodorhizone (4), deoxypodo-phyllotoxin (5), two phenylpropanoids, 1'-hydroxymyristicin (6) and its angeloyl ester (7). Compounds 6 and 7 were isolated for the first time from plant material and their structures were elucidated by means of extensive 1- and 2-dimensional NMR spectroscopy and high resolution mass spectrometry. In bioautographic tests on TLC plates the dichloromethane extract showed a significant antimicrobial activity. Falcarindiol was identified as the main active principle whereas the phenylpropanoids and lignans showed no activity.

  19. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  20. Semiconducting polyacetylene materials for energy-conversion applications

    NASA Astrophysics Data System (ADS)

    Kiss, Z.; Weinberger, B.

    1982-03-01

    Well controlled growth of semiconducting polyacetylene films by the Ziegler catalyst method was achieved. Thermal isomerization to the trans-(CH)/sub x/stage has yielded (CH)/sub x/films of p-type doping with an acceptor concentration of 10 to the sixteenth to 10 to the 17th power cu cm. Initial proof of concept experiments were also performed to grow polyacetylene by a plasma assisted process. The band edge of (CH)/sub x/ was measured. The technique consisted of measuring the photoresponse of a reverse biased (CH)/sub x/ solar cell, and studying the cut off in the response. The (CH)/sub x/ films had a band gap in the range of 1.4 to 1.5 eV, in good agreement with the measurement of absorption. A very important result of the successful demonstration of this technique is that very low absorption coefficients can be measured quite easily, yielding invaluable data on band tails in (CH)/sub x/.

  1. Charge-coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Anthony; Newville, Mathew; Engelhard, Mark H.; Sutton , Steven R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce), and thorium (Th), incorporated by a charge-coupled substitution with calci-um (Ca) for yttrium (Y) in YIG, namely 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single phase garnets Y3-xCa0.5xM0.5xFe5O12, synthesized by the citrate-nitrate combustion method, were obtained up to x = 0.7. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe-Mössbauer spectroscopy indicated that the samples are single phase, M4+ and Ca2+ cations are restricted to the c-site, the nature of M4+ has only a minor effect on the structure, and the local environments of both the tetrahedral and octahedral Fe3+ are systematically affected by the extent of substitution, especially on the tetrahedral sublattice. The charge coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases, compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature. These structural and thermodynamic findings shed light on possible incorporation of U in this garnet system.

  2. Charge-coupled substituted garnets (Y 3–x Ca 0.5x M 0.5x )Fe₅O₁₂ (M = Ce, Th): Structure and stability as crystalline nuclear waste forms

    DOE PAGES

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; ...

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y³⁺ = Ca²⁺ + M⁴⁺, where M⁴⁺ = Ce⁴⁺ or Th⁴⁺. Single-phase garnets Y3–xCa0.5xM0.5xFe₅O₁₂ (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffractionmore » and ⁵⁷Fe–Mössbauer spectroscopy indicated that M⁴⁺ and Ca²⁺ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe³⁺ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high-temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.« less

  3. Charge-coupled substituted garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): structure and stability as crystalline nuclear waste forms.

    PubMed

    Guo, Xiaofeng; Kukkadapu, Ravi K; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H; Sutton, Stephen R; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y(3+) = Ca(2+) + M(4+), where M(4+) = Ce(4+) or Th(4+). Single-phase garnets Y3-xCa0.5xM0.5xFe5O12 (x = 0.1-0.7) were synthesized by the citrate-nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and (57)Fe-Mössbauer spectroscopy indicated that M(4+) and Ca(2+) cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe(3+) are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  4. Examination of naturally occurring polyacetylenes and alpha-terthienyl for their ability to induce cytogenetic damage.

    PubMed

    MacRae, W D; Chan, G F; Wat, C K; Towers, G H; Lam, J

    1980-09-15

    alpha-Terthienyl and 5 polyacetylenes were examined for chromosome damaging activity using Syrian hamster cells. None of these naturally occurring compounds induced sister chromatid exchanges and neither alpha-terthienyl nor phenylheptatriyne induced chromosome aberrations.

  5. Polyacetylenes from the Apiaceae vegetables carrot, celery, fennel, parsley, and parsnip and their cytotoxic activities.

    PubMed

    Zidorn, Christian; Jöhrer, Karin; Ganzera, Markus; Schubert, Birthe; Sigmund, Elisabeth Maria; Mader, Judith; Greil, Richard; Ellmerer, Ernst P; Stuppner, Hermann

    2005-04-06

    A dichloromethane extract of root celery yielded falcarinol, falcarindiol, panaxydiol, and the new polyacetylene 8-O-methylfalcarindiol. The structure of the new compound was established by one- and two-dimensional (1D and 2D) NMR, mass spectrometry, and optical rotation data. Nonpolar extracts of roots and bulbs of carrots, celery, fennel, parsley, and parsnip were investigated for their content of polyacetylenes by high-performance liquid chromatography with diode array detection (HPLC-DAD). All five species contained polyacetylenes, although carrots and fennel only in minor amounts. Additionally, the cytotoxicity of the four polyacetylenes against five different cell lines was evaluated by the annexin V-PI assay. Falcarinol proved to be the most active compound with a pronounced toxicity against acute lymphoblastic leukemia cell line CEM-C7H2, with an IC(50) of 3.5 micromol/L. The possible chemopreventive impact of the presented findings is discussed briefly.

  6. Soluble silylated polyacetylene derivatives and their use as percursors to novel polyacetylene-type polymers

    DOEpatents

    Zeigler, John M.

    1989-01-01

    Polymerization of acetylenic monomers is achieved by using a catalyst which is the reaction product of a tungsten compound and a reducing agent effective to reduce W(VI) to W(III and/or IV), e.g., WCl.sub.6.(organo-Li, organo-Mg or polysilane). The resultant silylated polymers are of heretofore unachievable high molecular weight and can be used as precursors to a wide variety of new acetylenic polymers by application of substitution reactions.

  7. Gymnasterkoreaynes A-F, cytotoxic polyacetylenes from Gymnaster koraiensis.

    PubMed

    Jung, Hyun-Ju; Min, Byung-Sun; Park, Jin-Young; Kim, Young-Ho; Lee, Hyeong-Kyu; Bae, Ki-Hwan

    2002-06-01

    Six new polyacetylenes, gymnasterkoreaynes A-F (1-6), were isolated from the roots of Gymnaster koraiensis, together with 2,9,16-heptadecatrien-4,6-diyn-8-ol (7) and 1,9,16-heptadecatriene-4,6-diyn-3,8-diol (8), by bioassay-guided fractionation using the L1210 tumor cell line as a model for cytotoxicity. The structures of compounds 1-6 were established spectroscopically, which included 2D NMR experiments. Gymnasterkoreaynes A-F (1-6) are linear diacetylenes and are structurally related to falcarinol, panaxynol, panaxydiol, and panaxytriol. Of the compounds isolated, gymnasterkoreaynes B (2), C (3), F (6), and 1,9,16-heptadecatrien-4,6-diyn-3,8-diol (8) exhibited significant cytotoxicity against L1210 tumor cells with ED(50) values of 0.12-3.3 microg/mL.

  8. Correlations between Polyacetylene Concentrations in Carrot (Daucus carota L.) and Various Soil Parameters.

    PubMed

    Kjellenberg, Lars; Johansson, Eva; Gustavsson, Karl-Erik; Granstedt, Artur; Olsson, Marie E

    2016-08-31

    This study assessed the concentrations of three falcarinol-type polyacetylenes (falcarinol, falcarindiol, falcarindiol-3-acetate) in carrots and the correlations between these and different soil traits. A total of 144 carrot samples, from three different harvests taken a single season, were analysed in terms of their polyacetylene concentrations and root development. On one of the harvesting occasions, 48 soil samples were also taken and analysed. The chemical composition of the soil was found to influence the concentrations of falcarinol-type polyacetylenes in carrots. When the total soil potassium level was 200 mg/100 g soil, the concentration of falcarindiol (FaDOH) in the carrot samples was 630 μg/g DW, but when carrots were grown in soil with a total potassium level of 300 mg/100 g soil, the FaDOH concentration in the carrots fell to 445 μg/g DW. Carrots grown in soils generally low in available phosphorus exhibited higher levels of falcarindiol if the soil was also low in available magnesium and calcium. The concentrations of polyacetylenes in carrots were positively correlated with total soil phosphorus level, but negatively correlated with total soil potassium level. Of the three polyacetylenes analysed, FaDOH concentrations were influenced most by changes in soil chemical composition.

  9. Agrobacterium rhizogenes: Transformed root cultures for the study of polyacetylene metabolism and biosynthesis

    SciTech Connect

    Marchant, Y.Y.

    1988-02-01

    Biologically active polyacetylenes are produced at low levels by the roots of members of the Coreopsidinae subtribe in the Asteraceae. Ten taxa of Coreopsis and Bidens were tranformed with Agrobacterium rhizogenes Strain A/sub 4/ and hairy root cultures established. These cultures grew rapidly and produced the same arrays of polyacetylenes as intact roots. The use of transformed roots for the study of polyacetylene biosynthesis is described in this paper. The engineering of plants with resistance to herbicides is now a practical reality because there are economic, intellectual and environmental incentives for using recombinant DNA technology in crop improvement programs, and because the biochemical and genetic basis for herbicide resistance is a simple trait conferred by a single gene. The transformation of plants with genes conferring resistance to insects or disease is more daunting, however, as biologically active secondary metabolites such as some alkaloids are typically products of multienzyme reactions. Photoactive polyacetylenes are probably plant defense chemicals and they are derived by a sequence of desaturation steps from oleic acid, which occurs ubiquitously in higher plants. Although the acetylene pathway may encompass as many genetic messages as those for morphine biosynthesis, it is likley that the genes controlling the biosynthesis of polyacetylenes may be isolated, identified in the near future and transferred via Agrobacterium to economically important plants susceptible to pathogen attack. 58 refs., 4 figs., 3 tabs.

  10. Correlations between Polyacetylene Concentrations in Carrot (Daucus carota L.) and Various Soil Parameters

    PubMed Central

    Kjellenberg, Lars; Johansson, Eva; Gustavsson, Karl-Erik; Granstedt, Artur; Olsson, Marie E.

    2016-01-01

    This study assessed the concentrations of three falcarinol-type polyacetylenes (falcarinol, falcarindiol, falcarindiol-3-acetate) in carrots and the correlations between these and different soil traits. A total of 144 carrot samples, from three different harvests taken a single season, were analysed in terms of their polyacetylene concentrations and root development. On one of the harvesting occasions, 48 soil samples were also taken and analysed. The chemical composition of the soil was found to influence the concentrations of falcarinol-type polyacetylenes in carrots. When the total soil potassium level was 200 mg/100 g soil, the concentration of falcarindiol (FaDOH) in the carrot samples was 630 μg/g DW, but when carrots were grown in soil with a total potassium level of 300 mg/100 g soil, the FaDOH concentration in the carrots fell to 445 μg/g DW. Carrots grown in soils generally low in available phosphorus exhibited higher levels of falcarindiol if the soil was also low in available magnesium and calcium. The concentrations of polyacetylenes in carrots were positively correlated with total soil phosphorus level, but negatively correlated with total soil potassium level. Of the three polyacetylenes analysed, FaDOH concentrations were influenced most by changes in soil chemical composition. PMID:28231155

  11. Electronic coherence dynamics in trans-polyacetylene oligomers.

    PubMed

    Franco, Ignacio; Brumer, Paul

    2012-04-14

    Electronic coherence dynamics in trans-polyacetylene oligomers are considered by explicitly computing the time dependent molecular polarization from the coupled dynamics of electronic and vibrational degrees of freedom in a mean-field mixed quantum-classical approximation. The oligomers are described by the Su-Schrieffer-Heeger Hamiltonian and the effect of decoherence is incorporated by propagating an ensemble of quantum-classical trajectories with initial conditions obtained by sampling the Wigner distribution of the nuclear degrees of freedom. The electronic coherence of superpositions between the ground and excited and between pairs of excited states is examined for chains of different length, and the dynamics is discussed in terms of the nuclear overlap function that appears in the off-diagonal elements of the electronic reduced density matrix. For long oligomers the loss of coherence occurs in tens of femtoseconds. This time scale is determined by the decay of population into other electronic states through vibronic interactions, and is relatively insensitive to the type and class of superposition considered. By contrast, for smaller oligomers the decoherence time scale depends strongly on the initially selected superposition, with superpositions that can decay as fast as 50 fs and as slow as 250 fs. The long-lived superpositions are such that little population is transferred to other electronic states and for which the vibronic dynamics is relatively harmonic.

  12. Bioactive C₁₇-Polyacetylenes in Carrots (Daucus carota L.): Current Knowledge and Future Perspectives.

    PubMed

    Dawid, Corinna; Dunemann, Frank; Schwab, Wilfried; Nothnagel, Thomas; Hofmann, Thomas

    2015-10-28

    C17-polyacetylenes (PAs) are a prominent group of oxylipins and are primarily produced by plants of the families Apiaceae, Araliaceae, and Asteraceae, respectively. Recent studies on the biological activity of polyacetylenes have indicated their potential to improve human health due to anticancer, antifungal, antibacterial, anti-inflammatory, and serotogenic effects. These findings suggest targeting vegetables with elevated levels of bisacetylenic oxylipins, such as falcarinol, by breeding studies. Due to the abundant availability, high diversity of cultivars, worldwide experience, and high agricultural yields, in particular, carrot (Daucus carota L.) genotypes are a very promising target vegetable. This paper provides a review on falcarinol-type C17-polyacetylenes in carrots and a perspective on their potential as a future contributor to improving human health and well-being.

  13. Fluorine segregation in crystalline materials: structural control and solid-state [2+2] cycloaddition in CF(3)-substituted tetrathiafulvalene derivatives.

    PubMed

    Jeannin, Olivier; Fourmigué, Marc

    2006-04-03

    The well-known influence of long perfluorinated chains on the structures and stability of amphiphilic molecules in liquid crystalline mesophases or mesoscopic micellar arrangements is evaluated here in the realm of crystalline materials based on rigid aromatic molecules bearing only a limited number of CF(3) moieties. Tetrathiafulvalene (TTF) derivatives bearing one or two CF(3) groups, that is, (Z)- and (E)-(CF(3))(2)TTF ((Z)-1, (E)-1), EDT-TTF-CF(3) (2), and EDT-TTF(CF(3))(2) (3) (EDT=ethylenedithio) are prepared from the 1,3-dipolar reaction of methyl 4,4,4-trifluorotetrolate with ethylenetrithiocarbonate. The structures of neutral (Z)-1, (E)-1, 2, and 3 as indicated by single-crystal X-ray diffraction measurements reveal the recurrent formation of layered structures with a strong segregation of the fluorinated moieties and formation of fluorous bilayers, attributed to the amphiphilic character of those TTF derivatives upon CF(3) functionalization, and without need for longer C(n)F(2n+1) (n>1) perfluorinated chains. The short intermolecular distance between outer C==C double bonds observed in the layered structure of (E)-1 allows a solid-state [2+2] photocyclization with formation of chiral dyads incorporating the characteristic cyclobutane ring. These dyads containing two dihydrotetrathiafulvalene moieties facing each other exhibit reversible oxidation to the mixed-valence radical cation state and organize in the solid-state into the same layered structures with fluorous bilayers.

  14. Differential effects of falcarinol and related aliphatic C(17)-polyacetylenes on intestinal cell proliferation.

    PubMed

    Purup, Stig; Larsen, Eric; Christensen, Lars P

    2009-09-23

    Quantitative major polyacetylenes of carrots (falcarinol and falcarindiol) and American ginseng roots (falcarinol and panaxydol) were isolated and tested in human intestinal epithelial cells of normal (FHs 74 Int.) and cancer (Caco-2) origin. A hormesis effect was seen for all isolated polyacetylenes when added to Caco-2 cells in concentrations ranging from 1 ng/mL to 20 microg/mL. The relative inhibitory potency was falcarinol > panaxydol > falcarindiol. No hormesis effect was observed when adding the polyacetylenes to FHs 74 Int. cells. Instead, an inhibitory growth response was observed above 1 microg/mL. The relative inhibitory potency was panaxydol > falcarinol > falcarindiol. Maximal inhibition at 20 microg/mL corresponded to approximately 95% and 80% inhibition of cell proliferation in normal and cancer cells, respectively. Combinations of falcarinol and falcarindiol added to normal and cancer cells showed a synergistic response for the inhibition of cell growth. Furthermore, the oxidized form of falcarinol, falcarinon, showed a significantly less growth inhibitory effect in intestinal cells of both normal and cancer origin; hence, a hydroxyl group at C-3 may be important for activity of falcarinol-type polyacetylenes. Extracts of carrots, containing different amounts of falcarinol, falcarindiol, and falcarindiol 3-acetate had significant inhibitory effects on both normal and cancer cell proliferation. In cancer cells, the extract containing the highest concentration of falcarinol tended to have the highest growth inhibitory effect, in accordance with a higher potency of falcarinol than falcarindiol. The present study demonstrates that aliphatic C(17)-polyacetylenes are potential anticancer principles of carrots and related vegetables and that synergistic interaction between bioactive polyacetylenes may be important for their bioactivity.

  15. Differential Effects of Falcarinol and Related Aliphatic C17-Polyacetylenes on Intestinal Cell Proliferation

    PubMed Central

    2009-01-01

    Quantitative major polyacetylenes of carrots (falcarinol and falcarindiol) and American ginseng roots (falcarinol and panaxydol) were isolated and tested in human intestinal epithelial cells of normal (FHs 74 Int.) and cancer (Caco-2) origin. A hormesis effect was seen for all isolated polyacetylenes when added to Caco-2 cells in concentrations ranging from 1 ng/mL to 20 μg/mL. The relative inhibitory potency was falcarinol > panaxydol > falcarindiol. No hormesis effect was observed when adding the polyacetylenes to FHs 74 Int. cells. Instead, an inhibitory growth response was observed above 1 μg/mL. The relative inhibitory potency was panaxydol > falcarinol > falcarindiol. Maximal inhibition at 20 μg/mL corresponded to approximately 95% and 80% inhibition of cell proliferation in normal and cancer cells, respectively. Combinations of falcarinol and falcarindiol added to normal and cancer cells showed a synergistic response for the inhibition of cell growth. Furthermore, the oxidized form of falcarinol, falcarinon, showed a significantly less growth inhibitory effect in intestinal cells of both normal and cancer origin; hence, a hydroxyl group at C-3 may be important for activity of falcarinol-type polyacetylenes. Extracts of carrots, containing different amounts of falcarinol, falcarindiol, and falcarindiol 3-acetate had significant inhibitory effects on both normal and cancer cell proliferation. In cancer cells, the extract containing the highest concentration of falcarinol tended to have the highest growth inhibitory effect, in accordance with a higher potency of falcarinol than falcarindiol. The present study demonstrates that aliphatic C17-polyacetylenes are potential anticancer principles of carrots and related vegetables and that synergistic interaction between bioactive polyacetylenes may be important for their bioactivity. PMID:19694436

  16. Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents

    DOEpatents

    Aldissi, M.

    1984-06-27

    An electrically conductive block copolymer of polyisoprene and polyacetylene and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I/sub 2/ to give it an electrical conductivity in the metallic regime.

  17. Effects of altered crystalline structure and increased initial compressive strength of calcium sulfate bone graft substitute pellets on new bone formation.

    PubMed

    Urban, Robert M; Turner, Thomas M; Hall, Deborah J; Infanger, Susan I; Cheema, Naveed; Lim, Tae-Hong; Moseley, Jon; Carroll, Michael; Roark, Michael

    2004-01-01

    A new, modified calcium sulfate has been developed with a different crystalline structure and a compressive strength similar to many calcium phosphate materials, but with a resorption profile only slightly slower than conventional surgical-grade calcium sulfate. A canine bilateral defect model was used to compare restoration of defects treated with the modified calcium sulfate compared to treatment using conventional calcium sulfate pellets after 6, 13, and 26 weeks. The modified calcium sulfate pellets were as effective as conventional calcium sulfate pellets with regard to the area fraction and compressive strength of newly formed bone in the treated bone defects. Mechanical testing demonstrated that the initial compressive strength of the modified material was increased nearly three-fold compared to that of conventional surgical-grade calcium sulfate. This increase potentially allows for its use in a broader range of clinical applications, such as vertebral and subchondral defects.

  18. Dietary polyacetylenes of the falcarinol type are inhibitors of breast cancer resistance protein (BCRP/ABCG2).

    PubMed

    Tan, Kee W; Killeen, Daniel P; Li, Yan; Paxton, James W; Birch, Nigel P; Scheepens, Arjan

    2014-01-15

    Polyacetylenes of the falcarinol type are present in vegetables such as carrots and parsley. They display interesting bioactivities and hold potential as health-promoting and therapeutic agents. In this study, falcarinol, falcarindiol, falcarindiol 3-acetate and falcarindiol 3,8-diacetate were examined for their modulation on breast cancer resistance protein (BCRP/ABCG2), an efflux transporter important for xenobiotic absorption and disposition, and multidrug resistance in cancer. Falcarinol, falcarindiol, and falcarindiol 3-acetate were extracted from carrots and falcarindiol 3,8-diacetate prepared from falcarindiol. Their modulatory effects on ABCG2 were studied using three methods-mitoxantrone accumulation, vesicular transport, and ATPase assay. The polyacetylenes inhibited mitoxantrone (an ABCG2 substrate) efflux in ABCG2-overexpressing HEK293 cells. The inhibitory effect was confirmed in the vesicular transport assay, in which concentration-dependent inhibition of methotrexate (an ABCG2 substrate) uptake into ABCG2-overexpressing Sf9 membrane vesicles was observed (IC50=19.7-41.7µM). The polyacetylenes also inhibited baseline and sulfasalazine-stimulated vanadate-sensitive ATPase activities in ABCG2-overexpressing Sf9 membrane vesicles (IC50=19.3-79.3µM). This is the first report of an inhibitory effect of polyacetylenes on ABCG2. These results indicate a prospective use of polyacetylenes as multidrug resistance reversal agents, a possible role of ABCG2 in the absorption and disposition of polyacetylenes, and potential food-drug interactions between polyacetylene-rich foods and ABCG2 substrate drugs.

  19. Structural changes of polyacetylenes in American ginseng root can be observed in situ by using Raman spectroscopy.

    PubMed

    Baranska, Malgorzata; Schulz, Hartwig; Christensen, Lars P

    2006-05-17

    The presented results show the special advantage of Raman spectroscopy in the investigation of polyacetylenes in American ginseng (Panax quinquefolium L.) roots. The compounds are measured directly in the plant tissue without any preliminary sample preparation. The polyacetylene signal is strong and well-separated from other bands so the spectral impact of the surrounding biological matrix can be clearly distinguished. The Raman spectrum taken in situ from the fresh ginseng root revealed a characteristic polyacetylene key band at 2237 cm(-1) whereas in the spectrum obtained from dried root this band was shifted to about 2258 cm(-1). The latter is in good agreement with signals obtained from isolated standards, falcarinol (2258 cm(-1)) and panaxydol (2260 cm(-1)), occurring as predominant polyacetylenes in this species. The shift of the polyacetylene band observed in root extracts or at a certain stage of root drying indicates the molecular modification of polyacetylenes resulting from the loss of water. Furthermore, it was found that the process upon root hydration is reversible as the shift of polyacetylene band from 2258 to 2237 cm(-1) is observed. An explanation of this phenomenon can be an interaction of polyacetylene molecules with plant components in the presence of water molecules forming a stable entity in situ that is broken after dehydration (loss of water) of the fresh ginseng root. Application of the Raman mapping technique to ginseng roots of different size showed that the content of both main polyacetylenes decreases with increasing root size in accordance with quantitative high-performance liquid chromatography data.

  20. Effect of ultrasound and blanching pretreatments on polyacetylene and carotenoid content of hot air and freeze dried carrot discs.

    PubMed

    Rawson, A; Tiwari, B K; Tuohy, M G; O'Donnell, C P; Brunton, N

    2011-09-01

    The effect of ultrasound and blanching pretreatments on polyacetylene (falcarinol, falcarindiol and falcarindiol-3-acetate) and carotenoid compounds of hot air and freeze dried carrot discs was investigated. Ultrasound pretreatment followed by hot air drying (UPHD) at the highest amplitude and treatment time investigated resulted in higher retention of polyacetylenes and carotenoids in dried carrot discs than blanching followed by hot air drying. Freeze dried samples had a higher retention of polyacetylene and carotenoid compounds compared to hot air dried samples. Color parameters were strongly correlated with carotenoids (p<0.05). This study shows that ultrasound pretreatment is a potential alternative to conventional blanching treatment in the drying of carrots.

  1. Polyacetylenes from carrots (Daucus carota) improve glucose uptake in vitro in adipocytes and myotubes.

    PubMed

    El-Houri, Rime B; Kotowska, Dorota; Christensen, Kathrine B; Bhattacharya, Sumangala; Oksbjerg, Niels; Wolber, Gerhard; Kristiansen, Karsten; Christensen, Lars P

    2015-07-01

    A dichloromethane (DCM) extract of carrot roots was found to stimulate insulin-dependent glucose uptake (GU) in adipocytes in a dose dependent manner. Bioassay-guided fractionation of the DCM extract resulted in the isolation of the polyacetylenes falcarinol and falcarindiol. Both polyacetylenes were able to significantly stimulate basal and/or insulin-dependent GU in 3T3-L1 adipocytes and porcine myotube cell cultures in a dose-dependent manner. Falcarindiol increased peroxisome proliferator-activated receptor (PPAR)γ-mediated transactivation significantly at concentrations of 3, 10 and 30 μM, while PPARγ-mediated transactivation by falcarinol was only observed at 10 μM. Docking studies accordingly indicated that falcarindiol binds to the ligand binding domain of PPARγ with higher affinity than falcarinol and that both polyacetylenes exhibit characteristics of PPARγ partial agonists. Falcarinol was shown to inhibit adipocyte differentiation as evident by gene expression studies and Oil Red O staining, whereas falcarindiol did not inhibit adipocyte differentiation, which indicates that these polyacetylenes have distinct modes of action. The results of the present study suggest that falcarinol and falcarindiol may represent scaffolds for novel partial PPARγ agonists with possible antidiabetic properties.

  2. The polyacetylenes falcarinol and falcarindiol affect stress responses in myotube cultures in a biphasic manner.

    PubMed

    Young, Jette F; Christensen, Lars P; Theil, Peter K; Oksbjerg, Niels

    2008-01-01

    The effects of the bioactive polyacetylenes, falcarinol and falcarindiol, present in carrots, celery, celeriac and other umbelliferous vegetables, on the stress responses in primary myotube cultures, were studied. Biphasic responses on cellular stress responses in myotube cultures were investigated by exposing them to various concentrations of falcarinol and falcarindiol for 24 h before testing effects of 100 microM H(2)O(2) on the intracellular formation of reactive oxygen species (ROS), transcription of the antioxidative enzyme cytosolic glutathione peroxidase (cGPx), and the heat shock proteins (HSP) HSP70 and HO1. At low concentrations (1.6 to 25 microM) polyacetylenes caused a slightly accelerated intra-cellular ROS formation, increased cGPx transcription and decreased HSP70 and HO1 transcription. The increased cGPx transcription may be interpreted as an adaptive response to the increased ROS formation and may have caused a reduced demand for the protective functions of the HSPs. ROS formation, however, was substantially decreased after pre-incubation with both polyacetylenes at 50 and 100 microM, the cGPx transcription was reduced and the HSP70 and HO1 transcription increased, indicating a need for the protective and repairing functions of the HSPs. In conclusion, pre-incubation with low concentrations of both polyacetylenes prior to H(2)O(2) exposure induced a cytoprotective effect whereas higher concentrations had adverse effects.

  3. Polyacetylene levels in carrot juice, effect of pH and thermal processing.

    PubMed

    Aguiló-Aguayo, I; Brunton, N; Rai, D K; Balagueró, E; Hossain, M B; Valverde, J

    2014-01-01

    This research focuses on the study of polyacetylenes in carrot juice and their response to pH, storage and thermal processing conditions. Falcarindiol-3-acetate (FaDOAc) and falcarinol (FaOH) were in fresh carrot juice at concentrations of 73 and 233 μg/L, respectively. Reducing the pH of the raw carrot juice from its natural pH 6.13 to pH 3.5 resulted in 2 and 5 fold better extraction of FaDOAc and FaOH respectively in comparison to a control sample (pH 6.13). Polyacetylenes were retained better in acidified juices and cold storage temperatures (4 °C) for first week of storage with respect to untreated juices. An increase in FaDOAc and FaOH of 10- and 16-fold, respectively, as compared to raw unprocessed samples was observed when processing samples at 90 °C for 1 min. This was assumed to be due to cell wall polysaccharides dissolution. However, negative correlation between total polyacetylenes and hexoses was confirmed by (1)H NMR spectroscopy, indicating some biological links between polyacetylenes and soluble sugars.

  4. The Polyacetylenes Falcarinol and Falcarindiol Affect Stress Responses in Myotube Cultures in a Biphasic Manner

    PubMed Central

    Young, Jette F.; Christensen, Lars P.; Theil, Peter K.; Oksbjerg, Niels

    2008-01-01

    The effects of the bioactive polyacetylenes, falcarinol and falcarindiol, present in carrots, celery, celeriac and other umbelliferous vegetables, on the stress responses in primary myotube cultures, were studied. Biphasic responses on cellular stress responses in myotube cultures were investigated by exposing them to various concentrations of falcarinol and falcarindiol for 24 h before testing effects of 100 μM H2O2 on the intracellular formation of reactive oxygen species (ROS), transcription of the antioxidative enzyme cytosolic glutathione peroxidase (cGPx), and the heat shock proteins (HSP) HSP70 and HO1. At low concentrations (1.6 to 25 μM) polyacetylenes caused a slightly accelerated intra-cellular ROS formation, increased cGPx transcription and decreased HSP70 and HO1 transcription. The increased cGPx transcription may be interpreted as an adaptive response to the increased ROS formation and may have caused a reduced demand for the protective functions of the HSPs. ROS formation, however, was substantially decreased after pre-incubation with both polyacetylenes at 50 and 100 μM, the cGPx transcription was reduced and the HSP70 and HO1 transcription increased, indicating a need for the protective and repairing functions of the HSPs. In conclusion, pre-incubation with low concentrations of both polyacetylenes prior to H2O2 exposure induced a cytoprotective effect whereas higher concentrations had adverse effects. PMID:18846258

  5. Simultaneous determination of ginsenosides and polyacetylenes in American ginseng root (Panax quinquefolium L.) by high-performance liquid chromatography.

    PubMed

    Christensen, Lars P; Jensen, Martin; Kidmose, Ulla

    2006-11-29

    A method for simultaneous determination of ginsenosides and polyacetylenes in Panax quinquefolium L. (American ginseng) roots was developed. The ginsenosides Rb1, Rb2, Rc, Rd, Re, Rg1, Ro, malonyl-Rb1, malonyl-Rc, and malonyl-Rd and the polyacetylenes falcarinol and panaxydol were extracted from fresh ginseng roots in a sequential extraction process with 100% methanol followed by 80% aqueous methanol and quantified simultaneously in extracts by high-performance liquid chromatography using diode array detection. Separations were achieved with a phosphate buffer-acetonitrile gradient system using an RP-C18 column. Except for Rd, the present extraction method resulted in similar or significantly higher concentrations of both ginsenosides and polyacetylenes in comparison to commonly used extraction methods for these compounds. The contents of polyacetylenes and ginsenosides were determined in the root hairs, lateral roots, and main roots of 6 year old ginseng plants. The total mean concentrations of ginsenosides and polyacetylenes in root hairs were 31.0 g/kg fresh weight (FW) and 2.6 g/kg FW, respectively, whereas the concentrations of these bioactive compounds in the main roots were significantly lower with total mean concentrations of 17.8 g/kg FW for ginsenosides and 0.6 g/kg FW for polyacetylenes. The concentration of individual and total ginsenosides and polyacetylenes did not differ significantly between main roots of different sizes. Consequently, it is possible to do quantitative screening for ginsenosides and polyacetylenes to breed ginseng roots with higher levels of bioactive compounds.

  6. Microwave emulations and tight-binding calculations of transport in polyacetylene

    NASA Astrophysics Data System (ADS)

    Stegmann, Thomas; Franco-Villafañe, John A.; Ortiz, Yenni P.; Kuhl, Ulrich; Mortessagne, Fabrice; Seligman, Thomas H.

    2017-01-01

    A novel approach to investigate the electron transport of cis- and trans-polyacetylene chains in the single-electron approximation is presented by using microwave emulation measurements and tight-binding calculations. In the emulation we take into account the different electronic couplings due to the double bonds leading to coupled dimer chains. The relative coupling constants are adjusted by DFT calculations. For sufficiently long chains a transport band gap is observed if the double bonds are present, whereas for identical couplings no band gap opens. The band gap can be observed also in relatively short chains, if additional edge atoms are absent, which cause strong resonance peaks within the band gap. The experimental results are in agreement with our tight-binding calculations using the nonequilibrium Green's function method. The tight-binding calculations show that it is crucial to include third nearest neighbor couplings to obtain the gap in the cis-polyacetylene.

  7. Characterisation of polyacetylenes isolated from carrot (Daucus carota) extracts by negative ion tandem mass spectrometry.

    PubMed

    Rai, Dilip K; Brunton, Nigel P; Koidis, Anastasios; Rawson, Ashish; McLoughlin, Padraig; Griffiths, William J

    2011-08-15

    The potential use of negative electrospray ionisation mass spectrometry (ESI-MS) in the characterisation of the three polyacetylenes common in carrots (Daucus carota) has been assessed. The MS scans have demonstrated that the polyacetylenes undergo a modest degree of in-source decomposition in the negative ionisation mode while the positive ionisation mode has shown predominantly sodiated ions and no [M+H](+) ions. Tandem mass spectrometric (MS/MS) studies have shown that the polyacetylenes follow two distinct fragmentation pathways: one that involves cleavage of the C3-C4 bond and the other with cleavage of the C7-C8 bond. The cleavage of the C7-C8 bond generated product ions m/z 105.0 for falcarinol, m/z 105/107.0 for falcarindiol, m/z 147.0/149.1 for falcarindiol-3-acetate. In addition to these product ions, the transitions m/z 243.2 → 187.1 (falcarinol), m/z 259.2 → 203.1 (falcarindiol), m/z 301.2 → 255.2/203.1 (falcarindiol-3-acetate), mostly from the C3-C4 bond cleavage, can form the basis of multiple reaction monitoring (MRM)-quantitative methods which are poorly represented in the literature. The 'MS(3) ' experimental data confirmed a less pronounced homolytic cleavage site between the C11-C12 bond in the falcarinol-type polacetylenes. The optimised liquid chromatography (LC)/MS conditions have achieved a baseline chromatographic separation of the three polyacetylenes investigated within 40 min total run-time.

  8. Optical properties and photoexcitation of a novel liquid form of soluble polyacetylene

    NASA Technical Reports Server (NTRS)

    Tubino, R.; Dorsinville, R.; Lam, W.; Alfano, R. R.; Birman, J. L.

    1984-01-01

    Optical absorption, fluorescence emission, Raman scattering, and time-resolved emission experiments are reported on a new liquid form of soluble polyacetylene. This liquid consists of separate polyene chains, grown on activated sites of a polybutadiene chain. The depolarization ratios as well as the time-resolved spectrum of the secondary emission were measured. The relevant spectral features are discussed and analyzed in terms of the lack of interchain interactions which characterize the polymer in solution.

  9. Can trans-polyacetylene be formed on single-walled carbon-doped boron nitride nanotubes?

    PubMed

    Chen, Ying; Wang, Hong-xia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xiao-guang; Wang, Xuan-zhang

    2012-07-01

    Recently, the grafting of polymer chains onto nanotubes has attracted increasing attention as it can potentially be used to enhance the solubility of nanotubes and in the development of novel nanotube-based devices. In this article, based on density functional theory (DFT) calculations, we report the formation of trans-polyacetylene on single-walled carbon-doped boron nitride nanotubes (BNNTs) through their adsorption of a series of C(2)H(2) molecules. The results show that, rather than through [2 + 2] cycloaddition, an individualmolecule would preferentially attach to a carbon-doped BNNT via "carbon attack" (i.e., a carbon in the C(2)H(2) attacks a site on the BNNT). The adsorption energy gradually decreases with increasing tube diameter. The free radical of the carbon-doped BNNT is almost completely transferred to the carbon atom at the end of the adsorbed C(2)H(2) molecule. When another C(2)H(2) molecule approaches the carbon-doped BNNT, it is most energetically favorable for this C(2)H(2) molecule to be adsorbed at the end of the previously adsorbed C(2)H(2) molecule, and so on with extra C(2)H(2) molecules, leading to the formation of polyacetylene on the nanotube. The spin of the whole system is always localized at the tip of the polyacetylene formed, which initiates the adsorption of the incoming species. The present results imply that carbon-doped BNNT is an effective "metal-free" initiator for the formation of polyacetylene.

  10. Polyacetylene diversity and bioactivity in orange market and locally grown colored carrots (Daucus carota L.).

    PubMed

    Metzger, Brandon T; Barnes, David M

    2009-12-09

    Carrots contain a wide array of phytochemicals such as carotenoids, phenolics, alpha-tocopherol, and polyacetylenes. Carrots are most known for their pro-vitamin A carotenoids but also contain other phytochemicals with documented health benefits. The phytochemicals in colored carrots present a challenge and opportunity due to the wide diversity of potent bioactive compounds. Two commercial carrots, 1 wild carrot, and 13 colored carrot varieties were characterized phytochemically. The carrots were screened in an anti-inflammatory model of lipopolysaccharide-induced nitric oxide production. Deep Purple carrot had the highest concentration of total polyacetylenes, alpha-tocopherol, and total phenolics. Commercial fresh market and baby orange carrots both had high concentrations of pro-vitamin A carotenoids. Purple carrots had higher antioxidant capacity values due to their anthocyanin content. Only seven carrot varieties had inhibitory activity (IC(25) = 257-1321 microg/mL) in macrophage cells. Among the varieties tested during the selected growing season, Deep Purple had the highest polyacetylene content and other important antioxidant phytochemicals. Further work is needed to identify other potential anti-inflammatory phytochemicals in colored carrots on the basis of this research.

  11. Spectroscopic studies on bioactive polyacetylenes and other plant components in wild carrot root.

    PubMed

    Roman, Maciej; Dobrowolski, Jan Cz; Baranska, Malgorzata; Baranski, Rafal

    2011-08-26

    Polyacetylenes and other common plant components, such as starch, pectin, cellulose, and lignin, were studied in roots of the wild carrot (Daucus carota) subspecies D. carota subsp. gummifer and D. carota subsp. maximus by Raman spectroscopy. The components were measured in situ, directly in the plant tissue and without any preliminary sample preparation. The analysis was performed on the basis of the intense and characteristic key bands observed in the Raman spectrum. The two main carrot polyacetylenes falcarinol (1) and falcarindiol (2) have similar molecular structures, but their Raman spectra exhibit a small band shift in the symmetric -C≡C-C≡C- mode from 2258 cm⁻¹ to 2252 cm⁻¹. Quantum chemical calculations confirmed that the differences observed between the samples may be due to conformational and environmental changes. The polyacetylenes were also detected by Raman mapping, which visualized the distribution of the compounds across sections of carrot roots. The mapping technique was also applied to assess the distribution of lignin and polysaccharide compounds. The results showed the tissue-specific accumulation of starch and cell wall components such as lignin, pectin, and cellulose.

  12. In situ simultaneous analysis of polyacetylenes, carotenoids and polysaccharides in carrot roots.

    PubMed

    Baranska, Malgorzata; Schulz, Hartwig; Baranski, Rafal; Nothnagel, Thomas; Christensen, Lars P

    2005-08-24

    This paper presents an approach to simultaneously analyze polyacetylenes, carotenoids, and polysaccharides in carrot (Daucus carota L.) roots by means of Raman spectroscopy. The components were measured in situ in the plant tissue without any preliminary sample preparation. The analysis is based on the intensive and characteristic key bands observed in the Raman spectrum of carrot root. The molecular structures of the main carrot polyacetylenes, falcarinol and falcarindiol, are similar, but their Raman spectra exhibit specific differences demonstrated by the shift of their -C[triple bond]C- mode from 2258 to 2252 cm(-)(1), respectively. Carotenoids can be identified by -C=C- stretching vibrations (about 1520 and 1155 cm(-)(1)) of the conjugated system of their polyene chain, whereas the characteristic Raman band at 478 cm(-)(1) indicates the skeletal vibration mode of starch molecule. The other polysaccharide, pectin, can be identified by the characteristic band at 854 cm(-)(1), which is due to the -C-O-C- skeletal mode of alpha-anomer carbohydrates. The Raman mapping technique applied here has revealed detailed information regarding the relative distribution of polyacetylenes, carotenoids, starch, and pectin in the investigated plant tissues. The distribution of these components varies among various carrot cultivars, and especially a significant difference can be seen between cultivated carrot and the wild relative D. carota ssp. maritimus.

  13. CRYSTALLINE DESOXYRIBONUCLEASE

    PubMed Central

    Kunitz, M.

    1950-01-01

    A crystalline enzyme capable of digesting thymus nucleic acid (desoxyribonucleic acid) has been isolated from fresh beef pancreas. The enzyme called "desoxyribonuclease" is a protein of the albumin type. Its molecular weight is about 60,000 and its isoelectric point is near pH 5.0. It contains about 8 per cent tyrosine and 2 per cent tryptophane. It is readily denatured by heat. The denaturation is reversible if heated in dilute acid at pH about 3.0. The digestion of thymus nucleic acid by crystalline desoxyribonuclease is accompanied by a gradual increase in the specific absorption of ultraviolet light by the acid. The spectrophotometric measurement of the rate of increase in the light absorption can be conveniently used as a general method for estimating desoxyribonuclease activity. Details are given of the method for isolation of crystalline desoxyribonuclease and of the spectrophotometric procedure for the measurement of desoxyribonuclease activity. PMID:15406373

  14. Method for the preparation of novel polyacetylene-type polymers

    DOEpatents

    Zeigler, John M.

    1989-01-01

    Polymerization of acetylenic monomers is achieved by using a catalyst which is the reaction product of a tungsten compound and a reducing agent effective to reduce W(VI) to W(III) and/or IV), e.g., WCl.sub.6.(organo-Li, organo-Mg or polysilane). The resultant silylated polymers are of heretofore unachievable high molecular weight and can be used as precursors to a wide variety of new acetylenic polymers by application of substitution reactions.

  15. Method for the preparation of novel polyacetylene-type polymers

    SciTech Connect

    Zeigler, J.M.

    1989-03-14

    Polymerization of acetylenic monomers is achieved by using a catalyst which is the reaction product of a tungsten compound and a reducing agent effective to reduce W(VI) to W(III) and/or (IV), e.g., WCl/sub 6/.(organo-Li, organo-Mg or polysilane). The resultant silylated polymers are of heretofore unachievable high molecular weight and can be used as precursors to a wide variety of new acetylenic polymers by application of substitution reactions.

  16. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

    Tsapatsis, Michael (Inventor); Lai, Zhiping (Inventor)

    2008-01-01

    In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.

  17. Organic Radical Contrast Agents Based on Polyacetylenes Containing 2,2,6,6-Tetramethylpiperidine 1-Oxyl (TEMPO): Targeted Magnetic Resonance (MR)/Optical Bimodal Imaging of Folate Receptor Expressing HeLa Tumors in Vitro and in Vivo(a).

    PubMed

    Huang, Lixia; Yan, Chenggong; Cui, Danting; Yan, Yichen; Liu, Xiang; Lu, Xinwei; Tan, Xiangliang; Lu, Xiaodan; Xu, Jun; Xu, Yikai; Liu, Ruiyuan

    2015-06-01

    Nitroxides have great potential as magnetic resonance imaging (MRI) contrast agents for tumor detection. Polyacetylenes(PAs) containing 2,2,6,6-tetramethyl-piperidine oxyl (TEMPO) and poly(ethylene glycol) were synthesized via metathesis polymerization of the corresponding substituted acetylenes to be used for targeted bimodal MRI /optical imaging of tumors. The poly(ethylene glycol) in the polyacetylenes enables covalent conjugation of carboxyl fluorescein and folic acid (FA) with hydroxyl groups to develop targeted multifunctional organic radical contrast agents (ORCAs). In vitro studies confirm the excellent binding specificity and subsequent enhanced cellular internalization of the targeted ORCAs (PA-TEMPO-FI-FA) without cytotoxicity. In vivo T1-weighted MRI demonstrates the active tumor targeting ability of PA-TEMPO-FI-FA to generate specific contrast enhancement in mice bearing HeLa tumors. Moreover, longitudinal optical imaging displays high tumor accumulation after 1 h post-injection of PA-TEMPO-FI-FA. These results indicate that multifunctional ORCAs may provide a tumor-targeted delivery platform for further molecular imaging guided cancer therapy.

  18. Quantification of polyacetylenes in apiaceous plants by high-performance liquid chromatography coupled with diode array detection.

    PubMed

    Kramer, Maike; Mühleis, Andrea; Conrad, Jürgen; Leitenberger, Martin; Beifuss, Uwe; Carle, Reinhold; Kammerer, Dietmar R

    2011-01-01

    Polyacetylenes are known for their biofunctional properties in a wide range of organisms. In the present study, the most frequently occurring polyacetylenes, i.e. falcarinol, falcarindiol, and falcarindiol-3-acetate, were determined in six genera of the Apiaceae family. For this purpose, a straightforward and reliable method for the screening and quantification of the polyacetylenes using high-performance liquid chromatography coupled with diode array and mass spectrometric detection without tedious sample clean-up has been developed. Peak assignment was based on retention times, UV spectra, and mass spectral data. Quantification was carried out using calibration curves of authentic standards isolated from turnip-rooted parsley and Ligusticum mutellina, respectively. The references were unambiguously identified by Fourier transform-IR (FT-IR) spectroscopy, GC-MS, HPLC-MSn in the positive ionization mode, and 1H NMR and 13C NMR spectroscopy. To the best of our knowledge, the occurrence of falcarindiol-3-acetate in Anthriscus sylvestris and Pastinaca sativa has been reported for the first time. The data revealed great differences in the polyacetylene contents and varying proportions of individual compounds in the storage roots of Apiaceous plants. The results of the present study may be used as a suitable tool for authenticity control and applied to identify novel sources devoid or particularly rich in polyacetylenes, thus facilitating breeding programs for the selective enrichment and depletion of these plant secondary metabolites, respectively.

