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Sample records for crystalline substituted polyacetylenes

  1. 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.

  2. 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.

  3. Liquid crystalline light-emitting thermally stable readily processable substituted polyacetylenes

    NASA Astrophysics Data System (ADS)

    Tang, Ben Z.; Lam, Jacky W.; Luo, Jingdong; Dong, Yuping; Cheuk, Kevin K.; Xie, Zhiliang; Kwok, HoiSing

    2001-12-01

    Mesomorphic and luminescent poly(propiolates) with different skeleton structures (-{(R)CequalsC[CO2(CH2)6OCO-Biph- OC7H15]}n-; R equals H (1), CH3 (2), C6H5 (3), Biph equals biphenylyl} are synthesized. The backbone absorption in 2 and 3 are weak but upon photoexcitation, the polymers emit strong violet light of 369 nm, whose intensities are higher than that from poly(l-phenyl-l-octyne), a well-known highly-fluorescent polyacetylene. The main chain of 3 absorbs strongly at 380 nm, and the polymer is completely nonluminescent. All the polymers are thermally stable and form enantiotropic monolayer SmA phase, with 1 adopting well-ordered packing arrangements.

  4. 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.

  5. Phase Structures and Transition of Side-Chain Liquid Crystalline Polyacetylene

    NASA Astrophysics Data System (ADS)

    Chen, Er-Qiang; Ye, Chun; Cheng, S. Z. D.; Lam, Jacky W. Y.; Tang, Ben-Zhong

    2002-03-01

    A side-chain liquid crystalline polyacetylene, poly(5-[(4’-heptoxy-4-biphenylyl) carbonyl]oxy-1-pentyne) (-CH=C[(CH_2)3-OCO-Biph-OC_7H_15]n-), was synthesized. The polymerization catalyzed by WCl_6-Ph_4Sn under optimal condition produced the polymer of high molecular weight (up to 1.2 x 10^5), with predominantly a trans structure of good stereo-regularity. Both the smectic A (SA) and C (SC) phases were found, giving the d spacings of 2.3 and 3.3 nm, respectively. The coexistence of SA and SC is possible at low temperature range due to the specific molecular shape of the sample. Three broad transitions were observed upon heating: the flexible alkyl tails of the side-chain melts at 90 °C approximately, and the transformations from SA and SC to an isotropic melt occur at the peak temperatures of 160 and 170 °C, respectively. The separated SA and SC structures were obtained by the STM scanning at room temperature.

  6. Construction of Molecularly Imprinted Polymer Microspheres by Using Helical Substituted Polyacetylene and Application in Enantio-Differentiating Release and Adsorption.

    PubMed

    Liang, Junya; Wu, Yi; Deng, Jianping

    2016-05-18

    Chiral molecularly imprinted polymer microspheres (MIPMs) reported so far are majorly limited to being constructed by using achiral polymer together with chiral template. The present contribution reports on a unique type of chiral MIPMs consisting of chirally helical substituted polyacetylene, which are prepared through suspension polymerization by using (a)chiral acetylenics as monomer and chiral Boc-d/l-proline as template. The resulting MIPMs after removing the template show optical activity that is derived from the chirally helical structures of substituted polyacetylene. The microspheres demonstrate enantio-differentiating ability in releasing the enantiopure templates. A complete release of the template provides the chiral MIPMs. Worthy to mention is that the two chiral sources (chirally helical conformation and chiral template configuration) work in a synergistic way, obviously increasing the MIPMs' enantiodiscrimination ability. The present study develops a strategy for preparing chiral MIPMs, which are expected to find significant applications in chiral separation, enantioselective release of chiral drugs, etc. PMID:27117526

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  9. Mesomorphic and luminescent properties of disubstituted polyacetylenes bearing biphenyl pendants

    NASA Astrophysics Data System (ADS)

    Lam, Jacky W. Y.; Law, Chi Kong; Dong, Yuping; Wang, Jiannong; Ge, Weikun; Tang, Ben Zhong

    2003-01-01

    Liquid crystalline and light emitting properties of two new disubstituted polyacetylenes bearing biphenyl pendants (-{(R)CC[(CH 2) 4OCO-Biph-OC 7H 15]} n-, RCH 3 ( 1), C 6H 5 ( 2), Biph=4,4 '-biphenylyl) were investigated. Whereas 1 formed enantiotropic nematic phase, 2 was non-mesomorphic. Upon photoexcitation, the THF solutions of 1 and 2 emitted strong UV and blue light of 369 and 460 nm, respectively, whose quantum efficiencies were higher than that of poly(1-phenyl-1-octyne), a highly luminescent disubstituted polyacetylene.

  10. 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

  11. 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

    2015-01-01

    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

  12. 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.

  13. Interchain coupling and 3D modeling of trans-polyacetylene

    SciTech Connect

    Bronold, F.; Saxena, A.; Bishop, A.R.

    1992-01-01

    In spite of the success of the SSH model for trans-polyacetylene in interpreting many experimental results (e.g. optical and magnetic properties) there remain some aspects of the real material which are outside the scope of the simple 1D model. Especially ordering phenomena of doped and undoped trans-polyacetylene as well as transport properties (e.g. electronic and thermal conductivity) are beyond a 1D description. There are many attempts to construct a transport theory for this novel class of materials using solitons or polaxons as the basic ingredients. But so far it is not yet clear whether these typical 1D excitations still exist in crystalline transpolyacetylene. Therefore, to clarify the role which intrinsic self-localized nonlinear excitations characteristic of 1D models play in the bulk (3D) material, we study the stability of a polaronic excitation against interchain coupling. As a preliminary step we consider first two coupled t-(CH){sub x}-chains where the {pi}-electrons are allowed to hop from one chain to the other. Then we introduce a 3D generalization of the SSH model and study a polaron in a 3D crystalline environment.

  14. Interchain coupling and 3D modeling of trans-polyacetylene

    SciTech Connect

    Bronold, F.; Saxena, A.; Bishop, A.R.

    1992-09-01

    In spite of the success of the SSH model for trans-polyacetylene in interpreting many experimental results (e.g. optical and magnetic properties) there remain some aspects of the real material which are outside the scope of the simple 1D model. Especially ordering phenomena of doped and undoped trans-polyacetylene as well as transport properties (e.g. electronic and thermal conductivity) are beyond a 1D description. There are many attempts to construct a transport theory for this novel class of materials using solitons or polaxons as the basic ingredients. But so far it is not yet clear whether these typical 1D excitations still exist in crystalline transpolyacetylene. Therefore, to clarify the role which intrinsic self-localized nonlinear excitations characteristic of 1D models play in the bulk (3D) material, we study the stability of a polaronic excitation against interchain coupling. As a preliminary step we consider first two coupled t-(CH){sub x}-chains where the {pi}-electrons are allowed to hop from one chain to the other. Then we introduce a 3D generalization of the SSH model and study a polaron in a 3D crystalline environment.

  15. Crystallinity-dependent substitutional nitrogen doping in ZnO and its improved visible light photocatalytic activity.

    PubMed

    Yu, Zongbao; Yin, Li-Chang; Xie, Yingpeng; Liu, Gang; Ma, Xiuliang; Cheng, Hui-Ming

    2013-06-15

    Increasing visible light absorption of wide-bandgap photocatalysts (for example, ZnO and TiO2) plays a pivotal role in improving their photocatalytic activity. In this work, we show that substitutional nitrogen doping can be realized in semi-crystalline zinc oxide (ZnO) nanoparticles but fails for highly crystalline ZnO by heating the ZnO at a temperature of 400°C in gaseous ammonia atmosphere. The results suggest that substitutional nitrogen for lattice oxygen is strongly dependent on the crystallinity of ZnO. The nitrogen doped ZnO obtained shows an improved visible light photocatalytic activity in the degradation of organic dyes due to its increased visible light absorption. The origin of the increased visible light absorption is theoretically attributed to the formed N 2p localized states in the bandgap. PMID:23561822

  16. Staging in polyacetylene-iodine conductors

    NASA Astrophysics Data System (ADS)

    Baughman, R. H.; Murthy, N. S.; Miller, G. G.; Shacklette, L. W.

    1983-07-01

    Evidence is presented for the existence of highly conducting polyacetylene complexes with structures related to high-stage graphite, as well as structures related to first-stage graphite. X-ray diffraction measurements on polyacetylene-iodine complexes indicate equatorial lines at 7.7-8.0 and 13.8-14.3 Å. The shorter spacing arises in part from a structure in which iodine-rich planes alternate with planes of polyacetylene chains. The longer spacing, which disappears upon atmospheric exposure, is consistent with a structure analogous to third-stage graphite in which dopant-rich planes are separated by three close-packed planes of polyacetylene chains. The third-stage complex can be viewed as a perturbation of the structure of undoped polyacetylene, with the region between dopant layers consisting essentially of a one unit cell thickness of the parent polymer structure. Packing calculations for this model, in which a linear column of anions (I3- and/or I5-) displaces either every chain or every other chain in the dopant-rich layer, provide an interlayer spacing which is equal to that observed. Evidence consistent with third-stage structures (with both fractional occupation and complete occupation of the dopant plane) is also found by reexamination of published sorption data, which provides slope changes at close to the calculated limiting compositions for these structures [(CHI0.056)x and (CHI0.13)x]. However, a first-stage structure with alternating dopant arrays and polymer chains in the dopant plane [for which (CHI0.13)x is calculated] provides a better explanation for the second slope change, as well as for the composition obtained under dynamic vacuum, (CHI0.14)x. These results for iodine complexes are compared with those derived for the group VA halide complexes of polyacetylene.

  17. Phonons of the cis-polyacetylene chain

    NASA Astrophysics Data System (ADS)

    Faulques, Eric; Buisson, Jean-Pierre; Lefrant, Serge

    1995-12-01

    An investigation of the in-plane phonons of the cis-polyacetylene chain (CH)x and isotopic analogs (CD)x and (13CH)x is presented on the basis of a Fourier's dynamical D-matrix formalism. The conjugation is found to be similar to that of the trans-polyacetylene chain. Phonon dispersions have been calculated and follow the shapes predicted by Božović. Finally, the most interesting result is that phonon density of states exhibits van Hove singularities whose energies are close to those determined experimentally with incoherent inelastic neutron scattering.

  18. Preparation and performance of hydroxypropyl methylcellulose esters of substituted succinates for in vitro supersaturation of a crystalline hydrophobic drug.

    PubMed

    Yin, Ligeng; Hillmyer, Marc A

    2014-01-01

    We prepared hydroxypropyl methylcellulose (HPMC) esters of substituted succinates and examined their performance for improving the aqueous solubility of crystalline hydrophobic drugs in spray-dried dispersions (SDDs). From one HPMC, we synthesized five HPMC esters using various monosubstituted succinic anhydrides. These HPMC esters along with a commercial HPMC acetate succinate (HPMCAS) were spray-dried from solutions with phenytoin. The SDDs with different matrices at 10 wt % loading had very similar bulk properties with a minimal amount of detectable crystalline phenytoin as revealed by scanning electron microscopy (SEM), powder X-ray diffraction (powder XRD), and differential scanning calorimetry (DSC). In solution, while the SDD with HPMCAS was very effective at achieving high levels of phenytoin supersaturation initially, it was not competent at maintaining such supersaturation due to the rapid crystallization of the dissolved phenytoin. Alternatively, SDDs with several synthesized HPMC esters of substituted succinates not only achieved rather high initial supersaturation but also maintained high concentrations for extended time (i.e., 1.5 h and longer). Such maintenance was largely ascribed to the inhibition of phenytoin nucleation. Structure-property relationships were established, and the most successful systems contained a high degree of substitution and a combination of a thioether with neighboring weak electron-withdrawing groups in the substituted succinic anhydrides. The effective maintenance of supersaturated solutions was only found in SDDs with rather low drug loadings, which indicates the significance of sufficiently high concentrations of polymer additives in the dissolution media. PMID:24320108

  19. Structure of lithium-doped polyacetylene

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1989-12-01

    A trigonal structure with three polymer chains per lithium column is proposed for lithium-doped polyacetylene. A calculation of the x-ray diffraction profile, using the unit-cell dimension and the lithium concentration as the only variables, is in good agreement with the observed data. The proposed structure optimizes the electrostatic interactions by maximizing both the Li+-Li+ separations and the coordination of negatively charged carbons and positively charged lithiums. Unlike the tetragonal lattice found in polyacetylene complexed with larger alkali-metal ions (K+, Rb+, and Cs+), the trigonal structure permits the undoped and the doped phases to coexist without any significant lattice mismatch at the boundary between the two phases. While the chain axis expands by ~1% upon doping with lithium, the projected area per chain remains essentially unchanged.

  20. 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

  1. Structure of polyacetylene-iodine complexes

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Miller, G. G.; Baughman, R. H.

    1988-08-01

    We confirm the existence of a 15 Å period in iodine-doped polyacetylene and provide a new interpretation for this key feature as part of a general model for structural changes during iodine doping. The observed diffraction intensities for different samples suggest the existence of structures with two different types of dopant-containing layers: layers obtained by complete replacement of polyacetylene chains by iodine columns (F layers) and layers obtained by replacement of every other polyacetylene chain by an iodine column (P layers). The F layers in the heavily doped complex alternate with dopant-free layers of polyacetylene chains (U layers), corresponding to a (UF)n stacking sequence. The phase obtained at a lower dopant concentration, which provides the 15 Å spacing, is attributed to a (UPUF)n stacking sequence. At still lower dopant concentrations, one obtains a (UP)n stacking sequence. This model, along with published Raman, Mössbauer, and photoelectron spectroscopy data, suggests that the ratio of I-5 to I-3 increases in going from P layers to F layers. Intense and monotonically decreasing, diffuse x-ray scattering suggests that vacancies of size ˜3 Å are present, probably in iodine columns. A diffuse reflection at 3.1 Å, observed in all iodine-doped samples, is due to an average iodine-iodine distance in disordered columnar arrays. On the other hand, ordered arrays of iodine columns in oriented samples give rise to sharp meridional reflections. All ten observed reflections (down to 1.17 Å) in one sample could be indexed based on a 33.8 Å repeat corresponding to (-I-3-I-5-I-3-)n arrays. The observed diffraction pattern was calculated from this model without using any freely adjustable parameters.

  2. Dendrazawaynes A and B, antifungal polyacetylenes from Dendranthema zawadskii (Asteraceae).

    PubMed

    Rahman, Md Aziz Abdur; Cho, Soon-Chang; Song, Junsik; Mun, Hyeong-Tae; Moon, Surk-Sik

    2007-08-01

    Two new C(14) polyacetylenes dendrazawayne A(7) and dendrazawayne B (9) together with known C(13) polyacetylenes (2, 3), C(14) polyacetylenes (1, 4, and 8) and polyacetylene amides (5 and 6) were isolated from the roots of Dendranthema zawadskii. The structures of 7 and 9 were elucidated based on spectroscopic methods including 2D-NMR, HR-TOF-MS, IR, and UV. Compounds 1, 2, 3, 5, and 6 showed moderate activity against tumor cell lines (human small lung cancer cell line A549, melanoma SK-Mel-2, and mouse melanoma B16F1) with IC(50) values in the range of 7.4 - 30 microg/mL. Compounds 7 and 9, including other polyacetylenes, showed strong activity against the fungus Trichophyton (MIC: 5 - 10 microg/mL). PMID:17691057

  3. 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.

  4. Tuning magnetic exchange interactions in crystalline thin films of substituted Cobalt Phthalocyanine

    NASA Astrophysics Data System (ADS)

    Rawat, Naveen; Manning, Lane; Hua, Kim-Ngan; Headrick, Randall; Bishop, Michael; McGill, Stephen; Waterman, Rory; Furis, Madalina

    Magnetic exchange interactions in diluted organometallic crystalline thin film alloys of Phthalocyanines (Pcs) made of a organo-soluble derivatives of Cobalt Pc and metal-free (H2Pc) molecule and is investigated. To this end, we synthesized a organosoluble CoPc and successfully employed a novel solution-based pen-writing deposition technique to fabricate long range ordered thin films of mixtures of different ratios ranging from 1:1 to 10:1 H2Pc:CoPc. Our previous magnetic circular dichroism (MCD) results on the parent CoPc crystalline thin films identified different electronic states mediating exchange interactions and indirect exchange interaction competing with superexchange interaction. This understanding of spin-dependent exchange interaction between delocalized π-electrons with unpaired d spins along with the excitonic delocalization character enabled the further tuning of these interactions by essentially varying the spatial distance between the spins. Furthermore, high magnetic field (B < 25 T) MCD and magneto-photoluminescence show evidence of spin-polarized band-edge excitons in the same materials. This work was possible due to support by the National Science Foundation, Division of Materials Research MRI, CAREER and EPM program Awards: DMR-0722451, DMR-0821268, DMR-1307017 and DMR-1056589, DMR-1229217.

  5. Structural models for alkali-metal complexes of polyacetylene

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1990-02-01

    Structural models for a stage-2 complex are proposed for polyacetylene doped with less than about 0.1 potassium or rubidium atoms per carbon. These structures utilize as a basic motif an alkali-metal column surrounded by four planar-zig-zag polyacetylene chains, a structure found at the highest dopant levels. In the new stage-2 structures, each polyacetylene chain neighbors only one alkali-metal column, so the phase contains four polymer chains per alkali-metal column. Basic structural aspects for stage-1 and stage-2 structures are now established for both potassium- and rubidium-doped polyacetylene. X-ray-diffraction and electrochemical data show that undoped and doped phases coexist at low dopant concentrations (<0.06 K atom per C). X-ray-diffraction data, down to a Bragg spacing of 1.3 Å, for polyacetylene heavily doped with potassium (0.125-0.167 K atom per C) is fully consistent with our previously proposed stage-1 tetragonal unit cell containing two polyacetylene chains per alkali-metal column. There is no evidence for our samples requiring a distortion to a monoclinic unit cell as reported by others for heavily doped samples. The nature of structural transformations and the relationship between structure and electronic properties are discussed for potassium-doped polyacetylene.

  6. 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

  7. Structure and staging in polyacetylene charge-transfer complexes

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1989-10-01

    A structure is proposed for a stage-2 complex of polyacetylene which contains potassium as the dopant ion. This structure utilizes as a basic motif an alkali-metal column surrounded by four polyacetylene chains; this motif is also found in the tetragonal phase that appears at higher dopant concentrations. In the new structure, each polyacetylene is adjacent to one alkali-metal column, so the phase contains four polymer chains per alkali-metal column as compared with two chains per column for the tetragonal phase. X-ray diffraction and electrochemical data show that a mixture of undoped and doped phases are present at low dopant concentrations. In light of these results, general aspects of staging in n-doped and p-doped polyacetylene are discussed.

  8. Infrared-photoinduced-absorption studies in soluble trans-polyacetylene

    NASA Technical Reports Server (NTRS)

    Dorsinville, R.; Tubino, R.; Krimchansky, S.; Alfano, R. R.; Birman, J. L.

    1985-01-01

    The observation of photoinduced excitations in trans-polyacetylene in its liquid form in the frequency range from 2000 to 6000/cm is reported on. These measurements strongly suggest that transpolyacetylene is capable of supporting charged solitons even in solution.

  9. Compatibility of polyacetylene with lithium battery materials

    SciTech Connect

    Not Available

    1982-07-01

    The object of this research is to evaluate polyacetylene (CHx) as a replacement for carbon as the cathode material in primary lithium/thionyl chloride (Li/SOC12) and lithium/sulfur dioxide (Li/SO2) batteries. The choice of the Li/SOC12 inorganic electrolyte cell is based on the fact that it is the highest energy density system known to date. By itself, the favorable ratio of obtainable work to weight is not sufficient. For Navy applications, the rate at which the cell supplies energy - the power density - is very important. CHx is a lightweight material with extremely high effective surface area (60 m squared/g) and good electrical conductivity when doped, thus making it a good candidate for an electrode in a high power density cell.

  10. 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. PMID:22945796

  11. Helical polyacetylene synthesized with a chiral nematic reaction field

    PubMed

    Akagi; Piao; Kaneko; Sakamaki; Shirakawa; Kyotani

    1998-11-27

    Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications. PMID:9831554

  12. Insulator-metal transition in trans-polyacetylene

    NASA Astrophysics Data System (ADS)

    Conwell, E. M.; Jeyadev, S.

    1988-07-01

    Optical and energy-loss data suggest that the soliton lattice, which accounts for the low Pauli susceptibility χP at average doping concentrations <4% to 6%, persists to higher . We have calculated the eigenvalues for a trans-polyacetylene chain with the electrons in soliton states for the geometry and y values appropriate to metallic Na-doped polyacetylene and the Coulomb potential of the ions and solitons on other chains included. We find that, allowing for chains ~100 C-H units in length, we can account for χP in the metallic state.

  13. Cytotoxic polyacetylenes from the Red Sea sponge Siphonochalina siphonella.

    PubMed

    Ayyad, Seif-Eldin N; Angawy, Rihab; Alarif, Waliled M; Saqer, Esraa A; Badria, Farid A

    2014-01-01

    Two new polyacetylenes, callyspongenol-D (1) and callyspongendiol (2), the known polyacetylene dehydrosiphonochalynol (3), and the known triterpenoid sipholenol-A (4) were isolated from the Red Sea sponge Siphonochalina siphonella. Their chemical structures were elucidated on the basis of spectroscopic analyses. The cytotoxicity of the isolated compounds towards the human mammary carcinoma cell line MCF-7 was determined by the lactate dehydrogenase (LDH) assay, and compounds 4 and 1 were found to be the most toxic of the four, with IC50 values of 8.8 and 11.7 microM, respectively. PMID:24873032

  14. Sequestered fulvinol-related polyacetylenes in Peltodoris atromaculata.

    PubMed

    Ciavatta, M Letizia; Nuzzo, Genoveffa; Takada, Kentaro; Mathieu, Véronique; Kiss, Robert; Villani, Guido; Gavagnin, Margherita

    2014-07-25

    The Mediterranean dorid nudibranch Peltodoris atromaculata that had been collected while feeding on Haliclona fulva was shown to sequester long-chain fulvinol-like polyacetylene metabolites (compounds 2-5) from the prey. They were isolated along with previously reported bromorenierins from the diethyl ether extracts of both the mollusk and the sponge. Their structures were elucidated by NMR spectroscopy and tandem FABMS analysis. Compound 5 exhibited in vitro growth inhibitory effects against the SKMEL-28 melanoma cell line. PMID:24950030

  15. Effects of strong electric fields in a polyacetylene chain

    NASA Astrophysics Data System (ADS)

    Muniz, C. R.; Cunha, M. S.

    2015-07-01

    In this work, we study the effects related to the creation of electron/hole pairs via application of an external electric field that acts on a pristine trans-polyacetylene molecular chain at zero-temperature. This phenomenon is termed Schwinger-Landau-Zener (SLZ) effect and arises when a physical system, which can even be the vacuum, is under the action of a strong, static and spatially homogeneous electric field. Initially, we investigate how the electrical conductivity of the polyacetylene changes with the applied field, by considering the carriers production as well as the variation of the interband gap according to certain ab initio models. Next, we analyse the competition between the SLZ effect and another one associated with the incidence of an uniform electric field on one-dimensional crystals - the Bloch oscillations. We evaluate the conditions in which these latter can be destroyed by the particles created through the same field that induces them, and verify the possibility of occurrence of the Bloch oscillations inside the trans-polyacetylene with frequencies equal to or higher than the terahertz scale.

  16. Montiporic acid D, a new polyacetylene carboxylic acid from scleractinian coral Montipora digitata.

    PubMed

    Kodani, Shinya; Sato, Kanna; Higuchi, Tomihiko; Casareto, Beatriz E; Suzuki, Yoshimi

    2013-10-01

    A new polyacetylene carboxylic acid named montiporic acid D (1) was isolated along with a known polyacetylene alcohol, (Z)-13,15-hexadecadien-2,4-diyn-1-ol (2) from scleractinian coral Montipora digitata. The structures of compounds were determined by analyses of NMR and MS spectra. PMID:23432335

  17. 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.

  18. 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.

  19. Statics and adiabatic dynamics of nonlinear excitations in defected polyacetylene

    SciTech Connect

    Phillpot, S.R.; Baeriswyl, D.; Bishop, A.R.; Lomdahl, P.S.

    1985-01-01

    Within the Su, Schrieffer and Heeger model we have calculated, both analytically and numerically, the effects of model impurities on the electronic structure and lattice distortion of trans-polyacetylene. We find that the electron-phonon coupling may result in a fundamental alteration of the impurity level location. In simulated photoexcitation experiments on the defected system we find that, in addition to the kinks and breathers produced in the undefected system, ''trapped kinks'', excitons and polarons may also be produced. We suggest that the polarons produced in this novel way may be unusually stable and play an important role in hopping conduction mechanisms.

  20. The structure of metallic complexes of polyacetylene with alkali metals

    NASA Astrophysics Data System (ADS)

    Baughman, R. H.; Murthy, N. S.; Miller, G. G.

    1983-07-01

    The crystal structures of sodium, potassium, rubidium, and cesium doped polyacetylene have been determined using crystal packing and x-ray diffraction analyses. Each of these metallic complexes is tetragonal, with the polyacetylene chains forming a host lattice in which the alkali metal ions are present in channels. Lithium appears to be too small to stabilize the channel structure and an amorphous structure is observed. Predicted unit cell parameters and x-ray diffraction intensities are in agreement with observed values. Similarities with the alkali metal doped graphite suggest that hybridization between carbon pz orbitals and metal s orbitals occurs. Such hybridization is expected to result in a high conductivity component normal to the chain direction. On the other hand, direct overlap between polymer chains appears small, since alkali metal columns separate polymer chains. Compositions calculated for the channel structures (from meridional diffraction spacings, the intensity of equatorial diffraction lines, measured volume expansion, and distances in model complexes) all range from y=0.12 to 0.18 for (CHMy)x, where M is sodium, potassium, rubidium, or cesium.

  1. A long-lasting polyacetylene battery with high energy density

    NASA Astrophysics Data System (ADS)

    Nagatomo, T.; Honma, T.; Yamamoto, C.; Negishi, K.; Omoto, O.

    1983-05-01

    The polyacetylene battery has (CH)x films in different oxidation states as its electrodes. The experiments are carried out in the absence of air and moisture in an argon atmosphere in a dry glass vessel. The films have the dimensions 1.0 x 2.0 x 0.005 cm. The n-(CH)/LiClO4/p-(CH) battery (1.0 M LiClO4 in propylene carbonate) prepared by passing 2.14 C (dopant concentration y = 0.072) exhibits an open-circuit voltage of 3.5 V and an initial short-circuit current of 28 mA. No degradation of the polyacetylene battery is observed, even after 2000 successive charge/discharge cycles. Each cycle consists of a 10-min discharge at a constant resistance of 50 kohm and a 10-min charge at 0.1 mA, the stored charge being 0.06 C (y = 0.002). The batteries can be used at temperatures ranging from -20 C to 50 C.

  2. 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/.

  3. Charge oscillations and structure for alkali-metal-doped polyacetylene

    NASA Astrophysics Data System (ADS)

    Baughman, R. H.; Murthy, N. S.; Eckhardt, H.; Kertesz, M.

    1992-11-01

    Symmetry-breaking structural and charge oscillations are calculated for (CpHp)- lattices (p=5 to 9) and used to predict Coulombic expansion coefficients, x-ray photoelectron spectra, and crystallographic features that can be compared with experimental results. Extension of these predictions to other dopant concentrations is provided by derived analytical expressions. The parameters for the infinite lattices are derived from oligomer-ion results obtained from modified neglect of differential overlap calculations. Such calculations on oligomer ions with different parametrizations provide essentially identical changes in charge and structural parameters upon doping and these changes are in excellent agreement with the results of infinite-chain calculations. The degree to which oligomer-ion segments retain the structural parameters of charged arrays for the infinite lattice is remarkable. Derived geometries and charge distributions indicate two different types of charged defects, solitons (or antisolitons) and split solitons (or split antisolitons), and the geometry and charge distribution of the latter defects is shown to correspond to the average of those for two soliton lattices that have a relative shift of two CH units. At least in the absence of an external Coulomb field, soliton and split-soliton lattices for p odd are quasidegenerate, and the lattices for p even consist of alternating sequences of solitons and split antisolitons. Large oscillations in local chain-axis direction are predicted, which is a consequence of both oscillations in bond angles and the nonequivalence of even (and odd) bond lengths. Including these effects provides predicted Coulombic expansion coefficients that are in good agreement with observations for Na-doped polyacetylene. Much smaller bond-angle oscillations are predicted for anion lattices than for cation lattices, which can be at least partially explained by Coulomb effects. Observed 13C NMR chemical shifts are consistent with

  4. Metal-insulator transition in trans-polyacetylene

    NASA Astrophysics Data System (ADS)

    Conwell, E. M.; Mizes, H. A.; Jeyadev, S.