  19. Method for the preparation of novel polyacetylene-type polymers

    DOEpatents

    Zeigler, J.M.

    1987-11-09

    Polymerization of acetylenic monomers is achieved by using a catalyst which is the reaction product of a tungsten compound and a reducing agent effective to reduce W(VI) to W(III and/or IV), e.g., WCl/sub 6//center dot/(organo-Li, organo-Mg or polysilane). The resultant silylated polymers are of heretofore unachievable high molecular weight and can be used as precursors to a wide variety of new acetylenic polymers by application of substitution reactions. 1 tab.

  20. Soluble silylated polyacetylene derivatives, their preparation and their use as precursors to novel polyacetylene-type polymers

    DOEpatents

    Zeigler, J.M.

    1985-07-30

    Polymerization of acetylenic monomers is achieved by using a catalyst which is the reaction product of a tungsten compound and a reducing agent effective to reduce W(VI) to W(III and/or IV), e.g., WCl/sub 6/ x (organo-Li, organo-Mg or polysilanes). The resultant silylated polymers are of heretofore unachievable, high molecular weight and can be used as precursors to a wide variety of new acetylenic polymers by application of substitution reactions. They can be used as electrodes in batteries.

  1. Poly(acetylene) as a positive electrode in lithium sulfur oxyhalide cells

    NASA Astrophysics Data System (ADS)

    Calvert, Jeffrey M.; Weiner, Bryndyn; Smith, Jerry J.; Nowak, Robert J.

    1989-03-01

    Conductive poly(acetylene) film was employed as the positive electrode in primary lithium/thionyl chloride and lithium/sulfuryl chloride cells. Neutral (CH)x, doped to the metallic state upon in situ exposure to LiAlCl4/sulfur oxyhalide electrolytes, acts as a catalytic surface rather than as the active electrochemical element. Sulfur oxyhalides were reduced on(CH)x film at high rates as on PTFE-bonded Shawinigan carbon black felt. Electrode capacity was limited by the inability of the electrolyte to permeate the (CH)x film and the formation of a surface passive filmby discharge products.

  2. Use of a polyacetylene cathode in primary lithium-thionyl chloride cells

    SciTech Connect

    Not Available

    1983-10-01

    This report describes the work performed for the Navy with regard to the use of poly(acetylene), (CH)x, as a cathode material in a lithium/thionyl (Li/SOCl/sub 2/) battery. The objective of the project was three fold: (1) To characterize and understand the electrochemistry of (CH)x in a detailed manner, (2) To study the compatibility of (CH)x with SOCl/sub 2/ and (3) To synthesize and investigate 'modified' (CH)x polymers which may possess more desirable properties than the parent polymer.

  3. Production of an allelopathic polyacetylene in hairy root cultures of goldenrod (Solidago altissima L.).

    PubMed

    Inoguchi, Masahiko; Ogawa, Satoshi; Furukawa, Sanae; Kondo, Hirokiyo

    2003-04-01

    Hairy roots of goldenrod (Solidago altissima L.) were induced by infecting axenic plants with Agrobacterium rhizogenes strain A4. Growth and allelopathic polyacetylene (cis-dehydromatricaria ester, cis-DME) production of two independent hairy root clones were examined in several culture media and light regimes. cis-DME contents in hairy roots were at the same level as those in normal roots. cis-DME production in root cultures was several-fold lower than that of native plants and greatly repressed by light.

  4. Charge-coupled substituted garnets (Y 3–x Ca 0.5x M 0.5x )Fe₅O₁₂ (M = Ce, Th): Structure and stability as crystalline nuclear waste forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y³⁺ = Ca²⁺ + M⁴⁺, where M⁴⁺ = Ce⁴⁺ or Th⁴⁺. Single-phase garnets Y3–xCa0.5xM0.5xFe₅O₁₂ (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and ⁵⁷Fe–Mössbauer spectroscopy indicated that M⁴⁺ and Ca²⁺ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe³⁺ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high-temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  5. Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    SciTech Connect

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra

    2015-06-08

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single-phase garnets Y3–xCa0.5xM0.5xFe5O12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe–Mössbauer spectroscopy indicated that M4+ and Ca2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  6. Antiproliferative constituents in Umbelliferae plants II. Screening for polyacetylenes in some Umbelliferae plants, and isolation of panaxynol and falcarindiol from the root of Heracleum moellendorffii.

    PubMed

    Nakano, Y; Matsunaga, H; Saita, T; Mori, M; Katano, M; Okabe, H

    1998-03-01

    Methanol extracts of 36 samples of 21 Umbelliferae plants were screened for polyacetylenic compounds using the ELISA for panaxytriol, and their antiproliferative activity was checked by MTT assay using the tumor cell lines MK-1, HeLa and B16F10. The presence of antiproliferative polyacetylenes was suggested in Angelica acutiloba (fruit), Anethum graveolens (root), Bupleurum rotundifolium (fruit), Carum carvi (fruit and root), Coriandrum sativum (fruit), Cryptotaenia japonica (leaf), Glehnia littoralis (fruit), Heracleum moellendorffii (root) and Torilis japonica (fruit). Panaxynol and falcarindiol were successfully isolated from the root of Heracleum moellendorffii as antiproliferative polyacetylenes.

  7. Influence of Sous Vide and water immersion processing on polyacetylene content and instrumental color of parsnip (Pastinaca sativa) disks.

    PubMed

    Rawson, Ashish; Koidis, Anastasios; Rai, Dilip K; Tuohy, Maria; Brunton, Nigel

    2010-07-14

    The effect of blanching (95 +/- 3 degrees C) followed by sous vide (SV) processing (90 degrees C for 10 min) on levels of two polyacetylenes in parsnip disks immediately after processing and during chill storage was studied and compared with the effect of water immersion (WI) processing (70 degrees C for 2 min.). Blanching had the greatest influence on the retention of polyacetylenes in sous vide processed parsnip disks resulting in significant decreases of 24.5 and 24% of falcarinol (1) and falcarindiol (2) respectively (p < 0.05). Subsequent SV processing did not result in additional significant losses in polyacetylenes compared to blanched samples. Subsequent anaerobic storage of SV processed samples resulted in a significant decrease in 1 levels (p < 0.05) although no change in 2 levels was observed (p > 0.05). 1 levels in WI processed samples were significantly higher than in SV samples (p polyacetylene undergoes degradation such as oxidation, dehydrogenation when thermally treated forming oxidized form of 1 type molecules, in this case falcarindione, dehydrofalcarinol, dehydrofalcarinone. Thermal processing had a significant effect on instrumental color of parsnip samples compared to minimally processed in both SV and WI processed samples resulting in parsnip disks becoming darker, yellower and browner following processing and storage.

  8. Aliphatic C(17)-polyacetylenes of the falcarinol type as potential health promoting compounds in food plants of the Apiaceae family.

    PubMed

    Christensen, Lars P

    2011-01-01

    Many epidemiological studies have provided evidence that a high intake of fruits and vegetables is associated with a reduced risk for the development of cancer and cardiovascular diseases. Fruits and vegetables are known to contain health promoting components such as vitamins, minerals, antioxidants and dietary fibers, however, it is unclear which of these are responsible for the health promoting properties of fruits and vegetables. Aliphatic C(17)-polyacetylenes of the falcarinol type, which occur in common food plants of the Apiaceae family such as carrot, celeriac, parsnip and parsley, have demonstrated interesting bioactivities including antibacterial, antimycobacterial, and antifungal activity as well as anti-inflammatory, anti-platelet-aggregatory, neuritogenic and serotonergic effects. In addition, the cytotoxicity of falcarinol type polyacetylenes towards human cancer cells, bioavailability, and their potential anticancer effect in vivo indicates that these compounds may contribute to the health effects of certain vegetables and hence could be important nutraceuticals. The bioactivity of falcarinol type polyacetylenes occurring in food plants of the Apiaceae family, their possible mode of action and possible health promoting effects are discussed in this review as well as the effect of storage, processing and other factors that can influence the content of these compounds in particular root vegetables and products. Moreover, recent patents on bioactivity of falcarinol type polyacetylenes and inventions making use of this knowledge are presented and discussed.

  9. Purple carrot (Daucus carota L.) polyacetylenes decrease lipopolysaccharide-induced expression of inflammatory proteins in macrophage and endothelial cells.

    PubMed

    Metzger, Brandon T; Barnes, David M; Reed, Jess D

    2008-05-28

    Carrots ( Daucus carota L.) contain phytochemicals including carotenoids, phenolics, polyacetylenes, isocoumarins, and sesquiterpenes. Purple carrots also contain anthocyanins. The anti-inflammatory activity of extracts and phytochemicals from purple carrots was investigated by determining attenuation of the response to lipopolysaccharide (LPS). A bioactive chromatographic fraction (Sephadex LH-20) reduced LPS inflammatory response. There was a dose-dependent reduction in nitric oxide production and mRNA of pro-inflammatory cytokines (IL-6, IL-1beta, TNF-alpha) and iNOS in macrophage cells. Protein secretions of IL-6 and TNF-alpha were reduced 77 and 66% in porcine aortic endothelial cells treated with 6.6 and 13.3 microg/mL of the LH-20 fraction, respectively. Preparative liquid chromatography resulted in a bioactive subfraction enriched in the polyacetylene compounds falcarindiol, falcarindiol 3-acetate, and falcarinol. The polyacetylenes were isolated and reduced nitric oxide production in macrophage cells by as much as 65% without cytotoxicity. These results suggest that polyacetylenes, not anthocyanins, in purple carrots are responsible for anti-inflammatory bioactivity.

  10. Determination of polyacetylenes in carrot roots (Daucus carota L.) by high-performance liquid chromatography coupled with diode array detection.

    PubMed

    Christensen, Lars P; Kreutzmann, Stine

    2007-03-01

    A new high-performance liquid chromatographic method with diode array detection was developed for the separation and simultaneous determination of the carrot polyacetylenes falcarindiol (FaDOH), falcarindiol 3-acetate (FaDOAc) and falcarinol (FaOH) in carrot root extracts. The optimal chromatographic conditions were achieved on a C18 column with a linear gradient elution of water and acetonitrile as mobile phases, at the flow rate of 1.0 mL/min. All calibration curves of the three carrot polyacetylenes showed good linear regression (R2 > 0.998) within the test ranges. The developed method showed good precision for quantification of all polyacetylenes with overall intraday and interday variation of less than 3.3% and with average recovery rates of 99.2, 96.8 and 99.7% for FaDOH, FaDOAc and FaOH, respectively. The LOD (S/N = 3) and LOQ (S/N = 10) were less than 0.19 and 0.42 microg/mL, respectively, for all analytes. The established method was successfully used to determine the spatial distribution of FaDOH, FaDOAc and FaOH in six carrot genotypes (Bolero, Independent, Line 1, Mello Yello, Purple Haze and Tornado) by analysing peeled carrots and the corresponding peels for these polyacetylenes.

  11. Slit-Jet Discharge Studies of Polyacetylenic Molecules: Synthesis and High Resolution Infrared Spectroscopy of Diacetylene

    NASA Astrophysics Data System (ADS)

    Chang, Chih-Hsuan; Roberts, Melanie A.; Nesbitt, David J.

    2013-06-01

    Polyacetylenic molecules play an important role in both combustion chemistry as well as chemistry of the interstellar medium. This talk presents first high resolution infrared spectroscopic efforts on the simplest jet-cooled polyacetylene, namely diacetylene (C_4H_2). Specifically, the fundamental anti-symmetric C-H stretching mode (near 3333 cm^{-1}) and several hot combination bands of diacetylene have been investigated under sub-Doppler, jet cooled conditions in a pulsed supersonic slit discharge. Local Coriolis perturbations in the fundamental anti-symmetric C-H stretch manifold are observed and analyzed. Six hot bands are observed, including the H-C-C bending mode (v_8) not observed in previous room temperature studies. The observation of these hot bands under rotationally jet cooled conditions (T_{rot}=15.7(4) K) indicate the presence of highly non-equilibrium relaxation processes between vibration and rotation. G. Guelachvili, A. M. Craig, and D. A. Ramsay, J. Mol. Spectrosc. 105, 156 (1984)

  12. Inhibiting MDSC differentiation from bone marrow with phytochemical polyacetylenes drastically impairs tumor metastasis.

    PubMed

    Wei, Wen-Chi; Lin, Sheng-Yen; Lan, Chun-Wen; Huang, Yu-Chen; Lin, Chih-Yu; Hsiao, Pei-Wen; Chen, Yet-Ran; Yang, Wen-Chin; Yang, Ning-Sun

    2016-11-18

    Myeloid-derived suppressor cells (MDSCs) are implicated in the promotion of tumor metastasis by protecting metastatic cancerous cells from immune surveillance and have thus been suggested as novel targets for cancer therapy. We demonstrate here that oral feeding with polyacetylenic glycosides (BP-E-F1) from the medicinal plant Bidens pilosa effectively suppresses tumor metastasis and inhibits tumor-induced accumulation of granulocytic (g) MDSCs, but does not result in body weight loss in a mouse mammary tumor-resection model. BP-E-F1 is further demonstrated to exert its anti-metastasis activity through inhibiting the differentiation and function of gMDSCs. Pharmacokinetic and mechanistic studies reveal that BP-E-F1 suppresses the differentiation of gMDSCs via the inhibition of a tumor-derived, G-CSF-induced signaling pathway in bone marrow cells of test mice. Taken together, our findings suggest that specific plant polyacetylenic glycosides that target gMDSC differentiation by communicating with bone marrow cells may hence be seriously considered for potential application as botanical drugs against metastatic cancers.

  13. Isolation and structure elucidation of cytotoxic polyacetylenes and polyenes from Echinacea pallida.

    PubMed

    Pellati, Federica; Calò, Samuele; Benvenuti, Stefania; Adinolfi, Barbara; Nieri, Paola; Melegari, Michele

    2006-07-01

    Bioassay-guided fractionation of n-hexane extracts of Echinacea pallida (Asteraceae) roots led to the isolation and structure elucidation of two polyacetylenes (1, 3) and three polyenes (2, 4, 5). Two are known hydroxylated compounds, namely 8-hydroxy-pentadeca-(9E)-ene-11,13-diyn-2-one (1) and 8-hydroxy-pentadeca-(9E,13Z)-dien-11-yn-2-one (2). Two dicarbonylic constituents, namely pentadeca-(9E)-ene-11,13-diyne-2,8-dione (3) and pentadeca-(9E,13Z)-dien-11-yne-2,8-dione (4), were isolated and characterized for the first time. Furthermore, the structure elucidation of pentadeca-(8Z,13Z)-dien-11-yn-2-one (5) is described. The structure of the compounds isolated was determined on the basis of UV, IR, NMR (including 1D and 2D NMR experiments, such as 1H-1H gCOSY, gHSQC-DEPT, gHMBC, gNOESY) and MS spectroscopic data. The cytotoxic activity of the isolated constituents against MIA PaCa-2 human pancreatic adenocarcinoma cells was evaluated in the concentration range 1-100 microg/ml. Results show that the hydroxylated compounds (1, 2) have low cytotoxicity, while the more hydrophobic polyacetylenes (3) and polyenes (4, 5) displayed moderate activity.

  14. Novel polyacetylene derivatives and their inhibitory activities on acetylcholinesterase obtained from Panax ginseng roots.

    PubMed

    Murata, Kazuya; Iida, Daiki; Ueno, Yoshihiro; Samukawa, Keiichi; Ishizaka, Toshihiko; Kotake, Takeshi; Matsuda, Hideaki

    2017-01-01

    In our research program to identify cholinesterase and β-secretase inhibitors, we investigated Ginseng (root of Panax ginseng), a crude drug described as a multifunctional drug in the ancient Chinese herbal book Shennong Ben Cao Jing. Results from hexane and methanol extracts showed moderate inhibitory activities. This suggests that ginseng roots may be effective for the prevention of and therapy for dementia. We then focused on hexane extracts of raw ginseng root and dried ginseng root since the determination of hexane extract constituents has not been studied extensively. Activity-guided fractionation and purification led to the isolation of 4 polyacetylene compounds; homopanaxynol, homopanaxydol, (9Z)-heptadeca-1, 9-diene-4,6-diyn-3-one, and (8E)-octadeca-1,8-diene-4,6-diyn-3,10-diol. The chemical structures of these compounds, including stereochemistry, were determined. This is the first study to identify the structure of homopanaxynol and homopanaxydol. Moreover, the modes of action of some compounds were characterized as competitive inhibitors. This study showed, for the first time, that polyacetylene compounds possess acetylcholinesterase inhibitory activities.

  15. Inhibiting MDSC differentiation from bone marrow with phytochemical polyacetylenes drastically impairs tumor metastasis

    PubMed Central

    Wei, Wen-Chi; Lin, Sheng-Yen; Lan, Chun-Wen; Huang, Yu-Chen; Lin, Chih-Yu; Hsiao, Pei-Wen; Chen, Yet-Ran; Yang, Wen-Chin; Yang, Ning-Sun

    2016-01-01

    Myeloid-derived suppressor cells (MDSCs) are implicated in the promotion of tumor metastasis by protecting metastatic cancerous cells from immune surveillance and have thus been suggested as novel targets for cancer therapy. We demonstrate here that oral feeding with polyacetylenic glycosides (BP-E-F1) from the medicinal plant Bidens pilosa effectively suppresses tumor metastasis and inhibits tumor-induced accumulation of granulocytic (g) MDSCs, but does not result in body weight loss in a mouse mammary tumor-resection model. BP-E-F1 is further demonstrated to exert its anti-metastasis activity through inhibiting the differentiation and function of gMDSCs. Pharmacokinetic and mechanistic studies reveal that BP-E-F1 suppresses the differentiation of gMDSCs via the inhibition of a tumor-derived, G-CSF-induced signaling pathway in bone marrow cells of test mice. Taken together, our findings suggest that specific plant polyacetylenic glycosides that target gMDSC differentiation by communicating with bone marrow cells may hence be seriously considered for potential application as botanical drugs against metastatic cancers. PMID:27857157

  16. Synthesis of functionalized asymmetric star polymers containing conductive polyacetylene segments by living anionic polymerization.

    PubMed

    Zhao, Youliang; Higashihara, Tomoya; Sugiyama, Kenji; Hirao, Akira

    2005-10-19

    Novel 3-arm ABC, 4-arm ABCD, and 5-arm ABCDE asymmetric star polymers comprising the conductive polyacetylene precursor, poly(4-methylphenyl vinyl sulfoxide) (PMePVSO), and other segments, such as polystyrene, poly(alpha-methylstyrene), poly(4-methoxystyrene), poly(4-trimethylsilylstyrene), and poly(4-methylstyrene), were synthesized by the methodology based on living anionic polymerization using DPE-functionalized polymers. This methodology involves the addition reaction of a DPE-functionalized polymer to a living anionic polymer followed by the living anionic polymerization of MePVSO initiated from the in situ formed polymer anion with two, three, or four polymer segments. The resultant asymmetric star polymers possessed predetermined molecular weights, narrow molecular weight distributions (Mw/Mn < 1.03), and desired compositions as confirmed by SEC, 1H NMR, SLS, and elemental analysis. After thermal treatment, the PMePVSO segment in the star polymer could be completely converted into a conductive polyacetylene segment, evident from TGA and elemental analysis. These asymmetric star polymers are expected to exhibit interesting solution properties and unique microphase-separated morphological suprastructures with potential applications in nanoscopic conductive materials. Moreover, this methodology can afford the target asymmetric star polymers with arm segments varying in a wide range and enables the synthesis of more complex macromolecular architectures.

  17. The production and characterization of mid-gap states in trans-polyacetylene

    SciTech Connect

    Hoener, C.F.

    1988-08-01

    Photoinduced ir absorptions with much longer lifetimes and lower excitation energies than previously reported were observed after the photolysis of polyacetylene with upsilon > 5000 cm/sup -1/. These absorptions are similar to those previously reported to have millisecond lifetimes, and are attributed to charged bond-alternation defects. The persistent photoinduced absorptions could be depleted by photoexcitation of a transition with an absorption maximum near 4000 cm/sup -1/. Unpaired spins were observed to develop and be depleted at the same photolysis frequencies as the ir activity. These spins may be due to the charged defects. This would mean that the defects are charged polarons. The temperature required to dope polyacetylene chemically was measured for various dopants. This was taken to be a measure of the activation energy for the doping reaction. The activation energies were found to be much lower than predicted by stepwise reaction mechanisms. Photolysis with above-band-gap light did not alter the temperature required for reaction. The chemical stabilization of photoinduced defects does not occur at a perceptible rate at lower temperatures than the chemical doping reaction. 35 refs., 26 figs., 14 tabs.

  18. Effects of bioactive compounds from carrots (Daucus carota L.), polyacetylenes, beta-carotene and lutein on human lymphoid leukaemia cells.

    PubMed

    Zaini, Rana G; Brandt, Kirsten; Clench, Malcolm R; Le Maitre, Christine L

    2012-07-01

    New therapies for leukaemia are urgently needed. Carrots have been suggested as a potential treatment for leukaemia in traditional medicine and have previously been studied in other contexts as potential sources of anticancer agents. Indicating that carrots may contain bioactive compounds, which may show potential in leukaemia therapies. This study investigated the effects of five fractions from carrot juice extract (CJE) on human lymphoid leukaemia cell lines, together with five purified bioactive compounds found in Daucus carota L, including: three polyacetylenes (falcarinol, falcarindiol and falcarindiol-3-acetate) and two carotenoids (beta-carotene and lutein). Their effects on induction of apoptosis using Annexin V/PI and Caspase 3 activity assays analysed via flow cytometry and inhibition of cellular proliferation using Cell Titer Glo assay and cell cycle analysis were investigated. Treatment of all three lymphoid leukaemia cell lines with the fraction from carrot extracts which contained polyacetylenes and carotenoids was significantly more cytotoxic than the 4 other fractions. Treatments with purified polyacetylenes also induced apoptosis in a dose and time responsive manner. Moreover, falcarinol and falcarindiol-3-acetate isolated from Daucus carota L were more cytotoxic than falcarindiol. In contrast, the carotenoids showed no significant effect on either apoptosis or cell proliferation in any of the cells investigated. This suggests that polyacetylenes rather than beta-carotene or lutein are the bioactive components found in Daucus carota L and could be useful in the development of new leukemic therapies. Here, for the first time, the cytotoxic effects of polyacetylenes have been shown to be exerted via induction of apoptosis and arrest of cell cycle.

  19. Isolation, characterization and antimicrobial activities of polyacetylene glycosides from Coreopsis tinctoria Nutt.

    PubMed

    Guo, Jia; Wang, Ao; Yang, Ke; Ding, Hao; Hu, Yimin; Yang, Yumeng; Huang, Siqi; Xu, Jingguo; Liu, Tianxing; Yang, Haiyan; Xin, Zhihong

    2017-04-01

    Polyacetylene glycosides, (6Z, 12E)-tetradecadiene-8,10-diyne-1-ol-3(R)-O-β-D-glucopyranoside (trivially named coreoside E) and (6Z, 12E)-tetradecadiene-8,10-diyne-1-ol-3(R)-O-β-L-arabinopyranosyl-(1 → 2)-β-D-glucopyranoside (trivially named coreoside F), were isolated from buds of Coreopsis tinctoria Nutt., together with one known compound, coreoside B. Their chemical structures were elucidated by extensive spectroscopic analysis and on the basis of their chemical reactivities. Coreoside E exhibited high levels of antimicrobial activity against Staphylococcus aureus and Bacillus anthracis with minimum inhibitory concentrations of 27 ± 0.27 and 18 ± 0.40 μM, respectively, whereas coreoside F and coreoside B showed weak antimicrobial activity against S. aureus and B. anthracis.

  20. Plant growth regulating activity of three polyacetylenes from Helianthus annuus L.

    PubMed

    Hong, Si Won; Hasegawa, Koji; Shigemori, Hideyuki

    2009-01-01

    Three polyacetylenes, 8-(beta-D-glucopyranosyloxy)-3-hydroxy-1,9,14-pentadecatriene-4,6-diyne, termed "helian"(1), 8-acetoxy-3-hydroxy-1,9,14-pentadecatriene-4,6-diyne (2), and 3,8-dihydroxy-1,9,14-pentadecatriene-4,6-diyne (3) were isolated from seedlings of sunflower, Helianthus annuus L. cv Russia. Compounds 1 and 2, having a beta-glucose and an acetoxy group at C-8, respectively, showed a weak effect on the growth of roots and shoots of rice (Oryza sativa L.) and cress (Lepidium sativum L.), while compound 3, having a free hydroxyl group at C-8, exhibited a growth promoting effect on the roots and shoots of rice and cress.

  1. Branched 1,2,3-Triazolium-Functionalized Polyacetylene with Enhanced Conductivity.

    PubMed

    Wu, Jianhua; Wang, Cuifang; Zhou, Dandan; Liao, Xiaojuan; Xie, Meiran; Sun, Ruyi

    2016-12-01

    Metathesis cyclopolymerization of mono- or bissubstituted 1,6-heptadiynes is undergone to generate the ionic polyacetylenes (iPAs) with branched 1,2,3-ttriazolium pendants, which possess relatively high intrinsic ionic conductivities of 1.4 × 10(-5) -2.1 × 10(-5) S cm(-1) at 30 °C. The doping treatment with lithium bis(trifluoromethanesulfonyl)imide endows iPAs with enhanced ionic conductivities of 2.5 × 10(-5) -4.3 × 10(-5) S cm(-1) . Further doping with iodine, iPAs show ionic and electronic dual conductivities of 4.5 × 10(-5) -7.1 × 10(-4) and 1.5 × 10(-6) -4.5 × 10(-6) S cm(-1) , respectively. Therefore, the doped iPAs demonstrate the potential in the area of conducting polymers and polymeric electronics.

  2. Comparison of polyacetylene content in organically and conventionally grown carrots using a fast ultrasonic liquid extraction method.

    PubMed

    Søltoft, Malene; Eriksen, Morten Rosbjørn; Träger, Anne Wibe Braendholt; Nielsen, John; Laursen, Kristian Holst; Husted, Søren; Halekoh, Ulrich; Knuthsen, Pia

    2010-07-14

    A rapid and sensitive analytical method for quantification of polyacetylenes in carrot roots was developed. The traditional extraction method (stirring) was compared to a new ultrasonic liquid processor (ULP)-based methodology using high-performance liquid chromatography-ultraviolet (HPLC-UV) and mass spectrometry (MS) for identification and quantification of three polyacetylenes. ULP was superior because a significant reduction in extraction time and improved extraction efficiencies were obtained. After optimization, the ULP method showed good selectivity, precision [relative standard deviations (RSDs) of 2.3-3.6%], and recovery (93% of falcarindiol) of the polyacetylenes. The applicability of the method was documented by comparative analyses of carrots grown organically or conventionally in a 2 year field trial study. The average concentrations of falcarindiol, falcarindiol-3-acetate, and falcarinol in year 1 were 222, 30, and 94 mug of falcarindiol equiv/g of dry weight, respectively, and 3-15% lower in year 2. The concentrations were not significantly influenced by the growth system, but a significant year-year variation was observed for falcarindiol-3-acetate.

  3. Digestion of Crystalline Silicotitanate (CST)

    SciTech Connect

    DARREL, WALKER

    2004-11-04

    Researchers tested methods for chemically dissolving crystalline silicotitanate (CST) as a substitute for mechanical grinding to reduce particle size before vitrification. Testing used the commercially available form of CST, UOP IONSIV(R) IE-911. Reduction of the particle size to a range similar to that of the glass frit used by the Defense Waste Processing Facility (DWPF) could reduce problems with coupling cesium ion exchange to the vitrification process. This study found that IONSIV(R) IE-911 dissolves completely using a combination of acid, hydrogen peroxide, and fluoride ion. Neutralization of the resulting acidic solution precipitates components of the IONSIV(R) IE-911. Digestion requires extremely corrosive conditions. Also, large particles may reform during neutralization, and the initiation and rate of gas generation are unpredictable. Therefore, the method is not recommended as a substitute for mechanical grinding.

  4. Automated analytical standard production with supercritical fluid chromatography for the quantification of bioactive C17-polyacetylenes: a case study on food processing waste.

    PubMed

    Bijttebier, Sebastiaan; D'Hondt, Els; Noten, Bart; Hermans, Nina; Apers, Sandra; Exarchou, Vassiliki; Voorspoels, Stefan

    2014-12-15

    Food processing enterprises produce enormous amounts of organic waste that contains valuable phytochemicals (e.g. C17-polyacetylenes). Knowledge on the phytochemicals content is a first step towards valorisation. Quantification of C17-polyacetylenes is however often hampered by the lack of commercially available standards or by tedious multistep in-house standard production procedures. In the current study, a new and straightforward supercritical fluid chromatography purification procedure is described for the simultaneous production of 2 analytical C17-polyacetylene standards. Respectively, 5 and 6 mg of falcarinol and falcarindiol were purified in 17 h on analytical scale. After confirming the identity and quality (97% purity) by Nuclear Magnetic Resonance, accurate mass-Mass Spectrometry (am-MS) and Photo Diode Array (PDA) detection the C17-polyacetylene standards were used for the analysis of industrial vegetable waste with Liquid Chromatography coupled to PDA and am-MS detection. Measurements showed varying concentrations of C17-polyacetylenes in the organic waste depending on its nature and origin.

  5. Crystalline and Crystalline International Disposal Activities

    SciTech Connect

    Viswanathan, Hari S.; Chu, Shaoping; Reimus, Paul William; Makedonska, Nataliia; Hyman, Jeffrey De'Haven; Karra, Satish; Dittrich, Timothy M.

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

  6. Ground State Geometries of Polyacetylene Chains from Many-Particle Quantum Mechanics.

    PubMed

    Barborini, Matteo; Guidoni, Leonardo

    2015-09-08

    Due to the crucial role played by electron correlation, the accurate determination of ground state geometries of π-conjugated molecules is still a challenge for many quantum chemistry methods. Because of the high parallelism of the algorithms and their explicit treatment of electron correlation effects, Quantum Monte Carlo calculations can offer an accurate and reliable description of the electronic states and of the geometries of such systems, competing with traditional quantum chemistry approaches. Here, we report the structural properties of polyacetylene chains H-(C₂H₂)(N)-H up to N = 12 acetylene units, by means of Variational Monte Carlo (VMC) calculations based on the multi-determinant Jastrow Antisymmetrized Geminal Power (JAGP) wave function. This compact ansatz can provide for such systems an accurate description of the dynamical electronic correlation as recently detailed for the 1,3-butadiene molecule [J. Chem. Theory Comput. 2015 11 (2), 508-517]. The calculated Bond Length Alternation (BLA), namely the difference between the single and double carbon bonds, extrapolates, for N → ∞, to a value of 0.0910(7) Å, compatible with the experimental data. An accurate analysis was able to distinguish between the influence of the multi-determinantal AGP expansion and of the Jastrow factor on the geometrical properties of the fragments. Our size-extensive and self-interaction-free results provide new and accurate ab initio references for the structures of the ground state of polyenes.

  7. Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

    SciTech Connect

    Bi, Kedong E-mail: kedongbi@seu.edu.cn; Weathers, Annie; Pettes, Michael T.; Shi, Li E-mail: kedongbi@seu.edu.cn; Matsushita, Satoshi; Akagi, Kazuo; Goh, Munju

    2013-11-21

    Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m{sup −1} K{sup −1} near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, the PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion.

  8. Exploring the effects of pulsed electric field processing parameters on polyacetylene extraction from carrot slices.

    PubMed

    Aguiló-Aguayo, Ingrid; Abreu, Corina; Hossain, Mohammad B; Altisent, Rosa; Brunton, Nigel; Viñas, Inmaculada; Rai, Dilip K

    2015-03-02

    The effects of various pulsed electric field (PEF) parameters on the extraction of polyacetylenes from carrot slices were investigated. Optimised conditions with regard to electric field strength (1-4 kV/cm), number of pulses (100-1500), pulse frequency (10-200 Hz) and pulse width (10-30 μs) were identified using response surface methodology (RSM) to maximise the extraction of falcarinol (FaOH), falcarindiol (FaDOH) and falcarindiol-3-acetate (FaDOAc) from carrot slices. Data obtained from RSM and experiments fitted significantly (p < 0.0001) the proposed second-order response functions with high regression coefficients (R2) ranging from 0.82 to 0.75. Maximal FaOH (188%), FaDOH (164.9%) and FaDOAc (166.8%) levels relative to untreated samples were obtained from carrot slices after applying PEF treatments at 4 kV/cm with 100 number of pulses of 10 μs at 10 Hz. The predicted values from the developed quadratic polynomial equation were in close agreement with the actual experimental values with low average mean deviations (E%) ranging from 0.68% to 3.58%.

  9. Polyacetylenes from Notopterygium incisum–New Selective Partial Agonists of Peroxisome Proliferator-Activated Receptor-Gamma

    PubMed Central

    Liu, Xin; Noha, Stefan M.; Malainer, Clemens; Kramer, Matthias P.; Cocic, Amina; Kunert, Olaf; Schinkovitz, Andreas; Heiss, Elke H.; Schuster, Daniela

    2013-01-01

    Peroxisome proliferator-activated receptor gamma (PPARγ) is a key regulator of glucose and lipid metabolism and therefore an important pharmacological target to combat metabolic diseases. Since the currently used full PPARγ agonists display serious side effects, identification of novel ligands, particularly partial agonists, is highly relevant. Searching for new active compounds, we investigated extracts of the underground parts of Notopterygium incisum, a medicinal plant used in traditional Chinese medicine, and observed significant PPARγ activation using a PPARγ-driven luciferase reporter model. Activity-guided fractionation of the dichloromethane extract led to the isolation of six polyacetylenes, which displayed properties of selective partial PPARγ agonists in the luciferase reporter model. Since PPARγ activation by this class of compounds has so far not been reported, we have chosen the prototypical polyacetylene falcarindiol for further investigation. The effect of falcarindiol (10 µM) in the luciferase reporter model was blocked upon co-treatment with the PPARγ antagonist T0070907 (1 µM). Falcarindiol bound to the purified human PPARγ receptor with a Ki of 3.07 µM. In silico docking studies suggested a binding mode within the ligand binding site, where hydrogen bonds to Cys285 and Glu295 are predicted to be formed in addition to extensive hydrophobic interactions. Furthermore, falcarindiol further induced 3T3-L1 preadipocyte differentiation and enhanced the insulin-induced glucose uptake in differentiated 3T3-L1 adipocytes confirming effectiveness in cell models with endogenous PPARγ expression. In conclusion, we identified falcarindiol-type polyacetylenes as a novel class of natural partial PPARγ agonists, having potential to be further explored as pharmaceutical leads or dietary supplements. PMID:23630612

  10. Electron-nuclear-nuclear triple resonance of cis-rich polyacetylene —Evidence for negative spin sites of soliton

    NASA Astrophysics Data System (ADS)

    Kuroda, S.; Shirakawa, H.

    1991-03-01

    Electron-nuclear double resonance (ENDOR) and electron-nuclear-nuclear triple resonance (TRIPLE) spectra of stretch-oriented cis-rich polyacetylene at low temperatures show clear spectral turning points when the external magnetic field is parallel to the stretch direction. The difference between ENDOR and TRIPLE spectra, depending on the pumping frequency of the latter, provide direct evidence that the turning points are associated with the negative spin sites of the soliton, arising from electron correlation effect, as predicted from our previous ENDOR analysis.

  11. Solvent substitution

    SciTech Connect

    Not Available

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  12. Thiophenes, polyacetylenes and terpenes from the aerial parts of Eclipata prostrate.

    PubMed

    Xi, Feng-Min; Li, Chun-Tong; Han, Jun; Yu, Shi-Shan; Wu, Zhi-Jun; Chen, Wan-Sheng

    2014-11-15

    One new bithiophenes, 5-(but-3-yne-1,2-diol)-50-hydroxy-methyl-2,20-bithiophene (2), two new polyacetylenic glucosides, 3-O-b-D-glucopyranosyloxy-1-hydroxy-4E,6E-tetradecene-8,10,12-triyne (8), (5E)-trideca-1,5-dien-7,9,11-triyne-3,4-diol-4-O-b-D-glucopyranoside (9), six new terpenoid glycosides, rel-(1S,2S,3S,4R,6R)-1,6-epoxy-menthane-2,3-diol-3-O-b-D-glucopyranoside (10), rel-(1S,2S,3S,4R,6R)-3-O-(6-O-caffeoyl-b-D-glucopyranosyl)-1,6-epoxy menthane-2,3-diol (11), (2E,6E)-2,6,10-trimethyl-2,6,11-dodecatriene-1,10-diol-1-O-b-D-glucopyranoside (12), 3b,16b,29-trihydroxy oleanane-12-ene-3-O-b-D-glucopyranoside (13), 3,28-di-O-b-D-glucopyranosyl-3b,16b-dihydroxy oleanane-12-ene-28-oleanlic acid (14), 3-O-b-D-glucopyranosyl-(1?2)-b-D-glucopyranosyl oleanlic-18-ene acid-28-O-b-D-glucopyranoside (15), along with fifteen known compounds (1, 3–7, and 16–24), were isolated from the aerial parts of Eclipta prostrata. Their structures were established by analysis of the spectroscopic data. The isolated compounds 1–9 were tested for activities against dipeptidyl peptidase IV (DPP-IV), compound 7 showed significant antihyperglycemic activities by inhibitory effects on DPP-IV in human plasma in vitro, with IC50 value of 0.51 lM. Compounds 10–24 were tested in vitro against NF-jB-luc 293 cell line induced by LPS. Compounds 12, 15, 16, 19, 21, and 23 exhibited moderate anti-inflammatory activities.

  13. Crystalline boron nitride aerogels

    DOEpatents

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  14. Silylene-diethynyl-arylene polymers having liquid crystalline properties

    DOEpatents

    Barton, T.J.; Yiwei Ding.

    1993-09-07

    The present invention provides linear organosilicon polymers including diethynyl-(substituted)arylene units, and a process for their preparation. These novel polymers possess useful properties including electrical conductivity, liquid crystallinity, and/or photoluminescence. These polymers possess good solubility in organic solvents. A preferred example is produced according to the following reaction scheme. ##STR1## These polymers can be solvent-cast to yield excellent films and can also be pulled into fibers from concentrated solutions. All possess substantial crystallinity as revealed by DSC analysis and observation through a polarizing microscope, and possess liquid crystalline properties.

  15. A new disubstituted polyacetylene bearing 6-benzylaminopurine moieties: postfunctional synthetic strategy and sensitive chemosensor towards copper and cobalt ions.

    PubMed

    Ou, Daxin; Zhang, Liang; Huang, Yanfen; Lou, Xiaoding; Qin, Jingui; Li, Zhen

    2013-05-14

    A new 6-benzylaminopurine-functionalized disubstituted polyacetylene (P2) with strong green fluorescence is successfully synthesized by utilizing the postfunctional method. The polymer is soluble in common organic solvents, and its strong green fluorescence can be quenched by copper and cobalt ions with a detection limit down to 1.0 × 10(-8) (0.64 ppb) and 3.3 × 10(-8) mol L(-1) (1.94 ppb), respectively. Moreover, not much interference is observed from other metal ions, including Li(+) , Na(+) , K(+) , Fe(3+) , Fe(2+) , Ni(2+) , Hg(2+) , Mg(2+) , Al(3+) , Zn(2+) , Mn(2+) , Pb(2+) , Ba(2+) , Ca(2+) , Cd(2+) , Ag(+) , and Cr(3+) . Furthermore, P2 can be put into application using test strips, making P2 a practical, sensitive, and selective copper and cobalt probe.

  16. Crystalline Silica Primer

    USGS Publications Warehouse

    ,

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  17. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko, David J.

    2004-07-13

    The present invention provides phyllosilicate-polymer compositions which are useful as liquid crystalline composites. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while at the same time be transparent. Because of the ordering of the particles liquid crystalline composite, liquid crystalline composites are particularly useful as barriers to gas transport.

  18. The human crystallin gene families

    PubMed Central

    2012-01-01

    Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (α-crystallins) and the βγ-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision. PMID:23199295

  19. Simple, heart-smart substitutions

    MedlinePlus

    Coronary artery disease - heart smart substitutions; Atherosclerosis - heart smart substitutions; Cholesterol - heart smart substitutions; Coronary heart disease - heart smart substitutions; Healthy diet - heart smart substitutions; Wellness - heart smart substitutions

  20. Quantification of two polyacetylenes in Radix Ginseng and roots of related Panax species using a gas chromatography-mass spectrometric method.

    PubMed

    Liu, Ji-Hua; Lee, Che-Sum; Leung, Kit-Ming; Yan, Zhong-Kai; Shen, Bai-Hua; Zhao, Zhong-Zhen; Jiang, Zhi-Hong

    2007-10-31

    A sensitive method for quantitating the pharmacologically active polyacetylenes panaxynol and panaxydol in Radix Ginseng was developed using a capillary gas chromatography-mass spectrometric (GC-MS) method. The detection mode of selected ion monitoring (SIM) allowed sensitive and selective quantitation of the two compounds in ginseng. Method validation showed that the GC-MS method has much lower detection and quantitation limits than the high-performance liquid chromatography (HPLC)-UV method. This indicates that GC-MS is particularly useful for the analysis of polyacetylene compounds, which have relatively low abundances compared with ginsenosides in ginseng. Based on the quantitative results of different types of ginseng herbs, it was found that the panaxydol and panaxynol contents were higher in forest ginseng than in cultivated ginseng. This method was further applied to the quantitative analyses of panaxynol and panaxydol in Radix Notoginseng and American ginseng. The ratio of panaxydol to panaxynol can be utilized as a marker for differentiating ginseng, notoginseng, and American ginseng. This study introduces the first GC-MS method for the quantitative analysis of polyacetylenes in herbs of the Panax genus.

  1. Topological nonsymmorphic crystalline superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Ze; Liu, Chao-Xing

    2016-01-01

    Topological superconductors possess a nodeless superconducting gap in the bulk and gapless zero energy modes, known as "Majorana zero modes," at the boundary of a finite system. In this work, we introduce a new class of topological superconductors, which are protected by nonsymmorphic crystalline symmetry and thus dubbed "topological nonsymmorphic crystalline superconductors." We construct an explicit Bogoliubov-de Gennes type of model for this superconducting phase in the D class and show how Majorana zero modes in this model are protected by glide plane symmetry. Furthermore, we generalize the classification of topological nonsymmorphic crystalline superconductors to the classes with time reversal symmetry, including the DIII and BDI classes, in two dimensions. Our theory provides guidance to search for new topological superconducting materials with nonsymmorphic crystal structures.

  2. Topological Nonsymmorphic Crystalline Superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Ze; Liu, Chao-Xing

    Topological superconductors possess a nodeless superconducting gap in the bulk and gapless zero energy modes, known as ``Majorana zero modes'', at the boundary of a finite system. In this work, we introduce a new class of topological superconductors, which are protected by nonsymmorphic crystalline symmetry and thus dubbed ``topological nonsymmorphic crystalline superconductors''. We construct an explicit Bogoliubov-de Gennes type of model for this superconducting phase in the D class and show how Majorana zero modes in this model are protected by glide symmetry. Furthermore, we generalize the classification of topological nonsymmorphic crystalline superconductors to the classes with time reversal symmetry, including the DIII and BDI classes, in two dimensions. Our theory provides a guidance to search for new topological superconducting materials with nonsymmorphic crystal structures.

  3. Crystalline molecular flasks.

    PubMed

    Inokuma, Yasuhide; Kawano, Masaki; Fujita, Makoto

    2011-05-01

    A variety of host compounds have been used as molecular-scale reaction vessels, protecting guests from their environment or restricting the space available around them, thus favouring particular reactions. Such molecular 'flasks' can endow guest molecules with reactivities that differ from those in bulk solvents. Here, we extend this concept to crystalline molecular flasks, solid-state crystalline networks with pores within which pseudo-solution-state reactions can take place. As the guest molecules can spontaneously align along the walls and channels of the hosts, structural changes in the substrates can be directly observed by in situ X-ray crystallography during reaction. Recently, this has enabled observation of the molecular structures of transient intermediates and other labile species, in the form of sequential structural snapshots of the chemical transformation. Here, we describe the principles, development and applications of crystalline molecular flasks.

  4. Amorphous and Ultradisperse Crystalline Materials,

    DTIC Science & Technology

    The book sums up experimental and theoretical findings on amorphous and ultradisperse crystalline materials , massive and film types. Present-day... crystalline materials of metallic systems are presented. Emphasis is placed on inorganic film materials.

  5. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko; David J.

    2007-05-08

    The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

  6. Crystalline oxides on silicon.

    PubMed

    Reiner, James W; Kolpak, Alexie M; Segal, Yaron; Garrity, Kevin F; Ismail-Beigi, Sohrab; Ahn, Charles H; Walker, Fred J

    2010-07-20

    This review outlines developments in the growth of crystalline oxides on the ubiquitous silicon semiconductor platform. The overall goal of this endeavor is the integration of multifunctional complex oxides with advanced semiconductor technology. Oxide epitaxy in materials systems achieved through conventional deposition techniques is described first, followed by a description of the science and technology of using atomic layer-by-layer deposition with molecular beam epitaxy (MBE) to systematically construct the oxide-silicon interface. An interdisciplinary approach involving MBE, advanced real-space structural characterization, and first-principles theory has led to a detailed understanding of the process by which the interface between crystalline oxides and silicon forms, the resulting structure of the interface, and the link between structure and functionality. Potential applications in electronics and photonics are also discussed.

  7. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G.; Dosch, Robert G.

    1993-01-01

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  8. Liquid Crystalline Polymers

    DTIC Science & Technology

    1990-02-28

    Liquid crystalline polymers (LCPs); fibers ; thermotropic; lyotropic; processing; rheology; nonlinear optical (4L-" properties* blends* Q2 P- USTRACT...CowMnue on reverse if , cevwy and identify by block number) The remarkable mechanical properties and thermal stability of fibers fabricated from liquid...control of orientation falls short of allowing manipula- tion of macroscopic orientation (except for the case of uniaxial fibers ). This report

  9. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  10. Theoretical investigation of second hyperpolarizability of trans-polyacetylene: Comparison between experimental and theoretical results for small oligomers.

    PubMed

    de Andrade, Ageo Meier; Inacio, Patrícia Loren; Camilo, Alexandre

    2015-12-28

    The development of new conductive polymers nowadays is one of the most important technological areas in materials design. Computational investigation of desired properties in conductive polymers could save financial resources and time, but it is important to choose the methodology that produces good results comparing to experimental results. To verify the prediction of second hyperpolarizability (γ) in oligomers of Trans-Polyacetylene (TPA) by theoretical calculations, a series of semi-empirical, Hartree-Fock (HF), and Density Functional Theory (DFT) calculations were performed and analysed through linear fitting statistical analysis to investigate the accuracy of such theoretical predictions in comparison to the experimental ones. The results showed that HF and DFT methodologies do not describe γ with good accuracy, but the use of diffuse and polarizability functions in HF methodology provided better results than 3-21G and 6-31G functions. It was concluded that RM1 methodology better agrees with γ experimental results for TPA oligomers, and linear fitting statistical analysis is a useful tool to compare experimental and theoretical results.

  11. Energy Systems Based on Polyacetylene: Rechargeable Batteries and Schottky Barrier Solar Cells. Final Report, March 1, 1981-February 29, 1984

    DOE R&D Accomplishments Database

    MacDiarmid, A. G.

    1984-02-01

    The chief thrust of the research has been directed towards the evaluation of polyacetylene (CH){sub x}, the prototype conducting polymer as an electrode- active material in novel, rechargeable batteries employing nonaqueous electrolytes. The p-doped material, [(CH{sup +y})A{sub y}{sup -}]{sub x}, (where A{sup -} is an anion) in conjunction with a Li anode, shows excellent discharge characteristics, e.g., very little change in discharge voltage with change in discharge current and a high power density. Its energy density is also good but it shows poor shelf life. When (CH){sub x} is used as a cathode (Li anode), which results in the formation of the n-doped polymer, [Li{sub y} {sup +}(CH/sup -y/)]{sub x}, during discharge, good discharge plateaus and power densities are obtained together with excellent shelf life and good recyclability. The energy density is, however only moderate. Cells employing an [M{sub y}{sup +}(CH/sup -y/)]{sub x} (where M = Li, Na) anode and a TiS{sub 2} cathode show very good discharge and recycling characteristics but their energy density is poor.

  12. CRYSTALLINE SOYBEAN TRYPSIN INHIBITOR

    PubMed Central

    Kunitz, M.

    1947-01-01

    A study has been made of the general properties of crystalline soybean trypsin inhibitor. The soy inhibitor is a stable protein of the globulin type of a molecular weight of about 24,000. Its isoelectric point is at pH 4.5. It inhibits the proteolytic action approximately of an equal weight of crystalline trypsin by combining with trypsin to form a stable compound. Chymotrypsin is only slightly inhibited by soy inhibitor. The reaction between chymotrypsin and the soy inhibitor consists in the formation of a reversibly dissociable compound. The inhibitor has no effect on pepsin. The inhibiting action of the soybean inhibitor is associated with the native state of the protein molecule. Denaturation of the soy protein by heat or acid or alkali brings about a proportional decrease in its inhibiting action on trypsin. Reversal of denaturation results in a proportional gain in the inhibiting activity. Crystalline soy protein when denatured is readily digestible by pepsin, and less readily by chymotrypsin and by trypsin. Methods are given for measuring trypsin and inhibitor activity and also protein concentration with the aid of spectrophotometric density measurements at 280 mµ. PMID:19873496

  13. Nucleophilic Aromatic Substitution.

    ERIC Educational Resources Information Center

    Avila, Walter B.; And Others

    1990-01-01

    Described is a microscale organic chemistry experiment which demonstrates one feasible route in preparing ortho-substituted benzoic acids and provides an example of nucleophilic aromatic substitution chemistry. Experimental procedures and instructor notes for this activity are provided. (CW)

  14. Electron correlation and dimerization in trans-polyacetylene: Many-body perturbation theory versus density-functional methods

    NASA Astrophysics Data System (ADS)

    Suhai, Sándor

    1995-06-01

    Structural and energetic aspects of the Peierls-type lattice dimerization were investigated in infinite, one-dimensional, periodic trans-polyacetylene (t-PA) using many-body perturbation theory (MBPT) and density-functional theory (DFT). Cohesive properties and dimerization parameters were obtained first for the classical Coulomb potential in the Hartree approximation and then by gradually turning on exchange and correlation potentials. Besides the nonlocal Hartree-Fock exchange, several other exchange functionals were used incorporating gradient corrections as well. For MBPT, electron correlation was included up to the fourth order of the Mo/ller-Plesset scheme and the behavior of lattice sums for different PT terms was analyzed in detail. The electrostatic part of the infinite lattice sums was computed by the multipole expansion technique. In solving the polymer Kohn-Sham equations, the performance of several different correlation potentials was studied again including different gradient corrections. Atomic basis sets of systematically increasing size, in the range of double-zeta to triple-zeta (TZ) up to TZ (3df,3p2d), were used in all calculations to construct the symmetry-adapted (Bloch-type) polymer wave functions, to fully optimize the structures, and to extrapolate different physical quantities to the limit of a hypothetical infinite basis set. Comparison of the different DFT results with MBPT and with experiments demonstrated the importance of gradient terms both for exchange and correlation. On the other hand, the best DFT functional, using a medium-size atomic basis set, excellently reproduced the cohesive and dimerization energies obtained for infinite t-PA at the MP4/TZ(3d2f,3p2d) level and provided dimerization parameters close to experiment. The experimentally observed lattice spacing of 2.46+/-0.01 Å will be correctly predicted both at the MBPT and DFT levels with 2.48 and 2.44 Å, respectively.

  15. Hierarchically controlled helical graphite films prepared from iodine-doped helical polyacetylene films using morphology-retaining carbonization.

    PubMed

    Matsushita, Satoshi; Kyotani, Mutsumasa; Akagi, Kazuo

    2011-11-09

    One-handed helical graphite films with a hierarchically controlled morphology were prepared from iodine-doped helical polyacetylene (H-PA) films using the recently developed morphology-retaining carbonization method. Results from scanning electron microscopy indicate that the hierarchical helical morphology of the H-PA film remains unchanged even after carbonization at 800 °C. The weight loss of the film due to carbonization was very small; only 10-29% of the weight of the film before doping was lost. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same morphology as that of the original H-PA film and that of the helical carbon film prepared at 800 °C. The screwed direction, twisted degree, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the helical sense, helical pitch, and orientation state of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. X-ray diffraction and Raman scattering measurements showed that graphitic crystallization proceeds in the carbon film during heat treatment at 2600 °C. Transmission electron microscopy measurements indicate that ultrasonication of the helical graphite film in ethanol for several hours gives rise to a single helical graphite fibril. The profound potentiality of the present graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an enhancement in electrical conductivity and an evolution of electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis.

  16. Macroscopically Aligned Graphite Films Prepared from Iodine-Doped Stretchable Polyacetylene Films Using Morphology-Retaining Carbonization.

    PubMed

    Matsushita, Satoshi; Akagi, Kazuo

    2015-07-22

    We prepared graphite films using typical Shirakawa-type and stretchable polyacetylene (PA) films as precursors through a morphology-retaining carbonization. A macroscopically aligned PA film was prepared from the drawable PA film using a mechanical-stretching procedure. The degree of orientation of the aligned PA film was evaluated by measuring polarized infrared absorption spectra and an azimuthal-angle profile of a Laue X-ray diffraction (XRD) pattern. The carbonization was performed from the iodine-doped PA films as precursors at 800 °C. The carbon films were subsequently graphitized at 1400-3000 °C, yielding graphite films with almost the same surface morphology as that of the original PA films and that of the carbon films as precursors. The typical PA film graphitized at 2600 °C exhibited tensile strengths of up to 224 MPa, moduli of up to 10 GPa, and an average electrical conductivity of 2.5 × 10(2) S/cm. In contrast, the graphite film prepared from the stretched PA film presented a Laue XRD pattern in which graphitic crystal structures are aligned parallel to the direction of stretching of the PA film. The anisotropic graphite film showed an enhanced conductivity of up to 1.5 × 10(3) S/cm along the stretching direction. We demonstrated that an iodine-doped PA film is a highly efficient carbon source for producing graphite films with good mechanical and electrical properties. The total yield of a graphite film is as high as 61-74% at up to 3000 °C, which is considerably higher than that of polyacrylonitrile-based carbon fiber and polyimide-based graphite film.

  17. Simulation of melting in crystalline polyethylene

    NASA Astrophysics Data System (ADS)

    Zubova, E. A.; Balabaev, N. K.; Musienko, A. I.; Gusarova, E. B.; Mazo, M. A.; Manevitch, L. I.; Berlin, A. A.

    2012-06-01

    We carry out a molecular dynamics simulation of the first stages of constrained melting in crystalline polyethylene (PE). When heated, the crystal undergoes two structural phase transitions: from the orthorhombic (O) phase to the monoclinic (M) phase, and then to the columnar (C), quasi-hexagonal, phase. The M phase represents the tendency to the parallel packing of planes of PE zigzags, and the C phase proves to be some kind of oriented melt. We follow both the transitions O→M and M→C in real time and establish that, at their beginning, the crystal tries (and fails) to pass into the partially ordered phases similar to the RI and RII phases of linear alkanes, correspondingly. We discuss the molecular mechanisms and driving forces of the observed transitions, as well as the reasons why the M and C phases in PE crystals substitute for the rotator phases in linear alkanes.

  18. Single crystalline magnetite nanotubes.

    PubMed

    Liu, Zuqin; Zhang, Daihua; Han, Song; Li, Chao; Lei, Bo; Lu, Weigang; Fang, Jiye; Zhou, Chongwu

    2005-01-12

    We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures.

  19. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

  20. COLD DRAWING IN CRYSTALLINE POLYMERS

    DTIC Science & Technology

    alcohols, phenol) in Nylon 6 produced changes in the crystalline structure as well as plasticizer action; these two effects must therefore be carefully...distinguished. Changes in the crystalline structure were followed by changes in the infrared spectrum. Dynamic mechanical and thermogravimetric analysis

  1. Occupational exposures to respirable crystalline silica during hydraulic fracturing.

    PubMed

    Esswein, Eric J; Breitenstein, Michael; Snawder, John; Kiefer, Max; Sieber, W Karl

    2013-01-01

    This report describes a previously uncharacterized occupational health hazard: work crew exposures to respirable crystalline silica during hydraulic fracturing. Hydraulic fracturing involves high pressure injection of large volumes of water and sand, and smaller quantities of well treatment chemicals, into a gas or oil well to fracture shale or other rock formations, allowing more efficient recovery of hydrocarbons from a petroleum-bearing reservoir. Crystalline silica ("frac sand") is commonly used as a proppant to hold open cracks and fissures created by hydraulic pressure. Each stage of the process requires hundreds of thousands of pounds of quartz-containing sand; millions of pounds may be needed for all zones of a well. Mechanical handling of frac sand creates respirable crystalline silica dust, a potential exposure hazard for workers. Researchers at the National Institute for Occupational Safety and Health collected 111 personal breathing zone samples at 11 sites in five states to evaluate worker exposures to respirable crystalline silica during hydraulic fracturing. At each of the 11 sites, full-shift samples exceeded occupational health criteria (e.g., the Occupational Safety and Health Administration calculated permissible exposure limit, the NIOSH recommended exposure limit, or the ACGIH threshold limit value), in some cases, by 10 or more times the occupational health criteria. Based on these evaluations, an occupational health hazard was determined to exist for workplace exposures to crystalline silica. Seven points of dust generation were identified, including sand handling machinery and dust generated from the work site itself. Recommendations to control exposures include product substitution (when feasible), engineering controls or modifications to sand handling machinery, administrative controls, and use of personal protective equipment. To our knowledge, this represents the first systematic study of work crew exposures to crystalline silica during

  2. Review of crystalline structures of some selected homologous series of rod-like molecules capable of forming liquid crystalline phases.

    PubMed

    Zugenmaier, Peter

    2011-01-01

    The crystal structures of four homologous series of rod-like molecules are reviewed, two of which form hydrogen bonds and two with a symmetric chemical constitution. Many of the compounds investigated turn into liquid crystalline phases upon temperature increase. It is of valuable interest to know possible conformations and possible packing arrangements as prerequisites to model liquid crystalline structures. The hydrogen bonds of homologous series of pure 4-(ω-hydroxyalkyloxy)-4'-hydroxybiphenyl (HnHBP, n the alkyloxy tail length) are realized through head to tail arrangements of the hydroxyl groups and crystallize except one compound in chiral space groups without the molecules containing any asymmetric carbon. The hydrogen bonds of the homologous series of 4-substituted benzoic acids with various lengths of the tail provide dimers through strong polar bonding of adjacent carboxyl groups and thus provide the stiff part of a mesogenic unit prerequisite for liquid crystalline phases. The homologous series of dialkanoyloxybiphenyls (BP-n, n = 1, 19), of which nine compounds could be crystallized, show liquid crystalline behavior for longer alkane chain lengths, despite the high mobility of the alkane chain ends already detectable in the crystal phase. A single molecule, half a molecule or two half molecules form the asymmetric unit in a centrosymmetric space group. The homologous series of 1,4-terephthalidene-bis-N-(4'-n-alkylaniline) (TBAA-n) exhibit a large variety of packing arrangements in the crystalline state, with or without relying on the symmetry center within the molecules.

  3. Enhanced osteoconductivity of sodium-substituted hydroxyapatite by system instability.

    PubMed

    Sang Cho, Jung; Um, Seung-Hoon; Su Yoo, Dong; Chung, Yong-Chae; Hye Chung, Shin; Lee, Jeong-Cheol; Rhee, Sang-Hoon

    2014-07-01

    The effect of substituting sodium for calcium on enhanced osteoconductivity of hydroxyapatite was newly investigated. Sodium-substituted hydroxyapatite was synthesized by reacting calcium hydroxide and phosphoric acid with sodium nitrate followed by sintering. As a control, pure hydroxyapatite was prepared under identical conditions, but without the addition of sodium nitrate. Substitution of calcium with sodium in hydroxyapatite produced the structural vacancies for carbonate ion from phosphate site and hydrogen ion from hydroxide site of hydroxyapatite after sintering. The total system energy of sodium-substituted hydroxyapatite with structural defects calculated by ab initio methods based on quantum mechanics was much higher than that of hydroxyapatite, suggesting that the sodium-substituted hydroxyapatite was energetically less stable compared with hydroxyapatite. Indeed, sodium-substituted hydroxyapatite exhibited higher dissolution behavior of constituent elements of hydroxyapatite in simulated body fluid (SBF) and Tris-buffered deionized water compared with hydroxyapatite, which directly affected low-crystalline hydroxyl-carbonate apatite forming capacity by increasing the degree of apatite supersaturation in SBF. Actually, sodium-substituted hydroxyapatite exhibited markedly improved low-crystalline hydroxyl-carbonate apatite forming capacity in SBF and noticeably higher osteoconductivity 4 weeks after implantation in calvarial defects of New Zealand white rabbits compared with hydroxyapatite. In addition, there were no statistically significant differences between hydroxyapatite and sodium-substituted hydroxyapatite on cytotoxicity as determined by BCA assay. Taken together, these results indicate that sodium-substituted hydroxyapatite with structural defects has promising potential for use as a bone grafting material due to its enhanced osteoconductivity compared with hydroxyapatite.

  4. Sensitivity studies of crystalline beams

    SciTech Connect

    Wei, J.; Sessler, A.M.

    1996-07-01

    The equations of motion are presented, appropriate to interacting charged particles of diverse charge and mass, subject to the external forces produced by various kinds of magnetic fields and rf electric fields in storage rings. These equations have been employed in the molecular dynamics simulations for sensitivity studies of crystalline beams. The two necessary conditions for the formation and maintenance of crystalline beams are summarized. Effects of lattice shear and AG focusing, magnetic field imperfection, and ion neutralization on crystalline beam heating is presented.

  5. Molecular dynamics simulations of alkyl substituted nanographene crystals

    NASA Astrophysics Data System (ADS)

    Ziogos, Orestis George; Theodorou, Doros Nicolas

    2015-09-01

    Discotic polyaromatic molecules, similar to nanometric graphene flakes, constitute an interesting class of materials for organic electronic applications. Grafting flexible side chains around the periphery of such molecules enhances their processability and gives rise to diverse behaviours, such as the manifestation of liquid-crystalline character and anisotropic mechanical response. In this work, we examine by means of molecular dynamics simulations the properties of molecular crystals comprised of alkyl-substituted hexa-peri-hexabenzocoronene mesogens. Pristine and mono-substituted systems by hydrogen or iodine atoms are modelled, with variable side chain length. A general structural and mechanical robustness to peripheral substitution is reported, with the mesogens forming tightly packed molecular wires even at elevated temperature and pressure. In their discotic ordering, the molecules present relatively low translational mobility, a beneficial phenomenon for charge transport. A thermotropic dependence of the mechanical response is identified, with the systems behaving differently in their room-temperature crystalline phase and in their liquid-crystalline phase at elevated temperatures. The melting process is also examined, elucidating an initial negative expansion along a high symmetry direction and the existence of a metastable state, before falling into the final liquid-crystalline state. Dedicated to Professor Jean-Pierre Hansen, with deepest appreciation of his outstanding contributions to liquid and soft matter theory.

  6. Sustainability and substitutability.

    PubMed

    Fenichel, Eli P; Zhao, Jinhua

    2015-02-01

    Developing a quantitative science of sustainability requires bridging mathematical concepts from fields contributing to sustainability science. The concept of substitutability is central to sustainability but is defined differently by different fields. Specifically, economics tends to define substitutability as a marginal concept while fields such as ecology tend to focus on limiting behaviors. We explain how to reconcile these different views. We develop a model where investments can be made in knowledge to increase the elasticity of substitution. We explore the set of sustainable and optimal trajectories for natural capital extraction and built and knowledge capital accumulation. Investments in substitutability through knowledge stock accumulation affect the value of natural capital. Results suggest that investing in the knowledge stock, which can enhance substitutability, is critical to desirable sustainable outcomes. This result is robust even when natural capital is not managed optimally. This leads us to conclude that investments in the knowledge stock are of first order importance for sustainability.

  7. Circumstellar Crystalline Silicates: Evolved Stars

    NASA Astrophysics Data System (ADS)

    Tartar, Josh; Speck, A. K.

    2008-05-01

    One of the most exciting developments in astronomy in the last 15 years was the discovery of crystalline silicate stardust by the Short Wavelength Spectrometer (SWS) on board of ISO; discovery of the crystalline grains was indeed one of the biggest surprises of the ISO mission. Initially discovered around AGB stars (evolved stars in the range of 0.8 > M/M¤>8) at far-infrared (IR) wavelengths, crystalline silicates have since been seen in many astrophysical environments including young stellar objects (T Tauri and Herbig Ae/Be), comets and Ultra Luminous Infrared Galaxies. Low and intermediate mass stars (LIMS) comprise 95% of the contributors to the ISM, so study of the formation of crystalline silicates is critical to our understanding of the ISM, which is thought to be primarily amorphous (one would expect an almost exact match between the composition of AGB dust shells and the dust in the ISM). Whether the crystalline dust is merely undetectable or amorphized remains a mystery. The FORCAST instrument on SOFIA as well as the PACS instrument on Herschel will provide exciting observing opportunities for the further study of crystalline silicates.

  8. Dietary polyacetylenes, falcarinol and falcarindiol, isolated from carrots prevents the formation of neoplastic lesions in the colon of azoxymethane-induced rats.

    PubMed

    Kobaek-Larsen, Morten; El-Houri, Rime B; Christensen, Lars P; Al-Najami, Issam; Fretté, Xavier; Baatrup, Gunnar

    2017-03-22

    Falcarinol (FaOH) and falcarindiol (FaDOH) are found in many food plants of the Apiaceae family. Carrots are a major dietary source of these polyacetylenes. Feeding azoxymethane (AOM)-induced rats with carrots and purified FaOH have previously been shown to inhibit neoplastic transformations in the colon. FaOH and FaDOH have also shown to have a synergistic effect in vitro, resulting in a significant increased cytotoxic activity. Based on these findings the antineoplastic effect of FaOH and FaDOH (purity > 99%) was investigated in the AOM-induced rat model. Twenty rats received rat diet containing 7 μg FaOH per g feed and 7 μg FaDOH per g feed and 20 rats were controls receiving only rat diet. Then carcinogenesis was induced in all 40 rats with the carcinogen AOM. All animals received the designated diet for 2 weeks before AOM induction and continued on the designated diet throughout the experiment. Rats were euthanized 18 weeks after the first AOM injection and macroscopic polyp/cancers were measured, harvested and stained for histology. The difference in sizes of aberrant crypt foci (ACF) were analysed in a Wilcoxon rank sum test, in which the median number of small ACF was 218 in controls and 145 in polyacetylene treated rats (P < 0.001). Fifteen control rats and 8 treated rats had macroscopic tumors (P = 0.027). The number of tumors larger than 3 mm were 6 and 1 in control and treated rats, respectively (P = 0.032). In conclusion dietary supplements with FaOH and FaDOH reduced the number of neoplastic lesions as well as the growth rate of the polyps suggesting a preventive effect of FaOH and FaDOH on the development of colorectal cancer.

  9. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  10. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  11. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  12. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  13. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  14. Sugar substitutes during pregnancy

    PubMed Central

    Pope, Eliza; Koren, Gideon; Bozzo, Pina

    2014-01-01

    Abstract Question I have a pregnant patient who regularly consumes sugar substitutes and she asked me if continuing their use would affect her pregnancy or child. What should I tell her, and are there certain options that are better for use during pregnancy? Answer Although more research is required to fully determine the effects of in utero exposure to sugar substitutes, the available data do not suggest adverse effects in pregnancy. However, it is recommended that sugar substitutes be consumed in moderate amounts, adhering to the acceptable daily intake standards set by regulatory agencies. PMID:25392440

  15. Resorbable calcium phosphate bone substitute.

    PubMed

    Knaack, D; Goad, M E; Aiolova, M; Rey, C; Tofighi, A; Chakravarthy, P; Lee, D D

    1998-01-01

    The in vitro and in vivo properties of a novel, fully resorbable, apatitic calcium phosphate bone substitute (ABS) are described. The ABS was prepared from calcium phosphate precursors that were hydrated to form an injectable paste that hardens endothermically at 37 degrees C to form a poorly crystalline apatitic calcium phosphate (PCA). The PCA reaction product is stable in vivo as determined by FTIR and XRD analysis of rabbit intramuscular implants of ABS retrieved 4, 7, and 14 days postimplantation. Bone formation and resorption characteristics of the ABS material were characterized in a canine femoral slot defect model. Femoral slot defects in dogs were filled with either autologous bone implants or the ABS material. Sections of femoral bone defect site from animals sacrificed at 3, 4, 12, 26, and 52 weeks demonstrated that new bone formation proceeded similarly in both autograft and ABS filled slots. Defects receiving either material were filled with trabecular bone in the first 3 to 4 weeks after implantation; lamellar or cortical bone formation was well established by week 12. New bone formation in ABS filled defects followed a time course comparable to autologous bone graft filled defects. Histomorphometric evaluation of ABS resorption and new bone formation indicated that the ABS material was greater than 99% resorbed within 26 weeks; residual ABS occupied 0.36+/-0.36% (SEM, n = 4) of the original defect area at 26 weeks. Quantitatively and qualitatively, the autograft and ABS were associated with similar new bone growth and defect filling characteristics.

  16. Surfactant-induced postsynthetic modulation of Pd nanoparticle crystallinity.

    SciTech Connect

    Liu, Y.; Wang, C.; Wei, Y.; Zhu, L.; Li, D.; Jiang, J. S.; Markovic, N. M.; Stamenkovic, V. R.; Sun, S.

    2011-02-01

    Modulation of Pd nanoparticle (NP) crystallinity is achieved by switching the surfactants of different binding strengths. Pd NPs synthesized in the presence of weak binding surfactants such as oleylamine possess polyhedral shapes and a polycrystalline nature. When oleylamine is substituted by trioctylphosphine, a much stronger binding surfactant, the particles become spherical and their crystallinity decreases significantly. Moreover, the Pd NPs reconvert their polycrystalline structure when the surfactant is switched back to oleylamine. Through control experiments and molecular dynamics simulation, we propose that this unusual nanocrystallinity transition induced by surfactant exchange was resulted from a counterbalance between the surfactant binding energy and the nanocrystal adhesive energy. The findings represent a novel postsynthetic approach to tailoring the structure and corresponding functional performance of nanomaterials.

  17. Dynamic Characterization of Crystalline Supramolecular Rotors Assembled through Halogen Bonding.

    PubMed

    Catalano, Luca; Pérez-Estrada, Salvador; Terraneo, Giancarlo; Pilati, Tullio; Resnati, Giuseppe; Metrangolo, Pierangelo; Garcia-Garibay, Miguel A

    2015-12-16

    A modular molecular kit for the preparation of crystalline molecular rotors was devised from a set of stators and rotators to gain simple access to a large number of structures with different dynamic performance and physical properties. In this work, we have accomplished this with crystalline molecular rotors self-assembled by halogen bonding of diazabicyclo[2.2.2]octane, acting as a rotator, and a set of five fluorine-substituted iodobenzenes that take the role of the stator. Using variable-temperature (1)H T1 spin-lattice relaxation measurements, we have shown that all structures display ultrafast Brownian rotation with activation energies of 2.4-4.9 kcal/mol and pre-exponential factors of the order of (1-9) × 10(12) s(-1). Line shape analysis of quadrupolar echo (2)H NMR measurements in selected examples indicated rotational trajectories consistent with the 3-fold or 6-fold symmetric potential of the rotator.

  18. Synthesis of substituted pyrazines

    SciTech Connect

    Pagoria, Philip F.; Zhang, Mao Xi

    2016-10-04

    A method for synthesizing a pyrazine-containing material according to one embodiment includes contacting an iminodiacetonitrile derivative with a base and a reagent selected from a group consisting of hydroxylamine, a hydroxylamine salt, an aliphatic primary amine, a secondary amine, an aryl-substituted alkylamine a heteroaryl-substituted alkyl amine, an alcohol, an alkanolamine and an aryl alcoholamine. Additional methods and several reaction products are presented. ##STR00001##

  19. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  20. Molecular composites from liquid crystalline polymers and liquid crystalline thermosets

    SciTech Connect

    Benicewicz, B.C.; Douglas, E.P.; Hjelm, R.P. Jr.

    1993-07-01

    We propose a new approach to molecular composites. This approach uses a mixture of a liquid crystalline polymer and a liquid crystalline thermoset to enhance the miscibility. Preliminary neutron scattering data is presented on a system of short and long rod aromatic amides. The data is interpreted using the interpenetrating phase model of Debye and Bueche. The analysis indicates that the scattering is consistent with this model and shows a characteristic length scale in the range of 70 to 80 A. The intensity of the scattering is lower than calculated for the strong segregation limit, suggesting that there is some intermixing of the components.

  1. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

  2. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

    Rogers, Martin; Stevenson, Paige; Scribben, Eric; Baird, Donald; Hulcher, Bruce

    2002-01-01

    Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

  3. Diverse topics in crystalline beams

    SciTech Connect

    Wei, Jie; Draeseke, A.; Sessler, A.M.; Li, Xiao-Ping

    1995-11-27

    Equations of motion are presented, appropriate to interacting charged particles of diverse charge and mass, subject to the external forces produced by various kinds of magnetic fields and radio-frequency (rf) electric fields in storage rings. These equations are employed in the molecular dynamics simulations to study the properties of crystalline beams. The two necessary conditions for the formation and maintenance of crystalline beams are summarized. The transition from ID to 2D, and from 2D to 3D is explored, and the scaling behavior of the heating rates is discussed especially in the high temperature limit. The effectiveness of various cooling techniques in achieving crystalline states has been investigated. Crystalline beams made of two different species of ions via sympathetic cooling are presented, as well as circulating ``crystal balls`` bunched in all directions by magnetic focusing and rf field. By numerically reconstructing the original experimental conditions of the NAP-M ring, it is found that only at extremely low beam intensities, outside of the range of the original measurement, proton particles can form occasionally-passing disks. The proposed New ASTRID ring is shown to be suitable for the formation and maintenance of crystalline beams of all dimensions.

  4. Photoexcitations in Polyacetylene.

    DTIC Science & Technology

    1981-11-11

    recombination luminescence; (CH) X interband absorption edge; excitation energies ; Stokes shift; temperature 0....dependence; isomerization; phototransport...turns on sharply for excitation S energies greater than 2.k5e ; irLivin., as S;takes shift of 0.15eV. Studies of the temperature Ulependence kT 7K) -ci...Philadelphia, PA 19104 INov ~e!f M 81 Reproduction in whole or in part is permitted for any purpose of the United States Government Approved for public

  5. Process for producing amorphous and crystalline silicon nitride

    DOEpatents

    Morgan, Peter E. D.; Pugar, Eloise A.

    1985-01-01

    A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

  6. Process for producing amorphous and crystalline silicon nitride

    DOEpatents

    Morgan, P.E.D.; Pugar, E.A.

    1985-11-12

    A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of whiskers'' or needles is heated at temperature ranging from about 900 C to about 1,200 C to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900 C. 6 figs.

  7. Single crystalline mesoporous silicon nanowires.

    PubMed

    Hochbaum, Allon I; Gargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-10-01

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  8. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  9. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  10. CRYSTALLINE BEAMS AT HIGH ENERGIES.

    SciTech Connect

    WEI, J.; OKAMOTO, H.; YURI, Y.; SESSLER, A.; MACHIDA, S.

    2006-06-23

    Previously it was shown that by crystallizing each of the two counter-circulating beams, a much larger beam-beam tune shift can be tolerated during the beam-beam collisions; thus a higher luminosity can be reached for colliding beams [1]. On the other hand, crystalline beams can only be formed at energies below the transition energy ({gamma}{sub T}) of the accelerators [2]. In this paper, we investigate the formation of crystals in a high-{gamma}{sub T} lattice that also satisfies the maintenance condition for a crystalline beam [3].

  11. The substitutability of reinforcers

    PubMed Central

    Green, Leonard; Freed, Debra E.

    1993-01-01

    Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportion. At the center of the continuum are reinforcers that are independent with respect to each other; consumption of one has no influence on consumption of another. Psychological research and analyses in terms of substitutability employ standard operant conditioning paradigms in which humans and nonhumans choose between alternative reinforcers. The range of reinforcer interactions found in these studies is more readily accommodated and predicted when behavior-analytic models of choice consider issues of substitutability. New insights are gained into such areas as eating and drinking, electrical brain stimulation, temporal separation of choice alternatives, behavior therapy, drug use, and addictions. Moreover, the generalized matching law (Baum, 1974) gains greater explanatory power and comprehensiveness when measures of substitutability are included. PMID:16812696

  12. Aryl substitution of pentacenes

    PubMed Central

    Waterloo, Andreas R; Sale, Anna-Chiara; Lehnherr, Dan; Hampel, Frank

    2014-01-01

    Summary A series of 11 new pentacene derivatives has been synthesized, with unsymmetrical substitution based on a trialkylsilylethynyl group at the 6-position and various aryl groups appended to the 13-position. The electronic and physical properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films), thermoanalytical methods (DSC and TGA), cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives). X-ray crystallography has been specifically used to study the influence of unsymmetrical substitution on the solid-state packing of the pentacene derivatives. The obtained results add to our ability to better predict substitution patterns that might be helpful for designing new semiconductors for use in solid-state devices. PMID:25161729

  13. Lens Aging: Effects of Crystallins

    PubMed Central

    Sharma, K. Krishna; Santhoshkumar, Puttur

    2009-01-01

    The primary function of the eye lens is to focus light on the retina. The major proteins in the lens—a, b, and g-crystallins—are constantly subjected to age-related changes such as oxidation, deamidation, truncation, glycation, and methylation. Such age-related modifications are cumulative and affect crystallin structure and function. With time, the modified crystallins aggregate, causing the lens to increasingly scatter light on the retina instead of focusing light on it and causing the lens to lose its transparency gradually and become opaque. Age-related lens opacity, or cataract, is the major cause of blindness worldwide. We review deamidation, and glycation that occur in the lenses during aging keeping in mind the structural and functional changes that these modifications bring about in the proteins. In addition, we review proteolysis and discuss recent observations on how crystallin fragments generated in vivo, through their anti-chaperone activity may cause crystallin aggregation in aging lenses. We also review hyperbaric oxygen treatment induced guinea pig and ‘humanized’ ascorbate transporting mouse models as suitable options for studies on age-related changes in lens proteins. PMID:19463898

  14. Glycation precedes lens crystallin aggregation

    SciTech Connect

    Swamy, M.S.; Perry, R.E.; Abraham, E.C.

    1987-05-01

    Non-enzymatic glycosylation (glycation) seems to have the potential to alter the structure of crystallins and make them susceptible to thiol oxidation leading to disulfide-linked high molecular weight (HMW) aggregate formation. They used streptozotocin diabetic rats during precataract and cataract stages and long-term cell-free glycation of bovine lens crystallins to study the relationship between glycation and lens crystallin aggregation. HMW aggregates and other protein components of the water-soluble (WS) and urea-soluble (US) fractions were separated by molecular sieve high performance liquid chromatography. Glycation was estimated by both (/sup 3/H)NaBH/sub 4/ reduction and phenylboronate agarose affinity chromatography. Levels of total glycated protein (GP) in the US fractions were about 2-fold higher than in the WS fractions and there was a linear increase in GP in both WS and US fractions. This increase was parallelled by a corresponding increase in HMW aggregates. Total GP extracted by the affinity method from the US fraction showed a predominance of HMW aggregates and vice versa. Cell-free glycation studies with bovine crystallins confirmed the results of the animals studies. Increasing glycation caused a corresponding increase in protein insolubilization and the insoluble fraction thus formed also contained more glycated protein. It appears that lens protein glycation, HMW aggregate formation, and protein insolubilization are interrelated.

  15. Crystalline retinopathy in primary hyperoxaluria.

    PubMed

    Punjabi, Omar S; Riaz, Kamran; Mets, Marilyn B

    2011-04-01

    We present the case of a 2.5-month-old boy with type 1 primary hyperoxaluria and severe systemic oxalosis resulting in massive retinal crystalline deposition. Maculopathy was demonstrated by optical coherence tomography, and nystagmus was present. Electroretinography demonstrated retinal dysfunction, unusual in oxalosis.

  16. Bone graft substitutes.

    PubMed

    Bhatt, Reena A; Rozental, Tamara D

    2012-11-01

    Replacement of missing bone stock is a reconstructive challenge to upper extremity surgeons and decision-making with regards to available choices remains difficult. Preference is often given to autograft in the form of cancellous, cortical, or corticocancellous grafts from donor sites. However, the available volume from such donor sites is limited and fraught with potential complications. Advances in surgical management and medical research have produced a wide array of potential substances that can be used for bone graft substitute. Considerations in selecting bone grafts and substitutes include characteristic capabilities, availability, patient morbidity, immunogenicity, potential disease transmission, and cost variability.

  17. Generic Crystalline Disposal Reference Case

    SciTech Connect

    Painter, Scott Leroy; Chu, Shaoping; Harp, Dylan Robert; Perry, Frank Vinton; Wang, Yifeng

    2015-02-20

    A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

  18. No cheap substitutes.

    PubMed

    Griffiths, Peter

    2016-06-15

    The Nuffield Trust report on reshaping the healthcare workforce was published last month. Its conclusions were widely reported as a recommendation to 'train up' nurses as a solution to junior doctor shortages, with support workers, in turn, substituting for registered nurses.

  19. The Age of Substitutability

    ERIC Educational Resources Information Center

    Goeller, H. E.; Weinberg, Alvin M.

    1976-01-01

    Dwindling mineral resources might cause a shift from nonrenewable resources to renewable resources and inexhaustible elements such as iron and aluminum. Alternative energy sources such as breeder, fusion, solar, and geothermal power must be developed for production and recycling of materials. Substitution and, hence, living standards ultimately…

  20. Performing Substitute Teaching

    ERIC Educational Resources Information Center

    Bletzer, Keith V.

    2010-01-01

    Formal education is both a right and an obligation bestowed on young people in most all nations of the world. Teachers (adults) and students (youth) form a co-present dyadic contract that must be maintained within the classroom. Substitute teachers fill a role in sustaining the integrity of this teacher-student link, whenever teachers are absent.…

  1. Substitutions of aspartic acid for glycine-220 and of arginine for glycine-664 in the triple helix of the pro alpha 1(I) chain of type I procollagen produce lethal osteogenesis imperfecta and disrupt the ability of collagen fibrils to incorporate crystalline hydroxyapatite.

    PubMed Central

    Culbert, A A; Lowe, M P; Atkinson, M; Byers, P H; Wallis, G A; Kadler, K E

    1995-01-01

    We identified two infants with lethal (type II) osteogenesis imperfecta (OI) who were heterozygous for mutations in the COL1A1 gene that resulted in substitutions of aspartic acid for glycine at position 220 and arginine for glycine at position 664 in the product of one COL1A1 allele in each individual. In normal age- and site-matched bone, approximately 70% (by number) of the collagen fibrils were encrusted with plate-like crystallites of hydroxyapatite. In contrast, approximately 5% (by number) of the collagen fibrils in the probands' bone contained crystallites. In contrast with normal bone, the c-axes of hydroxyapatite crystallites were sometimes poorly aligned with the long axis of fibrils obtained from OI bone. Chemical analysis showed that the OI samples contained normal amounts of calcium. The probands' bone samples contained type I collagen, overmodified type I collagen and elevated levels of type III and V collagens. On the basis of biochemical and morphological data, the fibrils in the OI samples were co-polymers of normal and mutant collagen. The results are consistent with a model of fibril mineralization in which the presence of abnormal type I collagen prevents normal collagen in the same fibril from incorporating hydroxyapatite crystallites. Images Figure 1 Figure 2 Figure 3 PMID:7487936

  2. EELS from organic crystalline materials

    NASA Astrophysics Data System (ADS)

    Brydson, R.; Eddleston, M. D.; Jones, W.; Seabourne, C. R.; Hondow, N.

    2014-06-01

    We report the use of the electron energy loss spectroscopy (EELS) for providing light element chemical composition information from organic, crystalline pharmaceutical materials including theophylline and paracetamol and discuss how this type of data can complement transmission electron microscopy (TEM) imaging and electron diffraction when investigating polymorphism. We also discuss the potential for the extraction of bonding information using electron loss near-edge structure (ELNES).

  3. The crystalline sponge method updated

    PubMed Central

    Hoshino, Manabu; Khutia, Anupam; Xing, Hongzhu; Inokuma, Yasuhide; Fujita, Makoto

    2016-01-01

    Crystalline sponges are porous metal complexes that can absorb and orient common organic molecules in their pores and make them observable by conventional X-ray structure analysis (crystalline sponge method). In this study, all of the steps in the crystalline sponge method, including sponge crystal preparation, pore–solvent exchange, guest soaking, data collection and crystallographic analysis, are carefully examined and thoroughly optimized to provide reliable and meaningful chemical information as chemical crystallography. Major improvements in the method have been made in the guest-soaking and data-collection steps. In the soaking step, obtaining a high site occupancy of the guest is particularly important, and dominant parameters for guest soaking (e.g. temperature, time, concentration, solvents) therefore have to be optimized for every sample compound. When standard conditions do not work, a high-throughput method is useful for efficiently optimizing the soaking conditions. The X-ray experiments are also carefully re-examined. Significant improvement of the guest data quality is achieved by complete data collection at high angle regions. The appropriate disorder treatment of the most flexible ZnI2 portions of the host framework and refinement of the solvents filling the remaining void are also particularly important for obtaining better data quality. A benchmark test for the crystalline sponge method toward an achiral molecule is proposed with a guaiazulene guest, in which the guest structure (with ∼ 100% site occupancy) is refined without applying any restraints or constraints. The obtained data quality with R int = 0.0279 and R 1 = 0.0379 is comparable with that of current conventional crystallographic analysis for small molecules. Another benchmark test for this method toward a chiral molecule is also proposed with a santonin guest. The crystallographic data obtained [R int = 0.0421, R 1 = 0.0312, Flack (Parsons) = −0.0071 (11)] represents the

  4. Soliton structure in crystalline acetanilide

    NASA Astrophysics Data System (ADS)

    Eilbeck, J. C.; Lomdahl, P. S.; Scott, A. C.

    1984-10-01

    The theory of self-trapping of amide I vibrational energy in crystalline acetanilide is studied in detail. A spectrum of stationary, self-trapped (soliton) solutions is determined and tested for dynamic stability. Only those solutions for which the amide I energy is concentrated near a single molecule were found to be stable. Exciton modes were found to be unstable to decay into solitons.

  5. Soliton structure in crystalline acetanilide

    SciTech Connect

    Eilbeck, J.C.; Lomdahl, P.S.; Scott, A.C.

    1984-10-15

    The theory of self-trapping of amide I vibrational energy in crystalline acetanilide is studied in detail. A spectrum of stationary, self-trapped (soliton) solutions is determined and tested for dynamic stability. Only those solutions for which the amide I energy is concentrated near a single molecule were found to be stable. Exciton modes were found to be unstable to decay into solitons.

  6. Highly crystalline 2D superconductors

    NASA Astrophysics Data System (ADS)

    Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro

    2016-12-01

    Recent advances in materials fabrication have enabled the manufacturing of ordered 2D electron systems, such as heterogeneous interfaces, atomic layers grown by molecular beam epitaxy, exfoliated thin flakes and field-effect devices. These 2D electron systems are highly crystalline, and some of them, despite their single-layer thickness, exhibit a sheet resistance more than an order of magnitude lower than that of conventional amorphous or granular thin films. In this Review, we explore recent developments in the field of highly crystalline 2D superconductors and highlight the unprecedented physical properties of these systems. In particular, we explore the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase observed in out-of-plane magnetic fields and the superconducting state maintained in anomalously large in-plane magnetic fields. These phenomena are examined in the context of weakened disorder and/or broken spatial inversion symmetry. We conclude with a discussion of how these unconventional properties make highly crystalline 2D systems promising platforms for the exploration of new quantum physics and high-temperature superconductors.

  7. Biocompatibility of crystalline opal nanoparticles

    PubMed Central

    2012-01-01

    Background Silica nanoparticles are being developed as a host of biomedical and biotechnological applications. For this reason, there are more studies about biocompatibility of silica with amorphous and crystalline structure. Except hydrated silica (opal), despite is presents directly and indirectly in humans. Two sizes of crystalline opal nanoparticles were investigated in this work under criteria of toxicology. Methods In particular, cytotoxic and genotoxic effects caused by opal nanoparticles (80 and 120 nm) were evaluated in cultured mouse cells via a set of bioassays, methylthiazolyldiphenyl-tetrazolium-bromide (MTT) and 5-bromo-2′-deoxyuridine (BrdU). Results 3T3-NIH cells were incubated for 24 and 72 h in contact with nanocrystalline opal particles, not presented significant statistically difference in the results of cytotoxicity. Genotoxicity tests of crystalline opal nanoparticles were performed by the BrdU assay on the same cultured cells for 24 h incubation. The reduction of BrdU-incorporated cells indicates that nanocrystalline opal exposure did not caused unrepairable damage DNA. Conclusions There is no relationship between that particles size and MTT reduction, as well as BrdU incorporation, such that the opal particles did not induce cytotoxic effect and genotoxicity in cultured mouse cells. PMID:23088559

  8. Liquid crystalline order in mucus

    NASA Technical Reports Server (NTRS)

    Viney, C.; Huber, A. E.; Verdugo, P.

    1993-01-01

    Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.

  9. Hydrothermal Synthesis and Biocompatibility Study of Highly Crystalline Carbonated Hydroxyapatite Nanorods

    NASA Astrophysics Data System (ADS)

    Xue, Caibao; Chen, Yingzhi; Huang, Yongzhuo; Zhu, Peizhi

    2015-08-01

    Highly crystalline carbonated hydroxyapatite (CHA) nanorods with different carbonate contents were synthesized by a novel hydrothermal method. The crystallinity and chemical structure of synthesized nanorods were studied by Fourier transform infrared spectroscopy (FTIR), X-ray photo-electronic spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The biocompatibility of synthesized CHA nanorods was evaluated by cell viability and alkaline phosphatase (ALP) activity of MG-63 cell line. The biocompatibility evaluation results show that these CHA nanorods are biologically active apatites and potentially promising bone-substitute biomaterials for orthopedic application.

  10. The influence of the fungal pathogen Mycocentrospora acerina on the proteome and polyacetylenes and 6-methoxymellein in organic and conventionally cultivated carrots (Daucus carota) during post harvest storage.

    PubMed

    Louarn, Sébastien; Nawrocki, Arkadiusz; Edelenbos, Merete; Jensen, Dan F; Jensen, Ole N; Collinge, David B; Jensen, Birgit

    2012-01-04

    Many carrots are discarded during post harvest cold storage due to development of fungal infections, caused by, e.g., Mycocentrospora acerina (liquorice rot). We compared the susceptibility of carrots grown under conventional and organic agricultural practices. In one year, organically cultivated carrots showed 3× to 7× more symptoms than conventionally cultivated, when studying naturally occurring disease at 4 and 6 months, respectively. On the other hand, we have developed a bioassay for infection studies of M. acerina on carrots and observed that organic roots were more susceptible after one month of storage than conventional ones, but no differences were apparent after four or six months storage. Levels of polyacetylenes (falcarinol, falcarindiol and falcarindiol-3-acetate) did not change, whereas the isocoumarin phytoalexin (6-methoxymellein) accumulated in infected tissue as well as in healthy tissue opposite the infection. The proteomes of carrot and M. acerina were characterized, the intensity of 33 plant protein spots was significantly changed in infected roots including up regulation of defence and stress response proteins but also a decrease of proteins involved in energy metabolism. This combined metabolic and proteomic study indicates that roots respond to fungal infection through altered metabolism: simultaneous induction of 6-methoxymellein and synthesis of defence related proteins.