    1989-07-01

    We have calculated the band structure for a chain of doped trans-polyacetylene using the electronic part of the Su-Schrieffer-Heeger Hamiltonian plus the Coulomb potential arising from ions and charged solitons surrounding the chain. The lattice structure used was that determined by x rays for Na-doped polyacetylene. To agree with a number of experimental observations the donated electrons were taken to be in soliton states at all dopant concentrations. In obtaining the potential of a point charge on a chain in the metallic state, the confinement of the free electrons to a chain was taken into account. Because screening depends on the calculated energy levels, specifically on the density of states at the Fermi energy, η(EF), in the metallic state, which, in turn, depend on the potential used to obtain them, self-consistency was required in the calculations. The energy-level structure was found to depend strongly on the ion spacing, conveniently measured in terms of the average spacing a of C-H's along the chain. For ion spacing 5a, characteristic of the Na-ion-rich regions up to an average dopant concentration of ~6%, the chain remained semiconducting. For ion spacing 4a, which appears to characterize the next phase for Na doping, metallic behavior was found for a doped chain length of ~100 sites or more. Self-consistency was fulfilled with η(EF) equal to the value obtained from the saturation spin susceptibility in the metallic state. In addition to sufficiently long chains that the level spacing is comparable to kT, the metal-insulator transition is found to require considerable overlap of electron wave functions on adjacent solitons and a fairly deep potential well. The transition is best described as a Mott transition. Our model predicts that a sample in the metallic state at room temperature becomes semiconducting at lower temperature. Evidence for this is found in the temperature variation of the spin susceptibility and of ESR linewidth. It is argued that

  5. 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.

  6. Kinetics Of Isomerisation Reaction Of Oriented Polyacetylene Induced By Laser

    SciTech Connect

    Mammeri, S.; Belloum, M.; Tabacik, V.

    2008-09-23

    The impact of a laser's photons ({lambda} = 514.5 nm) on the surface of polyacetylene films (PA), composed of macromolecules PAcis and PAtrans produces simultaneously thermal and Raman diffusion [1]. The thermal effect initializes the isomerization of macromolecules PAcis to PAtrans [2]; this reaction is exothermic. Samples are polyacetylene oriented films synthesized horizontally or vertically in cis configuration and are subject to different laser powers during intervals of time which vary between 20 s and 250 s. The power (P ({lambda}), mW) of the laser is equivalent to the temperature T, of isomerization [3]. Isotherms are constructed and are characterized by the laser power applied. We have established theoretical models calculations with the aim of determining the kinetic parameters of the reaction of isomerization: the activation energy (Ea), the frequency factor of Arrhenius (A), and the rate constant (k). We concluded that even in the field of seconds, the isomerization is a complex process different from a reaction of order: 1, 7/10, 2/3, 3/5, 1/2, 2/5 and 1/4. The order 2/3 being the most suitable. The study determined, among others, the rate constants k 2/3 (T)(of the order 2/3 of the isomerization reaction)= 0.003337244, 0.0052149, 0.0209636, 0.043727 s-1 respectively for Laser powers 30, 120, 200 and 300 mW; activation energy 17.7844 kcal/mol and a factor of collision 19.066816 10{sup 6} s{sup -1}. These results are found to be close to the experimental results studied.

  7. Effect of contact between a current collector and a polyacetylene electrode on electrochemical behavior in polyacetylene/lithium batteries

    NASA Astrophysics Data System (ADS)

    Chen, S.-A.; Chiou, Y.-C.

    1984-05-01

    Organic batteries with a polyacetylene film (PA) as the anode, a lithium strip as the cathode, and lithium perchlorate dissolved in propylene carbonate as the electrolyte are constructed. Charging and discharging characteristics of three batteries with different types of PA electrode are investigated. Type a PA electrode involves mechanical pressed contact of nickel gauze with the upper portion of the PA electrode; charging and discharging of the battery are difficult due to the semiconducting characteristic of the PA. Type b involves a PA film which has one side coated with a sputtered palladium (Pd) film; good contact of the Pd current collector with the PA electrode makes charging and discharging easily manageable. Type c involves an iodine-doped PA film; the battery is easily charged and discharged, but cleaning the surface of the lithium electrode is necessary after a few cycles.

  8. 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.

  9. 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 PAGESBeta

    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 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

  10. 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. PMID:25853274

  11. 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.

  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. PMID:26451696

  13. Chaotic Soliton Dynamics in Photoexcited trans-Polyacetylene.

    PubMed

    Bernasconi, Leonardo

    2015-03-01

    We study the photogeneration of topological solitons in trans-polyacetylene and their time evolution using ab initio excited-state dynamics. The system is excited to the optically allowed 1(1)Bu state, and the atoms are then propagated classically using quantum mechanical forces computed using hybrid time-dependent density functional theory (TD-DFT). A soliton/antisoliton pair nucleates spontaneously and creates two independent solitons moving at constant velocity, similar to simulations based on uncorrelated lattice models like the Su-Schrieffer-Heeger (SSH) Hamiltonian [Su, W. P.; Schrieffer, J. R.; Heeger, A. J. Phys. Rev. Lett. 1979, 42, 1698]. At T = 0, the solitons coalesce into bound pairs with a two-soliton functional form, whereas chaotic dynamics, in the form of 2-bounce resonances, is observed at soliton/antisoliton collisions at T ≠ 0. This behavior is related to the onset of a strong correlation regime at short intersoliton distance, which is not accounted for by SSH simulations. PMID:26262671

  14. Bioactive Sesquiterpenoid and Polyacetylene Glycosides from Atractylodes lancea.

    PubMed

    Xu, Kuo; Jiang, Jian-Shuang; Feng, Zi-Ming; Yang, Ya-Nan; Li, Li; Zang, Cai-Xia; Zhang, Pei-Cheng

    2016-06-24

    Nine new sesquiterpenoids (1-9), five new polyacetylenes (10-14), and six known compounds were isolated from the rhizomes of Atractylodes lancea. These new chemical structures were established using NMR, MS, and ECD data. Notably, compounds 3-5, the aglycone of which possesses two stereogenic centers (C-5 and C-7), exhibited similar ECD spectra to compounds 1 and 2, the aglycone of which possesses one stereogenic center (C-7). Such a difference was supported by the experimental and calculated ECD data and single-crystallographic analyses of 3a. In addition, compound 3 inhibited lipopolysaccharide-induced NO production in BV2 cells with an IC50 value of 11.39 μM (positive control curcumin, IC50 = 4.77 μM); compound 4 showed better hepatoprotective activity against N-acetyl-p-aminophenol-induced HepG2 cell injury than the positive drug (bicyclol) at a concentration of 10 μM (p < 0.001). PMID:27228227

  15. Synthesis and characterization of a polyacetylene derivative with phenylazobenzene moieties.

    PubMed

    Gal, Yeong-Soon; Jin, Sung-Ho; Lyoo, Won Seok; Park, Jong-Wook; Lim, Kwon Taek

    2011-08-01

    A new polyacetylene derivative was prepared by the activated polymerization of 2-ethynylpyridine by using 4-(phenylazo)benzoyl chloride without any additional initiator or catalyst in high yield. The chemical structure of poly[2-ethynyl-N-(4-(phenylazo)benzoyl) pyridinium chloride [PEPABPC] was characterized by such instrumental methods as NMR, IR, and UV-visible spectroscopies to have a conjugated polymer backbone system with the designed azobenzene moieties. The electrooptical and electrochemical properties of PEPABPC were studied. The photoluminescence spectrum showed that the PL peak is at 597 nm corresponding to the photon energy of 2.07 eV. The cyclovoltammograms of PEPABPC exhibited the irreversible electrochemical behaviors between the oxidation and reduction peaks. The oxidation current density of PEPABPC versus the scan rates is approximately linear relationship in the range of 30 mV/sec-150 mV/sec. It was found that the the kinetics of the redox process of this polymer is controlled by the reactant diffusion process from the oxidation current density of PEPABPC versus the scan rates. PMID:22103202

  16. Polyacetylene fibril growth in soluble Ziegler-Natta catalysts

    SciTech Connect

    Aldissi, M.; Schue, F.

    1984-01-01

    Free-standing polyacetylene films prepared by using the soluble Ziegler-Natta catalyst Ti(OBu)/sub 4//AlEt/sub 3/ are of great interest for they exhibit an electrical conductivity in the metallic regime, 10/sup 3/ (Omega cm)/sup -1/, when doped with various donors or acceptors. Scanning electron microscopy shows that the as-formed films consist of randomly oriented fibrils with a diameter and an interfibrillar distance depending upon the polymerization conditions. A detailed mechanistic study of the polymerization at -78/sup 0/C showed that the number of active centers for polymerization of acetylene, which consists of Ti/sup III/ species, is only one part per thousand of the total amount of catalyst. The morphology of the films and the fibril dimensions have a great effect on the properties of the polymer when it is doped with electron donors or acceptors, chemically or electrochemically. The doping process consists of the diffusion of the doping ion into the film and its fibrils with known diffusion rates under well-defined conditions. The homogeneity of the material is consequently affected by the diffusion factor, and therefore it is important to study the nature of the host polymer.

  17. 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.

  18. 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. PMID:22271098

  19. Effect of charge transfer on chain dimension in trans-polyacetylene

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Shacklette, L. W.; Baughman, R. H.

    1987-08-01

    X-ray diffraction measurements on all-trans-polyacetylene are consistent with a chain-axis length elongation upon donor doping (+0.026 Å for lithium and +0.04 Å for potassium) and a chain-axis length contraction upon acceptor doping (-0.010 Å for iodine), where the changes refer to the length L of a C2H2 unit (2.457 Å in the undoped polymer). These new experimentally derived results for heavily doped compositions, which ignore possible corrections for cell nonorthogonality in the lithium and iodine complexes, are similar to experimental results for graphite intercalation complexes and are consistent with theoretical predictions for doped polyacetylene. The meridional diffraction lines observed at L and L/2 for potassium-doped polyacetylene indicate that there is no lattice symmetry element which includes a translation operation of L/2 in the chain-axis direction. The observations are consistent with a structural model in which alkali-metal ions with an intracolumn spacing of 4.96 Å are commensurate with the polymer chains for the composition (CHM0.125)x. The likely polymer chain-axis repeat length is 2L (i.e., C4H4) and a lattice symmetry element which includes a translation of L is expected.

  20. Single crystalline and rare earth substituted La{sub 2}RuO{sub 5} investigated by x-ray diffraction and EXAFS spectroscopy

    SciTech Connect

    Riegg, S.; Reller, A.; Ebbinghaus, S.G.

    2012-04-15

    Single crystals of La{sub 2}RuO{sub 5} were obtained from a BaCl{sub 2} flux. The structure was determined by single crystal x-ray diffraction and compared to earlier x-ray and neutron powder diffraction results. The local structures of Ru and La/Ln in pure La{sub 2}RuO{sub 5} and the rare earth substituted La{sub 2-x}Ln{sub x}RuO{sub 5} (Ln=Pr, Nd, Sm, Gd, Dy) polycrystalline samples were determined from the extended x-ray absorption fine structures (EXAFS) of the K- and L{sub III}-edges of Ru, La, and Ln, respectively. A four shell model was developed to reduce the number of refinable parameters in the fit of the EXAFS spectra. The distribution of the Ln-ions in the layered crystal structure was determined by a comparison of the coordination spheres obtained from the Ln-edges with the unsubstituted La{sub 2}RuO{sub 5}. Interatomic distances were compared to the values obtained from the single crystal diffraction and were found to agree very well. - Graphical abstract: The crystal structure of La{sub 2-x}Ln{sub x}RuO{sub 5} (Ln=Pr, Nd, Sm, Gd, Dy) is shown viewed along the c-axis. The alternating stacking of LaRuO{sub 4} and LnO layers leads to the formation of zig-zag layers of corner sharing RuO{sub 6} octahedra. The La sites in the LaRuO{sub 4} layers are represented by light blue spheres, while the La/Ln sites in the LnO layers are colored dark blue. EXAFS investigations reveal a cationic ordering with roughly 65% of the substituting Ln ions occupying the LnO layers. Highlights: Black-Right-Pointing-Pointer Structure determination of La{sub 2}RuO{sub 5} by single crystal x-ray diffraction. Black-Right-Pointing-Pointer Ru-K EXAFS investigations of La{sub 2-x}Ln{sub x}RuO{sub 5} powder samples. Black-Right-Pointing-Pointer EXAFS of La and Ln in La{sub 2-x}Ln{sub x}RuO{sub 5} powder samples using K- and L{sub III}-absorption edges. Black-Right-Pointing-Pointer Good agreement of EXAFS results and crystal structure data despite low symmetry space group. Black

  1. 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.

  2. Changes in the quaternary structure and function of MjHSP16.5 attributable to deletion of the IXI motif and introduction of the substitution, R107G, in the α-crystallin domain

    PubMed Central

    Quinlan, Roy A.; Zhang, Yan; Lansbury, Andrew; Williamson, Ian; Pohl, Ehmke; Sun, Fei

    2013-01-01

    The archael small heat-shock protein (sHSP), MjHSP16.5, forms a 24-subunit oligomer with octahedral symmetry. Here, we demonstrate that the IXI motif present in the C-terminal domain is necessary for the oligomerization of MjHSP16.5. Removal increased the in vitro chaperone activity with citrate synthase as the client protein. Less predictable were the effects of the R107G substitution in MjHSP16.5 because of the differences in the oligomerization of metazoan and non-metazoan sHSPs. We present the crystal structure for MjHSP16.5 R107G and compare this with an improved (2.5 Å) crystal structure for wild-type (WT) MjHSP16.5. Although no significant structural differences were found in the crystal, using cryo-electron microscopy, we identified two 24mer species with octahedral symmetry for the WT MjHSP16.5 both at room temperature and at 60°C, all showing two major species with the same diameter of 12.4 nm. Similarly, at room temperature, there are also two kinds of 12.4 nm oligomers for R107G MjHSP16.5, but in the 60°C sample, a larger 24mer species with a diameter of 13.6 nm was observed with significant changes in the fourfold symmetry axis and dimer–dimer interface. This highly conserved arginine, therefore, contributes to the quaternary organization of non-metazoan sHSP oligomers. Potentially, the R107G substitution has functional consequences as R107G MjHSP16.5 was far superior to the WT protein in protecting βL-crystallin against heat-induced aggregation. PMID:23530263

  3. 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.

  4. 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.

  5. Electrochromic poly(acetylene)s with switchable visible/near-IR absorption characteristics.

    PubMed

    Pauly, Anja C; Varnado, C Daniel; Bielawski, Christopher W; Theato, Patrick

    2014-01-01

    Ferrocene is incorporated into a poly(acetylene) derivative via the postpolymerization amidation of a polymer precursor bearing pentafluorophenyl ester-leaving groups with aminoferrocene. While the neutral polymer exhibits a strong absorbance at 553 nm due to its conjugated backbone, oxidation of the ferrocene moieties with silver tetrafluoroborate causes the material to absorb in the near-IR (λ max ≈ 1215 nm). Subsequent reduction of the oxidized polymer with decamethylferrocene restores the initial absorbance profile, demonstrating that the material features switchable visible/near-IR absorption characteristics. PMID:23996218

  6. 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. PMID:21114468

  7. Dimensional changes as a function of charge injection for trans-polyacetylene: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Sun, Guangyu; Kurti, Jeno; Kertesz, Miklos; Baughman, Ray H.

    2002-10-01

    Charge-induced dimensional changes allow conducting polymers and single walled carbon nanotubes to function as electromechanical actuators. The unit cell of the prototypical conducting polymer, trans-polyacetylene, was calculated as a function of charge injection using density functional theory in combination with ultrasoft pseudopotentials using the solid-state Vienna ab initio simulation package. Test calculations on the charged pyridinium molecular ion give results in good agreement with the experimental geometry. Strain versus charge relationships are predicted from dimensional changes calculated using a uniform background charge ("jellium") for representing the counterions, which we show provides results consistent with experiment for doped polyacetylenes. These jellium calculations are consistent with further presented calculations that include specific counterions, showing that hybridization between the guest dopant ions and the host polyacetylene chains is unimportant. The lack of guest-host orbital hybridization allows a qualitative rigid band interpretation of the amount of charge transfer for both acceptor and donor doping. For polyacetylene, asymmetry of strain along the chain with respect to the sign of the charge is predicted: negative charge elongates and positive charge shortens the polymer. For charge less than 0.05e per carbon, an approximately linear dependence is obtained for the dependence of chain-direction strain on the amount of injected charge.

  8. 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.

  9. 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.

  10. Post-column sodiation to enhance the detection of polyacetylene glycosides in LC-DAD-MS analyses: an example from Bidens gardneri (Asteraceae).

    PubMed

    Silva, Denise Brentan; Rodrigues, Edilene Delphino; da Silva, Gil Valdo José; Lopes, Norberto Peporine; de Oliveira, Dionéia Camilo Rodrigues

    2015-04-01

    The use of liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) in dereplication studies of medicinal plants is a common strategy, but the analyses of polyacetylenes by LC-ESI-MS are little explored and require huge efforts, especially if there are low concentrations in the extracts. A post-column sodiation strategy was successfully applied to enhance the detection of polyacetylene glycosides. Their molecular formulae were proposed by HRESI, whereas the polyacetylene chromophores were determined by UV data. The use of acetic acid in the mobile phase was essential to obtain satisfactory chromatographic resolution, and only the addition of sodium chloride solution allowed good mass spectra, internal calibration and undoubtedly the molar mass determination of polyacetylenes. This new approach has allowed the identification of polyacetylene glycosides from Bidens gardneri extract, guiding the isolation procedures, and two new compounds were obtained. The structures of the isolated polyacetylenes have been confirmed by 1D and 2D NMR, HRMS. PMID:25640130

  11. Two new polyacetylene derivatives from the Red Sea sponge Xestospongia sp.

    PubMed

    Ayyad, Seif-Eldin N; Katoua, Dina F; Alarif, Walied M; Sobahi, Tariq R; Aly, Magda M; Shaala, Lamiaa A; Ghandourah, Mohamed A

    2015-11-01

    Two new polyacetylenes (1 and 2), along with two known C-30 steroids (3 and 4) were identified from the Red Sea sponge, Xestospongia sp. The chemical structures were determined based on extensive spectroscopic measurements 1D (1H, 13C and DEPT) and 2D (COSY, HSQC and HMBC) NMR, UV, IR and MS. The new compounds 1 and 2 were evaluated for their antimicrobial and antitumor activities. 1 and 2 were active against multidrug- resistant bacteria with MICs ranged from 2.2 to 4.5 μM. No toxicity was recorded for the two tested compounds up to 5 μM using Artemia salina as a test organism. Compound 2 showed excellent antifungal activity against some pathogenic fungi such as Aspergillus niger and Candida albicans (MIC 2.2-2.5 μM) and antitumor activity against both Ehrlich ascites carcinoma and lymphocytic leukemia (LD50 5.0 μM). PMID:26618569

  12. GAS-PHASE ELECTRONIC SPECTRA OF POLYACETYLENE CATIONS: RELEVANCE OF HIGHER EXCITED STATES

    SciTech Connect

    Rice, C. A.; Rudnev, V.; Dietsche, R.; Maier, J. P.

    2010-07-15

    Transitions to higher electronic states of polyacetylene cations (HC{sub 2n}H{sup +}, n = 4, 5, 6) have been measured in the gas phase at {approx}20 K. The absorption spectra were obtained using a resonant two-color, two-photon fragmentation technique in an ion trap, allowing a direct comparison between laboratory and astrophysical data. The purpose was to investigate the relevance of such transitions to astronomical observations because the general expectation is that the bands could be too broad due to fast intramolecular processes. It is shown that the origin bands are still narrow enough (1-10 cm{sup -1}) to be considered, especially as the higher-lying transitions often possess large oscillator strengths.

  13. Switchable enantioseparation based on macromolecular memory of a helical polyacetylene in the solid state

    NASA Astrophysics Data System (ADS)

    Shimomura, Kouhei; Ikai, Tomoyuki; Kanoh, Shigeyoshi; Yashima, Eiji; Maeda, Katsuhiro

    2014-05-01

    In the chromatographic separation of enantiomers the order of elution is determined by the strength of diasteromeric interactions between the components of the mixture and a chiral stationary phase. For analytical purposes, it is ideal to have the minor component elute first, whereas in the preparative mode a faster elution of the major component is desirable. Here we describe a stationary phase constructed from a polyacetylene that bears 2,2‧-bisphenol-derived side chains in which chirality can be switched in the solid state prior to use. Both the macromolecular helicity of the polymer backbone and the axial chirality of the side chains can be switched in the solid state by interaction with a chiral alcohol, but importantly are maintained after removal of the chiral alcohol because of a memory effect. The chiral stationary phase thus prepared was used to separate the enantiomers of trans-stilbene oxide with the enantiomer elution order determined by the preseparation treatment.

  14. Lightweight rechargeable storage batteries using polyacetylene, /CH/x as the cathode-active material

    NASA Astrophysics Data System (ADS)

    Nigrey, P. J.; Macinnes, D., Jr.; Nairns, D. P.; MacDiarmid, A. G.; Heeger, A. J.

    1981-08-01

    It is pointed out that polyacetylene, (CH)x is the first example of a covalent organic polymer which may be chemically doped either p- or n-type to give a series of semiconductors and ultimately 'organic metals'. The electric conductivity can be varied over twelve orders of magnitude depending on the dopant concentration. A number of different dopant ions, solvents, electrolytes, electrolyte concentrations, and battery configurations have been investigated, only one of which is described in order to illustrate the potential application of (CH)x in batteries. The simplest battery configuration shown consists basically of a piece of (CH)x film, nearly all of which was immersed in a propylene carbonate solution of LiClO4. The top of the film was attached to a galvanostat. The negative terminal was attached to a lithium metal electrode immersed in the solution.

  15. Lcao-Gáspár-Kohn-Sham energy bands of trans-polyacetylene-chain

    NASA Astrophysics Data System (ADS)

    von Boehm, J.; Kuivalainen, P.; Calais, J.-L.

    1983-12-01

    The band structure of the dimerised trans-polyacetylene-chain ( d CC = 1.35 Å, d CC = 1.46 Å, ∡ CCC = 120° , d CH = 1.09 Å) is calculated with the (parameter-free, non-self-consistent) linear-combination-of-atomic-orbitals method using the Gáspár-Kohn-Sham (GKS) potential for the exchange and correlation. The calculated dimerisation gap of 1.6 eV agrees closely with experiment and also with other GKS calculations when the degree of dimerisation is taken into account. The calculated density of states agrees closely with the X-ray photoemission spectrum of Brundle.

  16. 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.

  17. 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.

  18. Local-density-functional results for the dimerization of trans-polyacetylene: Relationship to the band-gap problem

    NASA Astrophysics Data System (ADS)

    Mintmire, J. W.; White, C. T.

    1987-03-01

    We report the results of a computational study of the dimerization of the all-trans-polyacetylene chain within the local-density-func- tional formalism employing the Gáspár-Kohn-Sham exchange-correlation potential. Our calculated bond alternation at equilibrium is less than experimentally implied by roughly a factor of 3. Evidence is presented that suggests that this underestimation of dimerization is closely connected with the much discussed band-gap problem in local-density-functional theory.

  19. Metathetic polymerization of 1,3,5,7-cyclooctatetraene - a new approach to the synthesis of polyacetylene

    SciTech Connect

    Tlenkopachev, M.A.; Korshak, Yu.V.; Orlov, A.V.; Korshak, V.V.

    1987-05-01

    In recent years, there has been considerable interest in polyconjugated polymers which are used in the development of new photoconducting and electroconducting materials. The authors propose a new approach for the synthesis of polyacetylene by the polymerization of 1,3,5,7-cyclooctatetraene on metathesis catalysts. The authors tested various catalytic systems containing tungsten, molybdenum, and chromium. Chromium naphthenate catalysts did not display catalytic activity. The use of tungsten chloride and molybdenum chloride as Ziegler catalyst components gives insoluble polyacetylene powders ranging from brown to black. The system containing WCl/sub 6-n/(OCH(CH/sub 2/Cl)/sub 2/)/sub n/ (where n = 2-3) in combination with diethylaluminum chloride proved to be most active. However, the yield of insoluble polyacetylene in this case was virtually independent of the polymerization conditions and did not exceed a few percent. A much greater yield was obtained by condensing 1,3,5,7-cyclooctatetraene from the gas phase on a solid layer of a catalytic complex previously formed on the walls of the glass reactor or into a concentrated solution of the catalyst.

  20. Structural and electronic properties of trans-polyacetylene under local strain

    NASA Astrophysics Data System (ADS)

    Ketabi, S. A.

    2016-06-01

    A theoretical study is presented to investigate the structural and electronic properties of trans-polyacetylene (trans-PA) molecule under local strain. The influence of a local bending or compression of the space between neighboring carbon atoms on the band gap of the molecule was studied. Making use of an effective difference equation based on tight-binding procedure the band structure of trans-PA has been calculated. Our results indicate that the energy gap of the strained molecule modified significantly which affects the electronic properties of the molecule. We found that the size of the molecular gap is proportional to the bending angle so that for the bending perpendicular to π-orbitals plane the band gap reduced drastically and for the parallel one the band gap gradually increased. Furthermore, the current-voltage characteristics of the strained trans-PA molecule are studied. We found that under the local strain the threshold voltage for the current flow through the bent molecule decreased (increased) depending on the bending is perpendicular (parallel) to the molecule plane.

  1. 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.

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

    PubMed

    Barborini, Matteo; Guidoni, Leonardo

    2015-09-01

    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. PMID:26405437

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

    PubMed Central

    2015-01-01

    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. PMID:26405437

  4. Insecticidal and repellant activities of polyacetylenes and lactones derived from Atractylodes lancea rhizomes.

    PubMed

    Chen, Hai-Ping; Zheng, Li-Shi; Yang, Kai; Lei, Ning; Geng, Zhu-Feng; Ma, Ping; Cai, Qian; Du, Shu-Shan; Deng, Zhi-Wei

    2015-04-01

    During a screening program for new agrochemicals from Chinese medicinal herbs and local wild plants, the petroleum ether (PE) extract of Atractylodes lancea (Thunb.) rhizomes was found to possess repellent and contact activities against Tribolium castaneum adults. Bioactivity-directed chromatographic separation of PE extract on repeated silica-gel columns led to the isolation of two polyacetylenes, atractylodin and atractylodinol (1 and 2, resp.), and two lactones, atractylenolides II and III (3 and 4, resp.). The structures of the compounds were elucidated based on NMR spectra. The four isolated compounds were evaluated for their insecticidal and repellent activities against T. castaneum. Atractylodin exhibited strong contact activity against T. castaneum adults with a LD50 value of 1.83 μg/adult. Atractylodin and atractylenolide II also possessed strong repellenct activities against T. castaneum adults. After 4-h exposure, >90% repellency was achieved with atractylodin at a low concentration of 0.63 μg/cm(2) . The results indicated that atractylodin (1) and atractylenolide II (3) have a good potential as a source for natural repellents, and 1 has the potential to be developed as natural insecticide. PMID:25879503

  5. 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

  6. Skin Substitutes

    PubMed Central

    Howe, Nicole; Cohen, George

    2014-01-01

    In a relatively short timespan, a wealth of new skin substitutes made of synthetic and biologically derived materials have arisen for the purpose of wound healing of various etiologies. This review article focuses on providing an overview of skin substitutes including their indications, contraindications, benefits, and limitations. The result of this overview was an appreciation of the vast array of options available for clinicians, many of which did not exist a short time ago. Yet, despite the rapid expansion this field has undergone, no ideal skin substitute is currently available. More research in the field of skin substitutes and wound healing is required not only for the development of new products made of increasingly complex biomolecular material, but also to compare the existing skin substitutes. PMID:25371771

  7. Higher excited electronic transitions of polyacetylene cations HC2nH+ n = 2-7 in neon matrixes.

    PubMed

    Fulara, Jan; Grutter, Michel; Maier, John P

    2007-11-22

    The polyacetylene HC2nH+ n = 2-7 cations were produced from a mixture of diacetylene with helium in a hot cathode-discharge source. After a mass-selective deposition, their absorption spectra were studied in 6 K neon matrixes. Besides the known A2Pi <-- X2Pi system, several new transitions to higher excited 2Pi electronic states of these cations have been observed. In the case of HC4H+ and HC6H+, only one new weak absorption system has been detected with the onset at 336.1 and 417.2 nm, respectively. These C2Pi <-- X2Pi transitions form a series that extends to HC10H+. Two further electronic transitions are observed for HC8H+ through to HC14H+; a weaker B2Piu <-- X2Pig and a strong E2Piu <-- X2Pig in the UV. The integrated intensity of the UV system of the polyacetylene cations exceeds that of the A2Pi <-- X2Pi transition by an order of magnitude. PMID:17966999

  8. Inverted Solubility of the Pro 23 to Val Mutant of Human γD Crystallin-- Altered Phase Diagram from a Single Amino Acid Substitution and the Effect of PEG

    NASA Astrophysics Data System (ADS)

    McManus, J. J.; Lomakin, A.; Basan, M.; Ogun, O.; Pande, A.; Pande, J.; Benedek, G. B.