  11. High-performance liquid chromatography analysis of polyacetylenes and polyenes in Echinacea pallida by using a monolithic reversed-phase silica column.

    PubMed

    Pellati, Federica; Calò, Samuele; Benvenuti, Stefania

    2007-05-11

    In this study, a RP-HPLC method for the analysis of polyacetylenes and polyenes in Echinacea pallida roots and phytopharmaceuticals was developed. The reference compounds used for quantification were isolated from the plant material and their structures were determined on the basis of the analysis of UV, IR, NMR and MS data. The complete structure elucidation of three compounds, namely 8-hydroxy-tetradec-(9E)-ene-11,13-diyn-2-one (1), tetradec-(8Z)-ene-11,13-diyn-2-one (6) and pentadec-(8Z)-en-2-one (9) is described. In the analysis of the n-hexane extracts of E. pallida roots, the comparison between conventional and monolithic columns showed that the elution order in both cases is identical and the selectivity is equivalent. However, the retention times achieved by the monolithic column are shorter, resulting in a faster separation (20 min). Therefore, the analyses were carried out on a Chromolith Performance RP-18e (100 mm x 4.6 mm i.d.), with a gradient mobile phase composed by H(2)O and ACN at the flow rate of 2 mL/min. The column was thermostatted at 20 degrees C. The photodiode array detector monitored the eluent at 210 nm. The validation procedure confirmed that this technique affords reliable analysis of these components and is appropriate for the quality control of complex matrices, such as E. pallida roots and phytopharmaceuticals.

  12. Polyacetylene, (CH)/sub x/, as an emerging material for solar cell applications. Final technical report, March 19, 1979-March 18, 1980

    SciTech Connect

    Heeger, A.J.; MacDiarmid, A.G.

    1980-01-01

    Despite great theoretical and technological interest in polyacetylene, (CH)/sub x/, the basic features of its band structure have not been unambiguously resolved. Since photoconductivity and optical absorption data have frequently been used to infer information on the band structure of semiconductors, such measurements were carried out on (CH)/sub x/. The main results of an extensive study of the photoconductivity (..delta.. sigma/sub ph/) and absorption coefficient (..cap alpha..) in (CH)/sub x/ are presented. The absence of photoconductivity in cis-(CH)/sub x/, despite the similarity in optical properties indicates that ..delta.. sigma/sub ph/ in trans-(CH)/sub x/ is induced by isomerization. It is found that isomerization generates states deep inside the gap that act as safe traps for minority carriers and thereby enhance the photoconductivity. Compensation of trans-(CH)/sub x/ with ammonia appears to decrease the number of safe traps, whereas acceptor doping increases their number. Thus, chemical doping can be used to control the photoconductive response. The energy of safe traps inside the gap is independent of the process used to generate them; indicative of an intrinsic localized defect level in trans-(CH)/sub x/. A coherent picture based on the soliton model can explain these results, including the safe trapping.

  13. Polyacetylene, (CH){sub x}, as an Emerging Material for Solar Cell Applications. Final Technical Report, March 19, 1979 - March 18, 1980

    DOE R&D Accomplishments Database

    Heeger, A. J.; MacDiarmid, A. G.

    1980-06-05

    Despite great theoretical and technological interest in polyacetylene, (CH){sub x}, the basic features of its band structure have not been unambiguously resolved. Since photoconductivity and optical absorption data have frequently been used to infer information on the band structure of semiconductors, such measurements were carried out on (CH){sub x}. The main results of an extensive study of the photoconductivity (..delta.. sigma{sub ph}) and absorption coefficient (..cap alpha..) in (CH){sub x} are presented. The absence of photoconductivity in cis-(CH){sub x}, despite the similarity in optical properties indicates that ..delta.. sigma/sub ph/ in trans-(CH){sub x} is induced by isomerization. It is found that isomerization generates states deep inside the gap that act as safe traps for minority carriers and thereby enhance the photoconductivity. Compensation of trans-(CH){sub x} with ammonia appears to decrease the number of safe traps, whereas acceptor doping increases their number. Thus, chemical doping can be used to control the photoconductive response. The energy of safe traps inside the gap is independent of the process used to generate them; indicative of an intrinsic localized defect level in trans-(CH){sub x}. A coherent picture based on the soliton model can explain these results, including the safe trapping.

  14. Biomass and content of ginsenosides and polyacetylenes in American ginseng roots can be increased without affecting the profile of bioactive compounds.

    PubMed

    Christensen, Lars P; Jensen, Martin

    2009-04-01

    Fifty selected roots from a 7-year-old American ginseng (Panax quinquefolium L.) plant population grown in Denmark, with root weights varying from 191 to 490 g fresh weight (FW), were investigated for bioactive ginsenosides and polyacetylenes (PAs) in order to determine the correlation between the content of ginsenosides and PAs and root FW. PAs (falcarinol, panaxydol) and ginsenosides (Rb(1), Rb(2), Rb(3), Rc, Rd, Re, Rg(1)) were extracted from roots by sequential extraction with ethyl acetate and 80% methanol, respectively, and quantified in extracts by reverse-phase high-performance liquid chromatography (HPLC) using photodiode array detection. Total concentrations of PAs and ginsenosides varied between 150 and 780 mg/kg FW and 5,920 and 15,660 mg/kg FW, respectively. No correlation existed between the content of ginsenosides and PAs and root FW or between the total concentration of ginsenosides and PAs. Strong significant correlation was found between total content of ginsenosides and ginsenoside Rb(1) (r = 0.8190, P < 0.0001) and between total content of PAs and falcarinol (r = 0.9904, P < 0.0001). Based on the results of this study, it was concluded that it is possible to select large American ginseng roots for increased biomass production and concentration of bioactive ginsenosides and PAs without affecting the profile of bioactive compounds. Ginsenoside Rb(1) and falcarinol were found to be important selection parameters for identifying superior genotypes with the highest content of bioactive compounds.

  15. Ostrich crystallins. Structural characterization of delta-crystallin with enzymic activity.

    PubMed Central

    Chiou, S H; Lo, C H; Chang, C Y; Itoh, T; Kaji, H; Samejima, T

    1991-01-01

    Lens crystallins from the African ostrich (Struthio camelus) were isolated and characterized. Four crystallin fractions corresponding to alpha-, delta/beta- and beta-crystallins similar to those of duck crystallins were isolated, but epsilon-crystallin was found to be absent. The native molecular masses and subunit structures of the purified fractions were analysed by gel filtration. SDS/PAGE and isoelectric focusing, revealing various extents of heterogeneity in each orthologous crystallin class. An ion-exchange chromatographic method was used for the large-scale preparation of delta-crystallin suitable for structural and enzymic studies. It was unexpectedly found that the purified native delta-crystallin of ostrich lens possessed high argininosuccinate lyase activity, in contrast with chicken delta-crystallin. The c.d. spectra indicated a predominant beta-sheet structure in alpha- and beta-crystallins, and a significant contribution of alpha-helical structure in the delta-crystallin fraction. The estimate of secondary structures from c.d. spectroscopy for each crystallin class bears a resemblance to that of duck crystallins, except that ostrich delta-crystallin possesses much less helical content than duck delta-crystallin. Comparison of crystallin compositions and structures from aquatic and terrestrial birds revealed distinct differences. Images Fig. 1. Fig. 2. Fig. 3. PMID:1991029

  16. Sensory Substitution for Wounded Servicemembers

    DTIC Science & Technology

    2009-10-28

    traumatic brain injury (TBI) and two civilians, all with partial visual impairment , evaluated the vision sensory substitution systems. The servicemember...Mobility Augmentation; Wounded Service Members; Human-Centered Computing; Vision Augmentation, Vision , Balance and Hearing; Sensory Substitution-enabled...mitigation of vision sensory and mobility losses. 2) Improved the usefulness of available sensory substitution technologies for injured military

  17. Therapeutic Potential of α-Crystallin

    PubMed Central

    Nagaraj, Ram H.; Nahomi, Rooban B.; Mueller, Niklaus H.; Raghavan, Cibin T.; Ammar, David A.; Petrash, J. Mark

    2015-01-01

    Background The findings that α-crystallins are multi-functional proteins with diverse biological functions have generated considerable interest in understanding their role in health and disease. Recent studies have shown that chaperone peptides of α-crystallin could be delivered into cultured cells and in experimental animals with beneficial effects against protein aggregation, oxidation, inflammation and apoptosis. Scope of Review In this review, we will summarize the latest developments on the therapeutic potential of α-crystallins and their functional peptides. Major conclusions α-Crystallins and their functional peptides have shown significant favorable effects against several diseases. Their targeted delivery to tissues would be of great therapeutic benefit. However, α-crystallins can also function as disease-causing proteins. These seemingly contradictory functions must be carefully considered prior to their therapeutic use. General significance αA and αB-Crystallin are members of the small heat shock protein family. These proteins exhibit molecular chaperone and anti-apoptotic activities. The core crystallin domain within these proteins is largely responsible for these prosperities. Recent studies have identified peptides within the crystallin domain of both α- and αB-crystallins with remarkable chaperone and anti-apoptotic activities. Administration of α-crystallin or their functional peptides have shown substantial inhibition of pathologies in several diseases. However, α-crystallins have been shown to promote disease-causing pathways. These two sides of the proteins are discussed in this review. PMID:25840354

  18. Selenite sorption by carbonate substituted apatite

    SciTech Connect

    Moore, Robert C.; Rigali, Mark J.; Brady, Patrick

    2016-08-31

    The sorption of selenite, SeO32–, by carbonate substituted hydroxylapatite was investigated using batch kinetic and equilibrium experiments. The carbonate substituted hydroxylapatite was prepared by a precipitation method and characterized by SEM, XRD, FT-IR, TGA, BET and solubility measurements. The material is poorly crystalline, contains approximately 9.4% carbonate by weight and has a surface area of 210.2 m2/g. Uptake of selenite by the carbonated hydroxylapatite was approximately an order of magnitude higher than the uptake by uncarbonated hydroxylapatite reported in the literature. Distribution coefficients, Kd, determined for the carbonated apatite in this work ranged from approximately 4200 to over 14,000 L/kg. A comparison of the results from kinetic experiments performed in this work and literature kinetic data indicates the carbonated apatite synthesized in this study sorbed selenite 23 times faster than uncarbonated hydroxylapatite based on values normalized to the surface area of each material. Furthermore, the results indicate carbonated apatite is a potential candidate for use as a sorbent for pump-and-treat technologies, soil amendments or for use in permeable reactive barriers for the remediation of selenium contaminated sediments and groundwaters.

  19. Selenite sorption by carbonate substituted apatite

    DOE PAGES

    Moore, Robert C.; Rigali, Mark J.; Brady, Patrick

    2016-08-31

    The sorption of selenite, SeO32–, by carbonate substituted hydroxylapatite was investigated using batch kinetic and equilibrium experiments. The carbonate substituted hydroxylapatite was prepared by a precipitation method and characterized by SEM, XRD, FT-IR, TGA, BET and solubility measurements. The material is poorly crystalline, contains approximately 9.4% carbonate by weight and has a surface area of 210.2 m2/g. Uptake of selenite by the carbonated hydroxylapatite was approximately an order of magnitude higher than the uptake by uncarbonated hydroxylapatite reported in the literature. Distribution coefficients, Kd, determined for the carbonated apatite in this work ranged from approximately 4200 to over 14,000 L/kg.more » A comparison of the results from kinetic experiments performed in this work and literature kinetic data indicates the carbonated apatite synthesized in this study sorbed selenite 23 times faster than uncarbonated hydroxylapatite based on values normalized to the surface area of each material. Furthermore, the results indicate carbonated apatite is a potential candidate for use as a sorbent for pump-and-treat technologies, soil amendments or for use in permeable reactive barriers for the remediation of selenium contaminated sediments and groundwaters.« less

  20. Dual functional selenium-substituted hydroxyapatite

    PubMed Central

    Wang, Yanhua; Ma, Jun; Zhou, Lei; Chen, Jin; Liu, Yonghui; Qiu, Zhiye; Zhang, Shengmin

    2012-01-01

    Hydroxyapatite (HA) doped with trace elements has attracted much attention recently owing to its excellent biological functions. Herein, we use a facile co-precipitation method to incorporate selenium into HA by adding sodium selenite during synthesis. The obtained selenium-substituted HA products are needle-like nanoparticles which have  size and crystallinity that are similar to those of the pure HA nanoparticles (HANs) when the selenium content is low. HANs are found to have the ability to induce the apoptosis of osteosarcoma cells, and the anti-tumour effects are enhanced after incorporation of selenium. Meanwhile, the nanoparticles can also support the growth of bone marrow stem cells. Furthermore, the flow cytometric results indicate that the apoptosis induction of osteosarcoma cells is caused by the increased reactive oxygen species and decreased mitochondrial membrane potential. These results show that the selenium-substituted HANs are potentially promising bone graft materials in osteosarcoma treatment due to their dual functions of supporting normal cell growth and inducing tumour cell apoptosis. PMID:23741613

  1. Synthesis and characterization of nitrogen substituted zeolites

    NASA Astrophysics Data System (ADS)

    Dogan, Fulya

    The interest in basic solid materials, particularly for basic zeolites has considerably increased in the last two decades because of their potential use in catalysis and separation. Basic zeolites have most often been obtained by ion-exchange or impregnation with alkali metal cations or grafting of organic bases onto zeolite pore walls. Such materials often suffer from instability and/or pore blockage, because none of these approaches places basic sites directly into the zeolite framework. Recently zeolitic materials have been made with some of the bridging oxygen atoms in Si--O--Si and/or Si--O--Al linkages replaced by NH groups, i.e. by substitution of framework oxygen by nitrogen. As a result, the basic strength of the framework increases due to the lower electronegativity of nitrogen with respect to oxygen. In this study, solid base catalysts are obtained by nitrogen substitution of the faujasite type of zeolites under ammonia flow at high temperatures. The efficiency of the reaction is tested by using zeolites with different aluminum contents and extraframework cations and varying the reaction conditions such as ammonia flow rate, reaction temperature and duration. The characterization studies show that high levels of nitrogen substitution can be achieved while maintaining porosity, particularly for NaY and low-aluminum HY zeolites, without a significant loss in the crystallinity. 27Al and 29 Si MAS NMR experiments performed on the nitrogen substituted zeolites show dealumination of the framework and preferential substitution for Si--OH--Al sites at the early stages of the reaction (temperatures at 750--800 °C). No preference is seen for reactions performed at higher temperatures and longer reaction times (e.g., 850 °C and 48 h). X-ray PDF analysis performed on the modified zeolites show that the Si-N distance in the 1st shell is longer than Si-O bond distance and Si-Si/Al bond distance of the Si-O/N-Si/Al linkage decreases, as an indication of a decrease in

  2. Spectral Diversity Crystalline Fluoride Lasers,

    DTIC Science & Technology

    1981-01-01

    2 4.-. i1.34 I R TUNABLE Table IX XeF Pumoe TM3 +: YLF :1 .Tm:YLF exhibits nearly ideal parameters for high energy operation aa3x10-20cm 2 ESAT 0cm e...host crystal, lithium yttrium fluoride, LiYF*4 ( YLF )" 1..0 Introductin Within the realm of crystalline laser materials,. the class of fluorides...on the host crystal, lithium yttrium fluoride, LiYF4 - often shortened as YLF . Tables I and 12 show the mechanical, thermal, and optical properties

  3. Crystalline order on the paraboloid

    NASA Astrophysics Data System (ADS)

    Giomi, Luca; Bowick, Mark

    2006-03-01

    We describe an experimental and theoretical investigation of crystalline order on a two-dimensional paraboloid. In contrast to the sphere, the paraboloid exhibits both variable Gaussian curvature and a boundary. Both these features must be treated for a thorough theoretical understanding. A macroscopic model of a parabolic crystal can be obtained in the laboratory by assembling a single layer of soap bubbles on the surface of a rotating liquid, thus extending the classic work of Bragg and Nye on planar arrays of soap bubbles.

  4. Carbon substitution for oxygen in silicates in planetary interiors

    PubMed Central

    Sen, Sabyasachi; Widgeon, Scarlett J.; Navrotsky, Alexandra; Mera, Gabriela; Tavakoli, Amir; Ionescu, Emanuel; Riedel, Ralf

    2013-01-01

    Amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiOxC4-x tetrahedra. Calorimetric studies demonstrated these PDCs to be thermodynamically more stable than a mixture of SiO2, C, and silicon carbide. Here, we show by multinuclear NMR spectroscopy that substitution of C for O is also attained in PDCs with depolymerized silica-rich domains containing lithium, associated with SiOxC4-x tetrahedra with nonbridging oxygen. We suggest that significant (several percent) substitution of C for O could occur in more complex geological silicate melts/glasses in contact with graphite at moderate pressure and high temperature and may be thermodynamically far more accessible than C for Si substitution. Carbon incorporation will change the local structure and may affect physical properties, such as viscosity. Analogous carbon substitution at grain boundaries, at defect sites, or as equilibrium states in nominally acarbonaceous crystalline silicates, even if present at levels at 10–100 ppm, might form an extensive and hitherto hidden reservoir of carbon in the lower crust and mantle. PMID:24043830

  5. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkyl amino substituted triazine...

  6. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkyl amino substituted triazine...

  7. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkyl amino substituted triazine...

  8. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl amino substituted triazine...

  9. 40 CFR 721.10126 - Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato azo... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkyl amino substituted triazine...

  10. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ....-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic). 721.10214 Section 721.10214... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  11. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ....-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic). 721.10214 Section 721.10214... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  12. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ....-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic). 721.10214 Section 721.10214... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  13. Polyimides comprising substituted benzidines

    NASA Technical Reports Server (NTRS)

    Harris, Frank W. (Inventor)

    1991-01-01

    A new class of polyimides and copolyimides made from substituted benzidines and aromatic dianhydrides and other aromatic diamines. The polyimides obtained with said diamines are distinguished by excellent thermal, excellent solubility, excellent electrical properties such as very low dielectric constants, excellent clarity and mechanical properties making the polyimides ideally suited as coating materials for microelectronic apparatii, as membranes for selective molecular or gas separation, as fibers in molecular composites, as high tensile strength, high compression strength fibers, as film castable coatings, or as fabric components.

  14. Ferromagnetic viscoelastic liquid crystalline materials

    NASA Astrophysics Data System (ADS)

    Schlesier, Cristina; Shibaev, Petr; McDonald, Scott

    2012-02-01

    Novel ferromagnetic liquid crystalline materials were designed by mixing ferromagnetic nanoparticles with glass forming oligomers and low molar mass liquid crystals. The matrix in which nanoparticles are embedded is highly viscous that reduces aggregation of nanoparticles and stabilizes the whole composition. Mechanical and optical properties of the composite material are studied in the broad range of nanoparticle concentrations. The mechanical properties of the viscoelastic composite material resemble those of chemically crosslinked elastomers (elasticity and reversibility of deformations). The optical properties of ferromagnetic cholesteric materials are discussed in detail. It is shown that application of magnetic field leads to the shift of the selective reflection band of the cholesteric material and dramatically change its color. Theoretical model is suggested to account for the observed effects; physical properties of the novel materials and liquid crystalline elastomers are compared and discussed. [1] P.V. Shibaev, C. Schlesier, R. Uhrlass, S. Woodward, E. Hanelt, Liquid Crystals, 37, 1601 (2010) [2] P.V. Shibaev, R. Uhrlass, S. Woodward, C. Schlesier, Md R. Ali, E. Hanelt, Liquid Crystals, 37, 587 (2010)

  15. Genetics of Bietti Crystalline Dystrophy.

    PubMed

    Ng, Danny S C; Lai, Timothy Y Y; Ng, Tsz Kin; Pang, Chi Pui

    2016-01-01

    Bietti crystalline dystrophy (BCD) is an inherited retinal degenerative disease characterized by crystalline deposits in the retina, followed by progressive atrophy of the retinal pigment epithelium (RPE), choriocapillaris, and photoreceptors. CYP4V2 has been identified as the causative gene for BCD. The CYP4V2 gene belongs to the cytochrome P450 superfamily and encodes for fatty acid ω-hydroxylase of both saturated and unsaturated fatty acids. The CYP4V2 protein is localized most abundantly within the endoplasmic reticulum in the RPE and is postulated to play a role in the physiological lipid recycling system between the RPE and photoreceptors to maintain visual function. Electroretinographic assessments have revealed progressive dysfunction of rod and cone photoreceptors in patients with BCD. Several genotypes have been associated with more severe phenotypes based on clinical and electrophysiological findings. With the advent of multimodal imaging with spectral domain optical coherence tomography, fundus autofluorescence, and adaptive optics scanning laser ophthalmoscopy, more precise delineation of BCD severity and progression is now possible, allowing for the potential future development of targets for gene therapy.

  16. Liquid-crystalline physical gels.

    PubMed

    Kato, Takashi; Hirai, Yuki; Nakaso, Suguru; Moriyama, Masaya

    2007-12-01

    Liquid-crystalline (LC) physical gels are a new class of dynamically functional materials consisting of liquid crystals and fibrous aggregates of molecules that are called "gelators". Liquid-crystalline physical gels, which are macroscopically soft solids, exhibit induced or enhanced electro-optical, photochemical, electronic properties due to the combination of two components that form phase-separated structures. In this tutorial review, we describe the materials design and structure-property relationships of the LC physical gels. The introduction of self-assembled fibers into nematic liquid crystals leads to faster responses in twisted nematic (TN) mode and high contrast switching in light scattering mode. Furthermore, the LC physical gels can be exploited as a new type of materials for electro-optical memory. This function is achieved by the control of reversible aggregation processes of gelators under electric fields in nematic liquid crystals. Electronic properties such as hole mobilities are improved by the introduction of fibrous aggregates into triphenylene-based columnar liquid crystals. The incorporation of photochromic azobenzenes or electroactive tetrathiafulvalenes into the chemical structures of gelators leads to the preparation of ordered functional materials.

  17. Thermodynamics of rock forming crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1971-01-01

    Analysis of phase diagrams and cation distributions within crystalline solutions as means of obtaining thermodynamic data on rock forming crystalline solutions is discussed along with some aspects of partitioning of elements in coexisting phases. Crystalline solutions, components in a silicate mineral, and chemical potentials of these components were defined. Examples were given for calculating thermodynamic mixing functions in the CaW04-SrW04, olivine-chloride solution, and orthopyroxene systems.

  18. Structure Property Relationships in Liquid Crystalline Thermosets

    DTIC Science & Technology

    2003-04-25

    Adhesion Science and Technology , 2002, 16, 15-32 Jianxun Feng and Elliot P. Douglas, “Permeability of a liquid crystalline epoxy”, Materials Research...Arthur J. Gavrin and Elliot P. Douglas, “Cure behavior of liquid crystalline thermosets”, poster presentation at POLY Millenial 2000, Waikoloa, HI...December, 2000 Elliot P. Douglas, "Liquid crystalline thermosets", Massachusetts Institute of Technology , Cambridge, MA, April, 2000 Arthur J. Gavrin

  19. Modeling non-crystalline networks

    NASA Astrophysics Data System (ADS)

    Lei, Ming

    In this thesis, the author reports the modeling of both the static and the dynamical aspects of non-crystalline networks. Porous silicon and silica have attracted attention recently due to their unusual photoelectronic properties. Porosity is central to these striking properties which are not present in non-porous silicon and silica. We propose an algorithm that is effective in building fully-coordinated amorphous networks that are discontinuous in certain regions---that is, they contain large voids of mesoscopic or macroscopic dimensions. Such networks can be both porous and amorphous, and can also be finite in certain dimensions. Voids of arbitrary shapes and sizes are first superimposed on a crystalline silicon network. The atoms in the pore regions are removed. Local "defects" are created, then eliminated, as pairs of them are brought together by a defect migration process. The network is fully coordinated after the defect migration process. The Wooten Winer Weaire (WWW) algorithm, is then applied to make the network amorphous. Oxygen is inserted on every silicon-silicon bond to create a porous silica network. Silica networks in the form of an amorphous fiber and an amorphous film are created by this procedure. Distortions due to surface effects are investigated. The local atomic arrangement in these discontinuous networks is similar to that in bulk amorphous silica. Covalent bond lengths and angles in amorphous networks do not vary much because of the high energies associated with bond length and angle distortions. Therefore, they can be viewed as constraints that do not change with time in any significant way. Proteins, viewed as another type of non-crystalline network, are glued together by covalent bonds, hydrogen bonds, hydrophobic interactions, and other interactions. The concentration of constraints in some regions of the proteins are so high that these regions are rigid. The other regions are flexible. The flexible regions of protein can exhibit large

  20. 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.

  1. Reactions and Interactions in Liquid Crystalline Media

    DTIC Science & Technology

    1991-10-30

    conventional elastomers . At the isotropic to liquid crystalline phase transformation and in the liquid crystalline state, the elastomeric behavior...0.08 C=O OCN- 4 -CH 2- NCO0 (mole % crosslinking agent 1.0-2.5) R2 Crosslinked polymers (86 Scheme 6. Synthesis of liquid crystalline elastomers 86 by...2 ) (UH 2 ) In 1 6 O OH or ]OCN--- CH2 O-NCO 0 Crosslinked polymers (87)2 Scheme 7. Synthesis of liquid crystalline elastomers K7 by reaction of

  2. Substituted hydroxyapatites for bone repair.

    PubMed

    Shepherd, Jennifer H; Shepherd, David V; Best, Serena M

    2012-10-01

    Calcium phosphates such as hydroxyapatite have a wide range of applications both in bone grafts and for the coating of metallic implants, largely as a result of their chemical similarity to the mineral component of bone. However, to more accurately mirror the chemistry, various substitutions, both cationic (substituting for the calcium) and anionic (substituting for the phosphate or hydroxyl groups) have been produced. Significant research has been carried out in the field of substituted apatites and this paper aims to summarise some of the key effect of substitutions including magnesium, zinc, strontium, silicon and carbonate on physical and biological characteristics. Even small substitutions have been shown to have very significant effects on thermal stability, solubility, osteoclastic and osteoblastic response in vitro and degradation and bone regeneration in vivo.

  3. Elasticity of crystalline molecular explosives

    DOE PAGES

    Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; ...

    2015-04-14

    Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, andmore » an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.« less

  4. Elasticity of crystalline molecular explosives

    SciTech Connect

    Hooks, Daniel E.; Ramos, Kyle J.; Bolme, C. A.; Cawkwell, Marc J.

    2015-04-14

    Crystalline molecular explosives are key components of engineered explosive formulations. In precision applications a high degree of consistency and predictability is desired under a range of conditions to a variety of stimuli. Prediction of behaviors from mechanical response and failure to detonation initiation and detonation performance of the material is linked to accurate knowledge of the material structure and first stage of deformation: elasticity. The elastic response of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), and cyclotetramethylene tetranitramine (HMX), including aspects of material and measurement variability, and computational methods are described in detail. Experimental determinations of elastic tensors are compared, and an evaluation of sources of error is presented. Furthermore, computed elastic constants are also compared for these materials and for triaminotrinitrobenzene (TATB), for which there are no measurements.

  5. Explicit Substitutions and All That

    NASA Technical Reports Server (NTRS)

    Ayala-Rincon, Mauricio; Munoz, Cesar; Busnell, Dennis M. (Technical Monitor)

    2000-01-01

    Explicit substitution calculi are extensions of the Lambda-calculus where the substitution mechanism is internalized into the theory. This feature makes them suitable for implementation and theoretical study of logic-based tools such as strongly typed programming languages and proof assistant systems. In this paper we explore new developments on two of the most successful styles of explicit substitution calculi: the lambda(sigma)- and lambda(s(e))-calculi.

  6. Explicit Substitutions and All That

    NASA Technical Reports Server (NTRS)

    Ayala-Rincon, Mauricio; Munoz, Cesar

    2000-01-01

    Explicit substitution calculi are extensions of the lambda-calculus where the substitution mechanism is internalized into the theory. This feature makes them suitable for implementation and theoretical study of logic-based tools such as strongly typed programming languages and proof assistant systems. In this paper we explore new developments on two of the most successful styles of explicit substitution calculi: the lambda sigma- and lambda S(e)-calculi.

  7. Bietti crystalline dystrophy and choroidal neovascularisation.

    PubMed

    Gupta, B; Parvizi, S; Mohamed, M D

    2011-02-01

    Bietti crystalline dystrophy is a rare autosomal recessive condition characterised by the presence of crystals in the retina and is followed by retinal and choroidal degeneration. We present a novel finding of juxtafoveal choroidal neovascularisation in Bietti crystalline dystrophy and demonstrate a spectral domain optical coherence tomography image of this disorder.

  8. Vanadium interactions in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Backlund, D. J.; Gibbons, T. M.; Estreicher, S. K.

    2016-11-01

    The properties of interstitial vanadium (Vi) in Si and its interactions with the vacancy and the self-interstitial, as well as with hydrogen, are calculated using first-principles techniques. The stable configurations, gap levels, and binding energies agree well with the available experimental data. The nudged-elastic-band method is used to calculate the activation energies for diffusion of Vi in various charge states. They range from 1.46 (for Vi +) to 2.04 eV (for Vi -). The (trigonal) {Vi,H } pair has a binding energy of 1.15 eV, a donor level at Ec-0.61 eV , and possibly an acceptor level Ec-0.07 eV . Substitutional vanadium (Vs) can also trap H interstitials and form electrically active {Vs,H } and {Vs,H ,H } complexes.

  9. Displacement, Substitution, Sublimation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Sigmund Freund worked with the mechanisms of displacement, substitution, and sublimation. These mechanisms have many similarities and have been studied diagnostically and therapeutically. Displacement and substitution seem to fit in well with phobias, hysterias, somatiyations, prejudices, and scapegoating. Phobias, prejudices, and scapegoating…

  10. Thermodynamic studies on charge-coupled substituted synthetic monazite

    NASA Astrophysics Data System (ADS)

    Rawat, D.; Phapale, S.; Mishra, R.; Dash, S.

    2017-04-01

    Phosphate-based monazite ceramic is considered worldwide as a potential crystalline host matrix for immobilization of long-lived tri- and tetra-valent actinides present in high-level nuclear waste. Monazite is chemically stable with respect to the leaching processes and has high radiation stability. The present paper describes the influence of charged coupled (Ca2+, Th4+) substitution in place of La3+ on thermodynamic stability of synthetic monazite ceramics. XRD-analysis of Ca, Th substituted LaPO4 viz., La1-xCax/2Thx/2PO4 (0 ≤ x ≤ 1) points to the formation of ideal solid-solution in the entire range of composition. However, thermodynamic analysis indicates deviation from ideal solid-solution with a minima at x = 0.25. The substituted La1-xCax/2Thx/2PO4 system is found to be iso-entropic and stabilized mainly by enthalpy. Enthalpies of formation as a function of Ca2+, Th4+ substitution were analysed to provide insights into the development of thermodynamically stable nuclear waste matrix.

  11. Diffusion in porous crystalline materials.

    PubMed

    Krishna, Rajamani

    2012-04-21

    The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso- and micro-porous structures. In meso-porous materials, with pore sizes 2 nm < d(p) < 50 nm, there is a central core region where the influence of interactions of the molecules with the pore wall is either small or negligible; meso-pore diffusion is governed by a combination of molecule-molecule and molecule-pore wall interactions. Within micro-pores, with d(p) < 2 nm, the guest molecules are always under the influence of the force field exerted with the wall and we have to reckon with the motion of adsorbed molecules, and there is no "bulk" fluid region. The characteristics and physical significance of the self-, Maxwell-Stefan, and Fick diffusivities are explained with the aid of data obtained either from experiments or molecular dynamics simulations, for a wide variety of structures with different pore sizes and topology. The influence of adsorption thermodynamics, molecular clustering, and segregation on both magnitudes and concentration dependences of the diffusivities is highlighted. In mixture diffusion, correlations in molecular hops have the effect of slowing-down the more mobile species. The need for proper modeling of correlation effects using the Maxwell-Stefan formulation is stressed with the aid of examples of membrane separations and catalytic reactors.

  12. Dense crystalline packings of ellipsoids

    NASA Astrophysics Data System (ADS)

    Jin, Weiwei; Jiao, Yang; Liu, Lufeng; Yuan, Ye; Li, Shuixiang

    2017-03-01

    An ellipsoid, the simplest nonspherical shape, has been extensively used as a model for elongated building blocks for a wide spectrum of molecular, colloidal, and granular systems. Yet the densest packing of congruent hard ellipsoids, which is intimately related to the high-density phase of many condensed matter systems, is still an open problem. We discover an unusual family of dense crystalline packings of self-dual ellipsoids (ratios of the semiaxes α : √{α }:1 ), containing 24 particles with a quasi-square-triangular (SQ-TR) tiling arrangement in the fundamental cell. The associated packing density ϕ exceeds that of the densest known SM2 crystal [ A. Donev et al., Phys. Rev. Lett. 92, 255506 (2004), 10.1103/PhysRevLett.92.255506] for aspect ratios α in (1.365, 1.5625), attaining a maximal ϕ ≈0.758 06 ... at α = 93 /64 . We show that the SQ-TR phase derived from these dense packings is thermodynamically stable at high densities over the aforementioned α range and report a phase diagram for self-dual ellipsoids. The discovery of the SQ-TR crystal suggests organizing principles for nonspherical particles and self-assembly of colloidal systems.

  13. How Do Substitute Teachers Substitute? An Empirical Study of Substitute-Teacher Labor Supply

    ERIC Educational Resources Information Center

    Gershenson, Seth

    2012-01-01

    This paper examines the daily labor supply of a potentially important, but often overlooked, source of instruction in U.S. public schools: substitute teachers. I estimate a sequential binary-choice model of substitute teachers' job-offer acceptance decisions using data on job offers made by a randomized automated calling system. Importantly, this…

  14. Effect of ionic substitutions on the structure and dielectric properties of hafnia: A first principles study

    NASA Astrophysics Data System (ADS)

    Cockayne, Eric

    2008-04-01

    First principles calculations were used to study the effects of Si, Ti, Zr, and Ta (+N) substitutional impurities on the structure and dielectric properties of crystalline HfO2. The dielectric constant of monoclinic HfO2 can be enhanced by substituting more polarizable ions for Hf, but the band gap is decreased. Enhancing the permittivity without decreasing the band gap requires forming the tetragonal or cubic phase of HfO2. Among the ions studied, Si alone is found to stabilize a nonmonoclinic phase of HfO2 relative to the monoclinic phase, but only at an atomic concentration above about 20%. Various experiments have reported the formation of nonmonoclinic phases of HfO2 with increased permittivity when other ions are substituted for Hf. It is concluded that these structures are, in general, either metastable or are stabilized by extrinsic factors or by a layered arrangement of the substitutional cations.

  15. Observation of amorphous to crystalline phase transformation in Te substituted Sn-Sb-Se thin films

    SciTech Connect

    Chander, Ravi

    2015-05-15

    Thin films of Sn-Sb-Se-Te (8 ≤ x ≤ 14) chalcogenide system were prepared by thermal evaporation technique using melt quenched bulk samples. The as-prepared thin films were found amorphous as evidenced from X-ray diffraction studies. Resistivity measurement showed an exponential decrease with temperature upto critical temperature (transition temperature) beyond which a sharp decrease was observed and with further increase in temperature showed an exponential decrease in resistivity with different activation energy. The transition temperature showed a decreasing trend with tellurium content in the sample. The resistivity measurement during cooling run showed no abrupt change in resistivity. The resistivity measurements of annealed films did not show any abrupt change revealing the structural transformation occurring in the material. The transition width showed an increase with tellurium content in the sample. The resistivity ratio showed two order of magnitude improvements for sample with higher tellurium content. The observed transition temperature in this system was found quite less than already commercialized Ge-Sb-Te system for optical and electronic memories.

  16. The phase dependent photophysics and photochemistry of side-chain substituted liquid crystalline polyaryl cinnamates

    SciTech Connect

    Singh, S.; Creed, D.; Hoyle, C.E.

    1993-12-31

    The photochemical behavior of a polymethacrylate polymer with a side-chain cinnamate ester mesogen has been investigated. Photolysis at 313 nm of the polymer film in the smectic A or smectic B phase results in only a 2+2 cycloaddition reaction at low photolysis times. In contrast, photolysis (313 nm) of the polymer film in the nematic phase yields both 2+2 cycloaddition and photo-Fries products at short photolysis times. The preference for 2+2 cyloaddition product formation in the smectic phases is attributed to preferential reaction of cinnamate ester aggregates. Accordingly, photolysis at 366 nm where only aggregates absorb yields exclusively cycloadducts even after exhaustive photolysis for long time periods.

  17. gammaN-crystallin and the evolution of the betagamma-crystallin superfamily in vertebrates.

    PubMed

    Wistow, Graeme; Wyatt, Keith; David, Larry; Gao, Chun; Bateman, Orval; Bernstein, Steven; Tomarev, Stanislav; Segovia, Lorenzo; Slingsby, Christine; Vihtelic, Thomas

    2005-05-01

    The beta and gamma crystallins are evolutionarily related families of proteins that make up a large part of the refractive structure of the vertebrate eye lens. Each family has a distinctive gene structure that reflects a history of successive gene duplications. A survey of gamma-crystallins expressed in mammal, reptile, bird and fish species (particularly in the zebrafish, Danio rerio) has led to the discovery of gammaN-crystallin, an evolutionary bridge between the beta and gamma families. In all species examined, gammaN-crystallins have a hybrid gene structure, half beta and half gamma, and thus appear to be the 'missing link' between the beta and gamma crystallin lineages. Overall, there are four major classes of gamma-crystallin: the terrestrial group (including mammalian gammaA-F); the aquatic group (the fish gammaM-crystallins); the gammaS group; and the novel gammaN group. Like the evolutionarily ancient beta-crystallins (but unlike the terrestrial gammaA-F and aquatic gammaM groups), both the gammaS and gammaN crystallins form distinct clades with members in fish, reptiles, birds and mammals. In rodents, gammaN is expressed in nuclear fibers of the lens and, perhaps hinting at an ancestral role for the gamma-crystallins, also in the retina. Although well conserved throughout vertebrate evolution, gammaN in primates has apparently undergone major changes and possible loss of functional expression.

  18. DESIGNING ENVIRONMENTALLY BENIGN SOLVENT SUBSTITUTES

    EPA Science Inventory

    Since the signing of 1987 Montreal Protocol, reducing and eliminating the use of harmful solvents has become an internationally imminent environmental protection mission. Solvent substitution is an effective way to achieve this goal. The Program for Assisting the Replacement of...

  19. Nucleophilic Substitution by Benzodithioate Anions.

    ERIC Educational Resources Information Center

    Bonnans-Plaisance, Chantal; Gressier, Jean-Claude

    1988-01-01

    Describes a two-session experiment designed to provide a good illustration of, and to improve student knowledge of, the Grignard reaction and nucleophilic substitution. Discusses the procedure, experimental considerations, and conclusion of this experiment. (CW)

  20. Thick crystalline films on foreign substrates

    DOEpatents

    Smith, H.I.; Atwater, H.A.; Geis, M.W.

    1986-03-18

    To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 [mu]m) film on a foreign substrate, the film is formed so as to be thin (<1 [mu]m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns. 2 figs.

  1. Thick crystalline films on foreign substrates

    DOEpatents

    Smith, Henry I.; Atwater, Harry A.; Geis, Michael W.

    1986-01-01

    To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 .mu.m) film on a foreign substrate, the film is formed so as to be thin (<1 .mu.m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns.

  2. Molecular Engineering of Liquid Crystalline Polymers

    DTIC Science & Technology

    1992-03-27

    INTRODUCTION TO LIQUID CRYSTALS 14.2.1 Introduction to Low Molar Mass Liquid Crystals and Definitions 14.2.2 Liquid Crystalline Polymers 14.3 ISOMORPHISM...Crystals and Definitions A liquid crystalline or mesomorphic phase or mesophase refers to a state of matter in which the degree of order is between...monotropic, the definition of Gkc being apparent from Figure 7. It is easily seen how crystal perfectioning on annealing can lead to a "conversion" of an

  3. Electrochemical synthesis of highly crystalline copper nanowires

    SciTech Connect

    Kaur, Amandeep; Gupta, Tanish; Kumar, Akshay; Kumar, Sanjeev; Singh, Karamjeet; Thakur, Anup

    2015-05-15

    Copper nanowires were fabricated within the pores of anodic alumina template (AAT) by template synthesis method at pH = 2.9. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the structure, morphology and composition of fabricated nanowires. These characterizations revealed that the deposited copper nanowires were highly crystalline in nature, dense and uniform. The crystalline copper nanowires are promising in application of future nanoelectronic devices and circuits.

  4. Deamidation alters the structure and decreases the stability of human lens betaA3-crystallin.

    PubMed

    Takata, Takumi; Oxford, Julie T; Brandon, Theodore R; Lampi, Kirsten J

    2007-07-31

    According to the World Health Organization, cataracts account for half of the blindness in the world, with the majority occurring in developing countries. A cataract is a clouding of the lens of the eye due to light scattering of precipitated lens proteins or aberrant cellular debris. The major proteins in the lens are crystallins, and they are extensively deamidated during aging and cataracts. Deamidation has been detected at the domain and monomer interfaces of several crystallins during aging. The purpose of this study was to determine the effects of two potential deamidation sites at the predicted interface of the betaA3-crystallin dimer on its structure and stability. The glutamine residues at the reported in vivo deamidation sites of Q180 in the C-terminal domain and at the homologous site Q85 in the N-terminal domain were substituted with glutamic acid residues by site-directed mutagenesis. Far-UV and near-UV circular dichroism spectroscopy indicated that there were subtle differences in the secondary structure and more notable differences in the tertiary structure of the mutant proteins compared to that of the wild type betaA3-crystallin. The Q85E/Q180E mutant also was more susceptible to enzymatic digestion, suggesting increased solvent accessibility. These structural changes in the deamidated mutants led to decreased stability during unfolding in urea and increased precipitation during heat denaturation. When simulating deamidation at both residues, there was a further decrease in stability and loss of cooperativity. However, multiangle-light scattering and quasi-elastic light scattering experiments showed that dimer formation was not disrupted, nor did higher-order oligomers form. These results suggest that introducing charges at the predicted domain interface in the betaA3 homodimer may contribute to the insolubilization of lens crystallins or favor other, more stable, crystallin subunit interactions.

  5. Stability and cytotoxicity of crystallin amyloid nanofibrils

    NASA Astrophysics Data System (ADS)

    Kaur, Manmeet; Healy, Jackie; Vasudevamurthy, Madhusudan; Lassé, Moritz; Puskar, Ljiljana; Tobin, Mark J.; Valery, Celine; Gerrard, Juliet A.; Sasso, Luigi

    2014-10-01

    Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils.Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils. Electronic supplementary information (ESI) available: ThT fluorescence graphs of buffers and solvents used for

  6. Lattice strain induced magnetism in substituted nanocrystalline cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Rajnish; Kar, Manoranjan

    2016-10-01

    Strontium (Sr) substituted cobalt ferrite i.e. Co1-xSrxFe2O4 (x=0.00, 0.01, 0.015, 0.02, 0.05, 0.1) have been synthesized by the citric acid modified sol-gel method. Crystal structure and phase purity have been studied by the X-ray powder diffraction technique. The Rietveld refinement of XRD pattern using the space group Fd 3 bar m shows monotonically increasing of lattice parameter with the increase in Sr concentration. Magnetic hysteresis loops measurement has been carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of ±1.5 T. Magnetocrystalline anisotropy constant were calculated by employing the Law of Approach (LA) to the saturation. It is observed that magnetocrystalline anisotropy has anomaly for x=0.01 (Co0.99Sr0.01Fe2O4) sample. Strain mediated modification of magnetic properties in Sr substituted cobalt ferrite has been observed. The saturation magnetization for doping concentration i.e. x=0.01 abruptly increase while for x>0.01 decreases with the increase in Sr concentration. A correlation between lattice strain and magnetic behavior in non-magnetic Sr- substituted nano-crystalline cobalt ferrite has been reported.

  7. Magnetic behaviour of Neodymium-substituted strontium hexaferrite

    NASA Astrophysics Data System (ADS)

    Bhat, Bilal Hamid; Want, Basharat

    2016-03-01

    Neodymium-substituted strontium hexaferrites, Sr1- x Nd x Fe12O19 ( x = 0, 0.05, 0.10, 0.15, 0.20), have been successfully synthesized by using citrate precursor method. The synthesized samples were characterized by X-ray diffraction, Transmission electron microscopy and vibrating sample magnetometry. The X-ray diffraction results show that the prepared samples are crystalline in nature and are of single phase with the space group P63/mmc. Transmission electron microscopy results show that the prepared sample is composed of fine nanoparticles with an average size of 80 nm. The effect on magnetic behaviour of strontium hexaferrite with neodymium substitution was analysed by using first-order reversal curves (FORCs). FORC analysis was done in order to know the domain state of magnetization of the nanoparticles and the nature of magnetic interactions among the particles. FORC diagrams depict a single peak, suggesting that the substituted systems are formed of interacting nanoparticles.

  8. 14 CFR 1260.55 - Reports substitution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AGREEMENTS General Special Conditions § 1260.55 Reports substitution. Reports Substitution October 2000 Technical Reports may be substituted for the required Performance Reports. The title page of such reports... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Reports substitution. 1260.55 Section...

  9. 14 CFR 1260.55 - Reports substitution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AGREEMENTS General Special Conditions § 1260.55 Reports substitution. Reports Substitution October 2000 Technical Reports may be substituted for the required Performance Reports. The title page of such reports... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Reports substitution. 1260.55 Section...

  10. 14 CFR 1260.55 - Reports substitution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AGREEMENTS General Special Conditions § 1260.55 Reports substitution. Reports Substitution October 2000 Technical Reports may be substituted for the required Performance Reports. The title page of such reports... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Reports substitution. 1260.55 Section...

  11. 14 CFR 1260.55 - Reports substitution.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AGREEMENTS General Special Conditions § 1260.55 Reports substitution. Reports Substitution October 2000 Technical Reports may be substituted for the required Performance Reports. The title page of such reports... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Reports substitution. 1260.55 Section...