    2007-03-01

    Many genetic cataracts are the result of single point mutations in the amino acid sequence of lens crystallin proteins. The P23T mutation in human γD-crystallin (HGD) is associated with several different cataract phenotypes. The solubility of the protein shows an inverse temperature dependence. This is in contrast with the native protein. The replacement of Thr23 with a Ser or a Val residue shifts the location of the inverted solubility line to higher concentrations [1]. We describe the phase diagram of the P23V mutant of HGD, which exhibits aggregation, crystallization and liquid-liquid phase separation (LLPS). We have used QLS to probe the interactions of the protein in the soluble region of the phase diagram. We have developed a model to describe the observed retrograde solubility of the protein. Using PEG we introduce a so-called ``depletion interaction'' to further investigate the origin of the retrograde solubility. [1] A. Pande, O. Anunziata, N. Asherie, O. Ogun, G.B. Benedek, J. Pande, Biochemistry 44, 2491-2500 (2005).

  9. 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.

  10. 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.

  11. Optically Active Particles with Tunable Morphology: Prepared by Embedding Graphene Oxide/Fe3O4 in Helical Polyacetylene.

    PubMed

    Li, Weifei; Deng, Jianping

    2016-06-29

    We report a novel and straightforward methodology for constructing hybrid particles with tunable morphology (spherical vs nonspherical) by embedding inorganic components (graphene oxide and/or Fe3O4 nanoparticles) inside chiral helical polyacetylene. Scanning electron microscopic images ascertain the spherical or nonspherical morphology of the particles. The intense circular dichroism effects demonstrate that the hybrid particles (spherical, ellipsoid-like, and cake-like) possess remarkable optical activity. The use of the chiral magnetic hybrid particles in enantioselective crystallization of racemic phenylalanine demonstrates the kind of particles' significant potential applications in chiral technologies and chiral processes. The study not only creates an unprecedented type of chiral hybrid particles, but also provides a versatile strategy for preparing advanced functional hybrid particles with tunable morphology from polymers and even from inorganic and metallic materials. PMID:27285800

  12. Polyacetylene, (CH)/sub x/, as an emerging material for solar cell applications. Technical progress report, October, November, December 1979

    SciTech Connect

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

    1980-02-14

    Initial studies of p-n heterojunctions formed between undoped trans-(CH)/sub x/ and n-CdS are reported. The junctions were characterized by measurements of current vs voltage (I-V), capacitance vs voltage (C-V), and photovoltaic response spectra. The results are analyzed in terms of the standard heterojunction equations. It is concluded that undoped as-grown films of trans-(CH)/sub x/ are p-type with a residual acceptor concentration of 2 x 10/sup 18/ cm/sup -3/, and that in spite of the complex fibril morphology the semiconductor properties can be inferred by treating (CH)/sub x/ as an effective homogeneous medium. Detailed studies of the photovoltaic response at energies below the energy gap for (CH)/sub x/ imply the existence of a well-defined deep trapping state in polyacetylene with an energy near the center of the gap.

  13. H sub 3 PMo sub 12 O sub 40 -doped polyacetylene as a catalyst for ethyl alcohol conversion

    SciTech Connect

    Pozniczek, J.; Bielanski, A. ); Kulszewicz-Bajer, I.; Zagorska, M. ); Kruczala, K.; Dyrek, K. ); Pron, A. )

    1991-12-01

    A new and highly efficient catalyst was obtained by exploiting the unique ability of polyacetylene to incorporate heteropolyanions (HPA) of the Keggin type via oxidative doping. 12-Molybdophosphoric acid, 20.8 wt%, was introduced into the polymer. A uniform distribution of HPA over the cross section of the polymer film was found. However, the concentration of HPA seemed to be higher at the surface of the polymer fibers than in their bulk. The conversion of ethyl alcohol was used as a catalytic test reaction. The catalyst exhibited both acid-base activity (formation of ethylene and diethyl ether) as well as redox activity (formation of acetaldehyde). The acid-base activity was 10 times higher than that of unsupported H{sub 3}PMo{sub 12}O{sub 40}, and the redox activity was about 40 times higher.

  14. 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.

  15. Sensory Substitution

    NASA Astrophysics Data System (ADS)

    Verrillo, Ronald T.

    The idea that the cutaneous surface may be employed as a substitute for the eyes and ears is by no means a modern notion. Although the sense of touch has long been considered as a surrogate for both the visual and auditory modalities, the focus of this chapter will be on the efforts to develop a tactile substitute for hearing, especially that of human speech. The visual system is our primary means of processing information about environmental space such as orientation, distance, direction and size. It is much less effective in making temporal discriminations. The auditory system is unparalleled in processing information that involves rapid sequences of temporal events, such as speech and music. The tactile sense is capable of processing both spatial and temporal information although not as effective in either domain as the eye or the ear.

  16. Bioassay guided isolation of a new C18-polyacetylene, (+)-9(Z),17-octadecadiene-12,14-diyne-1,11,16-triol, from Cassonia barteri.

    PubMed

    Papajewski, S; Guse, J H; Klaiber, I; Roos, G; Süssmuth, R; Vogler, B; Walter, C U; Kraus, W

    1998-06-01

    A novel C18-polyacetylene, (+)-9( Z),17-octadecadiene-12,14-diyne-1,11,16-triol, has been isolated from the ethyl acetate extract of Cassonia barteri (Araliaceae) leaves collected in Cameroon. The structure determination was achieved by NMR, mass, IR, and UV spectroscopy. The new polyenyne shows antibacterial activity against Bacillus subtilis and Pseudomonas fluorescens, antifungal activity against Cladosporium cucumerinum, moiluscicidal activity against Biomphalaria glabrata at low concentrations, and in addition it possesses haemolytic activity. PMID:17253268

  17. Borate substituted ettringites

    SciTech Connect

    Csetenyi, L.J.; Glasser, F.P.

    1993-12-31

    The setting of cement is adversely affected by soluble borates. To reduce interference, the extent to which borate can be insolubilized has been investigated. One specific mechanism of insolubilization is by inclusion into ettringite. Ettringite, Ca{sub 6}Al{sub 2}(SO{sub 4}){sub 3}(OH){sub 12}{center_dot}26H{sub 2}O, is a normal and stable constituent of Portland cement. It has an open but non-zeolitic framework. Borate can substitute partially or fully for sulfate. Formation conditions, solubility and stability of borate ettringites, Ca{sub 6}Al{sub 2}(BO{sub 4}){sub 2-4}(OH,O){sub 12}{center_dot}26H{sub 2}O, are characterized using XRD, IR, DTA, and SEM. The potential durability of borate ettringites in a repository environment have been assessed by exposing it to Na-sulfate and Na-carbonate attack at different concentrations. Ion exchange occurs; back substitution of borate by sulfate is incomplete; high carbonate concentrations can, however, decompose borate ettringite. On heat treatment up to 85{degrees}C the crystalline morphology and the OH arrangement of the structure are altered, but the X-ray powder pattern, and hence its structural framework are largely unaffected. It is concluded that ettringite has potential to reduce the solubility of borate.

  18. Cataract-Linked γD-Crystallin Mutants Have Weak Affinity to Lens Chaperones α-Crystallins

    PubMed Central

    Mishra, Sanjay; Stein, Richard A.; Mchaourab, Hassane S.

    2012-01-01

    To test the hypothesis that α-crystallin chaperone activity plays a central role in maintenance of lens transparency, we investigated its interactions with γ-crystallin mutants that cause congenital cataract in mouse models. Although the two substitutions, I4F and V76D, stabilize a partially unfolded γD-crystallin intermediate, their affinities to α-crystallin are marginal even at relatively high concentrations. Detectable binding required further reduction of γD-crystallin stability which was achieved by combining the two mutations. Our results demonstrate that mutants and possibly age-damaged γ-crystallin can escape quality control by lens chaperones rationalizing the observation that they nucleate protein aggregation and lead to cataract. PMID:22289178

  19. Vitreous Substitutes.

    PubMed

    Foster, William Joseph

    2008-04-01

    Modern vitreoretinal surgery is a young science. While tremendous developments have occurred in instrument design and technique since Machemer first described vitrectomy surgery in 1973[1], the application of advanced materials concepts to the development of intra-ocular compounds is a particularly exciting area of research. To date, the development of vitreous substitutes has played a significant role in enabling the dramatic and progressive improvement in surgical outcome, but perhaps no other area of research has the potential to further improve the treatment of retinal detachment and other retinal disorders. While prior research has focused solely upon the ability of a compound to re-attach the retina, future research should seek to enable the surgeon to inhibit the development of proliferative vitreoretinopathy and re-detachment, the integration of stem-cell therapies with surgical retina, long-term delivery of medications to the posterior segment, and the promotion of more rapid and complete visual rehabilitation. PMID:19343097

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  2. 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. PMID:26723710

  3. 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.

  4. Energy systems based on polyacetylene: rechargeable batteries and Schottky barrier solar cells. Final report, March 1, 1981-February 29, 1984

    SciTech Connect

    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.

  5. Hückel-Hubbard-Ohno modeling of π-bonds in ethene and ethyne with application to trans-polyacetylene.

    PubMed

    Timár, Máté; Barcza, Gergely; Gebhard, Florian; Veis, Libor; Legeza, Örs

    2016-07-28

    Quantum chemistry calculations provide the potential energy between two carbon atoms in ethane (H3C-CH3), ethene (H2C[double bond, length as m-dash]CH2), and ethyne (HC[triple bond, length as m-dash]CH) as a function of the atomic distance. Based on the energy function for the σ-bond in ethane, Vσ(r), we use the Hückel model with Hubbard-Ohno interaction for the π electrons to describe the energies Vσπ(r) and Vσππ(r) for the σπ double bond in ethene and the σππ triple bond in ethyne, respectively. The fit of the force functions shows that the electron transfer matrix element and the Peierls coupling can be estimated with some precision whereas the Hubbard-Ohno parameters are insignificant at the distances under consideration. We apply the Hückel-Hubbard-Ohno model to describe the bond lengths and the energies of elementary electronic excitations of trans-polyacetylene, (CH)n, whereby we adjust the σ-bond potential for conjugated polymers. PMID:27348188

  6. Co-substitution of carbonate and fluoride in hydroxyapatite: Effect on substitution type and content

    NASA Astrophysics Data System (ADS)

    Zhu, Qing-Xia; Li, Ya-Ming; Han, Dan

    2015-04-01

    The nanosized hydroxyapatite substituted by fluoride and carbonate ions (CFHA) had been synthesized by aqueous precipitation method. CFHA had been considered as potential bone graft material for orthopedic and dental applications. The objective of this study was to determine the effects of simultaneously incorporated CO{3/2-} and F- on the substitution type and content. The morphologies of CFHAs were observed by TEM. The carbonate substitution type and content were characterized by FTIR. The fluoride contents were determined by F-selective electrode. The phase compositions and crystallinity of the samples were investigated by XRD. The fluoride and carbonate contents of CFHA increase with the dopant concentrations nonlinearly. The carbonate substitution has much more obvious effect on morphology compared with the fluoride substitution. The co-existence of CO{3/2-} and F- ions can influence the corresponding substitution fraction. The isomorphic substitution of sodium for calcium in the substitution process of CO{3/2-} can improve crystal degree and favor the B-type substitutions. Due to the closeness of the ion radii and equivalent substitution of F- and OH-, F- will occupy the OH- sites of HA crystals more easily, compelling most of the CO{3/2-} to be located in the B sites.

  7. Triamterene crystalline nephropathy.

    PubMed

    Nasr, Samih H; Milliner, Dawn S; Wooldridge, Thomas D; Sethi, Sanjeev

    2014-01-01

    Medications can cause a tubulointerstitial insult leading to acute kidney injury through multiple mechanisms. Acute tubular injury, a dose-dependent process, occurs due to direct toxicity on tubular cells. Acute interstitial nephritis characterized by interstitial inflammation and tubulitis develops from drugs that incite an allergic reaction. Other less common mechanisms include osmotic nephrosis and crystalline nephropathy. The latter complication is rare but has been associated with several drugs, such as sulfadiazine, indinavir, methotrexate, and ciprofloxacin. Triamterene crystalline nephropathy has been reported only rarely, and its histologic characteristics are not well characterized. We report 2 cases of triamterene crystalline nephropathy, one of which initially was misdiagnosed as 2,8-dihydroxyadenine crystalline nephropathy. PMID:23958399

  8. Crystalline Silica Primer

    USGS Publications Warehouse

    Staff- Branch of Industrial Minerals

    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.

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

    PubMed

    Matsushita, Satoshi; Kyotani, Mutsumasa; Akagi, Kazuo

    2011-11-01

    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. PMID:21970653

  10. 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.

  11. 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.

  12. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  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. 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.

  15. 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.

  16. Crystalline titanate catalyst supports

    SciTech Connect

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

    1991-12-31

    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.

  17. 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.

  18. COLLIDING CRYSTALLINE BEAMS.

    SciTech Connect

    WEI, J.

    1998-06-26

    The understanding of crystalline beams has advanced to the point where one can now, with reasonable confidence, undertake an analysis of the luminosity of colliding crystalline beams. Such a study is reported here. It is necessary to observe the criteria, previously stated, for the creation and stability of crystalline beams. This requires, firstly, the proper design of a lattice. Secondly, a crystal must be formed, and this can usually be done at various densities. Thirdly, the crystals in a colliding-beam machine are brought into collision. We study all of these processes using the molecular dynamics (MD) method. The work parallels what was done previously, but the new part is to study the crystal-crystal interaction in collision. We initially study the zero-temperature situation. If the beam-beam force (or equivalent tune shift) is too large then overlapping crystals can not be created (rather two spatially separated crystals are formed). However, if the beam-beam force is less than but comparable to that of the space-charge forces between the particles, we find that overlapping crystals can be formed and the beam-beam tune shift can be of the order of unity. Operating at low but non-zero temperature can increase the luminosity by several orders of magnitude over that of a usual collider. The construction of an appropriate lattice, and the development of adequately strong cooling, although theoretically achievable, is a challenge in practice.

  19. Colliding Crystalline Beams

    SciTech Connect

    Wei, Jie; Sessler, A.M.

    1998-06-01

    The understanding of crystalline beams has advanced to the point where one can now, with reasonable confidence, undertake an analysis of the luminosity of colliding crystalline beams. Such a study is reported here. It is necessary to observe the criteria, previously stated, for the creation and stability of crystalline beams. This requires, firstly, the proper design of a lattice. Secondly, a crystal must be formed, and this can usually be done at various densities. Thirdly, the crystals in a colliding-beam machine are brought into collision. We study all of these processes using the molecular dynamics (MD) method. The work parallels what was done previously, but the new part is to study the crystal-crystal interaction in collision. We initially study the zero-temperature situation. If the beam-beam force (or equivalent tune shift) is too large then over-lapping crystals can not be created (rather two spatially separated crystals are formed). However, if the beam-beam force is less than but comparable to that of the space-charge forces between the particles, we find that overlapping crystals can be formed and the beam-beam tune shift can be of the order of unity. Operating at low but non-zero temperature can increase the luminosity by several orders of magnitude over that of a usual collider. The construction of an appropriate lattice, and the development of adequately strong coding, although theoretically achievable, is a challenge in practice.

  20. 40 CFR 721.8780 - Substituted pyridine azo substituted phenyl.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted pyridine azo substituted... Specific Chemical Substances § 721.8780 Substituted pyridine azo substituted phenyl. (a) Chemical substance... substituted pyridine azo substituted phenyl (PMNs P-96-767 and P-96-773) are subject to reporting under...

  1. 40 CFR 721.8780 - Substituted pyridine azo substituted phenyl.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted pyridine azo substituted... Specific Chemical Substances § 721.8780 Substituted pyridine azo substituted phenyl. (a) Chemical substance... substituted pyridine azo substituted phenyl (PMNs P-96-767 and P-96-773) are subject to reporting under...

  2. 40 CFR 721.8780 - Substituted pyridine azo substituted phenyl.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted pyridine azo substituted... Specific Chemical Substances § 721.8780 Substituted pyridine azo substituted phenyl. (a) Chemical substance... substituted pyridine azo substituted phenyl (PMNs P-96-767 and P-96-773) are subject to reporting under...

  3. 40 CFR 721.8780 - Substituted pyridine azo substituted phenyl.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted pyridine azo substituted... Specific Chemical Substances § 721.8780 Substituted pyridine azo substituted phenyl. (a) Chemical substance... substituted pyridine azo substituted phenyl (PMNs P-96-767 and P-96-773) are subject to reporting under...

  4. 40 CFR 721.8780 - Substituted pyridine azo substituted phenyl.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted pyridine azo substituted... Specific Chemical Substances § 721.8780 Substituted pyridine azo substituted phenyl. (a) Chemical substance... substituted pyridine azo substituted phenyl (PMNs P-96-767 and P-96-773) are subject to reporting under...

  5. Liquid Crystalline Microemulsions

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Yueh; Petschek, Rolfe G.

    2000-03-01

    If an isotropic component of an emulsion is replaced by one having liquid crystalline (e.g. nematic) order the equilibrium behavior can change dramatically. There are long range enthalpic effects which can result in either repulsive or attractive interactions between the surfaces of an emulsion and entropic effects which generally result in an attractive interaction between these surfaces. We review briefly the possibility of stable blue-phase like microemulsions in mixtures of chiral nematics, appropriate surfactants and an incompatible isotropic solvent. We discuss the entropic effects in a lamellar phase, including the effects of changes in elastic constants and surface-nematic coupling. The effects of fluctuations on blue phases will be briefly discussed.

  6. 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.

  7. Nanocomposites with Crystalline Polymers

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2015-03-01

    The creation of ordered (layered) biomimetic materials typically follows a series of steps: first mix nanoparticles with water, organize the NPs by ice templating, evaporate the ice and then back fill with metal or polymer. We propose a simple method exploiting the in situ self-assembly of a crystalline polymer in the presence of nanoparticles to facilitate this process, and provide a completely new pathway for the synthesis of biomimetic materials. A suite of complementary experimental tools are used in this analysis. In parallel, we are developing theoretical tools to a priori predict the morphologies adopted by semicrystalline polymers. The convergence of these novel experimental and theoretical developments in the venerable field of semicrystalline polymers could lead to new applications for this largest class of commercially relevant polymeric materials. With Jacques Jestin, Brian Benicewicz, Dan Zhao, Longxi Zhao

  8. 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. PMID:15631421

  9. Managing Substitute Teaching.

    ERIC Educational Resources Information Center

    Jones, Kevin R.

    1999-01-01

    This news brief presents information on managing substitute teaching. The information is based on issues discussed at a summit meeting which included public school administrators and personnel directors from around the nation. The main topics of concern focused around four core components related to the management of substitute teaching:…

  10. 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.

  11. 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

  12. Topological Crystalline Insulators

    NASA Astrophysics Data System (ADS)

    Hsieh, Timothy

    2015-03-01

    Topological crystalline insulators (TCI) are new phases of matter in which nontrivial band topology and crystal symmetry unite to protect metallic states on the boundary. Remarkably, TCIs have been predicted and observed in the conveniently simple rocksalt SnTe class of IV-VI semiconductors. Despite the simple crystal structure, the interplay between topology and crystal symmetry in these materials have led to a rich variety of new phenomena, including the coexistence of massless and massive Dirac fermions arising from ferroelectric distortion and strain-induced flat band superconductivity. These new physical mechanisms are not only of intrinsic interest but may also find application in new transistor devices. After discussing the topological nature and potential uses of IV-VI family TCIs, I will present recent predictions of TCIs in several anti-perovskite materials. The origin of TCI in this new class of materials is strikingly different and involves the band inversion of two J = 3/2 quartets of Dirac fermions, which together form a ``Dirac octet.'' As interactions play a significant role in many anti-perovskites, this prediction serves as first step toward realizing TCIs in strongly correlated systems. This work is supported by NSF Graduate Research Fellowship No. 0645960 and DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0010526.

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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

  19. 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.

  20. Substitution of anticonvulsant drugs

    PubMed Central

    Steinhoff, Bernhard J; Runge, Uwe; Witte, Otto W; Stefan, Hermann; Hufnagel, Andreas; Mayer, Thomas; Krämer, Günter

    2009-01-01

    Changing from branded drugs to generic alternatives, or between different generic formulations, is common practice aiming at reducing health care costs. It has been suggested that antiepileptic drugs (AEDs) should be exempt from substitution because of the potential negative consequences of adverse events and breakthrough seizures. Controlled data are lacking on the risk of substitution. However, retrospective data from large medical claims databases suggest that switching might be associated with increased use of AED and non-AED medications, and health care resources (including hospitalization). In addition, some anecdotal evidence from patients and health care providers’ surveys suggest a potentially negative impact of substitution. Well-controlled data are needed to assess the real risk associated with substitution, allowing health care professionals involved in the care of patients with epilepsy to make informed decisions. This paper reviews currently available literature, based on which the authors suggest that the decision to substitute should be made on an individual basis by the physician and an informed patient. Unendorsed or undisclosed substitution at the pharmacy level should be discouraged. PMID:19707254

  1. Alkali metal crystalline polymer electrolytes.

    PubMed

    Zhang, Chuhong; Gamble, Stephen; Ainsworth, David; Slawin, Alexandra M Z; Andreev, Yuri G; Bruce, Peter G

    2009-07-01

    Polymer electrolytes have been studied extensively because uniquely they combine ionic conductivity with solid yet flexible mechanical properties, rendering them important for all-solid-state devices including batteries, electrochromic displays and smart windows. For some 30 years, ionic conductivity in polymers was considered to occur only in the amorphous state above Tg. Crystalline polymers were believed to be insulators. This changed with the discovery of Li(+) conductivity in crystalline poly(ethylene oxide)(6):LiAsF(6). However, new crystalline polymer electrolytes have proved elusive, questioning whether the 6:1 complex has particular structural features making it a unique exception to the rule that only amorphous polymers conduct. Here, we demonstrate that ionic conductivity in crystalline polymers is not unique to the 6:1 complex by reporting several new crystalline polymer electrolytes containing different alkali metal salts (Na(+), K(+) and Rb(+)), including the best conductor poly(ethylene oxide)(8):NaAsF(6) discovered so far, with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)(6):LiAsF(6). These are the first crystalline polymer electrolytes with a different composition and structures to that of the 6:1 Li(+) complex. PMID:19543313

  2. 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.

  3. 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

  4. The substitutability of reinforcers.

    PubMed

    Green, Leonard; Freed, Debra E

    1993-07-01

    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

  5. 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.

  6. Reversible mechanochromism and enhanced AIE in tetraphenylethene substituted phenanthroimidazoles.

    PubMed

    Misra, Rajneesh; Jadhav, Thaksen; Dhokale, Bhausaheb; Mobin, Shaikh M

    2014-08-21

    Tetraphenylethene (TPE) substituted phenanthroimidazoles 3a and 3b were designed and synthesized by the Suzuki cross-coupling reaction. They show reversible mechanochromic behavior with contrast colors between sky-blue and yellow green. The powder XRD studies show that destruction of a crystalline state into an amorphous state is responsible for mechanochromism. Hydrogen bonding interaction of a cyano-group in 3b results in enhanced AIE and improved thermal stability. PMID:24983656

  7. 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

  8. [Delegation yes, substitution no!].

    PubMed

    Schroeder, A

    2014-08-01

    The aging of society leads on the one hand to increasing case numbers and on the other hand to a reduction in the number of physicians available for patient treatment. The delegation and substitution of medical duties as a tried and tested method is increasingly being recommended in order to compensate for the lack of physicians. The Berufsverband der Deutschen Urologen (BDU, Professional Association of German Urologists) supports the guiding principle of the Bundesärztekammer (Federal Medical Council) of "delegation yes, substitution no" and rejects a substitution of medical duties by non-medical academic health personnel. Against the background of the demographic changes, the increasing need for treatment and the current deficiency of junior physicians, a more extensive inclusion of well-qualified and experienced non-medical personnel by the delegation of medically responsible duties (medical scope of practice) can be an appropriate measure to maintain a good medical service in practices, hospitals and nursing homes. PMID:25047595

  9. [Substitution therapy with diamorphine].

    PubMed

    Roy, Mandy; Bleich, Stefan; Hillemacher, Thomas

    2016-03-01

    After a long lead time the substitution with diamorphine was taken into the German catalogue of statutory health insurance in 2010. Currently about 570 patients are treated this way in 9 ambulances in Germany. The study phase as well as the clinical practice are showing the success of this therapy concerning physical and mental health of patients and their circumstances of social life. Thereby substitution with diamorphine is underlying very strict admission criteria regarding patients on the one hand and particular organizational requirements of the medical institution on the other hand. This article explains these criteria in detail as well as neurobiological information and clinical workflow is presented. Improvement of mandatory requirements could lead to a better reaching of patients who benefit from substitution with diamorphine. PMID:27029045

  10. ESR Measurement Of Crystallinity In Semicrystalline Polymers

    NASA Technical Reports Server (NTRS)

    Kim, Soon Sam; Tsay, Fun-Dow

    1989-01-01

    Photogenerated free radicals decay at different rates in crystalline and amorphous phases. Degree of crystallinity in polymer having both crystalline and amorphous phases measured indirectly by technique based in part on electron-spin-resonance (ESR) spectroscopy. Accuracy of crystallinity determined by new technique equals or exceeds similar determinations by differential scanning calorimetry, wide-angle x-ray scattering, or measurement of density.

  11. 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.

  12. 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.

  13. Nanostructures having crystalline and amorphous phases

    SciTech Connect

    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.

  14. 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.

  15. 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.

  16. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... substituted methyl styrene, methyl methacrylate, and substituted silane. 721.6920 Section 721.6920 Protection... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  17. 40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... substituted methyl styrene, methyl methacrylate, and substituted silane. 721.6920 Section 721.6920 Protection... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... substituted methyl styrene, methyl methacrylate, and substituted silane. 721.6920 Section 721.6920 Protection... acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted silane. (a... butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...

  19. 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. PMID:27305238

  20. 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…

  1. 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.…

  2. 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.

  3. 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.

  4. 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].

  5. Accordion-like oscillation of contracted and stretched helices of polyacetylenes synchronized with the restricted rotation of side chains.