  12. Theory of defects and dopants in amorphous and crystalline semiconductors

    NASA Astrophysics Data System (ADS)

    Stumm, Petra

    In this dissertation the structural and electronic consequences of defects and dopants in amorphous and crystalline semiconductors are investigated. The research that I have done explores these possibilities on a theoretical level. This work is aimed towards comprising a detailed study of the atomic scale structure and electrical properties of elemental and nitrogen doped ta-C. Further, results on a investigation of native defects in crystalline and amorphous GaN are reported. First principles methods are used for these calculations. Two structural tetrahedral amorphous carbon models were introduced, whose properties were in agreement with the available experimental data. The topological and electronic properties for different N doping concentrations were investigated. Substitutional N occurred in tetrahedral and pi bonded sites, which resulted in an increase of the Fermi energy, while N incorporation in strained network sites induced structural changes that lead to an increase in the spsp2 fraction of the material. Molecular dynamics simulations were employed to study defects in GaN, where charge transfer between the ions is included in an approximate fashion. We find good agreement for the band structure of wurtzite and zincblende GaN compared to other recent calculations, suggesting the suitability of our method to describe GaN. A 96 atom GaN supercell is used to study the relaxations and electronic properties of common defects in the crystal structure, including Ga and N vacancies and antisites. The prevalent conduction mechanisms in nitrogen doped tetrahedral amorphous carbon are identified and discussed. These results are compared to the recent experimental reports on N doping of ta-C and we find that the non-doping 3-fold N incorporation (Nsbsp{3}{0}) is energetically most likely, which explains the low doping efficiency seen in experiments. The electronic signatures of intrinsic defects in GaN are analyzed. Also, two 64 atom models of amorphous GaN at

  13. Polymer-mediated disruption of drug crystallinity.

    PubMed

    Rawlinson, Clare F; Williams, Adrian C; Timmins, Peter; Grimsey, Ian

    2007-05-04

    Ibuprofen (IB), a BCS Class II compound, is a highly crystalline substance with poor solubility properties. Here we report on the disruption of this crystalline structure upon intimate contact with the polymeric carrier cross-linked polyvinylpyrrolidone (PVP-CL) facilitated by low energy simple mixing. Whilst strong molecular interactions between APIs and carriers within delivery systems would be expected on melting or through solvent depositions, this is not the case with less energetic mixing. Simple mixing of the two compounds resulted in a significant decrease in the differential scanning calorimetry (DSC) melting enthalpy for IB, indicating that approximately 30% of the crystalline content was disordered. This structural change was confirmed by broadening and intensity diminution of characteristic IB X-ray powder diffractometry (PXRD) peaks. Unexpectedly, the crystalline content of the drug continued to decrease upon storage under ambient conditions. The molecular environment of the mixture was further investigated using Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectroscopy. These data suggest that the primary interaction between these components of the physical mix is hydrogen bonding, with a secondary mechanism involving electrostatic/hydrophobic interactions through the IB benzene ring. Such interactions and subsequent loss of crystallinity could confer a dissolution rate advantage for IB.

  14. Amorphous Semiconductor Nanowires Created by Site-Specific Heteroatom Substitution with Significantly Enhanced Photoelectrochemical Performance.

    PubMed

    He, Ting; Zu, Lianhai; Zhang, Yan; Mao, Chengliang; Xu, Xiaoxiang; Yang, Jinhu; Yang, Shihe

    2016-08-23

    Semiconductor nanowires that have been extensively studied are typically in a crystalline phase. Much less studied are amorphous semiconductor nanowires due to the difficulty for their synthesis, despite a set of characteristics desirable for photoelectric devices, such as higher surface area, higher surface activity, and higher light harvesting. In this work of combined experiment and computation, taking Zn2GeO4 (ZGO) as an example, we propose a site-specific heteroatom substitution strategy through a solution-phase ions-alternative-deposition route to prepare amorphous/crystalline Si-incorporated ZGO nanowires with tunable band structures. The substitution of Si atoms for the Zn or Ge atoms distorts the bonding network to a different extent, leading to the formation of amorphous Zn1.7Si0.3GeO4 (ZSGO) or crystalline Zn2(GeO4)0.88(SiO4)0.12 (ZGSO) nanowires, respectively, with different bandgaps. The amorphous ZSGO nanowire arrays exhibit significantly enhanced performance in photoelectrochemical water splitting, such as higher and more stable photocurrent, and faster photoresponse and recovery, relative to crystalline ZGSO and ZGO nanowires in this work, as well as ZGO photocatalysts reported previously. The remarkable performance highlights the advantages of the ZSGO amorphous nanowires for photoelectric devices, such as higher light harvesting capability, faster charge separation, lower charge recombination, and higher surface catalytic activity.

  15. Magnesium substitution in brushite cements.

    PubMed

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  16. Substitution systems and nonextensive statistics

    NASA Astrophysics Data System (ADS)

    García-Morales, V.

    2015-12-01

    Substitution systems evolve in time by generating sequences of symbols from a finite alphabet: At a certain iteration step, the existing symbols are systematically replaced by blocks of Nk symbols also within the alphabet (with Nk, a natural number, being the length of the kth block of the substitution). The dynamics of these systems leads naturally to fractals and self-similarity. By using B-calculus (García-Morales, 2012) universal maps for deterministic substitution systems both of constant and non-constant length, are formulated in 1D. It is then shown how these systems can be put in direct correspondence with Tsallis entropy. A 'Second Law of Thermodynamics' is also proved for these systems in the asymptotic limit of large words.

  17. Bone Graft Substitution and Augmentation.

    PubMed

    Nauth, Aaron; Lane, Joseph; Watson, J Tracy; Giannoudis, Peter

    2015-12-01

    Selection of appropriate bone graft or bone graft substitute requires careful recognition of the bone healing needs of the patient's specific clinical problem and a thorough understanding of the different properties possessed by the available bone grafts and substitutes. Although autogenous iliac crest bone graft remains the gold standard of treatment for delayed unions, nonunions, and bone defects, there are a number of promising alternatives available, and emerging evidence suggests that they can be very effective when used in the proper setting. Among these, reamer-irrigator-aspirator bone graft, bone marrow concentrate, bone morphogenetic proteins, and calcium phosphate cements have received a great deal of attention in the literature. This review describes these grafts in detail along with the evidence for their use. In addition, a framework is provided for selecting the appropriate graft or substitute based on their provided properties.

  18. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... substances identified generically as copper complex of (substituted sulfonaphthyl azo substituted...

  19. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... substances identified generically as copper complex of (substituted sulfonaphthyl azo substituted...

  20. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... substances identified generically as copper complex of (substituted sulfonaphthyl azo substituted...

  1. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... substances identified generically as copper complex of (substituted sulfonaphthyl azo substituted...

  2. Nucleation and growth studies of crystalline carbon phases at nanoscale

    NASA Astrophysics Data System (ADS)

    Mani, Radhika C.

    Understanding the nucleation and early stage growth of crystals from the vapor phase is important for realizing large-area single-crystal quality films, controlled synthesis of nanocrystals, and the possible discovery of new phases of materials. Carbon provides the most interesting system because all its known crystalline phases (diamond, graphite and carbon nanotubes) are technologically important materials. Hence, this dissertation is focused on studying the nucleation and growth of carbon phases synthesized from the vapor phase. Nucleation experiments were performed in a microwave plasma chemical vapor deposition (CVD) reactor, and the resulting carbon nanocrystals were analyzed primarily using electron nanodiffraction and Raman spectroscopy. These studies led to the discovery of two new crystalline phases of sp 3 carbon other than diamond: face-centered and body-centered cubic carbon. Nanodiffraction results revealed possible hydrogen substitution into diamond-cubic lattices, indicating that these new phases probably act as intermediates in diamond nucleation. Nucleation experiments also led to the discovery of two new morphologies for sp2 carbon: nanocrystals of graphite and tapered, hollow 1-D structures termed here as "carbon nanopipettes". A Kinetic Monte Carlo (KMC) algorithm was developed to simulate the growth of individual diamond crystals from the vapor phase, starting with small clusters of carbon atoms (or seeds). Specifically, KMC simulations were used to distinguish the kinetic rules that give rise to a star-shaped decahedral morphology compared to decahedral crystals. KMC simulations revealed that slow adsorption on the {111} step-propagation sites compared to kink sites leads to star-decahedral crystals, and higher adsorption leads to decahedral crystals. Since the surfaces of the nanocrystals of graphite and nanopipettes were expected to be composed primarily of edge-plane sites, the electrochemical behavior of both these materials were

  3. Influence of synthesis conditions on the crystallinity of hydroxyapatite obtained by chemical deposition

    NASA Astrophysics Data System (ADS)

    Toropkov, N. E.; Vereshchagin, V. I.; Petrovskaya, T. S.; Antonkin, N. S.

    2016-11-01

    The hydroxyapatite synthesis on a variety of substrates under various conditions was studied. It was shown that the increase in the temperature of the reaction medium increases the amount of nanocrystalline phase with an average crystallite size of 25 nm. Studies revealed that in addition to the pure hydroxyapatite, β-Ca3(PO4)2 along with calcium carbonates and carbonate-substituted hydroxyapatites were formed. A significant increase in phase crystallinity during the heating of reactants up to the reaction temperature was shown.

  4. Shear-induced conformation change in α-crystalline nylon6

    SciTech Connect

    Arabnejad, Saeid; Manzhos, Sergei; Shim, V. P. W.; He, Chaobin

    2014-12-01

    A study of shear deformation of α-crystalline nylon6 is undertaken, using dispersion-corrected density functional theory. The shear stress-strain relationship and shear strength for interlayer shear deformation are computed. A conformation change induced by shear is identified along twinning deformation, whereby the conformation of chains, specifically the location of non-H-bonded hydrogen atoms, changes continuously. This paves a way for the modulation of properties of this group of materials by small shear deformation, if the non-H-bonded hydrogens are chemically substituted to form non-equivalent conformations when deformed.

  5. Structure/function studies of dogfish α-crystallin, comparison with bovine α-crystallin

    PubMed Central

    Ghahghaei, A.; Rekas, A.; Carver, J.A.

    2009-01-01

    Purpose α-Crystallin is the major protein of the mammalian lens where it contributes to the refractive properties needed for vision and possibly to the stability of the tissue. The aim of this study was to determine whether the properties of α-crystallin have changed during the course of evolution. Methods Dogfish α-crystallin, which appeared over 420 million years ago, has been contrasted with bovine α-crystallin, which emerged around 160 million years later, by comparing their sizes, the microenvironments of their cysteine and tryptophan residues, their chaperone-like activities and the flexibility of their COOH-terminal extensions. Results Dogfish α-crystallin consists of αA- and αB-polypeptides, in a 1:5 ratio, and has a molecular mass of around 400 kDa. By contrast, the bovine protein is around 600-800 kDa in mass and has a 3:1 subunit ratio. Cysteine residues in the proteins were equally accessible to reaction with 5,5'-dithiobis-(2-nitrobenzoic acid). Quenching of fluorescence with acrylamide indicated tryptophan residues in the two proteins were in similar environments. The chaperone activity of dogfish α-crystallin was comparable to that of bovine α-crystallin in preventing the heat-induced precipitation of βL-crystallin but the dogfish protein was three times more effective at preventing insulin precipitation after reduction at 37 ˚C. 1H nuclear magnetic resonance spectroscopic studies showed that the last 17 amino acids of the dogfish αB polypeptide (V162-K178) have great conformational flexibility, are highly exposed to solvent and adopt little ordered conformation. This is comparable to, but slightly longer in length, than the COOH-terminal extension observed in mammalian α-crystallins. Conclusions The structure and properties of α-crystallin have changed relatively little during the evolutionary period from the emergence of sharks and mammals. PMID:19956560

  6. Hypoxic radiosensitizers: substituted styryl derivatives.

    PubMed

    Nudelman, A; Falb, E; Odesa, Y; Shmueli-Broide, N

    1994-10-01

    A number of novel styryl epoxides, N-substituted-styryl-ethanolamines, N-mono and N,N'-bis-(2-hydroxyethyl)-cinnamamides--analogues to the known radiosensitizers RSU-1069, pimonidazole and etanidazole--display selective hypoxic radiosensitizing activity. The styryl group, especially when substituted by electron withdrawing groups, was found to be bioisosteric to the nitroimidazolyl functionality. The most active derivative 2-(2'-nitrophenyl)ethen-1-yl-oxirane 8a displayed a sensitizer enhancement ratio (SER) of 5 relative to misonidazole.

  7. Liquid Crystalline Materials for Biological Applications.

    PubMed

    Lowe, Aaron M; Abbott, Nicholas L

    2012-03-13

    Liquid crystals have a long history of use as materials that respond to external stimuli (e.g., electrical and optical fields). More recently, a series of investigations have reported the design of liquid crystalline materials that undergo ordering transitions in response to a range of biological interactions, including interactions involving proteins, nucleic acids, viruses, bacteria and mammalian cells. A central challenge underlying the design of liquid crystalline materials for such applications is the tailoring of the interface of the materials so as to couple targeted biological interactions to ordering transitions. This review describes recent progress toward design of interfaces of liquid crystalline materials that are suitable for biological applications. Approaches addressed in this review include the use of lipid assemblies, polymeric membranes containing oligopeptides, cationic surfactant-DNA complexes, peptide-amphiphiles, interfacial protein assemblies and multi-layer polymeric films.

  8. Chiral selection on inorganic crystalline surfaces

    NASA Technical Reports Server (NTRS)

    Hazen, Robert M.; Sholl, David S.

    2003-01-01

    From synthetic drugs to biodegradable plastics to the origin of life, the chiral selection of molecules presents both daunting challenges and significant opportunities in materials science. Among the most promising, yet little explored, avenues for chiral molecular discrimination is adsorption on chiral crystalline surfaces - periodic environments that can select, concentrate and possibly even organize molecules into polymers and other macromolecular structures. Here we review experimental and theoretical approaches to chiral selection on inorganic crystalline surfaces - research that is poised to open this new frontier in understanding and exploiting surface-molecule interactions.

  9. Used fuel disposition in crystalline rocks

    SciTech Connect

    Wang, Y.; Hadgu, Teklu; Kalinina, Elena Arkadievna; Jerden, James L.; Copple, Jacqueline M.; Cruse, T.; Ebert, W.; Buck, E.; Eittman, R.; Tinnacher, R.; Tournassat, Christophe.; Davis, J.; Viswanathan, H.; Chu, S.; Dittrich, T.; Hyman, F.; Karra, S.; Makedonska, N.; Reimus, P.; Zavarin, Mavrik; Joseph, C.

    2016-09-01

    The U.S. Department of Energy Office of Nuclear Energy, Office of Fuel Cycle Technology established the Used Fuel Disposition Campaign (UFDC) in fiscal year 2010 (FY10) to conduct the research and development (R&D) activities related to storage, transportation and disposal of used nuclear fuel and high level nuclear waste. The objective of the Crystalline Disposal R&D Work Package is to advance our understanding of long-term disposal of used fuel in crystalline rocks and to develop necessary experimental and computational capabilities to evaluate various disposal concepts in such media.

  10. 'Vegetable' substitutes for diesel fuel

    SciTech Connect

    Not Available

    1981-07-22

    Research programs in the US, Brazil, South Africa and the Philippines on efforts to find a vegetable oil substitute for diesel fuel are reported. A narrowing price gap with diesel fuel and a favourable energy balance improve the prospects for such fuels. Much of the current work is centered on blends, rather than the use of the pure oil.

  11. Substitute Teaching: Sink or Swim.

    ERIC Educational Resources Information Center

    Duebber, Diane

    2000-01-01

    Advises new substitute teachers to be prepared, tote emergency activity folders, dress professionally (but wear flamingo earrings), be early, figure out the game plan, communicate expectations to students, enforce consequences, have a gimmick to reward cooperation, relish the teachable moment, leave the room tidy, and believe in themselves. (MLH)

  12. The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

    PubMed Central

    Ringstrand, Bryan; Oltmanns, Martin; Batt, Jeffrey A; Jankowiak, Aleksandra; Denicola, Richard P

    2011-01-01

    Summary The methodology to prepare 3-substituted 1,5-dibromopentanes I and their immediate precursors, which include 3-substituted 1,5-pentanediols VII or 4-substituted tetrahydropyrans VIII, is surveyed. Such dibromides I are important intermediates in the preparation of liquid crystalline derivatives containing 6-membered heterocyclic rings. Four dibromides 1a–1d containing simple alkyl and more complex fragments at the 3-position were prepared. 3-Propyl- and 3-pentyl-pentane-1,5-diol (2a,b) were prepared starting from either glutaconate or malonate diesters, while tetrahydropyrans 3c and 3d were obtained from tetrahydro-4H-pyran-4-one. The advantages and disadvantages of each route are discussed. Dibromides 1c and 1d were used to prepare sulfonium zwitterions 11c and 11d. PMID:21512596

  13. Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates.

    PubMed

    Chaudhry, Aqif A; Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

    2013-09-01

    A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO₃-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO₃-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO₃-HA. For silicate-substituted hydroxyapatite (SiO₄-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO₄-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy.

  14. Molecular structure and liquid-crystalline characteristics of chitosan phenylcarbamate.

    PubMed

    Kuse, Yasunori; Asahina, Daisuke; Nishio, Yoshiyuki

    2009-01-12

    Chitosan phenylcarbamate (CtsPC) samples were synthesized to have different degrees of substitution (DS) ranging from approximately 2.7 to approximately 3.7, and the lyotropic liquid crystallinity was mainly characterized by spectrophotometry. The products of DS>2.8 formed a cholesteric type of mesophase in concentrated solutions of >44 wt % with polar aprotic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO), and some of the solutions imparted vivid colorations because of selective visible light reflection. The cholesteric helical pitch increased with increasing temperature and with decreasing polymer concentration, but the helical sense remained left-handed under the adopted measurement conditions. It was also found that the helical pitch increased in proportion to the increment of DS, whereas an average degree of phenylcarbamoyl polyaddition in the side chains (DPs) rather affected the pitch distribution measuring an orderliness in the cholesteric structure. With a small increase in DPs (e.g., from 1.01 to 1.04), the cholesteric orderliness decreased and the temperature sensitivity of the pitch turned sluggish. Wide-angle X-ray diffractometry was also used for evaluating the distance and azimuth difference between adjacent nematic thin layers in the cholesteric mesophase.

  15. Valence band structure in crystalline pentacene thin films

    NASA Astrophysics Data System (ADS)

    Hatch, Richard; Huber, David; Höchst, Hartmut

    2009-03-01

    Organic semiconductors, such as pentacene (Pn), are beginning to show promise as a low-cost substitute for conventional semiconductors for a variety of electronic devices. The overlap of π-orbitals in the Pn crystal leads to molecular orbital-derived bands. We used angle-resolved photoemission spectroscopy (ARPES) to reveal the Pn in-plane band structure of the two highest occupied molecular orbital-derived bands in crystalline thin film Pn (grown on a Bi substrate) for various temperatures between 75 K and 300 K. We mapped these two bands in several crystallographic directions with special attention given to the region near the top of the valence band and show, within the limits of our experimental resolution, that temperature does not change the dispersions of these bands. We fit the band structure to a tight binding model and compared our results with recent theoretical predictions[1-2]. We also calculated the in-plane reciprocal effective mass for the M point and compared it with the measured mobility. [1] H. Yoshida et. al. Phys. Rev. B 77, 235205 (2008). [2] G. A. de Wijs et. al. Synth. Met. 139, 109 (2003).

  16. Radiolytic Gas Generation in Crystalline Silicotitanate Slurries

    SciTech Connect

    WALKER, DARREL

    2004-03-15

    This study measured the impact of crystalline silicotitanate (CST) solids on the rate of formation and composition of radiolytically generated gases in simulated Savannah River Site liquid waste. The tests used IONSIV (TM) IE-911 (UOP LLC, Molecular Sieves Division, Des Planes, IL), the engineered form of CST.

  17. Ionic conductivity in crystalline polymer electrolytes.

    PubMed

    Gadjourova, Z; Andreev, Y G; Tunstall, D P; Bruce, P G

    2001-08-02

    Polymer electrolytes are the subject of intensive study, in part because of their potential use as the electrolyte in all-solid-state rechargeable lithium batteries. These materials are formed by dissolving a salt (for example LiI) in a solid host polymer such as poly(ethylene oxide) (refs 2, 3, 4, 5, 6), and may be prepared as both crystalline and amorphous phases. Conductivity in polymer electrolytes has long been viewed as confined to the amorphous phase above the glass transition temperature, Tg, where polymer chain motion creates a dynamic, disordered environment that plays a critical role in facilitating ion transport. Here we show that, in contrast to this prevailing view, ionic conductivity in the static, ordered environment of the crystalline phase can be greater than that in the equivalent amorphous material above Tg. Moreover, we demonstrate that ion transport in crystalline polymer electrolytes can be dominated by the cations, whereas both ions are generally mobile in the amorphous phase. Restriction of mobility to the lithium cation is advantageous for battery applications. The realization that order can promote ion transport in polymers is interesting in the context of electronically conducting polymers, where crystallinity favours electron transport.

  18. Topological crystalline insulator SnTe nanoribbons

    NASA Astrophysics Data System (ADS)

    Dahal, Bishnu R.; Dulal, Rajendra P.; Pegg, Ian L.; Philip, John

    2017-03-01

    Topological crystalline insulators are systems in which a band inversion that is protected by crystalline mirror symmetry gives rise to nontrivial topological surface states. SnTe is a topological crystalline insulator. It exhibits p-type conductivity due to Sn vacancies and Te antisites, which leads to high carrier density in the bulk. Thus growth of high quality SnTe is a prerequisite for understanding the topological crystalline insulating behavior. We have grown SnTe nanoribbons using a solution method. The width of the SnTe ribbons varies from 500 nm to 2 μm. They exhibit rock salt crystal structure with a lattice parameter of 6.32 Å. The solution method that we have adapted uses low temperature, so the Sn vacancies can be controlled. The solution grown SnTe nanoribbons exhibit strong semiconducting behavior with an activation energy of 240 meV. This activation energy matches with the calculated band gap for SnTe with a lattice parameter of 6.32 Å, which is higher than that reported for bulk SnTe. The higher activation energy makes the thermal excitation of bulk charges very difficult on the surface. As a result, the topological surfaces will be free from the disturbance caused by the thermal excitations

  19. 40 CFR Appendix B to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Use Conditions Substitutes Application Substitute Decision Conditions Comments Electronics Cleaning w.... Electronics cleaning w/CFC-113 Dibromomethane Unacceptable High ODP; other alternatives exist....

  20. 40 CFR Appendix B to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Use Conditions Substitutes Application Substitute Decision Conditions Comments Electronics Cleaning w.... Electronics cleaning w/CFC-113 Dibromomethane Unacceptable High ODP; other alternatives exist....

  1. Evidence for variable crystallinity in bivalve shells

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Wehrmeister, U.

    2012-04-01

    Bivalve shells are used as important palaeoclimate proxy archives and monitor regional climate variations. The shells mostly exist of two crystalline polymorphic phases of calcium carbonate calcite (rombohedric) and aragonite (orthorhombic). Calcite is the most stable polymorph at standard conditions, whereas vaterite (hexagonal) is the least stable and only rarely found in these structures. Shells are characterized by organized structures and several micro architectures of mollusc shell structures have been identified: Nacre shows different types: columnar and bricked forms and consists of composite inorganic- organic at the nano-scale. They are well known to display a "brick and mortar" structure. By AFM and FIB/TEM methods it could be shown, that its nanostructure consists of the structures in the range of 50 - 100 nm [1, 2]. These structures are vesicles, consisting of CaCO3 and are individually coated by a membrane. Most probably, the mantle epithelian cells of the bivalve extrude CaCO3 vesicles. By Raman spectroscopic investigations the crystalline CaCO3 polymorphs calcite, aragonite and vaterite, as well as ACC were determined. For some species (Diplodon chilensis patagonicus, Hyriopsis cumingii) pure ACC (i.e. not intermingled with a crystalline phase) could be identified. The presence of an amorphous phase is generally deduced from the lack of definite lattice modes, whereas a broad Raman band in this region is to observe. In most of the cultured pearls (Pinctada maxima and genus Hyriopsis) the ν1-Raman band of ACC clearly displays an asymmetric shape and splits into two different bands according to a nanocrystalline and an amorphous fraction. The FWHMs of most of the crystalline fractions are too high for well crystallized materials and support the assumption of nanocrystalline calcium carbonate polymorph clusters in ACC. They are primarily composed of amorphous calcium carbonate (ACC) which is later transformed into a crystalline modification [3

  2. Crystalline, liquid crystalline, and isotropic phases of sodium deoxycholate in water

    SciTech Connect

    Su, Ziyang; Luthra, Suman; Krzyzaniak, Joseph F.; Agra-Kooijman, Dena M.; Kumar, Satyendra; Byrn, Stephen R.; Shalaev, Evgenyi Y.

    2012-09-06

    Sodium deoxycholate (NaDC) is an important example of bile salts, representing systems with complex phase behavior involving both crystalline and mesophase structures. In this study, properties of NaDC-water mixtures were evaluated as a function of composition and temperature via X-ray diffraction with synchrotron (sXRD) and laboratory radiation sources, water sorption, polarized light, hot-stage microscopy, and freezing-point osmometry. Several phases were detected depending on the composition and temperature, including isotropic solution phase, liquid crystalline (LC) phase, crystalline hydrate, and ice. The LC phase was identified as hexagonal structure by sXRD, with up to 14 high-order reflections detected. The crystalline phase was found to be nonstoichiometric hydrate, based on XRD and water sorption data. The phase diagram of NaDC-water system has been refined based on both results of this study and other reports in literature.

  3. Association of partially folded lens betaB2-crystallins with the alpha-crystallin molecular chaperone.

    PubMed

    Evans, Paul; Slingsby, Christine; Wallace, B A

    2008-02-01

    Age-related cataract is a result of crystallins, the predominant lens proteins, forming light-scattering aggregates. In the low protein turnover environment of the eye lens, the crystallins are susceptible to modifications that can reduce stability, increasing the probability of unfolding and aggregation events occurring. It is hypothesized that the alpha-crystallin molecular chaperone system recognizes and binds these proteins before they can form the light-scattering centres that result in cataract, thus maintaining the long-term transparency of the lens. In the present study, we investigated the unfolding and aggregation of (wild-type) human and calf betaB2-crystallins and the formation of a complex between alpha-crystallin and betaB2-crystallins under destabilizing conditions. Human and calf betaB2-crystallin unfold through a structurally similar pathway, but the increased stability of the C-terminal domain of human betaB2-crystallin relative to calf betaB2-crystallin results in the increased population of a partially folded intermediate during unfolding. This intermediate is aggregation-prone and prevents constructive refolding of human betaB2-crystallin, while calf betaB2-crystallin can refold with high efficiency. alpha-Crystallin can effectively chaperone both human and calf betaB2-crystallins from thermal aggregation, although chaperone-bound betaB2-crystallins are unable to refold once returned to native conditions. Ordered secondary structure is seen to increase in alpha-crystallin with elevated temperatures up to 60 degrees C; structure is rapidly lost at temperatures of 70 degrees C and above. Our experimental results combined with previously reported observations of alpha-crystallin quaternary structure have led us to propose a structural model of how activated alpha-crystallin chaperones unfolded betaB2-crystallin.

  4. [Evolution of urinary bladder substitution].

    PubMed

    Kock, N G

    1992-11-01

    The historical background to the currently used methods for continent bladder substitution is shortly outlined. The significance for the patient's quality of life of various methods for bladder reconstruction or urinary diversion is briefly discussed. The importance of reservoir configuration for achieving a high compliant urinary receptacle is pointed out. Factors affecting reabsorption of urinary constituents are stressed and the significance of an antireflux mechanism is discussed. Currently the majority of patients undergoing cystectomy for cancer or for other reasons can be offered bladder substitutes providing continence and easy emptying; that is, complete control over voiding. This can be achieved by orthotopic bladder reconstruction or by diverting the urine to the augmented and valved rectum or to the skin via a continent intestinal reservoir.

  5. Substitutes for School Nurses in Illinois

    ERIC Educational Resources Information Center

    Vollinger, Linda Jeno; Bergren, Martha Dewey; Belmonte-Mann, Frances

    2011-01-01

    The purpose of this descriptive study was to explore utilization of nurse substitutes in the school setting in Illinois. The literature described personnel who staff the school health office in the absence of the school nurse and the barriers to obtaining nurse substitutes. There were no empirical studies conducted on school nurse substitutes in…

  6. 40 CFR 721.5867 - Substituted phenol.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted phenol. 721.5867 Section... Substances § 721.5867 Substituted phenol. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted phenol (PMNs P-89-1125,...

  7. 40 CFR 721.4476 - Substituted imines.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted imines. 721.4476 Section... Substances § 721.4476 Substituted imines. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted imines (PMNs...

  8. 40 CFR 721.4476 - Substituted imines.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted imines. 721.4476 Section... Substances § 721.4476 Substituted imines. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted imines (PMNs...

  9. 40 CFR 721.4476 - Substituted imines.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted imines. 721.4476 Section... Substances § 721.4476 Substituted imines. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted imines (PMNs...

  10. 40 CFR 721.4476 - Substituted imines.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted imines. 721.4476 Section... Substances § 721.4476 Substituted imines. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted imines (PMNs...

  11. 40 CFR 721.4476 - Substituted imines.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted imines. 721.4476 Section... Substances § 721.4476 Substituted imines. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted imines (PMNs...

  12. Tele-substitutions in Heterocyclic Chemistry.

    PubMed

    Tišler, Miha

    2011-03-01

    Particular and rare examples of aromatic nucleophilic substitution are described as tele-substitution. Usually strong nucleophiles are involved and the entering group is introduced at a position distant from the expected leaving group. Examples of tele-substitution in various heteroaromatic systems are presented.

  13. 40 CFR 721.4280 - Substituted hydrazine.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted hydrazine. 721.4280... Substances § 721.4280 Substituted hydrazine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted hydrazine (PMN P-90-594)...

  14. 40 CFR 721.4280 - Substituted hydrazine.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted hydrazine. 721.4280... Substances § 721.4280 Substituted hydrazine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted hydrazine (PMN P-90-594)...

  15. 40 CFR 721.4280 - Substituted hydrazine.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted hydrazine. 721.4280... Substances § 721.4280 Substituted hydrazine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted hydrazine (PMN P-90-594)...

  16. 40 CFR 721.4280 - Substituted hydrazine.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted hydrazine. 721.4280... Substances § 721.4280 Substituted hydrazine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted hydrazine (PMN P-90-594)...

  17. 40 CFR 721.4280 - Substituted hydrazine.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted hydrazine. 721.4280... Substances § 721.4280 Substituted hydrazine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted hydrazine (PMN P-90-594)...

  18. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted acrylamide. 721.323... Substances § 721.323 Substituted acrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted acrylamide (PMN P-90-1687)...

  19. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted acrylamide. 721.323... Substances § 721.323 Substituted acrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted acrylamide (PMN P-90-1687)...

  20. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted acrylamide. 721.323... Substances § 721.323 Substituted acrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted acrylamide (PMN P-90-1687)...

  1. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted acrylamide. 721.323... Substances § 721.323 Substituted acrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted acrylamide (PMN P-90-1687)...

  2. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted acrylamide. 721.323... Substances § 721.323 Substituted acrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as substituted acrylamide (PMN P-90-1687)...

  3. 40 CFR 192.42 - Substitute provisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Substitute provisions. 192.42 Section... § 192.42 Substitute provisions. The regulatory agency may, with the concurrence of EPA, substitute for any provisions of § 192.41 of this subpart alternative provisions it deems more practical that...

  4. Resonant photodissociation in substituted benzenes

    NASA Astrophysics Data System (ADS)

    Scarborough, Tim; McAcy, Collin; Foote, David; Uiterwaal, Cornelis

    2011-05-01

    Cyclic aromatic molecules are abundant in organic chemistry, with a wide variety of applications, including pharmacology, pollution studies and genetic research. Among the simplest of these molecules is benzene (C6H6) , with many relevant molecules being benzene-like with a single atomic substitution. In such a substitution, the substituent determines a characteristic perturbation of the electronic structure of the molecule. We discuss the substitution of halogens into the ring (C6H5X), and its effects on the dynamics of ionization and dissociation of the molecule without the focal volume effect. In particular, using 800-nm, 50-fs laser pulses, we present results in the dissociation of fluorobenzene, chlorobenzene, bromobenzene and iodobenzene into the phenyl ring (C6H5) and the atomic halogen, and the subsequent ionization of these fragments. The impact of the ``heavy atom effect'' on a 1 (π , π*) -->3 (n , σ*) singlet-triplet intersystem crossing will be emphasized. Currently under investigation is whether such a dissociation can be treated as an effective source of the neutral substituent. This material is based upon work supported by the National Science Foundation under Grant No. PHY-0355235.

  5. Iridium-Catalyzed Allylic Substitution

    NASA Astrophysics Data System (ADS)

    Hartwig, John F.; Pouy, Mark J.

    Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced cyclometalation at the methyl group of this substituent to generate an iridium metalacycle bound by the COD ligand of the [Ir(COD)Cl]2 precursor and one additional labile dative ligand. Such complexes catalyze the reactions of linear allylic esters with alkylamines, arylamines, phenols, alcohols, imides, carbamates, ammonia, enolates and enolate equivalents, as well as typical stabilized carbon nucleophiles generated from malonates and cyanoesters. Iridium catalysts for enantioselective allylic substitution have also been generated from phosphorus ligands with substituents bound by heteroatoms, and an account of the studies of such systems, along with a description of the development of iridium catalysts is included.

  6. Shaped Ni nanoparticles with an unconventional hcp crystalline structure.

    PubMed

    Kim, Chanyeon; Kim, Cheonghee; Lee, Kangtaek; Lee, Hyunjoo

    2014-06-18

    Hourglass-shaped Ni nanoparticles were synthesized with a hexagonal close packed (hcp) structure. The unconventional crystalline structure could be stabilized by intensive utilization of hexadecylamine. The dense organic layer on the surface protected the meta-stable crystalline structure.

  7. Interaction of βA3-Crystallin with Deamidated Mutants of αA- and αB-Crystallins.

    PubMed

    Tiwary, Ekta; Hegde, Shylaja; Purushotham, Sangeetha; Deivanayagam, Champion; Srivastava, Om

    2015-01-01

    Interaction among crystallins is required for the maintenance of lens transparency. Deamidation is one of the most common post-translational modifications in crystallins, which results in incorrect interaction and leads to aggregate formation. Various studies have established interaction among the α- and β-crystallins. Here, we investigated the effects of the deamidation of αA- and αB-crystallins on their interaction with βA3-crystallin using surface plasmon resonance (SPR) and fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer (FLIM-FRET) methods. SPR analysis confirmed adherence of WT αA- and WT αB-crystallins and their deamidated mutants with βA3-crystallin. The deamidated mutants of αA-crystallin (αA N101D and αA N123D) displayed lower adherence propensity for βA3-crystallin relative to the binding affinity shown by WT αA-crystallin. Among αB-crystallin mutants, αB N78D displayed higher adherence propensity whereas αB N146D mutant showed slightly lower binding affinity for βA3-crystallin relative to that shown by WT αB-crystallin. Under the in vivo condition (FLIM-FRET), both αA-deamidated mutants (αA N101D and αA N123D) exhibited strong interaction with βA3-crystallin (32±4% and 36±4% FRET efficiencies, respectively) compared to WT αA-crystallin (18±4%). Similarly, the αB N78D and αB N146D mutants showed strong interaction (36±4% and 22±4% FRET efficiencies, respectively) with βA3-crystallin compared to 18±4% FRET efficiency of WT αB-crystallin. Further, FLIM-FRET analysis of the C-terminal domain (CTE), N-terminal domain (NTD), and core domain (CD) of αA- and αB-crystallins with βA3-crystallin suggested that interaction sites most likely reside in the αA CTE and αB NTD regions, respectively, as these domains showed the highest FRET efficiencies. Overall, results suggest that similar to WT αA- and WTαB-crystallins, the deamidated mutants showed strong interactionfor βA3-crystallin. Variable

  8. 40 CFR 721.1555 - Substituted phenyl azo substituted benzenediazonium salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... benzenediazonium salt. 721.1555 Section 721.1555 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1555 Substituted phenyl azo substituted benzenediazonium salt. (a... generically as a substituted phenyl azo substituted benzenediazonium salt (PMN P-92-652) is subject...

  9. 40 CFR 721.9545 - Substituted phenyl azo substituted sulfocarbopolycle, sodium salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... sulfocarbopolycle, sodium salt. 721.9545 Section 721.9545 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.9545 Substituted phenyl azo substituted sulfocarbopolycle, sodium salt... identified generically as a substituted phenyl azo substituted sulfocarbopolycle, sodium salt (PMN...

  10. 40 CFR 721.1555 - Substituted phenyl azo substituted benzenediazonium salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... benzenediazonium salt. 721.1555 Section 721.1555 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1555 Substituted phenyl azo substituted benzenediazonium salt. (a... generically as a substituted phenyl azo substituted benzenediazonium salt (PMN P-92-652) is subject...

  11. 40 CFR 721.9545 - Substituted phenyl azo substituted sulfocarbopolycle, sodium salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... sulfocarbopolycle, sodium salt. 721.9545 Section 721.9545 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.9545 Substituted phenyl azo substituted sulfocarbopolycle, sodium salt... identified generically as a substituted phenyl azo substituted sulfocarbopolycle, sodium salt (PMN...

  12. 40 CFR 721.1555 - Substituted phenyl azo substituted benzenediazonium salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... benzenediazonium salt. 721.1555 Section 721.1555 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1555 Substituted phenyl azo substituted benzenediazonium salt. (a... generically as a substituted phenyl azo substituted benzenediazonium salt (PMN P-92-652) is subject...

  13. 40 CFR 721.9545 - Substituted phenyl azo substituted sulfocarbopolycle, sodium salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... sulfocarbopolycle, sodium salt. 721.9545 Section 721.9545 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.9545 Substituted phenyl azo substituted sulfocarbopolycle, sodium salt... identified generically as a substituted phenyl azo substituted sulfocarbopolycle, sodium salt (PMN...

  14. 40 CFR 721.1555 - Substituted phenyl azo substituted benzenediazonium salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... benzenediazonium salt. 721.1555 Section 721.1555 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1555 Substituted phenyl azo substituted benzenediazonium salt. (a... generically as a substituted phenyl azo substituted benzenediazonium salt (PMN P-92-652) is subject...

  15. 40 CFR 721.1555 - Substituted phenyl azo substituted benzenediazonium salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... benzenediazonium salt. 721.1555 Section 721.1555 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1555 Substituted phenyl azo substituted benzenediazonium salt. (a... generically as a substituted phenyl azo substituted benzenediazonium salt (PMN P-92-652) is subject...

  16. 40 CFR 721.9545 - Substituted phenyl azo substituted sulfocarbopolycle, sodium salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... sulfocarbopolycle, sodium salt. 721.9545 Section 721.9545 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.9545 Substituted phenyl azo substituted sulfocarbopolycle, sodium salt... identified generically as a substituted phenyl azo substituted sulfocarbopolycle, sodium salt (PMN...

  17. 40 CFR 721.9545 - Substituted phenyl azo substituted sulfocarbopolycle, sodium salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... sulfocarbopolycle, sodium salt. 721.9545 Section 721.9545 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.9545 Substituted phenyl azo substituted sulfocarbopolycle, sodium salt... identified generically as a substituted phenyl azo substituted sulfocarbopolycle, sodium salt (PMN...

  18. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  19. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  20. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  1. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  2. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Butyl acrylate, polymer with... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  3. Dopant-specific unzipping of carbon nanotubes for intact crystalline graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Lim, Joonwon; Narayan Maiti, Uday; Kim, Na-Young; Narayan, Rekha; Jun Lee, Won; Sung Choi, Dong; Oh, Youngtak; Min Lee, Ju; Yong Lee, Gil; Hun Kang, Seok; Kim, Hyunwoo; Kim, Yong-Hyun; Ouk Kim, Sang

    2016-01-01

    Atomic level engineering of graphene-based materials is in high demand to enable customize structures and properties for different applications. Unzipping of the graphene plane is a potential means to this end, but uncontrollable damage of the two-dimensional crystalline framework during harsh unzipping reaction has remained a key challenge. Here we present heteroatom dopant-specific unzipping of carbon nanotubes as a reliable and controllable route to customized intact crystalline graphene-based nanostructures. Substitutional pyridinic nitrogen dopant sites at carbon nanotubes can selectively initiate the unzipping of graphene side walls at a relatively low electrochemical potential (0.6 V). The resultant nanostructures consisting of unzipped graphene nanoribbons wrapping around carbon nanotube cores maintain the intact two-dimensional crystallinity with well-defined atomic configuration at the unzipped edges. Large surface area and robust electrical connectivity of the synergistic nanostructure demonstrate ultrahigh-power supercapacitor performance, which can serve for AC filtering with the record high rate capability of -85° of phase angle at 120 Hz.

  4. Dopant-specific unzipping of carbon nanotubes for intact crystalline graphene nanostructures

    PubMed Central

    Lim, Joonwon; Narayan Maiti, Uday; Kim, Na-Young; Narayan, Rekha; Jun Lee, Won; Sung Choi, Dong; Oh, Youngtak; Min Lee, Ju; Yong Lee, Gil; Hun Kang, Seok; Kim, Hyunwoo; Kim, Yong-Hyun; Ouk Kim, Sang

    2016-01-01

    Atomic level engineering of graphene-based materials is in high demand to enable customize structures and properties for different applications. Unzipping of the graphene plane is a potential means to this end, but uncontrollable damage of the two-dimensional crystalline framework during harsh unzipping reaction has remained a key challenge. Here we present heteroatom dopant-specific unzipping of carbon nanotubes as a reliable and controllable route to customized intact crystalline graphene-based nanostructures. Substitutional pyridinic nitrogen dopant sites at carbon nanotubes can selectively initiate the unzipping of graphene side walls at a relatively low electrochemical potential (0.6 V). The resultant nanostructures consisting of unzipped graphene nanoribbons wrapping around carbon nanotube cores maintain the intact two-dimensional crystallinity with well-defined atomic configuration at the unzipped edges. Large surface area and robust electrical connectivity of the synergistic nanostructure demonstrate ultrahigh-power supercapacitor performance, which can serve for AC filtering with the record high rate capability of −85° of phase angle at 120 Hz. PMID:26796993

  5. Vacuolar processing enzyme plays an essential role in the crystalline structure of glutelin in rice seed.

    PubMed

    Kumamaru, Toshihiro; Uemura, Yuji; Inoue, Yoshimi; Takemoto, Yoko; Siddiqui, Sadar Uddin; Ogawa, Masahiro; Hara-Nishimura, Ikuko; Satoh, Hikaru

    2010-01-01

    To identify the function of genes that regulate the processing of proglutelin, we performed an analysis of glup3 mutants, which accumulates excess amounts of proglutelin and lack the vacuolar processing enzyme (VPE). VPE activity in developing seeds from glup3 lines was reduced remarkably compared with the wild type. DNA sequencing of the VPE gene in glup3 mutants revealed either amino acid substitutions or the appearance of a stop codon within the coding region. Microscopic observations showed that alpha-globulin and proglutelin were distributed homogeneously within glup3 protein storage vacuoles (PSVs), and that glup3 PSVs lacked the crystalline lattice structure typical of wild-type PSVs. This suggests that the processing of proglutelin by VPE in rice is essential for proper PSV structure and compartmentalization of storage proteins. Growth retardation in glup3 seedlings was also observed, indicating that the processing of proglutelin influences early seedling development. These findings indicate that storage of glutelin in its mature form as a crystalline structure in PSVs is required for the rapid use of glutelin as a source of amino acids during early seedling development. In conclusion, VPE plays an important role in the formation of protein crystalline structures in PSVs.

  6. Confinement and stability of a Crystalline Beam

    SciTech Connect

    Ruggiero, A.G.

    1993-05-10

    This technical report defines and describes a Crystalline Beam. This is an ordered state of matter made of electrically charged ions which are moving together in a storage ring with very high density and small velocity spread. In particular, the paper analyses the requirements for the confinement and the stability of the Beam. It is demonstrated that a storage ring made of one circular weak-focusing magnet, similar to a Betatron, is the most suitable for the confinement and stability of the Crystalline Beam. The disruptive effects of drift insertions have also been investigated. Requirements on final densities and velocity spreads are also calculated and reported. A matrix formalism is developed for the design of the storage ring. The important issue of the disruption caused by the curvature of the closed trajectory is not here discussed; it is the subject of a subsequent paper.

  7. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

    The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.

  8. Application of thermodynamics to silicate crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1972-01-01

    A review of thermodynamic relations is presented, describing Guggenheim's regular solution models, the simple mixture, the zeroth approximation, and the quasi-chemical model. The possibilities of retrieving useful thermodynamic quantities from phase equilibrium studies are discussed. Such quantities include the activity-composition relations and the free energy of mixing in crystalline solutions. Theory and results of the study of partitioning of elements in coexisting minerals are briefly reviewed. A thermodynamic study of the intercrystalline and intracrystalline ion exchange relations gives useful information on the thermodynamic behavior of the crystalline solutions involved. Such information is necessary for the solution of most petrogenic problems and for geothermometry. Thermodynamic quantities for tungstates (CaWO4-SrWO4) are calculated.

  9. Basic research challenges in crystalline silicon photovoltaics

    SciTech Connect

    Werner, J.H.

    1995-08-01

    Silicon is abundant, non-toxic and has an ideal band gap for photovoltaic energy conversion. Experimental world record cells of 24 % conversion efficiency with around 300 {mu}m thickness are only 4 % (absolute) efficiency points below the theoretical Auger recombination-limit of around 28 %. Compared with other photovoltaic materials, crystalline silicon has only very few disadvantages. The handicap of weak light absorbance may be mastered by clever optical designs. Single crystalline cells of only 48 {mu}m thickness showed 17.3 % efficiency even without backside reflectors. A technology of solar cells from polycrystalline Si films on foreign substrates arises at the horizon. However, the disadvantageous, strong activity of grain boundaries in Si could be an insurmountable hurdle for a cost-effective, terrestrial photovoltaics based on polycrystalline Si on foreign substrates. This talk discusses some basic research challenges related to a Si based photovoltaics.