    PubMed

    Yoshida, Yoshiaki; Mawatari, Yasuteru; Motoshige, Asahi; Motoshige, Ranko; Hiraoki, Toshifumi; Wagner, Manfred; Müllen, Klaus; Tabata, Masayoshi

    2013-03-13

    A chiral substituted acetylene, (s)-2-octyl propiolate, was stereoregularly polymerized using a catalyst, [Rh(nbd)Cl]2, at 40 °C in methanol to give the corresponding helical polymer, Ps2OcP. The changes of (1)H and (13)C NMR spectra in line shapes and splitting patterns were consistently interpreted in terms of restricted rotation around the ester O-*C bond, ~O-*C(ε)H(ε)(R)~, R = a branched CH(ε)3 in the ester side chains rather than the helix inversion with the aid of a 3-site jump model. Three peaks due to the branched methyl H(ε) proton and its C(η) carbon observed at 0 °C suggested the formation of three rotamers called A, B, and C, based on the presence of the contracted helix and stretched helix forms that have an intrinsic helical pitch. Furthermore, an accordion-like helix oscillation (HELIOS) along the main chain axis was proposed to explain the temperature dependence spectral changes observed in (1)H and (13)C NMR, UV-vis, and circular dicromism (CD) spectra. The temperature dependence UV-vis and CD spectra of Ps2OcP corroborate the presence of contracted and stretched one-handed helix sense polymers in solution in which the helical pitches and their persistence lengths depend on the temperature. PMID:23402213

  6. Use of on-flow LC/1H NMR for the study of an antioxidant fraction from Orophea enneandra and isolation of a polyacetylene, lignans, and a tocopherol derivative.

    PubMed

    Cavin, A; Potterat, O; Wolfender, J L; Hostettmann, K; Dyatmyko, W

    1998-12-01

    The CH2Cl2 extract of the leaves of Orophea enneandra displayed antifungal, antioxidant, and radical scavenging properties in bioautographic TLC assays. To obtain rapid information on the active compounds, on-flow LC/1H NMR and LC/UV/MS analyses of the antioxidant fraction were performed. The on-line information led rapidly to the partial identification of three closely related lignans, one tocopherol derivative, and one polyacetylene. This approach necessitated, however, large quantities to be injected to obtain satisfactory on-flow LC/1H NMR spectra, and isolation of the compounds was necessary to obtain complete NMR data. These compounds were isolated and identified as (-)-phylligenin (1), (-)-eudesmin (2), (-)-epieudesmin (3), polycerasoidol (4), and oropheic acid (5), a new polyacetylene. Their activities against the 2, 2-diphenyl-1-picrylhydrazyl radical and the fungus Cladosporium cucumerinum were investigated. This paper indicates the possibilities and limits of on-flow LC/1H NMR in this type of study. PMID:9868150

  7. Rapid method for simultaneous determination of flavonoid, saponins and polyacetylenes in folium ginseng and radix ginseng by pressurized liquid extraction and high-performance liquid chromatography coupled with diode array detection and mass spectrometry.

    PubMed

    Qian, Z M; Lu, J; Gao, Q P; Li, S P

    2009-05-01

    A rapid pressurized liquid extraction (PLE) and high-performance liquid chromatography coupled with diode array detection and mass spectrometry (HPLC-DAD-MS) method for the simultaneous determination of one flavonoid (panasenoside), nine saponins (ginsenoside Rg1, Re, Rf, Rg2, Rb1, Rc, Rb2, Rb3 and Rd) and two polyacetylenes (panaxydol and panaxynol) in folium ginseng and radix ginseng was developed. A Prevail C(18) rocket column (33 mm x 7 mm, 3.0 microm) and gradient elution were used during the analysis. Flavonoid was quantified at 355 nm, and saponins and polyacetylenes were determined at 203 nm. The chromatographic peaks of 12 investigated compounds in samples were unambiguously identified by compared their UV spectra and/or MS data with the related reference compounds. All calibration curves showed good linearity (r>0.999) within the test ranges. The intra- and inter-day variations for 12 analytes were less than 1.17% and 2.17%, respectively. The developed method was successfully applied to determine the investigated compounds in 10 samples of radix ginseng and folium ginseng, respectively. The result showed that PLE combined with rocket column HPLC analysis could provide a rapid method for analysis of compounds in traditional Chinese medicines (TCMs), which is helpful to comprehensive evaluation of quality of radix ginseng and folium ginseng. PMID:19272605

  8. Ductile crystalline-amorphous nanolaminates.

    PubMed

    Wang, Yinmin; Li, Ju; Hamza, Alex V; Barbee, Troy W

    2007-07-01

    It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper-zirconium glass nanolaminates. These nanocrystalline-amorphous nanolaminates exhibit a high flow stress of 1.09 +/- 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 +/- 1.7%, which is six to eight times higher than that typically observed in conventional crystalline-crystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5- to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous-crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility. PMID:17592136

  9. 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.

  10. 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

  11. Review of Crystalline Structures of Some Selected Homologous Series of Rod-Like Molecules Capable of Forming Liquid Crystalline Phases

    PubMed Central

    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. PMID:22174604

  12. Planar Flow Casting: Crystalline and Non-crystalline Ribbon Formation

    NASA Astrophysics Data System (ADS)

    Mattson, Joseph; Theisen, Eric; Steen, Paul

    2015-11-01

    Planar flow casting (PFC) is a single-stage continuous casting process used in the production of thin metallic sheets. Molten metal is ejected from a reservoir and forced through a small gap to freeze against a translating substrate. The process is typically `feed limited' which means that an imposed pressure drop determines the flow rate of metal to the solidification front, and thus the ultimate thickness of the solid sheet. Depending on the molten alloy, the substrate heat sink can provide sufficient cooling rates to produce a glassy (amorphous) metal. Otherwise, a crystalline solid is the result. In this talk, by relating ribbon thickness to residence time for both amorphous and crystalline products, we address the question: to what extent is processing `blind' to the solidification mechanism? Support from National Science Foundation (Awards 1400964 and 0966045); Metglas Inc.

  13. Clinical applications of skin substitutes.

    PubMed

    Nyame, Theodore T; Chiang, H Abraham; Orgill, Dennis P

    2014-08-01

    A unique understanding of the components of mammalian skin has led to the development of numerous skin substitutes. These skin substitutes attempt to compensate for functional and physiologic deficits present in damaged tissue. Skin substitutes, when appropriately applied in optimized settings, offer a promising solution to difficult wound management. The body of literature on skin substitutes increases as the understanding of tissue engineering and molecular biology expands. Given the high cost of these products, future randomized large prospective studies are needed to guide the clinical applications of skin substitutes. PMID:25085091

  14. Dual functional selenium-substituted hydroxyapatite.

    PubMed

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

    2012-06-01

    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

  15. 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.

  16. Methodologies in creating skin substitutes.

    PubMed

    Nicholas, Mathew N; Jeschke, Marc G; Amini-Nik, Saeid

    2016-09-01

    The creation of skin substitutes has significantly decreased morbidity and mortality of skin wounds. Although there are still a number of disadvantages of currently available skin substitutes, there has been a significant decline in research advances over the past several years in improving these skin substitutes. Clinically most skin substitutes used are acellular and do not use growth factors to assist wound healing, key areas of potential in this field of research. This article discusses the five necessary attributes of an ideal skin substitute. It comprehensively discusses the three major basic components of currently available skin substitutes: scaffold materials, growth factors, and cells, comparing and contrasting what has been used so far. It then examines a variety of techniques in how to incorporate these basic components together to act as a guide for further research in the field to create cellular skin substitutes with better clinical results. PMID:27154041

  17. Synthesis of novel sulfosalt materials with curved crystalline habits

    NASA Astrophysics Data System (ADS)

    Crawford, Guy Moore

    Minerals and man-made materials with circular crystalline habit are very rare. A group of the complex iron-containing sulfosalt minerals exhibit a non-commensurate layered crystalline structure and are found with curved crystals. Cylindrite, named because of its cylindrical crystal habit, is the most easily recognized member of the group. The other members of the family, franckeite, incaite and potosiite, have similar compositions and are all lamellar. The two incommensurate interpenetrating sublattices have different but definite structures. One sublattice is PbS-type pseudotetragonal and the other SnS 2-type pseudohexagonal. Iron is found in both sublattices. The detailed crystal structures of these minerals remains unsolved. With the exception of a few phase studies, little is known about the chemistry of the minerals or the mechanism that prompts the formation of these misfit-layered materials. As sulfides, these minerals are of interest for their potential electronic and magnetic applications. A series of synthesis reactions were carried out to examine the effects on the properties and structures of the sulfosalts that are induced by the substitutions into the crystal lattice. Other transition metals were substituted in the place of iron in the incommensurate minerals, and selenium and tellurium replaced sulfur in cylindrite. The structure and properties were evaluated by environmental scanning electron microscopy, X-ray diffraction and differential thermal analysis. Curved and lamellar features were observed in several phases of the synthetic substitutional products. No correlations were immediately evident relating the composition to the propensity to form curved features.* *This dissertation is multimedia (contains text and other applications not available in printed format). The CD requires the following system application: Microsoft Office.

  18. 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

  19. 40 CFR 721.10034 - Substituted pyridine coupled with diazotized substituted nitrobenzonitrile, diazotized...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted pyridine coupled with... Specific Chemical Substances § 721.10034 Substituted pyridine coupled with diazotized substituted... as substituted pyridine coupled with diazotized substituted nitrobenzonitrile, diazotized...

  20. 40 CFR 721.10034 - Substituted pyridine coupled with diazotized substituted nitrobenzonitrile, diazotized...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted pyridine coupled with... Specific Chemical Substances § 721.10034 Substituted pyridine coupled with diazotized substituted... as substituted pyridine coupled with diazotized substituted nitrobenzonitrile, diazotized...

  1. 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.

  2. 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.

  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. 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).

  5. The crystalline sponge method updated.

    PubMed

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

    2016-03-01

    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

  6. 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

  7. 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.

  8. 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

  9. Carbon substitution for oxygen in silicates in planetary interiors.

    PubMed

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

    2013-10-01

    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 SiO(x)C(4-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 SiO(x)C(4-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

  10. 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.

  11. Trifluoromethyl-substituted polymers

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Current work sponsored by the grant at Southwest Texas State University is directed toward the synthesis and characterization of: (1) N-alkylated polyamides derived from o-fluorinated diacids; (2) highly fluorinated polyethers; (3) polyesters derived from 2-hydroxy-2-propyl substituted arenes and/or 2,5-difluoroterephthalic acid; and (4) silicon-containing fluoropolymers. Work during the period from 1 July to 31 Dec. 1993 focused primarily on items 3 and 4 and on the development of a phosphorus containing modification of '12F-PEK.'

  12. Synthesis and liquid crystalline properties of trimellitimides and their sulfur analogues

    NASA Astrophysics Data System (ADS)

    Melon-Ksyta, D.; Orzeszko, A.; Czuprynski, Krzysztof

    2004-09-01

    A series of novel ester imides and thioimides have been synthesized from N-substituted trimellitimides and 4-hydroxybiphenyl or 4'-alkoxy-4-hydroxybiphenyls. The correlation between structure and behavior of the obtained compounds was studied. It has been found that imides without alkoxy tails are nonliquid crystalline while compounds possessing 4'-O-substituted biphenol moieties exhibit smectic phases. An introduction of sulfur atoms into an imide ring instead of oxygen atoms resulted in the fact that appropriate thioimides show monotropic SmA phases while the parent imides were nonliquid crystalline. Compounds with short aliphatic substituents (C1 - C4) show only SmA phases. The longer tails (C5) induce also SmC phases.

  13. 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.

  14. 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.

  15. Freely Suspended Liquid Crystalline Films

    NASA Astrophysics Data System (ADS)

    Sonin, A. A.

    2003-05-01

    Freely Suspended Liquid Crystalline Films Andrei A. Sonin Centre d'Etudes Atomiques de Saclay, France and Institute of Crystallography, Russian Academy of Sciences with a Foreword by Professor Noel Clark University of Colorado, USA This book provides a brief introduction to the physics of liquid crystals and to macroscopic physical parameters characterising freely suspended liquid crystalline (FSLC) films, and then reviews the experimental techniques for preparing these films, measuring their thicknesses, and investigating their physical properties and structural aspects. Molecular structures and defects of FSLC films and the problems of film stability, thinning and rupture are discussed in later chapters. Physical phenomena, such as orientational and phase transitions, Frederick's and flexoelectric effects, hydroelectrodynamics, etc., are also analysed. Finally, some applications of FSLC films in industry and in various branches of science are discussed. Specialists working in the physics of liquid crystals and in surface physics will find this book of interest. Industrial firms and their research centres investigating liquid crystals, biological membranes, detergent/surfactant/biomedical areas; and graduates and postgraduates in solid state physics and crystallography will also benefit from this book. The book has an easy-to-read style with just the minimum amount of mathematics necessary to explain important concepts. This is the first book dedicated exclusively to the physics of FSLC in almost a century since their discovery and last twenty years of their active studies. Andrei Sonin, a scientist in the area of FSLC and author of many articles on surface phenomena in liquid crystals, the properties and behaviour of thin liquid crystalline and surfactant films, has a long standing reputation in liquid crystals and surfactant systems and has been particularly active in issues involving surface interactions.

  16. Trifluoromethyl-substituted tetrathiafulvalenes

    PubMed Central

    Jeannin, Olivier; Barrière, Frédéric

    2015-01-01

    Summary A series of tetrathiafulvalenes functionalized with one or two trifluoromethyl electron-withdrawing groups (EWG) is obtained by phosphite coupling involving CF3-substituted 1,3-dithiole-2-one derivatives. The relative effects of the EWG such as CF3, CO2Me and CN on the TTF core were investigated from a combination of structural, electrochemical, spectrochemical and theoretical investigations. Electrochemical data confirm the good correlations between the first oxidation potential of the TTF derivatives and the σmeta Hammet parameter, thus in the order CO2Me < CF3 < CN, indicating that, in any case, the mesomeric effect of the substituents is limited. Besides, crystal structure determinations show that the deformation of the unsymmetrically substituted dithiole rings, when bearing one, or two different EWG, and attributed to the mesomeric effect of ester or nitrile groups, is not notably modified or counter-balanced by the introduction of a neighboring trifluoromethyl group. DFT calculations confirm these observations and also show that the low energy HOMO–LUMO absorption band found in nitrile or ester-substituted TTFs is not found in TTF-CF3, where, as in TTF itself, the low energy absorption band is essentially attributable to a HOMO→LUMO + 1 transition. Despite relatively high oxidation potentials, these donor molecules with CF3 EWG can be involved in charge transfer complexes or cation radical salts, as reported here for the CF3-subsituted EDT-TTF donor molecule. A neutral charge transfer complex with TCNQ, (EDT-TTF-CF3)2(TCNQ) was isolated and characterized through alternated stacks of EDT-TTF-CF3 dimers and TCNQ in the solid state. A radical cation salt of EDT-TTF-CF3 is also obtained upon electrocrystallisation in the presence of the FeCl4 − anion. In this salt, formulated as (EDT-TTF-CF3)(FeCl4), the (EDT-TTF-CF3)+• radical cations are associated two-by-two into centrosymmetric dyads with a strong pairing of the radical species in a singlet

  17. Trifluoromethyl-substituted tetrathiafulvalenes.

    PubMed

    Jeannin, Olivier; Barrière, Frédéric; Fourmigué, Marc

    2015-01-01

    A series of tetrathiafulvalenes functionalized with one or two trifluoromethyl electron-withdrawing groups (EWG) is obtained by phosphite coupling involving CF3-substituted 1,3-dithiole-2-one derivatives. The relative effects of the EWG such as CF3, CO2Me and CN on the TTF core were investigated from a combination of structural, electrochemical, spectrochemical and theoretical investigations. Electrochemical data confirm the good correlations between the first oxidation potential of the TTF derivatives and the σmeta Hammet parameter, thus in the order CO2Me < CF3 < CN, indicating that, in any case, the mesomeric effect of the substituents is limited. Besides, crystal structure determinations show that the deformation of the unsymmetrically substituted dithiole rings, when bearing one, or two different EWG, and attributed to the mesomeric effect of ester or nitrile groups, is not notably modified or counter-balanced by the introduction of a neighboring trifluoromethyl group. DFT calculations confirm these observations and also show that the low energy HOMO-LUMO absorption band found in nitrile or ester-substituted TTFs is not found in TTF-CF3, where, as in TTF itself, the low energy absorption band is essentially attributable to a HOMO→LUMO + 1 transition. Despite relatively high oxidation potentials, these donor molecules with CF3 EWG can be involved in charge transfer complexes or cation radical salts, as reported here for the CF3-subsituted EDT-TTF donor molecule. A neutral charge transfer complex with TCNQ, (EDT-TTF-CF3)2(TCNQ) was isolated and characterized through alternated stacks of EDT-TTF-CF3 dimers and TCNQ in the solid state. A radical cation salt of EDT-TTF-CF3 is also obtained upon electrocrystallisation in the presence of the FeCl4 (-) anion. In this salt, formulated as (EDT-TTF-CF3)(FeCl4), the (EDT-TTF-CF3)(+•) radical cations are associated two-by-two into centrosymmetric dyads with a strong pairing of the radical species in a singlet state

  18. 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. PMID:27228076

  19. Particle motion in crystalline beams

    SciTech Connect

    Haffmans, A.F.; Maletic, D.; Ruggiero, A.G.

    1994-04-20

    Studying the possibility of storing a low emittance (or ``cooled``) beam of charged particles in a storage ring, the authors are faced with the effect of space charge by which particles are repelled and influence each others` motion. The correct evaluation of the space-charge effects is important to determine the attainment and properties of Crystalline Beams, a phase transition which intense beams of ions can undergo when cooling is applied. In this report they derive the equations of motion of a particle moving under the action of external resorting forces generated by the magnets of the storage ring, and of the electromagnetic fields generated by the other particles. The motion in every direction is investigated: in the longitudinal, as well as vertical and horizontal direction. The external forces are assumed to be linear with the particle displacement from the reference orbit. The space-charge forces are comparable in magnitude to the external focusing forces. The equations of motion so derived are then used to determine confinement and stability conditions for the attainment of Crystalline Beams, using transfer matrices.

  20. 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…

  1. 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.

  2. Association of actin with alpha crystallins

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Boyle, D.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

    1993-01-01

    The alpha crystallins are cytosolic proteins that co-localize and co-purify with actin-containing microfilaments. Affinity column chromatography employing both covalently-coupled actin or alpha crystallin was used to demonstrate specific and saturable binding of actin with alpha crystallin. This conclusion was confirmed by direct visualization of alpha aggregates bound to actin polymerized in vitro. The significance of this interaction in relation to the functional properties of these two polypeptides will be discussed.

  3. The deposition of strontium-substituted hydroxyapatite coatings.

    PubMed

    Boyd, Adrian R; Rutledge, L; Randolph, L D; Mutreja, I; Meenan, B J

    2015-02-01

    Strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as strontium (Sr) has been shown to have the dual benefit of promoting bone formation and reducing bone resorption, in vivo. In this work, SrHA coatings were deposited onto polycrystalline titanium surfaces using radio frequency (RF) magnetron co-sputtering and compared to those deposited from HA alone. In particular, the influence of different levels of Sr-substitution of the sputtering targets (5 and 13% Sr-substituted HA targets) on the properties of the deposited coatings produced at a low discharge power level (150 W) were investigated using FTIR, XPS, XRD, ToFSIMS and AFM techniques (both before and after annealing at 500 °C). The results show that Sr could be successfully incorporated into the HA lattice to form SrHA coatings and that they contained no other impurities. However, the coating produced from the 13% Sr-substituted target had a higher Ca+Sr/P ratio (1.95±0.14) and Sr content when compared to the coating produced from the 5% Sr-substituted target (1.58±0.20). The deposition rate also decreased with increasing Sr content of the sputtering targets. Furthermore, as the Sr content of the coatings increased, so did the preferred 002 orientation of the coating along with increased surface roughness and heterogeneity of the surface features. Therefore, this study has shown that RF magnetron sputtering offers a means to control attendant properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface topography. PMID:25631262

  4. Control of crystallinity and porosity of covalent organic frameworks by managing interlayer interactions based on self-complementary π-electronic force.

    PubMed

    Chen, Xiong; Addicoat, Matthew; Irle, Stephan; Nagai, Atsushi; Jiang, Donglin

    2013-01-16

    Crystallinity and porosity are crucial for crystalline porous covalent organic frameworks (COFs). Here we report synthetic control over the crystallinity and porosity of COFs by managing interlayer interactions based on self-complementary π-electronic forces. Fluoro-substituted and nonsubstituted aromatic units at different molar ratios were integrated into the edge units that stack to trigger self-complementary π-electronic interactions in the COFs. The interactions improve the crystallinity and enhance the porosity by maximizing the total crystal stacking energy and minimizing the unit cell size. Consequently, the COF consisting of equimolar amounts of fluoro-substituted and nonsubstituted units showed the largest effect. These results suggest a new approach to the design of COFs by managing the interlayer interactions. PMID:23270524

  5. 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.

  6. Birefringence measurements on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Krüger, Christoph; Heinert, Daniel; Khalaidovski, Alexander; Steinlechner, Jessica; Nawrodt, Ronny; Schnabel, Roman; Lück, Harald

    2016-01-01

    Crystalline silicon has been proposed as a new test mass material in third generation gravitational wave detectors such as the Einstein telescope (ET). Birefringence can reduce the interferometric contrast and can produce dynamical disturbances in interferometers. In this work we use the method of polarization-dependent resonance-frequency analysis of Fabry-Perot-cavities containing silicon as a birefringent medium. Our measurements show a birefringence of silicon along the (111) axis of the order of {{Δ }} n≈ {10}-7 at a laser wavelength of 1550 nm and room temperature. A model is presented that explains the results of different settings of our measurements as a superposition of elastic strains caused by external stresses in the sample and plastic strains possibly generated during the production process. An application of our theory on the proposed ET test mass geometry suggests no critical effect on birefringence due to elastic strains.

  7. Crystalline silica: risks and policy.

    PubMed Central

    Hardy, T S; Weill, H

    1995-01-01

    Since the International Agency for Research on Cancer labeled crystalline silica a probable carcinogen in 1988, government regulations have required sand and other products to contain warning labels and researchers have attempted to quantitatively assess low-exposure risks. The uncertainties are unlikely to diminish any time soon, and little value exists in calculating such risks, as low exposures to this ubiquitous mineral are commonplace in both urban and rural areas due to many uncontrollable activities. What is certain is that regulatory resources targeted at continuing high-level occupational exposures would be much more likely to have beneficial public health consequences than continued attempts to assess low-exposure risks quantitatively. Images p152-a PMID:7737062

  8. Structural defects in crystalline silicon

    NASA Technical Reports Server (NTRS)

    Sirtl, E.

    1985-01-01

    The basic photovoltaic properties of a given crystalline silicon specimen seem to be governed by density and nature of two to three dimensional lattice defects. These are mainly generated by primary growth conditions as grain boundaries of more or less intrinsic character or second phase precipitates from supersaturated solutions of carbon or oxygen. Considerably high values of both solubility and diffusivity in connection with their abundance in common refractory material systems account for the predominance of the two particular elements. Unsaturated dislocations of different types very often can be seen as a consequence of the existence of more dimensional defects as described initially. The final performance of a solar cell is dependent of the concentration and distribution of recombination active centers in the different regions of this device. Typical representatives are fast diffusing transition metals in form of either single atoms or simple complexes. Their avoidance, annihilation, or removal is of great concern in different fields of electronic materials development.

  9. Elasticity of crystalline molecular explosives

    DOE PAGESBeta

    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, 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

  10. 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.

  11. 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…

  12. 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 benezenesulfonic acid reaction product with naphthalenesulfonato azo substituted phenyl azo... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10126 Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato...

  13. 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 benezenesulfonic acid reaction product with naphthalenesulfonato azo substituted phenyl azo... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10126 Alkyl amino substituted triazine amino substituted benezenesulfonic acid reaction product with naphthalenesulfonato...

  14. 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. PMID:26583701

  15. Synthesis, structure and phase behavior of liquid crystalline polyurethanes

    SciTech Connect

    Papadimitrakopoulos, F.

    1993-01-01

    This dissertation describes the synthesis, structure and phase behavior of polyurethanes based on the mesogenic biphenol 4,4'-bis (6-hydroxyhexoxy)biphenyl (BHHBP) and meta substituted tolylene/phenylene diisocynates. The structure-property relationships were determined as a function of hydrogen-bonding, the position of the methyl group in the tolylene diisocyanate moiety (TDI) and the biphenol moiety. The liquid crystalline phase (mesophase) and crystalline phase were investigated primarily with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and infrared spectroscopy. The influence of H-bonding on the structure and phase behavior of 1,4-LCPU-6 was determined by the synthesis of high molecular weight N-Methyl2,4-LCPU-65, using a novel high temperature polymerization of a biscarbamoyl chloride with the BHHBP mesogenic diol. In contrast to the regular ([alpha], [omega]-hexane diol) based polyurethanes (PUs), BHHBP derived polyurethanes (LCPUs) crystallize rapidly from their melts. Hexafluoroisopropanol fast solvent-evaporation casting or rapid cooling from the melt resulted in thin films or bulk samples with a glassy mesophase morphology. During the subsequent heating scan, the mesophase to crystal transition occurs. Highly oriented fibers were obtained for the mesogenic polyurethanes. Atomistic molecular simulations coupled with X-ray intensity refinement allowed determination of the crystalline chain conformation and packing characteristics for the 2,6-LCPU-6 and 1,3-LCPU-6 (2,6-TDI and 1,3-Phenylene Diisocynate (1,3-PDI) derived LCPUs). On the basis of structural similarity and well resolved WAXS powder patterns similar analysis was extended to the regular polyurethanes as well (2,6-PU-6 and 1,3-PU-6). The good correlation polymers suggest that melting is primarily controlled by the dissociation of H-bonds in the ordered domains.

  16. 40 CFR 721.3063 - Substituted phenyl azo substituted phenyl esters (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted phenyl azo substituted... Significant New Uses for Specific Chemical Substances § 721.3063 Substituted phenyl azo substituted phenyl... chemical substances identified generically as substituted phenyl azo substituted phenyl esters (PMNs...

  17. 40 CFR 721.3063 - Substituted phenyl azo substituted phenyl esters (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted phenyl azo substituted... Significant New Uses for Specific Chemical Substances § 721.3063 Substituted phenyl azo substituted phenyl... as substituted phenyl azo substituted phenyl esters (PMNs P-95-655, P-95-782 and P-95-871)...

  18. 40 CFR 721.3063 - Substituted phenyl azo substituted phenyl esters (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted phenyl azo substituted... Significant New Uses for Specific Chemical Substances § 721.3063 Substituted phenyl azo substituted phenyl... chemical substances identified generically as substituted phenyl azo substituted phenyl esters (PMNs...

  19. Crystalline mesophases: Structure, mobility, and pharmaceutical properties.

    PubMed

    Shalaev, Evgenyi; Wu, Ke; Shamblin, Sheri; Krzyzaniak, Joseph F; Descamps, Marc

    2016-05-01

    Crystalline mesophases, which are commonly classified according to their translational, orientational, and conformational order as liquid crystals, plastic crystals, and conformationally disordered crystals, represent a common state of condensed matter. As an intermediate state between crystalline and amorphous materials, crystalline mesophases resemble amorphous materials in relation to their molecular mobility, with the glass transition being their common property, and at the same time possessing a certain degree of translational periodicity (with the exception of nematic phase), with corresponding narrow peaks in X-ray diffraction patterns. For example, plastic crystals, which can be formed both by near-spherical molecules and molecules of lower symmetry, such as planar or chain molecules, can have both extremely sharp X-ray diffraction lines and exhibit glass transition. Fundamentals of structural arrangements in mesophases are compared with several types of disorder in crystalline materials, as well as with short-range ordering in amorphous solids. Main features of the molecular mobility in crystalline mesophases are found to be generally similar to amorphous materials, although some important differences do exist, depending on a particular type of mobility modes involved in relaxation processes. In several case studies reviewed, chemical stability appears to follow the extent of disorder, with the stability of crystalline mesophase found to be intermediate between amorphous (least stable) and crystalline (most stable) materials. Finally, detection of crystalline mesophases during manufacturing of two different types of dosage forms is discussed. PMID:27067607

  20. Stability and cytotoxicity of crystallin amyloid nanofibrils.

    PubMed

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

    2014-11-01

    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. PMID:25255060

  1. 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)

  2. 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...

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Chander, Ravi

    2015-05-01

    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.

  5. Crystalline silicotitanate gate review analysis

    SciTech Connect

    Schlahta, S.N.; Carreon, R.; Gentilucci, J.A.