  10. Nanoparticle Solubility in Liquid Crystalline Defects

    NASA Astrophysics Data System (ADS)

    Whitmer, Jonathan K.; Armas-Perez, Julio C.; Joshi, Abhijeet A.; Roberts, Tyler F.; de Pablo, Juan J.

    2013-03-01

    Liquid crystalline materials often incorporate regions (defects) where the orientational ordering present in the bulk phase is disrupted. These include point hedgehogs, line disclinations, and domain boundaries. Recently, it has been shown that defects will accumulate impurities such as small molecules, monomer subunits or nanoparticles. Such an effect is thought to be due to the alleviation of elastic stresses within the bulk phase, or to a solubility gap between a nematic phase and the isotropic defect core. This presents opportunities for encapsulation and sequestration of molecular species, in addition to the formation of novel structures within a nematic phase through polymerization and nanoparticle self-assembly. Here, we examine the solubility of nanoparticles within a coarse-grained liquid crystalline phase and demonstrate the effects of nanoparticle size and surface interactions in determining sequestration into defect regions.

  11. Nanoscale characterization of crystallinity in DSA® coating

    NASA Astrophysics Data System (ADS)

    Malmgren, C.; Hummelgård, M.; Bäckström, J.; Cornell, A.; Olin, H.

    2008-03-01

    Dimensionally Stable Anodes (DSA®) are used for industrial production of e.g. chlorine and chlorate. It is known that the superior electrocatalytical properties of DSA® is due to the large effective area of the porous coating. However, this knowledge is mainly found from in situ electrochemical measurements. Here, we used ex situ methods, AFM, TEM and gas porosimetry, for characterization at the nanoscale. The DSA® coating was found to consist of mono-crystalline grains with a size of 20-30 nm and with pores of about 10 nm in diameter. Using a simple geometrical model an effective area was calculated. For a typical coating thickness, an increase of about 1000 times in the effective surface area was found, which is consistent with in situ estimations. These results suggest that the dominating source of surface enlargement is due to nano-crystallinity.

  12. New transformations between crystalline and amorphous ice

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Chen, L. C.; Mao, H. K.

    1989-01-01

    High-pressure optical and spectroscopic techniques were used to obtain directly the ice I(h) - hda-ice transformation in a diamond-anvil cell, and the stability of the amorphous form is examined as functions of pressure and temperature. It is demonstrated that hda-ice transforms abruptly at 4 GPa and 77 K to a crystalline phase close in structure to orientationally disordered ice-VII and to a more highly ordered, ice-VIII-like structure at higher temperatures. This is the first time that an amorphous solid is observed to convert to a crystalline solid at low temperatures by compression alone. Phase transitions of this type may be relevant on icy planetary satellites, and there may also be implications for the high-pressure behavior of silica.

  13. Electronic Structure of Ti substituted hydroxyapatite: TiHap

    NASA Astrophysics Data System (ADS)

    Yin, Shuxia; Ellis, Donald

    2009-03-01

    Hydroxyapatite (Hap), with the chemical formula Ca10(PO4)6(OH)2, is the main mineral constituent of mammal tooth enamel and bone and has become an important biomaterial with medical applications. Hap also attracts increasing interest for use in environmental adsorbents and catalysts due to its porous nature and highly active ion-exchange character. Ti-modified Hap (TiHap) has been proved to possess high affinity to organic molecules and bacteria as well as high photocatalytic activity for their oxidative decomposition. The concentration of Ti^4+ is a key factor controlling TiHap crystallinity and catalytic efficiency. Here we studied the sorption mechanism of Ti^4+ on Hap using Density Functional Theory within periodic slab models. Ti^4+ or (Ti(OH)2)^2+, as the most likely ion exchange species with Ca^2+, were first considered in bulk Hap. A second charge compensated model considered includes both surface Ca ion vacancies and substitutional Ti^4+. To obtain insight of the energetic stability and microscopic crystal structure of TiHap, Ti substitution on different Ca sites and distributions at different atomic ratios are investigated in both bulk and surface models.

  14. Synthesis and Characterization of Zirconium Substituted Cobalt Ferrite Nanopowders

    SciTech Connect

    Rus, S. F.; Vlazan, P.; Herklotz, A.

    2016-01-01

    Nanocrystalline ferrites; CoFe2O4 (CFO) and CoFe1.9Zr0.1O4 (CFZO) have been synthesized through chemical coprecipitation method. Moreover, the role played by the zirconium ions in improving the magnetic and structural properties is analyzed. X-ray diffraction revealed a single-phase cubic spinel structure for both materials, where the crystallite size increases and the lattice parameter decreases with substitution of Zr. The average sizes of the nanoparticles are estimated to be 16-19 nm. These sizes are small enough to achieve the suitable signal to noise ratio in the high density recording media. An increase in the saturation magnetization with the substitution of Zr suggests the preferential occupation of Zr4+ ions in the tetrahedral sites. A decrease in the coercivity values indicates the reduction of magneto-crystalline anisotropy. We investigated spinel ferrites can be used also in recoding media due to the large value of coercivity 1000 Oe which is comparable to those of hard magnetic materials.

  15. Synthesis and Characterization of Zirconium Substituted Cobalt Ferrite Nanopowders

    DOE PAGES

    Rus, S. F.; Vlazan, P.; Herklotz, A.

    2016-01-01

    Nanocrystalline ferrites; CoFe2O4 (CFO) and CoFe1.9Zr0.1O4 (CFZO) have been synthesized through chemical coprecipitation method. Moreover, the role played by the zirconium ions in improving the magnetic and structural properties is analyzed. X-ray diffraction revealed a single-phase cubic spinel structure for both materials, where the crystallite size increases and the lattice parameter decreases with substitution of Zr. The average sizes of the nanoparticles are estimated to be 16-19 nm. These sizes are small enough to achieve the suitable signal to noise ratio in the high density recording media. An increase in the saturation magnetization with the substitution of Zr suggests themore » preferential occupation of Zr4+ ions in the tetrahedral sites. A decrease in the coercivity values indicates the reduction of magneto-crystalline anisotropy. We investigated spinel ferrites can be used also in recoding media due to the large value of coercivity 1000 Oe which is comparable to those of hard magnetic materials.« less

  16. Photorefractivity in liquid crystalline composite materials

    SciTech Connect

    Wiederrecht, G.P.; Wasielewski, M.R.

    1997-09-01

    We report recent improvements in the photorefractive of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfer reaction and improvement of the diffusion characteristics of the photogenerated ions. Intramolecular charge transfer dopants produce greater photorefractivity and a 10-fold decrease in the concentration of absorbing chromophores. The mechanism for the generation of mobile ions is discussed.

  17. University Crystalline Silicon Photovoltaics Research and Development

    SciTech Connect

    Ajeet Rohatgi; Vijay Yelundur; Abasifreke Ebong; Dong Seop Kim

    2008-08-18

    The overall goal of the program is to advance the current state of crystalline silicon solar cell technology to make photovoltaics more competitive with conventional energy sources. This program emphasizes fundamental and applied research that results in low-cost, high-efficiency cells on commercial silicon substrates with strong involvement of the PV industry, and support a very strong photovoltaics education program in the US based on classroom education and hands-on training in the laboratory.

  18. High efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Sah, C. T.

    1986-01-01

    The factors which may limit current crystalline silicon solar cells to less than 20 percent efficiency at AM 1 are investigated together with the factors which may limit the ultimate efficiency achievable. It was found that base recombination at residual defect and impurity recombination centers was the likely cause of the 20-percent efficiency barrier. Suggestions for design changes that would cut the losses due to recombinations are presented.

  19. Structural Characterization of Crystalline Ice Nanoclusters

    NASA Technical Reports Server (NTRS)

    Blake, David

    2000-01-01

    Water ice nanoclusters are useful analogs for studying a variety of processes that occur within icy grains in the extraterrestrial environment. The surface of ice nanoclusters prepared in the laboratory is similar to the surface of interstellar ice grains. In cold molecular clouds, the silicate cores of interstellar grains are typically approx. 100 nm in diameter and have a coating of impure amorphous water ice. Depositional, thermal and radiolytic processes leave the surface and subsurface molecules in a disordered state. In this state, structural defects become mobile and reactions of trapped gases and small molecules can occur. The large surface area of nanocluster deposits relative to their bulk allows for routine observation of such surface-mediated processes. Furthermore, the disordered surface and subsurface layers in nanocluster deposits mimic the structure of amorphous ice rinds found on interstellar dust grains. Transmission Electron Microscopy (TEM has been used tn characterize the crystallinity, growth mechanism, and size distribution of nanoclusters formed from a mixture of water vapor with an inert carrier gas that has been rapidly cooled to 77K. E M imaging reveals a Gaussian size distribution around a modal diameter that increases from approx. 15 to 30 nm as the percentage of water vapor within the mixture increases from 0.5 to 2.007, respectively . TEM bright and dark field imaging also reveals the crystalline nature of the clusters. h4any of the clusters show a mosaic structure in which crystalline domains originate at the center Other images show mirror planes that are separated by approx. 10 nm. Electron diffraction patterns of these clusters show that the clusters are composed of cubic ice with only a small hexagonal component. Further, the crystalline domain size is approximately the same as the modal diameter suggesting that the clusters are single crystals.

  20. Assessment of quartz materials crystallinity by x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Korovkin, M.; AnanIeva, L.; Nebera, T.; Antsiferova, A.

    2016-02-01

    The estimated degree of crystallinity of natural and synthetic grown quartz and quartzite by calculating the x-ray diffraction patterns. It is shown that the index of crystallinity of natural quartzite varies widely, reflecting the different degree of their transformation. The highest values of the index of crystallinity are characterized natural and synthetic single crystals of quartz.

  1. Effect of polylactic acid crystallinity on its electret properties

    NASA Astrophysics Data System (ADS)

    Guzhova, A. A.; Galikhanov, M. F.; Kuznetsova, N. V.; Petrov, V. A.; Khairullin, R. Z.

    2016-09-01

    Electret properties of the polylactic acid films with different degree of crystallinity due to different cooling and annealing conditions were studied. Samples with the higher degree of crystallinity showed more stable electret characteristics resulting from amorphous-crystalline interface boundary growth and capturing bigger amount of injected charge carriers by volume energy traps.

  2. The segal crystallinity index as it relates to crystallite size

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fibers are composed of crystals of cellulose that yield a diffraction pattern, although fibers from varying sources and histories are said to have different degrees of crystallinity. There are many methods to assess this crystallinity. One of the most popular is the Segal Crystallinity Index ...

  3. 21 CFR 522.313a - Ceftiofur crystalline free acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Ceftiofur crystalline free acid. 522.313a Section... § 522.313a Ceftiofur crystalline free acid. (a) Specifications. The product is a suspension of ceftiofur crystalline free acid. (1) Each milliliter (mL) contains 100 milligrams (mg) ceftiofur equivalents. (2) Each...

  4. 21 CFR 522.313a - Ceftiofur crystalline free acid.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Ceftiofur crystalline free acid. 522.313a Section... § 522.313a Ceftiofur crystalline free acid. (a) Specifications. The product is a suspension of ceftiofur crystalline free acid. (1) Each milliliter (mL) contains 100 milligrams (mg) ceftiofur equivalents. (2) Each...

  5. 21 CFR 522.313a - Ceftiofur crystalline free acid.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Ceftiofur crystalline free acid. 522.313a Section... § 522.313a Ceftiofur crystalline free acid. (a) Specifications. The product is a suspension of ceftiofur crystalline free acid. (1) Each milliliter (mL) contains 100 milligrams (mg) ceftiofur equivalents. (2) Each...

  6. 21 CFR 522.313a - Ceftiofur crystalline free acid.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Ceftiofur crystalline free acid. 522.313a Section... § 522.313a Ceftiofur crystalline free acid. (a) Specifications. The product is a suspension of ceftiofur crystalline free acid. (1) Each milliliter (mL) contains 100 milligrams (mg) ceftiofur equivalents. (2) Each...

  7. Crystalline to amorphous transformation in silicon

    SciTech Connect

    Cheruvu, S.M.

    1982-09-01

    In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects.

  8. The thermodynamic scale of inorganic crystalline metastability.

    PubMed

    Sun, Wenhao; Dacek, Stephen T; Ong, Shyue Ping; Hautier, Geoffroy; Jain, Anubhav; Richards, William D; Gamst, Anthony C; Persson, Kristin A; Ceder, Gerbrand

    2016-11-01

    The space of metastable materials offers promising new design opportunities for next-generation technological materials, such as complex oxides, semiconductors, pharmaceuticals, steels, and beyond. Although metastable phases are ubiquitous in both nature and technology, only a heuristic understanding of their underlying thermodynamics exists. We report a large-scale data-mining study of the Materials Project, a high-throughput database of density functional theory-calculated energetics of Inorganic Crystal Structure Database structures, to explicitly quantify the thermodynamic scale of metastability for 29,902 observed inorganic crystalline phases. We reveal the influence of chemistry and composition on the accessible thermodynamic range of crystalline metastability for polymorphic and phase-separating compounds, yielding new physical insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compounds can necessarily be synthesized, and propose a principle of 'remnant metastability'-that observable metastable crystalline phases are generally remnants of thermodynamic conditions where they were once the lowest free-energy phase.

  9. Partial Crystallinity in Alkyl Side Chain Polymers.

    NASA Astrophysics Data System (ADS)

    Sahni, Vasav; Prasad, Shishir; Villate, Johanna; Jiang, Zhang; Sinha, Sunil; Dhinojwala, Ali

    2009-03-01

    Surface freezing is the formation of a crystalline monolayer at the free surface of a melt at a temperature Ts, a few degrees above the bulk freezing temperature, Tb. This effect, i.e. Ts> Tb, common to many chain molecules, is in marked contrast with the surface melting effect, i.e. Ts<=Tb, shown by almost all other materials. Various theoretical and experimental studies have been done to characterize the monolayer formed when the surface freezes before the bulk. We have studied the structure of a novel crystalline surface monolayer on top of a disordered melt of the same material (poly(n-alkyl acrylate)s) using grazing incidence x-ray diffraction. The grazing incidence x-ray diffraction, surface tension, and bulk latent heat results show that there is partial side-chain crystallinity. Also, the surface tension results explain the trend of the difference between the surface order-to-disorder transition temperature and the bulk melting temperature (δT) as a function of side chain length. The behavior of the crystal length, crystal spacing and tilt with varying alkyl chain length and temperature was also studied.

  10. Properties of crystalline phase in waste glass

    SciTech Connect

    Usami, T.; Uruga, K.; Tsukada, T.; Miura, Y.; Komamine, S.; Ochi, E.

    2013-07-01

    Depending on the operating conditions of the vitrification process of high-level liquid waste, some crystalline phases can be present. The crystalline phase exists as molten salt at glass melting temperature. In this study, the chemical and physical properties of the crystalline phase were determined. Two samples rich in Mo and a sample rich in Re were examined. One of the samples rich in Mo was obtained from simulated waste solution and glass beads in a middle scale melter, while two other samples were made from mixed reagents. The chemical forms of the constituents were determined by XRD and SEM-EDX. When Mo is dominant, the crystal is mainly composed of molybdates of Na, Li, Ba and Ca, Na{sub 2}SO{sub 4} and CsReO{sub 4}. When Re is dominant, (Na{sub x}Cs{sub 1-x})ReO{sub 4} and NaLiMoO{sub 4} are added. The characteristic temperature and the heat of transition were determined by differential scanning calorimetry. The density of the molten salt at high temperature was measured from buoyancy. The density of the molten salt is larger than that of molten glass, and increases with Re content. (authors)

  11. Stamp forming optimization for formability and crystallinity

    NASA Astrophysics Data System (ADS)

    Donderwinkel, T. G.; Rietman, B.; Haanappel, S. P.; Akkerman, R.

    2016-10-01

    The stamp forming process is well suited for high volume production of thermoplastic composite parts. The process can be characterized as highly non-isothermal as it involves local quench-cooling of a molten thermoplastic composite blank where it makes contact with colder tooling. The formability of the thermoplastic composite depends on the viscoelastic material behavior of the matrix material, which is sensitive to temperature and degree of crystallinity. An experimental study was performed to determine the effect of temperature and crystallinity on the storage modulus during cooling for a woven glass fiber polyamide-6 composite material. An increase of two decades in modulus was observed during crystallization. As this will significantly impede the blank formability, the onset of crystallization effectively governs the time available for forming. Besides the experimental work, a numerical model is developed to study the temperature and crystallinity throughout the stamp forming process. A process window can be determined by feeding the model with the experimentally obtained data on crystallization.

  12. Molecular Sensing by Nanoporous Crystalline Polymers

    PubMed Central

    Pilla, Pierluigi; Cusano, Andrea; Cutolo, Antonello; Giordano, Michele; Mensitieri, Giuseppe; Rizzo, Paola; Sanguigno, Luigi; Venditto, Vincenzo; Guerra, Gaetano

    2009-01-01

    Chemical sensors are generally based on the integration of suitable sensitive layers and transducing mechanisms. Although inorganic porous materials can be effective, there is significant interest in the use of polymeric materials because of their easy fabrication process, lower costs and mechanical flexibility. However, porous polymeric absorbents are generally amorphous and hence present poor molecular selectivity and undesired changes of mechanical properties as a consequence of large analyte uptake. In this contribution the structure, properties and some possible applications of sensing polymeric films based on nanoporous crystalline phases, which exhibit all identical nanopores, will be reviewed. The main advantages of crystalline nanoporous polymeric materials with respect to their amorphous counterparts are, besides a higher selectivity, the ability to maintain their physical state as well as geometry, even after large guest uptake (up to 10–15 wt%), and the possibility to control guest diffusivity by controlling the orientation of the host polymeric crystalline phase. The final section of the review also describes the ability of suitable polymeric films to act as chirality sensors, i.e., to sense and memorize the presence of non-racemic volatile organic compounds. PMID:22303150

  13. The thermodynamic scale of inorganic crystalline metastability

    PubMed Central

    Sun, Wenhao; Dacek, Stephen T.; Ong, Shyue Ping; Hautier, Geoffroy; Jain, Anubhav; Richards, William D.; Gamst, Anthony C.; Persson, Kristin A.; Ceder, Gerbrand

    2016-01-01

    The space of metastable materials offers promising new design opportunities for next-generation technological materials, such as complex oxides, semiconductors, pharmaceuticals, steels, and beyond. Although metastable phases are ubiquitous in both nature and technology, only a heuristic understanding of their underlying thermodynamics exists. We report a large-scale data-mining study of the Materials Project, a high-throughput database of density functional theory–calculated energetics of Inorganic Crystal Structure Database structures, to explicitly quantify the thermodynamic scale of metastability for 29,902 observed inorganic crystalline phases. We reveal the influence of chemistry and composition on the accessible thermodynamic range of crystalline metastability for polymorphic and phase-separating compounds, yielding new physical insights that can guide the design of novel metastable materials. We further assert that not all low-energy metastable compounds can necessarily be synthesized, and propose a principle of ‘remnant metastability’—that observable metastable crystalline phases are generally remnants of thermodynamic conditions where they were once the lowest free-energy phase. PMID:28138514

  14. Strontium incorporation to optimize the antibacterial and biological characteristics of silver-substituted hydroxyapatite coating.

    PubMed

    Geng, Zhen; Cui, Zhenduo; Li, Zhaoyang; Zhu, Shengli; Liang, Yanqin; Liu, Yunde; Li, Xue; He, Xin; Yu, Xiaoxu; Wang, Renfeng; Yang, Xianjin

    2016-01-01

    Infection in primary total joint prostheses is attracting considerable attention. In this study, silver (Ag) was incorporated into hydroxyapatite (HA) using a hydrothermal method in order to improve its antimicrobial properties. Strontium (Sr) was added as a second binary element to improve the biocompatibility. The substituted HA samples were fixed on titanium (Ti) substrates by dopamine-assisted immobilization in order to evaluate their antibacterial and biological properties. The results showed that Ag and Sr were successfully incorporated into HA without affecting their crystallinity. Further, the antibacterial tests showed that all the Ag-substituted samples had good anti-bacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Despite their good antibacterial ability, the Ag-substituted samples showed evidence of cytotoxicity on MG63 cells, characterized by low cell density and poor spreadability. The addition of Sr to the Ag-substituted samples considerably reduced the cytotoxicity of Ag. Although the viability of the cells grown on the surfaces of co-substituted HA was not as high as that of the cells grown on the HA surfaces, it is believed that excellent antibacterial properties and good biological activity can be achieved by balancing the dosage of Sr and Ag.

  15. Epoxy + liquid crystalline epoxy coreacted network

    NASA Astrophysics Data System (ADS)

    Punchaipetch, Prakaipetch

    2000-10-01

    Molecular reinforcement through in-situ polymerization of liquid crystalline epoxies (LCEs) and a non-liquid crystalline epoxy has been investigated. Three LCEs: diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) and digylcidyl ether of 4-hydroxyphenyl-4″-hydroxybiphenyl-4 '-carboxylate (DGE-HHC), were synthesized and blended with diglycidyl ether of bisphenol F (DGEBP-F) and subsequently cured with anhydride and amine curing agents. Curing kinetics were determined using differential scanning calorimetry (DSC). Parameters for autocatalytic curing kinetics of both pure monomers and blended systems were determined. The extent of cure for both monomers was monitored by using Fourier transform infrared spectroscopy (FT-IR). The glass transitions were evaluated as a function of composition using DSC and dynamic mechanical analysis (DMA). The results show that the LC constituent affects the curing kinetics of the epoxy resin and that the systems are highly miscible. The effects of molecular reinforcement of DGEBP-F by DGE-DHBP and DGE-HHC were investigated. The concentration of the liquid crystalline moiety affects mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Scanning electron microscopy of the fracture surfaces shows changes in failure mechanisms compared to the pure components. Results indicate that mechanical properties of the blended samples are improved already at low concentration by weight of the LCE added into epoxy resin. The improvement in mechanical properties was found to occur irrespective of the absence of liquid crystallinity in the blended networks. The mechanism of crack study indicates that crack deflection and crack bridging are the mechanisms in case of LC epoxy. In case of LC modified epoxy, the crack deflection is the main mechanism. Moreover, the effect of coreacting an epoxy with a reactive monomer liquid crystalline epoxy as a matrix for glass fiber composites was investigated. Mechanical

  16. Generation of crystalline silica from sugarcane burning.

    PubMed

    Le Blond, Jennifer S; Horwell, Claire J; Williamson, Ben J; Oppenheimer, Clive

    2010-07-08

    Sugarcane leaves contain amorphous silica, which may crystallise to form crystalline silica polymorphs (cristobalite or quartz), during commercial sugarcane harvesting where sugarcane plants are burned. Respirable airborne particulate containing these phases may present an occupational health hazard. Following from an earlier pilot study (J. S. Le Blond, B. J. Williamson, C. J. Horwell, A. K. Monro, C. A. Kirk and C. Oppenheimer, Atmos. Environ., 2008, 42, 5558-5565) in which experimental burning of sugarcane leaves yielded crystalline silica, here we report on actual conditions during sugarcane burning on commercial estates, investigate the physico-chemical properties of the cultivated leaves and ash products, and quantify the presence of crystalline silica. Commercially grown raw sugarcane leaf was found to contain up to 1.8 wt% silica, mostly in the form of amorphous silica bodies (with trace impurities e.g., Al, Na, Mg), with only a small amount of quartz. Thermal images taken during several pre-harvest burns recorded temperatures up to 1056 degrees C, which is sufficient for metastable cristobalite formation. No crystalline silica was detected in airborne particulate from pre-harvest burning, collected using a cascade impactor. The sugarcane trash ash formed after pre-harvest burning contained between 10 and 25 wt% SiO(2), mostly in an amorphous form, but with up to 3.5 wt% quartz. Both quartz and cristobalite were identified in the sugarcane bagasse ash (5-15 wt% and 1-3 wt%, respectively) formed in the processing factory. Electron microprobe analysis showed trace impurities of Mg, Al and Fe in the silica particles in the ash. The absence of crystalline silica in the airborne emissions and lack of cristobalite in trash ash suggest that high temperatures during pre-harvest burning were not sustained long enough for cristobalite to form, which is supported by the presence of low temperature sylvite and calcite in the residual ash. The occurrence of quartz and

  17. Injectability of brushite-forming Mg-substituted and Sr-substituted alpha-TCP bone cements.

    PubMed

    Pina, S; Torres, P M C; Ferreira, J M F

    2010-02-01

    The influence of magnesium- and strontium-substitutions on injectability and mechanical performance of brushite-forming alpha-TCP cements has been evaluated in the present work. The effects of Mg- and Sr-substitutions on crystalline phase composition and lattice parameters were determined through quantitative X-ray phase analysis and structural Rietveld refinement of the starting calcium phosphate powders and of the hardened cements. A noticeable dependence of injectability on the liquid-to-powder ratio (LPR), smooth plots of extrusion force versus syringe plunger displacement and the absence of filter pressing effects were observed. For LPR values up to 0.36 ml g(-1), the percentage of injectability was always higher and lower for Mg-containing cements and for Sr-containing cements, respectively, while all the pastes could be fully injected for LPR > 0.36 ml g(-1). The hardened cements exhibited relatively high wet compressive strength values (~17-25 MPa) being the Sr- and Mg-containing cements the strongest and the weakest, respectively, holding an interesting promise for uses in trauma surgery such as for filling bone defects and in minimally invasive techniques such as percutaneous vertebroplasty to fill lesions and strengthen the osteoporotic bone.

  18. Functional Validation of Hydrophobic Adaptation to Physiological Temperature in the Small Heat Shock Protein αA-crystallin

    PubMed Central

    Posner, Mason; Kiss, Andor J.; Skiba, Jackie; Drossman, Amy; Dolinska, Monika B.; Hejtmancik, J. Fielding; Sergeev, Yuri V.

    2012-01-01

    Small heat shock proteins (sHsps) maintain cellular homeostasis by preventing stress and disease-induced protein aggregation. While it is known that hydrophobicity impacts the ability of sHsps to bind aggregation-prone denaturing proteins, the complex quaternary structure of globular sHsps has made understanding the significance of specific changes in hydrophobicity difficult. Here we used recombinant protein of the lenticular sHsp α A-crystallin from six teleost fishes environmentally adapted to temperatures ranging from -2°C to 40°C to identify correlations between physiological temperature, protein stability and chaperone-like activity. Using sequence and structural modeling analysis we identified specific amino acid differences between the warm adapted zebrafish and cold adapted Antarctic toothfish that could contribute to these correlations and validated the functional consequences of three specific hydrophobicity-altering amino acid substitutions in αA-crystallin. Site directed mutagenesis of three residues in the zebrafish (V62T, C143S, T147V) confirmed that each impacts either protein stability or chaperone-like activity or both, with the V62T substitution having the greatest impact. Our results indicate a role for changing hydrophobicity in the thermal adaptation of α A-crystallin and suggest ways to produce sHsp variants with altered chaperone-like activity. These data also demonstrate that a comparative approach can provide new information about sHsp function and evolution. PMID:22479631

  19. What happened to blood substitutes?

    PubMed

    Stowell, C P

    2005-11-01

    Concerns about the safety and adequacy of the blood supply have fostered twenty years of research into the so-called "blood substitutes" among them the oxygen carriers based on modified hemoglobin. Although none of these materials has yet been licensed for use in North America or Europe, the results of research and clinical trials have increased our understanding of oxygen delivery and its regulation. In particular, the examination of the basis for the vasoactivity observed with some of the hemoglobin based oxygen carriers has led to the insight that several colligative properties of hemoglobin solutions, such as their diffusion coefficient for oxygen, viscosity and colloid oncotic pressure, are important determinants of efficacy.

  20. Synthesis and properties of alkoxy- and alkenyl-substituted peralkylated imidazolium ionic liquids.

    PubMed

    Maton, Cedric; Brooks, Neil R; Van Meervelt, Luc; Binnemans, Koen; Schaltin, Stijn; Fransaer, Jan; Stevens, Christian V

    2013-10-21

    Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2](-)), and dicyanamide {[N(CN)2](-)} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2](-) and [N(CN)2](-). For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials.

  1. Use This Test to Spruce Up Your Substitute Teacher Program.

    ERIC Educational Resources Information Center

    Sendor, Elizabeth

    1982-01-01

    Presents and interprets an 18-question test to determine how well a school's substitute teacher program functions. Topics covered include substitute teacher screening and preparation, lists of substitutes, lesson plans, staff and student evaluation of substitutes, substitutes' salaries, legal considerations, and making substitutes feel needed.…

  2. Biologic and synthetic skin substitutes: An overview.

    PubMed

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd Yussof, Shah Jumaat

    2010-09-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing.

  3. Biologic and synthetic skin substitutes: An overview

    PubMed Central

    Halim, Ahmad Sukari; Khoo, Teng Lye; Mohd. Yussof, Shah Jumaat

    2010-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. Skin substitutes have important roles in the treatment of deep dermal and full thickness wounds of various aetiologies. At present, there is no ideal substitute in the market. Skin substitutes can be divided into two main classes, namely, biological and synthetic substitutes. The biological skin substitutes have a more intact extracellular matrix structure, while the synthetic skin substitutes can be synthesised on demand and can be modulated for specific purposes. Each class has its advantages and disadvantages. The biological skin substitutes may allow the construction of a more natural new dermis and allow excellent re-epithelialisation characteristics due to the presence of a basement membrane. Synthetic skin substitutes demonstrate the advantages of increase control over scaffold composition. The ultimate goal is to achieve an ideal skin substitute that provides an effective and scar-free wound healing. PMID:21321652

  4. Application of the Crystalline Sponge Method to Revise the Structure of the Phenalenone Fuliginone.

    PubMed

    Brkljača, Robert; Schneider, Bernd; Hidalgo, William; Otálvaro, Felipe; Ospina, Felipe; Lee, Shoukou; Hoshino, Manabu; Fujita, Makoto; Urban, Sylvia

    2017-01-30

    The structure of fuliginone was revised from a phenyl substituted phenalenone to a hydroxyl substituted phenalenone as a result of its re-purification via HPLC with subsequent NMR analysis together with an independent synthesis and analysis of the crystal structure, which was secured via the crystalline sponge method. On-flow High Performance Liquid Chromatography coupled to Nuclear Magnetic Resonance spectroscopy (HPLC-NMR) was employed to confirm the presence of the natural product in the plant extract and to monitor for any possible degradation or conversion of the compound.

  5. Solution properties of γ-crystallins: Hydration of fish and mammal γ-crystallins

    PubMed Central

    Zhao, Huaying; Chen, Yingwei; Rezabkova, Lenka; Wu, Zhengrong; Wistow, Graeme; Schuck, Peter

    2014-01-01

    Lens γ crystallins are found at the highest protein concentration of any tissue, ranging from 300 mg/mL in some mammals to over 1000 mg/mL in fish. Such high concentrations are necessary for the refraction of light, but impose extreme requirements for protein stability and solubility. γ-crystallins, small stable monomeric proteins, are particularly associated with the lowest hydration regions of the lens. Here, we examine the solvation of selected γ-crystallins from mammals (human γD and mouse γS) and fish (zebrafish γM2b and γM7). The thermodynamic water binding coefficient B1 could be probed by sucrose expulsion, and the hydrodynamic hydration shell of tightly bound water was probed by translational diffusion and structure-based hydrodynamic boundary element modeling. While the amount of tightly bound water of human γD was consistent with that of average proteins, the water binding of mouse γS was found to be relatively low. γM2b and γM7 crystallins were found to exhibit extremely low degrees hydration, consistent with their role in the fish lens. γM crystallins have a very high methionine content, in some species up to 15%. Structure-based modeling of hydration in γM7 crystallin suggests low hydration is associated with the large number of surface methionine residues, likely in adaptation to the extremely high concentration and low hydration environment in fish lenses. Overall, the degree of hydration appears to balance stability and tissue density requirements required to produce and maintain the optical properties of the lens in different vertebrate species. PMID:24282025

  6. Cement from magnesium substituted hydroxyapatite.

    PubMed

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  7. Substitutional doping in nanocrystal superlattices

    NASA Astrophysics Data System (ADS)

    Cargnello, Matteo; Johnston-Peck, Aaron C.; Diroll, Benjamin T.; Wong, Eric; Datta, Bianca; Damodhar, Divij; Doan-Nguyen, Vicky V. T.; Herzing, Andrew A.; Kagan, Cherie R.; Murray, Christopher B.

    2015-08-01

    Doping is a process in which atomic impurities are intentionally added to a host material to modify its properties. It has had a revolutionary impact in altering or introducing electronic, magnetic, luminescent, and catalytic properties for several applications, for example in semiconductors. Here we explore and demonstrate the extension of the concept of substitutional atomic doping to nanometre-scale crystal doping, in which one nanocrystal is used to replace another to form doped self-assembled superlattices. Towards this goal, we show that gold nanocrystals act as substitutional dopants in superlattices of cadmium selenide or lead selenide nanocrystals when the size of the gold nanocrystal is very close to that of the host. The gold nanocrystals occupy random positions in the superlattice and their density is readily and widely controllable, analogous to the case of atomic doping, but here through nanocrystal self-assembly. We also show that the electronic properties of the superlattices are highly tunable and strongly affected by the presence and density of the gold nanocrystal dopants. The conductivity of lead selenide films, for example, can be manipulated over at least six orders of magnitude by the addition of gold nanocrystals and is explained by a percolation model. As this process relies on the self-assembly of uniform nanocrystals, it can be generally applied to assemble a wide variety of nanocrystal-doped structures for electronic, optical, magnetic, and catalytic materials.

  8. Biomimetic processing of oriented crystalline ceramic layers

    SciTech Connect

    Cesarano, J.; Shelnutt, J.A.

    1997-10-01

    The aim of this project was to develop the capabilities for Sandia to fabricate self assembled Langmuir-Blodgett (LB) films of various materials and to exploit their two-dimensional crystalline structure to promote the growth of oriented thin films of inorganic materials at room temperature. This includes the design and synthesis of Langmuir-active (amphiphilic) organic molecules with end groups offering high nucleation potential for various ceramics. A longer range goal is that of understanding the underlying principles, making it feasible to use the techniques presented in this report to fabricate unique oriented films of various materials for electronic, sensor, and membrane applications. Therefore, whenever possible, work completed in this report was completed with the intention of addressing the fundamental phenomena underlying the growth of crystalline, inorganic films on template layers of highly organized organic molecules. This problem was inspired by biological processes, which often produce exquisitely engineered structures via templated growth on polymeric layers. Seashells, for example, exhibit great toughness owing to their fine brick-and-mortar structure that results from templated growth of calcium carbonate on top of layers of ordered organic proteins. A key goal in this work, therefore, is to demonstrate a positive correlation between the order and orientation of the template layer and that of the crystalline ceramic material grown upon it. The work completed was comprised of several parallel efforts that encompassed the entire spectrum of biomimetic growth from solution. Studies were completed on seashells and the mechanisms of growth for calcium carbonate. Studies were completed on the characterization of LB films and the capability developed for the in-house fabrication of these films. Standard films of fatty acids were studied as well as novel polypeptides and porphyrins that were synthesized.

  9. Raman Spectroscopy Of Glass-Crystalline Transformations

    NASA Astrophysics Data System (ADS)

    Haro, E.; Balkanski, M.

    1988-01-01

    Glass-crystalline transition is induced by laser irradiation on a GeSe bulk glass sample. The structural changes are detected by Raman spectroscopy. The speed of the crystallization process depends on the laser irradiation intensity. We have studied this crystallization process for three different powers of irradiation. It is found that the speed of crystallization increases with power. Stokes and anti-Stokes spectra were recorded during the transformation. From this data temperature was inferred at different stages of crystallization. The significance of this temperature is discussed.

  10. Pattern formation and coarsening in crystalline membranes

    NASA Astrophysics Data System (ADS)

    Vega, Daniel A.; Pezzutti, Aldo D.

    2011-03-01

    We study through a Brazovskii-Helfrich Hamiltonian the process of defect formation, annealing and coarsening of two dimensional crystalline membranes. In good agreement with the cosmological model of Kibble and Zurek, proposed to determine the density of topological defects at the onset of a symmetry breaking phase transition, we found that the collision of orientationally uncorrelated domains produces a structure of grains with an average density of topological defects controlled by the temperature of the quench. The strain field of the dislocations and disclinations generated during the phase separation process can induce the buckling of the membrane, slowing down the Lifshitz-Safran mechanism of coarsening observed in flat systems.

  11. Defect dynamics in crystalline buckled membranes

    NASA Astrophysics Data System (ADS)

    Pezzutti, Aldo D.; Vega, Daniel A.

    2011-07-01

    We study the dynamics of defect annihilation in flexible crystalline membranes suffering a symmetry-breaking phase transition. The kinetic process leading the system toward equilibrium is described through a Brazovskii-Helfrich-Canham Hamiltonian. In membranes, a negative disclination has a larger energy than a positive disclination. Here we show that this energetic asymmetry does not only affect equilibrium properties, like the Kosterlitz-Thouless transition temperature, but also plays a fundamental role in the dynamic of defects. Both unbinding of dislocations and Carraro-Nelson “antiferromagnetic” interactions between disclinations slow down the dynamics below the Lifshitz-Safran regime observed in flat hexagonal systems.

  12. Controlled synthesis of single-crystalline graphene

    SciTech Connect

    Xueshen, Wang Jinjin, Li Qing, Zhong; Yuan, Zhong; Mengke, Zhao; Yonggang, Liu

    2014-03-15

    This paper reports the controlled synthesis of single-crystalline graphene on the back side of copper foil using CH{sub 4} as the precursor. The influence of growth time and the pressure ratio of CH{sub 4}/H{sub 2} on the structure of graphene are examined. An optimized polymer-assisted method is used to transfer the synthesized graphene onto a SiO{sub 2}/Si substrate. Scanning electron microscopy and Raman spectroscopy are used to characterize the graphene.

  13. Crystalline silicotitanates for cesium/strontium removal

    SciTech Connect

    Brown, N.; Miller, J.; Sherman, J.

    1996-10-01

    A new class of inorganic ion exchangers called crystalline silicotitanates (CST) has been developed that exhibits very high selectivity for cesium and strontium in the highly alkaline radioactive wastes at the Hanford Site and other DOE sites. Tests have also shown that CSTs have high selectivity for cesium in acidic and neutral solutions. The ESP is supporting an effort at Sandia National Laboratories and Texas A & M University to further develop and characterize the important chemical and physical properties that will determine the applicability of CST to radioactive waste treatment at Hanford and other DOE facilities.

  14. Vibrational dynamics of crystalline L-alanine

    SciTech Connect

    Bordallo, H.N.; Eckert, J.; Barthes, M.

    1997-11-01

    The authors report a new, complete vibrational analysis of L-alanine and L-alanine-d{sub 4} which utilizes IINS intensities in addition to frequency information. The use of both isotopomers resulted in a self-consistent force field for and assignment of the molecular vibrations in L-alanine. Some details of the calculation as well as a comparison of calculated and observed IINS spectra are presented. The study clarifies a number of important issues on the vibrational dynamics of this molecule and presents a self-consistent force field for the molecular vibrations in crystalline L-alanine.

  15. Superacid Passivation of Crystalline Silicon Surfaces.

    PubMed

    Bullock, James; Kiriya, Daisuke; Grant, Nicholas; Azcatl, Angelica; Hettick, Mark; Kho, Teng; Phang, Pheng; Sio, Hang C; Yan, Di; Macdonald, Daniel; Quevedo-Lopez, Manuel A; Wallace, Robert M; Cuevas, Andres; Javey, Ali

    2016-09-14

    The reduction of parasitic recombination processes commonly occurring within the silicon crystal and at its surfaces is of primary importance in crystalline silicon devices, particularly in photovoltaics. Here we explore a simple, room temperature treatment, involving a nonaqueous solution of the superacid bis(trifluoromethane)sulfonimide, to temporarily deactivate recombination centers at the surface. We show that this treatment leads to a significant enhancement in optoelectronic properties of the silicon wafer, attaining a level of surface passivation in line with state-of-the-art dielectric passivation films. Finally, we demonstrate its advantage as a bulk lifetime and process cleanliness monitor, establishing its compatibility with large area photoluminescence imaging in the process.

  16. Optical density of the crystalline lens

    SciTech Connect

    Hemenger, R.P.

    1982-01-01

    The optical density for the noncataractous crystalline lens is written as a sum of two terms, each with a specific dependence on wavelength. The first term, proportional to 1/lambda 2, represents all light-scattering processes in the lens. The second term, assumed significant only for lambda less than or equal to 500 nm, accounts for absorption by lens pigments. By analyzing transmittance data on lenses of subjects aged 21 to 63 years, a spectrum for light absorption by lens pigment is derived and it is shown to be essentially the same for all of the lenses.

  17. Substitution rates in hepatitis delta virus.

    PubMed

    Krushkal, J; Li, W H

    1995-12-01

    Substitution rates were estimated for the coding and noncoding regions of the hepatitis delta virus (HDV). The estimated rates of synonymous substitution in HDV were lower than the rates of substitution at non-synonymous sites and in the noncoding region. HDV has lower synonymous substitution rates than the hepatitis C virus, though both are RNA viruses. The relatively low rate of synonymous substitution in HDV may be due to a strong preference of G and C nucleotides at third codon positions. Variation in substitution rate among HDV lineages may be correlated with the clinical development of the HDV-induced hepatitis. The phylogenetic tree inferred for 24 HDV strains reveals similarities between lineages isolated from the same geographic region.

  18. Computational study of cation substitutions in apatites

    SciTech Connect

    Tamm, Toomas . E-mail: tamm@yki.ttu.ee; Peld, Merike

    2006-05-15

    Density-functional theory plane-wave modeling of fluor- and hydroxyapatites has been performed, where one or two calcium ions per unit cell were replaced with cadmium or zinc cations. It was found that cadmium ions favor Ca(1) positions in fluorapatites and Ca(2) positions in hydroxyapatites, in agreement with experiment. A similar pattern is predicted for zinc substitutions. In the doubly substituted cases, where only hydroxyapatites were modeled, a preference for the substituting ions to be located in Ca(2) position was also observed. Displacement of the hydroxide ions from their symmetrical positions on the hexagonal axis can be used to explain the preferred configurations of substituting ions around the axis. -- Deformation of the hydroxide ion chain due to substitutions around the ion channel in substituted hydroxyapatites.

  19. Blood Substitutes: Effects on Drug Pharmacokinetics.

    DTIC Science & Technology

    1984-03-01

    RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS 1963-A - S . *.* , S. AD __ _ _ _ _? ,:-:t’ REPORT NUMBER: 2 BLOOD SUBSTITUTES: EFFECTS ON DRUG ...ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER.1-t 4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED FINAL REPORT BLOOD SUBSTITUTES: EFFECTS ON DRUG ...Identify by block number) Blood substitutes; perfluorocarbons; stroma-free hemoglobin; drug pharmaco- kinetics S. ADST RACT (Cn*tfe am revere dm* if

  20. Strong liquid-crystalline polymeric compositions

    DOEpatents

    Dowell, F.

    1993-12-07

    Strong liquid-crystalline polymeric (LCP) compositions of matter are described. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment. 27 figures.

  1. Strong liquid-crystalline polymeric compositions

    DOEpatents

    Dowell, Flonnie

    1993-01-01

    Strong liquid-crystalline polymeric (LCP) compositions of matter. LCP backbones are combined with liquid crystalline (LC) side chains in a manner which maximizes molecular ordering through interdigitation of the side chains, thereby yielding materials which are predicted to have superior mechanical properties over existing LCPs. The theoretical design of LCPs having such characteristics includes consideration of the spacing distance between side chains along the backbone, the need for rigid sections in the backbone and in the side chains, the degree of polymerization, the length of the side chains, the regularity of the spacing of the side chains along the backbone, the interdigitation of side chains in sub-molecular strips, the packing of the side chains on one or two sides of the backbone to which they are attached, the symmetry of the side chains, the points of attachment of the side chains to the backbone, the flexibility and size of the chemical group connecting each side chain to the backbone, the effect of semiflexible sections in the backbone and the side chains, and the choice of types of dipolar and/or hydrogen bonding forces in the backbones and the side chains for easy alignment.

  2. Intense and energetic radiation from crystalline undulators

    NASA Astrophysics Data System (ADS)

    Uggerhøj, U. I.; Wistisen, T. N.

    2015-07-01

    With the recent experimental confirmation of the existence of energetic radiation from a Small Amplitude, Small Period (SASP) crystalline undulator (Wistisen et al., 2014), the field of specially manufactured crystals, from which specific radiation characteristics can be obtained, has evolved substantially. In the present paper we show how the radiation spectra can be tuned, using electrons and positrons of energies from 100 MeV up to 20 GeV. The latter energy is relevant for possible experiments at the FACET facility at Stanford Linear Accelerator Center (SLAC), whereas 100 MeV has been chosen to show the potentialities connected to using crystalline undulators as radiation targets for Nuclear Waste Transmutation (NWT). Energies in the few hundred MeV range are relevant for the facilities at the MAinzer MIcrotron (MAMI). For the 20 GeV case we show explicitly that quantum corrections to the emission spectrum become very significant, an effect that may be observed in the near future using the FACET beam at SLAC.

  3. Crystalline-amorphous transition in silicate perovskites

    SciTech Connect

    Hemmati, M.; Chizmeshya, A. |; Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A.