    1997-11-01

    Crystalline silicotitanate (CST) is an ion-exchange method for removing radioactive cesium from tank waste to allow the separation of the waste into high- and low-level fractions. The CST, originally developed Sandia National Laboratories personnel in association with Union Oil Products Corporation, has both a high affinity and selectivity for sorbing cesium-137 from highly alkaline or acidic solutions. For several years now, the U.S. Department of Energy has funded work to investigate applying CST to large-scale removal of cesium-137 from radioactive tank wastes. In January 1997, an expert panel sponsored by the Tanks Focus Area met to review the current state of the technology and to determine whether it was ready for routine use. The review also sought to identify any technical issues that must be resolved or additional CST development that must occur before full implementation by end-users. The CST Gate Review Group concluded that sufficient work has been done to close developmental work on CST and turn the remaining site-specific tasks over to the users. This report documents the review group`s findings, issues, concerns, and recommendations as well as responses from the Tanks Focus Area expert staff to specific pretreatment and immobilization issues.

  6. Radiolysis of crystalline nickel oxalates

    NASA Astrophysics Data System (ADS)

    Basahel, S. N.; Diefallah, El-H. M.; El-Fass, M. M.; Al-Sabban, E. A.

    Radiolysis of crystalline K 2Ni(C 2O 4) 2);6H 2O, K 2Ni(C 2O 4) 2 and Ni(C 2O 4));2H 2O has been investigated. The results showed that in K 2Ni(C 2O 4) 2);6H 2O, the initial G(Ni 3+) has a value of 3.75 and drops to about 1.27 when the dose approaches 1.2 × 10 22 eV g -1. The decrease in G(Ni 3+) with increasing radiation dose is accompanied with an increase in G(Ni 2+). In the irradiated anhydrated complex, the results however show an increase in G(Ni 3+) and a decrease in G(Ni 2+) with increasing radiation dose. The radiolysis of Ni(C 2O 4)·2H 2O showed an increase in G(Ni 3+) with increasing radiation dose. A mechanism has been suggested to explain the observed results.

  7. Spectral diversity crystalline fluoride lasers

    SciTech Connect

    Jenssen, H.P.; Gabbe, D.R.; Linz, A.; Naiman, C.S.

    1981-01-01

    Within the realm of crystalline laser materials, the class of fluorides distinguishes itself mostly by the wide variety of laser wavelengths displayed. Laser operation has now been reported from 3.9 micrometers in the infrared to 286 nm in the ultraviolet. Many are operated flash-lamp pumped, while others have shown high utility as linear down conversion lasers and rare earth ion, while others are sensitized by other co-dopants which absorb the pump energy and transfer it to the active laser ions. The potential of large spectral diversity for laser operation is due both to the wide window of transparency that fluorides possess and the lower rates of nonradiative decay. The high band gap in the ultraviolet also leads to low linear absorption, low nonlinear refractive indices and multiphoton absorption. Additionally, the good chemical stability displayed by high-purity stoichiometric fluoride compounds allows their use with ultraviolet pump sources at high energies, without incurring UV-induced damage. The most recent research associated with such materials, particularly the host crystal, lithium yttrium fluoride, LiYF4 (YLF) is reviewed.

  8. Hydrophobic Core Mutations Associated with Cataract Development in Mice Destabilize Human γD-Crystallin*

    PubMed Central

    Moreau, Kate L.; King, Jonathan

    2009-01-01

    The human eye lens is composed of fiber cells packed with crystallins up to 450 mg/ml. Human γD-crystallin (HγD-Crys) is a monomeric, two-domain protein of the lens central nucleus. Both domains of this long lived protein have double Greek key β-sheet folds with well packed hydrophobic cores. Three mutations resulting in amino acid substitutions in the γ-crystallin buried cores (two in the N-terminal domain (N-td) and one in the C-terminal domain (C-td)) cause early onset cataract in mice, presumably an aggregated state of the mutant crystallins. It has not been possible to identify the aggregating precursor within lens tissues. To compare in vivo cataract-forming phenotypes with in vitro unfolding and aggregation of γ-crystallins, mouse mutant substitutions were introduced into HγD-Crys. The mutant proteins L5S, V75D, and I90F were expressed and purified from Escherichia coli. WT HγD-Crys unfolds in vitro through a three-state pathway, exhibiting an intermediate with the N-td unfolded and the C-td native-like. L5S and V75D in the N-td also displayed three-state unfolding transitions, with the first transition, unfolding of the N-td, shifted to significantly lower denaturant concentrations. I90F destabilized the C-td, shifting the overall unfolding transition to lower denaturant concentrations. During thermal denaturation, the mutant proteins exhibited lowered thermal stability compared with WT. Kinetic unfolding experiments showed that the N-tds of L5S and V75D unfolded faster than WT. I90F was globally destabilized and unfolded more rapidly. These results support models of cataract formation in which generation of partially unfolded species are precursors to the aggregated cataractous states responsible for light scattering. PMID:19758984

  9. Exposure to crystalline silica in abrasive blasting operations where silica and non-silica abrasives are used.

    PubMed

    Radnoff, Diane L; Kutz, Michelle K

    2014-01-01

    Exposure to respirable crystalline silica is a hazard common to many industries in Alberta but particularly so in abrasive blasting. Alberta occupational health and safety legislation requires the consideration of silica substitutes when conducting abrasive blasting, where reasonably practicable. In this study, exposure to crystalline silica during abrasive blasting was evaluated when both silica and non-silica products were used. The crystalline silica content of non-silica abrasives was also measured. The facilities evaluated were preparing metal products for the application of coatings, so the substrate should not have had a significant contribution to worker exposure to crystalline silica. The occupational sampling results indicate that two-thirds of the workers assessed were potentially over-exposed to respirable crystalline silica. About one-third of the measurements over the exposure limit were at the work sites using silica substitutes at the time of the assessment. The use of the silica substitute, by itself, did not appear to have a large effect on the mean airborne exposure levels. There are a number of factors that may contribute to over-exposures, including the isolation of the blasting area, housekeeping, and inappropriate use of respiratory protective equipment. However, the non-silica abrasives themselves also contain silica. Bulk analysis results for non-silica abrasives commercially available in Alberta indicate that many contain crystalline silica above the legislated disclosure limit of 0.1% weight of silica per weight of product (w/w) and this information may not be accurately disclosed on the material safety data sheet for the product. The employer may still have to evaluate the potential for exposure to crystalline silica at their work site, even when silica substitutes are used. Limited tests on recycled non-silica abrasive indicated that the silica content had increased. Further study is required to evaluate the impact of product recycling

  10. Ionic motion in crystalline cryolite.

    PubMed

    Foy, Lindsay; Madden, Paul A

    2006-08-10

    The character of the ion dynamics in crystalline cryolite, Na(3)AlF(6), a model double perovskite-structured mineral, has been examined in computer simulations using a polarizable ionic potential obtained by force-fitting to ab initio electronic structure calculations. NMR studies, and conductivity measurements, have indicated a high degree of mobility, in both Na(+) ion diffusion and reorientation of the AlF(6) octahedral units. The simulations reproduce the low-temperature (tilted) crystal structure and the existence of a transition to a cubic structure at elevated temperatures, in agreement with diffraction measurements, though the calculated transition temperature is too low. The reorientational dynamics of the AlF(6) octahedra is shown to consist of a hopping motion between the various tilted positions of the low-temperature form, even above the transition temperature. The rate of reorientation estimated by extrapolation to the temperature régime of the NMR measurements is consistent with the experimental data. In addition, we report a novel cooperative "tilt-swapping" motion of the differently tilted sublattices, just below the transition temperature. The perfect crystals show no Na(+) diffusion, in apparent disagreement with observation. We argue, following previous analyses of the cryolite phase diagram, that the diffusion observed in the experimental studies is a consequence of defects that are intrinsic to the thermodynamically stable form of cryolite. By introducing defects into the simulation cell, we obtain diffusion rates that are consistent with the NMR and conductivity measurements. Finally, we demonstrate a link between diffusion of the Na(+) ions and the reorientation of AlF(6) units, though the correlation between the two is not very strong. PMID:16884249

  11. Binding of actin to lens alpha crystallins

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    Actin has been coupled to a cyanogen bromide-activated Sepharose 4B column, then tested for binding to alpha, beta, and gamma crystallin preparations from the bovine lens. Alpha, but not beta or gamma, crystallins bound to the actin affinity column in a time dependent and saturable manner. Subfractionation of the alpha crystallin preparation into the alpha-A and alpha-B species, followed by incubation with the affinity column, demonstrated that both species bound approximately the same. Together, these studies demonstrate a specific and saturable binding of lens alpha-A and alpha-B with actin.

  12. First-principles calculations of a promising intermediate-band photovoltaic material based on Co-hyperdoped crystalline silicon

    NASA Astrophysics Data System (ADS)

    Dong, Xiao; Song, Xiaohui; Wang, Yongyong; Wang, Jinfeng

    2015-08-01

    Among the various atomic structures of Co doped in the Si lattice, the substitutional Co is the most stable structure and can cause an impurity band in the band gap of crystalline Si. The impurity band is partially filled by electrons and isolated from the valence band (VB) and conduction band (CB), which fulfills the conditions of an intermediate-band (IB) photovoltaic material. The dielectric constant indicates that the substitutional Co-doped Si material can cause sub-band-gap light absorption. These properties will make the Co-hyperdoped Si a promising IB material in photovoltaic fields.

  13. Genetics Home Reference: Bietti crystalline dystrophy

    MedlinePlus

    ... on PubMed Central Mansour AM, Uwaydat SH, Chan CC. Long-term follow-up in Bietti crystalline dystrophy. ... VD, Zhang J, Gesualdo C, Corte MD, Chan CC, Fielding Hejtmancik J, Simonelli F. An atypical form ...

  14. High-efficiency crystalline silicon technology development

    NASA Technical Reports Server (NTRS)

    Prince, M. B.

    1984-01-01

    The rationale for pursuing high efficiency crystalline silicon technology research is discussed. Photovoltaic energy systems are reviewed as to their cost effectiveness and their competitiveness with other energy systems. The parameters of energy system life are listed and briefly reviewed.

  15. 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.

  16. 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.

  17. 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.

  18. 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 benzenesulfonic acid copper compound (generic). 721.10126 Section 721.10126 Protection of... substituted phenyl azo substituted benzenesulfonic acid copper compound (generic). (a) Chemical substance and... substituted phenyl azo substituted benzenesulfonic acid copper compound (PMN P-06-689) is subject to...

  19. 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 benzenesulfonic acid copper compound (generic). 721.10126 Section 721.10126 Protection of... substituted phenyl azo substituted benzenesulfonic acid copper compound (generic). (a) Chemical substance and... substituted phenyl azo substituted benzenesulfonic acid copper compound (PMN P-06-689) is subject to...

  20. 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 benzenesulfonic acid copper compound (generic). 721.10126 Section 721.10126 Protection of... substituted phenyl azo substituted benzenesulfonic acid copper compound (generic). (a) Chemical substance and... substituted phenyl azo substituted benzenesulfonic acid copper compound (PMN P-06-689) is subject to...

  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. 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...

  3. 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...

  4. 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...

  5. Bone grafts and their substitutes.

    PubMed

    Fillingham, Y; Jacobs, J

    2016-01-01

    The continual cycle of bone formation and resorption is carried out by osteoblasts, osteocytes, and osteoclasts under the direction of the bone-signaling pathway. In certain situations the host cycle of bone repair is insufficient and requires the assistance of bone grafts and their substitutes. The fundamental properties of a bone graft are osteoconduction, osteoinduction, osteogenesis, and structural support. Options for bone grafting include autogenous and allograft bone and the various isolated or combined substitutes of calcium sulphate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. Not all bone grafts will have the same properties. As a result, understanding the requirements of the clinical situation and specific properties of the various types of bone grafts is necessary to identify the ideal graft. We present a review of the bone repair process and properties of bone grafts and their substitutes to help guide the clinician in the decision making process. PMID:26733632

  6. 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. PMID:25428098

  7. Resistance-induced antibiotic substitution.

    PubMed

    Howard, David H

    2004-06-01

    In many cases, physicians prescribe antibiotics without knowing whether an individual patient is infected with a susceptible or resistant pathogen. As the proportion of resistant organisms in a community increases, physicians substitute away from older-inexpensive drugs to newer, more expensive agents as first line therapy. This paper explores the implications of resistance-induced antibiotic substitution for epidemiological models to predict future resistance levels, efforts to measure the health care costs associated with resistance, and policies to improve physicians' antibiotic prescribing decisions. The extent of resistance-induced substitution in outpatient settings is documented using a data set consisting of observations on initial physician office visits for otitis media in the US controlling for new product introductions and price increases, per prescription antibiotic spending increased by 22% between 1980 and 1996, corresponding to a steep increase in resistance levels over the same period. PMID:15185388

  8. 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.

  9. Unified optical symbolic substitution processor

    NASA Astrophysics Data System (ADS)

    Casasent, David P.

    1990-07-01

    Symbolic substitution operations can be realized optically on a correlator. This is a very attractive and efficient architecture for symbolic substitution. It allows parallel multichannel realization with a fixed set of filters (on film or easily realized on low space bandwidth product spatial light modulators) using space and frequency-multiplexing or sequential filters. All basic logic, numeric and morphological image processing functions can be achieved by symbolic substitution. Moreover, all operations are possible on one multifunctional optical processor. Morphological operations are felt to be essential for ATR and pattern recognition preprocessing in clutter. They greatly improve the role for optics by allowing the same optical architecture to be used for low, medium and high level vision.

  10. 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. PMID:27494205

  11. 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

  12. Induced birefringence and dichroism in azo polymers. Comparison between amorphous and liquid crystalline polymers

    SciTech Connect

    Natansohn, A.; Brown, D.; Rochon, P.

    1993-12-31

    Macroscopic order can be induced in amorphous high-Tg azo polymers (usually containing electron-donor - electron-acceptor substituted azobenzene moieties) by exposure to polarized light. The phenomenon is based on a series of trans-cis-trans isomerization cycles and the induced birefringence is typically of 2x10{sup {minus}2}. The ordered domains can be returned to randomness ({open_quotes}erased{close_quotes}) using circularly polarized light. This paper will present a comparison between amorphous and liquid crystalline azo polymers. The most significant difference between these two types of polymers is that any other type of concert with the azo moiety. Consequently the dichroism and birefringence induced in the liquid crystalline polymers can be one order of magnitude higher than in the amorphous polymers. At the same time, however, the time required to achieve saturation also increases by at least one order of magnitude.

  13. Incorporation of V, Zn and Pb into the crystalline phases of Portland clinker

    SciTech Connect

    Andrade, F.R.D.; Maringolo, V.; Kihara, Y

    2003-01-01

    Burning of industrial wastes in cement kilns has an increasing environmental importance, brought about by the incorporation of potentially hazardous elements into clinker crystalline phases and partial substitution of primary fuel and raw materials. In this study, experimental clinkers were synthesized, with the addition of V, Zn and Pb to a standard raw meal, from which a control clinker was obtained for comparison. The three metals were chosen as they are present in the alternative fuel petcoke (V) and in industrial wastes (Zn, Pb) commonly burned in cement kilns. Electron microprobe and scanning electron microscope analysis revealed the preferential partition of these metals among the clinker crystalline phases. It was observed that V has shown a preferential partition towards C{sub 2}S. Zn appears in higher amounts in periclase, and C{sub 3}S has higher Zn contents than C{sub 2}S. Pb concentrates in minute spherules and partitions toward C{sub 3}S in small amounts.

  14. Fractured unconventional reservoirs in the Crystalline Basement

    NASA Astrophysics Data System (ADS)

    Plotnikova, Irina

    2015-04-01

    Since the late 1960-es, the crystalline basement of Tatarstan has been in the focus of intense geological and geophysical surveys. Since 1975, within the framework of the Subsoil Survey Program of Tatarstan, two extra deep wells have been drilled in the Republic, including: 20000-Minnibaevskaya well (bottomhole depth - 5,099 m, meters drilled in the basement - 3,215 m) and 20009-Novoelkhovskaya well (bottomhole depth - 5,881 m, meters drilled in the basement - 4,077 m), as well as 24 wells penetrating the basement at depth from 100 to 2,432 m. Reservoir properties of the crystalline basement rocks can be evaluated based on the resulting volumes of produced liquid, which vary from 0.027 to 125 m3/day. The highest flow rate was registered for well № 20000 Minnibaevskaya. Therefore, there are high-capacity reservoir zones in the crystalline basement of the eastern margin of the Russian Platform. The statement saying that natural reservoirs with significant sizes and fluid storage capacities occur everywhere within the Precambrian crystalline massive on the territory of Tatarstan can be justified by the following provisions: - deconsolidation and fracturing zones of the crystalline basement are registered by a full set of geological and geophysical methods applied in the process of geophysical well surveys and in the process of surface geophysical studies; - there is a certain regular pattern of crystalline basement zone distribution by area and by profile. Wide-spaced drilling into the crystalline basement helped to identify numerous zones of deconsolidation and fracturing with different fluid storage capacity and different extent of fluid saturation. Thickness of the crystalline basement reservoir zones varies from several meters to dozens of meters. Such zones were identified close to the crystalline basement top, As well as at depths more than 5 km. Well log survey was the key method used for reservoir differentiation in the crystalline basement. In total, 16

  15. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Poly(oxyalkylenediyl),.alpha... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  16. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Poly(oxyalkylenediyl),.alpha... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  17. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Poly(oxyalkylenediyl),.alpha... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  18. 40 CFR 721.10214 - Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Poly(oxyalkylenediyl),.alpha... Poly(oxyalkylenediyl),.alpha.-substituted carbomonocycle-.omega.-substituted carbomonocycle (generic... identified generically as poly(oxyalkylenediyl),.alpha.-substituted...

  19. '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.

  20. Microwave absorption properties of Al- and Cr-substituted M-type barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Qiu, Jianxun; Gu, Mingyuan; Shen, Haigen

    2005-09-01

    Aluminum- and chromium-substituted barium ferrite particles with single magnetic domain were prepared using self-propagating combustion method. The crystalline structure, size, coercivity and microwave absorption property of the particles were investigated by means of X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry and vector network analyzer. The results show that the crystalline structure of BaFe 12-xAl xO 19 is still hexagonal. But when the chromium substitution amount y exceeds 0.6, the extra chromium ions cannot enter the lattice of BaFe 12-yCr yO 19. After Fe 3+ is partly substituted with Al 3+ and Cr 3+, the microwave absorption properties of barium ferrite are improved. The maximum absorption reaches 34.76 dB. The ferromagnetic resonance is an important channel of barium ferrite to absorb microwaves with high frequency. Aluminum and chromium substitutions change the ferromagnetic resonant frequency of barium ferrite. The multipeak phenomenon of the ferromagnetic resonance increases the microwave absorption capability of barium ferrite.

  1. Synthesis of hydroxyapatite nanoparticles with tailorable morphologies and carbonate substitutions using a wet precipitation method.

    PubMed

    Peng, Fei; Veilleux, Eric; Schmidt, Megan; Wei, Mei

    2012-03-01

    Hydroxyapatite (HA) nanoparticles with different morphologies and variant levels of carbonate substitutions were synthesized using a wet precipitation method by adjusting the heating temperature and/or the initial ion concentration of the reaction system. Within the particles, crystalline domains with different lengths were aligned along each other and formed into nanoparticles with different sizes, shapes and topographies. Different from most reported studies, the nucleation, growth and morphology of the crystalline domains were found sensitive to heating temperature, but not significantly influenced by initial ion concentration within the studied range. The OH- and PO4(3-) ions within the HA particles were partially substituted by CO3(2-) ions. The substitution was dominated by the replacement of OH- instead of PO4(3-) in HA. The carbonate substitution was found to decrease with increasing heating temperature and/or initial ion concentration. Therefore, both the morphology and composition of the HA particles can be tailored by controlling the heating temperature and/or the initial ion concentration in the reaction system. Such synthesized HA nanoparticles can be used as biomaterials for bone tissue engineering. PMID:22755122

  2. Synthesis, characterization and biological evaluation of strontium/magnesium-co-substituted hydroxyapatite.

    PubMed

    Geng, Zhen; Wang, Renfeng; Li, Zhaoyang; Cui, Zhenduo; Zhu, Shengli; Liang, Yanqin; Liu, Yunde; Huijing, Bao; Li, Xue; Huo, Qianyu; Liu, Zhili; Yang, Xianjin

    2016-07-01

    The present study aims to investigate the contribution of two biologically important cations, Mg(2+) and Sr(2+), when co-substituted into the structure of hydroxyapatite (Ca10(PO4)6(OH)2, HA). The substituted samples were synthesized by a hydrothermal method that involved the addition of Mg(2+) and Sr(2+) containing precursors to partially replace Ca(2+) in the apatite structure. Four co-substituted HA samples with different concentrations of Mg(2+) and Sr(2+) ((Mg + Sr)/(Mg + Sr + Ca) = 30%) were investigated, and they were compared with pure HA. Experimental results showed that only a limited amount of Mg (Mg/(Mg + Ca + Sr) < 14%) could successfully substitute for Ca in HA. In addition, Mg substitution resulted in reduced crystallinity, thermal stability and lattice parameters of HA. In contrast, Sr could fully substitute for Ca. Furthermore, the addition of Sr increased the lattice parameters of HA. Here, we obtained the cation leach liquor by immersing the prepared samples in a culture medium for cell experiments. The in vitro study showed that 10Mg20Sr promoted better MG63 cell attachment, proliferation and differentiation than HA. Thus, the presence of an appropriate proportion of Mg and Sr could play a significant role in the increased biocompatibility of HA. PMID:26916949

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

    NASA Astrophysics Data System (ADS)

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

    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.

  4. Efficient aziridine synthesis in metastable crystalline phases by photoinduced denitrogenation of crystalline triazolines.

    PubMed

    de Loera, Denisse; Garcia-Garibay, Miguel A

    2012-08-01

    The solid-state photodenitrogenation of crystalline triazolines proceeds with high efficiency to form the corresponding aziridines in high chemical yields upon selection of the proper irradiation wavelength. It was shown that the solid-to-solid reactions occur by formation of the product in metastable crystalline phases. PMID:22794188

  5. Mesogen-jacketed liquid crystalline polymers.

    PubMed

    Chen, Xiao-Fang; Shen, Zhihao; Wan, Xin-Hua; Fan, Xing-He; Chen, Er-Qiang; Ma, Yuguo; Zhou, Qi-Feng

    2010-08-01

    This critical review covers the recent progress in the research of mesogen-jacketed liquid crystalline polymers (MJLCPs), special side-on side-chain liquid crystalline polymers with very short spacers or without spacers. MJLCPs can self-organize into supramolecular columnar phases with the polymer chains aligned parallel to one another or smectic phases with the backbones embedded in the smectic layers. The semi-rigid rod-like MJLCP with a tunable rod shape in both length and diameter provides an excellent building block in designing novel rod-coil liquid crystalline block copolymers which can self-assemble into hierarchical supramolecular nanostructures depending on the competition between liquid crystal formation and microphase separation (229 references). PMID:20559597

  6. Liquid Crystalline Materials for Biological Applications

    PubMed Central

    Lowe, Aaron M.; Abbott, Nicholas L.

    2012-01-01

    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. PMID:22563142

  7. Topological crystalline insulators in photonic systems

    NASA Astrophysics Data System (ADS)

    Zhang, Jianxiao; Rechtsman, Mikael; Liu, Chao-Xing

    Topological crystalline insulators are a class of materials with a bulk energy gap and edge or surface modes, which are protected by crystalline symmetry, at their boundaries. They have been realized in electronic systems: in particular, in SnTe. In this work, we propose a mechanism to realize photonic boundary states topologically protected by crystalline symmetry. We map this one-dimensional system to a two-dimensional lattice model with opposite magnetic fields, as well as opposite Chern numbers, in its even and odd mirror parity subspaces, thus corresponding to a topological mirror insulator. Furthermore, we test how sensitive and robust edge modes depend on their mirror parity by performing time dependent evolution simulation of edge modes in a photonic setting with realistic experimental parameters. C.-X.L. acknowledge the support from Office of Naval Research (Grant No. N00014-15-1-2675).

  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. Liquid crystalline thermosetting polyimides. Final report

    SciTech Connect

    Hoyt, A.E.; Huang, S.J.

    1993-07-01

    Phase separation of rodlike reinforcing polymers and flexible coil matrix polymers is a common problem in formulating molecular composites. One way to reduce phase separation might be to employ liquid crystalline thermosets as the matrix material. In this work, functionally terminated polyimide oligomers which exhibit lyotropic liquid crystalline behavior were successfully prepared. Materials based on 2,2{prime}-bis(trifluoromethyl)-4,4{prime}-diaminobiphenyl and 3,3{prime},4,4{prime}-biphenylenetetra-carboxylic dianhydride have been synthesized and characterized.

  10. Structural studies on bovine γ-crystallin

    PubMed Central

    Croft, L. R.; Waley, S. G.

    1971-01-01

    The amino acid sequences around the cysteine residues in the lens protein, γ-crystallin, were studied. Fraction II of the γ-crystallin from calf lens (Björk, 1964) was used. The protein was oxidized with performic acid and then hydrolysed with trypsin. Six peptides containing cysteic acid were isolated. One of the peptides contained three residues of cysteic acid and the others contained one residue of cysteic acid. We conclude that there are eight unique residues of cysteic acid in the oxidized protein. Amino acid analysis suggests that there are also eight residues of cysteic acid in the molecule, which thus contains only one polypeptide chain. PMID:5165918

  11. Tensile Deformation of Polyethylenes: Crystallinity Effects

    NASA Astrophysics Data System (ADS)

    Crist, Buckley; Metaxas, Costas

    2004-03-01

    The crystalline fraction of polyethylene can be reduced by increasing the cooling rate, the molecular weight or the fraction of comonomer. All three methods have been used in this study of tensile deformation which shows that true stress - true strain behavior depends systematically on morphology. The dependence of uniaxial yield stress on crystal thickness is well understood in terms of dislocation nucleation. Post yield flow is dominated by the strain hardening rate that is larger in polyethylenes of lower crystallinity. Noncrystalline polymer evidently reduces the plastic compliance while providing for elastic (reversible) strains. These observations are examined in terms of old and new theories for deformation of semicrystalline polymers.

  12. Monolithic aerogels with nanoporous crystalline phases

    NASA Astrophysics Data System (ADS)

    Daniel, Christophe; Guerra, Gaetano

    2015-05-01

    High porosity monolithic aerogels with nanoporous crystalline phases can be obtained from syndiotactic polystyrene and poly(2,6-dimethyl-1,4-phenylene)oxide thermoreversible gels by removing the solvent with supercritical CO2. The presence of crystalline nanopores in the aerogels based on these polymers allows a high uptake associated with a high selectivity of volatile organic compounds from vapor phase or aqueous solutions even at very low activities. The sorption and the fast kinetics make these materials particularly suitable as sorption medium to remove traces of pollutants from water and moist air.

  13. A Single-Crystalline Mesoporous Quartz Superlattice.

    PubMed

    Matsuno, Takamichi; Kuroda, Yoshiyuki; Kitahara, Masaki; Shimojima, Atsushi; Wada, Hiroaki; Kuroda, Kazuyuki

    2016-05-10

    There has been significant interest in the crystallization of nanostructured silica into α-quartz because of its physicochemical properties. We demonstrate a single-crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged α-quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li(+) only on the surface of silica nanospheres is effective for crystallization. PMID:27060365

  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, 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)...

  16. 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)...

  17. 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)...

  18. 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)...

  19. 40 CFR 721.9100 - Substituted quinoline.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted quinoline. 721.9100... Substances § 721.9100 Substituted quinoline. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted quinoline (PMN P-93-1183)...

  20. 40 CFR 721.9100 - Substituted quinoline.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted quinoline. 721.9100... Substances § 721.9100 Substituted quinoline. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted quinoline (PMN P-93-1183)...

  1. 40 CFR 721.3360 - Substituted ethanolamine.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted ethanolamine. 721.3360... Substances § 721.3360 Substituted ethanolamine. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as substituted ethanolamine (PMN P-91-490)...

  2. Ethynyl and substituted ethynyl-terminated polysulfones

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor)

    1984-01-01

    Ethynyl and substituted ethynyl-terminated polysulfones and a process for preparing the same are disclosed. These polysulfones are thermally cured to induce cross-linking and chain extension, producing a polymer system with improved solvent resistance and use temperature. Also disclosed are substituted 4-ethynylbenzoyl chlorides as precursors to the substituted ethynyl-terminated polysulfones and a process for preparing the same.

  3. Ethynyl and substituted ethynyl-terminated polysulfones

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor)

    1986-01-01

    Ethynyl and substituted ethynyl-terminated polysulfones and their synthesis are disclosed. These polysulfones are thermally cured to induce cross-linking and chain extension, producing a polymer system with improved solvent resistance and use temperatures. Also disclosed are substituted 4-ethynylbenzoyl chlorides as precursors to the substituted ethynyl-terminated polysulfones and a process for preparing the same.

  4. Permanent Teacher Preparation for Substitute Teachers.

    ERIC Educational Resources Information Center

    Hardman, Steve; Tippetts, Zachary

    2001-01-01

    Presents information about what should be communicated to substitute teachers and why it is important, focusing on the substitute teacher's role, classroom management tools, curriculum management, and preparing students for the substitute teacher by creating bridges that will help minimize the sense of separation students feel when they have a…

  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 721.9820 - Substituted triazole.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted triazole. 721.9820 Section... Substances § 721.9820 Substituted triazole. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as a substituted triazole (PMN P-90-1731)...

  7. 40 CFR 721.9820 - Substituted triazole.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted triazole. 721.9820 Section... Substances § 721.9820 Substituted triazole. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as a substituted triazole (PMN P-90-1731)...

  8. 40 CFR 721.9820 - Substituted triazole.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted triazole. 721.9820 Section... Substances § 721.9820 Substituted triazole. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as a substituted triazole (PMN P-90-1731)...

  9. 40 CFR 721.9820 - Substituted triazole.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted triazole. 721.9820 Section... Substances § 721.9820 Substituted triazole. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as a substituted triazole (PMN P-90-1731)...

  10. 40 CFR 721.9820 - Substituted triazole.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted triazole. 721.9820 Section... Substances § 721.9820 Substituted triazole. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as a substituted triazole (PMN P-90-1731)...

  11. 24 CFR 221.252 - Substitute mortgagors.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Substitute mortgagors. 221.252... Cost Homes § 221.252 Substitute mortgagors. (a) Selling mortgagor. The mortgagee may effect the release... approval of a substitute mortgagor, as provided by this section. (b) Purchasing mortgagor. The...

  12. 40 CFR 721.5867 - Substituted phenol.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 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,...

  13. 40 CFR 721.5867 - Substituted phenol.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 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,...

  14. 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,...

  15. 40 CFR 721.5867 - Substituted phenol.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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,...

  16. 40 CFR 721.5867 - Substituted phenol.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 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,...

  17. Transfer Printed Crystalline Nanomembrane for Versatile Electronic Applications

    NASA Astrophysics Data System (ADS)

    Seo, Jung-Hun

    Flexible electronics have traditionally been addressed low-frequency applications, since the materials for the traditional flexible electronics, such as polymer and non-crystalline inorganic semiconductors, have poor electronic properties. Fast flexible electronics that operate at radio frequencies (RF), particularly at microwave frequencies, could lead to a number of novel RF applications where rigid chip-based solid-state electronics cannot easily fulfill. Single-crystal semiconductor nanomembranes (NM) that can be released from a number of wafer sources are mechanically very flexible yet exhibit outstanding electronic properties that are equivalent to their bulky counterparts. These thin flexible single-crystal materials can furthermore be placed, via transfer printing techniques, to nearly any substrate, including flexible polymers, thus creating the opportunity to realize RF flexible electronics. In this thesis, various RF transistors made of semiconductor NMs on plastic substrates will be discussed. In addition, as a photonic application, the demonstration of large-area Si NM surface normal ultra-compact photonic crystal reflectors fabricated using the laser interference lithography technique (LIL) will be discussed. Particularly, the mechanism of LIL and NM transfer without using an adhesive layer will be introduced and their optical performance will be addressed. Lastly, the realization of selective substitutional boron doping, using heavily doped Si NM as a doping source, will be discussed. A detailed mechanism using computational modeling and experimental analyses will be provided. The fabrication of high voltage diamond p-i diodes and their performance will be discussed.

  18. 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.

  19. 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.

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. Crystallinity determination by curvefit procedure for a semi-crystalline polymer

    NASA Technical Reports Server (NTRS)

    Wakelyn, N. T.

    1985-01-01

    Wide angle X-ray scattering (WAXS) data from poly(etheretherketone) (PEEK) was resolved into a crystalline contribution represented as four reflections and an amorphous contribution represented as a broad, smoothly varying curve. The crystalline scatter is described as a linear combination of Cauchy and Gaussian functions while that of the amorphous halo is expressed as a cubic polynomial. Statistical analysis of the measured scattered intensity from an amorphous specimen with that calculated from the cubic polynomial, as a function of the combination parameter (fraction of Cauchy and Gaussian functions), suggests that the crystalline fraction of the polymer specimen studied is about 0.39.

  13. Urothermal Synthesis of Crystalline Porous Materials

    PubMed Central

    Zhang, Jian; Bu, Julia T.; Chen, Shumei; Wu, Tao; Zheng, Shoutian; Chen, Yigang; Nieto, Ruben A.; Feng, Pingyun

    2015-01-01

    Pores from Urea Urea derivatives are shown here to be a highly verstaile solvent system for the synthesis of crystalline solids. In particular, reversible binding of urea derivatives to framework metal sites has been utilized to create a variety of materials integrating both porosity and open-metal sites. PMID:20954225

  14. Smeared gap equations in crystalline color superconductivity

    SciTech Connect

    Ruggieri, M.

    2006-01-12

    In the framework of HDET, we discuss an averaging procedure of the NJL quark-quark interaction lagrangian, treated in the mean field approximation, for the two flavor LOFF phase of QCD. This procedure gives results which are valid in domains where Ginzburg-Landau results may be questionable. We compute and compare the free energy for different LOFF crystalline structures.

  15. 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

  16. Synthesis and Characterization of Zirconium Substituted Cobalt Ferrite Nanopowders

    DOE PAGESBeta

    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

  17. 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.

  18. 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.

  19. Heads or tails: how do chemically substituted fullerenes melt?

    PubMed

    Armstrong, Jeff; Mukhopadhyay, Sanghamitra; Bresme, Fernando; Fernandez-Alonso, Felix

    2016-06-29

    We address the question as to whether the melting of chemically substituted fullerenes is driven by the dynamics of the fullerene moiety (the head) or the substituted sub-unit (the tail). To this end, we have performed quasielastic neutron-scattering experiments and classical molecular-dynamics simulations as a function of temperature on the prototypical fullerene derivative phenyl-C61-butyric acid methyl ester. To enable a direct and quantitative comparison between experimental and simulation data, dynamic structure factors for the latter have been calculated from atomic trajectories and further convolved with the known instrument response. A detailed analysis of the energy- and momentum-transfer dependence of this observable in the quasielastic regime shows that melting is entirely driven by temperature-activated tail motions. We also provide quantitative estimates of the activation energy for this process as the material first enters a plastic-crystalline phase, followed by the emergence of a genuine liquid at higher temperatures. PMID:27087579

  20. Synthesis and Characterization of Zirconium Substituted Cobalt Ferrite Nanopowders.

    PubMed

    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. 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. The 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. In the present study the 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. PMID:27398535

  1. 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.

  2. X-ray diffraction and infrared spectroscopy analyses on the crystallinity of engineered biological hydroxyapatite for medical application

    NASA Astrophysics Data System (ADS)

    Poralan, G. M., Jr.; Gambe, J. E.; Alcantara, E. M.; Vequizo, R. M.

    2015-06-01

    Biological hydroxyapatite (BHAp) derived from thermally-treated fish bones was successfully produced. However, the obtained biological HAp was amorphous and thus making it unfavorable for medical application. Consequently, this research exploits and engineers the crystallinity of BHAp powders by addition of CaCO3 and investigates its degree of crystallinity using XRD and IR spectroscopy. On XRD, the HAp powders with [Ca]/[P] ratios 1.42, 1.46, 1.61 and 1.93 have degree of crystallinity equal to 58.08, 72.13, 85.79, 75.85% and crystal size equal to 0.67, 0.74, 0.75, 0.72 nm, respectively. The degree of crystallinity and crystal size of the obtained calcium deficient biological HAp powders increase as their [Ca]/[P] ratio approaches the stoichiometric ratio by addition of CaCO3 as source of Ca2+ ions. These results show the possibility of engineering the crystallinity and crystal size of biological HAp by addition of CaCO3. Moreover, the splitting factor of PO4 vibration matches the result with % crystallinity on XRD. Also, the area of phosphate-substitution site of PO4 vibration shows linear relationship (R2 = 0.994) with crystal size calculated from XRD. It is worth noting that the crystallinity of the biological HAp with [Ca]/[P] ratios 1.42 and 1.48 fall near the range 60-70% for highly resorbable HAp used in the medical application.

  3. 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. PMID:26478334

  4. 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.…

  5. 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.

  6. 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

  7. 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

  8. Sensory substitution as an artificially acquired synaesthesia.

    PubMed

    Ward, Jamie; Wright, Thomas

    2014-04-01

    In this review we explore the relationship between synaesthesia and sensory substitution and argue that sensory substitution does indeed show properties of synaesthesia. Both are associated with atypical perceptual experiences elicited by the processing of a qualitatively different stimulus to that which normally gives rise to that experience. In the most common forms of sensory substitution, perceptual processing of an auditory or tactile signal (which has been converted from a visual signal) is experienced as visual-like in addition to retaining auditory/tactile characteristics. We consider different lines of evidence that support, to varying degrees, the assumption that sensory substitution is associated with visual-like experiences. We then go on to analyse the key similarities and differences between sensory substitution and synaesthesia. Lastly, we propose two testable predictions: firstly that, in an expert user of a sensory substitution device, the substituting modality should not be lost. Secondly that stimulation within the substituting modality, but by means other than a sensory substitution device, should still produce sensation in the normally substituted modality. PMID:22885223

  9. Stable liquid crystalline phases of colloidally dispersed exfoliated layered niobates.

    PubMed

    Nakato, Teruyuki; Miyamoto, Nobuyoshi; Harada, Akiko

    2004-01-01

    Colloidally dispersed niobium oxide nanosheets obtained by exfoliation of layered niobates HNb(3)O(8) and HTiNbO(5) formed stable liquid crystalline phases; their liquid crystallinity was dependent on the niobate species exfoliated. PMID:14737341

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

    PubMed Central

    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

  11. 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

  12. Changes in zebrafish (Danio rerio) lens crystallin content during development

    PubMed Central

    Wages, Phillip; Horwitz, Joseph; Ding, Linlin; Corbin, Rebecca W.

    2013-01-01

    Purpose The roles that crystallin proteins play during lens development are not well understood. Similarities in the adult crystallin composition of mammalian and zebrafish lenses have made the latter a valuable model for examining lens function. In this study, we describe the changing zebrafish lens proteome during development to identify ontogenetic shifts in crystallin expression that may provide insights into age-specific functions. Methods Two-dimensional gel electrophoresis and size exclusion chromatography were used to characterize the lens crystallin content of 4.5-day to 27-month-old zebrafish. Protein spots were identified with mass spectrometry and comparisons with previously published proteomic maps, and quantified with densitometry. Constituents of size exclusion chromatography elution peaks were identified with sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Results Zebrafish lens crystallins were expressed in three ontogenetic patterns, with some crystallins produced at relatively constant levels throughout development, others expressed primarily before 10 weeks of age (βB1-, βA1-, and γN2-crystallins), and a third group primarily after 10 weeks (α-, βB3-, and γS-crystallins). Alpha-crystallins comprised less than 1% of total lens protein in 4.5-day lenses and increased to less than 7% in adult lenses. The developmental period between 6 weeks and 4 months contained the most dramatic shifts in lens crystallin expression. Conclusions These data provide the first two-dimensional gel electrophoresis maps of the developing zebrafish lens, with quantification of changing crystallin abundance and visualization of post-translational modification. Results suggest that some crystallins may play stage specific roles during lens development. The low levels of zebrafish lens α-crystallin relative to mammals may be due to the high concentrations of γ-crystallins in this aquatic lens. Similarities with mammalian crystallin expression continue

  13. 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.

  14. Crystalline cell research: Today and tomorrow

    SciTech Connect

    King, D.L.; Arvizu, D.E.

    1987-01-01

    Recent consolidation of the US Department of Energy Photovoltaic Program has enabled Sandia to assume a primary role in the continuing research and development of crystalline cell technology. Silicon material growth and characterization, one-sun and concentrator silicon cells, and single and multijunction III-V concentrator cells are all being considered. This expanded responsibility gives us the opportunity to review previous programs and to coordinate a specifically directed research effort that capitalizes on recent advances in all of the areas mentioned. This paper summarizes the status of current crystalline cell technology, identifies Sandia's proposed research direction, and provides well-supported efficiency projections for Si concentrator cells and for one-sun Si cells.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Cystoid Macular Edema in Bietti's Crystalline Retinopathy

    PubMed Central

    2014-01-01

    A 27-year-old man with progressive bilateral visual decline was diagnosed to have Bietti's crystalline dystrophy (BCD). Fluorescein angiography revealed bilateral petaloid type late hyperfluorescence implicating concurrent cystoid macular edema (CME). Optical coherence tomography exhibited cystoid foveal lacunas OU. During the follow-up of six years, intraretinal crystals reduced in amount but CME persisted angiographically and tomographically. CME is among the rare macular features of BCD including subfoveal sensorial detachment, subretinal neovascular membrane, and macular hole. PMID:24949209

  3. The Phase Diagram of Crystalline Surfaces

    NASA Astrophysics Data System (ADS)

    Anagnostopoulos, K.; Bowick, M. J.; Catterall, S. M.; Falcioni, M.; Thorleifsson, G.

    1996-03-01

    We report the status of a high-statistics Monte Carlo simulation of non-self-avoiding crystalline surfaces with extrinsic curvature on lattices of size up to 128 2 nodes. We impose free boundary conditions. The free energy is a gaussian spring tethering potential together with a normal-normal bending energy. Particular emphasis is given to the behavior of the model in the cold phase where we measure the decay of the normal-normal correlation function.

  4. Vibrational factor group splittings in crystalline aniline

    SciTech Connect

    Tripathi, G.N.R.

    1980-12-01

    Evidence for intermolecular dynamic coupling in the molecular vibrations of crystalline aniline has been obtained for the first time. The Raman intensity patterns in polycrytalline aniline at 77 K and the infrared polarization in the oriented aniline films at 40 K are investigated. The crystal spectra are interpreted to deduce the probable site (C/sub 1/) and factor group (D/sub 2h/). Some of the earlier vibrational assignments are revised.

  5. 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 ...

  6. Production of crystalline polymers via liquid crystal monomers

    NASA Technical Reports Server (NTRS)

    Labes, M.; Palos, C.

    1969-01-01

    Method produces crystalline polymers through a liquid crystalline phase of monomers. The monomer is polymerized while held in the liquid crystalline phase either thermally, photolytically, catalytically, or by X-ray or gamma ray irradiation, and can be performed in an electric or magnetic field that influences the molecular orientation.

  7. 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...

  8. 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...

  9. 21 CFR 522.313a - Ceftiofur crystalline free acid.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 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...

  10. 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...

  11. 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...

  12. 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)

  13. 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

  14. Increasing the conductivity of crystalline polymer electrolytes.

    PubMed

    Christie, Alasdair M; Lilley, Scott J; Staunton, Edward; Andreev, Yuri G; Bruce, Peter G

    2005-01-01

    Polymer electrolytes consist of salts dissolved in polymers (for example, polyethylene oxide, PEO), and represent a unique class of solid coordination compounds. They have potential applications in a diverse range of all-solid-state devices, such as rechargeable lithium batteries, flexible electrochromic displays and smart windows. For 30 years, attention was focused on amorphous polymer electrolytes in the belief that crystalline polymer:salt complexes were insulators. This view has been overturned recently by demonstrating ionic conductivity in the crystalline complexes PEO6:LiXF6 (X = P, As, Sb); however, the conductivities were relatively low. Here we demonstrate an increase of 1.5 orders of magnitude in the conductivity of these materials by replacing a small proportion of the XF6- anions in the crystal structure with isovalent N(SO2CF3)2- ions. We suggest that the larger and more irregularly shaped anions disrupt the potential around the Li+ ions, thus enhancing the ionic conductivity in a manner somewhat analogous to the AgBr(1-x)I(x) ionic conductors. The demonstration that doping strategies can enhance the conductivity of crystalline polymer electrolytes represents a significant advance towards the technological exploitation of such materials. PMID:15635406

  15. Liquid Crystalline Compositions as Gas Sensors

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr; Murray, John; Tantillo, Anthony; Wenzlick, Madison; Howard-Jennings, Jordan

    2015-03-01

    Droplets and films of nematic and cholesteric liquid crystalline mixtures were studied as promising detectors of volatile organic compounds (VOCs) in the air. Under increasing concentration of VOC in the air the detection may rely on each of the following effects sequentially observed one after the other due to the diffusion of VOC inside liquid crystalline matrix: i. slight changes in orientation and order parameter of liquid crystal, ii. formation of bubbles on the top of the liquid crystalline droplet due to the mass transfer between the areas with different order parameter, iii. complete isotropisation of the liquid crystal. All three stages can be easily monitored by optical microscopy and photo camera. Detection limits corresponding to the first stage are typically lower by a factor of 3-6 than detection limits corresponding to the beginning of mass transfer and isotropisation. The prototype of a compact sensor sensitive to the presence of organic solvents in the air is described in detail. The detection limits of the sensor is significantly lower than VOC exposure standards. The qualitative model is presented to account for the observed changes related to the diffusion, changes of order parameter and isotropisation.

  16. 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.

  17. Trends in substitution models of molecular evolution

    PubMed Central

    Arenas, Miguel

    2015-01-01

    Substitution models of evolution describe the process of genetic variation through fixed mutations and constitute the basis of the evolutionary analysis at the molecular level. Almost 40 years after the development of first substitution models, highly sophisticated, and data-specific substitution models continue emerging with the aim of better mimicking real evolutionary processes. Here I describe current trends in substitution models of DNA, codon and amino acid sequence evolution, including advantages and pitfalls of the most popular models. The perspective concludes that despite the large number of currently available substitution models, further research is required for more realistic modeling, especially for DNA coding and amino acid data. Additionally, the development of more accurate complex models should be coupled with new implementations and improvements of methods and frameworks for substitution model selection and downstream evolutionary analysis. PMID:26579193

  18. Formation of substituted oxa- and azarhodacyclobutanes.

    PubMed

    Dauth, Alexander; Rigling, Carla; Tsoung, Jennifer; Love, Jennifer A

    2013-12-01

    The preparation of substituted oxa- and azarhodacyclobutanes is reported. After exchange of ethylene with a variety of unsymmetrically and symmetrically substituted alkenes, the corresponding rhodium-olefin complexes were oxidized with H2O2 and PhINTs (Ts=p-toluenesulfonyl) to yield the substituted oxa- and azarhodacyclobutanes, respectively. Oxarhodacyclobutanes could be prepared with excellent selectivity for incorporation of the oxygen atom on the more substituted carbon atom of the alkene. At the same time, azarhodacyclobutanes showed good-to-excellent selectivity for heteroatom incorporation on the less substituted carbon. Furthermore, it was shown that steric modifications of the ancillary ligand have a significant influence on the selectivity of Rh-olefin complex formation as well as formation of the substituted azametallacycles. PMID:24307371

  19. Trends in substitution models of molecular evolution.

    PubMed

    Arenas, Miguel

    2015-01-01

    Substitution models of evolution describe the process of genetic variation through fixed mutations and constitute the basis of the evolutionary analysis at the molecular level. Almost 40 years after the development of first substitution models, highly sophisticated, and data-specific substitution models continue emerging with the aim of better mimicking real evolutionary processes. Here I describe current trends in substitution models of DNA, codon and amino acid sequence evolution, including advantages and pitfalls of the most popular models. The perspective concludes that despite the large number of currently available substitution models, further research is required for more realistic modeling, especially for DNA coding and amino acid data. Additionally, the development of more accurate complex models should be coupled with new implementations and improvements of methods and frameworks for substitution model selection and downstream evolutionary analysis. PMID:26579193

  20. Generation of crystalline silica from sugarcane burning.

    PubMed

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

    2010-07-01

    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

  1. 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

  2. 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

    NASA Astrophysics Data System (ADS)

    Lacivita, Valentina; Rèrat, Michel; Orlando, Roberto; Ferrero, Mauro; Dovesi, Roberto

    2012-03-01

    The longitudinal polarizability, αxx, and second hyperpolarizability, γxxxx, 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 γxxxx, 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 -(C2H2)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 αxx and γxxxx 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 αxx and 1010 for γxxxx). On the basis of previous systematic comparisons of results obtained with

  3. 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.

  4. Optical Spectroscopic Studies on Methoxy Substituted 2-4, Diphenyl Quinoline Derivatives Dispersed in Polystyrene Matrix

    NASA Astrophysics Data System (ADS)

    Bahirwar, B. M.; Gahane, D. H.; Atram, R. G.; Moharil, S. V.

    The electroactive and blue luminescent substituted diphenyl quinoline derivative OMe-DPQ and Cl -DPQ have been synthesized and characterized by FT-IR. The optical properties are investigated by UV-vis absorption and photoluminescence (PL) measurements. The polymeric compounds show two absorption peaks and exhibits intense blue photoluminescence in solid-state crystalline powder, in chloroform solution and blended thin films. OMe-DPQ and Cl-DPQ show intense blue emitting emission in different solvents. A narrow full width at half-maximum (FWHM) value of PL spectra can be obtained, may be useful for developing organic luminescent devices, solar cell devices, or in chemical sensors.

  5. Synthesis of new LC compounds with high optical anisotropy: pentaphenyl derivatives lateral substituted

    NASA Astrophysics Data System (ADS)

    Sasnouski, Genadz; Lapanik, Valery; Dabrowski, Roman; Dziaduszek, Jerzy

    2012-04-01

    A new pentaphenyl liquid crystalline (LC) compounds with 2,3-difluorobenzene moiety exhibiting wide nematic range have been prepared. The key stage is the condensation of the corresponding 3-dimethylaminopropanoyl-4-pentyl benzene hydrochloride with substituted methyl benzyl ketone in the presence of base leading to 3,6-disubstituted cyclohexenones. Methylation with methyl magnesium iodide followed by oxidative aromatization gives three-ring bromides, which are used in the Suzuki cross-coupling reaction. Pentaphenyl LC compounds possessing lateral methyl group have moderate melting points, improved solubility, and miscibility with another LC components. The new compounds could be useful in LC compositions with the high optical anisotropy.

  6. 40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... products with silica and substituted silane (generic). 721.10497 Section 721.10497 Protection of... 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)...

  7. 40 CFR 721.2577 - Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Copper complex of (substituted... Copper complex of (substituted sulfonaphthyl azo substituted phenyl) disulfonaphthyl azo, amine salt... significant new uses subject to reporting. (1) The chemical substances identified generically as...

  8. 40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... products with silica and substituted silane (generic). 721.10497 Section 721.10497 Protection of... 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)...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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

  16. Factors influencing α-crystallin association with phospholipid vesicles

    PubMed Central

    Cobb, Brian A.; Petrash, J. Mark

    2010-01-01

    Purpose Lens lipids undergo a number of changes with age, including an overall increase in phospholipid acyl chain saturation and a decrease in length. In addition, the amount of membrane bound α-crystallin increases dramatically with age and with the onset of cataract. The aim of this study was to determine if a link exists between age and cataract associated changes in lens lipids and the changes in α-crystallin membrane association. Methods Protein-free lipid vesicles composed of a wide variety of synthetic and lens-derived lipid vesicles were formed by sonication. These vesicles were used with fluorescent native and recombinant α-crystallin conjugates in vesicle binding assays. Vesicles were collected by centrifugation and bound α-crystallin was quantified with fluorescence intensity measurements. Results α-Crystallin complexes showed remarkably similar binding profiles for all lipid vesicles tested, regardless of lipid origin, phospholipid head group, acyl chain length or saturation, and inclusion of cholesterol. In addition, recombinant α-crystallin complexes bind to these vesicles in a manner that is essentially indistinguishable from that of native human and bovine α-crystallins. Unlike α-crystallin binding to lens membranes containing intrinsic proteins, binding of α-crystallin to protein-free vesicles was very high capacity and unsaturable. Conclusions We conclude from these data that the binding of α-crystallin to lens membranes is not lipid-specific. Furthermore, protein post-translational changes, such as phosphorylation, do not appear to alter α-crystallin binding to these vesicles. Given the linearity of the binding curves, we propose that the only limiting factor for normal α-crystallin membrane binding is available surface area on the bilayer. Finally, the present data suggests that increased in vivo membrane association of α-crystallin is not a result of lipid changes, but more likely a result of non-lipid factors such as the

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

    PubMed

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

    2015-11-01

    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%). PMID:26256343

  18. 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.

  19. Radiation effects and crystallinity in polyethylene

    NASA Astrophysics Data System (ADS)

    Keller, A.; Ungar, G.

    A survey is presented of a series of works on the influence of crystallinity on the radiation induced effects, cross-linking in particular, in polyethylene and paraffins. The principal theme is that the usual conception of random introduction of cross-links into a random assembly of chains needs to be modified in the presence of crystallinity in general and chain folding in particular. A long series of varied investigations on polyethylene have indeed demonstrated through a series of conspicuous effects that not only the ordering intrinsic to crystals and the increased intrachain contacts due to chain folding, but the higher level morphology, the nature and mutual arrangement in particular, have a major influence on the effectivity of the radiation leading to networks. Extension of the works to paraffins identified unsuspected mobility of both the radiation precursor species and the paraffin molecule itself (cross-linked and uncross-linked) within the crystal lattice, leading to phase segregation of the cross-linked species into microscopically identifiable domains together with identifying a trend for the cross-links themselves to form non-randomly in groups. The latter phenomenon, observed also in the molten state, indicates that the departure from randomness in the cross-linking process is much more deep-rooted than originally anticipated, and calls for a general reassessment of our knowledge of cross-linking. Other topics included as part of the general enquiry are the destruction of crystallinity, the promotion of hexagonal phase through radiation, the effect of morphology on chain scission and the general, still unsolved issue of how to assess cross-links by a direct analytical method (involving NMR). The hope is expressed that the bringing together of these varied pieces of work will serve the unification of presently widely diverse areas of experience and might influence developments in the radiation studies of paraffinoid substances.

  20. 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…

  1. 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.

  2. 40 CFR 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical 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 721.323 - Substituted acrylamide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical 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)...

  4. Substitute Teachers: Making Lost Days Count

    ERIC Educational Resources Information Center

    True, Charlene; Butler, Kyle; Sefton, Rachel

    2011-01-01

    As K-12 teachers and administrators grow increasingly concerned with issues of accountability, research-based methods, and intervention strategies, little discussion exists on the impact of substitute teachers in the classroom. In the rush to analyze test scores, are the days covered by substitute teachers even considered? Though districts are…

  5. 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…

  6. 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...

  7. 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.…

  8. Dimensions of Needs in Secondary Substitute Teaching.

    ERIC Educational Resources Information Center

    Dilanian, Seta Margo

    Following a brief review of research and literature regarding the needs of secondary school substitute teachers, suggestions for helping these teachers do an effective, professional job are offered. Research indicates that understanding of the subject matter along with understanding of various learning approaches enhances the substitute teacher's…

  9. 24 CFR 235.206 - Substitute mortgagors.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Substitute mortgagors. 235.206... MORTGAGE INSURANCE AND ASSISTANCE PAYMENTS FOR HOME OWNERSHIP AND PROJECT REHABILITATION Contract Rights and Obligations-Homes for Lower Income Families § 235.206 Substitute mortgagors. (a) Selling...

  10. 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 Section 721.323 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.323 Substituted acrylamide....