    1995-06-01

    CaSiO{sub 3} and MgSiO{sub 3} perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

  4. Topology of nonsymmorphic crystalline insulators and superconductors

    NASA Astrophysics Data System (ADS)

    Shiozaki, Ken; Sato, Masatoshi; Gomi, Kiyonori

    2016-05-01

    Topological classification in our previous paper [K. Shiozaki and M. Sato, Phys. Rev. B 90, 165114 (2014), 10.1103/PhysRevB.90.165114] is extended to nonsymmorphic crystalline insulators and superconductors. Using the twisted equivariant K theory, we complete the classification of topological crystalline insulators and superconductors in the presence of additional order-two nonsymmorphic space-group symmetries. The order-two nonsymmorphic space groups include half-lattice translation with Z2 flip, glide, twofold screw, and their magnetic space groups. We find that the topological periodic table shows modulo-2 periodicity in the number of flipped coordinates under the order-two nonsymmorphic space group. It is pointed out that the nonsymmorphic space groups allow Z2 topological phases even in the absence of time-reversal and/or particle-hole symmetries. Furthermore, the coexistence of the nonsymmorphic space group with time-reversal and/or particle-hole symmetries provides novel Z4 topological phases, which have not been realized in ordinary topological insulators and superconductors. We present model Hamiltonians of these new topological phases and analytic expressions of the Z2 and Z4 topological invariants. The half-lattice translation with Z2 spin flip and glide symmetry are compatible with the existence of boundaries, leading to topological surface gapless modes protected by the order-two nonsymmorphic symmetries. We also discuss unique features of these gapless surface modes.

  5. Cryoflotation: densities of amorphous and crystalline ices.

    PubMed

    Loerting, Thomas; Bauer, Marion; Kohl, Ingrid; Watschinger, Katrin; Winkel, Katrin; Mayer, Erwin

    2011-12-08

    We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77-87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (~0.81-1.40 g cm(-3)) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices I(h), I(c), II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm(-3), and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the d spacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets.

  6. Crystalline marble beats limestone for fluegas desulfurization

    SciTech Connect

    1996-05-01

    NovaCon Energy Systems, Inc. (Bedford, NY) has developed an alternative to conventional limestone sorbents. The new process uses a class of marble, selected with a proprietary model. Recent pilot- and full-scale demonstrations in pulverized-coal (PC) and circulating fluidized bed (CFB) boilers suggest that these patented sorbents outperform conventional limestone for the simultaneous control of SOx, NOx, and particulates during the combustion of coal and sulfur-rich fuels, such as oil, mixed municipal waste and used tires. Dubbed thermally active marbles (TAMs), these sorbents are chemically identical to grainy limestone (whose main constituent is calcium carbonate or calcite). However, thanks to the increased pressures and temperatures experienced during their geologic history, these metamorphic minerals have a regular crystalline structure that offers some advantages in the combustion zone. TAMs, on the other hand, enjoy better calcium-utilization rates because upon heating, they cleave along inter- and intra-crystalline faces, continuously exposing fresh surfaces. By minimizing the self-extinguishment suffered by limestone sorbents, TAMs are effective over operating temperatures from 1,200 F to 2,800 F, which is 400 F higher than other calcium-based sorbents. This allows them to be injected closer to the burner or combustion grate to maximize residence time in the unit.

  7. Anisotropy and Crystalline Structure in Polyaniline Films

    NASA Astrophysics Data System (ADS)

    Minto, C. D. G.; Vaughan, A. S.

    1996-03-01

    Films of polyaniline -- camphor sulphonic acid cast from m-cresol exhibit transport properties characteristic of a material stradelling the metal/insulator transition. This improvement in properties over traditional methods of polyaniline production has been suggested as being caused by the macromolecule adopting an expanded coil configuration in this solvent. Such films have been shown to be semi--crystalline and are presumed to be completely isotropic. We present here new results which demonstrate that such films are in fact appreciably aligned. X-ray scattering is utilised to expose the presence of molecular anisotropy within such films, the polymers forming a stacked structure with the molecules preferentially oriented parallel to the plane of the film. Similar measurements confirm that the molecules are randomly oriented within this plane. Such alignment considerably improves the transport properties. Anisotropy and the crystalline structure within these films, those cast from chloroform and those using the isolated enantiomeric counter ion are quantified and discussed. The results demonstrate that improved transport properties have arisen as a result of both polymer--solvent interactions and as a result of improved chain alignment.

  8. Crystallinity in apatites: how can a truly disordered fraction be distinguished from nanosize crystalline domains?

    PubMed

    Celotti, Giancarlo; Tampieri, Anna; Sprio, Simone; Landi, Elena; Bertinetti, Luca; Martra, Gianmario; Ducati, Caterina

    2006-11-01

    In the last decade synthetic apatites mimicking the human natural one have been widely prepared and characterized from the physico-chemical point of view; however a shading zone is still remaining related to the evaluation and distinction of the less crystalline part, almost amorphous, and the crystallographically well ordered, nano-sized part, inside the apatite itself. Actually natural apatite forming bone tissue can include both types of crystals whose prevalence is dependent from the specific bone evolution stage and the specialized tissue performance. The quantitative description of such a combination usually represents a puzzling problem, but the result can also clarify the definition of "crystallinity in apatite" that appears still controversial. Many different synthetic apatites, including those nucleated on organic templates, were analyzed with different techniques (X-ray diffraction, transmission electron microscopy, and so on) to clarify the true nature of the disordered part. The results, manipulated by the classical methodologies devised for substances with highly perturbed structural order, led to establish that only specifically prepared amorphous calcium phosphate is really a glass, while the distorted portion coexisting with more or less crystalline regions is simply nanocrystalline. Moreover, at the conceptual limit of crystallinity tending to zero, the two models surprisingly cease to be conflicting.

  9. A nonreciprocal racetrack resonator based on vacuum-annealed magnetooptical cerium-substituted yttrium iron garnet.

    PubMed

    Goto, Taichi; Onbasli, Mehmet C; Kim, Dong Hun; Singh, Vivek; Inoue, M; Kimerling, Lionel C; Ross, C A

    2014-08-11

    Vacuum annealed polycrystalline cerium substituted yttrium iron garnet (CeYIG) films deposited by radio frequency magnetron sputtering on non-garnet substrates were used in nonreciprocal racetrack resonators. CeYIG annealed at 800°C for 30 min provided a large Faraday rotation angle, close to the single crystal value. Crystallinity, magnetic properties, refractive indices and absorption coefficients were measured. The resonant transmission peak of the racetrack resonator covered with CeYIG was non-reciprocally shifted by applying an in-plane magnetic field.

  10. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  11. A novel Br-substituted diarylethene: Synthesis, crystal structure, and solvent dependent acidichromism

    NASA Astrophysics Data System (ADS)

    Zheng, Chunhong; Fan, Congbin; Pu, Shouzhi; Chen, Bing; Chen, Ben

    2016-11-01

    A novel Br-substituted diarylethene was synthesized, and its structure has been determined by single-crystal X-ray diffraction analysis. Its photochemical property in solution, a PMMA film, and single crystalline phase was studied. In solution, the absorption maximum of its closed-ring isomer shifted dramatically to shorter wavelengths with notable color change from violet to yellow upon the stimulation of trifluoroacetic acid. Moreover, the acidichromism showed obviously solvent-dependence. With enhancement of solvent polarity, the protonation-induced absorption maxima (Δλmax) and the response time became longer.

  12. Crystallinity and compositional changes in carbonated apatites: Evidence from {sup 31}P solid-state NMR, Raman, and AFM analysis

    SciTech Connect

    McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M.Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

    2013-10-15

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and {sup 31}P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse {sup 31}P NMR linewidth and inverse Raman PO{sub 4}{sup 3−}ν{sub 1} bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO{sub 3}{sup 2−} range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the {sup 31}P NMR chemical shift frequency and the Raman phosphate ν{sub 1} band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. - Graphical abstract: Carbonated apatite shows an abrupt change in spectral (NMR, Raman) and morphological (AFM) properties at a composition of about one carbonate substitution per unit cell. Display Omitted - Highlights: • Crystallinity (XRD), particle size (AFM) of carbonated apatites and bone mineral. • Linear relationships among crystallinity, {sup 31}P NMR and Raman inverse bandwidths. • Low and high carbonated apatites use different charge-balancing ion-loss mechanism.

  13. Preparing cationic cotton linter cellulose with high substitution degree by ultrasonic treatment.

    PubMed

    Zhang, Fulong; Pang, Zhiqiang; Dong, Cuihua; Liu, Zong

    2015-11-05

    As an important cellulose derivative, cationic cellulose has becoming an attractive material. However, it remains challenging to produce cationic cellulose with high substitute degree. In this paper, we successfully increased the substitute degree of cationic cellulose by introducing ultrasonic treatment, which efficiently breaks hydrogen bonds of the chemical structure of cationic cellulose. Properties of cationic cellulose were studied by scanning electron spectroscope (SEM), contact angle, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Experimental results show that the cationic cellulose has rougher surface and lower crystallinity degree as compared to the original sample. TGA analysis verifies that the thermostability of CLC decreases after the cationic modification. The residual of the cationic cellulose (25 wt%) after pyrolysis increases significantly as compared to that of the original cellulose (15 wt%).

  14. Enhanced early osteogenic differentiation by silicon-substituted hydroxyapatite ceramics fabricated via ultrasonic spray pyrolysis route.

    PubMed

    Honda, Michiyo; Kikushima, Koichi; Kawanobe, Yusuke; Konishi, Toshiisa; Mizumoto, Minori; Aizawa, Mamoru

    2012-12-01

    The influence of silicon-substituted hydroxyapatite (Si-HAp) on osteogenic differentiation was assessed by biological analysis. Si-HAp was prepared by ultrasonic spray pyrolysis (USSP) technique using various amounts of Si (0, 0.8, and 1.6 mass%). Chemical analysis revealed that Si was incorporated into the hydroxyapatite (HAp) lattice with no other crystalline phase and which caused the change of crystal structure. Biological analyses showed that the Si contents affected the cell proliferation and morphology, suggesting that there is an optimal Si content for cell culture. As for differentiation, alkaline phosphatase activity and osteocalcin production of Si-HAp were higher than those of HAp. Gene expression profiles also revealed that substitution of Si (0.8 mass%) up-regulated the expression levels of osteocalcin and especially Runx2, a master gene for osteoblast development. These results suggest that incorporating Si into the HAp lattice may enhance the bioactivity, particularly during early osteoblast development.

  15. 40 CFR 721.5340 - Substituted benzothiazole-azo-substituted benzoquinoline nickel complex (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-substituted benzoquinoline nickel complex (generic). 721.5340 Section 721.5340 Protection of Environment...-substituted benzoquinoline nickel complex (generic). (a) Chemical substance and significant new uses subject...-substituted benzoquinoline nickel complex (PMN P-99-897) is subject to reporting under this section for...

  16. 40 CFR 721.5340 - Substituted benzothiazole-azo-substituted benzoquinoline nickel complex (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-substituted benzoquinoline nickel complex (generic). 721.5340 Section 721.5340 Protection of Environment...-substituted benzoquinoline nickel complex (generic). (a) Chemical substance and significant new uses subject...-substituted benzoquinoline nickel complex (PMN P-99-897) is subject to reporting under this section for...

  17. 40 CFR 721.5340 - Substituted benzothiazole-azo-substituted benzoquinoline nickel complex (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-substituted benzoquinoline nickel complex (generic). 721.5340 Section 721.5340 Protection of Environment...-substituted benzoquinoline nickel complex (generic). (a) Chemical substance and significant new uses subject...-substituted benzoquinoline nickel complex (PMN P-99-897) is subject to reporting under this section for...

  18. 40 CFR 721.5340 - Substituted benzothiazole-azo-substituted benzoquinoline nickel complex (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-substituted benzoquinoline nickel complex (generic). 721.5340 Section 721.5340 Protection of Environment...-substituted benzoquinoline nickel complex (generic). (a) Chemical substance and significant new uses subject...-substituted benzoquinoline nickel complex (PMN P-99-897) is subject to reporting under this section for...

  19. 40 CFR 721.5340 - Substituted benzothiazole-azo-substituted benzoquinoline nickel complex (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-substituted benzoquinoline nickel complex (generic). 721.5340 Section 721.5340 Protection of Environment...-substituted benzoquinoline nickel complex (generic). (a) Chemical substance and significant new uses subject...-substituted benzoquinoline nickel complex (PMN P-99-897) is subject to reporting under this section for...

  20. 40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted alkyl ester, hydrolysis... ester, hydrolysis products with silica and substituted silane (generic). (a) Chemical substance and... alkyl ester, hydrolysis products with silica and substituted silane (PMNs P-06-276 and P-06-279)...

  1. 40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted alkyl ester, hydrolysis... ester, hydrolysis products with silica and substituted silane (generic). (a) Chemical substance and... alkyl ester, hydrolysis products with silica and substituted silane (PMNs P-06-276 and P-06-279)...

  2. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Comments Electronics Cleaning w/CFC-113 and MCF HFC-4310mee Acceptable Subject to a 200 ppm time-weighted... Electronics Cleaning w/CFC-113 and MCF Perfluoropolyethers Perfluoropolyethers are acceptable substitutes for... that for PFCs. Unacceptable Substitutes End-use Substitute Decision Comments Electronics Cleaning...

  3. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Comments Electronics Cleaning w/CFC-113 and MCF HFC-4310mee Acceptable Subject to a 200 ppm time-weighted... Electronics Cleaning w/CFC-113 and MCF Perfluoropolyethers Perfluoropolyethers are acceptable substitutes for... that for PFCs. Unacceptable Substitutes End-use Substitute Decision Comments Electronics Cleaning...

  4. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Comments Electronics Cleaning w/CFC-113 and MCF HFC-4310mee Acceptable Subject to a 200 ppm time-weighted... Electronics Cleaning w/CFC-113 and MCF Perfluoropolyethers Perfluoropolyethers are acceptable substitutes for... that for PFCs. Unacceptable Substitutes End-use Substitute Decision Comments Electronics Cleaning...

  5. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Comments Electronics Cleaning w/CFC-113 and MCF HFC-4310mee Acceptable Subject to a 200 ppm time-weighted... Electronics Cleaning w/CFC-113 and MCF Perfluoropolyethers Perfluoropolyethers are acceptable substitutes for... that for PFCs. Unacceptable Substitutes End-use Substitute Decision Comments Electronics Cleaning...

  6. 40 CFR Appendix D to Subpart G of... - Substitutes Subject to Use Restrictions and Unacceptable Substitutes

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Comments Electronics Cleaning w/CFC-113 and MCF HFC-4310mee Acceptable Subject to a 200 ppm time-weighted... Electronics Cleaning w/CFC-113 and MCF Perfluoropolyethers Perfluoropolyethers are acceptable substitutes for... that for PFCs. Unacceptable Substitutes End-use Substitute Decision Comments Electronics Cleaning...

  7. Interrelation between the crystallinity of polysaccharides and water absorption

    NASA Astrophysics Data System (ADS)

    Prusov, A. N.; Prusova, S. M.; Radugin, M. V.; Zakharov, A. G.

    2014-05-01

    The maximum sorption of water and its vapors is calculated using experimental data from calorimetric and effusion studies of flax, wood, and cotton cellulose. X-day diffraction is used to determine the crystallinity of cellulose samples. The equations relating crystallinity ( X) with maximum sorption and the enthalpy of interaction between cellulose and water are presented. Experimental results and the literature data on water sorption by chitin, chitosan and other polysaccharides show that our equations for calculating crystallinity are correct.

  8. Crosslinked crystalline polymer and methods for cooling and heating

    DOEpatents

    Salyer, Ival O.; Botham, Ruth A.; Ball, III, George L.

    1980-01-01

    The invention relates to crystalline polyethylene pieces having optimum crosslinking for use in storage and recovery of heat, and it further relates to methods for storage and recovery of heat using crystalline polymer pieces having optimum crosslinking for these uses. Crystalline polymer pieces are described which retain at least 70% of the heat of fusion of the uncrosslinked crystalline polymer and yet are sufficiently crosslinked for the pieces not to stick together upon being cycled above and below the melting point of said polymer, preferably at least 80% of the heat of fusion with no substantial sticking together.

  9. Lattice matched semiconductor growth on crystalline metallic substrates

    DOEpatents

    Norman, Andrew G; Ptak, Aaron J; McMahon, William E

    2013-11-05

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a metal or metal alloy substrate having a crystalline surface with a known lattice parameter (a). The methods further include growing a crystalline semiconductor alloy layer on the crystalline substrate surface by coincident site lattice matched epitaxy. The semiconductor layer may be grown without any buffer layer between the alloy and the crystalline surface of the substrate. The semiconductor alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter (a). The semiconductor alloy may further be prepared to have a selected band gap.

  10. Multisensory integration, sensory substitution and visual rehabilitation.

    PubMed

    Proulx, Michael J; Ptito, Maurice; Amedi, Amir

    2014-04-01

    Sensory substitution has advanced remarkably over the past 35 years since first introduced to the scientific literature by Paul Bach-y-Rita. In this issue dedicated to his memory, we describe a collection of reviews that assess the current state of neuroscience research on sensory substitution, visual rehabilitation, and multisensory processes.

  11. Educators Take Another Look at Substitutes

    ERIC Educational Resources Information Center

    Zubrzycki, Jaclyn

    2012-01-01

    The mythology surrounding the substitute teacher is not a pretty one: Paper airplanes, lost learning, bullying. But as schools collect more information about teacher absenteeism and its consequences, districts and schools are exploring ways to professionalize substitute teaching--or experiment with alternative ways of coping with teacher absences.…

  12. Substitute Your Way to a Real Job

    ERIC Educational Resources Information Center

    Stephens, Cathy

    2013-01-01

    For some, substitute teaching is a career choice. However, for the majority of new teachers, it is often a necessary gateway to landing a first job. Either way, it is a great way to sharpen one's skills. This article presents tips from principals, teachers, and human resource directors to make the most of the substitute teaching experience…

  13. 25 CFR 522.9 - Substitute approval.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 2 2011-04-01 2011-04-01 false Substitute approval. 522.9 Section 522.9 Indians NATIONAL INDIAN GAMING COMMISSION, DEPARTMENT OF THE INTERIOR APPROVAL OF CLASS II AND CLASS III ORDINANCES AND RESOLUTIONS SUBMISSION OF GAMING ORDINANCE OR RESOLUTION § 522.9 Substitute approval. If the Chairman fails...

  14. 25 CFR 522.9 - Substitute approval.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 2 2012-04-01 2012-04-01 false Substitute approval. 522.9 Section 522.9 Indians NATIONAL INDIAN GAMING COMMISSION, DEPARTMENT OF THE INTERIOR APPROVAL OF CLASS II AND CLASS III ORDINANCES AND RESOLUTIONS SUBMISSION OF GAMING ORDINANCE OR RESOLUTION § 522.9 Substitute approval. If the Chairman fails...

  15. Carboranylmethylene-substituted phosphazenes and polymers thereof

    NASA Technical Reports Server (NTRS)

    Allcock, H. R.; Scopelianos, A. G. (Inventor)

    1984-01-01

    Carboranylmethylene-substituted cyclophosphazenes are described which can be thermally polymerized into carboranylmethylene-substituted phosphazene polymers. The polymers are useful as thermally stable coatings. Also, due to the characteristics of these polymers in acting as a ligand for transition metals, metalocarboranylmethylene phosphazene polymers are described which can act as immobilized catalyst systems, and are electrically conductive and superconductive.

  16. Substitutes for Leadership: An Empirical Study.

    ERIC Educational Resources Information Center

    Howell, Jon P.; Dorfman, Peter W.

    The leadership substitutes hypothesis has been used to explain the occasional successes and frequent failures of leadership predictions. Three hypotheses were formulated to test the viability of the leadership substitutes concepts. Questionnaires were administered to hospital managers (N=63) and engineers (N=71). Instrumental and supportive leader…

  17. 40 CFR 721.8775 - Substituted pyridines.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.8775 Substituted pyridines. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted pyridine (PMN P-84-1219)...

  18. 25 CFR 522.9 - Substitute approval.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 2 2010-04-01 2010-04-01 false Substitute approval. 522.9 Section 522.9 Indians NATIONAL INDIAN GAMING COMMISSION, DEPARTMENT OF THE INTERIOR APPROVAL OF CLASS II AND CLASS III ORDINANCES AND RESOLUTIONS SUBMISSION OF GAMING ORDINANCE OR RESOLUTION § 522.9 Substitute approval. If the Chairman fails...

  19. Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

    PubMed Central

    Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

    2013-01-01

    A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ≈5 wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ∼1.1 wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

  20. Co-Ti co-substitution of M-type hexagonal barium ferrite

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhang, Huaiwu; Liu, Yinong; Liao, Yulong; Ma, Guokun; Yang, Hong

    2015-04-01

    This paper reports a study of Co-Ti equiatomic co-substitution of M-type hexagonal barium ferrites Ba(CoTi)xFe12-2xO19, with the objective to adjust coercivity to meet different application requirements. The ferrites, with x = 0.00-1.30, all exhibited the single-phase M-type barium ferrite structure. At x = 1.30, the saturation magnetization (MS) decreased by 27.7% to 47.5 Am2 kg-1 and the coercivity (HC) decreased from 4047 to 171 Oe, providing a wide control range of coercivity. Complex magnetic permeability (μ‧ and μ″) was measured to be μ‧max = 25 and μ″max = 1.5 (at 10 MHz). The value of μ‧ is much higher than that of un-doped barium ferrite (x = 0.00). Co-Ti substitution reduced the coercivity whilst increased magnetic permeability. These improvements in magnetic properties are attributed to Co and Ti occupancies at different sites in the barium ferrite crystalline structure. Substitution is preferred at 4f2, 2b and 2a sites at x < 0.50, but 2a and 4f1 sites at x < 1.15. In addition, the bulk density (ρ) of the sintered compound was found to increase with increasing Co-Ti substitution.

  1. Porous frameworks constructed by non-covalent linking of substitution-inert metal complexes.

    PubMed

    Itoh, Takahiro; Kondo, Mio; Sakamoto, Hirotoshi; Wakabayashi, Kaori; Kanaike, Mari; Itami, Kenichiro; Masaoka, Shigeyuki

    2015-09-14

    The incorporation of active sites into metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) is an attractive way to functionalise these materials. However, the methodology to organise substitution-inert metal-based secondary building units (SBUs) with active sites into MOFs or PCPs via coordination driven self-assembly is severely limited. In this study, we successfully assembled substitution-inert paddle-wheel Rh(II) dimers to afford three novel porous frameworks, Rh2(ppeb)4(THF)2 (1-THF), Rh2(ppeb)4(3-pentanone)2 (1-PN) and Rh2(ppeb)4(1-adamantylamine)2 (1-AD) (ppeb = 4-[(perfluorophenyl)ethynyl]benzoate), by using non-covalent interactions. Multipoint arene-perfluoroarene (Ar-Ar(F)) interactions, which allow the unidirectional face-to-face interaction mode of aromatic rings, were used to assemble the substitution-inert paddle-wheel Rh(II) dimers. The obtained frameworks were structurally characterisation by single crystal X-ray diffraction, and it is found that all structures exhibited a one-dimensional channel with active axial sites exposed to the pores. The porous properties of the obtained frameworks were also investigated by thermogravimetric analysis, gas adsorption and powder X-ray diffraction measurements. Moreover, the ligand substitution reaction at the active axial sites was examined at the crystalline state and the flexible structural transformation with the change of channel shapes and sizes was observed.

  2. Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

    NASA Astrophysics Data System (ADS)

    Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

    2017-02-01

    Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics.

  3. Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate

    PubMed Central

    Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

    2017-01-01

    Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd3+ in Ba2+ -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics. PMID:28205559

  4. Crystalline Structure, Defect Chemistry and Room Temperature Colossal Permittivity of Nd-doped Barium Titanate.

    PubMed

    Sun, Qiaomei; Gu, Qilin; Zhu, Kongjun; Jin, Rongying; Liu, Jinsong; Wang, Jing; Qiu, Jinhao

    2017-02-13

    Dielectric materials with high permittivity are strongly demanded for various technological applications. While polarization inherently exists in ferroelectric barium titanate (BaTiO3), its high permittivity can only be achieved by chemical and/or structural modification. Here, we report the room-temperature colossal permittivity (~760,000) obtained in xNd: BaTiO3 (x = 0.5 mol%) ceramics derived from the counterpart nanoparticles followed by conventional pressureless sintering process. Through the systematic analysis of chemical composition, crystalline structure and defect chemistry, the substitution mechanism involving the occupation of Nd(3+) in Ba(2+) -site associated with the generation of Ba vacancies and oxygen vacancies for charge compensation has been firstly demonstrated. The present study serves as a precedent and fundamental step toward further improvement of the permittivity of BaTiO3-based ceramics.

  5. Impurity segregation in zone-refined precursors for crystalline halide scintillators

    NASA Astrophysics Data System (ADS)

    Swider, S.; Lam, S.; Motakef, S.; Donohoe, E.; Coers, L.; Taylor, S.; Spencer, S.

    2015-06-01

    Successful growth of halide scintillator crystals depends on a supply of ultra-high purity (UHP) precursor materials. Metallic interstitials and substitutions may provide traps that quench luminescence. Oxygen impurities can create competing compounds within a matrix, such as oxyhalides, that disrupt crystallinity and nucleate cracks. Using mass spectroscopy and oxygen combustion analysis, we analyzed impurities in SrI2, EuI2, and YCl3 precursors before and after zone refining. The data show most alkali and alkali earth impurities segregated easily. However, with the exception of iron, many transition metals were incorporated into the solid. Reliable oxygen measurements proved difficult to achieve. Additional oxygen was measured in nitrates and sulfates, via ion chromatography. Zone refining reduced the overall impurity content, but levels remained above a 10 ppm target.

  6. Terahertz Imaging of the Distribution of Crystallinity and Crystalline Orientation in a Poly(ɛ-caprolactone) Film.

    PubMed

    Funaki, Chihiro; Toyouchi, Takuya; Hoshina, Hiromichi; Ozaki, Yukihiro; Sato, Harumi

    2017-01-01

    The distribution of crystallinity and the crystalline orientation of a poly(ɛ-caprolactone) (PCL) film have been studied using terahertz (THz) imaging. Terahertz images were developed by using the intensity ratio of the two spectral peaks at 1.42 and 2.03 THz that are assigned to the crystalline modes parallel and perpendicular to the c-axis (I⊥/I ||) of the PCL film. The obtained THz images show that the distribution of crystallinity and crystalline orientation vary considerably between the different regions in the PCL film, even though this inhomogeneity is not visible in the corresponding optical image. Our results clearly illustrate that THz imaging is a promising technique to characterize the physical properties of semi-crystalline polymers.

  7. Modeling of Crystalline Silicotitanate Ion Exchange Columns

    SciTech Connect

    Walker, D.D.

    1999-03-09

    Non-elutable ion exchange is being considered as a potential replacement for the In-Tank Precipitation process for removing cesium from Savannah River Site (SRS) radioactive waste. Crystalline silicotitanate (CST) particles are the reference ion exchange medium for the process. A major factor in the construction cost of this process is the size of the ion exchange column required to meet product specifications for decontaminated waste. To validate SRS column sizing calculations, SRS subcontracted two reknowned experts in this field to perform similar calculations: Professor R. G. Anthony, Department of Chemical Engineering, Texas A&038;M University, and Professor S. W. Wang, Department of Chemical Engineering, Purdue University. The appendices of this document contain reports from the two subcontractors. Definition of the design problem came through several meetings and conference calls between the participants and SRS personnel over the past few months. This document summarizes the problem definition and results from the two reports.

  8. Thermoelectric effects in topological crystalline insulators

    NASA Astrophysics Data System (ADS)

    Rameshti, Babak Zare; Asgari, Reza

    2016-11-01

    We investigate the electrical conductivity and thermoelectric effects in topological crystalline insulators in the presence of short- and long-range impurity interactions. We employ the generalized Boltzmann formalism for anisotropic Fermi surface systems. The conductivity exhibits a local minimum as doping varies owing to the Van Hove singularity in the density of states originated from the saddle point in the surface states' band structure. Suppression of the interband scattering of the charge carriers at high-energy Dirac points results in a maximum in the electrical conductivity. Whenever the Fermi level passes an extremum in the conductivity, the Seebeck coefficient changes sign. In addition, it is revealed that profound thermoelectric effects can be attained around these extrema points.

  9. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  10. Semiclassical and quantum polarons in crystalline acetanilide

    NASA Astrophysics Data System (ADS)

    Hamm, P.; Tsironis, G. P.

    2007-08-01

    Crystalline acetanilide is a an organic solid with peptide bond structure similar to that of proteins. Two states appear in the amide I spectral region having drastically different properties: one is strongly temperature dependent and disappears at high temperatures while the other is stable at all temperatures. Experimental and theoretical work over the past twenty five years has assigned the former to a selftrapped state while the latter to an extended free exciton state. In this article we review the experimental and theoretical developments on acetanilide paying particular attention to issues that are still pending. Although the interpretation of the states is experimentally sound, we find that specific theoretical comprehension is still lacking. Among the issues that that appear not well understood is the effective dimensionality of the selftrapped polaron and free exciton states.

  11. Reactive Liftoff of Crystalline Cellulose Particles

    PubMed Central

    Teixeira, Andrew R.; Krumm, Christoph; Vinter, Katherine P.; Paulsen, Alex D.; Zhu, Cheng; Maduskar, Saurabh; Joseph, Kristeen E.; Greco, Katharine; Stelatto, Michael; Davis, Eric; Vincent, Brendon; Hermann, Richard; Suszynski, Wieslaw; Schmidt, Lanny D.; Fan, Wei; Rothstein, Jonathan P.; Dauenhauer, Paul J.

    2015-01-01

    The condition of heat transfer to lignocellulosic biomass particles during thermal processing at high temperature (>400 °C) dramatically alters the yield and quality of renewable energy and fuels. In this work, crystalline cellulose particles were discovered to lift off heated surfaces by high speed photography similar to the Leidenfrost effect in hot, volatile liquids. Order of magnitude variation in heat transfer rates and cellulose particle lifetimes was observed as intermediate liquid cellulose droplets transitioned from low temperature wetting (500–600 °C) to fully de-wetted, skittering droplets on polished surfaces (>700 °C). Introduction of macroporosity to the heated surface was shown to completely inhibit the cellulose Leidenfrost effect, providing a tunable design parameter to control particle heat transfer rates in industrial biomass reactors. PMID:26057818

  12. Actuators Based on Liquid Crystalline Elastomer Materials

    PubMed Central

    Jiang, Hongrui; Li, Chensha; Huang, Xuezhen

    2013-01-01

    Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including the unique, high-stroke reversible mechanical actuation when triggered by external stimuli. This article reviews some recent exciting developments in the field of LCEs materials with an emphasis on their utilization in actuator applications. Such applications include artificial muscles, industrial manufacturing, health and microelectromechanical systems (MEMS). With suitable synthetic and preparation pathways and well-controlled actuation stimuli, such as heat, light, electric and magnetic field, excellent physical properties of LCE materials can be realized. By comparing the actuating properties of different systems, general relationships between the structure and the property of LCEs are discussed. How these materials can be turned into usable devices using interdisciplinary techniques is also described. PMID:23648966

  13. Energy transport in crystalline DNA composites

    SciTech Connect

    Xu, Zaoli; Xu, Shen; Tang, Xiaoduan; Wang, Xinwei

    2014-01-15

    This work reports on the synthesis of crystalline DNA-composited films and microfibers, and details the study of thermal energy transport in them. The transient electro-thermal technique is used to characterize the thermal transport in DNA composite microfibers, and the photothermal technique is used to explore the thermal transport in the thickness direction of DNA films. Compared with microfibers, the DNA films are found to have a higher thermal transport capacity, largely due to the carefully controlled crystallization process in film synthesis. In high NaCl concentration solutions, the bond of the Na{sup +} ion and phosphate group aligns the DNA molecules with the NaCl crystal structure during crystallization. This results in significant enhancement of thermal transport in the DNA films with aligned structure.

  14. αB-crystallin negative astrocytic inclusions.

    PubMed

    Barnett, Brad P; Bressler, Joseph; Chen, Terina; Hutchins, Grover M; Crain, Barbara J; Kaufmann, Walter E

    2011-04-01

    We report on an unusual pathological finding of astrocytes, observed in the brain of a 16-year-old African-American male with severe intellectual disability and spastic quadriplegia. The brain showed bilateral pericentral, perisylvian polymicrogyria and pachygyria, in conjunction with a large number of hypertrophic astrocytes with eosinophilic granular cytoplasmic inclusions. The astrocytic abnormality was more severe in the dysgenetic area but present throughout the cerebral cortex. Astrocytic inclusions stained with acid fuchsin, azocarmine and Holzer's stain, and were immunoreactive for GFAP, S-100, and ubiquitin, but not for αB-crystallin, filamin, vimentin, nestin, tau or α-synuclein. Based on the case and a review of the literature, the authors postulate that these astrocytic inclusions in the cerebral cortex reflect abnormalities in radial glial developmental processes, such as migration, differentiation, or glial-neuronal interaction function during neuronal migration.

  15. Reactive Liftoff of Crystalline Cellulose Particles

    NASA Astrophysics Data System (ADS)

    Teixeira, Andrew R.; Krumm, Christoph; Vinter, Katherine P.; Paulsen, Alex D.; Zhu, Cheng; Maduskar, Saurabh; Joseph, Kristeen E.; Greco, Katharine; Stelatto, Michael; Davis, Eric; Vincent, Brendon; Hermann, Richard; Suszynski, Wieslaw; Schmidt, Lanny D.; Fan, Wei; Rothstein, Jonathan P.; Dauenhauer, Paul J.

    2015-06-01

    The condition of heat transfer to lignocellulosic biomass particles during thermal processing at high temperature (>400 °C) dramatically alters the yield and quality of renewable energy and fuels. In this work, crystalline cellulose particles were discovered to lift off heated surfaces by high speed photography similar to the Leidenfrost effect in hot, volatile liquids. Order of magnitude variation in heat transfer rates and cellulose particle lifetimes was observed as intermediate liquid cellulose droplets transitioned from low temperature wetting (500-600 °C) to fully de-wetted, skittering droplets on polished surfaces (>700 °C). Introduction of macroporosity to the heated surface was shown to completely inhibit the cellulose Leidenfrost effect, providing a tunable design parameter to control particle heat transfer rates in industrial biomass reactors.

  16. Quinine substitutes in the confederate army.

    PubMed

    Hasegawa, Guy R

    2007-06-01

    During the Civil War, the unreliable supply and high cost of quinine forced the Confederate Army to use alternative treatments for malaria. Many quinine substitutes were mentioned in the literature of the time, but relatively few were advocated by Confederate officials and even fewer are described in surviving records. Medical supply officers often issued substitute remedies when quinine was requisitioned. Most alternative treatments were made from indigenous plants such as dogwood, willow (a constituent of which gave rise to aspirin), and tulip tree. High hopes were held for Georgia bark, which was thought to be closely related to cinchona, from which quinine was derived. Documentation of the effectiveness of quinine substitutes is scanty but is most plentiful for the external application of turpentine. The quinine substitutes were generally considered useful but not as effective as quinine. The Confederate Surgeon General's Office was active in seeking out and supplying troops with quinine substitutes.

  17. [Prophylaxis of dental caries using sugar substitutes].

    PubMed

    Eberle, G

    1984-12-01

    Among the three measures, which are capable of producing a preventive effect against caries only when applied combined, i.e. adequate fluoride supply, proper mouth hygiene and healthy nutrition, the latter is dealt with in greater detail. The use of sugar substitutes is discussed under the aspects of caries prevention, substitute composition and production technology as well as from a medical point of view. Among the presently available sugar substitutes with nutritive value are mentioned Xylite, Lycasine, Mannite, Sorbite, Palatinite, the non-calorific substitutes such as the natural Aspartame as well as the synthetic sweetening agents Saccharine and Cyclamate. The possibilities and limitations of using these sugar substitutes in the prevention of caries in adults and children are presented.

  18. Quantum vibrational polarons: Crystalline acetanilide revisited

    NASA Astrophysics Data System (ADS)

    Hamm, Peter; Edler, Julian

    2006-03-01

    We discuss a refined theoretical description of the peculiar spectroscopy of crystalline acetanilide (ACN). Acetanilide is a molecular crystal with quasi-one-dimensional chains of hydrogen-bonded units, which is often regarded as a model system for the vibrational spectroscopy of proteins. In linear spectroscopy, the CO stretching (amide I) band of ACN features a double-peak structure, the lower of which shows a pronounced temperature dependence which has been discussed in the context of polaron theory. In nonlinear spectroscopy, both of these peaks respond distinctly differently. The lower-frequency band exhibits the anharmonicity expected from polaron theory, while the higher-frequency band responds as if it were quasiharmonic. We have recently related the response of the higher-frequency band to that of a free exciton [J. Edler and P. Hamm, J. Chem. Phys. 117, 2415 (2002)]. However, as discussed in the present paper, the free exciton is not an eigenstate of the full quantum version of the Holstein polaron Hamiltonian, which is commonly used to describe these phenomena. In order to resolve this issue, we present a numerically exact solution of the Holstein polaron Hamiltonian in one dimension (1D) and 3D. In 1D, we find that the commonly used displaced oscillator picture remains qualitatively correct, even for relatively large exciton coupling. However, the result is not in agreement with the experiment, as it fails to explain the free-exciton band. In contrast, when taking into account the 3D nature of crystalline acetanilide, certain parameter regimes exist where the displaced oscillator picture breaks down and states appear in the spectrum that indeed exhibit the characteristics of a free exciton. The appearance of these states is a speciality of vibrational polarons, whose source of exciton coupling is transition dipole coupling which is expected to have opposite signs of interchain and intrachain coupling.

  19. Anisotropic surface chemistry of crystalline pharmaceutical solids.

    PubMed

    Heng, Jerry Y Y; Bismarck, Alexander; Williams, Daryl R

    2006-10-06

    The purpose of this study was to establish the link between the wetting behavior of crystalline pharmaceutical solids and the localized surface chemistry. A range of conventional wetting techniques were evaluated and compared with a novel experimental approach: sessile drop contact angle measurements on the individual facets of macroscopic (>1 cm) single crystals. Conventional measurement techniques for determining surface energetics such as capillary rise and sessile drops on powder compacts were found not to provide reliable results. When the macroscopic crystal approach was used, major differences for advancing contact angles, theta(a), of water were observed-as low as 16 degrees on facet (001) and as high as 68 degrees on facet (010) of form I paracetamol. theta(a) trends were in excellent agreement with X-ray photoelectron spectroscopy surface composition and known crystallographic structures, suggesting a direct relationship to the local surface chemistry. Inverse gas chromatography (IGC) was further used to probe the surface properties of milled and unmilled samples, as a function of particle size. IGC experiments confirmed that milling exposes the weakest attachment energy facet, with increasing dominance as particle size is reduced. The weakest attachment energy facet was also found to exhibit the highest theta(a) for water and to be the most hydrophobic facet. This anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates. theta(a) was found to be very sensitive to the local surface chemistry. It is proposed that the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.

  20. Unexpected strain-stiffening in crystalline solids.

    PubMed

    Jiang, Chao; Srinivasan, Srivilliputhur G

    2013-04-18

    Strain-stiffening--an increase in material stiffness at large strains--is a vital mechanism by which many soft biological materials thwart excessive deformation to protect tissue integrity. Understanding the fundamental science of strain-stiffening and incorporating this concept into the design of metals and ceramics for advanced applications is an attractive prospect. Using cementite (Fe3C) and aluminium borocarbide (Al3BC3) as prototypes, here we show via quantum-mechanical calculations that strain-stiffening also occurs, surprisingly, in simple inorganic crystalline solids and confers exceptionally high strengths to these two solids, which have anomalously low resistance to deformation near equilibrium. For Fe3C and Al3BC3, their ideal shear strength to shear modulus ratios attain remarkably high values of 1.14 and 1.34 along the (010)[001] and slip systems, respectively. These values are more than seven times larger than the original Frenkel value of 1/2π (refs 4, 5) and are the highest yet reported for crystalline solids. The extraordinary stiffening of Fe3C arises from the strain-induced reversible 'cross-linking' between weakly coupled edge- and corner-sharing Fe6C slabs. This new bond formation creates a strong, three-dimensional covalent bond network that resists large shear deformation. Unlike Fe3C, no new bond forms in Al3BC3 but stiffening still occurs because strong repulsion between Al and B in a compressed Al-B bond unsettles the existing covalent bond network. These discoveries challenge the conventional wisdom that large shear modulus is a reliable predictor of hardness and strength of materials, and provide new lessons for materials selection and design.

  1. Crystalline lens MTF measurement during simulated accommodation

    NASA Astrophysics Data System (ADS)

    Borja, David; Takeuchi, Gaku; Ziebarth, Noel; Acosta, Ana C.; Manns, Fabrice; Parel, Jean-Marie

    2005-04-01

    Purpose: To design and test an optical system to measure the optical quality of post mortem lenses during simulated accommodation. Methods: An optical bench top system was designed to measure the point spread function and calculate the modulation transfer function (MTF) of monkey and human ex-vivo crystalline lenses. The system consists of a super luminescent diode emitting at 850nm, collimated into a 3mm beam which is focused by the ex-vivo lens under test. The intensity distribution at the focus (point spread function) is re-imaged and magnified onto a beam profiler CCD camera. The optical quality in terms of spatial frequency response (modulation transfer function) is calculated by Fourier transform of the point spread function. The system was used on ex-vivo lenses with attached zonules, ciliary body and sclera. The sclera was glued to 8 separate PMMA segments and stretched radial by 5mm on an accommodation simulating lens stretching device. The point spread function was measured for each lens in the relaxed and stretched state for 5 human (ages 38-86 years) and 5 cynomolgus monkey (ages 53 - 67 months) fresh post mortem crystalline lenses. Results: Stretching induced measurable changes in the MTF. The cutoff frequency increased from 54.4+/-13.6 lp/mm unstretched to 59.5+/-21.4 lp/mm stretched in the post-presbyopic human and from 51.9+/-24.7 lp/mm unstretched to 57.7+/-18.5 lp/mm stretched cynomolgus monkey lenses. Conclusion: The results demonstrate the feasibility of measuring the optical quality of ex-vivo human and cynomolgus monkey lenses during simulated accommodation. Additional experiments are underway to quantify changes in optical quality induced by stretching.

  2. Homology models of human gamma-crystallins: structural study of the extensive charge network in gamma-crystallins.

    PubMed

    Salim, Asmat; Zaidi, Zafar H

    2003-01-17

    The lens is composed of highly stable and long-lived proteins, the crystallins which are divided into alpha-, beta-, and gamma-crystallins. Human gamma-crystallins belong to the betagamma superfamily. A large number of gamma-crystallins have been sequenced and have been found to share remarkable sequence homology with each other. Some of the gamma-crystallins from various sources have also been elucidated structurally by X-ray crystallographic or NMR spectroscopic experiments. Their three-dimensional structures are also similar having consisted of two domains each possessing two Greek key motifs. In this study we have constructed the comparative or homology models of the four major human gamma-crystallins, gammaA-,gammaB-, gammaC-, and gammaD-crystallins and studied the charge network in these crystallins. Despite an overall structural similarity between these crystallins, differences in the ion pair formation do exist which is partly due to the differences in their primary sequence and partly due to the structural orientation of the neighboring amino acids. In this study, we present an elaborate analysis of these charged interactions and their formation or loss with respect to the structural changes.

  3. Substituted Hydroxyapatites with Antibacterial Properties

    PubMed Central

    Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Różycka, Dagmara

    2014-01-01

    Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency. PMID:24949423

  4. [The child as a substitute].

    PubMed

    Sabbadini, A

    1989-01-01

    The feeling of temporarily not being oneself is a common phenomenon, with many manifestations in normality and psychopathology. I relate it here to the Freudian category of the uncanny (das Unheimliche) and to the literary device of the double (der Doppelgänger) and I consider the splitting in the ego and the distortion of the sense of identity to be their main psychological characteristics. An extreme instance of this phenomenon is represented by the replacement child, that is a child conceived with the conscious purpose on the part of its parents of substituting a dead sibling. Replacement children inevitably suffer from a sense of confusion in the area of self-identity and often display serious difficulties in the development of self-esteem and in the establishment of mature object-relationships. As illustrations of some of the problems encountered by replacement children, I briefly refer to the experiences of two great artists (Van Gogh and Dali) and I use clinical material from two of my psychoanalytic patients.

  5. Substituted androstanes as aromatase inhibitors

    NASA Astrophysics Data System (ADS)

    Levina, Inna S.

    1998-11-01

    The synthesis and structure-activity relationships of inhibitors of steroid aromatase which catalyses the last stage of a multistep biotransformation of cholesterol into estrogens, viz., aromatisation of C19-steroids into C18-phenolic steroids, are discussed. Compounds of the androstane series which are structurally related to the natural substrate, viz., androst-4-ene-3,17-dione, are the subjects of consideration. The review encompasses problems of synthesis of various substituted androstanes and their aromatase-inhibiting activities and structural requirements for selective specific aromatase inhibitors based on in vitro and in vivo structure-activity studies of compounds synthesised, their biological properties and the results of clinical trials. Special attention is paid to practical applications of aromatase inhibitors in the treatment of hormone-dependent mammary and ovarian tumours as well as benign prostatic tumours. In writing this report, the author has used all the information currently available in the chemical, biochemical, endocrinological and medicinal literature as well as in patents. The bibliography includes 173 references.

  6. Uproar over Milk Substitutes Act.

    PubMed

    1993-11-15

    Health policy activists lobbied 7 years for the Infant Milk Substitutes, Feeding Bottles and Infant Food Bill. Proponents of the bill say that it basically curtails unethical marketing practices, not the sales of baby foods, and argue that it was conceived to reduce the trend of mothers over-diluting commercial milk in order to reduce household expenses as well as stem the potential erosion of knowledge on locally available weaning foods. Even though the bill will become an Act only after its rules and regulations have been finalized, the government has already banned baby food advertisements on television and in other electronic media under its control. Women's groups now argue that the bill tends to focus almost exclusively upon the welfare of children and compromises the position of women who can not lactate adequately. Moreover, they hold that the bill may be used to compel wives to stay out of the formal workforce so that they may feed their babies. The intention of the bill may be meaningless without complementary legislation addressing the problems of working mothers. Specifically, amendments to the Maternity Benefits Act of 1961 would extend maternity leave to 4 months after delivery and lengthen the duration of nursing breaks. It is, however, feared that these changes may reduce employment prospects for women.

  7. Substituted hydroxyapatites with antibacterial properties.

    PubMed

    Kolmas, Joanna; Groszyk, Ewa; Kwiatkowska-Różycka, Dagmara

    2014-01-01

    Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions) and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency.