  11. Savvy Substitutions. Tricks of the Trade.

    ERIC Educational Resources Information Center

    Guhin, Paula

    2000-01-01

    Provides ideas for using throwaways and substitutions, such as homemade objects and everyday items, as art supplies and other resources in the art classroom. Throwaways and substitutions are a way to be environmentally caring, to extend meager supplies, and to supplement art budgets. (CMK)

  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. 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.

  14. (Preoxidation cleaning optimization for crystalline silicon)

    SciTech Connect

    Not Available

    1991-01-01

    A series of controlled experiments has been performed in Sandia's Photovoltaic Device Fabrication Laboratory to evaluate the effect of various chemical surface treatments on the recombination lifetime of crystalline silicon wafers subjected to a high-temperature dry oxidation. From this series of experiments we have deduced a relatively simple yet effective cleaning sequence. We have also evaluated the effect of different chemical damage-removal etches for improving the recombination lifetime and surface smoothness of mechanically lapped wafers. This paper presents the methodology used, the experimental results obtained, and our experience with using this process on a continuing basis over a period of many months. 7 refs., 4 figs., 1 tab.

  15. 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.

  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. Heat capacities of crystalline tetraalkylammonium salts

    NASA Astrophysics Data System (ADS)

    Manin, N. G.; Kustov, A. V.; Antonova, O. A.

    2012-05-01

    The behavior of crystalline tetraalkylammonium salts at 290-350 K was studied by differential scanning calorimetry. For tetraethyl- and tetrabutylammonium bromides (Et4NBr and Bu4NBr), the experimental heat capacities agreed well with the literature values. For tetrahexyl-, tetraheptyl-, and tetraoctylam-monium bromides (Hex4NBr, Hep4NBr, and Oct4NBr), phase transitions were found between crystal modifications whose characteristic temperatures depended significantly on the size of the cation. Empirical equations for the temperature dependences of the heat capacities of the salts within the ranges of homogeneous equilibrium phases were derived.

  18. Stable molecular configuration in crystalline carboxylic acids

    NASA Astrophysics Data System (ADS)

    Hayashi, Soichi; Umemura, Junzo; Nakamura, Ryoko

    1980-12-01

    The stable (lower enthalpy) molecular configurations of propionic, butyric, Jeric and lauric acids in the crystalline state have been examined via their atom-atom potentials. It was found that the cis configuration is more stable than the trans configuration for propionic, butyric and valeric acids, and that the trans configuration is more stable than the cis configuration for lauric acid, in accord with a previous IR spectral analysis. The potential energy of benzoic acid was recalculated using the positions of atoms given by Speakman, and indicates that the A form is more stable than the B form, in agreement with the results of previous work.

  19. 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.

  20. 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.

  1. Columnar Liquid-Crystalline Dibenzopentacenodithiophenes by Photocyclization.

    PubMed

    Cabral, Marilia G Belarmino; Pereira de Oliveira Santos, Deise M; Bentaleb, Ahmed; Hillard, Elizabeth A; Cristiano, Rodrigo; Gallardo, Hugo; Durola, Fabien; Bock, Harald

    2016-06-01

    The twofold glyoxylic Perkin reaction of perylene-3,9-diglyoxylic acid with thiophene-diacetic acid followed by oxidative photocylization and reaction with α-branched primary alkylamines yields columnar liquid-crystalline diimides with two sulfur atoms in the condensed arene system. A broad temperature range of the hexagonal columnar mesophase is induced by racemic doubly branched alkyl chains. The HOMO and LUMO energy levels of these thiophene-derived diimides qualify them as electron donors with respect to perylene diimides. PMID:27141916

  2. Body-scaled affordances in sensory substitution.

    PubMed

    Travieso, David; Gómez-Jordana, Luis; Díaz, Alex; Lobo, Lorena; Jacobs, David M

    2015-12-15

    The research field on sensory substitution devices has strong implications for theoretical work on perceptual consciousness. One of these implications concerns the extent to which the devices allow distal attribution. The present study applies a classic empirical approach on the perception of affordances to the field of sensory substitution. The reported experiment considers the perception of the stair-climbing affordance. Participants judged the climbability of steps apprehended through a vibrotactile sensory substitution device. If measured with standard metric units, climbability judgments of tall and short participants differed, but if measured in units of leg length, judgments did not differ. These results are similar to paradigmatic results in regular visual perception. We conclude that our sensory substitution device allows the perception of affordances. More generally, we argue that the theory of affordances may enrich theoretical debates concerning sensory substitution to a larger extent than has hitherto been the case. PMID:26587958

  3. 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

  4. 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. PMID:22983020

  5. Microbial formation of lanthanide-substituted magnetites by Thermoanaerobacter sp. TOR-39

    SciTech Connect

    Moon, Ji Won; Roh, Yul; Yeary, Lucas W; Lauf, Robert J; Rawn, Claudia J; Love, Lonnie J; Phelps, Tommy Joe

    2007-01-01

    Lanthanide (Nd, Gd, Tb, Ho, and Er)-substituted magnetites, LyFe3-yO4 (L, lanthanide) were microbially synthesized using L-mixed precursors, LxFe1-xOOH, where x was between 0.01 and 0.2. By combining lanthanides (normally considered toxic to microorganisms) into the akaganeite precursor phase, we were able to mitigate some of the toxicity enabling the microorganisms to produce L-substituted magnetites. A metal reducing bacterium, Thermoanaerobacter ethanolicus successfully converted the mixed akaganeite to L-substituted magnetite while avoiding the potentially toxic effects of soluble L-ions. At higher mixing levels (0.02 < x <0.05) the poor crystallinity of L-mixed precursors increased the concentration of soluble toxic L-ions in the media. Nevertheless, using L-mixed precursors enabled production of microbially synthesized L-substituted magnetite with considerably higher L-concentration than could be obtained when the lanthanides were added as soluble salts. This method can therefore be used to extend the application for nanofermentation to fields where there is a need for nanoscale materials that involve elements such as lanthanides that are toxic or inhibitory to bacterial growth.

  6. Effect of aluminum substitution on microwave absorption properties of barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Qiu, Jianxun; Zhang, Qiguo; Gu, Mingyuan; Shen, Haigen

    2005-11-01

    Aluminum substituted barium hexaferrites were prepared by the self-propagating combustion method and subsequent calcination at 850 °C. The crystalline structure, complex permittivity, complex permeability, and hyperfine parameters of BaFe12-xAlxO19 (x varies from 1.5 to 2.3 in steps of 0.2) were measured with x-ray diffraction (XRD), vector network analyzer and Mössbauer spectroscopy. The XRD results show that all Al3+ ions enter into the lattice of hexagonal barium ferrite. The substitution of Al3+ ions can greatly affect the complex permittivity and permeability of barium ferrite. With increasing substitution, the real part of complex permittivity increases gradually, and the peaks of the imaginary part of complex permeability shift into higher frequency band. When the substitution amount x is 1.9, the largest movement of the peaks is 1.95 GHz, which indicates that the ferromagnetic resonant frequency of barium ferrite increases by 1.95 GHz. The Al3+ ions preferentially occupy the 4f2, 2a, 4f1, and 12k sites in the subcrystalline structure up to x =1.9, and then the Al3+ ions mainly occupy 12k sites. This change also results in 2b sites with a large quadrupole splitting. These occupations lead to a variable magnetocrystalline anisotropy field.

  7. 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. PMID:26237014

  8. 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.

  9. Cryoflotation: densities of amorphous and crystalline ices.

    PubMed

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

    2011-12-01

    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. PMID:21879742

  10. 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.

  11. Interaction-enabled topological crystalline phases

    NASA Astrophysics Data System (ADS)

    Lapa, Matthew F.; Teo, Jeffrey C. Y.; Hughes, Taylor L.

    2016-03-01

    In this article we provide a general mechanism for generating interaction-enabled fermionic topological phases. We illustrate the mechanism with crystalline symmetry-protected topological phases in one, two, and three spatial dimensions. These nontrivial phases require interactions for their existence, and in the cases we consider, the free-fermion classification yields only a trivial phase. For the one- and two-dimensional phases we consider, we provide explicit exactly solvable models which realize the interaction-enabled phases. Similar to the interpretation of the Kitaev Majorana wire as a mean-field p -wave superconductor Hamiltonian arising from an interacting model with quartic interactions, we show that our systems can be interpreted as "mean-field" charge-4 e superconductors arising, e.g., from an interacting model with eight-body interactions or through another physical mechanism. The quartet superconducting nature allows for the teleportation of full Cooper pairs and, in two dimensions, for interesting semiclassical crystalline defects with non-Abelian anyon bound states.

  12. 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.

  13. Crystalline-silicon photovoltaics: Necessary and sufficient

    SciTech Connect

    Basore, P.A.; Gee, J.M.

    1995-01-01

    Photovoltaic (PV) energy systems have always been dominated by crystalline-silicon (c-Si) technology, and recent developments persuasively suggest that c-Si will continue to be the dominant technology well into the next century. The authors explain why c-Si technology is fairing much better than previously expected, and discuss the impact of improvements currently under development. They use a ground-up, engineering-based approach to predict the expected evolution of this type of PV system, and argue that c-Si PV will be in a position to compete for the US residential power market starting in about the year 2010. This market alone will provide the opportunity for PV to supply several percent of the electrical energy used in the United States. Crystalline-silicon technology is therefore not just necessary for building a near-term PV industry; it also offers a low-risk approach to meeting long-term goals for PV energy systems.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Templating gold nanorods with liquid crystalline DNA

    NASA Astrophysics Data System (ADS)

    De Sio, Luciano; Annesi, Ferdinanda; Placido, Tiziana; Comparelli, Roberto; Bruno, Vincenzo; Pane, Alfredo; Palermo, Giovanna; Curri, Maria Lucia; Umeton, Cesare; Bartolino, Roberto

    2015-02-01

    A liquid crystalline, negatively charged, whole-genome DNA is exploited to organize positively charged gold nanorods (GNRs) by means of electrostatic interaction. A mesoscopic alignment of the composite system along a preferred direction is obtained by casting a droplet of the DNA-nanorods solution onto an untreated glass substrate. Gel electrophoresis analysis enables evaluating the effective electric charge of the system, thus minimizing the DNA fragmentation. Polarized optical microscopy, combined with transmission and scanning electron microscopy, shows that, up to 20% in weight of GNR solution, the system exhibits both a long range order, induced by the liquid crystalline phase of the DNA, and a nanoscale organization, due to the DNA self-assembly. These evidences are confirmed by a polarized spectral analysis, which also points out that the optical properties of GNRs strongly depend on the polarization of the impinging probe light. The capability to organize plasmonic nanoparticles by means of DNA material represents a significant advance towards the realization of life science inspired optical materials.

  19. 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

  20. Skin substitutes and wound healing.

    PubMed

    Auger, F A; Lacroix, D; Germain, L

    2009-01-01

    Medical science has vastly improved on the means and methods available for the treatment of wounds in the clinic. The production and use of various types of skin substitutes has led to dramatic improvements in the odds of survival for severely burned patients, but they have also shown promise for many other applications, including cases involving chronic wounds that are not life threatening. Nowadays, more than 20 products are commercially available, more are undergoing clinical trials and a large number of new models are being investigated in various research laboratories worldwide. Many of the current products do not contain any living cells and vary in their capacity to harness the innate capacity of the body to heal itself. Others include living cells, of allogeneic or autologous origin, and are often referred to as 'cellular therapy' or 'tissue-engineered' products. Modifications and improvements are currently investigated that aim at improving the healing potential of those products through the use of recombinant growth factors and additional features such as microvascularization. Fundamental research into wound healing and scar-free regeneration raises the hope that we will eventually be able to restore almost completely the appearance and function of skin after the healing of wounds. PMID:19188757

  1. Wearable and implantable pancreas substitutes.

    PubMed

    Ricotti, Leonardo; Assaf, Tareq; Dario, Paolo; Menciassi, Arianna

    2013-03-01

    A lifelong-implanted and completely automated artificial or bioartificial pancreas (BAP) is the holy grail for type 1 diabetes treatment, and could be a definitive solution even for other severe pathologies, such as pancreatitis and pancreas cancer. Technology has made several important steps forward in the last years, providing new hope for the realization of such devices, whose feasibility is strictly connected to advances in glucose sensor technology, subcutaneous and intraperitoneal insulin pump development, the design of closed-loop control algorithms for mechatronic pancreases, as well as cell and tissue engineering and cell encapsulation for biohybrid pancreases. Furthermore, smart integration of the mentioned components and biocompatibility issues must be addressed, bearing in mind that, for mechatronic pancreases, it is most important to consider how to recharge implanted batteries and refill implanted insulin reservoirs without requiring periodic surgical interventions. This review describes recent advancements in technologies and concepts related to artificial and bioartificial pancreases, and assesses how far we are from a lifelong-implanted and self-working pancreas substitute that can fully restore the quality of life of a diabetic (or other type of) patient. PMID:22990986

  2. tert-butyl-substituted cyclooctatetraenes

    SciTech Connect

    Miller, M.J.; Lyttle, M.H.; Streitwieser, A. Jr.

    1981-05-08

    Reaction of cyclooctatetraene (COT) with tert-butyllithium provides a convenient synthesis of tert-butylcyclooctatetraene, 4. As a byproduct of the reaction mixture, 1,4-di-tert-butylcyclooctatriene has been isolated and converted to 1,4-di-tert-butylcyclooctatetraene, 5, by deprotonation with potassium amide and oxidation with iodine. An independent synthesis of 5 was developed from 9-oxabicyclo(6.1.0)octa-2,4,6-triene (cyclooctatetraene oxide), 9. The highly substituted compound 1,3,5,7-tetra-tert-butylcyclooctatetraene (6) has been prepared in 24% overall yield in four steps. The acetylenic ketone 27, prepared from (tert-butylethynyl)copper and pivaloyl chloride, undergoes condensation with dimethyl malonate to give the pyrone ester 28. This ester undergoes facile hydrolysis and decarboxylation in hot concentrated sulfuric acid to yield 4,6-di-tert-butyl-2H-pyran-2-one (22) which is converted to 6 in one step by photolysis in dilute solution.

  3. 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. PMID:12179211

  4. Crystalline sulfur dioxide: Crystal field splittings, absolute band intensities, and complex refractive indices derived from infra-red spectra

    NASA Astrophysics Data System (ADS)

    Khanna, R. K.; Zhao, Guizhi; Ospina, M. J.; Pearl, J. C.

    The infra-red absorption spectra of thin crystalline films of sulfur dioxide at 90 K are reported in the 2700-450 cm -1 region. The observed multiplicity of the bands in the regions of fundamental modes is attributed to crystal field effects, including factor group and LO—TO splittings, and naturally present minor 34S, 36S and 18O substituted isotopic species. Complex refractive indices determined by an iterative Kramers—Kronig analysis of the extinction data, and absolute band strengths derived from them, are also reported in this region.

  5. 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

  6. 40 CFR 721.5930 - Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic name). 721.5930 Section 721... Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic... identified generically as phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo...

  7. 40 CFR 721.5930 - Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic name). 721.5930 Section 721... Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic... identified generically as phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo...

  8. 40 CFR 721.5930 - Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic name). 721.5930 Section 721... Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic... identified generically as phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo...

  9. 40 CFR 721.5930 - Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic name). 721.5930 Section 721... Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic... identified generically as phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo...

  10. 40 CFR 721.5930 - Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic name). 721.5930 Section 721... Phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo(substituted phenyl)azo, sodium salt (generic... identified generically as phenylenebis[imino (chlorotriazinyl)imino(substituted naphthyl)azo...

  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. When You're Absent: Preparing for the Substitute.

    ERIC Educational Resources Information Center

    Fox, Brian A.

    1988-01-01

    Suggests ways classroom teachers can prepare for absences and help make substitute teaching productive. Recommends forming a list of preferred substitutes at the beginning of the school year; clarifying with students expected behavior; and preparing a permanent substitute packet. (LS)

  13. 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.

  14. 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.

  15. Substitution: An FGD vision reaches fruition

    SciTech Connect

    Feeney, S.

    1995-06-01

    Through Substitution, Phase I affected utilities can meet their Phase I SO{sub 2} allowance requirements by reductions made at a Phase II source. The thinking is that it might be more cost-effective for certain Phase II affected sources to make these SO{sub 2} reductions. This paper will discuss several examples of FGD-equipped, Phase II affected sources who decided to Substitute. Included will be the economics of two particular utilities, one who decided to participate in Substitution, and one who found it uneconomical.

  16. 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.

  17. 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.

  18. Liquid crystalline spinning of spider silk.

    PubMed

    Vollrath, F; Knight, D P

    2001-03-29

    Spider silk has outstanding mechanical properties despite being spun at close to ambient temperatures and pressures using water as the solvent. The spider achieves this feat of benign fibre processing by judiciously controlling the folding and crystallization of the main protein constituents, and by adding auxiliary compounds, to create a composite material of defined hierarchical structure. Because the 'spinning dope' (the material from which silk is spun) is liquid crystalline, spiders can draw it during extrusion into a hardened fibre using minimal forces. This process involves an unusual internal drawdown within the spider's spinneret that is not seen in industrial fibre processing, followed by a conventional external drawdown after the dope has left the spinneret. Successful copying of the spider's internal processing and precise control over protein folding, combined with knowledge of the gene sequences of its spinning dopes, could permit industrial production of silk-based fibres with unique properties under benign conditions. PMID:11279484

  19. 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

  20. 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.

  1. 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.

  2. Synthesis of new liquid crystalline diglycidyl ethers.

    PubMed

    Mohammed, Issam Ahmed; Hamidi, Rashidah Mohamed

    2012-01-01

    The phenolic Schiff bases I-VI were synthesized by condensation reactions between various diamines, namely o-dianisidine, o-tolidine and ethylenediamine with vanillin or p-hydroxybenzaldehyde and subsequent reactions between these phenolic Schiff bases and epichlorohydrin to produce new diglycidyl ethers Ia-VIa. The structures of these compounds were confirmed by CHN, FT-IR, (1)H-NMR, and (13)C-NMR spectroscopy. Their thermotropic liquid crystalline behavior was studied using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All the diglycidyl ethers prepared exhibit nematic mesophases, except for Va and VIa, which did not show any transition mesophases, but simply flow to liquids. PMID:22233565

  3. Mirrorless lasing in liquid crystalline materials

    NASA Astrophysics Data System (ADS)

    Cao, Wenyi; Finkelmann, Heino; Kim, Seok-Tae; Munoz, Antonio; Palffy-Muhoray, Peter; Taheri, Bahman; Twieg, Robert J.

    2002-06-01

    Cholesteric liquid crystals, because of their birefringence and periodic structure, and 1-d photonic band-gap materials. In the reflection band, classical light propagation is forbidden for one of the two eigenmodes; for this mode, the material acts as a distributed cavity host. This inherent distributed cavity effect modifies the fluorescence spectrum, and, if the material is optically pumped, allows population inversion and mirrorless lasing. We have studied emission from thin samples of liquid crystalline materials optically pumped by pico- and nanosecond laser pulses. We have observed laser emission, without an external cavity, from dye-doped liquid crystals, from pure cholesteric liquid crystals without dyes, and from cholesteric liquid crystal elastomers. We present the results of these experiments, discuss the relation between material properties and the lasing process, and consider promising materials and applications.

  4. Research on crystalline silicon solar cells

    SciTech Connect

    Milstein, J.B.; Tsuo, Y.S.

    1984-06-01

    Since the 16th IEEE Photovoltaic Specialists Conference, the focus of the Crystalline Silicon Solar Cell Task at the Solar Energy Research Institute (SERI) has narrowed somewhat. Responsibility for silicon material preparation and ribbon growth were consolidated at the Jet Propulsion Laboratory (JPL) at the end of FY 1983. Five subcontracts were awarded under RFP No. RB-2-02090, Research on Basic Understanding of High Efficiency in Silicon Solar Cells. JPL and Oak Ridge National Laboratory are also working on high-efficiency solar cell research under SERI subcontract. Reports of past solar cell improvements have prompted appreciable interest in the physical, chemical, and electrical transport properties of grain boundaries and other electrically active defects. Studies to achieve better understanding of the hydrogen passivation process are being conducted at various subcontractors, and our in-house research continues. This paper presents the results of these efforts as well as future directions.

  5. 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.

  6. Self-adjustable crystalline inorganic nanocoils.

    PubMed

    Wang, Peng-peng; Yang, Yong; Zhuang, Jing; Wang, Xun

    2013-05-01

    Biomacromolecules such as proteins, although extremely complex in microstructure, can crystallize into macro-sized crystals after self-adjusting their shapes, based on which the structure of biology is built. Inorganic nanowires/nanoribbons with a similar one-dimensional topology but much simpler structures can hardly be as flexible as macromolecules when constructing superlattice structures because of their inherent rigidity. Here we report the synthesis of crystalline indium sulfide nanoribbon-based nanocoils that are formed by spontaneous self-coiling of ultrathin nanoribbons. The nanostructures are flexible and appear as relatively random coils because of their ultrathin ribbon structures (~0.9 nm in thickness) with high aspect ratios. Moreover, the nanocoils can self-adjust their shapes and assemble into two-dimensional superlattices and three-dimensional supercrystals in solution. The ultrathin nanocoils are expected to bring new insights into the use of flexible nanocrystals as building blocks for constructing superstructures. PMID:23611283

  7. Synthesis of liquid crystalline epoxy monomers

    NASA Astrophysics Data System (ADS)

    Fabia, J.; Galina, H.; Mossety-Leszczak, B.; Ulanski, J.; Wojciechowski, Piotr; Wlochowicz, Andrzej

    2002-06-01

    A two-stage method of synthesis of liquid-crystalline diepoxy monomers has been developed. In the first stage, esterification of 4-hydroxyphenyl-4-hydroxybenzoate or 4,4'- biphenol or 4,4'-dihydroxyazobenzene was carried out using 4-penetenoic acid. The resulting olefinic precursors were oxidized with m-chloroperoxybenzoic acid to introduce the epoxy groups. The structure of products was confirmed by FT- IR and 1H NMR. Examinations on a polarization microscope with a hot plate confirmed the presence of mesomorphic phases in both the precursors and monomers. The phase transition temperatures were in the range of 73.5 (at cooling) to 128.0 degree(s)C for olefinic precursors and in the range 57.1 (at cooling) to 143 degree(s)C for epoxy compounds, as determined by DSC and thermo-optical analysis (TOA).

  8. 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

  9. Reactive Liftoff of Crystalline Cellulose Particles.

    PubMed

    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

  10. 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.

  11. 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.

  12. 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. PMID:23575634

  13. Physicochemical Characteristics of Bone Substitutes Used in Oral Surgery in Comparison to Autogenous Bone

    PubMed Central

    Berberi, Antoine; Samarani, Antoine; Nader, Nabih; Noujeim, Ziad; Dagher, Maroun; Kanj, Wasfi; Mearawi, Rita; Salemeh, Ziad; Badran, Bassam

    2014-01-01

    Bone substitutes used in oral surgery include allografts, xenografts, and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone, but little is currently known about their physicochemical characteristics. The aim of this study was to evaluate a number of physical and chemical properties in a variety of granulated mineral-based biomaterials used in dentistry and to compare them with those of autogenous bone. Autogenous bone and eight commercial biomaterials of human, bovine, and synthetic origins were studied by high-resolution X-ray diffraction, atomic absorption spectrometry, and laser diffraction to determine their chemical composition, calcium release concentration, crystallinity, and granulation size. The highest calcium release concentration was 24. 94 mg/g for Puros and the lowest one was 2.83 mg/g for Ingenios β-TCP compared to 20.15 mg/g for natural bone. The range of particles sizes, in terms of median size D50, varied between 1.32 μm for BioOss and 902.41 μm for OsteoSponge, compared to 282.1 μm for natural bone. All samples displayed a similar hexagonal shape as bone, except Ingenios β-TCP, Macrobone, and OsteoSponge, which showed rhomboid and triclinic shapes, respectively. Commercial bone substitutes significantly differ in terms of calcium concentration, particle size, and crystallinity, which may affect their in vivo performance. PMID:25143936

  14. 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.

  15. Bacterial biosynthesis of a calcium phosphate bone-substitute material.

    PubMed

    Thackray, Aniac C; Sammons, Rachel L; Macaskie, Lynne E; Yong, Ping; Lugg, Harriet; Marquis, Peter M

    2004-04-01

    A species of Serratia bacteria produces nano-crystalline hydroxyapatite (HA) crystals by use of a cell-bound phosphatase enzyme, located both periplasmically and within extracellular polymeric materials. The enzyme functions in resting cells by cleaving glycerol-2-phosphate (G-2-P) to liberate free phosphate ions which combine with calcium in solution to produce a cell-bound calcium phosphate material. Bacteria grown as a biofilm on polyurethane reticulated foam cubes were challenged with calcium and G-2-P in a bioreactor to produce a 3-D porous bone-substitute material. The scaffold has 1 mm macropores and 1 microm micropores. XRD showed the crystallites to be 25-28 nm in size, resembling HA before sintering and beta-tricalcium phosphate (beta-TCP, whitlockite) after. When biofilm was grown on titanium discs and challenged with calcium and G-2-P, a calcium phosphate layer formed on the discs. Biomineralisation is therefore a potential route to production of precursor nanophase HA, which has the potential to improve strength. The scaffold material produced by this method could be used as a bone-filler or as an alternative method for coating implants with a layer of HA. PMID:15332607

  16. Synthesis and Structural Characterization of Substituted 2-Phenacylbenzoxazoles

    PubMed Central

    Skotnicka, Agnieszka; Kolehmainen, Erkki; Czeleń, Przemysław; Valkonen, Arto; Gawinecki, Ryszard

    2013-01-01

    1H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl3-solutions contains also (Z)-2-(benzo[d]oxazol-2-yl)-1-phenylethenols (enolimine form). Intramolecular hydrogen bonding in the latter tautomer was found to be significantly weaker than that one in respective (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines. Integrals of the 1H NMR signals were used to evaluate the molar ratio of the tautomers. Strong electron-donating substituents were found to stabilize the ketimine tautomer. pKT (negative logarithm of the equilibrium constant, KT = [ketimine]/[enolimine]) was found to be linearly dependent on the Hammett substituent constant σ. The results of the MP2 ab initio calculations reveal enolimine including an intramolecular OH···N hydrogen bond to be the most stable form both with electron-donor and electron-acceptor substituents. The stability of ketimines is an intermediate of those found for enolimines and enaminones i.e., (E)-2-(benzo[d]oxazol-2(3H)-ylidene)-1-phenylethanones. 13C CPMAS NMR spectral data reveal that in the crystalline state the ketimine tautomer is predominant in p-NMe2 substituted congener. On the other hand, enolimine forms were detected there when the substituent has less electron-donating character or when it is an electron-acceptor by character. PMID:23439552

  17. 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.

  18. Chemical characterization of silicon-substituted hydroxyapatite.

    PubMed

    Gibson, I R; Best, S M; Bonfield, W

    1999-03-15

    Bioceramic specimens have been prepared by incorporating a small amount of silicon (0.4 wt %) into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HA] via an aqueous precipitation reaction to produce a silicon-substituted hydroxyapatite (Si-HA). The results of chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite. The Si-HA was produced by first preparing a silicon-substituted apatite (Si-Ap) by a precipitation process. A single-phase Si-HA was obtained by heating/calcining the as-prepared Si-Ap to temperatures above 700 degrees C; no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP), or calcium oxide (CaO), were observed by X-ray diffraction analysis. Although the X-ray diffraction patterns of Si-HA and stoichiometric HA appeared to be identical, refinement of the diffraction data revealed some small structural differences between the two materials. The silicon substitution in the HA lattice resulted in a small decrease in the a axis and an increase in the c axis of the unit cell. This substitution also caused a decrease in the number of hydroxyl (OH) groups in the unit cell, which was expected from the proposed substitution mechanism. The incorporation of silicon in the HA lattice resulted in an increase in the distortion of the PO4 tetrahedra, indicated by an increase in the distortion index. Analysis of the Si-HA by Fourier transform infrared (FTIR) spectroscopy indicated that although the amount of silicon incorporated into the HA lattice was small, silicon substitution appeared to affect the FTIR spectra of HA, in particular the P-O vibrational bands. The results demonstrate that phase-pure silicon-substituted hydroxyapatite may be prepared using a simple precipitation technique. PMID:10397946

  19. Calcium binding properties of gamma-crystallin: calcium ion binds at the Greek key beta gamma-crystallin fold.

    PubMed

    Rajini, B; Shridas, P; Sundari, C S; Muralidhar, D; Chandani, S; Thomas, F; Sharma, Y

    2001-10-19

    The beta- and gamma-crystallins are closely related lens proteins that are members of the betagamma-crystallin superfamily, which also include many non-lens members. Although beta-crystallin is known to be a calcium-binding protein, this property has not been reported in gamma-crystallin. We have studied the calcium binding properties of gamma-crystallin, and we show that it binds 4 mol eq of calcium with a dissociation constant of 90 microm. It also binds the calcium-mimic spectral probes, terbium and Stains-all. Calcium binding does not significantly influence protein secondary and tertiary structures. We present evidence that the Greek key crystallin fold is the site for calcium ion binding in gamma-crystallin. Peptides corresponding to Greek key motif of gamma-crystallin (42 residues) and their mutants were synthesized and studied for calcium binding. These peptides adopt beta-sheet conformation and form aggregates producing beta-sandwich. Our results with peptides show that, in Greek key motif, the amino acid adjacent to the conserved aromatic corner in the "a" strand and three amino acids of the "d" strand participate in calcium binding. We suggest that the betagamma superfamily represents a novel class of calcium-binding proteins with the Greek key betagamma-crystallin fold as potential calcium-binding sites. These results are of significance in understanding the mechanism of calcium homeostasis in the lens. PMID:11502736

  20. A liquid crystalline supramolecular complex of C60 with a cyclotriveratrylene derivative

    PubMed

    Felder; Heinrich; Guillon; Nicoud; Nierengarten

    2000-10-01

    Cyclotriveratrylene (CTV) derivatives substituted with 9 (1) or 18 (2) long alkyl chains have been prepared. Whereas no liquid crystalline behavior has been observed for 1, the CTV derivative 2 has mesomorphic properties. Indeed, at room temperature compound 2 exhibits a nematic phase characterized by cybotactic groups with a local lamello-columnar order. Both CTV derivatives 1 and 2 are able to form supramolecular complexes with C60 in the solid state. In both cases, the 2:1 host-guest species have been obtained as brown compounds. No liquid crystalline behavior was observed for the supramolecular complex [C60 is included in (1)2]. In contrast, observation of the brown product obtained from C60 and the CTV derivative 2 directly after preparation by polarized optical microscopy revealed a fluid birefringent phase at room temperature. When the sample is heated above 70 degrees C, the birefringence of the texture under the microscope disappears and the X-ray diffraction pattern is transformed into a pattern characteristic of a cubic phase. For the first time in thermotropic liquid crystals, the space group of this cubic phase can be assigned as I4(1)32. PMID:11072814

  1. Magnetooptical and crystalline properties of sputtered garnet ferrite film on spinel ferrite buffer layer

    NASA Astrophysics Data System (ADS)

    Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Kagami, Osamu; Tanabe, Takaya

    2016-09-01

    The purpose of this study is to provide garnet films for volumetric magnetic holography. Volumetric magnetic holography usually employs an easily obtainable short-wavelength laser (visible light, not infrared light) with a large diffraction intensity. Bi-substituted garnet ferrite with a large Faraday rotation is promising for volumetric magnetic holography applications in the visible light region. However, a garnet film without a deteriorated layer must be obtained because a deteriorated layer (minute polycrystalline grains containing an amorphous phase) is formed during the initial deposition on a glass substrate. In particular, the required magnetooptical properties have not been obtained in a thin garnet film (100 nm or less) after annealing (1 h, 700 °C, oxygen atmosphere). Therefore, there is a need for excellent garnet films with the required magnetooptical (MO) properties even if the films are thin. By using a spinel ferrite buffer layer for garnet film deposition, we could obtain a thin garnet film with excellent MO properties. We determined the effect of the initial buffer layer on the crystallinity of the deposited garnet films by observing the film cross section. In addition, we undertook a qualitative estimation of the influence of the crystallinity and optical properties of the garnet film on a glass substrate with a spinel ferrite buffer layer.

  2. Prediction of a new crystalline lithium phosphorus oxynitride -- Li2PO2N

    NASA Astrophysics Data System (ADS)

    Holzwarth, N. A. W.; Du, Yaojun A.

    2010-03-01

    Lithium phosphorus oxynitride materials have been investigated for many years, especially in relation to the thin film electrolye LiPON, developed at Oak Ridge National Laboratory.footnotetext J. B. Bates et al, Solid State Ionics 53-56 647-654 (1992). We have carried out first principles simulations of related crystalline materials in an attempt to understand the sources of stability and mechanisms of Li ion conductivity in these materials. Starting with crystalline LiPO3 which has twisted phosphate chains,footnotetextE. V. Marashova, Crystallography Reports 46 942-946 (2001). we consider the possibility of modifying the structure by substituting N and Li for O. The optimized structures are computed to have regularized phosphate chains which form planar -P-N-P-N- backbones. To the best of our knowledge, the new predicted crystals, which we call s1-Li2PO2N with a 24 atom unit cell and s2-Li2PO2N with a 12 atom unit cell, have not yet been observed experimentally. We suggest several possible exothermic reaction pathways to synthesize these crystals.

  3. Efficient Crystalline Si Solar Cell with Amorphous/Crystalline Silicon Heterojunction as Back Contact: Preprint

    SciTech Connect

    Nemeth, B.; Wang, Q.; Shan, W.

    2012-06-01

    We study an amorphous/crystalline silicon heterojunction (Si HJ) as a back contact in industrial standard p-type five-inch pseudo-square wafer to replace Al back surface field (BSF) contact. The best efficiency in this study is over 17% with open-circuit (Voc) of 0.623 V, which is very similar to the control cell with Al BSF. We found that Voc has not been improved with the heterojunction structure in the back. The typical minority carrier lifetime of these wafers is on the order of 10 us. We also found that the doping levels of p-layer affect the FF due to conductivity and band gap shifting, and an optimized layer is identified. We conclude that an amorphous/crystalline silicon heterojunction can be a very promising structure to replace Al BSF back contact.

  4. Distribution of single-walled carbon nanotubes in pyrene containing liquid crystalline asymmetric zinc phthalocyanine matrix.

    PubMed

    Tuncel, Sinem; Kaya, Esra Nur; Durmuş, Mahmut; Basova, Tamara; Gürek, Ayşe Gül; Ahsen, Vefa; Banimuslem, Hikmat; Hassan, Aseel

    2014-03-28

    A novel pyrene containing asymmetric Zn(II) phthalocyanine (AB3 type) was synthesized and characterized by various spectroscopic techniques as well as elemental analysis. A symmetric polyoxyethylene substituted Zn(II) phthalocyanine (B4 type) derivative was also prepared in order to compare the properties and determine the effect of the pyrene group on the phthalocyanine molecule. Composites of synthesized zinc(II) phthalocyanine-single wall carbon nanotubes (ZnPc-SWCNTs) containing 1 and 2 wt% carbon nanotubes were prepared by mixing these two components in dichloromethane followed by removal of the solvent and drying under vacuum. The liquid crystalline properties of the pure compounds and their composites were investigated in comparison with symmetric polyoxyethylene substituted Zn(II) phthalocyanine (B4 type) by using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction analysis. The distribution of the SWCNTs in the ordered matrix of the columnar mesophase of these derivatives was studied by the method of polarized Raman spectroscopy and scanning electron microscopy (SEM). It was shown that the nature of the mesophases was not altered in these composites. The I(V) dependencies for the films deposited onto interdigitated electrodes were measured and it was shown that the lateral conductivity tends to increase with increasing SWCNT concentration. PMID:24468739

  5. 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......

  6. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    SciTech Connect

    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.

  7. 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.

  8. Conformal, macroscopic crystalline nanoparticle sheets assembled with DNA.

    PubMed

    Ku, Jessie C; Ross, Michael B; Schatz, George C; Mirkin, Chad A

    2015-05-27

    A novel method for preparing conformal silica-embedded crystalline nanoparticle sheets via DNA programmable assembly provides independent control over nanoparticle size, nanoparticle spacing, and film thickness. The conformal materials retain the nanoparticle crystallinity and spacing after being transferred to flat or highly curved substrates even after being subjected to various mechanical, physical, and chemical stimuli. PMID:25864411

  9. Broadband Dielectric Investigation of Amorphous and Semi-Crystalline Polylactides

    NASA Astrophysics Data System (ADS)

    Kanchanasopa, Mantana; Runt, James

    2003-03-01

    Molecular dynamics of poly (L-lactide) and several L-lactide/meso-lactide random copolymers were investigated in the frequency domain using broadband dielectric spectroscopy. The dielectric relaxation spectra of fully amorphous and crystalline samples reveal the influence of crystalline content and microstructure on chain motion in the amorphous phase. Differences in relaxation strength of the segmental processes were observed in these samples. While the strength of the crystalline samples increases with temperature, that of the amorphous samples changes only very little or in the opposite direction with temperature. This behavior will be discussed in the context of a rigid amorphous phase. As expected, mean segmental relaxation time is longer and its distribution is broader (at lower frequencies) in samples with higher crystallinity. Differences in the details of the relaxation processes as a function of the crystallinity and morphology will be discussed.

  10. 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.

  11. [Guidelines for substitution treatments in prison populations].

    PubMed

    Michel, L; Maguet, O

    2005-01-01

    Care access for the drug addict patients in prison (in particular for the treatments of substitution) in France is very unequal from one establishment to another. This reflects the great variability of the practices of substitution and especially the absence of consensus on the methods of adaptation of these practices to the prison environment. Because of difficulties expressed by prisoners and medical staff on this subject and of stakes (let us recall that approximately 30% of the prisoners are dependent or abusers of one or more psychoactive substances), the formulation of recommendations or of a good practices guide of substitution in prison appeared necessary. Work that we detail here answers a ordering of the Advisory Commission of the Treatments of Substitution (September 2001) whose authors are members. It was presented at the session April 2003. It results from the confrontation of a review of the literature (including legal texts and official reports concerning substitution, the organization of the care in prison environment and the lawful framework), with a vast investigation. The latter was carried out near medical staff (22 prisons), penitentiary staff (3 prisons, 27 people met including directors of these establishments) and prisoners (7 establishments, 28 prisoners met) in the form of individual talks (semi-directing interviews with evaluation of the type of existing device and its knowledge by the penitentiary staff and the prisoners; statement of the suggestions, needs and requests of the medical, penitentiary staffs and of the prisoners). In the whole visited prisons, 7.8% (870) of the prisoners received substitution treatments (6.35% by buprenorphine, 1.44% by methadone), representing a proportion of substituted drug addicts (870 substituted for an evaluation of 3,350 prisoners drug addicts among the 11,168 prisoners of the 22 visited prisons) notably lower than that in free environment (56%, ie 96,000 substituted for an evaluated population of

  12. 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.

  13. CRYSTALLINS IN RETINAL GANGLION CELL SURVIVAL AND REGENERATION

    PubMed Central

    Piri, Natik; Kwong, Jacky MK; Caprioli, Joseph

    2013-01-01

    Crystallins are heterogeneous proteins classified into alpha, beta, and gamma families. Although crystallins were first identified as the major structural components of the ocular lens with a principal function to maintain lens transparency, further studies have demonstrated the expression of these proteins in a wide variety of tissues and cell types. Alpha crystallins (alpha A and alpha B) share significant homology with small heat shock proteins and have chaperone-like properties, including the ability to bind and prevent the precipitation of denatured proteins and to increase cellular resistance to stress-induced apoptosis. Stress-induced upregulation of crystallin expression is a commonly observed phenomenon and viewed as a cellular response mechanism against environmental and metabolic insults. However, several studies reported downregulation of crystallin gene expression in various models of glaucomatous nerodegeneration suggesting that that the decreased levels of crystallins may affect the survival properties of retinal ganglion cells and thus, be associated with their degeneration. This hypothesis was corroborated by increased survival of axotomized retinal ganglion cells (RGCs) in retinas overexpressing alpha A or alpha B crystallins. In addition to RGC protective functions of alpha crystallins, beta or gamma crystallins were implicated in RGC axonal regeneration. These findings demonstrate the importance of crystallin genes in RGC survival and regeneration and further in-depth studies are necessary to better understand the mechanisms underlying the functions of these proteins in healthy RGCs as well as during glaucomatous neurodegeneration, which in turn could help in designing new therapeutic strategies to preserve or regenerate these cells. PMID:23709342

  14. 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.

  15. A Sequential and Comprehensive Method for Effective Substitute Teaching

    ERIC Educational Resources Information Center

    Byer, John L.

    2008-01-01

    This article dealt with methods for making substitute teaching more effective. The purpose was to articulate a sequential method for maximizing the effectiveness of substitute teaching while providing substitutes with a comprehensive method for diligently and flexibly earning respect and using reflection to continually improve substitute teaching.…

  16. A Qualitative Study of the Perceptions of Substitute Teaching Quality.

    ERIC Educational Resources Information Center

    Cardon, Peter W.

    2002-01-01

    Surveyed Utah teachers, substitute teachers, substitute teacher managers, and principals to examine the perceived quality of substitute teachers, reasons for these perceptions, and potential effects of the perceptions. Substitute teaching was generally assumed to be low quality. Two perceptions driving this assumption were: low pay results in poor…

  17. Coulomb correlations and optical gap in polyacetylene

    SciTech Connect

    Baeriswyl, D.; Maki, K.

    1986-01-01

    A model including both electron-phonon coupling (as in the SSH Hamiltonian) and electron-electron interactions (on-site term U, nearest-neighbor term V) is treated within the variational scheme of Gutswiller. It is shown that for weak electron-phonon coupling the primary effect is a bond-order wave induced by electronic correlation, whereas the lattice dimerization is a secondary effect. Correspondingly the optical gap is mainly due to electronic correlation.

  18. 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.

  19. 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%.

  20. 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.

  1. 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.

  2. Analysis of human crystalline lens accommodation.

    PubMed

    Chien, Chang-Hai M; Huang, Tseng; Schachar, Ronald A

    2006-01-01

    The behavior of the human crystalline lens during accommodation is analytically studied. The lens is modeled as a closed axisymmetrical membrane shell of varying thickness enclosing an incompressible liquid. To simulate zonular tension associated with lenticular accommodation, an axisymmetrical radial force or displacement is imposed around the shell equator. Two second-order, simultaneous, nonlinear governing differential equations are derived. Numerical results, obtained from the investigation of human lens profiles of three independently published MRI images and a drawing of a microphotograph, demonstrate that when zonular traction within the physiological force range of the ciliary muscle is exerted, both central lens thickness and central optical power increase. Qualitatively, these increases are independent of lens shape. However, the magnitude of these changes is dependent on the initial profile of the lens and is enhanced by the "natural" variation in capsular thickness. Only when a pulling force significantly exceeds the force capacity of the ciliary muscle does the lens flatten and its central thickness and optical power decrease. PMID:16023655

  3. 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

  4. Topology of crystalline insulators and superconductors

    NASA Astrophysics Data System (ADS)

    Shiozaki, Ken; Sato, Masatoshi

    2014-10-01

    We complete a classification of topological phases and their topological defects in crystalline insulators and superconductors. We consider topological phases and defects described by noninteracting Bloch and Bogoliubov-de Gennes Hamiltonians that support additional order-two spatial symmetry, besides any of 10 classes of symmetries defined by time-reversal symmetry and particle-hole symmetry. The additional order-two spatial symmetry we consider is general and it includes Z2 global symmetry, mirror reflection, twofold rotation, inversion, and their magnetic point group symmetries. We find that the topological periodic table shows a periodicity in the number of flipped coordinates under the order-two spatial symmetry, in addition to the Bott periodicity in the space dimensions. Various symmetry-protected topological phases and gapless modes will be identified and discussed in a unified framework. We also present topological classification of symmetry-protected Fermi points. The bulk classification and the surface Fermi point classification provide a realization of the bulk-boundary correspondence in terms of the K theory.

  5. 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.

  6. A multiscale approach for modeling crystalline solids

    NASA Astrophysics Data System (ADS)

    Cuitiño, Alberto M.; Stainier, Laurent; Wang, Guofeng; Strachan, Alejandro; Çağin, Tahir; Goddard, William A.; Ortiz, Michael

    2001-05-01

    In this paper we present a modeling approach to bridge the atomistic with macroscopic scales in crystalline materials. The methodology combines identification and modeling of the controlling unit processes at microscopic level with the direct atomistic determination of fundamental material properties. These properties are computed using a many body Force Field derived from ab initio quantum-mechanical calculations. This approach is exercised to describe the mechanical response of high-purity Tantalum single crystals, including the effect of temperature and strain-rate on the hardening rate. The resulting atomistically informed model is found to capture salient features of the behavior of these crystals such as: the dependence of the initial yield point on temperature and strain rate; the presence of a marked stage I of easy glide, specially at low temperatures and high strain rates; the sharp onset of stage II hardening and its tendency to shift towards lower strains, and eventually disappear, as the temperature increases or the strain rate decreases; the parabolic stage II hardening at low strain rates or high temperatures; the stage II softening at high strain rates or low temperatures; the trend towards saturation at high strains; the temperature and strain-rate dependence of the saturation stress; and the orientation dependence of the hardening rate.

  7. 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).

  8. Thermal Conductivities of Crystalline Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Brill, Joseph

    2014-03-01

    As applications for organic semiconductors grow, it is becoming increasingly important to know their thermal conductivities, k. For example, for sub-micron electronic devices, values of k>k0 ~ 5 mW/cm/K are needed, while values kcrystalline organic semiconductors using frequency[2] and position dependent[3] ac-calorimetry; the thermal conductivities are then determined from the specific heats measured with differential scanning calorimetry. For rubrene, which has k

  9. 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)

  10. 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.

  11. Viscoelastic damping in crystalline composites and alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Raghavan; Ozisik, Rahmi; Keblinski, Pawel

    We use molecular dynamics simulations to study viscoelastic behavior of model Lennard-Jones (LJ) crystalline composites subject to an oscillatory shear deformation. The two crystals, namely a soft and a stiff phase, individually show highly elastic behavior and a very small loss modulus. On the other hand, when the stiff phase is included within the soft matrix as a sphere, the composite exhibits significant viscoelastic damping and a large phase shift between stress and strain. In fact, the maximum loss modulus in these model composites was found to be about 20 times greater than that given by the theoretical Hashin-Shtrikman upper bound. We attribute this behavior to the fact that in composites shear strain is highly inhomogeneous and mostly accommodated by the soft phase, corroborated by frequency-dependent Grüneisen parameter analysis. Interestingly, the frequency at which the damping is greatest scales with the microstructural length scale of the composite. Finally, a critical comparison between damping properties of these composites with ordered and disordered alloys and superlattice structures is made.

  12. Crystalline electric fields in mixed valent systems

    SciTech Connect

    Shapiro, S.M.

    1980-01-01

    The inelastic neutron studies of rare-earth-based mixed valent systems have all shown remarkably similar results: a broad quasielastic line with half width on the order of 10 MeV. This width exhibits a strong temperature dependence in those systems which undergo a valence transition and is only weakly temperature dependent in those systems which show no transition. A surprising result was the absence of crystalline electric field (CEF) excitations. Recent measurements on the alloy Ce/sub .9-x/La/sub x/Th/sub .1/ have revealed the existence of CEF excitations. For x = 0, the valence transition is strongly first order and occurs near T/sub 0/ approx. 150 K. The inelastic spectra exhibit the typical broad quasielastic scattering. As x increases, T/sub 0/ decreases due to internal pressure effects, and a well-defined, but broad, excitation appears near E = 15 MeV. This is interpreted as a CEF excitation between the GAMMA/sub 7/ and GAMMA/sub 8/ levels of the Ce/sup 3/+ ion. For x = 0.40, the valence transition is almost completely suppressed and the excitation becomes even sharper.

  13. Navigating the Waters of Unconventional Crystalline Hydrates.

    PubMed

    Braun, Doris E; Koztecki, Lien H; McMahon, Jennifer A; Price, Sarah L; Reutzel-Edens, Susan M

    2015-08-01

    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

  14. In Vivo Substrates of the Lens Molecular Chaperones αA-Crystallin and αB-Crystallin

    PubMed Central

    Andley, Usha P.; Malone, James P.; Townsend, R. Reid

    2014-01-01

    αA-crystallin and αB-crystallin are members of the small heat shock protein family and function as molecular chaperones and major lens structural proteins. Although numerous studies have examined their chaperone-like activities in vitro, little is known about the proteins they protect in vivo. To elucidate the relationships between chaperone function, substrate binding, and human cataract formation, we used proteomic and mass spectrometric methods to analyze the effect of mutations associated with hereditary human cataract formation on protein abundance in αA-R49C and αB-R120G knock-in mutant lenses. Compared with age-matched wild type lenses, 2-day-old αA-R49C heterozygous lenses demonstrated the following: increased crosslinking (15-fold) and degradation (2.6-fold) of αA-crystallin; increased association between αA-crystallin and filensin, actin, or creatine kinase B; increased acidification of βB1-crystallin; increased levels of grifin; and an association between βA3/A1-crystallin and αA-crystallin. Homozygous αA-R49C mutant lenses exhibited increased associations between αA-crystallin and βB3-, βA4-, βA2-crystallins, and grifin, whereas levels of βB1-crystallin, gelsolin, and calpain 3 decreased. The amount of degraded glutamate dehydrogenase, α-enolase, and cytochrome c increased more than 50-fold in homozygous αA-R49C mutant lenses. In αB-R120G mouse lenses, our analyses identified decreased abundance of phosphoglycerate mutase, several β- and γ-crystallins, and degradation of αA- and αB-crystallin early in cataract development. Changes in the abundance of hemoglobin and histones with the loss of normal α-crystallin chaperone function suggest that these proteins also play important roles in the biochemical mechanisms of hereditary cataracts. Together, these studies offer a novel insight into the putative in vivo substrates of αA- and αB-crystallin. PMID:24760011

  15. A Solid-State NMR Study of Selenium Substitution into Nanocrystalline Hydroxyapatite

    PubMed Central

    Kolmas, Joanna; Kuras, Marzena; Oledzka, Ewa; Sobczak, Marcin

    2015-01-01

    The substitution of selenium oxyanions in the hydroxyapatite structure was examined using multinuclear solid-state resonance spectroscopy (ssNMR). The study was supported by powder X-ray diffractometry (PXRD) and wavelength dispersion X-ray fluorescence (WD-XRF). Samples of pure hydroxyapatite (HA300) and selenate (HA300-1.2SeO4) or selenite (HA300-1.2SeO3) substituted hydroxyapatites were synthesized using the standard wet method and heated at 300 °C to remove loosely bonded water. PXRD data showed that all samples are single-phase, nanocrystalline hydroxyapatite. The incorporation of selenite and selenate ions affected the lattice constants. In selenium-containing samples the concentration of Se was very similar and amounted to 9.55% and 9.64%, for HA300-1.2SeO4 and HA300-1.2SeO3, respectively. PXRD and ssNMR data showed that the selenite doping significantly decreases the crystallite size and crystallinity degree. 31P and 1H NMR experiments demonstrated the developed surface hydrated layer in all samples, especially in HA300-1.2SeO3. 1H NMR studies showed the dehydroxylation of HA during the selenium oxyanions substitution and the existence of hydrogen bonding in structural hydroxyl group channels. 1H→77Se cross polarization NMR experiments indicated that selenites and selenates are located in the crystal lattice and on the crystal surface. PMID:25997001

  16. Strontium-substituted hydroxyapatite coatings deposited via a co-deposition sputter technique.

    PubMed

    Boyd, A R; Rutledge, L; Randolph, L D; Meenan, B J

    2015-01-01

    The bioactivity of hydroxyapatite (HA) coatings can be modified by the addition of different ions, such as silicon (Si), lithium (Li), magnesium (Mg), zinc (Zn) or strontium (Sr) into the HA lattice. Of the ions listed here, strontium substituted hydroxyapatite (SrHA) coatings have received a lot of interest recently as Sr has been shown to promote osteoblast proliferation and differentiation, and reduce osteoclast activity. In this study, SrHA coatings were deposited onto titanium substrates using radio frequency (RF) magnetron co-sputtering (and compared to those surfaces deposited from HA alone). FTIR, XPS, XRD, and SEM techniques were used to analyse the different coatings produced, whereby different combinations of pure HA and 13% Sr-substituted HA targets were investigated. The results highlight that Sr could be successfully incorporated into the HA lattice to form SrHA coatings. It was observed that as the number of SrHA sputtering targets in the study were increased (increasing Sr content), the deposition rate decreased. It was also shown that as the Sr content of the coatings increased, so did the degree of preferred 002 orientation of the coating (along with obvious changes in the surface morphology). This study has shown that RF magnetron sputtering (specifically co-sputtering), offers an appropriate methodology to control the surface properties of Sr-substituted HA, such as the crystallinity, stoichiometry, phase purity and surface morphology. PMID:25491990

  17. Crystal and Electronic Study of Neodymium-Substituted CuFeO2 Oxide

    NASA Astrophysics Data System (ADS)

    Ozkendir, Osman Murat

    2016-06-01

    Neodymium-substituted CuFeO2 samples were investigated according to their crystal and electronic properties via the general formula Nd x Cu1- x FeO2. The crystal structure analysis results revealed polycrystalline formations in the sample and a change in crystalline sizes with the substituted heavy fermion "Nd." Increasing the Nd amount in the sample was determined to cause a disturbance on the Cu-Fe planes that supports the formation of crystal structures with low crystal symmetries such as monoclinic or triclinic geometries. To obtain the background mechanisms of the crystal properties, the X-ray absorption fine structure spectroscopy technique was used to study the electronic properties of the samples. Prominent changes in the crystal structures due to 4 f electrons' contributions from the substituted Nd atoms as the main "role player" in the phase transitions were determined. The Nd atoms were observed as the key element guiding the entire phenomenon as a result of their large size and narrow 4 f levels. Also, magnetic properties of the samples were tested at room temperature and without an applied magnetic field by X-ray magnetic circular dichroism study due to previous studies that reported the parent oxide CuFeO2 to have magnetic ordering at T N = 11 K (-262 °C). Except the sample for x = 1.0 (NdFeO3), no magnetic ordering was observed at room temperature; i.e., all of the samples showed paramagnetic behaviors.

  18. Systematic investigation of chemical substitution in BaSnO3 using the combinatorial approach

    NASA Astrophysics Data System (ADS)

    Takeuchi, Ichiro; Shin, Jongmoon; Lee, Seunghun; Zhang, Xiaohang; Jaim, H. M. Iftekhar; Jeong, Se-Young

    BaSnO3 has been regarded as a possible material for photo-catalysis, dielectric capacitors, and transparent conductors. We are systematically investigating the effect of chemical substitution for A and B sites in BaSnO3 using a high-throughput methodology. We have thus far investigated the effect of substituting La and Sr for the Ba-site and Pb and Bi for the Sn-site. The composition spread films were prepared on MgO, SrTiO3 and LaAlO3 using combinatorial pulsed laser deposition. The lattice parameters and band-gap energies were found to continually change as a function of the concentration of each substitutional dopant. We find that the band gap can be tuned from 2.8 eV for BaSn0.05Pb0.95O3 to 4.5 eV for Ba0.05La0.95SnO3. Especially for Ba1-xLaxSnO3 with x in the range of 0.05 crystalline defects on electrical properties will also be discussed. This project is funded by AFOSR.

  19. Preparation of 1-Substituted Tetrahydro-β-carbolines by Lithiation-Substitution.

    PubMed

    Cochrane, Edward J; Hassall, Lorraine A; Coldham, Iain

    2015-06-01

    A method to prepare 1-substituted N-Boc-tetrahydro-β-carbolines was developed by lithiation followed by electrophilic substitution. The deprotonation to give the organolithium was optimized by in situ IR spectroscopy and showed that the Boc group rotates slowly at low temperature. The chemistry was applied to the synthesis of 9-methyleleagnine (N-methyltetrahydroharman) and 11-methylharmicine. PMID:25974712

  20. 40 CFR 721.3063 - Substituted phenyl azo substituted phenyl esters (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... phenyl esters (generic name). 721.3063 Section 721.3063 Protection of Environment ENVIRONMENTAL... esters (generic name). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as substituted phenyl azo substituted phenyl esters (PMNs...