  8. First principles investigation of substituted strontium hexaferrite

    NASA Astrophysics Data System (ADS)

    Dixit, Vivek

    This dissertation investigates how the magnetic properties of strontium hexaferrite change upon the substitution of foreign atoms at the Fe sites. Strontium hexaferrite, SrFe12O19, is a commonly used hard magnetic material and is produced in large quantities (around 500,000 tons per year). For different applications of strontium hexaferrite, its magnetic properties can be tuned by a proper substitution of the foreign atoms. Experimental screening for a proper substitution is a cost-intensive and time-consuming process, whereas computationally it can be done more efficiently. We used the 'density functional theory' a first principles based method to study substituted strontium hexaferrite. The site occupancies of the substituted atoms were estimated by calculating the substitution energies of different configurations. The formation probabilities of configurations were used to calculate the magnetic properties of substituted strontium hexaferrite. In the first study, Al-substituted strontium hexaferrite, SrFe12-x AlxO19 with x=0.5 and x=1.0 were investigated. It was found that at the annealing temperature the non-magnetic Al +3 ions preferentially replace Fe+3 ions from the 12 k and 2a sites. We found that the magnetization decreases and the magnetic anisotropy field increases as the fraction, x of the Al atoms increases. In the second study, SrFe12-xGaxO19 and SrFe12-xInxO19 with x=0.5 and x=1.0 were investigated. In the case of SrFe12-xGaxO19, the sites where Ga+3 ions prefer to enter are: 12 k, 2a, and 4f1. For SrFe12-xInxO19, In+3 ions most likely to occupy the 12k, 4f1 , and 4f2 sites. In both cases the magnetization was found to decrease slightly as the fraction of substituted atom increases. The magnetic anisotropy field increased for SrFe12-xGaxO 19, and decreased for SrFe12-xInxO19 as the concentration of substituted atoms increased. In the third study, 23 elements (M) were screened for their possible substitution in strontium hexaferrite, SrFe12-xMxO 19

  9. The influence of 1,2-alkanediol on the crystallinity of magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Effenberger, Fernando B.; Carbonari, A. W.; Rossi, L. M.

    2016-11-01

    Magnetic nanoparticles of magnetite have been synthesized by thermal decomposition and investigated by measuring the magnetic hyperfine field. Preformed Fe3O4 nanoparticles were used as seeds to produce a series of magnetic nanoparticles, with different sizes and shapes. Samples were characterized by X-ray diffraction, transmission electron microscopy, and magnetization measurements. The perturbed angular correlation (PAC) technique was used to study the influence of 1,2-octanediol on the seeding growth of the Fe3O4 by measuring hyperfine interactions. The nuclear probes 111In →111Cd were introduced into the samples through the synthesis of first core of Fe3O4, remained in the samples after the consecutive growth. The PAC results show the presence of two probe site fractions, one characterized by a well-defined magnetic dipole frequency with population fI and another characterized with a broad distributed electric quadrupole frequency with population fO, which were, respectively, assigned to probes at substitutional Fe sites in crystalline Fe3O4 formed at inner region of the nanoparticles and probes at non-crystalline iron oxide in the outer region of nanoparticles. A mathematical model was proposed to fit the behavior of fO with the particle size.

  10. Detection of chiral defects in crystalline organic solids using solid-state NMR spectroscopy.

    PubMed

    Berendt, Robert T; Munson, Eric J

    2011-05-01

    The marketing of enantiopure pharmaceuticals has become more common due to regulatory and safety concerns surrounding the potential differences in biological activity of opposite enantiomers. However, achieving the desired enantiopurity can be a challenge, and low levels of the undesired enantiomer (chiral impurity) may be present in the final product. The location and nature of this impurity can potentially alter pharmaceutically relevant properties. In this article, we show that it is possible to identify and quantitate the crystallographic locations of small amounts of one enantiomer (l) in the presence of predominantly the opposite D-enantiomer using solid-state nuclear magnetic resonance (NMR) spectroscopy. Proline was used as a model compound, and crystalline samples containing both D- and L-proline were prepared by solvent evaporation, lyophilization, spray drying, and cryogrinding. Isotopic labeling, (13)C cross polarization-magic angle spinning NMR spectral subtractions, and (1)H T(1) spin-lattice relaxation measurements allowed selective observation and characterization of the crystal environments into which the L-proline impurity was incorporated upon concurrent crystallization with D-proline. Results show that L-proline was incorporated in up to four different crystalline forms, including L-proline as a kinetically trapped substitutional chiral defect in the D-proline host crystal lattice.

  11. Modeling competitive substitution in a polyelectrolyte complex

    SciTech Connect

    Peng, B.; Muthukumar, M.

    2015-12-28

    We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longer than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution.

  12. The molecular refractive function of lens γ-crystallins

    PubMed Central

    Zhao, Huaying; Brown, Patrick H.; Magone, M. Teresa; Schuck, Peter

    2011-01-01

    γ-crystallins constitute the major protein component in the nucleus of the vertebrate eye lens. Present at very high concentrations, they exhibit extreme solubility and thermodynamic stability to prevent scattering of light and the formation of cataracts. However, functions beyond this structural role have remained mostly unclear. Here, we calculate molecular refractive index increments of crystallins. We show that all lens γ-crystallins have evolved a significantly elevated molecular refractive index increment, which is far above those of most proteins, including non-lens members of the βγ-crystallin family from different species. The same trait has evolved in parallel in crystallins of different phyla, including in the S-crystallins of cephalopods. A high refractive index increment can lower the crystallin concentration required to achieve a suitable refractive power of the lens, and thereby reduce their propensity to aggregate and form cataract. To produce a significant increase of the refractive index increment, a substantial global shift in the amino acid composition is required, which can naturally explain the highly unusual amino acid composition of γ-crystallins and their functional homologues. This function provides a new perspective for interpreting their molecular structure. PMID:21684289

  13. Direct optical imaging of structural inhomogeneities in crystalline materials.

    PubMed

    Grigorev, A M

    2016-05-10

    A method for optical imaging of structural inhomogeneities in crystalline materials is proposed, based on the differences in the optical properties of the structural inhomogeneity and the homogeneous material near the fundamental absorption edge of the crystalline material. The method can be used to detect defects in both semiconductors and insulators.

  14. Correlating DSC and X-Ray Measurements Of Crystallinity

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S.; Lowry, Lynn E.; Bankston, Clyde P.

    1991-01-01

    Experiment demonstrated approximate linear correlation between degree of crystallinity of multiphase polymer (as calculated from x-ray diffraction measurements) and heat of fusion of polymer (as calculated from differential scanning calorimetry (DSC) measurements). Correlation basis of simple new technique for estimating degree of crystallinity of specimens of polymer from DSC measurements alone.

  15. Single Molecule Study of Cellulase Hydrolysis of Crystalline Cellulose

    SciTech Connect

    Liu, Y.-S.; Luo, Y.; Baker, J. O.; Zeng, Y.; Himmel, M. E.; Smith, S.; Ding, S.-Y.

    2009-12-01

    This report seeks to elucidate the role of cellobiohydrolase-I (CBH I) in the hydrolysis of crystalline cellulose. A single-molecule approach uses various imaging techniques to investigate the surface structure of crystalline cellulose and changes made in the structure by CBH I.

  16. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    DOEpatents

    Lowden, Richard A.

    1994-01-01

    A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

  17. 78 FR 56273 - Occupational Exposure to Respirable Crystalline Silica

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-12

    ...The Occupational Safety and Health Administration (OSHA) proposes to amend its existing standards for occupational exposure to respirable crystalline silica. The basis for issuance of this proposal is a preliminary determination by the Assistant Secretary of Labor for Occupational Safety and Health that employees exposed to respirable crystalline silica face a significant risk to their health......

  18. Determinants of generic drug substitution in Switzerland

    PubMed Central

    2011-01-01

    Background Since generic drugs have the same therapeutic effect as the original formulation but at generally lower costs, their use should be more heavily promoted. However, a considerable number of barriers to their wider use have been observed in many countries. The present study examines the influence of patients, physicians and certain characteristics of the generics' market on generic substitution in Switzerland. Methods We used reimbursement claims' data submitted to a large health insurer by insured individuals living in one of Switzerland's three linguistic regions during 2003. All dispensed drugs studied here were substitutable. The outcome (use of a generic or not) was modelled by logistic regression, adjusted for patients' characteristics (gender, age, treatment complexity, substitution groups) and with several variables describing reimbursement incentives (deductible, co-payments) and the generics' market (prices, packaging, co-branded original, number of available generics, etc.). Results The overall generics' substitution rate for 173,212 dispensed prescriptions was 31%, though this varied considerably across cantons. Poor health status (older patients, complex treatments) was associated with lower generic use. Higher rates were associated with higher out-of-pocket costs, greater price differences between the original and the generic, and with the number of generics on the market, while reformulation and repackaging were associated with lower rates. The substitution rate was 13% lower among hospital physicians. The adoption of the prescribing practices of the canton with the highest substitution rate would increase substitution in other cantons to as much as 26%. Conclusions Patient health status explained a part of the reluctance to substitute an original formulation by a generic. Economic incentives were efficient, but with a moderate global effect. The huge interregional differences indicated that prescribing behaviours and beliefs are probably the

  19. Non-aqueous dispersion coatings based on crystalline oligomers

    SciTech Connect

    Jones, F.N.

    1993-12-31

    Amorphous oligomers and polymers are generally used in coatings; crystalline ones are avoided because of the difficulty of achieving homogeneous, defect-free films. However, dispersions of crystalline oligomers offer potential advantages of stability, useful application rheology, and excellent film properties. The authors describe non-aqueous dispersions of mixtures of crystalline and amorphous oligomers. An example is a dispersion of mixtures of crystalline (at ambient temperature) hydroxyl-functional oligomer of terephthalic acid and 1,6-hexanediol mixed with an amorphous hydroxyl-functional oligomer of terephthalic acid and glycidyl neodecanote. Microscopy, WAXD and DSC indicate that the dispersion particles are crystalline and have a diameter of 5 to 20 {mu}m. The dispersions are stable and are thixotropic. Coatings formulated with melamine and polyisocyanate resin crosslinkers form glossy, transparent film with excellent mechanical properties.

  20. Optimising reaction coordinates for crystallisation by tuning the crystallinity definition

    NASA Astrophysics Data System (ADS)

    Jungblut, Swetlana; Singraber, Andreas; Dellago, Christoph

    2013-12-01

    We apply maximum likelihood analysis to optimise crystallisation measures based on Steinhardt bond order parameters. Assuming that the size of the largest cluster of crystalline particles serves as a good reaction coordinate for the freezing transition, we write down the likelihood to observe the committor values computed for a large number of configurations. We then maximise the likelihood function by varying the parameters that enter the definition of crystallinity. For the crystallinity definition considered here this parameter set consists of the thresholds for the next-neighbour distance, the strength of the crystalline bonds and the number of crystalline connections. The optimum parameter set found by the likelihood maximisation differs considerably from the parameters that are commonly used, but leads only to a marginal improvement of the quality of the reaction coordinate.

  1. An assay for intermolecular exchange of alpha crystallin

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    An affinity column of alpha crystallin linked to cyanogen bromide-activated Sepharose was developed to study the exchange of alpha subunits. Alpha crystallin bound to the Sepharose-alpha complex was dissociated with 8 mol/l urea, followed by quantitation using high-performance reverse-phase liquid chromatography. The time course of binding at 37 degrees C showed a hyperbolic binding pattern reaching equilibrium between 6-18 hr. Under these conditions, binding of beta and gamma crystallins to the same matrix was less than 10% of the alpha values, as was binding of alpha to glycine-coupled Sepharose. This assay was used to demonstrate changes in the subunit exchange of alpha crystallins present in high molecular weight versus lower molecular weight aggregates of the human lens. These results show that this binding procedure was a specific reproducible assay that might be used to study intermolecular interactions of the alpha crystallins.

  2. Sugar and sugar substitutes. Comparisons and indications.

    PubMed

    Alfin-Slater, R B; Pi-Sunyer, F X

    1987-08-01

    Public confusion and concern about the use of sugar and sugar substitutes are widespread. Physicians must be prepared to answer patients' inquiries about these substances. Some population groups should avoid certain sugar substitutes. In particular, pregnant women and young children should avoid saccharin, and phenylketonuric homozygous persons should avoid aspartame. In a varied, balanced diet, the use of aspartame and saccharin is one safe way for the general population to enjoy sweet foods with fewer calories and less cariogenic potential. Sugar substitutes may be helpful in dietary compliance for overweight and diabetic patients.

  3. Isolation and characterization of βA3-crystallin associated proteinase from α-crystallin fraction of human lenses

    PubMed Central

    Chaves, J. M.

    2008-01-01

    Purpose The purpose was to characterize the properties of a proteinase activity associated with βA3-crystallin, which was isolated from the α-crystallin fraction of human lenses. Methods An inactive, Arg-bond hydrolyzing proteinase in the α-crystallin fraction, which was isolated from the water soluble (WS) protein fraction of 60- to 70-year-old human lenses, was activated by sodium deoxycholate treatment. The activated enzyme was purified by a three-step procedure that included a size-exclusion Agarose A1.5 m chromatography, non-denaturing preparative gel-electrophoresis, and size-exclusion HPLC. The purified proteinase was characterized for the proteinase type, proteolysis of bovine recombinant γB-, γC-, and γD-crystallins, and its presence in three different protein fractions of human lenses (i.e., α-crystallin, βH-crystallin, and membrane fractions). Results An inactive, Arg-bond hydrolyzing proteinase present in the α-crystallin fraction showed activity on treatment with detergents such as sodium deoxycholate, Triton X-100, octyl β-D-glucopyranoside, and CHAPS (3-[(3-cholamido propyl) dimethylammonio]-1-propanesulfonate). The sodium deoxycholate-activated enzyme was released from the α-crystallin fraction since it eluted at a lower molecular weight species than α-crystallin during size-exclusion Agarose A1.5 m chromatography. Following a three-step purification procedure, the enzyme showed three species between 22 kDa and 25 kDa during sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) analysis. The three protein bands were identified as βA3-, βB1-, and βB2-crystallin by the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and tandem mass spectrometric (ES-MS/MS) methods. Inhibitor studies revealed that the enzyme was a serine-type proteinase. Among the recombinant βA3-, βB1-, or βB2-crystallins, only the βA3-crystallin exhibited the proteinase activity following detergent treatment and size

  4. Irreversible thermodynamics of creep in crystalline solids

    NASA Astrophysics Data System (ADS)

    Mishin, Y.; Warren, J. A.; Sekerka, R. F.; Boettinger, W. J.

    2013-11-01

    We develop an irreversible thermodynamics framework for the description of creep deformation in crystalline solids by mechanisms that involve vacancy diffusion and lattice site generation and annihilation. The material undergoing the creep deformation is treated as a nonhydrostatically stressed multicomponent solid medium with nonconserved lattice sites and inhomogeneities handled by employing gradient thermodynamics. Phase fields describe microstructure evolution, which gives rise to redistribution of vacancy sinks and sources in the material during the creep process. We derive a general expression for the entropy production rate and use it to identify of the relevant fluxes and driving forces and to formulate phenomenological relations among them taking into account symmetry properties of the material. As a simple application, we analyze a one-dimensional model of a bicrystal in which the grain boundary acts as a sink and source of vacancies. The kinetic equations of the model describe a creep deformation process accompanied by grain boundary migration and relative rigid translations of the grains. They also demonstrate the effect of grain boundary migration induced by a vacancy concentration gradient across the boundary.

  5. Low-Dimensional Topological Crystalline Insulators.

    PubMed

    Wang, Qisheng; Wang, Feng; Li, Jie; Wang, Zhenxing; Zhan, Xueying; He, Jun

    2015-09-01

    Topological crystalline insulators (TCIs) are recently discovered topological phase with robust surface states residing on high-symmetry crystal surfaces. Different from conventional topological insulators (TIs), protection of surface states on TCIs comes from point-group symmetry instead of time-reversal symmetry in TIs. The distinct properties of TCIs make them promising candidates for the use in novel spintronics, low-dissipation quantum computation, tunable pressure sensor, mid-infrared detector, and thermoelectric conversion. However, similar to the situation in TIs, the surface states are always suppressed by bulk carriers, impeding the exploitation of topology-induced quantum phenomenon. One effective way to solve this problem is to grow low-dimensional TCIs which possess large surface-to-volume ratio, and thus profoundly increase the carrier contribution from topological surface states. Indeed, through persistent effort, researchers have obtained unique quantum transport phenomenon, originating from topological surface states, based on controllable growth of low-dimensional TCIs. This article gives a comprehensive review on the recent progress of controllable synthesis and topological surface transport of low-dimensional TCIs. The possible future direction about low-dimensional TCIs is also briefly discussed at the end of this paper.

  6. High efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Sah, C. Tang

    1986-01-01

    A review of the entire research program since its inception ten years ago is given. The initial effort focused on the effects of impurities on the efficiency of silicon solar cells to provide figures of maximum allowable impurity density for efficiencies up to about 16 to 17%. Highly accurate experimental techniques were extended to characterize the recombination properties of the residual imputities in the silicon solar cell. A numerical simulator of the solar cell was also developed, using the Circuit Technique for Semiconductor Analysis. Recent effort focused on the delineation of the material and device parameters which limited the silicon efficiency to below 20% and on an investigation of cell designs to break the 20% barrier. Designs of the cell device structure and geometry can further reduce recombination losses as well as the sensitivity and criticalness of the fabrication technology required to exceed 20%. Further research is needed on the fundamental characterization of the carrier recombination properties at the chemical impurity and physical defect centers. It is shown that only single crystalline silicon cell technology can be successful in attaining efficiencies greater than 20%.

  7. Crystalline and amorphous gold in chrysiasis.

    PubMed

    Benn, H P; von Gaudecker, B; Czank, M; Loeffler, H

    1990-01-01

    Skin biopsy specimens from five patients (three females and two males) treated parenterally with gold were investigated using transmission electron microscopy. X-ray microanalysis and electron diffraction were used to determine the dermal heavy metal content. Additional sections were stained for light microscopic examination. The amount of elemental gold administered to the patients over a period of years to alleviate rheumatoid arthritis lay between a minimum of 4.0 g and a maximum of 10.0 g. In one and the same patient dermal histiocytic gold aggregations in sun-exposed areas of skin displayed a different pattern and divergent physiochemical states from the gold deposits in non-UV-exposed skin, where aurosome-like amorphous formations are found in the cells of the upper dermis. Additional spherical particles are associated predominantly with phagolysosomes in melanophages beneath solar-irradiated epidermis. Convergent beam electron diffraction proves the crystalline nature of the spherical auriferous deposits. The occurrence of skin rash was not related to different physicochemical states of the precious metal.

  8. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2002-01-01

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  9. Crystalline rare-earth activated oxyorthosilicate phosphor

    DOEpatents

    McClellan, Kenneth J.; Cooke, D. Wayne

    2004-02-10

    Crystalline, transparent, rare-earth activated lutetium oxyorthosilicate phosphor. The phosphor consists essentially of lutetium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of lutetium gadolinium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Lu(.sub.2-x-z)Gd.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor also consists essentially of gadolinium yttrium oxyorthosilicate activated with a rare-earth metal dopant M and having the general formula Gd(.sub.2-x-z)Y.sub.x M.sub.z SiO.sub.5, wherein 0.00.ltoreq.x.ltoreq.1.95, wherein 0.001.ltoreq.z.ltoreq.0.02, and wherein M is selected from Sm, Tb, Tm, Eu, Yb, and Pr. The phosphor may be optically coupled to a photodetector to provide a radiation detector.

  10. Crystalline Organic Cavitands As Microcavity Materials

    NASA Astrophysics Data System (ADS)

    Kane, Christopher Michael

    There has been much interest in inefficiently packed molecular materials and their applications in gas storage, separations, catalysis, etc. Such known materials include metal-organic frameworks (MOFs), polymers of intrinsic microporosity (PIMs), container molecule materials, etc. One way to design inefficiently packed materials is to construct them from compounds that are incapable of close-packing, that is rigid scaffolds with enforced cavities that cannot be filled by self-packing. Cavitand molecules, tetrameric macrocycles derived from calix[4]resorcinarene derivatives, are well known for their propensity to form crystalline inclusion compounds with small molecules; for example, of the 169 examples of calix[4]resorcinarene scaffolds found in the Cambridge Structural Database (CSD), no guest-free forms exist. The guest-free forms of various cavitands, synthesized by literature methods, have been obtained as single crystals by sublimation. Gas inclusion compounds of these cavitands have also been isolated and studied by single crystal x-ray diffraction, thermogravimetric analysis, and 1 H NMR. Furthermore, some cavitand derivatives have shown promise as media for industrial separations (Kr vs. Xe, MeCl vs. DME, Propene vs. Propane).

  11. Navigating the Waters of Unconventional Crystalline Hydrates

    PubMed Central

    2015-01-01

    Elucidating the crystal structures, transformations, and thermodynamics of the two zwitterionic hydrates (Hy2 and HyA) of 3-(4-dibenzo[b,f][1,4]oxepin-11-yl-piperazin-1-yl)-2,2-dimethylpropanoic acid (DB7) rationalizes the complex interplay of temperature, water activity, and pH on the solid form stability and transformation pathways to three neutral anhydrate polymorphs (Forms I, II°, and III). HyA contains 1.29 to 1.95 molecules of water per DB7 zwitterion (DB7z). Removal of the essential water stabilizing HyA causes it to collapse to an amorphous phase, frequently concomitantly nucleating the stable anhydrate Forms I and II°. Hy2 is a stoichiometric dihydrate and the only known precursor to Form III, a high energy disordered anhydrate, with the level of disorder depending on the drying conditions. X-ray crystallography, solid state NMR, and H/D exchange experiments on highly crystalline phase pure samples obtained by exquisite control over crystallization, filtration, and drying conditions, along with computational modeling, provided a molecular level understanding of this system. The slow rates of many transformations and sensitivity of equilibria to exact conditions, arising from its varying static and dynamic disorder and water mobility in different phases, meant that characterizing DB7 hydration in terms of simplified hydrate classifications was inappropriate for developing this pharmaceutical. PMID:26075319

  12. Gravitational Effects of a Crystalline Quantum Foam

    NASA Astrophysics Data System (ADS)

    Crouse, David

    2017-01-01

    In this work, concepts in quantum mechanics and general relativity are used to derive the quantums of space and time. After showing that space and time, at the Planck scale, must be discrete and not continuous, various anomalous gravitational effects are described. It is discussed how discrete space necessarily imposes order upon Wheeler's quantum foam, changing the foam into a crystal. The forces in this crystal are gravitational forces due to the ordered array of electrically neutral Planck masses, and with a lattice constant on the order of the Planck length. Thus the crystal is a gravity crystal rather than the more common crystals (e.g., silicon) that rely on electromagnetic forces. It is shown that similar solid-state physics techniques can be applied to this universe-wide gravity crystal to calculate particles' dispersion curves. It is shown that the crystal produces typical crystalline effects, namely bandgaps, Brillouin zones, and effective inertial masses that may differ from the gravitational masses with possible values even being near zero or negative. It is shown that the gravity crystal can affect the motion of black holes in dramatic ways, imbuing them with a negative inertial mass such that they are pushed by the pull of gravity.

  13. Microscale material testing of single crystalline silicon

    NASA Astrophysics Data System (ADS)

    Yi, Taechung

    The mechanical properties of single crystalline silicon (SCS) in microscale are characterized using a uniaxial tension test. The samples are prepared using, various micromachining techniques. The dimensions of the tension specimen at the maximum stress region are 5 to 10 mum in thickness and 20 to 100 mum in width. The sample has two illumination marks on the top surface for strain measurement. The uniaxial tension test setup has been built to accommodate requirements such as sample handling, sample alignment, and friction elimination. Stress is measured using a commercial load cell. Strain is measured by laser interferometry. All the components are connected to a data acquisition board and controlled by a personal computer. Measured Young's moduli in three directions agree well with the reference values and verify the reliability of the setup and measurement procedure. The measured fracture strength is 0.6 GPa to 1.2 GPa, depending on sample preparation methods and loading directions. Preliminary work for fracture toughness measurements using a sharp initial crack is also presented. Future works include further investigation of fracture surfaces, fracture toughness measurement using crack opening criteria, and improvement of the testing apparatus.

  14. Bacterial Transport Experiments in Fractured Crystalline Bedrock

    USGS Publications Warehouse

    Becker, M.W.; Metge, D.W.; Collins, S.A.; Shapiro, A.M.; Harvey, R.W.

    2003-01-01

    The efficiency of contaminant biodegradation in ground water depends, in part, on the transport properties of the degrading bacteria. Few data exist concerning the transport of bacteria in saturated bedrock, particularly at the field scale. Bacteria and microsphere tracer experiments were conducted in a fractured crystalline bedrock under forced-gradient conditions over a distance of 36 m. Bacteria isolated from the local ground water were chosen on the basis of physicochemical and physiological differences (shape, cell-wall type, motility), and were differentially stained so that their transport behavior could be compared. No two bacterial strains transported in an identical manner, and microspheres produced distinctly different breakthrough curves than bacteria. Although there was insufficient control in this field experiment to completely separate the effects of bacteria shape, reaction to Gram staining, cell size, and motility on transport efficiency, it was observed that (1) the nonmotile, mutant strain exhibited better fractional recovery than the motile parent strain; (2) Gram-negative rod-shaped bacteria exhibited higher fractional recovery relative to the Gram-positive rod-shaped strain of similar size; and (3) coccoidal (spherical-shaped) bacteria transported better than all but one strain of the rod-shaped bacteria. The field experiment must be interpreted in the context of the specific bacterial strains and ground water environment in which they were conducted, but experimental results suggest that minor differences in the physical properties of bacteria can lead to major differences in transport behavior at the field scale.

  15. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2003-12-23

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  16. Post-shock relaxation in crystalline nitromethane

    NASA Astrophysics Data System (ADS)

    Rivera-Rivera, Luis A.; Sewell, Thomas D.; Thompson, Donald L.

    2013-02-01

    Molecular dynamics simulations of shocked (100)-oriented crystalline nitromethane were carried out to determine the rates of relaxation behind the shock wave. The forces were described by the fully flexible non-reactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)], 10.1021/jp000942q. The time scales for local and overall thermal equilibration in the shocked crystal were determined. The molecular center-of-mass and atomic kinetic energy distributions rapidly reach substantially different local temperatures. Several picoseconds are required for the two distributions to converge, corresponding to establishment of thermal equilibrium in the shocked crystal. The decrease of the molecular center-of-mass temperature and the increase of the atomic temperature behind the shock front exhibit essentially exponential dependence on time. Analysis of covalent bond distance distributions ahead of, immediately behind, and well behind the shock front showed that the effective bond stretching potentials are essentially harmonic. Effective force constants for the C-N, C-H, and N-O bonds immediately behind the shock front are larger by factors of 1.6, 2.5, and 2.0, respectively, than in the unshocked crystal; and by factors of 1.2, 2.2, and 1.7, respectively, compared to material sufficiently far behind the shock front to be essentially at thermal equilibrium.

  17. Synthesis of crystalline ceramics for actinide immobilisation

    SciTech Connect

    Burakov, B.; Gribova, V.; Kitsay, A.; Ojovan, M.; Hyatt, N.C.; Stennett, M.C.

    2007-07-01

    Methods for the synthesis of ceramic wasteforms for the immobilization of actinides are common to those for non-radioactive ceramics: hot uniaxial pressing (HUP); hot isostatic pressing (HIP); cold pressing followed by sintering; melting (for some specific ceramics, such as garnet/perovskite composites). Synthesis of ceramics doped with radionuclides is characterized with some important considerations: all the radionuclides should be incorporated into crystalline structure of durable host-phases in the form of solid solutions and no separate phases of radionuclides should be present in the matrix of final ceramic wasteform; all procedures of starting precursor preparation and ceramic synthesis should follow safety requirements of nuclear industry. Synthesis methods that avoid the use of very high temperatures and pressures and are easily accomplished within the environment of a glove-box or hot cell are preferable. Knowledge transfer between the V. G. Khlopin Radium Institute (KRI, Russia) and Immobilisation Science Laboratory (ISL, UK) was facilitated in the framework of a joint project supported by UK Royal Society. In order to introduce methods of precursor preparation and ceramic synthesis we selected well-known procedures readily deployable in radiochemical processing plants. We accounted that training should include main types of ceramic wasteforms which are currently discussed for industrial applications. (authors)

  18. Enantioselective synthesis of trifluoromethyl-substituted cyclopropanes.

    PubMed

    Denton, Justin R; Sukumaran, Dinesh; Davies, Huw M L

    2007-07-05

    The reaction of 1-aryl-2,2,2-trifluorodiazoethanes with alkenes, catalyzed by the adamantylglycine-derived dirhodium complex Rh2(R-PTAD)4, generates trifluoromethyl-substituted cyclopropanes with high diastereoselectivity (>94%) and enantioselectivity (88->98%).

  19. Stereoselective construction of nitrile-substituted cyclopropanes.

    PubMed

    Denton, Justin R; Cheng, Kevin; Davies, Huw M L

    2008-03-14

    Nitrile-substituted cyclopropanes are readily synthesized in a stereocontrolled fashion from the intermolecular cyclopropanation between 2-diazo-2-phenylacetonitrile and electron-rich olefins, catalyzed by the chiral dirhodium complex, Rh(2)(S-PTAD)(4).

  20. 47 CFR 76.130 - Substitutions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Network Non-duplication Protection, Syndicated Exclusivity and Sports Blackout § 76.130 Substitutions. Whenever, pursuant to the requirements of the network program...

  1. Research of Energy Substitution Strategy of China

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; kai, Chen

    For a long time, China's energy endowment structure determines the production structure and consumption structure of energy are coal-based.This situation is difficult to change for quite a long time. With the rapid economic growth, industrialization and urbanization, the demand for energy, especially for oil, natural gas will continue to increase. But the oil and gas supply can not meet the needs of rapid growth. The most direct way is to import, and imports will be charged by the international energy situation, and will affect energy and economic security. In view of our country abundant coal resources, we can consider to use coal substituting oil and natural gas to reduce dependence on foreign energy, to strengthen energy and economic security. Therefore, using translog production function, the text forecasts substitution elasticity and the marginal substitution rate between the capital, coal, oil and natural gas, and puts forward substitution program.

  2. Questioning nuclear waste substitution: a case study.

    PubMed

    Marshall, Alan

    2007-03-01

    This article looks at the ethical quandaries, and their social and political context, which emerge as a result of international nuclear waste substitution. In particular it addresses the dilemmas inherent within the proposed return of nuclear waste owned by Japanese nuclear companies and currently stored in the United Kingdom. The UK company responsible for this waste, British Nuclear Fuels Limited (BNFL), wish to substitute this high volume intermediate-level Japanese-owned radioactive waste for a much lower volume of much more highly radioactive waste. Special focus is given to ethical problems that they, and the UK government, have not wished to address as they move forward with waste substitution. The conclusion is that waste substitution can only be considered an ethical practice if a set of moderating conditions are observed by all parties. These conditions are listed and, as of yet, they are not being observed.

  3. Symbolic Substitution Using Shadow-Casting

    NASA Astrophysics Data System (ADS)

    Xue, Wei; Chen, Li-Xue; Li, Chun-Fei; Hu, Qiang-Sheng

    1989-02-01

    A new optical system for symbolic substitution is proposed. The system is composed of the lensless shadow-casting system combined with optical logical array and optical image storage elements. The LED's (light-emitting diode) are used as both a light source and a control element in the operation, so that symbolic substitution is implemented by all-photoelectric manipulation. Experimental principle, procedure and result are given.

  4. Nutrient-substituted hydroxyapatites: synthesis and characterization.

    PubMed

    Golden, D C; Ming, D W

    1999-01-01

    Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

  5. Nutrient-substituted hydroxyapatites: synthesis and characterization

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.

    1999-01-01

    Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

  6. Hyperfine magnetic fields in substituted Finemet alloys

    NASA Astrophysics Data System (ADS)

    Brzózka, K.; Sovák, P.; Szumiata, T.; Gawroński, M.; Górka, B.

    2016-12-01

    Transmission Mössbauer spectroscopy was used to determine the hyperfine fields of Finemet-type alloys in form of ribbons, substituted alternatively by Mn, Ni, Co, Al, Zn, V or Ge of various concentration. The comparative analysis of magnetic hyperfine fields was carried out which enabled to understand the role of added elements in as-quenched as well as annealed samples. Moreover, the influence of the substitution on the mean direction of the local hyperfine magnetic field was examined.

  7. Polymorphic phases of galactocerebrosides: spectroscopic evidence of lamellar crystalline structures.

    PubMed

    Bou Khalil, M; Carrier, D; Wong, P T; Tanphaichitr, N

    2001-06-06

    Fourier transform infrared spectroscopy was applied to study the structural and thermal properties of bovine brain galactocerebroside (GalCer) containing amide linked non-hydroxylated or alpha-hydroxy fatty acids (NFA- and HFA-GalCer, respectively). Over the temperature range 0-90 degrees C, both GalCer displayed complex thermal transitions, characteristic of polymorphic phase behavior. Upon heating, aqueous dispersions of NFA- and HFA-GalCer exhibited high order-disorder transition temperatures near 80 and 72 degrees C, respectively. En route to the chain melting transition, the patterns of the amide I band of NFA-GalCer were indicative of two different lamellar crystalline phases, whereas those of HFA-GalCer were suggestive of lamellar gel and crystalline bilayers. Cooling from the liquid-crystalline phase resulted in the formation of another crystalline phase of NFA-GalCer and a gel phase of HFA-GalCer, with a phase transition near 62 and 66 degrees C, respectively. Prolonged incubation of GalCer bilayers at 38 degrees C revealed conversions among lamellar crystalline phases (NFA-GalCer) or between lamellar gel and crystalline bilayer structures (HFA-GalCer). Spectral changes indicated that the temperature and/or time induced formation of the lamellar crystalline structures of NFA- and HFA-GalCer was accompanied by partial dehydration and by rearrangements of the hydrogen bonding network and bilayer packing mode of GalCer.

  8. Triaryl-Substituted Divinyl Ketones Cyclization: Nazarov Reaction versus Friedel-Crafts Electrophilic Substitution.

    PubMed

    Shirinian, Valerii Z; Lvov, Andrey G; Yadykov, Anton V; Yaminova, Liana V; Kachala, Vadim V; Markosyan, Ashot I

    2016-12-16

    The acid-catalyzed cyclization of a wide range of triaryl-substituted divinyl ketones has been studied. It was found that the reaction pathway strongly depends on the nature of the aryl substituent at the α-position to the carbonyl group. An electron-rich aromatic substituent promotes the reaction to proceed through the intramolecular Friedel-Crafts electrophilic substitution giving dihydronaphthalene derivatives. In contrast, the presence of an electron-deficient substituent is favorable for the Nazarov 4π-conrotatory cyclization yielding triaryl-substituted cyclopentenones. The electrophilic substitution reaction was applied to thiophene and thiazole derivatives.

  9. 77 FR 14732 - Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From the People's...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-13

    ... International Trade Administration Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules... of crystalline silicon photovoltaic cells, whether or not assembled into modules, from the People's.... \\1\\ See Crystalline Silicon Photovoltaic Cells, Whether or Not Assembled Into Modules, From...

  10. Preparation and structure of carbonated calcium hydroxyapatite substituted with heavy rare earth ions

    SciTech Connect

    Yasukawa, Akemi; Kandori, Kazuhiko; Tanaka, Hidekazu; Gotoh, Keiko

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer LnCaHap solid solution particles were prepared using five types of heavy rare earth ions by a precipitation method. Black-Right-Pointing-Pointer The length and the crystallinity of the LnCaHap particles first increased and then decreased with increasing Ln{sup 3+} contents. Black-Right-Pointing-Pointer A series of YCaHap solid solution particles formed with Y/(Y + Ca) = 0-0.10 were investigated using various methods in detail. -- Abstract: Calcium hydroxyapatite (CaHap) particles substituted five types of heavy rare earth ions (Ln: Y{sup 3+}, Gd{sup 3+}, Dy{sup 3+}, Er{sup 3+} and Yb{sup 3+}) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([X{sub Ln}]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [X{sub Y}] {<=} 0.10 for substituting Y system and at [X{sub Ln}] {<=} 0.01-0.03 for substituting the other Ln systems. LnPO{sub 4} was mixed with LnCaHap at higher [X{sub Ln}] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X{sub Y}] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail.

  11. Achondrite Binda; Ordinary Eucrite or the Only Crystalline Howardite?

    NASA Astrophysics Data System (ADS)

    Yanai, K.

    1996-03-01

    Binda meteorite, originally classified as howardite (Hey, 1966), was reclassified as eucrite of monomict breccia (Duke and Silver, 1967). Binda was recognized as the most Mg-rich eucrite (or most Fe-rich diogenite) with crystalline-unbrecciated texture for long time. Therefore Binda is believed to have genetic significance in relation to eucrites and diogenites, because in howardite group Binda is the only specimen with unbrecciated or monomict and crystalline texture. Re-examination of Binda was carried out by EPMA, microscope analysis and wet chemical analysis. Binda is the most common (ordinary) encrite showing crystalline texture with slightly brecciated.

  12. Effect of Crystallinity on Electrical Conduction in Polypropylene

    NASA Astrophysics Data System (ADS)

    Ikezaki, Kazuo; Kaneko, Takanobu; Sakakibara, Toshio

    1981-03-01

    The electrical conduction of 20 μm thick polypropylene films with different crystallinities has been studied at 72°C below 400 kV/cm. The field dependence of the current shows that the conduction mechanism in this polymer is ion hopping. The estimated ionic jump distance strongly depends on the polymer crystallinity, and it decreases from 100 Å to 45 Å as the crystallinity increases from 50.5% to 78%. Preheating of samples seriously affects the electrical conduction in polypropylene, so differences in conductivity, activation energy and jump distance obtained by different authors can be explained partly by differences in the thermal history of the samples used.

  13. Characterization of Cholesteric Cyclic Siloxane Liquid Crystalline Materials

    DTIC Science & Technology

    1991-11-01

    34AD-A256 128 CHARACIEUAThIONOFPCl LEST CCYCJC SILOXANE LIQUID CRYSTALLINE MATERIALS TI I Herbert E. Kii C r-• CTr Dept. of Chemical Engineering v... crystalline Materials . 18: 2422 S a.•mo) ... : 01 TJ suning. RR 1*1., Er SamlskI, •L CVa1e. W AMd 7. PWMoaG ORGAIRZAIIO "W3(SC) Sil AQM~SISfS) L. KNOW"ma...ordering of the NLO chromcphore can give rise to large response amplitudes, one system currently being investigated are liquid crystalline materials which

  14. Unilateral Crystalline Vitreoretinopathy: A Rare Entity Associated with Intraocular Inflammation

    PubMed Central

    Harshey, Kaustubh B.; Srinivasan, Karthik; Rengappa, Ramakrishnan; Ramasamy, Kim

    2015-01-01

    A 31-year-old Indian male presented with floaters and diminution of vision in the right eye. Ocular examination showed features of old anterior uveitis with posterior subcapsular cataract and fine, refractile crystals in the vitreous cavity and on the retinal surface. A thorough workup for all known causes of crystalline retinopathy was inconclusive. Unilateral crystalline retinopathy has been sparingly reported. This is the first report of unilateral, crystalline vitreoretinopathy in the absence of any demonstrable and known cause for intraocular crystals. PMID:26688764

  15. Comparison of the incremental and hierarchical methods for crystalline neon.

    PubMed

    Nolan, S J; Bygrave, P J; Allan, N L; Manby, F R

    2010-02-24

    We present a critical comparison of the incremental and hierarchical methods for the evaluation of the static cohesive energy of crystalline neon. Both of these schemes make it possible to apply the methods of molecular electronic structure theory to crystalline solids, offering a systematically improvable alternative to density functional theory. Results from both methods are compared with previous theoretical and experimental studies of solid neon and potential sources of error are discussed. We explore the similarities of the two methods and demonstrate how they may be used in tandem to study crystalline solids.

  16. Azobenzene-based organic salts with ionic liquid and liquid crystalline properties

    SciTech Connect

    Stappert, Kathrin; Muthmann, Johanna; Spielberg, Eike T.; Mudring, Anja -Verena

    2015-07-23

    Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn)2]; n = 6, 8, 10, 12, 14. The other one contains an n-alkyl-imidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m = 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12)2 (1d), Azo(-C1-Im-C12)2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180–240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O–C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O–C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. As a result, through irradiation with UV

  17. Azobenzene-based organic salts with ionic liquid and liquid crystalline properties

    DOE PAGES

    Stappert, Kathrin; Muthmann, Johanna; Spielberg, Eike T.; ...

    2015-07-23

    Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn)2]; n = 6, 8, 10, 12, 14. The other one contains an n-alkyl-imidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m =more » 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12)2 (1d), Azo(-C1-Im-C12)2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180–240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O–C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O–C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. As a result, through irradiation with UV-light (320–366 nm) all

  18. Thermal diffusivity of some crystalline rocks

    SciTech Connect

    Drury, M.J.

    1987-01-01

    Thermal diffusivity data at room temperature and uniaxial pressure of 1 MPa are reported for five sets of crystalline rocks - granite, granodiorite, gabbro, basalt and gneiss. Diffusivity ranges between approximately 0.6 and 1.9 mm/sup 2//s, the lower end of the range being appropriate for basic rocks and the upper end for quartz-bearing acidic rocks. The scatter in diffusivity for each data set is significantly more than that of thermal conductivity, because the diffusivity of water is typically less than 10% of the diffusivity of most common minerals, whereas water conductivity is 25 - 30% of the conductivity of the minerals. For a sample set of uniform mineralogy in which porosity varies, a greater variation of diffusivity than of conductivity is therefore expected. For three of the sets sufficient mineralogical data were available to permit the assessment of methods of estimating thermal diffusivity from mineral content. All models tested yielded higher mean values of diffusivity than the means of the measured values. No model was found to be able to predict diffusivity to better than approximately 20%, but if that accuracy is sufficient, a simple geometrical model, for which only quartz content must be known, is adequate. The diffusivity data have been combined with measurements of thermal conductivity and density to provide estimates of specific heat. These all tend to be higher than those reported in the literature. For some rocks, such as the basalts, this can be explained in terms of relatively high water content and the very high specific heat of water compared with that of most common minerals. For the granites and granodiorites, the new specific heat data redefine the previously published means and ranges, by increasing the data base by approximately an order of magnitude.

  19. Calculation of longitudinal polarizability and second hyperpolarizability of polyacetylene with the coupled perturbed Hartree-Fock/Kohn-Sham scheme: where it is shown how finite oligomer chains tend to the infinite periodic polymer.

    PubMed

    Lacivita, Valentina; Rèrat, Michel; Orlando, Roberto; Ferrero, Mauro; Dovesi, Roberto

    2012-03-21

    The longitudinal polarizability, α(xx), and second hyperpolarizability, γ(xxxx), of polyacetylene are evaluated by using the coupled perturbed Hartree-Fock/Kohn-Sham (HF/KS) scheme as implemented in the periodic CRYSTAL code and a split valence type basis set. Four different density functionals, namely local density approximation (LDA) (pure local), Perdew-Becke-Ernzerhof (PBE) (gradient corrected), PBE0, and B3LYP (hybrid), and the Hartree-Fock Hamiltonian are compared. It is shown that very tight computational conditions must be used to obtain well converged results, especially for γ(xxxx), that is, very sensitive to the number of k(->) points in reciprocal space when the band gap is small (as for LDA and PBE), and to the extension of summations of the exact exchange series (HF and hybrids). The band gap in LDA is only 0.01 eV: at least 300 k(->) points are required to obtain well converged total energy and equilibrium geometry, and 1200 for well converged optical properties. Also, the exchange series convergence is related to the band gap. The PBE0 band gap is as small as 1.4 eV and the exchange summation must extend to about 130 Å from the origin cell. Total energy, band gap, equilibrium geometry, polarizability, and second hyperpolarizability of oligomers -(C(2)H(2))(m)-, with m up to 50 (202 atoms), and of the polymer have been compared. It turns out that oligomers of that length provide an extremely poor representation of the infinite chain polarizability and hyperpolarizability when the gap is smaller than 0.2 eV (that is, for LDA and PBE). Huge differences are observed on α(xx) and γ(xxxx) of the polymer when different functionals are used, that is in connection to the well-known density functional theory (DFT) overshoot, reported in the literature about short oligomers: for the infinite model the ratio between LDA (or PBE) and HF becomes even more dramatic (about 500 for α(xx) and 10(10) for γ(xxxx)). On the basis of previous systematic

  20. Influence of Co2+ on the structural and magnetic properties of substituted magnetites obtained by the coprecipitation method

    NASA Astrophysics Data System (ADS)

    Velásquez, A. A.; Urquijo, J. P.

    2015-06-01

    In this paper we report the effect of divalent cobalt on the structural and magnetic properties of substituted magnetites, Fe 3- x Co x O 4, with γ=Co 2+/Fe = 0, 5, 10, 15, 20 and 30 % wt, synthesized by the coprecipitation method. The samples were characterized by Atomic Absorption Spectroscopy, X-ray Diffraction, room temperature Mössbauer Spectroscopy and Vibrating Sample Magnetometry. The effect of Co 2+ was found to depend strongly of the concentration employed in the synthesis process. For γ≤15 % the Co 2+ promotes the formation of particles more crystalline and with higher saturation magnetization, remanence and coercivity than those obtained in absence of this cation. A sequential increasing of the lattice parameter is observed, as well as a reduction in the hyperfine magnetic field of the Fe 2.5+sub spectrum, while the hyperfine magnetic field of the Fe 3+sub spectrum keeps almost constant. For γ=20 % and 30 % the crystallinity of the samples decreases, particle size distribution effects are evidenced and the saturation magnetization decreases drastically. The results suggest that for low Co 2+ contents the substitution of Fe 3+by Co 2+ at octahedral sites of the inverse spinel system is the dominant effect, while for the highest concentrations used the substitution of Fe 2+ by Co 2+ and the increasing of the particle size distribution are the dominant effects.